JP7042278B2 - A synthetic polymer membrane having a surface having a bactericidal action and a sterilization method using the surface of the synthetic polymer membrane - Google Patents

Description

The present invention relates to a synthetic polymer membrane having a surface having a bactericidal action and a sterilization method using the surface of the synthetic polymer membrane.

Recently, it has been announced that the nanosurface structure of black silicon, cicadas and dragonfly wings has a bactericidal action (Non-Patent Document 1). The physical structure of the nanopillars of black silicon, cicadas and dragonfly wings is said to exert a bactericidal action.

According to Non-Patent Document 1, the bactericidal action against Gram-negative bacteria is strongest in black silicon, and weakens in the order of dragonfly feathers and cicada feathers. Black silicon has nanopillars with a height of 500 nm, and cicada and dragonfly wings have nanopillars with a height of 240 nm. The static contact angle of these surfaces with water (hereinafter, may be simply referred to as "contact angle") is 80 ° for black silicon, 153 ° for dragonfly wings, and 153 ° for cicada wings. It is 159 °. It is considered that black silicon is mainly formed of silicon, and the wings of cicadas and dragonflies are formed of chitin. According to Non-Patent Document 1, the composition of the surface of black silicon is almost silicon oxide, and the composition of the surface of the wings of cicadas and dragonflies is lipid.

Japanese Patent No. 4265729 Japanese Unexamined Patent Publication No. 2009-166502 International Publication No. 2011/125486 International Publication No. 2013/183576 International Publication No. 2015/163018 (Patent No. 5788128) International Publication No. 2016/080245 (Patent No. 5933151) International Publication No. 2016/208540

Ivanova, E.P. et al., "Bactericidal activity of black silicon", Nat. Commun. 4: 2838 doi: 10.1038 / ncomms3838 (2013).

From the results described in Non-Patent Document 1, the mechanism by which bacteria are killed by nanopillars is not clear. Furthermore, the reason why black silicon has a stronger bactericidal action than the wings of dragonflies and cicadas is whether it is due to the difference in the height and shape of the nanopillar, or the difference in the surface free energy (which can be evaluated by the contact angle). It is unknown whether it is in the constituent substances or in the chemical properties of the surface.

Further, even if the bactericidal action of black silicon is utilized, there is a problem that black silicon has poor mass productivity and is hard and brittle, so that shape processability is low.

The present invention has been made to solve the above problems, and a main object thereof is to provide a synthetic polymer membrane having a surface having a bactericidal action and a sterilization method using the surface of the synthetic polymer membrane. To do. Another object of the present invention is to provide a synthetic polymer membrane having a surface having a bactericidal action, which is excellent in water resistance and / or mass productivity.

The synthetic polymer film of an embodiment of the present invention is a synthetic polymer film having a surface having a plurality of first convex portions, and when viewed from the normal direction of the synthetic polymer film, the plurality of synthetic polymer films. The two-dimensional size of the first convex portion is in the range of more than 20 nm and less than 500 nm, and has a crosslinked structure, wherein the crosslinked structure does not contain nitrogen and fluorine, and is an ethylene oxide unit and / or a water-soluble monomer. The minimum value of the dynamic storage polymer E'in the temperature range exceeding the glass transition temperature is Er'(Pa), the minimum temperature that gives Er'is Tr (K), and the gas constant R is 8. As 3J / mol · K, the crosslink density n obtained from the formula n = Er'/ (3 · R · Tr) is 2.8 × 10 ^-3 mol / cc or more and 9.5 × 10 ^-3 mol / cc. It is in the following range.

Here, the dynamic storage elastic moduli Er'(Pa) and Tr (K) are obtained by DMA (also referred to as dynamic mechanical analysis or dynamic viscoelasticity measurement).

In certain embodiments, the crosslink density n is 8.4 × 10 ^-3 mol / cc or less.

In certain embodiments, the crosslink density n is 5.8 × 10 ^-3 mol / cc or less.

In certain embodiments, the crosslink density n is 3.7 × 10 ^-3 mol / cc or more.

In one embodiment, the total content of ethylene oxide units and water-soluble monomer units contained in the crosslinked structure with respect to the entire synthetic polymer membrane is more than 40% by mass.

In one embodiment, the total content of ethylene oxide units and water-soluble monomer units contained in the crosslinked structure with respect to the entire synthetic polymer membrane is 70% by mass or less.

In certain embodiments, the dynamic storage modulus Er'is greater than 20 MPa and less than 90 MPa.

In certain embodiments, the dynamic storage modulus Er'is less than 75 MPa.

In certain embodiments, the crosslinked structure comprises a monomer unit having a siloxane bond.

The method for sterilizing a liquid according to an embodiment of the present invention is a method for sterilizing the liquid by contacting the surface of the synthetic polymer membrane according to any one of the above with a liquid containing water.

According to an embodiment of the present invention, a synthetic polymer membrane having a surface having a bactericidal action and a sterilization method using the surface of the synthetic polymer membrane are provided. According to an embodiment of the present invention, there is provided a synthetic polymer membrane having a surface having a bactericidal action, which is excellent in water resistance and / or mass productivity.

(A) and (b) are schematic cross-sectional views of synthetic polymer membranes 34A and 34B according to the embodiment of this invention, respectively. (A) to (e) are diagrams for explaining the manufacturing method of the moth-eye mold 100A and the structure of the moth-eye mold 100A. (A) to (c) are diagrams for explaining the manufacturing method of the moth-eye mold 100B and the structure of the moth-eye mold 100B. (A) shows an SEM image of the surface of the aluminum base material, (b) shows an SEM image of the surface of the aluminum film, and (c) shows an SEM image of a cross section of the aluminum film. (A) is a schematic plan view of a porous alumina layer of a mold, (b) is a schematic cross-sectional view, and (c) is a diagram showing an SEM image of a prototype mold. It is a figure for demonstrating the manufacturing method of the synthetic polymer membrane using the mold 100 for moth eye. (A) and (b) are diagrams showing SEM images of dead Pseudomonas aeruginosa on a surface having a moth-eye structure observed with an SEM (scanning electron microscope). It is a graph which shows the result of having measured the temperature dependence of the dynamic storage elastic modulus E'of the synthetic polymer membrane of Example 1. It is a graph which shows the relationship between the cross-linking density and the viable cell ratio of the synthetic polymer membrane of Examples 1-8 and Comparative Examples 2-7.

Hereinafter, a sterilization method using a synthetic polymer membrane having a bactericidal effect on the surface and the surface of the synthetic polymer membrane according to the embodiment of the present invention will be described with reference to the drawings.

In this specification, the following terms will be used.

"Sterilization (microbicidal)" refers to reducing the number of proliferative microorganisms (microorganisms) contained in objects such as objects and liquids and in a limited space.

"Microorganisms" include viruses, bacteria (bacteria) and fungi (molds).

"Antibacterial" broadly includes suppressing and preventing the growth of microorganisms, and also includes suppressing darkening and slimming caused by microorganisms.

The present applicant has developed a method for producing an antireflection film (antireflection surface) having a moth-eye structure using an anodized porous alumina layer. By using the anodized porous alumina layer, a mold having an inverted moth-eye structure can be manufactured with high mass productivity.

The present inventor has developed a synthetic polymer membrane having a bactericidal effect on the surface by applying the above technique (see, for example, Patent Documents 5, 6 and 7). For reference, all of the disclosures of Patent Documents 5, 6 and 7 are incorporated herein by reference.

The structure of the synthetic polymer membrane according to the embodiment of the present invention will be described with reference to FIGS. 1 (a) and 1 (b).

1 (a) and 1 (b) show schematic cross-sectional views of synthetic polymer membranes 34A and 34B according to the embodiment of the present invention, respectively. The synthetic polymer films 34A and 34B exemplified here are both formed on the base films 42A and 42B, respectively, but are not limited to this, of course. The synthetic polymer films 34A and 34B can be formed directly on the surface of any object.

The film 50A shown in FIG. 1A has a base film 42A and a synthetic polymer film 34A formed on the base film 42A. The synthetic polymer film 34A has a plurality of convex portions 34Ap on the surface, and the plurality of convex portions 34Ap constitute a moth-eye structure. When viewed from the normal direction of the synthetic polymer film 34A, the two-dimensional size Dp of the convex portion _34Ap is in the range of more than 20 nm and less than 500 nm. Here, the "two-dimensional size" of the convex portion 34Ap refers to the diameter corresponding to the area circle of the convex portion 34Ap when viewed from the normal direction of the surface. For example, when the convex portion 34Ap has a conical shape, the two-dimensional size of the convex portion 34Ap corresponds to the diameter of the bottom surface of the cone. Further, the typical distance D _int between adjacent portions of the convex portion 34Ap is more than 20 nm and 1000 nm or less. As illustrated in FIG. 1A, when the convex portions 34Ap are densely arranged and there is no gap between the adjacent convex portions 34Ap (for example, the bottom surfaces of the cones partially overlap), the convex portions are convex. The two-dimensional magnitude D _p of the part 34 Ap is equal to the distance D _int between the adjacencies. The typical height D _h of the convex portion 34Ap is 50 nm or more and less than 500 nm. As will be described later, the bactericidal action is exhibited even when the height D _h of the convex portion 34Ap is 150 nm or less. The thickness t _s of the synthetic polymer film 34A is not particularly limited, and may be larger than the height D _h of the convex portion 34Ap.

The synthetic polymer film 34A shown in FIG. 1A has a moth-eye structure similar to that of the antireflection film described in Patent Documents 1 to 4. In order to exhibit the antireflection function, it is preferable that there is no flat portion on the surface and the convex portions 34Ap are densely arranged. Further, the convex portion 34Ap has a shape in which the cross-sectional area (cross section parallel to the plane orthogonal to the incident light beam, for example, the cross section parallel to the plane of the base film 42A) increases from the air side toward the base film 42A side, for example. It is preferably conical. Further, in order to suppress light interference, it is preferable to arrange the convex portions 34Ap preferably randomly so as not to have regularity. However, these features are not necessary if the bactericidal action of the synthetic polymer membrane 34A is used exclusively. For example, the convex portions 34Ap do not need to be closely arranged, and may be regularly arranged. However, it is preferable that the shape and arrangement of the convex portion 34Ap are selected so as to effectively act on the microorganism.

The film 50B shown in FIG. 1B has a base film 42B and a synthetic polymer film 34B formed on the base film 42B. The synthetic polymer film 34B has a plurality of convex portions 34Bp on the surface, and the plurality of convex portions 34Bp constitute a moth-eye structure. The structure of the convex portion 34Bp of the synthetic polymer film 34B of the film 50B is different from the structure of the convex portion 34Ap of the synthetic polymer film 34A of the film 50A. The description of the features common to the film 50A may be omitted.

When viewed from the normal direction of the synthetic polymer film 34B, the two-dimensional size D _p of the convex portion 34 Bp is in the range of more than 20 nm and less than 500 nm. Further, the typical distance D _int between adjacent portions of the convex portion 34 Bp is more than 20 nm and 1000 nm or less, and D _p <D _int . That is, in the synthetic polymer film 34B, a flat portion exists between the adjacent convex portions 34Bp. The convex portion 34Bp is a columnar shape having a conical portion on the air side, and the typical height D _h of the convex portion 34Bp is 50 nm or more and less than 500 nm. Further, the convex portions 34Bp may be arranged regularly or irregularly. If the convex portions 34Bp are regularly arranged, D _int will also represent the period of the arrangement. This is, of course, the same for the synthetic polymer membrane 34A.

In the present specification, the "moss-eye structure" is a convex portion having a shape in which the cross-sectional area (cross section parallel to the membrane surface) increases, like the convex portion 34Ap of the synthetic polymer film 34A shown in FIG. 1 (a). Not only the nano-surface structure having an excellent reflective function composed of the portions, but also the cross-sectional area (cross-section parallel to the film surface) like the convex portion 34Bp of the synthetic polymer film 34B shown in FIG. 1 (b). Also includes a nanosurface structure composed of protrusions having a certain portion. In addition, in order to destroy the cell wall and / or the cell membrane of the microorganism, it is preferable to have a conical portion. However, the tip of the cone does not necessarily have to have a nano-surface structure, and may have a roundness (about 60 nm) of about the nano-pillar constituting the nano-surface structure of the cicada wings.

The mold for forming the moth-eye structure on the surface as illustrated in FIGS. 1 (a) and 1 (b) (hereinafter referred to as “moth-eye mold”) is an inverted moth-eye structure obtained by reversing the moth-eye structure. Have. If the anodized porous alumina layer having an inverted moth-eye structure is used as it is as a mold, the moth-eye structure can be manufactured at low cost. In particular, when a cylindrical moth-eye mold is used, a moth-eye structure can be efficiently manufactured by a roll-to-roll method. Such a mold for moth eye can be manufactured by the method described in Patent Documents 2 to 4.

With reference to FIGS. 2 (a) to 2 (e), a method for manufacturing the moth-eye mold 100A for forming the synthetic polymer film 34A will be described.

First, as shown in FIG. 2A, as the mold base material, the aluminum base material 12, the inorganic material layer 16 formed on the surface of the aluminum base material 12, and the aluminum deposited on the inorganic material layer 16 A mold base material 10 having a film 18 is prepared.

As the aluminum base material 12, a relatively highly rigid aluminum base material having an aluminum purity of 99.50 mass% or more and less than 99.99 mass% is used. The impurities contained in the aluminum base material 12 include iron (Fe), silicon (Si), copper (Cu), manganese (Mn), zinc (Zn), nickel (Ni), titanium (Ti), and lead (Pb). , Tin (Sn) and magnesium (Mg), preferably at least one element selected from the group, with Mg being particularly preferred. The mechanism by which pits are formed in the etching process is a local battery reaction, so ideally it does not contain any elements that are noble than aluminum and is a base metal Mg (standard electrode potential is-). It is preferable to use the aluminum base material 12 containing 2.36 V) as an impurity element. If the content of an element nobler than aluminum is 10 ppm or less, it can be said that the element is not substantially contained from the electrochemical point of view. The Mg content is preferably 0.1 mass% or more, and more preferably about 3.0 mass% or less. If the Mg content is less than 0.1 mass%, sufficient rigidity cannot be obtained. On the other hand, when the content is large, segregation of Mg is likely to occur. Even if segregation occurs near the surface forming the moth-eye mold, it does not pose an electrochemical problem, but Mg forms an anodic oxide film having a form different from that of aluminum, which causes a defect. The content of the impurity element may be appropriately set according to the shape, thickness and size of the aluminum base material 12 and the required rigidity. For example, when a plate-shaped aluminum base material 12 is produced by rolling, an appropriate Mg content of about 3.0 mass% is used, and an aluminum base material 12 having a three-dimensional structure such as a cylinder is produced by extrusion processing. In this case, the Mg content is preferably 2.0 mass% or less. When the Mg content exceeds 2.0 mass%, the extrusion processability generally deteriorates.

As the aluminum base material 12, for example, a cylindrical aluminum tube formed of JIS A1050, an Al—Mg-based alloy (for example, JIS A5052), or an Al—Mg—Si-based alloy (for example, JIS A6063) is used.

It is preferable that the surface of the aluminum base material 12 is subjected to bite cutting. If, for example, abrasive grains remain on the surface of the aluminum base material 12, conduction is likely to occur between the aluminum film 18 and the aluminum base material 12 in the portion where the abrasive grains are present. In places where there are irregularities other than the abrasive grains, it becomes easy to locally conduct electricity between the aluminum film 18 and the aluminum base material 12. Local conduction between the aluminum film 18 and the aluminum substrate 12 may cause a local battery reaction between the impurities in the aluminum substrate 12 and the aluminum film 18.

As the material of the inorganic material layer 16, for example, tantalum pentoxide (Ta ₂ O ₅ ) or silicon dioxide (SiO ₂ ) can be used. The inorganic material layer 16 can be formed, for example, by a sputtering method. When the tantalum pentoxide layer is used as the inorganic material layer 16, the thickness of the tantalum pentoxide layer is, for example, 200 nm.

The thickness of the inorganic material layer 16 is preferably 100 nm or more and less than 500 nm. If the thickness of the inorganic material layer 16 is less than 100 nm, defects (mainly voids, that is, gaps between crystal grains) may occur in the aluminum film 18. Further, when the thickness of the inorganic material layer 16 is 500 nm or more, the surface condition of the aluminum base material 12 makes it easy to insulate between the aluminum base material 12 and the aluminum film 18. In order to perform anodizing of the aluminum film 18 by supplying a current from the aluminum base material 12 side to the aluminum film 18, it is necessary for a current to flow between the aluminum base material 12 and the aluminum film 18. If a configuration is adopted in which an electric current is supplied from the inner surface of the cylindrical aluminum base material 12, it is not necessary to provide an electrode on the aluminum film 18, so that the aluminum film 18 can be anodized over the entire surface and an electric current is generated as the anodization progresses. The aluminum film 18 can be uniformly anodized over the entire surface without causing the problem that the aluminum film 18 is difficult to be supplied.

Further, in order to form the thick inorganic material layer 16, it is generally necessary to lengthen the film forming time. When the film forming time is long, the surface temperature of the aluminum base material 12 rises unnecessarily, and as a result, the film quality of the aluminum film 18 may deteriorate and defects (mainly voids) may occur. If the thickness of the inorganic material layer 16 is less than 500 nm, it is possible to suppress the occurrence of such a defect.

The aluminum film 18 is, for example, a film formed of aluminum having a purity of 99.99 mass% or more (hereinafter, may be referred to as “high-purity aluminum film”), as described in Patent Document 3. The aluminum film 18 is formed, for example, by using a vacuum vapor deposition method or a sputtering method. The thickness of the aluminum film 18 is preferably in the range of about 500 nm or more and about 1500 nm or less, and is, for example, about 1 μm.

Further, as the aluminum film 18, instead of the high-purity aluminum film, the aluminum alloy film described in Patent Document 4 may be used. The aluminum alloy film described in Patent Document 4 contains aluminum, a metal element other than aluminum, and nitrogen. In the present specification, the "aluminum film" includes not only a high-purity aluminum film but also an aluminum alloy film described in Patent Document 4.

When the aluminum alloy film is used, a mirror surface having a reflectance of 80% or more can be obtained. The average particle size of the crystal grains constituting the aluminum alloy film when viewed from the normal direction of the aluminum alloy film is, for example, 100 nm or less, and the maximum surface roughness Rmax of the aluminum alloy film is 60 nm or less. The content of nitrogen contained in the aluminum alloy film is, for example, 0.5 mass% or more and 5.7 mass% or less. The absolute value of the difference between the standard electrode potential of the metal element other than aluminum contained in the aluminum alloy film and the standard electrode potential of aluminum is 0.64 V or less, and the content of the metal element in the aluminum alloy film is 1.0 mass. It is preferably% or more and 1.9 mass% or less. The metal element is, for example, Ti or Nd. However, the metal element is not limited to this, and other metal elements (for example, Mn, Mg, Zr, V and others) in which the absolute value of the difference between the standard electrode potential of the metal element and the standard electrode potential of aluminum is 0.64 V or less are used. It may be Pb). Further, the metal element may be Mo, Nb or Hf. The aluminum alloy film may contain two or more of these metal elements. The aluminum alloy film is formed, for example, by the DC magnetron sputtering method. The thickness of the aluminum alloy film is also preferably in the range of about 500 nm or more and about 1500 nm or less, for example, about 1 μm.

Next, as shown in FIG. 2B, the surface 18s of the aluminum film 18 is anodized to form a porous alumina layer 14 having a plurality of recesses (pores) 14p. The porous alumina layer 14 has a porous layer having a recess 14p and a barrier layer (the bottom of the recess (pore) 14p). It is known that the distance between adjacent recesses 14p (distance between centers) corresponds to approximately twice the thickness of the barrier layer and is substantially proportional to the voltage at the time of anodization. This relationship also holds for the final porous alumina layer 14 shown in FIG. 2 (e).

The porous alumina layer 14 is formed, for example, by anodizing the surface 18s in an acidic electrolytic solution. The electrolytic solution used in the step of forming the porous alumina layer 14 is, for example, an aqueous solution containing an acid selected from the group consisting of phosphoric acid, tartaric acid, phosphoric acid, sulfuric acid, chromic acid, citric acid, and malic acid. For example, the surface 18s of the aluminum film 18 is anodized with an oxalic acid aqueous solution (concentration 0.3 mass%, liquid temperature 10 ° C.) at an applied voltage of 80 V for 55 seconds to form the porous alumina layer 14.

Next, as shown in FIG. 2C, the porous alumina layer 14 is brought into contact with the alumina etchant and etched by a predetermined amount to enlarge the opening of the recess 14p. The etching amount (that is, the size and depth of the recess 14p) can be controlled by adjusting the type / concentration of the etching solution and the etching time. As the etching solution, for example, 10 mass% phosphoric acid, an aqueous solution of an organic acid such as formic acid, acetic acid, or citric acid, sulfuric acid, or a mixed aqueous solution of chromic acid phosphate can be used. For example, etching is performed for 20 minutes using an aqueous phosphoric acid solution (10 mass%, 30 ° C.).

Next, as shown in FIG. 2D, the aluminum film 18 is partially anodized again to grow the recess 14p in the depth direction and thicken the porous alumina layer 14. Here, since the growth of the recess 14p starts from the bottom of the recess 14p that has already been formed, the side surface of the recess 14p becomes stepped.

Further, after this, if necessary, the porous alumina layer 14 is further etched by contacting it with the alumina etchant to further expand the pore size of the recess 14p. As the etching solution, it is preferable to use the above-mentioned etching solution as well, and in reality, the same etching bath may be used.

As described above, by alternately repeating the above-mentioned anodizing step and etching step a plurality of times (for example, 5 times: anodizing 5 times and etching 4 times), the process was inverted as shown in FIG. 2 (e). A mold for moth-eye 100A having a porous alumina layer 14 having a moth-eye structure can be obtained. By ending with the anodizing step, the bottom of the recess 14p can be pointed. That is, a mold capable of forming a convex portion having a sharp tip is obtained.

The porous alumina layer 14 (thickness t _p ) shown in FIG. 2 (e) has a porous layer (thickness corresponds to the depth D _d of the recess 14 p) and a barrier layer (thickness t _b ). Since the porous alumina layer 14 has a structure in which the moth-eye structure of the synthetic polymer film 34A is inverted, the same symbol may be used for the corresponding parameter that characterizes the size thereof.

The recess 14p of the porous alumina layer 14 is, for example, conical and may have a stepped side surface. The two-dimensional size of the recess 14p (diameter equivalent to the area circle of the recess when viewed from the normal direction of the surface) D _p is more than 20 nm and less than 500 nm, and the depth D _d is about 50 nm or more and less than 1000 nm (1 μm). It is preferable to have. Further, it is preferable that the bottom of the recess 14p is sharp (the bottom is a point). When the recesses 14p are tightly filled, assuming that the shape of the recesses 14p when viewed from the normal direction of the porous alumina layer 14 is a circle, the adjacent circles overlap each other, and the saddle portion is formed between the adjacent recesses 14p. It is formed. When the substantially conical recesses 14p are adjacent to each other so as to form a saddle, the two-dimensional size Dp of the recesses _14p is equal to the distance D _int between the neighbors. The thickness _tp of the porous alumina layer 14 is, for example, about 1 μm or less.

Under the porous alumina layer 14 shown in FIG. 2 (e), the aluminum residual layer 18r that has not been anodized is present in the aluminum film 18. If necessary, the aluminum film 18 may be anodized substantially completely so that the aluminum residual layer 18r is not present. For example, when the inorganic material layer 16 is thin, an electric current can be easily supplied from the aluminum base material 12 side.

The method for producing a mold for moth-eye exemplified here can produce a mold for producing the antireflection film described in Patent Documents 2 to 4. Since the antireflection film used for high-definition display panels is required to have high uniformity, selection of the material of the aluminum base material, mirror finishing of the aluminum base material, control of the purity and components of the aluminum base material as described above are required. However, since high uniformity is not required for the bactericidal action, the above-mentioned method for producing a mold can be simplified. For example, the surface of the aluminum substrate may be directly anodized. Further, even if pits are formed due to the influence of impurities contained in the aluminum base material at this time, the moth-eye structure of the finally obtained synthetic polymer film 34A is only locally disturbed and has a bactericidal action. It is considered that there is almost no effect.

Further, according to the above-mentioned method for manufacturing a mold, it is possible to manufacture a mold having a low regularity of arrangement of recesses, which is suitable for manufacturing an antireflection film. When utilizing the bactericidal properties of the moth-eye structure, it is considered that the regularity of the arrangement of the convex portions does not affect. A mold for forming a moth-eye structure having regularly arranged protrusions can be manufactured, for example, as follows.

For example, after forming a porous alumina layer having a thickness of about 10 μm, the formed porous alumina layer may be removed by etching, and then anodizing may be performed under the conditions for forming the porous alumina layer described above. The porous alumina layer having a thickness of 10 μm is formed by increasing the anodizing time. When such a relatively thick porous alumina layer is generated and the porous alumina layer is removed, the porous alumina layer is regularly arranged without being affected by the unevenness and processing strain due to the grains existing on the surface of the aluminum film or the aluminum substrate. It is possible to form a porous alumina layer having recesses. For removing the porous alumina layer, it is preferable to use a mixed solution of chromic acid and phosphoric acid. Galvanic corrosion may occur if etching is performed for a long period of time, but a mixed solution of chromic acid and phosphoric acid has the effect of suppressing galvanic corrosion.

The moth-eye mold for forming the synthetic polymer film 34B shown in FIG. 1 (b) can also be basically manufactured by combining the above-mentioned anodizing step and etching step. With reference to FIGS. 3 (a) to 3 (c), a method for manufacturing the moth-eye mold 100B for forming the synthetic polymer film 34B will be described.

First, a plurality of recesses (pores) are prepared by preparing the mold base material 10 and anodizing the surface 18s of the aluminum film 18 in the same manner as described with reference to FIGS. 2 (a) and 2 (b). The porous alumina layer 14 having 14p is formed.

Next, as shown in FIG. 3A, the porous alumina layer 14 is brought into contact with the alumina etchant and etched by a predetermined amount to enlarge the opening of the recess 14p. At this time, the etching amount is reduced as compared with the etching process described with reference to FIG. 2 (c). That is, the size of the opening of the recess 14p is reduced. For example, etching is performed for 10 minutes using an aqueous phosphoric acid solution (10 mass%, 30 ° C.).

Next, as shown in FIG. 3B, the aluminum film 18 is partially anodized again to grow the recess 14p in the depth direction and thicken the porous alumina layer 14. At this time, the recess 14p is grown deeper than the anodizing step described with reference to FIG. 2 (d). For example, an oxalic acid aqueous solution (concentration 0.3 mass%, liquid temperature 10 ° C.) is used to perform anodizing at an applied voltage of 80 V for 165 seconds (55 seconds in FIG. 2 (d)).

After that, the etching step and the anodizing step are alternately repeated a plurality of times in the same manner as described with reference to FIG. 2 (e). For example, by alternately repeating the etching step three times and the anodizing step three times, as shown in FIG. 3C, a moss-eye mold 100B having a porous alumina layer 14 having an inverted mos-eye structure is obtained. Be done. At this time, the two-dimensional size D _p of the recess 14 p is smaller than the distance between adjacent D _int (D _p <D _int ).

The size of microorganisms depends on the type. For example, Pseudomonas aeruginosa has a size of about 1 μm, but some bacteria have a size of several hundred nm to about 5 μm, and fungi have a size of several μm or more. For example, a convex portion having a two-dimensional size of about 200 nm is considered to have a bactericidal action against microorganisms having a size of about 0.5 μm or more, but has a bactericidal action against bacteria having a size of several hundred nm. , The convex part may not exhibit sufficient bactericidal action because it is too large. The size of the virus ranges from several tens of nm to several 100 nm, and many of them have a size of 100 nm or less. Although the virus does not have a cell membrane, it has a protein shell called a capsid that surrounds the viral nucleic acid. Viruses are divided into viruses having a membranous envelope on the outside of the shell and viruses having no envelope. In a virus with an envelope, since the envelope is mainly composed of lipids, it is considered that the convex portion acts on the envelope in the same manner. Examples of the enveloped virus include influenza virus and Ebola virus. In viruses that do not have an envelope, it is thought that the protrusions act similarly on the shell of this protein called capsid. When the convex portion has an element of nitrogen, the affinity with the protein composed of amino acids can be strengthened.

Therefore, the structure of a synthetic polymer membrane having a convex portion capable of exhibiting a bactericidal action against a microorganism having a diameter of several hundred nm or less and a method for producing the same will be described below.

Hereinafter, the convex portion having the two-dimensional size of more than 20 nm and less than 500 nm of the synthetic polymer film exemplified above is referred to as a first convex portion. Further, the convex portion formed by superimposing on the first convex portion is referred to as a second convex portion, and the two-dimensional size of the second convex portion is the two-dimensional size of the first convex portion. It is smaller than the halfbeak and does not exceed 100 nm. When the two-dimensional size of the first convex portion is less than 100 nm, particularly less than 50 nm, it is not necessary to provide the second convex portion. Further, the concave portion of the mold corresponding to the first convex portion is referred to as a first concave portion, and the concave portion of the mold corresponding to the second convex portion is referred to as a second concave portion.

Even if the method of forming the first recess of a predetermined size and shape by alternately performing the above-mentioned anodizing step and the etching step is applied as it is, the second recess cannot be formed.

FIG. 4A shows an SEM image of the surface of the aluminum base material (reference numeral 12 in FIG. 2), and FIG. 4B shows an SEM image of the surface of the aluminum film (reference numeral 18 in FIG. 2). 4 (c) shows an SEM image of a cross section of the aluminum film (reference numeral 18 in FIG. 2). As can be seen from these SEM images, grains (crystal grains) are present on the surface of the aluminum base material and the surface of the aluminum film. The grains of the aluminum film form irregularities on the surface of the aluminum film. This surface roughness affects the formation of recesses during anodization and thus prevents the formation of second recesses with D _p or D _int less than 100 nm.

Therefore, the method for producing the mold used for producing the synthetic polymer film according to the embodiment of the present invention includes (a) a step of preparing an aluminum film deposited on an aluminum base material or a support, and (b). Anodizing step of forming a porous alumina layer having a first recess by applying a first level voltage while the surface of an aluminum base material or an aluminum film is in contact with an electrolytic solution, and (c). After the step (b), the porous alumina layer was brought into contact with the etching solution to enlarge the first recess, and after the step (d) step (c), the porous alumina layer was brought into contact with the electrolytic solution. In the state, it includes a step of forming a second recess in the first recess by applying a second level voltage lower than the first level. For example, the first level is above 40V and the second level is below 20V.

That is, in the anodizing step at the first level voltage, a first recess having a size not affected by the grain of the aluminum substrate or the aluminum film is formed, and then the thickness of the barrier layer is reduced by etching. After making it smaller, a second recess is formed within the first recess in the anodizing step at a second level voltage lower than the first level. Forming the second recess in this way eliminates the effects of grain.

With reference to FIG. 5, a mold having a first recess 14pa and a second recess 14pb formed in the first recess 14pa will be described. 5 (a) is a schematic plan view of the porous alumina layer of the mold, FIG. 5 (b) is a schematic cross-sectional view, and FIG. 5 (c) shows an SEM image of the prototype mold.

As shown in FIGS. 5A and 5B, the surface of the mold according to the present embodiment has a plurality of first recesses 14pa having a two-dimensional size within a range of more than 20 nm and less than 500 nm. It further has a plurality of second recesses 14pb formed so as to be superimposed on the first recess 14pa. The two-dimensional size of the plurality of second recesses 14pa is smaller than the two-dimensional size of the plurality of first recesses 14pa and does not exceed 100 nm. The height of the second recess 14pb is, for example, more than 20 nm and 100 nm or less. It is preferable that the second recess 14pb also includes a substantially conical portion like the first recess 14pa.

The porous alumina layer shown in FIG. 5 (c) was manufactured as follows.

As the aluminum film, an aluminum film containing 1 mass% of Ti was used. An oxalic acid aqueous solution (concentration 0.3 mass%, temperature 10 ° C.) was used as the anodic oxide solution, and a phosphoric acid aqueous solution (concentration 10 mass%, temperature 30 ° C.) was used as the etching solution. After anodizing at a voltage of 80 V for 52 seconds, etching was performed for 25 minutes, followed by anodizing at a voltage of 80 V for 52 seconds and etching for 25 minutes. After that, anodizing at 20 V was performed for 52 seconds, etching was performed for 5 minutes, and anodizing at 20 V was performed for 52 seconds.

As can be seen from FIG. 5 (c), a second recess having a D _p of about 50 nm is formed in the first recess having a D _p of about 200 nm. In the above manufacturing method, when the voltage of the first level was changed from 80V to 45V to form the porous alumina layer, the first recess having a D _p of about 100 nm was contained in the first recess having a D _p of about 50 nm. Two recesses were formed.

When a synthetic polymer film is produced using such a mold, a synthetic polymer having a convex portion obtained by reversing the structure of the first concave portion 14pa and the second concave portion 14pb shown in FIGS. 5 (a) and 5 (b). A membrane is obtained. That is, a synthetic polymer film having a plurality of second convex portions formed by superimposing on the plurality of first convex portions can be obtained.

The synthetic polymer film having the first convex portion and the second convex portion formed so as to be superimposed on the first convex portion is relatively large, 5 μm or more, from a relatively small microorganism of about 100 nm. It may have a bactericidal action against microorganisms.

Of course, depending on the size of the target microorganism, only recesses having a two-dimensional size within the range of more than 20 nm and less than 100 nm may be formed. A mold for forming such a convex portion can be produced, for example, as follows.

Anodization is performed using a neutral salt solution (ammonium borate, ammonium citrate, etc.) such as an aqueous solution of ammonium tartrate, or an organic acid (maleic acid, malonic acid, phthalic acid, citric acid, tartrate, etc.) having a small degree of ion dissociation. A barrier-type anodic oxide film is formed, the barrier-type anodic oxide film is removed by etching, and then anodized at a predetermined voltage (the second level voltage described above) to obtain a two-dimensional size. Recesses within the range of more than 20 nm and less than 100 nm can be formed.

For example, as the aluminum film, an aluminum film containing 1 mass% of Ti is used, and a barrier type anodized film is anodized at 100 V for 2 minutes using an aqueous tartaric acid solution (concentration 0.1 mol / l, temperature 23 ° C.). To form. After that, the barrier type anodized film is removed by etching with an aqueous phosphoric acid solution (concentration: 10 mass%, temperature: 30 ° C.) for 25 minutes. Then, in the same manner as above, an oxalic acid aqueous solution (concentration 0.3 mass%, temperature 10 ° C.) was used as the anodic oxide solution, anodizing at 20 V was performed for 52 seconds, and etching using the above etching solution was performed alternately for 5 minutes. By repeating anodizing 5 times and etching 4 times, recesses having a two-dimensional size of about 50 nm can be uniformly formed.

As described above, molds for moth-eyes capable of forming various moth-eye structures can be manufactured.

Next, with reference to FIG. 6, a method for producing a synthetic polymer membrane using the moth-eye mold 100 will be described. FIG. 6 is a schematic cross-sectional view for explaining a method of manufacturing a synthetic polymer membrane by a roll-to-roll method. Hereinafter, a method of producing a synthetic polymer film on the surface of a base film as a workpiece by using the above-mentioned roll type will be described, but the method of producing a synthetic polymer film according to the embodiment of the present invention is described below. Synthetic polymer films can be produced on the surface of various workpieces using other shapes, not limited to the above.

First, a cylindrical moth-eye mold 100 is prepared. The cylindrical moth-eye mold 100 is manufactured by, for example, the manufacturing method described with reference to FIG.

As shown in FIG. 6, the base film 42 having the ultraviolet curable resin 34'on the surface is pressed against the moth-eye mold 100, and the ultraviolet curable resin 34'is irradiated with ultraviolet rays (UV) to cure the ultraviolet rays. The resin 34'is cured. As the ultraviolet curable resin 34', for example, an acrylic resin can be used. The base film 42 is, for example, a PET (polyethylene terephthalate) film or a TAC (triacetyl cellulose) film. The base film 42 is unwound from an unwinding roller (not shown), and then the ultraviolet curable resin 34'is applied to the surface thereof by, for example, a slit coater or the like. The base film 42 is supported by the support rollers 46 and 48, as shown in FIG. The support rollers 46 and 48 have a rotation mechanism and convey the base film 42. Further, the cylindrical moth-eye mold 100 is rotated in the direction indicated by the arrow in FIG. 6 at a rotation speed corresponding to the transport speed of the base film 42.

Then, by separating the moth-eye mold 100 from the base film 42, a synthetic polymer film 34 to which the inverted moth-eye structure of the moth-eye mold 100 is transferred is formed on the surface of the base film 42. The base film 42 having the synthetic polymer film 34 formed on the surface thereof is wound by a winding roller (not shown).

The surface of the synthetic polymer film 34 has a moth-eye structure in which the nano-surface structure of the moth-eye mold 100 is inverted. The synthetic polymer films 34A and 34B shown in FIGS. 1 (a) and 1 (b) can be produced depending on the nanosurface structure of the moth-eye mold 100 to be used. The material for forming the synthetic polymer film 34 is not limited to the ultraviolet curable resin, and a photocurable resin that can be cured with visible light can be used, or a thermosetting resin can also be used.

The bactericidal property of a synthetic polymer membrane having a moth-eye structure on its surface has a correlation not only with the physical structure of the synthetic polymer membrane but also with the chemical properties of the synthetic polymer membrane. For example, the applicant of the present application has, as chemical properties, the contact angle of the surface of the synthetic polymer film (Patent Document 5), the concentration of nitrogen element contained in the surface (Patent Document 6), the concentration of nitrogen element, and further ethylene. We found a correlation with the content of oxide units (-CH ₂ CH ₂ O-) (Patent Document 7).

FIG. 7 shows an SEM image shown in Patent Document 6 (FIG. 8). 7 (a) and 7 (b) are views showing SEM images of Pseudomonas aeruginosa that died on the surface having the moth-eye structure shown in FIG. 1 (a) observed with an SEM (scanning electron microscope).

Looking at these SEM images, it can be seen that the tip of the convex part has invaded the cell wall (adventitia) of Pseudomonas aeruginosa. Further, looking at FIGS. 7 (a) and 7 (b), it does not appear that the convex portion has penetrated the cell wall, but it appears that the convex portion has been incorporated into the cell wall. This may be explained by the mechanism suggested in the Supplemental Information of Non-Patent Document 1. That is, the outer membrane (lipid bilayer) of Gram-negative bacteria deforms in close proximity to the convex part, so that the lipid bilayer locally undergoes a transition similar to the first-order phase transition (spontaneous reorientation). It is possible that an opening was formed in a portion close to the convex portion, and the convex portion invaded this opening. Alternatively, the convex part may have been taken up by a mechanism (endocytosis) that takes in a polar substance (including a nutrient source) possessed by the cell.

When the present inventor further investigated a synthetic polymer membrane suitably used for sterilizing a liquid containing water, the synthetic polymer membranes described in Patent Documents 5 to 7 have mass productivity (transferability) and / Or it was found that there was room for improvement in water resistance.

The synthetic polymer membranes described in Patent Documents 5 to 7 used acrylates containing an element of nitrogen and / or an element of fluorine. A quaternary ammonium salt containing a nitrogen element, an amino group, an amide group, and a urethane bond may contribute to the decrease in transferability and / or water resistance. Since a compound containing a quaternary ammonium salt, an amino group, or an amide group has high permeability to a mold release agent, there is a concern that the mold release property may be lowered. Further, since the compound having a urethane bond has a relatively high viscosity, it tends to reduce the releasability. Therefore, when mass-produced by the roll-to-roll method, the productivity is lowered. In addition, since the compound containing an element of nitrogen has high polarity, it has a disadvantageous effect on water resistance. On the other hand, when an acrylate containing a fluorine element is used, it has an advantageous effect on releasability, but it has high water repellency and makes it difficult for water to permeate. As a result, there is concern that the effect of sterilizing liquids containing water will be weakened.

Therefore, the present inventor prepared various synthetic polymer films using acrylates (containing methacrylate) containing neither nitrogen element nor fluorine element, and evaluated transferability and water resistance as well as bactericidal property. Sample films having different contents and cross-linking densities of water-soluble monomers and / or ethylene oxide units (-CH ₂ CH ₂ O-, hereinafter sometimes referred to as "EO units") contained in the synthetic polymer film were prepared.

Here, the water-soluble monomer means that the amount of water (about 20 ° C.) required to dissolve 1 g or 1 ml of the monomer is less than 100 ml. As the water-soluble monomer, those in which the amount of water (about 20 ° C.) required to dissolve 1 g or 1 ml of the monomer is less than 30 ml are preferable.

The water-soluble monomer has a hydroxyl group, a carbonyl group and / or a carboxyl group. Examples of the monomer having a hydroxyl group include 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate and the like. Examples of the monomer having a carbonyl group include 2-acetoacetoxyethyl methacrylate and the like. Examples of the monomer having a carboxyl group include acrylic acid, methacrylic acid, 2-methacrylyloxyethyl succinic acid and the like.

[Synthetic polymer membrane]
Using ultraviolet curable resins having different compositions, a sample film having the same structure as the film 50A shown in FIG. 1A was prepared. The raw materials used are shown in Table 1.

As the sample film of the synthetic polymer film, like the synthetic polymer films described in Patent Documents 5 to 7, Reference Examples 1 to 4 containing a nitrogen element and / or a fluorine element, transferability and / or water resistance are improved. Examples 1 to 9 and Comparative Examples 1 to 9 were prepared. The compositions of Reference Examples 1 to 4 are shown in Table 2, the compositions of Examples 1 to 9 are shown in Table 3, and the compositions of Comparative Examples 1 to 9 are shown in Table 4. In Table 2, (N) after the abbreviation of the acrylic monomer indicates that it contains a nitrogen element, and (F) indicates that it contains a fluorine element. In Comparative Example 1, the same ultraviolet curable resin as in Example 1 was used, and the moth-eye structure was not formed. That is, the sample film of Comparative Example 1 is a film (flat plate) having a flat surface.

As the base film 42A, a PET film having a thickness of 50 μm (A4300 manufactured by Toyobo Co., Ltd.) was used. As a method for producing the synthetic polymer film, a synthetic polymer film 34A having a moth-eye structure on the surface was produced by using the moth-eye mold 100A in the same manner as described with reference to FIG. The exposure amount was about 200 mJ / cm ² (based on light having a wavelength of 375 nm). In each sample film, D _p was about 200 nm, D _int was about 200 nm, and D _h was about 150 nm. In each case, a synthetic polymer film was prepared without solvent.

For each sample film, the evaluation results of bactericidal property, transferability and water resistance, and the content of water-soluble monomer unit and / or ethylene oxide unit (EO unit) are shown in Tables 5 to 7 below. Table 5 shows Reference Examples 1 to 4, Table 6 shows Examples 1 to 9, and Table 7 shows Comparative Examples 1 to 9.

[Evaluation of bactericidal properties]
The bactericidal property against the bacterial solution (water) scattered on the sample film was evaluated. Since the bactericidal property of the sample film to which the bacterial solution was applied was evaluated when it was left at room temperature and in the air, the influence of drying was added. Here, the bactericidal property against Staphylococcus aureus was evaluated. The specific evaluation method is as follows. An experiment was conducted with N = 3 for each sample film.
(1) A bacterial solution containing Staphylococcus aureus was prepared using 1/500 NB medium so that the initial number of bacteria was 1E + 06CFU / mL.
(2) 10 μL of the above bacterial solution was dropped onto each sample film (5 cm square).
(3) After leaving the sample in the air at room temperature (about 25 ° C.) for 15 minutes, the SCDLP medium was poured over the sample film to wash out the bacteria (washout solution).
(4) The wash-out solution was appropriately diluted with PBS, cultured on a standard agar medium or the like, and the number of bacteria was counted.

The bactericidal property was evaluated based on the bactericidal property of the reference film. As a reference film, a PET film having a thickness of 50 μm (A4300 manufactured by Toyobo Co., Ltd.) used as a base film was used. For the PET film, the number of bacteria was counted by the above procedure, and the bactericidal property of each sample film was evaluated by the ratio (%) of the number of bacteria of each sample film to the number of bacteria obtained for this PET film. Specifically, the viable cell rate was determined according to the following formula.
Viability rate (%) = number of bacteria in each sample film (total of N = 3) / number of bacteria in PET film (total of N = 3) x 100

The criteria for determining the bactericidal property were: ⊚: 0%, 〇: more than 0% and less than 10%, Δ: 10% or more and less than 50%, ×: 50% or more, based on the viable cell rate. That is, if the viable cell rate is less than 50%, it can be used.

[Evaluation of transferability]
In order to evaluate the transferability, an aluminum film (thickness: about 1 μm) is formed on a glass substrate (about 5 cm × about 5 cm), and anodizing and etching are alternately repeated on the aluminum film in the same manner as described above. Porous alumina layer (D _p is about 200 nm, D _int is about 200 nm, D _h is about 150 nm) was formed. The surface of the obtained porous alumina layer was washed with oxygen plasma (100 W, 25 seconds) to adjust the contact angle with water to 100 ° to 110 °. This is to reduce the mold releasability of the mold surface with respect to the UV curable resin.

A synthetic polymer film was formed 10 times on a PET film using an ultraviolet curable resin. Forming a synthetic polymer film on a PET film is expressed as transferring the synthetic polymer film onto the PET film. A UV lamp (product name: LIGHT HANMAR6J6P3) manufactured by Fusion UV Systems was used for ultraviolet irradiation, and the exposure amount was about 200 mJ / cm ² (based on 375 nm light). The transfer is performed by hand, and the transfer is performed 10 times. The index is the feeling of lightness at the time of transfer (the degree of force required to peel the mold from the synthetic polymer membrane) and the state of the surface of the mold at the time of transfer. And said.
〇: No change after 10 transcriptions.
Δ: After 10 transfers, the mold tends to be heavier when peeled off, but there is no problem such as the synthetic polymer film (ultraviolet curable resin) remaining on the surface of the mold.
X: A problem occurred in which a synthetic polymer film remained on the surface of the mold during 10 transfers.
XX: A problem occurred in which a synthetic polymer film remained on the entire surface of the mold during 10 transfers.
Here, the ones of 〇 and △ can be used.

[Evaluation of water resistance]
Each sample film was immersed in water, left at 37 ° C. for 72 hours, then taken out of the water, and the state of each sample film was visually observed.
〇: There was no change from before immersion.
Δ: There is whitening, but there is no part where the synthetic polymer film is peeled off from the base film.
X: There is a part where the synthetic polymer film is peeled off from the base film.
XX: The synthetic polymer film is peeled off from the base film on almost the entire surface.
Here, the one whose judgment is ○ or Δ is considered to be usable.

[Crosslink density]
Since the synthetic polymer film produced here is formed of an ultraviolet curable resin containing a polyfunctional acrylate, it has a crosslinked structure (mesh structure). As is well known, the crosslink density of a polymer having a crosslinked structure is a temperature that gives Er'with the minimum value of the dynamic storage elastic modulus E'in the temperature range exceeding the glass transition temperature as Er'(Pa). Is Tr (K), and the gas constant R is 8.3 J / mol · K, and is obtained from the equation of n = Er'/ (3 · R · Tr).

When it is difficult to specify the minimum value of the dynamic storage elastic modulus E'in the temperature range exceeding the glass transition temperature, the minimum value of the dynamic storage elastic modulus E'in the temperature range exceeding the glass transition temperature is Er'. It may be (Pa), and the minimum temperature at which Er'is given may be Tr (K).

Here, the dynamic storage elastic modulus Er'(Pa) is determined by DMA (Dynamic Mechanical Analysis: dynamic mechanical analysis or dynamic viscoelastic measurement). Here, it was obtained as follows.

Using a viscoelasticity measuring device (product name: DMA7100) manufactured by Hitachi High-Tech Science Co., Ltd., in a tensile mode, under the conditions of a measurement temperature range of -50 ° C to 250 ° C, a heating rate of 5 ° C / min, and a frequency of 10 Hz. , The temperature change of the dynamic storage elastic modulus E'was measured. The minimum value (typically the minimum value) of the dynamic storage elastic modulus E'in the temperature region exceeding the glass transition temperature Tg is defined as the dynamic storage elastic modulus Er', and the minimum temperature giving Er'is Tr (K). did. The glass transition temperature Tg was determined as, for example, a temperature at which the loss elastic modulus E ″ has a maximum value (peak value). The test piece had a length of 35 mm, a width of 5 mm, and a thickness of 1 mm, and the length of the unclamped portion was 20 mm.

FIG. 8 shows the results of measuring the temperature dependence of the dynamic storage elastic modulus E'of the synthetic polymer membrane of Example 1. In the temperature range exceeding the glass transition temperature (near room temperature), the dynamic storage elastic modulus E'decreases and takes a minimum value at 91 ° C. (Tr = 91 + 273K). The dynamic storage elastic modulus Er'at 91 ° C. is 53 MPa. From these values, according to the above formula, the crosslink density n is 5.8 × 10 ^-3 mol / cc. Similarly, the crosslink densities were determined for Reference Examples 1 to 4, Examples 1 to 9, and Comparative Examples 1 to 9.

In Tables 5 to 7, Tr is expressed in degrees Celsius (° C.), but the absolute temperature (K) is used for the calculation of the crosslink density. Further, the "water-soluble m amount" in Tables 5 to 7 represents the mass% of the water-soluble monomer with respect to the whole of each ultraviolet curable resin, and the "EO amount" is an ethylene oxide unit with respect to the whole of each ultraviolet curable resin (the amount of ethylene oxide). Represents the mass% of (EO unit).

See Table 5.

The synthetic polymer films of Reference Examples 1 to 4 are prepared by using an acrylic monomer containing a nitrogen element and / or a fluorine element, and the crosslinked structure contains a nitrogen element and / or a fluorine element. In addition, these synthetic polymer membranes contain a water-soluble monomer unit and an EO unit. The "water-soluble monomer unit" refers to a structural unit after the water-soluble monomer is polymerized.

Reference Examples 1 to 3 containing an element of nitrogen have excellent bactericidal properties, but have poor transferability. Reference Example 4 containing a fluorine element is excellent in transferability and water resistance, but has low bactericidal property. It is presumed that this is because the water-repellent effect of the fluorine element makes it difficult for bacteria contained in water to approach the surface of the synthetic polymer film.

Next, refer to Table 6.

The synthetic polymer membranes of Examples 1 to 9 do not contain either a nitrogen element or a fluorine element in the crosslinked structure, and have an ethylene oxide unit and / or a water-soluble monomer unit. All synthetic polymer membranes have a crosslink density n in the range of 2.8 × 10 ^-3 mol / cc or more and 9.5 × 10 ^-3 mol / cc or less, and are either bactericidal, transferable or water resistant. Is also at a usable level.

From the viewpoint of bactericidal properties, the crosslink density n is preferably 8.4 × 10 ^-3 mol / cc or less, and more preferably 5.8 × 10 ^-3 mol / cc or less.

From the viewpoint of water resistance, the crosslink density n is preferably 3.7 × 10 ^-3 mol / cc or more.

The total content of the ethylene oxide unit and the water-soluble monomer unit contained in the crosslinked structure is more than 40% by mass. Since the water resistance of Examples 2, 4 and 5 is slightly inferior, it is considered that the total content of the ethylene oxide unit and the water-soluble monomer unit contained in the crosslinked structure is preferably 70% by mass or less.

The dynamic storage elastic modulus Er'is in the range of more than 20 MPa and less than 90 MPa. Since the bactericidal properties of Examples 6 and 7 are slightly inferior, it is considered that the dynamic storage elastic modulus Er'is preferably less than 75 MPa.

Example 9 is made of a mixture of the ultraviolet curable resin of Example 6 and an acrylic monomer having a siloxane bond, and has improved bactericidal properties. A compound having a siloxane bond (silicone compound) is often used as a material for imparting releasability, like a fluorine-based compound. From the comparison between Example 9 and Example 6, it is considered that the use of the monomer having a siloxane bond can improve the releasability, that is, the transferability, without sacrificing the bactericidal property.

Next, refer to Table 7.

Similar to the synthetic polymer membranes of Examples, the synthetic polymer membranes of Comparative Examples 1 to 9 do not contain either nitrogen element or fluorine element in the crosslinked structure. Further, the synthetic polymer membranes of Comparative Examples 1 to 7 have an ethylene oxide unit and / or a water-soluble monomer unit.

The synthetic polymer film of Comparative Example 1 is a synthetic polymer film that uses the same ultraviolet curable resin as that of Example 1 and does not form a moth-eye structure, and has poor bactericidal properties. That is, it can be seen that the bactericidal property is imparted or improved by having the moth-eye structure on the surface of the synthetic polymer film.

The synthetic polymer membranes of Comparative Examples 2 to 4 have excellent bactericidal properties, but have poor water resistance. The crosslink density n of these synthetic polymer membranes is 2.3 × 10 ^-3 mol / cc or less. From the comparison with the examples, it can be seen that if the crosslink density n is too small, the water resistance is lowered.

The synthetic polymer membranes of Comparative Examples 5 to 7 have excellent water resistance but poor bactericidal properties. The crosslink density n of these synthetic polymer membranes is 11.0 × 10 ^-3 mol / cc or more. As is clear from the graph showing the relationship between the crosslink density and the viable cell ratio of the synthetic polymer membranes of Examples 1 to 8 and Comparative Examples 2 to 7 shown in FIG. 9, if the crosslink density n is too large, the bactericidal property It can be seen that

From this, in order for water to be sterilized by contacting with the surface of the synthetic polymer membrane, the surface of the synthetic polymer membrane must have sufficient hydrophilicity and crosslink density to be swollen by water. Is considered preferable. That is, it is considered that the probability that the polymer chain on the surface of the synthetic polymer membrane interacts with the bacteria contained in water increases, and as a result, the bactericidal property is improved.

The synthetic polymer membranes of Comparative Examples 8 and 9 do not contain ethylene oxide units and have poor bactericidal properties. From this, it is considered that the ethylene oxide unit contributes to the bactericidal property.

The synthetic polymer membrane according to the embodiment of the present invention can sterilize water adhering to the surface thereof in a short time. Therefore, infection can be suppressed / prevented by arranging the hand dryer on the inner surface of the manual insertion space.

The synthetic polymer membrane according to the embodiment of the present invention is suitably used for applications in which it is desired to sterilize water in a short time.

34A, 34B Synthetic polymer film 34Ap, 34Bp Convex 42A, 42B Base film 50A, 50B Film 100, 100A, 100B Moss eye mold

Claims (10)

A synthetic polymer membrane having a surface with a plurality of first protrusions.
When viewed from the normal direction of the synthetic polymer film, the two-dimensional size of the plurality of first convex portions is in the range of more than 20 nm and less than 500 nm.
It has a cross-linked structure, and the cross-linked structure does not contain nitrogen elements and fluorine elements.
The crosslinked structure has ethylene oxide units and water-soluble monomer units, or has ethylene oxide units and does not contain water-soluble monomer units.
The minimum value of the dynamic storage elastic modulus E'in the temperature range exceeding the glass transition temperature is Er'(Pa), the minimum temperature that gives Er'is Tr (K), and the gas constant R is 8.3 J / mol · K. As a result, the cross-linking density n obtained from the equation of n = Er'/ (3 ・ R ・ Tr) is in the range of 2.8 × 10 ^-3 mol / cc or more and 9.5 × 10 ^-3 mol / cc or less. , Synthetic polymer film. The synthetic polymer membrane according to claim 1, wherein the crosslink density n is 8.4 × 10 ^-3 mol / cc or less. The synthetic polymer membrane according to claim 1 or 2, wherein the crosslink density n is 5.8 × 10 ^-3 mol / cc or less. The synthetic polymer membrane according to any one of claims 1 to 3, wherein the crosslink density n is 3.7 × 10 ^-3 mol / cc or more. The synthetic height according to any one of claims 1 to 4, wherein the total content of the ethylene oxide unit and the water-soluble monomer unit contained in the crosslinked structure with respect to the entire synthetic polymer membrane is more than 40% by mass. Molecular membrane. The synthetic polymer membrane according to claim 5, wherein the total content of the ethylene oxide unit and the water-soluble monomer unit contained in the crosslinked structure with respect to the entire synthetic polymer membrane is 70% by mass or less. The synthetic polymer membrane according to any one of claims 1 to 6, wherein the minimum value Er'of the dynamic storage elastic modulus is more than 20 MPa and less than 90 MPa. The synthetic polymer membrane according to claim 7, wherein the minimum value Er'of the dynamic storage elastic modulus is less than 75 MPa. The synthetic polymer membrane according to any one of claims 1 to 8, wherein the crosslinked structure contains a monomer unit having a siloxane bond. A method for sterilizing a liquid containing water by contacting the surface of the synthetic polymer membrane according to any one of claims 1 to 9.

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