JP6581296B2 - Synthetic polymer membrane having a surface with bactericidal action - Google Patents

Description

  The present invention relates to a synthetic polymer film having a surface having a bactericidal action, a sterilization method using the surface of the synthetic polymer film, a mold for producing a synthetic polymer film, and a method for producing the mold. The “mold” here includes molds used in various processing methods (stamping and casting), and is sometimes referred to as a stamper. It can also be used for printing (including nanoprinting).

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

  According to Non-Patent Document 1, black silicon has the strongest bactericidal action against Gram-negative bacteria, and becomes weaker in the order of dragonfly wings and cicada wings. Black silicon has nanopillars with a height of 500 nm, and semi and dragonfly wings have nanopillars with a height of 240 nm. In addition, the static contact angle of water on these surfaces (hereinafter sometimes simply referred to as “contact angle”) is 80 ° for black silicon, whereas 153 ° for dragonfly, 159 °. Black silicon is mainly formed from silicon, and the wings of cicada and dragonfly are considered to be formed from chitin. According to Non-Patent Document 1, the composition of the surface of black silicon is approximately silicon oxide, and the composition of the surfaces of semi- and dragonfly wings is lipid.

Japanese Patent No. 4265729 JP 2009-166502 A International Publication No. 2011/125486 International Publication No. 2013/183576

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. In addition, the reason why black silicon has a stronger bactericidal action than dragonflies and semi-wings is the difference in height and shape of nanopillars, or the difference in surface free energy (which can be evaluated by contact angle). It is unclear whether it is in the constituent material or the chemical nature of the surface.

  Even when the sterilizing action of black silicon is used, black silicon is poor in mass productivity and has a problem that its shape workability is low because it is hard and brittle.

  The present invention has been made to solve the above-mentioned problems, and its main purpose is a synthetic polymer film having a surface having a bactericidal action, a sterilization method using the surface of the synthetic polymer film, and a synthesis. An object of the present invention is to provide a mold and a mold manufacturing method for manufacturing a polymer film. It is another object of the present invention to provide a synthetic polymer film having a surface having a bactericidal action and excellent in water resistance. Here, the “synthetic polymer film having excellent water resistance” means that (1) when a film having a synthetic polymer film and a base film is brought into contact with water for a certain period of time, the entire film is curled. Suppressed, (2) Suppressed from peeling the synthetic polymer film from the base film when the film having the synthetic polymer film and the base film is contacted with water for a certain period of time, and (3) Synthesis When the polymer membrane is brought into contact with water, it means a synthetic polymer membrane having at least one of the effects of few components eluted from the synthetic polymer membrane.

  A synthetic polymer film according to an embodiment of the present invention is a synthetic polymer film having a surface having a plurality of convex portions, and when viewed from the normal direction of the synthetic polymer film, 2 of the plurality of convex portions. The dimensional size is in the range of more than 20 nm and less than 500 nm, the surface has a bactericidal effect, and the total concentration of nitrogen element forming primary amine and nitrogen element forming secondary amine is 0 The number of moles of ethylene oxide units contained in 1 g is more than 0.0020 and not more than 0.0080.

  In one embodiment, the total concentration of the nitrogen element forming the primary amine and the nitrogen element forming the secondary amine is 0.33 at% or more.

  A synthetic polymer film according to another embodiment of the present invention is a synthetic polymer film having a surface having a plurality of protrusions, and the plurality of protrusions when viewed from the normal direction of the synthetic polymer film. The two-dimensional size is in the range of more than 20 nm and less than 500 nm, the surface has a bactericidal effect, and includes a urethane acrylate structure, which is 1,2-octanedione, 1- [4 Includes atomic groups derived from-(phenylthio)-, 2- (O-benzoyloxime).

  In one embodiment, the urethane acrylate structure includes a repeating structure of ethylene oxide units. For example, when the repeating number of the repeating structure is n (n is an integer of 2 or more), the urethane acrylate structure includes a repeating structure where n is 9.

  In one embodiment, the urethane acrylate structure includes a polymer of urethane acrylate monomers having three or more functions.

  In one embodiment, the urethane acrylate monomer includes a heterocyclic ring containing elemental nitrogen.

  In one embodiment, the heterocyclic ring is a cyanuric ring.

  According to an embodiment of the present invention, a synthetic polymer film having a surface having a bactericidal action, a sterilization method using the surface of the synthetic polymer film, a mold for producing the synthetic polymer film, and a method for producing the mold are provided. Is done. According to the embodiment of the present invention, there is further provided a synthetic polymer membrane having a surface having a bactericidal action and excellent in water resistance. Here, the “synthetic polymer film having excellent water resistance” means that (1) when a film having a synthetic polymer film and a base film is brought into contact with water for a certain period of time, the entire film is curled. Suppressed, (2) Suppressed from peeling the synthetic polymer film from the base film when the film having the synthetic polymer film and the base film is contacted with water for a certain period of time, and (3) Synthesis Synthesis having at least one of the effects of suppressing degradation of the bactericidal effect (including bactericidal and antibacterial properties) of the synthetic polymer membrane when the polymer membrane is contacted with water for a certain period of time A polymer membrane.

(A) And (b) is typical sectional drawing of the synthetic polymer membranes 34A and 34B by embodiment of this invention, respectively. (A)-(e) is a figure for demonstrating the manufacturing method of the moth-eye type | mold 100A, and the structure of the moth-eye type | mold 100A. (A)-(c) is a figure for demonstrating the manufacturing method of the moth-eye type | mold 100B, and the structure of the moth-eye type | mold 100B. (A) shows the SEM image of the surface of an aluminum base material, (b) shows the SEM image of the surface of an aluminum film, (c) shows the SEM image of the cross section of an aluminum film. (A) is a typical top view of the type | mold porous alumina layer, (b) is typical sectional drawing, (c) is a figure which shows the SEM image of the prototype | mold type | mold. It is a figure for demonstrating the manufacturing method of the synthetic polymer film | membrane using the type | mold 100 for moth eyes. (A) And (b) is a figure which shows the SEM image which observed the Pseudomonas aeruginosa dead on the surface which has a moth-eye structure with SEM (scanning electron microscope). It is a graph which shows the evaluation result of bactericidal property.

  Hereinafter, with reference to the drawings, according to an embodiment of the present invention, a synthetic polymer film having a sterilizing effect on the surface, a sterilization method using the surface of the synthetic polymer film, and a method for producing the synthetic polymer film A mold and a method for manufacturing the mold will be described.

  In the present specification, the following terms will be used.

  “Sterilization (microbicidal)” refers to an effective reduction in the number of proliferating microorganisms contained in objects such as objects and liquids and in limited spaces.

  “Microorganism” includes viruses, bacteria, and fungi.

  “Antimicrobial” broadly includes suppressing and preventing the growth of microorganisms, and 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 (for example, Patent Documents 1 to 4). For reference, the entire disclosure of Patent Documents 1 to 4 is incorporated herein.

  The present inventor has developed a synthetic polymer film having a bactericidal effect on the surface by applying the above technique.

  With reference to FIGS. 1A and 1B, the structure of a synthetic polymer membrane according to an embodiment of the present invention will be described.

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

A film 50A shown in FIG. 1A includes 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 constitutes a moth-eye structure. When viewed from the normal direction of the synthetic polymer film 34A, the two-dimensional size D _p 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 protrusion 34Ap refers to the area equivalent circle diameter of the protrusion 34Ap when viewed from the normal direction of the surface. For example, when the convex portion 34Ap is conical, the two-dimensional size of the convex portion 34Ap corresponds to the diameter of the bottom surface of the cone. Further, a typical inter-adjacent distance D _int of the convex portion 34Ap is more than 20 nm and not more than 1000 nm. As illustrated in FIG. 1A, when the protrusions 34Ap are densely arranged and there is no gap between the adjacent protrusions 34Ap (for example, the bottom surfaces of the cones partially overlap), The two-dimensional size D _p of the portion 34Ap is equal to the inter-adjacent distance D _int . A typical height D _h of the convex portion 34Ap is not less than 50 nm and less than 500 nm. As will be described later, even if the height D _h of the convex portion 34Ap is 150 nm or less, the bactericidal action is exhibited. There is no particular limitation on the thickness t _s of the synthetic polymer film 34A, be greater than the height D _h of the convex portion 34Ap.

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

  A 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 protrusions 34Bp on the surface, and the plurality of protrusions 34Bp constitutes a moth-eye structure. In the film 50B, the structure of the convex part 34Bp of the synthetic polymer film 34B is different from the structure of the convex part 34Ap of the synthetic polymer film 34A of the film 50A. Description of 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 34Bp is in the range of more than 20 nm and less than 500 nm. In addition, a typical inter-adjacent distance D _int of the convex portion 34Bp is more than 20 nm and not more than 1000 nm, and D _p <D _int . That is, in the synthetic polymer film 34B, there is a flat portion between the adjacent convex portions 34Bp. The convex portion 34Bp has a cylindrical shape having a conical portion on the air side, and a typical height D _h of the convex portion 34Bp is 50 nm or more and less than 500 nm. The convex portions 34Bp may be regularly arranged or irregularly arranged. When the convex portions 34Bp are regularly arranged, D _int also represents the period of the arrangement. Of course, the same applies to the synthetic polymer film 34A.

  In the present specification, the “moth eye structure” is a convex having a shape in which the cross-sectional area (cross section parallel to the film surface) increases like the convex portion 34Ap of the synthetic polymer film 34A shown in FIG. In addition to the nano-surface structure having an excellent reflecting function, the cross-sectional area (cross section parallel to the film surface) is similar to the convex part 34Bp of the synthetic polymer film 34B shown in FIG. Includes a nano-surface structure composed of convex portions having a certain portion. In addition, in order to destroy the cell wall and / or cell membrane of a microorganism, it is preferable to have a conical portion. However, the conical tip does not necessarily have a nano surface structure, and may have a roundness (about 60 nm) that is about the size of a nano pillar that constitutes the nano surface structure of a semi-wing.

  A mold for forming a moth-eye structure as illustrated in FIGS. 1A and 1B on the surface (hereinafter referred to as “moth-eye mold”) is an inverted moth-eye structure obtained by inverting the moth-eye structure. Have. If an anodized porous alumina layer having an inverted moth-eye structure is used as a mold as it is, 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 moth-eye mold can be manufactured by the methods described in Patent Documents 2 to 4.

  A manufacturing method of the moth-eye mold 100A for forming the synthetic polymer film 34A will be described with reference to FIGS.

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

  As the aluminum substrate 12, a relatively rigid aluminum substrate having an aluminum purity of 99.50 mass% or more and less than 99.99 mass% is used. As impurities contained in the aluminum substrate 12, iron (Fe), silicon (Si), copper (Cu), manganese (Mn), zinc (Zn), nickel (Ni), titanium (Ti), lead (Pb) It is preferable that at least one element selected from the group consisting of tin (Sn) and magnesium (Mg) is included, and Mg is particularly preferable. The mechanism by which pits (dents) are formed in the etching process is a local cell reaction, and therefore ideally contains no element nobler than aluminum and is a base metal, Mg (standard electrode potential is − It is preferable to use an aluminum substrate 12 containing 2.36V) as an impurity element. If the content of an element nobler than aluminum is 10 ppm or less, it can be said that the said element is not included substantially from an electrochemical viewpoint. The Mg content is preferably 0.1% by mass or more, and more preferably in the range of about 3.0% by 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 rate increases, Mg segregation easily occurs. Even if segregation occurs in the vicinity of the surface forming the moth-eye mold, there is no electrochemical problem. However, Mg forms an anodic oxide film having a form different from that of aluminum, which causes defects. What is necessary is just to set suitably the content rate of an impurity element according to the rigidity required according to the shape of the aluminum base material 12, thickness, and a magnitude | size. For example, when the plate-shaped aluminum substrate 12 is produced by rolling, an appropriate Mg content is about 3.0 mass%, and the aluminum substrate 12 having a three-dimensional structure such as a cylinder is produced by extrusion. When it does, it is preferable that the content rate of Mg is 2.0 mass% or less. If the Mg content exceeds 2.0 mass%, extrusion processability generally decreases.

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

  The surface of the aluminum base 12 is preferably subjected to bite cutting. If, for example, abrasive grains remain on the surface of the aluminum base 12, electrical conduction between the aluminum film 18 and the aluminum base 12 is facilitated in a portion where the abrasive grains exist. In addition to the abrasive grains, where there are irregularities, local conduction between the aluminum film 18 and the aluminum substrate 12 is likely to occur. When local conduction is made between the aluminum film 18 and the aluminum base 12, there is a possibility that a battery reaction occurs locally between the impurities in the aluminum base 12 and the aluminum film 18.

As a material of the inorganic material layer 16, for example, tantalum oxide (Ta ₂ O ₅ ) or silicon dioxide (SiO ₂ ) can be used. The inorganic material layer 16 can be formed by sputtering, for example. When a tantalum oxide layer is used as the inorganic material layer 16, the thickness of the tantalum oxide 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 in some cases. Further, when the thickness of the inorganic material layer 16 is 500 nm or more, the aluminum base 12 and the aluminum film 18 are easily insulated from each other depending on the surface state of the aluminum base 12. In order to anodize the aluminum film 18 by supplying current to the aluminum film 18 from the aluminum substrate 12 side, it is necessary that a current flow between the aluminum substrate 12 and the aluminum film 18. If a configuration is adopted in which current is supplied from the inner surface of the cylindrical aluminum substrate 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 the current is increased as the anodization proceeds. Therefore, the aluminum film 18 can be uniformly anodized over the entire surface without causing a problem that it is difficult to be supplied.

  In order to form the thick inorganic material layer 16, it is generally necessary to lengthen the film formation time. When the film formation time is lengthened, the surface temperature of the aluminum base 12 is unnecessarily increased. As a result, the film quality of the aluminum film 18 is deteriorated, and defects (mainly voids) may occur. If the thickness of the inorganic material layer 16 is less than 500 nm, the occurrence of such a problem can be suppressed.

  The aluminum film 18 is, for example, a film formed of aluminum having a purity of 99.99 mass% or more (hereinafter, also referred to as “high-purity aluminum film”) as described in Patent Document 3. . The aluminum film 18 is formed using, for example, a vacuum 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, for example, about 1 μm.

  As the aluminum film 18, an aluminum alloy film described in Patent Document 4 may be used instead of the high-purity aluminum film. The aluminum alloy film described in Patent Document 4 includes 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 grain size of the crystal grains constituting the aluminum alloy film as 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 rate of nitrogen contained in the aluminum alloy film is, for example, not less than 0.5 mass% and not more than 5.7 mass%. The absolute value of the difference between the standard electrode potential of a 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. % Or more and 1.9 mass% or less is preferable. The metal element is, for example, Ti or Nd. However, the metal element is not limited to this, and other metal elements whose 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 (for example, Mn, Mg, Zr, V, and Pb). Furthermore, 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 by, for example, a DC magnetron sputtering method. The thickness of the aluminum alloy film is also preferably in the range of about 500 nm to about 1500 nm, for example, about 1 μm.

  Next, as shown in FIG. 2B, the porous alumina layer 14 having a plurality of recesses (pores) 14p is formed by anodizing the surface 18s of the aluminum film 18. 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 interval between the adjacent recesses 14p (center-to-center distance) corresponds to approximately twice the thickness of the barrier layer and is approximately proportional to the voltage during anodization. This relationship also holds for the final porous alumina layer 14 shown in FIG.

  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 oxalic acid, tartaric acid, phosphoric acid, sulfuric acid, chromic acid, citric acid, and malic acid. For example, the porous alumina layer 14 is formed by anodizing the surface 18 s of the aluminum film 18 using an oxalic acid aqueous solution (concentration 0.3 mass%, liquid temperature 10 ° C.) at an applied voltage of 80 V for 55 seconds.

  Next, as shown in FIG. 2 (c), the porous alumina layer 14 is brought into contact with an alumina etchant and etched by a predetermined amount to enlarge the opening of the recess 14p. The amount of etching (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 an etchant, for example, 10 mass% phosphoric acid, an organic acid such as formic acid, acetic acid, or citric acid, an aqueous solution of sulfuric acid, or a mixed aqueous solution of chromic phosphoric acid can be used. For example, etching is performed for 20 minutes using a phosphoric acid aqueous 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 to thicken the porous alumina layer 14. Here, since the growth of the recess 14p starts from the bottom of the already formed recess 14p, the side surface of the recess 14p is stepped.

  Further thereafter, if necessary, the porous alumina layer 14 is further etched by bringing it into contact with an alumina etchant to further enlarge the hole diameter of the recess 14p. As the etchant, it is preferable to use the above-described etchant, and in practice, the same etch bath may be used.

  In this way, the above-described anodizing step and etching step were alternately repeated a plurality of times (for example, 5 times: anodizing 5 times and etching 4 times), thereby being inverted as shown in FIG. A moth-eye mold 100A having a porous alumina layer 14 having a moth-eye structure is obtained. By finishing with the anodizing step, the bottom of the recess 14p can be pointed. That is, a mold capable of forming a convex part with 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 14p) and a barrier layer (thickness t _b ). Since the porous alumina layer 14 has a structure obtained by inverting the moth-eye structure of the synthetic polymer film 34A, the same symbol may be used for the corresponding parameter characterizing the size.

The concave portion 14p of the porous alumina layer 14 is, for example, conical and may have stepped side surfaces. Two-dimensional size of the recess 14p is D _p (area equivalent circle diameter of the recess when viewed from the direction normal to the surface) is less than 20nm ultra 500 nm, the depth D _d in the order of less than 50nm over 1000 nm (1 [mu] m) Preferably there is. Moreover, it is preferable that the bottom part of the recessed part 14p is pointed (the bottom is a point). When the recesses 14p are densely packed, 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 with each other, and a flange portion is formed between the adjacent recesses 14p. It is formed. Incidentally, when the concave portion 14p of the substantially conical adjacent so as to form a saddle, two-dimensional size D _p of the concave portion 14p is equal to the distance between adjacent D _int. The thickness t _p of the porous alumina layer 14 is, for example, about 1 μm or less.

  In addition, under the porous alumina layer 14 shown in FIG. 2E, an aluminum remaining 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 remaining aluminum layer 18r does not exist. For example, when the inorganic material layer 16 is thin, current can be easily supplied from the aluminum substrate 12 side.

  The method for producing a moth-eye mold exemplified here can produce a mold for producing an antireflection film described in Patent Documents 2 to 4. Anti-reflective coatings used in high-definition display panels are required to have high uniformity. Therefore, as described above, the selection of the aluminum base material, mirror finishing of the aluminum base, and control of the purity and composition of the aluminum film However, since high uniformity is not required for the bactericidal action, the above-described mold manufacturing method can be simplified. For example, the surface of the aluminum substrate may be directly anodized. At this time, even if pits are formed due to the influence of impurities contained in the aluminum base material, only a local structural disorder occurs in the moth-eye structure of the finally obtained synthetic polymer film 34A, which has a sterilizing effect. There is little impact.

  Further, according to the above-described mold manufacturing method, a mold having a low regularity of the arrangement of the recesses, which is suitable for manufacturing the antireflection film, can be manufactured. When utilizing the bactericidal property 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 convex portions can be manufactured as follows, for example.

  For example, after a porous alumina layer having a thickness of about 10 μm is formed, the produced porous alumina layer is removed by etching, and then anodization is performed under the conditions for producing the porous alumina layer described above. The porous alumina layer having a thickness of 10 μm is formed by increasing the anodic oxidation time. When a relatively thick porous alumina layer is generated in this way and this porous alumina layer is removed, the porous alumina layer is regularly arranged without being affected by irregularities or processing strain caused by grains present on the surface of the aluminum film or the aluminum substrate. A porous alumina layer having a concave portion can be formed. In addition, it is preferable to use the liquid mixture of chromic acid and phosphoric acid for the removal of a porous alumina layer. When etching is performed for a long time, galvanic corrosion may occur, but a mixed solution of chromic acid and phosphoric acid has an effect of suppressing galvanic corrosion.

  The moth-eye mold for forming the synthetic polymer film 34B shown in FIG. 1B can also be basically manufactured by combining the anodizing step and the etching step described above. A method for manufacturing the moth-eye mold 100B for forming the synthetic polymer film 34B will be described with reference to FIGS.

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

  Next, as shown in FIG. 3A, the opening of the recess 14p is enlarged by etching the porous alumina layer 14 by contacting the alumina etchant by a predetermined amount. At this time, the etching amount is reduced as compared with the etching process described with reference to FIG. That is, the size of the opening of the recess 14p is reduced. For example, etching is performed for 10 minutes using a phosphoric acid aqueous 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 to thicken the porous alumina layer 14. At this time, the recess 14p is grown deeper than in the anodic oxidation step described with reference to FIG. For example, anodic oxidation is performed for 165 seconds at an applied voltage of 80 V using an oxalic acid aqueous solution (concentration: 0.3 mass%, liquid temperature: 10 ° C. (55 seconds in FIG. 2D)).

Thereafter, as described with reference to FIG. 2E, the etching process and the anodic oxidation process are alternately repeated a plurality of times. For example, by alternately repeating the etching process three times and the anodic oxidation process three times, a moth-eye mold 100B having a porous alumina layer 14 having an inverted moth-eye structure is obtained as shown in FIG. It is done. At this time, the two-dimensional size D _p of the recess 14p is smaller than the inter-adjacent distance D _int (D _p <D _int ).

  The size of the microorganism varies depending on its type. For example, although the size of Pseudomonas aeruginosa is about 1 μm, some bacteria have a size of several hundred nm to about 5 μm, and fungi are 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 for bacteria having a size of several hundred nm. The convex part is too large, and there is a possibility that a sufficient bactericidal action is not exhibited. Moreover, the size of the virus is several tens of nm to several hundreds of nm, and many have a size of 100 nm or less. The virus does not have a cell membrane, but has a protein shell called a capsid that surrounds the viral nucleic acid. Viruses can be divided into viruses having a membrane-like envelope outside the shell and viruses not having an envelope. In a virus having an envelope, since the envelope is mainly composed of lipid, it is considered that the convex portion acts on the envelope in the same manner. Examples of the virus having an envelope include influenza virus and Ebola virus. In viruses that do not have an envelope, it is thought that the convex portion acts on the protein shell called capsid in the same manner. When the convex part has a nitrogen element, affinity with a protein composed of amino acids may be increased.

  Therefore, the structure of a synthetic polymer film having a convex portion capable of exhibiting a bactericidal action even for microorganisms of several hundred nm or less and a manufacturing method thereof will be described below.

  Hereinafter, the convex portion of the synthetic polymer film exemplified above having a two-dimensional size in the range of more than 20 nm and less than 500 nm is referred to as a first convex portion. Moreover, the convex part formed so as to overlap the first convex part is called a second convex part, and the two-dimensional size of the second convex part is the two-dimensional size of the first convex part. Smaller than 100 nm and not exceeding 100 nm. In addition, when the two-dimensional size of the first protrusion is less than 100 nm, particularly less than 50 nm, it is not necessary to provide the second protrusion. 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 above-described method for forming the first concave portion having a predetermined size and shape is applied as it is by alternately performing the anodizing step and the etching step, the second concave portion cannot be formed.

4A shows an SEM image of the surface of the aluminum base (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). FIG. 4C 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 substrate and the surface of the aluminum film. The grain of the aluminum film forms irregularities on the surface of the aluminum film. The unevenness on the surface affects the formation of the recess during anodic oxidation, thus preventing the formation of the second recess with D _p or D _int smaller than 100 nm.

  Therefore, a mold manufacturing method according to an embodiment of the present invention includes: (a) a step of preparing an aluminum film deposited on an aluminum substrate or support; and (b) an electrolysis of the surface of the aluminum substrate or aluminum film. An anodic oxidation step of forming a porous alumina layer having a first recess by applying a first level voltage in contact with the liquid; and (c) after step (b), the porous alumina layer. An etching process for enlarging the first recess by contacting the etching solution, and (d) after the step (c), the porous alumina layer is in contact with the electrolytic solution and lower than the first level. Forming a second recess in the first recess by applying a second level voltage. For example, the first level is above 40V and the second level is below 20V.

  That is, a first recess having a size that is not affected by the grain of the aluminum base material or the aluminum film is formed in the anodizing process at the first level voltage, and then the thickness of the barrier layer is reduced by etching. After the reduction, the second recess is formed in the first recess by an anodic oxidation step at a second level voltage lower than the first level. When the second concave portion is formed by such a method, the influence of grains is eliminated.

  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. FIG. 5A is a schematic plan view of a porous alumina layer of the mold, FIG. 5B is a schematic cross-sectional view, and FIG. 5C 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 whose two-dimensional size is in the range of more than 20 nm and less than 500 nm, and a plurality of It further has a plurality of second recesses 14pb formed so as to overlap the first recess 14pa. The two-dimensional size of the plurality of second recesses 14pb 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 not more than 100 nm. Similarly to the first recess 14pa, the second recess 14pb preferably includes a substantially conical portion.

  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 anodizing solution, and an phosphoric acid aqueous solution (concentration 10 mass%, temperature 30 ° C.) was used as the etching solution. After performing anodic oxidation at a voltage of 80 V for 52 seconds, etching was performed for 25 minutes, followed by anodic oxidation at a voltage of 80 V for 52 seconds and etching for 25 minutes. Thereafter, anodic oxidation at 20 V was performed for 52 seconds, etching was performed for 5 minutes, and anodic oxidation at 20 V was further performed for 52 seconds.

Figure 5 (c) As can be seen from, among D _p is in the first recess of about 200 nm, a second recess of D _p is about 50nm is formed. In the above manufacturing method, when the first level voltage is changed from 80 V to 45 V to form a porous alumina layer, the first recess having D _p of about 100 nm is formed in the first recess having 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 inverting the structure of the first concave portion 14pa and the second concave portion 14pb shown in FIGS. 5 (a) and (b). A membrane is obtained. That is, a synthetic polymer film further having a plurality of second protrusions formed so as to overlap with the plurality of first protrusions is obtained.

  As described above, the synthetic polymer film having the first convex portion and the second convex portion formed so as to overlap the first convex portion is made from a relatively small microorganism of about 100 nm to a relatively large size of 5 μm or more. Can have bactericidal action against microorganisms.

  Of course, depending on the size of the target microorganism, only a recess having a two-dimensional size in 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 manufactured as follows, for example.

  Anodic oxidation using neutral salt aqueous solution (ammonium borate, ammonium citrate, etc.) such as ammonium tartrate aqueous solution and organic acids (maleic acid, malonic acid, phthalic acid, citric acid, tartaric acid, etc.) with low ion dissociation The 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). Recesses in the range of more than 20 nm and less than 100 nm can be formed.

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

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

  Next, a method for producing a synthetic polymer film using the moth-eye mold 100 will be described with reference to FIG. FIG. 6 is a schematic cross-sectional view for explaining a method for producing a synthetic polymer film by a roll-to-roll method.

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

  As shown in FIG. 6, ultraviolet curing is performed by irradiating ultraviolet curing resin 34 ′ with ultraviolet rays (UV) in a state in which base film 42 provided with ultraviolet curing resin 34 ′ is pressed against moth-eye mold 100. 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 unillustrated unwinding roller, and then an ultraviolet curable resin 34 'is applied to the surface by, for example, a slit coater. As shown in FIG. 6, the base film 42 is supported by support rollers 46 and 48. The support rollers 46 and 48 have a rotation mechanism and convey the base film 42. The cylindrical moth-eye mold 100 is rotated in a direction indicated by an arrow in FIG. 6 at a rotational speed corresponding to the transport speed of the base film 42.

  Thereafter, 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 is wound up by a winding roller (not shown).

  The surface of the synthetic polymer film 34 has a moth-eye structure obtained by inverting the nano-surface structure of the moth-eye mold 100. Depending on the nano-surface structure of the moth-eye mold 100 to be used, the synthetic polymer films 34A and 34B shown in FIGS. 1A and 1B can be produced. The material for forming the synthetic polymer film 34 is not limited to an ultraviolet curable resin, and a photocurable resin that can be cured with visible light can be used, and a thermosetting resin can also be used.

  The bactericidal property of a synthetic polymer film having a moth-eye structure on the surface has a correlation not only with the physical structure of the synthetic polymer film but also with the chemical properties of the synthetic polymer film. For example, the applicant of the present application, as a chemical property, the contact angle of the surface of the synthetic polymer film (Patent Publication 1: Patent No. 5788128) and the concentration of nitrogen element contained in the surface (International Publication No. 2: International Publication No. 2). Correlation with No. 2016/080245) was found. As described in International Publication No. 2, the nitrogen element concentration on the surface is preferably 0.7 at% or more. For the purpose of reference, the entire contents of the above-mentioned Patent Publication 1 and International Publication 2 are incorporated herein by reference.

  FIG. 7 shows an SEM image shown in International Publication 2 (FIG. 8). FIGS. 7A and 7B are views showing SEM images of Pseudomonas aeruginosa dying on the surface having the moth eye structure shown in FIG. 1A, observed with a scanning electron microscope (SEM).

  Looking at these SEM images, it can be seen that the tip of the convex portion has entered the cell wall (outer membrane) of Pseudomonas aeruginosa. 7A and 7B, it does not appear that the convex portion has broken through the cell wall, and it appears as if the convex portion has been taken into the cell wall. This may be explained by the mechanism suggested in Supplemental Information of Non-Patent Document 1. That is, when the outer membrane (lipid bilayer) of Gram-negative bacteria deforms close to the convex part, the lipid bilayer locally undergoes a transition similar to the first-order phase transition (spontaneous reorientation). An opening may be formed in a portion close to the convex portion, and the convex portion may have entered the opening. Or the convex part may be taken in by the mechanism (endocytosis) which takes in the substance (including a nutrient source) which has polarity which a cell has.

  Heretofore, the antireflection film disposed on the surface of the liquid crystal television manufactured and sold by the present applicant has hydrophilicity. This is for facilitating wiping off oil such as fingerprints attached to the moth-eye structure. If the moth-eye structure is not hydrophilic, the aqueous cleaning liquid cannot effectively enter between the convex parts of the moth-eye structure, and the oil and fat cannot be wiped off.

  According to the study of the present inventor, it has been found that a synthetic polymer film having hydrophilicity as used in a conventional antireflection film has a problem in water resistance. For example, if the film 50A having the structure shown in FIG. 1A is kept in contact with water for a long time (for example, all day and night), the entire film 50A is curled or the synthetic polymer film 34A is formed as a base film ( For example, a PET film) 42A may peel off. Further, if the synthetic polymer membrane is kept in contact with water for a certain period of time, the sterilizing effect of the synthetic polymer membrane may be reduced.

  Therefore, in the embodiment according to the present invention, it was studied to improve the water resistance of the film 50A by changing the composition of the resin forming the synthetic polymer film 34A. In the following, acrylic resin (having ultraviolet curability) was used as a material for forming the synthetic polymer film 34A.

[1] Suppression of curling and / or film peeling First, when a film having a synthetic polymer film and a base film is brought into contact with water for a certain period of time, the entire film is curled, and / or the synthetic polymer. It was studied to suppress the peeling of the film from the base film.

  Here, the acrylic resin is an acrylic resin having a different content of urethane acrylate and ethylene oxide group or ethylene oxide unit (which is a structural unit in which ethylene oxide is ring-opened; hereinafter may be referred to as “EO unit”). Were mixed to adjust the proportion of EO units contained in the entire acrylic resin. When the number of EO units is large, the synthetic polymer film 34A becomes a film rich in flexibility and hydrophilicity. However, when there are too many EO units, the hydrophilicity becomes too strong. In view of this, the inventors have studied to suppress the occurrence of curling and / or film peeling of the film by reducing the number of EO units as compared with the conventional film for antireflection film.

[Synthetic polymer membrane]
A sample film having the same structure as the film 50A shown in FIG. Ten types of resins A1 to A5, B, C1 to C2, D and E shown in Table 1 below are used as an acrylic resin (acrylate monomer or acrylate oligomer) for producing a synthetic polymer film 34A having a moth-eye structure on the surface. It was. Hereinafter, the same A1 to A5, B, C1 to C2, D, and E as those of the resin are also specified for the name of the sample film. Table 1 shows the composition of each resin (% in Table 1 is% by mass). The chemical structural formulas of the acrylic resins I to V are shown in [Chemical Formula 1] to [Chemical Formula 5], respectively. Table 1 shows the molecular weight (MW) of each of the acrylic resins I to V and the number of EO units contained in one molecule, and 1 g of each of the resins A1 to A5, B, C1 to C2, D, and E. The number of moles of EO units contained is shown. Table 1 describes in order from the smallest number of moles of EO units. Table 1 shows the nitrogen element at% calculated based on the composition and chemical formula for each of the resins A1 to A5, B, C1 to C2, D, and E. Table 1 includes the total nitrogen element concentration of the nitrogen element forming the primary amine and the nitrogen element forming the secondary amine, and all the nitrogen elements (ie, the nitrogen element forming the tertiary amine). The calculated nitrogen element concentration is also shown.

Each of the resins A1 to E is dissolved in MEK (manufactured by Maruzen Petrochemical Co., Ltd.) to give a solution having a solid content of 70% by mass, applied onto the base film 42A, and the MEK is removed by heating, whereby the thickness is about 25 μm. A film of ˜50 μm was obtained (sample film C2 only 3 μm thick). As the base film 42A, a PET film having a thickness of 50 μm (A4300 manufactured by Toyobo Co., Ltd.) was used. Thereafter, a synthetic polymer film 34A having a moth-eye structure on the surface was produced using the moth-eye mold 100A by the same method as described with reference to FIG. The exposure amount was about 200 mJ / cm ² . D _p is about 200nm in each sample film, D _int of about 200nm, D _h is about 150 nm.

  The acrylic resin I is urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd .: trade name UA-7100) and contains nitrogen element. The chemical formula shown in [Chemical Formula 1] is estimated. The acrylic resin I includes a repeating structure of EO units (the number of repetitions is 9). The acrylic resin I is a trifunctional urethane acrylate. The acrylic resin I contains a cyanuric ring that is a heterocyclic ring (heterocycle) containing a nitrogen element.

  The acrylic resin II is ε-caprolactone-modified tris- (2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd .: trade name A93001CL) and contains nitrogen element. The acrylic resin II contains EO units but does not contain a repeating structure of EO units. Acrylic resin II is a trifunctional acrylate. The acrylic resin II contains a cyanuric ring that is a heterocyclic ring containing a nitrogen element.

  The acrylic resins III to V do not contain nitrogen element. Acrylic resin III is ethoxylated pentaerythritol tetraacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd .: trade name ATM-35E), acrylic resin IV is 4-hydroxybutyl acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd .: abbreviation 4-HBA), acrylic Resin V is pentaerythritol triacrylate (57% triester) (Shin Nakamura Chemical Co., Ltd .: A-TMM-3LM-N).

  The acrylic resin III includes a repeating structure of EO units (the number of repetitions is 35 or less). Acrylic resin III is a tetrafunctional acrylate. Acrylic resins IV and V do not have EO units. Acrylic resin IV is a monofunctional acrylate. Acrylic resin IV is a monofunctional acrylate. The acrylic resin V is a trifunctional acrylate. The acrylic resins III to V do not include a cyclic structure.

  When the synthetic polymer film 34A is produced using each of the acrylic resins I to V, as a polymerization initiator, IRGACURE819 (bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, manufactured by BASF) is used. A molecular weight of 418.5) was used.

  Each sample film A to E was evaluated as follows.

[Evaluation of bactericidal properties]
The bactericidal properties of the sample film were evaluated as follows.

1. 1. Thawed frozen frozen beads with Pseudomonas aeruginosa (purchased from the National Institute of Technology and Evaluation Technology) for 24 hours in a 37 ° C. culture medium. Centrifugation (3000 rpm, 10 minutes)
3. 3. Discard the culture supernatant. 4. Add sterile water and stir, then centrifuge again. 5. The bacterial stock solution (the number of bacteria is on the order of 1E + 08 CFU / mL) is obtained by repeating the operations 2 to 4 three times. Prepare bacterial dilution A (the number of bacteria is on the order of 1E + 06 CFU / mL) Bacterial dilution A: 100 μL of bacterial stock solution + 9.9 mL of sterile water
7). NB medium (Eiken Chemical Co., Ltd., normal bouillon medium E-MC35) as a nutrient source was added to Bacteria Diluent A to a concentration of 1/500, and Bacteria Diluent B (Bacteria Bacteria) diluted 10 times The number is on the order of 1E + 05 CFU / mL) (according to JISZ2801 5.4a))
Bacterial dilution B: Bacterial dilution A1 mL + sterile water 8.98 mL + NB medium 20 μL
8). 400 μL of the bacterial dilution B (the number of bacteria in the bacterial dilution B at this time may be referred to as “initial bacterial count”) is dropped on each sample film, and a cover (eg, a cover glass) is placed on the bacterial dilution B. And adjust the amount of bacterial dilution B per unit area

  Here, the initial number of bacteria was 3.5E + 05 CFU / mL.

9. Leave in an environment with a constant temperature of 37 ° C and relative humidity of 100% (Leave time: 4 hours, 24 hours)
10. Put the entire sample film with the bacterium dilution solution B and 9.6 mL of sterilized water into a filter bag, and rub it by hand from above the filter bag to thoroughly wash away the bacteria on the sample film. The washing solution in the filter bag is obtained by diluting the bacterium dilution solution B 25 times. This washing solution may be referred to as a bacteria dilution solution B2. When there is no increase / decrease in the number of bacteria in the bacterial dilution B, the bacterial dilution B2 is in the order of 1E + 04 CFU / mL.

  11. A bacterial dilution C is prepared by diluting the bacterial dilution B2 10 times. Specifically, 120 μL of the washing solution (bacterial dilution solution B2) is prepared in 1.08 mL of sterilized water. The bacterial dilution C is in the order of 1E + 03 CFU / mL when the bacterial count in the bacterial dilution B does not increase or decrease.

  12 In the same manner as the preparation of the bacterial dilution C, the bacterial dilution C is diluted 10 times to prepare the bacterial dilution D. The bacterial dilution D is in the order of 1E + 02 CFU / mL when the number of bacteria in the bacterial dilution B does not increase or decrease. Furthermore, the bacterial dilution D is prepared by diluting the bacterial dilution D ten times. The bacterial dilution E is in the order of 1E + 01 CFU / mL when the bacterial count in the bacterial dilution B is not increased or decreased.

  13. 1 mL of bacterial dilution B2 and bacterial dilutions C to E were dropped into Petrifilm (registered trademark) medium (manufactured by 3M, product name: AC plate for measuring viable cell count) at 37 ° C. and relative humidity of 100%. 48 hours after culturing, the number of bacteria in the dilution B2 is counted.

  In JISZ2801, 5.6h), phosphate buffered saline is used when preparing the diluted solution, but here sterilized water was used. It has been confirmed that even if sterilized water is used, the bactericidal effect due to the physical structure and chemical properties of the surface of the sample film can be examined.

[Evaluation of antibacterial properties]
According to JIS Z 2801, the antibacterial activity value obtained from the number of bacteria after 24 hours of culture was 2.0 or more (99% or more killing rate), and it was assumed that there was an antibacterial effect. A base film (PET film) was used as the reference film. The antibacterial activity value is a logarithmic value of a number obtained by dividing the number of bacteria after 24-hour culture of PET film by the number of bacteria after 24-hour culture of each sample film.

  FIG. 8 is a graph showing the evaluation results of bactericidal properties. In FIG. 8, the horizontal axis represents the standing time (hours), and the vertical axis represents the number of bacteria (CFU / mL) in the bacteria dilution B2. In FIG. 8, for ease of viewing, when the number of bacteria is 0 (ND), it is plotted as 0.1. Table 2 below shows the number of bacteria and the antibacterial activity value after culturing. In addition, the data of PET2 was used for calculation of the antibacterial activity value of the sample film C1, and the data of PET1 was used for the other sample films.

  As can be seen from FIG. 8 and Table 2, the samples other than the sample film C1 have an antibacterial activity value of 2.0 or more, and have antibacterial properties. The antibacterial activity values of the sample films C2 and B are 2.6 and 3.2, respectively. The sample films A1, A2 and A3 have an antibacterial activity value of 6.2 and can be said to have bactericidal properties. Here, when the antibacterial activity value is 6.0 or more, it is assumed to have bactericidal properties. The results of evaluating the antibacterial and bactericidal properties in this way are shown in Table 1 by ○ / x. ○ indicates antibacterial or bactericidal properties, and × indicates antibacterial or no bactericidal properties, respectively.

[Evaluation of curling and film peeling]
A sample film is placed on a black acrylic plate, and 400 μL of pure water is dropped on the sample film. Cover with a spreader (3M Petri film lid). These were put in a case together with absorbent cotton soaked with pure water and sealed with tape. This is to keep the environment in the case at about 100% humidity.

  A thermostat (IQ820 manufactured by Yamato Scientific Co., Ltd.) is set to 37 ° C., and a beaker containing 200 mL of pure water is set in the thermostat. As a result, the relative humidity in the thermostat is also about 100%. The case prepared above is left in this thermostat for 4 hours. Then switch off the thermostat and leave it for 15 hours. When the temperature was confirmed after 15 hours, the temperature had dropped to room temperature (about 20 ° C.).

  The state of the film in the case returned to room temperature is visually confirmed.

  Observe whether and how much the film in the case is curled. The evaluation results are shown in Table 1, with “◯” indicating no curling at all, “Δ” indicating curling only at the end, and “×” indicating curling as the lid is lifted.

  In addition, the film in the case is observed and whether or not the film is peeled off. The evaluation results are shown in Table 1, where “O” indicates that no film peeling is observed, “Δ” indicates that film peeling is partially observed, and “X” indicates that film peeling is observed as a whole.

  When the results of curl / film peeling in Table 1 are compared with the results of EO unit mole number, when the EO unit mole number is 0.0100 or more, film peeling occurs at least partially, and the resin E Curling is recognized at the edges except for the film used. Conversely, when the EO unit mole number is 0.0080 or less, film peeling does not occur. Moreover, curl was only recognized at the edge only in the film using the resin A1. From these facts, it can be said that the occurrence of curl and / or film peeling of the film can be suppressed by setting the EO unit mole number to 0.0080 or less.

  About antibacterial property and bactericidal property, it has at least antibacterial property except the film using resin C1. From the viewpoint of antibacterial properties, it is considered preferable to contain more than 0.0020 EO units. Resins A4, A5, D, and E have not been evaluated this time. However, based on the evaluation results of resins having the same or similar compositions so far, these resins have antibacterial and bactericidal properties. it seems to do.

  Table 1 includes the total nitrogen element concentration of the nitrogen element forming the primary amine and the nitrogen element forming the secondary amine, and all the nitrogen elements (ie, the nitrogen element forming the tertiary amine). The calculated nitrogen element concentration is also shown. The evaluation results for antibacterial and bactericidal properties correlate with the nitrogen element concentration of the nitrogen element forming the primary amine or the secondary amine as compared to the nitrogen element concentration including the nitrogen element forming the tertiary amine. Seems to have a relationship. The reason is considered as follows. Since the nitrogen element forming the tertiary amine has low basicity, it is considered that the contribution to the bactericidal property of the synthetic polymer film is low. Further, in the acrylic resins I and II containing nitrogen element, the nitrogen element forming the tertiary amine forms a ring. The nitrogen element forming the ring is present at a position relatively far from the surface of the synthetic polymer film and has a large distance from the microorganism, and therefore, the contribution to the bactericidal properties of the synthetic polymer film is considered to be low.

  In the above-mentioned International Publication No. 2, from the viewpoint of bactericidal properties, the nitrogen element concentration on the surface is preferably 0.7 at% or more, but this time, a resin having a lower nitrogen element concentration is used. However, it was found that bactericidal properties can be obtained. If the total nitrogen element concentration of the nitrogen element forming the primary amine and the nitrogen element forming the secondary amine is at least 0.293 at% (resin C2), it can be said that it can have antibacterial properties. By rounding off the third digit after the decimal point, if the total nitrogen element concentration of the nitrogen element forming the primary amine and the nitrogen element forming the secondary amine is 0.29 at% or more, it may have antibacterial properties. It can be said. In order to have bactericidal properties, the total nitrogen element concentration of the nitrogen element forming the primary amine and the nitrogen element forming the secondary amine is preferably 0.327 at% or more (resin A1). When the third digit after the decimal point is rounded off, the total nitrogen element concentration of the nitrogen element forming the primary amine and the nitrogen element forming the secondary amine is 0.33 at% or more in order to have bactericidal properties. It is preferable. At this time, it is considered that the number of moles of EO units contained in 1 g of the resin is preferably 0.0040 or more.

  Resins A1, C2, A2, B, and A3 in Table 1 have at least antibacterial properties, and curling and film peeling are suppressed. In particular, resins A1, A2 and A3 obtained by mixing acrylic resin I (urethane acrylate) and acrylic resin V (trifunctional acrylate, which does not have an EO unit) have bactericidal properties. Among these, the resins A2 and A3 are most balanced without curling in the water resistance test.

  Since the resins A1, C2, A2, B, and A3 contain EO units at an appropriate ratio and have hydrophilicity, the stains can be wiped off by spraying with water. Further, since it has flexibility, it has excellent scratch resistance.

  In addition, as can be seen from the SEM image of FIG. 7, the convex part to which Pseudomonas aeruginosa is not attached is substantially parallel to the normal direction of the synthetic polymer film, whereas the convex part to which Pseudomonas aeruginosa is attached. Some parts are tilted toward the direction of Pseudomonas aeruginosa. More convex portions can come into contact with microorganisms by tilting the convex portion. It is considered that a synthetic polymer film having convex portions on the surface that can tilt (become) in the direction of microorganisms can have a more excellent bactericidal effect. There is a possibility that the resin containing the EO unit moderately exhibits a bactericidal effect due to this bending.

[2] Suppression of elution from synthetic polymer membrane into water (selection of optimum initiator)
Subsequently, depending on the type of the synthetic polymer membrane, some components may be eluted from the synthetic polymer membrane when contacted with water. Also, the amount of elution may vary greatly depending on the type of initiator. Therefore, using various initiators, sample films D1 to D5 obtained by curing the above acrylic resin I (urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd .: trade name UA-7100)) were prepared, and the amount of elution was evaluated. The composition of the resin composition used for the preparation of the sample films D1 to D5 is shown in Table 3. As an initiator, the following IRGACURE (registered trademark) manufactured by BASF was used.

IRGACURE 819: Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide
IRGACURE TPO: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide
IRGACURE OXE-01: 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)]
IRGACURE OXE-02: Ethanone, 1- [9-Ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (0-acetyloxime)
IRGACURE OXE-03: Oxime ester type, chemical structure is unknown.

  Sample films D1 to D5 were prepared as follows. The sample films D1 to D5 have a flat surface (no moth-eye structure).

  A PET film (A4300 manufactured by Toyobo Co., Ltd.) having a thickness of 75 μm was prepared as a base film. On this PET film, the MEK solution of the resin composition for each sample film was dropped and stretched almost uniformly with a bar coater so as to have a thickness of several tens of μm. Thereafter, MEK was removed by heating in an oven at 100 ° C. for 1 minute. The MEK solution of the resin composition was prepared by adding 43 g of MEK (manufactured by Maruzen Petrochemical Co., Ltd.) to 100 g of acrylic resin I.

  Thereafter, the resin composition layer was sandwiched between a PET film and a glass plate and pressed with a roller to obtain a resin composition layer having a uniform thickness (for example, 10 μm to 40 μm).

Under a nitrogen atmosphere, ultraviolet rays were irradiated from the glass plate side to cure the resin composition. For UV irradiation, a UV lamp (manufactured by Fusion UV Systems: Light Hammer 6 J6P3, maximum output 200 W / cm) was used, and irradiation was performed at an output level of 45% (50 mW / cm ² ) for 30 seconds. The exposure amount was 1500 mJ / cm ² . In this way, sample films D1 to D5 were obtained.

  The eluate of each sample film D1 to D5 with water was quantified as follows.

  1. 2 mL of pure water was dropped on each of the sample films D1 to D5 arranged on the acrylic substrate and covered with a plastic lid. The lid had a recess having a depth of about 50 μm, and the lid was placed so that pure water was located in the space formed between each sample film D1 to D5 and the recess. In this state, each of the sample films D1 to D5 was placed in a sealed container having a relative humidity of 90% or more. Absorbent cotton or the like sufficiently containing pure water was placed in the sealed container, and the relative humidity was kept at 90% or more.

  2. The airtight container which accommodated each sample film D1-D5 was left to stand in a 37 degreeC thermostat for 24 hours.

  3. The sealed container taken out from the thermostat was opened, the lid was removed, and water on each of the sample films D1 to D5 was collected.

  4). The amount of evaporation residue contained in 1 μL of water was calculated from the amount of change in frequency of the quartz crystal microbalance (QCM). The mass (mg) of the eluate (evaporation residue) per 100 mL of water was calculated and shown in Table 4.

  As can be seen from Table 4, it can be said that the sample film D3 has the least amount of components eluted by water and the most excellent stability when contacted with water. From this, it can be said that IRGACURE OXE-01 is preferable to IRGACURE 819 manufactured by BASF as the initiator.

Further, using the same resin composition as that of the sample film D3, a synthetic polymer film 34A having the moth-eye structure shown in FIG. 1A was produced by the same method as described above, and a sample film D6 was obtained. D _p is about 200nm in the sample film D6, D _int of about 200nm, D _h is about 150 nm. When the antibacterial activity value of the obtained sample film D6 was determined in the same manner as described above, it was 5.8 and was cured using IRGACURE 819 (see sample films A1, A2, and A3 in Table 2). It was found to have bactericidal properties equivalent to

  IRGACURE OXE-01 is decomposed by ultraviolet irradiation, and the generated radical is added to the double bond of the acrylate group. Specifically, IRGACURE OXE-01 decomposes as shown in the following chemical formula 6 to generate two types of radicals (atomic group A and atomic group B). This atomic group A and atomic group B are added to the double bond of the acrylate group of acrylic resin I (urethane acrylate), and radical polymerization is started.

  Therefore, the acrylate resin cured using IRGACURE OXE-01 as an initiator contains atomic group A and atomic group B (fragment) derived from IRGACURE OXE-01. Here, the urethane structure produced by polymerization of trifunctional urethane acrylate (UA-7100) contains atomic group A and atomic group B derived from IRGACURE OXE-01. By having such a urethane structure, it is considered that less components are eluted when contacted with water.

  Further, in the acrylic resin composition capable of suppressing the occurrence of the curl and film peeling described above, by using IRGACURE OXE-01 instead of IRGACURE 819, while suppressing the occurrence of curl and film peeling, water and A synthetic polymer membrane with few components eluted when contacted is obtained.

  The synthetic polymer film according to the embodiment of the present invention is suitably used, for example, for applications that suppress the occurrence of slimming of the surface that contacts water. For example, by attaching a synthetic polymer film to the inner wall of a water container used in a humidifier or ice making machine, it is possible to suppress the occurrence of sliminess on the inner wall of the container. Slimming is caused by a biofilm formed by extracellular polysaccharide (EPS) secreted by bacteria attached to the inner wall or the like. Therefore, the occurrence of sliminess can be suppressed by killing bacteria attached to the inner wall or the like.

  As described above, the liquid can be sterilized by bringing the liquid into contact with the surface of the synthetic polymer film according to the embodiment of the present invention. Similarly, the gas can be sterilized by bringing the gas into contact with the surface of the synthetic polymer film. Microorganisms generally have a surface structure that tends to adhere to the surface of an object in order to increase the probability of contact with organic matter that is a nutrient source. Therefore, when a gas or liquid containing microorganisms is brought into contact with the bactericidal surface of the synthetic polymer film according to the embodiment of the present invention, the microorganisms try to adhere to the surface of the synthetic polymer film. It will be sterilized.

  Here, the bactericidal action of the synthetic polymer membrane according to the embodiment of the present invention has been described for Pseudomonas aeruginosa, which is a gram-negative bacterium, but is not limited to gram-negative bacteria, and also sterilizes against gram-positive bacteria and other microorganisms. It is considered to have an action. Gram-negative bacteria have one feature in that they have a cell wall containing an outer membrane, but Gram-positive bacteria and other microorganisms (including those that do not have a cell wall) also have a cell membrane, and the cell membrane is also outside of Gram-negative bacteria. Like the membrane, it is composed of a lipid bilayer membrane. Therefore, the interaction between the convex portions on the surface of the synthetic polymer membrane according to the embodiment of the present invention and the cell membrane is considered to be basically the same as the interaction with the outer membrane.

  The synthetic polymer film having a bactericidal surface according to an embodiment of the present invention can be used in various applications such as a sterilizing surface around water. A synthetic polymer film having a bactericidal surface according to an embodiment of the present invention can be manufactured at low cost.

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

Claims (5)

A synthetic polymer film having a surface having a plurality of convex portions,
When viewed from the normal direction of the synthetic polymer film, the two-dimensional size of the plurality of convex portions is in the range of more than 20 nm and less than 500 nm, and the surface has a bactericidal effect,
Including urethane acrylate structure,
The synthetic polymer film, wherein the urethane acrylate structure includes an atomic group derived from 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)].   The synthetic polymer film according to claim 1, wherein the urethane acrylate structure includes a repeating structure of ethylene oxide units.   The synthetic polymer film according to claim 1, wherein the urethane acrylate structure includes a polymer of urethane acrylate monomers having three or more functions.   The synthetic polymer film according to claim 3, wherein the urethane acrylate monomer includes a heterocyclic ring containing a nitrogen element.   The synthetic polymer film according to claim 4, wherein the heterocyclic ring is a cyanuric ring.

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