JP7636979B2 - Method for manufacturing adhesion prevention structure, manufacturing device for adhesion prevention structure, and adhesion prevention structure - Google Patents

Description

The present invention relates to a method for manufacturing an adhesion prevention structure, an apparatus for manufacturing an adhesion prevention structure, and an adhesion prevention structure.

COVID-19, an infectious disease caused by the new coronavirus (SARS-CoV-2), has caused a global outbreak (pandemic), with direct person-to-person infection being largely due to human behavior (people movement). On the other hand, as for indirect infection via objects, it is important to prevent the virus from attaching to the surfaces of materials and objects in the living environment, or to endow the surfaces of objects with properties that can inactivate the virus, as an infection prevention measure.

In recent years, people have become more conscious of hygiene in their living environments, for example, there is a growing awareness of hygiene and antibacterial measures for tableware, glasses, sinks, kitchen areas, toilets, toilet areas, bathtubs, bathroom areas, washroom areas, clothing, etc. Furthermore, there is a strong desire to reduce the risk of infection or secondary infection by inactivating not only bacteria, mold and other fungi, but also pathogenic viruses and making the items surrounding people's living environments antibacterial and antiviral.

On the other hand, antibacterial technologies with scientific evidence include (1) organic coatings and (2) material-derived antibacterial technologies, and (3) surface texture is attracting attention as a new technology (see, for example, Non-Patent Document 1).
The organic coating in (1) above is a photosensitizer and a polymer electrolyte (a positively charged cation such as a polycation), and the origin of the material given is copper, silver, zinc, titanium dioxide, etc.
Evidence regarding the antibacterial mechanisms of each of these methods has already been reported, and both the organic coating method (1) and the material-derived method (2) are due to almost the same mechanism, which can be classified into the following three categories.
(i) Damage to cell structure due to reactive (oxygen) species; (ii) Damage to genetic information due to reactive species and metal ions; (iii) Prevention of adhesion to and damage to cell membranes.

The antibacterial and antiviral properties of surface texture mentioned above (3) focuses on the third mechanism, "adhesion and damage," and the key point is the principle that "viruses cannot survive and spread without a host (something to attach to)." In other words, since one of the living conditions that can cause viral infection is touching the surface of a host (object), the antiviral function can be improved by "making it difficult for the host, floating matter (particles) and bacteria (cells), to adhere and remain (removal by increasing slipperiness = anti-fouling)."

In addition, for the purpose of imparting microbial adhesion prevention properties to the surface of an article, a molded article has been proposed that has a microstructure on its surface that has multiple protrusions of at least two different shapes, the multiple protrusions having the same height and arranged periodically in a plan view, and at least one of the at least two shapes has a two-fold rotational symmetry shape or an axisymmetric shape (see, for example, Patent Document 1).

JP 2016-68347 A

Imani S. M. , Ladouceur L. , Marshall T. , MacLachlan R. , Soleymani L. , Didar T. F. : Antimicrobial Nanomaterials and Coatings: Current Mechanisms and Future Perspectives to Control the Spread of Viruses Including SARS-CoV-2, ACS Nano, 14(10):12341-12369 (2020)

However, not all fine structures exhibit excellent sliding properties (anti-adhesion properties) that can withstand practical use. The fine structure described in Patent Document 1 is a simple uneven structure, and it is thought that not much sliding properties can be expected. As surface textures that exhibit extremely high sliding properties (anti-adhesion properties) and liquid repellency due to the fine structure, "hierarchical structures" and "re-entrant structures" have been suggested. Furthermore, in Patent Document 1, multiple convex portions have the same height and are periodically arranged in a planar view, and at least one of the at least two types of shapes is a two-fold rotational symmetric shape or line symmetric shape, and it does not have a "hierarchical structure" consisting of a long-period anti-adhesion structure and a short-period anti-adhesion structure, nor does it have a "re-entrant structure" with a reverse tapered shape in the depth direction. Furthermore, the multiple convex portions are not formed by irradiating a short-pulse laser beam, and a direct processing method that is industrially practical at a low cost and at a high speed cannot be realized.

The present invention aims to provide an adhesion prevention structure that can effectively prevent the adhesion of particulate matter such as bacteria, viruses, and dust, and to provide a manufacturing method for an adhesion prevention structure that can be formed at industrially practical cost and at high speed by a direct processing method, an apparatus for manufacturing an adhesion prevention structure, and an adhesion prevention structure.

The means for solving the above problems are as follows.
<1> A method for producing an adhesion prevention structure, comprising the step of irradiating at least a part of a surface of an object with short-pulse laser light to form an adhesion prevention structure that prevents adhesion of particulate matter.
<2> A method for producing an adhesion prevention structure, characterized in that the adhesion prevention structure is produced using a mold in which an adhesion prevention structure that prevents adhesion of particulate matter is formed by irradiating short-pulse laser light onto at least a portion of the surface of the mold.
<3> The method for producing an adhesion-preventing structure according to any one of <1> and <2>, wherein the particulate matter is at least one selected from the group consisting of viruses, bacteria, and dust.
<4> The method for producing an adhesion prevention structure according to any one of <1> to <3>, wherein the adhesion prevention structure has a short period adhesion prevention structure and a long period adhesion prevention structure.
<5> The shortest distance between the centers of adjacent recesses in the short period adhesion prevention structure is less than 1 μm,
The method for producing an adhesion prevention structure according to <4> above, wherein the shortest distance between the centers of adjacent recesses in the long period adhesion prevention structure is 1 μm or more.
<6> The method for producing an adhesion prevention structure according to any one of <4> and <5>, wherein the short period adhesion prevention structure is formed on at least a convex apex of the long period adhesion prevention structure.
<7> The method for producing an adhesion prevention structure according to any one of <1> to <6>, wherein the adhesion prevention structure is formed by an interference machining method.
<8> The method for producing an adhesion prevention structure according to <7>, wherein the interference processing is performed by a surface wave interference processing method.
<9> The method for producing an adhesion prevention structure according to <7>, wherein the interference processing is performed by a multi-beam interference processing method.
<10> The method for producing an adhesion prevention structure according to any one of <1> to <3>, wherein the adhesion prevention structure is formed by a percussion processing method.
<11> The method for producing an adhesion prevention structure according to any one of <1> to <3>, wherein the adhesion prevention structure is formed by a reverse taper processing method.
<12> An apparatus for manufacturing an adhesion prevention structure, comprising: a means for forming an adhesion prevention structure that prevents adhesion of particulate matter by irradiating at least a part of a surface of an object with short-pulse laser light.
<13> An adhesion prevention structure, characterized by being manufactured by the manufacturing method for an adhesion prevention structure according to any one of <1> to <11>.

The present invention provides an adhesion prevention structure that can effectively prevent the adhesion of particulate matter such as bacteria, viruses, and dust, and can be formed at industrially practical cost and at high speed by a direct processing method, an adhesion prevention structure manufacturing method, an adhesion prevention structure manufacturing device, and an adhesion prevention structure.

FIG. 1 is a diagram showing an example of a laser processing apparatus used for laser processing according to a surface wave interference processing method of the first embodiment. FIG. 2A is a diagram showing an example of an adhesion prevention structure produced by the surface wave interference processing method of the first embodiment. FIG. 2B is a diagram showing another example of the adhesion prevention structure produced by the surface wave interference processing method of the first embodiment. FIG. 2C is a diagram showing another example of the adhesion prevention structure produced by the surface wave interference processing method of the first embodiment. FIG. 3 is a diagram showing an example of a processed test piece having an adhesion prevention structure formed thereon, which was used in the antibacterial test of Example 1. FIG. 4 is a diagram showing an example of an optical unit used in the multi-beam interference processing method of the second embodiment. FIG. 5A is a diagram showing an example of an adhesion prevention structure using two beams produced by the multi-beam interference processing method of the second embodiment. FIG. 5B is a diagram showing an example of an adhesion prevention structure with four beams produced by the multi-beam interference processing method of the second embodiment. FIG. 6A is a diagram showing an example of an adhesion prevention structure produced by the percussion processing method of Example 3. FIG. 6B is a diagram showing another example of an adhesion prevention structure produced by the percussion processing method of Example 3. FIG. 7 is a diagram showing an example of an optical unit used in the reverse taper processing method of the fourth embodiment. FIG. 8 is a diagram showing an example of an adhesion prevention structure produced by the reverse taper processing method of the fourth embodiment.

(Method and device for manufacturing adhesion prevention structure)
The method for manufacturing an adhesion prevention structure of the present invention includes a step of irradiating at least a portion of the surface of an object with short-pulse laser light to form an adhesion prevention structure that prevents adhesion of particulate matter, and further includes other steps as necessary.

The manufacturing device for an adhesion prevention structure of the present invention has a means for forming an adhesion prevention structure that prevents adhesion of particulate matter by irradiating at least a portion of the surface of an object with short-pulse laser light, and further has other means as necessary.

The method for manufacturing an adhesion prevention structure of the present invention can be suitably carried out by the apparatus for manufacturing an adhesion prevention structure of the present invention, and the step of forming the adhesion prevention structure can be carried out by a means for forming the adhesion prevention structure, and the other steps can be carried out by other means.

In the present invention, by irradiating at least a part of the surface of an object with a short-pulse laser beam, an adhesion prevention structure that effectively prevents adhesion of particulate matter such as bacteria, viruses, dust, etc. For example, since viruses as particulate matter cannot be maintained or spread without a host (object to which they adhere), an anti-viral function can be imparted by forming an adhesion prevention structure that makes it difficult for viruses to adhere and remain on the surface of the object.
According to the method for producing an adhesion preventive structure of the present invention, an adhesion preventive structure having an excellent adhesion preventive effect can be realized by a direct processing method that is high speed and at an industrially practical cost.

＜Target Object＞
The object is not particularly limited in shape, size, material, structure, etc., so long as the particulate matter can be attached to the surface thereof, and can be appropriately selected depending on the purpose.
The shape of the object is not particularly limited and can be appropriately selected depending on the application of the object, etc., and examples thereof include a flat plate, a square, a rectangular, a rectangular, a prismatic, a cylindrical, a cylindrical, a spherical, an oval sphere, an amorphous, etc. The surface of the object is not limited to a flat surface, and may be a curved surface, or a combination of a flat surface and a curved surface.
The structure of the object may be a single layer structure or a multi-layer structure. The size of the object may be appropriately selected depending on the application of the object, etc.

The material of the object is not particularly limited and can be appropriately selected depending on the application of the object, etc., and examples thereof include metal, resin, glass, ceramics, fiber, paper, brick, rubber, etc. Among these, resin, metal, and fiber are preferable.
Examples of the resin include polycarbonate resin, polystyrene resin, fluorine-based acrylic resin, epoxy acrylate resin, methylstyrene resin, fluorene resin, polyethylene resin, polypropylene resin, polyurethane resin, polymethylpentene resin, polybutene resin, polyvinyl alcohol, polyvinyl chloride, polyvinylidene fluoride, polyamide, polyimide, polymethyl methacrylate, cycloolefin polymer, polyethylene terephthalate, polyethylene naphthalate, polyether ether ketone, polyether sulfone, polyether ether imide, polyphenylene sulfide, ethylene-vinyl acetate copolymer, acrylic-styrene copolymer, styrene-butadiene-acrylonitrile copolymer, silicone resin, polylactic acid, cellulose, acrylic resin, polyester resin, polyolefin resin, general-purpose plastic, engineering plastic, super engineering plastic, etc. These may be used alone or in combination of two or more.

Examples of the metals include gold, platinum, silver, copper, copper alloys, iron, lead, zinc, tin, titanium, vanadium, chromium, nickel, tungsten, aluminum, aluminum alloys, magnesium, solder, steel, brass, carbon steel, stainless steel, and duralumin. These may be used alone or in combination of two or more.

Examples of the fibers include synthetic fibers such as polyester and polypropylene; semi-synthetic fibers such as cellulosic fibers and protein fibers; regenerated fibers such as rayon; and inorganic fibers such as glass fibers and carbon fibers. These may be used alone or in combination of two or more types.

Specific examples of the objects include tableware, glasses, sinks, kitchen areas, toilets, toilet areas, bathtubs, bathroom areas, washroom areas, building materials, clothing and decorative items, clothing, furniture and home appliances, miscellaneous goods and daily necessities, washroom and bath supplies, kitchen supplies, equipment and transport machinery, tools, stationery and office supplies, printed matter, exercise equipment and sporting goods, medical and health supplies, beverage and food packaging, and pet and animal care products.

<Particles>
The particulate matter is not particularly limited as long as it is a particulate substance and can be appropriately selected depending on the purpose, and examples thereof include viruses, bacteria, mold spores, pollen, dust (metal dust, mineral dust, animal dust, plant dust), yellow sand, etc. These particulate matters float in the atmosphere and become aerosol particles.

The viruses include various viruses, regardless of the type of genome, whether or not they have an envelope, and the like.
Examples of the viruses include rhinovirus, poliovirus, foot and mouth disease virus, rotavirus, norovirus, enterovirus, hepatovirus, astrovirus, sapovirus, hepatitis E virus, influenza A, B or C virus, parainfluenza virus, mumps virus, measles virus, human metapneumovirus, respiratory syncytial virus, Nipah virus, Hendra virus, yellow fever virus, dengue virus, Japanese encephalitis virus, West Nile virus, hepatitis B virus, hepatitis C virus, eastern and western equine encephalitis virus, Onyong-nyong virus, rubella virus, Lassa virus, and Junin virus. , Machupo virus, Guanarito virus, Sabia virus, Crimean-Congo hemorrhagic fever virus, sandfly fever/Hantavirus, Sin Nombre virus, rabies virus, Ebola virus, Marburg virus, bat lyssavirus, human T-cell leukemia virus, human immunodeficiency virus, human coronavirus, SARS coronavirus, human porvovirus, polyoma virus, human papilloma virus, adenovirus, herpes virus, varicella/zoster virus, EB virus, cytomegalovirus, smallpox virus, monkeypox virus, cowpox virus, mollusipox virus, parapox virus, Zika virus, etc. These may be used alone or in combination of two or more.

The bacteria include a variety of bacteria, whether gram positive, gram negative, aerobic, or anaerobic in nature.
Examples of the bacteria include Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus, Streptococcus pneumoniae, Haemophilus influenzae, Bordetella pertussis, Salmonella enteritidis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Vibrio, Salmonella enterica, Vibrio cholerae, Shigella, Bacillus anthrax, Mycobacterium tuberculosis, Clostridium botulinum, Clostridium tetani, Streptococcus, Bacillus cereus, Bacillus subtilis, Lactobacillus, Helicobacter pylori, etc. These may be used alone or in combination of two or more kinds.

<Short pulse laser light>
The short-pulse laser light has a pulse width of nanoseconds (1×10 ⁻⁹ seconds) or less, and the pulse width of the short-pulse laser light is preferably on the order of femtoseconds (10 ⁻¹⁵ seconds) to picoseconds (10 ⁻¹² seconds).
The femtosecond laser has a very short pulse of 1 to 999×10 ⁻¹⁵ seconds, and is known to be almost unaffected by heat diffusion in ablation processing through absorption of laser energy.
The femtosecond laser is a highly coherent laser, and when two femtosecond lasers are superimposed using an appropriate optical system, interference fringes of light intensity (interference fringes) are generated. In this way, by using the interference of femtosecond lasers, it is possible to easily and efficiently process a periodic structure or periodic refractive index change on the order of tens to hundreds of μm in an area of tens to hundreds of μm without going through a complicated process such as photolithography.

The repetition frequency of the short pulse laser light is preferably 10 kHz to 1 MHz, and more preferably 500 kHz to 1 MHz.
The laser light source in the pulsed laser is not particularly limited and can be appropriately selected depending on the purpose. Examples of the laser light source include an excimer laser, a Nd:YAG laser, a Nd: _YVO4 laser, and a semiconductor laser.
The laser light source of the pulsed laser can repeatedly output a short-pulse laser beam having a constant peak intensity. The short-pulse laser beam is composed of a pulse train including a plurality of pulses each having a constant peak intensity.

<Adhesion prevention structure>
The adhesion prevention structure may be formed on at least a portion of the surface of the object, but from the standpoint of adhesion prevention effect, it is preferable that it be formed on more than half of the surface of the object, and it may be formed on the entire surface of the object.
The adhesion preventing structure is not particularly limited and may be appropriately selected depending on the purpose, but it is preferable that the structure has a hierarchical structure from the viewpoint of the adhesion preventing effect against particulate matter.
The hierarchical structure preferably has, for example, a short periodic adhesion preventive structure and a long periodic adhesion preventive structure in terms of the adhesion preventive effect on particulate matter.
The shortest distance between the centers of adjacent recesses in the short period adhesion prevention structure (hereinafter sometimes referred to as "pitch") is preferably less than 1 μm, more preferably 0.1 μm or less, even more preferably 0.01 μm or less, particularly preferably 0.005 μm or less, and even more preferably 0.001 μm or less.
The shortest distance between the centers of adjacent recesses in the long period adhesion prevention structure (hereinafter sometimes referred to as "pitch") is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, particularly preferably 50 μm or more, and even more preferably 100 μm or more, taking into consideration the size of the substance (particle) that prevents adhesion, etc. The pitch to be selected is determined by taking into consideration the design of the target object (product), for example, a small pitch is selected if transparency is required.

The short-period adhesion prevention structure is preferably formed at least on the convex apex of the long-period adhesion prevention structure in terms of the adhesion prevention effect against particulate matter.

<Method of forming adhesion prevention structure>
The adhesion prevention structure is not particularly limited and can be appropriately selected depending on the purpose, but is preferably formed by, for example, an interference processing method.
The interference processing method includes a surface wave interference processing method and a multi-beam interference processing method.

- Surface wave interference processing method -
Birnbaum discovered in 1965 that a periodic structure of wavelength size can be "instantaneously" formed on the bottom surface of a laser processing mark (Birnbaum M.: Semiconductor surface damage produced by ruby lasers, J. Appl. Phys., 36(11), 3688-3689 (1965)).
It has been elucidated that the periodic structure is an ablation phenomenon in which standing waves formed by the interference of incident light with plasma waves or scattered light on the surface selectively sublimate the surface of a material, and this phenomenon is called the "surface wave interference processing method." In other words, there are two principles for processing materials with a laser: thermal processing and ablation (sublimation). If the laser power is sufficient, only ablation occurs and no heat is generated. If the laser power is insufficient, both ablation and thermal processing occur. And if the laser power is low, only thermal processing occurs. In the case of a pulsed laser, which of these two situations occurs depends on the pulse width.

Surface wave interference processing utilizes the fact that when the surface of a certain material such as metal or resin is irradiated with a femtosecond laser with a pulse width shorter than the thermal relaxation time of the solid, surface plasma waves (surface waves) are excited in the material. Selective ion emission occurs in areas where the laser energy intensity exceeds a threshold, resulting in processing, and a diffraction grating-like fine periodic structure appears. This phenomenon is formed in a self-organizing manner, so the period of the unevenness can be matched even if the entire surface is scanned.
Surface wave interference processing using a femtosecond laser makes it possible to form several thousand microstructures with a width of several mm at an ultra-high speed of several mm per second.
It has been theoretically shown that the pitch a of the periodic structure produced by surface wave interference processing varies according to the relationship a = λ/(1 ± sin θ) depending on the laser wavelength λ and the incident angle θ (see the paper listed below).
・Campbell EEB, Ashkenasi D, Rosenfeld A: Ultra-short-pulse laser irradiation and ablation of dielectrics, Materials Science Forum, 301, 123-144 (1999)
・Sakabe S, Hashida M, Tokita S, Namba S, Okamuro K: Mechanism for self-formation of periodic grating structures on a Metal surface by a femtosecond laser pulse, Physical Review B, 79, 33409-1-33409-4 (2009)
For details of the surface wave interference processing method, reference can be made to, for example, the description in "Birnbaum M.: Semiconductor surface damage produced by ruby lasers, J. Appl. Phys., 36(11), 3688-3689 (1965)".

- Multi-beam interference processing method -
The multi-beam interference processing method uses a femtosecond laser to arbitrarily generate optical interference patterns in the micrometer and nanometer range within the laser spot, so that it can realize periodic structures of tens to hundreds of lines with a single laser sweep, even with a nanometer pitch smaller than the laser spot diameter, and can perform high-speed processing. In addition, by selecting the optical conditions, it is also possible to form three-dimensional structures.
For example, by using a femtosecond laser processing device and a spatial light phase modulator, it is possible to process with a pitch of several hundred nm, and by changing the number of light beams and inserting a phase plate into only one laser beam, it is possible to form interference patterns with different three-dimensional shapes.
For details of the multi-beam interference processing method, for example, the description in "A. A. Maznev, T. F. Crimmins, and K. A.: How to make femtosecond pulses overlap, Optics LEetters, Vol. 23, No. 17, 1378-1380, (1998)" can be referred to.

-Percussion processing method-
The adhesion prevention structure is not particularly limited and can be appropriately selected depending on the purpose, but is preferably formed by, for example, a percussion processing method.
Percussion processing is a laser processing method that uses intermittent laser irradiation, in which pulse processing is performed on the workpiece at time intervals, at fixed intervals, or a combination of these shots are repeated continuously.
By combining the percussion processing method with controlling the irradiation pitch of the nanosecond pulse laser on the order of micrometers, it is possible to simultaneously form fine periodic structures with different periodicities, that is, micrometer pitch and nanometer pitch.
A desired three-dimensional shape can be obtained by using the percussion processing method, which performs intermittent laser irradiation, and changing the irradiation pattern on a two-dimensional plane. As a method of this, a periodic structure can be formed on the surface of an object by performing percussion processing while moving the laser irradiation point and the object to be irradiated with the laser relatively. Furthermore, by combining the percussion processing method with controlling the irradiation pitch of the nanosecond pulse laser on the order of micrometers (i.e., 1 micrometer to 100 micrometers), two different fine periodic structures with a pitch shorter than the order of micrometers can be simultaneously formed.
The ultrashort pulse laser can be irradiated by the percussion processing method, which irradiates at a specified distance and time interval. This makes it possible to easily adjust the overlap rate of the laser spot diameter to form a periodic structure on the surface of the target object, thereby controlling the surface wave interference and the pitch of the periodic structure.
For details of the percussion processing method, reference can be made to the descriptions in, for example, JP-A-2020-66824 and JP-A-2020-146725.

- Reverse taper processing method -
The adhesion prevention structure is not particularly limited and can be appropriately selected depending on the purpose, but it is preferable to form it by, for example, a reverse taper processing method.
In short-pulse laser processing, not only processing that narrows the processing area from the light incident side toward the light traveling direction ("forward taper processing"), but also processing that expands the processing area from the light incident side toward the light traveling direction ("reverse taper processing") is required. This is because the reverse taper processing eliminates the restriction of the three-dimensional shape of the cross section, and can have any shape, making three-dimensional direct processing possible.
The convex part with a constriction at the base and a reverse tapered shape is called a "reentrant structure." A "reentrant structure" with a reverse taper angle of several tens of degrees can be formed by using an optical unit that uses a femtosecond laser.
For details of the reverse taper processing method, reference can be made to the description of Japanese Patent Application No. 2020-174320, for example.

(Method for manufacturing the adhesion prevention structure of the second embodiment)
The second form of the method for manufacturing an adhesion prevention structure of the present invention involves manufacturing an adhesion prevention structure using a mold in which an adhesion prevention structure that prevents adhesion of particulate matter is formed by irradiating short-pulse laser light onto at least a portion of the surface of the mold.
According to the second form of the manufacturing method for an adhesion prevention structure of the present invention, a mold is produced having an adhesion prevention structure formed on its surface that prevents particulate matter such as bacteria, viruses, and dust, and this mold can be used to rapidly mass-produce adhesion structures having an adhesion prevention structure on its surface, for example, by injection molding, blow molding, nanoimprinting, etc.

(Adhesion prevention structure)
The adhesion-preventing structure of the present invention is produced by the method for producing an adhesion-preventing structure of the present invention.
The adhesion preventive structure of the present invention has an adhesion preventive structure that prevents adhesion of particulate matter on at least a portion of its surface, and therefore can effectively prevent adhesion of particulate matter such as bacteria, viruses, and dust.

The following describes examples of the present invention, but the present invention is not limited to these examples.

Example 1
<Formation of adhesion prevention structure by surface wave interference processing method>
As shown in Fig. 1, a femtosecond laser processing device 10 (PHAROS SP, pulse width 234 fs, central wavelength 514 nm, repetition frequency 60 kHz, Light Conversion), which is one of ultrashort pulse lasers, was used to perform shot processing on a glass single fiber (fiber diameter 125 μm, manufactured by Furukawa Electric Co., Ltd.) as a workpiece 15 at a scanning speed of 0.5 mm/s in both x-y axial directions. In Fig. 1, 11 is a laser head, 12 is a beam expander, 13 is a mirror, 14 is a condenser lens, and 16 is an XYZ stage.
The processing conditions were a fixed spot diameter of 6.9 μm, a fluence of 2.34 to 18.36 J/cm ² , an overlap rate of 0 to 90%, and a pitch of 0.7 to 7 μm.
The adhesion prevention structures shown in Figures 2A to 2C were formed using the femtosecond laser processing apparatus shown in Figure 1. Figure 2A shows an adhesion prevention structure fabricated under conditions of fluence (F) = 8.88 J/cm ² and overlap ratio (OR) = 0%, and the pitch of the long-period adhesion prevention structure was 9 μm.
FIG. 2B shows an adhesion prevention structure fabricated under conditions of a fluence (F) of 13.69 J/cm ² and an overlap ratio (OR) of 50%, and the pitch of the short-period adhesion prevention structure was 950 nm.
Fig. 2C shows an adhesion prevention structure fabricated under the conditions of fluence (F) = 4.46 J/ ^cm2 and overlap ratio (OR) = 90%. Although the pitch cannot be determined because it is a random structure, the pitch of the long-period adhesion prevention structure was approximately 2 to 6 μm.

Next, antibacterial tests were conducted as follows using test pieces with anti-adhesion structures formed by the above-mentioned surface wave interference processing method.

<Antibacterial Test>
- Preparation of processed test pieces -
The test pieces were processed using a picosecond pulse laser (TrueMicro5000 series, TRUMPF Germany) with a wavelength of 515 nm, a pulse width of 190 fs, and a maximum repetition rate of 600 kHz.
The processing conditions for the surface wave interference processing were as follows: stainless steel (SUS304, thickness 0.3 mm, surface roughness Ra=0.02 μm) was used as a test piece, repetition frequency 400 kHz, pulse width 190 fs, average output 8.2 W, and spot diameter φ20 μm.
For the optical system of the laser processing, a scanning optical system combining a galvanometer scanner, an expander, and an f-θ lens was adopted, and surface wave interference processing (pitch 500 nm) was performed on a 50 mm x 50 mm portion of a 60 mm x 60 mm test piece, as shown in Figure 3.
The processed test pieces were sterilized by heating at 60° C. for 1 hour in a dry heat sterilizer before use.

- Antibacterial evaluation -
An antibacterial test was carried out based on JIS Z2801:2010 "Antibacterial processed products - Antibacterial test method and antibacterial effect", 5. Test method (URL: http://kikakurui.com/z2/Z2801-2012-01.html).
A suspension of Escherichia coli (NBRC3972) was used as the test bacteria.
As a specific procedure, the entire surface of a pre-prepared processed test piece was wiped with absorbent cotton soaked in ethanol.
0.4 mL of E. coli suspension with a concentration controlled to 6.3 x 10 ⁵ cfu/mL was dropped onto the dried processed test piece, and a polypropylene film (VF-10, manufactured by Kokuyo Co., Ltd.) cut to 40 mm x 40 mm was placed on top to thinly spread and cover the surface of the processed test piece to prevent drying. The processed test piece in this state was left to stand for 24 hours in an environment of 35°C and humidity of 90% RH or more.
The processed test piece was then washed and the collected bacterial solution was cultured on an agar medium, and the number of colonies was counted to calculate the number of live bacteria on the original processed test piece. The antibacterial activity value R was calculated using the following formula (i), and the antibacterial property was evaluated according to the following criteria. The results are shown in Table 1.
Antibacterial activity value R=Ut-At Formula (i)
where Ut is the logarithm of the viable cell count after the reaction on the unprocessed test piece, and At is the logarithm of the viable cell count after the reaction on the processed test piece.
[Evaluation Criteria]
×: R<2.0, no antibacterial effect observed. ◯: 2.0≦R≦3.0, antibacterial effect observed. ⊚: 3.0<R, strong antibacterial effect observed.

表１の結果から、表面波干渉加工法により形成した付着防止構造を有する加工試験片は、良好な抗菌性を有することがわかった。

The results in Table 1 show that the processed test pieces having the adhesion prevention structure formed by the surface wave interference processing method have good antibacterial properties.

Example 2
<Formation of adhesion prevention structure by multi-beam interference processing method>
As shown in FIG. 4, a commercially available femtosecond pulse laser (Pharos-6W, Light Conversion, Republic of Lithuania) was used as the laser oscillator 21 with a wavelength of 515 nm, a pulse width of 277 fs, and a repetition rate of 10 kHz.
As shown in Fig. 4, the optical unit 20 used in the multi-beam interference processing method is composed of a spatial light phase modulator 22 (LCOS-SLM, manufactured by Hamamatsu Photonics Co., Ltd.), a collimator lens 23 for converting the light branched by the spatial light phase modulator 22 into parallel light, a beam expander 24 for adjusting the laser spot diameter, a mask 26 with two holes (hole diameter = 200 µm), and a condenser lens 27. In Fig. 4, 25 denotes a mirror and 28 denotes a workpiece (object to be processed).
The processing conditions for the multi-beam interference processing were as follows: stainless steel (SUS304, thickness 1 mm, surface roughness Ra=0.03 μm) was used as the workpiece (object to be processed) 28, repetition frequency 10 kHz, pulse width 290 fs, average output 235 mW, and spot diameter 64 μm.
The stage on which the workpiece was placed moved at a speed of 0.5 mm/s, and 60 grooves could be formed per shot.
By using the above-mentioned multi-beam interference processing method, it was possible to form a lattice-shaped anti-adhesion structure in one axis (x) direction by two-beam interference as shown in FIG. 5A, and it was possible to form a lattice-shaped anti-adhesion structure in two axes (x-y) directions by four-beam interference as shown in FIG. 5B.
5A and 5B had a pitch of 1 μm. In other words, according to this method, not only an adhesion prevention structure in one direction but also an adhesion prevention structure in two directions can be simultaneously provided.
In this case, the relationship between the diffraction angle Ψ and the irradiation angle θ is expressed by the following equation (1).
Here, the composite focal length F=(f ₁ ×f ₃ )/(f ₂ ×f ₄ ).

The pitch τ of the adhesion prevention structure (fine periodic structure) pattern is expressed by the following equation (2) using the wavelength λ and the irradiation angle θ.
In other words, by applying the processing method of this invention, a hierarchical structure can be produced by providing a long-period adhesion prevention structure and a short-period adhesion prevention structure of a predetermined pitch to the same surface.

Example 3
<Formation of anti-adhesion structure by percussion processing method>
Carbon steel (surface roughness Ra=0.3 μm, manufactured by Hitachi Metals, Ltd.) was used as the metal sample, which was cut into a size of 20 mm×20 mm to prepare a processed sample piece.
The processed sample pieces were immersed in a piranha solution in which concentrated sulfuric acid was mixed in a volume ratio of 3 parts and 30% hydrogen peroxide solution in a volume ratio of 1 part, then removed, washed with ion-exchanged water, and dried.
The processed sample piece that had been pretreated as described above was divided into four equal-sized squares, and percussion processing was performed on the four divided areas as follows.
A nanosecond laser processing device (oscillation wavelength 532 nm, maximum output 10 W) was used for the laser processing. A scanning optical system combining a galvanometer scanner, an expander, and an f-θ lens was used as the optical system for the laser processing. Two attenuation plates were used to control the laser output. A galvanometer mirror was used for the sweeping method. The laser spot diameter was 16 μm using an expander 8 times and an f-θ lens with a focal length of 100 mm. The diameter of the laser on the surface of the processed sample piece was 16 μm, and the pitch was controlled to be 40 μm by changing the sweep speed of the laser light. The number of shots of laser irradiation per location was set to 80.
By the above-described percussion processing method, the adhesion prevention structure shown in FIG. 6A and FIG. 6B was formed.
FIG. 6A shows an adhesion prevention structure formed under the condition of a fluence (F) of 4.98 J/cm ² .
FIG. 6B shows an adhesion prevention structure formed under the condition of a fluence (F) of 9.95 J/cm ² .
6A and 6B are laser confocal microscope photographs taken using the percussion processing method, in which crater-like holes were observed in the direction of laser light propagation. The bank-like outer edges around the microscopic holes are thought to have been formed by the Marangoni effect of the ultrashort pulse laser.

Example 4
<Formation of adhesion prevention structure by reverse taper processing method>
As shown in Fig. 7, the optical unit 30 used in the reverse taper processing method is composed of a beam expander 32 for collimation adjustment, a pair of first and second step mirrors 33 and 34 for varying the irradiation angle, a Dove prism 35 for rotating the laser beam, and an aspheric lens 37 (f = 17 mm to 20 mm). In Fig. 7, 31 is a laser head, 36 is a scanner mirror (fixed), and 38 is a work (object to be processed).
By changing the angles of the first step mirror 33 and the second step mirror 34, the distance of the laser beam from the center of the aspheric lens 37 can be adjusted, and the reverse taper angle can be varied in an analog manner. In addition, the Dove prism 35 can be rotated by a motor to perform reverse taper processing.
By the above-mentioned reverse taper processing method, an adhesion prevention structure shown in Fig. 8 was formed. Fig. 8 shows an adhesion prevention structure formed under the conditions of an output of 500 mW and an overlap rate (OR) of 90%.

REFERENCE SIGNS LIST 10 laser processing device 11 laser head 12 beam expander 13 mirror 14 condenser lens 15 workpiece 16 XYZ stage 20 optical unit 21 laser oscillator 22 spatial light phase modulator 23 collimator lens 24 beam expander 25 mirror 26 mask 27 condenser lens 28 workpiece 30 optical unit 31 laser head 32 beam expander 33 first step mirror 34 second step mirror 35 Dove prism 36 scanner mirror 37 aspheric lens 38 workpiece

Claims (11)

A method for manufacturing an adhesion prevention structure, comprising the steps of irradiating at least a portion of a surface of an object with short-pulse laser light and forming an adhesion prevention structure that prevents the adhesion of particulate matter by a reverse taper processing method . A method for manufacturing an adhesion prevention structure, characterized in that an adhesion prevention structure is manufactured using a mold in which an adhesion prevention structure that prevents the adhesion of particulate matter is formed by irradiating at least a portion of the surface of the mold with short pulse laser light and using a reverse taper processing method. A method for manufacturing an adhesion prevention structure, comprising the steps of irradiating at least a portion of the surface of a fiber with short-pulse laser light and forming an adhesion prevention structure having a non-uniform pitch in the range of 2 to 6 μm for preventing the adhesion of particulate matter by a surface wave interference processing method. A method for manufacturing an adhesion prevention structure, comprising the steps of irradiating at least a portion of the surface of an object with short-pulse laser light and simultaneously forming a two-directional lattice-shaped adhesion prevention structure that prevents the adhesion of particulate matter by a multi-beam interference processing method. The method for producing an adhesion-preventing structure according to claim 1 , wherein the particulate matter is at least one selected from the group consisting of viruses, bacteria, and dust. The method for producing an adhesion prevention structure according to claim 1 , wherein the adhesion prevention structure has a short period adhesion prevention structure and a long period adhesion prevention structure. the shortest distance between the centers of adjacent recesses in the short period adhesion prevention structure is less than 1 μm;
The method for producing an adhesion prevention structure according to claim 6 , wherein the shortest distance between the centers of adjacent recesses in the long period adhesion prevention structure is 1 μm or more. The method for producing an adhesion prevention structure according to claim 6 or 7 , wherein the short period adhesion prevention structure is formed at least on a convex apex of the long period adhesion prevention structure. An apparatus for manufacturing an adhesion prevention structure, comprising: a means for irradiating at least a portion of a surface of an object with short-pulse laser light and forming an adhesion prevention structure that prevents the adhesion of particulate matter by a reverse taper processing method . An apparatus for manufacturing an adhesion prevention structure, comprising a means for irradiating at least a portion of the surface of a fiber with short-pulse laser light and forming an adhesion prevention structure having a non-uniform pitch in the range of 2 to 6 μm for preventing the adhesion of particulate matter by a surface wave interference processing method. An apparatus for manufacturing an adhesion prevention structure, comprising a means for simultaneously forming a two-directional lattice-shaped adhesion prevention structure that prevents the adhesion of particulate matter by irradiating at least a portion of the surface of an object with short-pulse laser light and using a multi-beam interference processing method.