Liquid-lubricating film and article provided with liquid-lubricating film

Abstract

To provide a liquid-lubricating film capable of being formed on a flat surface and achieving high liquid lubricity.SOLUTION: There is provided a liquid-lubricating film formed on a surface of a base material, the liquid-lubricating film comprising: an underlayer including a bonding structure that bonds to the surface and has a hydroxyl group, and a hydrophobic group composed of a single bond extending from the bonding structure; and a lubricating layer including a lubricating oil, where the lubricating oil contains a first lubricant having a hydrophilic group.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to synovial membranes and articles comprising synovial membranes. [Background technology]

[0002] Water-repellent (liquid-repellent) technology is expected to be a method for obtaining functional surfaces that are in high industrial demand, such as antifouling surfaces. For example, a technology for obtaining a high contact angle by mimicking the surface of a lotus leaf (lotus effect) has been researched for many years. In addition, unlike the lotus effect, slippery liquid-infused porous surfaces (SLIPS) have also been reported as a synovial technology that allows various liquids to slide smoothly off surfaces with low contact angle hysteresis (for example, Non-Patent Document 1).

[0003] Techniques for imparting synovial properties to flat surfaces rather than microporous surfaces have also been reported. For example, Non-Patent Document 2 reports the formation of a synovial membrane by grafting dimethylpolysiloxane (PDMS) molecules onto a flat substrate surface and then applying normal (unmodified) silicone oil (liquid PDMS) as a lubricant thereto. Non-Patent Document 3 reports the formation of a synovial membrane by modifying a flat substrate surface with fluorocarbon molecules and then applying a fluorocarbon-based lubricant (perfluorodecalin) thereto. Furthermore, Patent Document 1 discloses a synovial membrane comprising a base membrane having pendant phenyl groups, which are π-electron functional groups, on the surface of a flat substrate, and a layer of a liquid synovial agent having, within its molecule, a π-interaction portion that bonds with the π-electron functional group of the base membrane through π interaction and a synovial action portion that has low affinity for the target fluid. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Nature volume477, pages443-447(2011) [Non-patent document 2] Nature Sustainability, volume 2, pages 1097-1105(2019) [Non-patent document 3] Nature Biotechnology, volume 32, pages 1134-1140(2014) [Patent documents]

[0005] [Patent Document 1] Patent No. 6678018 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the SLIPS of Non-Patent Document 1 is unsuitable for mass production because it takes a long time to produce a microporous surface, and the microporous structure is prone to breakage. Although synovial membranes on flat surfaces have also been reported (Non-Patent Documents 2-3, Patent Document 1, etc.), these are limited to combinations of specific surfaces and specific lubricants. From the perspectives of reducing production costs and environmental impact, shortening production time, and improving durability and transparency, the search for new materials is desired.

[0007] The present invention has been made in view of the above problems. The present invention provides a synovial membrane that can be formed on a flat surface and exhibits high synovial properties. [Means for solving the problem]

[0008] As a result of extensive research into achieving the above object, the inventors have found that the above object can be achieved by the following configuration: In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits.

[0009] [1] A synovial membrane formed on the surface of a substrate, an underlayer bonded to the surface and including a bonding structure having a hydroxyl group and a hydrophobic group formed by a single bond extending from the bonding structure; a lubricating layer containing a lubricating oil, The synovial membrane, wherein the lubricating oil comprises a first lubricant having a hydrophilic group. [2] The synovial membrane described in [1], wherein the first lubricant is at least one selected from the group consisting of silicone-based lubricants and hydrocarbon-based lubricants. [3] The synovial membrane described in [2], wherein the first lubricant is a silicone-based lubricant. [4] The synovial membrane according to any one of [1] to [3], wherein the hydrophilic group is introduced into at least one location selected from the group consisting of one end of the main chain of the first lubricant, both ends of the main chain, and a side chain. [5] The synovial membrane described in [4], wherein the hydrophilic group is introduced at one or both ends of the main chain. [6] The synovial membrane according to any one of [1] to [5], wherein the hydrophilic group is at least one selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group. [7] The synovial membrane according to any one of [1] to [6], wherein the HLB value of the first lubricant is 6 or less. [8] The synovial membrane according to any one of [1] to [7], wherein the lubricating oil further contains a second lubricant that does not have a hydrophilic group. [9] The synovial membrane according to any one of [1] to [8], wherein the HLB value of the lubricating oil is 0.008 or more.

[10] The synovial membrane according to any one of [1] to [8], wherein the HLB value of the lubricating oil is 0.01 or more.

[11] The synovial membrane according to any one of [1] to [8], wherein the HLB value of the lubricating oil is 0.03 or more.

[12] The synovial membrane according to any one of [1] to

[11] , wherein the hydrophobic group of the underlayer is at least one selected from the group consisting of a hydrocarbon group and a fluorocarbon group.

[13] The synovial membrane according to any one of [1] to

[12] , wherein the hydrophobic group is linear.

[14] The synovial membrane according to

[13] , wherein the hydrophobic group has 1 to 8 carbon atoms.

[15] The synovial membrane according to any one of [1] to

[14] , wherein the underlayer contains a reaction product of an alkoxysilane having a hydrophobic group or a reaction product of a metal alkoxide having a hydrophobic group.

[16] The synovial membrane according to any one of [1] to

[15] , wherein the surface of the substrate on which the synovial membrane is formed has hydroxyl groups.

[17] The synovial membrane according to any one of [1] to

[16] , wherein the surface of the substrate on which the synovial membrane is formed has a surface roughness (Rq) of 10 nm or less.

[18] An article comprising a substrate on which a synovial membrane according to any one of [1] to

[17] is formed. [Effects of the Invention]

[0010] The present invention provides a synovial membrane that can be formed on a flat surface and exhibits high synovial properties. [Brief explanation of the drawings]

[0011] [Figure 1] 1(a) and (b) are schematic cross-sectional views of the synovial membrane of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes embodiments of the present invention, but the present invention is not limited to the following embodiments. Furthermore, among the components in the following embodiments, components that are not recited in the claims that represent the highest concepts are described as optional components.

[0013] [synovial membrane] 1(a) and (b), the synovial membrane 100 of this embodiment has a base layer 10 having hydrophobic groups 11 and a lubricating layer 20 containing a first lubricant 21 having hydrophilic groups 22, both formed on a surface 50a (flat surface) of a substrate 50. The base layer 10 is bonded to the surface 50a and includes a bonding structure 12 having a hydroxyl group 13, and a hydrophobic group 11 consisting of a single bond extending from the bonding structure 12.

[0014] The present inventors discovered that forming a base layer 10 on the surface 50a and applying a first lubricant 21 having hydrophilic groups 22 thereto exhibits excellent synovial properties with aqueous liquids, leading to the present invention. This discovery by the present inventors was surprising, since oils having hydrophilic groups usually have a high affinity with aqueous liquids and reduce synovial properties. The mechanism by which the synovial film 100 of this embodiment exhibits excellent synovial properties is presumed to be as follows.

[0015] Hydroxyl groups 13 are often present on the surface 50a (e.g., a glass surface) of the substrate 50, and even if an underlayer 10 (e.g., a reaction product of a silane coupling agent) is formed on the surface, the hydroxyl groups 13 may remain. It is also difficult to completely remove the hydroxyl groups 13 from the underlayer 10; the underlayer 10 itself contains hydroxyl groups 13. These hydroxyl groups 13 form hydrophilic sites, which may reduce the lubrication properties for aqueous liquids. In this embodiment, by applying the first lubricant 21 to the underlayer 10, the hydrophilic groups 22 interact with the hydroxyl groups 13 on the underlayer 10 and the surface 50a (e.g., hydrogen bonding, dipole-dipole interactions, etc.), and the hydroxyl groups 13 are sufficiently covered from above with lubricating moieties 23 (e.g., silicone chains, hydrocarbon chains, etc.). This forms a uniform lubricating layer 20 whose surface is covered with the lubricating moieties 23 and has no hydrophilic sites, resulting in excellent lubrication properties.

[0016] Furthermore, due to the interaction between the hydrophilic groups 22 and the hydroxyl groups 13, the first lubricant 21 can be strongly adsorbed to the underlayer 10. Furthermore, the molecular chains of the hydrophobic groups 11 and the lubricating portions 23 (silicone chains, hydrocarbon chains, etc.) of the first lubricant become entangled, making it easier for the first lubricant 21 to remain on the surface 50a.

[0017] Furthermore, the frictional force (slipperiness) of the synovial membrane 100 depends on the fluidity of the lubricating layer 20, which in turn is affected by the fluidity of the base layer 10. For example, if the hydrophobic groups 11 of the base layer 10 were π-electron-containing functional groups such as phenyl groups, the π-electron interactions between the phenyl groups would harden the surface of the base layer 10 and reduce its fluidity. Naturally, this would also reduce the fluidity of the overlying lubricating layer 20. In contrast, the hydrophobic groups 11 of the base layer 10 of this embodiment are flexible molecular chains composed of single bonds. The flexible molecular chains of the hydrophobic groups 11 move like a liquid, promoting the fluidity of the lubricating layer 20. In this way, the first lubricant 21 can exhibit high fluidity while remaining on the surface 50a, thereby further improving the synovial properties of the synovial membrane 100. The mechanism explained above is merely speculation and does not limit the technical scope of the present invention. The synovial membrane 100 of this embodiment will be described in detail below.

[0018] <Underlayer> The underlayer 10 is bonded (covalently bonded) to the surface 50a of the base material 50 and includes a bonding structure 12 having a hydroxyl group 13, and a hydrophobic group 11 formed by a single bond extending from the bonding structure 12. By providing the underlayer 10, the hydroxyl group 13 and the hydrophobic group 11 can be introduced onto the surface 50a.

[0019] The underlayer 10 preferably contains, for example, a reaction product of an alkoxysilane having a hydrophobic group 11 or a reaction product of a metal alkoxide having a hydrophobic group 11. The reaction product is, for example, a hydrolysis condensation product. The alkoxysilane having a hydrophobic group 11 is a so-called silane coupling agent, and the metal alkoxide having a hydrophobic group 11 is a metal-based coupling agent such as a titanium-based coupling agent, an aluminum-based coupling agent, or a zirconium-based coupling agent. The use of these coupling agents allows the underlayer 10 to be efficiently formed. The alkoxy groups of the coupling agent are hydrolyzed and bonded to each other (polymerized), and further react with hydroxyl groups present on the surface 50a to form the bonded structure 12. Some of the hydrolyzed alkoxy groups remain in the bonded structure 12 as hydroxyl groups 13. A plurality of hydrophobic groups 11 extend in a brush-like manner from the surface of the bonded structure 12 formed by the polymerization of the coupling agent. When the underlayer 10 is a reaction product of a silane coupling agent, the hydrophobic group 11 may be directly bonded to the Si atom of the bonding structure 12, or a spacer (divalent functional group) may be present between the hydrophobic group 11 and the Si atom. For example, the hydrophobic group 11 and the Si atom may be linked by a divalent amino group or an ether bond.

[0020] The hydrophobic group 11 is a monovalent functional group bonded to the bond structure 12 and is composed of only single bonds. The hydrophobic group 11 is a more flexible functional group than π-electron-containing functional groups such as a carbon-carbon double bond, a carbon-carbon triple bond, or an aromatic ring. This increases the fluidity of the lubricating layer 20, thereby further improving the synovial properties of the synovial membrane 100. Examples of the hydrophobic group 11 include hydrocarbon groups and fluorocarbon groups, and hydrocarbon groups are more preferred. The hydrophobic group 11 may be linear or branched, and may form a ring in part or in whole. The ring may be monocyclic or polycyclic, such as a cage structure. The ends of multiple (e.g., two) hydrophobic groups 11 may be linked to each other. The following [Chemical Formula 1] shows an example of the chemical structure of the hydrophobic group 11 bonded to a Si atom. The following examples of hydrophobic group 11 are hydrocarbon groups, but the hydrophobic group 11 may be a fluorocarbon group in which some or all of the hydrogen atoms of these hydrocarbon groups have been substituted with fluorine atoms. In addition, in the following examples of hydrophobic group 11, the hydrophobic group 11 and the Si atom are directly bonded, but the hydrophobic group 11 and the Si atom may also be linked via a divalent amino group, an ether bond, or the like.

[0021] [ka]

[0022] From the viewpoint of obtaining better effects of the present invention, the hydrophobic group 11 is preferably a straight chain, and more preferably a straight chain hydrocarbon group. When the hydrophobic group 11 is a straight chain, the number of carbon atoms therein is preferably 1 to 12, and more preferably 1 to 8. If the hydrophobic group 11 has a straight chain structure with a number of carbon atoms within the above range, the hydrophilic group 22 of the first lubricant 21 can more easily interact with the hydroxyl group 13 contained in the bonding structure 12.

[0023] The hydrophobic groups 11 contained in the underlayer 10 may be one type of hydrophobic group, or a mixture of multiple types of hydrophobic groups. The underlayer 10 may be, for example, a monolayer (self-assembled monolayer, SAM) formed using a silane coupling agent or the like, but is not limited thereto and may also be a multilayer. The thickness of the underlayer 10 is not particularly limited and may be, for example, 2 nm (monolayer) to 2 mm, or 2 nm to 800 μm.

[0024] <Lubricant layer> The lubricating layer 20 is mainly composed of a lubricating oil 24. The lubricating oil 24 is liquid in the environment (temperature and atmospheric pressure) in which the synovial membrane 100 is used, and provides fluidity to the lubricating layer 20. The environment in which the synovial membrane 100 is used is not particularly limited, but may be, for example, room temperature and atmospheric pressure (e.g., room temperature 20°C, atmospheric pressure 1 atm = 101.33 kPa). The lubricating oil 24 contains a first lubricant 21 having a hydrophilic group 22.

[0025] The first lubricant 21 has hydrophilic groups 22 but is not water-soluble, and provides the synovial membrane 100 with synovial properties in aqueous liquids. When the water-insoluble first lubricant 21 is mixed with water, phase separation can be visually confirmed. The water-insoluble first lubricant 21 has a low HLB (Hydrophile Lipophile Balance) value, for example, 6 or less. The lower limit of the HLB value of the first lubricant 21 is not particularly limited, but since the first lubricant 21 has hydrophilic groups 22, it is greater than 0 (zero), for example, 0.0008 or greater. In this specification, the HLB value is calculated according to the Griffin method by "(total molecular weight of hydrophilic group moieties / total molecular weight) x 20".

[0026] The first lubricant 21 includes a hydrophilic group 22 and a hydrophobic lubricating portion 23. The first lubricant 21 is obtained by introducing the hydrophilic group 22 into a hydrophobic compound (lubricating portion 23) such as oil that exhibits lyophobicity (hydrophobicity) with respect to the aqueous liquid that is the synovial fluid. The hydrophilic group 22 is a monovalent functional group and is introduced directly into the lubricating portion 23 or indirectly via a spacer (divalent functional group). For example, the hydrophilic group 22 is introduced into one end of the main chain of the first lubricant 21, both ends of the main chain, or a side chain, and is preferably introduced into one end or both ends of the main chain. The number of hydrophilic groups 22 introduced into one molecule of the first lubricant 21 is not particularly limited as long as the effects of the present invention are achieved, but is, for example, 1 to 4, preferably 1 to 2.

[0027] In this embodiment, examples of the hydrophilic group 22 include a hydroxyl group (-OH), an amino group (-NH), a carboxyl group (-COOH), a sulfo group (sulfonic acid group) (-SO3H), a sulfate ester group, a phosphate ester group, and a quaternary ammonium group. The hydrophilic group 22 is preferably a functional group that forms a hydrogen bond with water, and among these, a hydroxyl group (-OH), an amino group (-NH2), or a carboxyl group (-COOH) is preferred because of their ease of interaction with the hydroxyl group 13. The hydrophilic group 22 may be ionized.

[0028] The lubricating portion 23 is not particularly limited as long as it is lyophobic (hydrophobic) to the water-based liquid that is the synovial fluid target, and may include, for example, a silicone chain, a hydrocarbon chain, or the like, which may be a straight chain or a branched chain. The lubricating portion 23 constitutes at least the main chain of the first lubricant 21. In this specification, a lubricating portion 23 that includes a silicone chain will be referred to as a silicone-based lubricant, and a lubricating portion 23 that includes a hydrocarbon chain will be referred to as a hydrocarbon-based lubricant.

[0029] The first lubricant 21 may be liquid or solid in the environment in which the synovial membrane 100 is used (e.g., at room temperature and normal pressure). The molecular weight of the first lubricant 21 is not particularly limited as long as it is within a range in which the effects of the present invention can be achieved. When the first lubricant 21 is liquid, the lubricating oil 24 (liquid) contained in the lubricating layer 20 may consist of the first lubricant 21 (liquid) alone, or may be a mixture of the first lubricant 21 (liquid) and a second lubricant (liquid, not shown) described below. When the first lubricant 21 is solid, the lubricating oil 24 (liquid) contained in the lubricating layer 20 is a mixture of the first lubricant 21 (solid) and a second lubricant (liquid) described below. The solid first lubricant 21 may be dissolved or dispersed in the second lubricant; however, from the viewpoint of obtaining better effects of the present invention, it is preferable that the first lubricant (solid) 21 be dissolved in the second lubricant (liquid).

[0030] The first lubricant 21, which is liquid in the environment in which the synovial membrane 100 is used, is preferably, for example, a silicone-based lubricant (silicone oil) or a hydrocarbon-based lubricant (hydrocarbon oil). The silicone-based oil may be a modified silicone oil obtained by introducing hydrophilic groups 22 into silicone oil such as polydimethylsilicone (PDMS), polymethylphenylsilicone, or methylhydrogensilicone, and examples thereof include amino-modified silicone oil, carboxy-modified silicone oil, and carbinol-modified silicone oil. Examples of hydrocarbon-based oils include higher alcohols having a lubricating portion 23 with 5 to 18 carbon atoms, higher fatty acids (e.g., oleic acid), and higher aliphatic amines. Examples of the first lubricant 21, which is solid in the environment in which the synovial membrane 100 is used, include, for example, octadecylamine.

[0031] As described above, the lubricating oil 24 of the lubricating layer 20 may further contain a second lubricant (not shown) that does not have a hydrophilic group, in addition to the first lubricant 21. The second lubricant becomes entangled with the lubricating portion 23 (e.g., silicone chain, hydrocarbon chain) of the first lubricant 21 and remains within the lubricating layer 20, contributing to improved synovial properties.

[0032] The second lubricant is liquid in the environment (for example, normal temperature and normal pressure) in which the synovial membrane 100 is used. The molecular weight of the second lubricant is not particularly limited as long as it is within a range in which the effects of the present invention can be achieved.

[0033] Examples of hydrophilic groups not contained in the second lubricant include those similar to the hydrophilic group 22 contained in the first lubricant 21 described above. The second lubricant does not contain a hydrophilic group and includes a lubricating portion that is lyophobic (hydrophobic) to the water-based liquid that is the synovial fluid target. Examples of the lubricating portion of the second lubricant include those similar to the lubricating portion 23 of the first lubricating portion 21 described above, and preferred embodiments are also similar. Examples of the second lubricant include silicone-based lubricants (silicone-based oils) and hydrocarbon-based lubricants (hydrocarbon-based oils). Examples of silicone-based oils include silicone oils such as polydimethylsilicone (PDMS), polymethylphenylsilicone, and methylhydrogensilicone; and modified silicone oils in which functional groups other than hydrophilic groups (e.g., phenyl groups, methacrylic groups, alkyl groups, thiol groups, epoxy groups, etc.) are introduced into these silicone oils. Examples of hydrocarbon-based oils include hydrocarbons with 5 to 18 carbon atoms. Other general-purpose lubricating oils may also be used as the second lubricant.

[0034] From the viewpoint of obtaining a better effect of the present invention, the HLB value of the lubricating oil 24 consisting of the mixture of the first lubricant 21 and the second lubricant is preferably, for example, 0.008 or more, 0.01 or more, or 0.03 or more. Furthermore, the lubricating oil 24 (mixture) is not water-soluble, and the upper limit of the HLB value is, for example, 6 or less.

[0035] The mixing ratio of the first lubricant 21 to the second lubricant is not particularly limited, and is preferably adjusted so that the HLB value of the mixture (lubricant 24) falls within the above-mentioned range. For example, the mixing ratio may be adjusted appropriately within the range of mass ratio [(second lubricant) / (first lubricant)] = 0 / 1 to 100 / 1, 0 / 1 to 50 / 1, or 0 / 1 to 10 / 1. As shown in the examples described below, in the lubricant 24 consisting of the mixture, even if the content of the second lubricant is greater than the content of the first lubricant 21 (even if the mass ratio exceeds 1 / 1), the resulting synovial film 100 exhibits high synovial properties. While sufficient synovial properties cannot be obtained by using only the second lubricant, the lubricant 24 of this embodiment can significantly improve synovial properties by using a relatively small amount of the first lubricant 21 in combination.

[0036] The first lubricant 21 may be composed of one type of lubricant or a mixture of two or more types of lubricants. The second lubricant may be composed of one type of lubricant or a mixture of two or more types of lubricants. From the viewpoint of obtaining good compatibility or dispersibility, it is preferable that all of the lubricants contained in the lubricating oil 24 (the first lubricant 21 and the second lubricant) be lubricants of the same type. For example, all of the lubricants may be silicone-based lubricants, or all of the lubricants may be hydrocarbon-based lubricants.

[0037] The thickness of the lubricating layer 20 is not particularly limited as long as it is within a range that achieves the effects of the present invention, and may be, for example, 10 μm to 500 μm.

[0038] The lubricating layer 20 may be composed only of the lubricating oil 24. That is, the lubricating layer 20 may be composed only of the first lubricant 21, or may be composed only of a mixture of the first lubricant 21 and the second lubricant. Furthermore, the lubricating layer 20 may contain other components in addition to the lubricating oil 24, as long as the effects of the present invention are achieved. Examples of other components include general-purpose additives such as thickeners and various fillers. The main component of the lubricating layer 20 is the lubricating oil 24, and the proportion of the lubricating oil 24 in the lubricating layer 20 is, for example, higher than 50% by mass, 95% to 100% by mass, or 98% to 100% by mass.

[0039] [Base material] The material of the substrate 50 on which the synovial membrane 100 is formed is not particularly limited, and examples thereof include glass such as quartz glass, soda glass, aluminosilicate glass, borosilicate glass, alkali-containing glass, and alkali-free glass; synthetic resins (plastics) such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polycarbonate (PC), and polyvinyl chloride (PVC); metals such as iron (steel), aluminum, and stainless steel; and ceramics. Because the synovial membrane 100 of this embodiment can be formed on a flat surface, surface roughening (forming micropores) of the substrate 50 is not necessary. This reduces manufacturing costs, environmental impact, and manufacturing time.

[0040] The surface 50a on which the synovial membrane 100 is formed may be flat, and for example, the surface roughness (Rq) of the surface 50a may be 10 nm or less. A flat surface 50a has higher durability than a rough surface on which micropores are formed. Furthermore, the flat surface 50a, on which the synovial membrane 100 is formed, further promotes flattening, thereby efficiently suppressing light scattering. This allows the synovial membrane 100 of this embodiment to have high transparency. For example, the synovial membrane 100 preferably has a transmittance of 90% or more in the visible light range (for example, wavelengths of 400 nm to 800 nm).

[0041] Furthermore, from the viewpoint of increasing the adhesive strength with the synovial membrane 100, it is preferable that hydroxyl groups 13 are present on the surface 50a of the substrate 50. Hydroxyl groups 13 are often originally present on the surface 50a of the substrate 50, but hydroxyl groups 13 may be formed on the surface 50a by surface treatment (hydrophilization treatment) such as plasma treatment, UV / O3 treatment, or strong alkali treatment.

[0042] [Method of manufacturing synovial membrane] The method for producing the synovial membrane 100 of this embodiment is not particularly limited, and it may be produced by a general-purpose method. An example of the production method will be described below. The method for producing the synovial membrane 100 may include the following steps S1 to S3. Step S1: Preparing a substrate 50; Step S2: forming the underlayer 10; and Step S3: Forming the lubricating layer 20.

[0043] <Process S1> First, the substrate 50 is prepared, and if necessary, the surface 50a is subjected to a hydrophilic treatment to form the hydroxyl groups 13.

[0044] <Process S2> Next, the underlayer 10 is formed on the surface 50a. The method for forming the underlayer 10 is not particularly limited. For example, the underlayer 10 can be formed by treating the surface 50a by a general method using an alkoxysilane (silane coupling agent) having a hydrophobic group 11 or a metal alkoxide (metal-based coupling agent) having a hydrophobic group 11. A bond structure 12 is formed by reaction of the alkoxide of the coupling agent, and a structure in which multiple hydrophobic groups 11 extend in a brush-like manner is formed from the bond structure 12. The amount of coupling agent used may be adjusted appropriately depending on the desired film thickness of the underlayer 10.

[0045] <Process S3> The lubricating layer 20 is formed on the formed underlayer 10. The method for forming the lubricating layer 20 is not particularly limited, and for example, the lubricating oil 24 (a first lubricant or a mixture of the first lubricant and the second lubricant) may be applied to the surface 50a by a general-purpose method. The application method is also not particularly limited, and spin coating, dipping, squeegeeing, casting, etc. may be used. The amount of the lubricating oil 24 used may be adjusted appropriately depending on the desired film thickness of the lubricating layer 20. Furthermore, if necessary, components other than the lubricating oil 24 (general-purpose additives, etc.) may be mixed with the lubricating oil 24 and applied to the surface 50a together with the lubricating oil 24.

[0046] [Synovial fluid] Examples of aqueous liquids that can serve as synovial fluid for the synovial membrane 100 include water itself, liquid compositions whose main component is water, and liquid compositions containing water. Specific examples include distilled water, ion-exchanged water, RO water, pure water, ultrapure water, Milli-Q water, seawater, saline solution, buffer solution, rainwater, muddy water, and bodily fluids such as blood, water-based foods and seasonings, water-based chemicals, and ready-mixed concrete (so-called ready-mixed concrete before it hardens).

[0047] The aqueous liquid may be an aqueous solvent (a water-soluble solvent or a water-miscible solvent) itself, a mixture of water and an aqueous solvent, or a liquid composition containing these. Examples of aqueous solvents include the following organic compounds and inorganic compounds. Organic compounds: acetaldehyde, acetic acid, acetone, acetonitrile, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-butoxyethanol, butyric acid, diethanolamine, diethylenetriamine, dimethoxyethane, dimethylformamide, 1,1-dimethylhydrazine, 1,2-dimethylhydrazine, dimethyl sulfoxide, 1,4-dioxane, ethanol, ethylamine, ethylene glycol, formic acid, furfuryl alcohol, glycerol, methanol, methyldiethanolamine, methyl isocyanide, N-methyl-2-pyrrolidone, 1-propanol, 1,3-propanediol, 1,5-pentanediol, 2-propanol, propanoic acid, propylene glycol, pyridine, sulfolane, tetrahydrofuran, triethylene glycol. Inorganic compounds: hydrazine, nitric acid, hydrogen peroxide, hydrofluoric acid, sulfuric acid, hydrochloric acid.

[0048] The synovial membrane 100 of the present embodiment described above can be formed on a flat surface and exhibits high synovial properties with respect to aqueous liquids. Furthermore, the synovial membrane 100 has high durability and transparency, and can reduce production costs, environmental impact, and production time.

[0049] [Articles with synovial membranes] The synovial membrane 100 of this embodiment can be applied to a variety of articles. Examples of articles equipped with the synovial membrane 100 (articles including a substrate 50 on which the synovial membrane 100 is formed) include solar cells, power transmission lines, transportation equipment (automobiles, ships, aircraft, etc.), building materials and buildings (roofs, windows, walls, concrete formwork), and heat exchangers. These articles are often used outdoors, and the provision of the synovial membrane 100 can provide anti-fouling properties against rain, snow, mud, and other contaminants. It can also prevent ready-mix concrete from adhering to concrete formwork, etc. Furthermore, since the heat exchange efficiency of heat exchangers decreases if water droplets remain attached, the provision of the synovial membrane 100 of this embodiment can prevent this decrease. Furthermore, because the synovial membrane 100 has high translucency in the visible light range, it can be applied to window glass, automobile windshields, and other optical devices, such as displays, telescopes, microscopes, and cameras, without impairing visibility or translucency. Other examples of articles that include the synovial membrane 100 include medical instruments, food containers, etc. By providing the synovial membrane 100, it is possible to prevent body fluids such as blood, or water-soluble foods and seasonings from adhering to the article. Furthermore, examples of articles that include the synovial membrane 100 include the surfaces of fibers, fabrics, films (e.g., packaging films), and resist films used in semiconductor manufacturing, as well as the inner walls of containers and liquid transport tubes.

[0050] Furthermore, the synovial membrane 100 of this embodiment can be easily formed into a fine pattern on its flat surface 50a, which can be used as a liquid transport channel (flow path). An example of an article in which the synovial membrane 100 is formed as a liquid transport channel is a microreactor. A microreactor is a continuous production chemical reaction device that can rapidly mix raw materials in a minute flow path of about tens to hundreds of micrometers and precisely control the reaction temperature, and is expected to dramatically improve the manufacturing efficiency of pharmaceuticals, fine chemicals, and the like. [Example]

[0051] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0052] [Materials used to make synovial membrane]

[0053] [Table 1]

[0054] [Table 2]

[0055] [Table 3]

[0056] [Sample preparation] <Sample 1-1> (a) Base material A glass plate (water-polished glass slide, 1.0 mm thick, manufactured by Muto Chemical Co., Ltd.) was prepared. The surface roughness of the glass plate was measured using an atomic force microscope (AFM, Oxford Instruments, Asylum Research, MFP-3D Origin), and was found to be Rq = 0.316 nm.

[0057] (b) Formation of the base layer The surface of the glass plate was subjected to a silane coupling treatment using Silane 1 by the method described below, to form an undercoat layer.

[0058] The glass plate was irradiated with plasma for 1 minute using a plasma cleaner (PiB-10, Vacuum Devices). A solution was prepared by mixing 1 mL of alkoxysilane (Silane 1), 20 mL of hexane (Nacalai Tesque, purity >95%), and 1 μL of hydrochloric acid (Fujifilm Wako Pure Chemical Industries, Ltd.) and stirring for 3 hours. The hydrophilic glass plate was then immersed in the solution for 20 hours. After immersion, the glass plate was washed sequentially with acetone (Fujifilm Wako Pure Chemical Industries, Ltd.), hexane (Nacalai Tesque, purity >95%), and ultrapure water (resistance: 18.2 MΩ, purified with DirectQ-3UV, Merck KGaA).

[0059] (c) Formation of a lubricating layer Approximately 8 μL / cm on the formed underlayer2 Lubricant 1 was spread using a micropipette to form a lubricating layer.

[0060] <Samples 1-2 to 16> Using the alkoxysilanes and lubricating oils shown in Tables 4 to 6, synovial films were formed on glass plates in the same manner as for Sample 1, to obtain Samples 1-2 to 16.

[0061] <Samples 17-1 to 18-4, and 19> Samples 17-1 to 17-8 having only an underlayer were prepared using the alkoxysilanes shown in Table 7. Samples 17-1 to 17-8 were prepared in the same manner as Sample 1, except that no lubricating layer was formed. Samples 18-1 to 18-4 having only a lubricating layer were prepared using the lubricating oils shown in Table 7. Samples 18-1 to 18-4 were prepared in the same manner as Sample 1, except that no undercoat layer was formed. As sample 19, a sample having no underlayer or lubricating layer, that is, a glass substrate, was prepared.

[0062] [Synovial fluid evaluation] A 5 μL drop of water was dropped onto the surface of each of the obtained samples 1-1 to 19, and the surface was tilted 5 degrees from the horizontal plane to evaluate whether the water droplet slid down. The evaluation results are shown in Tables 4 to 7, with "Good" indicating that synovial fluid formed when tilted 5 degrees, and "Poor" indicating that synovial fluid did not form.

[0063] [Table 4]

[0064] [Table 5]

[0065] [Table 6]

[0066] [Table 7]

[0067] As shown in Table 4, Samples 1-1 to 5-2, which had a lubricating layer made of modified silicone oil having a hydrophilic group (hydroxyl group or amino group), had good synovial properties (evaluation result: ◯). The HLB values ​​of the modified silicone oils 1 to 5 used in Samples 1-1 to 5-2 were all 6 or less. On the other hand, as shown in Table 5, Samples 6-1 to 12, which had lubricating layers made of modified and unmodified silicone oils without hydrophilic groups, had poor synovial properties (evaluation result: ×). Also, Sample 13 shown in Table 5, which had a lubricating layer containing modified silicone oil (lubricant 13) with hydrophilic groups (hydroxyl groups), had poor synovial properties (evaluation result: ×). This is because the HLB value of Lubricant 13 used in Sample 13 was greater than 6, making it water-soluble and therefore unable to function as a lubricant (it was not a lubricant of the present invention).

[0068] As shown in Table 6, Sample 14, which had a lubricating layer made of hydrocarbon oil having a hydrophilic group (carboxy group), had good synovial properties (evaluation result: ◯). On the other hand, sample 16 having a lubricating layer made of hydrocarbon oil (lubricant 16) having no hydrophilic group exhibited poor synovial properties (evaluation result: ×).

[0069] Furthermore, as shown in Table 7, samples 17-1 to 17-8 having only an underlayer, samples 18-1 to 18-4 having only a lubricating layer, and sample 19 (i.e., a glass substrate) having neither an underlayer nor a lubricating layer were confirmed to have poor synovial properties (evaluation result: ×).

[0070] [Sample preparation] <Sample M1> Sample M1 was prepared in the same manner as samples 1-5 (using silane 5 for the underlayer), except that in forming the lubricating layer, a mixture of lubricant 4 and lubricant 3 (both of which are PDMS with hydroxyl groups introduced at both ends and have different HLB values) was used in the proportions shown in Table 8.

[0071] <Samples M11 to M13> Samples M11 to M13 were prepared in the same manner as sample M1, except that in forming the lubricating layer, a mixture of lubricant 6 (PDMS) and lubricant 1 (PDMS with a hydroxyl group introduced at one end) was used in the proportions shown in Table 9.

[0072] <Samples M21 to M25> Samples M21 to M25 were prepared in the same manner as sample M1, except that in forming the lubricating layer, a mixture of lubricant 6 (PDMS) and lubricant 5 (PDMS with amino groups introduced at both ends) was used in the proportions shown in Table 10.

[0073] <Samples M31 to M35> Samples M31 to M35 were produced in the same manner as sample M1, except that a mixture of lubricant 16 (1-octadecene) and lubricant 14 (oleic acid) was used in the ratio shown in Table 11 when forming the lubricating layer.

[0074] <Sample M41> Sample M41 was produced in the same manner as Sample M1, except that a mixture of Lubricant 16 (1-octadecene) and Lubricant 15 (octadecylamine) was used in the formation of the lubricating layer in the ratio shown in Table 12.

[0075] [Synovial fluid evaluation] The synovial fluidity was evaluated using the same method and evaluation criteria as for Samples 1-1 to 19 described above. That is, a 5 μL drop of water was dropped onto the surface of the obtained sample, and the surface was tilted 5 degrees from the horizontal plane to evaluate whether the water drop slid off. The evaluation results are shown in Tables 8 to 12, with "Good" indicating that synovial fluid formed when tilted 5 degrees, and "Poor" indicating that synovial fluid did not form. For comparison, the evaluation results of samples 3-5 and 4-1 are also shown in Table 8, the evaluation results of samples 1-5 and 6-5 in Table 9, the evaluation results of samples 5-1 and 6-5 in Table 10, the evaluation results of samples 14 and 16 in Table 11, and the evaluation results of sample 16 in Table 12.

[0076] [Table 8]

[0077] [Table 9]

[0078] [Table 10]

[0079] [Table 11]

[0080] [Table 12]

[0081] As shown in Table 8, sample M1, which used a mixed oil of two types of modified silicone oils with hydroxyl groups (lubricants 3 and 4) in the lubricating layer, had good synovial properties (evaluation result: ◯), similar to samples 3-5 and 4-1, which used lubricants 3 and 4 alone, respectively. The HLB values ​​of the lubricants used in each sample are shown in Table 8.

[0082] As shown in Tables 9 to 12, samples M11 to M13, M21 to 25, M31 to 35, and M41, which used mixtures (lubricants) of lubricants having hydrophilic groups (lubricants 1, 5, 14, and 15) and lubricants not having hydrophilic groups (lubricants 6 and 16) in the lubricating layer, had good synovial properties (evaluation result: ◯), similar to samples using each lubricant having a hydrophilic group alone. The HLB value of each mixture (lubricant) with good synovial properties was 0.008 or more. On the other hand, Samples 6-5 and 16, which used oils 6 and 16 (HLB=0) without hydrophilic groups alone, exhibited poor synovial properties (evaluation result: ×). [Industrial Applicability]

[0083] The synovial membrane of the present invention can form an antifouling surface and can be used, for example, in solar cells, automobiles, medical equipment, buildings, food containers, etc. Furthermore, a flow path can be formed on a flat surface using the synovial membrane of the present invention and used in a microreactor, etc. [Explanation of symbols]

[0084] 10 Base layer 11 Hydrophobic groups 12 Bonded structure 13 Hydroxyl group 20 Lubricating layer 21 First Lubricant 22 Hydrophilic group 23 Lubrication section 50 Base material 50a surface 100 Synovial membrane

Claims

1. A synovial membrane formed on the surface of a substrate, an underlayer bonded to the surface and including a bonding structure having a hydroxyl group and a hydrophobic group formed by a single bond extending from the bonding structure; a lubricating layer containing a lubricating oil, The synovial membrane, wherein the lubricating oil comprises a first lubricant having a hydrophilic group.

2. The synovial membrane of claim 1 , wherein the first lubricant is at least one selected from the group consisting of silicone-based lubricants and hydrocarbon-based lubricants.

3. The synovial membrane of claim 2 , wherein the first lubricant is a silicone-based lubricant.

4. The synovial membrane according to any one of claims 1 to 3, wherein the hydrophilic group is introduced into at least one location selected from the group consisting of one end of the main chain of the first lubricant, both ends of the main chain, and a side chain.

5. The synovial membrane according to claim 4 , wherein the hydrophilic group is introduced at one or both ends of the main chain.

6. The synovial membrane according to any one of claims 1 to 5, wherein the hydrophilic group is at least one selected from the group consisting of a hydroxyl group, an amino group, and a carboxyl group.

7. The synovial membrane according to any one of claims 1 to 6, wherein the first lubricant has an HLB value of 6 or less.

8. The synovial membrane of any one of claims 1 to 7, wherein the lubricating oil further comprises a second lubricant having no hydrophilic groups.

9. The synovial membrane according to any one of claims 1 to 8, wherein the lubricating oil has an HLB value of 0.008 or more.

10. The synovial membrane according to any one of claims 1 to 8, wherein the lubricating oil has an HLB value of 0.01 or more.

11. The synovial membrane according to any one of claims 1 to 8, wherein the lubricating oil has an HLB value of 0.03 or more.

12. The synovial membrane according to any one of claims 1 to 11, wherein the hydrophobic group of the underlayer is at least one selected from the group consisting of a hydrocarbon group and a fluorocarbon group.

13. The synovial membrane according to any one of claims 1 to 12, wherein the hydrophobic group is linear.

14. The synovial membrane of claim 13, wherein the hydrophobic group has 1 to 8 carbon atoms.

15. The synovial membrane according to any one of claims 1 to 14, wherein the underlayer comprises a reaction product of an alkoxysilane having the hydrophobic group or a reaction product of a metal alkoxide having the hydrophobic group.

16. The synovial membrane according to any one of claims 1 to 15, wherein the surface of the substrate on which the synovial membrane is formed has hydroxyl groups.

17. The synovial membrane according to any one of claims 1 to 16, wherein the surface roughness (Rq) of the surface of the substrate on which the synovial membrane is formed is 10 nm or less.

18. An article comprising a substrate having a synovial membrane formed thereon according to any one of claims 1 to 17.

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