Adsorbed monomolecular film and method of manufacturing the same

Abstract: The invention seeks to provide a method of forming a monomolecular film of fluorine-containing molecules on a substrate surface such that the film has an uniform thickness with minimal surface irregularities and is substantially pin hole free. The invention also provides for a substrate obtained by using the same method which has excellent water-and oil-repelling, anti-fogging, and anti-contaminating properties. The monomolecular film is formed on the substrate surface either directly or via a given protective film. The monomolecular film coating is characterized by a plurality of different chlorosilane-based surface active materials which are different in molecular length have a fluorine group. The surface irregularities of the film are generally confined to the molecular level.

Description: This invention relates to a substrate comprising a functional monomolecular film and, more particularly, a water-repellent, oil-repellent, anti-fogging and/or anti-contaminating monomolecular film. Heretofore, for improving the water- and oil-repelling properties of substrate surfaces, it has been a known practice to coat silicon-based surface active agents onto substrate surfaces or fluorocarbon-based polymer suspensions onto substrate surfaces. Generally, a material with a fluorine resin coating is obtained by coarsening the surface by means of electrolytic etching or surface roughening to increase adhesion with a fluorine-based polymer. The surface is coated with a fluorine-based polymer suspension, followed by baking. The prior art substrate has improved water- and oil-repelling properties and can be readily manufactured. However if the film coating on the substrate surface is insufficiently thin, it results in generation of pin holes, so that sufficient water- and oil-repelling properties cannot be obtained. In addition, even if the film coating is sufficiently thick, its water- and oil-repelling properties are sometimes inadequate. Furthermore, where a water-repelling oil-repelling film is provided on a transparent substrate such as a glass substrate, the transparency thereof is deteriorated due to the film thickness that is needed. In addition, the surface and the fluorine-based polymer coating are weakly coupled together for there are no chemical bonds between the two. Therefore, when the material is used for a substantially long time, the adhesion deteriorates resulting in a separation of the fluorine-based coating from the surface of the material. Japanese Journal of applied physics, vol. 26, No. 10, 10.10.87, Tokyo JP, pages 1622-1626 discloses C₁₈MNA (N-octadecyl-2-methyl-4-nitroaniline)- containing multilayers obtained using an alternating deposition technique of LB monolayers. It is the object underlying the present invention to provide a material with a fluorine-based coating which is substantially free of pin holes, uniform in thickness, and which has excellent water- and oil-repelling properties. According to the present invention this object is obtained with a substrate comprising a monomolecular film having surface irregularities which are confined to a molecular level comprising at least two different straight carbon chain systems with -CF₃ end groups having different molecular lengths said molecules being covalently bonded through a to the substrate surface either directly or through an inner layer. The present invention further provides a process of manufacturing the substrate according to the present invention by a chemical adsorption process comprising the steps of: preparing a coating composition comprising a blend surface active material in a non-aqueous solvent, the blend surface active material comprising two different straight carbon chain systems with -CF₃ end groups different in the molecular chain length and having at one end a halosilane or alkoxysilane group; and contacting said coating composition with a substrate having at the surface thereof an active hydrogen capable of reacting with said halosilane or alkoxysilane group, thereby forming a monomolecular film on the substrate surface. It is preferred that the process of the present invention comprises the steps of: preparing a coating composition comprising a surface active material in a non-aqueous solvent, the surface active material having at one end a halosilane or alkoxysilane group, contacting said coating composition with a substrate having at the surface thereof an active hydrogen capable of reacting with said halosilane or alkoxysilane group, thereby forming an inner layer on the substrate surface; adding hydroxyl groups (-OH), amino groups (-NH₂), or imino groups (=NH) on said inner layer surface; preparing a coating composition comprising a blend surface active material in a non-aqueous solvent, the blend surface active material comprising two different straight carbon chain systems with -CF₃ end groups different in the molecular chain length and having at one end a halosilane or alkoxysilane group; and contacting said coating composition with said inner layer having at the surface thereof an active hydrogen capable of reacting with said halosilane or alkoxysilane group, thereby laminating a monomolecular film onto said inner layer surface. It is preferable in this invention that the monomolecular film is formed as a lamination on an inner layer and said inner layer has a substantially uniform thickness. It is preferable in this invention that the at least two different straight carbon chain systems with -CF₃ end groups are alkyl fluoride groups. It is preferable in this invention that the inner layer is directly bonded to the substrate surface through covalent -Si-bonds and also bonded to the monomolecular film through covalent -Si- bonds. It is preferable in this invention that the monomolecular film has either water-repelling, oil-repelling, anti-fogging property or an anti-contaminating properties. It is preferable in this invention that the monomolecular film comprises at least two different groups selected from the group consisting of the formula [I] F(CF₂) m (CH₂) n Si(R q )(O 3-q ) wherein m represents an integer ranging from 1 to 15, n represents an integer ranging from 0 to 15, the sum of m and n ranges from 10 to 30, q represents an integer ranging from 0 to 2, and R represents an alkyl group or an alkoxyl group, and F(CF₂) s (CH₂) t A(CH₂) p Si(R q )(O 3-q ) wherein s represents an integer ranging from 1 to 8, t represents an integer ranging from 0 to 2, p represents an integer ranging from 5 to 25, q represents an integer ranging from 0 to 2, A represents a member of a group consisting of an oxy group(-0-), a carbonyl group ( C=O), a carboxyl-ester group (-COO-) and dimethylsilylene group (-Si(CH₃)₂-), and R represents an alkyl group or an alkoxyl group. It is preferable in this invention that the molecules of the blend surface active material have at one end the trifluoromethyl group (-CF₃) and at the other end a chlorosilane group It is preferable in this invention that the blend surface active material contains a silane surface active material represented by the formula; F(CF₂) m (CH₂) n Si(R q )(X 3-q ) wherein m represents an integer ranging from 1 to 15, n represents an integer ranging from 0 to 15, the sum of m and n ranges from 10 to 30, q represents an integer ranging from 0 to 2, and R represents an alkyl group or an alkoxyl group, X represents a halogen atom or an alkoxyl group, and by the formula: F(CF₂) s (CH₂) t A(CH₂) p Si(R q )(X 3-q ) wherein s represents an integer ranging from 1 to 8, t represents an integer ranging from 0 to 2, p represents an integer ranging from 5 to 25, q represents an integer ranging from 0 to 2, X represents a halogen atom or an alkoxyl group, R represents an alkyl group or an alkoxyl group, A represents a member of a group consisting of an oxy group (-0-), a carbonyl group ( C=O), a carboxyl-ester group (-COO-) and dimethylsilylene group (-Si(CH₃)₂-). Figure 1 is a schematic sectional view, enlarged in scale to the molecular level, showing an inner layer having vinyl groups on the surface of a substrate as described in Example 1 of this invention. Figure 2 is a schematic sectional view, enlarged in scale to the molecular level, showing the inner layer forming hydroxy groups on the surface of a substrate as described in Example 1 of this invention. Figure 3 is a schematic sectional view, enlarged in scale to the molecular level, showing the inner layer forming amino groups on the surface of a substrate as described in Example 1 of this invention. Figure 4 is a schematic sectional view, enlarged in scale to the molecular level, showing the laminating monomolecular film on the inner layer surface of a substrate as described in Example 1 of this invention. Figure 5 is a schematic sectional view, enlarged in scale to the molecular level, showing the monomolecular film on a substrate as described in Example 1 of this invention. Figure 6 is a schematic sectional view, enlarged in scale to the molecular level, showing the monomolecular film on the surface of a Nylon-6,6 substrate as described in Example 2 of this invention. According to the invention, the problems of the prior art are solved by a water-repelling, oil-repelling, anti-fogging, and anti-contaminating monomolecular film according to the invention formed on a substrate surface, the monomolecular film having minimal surface irregularities confined to the molecular level. By applying onto the substrate surface the monomolecular film according to the invention, a coating in the form of a monomolecular film can be obtained which has minimal surface irregularities confined to the molecular level. Because the surface has minimal irregularities and the molecules constituting the monomolecular film contain fluorine, the area of contact between water drops and the film surface can be reduced. Thus the film itself can have a very high water-repelling property. The film similarly repels oil drops, and therfore provides an improved oil-repelling property. With both these effects, the anti-fogging and anti-contaminating properties can also be improved. The substrate to be used according to the invention is selected from materials such as pure metals, e.g., aluminum, copper and iron, alloys or like composite materials, semiconductors, fiber, cloth, fabric, fur, leather, wood e.g., silicon and germanium, glass and plastics. According to the invention, a hydrophilic substrate is used. Where the substrate is made of a common base metal or a semiconductor, it is made hydrophilic by a natural oxide film formed on its surface. In case of a relatively non-hydrophilic substrate such as a plastic substrate, hydrophilic properties are imparted by, for instance, a corona treatment, plasma treatment or an ion beam irradiation. Furthermore, with a relatively non-hydrophilic substrate, it is recommended to form a monomolecular film in advance of a surface active material having unsaturated carbon-carbon bond groups by using such means as a Langmuir-Blodgett's technique (hereinafter referred to as LB process) or a chemical adsorption process and then forcibly rendering the film hydrophilic by such means as causing breakage of the unsaturated bonds in an atmosphere containing oxygen or nitrogen. This is preferred because many hydrophilic groups are formed on the surface of the substrate, and a high concentration of the monomolecular film can be obtained at the surface of the substrate. As a reagent for rendering the substrate surface hydrophilic the following compounds may be used CH₂=CH-(CH₂) n -SiCl₃ and CH₂=CH-(CH₂) n -COOH (wherein n represents an integer desirably of from 10 to 20). The monomolecular film may be formed by ordinary means such as the LB process or the chemical adsorption process. Unsaturated bonds may be broken by ordinary means such as treatment with an electron beam, X-rays, gamma-rays, ultraviolet rays or an ion beam, plasma or corona treatment. However, plastics having =NH groups such as polyamide or polyurethane substrates do not require a surface oxygen treatment. Since =NH groups have active hydrogens, it is relatively easy to reduce the groups by initiating the dehydrochloric acid reaction using the chlorosilyl groups of the surface active material. The film coating according to the invention is formed by utilizing a very thin monomolecular film, and therefore the initial surface state of the substrate may be maintained as such. The monomolecular film according to the invention may be formed on the substrate either directly or via, e.g., a protective film. Particularly, the monomolecular film according to the invention is suitably formed via such a functional film as a protective film, an anti-reflection film or an infrared-absorbing film. By doing so, it is possible to maintain high anti-reflecting or infrared-adsorbing properties for a long time while also obtaining a protective or similar functional effect in addition to the water-repelling, oil-repelling, anti-fogging and anti-contaminating effects owing to the monomolecular film. According to the invention, on a substrate surface there is formed either directly or via an intermediate film, such as a protective film, a water-repelling, oil-repelling, anti-fogging or anti-contaminating film in the form of a monomolecular film, which contains a plurality of different kinds of fluorine (F) containing groups having different molecular lengths. The monomolecular film may be formed by the LB process, the chemical adsorption process or any other usual process. In the chemical adsorption process, the reagent is adsorbed via chemical bonds to the substrate, and therefore this process is preferred for maintaining very close contact with the substrate. Moreover, a high mechanical strength of the monomolecular film can be obtained. When the LB process is used to form the monomolecular film according to the invention, e.g., a carboxylic acid (-COOH) having an alkyl fuoride group in the molecule, a carboxylic acid salt, an ester, a trialcoxysilane or a trihydro- silane may be used. When the chemical adsorption process is used to form the monomolecular film according to the invention, a fluorochlorosilane-based surface active material containing an alkyl fluoride group and a chlorosilyl group, a fluorotitanium-based surface active material containing an alkyl fluoride group and a titanate group, or a fluorothiol surface active material having an alkyl fluoride group and a thiol group may be used. As for the fluorochlorosilane-based surface active materials to be used according to the invention, they are suitably represented by the formulae [A] and [B]. These fluorochlorosilane-based surface active materials are suitable because they are readily available and have pronounced water-repelling, oil-repelling, anti-fogging and anti-contaminating effects. They are suitably represented by the formulae; CF₃(CH₂)₂Si(CH₃)₂(CH₂)₁₅SiCl₃, CF₃(CF₂)₃(CH₂)₂Si(CH₃)₂(CH₂)₉SiCℓ₃, CF₃CH₂O(CH₂)₁₅SiCl₃, CF₃COO(CH₂)₁₅SiCl₃, CF₃(CF₂)₉(CH₂)₂SiCl₃, CF₃(CF₂)₇(CH₂)₂SiCl₃, and CF₃(CF₂)₅(CH₂)₂SiCl₃. As the fluorotitanium-based or fluorothiol-based surface active materials for producing the monomolecular film according to the invention by the chemical adsorption process, compounds obtained by substituting titanate or thiol for the chlorosilyl group of the above chlorosilane-based surface active material may be used. When an alkoxysilane-based surface active material is used, adsorption is effected with an alcohol removal reaction when forming a chemically adsorbed monomolecular film. When a fluorothiol-based surface active material is used, adsorption is effected with a hydrous reaction. These surface active materials are, therefore, preferred to surface active materials having chlorosilyl groups, because they do not cause damage to even metal substrates. The invention can be widely applied to the following uses. Materials made of, e.g., metal, ceramic or plastic, glass, wood, stone, fiber, cloth, fabric, fur and leather are suitable substrates. The surface of the substrate can also be coated with, e.g., paint. Examples of cutlery: a kitchen knife, scissors, a knife, a cutter, a graver, a razor, hair clippers, a saw, a plane, a chisel, a gimlet, a badkin, bite (cutting tools), a edge of a drill, a edge of a mixer, a juicer, a blade of a mill, a blade of a lawn mower, a punch, a straw cutter, a staple of a stapler, a can opener or a surgical knife. Examples of needles: an acupuncture needle, a sewing needle, a matting needle, an injection needle, a surgical needle and a safety pin. Examples of products in pottery (ceramics) industry: products made of pottery, glass, ceramics or enameled products. For example, sanitary potteries (e.g., a chamber pot, a wash-bowl or a bathtub), tableware (e.g., a rice-bowl teacup, a dish (plate), a bowl, a teacup, a glass, a bottle, a coffee-pot (siphon), a pan, an earthenware mortar or a cup), vases (e.g., a flower bowl, a flowerpot or a bud vase), water tanks (e.g. a breeding cistern or an aquarium water tank), chemical experiment appliances (e.g., a beaker, a reactor vessel, a test tube, a flask, a laboratory dish, a condenser, a mixing rod, a stirrer, a mortar, a bat or a syringe) a roof tile, enameled ware, an enameled washbowl or an enameled pan. Examples of molding parts: dies for press molding, dies for cast molding, dies for injection molding, dies for transfer molding, dies for compression molding, dies for transfer molding, dies for inflation molding, dies for vacuum molding, dies for blow forming, dies for extrusion molding, dies for fiber spinning and a calendar processing roll. Examples of forming molds for food: cake, cookies, bread-baking, chocolate, jelly, ice cream, an oven ware and an ice tray. Examples of cookware: kitchen utensils (a pan and a pot), a kettle, a pot, a frying-pan, a hot plate, a gridiron net and a takoyaki plate. Examples of resin(s): a polyolefin such as a polypropylene and polyethylene, a polyvinylchloride plastic, a polyamide, a polyimide, a polyamideimide, a polyester, an aromatic polyester, a polycarbonate, a polystyrene, a polysulfide, a polysulfone, a polyethersulfone, a polyphenylenesulfide, a phenolic resin, a furan resin, a urea resin, an epoxy resin, a polyurethane, a silicon resin, an ABS resin, a methacrylic resin, an acrylate resin, a polyacetal, a polyphenylene oxide, a polymethylpentene, a melamine resin, an alkyd resin and an unsaturated polyester cured resin. Examples of rubber(s): a styrene-butadiene rubber, a butyl rubber, a nitrile rubber, a chloroprene rubber, a polyurethane rubber and a silicon rubber. Examples of household electric appliances: a refrigerator, a freezer, an air conditioner, a juicer, a mixer, a blade of an electric fan, a lighting apparatus, a dial plate and a dryer for a perm. Examples of sporting goods: skis, a fishing rod, a pole for the pole vault, a boat, a yacht, a surfboard, a fishing line and a float. Examples of vehicle parts to which the present invention can be applied: (1) ABS resin: a lamp cover, an installment pannel, trimming parts, a protector for a motorcycle. (2) Cellulose plastic: a car mark, a steering wheel (3) FRP (fiber reinforced plastics): a bumper, an engine cover (jacket) (4) Phenolic resin: a brake (5) Polyacetal: wiper gear, a gas valve (6) Polyamide: a radiator fan (7) Polyacrylate (polycondensation polymerization by bisphenol A and pseudo phthalic acid): a direction indicator lamp (or lense), a cowl board lense, a relay case (8) Polybutylene terephthalate (PBT): a rear end, a front fender (9) Poly amino-bismaleimide : engine parts, a gear box, a wheel, a suspension drive system (10) Methacrylate resin: a lamp cover lens, a meter pannel and its cover, a center mark (11) Polypropylene: a bumper (12) Polyphenylene oxide : a radiator grill, a wheel cap (13) polyurethane: a bumper, a fender, an installment pannel, a fan (14) Unsaturated polyester resin: a body, a fuel tank, a heater housing, a meter pannel. Examples of office supplies: a desk, a chair, a bookshelf, a rack, a telephone stand table, a rule (measure) and a drawing instrument. Examples of building materials: materials for a roof, an outer wall and interiors. Roof materials such as, e.g., brick, slate and tin (a galvanized iron sheet). Outer wall materials such as wood (including processed manufactured wood), mortar, concrete, ceramic sizing, metallic sizing, brick, stone, plastic and metal like an aluminium. Interior materials such as wood (including processed wood), metal like an aluminium, plastic, a paper and fiber. Examples of building stones: granite, marble and others for use as, e.g., a building material, an architecture, an ornament, a bath, a grave stone, a monument, a gatepost, a stone wall and a paving stone. Examples of the others: a high resisting voltage insulator such as a thermos bottle, a power supplying insulator for a vacuum system machinery or a spark plug, which has high water-repellent, oil-repellent, anti-fogging and anti-contamination effects. Specific examples of the process of chemical adsorption of a water-repelling oil-repelling anti-fogging, anti-contaminating film coating according to the invention will now be described with reference to Figures 1 to 5. Example 1 A solution containing 80 % wt n-hexadecane, 12 % wt carbon tetrachloride and 8 % wt chloroform was prepared by using CH₂=CH-(CH₂)₁₆-SiCl₃ as a silane surface active material and dissolving the same to a concentration of 3 x 10⁻³ to 5 x 10⁻² mol, and a tempered glass substrate 1, as shown in Figure 1, was dipped into this solution and held at room temperature for one hour. Since the surface of the substrate 1 contained hydroxyl groups, a reaction occurred between the chlorosilyl groups of the chlorosilane-based surface active material and the hydroxyl groups, thus forming on the surface bonds represented by the formula [1]. The tempered glass 1 was then washed with Freon 113 to remove the material remaining on the surface without reaction, followed by washing with water or exposing to air to react with moisture in the air. The -SiCl group was changed to a - SiOH group as in formula [2]. Each silanol group (-SiOH) was then dehydrated and crosslinked to form a siloxane bond (-SiO-) as in formula [3]. By the consecutive reaction, a single adsorbed monomolecular film 3 having vinyl (CH₂=CH-) groups 2 was formed to a thickness of about 2.5 nm such that it was chemically bonded (i. e., covalently bonded) to a protective film via oxygen atoms. This glass substrate 1 was irradiated with about 3 Mrad. of X-rays in an atmosphere containing oxygen and also in an atmosphere containing nitrogen. When the substrate 1 was irradiated in the oxygen-containing atmosphere, a monomolecular film 3' (inner layer), as shown in Figure 2, was obtained, which contained hydroxyl (-OH) groups 4 added to the vinyl groups 2. When the irradiation was carried out in the nitrogen-containing atmosphere, a monomolecular film 3'' (inner layer) was obtained, as shown in Figure 3, which contained amino groups (-NH₂) 5 added to the vinyl groups 2. The addition of the functional groups, i.e., the -OH, -NH₂ and - NH groups, to the vinyl groups, was confirmed as a result of a FTIR analysis. Subsequent to the addition of -OH groups, a solution containing 80 % wt n-hexadecane, 12 % wt carbon tetrachloride and 8 % wt chloroform was prepared by using CF₃(CF₂)₇ (CH₂)₂SiCl₃ and CF₃CH₂O(CH₂)₁₅SiCl₃ as respective chemical adsorption materials and dissolving these reagents to respective concentrations of about 2 x 10⁻³ to 5 x 10⁻² Mol and at a mixing ratio of 3 : 1 to 1 : 3, and the glass substrate 1 forming the monomolecular film 3', as shown in Figure 2, was dipped into the solution and held for one hour. Since -OH groups 4 were exposed at the surface of the substrate 1, the chlorosilic groups of the chlorosilane-based surface active material having fluorine and -OH groups 4 reacted. Thus, bonds represented by formulae [4] and [5] were produced on the surface substantially at the above mixing ratio. This reaction proceeded substantially as in the above formulae [1] to [3]. Thus, a high concentration monomolecular lamination film 7 can be obtained on the surface of the glass substrate 1, as shown in Figure 4. The film 7 includes a covalently bonded monomolecular film 6 which has a fluorine group and surface irregularities of the molecular level. The monomolecular film is chemically bonded (i. e., covalently bonded) to the inner layer 3'. The water wetting angle measured at the surface of the monomolecular film 6 was from 140° to 150°. The measured value showed an improvement by about 20° to 30° from 120°, which was obtained by using only a single kind of fluorosilane-based surface active material. The resultant glass, therefore, can be used to obtain a wiper-free vehicle window glass and to prevent fogging on, for instance, glass lens surfaces. These effects can be obtained by forming a monomolecular film containing alkyl fluoride groups on the outer most substrate surface wherein the alkyl fluoride groups have different molecular lengths, such as formulae 4 and 5, with the surface being substantially pin hole free. Where no intermediate monomolecular film is necessary between the surface water-repelling oil-repelling film and the glass substrate, a single covalently bonded monomolecular film 8 containing fluorine may be formed on a glass surface directly, as shown in Figure 5, by using a chlorosilane-based surface active material having fluorine and a mixing ratio of, for example, 1 : 1. Such a glass was shown to have sufficient water- and oil-repelling properties. Where a plurality of intermediate monomolecular films are necessary, the steps of chemical adsorption and subsequent radiation irradiation are repeated a number of times corresponding to the necessary number of laminated films. For example CH₂=CH(CH₂)₁₆-SiCl₃ and a plurality of different chlorosilane-based surface active materials having a fluorine group and different molecular lengths can be used as adsorption reagents. By doing so, a water-repelling, oil-repelling film having a single fluorine-containing monomolecular film can be formed on a glass surface via a number of intermediate laminated monomolecular films. In the above example, as to the reagent for forming the outermost monomolecular film containing fluorine and dimethylsilylene or oxygen atom or a carboxy ester the following can be used; CF₃(CH₂)₂Si(CH₃)₂(CH₂)₁₅SiCl₃, F(CF₂)₄(CH₂)₂Si(CH₃)₂(CH₂)₉SiCl₃, CF₃COO(CH₂)₁₅SiCl₃, CF₃(CF₂)₉(CH₂)₂SiCl₃, CF₃(CF₂)₅(CH₂)₂SiCl₃. Example 2 A chemical adsorbing solution was prepared by using Freon 113, CF₃(CF₂)₇(CF₂)₂SiCl₃ and CF₃CH₂O(CH₂)₁₅SiCl₃ as silane surface active materials. The surface active materials were each dissolved to a concentration of 1 % wt. A Nylon-6,6 substrate was dipped into this solution and held at room temperature for one hour. Since the surface of the Nylon-6,6 substrate contained imino groups (=NH), a reaction occurred between the chlorosilyl groups of the chlorosilane-based surface active material, and the imino groups formed surface bonds as represented in the formulae [6] and [7]. This reaction proceeded substantially as in formulae [1] to [3]. Thus, a high concentration monomolecular film 9 can be obtained on the surface of the Nylon-6,6 substrate 10, as shown in Figure 6. The monomolecular film 9 has a fluorine group and surface irregularities of the molecular level. The monomolecular film is chemically bonded (i. e., covalently bonded) to the substrate 10. The water wetting angle measured at the surface of the monomolecular film 9 was from 140° to 150°. A water-repelling, oil-repelling film having a single fluorine-containing monomolecular film was formed on the substrate 10. Example 3 This example, like Example 1, concerns the formation of the water-repelling, oil-repelling, anti-fogging, anti-contaminating film coating by the LB process using a tempered glass substrate. A blend surface active material was obtained by mixing two different surface active materials, i.e., CF₃(CF₂)₇(CH₂)₂COOH and CF₃CH₂O(C H₂)₁₅COOH at a mixing ratio of 1 : 1, and 10 mg were dissolved in 100 g of chloroform. The solution was then smoothly developed on the water surface. A tempered glass substrate as in Example 1 was then dipped into the solution at a speed of 1 cm/min. under a pressure of 50 mN/m and then raised. As a result, a film coating having molecular surface irregularities and containing alkyl fluoride groups was formed on the tempered glass substrate. This film coating had the same water-repelling property as the film obtained in Example 1. The water-repelling effect obtained in this example is attributable to the fact that, like in Example 1, the monomolecular film containing alkyl fluoride groups is formed as the outermost surface layer on the substrate. The alkyl fluoride groups are characterized by having different constituent molecules of different molecular lengths. Any of the above examples can also use two different surface active materials in combination. By using three or more different reagents, a monomolecular film having three or more different reagents can be obtained. Such a monomolecular film has similar water- and oil-repelling effects. Where a glass surface has a protective film or anti-reflection film such as a metal or a metal oxide film, or an infrared-adsorbing film such as a color formed infrared film, a covalently bonded film can be formed by appropriately controlling the adsorption time as long as the surface has hydrophilic groups such as hydroxy groups. Such films can be obtained under similar conditions by using, in lieu of the above chlorosilane-based surface active materials, fluorotitanate-based surface active materials such as a combination of F(CF₂)₈Si(CH₃) ₂(CH₂)₉TiOCH(CH₃)₂ and CF₃(CF₂)₉ (CH₂)₂TiOCH(CH₃)₂, or F(CF₂)₄(CH₂) ₂Si(CH₃)₂(CH₂)₉TiCl₃, CF₃(CF₂)₅ (CH₂)₂SiTi₃, or a fluorothiol-based surface active material such as a combination of F(CF₂)₄(CH₂)₂₀(C H₂)₁₅SH and CF₃(CF₂)₉(CH₂)₂SH or such adsorption liquids which can be obtained by adding, for instance, CH₃(CH₂)₁₉SH to chlorosilane-based or fluorotitanate-based or fluorothiol-based surface active materials. While the above examples are primarily concerned with tempered glass substrates, the invention is applicable to all kinds of glass which require improved water- and oil-repelling properties such as window glass or mirror used for buildings or vehicles, trains and airplanes or glass vessels or lenses. With a glass substrate having surface irregularities on the order of microns, the anti-contaminating property is slightly inferior. However, the water wetting angle is from 145° to 155°, and the water- and oil-repelling properties and anti-fogging property are improved. The water-repelling, oil-repelling, anti-fogging, anti-contaminating film coating according to the invention can be formed not only on glass substrates, but the invention is applicable to substrates made of, e.g., metals, semiconductors and plastics as well. As has been described in the foregoing, the water-repelling, oil-repelling, anti-fogging, anti-contaminating film coating according to the invention comprises a monomolecular film formed on a substrate surface and having minimal surface irregularities which are confined to irregularities at the molecular level. Thus, it is possible to form a higher density organic thin film coating, which is substantially free of pin holes, has a uniform thickness, is very thin and has excellent water- and oil-repelling properties. That is, with the treatment according to the invention, it is possible to obtain a highly durable surface treatment and prevent the contamination, fogging and wetting of substrate surfaces. As has been shown, the invention is greatly beneficial to industry.

Claims: A substrate comprising a monomolecular film having surface irregularities which are confined to a molecular level comprising at least two different straight carbon chain systems with -CF₃ end groups having different molecular lengths said molecules being covalently bonded through a to the substrate surface either directly or through an inner layer. The substrate according to claim 1, wherein the monomolecular film is formed as a lamination on an inner layer and said inner layer has a substantially uniform thickness. The substrate according to claim 1, wherein said inner layer is directly bonded to a substrate surface by covalent bonds. The substrate according to claim 1, wherein said monomolecular film comprises at least two different groups selected from the group consisting of F(CF₂) m (CH₂) n Si(R q )(O 3-q ) wherein m represents an integer ranging from 1 to 15, n represents an integer ranging from 0 to 15, the sum of m and n ranges from 10 to 30, q represents an integer ranging from 0 to 2, and R represents an alkyl group or an alkoxyl group, and F(CF₂) s (CH₂) t A(CH₂) p Si(R q )(O 3-q ) wherein s represents an integer ranging from 1 to 8, t represents an integer ranging from 0 to 2, p represents an integer ranging from 5 to 25, q represents an integer ranging from 0 to 2, A represents a member of a group consisting of an oxy group (-0-), a carbonyl group (C=0), a carboxyl-ester group (-COO-) and dimethylsilane group (-Si(CH₃)₂-), and R represents an alkyl group or an alkoxyl group. The substrate according to claim 1, wherein said at least two different straight carbon chain systems having different molecular lengths are oriented substantially vertically to the substrate surface. A process of manufacturing a substrate according to claim 1 by a chemical adsorption process comprising the steps of: preparing a coating composition comprising a blend surface active material in a non-aqueous solvent, the blend surface active material comprising two different straight carbon chain systems with -CF₃ end groups different in the molecular chain length and having at one end a halosilane or alkoxysilane group; and contacting said coating composition with a substrate having at the surface thereof an active hydrogen capable of reacting with said halosilane or alkoxysilane group, thereby forming a monomolecular film on the substrate surface. The process of claim 6, wherein each molecule of the blend surface active material has at one end a trifluoromethyl group (-CF₃) and at another end a chlorosilane group (-SiCl). The process of claim 6, wherein said blend surface active material comprises a silane surface active material represented by the formula: F(CF₂) m (CH₂) n Si(R q )(X 3-q ) wherein m represents an integer ranging from 1 to 15, n represents an integer ranging from 0 to 15, the sum of m and n ranges from 10 to 30, q represents an integer ranging from 0 to 2, and R represents an alkyl group or an alkoxyl group, X represents a halogen atom or an alkoxyl group, and by the formula: F(CF₂) s (CH₂) t A(CH₂) p Si(R q )(X 3-q ) wherein s represents an integer ranging from 1 to 8, t represents an integer ranging from 0 to 2, p represents an integer ranging from 5 to 25, q represents an integer ranging from 0 to 2, X represents a halogen atom or an alkoxyl group, R represents an alkyl group or an alkoxyl group, A represents a member of a group consisting of an oxy group (-O-), a carbonyl group (C=0), a carboxyl-ester group (-C00-) and dimethylsilylene group (-Si(CH₃)₂-). The process of claim 6 comprising the steps of: preparing a coating composition comprising a surface active material in a non-aqueous solvent, the surface active material having at one end a halosilane or alkoxysilane group, contacting said coating composition with a substrate having at the surface thereof an active hydrogen capable of reacting with said halosilane or alkoxysilane group, thereby forming an inner layer on the substrate surface; adding hydroxyl groups (-OH), amino groups (-NH₂), or imino groups (=NH) on said inner layer surface; preparing a coating composition comprising a blend surface active material in a non-aqueous solvent, the blend surface active material comprising two different straight carbon chain systems with -CF₃ end groups different in molecular chain length and having at one end a halosilane or alkoxysilane group, and contacting said coating composition with said inner layer having at the surface thereof an active hydrogen capable of reacting with said halosilane or alkoxysilane group, thereby laminating a monomolecular film onto said inner layer surface.

Inventors: OGAWA KAZUFUMI, OOTAKE TADASHI, SOGA MAMORU, OGAWA, KAZUFUMI, OOTAKE, TADASHI, SOGA, MAMORU
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1991
Main classification: B05D1
IPC codes: C09K3, B05D1, C09D4, B32B7, C08J7, B32B9