Hydrophilic chemically adsorbed film & method of manufacturing the same

Abstract: A chemically adsorbed film containing hydrophilic groups is formed on a substrate such that it is chemically bonded by Si covalent bonds to the substrate. The adsorbed film has an improved hydrophilic property. In addition, the film provides an excellently durable and transparent fog-proof substrate. According to the method of the invention, a substrate containing hydrophilic groups is contacted with a non-aqueous solution containing a surface active material having straight chain molecules each having at one end a chlorosilyl group and at the other end at least one functional group selected from the group consisting of a bromo group, iodo group, cyano group, thiocyano group, chlorosilyl group etc. to cause a dehydrochlorination reaction between hydrophilic groups on the substrate surface and chlorosilyl groups of the surface active material, thereby forming a chemically adsorbed film on the substrate surface. The functional group at the other end of the surface active material is converted into at least one hydrophilic group selected from the group consisting of -OH, -COOH, -NH 2 , =NH, -N + R 3 X - (X representing a halogen atom, R represents a lower alkyl group), -NO 2 , -SH, and -SO 3 H groups.

Description: The present invention relates to a method of manufacturing'a hydrophilic chemically adsorbed film. More particularly, the invention relates to a method of manufacturing a hydrophilic chemically adsorbed film, in which hydrophilic functional groups are secured by chemical bonds to chemically adsorbed molecules. It has been required in various fields to make the surface of a hydrophobic material hydrophilic. For example, it is required to make the surface of plastics, fibers, ceramics and like materials hydrophilic. Taking synthetic fibers, for example, if the surface of polyester, polyolefin and like synthetic fibers can be made hydrophilic, their use for clothing such as underwear and their industrial use such as wipers are expected to be further increased. It is important in industries to provide a technique of forming richly versatile molecules as a method of manufacturing a chemically adsorbed film, which is hydrophilic to a desired extent. Heretofore, plasma treatment or the like is well known as means for making the surface of plastics, fibers, ceramics and like material hydrophilic. As a different means, the Ogawa method has been proposed in which functional groups having particular functions are incorporated in advance in a surface active material for chemical adsorption to form a specific chemically adsorbed film, as disclosed in, for example, US-A-4,673,474. However, plasma treatment can not impart a sufficient hydrophilic property. In addition, its process is complicated. Further, with the above Ogawa method it is difficult to incorporate in advance hydrophilic groups in the surface active material itself, thus imposing great restrictions on the manufacture of chemically adsorbed films which are hydrophilic to a desired extent. That is, this method is poorly versatile. When the relative humidity is high or during the low temperature winter season, fog may be produced, for example, on vehicle window glass or on bathroom mirrors. Fog is produced due to inferior heat conductivity of the optical substrate of the vehicle window glass or bathroom mirror. When the atmospheric temperature is suddenly increased or when one surface contacts a high temperature air atmosphere while the other surface remains cool, water content in the air is condensed on the surface. This is referred to as fog. In the rainy season, for example, the relative humidity of air is saturated, and fog is readily produced with condensation as one breathes or sweats. It is well known in the art to prevent this fog formation by applying coating chemicals or resins containing hydrophilic compounds such as polyvinyl alcohol and polyethylene glycol on the optical material surface or by applying a hydrophilic film thereto. However, by coating hydrophilic resins on the optical material surface or by applying a hydrophilic film thereto, the transparency of the material is sacrificed. In addition, separation or flaws may occur. Further, the method of coating hydrophilic chemicals or resins poses problems in that durability is low, although the cost is low. Heretofore, there have been various proposals of providing a fog-proof property to the surface, which can be readily fogged by steam or water drops such as on window glass, bathroom mirrors and glass lenses. There are many proposed methods of improving the fog-proof property of glass, plastic and other substrates; for example a method of coating a hydrophilic coating film of denatured polyethylene glycol or poly(hydroxyethyl methacrylate) or a method of coating various silicone-based resins. The silicone-based resins, however, are less transparent, and therefore they require a very small coating thickness if they are to be coated while maintaining the color tone or luster of the substrate. However, since they are less hard and have an inferior scratch-proof property, by reducing the thickness of coating film durability is reduced. Likewise, denatured polyethylene glycol or poly(hydroxyethyl methacrylate) is poorly wear-resistant and inferior in durability. US-A-4, 539, 061 discloses a process for the production of a plurality of monolayer structures wherein molecules having Trichlorosilane groups at one end thereof are attached to a substrate. Said molecules have functional groups at the opposite end, which may be converted into hydrophilic groups such as -OH or -COOH groups. EP-A-0, 282, 188 discloses a recording medium which comprises a base body, a recording layer and a protection layer made from a silane surface active agent containing fluorine atoms and polymerized with the recording layer. It is the object of the present invention to provide a method of manufacturing a chemically adsorbed film incorporating groups which can solve the above problems inherent of the prior art. This object is achieved by a method of manufacturing a hydrophilic chemically adsorbed film comprising: a) contacting a substrate containing hydrophilic groups with a non-aqueous solution containing a fluorocarbon-based surface active material having chlorosilyl groups at both molecular ends to cause a reaction between hydroxyl groups on said substrate surface and chlorosilyl groups at one molecular end of the fluorocarbon-based surface active material, and b) washing with a non-aqueous organic solution and reacting with water, thereby forming on said substrate a chemical adsorbed film having hydroxyl groups secured to the substrate surface via the chemically absorbed fluorocarbon-based material. It is preferable in this invention that the fluorocarbon-based surface active material containing the chlorosilyl groups at both molecular ends is represented by the formula X p Cl 3-p SiR 1 (CF 2 ) n R 2 S iX q Cl 3-q where n represents an integer, R 1 and R 2 represent an alkylene group or a substituted group containing a Si or oxygen atom, X represents a hydrogen atom, an alkyl or an alkoxyl group substitution group, and p and q represent 1 or 2. The object is further achieved by a method of manufacturing a hydrophilic chemically adsorbed film comprising: i) contacting a substrate containing hydrophilic groups with a non-aqueous solution containing a surface active material having a chlorosilyl group at one molecular end and a reactive functional unsaturated group at the other molecular end to cause a reaction between hydroxyl groups of said substrate surface and chlorosilyl groups at one molecular end of the surface active material, ii) removing non-reacted surface active material remaining on the substate by washing with a non-aqueous organic solution, thereby forming a chemically adsorbed inner layer film on the substrate, iii) converting the reactive functional groups on the surface of said inner layer film into groups which are ractive with the chlorosilyl group, iv) contacting the substrate with a non-aqueous solution containing a fluorocarbon-based surface active material containing chlorosilyl groups at opposite ends to cause a reaction between active groups of said inner layer film and chlorosilyl groups at one molecular end of the fluorocarbon-based surface active material, and v) removing non-reacted fluorocarbon-based surface active material remaining on the substrate by washing with a non-aqueous organic solution and then reacting with water, thereby forming a hydrophilic laminated fluorocarbon-based chemically adsorbed film bonded to the inner layer film. Figures 1 (a)-(c) show a glass spectacle lens as in example 16 of the invention. Figures 2 (a)-(d) show a poly(ethylene terephtarate) film as in example 17 of the invention. Figures 3 (a)-(d) show a glass substrate as in example 18 of the invention. According to the invention, hydrophilic functional groups are secured by chemical bonds and via chemically adsorbed molecules to a substrate surface. Thus, there is no need of incorporating in advance a particular hydrophilic group in the surface active material, and it is possible to manufacture a chemically adsorbed monomolecular film, which is hydrophilic to a comparatively freely controllable extent. To provide the fog-proof property, a readily ionizable functional group is used as the hydrophilic group. More specifically, a fog-proof substrate is provided, which is an optical material with a chemically adsorbed monomolecular film, manufactured with the method according to the invention provided on the substrate surface. The monomolecular film features a coating film that is provided with straight chain molecules containing hydrophylic groups chemically bonded via siloxane bonds. A preferred structure is that the hydrophilic group is at least one functional group selected from the group consisting of -OH, -COOH, -NH 2 , -N + R 3 X - (R representing an lower alkyl group, X representing a halogen atom), -NO 2 and -SO 3 H groups. Further, in the above structure the hydrogen atom of the -COOH or -SO 3 H group is preferably substituted by an alkali metal, an alkaline earth metal or other metals. For example, an alkali metal selected from lithium, sodium, potassium, rudidium, cesium, francium, an alkaline earth metal selected from beryllium, magnesium, calsium, strontium, barium, radium, and other metals selected from chromium, manganese, iron, cobalt, nickel , copper, zirconium etc. Further, with the above structure of the fog-proof substrate in which straight chain molecules containing hydrophilic functional groups are secured via siloxane bonds to the substrate surface of the optical material, when condensation forms on the surface, water drops wet the substrate surface and do not produce fog which extends over the entire surface. Further, since the monomolecular film is chemically adsorbed, it does not separate. Further, since it has a thickness at the nanometer level, it is excellently transparent, does not interfere with the optical performance of the substrate and may be made excellently durable. Further, when it is desired to provide a water-repelling property in addition to hydrophilic property, fluorine atoms are introduced in advance. More particularly, a fluorine-containing monomolecular film is formed on a substrate surface via siloxane bonds, and hydrophilic groups are secured to the surface of the chemically adsorbed film. It is thus possible to further improve the hardness of the chemically adsorbed film. The chlorosilane-based surface active material capable of use according to the invention is not limited to those in the form of a straight chain as noted above. It is possible to use a branched alkyl fluoride or hydrocarbon group or those having a substituted alkyl fluoride or hydrocarbon group with silicon at one end (i.e., those represented by the formula R 2 S i C l 2 , R 3 S i C l , R 6 R 7 S i Cl 2 or R 6 R 7 R 8 S i C l, where R, R 6 , R 7 and R 8 represents an fluorocarbon group or hydrocarbon group). To increase the adsorption density, however, the straight chain form is preferred. Further, by chemically adsorbing a material having chlorosilyl groups, e.g., SiCl 4 , SiHCl 3 , SiH 2 Cl 2 , and Cl ( SiCl 2 O)n Cl 3 (where n represents an integer in a range from 1 to 20), for forming an inner layer, and then reacting it with water, surface chlorosilyl bonds are converted to hydrophilic silanol bonds, thus making the hydrophilic monomolecular on the substrate before making the hydrophilic monolayer. Among the materials containing chlorosilyl groups, tetrachlorosilane (SiCl 4 ) is preferred in that it is highly reactive and low in molecular weight. It can, therefore, provide silanol bonds at a high density. In this way, it is possible to make a substrate highly hydrophilic. Moreover to this surface, a chlorosilane-based surface active material containing fluorocarbon groups may be chemically adsorbed. In this way, a chemically adsorbed film suitably having an increased density can be obtained. Any substrate may be used which contains -OH, -COOH, -NH 2 , =NH or other hydrophilic groups at its surface. A substrate such as a plastic film containing relatively few hydroxyl groups at the surface, may be chemically treated by means such as ozone oxidation, plasma treatment, corona treatment, or electron beam irradiation to obtain a substrate containing increased hydrophilic groups and which are suitable for the invention. Polyamide resins and polyurethane resins have surface imino groups (=NH) and therefore do not require any pre-treatment. Since the surface active material reacts with water, the non-aqueous organic solvent to be used according to the invention may have as low a water content as possible and sufficiently dissolves the surface active material. Examples are those solvents which have long chain alkyl groups, aromatic hydrocarbons, saturated ring compound and halogen-containing hydrocarbons. Example 1 As shown in Figure 1 (a), a hydrophilic poly(ethylene terephthalate) film substrate 211 was prepared. The substrate sarface was oxidized. The surface may be oxidized, for example, to be hydrophilic by treating with dichromic acid. After drying well, the substrate was dipped and held for about two hours in a freon 113 solution.. The solution was prepared by dissolving a chemical adsorbed material having two trichlorosilyl groups at molecule ends, for example Cl 3 Si (CH 2 ) 2 (CF 2 ) 6 (CH 2 ) 2 SiCl 3 to a concentration of about 2 wt. %. Since the surface of the glass substrate 211 contained many hydroxyl groups 212, a dehydrochlorination reaction was thus brought about between -SiCl groups at either end of molecules of the chemical adsorbed material, producing bonds represented by the formula [48] over the entire substrate surface. Subsequently, the substrate was washed well using an organic solvent (i.e., freon 113) to remove excess chemical adsorbed material remaining on its surface, and then washed with water and dried. As a result, a siloxane-based monomolecular layer represented by the formula [49] was formed such that it was secured by chemical bonds (or covalent bonds) to the substrate surface. The chemical bond is via a siloxane bond. The formation of the chemically adsorbed monomolecular film 213 was confirmed by FTIR spectroscopy and the thickness was about 1.5 nanometers (nm), as shown in Figure 1 (b). It was firmly bonded such that it did not separate. By subsequently carrying out the steps, from the chemical adsorption step to the water washing and drying step, a di-molecular layer 214 as shown in Figure 1 (c) was obtained. The formation of the chemically adsorbed monomolecular film was confirmed by FTIR spectroscopy and the thickness was about 3.0 nanometers (nm). It was firmly bonded such that it did not separate. Likewise, by repeating the steps from the chemical adsorption step to the water washing and dry step for a required number of layers, a laminated monomolecular chemically adsorbed film based on fluorocarbon was obtained, the surface of which was covered by hydroxyl groups, and which was a little hydrophilic, fog-proof, oil-repelling and had a very high adhesion. While in the above the Examples, Cl 3 Si (CH 2 ) 2 (CF 2 ) 6 (CH 2 ) 2 SiCl 3 were used, other compounds may be used as well. Examples of such compounds are Cl 3 Si (CH 2 ) 2 (CF 2 ) 8 (CH 2 ) 2 SiCl 3 , and Example 2 As shown in Figure 2 (a), a hydrophilic glass substrate 211 was prepared. After drying well, the substrate was dipped and held for about two hours in a solution of 80 wt. % n-hexadecane (or toluene or xylene or bicyclohexyl), 12 wt. % of carbon tetrachloride and 8 wt. % chloroform, the solution being a chemical adsorbed material containing 1 wt. % of the molecule of which had a trichlorosilyl group at one end and had a vinyl group at the other end; for example: CH 2 = CH - (CF 2 ) 6 - (CH 2 ) 2 SiCl 3 Since the surface of the ceramic substrate contained many hydroxyl groups 212, a dehydrochlorination reaction was brought about between -SiCl groups of the chemical adsorbed material and hydroxyl groups of the substrate surface. A monomolecular layer represented by the formula [49]: was formed over the entire substrate surface. The substrate was then washed with freon 113 to remove the unreacted material remaining on the surface, followed by washing with water or exposing to air containing moisture. The -SiCl group was changed to a -SiOH group as in formula [50]. Each silanol group (-SiOH) was then dehydrated and crosslinked to form a siloxane bond (-SiO-) after drying as in formula [51]. Drying temperature may be room temperature or above. An adsorbed monomolecular film 215 was obtained on the surface of the substrate as shown Figure 2(b). The adsorbed monomolecular film has a fluorocarbon group and is chemically bonded (i.e., covalently bonded) to the substrate. The chemical bond is via a siloxane bond. The formation of the chemically adsorbed monomolecular film was confirmed by FTIR spectroscopy and the thickness was about 1.5 nanometers (nm). It was firmly bonded such that it did not separate. The substrate was irradiated with an energy beam such as an electron beam, an ion beam, gamma rays or ultraviolet ways in a reactive gas atmosphere (for instance irradiated with about 5 Mrads. of an electron bean in air). As a result, a monomolecular layer 216 represented by formulas [52] to [54]: was formed such that it was chemically bonded to the surface, as shown in Figure 2 (c). By carrying out the steps from the chemical adsoprtion step using CH 2 = CH - (CF 2 ) 6 - (CH 2 ) 2 SiCl 3 to the water washing step, a di-molecular film 217 containing fluorocarbon groups as shown in Figure 2 (d) was obtained. Likewise, by repeating the steps from the chemical adsorption step to the energy beam irradiation step for a desired number of layers, a laminated chemically adsorbed monomolecular film was obtained, the surface of which was covered by hydroxyl groups and/or imino groups, and which was a little hydrophilic and oil-repelling and had a very high adhesion. Example 3 As shown in Figure 3(a), a polycarbonate substrate having a thickness of 1.2 mm and a diameter of 60 mm was fixed to another polycarbonate substrate using a UV-setting adhesive. The substrate thus obtained was oxygen plasma treated in a UV dry stripper ("UV-1" manufactured by Samco International Co.) at an oxygen flow rate of 1 liter/min. for 10 minutes to oxidize the surface. The substrate was dipped and held in a freon 113 solution containing the chemical adsorbed material: HSi (CH 3 ) 2 (CH 2 ) 2 (CF 2 ) 6 (CH 2 ) 2 SiCl 3 at a concentration of about 2 wt. %. Since the surface of the hydrophilic substrate contained many hydroxyl groups 212, a dehydrochlorination reaction was brought about between -SiCl groups of the chemical adsorbed material and hydroxyl groups of the substrate surface. A monomolecular layer as represented by formula [55]: was formed over the entire substrate surface. The substrate was then washed well with an organic solvent (i.e., freon 113) to remove non-reacted chemical adsorbed material remaining on its surface. A laminated chemically adsorbed monomolecular film 218 based on fluorocarbon was obtained by the formula [56] which had its surface covered by -SiH groups, as shown in Figure 3(b). The substrate was treated for about 10 hours with a H 2 O 2 solution containing KF, KHCO 3 , MeOH and THF. A monomolecular layer 219 represented by the formula [57] was thus formed such that it was chemically bonded to the surface, as shown in Figure 3(c). By subsequently carrying out the steps from the chemical adsorption step using HSi (CH 3 ) 2 (CH 3 ) 2 (CF 2 ) 6 (CH 2 ) 2 SiCl 3 to the H 2 O 2 treatment step, a laminated molecular film 220 containing carbon fluoride groups shown in Figure 3(d) was obtained. Likewise, by repeating the steps from the chemical adsorption step to the H 2 O 2 treatment step for a desired number of layers, a laminated chemically adsorbed monomolecular film based on fluorocarbon could be obtained, which had its surface covered by hydroxyl groups, was a little hydrophilic and oil-repelling and had a very high adhesion. By using Cl 3 Si (CH 2 ) 2 (CF 2 ) 6 (CH 2 ) 2 SiCl 3 in the last chemical adsorption step in the above example, a laminated chemically adsorbed monomolecular film based on fluorocarbon, the surface of which is fog-proof, water- and oil-repelling, and transparent can be obtained. That is, since the fluorine-containing monomolecular film is formed on a substrate surface via siloxane bonds (or covalent bonds), it is excellently scratch-proof, wear-resistant, fog-proof and oil-repelling. Further, since many hydrophilic groups are secured to the surface of chemically adsorbed monomolecular film, excellent fog-proof and oil-repelling properties can be obtained. Further, with the preferred structure according to the invention, a laminated chemically adsorbed film containing fluorine is formed, and an excellently oil-repelling film can be obtained. Further, with the method of manufacture according to the invention a fog-proof and oil-repelling monomolecular film according to the invention can be manufactured efficiently and effectively. Further, by repeatedly carrying out the method of manufacture, a laminated film can be obtained efficiently. Further, with the method of manufacture according to the invention; a fog-proof oil-repelling laminated monomolecular film can be manufactured efficiently and logically. As has been shown, the invention is greatly beneficial to industry.

Claims: A method of manufacturing a hydrophilic chemically adsorbed film comprising: (a) contacting a substrate containing hydrophilic groups with a non-aqueous solution containing a fluorocarbon-based surface active material having chlorosilyl groups at both molecular ends to cause a reaction between hydroxyl groups on said substrate surface and chlorosilyl groups at one molecular end of said fluorocarbon-based surface active material, and (b) washing with a non-aqueous organic solution and reacting with water, thereby forming on said substrate a chemically adsorbed film having hydroxyl groups secured to the substrate surface via the chemically adsorbed fluorocarbon-based material The method of manufacturing a hydrophilic chemically adsorbed film according to claim 1, wherein said fluorocarbon-based surface active material containing the chlorosilyl groups at both molecular ends is represented by the formula X p Cl 3-p SiR 1 (CF 2 ) n R 2 SiX q Cl 3-q wherein n represents an integer, R 1 and R 2 represent an alkylene group or a substitute group containing an Si or oxygen atom, X represents a hydrogen atom, an alkyl or an alkoxyl group substitution group, and p and q represent 1 or 2. A method of manufacturing a hydrophilic chemically adsorbed film comprising: (i) contacting a substrate containing hydrophilic groups with a non-aqueous solution containing a surface active material having a chlorosilyl group at one molecular end and a reactive functional unsaturated group at the other molecular end to cause a reaction between hydroxyl groups of said substrate surface and chlorosilyl groups at one molecular end of said surface active material, (ii) removing non-reacted surface active material remaining on said substrate by washing with a non-aqueous organic solution, thereby forming a chemically adsorbed inner layer film on said substrate, (iii) converting reactive functional groups on the surface of said inner layer film into groups which are reactive with the chlorosilyl group, (iv) contacting the substrate with a non-aqueous solution containing a fluorocarbon-based surface active material containing chlorosilyl groups at opposite ends to cause a reaction between active groups of said inner layer film and chlorosilyl groups at one molecular end of said fluorocarbon-based surface active material, and (v) removing non-reacted fluorocarbon-based surface active material remaining on said substrate by washing with a non-aqueous organic solution and then reacting with water, thereby forming a laminated fluorocarbon-based chemically adsorbed film bonded to said inner layer film.

Inventors: MINO NORIHISA, OGAWA KAZUFUMI, SOGA MAMORU, MINO, NORIHISA, OGAWA, KAZUFUMI, SOGA, MAMORU
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD
Application year: 1992
Main classification: B29D11
IPC codes: G02B1, B05D1