the surface treatment agents for medical devices of the present invention contain a copolymer of a hydrophilic functional group - containing monomer and an epoxy group - containing monomer . by chemically fixing such a copolymer to the surface of a medical device such as a catheter , it is possible to give it not only lubricity but also resistance to lubricity reduction ( i . e ., lubricant durability ). in the present invention , the constituent hydrophilic functional group - containing monomer of the copolymer is not particularly limited , and any monomers with various hydrophilic groups can be used . the hydrophilic functional group - containing monomer may suitably be a deliquescent monomer , i . e ., a monomer having properties of spontaneously absorbing moisture ( water vapor ) from the air and forming an aqueous solution . the hydrophilic functional group of the hydrophilic functional group - containing monomer is preferably a polyoxyalkylene group , a metal salt - containing hydrophilic group , a halogen salt - containing hydrophilic group , a zwitterionic group or the like in view of lubricity and its durability . suitable examples of the polyoxyalkylene group - containing monomer include compounds represented by the following formula ( i ): wherein ao groups are the same as or different from one another and each represent an oxyalkylene unit ; r 11 represents a hydrogen atom or a methyl group ; p represents an integer of 1 to 50 ; and r 12 represents a hydrogen atom or a c1 to c20 alkyl group . the number of carbon atoms in each oxyalkylene unit ( ao ) is preferably 2 to 4 ( e . g ., oxyethylene unit , oxypropylene unit , oxytetramethylene unit ). when different oxyalkylene units are present , they may be attached in blocks , randomly , or in an alternating fashion . examples of c1 to c20 alkyl groups for r 12 include linear or branched groups such as methyl , ethyl , and propyl groups . specific examples of the polyoxyalkylene group - containing monomer include methoxypolyethylene glycol mono ( meth ) acrylate , polyethylene glycol mono ( meth ) acrylate , methoxypolypropylene glycol mono ( meth ) acrylate , polypropylene glycol mono ( meth ) acrylate , ethylene glycol - propylene glycol ( meth ) acrylate , and poly ( ethylene glycol - propylene glycol ) mono ( meth ) acrylate . suitable examples of the metal salt - containing hydrophilic group - containing monomer include monomers containing an alkali metal salt - containing hydrophilic group or an alkaline earth metal salt - containing hydrophilic group ( alkali metal salt - containing monomers and alkaline earth metal salt - containing monomers ). examples of alkali metal salt - containing monomers include alkali metal salts of acrylic acid such as sodium acrylate and potassium acrylate ; alkali metal salts of methacrylic acid such as sodium methacrylate and potassium methacrylate ; alkali metal salts of itaconic acid such as sodium itaconate and potassium itaconate ; alkali metal salts of 3 - vinylpropionic acid such as sodium 3 - vinylpropionate and potassium 3 - vinylpropionate ; alkali metal salts of vinylsulfonic acid such as sodium vinylsulfonate and potassium vinylsulfonate ; alkali metal salts of 2 - sulfoethyl ( meth ) acrylate such as sodium 2 - sulfoethyl ( meth ) acrylate and potassium 2 - sulfoethyl ( meth ) acrylate ; alkali metal salts of 3 - sulfopropyl ( meth ) acrylate such as sodium 3 - sulfopropyl ( meth ) acrylate and potassium 3 - sulfopropyl ( meth ) acrylate ; alkali metal salts of 2 - acrylamide - 2 - methylpropanesulfonic acid such as sodium 2 - acrylamide - 2 - methylpropanesulfonate and potassium 2 - acrylamide - 2 - methylpropanesulfonate ; and alkali metal salts of styrenesulfonic acid such as sodium styrenesulfonate and potassium styrenesulfonate . examples of alkaline earth metal salt - containing monomers include alkaline earth metal salt - containing monomers that correspond to the aforementioned alkali metal salt - containing monomers . in particular , alkali metal salts of ( meth ) acrylic acid are preferred , and potassium 3 - sulfopropyl methacrylate is particularly preferred . suitable examples of the halogen salt - containing hydrophilic group - containing monomer include monomers containing a chlorine salt - or bromine salt - containing hydrophilic group ( chlorine salt - containing monomers and bromine salt - containing monomers ). in particular , preferred are compounds represented by the following formula ( ii ) and the like : wherein a represents an oxygen atom or nh ; b represents a c1 to c4 alkylene group ; r 21 represents a hydrogen atom or a methyl group ; r 22 , r 23 and r 24 are the same as or different from one another and each represent a c1 to c4 alkyl group ; and x − represents a halogen ion . a is preferably an oxygen atom . examples of b include linear or branched alkylene groups such as methylene , ethylene , and propylene groups . methylene and ethylene groups are preferred among these . examples of r 22 to r 24 include linear or branched alkyl groups such as methyl , ethyl , and propyl groups . methyl and ethyl groups are preferred among these . examples of x ( halogen atom ) include fluorine , chlorine , and bromine . chlorine is preferred among these . examples of halogen salt - containing hydrophilic group - containing monomers represented by the formula ( ii ) include 2 -( methacryloyloxy ) ethyl trimethylammonium chloride ( 2 -( methacryloyloxy ) ethyl trimethylaminium chloride ), 2 -( acryloyloxy ) ethyl trimethylammonium chloride ( 2 -( acryloyloxy ) ethyl trimethylaminium chloride ), 2 -( methacryloyloxy ) ethyl dimethylethylammonium chloride ( 2 -( methacryloyloxy ) ethyl dimethylethylaminium chloride ), and 2 -( acryloyloxy ) ethyl dimethylethylammonium chloride ( 2 -( acryloyloxy ) ethyl dimethylethylaminium chloride ). examples of the zwitterionic group - containing monomer ( zwitterionic group - containing compound : compound bearing a center of permanent positive charge and a center of negative charge ) include various zwitterionic monomers such as carboxybetaines , sulfobetaines , and phosphobetaines . other examples include compounds represented by formula ( iii ) below , and in particular compounds represented by formula ( iv ) below are suitable . in the formula , r 31 represents — h or — ch 3 ; x represents — o —, nh — or n + —; m represents an integer of 1 or greater ; and y represents a zwitterionic group or a halogen group ( e . g . cl − , br − , f − ). in the formula ( iii ), r 31 is preferably — ch 3 , x is preferably — o —, and m is preferably an integer of 1 to 10 . in the zwitterionic group designated by y , the cation may be a quaternary ammonium cation such as tetraalkylammonium , and the anion may be a carboxylate , sulfonate , phosphate or the like anion . in the formula , r 31 represents — h or — ch 3 ; p and q each represent an integer of 1 or greater ; and y 1 and y 2 are ionic functional groups with opposite charges . in the formula ( iv ), p is preferably an integer of 2 or greater , and more preferably an integer of 2 to 10 ; and q is preferably an integer of 1 to 10 , and more preferably an integer of 2 to 4 . moreover , preferred r 31 is the same as described above . y 1 and y 2 are as described for the cation and anion above . typical suitable examples of the zwitterionic monomer include compounds represented by the following formulae ( iv - 1 ) to ( iv - 4 ): wherein r 31 represents a hydrogen atom or a methyl group ; and p and q each represent an integer of 1 to 10 , wherein r 31 represents a hydrogen atom or a methyl group ; and p and q each represent an integer of 1 to 10 , wherein r 31 represents a hydrogen atom or a methyl group ; r 32 represents a c1 to c6 hydrocarbon group ; and p and q each represent an integer of 1 to 10 , wherein r 31 represents a hydrogen atom or a methyl group ; r 33 , r 34 and r 35 are the same as or different from one another and each represent a c1 or c2 hydrocarbon group ; and p and q each represent an integer of 1 to 10 . examples of compounds represented by the formula ( iv - 1 ) include dimethyl ( 3 - sulfopropyl )( 2 -( meth ) acryloyloxyethyl )- ammonium betaine . examples of compounds represented by the formula ( iv - 2 ) include dimethyl ( 2 - carboxyethyl )-( 2 -( meth ) acryloyloxyethyl ) ammonium betaine . examples of compounds represented by the formula ( iv - 3 ) include dimethyl ( 3 - methoxyphosphopropyl )( 2 -( meth ) acryloyloxyethyl )- ammonium betaine . examples of compounds represented by the formula ( iv - 4 ) include 2 -( meth ) acryloyloxyethyl phosphorylcholine . other zwitterionic monomers include 2 -( meth ) acryloyloxyethyl carboxybetaine and 2 -( meth ) acryloyloxyethyl sulfobetaine . the hydrophilic functional group - containing monomer may also be a quaternary ammonium salt monomer represented by the following formula : wherein a represents an oxygen atom or nh ; b and d are the same as or different from each other and each represent a c1 to c4 alkylene group ; r 41 represents a hydrogen atom or a methyl group ; and r 42 and r 43 are the same as or different from each other and each represent a c1 to c4 alkyl group . a is preferably an oxygen atom . examples of b and d include linear or branched alkylene groups such as methylene , ethylene , and propylene groups . methylene and ethylene groups are preferred among these . examples of r 42 and r 43 include those described above for r 22 to r 24 . examples of the quaternary ammonium salt monomer include [ 2 -( methacryloyloxy ) ethyl ] dimethyl -( 3 - sulfopropyl ) ammonium hydroxide . the hydrophilic functional group - containing monomers may be used alone or in combinations of two or more . the constituent epoxy group - containing monomer of the copolymer in the present invention may be , for example , an epoxy group - containing polymerizable vinyl monomer containing an epoxy group and a polymerizable carbon - carbon double bond in the molecule . examples of the epoxy group - containing polymerizable vinyl monomer include epoxy group - containing ( meth ) acrylic acid ester monomers and epoxy group - containing ether monomers . examples of epoxy group - containing ( meth ) acrylic acid ester monomers include epoxy group - containing ( meth ) acrylic acid esters , specifically glycidyl ( meth ) acrylate , hydroxybutyl acrylate glycidyl ether and 2 - methyloxiranylmethyl ( meth ) acrylate . examples of epoxy group - containing ether monomers include epoxy group - containing linear , branched or cyclic aliphatic ether monomers such as vinyl glycidyl ether , allyl glycidyl ether , isopropenyl glycidyl ether , and 4 - vinylcyclohexyl glycidyl ether ; and epoxy group - containing aromatic ether monomers such as 3 - vinylbenzyl glycidyl ether and 4 - vinylbenzyl glycidyl ether . in view of lubricity and its durability , epoxy group - containing ( meth ) acrylic acid ester monomers are preferred among these , and glycidyl ( meth ) acrylate is particularly preferred . the epoxy group - containing monomers may be used alone or in combinations of two or more . the copolymer of a hydrophilic functional group - containing monomer and an epoxy group - containing monomer can be produced by known radical polymerization processes . the copolymerization may be carried out by any process , such as , for example , known photo - or thermally - induced radical polymerization processes . specifically , a photopolymerization initiator , a hydrophilic functional group - containing monomer and an epoxy group - containing monomer may be charged in liquid form or in the form of a solution into a transparent vessel made of glass , pet , polycarbonate or the like , followed by irradiation with uv light to allow radical polymerization ( photo - radical polymerization ) to proceed , whereby the copolymer can be prepared . the radical - polymerizable monomers ( in liquid form ) or solution thereof may contain a known polymerization inhibitor such as 4 - methylphenol . examples of polymerization initiators include carbonyl compounds , organic sulfur compounds such as tetraethylthiuram disulfide , persulfides , peroxides , redox compounds , azo compounds , diazo compounds , halogen compounds , and photoreducing dyes . among these , carbonyl compounds , peroxides , and azo compounds are preferred . preferred among carbonyl compounds serving as initiators for photo - induced radical polymerization are benzophenone and derivatives thereof ( benzophenone compounds ). for example , suitable are benzophenone compounds represented by the following formula : wherein r 1 to r 5 and r 1 ′ to r 5 ′ are the same as or different from one another and each represent a hydrogen atom , an alkyl group , a halogen ( fluorine , chlorine , bromine , iodine ), a hydroxyl group , a primary , secondary , or tertiary amino group , a mercapto group , or a hydrocarbon group that may contain an oxygen , nitrogen , or sulfur atom , and any two adjacent groups of r 1 to r 5 and r 1 ′ to r 5 ′ may be joined to each other to form a ring together with the carbon atoms to which they are attached . specific examples of the benzophenone compound include benzophenone , xanthone , 9 - fluorenone , 2 , 4 - dichlorobenzophenone , methyl o - benzoylbenzoate , 4 , 4 ′- bis ( dimethylamino ) benzophenone , and 4 , 4 ′- bis ( diethylamino ) benzophenone . particularly preferred among these are benzophenone , xanthone , and 9 - fluorenone because these compounds allow polymer brushes to be formed well . the initiator for photo - induced radical polymerization may also suitably be a thioxanthone compound because it provides a high polymerization rate and can easily be adsorbed on and / or reacted with rubber or the like . for example , suitable are compounds represented by the following formula : wherein r 6 to r 9 and r 6 ′ to r 9 ′ are the same as or different from one another and each represent a hydrogen atom , a halogen atom , or an alkyl , cyclic alkyl , aryl , alkenyl , alkoxy , or aryloxy group . examples of thioxanthone compounds represented by the above formula include thioxanthone , 2 - isopropylthioxanthone , 4 - isopropylthioxanthone , 2 , 3 - diethylthioxanthone , 2 , 4 - diethylthioxanthone , 2 , 4 - dichlorothioxanthone , 2 - methoxythioxanthone , 1 - chloro - 4 - propoxythioxanthone , 2 - cyclohexylthioxanthone , 4 - cyclohexylthioxanthone , 2 - vinylthioxanthone , 2 , 4 - divinylthioxanthone , 2 , 4 - diphenylthioxanthone , 2 - butenyl - 4 - phenylthioxanthone , and 2 - p - octyloxyphenyl - 4 - ethylthioxanthone . preferred among these are those which are substituted at one or two , especially two , of r 6 to r 9 and r 6 ′ to r 9 ′ with alkyl groups . more preferred is 2 , 4 - diethylthioxanthone . light irradiation allows radical polymerization of the monomers to proceed . here , ultraviolet light sources with an emission wavelength mainly in the ultraviolet region , such as high - pressure mercury lamps , metal halide lamps , and led lamps , can be suitably used . the light dose may be appropriately chosen in view of polymerization time and uniform progress of the reaction . moreover , in order to prevent inhibition of polymerization due to active gas such as oxygen in the reaction vessel and the reaction tube , oxygen is preferably removed from the reaction vessel , the reaction tube and the reaction solution during or before the light irradiation . to this end , appropriate operations may be performed . for example , an inert gas such as nitrogen gas or argon gas is inserted into the reaction vessel , the reaction tube and the reaction solution to discharge active gas such as oxygen from the reaction system and replace the atmosphere in the reaction system with the inert gas . moreover , in order to prevent inhibition of the reaction due to oxygen or the like , for example , a measure may appropriately be taken in which an ultraviolet light source is placed such that no air layer ( oxygen content : 15 % or higher ) exists between the reaction vessel made of glass , plastics or the like and the reaction solution or the modification target . the ultraviolet wavelength suitably ranges from 300 to 400 nm . such a wavelength allows a polymer to be formed well . examples of light sources that can be used include high - pressure mercury lamps , leds with a center wavelength of 365 nm , and leds with a center wavelength of 375 nm . more preferred is irradiation with led light having a wavelength of 355 to 380 nm . in particular , leds or the like having a center wavelength of 365 nm , which is close to the excitation wavelength ( 366 nm ) of benzophenone , are preferred in view of efficiency . light with a wavelength of 300 nm or longer is preferred , with light having a wavelength of 355 nm or longer being more preferred . light having a wavelength of longer than 400 nm , however , is less likely to activate the photopolymerization initiator , with the result that the polymerization reaction is not allowed to easily proceed . thus , light having a wavelength of 400 nm or shorter is preferred . although led light is suitable in that it is in a narrow wavelength range and does not include light with other wavelengths than the center wavelength , a mercury lamp or the like can also achieve similar effects to led light by using a filter to block light having a wavelength of shorter than 300 nm . preferred among initiators for thermally - induced radical polymerization are peroxides and azo compounds . “ peroxide ” refers to those containing a — o — o — group , and examples include peroxyesters , peroxyketals , dialkyl peroxides , diacyl peroxides , and peroxycarbonates . in particular , organic peroxides such as benzoyl peroxide ( bpo ) and lauroyl peroxide ( lpo ) are preferred . “ azo compound ” refers to those containing a — n ═ n — group , and examples include 2 , 2 ′- azobis ( 4 - methoxy - 2 , 4 - dimethylvaleronitrile ), 2 , 2 ′- azobis ( 2 , 4 - dimethylvaleronitrile ), 2 , 2 ′- azobis ( isobutyronitrile ) ( aibn ), 2 , 2 ′- azobis ( 2 - methylbutyronitrile ), 1 , 1 ′- azobis ( cyclohexane - l - carbonitrile ), 1 -[( 1 - cyano - 1 - methylethyl ) azo ] formamide , 2 , 2 ′- azobis [ 2 -( 2 - imidazolin - 2 - yl ) propane ] dihydrochloride , 2 , 2 ′- azobis [ 2 -( 2 - imidazolin - 2 - yl ) propane ] disulfate dihydrate , 2 , 2 ′- azobis [ 2 -( 2 - imidazolin - 2 - yl ) propane ], 2 , 2 ′- azobis ( 2 - amidinopropane ) dihydrochloride , and 2 , 2 ′- azobis [ n -( 2 - carboxyethyl )- 2 - methylpropionamidine ] n - hydrate . among these , azobisisobutyronitrile ( aibn ) and the like are preferred . in addition to the copolymer prepared , for example , as described above , the surface treatment agents for medical devices of the present invention may contain additional components such as a solvent in amounts that do not impair the effects . examples of objects ( medical devices ) to be treated with the surface treatment agents for medical devices include thermoplastic elastomers such as nylon , polyester , and polyurethane , and dynamically crosslinked thermoplastic elastomers prepared from these elastomers . examples of nylon include nylon 6 , nylon 66 , nylon 11 , and nylon 12 . moreover , the dynamically crosslinked thermoplastic elastomer is preferably obtained by dynamically crosslinking a halogenated butyl rubber in a thermoplastic elastomer . in this case , the thermoplastic elastomer is preferably nylon , polyurethane , or the like . medical devices of the present invention can be prepared by treating the surface of a medical device with the surface treatment agent described above , and examples include those obtained by at least partially treating the outer surface and / or inner surface of a medical device with the surface treatment agent . the treatment with the surface treatment agent may be carried out by any method that allows the surface treatment agent to make contact with the surface of a medical device , and examples include a method in which the treatment agent is fixed to the surface of a medical device by coating , spraying , immersion or the like . in particular , for fixing on the surface , the surface treatment is preferably carried out with the aid of heat and / or an acid . the treatment with heat maybe carried out , for example , at 80 ° c . to 130 ° c . for 10 minutes to 10 hours . the treatment with an acid may be carried out using an inorganic or organic acid or the like appropriately chosen for fixing and the like . the treatment is preferably applied to an area that requires lubricity , and the treatment may be applied to the entire surface . particularly preferred examples of medical devices of the present invention are catheters , and the present invention gives them not only lubricity but also lubricant durability . the present invention is more specifically described with reference to examples below . the present invention is , however , not limited to these examples . to a solution mixture of 5 ml of water and 4 ml of ethanol were added 0 . 65 g of an 80 % aqueous solution of trimethyl - 2 - methacryloyloxyethyl ammonium chloride ( an 80 % aqueous solution of 2 -( methacryloyloxy ) ethyl trimethylammonium chloride ) and 0 . 36 g of glycidyl methacrylate . to this was added 1 ml of a solution of benzophenone in methanol ( 2 mg / 10 ml methanol ), and the mixture was put in a 20 - ml vial . the vial was covered with a lid and purged with a flow of ar gas . then , polymerization was carried out with stirring by irradiation from a 365 nm uv - led ( 5 mw / cm 2 ) ( irradiation time : 6 hours ). the surface of a tube made of nylon 12 was coated with the resulting polymer and held at 100 ° c . for 5 hours to fix the polymer . thus , a surface - treated tube was prepared . to a solution mixture of 5 ml of water and 4 ml of ethanol were added 0 . 91 g of an 80 % aqueous solution of trimethyl - 2 - methacryloyloxyethyl ammonium chloride and 0 . 21 g of glycidyl methacrylate . to this was added 1 ml of a solution of benzophenone in methanol ( 2 mg / 10 ml methanol ), and the mixture was put in a 20 - ml vial . the vial was covered with a lid and purged with a flow of ar gas . then , polymerization was carried out with stirring by irradiation from a 365 nm uv - led ( 5 mw / cm 2 ) ( irradiation time : 3 hours ). the surface of a tube made of nylon 12 was coated with the resulting polymer and held at 100 ° c . for 5 hours to fix the polymer . thus , a surface - treated tube was prepared . to a solution mixture of 5 ml of water and 4 ml of ethanol was added 0 . 91 g of an 80 % aqueous solution of trimethyl - 2 - methacryloyloxyethyl ammonium chloride . to this was added 1 ml of a solution of benzophenone in methanol ( 2 mg / 10 ml methanol ), and the mixture was put in a 20 - ml vial . the vial was covered with a lid and purged with a flow of ar gas . then , polymerization was carried out with stirring by irradiation from a 365 nm uv - led ( 5 mw / cm 2 ) ( irradiation time : 2 . 5 hours ). thereafter , 0 . 21 g of glycidyl methacrylate dissolved in 1 . 5 ml of water and 1 ml of ethanol was added , and the resulting mixture was further subjected to irradiation from a uv - led ( 5 mw / cm 2 ) for 1 hour . the surface of a tube made of nylon 12 was coated with the resulting polymer and held at 100 ° c . for 5 hours to fix the polymer . thus , a surface - treated tube was prepared . to a solution mixture of 5 ml of water and 4 ml of ethanol were added 0 . 62 g of potassium 3 -( methacryloyloxy ) propanesulfonate ( potassium 3 - sulfopropyl methacrylate ) and 0 . 36 g of glycidyl methacrylate . to this was added 1 ml of a solution of benzophenone in methanol ( 2 mg / 10 ml methanol ), and the mixture was put in a 20 - ml vial . the vial was covered with a lid and purged with a flow of ar gas . then , polymerization was carried out with stirring by irradiation from a 365 nm uv - led ( 5 mw / cm 2 ) ( irradiation time : 3 hours ). the surface of a tube made of nylon 12 was coated with the resulting polymer and held at 100 ° c . for 5 hours to fix the polymer . thus , a surface - treated tube was prepared . to a solution mixture of 5 ml of water and 4 ml of ethanol were added 0 . 71 g of [ 2 -( methacryloyloxy ) ethyl ] dimethyl -( 3 - sulfopropyl ) ammonium hydroxide and 0 . 36 g of glycidyl methacrylate . to this was added 1 ml of a solution of benzophenone in methanol ( 2 mg / 10 ml methanol ), and the mixture was put in a 20 - ml vial . the vial was covered with a lid and purged with a flow of ar gas . then , polymerization was carried out with stirring by irradiation from a 365 nm uv - led ( 5 mw / cm 2 ) ( irradiation time : 3 hours ). the surface of a tube made of nylon 12 was coated with the resulting polymer and held at 100 ° c . for 5 hours to fix the polymer . thus , a surface - treated tube was prepared . an amount of 5 . 8 g of trimethyl - 2 - methacryloyloxyethyl ammonium chloride and 1 . 07 g of glycidyl methacrylate were dissolved in 25 ml of ethanol . to this was added 0 . 05 g of aibn , and the mixture was put in a 20 - ml vial . the vial was covered with a lid and purged with a flow of ar gas . then , the vial was placed in a water bath at 60 ° c ., and polymerization was carried out for 4 hours with stirring . the surface of a tube made of nylon 12 was coated with the resulting polymer and held at 100 ° c . for 5 hours to fix the polymer . thus , a surface - treated tube was prepared . an amount of 5 . 8 g of trimethyl - 2 - methacryloyloxyethyl ammonium chloride and 1 . 07 g of glycidyl methacrylate were dissolved in 25 ml of ethanol . to this was added 0 . 07 g of benzoyl peroxide ( bpo ), and the mixture was put in a 20 - ml vial . the vial was covered with a lid and purged with a flow of ar gas . then , the vial was placed in a water bath at 60 ° c ., and polymerization was carried out for 4 hours with stirring . the surface of a tube made of nylon 12 was coated with the resulting polymer and held at 100 ° c . for 5 hours to fix the polymer . thus , a surface - treated tube was prepared . a tube made of nylon 12 was used as it was . used was a tube made of nylon 12 , the surface of which was coated with a 5 % solution of methyl vinyl ether - maleic anhydride ( gantrez - an 16 , produced by ips ) in methanol . it should be noted that nylon 12 is a material often used in vascular catheters , and methyl vinyl ether - maleic anhydride is a typical lubricant to provide the surface with lubricity . the surface - treated tubes prepared in the examples and comparative examples were evaluated as follows . water was applied to the surface of each tube , and the sliding properties of the surface were then subjectively evaluated by touching with a human finger . the subjective evaluation was carried out by ten persons according to the following rating scale of 1 - 5 : a rating of 5 corresponds to a tube with good sliding properties and a rating of 1 corresponds to a tube with so poor sliding properties that the finger never slides on the surface . the average rating was calculated . after water was applied to the surface of each tube , the tube was held between fingers and moved by sliding on the fingers . this cycle was repeated 100 times . then , the subjective evaluation was again carried out by ten persons according to the rating scale for lubricity , and the average rating and the rate of decrease from the initial lubricity were calculated . table 1 shows that the nylon surfaces in the examples each had high lubricity , good durability , and quite a low rate of decrease in lubricity . in contrast , comparative example 1 had quite poor lubricity ; comparative example 2 , in which a commonly used product was used , had moderately high initial lubricity , but had low durability and quite a high rate of decrease in lubricity . these results demonstrated that by using a surface treatment agent containing a copolymer of a hydrophilic functional group - containing monomer and an epoxy group - containing monomer and fixing the polymer on the surface of a catheter or the like , it is possible to simultaneously give it sufficient lubricity and lubricant durability .
provided are surface treatment agents that enable surfaces with a chemically fixed lubricant to be produced instead of a resin coating which has drawbacks , such as that lubricity is reduced due to separation , peeling or the like of the coating during the movement within a vessel or tube ; and medical devices , such as catheters , having a surface at least partially treated with such a surface treatment agent . the present invention relates to a surface treatment agent for medical devices which contains a copolymer of a hydrophilic functional group - containing monomer and an epoxy group - containing monomer .