Patent Publication Number: US-2021179963-A1

Title: Lubricant for medical device and medical device

Description:
The application is a continuation application based on a PCT Patent Application No. PCT/JP2019/031797, filed Aug. 13, 2019, whose priority is claimed on Japanese Patent Application No. 2018-191189, filed Oct. 9, 2018. The contents of both the PCT Application and the Japanese Application are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a lubricant for a medical device and the medical device. 
     Description of Related Art 
     In recent years, gas low-temperature sterilization has been widely used as sterilization treatment for a medical device. For example, hydrogen peroxide gas is often used as sterilization gas in the gas low-temperature sterilization. 
     Examples of a medical device to be subjected to sterilization treatment include devices, such as an endoscope that is used while being inserted into the body, and endoscopic devices that are used together with an endoscope. In such a medical device, tubular members or shaft-like members are movably inserted into a flexible tube. A lubricant is used in order to facilitate the movement of the tubular members or the shaft-like members in the flexible tube. The lubricant reduces friction between the inner circumference surface of the flexible tube and the tubular members or the shaft-like members. 
     However, there is a possibility that sterilization gas may chemically react with not only bacteria adhering to the medical device but also a lubricant and each member of the medical device. 
     Particularly, lubricants for a medical device often include molybdenum disulfide. Molybdenum disulfide is a solid anti-friction material. Sulfur components contained in molybdenum disulfide are likely to chemically react with sterilization gas components in a gas low-temperature sterilization process. For example, sulfurous acid, sulfuric acid, and the like are generated in a case where molybdenum disulfide chemically reacts with hydrogen peroxide. As a result, the resin, metal, and the like of the respective members of a medical device deteriorate or corrode. 
     For example, Japanese Unexamined Patent Application, First Publication No. H11-318814 discloses a technique in which a material having a catalytic action on hydrogen peroxide or the low-temperature plasma of hydrogen peroxide is used for a structural member of an insertion portion of an endoscope in order to improve the resistance of the insertion portion of the endoscope to hydrogen peroxide. 
     In the Japanese Unexamined Patent Application, examples of a material having a catalytic action on the low-temperature plasma of hydrogen peroxide include silver, copper, nickel, palladium, and platinum. 
     SUMMARY OF THE INVENTION 
     A lubricant for a medical device of a first aspect of the invention includes an anti-friction material and a radical scavenger. 
     A medical device of a second aspect of the invention includes the lubricant for a medical device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view showing the schematic configuration of an endoscope that is an example of a medical device according to an embodiment of the present invention. 
         FIG. 2  is a schematic cross-sectional view of an insertion portion of the endoscope that is an example of the medical device according to the embodiment of the present invention. 
         FIG. 3  is a schematic enlarged view of a portion A of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A lubricant for a medical device and the medical device of embodiments of the present invention will be described below with reference to the accompanying drawings. 
       FIG. 1  is a schematic perspective view showing the schematic configuration of an endoscope that is an example of a medical device according to an embodiment of the present invention.  FIG. 2  is a schematic cross-sectional view of an insertion portion of the endoscope that is an example of the medical device according to the embodiment of the present invention.  FIG. 3  is a schematic enlarged view of a portion A of  FIG. 2 . 
     An endoscope  10  (medical device) of the present embodiment shown in  FIG. 1  is a medical endoscope that is used while being inserted into the body of a patient. Sterilization treatment to be applied to the endoscope  10  is gas low-temperature sterilization. The type of gas low-temperature sterilization treatment is not particularly limited. Examples of gas low-temperature sterilization treatment suitable for the endoscope  10  include hydrogen peroxide low-temperature plasma sterilization, hydrogen peroxide gas low-temperature sterilization, ethylene oxide gas sterilization, and the like. 
     The endoscope  10  includes an insertion portion  11  and an operating portion  12 . 
     The insertion portion  11  is formed in the form of a flexible tube in order to be inserted into the body of a patient. The insertion portion  11  includes a distal end portion  14 , a bending portion  15 , and a flexible tube portion  16  that are arranged in this order from the distal end in an insertion direction. Although not shown in  FIG. 1 , an endoscopic channel (to be described later) extending in the longitudinal direction of the insertion portion  11  is disposed in the insertion portion  11  so that an endoscopic device is inserted into the endoscopic channel. 
     The distal end portion  14  is disposed at a portion that includes the most distal end of the endoscope  10 . The distal end portion  14  includes an end effector of the endoscope  10  that functions as a manipulator. For example, in the present embodiment, an imaging device, such as a CCD, and an imaging optical system including an appropriate lens are provided in the distal end portion  14  in order to acquire the image of an object to be investigated. In the present embodiment, the distal end portion  14  has a columnar appearance. 
     The imaging device is disposed on the image surface of the imaging optical system. The imaging device photoelectrically converts received light to generate image signals. 
     The image signals generated by the imaging device are transmitted to the operating portion  12  to be described later through metal wires. The image signals may be subjected to signal processing as necessary before being transmitted to the operating portion  12 . 
     The metal wires include a signal line and a power line. The signal line supplies a control signal to the imaging device. The power line supplies a drive voltage to the imaging device. The metal wires are put together in a cable. 
     However, the imaging device may be disposed in the operating portion  12  to be described later. In this case, the distal end of an image guide, which transmits a light image to the imaging device, is disposed on the image surface of the imaging optical system. The image guide extends up to the operating portion  12 , in which the imaging device is disposed, via the inside of the bending portion  15  and the flexible tube portion  16  to be described later. A bundle of optical fibers may be used as the image guide. 
     An image acquired by the distal end portion  14  is transmitted as image signals or image light through the metal wires or the bundle of optical fibers in the bending portion  15  and the flexible tube portion  16  to be described later. The metal wires or the bundle of optical fibers form a linear image transmission cable. 
     The distal end of the distal end portion  14  is provided with an imaging window, an illumination window, and an opening  14   a . The opening  14   a  communicates with an endoscopic channel to be described later. 
     The bending portion  15  is connected to the proximal end of the distal end portion  14 . The bending portion  15  is a tubular portion that is adapted to be bendable in order to change the direction of the distal end portion  14 . 
     The bending portion  15  includes, for example, a plurality of annular nodal rings. The plurality of nodal rings are rotatably connected to each other. Operating wires to be described later are inserted into the plurality of nodal rings. 
     For example, linear members, such as electrical wires connected to the imaging device of the distal end portion  14  and a fiber light guide extending up to the illumination window, are accommodated in the bending portion  15 . 
     The linear members, such as the operating wires, the image transmission cable, and the fiber light guide having been described above, are inserted into the flexible tube portion  16  to be described later and extend up to the operating portion  12  to be described later. 
     The bending portion  15  is covered with an outer tube  15   a.    
     The flexible tube portion  16  is a tubular portion that connects the bending portion  15  to the operating portion  12  to be described later. 
     As shown in a cross-section in  FIG. 2 , the flexible tube portion  16  includes a flexible tube  23 . A lumen  23   a  penetrates the flexible tube  23  in the longitudinal direction of the flexible tube  23 . Long built-in elements, such as an endoscopic channel  24  (insertion member), an image transmission cable  25  (insertion member), a fiber light guide  26  (insertion member), and operating wires  27  are inserted into the lumen  23   a  of the flexible tube  23 . 
     The flexible tube  23  includes a flex  22 , a stainless steel blade  21 , and an outer tube  20 . The flex  22 , the stainless steel blade  21 , and the outer tube  20  are arranged in this order from the inner circumference portion of the flexible tube  23  toward the outer circumference portion thereof. 
     The flex  22  is formed of a belt-like member that is made of, for example, metal or a resin and is helically wound. The inner circumference surface of the flex  22  forms an inner circumference surface  23   b  of the flexible tube  23 . The lumen  23   a  is a space inside the inner circumference surface  23   b.    
     The stainless steel blade  21  is formed in the form of a net-like tube that is woven with a stainless steel wire. The stainless steel blade  21  covers the flex  22  from the outer circumference side. The stainless steel blade  21  overlaps the flex  22 . 
     The outer tube  20  is a tubular member made of a soft resin. The outer tube  20  covers the stainless steel blade  21  from the outer circumference side. The outer tube  20  overlaps the stainless steel blade  21 . 
     According to this structure, the flexible tube  23  can be bent in an appropriate direction in a state where the flexible tube  23  maintains a substantially circular cross-section. 
     The endoscopic channel  24  is a tubular member that forms an insertion passage into which an appropriate medical device, for example, an endoscopic device, a catheter, and the like, can be inserted. The distal end of the endoscopic channel  24  penetrates the distal end surface of the distal end portion  14  (see  FIG. 1 ). The distal end of the endoscopic channel  24  forms an opening through which an endoscopic device, a catheter, and the like come in and out. 
     The distal end of the endoscopic channel  24  communicates with the opening  14   a  (see  FIG. 1 ). 
     The proximal end of the endoscopic channel  24  is connected to a forceps valve  12   c  (see  FIG. 1 ) provided on the operating portion  12  to be described later. 
     The endoscopic channel  24  is formed of, for example, a flexible resin tube. The endoscopic channel  24  can be bent together with the flexible tube portion  16 . It is more preferable that a material allowing an endoscopic device, a catheter, and the like being in contact with an inner circumference surface  24   b  of the endoscopic channel  24  to easily slide is selected as the resin material of the endoscopic channel  24 . 
     For example, a polyethylene resin, a fluorine-based resin, a urethane-based resin, and the like may be used as the material of the endoscopic channel  24 . 
     The image transmission cable  25  transmits an image, which is acquired by the imaging optical system of the distal end portion  14 , to the operating portion  12  as image signals or image light. For example, in a case where the image transmission cable  25  transmits image signals, a linear body including a metal wire covered with a flexible resin tube is used as the image transmission cable  25 . For example, in a case where the image transmission cable  25  transmits image light, a linear body including an optical fiber covered with a flexible resin tube is used as the image transmission cable  25 . 
     The fiber light guide  26  supplies illumination light. The illumination light is supplied from the illumination window of the distal end portion  14  in order to illuminate the outside. A structure where an optical fiber transmitting illumination light is covered with a flexible resin tube is used as the fiber light guide  26 . 
     The distal end of the fiber light guide  26  is disposed so as to face the illumination window of the distal end portion  14 . The fiber light guide  26  extends into the flexible tube  23  via the distal end portion  14  and the bending portion  15 . The proximal end of the fiber light guide  26  is optically coupled to a light source disposed in the operating portion  12  to be described later. 
     The operating wires  27  transmit a driving force for bending the bending portion  15 . For example, in a case where the bending portion  15  is adapted to be bendable in two axis directions, four operating wires  27  are provided as shown in  FIG. 2 . Each of the distal ends of the operating wires  27  is connected to a connection member (not shown) provided at the distal end of the bending portion  15 . The operating wires  27  are divided into positions that face each other with a central axis of the bending portion  15  interposed therebetween in two directions orthogonal to the central axis in the bending portion  15  and are inserted into the nodal rings. 
     Each operating wire  27  is inserted into a coil sheath  28  (insertion member) for the purpose of maintaining a constant path length in the flexible tube  23  even though the flexible tube  23  is bent. 
     Each coil sheath  28  has a structure where a metal wire is closely wound. Each coil sheath  28  has an inner diameter substantially equal to the outer diameter of the operating wire  27 . 
     The coil sheaths  28  are inserted into the flexible tube portion  16 . The coil sheaths  28  cover the operating wires  27  from the outer circumference side. 
     The distal ends of the respective coil sheaths  28  are fixed to a cap (not shown) provided at the proximal end of the bending portion  15 . The proximal ends of the respective coil sheaths  28  are fixed to a fixing plate (not shown) provided in the operating portion  12 . 
     Each coil sheath  28  is not particularly fixed in the flexible tube  23 . As a result, each coil sheath  28  can be moved in a gap formed in the flexible tube  23 . However, the entire length of each coil sheath  28  is not changed even though each coil sheath  28  is moved or bent in the flexible tube  23 . 
     The endoscopic channel  24 , the image transmission cable  25 , the fiber light guide  26 , and the coil sheaths  28  are accommodated in the flexible tube  23 . The endoscopic channel  24 , the image transmission cable  25 , the fiber light guide  26 , and the coil sheaths  28  are almost parallel to each other in the flexible tube  23 . Each of the endoscopic channel  24 , the image transmission cable  25 , the fiber light guide  26 , and the coil sheaths  28  is a flexible linear insertion member. 
     In a case where the flexible tube  23  is bent, each insertion member is also deformed depending on the deformation of the flexible tube  23 . The respective insertion members slide on each other while being in contact with each other, or slide on the inner circumference surface  23   b  of the flexible tube  23  while being in contact with the inner circumference surface  23   b . In this case, a friction force acts between each insertion member and the flexible tube  23 . As a result, a deformation load corresponding to the magnitude of a friction force is generated in a case where the flexible tube  23  is deformed. Since the flexible tube portion  16  cannot be smoothly inserted into the body of a patient in a case where the deformation load is increased, a burden on not only an operator but also a patient is increased. 
     A lubricant layer  17  (a lubricant) is formed on the surface of each insertion member in the present embodiment. In a case where the lubricant layers  17  of the respective insertion members are to be distinguished from each other in the following description, lowercase alphabet letters a, b, c, and d are added for distinguishment. A lubricant layer  17   a  is a lubricant layer  17  that is formed on an outer circumference surface  24   a  of the endoscopic channel  24 . A lubricant layer  17   b  is a lubricant layer  17  that is formed on an outer circumference surface  25   a  of the image transmission cable  25 . A lubricant layer  17   c  is a lubricant layer  17  that is formed on an outer circumference surface  26   a  of the fiber light guide  26 . A lubricant layer  17   d  is a lubricant layer  17  that is formed on an outer circumference surface  28   a  of each coil sheath  28 . 
     However, an adherend on which the lubricant layer  17  is to be formed is not limited to the respective insertion members having been described above. 
     For example, the lubricant layer  17  may be formed on the surfaces of other insertion members (not shown) in the lumen  23   a  of the flexible tube  23 . For example, the lubricant layer  17  may be disposed on the inner circumference surface  23   b . For example, part of each lubricant layer  17  may adhere to the other members provided in the lumen  23   a  so as to be disposed in the lumen  23   a.    
     In addition, the lubricant layer  17  may be disposed on any member as long as the member is apart of the endoscope  10 . For example, the lubricant layer  17  may be disposed on the surfaces of appropriate device bodies that slide on each other in the endoscope  10 . 
     The specific structure of the lubricant layer  17  will be described after the description of the operating portion  12 . 
     As shown in  FIG. 1 , the operating portion  12  is part of the device that is used by an operator in order to operate the endoscope  10 . Examples of an operation using the operating portion  12  can include an operation for pulling the operating wires  27  in order to change the amount of bending of the bending portion  15 . The operating portion  12  includes, for example, an operation switch  12   a , operation knobs  12   b , and the like. 
     The forceps valve  12   c  is provided on the distal end side of the operating portion  12  in order to allow an endoscopic device, a catheter, and the like to be inserted into the endoscopic channel  24 . The forceps valve  12   c  includes a valve body that prevents the back flow of fluid in the endoscopic channel  24 . As a result, the back flow of fluid in the endoscopic channel  24  is prevented in a case where an endoscopic device, a catheter, and the like are inserted and removed through the forceps valve  12   c.    
     As schematically shown in  FIG. 2 , the respective lubricant layers  17  are provided in the form of a layer on the outer circumference surface  24   a  of the endoscopic channel  24 , the outer circumference surface  25   a  of the image transmission cable  25 , the outer circumference surface  26   a  of the fiber light guide  26 , and the outer circumference surfaces  28   a  of the coil sheaths  28 , respectively. The endoscopic channel  24 , the image transmission cable  25 , the fiber light guide  26 , and the coil sheaths  28  form part of the device body of the endoscope  10 . The endoscopic channel  24 , the image transmission cable  25 , the fiber light guide  26 , and the coil sheaths  28  are the adherends for the lubricant layers  17 . 
     In the present embodiment, the adherends for the lubricant layers  17   a ,  17   b ,  17   c , and  17   d  are different from each other but the lubricant layers  17   a ,  17   b ,  17   c , and  17   d  have the same structure. The structure of the lubricant layer  17  will be described below using the lubricant layer  17   a  as an example. The following description of the lubricant layer  17   a  is also applied to the lubricant layers  17   b ,  17   c , and  17   d  likewise except for a difference in adherend. 
     The lubricant layer  17   a  provided on the outer circumference surface  24   a  of the endoscopic channel  24  is schematically shown in  FIG. 3 . 
     As schematically shown in  FIG. 3 , the lubricant layer  17   a  has an anti-friction material  17 A and a radical scavenger  17 B and is provided in the form of a layer on the outer circumference surface  24   a . In the present embodiment, the anti-friction material  17 A and the radical scavenger  17 B are substantially uniformly mixed in the lubricant layer  17   a.    
     Appropriate additives, for example, inorganic fillers, organic fillers, and the like may be contained in the lubricant layer  17   a  in addition to the anti-friction material  17 A and the radical scavenger  17 B. Moreover, an ion exchanger may be included in the lubricant layer  17   a  in addition to the anti-friction material  17 A and the radical scavenger  17 B. 
     The thickness of the lubricant layer  17   a  is not particularly limited as long as a friction reduction effect required for the endoscopic channel  24  is obtained. For example, an appropriate thickness may be determined as the thickness of the lubricant layer  17   a  in consideration of the stability of adhesion of the anti-friction material  17 A and the radical scavenger  17 B to the outer circumference surface  24   a.    
     In addition, the thickness of the lubricant layer  17   a  does not need to be constant. As long as a required friction reduction effect can be obtained, the lubricant layer  17   a  may not cover part of the outer circumference surface  24   a.    
     The layered structure schematically shown in  FIG. 3  is exemplary. The layered structure of the lubricant layer  17   a  is not limited to the layered structure shown in  FIG. 3 . 
     For example, the lubricant layer  17   a  shown in  FIG. 3  is drawn so that the anti-friction material  17 A and the radical scavenger  17 B are multiply stacked in a thickness direction. However, the thicknesses of the anti-friction material  17 A and the radical scavenger  17 B do not need to be equal to each other as shown in  FIG. 3 . The lubricant layer  17   a  may be a layered body of a mixture of the anti-friction material  17 A and the radical scavenger  17 B. 
     The anti-friction material  17 A and the radical scavenger  17 B are disposed on the outer circumference surface  24   a  in a state where the anti-friction material  17 A and the radical scavenger  17 B are exposed to the lumen  23   a . It is more preferable that the anti-friction material  17 A and the radical scavenger  17 B are closely adjacent to each other. However, the anti-friction material  17 A and the radical scavenger  17 B may be away from each other. The anti-friction material  17 A and the radical scavenger  17 B may be distributed in the shape of an island larger than the particle sizes thereof and may be adjacent to each other or away from each other with the shape of an island as a unit. 
     Even though the anti-friction material  17 A and the radical scavenger  17 B are multiply stacked in the thickness direction as shown in  FIG. 3 , the anti-friction material  17 A and the radical scavenger  17 B are mixed with each other and dispersed according to the percentage contents thereof as seen in the thickness direction. As a result, both the anti-friction material  17 A and the radical scavenger  17 B are exposed to the surface of the lubricant layer  17   a.    
     An appropriate solid lubricant not affecting the durability of an adherend, such as the endoscopic channel  24 , is used as the material of the anti-friction material  17 A. Examples of the solid lubricant suitable for the anti-friction material  17 A include molybdenum disulfide (MoS 2 ), graphite, fluororesin particles, graphite fluoride, boron nitride, and the like. Examples of the fluororesin particles include polytetrafluoroethylene (PTFE), PFA (a copolymer of tetrafluoroethylene (C 2 F 4 ) and perfluoroalkoxyethylene), and the like. 
     The anti-friction material  17 A may be formed of one type of solid lubricant, and may be formed of a mixture of a plurality of types of solid lubricants. 
     The radical scavenger  17 B is a material that deactivates a radical. A radical is also referred to as a free radical. The radical scavenger  17 B is used in order to improve the sterilization resistance of an adherend for the anti-friction material  17 A or the lubricant layer  17 . 
     The inventor has investigated in earnest for the further improvement of the sterilization resistance of the anti-friction material  17 A and an adherend in gas low-temperature sterilization treatment using sterilization gas. The inventor has newly found that the sterilization resistance of the anti-friction material  17 A and an adherend can be significantly improved in a case where the lubricant layer  17  is formed through a combination of the anti-friction material  17 A and a radical scavenger. As a result, the inventor has reached the present invention. 
     The mechanism of the action of the sterilization gas in the gas low-temperature sterilization is complex. Accordingly, it is not considered that only the presence of a radical in the sterilization gas contributes to a chemical reaction related to sterilization in the gas low-temperature sterilization. However, according to the inventor&#39;s investigation, in a case where a radical scavenger is contained in the lubricant layer  17 , better sterilization resistance is obtained as compared to metal particles that are said to have a catalytic action on the sterilization gas. 
     The type of the radical scavenger  17 B is not particularly limited as long as the radical scavenger is a material that can deactivate a radical generated in gas low-temperature sterilization. Examples of a radical generated in the case of hydrogen peroxide gas sterilization include an oxygen radical, a hydroxyl radical, and the like. 
     Examples of a compound suitable for the radical scavenger  17 B include one or more compounds selected from a group consisting of hydroquinone, benzoquinone, 4-tert-butylpyrocatechol, tert-butylhydroquinone, 2-tert-butyl-4,6-dimethylphenol, butylhydroxytoluene, 2,6-di-tert-butylphenol, and hydroquinone monomethyl ether. Hydroquinone is also called 1,4-benzenediol, p-benzenediol, or the like. 
     The isomers of benzoquinone include 1,4-benzoquinone (p-benzoquinone) and 1,2-benzoquinone (o-benzoquinone). At least one of 1,4-benzoquinone and 1,2-benzoquinone can be used as the benzoquinone in the radical scavenger  17 B. 
     Particularly, it is more preferable that at least one of hydroquinone and benzoquinone is contained in the radical scavenger  17 B. 
     The content of the anti-friction material  17 A in the lubricant layer  17   a ( 17 ) may be determined depending on friction reduction effect required for the insertion member. Hereinafter, the content of the anti-friction material  17 A and the content of the radical scavenger  17 B represent the contents thereof in the lubricant layer  17   a ( 17 ) as long as being not particularly specified. 
     For example, it is more preferable that a coefficient of dynamic friction between each insertion member and the flexible tube  23  is 0.500 or less in the case of the endoscope  10 . For example, it is still more preferable that a coefficient of dynamic friction between each insertion member and the flexible tube  23  is 0.470 or less in the case of the endoscope  10 . 
     The content of the radical scavenger  17 B may be determined depending on durability of the lubricant layer  17   a ( 17 ) regarding to the friction reduction effect that is required for the insertion member. For example, as durability required for the endoscope  10 , it is more preferable that a coefficient of dynamic friction is 0.500 or less even after gas low-temperature sterilization is performed 200 or more times. 
     Specifically, the content of the radical scavenger  17 B may be 0.1 mass % or more and 70 mass % or less. In this case, the content of the anti-friction material  17 A may exceed 30 mass % and may be less than 99.9 mass %. 
     It is more preferable that the content of the radical scavenger  17 B is 10 mass % or more and 70 mass % or less. In this case, it is more preferable that the content of the anti-friction material  17 A exceeds 30 mass % and is less than 90 mass %. 
     There is a concern that it may be difficult for a chemical reaction between the sterilization gas and the anti-friction material  17 A to be suppressed in a case where the content of the radical scavenger  17 B is less than 0.1 mass %. 
     There is a concern that the friction reduction effect of the lubricant layer  17   a  may be reduced due to a relative reduction in the content of the anti-friction material  17 A in a case where the content of the radical scavenger  17 B exceeds 70 mass %. 
     For example, in a case where the radical scavenger  17 B is made of benzoquinone, the content of benzoquinone may be 0.1 mass % or more and 70 mass % or less. 
     For example, in a case where the radical scavenger  17 B is made of hydroquinone, the content of hydroquinone may be 10 mass % or more and 70 mass % or less. 
     The above-mentioned lubricant layer  17  can be manufactured, for example, as follows. 
     First, a material to be applied is prepared in order to form the lubricant layer  17 . At least the anti-friction material  17 A and the radical scavenger  17 B are mixed with each other to manufacture the material to be applied. The above-mentioned additives and the like may be contained in the material to be applied in addition to the anti-friction material  17 A and the radical scavenger  17 B. 
     Then, the material to be applied is applied to the surface of an adherend. A dry application method or a wet application method is used as a method of applying the material to be applied. 
     Examples of the dry application method include spray application, rubbing application, and the like. In the case of the rubbing application, for example, a material to be applied may be rubbed on the surface of an adherend while a pressing force is applied to the material to be applied by, for example, an application jig, a hand, or the like. In the case of the rubbing application, for example, a material to be applied adhering to the surface of an adherend may be swept along the surface of the adherend by an application jig, a hand, or the like. 
     As the wet application method, dispersed liquid to be applied in which a material to be applied is dispersed in a solution to be applied may be formed and may be then applied to an adherend by, for example, spraying, dipping, or the like. After that, for example, the solution to be applied is evaporated by the heating of the adherend or the like, so that the lubricant layer  17  is formed on the surface of the adherend. 
     In this way, the lubricant layers  17   a ,  17   b ,  17   c , and  17   d  are formed on the surfaces of the insertion members formed of the endoscopic channel  24 , the image transmission cable  25 , the fiber light guide  26 , and the coil sheaths  28 , respectively. 
     Each insertion member on which the lubricant layer  17  is formed is inserted into the flexible tube  23  as shown in  FIG. 2 . The insertion members are fixed to fixing counterpart members at fixing positions, respectively. The operating wires  27  are inserted into the coil sheaths  28 , respectively. 
     The endoscope  10  is manufactured as described above. 
     Next, the action of the lubricant layer  17  will be mainly described with regard to the action of the endoscope  10 . 
     The endoscope  10  is a medical device that is used after being subjected to gas low-temperature sterilization. The endoscope  10  is repeatedly subjected togas low-temperature sterilization. 
     In the gas low-temperature sterilization, microorganisms to be subjected to sterilization chemically react with reactive components caused by the sterilization gas and are thus destroyed. However, the reactive components caused by the sterilization gas also chemically attack the structural members of the endoscope  10 . As a result, there is a concern that the reactive components caused by the sterilization gas may cause the structural members to deteriorate. 
     Examples of the reactive components caused by the sterilization gas include ions that are ionized by the sterilization gas, radicals that are generated due to the sterilization gas, highly reactive intermediates that are generated in a sterilization process, and the like. 
     According to the lubricant layer  17 , since the anti-friction material  17 A and the radical scavenger  17 B are mixed with each other, the deterioration of the anti-friction material  17 A in a sterilization process is significantly suppressed. 
     The mechanism of a reaction in a sterilization process is complex. Accordingly, the specific action of the radical scavenger  17 B is not specified with regard to an action for suppressing the deterioration of the anti-friction material  17 A. However, it is considered that at least radicals likely to react with a compound forming the anti-friction material  17 A are deactivated by the radical scavenger  17 B positioned near the anti-friction material  17 A due to the action of the radical scavenger  17 B. 
     For example, in a case where molybdenum disulfide is contained in the anti-friction material  17 A and hydrogen peroxide is used as the sterilization gas, the hydrogen peroxide is chemically combined with sulfur components of the molybdenum disulfide and sulfurous acid and sulfuric acid are generated. In a case where part of the molybdenum disulfide is consumed by a reaction, the lubricity of the anti-friction material  17 A is reduced due to the destruction of molecular structure having lubricity. In addition, reaction products, such as sulfurous acid and sulfuric acid, cause the structural members of the endoscope  10  to corrode. 
     The radical scavenger  17 B can suppress the chemical reaction of molybdenum disulfide that is caused by radicals generated during the gas low-temperature sterilization. As a result, the radical scavenger  17 B can prevent a reduction in the lubricity of molybdenum disulfide and the deterioration of the structural members of the endoscope  10  caused by reaction products. 
     Even in a case where molybdenum disulfide is not contained in the anti-friction material  17 A, the chemical structure of the anti-friction material  17 A is damaged due to a reaction between the anti-friction material  17 A and radicals. As a result, it is considered that the friction reduction action of the anti-friction material  17 A deteriorates. In this case, even though reaction products generated due to a reaction between the anti-friction material  17 A and radicals do not cause the structural members of the endoscope  10  to deteriorate, the deterioration of the anti-friction material  17 A causes the frictional property of the insertion members to deteriorate. 
     However, the deterioration of the anti-friction material  17 A caused by these radicals can be suppressed in the present embodiments by the radical scavenger  17 B. 
     According to the lubricant layer  17  of the present embodiment and the endoscope  10  including the lubricant layer  17 , resistance to gas low-temperature sterilization is improved as described above. 
     An example of a case where the medical device in which the lubricant for a medical device of the embodiment is used is a medical endoscope has been described in the description of the embodiment. However, the medical device is not limited to an endoscope as long as the medical device is a medical device to be subjected to gas low-temperature sterilization. Examples of the medical device in which the lubricant for a medical device of the embodiment is used include an endoscopic device, an energy device, and the like. 
     EXAMPLES 
     Examples 1 to 8 of the lubricant for a medical device (hereinafter referred to as the lubricant) of the embodiment will be described below together with Comparative Examples 1 and 2. 
     Table 1 shows the composition and evaluation results of lubricants of Examples 1 to 8 and Comparative Examples 1 and 2. However, the reference numerals of the names of the members will be omitted in Table 1. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Lubricant 
                 Evaluation results 
               
            
           
           
               
               
               
            
               
                   
                 Coefficient of dynamic friction 
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Anti-friction material 
                 Radical scavenger 
                 Catalyst 
                 Before 
                 After 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                 Content 
                   
                 Content 
                   
                 Content 
                 sterilization 
                 sterilization 
                 Difference 
                 Comprehensive 
               
               
                   
                 Material 
                 (mass %) 
                 Material 
                 (mass %) 
                 Material 
                 (mass %) 
                 test (a) 
                 test (b) 
                 (b − a) 
                 evaluation 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Example 1 
                 MoS 2   
                 25 
                 Hydroquinone 
                 75 
                 — 
                 — 
                 0.480 
                 0.483 
                 0.003 
                 B 
               
               
                 Example 2 
                 MoS 2   
                 70 
                 Hydroquinone 
                 30 
                 — 
                 — 
                 0.450 
                 0.465 
                 0.015 
                 A 
               
               
                 Example 3 
                 MoS 2   
                 90 
                 Hydroquinone 
                 10 
                 — 
                 — 
                 0.440 
                 0.460 
                 0.020 
                 A 
               
               
                 Example 4 
                 MoS 2   
                 91 
                 Hydroquinone 
                 9 
                 — 
                 — 
                 0.438 
                 0.475 
                 0.037 
                 B 
               
               
                 Example 5 
                 MoS 2   
                 25 
                 Benzoquinone 
                 75 
                 — 
                 — 
                 0.479 
                 0.485 
                 0.006 
                 B 
               
               
                 Example 6 
                 MoS 2   
                 40 
                 Benzoquinone 
                 60 
                 — 
                 — 
                 0.459 
                 0.469 
                 0.010 
                 A 
               
               
                 Example 7 
                 MoS 2   
                 99 
                 Benzoquinone 
                 1 
                 — 
                 — 
                 0.431 
                 0.465 
                 0.034 
                 A 
               
               
                 Example 8 
                 MoS 2   
                 99.95 
                 Benzoquinone 
                 0.05 
                 — 
                 — 
                 0.430 
                 0.490 
                 0.060 
                 B 
               
               
                 Comparative 
                 MoS 2   
                 100 
                 — 
                 — 
                 — 
                 — 
                 0.430 
                 0.582 
                 0.152 
                 C 
               
               
                 Example 1 
               
               
                 Comparative 
                 MoS 2   
                 90 
                 — 
                 — 
                 Pt 
                 10 
                 0.455 
                 0.509 
                 0.054 
                 C 
               
               
                 Example 2 
               
               
                   
               
            
           
         
       
     
     Example 1 
     Example 1 is an example of the lubricant layer  17  of the embodiment. As shown in Table 1, molybdenum disulfide (MoS 2 ) was used as an anti-friction material  17 A of a lubricant used in a lubricant layer  17  of Example 1. 
     The molybdenum disulfide was prepared as powder having a particle size of 10.0 μm or less. 
     Hydroquinone was used as a radical scavenger  17 B of the lubricant. 
     The hydroquinone was prepared as powder having a particle size of 10.0 μm or less. 
     The molybdenum disulfide and the hydroquinone were mixed with each other in order to prepare a material to be applied. A mass ratio of the molybdenum disulfide to the hydroquinone was set to 25:75. Accordingly, the material to be applied was prepared. 
     A planar silicone base material having a size of 100 mm×100 mm was used as an adherend used to form an evaluation sample. A silicone rubber sheet (manufactured by AS ONE Corporation) was used as the silicone base material. 
     The material to be applied was applied to the silicone base material by a dry method. The thickness of an applied layer was set to 10 μm. Accordingly, an evaluation sample of Example 1 was formed. In the lubricant of this evaluation sample, the content of the hydroquinone in the lubricant layer  17  was set to 75 mass %. 
     Examples 2 to 4 
     An evaluation sample of Example 2 was formed in the same manner as that of Example 1 except that the content of the hydroquinone was set to 30 mass %. 
     An evaluation sample of Example 3 was formed in the same manner as that of Example 1 except that the content of the hydroquinone was set to 10 mass %. 
     An evaluation sample of Example 4 was formed in the same manner as that of Example 1 except that the content of the hydroquinone was set to 9 mass %. 
     Example 51 
     In an evaluation sample of Example 5, benzoquinone was used instead of the hydroquinone of Example 1. The content of the benzoquinone in the lubricant layer  17  was set to 75 mass %. 
     The evaluation sample of Example 5 was manufactured in the same manner as that of Example 1 except that a material to be applied in which molybdenum disulfide and the benzoquinone having the above-mentioned content were mixed with each other was used. The benzoquinone was prepared as powder having a particle size of 10.0 μm or less. 
     Examples 6 to 81 
     An evaluation sample of Example 6 was formed in the same manner as that of Example 5 except that the content of the benzoquinone was set to 60 mass %. 
     An evaluation sample of Example 7 was formed in the same manner as that of Example 5 except that the content of the benzoquinone was set to 1 mass %. 
     An evaluation sample of Example 8 was formed in the same manner as that of Example 5 except that the content of the benzoquinone was set to 0.05 mass %. 
     Comparative Examples 1 and 2 
     An evaluation sample of Comparative Example 1 is different from that of Example 1 in that only molybdenum disulfide is used as a lubricant. 
     Molybdenum disulfide was applied to the same silicone base material as that of Example 1 by a dry method, so that the evaluation sample of Comparative Example 1 was manufactured. The thickness of an applied layer was set to 10 μm. 
     In an evaluation sample of Comparative Example 2, platinum (Pt) was used instead of the radical scavenger of Example 1. The content of the platinum in the lubricant was set to 10 mass %. 
     The lubricant of Comparative Example 2 was applied to a silicone base material in the same manner as that of Example 1 except that the composition of a material to be applied was different from that of Example 1. 
     [Evaluation] 
     The evaluation sample of each Example and the evaluation sample of each Comparative Example were subjected to gas low-temperature sterilization 200 times (sterilization test). The gas low-temperature sterilization was performed by a hydrogen peroxide low-temperature plasma sterilization method using STERRAD (registered trademark) NX (registered trademark) (product name; manufactured by Johnson &amp; Johnson K.K.). 
     The coefficient of dynamic friction of the surface of the evaluation sample to which the lubricant was applied was measured before the sterilization test and after the sterilization test. A surface property tester TRIBIGEAR (registered trademark) TYPE: 14FW (product name; manufactured by Shinto Scientific Co., Ltd.) was used for the measurement of the coefficient of dynamic friction. A stainless steel plate having a thickness of 1 min and a width of 25 mm was used as a counterpart member. Test conditions included a speed of 1000 mm/min, a stroke of 15 mm, 500 times of reciprocation, and an applied load of 500 gf (4.9 N). 
     A comprehensive evaluation was made as three levels of “very good” (“A” in Table 1). “good” (“B” in Table 1), and “no good” (“C” in Table 1). 
     A comprehensive evaluation in a case where a coefficient of dynamic friction after sterilization treatment was 0.470 or less was defined as “very good”. 
     A comprehensive evaluation in a case where a coefficient of dynamic friction after sterilization treatment was higher than 0.470 and lower than 0.500 was defined as “good”. 
     A comprehensive evaluation in a case where a coefficient of dynamic friction after sterilization treatment was higher than 0.500 was defined as “no good”. 
     [Evaluation Result] 
     As shown in Table 1, the coefficients (a) of dynamic friction of Examples 1 to 8 before the sterilization test (hereinafter simply referred to as the coefficients (a) of dynamic friction) were 0.480, 0.450, 0.440, 0.438, 0.479.0.459, 0.431, and 0.430, respectively. The coefficients (b) of dynamic friction of Examples 1 to 8 after 200 times of the sterilization test (hereinafter simply referred to as the coefficients (b) of dynamic friction) were 0.483, 0.465, 0.460, 0.475.0.485, 0.469, 0.465, and 0.490, respectively. 
     The coefficients (a) of dynamic friction of Comparative Examples 1 and 2 were 0.430 and 0.455, respectively. The coefficients (b) of dynamic friction of Comparative Examples 1 and 2 were 0.582 and 0.509, respectively. 
     The coefficients of dynamic friction of all of the respective Examples and the respective Comparative Examples were increased after the sterilization test. It is considered that the reason for this is that the friction characteristics of the lubricants deteriorate due to sterilization treatment. 
     It is considered that the degree of deterioration of friction characteristics corresponds to the amount of reacting molybdenum disulfide. Accordingly, it is considered that sulfurous acid, sulfuric acid, and the like were generated according to the degree of deterioration of frictional property. 
     Since the coefficients (b) of dynamic friction of Examples 2, 3, 6, and 7 were 0.470 or less, Examples 2, 3, 6, and 7 were evaluated as “very good”. 
     Since the coefficients (b) of dynamic friction of Examples 1, 4, 5, and 8 were higher than 0.470 and lower than 0.500. Examples 1, 4, 5, and 8 were evaluated as “god”. 
     In contrast, both the comprehensive evaluations of Comparative Examples 1 and 2 were “no good”. 
     In a case where Examples 1 to 4 were compared with each other, the coefficient (a) of dynamic friction was higher as the content of hydroquinone was higher. It is considered that the reason for this is that Examples 1 to 4 had configuration where the content of molybdenum disulfide contributing to frictional property is lower as the content of hydroquinone is higher. 
     In contrast, the amount of increase in the coefficient (b) of dynamic friction based on the coefficient (a) of dynamic friction (a difference (b-a) in Table 1) was smaller as the content of hydroquinone was higher. It is considered that the reason for this is that the deterioration of molybdenum disulfide was more suppressed as the content of hydroquinone was higher. 
     Among Examples 1 to 4, the friction characteristics of Examples 2 and 3 were particularly excellent in that the coefficient of dynamic friction was maintained at 0.470 or less even after sterilization treatment was performed 200 times. 
     In a case where Examples 5 to 8 were compared with each other, the coefficient (a) of dynamic friction was higher as the content of benzoquinone was higher. It is considered that the reason for this is that Examples 5 to 8 had configuration where the content of molybdenum disulfide contributing to friction characteristics is lower as the content of benzoquinone is higher. 
     In contrast, the amount of increase in the coefficient (b) of dynamic friction based on the coefficient (a) of dynamic friction was smaller as the content of benzoquinone was higher. It is considered that the reason for this is that the deterioration of molybdenum disulfide was more suppressed as the content of benzoquinone was higher. 
     Among Examples 5 to 8, the frictional property of Examples 6 and 7 were particularly desireable in that the coefficient of dynamic friction was maintained at 0.470 or less even after sterilization treatment was performed 200 times. 
     In contrast, in Comparative Example 1, the coefficient (a) of dynamic friction was good but the coefficient (b) of dynamic friction thereof significantly deteriorated. As a result, the comprehensive evaluation of Comparative Example 1 was “no good”. It is considered that the amount of change in the coefficient of dynamic friction before and after the sterilization test was significantly increased since the radical scavenger was not contained in the Comparative Example 1. 
     Even in Comparative Example 2, the coefficient (a) of dynamic friction was good but the coefficient (b) of dynamic friction thereof significantly deteriorated. As a result, the comprehensive evaluation of Comparative Example 2 was “no good”. 
     In Comparative Example 2, the deterioration of molybdenum disulfide could be suppressed to some extent by a platinum catalyst. However, for example, the amount of change in the coefficient of dynamic friction of Comparative Example 2 was increased 2.7 times in comparison with Example 3 including the same amount of hydroquinone as Comparative Example 2. As a result, the coefficient (b) of dynamic friction of Comparative Example 2 was higher than 0.500. 
     It was found that hydroquinone was significantly superior to a platinum catalyst in terms of an effect of suppressing the reaction of sterilization gas to molybdenum disulfide. 
     In a case where the magnitudes of the coefficients (a) of dynamic friction of Comparative Example 2 and Example 3 were compared with each other, the coefficient (a) of dynamic friction of Example 3 was lower than that of Comparative Example 2 by 0.015. A platinum catalyst caused friction characteristics to deteriorate in comparison with hydroquinone as described above in a case where the contents were the same. Accordingly, it is considered that the coefficient (b) of dynamic friction is also increased since the coefficient (a) of dynamic friction is further increased in a case where the content of a platinum catalyst is further increased. 
     While preferred embodiment of the invention and the respective examples of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.