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  Method of polishing the inner peripheral end surfaces of substrates for a recording medium using a brushRelated Patent Categories: Abrading, Abrading Process, Glass Or Stone AbradingThe Patent Description & Claims data below is from USPTO Patent Application 20070254561. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATION [0001] This application is an application filed under 35 U.S.C. .sctn.111(a) claiming benefit pursuant to 35 U.S.C. .sctn.119(e) of the filing date of Provisional Application No. 60/606,882, filed on Sep. 3, 2004, pursuant to 35 U.S.C. .sctn.111(b). TECHNICAL FIELD [0002] The present invention relates to a method of polishing the inner peripheral end surfaces of substrates for a recording medium and a method of producing the substrates by using the above method, etc. BACKGROUND ART [0003] An aluminum substrate has been widely used as a substrate for a magnetic recording medium such as a magnetic disk. As the magnetic disks are being produced in smaller sizes and smaller thickness but record data at a higher density, an aluminum substrate is being gradually replaced by a glass substrate having superior surface flatness and substrate strength. As glass substrates for magnetic recording medium, there have been used chemically reinforced glass substrates for enhancing the substrate strength and crystallized glass substrates featuring increased substrate strength based on the crystallization. [0004] Accompanying the trend toward high-density recording, further, the magnetic head is being changed from a thin-film head to a magneto-resistive head (MR head) and to a giant magneto-resistive head (GMR head). It is therefore expected that reproducing the contents of the magnetic recording medium of the glass substrate by using magneto-resistive heads will become standard in the future. [0005] Thus, a variety of improvements have been made to the magnetic disk for high-density recording. Advances in the magnetic disk, however, are also accompanied by new problems concerning the glass substrate for the magnetic recording medium. One of them is to properly clean the surfaces of the glass substrate. That is, adhesion of a foreign matter on the surfaces of the glass substrate could become a cause of defects in the thin film formed on the surfaces of the glass substrate or a cause of protuberances formed on the surfaces of the thin film. Further, in reproducing the contents of the magnetic recording medium on the glass substrate by using a magneto-resistive head, if the flying height (floating height) of the head is lowered to increase the recording density, there may often occur erroneous reproducing operation or a phenomenon that the reproduction is not accomplished. The cause stems from the protuberances that are formed on the surface of the magnetic disk due to particles on the glass substrate turning into thermal asperity, generating heat in the magneto-resistive head, varying the resistance of the head, and adversely affecting the electromagnetic conversion. [0006] A principal cause of foreign matter on the surface of the glass substrate for the magnetic recording medium described above is that the end surface of the glass substrate is not smooth and, hence, the end surface abrades the wall surface of a resin casing, whereby resin or glass particles formed by the abrasion, as well as other particles trapped on the inner peripheral end surface and the outer peripheral end surface of the glass substrate, adhere to the surfaces. [0007] Patent document 1 (JP-A-11-221742) discloses a polishing method wherein a disk-like glass substrate (substrate for a recording medium) having a circular hole at the central portion is immersed in a polishing solution containing free grains, and the end surfaces of the glass substrate are polished by being brought into rotational contact with a polishing brush or a polishing pad by using a polishing solution containing the free grains. [0008] When the inner peripheral end surface of the substrate is to be polished by using the above slurry and the polishing brush, the polishing is effected by rotating the brush while dripping the slurry onto the center hole of the object to be polished which is formed by stacking a plurality of pieces of substrates aligned with the center holes of other disk-like substrates having center holes, or inserting a rod-like polishing brush in the center hole in a state where the object to be polished is immersed in the slurry. According to this polishing method, however, the temperature rises due to the friction with the object to be polished, the polishing material slurry and the polishing brush. The rise in temperature causes the rate of polishing to vary and makes it difficult to conduct the polishing while maintaining a correct amount of working. On the other hand, a stack of substrates have been chamfered at the end surfaces and form dented portions at the chamfered portions among the upper and lower substrates. A difficulty is involved if it is attempted to polish the dented portions maintaining the same working precision as for other end surfaces. It is desired to enhance the dimensional precision of the center holes of the disk-like substrates for a recording medium. Therefore, it is necessary to enhance the working precision in polishing the inner peripheral end surfaces. [0009] [Patent document 1] Japanese Unexamined Patent Publication (Kokai) No. 11-221742 DISCLOSURE OF THE INVENTION [0010] It is, therefore, an object of the present invention to provide a method of polishing the inner peripheral end surfaces of substrates while maintaining a sufficiently high working precision at the time of polishing the inner peripheral end surfaces of a plurality of disk-like substrates for a recording medium. [0011] The present invention provides a method of polishing the inner peripheral end surfaces of disk-like substrates for a recording medium and a method of producing the substrates by using the method described below. [0012] (1) A method of polishing the inner peripheral end surfaces of disk-like substrates for a recording medium using a brush comprising: [0013] providing a plurality of pieces of disk-like substrates for a recording medium having a circular hole at the central portion thereof thereby forming an inner peripheral end surface, and aligning and stacking the circular holes to form an object to be polished having the circular hole at the central portion thereof; [0014] bringing a polishing material slurry containing a polishing material into contact with the object to be polished; and [0015] inserting a polishing brush having brush hairs studded on the periphery of a rod-like shaft into the circular hole of the object to be polished in a state where the slurry is brought into contact with the object to be polished, and rotating the polishing brush with the shaft as a center to polish the inner peripheral end surfaces of the substrates; [0016] wherein the polishing material slurry is controlled to remain at a constant temperature. [0017] (2) The method of polishing using a brush according to (1) above, wherein the polishing brush is rotated and is reciprocally moved in a direction of inserting the brush relative to the object to be polished to effect the polishing. [0018] (3) A method of producing disk-like substrates for a recording medium including a step of effecting the method of polishing using a brush according to (1) or (2) above. [0019] (4) A substrate produced by the method of producing disk-like substrates for a recording medium according to (3) above. [0020] (5) A method of producing a magnetic recording medium including a step of effecting the method of polishing using a brush according to (1) or (2) above. Continue reading... Full patent description for Method of polishing the inner peripheral end surfaces of substrates for a recording medium using a brush Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method of polishing the inner peripheral end surfaces of substrates for a recording medium using a brush patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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