Abstract: A magnetic tape cassette whose reliability is considerably improved by preventing triboelectrification by tape-and-guide friction. A metal tape guide for guiding the magnetic tape while in contact with the back surface of the tape. The substrate of the magnetic tape is made of polyethylene terephthalate or polyethylene naphthalate, and has a surface specific resistance R.sub.s of 10.sub.8 .OMEGA./cm.sup.2 or more. The tape guide is made of stainless steel or aluminum, and the surface roughness of the tape guide is such that the root mean square roughness value R.sub.rms, as determined by height from a reference surface, is 60 nm or lower. Also, the back surface of the tape may be provided with 30 to 400 protrusions of a height of 300 nm per 0.1 mm.sup.2.

Abstract: A magnetic tape cassette having a guide pole which is in sliding contact with the magnetic surface of the tape produced in such a manner as to improve the running characteristics of the tape while being capable of being manufactured at a low cost. A cylindrical stainless steel base member is subjected to a barreling treatment so as to secure fine particles of an inorganic material having a Moh's hardness of greater than 9 to the slide surface of the guide post. Moreover, the surface of the guide pole can be finished by a surface rolling to reduce the number of scratch-like grooves in the slide surface having a depth of more than 0.2 .mu.m and a width of less than 40 .mu.m to less than 11 per millimeter in the sliding direction of the tape.

Abstract: A magnetic tape cassette having a guide pole which is in sliding contact with the magnetic surface of the tape produced in such a manner as to improve the running characteristics of the tape while being capable of being manufactured at a low cost. A cylindrical stainless steel base member is subjected to a barreling treatment so as to secure fine particles of an inorganic material having a Moh's hardness of greater than 9 to the slide surface of the guide post. Moreover, the surface of the guide pole can be finished by a surface rolling to reduce the number of scratch-like grooves in the slide surface having a depth of more than 0.2 .mu.m and a width of less than 40 .mu.m to less than 11 per millimeter in the sliding direction of the tape.

Abstract: A magnetic tape cassette having a guide pole which is in sliding contact with the magnetic surface of the tape produced in such a manner as to improve the running characteristics of the tape while being capable of being manufactured at a low cost. A cylindrical stainless steel base member is subjected to a barreling treatment so as to secure fine particles of an inorganic material having a Moh's hardness of greater than 9 to the slide surface of the guide post. Moreover, the surface of the guide pole can be finished by a surface rolling to reduce the number of scratch-like grooves in the slide surface having a depth of more than 0.2 .mu.m and a width of less than 40 .mu.m to less than 11 per millimeter in the sliding direction of the tape.

Abstract: A flexible magnetic disk in which the friction between the magnetic sheet of the disk and a positioning member is reduced, the magnetic sheet is positioned properly and without offset each time it is loaded in a reading/reproducing device, and the tracking accuracy and dimensional accuracy are satisfactory. A protective layer is provided around the periphery of a central hole in the magnetic sheet. The protective layer is made of a composition containing a compound which has an acrylic or methacrylic acid ester bond at one or both of a main chain terminal and a side chain thereof. The compound is one which is cured by radiation. The thickness of the protective layer should be 30 microns or less, and the surface irregularity of the protective layer should be 0.03 microns or more represented in terms of a central line average roughness at a cutoff of 2.5 mm.

Abstract: A magnetic recording medium comprising a non-magnetic support having coated thereon a magnetic layer, the magnetic layer containing (i) ferromagnetic alloy particles having an average length in the long axis of 0.25 .mu.m or less and (ii) fatty acid components comprising behenic acid in an amount of 20 to 75 wt%, stearic acid in an amount of 10 to 45 wt% and oleic acid in an amount of 10 to 45 wt% based on the total weight of the three fatty acids.

Abstract: A method for forming protective layer on a surface portion surrounding the edge of a central aperture of a flexible magnetic disc sheet is described, comprising providing a radiation polymerizable composition on a surface portion surrounding the edge of the central aperture of the flexible magnetic disc sheet by screen printing, and hardening the composition by exposure to radiation; a flexible magnetic disc is also described, wherein a protective layer by the foregoing method is provided, with said protective layer having an inner diameter larger than the diameter of the aperture of the disc sheet and an outer diameter smaller than the diameter of the aperture of a jacket enclosing the disc sheet.

Abstract: A flexible magnetic disk comprises a jacket and a flexible magnetic disk sheet housed in the jacket. The flexible magnetic disk sheet is provided at the center with a circular hole for engagement with a sheet positioning member of an information writing and read-out apparatus. The jacket has an aperture for exposing the circular hole of the flexible magnetic disk sheet. The peripheral edge portion of the circular hole which comes into contact with the sheet positioning member is embossed to decrease the coefficient of friction of the peripheral edge portion to 0.45 or less, so that the flexible magnetic disk sheet is correctly positioned by the sheet positioning member.

Abstract: A flexible disk comprises a flexible disk jacket having a central opening and a disk-like magnetic recording medium having a central opening smaller than the central opening of the flexible disk jacket in diameter. The recording medium is accommodated for rotation in the flexible disk jacket so that their central openings are concentrically positioned and the portion of the recording medium surrounding the central opening is exposed through the central opening of the jacket, thereby giving access thereto. The portion of the recording medium surrounding the central opening is provided with a protective layer on one side thereof and a reinforcement ring on the other side thereof. The protective layer is formed of a composition which contains a compound with at least one unsaturated bond per molecule that is polymerizable by ultraviolet rays, and which has been cured by exposure to ultraviolet rays.

Abstract: A method for forming protective layer on a surface portion surrounding the edge of a central aperture of a flexible magnetic disc sheet is described, comprising providing a radiation polymerizable composition on a surface portion surrounding the edge of the central aperture of the flexible magnetic disc sheet by screen printing, and hardening the composition by exposure to radiation; a flexible magnetic disc is also described, wherein a protective layer by the foregoing method is provided, with said protective layer having an inner diameter larger than the diameter of the aperture of the disc sheet and an outer diameter smaller than the diameter of the aperture of a jacket enclosing the disc sheet.

Abstract: An apparatus for driving a flexible magnetic disk comprises an upper member and a lower member for positioning a flexible magnetic disk sheet of the flexible magnetic disk by engagement with a circular hole at the center of the magnetic disk sheet. A lubricating material is applied onto the surfaces of the upper members and the lower members, thereby to decrease the coefficient of friction of the upper member with respect to the magnetic disk sheet to a value within the range of 0.45 or less, and that of the lower member to a value within the range of 0.30 or less.

Abstract: A flexible magnetic disc comprising a magnetic sheet having on at least a part thereof a protective layer comprising (a) a straight or branched chain compound having an acrylic or methacrylic acid ester moiety on the end of at least one of the principal chain and the side chain, (b) an aromatic ketone, and (c) a silicone lubricant, said layer being hardenable by photopolymerization.

Abstract: A flexible magnetic disk sheet is described, including a central circular hole therein, having a protecting layer formed thereon using (a) a compound including one or more atomic group providing lubricity at at least one end of a main chain or a side chain of molecular of the compound and one or more ester bonds of acrylic acid or methacrylic acid at at least one end of a main chain or a side chain of molecule of the compound, and (b) an aromatic ketone, wherein said protective layer is formed on a surface portion surrounding the edge of the central circular hole of a flexible magnetic disk sheet.

Abstract: A flexible magnetic disk comprises a jacket and a flexible magnetic disk sheet housed in the jacket. The flexible magnetic disk is provided at the center with a circular hole for engagement with a sheet positioning member of an information writing and read-out apparatus. The jacket has an aperture for exposing the circular hole of the flexible magnetic disk sheet. The peripheral edge portion of the circular hole which comes into contact with the sheet positioning member is provided with at least one lubricant layer to decrease the coefficient of friction of the peripheral edge portion to 0.45 or less, so that the flexible magnetic disk sheet is correctly positioned by the sheet positioning member.

Abstract: A magnetic recording medium is disclosed which is comprised of a non-magnetic support base having a magnetic layer on one surface and a silicone oil layer formed on the opposite surface. The silicone oil layer does not produce dropouts and eliminates scraping and therefore eliminates dust particles that collect and build up in the area of the magnetic head. The silicone layer is formed from a silicone-containing compound having a viscosity of at least 6,000 centistokes at 25.degree. C.

Abstract: A magnetic recording medium comprising a nonmagnetic flexible substrate, a magnetic layer provided on the surface of the substrate and containing ferromagnetic grains dispersed in a binder, and a back layer provided on the back surface of the substrate. The magnetic recording medium has a stiffness (S.sub.TD) of 6.0 or less. The friction coefficient (.mu..sub.B) of the back layer surface with respect to the axial direction of a loading post in a video tape recorder is controlled to satisfy the condition:0.ltoreq..mu..sub.B .ltoreq.0.1S.sub.TD -0.05so as to make the magnetic recording medium highly resistant to damage due to movement in a video tape recorder.

Abstract: The present invention relates to an improved magnetic recording medium comprising a magnetic recording layer on the surface of a non-magnetic support, in which the magnetic recording layer contains a fatty acid, high viscosity silicone oil and fatty acid ester.

Abstract: A magnetic recording medium comprising a base and a magnetic layer formed thereon is disclosed. The coefficient of friction (.mu..sub.B) of the surface opposite to the magnetic layer in transversal direction against the axial direction of loading post is under the straight line represented by the formula: .mu..sub.B =0.1S.sub.TD -0.05 (wherein S.sub.TD is the stiffness of the medium in transversal direction and 0.5<S.sub.TD .ltoreq.6.0), and the total thickness of the medium is 15.5.mu. or less.

Abstract: In a view finder for cameras comprising a sight field for viewing an object to be photographed, the improvement which comprises mark means in said sight field for guiding on the centering of said object to be photographed and on the proper photographing distance from said object to be photographed is disclosed.