| CPC G11B 5/78 (2013.01) [G11B 5/7028 (2013.01); G11B 5/70678 (2013.01); G11B 5/71 (2013.01); G11B 5/714 (2013.01); G11B 5/7253 (2020.08); G11B 5/7334 (2019.05)] | 20 Claims |
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1. A magnetic tape comprising:
a non-magnetic support; and
a magnetic layer including a ferromagnetic powder,
wherein a fluorine-containing compound is included in a portion on the non-magnetic support on a magnetic layer side, and
a ratio θr of a water contact angle (θafter) measured on a surface of the magnetic layer after sliding on a magnetic head to a water contact angle (θbefore) measured on the surface of the magnetic layer before sliding on the magnetic head is 0.70 or more,
wherein the water contact angle is measured as follows:
a tape sample having any length enough to measure the water contact angle and a tape sample having a length of 100 m are cut out from any position in the longitudinal direction of the same magnetic tape; for the tape sample having any length, a water contact angle θbefore is obtained without sliding on the magnetic head; for the tape sample having a length of 100 m, a water contact angle θafter is obtained after sliding on the magnetic head; the sliding between the magnetic tape and the magnetic head is performed by a reel tester at a running speed of 4 m/sec and a tension applied in longitudinal direction of the magnetic tape of 100 gf, in an environment of an atmosphere temperature of 23° C.±1° C. and a relative humidity of 50%; the water contact angle is an arithmetic average of values obtained by measuring the tape sample to be measured at six different locations of the magnetic layer surface by a θ/2 method in a measurement environment of an atmosphere temperature of 25° C. and a relative humidity of 50%, and
the fluorine-containing compound is one or more fluorine-containing polymers, the fluorine-containing polymer being a polymer having a branched structure that includes a repeating unit represented by General Formula (1) and at least one repeating unit selected from the group consisting of a repeating unit represented by General Formula (2) and a repeating unit represented by General Formula (3):
 in General Formula (1),
R1 and R2 each independently represent a hydrogen atom or a methyl group,
L1 and L2 each independently represent a divalent linking group,
Rf1, Rf2, Rf3, and Rf4 each independently represent a fluorine atom or a perfluoroalkyl group,
u represents an integer of 1 or more,
p represents an integer of 2 or more,
t represents an integer of 0 or more,
a plurality of Rf1's may be the same as or different from each other,
a plurality of Rf2's may be the same as or different from each other,
in a case where there are a plurality of Rf3's, the plurality of Rf3's may be the same as or different from each other,
in a case where there are a plurality of Rf4's, the plurality of Rf4's may be the same as or different from each other,
 in General Formula (2),
R3 represents a hydrogen atom or a methyl group,
L3 represents a single bond or a divalent linking group,
X1 represents —OH, —COOH, —PO3H, {—OP(═O)(OH)2}, —OM1, —CO2M1, —SO3M1, —NT1T2, an epoxy group, an alicyclic epoxy group, an oxazoline group, —NG1G2G3E1, or a group having a betaine structure,
M1 represents alkali metal, alkaline earth metal, Mg, Al, or Q1Q2Q3Q4N+,
Q1, Q2, Q3, and Q4 each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms,
T1 and T2 each independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms,
T1 and T2 may be bonded,
E1 represents an anion,
G1, G2, and G3 each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atom,
 in General Formula (3),
R4 represents a hydrogen atom, a fluorine atom, a chlorine atom, or an alkyl group having 1 to 20 carbon atoms,
U1 and U2 each independently represent —O—, —S—, —COO—, —OCO—, —CONH—, —NHCOO—, or NH—
R5 and R6 each independently represent a hydrogen atom, an aliphatic hydrocarbon group, an aryl group, or a heteroaryl group,
R5 and R6 may be bonded,
L4 represents a single bond or a divalent linking group.
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