Resin film with controlled youngs modulus
To provide a resin film, of which dimensional stability required of an ultra-high density recording medium can be controlled easily by drive tension, and which has processability at high temperature in a processing step of the resin film into a magnetic recording medium. A resin film having a Young's modulus in the film longitudinal direction of 1 GPa or more and a film thickness of 1 μm or more, wherein the product of the Young's modulus in the longitudinal direction and the thickness is 5 GPa·μm or more and 20 GPa·μm or less and wherein a dimensional change in the film longitudinal direction is −2% or more and +2% or less when the film is heated at a rate of 5° C./min under a load of 2 kg/mm 2 applied in the longitudinal direction and the temperature has reached 110° C., the resin film satisfying at least either of the following (1) or (2): (1) the Young's modulus in the film longitudinal direction is 6 GPa or less and the film thickness is 4.5 μm or less; and (2) the Young's modulus in the film longitudinal direction is 4 GPa or less and the film thickness is 6 μm or less.
1. A resin film having a Young's modulus in the film longitudinal direction of 1 GPa or more and a film thickness of 1 μm or more,
wherein the product of the Young's modulus in the longitudinal direction and the thickness is 5 GPa·μm or more and 20 GPa·μm or less,
wherein a dimensional change in the film longitudinal direction is −2% or more and +2% or less when the film is heated at a rate of 5° C./min under a load of 2 kg/mm 2 applied in the longitudinal direction and the temperature has reached 110° C., and
wherein the resin film satisfies at least either of the following (1) or (2):
(1) the Young's modulus in the film longitudinal direction is 6 GPa or less and the film thickness is 4.5 μm or less; and
(2) the Young's modulus in the film longitudinal direction is 4 GPa or less and the film thickness is 6 μm or less,
wherein the resin film is formed of at least one resin selected from the group consisting of aromatic polyesters, polyether ketones, polyarylene sulfides, polyolefins, aliphatic polyamides, and semi-aromatic polyamides.
2. The resin film according to claim 1 , wherein a tan δ peak temperature measured by DMA of a resin which forms the resin film is in the range of 100° C. or more.
3. The resin film according to claim 1 , wherein the resin film is formed of at least the aromatic polyesters, and the aromatic polyesters are aromatic copolyesters in which dimer components represented by the following formulas (I) and (II) are copolymerized in the range of 0.3 to less than 5 mol % based on the number of moles of repeating units of the aromatic polyester:
—C(O)-RA-C(O)— (I) and
—O-RA-O— (II),
wherein RA in the structural formulas (I) and (II) represents a C 31 -C 51 alkylene group which may contain a cyclic ring(s) and a branched chain(s).
4. The resin film according to claim 1 , wherein the resin film is a laminated film composed of two or more layers, the front and rear surfaces thereof having different degrees of roughness, wherein an average surface roughness Ra of a flatter layer is 0.5 nm or more and less than 4.0 nm.
5. The resin film according to claim 1 , wherein the resin comprises a matrix resin and a heat resistant resin having a higher glass transition temperature than the matrix resin.
6. The resin film according to claim 5 , wherein the heat resistant resin having a higher glass transition temperature than the matrix resin is at least one selected from the group consisting of polyimides, polyether imides, polyether ketones, and polyether ether ketones, and is contained in the resin in an amount in the range of 0.5 to 25 mass % based on the mass of the whole resin.
7. The resin film according to claim 1 , wherein a temperature expansion coefficient and a humidity expansion coefficient in the film width direction are in the ranges of −8 to 10 ppm/° C. and 1 to 8.5 ppm/% RH, respectively.
8. The resin film according to claim 1 , wherein the film is used as a base film of a magnetic recording tape.
9. The resin film according to claim 8 , wherein the film is used as a base film of a high-density magnetic recording tape in which a track position is adjusted by controlling tension applied in the running direction of the magnetic recording tape.