Polyethylene naphthalate film
AssigneeDiafoil Company, Limited
InventorsSeiji Sakamoto, Yoshinori Sato
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Abstract
Disclosed herein is a biaxially oriented polyethylene naphthalate film having a center line average roughness [Ra(.mu.m)] and a film thickness [T(.mu.m)] which satisfy the following formula: ##EQU1## produced by the electrostatic cooling method from polymethylene naphthalate having a resistivity of 1.times.10.sup.7 to 5.times.10.sup.8 .OMEGA..cm as measured in the molten state.
Claims14
A biaxially oriented polyethylene naphthalate film having a center line average roughness Ra .mu.m and a film thickness T .mu.m defined by the following relationship:
- ##EQU12## prepared by electrostatically cooling a polyethylene naphthalate sheet prepared from a polyethylene naphthalate melt having a resistivity of 1.times.10.sup.7 to 5.times.10.sup.8 .OMEGA..cm as measured in the molten state.
A biaxially oriented polyethylene naphthalate film having a center line average roughness Ra .mu.m and a film thickness T .mu.m defined by the relationship:
- ##EQU13## prepared by:
- extruding polyethylene naphthalate containing a phosphorus compound which controls the resistivity of the molten polyethylene naphthalate to within the range of 1.times.10.sup.7 to 5.times.10.sup.8 .OMEGA..cm, as measured in the molten state, and which contains from 0.01-1 wt. % of inert fine particles, at a temperature ranging from 280.degree. C.-320.degree. C. into a film;
- electrostatically cooling said polyethylene naphthalate film such that the degree of crystallinity of the film ranges from 28-50%;
- stretching the film obtained in two directions;
- and
- heat-treating the biaxially oriented film obtained at 120.degree. C.-250.degree. C.
A magnetic tape, comprising:
- a biaxially oriented polyethylene naphthalate film having a center line average roughness [Ra(.mu.m)] and a film thickness [T(.mu.m)] defined by the following relationship:
- ##EQU14## which is prepared by electrostatically cooling a polyethylene naphthalate sheet prepared from a polyethylene naphthalate melt having a resistivity of 1.times.10.sup.7 to 5.times.10.sup.8 .OMEGA..cm, as measured in the molten state, and
- a magnetic layer coated on said film.
Dependencies are inferred from the claim text.