Cellulose acylate film, stretched cellulose acylate film, and method and apparatus for producing the same
AssigneeFuji Photo Film Co., Ltd.
InventorsMasaaki Otoshi, Kiyokazu Hashimoto
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Abstract
According to the present invention, a cellulose acylate film difficult to be broken even if the stretching ratio is increased upon stretching and whose retardation (Re) is easily controllable to a desired value can be produced by melt film forming. Accordingly, a stretched cellulose acylate film highly oriented and having an appropriate retardation (Re) required from liquid crystal display device manufacturers can be produced.
Claims48
A method for producing a cellulose acylate film by melt film forming, including discharging a molten resin melted in an extruder on a running or rotating cooling support through a die in a form of a sheet, thereby solidifying the discharged molten resin by cooling, the method comprising:
- measuring a retardation (Re) in a case where a lengthwise direction of the cellulose acylate film corresponds to the slow axis;
- and
- controlling the temperature of the molten resin at an outlet of the die so that the measured retardation falls into the range of −10 nm to 80 nm.
A method for producing a cellulose acylate film by melt film forming, including discharging a molten resin melted in an extruder on a running or rotating cooling support through a die in a form of a sheet, thereby solidifying the discharged molten resin by cooling, the method comprising:
- controlling a temperature of the molten resin at an outlet of the die to a glass transition temperature (Tg)+70° C. to Tg +150° C.;
- and
- controlling a lip clearance ratio (D/W) which is a ratio of a lip clearance (D) of the die to a thickness (W) of the molten resin extruded through the die to the range of 1.5 to 10.
A cellulose acylate film produced by melt film forming, satisfying the following property values:
- (a) a retardation (Re) in a case where a lengthwise direction of the film corresponds to a slow axis of −10 nm to 80 nm,
- (b) when X represents a degree of substitution by an acetyl group and Y represents a total degree of substitution by a propionyl group, a butyryl group, a pentanoyl group and a hexanoyl group, an acylate group having a following degree of substitution:
- 2.0≦X+Y≦3.0, 0≦X≦2.0, 1.2≦Y≦2.9,
- and
- (c) a yellowness index (YI value) of 10 or less.
An apparatus for producing a cellulose acylate film by melt film forming which discharges a molten resin melted in an extruder on a running or rotating cooling support through a die in a form of a sheet and solidifies the extruded molten resin by cooling, the apparatus comprising:
- a heater for heating at least an outlet of the die;
- a measuring device which measures a retardation (Re) in a case where a lengthwise direction of the cellulose acylate film corresponds to a slow axis;
- and
- a temperature control device which controls the heater so that the measured retardation falls into the range of −10 nm to 80 nm.
An apparatus for producing a cellulose acylate film by melt film forming which discharges a molten resin melted in an extruder on a running or rotating cooling support through a die in the form of a sheet and solidifies the discharged molten resin by cooling, the apparatus comprising:
- a heater for heating at least an outlet of the die;
- a temperature sensor which measures a temperature of the molten resin at the outlet of the die without contact;
- a temperature control device which controls the heater so that the temperature of the molten resin measured by the temperature sensor falls into a range of a glass transition temperature (Tg) of the molten resin +70° C. to Tg +150° C.;
- and
- a speed control device which controls a running or rotating speed of the cooling support so that a lip clearance ratio (D/W) which is a ratio of a lip clearance (D) of the die to a thickness (W) of the molten resin discharged through the die falls into the range of 1.5 to 10.
Dependencies are inferred from the claim text.