Process for reducing core-set curling tendency and core-set curl of polymeric film elements

A method for heat tempering a self-supporting film having a thickness in the range of about 2 to 50 mils and formed from poly(ethylene terephthalate) having a Tg above about 60.degree. C., determined in a differential scanning calorimeter at a heating rate of 20.degree. K./minute, to reduce the core-set curling tendency of said film without substantially distorting or shrinking said film,

• said method comprising maintaining said film for a period of about 0.1 to about 1,500 hours at a temperature of from about 38.degree. C. to about 4.degree. C. below the Tg of said poly(ethylene terephthalate) and an ambient relative humidity less than 100% until the core-set curling tendency of said film is reduced at least 30%,
• said reduction in core-set curling tendency being measurable as the change in the number of ANSI curl units that the heat-tempered film undergoes upon core-setting on a 3-inch o.d. core at 49.degree. C. and 50% RH for 24 hours, compared to the change in the number of ANSI curl units that the corresponding film which has not been subjected to said heat-tempering undergoes upon core-setting in the same manner, said ANSI curl units being measured in each instance in accordance with Test Method A, ANSI PH 1.29-1971 with respect to the same reference surface of the film.

A method for heat tempering a self-supporting biaxially-oriented, heat-set, heat-relaxed poly(ethylene terephthalate) film having a thickness of from about 2 to 50 mils and comprising at least one radiation sensitive layer to reduce the core-set curling tendency of said film without substantially distorting or shrinking said film, said poly(ethylene terephthalate) having a Tg of about 99.degree. to 112.degree. C., as determined by a differential scanning calorimeter (DSC) trace, which method comprises winding the film on a core of from about 6 inches to 12 inches outer diameter to form a roll of film and heating said roll at a temperature in the range of from about 40.degree. C. up to about 4.degree. C. below the Tg of the polymer for from about 0.25 to about 500 hours until the change in the number of ANSI curl units that the resulting film undergoes is about 22 to 69% below the change in the number of ANSI curl units that the corresponding poly(ethylene terephthalate) film which has not been subjected to said heat tempering undergoes upon core-setting under like conditions, said ANSI curl units being measured in accordance with Test Method A ANSI PH 1.29-1971 in each instance with respect to the same reference surface of the film.

A method for heat tempering a self-supporting film having a thickness in the range of about 2 to 50 mils and formed from poly(ethylene-2,6-naphthalene dicarboxylate) having a Tg above about 60.degree. C., determined in a differential scanning calorimeter at a heating rate of 20.degree. K./minute, to reduce the core-set curling tendency of said film without substantially distorting or shrinking said film,

• said method comprising maintaining said film for a period of about 0.1 to about 1,500 hours at a temperature of from about 30.degree. C. up to the Tg of said poly(ethylene-2,6-naphthalene dicarboxylate) and an ambient relative humidity less than 100% until the core-set curling tendency of said film is reduced at least 15%,
• said reduction in core-set curling tendency being measurable as the change in the number of ANSI curl units that the heat-tempered film undergoes upon core-setting on a 3-inch o.d. core at 49.degree. C. and 50% RH for 24 hours, compared to the change in the number of ANSI curl units that the corresponding film which has not been subjected to said heat-tempering undergoes upon core-setting in the same manner, said ANSI curl units being measured in accordance with Test Method A ANSI PH 1.29-1971 in each instance with respect to the same reference surface of the film.

A self-supporting thermoplastic polymer film characterized in that said film is a heat-tempered film having reduced core-set curling tendency and that the change in ANSI curl units that said film undergoes upon being maintained in rolled condition for 2200 hours at a temperature of 21.degree. C. and R.H. up to 50% is at least 15% less than the change in the number of ANSI curl units that the corresponding film which is not heat-tempered undergoes upon core-setting under like conditions, said ANSI curl units being measured in accordance with Test Method A, ANSI PH 1.29-1971 in each instance with respect to the same reference surface of the film.

A self-supporting, noncellulosic thermoplastic film characterized in that said film is a heat-tempered film having reduced core-set curling tendency and that the change in ANSI curl units that said film undergoes upon being maintained in rolled condition for 2200 hours at a temperature of 21.degree. C. and R.H. up to 50% is no more than 14 ANSI curl units measured at 50% R.H., said ANSI curl units being measured in accordance with Test Method A, ANSI PH 1.29-1971 with reference to the same surface of the film.

A multilayered radiation sensitive film element comprising a support and at least one radiation sensitive layer, said support comprising a thermoplastic polymer film having a thickness of about 2 to 10 mils, said polymer being poly(ethylene terephthalate), poly(1,4-cyclohexylene dimethylene terephthalate), or poly(ethylene-2,6-naphthalene dicarboxylate), said film element being characterized in that said polymer film is a heat-tempered film having reduced core-set curling tendency and in that the change in ANSI curl units that said element undergoes upon being maintained in rolled condition for 2200 hours at a temperature of 20.degree. C. and relative humidity (R.H.) up to 50% is .+-. 14 ANSI curl units, said ANSI curl units being measured at 50% R.H. in accordance with Test Method A ANSI PH 1.29-1971 with reference to the same surface of the film.

A microfiche comprising a thermoplastic polymer film support having a thickness of about 2 to 10 mils, said polymer being poly(ethylene terephthalate), said microfiche being characterized in that said polymer film is a heat-tempered film having reduced core-set curling tendency and said microfiche being further characterized in that the curl value of said microfiche is not more than .+-. 9 ANSI curl units, said ANSI curl units being measured at 50% R.H. in accordance with Test Method A ANSI PH 1.29-1971.