Polyimide-based resin film, substrate for display device, and optical device using the same

A polyimide-based resin film wherein a thermal hysteresis gap at a temperature of 50° C. or more and 150° C. or less is 100 μm or more and 500 μm or less,

• wherein the thermal hysteresis gap is measured through a change of length in a longitudinal direction (dimension change gap, y-axis) at 100° C., on a graph that measures a thermal expansion change mode by performing a temperature rising step to 260° C. at a temperature rising rate of 5° C./min using TA Instruments, and then performing a cooling step to 50° C. at a cooling rate of 4° C./min,
• wherein the thermal hysteresis gap is measured from a polyimide-based resin film sample having a thickness of 10±1 μm, and
• wherein the polyimide-based resin film comprises a polyimide-based resin containing a polyimide repeating unit represented by the following Chemical Formula 1:
• wherein, in the Chemical Formula 1,
• X1 is an aromatic tetravalent functional group containing an ether group,
• Y1 is a divalent functional group represented by the following Chemical Formula 3,