Light sensitive silver halide element having photographic film base with improved curl stability

A light-sensitive silver halide photographic element having at least one silver halide containing emulsion layer on a film base, the film base being a coextruded laminate having a first layer and a second layer, the first layer being a polyester of an aromatic dicarboxylic acid or a dialkyl ester thereof and an alkylene glycol adjacent to the emulsion layer, the second layer being a polyester having a humidity expansion coefficient greater than 5.times.10.sup.-5 ##EQU8## (RH is relative humidity) and a Young's modulus at 50% relative humidity greater than 300 kPSI, the thickness of the second layer is defined by the formula;

• 0. 3h.sub.2.sup.0 <h.sub.2 <1.2h.sub.2.sup.0 I
• where h.sub.2.sup.0 is the thickness of the second layer to obtain zero curl and is determined by formula ##EQU9## where the values a, b and c are obtained by the following formulas III, IV and V respectively;
• a=.phi.E'.sub.2 -E'.sub.e h.sub.e -E'.sub.1 h.sub.1 III
• b=.phi.(h.sub.e +h.sub.1)E'.sub.2 +.phi.h.sub.1 E'.sub.2 -(h.sub.e +h.sub.1)h.sub.e E'.sub.e -h.sub.1 (E'.sub.e h.sub.e+ E'.sub.1 h.sub.1)IV
• c=.phi.(h.sub.e +h.sub.1)h.sub.1 E'.sub.1 V
• .phi. in the above formulas is determined by the following formula VI ##EQU10## where E'.sub.e, E'.sub.1 and E'.sub.2 are determined by the formula ##EQU11## where i is layer 1, 2 or e respectively and v.sub.i is the Poisson's ratio of layer i (layer 1, 2 or e respectively) and where h.sub.e, E.sub.e and .alpha..sub.e are the thickness, Young's modulus and HEC respectively of the emulsion layer;
• h.sub.1 E.sub.1 and .alpha..sub.1 are the thickness, Young's modulus and HEC respectively of the first layer of the film base;
• and h.sub.2, E.sub.2 and .alpha..sub.2 are the thickness, Young's modulus and HEC respectively of the second layer of the film base.