Photographic multilayer film base comprising 1,4-cyclohexane dimethanol

An imaging element comprising at least one light-sensitive or heat-sensitive imaging layer over a support comprising a biaxially stretched, semicrystalline multilayer film base comprising at least three support layers and at least two tie layers:

• a) a core layer of a first PET-based polyester material comprising one or more polyester resins;
• b) adjacent to the two face surface of the core layer, respectively, a first and a second outer layer of, respectively, a second and third PET-based polyester material comprising one or more polyester resins, in which materials the total level of repeat units derived from 1,4-cyclohexane dimethanol is greater than the mol % in the core layer, based on total glycol component in the material;
• wherein between the core layer and each outer layer there is, respectively, a first and second tie layer, each having one surface side in contact with the core layer and the other surface side in contact with an outer layer, which tie layers independently comprise one or more CHDM modified PET based polyester;
• wherein the average CHDM mol % in each tie layer is at least 20 mol % higher than the mol % CHDM, if any, in the core layer, and at least 30-mol % lower than the mol % CHDM in the outer layer in which it is in contact;
• wherein the tie layers each contain at least one constituent CHDM-modified PET polyester wherein the difference in the mol %, of 1,4-cyclohexane dimethanol between said at least one constituent CHDM modified PET polyester and the overall mol % in the core layer, and also between the same or an optional additional CHDM modified PET polyester and the overall mol % in the outer layer with which the tie layer is in contact, is less than 50 mol %;
• wherein the peel strength, in Newtons/meter, of each of said two outer layers in contact, respectively, with the first and second tie layer is at least twice the peel strength of the film in the absence of the tie layer;
• and
• wherein the total thickness of said multilayer film base is 25 to 200 microns, the ratio of the thickness of said core layer to the sum of the other support layers, excluding tie layers, in the multilayer film base is in the range 1:20 to 20:1 and said two tie layers are no more than 20 microns thick.

A method of making a semicrystalline multilayer film base comprising coextruding a multilayer sheet comprising first coextruded sheet layer, an intermediate coextruded sheet layer, and a second coextruded sheet layer, and then biaxially stretching the coextruded multilayer sheet to obtain a semicrystalline multilayer film base comprising at least two support layers and at least one tie layer, which film base comprises:

• a) a first layer, derived from the first coextruded sheet layer, of a first PET-based polyester material comprising one or more polyester resins;
• b) on one side of the first layer, a second layer, derived from the second coextruded sheet layer, of a PET-based polyester material comprising one or more polyester resins,
• wherein the total level of repeat units derived from 1,4-cyclohexane dimethanol in at least one of the first and second layers is at least 3.5 mole %;
• wherein the difference in the mol %, of 1,4-cyclohexane dimethanol between the first layer and the second layer is more than 50 mol %;
• (c) between the first layer and the second layer a tie layer, derived from the intermediate coextruded sheet layer, having one surface in contact with a surface of the first layer and a second surface in contact with a surface of the second layer, said tie layer comprising at least one CHDM-modified PET based polyester;
• wherein the average CHDM mol % in the tie layer is at least 20 mol % higher than the mol % CHDM, if any, in the layer containing the lower mol % CHDM, and at least 30-mol % lower than the mol % CHDM in the layer containing the higher mol % CHDM;
• wherein the second tie layer contains at least one constituent CHDM-modified PET polyester wherein the difference in the mol %, of 1,4-cyclohexane dimethanol between said at least one constituent CHDM modified PET polyester and the overall mol % in the core layer, and also between the same or an optional additional CHDM modified PET polyester and the overall mol % in the third layer, is less than 50 mol %, and
• wherein the total thickness of said multilayer film base is 25 to 200 microns, the ratio of the thickness of said first layer to the sum of the one or more other support layers, excluding tie layers, in the multilayer film base is in the range 1:20 to 20:1 and the thickness of the tie layer is not more than 20 microns;
• and
• wherein the coextruded multilayer film base exhibits a peel strength, in Newtons/meter, of each of said first and second layers in contact with the tie layer, of at least twice the peel strength in the absence of the tie layer.