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AssigneeEastman Chemical Company
InventorsMarcus David Shelby, Michael Eugene Donelson, Bradley Howard Dayvolt, Alan Kent Wilson, Bryan Scott Kirkman
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The present invention relates to cellulose esters having low hydroxyl content for use in optical applications, such as liquid crystal display (LCD) films. Films made with low hydroxyl levels and a given ratio of non-acetyl ester to hydroxyl level have been found to have low intrinsic birefringence. These films can be cast, molded, or otherwise oriented without an appreciable birefringence or optical distortion (i.e. retardation). Such features make these films useful in polarizer, protective, and compensator films as well as molded optical parts, such as lenses. Furthermore, it has also been found that resins of the present invention can also be made to have “+C plate” behavior either by melt or solvent based processing, a characteristic which is not typical of cellulose esters. Such +C behavior allows films to be produced having unique compensatory behavior. Other embodiments of the invention relate to methods melt casting films while minimizing birefringence formation.
A cellulose acetate propionate comprising at least one acetyl group wherein the ratio of the degree of substitution of non-acetyl ester groups (DSNAC) to degree of substitution of hydroxyl groups (DSOH) is 15 to 200 and the non-acetyl ester groups degree of substitution is from 1.1 to 1.75,
A cellulose acetate propionate comprising at least one acetyl group wherein the ratio of the degree of substitution of non-acetyl ester groups (DSNAC) to degree of substitution of hydroxyl groups (DSOH) is 15 to 200 and the non-acetyl ester groups degree of substitution is from 1.1 to 1.6,
A cellulose acetate propionate comprising at least one acetyl group wherein the glass transition temperature of said mixed cellulose ester is from 100° to 200° C.;
Dependencies are inferred from the claim text.