The present invention provides a polyarylate resin which is excellent in heat-resisting properties, abrasion-resisting properties, solubility properties in non-halogenated organic solvents, a water vapor-barrier property, mechanical properties, liquid sag-resisting properties and deformation-resisting properties (such as adhesive properties). The present invention relates to a polyarylate resin comprising a dihydric phenol residue shown in general formula (1) and an aromatic dicarboxylic acid residue shown in general formula (2), a film comprising the same and a laminated product thereof:

##STR00001##

(wherein X represents a liner or branched bivalent hydrocarbon group having 4 to 8 carbon atoms.)

##STR00002##

(wherein R.sup.1 and R.sup.2 respectively and independently represent a monovalent hydrocarbon group having 1 to 6 carbon atoms, which may be substituted by one or more halogen atoms, or a halogen atom, and p and q respectively and independently represent an integer of 0 to 4.).

Processes are described for purifying a biphenyldicarboxylic acid product containing one or more impurities, particularly at least formylbiphenylcarboxylic acid. In the processes, at least a portion of the biphenyldicarboxylic acid product is contacted with an alcohol under conditions effective to esterify at least part of the biphenyldicarboxylic acid and at least part of the formylbiphenylcarboxylic acid and produce an esterification effluent containing biphenyldicarboxylic acid diester and formylbiphenylcarboxylic acid ester. At least part of the biphenyldicarboxylic acid diester is then separated from the esterification effluent by crystallization. Advantageously, a polyester product may be produced from the separated biphenyldicarboxylic acid diester.

Bibenzoate copolyesters are based on (4,4-biphenyl dicarboxylic acid-co-3,4-biphenyl dicarboxylic acid) as the diacid component, and on an alicyclic diol compound such as 1,4-cyclohexanedimethanol as a portion of the diol component. Copolyesters are based on 4,4-biphenyl dicarboxylic acid, and/or 3,4-biphenyl dicarboxylic acid as the diacid component and may include a multifunctional acid. Copolymers may optionally base an essentially amorphous morphology, high glass transition temperature, high elongation at break, and/or high melting temperature. A method to make the copolymers controls the characteristics of the copolyester selected from one or a combination of amorphous morphology or degree of crystallinity, Tg, Tm, tensile modulus, flexural modulus, elongation at break, and so on, by selecting the proportions of the 4,4-biphenyl dicarboxylic acid or ester producing equivalent thereof, 3,4-biphenyl dicarboxylic acid or ester producing equivalent thereof, and/or the proportion of the 1,4-cyclohexanedimethanol in the diol component.

Bibenzoate copolyesters are based on (4,4-biphenyl dicarboxylic acid-co-3,4-biphenyl dicarboxylic acid) as the diacid component, and on an alicyclic diol compound such as 1,4-cyclohexanedimethanol as a portion of the diol component. Copolyesters are based on 4,4-biphenyl dicarboxylic acid, and/or 3,4-biphenyl dicarboxylic acid as the diacid component and may include a multifunctional acid. Copolymers may optionally base an essentially amorphous morphology, high glass transition temperature, high elongation at break, and/or high melting temperature. A method to make the copolymers controls the characteristics of the copolyester selected from one or a combination of amorphous morphology or degree of crystallinity, Tg, Tm, tensile modulus, flexural modulus, elongation at break, and so on, by selecting the proportions of the 4,4-biphenyl dicarboxylic acid or ester producing equivalent thereof, 3,4-biphenyl dicarboxylic acid or ester producing equivalent thereof, and/or the proportion of the 1,4-cyclohexanedimethanol in the diol component.

An electrophotographic photosensitive member includes a photosensitive layer. The photosensitive layer contains a charge generating material, a hole transport material, and a binder resin. The binder resin contains a polyarylate resin represented by general formula (1). In general formula (1), r and s each represent an integer of at least 0 and no greater than 49 and t and u represents an integer of at least 1 and no greater than 50. Furthermore, r+s+t+u=100 and r+t=s+u. X and Y each represent, independently of one another, a divalent group represented by chemical formula (1-1), (1-2), (1-3), or (1-4). ##STR00001##

An electrophotographic photosensitive member includes a photosensitive layer. The photosensitive layer contains a charge generating material, a hole transport material, and a binder resin. The binder resin contains a polyarylate resin represented by general formula (1). In general formula (1), r and s each represent an integer of at least 0 and no greater than 49 and t and u represents an integer of at least 1 and no greater than 50. Furthermore, r+s+t+u=100 and r+t=s+u. X and Y each represent, independently of one another, a divalent group represented by chemical formula (1-1), (1-2), (1-3), or (1-4). ##STR00001##

Liquid crystalline hydroquinone-3,4-biphenyl dicarboxylate polyesters, and methods of making them. The polyesters may be melt processed at a temperature below the thermal decomposition temperature and the isotropic temperature, and may form a liquid crystalline glass phase. The polyesters may be formed by polycondensation of hydroquinone or a hydroquinone derivative with 3,4-biphenyl dicarboxylic acid.

Liquid crystalline hydroquinone-3,4-biphenyl dicarboxylate polyesters, and methods of making them. The polyesters may be melt processed at a temperature below the thermal decomposition temperature and the isotropic temperature, and may form a liquid crystalline glass phase. The polyesters may be formed by polycondensation of hydroquinone or a hydroquinone derivative with 3,4-biphenyl dicarboxylic acid.

Liquid crystalline hydroquinone-3,4-biphenyl dicarboxylate polyesters, and methods of making them. The polyesters may be melt processed at a temperature below the thermal decomposition temperature and the isotropic temperature, and may form a liquid crystalline glass phase. The polyesters may be formed by polycondensation of hydroquinone or a hydroquinone derivative with 3,4-biphenyl dicarboxylic acid.

Liquid crystalline hydroquinone-3,4-biphenyl dicarboxylate polyesters, and methods of making them. The polyesters may be melt processed at a temperature below the thermal decomposition temperature and the isotropic temperature, and may form a liquid crystalline glass phase. The polyesters may be formed by polycondensation of hydroquinone or a hydroquinone derivative with 3,4-biphenyl dicarboxylic acid.