The present invention relates to an electrophotographic photoreceptor comprising: a conductive support; and a photosensitive layer disposed on the conductive support, wherein the photosensitive layer includes a polyester resin containing a dihydric phenol residue and a dicarboxylic acid residue, and the dihydric phenol residue includes at least one dihydric phenol residue selected from the group of the specific dihydric phenol residues, and the other specific dihydric phenol residue.

The polymer includes a first structural unit represented by formula (1), a second structural unit represented by formula (2), and a third structural unit represented by formula (3). R.sup.1, R.sup.2, R.sup.10 and R.sup.11 each independently represent a halogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, a monovalent halogenated hydrocarbon group having 1 to 20 carbon atoms, a nitro group or a cyano group; R.sup.3A, R.sup.3B R.sup.4A and R.sup.4B each independently represent a methylene group or an alkylene group having 2 to 4 carbon atoms; Z.sup.A to Z.sup.D each independently represent —O— or —S—; and L represents a divalent group represented by formula (3-1) or (3-2), wherein R.sup.a represents a divalent alicyclic hydrocarbon group having 5 to 30 ring atoms or a divalent fluorinated alicyclic hydrocarbon group having 5 to 30 ring atoms.

##STR00001##

Polycarbonate block copolymers are provided, which have: (A) a polyester block of chemical formula 1; and (B) a polycarbonate block derived from a dihydric phenol of chemical formula 3 compound and phosgene. The copolymers may be prepared by (1) polymerizing ester oligomers to form a compound of chemical formula 1; and (2) copolymerizing the ester oligomer obtained in (1) with a polycarbonate oligomer prepared from a dihydric phenol compound of chemical formula 3 and phosgene, in the presence of a polymerization catalyst. The block copolymer may have a viscosity average molecular weight (Mv) of 10,000 to 200,000. The thermoplastic copolymer resins have excellent heat resistance, transparency, impact strength, and fluidity, and thus can be usefully applied in various products, including office devices, electric/electronic products, and automotive interior/exterior parts;

##STR00001##

The present invention aims to provide a means by which a cured product to be obtained has a low dielectric loss tangent and higher heat resistance. Specifically, provided is an active ester resin that is a reaction product of a first aromatic compound having two or more phenolic hydroxy groups, a second aromatic compound having a phenolic hydroxy group, and a third aromatic compound having two or more carboxy groups and/or an acid halide thereof or an esterified compound thereof, in which at least one of the first aromatic compound, the second aromatic compound, and the third aromatic compound and/or the acid halide thereof or the esterified compound thereof has an unsaturated bond-containing substituent.

A sheet formed from a carbon fiber reinforced thermoplastic resin with a simplified production process and excellent mechanical characteristics, and a production method of said sheet is provided. This sheet is formed from a carbon fiber reinforced thermoplastic resin that contains carbon fibers, dichloromethane, and a thermoplastic resin containing at least one of a polycarbonate resin and a polyarylate resin, and the content of the dichloromethane contained in the sheet is 10-10,000 ppm by mass.

A thermoplastic resin (A) including, in its main chain structure, a unit (i) having a biphenyl group, a unit (ii) having a substituent biphenyl group, a unit (iii) having a specific number of atoms in its main chain, and a unit (iv) having a specific number of atoms in its main chain provides a thermoplastic resin which has a low liquid crystal phase transition temperature and a low isotropic phase transition temperature, is highly thermally conductive, and can be processed by molding at a low melting temperature.

A thermoplastic resin (A) including, in its main chain structure, a unit (i) having a biphenyl group, a unit (ii) having a substituent biphenyl group, a unit (iii) having a specific number of atoms in its main chain, and a unit (iv) having a specific number of atoms in its main chain provides a thermoplastic resin which has a low liquid crystal phase transition temperature and a low isotropic phase transition temperature, is highly thermally conductive, and can be processed by molding at a low melting temperature.

A liquid-crystal polymer includes at least one repeating unit having a spiro structure, and the repeating unit occupies 1 mol % to 20 mol % of the liquid-crystal polymer. The liquid-crystal polymer is composed of the following repeating units: 1 mol % to 20 mol % of ##STR00001##
10 mol % to 35 mol % of ##STR00002##
10 mol % to 35 mol % of ##STR00003##
10 mol % to
50 mol % of ##STR00004##
and 10 mol % to 40 mol % of ##STR00005##
AR.sup.1 is ##STR00006##
wherein each of ring R and ring S is independently a C.sub.3-20 ring, ring R and ring S share a carbon atom, and each of K.sup.1 and K.sup.2 is independently a C.sub.5-20 conjugated system. Each of AR.sup.2, AR.sup.3, AR.sup.4, and AR.sup.5 is independently AR.sup.6 or AR.sup.6—Z—AR.sup.7.

A retardation film includes a polyester-series resin exhibiting a negative orientation birefringence and a forward wavelength dispersibility in retardation in combination with a polyamide-series resin exhibiting a positive orientation birefringence and a flat dispersibility in retardation. The polyester-series resin may contain a constitutional unit having a fluorene-9,9-diyl group, and the polyamide-series resin may contain a constitutional unit having an alicyclic skeleton. The polyester-series resin may contain at least one constitutional unit selected from a fluorenedicarboxylic acid unit (A1) containing a unit of the formula (1) and a fluorenediol unit (B1) containing a unit of the formula (2):

##STR00001##

wherein R.sup.1 and R.sup.2 each represent a substituent; k and m each denote an integer of 0 to 8; X.sup.1a, X.sup.1b, X.sup.2a, and X.sup.2b each represent a hydrocarbon group; A.sup.1a and A.sup.1b each represent an alkylene group; n1 and n2 each denote an integer of not less than 0. The retardation film has both a high retardation expression and a reciprocal wavelength dispersibility.

The present application discloses a bending-resistant polyester film and its production method thereof. The chemical structure of the bending-resistant polyester composition comprises monomers having elastic conformation. The film made from the composition of polyester of the present invention through production processes such as melt extrusion and biaxial drawing still has excellent flexibility and optical properties.