A semi-crystalline biaxially oriented film comprising a copolyester which comprises repeating units derived from an aliphatic glycol, an aromatic dicarboxylic acid, and the monomer of formula (I): (I) wherein n=2, 3 or 4, Z is C═O, and wherein comonomer (I) constitutes a proportion of the glycol fraction of the copolyester and is present in an amount of at least about 4 mol % of the glycol fraction of the copolyester. ##STR00001##

A polymer dispersion is disclosed. The polymer dispersion includes a liquid crystal polymer powder, a polyamide acid, and a solvent. A solid content of the polymer dispersion includes the liquid crystal polymer powder and the polyamide acid. The liquid crystal polymer powder has a mass ratio of 20% to 30% in the solid content. The polyamide acid has a mass ratio of 70% to 80% in the solid content. The polyamide acid is obtained by mixing two kinds of diamines and two kinds of dianhydrides together, causing the diamines and the dianhydrides to be polymerized with each other. Both two kinds of diamines and two kinds of dianhydrides comprise a liquid crystal structure and a flexible structure respectively. A method of preparing the polymer dispersion, and a method for preparing a polymer composite film using the polymer dispersion are also disclosed.

The present invention provides a polyimide precursor that serves to produce a cured film that has high light permeability in combination with low birefringence and low linear thermal expansion. The polyimide precursor includes at least an acid dianhydride residue as represented by Formula (1), a diamine residue as represented by Formula (2), and one or more diamine residues as represented by Formula (3), the acid dianhydride residue as represented by Formula (1) accounting for 50 mol % or more of the total quantity of acid dianhydride residues in the polyimide precursor, the diamine residue as represented by Formula (2) accounting for 50 mol % or more of the total quantity of diamine residues in the polyimide precursor, and the diamine residue as represented by Formula (3) accounting for 15 mol % or less of the total quantity of diamine residues in the polyimide precursor.

The present invention provides a polyimide precursor that serves to produce a cured film that has high light permeability in combination with low birefringence and low linear thermal expansion. The polyimide precursor includes at least an acid dianhydride residue as represented by Formula (1), a diamine residue as represented by Formula (2), and one or more diamine residues as represented by Formula (3), the acid dianhydride residue as represented by Formula (1) accounting for 50 mol % or more of the total quantity of acid dianhydride residues in the polyimide precursor, the diamine residue as represented by Formula (2) accounting for 50 mol % or more of the total quantity of diamine residues in the polyimide precursor, and the diamine residue as represented by Formula (3) accounting for 15 mol % or less of the total quantity of diamine residues in the polyimide precursor.

A polymer is disclosed, represented by Chemical Formula 1 or Chemical Formula 2: ##STR00001## wherein, in Chemical Formula 1 and Chemical Formula 2, Ar.sup.1, Ar.sup.2, R.sup.3, s, x, and y are defined in the detailed description.

A polymer is disclosed, represented by Chemical Formula 1 or Chemical Formula 2: ##STR00001## wherein, in Chemical Formula 1 and Chemical Formula 2, Ar.sup.1, Ar.sup.2, R.sup.3, s, x, and y are defined in the detailed description.

An alignment layer composition including a copolymer of a dianhydride compound and a diamine compound, the copolymer including a repeating unit represented by chemical formula (1); and a repeating unit represented by chemical formula (2):

##STR00001##

wherein R.sub.1 is a tetravalent organic group derived from an alicyclic dianhydride or an aromatic dianhydride, and wherein R.sub.1 includes a phenyl ester group.

An alignment layer composition including a copolymer of a dianhydride compound and a diamine compound, wherein the copolymer includes a repeating unit represented by Formula 1:

##STR00001##

wherein each of Ar.sub.1 and Ar.sub.2 is independently a substituted or unsubstituted aromatic group comprising 6 to 30 carbon atoms, X is an electron donating group, and

##STR00002##

is an ester group, wherein “*” indicates a point of attachment to the aromatic groups Ar.sub.1 and Ar.sub.2.

The present disclosure provides a low-dissipation flexible copper clad laminate, which includes a copper foil and a polyimide film. The polyimide film is attached to the copper foil. The polyimide film includes a polyimide, and the polyimide has a structure represented by formula (I). Formula (I) is defined as in the specification.

The present invention provides a resin composition comprising the following resin (a) and filler particles. The use of this composition makes it possible to obtain a separator having excellent heat resistance. Resin (a): a copolymer comprising a structural unit represented by a formula (1) and a structural unit represented by a formula (2), ##STR00001##
wherein M.sup.n+ represents a metal ion, and n represents the valence thereof, ##STR00002##