The invention provides a crystalline wholly aromatic polyester that is capable of improving slidability and thermal stability at the time of molding, while having heat resistance. The crystalline wholly aromatic polyester is a polycondensate of an aromatic dicarboxylic acid and an aromatic diol, wherein a structural unit derived from the aromatic dicarboxylic acid comprises structural unit (I) of formula (1):

##STR00001##

structural unit (II) of formula (2):

##STR00002##

and structural unit (III) of formula (3):

##STR00003##

and a structural unit derived from the aromatic diol comprises structural unit (IV) of formula (4):

##STR00004##

wherein 30 mol %≤structural unit (I)≤40 mol %; 5 mol %≤structural unit (II)≤10 mol %; 5 mol %≤structural unit (III)≤10 mol %; and 45 mol %≤structural unit (I)+structural unit (II)+structural unit (III)≤50 mol %.

The invention provides a crystalline wholly aromatic polyester that is capable of improving slidability and thermal stability at the time of molding, while having heat resistance. The crystalline wholly aromatic polyester is a polycondensate of an aromatic dicarboxylic acid and an aromatic diol, wherein a structural unit derived from the aromatic dicarboxylic acid comprises structural unit (I) of formula (1):

##STR00001##

structural unit (II) of formula (2):

##STR00002##

and structural unit (III) of formula (3):

##STR00003##

and a structural unit derived from the aromatic diol comprises structural unit (IV) of formula (4):

##STR00004##

wherein 30 mol %≤structural unit (I)≤40 mol %; 5 mol %≤structural unit (II)≤10 mol %; 5 mol %≤structural unit (III)≤10 mol %; and 45 mol %≤structural unit (I)+structural unit (II)+structural unit (III)≤50 mol %.

The present invention relates to triarylmethane compounds of the formula (I), which suitable as monomers for preparing thermoplastic resins having beneficial optical properties and which can be used for producing optical devices. R.sup.1, R.sup.2 are e.g. hydrogen; Y is an alkylene group having 2, 3 or 4 carbon atoms, Ar is selected from mono- or polycyclic aryl and mono- or polycyclic hetaryl; X.sup.1, X.sup.2, X.sup.3, X.sup.4 are CH, C—R.sup.x or N, provided that in each ring at most two of X.sup.1, X.sup.2, X.sup.3, X.sup.4 are N; R.sup.x is e.g. halogen, CN or CH═CH.sub.2. The invention also relates to thermoplastic resins comprising a polymerized unit of the compound of formula (I).

##STR00001##

A polyester carbonate resin is provided, which includes a structural unit derived from a compound represented by general formula (1), a structural unit derived from a compound represented by general formula (2), a structural unit derived from a dicarboxylic acid or a derivative thereof, and a structural unit derived from a carbonic acid diester. The polyester carbonate can be used, e.g., in optical systems. ##STR00001##

A polyester carbonate resin is provided, which includes a structural unit derived from a compound represented by general formula (1), a structural unit derived from a compound represented by general formula (2), a structural unit derived from a dicarboxylic acid or a derivative thereof, and a structural unit derived from a carbonic acid diester. The polyester carbonate can be used, e.g., in optical systems. ##STR00001##

The resin composition includes a liquid crystal polyester resin (A) and a filler (B), in which (1) liquid crystal polyester resin (A) contains a structural unit (I) derived from 6-hydroxy-2-naphthoic acid, a structural unit (II) derived from an aromatic diol compound, and a structural unit (III) derived from an aromatic dicarboxylic acid compound, wherein structural unit (III) contains a structural unit (IIIA) derived from terephthalic acid and/or a structural unit (IIIB) derived from 2,6-naphthalenedicarboxylic acid, (2) 40% by mol≤structural unit (I)≤75% by mol, 12% by mol≤structural unit (II)≤30% by mol, and 12% by mol≤structural unit (III)≤30% by mol, (3) filler (B) is at least one of silica, mica, and talc, and (4) the resin composition has a dielectric tangent of 1.0×10.sup.−3 or less as measured by a cavity resonator perturbation method at 10 GHz.

The resin composition includes a liquid crystal polyester resin (A) and a filler (B), in which (1) liquid crystal polyester resin (A) contains a structural unit (I) derived from 6-hydroxy-2-naphthoic acid, a structural unit (II) derived from an aromatic diol compound, and a structural unit (III) derived from an aromatic dicarboxylic acid compound, wherein structural unit (III) contains a structural unit (IIIA) derived from terephthalic acid and/or a structural unit (IIIB) derived from 2,6-naphthalenedicarboxylic acid, (2) 40% by mol≤structural unit (I)≤75% by mol, 12% by mol≤structural unit (II)≤30% by mol, and 12% by mol≤structural unit (III)≤30% by mol, (3) filler (B) is at least one of silica, mica, and talc, and (4) the resin composition has a dielectric tangent of 1.0×10.sup.−3 or less as measured by a cavity resonator perturbation method at 10 GHz.

A polymer includes a plurality of repeated polymerized units according to scheme (2): ##STR00001##

A polymer includes a plurality of repeated polymerized units according to scheme (2): ##STR00001##

A resin includes a unit represented by Chemical Formula 1, a method for preparing the same, a resin composition including the same, and a molded article including the resin composition

##STR00001## in Chemical Formula 1, Ar1, Ar2, R1, r1, X1 to X4, Z1, Z2, a and b are described herein.