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.

The present invention provides an aromatic polyester having several operative functional groups and a method for producing same. An aromatic polyester comprising a polycarboxylic acid component and a polyhydric alcohol component as a copolymerization component, wherein the aromatic polyester comprises a polycarboxylic acid component having an operative functional group by 50 mol % or more when a total amount of the polycarboxylic acid component is taken as 100 mol %, and the aromatic polyester comprises an aromatic polyhydric alcohol component by 50 mol % or more when a total amount of the polyhydric alcohol component is taken as 100 mol %.

The present invention provides new classes of phenol compounds, including those derived from tyrosol and analogues, useful as monomers for preparation of biocompatible polymers, and biocompatible polymers prepared from these monomeric phenol compounds, including novel biodegradable and/or bioresorbable polymers. These biocompatible polymers or polymer compositions with enhanced bioresorbability and processibility are useful in a variety of medical applications, such as in medical devices and con-trolled-release therapeutic formulations. The invention also provides methods for preparing these monomeric phenol compounds and biocompatible polymers.

The present invention concerns the use of a compound having the following formula (I), for the preparation of a polymer. The present invention also concerns the polymers obtained from polymerization of compound of formula (I), and their processes of preparation.

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The present invention concerns the use of a compound having the following formula (I), for the preparation of a polymer. The present invention also concerns the polymers obtained from polymerization of compound of formula (I), and their processes of preparation.

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An electrostatic image developing toner includes an amorphous polyester resin, a crystalline polyester resin, and C.I. Pigment Red 57:1, wherein a Net intensity N.sub.Mg of an Mg element, the Net intensity N.sub.Mg of being determined by X-ray fluorescence analysis, is 0.10 kcps or more and 0.40 kcps or less.

An electrostatic image developing toner includes an amorphous polyester resin, a crystalline polyester resin, and C.I. Pigment Red 57:1, wherein a Net intensity N.sub.Mg of an Mg element, the Net intensity N.sub.Mg of being determined by X-ray fluorescence analysis, is 0.10 kcps or more and 0.40 kcps or less.

A toner including toner particles having a resin component containing a crystalline resin and an amorphous resin, in which the resin component contains a tetrahydrofuran-insoluble component, and the content of the tetrahydrofuran-insoluble component with respect to the content of the resin component is 5.0% to 80.0% by mass, wherein a maximum endothermic peak temperature of the tetrahydrofuran-insoluble component is 55.0 to 80.0° C., and the amount of heat absorption in the maximum endothermic peak of the tetrahydrofuran-insoluble component is 10.0 to 80.0 Pa, and toner particles have a structure which comprises a matrix containing the crystalline resin and domains containing the amorphous resin.

An electrostatic image developing toner includes an amorphous polyester resin, a crystalline polyester resin, and C.I. Pigment Red 57:1, wherein a Net intensity N.sub.Mg of an Mg element, the Net intensity N.sub.Mg of being determined by X-ray fluorescence analysis, is 0.10 kcps or more and 0.40 kcps or less.

An electrostatic image developing toner includes an amorphous polyester resin, a crystalline polyester resin, and C.I. Pigment Red 57:1, wherein a Net intensity N.sub.Mg of an Mg element, the Net intensity N.sub.Mg of being determined by X-ray fluorescence analysis, is 0.10 kcps or more and 0.40 kcps or less.