Binder resin for electrophotographic toner and toner containing the same

A binder resin for an electrophotographic toner, which comprises a mixture of polymers comprising styrenic monomer units with or without acrylic or methacrylic monomer units, said resin having at least one peak value of molecular weight in each of the molecular weight ranges of less than 30,000 and not less than 150,000, respectively in a chromatogram as measured by gel permeation chromatography, and satisfying the following inequalities (1)-(4):

• 110<54.54+0.64.times.10.sup.-3 .times.P.sub.1 +0.815.times.T.sub.1 +0.314.times.S.sub.2 <123 (1)
• 175<5.19+0.0583.times.10.sup.-3 .times.P.sub.2 +1.227.times.T.sub.1 +2.45.times.S.sub.2 <215 (2)
• 5.32<2.74+0.2585.times.log P.sub.1 +0.02210.times.T.sub.1 +0.0125.times.S.sub.2 <5.65 (3)
• 55<T.sub.2 -120 (4)
• wherein
• P.sub.1 :
• the highest peak value of molecular weight in the molecular weight range of less than 30,000 in a chromatogram as measured by gel permeation chromatography;
• P.sub.2 :
• the highest peak value of molecular weight in the molecular weight range of not less than 150,000 in a chromatogram as measured by gel permeation chromatography;
• S.sub.2 :
• percentage of the area of the molecular weight range or not less than 30,000 to the whole area of chromatogram as measured by gel permeation chromatography;
• T.sub.1 :
• the glass transition temperature (Tg, .degree.C.) of said resin;
• T.sub.2 :
• the temperature (.degree.C.) providing the storage modulus (G') of 100,000 dyne/cm.sup.2, in measuring the dynamic viscoelasticity of said resin under the condition of 20 Hz of frequency and in the melted situation at not less than 100.degree. C.;
• and
• T.sub.3 :
• the temperature (.degree.C.) providing the absolute value of the complex viscoelastic coefficient (1.eta.*1) of 10,000 poise, in measuring the dynamic viscoelasticity of said resin under the condition of 20 Hz of frequency and in the melted situation at not less than 100.degree. C.