US Patent 7638251 Toner

The invention provides a toner which is excellent in its low-temperature fixing property and high-temperature offset resistance regardless of the types of paper, and constantly provides high-quality images regardless of environments and does not generate image defects even after prolonged use. In a master curve of the toner at a reference temperature of 150° C., a difference between a storage modulus at a frequency of 0.1 Hz and a storage modulus at a frequency of 1000 Hz is set in a rage from 0 to 2.5×105 Pa, where the activation energy determined from a shift factor is brought to a range from 50 to 130 kJ/mol.