Abstract: A polymer expanded particle and an expanded toner having small pores, and a production method thereof are provided. A polymer expanded particle comprises micropores having an average pore diameter of less than 50 ?m. An expanded toner comprises micropores having an average pore diameter of 1 ?m to less than 3 ?m, wherein volume average particle diameter is 5 ?m to less than 15 ?m. A method for producing a polymer expanded particle comprises a first step for mixing specific polymer particles with high pressure gas or supercritical fluid, to prepare a mixture, a second step for impregnating with the high pressure gas or the supercritical fluid to the inside of the polymer particles, and a third step for reducing pressure and temperature of the mixture, to form the polymer expanded particle, wherein the pressure and temperature in the third step is reduced for 5 minutes or less from a state of 20 MPa or greater and 60° C. or greater to a state of less than 1 MPa and less than 30° C., respectively.

Abstract: A method for producing covered particles, comprising: a mixing step of mixing a fluid containing particles comprising at least one type of substance selected from among metals, metal oxides and ceramics, a silsesquioxane having a functional group with an affinity for carbon dioxide, and supercritical carbon dioxide; and a covering step of reducing pressure of the fluid to gasify the supercritical carbon dioxide, while adhering the silsesquioxane onto the particles, and thereby obtaining covered particles comprising the particles and silsesquioxane covering the particles.