Abstract: Provided are: a filter medium with high dust collection efficiency, low pressure loss, and a long lifespan; and a filter material used for the filter medium. This composite structure includes ultrafine fibers having a fiber diameter of less than 500 nm, and beads. The outermost surface of the composite structure has at least 500/mm2 of beads with a diameter of 5 ?m or more. The ultrafine fibers and the beads preferably have the same component.

Abstract: A spinneret (1) for electrostatic spinning is configured from a structure of an electrically conductive metal material. The structure is provided with a long-axis direction (X), a short-axis direction (Z), and a thickness direction (Y). An inflow port (10) for a spinning starting material fluid is provided to one surface of the structure. A plurality of protrusions (5) are formed on another surface of the structure so as to be aligned along the long-axis direction (X). Each of the plurality of protrusion (5) extends so as to protrude from the structure. The protrusions (5) have, provided to apexes (2) thereof, discharge holes (4) for discharging the starting material fluid. The pitch of the discharge holes (4) exceeds 1 mm.

Abstract: An object of the invention is to provide a filter medium having high collection efficiency of dust and low pressure drop. The invention relates to a filter medium including ultrafine fibers subjected to electrospinning, in which the ultrafine fibers have a plurality of ester bonds in a molecule. A mean fiber diameter of the ultrafine fibers is preferably in the range of 10 to 5,000 nanometers, and the ultrafine fibers are preferably ultrafine fibers composed of polylactic acid, polyethylene terephthalate, polymethyl methacrylate or polycarbonate. Moreover, another object is to provide a production method for a fibrous structure for a filter medium, including a step of preparing a spinning solution in which a resin having a plurality of ester bonds in a molecule is dispersed or dissolved in a solvent, and a step of obtaining the fibrous structure including ultrafine fibers by performing electrospinning of the spinning solution.

Abstract: A spinneret (1) for electrostatic spinning is configured from a structure of an electrically conductive metal material. The structure is provided with a long-axis direction (X), a short-axis direction (Z), and a thickness direction (Y). An inflow port (10) for a spinning starting material fluid is provided to one surface of the structure. A plurality of protrusions (5) are formed on another surface of the structure so as to be aligned along the long-axis direction (X). Each of the plurality of protrusion (5) extends so as to protrude from the structure. The protrusions (5) have, provided to apexes (2) thereof, discharge holes (4) for discharging the starting material fluid. The pitch of the discharge holes (4) exceeds 1 mm.