Abstract: An optical fiber ribbon comprises a plurality of optical fibers arranged in parallel and a connecting resin layer containing a ribbon resin for coating and connecting the plurality of optical fibers, wherein each of the plurality of optical fibers has an outer diameter of 220 ?m or less; and the ribbon resin contains a cured product of urethane (meth)acrylate, and an amount of silicon is 5 ppm or more and 80000 ppm or less and an amount of tin is 5 ppm or more and 30000 ppm or less at the surface of the connecting resin layer.

Abstract: The optical fiber comprises a glass fiber comprising a core and a cladding, a primary resin layer in contact with the glass fiber and covering the glass fiber, and a secondary resin layer covering the primary resin layer, wherein the primary resin layer contains a cured product of a resin composition containing a urethane (meth)acrylate oligomer, a monomer, a photopolymerization initiator and an aromatic acid compound, a content of the aromatic acid compound is 20 ppm or more and 12000 ppm or less based on a total amount of the resin composition, and Young's modulus of the primary resin layer is 0.6 MPa or less at 23° C.±2° C.

Abstract: The resin composition according to an aspect of the present disclosure is a resin composition containing a photopolymerizable compound comprising urethane (meth)acrylate and a polyrotaxane, and a photopolymerization initiator, and the content of the polyrotaxane is 0.05% by mass or more and 11% by mass or less based on the total amount of the photopolymerizable compound.

Abstract: The pressure reduction valve includes: a cylindrical portion, a piston and a spring. The cylindrical portion includes an inlet communicating with the primary side flow path and an outlet communicating with the secondary side flow path. The piston fitted into the cylindrical portion is slidable along an axis direction of the cylindrical portion within the cylindrical portion, and defines, within the cylindrical portion, a space communicating with the inlet and the outlet. The spring applies, to the piston, a force acting toward the space. The outlet is displaced in one direction from the center of the piston when seen in the axis direction. The force applied to the piston by the spring is distributed so as to deviate from the center of the piston to the side of the outlet.

Abstract: A valve element of a pressure reducing valve includes a taper portion seated on an inner periphery of a valve hole that includes a first area, a second area and a third area in order from an upstream side. The first area is provided such that, when the valve element is open, the height of a passage defined between the first area and the taper portion gradually reduces toward a downstream side. The second area is provided such that the height of a passage defined between the second area and the taper portion is constant when the valve element is open and the entire second area contacts the taper portion when the valve element is closed. The third area is provided such that, when the valve element is open, the height of a passage defined between the third area and the taper portion gradually increases toward the downstream side.

Abstract: The pressure reduction valve includes: a cylindrical portion, a piston and a spring. The cylindrical portion includes an inlet communicating with the primary side flow path and an outlet communicating with the secondary side flow path. The piston fitted into the cylindrical portion is slidable along an axis direction of the cylindrical portion within the cylindrical portion, and defines, within the cylindrical portion, a space communicating with the inlet and the outlet. The spring applies, to the piston, a force acting toward the space. The outlet is displaced in one direction from the center of the piston when seen in the axis direction. The force applied to the piston by the spring is distributed so as to deviate from the center of the piston to the side of the outlet.

Abstract: A valve element of a pressure reducing valve includes a taper portion seated on an inner periphery of a valve hole that includes a first area, a second area and a third area in order from an upstream side. The first area is provided such that, when the valve element is open, the height of a passage defined between the first area and the taper portion gradually reduces toward a downstream side. The second area is provided such that the height of a passage defined between the second area and the taper portion is constant when the valve element is open and the entire second area contacts the taper portion when the valve element is closed. The third area is provided such that, when the valve element is open, the height of a passage defined between the third area and the taper portion gradually increases toward the downstream side.