Patent ID: 8013084

Claim:
A manufacturing method of an optical material, the method comprising: blending an inorganic compound (a) containing at least one of a sulfur atom and a selenium atom and a compound (b) represented by a following formula (I) in a tank, the compound (a) and the compound (b) being blended at a ratio of 1 mass % or more and 50 mass % or less of the compound (a) and 50 mass % or more and 99 mass % or less of the compound (b) relative to a total mass of a mixture of the compound (a) and the compound (b); mixing a compound (c) containing at least one thiol (SH) group; preliminarily polymerizing at least the compound (a) and the compound (b) by blending and polymerizing the compounds in the tank; cooling the compounds; and deaerating the compounds, wherein the compound (c) is mixed during any one of the preliminary polymerizing, the cooling and the deaerating, a viscosity of the obtained composition is measured during at least one of the preliminarily polymerizing, the cooling and the deaerating, and when the viscosity reaches a predetermined value, a control is performed to terminate an ongoing one of the preliminarily polymerizing, the cooling and the deaerating and start a succeeding one of the preliminarily polymerizing, the cooling and the deaerating, when the control is performed during the preliminarily polymerizing, the control is performed so that the viscosity is kept at or lower than the predetermined value, and when the control is performed during the cooling after the control is performed in the preliminarily polymerizing, the cooling is terminated when the viscosity reaches a second predetermined value that is larger than the predetermined value (m represents an integer of 0 to 4, and n represents an integer of 0 to 2).