초록 ▼

A cavity22in an injection molding assembly includes a lower mold insert21for shaping a lens convex surface and an upper mold insert20for shaping a lens concave surface. When the heated injection molding assembly is cooled and a lens is ejected after a molten resin is pressurized by the upper mold in

A cavity22in an injection molding assembly includes a lower mold insert21for shaping a lens convex surface and an upper mold insert20for shaping a lens concave surface. When the heated injection molding assembly is cooled and a lens is ejected after a molten resin is pressurized by the upper mold insert20, the temperature of the lower mold insert21is lowered below the temperature of the upper mold insert20, which prevents the molded lens from bending at a central portion and enable high transfer precision of insert shapes.

대표청구항 ▼

1. A method of injection molding a plastic lens, comprising the steps of; providing a cavity for molding the lens including a pair of cavity forming members for shaping a convex surface and a concave surface of the lens disposed oppositely with each other inside an injection molding assembly; heati

1. A method of injection molding a plastic lens, comprising the steps of; providing a cavity for molding the lens including a pair of cavity forming members for shaping a convex surface and a concave surface of the lens disposed oppositely with each other inside an injection molding assembly; heating the injection molding assembly; filling a molten resin in the cavity for molding the lens; pressurizing the molten resin; cooling the injection molding assembly to cool and solidify the molten resin to mold the lens in the cavity; and ejecting the lens from the cavity, wherein the temperature of the cavity forming member for shaping the convex surface is lowered below the temperature of the cavity forming member for shaping the concave surface during the cooling of the injection molding assembly . 2. The method of injection molding the plastic lens according to claim 1, wherein the lens is a meniscus lens having a larger thickness of a peripheral portion than a thickness of a central portion. 3. The method of injection molding the plastic lens according to claim 2, wherein a difference in temperature between the cavity forming member for shaping the convex surface and the cavity forming member for shaping the concave surface is enlarged in proportion to an increase of the power of the lens molded in the cavity. 4. The method of injection molding the plastic lens according to claim 1, wherein the time to cool the injection molding assembly is lengthened in proportion to an increase of the power of the lens molded in the cavity. 5. The method of injection molding the plastic lens according to claim 1, wherein the temperature of the cavity forming member for shaping the convex surface is lowered below the temperature of the cavity forming member for shaping the concave surface from pressurization of the molten resin to ejection of the lens. 6. The method of injection molding the plastic lens according to claim 1, wherein the lens is a spectacle lens, and wherein a cooling time of the spectacle lens with the same power is lengthened in proportion to an increase in the astigmatic power of the spectacle lens. 7. The method of injection molding the plastic lens according to claim 1, wherein the injection molding assembly is heated and cooled by means of a temperature controlling fluid. 8. The method of injection molding the plastic lens according to claim 7, wherein a heating fluid and a cooling fluid are used as the temperature controlling fluid. 9. The method of injection molding the plastic lens according to claim 1, wherein the lens is a spectacle lens and wherein the injection molding assembly has at least two temperature curves relating to molding a weak lens and a strong lens for minus lenses and at least one temperature curves for a plus lens, the temperature of the injection molding assembly being controlled in accordance with the temperature curves. 10. The method of injection molding the plastic lens according to claim 9, wherein another different temperature curve is prepared for a semi-finished lens of which one side is later molded, the semi-finished lens being molded by controlling temperature of the injection molding assembly in accordance with the different temperature curve. 11. The method of injection molding the plastic lens according to claim 9, wherein the time to cool the injection molding assembly after pressurization the molten resin is set by being grouped according to lens spherical power and lens astigmatic power when a minus lens and a plus lens are molded. 12. The method of injection molding the plastic lens according to claim 11, wherein the time to cool the injection molding assembly after pressurizing the molten resin is set by being grouped on the basis of the sum of lens spherical power and lens astigmatic power in molding the minus lens. 13. A method of injection molding a plastic lens comprising: molding the lens from a molten resin in a cavity formed by a pair of cavity forming members for shaping the lens inside a heated injection molding assembly; cooling the injection molding assembly to cool and solidify the molten resin to mold the lens in the cavity; and ejecting the lens from the cavity, wherein bending of the lens at a thinner portion of the lens during manufacture of the lens is substantially prevented by at least one of controlling a temperature of a first of the pair of cavity forming members to be below a temperature of a second of the pair of cavity forming members during the cooling of the injection molding assembly, and controlling a cooling time of the injection molding assembly to be longer in proportion to an increase in the power of the lens molded in the cavity. 14. The method according to claim 13, wherein said first cavity forming member is for shaping a convex surface of the lens and said second cavity forming member is for shaping a concave surface of the lens. 15. The method according to claim 13, wherein said molding comprises: heating the injection molding assembly; filling a molten resin in the cavity for molding the lens; and pressurizing the molten resin. 16. The method according to claim 13, wherein said bending is substantially prevented by controlling a temperature of a first of the pair of cavity forming members to be below a temperature of a second of the pair of cavity forming members. 17. The method according to claim 14, wherein said bending is substantially prevented by controlling a temperature of said first cavity forming member to be below a temperature of said second cavity forming member. 18. The method according to claim 13, wherein said bending is substantially prevented by controlling a cooling time of the injection molding assembly to be longer in proportion to an increase in the power of the lens molded in the cavity. 19. The method according to claim 18, wherein the lens is a spectacle lens, and wherein a cooling time of the spectacle lens with the same power is longer in proportion to an increase in the astigmatic power of the spectacle lens. 20. The method according to claim 18, wherein the lens is a spectacle lens and wherein the injection molding assembly has at least two temperature curves relating to molding a weak lens and a strong lens for minus lenses and at least one temperature curve for a plus lens, the temperature of the injection molding assembly being controlled in accordance with the temperature curves. 21. The method according to claim 20, wherein another different temperature curve is prepared for a semi-finished lens of which one side is later molded, the semi-finished lens being molded by controlling temperature of the injection molding assembly in accordance with the different temperature curve. 22. The method according to claim 20, wherein the time to cool the injection molding assembly after pressurizing the molten resin is set by being grouped according to lens spherical power and lens astigmatic power when a minus lens and a plus lens are molded. 23. The method according to claim 22, wherein the time to cool the injection molding assembly after pressurizing the molten resin is set by being grouped on the basis of the sum of lens spherical power and lens astigmatic power in molding the minus lens. 24. The method according to claim 13, wherein said cooling is conducted in accordance with at least one temperature curve so as to cool and solidify the molten resin to mold the lens in the cavity. 25. The method according to claim 13, wherein the lens is a minus lens having a thickness at a central portion of the lens that is less than a thickness at a peripheral portion of the lens. 26. A method of injection molding a plastic lens comprising the steps of: filling a molten resin in a cavity formed by a pair of cavity forming members for shaping a convex surface and a concave surface of the lens inside a heated injection molding assembly; pressurizing the molten resin; cooling the injection molding assembly to cool and solidify the molten resin to mold the lens in the cavity; and ejecting the lens from the cavity, wherein said cooling comprises at least one of (i)controlling a cooling time of the injection molding assembly to be longer in proportion to an increase in the power of the lens molded in the cavity, and(ii)controlling a temperature of the cavity forming member for shaping the convex surface to be lower than a temperature of the cavity forming member for shaping the concave surface, during the cooling of the injection molding assembly. 27. The method according to claim 26, wherein said cooling comprises controlling a temperature of the cavity forming member for shaping the convex surface to be lower than a temperature of the cavity forming member for shaping the concave surface. 28. The method according to claim 26, wherein said cooling comprises controlling a cooling time of the injection molding assembly to be longer in proportion to an increase in the power of the lens molded in the cavity. 29. The method according to claim 28, wherein the lens is a spectacle lens, and wherein a cooling time of the spectacle lens with the same power is longer in proportion to an increase in the astigmatic power of the spectacle lens. 30. The method according to claim 28, wherein the lens is a spectacle lens and wherein the injection molding assembly has at least two temperature curves relating to molding a weak lens and a strong lens for minus lenses and at least one temperature curve for a plus lens, the temperature of the injection molding assembly being controlled in accordance with the temperature curves. 31. The method according to claim 30, wherein another different temperature curve is prepared for a semi-finished lens of which one side is later molded, the semi-finished lens being molded by controlling temperature of the injection molding assembly in accordance with the different temperature curve. 32. The method according to claim 30, wherein the time to cool the injection molding assembly after pressurizing the molten resin is set by being grouped according to lens spherical power and lens astigmatic power when a minus lens and a plus lens are molded. 33. The method according to claim 32, wherein the time to cool the injection molding assembly after pressurizing the molten resin is set by being grouped on the basis of the sum of lens spherical power and lens astigmatic power in molding the minus lens. 34. The method according to claim 26, wherein said cooling is conducted in accordance with at least one temperature curve so as to cool and solidify the molten resin to mold the lens in the cavity. 35. The method according to claim 26, wherein the lens is a minus lens having a thickness at a central portion of the lens that is less than a thickness at a peripheral portion of the lens. 36. A method of injection molding a plastic lens comprising the steps of: filling a molten resin in a cavity formed by a pair of cavity forming members for shaping a convex surface and a concave surface of the lens inside a heated injection molding assembly; pressurizing the molten resin; cooling the injection molding assembly to cool and solidify the molten resin to mold the lens in the cavity; and ejecting the lens from the cavity, wherein at least one of the following conditions is satisfied: (i)said cooling comprises controlling a temperature of the cavity forming member for shaping the convex surface to be lower than a temperature of the cavity forming member for shaping the concave surface, during the cooling of the injection molding assembly, and(ii)the lens is a spectacle lens and the injection molding assembly has at least two temperature curves relating to molding a weak lens and a strong lens for minus lenses and at least one temperature curve for a plus lens, and wherein the temperature of the injection molding assembly is controlled in acco rdance with the temperature curves. 37. The method according to claim 26, wherein said cooling comprises controlling a cooling time of the injection molding assembly to be longer in proportion to an increase in a sum of the spherical power and the astigmatic power of the lens molded in the cavity.