Plastic Lens Casting Mold Inversion and CO2 Displacement

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Solution Overview

Problem

Manufacturing plastic lenses with high viscosity and rapid initial polymerization rates faces challenges in removing bubbles and preventing optical defects, such as flow traces and striae, due to the rapid polymerization and high viscosity of the starting material liquids, which complicates the removal of gaskets and increases the risk of optical defects.

Innovation Solution

A method involving a casting mold with a discharge hole for removing gases, filled with carbon dioxide, and a gasket with a discharge outlet part, where the mixture is cast nearly perpendicular to the horizontal plane, and the mold is tilted to remove bubbles, followed by sealing and controlled polymerization to minimize optical defects and facilitate gasket removal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a high viscosity starting material liquid is used, then the strength of the molded article is improved, but bubble removal becomes difficult

Engineering Contradiction:

Improvestrength of molded articleVSAvoidbubble entrapment

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The casting mold is inverted during the casting process, with the discharge hole positioned at the uppermost point. This inversion allows bubbles to naturally rise and escape through the discharge hole during filling, effectively removing the harmful effect of bubble entrapment while maintaining the use of high viscosity starting material liquid for strong molded articles

Inventive Principle:

Principle #13The other way round (Inversion)

2Productivity

If a high initial polymerization rate is used, then the productivity is improved, but optical defects increase

Engineering Contradiction:

Improvepolymerization speedVSAvoidoptical quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The cavity is pre-filled with carbon dioxide gas before casting the starting material liquid. This preliminary action prevents air from being trapped during the rapid polymerization process, eliminating the cause of optical defects such as striae and flow traces while maintaining the high polymerization rate for improved productivity

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If the casting hole is widened to facilitate casting of high viscosity material, then the ease of operation is improved, but the strength of the polymerized portion becomes greater making gasket removal difficult

Engineering Contradiction:

Improvecasting easeVSAvoidgasket removal ease

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The discharge hole is positioned at the uppermost point of the casting mold, separate from the casting hole. This extraction of the gas escape function to a dedicated discharge hole allows the casting hole to be optimized for material filling while the discharge hole facilitates bubble removal and eases gasket removal by providing a separate escape path for polymerized material and gases

Inventive Principle:

Principle #2Taking out (Extraction)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method effectively reduces bubble entrainment and optical defects, allowing for the easy removal of the gasket and producing high-strength, defect-free plastic lenses with improved manufacturing efficiency.

Implementation Method 1

a step of filling the cavity with carbon dioxide

Methodology Applied

Scientific EffectGas displacement:

Implementation Method 2

a step of tilting the casting mold to a prescribed angle and maintaining for a prescribed period in a state where the discharge hole is positioned at a top

Methodology Applied

Scientific EffectBuoyancy: Archimedes' Principle (Buoyancy)

Implementation Method 3

mixing plural polymerizable components, and immediately after mixing, casting a mixture into a casting mold and conducting polymerization

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Data Source

PatentUS7919020B2Method of manufacturing plastic lens, gasket for molding plastic lens, casting mold for molding plastic lens, casting jig for plastic lens starting material liquid, holding member for plastic lens casting mold, and plastic lens manufacturing apparatus

Publication Date: 2011.04.05 HOYA CORPORATION

AI summary

A method of manufacturing a plastic lens by mixing plural polymerizable components, and immediately after mixing, casting a mixture into a casting mold and conducting polymerization to obtain a molded article. A method of manufacturing a plastic lens by casting a plastic lens starting material liquid flowing out of a casting jig opening into a casting mold and curing the above starting material liquid to form a molded article. A gasket for molding plastic lens comprised of a cylindrical member comprising openings for fitting by insertion of two molds. A casting mold for molding plastic lens, wherein the above molds are detachably held in the above openings of the above gasket so that molding surfaces of the two molds are positioned opposite at a prescribed interval to form a cavity corresponding to a lens shape within the above cylindrical member. A casting jig for plastic lens starting material liquid equipped with a nozzle for casting a plastic lens starting material liquid into the casting mold. A method of manufacturing a plastic lens comprising casting of a plastic lens starting material liquid into a casting mold held by a holding member and curing the above starting material liquid to form a molded article. A holding member for plastic lens casting mold for holding a casting mold for molding a plastic lens.