What Are the Materials of Optical Lens, the Difference Between Pc, Pmma and Silicone Lens

With the continuous development of the optical industry, the demand for high precision optical lenses is also increasing. Nowadays, optical lenses are widely used in various high-tech fields, such as security, automotive, digital cameras, high-power lasers, optical instruments, etc. According to different applications, lenses are processed into different shapes, such as convex lenses, concave lenses, TIR lenses, fly-eye lenses, matrix lenses, etc.

For optical lenses, the materials can be divided into below 4 types.

1. Glass Lens

Glass lenses are more expensive and easier to break, so they are often used in less active situations, but the light transmission rate is very high and can reach about 97%.

2. Silicon Lens

Silicon lenses have good high temperature resistance, can withstand temperatures up to 200 degrees Celsius, high strength, UV resistance, anti-yellowing, strong resistance to fall, light transmission rate reaches about 94%, due to excellent fluidity, suitable for processing complex shapes and micro-structure LSR lenses.

3.PMMA Lens

PMMA lens, also known as acrylic lens, can withstand temperatures of 70 degrees Celsius, heat deformation temperature of 90 degrees Celsius, so the temperature resistance is poor, more suitable for high-temperature injection molding, production efficiency is relatively high, 3mm thickness of PMMA lens light transmission rate of 93% or so. But the molding is brittle, not suitable for complex shape products.

4. PC Lens

PC lens professional name for polycarbonate lens, is a PC plastic, has a very strong toughness, impact resistance is relatively good, can withstand 130 degrees Celsius high temperature, very suitable for high temperature injection molding, so the production efficiency is relatively high, but the light transmission rate is slightly lower, only about 89%.

What is the difference between silicone lens, PC lens and PMMA lens?

1. Light Transmittance

PC lens light transmittance is about 89%, which is relatively poor, temperature resistance 110 degrees to 150 degrees.

PMMA transmittance is about 92%, temperature resistance of 70 degrees Celsius.

LSR optical silicon lens light transmittance can reach about 96%, has excellent optical transparency performance, far more than PMMA and PC lenses, temperature resistance -40 to 200 degrees Celsius.

2. Residual Stress 

The residual stress inside the molded product may cause deformation and rupture of the lens, resulting in birefringence of the optical product, which directly affects the optical performance and makes it difficult to ensure safety.

PC and PMMA thermoplastic molding process is a physical change, the linear molecular chain in the injection flow rate and molding gradient temperature changes under the influence of the stretching and compression of the molecular chain by rapid cooling stereotypes, in an unstable arrangement, can not be restored to the original free steady state, resulting in a more serious stress can not be released.

Two-component liquid silicone LSR is thermoplastic chemically reactive molding, injected into the high temperature mold at low temperature, and the cross-linking reaction between molecular chains will occur gradually only when the material reaches a certain high temperature, and basically no residual stress occurs during the whole curing and molding process. 

3.Refractive Rate

In terms of refractive rate, PC is about 1.526, PMMA is about 1.592, and glass is about 1.523, all of which have a certain degree of dispersion and easily cause visual fatigue.

Wacker optical silicone is 1.41, which can maintain a stable low refractive ratio in high and low temperature environment and multiple wavelengths of light, with a low degree of dispersion, and can obtain a high definition imaging effect. 

4. Density

The relative density of PC is generally about 1.2g/cm3, PMMA is generally 1.18g/cm3, LSR optical silicone is 1.12g/cm3, LSR molding silicone lens products ensure the function of certain conditions, reduce the finished lenses' weight-to-capacity ratio, conducive to the lightweight of the optical lens.

The low density makes the LSR silicon lens has another major advantage, which is made of silicone than the same size of glass, the LSR lens will be much lighter, comparing to the density of PC and PMMA, silicon lens is also slightly lower.

Our factory specializes in the production of high precision and high quality liquid silicone injection molding products for more than 10 years, thanks to the professional engineering team, in-plant mold manufacturing department, advanced production equipment, perfect quality management system, such as ISO9001, ISO14001, ISO13485 and IATF16949, for custom optical liquid silicone lens, please contact us, welcome to visit our factory.