Spectacle lens FAQ

Up to what temperature can multi coated lenses withstand?

Glass lenses can withstand over 300℃.

Plastic lenses can withstand up to about 60℃.

However, please refrain from leaving them unattended in hot and humid places for long periods of time.

What lenses are suitable for use when working in hot places?

Glass lenses are generally more preferable than plastic lenses.

When choosing plastic lenses, Beluna is recommended as a non-coated lens and Beluna HX is recommended as a lens with hard multi coating.

Are glass eyeglasses or plastic eyeglasses better for people who go in and out of refrigerated warehouses?

Such work involves environments where the lenses get foggy or condensation builds up on them due to differences in temperature.

Glass lenses are preferable in terms of durability due to multi coating.

However, glass lenses have a drawback in that they stay foggy for longer periods of time than plastic lenses because it takes longer for them to return to room temperature once they are cooled.

When taking this into consideration, plastic lenses only with hard coating are recommended for professional use.

How heat-resistant are non-coated plastic lenses?

The levels of heat resistance in plastic are generally represented by Tg (glass-transition temperature).

To give a description of Tg through a simple image; plastic begins to deform at a certain temperature when it is gradually exposed to heat.

This temperature is known as Tg.

Although it depends on the material, the Tg of lenses offered by Tokai Optical is between 70℃ and 124℃.

Are polarizing lenses susceptible to moisture?

Polarizing effects are attained by tinting a material known as polyvinyl alcohol and blending this membranous material into the lens.

The material becomes too soft and stops producing polarizing effects when wet because it is susceptible to moisture.

Materials for polarizing lenses are safely protected from humidity in special rooms at Tokai Optical’s factories.

Please remember that materials for polarizing lenses are so delicate that such measures are required.

Why have my plastic photochromic lenses stopped reacting?

The cause of poor photochromic functions may be a combination of numerous factors such as intermolecular fatigue caused by repeated photochromic reactions, deterioration due to heat or ultraviolet radiation, deterioration due to oxidation with oxygen, and the penetration of moisture through scratches that are too small to detect from outside.

Why is contrast enhanced with light shielding glasses?

Contrast is differences in factors such as light, darkness, and color.

Light shielding glasses absorb light of short wave lengths that have high amounts of energy and let in light of other wave lengths.

Therefore, contrast is enhanced because it becomes easier to distinguish the intensity of the light of other wave lengths when light of short wave lengths, which is a cause of glare, is absorbed.

Why do objects appear brighter with CCP400 AC (yellow)?

CCP400 AC absorbs only short wave lengths (blues) and lets in other wave lengths.

This is why CCP400 AC makes objects appear brighter when compared with regular sunglasses that are designed to cut out factors such as glare (those that absorb overall wave lengths).

(Note) This does not mean that CCP400 AC makes the entire environment appear brighter. It means that the object is to feel brighter than when regular sunglasses designed to block out light are worn.

Is it true that the TS, NA, and AC in the CCP400 series are also effective at night?

Wave length dependency is lower at night than in the daytime because color saturation is lower at night.

Using lenses that absorb only short wave lengths and let in other wave lengths makes it easier to make distinctions between objects than when wearing regular sunglasses designed to absorb overall light on the premise that the user is trying to block out the glare from the headlights of oncoming vehicles at night.

(Note) Vision varies between individuals.