UV Glass

I’m not sure it is the case. See this thread, in which two Toyota sources identified the front door glass as a “UV cut” type: Do windows and/or windshield have UVA and UVB protection? | PriusChat

Toyota in Japan later posted an FAQ answer (page in Japanese) with a bit more information. I don’t know if it applies to vehicles built for the U.S. market, but according to the chart, the “UV cut ratio” for the front door glass is 90%, 91%, or 99%, depending on the type.

 

Mine are double glazed.

 

There are 3 types of glass on my Prius Excel (2017). Starting at the back... The boot/trunk says Nippon UV, the small rear window says Nippon UV, the main rear door window says AGC Temperlite, the front door window says AGC Lamisafe, the small window at the front says AGC Temperlite, and the windscreen says AGC Lamisafe.



The Nippon UV is mentioned in news from 2016 on many websites, but this is one such example Nippon Sheet Glass product can shield car riders from UV rays - Nikkei Asian Review where it boasts how it's one of the only automotive glass products to UV cut even the longer UV wavelengths:

"the company tweaked the combination of inorganic materials used as additives in back-seat glass, enabling all vehicle windows to block UV rays with wavelengths of up to 400nm"

So that covers the three windows at the rear of the car (boot/trunk + the small rear window on each side).

According to the other manufacturer, AGC here AGC glass blocks harmfull UV rays for skin cancer protection. all their tempered glass is 99% UV cut in all directions. As an interesting side note, it also says the glass is water repellent.

Obviously "tempered glass" applies the AGC Temperlite on the main rear door windows and small front side windows. More info here: Tempered Glass Temperlite™

The AGC Lamisafe on the main front door window + windscreen is covered here AGC laminated windshields offers protection and safe driving. and point 04 on the page says "Protects your skin, total block of ultraviolet (UV) rays". As another interesting side note, it also claims to protect against someone smashing through the window for "up to 10 minutes".

Another AGC page here Offering Value to Customers ｜ CSR ｜ AGC says "The UV-cutting performance of these products has been recognized both in Japan and around the world. According to measurement standards set by the Japan Cosmetic Industry Association, the block rate is equivalent to its highest rankings of SPF50+ and PA++++. Likewise, the products have been certified by the Skin Cancer Foundation, a U.S.-based organization".

I can't find specific wavelength information for the AGC glass, but SPF50+ is extremely good UVB protection, and PA++++ is very good UVA protection. UVA is defined as 320nm to 400nm, which coincides with the 400nm quoted by Nippon. Maybe the Nippon UV provides slightly better UVA cutting, but if it does it's not a huge amount more.

I added tints to my rear windows, which offers some of the protection of lamination, and additional UV protection. That's effectively given me lamination in all but the very small front side windows. Happy days!

 

i've done a lot of searching regarding auto glass and uv protection. most of the info is fairly ambiguous, including regulations and manufacturer specs.

 

I had read something before that all modern cars block so much UV that one wouldn't need sunscreen. Indeed, over several decades of riding in cars without sunscreen, I've never been burnt when the windows are closed, so I believe this is true.

On the Prius and some luxury cars (esp. SUVs) I've noticed there's a slight tint, which probably reduces solar (greenhouse) heating, which would make the air conditioner work harder, thus wasting energy that could be used by the traction motor, thus getting higher fuel economy.

On my 2018, the rear windows are tinted darker than the front side windows, and the windshield doesn't seem to be tinted at all.

 

considerable?

 

My understanding is that Laminated glass blocks both UVA & UVB. Side windows generally only UVB.

Fact sheet - Tinted windows - National Cancer Control Policy

 

G'day,

The glass itself is made in very expensive flat/float glass factories and most flat-glass production goes to commercial and domestic windows - I'm thinking cars are a small part of this market so car-makers have to take the normally made glass and get secondary processors to make their 'special' windows from this normal window glass.

Laminators (sandwich heat-shaped glass around a plastic film) and temperers (heat-stress multiple small patches so it breaks in little pieces, not life-threatening slivers as normal window glass will). These are physical safety features, not anything to do with UV properties.

Surface films or treatments can be done by the flat glass factory or later as a secondary process.

Now for the chemistry.......
Window glass normally has a "significant" iron content (still much less than 1%wt but more than any other colour-producing ion present). The iron usually comes as traces in the sand and limestone/dolomite in the batch mix. Melting conditions mean the glass ends up a greenish hue unless the window-glass-maker adds extra chemicals/oxides to change the this (e.g. grey may be a smidgin of nickel oxide). But this would require a big market for this coloured glass to justify this interruption to '24-7-365' normal flat-glass production.
So, naturally, there is enough iron (the ferric ion is a strong UV absorber) in normal window glass, that at the thickness used in car windows, harmful frequency/wavelength UV is absorbed almost totally, so skin and corneas are not affected.
And ozone holes are only at the poles where not much car-driving occurs.

Everything else is just car-maker marketing, as far as I would skeptically believe.

David S..

 

And from the 2010 New Car Features:

 

D'ya think they might still be considering it?

No science explanation here but I always understood that regular glass absorbed most UV light anyway and always did.

 

Reality: Glass filters out only one kind of radiation -- UVB rays. But UVA rays, which penetrate deeper, canstill get through. That's why many adults have more freckles on their left side than their right -- it's from UVexposure on that side through the car window when driving.

 

Spot on. Apart from the fact that you obviously mean right side

 

The following simplification extracted from Wiki:-

Suntan, freckling and sunburn are familiar effects of over-exposure, along with higher risk of skin cancer. Livingthings on dry land would be severely damaged by ultravioletradiation from the Sun if most of it were not filtered out bythe Earth's atmosphere.[1] More-energetic, shorter-wavelength "extreme" UV below 121 nm ionizes air sostrongly that it is absorbed before it reaches the ground.[2]Ultraviolet is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates, includinghumans.[3] The UV spectrum thus has effects both beneficial and harmful to human health.

Unquote.

 

G'day,

RCO posted:
"...regular glass absorbed most UV light...".

As a (long) retired glass technologist, I don't know quite what you mean by 'regular'? Too many different 'glasses' in this world, - like 'plastics', but not quite as bad. But nit-picks aside, I agree with you.

Pure glassy/vitreous silica transmits a good proportion of incident UV hence UV lamps use vitreous silica ('quartz') in their construction to transmit as much UV as possible.
"Pure" soda-lime glass (the type of glass used to form bottles, windows, etc) would be a fairly good UV transmitter - but commercial soda-lime glass is never truly "pure". "Pure", it would be too expensive and difficult to make unless totally electrically 'melted'.

It's the unavoidable contaminants and minor additives in glasses that do the light absorbing to give a glass its colour and UV 'protection'.

Iron is a strong UV absorber in its ferric state and does the bulk of absorbing our sea-level, natural UV (400nm wavelength and shorter). The other iron presence in glasses, the ferrous ion, is a fair infra-red absorber.
As commercial 'white' glass has both ferric and ferrous ions present in significant concentrations, these taking out the blue and red visible wavelengths of the human-visible spectrum, leaves this glass with a greenish hue.

Coloured glasses can be produced by addition of small amounts of stuff like chromium oxide (green), cobalt oxide (deep blue) and nickel oxide (browny-grey). The ultimate UV-absorbing commercial glass is amber glass (think beer bottles) which is due to a ferric-ion+sulphide-ion chromophore, a delicate balance of oxidised (ferric) and reduced (sulphide) ions the glass-maker has to control. Probably not a recommended glass for trying to watch the road ahead through, unless as a very thin windscreen.

The amount of any wavelength getting through a piece of glass depends on its transmittance at the particular wavelength, the incident amount of the wavelength, and most importantly, the thickness of the piece of glass. The presence of any surface treatments (more reflectance) or sandwiched plastic film (more absorbance) may reduce even more the net transmission of certain wavelengths.

Given the years we've been driving cars behind conventional window glass, I am not aware of any studies showing any problem to our eyes or skin from the level of UV coming through windscreen glass, old or new. I don't think this would be due to a conspiracy of the world's glassmakers, or car-makers for that matter, trying to conceal 'the truth'. We are not talking tobacco and cancer here.

Leaning your arm out an open driver-side window in direct summer sunshine for hours on end is a different matter.

From the melanoma capital of the world,

David S.