Keycap SCIENCE! Warning; many pictures inside!

[OleVoip]

Curiously, there appears to be a halo of sort around the legend which can be enhanced by tweaking the light levels. This could just be an artifact of the crappy usb microscope I used to take the photo.

Yep, this could very well be some local contrast enhancement artefact. See also unsharp masking.

[Chyros]

You mean like the Acer keycaps, right? Yes, some older Dell AT101s also appear to have it. It's still a mystery to me. Not bad printing though.

[keycap]

I can't be too sure but I think that the Acer keycaps use really, really deep laser etching. I don't know why the legends go so deep into the keycap though. But the contrast of the legends on the Acer caps is much more comparable to the AT101W's lasered legends than any of the dye-sub, double-shot or pad-printed legends shown. And the surface texture of the Acer legends is rough and not consistent with the texture of the key itself.

And the Acer caps are ABS, right? I've never seen dye-sub ABS caps but I've most certainly seen lots of lasered ABS caps.

[Chyros]

Deep laser etching is one of the things you'd think, but the surface of the keycaps appear untouches and they don't feel like they have any profile at all. Laser etching, especially really deep, would attract dirt, too, and the writing is rather sharp and high-contrast for laser etching.

[keycap]

I have no clue then. Maybe they used some other method to burn the surface of the keycap instead of charring it with a laser?

I do know that laser-etching can be sharp. Some of my boards use laser-etching that has no profile and it's very sharp, but it's still laser-etching nonetheless. I took a few pictures to explain:

Spoiler:

So here are three different sets of keycaps from three different boards. The keycaps from the top are from a Model M, the keycaps in the middle are from a Compaq NMB dome board, and the keycaps on the bottom are from a Chicony KB-2961. The IBM keycaps are (obviously) dye-sub and the rest are lasered. But the lasered legends on the Compaq are so sharp and you can't even feel them on the keycaps. It's strange, but it's certainly not pad-printing.



Here is a higher quality image of the Compaq lasered keycap up close. You'll notice that it has very sharp and clean lettering, being a lasered keycap:



And here's the IBM dye-sub keycap. In comparison to the lasered Compaq keycap, the IBM dye-sub looks more blurry, but the font is much darker and much more bold. Typical for a dye-sub.



The Chicony lasered keycaps are a lot less sharp and the laser-etching is very apparent. You can put your finger on any key and you will feel the laser-etched font. But the Compaq lasered keycaps aren't like this.

[ohaimark]

Remember when I was positing that high intensity UV light was used, Chyros? I think that, after further research, my hypothesis could be a theory.

The only circumstances that I can think of in which material blackens, but doesn't burn, are:

A) situations in which the substrate is sensitive to a compound or energy form.

B) oxygen deprived environments.

So...

A) the plastic has a material which responds to a certain stimuli, turning it dark (per my UV theory).

B) the lasering and/or heat exposure occurred in an oxygen deprived/near vacuum environment, resulting in pyrolysis and mild carbonization -- that would be quite inefficient on an industrial scale, as pressurization and equalization would need to occur with each batch.

I think the former is more likely; it would explain the slight texture changes on the surface as mild heat deformation and plastic breakdown resulting from UV laser induced Titanium Dioxide (or equivalent compound) photocatalysis.

Possible references:

1) http://www.coherent.com/applications/in ... PageID=308

"The UV laser offers a unique feature when marking on white plastic which contains Titanium Dioxide. TiO2 turns a dark grey due to a photo chemical reaction. The result is a highly durable, high quality mark while the plastic matrix remains unchanged. UV laser marking is used in medical and electronic applications where hygienic cleaning or visual high quality markings are required."

2) http://www.fobalaser.com/applications/m ... /plastics/

"Hygienic laser engraving and marking of plastics for medical technology with the help of UV laser markers. The product surface is colored photochemically. The marking process produces such little heat, that sensitive products and delicate materials remain largely unharmed. The surface of materials marked in such a manner remains smooth, making it impossible for germs to take root."

3) http://www.fobalaser.com/applications/p ... r-marking/

"Plastic bonds are broken and the carbon from these bonds is released. The discoloration thus produced ranges between gray to blue-gray and black."

[keycap]

Very interesting. That is very likely the method that they used for printing legends. I've never seen any dye-sub ABS keycaps before, and I really would like to see some, but it seems that Acer used some sort of UV printing, just like what you said. I don't think that any other manufacturers have used this method for keyboards, have they?

[Chyros]

Yes, this method seems by far the most logical to me. I thought it was only used for black keycaps, but apparently it's also used for white ones, and all my analyses support the idea.

[berserkfan]

amazing! even after a tiring day at work, I run into this just before I go to bed, and even if the thread doesn't wake me up, it intrigues me enough to keep me reading at a time when I would really be falling asleep otherwise.

But does it basically mean that the best lasered keycaps can be more lasting than the best dyesubs? A good laser can reach more deeply into the plastic than the dye before the dye spreads out and gets blurry?

Also with the vivid nature of the lasered examples, should we conclude that good lasered keycaps are really awesome, and not at all comparable to the lasered PBTs from China that we are so familiar with that we think all lasered keycaps have grayish legends?

Or am I just too sleepy and understanding everything wrong?

[Chyros]

amazing! even after a tiring day at work, I run into this just before I go to bed, and even if the thread doesn't wake me up, it intrigues me enough to keep me reading at a time when I would really be falling asleep otherwise.

But does it basically mean that the best lasered keycaps can be more lasting than the best dyesubs? A good laser can reach more deeply into the plastic than the dye before the dye spreads out and gets blurry?

Also with the vivid nature of the lasered examples, should we conclude that good lasered keycaps are really awesome, and not at all comparable to the lasered PBTs from China that we are so familiar with that we think all lasered keycaps have grayish legends?

Or am I just too sleepy and understanding everything wrong?

The durability of lasered keycaps is significantly dependent on what material the cap is made out of. Lasered ABS appears to not last as long as lasered PBT.

Some lasering is really good, but not as good as good dyesub and especially doubleshot. Doubleshot doesn't resist shine or yellowing as much as PBT does, but offers the highest quality legends.

Dyesub only starts to bleach or smudge after a very long time. I've only observed blurring and fading with keycaps from the 80s. This might also have been a quality intrinsic to the printing at the time, but I doubt that based on what we've seen so far.