Epson Inkjet Printer that Prints White

[peteski]

This reads like something written by someone who failed Philosophy 101.  Either it looks white to the typical eye or it doesn't.   It can't look white without reflecting broad spectrum visible light, and if something reflects broad spectrum visible light, then we say it looks white.

Ben,
Please do not attribute this statement to me.  I didn't make it and I agree that it is wonky.  If you fully quoted me it would have read:
Exactly. Quoting the website: "Epson UltraChrome HDR White Ink introduces an all-new Organic Hollow Resin Particle Technology, which forces light to randomly scatter, producing the illusion of seeing the color white."


EDIT:
URL of the webpage I quoted: http://www.epson.com/cgi-bin/Store/jsp/Pro/SeriesStylusProWT7900/Overview.do?cookies=no&com.broadvision.session.new=Yes

[jagged ben]

Peteski,
Sorry that was unintentional.  I knew you were quoting, and I shouldn't have let it be ambiguous in my requote.

[peteski]

Peteski,
Sorry that was unintentional.  I knew you were quoting, and I shouldn't have let it be ambiguous in my requote.

No problem - I just didn't want to be connected with such silliness.  But OTOH, why would Epson would post such nonsense on their official website?  Maybe they did develop some light scattering ink that looks white? 

[Zox]

No problem - I just didn't want to be connected with such silliness.  But OTOH, why would Epson would post such nonsense on their official website?  Maybe they did develop some light scattering ink that looks white? 

My guess is that, in order to make an opaque white thin enough to print via an inkjet, they've developed some sort of retro-reflective nanomaterial. So it's technically not "white"; it's a collection of tiny mirrors.

The orientation of the nano-mirrors would be random enough that you wouldn't get a reflected image, just an impression of the general light level of the room, so it would look white when the room lights are white.

(Caveat: I don't have any inside knowledge--this is just a theory.)

[peteski]

My guess is that, in order to make an opaque white thin enough to print via an inkjet, they've developed some sort of retro-reflective nanomaterial. So it's technically not "white"; it's a collection of tiny mirrors.

The orientation of the nano-mirrors would be random enough that you wouldn't get a reflected image, just an impression of the general light level of the room, so it would look white when the room lights are white.

(Caveat: I don't have any inside knowledge--this is just a theory.)

Sounds like a reasonable explanation.
And even when viewing either a white piece of paper or white paint in a room illuminated with colored light, the reflected light is that of the colored light illuminating the room instead of white.  So, in a similar scenario, nano-mirrors randomly scattering light would act like white paint.

So if this nano-mirror ink is used under standard translucent CYM inks, it probably also simulates a white undercoat (by random scattering of the ambient light filtered through the translucent inks.   Hey, that might work. I wonder how it photographs (close-up)?

[GaryHinshaw]

There is quite a bit of interesting literature on this subject, much of which is not very accessible without the right background.  I don't have a good understanding of the technology Epson is claiming, but I'm sure that the idea is as Lord Zox notes: to enhance the scattering properties of their ink in a thin film.  Here are a few references which make for some interesting reading, for those so inclined:

1. DuPont Ti-Pure titanium dioxide.  This semi-technical brochure describes why titanium pigment is so good for producing thin, opaque coatings: namely the particles have a high index of refraction and are (ironically) transparent in the visible portion of the spectrum.   Every time light passes through a pigment particle it scatters by a large angle (on average).  Thus, when light is incident on a thin film, it is more likely to scatter a few times and escape from the nearby incident surface (i.e. to reflect) than it is to scatter many times to reach the more distant far side of the film (i.e. to transmit).  See their Figure 3.

[Aside: their Figure 6 has a nice illustration of the hiding power of different white pigments.  Zinc oxide has a lower index of refraction than titanium dioxide, so a larger fraction of the light transmits through the zinc film.  This is the feature I exploited when I was trying paints in my fading fast thread.]

2. Hollow latex particles: synthesis and applications.  (You may need a subscription to access this.  Sorry if you do.)  This is a technical article on hollow particle synthesis, but their section 4 lists some applications of the technology, and one of them is as a pigment additive.  The effect of making particles hollow is to add more scattering sites per particle (every material interface produces a scattering).  But I'm unclear as to whether these latex particles can act as a pigment in their own right, or if they need to be used in conjunction with other pigments. 

Re the Epson statement: "...which forces light to randomly scatter, producing the illusion of seeing the color white."  I think the only misnomer here is the word illusion.  By enhancing the scattering efficiency, you produce more reflected light.  If you can achieve that over the full visible spectrum, the reflected light will be white light.  Titanium dioxide has a very high index of refraction over the full visible spectrum.

-gfh

P.S. jb, I think you meant Physics 101, not Philosophy 101, no?

[jagged ben]

My guess is that, in order to make an opaque white thin enough to print via an inkjet, they've developed some sort of retro-reflective nanomaterial. So it's technically not "white"; it's a collection of tiny mirrors.

The orientation of the nano-mirrors would be random enough that you wouldn't get a reflected image, just an impression of the general light level of the room, so it would look white when the room lights are white.

Again, I think you're just redescribing what white is.   Anything that is white already does what your describing at nanometer scale.  (Except I don't think that the 'retro-reflective' part doesn't make much sense, because that would look something like a mirror at a macro level as well.  Scattering is part of looking white, retro-reflectors don't scatter so much by definition.)

I think maybe what Epson is trying to tell us is that it is only through deposition via their proprietary inkjet process that the stuff will appear white.  If you break open the cartridge, you won't find a liquid inside that looks white, unlike ordinary inks.   Or, perhaps they're trying to tell us it only ends up looking white on certain materials or under certain other conditions.  If it doesn't always look white, then you could say it isn't white per se.  If that's the case, they ought to tell us something about those conditions.

Gary, I agree that if not for the word 'illusion' it wouldn't be an absurd statement.   "Effect" would have been a better choice.  But no, I did not mean Physics 101, I did indeed mean Philosophy 101.    As in, things one learns in first year Philosophy in college, by comparing the opinions of those such as Descartes and Hume.  At issue is this: our experiences of certain types of sense data are undeniably valid in so far as we attribute only the qualities of sense data to them.  (e.g. "I think therefore I am.")   You can't prove or disprove what someone else sees, or thinks,  just as you can't validly prove or disprove that someone else is not feeling pain or hearing a sound inside their head.  You may be able to convince someone that the cause of their experience is an illusion or a hallucination, but it's still what they see (or feel, or hear).    Thus someone who 'sees white' undeniably sees white.  Period, end of that part of the discussion.  You may move on, if you wish, to why they see white, and whether or not its a valid perception of looking at something outside of them that looks white to everyone else.   But they still see white.  Put another way, if Epson had said "the illusion of being white' instead of 'the illusion of seeing white', then maybe they graduate to second year philosophy.      

[peteski]

This thread turned out to be pretty educational. Thanks guys!  I never really seriously contemplated the specific science behind why white is white.  BTW Gary, I was able to access both of the sources you posted. Any watching the Joy of painting on PBS, I recall them using titanium white oil paints. 

[Zox]

Again, I think you're just redescribing what white is.   Anything that is white already does what your describing at nanometer scale.  (Except I don't think that the 'retro-reflective' part doesn't make much sense, because that would look something like a mirror at a macro level as well.  Scattering is part of looking white, retro-reflectors don't scatter so much by definition.)

What I was going for was the difference between "here's something that's white, now let's spray on a really thin layer" and "here's something that's specifically tailored to look white when applied in a really thin layer." So in that sense, yeah, we're saying the same thing.

As for scattering, my thought was that each individual particle/nanoball/whatever would be reflective, but they'd have (partly or fully) random orientations, which provides the scattering. Sort like glitter, except fine enough that you can't see the individual sparkles.

Again, I'm not an expert--just trying to come up with a rationale for Epson's "not white, but looks white" description.

[sirenwerks]

Again, I'm not an expert--just trying to come up with a rationale for Epson's "not white, but looks white" description.

It could be because nothing really has color.  Color is human perception of what our cones register, or translate from the spectral reflectance of an object.  The data used by our cones is the spectral wavelength of light that is not absorbed by the object we observe.  The apple is not red, the apple's molecular make-up is absorbing all of the spectral temperatures except for the ones human cones are triggered into perceiving as red.

An object that absorbs all wavelengths "is" black.  Stare at a light bulb that emits the full spectrum of wavelengths and all of them reach your eye to create the perception of white.  It looks (blindingly) white, but wavelengths themselves have no color.

[DKS]

It could be because nothing really has color.  Color is human perception of what our cones register, or translate from the spectral reflectance of an object.  The data used by our cones is the spectral wavelength of light that is not absorbed by the object we observe.  The apple is not red, the apple's molecular make-up is absorbing all of the spectral temperatures except for the ones human cones are triggered into perceiving as red.

An object that absorbs all wavelengths "is" black.  Stare at a light bulb that emits the full spectrum of wavelengths and all of them reach your eye to create the perception of white.  It looks (blindingly) white, but wavelengths themselves have no color.

Thank you, doctor. And since we are responding to the data received via a message board, and not from you as an entity, you do not exist.

[sirenwerks]

Thank you, doctor. And since we are responding to the data received via a message board, and not from you as an entity, you do not exist.

I feel like it sometimes.  And sometimes I just feel like I come from another planet.  Kinda like that episode of Star Trek where the aliens only speak in analogy.  But semantically, Epson's word choice was defendable in court. 

[GaryHinshaw]

It is a rather remarkable fact that we can perceive an apparent rainbow of colors with only 3 types of receptors.  Similarly, a computer screen can generate the same apparent rainbow of colors with only 3 colors of pixels.   

Photometricians measure radiant power, P(f), in Watts per Hz: this tells you how much power is carried by a light wave at each frequency.   It's true that many different spectra, P(f), can excite the 3 eye sensors by the same amount, and therefore produce the same perceived color.   In it's simplest form, white light has equal intensity at all (visible) frequencies, P(f) = constant.  But a computer screen generates white by firing the R, G, and B pixels in equal amounts.  This produces a *very* different intensity spectrum (which you could see by putting it through a prism) but the same perceived colour in humans, unless they are color blind.  So there is no unique spectrum of "white light."

It's possible that Epson has some ink formulation that reflects white light (typically sunlight or room lighting) with a very "bumpy" spectrum, P(f), which happens to stimulate the 3 human color sensors equally.  However, my guess is that the particles in their pigment scatter light efficiently enough that most of it reflects back, in which case the reflected spectrum is close to the incident spectrum.  In either case the reflected light stimulates the eye in the same way, and is, by all accounts "white."

-gfh

P.S. The only Philosophy class I took in college was Logic.   

[sirenwerks]

Just a conjecture here, because I know nothing more about physical engineering than what I can imagine, but could it be the hollow aspect of this material, if it has some white quality to it but still some translucency is using the two surface areas (outside and inside) to create two differently situated reflecting surfaces?  Kinda like a balloon when it's blown up?  If the outside surface can let light in, and the interior surface can reflect it and get it to bounce around inside, then it could be acting in one of two ways (or both) 1. creating a cold light source akin to bioluminescence (without the actual generation of light) or 2. creates a scenario similar to backlighting.  This is just me thinking out loud, no fact or science to back it up, just imagineering in the noggin'.