- #1
chhitiz
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and if they are, to what extent?
Are phosphor sheets used in CRTs transparent?
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Discussion Overview
The discussion centers on the transparency of phosphor sheets used in cathode ray tubes (CRTs), exploring the properties of phosphors and their potential applications in transparent coatings. Participants examine the context of visibility in CRTs, the scale of phosphor particles, and alternative technologies.
Discussion Character
- Debate/contested
- Exploratory
- Technical explanation
Main Points Raised
- Some participants question whether phosphor sheets are transparent and suggest that the visibility of a CRT when turned off may indicate transparency.
- Others propose examining the phosphor surface with a magnifying glass and flashlight to assess transparency.
- A participant inquires about the scale of individual phosphor particles and whether their size and embedding in a plastic sheet would affect transparency.
- There is a suggestion that a transparent coating with phosphor properties could be developed, raising questions about excitation methods and associated issues like X-ray generation.
- One participant explains that CRT technology uses high voltage to accelerate electron beams, which can cause phosphors to emit light without needing excessive voltage.
- Another participant asserts that phosphors cannot be transparent even if embedded in a plastic film due to differences in refractive indexes, suggesting that transparent luminescent materials exist in other forms like glasses or single crystals.
Areas of Agreement / Disagreement
Participants express differing views on the transparency of phosphor sheets, with no consensus reached on the topic. Various hypotheses and questions remain unresolved.
Contextual Notes
The discussion includes assumptions about the properties of phosphors, the scale of particles, and the implications of different materials on transparency. There are also references to alternative technologies that may provide solutions, but these are not fully explored.
- #2
berkeman
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chhitiz said:
I don't think they are, but it would take some digging to figure this out. What is the context of the question?
- #3
chhitiz
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well, if you look at a CRT TV turned off, you just see blackness (and a bit of reflection of the screen), not tiny red green blue dots, so i think, maybe they are transparent.
- #4
berkeman
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chhitiz said:
Look closer with a magifying glass...
- #5
berkeman
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berkeman said:
And use a flashlight. You should be able to see the phosphur surface, not the inside of the CRT.
- #6
chhitiz
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how very stupid of me. another thing, can you tell me if the indivudual particles of phosphor are at micro or nano scale? if they they are nano sized and embedded (closely packed) in a plastic sheet, would it be transparent.
- #7
berkeman
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chhitiz said:
It sounds like you would like to have a way to have a transparent coating that has the properties of phosphor? Are you going to use an electron beam to excite the phosphor? Are you aware of the X-ray generation issues with using an electron beam to excite phosphor?
- #8
Baluncore
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The CRT EHT voltage was used to accelerate an electron beam that could then be focussed and deflected to raster scan the phosphor screen. There is no need for EHT to cause a phosphor to emit visible light. The generation of X-rays of 10 to 30keV is best avoided.
Visible light has an Energy = Plank's constant x Frequency. Three volts is sufficient as is demonstrated by the forward voltage of light emitting diodes.
Maybe consider electroluminescent display technology where a phosphor is placed between the plates of a capacitor. http://en.wikipedia.org/wiki/Electroluminescence
Visible light has an Energy = Plank's constant x Frequency. Three volts is sufficient as is demonstrated by the forward voltage of light emitting diodes.
Maybe consider electroluminescent display technology where a phosphor is placed between the plates of a capacitor. http://en.wikipedia.org/wiki/Electroluminescence
- #9
Alkim
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These phosphors can not be transparent even if embedded in a plastic film due to the difference between the refractive indexes of the polymer and the inorganic phosphor particles. However, if you need a transparent luminescent material there are glasses and single crystals for this purpose.
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