[Beowulf] cold cathode fluorescent backlighting

[Thomas H Dr Pierce]

Dear Julia,

        your question: "Firstly, do Liquid Crystal Display TV or computer 
monitors emit any ionizing radiation? "

        CRT computer monitors emit a small amount of radiation. LCD 
display do not emit radiation (beyond light).

from http://en.wikipedia.org/wiki/Cathode_ray_tube
Ionizing radiation: CRTs emit a small amount of X-ray band radiation as a 
result of the electron beam's bombardment of the shadow mask/aperture 
grille and phosphors. Almost all of this radiation is blocked by the thick 
leaded glass in the screen, so the amount of radiation escaping the front 
of the monitor is widely considered harmless. The Food and Drug 
Administration regulations in 21 C.F.R. 1020.10 are used to strictly 
limit, for instance, television receivers to 0.5 milliroentgens per hour 
(mR/h) (0.13 µC/(kg·h) or 36 pA/kg) at a distance of 5 cm from any 
external surface; most CRT emissions fall well below this limit [1].

Your question "If the LCD screen becomes damaged through the inadvertent 
use of the wrong typed of cleaner or by using any abrasive cloth  could it 
expose one to increased ionizing radiation?"

No. 

In a LCD display damaging the display results in poor viewing of the 
liquid crystals.  You can only make the display murky or dim by using an 
abrasive on the screen and over-cleaning it...

        http://en.wikipedia.org/wiki/Lcd_display

There is a small fluorescent light in a display but it is very safe.  All 
fluorescent lights need a mechanism to ionize the plasma to make the 
fluorescent tube light up. The usual methods involve electrons (beta 
radiation) and those are low energy. 

        http://en.wikipedia.org/wiki/Fluorescent_lighting

There are occasional lighting methods  that can have a health issue. This 
was more common in the past with radium paint, and  less so  today with 
tritum lighting. 

http://en.wikipedia.org/wiki/Self-powered_lighting
------
Sincerely,

   Tom Pierce
 



"julia howard" <juliarachelhoward at googlemail.com> 
Sent by: beowulf-bounces at beowulf.org
05/25/2007 03:14 PM

To
beowulf at beowulf.org
cc

Subject
[Beowulf] cold cathode fluorescent backlighting






Not having an Electronics background my questions may seem naive.  However 
as the following issues give me concern I should very much appreciate it 
if they could be sorted out with some reliable knowledge. 

Firstly, do Liquid Crystal Display TV or computer monitors emit any 
ionizing radiation? 
I f the LCD screenbecomes damaged through the inadvertent use of the wrong 
typed of cleaner or by using any abrasive cloth  could it expose one to 
increased ionizing radiation?

Regarding the cold cathode fluorescent backlights of monitors I read in 
the Wikipedia encyclopedia under Cold Cathode that some ccfls use a source 
of beta radiation to start the ionization process. I f this is the case 
then could LCD televisions expose us to beta or gamma radiation. I should 
like to replace my CRT TV with a LCD TV, but the thought of a radioactive 
material being present causes me much anxiety. 

Looing forward to your informed response,

Julia Howard
email: juliarachel_howard at yahoo.co.uk
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