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Browse Prior Art Database

Fluorescent Lamp Pre-heating System

IP.com Disclosure Number: IPCOM000110004D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 3 page(s) / 74K

Publishing Venue

IBM

Related People

Nakano, M: AUTHOR [+2]

Abstract

The structure of a conventional liquid crystal display module is shown in Fig. 1. In many cases, backlight for the liquid crystal display utilizes a hot cathode fluorescent lamp. Construction of the hot cathode fluorescent lamp is shown in Fig. 2. The light emission sequence is described as follows. 1. Each filament located at the edge of the bulb is heated for 1 - 2 seconds so that it can easily emit thermoelectrons. 2. High voltage applied between two cathodes starts discharging. 3. Mercury staying inside the glass bulb goes into an excitated state by the energy of the thermoelectrons. 4. Mercury radiates some wavelength of ultraviolet radiation whose wavelengths are 185, 254, 313, and 365 nanometers. 5.

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Fluorescent Lamp Pre-heating System

       The structure of a conventional liquid crystal display
module is shown in Fig. 1.  In many cases, backlight for the liquid
crystal display utilizes a hot cathode fluorescent lamp.
Construction of the hot cathode fluorescent lamp is shown in Fig. 2.
The light emission sequence is described as follows.
1.   Each filament located at the edge of the bulb is heated for 1 -
2 seconds so that it can easily emit thermoelectrons.
2.   High voltage applied between two cathodes starts discharging.
3.   Mercury staying inside the glass bulb goes into an excitated
state by the energy of the thermoelectrons.
4.   Mercury radiates some wavelength of ultraviolet radiation whose
wavelengths are 185, 254, 313, and 365 nanometers.
5.   Phosphors coated on the glass bulb emit fluorescent light by the
energy of ultraviolet radiation with its wavelength of 254
nanometers.

      In this way, an amount of the mercury is determined by the
vapor pressure of mercury, and the vapor pressure of mercury is
determined by the glass bulb temperature.  In conclusion, the amount
of fluorescent light is determined according to the glass bulb
temperature.  An experiment showed that light output of the
fluorescent lamp became less than 70 percent of the maximum luminance
when the ambient temperature was no more than 10 degrees centigrade.

      When the glass bulb temperature is so low, light output from
backlight becomes too small to use fo...