Browse Prior Art Database

Liquid Crystal Display Backlight with Polarization

IP.com Disclosure Number: IPCOM000114971D
Original Publication Date: 1995-Feb-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 94K

Publishing Venue

IBM

Related People

Mogi, M: AUTHOR [+2]

Abstract

Disclosed is a optical device for backlighting device for Liquid Crystal Display (LCD) which enables to increase backlighting efficiency by using polarization method.

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This is the abbreviated version, containing approximately 52% of the total text.

Liquid Crystal Display Backlight with Polarization

      Disclosed is a optical device for backlighting device for
Liquid Crystal Display (LCD) which enables to increase backlighting
efficiency by using polarization method.

      Every Twisted Nematic (TN) and Super Twisted Nematic (STN) LCDs
have two polarizer film in order to obtain polarized light.  On the
other hand, conventional backlighting devices emits no polarized
light.  Theoretically 50 percent, actually 58 percent of light
intensity from backlight device is absorbed by this polarizer film.
There is no example in the world which has light emission with
polarization from backlighting device.  If one can get 100 percent
polarized light emission from backlighting device without any
absorption or dissipation, one can get following two merits.
  1.  One can get double as brighter front-of-screen quality as
       conventional LCD.
  2.  There is no need for one polarizer film out of two.

The following describes the way to get this polarized light.

      When an incident light goes from one material (material-1) into
another material (material-2) whose refraction indexes are n1 and n2
respectively, transmission ratio of parallel polarization wave
(P-wave) and senkrecht polarization wave (S-wave) are shown as
followings.
  Tp = 1 -
(tan(theta(i)-theta(t)))(1/2)/(tan(theta(i)+theta(t)))(1/2)
  Ts = 1 -
(sin(theta(i)-theta(t)))(1/2)/(sin(theta(i)+theta(t)))(1/2)
           where Tp : transmission ratio of p-wave  ( - )
                 Ts : transmission ratio of s-wave  ( - )
           theta(i) : incident angle          (rad)
           theta(t) : transmission angle      (rad)

Relation between theta(i) and theta(t) is shown as following formula
known as Snell's law.
  n1...