Browse Prior Art Database

Liquid Crystal Display Screen Uniformity Improvement Method

IP.com Disclosure Number: IPCOM000119136D
Original Publication Date: 1997-Dec-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 77K

Publishing Venue

IBM

Related People

Hanzawa, F: AUTHOR [+4]

Abstract

A brighter line image near by the Cold cathode Fluorescent Lamp (CFL) is one of the problems with narrow framed Liquid Crystal Display (LCD) development. Gray-line print on the white-sheet side along the CFL is effective in eliminating this image, but it has a potential to make uncomfortable uniformity caused by white-sheet warping from sticking at the area between the lamp reflector and the Lightpipe (Poly Methyl Methacrylate (PMMA)) under temperature stress. This article describes two solutions to improve the uniformity that does not depend on gray-line print on white-sheet.

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Liquid Crystal Display Screen Uniformity Improvement Method

      A brighter line image near by the Cold cathode Fluorescent Lamp
(CFL) is one of the problems with narrow framed Liquid Crystal
Display (LCD) development.  Gray-line print on the white-sheet side
along the CFL is effective in eliminating this image, but it has a
potential to make uncomfortable uniformity caused by white-sheet
warping from sticking  at the area between the lamp reflector and the
Lightpipe (Poly Methyl Methacrylate (PMMA)) under temperature stress.
This article describes  two solutions to improve the uniformity that
does not depend on gray-line  print on white-sheet.

      Fig. 1 shows a root-cause of this problem, how to get the
appearance of a brighter line image.  The difference of a linear
expansion coefficient between the white-sheet and a Lightpipe (PMMA)
is the origin (Fig. 2).  One solution is to add dual slits to the
side of a white-sheet along the print to separate the part that is
painted from the major part of the sheet.  These slits free the major
part, thus, warping caused by sticking is eliminated (Fig. 3).
Another solution is to block the unexpected light path by
light-absorbing print  on the face side of the Lightpipe.  Therefore,
the brighter line image problem has not occurred.  This design gives
tolerance against misalignment of a lamp reflector (Fig. 4).

This application is a lighting device for houses, buildings,
advertisements, etc.