Browse Prior Art Database

A backlight unit with no repeating bright lines near a light Source

IP.com Disclosure Number: IPCOM000013073D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2003-Jun-12
Document File: 4 page(s) / 141K

Publishing Venue

IBM

Abstract

A backlight unit with no repeating bright lines near a light Source Disclosed is a backlight unit for a Liquid Crystal Display (LCD) with no repeating bright lines near a light source. This invention describes the mechanism of a problem of having an unexpected peak luminance near the Cold Cathode Fluorescent Lamp (CCFL) and the proposal to solve this problem. Figure.1 is a sketch of a light pipe used for a conventional backlight. l

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A backlight unit with no repeating bright lines near a light Source

A backlight unit with no repeating bright lines near a light Source

Disclosed is a backlight unit for a Liquid Crystal Display (LCD) with no repeating bright lines near a light source. This invention describes the mechanism of a problem of having an unexpected peak luminance near the Cold Cathode Fluorescent Lamp (CCFL) and the proposal to solve this problem.

<The mechanism of this problem> Figure.1 is a sketch of a light pipe used for a conventional backlight.

l

d

P 2

PPnPn-1

Reflecter

upside

downside

c

1δτ・・

(α,β)

n-1

f (x)

γ1

P0

1

f (x)

2f (x)

b

0Lamp

With the corner sharping, no bright line appears on the light guide. However, with the chamfering on at least one of the downside and upside edge of the inlet surface, the repeating bright lines appear parallel to the CCFL on the light guide. Position of the repeating bright lines are shown as the following equation.

fn(x) = An x + Bn

)γAa-((tan(θ )-n-1 cos(-2( n-1-θ ))+sin(-2(γ n-1-θ )) cos(-2(γ n-1-θ ))-An-1 sin(-2(γ n-1-θ ))

An-1 cos(-2(γ n-1-θ ))+sin(-2(γ n-1-θ ))

cos(-2(γ n-1-θ ))-An-1 sin(-2(γ n-1-θ ))

a

f (x)

f (x) n

γ0

Die lect ric =μ

Y

×

(0,0)

XFigure.1 A sketch of generally light pipe

Bn-1

tan(θ )-An-1

1

[This page contains 3 pictures or other non-text objects]

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< Pnx <

)γAa-((tan(θ )-n-1 cos (-2( n-1 -θ ))+sin(-2(γ n-1 -θ )) cos (-2(γ n-1 -θ ))-An-1 sin(-2(γ n-1 -θ ))

A n-1 cos (-2(γ n-1 -θ ))+sin(-2(γ n-1 -θ ))

cos (-2(γ n-1 -θ ))-An-1 sin(-2(γ n-1 -θ ))

Table.1 and Figure. 2 are the results of calculation with actual dimensions. In this calculation, the light guide was a wedge-shaped type, like Figure 1.

a= 2.5mm, b= 1.0mm, l= 275.2mm, c= 0.1mm, d= 0.1mm,·=1.49,
·:= 0.05, ·:= 2.45

Table.1 The bright line point

Number The right line
point[mm]

Bn-1

tan(θ )-An-1

The bright lines
width [mm]

1st 0 ~4.49491

2nd 8.84543 ~ 9.03843 0.19300

3rd 13.3454 ~ 13.6354 0.28995

4th 17.8984 ~ 18.2852 0.38687

5th 22.5037 ~ 22.9874 0.48375

6th 27.1608 ~ 27.7414 0.58057

7th 31....