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BEF原理


Presentation Outline
1. Optics 2. General Product introduction

?
?

BEF, DBEF, DRPF, ESR
BEF-RP, ThinBEFIIT, ThinBEFIIM

3. New Product 4. New Delivery Format 5. Application

折射原理
? 描述光的传输特性: 从某种介质 (n1) 进入不同折射率的另 一种介质 (n2) ? 定义为折射定理 ? n1 sin (?1) = n2 sin (?2) ? 光向较高折射率介质方向“弯折”

?1

n1 n2 > n1 ?2

n2

全反射原理 (TIR)
? 当光从光密介质进入光疏介质时, n1 > n2, ?2 可达 90° ?1 = ?c (临界角) => ?2 = 90° (几何光学) ?2 n2

?c ? 等于临界角时, 光无法离开介质1

n1

? 大于临界角后, 光束全部反射回介质1内部

Reflection- Two Types

Specular

Diffuse

Mirror Surface - glossy

Scattering - hazy, matte

Most surface exhibit some combination of specular and diffuse reflectance.

Optical Coupling
TIR
n n

TIR Failure

n

光耦合原理(wet out)
? 全反射失效造成正交BEF膜片组中的光泄漏 ? 下BEF顶角与上BEF底面贴合时, 光线可能直接漏出=> 形成亮点

Coupled Ray Top BEF

Crossed Films
Bottom BEF

TIR Ray

BEF II - Optical Coupling Solution
NON Prism Pattern : Very tightly controlled peak height ? Peaks 1 - 2mm higher ? 0.7 mm increments
1 - 2 mm higher

? Provides controlled spacer for crossed sheets ? Isolates coupling below eye resolution ? BEF III “chaos pattern” varies height along prisms

BEF Moiré - Two Cases
Pixel Moiré
? Periodic BEF grooves make Moiréwith LCD pixel structure.

Reflective Moiré ? Ambient image of top BEF groove pattern reflected by plano side of bottom BEF results in beat pattern.
LCD Top BEF

LCD BEF

Solutions: reduced reflection, reduced coherence, rotation, matte. Common solution is top diffuser.

Polarization - Two Types
1. Unpolarized 2. Linear ? Describe polarization by orientation of electric field vector. (Magnetic field vector is always perpendicular) ? Human eye doesn’t “see” polarization, but we can see polarization effects. ? Human eye responds to square of the electric field magnitude

非偏振光
? 光是电磁波(物理光学的概念) ? 电磁场矢量随机分布 ? 在任意时点无法预计电场振动方向
以离开纸面方向传播的光线为例

? 例如日光, 白炽灯, ...
? 电场方向随机分布

Polarization Description
? To describe different polarization states, it is necessary to establish a reference plane. This plane is called the Plane of Incidence.
Incident Light Reflected Light

? The plane which is perpendicular to the interface and contains all the light propagation vectors is the Plan of Incidence
Refracted (Transmitted)

(POI = paper for this example)

Light

Linear Polarization
? Electric field vector is fixed to one plane. For convenience, we set this plane either paralled or perpendicular to the plane of incidence. ? Two linear polarization states : S and P
– S polarized light is perpendicular to the POI – P polarized light is paralled to the POI

Pictorially

S polarization

P polarization

Pixel Moiré - Example
Periodic Structure #1 Periodic Structure #2

Moiré Fringes
Solutions: ? Rotational misalignment increases fringe frequency - slight BEF bias minimizes pixel moiré

Moire Spatial frequency
? The width of the dark moiré fringes, (1/Pitch)

W = 1/p = d1d2/(d1-d2)
? Or equivalently, the pitch of the fringes = the difference in the line frequencies

P = 1/d2 – 1/d1

TBEF on 30mm line/64mm gap line set

Pixel Moire Example

Reflective Moire:
BEFII on Thin BEF

How To Increase Brightness?
?增加入射光量
? 增加燈管數目 ? 提高管電流

?改變玻璃製程
? 提高panel開口率

?提高發光效率
? 輕,薄的光學增光膜

2 1

導光板

3

光學

冷陰極射線管

增光片

底反射片
7 6

Backlight Components

燈管 反射片
4

外框架

擴散片

5

Light Efficiency in Backlite LCD
Surface reflection Analyser Color Filter LC Polarizer Lite pipe Backlit 90% 90% 30%
95%

5% 6% 7%
23%

40% 60% 100%

24% 60%

Backlight Construction
Goal: Create an area source from either a point or a line of light - line source: fluorescent lamp - point source: light emitting diode Light Management Films

Lightguide

Light Management Films - Reflector ? Lightguide accepts output from light sources and distributes over an area ? Light management films manipulate exiting light for optimum viewing

BEF Diffusion sheet Light lead board LCD Reflection sheet (4003T) Back light unit case

3 EDL光學膜技術總覽

増光膜

DBEF-E DBEF-D400
BEF-RP

3M 光學膜

ESR
DRPF

聚光膜

BEFII 90/24 BEFII 90/50 BEFIII 90/50T

BEFIII 90/50M
ThinBEFIIT, ThinBEFIIM RBEF

BEF
( Brightness Enhancement Film)

BEFII
BEF II 90/50

Acrylic Resin

90?
50mm

125mm

155mm

PET

BEF - III
BEF III 90/50

Acrylic Resin

90?
50mm

155~160mm 125mm

PET

BEF Operation
NO BEF
? Wide angular range of exiting light ? Blue rays are directed to the viewer ? Red rays miss the viewer and are wasted

WITH BEF – 2 Steps
Step #1 ? Red rays are refracted towards viewer ? Blue rays experience TIR and return to backlight

Step #2 ? Diffuse reflections in backlight recycle blue rays ? New exiting rays SID be transmitted by the BEF or returned to backlight for further recycling

? Crossed BEF sheets can provide further increase

Cones of Light in BEF
High Angle Flux

36.8%
Useful Flux

5.1%

11.8%

Recycled Flux (by another prism)

Incident Flux

46.3%
Recycled Flux

Summary of prism angle
and RI response
n = 1.6
1.5 1.4 b = 90° 110° 130° b

n

Increasing (n) refractive index shrinks the cut-off angle

Increasing (b) the prism angle widens the cut-off angle

X-BEF in HH Lightguide

BEF as recycling film BEF as redirecting and recycling film Non-axial extraction Diffuser Sheet Wedge or slab with extraction features

Conscope result
Thin BEF 90/24 – 0.062 mm Thin BEF 90/24 – 0.062 mm Diffuser Lightguide – 0.705 mm Light Guide ESR

Specular Reflector

Reflective Moiré vs Newton Rings
Reflective Moiré
With Backlight On, Reflective Moiré is most visible looking along the grooves It is not so visible perpendicular to top film grooves Newton Rings are visible from all directions

Visibility Study

Backlight


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