1

Color Filter for TFTLCD

W. T. Cheng

Dept. Ch. E./NCHU

•Introduction

•Color Principle

•Design of Color Pixel

•Fabricating Method

•Inspection & Test

•Future Trend

•Black Matrix

Outline

2

Introduction

Milestone of Color Displays (2-1)

LG. Phlilips LCD Co. Ltd.

3

Milestone of Color Displays (2-2)

LG. Phlilips LCD Co. Ltd.

TFT LCD Industry Supply Chain

Array

4

TFT-array and Color-filterSubstrates

Samsung Electronics

Reduction of photo-induced leakagecurrent in a TFT

Samsung Electronics

5

Color Principle

Generating Primaries (3-1)

6

Generating Primaries (3-2)

EmissiveDisplay

Sony Electronics

Generating Primaries (3-3)

7

Color Mixing

Modulation of Primaries: Additive

8

Modulation of Primaries: Subtractive

Additive & Subtractive Color System

9

Design of Color Pixel

Color Pixel

Samsung Electronics

10

How an LCD produces colors？

Samsung Electronics

Representation of Color

11

CIE Color Coordinates

0.20

0.25

0.30

6 8 10 12 14 16 18

9.4”

8.4”

7.8”

6.5”

12.1”

11.3”

10.4”

15.0”

14.1”

13.3”

12.1”

10.4” 14.1”

15.0”

Diagonal Size of Screen (inch)

Pixe

lPi

tch

(mm

)

85

90

95

100105

110

120

130

0.15

140

150160170

115

125

(ppi)

12.1”

12.1”

14.1”

15.0”

VGA(640x480)(921,600)

SVGA(800x600)(1.44M)

XGA(1024x768)

(2.36M)

SXGA+(1400x1050)

(4.41M)

UXGA(1600x1200)

(5.76M)

QXGA(2048x1536)

(9.44M)

15.0”

17.0”

13.3”

Pixel Pitch vs. Diagonal Size of Screen

12

Pixel Size and Resolving Power of Human Eye

Total # Colors

13

Gray Scale Generation

Consideration for Color Design

14

Color : An Attribute for Image Quality

•Display Quality

•Color Quality

•Chromaticity Diagram

Fabricating Method

15

Color Filter Forming Methods(2-1)

Color Filter forming methods (2-2)

ResolutionResolution Colorspectra ReliabilityDescriptionMethod name

Gelatin dyeing method

Pigment impregnation method

Patterned resin is dyed

Resin containing pigmentsmade into a pattern

Printing method

Color ink containing pigmentprinted on substrate

Electro-deposition method

Pigment with resin is electro-deposited on the substrate

Features

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•Pigmented Photosensitive Red, Green, Blue color

filter resins

•Dyed Photosensitive Cyan, Magenta, Yellow color

filter resins (materials in development)

•Dyed Photosensitive Red, Green, Blue color filter

resins (materials in development)

Color Filter Materials

PDCR Mechanism for CF

Photo initiator

Polymer/Monomer

Dispersant

Pigment

Beforeexposure

UV

Afterexposure

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

17

PDCR Composition for CF

•Acrylic resin with multi functional group

•Reactive monomer

•Organic pigment

•Photo-initiator

•Solvent

•Additive

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

Electro-deposition for Color Filter

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

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Electro-deposition Mechanism for CF

+ - + - -+ +

-

-----

++

++

++

-

Pigment containingresin with negative charge

2H20 → 2OH- + 2H+ + 2e

2OH-→ H2O + O-2

2O-2→O2

-COO- + H+ → -COOH

Pigment containingresin with positive charge

2H20 + 2e → 2OH- + 2H+

2H+→H2

-NR2+ + OH- → -NR2 + H2O

Anionic Type Cationic Type

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

Inverse Transfer Printing

Toppan Printing Co. Ltd.

19

Pigment Dispersion (2-1)

Everest Tech. Co. Ltd.

Pigment Dispersion (2-2)

Everest Tech. Co. Ltd.

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Ink-jet Thermal transfer Printing (4-1)

Creo Inc., Canada

Ink-jet Thermal transfer Printing (4-2)

Creo Inc., Canada

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Ink-jet Thermal transfer Printing (4-3)

Creo Inc., Canada

Ink-jet Thermal transfer Printing (4-4)

The color line width is ~100 μm and

the black matrix lines are ~20 μm wide.

Creo Inc., Canada

22

Spin-less Coating Technology(Slit/Patch Coating)

Toray Industries, Inc.

Comparison of Pigment Dispersion andInk Printing Methods for Large size CF

Color formingmethod

Filmprocess

Maskprocess

Colorlayeruniformity

Degreeof freedom

Savingmaterial

PigmentDispersion

InkPrinting

1. SC

2. SC+Slit

3. Slit(spin less)

Cost

1. Convextransfer

2. Concavetransfer

3. Ink jet

4. Inversetransfer

3

3

3

◎

◎

×

×

○

○

○

○

○

○

×

◎

◎

◎

◎

◎ ◎

◎

◎◎

◎

○

× ×

×

×

×

1

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

△

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Black Matrix

Cr Process for Black MatrixGlass substrate

Cr deposition

Positive resist coating

UV exposure

Development

Etching & Striping

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

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Process for Photosensitive BM Resin

Spin coating

Soft baking

UV Exposure

Development

Post baking

Process step Critical parameters

Spin coating Spin speed determines

Final film thickness

Soft baking Solvent baking affects

Develop time

UV Exposure Exposure dose affects

Development Developing window

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

Photosensitive BM for CF (2-1)

Brewer Science, Inc.

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Photosensitive BM for TFTLCD (2-2)

Brewer Science, Inc.

Properties of Various BM Processes

Items Photopolymer+ Ni plating

Lift off Blackresist

Blacklaser

Etch

Numberof process

Thickness(μm)at OD=3

Reflection(%)

Reliability

Shieldingmaterial

Cost

9

1.0

1~2

○

Nickel

△

10

0.4

<10

○

Graphite

△

7

1.0

<2

○

Carbonblack

Carbonblack

<2

○

0.8

8

○ △

8

<4

0.3

◎

×

CrO/Cr

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

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Black Resist Composition

•Polymer with multi functional group

•Reactive monomer

•Carbon black

•Photo-initiator

•Solvent

•Additive

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

Inspection & Test

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UnPacker Clean BM RGB

Polish ITO Cutting Packer

BMI RGBI

ITI Final Inspection OQC

Process Control for Color Filter

PS/PSICutting

IPQC

LDR

ProcessG

ProcessB

ProcessG

IPQC

BIPQC

R

IPQC

ULD

IPQC(Appearanc)

RGIRepair

OKNGRPNG OK

Quality Control of RGB Process

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CF Defects (7-1)

Bumps

CF Defects (7-2)

White dents

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CF Defects (7-3)

Oil/EBR solvent

Contaminates

CF Defects (7-4)Metal/Glass debris

BM released

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CF Defects (7-5)

Scratch

CF Defects (7-6)

Color layer peeling

Non-uniform Color

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CF Defects (7-7)

Contaminated scale

Requirements of CF

DisplayQuality

Special transmittance

Contrast

Uniformity

Flatness

Non-defect

Compatibilitywith

Post process

Thermal resistance

Chemical resistance

Sealing property

Reliability

Light resistance

Thermal resistance

(Long-run)

Running

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

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Spectral transmittance and Chromaticity of CF(Transmissive LCD TV)

LG.Philips LCD Co. Ltd.

Spectral transmittance and Chromaticity of CF(Transmissive PC Type)

LG.Philips LCD Co. Ltd.

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Future Trend

● AV Enjoyment Anytime AnyplaceIn the gym

● Free-Style Setting to Match Any AV Viewing Situation

In the kitchen In the car

Bedroom TV Personal TV AV Entertainment

Easy to carry

Applications of LCD TV (2-1)

Sharp Co. Ltd.

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In the living room In the personal &dining room

In the bedroom

Applications of LCD TV (2-2)

Sharp Co. Ltd.

•COA (Color Filter on Array)•TOC (TFT on Color Filter)•SOC (Spacer on Color Filter)•ROC (Ribs on Color Filter)•CF integrated LED•CF integrated OELD

Advanced Color Filter

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

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LG.Philips LCD Co. Ltd.

Super IPS

CF on TFT Array

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TFT Array on CF (5-1)Upper glass substrate Common electrode

BM2 Pixel

BM1Buffer/overcoat

Lower glass substrate

Cst

CF

TFT

LG.Philips LCD Co. Ltd., IDRC 2000

BCB (benzocyclobutene), an organic insulation material as the passivation layer,provides more prominent higher Aperture ratio.

TFT Array on CF (5-2)

LG.Philips LCD Co. Ltd., IDRC 2000

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( b ) C F fo r m a tio n

( c ) P la na r iz a t io n & B u ffe r S iN x d ep o s it io n

( d ) L o w te m p er a tu r e T F T fa b r ic a t io n

( a ) L o w er B M fo r m a tio n

LG.Philips LCD Co. Ltd. , IDRC 2000

TFT Array on CF (5-3)

TFT Array on CF (5-4)

Source electrodeDrain electrode Gate

Color filter

SiNx/Overcoat

BM

LG.Philips LCD Co. Ltd., IDRC 2000

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0

10

20

30

40

50

60

70

80

90

100

400 450 500 550 600 650 700 750 800

Wavelength (nm)

% Transmission

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.2 0.4 0.6 0.8x

y

Conventional

TOC

NTSC

TFT Array on CF (5-5)

LG.Philips LCD Co. Ltd. , IDRC 2000

Spacer and Ribs on CF

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•RBG color resist

•Photosensitive BM (Black Matrix) resin

•Color filter on array photo-resist to increaseaperture numbers resulting in high definitionmobile display (HDMD).

CF Materials and Processes Development

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

HR-Color TFT LCD(Pixel Density>200ppi)

1. Micro Reflective Structure2. Super High Aperture Ratio3. High Contrast Reflection

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

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•high optical density•high volume resistivity•low reflectivity•high heat resistance•light and chemical resistance•high sensitivity and high resolution•simple process•aqueous alkaline development•safer solvent based formulation•uniform coating with no pinholes,striations or particles•environmentally safe and low cost

Needs of Photosensitive BM Resin

NCHU_Dept.Ch.E./2005CF_notes/W. T. Cheng

- Reduced material cost

- Higher throughput equipments

- Larger substrate with improved

productivity

Cost Reduction

Standardization

-Replacing CRT Products:Monitor, LCD-TV

-Creating new application area:Game, Web-Pad, PDA, HHP,GPS, PSP, Medical display, etc.

Market Growth

Evolution of Technology

HigherPerformance

CRTCompatible

Lower CostProcessProduct Glass Parts

TFTTFT--LCD Business VisionLCD Business Vision