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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
4
TFT-array and Color-filterSubstrates
Samsung Electronics
Reduction of photo-induced leakagecurrent in a TFT
Samsung Electronics
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
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
16
•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
18
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.
20
Ink-jet Thermal transfer Printing (4-1)
Creo Inc., Canada
Ink-jet Thermal transfer Printing (4-2)
Creo Inc., Canada
21
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
△
23
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
24
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.
25
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
26
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
27
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
31
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
32
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.
33
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.
34
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
36
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
37
( 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
38
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
39
•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
40
•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