High performance color filters improve the brilliancy of liquid crystal ...
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High performance color filters improve the brilliancy of liquid crystal displays Dr. Hans Reichert Head of Colorants Research, BASF Schweiz AG, Basel BASF Research Press Conference on May 27, 2014 A closer look at a full color liquid crystal display 2
Transcript of High performance color filters improve the brilliancy of liquid crystal ...
High performance color filters improve the brilliancy of liquid crystal displaysDr. Hans Reichert Head of Colorants Research, BASF Schweiz AG, Basel
BASF Research Press Conference on May 27, 2014
A closer look at a full color liquid crystal display
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Cross-section of a display
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Color filtersProtective layer
PhotospacerAlignment layer
Thin film transistorsGlass substrate
Polarizer
Backlight
Reflective film
Polarizer
Diffusion film
Liquid crystalsAlignment layer
Glass substrate
Liquid crystals as a light switchIlluminated state
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Liquid crystals align with a helicaltwist between predefinedalignment layers
Non-polarized backlight ispolarized by first polarization filter
Polarization plane of the lightis twisted while passing throughthe liquid crystals
Light with twisted polarizationplane can pass throughsecond polarizer
Display is illuminated
Alignment layer
Alignment layer
Liquid crystals
Polarizer
Polarizer
Non-polarized white backlight
Liquid crystals as a light switch Dark state
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V
Alignment layer
Alignment layer
Liquid crystals
Polarizer
Polarizer
Non-polarized white backlight
Applying a voltage betweenthe alignment layers causesthe liquid crystals to stand upright
Polarized light passesthrough liquid crystal cellwithout being twisted
Light cannot passsecond polarizer
Display is dark
Backlight
Close-up of a pixel
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Each pixel is made of subpixels withred, green and blue color filters
Each color filter is connectedto a cell of liquid crystals to control theamount of light that can pass through
Polarizer
Thin film transistor
Color filter
PolarizerGlass
Transparent electrode
GlassLiquid crystals
Crystals can scatter and depolarizethe light and cause light leakage
The smaller the crystals the lower the scattering and the better the display
Scattered light
Light leakage
Higher brightness Higher brilliancy Higher contrast ratio
Minimizing scattering leads to
Development of red color filter grades
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paint grade not usable for color filter applications due to low contrast ratio
first color filter grade launched in 1997
launched in 2005, used in mobile, monitor and TV applications
since 2013 state of the art color filter red, used in high end TVs and tablet PCs
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1000
2000
3000
4000
5000
6000
Irgazin®
Red BOIrgaphor®
Red BT-CF Irgaphor®
Red BK-CF Irgaphor®
Red S 3621 CF
Contrast ratio
Electron microscope pictures of red color filter grades
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200 nm
Irgaphor®
Red BT-CFIrgaphor®
Red BK-CFIrgaphor®
Red S 3621 CF
[ca. 80nm]Contrast ratio: 1000
[ca. 40nm] Contrast ratio: 2500
[< 40nm]Contrast ratio > 5500
Crystal morphology – platelet-like structures
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200 nm
NH
O
O
NH
NH
O
O
NH
NH
O
O
NH
NR
O
O
NH
Growth rate:
Hydrogen bonding
van der Waals
nonpolar
polarnonpolar
hydrogenbonds
interactions
van der Waalsinteractions
> >
From raw materials to color filters
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Dispersant, Binder
Surface treatment Photoinitiator, Monomer
Rawmaterials
Crudecolorant
Micronizedparticles
Color filter grade
Synthesis Micronization
Dispersion Resistformulation
Color filter productionby photolithography
Our contribution to LCD performanceHigher image quality (color purity, contrast, brightness) and higher productivity
BASF Research Press Conference on May 27, 2014
NanotechnologySmall dimensions – great opportunities
