Touch panel
Basics
Setup
SSG Simple Sensor Glass
Structure
ITO Indium-Tin-Oxide
SITO Single-sided ITO layer
DITO Double-sided ITO layer
Bonding
OCA Optical Clear Adhesive (dry bonding)
LOCA Liquid Optical Clear Adhesive (wet bonding) [1]
OCR Optical Clear Resin [2]
Air Gap
Gel
Production
Production of OGS [3]
Touch Technologies
Projected Capacitive Touch
Self Capacitance
Capacitance of a single electrode to ground is increased by the human body capacitance while touching.
Cs_touch = Cs + Cg
| Advantages | Disadvantages |
| Simple, low-cost | limited to 1 or 2 touches |
| single layer possible | lower accuracy |
| long distance field protection | |
| active guard possible | |
| fast measurement |
Mutual Capacitance
Capacitance between two electrodes is decreased by human body capacitance while touching.
Cs_touch = Cs_idle – Cg
| Advantages | Disadvantages |
| detect 2 and more touches | more complex, higher cost |
| higher touch accuracy | two layers needed (or 1 layer with bridges) |
| flexible in pattern design |
Surface Capacitive Touch
| Advantages | Disadvantages |
| excellent drag performance with extremely smooth surface | no multi-touch possible |
| resistant to contamination | calibration drift & susceptible to EMI |
Resitive Touch
- Analog Resistive
- Analog Multi-Touch Resistive (AMR)
Digital Multi-Touch Resistive (DMR)
| Advantages | Disadvantages |
| multi-touch | poor durability (PET top surface) |
| simple & familiar resistive technology | poor optical performance |
| Lower cost than p-cap | Non-zero touch force |
Acoustic Touch
- Surface Acoustic Wave (SAW)
- Acoustic Pulse Recognition (APR)
- Dispersive Signal Technology (DST)
Optical Touch
- Traditional Infrared (IR)
- Waveguide Infrared
- Multi-Touch Infrared
- Camera-Based Optical
- Planar Scatter Detection (PSD)
- Vision-Based
Force Sensing Touch
Touch Structures
Out-Cell
A standard touch screen is laminated directly on top of the LCD module.
One Glass Solution (OGS)
Sensor on cover-glass
Glass on Glass (GG)
Sensor on separate glass
On-Cell
The touch sensor is an X-Y array of capacitive electrodes deposited on the top or bottom surface of the color-filter substrate.
On-Cell / In-Cell structure[4]
In-Cell
The touch sensor is physically inside the LCD cell. (pixel electrode can be shared)
Charge Sensing (In-Cell)
Surface Treatments
anti-glare AG
Changes specular reflection into diffuse reflection
anti-fingerprint AF
anti-reflection AR
Reduces specular reflection
other
anti-corruption AC allows permanent Sharpie ink to be wiped off
anti-microbial AM for healthcare applications
anti-bacterial AB for healthcare applications
anti-stiction reduces finger-sticking friction
anti-crack coating increases durability at lower cost than Gorilla glass
Source
Fundamentals of Projected-Capacitive Touch Technology http://www.walkermobile.com/Touch_Technologies_Tutorial_Latest_Version.pdf
Information DISPLAY "LCD In-Cell Touch" http://informationdisplay.org/IDArchive/2010/March/FrontlineTechnologyLCDInCellTouch.aspx
