Comparison of TFT LCD Touchscreen Technologies

Touch technology – the right choice

You have planned the integration of a touchscreen in combination with an LCD panel? Or you want to upgrade your industrial monitor with a touch-screen? On this site we focus on the advantages and disadvantages of different touch-technologies.

Touch Displays – the easiest solution

The assembly of touch-screen panels to TFT displays requires a lot of experience and equipment independent which touchscreen-technology is used. The most important thing: a dust-free and clean surrounding.

You don`t have a clean room and the required equipment? There is a solution with LCD display and standard laminated touch-sensor. You get a tested touch-display unit. We call this units Touch-Displays. Touch-displays are available with:

• resistive Touch Panel                     
• PCAP Touchscreen (PCT, projected capacitive touchscreen)

Resistive Touch

The resistive touchscreen technology is very easily integrable and operable. That`s the reason why resistive touch-panels are most widely used in the industry.

Operability: very good  

Resistive touch-sensors are controllable with fingers, pencils and even gloves.

Optical Properties: moderate

The problems with resistive touchscreens are the spacers between the glass carrier material and the polyester top foil which cause optical restrictions. Most resistive touch-screens have a roughened or etched surface so that the spacers are not visible. This enables a light transmission of only 80%. Fingerprints are not visible.

If the Touchscreen is equipped with a clear foil the transmission rises to 90% but spacers are visible and fingerprints are visible.

Installation: easy

The integration of resistive touch screens is easy and no special knowledge is necessary. These touch screens are mostly insensitive to electric radiation and easy sealable for IP65.

Stability: great

The surface foil of resistive touchscreens has a degree of hardness of 3H which is normally hard enough for every industrial application. Only sharp and acute materials can scratch the surface.

Durability: great

4- and 5-wire touchscreen panels are robust enough for 1-5 million touches on one point. This is more than enough for the industry.

Costs: inexpensive

Resistant sensors are produced in large quantities and the production processes are matured. This causes high quantities for great prices.

Resistive Touch-Screen and Touch-Display by distronik

Capacitive Touch Screen

The capacitive touch sensor has a great light transmission but requires a bit of technical experience (technical principle of capacitive technology).

Operability: limited

The ITO coated carrier material requires a conductive connection to the ground. So the touch sensor can only be triggered by fingers or conductive pencils.

Optical Properties: very good

The ITO coating and the glass are translucent. Glass has a refractive index of 4% which creates a light transmission of 96%. Fingerprints are visible on smooth surfaces.

Installation: challenging

The close proximity to grounded metallic materials causes problems although the ITO coated glass has a SiO2 layer (quartz). This means that a distance of the capacitive touch sensor and metal front or metal housing is needed. The cable set requires a great ground connection as well. Capacitive touch screens are sealable but only with distance to metal parts.

Stability: very good

Glass is very solid and available in several thicknesses. The conductive ITO layer is covered with a quartz-coating. This makes the touch sensor very scratch-resistant.

Durability: very good

Glass and quartz are very hard materials (7H hardness) which enable over 160 million touches on one point.

Costs: higher price range

The coating is laborious, requires highest precision and the number of quantity is not that high. The touch controller is more complicated as well.

Capacitive Touch Screens by distronik

Projected Capacitive Touch Screen

PCAP touchscreens are very widespread. Nearly every smartphone and tablet is equipped with one of these. PCAP enables various housing possibilities.

Operability: good

PCAP touch sensors are equivalent to “normal” capacitive touch-screen sensors but there are ITO electrodes. These partly enable operability with gloves. In this case the touch controller needs to be prepared and programmed. Special touch pens are available for PCAPs as well.

Optical Properties: very good

High light transmission allows brilliant pictures. PCAPs are bondable to TFT panels as well. This is the best optic possibility.

Installation: moderate – easy

If the PCAP touch is equipped with a cover glass which goes beyond the active area, the integration is easy. The PCAP devices are sealable and metal bezels aren`t close to the active surface so there are no influences with the ground. It is way more complicated if no cover glass is desired.

Stability: very good

The same applies here as to capacitive touchscreen modules however with additional bonded cover glass for more stability.

Durability: very good

More than 160 million touches on one point are possible.

Costs: moderate – expensive

Many variations possible, customised cover glass with screen printing, own dimensions – mostly everything is customised with individual unit costs.

distronik products: Projected Capacitive Touch, PCAP Panels

Infrared touch technology

This technology is not established and the market is very small. The only field of application are cash machines (filter glass for limited viewing angle).

SAW Touch (surface acoustic wave)

The acoustic wave technology is not established as well because it`s difficult to seal this touch sensor. An advantage of this technology is the z-axis.