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4. Our Solutions -> 2.2.2 Technologies - Touchscreen solutions - resistive 4. Our Solutions -> 2.2.2 Technologies - Touchscreen solutions - resistive

Resistive touchscreens



Resistive Touchscreens were the real breakthrough in common use touchscreen technology. With resistive touchscreens also came flexible, cost effective touchscreen technology which is available for industrial and medical use. Nowadays resistive technology is a mature well known technology. Resistive technology has been available within the SCHURTER group for nearly 20 years. SCHURTER has built upon extensive knowledge of resistive technology, the manufacturing of the products and the materials used. SCHURTER can help you to fulfil your needs with a wide range of standard 4-wire, 5-wire and 8-wire sensors. If in the unlikely case a standard sensor will not fit your display, SCHURTER can assist you with the design of a custom made resistive touchscreen.

Highly reliable resistive touch solutions

The three characteristics that a resistive touchscreen must have are:

 1)  Electrical Reliability: all internal electrical functions should be sufficiently reliable in detecting touch input signals correctly while avoiding short and broken conductive surface and trace circuits. This applies not only to the touch panel itself, but also controller hardware integrated or designed into the system.

 2)  Transparency: a touchscreen has to be sufficiently clear to allow most of the light from the underlying display to pass to the operators' eyes. If used outdoors, a touchscreen should eliminate light reflection in order to ensure that the user is able to clearly see items displayed on the LCD without interference from the environment.

 3)  Durability: the touchscreen should withstand long-term use, surviving impacts and various methods of daily operation. The touchscreen should operate normally with disparate touch media (gloves, stylus).

Thus, in an ideal world, a resistive touchscreen would be infinitely strong and infinitely thin, built with layers of film (or glass) and conductive material that are 100% clear. The conductive material would also be supremely flexible, perfectly controlled within a specified resistance range, and applied with perfect uniformity. Obviously, this type of product does not and cannot exist. In reality, a touchscreen is a complicated piece of engineering born of compromises between clarity, electronics, and physics.

The specialists within SCHURTER can help you with making the best choices for your application. Please contact your local representative who will assist you in finding your best solution.

Controller


Resistive controllers are widely available on the market. Next to standard controller PCB’s many microprocessors also have a build in resistive controller available. The advantage of resistive technology is the easier exchangeability of touchscreen controllers and its EMC robustness. Resistive touchscreens are however not suitable for multi-touch functionality, for this feature PCAP technology is required.

Overlay

The overlay for resistive technology has to be made of flexible material. This is due to the mechanical nature of its functionality. The most common material used for resistive touchscreens is polyester (PET). Resistive touchscreens can be used without any additional overlay of a protection layer. The sensor can be directly integrated into your product. If you would like to use a touchscreen in combination with a graphical overlay and/or membrane switches, resistive technology is the ideal technology to combine all these products together.

Sensor

The resistive sensor could be built of different constructions. The most common construction is the film/glass construction. In this system we make use of a conductive PET film with ITO coating laminated onto a conductive substrate of ITO glass. The two layers are mechanically separated by the printing of so called spacer dots. When you operate the Touchscreen, the two layers are mechanical pressed onto each other and will make an electrical contact. The ratio of resistance values in top and bottom circuit will represent the X and Y location of the touch location. Alternatively other constructions are available such as:


- Film/film/glass: this construction is used when special glass is required. Glass could be toughened, processed or make use of a wired shielding.


- Overlay/film/glass: this construction is ideal for closed front side solutions. The graphical overlay is bonded onto the Touchscreen sensor and will seal your system for dust and moisture.


Next to the different constructions there are 4 different technologies available within the resistive system:


1) 4-wire resistive; most common used technology. There are 2 electrodes for the X direction on the top circuit and 2 electrodes for the Y direction on the bottom circuit. This is the most flexible and cost effective technology.


2) 5-wire resistive; this technology is suitable in harsh environments with a high number of operations required. The 4 electrodes are specially designed on the bottom circuit and sensed by the top film. As the electrodes are burned into the glass, a very durable system is created.


3) 8-wire resistive: this technology is like the 4-wire resistive but has extra sense lines for each electrode. This extra sense line is used to compensate resistance changes in fast changing temperatures. This will give you a stable system in environments with constantly changing temperatures.


4) Matrix/digital technology: in this technology the contact fields are defined within the conductive layers of the touchscreens. This will give you a very robust and reliable system but is not as flexible in the software design as the above mentioned technologies.


As you can see, many solutions are available and well known to SCHURTER. Please discuss with your representative the best resistive technology for your application.

Advanced resistive

Within SCHURTER we have several advanced resistive touchscreens. Optimized for specific applications.


A) Glass-Foil-Glass (GFG) touchscreens for general purposes

GFG touchscreens are mostly used for industrial or outdoor applications because they are designed to meet more stringent specifications than the standard FG (Film-Glass) resistive touchscreens.

GFG touch products can offer high resistance to scratch, abrasion and chemicals (e.g. sulfuric acid, diesel or kerosene). These features are often required in industrial applications of touch products. For outdoor applications, we offer the GFG LR (low reflective) value-added touchscreen.

The principle of GFG touch panel is to add an extra layer of 0.2mm thin glass on the surface of the traditional resistive touch panel. The GFG touch panel is more scratch-resistant than the standard resistive products and can be operated smoothly with gloved touch.


B) GFG for Outdoor

The GFG LR (low reflective) touchscreen is designed to meet the needs of outdoor touch applications; it adds an AR (anti-reflective) coating on the cover glass of the GFG touchscreen. Polarizer film and retarder film are added in the middle and bottom layers, reducing the reflectivity to around 1.5% while maintaining the light transmission rate at 76% or above.

The GFG LR touchscreen is also a great option for handheld devices that are used outdoors (handheld instruments, tablet PC, etc.


C) GFG with EMI-shielding

Besides scratch-resistance, chemical resistance and low reflectivity, touch products used in harsh environments also require EMI resistance in their design to prevent noise interference from the environment as well as causing interference to other instruments. For the purpose of EMI resistance, we can add an EMI shielding layer to the GFG LR touchscreen. Depending on the size of the touch panel, the material of the EMI shielding layer can be ITO glass with surface resistance of 5 ohm/sq or above, or metal mesh with resistance of 1 ohm/sq or less. The EMI shielding layer is added in the front or to the back of the touchscreen. The anti-EMI GFG LR touch screen can fulfil the needs of customers who require higher EMI resistance.

If mesh is chosen as the design for the EMI shielding layer, SCHURTER will offer the mesh angle test kit for customers to test the LCD and mesh angle to prevent negative optical effects. We shall communicate with the customers in detail to provide the most appropriate design for their product. If you have needs for the anti-EMI GFG LR touch products, please contact our sales staff. We will be delighted to be of your service.

Specifications

The general specifications of our resistive touchscreens are:

Optical

  -  Surface finish: Antiglare or Clear

  -  Light transmission:  > 80%

  -  Haze:  1.5~20% (depends on design)

Mechanical

  -  Sizes:  3″ to 24″ diagonal size

  -  Construction:  Film-on-glass, Film-Film-PC or others

  -  ITO glass thickness:  0.7mm, 1.1mm, 1.8mm, 2.8mm

  -  Tail design: FPC type,  Integral tail or others

  -  Tail terminator:  ZIF, Berg, AMP, AMP compatible or others

  -  Input method:  finger, gloved finger, stylus

  -  Activation force:  0.1N to 1.0N depending on design

  -  Surface hardness:  3H or higher

Environmental

  -  Operating temperature:  -20℃ to 70℃

  -  Storage temperature:  -40℃ to 80℃

  -  Operating humidity:  if temp. ≧ 40°C, humidity less than 80% RH

                                         if temp. < 40°C, humidity less than 90% RH

  -  No dew condensation

  -  Storage humidity: ambient humidity

Electrical

  -  Insulation resistance:  10M ohm@25V DC

  -  Linearity:  < 1.5% for 4-, 8-wire touch

                      < 1.0% for 5-wire touch inner area

                      < 1.5% for 5-wire touch perimeter area

  -  Contact bounce:  < 15ms

  -  Operating voltage:  5.5 V

  -  Contact current:  70mA (maximum

Applications

Our resistive touchscreens are implemented in many different applications and highly demanding markets.

As a manufacturer of customer specific touchscreens SCHURTER understands that touchscreens are a vital part of your application. For this reason SCHURTER specialises itself in every market possible.

From the Medical market to the Automation market, you can find SCHURTER’s customer specific touchscreens everywhere. As a result SCHURTER has gathered specific knowledge regarding each market, making SCHURTER the perfect partner for your Man Machine Interface needs.

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