PCAP technologies Projected Capacitive Touch Panel

Recently, projected capacitive type touch panel with characteristic of multi-input by fingers has been drawing attention. Projected Capacitive Touch Panel is also referred to as "PCAP". GUNZE designs and sells variety of customized products using PCAP technologies.

Method and Structure

Capacitive touch panel is a type of touch panel which captures minor electrical alteration of finger input.
It consists of transparent electrode films which electrodes are patterned vertically & horizontally and detect input location by identifying where electrical alternation occur using IC (touch panel controller). (Fig.1)

Adjustment of input position to be detected just by bringing finger close to the surface of sensor without actually finger directly touching the sensor is possible, and this enables using materials such as glass as cover material which is placed on the input surface side making designable touch panel having durability against scratch with better environmental resistance.

In electromagnetism and electronics, "capacitance" is the ability of a body to hold an electrical charge. Capacitance is also a measure of the amount of electrical energy stored (or separated) for a given electric potential. The SI unit of capacitance is the farad; 1 farad is 1 coulomb per volt.
Unlike other touch panel method, performance of capacitive touch panel relies upon its controller. Thus, it is necessary to consider touch panel and IC in sets.

example of the application to smart phone

Detection principle of capacitive touch panel

Fig.1 Detection principle of capacitive touch panel

Detection Principle

In term of configuration of capacitive touch panel, it is the same as matrix type which electrode patterns of horizontal and vertical are in reticular patterns, and insulation between electrode patterns on the conductive layers is considered as condenser.
There are 2 different electrode patterns for the sensor where grid patterns are linear and diamond. Appropriate capacitance of insulator (dielectric substance) is obtained when voltage is applied to electrode patterns which lie next to each other and potential difference occurs between the electrodes.
Since human body contains high water content and have electrical conductivity, capacitance between electrodes increase when finger comes near the sensor detecting input coordinate by identifying capacitance where horizontal (x) and vertical (y) lines change. (Fig.1)

Advantage of Film Material

Typical materials used to designing capacitive touch panel are glass and film. GUNZE has developed film-based projected capacitive touch panel taking advantage of in-house film material development. Film-based projected capacitive touch panel may be offered with advantages of thinness, lightweight, reasonable price, and ease of bonding process when compared to glass-based projected capacitive touch panel. (Fig.2)

Cross Section of Capacitive Touch Panel

Fig.2 Cross section of capacitive touch panel

GUNZE's Advantage!  Flexible support of customized solution including size, specification, order lot, and etc.

COF (Chip On Flexible Prited Circuit) Technology

COF stands for "Chip On Flexible Printed Circuit" and is a mounting technology where IC chip is mounted directly on top of Flexible Printed Circuit. This technology has an advantage of making IC mounting area smaller as it is suitable for miniaturization of capacitive touch panel when applying it to product. (Fig.3)

Controller Chip, COF, Controller Board With Flexible Prited Circuit and Peripheral Circuit

Fig.3 Touch panel controller


Film-based capacitive touch panel is used with placing cover material on the housing considering the design of final product and improving the durability.
GUNZE may design and offer distinctive touch panel designing using great variation of cover materials such as glass, acrylic board, decorative cover with black printing, IMT(Insert Molding Transcription), and functional film (anti-finger print film, AR film, and HD(High Durability) film. (Fig.4)

Cover variations Decorative Cover, Glass, Plastic, Anti-Finger Print Film, AR Film, HD Film, IMT(Insert Molding Transcription)

Fig.4 Cover variations

Multi-Touch (Simultaneous Multi -Input)

In order to have multi-touch with traditional resistive touch panel, it is done by software process.
When 2 points on resistive touch panel is touched simultaneously, position in the middle is detected. With this characteristic, processing the data by time-lag of 2 positions makes resistive touch panel to have multi-touch. Because of its detection principle, resistive touch panel is unsuitable for gesture operation as input force is necessary in order to make upper and lower conductive layer contact each other.

As for multi-touch on capacitive touch panel, simultaneous multi-input of 3-point or more is possible by structure of sensor (hardware).Smooth slide input and stress less gesture operation are possible as input position of capacitive touch panel is detected without finger contacting the surface of sensor, but putting finger close to the surface of sensor.(Fig.5)

Flick  Originally assigned operations are performed by flicking the display in one of 8 directions. For example, scroll operation is performed when the display is flicked to the upper direction. Pan  When touched & dragged, the object transfers and stops when released. Rotate  When touched & turned, the object rotates and stops when released. Zoom  Expanding or shrinking a touched object is possible by separating or approximating the distance of 2 fingers.

Fig.5 Gesture operation

Touch Panel Controller

IC (Touch Panel Controller) used with GUNZE capacitive touch panel is available in forms of chip only, COF(Chip On Flexible Printed Circuit) where chip is mounted onto Flexible Printed Circuit, and controller board with peripheral circuit. Please select one from these 3 configurations which suits the best to your product.
As development of the controller is headed to have high functional performance, it has progressed from single touch to multi-touch gesture, and to multi-touch all point. GUNZE offers customers capacitive touch panel along with controller that meet the requirement of customers. (Fig.3)

Window Logo Certification

PC operation has become simple and easy with the appearance of gesture operation which Microsoft "Windows 7" supports.
GUNZE has developed 15.0" film-based capacitive touch panel prior to other companies and also developed IC (Touch Panel Controller) which detect the input location in parallel with the development of touch panel and achieved to have multi-touch input. GUNZE obtained "Windows Touch" certification for "Windows 7" with these 2 products.



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