Electronic enthusiasts in October "hot touch technology special issue " hot download, how can you lack!
Admittedly, the touch technology that was born in the 1980s was so unknown before the Apple iPhone was born. Since then, with the development of smart phones, the development of touch screen technology has made greater progress in just a few years than the previous ten years. The development of capacitive screens from some manufacturers to the current capacitive screen is the mainstream; from the beginning The separation of the screen and the touch screen has led to the development of in-cell and on-cell technologies. According to forecasts by relevant market research institutions, global tablet PC sales will reach 248.6 million units by the end of 2015. In terms of smartphones, global smartphone sales are expected to reach 1.05 billion units by 2015. Such a huge number is enough to prompt us to take a closer look at these mainstream technologies.
Talk about capacitive touch technology
Our so-called capacitive touch screen refers to a transparent special metal conductive material pasted on the glass surface. When a finger touches on the metal layer, the capacitance of the contact will change, so that the frequency of the oscillator connected to it will change. By measuring the frequency change, the touch position can be determined to obtain information.
Its structure is mainly to coat a transparent film body layer on the glass screen, and then add a protective glass outside the conductor layer. The double glass design can completely protect the conductor layer and the sensor.
Schematic diagram of capacitive touch screen structure
The specific working principle is as follows:
The capacitive touch screen is plated with long and narrow electrodes on all four sides of the touch screen to form a low-voltage AC electric field in the conductive body. When touching the screen, due to the electric field of the human body, a coupling capacitor will be formed between the finger and the conductor layer. The current from the four electrodes will flow to the contact, and the current is proportional to the distance from the finger to the electrode. The controller behind the touch screen will It will calculate the proportion and strength of the current, and accurately calculate the position of the touch point.
The double glass of the capacitive touch screen can not only protect the conductor and the sensor, but also effectively prevent the external environmental factors from affecting the touch screen. Even if the screen is stained with dirt, dust or oil stains, the capacitive touch screen can still accurately calculate the touch position.
With its inherent advantages, the position of capacitive screens in manufacturers is becoming more and more important. At present, the main technologies of projected capacitive touch panels with multi-touch applications are divided into two types: filmtype and glasstype. Specifically, the Apple camp uses glass projected capacitors (glasstype), and Non-Ping camp is mainly based on film projected capacitor (filmtypePET)
The current mainstream thin-film structure is to ITO through lithography or printing on PET film, the outer layer is protective glass called GFF (Glass-Film-Film) structure; and the mainstream glass-type structure is to use touch sensors in ITO On the glass, the outer layer plus a piece of protective glass is a GG (Glass-Glass) structure.
Although capacitive technology has dominated the consumer electronic touch market, in order to expand the application level of touch and bring consumers a better user experience, today's capacitive touch technology still has some key factors that need to be improved, including Reduce costs, achieve finger suspension control, glove control, noise management, control when fingers or surfaces are wet, faster feedback and response, save battery power, more sensitive pressure sensing, active stylus support, Good software / hardware integration, etc.
These goals have brought many new challenges to touch solution providers. First, they will encounter many problems from materials to manufacturing processes in terms of cost reduction.
As far as the current situation is concerned, the GFF structure is limited to the high-end ITO film materials in the hands of a few Japanese merchants, and the GG bonding yield is generally low, which is also the main reason for the high cost of the projected capacitive touch module.
Metal grid touch screen
This has prompted manufacturers to use cheaper metal meshes (Metal mesh), silver nanowires (Silver nanowires), carbon nanotubes, conductive polymers, graphene, and ITO inks to replace ITO materials, but due to insufficient industrial chain And other problems have led to the replacement of ITO with new materials is still in the preparatory stage, rather than the actual implementation.
With the development of many ITO alternative materials, more and more projected capacitive sensors will begin to adopt new ITO alternative materials in the next few years. Whether for panel and touch module suppliers, ITO alternative materials represent new market competition, but also bring new opportunities.
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