Pros and Cons of Capacitive Touchscreens

Capacitive Touch Screen (PCAP)

Projected capacitive touchscreen contains X and Y electrodes with insulation layer between them. The transparent electrodes are normally made into diamond pattern with ITO and with metal bridge.

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Human body is conductive because it contains water. Projected capacitive technology makes use of conductivity of human body. When a bare finger touches the sensor with the pattern of X and Y electrodes, a capacitance coupling happens between the human finger and the electrodes which makes change of the electrostatic capacitance between the X and Y electrodes. The touchscreen controller detects the electrostatic field change and the location.

Pros of Capacitive Touchscreen (CTP)

• Looks sharper and brighter
  
  Capacitive Touch Screen uses glass substrate which has high transparency compared with plastic film used by resistive touch panels. Plus, optical bonding and glass surface treatment which make CTP good picture quality and contrast.
• Better Human Machine Experience
  
  Because capacitive touchscreens register touch via the human body’s electrical current, they require less operating pressure than resistive touch panel glass. It supports touch gestures and multi-touch which makes it much better user experience of touch.
• Incredible durability
  
  Because the cover glass is used in front which can be extremely high hardness (>9H), it is extremely durable for touch which can exceed 10 million touches. It also prevents from scratches and easy to clean which makes it prevailing resistive touch panels.
• Size and Appearance
  
  Capacitive touchscreen can be made for very large size (100 inches) and the cover lens can be decorated with different colors, shapes, holes to provide users flexible designs.

Cons of Capacitive Touchscreen (CTP)

• Cost
  
  Capacitive Touchscreen manufacturing process is relatively more expensive and the cost can be high.
• Immunity to Objects/Contaminants on Screen
  
  Capacitive Touchscreen needs special design and uses special controllers to make it used in special applications, such as using glove to touch, or with water, salt water environment. The cost can be even higher.
• Damage
  
  The cover lens can crack. In order to prevent glass debris to fly, a film or optical bonding is needed in the manufacturing process to make the price even higher.
• Interferes
  
  Capacitive Touchscreen is easily to be affected by ESD or EMI, special designs have to be considered in the design which can drive the price higher. Special calibration has to be carried out with the help of the controller manufacturer.
• Power and wake up
  
  The power used in capacitive Touchscreen can be higher than resistive touch panel. Sometimes, a hot button has to be designed to wake up the touch function.

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5 Types of Touchscreen with Their Pros and Cons

With the growth of smart devices, the application of touchscreens is getting closer and closer to our life. Various electronic devices, vehicle tools, daily entertainment equipment, shopping navigation equipment, etc., and the LCD touchscreen has already been integrated into our daily life. When we meet various touch technologies and choose a device with a touchscreen, many questions often arise. What are the advantages of touch displays, and how to choose a better one? Today I will show you a brief introduction to 5 common types of touch screens, as well as their advantages and disadvantages.

According to the touch principle, touch screens can be divided into five basic types: capacitive touchscreens, resistive touchscreens, infrared technology touchscreens, surface acoustic wave technology touchscreens, and low electromagnetic guidance touchscreens. In fact, there are four types of touch screens that we often come into contact with at present, they are resistive touch, capacitive touch, infrared and surface acoustic wave touch. We mainly introduce the differences between these 4 types of touch displays.

1: Capacitive Touchscreen

The technology of the capacitive touch is inseparable from the human body. It needs the mutual induction of the human body current and the ITO conductive layer to work.

First of all, the capacitive touch has 4 layers of glass. The inner surface of the glass and the interlayer are each coated with a layer of ITO. The outermost layer is a protective layer of silica glass. The interlayer ITO coating is used as the working surface, and the electrodes are respectively drawn out from the four corners. when there is a touch with the human body, the finger and the working surface form a current, and the current flows out from the electrodes on the four corners of the touch screen, and the electrodes can sense the change of the surface charge and then determine the coordinates of the touch point. Capacitive touchscreens require only touch, not pressure.

Pros of Capacitive Touchscreen

1. The capacitive touch has fewer corrections working after production, which can improve work efficiency and reduce the generation of defective products;

2. Long working life;

3. Light transmittance and clarity are better than the resistive touchscreen;

4. Capacitive touch is easy to design on large-size LCD display and the cost is relatively low;

5. Can support multi-touch technology.

Cons of Capacitive Touchscreens

1. When a large-area palm or a handheld conductor is close to the capacitive touch display, even if there is no touch on the screen panel, it can also cause a touch action on the display panel;

2. For objects such as wearing gloves or holding an insulating object, the touch does not work, because the insulation medium is added, and the touch point will move;

2. The light transmittance of the capacitive touch screen is not uniform, and there is a problem with color distortion. Due to the reflection of light between the layers, the image characters will be blurred;

4. When the ambient temperature and humidity change, it will cause the capacitive touch point to move and the touch will be inaccurate.

2: Resistive Touchscreen

A resistive touchscreen is a type of touchscreen that uses pressure sensing for control.

It uses two layers of ITO (Indium Tin Oxide) plastic film (ITO+Glass) coated with conductive function. The side of adjacent to the film and glass are all coated with ITO coating. When there is no pressure, there is a gap between the two layers of ITO, and the certain gap is in a non-conductive state. When there is pressure, whether it is human finger pressure or object pressure, the two ITO layers will contact to form a current signal, and then convert the corresponding pressure point by detecting the X-axis and Y-axis voltage changes to complete the touch processing of the entire screen mechanism.

Pros of Resistive Touchscreens

1. Mature technology, low cost;

2. Good environmental adaptability, no worry about the influence of dust, water vapor and oil pollution;

3. Good stability, both the human body and objects can be touched;

4. The precision of the resistive touch screen is high; it is easy to design on a large resolution LCD screen;

Cons of Resistive Touchscreens

1. The touchscreen is easily scratched and the makes the touch is unavailable;

2. Poor light transmission, easy to increase battery consumption;

3. When multi-touch is used, due to unbalanced pressure, the tactility is not good, and the touch point will be incorrect;

4. Relatively low touch sensitivity.

Click this to check the Difference Between Resistive Touchscreen and Capacitive Touchscreen.

3: Infrared  Touchscreen

The infrared touchscreen is easy to install, just add a light spot distance frame on the LCD display panel, no need to coat any IoT. The infrared touch display uses the dense infrared matrix in the X and Y directions to detect and locate the touch point. When the user touches the screen, the touching object will block the two horizontal and vertical infrared rays passing through the position, so as to obtain the position of the touch point to realize the touch. Any touching object can change the infrared rays on the contacts to realize the touch screen operation.

Pros of Infrared Touchscreen

1. The infrared touchscreen is not affected by the current, voltage and static electricity;

2. Low price, easy installation, no need for any controller;

3. Compatible with computers of various grades.

Cons of Infrared Touchscreen

1. Difficult to use on large size LCD screens;

2. Easily disturbed by external light,

3. The infrared touch screen is not waterproof or oil-proof, and any small foreign objects will cause errors and affect its performance.

4. Surface Acoustic Wave Touchscreen

The touch screen part surface of acoustic wave touch can be in a flat, spherical or cylindrical glass plate, a piece of glass installed in front of the CRT, LED, LCD or plasma display screen. This glass has been strengthened and specially treated, and it is installed on the surface of the display. Vertical and horizontal ultrasonic senders are installed on the upper left and lower right corners of the glass, and ultrasonic receivers are installed in the upper right and low left corners. when the finger touches the glass surface, the finger absorbs part of the sound wave energy, the controller records this anomaly and calculates the position of the touch point.

Pros Surface Acoustic Wave Touchscreen

1. High clarity and good light transmittance.

2. Highly durable, good scratch resistance and responsive.

3. Not affected by environmental factors such as temperature and humidity, high resolution, and long prolife;

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4. High light transmittance, can maintain clear and bright image quality;

Cons of Surface Acoustic Wave Touchscreen

1. Applicable to smaller screens, hard to use on larger screens more than 30 inches;

2. Susceptible to moisture damage, so not suitable for many industrial and commercial applications;

3. Dirty surfaces can cause dark spots on the screen and require regular cleaning

RJOYTEK LCD TOUCH SOLUTION

Introduced so much knowledge about touchscreens, we provide customers with personalized LCD TFT display solutions, we provide different touch technology TFT LCD panel customization according to customer requirements, and design touch solutions that meet the requirements according to user application scenarios, such as different material glove touch, water environment touch, saltwater environment touch, hover touch, 3D (force) touch, haptic touch, etc. Orient Display can also provide very low cost fixed area button touch, single (one) finger touch, double finger (one finger+ one gesture) touch, 5 finger touch, 10 points touch or even 16 points touch.

Anything help you need, please contact us!

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How it works: The technology of touch screens

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When the touch technology is deposited on the cover glass using the sensor on lens approach, you end up with a separate touch module that can be sold to the LCD display assemblers. This would mean more revenues for the touch technology manufacturers who would supply these modules.

On the other hand, the on-cell alternative means that the LCD panel manufacturers can add these touch layers onto their own panels. The display assemblers would then just have to purchase a simple cover glass to complete the display. The touch module makers would be cut out of the process.

For now, it appears that the sensor on lens approach has an advantage over on-cell solutions. The on-cell approach means that LCD makers would have to make two separate models of each panel: one with touch and one without. This could add cost to an industry that is already running on razor-thin margins. Also, on-cell touch is limited to the size of the LCD panel; sensor on glass modules can be larger than the LCD panel, providing room for the dedicated touch points that are part of many smartphone designs.

LCD vs. OLED

In case you've been wondering where OLED displays fit into all this: An OLED display stack is somewhat different from an LCD stack. It only requires one substrate (glass) layer as opposed to LCD's two, and the OLED material layer is much thinner than the LCD layer. As a result, the finished display can be half as thick as an LCD panel, saving weight and thickness -- which is important in a smartphone design.

(A number of smartphones today use a form of active-matrix OLED display called Super AMOLED; these include several Samsung devices such as the and the Motorola Droid Razr M).

As a practical matter, glass is still used as the encapsulating layer, so OLEDs generally have two layers of glass. In addition, not all OLEDs are RGB -- some use white emitters instead to try to reduce the differential aging problem, and add a color filter layer to the stack.

In spite of all this, as far as touch screen technologies are concerned, OLEDs are more like LCDs than they are different: Both have active matrix TFT backplanes, and both tend to have a cover glass layer for protection. So essentially the same stack configurations are available to OLED panels.

What's next for touch

No matter which solution wins out, it is clear that pro-cap technology is the best method for touch screens on mobile devices -- at least for the foreseeable future. Still, there are some changes already showing up in touch screen technology.

For example, some panel makers are creating "in-cell" touch panels, where one of the conductive layers actually shares the same layer as the thin film transistors (TFTs) used to switch the display's sub-pixels on and off. (These transistors are fabricated directly on the semiconductor backplane of the display.) This approach not only reduces the electromagnetic noise in the system, but also uses a single integrated controller for both the display and the touch system. This reduces part counts and can make the display component thinner, lighter, more energy efficient and more reliable.

This approach only makes sense for very high volume products, such as a smartphone from a major vendor that is expected to sell millions of units, because the panel will have to be made specifically for that unique model. The first products using "in-cell" touch technology have already appeared on the market, such as the new , but it looks as though it will take years before this approach will become a widespread solution.

Additional resources

For more information about touch display technology, check out these sites:

Fundamentals of Touch Technologies and Applications (PDF)

A "short" course (207 slides long) covering a variety of topics covering touch technology; it accompanied a talk by Geoff Walker of Walker Mobile presented at the Society for Information Display's conference.

How Touch Computing Works

An easy-to-understand description of current touch technologies by the Intel Free Press.

Touch Screens 101

A description of the four types of touch technologies offered by Planar Systems, which specializes in digital display technology.

Touchscreens 101: Understanding Touchscreen Technology and Design (PDF)

A white paper offering the basics of touch technology by Steve Kolokowsky, senior elect design engineer, and Trevor Davis, senior business development manager at the Cypress Semiconductor Corp.

Touch Screens: A Pressing Technology (PDF)

A paper from Timothy Hoye and Joseph Kozak of the University of Pittsburgh about basic touch screen technology.

Touch Screen Middle East

A site from a touch screen equipment supplier that offers a lot of good information about the variety of available touch screen technologies.

Some device manufacturers are also adding stylus support to their products. The new higher-resolution displays make it useful for some users to have access to a pointing or writing device that has a finer tip than a finger. Some devices rely on an "active" stylus that can be sensed by the pro-cap system, such as the Samsung Galaxy Note. Others, such as the , are choosing single-point infrared optical sensing that can detect the position of any pointed object on the screen.

Meanwhile, system designers are developing new ways to interact with mobile devices via touch, such as and . Even as other modes of interaction -- such as speech recognition for voice input -- become more sophisticated, touch is likely to remain the primary way we control our devices.

In-Cell, On-Cell and OGS, three capacitive touch screen technologies

Structure of LCD touch screen

We can divide an LCD capacitive touch screen into three parts structurally. From top to bottom, there are cover glass, touch screen and LCD display. 

Usually, touch screens and LCD displays are produced separately and glued together with air bonding technology. So, there will be an air gap between touch screen and LCD display.

Air bonding & Optical bonding technology for LCD touch screen

Air bonding is a simpler manufacturing technology with a high yield rate. Double-sided adhesive fixes touch screen and display panel around  perimeter.  However, there is an air gap between display panel and touch screen, which makes the whole display thicker. Reflected light and dust in air gap make screens less clear, too.

Optical bonding on the other hand, is to glue touch panel onto LCD screen with optical adhesive.  Full-fit technology eliminates the air gap between layers. Less  reflected light means better display. However, Optical bonding is an expensive technology. Now only a small number of customers with special needs choose this type of  touch screen. As more and more end-users demand better LCD display, optical LCD touch screen will become mainstream.

Three technologies of capacitive touch screen display

In-Cell, On-Cell and OGS（One Glass Solution） are three new ways to create capacitive touch screen display.

In-Cell refers to embedding touch panel function into liquid crystal pixels, that is, embedding touch sensor function inside LCD screen. Traditional touch panel is no longer necessary. In-cell is an innovation of loading circuits onto liquid crystal. This kind of LCD is much thinner with better readability in sunlight.

On-Cell means embedding touch screen between color filter substrate and polarizer, in other words, equipping sensor on  LCD panel. Although manufacture of on-cell screens is easier than In-Cell, there are still thickness and color uneven problems. 

OGS technology is to fit touch screen and protective glass together. Inside of protective glass is ITO conductive layer. Coating and lithography are done directly on the glass. This makes touch screen thinner and cheaper. However, protective glass is usually tempered first, then coated, etched, and finally cut. Cutting tempered glass is difficult with low yield rate. Capillary cracks on the edge will weaken the cut glass.

Summary

Amongst the three types of capacitive touch screens, they have different pros & cons in following areas.

    • Permeability: OGS is the best, followed by In-Cell and On-Cell.
    • Thinness: In-Cell is the winner. OGS and On-Cell are next.
    • Touch effect: OGS touch sensitivity is better than In-Cell & On-Cell.
    • Production difficulty & cost: In-Cell and On-Cell are more difficult and costly than OGS.

Contact us to discuss your requirements of infrared touch screen for retail. Our experienced sales team can help you identify the options that best suit your needs.