What is Touch Panel???

The touch panel is a device that operates by touching the display directly with human fingers (or dedicated pen), so that the sensors on the touch panel device detect human fingers to conduct certain actions. Touch panels are used for many kind of device, for example, Smartphones, Tablets, Car Navigation Systems, ATM and it is to divide in five types of detecting systems. Those are, the Projected Capacitive Type, the Surface Capacitive type, the Resistive Touch Panel Display type, the Ultrasonic Wave type and the Infrared type. Recently, due to the explosive growth of smartphones, the Projected Capacitive Type is becoming mainstream of the touch panel industry. Since the projected capacitive type is so called the “Multiple Touch Panel”, it can detect multiple touches at the same time which are actions that are necessary in smartphone operation.

The Resistive Touch Panel Type

  • The resistive touch display type is composed with transparent conductive film (a.k.a. ITO film) that is formed mainly with film and glass.
  • Two transparent conductive films are bonded to face each other and when a finger touches the panel, the transparent conductive films are to contact each other to input the signal.
  • Between the upper and lower conductive film, there are insulators that are called “Dot Spacer”.
  • The dot spacers prevent the upper and lower conductive film from short-circuiting to each other.

111

Projected Capacitive Type

  • In recent years, the Projected Capacitive Type has reached a higher demand since the use for Smartphones has become popular. Since it can detect two points at the same time, it is able to correspond with the “Multi Touch” that is the characteristics of smartphones and tablets devices.
  • Inside the touch panel, there are two transparent electrodes: the x-axis and the y-axis and they intersect each other to form a perpendicular line. Dozens of electrodes are composed in the touch panel and each electrode is to detect capacity value.
  • When a finger touches the touch panel, the capacity of the x-axis and the y-axis around the finger increases and makes a capacity difference between other electrodes. The device reads this capacity difference and detects the position where the finger touched

11

 

Testing Properties of Touch Panels

1. Surface Abrasion Resistance

The testing machine conducts an abrasion resistance test for the surface material used on the touch panel screen. These tests imitate the usage on how the touch panel screen devices are used in daily life. For example, the testing machine rubs the surface of touch panel with a piece of cloth to imitate the condition when the smartphone is inside a pocket.

2. Flexibility

Since the ITO Film has a stiff characteristic, when it is formed into soft film, the film can easily get cracks or bends. Recently, flexible ITO films are produced from utilizing the printing method. The ITO films are produced through a roll to roll process and thus, to have efficiency in the production line, testing machines that evaluate stiffness and bending endurance for the ITO films are used for line production quality checks, rather than to be used as an item to check the durability in daily consumer use.

3. Adherability

Smartphones and tablets are layered with various thin films. Coatings to perform satisfactorily must adhere to the substrates on which they are applied. Cross cut exfoliation testing evaluates the adhesive property of each layered parts. It is most useful in providing relative ratings for a series of coated panels exhibiting significant differences in adhesion.

4. Scratch Hardness

The pencil scratch hardness testing is to evaluate a surface hardness of displays and exterior parts. The test is to conduct with the dedicated pencil. The operator is to scratch a sample with the pencils to one direction and changes pencil’s hardness scales until a pencil makes a scratch on the sample. The operator determines the “pencil scratch hardness” by figuring out the hardest pencil that did not make a scratch on the samples.

Test Equipment for Touch Panels

6

  1. Yasuda Taber Type Abrasion Tester

Used to evaluate the abrading endurance of flat surface materials when they are abraded with an abrading wheel. The operator is to place the abrading wheel to the rotating test specimen at a prescript load and abrade the test specimen. After the test is completed, the abraded mass, volume, thickness and optical difference will be measured. This tester is widely used in testing of plastics, rubber, decorative sheet, leather, paper and paint surface.

  1. Yasuda Colour Fastness Rubbing Tester

Used to evaluate the colour fastness of textile products, leather, rubber and plastics against abrasion. The operator will place the test specimen on the round surface and the test specimen is to be abraded with an abrading head which is attached with a white cloth. After the test is completed, the degree of colour fastness will be judged according to the gray scale. The tester can be also used to conduct abrasion-resistance tests on paper board and ink coating.

  1. Yasuda Paint Film Bending Tester

Used to evaluate the bending endurance of paint and varnish coated film according to the cylindrical form mandrel method. The operator will place the coated film testing board on the outer side and bend it at a speed so that it takes 1 to 2 seconds to bend the testing board 180 degree. The coated film test specimen will then be inspected for cracks and peels.

  1. Yasuda Gardner Type Falling Sand Abrasion Tester

Used to evaluate the abrading endurance of paint and plate coated film surface. Dropping the standard testing sand from a prescript height to the test specimen which is attached at a 45 degree angle. The operator will need to measure the amount of sand and time it took for the surface of the coated film to be exposed.

  1. Yasuda Automatic Cross Cut Exfoliation Tester

Used to evaluate the adhesion of coated film according to the cross cut method. The operator is to check and evaluate the surface of the coated film after it has been grid cut until the grid cut reaches the basis material. Since the tester cuts electronically, it will allow the operator to have accurate test results.

  1. Yasuda Electric System Pencil Scratch Hardness Tester

Used to evaluate the hardness of the coated film according to the testing machine method. Scratching the paint surface with a pencil attached at 45 degree angle. The operator is to determine the hardest pencil that does not tear or damage the coated film. The tester can also be used to evaluate the hardness of decorative sheet and resistance to solvents on enamelled wire.