Here are a few topics we believe may be of interest to Designers of Display Modules. This Bulletin Board will be accumulative, and we shall add more information on a weekly basis.

1. Missing Optimization of the TFT Display Appearance

Without display optimization, the resulting TFT Module visual integrity will be compromised. With proper awareness of the types of available TFT glass, an OEM can select the best TFT glass option to enhance performance. Here are some variables to be considered when Designing a TFT Module:

• Recognizing proper resolution to capture detailed images.
• Plan for enough speed to maintain smooth images.
• Select Wide Viewing Angles for Applications requiring such features.
• Planning for proper Color Gamut (Range) based on Applications.
• Sunlight Readable Displays for Indoor/Outdoor Application.
• Use of OCA in the Stacking of the Sub-Systems

2. Critical Backlighting Consideration

As a frequent design dilemma, standard TFT Display Modules as well as most customer designs provide less than optimum backlight intensity necessary to address bright ambient conditions and/ or outdoor usage. Typical standard off-the-shelf TFT Display Modules offer 400 to 800 NITS. Application specific intensities can require backlighting as high as 2,000 NITS and even greater. Proper Backlight is critical in certain challenging environments and must not be overlooked. Tooling costs for customizing back lights are inexpensive.

• Recognizing proper resolution to capture detailed images.
• Plan for enough speed to maintain smooth images.
• Select Wide Viewing Angles for Applications requiring such features.
• Planning for proper Color Gamut (Range) based on Applications.
• Sunlight Readable Displays for Indoor/Outdoor Application.
• Use of OCA in the Stacking of the Sub-Systems

3. Touch Panel Designs

• Touch Panels are common peripheral Sub-Systems to TFT Modules. In the market, there are numerous off-the-shelf Touch Panel products available as add-ons to a TFT Module. However, off the shelf Touch Panels many not match-up well to a desired TFT Glass design and thus either the selection of the TFT Glass or the Touch Panel may be compromised. Tooling for customized or modified Touch Panels is inexpensive and should be considered in the best interest of achieving the best Touch Panel complement to the desired TFT Glass.
• Sensitivity adjustments can be made to compensate sensitivity due to wearable articles such as Gloves or transparent sheeting. Standard off the shelf products do not offer such adjustment options.
• The sensor IC’s Algorithm can be adjusted to compensate for bombardment of EMI/RFI interference generated internal to the device, external emissions or by harsh environments such as rain, snow, ice or objects that may fall on the surface of the Touch Panel. Standard off the shelf products do not offer any such adjustment features.
• It is best practice to test the sensitivity of the Touch Panel to insure there will be no areas on the screen that has higher or lower capacitive coverage thus making the Touch Panel inconsistent in its response to touch inputs. such cases, it is necessary to have the Touch Panel supplier adjust the sensitivity by introducing corresponding software through the touch sensor IC.
• All Touch Panels will need a Cover Lens that can be provided as part of the TFT Module or from an external Cover Lens that is joined through external hardware mounting. See Cover Lens discussion below.
• For Optimizing TFT view performance Touch Panels are to be joined to the TFT glass by applying OCA (Optical Clear Adhesive). OCA eliminates the resulting air gap spacing when TFT glass and Touch Panels are joined together mechanically. Thus, through the application of OCA the air gap spacing is eliminated and internal reflection is greatly reduced resulting in a more optimized TFT Display performance.

4. Cover Lens Optimizing Visual Performance and Scratch / Impact Resistance

• Optimizing TFT view performance Touch Panels are to be joined to the TFT glass by applying OCA (Optical Clear Adhesive). OCA eliminates the resulting air gap spacing when Cover Glass-Touch Panels-TFT Glass-Backlights are Stacked together.
• Cover Lenses are necessary to protect Touch Panels from scratches or liquid contact. Cover Glass ranges from 1 mm to 3 mm. Cover Lenses are applied as part of the TFT Module to protect the TFT from the outside environment. In either case, it is recommended to use Optical Clear Adhesive to bond the Cover Lens directly to the Touch Panel or TFT glass. Cover Lenses also can include Anti-Glare finishes. UV protective film and Black Masks to outline the Active Area of the display.
• Cover Lenses also play an important role in protecting the Front Panel of the Display Module from Impact Damage. Attention must be paid to the Human Interface(Drops, Rough Handling, Vandalism….etc. of your device in order to determine the amount of impact your Cover Glass shall withstand. The following is a table providing a general physical reference on how Cover Glass grading is documented.

The IK rating means the degrees of protection provided by enclosures for electrical equipment against external mechanical impacts or shocks in joules. The IK rating consists of two digits (00 to 10) after the term ‘IK’ (e.g. IK05).

IK ratings are an international numeric classification specified in accordance with IEC 62262:2002 and IEC 60068-2-75:1997.