Specification and Design
Guidelines for Mounting Light Sheets
This application note explains the recommended methods of mounting Cooledge light sheets to various surfaces for installation.
Light sheets are able to operate simply suspended in air with no substrate. However, due to their flexible nature, in most applications they will need to be affixed to a more rigid substrate. There are several recommended mounting methods. The preferred solution will depend on the materials used and required environmental operating conditions.
Recommended Mounting Methods
Any of the following methods of mounting light sheet are recommended and the choice will depend upon the installation conditions and installer preference.
1. Double-sided adhesive tape
For installations where a relatively clean mounting surface is available and sheet lengths are not so long that using DS tape becomes unwieldy, this method may be the simplest to use.
The selection of a suitable tape depends on the surface material to which the light sheets will be mounted (not recommended for wood or drywall), and the environmental conditions of the application.
The back side of the light sheets is PET (Polyethylene terephthalate). Many acrylic based adhesives give a good bond to this material. Rubber based adhesives are not recommended.
A commonly used adhesive tape is 3M 467MP. This is 3M 200MP clear acrylic-based adhesive approximately 0.002” (0.05mm) thick, with a kraft paper liner. This tape is available in rolls from 0.5” (12.7mm) to 24” (610mm) wide. The adhesive bonds well to the PET material of the light sheets, as well as most metals and plastics and has good resistance to both heat and moisture.
Many other adhesive tapes are available and may be suitable for mounting light sheets, but should be tested on a sample before confirming selection.
Before adhering light sheet, ensure that the surface is clean and free from dust and debris. Some adhesives may require the use of a surface preparation or primer.
Narrow light sheets such as the W028 (nom. 1.1”) and W036 (nom. 1.4”) models can usually be secured with a ½” (12.7mm) wide strip along each edge, as shown in Figure 1 below:
For wider light sheets, differential thermal expansion between the light sheet and the substrate may cause the light sheet to bow up if it is only secured along the edges as shown in Figure 2.
In this case additional strips of adhesive may be added in the center of the product as in figure 3 below.
Alternatively, a wide tape may be used to completely cover the back side of the light sheet as in Figure 4, but this can make installation more difficult.
This method is more suited to situations where light sheets are being inserted into an enclosed space – for example, sandwiched between two pieces of glass held by mullions.
All Cooledge light sheets are supplied with a transparent border on both edges approximately 0.4” (10mm) wide. This region can be used to mechanically clamp the light sheet to the substrate as shown in Figure 5.
Fig. 5. (cross section)
Care should be taken in the design to ensure that any electrically conductive clamping elements do not come in contact with the active region between the transparent borders. Should the clamps contact electrically active areas of the light sheet damage to the product may occur.
The mechanical grip of the clamp can be increased by adding a shallow “tongue-and-groove” feature into which the light sheet border is formed as shown in Figure 6:
Fig 6: (cross section)
As noted earlier, differential thermal expansion between the light sheet and substrate may cause to the light sheet to bow, usually at elevated temperatures.
3. Mechanical Fasteners
The transparent border of the light sheet described previously can also be punched at periodic intervals and the light sheet attached with mechanical fasteners (e.g. screws, rivets) as shown in figure 7. Ensure that all fasteners are located outside of the active area of the light sheet and at least 0.2” (5mm) away from any component.
Fig. 7. (cross section)
Washers should always be used in conjunction with screws/bolts in order to prevent the tightening action from causing tearing in the light sheet.
As noted above in the clamping guidelines, care should always be taken to ensure that the fasteners only contact the transparent border region and not any electrically active regions of the light sheet. For this reason nylon washers are recommended when using screws/bolts.
Care & Handling Guidelines
- Always handle light sheets by the transparent border running the length of the sheet on both sides.
- Avoid handling, scraping, rubbing, or wiping the active area of the sheet between the clear borders. Although the LEDs and drive components are bonded strongly to the plastic base material, it is possible to remove them or damage the electrical connection if not handled with care.
- Avoid penetrating the active area of the sheet for any reason. Mounting holes for fasteners may be located in the clear border areas along the length of the sheets.
- As with all electronics, light sheets are susceptible to damage from Electrostatic Discharge (ESD). Where possible avoid situations that are conducive to creating static (eg. don’t rub any balloons before handling…).