DONTECH Heat Shield™ Transparent IR blocking filters

• Reduces thermal loading of LCD’s used in direct sunlight applications
• Reduces heat transfer from plasma displays and backlight assemblies
• Can reduce or prevent LCD “brown out” or failure due to thermal stress
• Provides > 80% IR blocking efficiency compared to non-shielded filters
• Provides effective EMI/RFI shielding when constructed with conductive buss

Heat Shield™ IR Blocking filters are designed to reduce the thermal loading on liquid crystal display’s (LCD’s) used in direct sunlight (e.g., marine, military, outdoor signage applications).

By significantly reducing the transmission of near-infrared and infrared radiation, Heat Shield™ filters reduce electronic display temperatures when exposed to direct sunlight and elevated thermal loading and minimizes display “brown out”.

Product Specifications: 

Substrates:  glass, acrylic, polycarbonate, PET or acetate films. 
Sizes available up to 2 ft. x 6 ft.

Optical Properties:  filters will appear neutral gray in color with approximately 50% photopic transmission.  Additional protective, scratch and abrasion resistant hard coatings are added to plastic filters.  Antiglare and antireflective coatings can be added to increase transmission and reduce specular reflection.

Heat Shield™ Performance Test Results
To verify the performance of Dontech’s Heat Shield™ a test configuration was set up to measure the rate of temperature increase versus time.  Results are shown in Table 1 and Figure 1.

Table 1

Sample Configuration and Rate of Temperature Increase:

*values are obtained from the slope of the trend line of the plotted data.

Figure 1  Performance Heat Shield™  in reduction of thermal loading on display

Graph:-linear portion of the graphs is due to residual heat contained in the display that had not been detected by the thermocouple.  Once the light was turned on, the display and environment reached equilibrium within approximately 30 seconds; the remainder of the data is linear.  Data was solely acquired to determine the rate of increase of the display temperature.

Thermal Test Configuration and Methods:

Two areas of testing were addressed on two different configurations of heat reflector panels in comparison to the panel without a heat reflector.  Heat Reflector testing was simulated with a halogen lamp and optical testing including transmission and reflection were performed. 

The following outlines the configuration of the samples:

Sample 1:  General lens configuration with HR04-0611 rear surface

Sample 2: General lens configuration with HR03-0411 rear surface

Sample 3: General lens configuration without a heat reflector

Tests:

Heat Reflector

Heat and Light Source:  One unfiltered, 500 watt, double ended quartz halogen bulb positioned 45° above the horizontal filter surface.  The bulb was focused on the center of the display and was approximately 15 inches from the center of the display. 

Fixture:  The display was encased in 1” thick aluminum covered foam insulation.  All internal seams and edges were taped with aluminum tape.  The fixture was made such that the filter panel rested horizontally on a 10”x6” opening approximately 1” above the display.  A digital readout thermocouple was fixed in the center of the exposed portion of the display.

Measurements:  Temperature readings were recorded in 30 second intervals.  Note that the starting ambient temperature was not the same for every test.  The differences in starting temperature can be estimated from the following graph.  Results were calculated in order to report the rate at which the temperature increased. 

The fixture was covered with a 1” piece of foam for five minutes prior to testing to allow the halogen to reach a uniform heat and light intensity.  After each test, the fixture and display were cooled to ambient temperature for 30-45 min. 

Table 2

Optical Performance – Specular Reflection and Transmission
(Table 2, Figure 2 and Fig. 3)

Transmission, Haze and Reflection

                                                   
Figure 2

Figure 3