Evaluation of Privacy Films using Automated Absolute Reflectance Measurement

Download PDF October 4, 2017


Privacy Films
V-750 UV-Visible/NIR Spectrophotometer

Privacy films for smartphone displays are used to prevent bystanders from viewing the user’s phone. These films are composed of louver layers of transparent and light shielding layers that are interlaminated. Depending on the height and pitch of the louver layers, the screen view can be obstructed at specific viewing angles.

Absolute reflectance can be used to evaluate the viewing angle or the transmittance of the louver layers. By rotating the sample, source and/or detector angles around the sample, transmittance values can be obtained for a variety of different viewing angles (Figure 2).

In this application note, the angular dependence of the transmittance spectra of a privacy film is studied using absolute reflectance measurement.

Figure 1. Structure of louver layer.


Figure 2. Schematic of absolute reflectance measurement accessory.


Measurement Conditions
Detection AngleIncidence Angle-60-60º
Measurement IntervalMeasurement Mode%T, asynchronous
Wavelength Range380-780 nmBandwidth5 nm
Scan Speed400 nm/minResponse0.96 sec


UV-0033, V-750, UV-Visible spectrophotometer, ARMN-919 Automated Absolute Reflectance measurement, Privacy Films


Figure 3. 3D plot of the transmittance spectra as a function of wavelength and incidence angle.

The 3D plot in Figure 3 shows the transmittance spectra as a function of wavelength and incidence angle. Figure 4 illustrates the transmittance spectra at varying incidence angles and Figure 5 is the angle dependence transmittance spectra at 550 nm. These data reveal that the privacy film absorbs blue light below 400 nm while keeping the transmittance constant above 400 nm, indicating that the film displays light without inducing a large color change. Figure 5 shows a transmittance of 5% near the viewing angle of ±32.5º, suitable for user privacy.

Figure 4. Transmittance spectrum of privacy film
obtained every 10º.
Figure 5. The angle dependence of the transmittance spectra at 550 nm.

About the Author

Leah Pandiscia received her PhD from Drexel University where she studied Biophysical Chemistry. She is a Spectroscopy Applications Scientist at JASCO.