Evaluation of Privacy Films by Absolute Reflectance Measurement

Introduction

**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.

Experimental

Measurement Conditions
Detection Angle	0°	Incidence Angle	-60-60º
Measurement Interval	2°	Measurement Mode	%T, asynchronous
Wavelength Range	380-780 nm	Bandwidth	5 nm
Scan Speed	400 nm/min	Response	0.96 sec

Keywords

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

Results

**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.

Transmittance spectrum of privacy film obtained every 10º — **Figure 4.** Transmittance spectrum of privacy film
obtained every 10º.

**Figure 5.** The angle dependence of the transmittance spectra at 550 nm.

JASCO

Industry

Technique

Evaluation of Privacy Films using Automated Absolute Reflectance Measurement

Introduction

Experimental

Keywords

Results

About the Author

Industry

Technique

Introduction

Experimental

Keywords

Results

Featured Products:

V-730 UV-Visible Spectrophotometer

V-750 UV-Visible Spectrophotometer

V-760 UV-Visible Spectrophotometer

About the Author