Optimization of retarder parameters for switchable privacy mode automotive displays under asymmetric viewing conditions

Figures & data

Figure 1. (a) Illustration of the driver’s and co-driver’s viewing angles for the SPM display studied in this paper. θ and ϕ are the polar and azimuthal incident angles of light. (b) is an optical structure of the SPM display panel. TP, MP, and BP indicate the top, middle, and bottom polarizers, respectively. $\alpha$ and $\text{β}$ are the polar and azimuthal pre-tilt angles of the liquid crystal, respectively. ${\phi }_R$ is the slow axis of the retarder.

Table 1. Simulation parameters used in the study.

TN LC
Polar pretilt angle (${\alpha }_{\mathrm{TN}}$)	6^o
Azimuthal pretilt angle (${\text{β}}_{\mathrm{TN}}$)	−45^o(bottom), 45^o (top), 90^o right-handed twist
Cell gap ($d_{\mathrm{TN}}$)	5 µm
$n_e$ (at λ = 550 nm)	1.61
$n_o$ (at λ = 550 nm)	1.49
${ϵ}_{\parallel }$	8.6
${ϵ}_{\mathrm{\perp }}$	3.3
$K_{11}$	11.7 pN
$K_{22}$	5.5 pN
$K_{33}$	14 pN
IPS LC
Polar pretilt angle (${\alpha }_{\mathrm{IPS}}$)	2^o
Azimuthal pretilt angle (${\text{β}}_{\mathrm{IPS}}$)	90^o
Cell gap ($d_{\mathrm{IPS}}$)	3.5 µm
$n_e$ (at λ = 550 nm)	1.58
$n_o$ (at λ = 550 nm)	1.48
${ϵ}_{\parallel }$	9.3
${ϵ}_{\mathrm{\perp }}$	4
$K_{11}$	10.9 pN
$K_{22}$	9.5 pN
$K_{33}$	15.4 pN
Polarizer
Top polarizer transmission axis	90^o
Middle polarizer transmission axis	0^o
Bottom polarizer transmission axis	45^o
Retarder
Slow axis (${\phi }_R$)	58∼67.5^o
$n_x$ (at λ = 550 nm)	1.54
$n_y$ (at λ = 550 nm)	1.46
Thickness ($d_R$)	3.43 µm
$R_{\mathrm{in}}$	275 nm
dRin/dλ	0.2∼0.7
NZ coefficient	−0.7∼1.7

Figure 2. (a) TR vs. polar viewing angle $\theta$ of the O-mode TN display panel with PD HWP. This TR profile was obtained along the horizontal viewing direction. (b) specifies the polarization state change of incident light after passing through BP, TN, and HWP on the Poincaré sphere at 0 V state. Techwiz 2D was used for the calculation in (a), while Techwiz Polar was used for the Poincaré notation of the polarization state evolution.

Figure 3. Contour plots of TR in privacy mode when (a) PD and (b) ND HWP were used. (c) and (d) correspond to TR profiles in share mode. Techwiz 2D was used for this calculation.

Figure 4. Poincaré plot of the polarization state after passing through ND HWP at the (a) driver’s and (b) co-driver’s viewing directions in privacy mode with 2.2 V applied. ${\phi }_R$ is 60^o in this example. (c) shows the distance $l_{-S1}$from the polarization state to the – S₁ axis vs. ${\phi }_R$ at the driver’s viewing direction in privacy mode, and (d) reflects the distance $l_{+S1}$from the polarization state to the + S₁ axis vs. ${\phi }_R$ at the co-driver viewing direction in privacy mode. (e–f) correspond to the distance $l_{+S1}$ from the final polarization state to the + S₁ axis in share mode with 0 V applied. The numbers in the graphs correspond to the averaged TR value for RGB light. Techwiz Polar was used for this calculation.

Figure 5. Poincaré plot of the polarization state after ND HWP at the (a) driver’s and (b) co-driver’s viewing directions in privacy mode with 2.2 V applied. (c) represents $l_{-S1}$ vs. dR_in/dλ of HWP at the driver’s viewing direction in privacy mode, and (d) displays $l_{+S1}$vs. dR_in/dλ of HWP at the co-driver’s viewing direction in privacy mode. (e–f) correspond to $l_{+S1}$ in share mode with 0 V applied. The numbers in the graphs correspond to the averaged TR value for RGB light. Techwiz Polar was used for this calculation.

Figure 6. Poincaré plot of the polarization state after ND HWP at the (a) driver’s and (b) co-driver’s viewing directions in privacy mode with 2.2 V applied. (c) presents $l_{-S1}$vs. NZ coefficient of HWP at the driver’s viewing direction in privacy mode, and (d) portrays $l_{+S1}$vs. NZ coefficient of HWP at the co-driver’s viewing direction in privacy mode. (e–f) correspond to $l_{+S1}$ in share mode with 0 V applied. The numbers in the graphs correspond to the averaged TR value for RGB light. Techwiz Polar was used for this calculation.

Figure 7. TR vs. polar viewing angle of a display panel along the horizontal viewing direction when the optimized HWP was used and the contour plots of TR in the (b) privacy mode and the (c) share mode when the optimized HWP was used. Techwiz 2D was used for this calculation.

Figure 8. Demonstration simulation images observed at the (a) driver’s and (b) co-driver’s viewing directions in privacy mode. (c) and (d) are the corresponding images in share mode. The simulation parameters for the TN-LCD panel and the compensation film are identical to Figure 7. Techwiz 2D was used for this calculation.