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Abstract
Vertically-Aligned Fringe-Field Switching (VA-FFS) liquid crystal (LC) mode is known for its intrinsic submillisecond fast response time due to existence of self-imposed boundaries of virtual walls. In this paper, we investigate the effects of electrode structure and LC dielectric anisotropy. The performance of VA-FFS with conventional 2D and 3D electrode designs are compared. By using the 3D electrode design, higher transmission and faster response time are found possible as a result of having less dark states and at the same time having more virtual walls surrounding a 3D pixel. In the second part, we investigate the difference between VA-FFS LC mode employing LC materials with positive and negative dielectric anisotropy, while keeping all other factors the same. We found that, in general, positive LC materials can provide faster response time whereas negative LC materials can provide higher transmission. In the case of 2D design, however, negative LC is found to have rather unexpected slow response times due to i) existence of a 2-step switching process and ii) disappearance of virtual wall, which have never been reported or published before for VA-FFS. In this paper, we will show that, by using a 3D design, both of these problems for negative LC can be improved such that 3D design can help maintain the stability of virtual walls and also help bring the response time of negative LC closer to that of positive LC. VA-FFS LC has been actively researched for VR/AR application in recent years.
© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
1. Introduction
Vertically-Aligned Fringe-Field Switching (VA-FFS) liquid crystal (LC) mode has the attractive feature of having an “inherent” sub-millisecond fast response time without the use of a very thin cell gap structure or other liquid crystal phases [1–3]. A major mechanism responsible for the capability of delivering such unusual fast response time is due to the existence of “self-imposed boundaries” [1–3] or “virtual walls” [4–7]. These self-imposed boundaries or virtual walls are formed as a result of disclinations (or unswitched LC molecules) which appear above and between the pixel electrodes of a VA-FFS LC cell at field-on state as shown in Fig. 1. This concept has also recently been employed and further developed for use in in-plane type of switching with a zero-rubbing angle, which resulted in faster response time [5–10]. These developments have been very active in recent years as they have potential for use in VR /AR technology which requires fast response time in LC devices [8–13].
Fig. 1. Structure and switching of a VA-FFS LC cell at field-on state showing the existence of disclinations which can help create the “self-imposed boundaries” or “virtual walls.”
In the originally proposed design [1–3], we only studied 2D electrode in which the structure only varies periodically along the x-direction as shown in Fig. 2(a). In Fig. 2(a), W is the electrode width of the pixel electrode whereas G is electrode gap between the pixel electrode. As shown in both Fig. 1 and Fig. 2, the electrode is in the form of Fringing-Field-Switching (FFS) [14] where the slit pixel electrode is located in the bottom substrate above a continuous common electrode with an insulating layer between them. Recently, 3D electrode design, i.e. electrode design also varies periodically along the y direction (i.e. the transverse direction), has also been proposed [11,15] as shown in Fig. 2(b) for further studies of this VA-FFS LC mode. Our interest in 3D pattern [15] arised from the speculation that it may help reduce the disclination lines along the y-direction, which could hinder this liquid crystal mode from achieving its maximum potential transmission. Moreover, by using a 3D design, we may be able to create even “smaller liquid crystal domains” in the x-y plane. Thus, it may further improve the response speed since smaller domains tend to result in faster response time. This is quite similar to what we observe in e.g. the response time of Polymer Dispersed Liquid Crystal (PDLC) and nano-PDLC [16–17]. By having smaller liquid crystal domains in nano-PDLC, we can achieve faster response time in nano-PDLC compared to the PDLC due to smaller domain size in nano-PDLC which result in having more anchoring forces from the surrounding polymers and hence faster response time.
Our original proposed design had been based on the use of positive LC (i.e. with positive dielectric anisotropy) [1–3]. Since then, negative LC has also been used for a 3D VA-FFS with 3D design [11]. As far as we know, there is no report on comparing the differences between VA-FFS LC mode using positive and negative dielectric anisotropy. In this paper, we also intend to investigate and compare difference between positive and negative LC anisotropy for VA-FFS mode. In particular, we compare difference in the transmission and response time. Possible mechanisms resulting in their differences are also investigated. In order to have fairer comparison, the material parameters that we use for both positive and negative LC materials will be all the same except their sign of dielectric anisotropy. We have chosen to compare them in this way because the resulting response time difference between them will then be mainly due to the difference in switching mechanism and not due to other factors or parameters such as difference in viscosity or elastic constant values, etc.
2. Comparison of 2D & 3D VA-FFS
2.1 Device & material
The simulations of the LC devices were carried out using commercial simulation software 3D LCD Techwiz (Sanayi, Korea). The LC material parameters used in the simulations are the same as E7 whose physical properties are listed as follows [1]: ${\textrm{K}_{11}}$=11.7 pN, ${\textrm{K}_{22}}$=8.8 pN, ${\textrm{K}_{33}}$=19.5 pN, $\Delta \textrm{n}$=0.223 (${n_e}$=1.723, ${n_o}$=1.5), $\Delta {\varepsilon }$=14.4 (${\varepsilon _ \bot }$=18.4, ${\varepsilon _\parallel }$=4), and ${\gamma _1}$ = 150 mPa${\cdot}$s. The VA-FFS electrode width W is varied between 1µm to 8µm whereas electrode gap G is varied between 1µm to 6µm. The cell gap is fixed at 5µm for this particular simulation.
2.2 Results and discussion
Figure 3 compares the transmission versus applied voltage (T-V) curves of i) 2D VA-FFS with linear polarizers, ii) 3D VA-FFS with linear polarizers and iii) 3D VA-FFS with circular polarizers (The reason for also using circular polarizers for 3D will be explained below). The electrode dimensions of the 2D VA-FFS were chosen to be W = 4µm and G = 1µm whereas for 3D VA-FFS and circular 3D VA-FFS the dimensions were chosen to be W = 7µm and G = 1µm for maximizing their transmissions. From the plots in Fig. 3, after normalization, we found that the normalized maximum transmission of 2D VA-FFS with linear polarizers is ∼ 57% with operation voltage of 16.2V. The normalized transmission of 3D VA-FFS with linear polarizers is ∼ 44% with operation voltage of 12.8V. However, by using 3D VA-FFS with circular polarization, as shown in Fig. 3, the normalized transmission can be improved to about 66.3% with same operation voltage of 12.8V. Therefore, the proposed 3D VA-FFS structure with circularly polarized light can indeed improve the overall potential transmission performance of the VA-FFS LC mode.
Fig. 3. Comparison of the Transmission vs. voltage (T-V) curves between VA-FFS mode with 2D and 3D electrode designs. Use of 3D VA-FFS with circular polarizers indeed improves the overall transmission of VA-FFS (note that without circular polarizers, transmission may decrease since LC molecules rotate along the polarizer axes.)
Figure 4 shows their corresponding top-view brightness distribution profiles between the 2D VA-FFS and Circular 3D VA-FFS pixels. From Fig. 4(a) and Fig. 4(b), we see clearly that the disclinations (or deadzones) appear as darker states, while less disclinations in devices with 3D with circular polarizer as shown in Fig. 4(c). This leads to an overall increase of transmission in the 3D VA-FFS with circular polarizer compared that of 2D VA-FFS as shown in Fig. 3.
Fig. 4. Top-view of the transmission of (a) 2D VA-FFS with linear polarizers and (b) 3D VA-FFS with linear polarizers and (c) 3D VA-FFS with circular polarizers.
The reason we need to use circular polarizers for the 3D VA-FFS is that the LC molecules now are able to rotate in all different directions under an applied electric field. Hence, the LC molecules which rotate along or around the polarizer transmission axes tend to form a dark state since little or no retardation is induced by the LC molecules. As a result, many dark fringes or dead zones would be observed leading to low transmission as shown in Fig. 4(b). By using circular polarizers, this dark fringes or dead zones problem can be much reduced as shown in Fig. 4 (c) since bright state can be formed no matter which direction of the LC molecules rotates.
As far as response time is concerned, Table 1 compares the response times (rise and fall) between 2D and 3D VA-FFS with various electrode widths W (3-8 µm) under the same electrode gap G (2µm). As shown in Table 1, both rise and fall times are shortened in the case of 3D VA-FFS compared to those of 2D VA-FFS. As described earlier, this improvement is believed to be due to the reduction of “effective” domain size of a pixel which is like having an increase in anchoring forces produced by the surrounding polymers as in the case of nano-PDLC compared to PDLC. This can be observed by the fact that each individual pixel in the 3D design has virtual walls (or disclinations) in all four different directions as shown in Fig. 4(b) and Fig. 4(c), whereas the 2D pixel only has virtual walls (or disclinations) on two sides, i.e. only on the right and on the left hand sides of the pixel as shown in Fig. 4(a).
Table 1. Comparison of the response time between 2D VA-FFS and 3D VA-FFS (circular polarizer) LC modes
3. Comparison of LC with positive and negative dielectric anisotropy
3.1 Device & material
In this section, we compare the difference between positive (with positive dielectric anisotropy) and negative (with negative dielectric anisotropy) VA-FFS LC in 2D and 3D electrode designs. Since the 3D electrode design introduced in the previous section has separate pixel electrodes, the connection of electric circuits is challenging for fabrication since pixels are not connected. A “reversed” structure as shown in Fig. 5. This structure is also similar to that reported in [11]. In this “reversed” structure, pixel electrodes are connected together with electrode gap G (appear as square holes) in the middle regions as shown in Fig. 5. Hence, electrode width W in Fig. 2(b) now becomes electrode gap G in Fig. 5 whereas electrode gap G in Fig. 2(b) now becomes electrode width W in Fig. 5. The principles, working mechanism and simulation results of this “reversed” electrode design are similar to our originally proposed 3D electrode design shown in Fig. 2(b).
We choose E7 LC material parameters for our positive LC simulations. The properties are shown in Table 2. As described earlier, we have chosen to simulate the negative LC using identical LC parameters (except for their sign of dielectric anisotropy) so that we can have a fairer comparison between positive and negative VA-FFS. The difference between them will thus be solely due to the different sign in dielectric anisotropy and not in other factors. This can help rule out possible effects of e.g. having a larger viscosity in negative LC which often leads to slower response time. The parameters of this “negative E7” are also shown in Table 2. The cell gap d used for the simulations for the comparison is 3µm.
Table 2. Material properties of LC molecules for simulation
3.2 Comparison of positive and negative LC in devices with 2D electrode
Figure 6(a) shows the T-V curves obtained for the positive LC and negative LC in 2D electrode design. The results in Fig. 6(a) show that maximum transmission of negative VA-FFS is higher compared to that of positive VA-FFS. Here, at w = 2µm, g = 3µm, the negative VA-FFS’s transmittance can reach ∼ 76%, while the positive VA-FFS’s transmittance is ∼ 55%. The major reason for having this difference is that the positive LC molecules remain stationery and form “firm” virtual walls and hence dark states above the middle of pixel electrode (or electrode gap) regions since the E field in these regions are mainly vertical or zero. However, for negative LC, the molecules above these regions will also rotate at a later stage and form bright states resulting in higher transmission. The difference between these positive and negative LC switching mechanisms will be described in more detail later. Figure 6(b) shows comparison of the Transmission vs. time (T-t) between positive and negative LC. Figure 6(b) shows that positive LC has a much faster rise time and also fall time compared to that for the negative LC. These differences will be discussed below.
Figure 7 shows comparison of the rise time obtained for positive and negative VA-FFS with 2D electrode design. As shown in Fig. 7(a) and Fig. 7(b), the rise time of the negative LC is much longer compared to that of positive LC in all electrode dimensions. The rise time of positive VA-FFS is below 3ms whereas the rise time of negative VA-FFS can be longer than 15ms.
Fig. 7. Comparison of rise time between negative and positive LC for 2D electrode with (a) different gap, w = 3µm (b) different width, g = 3µm
Although such difference in rise time between positive and negative LC may be attributed to the difference in applied voltage since the turn-on voltage for negative LC is lower as shown in Fig. 6(a). However, even if we deliberately increased the turn-on voltage for negative LC, we found that the rise time was still longer than 10 ms (not shown here). This showed that lower operation voltage is not main reason for having such a slow rise time. We therefore further analyze the turn-on process as follows.
Figures 8(a) and 8(b) show the top-view turn-on process in negative and positive VA-FFS. The LC molecules are distinguished into several zones depending on their positions relative to electrodes. For positive VA-FFS as shown in Fig. 8(a), region A is the center of pixel electrode, region C is the center of electrode gap, and region B is the area between A and C. For negative VA-FFS as shown in Fig. 8(b), region D represents the center of pixel electrode, region F represents the center of electrode gap and region E represents the area between D and F. The corresponding regions A to C of the positive VA-FFS are shown in Fig. 9(a) whereas the corresponding regions D to F of the negative VA-FFS are shown in Fig. 9(b) for the cross-sectional LC director profile distribution and also the electric field direction (arrow direction).
Fig. 8. Comparison of turn-on process between (a) positive and (b) negative LC with 2D electrode. Note that with negative LC it takes longer time to switch (become brighter).
Fig. 9. The cross-sectional LC director profile in (a) positive VA-FFS (b) negative VA-FFS. The A to F regions correspond to the A to F regions in Fig. 8.
As shown in Fig. 8(a) and Fig. 9(a), for positive LC, middle of A and C don’t switch, remain stationery even after a long time, thus forming firm virtual walls. However, for negative LC, middle regions of D and F don’t switch initially a shown in Fig. 8(b) and Fig. 9(b), but they will gradually switch (brighter) at a later time, e.g. at 7 ms for middle region of D and 15 ms at middle region of F, as shown in Fig. 8(b). Note these A, C, D and F correspond to regions with mainly vertical fields (or zero field). Hence for positive LC molecules they remain vertical and form virtual walls whereas for negative LCs they have less clear rotation direction in these regions initially and hence rotate only at a later time.
Analysis of the azimuthal rotation of the LC molecules at 0.9µm above the bottom substrate surface in LC layer are shown in Fig. 10. Figure 10(a) shows that positive LC only involves rotation along one plane (x-z), while the negative LC also involves rotation along the y-z plane (starting from region D) as shown from Fig. 10(b) to Fig. 10(d). As shown in Fig. 10(a), the positive LC molecules’ directors are distributed along the x-axis only (at 3 ms) and continue to remain on this same plane even after a long time. However, the molecular rotation direction of negative LC varies through time. At 3 ms, the rotation direction is mainly along the x-axis direction as shown in Fig. 10(b). However, at 7 ms, molecules in middle of region D start to rotate to the y-axis direction and this change in rotation direction starts to influence other neighboring molecules whose rotation directions are initially parallel to the x-axis. Eventually at 30 ms, all molecules will rotate and tilt along the y direction. These differences occurred because positive LC molecules response and aligned with the E field direction only, so they rotate and remain along the x-z plane only as shown in Fig. 10(a). However, for negative LC, the molecules can respond and align to any orthogonal direction of E field. Thus, they initially rotate and lie only on the x-z plane as shown in Fig. 10(b) but later rotate and align along the y-axis or other directions (orthogonal to the applied E fields) as shown in Fig. 10(c) and Fig. 10(d). Thus, the LC molecular rotation for positive LC is much simpler which involves LC rotation along one plane only. However, the negative LC rotation involves a more complicated 2-step process which involves first rotation along the x-z plane and then a second step which involves rotation along the y-z plane. The first step process (x-z plane) is fast since LC molecules know exactly which direction to rotate initially along the x-z plane in response to fringing electric-field as shown in Fig. 9(b) which is like having a clear pretilt angle. On the other hand, the second step process (along y-z plane) is a relatively slow process since LC directors don’t know exactly which direction to rotate initially, which is like not having a clear pretilt angle. The LC molecules in the second step process thus only start to rotate mainly after the first step process finish. This can be observed and confirmed by the much faster (steeper) slope on the T-t curve in Fig. 6(b) during the first 3 ms whereas the slope becomes less steep after about 3 ms for the negative LC. This much more complicated 2-step LC rotation process for the 2D negative VA-FFS has not been previously reported in literature and is believed to be responsible for the slow switching in 2D negative VA-FFS.
Fig. 10. LC director profile from top view at the depth of 0.9µm from bottom substrate surface of LC layer for (a) positive VA-FFS at 5ms (b) negative VA-FFS at 3ms (c) negative VA-FFS at 7ms and (d) negative VA-FFS at 30ms
Note that all previous reports on 2D VA-FFS have been based on positive LC only [1–4] and thus the response times were usually very fast since the LC rotation mechanism is much simpler and virtual walls always exist. However, as shown from simulations results in this paper, response time for 2D VA-FFS using negative LC can be very different from the positive LC. The negative LC involves a two-step process as described above and hence can lead to a much slower response time. However, negative LC does have the advantage of having higher transmission as described earlier. Moreover, as will be described later, 3D electrode design may be used to help improve this slow response time problem of negative LC.
Figure 11 shows the comparison of the fall time obtained for positive VA-FFS and negative VA-FFS with 2D electrode design. From Fig. 11(a) and Fig. 11(b), we can see that the fall time of negative LC is also slower than that of positive LC at all electrode dimensions. This is due to the fact that there is less or even no disclination or “virtual wall” in the negative LC (the last frame in Figs. 8 (a) and (b)). Disclination appears as dark region. Disclination is formed by LC molecules that do not rotate. In VA-FFS, these LC molecules form virtual walls, and provide “extra” restoring force to other LC molecules. When LC molecules begin to relax back to the off-state, the restoring force can help accelerate the process, and reduce the fall time. Since positive VA-FFS has more “firm” and stationery disclinations (or virtual walls), it has faster fall time. Note that although there may be no apparent virtual walls or disclination left for negative LC at the end of switching time, there is still a standing (unswitched) layer of LC molecules along the horizontal direction in the upper region of the LC bulk [1–3], which can also help restore the LC molecules during the relaxing process and hence shorten the fall time.
Fig. 11. Comparison of fall time between negative and positive LC w = 3µm, g = 3-6 µm (b) g = 3µm, w = 2-5µm
3.3 Comparison of positive and negative LC in devices with 3D electrode
Figure 12 (a) shows the comparison of the T-V plots obtained for positive VA-FFS and negative VA-FFS in 3D electrode design. Figure 12(a) shows that negative LC still has higher transmittance compared to the positive LC. Again, this is due to the fact that positive LC molecules can only rotate and align along the E field directions where negative LC molecules are allowed to rotate and align along different azimuthal directions orthogonal to the E fields. Positive LC thus result in more disclinations and dark state at the ON state compared to the negative VA-FFS. Figure 12(b) shows T-t plots obtained for positive VA-FFS and negative VA-FFS. Figure 12 (b) shows that the rise time and fall time of the negative LC now become more similar to those obtained for positive LC. As will be shown below, fall time is found to be still slower than the rise time but the difference is much less compared to those obtained in 2D.
Fig. 12. Comparison of a) V-T and b) T-t curves for negative and positive LC with 3D electrode design (w = 3µm, g = 5 µm).
Figure 13 shows comparison of the rise time obtained for positive and negative VA-FFS with 3D electrode design. Negative LC continues to have longer rise time compared to that of positive LC. However, the difference in rise time between positive and negative LC in 3D is significantly less compared to the difference that exists in 2D case. The reason for having this remarkable difference is that the electric field distribution in 3D becomes more confined and symmetrical in all directions and hence can help “limit or restrict” the options for possible molecular rotation direction. In other words, 3D can help LC molecules determine rotating directions more effectively and quickly. On the other hand, in the 2D negative LC case as described earlier, the second step rotation process is a much slower process since it doesn’t have a clear rotation direction initially.
Fig. 13. Comparison of rise time between negative and positive LC (a) w = 3µm, g = 3-7µm (b) g = 3µm, w = 1-5µm.
Figure 14 shows the comparison of the fall time obtained for positive VA-FFS and negative VA-FFS with 3D electrode design. The fall time of negative LC is, in general, slower than those obtained for positive LC as well. Again, this is believed to be due to the difference in the amount of disclinations that exists for positive and negative LC as will be shown in Fig. 15. Positive LC in general has more disclinations (or virtual walls) which can help restore the LC molecules more quickly and effectively.
Fig. 14. Comparison of fall time between negative and positive LC (a) w = 3µm, g = 3-7µm (b) g = 3µm, w = 1-5µm.
Fig. 15. The top-view brightness profile at ON-state for (a) positive and (b) negative LC in 3D electrode design
Figure 15 shows the top-view brightness profile at ON-state for the positive and negative LC respectively in 3D electrode design. The virtual walls in device using positive LC are thicker, which can help consolidate the wall structure and hence exhibit faster fall time compared to negative LC as was described in Fig. 14. In positive VA-FFS, the disclinations appear in the center of pixel electrodes as stripes, and in the center of holes (electrode gap). In negative VA-FFS, due to the symmetric electric field on all directions in 3D pattern, virtual walls would exist at the center of pixel electrodes in the shape of spots and also appear along the edge of pixel electrode.
Figure 16 shows the corresponding LC director distribution profiles at the depth of 0.9µm from the surface of bottom substrate for a) positive LC and b) negative LC in 3D electrode design. The circled regions correspond to the disclinations (dark regions) in Fig. 15. As can be seen from Fig. 16(a) that there are relatively more LC molecules that remain vertical in the positive LC compared to that of negative LC. Most negative LC molecules can rotate even around the middle regions of the pixel electrode and electrode gap. On the other hand, most LC molecules remain vertical around the middle regions of the pixel electrode and electrode gap for positive LC. Note that the negative LC molecules that rotate between the disclinations in 3D case tend to have clearer sense of rotation direction compared to those in 2D negative case since there are additional electric fields generated from different directions in the 3D pattern which can help guide the LC molecular rotation direction more clearly.
Fig. 16. The LC direction distribution profiles at ON-state for (a) positive and (b) negative LC in 3D electrode design. Circled regions correspond to the disclinations or “virtual walls” regions.
Note that in 3D negative VA-FFS it has clear disclinations (virtual walls) which is different from the 2D negative case. This is because electric fields in 3D pattern are equal on all directions, thus the LC molecules in the center of pixel electrode and electrode gap are forced to remain static. This increase in stability of the disclinations or virtual walls in 3D electrode design is quite similar to that observed in Short-pitch-lurch control In-Plane-Switching (SLC-IPS) reported by Japan Display Corporation (JDC) [8] where the trunk part and branch part of electrodes (resembles a 3D electrode design) were found to help improve the stability of the LC molecular movement and hence help also improve response speed of the LC device.
4. Conclusion
In this paper, we have proposed and reported results obtained for a 3D electrode design for the fast response VA-FFS LC mode. We have found that, compared to conventional 2D design, 3D electrode design can help improve the maximum possible light transmission and, under the same electrode dimensions, help shorten the response time of this fast-response VA-FFS LC mode. These improvements occur as a result of having i) less disclinations along the y-direction which helps improve the maximum possible light transmission after using circularly polarized light and ii) having more disclinations or “virtual walls” around or surrounding a 3D pixel compared to the 2D pixel, which can provide more “effective” restoring forces for the LC pixel for a given electrode dimension and hence help lead to faster response time.
In the second part of this paper, we investigate the difference between positive and negative LC for 2D and 3D electrode designs. Positive LC is found to provide faster response time whereas negative LC can provide higher transmission. Due to the fact that positive LC only aligns along the E field direction, positive LC involves a much simpler switching process or mechanism which always provides fast response time with firm and stable virtual walls. However, for the negative LC, we have found that in 2D case it has unusual slow response time (particularly the rise time) which is very different from what we have seen for VA-FFS LC in previous studies which mainly involved positive LC. In this paper, we have found that a “two-step” switching process or mechanism is chiefly responsible for this rather slow response time phenomenon of the negative LC in 2D case. The first-step switching process is fast since LC molecules have clear rotation direction whereas the second-step process is slow since the LC molecules don’t have a very clear rotation direction initially. However, by using a 3D electrode design, we have found that we are able to reduce the difference between the positive and negative LC response times since the 3D electrode structure can offer symmetric electric fields from all different direction which can help “limit or restrict” possible LC rotation direction for the negative LC and hence provide clearer rotation directions for the negative LC and hence help improve its response time significantly.
Therefore, it is believed that 3D electrode design can help provide more firm and stable virtual walls, and help accelerate the switching process, in particular for the negative LC materials. The negative LC has the advantage of having higher potential light transmission. However, its virtual walls stability can be less than that for positive LC since the negative LC molecules are allowed to switch to other orthogonal directions relative to the E field direction. On the other hand, positive LC always provides fast switching with firm virtual walls. Its main disadvantage is that they tend to have lower possible maximum transmission. In practice, positive LC usually has lower viscosity and hence tends to lead to faster response time. However, from the studies in this paper, we have found that, by having similar LC parameters, it is possible to have similar response time for both positive and negative LCs by using a 3D electrode design since 3D electrode can help limit the possible rotation directions for negative LC.
The studies in this paper can help offer new and further insights for the development of VR/AR technology since they often require fast response time of LC devices. In particular, the results in this paper show that the use of 3D electrode design may help improve the stability of virtual walls, accelerate the switching speed of LC molecules and improve the potential maximum transmission make this 3D design look very promising. These results reported in this paper are quite consistent with the 3D-like SLC-IPS technology reported by the company JDI for their improvement in stability and response speed of advanced LC devices with virtual walls for VR/AR applications.
Funding
Ministry of Science and Technology, Taiwan (104-2221-E-002-166, 105-2221-E-002-163).
Disclosures
The authors declare no conflicts of interest.
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