cholesteric lcd display brands

A cholesteric liquid crystal display (ChLCD) is a display containing a liquid crystal with a helical structure and which is therefore chiral. Cholesteric liquid crystals are also known as chiral nematic liquid crystals.

KDI has world class manufacturing expertise in roll to roll manufacturing of liquid crystal films, face shield lenses, and other functional flexible materials in including the award winning flexible Boogie Board eWriter LCD films.

The eWriter works on the principle of anisotropic flow, a unique feature of cholesteric liquid crystals, in which crystals flow at different rates, depending on the direction of pressure being applied.

GEI is among the very few companies offering the amazing technology of ChLCD — cholesteric liquid crystal displays, also known as bi-stable — that can hold a color image even after its power is turned off. This makes ChLCD the perfect technology for electronic shelf label (ESL) applications as it offers excellent readability with incredible savings in energy costs as power is required only when the display needs to be changed.

There are many other applications for ChLCD. Most importantly, GEI is fully authorized to use this technology. For more information or a quote, please visit our Contact page. Some overall specifications of GEI’s ChLCD modules include…

A cholesteric liquid-crystal display (ChLCD) is a display containing a liquid crystal with a helical structure and which is therefore chiral. Cholesteric liquid crystals are also known as Bragg Reflection).

The technology is characterized by stable states i.e. focal conic state (dark state) and planar state (bright state). Displays based on this technology are called “bistable” and don’t need any power to maintain the information (zero power). Because of the reflective nature of the ChLCD, these displays can be perfectly read under sunlight conditions.

A US company, Kent Displays, has developed "no power" Liquid Crystal Displays using Polymer Stabilized Cholesteric Liquid Crystals: these are known as ChLCD screens.mobile phone, allowing it to change colours, and keep that colour even when power is cut off.

(PhysOrg.com) -- Currently the screens of e-readers come in two colors, black and white. While the Nook does have a color version out but that screen is an LCD and not an e-ink. While for a while that did create a debate about eyestrain but other companies are looking to catch up to the color.

Fujitsu recently demonstrated a prototype of their next generation cholesteric LCD color digital paper module at the International Digital Publishing Expo. The machine uses a set of Cholesteric liquid crystals to create the display. Cholesteric liquid crystals are different from other methods of creating color LCD displays because this method does not require polarizing plates, reflecting plates, color filters or back lights in order to create the display, which allows them to be thinner than other LCD options.

The trial model, which weighs only weighs 220g, is running a Linux-based operating system, unlike previous versions put out by Fujitsu that used Windows. This new model has an enhanced processing speed, with a write speed of 0.7 seconds and the complete elimination of dithering on the 4,096-color range display that is 8" on the diagonal. The final screen resolution is 157 dpi with a contract ratio of 8:1.

To achieve broadband photonic elements, CLC paints are first prepared using an optimized composition for coating. A cRM with a photopolymerizable methacrylate group is a core component of the CLC paints, as shown in Fig. 1a. Due to the presence of an R-configured naphthyl group, simply adjusting the concentration of the cRM in the nematic liquid crystal (NLC) medium enables the formation of cholesteric mesophases. In this study, a monoacrylate monomer (mRM) and a diacrylate monomer (dRM) are purposely used not only as the NLC host but also as chemical crosslinkers1b). For the CLC paints obtained with the cRM and dRM, the growth of a needle-like texture is observed in the POM microphotographs after a few minutes (Figure S1 in the Supporting Information). However, the CLC paints with the mRM maintain their ordered structure without any phase separation, which results in their dramatically enhanced processability, even at the room temperature (Figure S2 in the Supporting Information). In the planar anchoring condition, the molecules lie down on the surface and the HA of self-assembled helical nanostructure is parallel to the surface normal. Therefore, the mRM and dRM mixtures doped with 12, 10, and 8 wt% cRM clearly exhibit the selective reflection of blue, green, and red light, respectively (insets in Fig. 1b).

CLC paints with unique optical properties and a suitable viscoelasticity can be used for various applications, such as architectural coatings, colorimetric sensors, and information displays2a, the pinky, ring, and middle fingers covered with the CLC films are red, green, and blue, respectively. The ability to localize the presence and color of the CLC paints is further described. The artificial nails on the thumb and index fingers illustrate prototypical symbols of the cholesteric character. When the CLC paints described above are cast on a glass substrate, a free-standing and circular-polarizing photonic material with macroscopic dimensions can be fabricated. The cast sample is evenly sheared with a bar coater. Then, the in situ photopolymerization of the coated sample is performed to obtain a robust optical film. The photoinitiated polymerization is induced by exposure to 365 nm UV light for 10 min. Based on a field adhesion method (ASTM D3359), the CLC films exhibit better mechanical properties than the CLC paints (Figure S3 in the Supporting Information)

Application of the chirophotonic crystal paints as fingernail polish (a). Macroscopic images of three free-standing CLC films illustrating the iridescence inherent to the cholesteric mesophase and the retention of the blue, green, and red reflection colors (b). Transmittance spectra indicating that the photopolymerized CLC paints reflect red, green, and blue (c). DMA thermograms of FB (d). Transformation of the CLC paints to films after UV polymerization (e)

The polymeric stabilization of the CLC paints can be easily handled with a tweezer (Fig. 2b). The thickness of the CLC films is controlled to 10 μm. The colors of the CLC films observed by the naked eye are nearly the same as those of the CLC paints. The proposed fully reactive cholesteric system is intentionally designed to minimize phase separation during photopolymerizationR), green (FG), and blue (FB) colors, respectively. The corresponding characteristic light reflections are λmax = 435, 525, and 630 nm, respectively (Fig. 2c). These results also indicate good dimensional stability. The nearly identical positions of the reflection notches of the CLC paints and films indicate that the P value is not affected by the photopolymerization (Figure S4 in the Supporting Information). The thermomechanical properties of the CLC films are examined by a dynamic mechanical analyzer (DMA). In the example at the top, the FB sample exhibits good flexibility. It has a glass transition temperature (Tg) of 85 °C (obtained from the peak value of the tan δ curve) and a storage modulus (E′) of 1.2 GPa at room temperature (Fig. 2d). The thermomechanical properties determined by DMA are in good agreement with those measured by DSC, which confirms that Tg = 85 °C (Figure S5 in the Supporting Information). Under these conditions, the conversion of the chiral and achiral RMs is calculated by monitoring the change in the transmittance area of the FTIR peak at 810 cm−1, which is the out-of-plane bending vibration peak of the acrylate group2e shows that the conversion is 81%.

After the copolymerization of the chiral and achiral RMs, the CLC films are stable to chemical attack. The chemical stability of the CLC paints is first tested by dropping various solvents on them. The helical nanostructures of the CLC paints are damaged by the attack of organic solvents. For example, the CLC paints are fully dissolved and completely lose their reflection colors when exposed to chloroform. The ordered structure is disrupted by the penetration of the solvent molecules. However, the CLC films can withstand common organic solvents, as shown by the summarized results in Figure S6 in the Supporting Information. Based on the chemical stability tests, it is concluded that the construction of the crosslinked helical nanostructure is an effective method for obtaining robust photonic materials. Furthermore, it should be noted that it is possible to fabricate a patterned optical object if a photomask is applied3a. The butterfly-shaped object is free-standing (Fig. 3b). Due to the properties of the cholesteric mesophase, it retains the blue reflection and the notch at approximately 435 nm when probed with right-handed (RH) circularly polarized light (CPL). However, left-handed (LH) CPL is transmitted, and no reflection color is observed (Fig. 3c)3d.

The mirror-like silver reflection of F3 is illustrated in Fig. 5a. A common illustration of the cholesteric mesophase is visible behind F3 (Fig. 5b). The microstructures of the CLC films are observed by 1D WAXD. A broad peak appears at approximately 2θ = 20.13°, indicating the existence of the cholesteric mesophase (Figure S9 in the Supporting Information). The peak at 0.44 nm originates from the liquid-like correlation of the anisotropic molecules. The strong birefringence and oily streaked texture detected by POM further support the successful transfer of the chiral property and helical information of the CLC paints to the corresponding films (Figure S10 in the Supporting Information). To visualize the distinct helical nanostructures within the broadband mirrors, SEM is employed. As shown in Fig. 5c, the cross-sectional SEM image of F3 has a 30 μm-thick layer (three stacked 10 μm layers of CLCs). The lengths of Pred = 420 nm, Pgreen = 350 nm, and Pblue = 290 nm are measured. The red, green, and blue layers of F3 have 24, 28, and 34 pitches, respectively. Note that only a single helical nanostructure constructed by the self-assembly of the CLC paints in the red, green, and blue layers of F3 is schematically illustrated in Fig. 5d.

Electrowetting display (EWD), which is based on the quick manipulation of microfluid, is a type of reflective electronic paper display technology [1]. Compared with the commercialized electronic paper product of electrophoresis display (EPD), EWD has the same advantages, including low energy consumption, visual healthy and flexibility. Moreover, EWD is capable of realizing “color” and “video” display simultaneously, which is rather difficult to achieve by other reflective display technologies [2]. Therefore, EWD has become one of the mainstreams of electronic paper display in recent decade.

The concept of EWD was pioneered by G. Beni et al. [3, 4] in 1981, who used the electrowetting effect to manipulate the liquid movement in the pixel structure, so as to change the optical spatial coherence in the pixel, and realize display by switching between white and colored state. Fundamentally, electrowetting is based on electrocapillarity, which was first discovered by Gabriel Lippmann in 1875 and raised the famous Young-Lippmann equation [5]. In 1993, Berge proposed the concept of electrowetting based on dielectric layer [6], which became the basis of modern electrowetting devices [7], such as displays, lenses [8], microfluidic platform [9], heat transfer [10], energy conversion [11] etc. In 2003, Robert A. Hayes reported a video-speed electronic paper based on electrowetting [1], and started the research of EWD technology officially.

So far, the performance of EWD devices have been greatly improved in the past 2 decades, including the reflectivity [12], response time [13] and reliability [14, 15]. EWD prototypes with high brightness and video-speed has also been demonstrated. However, the EWD color display is still unsatisfactory, due to the difficulties in achieving high brightness and high color gamut simultaneously [16]. For reflective color display, the additive color mixing with red (R), green (G) and blue (B) color filter is unfavorable, since each of the color subpixels absorbs roughly 2/3 of the incident white light and thus reduce the brightness/gamut performance [17]. By contrast, subtractive color, mixing with vertical cyan (C), magenta (M) and yellow (Y) stack, is more promising for reflective EWD with wide color gamut while maintaining high reflectivity [18–20]. As reported by H. You et al. [18], the CMY color EWD layers can be switched and are responsible for RGB light control independently in the vertical direction. By controlling the opening rate of each layer, the three primary colors of different gray scales can be obtained, and finally achieve full color display.

Currently, although the multi-layered EWD configuration can achieve high brightness in principle, however, it also causes evident light loss due to the excessive number of functional layers and limit the brightness of the device ultimately. To reduce the light loss, this study report a new approach to enhance the optical performance of the EWD device. Selective reflection films made of polymer cholesteric liquid crystal (PCLC) were added under each layer to reflect the light that has been modulated. The reflectance and color gamut of this new EWD device structure were studied by experiment and simulation, and both results show that this method greatly enhanced the reflectivity and color gamut of tri-layers EWD.

In tri-layered EWD device, CMY oils are used to absorb RGB light respectively. As shown in Figure 1B, when the visible light passes through the layer consisting of Y oil, the blue light is absorbed, whereas the red and green light pass through the Y oil layer. Subsequently, the transmitted light continues to pass through the M oil layer, and the green light is absorbed. In this process, only the red light can pass, and is absorbed by Coil finally. Therefore, when the three layers of ink are spread, the pixels show black. By contrast, when the three layers of ink are contracted, the visible light can pass through the open area, thus resulting in white pixels. It can be inferred that the modulation of the three ink layers on the RGB tri-color light is independent. Moreover, by controlling the open rate of each layer of ink, the absorption of RGB light can be adjusted, and the full-color display can finally be realized.

However, it should be emphasized that the aforementioned mechanism to realize color display suffers from strong losses in the process of light passing through the entire device and reflecting back in a three-layer superimposed EWD device, although in principle other ink layers have no effect on the light outside the absorption spectrum. Taking the blue light as an example, the blue light in the reflected spectrum is regulated by the uppermost yellow ink layer, which has already been completed by the first layer of EWD devices. However, the regulated blue light still needs to pass through the lower two layers of the device to reach the reflective film and again go through the three layers of the device before it comes to human eyes. In this process, the intensity of the blue light is weakened by the absorption of the material, the reflection of the interface and the diffraction of the structure, which eventually leads to a significant reduction in the reflectivity of the blue light.

In order to realize the selective reflection of the visible spectrum, PCLC films were employed as the dichromatic reflector in this work. Cholesteric liquid crystal (CLC) is a kind of one-dimensional photonic material with a chiral-spiral structure with Bragg reflective properties, which reflect circularly polarized light in the same direction as its chiral spiral (plus references). According to the Bragg reflection, the reflected band λo of CLC is directly related to its pitch P and refractive index, which can be described by following formula:

An optical model of tri-layer EWD device is built in software to simulate the effect of adding PCLC films on the reflectivity and color gamut of the device. The side view and equiaxial view of the optical model are shown in Figure 3A. To save computing resource, the model is composed of an array of 50 × 50 pixels. The geometric and optical parameters of each functional layer are set according to the sample in the experiment, where the thickness and refractive index of each layer are shown in Figure 3C. The absorption spectrum of CMY oil and the reflection spectrum of PCLC films are set according to the results in Figures 2B,D. In the simulation model, the reflector used in the model is the standard Lambert diffuse reflective surface, and the light source is the D65 standard white parallel light source, which shines on the device at an angle of 45°. A monitor is set vertically above the device as a sensor to record the light intensity and color coordinates of the reflected light. By establishing the switching states of different membrane layers, the reflected light intensity and the reflected light color coordinates of the device when displaying six primary colors (namely RGB, CMY, black and white) are simulated and calculated.

In order to optically characterize the performance of EWD devices, a system (Figure 3B) was built in the dark room, according to the electronic paper display measurement standard IEC-62679. In the test system, a collimated D65 light source with divergence angle less than 5° and illuminance higher than 65,000 Lux was used to illuminate on the center of the display screen under test. The angle between the lighting direction and the measured EWD device surface is 45°. To measure the brightness and chromaticity coordinates of the six primary colors on EWD device, a colorimeter (Topcon, SR-UL1R) was putted perpendicular to the surface of the EWD device with a measuring distance of 50 cm.

Generally, the color gamut refers to the range of colors that the display device can show. For subtractive color mixing implemented by CMY, the color that can be achieved is the area enclosed by a hexagonal shape on the chromaticity map connected by the color coordinates of the CMYRGB six primary colors. The NTSC color gamut coverage of the display GEWD is usually defined as the ratio between the hexagonal area SEWD and the NTSC standard triangle area SNTSC . It can be calculated by following formula:

The value of the SNTSC is 0.1582, and the color display gamut of the device can be calculated by testing the chromaticity coordinates of the display in the C, M, Y, R, G, B primary colors in the CIE1931 chromaticity space.

As EWD is a type of reflective display technology, the reflectivity which determines the display brightness is an important parameter. It can be seen from both the simulation and experimental results that the reflectivity of the device has been significantly improved by adding the PCLC films. Specifically, the most significant improvement is the reflectivity of the cyan. For cyan display, it is necessary to open the ink of the upper Y and M layers and close the ink of the lower C layer. In such conditions, the red light is absorbed while the blue light and green light are reflected. This is realized by using the two reflective layers of RF-B and RF-G, which help to reflect the blue light and green light subsequently before they go through the tri-layer device. Therefore, the loss of the blue light and green light is greatly minimized, thus significantly improving the reflectivity of cyan. Similarly, the reflectivity of the blue and green has also been significantly improved. Regarding to the blue, it is necessary to absorb the green and red light, while reflect the blue light. This is accomplished by using the RF-B reflective layer to reflect the blue light after it passing through the uppermost device, thus saving the blue light to the greatest extent. For green, it is necessary to absorb the blue and red light, while reflect the green light. It can be seen from Figure 2B that the bottom cyan ink has a certain absorption of green light. Hence, when the RF-G reflective layer does not need to pass through the lowest layer of the device, the green light reflectance is improved more than the blue light. Meanwhile, the results show that the least increase in reflectivity is the red, due to the fact that the cyan ink that regulates the red light is located in the lowest layer, and the red light must pass through the three-layer device anyway, so the presence or absence of RF has little effect on the reflectivity of the red light. Overall, after the addition of PCLC films, the overall reflectivity of the device has been increased by more than 30%, mainly from the increasement of the reflectivity of the blue light and green light. Therefore, by adding a selective reflective layer between the display layers, it is indeed possible to greatly improve the reflectivity of the device by reducing the invalid light loss when light passes through the three layers of the device.

It can be inferred from the above results that the addition of PCLC films with selective reflection characteristics greatly improves the reflectivity of the blue light and green light, via directly reflecting the blue light and green light without passing through the three layers of EWD devices. Both the reflectivity and the color gamut of the tri-layer EWD device have been significantly improved, which can help to mitigate the problems in the current color EWD display device.

We proposed a novel full-color reflective electrowetting display device, consisting of three independent PCLC reflection films that can reflect the red, green and blue circularly polarized light respectively. PCLC films embedded in the device can effectively reduce the reflectance and gamut value. The results of simulation and experiment are in good agreement. It is demonstrated that with the PCLC films, the reflectivity is improved by 20%, while the color gamut is improved by 80%, which is sufficient for the daily display demand of E-paper. The proposed EWD device containing PCLC reflection films provide a new strategy to improve the brightness and color gamut of current EWD device, and is promising for realizing the full-color E-paper display. It is of great significance for the promotion and application of full-color video electro-wetting electronic paper display devices.

This research was funded by National Key R&D Program of China (2021YFB3600602), Science and Technology Program of Guangzhou (Nos. 202201,010351, 2019,050001), Natural Science Foundation of Guangdong Province (Nos. 2020A1515010715, 2021A1515010623), Program for Chang Jiang Scholars and Innovative Research Teams in Universities (No. IRT_17R40), Program for Guangdong Innovative and Enterpreneurial Teams (No. 2019BT02C241). This work also supported by the Guangdong Provincial Key Laboratory of Optical Information Materials and Technology (No. 2017B030301007), Guangzhou Key Laboratory of Electronic Paper Displays Materials and Devices (201705030007) and the 111 Project.

2. Feenstra B, Hayes R, Van Dijk R, Boom R, Wagemans M, Giraldo A, et al. (2006).Electrowetting-based displays: bringing microfluidics alive on-screen. in: IEEE International Conference on Micro Electro Mechanical Systems: 22-26 Jan. 2006: Turkey

12. Wu H, Hayes RA, Li F, Henzen A, Shui L, Zhou G. Influence of fluoropolymer surface wettability on electrowetting display performance. Displays (2018) 53:47–53. doi:10.1016/j.displa.2018.02.002

13. Dou Y, Tang B, Groenewold J, Li F, Yue Q, Zhou R, et al. Oil motion control by an extra pinning structure in electro-fluidic display. Sensors (2018) 18(4):1114. doi:10.3390/s18041114

14. Zhou R, Ye Q, Li H, Jiang H, Tang B, Zhou G. Experimental study on the reliability of water/fluoropolymer/ITO contact in electrowetting displays. Results Phys (2019) 12:1991–8. doi:10.1016/j.rinp.2019.02.037

15. Dou Y, Chen L, Li H, Tang B, Henzen A, Zhou G. Photolithography fabricated spacer arrays offering mechanical strengthening and oil motion control in electrowetting displays. Sensors (2020) 20(2):494. doi:10.3390/s20020494

16. Kuo SW, Chang YP, Cheng WY, Lo KL, Lee DW, Lee HH, et al. 34.3: Novel development of multi-color electrowetting display. SID symposium. Dig Tech Pap (2010) 40(1):483–6.

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The global awareness of sustainable environmental protection has risen, making e-paper a popular fried chicken among “carbon reduction products”, attracting major manufacturers to compete, and panel manufacturer AUO (2409-TW) joined hands at the 2022 Touch Taiwan Smart Display Exhibition Iridescent Optoelectronics and TPV Technology (TPV) launched cholesteric liquid crystal display technology (CLCD), aiming at the application market of electronic paper, which also heralded the official entry of cholesteric liquid crystal technology into the first year of development.

Cholesterol liquid crystal technology is not a new technology. In the past, like electronic ink technology and other electronic technologies, it has not received much attention from the industry. The main reason is that the global awareness of environmental protection was not high at that time, and transmissive display technology was booming, which squeezed the market’s impact on reflection. The so-called reflective display technology, in simple terms, does not emit light by itself, and must reflect the display content through an additional light source, which can save power compared to ordinary displays.

AUO exhibited for the first time this year a 7.9-inch reflective display using cholesteric liquid crystal technology. The driving voltage can be interrupted during static display, and the screen can be displayed using ambient light without any backlight, which greatly reduces power consumption, and does not require the use of color filters and polarized lights. The reflectance and color saturation are better than those of commercially available color electronic paper, and it will be applied to the education market and outdoor public display in the future.

AUO’s 7.9-inch reflective display is jointly developed, designed and manufactured with Iridescent Optoelectronics and TPV Technology (TPV). Among them, Iridescent Optoelectronics masters cholesteric liquid crystal technology, AUO provides panel design, and TPV is responsible for back-end assembly. It is understood that, The product is expected to be mass-produced in the second half of the year and officially launched to the market in the second quarter of next year.

Compared with e-paper using e-ink on the market, cholesteric liquid crystal display technology has advantages in color performance, page changing speed, and no afterimage, and also highlights the characteristics of liquid crystal. However, AUO’s announcement to enter the e-paper market has also attracted attention from all walks of life. , General Manager of AUO Ke Furen said that the reflective technology has multiple application fields, including education, transportation, smart cities, etc., and will have multiple applications in the future. Cholesterol liquid crystal also has bistable characteristics, which is expected to save power, and the material is shared with liquid crystal. , the future supply elasticity is stable.

Cholesterol liquid crystal technology has been in existence for more than ten years, but there is still no actual product launched on the market. Iridescent technology, which holds related technology, can be described as a sword in ten years. After its establishment in 2012, it was originally intended to cooperate with Japan’s Fujitsu. , but with the withdrawal of Fuji Group, Iridescent Optoelectronics was silent for a long time, until 2018, the electronic paper technology once again attracted market attention, and it also made major display manufacturers find Iridescent Optoelectronics again.

After receiving capital injection, Iridescent Optoelectronics continued to develop cholesteric liquid crystals and accelerated the product development process with the assistance of major manufacturers. Iridescent Optoelectronics also participated in the 2022 Touch Taiwan for the first time this year. It is expected that this year will be the first year for the development of cholesteric liquid crystal technology. , Rainbow Optoelectronics also uses the characteristics of liquid crystal technology. In the future, it is expected to launch products that join solar panels (solar panels), so that the products can generate electricity by themselves, and further achieve the vision of sustainable environmental protection.

There are dozens of e-paper technologies. In recent years, the fastest-growing and most well-known in the market is the e-ink technology used by Yuantai. Although the color rendering is still relatively limited at this stage, it has changed from black and white to the present. Five-color electronic ink controls color, including e-book readers, ESL (electronic shelf label) applications are the main battlefield, and cholesteric liquid crystal has more advantages in color and page changing speed. In the future, the market is expected to focus on education and outdoor signage. Each has its own niche.