Reflective LCDs Research Articles

49‐1: Invited Paper: Novel Brightness Enhancement Technology for Reflective LCDs

Reflective LCDs have a great advantage of low power consumption, but the brightness is not consistently sufficient because ambient light is used as a light source. To increase light efficiency, we combined reflective LCDs and the Pancharatnam‐Berry deflector (PBD), a diffractive optical element that controls the propagation of incident light. We confirmed that on‐axis brightness is increased by 2.2 times against the incident collimated light from a polar angle of 30° when compared to a reflective LCD without PBD.

31‐3: In‐cell touch supported novel reflective LCD mode Development

The novel display mode for in‐cell touch reflective LCDs was developed. The basic optical display performance in test cells was almost same as conventional VA. In addition, the touch performance of the prototype in‐cell touch reflective module (the simple modification of the transmissive) was equivalent to the conventional transmissive. The optimal panel design for this display mode is currently under development.

P‐12.10: Study on Optical Performance of Nomally White Reflective LCD

The optical performance of normally white reflective LCDs with various liquid crystal cell parameters and light scattering structures was investigated. The reflectivity and reflective CR both increased first and then decreased as the twist angle increased, whereas the color coordinate of white showed obvious cell gap dependency. Meanwhile, research revealed that while the light‐diffusing film had obvious advantages in terms of reflective optical performance, it could cause significant losses in transmissivity and transmissive CR, necessitating different design considerations for Full‐Reflective LCD and Trans‐Reflective LCD. Finally, the optimum design parameters were applied to our RLCD, which improved the reflectivity and CR while also achieving a better display effect of white pattern.

47‐3: Invited Paper: Development of Reflective LCDs with High Contrast Ratio and High Reflectivity

A kind of reflective mode LCD was reported years ago by professor Shin‐Tson Wu, called Mixed‐mode Twisted Nematic (MTX) LCD[1]. Based on MTN mode RLCD, we promoted the contrast ratio and reflectivity of RLCD by optimizing the cell structure and pixel design. Meanwhile, according to controlling the different optical layer axis directions and using new type materials, the contrast ratio and reflectivity are increased further. To improve the visibility of RLCD in a dark environment, we also developed the front light unit solution.

Printed Electrochromic Displays – Superior to Reflective Segmented LCDs?

Printed Electrochromic Displays – Superior to Reflective Segmented LCDs?

P‐150: Extended Jones matrix for the reflective liquid crystal display at oblique incidence

Jones matrix for the general reflective birefringent medium at normal incidence was published recently [1]. In this paper, this Jones matrix formulation is extended for the reflective liquid crystal display at oblique incidence. Numerical simulation results for reflective LCDs using this extended matrix method were carried out and compared with those of the unfolding method by Ge et al. [2] and those of the Berreman's 4 x 4 method [3].

Paper] Axis-symmetric Alignment Achieved by using a Mortarshaped Pixel Structure for Fast Switching Twistedvertically aligned-mode Reflective LCDs

Paper] Axis-symmetric Alignment Achieved by using a Mortarshaped Pixel Structure for Fast Switching Twistedvertically aligned-mode Reflective LCDs

COLORIMETRIC PROPERTY OF GUEST-HOST LIQUID CRYSTAL DISPLAYS

A bright reflective LCD without a backlight is a key device for portable information systems. The guest-host LCDs use the absorption anisotropy effect of dichroic dyes and have a wide viewing angle cone. The GH-LCD does not need complicated designs of optical compensation in birefringence or optical rotatory power modes. One of the applications of GH-LCDs is a black and white display which works as a light shutter of a full color reflective display with micro-color filters. It is necessary to mix dyes for an achromatic display. The Newton-Raphson method is useful for the calculation of optimum dye concentrations in order to display the designed color. In this work, the judgement of the calculated results is discussed. As a result, the calculated result with Newton-Raphson method is quickly and easily evaluated. The process gives us a helpful guideline in the fabrication of the reflective color LCDs and it is expected that the precise color matching improves the quality of LCDs.

Optical fine-tuning for improving the dark level of a reflective liquid crystal display.

Optical fine-tuning was performed to reduce blue light leakage in a conventional reflective LCD and to obtain a reflective LCD with a better contrast ratio. Total light leakage in the dark state was examined by simulation, according to the optical axes of the half-wave plate and LC layer and the central wavelength used in the optical design of the LCD. The contrast ratio of the reflective LCD could be improved by more than fivefold, compared to that of a conventional LCD with a wide-band optical design, when the optical axis angles of the half-wave plate and the LC layer were 75° and 15.68°, respectively, and the central wavelength was 520 nm. Therefore, such optical fine-tuning can be applied to reflective LCDs to increase their contrast ratio.

Reflective liquid crystal display for better productivity.

Most reflective LCDs so far proposed require a very thin cell gap of approximately 1.5μm to satisfy the quarter-wave retardation condition when used with a half-wave retardation film to obtain an acceptable broadband performance over the entire visible range. On the other hand, the inevitable difficulty associated with precise manufacturing of thin cell gap devices is likely to deteriorate the yield, thereby increasing the production cost. This paper proposes a reflective LCD with a larger cell thickness to achieve better productivity. The proposed reflective LCD consists of a tactically arranged stack of a half-wave retardation film, a quarter-wave retardation film, and a liquid-crystal (LC) layer whose optical performance has been confirmed both by simulation and experiment. The optimal optical configuration to obtain an excellent dark state in the visible range was determined by the Mueller matrices calculus as applied to each optical component. The simulated and experimental results showed that the proposed reflective LC structure has excellent electro-optical properties and is expected to be useful for the next generation LCD industry.

(L)乳酸手性衍生物的含氟二苯乙炔液晶的合成

1-[(1-ethoxycarbonyl)-ethyl]-4-[4-(2,3,5,6-tetrafluoro-4-alkoxy-phenyl)ethynyl)-phenyl] terephthalates have been synthesized(n=5,6,7,8)and studied by thermal polarizing microscopy and DSC measurement.The effect of fluorosubstituent and bridge on the mesomorphic properties were discussed.These compounds exhibit enantiotropic cholesteric phase and low viscosity high birefringence and chemical stability.These compounds can be used for reflective LCDs and adaptive optics system.The target compounds were synthesized by Sonogashira cross coupling.

50.3: Low Power, High Image Quality Color Reflective LCDs Realized by Memory‐in‐Pixel Technology and Optical Optimization Using Newly‐Developed Scattering Layer

AbstractReflective color LCDs with high image quality, which have very low power consumption when displaying still images and can also display moving pictures, have been developed. Two key technologies are Memory‐in‐Pixel (MIP) fabrication using LTPS technology, and another is optical property optimization by adopting a newly‐developed scattering layer.

P‐75: Improved Optical Characteristics of a Front‐Light System Using Fine‐Pitch Patterned OLED

AbstractWe have been developing a front‐light system that uses an OLED light source patterned with a fine pitch. This system can be used in reflective LCDs, electrophoretic displays (EPD), microelectromechanical systems (MEMS) and other applications. In this paper, we present a new structural design for an OLED front‐light system. In the new system, the space between a pair of glass substrates is filled with resin, and a pattern of black resin is formed on the counter‐substrate such that it corresponds to a pattern of Al cathodes. The new system has excellent characteristics as a front‐light. Light is used more efficiently than in the conventional design, and the reflection of ambient light can be avoided.

Novel front‐light system using fine‐pitch patterned OLED

Abstract— A novel front‐light system that uses an organic light‐emitting‐diode (OLED) light source patterned with a fine pitch has been developed. The front‐light system has the following characteristics: (1) excellent uniformity within the light‐emitting area; (2) emittance that is consistent at all viewing angles; (3) no light leakage at any viewing angle from the side of the observer. This system can be adopted for reflective LCDs, electrophoretic displays (EPDs), microelectromechanical systems (MEMS), and other applications.

Model-free method for measuring the full Jones matrix of reflective liquid-crystal displays

We present a method for measuring all eight parameters in- cluding the signs of the Jones matrices of liquid-crystal displays. The method can be applied to measure the Jones matrices for all address- able gray levels thus delivering the specifications needed for calculating characteristic curves for arbitrary input and output polarizations. Unlike other approaches, we do not rely on a physical model of the LCD. Thus, it is possible to measure the Jones matrices of a more complex optical system in one step e.g., when a reflective LCD is used in combination with a beamsplitter. Though the method presented is, in principle, appli- cable for transmissive and reflective LCDs, calculations and experiments are only shown using the example of a reflective liquid-crystal-on-silicon

4.2: International Metrology Standards for Reflective LCDs

AbstractThis paper summarizes the development of metrology for reflective LCDs from the late 1970s to our days, it introduces the two different approaches used in the LCD industry (directional and multi‐directional illumination) and explains the distinct differences in the results obtained with the two methods. The current status of the standardization of measuring methods for reflective LCDs by the WG2 of IEC TC110 is presented and an outlook is given of the work to be done before finalization of this standard, especially when the recently initiated horizontal harmonization activity of the IEC TC110 is supposed to be taken into account.

44.2: Novel Front‐light System Using Fine‐pitch Patterned OLED

AbstractWe have developed a novel front‐light system that uses an organic light emitting diode (OLED) light source patterned with a fine pitch. The front‐light system has the following characteristics: 1. Excellent uniformity within the light emitting area; 2. Emittance that is consistent at all viewing angles; 3. No light leakage at any viewing angle from the side of the observer. This system can be adopted for reflective LCDs, electrophoretic displays (EPD), microelectromechanical systems (MEMS) and other applications.

Measurement of light incident on mobile displays in various environments

Abstract— By using a single‐lens digital camera with an attached 180° fisheye lens, the incident light at the surface of a mobile display in 112 different environments, including outdoor and indoor environments and inside an automobile, were measured. The data were analyzed for some typical environments in which mobile displays are used. The results of this research can be used in the design of reflective and transflective LCDs, making maximum use of ambient light.

P-149: Super Reflective Color LCDs Being Able to Display Moving Images without Polarizers

Novel reflective color LCDs without polarizers have been developed with using PDLCs and retro-reflectors. By eliminating polarizers, brightness of our newly developed LCDs has been increased by 51% compared to conventional reflective LCDs, and there still is much room to be improved. What's more, our LCDs can be displayed not only bright text images but also color moving images on, since their response time and driving voltage are significantly fast (63ms) and low (5.5 volts).

P-152: High Performance Reflective and Transflective Displays Using Guest-Host Liquid Crystal Gels

Two high performance reflective guest-host liquid crystal displays (GH LCDs) using a dual-frequency liquid crystal (DFLC) gel and a negative liquid crystal (NLC) gel are developed. These polarizer-free GH-LCDs exhibit ∼50% reflectance, ∼200:1 contrast ratio, and <5 ms response time. Such reflective LCDs can also be used in double cell gap transflective displays.