Hideya Murai

Preparation and characteristics of new reverse mode film of polymer dispersed liquid crystal type

A reverse mode operation has been achieved in a polymer dispersed liquid crystal (PDLC) film by a novel methodology. A mixture of a dual frequency addressable liquid crystal (crossover frequency (fc): 13 kHz at 298 K), an acryl monomer and an acryl oligomer was irradiated by UV light under the application of an electric field [50 V, 100 Hz(≪fc)] to give a reverse mode PDLC film. The film thus prepared shows 95% transmittance in the absence of an applied voltage (OFF state), while the transmittance decreases to 5% by applying 50 V at 50 kHz (≳fc) (ON state). Upon removal of the applied voltage, the film transmittance returns to 95%. The response time (the ON time: 24 ms and the OFF time: 74 ms) are similar to those of normal mode PDLC films.

Electro-optic properties for liquid crystal phase gratings

A new type of liquid crystal device was developed by applying a concept of liquid crystal phase gratings (LCPGs). LCPGs are composed of square-wave phase gratings constructed with poly(methyl methacrylate) and liquid crystals which fill the grating grooves. The typical sizes of the phase grating are 10 micrometers in width and 2 micrometers in depth. The transmitted light wavelength can be easily controlled by changing applied voltage. The transmittance varied from less than 1 for monochromatic polarized light, when applied voltage varied from 0 V to 5 V. Rise times for the light varied from 0.2 ms to 7 ms with applied voltage, and were inversely proportional to the square of the applied voltage. Decay times, which depend slightly on the applied voltage, were about 4 ms. A transmitted light, i.e., an observed color (e.g., R,G,B and white), was dependent on not only applied voltage but also grating depth. When two of the LCPGs were combined in such a way that their grating lines were oriented perpendicular to each other, these LCPGs were applicable to nonpolarized light.

Electro-optic properties of liquid crystal phase gratings and their simulation using a homogeneous alignment model

Abstract Electro-optic properties of liquid crystal phase gratings (LCPGs), regarding groove depth, temperature and a cell gap, have been studied. The off response times are proportional to the square of the groove depth. The transmitted light colour depends on temperature. When there is a gap between the grating and the opposite substrate, their transmittance–voltage curve has a maximum and a minimum. The authors have also simulated the LCPG properties using a homogeneous alignment model. The simulating results coincide with experimental results; therefore the simulation method is considered useful to predict LCPG properties.

Homeotropic reverse-mode polymer-liquid crystal device

We have proposed a new type of reverse-mode polymer-liquid crystal device: homeotropic reverse-mode polymer-liquid crystal (HRPLC). This device consists of a liquid crystal with a dielectric constant having negative anisotropy and a pair of glass plates covered with a homeotropic alignment layer. The HRPLC’s operation is the reverse of the usual; i.e., it is clear when no voltage is applied and opaque under applied voltage. We have confirmed that the HRPLC operates well in reverse mode and have studied the dependence of its properties on liquid crystal material, curing process, and cell thickness. Experimental results indicate the HRPLC has a 30:1 contrast ratio over an operating voltage range of 0–11 V. In special fabrication conditions, the transmittance–voltage curve of the HRPLC drops to a minimum at a certain voltage level and begins to increase at that point. We have proposed a model to explain this result.

Stabilization of Epoxy-Based Polymer-Dispersed Liquid Crystal Films by Addition of Excess Hardener

Abstract Polymer-dispersed liquid crystal (PDLC) films whose matrices consist of two-component epoxy resins have been studied. Their driving voltage and response time depend on the epoxy oligomer/hardener ratio in the epoxy resin. When an excess of the hardener (polythiol) is mixed in the epoxy resin, PDLC films which have the following superior properties have been successfully fabricated. 1) The driving voltages are lower than that of the PDLC film which contain an equal amount of the epoxy oligomer and the hardener. 2) The driving voltage and response time do not change with time. On the other hand, when an equal amount of the oligomer and the hardener are mixed in the epoxy resin, the driving voltage and response time of the PDLC film vary with the time. The driving voltage change of the PDLC films is related to the change of their admittance by the use of a two-phase model, in which spherical droplets are dispersed in the matrix.

RANDOM AND POSITION-CONTROLLED 4-DOMAIN CTN-LCDS WITH WIDE VIEWING ANGLE

We have developed two types of 4-domain complementary TN (CTN) LCDs: a random type and a position-controlled type. The LC layer in each of the 4-domain CTN-LCDs is divided into four kinds of domain, each of which has directions. The 4-domain CTN-LCDs have wide contrast ratio without light masking layers. In the fabrication, each of their substrates was rubbed in only one direction; no additional step was required, in contrast to the conventional TN-LCD process. We have also fabricated 4-domain CTN TFT panels and confirmed that they have wide viewing angle characteristics without grey scale inversion. a different combination of twist and tilt viewing angle characteristics and high

Liquid crystal photo-alignment layers made from aromatic bismaleimides

We propose a new type of liquid crystal photo-alignment layer made from aromatic bismaleimides. Aromatic bismaleimides are expected to react anisotropically by irradiation of polarized ultraviolet (UV) light. In the fabrication process of the new photo-alignment layers the curing process is much shorter than that needed for conventional polymeric types of photo-alignment layers. We have proved that the use of aromatic bismaleimides enables liquid crystal molecules to be aligned homogeneously by irradiation of polarized UV light. In particular N,N′-p-phenylenebismaleimide shows good photo-alignment characteristics and high UV sensitivity. In studying the relationship between molecular structures of aromatic bismaleimides and photo-alignment properties, we find that aromatic bismaleimides that have a linear molecular structure and resonance structure produce good photo-alignment layers.

Preparation and Optical Properties of a Reverse-Mode Polymer Dispersed Liquid Crystal Film

Two new types of reverse-mode polymer-dispersed liquid crystal films have been developed and successfully produced. The first was produced by UV-curing of a mixture of dual frequency addressable liquid crystal (DFALC) and UV-curable polymers under an applied voltage at a frequency lower than the crossover frequency (f c ) of the DFALC. This first type is referred to as a dual frequency type. The second type was produced by injecting a liquid crystal having negative dielectric anisotropy into a specially prepared porous polymer film from which liquid crystal having positive dielectric anisotropy had previously been extracted. The type thus produced through such “negative-for-positive” substitution is referred to as a substitution type. While the dual frequency type can not be driven at a low frequency, substitution type can, which gives it a distinct advantage. Other electro-optic characteristics of the two types of films, including alignment properties of the liquid crystal molecules, are also discussed.

Chip-level and package-level seamless interconnect technologies for advanced packaging

Package-process-oriented thick-Cu-wiring technologies have been developed for forming chip-level and package-level seamless interconnects between an LSI chip and the package substrate. Chip-level seamless interconnects are formed using a resin CMP process. Package-level seamless interconnects are formed by embedding a thinned chip into a resin on Cu base plate. A package with package-level seamless interconnects is thinner and has lower thermal resistance, better power delivery, and finer-pitch interconnects than a conventional flip-chip ball grid array package.

22.2: RGB-Stacked Holographic Polymer Dispersed Liquid Crystal Device for Color Reflective Display

In stacking holographic PDLC devices, the parallax in the stack and the viewing angle should be considered. Based on a thin glass substrate (thickness = 0.1mm) assembly technique and an optical setup with a lenticular-lens array, RGB-stacked HPDLC devices with a low parallax and a large viewing angle (>15 degrees) have been developed.