Magnetically aligned nematic liquid crystai (NLC) cells were prepared using three kinds of non-rubbed polyimides (Pls) having different surface tension (polarity) as alignment films. The effects of the degree of polarity of PI on LC alignment were studied in terms of the observation of the texture and the isotropic to nematic (I-N) phase transition and the polar anchoring energy measurement. On the I-N phase transition first nematic phase appeared in the bulk for cells with PI having moderate and low degree of polarity, while it appeared from the surfaces for a cell with PI having a high polarity.
To reduce the leakage current of thin film transistors, we did post-oxidation after gate polysilicon patterning. This post-oxidation makes structural change of gate poly-silicon. It reduces the leakage current with negligible reduction of on-current. The characteristics of thin film transistor (TFT) was measured for various lengths of lightly-doped drain (LDD) region. This new device structure of TFT shows more stable off-current as increasing the source-drain voltages than that of conventional TFT. This reduction of leakage current was attributed to the reduction of drain junction field.
In this study, the characteristics of a TFT driven OCB-mode LCD, which has been succssfully made in our lab, will be reported. The electro-optical properties as well as the response time as a function of temperature were investigated in a detail manner. It is found that the response time between gray scale switching is still less than 600 ms even at the temperature -30℃. The initial switching time is dependent on the initial switching voltage and it can be reduced to 139 seconds as the initial switching voltage is up to 10 volts at -30℃. But the power-off switching time is independent of the voltage. We also illustrate the dependency of viewing angle properties, including the iso-contrast and the gray scale inversion, on temperature. From the experimental data, we conclude that within 0℃ to 40℃, the viewing angle can extend to 40 degrees.
The amorphous silicon films deposited by low pressure chemical vapor deposition are crystallized by the various annealing techniques including low-temperature furnace annealing, excimer laser annealing and two-step annealing. Two-step annealing, which is the combination of furnace annealing at 600 ℃ for 24h and the sequential furnace annealing at 950 ℃/1h or the excimer laser annealing, is found to reduce the in-grain defects significantly without changing the grain boundary structure. As a consequence, the performance of the poly-Si thin film transistors (TFT's) produced by employing the two-step annealing has been improved remarkably if compared with those of one-step annealing.
To clarify the pretilt angle generation mechanism in photo-alignment method, we investigated the anisotropic properties of photo-alignment polymer PVCN-F, poly (vinyl fluoro cinnamate), and flowing induced pretilt angle. We measured the dichroic UV absorption and birefringence of photo-alignment layer to evaluate the degree of the photo induced anisotropy. It was observed that the UV exposure time dependence of birefringence and UV dichroism of PVCN-F shows the similar tendency. The anisotropy of PVCN-F increases rapidly in the beginning as the UV exposure time increase. The pretilt angle with considerable magnitude (more than 3°) appears in saturation region of anisotropy. It is shown that there is no direct relationship between anisotropy and pretilt angle. Therefore, these two properties seem to have the independent behavior each other.
This paper introduces the ability of the LCD simulation program, which is developed by ourselves. This program provides an effecient tool for designing, estimating and also for educating the LCD displays. It'S ability for application to many fields of LCD types, i.e., TN, mono-STN, film-STN, double layer STN, TFT, reflective LCDs, makes this program powerful. This program is expressed under the GUI environment which provides the program to be friendly to the users. The simulation is constructed in the calculation of LC alignment and optical calculation of normal as well as oblique incidence. The simulator basically analyse the items that LCD 5000,which is for LCD measurement, provides and more.
In this paper, we report the design of a reflection type STN color LCD on the CIE chromaticity diagram. The area of the locus on the CIE chromaticity diagram and the luminance for each color are two parameters by which we select the proper condition of a panel to display colors. We fabicated a 320×240 module driven by a PWM drive circuit.
The DC PDP cell structure with a wall cathode and auxiliary anode showed good characteristics, however it is difficult to fabricate. We propose a new cell structure which combines the surface discharge and the wall auxiliary anode. The feature of the new cell structure is the employment of a surface discharge with a wall auxiliary anode. We have investigated the characteristics of the new modified cell structure with the 2-dimensional computer simulation and compared with characteristics of the previous cell structures.
PDP is the most adequate display device for the large size displays compared to the other ones. We have developed the 200" multi screen system by assembling the DC PDP unit panels, which has the resolution of 1280×1024 and 640×480. In this paper, We will describe the structure and characteristics of this system and signal transmisson.
Colorimetric reproduction requires calibrated color output devices. One way to characterize a color output device is to use a three-dimensional look-up table (LUT) which maps the tristimulus values to the control values of the output device. This paper presents this technique applied to the liquid crystal (LC) projection TV (PTV). We used colorimetric simulation to predict the tristimulus values and to assess the suitability of interpolation function method for the ideal model. Using the forward model, a LUT mapping the control values to the output CIE XYZ values is generated. Finer regular grids are then constructed in the CIE XYZ space. According to our simulations, the LUT model and the cubic interpolator used can well characterize color reproduction for LC PTV
A novel electron gun with a superposition of the electrostatic focus region and the deflection region^<(1)> has been designed for projection TV tube. Compared to the conventional projection gun, the Deflection lens (DFL) gun has a better magnification factor, better spherical aberration coefficient and better control of the space charge effect. The DFL gun needs a unique dynamic off-axis correction lens region to compensate for the deflection defocusing. A series of computer modeling results shows that the DFL gun gives a 5^<mA> (5% gaussian) beam spot size of 0.25 mm in a 9" 90° deflection angle tube with 30kv anode voltage.
Brightness improvement is a very important issue in color monitor tube (CMT), especially in multimedia display and low power issue. Multimedia applications require brightness at higher levels, and lower power tube is for energy saving. In this report, we will discuss the factors that affect brightness and its relative items-brightness uniformity and color purity of the CMT. There are many items which will improve the brightness, brightness uniformity and color purity. They include improving phosphors efficiency, changing the color points of phosphors, Cr-free photoresist, reducing the electron backscattering, increasing the uniformity of aluminum layer and matrix hole size, improving the landing and doming phenomena, a good screen outside coating and a good panel glass transmission, etc. We will discuss these items in this report.
Distortion and linearity have been measured by a bare eye. However this is unreliable because it depends on observer's experience and subjective judgement. To improve these problems, we developed a system which calculates distortion and linearity by image processing technique. This system consists of a computer controlled robot attached with a CCD camera.
A new type of anti-reflection anti-static coating for color monitor tubes (CMT) was developed in Philips to improve users comfort and visibility. Apart from the traditional direct etching or anti-glare coating, the suppression of ambient light reflection is accomplished by a double layer interference optical thin film. Meanwhile, the conductive particles contained in this thin film reduce the surface resistance to certain low level. In direct etching or anti-glare coating, the rough screen surface diffuses the surrounding ambient light into a blur image with sacrifice in resolution at the same time. The new type of anti-reflection anti-static coating is designed to reduce the specular reflectivity of ambient light from 4.5% (the reflectivity of uncoated screens) to 1.5%.
An LCD backlight with an extremely simple structure has been developed utilizing a flat discharge volume with insulated electrodes, A 5.6-in. diagonal discharge volume is a mere open space. The thickness of the volume can be varied from device to device between 1 and 3 mm. Hg is admitted into the volume together with Ar. A pair of electrodes is provided at the top and bottom portions of the front glass plate, with a 70 μm-thick dielectric layer covering the electrodes. Phosphor is deposited on the rear glass plate so that visible emission can be extracted from the discharge volume efficiently. Each of the electrodes is driven by trains of negative pulses, 180° out of phase to each other. Luminance uniformity was measured to be within ±7% when a diffuser sheet is not used. Luminance can be dimmed down to 2% of the peak value by extending the pulse period. Since the conductive electrodes are insulated from the discharge, and since the phosphor is not attacked by ion bombardments, long lifetime can be expected.
The development of short-arc metal halide lamp for LCD-based projector use has been accomplished using Dy-Nd-Cs iodides. Observed light efficiency exceeds 73 lumen/watt, with total luminous flux greater than 11,000 lumens. Lifetime tests have been demonstrated longer than 4000 hour to a 50% luminous decay, with a slower decay curve than commercially available products.
Thermal behavior of shadow mask is a critical problem of flat square tube design, especially for the size of tube is bigger than fourteen inches. To prevent the misregister of electron beam with respect to phosphor dots, the common solution for most of CMT factories is using low thermal expansion coefficient mask material Invar instead of Iron material. However, the price of Invar is more expensive than that of Iron mask. For the cost reduction purpose, Philips developed a new 15" CMT with Iron mask and the suspension system was changed with bi-metal thermal compensation spring. This paper presents the finite element simulation model to select bi-metal spring for 15" Iron mask CMT, and makes a comparison between simulation results and the thermal performance of tube compensated by this bi-metal spring.