• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.33B no.1
• /
• pp.49-56
• /
• 1996

In this paper, as a new grey scale method for simple matrix LCDs, the grey scale method using the new code scheme was proposed. The experiment and the characteristic estimation for the new grey scale method were performed by the simulation of the 16 and 32 grey patterns and the calculation of the driving voltages. As a result of the experiment and the characteristic estimation, the 16 grey mode using the 3 bits code scheme, (7, 5, 3) has the maximum driving voltage which is reduced by 19% and 9.6% each compared with the values in the conventional grey modes discussed in this paper. And the extent of improvement in the driving voltage characteristics is increased much as the number of grey levels increases. On the other hand, as a result of the grey image estimation through the grey pattern simulation, the 3 bits 16 grey mode degrades the characteristics of the grey image more or less compared with the conventional grey method but the extent of this characteristic degradation is much reduced with the increase in the number of grey levels such as 32 grey scale, etc. Consequently the grey scale method using the new code scheme proposed in this paper is confirmed as a method that it minimized the degradation of grey characteristics and improves the driving voltage characteristics effectively.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07a
• /
• pp.489-492
• /
• 2005

We report new polymer stabilized ferroelectric liquid crystal (PSFLC) cells with mechanical stability which is achievable by introducing photospacers in the cells. It was found that the mechanical st ability of the PSFLC cell was effected by introduction of photo spacers. We analyzed the dependence of mechanical stability and memory property on the density of photospacers in the PSFLC cell. The stability and memory properties of PSFLC Cells depending on photospacer density are discussed. 1. Introduction Recently, flexible displays have attracted much attention because they have remarkable advantages: thinner, lighter, non-breakable and conformable features. Flexible displays have various potential applications such as e-book and e-paper displays utilizing the distinct features. E-book and E-paper displays demand very low power consumption, so that bistable memory liquid crystal modes are required in case of flexible plastic LCDs for those application. Three kinds of memory LC modes have been developed; bistable nematic, bistable cholesteric and bistable FLC. Among them SSFLC as one of bistable FLC has big advantages such as low driving voltage, wide view angle and fast response time, SSFLC cells are, however, very weak against mechanical shock. Polymer stabilized FLC (PSFLC) has been developed to overcome the poor mechanical stability of SSFLC. PSFLC was known to have network structure that FLCs are oriented with smectic layer ordering in polymer network. The polymer network stabilizes the FLC orientation, which leads to improvement of mechanical stability of PSFLCD. A lot of studies have been done for the application of PSFLC to flexible $LCDs.^{[1{\sim}12]}$ However, it should be noted that PSFLC does not have sufficient mechanical stability for the particular applications such as smart card LCD, where LCD is highly bendable.Bead spacer was mainly used to maintain cell gap of conventional PSFLCDs. But the spacer density of it is not locally uniform in the cell, so that it is generally difficult that the PSFLCDs with bead spacers show sufficient mechanical stability. In order to more improve the mechanical stability of PSFLCDs, we introduced photospacers into PSFLCDs. In this paper, we describe the improvement of mechanical stability by introducing photospacers into PSFLCDs.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.3
• /
• pp.795-801
• /
• 2010

As the fabrication technology of LCDs (Liquid Crystal Displays) advances, the size of mother glass substrates is getting larger, and the fabrication process is becoming finer. Accordingly, the importance of cleaning processes grows in the fabrication process of LCDs. In this study, we have compared and evaluated the particle removal efficiency for three different methods of physical cleaning, which are brush, bubble jet, and aqua/air cleaning. Using the seventh generation glass substrate, the particle removal efficiency has been investigated by changing operation conditions such as a flow rate of deionized water, pressure, contact depth between a brush bristle and a glass substrate, and so forth. In the case of brush cleaning, the cleaning efficiency barely changes after a critical point when the contact depth is varied. While the cleaning efficiency of bubble jet cleaning is almost independent of pressure, that of aqua/air cleaning is affected by pressure up to a critical point, but is not changed after it. We note the brush cleaning is the most effective among the three cleaning methods under our experimental conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.429-429
• /
• 2007

For various applications of liquid crystal displays (LCDs), the uniform alignment of liquid crystal (LC) molecules on treated surfaces is significantly important. Generally, a rubbing method has been widely used to align the LC molecules on polyimide (PI) surfaces. Rubbed PI surfaces have suitable characteristics, such as uniform alignment. However, the rubbing method has some drawbacks, such as the generation of electrostatic charges and the creation of contaminating particles. Thus, we strongly recommend a non contact alignment technique for future generations of large high-resolution LCDs. Most recently, the LC aligning capabilities achieved by ultraviolet and ion-beam exposures which are non contact methods, on diamond-like carbon (DLC) inorganic thin film layers have been successfully studied because DLC thin films have a high mechanical hardness, a high electrical resistivity, optical transparency, and chemical inertness. In addition, nitrogen-doped DLC (NDLC) thin films exhibit properties similar to those of the DLC thin films and a higher thermal stability than the DLC thin films because C:N bonding in the NDLC thin filmsis stronger against thermal stress than C:H bonding in the DLC thin films. Our research group has already studied the NDLC thin films by an ion-beam alignment method. The $SiN_x$ thin films deposited by plasma-enhanced chemical vapor deposition are widely used as an insulation layer for a thin film transistor, which has characteristics similar to those of DLC inorganic thin films. Therefore, in this paper, we report on LC alignment effects and pretilt angle generation on a $SiN_x$, thin film treated by ion-beam irradiation for various N ratios

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.430-430
• /
• 2007

In general, polyimides (PIs) are used in liquid crystal displays (LCDs) as alignment layer of liquid crystals (LCs). Up to date, the rubbing alignment technique has been widely used to align liquid crystals on the PI surface, which is suitable for mass-production of LCDs because of its simple process and high productivity. However, this method has some disadvantages. Rubbed PI surfaces include the debris left by the cloth and the generation of electrostatic charges during rubbing process. Therefore, rubbing-free techniques for LC alignment are strongly required in LCD technology. In this experiment, PI was uniformly coated on indium-tin-oxide electrode substrates to form LC alignment layers using a spin-coating method and the PI layers were subsequently imidized at 433 K for 1 h. The thickness of the PI layer was set at 50 nm. The LC alignment layer surfaces were exposed to an $Ar^+$ ion-beam under various ion-beam energies. The antiparallel cells and twisted-nematic (TN) cells for the measurement of pretile angle and electro-optical characteristics were fabricated with the cell gap of 60 and $5\;{\mu}m$, respectively. The LC cells were filled with nematic LC (NLC, MJ001929, Merck) and were assembled. The NLC alignment capability on ion-beam-treated PI was observed using photomicroscope and the pretilt angle of the NLC was measured by the crystal-rotation method at room temperature. Voltage-transmittance (V-T) and response time characteristics of the ion-beam irradiated TN cell were measured by a LCD evaluation system.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.186-186
• /
• 2000

After LeComber et al. reported the first amorphous hydrogenated silicon (a-Si: H) TFT, many laboratories started the development of an active matrix LCDs using a-Si:H TFTs formed on glass substrate. With increasing the display area and pixel density of TFT-LCD, however, high mobility TFTs are required for pixel driver of TF-LCD in order to shorten the charging time of the pixel electrodes. The most important of these drawbacks is a-Si's electron mobiliy, which is the speed at which electrons can move through each transistor. The problem of low carier mobility for the a-Si:H TFTs can be overcome by introducing polycrystalline silicon (poly-Si) thin film instead of a-Si:H as a semiconductor layer of TFTs. Therefore, poly-Si has gained increasing interest and has been investigated by many researchers. Recnetly, fabrication of such poly-Si TFT-LCD panels with VGA pixel size and monolithic drivers has been reported, . Especially, fabricating poly-Si TFTs at a temperature mach lower than the strain point of glass is needed in order to have high mobility TFTs on large-size glass substrate, and the monolithic drivers will reduce the cost of TFT-LCDs. The conventional methods to fabricate poly-Si films are low pressure chemical vapor deposition (LPCVD0 as well as solid phase crystallization (SPC), pulsed rapid thermal annealing(PRTA), and eximer laser annealing (ELA). However, these methods have some disadvantages such as high deposition temperature over $600^{\circ}C$, small grain size (<50nm), poor crystallinity, and high grain boundary states. Therefore the low temperature and large area processes using a cheap glass substrate are impossible because of high temperature process. In this study, therefore, we have deposited poly-Si thin films on si(100) and glass substrates at growth temperature of below 40$0^{\circ}C$ using newly developed high rate magnetron sputtering method. To improve the sputtering yield and the growth rate, a high power (10~30 W/cm2) sputtering source with unbalanced magnetron and Si ion extraction grid was designed and constructed based on the results of computer simulation. The maximum deposition rate could be reached to be 0.35$\mu$m/min due to a high ion bombardment. This is 5 times higher than that of conventional sputtering method, and the sputtering yield was also increased up to 80%. The best film was obtained on Si(100) using Si ion extraction grid under 9.0$\times$10-3Torr of working pressure and 11 W/cm2 of the target power density. The electron mobility of the poly-si film grown on Si(100) at 40$0^{\circ}C$ with ion extraction grid shows 96 cm2/V sec. During sputtering, moreover, the characteristics of si source were also analyzed with in situ Langmuir probe method and optical emission spectroscopy.

• Proceedings of the KIEE Conference
• /
• 1999.07d
• /
• pp.1786-1788
• /
• 1999

In this paper, we studied Surface Discharge Type Flat Fluorescent Lamp with High Luminance for LCD Backlighting, Liquid Crystal display(LCDs) demand the use of fluorescent lamp as the backlighting source. This lamp is Surface Discharge Type structure with a pair of Sodalime glass, insulator layer, phosphor layer, and Xe gas gap. In spite of its simple structure, the lamp has uniform and stable discharge over entire volume. Till now, we measured the current-voltage(V-I), Firing Voltage, Sustain Voltage for 0.5mm, 1mm electrode gap. In experiment result, long gap cell structure cause high firing voltage. The rising in firing voltage in long gap structure could not be explained by paschen's law because of non-uniform electric field.

• Proceedings of the KIEE Conference
• /
• 1999.07d
• /
• pp.1750-1752
• /
• 1999

An active-matrix liquid crystal display (LCD) using thin film transistors (TFTs) has been widely recognized as having potential for high-quality color flat-panel displays. Pixel-Design Array Simulation Tool (PDAST) was used to profoundly understand the gate signal distortion and pixel charging capability, which are the most critical limiting factors for high-quality TFT-LCDs. Since PDAST can simulate the sate, data and pixel voltages of a certain pixel on TFT array at any time and at any location on an array, the effect of the new set of capacitance models on the pixel operations can be effectively analyzed. The set of models which is adopted from VLSI interconnections calculate more precise capacitance. The information obtained from this study could be utilized to design the larger area and finer image quality panel.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.198.1-198.1
• /
• 2016

Organic light-emitting diode (OLED) displays have promising potential to replace liquid crystal displays (LCDs) due to their advantages of low power consumption, fast response time, broad viewing angle and flexibility. Organic light emitting materials are vulnerable to moisture and oxygen, so inorganic thin films are required for barrier substrates and encapsulations.[1-2]. In this work, the silicon-based inorganic thin films are deposited on plastic substrates by plasma-enhanced chemical vapor deposition (PECVD) at low temperature. It is necessary to deposit thin film at low temperature. Because the heat gives damage to flexible plastic substrates. As one of the transparent diffusion barrier materials, silicon oxides have been investigated. $SiO_x$ have less toxic, so it is one of the more widely examined materials as a diffusion barrier in addition to the dielectric materials in solid-state electronics [3-4]. The $SiO_x$ thin films are deposited by a PECVD process in low temperature below $100^{\circ}C$. Water vapor transmission rate (WVTR) was determined by a calcium resistance test, and the rate less than $10.^{-2}g/m^2{\cdot}day$ was achieved. And then, flexibility of the film was also evaluated.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.957-961
• /
• 2004

In order to realize high performance thin film transistor (TFT) on plastic substrate, Si film was deposited on plastic substrate at 170$^{\circ}C$ by using inductivity coupled plasma chemical vapor deposition (ICPCVD). Hydrogen concentration in as-deposited Si film was 3.8% which is much lower than that in film prepared by using conventional plasma enhanced chemical vapor deposition (PECVD). Si film was deposited as micro crystalline phase rather than amorphous phase even at 170$^{\circ}C$ because of high density plasma. By step-by-step Excimer laser annealing, dehydrogenation and recrystallization of Si film were carried out simultaneously. With step-by-step annealing and optimization of underlayer structure, it has succeeded to achieve large grain size of 300nm by using ICPCVD. Base on these results, poly-Si TFT was fabricated on plastic substrate successfully, and it is sufficient to drive pixels of OLEDs, as well as LCDs.