• Transactions of Materials Processing
• /
• v.24 no.2
• /
• pp.83-88
• /
• 2015

For chromaticity correction, it is necessary to dispense high viscosity phosphor slurry since it greatly affects the performance of white LEDs. However, it is quite difficult to dispense high viscosity fluorescent materials. In the current study, micro-discharge electrostatic printing has been used for dispensing various high viscosity phosphor slurries. We have achieved dispersions of up to 50 µg using drop on demand (DOD) discharge experiments. The experiments were conducted with different combinations of process variables such as applied voltage, pneumatic pressure, and frequency.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.25 no.2
• /
• pp.124-131
• /
• 2016

Several research works for finding and optimizing the methods of dispensing high viscosity phosphor used in the fabrication of white LED's are currently in progress. High viscosity phosphor dispensing with a high accuracy is crucial because the dispensing rate and uniformity directly affect parameters such as the CIE chromaticity diagram, color temperature and luminous flux of white LED's. This study presents a novel method of dispensing high viscosity phosphor using electrohydrodynamic printing. The dispensing rate was optimized less than 0.01 mg phosphor using experiments and optimizing the process parameters including the standoff distance from the nozzle to the substrate, ink supply pressure, and multi-step pulsed waveform magnitude ratio. The dispensing rate was measured by dispensing 20 dots using drop-on-demand with the optimized parameters, and the experiments were repeated 10 times to maximize the data accuracy. The average dispensing rate that can be reliably used for high viscosity phosphor dispensing was 0.0052 mg.

• Clean Technology
• /
• v.20 no.2
• /
• pp.97-102
• /
• 2014

Currently various studies are underway for dispensing high-viscosity phosphor. These studies have reported limitations and challenges in the dispensing process. The discharged amount of phosphor was approximately the same each time which is important for the implementation of high-efficiency white LED technology. This paper present high-viscosity phosphor dispensing process for white LED implementation by using electrostatic printing technology. The voltage controlled DOD (Drop-On-Demand) discharge experiment was studied to determine angle of drop meniscus at nozzle and dot diameter. With increase in Discharge voltage, the discharge angle of meniscus increased while dot diameter decreased. Therefore it can be concluded that we can control the discharge rate by controling the discharge angle of meniscus.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1998.06a
• /
• pp.391-394
• /
• 1998

Electroluminescence is the light emission obtained by an electrical excitation energy passing through a phosphor under an applied high electrical field. EL are paid much attention on flat panel display as a backlight and indicator, which are divided into ACPRL(alternating-current powder electroluminescent) and ACTFEL(alternating-current powder electroluminescent). In this paper, Electric and emission properties on ACPEL are investigated based on ZnS:Cu phosphor. The basic structure on this is ITO glass/phosphor/insulator/ backelectrode, CR-M which has high efficiency on thermal properties and dielectric Properties was introduced and BaTiO$_3$ as a insulating layer in order to increase app1ied electric field on phosphor. Changing on Dielectric and emission Properties was caused by a different viscosity of binder which filled on space between phosphor particle. 60cd/$m^2$ under 60V, 2kHz sinusoidal was gotten from ACPELD prepared in this work.