Phosphor Slurry Research Articles

Formation of Coated Phosphor Layers by Rotation–Revolution for Remote-Phosphor LED Bulbs and Characterization of LED Light Bulb With Super High Color Rendition

We have developed a new system for coating phosphor globes used in remote-phosphor-type light-emitting diode (RP-LED) bulbs. The system has a rotation–revolution coating apparatus and a heating unit. After dispensing a phosphor slurry mixed with phosphor powder and silicone resin into globes, the phosphor slurry is uniformly coated on the entire inner surface of the globes by the coating system. The phosphor slurry is then cured. We obtained phosphor globes having a phosphor layer with a uniform thickness on the entire inner surface of the globes. We prepared RP-LED bulbs combined with an LED chip-on-board (COB) that emitted light with a wavelength of 400 nm, and phosphor globes containing red, green, and blue phosphor powders obtained using the coating system. The bulbs have a high color rendering because their spectrum is almost the same as that of blackbody radiation. The RP-LED bulbs having a phosphor layer with uniform thickness had more uniform chromaticity and luminescence distribution than an RP-LED bulb having a phosphor layer with nonuniform thickness. The total luminous flux of the RP-LED bulbs was 29% higher than that of a bulb mounted on a COB covered with a phosphor layer. Furthermore, the semiangle at half-power of the RP-LED bulbs was much larger than that of the bulbs mounted on a COB with a phosphor layer.

Red-Phosphor-Dot-Doped Array in Mirror-Surface Substrate Light-Emitting Diodes

Micro-patterned red-phosphor-dot-doped array in mirror-surface substrate light-emitting diodes (LEDs), which are primarily characterized with imbedded red phosphor dots in yellow phosphor slurry and an installed mirror on the substrate surface, are investigated. These dots scatter lights in different colors, compensate the long waveband in LED spectra, and allow exiting blue rays to escape in large angles. This mirror surface reflects downward blue lights emitted by chips, blends various-wavelengthed light beams, and enhances the cooling effect on the entire module. With the aid of these two modifications, the quantum efficiency (QE) and the luminous efficacy of radiation (LER) have been typically elevated by 16.6% and 38.8%, respectively. Proposed modules can be used in the LED industry for guiding improvements of QE, LER, and yellow–blue ratio uniformity.

실리콘 수지 혼합비율에 따른 Pre-form 형광체 막 특성 변화에 관한 연구

The effect of the viscosity of phosphor slurry prepared by mixing two types of sil- icone resins with different viscosities in various ratios on the properties of pre-formed phosphor films was investigated. The pre-formed phosphor films manufactured using these phosphor slurries were evaluated for curing characteristics, breaking strength, shear strength, and optical properties. The test results demonstrated that increasing the amount of high-viscosity silicone resin in the composite resin resulted in decreased curing reaction rate, decreased breaking strength, and correlated color temperature, whereas the viscosity and adhesion strength of the composite resin increased. Among seven different mixing ratios of the low- and high-viscosity silicone resins prepared for the composite resin, white- light emission was realized for the ratio 70:30, and the pre-formed phosphor film with this ratio exhibited high breaking strength and low adhesion strength. The breaking strength thus obtained was 24.0 MPa, the adhesion strength was 0.17 MPa, the color temperature was 5,650 K, and the two chromaticity coordinates (CIE(x, y) (1931)) were (0.3293, 0.3251).

Facile Preparation and Ultrastable Performance of Single-Component White-Light-Emitting Phosphor-in-Glass used for High-Power Warm White LEDs.

Long lifetime, excellent chromatic stability, and easily obtainable white light are becoming three outstanding challenges faced by the state-of-the-art high-power white LEDs. This study explored a novel single-component white-light-emitting phosphor-in-glass (PiG) for the first time. It has a quantum efficiency of 26.2% and exhibits excellent heat-resistance and good humidity-resistance characteristics which are rarely reported in traditional phosphor slurry. A proof-of-concept warm white LEDs was fabricated by combining PiG with near-ultraviolet chip-on-board (n-UV COB). This method reported in this letter will open a new and simple approach to obtain excellent performance single-component luminescent convertor for advanced high-power white LEDs.

스퀴징 공정변수에 따른 형광체막 성형 거동에 관한 연구

It was confirmed that when phosphor slurry is formed in the cavity of an elastic mold, the pressure distribution of the phosphor slurry varies as a function of the major squeegee parameters (squeegee angle, squeegee velocity, and the viscosity of the phosphor slurry). The higher the slurry viscosity, the faster the squeegee velocity, and the smaller the squeegee angle, the higher the filling completeness of the phosphor slurry. The optimum conditions for complete filling of the phosphor slurry were found when the squeegee angle was between 30 to 45 degrees, squeegee velocity at 40 to 70mm/sec, and the viscosity of the phosphor slurry composite was at 6,556 cps (i.e. phosphor content around 50 wt. %).

전기수력학 프린팅 시스템을 이용한 고점도 형광체의 정량 토출 연구

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.

Conformal Phosphor Distribution for White Lighting Emitting Diode Packaging by Conventional Dispensing Coating Method With Structure Control

Conformal phosphor distribution is a well known way to improve optical performance for white light emitting diode (LED) packaging. However, it is difficult to be realized by mature and cheap dispensing coating methods. In this paper, with consideration given to the effect of boundary constraint on liquid wetting morphology, a method to achieve phosphor conformal distribution is presented by conventional dispensing coating with controlling the slanting angle of reflector cups. The numerical simulations and experiments on phosphor dispensed into reflector cups with different slanting angles are conducted. The results show that uniform phosphor distribution can be obtained when the slanting angle is the same as the contact angle between the phosphor slurry and the reflector cup side wall. The rule can be used to guide the design of the reflector cup and a simple change of reflector cup can realize phosphor conformal coating for white LEDs by the low cost traditional dispensing coating process.

Improved production of ZnS blue phosphor powder

The production procedure of ZnS:Ag:Cl blue phosphor powder is still complicated, although it is widely used for color displays. The complication mainly comes from handling of the by-product Na2S4, which covers the surface of grown ZnS particles in a crucible. The formation of Na2S4 introduces serious problems in many factors such as (i) CL intensity and color, (ii) particle size distribution, (iii) sintering of heated products, (iv) photodarkening of powders, and (v) stability of PVA phosphor slurry. These problems are clarified in this paper. It is shown that the blue phosphor powder can be produced by a more simplified procedure than before, with high reproducibility. The ZnS:Ag:Cl phosphor powder produced by the present procedure is well suitable for blue primary in color screens of FED and CRT.

Manufacturing a phosphor screen for color CRT.

This article describes how to make a phosphor screen with slurry method. The peculiar technologies in the color screen manufacturing are especially described in detail. Those are concerned with screen configuration, photoresists, principle of light source correction, print-down in negative matrix, pre-coating, phosphor slurry, slurry coating, developement of exposed films, and filming.