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A subsidiary of Japan Pacific Cement Co., Ltd., Japan's Ceratec Co., Ltd. (headquarters: Sendai City), which is engaged in the production of high-performance ceramic products, has developed PhosCera, a fluorescent plate for LED lamps, which is composed of only high-performance ceramic components. Sample supply has recently begun. Ceratec expects to achieve low prices through mass production and the like. The company claims that this is the first time in Japan to sell LED fluorescent panels made of high-performance ceramic components.
The fluorescent plates developed this time are mainly used for LED lamps using remote phosphors. The remote phosphor refers to a method in which a fluorescent plate is disposed separately from a substrate in which a plurality of blue LED elements (used as a heat source and a light source) are packaged. The phosphors of the green, yellow and red colors (average particle size of 10 to 20 m) in the fluorescent plate coating are excited by the blue LED light source to emit light of various colors. When these lights are mixed, an illumination such as white is formed. The fluorescent plates developed this time are mainly used for large-scale LED lighting fixtures such as large commercial facilities and factories.
On the surface of the green, yellow and red phosphor particles, a layer of fine special ceramic particles (having a particle size of several nm) is first coated as a bonding layer, and then such particles and ceramic particles forming the coating mother phase (average particle diameter) 10 to 20 m), and disperse it in a solvent to prepare an ink, and then apply the ink to the surface of the heat-resistant glass (inner side) as a base material of the fluorescent sheet by screen printing, and then dry and fire to form The coating of the fluorescent sheet. It is estimated that the coating can be adhered to the surface of the glass by the bonding function of the ceramic particles. On the prototype, the thickness of the coating of the green, yellow and red phosphors uniformly dispersed in the ceramic matrix is ​​about 80 m.
According to Ceratec, ceramic particles are binders for forming coatings. The main component is SiO2 ceramics. The phosphors are made of YAG (a garnet structure crystal composed of yttrium and aluminum composite oxide Y3Al5O12) phosphors and sulfide fluorescence. Powder composition. Generally, moisture in the air easily causes deterioration of the phosphor, but after the phosphor is mixed in the matrix phase of the ceramic particles, moisture can be blocked and durability can be improved.
Makita, a remote phosphor-based LED luminaire supplied by other companies, is estimated to use a resin glue called an organic binder to fix the phosphors. According to Ceratec, the heat resistance, light resistance and luminous efficiency of the luminaire are all improved compared with the products using organic binders, and the luminous efficiency is greatly improved.
Regarding the heat resistance, in the long-term heat resistance test (temperature of 150 ° C and 200 ° C, dry environment) using a prototype, the relative light emission luminance did not change after 2000 hours of exposure test. In the case of using the original organic binder, the relative illuminance is gradually decreased by several percentage points, especially at a temperature of 200 ° C, and the coating is peeled off from the substrate glass in the test. The heat resistance of the sample is above 500 °C.
In the long-term moisture resistance test (temperature: 85 ° C, relative humidity: 85 RH), the result that the relative luminescence brightness hardly deteriorated after 2,000 hours was obtained. It can be confirmed that the phosphor is sufficiently protected.
When a fluorescent sheet for LED is used in a lighting fixture, the color rendering index (representing the wavelength spectrum of the light contained) is very close to natural light, which is excellent. By changing the mixing ratio of the green, yellow and red phosphors, the color tone of the illumination light and the like can be adjusted to an optimum state.
According to Ceratec, the luminescent sheet developed this time has excellent light resistance, so it can be used for applications such as ultraviolet LEDs and lasers that require excellent light resistance.