The sealant of solar battery plays the role of adhesive of the back sheet that protects the cells from heat and salinity. Currently, a synthetic resin called ethylene-vinyl acetate (EVA) is widely used as the material of the sealant. However, EVA might cause electric leakage inside the solar battery and decrease the output because it is easily permeated by moisture. Dainippon Printing used polyolefin in place of EVA for its sealant because it is not so easily permeated by moisture as EVA. However, polyolefin resin is liable to break and lose transparency as heat resistance increases, resulting in poor intake of sunlight. This is why EVA is more popular than polyolefin. Dainippon overcome the drawback of polyolefin by improving the blending of materials. Its new sealant has 10 times higher ability to block moisture than the existing sealant and avoids power decline due to leakage.
Because Dainippon got favorable responses from customers that have been testing the new sealant, it will mass produce the new sealant in its existing plants instead of building a new plant for it. The price will be the same as the existing sealant, the company said. The company is also scheduled to mass produce new back sheets with improved insulating performance. According to Japan Photovoltaic Expansion Center, the average price of a residential photovoltaic generation system in the second quarter of this year decreased 10% from the same period of the previous year to 500,000 yen per kW mainly because of the price competition with products from China. A research company in Tokyo forecasts that the world market of materials of solar battery will increase 2.7 times over the level in 2010 to about 6,800 billion yen in 2020. All Japanese companies involved in the photovoltaic generation business are busily occupied with the development of even higher performance products that can be offered at a more competitive price.