Green Day frontman Billie Joe Armstrong has revealed that work on their new album 21st Centrury Breakdown nearly put him in hospital.In an interview with The Sun, Armstrong said: “We had set the bar so high with American Idiot. We all became sick as dogs. I was close to being hospitalised but they caught me in time. I had the boogie woogie flu.”Armstrong added that the bulk of the album’s ideas was stored on his phone. “I got a BlackBerry and started to write down every idea for a lyric on it,” said Armstrong. “ I had many a sleepless night where I’d get something and have to get up and tap it into my BlackBerry.”21st Century will be released on May 15 through Warners. The band's new single, Know Your Enemy, is released on April 27.