Image.xcassets(launch images)

When I run the program on the simulator it compiles and works but when I run it on my iphone 4s or ipad I get this error, "/Images.xcassets: Failed to write PNG data for the launch image set from "LaunchImage.launchimage/default@2x_.png" to "/Users//Library/Developer/Xcode/DerivedData/-beztspdlisttjcapcmvmykoyzuxn/Buil d/Products/Debug-iphoneos/app/LaunchImage-700@2x.png".