You'll need a layer 2 switch connected between the VLANs because the SRX will stop broadcast from flooding into another layer 3 network, that's the fundamentals of routing.
You could try using directed broadcast but I'm not sure if it will work. This KB article describes how to set it up.
http://www.juniper.net/techpubs/en_US/junos15.1/topics/concept/targeted-broadcast-overview.html