You shouldn't have to use thread locker, make sure your tightening them down properly, the threads should be properly lubricated and you will most likely need a special tool that hooks onto the reverse side of the bolt, they should be fairly tight ~5nm for steel bolts if memory serves but I'm doubting you have a torque wrench so I won't bother looking

Make sure the bolts are short enough so they are bottoming out against the chainring not themselves, if this is the case you need new chain ring bolts and no amount of threadlocker will help, infact if your having problems with it threadlocker would probably only make your life much more complicated