Shoulders are very involved in benching, as are triceps. They are secondary muscles worked. Strength buildup in both of these areas will greatly aid your bench. Do not become a "shoulder" bencher though, "feel" the chest when you work it. It is easy to let your shoulders do too much of the work, thus not much gain in your chest.
-------------- The one goal you will NEVER achieve is the one you never attempt.
If you widen your grip and press a little bit towards your feet as you come up it lessens the involvement of your shoulders and hits your chest harder. But don't make the mistake of training only the muscle groups that you think look impressive (chest, biceps) your physique will lokk tons better if you hit all of your muscle groups!