In case you do not want to see notifications for iMessage, go to Settings > Notification Center and move Messages app to Not in notification center. Also disable Banners or Alerts for it, and set it to None.
Now Messages will not be showing on iPhone, but you will have a notification sound and unread number showing as Badge app icon.
In case you dont want to be disturbed by a sound, temporary disable sound also.
PS. This will not showup normal SMS messages also, but you will get sound notification and badge.
Very fast temporary solution, is to enable Do not disturb mode on iPhone.
Settings > Do not disturb.
This will allow calls (if you set so), but disable all notifications until swithed off again.