On the Null Scrolls in Minkowski 3-space

We study ruled surfaces with lightlike ruling in Minkowski 3-space which are said to be null-scrolls.Even that the result is a consequence of some well-known results involving the Gauss map, we give another approach to classify all null-scrolls under the condition where is the Laplace operator with respect to the first fundamental form and the set of 3 real matrices.