Curves on irrational ruled surfaces whose complements are of non-general type

Let $B$ be a curve on an irrational ruled surface $X$. We prove that the logarithmic Kodaira dimension of $X-B$ equals the Iitaka dimension of $K_X+B$ and give a rough configuration of $B$ when the logarithmic Kodaira dimension of $X-B$ is less than two. Next, we study the logarithmic multicanonical system of $X-B$ when the logarithmic Kodaira dimension of $X-B$ equals one and prove that its logarithmic $m$-canonical system gives either a ${\mathbb{P}}^1$-fibration or an elliptic fibration if $m\ge 12$.