WordPress: Custom Logo Login

custom-logo.php

/*--- Custom Login Image ---*/

function my_custom_login_logo() {
    echo '<style type="text/css">
        h1 a {
        background-image:url('.get_bloginfo('template_directory').'/images/login_logo.png) !important;
         }
    </style>';
}

add_action('login_head', 'my_custom_login_logo');