The design of a screen for outdoor use is totally different than a "normal" indoor screen. A common design for outdoor use is called transreflective, basically the light for the screen comes from the front and is reflected back. That means that the brighter the light the better so outdoors works great. In the cf-01 we have a transmissive screen which has the light coming from behind. So to use it outdoors you would need a back light that is brighter than the sunlight landing on the screen, which is a very tall order.
There is a company, Man and Machine I think, that can apply a layer to the lcd itself that increases brightness but it is still not outdoors bright. This was discussed on a toshiba libretto list a few years ago and while the addition of this layer did increase brightness, thereby allowing lower backlight settings and the expected battery life increase, it was very expensive ($500 I think) and required sending the computer to them to be rebuilt.
I have never seen any sort of film that could be applied to the surface that would fix this problem. When displays are used outdoors they are either designed for it or placed within some sort of hood to shield them from the light.