make loaded swf invisible

I'm using this code to load in a random swf. I would like to make it invisible until I need it further down the timeline.
I can't make it invisible. Am I coding wrong or is there some other principal at work.

Thanks

var openPixs:Array = new Array ("openPix1.swf", "openPix2.swf", "openPix3.swf", "openPix4.swf");
function randomBackground() {
var randomNumber = random (openPixs.length);
_root.w1.word1x.pix1.loadMovie (openPixs[randomNumber]);
_root.w1.word1x.pix1._visible = false;
};

randomBackground();