It's not illegal in Europe except maybe Germany and that's more because of not being able to assign moral rights in work for hire than anything to do with at work/not at work.

I work in Europe and every company I've ever worked for has had a substantially similar clause.

It's legal and automatic that the company has rights to invetions you came up with at work (if invention is associated in any way with your tasks) but company has no right to anything you do, think or create outside of your working hours with your own equipment.

That's the way it is in Poland.