That's a bugger, works for me with touchpad (don't have a touchscreen).
Let's go simple and write up a small script for your startup applications.
1. Go to the 9 dots square that has smart tip Show Applications and click.
2. Start to type in (without quotes) "startup" and choose Startup Applications.
3. Choose Add
4. Type in a meaningful name, eg
5. Get the name of your touchscreen device from
For my touchpad
I have this
DELL0811:00 044E:120A Touchpad id=13
simply type in
but very occasionally, with the addition or removal of devices those numbers can change, so better is
xinput disable "DELL0811:00 044E:120A Touchpad"
6. I give it a meaningful description eg
"Turns TouchPad Off from startup"
7. Apply the changes, and reboot
Here's a couple of pictures of what mine looks like.
So you need only substitute touchscreen for my touchpad, and your touchscreen identifier from xinput for my touchpad identifier. Don't forget the quotation marks with the xinput command.
Let us know how you go.