I managed to open it and clean the space between the LCD and the backlight based on the video from the below link.
However, it was really really difficult to make dust free. After removing white dusts, black dusts came up. After cleaning black dusts, white dusts came back. You will need an alcohol swab, a clean microfiber towllette, camera lens dust blower (Don't use the one from canister as it sometimes blows some liquid that is very very difficult to clean up), and Scotch Magic tape.
Long time ago, I thought it's sealed around the space, but it was clearly detachable. Try or not try, it's up to you.