Backlight panels for station ads

This is is how I have built the large advertisement panels of the Shin-Yukari station entrance hall:

• Cut 1-mm-thick transparent acrylic sheet to size
• Using a sharp knife, score horizontal lines every 1 mm at the back of the sheet. They will reflect the light coming from the top side towards the front of the panel.
• Glue aluminum foil on the left, bottom and right sides of the acrylic sheet to prevent light from leaking from these sides.
• Cut a thin white styrene sheet to size and paste it at the back of the acrylic panel.
• Print, cut and paste the ad, glue it on the front of the acrylic piece
• LEDs must be attached to the top of the panel (top of the transparent acrylic sheet)