Transparent substrate provided with thin multilayer coating

A transparent substrate constituting a high-temperature heating device with a multilayer thin film coating, wherein

• the multilayer thin film coating includes a lower dielectric layer, a lower protective layer, a metal functional layer having an infrared reflection function, an upper protective layer, and an upper dielectric layer, which are sequentially laminated on the transparent substrate,
• the thickness of the metal function layer is 12 nm or more, and
• the thickness of the lower protective layer is larger than that of the upper protective layer and the thickness of the lower protective layer is 2 nm or more,
• wherein the lower dielectric layer includes a lower barrier layer and a planarization layer on the lower barrier layer, and the planarization layer is formed in contact directly under the lower protective layer, and
• wherein the planarization layer is formed by doping silicon nitride with zirconium (Zr).