A mono or multi-layer polyester film, wherein at least one layer of the film comprises at least one polyester in an amount ranging from 20.0 to < 70 wt.-% and a surface-treated filler material product in an amount ranging from > 30 to 80.0 wt.-%, based on the total weight of the layer, wherein the surface-treated filler material product comprises A) at least one ground calcium carbonate-comprising filler material having a weight median particle size d 50 in the range from 0.5 μm to 3.0 μm, and B) a treatment layer on the surface of the at least one ground calcium carbonate-comprising filler material comprising i. a phosphoric acid ester blend of one or more phosphoric acid mono-ester and salty reaction products thereof and/or one or more phosphoric acid di-ester and salty reaction products thereof, and/or ii. at least one saturated aliphatic linear or branched carboxylic acid and salty reaction products thereof, and/or iii. at least one aliphatic aldehyde and/or salty reaction products thereof, and/or iv. at least one mono-substituted succinic anhydride consisting of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from at least C 2 to C 30 in the substituent and/or salty reaction products thereof, and/or v. at least one polydialkylsiloxane, and/or vi. mixtures of the materials according to i. to v., wherein the surface-treated filler material product comprises the treatment layer in an amount of from 0.1 to 2.3 wt.-%, based on the total dry weight of the at least one ground calcium carbonate-comprising filler material. A) at least one ground calcium carbonate-comprising filler material having a weight median particle size d 50 in the range from 0.5 μm to 3.0 μm, and B) a treatment layer on the surface of the at least one ground calcium carbonate-comprising filler material comprising i. a phosphoric acid ester blend of one or more phosphoric acid mono-ester and salty reaction products thereof and/or one or more phosphoric acid di-ester and salty reaction products thereof, and/or ii. at least one saturated aliphatic linear or branched carboxylic acid and salty reaction products thereof, and/or iii. at least one aliphatic aldehyde and/or salty reaction products thereof, and/or iv. at least one mono-substituted succinic anhydride consisting of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from at least C 2 to C 30 in the substituent and/or salty reaction products thereof, and/or v. at least one polydialkylsiloxane, and/or vi. mixtures of the materials according to i. to v., wherein the surface-treated filler material product comprises the treatment layer in an amount of from 0.1 to 2.3 wt.-%, based on the total dry weight of the at least one ground calcium carbonate-comprising filler material. i. a phosphoric acid ester blend of one or more phosphoric acid mono-ester and salty reaction products thereof and/or one or more phosphoric acid di-ester and salty reaction products thereof, and/or ii. at least one saturated aliphatic linear or branched carboxylic acid and salty reaction products thereof, and/or iii. at least one aliphatic aldehyde and/or salty reaction products thereof, and/or iv. at least one mono-substituted succinic anhydride consisting of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from at least C 2 to C 30 in the substituent and/or salty reaction products thereof, and/or v. at least one polydialkylsiloxane, and/or vi. mixtures of the materials according to i. to v.,