Surface treatment agent

A composition comprising a (A) fluoropolyether group-containing polymer and a (B) siloxane polymer, wherein

• the fluoropolyether group-containing polymer is a copolymer represented by the following formula (1) or (2):
• wherein
• RF1 is Rf1—RF—Oq—;
• RF2 is —Rf2p—RF—Oq—;
• Rf1 is a C1-16 alkyl group optionally substituted with one or more fluorine atoms;
• Rf2 is a C1-6 alkylene group optionally substituted with one or more fluorine atoms;
• RF is each independently a divalent fluoropolyether group;
• p is 0 or 1;
• q is each independently 0 or 1;
• R4 is each independently at each occurrence R4a or R4b;
• R4a is each independently at each occurrence a divalent organic group having a crosslinkable group;
• R4b is each independently at each occurrence a divalent organic group not having a crosslinkable group;
• the crosslinkable group is a group containing a carbon-carbon double bond, a carbon-carbon triple bond, a cyclic ether group, a hydroxyl group, a thiol group, an amino group, an azide group, a nitrogen-containing heterocyclic group, an isocyanate group, a halogen atom, a phosphoric acid-containing group, or a silane coupling group;
• or a precursor group thereof;
• n is an integer of 1 to 100;
• Xa is each independently a divalent organic group;
• Xb is each independently a divalent organic group;
• Ra is each independently an alkyl, phenyl, —SRa1, —ORa2, —NRa32,
• Ra1, Ra2, Ra3, Ra4, Ra5, and Ra6 are each independently an alkyl group or a phenyl group;
• and
• Ra7 is a hydrogen or halogen atom,
• and
• the siloxane polymer has a number average molecular weight of more than 350 and less than 10,000.