Surface treatment composition

1. A surface treatment composition comprising a perfluoropolyether group-containing silane compound and a solvent, wherein

a proportion of the perfluoropolyether group-containing silane compound based on 100 parts by mass of a total amount of the perfluoropolyether group-containing silane compound and the solvent is in the range from 60 parts by mass to 99 parts by mass;

the perfluoropolyether group-containing silane compound is at least one perfluoropolyether group-containing silane compound represented by formula (A1), (A2), (C1), (C2), (D1) or (D2):

wherein:

each PFPE, at each occurrence, is independently a group represented by formula:

—(OC 6 F 12 ) a —(OC 5 F 10 ) b —(OC 4 F 8 ) c —(OC 3 X 10 6 ) d —(OC 2 F 4 ) e —(OCF 2 ) f —

wherein a, b, c, d, e and f are each independently an integer of 0 or more and 200 or less, the sum of a, b, c, d, e and f is at least 1, the occurrence order of the respective repeating units in parentheses with a, b, c, d, e or f is not limited in the formula, and each X 10 , at each occurrence, independently is a hydrogen atom, a fluorine atom or a chlorine atom;

each Rf, at each occurrence, independently represents an alkyl group having 1 to 16 carbon atoms, optionally substituted with one or more fluorine atoms;

each R 13 , at each occurrence, independently represents a hydroxyl group or a hydrolyzable group;

each R 14 , at each occurrence, independently represents a hydrogen atom or an alkyl group having 1 to 22 carbon atoms;

each R 11 , at each occurrence, independently represents a hydrogen atom or a halogen atom;

each R 12 , at each occurrence, independently represents a hydrogen atom or a lower alkyl group;

n1 with respect to each (—SiR 13 n1 R 14 3-n1 ) unit is independently an integer of 0 to 3;

each X 1 , at each occurrence, independently represents a single bond or a di- to decavalent organic group;

each X 2 , at each occurrence, independently represents a single bond or a divalent organic group;

each t, at each occurrence, is independently an integer of 2 to 10;

each α1, at each occurrence, is independently an integer of 1 to 9;

each α1′ is independently an integer of 1 to 9;

each X 5 , at each occurrence, independently represents a single bond or a di- to decavalent organic group;

each γ1, at each occurrence, is independently an integer of 1 to 9;

each γ1′ is independently an integer of 1 to 9;

each R a , at each occurrence, independently represents —Z 3 —SiR 71 p1 R 72 q1 R 73 r1 ;

each Z 3 , at each occurrence, independently represents a divalent organic group, and does not contain a siloxane bond;

each R 71 , at each occurrence, independently represents R a′ ;

R a′ has the same meaning as R a ;

the number of Si linearly linked via a Z 3 group in R a is at most 5;

each R 72 , at each occurrence, independently represents a hydroxyl group or a hydrolyzable group;

each R 73 , at each occurrence, independently represents a hydrogen atom or a lower alkyl group;

each p1, at each occurrence, is independently an integer of 0 to 2;

each q1, at each occurrence, is independently an integer of 1 to 3;

each r1, at each occurrence, is independently an integer of 0 to 2;

provided that the sum of p1, q1 and r1 with respect to (—Z 3 —SiR 71 p1 R 72 q1 R 73 r1 ) is 3;

each R b , at each occurrence, independently represents a hydroxyl group or a hydrolyzable group;

each R c , at each occurrence, independently represents a hydrogen atom or a lower alkyl group;

k1 is 3;

l1 and m1 are 0;

each X 7 independently represents a single bond or a di- to decavalent organic group;

each δ1 is independently an integer of 1 to 9;

each δ1′ is independently an integer of 1 to 9;

each R d , at each occurrence, independently represents —Z 4 —CR 81 p2 R 82 q2 R 83 r2 ;

each Z 4 , at each occurrence, independently represents an oxygen atom or a divalent organic group;

each R 81 , at each occurrence, independently represents R d′ ;

R d′ has the same meaning as R d ;

the number of C linearly bonded via a Z 4 group in R d is at most 5;

each R 82 , at each occurrence, independently represents —Y—SiR 85 n2 R 86 3-n2 ;

each Y, at each occurrence, independently represents a divalent organic group;

each R 85 , at each occurrence, independently represents a hydroxyl group or a hydrolyzable group;

each R 86 , at each occurrence, independently represents a hydrogen atom or a lower alkyl group;

n2 with respect to a (—Y—SiR 85 n2 R 86 3-n2 ) unit independently represents an integer of 1 to 3;

each R 83 , at each occurrence, independently represents a hydrogen atom, a hydroxyl group or a lower alkyl group;

each p2, at each occurrence, is independently an integer of 0 to 3;

each q2, at each occurrence, is independently an integer of 0 to 3;

each r2, at each occurrence, is independently an integer of 0 to 3;

provided that the sum of p2, q2 and r2 with respect to (—Z 4 —CR 81 p2 R 82 q2 R 83 r2 ) is 3;

each R e , at each occurrence, independently represents —Y—SiR 85 n2 R 86 3-n2 ;

each R f , at each occurrence, independently represents a hydrogen atom, a hydroxyl group or a lower alkyl group;

each k2, at each occurrence, is independently 0 or 1;

each l2, at each occurrence, is independently 2 or 3; and

each m2, at each occurrence, is independently 0 or 1;

provided that the sum of k2, l2 and m2 with respect to (CR d k2 R e l2 R f m2 ) is 3.

2. The surface treatment composition according to claim 1 , wherein the solvent is a fluorine atom-containing solvent.

3. The surface treatment composition according to claim 2 , wherein a content of water contained in the solvent is 100 ppm by mass or less.

4. The surface treatment composition according to claim 1 , having a viscosity in the range from 10 to 1000 mPa·s.

5. The surface treatment composition according to claim 1 , wherein X 10 is a fluorine atom.

6. The surface treatment composition according to claim 1 , further comprising one or more other components selected from a fluorine-containing oil, a silicone oil, an alcohol, a catalyst, a transition metal, a halide ion, a silane coupling agent, and a compound containing an atom having an unshared electron pair in a molecular structure.

7. The surface treatment composition according to claim 1 , wherein the composition is used as an antifouling coating agent or a water-proof coating agent.

8. The surface treatment composition according to claim 1 , for vacuum deposition.

9. A pellet comprising the surface treatment composition according to claim 1 .

10. An article comprising a base material, and a layer formed from the surface treatment composition according to claim 1 , on a surface of the base material.

11. The article according to claim 10 , wherein the article is an optical member.