Provided are a fluoropolyether compound having high heat resistance and capable of maintaining a surface protection layer even under high temperature, and a lubricant and a magnetic disk that contain the fluoropolyether compound. The fluoropolyether compound includes: three groups whose main chain contains a perfluoropolyether chain; and a trivalent linking group represented by Formula (1) below, the three groups being bound together via the trivalent linking group:

##STR00001##

where R.sub.1 is a saturated hydrocarbon group having 1 to 3 carbon atoms, a perfluoroalkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a hydroxyl group, or an amino group, and A.sub.1, A.sub.2, and A.sub.3 are each independently an aromatic group.

This fluorine-containing ether compound is represented by Formula (1).

R.sup.1—R.sup.2—CH.sub.2—R.sup.3—CH.sub.2—R.sup.4—R.sup.5  (1) (in Formula (1), R.sup.1 is an aryl group or an aralkyl group, R.sup.2 is a divalent linking group having 0 or 1 polar group, R.sup.3 is a perfluoropolyether chain, R.sup.4 is a divalent linking group having 2 or 3 polar groups, and R.sup.5 is an aryl group or an aralkyl group.)

This fluorine-containing ether compound is represented by formula (1) shown below.

R.sup.1—CH.sub.2—R.sup.2—CH.sub.2—R.sup.3  (1)

In formula (1), R.sup.2 is a perfluoropolyether chain represented by a formula (2) shown below. R.sup.1 is a terminal group that is bonded to R.sup.2 via a CH.sub.2 group, and is represented by a formula (3) shown below. R.sup.3 is bonded to R.sup.2 via a CH.sub.2 group, is a terminal group having at least one hydroxyl group, and may be the same as, or different from, R.sup.1.

—(CF.sub.2).sub.p-1—O—((CF.sub.2).sub.pO).sub.q—(CF.sub.2).sub.p-1—  (2)

In formula (2), p represents an integer of 2 to 3, and q indicates the average polymerization degree and is a number within a range from 1 to 20.

—O(CH.sub.2—CH(OH)—CH.sub.2—O).sub.2—CH.sub.2—(CH.sub.2).sub.n,—OH  (3)

In formula (3), n represents an integer of 1 to 8.

To provide a lubricant solution capable of forming a uniform coating film by using a solvent composition which has a small impact on the global environment and which is excellent in solubility of the fluorinated ether compound, and a method for producing a substrate provided with a lubricant coating film. A lubricant solution comprising a solvent composition which comprises a HCFO and at least one member selected from the group consisting of 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorohexane, 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorooctane, nonafluorobutyl methyl ether, nonafluorobutyl ethyl ether and 3-methoxy-4-trifluoromethyl-1,1,1,2,2,3,4,5,5,5-decafluoropentane, and a fluorinated ether compound which is a fluorinated ether compound having a perfluoropolyether chain and CF.sub.3 groups at both terminals, wherein the perfluoropolyether chain does not have a branched structure.

Provided are a magnetic disk and, in particular, a compound which makes it possible to realize a lubricant having excellent heat resistance and solubility in a fluorine-based solvent. A perfluoropolyether compound in accordance with an aspect of the present invention has, in hydrocarbon groups at both terminals thereof, five or six hydroxyl groups in total.

The present invention relates to a composition for lubricating a propulsion system of an electric or hybrid vehicle, comprising at least one base oil and at least one fire retardant corresponding to formula (I)
R.sub.F-L-R.sub.H  (I) in which R.sub.F is a perfluorinated or partially fluorinated group, R.sub.H is a hydrocarbon-based group, and L is a linker. The invention also relates to the use of at least one fire retardant of formula (I), in a composition for lubricating a propulsion system of an electric or hybrid vehicle, including at least one battery, to give it ignition-resistance properties. Finally, the invention relates to a process for cooling and fire-protecting a battery of a propulsion system of an electric or hybrid vehicle, comprising at least one step of placing at least one battery, in particular a lithium-ion or nickel-cadmium battery, in contact with a composition according to the invention.

A fluorine-containing ether compound represented by a formula (1) shown below.

R.sup.1—(O(CH.sub.2).sub.a).sub.b-[A]-[B]—O—CH.sub.2—R.sup.2—CH.sub.2—R.sup.3  (1)

(In the formula (1), R.sup.1 is an alkyl group which may have a substituent, or an organic group having at least one double bond or triple bond. Further, a represents an integer of 2 to 4, and b is 0 or 1. [A] is represented by a formula (2): —(OCH.sub.2CH(OH)CH.sub.2).sub.c— (wherein c is 1 or 2). [B] is represented by a formula (3): —(O(CH.sub.2).sub.eCH(OH)CH.sub.2).sub.d— (wherein d is 0 or 1, and e represents an integer of 2 to 4). However, the sum of c in the formula (2) and d in the formula (3) is 2. R.sup.2 is a perfluoropolyether chain. R.sup.3 is represented by a formula (4): —(OCH.sub.2CH(OH)CH.sub.2).sub.2—O—CH.sub.2(CH.sub.2).sub.fOH (wherein f represents an integer of 2 to 5).

The present invention relates to a magnetic recording medium in which a lubricant layer contains a compound A represented by general formula (1) and a compound B represented by general formula (2), satisfying (A/B)=0.2 to 3.0, and has an average thickness of 0.8 nm to 2 nm. R.sup.1—C.sub.6H.sub.4OCH.sub.2CH(OH)CH.sub.2OCH.sub.2—R.sup.2—CH.sub.2OCH.sub.2CH(OH)CH.sub.2OH . . . (1) (R.sup.1 is an alkoxy group having 1 to 4 carbon atoms. R.sup.2 is —CF.sub.2O(CF.sub.2CF.sub.2O).sub.x(CF.sub.2O).sub.yCF.sub.2— (x, y=0 to 15), —CF.sub.2CF.sub.2O(CF.sub.2CF.sub.2CF.sub.2O).sub.zCF.sub.2CF.sub.2— (z=1 to 15), —CF.sub.2CF.sub.2CF.sub.2O(CF.sub.2CF.sub.2CF.sub.2CF.sub.2).sub.nCF.sub.2CF.sub.2CF.sub.2— (n=0 to 4). HOCH.sub.2CF.sub.2CF.sub.2O(CF.sub.2CF.sub.2CF.sub.2O).sub.mCF.sub.2CF.sub.2CH.sub.2OCH.sub.2CH(OH)CH.sub.2OH . . . (2) (m is an integer).

A fluorine-containing ether compound represented by R.sup.1—R.sup.2—CH.sub.2—R.sup.3—CH.sub.2—R.sup.4—R.sup.5 is provided. (R.sup.3 is a perfluoropolyether chain; R.sup.1 and R.sup.5 are each independently any one of an alkyl group that may have a substituent, an organic group having at least one double bond or at least one triple bond, and a hydrogen atom; and —R.sup.2—CH.sub.2—R.sup.3 is represented by Formula (2), and R.sup.3—CH.sub.2—R.sup.4— is represented by Formula (3))
-[A]-[B]—O—CH.sub.2—R.sup.3  (2)
R.sup.3—CH.sub.2—O—[C]-[D]-  (3)
([A] is represented by Formula (4), [B] is represented by Formula (5), [C] is represented by Formula (6), [D] is represented by Formula (7), and in the formula, a and b are integers of 0 to 2, c is an integer of 2 to 5, d and f are integers of 0 to 2, and e is an integer of 2 to 5, and at least one of b and d in the formula is 1 or more) ##STR00001##

Provided is a compound with which a lubricant having excellent adhesion to a magnetic disk, particularly to a protective layer can be provided. A perfluoropolyether compound in accordance with one aspect of this invention has a structure in which two perfluoropolyethers are bonded to each other through an aliphatic ether, the aliphatic ether including a carbon atom to which a primary alcohol is bonded.