A sulfonic acid derivative, wherein the sulfonic acid derivative is represented by the following general formula (1):

R.sup.1COOCH.sub.2CH.sub.2CFHCF.sub.2SO.sub.3.sup.−M.sup.+  (1)

where: R.sup.1 represents a monovalent organic group having carbon number of 1 to 200, having at least one hydroxyl group and optionally having a substituent other than the hydroxyl group; and M.sup.+ represents a counter cation.

A sulfuric acid ester containing a plurality of carbonyl groups or a salt thereof, and a surfactant. The sulfuric acid ester is a compound represented by the following formula:
R.sup.1—C(═O)—R.sup.2—C(═O)—R.sup.3—OSO.sub.3X
wherein R.sup.1, R.sup.2 and R.sup.3 are defined herein; X is H, a metal atom, NR.sup.4.sub.4, imidazolium optionally containing a substituent, pyridinium optionally containing a substituent, or phosphonium optionally containing a substituent, where R.sup.4s are each H or an organic group and are the same as or different from each other; and any two of R.sup.1, R.sup.2, and R.sup.3 optionally bind to each other to form a ring. Also disclosed is a surfactant containing the sulfuric acid ester and an aqueous dispersant containing the sulfuric acid ester.

An optical filter includes: an absorption layer including a first near-infrared absorbing dye (D1), a second near-infrared absorbing dye (D2), and a transparent resin; and a reflection layer including a dielectric multilayer film. The dye (D1) and the dye (D2) are squarylium compounds satisfying following (1) to (3). (1) The dye (D1) has a maximum absorption wavelength λ.sub.max(D1) within a range of 680 to 730 nm, and the difference between a wavelength at which a transmittance is 80% on the shorter wavelength side than λ.sub.max(D1) when the concentration is adjusted such that a transmittance at λ.sub.max(D1) is 10%, and λ.sub.max(D1) is 100 nm or less. (2) The dye (D2) has a maximum absorption wavelength λ.sub.max(D2) within a range of 720 to 770 nm. (3) A value obtained by subtracting λ.sub.max(D1) from λ.sub.max(D2) is 30 nm or more and 85 nm or less.

An optical filter includes: an absorption layer including a first near-infrared absorbing dye (D1), a second near-infrared absorbing dye (D2), and a transparent resin; and a reflection layer including a dielectric multilayer film. The dye (D1) and the dye (D2) are squarylium compounds satisfying following (1) to (3). (1) The dye (D1) has a maximum absorption wavelength λ.sub.max(D1) within a range of 680 to 730 nm, and the difference between a wavelength at which a transmittance is 80% on the shorter wavelength side than λ.sub.max(D1) when the concentration is adjusted such that a transmittance at λ.sub.max(D1) is 10%, and λ.sub.max(D1) is 100 nm or less. (2) The dye (D2) has a maximum absorption wavelength λ.sub.max(D2) within a range of 720 to 770 nm. (3) A value obtained by subtracting λ.sub.max(D1) from λ.sub.max(D2) is 30 nm or more and 85 nm or less.

A dimming agent according to one or more embodiments is disclosed that may include at least one of terbium, praseodymium, manganese, titanium. A diffuse reflection intensity of the dimming agent in a wavelength of from 400 nm to 750 nm may be 80% or less.

Provided are: a fluorine-containing ether compound, a fluorine-containing ether composition, and a coating liquid that are capable of forming a surface layer having excellent durability; and an article that has a surface layer having excellent durability. The present invention provides a fluorine-containing ether compound represented by formula (A1) or formula (A2) below.

R.sup.fO—(R.sup.f1O).sub.m—R.sup.1-L.sup.1-R.sup.2-Q.sup.1(-T).sub.n  formula (A1)

(T-).sub.nQ.sup.1-R.sup.2-L.sup.1-R.sup.1—O—(R.sup.f1O).sub.m—R.sup.1-L.sup.1-R.sup.2-Q.sup.1(-T).sub.n  formula (A2)

In the formulae, symbols are as defined in the description.

A light-absorbing material includes a compound represented by the formula (1) below. In the formula (1), L.sup.1 to L.sup.3 are each independently represented by the formula (2) or (3) below:

##STR00001##

Provided are an ultraviolet absorbing agent including a compound represented by Formula (1), in which the ultraviolet absorbing agent has a maximum absorption wavelength in a wavelength range of 350 to 390 nm in an ethyl acetate solution, and a value obtained by dividing an absorbance at a wavelength of 430 nm by an absorbance at the maximum absorption wavelength is 0.01 or less, a resin composition, a cured substance, and an optical member which include the ultraviolet absorbing agent, a method of producing an ultraviolet absorbing agent, and a compound. In Formula (1), X.sup.1 and X.sup.2 each independently represent a cyano group or the like, R.sup.1 and R.sup.2 each independently represent an alkyl group or the like, and R.sup.3 and R.sup.4 each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group, or an aryloxy group.

##STR00001##

A sulfonium salt represented by a following general formula (1),

##STR00001##

wherein in the general formula (1), each of R.sup.1 to R.sup.3 is independently an alkyl group, an aryl group, or a heteroaryl group;

at least one carbon-carbon single bond contained in the alkyl group is optionally substituted with a carbon-carbon double bond or a carbon-carbon triple bond;

at least one methylene group contained in the alkyl group is optionally substituted with at least one divalent heteroatom-containing group;

Ar.sup.1 is an arylene group;

at least one of R.sup.1, R.sup.2, R.sup.3 and Ar.sup.1 has at least one substituent (R);

at least two of R.sup.1 to R.sup.3, Ar.sup.1, and substituent (R) optionally form a ring;

A is a divalent group selected from a group consisting of —S—, —SO—, and —SO.sub.2—;

Ar.sup.1 is substituted with A at an ortho-position with respect to a sulfonio group (S.sup.+); and

X.sup.− is an anion.

Amines and amine derivatives that improve the buffering range, and/or reduce the chelation and other negative interactions of the buffer and the system to be buffered. The reaction of amines or polyamines with various molecules to form polyamines with differing pKa's will extend the buffering range, derivatives that result in polyamines that have the same pKa yields a greater buffering capacity. Derivatives that result in zwitterionic buffers improve yield by allowing a greater range of stability.