Composition for infrared-absorbing layers, infrared-cut filter, and imaging apparatus

1. A composition for infrared-absorbing layers, comprising:

a compound formed by copper ion and a phosphonic acid represented by the following formula (a); and

at least one selected from the group consisting of a phosphoric acid diester represented by the following formula (b1) and a phosphoric acid monoester represented by the following formula (b2):

wherein

fine particles containing at least the compound are dispersed,

a content of the phosphonic acid is 0.85 or more times and less than 2.5 times a total content of the phosphoric acid diester and the phosphoric acid monoester on a molar basis,

the content of phosphonic acid is 0.45 times to 0.9 times a content of the copper ion on a molar basis, and

in the formulae, R 1 is an alkyl group with 2 to 4 carbon atoms, R 21 , R 22 , and R 3 are each a monovalent functional group represented by —(CH 2 CH 2 O) n R 4 wherein n is an integer of 1 to 25 and R 4 is an alkyl group with 6 to 25 carbon atoms, and R 21 , R 22 , and R 3 are the same or different functional groups.

2. The composition for infrared-absorbing layers according to claim 1 , wherein the fine particles have an average particle diameter of 5 nm to 200 nm.

3. The composition for infrared-absorbing layers according to claim 1 , wherein the fine particles are formed at least by the copper ion, the phosphonic acid, and at least one of the phosphoric acid diester and the phosphoric acid monoester.

4. The composition for infrared-absorbing layers according to claim 1 , further comprising phosphoric acid.

5. The composition for infrared-absorbing layers according to claim 4 , wherein the fine particles are formed at least by the copper ion, the phosphonic acid, at least one of the phosphoric acid diester and the phosphoric acid monoester, and the phosphoric acid.

6. The composition for infrared-absorbing layers according to claim 4 , wherein

the R 1 of the phosphonic acid is a butyl group, and

when two hydroxy groups contained in one molecule of the phosphonic acid, one hydroxy group contained in one molecule of the phosphoric acid diester, one hydroxy group contained in one molecule of the phosphoric acid monoester, and two hydroxy groups contained in one molecule of the phosphoric acid are defined as reactive hydroxy groups, a content of the reactive hydroxy groups is 1.95 times to 2.5 times a content of the copper ion on a molar basis.

7. The composition for infrared-absorbing layers according to claim 1 , wherein when two hydroxy groups contained in one molecule of the phosphonic acid, one hydroxy group contained in one molecule of the phosphoric acid diester, one hydroxy group contained in one molecule of the phosphoric acid monoester, and two hydroxy groups contained in one molecule of phosphoric acid optionally contained in the composition are defined as reactive hydroxy groups, a content of the reactive hydroxy groups is 2.08 times to 2.5 times a content of the copper ion on a molar basis.

8. The composition for infrared-absorbing layers according to claim 7 , wherein the R 1 of the phosphonic acid is an ethyl group.

9. The composition for infrared-absorbing layers according to claim 1 , being free of phosphoric acid, wherein

the R 1 of the phosphonic acid is a butyl group, and

when two hydroxy groups contained in one molecule of the phosphonic acid, one hydroxy group contained in one molecule of the phosphoric acid diester, and one hydroxy group contained in one molecule of the phosphoric acid monoester are defined as reactive hydroxy groups, a content of the reactive hydroxy groups is 2.08 times to 2.3 times a content of the copper ion on a molar basis.

10. The composition for infrared-absorbing layers according to claim 1 , further comprising a matrix component.

11. The composition for infrared-absorbing layers according to claim 10 , wherein the matrix component is a polysiloxane.

12. The composition for infrared-absorbing layers according to claim 10 , wherein the content of phosphonic acid is 10 to 50 parts by mass with respect to 100 parts by mass of the matrix component.

13. An infrared-cut filter comprising:

an infrared-absorbing layer formed using the composition for infrared-absorbing layers according to claim 1 .

14. An imaging apparatus comprising:

the infrared-cut filter according to claim 13 ; and

an imaging sensor on which light transmitted through the infrared-cut filter is incident.

15. The infrared-cut filter according to claim 13 , wherein the infrared-cut filter has a spectral transmittance of 70% or more in the range of wavelengths 400 nm to 600 nm, the infrared-cut filter has a spectral transmittance of 5% or less in the range of wavelengths 800 nm to 1100 nm, and the infrared-absorbing layer has a thickness of 40 μm to 250 μm.

16. The infrared-cut filter according to claim 13 , wherein the infrared-absorbing layer has a thickness of 40 μm to 200 μm.

17. An infrared-cut filter comprising:

a first infrared-absorbing layer and a second infrared-absorbing layer that are formed using the composition for infrared-absorbing layers according to claim 1 ; and

an intermediate protective layer disposed between the first infrared-absorbing layer and the second infrared-absorbing layer.

18. The infrared-cut filter according to claim 17 , wherein the intermediate protective layer comprises a hydrolysis-condensation product of an alkoxysilane as a main component.