Film, liquid composition, optical element, and imaging apparatus
A film ( 1 ) includes hollow particles ( 10 ) and a binder ( 20 ). The hollow particles are made of a material having a refractive index of 1.15 to 2.70. The binder ( 20 ) is formed of at least a polysilsesquioxane and binds the hollow particles ( 10 ). The film ( 1 ) satisfies at least one of requirements Ib/Ia≥0.7 and Ib/Ic≥0.3. Ia is an absorbance derived from a hydrocarbon group not directly bonded to a silicon atom, the absorbance being determined by attenuated total reflection using a Fourier transform infrared spectrophotometer. Ib is an absorbance derived from a bond between a silicon atom and a non-reactive functional group. Ic is an absorbance derived from a bond between a silicon atom and a hydroxy group.
1. A film comprising:
hollow particles made of a material having a refractive index of 1.15 to 2.70; and
a binder, comprising a polysilsesquioxane, that binds the hollow particles,
the film having an absorbance spectrum capable of being measured by an attenuated total reflection method with a Fourier transform infrared spectrometer,
the absorbance spectrum having an absorbance of Ia determined based on a local maximum of absorbance in an absorption band that is derived from a hydrocarbon group not directly bonded to a silicon atom, an absorbance of Ib determined based on a local maximum of absorbance in an absorption band that is derived from a bond between a silicon atom and a non-reactive functional group, and an absorbance of Ic determined based on a local maximum of absorbance in an absorption band that is derived from a bond between a silicon atom and a hydroxy group,
wherein at least one of requirements Ib/Ia≥0.7 and Ib/Ic≥0.3 is satisfied.
2. The film according to claim 1 , wherein the requirements of Ib/Ia≥0.7 and Ib/Ic≥0.3 are further satisfied.
3. The film according to claim 1 , wherein
the absorbance spectrum further having a first absorbance of Id at a first wavenumber, a second absorbance of Ie at a second wavenumber greater than the first wavenumber, and a third absorbance of If at a third wavenumber greater than the second wavenumber,
each of Id, le, and If is determined based on a local maximum of absorbance in an absorption band that is derived from a bond between one oxygen atom and two silicon atoms,
wherein at least one of requirements of Id/Ib≤60, Ie/Ib≤20, and If/Ib≤174 is satisfied.
4. The film according to claim 3 , wherein the requirements of Id/Ib≤60, Ie/Ib≤20, and If/Ib≤174 are further satisfied.
5. The film according to claim 1 , wherein the polysilsesquioxane comprises a first polysilsesquioxane that has a hydrocarbon group including 16 or less carbon atoms, the hydrocarbon group bonding to a silicon atom.
6. The film according to claim 1 , wherein the hollow particles have an average particle diameter of 10 to 150 nm.
7. The film according to claim 1 , wherein the hollow particles are made of at least one selected from the group consisting of silica, magnesium fluoride, alumina, aluminosilicate, titania, and zirconia.
8. The film according to claim 1 , having a refractive index of 1.35 or less.
9. A liquid composition, comprising:
hollow particles made of a material having a refractive index of 1.15 to 2.70;
a polysilsesquioxane; and
a solvent,
the liquid composition capable of being cured to form a film having an absorbance spectrum capable of being measured by an attenuated total reflection method with a Fourier transform spectrometer,
the absorbance spectrum having an absorbance of Ia determined based on a local maximum of absorbance in an absorption band that is derived from a hydrocarbon group not directly bonded to a silicon atom, an absorbance of Ib determined based on a local maximum of absorbance in an absorption band that is derived from a bond between a silicon atom and a non-reactive functional group, and an absorbance of Ic determined based on a local maximum of absorbance in an absorption band that is derived from a bond between a silicon atom and a hydroxy group,
wherein at least one of requirements Ib/Ia≥0.7 and Ib/Ic≥0.3 is satisfied.
10. The liquid composition according to claim 9 , wherein the requirements of Ib/Ia≥0.7 and Ib/Ic≥0.3 are satisfied.
11. The liquid composition according to claim 9 , wherein
the absorbance spectrum further having a first absorbance of Id at a first wavenumber, a second absorbance of Ie at a second wavenumber greater than the first wavenumber, and a third absorbance of If at a third wavenumber greater than the second wavenumber,
each of Id, le, and If is determined based on a local maximum of absorbance in an absorption band that is derived from a bond between one oxygen atom and two silicon atoms,
wherein at least one of requirements of Id/Ib≤60, Ie/Ib≤20, and If/Ib≤174 is satisfied.
12. The liquid composition according to claim 11 , wherein the requirements of Id/Ib≤60, Ie/Ib≤20, and If/Ib≤174 are satisfied.
13. The liquid composition according to claim 9 , wherein the polysilsesquioxane comprises a first polysilsesquioxane that has a hydrocarbon group including 16 or less carbon atoms, the hydrocarbon group bonding to a silicon atom.
14. The liquid composition according to claim 9 , wherein the hollow particles have an average particle diameter of 10 to 150 nm.
15. The liquid composition according to claim 9 , wherein the hollow particles are made of at least one selected from the group consisting of silica, magnesium fluoride, alumina, aluminosilicate, titania, and zirconia.
16. An optical element comprising the film according to claim 1 .
17. An imaging apparatus comprising the optical element according to claim 16 .