Coating composition for the formation of low refractive index layer, antireflection film, polarizing plate and liquid crystal display device

1. A coating composition for the formation of a low refractive index layer, comprising:

a fluorine-containing olefin-based polymer that has a polysiloxane segment represented by formula 1 in its main chain, has a fluorine content of 30 mass % or more, and contains a plurality of ethylenically unsaturated groups;

a hollow silica fine particle having an average particle diameter of 5 to 200 nm and a refractive index of 1.17 to 1.40:

wherein R 1 and R 2 , which may be the same or different, each represents a hydrogen atom, an alkyl group, an alkyl halide group or an aryl group; and

a polysiloxane compound having a reactive organic functional group represented by formula 7:

wherein R 1 to R 4 each represents a substituent having a carbon number of 1 to 20; when each substituent is present in a plural number, these groups may be the same or different; at least one group of R 1 , R 3 and R 4 represents a reactive organic functional group; x represents an integer satisfying 1≦x≦4; y represents an integer satisfying 10≦y≦500; z represents an integer satisfying 0≦z≦500; and the compound may be a random copolymer or a block copolymer.

2. The coating composition for the formation of a low refractive index layer as claimed in claim 1 ,

wherein the fluorine-containing olefin-based polymer has a structural unit containing a polysiloxane segment represented by formula 1 originated in (c) an azo group-containing polysiloxane compound.

3. The coating composition for the formation of a low refractive index layer as claimed in claim 1 , which further comprises a non-hollow silica fine particle.

4. The coating composition for the formation of a low refractive index layer as claimed in claim 1 , which further comprises a polyfunctional (meth)acrylate compound having two or more (meth)acryloyl groups within one molecule.

5. The coating composition for the formation of a low refractive index layer as claimed in claim 1 ,

wherein the hollow silica fine particle is surface-treated with at least one of a hydrolysate of an organosilane represented by formula (1) and a partial condensate thereof:

(R 10 ) m —Si(X) 4-m   Formula (1)

wherein R 10 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, X represents a hydroxyl group or a hydrolyzable group, and m represents an integer of 1 to 3.

6. The coating composition for the formation of a low refractive index layer as claimed in claim 3 ,

wherein at least one of the hollow silica fine particle and the non-hollow silica fine particle is surface-treated with at least one of a hydrolysate of an organosilane represented by formula (1) and a partial condensate thereof:

(R 10 ) m —Si(X) 4-m   Formula (1)

wherein R 10 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, X represents a hydroxyl group or a hydrolyzable group, and m represents an integer of 1 to 3.

7. An antireflection film comprising:

a transparent support;

at least one hard coat layer; and

a low refractive index layer located as an outermost layer,

wherein the low refractive index layer is a layer formed by curing a coating composition for the formation of a low refractive index layer by ionizing radiation,

wherein the coating composition for the formation of a low refractive index layer comprises:

a fluorine-containing olefin-based polymer that has a polysiloxane segment represented by formula 1 in its main chain, has a fluorine content of 30 mass % or more, and contains a plurality of ethylenically unsaturated groups; and

a hollow silica fine particle having an average particle diameter of 5 to 200 nm and a refractive index of 1.17 to 1.40:

wherein R 1 and R 2 , which may be the same or different, each represents a hydrogen atom, an alkyl group, an alkyl halide group or an aryl group.

8. The antireflection film as claimed in claim 7 ,

wherein at least one of the hard coat layer and the low refractive index layer comprises:

(a) at least one of: a hydrolysate of an organosilane having a hydroxyl group or hydrolyzable group directly bonded to silicon; and a partial condensate thereof; and

(b) at least one metal chelate compound comprising: (i) a center metal including a metal selected from Zr, Ti and Al; and (ii) ligands including an alcohol represented by formula R 3 OH, wherein R 3 represents an alkyl group having a carbon number of 1 to 10, and a compound represented by formula R 4 COCH 2 COR 5 , wherein R 4 represents an alkyl group having a carbon number of 1 to 10, and R 5 represents an alkyl group having a carbon number of 1 to 10 or an alkoxy group having a carbon number of 1 to 10.

9. The antireflection film as claimed in claim 7 ,

wherein the antireflection film has a surface roughness Ra (centerline average roughness) of 0.10 μm or less and a transmitted image clarity of 60% or more.

10. The antireflection film as claimed in claim 7 ,

wherein the hard coat layer has an internal haze of 10% or more.

11. The antireflection film as claimed in claim 7 ,

wherein an intensity of scattered light at an outgoing angle of 30° in a scattered light profile of the hard coat layer as measured by a goniophotometer is from 0.01 to 0.2% based on an intensity of light at an outgoing angle of 0°.

12. The antireflection film as claimed in claim 7 ,

wherein at least one high refractive index layer having a refractive index higher than that of the transparent support is provided on the hard coat layer.

13. A polarizing plate comprising:

a polarizing film; and

two protective films on both sides of the polarizing film,

wherein the antireflection film claimed in claim 7 is used for one of the two protective films.

14. The polarizing plate as claimed in claim 13 ,

wherein the other one, which is not the antireflection film, of the two protective films is an optical compensation film having an optically anisotropic layer, the optically anisotropic layer comprising a compound having a discotic structural unit in which a disc plane of the discotic structural unit is inclined with respect to a surface of the protective film, and an angle made by the disc plane of the discotic structural unit and the surface of the protective film is changing in a depth direction of the optically anisotropic layer.

15. A liquid crystal display device comprising:

a display; and

the antireflection film claimed in claim 7 as an outermost surface layer of the display.

16. A liquid crystal display device comprising:

a display; and

the polarizing plate claimed in claim 13 as an outermost surface layer of the display.

17. An antireflection film comprising:

a transparent support;

at least one hard coat layer; and

a low refractive index layer located as an outermost layer,

wherein the low refractive index layer is a layer formed by curing the coating composition for the formation of a low refractive index layer claimed in claim 1 by ionizing radiation,

wherein at least one of the hard coat layer and the low refractive index layer comprises:

(a) at least one of: a hydrolysate of an organosilane having a hydroxyl group or hydrolyzable group directly bonded to silicon; and a partial condensate thereof; and

(b) at least one metal chelate compound comprising: (i) a center metal including a metal selected from Zr, Ti and Al; and (ii) ligands including an alcohol represented by formula R 3 OH, wherein R 3 represents an alkyl group having a carbon number of 1 to 10, and a compound represented by formula R 4 COCH 2 COR 5 , wherein R 4 represents an alkyl group having a carbon number of 1 to 10, and R 5 represents an alkyl group having a carbon number of 1 to 10 or an alkoxy group having a carbon number of 1 to 10.