Interlayer film for laminated glass

1. An interlayer film, comprising a composition comprising:

a polyvinyl acetal with an acetalization degree of from 60 to 80 mol %, a content of a vinyl ester monomer unit of from 0.1 to 20 mol % and a viscosity-average degree of polymerization of from 1400 to 4000, and

light-diffusing fine particles having an average particle size of from 0.20 to 10 μm,

wherein an absolute value difference between a refractive index of the light-diffusing fine particles and a refractive index of the composition excluding the light-diffusing fine particles is 0.20 or more;

a haze as measured in accordance with JIS K 7105 for a laminated glass prepared by sandwiching the interlayer film between two glass sheets with a thickness of 3 mm is 20% or less, and

the interlayer film satisfies formulas (1) and (2):

( A−B )/ A< 0.80  (1); and

1.00×10 −2 <( b/y )/( a/x )<2.00×10 −1   (2),

wherein A is a peak-top molecular weight of the polyvinyl acetal as measured by a differential refractive index detector in gel-permeation chromatographic measurement of said interlayer film heated at 230° C. for 3 hours;

a is a signal strength at the peak-top molecular weight A;

B is a peak-top molecular weight of the polyvinyl acetal as measured by an absorptiometer, measured at 280 nm wavelength, in gel-permeation chromatographic measurement of said interlayer film heated at 230° C. for 3 hours;

b is a signal strength at the peak-top molecular weight B;

x is a signal strength at a peak-top molecular weight as measured by a differential refractive index detector in gel-permeation chromatographic measurement of a monodisperse polymethyl methacrylate with a weight-average molecular weight of about 85,000; and

y is a signal strength at a peak-top molecular weight as measured by an absorptiometer, measured at 220 nm wavelength, in gel-permeation chromatographic measurement of said monodisperse polymethyl methacrylate.

2. The interlayer film of claim 1 , which further satisfies formulas (3) and (4):

( A−C )/ A< 0.80  (3); and

5.00×10 − <( c/y )/( a/x )<7.00×10 −2   (4),

wherein A is a peak-top molecular weight of the polyvinyl acetal as measured by a differential refractive index detector in gel-permeation chromatographic measurement of said interlayer film heated at 230° C. for 3 hours;

C is a peak-top molecular weight of the polyvinyl acetal as measured by an absorptiometer, measured at 320 nm wavelength, in gel-permeation chromatographic measurement of said interlayer film for a laminated glass heated at 230° C. for 3 hours;

c is a signal strength at the peak-top molecular weight C

a is a signal strength at the peak-top molecular weight A;

x is a signal strength at a peak-top molecular weight as measured by a differential refractive index detector in gel-permeation chromatographic measurement of a monodisperse polymethyl methacrylate with a weight-average molecular weight of about 85,000; and

y is a signal strength at a peak-top molecular weight as measured by an absorptiometer, measured at 220 nm wavelength, in gel-permeation chromatographic measurement of said monodisperse polymethyl methacrylate.

3. The interlayer film of claim 1 ,

wherein said polyvinyl acetal is a polyvinyl butyral.

4. The interlayer film of claim 1 , further comprising a plasticizer.

5. The interlayer film of claim 4 , wherein the plasticizer is triethylene glycol di(2-ethylhexanoate).

6. The interlayer film of claim 1 ,

wherein said light-diffusing fine particles comprise an inorganic compound.

7. The interlayer film of claim 6 ,

wherein said inorganic compound is a metal oxide.

8. The interlayer film of claim 7 , wherein said metal oxide is titanium oxide.

9. The interlayer film of claim 7 , wherein said metal oxide is zinc oxide.

10. The interlayer film of claim 6 ,

wherein the composition comprises said light-diffusing fine particles in an amount from 0.001 to 0.040% by mass of the composition.

11. A laminated glass consisting of:

the interlayer film of claim 1 and

a plurality of glass sheets bonded via the interlayer film.

12. A light diffusion plate, comprising:

the laminated glass of claim 11 , as a structural component.