Diffuse reflector, diffuse reflective article, optical display, and method for producing a diffuse reflector

1. A diffuse reflector comprising a consolidated nonwoven sheet having a thickness standard deviation of about 15 μm or less and a photopic reflectance of at least about 94% over the wavelength range of 380 nm to 780 nm.

2. The diffuse reflector of claim 1 , wherein said thickness standard deviation is about 10 μm or less.

3. The diffuse reflector of claim 1 , wherein said consolidated nonwoven sheet has an average thickness of from about 150 μm to about 400 μm.

4. The diffuse reflector of claim 1 produced by a method comprising calendering a nonwoven sheet having a first average thickness, a first thickness standard deviation and a first photopic reflectance, and thereby forming said consolidated nonwoven sheet having a consolidated average thickness less than said first average thickness, a consolidated thickness standard deviation less than said first thickness standard deviation, and a consolidated photopic reflectance substantially identical to said first photopic reflectance.

5. The diffuse reflector of claim 4 wherein said calendering is carried out at from about 500 pli (87 kN/m) to about 2,000 pli (350 kN/m).

6. The diffuse reflector of claim 1 , wherein said consolidated nonwoven sheet comprises a plurality of plexifilamentary film-fibrils, wherein said plexifilamentary film-fibrils comprise polymer containing pores, and wherein the specific pore volume is at least about 10 cm 3 /m 2 for pores having a mean pore diameter as measured by mercury porosimetry of from 0.01 μm to 1.0 μm.

7. A diffuse reflective article comprising a diffuse reflector of light positioned within a structure defining an optical cavity, wherein said diffuse reflector of light comprises a consolidated nonwoven sheet having a thickness standard deviation of about 15 μm or less and a photopic reflectance of at least about 94% over the wavelength range of 380 nm to 780 nm.

8. An optical display, comprising:

(i) a structure defining an optical cavity;

(ii) a light source positioned within said optical cavity;

(iii) a display panel through which light from said light source passes; and

(iv) a diffuse reflector positioned within said optical cavity for reflecting light from said light source toward said display panel, wherein said diffuse reflector of light comprises a consolidated nonwoven sheet having a thickness standard deviation of about 15 μm or less and a photopic reflectance of at least about 94% over the wavelength range of 380 nm to 780 nm.

9. A method for producing a diffuse reflector comprising a consolidated nonwoven sheet, comprising applying mechanical force to a nonwoven sheet having a first average thickness, a first thickness standard deviation and a first photopic reflectance, and thereby forming a consolidated nonwoven sheet having a consolidated average thickness less than said first average thickness, a consolidated thickness standard deviation less than said first thickness standard deviation, and a consolidated photopic reflectance substantially identical to said first photopic reflectance.

10. The method of claim 9 , wherein said consolidated average thickness is from about 75% to about 95% of said first average thickness, and said consolidated thickness standard deviation is from about 25% to about 55% of said first thickness standard deviation.

11. The method of claim 9 , wherein said consolidated average thickness is from about 150 μm to about 400 μm.

12. The method of claim 9 , wherein said consolidated thickness standard deviation is about 15 μm or less.

13. The method of claim 9 , wherein said consolidated thickness standard deviation is about 10 μm or less.

14. The method of claim 9 , wherein said diffuse reflector has a photopic reflectance of at least about 94% over the wavelength range of 380 nm to 780 nm.

15. The method of claim 9 , wherein said nonwoven sheet comprises a plurality of plexifilamentary film-fibrils, wherein said plexifilamentary film-fibrils comprise polymer containing pores, and wherein the specific pore volume is at least about 10 cm 3 /m 2 for pores having a mean pore diameter as measured by mercury porosimetry of from 0.01 μm to 1.0 μm.

16. The method of claim 9 , wherein said applying mechanical force comprises calendering.

17. The method of claim 16 , wherein said calendering is carried out at from about 500 pli (87 kN/m) to about 2,000 pli (350 kN/m).

18. The method of claim 9 , wherein said consolidated nonwoven sheet further comprises on at least one face thereof a binder layer comprising a binder and a scatterer of visible light dispersed in said binder.

19. The method of claim 9 , wherein said nonwoven sheet comprises a laminate of a plurality of layers of nonwoven sheet.

20. A method of improving light reflectivity in a device requiring diffuse reflectivity of light comprising:

(i) providing a diffuse reflector comprising a consolidated nonwoven sheet having a thickness standard deviation of about 15 μm or less and a photopic reflectance of at least about 94% over the wavelength range of 380 nm to 780 nm; and

(ii) positioning said diffuse reflector within said device to cause light energy to reflect off of said diffuse reflector.