DURABLE AND SCRATCH-RESISTANT ANTI-REFLECTIVE ARTICLES

• US 20150323705A1
• Filed: 05/07/2015
• Published: 11/12/2015
• Est. Priority Date: 05/12/2014
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Hart, Shandon Dee, Koch, Karl William III, Paulson, Charles Andrew
• Granted Patent: US 9,335,444 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: C03C 17/3435 comprising a nitride, oxynitride, boronitride or carbonitride
• CPC Class Codes: C03C 21/002 to perform ion-exchange between alkali ions C03C21/005 takes precedence
• CPC Class Codes: C03C 2217/734 comprising an alternation of high and low refractive indexes
• CPC Class Codes: C03C 2217/78 Coatings specially designed to be durable, e.g. scratch-resistant
• CPC Class Codes: G02B 1/11 Anti-reflection coatings
• CPC Class Codes: G02B 1/115 Multilayers
• CPC Class Codes: G02B 1/14 Protective coatings, e.g. hard coatings
• CPC Class Codes: G02B 1/18 Coatings for keeping optical surfaces clean, e.g. hydrophobic or photo-catalytic films G02B1/16 takes precedence
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G02B 5/0221 the surface having an irregular structure G02B5/0226 takes precedence
• CPC Class Codes: G02B 5/0278 used in transmission

Abstract

Embodiments of durable, anti-reflective articles are described. In one or more embodiments, the article includes a substrate and an optical coating disposed on the major surface. The optical coating includes an anti-reflective coating and a scratch-resistant coating forming an anti-reflective surface. The article exhibits a maximum hardness of 12 GPa or greater, as measured on the anti-reflective surface by a Berkovich Indenter Hardness Test along an indentation depth of about 100 nm or greater. The articles of some embodiments exhibit a single side average light reflectance measured at the anti-reflective surface of about 8% or less over an optical wavelength regime in the range from about 400 nm to about 800 nm and a reference point color shift in transmittance or reflectance of less than about 2. In some embodiments, the article exhibits an angular color shift of about 5 or less at all angles from normal incidence to an incident illumination angle that is 20 degrees or greater.

Claims

1. An article comprising:

a substrate having a major surface; and

an optical coating disposed on the major surface and forming an anti-reflective surface, the optical coating comprising an anti-reflective coating,

the article exhibiting a maximum hardness of about 12 GPa or greater as measured on the anti-reflective surface by a Berkovich Indenter Hardness Test along an indentation depth of about 100 nm or greater;

wherein the article exhibits a single side average light reflectance measured at the anti-reflective surface of about 8% or less over an optical wavelength regime in the range from about 400 nm to about 800 nm and either one or both of;

article transmittance color coordinates in the (L*, a*, b*) colorimetry system at normal incidence under an International Commission on Illumination illuminant exhibiting a reference point color shift of less than about 2 from a reference point as measured at the anti-reflective surface, the reference point comprising at least one of the color coordinates (a*=0, b*=0) and the transmittance color coordinates of the substrate, and

article reflectance color coordinates in the (L*, a*, b*) colorimetry system at normal incidence under an International Commission on Illumination illuminant exhibiting a reference point color shift of less than about 5 from a reference point as measured at the anti-reflective surface, the reference point comprising at least one of the color coordinates (a*=0, b*=0), the color coordinates (a*=−

2, b*=−

2), and the reflectance color coordinates of the substrate,

wherein, when the reference point is the color coordinates (a*=0, b*=0), the color shift is defined by √

((a*_article)²+(b*_article)²),

wherein, when the reference point is the color coordinates (a*=−

2, b*=−

2), the color shift is defined by √

((a*_article+2)²+(b*_article+2)²), and

wherein, when the reference point is the color coordinates of the substrate, the color shift is defined by √

((a*_article−

a*_substrate)²+(b*_article−

b*_substrate)²).

2. The article of claim 1, wherein the article exhibits an angular color shift of about 5 or less at an incident illumination angle that is 20 degrees or greater, referenced to normal incidence, under an International Commission on Illumination illuminant selected from the group consisting of A series illuminants, B series illuminants, C series illuminants, D series illuminants, and F series illuminants, wherein angular color shift is calculated using the equation √

((a*₂−

a*₁)²+(b*₂−

b*₁)²), with a*₁, and b*₁ representing the coordinates of the article when viewed at normal incidence and a*₂, and b*₂ representing the coordinates of the article when viewed at the incident illumination angle.

3. The article of claim 2, wherein the article exhibits an angular color shift of about 5 or less at all incident illumination angles in the range from about 20 degrees to about 60 degrees.

4. The article of claim 2, wherein the substrate has a hardness less than the maximum hardness of the article.

5. The article of claim 1, wherein the article exhibits an abrasion resistance after a 500-cycle abrasion using a Taber Test on the anti-reflective surface comprising any one or more of

about 1% haze or less, as measured using a hazemeter having an aperture, wherein the aperture has a diameter of about 8 mm,

an average roughness Ra, as measured by atomic force microscopy, of about 12 nm or less,

a scattered light intensity of about 0.05 (in units of 1/steradian) or less, at a polar scattering angle of about 40 degrees or less, as measured at normal incidence in transmission using an imaging sphere for scatter measurements, with a 2 mm aperture at 600 nm wavelength, and

a scattered light intensity of about 0.1 (in units of 1/steradian) or less, at a polar scattering angle of about 20 degrees or less, as measured at normal incidence in transmission using an imaging sphere for scatter measurements, with a 2 mm aperture at 600 nm wavelength.

6. The article of claim 1, wherein the anti-reflective coating comprises a plurality of layers, wherein the plurality of layers comprises a first low RI layer, a second high RI layer, and an optional third layer.

7. The article of claim 6, wherein the anti-reflective coating comprises a plurality of periods such that the first low RI layer and the second high RI layer alternate.

8. The article of claim 7, wherein the anti-reflective coating comprises up to about 10 periods.

9. The article of claim 1, wherein the single side average light reflectance is about 2% or less over the optical wavelength regime at a viewing angle in the range from about 6 degrees to about 40 degrees.

10. The article of claim 1, wherein the substrate comprises an amorphous substrate or a crystalline substrate.

11. The article of claim 10, wherein the amorphous substrate comprises a glass selected from the group consisting of soda lime glass, alkali aluminosilicate glass, alkali containing borosilicate glass and alkali aluminoborosilicate glass.

12. The article of claim 11, wherein the glass is chemically strengthened and comprises a compressive stress (CS) layer with a surface CS of at least 250 MPa extending within the chemically strengthened glass from a surface of the chemically strengthened glass to a depth of layer (DOL) of at least about 10 μ

m.

13. The article of claim 1, further comprising an easy-to-clean coating, a diamond-like coating or a scratch-resistant coating disposed on the optical coating.

14. The article of claim 1, wherein the optical coating comprises a scratch resistant layer having a thickness in the range from about 1 micrometer to about 3 micrometers.

15. The article of claim 14, wherein the anti-reflective coating is disposed between scratch resistant layer and the substrate.

16. The article of claim 14, wherein the scratch resistant layer is disposed between the substrate and the anti-reflective coating.

17. The article of claim 14, wherein the anti-reflective coating comprises a first portion and a second portion, and wherein the scratch resistant layer is disposed between the first portion and the second portion.

18. An article comprising:

a substrate having a major surface; and

an optical coating disposed on the major surface forming an anti-reflective surface, wherein the optical coating comprises at least one anti-reflective coating and a scratch resistant layer disposed between the anti-reflective coating and the substrate,

wherein the article exhibits a maximum hardness of about 12 GPa or greater as measured on the anti-reflective surface by a Berkovich Indenter Hardness Test along an indentation depth of about 50 nm or greater,

wherein the article exhibits, under a D65 or F2 illuminant at normal incidence,

an average visible photopic reflectance of about 10% or less over the optical wavelength regime, as measured on the anti-reflective surface.

article transmittance color coordinates in the (L*, a*, b*) colorimetry system exhibiting a reference point color shift of less than about 2 from a reference point as measured at the anti-reflective surface, the reference point comprising at least one of the color coordinates (a*=0, b*=0) and the transmittance color coordinates of the substrate, and

article reflectance color coordinates in the (L*, a*, b*) colorimetry system exhibiting a reference point color shift of less than about 5 from a reference point as measured at the anti-reflective surface, the reference point comprising at least one of the color coordinates (a*=0, b*=0), the color coordinates (a*=−

2, b*=−

2), and the reflectance color coordinates of the substrate,

wherein, when the reference point is the color coordinates (a*=0, b*=0), the color shift is defined by √

((a*_article)²+(b*_article)²),

wherein, when the reference point is the color coordinates (a*=−

2, b*=−

2), the color shift is defined by √

((a*_article+2)²+(b*_article+2)²), and

wherein, when the reference point is the color coordinates of the substrate, the color shift is defined by √

((a*_article−

a*_substrate)²+(b*_article−

b*_substrate)²).

19. The article of claim 18, wherein the article exhibits an angular color shift of about 5 or less at an incident illumination angle that is 20 degrees or greater from normal incidence, under an International Commission on Illumination illuminant selected from the group consisting of A series illuminants, B series illuminants, C series illuminants, D series illuminants, and F series illuminants, wherein angular color shift is calculated using the equation √

((a*₂−

a*₁)²+(b*₂−

b*₁)²), with a*₁, and b*₁ representing the coordinates of the article when viewed at normal incidence and a*₂, and b*₂ representing the coordinates of the article when viewed at the incident illumination angle.

20. The article of claim 18, wherein the substrate has a hardness less than the maximum hardness of the article.

21. The article of claim 18, wherein the anti-reflective coating comprises a plurality of layers, the plurality of layers comprising at least one first low RI layer and a second high RI layer, and the combined thickness of the first low RI layers or the combined thickness of the second high RI layers is less than about 500 nm.

22. The article of claim 18, wherein the average visible photopic reflectance is about 2% or less over the optical wavelength regime.

23. The article of claim 18, wherein the substrate comprises an amorphous substrate or a crystalline substrate.

24. The article of claim 18, wherein the optical coating comprises a thickness and a plurality of layers comprising a nitride or oxy-nitride material, and where the combined thickness of the layers comprising a nitride or an oxyinitride is 50% or greater of the thickness of the optical coating.

25. The article of claim 18, wherein the scratch-resistant layer comprises a nitride or an oxy-nitride material and has a thickness of 200 nm or greater, and wherein the anti-reflective coating comprises a plurality of high refractive index layers having a refractive index greater than about 1.85 and a plurality of low refractive index layers having a refractive index less than about 1.75.

26. The article of claim 18, wherein the plurality of high refractive index layers comprises a nitride or oxy-nitride material, and the plurality of low refractive index layers have a combined thickness of less than about 200 nm.

27. The article of claim 18, wherein the angular color shift is less than about 2.

28. The article of claim 18, wherein the optical coating comprises a thickness and a plurality of layers comprising a high refractive index material with a refractive index greater than about 1.8, and wherein the combined thickness of the plurality of layers comprising the high refractive index material is 50% or greater of the thickness of the optical coating.

29. The article of claim 18, wherein the optical coating comprises a thickness and a plurality of layers comprising a high refractive index material with a refractive index greater than about 1.8, and wherein the combined thickness of the plurality of layers comprising a high refractive index material is 70% or greater of the top-most 500 nm of the optical coating.

30. The article of claim 18, wherein the substrate has a hardness less than the maximum hardness of the article.