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US-12625302-B2 - Low-color scratch-resistant articles with a multilayer optical film

US12625302B2US 12625302 B2US12625302 B2US 12625302B2US-12625302-B2

Abstract

Articles that exhibit scratch-resistance and improved optical properties. In some examples, the article exhibits a color shift of about 2 or less, when viewed at an incident illumination angle in the range from about 0 degrees to about 60 degrees from normal under an illuminant. In one or more embodiments, the articles include a substrate, and an optical film disposed on the substrate. The optical film includes a scratch-resistant layer and an optical interference layer. The optical interference layer may include one or more sub-layers that exhibit different refractive indices. In one example, the optical interference layer includes a first low refractive index sub-layer and a second a second high refractive index sub-layer. In some instances, the optical interference layer may include a third sub-layer.

Inventors

  • Robert Alan Bellman
  • Shandon Dee Hart
  • Karl William Koch, III
  • Charles Andrew Paulson
  • James Joseph Price

Assignees

  • CORNING INCORPORATED

Dates

Publication Date
20260512
Application Date
20230613

Claims (20)

  1. 1 . A cover article comprising: a substrate having a surface, and an optical film disposed on the substrate surface forming a coated surface, the optical film comprising a scratch-resistant layer and an optical interference layer; wherein the optical interference layer comprises a first low refractive index (RI) sub-layer and a second high refractive index (RI) sub-layer, wherein the difference between the refractive index of the first low RI sub-layer and the refractive index of the second high RI sub-layer is 0.01 or greater; wherein the cover article comprises an average hardness of 8 GPa or greater, as measured by a Berkovich Indenter Hardness Test along indentation depths of 100 nm or greater; wherein the cover article further comprises a color shift of 2 or less, when viewed at each of the incident illumination angles in the range from 5 degrees to about 45 degrees from normal incidence under an illuminant comprising CIE A illuminants, CIE B illuminants, CIE C illuminants, CIE D illuminants or CIE F illuminants; and further wherein color shift is determined by the equation √((a* 2 −a*i) 2 +(b* 2 −b*i) 2 ), where a*i and b*i are coordinates of the article when viewed at normal incidence and a*2 and b*2 are coordinates of the article viewed at each of the incident illumination angles, and wherein the coordinates of the article when viewed at normal incidence and at each of the incident illumination angles are both in transmittance or reflectance.
  2. 2 . The cover article of claim 1 , wherein the scratch-resistant layer comprises one or more of AlN, Si 3 N 4 , AlO x N y , SiO x N y , Al 2 O 3 , Si x C y , Si x O y C z , ZrO 2 , TiO x N y , diamond, diamond-like carbon, silicon nitride, silicon oxynitride, and Si u Al v O x N y .
  3. 3 . The cover article of claim 1 , wherein the scratch-resistant layer has a physical thickness of from 0.1 micrometres to 3 micrometres.
  4. 4 . The cover article of claim 1 , wherein the cover article comprises a color shift of 2 or less, when viewed at least one incident illumination angle in the range from 5 degrees to 60 degrees from normal incidence under an illuminant comprising CIE A illuminants, CIE B illuminants CIE C illuminants, CIED illuminants or CIEF illuminants, and further wherein color shift is determined by the equation √((a* 2 −a* 1 ) 2+(b* 2 −b* 1 ) 2 ), where a* 1 and b* 1 are coordinates of the article when viewed at normal incidence and a* 2 , and b* 2 are coordinates of the article viewed at the at least one incident illumination angle, and wherein the coordinates of the article when viewed at normal incidence and at the at least one incident illumination angle are both in transmittance or reflectance.
  5. 5 . The cover article of claim 1 , wherein the first low RI sub-layer comprises a contiguous and uninterrupted sub-layer of SiO 2 that is disposed in direct contact with the substrate surface.
  6. 6 . The cover article of claim 1 , wherein the first low RI sub-layer has a refractive index from about 1.4 to about 1.5, as measured from about 380 nm to about 750 nm.
  7. 7 . The cover article of claim 1 , wherein the optical interference layer comprises a physical thickness of (1) from about 50 nm to about 300 nm, (2) from about 50 nm to about 450 nm, (3) from 50 nm to about 500 nm or (4) from 50 nm to about 800 nm.
  8. 8 . The cover article of claim 1 , wherein the second high RI sub-layer comprises an optical thickness (n*d) in the range from about 2 nm to about 200 nm where n is the refractive index and d is the physical thickness of the second high RI sub-layer.
  9. 9 . The cover article of claim 1 , wherein the substrate comprises a glass selected from the group consisting of soda lime glass, alkali aluminosilicate glass, alkali containing borosilicate glass and alkali aluminoborosilicate glass.
  10. 10 . The cover article of claim 1 , wherein the substrate comprises a crystalline substrate, or a glass ceramic substrate.
  11. 11 . The cover article of claim 1 , wherein: the first low RI sub-layer comprises silicon-containing oxide disposed on the substrate surface, and a physical thickness from 12 nm to about 135 nm; the second high RI sub-layer comprises a silicon-containing nitride or a silicon-containing oxynitride; and, the scratch resistant layer comprises a silicon-containing nitride, a silicon-containing oxynitride or Si u Al v O x N y , and a physical thickness of from 0.1 micrometres to 3 micrometres.
  12. 12 . The cover article of claim 11 , wherein: the silicon-containing oxide comprises SiO 2 or SiO, the silicon-containing nitride comprises Si 3 N 4 , and the silicon-containing oxynitride comprises Si u Al v O x N y or SiO x N y .
  13. 13 . The cover article of claim 1 , wherein the cover article is part of a smart phone, a mobile phone, a tablet, a computer, or a navigation system.
  14. 14 . The cover article of claim 1 , wherein the optical interference layer further comprises a third sub-layer which has (1) a same RI as the first low RI sub-layer; (2) a same RI as the second high RI sub-layer, or (3) a medium RI that is between the RI of the first low RI sub-layer and the RI of the second high RI sub-layer.
  15. 15 . The cover article of claim 1 , further comprises: a capping layer disposed on the scratch-resistant layer, the capping layer comprises a contiguous and uninterrupted sub-layer of SiO 2 , and a physical thickness of from 0 to 100 nm.
  16. 16 . The cover article of claim 1 , further comprises: a capping layer disposed on the scratch-resistant layer, the capping layer comprises two or more materials or two or more sub-layers.
  17. 17 . The cover article of claim 16 , wherein the two or more sub-layers of the capping layer have different refractive indices and include layers with high refractive indices (H) and low refractive indices (L) where the high refractive indices (H) and the low refractive indices (L) are with respect to one another.
  18. 18 . The cover article of claim 17 , wherein the two or more sub-layers of the capping layer are arranged so that high and low refractive index sub-layers alternate.
  19. 19 . The cover article of claim 18 , wherein the two or more sub-layers of the capping layer have a thickness each or combined in the range from about 4 nm to about 50 nm.
  20. 20 . The cover article of claim 16 , wherein the capping layer includes a silane-based low-friction sub-layer having a thickness in the range from about 0.1 nm to about 20 nm, disposed on underlying sub-layers of the capping layer.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation application and claims the benefit of priority under 35 U.S.C. § 120 of Ser. No. 17/529,352, filed Nov. 18, 2021, now U.S. Pat. No. 11,714,213, which is a continuation application and claims the benefit of priority under 35 U.S.C. § 120 of Ser. No. 16/386,759, filed Apr. 17, 2019, now U.S. Pat. No. 11,231,526, which is a continuation application and claims the benefit of priority under 35 U.S.C. § 120 of Ser. No. 15/142,508, filed Apr. 29, 2016, now U.S. Pat. No. 10,444,408, which is a divisional application and claims the benefit of priority under 35 U.S.C. § 120 of Ser. No. 14/480,898, filed Sep. 9, 2014, now U.S. Pat. No. 9,366,784, which in turn claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 62/034,412 filed on Aug. 7, 2014, of U.S. Provisional Application Ser. No. 61/954,697 filed on Mar. 18, 2014, and of U.S. Provisional Application Ser. No. 61/877,568 filed on Sep. 13, 2013, the contents of which are relied upon and incorporated herein by reference in their entirety. Application Ser. No. 15/142,508 filed on Apr. 29, 2016 is a continuation-in-part application and claims the benefit of priority under 35 U.S.C. § 120 of U.S. application Ser. No. 14/331,656 filed Jul. 15, 2014, now U.S. Pat. No. 9,079,802, which is a continuation and claims the benefit of priority under 35 U.S.C. § 120 of U.S. application Ser. No. 14/262,066 filed on Apr. 25, 2014, now U.S. Pat. No. 9,359,261, which in turns claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 61/954,697 filed on Mar. 18, 2014, of U.S. Provisional Application Ser. No. 61/877,568 filed on Sep. 13, 2013, and of U.S. Provisional Application Ser. No. 61/820,407 filed on May 7, 2013, the contents of which are relied upon and incorporated herein by reference in their entirety. BACKGROUND The disclosure relates to articles with scratch resistance, abrasion resistance or a combination thereof, which also exhibit retained optical properties and more particularly to articles that exhibit a high hardness and low color shift when viewed at different incident illumination angles. Cover and housing substrates are often used in consumer electronic products to protect critical devices within the product, to provide a user interface for input and/or display, and/or many other functions. Such consumer electronic products include mobile devices, such as smart phones, mp3 players and computer tablets. Cover and housing substrates may also be used in architectural articles, transportation-related articles, appliance articles, or any article that requires some transparency, scratch-resistance, abrasion resistance or a combination thereof. These applications and others also often demand durable (e.g., scratch-resistant) cover and housing substrate, which also has strong optical performance characteristics. Often, the cover substrate includes glass for this purpose; however other substrates may be used. Strong optical performance in terms of maximum light transmission and minimum reflectivity are required in cover substrate applications (and potentially in some housing substrate applications). Furthermore, cover substrate applications require that the color exhibited or perceived, in reflection and/or transmission, does not change appreciably as the viewing angle (or incident illumination angle) is changed. This is because, if the color, reflectivity or transmission changes with viewing angle to an appreciable degree, the user of the product incorporating the cover glass will perceive a change in the color or brightness of the display, which can diminish the perceived quality of the display. Of these changes, a change in color is often the most noticeable and objectionable to users. Known cover substrates include glass and film combinations can often exhibit a variety of different types of scratches after use in harsh operating conditions. In some instances, a significant portion of those scratches are microductile scratches, which typically include a single groove in a material having extended length and with depths in the range from about 100 nm to about 500 nm. Microductile scratches may be accompanied by other types of visible damage, such as sub-surface cracking, frictive cracking, chipping and/or wear. Evidence suggests that a majority of such scratches and other visible damage is caused by sharp contact that occurs in a single contact event. Once a significant scratch appears on the cover substrate, the appearance of the product is degraded since the scratch causes an increase in light scattering, which may cause significant reduction in brightness, clarity and contrast of images on the display. Significant scratches can also affect the accuracy and reliability of touch sensitive displays. A portion of such scratches and other visible damage as described above may also be caused by multiple contact events (incl