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EP-4735396-A1 - METHOD FOR AFFECTING GLASS STRENGTH

EP4735396A1EP 4735396 A1EP4735396 A1EP 4735396A1EP-4735396-A1

Abstract

A method for reducing the strength of a first sheet of glass is described. A portion of a first major surface of the first sheet of glass is treated with a first powder to reduce the strength of the first sheet of glass. The first powder comprises particles having a particle size distribution, the particle size distribution having: a mean particle diameter between 1 µm and 250 µm; and a median particle diameter of greater than 5 µm. Glass sheets treated using such a method may be used to make a laminated glazing, wherein the first glass sheet is laminated to a sheet of glazing material using an interlayer structure comprising at least one sheet of adhesive interlayer material. The strength of the first sheet of glass may be reduced prior to, or after, being laminated to the sheet of glazing material.

Inventors

  • ROGERS, GARY
  • HURST, MICHAEL
  • WILLIAMS, Jonathan Mark

Assignees

  • Pilkington Group Limited

Dates

Publication Date
20260506
Application Date
20240628

Claims (20)

  1. 1. A method for reducing the strength of a first sheet of glass, the first glass sheet having a first major surface and a second opposing major surface; the method comprising: a treatment step, the treatment step comprising treating a portion of the first major surface of the first sheet of glass with a first powder to reduce the strength of the first sheet of glass; wherein the first powder comprises particles having a particle size distribution, the particle size distribution having: a mean particle diameter between 1 pm and 250 pm; and a median particle diameter of greater than 5 pm.
  2. 2. A method according to claim 1, wherein the median particle diameter of the particle distribution of the first powder is not more than 100 pm
  3. 3. A method according to claim 1 or claim 2, wherein the particle size distribution of the first powder has a D 10 greater than 1 pm and preferably not more than 20 pm.
  4. 4. A method according to any of the preceding claims, wherein the particle size distribution of the first powder has a D90 greater than 50 pm and/or a D90 less than 500 pm.
  5. 5. A method according to any of the preceding claims, wherein the particle size distribution of the first powder has a span defined as (D90 - D10)/D50 of between 0.5 and 15.
  6. 6. A method according to any of the preceding claims, wherein the particle size distribution of the first powder has D90 - D10 of at least 30 pm and/or D90 - D10 of at most 400 pm.
  7. 7. A method according to any of the preceding claims, wherein the particle size distribution of the first powder has a mode particle diameter of at least 50 pm and/or a mode particle diameter of a most 300 pm.
  8. 8. A method according to any of the preceding claims, wherein the particles have a Vickers Hardness greater than 5.2 GPa, preferably greater than 5.6 GPa, more preferably greater than 5.8GPa, even more preferably greater than 6 GPa.
  9. 9. A method according to any of the preceding claims, wherein the first powder comprises a glassy material, pumicite, basalt or amorphous aluminosilicate.
  10. 10. A method according to any of the claims 1 to 8, wherein the first powder has a composition comprising (by weight) 40-75% SiC>2, 5-20% AI2O3, 0-10% Na2O, 0-10% K2O, 0-15% Fe2C>3, and 0-20% CaO.
  11. 11. A method according to any of the claims 1 to 7, wherein the first powder comprises at least one of cerium oxide, titanium oxide, diamond, calcium carbonate, silicic anhydride, sodium hydrogen phosphate, silicon nitride, silicon carbide and aluminium oxide.
  12. 12. A method according to any of the preceding claims, wherein the first powder is applied to the first major surface of the first sheet of glass using a powder applicator, preferably wherein the powder applicator comprises at least one of a cloth, a brush, a blade and a roller.
  13. 13. A method according to any of the preceding claims, wherein during the treatment step the first powder is directed toward the first major surface of the first sheet of glass using a fluid carrier, preferably wherein the fluid comprises a gas such as nitrogen or air; or a liquid such as water; and/or wherein a liquid is used during the treatment step when the first sheet of glass is treated with the first powder.
  14. 14. A method according to any of the preceding claims, wherein the second major surface of the first sheet of glass is treated with a second powder, the second powder having a composition and comprising particles having a particle size distribution, preferably wherein the particle size distribution of the second powder is the same as the particle size distribution of the first powder and/or wherein the composition of the second powder is the same as a composition of the first powder.
  15. 15. A method according to any of the preceding claims, wherein the first sheet of glass is a soda- lime-silicate glass having a composition comprising (by weight), SiO 2 69 - 74 %; A1 2 O 3 0 - 3 %; Na 2 O 10 - 16 %; K 2 O 0 - 5 %; MgO 0 - 6 %; CaO 5 - 14 %; SO3 0 - 2 %; and Fe 2 C>3 0.005 - 2 %; and/or wherein the first sheet of glass has a thickness between 1mm and 5mm.
  16. 16. A method according to any of the preceding claims, wherein the first sheet of glass has been produced using a float process, and wherein the first major surface of the first sheet of glass is the tin side and the second major surface of the first sheet of glass is the air side.
  17. 17. A method according to any of the preceding claims, wherein the first sheet of glass is a pane of a laminated glazing, the laminated glazing comprising the first sheet of glass joined to a sheet of glazing material by an interlayer structure comprising at least one sheet of adhesive interlayer material, the pane of the laminated glazing having an exposed major surface, and wherein the exposed major surface comprises the first major surface of the first sheet of glass, preferably wherein the exposed major surface of the pane of the laminated glazing is surface one or surface four of the laminated glazing.
  18. 18. A method of making a laminated glazing comprising the steps: (i) providing a first glass sheet having a first major surface and a second opposing major surface; (ii) reducing the strength of the first sheet of glass using a method according to any of the claims 1 to 16; and (iii) laminating the first glass sheet to a sheet of glazing material using an interlayer structure comprising at least one sheet of adhesive interlayer material; wherein the first major surface of the first sheet of glass faces the interlayer structure or wherein the second major surface of the first sheet of glass faces the interlayer structure.
  19. 19. A method according to claim 18, wherein step (ii) takes place before step (iii) and wherein following step (iii) the first major surface of the first sheet of glass faces the interlayer structure.
  20. 20. A method according to claim 19, wherein the first major surface of the first sheet of glass is surface two or surface three of the laminated glazing.

Description

METHOD FOR AFFECTING GLASS STRENGTH The present invention relates to a method of reducing the strength of a sheet of glass and to a method of making a laminated glazing including the sheet of glass that has had the strength thereof reduced. Such a laminated glazing may be used as a window in an automobile, in particular as a vehicle windscreen. Conventional laminated glazings for automotive windscreens comprise two plies of soda-lime- silicate glass joined by a sheet of polyvinyl butyral (PVB). Typically, each glass sheet is 2.1mm thick and the PVB sheet is typically 0.76mm thick. As is known in the art, a laminated automotive windscreen provides the driver of the vehicle with improved safety benefits. However, vehicle manufacturers are also addressing vehicle safety in the event of a forward collision with a pedestrian. In the event of a collision with a pedestrian, the pedestrian’s head may impact the vehicle windscreen thereby causing further injury to the pedestrian. W02013181505A1 describes a glass laminate including at least one chemically strengthened glass sheet with a thickness not exceeding 2.0 mm and a polymer interlayer between the glass sheets. Flaws are created in the surface of one of the glass sheets in order to weaken the glass laminate upon an impact event on a first side of the laminate, while retaining the strength of the laminate upon impact on the opposing second side of the laminate. EP2062862A1 describes a sheet glass laminate structure produced by laminating at least three sheet glasses each having a thickness of less than 1 mm through an intermediate layer between two adjacent sheet glasses. WO2019245819A1 describes a glass laminate construction with controlled breakage for pedestrian safety. WO202115654A1 describes a laminated glass for a vehicle that has been subjected to a strength levelling process which may include using a powder that has an average particle diameter of 10 nm to 100 pm. It is well known in the art to polish materials such a glass to improve the optical quality thereof. The use of cerium oxide (or ceria) has been used for many years in polishing glass surfaces, see for example US2,383,500. US2,597,182 describes smoothing glass blanks using a smoothing technique which is employed between grinding and polishing steps. A mixture of rouge and pumice is used as the abrasive. Such grinding, smoothing and polishing processes were widely used before the development of the float process. US2012/0094578A1 describes heterocoagulate composite structures having a plurality of first particles (typically nanoparticles) on the surface of a second particle (typically a microparticle) for use in polishing compositions for both removing stains and polishing glass. The first particles contain cerium oxide and the second particle contains silicon oxide, aluminium oxide and/or zirconium oxide. In a heterocoagulate, the first particles are maintained on the surface of the second particle by electrostatic forces. W02003/091351A2 describes an unexpanded perlite ore polishing composition. The composition comprises a base material having grains of unexpanded perlite ore of a selected distribution of particle sizes which undergo fracturing of the grains as a function of an abrasive force applied to the base material. The selected distribution of particle sizes includes a significant volume of grains of unexpanded perlite ore having a (d90) particle size in a range of about 101 to about 229 pm. The base material is responsive to an abrasive force being applied thereto during polishing resulting in continued fracturing of the grains of unexpanded perlite ore to yield a final polishing composition having a sufficiently low level of abrasiveness under said abrasive force making it suitable for use in polishing. Compositions for polishing acrylic dentures and CRT tube surfaces using the unexpanded perlite ore polishing composition and methods for polishing the same are also described. Unexpanded perlite ore polishing compositions and use thereof is also described in US2003/0203337A1 and US2003/0224702A1. The perlite ore polishing compositions described in W02003/091351A2, US2003/0203337A1 and US2003/0224702A1 have an initial selected particle size distribution that varies with use because there is a continued fracturing of the grains of unexpanded perlite during polishing under an abrasive force. JP2002-114968 A describes an abrasive material for polishing that is made of magnetic particles to aid removal and recovery of abrasive waste material and abrasive material for subsequent reuse. US2013/0005222A1 describes a method for finishing an edge of a glass sheet comprising a first grinding step and a second polishing step using different abrasive wheels. The grinding and polishing wheels have grits embedded in a polymer matrix. WO2012/162446A1 describes a method for providing a textured glass substrate. The textured glass substrate can be used in photovoltaic cells. A photovoltaic device