Search

EP-3948372-B1 - HEATABLE WINDSHIELDS

EP3948372B1EP 3948372 B1EP3948372 B1EP 3948372B1EP-3948372-B1

Inventors

  • MA, Zhixun
  • POLCYN, ADAM, D.
  • WAGNER, ANDREW

Dates

Publication Date
20260506
Application Date
20200326

Claims (5)

  1. A coated article comprising: a substrate (12); a first dielectric layer (20) over at least a portion of the substrate; a first metallic layer (28) over at least a portion of the first dielectric layer; a first primer layer (30) over at least a portion of the first metallic layer; a second dielectric layer (32) over at least a portion of the first primer layer; a second metallic layer (42) over at least a portion of the second dielectric layer; a second primer layer (44) over at least a portion of the second metallic layer; a third dielectric layer (46) over at least a portion of the second primer layer; a third metallic layer (56) over at least a portion of the third dielectric layer; a third primer layer (58) over at least a portion of the third metallic layer; and a fourth dielectric layer (60) over at least a portion of the third primer layer; wherein a total combined thickness of the metallic layers is at least 30 nanometers, and no more than 60 nanometers, wherein the first metallic layer has a thickness of at least 9.0 nm [90 Å] and at most 14.0 nm [140 Å], the second metallic layer has a thickness of at least 11.0 nm [110 Å] and at most 14.0 nm [140 Å]; and/or the third metallic layer has a thickness of at least 9.0 nm [90 Å] and at most 15.0 nm [150 Å], wherein the coated article has a visible light transmittance of at least 70%.
  2. The coated article according to claim 1, further comprising: a fourth metallic layer (70) over at least a portion of the fourth dielectric layer; a fourth primer layer (72) over at least a portion of the fourth metallic layer; and a fifth dielectric layer (74) over at least a portion of the fourth primer layer;
  3. The coated article according to any one of the preceding claims, wherein at least one of the metallic layers comprises at least one of silver, copper, gold, aluminum, mixtures thereof, or alloys thereof.
  4. The coated article according to any one of the preceding claims, wherein at least one dielectric layer comprises a silicon nitride film.
  5. The coated article according to any one of the preceding claims, further comprising an outermost protective coating (84).

Description

BACKGROUND OF THE INVENTION Field of the Invention The invention relates generally to vehicle transparencies, such as vehicle windshields, and in one particular embodiment, to a heatable vehicle windshield. Technical Considerations Passing electric current through a conductor on a laminated vehicle windshield will raise the temperature of the windshield. This is particularly useful in colder climates for defogging and melting ice and/or snow on the windshield. In wire-heated windshields, fine electrically-conductive wires are placed between the windshield plies. The wires are connected to a power source, such as a conventional 14 volt vehicle alternator. The wires have sufficiently low resistance to provide a windshield with a power density of 5 to 7 watts per decimeter squared (W/dm2). A problem with wire-heated windshields is that the wires can be seen by the vehicle's occupants, which is aesthetically undesirable and can interfere with visibility through the windshield. If the diameter of the wires is decreased to try to reduce the visibility of the wires, the number of wires must be increased to maintained the desired power density, which adversely decreases the total solar energy transmitted (TSET) by the windshield. If the height of the windshield increases, the wires must be longer to maintain the desired power density. Longer wires are also undesirable with respect to aesthetics and/or transmittance. Some heated windshields use transparent conductive coatings rather than wires. These coatings, however, have their own drawback. For example, conventional heated windshield coatings typically have a sheet resistance of 2 ohms per square (Ω/□) or greater. A conventional 14v (80 ampere, 1,120 watt) alternator does not provide enough voltage to power a conventional heated windshield coating to a temperature sufficient for de-icing. Therefore, for vehicles with these coatings, the vehicles must be altered to increase the available voltage. For example, the alternator can be replaced with a 42v alternator, or a DC to DC converter can be added to step-up the voltage from a 14v alternator. These solutions, however, increase the cost and complexity of the vehicle electrical system. The document US 2016/223729 A1 discloses a coated article of the prior art. Therefore, it would be desired to provide a transparency that reduces or eliminates at least some of the problems associated with conventional heatable transparencies. SUMMARY OF THE INVENTION The invention is directed to lower the sheet resistance of a coated transparency by adding metallic silver layers in a coating stack. Specifically, the total amount of silver within the coating stack is between 30 nm and 60 nm; between 35 and 47 nm; between 35 and 43 nm or between 40 and 47 nm. As the silver thickness increases, the sheet resistance lowers. However, if the total thickness of the silver layers in a coating is too thick, the transmittance is reduced to below 70%, which is unacceptable. Additionally, if the total silver thickness is too thick, the color of the glass will appear red, which is undesirable. Thus, the invention is directed to a coating stack that has an adequately thick total silver to provide a sheet resistance to allow for de-icing with a 14v alternator, and having a light transmittance above 70%, preferably above 70.5%, more preferably above 71%. The invention relates to a coated article according to claim 1. The invention may optionally further comprise a fourth metallic layer positioned over the fourth dielectric layer, and a fifth dielectric layer positioned over at least a portion of the fourth metallic layer. Further preferred embodiments are defined in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described with reference to the following drawing figures wherein like reference numbers identify like parts throughout. Fig. 1a is a cross-sectional view (not to scale) of an example not according to the invention.Fig. 1b is a cross-sectional view (not to scale) of an example not according to the invention.Fig. 2a is a cross-sectional view (not to scale) of an example not according to the invention.Fig. 2b is a cross-sectional view (not to scale) of an example not according to the invention.Fig. 3a is a cross-sectional view (not to scale) of a non-limiting coating according to the invention.Fig. 3b is a cross-sectional view (not to scale) of a non-limiting coating according to the invention.Fig. 4a is a cross-sectional view (not to scale) of a non-limiting coating according to the invention.Fig. 4b is a cross-sectional view (not to scale) of a non-limiting coating according to the invention.Figs. 5a-b are cross-sectional views (not to scale) of non-limiting first dielectric layer embodiments according to the invention.Figs. 6a-d are cross-sectional views (not to scale) of non-limiting second dielectric layer embodiments according to the invention.Figs. 7a-d are cross-sectional views (not to scale) of non-limi