Hydrophilic coatings, methods for depositing hydrophilic coatings, and improved deposition technology for thin films

• US 20060121315A1
• Filed: 12/02/2005
• Published: 06/08/2006
• Est. Priority Date: 12/03/2004
• Status: Active Grant

• Current Assignee: Cardinal CG Company (Cardinal Glass Industries Incorporated)
• Original Assignee: Cardinal CG Company (Cardinal Glass Industries Incorporated)
• Inventors: Hartig, Klaus, Brownlee, James, Krisko, Annette, Pfaff, Gary, Myli, Kari, German, John
• Granted Patent: US 7,923,114 B2
• Time in Patent Office: Days
• US Class Current: 428/702
• CPC Class Codes: C03C 17/36 at least one coating being a metal
• CPC Class Codes: C03C 17/366 Low-emissivity or solar control coatings
• CPC Class Codes: C03C 2217/71 Photocatalytic coatings
• CPC Class Codes: C03C 2217/75 Hydrophilic and oleophilic coatings
• CPC Class Codes: C03C 2217/78 Coatings specially designed to be durable, e.g. scratch-resistant
• CPC Class Codes: C03C 2218/154 by sputtering
• CPC Class Codes: C03C 2218/365 Coating different sides of a glass substrate
• CPC Class Codes: C23C 14/08 Oxides C23C14/10 takes precedence
• CPC Class Codes: C23C 14/3464 using more than one target C23C14/56 takes precedence
• CPC Class Codes: Y10T 428/252 Glass or ceramic [i.e., fired or glazed clay, cement, etc.] [porcelain, quartz, etc.]
• CPC Class Codes: Y10T 428/266 of base or substrate

Abstract

The invention provides certain embodiments that involve sputtering techniques for applying a mixed oxide film comprising silica and titania. In these embodiments, the techniques involve sputtering at least two targets in a common chamber (e.g., in a shared gaseous atmosphere). A first of these targets includes silicon, while a second of the targets includes titanium. Further, the invention provides embodiments involving a substrate bearing a hydrophilic coating, which can be deposited by sputtering or any other suitable thin film deposition technique. The invention also provides techniques and apparatuses useful for depositing a wide variety of coating types. For example, the invention provides thin film deposition technologies in which sputtering apparatuses or other thin film deposition apparatuses are employed.

Claims

1. A substrate with a first surface bearing a coating that comprises a compound region, the compound region comprising a photocatalyst, the photocatalyst being a first material, the compound region also comprising a second material, wherein said first and second materials are different materials, wherein the coating has a total thickness of at least about 50 angstroms but less than about 400 angstroms, wherein the substrate when uncoated has a first visible reflectance, wherein the substrate when bearing the coating has a second visible reflectance, and wherein the second visible reflectance is no more than about 3% greater than the first visible reflectance, each such visible reflectance being a film-side visible reflectance measured off the first surface of the substrate.

2. The substrate of claim 1, wherein the second visible reflectance is no more than about 1% greater than the first visible reflectance.

3. The substrate of claim 1, wherein the second visible reflectance is no more than about 0.75% greater than the first visible reflectance.

4. The substrate of claim 1, wherein the coating has a photocatalytic reaction rate characterized by an acetone decomposition slope of at least about 0.03.

5. The substrate of claim 1, wherein the compound region includes at least three films each having a thickness of about 45 angstroms or less.

6. The substrate of claim 1, wherein the compound region includes a subset of films, the subset having a composite refractive index of about 2.1 or less, the subset comprising at least three films each having a thickness of between about 10 angstroms and about 45 angstroms, wherein the compound region further includes an exposed outermost film, said outermost film comprising titania and having a thickness of at least about 20 angstroms.

7. The substrate of claim 1, wherein the compound region comprises alternating films of said first material and said second material, each such film having a thickness of less than about 45 angstroms, wherein said alternating films have a combined thickness of less than about 200 angstroms.

8. The substrate of claim 7, wherein said combined thickness is less than about 150 angstroms.

9. The substrate of claim 5, wherein said first material is titania, and at least two of said films comprise titania.

10. The substrate of claim 9, wherein at least three of said films comprise titania.

11. The substrate of claim 5, wherein said first material is titania that is substantially or entirely amorphous, at least one of said films comprising titania that is substantially or entirely amorphous.

12. The substrate of claim 5, wherein said second material is silica, and at least two of said films comprise silica.

13. The substrate of claim 1, wherein the compound region comprises alternating films of said first material and said second material, said first material being titania, said second material being silica, and wherein the compound region has at least five such alternating films each having a thickness of between about 10 angstroms and about 45 angstroms.

14. The substrate of claim 1, wherein the compound region comprises the following films, in sequence outwardly:

a film comprising titania and having a thickness of between about 10 angstroms and about 30 angstroms;

a film comprising silica and having a thickness of between about 5 angstroms and about 30 angstroms;

a film comprising titania and having a thickness of between about 10 angstroms and about 30 angstroms;

a film comprising silica and having a thickness of between about 5 angstroms and about 30 angstroms; and

an exposed outermost film comprising titania and having a thickness of between about 10 angstroms and about 45 angstroms.

15. The substrate of claim 5, wherein the coating includes a desired film between the substrate'"'"'s first surface and the compound region, the desired film having a physical thickness of at least about 30 angstroms.

16. The substrate of claim 5, wherein the total thickness of the coating is less than about 200 angstroms.

17. The substrate of claim 5, wherein the coating is substantially or entirely amorphous.

18. The substrate of claim 1, wherein the compound region comprises a mixed film including both said first and second materials.

19. The substrate of claim 18, wherein the mixed film has a refractive index of about 2.1 or less.

20. The substrate of claim 19, wherein the refractive index is about 1.7 or less.

21. The substrate of claim 18, wherein the first material is titania, and the mixed film comprises titania in an amount that is less than about 30% by weight relative to the total weight of the mixed film.

22. The substrate of claim 18, wherein the mixed film is a mixed oxide film comprising titanium, silicon, and oxygen.

23. The substrate of claim 18, wherein the mixed film has a thickness of less than 100 angstroms, the mixed film defining an exposed outermost face of the coating.

24. The substrate of claim 18, wherein the mixed film is entirely or substantially amorphous.

25. The substrate of claim 18, wherein the mixed film includes both amorphous and crystalline domains.

26. The substrate of claim 25, wherein said first material is titania, and the mixed film has a degree of crystallization that is less than about 20%.

27. The substrate of claim 25, wherein said first material is titania, and the mixed film comprises titanium dioxide crystals embedded in an entirely or substantially amorphous film.

28. The substrate of claim 27, wherein the titanium dioxide crystals have an average size of between about 5 nm and about 50 nm.

29. The substrate of claim 28, wherein the average size is between about 5 nm and about 25 nm.

30. The substrate of claim 18, wherein said first material is titania, said second material is silica, and the mixed film is a sputtered film.

31. The substrate of claim 25, wherein the mixed film includes an inner thickness that is an entirely or substantially amorphous mix of said first and second materials, said mixed film also including an outer thickness comprising crystals of said first material.

32. The substrate of claim 31, wherein said outer thickness comprises crystals of said first material embedded in film that is entirely or substantially amorphous.

33. The substrate of claim 32, wherein said first material is titania, and the crystalline domains comprise titanium dioxide crystals.

34. The substrate of claim 33, wherein said outer thickness defines an exposed outermost face of the coating.

35. The substrate of claim 18, wherein the mixed film is a mixed oxide film having a thickness of less than about 75 angstroms, the mixed oxide film defines an exposed outermost face of the coating, the first material is titania, the mixed oxide film comprises titania in an amount that is less than about 30% by weight relative to the total weight of the mixed oxide film, and the mixed oxide film is substantially or entirely amorphous.

36. The substrate of claim 18, wherein said first material is titania, and said second material is zirconia.

37. The substrate of claim 36, wherein the compound region includes domains consisting essentially of entirely or substantially amorphous titania and at least one domain characterized by blending together of titania and zirconia.

38. The substrate of claim 36, wherein the mixed film comprises at least some ZrTiO₄.

39. The substrate of claim 38, wherein the mixed film comprises a mixture including both ZrTiO₄ and ZrO₂.

40. The substrate of claim 23, wherein the coating includes a desired film between the substrate'"'"'s first surface and the mixed film, the desired film having a physical thickness of at least about 30 angstroms.

41. The substrate of claim 18, wherein the total thickness of the coating is less than about 200 angstroms.

42. The substrate of claim 1, wherein the substrate is part of a multiple-pane insulating glazing unit having a between-pane space, the first surface of the substrate being an exterior surface of the unit and thus facing generally away from the between-pane space.

43. The substrate of claim 1, wherein the substrate is a glass sheet.

44. A substrate with a first surface bearing a coating that comprises a compound region, the compound region comprising a photocatalyst, the photocatalyst being a first material, the compound region also comprising a second material, wherein said first and second materials are different materials, the coating having a total thickness of less than about 250 angstroms, wherein the coating has a photocatalytic reaction rate characterized by an acetone decomposition slope of at least about 0.03.

45. The substrate of claim 44, wherein the acetone decomposition slope is at least about 0.038.

46. The substrate of claim 44, wherein the substrate when uncoated has a first visible reflectance, wherein the substrate when bearing the coating has a second visible reflectance, and wherein the second visible reflectance is no more than about 3% greater than the first visible reflectance, each such visible reflectance being a film-side visible reflectance measured off the first surface of the substrate.

47. The substrate of claim 46, wherein the second visible reflectance is no more than about 1% greater than the first visible reflectance.

48. The substrate of claim 47, wherein the second visible reflectance is no more than about 0.75% greater than the first visible reflectance.

49. The substrate of claim 44, wherein the compound region includes at least three films each having a thickness of between about 10 angstroms and about 45 angstroms.

50. The substrate of claim 44, wherein the compound region includes a subset of films, the subset having a composite refractive index of about 2.1 or less, the subset comprising at least three films each having a thickness of between about 10 angstroms and about 45 angstroms, wherein the compound region further includes an exposed outermost film, said outermost film comprising titania and having a thickness of at least about 20 angstroms.

51. The substrate of claim 44, wherein the compound region comprises alternating films of said first material and said second material, each such film having a thickness of less than about 45 angstroms, wherein said alternating films have a combined thickness of less than about 200 angstroms.

52. The substrate of claim 51, wherein said combined thickness is less than about 150 angstroms.

53. The substrate of claim 49, wherein said first material is titania, and at least two of said films comprise titania.

54. The substrate of claim 53, wherein at least three of said films comprise titania.

55. The substrate of claim 49, wherein said first material is titania that is substantially or entirely amorphous, at least one of said films comprising titania that is substantially or entirely amorphous.

56. The substrate of claim 49, wherein said second material is silica, and at least two of said films comprise silica.

57. The substrate of claim 44, wherein the compound region comprises alternating films of said first material and said second material, said first material being titania, said second material being silica, and wherein the compound region has at least three such alternating films each having a thickness of between about 10 angstroms and 45 angstroms.

58. The substrate of claim 44, wherein the compound region comprises the following films, in sequence outwardly:

a film comprising titania and having a thickness of between about 10 angstroms and about 30 angstroms;

a film comprising silica and having a thickness of between about 5 angstroms and about 30 angstroms;

a film comprising titania and having a thickness of between about 10 angstroms and about 30 angstroms;

a film comprising silica and having a thickness of between about 5 angstroms and about 30 angstroms, and;

an exposed outermost film comprising titania and having a thickness of between about 10 angstroms and about 45 angstroms.

59. The substrate of claim 49, wherein the coating includes a desired film between the substrate'"'"'s first surface and the compound region, the desired film having a physical thickness of at least about 30 angstroms.

60. The substrate of claim 49, wherein the coating is substantially or entirely amorphous.

61. The substrate of claim 44, wherein the compound region comprises a mixed film including both said first and second materials.

62. The substrate of claim 61, wherein the mixed film has a refractive index of about 2.1 or less.

63. The substrate of claim 62, wherein the refractive index is about 1.7 or less.

64. The substrate of claim 61, wherein the first material is titania, and the mixed film comprises titania in an amount that is less than about 30% by weight relative to the total weight of the mixed film.

65. The substrate of claim 61, wherein the mixed film comprises an oxide that includes silicon, titanium, and oxygen.

66. The substrate of claim 61, wherein the oxide film is a mixed oxide film having a thickness of less than 100 angstroms, the mixed oxide film defining an exposed outermost face of the coating.

67. The substrate of claim 61, wherein the mixed film is entirely or substantially amorphous.

68. The substrate of claim 61, wherein the mixed film includes both amorphous and crystalline domains.

69. The substrate of claim 68, wherein said first material is titania, and the mixed film has a degree of crystallization that is less than about 20%.

70. The substrate of claim 68, wherein said first material is titania, and the mixed film comprises titanium dioxide crystals embedded in an entirely or substantially amorphous film.

71. The substrate of claim 70, wherein the titanium dioxide crystals have an average size of between about 5 nm and about 25 nm.

72. The substrate of claim 68, wherein the mixed film includes an inner thickness that is an entirely or substantially amorphous mix of said first and second materials, said mixed film also including an outer thickness comprising crystals of said first material.

73. The substrate of claim 61, wherein the mixed film is a mixed oxide film having a thickness of less than about 75 angstroms, the mixed oxide film defines an exposed outermost face of the coating, the first material is titania, the mixed oxide film comprises titania in an amount that is less than about 30% by weight relative to the total weight of the mixed oxide film, and wherein the mixed oxide film is substantially or entirely amorphous.

74. The substrate of claim 66, wherein the coating includes a desired film between the substrate'"'"'s first surface and the mixed oxide film, the desired film having a physical thickness of between about 30 angstrom and about 100 angstroms.

75. The substrate of claim 61, wherein the total thickness of the coating is less than about 175 angstroms.

76. The substrate of claim 61, wherein the mixed film is a sputtered film comprising silica and titania, said sputtered film having been produced by co-sputtering first and second targets, wherein the first target carries a sputterable material consisting essentially of a metallic material comprising titanium, and wherein the second target carries a sputterable material containing silicon as a major component, said targets being co-sputtered in a single sputtering bay.

77. The substrate of claim 44, wherein the substrate is part of a multiple-pane insulating glazing unit having a between-pane space, the first surface of the substrate being an exterior surface of the unit and thus facing generally away from the between-pane space.

78. The substrate of claim 44, wherein the substrate is a glass sheet.

79. A glass sheet having generally-opposed first and second major surfaces, the first major surface bearing a coating that comprises a compound region, the compound region comprising a photocatalyst, the photocatalyst being a first material, the compound region also comprising a second material, wherein said first and second materials are different materials, wherein the compound region is a sputtered mixed oxide film including both said first and second materials, the sputtered mixed oxide film having a thickness of at least about 40 angstroms but less than about 250 angstroms, the sputtered mixed oxide film defining an exposed outermost face of the coating, wherein said first material is titania and the sputtered mixed oxide film comprises titania in an amount that is less than about 30% by weight relative to the total weight of the sputtered mixed oxide film, wherein the glass sheet when uncoated has a first visible reflectance, wherein the glass sheet when bearing the coating has a second visible reflectance, and wherein the second visible reflectance is no more than about 3% greater than the first visible reflectance, each such visible reflectance being a monolithic film-side visible reflectance measured off the first major surface of the glass sheet, the glass sheet being part of a multiple-pane insulating glazing unit having a between-pane space, the first major surface of the glass sheet being an exterior surface of the unit and thus facing generally away from the between-pane space.

80. A glass sheet having generally-opposed first and second major surfaces, the first major surface bearing a coating that comprises a compound region, the compound region comprising titania and silica, wherein the compound region is a sputtered mixed oxide film having been produced by co-sputtering first and second targets, where the first target carried a sputterable material consisting essentially of titanium and the second target carried a sputterable material consisting essentially of silicon and aluminum, said co-sputtering having been carried out reactively in a single sputtering bay containing an oxidizing atmosphere, the sputtered mixed oxide film having a thickness of at least about 40 angstroms but less than about 250 angstroms, the sputtered mixed oxide film defining an exposed outermost face of the coating, the glass sheet being part of a multiple-pane insulating glazing unit having a between-pane space, the first major surface of the glass sheet being an exterior surface of the unit and thus facing generally away from the between-pane space.

81. A glass sheet having generally-opposed first and second major surfaces, the first major surface bearing a coating that comprises a compound region, the compound region comprising a photocatalyst, the photocatalyst being a first material, the compound region also comprising a second material, wherein said first and second materials are different materials, wherein the compound region includes at least three films each having a thickness of between about 10 angstroms and about 45 angstroms, wherein at least one of said films is an exposed outermost film of the coating, the coating having a total physical thickness of less than about 250 angstroms, the glass sheet being part of a multiple-pane insulating glazing unit having a between-pane space, the first major surface of the glass sheet being an exterior surface of the unit and thus facing generally away from the between-pane space.

82. The substrate of claim 82, wherein the compound region comprises the following films, in sequence outwardly from the first major surface of the substrate:

a film comprising titania and having a thickness of between about 10 angstroms and about 30 angstroms;

a film comprising silica and having a thickness of between about 5 angstroms and about 30 angstroms;

a film comprising titania and having a thickness of between about 10 angstroms and about 30 angstroms;

a film comprising silica and having a thickness of between about 5 angstroms and about 30 angstroms; and

a film that is the exposed outermost film of the coating and comprises titania and has a thickness of between about 10 angstroms and about 45 angstroms.

83. A sheet-like substrate having generally-opposed first and second major surfaces, the first major surface bearing a coating that comprises a hydrophilic film, the hydrophilic film comprising a compound that includes atoms of titanium, silicon, and oxygen, the hydrophilic film having an outermost face with an average surface roughness Ra of less than 1.8 nm, wherein the hydrophilic film has a physical thickness of less than about 300 angstroms.

84. The substrate of claim 83, wherein the substrate when uncoated has a first visible transmittance, wherein the substrate when bearing the coating has a second visible transmittance, and wherein the second visible transmittance is less than 5% greater than the first visible transmittance.

85. The substrate of claim 84, wherein the second visible transmittance is less than 3% greater than the first visible transmittance.

86. The substrate of claim 85, wherein the second visible transmittance is less than about 1% greater than the first visible transmittance.

87. The substrate of claim 83, wherein the hydrophilic film has a refractive index of greater than 1.4 but less than 2.45.

88. The substrate of claim 87, wherein the refractive index is greater than 1.45 but less than 2.4.

89. The substrate of claim 88, wherein the refractive index is greater than 1.5 but less than 2.25.

90. The substrate of claim 83, wherein the hydrophilic film is a sputtered film, the physical thickness of the sputtered film varying by less than 40 angstroms over the first major surface.

91. The substrate of claim 83, wherein the physical thickness of the hydrophilic film is between about 30 angstroms and about 200 angstroms.

92. The substrate of claim 83, wherein the compound of the hydrophilic film has between about 10 and about 50 atomic percent titanium, relative to the total number of metal atoms in the hydrophilic film.

93. The substrate of claim 83, wherein the compound of the hydrophilic film has between about 90 and about 50 atomic percent silicon, relative to the total number of metal atoms in the hydrophilic film.

94. The substrate of claim 83, wherein the substrate is a sheet of glass containing sodium.

95. The substrate of claim 83, wherein the substrate is a sheet of glass having a major dimension of at least 1 meter.

96. The substrate of claim 83, wherein the second major surface of the substrate bears a low-emissivity coating including at least one infrared-reflective film comprising silver.

97. The substrate of claim 83, wherein the coating includes at least one amorphous film between the hydrophilic film and the first major surface of the substrate.

98. The substrate of claim 83, wherein the average surface roughness Ra is less than 1.6 nm.

99. The substrate of claim 98, wherein the average surface roughness Ra is less than 0.6 nm.

100. The substrate of claim 83, wherein the substrate is provided in combination with a window frame on an exterior wall of a building, the substrate being mounted in the window frame such that the hydrophilic film is exposed to an outdoor environment.

101. The substrate of claim 100 wherein the hydrophilic film is exposed to periodic contact with rain.

102. The substrate of claim 83, wherein the substrate is part of a multiple-pane insulating glass unit.

103. A glass sheet having generally-opposed first and second major surfaces, the first major surface bearing a coating that comprises an outermost hydrophilic film, the hydrophilic film comprising a compound that includes atoms of titanium, silicon, and oxygen, wherein the glass sheet when uncoated has a first visible transmittance, wherein the glass sheet when bearing the coating has a second visible transmittance, and wherein the second visible transmittance is less than about 3% greater than the first visible transmittance.

104. The glass sheet of claim 103, wherein the second visible transmittance is less than about 1% greater than the first visible transmittance.

105. The glass sheet of claim 103, wherein the hydrophilic film has an outermost face with an average surface roughness Ra of less than 1.8 nm.

106. The glass sheet of claim 103, wherein the hydrophilic film is a sputtered film, the physical thickness of the sputtered film varying by less than 40 angstroms over the first major surface.

107. The glass sheet of claim 103, wherein the physical thickness of the hydrophilic film is between about 30 angstroms and about 200 angstroms.

108. The glass sheet of claim 103, wherein the hydrophilic film has a refractive index of greater than 1.45 but less than 2.25.

109. The glass sheet of claim 103, wherein the second major surface of the glass sheet bears a low-emissivity coating including at least one infrared-reflective film comprising silver.

110. The glass sheet of claim 103, wherein the glass sheet is provided in combination with a window frame on an exterior wall of a building, the glass sheet being mounted in the window frame such that the hydrophilic film is exposed to an outdoor environment.

111. The glass sheet of claim 110, wherein the hydrophilic film is exposed to periodic contact with rain.

112. The glass sheet of claim 103, wherein the glass sheet is part of a multiple-pane insulating glass unit.

113. A glass sheet having generally-opposed first and second major surfaces, the first major surface bearing a coating that comprises a sputtered hydrophilic film, the sputtered hydrophilic film comprising a compound that includes atoms of titanium, silicon, and oxygen, the sputtered hydrophilic film having a refractive index of greater than 1.45 but less than 2.25, and wherein the sputtered hydrophilic film has a physical thickness of between about 30 angstroms and about 200 angstroms.

114. The glass sheet of claim 113, wherein the glass sheet when uncoated has a first visible transmittance, wherein the glass sheet when bearing the coating has a second visible transmittance, and wherein the second visible transmittance is less than 3% greater than the first visible transmittance.

115. The glass sheet of claim 114, wherein the second visible transmittance is less than about 1% greater than the first visible transmittance.

116. The glass sheet of claim 113, wherein the sputtered hydrophilic film has an outermost face with an average surface roughness Ra of less than 1.8 nm.

117. The glass sheet of claim 116, wherein the average surface roughness Ra is less than 1.6 nm.

118. The glass sheet of claim 117, wherein the average surface roughness Ra is less than 0.6 nm.

119. The glass sheet of claim 113, wherein the second major surface of the glass sheet bears a low-emissivity coating including at least one infrared-reflective film comprising silver.

120. The glass sheet of claim 113, wherein the glass sheet is provided in combination with a window frame on an exterior wall of a building, the glass sheet being mounted in the window frame such that the sputtered hydrophilic film is exposed to an outdoor environment.

121. The glass sheet of claim 120, wherein the sputtered hydrophilic film is exposed to periodic contact with rain.

122. The glass sheet of claim 113, wherein the glass sheet is part of a multiple-pane insulating glass unit.

123. A glass sheet having generally-opposed first and second major surfaces, the first major surface bearing a coating that comprises an amorphous hydrophilic film, the amorphous hydrophilic film comprising a compound that includes atoms of titanium, silicon, and oxygen, wherein the amorphous hydrophilic film has a thickness of less than about 250 angstroms.

124. The glass sheet of claim 123, wherein the glass sheet when uncoated has a first visible transmittance, wherein the glass sheet when bearing the coating has a second visible transmittance, and wherein the second visible transmittance is less than 3% greater than the first visible transmittance.

125. The glass sheet of claim 124, wherein the second visible transmittance is less than about 1% greater than the first visible transmittance.

126. The glass sheet of claim 123, wherein the amorphous hydrophilic film has a refractive index of greater than 1.45 but less than 2.25.

127. The glass sheet of claim 123, wherein the amorphous hydrophilic film has an outermost face with an average surface roughness Ra of less than 1.8 nm.

128. The glass sheet of claim 123, wherein the amorphous hydrophilic film is a sputtered film, the physical thickness of the sputtered film varying by less than 40 angstroms over the first major surface.

129. The glass sheet of claim 123, wherein the second major surface of the glass sheet bears a low-emissivity coating including at least one infrared-reflective film comprising silver.

130. The glass sheet of claim 123, wherein the glass sheet is provided in combination with a window frame on an exterior wall of a building, the glass sheet being mounted in the window frame such that the amorphous hydrophilic film is exposed to an outdoor environment.

131. The glass sheet of claim 130, wherein the amorphous hydrophilic film is exposed to periodic contact with rain.

132. The glass sheet of claim 123, wherein the glass sheet is part of a multiple-pane insulating glass unit.