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1. US20090169859 - Article Comprising a Mesoporous Coating Having a Refractive Index Profile and Methods for Making Same

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[ EN ]

Claims

1.- 34. (canceled)
35. An article comprising a substrate having a main surface covered with a coating at least part of which coating is mesoporous, wherein the mesoporous part of said coating comprises a refractive index profile with optical function with variation imposed by mesopore content and/or filling ratio of the mesopores.
36. The article of claim 35, wherein the refractive index variation is monotone, decreasing along any axis which is perpendicular to the surface of the substrate underlying the mesoporous part of said coating and oriented away from the substrate.
37. The article of claim 35, wherein the mesoporous coating comprising a refractive index profile has a thickness ranging from 50 to 500 nm.
38. The article of claim 35, further defined as an optical fiber or optical lens.
39. The article of claim 35, further defined as having an average reflection factor in the visible region Rm of lower than 2%.
40. The article of claim 39, further defined as having an average reflection factor in the visible region Rm of lower than 0.75%.
41. The article of claim 35, wherein the coating comprising a refractive index profile comprises a silica-based matrix comprising silanol groups.
42. The article of claim 41, wherein at least part of the silanol groups have been derivatized to hydrophobic groups by reacting with a hydrophobic reactive compound.
43. The article of claim 35, wherein the coating has a hydrophobic matrix.
44. The article of claim 35, wherein the refractive index profile gradually varies.
45. The article of claim 35, wherein the whole volume filled by the coating comprising a refractive index profile is mesoporous.
46. The article of claim 35, wherein at least one localized area of the coating comprising a refractive index profile is mesoporous until a certain depth of said coating.
47. The article of claim 35, wherein the whole coating comprising a refractive index profile is mesoporous until a certain depth of said coating.
48. The article of claim 35, wherein at least one localized area of the coating comprising a refractive index profile is mesoporous along the whole depth of said coating.
49. A method for making an article of claim 35, comprising:
a) providing a substrate;
b) preparing a precursor sol of a mesoporous film comprising at least one inorganic precursor agent, at least one pore-forming agent, at least one organic solvent, and water;
c) depositing a film of the precursor sol prepared in the previous step onto a main surface of the substrate;
d) removing the pore-forming agent from at least part of the coating comprising the film deposited in step c);
e) recovering a substrate having a main surface covered with a coating, part of which at least is mesoporous;
wherein in step d), the pore-forming agent is partially removed from at least part of the coating comprising the film deposited in step c) so as to create in said part of the coating a refractive index gradient which is perpendicular to the surface of the substrate underlying said part of the coating and directed towards the surface of said coating which is closest to the substrate.
50. The method of claim 49, wherein the inorganic precursor agent is of formula:

          M(X) 4  (I)
wherein M is a tetravalent metal or metalloid and the X groups independently are hydrolysable groups.
51. The method of claim 50, wherein M is Ti, Zr, Hf, Sn or Si.
52. The method of claim 50, wherein the X groups are independently alkoxy, acyloxy, or halogen groups.
53. The method of claim 49, wherein the pore-forming agent is cetyl trimethylammonium bromide, cetyl trimethylammonium chloride, ethylene oxide and a propylene oxide three-block copolymer, ethylene oxide and a propylene oxide two-block copolymer, or poly(ethylenoxy)alkyl-ethers.
54. The method of claim 49, further comprising a step of introducing at least one hydrophobic precursor agent bearing at least one hydrophobic group into the precursor sol before the step of depositing the film of the precursor sol.
55. The method of claim 49, wherein the precursor sol further comprises a catalyst capable of hydrolyzing the inorganic precursor agent.
56. The method of claim 49, further comprising consolidating the film deposited in steps c) and d).
57. The method of claim 56, further comprising a step of treating the film subsequent to the deposition step, or, if present, subsequent to the consolidation step, with at least one hydrophobic reactive compound bearing at least one hydrophobic group, provided that, if a hydrophobic precursor agent bearing at least one hydrophobic group has been introduced into the precursor sol, said hydrophobic reactive compound is different from said hydrophobic precursor agent.
58. The method of claim 49, further defined as comprising at least the following steps:
a) providing a substrate;
b) preparing a precursor sol of a mesoporous film comprising at least one inorganic precursor agent, at least one pore-forming agent, at least one organic solvent, and water;
c) depositing a film of the precursor sol prepared in the previous step onto a main surface of the substrate;
d) depositing onto the film resulting from the previous step a precursor sol of a mesoporous film comprising at least one inorganic precursor agent, at least one pore-forming agent, at least one organic solvent, and water;
e) removing the pore-forming agent at least partially from at least part of the coating comprising the films deposited;
f) recovering a substrate having a main surface covered with a multilayered coating, part of which at least is mesoporous and has a refractive index profile decreasing away from the substrate along any axis which is perpendicular to the surface of the substrate underlying said mesoporous part of said coating;
wherein in step d), the pore-forming agent represents a higher percentage of the precursor sol total mass as compared to that of the pore-forming agent in the precursor sol used to make the film obtained in the previous step.
59. The method of claim 58, wherein the precursor sol further comprises a catalyst capable of hydrolyzing the inorganic precursor agent.
60. The method of claim 58, further comprising consolidating the film deposited in steps c) and d).
61. The method of claim 60, further comprising a step of treating the film subsequent to the deposition step, or, if present, subsequent to the consolidation step, with at least one hydrophobic reactive compound bearing at least one hydrophobic group, provided that, if a hydrophobic precursor agent bearing at least one hydrophobic group has been introduced into the precursor sol, said hydrophobic reactive compound is different from said hydrophobic precursor agent.
62. The method of claim 58, further comprising repeating step d) at least once, wherein, in each step d), the pore-forming agent represents a higher percentage of the precursor sol total mass as compared to that of the pore-forming agent in the precursor sol used to make the film obtained in the previous step.
63. The method of claim 58, wherein the inorganic precursor agent is of formula:

          M(X) 4  (I)
wherein M is a tetravalent metal or metalloid and the X groups independently are hydrolysable groups.
64. The method of claim 63, wherein M is Ti, Zr, Hf, Sn or Si.
65. The method of claim 63, wherein the X groups are independently alkoxy, acyloxy, or halogen groups.
66. The method of claim 58, wherein the pore-forming agent is cetyl trimethylammonium bromide, cetyl trimethylammonium chloride, ethylene oxide and a propylene oxide three-block copolymer, ethylene oxide and a propylene oxide two-block copolymer, or poly(ethylenoxy)alkyl-ethers.
67. The method of claim 58, further comprising a step of introducing at least one hydrophobic precursor agent bearing at least one hydrophobic group into the precursor sol before the step of depositing the film on the precursor sol.
68. The method of claim 67, wherein all the steps thereof are conducted at a temperature ≦150° C.
69. The method of claim 68, wherein all the steps thereof are conducted at a temperature ≦110° C.
70. The method of claim 58, wherein the removal of the pore-forming agent is performed by degradation, oxygen plasma-assisted oxidation, argon plasma-assisted oxidation, by ozone oxidation, corona discharge, or light-irradiation photodegradation calcination, solvent extraction, or supercritical fluid extraction.
71. The method of claim 58, wherein the pore-forming agent has been removed from the whole volume filled by the coating.
72. The method of claim 58, wherein the pore-forming agent has been removed along the whole depth of at least one localized area of the coating.
73. The method of claim 49, wherein the hydrophobic precursor agent is selected from compounds and mixtures of compounds of formula (II) or (III):

          (R 1) n1(R 2) n2M  (II)

          or

          (R 1) n3(R 4) n4M-R′-M(R′) n5(R 5) n6  (III)
wherein:
M is a tetravalent metal or metalloid;
R 1, R 3 and R 5, independently, are saturated or unsaturated and substituted or unsubstituted hydrocarbon hydrophobic group or fluorinated or perfluorinated analogous groups of said hydro carbon hydrophilic groups;
R 2, R 4 and R 6, independently, are hydrolysable groups;
R′ is a divalent group;
n 1 is an integer ranging from 1 to 3, n 2 is an integer ranging from 1 to 3, n 1+n 2=4; and
n 3, n 4, n 5, and n 6 are integers ranging from 0 to 3 provided that the sums of n 3+n 5 and n 4+n 6 are different from zero, and n 3+n 4=n 5+n 6=3.
74. The method of claim 73, wherein M is Si, Sn, Zr, Hf or Ti.
75. The method of claim 73, wherein said hydrocarbon hydrophobic groups are alkyl, vinyl, or aryl groups.
76. The method of claim 73, wherein said hydrolysable groups are alkoxy groups, —O—C(O)R acyloxy groups where R is a C 1-C 6 alkyl radical, and/or halogens.
77. The method of claim 73, wherein R′ is an alkylene or arylene group.
78. The method of claim 73, wherein the mole ratio of the hydrophobic precursor agent to the inorganic precursor agent varies from 10:90 to 50:50.
79. The method of claim 78, wherein the mole ratio of the hydrophobic precursor agent to the inorganic precursor agent is equal to 40:60.
80. The method of claim 49, further comprising a step of treating the film subsequent to the deposition step, or, if present, subsequent to the consolidation step, with at least one hydrophobic reactive compound bearing at least one hydrophobic group, provided that, if a hydrophobic precursor agent bearing at least one hydrophobic group has been introduced into the precursor sol, said hydrophobic reactive compound is different from said hydrophobic precursor agent.
81. The method of claim 80, wherein the step of introducing said hydrophobic reactive compound is conducted before, after or during the step of removing the pore-forming agent.
82. The method of claim 80, wherein the hydrophobic reactive compound is of formula (IX):

          (R 1) 3(R 2)M  (IX)
wherein:
M is a tetravalent metal or metalloid;
the R 1 groups, independently, are saturated or unsaturated hydrocarbon hydrophobic groups; and
R 2 is a hydrolysable group.
83. The method of claim 82, wherein M is Si, Sn, Zr, Hf or Ti.
84. The method of claim 82, wherein said hydrocarbon hydrophobic groups are methyl, ethyl, vinyl, and/or aryl groups.
85. The method of claim 82, wherein said hydrolysable groups are alkoxy groups, —O—C(O)R acyloxy groups in which R is an alkyl radical, substituted or unsubstituted amino groups, and/or halogens.
86. The method of claim 82, wherein the hydrophobic reactive compound is a trialkylchlorosilane, a trialkylalkoxysilane, a fluoroalkyl alkoxysilane, a fluoroalkyl chlorosilane, a trialkylsilazane, or a hexaalkyldisilazane.
87. The method of claim 80, wherein a treatment of the film with ultrasounds is conducted during the step of treating said film with at least one hydrophobic reactive compound bearing at least one hydrophobic group.
88. The method of claim 49, wherein all the steps thereof are conducted at a temperature ≦150° C.
89. The method of claim 88, wherein all the steps thereof are conducted at a temperature ≦110° C.
90. The method of claim 49, wherein the partial removal of the pore-forming agent is performed by controlled degradation, oxygen plasma-assisted oxidation, argon plasma-assisted oxidation, by ozone oxidation, corona discharge, or light-irradiation photodegradation.
91. The method of claim 49, wherein the pore-forming agent has been removed until a certain depth from at least one localized area of the mesoporous coating comprising a refractive index profile.
92. The method of claim 49, wherein the pore-forming agent has been removed until a certain depth from the whole coating.