U.S. patent application number 12/664642 was filed with the patent office on 2010-07-22 for optical article coated with an antireflection coating comprising a sublayer partially formed under ion assistance and manufacturing process.
This patent application is currently assigned to Essilor International (Compagnie Generale d'Optique). Invention is credited to Luc Nouvelot, Johann Rotte, Karin Scherer, Daniel Vallet.
Application Number | 20100183857 12/664642 |
Document ID | / |
Family ID | 39899041 |
Filed Date | 2010-07-22 |
United States Patent
Application |
20100183857 |
Kind Code |
A1 |
Nouvelot; Luc ; et
al. |
July 22, 2010 |
Optical Article Coated with an Antireflection Coating Comprising a
Sublayer Partially Formed under Ion Assistance and Manufacturing
Process
Abstract
The invention relates to an optical article provided with
antireflection properties, comprising a substrate having at least
one main surface coated with an antireflection coating comprising,
starting from the substrate: a sub-layer comprising two adjacent
layers formed from the same material, the sum of the thicknesses of
the two adjacent layers being greater than or equal to 75 nm; and a
multilayered antireflection stack comprising at least one high
refractive index layer and at least one low refractive index layer,
the deposition of the first of said two adjacent layers of the
sub-layer having been carried out without ion assistance and the
deposition of the second of said two adjacent layers of the
sub-layer having been carried out under ion assistance. The
invention also relates to a process for manufacturing such an
optical article.
Inventors: |
Nouvelot; Luc; (Charenton Le
Pont, FR) ; Rotte; Johann; (Charenton Le Pont,
FR) ; Scherer; Karin; (Charenton Le Pont, FR)
; Vallet; Daniel; (Charenton Le Pont, FR) |
Correspondence
Address: |
FULBRIGHT & JAWORSKI L.L.P.
600 CONGRESS AVE., SUITE 2400
AUSTIN
TX
78701
US
|
Assignee: |
Essilor International (Compagnie
Generale d'Optique)
Charenton Le Pont
FR
|
Family ID: |
39899041 |
Appl. No.: |
12/664642 |
Filed: |
June 12, 2008 |
PCT Filed: |
June 12, 2008 |
PCT NO: |
PCT/FR2008/051051 |
371 Date: |
December 14, 2009 |
Current U.S.
Class: |
428/213 ;
427/569; 427/595; 428/212 |
Current CPC
Class: |
C23C 14/024 20130101;
C23C 14/022 20130101; G02C 7/022 20130101; Y10T 428/2495 20150115;
G02B 1/116 20130101; G02B 5/285 20130101; C23C 14/546 20130101;
C23C 14/22 20130101; G02B 1/14 20150115; C23C 14/30 20130101; G02C
2202/16 20130101; C23C 14/10 20130101; G02B 1/115 20130101; Y10T
428/24942 20150115 |
Class at
Publication: |
428/213 ;
427/595; 427/569; 428/212 |
International
Class: |
B32B 7/02 20060101
B32B007/02; B05D 5/06 20060101 B05D005/06; H05H 1/24 20060101
H05H001/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2007 |
FR |
0755749 |
Claims
1.-23. (canceled)
24. An optical article with antireflection properties, comprising a
substrate having at least one main surface coated with an
antireflection coating comprising, starting from the substrate: a
sub-layer comprising two adjacent layers, the sum of the
thicknesses of the two adjacent layers being greater than or equal
to 75 nm; and a multilayered antireflection stack comprising at
least one high refractive index layer and at least one low
refractive index layer, wherein the deposition of the first of the
sub-layer two adjacent layers has been carried out without ion
assistance and the deposition of the second of the sub-layer two
adjacent layers has been carried out under ion assistance.
25. The article of claim 24, wherein the two adjacent layers of the
sub-layer are formed from the same material.
26. The article of claim 24, wherein the thickness ratio of the
sub-layer two adjacent layers to each other varies from 9:1 to
1:9.
27. The article of claim 26, wherein the thickness ratio of the
sub-layer two adjacent layers to each other varies from 4:6 to
6:4.
28. The article of claim 24, wherein the sum of the thicknesses of
the two adjacent layers is greater than or equal to 80 nm.
29. The article of claim 28, wherein the sum of the thicknesses of
the two adjacent layers is greater than or equal to 100 nm.
30. The article of claim 29, wherein the sum of the thicknesses of
the two adjacent layers is greater than or equal to 150 nm.
31. The article of claim 24, wherein the sub-layer two adjacent
layers are SiO.sub.2-based layers.
32. The article of claim 31, wherein the sub-layer two adjacent
layers are free of Al.sub.2O.sub.3.
33. The article of claim 31, wherein the sub-layer two adjacent
layers consist of SiO.sub.2 layers.
34. The article of claim 24, wherein the sub-layer comprises, in
addition to the two adjacent layers, at most three layers
interleaved between the substrate and the two adjacent layers.
35. The article of claim 24, further defined as comprising an ASTM
BAYER value greater than or equal to 4.5 of the standard ASTM F
735.81.
36. The article of claim 24, wherein all the low refractive index
layers of the multilayered stacks comprise a mixture of SiO.sub.2
and Al.sub.2O.sub.3.
37. The article of claim 36, wherein all the low refractive index
layers of the multilayered stacks consist of a mixture of SiO.sub.2
and Al.sub.2O.sub.3.
38. The article of claim 24, wherein the high refractive index
layers of the multilayered stack comprise at least one of
TiO.sub.2, PrTiO.sub.3, or ZrO.sub.2, or combinations thereof.
39. The article of claim 24, further defined as an ophthalmic
lens.
40. A process for manufacturing an optical article with
antireflection properties, comprising: providing an optical article
comprising a substrate having at least one main surface; depositing
onto a main surface of the substrate a sub-layer having an exposed
surface, where the sub-layer comprises two adjacent layers, the sum
of the thicknesses of the two adjacent layers being greater than or
equal to 75 nm; depositing onto the exposed surface of the
sub-layer a multilayered antireflection stack comprising at least
one high refractive index layer and at least one low refractive
index layer, recovering an optical article comprising a substrate
having one main surface coated with an antireflection coating
comprising the sub-layer and the multilayered stack, wherein the
deposition of the first of the sub-layer two adjacent layers is
carried out without ion assistance and the deposition of the second
of the sub-layer two adjacent layers is carried out under ion
assistance.
41. The process of claim 40, wherein the two adjacent layers of the
sub-layer are formed from the same material.
42. The process of claim 40, wherein the sum of the thicknesses of
the two adjacent layers is greater than or equal to 80 nm.
43. The process of claim 42, wherein the sum of the thicknesses of
the two adjacent layers is greater than or equal to 100 nm.
44. The process of claim 43, wherein the sum of the thicknesses of
the two adjacent layers is greater than or equal to 150 nm.
45. The process of claim 40, wherein the sub-layer two adjacent
layers are SiO.sub.2-based layers.
46. The process of claim 45, wherein the sub-layer two adjacent
layers are free of Al.sub.2O.sub.3.
47. The process of claim 45, wherein the sub-layer two adjacent
layers consist of SiO.sub.2 layers.
48. The process of claim 40, wherein the deposition of each of the
sub-layer of the antireflection coating layers is carried out by
vacuum evaporation.
49. The process of claim 40, wherein, prior to depositing the
sub-layer, the surface of the substrate is submitted to a physical
or a chemical activation treatment selected from a bombardment
using energetic species, a corona discharge treatment, an ion
spallation treatment, an ultraviolet treatment or a plasma
treatment under vacuum, an acid or base treatment and/or a solvent
treatment, or combinations of these treatments.
50. The process of claim 40, wherein the deposition of one or more
of the multilayered antireflection stack layers is carried out
under ion assistance.
51. The process of claim 40, wherein the thickness ratio of the
sub-layer two adjacent layers to each other varies from 9:1 to
1:9.
52. The process of claim 51, wherein the thickness ratio of the
sub-layer two adjacent layers to each other varies from 4:6 to 6:4.
Description
[0001] The invention relates to an optical article comprising a
substrate coated with an antireflection coating comprising a
sub-layer, having in particular an improved abrasion resistance, as
well as a process for manufacturing such an optical article.
[0002] In the ophthalmic optics field, it is usual to coat an
ophthalmic lens with various coatings so as to impart various
mechanical and/or optical properties to this lens. Thus,
classically, coatings such as impact-resistant, anti-abrasion
and/or antireflection coatings are successively formed onto an
ophthalmic lens.
[0003] An antireflection coating is defined as being a coating,
deposited onto the surface of an optical article, which improves
the antireflection properties of the final optical article. It
enables to reduce the light reflection at the article-air interface
within a substantially broad range of the visible spectrum.
[0004] Anti-reflection coatings are well known and classically
comprise a mono-layer or multi-layer stack of dielectric materials
such as SiO, SiO.sub.2, Al.sub.2O.sub.3, MgF.sub.2, LiF,
Si.sub.3N.sub.4, TiO.sub.2, ZrO.sub.2, Nb.sub.2O.sub.5,
Y.sub.2O.sub.3, HfO.sub.2, Sc.sub.2O.sub.3, Ta.sub.2O.sub.5,
Pr.sub.2O.sub.3, or combinations thereof.
[0005] As is also well known, antireflection coatings are
preferably multilayered coatings comprising alternatively high
refractive index layers and low refractive index layers.
[0006] It is known to interleave a relatively thick sub-layer
between the substrate and the high refractive index and low
refractive index layers of the antireflection coating so as to
improve the abrasion resistance and/or scratch resistance of said
coating. This sub-layer may comprise one or more layer(s).
[0007] The deposition of the layers forming the sub-layer and the
multilayered antireflection stack is traditionally made by vapor
phase deposition, optionally under ion beam assistance. The ion
assisted deposition method or IAD is notably described in the US
patent application 2006/017011 and in the U.S. Pat. No. 5,268,781.
It does not require any heating of the substrates, which is
interesting for coating heat-sensitive substrates such as glass or
plastic substrates.
[0008] The evaporation under ion assistance consists in depositing
onto a substrate a film of material by vacuum evaporation by
simultaneously bombarding the surface of the substrate with an ion
beam delivered by an ion gun. The ion bombardment leads to an
atomic rearrangement in the coating being formed, which increases
its density. The IAD not only allows an improvement of the
deposited layer adhesion, but also an increase in their refractive
index.
[0009] The patent application WO 2005/059603, in the name of the
applicant, describes an ophthalmic lens substrate coated with a
multilayered colored antireflection coating, deposited without ion
assistance, and with an anti-fouling coating. The antireflection
coating is composed of a 100-110 nm-thick silica sub-layer, and of
visible-absorbing, substoichiometric titanium dioxide TiO.sub.x
(x<2)-based, alternating high refractive index layers and low
refractive index layers (LI) based on SiO.sub.2 doped with 1-5% by
weight of Al.sub.2O.sub.3, relative to the total weight of
SiO.sub.2+Al.sub.2O.sub.3.
[0010] Prior to depositing the antireflection coating, the surface
of the substrate is submitted to a treatment to improve the
adhesion of the sub-layer. This surface preparation, called IPC
(Ion Pre-cleaning) does consist in an ion bombardment pre-cleaning
of the substrate through argon ions using an ion gun.
[0011] The optical article manufactured according to the teaching
of the patent application WO 2005/059603 has good abrasion
resistance properties, which may nevertheless be further
improved.
[0012] The Japanese patent H05-034502 describes the preparation of
optical articles comprising an antireflection coating composed of a
0.125.lamda. to 0.8.lamda.-thick laminated sub-layer, with
.lamda.=500 nm and of an antireflection stack comprising a high
refractive index layer interleaved between two low refractive index
layers.
[0013] The laminated sub-layer comprises the following three
layers, that all have been deposited without ion assistance: a
SiO.sub.2 layer with a low thickness (0.05.lamda.-0.15.lamda.) and
a refractive index n=1.45-1.47, a Ta.sub.2O.sub.5 layer with a very
low thickness (0.01.lamda.-0.10.lamda.) and a refractive index
n=2-2.1, and a SiO.sub.2/Al.sub.2O.sub.3 layer with a high
thickness (0.75.lamda.-1.50.lamda.) and a refractive index
n=1.48-1.52, these three layers being deposited onto the substrate
in the order they have been mentioned.
[0014] Using this three-layered sub-layer instead of a single
SiO.sub.2/Al.sub.2O.sub.3 layer makes it possible to improve the
heat resistance properties of the optical article. This patent does
not relate to any abrasion resistance improvement.
[0015] The European patents EP 1184685 and EP 1184686 (Hoya
Corporation) describe an optical element comprising a plastic
substrate coated with a Nb (niobium metal) or SiO.sub.2 sub-layer
and an antireflection stack. The sub-layer (only if composed of
niobium), and some layers within the antireflection stack may be
deposited by evaporation under argon ion assistance. The thus
prepared article has a good thermal and scratch resistance, knowing
that the abrasion resistance thereof has not been evaluated.
[0016] It is thus an objective of the present invention to provide
a transparent optical article, in particular an ophthalmic lens,
comprising a mineral or an organic glass substrate and an
antireflection coating including a sub-layer, which does
advantageously possess both abrasion resistance and adhesion
properties improved as compared to the optical articles of the
prior art.
[0017] The prepared optical articles should retain outstanding
transparency properties, have a good resistance to a hot water-dip
treatment followed with a superficial mechanical stress, and be
free of any optical defects.
[0018] A further objective of the invention is a method for
manufacturing optical articles such as previously mentioned, which
could be easily integrated into the classical optical article
manufacturing chain and would preferably avoid heating the
substrate.
[0019] The previously mentioned inventors have found that modifying
the process for making the antireflection coating sub-layer would
enable to aim at all the previously mentioned objectives.
[0020] The hereabove mentioned objectives are thus aimed at
according to the invention through an optical article with
antireflection properties, comprising a substrate having at least
one main surface coated with an antireflection coating comprising,
starting from the substrate: [0021] a sub-layer comprising two
adjacent layers which are preferably formed from the same material,
the sum of the thicknesses of these two adjacent layers being
greater than or equal to 75 nm; and [0022] a multilayered
antireflection stack comprising at least one high refractive index
layer and at least one low refractive index layer,
[0023] the deposition of the first of said sub-layer two adjacent
layers having been carried out without ion assistance and the
deposition of the second of said sub-layer two adjacent layers
having been carried out under ion assistance.
[0024] The invention further relates to a manufacturing process of
such an optical article provided with antireflection properties,
comprising at least the following steps of:
[0025] providing an optical article comprising a substrate having
at least one main surface;
[0026] depositing onto a main surface of the substrate a sub-layer
having an exposed surface, where said sub-layer comprises two
adjacent layers which are preferably formed from the same material,
the deposition of the first of these two adjacent layers being
carried out without ion assistance, the deposition of the second of
these two adjacent layers being carried out under ion assistance,
and the sum of the thicknesses of the two adjacent layers being
greater than or equal to 75 nm;
[0027] depositing onto said exposed surface of the sub-layer a
multilayered antireflection stack comprising at least one high
refractive index layer and at least one low refractive index
layer,
[0028] recovering an optical article comprising a substrate having
one main surface coated with an antireflection coating comprising
said sub-layer and said multilayered stack.
[0029] In the present application, when an optical article is
provided with one or more coating(s) on its surface, "depositing a
layer or a coating onto the article" is intended to mean that a
layer or a coating is deposited onto the visible surface (exposed)
of the article external coating, that is to say its outermost
coating relative to the substrate.
[0030] As used herein, a coating which lies "on" a substrate or
which has been deposited "onto" a substrate is defined as a coating
which (i) is positioned over the substrate, (ii) is not necessarily
in contact with the substrate, i.e. one or more intermediary
coating(s) may be arranged between the substrate and the coating of
interest, and (iii) does not necessarily cover the substrate in
full.
[0031] When a "layer 1 is placed under a layer 2", it means that
the layer 2 is the farthest from substrate as compared to the layer
1.
[0032] As used herein, an "antireflection multilayered stack" is
intended to mean the multilayered stack of the antireflection
coating which has been deposited onto the antireflection coating
sub-layer. In the following description, it will be simply referred
to as the "multilayered stack."
[0033] The optical article prepared according to the invention
comprises a substrate, preferably transparent, in mineral or
organic glass having rear and front main faces, at least one of
which being coated with an anti-reflection coating comprising a
sub-layer coated with a multilayered stack, preferably both main
faces thereof. The multilayered stack does preferably directly
contact the sub-layer.
[0034] As used herein, the rear face (generally the concave face)
of the substrate is the face which, in use, is the closest to the
wearer's eye. On the contrary, the front face (generally the convex
face) of the substrate is the face which, in use, is the farthest
from the wearer's eye.
[0035] Generally speaking, the sub-layer and the multilayered stack
of the antireflection coating of the optical article of the
invention may be deposited onto any substrate, and preferably onto
organic glass substrates, for example a thermoplastic or
thermosetting plastic material.
[0036] To be mentioned as thermoplastic materials to be suitably
used as substrates are (meth)acrylic (co)polymers, particularly
methyl poly(methacrylate) (PMMA), thio(meth)acrylic (co)polymers,
polyvinylbutyral (PVB), polycarbonates (PC), polyurethanes (PU),
poly(thiourethanes), polyol allylcarbonate (co)polymers,
thermoplastic copolymers of ethylene/vinyl acetate, polyesters such
as polyethylene terephthalate (PET) or polybutylene terephthalate
(PBT), polyepisulfides, polyepoxides, polycarbonate and polyester
copolymers, cyclo-olefin copolymers such as copolymers of ethylene
and norbornene or ethylene and cyclopentadiene and combinations
thereof.
[0037] By (co)polymer, it is meant a copolymer or a polymer. By
(meth)acrylate, it is meant an acrylate or a methacrylate.
[0038] Preferred substrates of the invention include substrates
obtained by the polymerization of alkyl (meth)acrylates, in
particular C.sub.1-C.sub.4 alkyl (meth)acrylates such as methyl
(meth)acrylate and ethyl (meth)acrylate, polyethoxylated aromatic
(meth)acrylates such as the polyethoxylated bisphenolate
di(meth)acrylates, allyl derivatives such as aliphatic or aromatic
polyol allyl carbonates, linear or branched, thio(meth)acrylates,
episulfides, and precursor mixtures of polythiols and
polyisocyanates (to give polythiourethanes).
[0039] As used herein, a polycarbonate (PC) means both
homopolycarbonates and copolycarbonates and block copolycarbonates.
Polycarbonates are commercially available, for example from the
GENERAL ELECTRIC COMPANY under the trade name LEXAN.RTM., the
TEIJIN company under the trade name PANLITE.RTM., the BAYER company
under the trade name BAYBLEND.RTM., the MOBAY CHEMICHAL Corp. under
the trade name MAKROLON.RTM. and the DOW CHEMICAL Co. under the
trade name CALIBRE.RTM..
[0040] Suitable examples of polyol allyl carbonate (co)polymers to
be mentioned include (co)polymers of ethyleneglycol bis(allyl
carbonate), of diethyleneglycol bis 2-methyl carbonate, of
diethyleneglycol bis(allyl carbonate), of ethyleneglycol
bis(2-chloro allyl carbonate), of triethyleneglycol bis(allyl
carbonate), of 1,3-propanediol bis(allyl carbonate), of
propyleneglycol bis(2-ethyl allyl carbonate), of 1,3-butenediol
bis(allyl carbonate), of 1,4-butenediol bis(2-bromo allyl
carbonate), of dipropyleneglycol bis(allyl carbonate), of
trimethyleneglycol bis(2-ethyl allyl carbonate), of
pentamethyleneglycol bis(allyl carbonate), of isopropylene
bisphenol A bis(allyl carbonate).
[0041] Particularly recommended substrates are the substrates
obtained by (co)polymerization of diethyleneglycol bis allyl
carbonate, marketed, for example, under the trade name CR-39.RTM.
by the PPG Industries company (ESSILOR ORMA.RTM. lenses).
[0042] Other particularly recommended substrates further include
substrates obtained by polymerization of thio(meth)acrylic
monomers, such as those described in the French patent application
FR 2 734 827.
[0043] The substrates may obviously be obtained by polymerizing
mixtures of the above monomers or they also may comprise
combinations of these polymers and (co)polymers.
[0044] Preferred organic substrates are those having a thermal
expansion coefficient ranging from 50.10.sup.-6.degree. C..sup.-1
to 180.10.sup.-6.degree. C..sup.-1, preferably from
100.10.sup.-6.degree. C..sup.-1 to 180.10.sup.-6.degree.
C..sup.-1.
[0045] Prior to depositing the sub-layer onto the substrate
optionally coated for example with an abrasion- and/or
scratch-resistant layer, it is usual to submit the surface of said
optionally coated substrate, to a physical or chemical activation
treatment, to improve the adhesion of the sub-layer. This
pre-treatment is generally carried out under vacuum. It may be a
bombardment with energetic species, for example an ion beam method
("Ion Pre-Cleaning" or "IPC") or an electron beam method, a corona
treatment, an ion spallation treatment, an ultraviolet treatment or
a plasma treatment under vacuum, typically an oxygen or an argon
plasma. It may also be an acid or a base surface treatment and/or a
solvent surface treatment (using water or an organic solvent). Many
treatments may be combined. Thanks to these cleaning treatments,
the cleanliness of the substrate surface is optimized.
[0046] By energetic species, it is meant species with an energy
ranging from 1 to 300 eV, preferably from 10 to 150 eV, and more
preferably from 10 to 150 eV and most preferably from 40 to 150 eV.
Energetic species may be chemical species such as ions, radicals,
or species such as photons or electrons.
[0047] The preferred pre-treatment of the substrate surface is the
ion bombardment treatment, performed by means of an ion gun, the
ions being particles made of gas atoms from which one or more
electron(s) is or are extracted. Argon (Ar.sup.+ ions) is
preferably employed as ionized gas, but also oxygen, or
combinations thereof, under an accelerating voltage typically
ranging from 50 to 200 V, a current density typically ranging from
10 to 100 .mu.A/cm.sup.2 on the activated surface, and typically
under a residual pressure in the empty chamber which may vary from
8.10.sup.-5 mbar to 2.10.sup.-4 mbar.
[0048] According to the present invention, a sub-layer is used in
combination with a multilayered stack comprising at least one high
refractive index layer and at least one low refractive index
layer.
[0049] As used herein, a "sub-layer" or "an adhesion layer" is
intended to mean a coating that has been deposited onto the
substrate (bare or coated) prior to depositing the multilayered
stack of the invention. The sub-layer should be sufficiently thick
to promote the abrasion resistance of the antireflection coating,
but preferably not to the point there are to much overall stress
which may lead to adherence problems.
[0050] Because it is relatively thick, the sub-layer does not
typically take part to the anti-reflecting optical function,
particularly where it has a refractive index close to the bare
substrate, if the sub-layer is deposited onto the bare substrate,
or close to the coating if the sub-layer is deposited onto a coated
substrate.
[0051] The sub-layer of the invention is a multilayered sub-layer
(laminated), preferably a bilayer. In the latter case, it does not
comprise any further layers other than both adjacent layers
preferably formed from the same material and the sum of physical
thicknesses of which is greater than or equal to 75 nm.
[0052] The sum of these thicknesses is preferably greater than or
equal to 80 nm, more preferably greater than or equal to 100 nm and
even more preferably greater than or equal to 150 nm. The sum of
the thicknesses of these two adjacent layers is typically lower
than 250 nm, more preferably lower than 200 nm.
[0053] The antireflection coating sub-layer of the invention
comprises two adjacent layers preferably of a similar chemical
nature but having different characteristics because of the two
different deposition methods used.
[0054] Thus, the second of these two adjacent layers to be
deposited does posses a higher density as compared to that of the
first one, because it was formed under ion assistance whereas the
first of these two adjacent layers to be deposited was not. In the
following, the first of these two adjacent layers to be deposited
will be referred to as being the sub-layer "lower layer" whereas
the second of these two adjacent layers to be deposited will be
referred to as being the sub-layer "higher layer".
[0055] These two adjacent layers of the sub-layer are preferably
formed from the same material, which means then, in the context of
the present application, that they were formed from the same
material, for example by evaporation of the same compound (or the
same combination of compounds).
[0056] The lower layer and the higher layer of the sub-layer are
preferably SiO.sub.2-based layers. They may comprise in addition to
silica, one or more other materials traditionally used for forming
sub-layers, for example one or more materials selected from the
dielectric materials hereabove and hereafter described in the
present specification. There are preferably, SiO.sub.2-based layers
that are free of Al.sub.2O.sub.3, and most preferably they consist
in SiO.sub.2.
[0057] The lower layer and the higher layer of the sub-layer of the
present invention preferably comprise at least 70% by weight of
SiO.sub.2, more preferably at least 80% by weight and even more
preferably at least 90% by weight of SiO.sub.2. As already stated,
they each comprise in an optimal embodiment 100% by weight of
silica.
[0058] The thickness ratio of the sub-layer lower layer to the
sub-layer higher layer does preferably range from 9:1 to 1:9, more
preferably from 4:6 to 6:4. Depending on the embodiment illustrated
in the experiment section, this ratio is 1:1. The thicknesses that
are mentioned in the present application are physical thicknesses,
unless otherwise stated.
[0059] When formed from the same material, the lower layer and the
higher layer of the sub-layer may be differentiated, in particular
by means of a transmission electron microscopy, by an ion beam
analysis (RBS) or, where possible, may be evidenced by diffusing a
colored material, using their different porosities.
[0060] The sub-layer of the invention comprises at least the two
previously mentioned adjacent layers. It may comprise additional
layers, preferably at most three additional layers, more preferably
at most two other layers, interleaved between the optionally coated
substrate and said two adjacent layers, particularly if the
optionally coated substrate has a high refractive index. These
additional layers are preferably thin layers, which function
consists in restraining the reflections at the substrate-sub-layer
interface (or at the abrasion- and/or scratch-resistant
coating-sub-layer interface depending on the situation).
[0061] Thus, when the substrate has a high refractive index (i.e. a
refractive index greater than or equal to 1.55, preferably greater
than or equal to 1.57) and the sub-layer has been deposited
directly onto the substrate or the substrate is coated with an
abrasion- and/or scratch-resistant coating with a high refractive
index (that is to say greater than or equal to 1.55, preferably
greater than or equal to 1.57), preferably based on epoxysilanes,
and the sub-layer has been deposited directly onto this abrasion-
and/or scratch-resistant coating, the sub-layer comprises
preferably, in addition to the two adjacent layers preferably
formed from the same material and the sum of physical thicknesses
of which is greater than or equal to 75 nm, one layer with a high
refractive index and with a thickness lower than or equal to 80 nm,
more preferably lower than or equal to 50 nm and even more
preferably lower than or equal to 30 nm. This layer with a high
refractive index does directly contact the high index substrate or
the high index abrasion- and/or scratch-resistant coating. This
embodiment may obviously be used even if the substrate (or the
abrasion- and/or scratch-resistant coating) has a refractive index
lower than 1.55
[0062] As an alternative, the sub-layer comprises, in addition to
the two adjacent layers preferably formed from the same material
and the sum of physical thicknesses of which is greater than or
equal to 75 nm and to the hereabove mentioned high refractive index
layer, one layer composed of a low refractive index material (i.e.
lower than or equal to 1.55, preferably lower than or equal to
1.52, more preferably lower than or equal to 1.50) based on
SiO.sub.2 and free of Al.sub.2O.sub.3 or not, with a thickness
lower than or equal to 80 nm, more preferably lower than or equal
to 50 nm and even more preferably lower than or equal to 30 nm,
onto which said high refractive index layer is deposited.
[0063] Typically, in this instance, the sub-layer comprises, that
have been deposited in this order starting from the substrate, a 25
nm-thick SiO.sub.2 layer, a 10 nm-thick ZrO.sub.2 layer, said
"lower layer" of the sub-layer and said "higher layer" of the
sub-layer.
[0064] The various layers of the sub-layer are preferably deposited
by vacuum evaporation.
[0065] The IAD operation the sub-layer higher layer does undergo
may be performed by means of an ion gun, where ions are particles
composed of gas atoms from which one or more electron(s) is or are
extracted. It does preferably consist in bombarding the surface to
be treated with oxygen ions, having a current density typically
ranging from 10 to 200 .mu.A/cm.sup.2, preferably from 30 to 100
.mu.A/cm.sup.2 on the activated surface and typically under a
residual pressure in the empty chamber which may vary from
6.10.sup.-5 mbar to 2.10.sup.-4 mbar, preferably from 8.10.sup.-5
mbar to 2.10.sup.-4 mbar. Other ionized gases may be used either
combined with oxygen, or not, as for example argon, nitrogen, in
particular a mixture of O.sub.2 and argon according to a volume
ratio ranging from 2:1 to 1:2.
[0066] It is recommended not to deposit the sub-layer lower layer
under ion assistance. Otherwise, it is as if a sub-layer comprising
only one layer with a thickness greater than or equal to 75 nm and
a high density was deposited, which causes a decrease in the
adhesion of some antireflection coating layers.
[0067] Without wishing to be bound to any particular theory,
applicant believe that depositing a sub-layer with a thickness
greater than or equal to 75 nm under ion assistance gives a more
dense sub-layer, which may result in an excessive compression of
the antireflection coating and thus may cause a decrease in the
adhesion properties thereof. Conducting the deposition of the
sub-layer according to the process of the invention enables to
improve the abrasion resistance of the final article while limiting
the increase in the compressive stress so as to avoid any
antireflection coating structural weakening.
[0068] The sub-layer of the invention has a total thickness greater
than or equal to 75 nm, preferably greater than or equal to 80 nm,
more preferably greater than or equal to 100 nm and even more
preferably greater than or equal to 150 nm. Its thickness is
typically lower than 250 nm, more preferably lower than 200 nm.
[0069] The multilayered stack of the antireflection coating is
preferably deposited directly onto the exposed surface of the
sub-layer, that is to say directly onto the exposed surface of the
sub-layer higher layer.
[0070] Optionally, the exposed surface of the sub-layer may be
submitted, prior to depositing the first layer of the multilayered
stack, to a physical or a chemical activation treatment which may
be selected from the pre-treatments the substrate may undergo prior
to depositing the sub-layer and which have already be mentioned
hereabove. The preferred pre-treatment is an ion bombardment.
Traditionally conducted under vacuum, by using an ion gun-generated
argon ion beam for instance, it typically enables from the one hand
to improve the abrasion resistance properties of the antireflection
coating, and from the other hand to reinforce its adhesion
properties, particularly the adhesion of the multilayered stack to
the sub-layer.
[0071] Such physical or a chemical activation treatments may also
be performed on the surface of one or more layer(s) of the
multilayered stack, particularly on the surface of the next to last
layer of this stack.
[0072] In the present application, a layer of the multilayered
stack of the antireflection coating (AR) is said to be a high
refractive index layer (HI) when its refractive index is greater
than 1.55, preferably greater than or equal to 1.6, more preferably
greater than or equal to 1.7, even more preferably greater than or
equal to 1.8 and most preferably greater than or equal to 1.9. A
layer of the multilayered stack of the antireflection coating is
said to be a low refractive index layer (LI) when its refractive
index is lower than or equal to 1.55, preferably lower than or
equal to 1.52. more preferably lower than or equal to 1.50.
[0073] Unless otherwise stated, the refractive indexes to which it
is referred to in the present application are expressed at
25.degree. C. for a wavelength of 550 nm.
[0074] The HI layers are traditional high refractive index layers,
well known in the art. They typically comprise one or more mineral
oxides such as, without limitation, zirconia (ZrO.sub.2), titanium
dioxide (TiO.sub.2), tantalum pentoxide (Ta.sub.2O.sub.5),
neodymium oxide (Nd.sub.2O.sub.5), praseodymium oxide
(Pr.sub.2O.sub.3), praseodymium titanate (PrTiO.sub.3),
La.sub.2O.sub.3, Dy.sub.2O.sub.5, Nb.sub.2O.sub.5, Y.sub.2O.sub.3.
Optionally, the high index layers may also contain silica or
alumina, provided that their refractive index be greater than 1.55,
preferably greater than or equal to 1.6, more preferably greater
than or equal to 1.7 and even more preferably greater than or equal
to 1.9. Preferred materials include TiO.sub.2, PrTiO.sub.3,
ZrO.sub.2 and combinations thereof.
[0075] According to a particular embodiment of the invention, at
least one HI layer of the multilayered stack is a TiO.sub.2-based
layer which high refractive index is particularly interesting. It
is preferably deposited under ion assistance (IAD), which increases
the compression of this layer and thus its refractive index.
[0076] According to a further particular embodiment of the
invention, at least one HI layer of the multilayered stack is a
PrTiO.sub.3-based layer which high thermal resistance is
particularly interesting.
[0077] The LI layers are also well known and may comprise, without
limitation, SiO.sub.2, MgF.sub.2, ZrF.sub.4, alumina
(Al.sub.2O.sub.3), AIF.sub.3, chiolite (Na.sub.3Al.sub.3F.sub.14),
cryolite (Na.sub.3[AlF.sub.6]), and combinations thereof,
preferably SiO.sub.2 or SiO.sub.2 doped with alumina, which
contributes to increase the antireflection coating thermal
resistance. SiOF layers (SiO.sub.2 doped with fluorine) may also be
used. Of course, mixtures of these compounds with optionally one or
more other materials selected from the dielectric materials
previously described in the present specification are such that the
refractive index of the resulting layer is such as defined
hereabove (1.55).
[0078] When a LI layer comprising a mixture of SiO.sub.2 and
Al.sub.2O.sub.3 is used, it preferably comprises from 1 to 10%,
more preferably from 1 to 8% and even more preferably from 1 to 5%
by weight of Al.sub.2O.sub.3 relative to the total weight of
SiO.sub.2+Al.sub.2O.sub.3 in this layer. An excessive amount of
alumina may be detrimental to the adhesion of the AR coating.
[0079] For example, SiO.sub.2 doped with 4% or less Al.sub.2O.sub.3
by weight, or SiO.sub.2 doped with 8% Al.sub.2O.sub.3 may be
employed. Commercially available SiO.sub.2/Al.sub.2O.sub.3
combinations may be used, such as LIMA.RTM. marketed by Umicore
Materials AG (refractive index n=1.48-1.50 at 550 nm), or L5.RTM.
marketed by Merck KGaA (refractive index n=1.48 at 500 nm).
[0080] According to a preferred embodiment, at least one LI layer
of the multilayered stack comprises a mixture of SiO.sub.2 and
Al.sub.2O.sub.3, preferably consists in a mixture of SiO.sub.2 and
Al.sub.2O.sub.3. According to another preferred embodiment, all the
LI layers of the multilayered stack comprise a mixture of SiO.sub.2
and Al.sub.2O.sub.3, preferably consist in a mixture of SiO.sub.2
and Al.sub.2O.sub.3. In the latter case, it is particularly
preferred when the higher layer and the lower layer of the
sub-layer are SiO.sub.2-based layers free of Al.sub.2O.sub.3.
[0081] Typically, the HI layers have a physical thickness varying
from 10 to 120 nm, and the LI layers have a physical thickness
varying from 10 to 100 nm.
[0082] Preferably, the whole thickness of the antireflection
coating is lower than 1 micrometer, more preferably lower than or
equal to 800 nm and even more preferably lower than or equal to 500
nm. The whole thickness of the antireflection coating is typically
higher than 100 nm, preferably higher than 150 nm.
[0083] Even preferably, the multilayered stack comprises at least
two low refractive index layers (LI) and at least two high
refractive index layers (HI). Preferably, the layer total number in
the multilayered stack is lower than or equal to 8, more preferably
lower than or equal to 6.
[0084] LI and HI layers must not necessarily be alternated in the
stack, although they also may according to an embodiment of the
invention. Two HI layers (or more) may be deposited onto one
another; as well as two LI layers (or more) may be deposited onto
one another. It is thus interesting as regards the abrasion
resistance to stack onto one another for example a ZrO.sub.2 HI
layer and a TiO.sub.2 HI layer rather than using a TiO.sub.2 layer
instead of these two adjacent HI layers.
[0085] The sub-layer is preferably adjacent to a high refractive
index layer (HI) in the multilayered stack.
[0086] According to another preference, the outer layer of the
multilayered stack, that is to say the layer that is the most
distant from the substrate, is a layer comprising a combination of
silicon dioxide and aluminium oxide, in preferred amounts such as
those previously described.
[0087] The various layers of the multilayered stack, the so called
"optical layers", are preferably deposited by vacuum deposition
according to one of the following methods: i) by evaporation,
optionally assisted by an ion beam; ii) by spraying with an ion
beam; iii) by cathode sputtering; iv) by plasma assisted chemical
vapor deposition. These various techniques are described in "Thin
Film Processes" and "Thin Film Processes II," Vossen & Kern,
Ed., Academic Press, 1978 and 1991, respectively. The particularly
recommended technique is vacuum evaporation.
[0088] Preferably, the deposition of each of the antireflection
coating layers is performed by vacuum evaporation. Such a process
does advantageously avoid heating the substrate, which is
particularly interesting for organic glasses.
[0089] A treating step with energetic species such as previously
defined may also be carried out, simultaneously with depositing one
or more amongst the various layers of the multilayered stack. In
particular, working under ion assistance, preferably with oxygen
ions, enables to pack said layers while they are being formed.
[0090] Optionally, the deposition of one or more layer(s) of the
multilayered stack and/or of the sub-layer is performed within a
chamber under vacuum and with gas feeding during the deposition
step. In concrete terms, a gas such as, without limitation, argon,
oxygen or combinations thereof, is introduced into the chamber for
the deposition under vacuum while a layer is being deposited.
[0091] This modification to the process for depositing this layer
generally enables to limit the stress in the antireflection coating
and to reinforce the adhesion of the layers thereof. When such
deposition method is used, that is called deposition under gas
pressure regulation, is used, it is preferred to work under an
oxygen atmosphere (so called "passive oxygen").
[0092] It is well known that optical articles have a tendency to
get charged with static electricity, especially when they are
cleaned under dry conditions by rubbing their surface with a cloth
or with a piece of foam or polyester. As a consequence, they may
attract and fix small particles in the vicinity, such as dusts, as
long as the charge remains on the article. It is well known in the
art that an article can be rendered antistatic through
incorporation in its surface of one electrically conductive layer.
Such method has been applied in the world patent application WO
01/55752 and in the patent EP 0834092. This layer helps in quickly
dissipating the charges.
[0093] By "antistatic", it is meant the property of not retaining
and/or developing an appreciable electrostatic charge. An article
is generally considered to have acceptable antistatic properties
when it does not attract or fix dust or small particles after one
of the surfaces thereof has been rubbed with an appropriate
cloth.
[0094] Many methods exist for quantifying the antistatic properties
of a material.
[0095] One of these methods consists in evaluating the static
potential of the material. When the static potential of the
material (measured when the article has not been charged) is 0
KV+/-0.1 KV (in absolute value), the material is said to be
antistatic; on the contrary when its static potential is different
from 0 KV+/-0.1 KV (in absolute value), the material is said to be
static.
[0096] According to another method, the ability of a glass to
evacuate a static charge created after rubbing with a cloth or any
other electrostatic charge generation process (charge applied by
corona . . . ) can be quantified by measuring the time required for
said charge to be dissipated. Thus, antistatic glasses have a
discharge time in the order of 100 milliseconds, preferably 200 ms
or less, while static glasses have a discharge time in the order of
several tenth seconds.
[0097] The article of the invention can be rendered antistatic
through the incorporation of at least one electrically conductive
layer within the multilayered stack. The electrically conductive
layer may be located anywhere in the antireflection coating,
provided that it does not impair significantly the anti-reflection
properties thereof. It may for example be deposited onto the
sub-layer of the invention and thus form the first layer of the
multilayered stack. It is preferably located between two dielectric
layers of the multilayered stack and/or under a low refractive
index layer of the multilayered stack.
[0098] The electrically conductive layer has to be sufficiently
thin so as not to impair transparency of the antireflection
coating. Generally, its thickness ranges from 0.1 to 150 nm and
better from 0.1 to 50 nm, depending on its nature. A thickness
lower than 0.1 nm does generally not allow to obtain a sufficient
electrical conductivity, while a thickness higher than 150 nm does
generally not allow to obtain the required transparency and low
absorption characteristics.
[0099] The electrically conductive layer is preferably made from an
electrically conductive and highly transparent material. In such a
case, its thickness preferably ranges from 0.1 to 30 nm, more
preferably from 1 to 20 nm and even more preferably from 1 to 15
nm. The electrically conductive layer preferably comprises a metal
oxide chosen from indium oxides, tin oxides, zinc oxides and
mixtures thereof. Indium-tin oxide (In.sub.2O.sub.3:Sn, indium
oxide doped with tin) and tin oxide (In.sub.2O.sub.3) are
preferred. According to the most preferred embodiment of the
invention, the electrically conductive and optically transparent
layer is an indium-tin oxide layer, abbreviated as ITO.
[0100] Generally, the electrically conductive layer contributes to
the anti-reflection properties and is a high refractive index layer
of the AR coating. Examples are layers made from an electrically
conductive and highly transparent material such as ITO layers.
[0101] The electrically conductive layer may also be a very thin
noble metal layer (Ag, Au, Pt, etc.), typically of less than 1 nm
thick, preferably of less than 0.5 nm thick.
[0102] As a particularly advantageous characteristic, the
multilayered stack of the antireflection coating comprises at least
four dielectric layers, preferably four or five, and optionally one
electrically conductive layer which imparts to the article its
antistatic properties.
[0103] In a preferred embodiment of the invention, the
antireflection coating of the invention comprises, in the
deposition order onto the substrate surface, a bilayered SiO.sub.2
sub-layer with a thickness greater than or equal to 75 nm in
accordance with the invention, a ZrO.sub.2 layer, typically with a
thickness of from 10 to 40 nm and preferably of from 15 to 35 nm, a
SiO.sub.2 layer or a SiO.sub.2/Al.sub.2O.sub.3 layer, preferably a
SiO.sub.2/Al.sub.2O.sub.3 layer typically with a thickness of from
10 to 40 nm and preferably of from 15 to 35 nm, a TiO.sub.2 layer,
typically with a thickness of from 40 to 150 nm, preferably of from
50 to 120 nm, a ZrO.sub.2 layer, typically with a thickness of from
8 to 30 nm and preferably of from 10 to 25 nm, optionally an
electrically conductive layer, preferably an ITO layer, typically
with a thickness of from 0.1 to 30 nm, preferably of from 1 to 20
nm, and a SiO.sub.2 layer or SiO.sub.2/Al.sub.2O.sub.3 layer,
preferably a SiO.sub.2/Al.sub.2O.sub.3 layer typically with a
thickness of from 40 to 150 nm, preferably of from 50 to 100
nm.
[0104] It is preferred that the multilayered stack of the invention
comprises an electrically conductive layer, and more preferred that
the article of the invention comprises a stack composed of
TiO.sub.2/ZrO.sub.2/electrically conductive layer, the first layer
mentioned being the nearest from the substrate.
[0105] According to a particularly preferred embodiment of the
invention, are successively deposited, starting from the surface of
the substrate optionally coated with one or more functional
coatings, a SiO.sub.2 sub-layer according to the invention with a
thickness greater than or equal to 120 nm composed of two adjacent
layers formed preferably from the same material, a ZrO.sub.2 layer
with a thickness of from 20 to 30 nm, a SiO.sub.2/Al.sub.2O.sub.3
layer with a thickness of from 20 to 30 nm, a TiO.sub.2 layer with
a thickness of from 75 to 110 nm, a ZrO.sub.2 layer with a
thickness of from 10 to 20 nm, an ITO layer with a thickness of
from 2 to 18 nm, and a SiO.sub.2/Al.sub.2O.sub.3 layer with a
thickness of from 60 to 90 nm.
[0106] The electrically conductive layer, which is typically a high
refractive index layer of the antireflection stack, may be
deposited according to any suitable method, for example by vacuum
evaporation deposition, preferably ion-beam-assisted (IAD), or by
means of a cathode sputtering or ion beam method.
[0107] When present, the three TiO.sub.2/ZrO.sub.2/electrically
conductive layer (preferably ITO) successive layers are preferably
all three deposited under ion assistance (IAD), preferably under
oxygen ion assistance.
[0108] The sub-layer and the multilayered stack may be deposited
directly onto a bare substrate. In some applications, it is
preferred that the main surface of the substrate be coated with one
or more functional coating(s) prior to depositing the
antireflection coating of the invention. These functional coatings
classically used in optics may be, without limitation, an
impact-resistant primer layer, an abrasion- and/or a
scratch-resistant coating, a polarized coating, a photochromic
coating, an antistatic coating or a colored coating.
[0109] The sub-layer and the multilayered stack are preferably
deposited onto an abrasion- and/or scratch-resistant coating. The
abrasion- and/or scratch-resistant coating may be any layer
classically used as an abrasion- and/or scratch-resistant coating
in the field of ophthalmic lenses.
[0110] The abrasion- and/or scratch-resistant coatings are
preferably poly(meth)acrylate- or silane-based hard coatings,
comprising typically one or more inorganic fillers so as to improve
the hardness and/or the refractive index of the coating once
cured.
[0111] Abrasion- and/or scratch-resistant hard coatings are
preferably prepared from compositions comprising at least one
alkoxysilane and/or or a hydrolyzate thereof, resulting for example
from a hydrolysis with a hydrochloric acid solution. After the
hydrolysis step which typically lasts for 1 to 24 h, preferably for
2 to 6 h, condensation and/or curing catalysts may optionally be
added. A surfactant is also preferably added to the composition so
as to improve the optical quality of the deposit.
[0112] Recommended coatings according to the invention include
coatings based on epoxysilane hydrolyzates such as those described
in the patents FR 2702486 (EP 0614957), U.S. Pat. No. 4,211,823 and
U.S. Pat. No. 5,015,523.
[0113] Many examples of condensation and/or curing catalysts that
may be suitably used are given in "Chemistry and Technology of the
Epoxy Resins", B. Ellis (Ed.) Chapman Hall, New York, 1993 and
"Epoxy Resins Chemistry and Technology" 2d edition, C. A. May
(Ed.), Marcel Dekker, New York, 1988.
[0114] A preferred abrasion- and/or scratch-resistant coating
composition is disclosed in the French patent FR 2702486, in the
name of the applicant. It comprises an epoxy trialkoxysilane and
dialkyl dialkoxysilane hydrolyzate, colloidal silica and a
catalytic amount of an aluminium-based curing catalyst such as
aluminium acetylacetonate, the remaining of the composition being
essentially comprised of solvents typically used for formulating
these compositions. Preferably, the hydrolyzate used is a
.gamma.-glycidoxypropyltrimethoxysilane (GLYMO) and
dimethyldiethoxysilane (DMDES) hydrolyzate.
[0115] The abrasion- and/or scratch-resistant coating composition
may be deposited onto the main surface of the substrate by
dip-coating or spin-coating. It is then cured by means of the
appropriate method (preferably thermal curing, UV-curing).
[0116] The thickness of the abrasion- and/or scratch-resistant
coating typically varies from 2 to 10 .mu.m, preferably from 3 to 5
.mu.m.
[0117] Prior to depositing the abrasion- and/or scratch-resistant
coating, it is possible to deposit onto the substrate a primer
coating to improve the impact resistance and/or the adhesion of the
subsequent layers in the end product.
[0118] Such coating may be any impact-resistant primer layer
classically used for articles made from a transparent polymer
material, such as ophthalmic lenses.
[0119] Preferred primer compositions include for example
thermoplastic polyurethane-based compositions, such as those
described in the Japanese patents JP 63-141001 and JP 63-87223,
poly(meth)acrylic primer compositions, such as those described in
the American patent U.S. Pat. No. 5,015,523, thermosetting
polyurethane-based compositions, such as those described in the
patent EP 0404111 and poly(meth)acrylic type latex- or polyurethane
type latex-based compositions, such as those described in the
patents U.S. Pat. No. 5,316,791 and EP 0680492.
[0120] Polyurethane-based compositions and latex-based compositions
are the preferred primer compositions, particularly polyurethane
latex type primer compositions.
[0121] The poly(meth)acrylic type latexes are latexes of copolymers
mainly composed of a (meth)acrylate, such as for example ethyl,
butyl, methoxyethyl or ethoxyethyl (meth)acrylate, with a generally
minor amount of at least one other co-monomer, such as for example
styrene.
[0122] Preferred poly(meth)acrylic latexes are latexes of acrylate
and styrene copolymers. Such latexes of acrylate and styrene
copolymers are commercially available from the ZENECA RESINS
company under the trade name NEOCRYL.RTM..
[0123] Polyurethane latexes are also known and commercially
available. To be mentioned as suitable examples are polyester
unit-containing polyurethane latexes. Such latexes are also
marketed by the ZENECA RESINS company under the trade name
NEOREZ.RTM. and by the BAXENDEN CHEMICALS company under the trade
name WITCOBOND.RTM..
[0124] Marketed primer compositions to be suitably used according
to the invention include the Witcobond.RTM. 232, Witcobond.RTM.
234, Witcobond.RTM. 240, Witcobond.RTM. 242, Neorez.RTM. R-962,
Neorez.RTM. R-972, Neorez.RTM. R-986 and Neorez.RTM. R-9603
compositions.
[0125] Combinations of these latexes, particularly of polyurethane
latexes and poly(meth)acrylic latexes may also be used in the
primer compositions.
[0126] These primer compositions may be deposited on the article
sides by dip-coating or spin-coating, thereafter be dried at a
temperature of at least 70.degree. C. and up to 100.degree. C.,
preferably of about 90.degree. C., for 2 minutes to 2 hours,
typically for about 15 minutes, to form primer layers having
thicknesses, after curing, ranging from 0.2 to 2.5 .mu.m,
preferably from 0.5 to 1.5 .mu.m.
[0127] The optical article of the invention may also comprise
coatings formed on the antireflection coating that may modify the
surface properties thereof, such as hydrophobic and/or oleophobic
coatings (anti-fouling top coat). These coatings are preferably
deposited onto the outer layer of the antireflection coating. The
thickness thereof is generally lower than or equal to 10 nm,
preferably ranging from 1 to 10 nm, more preferably from 1 to 5
nm.
[0128] There are typically coatings of the fluorosilane or
fluorosilazane type. They may be obtained by depositing a
fluorosilane or fluorosilazane precursor, comprising preferably at
least two hydrolyzable groups per molecule. Fluorosilane precursors
preferably comprise fluoropolyether moieties and more preferably
perfluoropolyether moieties. These fluorosilanes are well known and
are described, amongst others, in the patents U.S. Pat. No.
5,081,192, U.S. Pat. No. 5,763,061, U.S. Pat. No. 6,183,872, U.S.
Pat. No. 5,739,639, U.S. Pat. No. 5,922,787, U.S. Pat. No.
6,337,235, U.S. Pat. No. 6,277,485 and EP 0933377.
[0129] A preferred hydrophobic and/or oleophobic coating
composition is marketed by the Shin-Etsu Chemical company under the
trade name KP 801M.RTM.. Another preferred hydrophobic and/or
oleophobic coating composition is marketed by the Daikin Industries
company under the trade name OPTOOL DSX.RTM.. It is a fluorinated
resin comprising perfluoropropylene groups.
[0130] Typically, an optical article of the invention comprises a
substrate successively coated with an impact-resistant primer
layer, an abrasion- and/or scratch-resistant layer, a sub-layer of
the invention, a multilayered antireflection stack and a
hydrophobic and/or oleophobic coating. The article of the invention
is preferably an optical lens, more preferably an ophthalmic lens
for eyeglasses, or an optical or an ophthalmic lens blank. The lens
may be a polarized lens or a photochromic lens.
[0131] Due to its sub-layer resulting from the process according to
the invention, the optical article of the invention possesses
improved abrasion resistance properties as compared to the same
article with a traditionally deposited sub-layer. These abrasion
resistance properties may be evaluated according to the Bayer test
ASTM, described in the experiment section.
[0132] The optical articles of the invention have preferably a
BAYER value greater than or equal to 4.5 according to the ASTM
standard F 735.81, more preferably greater than or equal to 5 and
even more preferably greater than or equal to 5.2.
[0133] The various layers of the antireflection coating have good
adhesion properties, particularly at the substrate interface. The
adhesion properties of the whole antireflection coating to the
substrate have been controlled by means of the test ordinarily
called "the n.times.10 blow test", by following the procedure
described in the world patent application WO 99/49097.
[0134] The optical article of the invention has a high thermal
resistance, evaluated through its critical temperature, defined as
being the temperature from which cracks can be observed in the
antireflection coating. The critical temperature of an article of
the invention is preferably greater than or equal to 80.degree. C.,
more preferably greater than or equal to 85.degree. C. and even
more preferably greater than or equal to 90.degree. C.
[0135] The optical article of the invention does not absorb or does
barely absorb in the visible range, which means, in the context of
the present application, that the transmission factor thereof in
the visible range .tau..sub.v, also called luminous transmittance,
is greater than 90%, more preferably greater than 95%, even more
preferably greater than 96% and most preferably higher than
97%.
[0136] The .tau.v factor does correspond to an international
definition (standard ISO 13666:1998) and is measured in accordance
with the standard ISO 8980-3. It is defined within the wavelength
range ranging from 380 to 780 nm.
[0137] Preferably, the light absorption of the coated article of
the invention is lower than or equal to 1%. Even preferably, the
mean reflection factor in the visible (400-700 nm) of an article
coated with an antireflection coating of the invention, written
R.sub.m, is lower than 2.5% per face, more preferably lower than 2%
per face and even more preferably lower than 1% per face of the
article. In a most preferred embodiment of the invention, the
article comprises a substrate both main surfaces of which are
coated with an antireflection coating of the invention and has a
R.sub.m total value (reflection values cumulated because of the two
faces) lower than 1%, preferably ranging from 0.7 to 0.8%. The
procedures to obtain such R.sub.m values are well known from the
man skilled in the art.
[0138] In the present application, the "mean reflection factor" is
such as defined in the standard ISO 13666:1998 and measured in
accordance with the standard ISO 8980-4, that is to say it
corresponds to the average spectral reflection from 400 to 700
nm.
[0139] The following examples are meant to illustrate the invention
and are not to be interpreted as limiting the scope thereof.
EXAMPLES
1. General Procedures
[0140] The optical articles used in the examples comprise an
ORMA.RTM. lens substrate from ESSILOR with a diameter of 65 mm, a
power of -2.00 diopters and a thickness of 1.2 mm, coated (except
example C2) with an impact-resistant primer based on a polyurethane
latex comprising polyester units, cured to 90.degree. C. for 1 hour
(Witcobond.RTM. 234 from BAXENDEN CHEMICALS modified through
dilution to reduce the viscosity thereof, spin-coating at 1500 rpm
for 10 to 15 seconds) thereafter with the abrasion-resistant and
scratch-resistant coating (hard coat) disclosed in example 3 of the
patent EP 0614957 (with a refractive index of 1.50), based on a
GLYMO and DMDES hydrolyzate, colloidal silica and aluminium
acetylacetonate, with an antireflection coating and lastly with an
anti-fouling coating.
[0141] Said abrasion-resistant and scratch-resistant coating was
obtained by depositing and curing a composition comprising by
weight, 224 parts of GLYMO, 80.5 parts of HCl 0.1 N, 120 parts of
DMDES, 718 parts of 30% by weight colloidal silica in methanol, 15
parts of aluminium acetylacetonate and 44 parts of ethyl
cellosolve. The composition further comprises 0.1% by weight
relative to the total weight of the composition of a surfactant
FLUORAD.TM. FC-430.RTM. from the 3M company.
[0142] The layers of the sub-layer and of the multilayered stack of
the antireflection coating were deposited without heating the
substrates, by vacuum evaporation, optionally, when specified,
ion-beam-assisted and/or with oxygen feeding during the deposition
(evaporation source: electron gun).
[0143] The SiO.sub.2/Al.sub.2O.sub.3 mixture used in the examples
is L5.RTM. marketed by Merck KGaA. The antistatic layers are made
from indium-tin oxide, abbreviated as ITO, available from Optron
Inc.
[0144] The anti-fouling coating was obtained by vacuum evaporation
of the OF110 compound provided by the Optron Inc. Company
(thickness: 2-5 nm).
[0145] The device used for the deposition belongs to a Leybold 1104
apparatus fitted with an electron gun ESV14 (8 kV) for evaporating
oxides, with a Joule effect crucible for depositing the top coat
and with an End-Hall type ion gun (KR1 for examples 1, 2 and C1,
Commonwealth Mark II for example C2) for the preliminary phase of
the substrate surface preparation with argon ions (IPC) and
optionally for that of the sub-layer (example C1 only), as well as
for depositing layers under ion assistance.
[0146] The thickness of the layers is controlled by means of a
quartz scale.
2. Procedures
[0147] The process for manufacturing optical articles did comprise
the introduction of the substrate coated with a primer coating
(except example C2) and with an abrasion-resistant coating into a
vacuum deposition chamber, a pumping operation until a secondary
vacuum was reached, then an activation of the substrate surface
using an argon ion beam (IPC: 2 minutes, 18 cm.sup.3/min, 3 A for
examples 1, 2 and C1; 2 minutes, 13 sccm, 2.5 A for example C2),
the interruption of the ion irradiation, the successive evaporation
of the antireflection coating required number of layers, a
deposition of the anti-fouling coating (top coat) and lastly a
ventilation operation were performed.
[0148] Formation of the Antireflection Coating According to the
Process of the Invention (Examples 1 and 2)
[0149] The process for manufacturing the antireflection coating of
the invention comprises: [0150] The deposition of a bilayered
SiO.sub.2 sub-layer comprising: i) the deposition onto the
substrate coated of a first SiO.sub.2 layer at a rate of 1 nm/s
(without ion assistance) until a thickness of 75 nm was reached
(controlled by means of a quartz scale). The closure element of the
electron gun is closed and the evaporation stopped; ii) the
deposition onto this first layer of a second SiO.sub.2 layer at a
rate of 1 nm/s under oxygen ion assistance (corresponding to 15
cm.sup.3/min -2 A). The deposition of this second layer is
conducted by priming the ion gun, preferably with the selected
oxygen flow rate. Once the ion beam has been formed and stabilized,
the silica granulates are pre-heated again with the electron gun,
and the closure element of the electron gun is opened so as to
deposit 75 nm thick silica through concomitant ion bombardment. The
electron gun closure element is closed, then the evaporation and
the ion bombardment are stopped. [0151] The deposition of a
multilayered antireflection stack comprising the deposition of the
first HI layer (ZrO.sub.2) at a rate of 0.3 nm/s, the deposition of
the first LI layer (SiO.sub.2/Al.sub.2O.sub.3) at a rate of 0.7
nm/s, the deposition of the second HI layer (TiO.sub.2, from
pre-molten granulates) at a rate of 0.3-0.5 nm/s and under oxygen
ion assistance (corresponding to 15 cm.sup.3/min-2 A for Example 1
and to 18 cm.sup.3/min-3 A for Example 2), the deposition of a
third HI layer (ZrO.sub.2) at a rate of 0.30 nm/s and under oxygen
ion assistance (corresponding to 15 cm.sup.3/min-2 A), the
deposition of an ITO layer at a rate of 0.2-0.5 nm/s and under
oxygen ion assistance (corresponding to 15 cm.sup.3/min-2 A), and
lastly the deposition of the second LI layer
(SiO.sub.2/Al.sub.2O.sub.3) at a rate of 1 nm/s.
Formation of the Antireflection Coating in the Comparative Examples
C1 and C2
[0152] The formation of the antireflection coating comprises the
step of depositing the SiO.sub.2 sub-layer onto the coated
substrate at a rate of 1 nm/s, under an O.sub.2 atmosphere and a
pressure of 1.5.10.sup.-4 mBar (example C1 only), optionally
activating the sub-layer surface by means of an argon ion beam (the
same treatment as IPC already performed directly on the substrate,
example C1 only), stopping the ion irradiation, depositing the
first HI layer (ZrO.sub.2) at a rate of 0.3 nm/s, depositing the
first LI layer (SiO.sub.2/Al.sub.2O.sub.3) at a rate of 0.7 nm/s,
depositing the second HI layer (TiO.sub.2 from premolten
granulates) at a rate of 0.3-0.5 nm/s, under oxygen ion assistance
(corresponding to 18 cm.sup.3/min-3 A for C1 and 2.5 A -120 V for
C2), and optionally under an O.sub.2 atmosphere (under a pressure
of 1.10.sup.-4 mBar, example C2 only), depositing the third HI
layer (ZrO.sub.2) at a rate of 0.3 nm/s and optionally under oxygen
ion assistance (corresponding to 15 cm.sup.3/min-2 A, example C1
only), depositing an ITO layer at a rate of 0.2-0.5 nm/s and under
oxygen ion assistance (corresponding to 15 cm.sup.3/min-2 A for C1
and 2.5 A -120 V for C2), and lastly depositing the second LI layer
(SiO.sub.2/Al.sub.2O.sub.3) at a rate of 1 nm/s.
[0153] The contents of the optical articles obtained in examples 1,
2 and comparative examples C1 and C2 is detailed hereunder:
TABLE-US-00001 ##STR00001## ##STR00002## ##STR00003## The sub-layer
appears in grey. (a) Treatment through ion bombardment of the layer
surface prior to depositing the next layer. (b) Oxygen supply for
the deposition. (c) Deposition of the layer under ion
assistance.
3. Characterization of the Abrasion Resistance
[0154] The abrasion resistance of the articles manufactured was
evaluated by determining the BAYER values by means of the Bayer
test (Bayer sand method) in accordance with the standard ASTM F
735.81, with a higher Bayer value meaning a higher abrasion
resistance. The Bayer sand value is considered to be good when R is
between 3.4 and 4.5, and to be outstanding when R is equal to or
higher than 4.5.
[0155] Such test consists in making simultaneously oscillate a
sample glass and a reference glass with a given reciprocating
motion in a tray containing an abrasive powder (about 500 g sand)
with a defined particle size at a frequency of 100 cycles/minute
for 2 minutes. Measurements of the sample glass "before/after" are
compared with those of a reference glass, indeed a CR-39.RTM.-based
bare glass for which the BAYER value is set to 1. The Bayer sand
value is R.dbd.H reference glass/H sample glass.
[0156] The diffusion measurements were conducted using a Hazeguard
system model XL-211 manufactured by Pacific Scientific.
4. Results
[0157] The results of the abrasion resistance measurements are
given in Table 1 hereunder.
TABLE-US-00002 TABLE 1 Bayer Test ASTM (BAYER Example SAND) 1 6.0 2
5.4 Comparative 1 4.7 Comparative 2 4.8
[0158] The lenses of examples 1 and 2 have a better abrasion
resistance than those of the comparative examples do.
* * * * *