Note: Descriptions are shown in the official language in which they were submitted.
S~79
Transparent, laminated, light polarizing glasses are
used extensively in the making of medical, ophthalmic, sun,
and protective spectacle lenses, but they could also be
utilized in other fields as, for example, instrument lenses,
windows for vehicles of all kinds (air, sea, land), wi~dows
for buildings, and the like.
The manufacture of polarizing glasses raises various
problems related to the solubility of the polarizing materials
(generally the polarizing particles) in the surrounding
environments (water, chemical products even in weak concen-
trations, etc.), as well as their very low mechanical
strength. This has led researchers to devise various means
of protection as, for example, by incorporating the polarizing
particles in a polymer film.
In general, the products are recognized as having very
low surface hardness, a very marked sensitivity to scratching,
and an incompatibility with the majority of the current
cosmetic products.
For all that, attempts to obtain glass lenses have
consisted in associating an organic polarizing film of the
polyvinyl alcohol type with one or two ("sandwich") elements
of glass. These attempts have come up against a n~mber of
dif~iculties such as:
the complexity of bonding the polarizing film to an
optical su~strate with~ut deforming the direction o polarization,
as indicated in French Patent ~o. 76.18891, filed June ~,
1976 by American Optical Corporation;
--1--
12~557g
the weight of the assemblies thus obt~ined are not
compatible wit~, for e~ample, the conventional lenses
utilized in spectacles C10-25 grams); and
the extremely high cost o such products which is a
result of their complexity.
For these reasons, t~ese products are not much used for
application~ of the "general public" type such as spectacle
making.
~ore recently, attempts were conducted to provide
polariz~ng films of the polyvinyl acetate or ~olyvinyl
butyrate type bonded onto the concave face of an inorganic
spectacle glass. This approach also proved fruitless
because of t~ree ma~or dïfficulties:
the very poor optical $uality of such ~ilms;
the necessity for protecting them from moisture; and
t~eir sensitivity to scratching.
In spite of all these handicaps, a product o~ this type
is available in commerce under the name of "POLAROID"
lenses. In this product the ~olarizing material is contained
in polyvinyl ~ilms laminated front and back to thin ~ilms of
celluiose and protected by ~ thin strip of melamine.
As with all materials of this type, the gre~t disad~an-
tage in using this type of product is its very great sensi-
tivity to scratching when compared to conventional products
which are inorganic qlasses.
In addition to all this, all the products curr~ntly (or
formerly~ on the mar~et do not satisfy a present need of
consumers which is to have at ~eir disoosal inorsanic
photochromic glasses (tha~ i3 ~0 say an op~ical ~-ansmission
which varies wi~h ~he conditions of lighting~ and ~olari2ing,
colorable, and/or filtering if it i5 needed~ ~uch a product
in order to be perfectly suitable, should not b~ subjec~ ~o
* trade mark.
--2--
iZ~2~579
any limitation a~out the design o~ the shape and the radius
of curvature in order to satisfy, without any restriction,
all the needs for making medical, ophthalmic, a~d ~rotective
spectacles.
Summary of the Invention
The present invention aims to provide a laminated,
transparent, polarizing glass which is free of the deficiencies
reviewed above and permits satisfaction of the above-mentioned
needs.
More precisely, the invention is concerned with a
laminated, transparent, polarizing glass characterized in
that it comprises:
(a) a support of inorganic or organic glass;
~ ) a coating with polarizing properties deposited
upon one of the faces of the support; and
~ c~ an optically transparent, continuous composite
film constituted on one side by a thickness of thermoplastic
polyurethane with adhesive properties, and on t~e other side
by a thickness of thermosetting polyurethane with anti-
lacerating and self-healing properties, the thermoplastic
polyurethane side adhering to the coating with polarizing
properties.
The invention is also concerned with a process for
o~taining such a laminated, transparent, polarizing glass
characterized in that it comprise3 the following steps:
(a). forming parall~l microgrooves on a sur~ace of an
inorganic or organic glass support which is to receive the
polarizing coating, these grooves frequently being ma~e with
the aid of a very gentle a~rasion of the afore~aid su~port
carefully washing the surface of the sup~ort which
is to receive the polari2ing coating and drying this ~urface;
~ ~4f~"~5579
(c~ depositing on the washed and dried surface of the
support a mixture o~ three organic colorants corresponding
to the thres primary colors and exhibiting a nematic state
to form a coating demonstrating polarizing ~roperties;
~ d) treating the resulting polarizing coating with an
a~ueous solution of inorganic salts having an acid pH
(normaily ~y immersing into said solution~ in order to
reduce the water solu~ility of the aforesaid polarizing
coating; and
(e) applying the composite film of polyurethane by
subjecting it first to moderate temperature and pressure
conditions in o~er to insure a ~rinkle-~ree and gradual
flow or spreading out and an adherence o the film upon the
polarizing coating, and thereafter to ele~ated temperature
and pressure conditions to reinforce the mechanical ~ond
between the fi}m and the coating and to complete the cross-
linking of the composite film.
Brief Descri~tion of the Drawings
FIGURE 1 is a view in cross section of a laminated
polarizing glass according to the invention; and
- FIGURE Z is a schematic ~Lew illustrating the protection
of the edge of a spectacle glass lens according to the
invention through a coating of polymerized resin.
As is illustrated LQ FIGURE 1, the support 1 can be
composed of an inorganic or organic glass of any composition
and shape. ~L~i5 can be, among others, a glass ~Yh_~iting
photochromic properties; in particular, a blank of sPectacle
glass (corrective, solar, or protective~.
The polari2ing coating can ~e of ~arious types. One
type of suitable polari2ing coating is ormed of a mixture
of three colorants corresponding to the three primary colors
blue-red-yellow and exhi~iting a nematic state. Th~ colorant
12255~79
molecules ar~ oriented spontaneously on t~e ~ase support
through the grace of a pr~-alignm~nt created by a very
slight a~rasive parallel brushing of the surrace of the
support to ~e coated. This brushing creates parallel micro-
grooves of very little depth and width (less than 0.5 ~).
The coating ohtained exhibits a dichroic effect in the.
vicinity of 10 and a high water solubility. One can reduce
this water solubility by a surface stabilization treatment
with the aid of an aqueous solution of inorganic salts
having an acid pH. Suitable organic colorants are sold by,
among others, the 3M Company of 5t. Paul, ~nnesota, U.S.A.,
under the brand name ~3M Veri-light 25".
Techni~ues concerning this type of polarizing coating
can also ~e found in U.S. Patents Nos. 2,544,659 and 2,481,830.
The composite film (3) is advantageously composed of
the composite film described in British Patent ~o. 1,576,3~4.
According to a preferred embodiment, a continuous com-
posite ~ilm is constituted on one side by a thickness of
thermoplastic polyurethane, and on the other side by a
thickness of thermosetting polyurethane, the aforesaid
thermoplastic polyurethane being joined to the coating
exhibiting polarizing properties and being formed from an
aliphatic diisocyanate and an aliphatic diacid polyester
diol or a polyglycol ether diol, each of said diols ha~ing a
molecular weight of 50a-4000, and said thermosetting ?oly-
urethane being the product of (a~`a polyglycol ether resulting
fro~ the combination of epoxy-1,2 propane with 2,2-bis ~ydroxy-
methyl)l-butanol and containing 1~5-12~ by weight of ~ree
hydroxyls, and tb~ a biuret of 1,6-hexamethylane diisocyanate
! 30 containing 21-22% by weight of isocyanate groups, the weight
of said biuret being composed o~ between 0.9 and 1~1 times
_5_
12~5579
the weight of said polyglycol ether, the thickness of the
thermoplastic polyurethane ranging a~out ~.01-0.8 mm and the
thickness of t~e thermosetting polyurethane ranging about
0.2-Q.~ mm.
The application of this composite film (3) upon the
polarizing coating (2~ i~ effected through the ap~lication
of heat and pressure, as will be described in more detail
below.
Once the laminated transparent glass with three ~lies
1-2-3 is completed, it can be subjected to any pQssibly
necessary finishing operations. For example, in the case
where the laminated glass is a blank or a spectacle lens,
it can ~e subjected to the operation called "edging" (finishing`
of the contour in order to fit the gla~s to the shape of the
frame into which it is to be affixed~.
This edging operation has the disadvantage of breaking
the thin skin layer formed upon the polarizing coating at
the level of the edge of the glass so that there exists a
risk that moisture may penetrate into the laminate and
eventually bring about a destruction of the polarizing layer
through unsticking, as tests of resistance to atmospheric
agents have shown. In order to surmount this difficulty it
is advisable, according to the invention, to protect the
edge of the glass, after edging the latter, wi~h a coating
of a resin which is polymerized in situ.
The inventive laminated glasses exhibit polarizing
effects ranging between ;0-98% and optical transmissions at
2 mm ranging between 25-45~, those values being a function
of the quantities of polarizing molecules, ~heir structure,
and their dichroic efect. These prod~cts conform pèrCect~y
to all the prevailing standaras in the field Q~ s?ectacle
ma~ing.
It is fitting to note, in passing, th~ the inven~ive
laminated glasses can then b~ colored, if desired, b~ the
l~Z5579
process described in French Patent No. 81.22718 filed by the
present applicant on December 4, 1981; now French Patent
Publication 2,517,712 (1984). In this manner, it is
possible to easily produce new and desirable products,
namely, photochromic polyarizing glasses which are easily
tinta~le and which are able to cut off ultraviolet radiation
and have the widest variety of shapes and curvatures without
any limitation.
Finally, although in the present application refere~ce
~s made more specially to a laminated glass destined for
spectacle making, this application is not so lLmited. As a
matter of fact, such glass can find perfect application in
other fields, for example, as windows for vehicles (automobiles,
boats, trucks~ or for buildings, or as reading windows of
digital indicators utilized i~ electronic instrumentation or
timepieces under the name ~liquid crystal display". Generally
speaking, the invention is useful in all fields where
polarization of incident.or reflected light can provide
comfort or increased technical possibilities to the user.
~e description which follows, presented with respect
to the attached drawings, given by way of non-limiting
examples, will make it easy to understand how the invention
can be carried out, the particularities which appe~_ both in
the drawings and in the text do, of course, form ~ar~ of
the said invention.
- DescriPtion of Praferred Embodiments
In FIGURE 1 is shown a laminated polarizing glass
according to ~he invention: more precisely, a ~lank for a
spectacle glass machined according ~o th requisite optical
-7-
1~5579
specifications. T~e glass is comprised of a support 1 of an
inorganic or organic glass with or without photochromic
properties, a polarizing coating 2 deposited upon the conc~ve
face of the.support, and an optically transparent, continuous
composite film ~ composed of a layer 4 of thermoplastic
polyurethane having adhesive properties and a layer 5 of
thermosetting polyurethane having anti-lac~rating and self-
healing properties, the thermoplastic polyurethane adhering
to coating 2.
In FIGURE 2 is shown a spectacle glass lens made into
the desired shape through edging the blan~ of FIGURE 1. The
glass is provided on i~s edge with a coating 6 of resin
polymerized in situ for protection against the penetration
of water.
A glass support endowed with photochromic properties
constitutes a pre~erred embodiment of carrying o~t the
invention.
The following is a non-limiting e~ample illustrating
the invention.
Example
~ he application of the polarizing coating upon an
inorganic photochromic glass support is effected as follows
in eight phases:
Phase 1: Preparation of the Surface
This step has the objective of permitting a pre-alisnmen~
of the organic molecules to he deposited through a very
sl~ght abrasi~e brushing of the surface to be covered~ To
this end one.can utili2e, for ex~mple, a thick ro~ary disc,
preferably polyester foam impregnated with an abrasive, such
1~5579
as an oxide of the zirconia type (ZrO2) or, preferably,
alumina (A12O3~ in suspension in water. The edge of the
disc is applied against the surfàce so as to foa~n parallel
microgrooves in the latter. The duration of thè operation
can take, by way of illustration, a~out 3-30 seconds, the
time being a function of the surface hardness of the support
to be covered. Ordinarily, 10 seconds will be sufficient
for inorganic glasses.
Phase 2: First Washing of the Surface
This operation has the objective of clearing the surface
of the inorganic oxide residues utilized in the preceding
step. This can be effected, for example, by brushing the
surface with apparatus similax to the preceding step but
wherein the a~rasive in suspension is replaced with natural
water at ambient temperature. This operation lasts, for
example, a~out 10-30 seconds.
Phase 3: Second Washinq of the Surface
This operation has the objective of chemically preparing
the surface to be covered to give it a high level of cleanli-
ness. In this operation the support, preferably subjectedto a movement of horizontal rotation (for example at ;Q0
rpm), is continuously sprayed with deionized water ha~ing a
resistivity of about 10-17 ohm cm which, depending upon the
support, may or may not contain a small proportion of a
surface tension agent (for example 1~ by volume alcoholl.
The duration of this operation às, for example, on the order
of 5-10 seconds.
iZ~S5~79
Phase 4: Drying of the Surface
One dries the surface of the support, previously
prepared by a ~ery clean rinse, ~or example by exposure of
the support, while rotating, under a 75-watt ~.R. lamp for
several seconds (for example 5-10 seconds).
Phase 5: Stabilization of the Su~port
In this operation the support to be covered is sta~ilized
to temperature and humidity for about 1 minute 30 seconds in
a cabinet.at 30Cl1C and 50~l5% humidity. The same cabinet
is utilized for the following phase.
Phase 6: Deposition of the Polarizing Coating
In this phase organic molecules of the "nematic" type,
comprised o~ a mixture of three azo-based colorants ~lue-
red-yellow) in solution in water, are deposited and oriented.
; The proportion of the three colorants (marketed by the 3~
Company under the name n 3M Vari-Light 25"1 is determined so
as to obtain a maximum polarizing effect, which effect is
linked to the formation of elongated crystals in very precise
ranges of temperatures and humidities (30+1C and 5Q+5~
relative humi~i~y~. The resulting coating has a slight gray
color. A slightly alkaline wetting agent is generally
associated with the mixture of colorants, its role being to
promote the formation of aggregates of organic molecules.
The concentrations of the recommended wetting agent are on
the order of a few percent, pre~erably 1-2~ hy volume.
In this phase the support is sprinkled wi~h the solution
of organic molecule~ in the ratio of about 1.5-5 ml or
li~uid for a support ha~ing a diameter between 5a-80 ~m.
~he support is set in a hori20ntal rotation, for e~ample,
, ~
~ ~ 5579
1000 rpm, during, for example, 30-45 seconds, in order to
orient the organic molecules according to the pre-alignment
generated previously through brushing, and to evapora~e
through centriugation the solvent o~ the initial solution.
The deposit obtained exhibits a dichroic effect in the
vicinity of 10 and a high solubility in water. The quantity
of the solution of organic molecules and the speed of centri-
fugation impart to the support a level of polarization
ranging ~etween about 90~ and 50~ for optical transmissions
at 550 nm ranging between 25% and 45%.
Phase 7: Stabilization ?reatment of the Surface
This step has the objective to reduce the water soiu-
bility o the previously formed, oolarizing coating. To
accomplish this the supports are treated by immersion for 10
seconds into an aqueous solution of inorganic salts having
an acid pH (for example 3.2~. The inorganic saLts generally
employed are mixtures of iron and calcium salts in aqueous
solution. This produces an ionic diffusicn in the surface
with the formation, with the organic colorant molecules, of
a metal sulfonate which is insoluble in water. Other salts
which are usable are described ln above-cited U.S. paten~s.
hase ~: Last Rinsing of the Surface
In this step the product obtained is rinsed through
total immersion into natural water at ambient temperature.
The lens produced is polarizing and the treatment of
the surface operates to impart an ~frective insensitivity
to water to t~e surface of the polarizing coating.
The application of the composite polyurethane iLm can
be effected as described in the British oatent previously
cited, but it is preferably produced as described in French
-lL-
i~25579
patent No. 81.18678, filed October 5, 1981, by the applicant
under the title "Laminated Ophthalmic Glass and Method of Makingl';
now French Patent Publication 2,513,940, except that the opera-
tion of cleaning the glass lens is omitted. Briefly, this
process consists in placing the thermoplastic polyurethane side
of the composite film into contact with the polarizing coating
carried by the support, pressing the composite fiLm against
said coating at ambient ~emperatur~ or at a moderately
elevated temperature (40-80C for example~ and under a
moderately elevated pressure ~-5 bars for example), in
order to insure a uniformly progressive flow or spreading
free from wrinkles and an adherence of the film upon the
coating, and then subjecting the resulting laminate to
elevated temperatures and pressures ~75-150C and S-25
bars, for example~ for a sufficient length of time ~0.5-4
hours, for example) in order to reinforce the mechanical
bond between the composite film and the polarizing coating,
and to eliminate gaseous inclusions.
The resulting laminated glass lens blank can be subjected,
if necessary, to edging. This edging is carried out on a
blank previously heated to 110C+10C for about 30 minutes
in order to temporarily increase the adherence of the polarizing
coating to the composite film.
Ater edging, a thin layer of organic resin capable of
being polymerized in situ is applied to the edge o~ the
glass lens in order to physically protect the ~olarizing
coating against possible penetration of water. It is possible
to use, for example, a resin polymerizable by ultrAviolet
radiation such as the resin LOCTITE~ mar~eted in France by
the Society F~AMET in Senlis. ~ treatment of S seconds with
a 1500-watt xenon ultra~iolet lamp suffic~s to harden thi~
resin.
1~5579
The protective coating of resin is polymerized to a
thickness of a few hundredths of a millimeter and is perfectly
transparent ànd colorless. The finished glass obtained can
then be mounted in spectacles without any fear of deteriora-
tion, as de~onstrated by tests of more than 252 hours at
50C and 98~ relative humidity in a weathering chamber
followed by an extended immersion in water (several weeks ) .
-13-
