Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-03-17
2002-11-05
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S110000, C524S287000, C524S559000, C252S586000, C351S162000, C525S305000, C525S313000, C526S219600, C526S329200
Reexamination Certificate
active
06476103
ABSTRACT:
The presently claimed invention deals with:
a novel photochromic organic material;
the use of at least one plasticizer for the preparation of said novel material;
said preparation;
photochromic articles constituted wholly or in part by said novel material.
The implementation of a photochromic ophthalmic lens of plastic material is delicate. Ideally, the polymer matrix of such a lens must be:
thermoreticulated;
exempt from optical distortion in its mass;
suited to receive and to be thermoreticulated in the presence of photochromic coloring agent(s) selected notably from the spiroxazines and the chromenes;
in a way as to generate a material which possesses a high initial transmission before exposure and a significant darkening capacity after exposure, all this with rapid darkening and lightening kinetics and acceptable mechanical properties. Furthermore, the material must also possess a low thermal dependence, a high resistance to fatigue and a refractive index as high as possible . . .
From the prior art, copolymers are known which are convenient for the manufacture of organic spectacle lenses and notably the copolymers desribed in the Application WO-A-92/05209. Said copolymers are obtained by radical polymerization of a first monomer of formula (A):
in which a and b are whole numbers from 0 to 4, R
1
and R
2
═H or CH
3
, R
3
═—O—, —S—, —CO—, —SO
2
—, —CH
2
—, —CH═CH— or —C(CH
3
)
2
—;
with a second monomer which can consist of styrene or one of its derivatives;.
and, optionally, a third monomer which can be selected from the vinylic aromatic compounds and aromatic methacrylates;
in the presence of an initiator of the peroxide type and a chain transfer agent selected from various brominated compounds.
Such copolymers have had a presentiment of constituting the polymer matrix of photochromic articles.
Nevertheless, when an attempt is made to incorporate photochromic coloring agents into the copolymerizable composition in order to confer photochromic properties to the matrix obtained after copolymerization, it is noticed that said coloring agents are destroyed by the peroxide initiator.
Even if said peroxide initiator is replaced by a gentler radical polymerization initiator, such as a diazo compound such as azo-bis-isobutyronitrile, the material which is obtained is still unsatisfactory since the photochromic coloring agents are inhibited by the brominated chain transfer agent which is used.
It can be envisaged to incorporate further coloring agents in the matrix, notably by a process of specific thermal diffusion. But, the efficiency of such a process of manufacture is debatable and, in any case, this complicates the process of manufacture and adds to the cost of the material.
There is therefore a real need for perfomant photochromic materials which are prepared from an easy and inexpensive process of manufacture.
The Applicant, confronted with this technical problem, has already proposed photochromic organic materials its Patent Applications FR 9508424 and FR 9514343, respectively filed Jul. 12, 1995 and Dec. 5, 1995,these photochromic organic materials having a refractive index of greater than 1.55 and being exempt from optical distortions. These materials, based on at least one monomer of formula (1)
in which R═H or CH
3
and m and n are independently 1 or 2, exhibit good photochromic and optical properties. Nevertheless, these compounds can be blamed for not being sufficiently dark in the darkened state, and they also possess darkening and lightening kinetics which are too slow . . .
The novel material, the first subject of the invention, constitutes from this point of view a perfecting of said materials according to FR 9508424 and FR 9514343. It displays generally a faster photochromic response as well as being darker in the darkened state; at the same time as exhibiting suitable mechanical and optical properties. Within the framework of the invention, a novel photochromic material has been perfected with improved photochromic properties, without this improvement of said photochromic properties being obtained at the expense of the mechanical properties. This improvement is based on the intervention of at least one plasticizer in the formulation of the material.
Characteristically, the photochromic organic material of the present invention contains in its structure, more or less bound to said structure, at least one plasticizer.
Said photochromic organic material, which possesses a refractive index of greater than or equal to 1.55 and which is exempt from optical distortions, is a material obtainable by radical polymerization of a composition containing:
(a) at least one monomer of formula (1):
in which R═H or CH
3
and m and n are independently 1 or 2;
(b) at least one aromatic monovinylic monomer of formula (II):
in which R
1
═H or CH
3
; said monovinylic monomer consisting advantageously of styrene;
(c) an effective amount of at least one photochromic coloring agent which confers to said material photochromic properties; said coloring agent being selected from the group of spiroxazines, spiropyrans and chromenes;
(d) at least one plasticizer advantageously selected from the phthalates.
Said composition generally further contains an effective amount of at least one chain transfer agent and an effective amount of at least one radical polymerization initiator. It is furthermore susceptible of further containing:
(e) at least one aromatic divinylic monomer of formula (III):
in which R
1
═H or CH
3
; said divinylic monomer advantageously consisting of divinylbenzene.
and/or
(f) at least one (meth)acrylic monomer of formula (IV):
CH
2
═C(R)—COOR′
in which R═H or CH
3
and R′ is a linear or branched alkyl radical having from 4 to 16 carbon atoms, an optionally substituted methylphenyl or methylphenoxy radical or a polyoxyethyloxy group of formula —(CH
2
—CH
2
O)
n
R″ in which n is a whole number ranging from 1 to 10 and R″═CH
3
or C
2
H
5
;
said (meth)acrylic monomer advantageously consisting of ethylhexylmethacrylate.
and/or
an effective amount of at least one non-photochromic coloring agent, with the hypothesis of desiring to confer a base tint to the material.
The nature and quantity of each of the components intervening, or susceptible of intervening, in the composition of the material of the invention will now be examined more in detail.
The monomer(s) (a) of formula (I) are well known and are commercially available. It is noted that this means the first monomers of formula (A) in the sense of the document WO-A-92/05209. The monomer of formula (I) in which R═H and m═n=2 is particularly preferred. Said monomer is notably marketed by Akzo Nobel (NL), under the brand name of Diacryl 121.
The monomers of formula (I) intervene generally in the composition to be polymerized at 50 to 90% by weight. If they intervene in a smaller quantity, the polymerizable composition (or matrix) has a tendence to retract during the polymerization, which induces a premature turning-out from the mould, which, in turn is responsible for a deterioration of the optical properties of the final material. If they intervene in a larger quantity, it is also observed that the final material possesses mediocre optical properties.
The aromatic monovinylic monomers (b) of formula (II)—styrene and/or methylstyrene—intervene in combination with the monomers of formula (D) to slacken the polymer network. The intervention, at this level, of styrene is particularly advantageous insofar as where the polymerized compound possesses a rather high refractive index (n=1.595). Said styrene constitutes the particularly preferred compound of this class of monomers.
Said monomers of formula (II) generally intervene in the composition to be polymerized at 5 to 40% by weight, advantageously at 8 to 30% by weight. If they intervene in a too small a quantity, the anticipated effect at the level of the tensions within the matrix are not observed (birefringence phenomena are observed . . . ); a matrix is also obtained which p
Baney Bruno
Henry David
Corning Incorporated
Nwaneri Angela N.
Rogalskyj Peter
Sanders Kriellion A.
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