WO1994027169A1

WO1994027169A1 - Lens

Info

Publication number: WO1994027169A1
Application number: PCT/AT1994/000065
Authority: WO
Inventors: Werner Fiala
Original assignee: Bifocon Optics Forschungs- Und Entwicklungs Gmbh
Priority date: 1993-05-14
Filing date: 1994-05-13
Publication date: 1994-11-24
Also published as: ATA95693A

Abstract

Disclosed is an ophtalmic lens made of at least one birefringent material, using a liquid single crystal elastomer (1) or a liquid single crystal duromer as birefringent material. Disclosed also is a process for producing such a lens.

Description

L lens

The invention relates to an ophthalmic lens made of at least one birefringent material, as well as processes for its production and the use of special birefringent materials for ophthalmic lenses.

Multifocal birefringent lenses in general and multifocal birefringent ophthalmic lenses in particular are already known per se. The corresponding concepts are e.g. published in US Pat. Nos. 4,981,342, 5,073,021 and 5,142,411, in European Application EP-0 308 705 A2, and in PCT / AT91 / 00042 (Publication No. WO 91/14189) .

The cited patent and application documents mention that in birefringent multifocal lenses, polymers can be used which can be made birefringent by stretching. So in the

United States Patent 4,981,342 stated that polymers according to United States Patent 4,384,107; 4,393,194; 4,933,196; 4,433,132; 4,446,305; 4,461,888; 4,461,887; 4,503,248; 4,520,189; 4,521,588; 4,575,413; 4,575,547; 4,608,429 and 4,626,125 can be made birefringent by stretching, and thus in lenses or lens systems according to USA 4,981,342 could be used. These and other birefringent plastics basically represent thermoplastics of high polarizability, which are deformed (stretched) linearly by applying an external mechanical field and which become optically birefringent due to the anisotropy that occurs during this stretching process. A disadvantage of stretched birefringent thermoplastics is that the often high degrees of stretching required to achieve the desired birefringence necessitate a high mechanical anisotropy of these birefringent materials, which, for example, makes machining very difficult or impossible. Furthermore, only very thin films (of a fraction of a millimeter on the order of magnitude) of highly birefringent polymers have been successfully produced (see the US patents on birefringent polymers cited in the introduction), which are not suitable for producing birefringent ophthalmic lenses, since the Sample thickness must be greater than the arrow height (contact lenses, intracorne lens) or center thickness (intraocular lens) of the lens to be manufactured. Finally, it should be mentioned that, as far as is known, the stretched thermoplastics have low gas permeability, which means that their use in birefringent contact and intracorneal lenses can be problematic.

US Pat. No. 5,073,021 (Marron) states that a transparent plastic which contains liquid crystal material could be used in bifocal ophthalmic lenses, the liquid crystal molecules being aligned by an electric field during the polymerization process. Because of the anisotropy then existing because of this alignment, such a plastic is optically birefringent. An analog method for the production of electrostatically aligned and in this state cross-linked ferroelectric liquid-crystalline polymers is proposed in JP 02-047 628.

Measurements of - for the applications intended with such materials, eg in non-linear optics meaningless - gas permeability are not known. Only thin films of such liquid-crystalline polymers aligned in a field have hitherto been produced; There are no specific indications of how spatial lenses with a curved surface can be produced. For these reasons, such birefringent polymers oriented in the field have not previously been used in birefringent ophthalmic lenses.

The object of the invention is to create a precisely producible lens for ophthalmic purposes from birefringent material, and to specify methods for the production thereof.

According to the invention this is achieved in that a liquid single crystal elastomer or a liquid single crystal duromer is used as the birefringent material. Liquid single-crystal elastomers or duromers are special liquid-crystalline elastomers or duromers with a fixed anisotropic network structure.

Liquid-crystalline elastomers and -duromers are polymer networks which, for. B. can be produced in that the polymer chains of liquid crystalline side chain polymers are linked together by bifunctional molecules. In these materials, the chain segments and the mesogenic groups are movable above the glass transition temperature, but the material as such retains its dimensional stability as a result of the crosslinking. In the mechanically unloaded state, the orientation of the nematic director of the mesogenic groups is macroscopically inconsistent and the elastomer appears opaque. However, if a sample of an elastomeric material such. B. an elastomer film above stretched uniaxially, the directors of the mesogenic groups orient themselves parallel to the direction of the tensile stress. The sample becomes transparent and corresponds in its optical properties to a single crystal of the same dimension. If the elastomer sample is relieved, it returns to the disordered, opaque state due to its elasticity.

In the case of liquid single-crystal elastomers or -duromers, in order to preserve the single-crystal state, elastomers containing reactive residues with at least one unreacted functional group are uni- or biaxially oriented in a first step by the action of a mechanical tension, and this orientation in one subsequent second step fixed by linking at least some of the reactive radicals with polymer chains.

In contrast to conventional liquid crystal polymers, liquid single crystals, and in particular liquid single crystal elastomers and liquid single crystal duromers with a fixed anisotropic network structure, have only been known for a few years. Such systems were first described in 1991 in Macromol.Chem.Rapid Commun. 12, 717-726 (1991), the new expression "liquid single crystal elastomer" (original: "liquid single crystal elastomer, LSCE") also being coined. These novel liquid single-crystal polymers and duromers and their preparation are described in detail in German patent application DE 41 24 859 A1 and in international application PCT / EP92 / 01591 (WO 93/03114). The orientation or anisotropy required for the elastomers after the synthesis process is very great in comparison to the above-mentioned stretching given weak mechanical fields. These liquid-crystalline elastomers contain reactive residues with unreacted functional groups, as a result of which this orientation is fixed ("chemically frozen") in a subsequent second step by linking at least some of the reactive residues with polymer chains, so that birefringence occurs without the application of any outer fields exist. preserved.

Furthermore, by varying the concentration of the crosslinking components, these liquid single crystals can be given both the properties of elastomers and of duromers; the total crosslinking density for elastomers is typically between 2 and 20%, for duromers i.a. over 50%.

In contrast to both the birefringent thermoplastic and the conventional liquid-crystalline polymers, liquid single-crystal elastomers or duromers can be produced in practically any geometry and size. Furthermore, the birefringence can be set in these materials by varying the composition; the birefringence of, for example, Δn = 0.15 measured on a sample is in any case sufficient for the use of such liquid single-crystal elastomers in ophthalmic lenses. Since these materials are elastomers, they have the typical high gas permeability, making them particularly suitable for use in contact and intracorneal lenses. The Shore hardness of the elastomers can be increased if necessary by lowering the temperature, so that it is ensured that these materials can be machined. Furthermore, newer machining processes, such as eroding or cutting with Lasers can be used to produce curved surfaces. A variety of such methods are mentioned, for example, in patent class B23K 26/00. As a rule, neodymium and C0 ₂ ~ lasers are used for processing plastics. The evaporation or decomposition products obtained are predominantly gaseous; any decomposition products adhering to the processed body can be removed by a subsequent polishing step.

As mentioned, the use of liquid single-crystal elastomers in contact lenses is advantageous because elastomers have a high gas permeability, which ensures the necessary supply of oxygen to the cornea. Furthermore, elastomers have the material characteristics of soft contact lenses, with the wearing comfort of soft contact lenses being considered to be particularly high.

Liquid single-crystal thermosets have a comparatively lower gas permeability, but give a contact lens greater dimensional stability and also better optical properties.

The use of liquid single-crystal elastomers in bi- and multifocal intraocular lenses is appropriate when the lens is to be folded or rolled up during the implantation process. Monofocal intraocular lenses are made, for example, of optical quality silicone rubber; the lens is implanted in folded form and unfolds again in the eye due to the elasticity of the lens material. The advantage of such lenses is that the surgical incision of the cornea required for implantation can be very small ("single stitch implantation"). The optical egg Properties of such lenses, however, generally lag behind those of fixed lenses. The gas permeability of elastomers is irrelevant for intraocular lenses.

The use of liquid single-crystal thermosets in bi- and multifocal intraocular lenses is appropriate if special importance is attached to the good optical quality of the lens.

From these explanations it can be seen that the novel liquid single-crystal elastomers or duromers can be optimally adapted to the specific requirements of ophthalmic birefringent lenses by modifying the mechanical and optical properties. Neither thermoplastics nor conventional liquid crystal polymers offer these possibilities of adaptation.

The invention further relates to a method for producing a lens from a birefringent liquid single crystal elastomer or liquid single crystal duro, and the use of these materials in ophthalmic lenses.

Further advantages and details of the invention are explained in more detail with reference to the following description of the figures.

FIGS. 1 a and 1 b show a highly schematic first exemplary embodiment for producing a lens according to the invention. 2a, 2b and 2c show a second manufacturing process in a schematic representation. 3a to 3e show a third manufacturing method. 4a and 4b show an alternative shape for shaping a lens. 5a, 5b and 5c schematically show a further embodiment of a manufacturing method according to the invention.

In order to produce a lens, that is to say a transparent optical component with at least one curved surface, from a liquid single-crystal elastomer or duromer, the methods described below can advantageously be used. In general, a lens will have two opposite, differently curved lens surfaces, especially if it is intended for ophthalmic purposes. Typical are biconvex, biconcave, plano-convex, plano-concave, concave-convex and convex-concave lens shapes. Other lens shapes are also conceivable for special cases.

According to the production process shown in FIGS. 1 a and 1 b, a liquid-crystalline elastomer made stable in shape by pre-cross-linking is initially assumed. In general, liquid-crystalline elastomers, from which the liquid single-crystal elastomers / duromers with fixed anisotropic network structure are then formed, can preferably be selected from the group of elastomers of the formula I,

(D

V Sp R

B

wherein

(P) a polymer chain unit,

Sp is a bivalent spacer group,

B an organic "rod-like" residue with at least two six-membered groups, a "disc-like" or a "board-like" residue, V is a polymer chain crosslinking group and

R is a reactive radical containing at least one unreacted functional group.

Formula I describes the preferred elastomers only in a highly schematic manner. So it is z. B. does not require that each main chain unit carries an esogenic unit. Formula I is also intended to include copolymers with different polymer chain units. In addition, the number of groups V, R and Sp - B generally does not match. Despite these shortcomings, Formula I appears to be suitable for the diagrammatic representation of the preferred elastomers and is therefore used.

The production of liquid-crystalline elastomers, in particular of the formula I, is carried out analogously to known polymerization processes, as described in the literature (for example in the standard works such as Ocian, Principles of Polymerization, McGraw Hill, New

York), under reaction conditions that are known and suitable for the reaction. It is also possible to use variants which are known per se and are not mentioned here in detail.

Further details on suitable liquid-crystalline elastomers and the formation of liquid single-crystal elastomers / thermosets by stretching and further crosslinking can be found in the already mentioned DE-A1 41 24 859 and WO 93/03114.

A liquid-crystalline elastomer, for example of the above formula I, is stretched inaxially by the action of a mechanical stress. By applying a mechanical tension, an orientation in the Elastomer is generated and this orientation is "chemically frozen" in a second crosslinking process. A liquid single-crystal elastomer is thus obtained. An example of a cuboid body 1 made of a liquid single-crystal elastomer is shown in FIG. By removing material, for example milling or grinding, one or more bifocal lenses 2 can now be formed from this body 1, as shown in FIG. 1b. The optical axis is provided with the reference number 3. It runs straight in the finished lens 2.

If the Shore hardness is not sufficient for machining, the elastomer can preferably be cooled below the glass transition temperature. By suitable selection of the components, this glass transition temperature can be selected below body temperature and preferably below room temperature, so that the lens exhibits an elastomeric behavior in these temperature ranges.

If processing by laser is planned, the sample can of course also be processed at a temperature above the glass transition temperature.

In the method shown to 2c in Fig. 2a is from an already oriented film l ¹ starting from a Flüs¬ sigeinkristall elastomer. With this film, the orientation has already been fixed by a second crosslinking process. This film is now inserted and deformed into a mold 4, which is rotationally symmetrical about the axis 5, with mold halves 4a and 4b. While it is kept in this deformed state, a third crosslinking process takes place around the film, that is, even after the mold 4 has been removed from the mold to keep embossed curvature. In order to finally obtain the desired lens 2 according to FIG. 2c, as a rule only one surface, namely the lower one in the example shown, has to be produced by a suitable processing method, while the other surface already by the Form 4 was specified and maintained through the third networking process. In the lens 2, the optical axis 3 is "bent", that is to say in all cuts with cutting planes which are parallel to the plane formed by the axis of rotational symmetry and the optical axes, the optical axis is curved in a circle. As ray tracing analyzes have shown, the imaging quality of such a lens for the extraordinary rays is only insignificantly affected as long as the angles between the incident light rays and the optical axes are close to 90 °. The orientation of the optical axes is irrelevant for the ordinary rays anyway.

In the method shown in FIGS. 2a to 2c, three networking processes are therefore provided. The first is used for the synthesis of a liquid-crystalline elastomer network, in which there is no orientation yet, but there is already a certain dimensional stability. The second crosslinking process is used to freeze an orientation generated by mechanical stress. The third crosslinking process then serves to maintain the outer shape of the raw lens. The degree of crosslinking or the crosslinking density is increased with each crosslinking process.

In the method shown in FIGS. 3a to 3e, only two networking processes are necessary. As always, the first serves to actually form a formal bile liquid-crystalline elastomer network without orientation, as shown, for example, in FIG. 3 a and provided with the reference number 6.

By applying a tension (arrows 7), the polycrystalline film 6 of FIG. 3a is now stretched uniaxially, as a result of which it is oriented and birefringent. While the tension is maintained by the tensioning device 8, the two mold halves 4a and 4b are now applied to the polycrystalline film 6 in order to then reach the position shown in FIG. 3d. If one were to open the mold halves 4a and 4b again in FIG. 3d without further measures and the tension was released by the tensioning device 8, one would again become the unoriented and reshaped film of FIG

Fig. 3a come back. In order to "freeze" the desired state according to 3d, however, a second crosslinking takes place before the mold is opened and the tension is released. This second networking has a dual function. On the one hand, it freezes the orientation or double refraction caused by the tension, on the other hand, this crosslinking also maintains the external shape predetermined by the mold halves 4a and 4b, so that a molded liquid single-crystal elastomer 1 "is obtained

Liquid single-crystal elastomers can, as is schematically indicated in FIG. 3e by vertical lines, separate the areas outside the mold in order to obtain a birefringent body with a curved surface, that is to say a pre-lens. In order to obtain the final lens, one of the two lens surfaces can then be machined, as in FIG. 2c, for example. The method shown in FIGS. 3a to 3e still permits a particularly advantageous variant, which is particularly promising if the two lens radii are not significantly different from one another. Then it is namely possible to obtain a finished lens by corresponding complementary shaping of the mold halves 4a and 4b (corresponding to the lens radii R1 and R2), in which none of the two lens surfaces can be machined.

As shown in FIGS. 4a and 4b, instead of the two-part mold 4a, 4b, a one-part mold 4c can also be used, which has openings 9 in the region of curvature, via these openings 9 a negative pressure under the film 6 or the liquid single crystal which arises after crosslinking -Elastomer 1 "are generated, so that an adaptation to the concave shape 4c is possible despite the application of a tension via the tensioning device 6.

In the exemplary embodiment shown in FIGS. 5a to 5c, a lens 2 is also produced, in which the lens surfaces no longer have to be machined. The starting point is a circular plate of an already anisotropically oriented liquid single crystal elastomer. This plate 1 of FIG. 5a is now placed in a lens mold 4a, 4b, in which the two radii of the mold have the complementary values of the radii of the lens to be produced. The mold is closed, which results in the plate 1 being deformed (FIG. 5b). Of course, these reshapings must remain small in order not to cause the plate 1 to reorient. This is the case if the two radii of the lens have only slightly different or concentric values. When the mold 4a, 4b is closed, the liquid single-crystal elastomer is networks, so the degree of crosslinking further increased. The anisotropic orientation already given remains unchanged. In addition, the outer shape corresponding to the mold halves 4a and 4b is also retained. An essentially finished lens 2 is then obtained, in which, if necessary, only the edges need to be post-treated (FIG. 5c).

In the above, a liquid single crystal elastomer was particularly treated. However, other polymers are also conceivable and possible, in particular duromers. In general, the deformability of the resulting lens can be adjusted via the crosslinking density or degree of crosslinking. It is also possible, to form bifocal or general multifocal lenses, to combine two liquid single-crystal partial lenses which differ in their material, their orientation, their orientation and / or their outer shape to form an ophthalmic lens. Liquid single-crystal partial lenses can also be combined with a partial lens made of another material to form a structural unit.

Of course, the invention is not limited to the lens shape shown in the exemplary embodiments. Rather, other lens shapes are also conceivable and possible, in particular those which are known for ophthalmic purposes.

Claims

Patent claims:

1. Ophthalmic lens made of at least one birefringent material, characterized in that a liquid single-crystal elastomer (1) or a liquid single-crystal duromer is used as the birefringent material.

3. Lens according to claim 1, characterized in that the lens is a contact lens.

3. Lens according to claim 2, characterized in that the lens is an intraocular lens.

4. Lens according to claim 1, characterized in that the lens is an intracorneal lens.

5. Use of a birefringent liquid single crystal elastomer or liquid single crystal

Duromeric lens as an ophthalmic lens, in particular as a contact lens, intraocular lens or intracorneal lens.

6. A method for producing a lens according to one of claims 1 to 4, characterized in that starting from a body made of a liquid crystal elastomer (1) or -Duro he the curved lens surfaces of the lens (2) by material ent- remote processing are formed (Fig. la, lb).

7. The method according to claim 6, characterized in that the lens by machining, such as milling, grinding or the like. is formed.

8. The method according to claim 6, characterized in that the lens is formed by cutting or eroding by means of a laser.

9. A method for producing a lens according to one of claims 1 to 4, characterized in that a liquid single-crystal elastomer or -Duromer (l ¹ ) is deformed with anisotropic network structure already fixed and is finally crosslinked in the deformed shape by a further crosslinking process ( 2a-2c; Fig.6a-6c).

10. A method for producing a lens according to one of claims 1 to 4, characterized in that a polycrystalline liquid-crystalline elastomer (6) containing reactive residues with non-converted functional groups is oriented by the action of a mechanical stress and is kept deformed in its outer shape and then in a crosslinking process both the orientation and the outer shape are fixed by linking at least some of the reactive residues with polymer chains (FIGS. 4a - 4e).

11. The method according to claim 9 or 10, characterized gekenn¬ characterized in that the deformation by means of a preference two-part mold (4).

12. The method according to claim 11, characterized in that at least one molding surface (4a) of the mold

(4) complementary to a lens surface of the lens (2).

13. The method according to claim 12, characterized in that a second opposing molding surface (4b) is curved substantially parallel to the molding surface (4a) (Fig.2b).

14. The method according to claim 12, characterized in that a second opposing molding surface

(4b) is complementary to one of the lens surfaces of the lens (2) (Fig.4c, 4d).

15. The method according to any one of claims 11 to 14, characterized in that the mold (4c) has a depression or elevation with openings (9) which can be subjected to negative pressure.

16. The method according to any one of claims 1 to 15, characterized in that on the preformed

Liquid single-crystal elastomer (1 *) or duromer is formed by at least one curved lens surface by machining, such as milling, grinding or laser ablation, (FIG. 2c).

17. The method according to claim 6 or 16, characterized gekenn¬ characterized in that the material is cooled before or during the material-removing processing to a temperature below the glass transition temperature.