NO310760B1 - Method and apparatus for making contact lenses - Google Patents

Abstract

A measured-out quantity of a material which can be crosslinked by exposure to a suitable form of energy, in particular UV light (3), is introduced into a two-part mould (1), the cavity (15) of which defines the shape of a moulded part (CL) to be produced. The two mould halves (11, 12) are kept at a small distance from each other, so that there is formed between them a thin annular gap (16), which is in connection with the mould cavity (15) and through which excess material can escape. The crosslinkage is initiated by exposure to the chosen form of energy, exposure being spatially limited to the cavity (15) by suitable masking (21), so that material outside the mould cavity is not crosslinked. In this way, moulded parts which do not require secondary finishing are obtained, and the mould is reusable. The process is suitable in particular, but not exclusively, for the production of contact lenses. <IMAGE>

Description

The present invention relates to a method for producing contact lenses and a device for producing them.

Contact lenses are manufactured in large numbers commercially, and are preferably finished according to the so-called form-respectively full-form methods. With these methods, the lens is produced between two forms in its final form, so that neither a subsequent processing of the surface of the lens nor a processing of the edge is necessary. The mold method is described, for example, in PCT WO 87/04390 or in EP-PA 0 367 513.

In this known mold method, the geometry of the manufactured contact lens is determined by the cavity of the mold. The contact lens edge is simultaneously formed by the mold, which usually consists of two mold halves. The geometry of the edge is determined by the contour of both mold halves in the area where they touch each other.

For the production of a contact lens, a specific quantity of the liquid starting material is first brought into the female mold half. The mold is then closed by attaching the male mold half. Usually, the starting material is somewhat overdosed so that the excess quantity is displaced when closing the mold in an overflow space connected to the mold cavity. The subsequent polymerization or cross-linking of the starting material takes place by irradiation with UV light or with heat or by non-thermal methods. There, both the starting material in the mold cavity and the excess material in the overflow chamber are hardened. The hardening of the excess material may take place somewhat delayed as it is possibly inhibited at the start by oxygen from the air. In order to achieve a flawless separation of the contact lens from the excess material, a good seal or displacement of the excess material must be achieved in the contact zone of the two mold halves. Only in this way can flawless contact lens edges be achieved.

As materials for the form, plastics such as polypropylene are preferably used today. The molds are produced by injection molding and are only used once (disposable molds). This is due, among other things, to the forms being partially contaminated by the surplus material, being damaged by separation from the contact lens or irreversibly changed in partial areas.

In the case of injection-molded forms, fluctuations in the measurement must also be taken into account due to fluctuations in the manufacturing process (temperature, pressure, material properties). In addition, a shrinkage of the shape may also occur after injection molding. These significant changes in shape can lead to fluctuations in the parameters of the manufactured contact lens (peak refractive value, diameter, base curve, average thickness, and so on), which can lead to a reduction in the quality of the lenses and thus a reduced yield. With insufficient sealing between both mold halves, the excess material is not properly separated, which leads to the formation of so-called webbing on the contact lens edge. In the case of stronger prominence, this can lead to cosmetic defects at the edge of the lens as well as irritation to the wearers of such a lens, which means that such lenses must be sorted out during an inspection.

Especially due to the quality requirements at the contact edge, the molds are only used once, as a certain deformation of the mold in the contact area cannot be ruled out with certainty.

In US 4,113,224, a further mold method is described for the production of, among other things, contact lenses. In this method, a mold is used whose cavity is not completely closed, but is connected via a thin annular gap with an annular reservoir channel (overflow chute) which surrounds the cavity. Via the annular gap, the material from the reservoir can flow behind, into the mold cavity under the cross-linking, to compensate for the relatively large volume loss with the commonly used lens materials.

The cross-linking of the material in the reservoir channel can be prevented by means of an inhibiting gas atmosphere or by shielding from the energy irradiation used to provide cross-linking. In order to ensure this afterflow of the material to the mold cavity, at least initially, the material located in the mold cavity is only irradiated in a central area which is smaller than the diameter of the mold cavity, or this central area is irradiated with a higher radiation intensity than in the surrounding edge areas of the mold cavity. After cross-linking in the central area has begun and has progressed to a certain extent, the edge area with adjacent annular gap and the material in the reservoir channel is also exposed to full irradiation and cross-linked. In this way, the above-mentioned burrs and webbing are also formed, so that contact lenses produced according to this known method require mechanical post-processing.

The aim of the present invention thus consists in further developing a method and a device of a molding type and thereby improving it significantly, so that the above-described difficulties and problems in connection with the manufacture of contact lenses can be avoided. In particular, such conditions have been provided that the used molds or the mold halves can be used further and that a degree or webbed formation on the produced contact lenses is avoided, so that the sorting rate of contact lenses is extremely low, respectively a mechanical or special finishing of contact lenses is omitted.

The task that forms the basis of the invention is solved by the precautions or special features described in the characteristic in the independent method claim or the independent device claim. Particularly suitable and advantageous embodiments of the method of the invention and the device of the invention are given in the independent claims.

By "cross-linking" is meant here and in the following summarily any type of reaction in which the material, by polymerization of a suitable monomer, oligomer and/or prepolymer, and/or a mixture of these, is transferred to a state in which it retains a defined shape given of the mold cavity. Suitable materials and polymerization/crosslinking reactions are known to the person skilled in the art, typical examples are those mentioned in US 4 13 224 and the publications indicated there.

According to the general, basic idea of the invention, the polymerisation or cross-linking of the starting material is also limited to the area for the production of contact lenses. Any surplus material is not polymerized or cross-linked. Partial areas of the contact lens edge are not formed by the method of the invention by a mechanical limitation of the material at the mold walls, but by a spatial limitation of the energy irradiation (usually UV or other radiation) which triggers the polymerization or the cross-linking. With both of these measures, in a preferred embodiment, contact between both mold halves can be avoided, so that these are not deformed and can thus be used further. Moreover, the problem of volume loss that occurs during cross-linking can thus also be easily circumvented, without the need, as for example in US 4,113,224, for mechanical reworking of the contact lens.

Further features and advantages of the methods of the invention and the device of the invention are given in the following description of exemplary embodiments in connection with the figures, where: Figure 1 shows a cross-section of a first exemplary embodiment of a device according to the invention in a closed state of the shape of the method of the invention, Figure 2 shows detail II in Figure 1 in a strong magnification and Figures 3-5 show details analogous to Figure 2 of three further exemplary embodiments of the device of the invention, Figures 6A-C show a further exemplary embodiment of

invention device,

Figures 7A-C show a further exemplary embodiment of

the device of the invention,

Figure 8A-C shows a variant of the embodiment examples in Figure

7A-C,

Figures 9A-C show a further exemplary embodiment of

the invention device, and

Figures 10-11 each show a further variant of the method of the invention, in which a mold half is always used as packaging.

The device shown in figure 1 has been developed for the production of contact lenses from a liquid starting material that can be polymerized or cross-linked by UV irradiation. In terms of manufacturing, it comprises a form 1 produced here in a closed state and an energy source 2a, here a UV light source, as well as means 2b for directing the energy from the energy source in the form of an essentially parallel beam 3 to the form 1. The energy source 2a and the means 2b can of course also be combined into a simple unit.

In its general design, the manufactured device is structured like the device described in the publication used as the state of the art, so that the following description of the essential points and the invention-relevant difference from the state of the art can be limited. Details of the general structure, dimensioning, material and stabilization issues, and so on as well as examples of materials relevant for molded bodies and method technical aspects, are discussed in great detail in EP-A-0 367 513 and especially in US 4 113 224.

The mold 1 consists of two mold parts or mold halves 11 and 12, each of which has a curved mold surface 13 and 14, respectively, which together define a mold cavity 15 which in turn determines the shape of the manufactured contact lens CL (figure 2). The shape surface 13 in the drawing of the upper shape half 11 is convex and determined by the back or base surface of the contact lens with its associated edge area; this mold half is usually called the father mold half. Conversely, the second mold part 14 is correspondingly referred to as the mother mold half, and is concavely shaped and determines the front surface of the manufactured contact lens also together with the associated edge areas thereof.

The mold cavity 15, in contrast to the previously known molds mentioned in the documents WO 87/04390 or EP-A-0 367 513, is not completely and tightly closed, but is in the shown embodiments in the areas at the edge of the mold circuit which define the edge of the produced contact lenses , open around the entire ring and are there in connection with a relatively narrow ring gap 16, as is also the case with the mold shown in US 4 113 224. The ring gap 16 is limited or formed by the flat mold walls 16 and 17 on the mold halves 11 and mold halves 12 respectively. To prevent a complete closure of the mold, the mother mold 12 is equipped with. spacers, for example in the form of several spacer bolts 19a and 19b respectively which cooperate with a collar or flange 20 on the father mold 11 and which keep both mold halves at such a large distance that they secure the annular gap 16. The spacer can, as symbolically indicated in figure 1 by means of the right spacer bolt 19b with a screw, also be adjustable or formed by springs. In this way, the two mold halves under the mesh can be moved towards each other by means of shrinkage compensation either by setting the spacers (symbolically indicated by the direction of rotation arrow 19c) or against a spring force. The form can of course be opened and closed in the usual way using a closing device only indicated by the arrow symbol. The setting of the distance of both mold halves for waste removal can be done, for example, with the help of this external closing unit.

In another embodiment, not shown here, the mold can instead of annular gap 16 and spacer 19a and 19b respectively be equipped with a number of segment-shaped slots where the space between the individual segment slots takes over the function of the spacer. Other configurations are of course also possible.

Both mold halves 11 and 12 consist of a material that is as transparent as possible for the chosen form of energy, here in the case of UV light, for example polypropylene or another polyolefin which is usually used for such purposes. As the irradiation with UV light here is only one-sided, and also takes place from the upper side, really only the upper, that is, the father form 11, needs to be UV-translucent. Naturally, the same applies to the irradiation from below through the mother form. According to a particularly suitable and advantageous embodiment of the invention, at least the UV-light irradiated mold half consists of quartz. This material not only has a very good UV translucency, but is also very hard and resistant, so that molds made from this material can very well be used again. The prerequisite, however, as explained in more detail below, is that the mold is powerless or not completely closed so that the mold halves are not damaged by contact. The alternative to quartz is UV-translucent special glass or sapphire. Due to the possibility of reusing the mold or the mold half, the production of this can entail relatively high costs in order to obtain molds with extremely high precision and reproducibility. The mold halves in the area of the manufactured lens, i.e. the cavity or the actual mold surfaces do not touch each other, damage by contact is excluded. This ensures a long service life for the molds. This also has favorable consequences on the reproducibility of the manufactured contact lenses in general.

In the case of one-sided energy irradiation, the mold half on the opposite side in relation to the energy source can in principle be made of any material that is compatible with the crosslinkable or crosslinked material or component thereof. When using metal, you must, depending on the type of energy irradiation, take into account any reflections that may lead to unwanted effects such as over-illumination, edge distortion or the like. Absorbent materials do not show this disadvantage.

Thus, the device and in particular the form 1 essentially corresponds to that described in US 4 113 224 supra. The most marked and the most important difference compared to what is described there now lies, according to the main idea of the present invention, in that the irradiation of the material from which the contact lenses are made, with the form of energy that causes crosslinking, is limited to the mold cavity, that is that only the crosslinkable material located in the mold cavity is irradiated with the appropriate form of energy, here UV radiation, and only the material located in the cavity is crosslinked. In particular, the material located in the annular gap that surrounds the mold cavity and that located in any reservoir that is in connection with the annular gap is not supplied with energy and is not cross-linked. By "mold cavity" is meant here any cavity in the closed mold defined by the complete contour of the contact lens to be manufactured. The annular gap 16 that leads out of the mold cavity thus does not belong to the mold cavity 15.

For the practical execution of this main idea of the invention, in accordance with the embodiment of the device shown in Figures 1 and 2, on the mold walls 17 within the area of the annular gap 16, an impenetrable for the form of energy used, here i.e. UV light, has been aimed ( or at least not very permeable compared to the permeability of the mold) mask 21 which extends to near the mold cavity and shields against radiated energy except for all other parts, cavities or surfaces of the mold which are or can come into contact with the liquid here, not -cross-linked and possibly excess material. Partial areas of the lens edge are formed by the method of the invention not by a limitation of the material at mold walls, but with a spatial limitation of the polarization- or cross-linking-triggering irradiation or other forms of energy. Details of this are explained below using figures 2 to 5.

When using UV light, the mask can preferably be a thin chrome layer which can be produced according to methods known, for example, in the photo or UV-1 itograph. As mask material, other metals or metal oxides are also relevant. The mask can also be coated with a protective layer, for example of silicon dioxide when quartz is used as material for the mold or the mold half. The mask does not necessarily have to be fixed, it can, for example, also be removable or replaceable. Moreover, it is not absolutely necessary, although it is advantageous, that the mask is arranged as in figures 2 to 5. It can in principle be placed anywhere on or near the mold, as long as it can fulfill its intended function, namely the shielding of all mold areas which carries non-cross-linked material, with the exception of the mold cavity. In principle, one can even refrain from a mask or masking of the mold when it is otherwise possible to limit the energy irradiation, possibly taking into account the optical effect of the mold locally on the mold cavity. In the case of UV irradiation, this can be achieved, for example, by a spatially limited light source, a suitable lens device, possibly in combination with external masks, blinders or the like and taking into account the optical effect of the shape.

The individual steps in the production of a contact lens are essentially the following: Dosing of the liquid, non-crosslinked starting material in the female half-form 12 with open form 1. As a rule, it is overdosed, i.e. the dosed volume is greater than volume of mold cavity 15 respectively the contact lens CL to be produced.

Closing the mold 1. When closing both mold halves, the excess material is displaced into the annular gap 16 between both mold halves 11 and 12. The annular gap 16 is chosen so wide and high (Ay) that a contact of both mold halves in the area of masking 21 is safely avoided. The guiding and positioning (the spacing) of both mold halves takes place with the help of external guiding and stop elements, here symbolized by distance bolts 19a and 19b, such as those which are in principle known in the device from US 4 113 224. Typical gap height Ay is for the production of contact lenses in the area below about 100 jjm. Experiments have shown that, at least when parallel energy radiation is used, it is possible to have a clear edge structuring for the contact lens to be manufactured, also with slit heights of around 1 mm. Conversely, however, it is easily possible to reduce the width or height of the annular gap to practically zero, when only the mold is closed forcelessly, where the mold halves thus lie on top of each other without external load. In this way, only a film of non-densified material with a thickness of less than 1 µm remains between the mold half in the area of the annular gap and which, due to the shielding from UV radiation, cannot lead to the formation of any webbing. Due to the forceless closing of the form, it is not damaged, at least with suitable material selection.

Polymerization or cross-linking of the material in the mold cavity 15. Upon irradiation with UV light (or normal irradiation with a suitable form of energy), polymerization or cross-linking of the starting material takes place in the area corresponding to the contact lens to be produced.

Opening the mold and removing the cross-linked lens. After the polymerization or cross-linking of the starting material in the mold cavity 15, the mold halves 11 and 12 are moved apart, for example by means of a device not shown, and the mold 1 thereby opened. In this way, the lens CL becomes freely available and can be removed manually or possibly with the help of a device not shown. Thereby, if desired, it can be taken care of by suitable, per se known precautions, in that the contact lens produced in this way is preferably retained on one or the other mold half. Suitable measures are, for example, described in US 4 113 224.

Figure 2 shows the design of the mold 1 in the transition area between the mold cavity 15 and the ring channel 16 in an enlarged detail. The cavity 15 here, for example, has a design that corresponds to the typical edge geometry of a so-called soft contact lens CL. The cavity and thus the lens edge is here formed by two wall surfaces 22 and 23 standing at right angles to each other, which are formed on the male and female mold halves 11 and 12 respectively. The width and height of these two wall surfaces and the edge area defined by them on the contact lens are denoted by X and Y respectively. Naturally, the lens edge can also be somewhat rounded in practice.

As can be clearly seen, the cylindrical wall surface 23 of the female mold half part 12 does not reach all the way to the straight wall surface 22 or to the transition-free wall surface 17 of the male mold half part 11, but Ay is higher so that the already mentioned annular gap 16 between the wall surface 17 and the wall surface 18 on both the mold halves 12 and 13 are formed and remain free respectively.

The mask, which in this embodiment is placed on the wall surface 17 of the father mold half 11, reaches horizontally exactly to the extension 23a on the wall surface 23 of the mother mold half 12. When the UV light that affects the cross-linking falls into the mold in parallel beam bundles 3 vertically on the wall surface 22 and 17 respectively parallel with the cylindrical wall surface 23, the space that is located vertically under the mask 21 is shielded and only the material that is located within the cavity, i.e. within the imaginary wall extension 23a is cross-linked and a clear and burr-free lens edge is formed that does not require any mechanical finishing. When using parallel energy radiation, the contour of the mask 16 is transferred two-dimensionally parallel (here) downwards in the edge area of the contact lens, apart from the generally negligible bending and scattering effects in practice. If, therefore, the two mold halves 11 and 12 are separated from each other by the annular gap 16 with height Ay, the edge is formed in the outward direction in the area which occurs due to this displacement by the spatial limitation of the energy radiation.

In principle, it is also possible to use the bending and/or scattering effects in a targeted manner to achieve a desired blurred contour or a slightly rounded edge of the contact lens being manufactured. The same effect can also be achieved with masks with locally variable translucency. Streams with sharp edges on the manufactured shaped bodies can be rounded off by means of targeted incomplete cross-linking and by dissolving the incompletely cross-linked area with a suitable dissolving agent which can also be the non-branched material itself. When using HEMA (hydroxyethyl methacrylate), for example isopropanol is a suitable solvent.

After de-shaping the manufactured contact lens, non-cross-linked material stuck to the molds can be simply washed away with a suitable solvent which, depending on the material, can also be water.

In the embodiment of the device of the invention as shown in Figure 3, the irradiation with the cross-linking energy takes place through the mother mold half 12, that is from below in the figure. Consequently, the mask 21 is placed on the wall surface 18 of the mother mold half 12 instead of on the wall surface 17 of the father mold half 11. Beyond this, there are no differences in the embodiments in figures 1 and 2.

In the embodiment in Figure 4, the energy irradiation again takes place from the side from the mold half 11 and the mask 21 is again located on the wall surface 17 of this mold half. The mold half part 12 is not drawn up high along the sides, that is to say it lacks the cylindrical wall surface in the mold half part which in figure 2 is denoted by 23. For this reason, the annular gap 16 is correspondingly wider and higher. Experiments have shown that when manufacturing contact lenses with regular dimensions, this configuration also leads to flawless results.

The design example according to figure 5 corresponds entirely to that according to figure 4 with the difference that no energy radiation here again occurs from the underside through the mother mold half 12 and that the mask 21 is placed on the wall surface 18 of this mold half.

It should be clear that the irradiation of the crosslinkable material located in the mold cavity with energy which causes crosslinking can not only take place from one side, but can take place from both sides. It must here only be ensured that the energy only reaches the cavity and is effectively kept away from the other parts. For example, this can be achieved with two or possibly more masks arranged therefor. Incidentally, the mask or masks must not necessarily be arranged on the surface of the mold walls, but they can also be placed on the inner mold wall. Preferably, the mesh or the meshes are arranged on a wall surface that is in contact with non-cross-linked material or barely below it, as unwanted bending or scattering effects can largely be excluded in this way.

According to a further embodiment, both mold halves can later be used as packaging for the contact lens. For this, both the father mold half part 11 and the mother half part 12 can be used, the overall mold must only be formed accordingly. This can be seen in Figure 10 and Figure 11 respectively, where always a mold half (in Figure 10 the father mold half 11, in Figure 11 the mother mold half 12) can later be used as packaging. These mold halves can respectively be made as disposable mold halves, while the other mold half can always be made as a reusable mold half (for example from quartz or sapphire). The mask 21 is placed on the reusable mold half. The irradiation with energy in the form of a UV beam beam 3 always takes place through the reusable mold half which is well translucent for the energy irradiation (with the exception of masked areas). In order for the lens, which after polymerization has the shape of the cavity 15, to adhere to the disposable mold half, this disposable mold half can be similarly pretreated. The excess, non-polymerized material which after polymerization is located in the area of the mask 21 can then be removed from this mold half. The polymerized lens which adheres to the disposable mold halves can be hydrated during the further processing of this mold half if hydration is necessary. The finished lens is later packaged in disposable mold halves, by, for example, the disposable mold half being closed with a cover foil and sealed.

A further problem with production according to previously known methods is that air inclusions can occur when the mold is closed. However, air inclusions in the lens result in the lens being rejected during subsequent inspection (quality control). Previously, the mold was closed slowly to achieve a complete removal of air from the mold cavity (the mold cavity). This comparatively slow closing of the mold, however, requires a relatively long time.

Thus, according to a further aspect of the invention, it is desirable to provide a method and device of the aforementioned type for which the efficiency is high, that is to say that the shape is used effectively, and for which the wastage is comparatively low, where the task always consists in to produce contact lenses that are free from air inclusions.

In terms of procedure, this is solved by filling the mold cavity with starting materials that are still at least partially in a non-cross-linked state. This means that when the mold is filled, no more air will be present in the mold, whereby air inclusions can be completely avoided. As a result, the mold can be closed more quickly and thus used more efficiently, while at the same time comparatively very low costs. Moreover, in this way too, an exact dosage of the required quantity of the starting material is automatically added, as the filling takes place with the starting material.

In a variant of the method, when filling the mold cavity, this can be brought into connection with the surrounding reservoir where the starting material is present and from which the mold cavity is filled. This is a variant of the method which entails particularly low technical costs.

In a further method variant, the mold is also closed in the starting material to exclude any risk of air somehow finding its way into the mold cavity during the closing.

In a further variant, a form is used which comprises a container and a piston-like displaceable contact lens in this container. This contact lens is movable for opening and closing the mold against the surrounding container wall and is movable on this container wall. Due to the opening of the mould, the starting material is supplied between the container wall and , the contact lens and the starting material is again fed back during closing of the mould. During the movement of the displaceable contact lens from the surrounding container wall, the space between the displaceable contact lens and the container wall is filled with the starting material without air being able to penetrate into this space. After that, the output material that is located between the contact lenses and the container wall is again drained off by movement of the displaceable contact lens on the container wall, whereby the material that is located in the mold cavity naturally remains in it. Even when moving the contact lens on the container wall, air cannot enter the mold cavity, and air-entrapped lenses can be produced in a simple and efficient way.

For example, a mold with two mold parts can be used, where one mold half is placed on the container wall and the other mold half on the displaceable mold part. Thereby, a mold can be used with a father mold half and a mother mold half where the father mold half is placed on the container wall and the mother mold half is placed on the displaceable mold part. Pumps can preferably be used for the supply and removal of the starting material. In a further preferred method variant, the piston can be driven to supply and remove the starting material.

The cross-linked molded body can be removed from the mold in a particularly simple manner by rinsing from the mold with the help of the starting material. This can happen, for example, in the way that the molded body is detached from the mold due to the flow of the starting material when the mold is opened and then flushed out of the mold when it is closed.

In a variant of the method, the mold is opened and closed again in a first cycle. Then, at least the cross-linking that is necessary for the lenses to be able to be removed from the mold by irradiation with energy takes place. In a second cycle, the mold is opened again, whereby the lens is detached from the mold. Then the piston-like mold part is again moved in relation to the opposite container wall, the mold is closed again, whereby the cross-linked lens is flushed out from the mold. This "two-cycle" variant of the method is characterized by the fact that the production of the lens takes place in the first cycle, after which the lens is flushed out of the mold in a second cycle. In the "flush cycle" the mold can be cleaned at the same time.

The method variant just described can either run so that a "manufacturing cycle" first occurs (first cycle) and then a separate "flushing cycle" (second cycle, for example with a flushing liquid), but can also run so that the flushing coincides with the manufacturing cycle of a new lens, i.e. by refilling new starting material in the mold cavity, at the same time as the lens produced in the previous cycle is flushed out of the mold. The "two-cycle" variant of the method thus becomes a "one-cycle" variant.

The cross-linked lens can also be removed from the mold with a gripping device. This can happen in such a way that the lens is removed from the mold by means of a gripping device outside the space between the displaceable mold part and placed on the displaceable mold part which lies above the container wall. The mold part which is placed on the displaceable mold part can be held there by negative pressure and can then be detached from this with positive pressure.

In a further method variant, the mold is not completely closed after introducing the starting material into the mold cavity, so that there remains an open annular gap that surrounds the mold cavity containing this compound of uncrosslinked starting material. Thereby, on the one hand, the volume loss during cross-linking can be offset by the output material in the annular gap flowing back into the mold cavity. On the other hand, it is also avoided that the mold halves are pressed hard against each other during the production of the molded bodies. Especially due to the danger of the mold halves being irreversibly changed by mechanical stress, the mold halves have previously only been used once as explained. According to this variant of the method, it is possible to use the mold halves several times.

It is also conceivable that the mold closes during cross-linking of the material due to cross-linking loss.

In any case, however, it is important that a starting material is used which, before cross-linking, is at least viscous so that the starting material can flow through the ring gap into the mold cavity to compensate for loss.

Device-wise, the problem of possible air inclusions is solved by the fact that the mold cavity during filling is arranged in the starting material which is still at least partially in a non-cross-linked state. Thereby, it is achieved that no more air can be present in the mold at the starting point when filling, whereby air inclusions are completely avoided. As a result, the mold can be closed more quickly and thereby used more efficiently, which can also happen at comparatively low costs.

In one embodiment, this device comprises a reservoir for supplying the starting material which surrounds the mold cavity. This reservoir is connected to the mold cavity. When filling the mold cavity, the reservoir is connected to the mold cavity and fills it. This allows several constructive particularly simple continuations which will be explained in more detail below.

In a further exemplary embodiment, the device comprises means for closing the mold, arranged in the starting material, whereby here too the mold is always closed in the starting material so that no air enters the mold cavity.

In another preferred embodiment, the mold comprises a container and a piston-like displaceable mold part in this container which is movable for opening and closing the mold from its surrounding container wall and is movable on this container wall. An inlet is placed in the container through which, in the open state, output material flows between the container wall and the mold part. Furthermore, an outlet is placed in the container through which the output material in the closed state again flows out. This design example is constructively simple and also inexpensive and therefore well suited for practical use.

The mold preferably has two mold halves where one mold half is placed on the container wall and the other on the displaceable mold part. The mold has a father mold half and a mother mold half. It is preferred that the father mold half is placed on the container wall and the mother mold half is placed on the displaceable mold part. With this design, the contact lens can later be very easily removed from the mold.

For supplying and/or removing the starting material, pumps are preferably used which, when opening the mold through the inlet, supply the starting material between the container wall and the mold part and, when closing the mold again, lead the materials away through the outlet. Such pumps work reliably and thus do not incur any special costs.

In a further exemplary embodiment, the device is equipped with means for operating the piston-like displaceable mold part. This can itself be equipped with a device that works without a pump, but also a device with a pump, to move the piston-like displaceable mold part in the direction of the overlying container wall and thus once again press out the starting material that is located between the mold halves.

In a further exemplary embodiment, the device also has an assigned means for achieving a flow. This flow loosens the lens from the mold when the mold is opened and flushes it out of the mold when the mold is closed. This agent can be in the form of nozzles or similarly effective agents. It is important that they achieve a flow or a swirl of the starting material which is located between the mold halves, so that the contact lens can be removed from the mold halves by flow or by means of swirling.

In a further embodiment of the device, in a first cycle ("manufacturing cycle"), the starting material first flows through the inlet between the container wall and displaceable mold part and then again out through the outlet. The source of energy then irradiates the mold with an amount of energy that is necessary for the mold lens to be removed from the mold, so that cross-linking takes place. Then in a second cycle, for example, the starting material flows again through the inlet between the container wall and movable mold part, detaches the lens from the mold and flushes it through the outlet.

This "two-cycle" device is characterized by the fact that the production of the lens takes place in the first cycle, after which it is flushed out of the mold in the second cycle (rinse cycle, cleaning cycle), whereby the mold is simultaneously cleaned.

This device can either be designed as described in that there is first a "manufacturing cycle" (first cycle) and then a separate "flushing cycle" (second cycle), but it can be designed so that the flushing coincides with the manufacturing cycle of a new lens, i.e. by filling new starting material in the mold cavity at the same time as the lens produced in the previous cycle is flushed out of the mold. The "two-cycle" device thus becomes a "one-cycle" device. In the "one-cycle" device, however, the starting material must be used for flushing, while the use of a special cleaning liquid is possible in the "two-cycle" device in the flushing cycle.

A gripping device can be used to remove the lens, which takes the lens out of the mold. In a preferred embodiment, the container has for this purpose, on one of the container walls different from a shaping surface, a bulge or niche which essentially extends in the direction of movement of the displaceable mold part. The gripping device is arranged in this bulge or niche. The displaceable mold part exhibits, on an outer wall that does not lie opposite the moldable container wall, an indentation into which the gripping device places the removed lens. This is a structurally particularly appropriate and simple embodiment of the device.

This device can also be further developed in such a way that the displaceable mold part has a channel leading to the indentation which can be connected to a source of negative or positive pressure. The channel is then, when the gripping device lies against the lens to be taken out in the indentation of the mold part, connected to the underpressure source. The overpressure source is then connected to detach the lens. Thus, the lens can be manufactured in one cycle and taken out in the next cycle, placed on the mold part and then removed from the mold part. This is possible both for a device designed as a "two-cycle" device and for a device designed as a "one-cycle" device.

In a further embodiment of the device, the mold is equipped with spacers which keep both mold halves when the mold is closed at a small distance from each other so that an annular gap is formed which surrounds the mold cavity and is connected to it.

Thereby, on the one hand, the volume loss that occurs during cross-linking can be compensated for, as the starting material can flow through the annular gap to the mold cavity. On the other hand, this prevents the mold halves from pressing hard against each other during the production of the lenses. In particular, due to the danger that the mold half is reversibly changed by a mechanical load, the mold halves have so far only been used once, as explained above. If this embodiment of the device is used, it is possible to use the mold halves several times. In addition, it is also possible to further develop the device so that the mold is equipped with elastic means or regulating means which allow the approach of both mold halves due to the cross-linking loss.

In particular, optical lenses and especially contact lenses can be produced according to the method or with the described device.

The embodiment of the device of the invention shown in Figure 6A-C has been developed for the production of contact lenses from a liquid starting material, which can, for example, be polymerized or cross-linked by UV irradiation. Figure 6A shows form 1 in the closed state. The mold 1 is arranged in a container which is filled with non-crosslinked liquid starting material M. In addition, the arrangement comprises an energy source in the form of a UV light source 2a as well as means 2b which directs the energy from the UV light source 2a in the form of parallel beam bundles 3 against the mold 1. This means 2a can in particular also comprise a blender which is arranged between the UV light source 2a and the container 10. Of course, the UV light source 2a and the means 2b can be assembled into a simple unit.

The mold 1 comprises two mold halves 11 and 12, each of which has a curved mold surface 13 and 14, respectively, which together define a mold cavity 15 which in turn determines the shape of the contact lens CL to be manufactured. The upper mold half 11 on the mold surface 13 is concave and determines the front surface with the associated edge area. Usually, this mold half 11 is referred to as the mother mold half. The mold half 12 on the mold surface 14 is convex and determines the back or base surface of the contact lens CL and the associated edge area thereof. This mold half 12 is usually referred to as the father mold half.

The space between both mold halves 11 and 12 and thus also the cavity 15 is filled with non-cross-linked starting material M during the entire manufacturing process. According to the general idea of the invention, in all cases at least the mold cavity is completely filled with the starting material which is in the non-cross-linked state. In figure 6B it can be seen that the upper mold half 6, even in the opened state, does not completely protrude from the starting material M and the space between the mold halves 11 and 12 always remains below the liquid level of the starting material M which is located in the container 10. Thus the space between both mold halves and especially also the mold cavity constantly in connection with the starting material M which is in the container 10. Thus, at no time can air enter the space between the two mold halves 11 and 12.

When the mold cavity is filled and the mold is closed (figure 6A), it is irradiated with UV rays 3 and thereby a cross-linking of the lens is achieved.

After cross-linking, the mold is opened and the contact lens CL is removed, i.e. loosened and taken out of the mold. In Figure 6C, the gripping device 4 is symbolically indicated for this purpose, and when the upper mold half is lifted, the contact lens CL is taken out of the father mold half 12 (Figure 6B) and removed from the mold

(Figure 6C). The opening of the mold and removal of the contact lenses from the mold can also take place in a different way, which will be explained with the help of other design examples. After the removal of the contact lens, the mold can now be closed again and a new contact lens CL produced.

As the total manufacturing process according to Figure 6A-C takes place below the liquid level of the starting material M in the container 10, no air can enter the space between the two mold halves 11 and 12 and especially not in the mold cavity 15. As the opening and closing of the mold takes place below the liquid mirror, the mold can also be closed relatively quickly, which was not possible according to the method or the device according to the state of the art. Contact lenses that are free of any air inclusions can thus be manufactured efficiently and at low cost.

In the embodiment as shown in Figure 6A-C, the irradiation of the mold with UV rays on the material in the mold cavity is limited, whereby only the material located in the mold cavity 15 is cross-linked. In particular, the starting material in the annular gap 16 which surrounds the mold cavity 15, and the other starting material M which is located in container 10, are not irradiated with energy and not cross-linked. By the mold cavity is meant here any cavity in the closed mold which is defined by the complete shape of the lens to be produced, in particular the contact lens CL. The annular gap 16 which opens into the mold cavity does not therefore belong to the mold cavity 15.

For the practical implementation, according to figures 6A-C, in the area of the annular gaps 16, there is a mask 21 on the mold wall which, for the energy used, here i.e. UV light, is opaque (or at least poorly translucent compared to the translucency in the mold), and which extends all the way from the mold cavity and which shields all other parts, cavities or surfaces in the mold that are in contact with or may come into contact with liquid, non-cross-linked or possibly excess material, against the radiated energy. The partial area of the lens edge is not formed by a limitation of the material at the mold walls, but by a spatial limitation of the radiation or other energy that triggers polymerization or crosslinking. The side walls in the upper mold half are also equipped with meshes 21 to prevent the starting material M which surrounds the mold in container 10 from being cross-linked.

A further embodiment of the device of the invention is shown in Figures 7A-C. In this embodiment, one mold half, here the father mold half, is formed by a wall in the container 10a, here by the container bottom 100a. The father mold half is directly formed in the container bottom 100a. In the container 10a, there is also placed a piston-like displaceable mold part 11a which, in relation to the opposite container wall, here the container bottom 100a, can be moved towards and from the container bottom along the side walls of the container. In this way, the mold can be opened and closed. The mold part 11a is, on the plate 17a which faces the container bottom, correspondingly formed as a female mold half.

The container bottom 100a and the mold surface 17a define in the closed state the shape (figure 7A) of the mold cavity 15a. It is obvious that the mold part does not necessarily have to be designed like a piston, it can also be designed as a membrane on which the mold half is attached. Other forms of volume change are also conceivable.

In the container 10a, here in the container bottom 100a, an inlet 101a is placed through which the output material in the space between the mold part 11a and the container bottom 100a can flow. For this purpose, the space between the mold part 11a and the container bottom 100a is constantly in contact with a reservoir R. By means of pumps Pl and P2 with inlet 101a and outlet 102a, respectively, the outlet material can be supplied or removed from the space between the mold part 11a and the container bottom 100a, where it is important that the space between the mold part 11a and the container bottom 100a is constantly filled with the starting material M, so that no air can penetrate into this space. The pumps Pl and P2 are manufactured with an integrated non-return valve, but pumps without an integrated non-return valve can also be used and these can be separately inserted between the pump and the container, respectively, depending on the type of pump, such a non-return valve can also be avoided.

In the case of a closed form (figure 7A), the form is irradiated with energy, here again UV radiation. Here too, for example, the form is irradiated with energy from above. The networking is thereby initiated. Then the cross-linked molded body CL is taken out of the mold and removed. For this purpose, liquid starting material M is supplied by means of the pump Pl through the inlet 101a in the space between the container bottom 100a and the mold part 1a, the piston-like mold part 1a is moved upwards (figure 7B). The contact lens, here in the form of contact lens CL, can now be detached from the mold and taken out of the mold. This can, for example, be done with the help of a special gripping device, such as the one already described with the help of Figure 1. However, the contact lens CL can also be flushed out of the mold, as explained in more detail below.

The piston-like, displaceable mold part 11a is then moved downwards again and the material located between the mold part 11a and the container bottom 100a is released through the outlet 102a (figure 7C). The material can be emptied using the pump P2 located at the outlet.

In principle, one can imagine here that the piston-like, displaceable mold part 11a is only driven by means of liquid output material supplied or taken out between the mold part 11a and the container bottom 100a, so that the pumps Pl and P2 provide the necessary operating energy. It is also conceivable that there are no pumps and that the piston-like, displaceable mold part 11a is driven mechanically, that the starting material is sucked in by upward movement and pushed out by downward movement. Naturally, a combination with pumps and mechanical operation is also possible.

A mesh 21a is placed on the mold part 11a. This extends, in the same way as previously on the upper mold surface 11 in figures 6A-C, over the annular gap 16a except for the mold cavity 15a, as well as possibly along the side edges of the piston-like, displaceable mold part 1a. If the mold is irradiated with UV radiation 3, cross-linking and formation of the contact lens thus takes place in the area of the mold cavity 15a. The material in the other areas, especially in the annular gap 16a as well as other starting material in the container 10a is not cross-linked. For the materials as well as the production and application of such masks, basically the same considerations apply as above in connection with Figure 6A-C.

Figure 8A-C shows an embodiment of the device which is in principle very similar to the embodiment in Figure 7A-C. One difference is, of course, that the design example according to Figure 8A-C at the outlet 102a is not equipped with pump P2, but that the outlet 102a is formed as a flap which can have the shape of a plate or flap respectively. In the explanation of figures 8A-C, the removal from the form of the contact lens CL shall be described in particular in the following. The filling of the mold cavity 15a takes place analogously to the design example according to Figure 7A-C by means of the pump Pl. If the mold is closed (figure 8A), the contact lens CL is produced by cross-linking by means of irradiation of the mold with UV radiation 3.

During the upward movement of the piston-like mold part 1a (Figure 8B), liquid starting material flows into container 10a between the container bottom 100a and the piston-like, displaceable mold part 1a. The inlet 101a can be shaped like a nozzle or a similar flow-causing means. By supplying the liquid starting material through the inlet, the cross-linked contact lens CL is lifted from the mold and, by corresponding arrangement of the nozzle, flushed in the direction of the outlet 102a with the help of the obtained current. This is here designed as a lask or plate that can change shape. Upon downward movement of the piston-like shaped part 11a (Figure 8C), the ladle is changed in shape by the applied pressure and makes the outlet 102a free so that the liquid output material together with the contact lens CL can be flushed out through the outlet 102a. The contact lens can be collected in a strainer S that allows the liquid starting material to pass through. The starting material can, for example, be recycled and used again, possibly after cleaning it. While the contact lens is flushed out, the mold cavity 15a is filled again with new starting material for the irradiation with UV irradiation 3 so that this can be cross-linked in the same way to a new contact lens CL.

Above, it is described that liquid starting material is fed to the container 10a for loosening and rinsing and that the mold cavity 15a is filled again in the same cycle and UV radiation 3 is supplied again when the mold is closed for cross-linking and production of the next contact lens CL in the mold. The device thus works quasi as a "one-cycle" device. In each cycle (up and down movement of the piston-like mold part lia), a contact lens is produced and flushed out of the mold.

However, it is also possible that the manufacture of the contact lens takes place in a first cycle ("manufacturing cycle"), so that the piston-like mold part 11a moves upwards, the liquid starting material flows in between the mold part 11a and the container bottom 100a, and that the mold parts 11a then move back. In the closed state, the form is then irradiated with UV radiation 3, whereby cross-linking takes place and the contact lens CL is produced. Now the contact lens can be flushed out of the mold in a separate second cycle ("flushing cycle"), without any new contact lens being produced in this cycle, while with the "one-cycle" device a new contact lens is again produced. Liquid starting materials can thus also be used for flushing with the "two-cycle" device, but another cleaning liquid can also be used. This is particularly an advantage because the mold during the flushing cycle can be cleaned particularly well before the starting material again flows into the next cycle and the next contact lens CL is produced. In the embodiment according to Figure 8A-C, there is thus both a "one-cycle" operation (in each cycle a contact lens is produced) and also a "two-cycle" operation (in the first cycle a contact lens is produced, in the next cycle it is rinsed it out and the mold is cleaned, without a new contact lens being manufactured) possible.

A further embodiment of the device of the invention is shown in Figure 9A-C. This embodiment also corresponds in principle to that described with the help of Figure 7A-C and Figure 8A-C, but nevertheless differs significantly from these in that it comprises a differently designed piston-like, displaceable mold part 11b. Moreover, the container 10b is also designed significantly differently, as it is equipped in one side wall 103b with a bulge or niche 104b which extends in the direction of movement of the piston-like shaped part 11b. A gripping device 4b is arranged in this niche 104b. The mold part 11b has on its outer wall 113b exactly in the area in which the niche 104b is placed in the side wall 103b of the container 11b, an indentation 114b. The mold part 11b also has a channel 115b which can be connected to a negative pressure source or positive pressure source P3. The gripping device 4b can optionally be connected to this underpressure or overpressure source P3.

The production of the contact lens CL by cross-linking by means of irradiation of the form with UV radiation 3a takes place again by the same technique and method, as that which has already been described with reference to Figures 7A-C and Figures 8A-C. In the explanation of Figures 9A-C, the technique and method for removing the contact lens CL from the mold can therefore be reviewed. If the form is closed, the form is irradiated again with UV irradiation 3 and the contact lens CL is produced by cross-linking (figure 9A). The starting material is then pumped in between mold part 11b and container bottom 100b by means of pump P1 and mold part 11b is moved upwards (figure 9B). Now the gripping device 4b is swung out of the niche 104b and over the contact lens CL. The gripping device 4b has in its gripping plate 40b a bore through which negative pressure can be applied by means of the negative pressure source P3 so that the contact lens CL is lifted up and sucked against the gripping plate 40b. If the contact lens CL is sucked firmly onto the gripping plate 40b, the gripping device 104b is swung back to the niche 104b and the mold part 11b is again moved downwards. Hereby, the liquid starting material which is located between the mold part 11b and the container bottom 100b is sucked out by means of pump P2 (figure 9C).

The gripping device located in the niche 104b thereby either slides along the outer wall 113b of the mold part 11b or is held in the niche 104b until the gripping plate 40b is located above the indentation 114b on the outer wall of the mold part 11b. At this point, excess pressure is applied through the bore in the gripper plate 40b so that the contact lens CL is detached from the gripper plate 40b and placed in the indentation 114b. Through the channel 115b which leads to the indentation 114b, negative pressure is applied at the same time to release the contact lens CL from the gripping plate 40b so that the contact lens CL is easily placed from the gripping plate 40b in the indentation 114b (figure 9A).

When the mold part 11b is moved upwards, the indentation 114b on the mold part 11b is located outside the container 10b (figure 9B). If excess pressure is now applied through the channel 115, the contact lens CL detaches from the indentation 114b and can be transferred for further processing. Here, it can be particularly noted that the side wall 103b can extend upwards and can have a further niche in which the contact lens CL can be placed or flushed in. Thereby, a better guidance of the mold part 11b is achieved and a sparing of its corresponding sealing surfaces which slide along the container wall.

For the application of overpressure or underpressure, figures 9A-C show a pump P3 whose overpressure connection HP or underpressure connection NP, depending on the position of the piston-like, displaceable mold part, is connected to the channel 115b or to the bore in the gripping plate 40b. This pump P3 can suck out the starting material from the reservoir R in which the starting material is present, whereby the required pressure is achieved. In Figure 9A-C, two separate reservoirs are shown at the inlet 101b and the outlet 102b which are connected to the pumps P1 and P2 and P3 respectively, but it is obvious that it is also possible that it is one and the same reservoir.

It should also be noted at this point that the embodiment according to Figure 9A-C can also work both as a "one-cycle" device as well as a "two-cycle" device. In all cases, with the "one-cycle" device, it must be taken into account that the starting material only flows into container 10b. With the "two-cycle" device, on the other hand, in the second cycle, in which the contact lens CL is removed, a cleaning liquid can be added.

Furthermore, it is clear that the device shown by means of the figure, instead of only one cavity, can also contain several cavities so that several contact lenses can be produced simultaneously in one cycle. This variation is particularly effective.

In addition, in the variant with a piston-active mold part, flow control can be purposefully carried out in such a way that the flask-like mold part is first mechanically affected and that the starting material is released somewhat delayed when fed into the container or, when removed, is released somewhat delayed from the container. This also applies to the variants where both pumps and mechanical operation of the piston are used. With these measures, a desired underpressure can be achieved during supply, or a desired overpressure can be achieved in the container during removal, or the pressure in the container can generally be affected.

Furthermore, one can also imagine a variant in which the number of cycles, in which a new contact lens is manufactured, can vary. For example, a sensor can detect whether a contact lens in the mold has really been washed out and only then, when the sensor has detected such a washed-out contact lens, the mold is completely closed and a new contact lens is produced. If the sensor does not detect any flushed contact lens, then the form is flushed once more until the contact lens is flushed out of the form.

For contact lenses, HEMA (hydroxyethyl methyl acrylate) or poly-HEMA can, for example, often be used as a starting material which is cross-linked after irradiation with UV light, especially in a mixture with a suitable cross-linker such as ethylene glycol dimethacrylate. For other contact lenses, depending on the area of application, other crosslinkable materials may be used, where the release of the crosslinking is possible, depending on the type of crosslinkable material, also with other forms of energy, for example as electron irradiation, y-irradiation or thermal energy and so on. In the manufacture of contact lenses, starting materials that can crosslink under UV light are common, but not necessary.

According to a further aspect of the invention, special prepolymers come into consideration as starting materials, especially those based on polyvinyl alcohol which contain cyclic acetal groups and crosslinkable groups.

Contact lenses based on polyvinyl alcohol are already known. Thus, for example, EP 216,074 describes contact lenses that contain polyvinyl alcohols that contain (meth)acryloyl groups bonded over urethane groups. EP 189,375 describes contact lenses with polyvinyl alcohols cross-linked with polyepoxides.

In addition, special acetals which contain crosslinkable groups are already known, in this context reference should be made, for example, to EP 201,693, EP 215,245 and EP 211,432. EP 201,693 describes, among other things, acetals of non-branched aldehydes with 2 to 11 carbon atoms which carry terminal amino groups which are substituted with a C3-24-olefinically unsaturated, organic radical. This organic radical has a functionality that attracts the electrons of the nitrogen atom, moreover, the olefinically unsaturated functionality is polymerizable. In EP 201,693 this type of acetals with 1,2-diol, 1,3-diol, polyvinyl alcohol or a cellulose is required. However, the type of product is not specifically described.

When an acetal according to EP 201,693 is mentioned at all in connection with, for example, polyvinyl alcohols, as is the case, among other things, in example 17 in this patent description, the acetal which is polymerizable over its olefinic group is first copolymerized, for example with vinyl acetate. The copolymer thus produced is then reacted with polyvinyl alcohol and an emulsion is produced containing 37$ of solids with a pH value of 5.43 and a viscosity of 11,640 cPs.

In contrast, the present invention is aimed at prepolymers containing the 1,3-diol basic skeleton whereby a certain percentage of the 1,3-diol units are modified to 1,3-dioxane which in the 2-position has a polymerisable but not polymerized residue. The polymerizable residue is in particular an aminoalkyl residue to whose nitrogen atom a polymerizable group is attached. The present invention also relates to cross-linked homo- or copolymers of the aforementioned prepolymer, methods for producing new prepolymers and homo- or copolymers produced therefrom, contact lenses of said homo- or copolymer and methods for producing contact lenses using said homo- or copolymers.

The prepolymers of the invention are preferably a derivative of a polyvinyl alcohol with a molecular weight of at least about 2000, which contains from about 0.5 to about 80, calculated on the number of hydroxyl groups on the polyvinyl alcohol, units of formula I

where R stands for lower alkyl with up to 8 carbon atoms, R^ stands for hydrogen or lower alkyl and R<2> stands for an olefinically unsaturated, electron-withdrawing, copolymerizable residue with preferably up to 25 carbon atoms. R<2> stands for example for an olefinically unsaturated acyl radical of formula R<3->C0-, where R<3> stands for an olefinically unsaturated copolymerizable radical with 2 to 24 carbon atoms, preferably with 2 to 8 carbon atoms, especially with 2 to 4 carbon atoms. In another embodiment, the residue R<2> stands for a residue of the formula II

where q stands for 0 or 1 and R<4> and R<5> independently of each other stand for the lower alkylene of 2 to 8 carbon atoms, the arylene of 6 to 12 carbon atoms, a saturated, bivalent, cycloaliphatic group of 6 to 10 carbon atoms, the arylene alkylene or alkylenearylene with 7 to 14 carbon atoms or arylenealkylene-

the aryl with 13 to 16 carbon atoms and where R<3> has the meaning given above.

The prepolymer of the invention is thus in particular a derivative of a polyvinyl alcohol with a molecular weight of at least about 2000, which contains from about 0.5 to about 80$, calculated on the number of hydroxyl groups on the polyvinyl alcohol, units of formula III

where R stands for lower alkylene, R-'- stands for hydrogen or lower alkyl, p has the value 0 or 1, q stands for 0 or 1, R<3 >stands for an olefinic, unsaturated copolymerizable residue with 2 to 8 carbon atoms and R< 4> and R^ independently represent lower alkylene of 2 to 8 carbon atoms, arylene of 6 to 12 carbon atoms, a saturated, bivalent, cycloaliphatic group of 6 to 10 carbon atoms, arylenealkylene or alkylenearylene of 7 to 14 carbon atoms or arylenealkylenearylene of 13 to 16 carbon atoms.

The lower alkylene R preferably has up to 8 carbon atoms and can be straight-chain or branched. Suitable examples are octylene, hexylene, pentylene, butylene, propylene, ethylene, methylene, 2-propylene, 2-butylene or 3-pentylene. Preferably, the lower alkylene R has up to 6 and especially up to 4 carbon atoms. Particularly preferred are the compounds methylene and butylene.

R<1> preferably stands for hydrogen or lower alkyl with up to 7, especially up to 4 carbon atoms, preferably hydrogen. The lower alkylene R<4> or R<5> preferably has 2 to 6 carbon atoms and is particularly straight chain. Suitable examples are propylene, butylene, hexylene, dimethylethylene and particularly preferred ethylene.

The arylene R<4> or R^ is preferably phenylene which is unsubstituted or substituted by lower alkyl or lower alkoxy, especially 1,3-phenylene or 1,4-phenylene or methyl-1,4-phenylene.

A saturated, bivalent, cycloaliphatic group R<4> or R<5> is preferably cyclohexylene or cyclohexylene-lower alkylene, for example cyclohexylenemethylene which is unsubstituted or substituted with one or more methyl groups, for example trimethylcyclohexylenemethylene, as the bivalent isophorone residue.

The aryl unit of the alkylene arylene or the arylene alkylene R<4> or R<5> is preferably the phenyl which is unsubstituted or substituted by lower alkyl or lower alkoxy, the alkylene unit of this preferably lower alkyl such as methylene or ethylene, especially methylene. Preferably, this type of residue R<4> or R<5> is thus phenylenemethylene or methylenephenylene.

The arylenealkylarylene R<4> or R^ is preferably phenylene-lower alkylene-phenylene with up to 4 carbon atoms in the alkylene unit, for example phenyleneethylenephenylene.

The radicals R<4> and R^ independently of each other preferably stand for lower alkylene with 2 to 6 carbon atoms, phenylene, cyclohexylene or cyclohexylene-lower alkylene which is unsubstituted or substituted by lower alkyl, phenylene-lower alkylene, lower alkylene-phenylene or phenylene-lower alkylene- the phenyl which is unsubstituted or substituted with lower alkyl.

The term "low" means within the scope of the present invention in the context of residues and compounds, unless otherwise stated, residues or compounds with up to 7 carbon atoms, preferably with up to 4 carbon atoms.

Lower alkyl in particular has up to 7 carbon atoms, preferably up to 4 carbon atoms and is, for example, methyl, ethyl, propyl, butyl or tert-butyl.

Alkoxy has in particular up to 7 carbon atoms, preferably up to 4 carbon atoms and is, for example, methoxy, ethoxy, propoxy, butoxy or tert-butoxy.

The olefinically unsaturated copolymerizable radical R<3> with 2 to 24 carbon atoms preferably stands for alkenyl with 2 to 24 carbon atoms, especially alkenyl with 2 to 8 carbon atoms and particularly preferred alkenyl with 2 to 4 carbon atoms, for example ethenyl, 2-propenyl, 3-propenyl, 2-butenyl, hexenyl, octenyl or docenyl. Preferably, the meaning is ethenyl and 2-propenyl so that the group -C0-R<3> stands for the acyl residue of acrylic acid or methacrylic acid.

The bivalent group —R<4->NH-CO-0- is present when q stands for 1 and is absent when q stands for 0. Prepolymers in which q stands for 0 are preferred.

The bivalent group -C0-NH-(R<4>-NH-C0-0)q-R<5->0- is present when p stands for 1 and absent when p stands for 0. Prepolymers in which p stands for 0 , is preferred.

In prepolymers in which p stands for 1, the index q preferably stands for 0. In particular, prepolymers are preferred where p stands for 1, the index q stands for 0 and R^ stands for the lower alkylene.

A preferred prepolymer according to the invention is thus in particular a derivative of a polyvinyl alcohol with a molecular weight of at least about 2000, which contains from about 0.5 to 80$, calculated on the number of hydroxyl groups on the polyvinyl alcohol, units of formula III, where R stands for lower alkylene with up to 6 carbon atoms, p stands for 0 and R<3> stands for alkenyl with 2 to 8 carbon atoms.

A further preferred prepolymer according to the invention is thus in particular a derivative of a polyvinyl alcohol with a molecular weight of at least about 2000, which contains from about 0.5 to about 80$, calculated on the number of hydroxyl groups on the polyvinyl alcohol, units of formula III , where R stands for lower alkylene with up to 6 carbon atoms, p stands for 1, q stands for 0, R<5> stands for lower alkylene with 2 to 6 carbon atoms and R<3> stands for alkenyl with 2 to 8 carbon atoms.

A further preferred prepolymer according to the invention is thus in particular a derivative of a polyvinyl alcohol with a molecular weight of at least 2000 which contains from about 0.5 to about 80$, calculated on the number of hydroxyl groups on the polyvinyl alcohol, of units of formula III, where R stands for lower alkylene of up to 6 carbon atoms, p stands for 1, q stands for 1, R<4> stands for lower alkylene of 2 to 6 carbon atoms, phenylene, cyclohexylene or cyclohexylene-lower alkylene which is unsubstituted or substituted with lower alkyl, phenylene -lower alkylene, lower alkylene-phenylene or phenylene-lower alkylene-phenylene which is unsubstituted or substituted with lower alkyl, R<5> stands for lower alkylene with 2 to 6 carbon atoms and R<3> stands for alkenyl with 2 to 8 carbon atoms.

The prepolymers of the invention are derivatives of polyvinyl alcohol with a molecular weight of at least about 2000 which contain from about 0.5 to about 80% units of formula III calculated on the number of hydroxyl groups on the polyvinyl alcohol, especially about 1 to 50%, preferably about 1 to 25%, preferably 2 to 15% and most preferably about 3 to 10%. The prepolymers of the invention intended for the production of contact lenses contain in particular from about 0.5 to about 25% units of formula III in relation to the number of hydroxyl groups on the polyvinyl alcohol, in particular about 1 to 15% and preferably from about 2 to 12%.

Polyvinyl alcohol, which can be derivatized according to the invention, preferably has a molecular weight of at least 10,000. As an upper limit, the polyvinyl alcohol can have a molecular weight of up to 1,000,000. Preferably, the polyvinyl alcohol has a molecular weight of up to 300,000, preferably up to about 100,000 and most preferably up to around 50,000.

Generally, the suitable polyvinyl alcohols of the invention have mainly a poly-(2-hydroxy)ethylene structure. The derivatized polyvinyl alcohols of the invention can also have hydroxy groups in the form of 1,2-glycols, for example copolymer units of 1,2-dihydroxyethylene which can be produced by alkaline hydrolysis of vinyl acetate-vinylene carbonate copolymers.

In addition, the derivatized polyvinyl alcohols of the invention can also contain a small proportion, for example up to 20%, preferably up to 5%, copolymer units of ethylene, propylene, acrylamide, methacrylamide, dimethacrylamide, hydroxyethyl methacrylate, methyl methacrylate, methyl acrylate, ethyl acrylate, vinypyrrolidone, hydroxyethyl acrylate, allyl alcohol, styrene or similar commonly used comonomers.

Common commercial polyvinyl alcohols can be used, such as Vinol® 107 from the company Air Products (MW = 22,000 to 31,000, 98-98.5% hydrolyzed), Polysciences 4397 (MW = 25,000, 98.5% hydrolyzed), BF 14 from Chan Chun, Elvanol 90-50 from DuPont, UF-120 from Unitika, Moviol® 4-88, 10-98 and 20-98 from Hoechst. Other manufacturers are e.g. Nippon Gohsei (Gohsenol®), Monsanto (Gelvatol®), Wacker (Polyviol®) or the Japanese manufacturers Kuraray, Denki and Shin-Etsu.

As already mentioned, copolymers of hydrolyzed vinyl acetates can also be used, which can for example be produced as hydrolyzed ethylene vinyl acetate (EVA) or vinyl chloride vinyl acetate, N-vinyl pyrrolidone vinyl acetate and maleic anhydride vinyl acetate.

Polyvinyl alcohol is usually produced by hydrolysis of the corresponding homopolymer polyvinyl acetate. In a preferred embodiment, the derivatized polyvinyl alcohol of the invention contains less than 50% polyvinyl acetate units, especially less than 20% polyvinyl acetate units.

The compounds containing units of formula III can be prepared in a manner known per se, for example a polyvinyl alcohol with a molecular weight of at least 2000, which contains units of formula IV

with about 0.5 to 80%, in relation to the number of hydroxyl groups in the compound of formula IV, is converted to a compound of formula V where R' and R" independently of each other stand for hydrogen, lower alkyl or lower alkanoyl, such as acetyl or propionyl, and the second variable has the meaning given for formula III, especially in acidic medium Alternatively, a polyvinyl alcohol having a molecular weight of at least about 2000 and containing units of formula IV may be reacted with a compound of formula VI where the variables are defined as for the compound of formula V, especially under acidic conditions, and the cyclic acetal thus prepared is then reacted with a compound of formula VII

where the variables are defined as for the compound with formula

V.

Alternatively to this, the reaction product can have a compound of formula IV where a compound of formula VI such as the product described above is reacted with a compound of formula VIII

where R<3> for example stands for C2_8~alkenyl °S X stands for a reactive group, for example for etherified or esterified hydroxy, e.g. halogen, especially chlorine.

Compounds of formula V where p stands for 0 are known, for example, from EP 201,693. Compounds of formula VI are also described there. Compounds of formula VII are known in and of themselves and can be prepared in a known manner. An example of a compound of formula VII where q stands for 0 is isocyanoethyl methacrylate. An example of a compound of formula VII where q stands for 1 is the reaction product of isophorone diisocyanate with 0.5 equivalents of hydroxyethyl methacrylate. Compounds of formula VIII are known per se, a typical example being methacryloyl chloride. Compounds of formula V, where p and/or q stand for 1, can be prepared from the above-mentioned compound in a manner known per se, for example by reacting a compound of formula VI with isocyanatoethyl methacrylate or by reacting a compound with formula VI with isophorone diisocyanate, which is previously terminated with 0.5 equivalents of hydroxyethyl methacrylate.

Surprisingly, the prepolymers of formula I and III are exceptionally stable. This is unexpected for the person skilled in the art, as, for example, highly functional acrylates are usually stabilized. If this type of compound is not stabilized, rapid polymerization usually occurs. However, such spontaneous cross-linking by homopolymerisation does not take place for the prepolymers of the invention. The prepolymers of formula I and III can also be purified in a known manner, for example by precipitation with acetone, dialysis or ultrafiltration, where ultrafiltration is particularly preferred. With this purification method, the prepolymers of formula I and III can be produced in extremely pure form, for example as a concentrated aqueous solution, which is free or at least mainly free of reaction products such as salts, and from starting substances such as compounds of formula V or others not -polymerized components.

The preferred purification method of the prepolymers of the invention, an ultrafiltration, can be carried out in a known manner. Here, it is possible to repeat the ultrafiltration several times, for example two to ten times. Alternatively to this, the ultrafiltration can be carried out continuously until the desired degree of purity is achieved. The desired degree of purity can be chosen sufficiently high. A suitable measure of the degree of purity is, for example, the coking salt content in the solution, which can be examined in a known manner.

On the other hand, the prepolymers of the invention with formulas I and III respectively can be crosslinked very efficiently and purposefully, in particular by photocrosslinking.

During the photocrosslinking, a photoinitiator is preferably added which can initiate a radical crosslinking. Examples of this are known to those skilled in the art, in particular the photoinitiators benzoin methyl ether, 1-hydroxycyclohexylphenyl ketone, Darocure 1173 or the Irgacure type can be mentioned. The cross-linking can be triggered by actinic radiation such as UV light or ionizing radiation, such as y-radiation or X-ray radiation.

The photopolymerization is preferably carried out in a solvent. As a solvent, mainly all solvents are suitable which dissolve the polyvinyl alcohol and optionally the additional vinylic comonomers used, for example water, alcohols such as lower alkanols such as ethanol or methanol, in addition to carboxylic acid amides such as dimethylformamide or dimethylsulfoxide, further mixtures of suitable solvents such as mixtures of water with an alcohol, such as a water/water or a water/methanol mixture.

The photocrosslinking preferably takes place directly from an aqueous solution of the prepolymers of the invention, which can be produced as a result of the preferred purification method, an ultrafiltration, optionally after the addition of a further vinylic comonomer. The photocrosslinking can, for example, take place in an aqueous solution of around 15 to 40%.

The process for producing the polymers of the invention can be characterized by photocrosslinking a prepolymer containing units of formula I or II, especially in substantially pure form, that is to say, for example, after one or more ultrafiltrations, preferably in solution, especially in aqueous solution, in the absence or presence of an additional vinylic comonomer.

The vinylic comonomer which, according to the invention, can further be modified by the photocrosslinking, can be hydrophilic, hydrophobic or a mixture of a hydrophilic and a hydrophobic vinylic monomer. Suitable vinylic monomers include in particular all those which are usually used in the manufacture of contact lenses. By a hydrophilic vinylic monomer is meant a monomer that gives a polymer that is water-soluble or can at least absorb 10% by weight of water as a homopolymer. By analogy is meant a hydrophobic, vinylic monomer, a monomer which typically gives a polymer which is water insoluble and can absorb less than 10% by weight of water.

In general, between 0.01 and 80 units of a typical vinylic comonomer react per unit with formula I respectively formula

III.

If a vinylic comonomer is used, the cross-linked polymer according to the invention preferably contains an amount between about 1 and 15%, preferably between about 3 and 8%, of units of formula I respectively III, calculated for the number of hydroxyl groups on the polyvinyl alcohol, which react with about 0.1 to 80 units of the vinylic monomer.

The proportion of vinylic comonomer is, if this is used, preferably 0.5 to 80 units per unit of formula I, in particular 1 to 30 units of vinylic comonomer per unit with formula I and preferably 5 to 20 units per unit of formula I.

It is also preferred to use a hydrophobic vinylic comonomer or a mixture of a hydrophobic vinylic comonomer with a hydrophilic vinylic comonomer, where this mixture contains at least 50% by weight of a hydrophobic vinylic comonomer. In this way, the mechanical properties of the polymer can be improved without the water content being significantly reduced. In principle, however, it applies that both conventional hydrophobic vinylic comonomers and conventional hydrophilic vinylic comonomers are suitable for copolymerization with polyvinyl alcohol containing groups of formula I.

Suitable hydrophobic vinylic comonomers are, without this enumeration being limiting, C^_^3 alkyl acrylates and —methacrylates, C3—1g-alkylacrylamide and —methacrylamide, acrylonitrile, methacrylonitrile, vinyl C^.^g-alkanoate, ^ 2- 18~ alkene, C2_i8~naloalken» styrene, C^_^-alkylstyrene, vinyl alkyl ether, where the alkyl part has 1 to 6 carbon atoms, ^ 2- 10' perfluoroalkyl acrylate and — methacrylate or corresponding partially fluorinated acrylates and methacrylates, C3_i2_perfluoroalkyl-ethyl- thiocarbonylaminoethyl acrylate and -methacrylate, acryloxy- and methacryloxy-alkylsiloxane, N-vinylcarbazole, C1-22-alkyl esters of maleic acid, fumaric acid, itaconic acid, mesaconic acid and the like. Preferred are, for example, C1-4 alkyl esters of vinylically unsaturated carboxylic acids with 3 to 5 carbon atoms or vinyl esters of carboxylic acids with up to 5 carbon atoms.

Examples of suitable hydrophobic vinyl comonomers are methacrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, styrene, chloroprene, vinyl chloride, vinylidene chloride, acrylonitrile, 1-butene -butadiene, methacrylonitrile, vinyltoluene, vinyl ethyl ether, perfluorohexyl-ethylthiocarbonylaminoethyl methacrylate, isobornyl methacrylate, trifluoroethyl methacrylate, hexafluoroisopropyl methacrylate, hexafluorobutyl methacrylate, tris-trimethylsilyloxy-silyl-propyl methacrylate, 3-methacryloxypropylpentamethyldisiloxane and bis(methacryloxypropyl)tetramethyldisiloxane.

Suitable hydrophilic vinyl comonomers are, hydroxy substituted lower alkyl acrylates and -methacrylates, acrylamide, methacrylamide, lower alkyl acrylamide and -methacrylamide, ethoxylated acrylates and methacrylates, hydroxy substituted lower alkyl acrylamides and -hydroxy substituted lower alkyl vinyl ethers, sodium methylene sulfonate, sodium styrene-sul ,phonate, 2-acrylamido-2-methylpropanesulfonic acid, N-vinyl-pyrrole, N-vinylsuccinimide, N-vinylpyrrolidone, 2- or 4-vinylpyridine, acrylic acid, methacrylic acid, amino- (where the term "amino" also includes quaternary ammonium), mono-lower alkylamino- or di-lower alkylamino-lower alkyl acrylates and methacrylates, allyl alcohol and the like. Preferred are, for example, C2_4~alkyl(meth)acrylates substituted with hydroxy, 5- to 7-membered N-vinyl lactam, N,N-di-C^_4-alkyl(meth)acrylamide and vinylically unsaturated carboxylic acids with a total of 3 to 5 carbon atoms.

Examples of suitable hydrophilic vinylic comonomers are hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylamide, methacrylamide, dimethylacrylamide, allyl alcohol, vinylpyridine, vinylpyrrolidone, glycerin methacrylate, N-(1,1-dimethyl-3-oxobutyl)acrylamide and the like.

Preferred hydrophobic vinylic comonomers are methyl methacrylate and vinyl acetate.

Preferred hydrophilic vinylic comonomers are 2-hydroxyethyl methacrylate, N-vinylpyrrolidone and acrylamide.

The contact lenses according to the invention have a large number of unusual and very advantageous properties. Among these properties, mention must be made, for example, of the excellent compatibility with the human cornea, which is due to a balanced adaptation of water content, oxygen permeability and mechanical properties.

Furthermore, it can be emphasized that the contact lenses of the invention can be produced very simply and efficiently in relation to the state of the art. This is due to several factors. On the one hand, the starting materials are inexpensive to acquire or to manufacture. Secondly, the advantage is stated that the prepolymer is surprisingly stable so that they can be subjected to a high degree of purification. For cross-linking, a material can thus be added which practically does not require any subsequent purification, such as, in particular, an expensive extraction of non-polymerized components. Moreover, the polymerization can take place in aqueous solutions, so that a subsequent hydration step is not necessary. Finally, the photopolymerization takes place within a short time, so that the manufacturing process for the contact lenses of the invention is also advantageous from a commercial point of view.

In the following illustrative examples, other quantities, unless otherwise expressly stated, are given on a weight basis, while all temperatures are given in °C.

Example la):

To 105.14 parts of aminoacetaldehyde-dimethylacetal and 101.2 parts of triethylamine in 200 parts of dichloromethane, under ice-cooling, 104.5 parts of methacryloyl chloride dissolved in 105 parts of dichloromethane are added dropwise, at a maximum of 15° C. during 4 hours. After completion of the reaction, the dichloromethane phase was washed with 200 parts of water, then with 200 parts of IN HCl solution, then twice with 200 parts of water. After drying with anhydrous magnesium sulfate, the dichloromethane phase was evaporated and stabilized with 0.1%, starting from the reaction product, with 2,6-di-tert-butyl-p-cresol. After distillation at 90°C/10-<3 >mbar, 112 g of methacrylamidoacetaldehyde-dimethyl acetal was obtained as a colorless liquid, boiling point 92°C/10"<3> mbar (65% yield).

Example lb):

52.6 g of aminoacetaldehyde-dimethylacetal was dissolved in 1,150 ml of deionized water and cooled under ice cooling to 5°C. Then, 50 ml of methacrylic acid chloride and 50 ml of 30% caustic soda were added simultaneously over the course of 40 minutes, so that the pH value remained at 10 and the temperature did not rise above 20° C. After the addition was finished, the remaining content of aminoacetaldehyde-dimethylacetal was determined to be 0 .18% by chromatography. By further addition of 2.2 ml of methacrylic acid chloride and 2.0 ml of 30% caustic soda, the amine was completely reacted. Then a solution was stabilized with 1N hydrochloric acid (pH = 7). The aqueous phase was extracted with 50 ml of petroleum ether and washed with water. The petroleum ether phase contained 3.4 g of by-product. The aqueous phases were combined and 402.8 g of a 20.6% solution of methacrylamidoacetaldehyde-dimethylacetal was added. According to the chromatogram, the product content is 98.2%.

Example 2:

10 parts of polyvinyl alcohol with a molecular weight of 22,000 and a degree of saponification of 97.5-99.5% were dissolved in 90 parts of water, 2.5 parts of methacrylamidoacetaldehyde-dimethyl acetal were added and acidified with 10 parts of concentrated hydrochloric acid. The solution was stabilized with 0.02 part of 2,6-di-tert-butyl-p-cresol. After stirring for 20 hours at room temperature, the solution was adjusted to pH 7 with 10% caustic soda and then ultrafiltered seven times over a 3kD membrane (ratio 1:3). After evaporation, an 18.8% aqueous solution of methacrylamidoacetaldehyde-1,3-acetal of polyvinyl alcohol with a viscosity of 2240 cP at 25°C was obtained.

Example 3:

10 parts of the solution of methacrylamidoacetaldehyde-1,3-acetals of polyvinyl alcohol prepared according to Example 2 was photochemically cross-linked by adding 0.034 parts of Darocure 1173 (Ciba-Geigy). This mixture, as a 100 micron thick layer between two glass plates, was illuminated with 200 pulses from a 5000 watt illumination device from the company

Staub. This resulted in an almost transparent foil with a solids content of 31%.

Example 4:

110 g of polyvinyl alcohol (Moviol 4-88, Hoechst) was dissolved in 440 g of deionized water at 90°C and cooled to 22°C. 100.15 g of a 20.6% aqueous solution of methacrylamidoacetaldehyde-dimethyl acetal, 38.5 g of concentrated hydrochloric acid (37% p.a., Merck) and 44.7 g of deionized water were added thereto. The mixture was stirred at room temperature for 22 hours and then adjusted to pH 7.0 with a 5% NaOH solution. This solution was diluted with deionized water to 3 liters, filtered and ultrafiltered through a 1-KD-Omega membrane from the company Filtron. After three times the sample volume had passed through, the solution was concentrated. 660 g of a 17.9% solution of meacrylamidoacetaldehyde-1,3-acetals of polyvinyl alcohol with a viscosity of 210 cP were obtained. The intrinsic viscosity of the polymer was 0.319. The nitrogen content was 0.96%. According to NMR research, 11 mol% of the OH groups are acetalized and 5 mol% of the OH groups are acetylated. By concentrating the aqueous polymer solution under reduced pressure and air suction, a 30.8% solution with a viscosity of 3699 cP was obtained.

Example 5;

133.3 g of a 15% polyvinyl alcohol solution (Moviol 4-88, Hoechst) was added to 66.6 g of deionized water, 3.3 g of monomeric 4-methacrylamidobutyraldehyde-diethyl acetal and 20.0 g of concentrated hydrochloric acid (37% p.a., Merck) and stirred for 8 hours at room temperature. The solution was then adjusted to pH 7 with 5% caustic soda. After ultrafiltration of this solution over a 3 KD-Omega membrane from the company Filtron, where the sodium chloride content in the polymer solution was reduced from 2.07% to 0.04%, resulted in a 20% polymer solution of methacrylamidobutyraldehydo-1,3-acetals of polyvinyl alcohol with a viscosity of 400 cP. The intrinsic viscosity of the polymer was 0.332. The nitrogen content was

0.41%. According to NMR investigations, 7.5 mol% of the OH groups are loaded with acetal groups and 7.3 mol% of the OH groups are loaded with acetate groups.

Example 6;

200 g of a 10% polyvinyl alcohol solution (Moviol 4-88, Hoe,chst) was added to 2.4 g (14.8 mmol) of aminobutyraldehyde diethyl acetate (Fluka) and 20 g of concentrated hydrochloric acid (37% p.a., Merck). The solution was stirred for 48 hours at room temperature and then neutralized with 10% caustic soda. The solution was diluted to 400 ml. 200 ml of this solution was further processed according to example 7. To the other 200 ml of this solution, 0.85 g (8.1 mmol) of methacrylic acid chloride (Fluka) was added and the pH value was maintained at pH = 10 with 2N caustic soda. After 30 minutes at room temperature, the pH value was adjusted to 7.0 and the solution was purified over a 3-KD-0mega membrane from the company Filtron analogously to example 5. After concentration, a 27.6% polymer solution of methacrylamidobutyraldehydo- 1,3-acetal of polyvinyl alcohol with a viscosity of 2920 cP. The intrinsic viscosity of the polymer was 0.435. The nitrogen content was 0.59%.

Example 7:

200 ml of the polymer solution from example 6 was added with 1.3 g (8.5 mmol) of 2-isocyanatoethyl methacrylate and maintained at a pH value of 10 with 2N caustic soda. After 15 minutes at room temperature, the solution was neutralized with 2N hydrochloric acid and ultrafiltered analogously to example 6. After concentration, a 27.1% polymer solution of 4-(2-methacryloylethylureido)butyraldehydo-1,3-acetal of polyvinyl alcohol was obtained with a viscosity of 2320 cP. The intrinsic viscosity of the polymer was 0.390. The nitrogen content was 1.9%.

Example 8:

The 30.8% polymer solution according to example 4 with a viscosity of about 3600 cP was added 0.7% Darocure 1173 (in relation to the content of polymer). The solution was filled in a transparent polypropylene contact lens mold, the mold was closed. Using a 200 watt Oriel UV lamp, the solution was illuminated for 6 seconds at a distance of 18 cm. The mold was opened and the finished contact lens can be removed. The contact lens is transparent and has a water content of 61%. The modulus was 0.9 mPa, the elongation at break 50%. The contact lens was autoclaved at 121°C for 40 minutes. No change in shape could be detected on such a changed contact lens.

Example 9:

0.0268 g of Darocure 1173 (0.7% in relation to the polymer content) and 0.922 g of methyl methacrylate were added to 10.00 g of a 27.1% polymer solution according to example 7. After adding 2.3 g of methanol, a clear solution was obtained. This solution was illuminated analogously to example 8 with a 200 watt Oriel lamp for 14 seconds. A transparent contact lens with a water content of 70.4% was obtained.

Example 10:

12.82 g of a 24.16% solution of the prepolymer from example 4 was added with 1.04 g of acrylamide and 0.03 g of Darocure 1173. The clear solution was then illuminated analogously to example 8 with a 200 watt Oriel lamp for 14 seconds . A contact lens with a water content of 64.4% was obtained.

Claims (62)

1. Method for the production of contact lenses from a material that can be cross-linked by irradiation with suitable energy (3), in a form (1) which is at least partially translucent to the energy that causes the cross-linking, which form (1) has a cavity (15) which determines the shape of the contact lens (CL), where the material is brought into the mold at least partially in a not yet cross-linked state, and in this is cross-linked by irradiation with energy that causes cross-linking to a sufficient extent so that the contact lens can be removed from the mold (1), and where the irradiation which causes the cross-linking is spatially limited to the area of the mold cavity (15), characterized in that the irradiation is spatially limited to the entire mold cavity (15) including its edge by means of a masking (21) of the mold (1) that is at least partially impervious to the radiation energy ), whereby the final shape of the contact lens (CL), including the contact lens edge, is determined, and that no mechanical finishing of the contact lens (CL) edges is carried out. 2. Method according to claim 1, characterized in that radiation energy is used as the energy which causes the cross-linking, in particular UV radiation, radiation, electron radiation or thermal radiation. 3. Method according to claim 2, characterized in that the radiation energy is used in the form of essentially parallel beam bundles (3). 4. Method according to one or more of the preceding claims, characterized in that a form (1) is used which, at least on one side, is well translucent for the energy that causes the cross-linking, and that the spatial limitation of the energy irradiation takes place at parts of the form which are made of parts that poorly or do not pass through the energy that causes the cross-linking. 5 . Method according to one or more of claims 1 to 4, characterized in that a mold (1) is used which, at least from one direction, is well translucent for the energy that causes cross-linking, and that the spatial limitation of the energy irradiation occurs by a mask (21) on the outside of the mold cavity (15) or placed on the mold, which is little or no translucent to the energy that causes the crosslinking. 6. Method according to claim 5, characterized in that the mask (21) is arranged in the area at the separation planes or the separation rafts of the various mold parts, especially in the areas (17, 18) which are in contact with the cross-linked material. 7. Method according to one or more of claims 1 to 6, characterized in that the mold (1) after introducing the material into the mold cavity (15) is not completely closed, so that at least one gap (16) containing non-cross-linked material which is in connection with the mold cavity and preferably surrounds it, remains open and that the energy which causes cross-linking is kept away from the material located in this gap (16). 8. Method according to claim 7, characterized in that the mold (1) is further closed as a result of cross-linking shrinkage during the progressing cross-linking of the material. 9. , Method according to claim 7, characterized in that a material is used which before cross-linking is at least tough and liquid, and that a reservoir is placed that is not irradiated by the energy that causes the cross-linking from which reservoir the material for loss compensation can flow through the gap (16) into the mold cavity (15). 10. Method according to one or more of the above stated claims 1 to 9, characterized in that the non-cross-linked or partially cross-linked material which is adhered to the contact lens (CL) after removal from the mold, is removed by rinsing with a suitable solvent. 11. Method according to one or more of claims 1 to 10, characterized in that the mold (1) is closed without force, so that both mold halves (11, 12) lie on top of each other without further load. 12. Method according to one or more of the above stated claims 1 to 11, characterized in that the filling of the mold cavity (15) takes place at least partially as starting material (M) which is still in a cross-linked state. 13. Method according to claim 12, characterized in that for filling the mold cavity (15), this is brought into connection with a reservoir (R) which surrounds the mold cavity, in which the starting material is placed and from which the mold cavity (15) is flooded. 14. Method according to claim 12 or 13, characterized in that the mold (1) is closed in the starting material. 15. Method according to one or more of claims 12 to 14, characterized in that a mold is used which comprises a container (10a, 10b) and a movable mold part (lia, 11b) in this container, which can be moved away for opening and closing the mold from the above container wall (100a, 100b) and is movable on this container wall, where during opening of the mold the output material is supplied between the container wall (100a, 100b) and the mold part (lia, 11b) and the output material is again taken away during the closing of the mold. 16. Method according to claim 15, characterized in that a mold part with two mold halves is used, where one mold half is placed on the container wall (100a, 100b) and the other mold half is placed on the displaceable mold part (lia, 11b). 17. Method according to claim 16, characterized in that a mold is used with a male mold half and a female mold half, where the male mold half is placed on the container wall (100a, 100b) and the female mold half is placed on the displaceable mold part (lia, 11b ). 18. Procedure According to one or more of claims 15 to 17, characterized in that pumps (Pl, P2) are used for the supply and removal of the starting material. 19. Method according to one or more of claims 15 to 17, characterized in that the displaceable mold part (11a, 11b) is driven to supply and remove the starting material. 20. Method according to one or more of claims 12 to 19, characterized in that the cross-linked contact lens (CL) is removed from the mold by flushing with the starting material. 21. Method according to one or more of claims 15 to 19 and according to claim 20, characterized in that the contact lens (CL) is released from the mold by the flow of the starting material when opening the mold and is flushed out of the mold when closing the mold. 22. Method according to claim 20, characterized in that in a first cycle the mold is opened and closed again, then irradiation with energy that is at least sufficient to provide sufficient cross-linking so that the contact lens (CL) can be removed from the mold, and that the mold in a second cycle is opened, whereby the contact lens is released from the mold and where then the mold part (lia) when closing the mold is again moved to the container wall (100a) above, from where the cross-linked contact lens is flushed out of the mold. 23. Method according to one or more of claims 12 to 19, characterized in that the cross-linked contact lens is removed from the mold by a gripping device (4). 24. Method according to one or more of claims 15 to 19 and according to claim 23, characterized in that the molded body (CL) which has been removed from the mold by means of the gripping device (4,4b) outside the space between the displaceable mold part (11b) and the overlying container wall (100b) is placed on the displaceable mold part. 25. Method according to claim 24, characterized in that the contact lens placed on the displaceable mold part is held firmly on this by means of negative pressure (NP) and then again released by means of positive pressure (HP). 26. Method according to one or more of claims 12 to 25, characterized in that the mold is not completely closed after the introduction of the starting material into the mold cavity, so that an annular gap containing non-cross-linked starting material, which surrounds the mold cavity and is connected to it, remains open. 27. Method according to claim 26, characterized in that the mold is further closed during the advanced cross-linking of the material due to material shrinkage. 28. Method according to claim 27, characterized in that at least one tough and liquid starting material for the crosslinking is used, and that for shrinkage compensation can flow to the starting material through the annular gap (16) of the mold cavity (15). 29. Method according to one or more of the above stated claims, characterized in that the starting material is a prepolymer, where it is a derivative of a polyvinyl alcohol with a molecular weight of at least about 2000, which contains from about 0.5 to about 80% of the number hydroxyl groups in the polyvinyl alcohol of units of formula I, where R stands for lower alkyl with up to 8 carbon atoms, R<1> stands for hydrogen or lower alkyl and R<2> stands for an olefinically unsaturated, electron-withdrawing, copolymerizable residue with preferably up to 25 carbon atoms. 30. Method according to claim 29, characterized in that the starting material is a prepolymer, where R<2> stands for an olefinically unsaturated acyl residue with the formula R<3->C0-, where R<3> stands for an olefinically unsaturated copolymerizable C2-24" residue , preferably C2_8-residue" especially C2_4-residue. 31. Method according to claim 30, characterized in that the starting material is a prepolymer, where R<3> stands for C2_g-alkenyl. 32. Process according to claim 29, characterized in that the starting material is a prepolymer, where the residue R2 stands for a residue with the formula II, where q stands for zero or one and R<4> and R<5> independently of each other stand for C2_8_lower alkylene» c6-12"ary^ene» a saturated bivalent C^_^Q-cycloaliphatic group, 07.14<a>rylenal- the alkylene or -alkylenearylene or the Cj^i^-arylenealkylenearylene, and where R<3> stands for an olefinically unsaturated copolymerizable C'2-24_res't» preferably C2_8~<r>est, most preferably C2_4~<r>est. 33. Method according to claim 29, characterized in that the prepolymer is a derivative of a polyvinyl alcohol with a molecular weight of at least 2000, which contains about 0.5 to about 80% in relation to the number of hydroxyl groups in the polyvinyl alcohol, units with the formula III, where R stands for lower alkyl, R<*> stands for hydrogen or lower alkyl, p stands for zero or one, q stands for zero or one, R<3> stands for an olefinically unsaturated copolymerizable C2_s_ residue and R<4> and R^ independently stand for C2_s_ lower alkylene, C^-^-arylene, a saturated bivalent cycloaliphatic Cfc.iQ group, <C>7_i7-arylenealkylene or -alkylenearylene or C-^.-^-arylenealkylenearylene• 34. Process according to claim 33, characterized in that the starting material is a prepolymer, where R stands for lower alkyl with up to 6 carbon atoms, p stands for zero and R<3> stands for C2_8-alkenyl• 35., Process according to claim 33, characterized in that the starting material is a prepolymer, where R stands for the lower alkylene with up to 6 carbon atoms, p stands for one, q stands for zero, R<5> stands for the C2_6-lower alkylene and R<3> stands for C2_8 "alkenyl• 36. Process according to claim 33, characterized in that the starting material is a prepolymer, where R stands for lower alkylene with up to 6 carbon atoms, p stands for one, q stands for one, R<4> stands for C2_£,-lower alkylene, phenylene, unsubstituted or substituted with lower alkyl, cyclohexylene or cyclohexylene-lower alkyl, unsubstituted or with lower alkyl substituted phenylene-lower alkyl, lower alkylene-phenylene or phenylene-lower alkylene-phenylene, R<5> stands for C2-k-lower alkylene and R<3> stands for C2_8-<a>lkenyl• 37. Method according to claim 29, characterized in that the starting material is a prepolymer, where it is a derivative of a polyvinyl alcohol with a molecular weight of at least about 2000, which contains from about 1 to about 15%, in relation to the number of hydroxyl groups in the polyvinyl alcohol, units with the formula I. 38. Method according to one or more of claims 1 to 37, characterized in that a mold half (11, 12) in the mold (1) is used as packaging for the contact lens (CL). 39. Method according to claim 38, characterized in that the female mold half (12) is used as packaging for the contact lens. 40. Method according to claim 38 or 39, characterized in that one of the mold halves (11, 12) is designed as a reusable mold half and the other mold half (12, 11) is designed as a disposable mold half, where the disposable mold half is used as packaging for the contact lens. 41. Method according to claim 40, characterized in that the male mold half (11) is designed as a reusable mold half, and the female mold half (12) is designed as a disposable mold half, where the female mold half (12) is used as packaging for the contact lens. 42. Device for the production of contact lenses comprising a mold (1) which can be opened and closed, and which has a mold cavity (15) which determines the shape of the contact lens (CL), which mold (1) is intended for receiving a cross-linked material and is designed translucent for externally supplied energy irradiation which causes cross-linking of the material, and with a source (a) for the energy irradiation as well as with means (2b) for irradiating the mold (1) and with a means for spatially limiting the irradiation to the area of the mold cavity (15), characterized in that the means for spatially limiting the energy irradiation of the mold is designed as a non- or slightly translucent masking (21) of the mold (1), which masking is arranged so that the entire mold cavity (15), including its edge area, is irradiated, whereby the contact lens's ( CL) final shape, including its edge area, is determined. 43. Device according to claim 42, characterized in that the mold (1) is equipped with a mask (21) which is not or is only slightly translucent to the energy that causes crosslinking, which, with the exception of the mold cavity (15), shields all non-crosslinked material that can be contained in the mold cavity (16) or the mold floats (17,18) which can come into contact with the material, against the energy that causes cross-linking. 44. Device according to claim 42 or 43, characterized in that the mold (1) comprises two mold halves (11,12) which are separated along a dividing surface (17,18) and that the mask (21) is arranged on one of both mold halves (11,12) ) and/or on both mold halves in the area at the separating surface (17,18) outside the mold cavity (15). 45. Device according to claim 44, characterized in that the source (2a) provides UV radiation and that at least one of the mold halves (11,12) in the mold (1) is made of UV-translucent material, especially quartz. 46. Device according to claim 45, characterized in that the mask (21) consists of a layer of material which is non-translucent to UV radiation, in particular a metal-one metal oxide layer, in particular a chromium layer. 47. Device according to one of claims 42 to 46, characterized in that the mold (1) is equipped with spacers (19a, 19b), where both mold halves (11, 12) when the mold is closed must maintain a small distance (Ay) from each other so that a gap (16) is formed which preferably surrounds the mold cavity (15) and which is in connection with this, and that the mask (21) is arranged in the area of this gap. 48. Device according to claim 47, characterized in that the mold (1) is equipped with elastic means or adjustable means (19b) which allow an approximation of the mold halves (11,12) as a result of the crosslinking shrinkage. 49. Device according to any one of claims 42 to 48, characterized in that when filling the mold cavity (15) the starting material (M) is placed while it is at least partially in a non-cross-linked state. 50. Device according to claim 49, characterized in that it comprises a reservoir (R) for delivering the starting material, where the reservoir surrounds the mold cavity (15) and is connected to the mold cavity (15), and when filling the mold cavity, the reservoir (R) is connected to the mold cavity ( 15) and fills this. 51. Device according to claim 49 or 50, characterized in that it comprises means for closing (la) the mold (1) where the starting material is arranged. 52. Device according to one of claims 49 to 51, characterized in that the mold comprises a container (10a, 10b) and a mold part (lla.llb) that can be moved in this container, for opening and closing the mold from the overlying container wall (100a, 100b) is movable back and forth on this container wall (100a, 100b), and that an inlet (101a, 101b) is placed in the container through which the output material during opening of the mold flows between the container wall (100a, 100b) and the mold part (lla, llb), and that the container is equipped with an outlet (102a, 102b), through which the starting material flows out again during closing of the mold. 53. Device according to claim 52, characterized in that the mold consists of two mold halves, where one mold half is placed on the container wall (100a, 100b) and the other is placed on the displaceable mold part (lia, 11b). 54. Device according to claim 53, characterized in that the mold has a male mold half and a female mold half, and that the male mold half is placed on the container wall (100a, 10-0b) and the female mold half is placed on the displaceable mold part (lia, 11b ). 55. Device according to one of the claims 52 to 54, characterized in that it is equipped with pumps (P1.P2), which, when the mold is opened, supply the starting material through the inlet (101a, 101b) or the container wall (100a, 100b) and the mold part (lia, 11b ) and when closing again leads away the output material through the outlet (102a, 102b). 56. Device according to one of claims 52 to 54, characterized in that it is equipped with means for operating the displaceable mold part (lla.llb). 57. Device according to one of the claims 49 to 56, characterized in that it is equipped with a means for achieving a flow, which when opening the mold loosens the contact lens and when closing the mold flushes out the contact lens. 58. Device according to one or more of claims 49 to 56, characterized in that a gripping device (4) is arranged which removes the cross-linked contact lens (CL) from the mold. 59. Device according to one of the claims 52 to 56 and 58, characterized in that the container (10b) on one of the container walls (100b) which is not one of the shaping surfaces (100b), has a bulge or niche (104b), which extends in the essential in the direction of the movement of the displaceable mold part (11b), where a gripping device (4b) is arranged in this protrusion or niche (104b), and that the displaceable mold part (11b) on one of the outer walls (113b), which does not lies opposite the forming container wall (100b), has an indentation (114b), in which the gripping device (4b) places the removed contact lens (CL). 60. Device according to claim 59, characterized in that the displaceable form part has a channel (115b) which leads to the indentation which can be connected to a negative or positive pressure source (P3), whose channel (115b) then, when the gripping device (4b) places the removed contact lens ( CL) in the indentation (114b) in the mold part (11b), is connected to the negative pressure source and then to release the lens, the positive pressure device is connected. 61. Device according to one of claims 53 to 60, characterized in that the mold is equipped with spacers (19), which keep the mold halves when the mold is closed at a small distance from each other, so that an annular gap (16) is formed which surrounds the mold cavity (15) and stands in connection with this. 62. Device according to claim 61, characterized in that the mold is equipped with elastic means or displacement means, which enable a following approximation of both mold parts by material shrinkage.