HK1136801B - Method for blocking a lens blank and adhesive composition - Google Patents

Description

Method for bonding lens blanks and adhesive composition

Technical Field

The present invention relates generally to the bonding of an optical glass ophthalmic lens blank (blank) to a lens holder block (block) ("lens block") to support the lens blank during lens production, as used on a large scale in a lens dispensing shop, i.e. a manufacturing shop for manufacturing individual ophthalmic lenses from customized materials (polycarbonate, mineral glass, CR39, high index (HI index), etc.) according to prescription.

More particularly, the invention relates to a method of bonding (blocking) lens blanks, the use of an adhesive composition in lens bonding and the adhesive composition itself, wherein a radiation-curable material is used as the adhesive in each case. In the context of the present application "radiation curable material" refers to liquid chemical resin compounds that are chemically sensitive to certain wavelengths of electromagnetic radiation that cause the resin to cure, i.e. the material converges to synthesize a solid when illuminated by these "light activated" waves. In other words, the material will change phase from a liquid to a solid when exposed to the above mentioned electromagnetic radiation, in particular ultraviolet ("UV") and high visible spectrum ("VIS").

Background

An ophthalmic lens blank generally comprises a first face having a predetermined curvature and a second face opposite the first face on which a desired surface profile is produced by a machining process. The overall process, commonly referred to as "lens surfacing", generally aims to produce a finished ophthalmic optical glass lens in which the curvatures of the first and second faces cooperate to produce the desired optical properties.

In a prescription workshop (prescription works), the following main processing steps are usually carried out: first, an appropriate right and/or left optical glass lens blank is removed from the semi-finished product library. The term "semi-finished product" is used to indicate: the blank of an ophthalmic optical glass lens, which is usually round or oval in plan view and not yet edged, has been machined or otherwise contoured on one of its two optically active faces. The blank of the optical glass ophthalmic lens is then ready for the bonding operation, i.e. the application of a suitable protective film or a suitable protective lacquer, in order to protect the optically active face, i.e. the first face or bonding face, which has been machined or profiled.

Then, so-called "bonding" of the optical glass ophthalmic lens blank is performed. During this time, the optical glass ophthalmic lens blank is attached to a suitable lens block, for example according to german standard DIN 58766. To this end, the lens block is first placed in a predetermined position relative to the protected first face of the optical glass ophthalmic lens blank, and the space between the lens block and the optical glass ophthalmic lens blank is then filled with a molten material (usually a metal alloy or wax) in this position. Once the molten material solidifies, the lens block forms a holder or support for machining the second face of the optical glass ophthalmic lens blank. The lens block is gripped by chucks or other suitable coupling means during lens production to provide a particularly secure mounting for a profiling machine while avoiding damage to the lens.

The lens surfacing is then carried out using a profilometer, typically having some type of cutter, which moves across the second face of the optical glass ophthalmic lens blank to conform the macroscopic geometry (macrogeometry) of the second face to the prescription requirements. The lens blank may be stationary or rotating during the cutting operation, depending on the particular profiling machine used. Typical machining processes for surfacing optical glass ophthalmic lenses include single point diamond turning, diamond tool fly cutting, milling, grinding processes, the use of which depends on the lens material.

The ophthalmic spectacle lenses are then usually subjected to a fine processing, wherein the pre-processed second face of the corresponding ophthalmic spectacle lens blank is formed into the desired micro-geometry (micro-geometry). Depending on the material of the spectacle optical glass lens, the fine machining process is divided into a fine grinding operation and a subsequent polishing operation or, if a polishable second face has already been produced in a pre-machining stage, only a polishing operation, among others.

The ophthalmic lens is separated from the wafer block ("deblocking") only after the polishing step, before the cleaning step and possibly further fine processing steps are carried out, such as applying an anti-reflection coating or a hardening coating to the ophthalmic lens. Thus, the lens block remains on the optical glass lens during (at least) a plurality of processing operations and must be reliably retained thereon during these operations.

Other bonding materials for lens bonding have recently been proposed to overcome some of the disadvantages created by the use of metal alloys or waxes as classical binders-too long time required for curing before the bonded lens is safely released to subsequent processing operations, lens distortion problems caused by heat associated with the molten material, and possible contamination of the lens, to name but a few. These other bonding materials include radiation curable materials.

In this respect, patent document US2005/0139309a describes a UV light-cured adhesive material for reducing shrinkage caused by polymerization. Although this development is a significant step forward in allowing UV curable materials to be used for lens bonding, it still exhibits shrinkage on the order of 3%. This amount of shrinkage is generally not severe when the UV-curable adhesive is used in thinner (typically less than 3 mm) and uniform thickness; but it has serious limitations when a thicker profile of adhesive is required.

The problem of shrinkage becomes even more pronounced when bonding lenses having a very non-uniform profile, thus requiring the use of a non-uniform profile adhesive. An example of this is shown in fig. 10, which shows a flat-top bi-optic lens blank 10 having a discrete step 12 between the bi-optic zone 14 and base curve 16, bonded to a lens block 18 by a UV curable adhesive 20. As is evident from fig. 10, shrinkage becomes a problem when the gap 22 between the bifocal segment 14 and the lens block 18 is significantly different from the gap 24 directly above the bifocal segment 14. In this case, the difference in shrinkage caused by the difference in thickness of the UV-cured adhesive 20 can cause severe/undesirable distortion directly over the dual-light section 14.

In an attempt to overcome the shrinkage problems associated with the UV light curable adhesive materials described above, it has been proposed to use a large number (7 or 8) of different block curves to approximately match the imaginary lens base curve, thereby keeping the adhesive thickness sufficiently uniform to minimize the effects of residual shrinkage. Fig. 11 illustrates the prior art using a plurality of lens blocks 18, each lens block 18 having a lens mounting face 26 with a predetermined block curve, wherein the block curves vary from lens block 18 to lens block 18. In the illustrated example, the lens block 18 includes a substantially spherical lens mounting face 26 having block curves of a)0.5 diopters, b)2 diopters, c)6 diopters and d)10 diopters, respectively, substantially matching the corresponding curvature of the lens curve, i.e., the bonding face 28 of the bonded lens blank 10. It should be noted that in fig. 11, for simplicity of illustration, only 4 different lens blocks 18 are shown; the system actually uses 7 or 8 different lens blocks, as described above. As is evident from fig. 11, the UV-curable adhesive 20 located in each case between the lens blank 10 and the lens block 18 has a thin and substantially uniform thickness, so that there is no severe distortion caused by shrinkage of the UV-curable adhesive 20.

However, the method using a large number of different billet baselines does not help the situation shown in fig. 10. Another problem associated with multiple piece baselines is the management of these numerous baselines. The correct lens block needs to be selected initially to match the lens curve and then after deblocking (assuming the lens blocks are reused) they need to be sorted appropriately according to curve and stored in respective holders/dispensers. Thus, the approach described using multiple block curves increases the complexity of the production process, increases the likelihood of error, and thus increases the manufacturing cost of the lens.

Disclosure of Invention

It is an object of the present invention to provide a method of bonding lens blanks in which the number of block curves required to cover the full range of standard lenses is minimised and which addresses the problems associated with shrinkage caused by the use of radiation curable materials as binders. The object of the present invention also consists in providing an adhesive composition for bonding lenses which is capable of being cured by radiation and which achieves the above-mentioned objects.

According to one aspect of the present invention, there is provided a method of bonding a lens blank having a bonding surface with a predetermined curvature, the method comprising the steps of:

(a) providing a plurality of lens blocks, each lens block having a lens mounting face with a predetermined block curve, wherein the lens blocks all have the same block curve;

(b) removing a lens block from said plurality of lens blocks;

(c) mixing a binder composition comprising a liquid binder in an unpolymerized state and curable by ultraviolet or visible light and a filler as a non-polymeric solid;

(d) applying the adhesive composition to at least one of the adhesive surface of the lens blank and the lens mounting surface of the lens block;

(e) pushing said lens blank toward said lens block with the bonding surface of said lens blank facing the lens mounting surface of said lens block; and

(f) generating ultraviolet or visible light and transmitting such light to the adhesive composition, the light having a wavelength and intensity and being applied for a time sufficient to cure the adhesive composition;

(g) wherein the filler is comprised of solid particles having a particle size of 1 mm or less, and the mixing ratio of the binder and the filler is selected such that, upon curing, the binder composition changes size and polymerizes exothermically, thereby enabling the binder composition to be cured without undue stress on the lens blank and without debonding the lens blank from the binder composition.

According to another aspect of the present invention, there is provided a method of bonding a lens blank having a bonding surface with a predetermined curvature, the method comprising the steps of:

(a) providing a plurality of lens blocks, each lens block having a lens mounting face with a predetermined block curve, wherein said lens blocks have only a few different block curves;

(b) selecting a lens block having a particular block curve based on said curvature of the bonding surface of said lens blank such that said block curve matches the curvature of said bonding surface as well as possible;

(c) mixing a binder composition comprising a uv or visible light curable liquid binder in an unpolymerized state and a filler which is a non-polymeric solid;

(d) applying said adhesive composition to at least one of an adhesive surface of said lens blank and a lens mounting surface of said lens block;

(e) pushing said lens blank toward said lens block with the bonding surface of said lens blank facing the lens mounting surface of said lens block; and

(f) generating ultraviolet or visible light and transmitting such light to the adhesive composition, the light having a wavelength and intensity and being applied for a time sufficient to cure the adhesive composition;

(g) wherein the filler is comprised of solid particles having a particle size of 1 mm or less, and the mixing ratio of the binder and the filler is selected such that, upon curing, the binder composition changes size and polymerizes exothermically, thereby enabling the binder composition to be cured without undue stress on the lens blank and without debonding the lens blank from the binder composition.

First, both methods have in common that the number of briquette curves is reduced as compared with the above-described prior art. The first method described above, which uses only one block curve, is ideal, and even if several different block curves are used according to the second method, such as 2 or 3 block curves, it is considered to be significantly better than the method using 7 or 8 block curves in terms of reducing the complexity of the production process, the probability of error, and the cost of lens manufacture.

Furthermore, in comparison with the above-described prior art again, the method according to the invention has in common the use of an adhesive composition comprising a UV-or visible-curable liquid adhesive in the unpolymerized state and a filler as a non-polymeric solid, in particular wherein the mixing ratio of the adhesive and the filler is selected such that the exothermic heat of polymerization and the dimensional change of the adhesive composition upon curing are sufficiently low that the adhesive composition can be cured without causing undue stress on the lens blank and without debonding the lens blank from the adhesive composition.

The use of fillers has several advantages in this respect. Since a significant portion of the shrinkage results from the structural change of the material during polymerization, the filler, which is a non-polymeric solid, can be physically introduced into the liquid (non-polymeric) compound, thereby reducing the shrinkage by at least the volume percent of the filler material introduced.

Furthermore, while typical UV or light radiation curable materials are considered to be relatively "low T" cured, they still have some level of exotherm during the curing process. In some cases, particularly when the volume of the UV/VIS material is high, the exothermic reaction can raise the material temperature to 20 to 40 ℃ above the initial liquidus temperature. These higher process temperatures in turn can create thermal stresses in the lens blank due to the different CTE (coefficient of thermal expansion) between the lens blank, the lens block and the adhesive. Thus, in addition to reducing polymerization-induced shrinkage, the volume of the UV/VIS curable material is reduced by the incorporation of fillers, correspondingly reducing the exothermic composition of the curing reaction, resulting in lower final process temperatures and lower thermal expansion.

The combined effect of simultaneously reducing both sources of shrinkage (structural changes during polymerization and polymerization exotherm) is very beneficial for the ability to successfully bond lenses using non-constant UV/VIS material thickness, especially where only one or a few block curves are used to bond a full range of standard lenses.

Another important benefit of using fillers is that costs are reduced by reducing the amount of UV/VIS curable material. UV/VIS curable materials use relatively expensive chemicals, and in particular photoinitiators for initiating electromagnetic radiation (UV/VIS) curing tend to be very expensive, with the result that the cost of the adhesive compound is relatively high. In addition, once cured, the compound cannot return to a liquid (unpolymerized) state. This means that it can no longer be recycled by remelting in a manner similar to wood metal or blocking wax (or other thermoplastics such as e-caprolactone).

In the first method described above, i.e. in the case where all lens blocks have the same block curve, the lens blocks preferably all have a substantially spherical lens mounting face comprising the same block curve selected according to the distribution of the curvature of the bonding face of the lens blank to be bonded to a particular population. This advantageously allows for different distributions to occur for different populations, thus requiring different compact curves to minimize material usage. For example, certain asian populations are known to be biased toward a lower (flatter) baseline as compared to western european or north american populations. This will result in a slightly lower slab curve being selected to better optimize (minimize) material usage, and/or final optical performance.

In the second method described above, i.e. in the case where the lens blocks have only a few different block curves, the lens blocks preferably each have a substantially spherical lens mounting face, wherein two lens blocks of different block curves are provided, namely a lens block having a concave block curve in the range of 0 to 4 diopters and a lens block having a concave block curve in the range of 4 to 8 diopters. However, the above-mentioned block curve may also be convex, depending on the geometry of the bonding face of the lens blank to be bonded.

In a preferred embodiment of the second method, the step of selecting a lens blank is performed with the effect that in the bonded state of the lens blank, the gap between the lens mounting face of the lens blank and the bonding face of the lens blank is smallest in the central area of the lens blank. Thus, the absolute shrinkage of the adhesive composition is (even more) minimized in the center, so that the stresses, if any, induced in the bonded lens blank are very small, especially near the MRP (major reference point).

In principle, the lens block used may be opaque or even opaque to all kinds of light, wherein UV or visible light is transmitted through the lens blank to the adhesive composition, causing curing of the adhesive composition. However, it is preferred to use a lens block that transmits UV or visible light, wherein in all methods, the steps of generating UV or visible light and transmitting such light to the adhesive composition preferably include transmitting light through the lens block to the adhesive composition.

In accordance with the present invention, there is also provided an adhesive composition for use in lens bonding. The adhesive composition includes: (a) a binder curable by UV or visible light which is liquid in a polymerized state, and (b) a filler which is a non-polymerized solid, wherein a mixing ratio of the binder and the filler is in a range of 70% by weight of the binder to 30% by weight of the filler and 30% by weight of the binder to 70% by weight of the filler. Tests have shown that mixing ratios in this range are effective to result in a sufficiently low exotherm of polymerization and dimensional change of the adhesive composition upon curing that the adhesive composition can be cured without undue stress on the lens blank and without debonding the lens blank from the adhesive composition. The adhesive composition comprising the filler also results in a reduction of costs when used for lens bonding compared to the use of conventional radiation-cured adhesive materials, as already explained above. Also, this adhesive composition ultimately represents a "progression" that reduces the number of block curves required to cover the full range of standard lenses in lens manufacture (see explanation above).

The filler is preferably comprised of solid particles that provide sufficient rigidity to the cured adhesive composition to prevent all or part of the bonded lens from bending and shifting.

Preferably the geometry of the filler particles is generally spherical, but cylindrical or irregular geometries are equally suitable. The spherical geometry has the advantage of improving (reducing) the viscosity of the liquid binder composition.

The particle size of the filler generally needs to be smaller than the minimum gap between the lens blank to be bonded and the intended lens block. A minimum gap of 2 mm is currently preferred, which means that the largest particles should be less than 2 mm, preferably equal to or less than 1 mm.

For ease of deblocking, it is preferred to include a small amount of metal fibers, granules or powder in the filler, preferably aluminum fibers in an amount of 1 to 2 weight percent of the total composition. This number of fibers provides sufficient absorption of microwave energy, significantly accelerating the heating of the cured bonding material by the microwave energy, thereby causing the bonding material to "soften" before it is deblocked.

Preferably, the filler material is transparent and/or translucent to the light activation wavelength of UV and/or visible light in order to accelerate the curing of the adhesive composition.

The filler material may also have low moisture absorption characteristics, which is important if or when a fully bonded lens is placed in a vacuum chamber commonly used in film coating processes.

Continuing with the concept of the present invention, the filler material may have a glass transition temperature (Tg) between 25 ℃ and 80 ℃. By using such filler materials, certain mechanical properties-e.g. sufficient stiffness and hardness-can be obtained at the temperature of the surfacing process (typically close to room temperature), which properties can then be altered by raising the temperature above Tg to facilitate deblocking. In this regard, an upper limit of 80 ℃ may ensure that, to facilitate deblocking, it is not necessary to raise the temperature of the cured adhesive material above a temperature at which permanent damage to the finished lens may occur.

Finally, it is preferred that the filler material is selected from the group comprising a UV or visible light curable binder in a regrind (regrind) state and a plastic material comprising: e-caprolactone, terpolymers derived from ethyl-methyl-acrylate-acrylic acid, polycarbonate, Polyethylene (PET), high methacrylic acid resins, ethyl methacrylate resins, methacrylate copolymer resins, butyl methacrylate resins and methyl methacrylate/n-butyl methacrylate copolymer resins. In addition to this, the corresponding advantages of the above-described filler material will be apparent from the following description of a preferred embodiment of the invention.

Drawings

The invention is explained in more detail below on the basis of preferred embodiments and with reference to the drawings. In the drawings:

fig. 1 is a perspective view of an optical glass ophthalmic lens bonding apparatus that can be used in a bonding method according to the present invention.

Fig. 2 is a sectional view taken along line II-II in fig. 1.

Fig. 3 is a partial perspective view illustrating a lens blank being supported on a lens block by a lens conveyor.

Fig. 4 is a partial perspective view illustrating the placement of a lens blank onto a lens block and illustrating the adhesive composition dispenser in a retracted position.

Fig. 5 is a partial perspective view illustrating the lens conveyor prior to picking up the lens blank and illustrating the adhesive composition dispenser in an extended position.

Fig. 6 is a sectional view taken along line VI-VI in fig. 4.

Fig. 7 shows in cross-section 4 lens blanks, each having a different predetermined curvature of the bonding face, which are bonded according to a first method of the invention, wherein the same lens block and adhesive composition comprising a liquid UV/VIS-curable adhesive in the unpolymerized state and a filler as a non-polymeric solid is used.

Fig. 8 shows in cross-section 4 lens blanks, each having a different predetermined curvature of the bonding face, which are bonded according to the second method of the invention, wherein only two different bonding curves are used for the lens blocks, and wherein the adhesive composition used comprises a liquid UV/VIS-curable adhesive in the unpolymerized state and a filler as a non-polymeric solid.

Fig. 9 is a graph illustrating a typical distribution of the front arc of an optical glass ophthalmic lens for a given population.

Fig. 10 shows, in plan view and in cross-section along line X-X, respectively, an ophthalmic spectacle lens blank comprising a bifocal segment (left side) bonded to a lens block (right side) in a conventional manner.

Fig. 11 shows in cross-section 4 lens blanks, each having a different predetermined curvature of the binding face, which are bound according to conventional methods using a plurality of different lens blocks each having a different binding curve to closely match the curvature of the binding face of the assigned lens blank.

Detailed Description

An apparatus for bonding an ophthalmic spectacle lens is generally indicated by reference numeral 30 in the drawings. The adhesive device 30 comprises a cabinet having a top 32 and a cover structure 34 for partially enclosing the top 32. The lens transmitter 36 is movably mounted on a first linear drive 38 that is fixed to the top portion 32. The first linear drive 38 has a first servo motor or stepper motor unit for moving the lens conveyor 36 or monitoring its position accordingly.

The bonding apparatus 30 has, aligned with the first linear drive 38 and housed in the cabinet top 32, an imaging station 40, a detection station 42 and a lens bonding station 44. The bonding apparatus 30 houses (see fig. 2) a camera 46 focused on the imaging stage 40, an adhesive composition reservoir 48, and a pump unit 50 for pumping the adhesive composition to the lens bonding stage 44. The bonding device 30 also includes a controller in the form of a central processing unit 52 for controlling its operation.

The imaging station 40 is used for lens orientation by means of a screen 56 for displaying lens orientation information generated by the central processing unit 52 based on image information received from the camera 46 to ensure that the lens blank 54 is properly aligned and oriented from the beginning of the bonding process. For further details of the structure and function of the imaging table 40, please refer to patent document US2005/0139309

Once the orientation and position parameters of the lens blank 54 have been determined, the lens blank 54 is transferred from the lens imaging station 40 to the inspection station 42 with the lens conveyor 36 to inspect the bonding surface 58 of the lens blank 54. Similarly, for further details of the structure and function of the lens conveyor 36 and the detection station 42, reference may be made to the patent document US 2005/0139309.

Once the bonding surface 58 of the lens blank 54 has been probed, the lens blank 54 is transferred from the probing station 42 to the lens bonding station 44 using the lens conveyor 36. The lens bonding station 44 includes a UV and visible light transmissive lens block holder 60 for receiving and holding a lens block 62 with a lens mounting face 64 of the lens block 62 facing upwardly. In this case, the lens block 62 should be a transparent material capable of transmitting light in at least the ultraviolet spectrum, and preferably also in the visible spectrum. For further structural and functional features of the lens block 62, in particular the clamping portion of the lens block 62 which enables the lens block 62 to be held in the lens bonding station 44 and thus fixed on a spindle of a surfacing machine (not shown), reference is made to patent document US 2005/0250430.

A UV light source 66 (see fig. 6) is associated with the lens block holder 60 and is mounted to direct light through an aperture 68 in the lens block holder 60 and then through the transmissive lens block 62. The light source driver may form part of the central processing unit 52 and be connected to the ultraviolet light source 66 to control activation and deactivation of the UV light source 66. The UV light source 66 may comprise a flash lamp that emits a high intensity, short duration pulse of light in the ultraviolet and visible spectrum.

A dispenser for dispensing a UV/vis curable adhesive composition is generally indicated by the numeral 70. The dispenser 70 has a dispenser nozzle 72 located at one end of a dispenser arm 74. An arm actuator, which may be a motor or linear actuator or other actuator as shown at 76, is provided for moving the dispenser arm 74 from an extended position (fig. 5) adjacent the lens mounting surface 64 to a retracted position (fig. 4) exposing the lens mounting surface 64 and the lens conveyor 36 so as not to interfere with mounting the lens blank 54 on the lens mounting surface 64 of the lens block 62 (and vice versa)

The distributor arm 74 controls only the position of the distributor nozzle 72. Thus, the distributor arm 74 may be telescoping rather than rotating as shown, and may be controlled by a linear actuator, such as a hydraulically actuated piston in a cylinder.

The dispenser nozzle 72 is in fluid communication with the adhesive composition reservoir 48 through the pump unit 50, and the pump unit 50 delivers the adhesive composition to the dispenser nozzle 72. Alternatively, the adhesive composition reservoir 48 may be pressurized, thereby avoiding the need for a pump.

It should be noted that in the illustrated embodiment, the adhesive composition reservoir 48 is a-preferably replaceable-pre-packaged unit already containing a ready-mixed adhesive composition consisting of unpolymerized (i.e., liquid) UV/VIS curable adhesive and a suitable filler as a non-polymeric solid. Alternatively, however, the bonding apparatus may be provided with a mixing unit for preparing the adhesive composition from the above-mentioned components, which may be stored separately in suitable containers replaceably mounted on the bonding apparatus 30.

The dispenser nozzle 72 is equipped with a valve or other shut-off mechanism that is connected to the central processing unit 52 to control the dispensing of the adhesive composition through the nozzle 72 when the dispenser nozzle 72 is in the deployed position. Different control structures may be used. A simple control is to monitor the time that the nozzle 72 remains open. Other controllers such as metering pumps may also be used. In general, regardless of the control chosen, a measured amount of adhesive composition should be dispensed that will then fill the gap between the adhesive face 58 of the lens blank 54 and the lens mounting face 64 of the lens block 62.

In use, a measured amount of the UV/VIS-curable adhesive composition is dispensed onto the lens mounting face 64 of the lens block 62 through the dispenser nozzle 72 of the dispenser 70. The lens blank 54 is moved by the lens conveyor 36 over the lens block 62 such that the adhesive surface 58 of the lens blank 54 faces the lens mounting surface 64. The lens conveyor 36 then moves the lens blank 54 toward the lens mounting surface 64 and into the liquid adhesive composition 78 (see fig. 6) until the adhesive surface 58 of the lens blank 54 is a predetermined distance from the lens mounting surface 64 of the lens block 62.

Since the geometry and spatial relationship between the adhesive face 58 and the lens mounting face 64 is known, the amount of adhesive composition 78 required can be automatically calculated and dispensed without operator intervention.

At this stage, UV light is generated by the UV light source 66 and transmitted through the lens block 62 at a wavelength, intensity, and duration sufficient to cure the adhesive composition 78, thereby bonding the lens blank 54 to the lens block 62.

As a final step, the lens block 62 and the lens blank 54 adhered thereto may be removed from the lens bonding station 44 and released from the lens conveyor 36.

Fig. 7 illustrates the bonding results obtained by the bonding process comprising the following steps:

(a) providing a plurality of lens blocks 62, each lens block having a lens mounting face 64 with a predetermined block curve, wherein said lens blocks 62 have the same block curve, -said lens blocks 62 all having a substantially spherical lens mounting face 64 with a block curve of 5 diopters in the illustrated embodiment;

(b) removing a lens block 62 from the plurality of lens blocks 62- -in the dispensing shop, the lens blocks 62 are typically stored in a storage/dispensing container from which each lens block 62 can be removed; in this case, there is no need to select, as the lens blocks 62 are all identical;

(c) mixing an adhesive composition 78 comprising a UV or VIS curable liquid adhesive in an unpolymerized state and a filler which is a non-polymeric solid, wherein the mixing ratio of the adhesive and filler is selected such that the exothermic heat of polymerization and dimensional change of the adhesive composition 78 upon curing is sufficiently low that the adhesive composition 78 can be cured without creating undue stress on the lens blank 54 and without de-bonding the lens blank 54 from the adhesive composition 78-as previously described, such mixing may be performed shortly before dispensing the adhesive composition 78 for bonding purposes, even in the bonding apparatus 30, or alternatively at an earlier time, possibly already outside the lens dispensing shop;

(d) preferably applying the adhesive composition 78 to the lens mounting surface 64 of the lens block 62;

(e) pushing the lens blank 54 toward the lens block 62-and vice versa or from both sides; it is apparent that relative movement between the lens blank 54 and the lens block 62 is important-wherein the adhesive surface 58 of the lens blank 54 faces the lens mounting surface 64 of the lens block 62; and

(f) generating UV or visible light and transmitting such light to the adhesive composition 78, the wavelength and intensity of the light and the duration of application being sufficient to cure the adhesive composition;

in contrast to the prior art depicted in fig. 11, fig. 7 shows a lens blank 54 having the same curvature of the bonding surface as fig. 11: (a)0.5 diopters, (b)2 diopters, (c)6 diopters, and (d)10 diopters, but in the present case they are now bonded on only one blank curve of 5 diopters. This helps to illustrate the problems associated with the reduced number of briquette curves and why the proposed solution is considered advantageous.

It is first seen from fig. 7 that although the amount of bonding material used is significantly greater than that used in fig. 11, the amount of bonding material used does not initially appear to be that much, since the individual block curves can be selected to best fit the majority of the ophthalmic lenses in the statistical distribution of the lens base curve.

In this regard, fig. 9 illustrates a typical baseline (front arc) distribution for a given population. Due to this distribution and in view of the correct choice of the optimal slab curve, the use of binder material is only increased by 10 to 15% in the solution using 1 slab curve compared to the use of 7 slab curves. If two compact curves are used, the binder material used is calculated to be only 6% more than if 7 compact curves were used. This slight increase in bond material consumption is easily compensated by the cost reduction associated with managing only 1 or 2 billet curves, as compared to the commonly seen case of using a large number of curves.

One problem caused when using a small number of compact curves is evident from fig. 7a), b) and d). It is a problem of uneven shrinkage associated with non-constant adhesive material thickness. Shrinkage is primarily due to polymerization of the UV/VIS curing adhesive, but can also result from thermal effects when these materials are cured. Depending on the type of chemicals used and the temperatures reached during curing, material shrinkage in the range of 2-10% or even more can be seen. The elevated temperature may come from the energy of the curing radiation, but may also come from the exotherm generated by the chemical reaction during the polymerization. Temperatures 10 to 40 ℃ higher than the initial room temperature can be easily reached; and when the bonded assembly cools to room temperature, it will contract depending on the different CTE (coefficient of thermal expansion) and mechanical properties of the final assembly. This shrinkage is internally limited and may cause undesirable mechanical (thermal) stresses in the final assembly.

While shrinkage is a three-dimensional effect, it is generally believed that axial shrinkage at a given point is directly proportional to the thickness of the UV/VIS cured adhesive at that point. It can clearly be seen that if there is sufficient shrinkage, this results in a change in the geometry of the adhesive material. This variation can have two undesirable consequences: one is the de-bonding of the lens blank from the adhesive material due to the adhesive material being "pulled" away from the lens blank. In fig. 7a) the debonding is more likely to occur at the center of the lens blank 54, while in fig. 7d) it can be seen that it is more likely to occur at the edge. In this case fig. 7a) is considered the worst case, where any debonding at the center may result in unacceptable distortion at the center due to the loss of support of the lens blank 54 during surfacing. In addition to this, even if no debonding occurs, because of the final thin-centered lens geometry, shrinkage at the center may tend to modify the final curvature at the center, thereby introducing refractive error. The situation seen in fig. 7d) is less critical with respect to refractive error, since the center of the lens remains thick (positive refractive power) and therefore has a high stiffness and is better able to withstand the stress from shrinkage.

To solve the above problems, the present invention adds a specifically selected filler as a non-polymeric solid to a UV/VIS curable material, among other measures, as will be explained in detail below.

Reference is now made to fig. 8, which illustrates the bonding results obtained by another bonding process comprising the following steps:

(a) providing a plurality of lens blocks 62, each lens block having a lens mounting face 64 with a predetermined block curve, wherein said lens blocks 62 have only a few different block curves; likewise, in this embodiment the lens blocks 62 all have substantially spherical lens mounting faces 64, and the lens blocks 62 have only two different block curves, namely lens blocks 62 (fig. 8a) and b)) containing a concave block curve of 0.5 diopter, and lens blocks 62 (fig. 8c) and d)) containing a concave block curve of 5 diopter; and

(b) based on the curvature of the adhesive surface 58 of the lens blank 54, a lens block 62 having a particular block curve is selected such that the block curve matches as well as possible the curvature of the adhesive surface 58-in the embodiment shown, this step is performed with the effect of: in the bonded state of the lens blank 54, the gap between the lens mounting face 64 of the lens block 62 and the bonding face 58 of the lens blank 54 is minimized in the central region of the lens block 62 to minimize or even inhibit the introduction of stress into the bonded lens blank 54; thus, the 0.5 base lens block 62 is assigned to the 0.5 and 2 base lens blanks 54 (fig. 8a) and b)), while the 5 base lens block 62 is assigned to the 6 and 10 base lens blanks 54 (fig. 8c) and d)).

The remaining steps of the alternative process are the same as steps c) - (f) discussed above with reference to fig. 7.

As for the material conditions to be satisfied by the adhesive composition 78 containing the UV or VIS curable adhesive which is liquid in an unpolymerized state and the filler as a non-polymeric solid, the following are noted.

It is often desirable to obtain certain mechanical and thermal properties in the cured material. These characteristics include that good lens support can be achieved while maintaining or even improving the ability to deblock the lens when desired. By "deblocking" in this application is meant the release of the adhesive bond between the lens and the adhesive composition by chemical, thermal, mechanical or other means, or any practical combination thereof.

Multifunctional fillers or specific combinations of fillers can be used to maintain or improve material properties while reducing shrinkage, reaction exotherm, and cost. Another potential function of the filler is to improve the bonding characteristics under certain controlled conditions to make deblocking easier.

The cured material generally needs to be sufficiently rigid to prevent bending or movement of the lens or lens area immediately adjacent the cutting tool during the machining process. However, the flexible adhesive material can more easily "peel" the material off of the lens during the deblocking process. Hard, brittle materials are difficult to peel and tend to break into smaller parts, while soft, flexible and cohesive materials are more easily peeled off in one piece.

If mechanical stripping is chosen rather than other deblocking methods, the stiffness value of the preferred material will be high enough to be surface processed while low enough to be deblocked, or the preferred material will undergo a "softening" process prior to deblocking. Such a "softening" process may be heating the adhesive material, for example, by immersion in warm water, or exposure to other forms and/or wavelengths of radiation, such as infrared or microwave. In such cases, to better support deblocking, the binder composition should be designed to have certain modifiable properties, such as a reduction in hardness, possibly including a reduction in tackiness as well.

Small amounts of metal fibers, particles or powders may be added to the filler to enhance the heating of the cured bonding material by the microwave energy. Small amounts (1-2% by weight of the total composition) of fine aluminum fibers mixed in the liquid binder are not sufficient to prevent curing because the UV radiation can still easily penetrate the binder, but still provide sufficient absorption of microwave energy to significantly accelerate heating of the material. The microwave exposure time of 15 seconds is the total time required to raise the temperature of the material from 30 ℃ to 25 ℃ and 20 seconds without the aluminum fibers.

Other possibilities for causing the cured binder material to be heated up rapidly to facilitate deblocking by "softening" the cured binder material are to add small amounts (1-5% by weight of the total filler) of generally high resistance metal particles and to use induction heating elements to induce current in the particles. The high resistance to the current correspondingly generates heat in the particles, which is then transferred to the surrounding material, thereby heating the binding compound. Other non-metallic conductive materials, such as carbon, and certain semiconductive particles may also be used in the induction heating technique.

One example of a multifunctional filler material that can be used to maintain or improve hardness and rigidity at the temperatures of conventional surfacing processes, but which enhances flexibility during deblocking is e-caprolactone. e-caprolactone (also known as polycaprolactone) is a thermoplastic monomer and is sufficiently transparent to transmit UV and/or visible light to allow the matrix comprising a liquid UV binder and e-caprolactone particles as a non-polymeric solid filler to cure. E-caprolactone at a fill ratio of up to 65 weight percent has been successfully cured and tested for adhesion to lens blanks and lens blocks and hardness. Such a material may be chosen to be relatively hard (e.g. shore D hardness of 50 to 70) at room temperature, and then after surface processing the cured adhesive material may be heated and allowed to reach a point where the e-caprolactone softens (e.g. shore D hardness of 10 to 40) but does not become liquid. These temperatures are low enough (e.g., between 35 ℃ and 60 ℃) so as not to damage the lens. The UV/visible light curable binder composition in the matrix remains solid, but the e-caprolactone particles are already significantly softer at these temperatures, resulting in a softer overall matrix, significantly improving the ease of removal of the bonding material from the lens. e-caprolactone has a relatively low glass transition temperature (Tg) and therefore all processing is done in this case at temperatures above Tg. Other materials similar to e-caprolactone can also be identified.

Another variation is to use a filling material with a Tg above the surfacing process temperature (typically near room temperature) but below the temperature at which permanent damage to the surfaced lens can occur (80 ℃). The MatWeb (www.matweb.com) database lists 235 polymeric materials with a Tg between 25 ℃ and 80 ℃. They can be used to achieve certain mechanical properties (e.g. high stiffness and hardness) at process temperatures, which are then changed by raising the temperature above Tg. One such material in question is the "Escor AT320EMA terpolymer" of exxonMobil (ExxonMobile). It is ethyl-methyl-acrylate-acrylic acid. It is solid at room temperature and can be mixed in solid particulate form with a liquid UV/VIS-curable binder material. Because it is acrylic-based in nature, it provides a good bonding surface for acrylic-based UV/VIS curable adhesive materials.

Another material that has been demonstrated to have many of the desired functions as a filler for this application is sold by Lucite International Special copolymer, Inc. (Lucite International specialty copolymer), under the trademark LUCITEThe material of (1). These materials may be, for example, high methacrylic resins, ethyl methacrylate resins, methacrylate copolymer resins, or butyl methacrylate resins. Their properties include a range of molecular weights from low to high, a Charkon hardness (Tukon hardness) between 1 and 20(Knoop No., Knoop hardness number), and a Tg between 15 ℃ and 110 ℃. One of such materials that has proven effective for the present application is one having a Tg of 36 deg.C(methyl methacrylate/n-butyl ester copolymer). It is softer, knoop hardness value 4, but if used at a fairly high fill fraction (60% to 70%), it ensures sufficient hardness for surfacing, while facilitating deblocking due to the relatively low hardness and specific thermal properties. One of these productsAn additional benefit is that they can be purchased directly as small diameter beads. Typical beads are 10 to 200 microns in diameter, which allows them to be used directly without a pretreatment process for grinding larger particles to an acceptable size.

The filler should also be non-abrasive and non-destructive to the cutting tool. If a cutting or grinding tool is used to cut through the cured adhesive material, it should not damage the tool. Some increased wear may be acceptable in some cases, and the amount of increased wear that a customer can tolerate is generally determined by the overall process economics.

Preferred filler particle geometries (generally spherical) and sizes (less than 2 mm, more preferably equal to or less than 1 mm) have been discussed above. Another important characteristic of the filler is that it must not impede or unduly slow the curing process by blocking or in some way inhibiting UV and/or visible electromagnetic energy from reaching the photoinitiator embedded in the UV/VIS-curable binder material. Thus, the property of being transparent and/or translucent to the light-activating wavelength is considered to be very important for selecting compatible fillers.

Another desirable feature or function of the filler material is to reduce outgassing by incorporating a material with very low outgassing, thereby greatly reducing the "pump down time" if and when a fully bonded lens is introduced into the vacuum chamber typically used in thin film coating processes. The three main sources of outgassing are VOC (volatile organic compound) emissions of solvents, uncured remnants of liquid resins, and moisture trapped in the bonded material. All three materials can be vaporized in vacuum and cause a situation: it is difficult or slower than expected to reach the vacuum level required by the coating process.

In the case of organic solvents, the preferred method is to avoid the introduction of any solvent in the liquid compound. This means that there is a general tendency to use 100% solids type resins to ensure that no solvent is absorbed and left in the cured adhesive material. Incomplete curing can be one cause of liquid resin remaining in the "cured" material. This problem is usually solved by: further provides UV/VIS transparent/translucent filling and provides better curing techniques such as better focused high power light source to scan the lens block or ultra high power xenon flash lamp technology. The third case is the moisture content. In this case, it becomes important to select a material with low hygroscopicity for the filler. Examples of such materials are polycarbonate and PET (polyester) based materials, to name only two.

Finally, a strongly preferred method is to directly reuse the UV/VIS-cured binder material in the regrind state as filler. It is proposed that after the lens is deblocked, rather than discarding the cured UV bonding material, it is simply put into a small grinder designed to regrind the material to the appropriate particle size. The regrind material is then mixed with fresh uncured UV/VIS-cured binder material in the appropriate mixing ratio using known measuring techniques and apparatus and methods. A metering screw using a mixing nozzle is one solution. Preferred mixing ratios are filler particles: the liquid UV/VIS curable adhesive material is between 40%/60% and 70%/30%. This arrangement allows for the two components to be mixed in relatively precise proportions, either continuously or on demand, and can also be used to deliver the correct amount of mixed adhesive composition to the lens block. Another simpler solution is to simply weigh the correct amount of each ingredient in batches and mix with a powered hand mixer, such as a hand drill assisted mixer.

One of the main advantages of using regrind is that the generally desired shrinkage and reduced exotherm obtained with other fillers, while at the same time providing a greater cost reduction than with these other fillers. The cured adhesive material is typically eventually discarded, so it is economically and environmentally beneficial to recover it from 50% to 70%. Cost-effectiveness is achieved because its cost is close to zero. The only cost is the cost of processing, grinding and mixing. The environmental benefit results from a significant reduction in the amount of disposal. Another advantage is that the new uncured material bonds very well to the cured material because of the chemical similarity between the two. It is also an advantage that any change in the mixing ratio does not affect the final mechanical and thermal properties, such as temperature dependent hardness/flexibility, softening point, etc. This will simplify mixing and quality control of the mixed binder composition, since the tolerance for mixing errors is much larger. Other advantages include a "all-in-one" compound design that has consistent and predictable UV transmission, is not affected by heterogeneous or incompletely compatible fillers, no filler quality variation, and the like.

It is noted here that the last two paragraphs above assume that a "pure" uncured and unfilled UV/VIS-cured binder material is used initially, and then after the material has been cured it is ground and used as a filler for a new liquid (uncured) material. In this regard, when a lens is deblocked, the UV/VIS-cured adhesive material is recycled by being ground and mixed into new unpolymerized UV/VIS-cured material as a non-polymeric solid filler.

Example 1

Tests were carried out on a mixture consisting of 60% by weight of Suway (Solvay) "polycaprolactone C6500" with a particle size of 3 mm, and 40% by weight of a "General # 3" UV-curable adhesive compound (PL110284-02, date of manufacture: 1 month 23 day, 06-01) containing acrylic resin, monomers and initiator, sold by MotionFab corporation (609891NB Ltd.) of Moncton, N.Bronsted, Canada. (General #3 binding Compound is previously referred to asSold by Micro Optics design corporation (Micro Optics design corporation) located in Moncton, N.B.Broussonev, Canada). In the following examples, the individual components of the adhesive composition, i.e. the liquid UV-curable adhesive and the solid filler particles, were thoroughly mixed by hand.

After a 10 second exposure time using a "Fusion" UV lamp fitted with a "D" bulb (available from Fusion UV systems, Clopper road 910 to Gaithersburg, Md., 20878-.

The main drawbacks of this material seem to be the too large particle size and the relatively high cost of C6500. The hardness of the mixed and cured samples at room temperature was measured to be between 39 and 55 shore D hardness, matching very closely the hardness of cured General #3(38 shore D hardness) and C6500 measured as 57 shore D hardness. One multiple reading gives an average hardness value of 45.6 shore D. The large variation in hardness of each component and the closely related reasons are attributed to the large particle size, and the probability that the measurement point is measured directly on or between the C6500 particles. Furthermore, the C6500 particles were covered by General #3 of non-uniform thickness, which further increased the unpredictability of the measurements.

It is clearly seen that at a deblocking temperature of 50 c, the cured binder composition measured was softened and the average hardness was reduced to 35 shore D hardness, facilitating deblocking.

The large particle size of C6500 is considered a problem, mainly for two reasons: first, this increases the minimum gap achievable between the lens blank and the lens block, thus increasing the amount of material required for bonding; the second problem is believed to be irregular shrinkage, causing small ripples or variations in the refractive power in very thin lenses. This may be explained by the fact that the shrinkage between the particles is greater than the shrinkage directly on the particles, another possible contributor being that the change in hardness causes a change in the stiffness of the support provided by the cured binder material.

Example 2

Will be supplied by Lucite International Special copolymers, Inc(methyl methacrylate/n-butyl copolymer) and General #3 in 60% by weight2550 to 40% by weight of UV compound. This increases the overall hardness of the cured adhesive composition to 40.4 shore D hardness and achieves a much lower hardness differential.

Used in2550 are particular samples of generally spherical or ellipsoidal particles having an irregular diameter of between 15 and 460 microns and an average particle size of 350 microns.

The low Tg (36 ℃) and relatively low 28 shore D hardness of the cured mixture at the deblocking temperature of 50 ℃ has a good combination of stiffness at process (surfacing) temperatures and high flexibility at deblocking temperatures. A particle size of 350 microns is also believed to have the advantage of providing uniform shrinkage and support and possibly a minimum gap of less than 0.5 mm. Finally, the process is carried out in a batch,2550 the UV transparent/translucent nature of the filler allows for easy curing of the adhesive composition under all the different light sources tested.

Example 3

A third compound was prepared using "Escor AT320EMA-AA Terpolymer" from Exxon Mobil. Again, 60% by weight Escor AT320 filler to 40% by weight General #3 was used.

The filler particles had an irregular geometry and had a particle size that passed through a 1.5 mm mesh screen.

This adhesive composition is considered a preferred material from the thermal property point of view and tested for its supportive nature at a surface processing temperature of 23 ℃ and a deblocking temperature between 55 ℃ and 60 ℃. The hardness was lower at 25 ℃ at 25 Shore D, decreasing with a slope of 0.4 Shore D per ℃ C. This hardness is lower than the 38 Shore D hardness of General #3, so it is believed that other products in this family of filler materials can provide better stiffness at surface processing temperatures between 20 and 25 ℃.

Example 4

A fourth compound was prepared and tested using 50 weight percent pure General #3 made from cured (i.e., polymerized) as a filler and 50 weight percent liquid (uncured) General # 3. In this case, the binder composition that was finally cured was General #3, since the filler was also General # 3.

The solidified material was ground to a particle size of between 0.5 and 1.5 mm with an average size of 1 mm. The shape of these particles is very irregular due to the milling process used. It may be difficult to obtain higher filler ratios, possibly due to irregular particle geometries.

This material has all the advantages of other fillers tested, including low shrinkage and low exothermic heat of polymerization. The filler in the polymerized state, i.e. as a non-polymerized solid, is UV transparent and forms a very coherent mass of solid material with unfilled material having the same mechanical and thermal properties. The main advantages of this method of recycling the adhesive material itself are low cost and reduced material waste.

Example 5

A fifth adhesive material was prepared by adding a small aluminum fiber ("aluminum fiber" Al Mg S Kurzfaser F35 ") available from alcoko GmbH & co.kg, hamburger, germany, in an amount of 2% by weight of the total filler to the uncured binder composition prepared according to example 4 above.

The shape and size of the fibers are very irregular. They have a length of between 0.5 mm and 3 mm and a diameter of between 0.1 and 0.5 mm.

The purpose of the fibers is only to shorten the heating time by using the energy of the microwave. This has proven to be very effective for this purpose.

The present invention provides a novel lens adhesive material (adhesive composition) which substantially overcomes the disadvantages of previous adhesive materials. The new materials combine conventional UV and/or visible light (VIS) curable polymeric materials with specially selected fillers as non-polymeric solids to achieve or improve certain desired material properties, including low shrinkage, low exothermic heat of polymerization, and improved deblocking capability, while reducing the high costs associated with such UV/VIS radiation curable materials. This novel material can be used in a method for bonding a lens blank to a lens block having a lens mounting face with a predetermined block curve, wherein the number of block curves required to cover a full range of standard lenses is minimized.

List of reference numerals:

10 lens blank

12 discontinuous step

14 double light section

16 base line

18 lens block

20 UV-curable adhesive

22 gap

24 gap

26 lens mounting surface

28 adhesive surface

30 bonding device

32 top part

34 cover structure

36 lens transmitter

38 first linear actuator

40 imaging table

42 probing station

44 lens bonding table

46 Camera

48 adhesive composition reservoir

50 pump unit

52 central processing unit

54 lens blank

56 mesh screen

58 adhesive surface

60 lens blank block support

62 lens block

64 lens mounting surface

66UV light source

68 aperture

70 Dispenser

72 distributor nozzle

74 distributor arm

76 Motor

78 Binder composition

Claims (13)

1. A method of bonding a lens blank (54) having a bonding surface (58) with a predetermined curvature, the method comprising the steps of:

(a) providing a plurality of lens blocks (62), each lens block having a lens mounting face (64) with a predetermined block curve, wherein the lens blocks (62) all have the same block curve;

(b) removing a lens block (62) from said plurality of lens blocks (62);

(c) mixing a binder composition (78), the binder composition (78) comprising a liquid binder in an unpolymerized state and curable by ultraviolet or visible light and a filler as a non-polymeric solid;

(d) applying the adhesive composition (78) to at least one of the adhesive surface (58) of the lens blank (54) and the lens mounting surface (64) of the lens block (62);

(e) urging said lens blank (54) toward said lens block (62) with an adhesive surface (58) of said lens blank (54) facing a lens mounting surface (64) of said lens block (62); and

(f) generating ultraviolet or visible light and transmitting said light to said adhesive composition (78), said light having a wavelength and intensity and being applied for a time sufficient to cure said adhesive composition (78);

(g) wherein the filler is comprised of solid particles having a particle size of 1 mm or less, and the binder and the filler are mixed in a ratio in a range of 70% by weight binder to 30% by weight filler and 30% by weight binder to 70% by weight filler, such that upon curing, the binder composition (78) dimensionally changes and polymerizes exothermically, thereby enabling the binder composition (78) to be cured without undue stress on the lens blank (54) and without debonding of the lens blank (54) from the binder composition (78).

2. The method of claim 1, wherein the lens blocks (62) each have a substantially spherically shaped lens mounting face (64) comprising the same block curve selected according to the distribution of curvature of the bonding face (58) of the lens blank (54) to be bonded for a particular population.

3. The method of claim 1, wherein the lens block (62) is transparent to ultraviolet or visible light, and wherein the step of generating ultraviolet or visible light and transmitting the light to the adhesive composition (78) comprises transmitting light through the lens block (62) to the adhesive composition (78)

4. A method of bonding a lens blank (54) having a bonding surface (58) with a predetermined curvature, the method comprising the steps of:

(a) providing a plurality of lens blocks (62), each lens block having a lens mounting face (64) with a predetermined block curve, wherein said lens blocks (62) have only a few different block curves;

(b) selecting a lens block (62) having a particular block curve based on said curvature of said bonding surface (58) of said lens blank (54) such that said block curve matches as well as possible said curvature of said bonding surface (58);

(c) mixing a binder composition (78) comprising a liquid binder in the unpolymerized state, uv or visible curable, and a filler as a non-polymeric solid;

(d) applying said adhesive composition (78) to at least one of an adhesive surface (58) of said lens blank (54) and a lens mounting surface (64) of said lens block (62);

(e) urging said lens blank (54) toward said lens block (62) wherein said adhesive surface (58) of said lens blank (54) faces said lens mounting surface (64) of said lens block (64); and

(f) generating ultraviolet or visible light and transmitting said light to said adhesive composition (78), said light having a wavelength and intensity and being applied for a time sufficient to cure said adhesive composition (78);

(g) wherein the filler is comprised of solid particles having a particle size of 1 mm or less, and the binder and the filler are mixed in a ratio in the range of 70% by weight binder to 30% by weight filler and 30% by weight binder to 70% by weight filler, such that upon curing, the binder composition (78) changes size and polymerizes exothermically, thereby enabling the binder composition (78) to be cured without undue stress on the lens blank (54) and without de-bonding the lens blank (54) from the binder composition (78)

5. The method according to claim 4, wherein the lens blocks (62) each have a substantially spherical lens mounting face (64), wherein lens blocks (64) having only two different block curves are provided, namely lens blocks (62) having concave block curves in the range of 0 to 4 diopters and lens blocks (62) having concave block curves in the range of 4 to 8 diopters.

6. The method of claim 4 or 5, wherein the step of selecting the lens blank (62) has the effect that, in the bonded state of the lens blank (54), the gap between the lens mounting face (64) of the lens blank (62) and the bonding face (58) of the lens blank (54) is smallest in a central region of the lens blank (62).

7. The method of claim 4, wherein the lens block (62) is transparent to ultraviolet or visible light, and wherein the step of generating ultraviolet or visible light and transmitting the light to the adhesive composition (78) comprises transmitting light to the adhesive composition (78) through the lens block (62).

8. An adhesive composition (78) for lens bonding, comprising:

a UV or visible light curable binder which is liquid in the non-polymerized state, and

a filler as a non-polymeric solid;

wherein the filler is composed of solid particles having a particle size of 1 mm or less, and wherein a mixing ratio of the binder and the filler is in a range of 70% by weight of the binder to 30% by weight of the filler and 30% by weight of the binder to 70% by weight of the filler.

9. The adhesive composition (78) of claim 8, wherein the filler particles are spherical in geometry.

10. The binder composition (78) of claim 8, wherein the filler comprises 1-2% by weight of the total composition of aluminum fibers.

11. The adhesive composition (78) of claim 8, wherein the filler material is transparent and/or translucent to the light-activated wavelength of ultraviolet and/or visible light.

12. The adhesive composition (78) of claim 8, wherein the filler has a glass transition temperature between 25 ℃ and 80 ℃.

13. The adhesive composition (78) of claim 8, wherein the filler material is selected from the group consisting of:

an ultraviolet or visible light curable binder in a regrind state; and

a plastic material comprising: e-caprolactone, terpolymers derived from ethyl-methyl-acrylate-acrylic acid, polycarbonate, polyethylene, high methacrylic acid resins, ethyl methacrylate resins, methacrylate copolymer resins, butyl methacrylate resins, and methyl methacrylate and n-butyl methacrylate copolymer resins.