EP2648875A1

EP2648875A1 - Methods and compositions for lens blocking

Info

Publication number: EP2648875A1
Application number: EP11806041.7A
Authority: EP
Inventors: Alain H. Lamon
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2010-12-10
Filing date: 2011-12-09
Publication date: 2013-10-16
Also published as: JP2014501629A; WO2012078969A1; JP5902710B2; GB201020965D0

Abstract

Disclosed is a lens blocking composition and lens blocks as well as methods of blocking and processing a lens. In particular, a thermoplastic lens blocking composition for blocking an optical substrate in a processing position is disclosed that comprises a blend of a homopolymer or copolymer of epsilon-caprolactone having a number average molecular weight greater than 4,000 and a resin based on a bisphenol or a bisphenol-derivative. The composition is solid at 25 degrees Celcius and 1 atm.

Description

METHODS AND COMPOSITIONS FOR LENS BLOCKING The present invention relates generally to lens blocking compositions and lens blocks as well as methods of blocking and processing a lens.

Background Presently the most common method used to hold a lens in place during processing (e.g. machining, grinding, polishing and/or any other desired or necessary treatment so as to form a commercially usable lens) makes use of a low-melting-temperature metal alloy to form or attach - "block" - a major surface (i.e.. the major surface opposite of the major surface to be processed) of a lens blank to a machine-block/mandrel. This procedure is often referred to as "lens blocking". Lens blocks are generally cylindrical or truncated conical in form generally with one end (i.e. the end facing towards the lens blank), having a wider portion. Lens blocks used for ophthalmic lenses are generally about 35 to about 85 mm in diameter. A common low-melting-temperature metal alloy comprises bismuth, tin, lead, cadmium, indium, and antimony.

Prior to attaching the lens block onto the major surface of the lens blank, a tape may be first applied onto the surface, whereby the lens block is subsequently formed or attached onto the applied tape. The use of such a surface tape can help to prevent the lenses from being scratched by the metal alloy, serve as a heat shield (e.g ., to protect a plastic lens from warping due the heat of the metal alloy), and/or facilitate better or enhance further metal alloy adherence. Tapes for this purpose are commercially available (e.g. under the trade designation 3M Surface Saver from 3M Company) and may be applied by placing the lens in a small chamber, stretching the tape over the chamber, and applying a partial vacuum.

After the desired processing of the exposed surface of the lens, the metal alloy lens block is typically deblocked through shock deblocking (i .e. striking the lens to-be-deblocked with a ring or hammer) or hot-water deblocking. The former is the most commonly used method of deblocking. In shock deblocking, the metal alloy lens block drops off the lens due to the mechanical shock. In hot-water deblocking, lenses-to-be-deblocked are immersed in a tank with hot water so that the metal alloy melts and thus flows off the lenses. The liquid metal alloy drips to the bottom of the tank and there is a valve at the bottom of the tank through which the liquid metal alloy can be recovered and recycled (i.e. used again for forming lens blocks).

After deblocking, if applicable the surface tape is removed and the lens is cleaned.

Unfortunately, many of the present metal alloy materials used as lens blocks pose significant environmental and health hazards.

Lens blocking compositions that are not metal alloys are known. In the following such compositions will be generally referred to as non-metal-alloy blocking compositions, and lens blocks made therefrom as non-metal-alloy lens blocks. Non-metal-alloy lens blocking compositions include for example compositions based on waxes or curable/cured thermoset materials or thermoplastic materials.

For example, US 7101920 (Bonfini et al), discussing that mounting by pressing and removing operations of the button (lens blank) to and from the wax-blocks during

processing consumes a significant amount of time and is prone to error and the conventional ways of removing wax-based lens blocks from the lens buttons after processing include mechanically prying or heating the mandrel so that the blocking wax melts, discloses a water-soluble wax formulation for use as a lens block and that the lens block can be removed from the lens after machining by rinsing with warm water.

WO 94/08788 (Salamon and Demarco), for example, discusses the use of a radiation curable adhesive as a blocking/deblocking adhesive, wherein during attachment of the lens blank and lens block, the assembly is exposed to an initial irradiation to fix the lens blank to the lens block to assure proper alignment, and thereafter, the assembly is again exposed to radiation for a further period of time to fully cure the adhesive. It is discussed that following working of the exposed surface of the lens blank, the lens assembly then is placed in an appropriate debonding solution, for example water and detergent, acetone, and the like, for a sufficient period of time to debond the lens piece from the lens block. It is discussed that deblocking times may be as much as one hour or more, but it is preferred, however, to maintain a deblocking time of less than about forty minutes, preferably less than about thirty minutes, and that in order to accelerate deblocking, it is preferred that the

temperature of the solution, especially with respect to the aqueous based solutions, be maintained at temperatures from room temperature up to, preferably, about 80°C.

As another example, US 5,763,075 (Benjamin et al) discloses lens blocks comprising a solidified mass of thermoplastic blocking composition, the composition being solid at 21°C and having a sufficiently low melting or softening point such that the composition may be placed adjacent to an ophthalmic lens blank while at its melting or softening point without damaging the lens blank. It is disclosed that the thermoplastic blocking composition may comprise a thermoplastic material selected from the group consisting of polyesters, polyurethanes, ionomer resins of ethylene copolymers, polyester-polysiloxane block copolymers, segmented copolyesters and polyetheresters, ethylene vinyl acetate resins and copolymers, polycaprolactones and blends of polycaprolactones. It is disclosed that lenses may be deblocked for example by melting the blocking composition in hot water or, if an appropriate balance of adhesion can be achieved (e.g. providing blocking compositions that adhere to the lens blank with a sufficient strength to avoid unintended detachment of the lens during processing, yet allow deblocking of the lens using traditional shock deblocking), by shock deblocking. It is stated that the level of adhesion of blocking compositions comprising polycaprolactone polymers may often be too high causing difficulties when user attempts to deblock the lens and block.

WO 2010/052248 (Paillet et al.) - indicating that polycaprolactone thermoplastic blocks described in the US 5,763,075 family have a low Shore D hardness of 35 - describes a preformed optical substrate block comprising a thermoplastic block used to allow a optical substrate to be blocked on the preformed optical substrate block wherein the thermoplastic block is formulated from a composition comprising a shellac and a piasticizer where the shellac and the piasticizer are chosen so as to have the softening point of the thermoplastic material greater than or equal to 60°C and smaller than or equal to 85°C. Methods of blocking an optical substrate to be machined using such preformed blocks include a surface heating step in which a surface of the preformed substrate block is heated at a docking temperature greater than or equal to 50°C and smaller than or equal to 60°C and a docking step in which the optical substrate is docked to the heated surface of the preformed substrate block so as to be positioned in a machining position.

Summary of Invention

Although non-metal-alloy blocking compositions are known and/or have been suggested, presently their industrial use in processing lenses is quite limited even though there is a strong and long-time desire to replace metal alloy lens blocks due to inter alia toxicity and environmental issues. A part of the issue seems to be that non-metal alloy blocks often lack toughness and/or strength desirable in-line production facilities for processing of optical substrates. In addition it seems that some non-metal-alloy lens block compositions have adhesive properties, e.g. not adhesive or too adhesive, which are undesirable for blocking and/or deblocking. Also for non-metal-alloy lens blocking compositions it seems that recycling is often precluded either on hand the block composition itself and/or on hand the blocking method (e.g. curing) and/or deblocking methods (e.g. melting in hot water). It has been found the use of blends of polycaprolactone(s) having molecular weight(s) higher than 4000 and resin(s) of a bisphenol or a bisphenol-derivative can advantageously allow for the provision of a lens blocking composition having desirable toughness/ mechanical strength suitable for in-line production, e.g. machining of len substrates.

Without wanting to be bound by a particular theory it seems that the use of a resin with a bisphenol or a bisphenol-derivative backbone facilitates the provision of a desirable level of resistance to shear stresses/structural failure of lens block and resistance to

compression/deformation of lens block during processing operation as well as favorable adhesion properties, while the polycaprolactone or polycaprolactones act(s) as modifier to further enhance the properties of the resin e.g. further facilitating the provision of toughness and/or flexibility while limiting brittleness. In addition such composition may be formulated such that during use in blocking the optical substrate and later in deblocking from the processed optical substrate the composition remains thermoplastic. This is favorable in that this may then allow for an option of recycling the lens block composition, if desired.

Accordingly according to one aspect of the present invention there is provided a

thermoplastic lens blocking composition for blocking an optical substrate in a processing position, wherein the composition comprises a blend comprising:

a homopolymer or copolymer of epsilon-caprolactone having a number average molecular weight greater than 4,000, and

a resin based on a bisphenol or a bisphenol-derivative;

wherein the composition is solid at 25°C and 1 atm.

As already indicated the use of such blends allows one to obtain a lens blocking composition having an advantageous combination of properties particular suited for lens blocking. In addition, it has been surprisingly observed that blends may be provided that seem to exhibit a single, composition dependent softening/melting point suggesting that such blends of a homopolymer or copolymer of epsilon-caprolactone having a number average molecular weight greater than 4,000, and a resin based on a bisphenol or a bisphenol-derivative may unexpectedly be miscible blends forming thus a single phase.

For further facilitation of desirable levels of the hardness/strength of lens blocks made from lens blocking compositions described herein, such compositions may desirably have a Shore D hardness equal to or greater than 45 at 23±2°C and 55±5% relative humidity. (Shore D hardness may be measured in accordance to ASTM D2240-05 (2010) using for example HP Series Durometer from Bareiss, Oberdischingen, Germany.) In aiding further minimization of a potential towards unsuitable brittleness, lens blocking compositions described herein may desirably have a Shore D hardness less than 65 at 23±2°C and 55±5% relative humidity, in particular less than 60 at 23±2°C and 55±5% relative humidity, more particularly less 55 at 23±2°C and 55+5% relative humidity. For further facilitating resistance to shear stress, lens blocking compositions described herein may desirably have an overlap shear strength resistance equal to or greater than 1 MPa at 23±2°C and 55±5% relative humidity, in particular equal to or greater than 2 MPa at 23±2°C and 55±5% relative humidity, more particularly equal to or greater than 2.5 MPa at 23°C and 55±5% relative humidity. (Overlap shear strength may be measured in accordance to ASTM D 1002-05 for example as described infra.)

For further facilitation of desirable toughness/flexibility, lens blocking compositions described herein may desirably have an overlap shear strength resistance equal to or less than 10 MPa at 23±2°C and 55±5% relative humidity, in particular equal to or less than 8 MPa at 23+2°C and 55±5% relative humidity, more particularly equal to or less than 6 MPa at 23+2°C and 55±5% relative humidity.

To further facilitate minimization of any potential of unsuitable deformation due to compression forces (e.g. during machining), lens blocking compositions described herein may desirably have a compression resistance equal to or greater than 5 MPa at 23±2°C and 55±5% relative humidity, in particular equal to or greater than 6 MPa at 23±2°C and 55+5% relative humidity, more particularly equal to or greater than 7 MPa at 23±2°C and 55+5% relative humidity. (Compression resistance may be measured in accordance to ASTM D 695-10 for example as described infra.)

To further facilitate desirable toughness/flexibility, lens blocking compositions described herein may desirably have a compression resistance equal to or less than 25 MPa, in particular equal to or less than 20 MPa, more particularly equal to or less than 15 MPa. According to a second aspect of the present invention there is provided a lens block made using a lens blocking composition described herein. Another aspect of the present invention is a method of blocking an optical substrate to be processed comprising :

a) providing an optical substrate having a face generally opposite to that one to be processed ;

b) providing an machine-block having a first surface onto which the optical substrate is to be blocked ;

c) providing a lens blocking composition as described herein ;

the method further including the steps of:

d) warming the lens blocking composition so that the lens blocking composition has a mass flow such that it is dispensable;

e) dispensing warmed lens blocking composition onto the first surface of the machine-block;

f) positioning the optical substrate onto the warmed lens blocking composition provided on the first surface of the machine-block so that said face of optical substrate generally faces towards the machine-block; and

g) allowing the lens blocking composition to cool and/or cooling the lens blocking composition such that it solidifies.

A further aspect of the present invention is a method of processing an optical substrate, wherein the method includes steps of blocking as described herein and further includes steps of processing and deblocking the processed optical substrate, said steps being :

h) processing the optical substrate;

i) after processing, warming the processed optical substrate-composition-machine- block assembly to a temperature equal to or greater than the onset of softening or melting point of the lens blocking composition ;

j) separating the assembly to give two sub-assemblies, one being processed optical substrate-composition and the other being composition-machine-block; and k) removing composition from the processed optical substrate.

Methods described herein are advantageous in that they are clean in handling and lend themselves for use in in-line production facilities or machines for, as applicable, blocking or processing optical substrates (in particular lens blanks, more particularly ophthalmic lens blanks). In addition the methods of blocking described herein allow for favorable accuracy in blocking since optical substrate may be positioned as desired or needed in the warmed (and thus viscous) lens blocking composition and then held in that position when the lens blocking composition solidifies. In addition it has been found that lens blocking compositions described herein are generally sticky/adhesive when warmed which advantageously lends to accurate positioning and further allows for the optical substrate to held in position during the time period between positioning and solidification .

Detailed Description

Throug hout the following and the aforesaid, it wi l l be u nderstood that an optical substrate may be favorably a lens blank, more favorably an ophthalmic lens blank.

Thermoplastic lens blocking compositions described herei n have many advantages over traditional metal al loys including for example, the compositions are non-toxic and environmentally safe.

As mentioned supra, a thermoplastic lens blocking composition for blocking an optical substrate in a processing position in accordance to the present invention comprises a blend comprising :

a homopolymer or copolymer of epsilon-caprolactone having a number average molecu lar weight greater than 4,000, and

a resin based on a bisphenol or a bisphenol-derivative;

wherein the composition is solid at 25°C and 1 atm .

Typical ly the lens blocking composition is solid at 25°C and 1 atm. It will be appreciated by the skilled reader that a solid, u nli ke a liqu id, tends to keep its form with no (or, if any, minimal) apparent mass flow or spreading out like a liqu id or a gas, while a liqu id, unlike a solid, has no fixed shape, but instead has a characteristic readiness to flow. Moreover, it wou ld not be possible to measu re an apparent viscosity of a solid (i .e. a solid has no measurable viscosity) for example using the ASTM standard Test Method for Apparent Viscosity (ASTM D2556) .

In the following homopolymer or copolymer of epsilon-caprolactones will be generally referred to as polycaprolactones.

It is to be recognized that bisphenol or bisphenol-derivative based resin is not acting as a filler (solid extender) for polycaprolactone, or vice versa ; nor is bisphenol or bisphenol- derivative based resin present as particu lates in polycaprolactone, or vice versa . As mentioned supra, it has been surprisingly observed that blends of a polycaprolactone having a number average molecu lar weig ht greater than 4,000 and a resin based on a bisphenol or a bisphenol-derivative based resin may be provided that seem to exh ibit a single, composition-dependent softening/melting point suggesting that such blends are unexpectedly miscible blends and thus single phasic. This is advantageous for allowing efficient and effective recycling and for general ease in use blocking/deblocking, especially in methods described herein. As already indicated the use of such blends allows one to obtain a lens blocking composition having an advantageous combination of properties particular suited for lens blocking. In addition as indicated supra, compositions including a blend comprising polycaprolactone(s) and bisphenol- or bisphenol-derivative based resin(s) may be advantageously formulated so that during use in blocking the optical substrate and in deblocking from the processed optical substrate the composition remains thermoplastic. In methods described herein or other methods of processing optical substrates, for ease in handing and/or ease in deblocking or removing composition from a lens, a tape or a machine-block, when the composition is solid, desirably the lens blocking composition is non-tacky or substantially non-tacky when the lens blocking composition is solid. The term "tack" as used hereinabove is intended to designate the tacky or sticky nature of a composition. Tack can generally be determined by what is referred to as the thumb test in which the thumb is pressed against the surface being considered and then removed to determine the tacky or sticky nature of the surface. Alternatively tack may be measured in accordance ASTM D2979-01(2009) "Inverted Probe Tack Test". In this test values of tack are measured (at 23±2°C and 55±5% relative humidity) in grams of force; i.e. grams of force required to remove at a speed of 10 mm per second the end of a stainless steel rod (5.0 mm in diameter) from the surface of an solidified coating (at least 3mm thick) of lens blocking composition to which to the rod has been placed into contact for 10.0 second (contact speed 10 mm/ second). By the term "substantially nontacky" is intended a tack of less than 11 g/cm² of force, more particularly a tack of less than about 6 g/cm². Non-tacky is intended a tack of 1 to 0 g/cm², in particular 0 g/cm².

As mentioned supra, favorable lens blocking compositions may have a Shore D hardness equal to or greater than 45 at 23±2°C and 55±5% relative humidity. In addition or alternatively thereto lens blocking compositions may favorably have a Shore D hardness less than 65 at 23±2°C and 55±5% relative humidity, in particular less than 60, more particularly less than 55.

As mentioned supra, favorable lens blocking compositions may have an overlap shear strength resistance equal to or greater than 1 MPa at 23±2°C and 55±5% relative humidity, in particular equal to or greater than 2 M a, more particularly equal to or greater than 2.5 MPa. In addition or alternatively thereto, lens blocking compositions may favorably have an overlap shear strength resistance equal to or less than 10 MPa at 23±2°C and 55±5% relative humidity, in particular equal to or less than 8 MPa, more particularly equal to or less than 6 MPa.

As mentioned supra, favorable lens blocking compositions may have compression resistance equal to or greater than 5 MPa at 23±2°C and 55±5% relative humidity, in particular equal to or greater than 6 MPa, more particularly equal to or greater than 7 MPa. In addition or alternatively thereto, lens blocking compositions may favorably have a compression resistance equal to or less than 25 MPa at 23±2°C and 55+5% relative humidity, in particular equal to or less than 20 MPa, more particularly equal to or less than 15 MPa.

As indicated supra, for use in methods described herein or, if applicable other methods or sub-processes used in processing lens, it is desirable that a lens block made of a lens blocking composition described herein is solid at potentially ambient temperatures at processing-sites. Favorably, lens blocking compositions are solid at potential ambient temperatures at processing-sites. More favorably the lens blocking composition are solid up to and including 30°C, even more favorably up to and including 33°C, and most favorably up to about 35°C.

Desirably the onset of the softening/melting-point range of lens blocking compositions described herein may be equal to or greater than 35°C, more desirably equal to or greater than 40°C.

Favorably the end point of the softening/melting-point range of lens blocking compositions described herein may be equal to or less than 68°C, more favorably equal to or less than 63°C. For use in methods described herein or other methods where a lens blocking composition may be dispensed in a non-solidified state, provision of lens blocking

compositions having such softening/melting point range end points can be advantageous in terms of low energy comsumption . In conjunction with desirable onset points of 35°C or greater (or more desirably 40°C or greater), a short softening/melting point range can be useful in terms of allowing for short/rapid cycle for in-line production e.g. in methods described herein .

Overall energy efficacy may be aided or further aided through provision of compositions having heat of fusion equal to or less than 65 J/g. Similarly allowing for short/rapid cycle times may be aided or further aided through the provision of compositions having such heats of fusion . Lens blocking compositions may desirably have a softening/melting-point within the range greater than 40°C and less than 60°C. Such softening/melting-points may be advantageous in terms of energy efficacy and/or time cycle as can be understood from the aforesaid. The aforesaid mentioned, softening/melting point, onset and end point of softening/melting point range as well as heat of fusion may each be determined in accordance with ASTM D 3418-03 e.g. as described infra.

Lens blocking compositions described herein may be favorably provided such that the viscosity is equal to or greater than 19 Pa.s at 70°C with a spindle No. 7 at 2 rpm, more favorably equal to or greater than 25 Pa.s at 70°C with a spindle No. 7 at 2 rpm, most favorably equal to or greater than 35 Pa.s at 70°C with a spindle No. 7 at 2 rpm. For use in methods described herein or other methods where lens blocking composition may be dispensed in a non-solidified state, provision of lens blocking compositions having such viscosities can be advantageous in terms of ease of handling and/or cleanliness in dispensing (e.g. not messy and/or having undesirable runniness) and/or, if applicable, docking of optical substrate in a blocking step.

Lens blocking compositions described herein may be favorably provided such that the viscosity equal to or less than 500 Pa.s at 70°C using a spindle No. 7 at 2 rpm, more favorably equal to or less than 375 Pa.s, most favorably equal to or less than 175 Pa.s. For use in methods described herein or other methods where a lens blocking composition may be dispensed in a non-solidified state, provision of lens blocking compositions having viscosity as described in the aforesaid sentence can be advantageous, as applicable, in terms of ease and/or quickness of dispensing.

Generally viscosity may be measured in accordance to ASTM D2556-93a (reapproved 1997), using e.g. a BROOKFIELD (RV model) DVIII ULTRA Rheometer equipped with a THERMOSEL heating system (commercially available by Brookfield Engineering GmbH, Germany).

Favorable polycaprolactones may have the following general formula (PCL I):

Q'-[0-(CH₂)₅-C(0)]_m-Q" and/or the following general formula (PCL II):

Q'-[0-(CH₂)₅-C(0)]_m-0(CH₂)₂0(CH₂)₂0-[C(0)-(CH₂)5-0]_m ^»-Q"; and/or the following general formula (PCL III):

C-[CH₂0-[C(0)-(CH₂)₅-0]_m-Q']₄ wherein Q' and Q" are end groups, such as H, CH₃.

As mentioned supra, lens blocking compositions described herein are provided such that they are thermoplastic and further that during use in blocking the optical substrate and in deblocking from the processed optical substrate the composition remains thermoplastic. As will be described in more detail infra resins based on a bisphenol or a bisphenol-derivative that are traditionally considered a thermosetting resin, such as diglycidyl ether of bisphenol A epoxy resins, may be used as a bisphenol or a bisphenol-derivative based resin. In such cases the composition will not be cured, nor hardened. Moreover despite the fact that the composition includes a thermosetting resin it will be provided and used as a thermoplastic resin.

In such cases as described in the previous paragraph, it may be favorable to use

polycaprolactones having a OH value less than 30 mg KOH/g, more favorably a OH value less than 15 mg KOH/g. Generally OH value (given as the mg of KOH equivalent to the hydroxyl content of 1 g of sample) may be determined through automated potentiometric titration in accordance to ASTM E 1899-08, for example using automated titrators of the type of the Titrando series commercially available by Metrohm, Herisau, Switzerland.

As indicated supra, polycaprolactones used in lens blocking compositions have at least a number average molecular weight of 4000. Polycaprolactones may favorably have a number average molecular weight equal to and greater than 8,000 further enhancing strength and at the same allowing for desired and/or needed viscosity when warmed. Desirably polycaprolactones may have a number average molecular weight equal to and less than 80,000.

Favorably polycaprolactones may have a softening/melting-point range within the temperature range from 40°C up to and including 65°C.

Suitable polycaprolactones may include 2000 series polycaprolactones (diols), 4000 series polycaprolactones (tetrols), and the 6000 series (thermoplastic homopolyers) supplied by Perstorp UK Limited under the trade designation CAPA, such as CAPA 2803, CAPA 2403D, CAPA 4801, CAPA 6100, CAPA 6200, CAPA 6250, CAPA 6400, CAPA 6430, CAPA 6500, CAPA 6500C, CAPA 6506, and CAPA 6800. Other suitable polycaprolactones may include polycaprolactones available under the trade designation TONEsupplied by Union Carbide Corporation Danbury, Connecticut, such as TONE 300 and TONE 700.

To allow for a desirable steering of desired or needed composition properties, lens blocking compositions may favorably include a plurality of polycaprolactones. A lens blocking composition may for example desirably include a higher and a lower molecular weight polycaprolactone wherein the higher molecular weight polycaprolactone has a number average molecular weight greater than 20,000, and the lower molecular weight

polycaprolactone has a number average molecular weight equal to or less than 20,000. The ratio of lower molecular weight polycaprolactone to higher molecular weight

polycaprolactone (pel-lower : pel-higher) may suitably be in the range from 100:1 to 2:1 inclusive, more suitably 50:1 to 2.5:1 inclusive; and most suitably 25:1 to 3:1 inclusive.

As stated supra, lens blocking compositions described herein comprise a blend comprising a polycaprolactone (for example either a single or a plurality of polycaprolactones) and a bisphenol- and/or bisphenol derivative-based resin (for example a single or a plurality of such resins). Favorably the ratio of the total weight amount of polycaprolactone(s) to the total weight amount of bisphenol- and/or bisphenol derivative-based resin(s)

(polycaprolactone(s) : said resin(s)) may be in the range of 1:1 to 3:1 inclusive, more favorably 1.2:1 to 2.4:1 inclusive, and most favorably 1.5:1 to 2:4:1 inclusive.

Suitable bisphenol and/or bisphenol-derivative based resins may include an entity of the following general Formula (I): and/or an entity of the following general Formula (la):

Q¹-0-Ph-CR2-Ph-0-[CH₂CH(OH)CH₂-0-Ph-CR₂-Ph -0]_n-Q²; and/or an entity of the following general Formula (II): and/or an entity of the following general Formula (Ila):

Q¹-0-Ph-R²-Ph-0-[CH₂CH(0H)CH₂-0-Ph-R²-Ph -0]_n-Q²; wherein for Formula (I) and Formula (la)

R is independently H, CH₃, Ph², CF₃, or CH₂CH₃; Wherein for Formula (II) and Formula (Ila)

-R²- is meta -C(CH₃)₂Ph³C(CH₃)₂-; para -C(CH₃)₂Ph⁴C(CH₃)₂-; -C(CCI₂)-; -C(C₅H₁₀)-; -C(CH₂ CH(CH₃)CH₂C(CH₃)₂CH₂)-; or -S(0)₂-; wherein for Formula (I) and Formula (II):

-R³- is -CH₂CH(OH)CH₂- or -C(O)-;

n is 1 or greater; wherein for Formula (la) and Formula (Ila):

n is 0 or 1 or greater; and wherein for Formula (I), Formula (la), Formula (II) and Formula (Ila):

the group at the 3^rd position of Ph (where -CR₂- or -R²-, as applicable, is denoted to be at the 1^st position) is independently H, CH₃, CH(CH₃)₂, or Ph⁵;

and

Q¹ and Q² represent end groups that may be the same or different.

As mentioned supra, unexpected it seems that the use of a resin with a bisphenol or a bisphenol-derivative backbone facilitates the provision of a desirable level of resistance to shear stresses/structural failure of lens block and resistance to compression/deformation of lens block during processing operation as well as favorable adhesion properties (e.g.

favorable in blocking and later to be able to be deblock). The provision of favorable adhesion properties is further facilitated through the use of a resin including a entity including a -CH₂CH(OH)CH₂- group within the bisphenol backbone, for example as exhibiting by resins of Formula la and Ila as well as Formula I and II when R³ is - CH₂CH(OH)CH₂-.

End groups of resins, e.g. Q¹ and Q² of given Formulas, may be suitably and independently be epoxy, alpha-glycol, phenoxy, vinyl ester, alcohol, amido, imido, or carbonyl groups. Surprisingly it has been found that the use of traditional thermosetting resins, including e.g. epoxy, alpha-glycol, phenoxy end groups, as thermoplastic resins may be particularly useful (e.g. for stability and/or compatibility with polycaprolactones, especially stability in terms to shelf life when using epoxy terms). Favorably bisphenol and/or bisphenol-derivative based resins include resins comprising an entity according to Formula (la) or Formula (Ila) where Q¹ and Q² are independently epoxy or alpha-glycol groups.

Bisphenol and/or bisphenol-derivative based resin may favorably include an entity according to Formula (la) OR Formula (Ila) where Q¹ and Q² are both CH₂CH(-0-)CH₂ and the group at the 3^rd position of Ph is H, and R is independently H or CH₃.

It has been found that particular useful resins comprise an entity according the Formula :

Such diglycidyl ether of bisphenol A epoxy resins ("DGEBA" or "BADGE") are commercially available, for example from Hexion Specialty Chemicals, Germany under trade designation EPON or EPIKOTE in USA and Europe, respectively. Examples of particular suitable resins include e.g. EPIKOTE 828, EPIKOTE 1001 and EPIKOTE 1002. DGBEA epoxy resins are also commercially available from Dow Chemicals, Stade, Germany under the trade designation DER and from Leuna Harze, Leuna, Germany under the trade designation EP1LOX.

As indicated supra, bisphenol and/or bisphenol-derivative based resins may include a mixture of entities; e.g. similar types of entities having different molecular weights (i.e. different n values) and/or different types of entities.

Referring to all the Formulas shown above for bisphenol and/or bisphenol-derivative based resins, average values of n up to 8, in particular in the range from 0.2 up to and including 8, more particularly in the range from 1 up to and including 7, even more particularly in the range from 2 up to and including 6 have been found desirable, in particular in terms of strength and/or viscosity.

Favorably the number average molecular weight of the bisphenol and/or bisphenol- derivative based resin may be up to 2800, in particular from 350 up to 2800. For balancing desired and/or needed properties, in particular viscosity and softening/melting point behavior, bisphenol and/or bisphenol-derivative based resins favorable have a softening and/or melting point less than 100°C, in particular less than 90°C, more particularly less than 80°C.

If desired, lens blocking compositions described herein may include an additive (e.g. a single additive or a plurality of additives) if desired. Such additives may be dissolved or suspended. Such additives may include e.g. extenders/fillers, colorants or other polymers.

Suitable particle-additives for use (typically used as extenders/fillers) generally comprise inorganic or organic, particulate (e.g. up to including 500 micron average particle diameter) or fibrous (e.g. up to 5000 micron average length) materials which are substantially insoluble in the continuous phase. Morphologies may include spheres, bubbles, expandable bubbles, particulate materials, filaments, microfibers, flakes and platelet type materials, as well as combinations of these. They may have a solid, porous, or hollow structure.

Suitable inorganic filler (solid extender) materials may include glass, amorphous and crystalline silica, soda lime borosilicate, amorphous sodium/potassium/aluminum silicate glass, alumina, iron oxides, calcium metasilicate. calcium carbonate, calcium sulfate (in either a particulate or microfiber form), kaolin, mica, talc, barium sulfate, boron fibers, carbon fibers, glass fibers, ground glass fibers, flake glass, metallic fibers, feldspar, barium ferrite, titanium oxide, and ceramics. Particularly suitable inorganic filler materials include fumed silica (e.g. such that available under the trade designation AEROSIL R202 from

Degussa AG, 63403 Hanau-Wolfgang, Germany); ground calcium carbonate (e.g. like that available under the Imerseal 75 from from Imerys Minerals Ltd., Par Cornwall, England); glass bubbles as an extender (such as glass bubbles A20/1000 from 3M Deutschland GmbH, 41453 Neuss, Germany). Iron oxide (Fe₃0₄) (e.g. such as that available under the trade designation MAGNIF 25 from Minelco B.V, 4782 PW Moerdijk, NL) may be suitably used as a filler and at the same providing e.g. thermal conductivity and coloring.

Suitable organic filler (solid extender) materials include thermoplastic expanded

microspheres, such as those available under trade designation EXPANCEL (e.g. EXPANCEL 461 DE 20) from Akzo Nobel, Netherlands; and thermoset microballons, such as those available under the trade designation UCAR (e.g. UCAR BJO-0950, BJO-0820, BJO-0900, BJO-0840, BJO-09300) from Union Carbide, Danbury Conn. USA. Pigments and dyes may be used as colorant. Suitable colorants may include a blue dye based on 1,4-bis (isopropylamino) anthraquinone, commercially available under trade designation Oil Blue A from Keystone Aniline Corporation Chicago IL 60612 USA, or yellow dye 2635 (N,N-diethyl-4-phenyldiazenyl-aniline) available from Allied Chemicals USA

Phenoxy resins may be applied as a performance modifier dissolved in lens blocking compositions to further facilitate flexibility of a lens blocks made of such compositions. Suitable phenoxy resins include phenoxy resins available under the trade designation PAPHEN, such as PAPHEN PKHP200 from Phenoxy Associates, Rock Hill, S.C. USA. EVA (ethylene vinyl acetate) resins having a VA content equal to or greater than 40% (allowing for solubility) may be used to further facilitate flexibility. Suitably EVA resins are

commercially available under the trade designation ELVAX from Dupont de Nemours, Delware, USA. Dissolved additives (e.g. phenoxy and/or EVA) may be have a concentration up to and including 15 wt %.

It will appreciated that suitable concentrations of additive in the lens blocking composition will depend on the particular additive or additives selected, their properties, the particular polycaprolactone(s) and bisphenol and/or bisphenol derivative resin(s) employed, and the desired end properties of the lens blocking composition.

While an additive or additives may be used as extenders, to enhance and/or modify particular properties, it will be understood that it is desired that if additives are used that the additives are selected such that they are not detrimental with respect to the use and performance of the lens blocking composition for lens blocking or with respect to the optical substrate. For example, for lens blocking compositions comprising bisphenol- and/or bisphenol derivative resins that are traditionally thermosetting resins but used as here as thermoplastic resins, desirably such compositions are free or essentially free (less than 0.005%) of any component that could initiate curing or hardening of the material, such as catalysts. To generally ensure that the optical substrate may not be distorted or unwontedly modified in some other way by the lens blocking composition, desirably lens blocking compositions are favorably free or essentially free (less than 1%) of plasticizers, such as polyester gum resins, phthalate-based plasticizers, trimelliatates, adipate-based plasticizers, sebacate-based plasticizers, maleates, benzoates, epoxidized vegetable oils, sulfonamides, organophosphates, acetylated monoglycerides, and alkyl citrates. Generally for safety and toxicity reasons lens blocking composition are favorably free or essentially free (less than 1%) of solvents, such as acetone, ketones, chlorobenzene, benzenes/ benzene derivatives, carbon tetrachloride, methanes, and hexanes. It is desired that lens blocking compositions remain substantially homogeneous (that is, it does not undergo macroscopic phase separation or, if applicable, particle sedimentation) during use and more desirably during prolonged storage prior to use. Also it is desired that lens blocking compositions retain their desired physical properties when repeatedly cycled between the warm and cool states, allowing for among other things favorable recyclable. Thus the selection of ingredients can be guided in part by a desire to preserve homogeneity and/or thermal reversibility.

Lens blocking compositions described herein may be prepared by mixing either by hand or mechanically mixing. During and/or before mixing, the components are typically warmed sufficiently to completely melt the polycaprolactone(s) and bisphenol- and/or bisphensol derivative based resin(s) and, if applicable any other thermoplastic components. Mixing may be performed using any suitable mixing device typically used to mix vicious liquids, such as kettles equipped with a mechanical stirrer, extruders, bead-mill mixers.

Lens blocking compositions described herein may be formed in pre-formed lens blocks, for example for use in methods described in WO 2010/052248. Such pre-formed lens blocks may have, as desired or needed, a thickness of 1 to 50 mm and a diameter of 20 mm to 120 mm. However it is preferable to use lens blocking compositions described herein in methods described herein, wherein the lens block is made and formed of lens blocking composition in situ in-line. (The term lens block is to encompass the use of blocks made with lens blocking compositions described herein with all type of optical substrates.)

As stated supra, a method of blocking an optical substrate to be processed comprises:

a) providing an optical substrate substrate having a face generally opposite to that one to be processed ;

b) providing an machine-block having a first surface onto which the optical substrate is to be blocked;

c) providing a lens blocking composition as described herein;

and the further steps including :

f) positioning the optical substrate onto the warmed lens blocking composition provided on the first surface of the machine-block so that the face of the optical substrate generally faces towards the machine-block; and g) allowing the lens blocking composition to cool and/or cooling the lens blocking composition such that it solidifies.

Favorably the warming step (d) may comprise warming the lens blocking composition to a temperature equal to or greater than the onset of softening or melting point of the lens blocking composition, more favorably equal to or greater than the softening or melting point of the lens blocking composition, and most favorably equal to or greater than the end-point of the softening/melting point range. Desirable warming temperatures may be greater than 40°C, equal to or greater than 50°C, and most desirable equal to or greater than 60°C. It will be appreciated that the selected warming temperature will depend on the particular softening point/melting point the particular lens blocking composition, viscosity of the composition at warming-temperature and selected method of dispensing. Desirably the warming step (d) is carried out at temperature lower than that that could thermally distort the optical substrate. For example polymeric optical substrates, (polycarbonate, polymethyl- methacrylate, cyclic-olefins copolymer) may be sensitive to distortion at higher

temperatures, i.e. temperatures in excess of 80° may cause distortion in optical

characteristics. Accordingly it is favorable to carried out warming step (d) at a temperature lower than 80°C, to ensure that the lens blocking composition is lower than 80°C in positioning step (f).

In step (e) the warmed lens blocking composition may be dispensed onto the first surface of the machine-block by a manner suitable for dispensing, e.g. pushing/injecting through a nozzle e.g. under pressure, pouring, pumping. Favorable the lens blocking composition is dispensed onto the first surface of the machine-block such that the lens blocking

composition forms a mound of warmed composition centered on the first surface of the machine-block, so that step (f) - the positioning the optical substrate (in particular the face of the optical substrate, said face may or may not be covered with tape (see infra)) onto the warmed lens blocking composition provided on the first surface of the machine-block - may include pressing down and spreading of the lens blocking composition outwardly. In step (f) the optical substrate is positioned in its desired and/or needed positioned for processing.

Typically the face of the optical substrate (i.e. that face generally opposite to that one to be processed) is positioned so that generally faces towards the machine-block

After positioning, in step (g) the lens block composition is allowed to cool and/or is cooled so that the lens blocking composition solidifies. In this manner the optical substrate is effectively and efficiently blocked. The solidified lens block, depending on dimensions of the particular optical substrate and/or machine block and the dimensions of the processing operations, may an outer diameter from 20 to 120 mm and may have at its thickest point a thickness from 3 to 50 mm. Transforming the lens blocking composition from its warmed state to a cool, solidified state requires loss of thermal energy and this can be carried out using a variety of cooling techniques. Cooling can take place under ambient conditions in the presence of air only. Cooling can also be expedited using e.g. forced air or exposure to cold air or chilling (e.g. cooling rings shaped to surround in-line formed block of lens blocking composition and circulate a cool liquid, such as chilled water).

In methods of processing an optical substrate, the method includes the aforesaid steps and the further steps of processing and deblocking the processed optical substrate, said steps being:

h) processing the optical substrate;

i) after processing, warming the processed optical substrate-composition-machine- block assembly to a temperature equal to or greater than the onset of softening or melting point of the lens blocking composition;

Processing the optical substrate may include e.g. machining, grinding, polishing and/or any other desired or necessary treatment so as to form commercially usable optical objects, such as lens, in particular ophthalmic lens.

The warming step (i) - comprising warming the processed optical substrate-composition- machine-block assembly to a temperature equal to or greater than the onset of softening or melting point of the lens blocking composition - is favorably carried out, depending the particular lens block composition, at a temperature just sufficient to be able to separate (e.g. pull) the block of lens blocking composition apart to provide two sub-assemblies in step (j). This is typically favorable in two-fold: ease in handling (not messy or runny) and energy efficiency. Similar to the warming step (d), the warming step (i) is favorably carried out at temperature lower than that that could thermally distort the optical substrate. Hereto it is favorable to carried out the warming step (i) at a temperature lower than 80°C. After separating the assembly to give two-sub-assemblies in step (j), composition is removed from the processed optical substrate in step (k). In methods described herein, the face of the optical substrate may be desirably provided with a tape prior to the step of positioning the optical substrate onto the warmed lens blocking composition provided on the first surface of the machine-block. In such desired embodiments the tape covered face would be placed onto and come in contact with the warmed lens blocking composition du ring the positioning step (f) . The provision of a tape may allow for easier removal of the composition from the processed optical su bstrate. Step (k) may then advantageously include peeling the tape off said face of processed optical su bstrate, whereby composition may be peeled away with the tape and thus removed from the processed optical substrate. Add itionally or alternatively the method may favorably comprise a step of removing composition from the tape, in particular said removing resolidified composition from the tape. "Alternatively" as an alternative route to removing composition from the face of the processed optical su bstrate (e.g. remove composition from tape first, then peel tape off) ; or "additionally" when e.g . recycling of lens blocking composition is desired.

Just as the face of the optical su bstrate may be advantageous provided with a tape, in methods described herein the first su rface of the mach ine-block may be provided with a tape prior to the step of dispensing warmed lens blocking composition onto said first surface of the machine-block. In such methods, after the step (j) separating the assembly to give two su b-assemblies; the method may favorably i nclude a step of removing composition from the fi rst surface of the machine-block. Such step may favorably include peeling the tape off said surface of the machine-block. Hereto such methods may comprise a step of removing composition from the tape, in particular said removi ng re-solidified composition from the tape.

When removing ta pe from processed optical su bstrate or machine-block, as applicable, the lens blocking composition may be warm or already re-cooled and thus re-solidified . The latter is favored .

Su itable tapes include ta pes available u nder the trade designation 3M SURFACE SAVER (e.g No. 1640) from 3M Company, St. Paul, Minn. USA.

Examples

The invention wi l l be il lustrated in the following Examples. The following examples are merely for illustrative pu rposes only and are not meant to be limiting on the scope of the a ppended clai ms. Table of materials:

Test Methods

Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens by Tension Loading according to ASTM D1002-05

Overlap Shear Strength was determined in accordance to ASTM D1002-05

Two 2024 T3 tempered clad aluminium alloy test strips (commercially available as from KDI KMS AERO, France) were used each measuring 100 mm by 25 mm by 1.6 mm and each acid etched prior to use. Etching included the following steps: degreasing (immersed into a 10% watery solution of Oakite Aluminium cleaner 164 (commercially available by Oakite Products Inc., U.S. A) at 85°C +/- 5°C for 10 minutes); rinsing in water; dipping in acid at 65°C +/- 3°C for 10 minutes (acid composition 44.8g Sodium dichromate, 332g sulphuric acid 66°Be (degree Beaume is an indication of the concentration of the sulphuric acid)), rinsing in water; and drying (e.g. for 15 minutes at room temperature (23°C +/- 2°C) followed by 10 minutes drying at 65°C +/-5°C in a forced air oven).

Composition to be tested was heated to a temperature between 70-80°C and dispensed onto the end portion of one test strip, and the applied coating was sprinkled with solid glass beads having a diameter of 800-900 pm (CVP sas, France) corresponding to about 5 wt% of the mass of test composition applied onto the test strip. (Glass beads were used as a "spacer" to facilitate provision of thedesired end layer thickness of 900 pm upon complete formation of joint). The coating with beads was covered by an end portion of the second test strip to provide an overlap of 12.5 mm. The two ends were pressed together, and any excess composition e.g. pressed out the sides was removed with a spatula. The overlapped strips were clamped together using two binder clips. Specimen was left to cool at 23°C +/- 2°C and 55 +/- 5% relative humidity for 24h prior to testing.

After the 24 h cooling period the binder clips were removed, and the prepared bonds were tested to failure at 23°C +/-2°C and 55 +/- 5% relative humidity as described in ASTM D 1002-05 using a Zwick tensile tester, Model 1476 (commercially available by Zwick GmbH & Co. KG , 89079 Ulm, Germany), operating at a crosshead speed of 2.5 mm/min. Five test specimens were tested per test composition and failing load values averaged (the results given in MPa).

(In the testing of exemplary compositions detailed infra, 90% of observed failures were failures in the cohesion of the composition and the remaining failures in adhesion to metal.) Compressive Properties of Rigid Plastics according to ASTM D695-10

Compressive strength was determined in accordance to ASTM D695-10 Test specimens were prepared by heating the composition to be tested to 70 - 80°C, pouring the then warm, vicious composition into a cylindrical PTFE mould cavity (35mm (length) x 14 mm (inner diameter)), allowing the composition to cool, and finally removing the solidified composition from the mould to obtain test specimen having an overall length of 35 mm and an outer diameter of 14 mm.

Individual test specimens were placed between the surfaces of a compression tool consisting of two round stainless steel plates (15 mm (height) x 140 mm (diameter)). The testing was conducted at 23°C +/-2°C and 55 +/- 5% relative humidity, applying a crosshead speed of 5 mm/min using a Zwick tensile tester, Model 1476 (commercially available by Zwick GmbH & Co. KG, 89079 Ulm, Germany).

Compressive strength was then calculated by dividing the maximum compressive load carried by the test specimen during the test by the original minimum cross-sectional area of the test specimen. Five test specimens were tested per test composition and the results averaged. The results are expressed in MPa.

Rubber Property - Durometer Hardness according to ASTM D2240-05 Shore D hardness was measured in accordance with ASTM D2240-05

Test specimens were prepared by heating the composition to be tested to 70 - 80°C and then pouring the then warm, vicious composition into a cylindrical mould cavity (100 mm (inner length) x 50mm (inner width) x 6mm (height)), allowing the composition to cool, and finally removing the re-solidified composition from the mould to obtain rectangular plate^¬ like test specimen having an overall length of 100 mm, width 50 mm and height 6 mm. Once removed from the mould, the sample was promptly tested at 23°C +/- 2°C and 55 +/- 5% relative humidity for Shore D hardness using a durometer of the HP series (Shore D type) commercially available from Bareiss, Oberdischingen, Germany. The means of testing were done manually. Five test specimens were tested per composition and results averaged. Apparent Viscosity of Adhesives Having Shear Rate Dependent Flow Properties according to ASTM D 2556-93a (reapproved 1997)

Viscosity was measured at 70°C in accordance with ASTM D 2556-93a (reapproved 1997) using a Brookfield (RV model) DVIII ULTRA Rheometer equipped with a THERMOSEL™ heating system (commercially available by Brookfield Engineering GmbH, Germany) with a Spindle No. 7.

16-20 grams of solid composition to be tested (amount used was that that provided about 20 ml of molten composition) were introduced into the test container of the heating system, the container being pre-heated to 70°C +/-0.2°C, and the composition melted resulting in approximately 20ml of molten (liquid) test composition. Thereafter spindle was immersed into liquid to its standard depth. After a 15 minute dwell time (to allow the spindle to adjust to the measurement temperature), the viscometer is started at a rotational speed of 2 rpm/min. This speed was then maintained for 1 minute, without stopping the motor, the speed was increased to 4 rpm/min, maintained for 1 minute, increased to 10 rpm, maintained 1 minute, and then increased to 20 rpm/min and maintained 1 minute. Readings were recorded at the end of each minute. Three independent samples were tested and the results averaged.

Transition Temperatures and Enthalpies of Fusion and Crystallization of polymers by Differential Scanning Calorimetry (DSC) according to ASTM D 3418-03

Measurements performed in accordance to ASTM D 3418-03 were done using a Differential Scanning Calorimeter DSC 1 STARe System available from Mettler Toledo, Germany. After calibration of the DSC and stabilization of the sample container (pan) at 0°C, a 15-20 mg sample of the composition to be tested was weighed in and placed within the sample container. A purge nitrogen gas flow rate was maintained at a flow rate of 200 ml/min during calibration and all thermal cycles. A preliminary thermal cycle was first recorded by heating the sample at a rate of 10°C/min up to 150°C, in order to erase previous thermal history. In a next step the composition was cooled to 0°C at a rate of 10°C/min and the cooling curve recorded. Then the temperature was held for 5 minutes before repeating to heat the test composition sample at a rate of 10°C/min up to 150°C. The heating curve was recorded and used to calculate the normalized enthalpy of transition (heat of fusion) reported in J/g. Further recorded and reported were: melting onset temperature in °C, melting peak temperature in °C and melting end temperature in °C. Two Differential Scanning Calorimetry measurements were run per test composition and the test results averaged. Preparation of exemplary lens blocking compositions El to E5

The exemplary compositions E13 to E17 were made using a DISPERMAT CV/S model mixer commercially available from VMA Getzmann, Germany. Prior to compounding a double jacket mixing bowl, which is an integrated part of the DISPERMAT CV/S mixer, was preheated to a set temperature of 100-105°C. Once the set temperature of 100-105°C was reached, poiycaprolactone (CAPA 6100) was added to the double jacket mixing bowl. Once the poiycaprolactone was completely melted, the DISPERMAT mixer was started at 2000 rpm/min. DGEBA (Epikote 1001) was slowly added and melted. The blend was mixed for 60 minutes at 90-100°C before pouring into suitable cartridges for further use e.g. in methods of blocking/processing optical substrates.

Preparation of exemplary lens blocking compositions E6 to E 17 Exemplary compositions E6 to E17 were made similar to El to E5 except once the poiycaprolactone (CAPA 6100) was completely melted and the DISPERMAT mixer was started at 2000 rpm/min, a second poiycaprolactone (CAPA 6400) was slowly mixed in and melted. And thereafter in a following step DGEBA epoxy resin (Epikote 1001) was then slowly added and melted. The blend mixed for 60 minutes at 90 - 100°C. If phenoxy resin was used as an additive (e.g. E8 and E13), after adding DGEBA but before the 60 minute- mixing, phenoxy resin was added in and dissolved. If any other additive was used, they were added after the 60 minute-mixing, and once they were added the mixture was then stirred for an additionally 30 minutes at 100°C. Thereafter, compositions were poured into suitable cartridges for further use e.g. in methods of blocking/processing optical substrates.

Exemplary Lens Blocking Compositions and Corresponding Test Results Tables 1 & 2, respectively:

The following provides examples of lens blocking compositions including a blend of an epoxy resin based on Bisphenol A (DGEBA) and a poiycaprolactone (PCL) having a number average molecular weight greater (M_n) than 4000, specifically about 10,000.

E 1 E 2 E 3 E 4 E 5

Shore D hardness 55 53 53 52 54

DSC

onset(°C) 42,9 42,5 46,6 45,7 43,5

peak (°C) melting point 53,2 53,2 57,4 51,9 54,2

end (°C) 57,3 56.0 61,2 56, 1 56,4

delta H (J/g) 43,8 49,8 47,3 54,2 56,6

Viscosity (Pa.s) at 70°C

2 rpm 21.3 19.0 19,3 19.6 19.0

4 rpm 21.4 19.7 19.9 20.3 19.6

10 rpm 21.6 20.0 20.1 21.4 20.3

Test results demonstrates good compatibility between the polycaprolactone and DGEBA, in particular the DSC shows in each case a single peak for a melting point with a relative narrow melting ranges suggesting that the blends are miscible blends and single phasic.

Lens blanks were prepared from the exemplary lens blocking compositions, and examined in terms of lens blocking performance in regard to flexibility, 40/60, 30/60 and 25/60 blends (DGEBA/PCL) were good; the 50/60 borderline and the 20/60 borderline-to-brittle.

Tables 3 & 4, respectively

The following table provides examples of blends with two polycaprolactones, one having a number average molecular weight about 37,000 (PCL-h) and the other about 10,000 (PCL-I) and DGEBA. One example includes in addition dissolved phenoxy resin. Rl to R4 refer to references examples of individual components.

*R 4 is theoretical example - values under DSC are extrapolated from that measured for respective 100% PCL components; ** out of scale > 1000 Pa.s

Exemplary lens blocking compositions provided excellent performance and handling in lens blocking/processing when used in methods as described herein.

Tables 5 & 6, respectively

The following include examples with iron oxide as an additive:

Test method E 9 E 10 E 11 E 12 E 13

Shore D hardness 53 53 54 55 51

DSC

onset(°C) 49,0 47,2 47,9 50,6 44.8

peak (°C) melting point 57,1 54,2 54,0 56,9 48.5

end (°C) 59,9 57,2 56,4 59,1 50.5

delta H (J/g) 37,7 33,9 33,7 26,7 36.4

Viscosity (Pa.s) at 70°C 44,2 66,1 75,3 82,5 66.2

SPINDLE 7 at 2 rpm

OLS Shear Strength (MPa) 4,6 5 4,9 4,8 3.5

Compressive Strength

(MPa) 9,9 10,2 11,4 11,8 10.2

It has been observed that iron oxide besides being an extender acts functionally increasing viscosity and allowing for enhanced thermal conductivity of lens blocking composition (e.g. note difference in heat of fusion in comparison to that of E7 or E8) allowing for observed faster rates of warming and cooling when using these exemplary lens blocking compositions in methods described herein.

Tables 7 & 8, respectively

The following include examples with other additives:

ompress ve trengt MPa . 1 . . .

The results of the aforesaid compositions demonstrates the possibility of using different types of additives, e.g. dye and various types of extenders/fillers (e.g. from low density fillers such as glass bubbles to higher density fillers such as fumed silica or calcium carbonate) with minimal effect on mechanical properties of the resulting lens blocks made of said exemplary compositons. The physical property changed the most was the viscosity (see examples E15 and E17). In using such highly vicious lens blocking compositions in methods described herein dispensing was done under greater pressure. Also during use in methods described herein filler sedimentation was not observed .

Claims

1. A thermoplastic lens blocking composition for blocking an optical su bstrate in a processing position, wherein the composition com prises a blend comprising :

a homopolymer or copolymer of epsilon-caprolactone having a nu mber average molecular weight greater than 4,000, and

a resin based on a bisphenol or a bisphenol-derivative;

wherein the composition is solid at 25°C and 1 atm .

2. A composition according to clai m 1, wherein the composition is provided such that du ring use in blocking the optical su bstrate and in deblocking from a processed optical su bstrate the composition remai ns thermoplastic.

3. A composition according to claim 1 or claim 2, wherein the composition is solid u p to and i ncluding 30°C, in particu lar u p to and incl uding 33°C, more particu larly up to 35°C;

and/or the composition when solid is non-tacky or substantially non-tacky.

4. A composition according to any one of the preceding claims, wherein the lens blocking composition has a Shore D hard ness equal to or g reater than 45 at 23+2°C and 55+5% relative humidity.

5. A composition according to any one of the preceding claims, wherein the lens blocking composition has a Shore D hardness less than 65 at 23±2°C and 55±5% relative humidity, in particu lar less than 60 at 23±2°C and 55±5% relative hu midity, more particularly less than 55 at 23±2°C and 55±5% relative hu midity.

6. A com position accord ing to any one of the preced ing claims, wherein the composition has an overlap shear strength resistance equal to or greater than 1 M Pa at 23±2°C and 55±5% relative humidity, in particular equal to or greater than 2 MPa at 23±2°C and 55±5% relative hu midity, more particularly equal to or greater than 2.5 MPa at 23±2°C and 55±5% relative hu midity.

7. A composition according to any one of the preceding claims, wherein the composition has an overlap shear strength resistance equal to or less than 10 MPa at 23±2°C and 55±5% relative hu midity, in particu lar equal to or less than 8 M Pa at 23±2°C and 55±5% relative humidity, more particularlyequal to or less than 6 MPa at 23±2°C and 55±5% relative humidity.

8. A composition according to any one of the preceding claims, wherein the composition has compression resistance equal to or greater than 5 MPa at 23±2°C and 55±5% relative humidity, in particular equal to or greater than 6 MPa at 23±2°C and 55±5% relative humidity, more particularly equal to or greater than 7 MPa at 23±2°C and 55±5% relative humidity.

9. A composition according to any one of the preceding claims, wherein the composition has compression resistance equal to or less than 25 MPa at 23±2°C and 55±5% relative humidity, in particular equal to or less than 20 MPa at 23±2°C and 55±5% relative humidity, more particularly equal to or less than 15 MPa at 23±2°C and 55±5% relative humidity.

10. A composition according to any one of the preceding claims, wherein the composition has a softening/melting-point-onset equal to or greater than 35°C, in particular equal to or greater than 40°C.

11. A composition according to any one of the preceding claims, wherein the composition has a softening/melting-point-range end-point equal to or less than 68°C, in particular equal to or less than 63°C.

12. A composition according to any one of the preceding claims, wherein the composition has a softening/melting-point greater than 40° and less than 60°C.

13. A composition according to any one of the preceding claims, wherein the composition has a heat of fusion equal to or less than 65 J/g.

14. A composition according to any one of the preceding claims, wherein the composition has a viscosity equal to or greater than 19 Pa.s at 70°C using a spindle No. 7 at 2 rpm, in particular equal to or greater than 25 Pa.s at 70°C with a spindle No. 7 at 2 rpm, more particularly equal to or greater than 35 Pa.s at 70°C with a spindle No. 7 at 2 rpm.

15. A composition according to any one of the preceding claims, wherein the composition has a viscosity equal to or less than 500 Pa.s at 70°C using a spindle No. 7 at 2 rpm, in particular equal to or less than 375 Pa.s at 70°C using a spindle No. 7 at 2 rpm, more particularly equal to or less than 175 Pa.s at 70°C using a spindle No. 7 at 2 rpm.

16. A composition according to any one of the preceding claims, wherein the homopolymer or copolymer of epsilon-caprolactone has the following general formula (PCL I) :

Q'-[0-(CH₂)_s-C(0)]_m-Q" and/or the following general formula (PCL II) :

Q'-[0-(CH₂)5-C(0)]_m.-0(CH₂)₂0(CH₂)₂0-[C(0)-(CH₂)₅-0]_m..-Q"; and/or the following general formula (PCL III) :

C-[CH₂0-[C(0)-(CH₂)₅-0]_m-Q']₄ wherein Q' and Q" are end groups.

17. A composition according to any one of the preceding claims, wherein the homopolymer or copolymer of epsilon-caprolactone has a OH value less than 30 mg KOH/g, in particular a OH value less than 15 mg KOH/g.

18. A composition according to any one of the preceding claims, wherein the homopolymer or copolymer of epsilon-caprolactone has a number average molecular weight equal to and greater than 8,000

19. A composition according to any one of the preceding claims, wherein the homopolymer or copolymer of epsilon-caprolactone has a number average molecular weight equal to and less than 80,000.

20. A composition according to any one of the preceding claims, wherein the homopolymer or copolymer of epsilon-caprolactone has a softening/melting-point range within the temperature range from 40°C up to and including 65°C.

21. A composition according to any one of the preceding claims, wherein the composition comprises a plurality of homopolymer or copolymer of epsilon-caprolactones.

22. A composition according to any one of the preceding claims, wherein the composition includes a higher and a lower molecular weight polycaprolactone wherein the higher molecular weight polycaprolactone is a homopolymer or copolymer of epsilon-caprolactone having a number average molecular weight greater than 20,000, and the lower molecular weight polycaprolactone is a homopolymer or copolymer of epsilon-caprolactone having a number average molecular weight equal to or less than 20,000.

23. A composition according to claim 22, wherein the ratio of lower molecular weight polycaprolactone to higher molecular weight polycaprolactone is in the range from 100:1 to 2:1 inclusive, more suitably 50:1 to 2.5:1 inclusive; and most suitably 25:1 to 3:1 inclusive.

24. A composition according to any one of the preceding claims, wherein the ratio of the total weight amount of homopolymer or copolymer of epsilon-caprolactone to the total weight amount of bisphenol- and/or bisphenol derivative-based resin is in the range of 1:1 to 3:1 inclusive, in particular 1.2:1 to 2.5:1 inclusive, more particularly 1.5:1 to 2:4:1 inclusive.

25. A composition according to any one of the preceding claims, wherein the bisphenol and/or bisphenol-derivative based resin includes an entity of the following general Formula (I): Q^O-t^-O-Ph-CFVPh-OL-Q²; and/or an entity of the following general Formula (la) :

Q¹-0-Ph-CR₂-Ph-0-[CH₂CH(OH)CH₂-0-Ph-CR₂-Ph -0]_n-Q²; and/or an entity of the following general Formula (II): and/or an entity of the following general Formula (Ila) :

Q¹-0-Ph-R²-Ph-0-[CH₂CH(OH)CH₂-0-Ph-R²-Ph -0]_n-Q²;

wherein for Formula (I) and Formula (la)

R is independently H, CH₃, Ph², CF₃, or CH₂CH₃;

Wherein for Formula (II) and Formula (Ila) -R²- is meta -C(CH₃)₂Ph³C(CH₃)₂-; para -C(CH₃)₂ ⁴C(CH₃)₂- ; -C(CCI₂)-; -C(C₅H₁₀)-; -C(CH₂ CH(CH₃)CH₂C(CH₃)₂CH₂)- ; or -S(0)₂-; wherein for Formula (I) and Formula (II) :

-R³- is -CH₂CH(OH)CH₂- or -C(O)- ;

n is 1 or greater; wherein for Formula (la) and Formula (Ha) :

n is 0 or 1 or greater; and wherein for Formula (I), Formula (la), Formula (II) and Formula (Ha) :

and

Q¹ and Q² represent end groups that may be the same or different.

26. A composition according to claim 25, wherein Q¹ and Q² are independently epoxy, alpha-glycol, phenoxy, vinyl ester, alcohol, amido, imido, or carbonyl groups, in particular epoxy, alpha-glycol, and phenoxy groups

27. A composition according to claim 25 or 26, wherein the bisphenol and/or bisphenol- derivative based resin includes an entity according to Formula (la) or Formula (Ila) where Q¹ and Q² are independently epoxy or alpha-glycol groups.

28. A composition according to any one of claims 25 to 27, wherein the bisphenol and/or bisphenol-derivative based resin includes an entity according to Formula (la) or Formula (Ila) where Q¹ and Q² are both CH₂CH(-0-)CH₂ and the group at the 3^rd position of Ph is H, and R is independently H or CH₃.

29. A composition according to any one of the preceding claims, wherein the bisphenol and/or bisphenol-derivative based resin includes an entity according the Formula :

30. A composition according to any one of claims 25 to 29, wherein the bisphenol and/or bisphenol-derivative based resin includes a plurality of entities.

31. A composition according to any one of claims 25 to 30, wherein the average value of n is up to 8, in particular in the range from 0.2 up to and 8, more particularly in the range from 1 up to and including 7, even more particularly from 2 up to and including 6

32. A composition according to any one of the preceding claims, wherein the number average molecular weight of the bisphenol and/or bisphenol-derivative based resin is up to 2800, in particular from 350 up to 2800;

and/or

wherein the bisphenol and/or bisphenol-derivative based resin has a softening and/or melting point less than 100°C, in particular less than 90°C, more particularly less than 80°C.

33. A len block made of a composition according to any one of the preceding claims.

34. A method of blocking an optical substrate to be processed comprising :

a) providing an optical substrate having a face generally opposite to that one to be processed;

c) providing a lens blocking composition according to any one of claims 1 to 32; the method further including the steps of:

f) positioning the optical substrate onto the warmed lens blocking composition provided on the first surface of the machine-block so that said face of optical substrate generally faces towards machine-block; and

35. A method of processing an optical substrate, wherein the method includes the steps according to claim 34 and further includes steps of processing and deblocking the processed optical substrate, said steps being : h) processing the optical substrate;

36. A method according to claim 34 or claim 35, wherein said face of the optical substrate is provided with a tape prior to the positioning step (f).

37. A method according to claim 36 as dependent on claim 35, wherein the step of removing composition from the processed optical substrate includes peeling said tape off said face of the processed optical substrate.

38. A method according to claim 36 or 37 as dependent directly or indirectly on claim 35, wherein the method comprises a step of removing composition from the tape, in particular said removing re-solidified composition from the tape.

39. A method according to any one of claims 34 to 38, wherein said first surface of the machine-block is provided with a tape prior to the step of dispensing warmed lens blocking composition onto said first surface of the machine-block.

40. A method according to claim 35 or any one of claims 36 to claim 39 as dependent directly or indirectly on claim 35, wherein after separating the assembly to give two subassemblies; the method includes a step of removing composition from the first surface of the machine-block.

41. A method according to claim 40, wherein the step of removing composition from the first surface of the machine-block includes peeling said tape off said first surface.

42. A method according to claim 40 or 41, wherein the method comprises a step of removing composition from the tape, in particular said removing re-solidified composition from the tape.

43. A method according to any one of claims 34 to 42, wherein a step of warming is carried out at a temperature lower than that that would cause distortion of the optical substrate.

44. A composition according to any one of claims 1 to 32 or method according to any one claims 34 to 43, wherein the optical substrate is a lens blank, in particular an ophthalmic lens blank.