Method, apparatus and adhesive composition for ophthalmic lens blocking

Abstract

A method is provided for blocking a lens according to which a lens block is obtained which transmits UV and visible light. An adhesive curable by light within the UV and visible spectrum is applied between the lens blank and a lens mounting face of the lens block. The lens blank is placed adjacent the lens block with the adhesive extending therebetween. UV light is applied to cure the adhesive. The adhesive is selected to have a suitable low dimensional change on setting so as not to impart any undue stresses on the lens blank which being capable of total adhesive failure without lens damage or leaving a residue upon application of a suitable stripping force.

1 . A method for blocking a lens blank comprising the steps of: 
 (i) obtaining a lens block which is transmits UV and visible light;.    (ii) applying an adhesive curable by at least one of visible and UV light to at least one of a first face of a lens blank and said lens block;    (iii) urging said lens blank torward said lens block with said first face of said lens blank facing said lens mounting face and a second face, opposite said first face facing away from said lens mounting face;.    (iv) generating UV and visible light and transmitting the light to said adhesive through said lens block, said light being of a wavelength and an intensity and applied for a time interval sufficient to cause setting of said adhesive.    (v) said adhesive being selected to have a dimensional change upon setting low enough to be capable of setting in less than 30 seconds without imparting undue stresses on said lens blank and capable of total adhesive failure without lens or lens blank damage or leaving residue on said lens upon application of a sufficient stripping force acting between said lens blank and said lens block.    
     
     
         2 . The method of  claim 1  wherein: 
 said block is oriented with said mounting face substantially horizontal during steps (ii) , (iii) and (iv); and,    said lens blank is maintained at a predetermined orientation relative to said lens block during steps (iii) and (iv).    
     
     
         3 . The method of  claim 2  wherein: 
 the contour of said first face is determined prior to step (iii); and,    said first face is maintained at a predetermined spaced apart distance, from said lens mounting face during step (iv).    
     
     
         4 . A method for blocking a lens comprising the steps of: 
 (i) placing a lens blank on a lens orienting station;    (ii) determining lens orientation and position parameters;    (iii) transporting said lens blank to a probing station while maintaining said orientation from step (ii);    (iv) mapping a first face contour of said lens blank while maintaining said orientation and generating and storing surface contour data;    (v) installing a UV and visible light transmissive lens mounting block in a lens blocking station;    (vi) applying an adhesive curable by light within the UV and visible spectrum to at least one of said lens mounting face and said first face;    (vii) transporting said lens blank to said lens blocking station and positioning said lens blank over said lens mounting face with said first face facing said lens mounting face while maintaining said orientation;    (viii) moving said lens blank toward said lens mounting face adhesive until said first face is a predetermined distance from said lens mounting face and said adhesive extends between said lens mounting face and said first face;    (ix) transmitting UV and visible light through said lens block at a wavelength and an intensity and for a duration sufficient to cause said adhesive to cure thereby bonding said lens blank to said lens block;    (x) referencing said first face surface contour data to a datum associated with said lens block and recording the referenced data; and,    (xi) removing said lens block with said lens blank attached thereto from said blocking station.    
     
     
         5 . The lens blocking method of  claim 4  wherein said lens blank has a second face opposite said first face and including the further steps of: 
 determining a position of said second face; and,    referencing said position of said second face relative to said datum on said lens block.    
     
     
         6 . The lens blocking method of  claim 5  wherein said adhesive is selected to: 
 be of a sufficiently high viscosity to avoid spillage during steps (ix), (x) and (xi);    upon curing provide support to resist lens deflection during lens generation;    absorb vibration imparted to said lens by a lens surfacing tool during said lens generation; and,    be capable of total adhesive failure without lens or lens block damage or leaving residue on said lens upon application of a sufficient stripping force acting between said lens blank and said lens block.    
     
     
         7 . The lens blocking method of  claim 6  wherein said adhesive is further selected to: 
 be capable of setting in less than 30 seconds without imparting undue stress on said lens blank; and,    not deform under heat associated with lens coating curing.    
     
     
         8 . The method of  claim 4  wherein step (ii) comprises the following substeps: 
 (a) generating a desired lens blank position and orientation image on a screen;    (b) generating an image on the screen depicting the orientation of the lens blank on the lens orienting station; and,    (c) positioning and orienting the lens blank to cause the image in step (b) to correspond to the image in step (a).    
     
     
         9 . The method of  claim 7  wherein step (ii) is carried out using computer image recognition to generate orientation and position parameters which are stored and form part of the first face surface contour data, which are referenced in step  9 .  
     
     
         10 . An apparatus for blocking an ophthalmic lens blank comprising; 
 a lens blank receiving station for receiving said lens blank;    a lens blocking station having a lens block support for receiving a UV and visible light transmissive lens block and supporting said lens block with a lens mounting face of said lens block in a desired orientation, said lens block support being capable of transmitting UV and visible light;    a lens transporter having a lens holder for selectively picking up and holding said lens blank, moving said lens blank over said lens block support and moving said lens blank toward said lens blank support; and,    a light source associated with said lens block support for emitting UV and visible light and directing said light through said lens block;    a light source actuator connected to said light source for controlling activation and deactivation of said light source;    an adhesive dispenser associated with said lens blocking station for dispensing a UV and visible light curable adhesive for bonding a lens blank on said lens mounting face;    a dispenser actuator connected to said dispenser for causing said dispenser to dispense said adhesive;    a controller communicating with said transporter, said dispenser actuator and said light source actuator to control the operation thereof.    
     
     
         11 . An apparatus of  claim 10  wherein; 
 said dispenser includes a dispenser nozzle and a nozzle manipulator connected thereto for moving said nozzle between a deployed position adjacent said lens mounting face of a lens block supported on said lens block support and a retracted position clear of said lens blank and said transporter, and,    said controller further communicates with said nozzle manipulator to control deployment and retraction of said nozzle.    
     
     
         12 . The apparatus of  claim 11  wherein said first station includes: 
 a lens orientation indicator having a first image generator for generating a desired lens orientation image and a second image generator for generating a second image indicating actual orientation of said lens blank; and,    an image comparator communicating with said first and second image generators for displaying said first image relative to said second image to guide manipulation of said lens blank to cause said actual orientation to correspond to said desired orientation.    
     
     
         13 . The apparatus of  claim 12  wherein: 
 said apparatus further includes a probing station on which said lens blank may be placed by said lens transporter, said probing station includes a plurality of lens probing elements for mapping the contour of a first face of said lens blank to determine a first face contour;    said controller communicates with said probing station to receive information on the contour of said first face relative to a first datum;    said transporter is configured to move. said lens blank between said probing station and said blocking station while maintaining said lens blank in said desired orientation;    said controller is configured to cause said transporter to place said lens adjacent said lens block with said first face a predetermined fixed distance apart from said lens mounting face and maintain said fixed distance during curing of said adhesive; and,    said controller translates said first face contour information to a second datum associated with said lens block and stores said information relative to said second datum.    
     
     
         14 . The apparatus of  claim 13  wherein: 
 said lens transporter includes a second face position probe for determining the position of said second face relative to said first face and transmits said second face position to said controller.    
     
     
         15 . The apparatus of  claim 13  wherein: 
 said dispenser nozzle is mounted on a dispenser arm movably mounted to a dispenser body;    said dispenser includes an arm actuator communicating with said controller for moving said dispenser arm relative to said dispenser body between said deployed and retracted positions;    said nozzle fluidly communicates with a UV curable adhesive source having pressurizing means for supplying said UV curable adhesive to said nozzle;    said controller communicates with a shut-off mechanism associated with said nozzle to control dispensing of said adhesive through said nozzle.    
     
     
         16 . The apparatus of  claim 14  wherein: 
 said dispenser nozzle is mounted on a dispenser arm movably mounted to a dispenser body;    said dispenser includes an arm actuator communicating with said controller for moving said dispenser arm relative to said dispenser body between said deployed and retracted positions;    said nozzle fluidly communicates with a UV curable adhesive source through a pump for supplying said adhesive to said nozzle;    said controller communicates with a shut-off mechanism associated with said nozzle to control dispensing of said adhesive through said nozzle.    
     
     
         17 . The apparatus of  claim 16  wherein: 
 said apparatus includes a UV shield for shielding an operator from UV light when said UV light source is activated.    
     
     
         18 . The apparatus of  17  wherein: 
 said UV shield is mounted to said transporter; and,    said UV shield is connected to a safety sensor which communicates with said transporter to interrupt motion of said transporter when said shield encounters an obstruction.    
     
     
         19 . The apparatus of  claim 18  wherein: 
 said safety sensor communicates with said controller and said controller causes said motion of said transporter to be interrupted.    
     
     
         20 . The use in lens blocking of a radiation curable coating composition comprising: 
 radiation curable organic resin;    an adhesion promoter;    a cohesive hardener; and    a photoinitiator.    
     
     
         21 . A radiation curable coating composition comprising: 
 a radiation curable organic resin;    an adhesion promoter, and    a cohesive hardener.    
     
     
         22 . The coating composition as claimed in  claim 21 , wherein the coating composition is characterized by a hardness value of greater than about 75A.  
     
     
         23 . The coating composition as claimed in  claim 22 , wherein the coating composition is characterized by a hardener value of greater than about 88A.  
     
     
         24 . The coating composition as claimed in  claim 21  wherein the adhesion promoter is an electrophilic, electron deficient compound.  
     
     
         25 . The coating composition as claimed in  claim 21 , wherein the adhesion promter is an acidic compound that is able to dissociate in an aqueous solution or water to yield hydrated protons.  
     
     
         26 . The coating composition as claimed in  claim 24 , wherein the cohesive hardener is a multi-functional ethylenically-capped monomer or oligomer with at least three functional groups.  
     
     
         27 . The coating composition as claimed in  claim 26 , wherein the hardener is selection from the group consisting of triacrylate, tris (2-hydroxyethyl) isocyanuarate triacrylate, dipentaerythritol pentaacrylate, pentaeyrthritol tetraacrylate, ethoxylated (4) pentaeryritol tetraacrylate, ethoxylated (3) trimethylolpropane triacrylate, ethyloxylated (6) trimethylolpropane triacrylate, or ethyloxylated (9) trimethylolpropane triacrylate.  
     
     
         28 . The coating composition as claimed in  claim 27 , wherein the radiation curable organic resin is selected from the group consisting of an aliphatic urethane, an aromatic urethane, a polyester, a polyether, or an epoxy.  
     
     
         29 . The coating composition as claimed in  claim 28 , further comprising a photoinitiator.  
     
     
         30 . The coating composition as claimed in  claim 29 , wherein this photoinitiator can undergo Norris type-1 cleavage.