CA2037703C - Laser curing of contact lens - Google Patents
Laser curing of contact lens Download PDFInfo
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- CA2037703C CA2037703C CA002037703A CA2037703A CA2037703C CA 2037703 C CA2037703 C CA 2037703C CA 002037703 A CA002037703 A CA 002037703A CA 2037703 A CA2037703 A CA 2037703A CA 2037703 C CA2037703 C CA 2037703C
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- Prior art keywords
- contact lens
- lens material
- curing
- laser
- irradiated
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- 239000000463 material Substances 0.000 claims abstract description 51
- 238000000034 method Methods 0.000 claims abstract description 25
- 230000005855 radiation Effects 0.000 claims abstract description 11
- 230000001678 irradiating effect Effects 0.000 claims abstract description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 15
- 239000001301 oxygen Substances 0.000 claims description 15
- 229910052760 oxygen Inorganic materials 0.000 claims description 15
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 10
- 239000007789 gas Substances 0.000 claims description 8
- 229910052786 argon Inorganic materials 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 5
- 239000000523 sample Substances 0.000 description 27
- 239000000203 mixture Substances 0.000 description 18
- 239000000178 monomer Substances 0.000 description 18
- 239000000017 hydrogel Substances 0.000 description 16
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 15
- 239000000758 substrate Substances 0.000 description 11
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 9
- 238000002835 absorbance Methods 0.000 description 8
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 8
- 229910052753 mercury Inorganic materials 0.000 description 8
- 239000011780 sodium chloride Substances 0.000 description 7
- 238000000862 absorption spectrum Methods 0.000 description 6
- CREMABGTGYGIQB-UHFFFAOYSA-N carbon carbon Chemical compound C.C CREMABGTGYGIQB-UHFFFAOYSA-N 0.000 description 3
- 239000011203 carbon fibre reinforced carbon Substances 0.000 description 3
- 238000012544 monitoring process Methods 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 229920002818 (Hydroxyethyl)methacrylate Polymers 0.000 description 2
- BQZJOQXSCSZQPS-UHFFFAOYSA-N 2-methoxy-1,2-diphenylethanone Chemical compound C=1C=CC=CC=1C(OC)C(=O)C1=CC=CC=C1 BQZJOQXSCSZQPS-UHFFFAOYSA-N 0.000 description 2
- DBCAQXHNJOFNGC-UHFFFAOYSA-N 4-bromo-1,1,1-trifluorobutane Chemical compound FC(F)(F)CCCBr DBCAQXHNJOFNGC-UHFFFAOYSA-N 0.000 description 2
- WOBHKFSMXKNTIM-UHFFFAOYSA-N Hydroxyethyl methacrylate Chemical compound CC(=C)C(=O)OCCO WOBHKFSMXKNTIM-UHFFFAOYSA-N 0.000 description 2
- 239000012300 argon atmosphere Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- STVZJERGLQHEKB-UHFFFAOYSA-N ethylene glycol dimethacrylate Substances CC(=C)C(=O)OCCOC(=O)C(C)=C STVZJERGLQHEKB-UHFFFAOYSA-N 0.000 description 2
- CSJDCSCTVDEHRN-UHFFFAOYSA-N methane;molecular oxygen Chemical compound C.O=O CSJDCSCTVDEHRN-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000003292 diminished effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 229910052743 krypton Inorganic materials 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000000411 transmission spectrum Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/00009—Production of simple or compound lenses
- B29D11/00038—Production of contact lenses
- B29D11/00125—Auxiliary operations, e.g. removing oxygen from the mould, conveying moulds from a storage to the production line in an inert atmosphere
- B29D11/00134—Curing of the contact lens material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
- B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
- B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
- B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
- B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
- B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
- B29C2035/0838—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using laser
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2011/00—Optical elements, e.g. lenses, prisms
- B29L2011/0016—Lenses
- B29L2011/0041—Contact lenses
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S522/00—Synthetic resins or natural rubbers -- part of the class 520 series
- Y10S522/913—Numerically specified distinct wavelength
Landscapes
- Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Ophthalmology & Optometry (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- Physics & Mathematics (AREA)
- Oral & Maxillofacial Surgery (AREA)
- Toxicology (AREA)
- Polymerisation Methods In General (AREA)
- Eyeglasses (AREA)
- Treatments Of Macromolecular Shaped Articles (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
- Optical Couplings Of Light Guides (AREA)
- Heating, Cooling, Or Curing Plastics Or The Like In General (AREA)
- Testing Of Optical Devices Or Fibers (AREA)
- Radiation-Therapy Devices (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
Abstract
A process for curing a photopolymerisable contact lens material comprising the step of irradiating the photopolymerisable contact lens material with laser radiation having a wavelength of between approximately 200nm to approximately 400 nm for a predetermined time period.
Description
- 2 - ~~~~~~~9a The present invention relates to a process for curing a photopolymerisable contact lens material using coherent radiation.
Soft contact lenses are presently manufactured by infecting a hydrogel monomer mix into a mould which is rotated and exposed to ultraviolet radiation from a mercury lamp to photopolymerise the monomer mix. The hydrogel monomer mix consists of hydroxyethyl methacrylate, ethylene glycol dimethacrylate, ethylene glycol and a benzoin methyl ether photoinitiator. The hydrogel monomer mix is usually exposed to the ultraviolet radiation from an array of mercury lamps for at least ten minutes to induce phatopolymerisation after which the moulds are immersed in hot water to remove the ethylene glycol and other unpolymerised materials and to release the lens from the mould. The polymerisation process must be carried out in the presence of an unreactive gas, for example nitrogen, in order to exclude oxygen which if present would inhibit the polymerisation.
A ma,~or disadvantage of the above process is that all extraneous radiations from the mercury lamps must be removed using optical filters. The optical filters and the mercury lamps must be water cooled both to filter _ d ~i v "~ ' ~ ~ er>
out infrared radiation and also to prevent overheating.
Also, the mercury lamps have a limited lifetime and must be replaced periodically. Moreover, the ultraviolet radiation output from the mercury lamps decreases with operating time and therefore requires regular monitoring. In addition most of the energy of the. lamps is discarded.
An object of the present invention is to mitigate the above disadvantages of curing contact lenses.
According to the invention there is provided a process for curing a photopolymerisable contact lens material comprising the step of irradiating the photopolymerisable contact lens material with laser radiation having a wavelength of between approximately 200nm to app~~oximately 400nm, for a predetermined time period.
Preferably the contact lens material comprises a hydrogel monomer mix. The hydrogel monomer mix preferably comprises hydroxyethyl methacrylate, ethylene glycol dimethacrylate, ethylene glycol and a benzoin methyl ether photoinitiator.
Further preferably, the contact lens material is rotated in a mould during laser irradiation.
More preferably, the contact lens material is irradiated in an oxygen free environment. Further preferably, the contact lens material is irradiated in the presence of a gas unreactive relative to the contact lens material under the conditions of curing. The unreactive gas is preferably, argon, or nitrogen.
Suitable lasers preferably comprise the excimer lasers (XeF, XeGl and KrF operating at 351nm, 308nm and 248nm respectively) the nitrogen laser operating at 337nm, solid state lasers operating at approximately 355nm, and the ultraviolet output radiation of the Argon and Krypton ion lasers.
The selected lasers operate at suitable pulse energy levels and repetition rates to achieve photopolymerisation of the contact lens material in a reasonably short time period.
The advantages of the: invention are that there is improved control and shorter polymerisation.times are achieved, and there is less maintenance required of the laser equipment than for mercury lamps and attendant technology. In addition, the use of a laser enables automation of the process to be achieved easily and also there is no cooling or optical filtering equipment necessary as with mercury lamps.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:-Figure 1 is a diagrammatic view of an apparatus for carrying out the process according to the invention;
Figure 2 is a diagrammatic view of an apparatus for monitoring the amount of photopolymerisstion in a sample of contact lens material;
Figure 3a, 3b and 3c are graphs showing the change in an infrared spectrum during photopolymerisation;
~~~'~~~~.
Figure 4 is a graph showing the curing curve of a contact lens material irradiated as described in example l;
Figure 5 is a graph showing the curing curve of a contact lens material irradiated as described in example 2;
Figure 6 is a graph showing curing curves of a contact lens material irradiated as described in example 3;
Figure 7 is a graph showing a curing curve of a contact lens material irradiated as described in example 4;
Figure 8 is a graph showing curing curves of a contact lens material irradiated as described in example 5;
Figure 9 is a graph showing a curing curve of a contact lens material irradiated as described in example 6:
Figure 10 is a graph showing curing curves of a contact lens material irradiated as described in example 7; and Figure 11 shows the absorption spectrum of a cured sample of contact lens material.
Referring now to Figure 1, there is shown therein an apparatus generally indicated at 10 for carrying out the process according to the invention. A conventional soft contact lens material 11 in the form of a hydrogel monomer mix is placed in a rotatable mould 12 which can _ 6 _ r~ ~a -~ y a.? a LY.~ ~~v be rotated at a suitable speed for example 350rpm as is known in tha art. The lens material 11 and mould 12 are located in a housing 13 defining a substantially oxygen free chamber 14. The chamber 14 has an unreactive gas such as nitrogen or argon introduced therein. The mould 12 containing the contact lens material 11 is rotated at a suitable speed so as to form an inner concave surface on the eventual lens. The ultraviolet laser 15 is then operated producing a laser beam 20 which is directed onto the lens material il at a suitable pulse energy level and repetition rate and for a sufficient period of time to polymerise the contact lens material 11. Clearly, the laser beam 20 is of a sufficient width to cover the lens material 11 or it may be off-set from the axis of rotation to enable all the lens material to be irradiated.
The degree of polymerisation of the contact lens material 11 can be continuously monitored using the arrangement shown in Figure 2, or a similar arrangement.
As shown, the contact lens material 11 is placed on a NaCl substrate l6 in a chamber 14' defined by a~housing 13'. The chamber 14' is oxygen free and argon gas is introduced via a conduit 17. An ultraviolet laser beam 20' is directed into the chamber 14' _vi_a a window 18 and is reflected by a quartz prism 19 and directed onto the contact lens material 11. The substrate 16 may be rotated in conventional manner.
An infrared light beam 21 is directed through the contact lens material 11 and the infrared beam 21' transmitted by the sample 11 is monitored by an infrared spectrometer 22. A reference infrared light beam 23 is also directed into the chamber 14' and the transmitted reference beam 23' is also monitored by the spectrometer 22. The output spectrum of the spectrometer 22 demonstrating the progressive cure of the lens material 11 is shown in Figures 3a, 3b and 3c. The spectrometer 22 compares the sample beam 21' with the reference beam 23' and provides the IR absorbance spectrum of the sample material 11 as shown in each of Figures 3a, 3b and 3c. In Figures 3a, 3b and 3c the absorbance peak B
is the carbon oxygen c=o absorbance peak at 1720 cm 1 and the absorbanee peak A is the carbon carbon cmc absorbance at peak 1640 cm 1. Figure 3a provides the absorbance spectrum prior to any polymerisation of the sample material 11 and thus the carbon carbon, c=c absorbance peak is at a maximum as shown by Ao.
Figure 3b represents the absorbance spectrum at an intermediate stage of polymerisation of the sample material 11 and thus the carbon carbon, c=c absorbance peak Ai has reduced in size. Figure 3c represents the absorbance spectrum after a time t when almost complete polymerisation of the sample 11 has occurred and thus the absorbance peak A has diminished in size as shown to At. It will be clear that the size of the carbon oxygen c~o absorbance peak remains constant as this is not affected by the polymerisation of the sample contact lens material 11.
As is known in the art, due to the absorbance by the monomex the amount of infrared absorption decreases with polymerisation of a hydrogel monomer mix, and Figure 3a illustrates no polymerisation, Figure 3b illustrates a moderate amount of polymerisation and Figure 3c illustrates almost complete transmission of the infrared sample beam 21' at 1640cm 1 and thus almost complete polymerisation of the contact lens material 11' .
~~;~~'~'~~~
A sample o~ typically 10 micro-litres of conventional hydrogel monomer mix was spread on a CaF
substrate and exposed in an oxygen free chamber to a XeF
excimer laser emitting laser beam of 351nm pulses at a 4Hz repetition rate and with a pulse energy of 35mJ.
The degree of polymerisation was monitored periodically using the infrared technique described above. The results are shown in Figure 4 which is a graph illustrating fraction polymerised against time in minutes. As shown, the sample was approximately 85~
polymerised after six minutes.
A sample of 10 micro-litres of conventional hydrogel monomer mix was spread on a CaF substrate and exposed in an oxygen free chamber to an N2 laser emitting a laser beam of 337nm pulses at a 4Hz repetition frequency and with a pulse energy of 0.3mJ. The degree of polymerisation Was monitored periodically using the infrared technique described above. The results are shown in Figure 5 which is a graph similar to that of Figure 4. As shown, the sample was approximatley 85~
polymerised after three minutes and almost completely polymerised after six minutes.
A sample of 10 micro-litres of conventional hydrogel monomer mix was spread on a NaCl substrate and exposed in an oxygen free chamber to an N2 laser emitting a laser beam of 337nm pulses at 100Hz repetition frequency and with a pulse energy of 0.7mJ. The degree of ~~~~~ s polymerisation was monitored continuously using the infrared technique described above. A similar sample of monomer mix was similarly exposed to the laser irradiation but with the N2 laser operating at 100Hz repetition frequency but with a pulse energy of 0.3mJ.
The results are shown in Figure 6 which is a graph similar to that in Figure 5. As shown, 0.7mJ pulses appear to be the least energy required to achieve over 90% curing in two minutes.
A sample of 10 micro-litres of conventional hydrogel monomer mix was spread on a NaCl substrate and exposed in an oxygen free chamber to an N2 laser emitting a laser beam of 337nm pulses at lOHz repetition frequency and with a pulse energy of 0.75mJ. The degree of polymerisation was monitored continuously using the infrared technique described above. The results are shown in Figure 7 from which it will be observed that 90%
curing Was achieved in five minutes at which time the laser Was switched off however, the curing continued reaching 100% cure in about 1.5 hours in the absence of further irradiation.
A sample of 10 micro-litres of conventional hydrogel monomer mix was spread on a NaCl substrate and exposed in an oxygen free chamber to an N2 laser emitting a laser beam of 337nm pulses at 100Hz repetition frequency and with a pulse energy of 0.7mJ. The degree of polymerisation was monitored continuously using the infrared technique described above. A similar sample of monomer mix was also spread on an NaCl substrate and was exposed in an oxygen free environment to an N2 laser emitting a laser beam of 337 nm pulses at lOHz repetition frequency and with a pulse energy of 0.75mJ. The sample was monitored and the results are shown in Figure 8 from which it will be noted that at the lower pulse rate of lOHz the curing rate was slower. The lower rate of lOHz simulates the effect which would be obtained if say a laser operating at 100Hz repetition rate was used to sequentially scan ten samples.
A sample of 10 micro-litres of conventional hydrogel monomer mix was spread on a NaCl substrate and exposed in an oxygen free chamber to an XeF excimer laser with 4mJ
pulses at 100Hz repetition rate. The laser was intermittently switched on and off and the degree of polymerisation was monitored continuously using the infrared technique described above. The results are shown in Figure 9 from which it will be noted that curing clearly continues after the laser has been turned off (the value of F rises from 0.4 to 0.6 during the two minutes after the initial laser irradiation phase). Once the fraction cured reaches about 0.9 however, the presence of the laser beam appears to have only a minimal affect on the curing rate.
c~vTnrtnr ~ 7 A sample of 10 micro-litres of conventional hydrogel monomer mix was spread on a NaCl substrate and exposed in an oxygen free chamber to an XeF excimer laser with 0.35mJ pulses at 100Hz repetition rate. A similar sample was also spread on a Nacl substrate and exposed in an oxygen free chamber to an XeF excimer laser with 25mJ
pulses at lOHz repetition rate. The degree of w - m -polymerisation was monitored continuously and the results are shown in Figure 10. The upper trace at the 100Hz repetition rate has an average irradiated power of 35mW
yet it has a faster initial cure rate than the lOHz trace which has an average power of 250mW. It appears that a higher repetition rate produces a higher initial cure rate.
A sample of 26 micro-litres of conventional hydrogel monomer mix was deposited in a contact lens mould (see Figure 1) rotating at a speed of 350 rpm. The sample was exposed in an argon atmosphere to an N2 laser beam (337nm) operating at 100Hz repetition rate with a pulse energy of 3mJ. After 2 minutes the mould was removed from the argon atmosphere, and soaked in hot water after which the polymerised contact lens was removed. The contact lens was free from visual blemishes and fudged to be suitable for use.
The technique for monitoring the degree of polymerisation of a sample of contact lens material during laser irradiation can normally ~c,nly be carried out on thin samples of lens material. The technique cannot be carried out successfully on samples of contact lens material which are of sufficient volume to produce an actual contact lens as such volumes are~too great to enable a quantitative measurement of the transmission spectrum of an infrared light beam. The results of the tests on the small volumes in examples 1 to 7 clearly demonstrate the parameters for successful photopolymerisation of a conventional contact lens material.
In Figure il there is shown the absorption spectrum of a l.4mm thick cured sample of a conventional hydrogel contact lens material. From this curve the_ optimum curing laser Wavelengths are determined. As shown, laser light above 380nm is impractical since only a small fraction of it will be absorbed (8$ over a lmm depth).
On the shorter wavelength side, the material absorbs strongly around 300nm and below and so only very thin layers could be cured with these wavelengths. It appears that the optimum laser wavelengths for photopolymerisation is within a range of approximately 300nm to approximately 380nm and so the most useful lasers are likely to be the XeCl and XeF excimer lasers (308 and 351nm respectively) and the N2 laser (337nm).
The invention is not limited~to the embodiments described herein which maybe modified or varied without departing from the scope of the invention.
Soft contact lenses are presently manufactured by infecting a hydrogel monomer mix into a mould which is rotated and exposed to ultraviolet radiation from a mercury lamp to photopolymerise the monomer mix. The hydrogel monomer mix consists of hydroxyethyl methacrylate, ethylene glycol dimethacrylate, ethylene glycol and a benzoin methyl ether photoinitiator. The hydrogel monomer mix is usually exposed to the ultraviolet radiation from an array of mercury lamps for at least ten minutes to induce phatopolymerisation after which the moulds are immersed in hot water to remove the ethylene glycol and other unpolymerised materials and to release the lens from the mould. The polymerisation process must be carried out in the presence of an unreactive gas, for example nitrogen, in order to exclude oxygen which if present would inhibit the polymerisation.
A ma,~or disadvantage of the above process is that all extraneous radiations from the mercury lamps must be removed using optical filters. The optical filters and the mercury lamps must be water cooled both to filter _ d ~i v "~ ' ~ ~ er>
out infrared radiation and also to prevent overheating.
Also, the mercury lamps have a limited lifetime and must be replaced periodically. Moreover, the ultraviolet radiation output from the mercury lamps decreases with operating time and therefore requires regular monitoring. In addition most of the energy of the. lamps is discarded.
An object of the present invention is to mitigate the above disadvantages of curing contact lenses.
According to the invention there is provided a process for curing a photopolymerisable contact lens material comprising the step of irradiating the photopolymerisable contact lens material with laser radiation having a wavelength of between approximately 200nm to app~~oximately 400nm, for a predetermined time period.
Preferably the contact lens material comprises a hydrogel monomer mix. The hydrogel monomer mix preferably comprises hydroxyethyl methacrylate, ethylene glycol dimethacrylate, ethylene glycol and a benzoin methyl ether photoinitiator.
Further preferably, the contact lens material is rotated in a mould during laser irradiation.
More preferably, the contact lens material is irradiated in an oxygen free environment. Further preferably, the contact lens material is irradiated in the presence of a gas unreactive relative to the contact lens material under the conditions of curing. The unreactive gas is preferably, argon, or nitrogen.
Suitable lasers preferably comprise the excimer lasers (XeF, XeGl and KrF operating at 351nm, 308nm and 248nm respectively) the nitrogen laser operating at 337nm, solid state lasers operating at approximately 355nm, and the ultraviolet output radiation of the Argon and Krypton ion lasers.
The selected lasers operate at suitable pulse energy levels and repetition rates to achieve photopolymerisation of the contact lens material in a reasonably short time period.
The advantages of the: invention are that there is improved control and shorter polymerisation.times are achieved, and there is less maintenance required of the laser equipment than for mercury lamps and attendant technology. In addition, the use of a laser enables automation of the process to be achieved easily and also there is no cooling or optical filtering equipment necessary as with mercury lamps.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:-Figure 1 is a diagrammatic view of an apparatus for carrying out the process according to the invention;
Figure 2 is a diagrammatic view of an apparatus for monitoring the amount of photopolymerisstion in a sample of contact lens material;
Figure 3a, 3b and 3c are graphs showing the change in an infrared spectrum during photopolymerisation;
~~~'~~~~.
Figure 4 is a graph showing the curing curve of a contact lens material irradiated as described in example l;
Figure 5 is a graph showing the curing curve of a contact lens material irradiated as described in example 2;
Figure 6 is a graph showing curing curves of a contact lens material irradiated as described in example 3;
Figure 7 is a graph showing a curing curve of a contact lens material irradiated as described in example 4;
Figure 8 is a graph showing curing curves of a contact lens material irradiated as described in example 5;
Figure 9 is a graph showing a curing curve of a contact lens material irradiated as described in example 6:
Figure 10 is a graph showing curing curves of a contact lens material irradiated as described in example 7; and Figure 11 shows the absorption spectrum of a cured sample of contact lens material.
Referring now to Figure 1, there is shown therein an apparatus generally indicated at 10 for carrying out the process according to the invention. A conventional soft contact lens material 11 in the form of a hydrogel monomer mix is placed in a rotatable mould 12 which can _ 6 _ r~ ~a -~ y a.? a LY.~ ~~v be rotated at a suitable speed for example 350rpm as is known in tha art. The lens material 11 and mould 12 are located in a housing 13 defining a substantially oxygen free chamber 14. The chamber 14 has an unreactive gas such as nitrogen or argon introduced therein. The mould 12 containing the contact lens material 11 is rotated at a suitable speed so as to form an inner concave surface on the eventual lens. The ultraviolet laser 15 is then operated producing a laser beam 20 which is directed onto the lens material il at a suitable pulse energy level and repetition rate and for a sufficient period of time to polymerise the contact lens material 11. Clearly, the laser beam 20 is of a sufficient width to cover the lens material 11 or it may be off-set from the axis of rotation to enable all the lens material to be irradiated.
The degree of polymerisation of the contact lens material 11 can be continuously monitored using the arrangement shown in Figure 2, or a similar arrangement.
As shown, the contact lens material 11 is placed on a NaCl substrate l6 in a chamber 14' defined by a~housing 13'. The chamber 14' is oxygen free and argon gas is introduced via a conduit 17. An ultraviolet laser beam 20' is directed into the chamber 14' _vi_a a window 18 and is reflected by a quartz prism 19 and directed onto the contact lens material 11. The substrate 16 may be rotated in conventional manner.
An infrared light beam 21 is directed through the contact lens material 11 and the infrared beam 21' transmitted by the sample 11 is monitored by an infrared spectrometer 22. A reference infrared light beam 23 is also directed into the chamber 14' and the transmitted reference beam 23' is also monitored by the spectrometer 22. The output spectrum of the spectrometer 22 demonstrating the progressive cure of the lens material 11 is shown in Figures 3a, 3b and 3c. The spectrometer 22 compares the sample beam 21' with the reference beam 23' and provides the IR absorbance spectrum of the sample material 11 as shown in each of Figures 3a, 3b and 3c. In Figures 3a, 3b and 3c the absorbance peak B
is the carbon oxygen c=o absorbance peak at 1720 cm 1 and the absorbanee peak A is the carbon carbon cmc absorbance at peak 1640 cm 1. Figure 3a provides the absorbance spectrum prior to any polymerisation of the sample material 11 and thus the carbon carbon, c=c absorbance peak is at a maximum as shown by Ao.
Figure 3b represents the absorbance spectrum at an intermediate stage of polymerisation of the sample material 11 and thus the carbon carbon, c=c absorbance peak Ai has reduced in size. Figure 3c represents the absorbance spectrum after a time t when almost complete polymerisation of the sample 11 has occurred and thus the absorbance peak A has diminished in size as shown to At. It will be clear that the size of the carbon oxygen c~o absorbance peak remains constant as this is not affected by the polymerisation of the sample contact lens material 11.
As is known in the art, due to the absorbance by the monomex the amount of infrared absorption decreases with polymerisation of a hydrogel monomer mix, and Figure 3a illustrates no polymerisation, Figure 3b illustrates a moderate amount of polymerisation and Figure 3c illustrates almost complete transmission of the infrared sample beam 21' at 1640cm 1 and thus almost complete polymerisation of the contact lens material 11' .
~~;~~'~'~~~
A sample o~ typically 10 micro-litres of conventional hydrogel monomer mix was spread on a CaF
substrate and exposed in an oxygen free chamber to a XeF
excimer laser emitting laser beam of 351nm pulses at a 4Hz repetition rate and with a pulse energy of 35mJ.
The degree of polymerisation was monitored periodically using the infrared technique described above. The results are shown in Figure 4 which is a graph illustrating fraction polymerised against time in minutes. As shown, the sample was approximately 85~
polymerised after six minutes.
A sample of 10 micro-litres of conventional hydrogel monomer mix was spread on a CaF substrate and exposed in an oxygen free chamber to an N2 laser emitting a laser beam of 337nm pulses at a 4Hz repetition frequency and with a pulse energy of 0.3mJ. The degree of polymerisation Was monitored periodically using the infrared technique described above. The results are shown in Figure 5 which is a graph similar to that of Figure 4. As shown, the sample was approximatley 85~
polymerised after three minutes and almost completely polymerised after six minutes.
A sample of 10 micro-litres of conventional hydrogel monomer mix was spread on a NaCl substrate and exposed in an oxygen free chamber to an N2 laser emitting a laser beam of 337nm pulses at 100Hz repetition frequency and with a pulse energy of 0.7mJ. The degree of ~~~~~ s polymerisation was monitored continuously using the infrared technique described above. A similar sample of monomer mix was similarly exposed to the laser irradiation but with the N2 laser operating at 100Hz repetition frequency but with a pulse energy of 0.3mJ.
The results are shown in Figure 6 which is a graph similar to that in Figure 5. As shown, 0.7mJ pulses appear to be the least energy required to achieve over 90% curing in two minutes.
A sample of 10 micro-litres of conventional hydrogel monomer mix was spread on a NaCl substrate and exposed in an oxygen free chamber to an N2 laser emitting a laser beam of 337nm pulses at lOHz repetition frequency and with a pulse energy of 0.75mJ. The degree of polymerisation was monitored continuously using the infrared technique described above. The results are shown in Figure 7 from which it will be observed that 90%
curing Was achieved in five minutes at which time the laser Was switched off however, the curing continued reaching 100% cure in about 1.5 hours in the absence of further irradiation.
A sample of 10 micro-litres of conventional hydrogel monomer mix was spread on a NaCl substrate and exposed in an oxygen free chamber to an N2 laser emitting a laser beam of 337nm pulses at 100Hz repetition frequency and with a pulse energy of 0.7mJ. The degree of polymerisation was monitored continuously using the infrared technique described above. A similar sample of monomer mix was also spread on an NaCl substrate and was exposed in an oxygen free environment to an N2 laser emitting a laser beam of 337 nm pulses at lOHz repetition frequency and with a pulse energy of 0.75mJ. The sample was monitored and the results are shown in Figure 8 from which it will be noted that at the lower pulse rate of lOHz the curing rate was slower. The lower rate of lOHz simulates the effect which would be obtained if say a laser operating at 100Hz repetition rate was used to sequentially scan ten samples.
A sample of 10 micro-litres of conventional hydrogel monomer mix was spread on a NaCl substrate and exposed in an oxygen free chamber to an XeF excimer laser with 4mJ
pulses at 100Hz repetition rate. The laser was intermittently switched on and off and the degree of polymerisation was monitored continuously using the infrared technique described above. The results are shown in Figure 9 from which it will be noted that curing clearly continues after the laser has been turned off (the value of F rises from 0.4 to 0.6 during the two minutes after the initial laser irradiation phase). Once the fraction cured reaches about 0.9 however, the presence of the laser beam appears to have only a minimal affect on the curing rate.
c~vTnrtnr ~ 7 A sample of 10 micro-litres of conventional hydrogel monomer mix was spread on a NaCl substrate and exposed in an oxygen free chamber to an XeF excimer laser with 0.35mJ pulses at 100Hz repetition rate. A similar sample was also spread on a Nacl substrate and exposed in an oxygen free chamber to an XeF excimer laser with 25mJ
pulses at lOHz repetition rate. The degree of w - m -polymerisation was monitored continuously and the results are shown in Figure 10. The upper trace at the 100Hz repetition rate has an average irradiated power of 35mW
yet it has a faster initial cure rate than the lOHz trace which has an average power of 250mW. It appears that a higher repetition rate produces a higher initial cure rate.
A sample of 26 micro-litres of conventional hydrogel monomer mix was deposited in a contact lens mould (see Figure 1) rotating at a speed of 350 rpm. The sample was exposed in an argon atmosphere to an N2 laser beam (337nm) operating at 100Hz repetition rate with a pulse energy of 3mJ. After 2 minutes the mould was removed from the argon atmosphere, and soaked in hot water after which the polymerised contact lens was removed. The contact lens was free from visual blemishes and fudged to be suitable for use.
The technique for monitoring the degree of polymerisation of a sample of contact lens material during laser irradiation can normally ~c,nly be carried out on thin samples of lens material. The technique cannot be carried out successfully on samples of contact lens material which are of sufficient volume to produce an actual contact lens as such volumes are~too great to enable a quantitative measurement of the transmission spectrum of an infrared light beam. The results of the tests on the small volumes in examples 1 to 7 clearly demonstrate the parameters for successful photopolymerisation of a conventional contact lens material.
In Figure il there is shown the absorption spectrum of a l.4mm thick cured sample of a conventional hydrogel contact lens material. From this curve the_ optimum curing laser Wavelengths are determined. As shown, laser light above 380nm is impractical since only a small fraction of it will be absorbed (8$ over a lmm depth).
On the shorter wavelength side, the material absorbs strongly around 300nm and below and so only very thin layers could be cured with these wavelengths. It appears that the optimum laser wavelengths for photopolymerisation is within a range of approximately 300nm to approximately 380nm and so the most useful lasers are likely to be the XeCl and XeF excimer lasers (308 and 351nm respectively) and the N2 laser (337nm).
The invention is not limited~to the embodiments described herein which maybe modified or varied without departing from the scope of the invention.
Claims (9)
1. A process for curing a photopolymerisable contact lens material comprising the step of irradiating the photopolymerisable contact lens material with pulsed laser radiation having a wavelength of between approximately 200nm to approximately 400nm for a predetermined time period.
2. A process as claimed in Claim 1, wherein the laser radiation has a wavelength of between approximately 300nm to approximately 380nm.
3. A process as claimed in Claim 1, wherein the contact lens material is irradiated in an oxygen free environment.
4. A process as claimed in Claim 2, wherein the contact lens material is irradiated in an oxygen free environment.
5. A process as claimed in claim 1, wherein the contact lens material is irradiated in the presence of a gas unreactive relative to the contact lens material under the conditions of curing.
6. A process as claimed in Claim 2, wherein the contact lens material is irradiated in the presence of a gas unreactive relative to the contact lens material under the conditions of curing.
7. A process as claimed in Claim 5, wherein the gas is argon or nitrogen.
8. A process as claimed in any preceding claim, wherein the contact lens material is rotated in a mould during irradiation.
9. A process as claimed in any preceding claim wherein the laser operates at selected pulse energy levels and repetition rates to achieve photopolymerisation of the contact lens material in a reasonably short time period.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US903/90 | 1990-03-13 | ||
| IE90390A IE65863B1 (en) | 1990-03-13 | 1990-03-13 | Laser curing of contact lens |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2037703A1 CA2037703A1 (en) | 1991-09-14 |
| CA2037703C true CA2037703C (en) | 2000-05-02 |
Family
ID=11019586
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002037703A Expired - Fee Related CA2037703C (en) | 1990-03-13 | 1991-03-07 | Laser curing of contact lens |
Country Status (11)
| Country | Link |
|---|---|
| US (1) | US5154861A (en) |
| EP (1) | EP0447169B1 (en) |
| JP (1) | JPH05188330A (en) |
| KR (1) | KR0161690B1 (en) |
| CN (1) | CN1028803C (en) |
| AT (1) | ATE116195T1 (en) |
| BR (1) | BR9100977A (en) |
| CA (1) | CA2037703C (en) |
| DE (1) | DE69106182T2 (en) |
| ES (1) | ES2069199T3 (en) |
| IE (1) | IE65863B1 (en) |
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| WO1996003666A1 (en) * | 1994-07-26 | 1996-02-08 | Bausch & Lomb Incorporated | Method of polymerizing methacrylate-based compositions |
| US5760100B1 (en) | 1994-09-06 | 2000-11-14 | Ciba Vision Corp | Extended wear ophthalmic lens |
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| US5858163A (en) * | 1996-03-22 | 1999-01-12 | Gerber Optical, Inc. | Apparatus for making ophthalmic lenses by vacuum lamination |
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| JP3772243B2 (en) * | 1996-09-25 | 2006-05-10 | 湘南デザイン株式会社 | Molding method of duplicate product |
| DE19706846A1 (en) * | 1997-02-21 | 1998-09-03 | Bodenseewerk Geraetetech | Device for light-initiated chemical crosslinking of material |
| US6008264A (en) | 1997-04-30 | 1999-12-28 | Laser Med, Inc. | Method for curing polymeric materials, such as those used in dentistry, and for tailoring the post-cure properties of polymeric materials through the use of light source power modulation |
| US6282013B1 (en) | 1997-04-30 | 2001-08-28 | Lasermed, Inc. | System for curing polymeric materials, such as those used in dentistry, and for tailoring the post-cure properties of polymeric materials through the use of light source power modulation |
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| US6103148A (en) * | 1998-02-19 | 2000-08-15 | Technology Resources International Corporation | Method for curing a lens-forming fluid |
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| US7235195B2 (en) * | 2002-09-06 | 2007-06-26 | Novartis Ag | Method for making opthalmic devices |
| US20060202368A1 (en) * | 2005-03-09 | 2006-09-14 | Yasuo Matsuzawa | Method for producing contact lenses |
| JP4577103B2 (en) * | 2005-06-10 | 2010-11-10 | 株式会社デンソー | Laser welding quality determination method and apparatus |
| US20080185744A1 (en) * | 2007-02-01 | 2008-08-07 | Bausch & Lomb Incorporated | Thermal Conductive Curing of Ophthalmic Lenses |
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| US4113224A (en) * | 1975-04-08 | 1978-09-12 | Bausch & Lomb Incorporated | Apparatus for forming optical lenses |
| GB2082107A (en) * | 1980-08-15 | 1982-03-03 | Philips Electronic Associated | Plastics optical elements which comprise a moulded plastics material coated on one face with a photopolymerized resin |
| EP0202803A3 (en) * | 1985-05-14 | 1987-06-03 | Commonwealth Of Australia Department Of Industry Technology And Commerce | Laser curing of coatings and inks |
| US4701288A (en) * | 1985-06-05 | 1987-10-20 | Bausch & Lomb Incorporated | Method of making articles of dissimilar polymer compositions |
| JPH01163027A (en) * | 1987-12-21 | 1989-06-27 | Matsushita Electric Ind Co Ltd | Method and device for molding optical element |
-
1990
- 1990-03-13 IE IE90390A patent/IE65863B1/en not_active IP Right Cessation
-
1991
- 1991-03-01 US US07/662,854 patent/US5154861A/en not_active Expired - Lifetime
- 1991-03-07 CA CA002037703A patent/CA2037703C/en not_active Expired - Fee Related
- 1991-03-12 AT AT91302036T patent/ATE116195T1/en active
- 1991-03-12 ES ES91302036T patent/ES2069199T3/en not_active Expired - Lifetime
- 1991-03-12 KR KR1019910003917A patent/KR0161690B1/en not_active IP Right Cessation
- 1991-03-12 DE DE69106182T patent/DE69106182T2/en not_active Expired - Fee Related
- 1991-03-12 CN CN91101618A patent/CN1028803C/en not_active Expired - Fee Related
- 1991-03-12 EP EP91302036A patent/EP0447169B1/en not_active Expired - Lifetime
- 1991-03-12 BR BR919100977A patent/BR9100977A/en not_active IP Right Cessation
- 1991-03-13 JP JP3048050A patent/JPH05188330A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| ATE116195T1 (en) | 1995-01-15 |
| EP0447169B1 (en) | 1994-12-28 |
| BR9100977A (en) | 1991-11-05 |
| IE65863B1 (en) | 1995-11-29 |
| DE69106182D1 (en) | 1995-02-09 |
| KR910016471A (en) | 1991-11-05 |
| CN1028803C (en) | 1995-06-07 |
| CN1055069A (en) | 1991-10-02 |
| KR0161690B1 (en) | 1999-02-18 |
| EP0447169A1 (en) | 1991-09-18 |
| US5154861A (en) | 1992-10-13 |
| JPH05188330A (en) | 1993-07-30 |
| DE69106182T2 (en) | 1995-09-07 |
| IE900903A1 (en) | 1991-09-25 |
| CA2037703A1 (en) | 1991-09-14 |
| ES2069199T3 (en) | 1995-05-01 |
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