EP1295181A2 - Method for making or adding structures to an article - Google Patents

Method for making or adding structures to an article

Info

Publication number
EP1295181A2
EP1295181A2 EP01948900A EP01948900A EP1295181A2 EP 1295181 A2 EP1295181 A2 EP 1295181A2 EP 01948900 A EP01948900 A EP 01948900A EP 01948900 A EP01948900 A EP 01948900A EP 1295181 A2 EP1295181 A2 EP 1295181A2
Authority
EP
European Patent Office
Prior art keywords
multiphoton
salts
photosensitizer
ofthe
curable
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01948900A
Other languages
German (de)
English (en)
French (fr)
Inventor
Robert J. Devoe
Brook F. Duerr
Patrick R. Fleming
Harvey W. Kalweit
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
3M Innovative Properties Co
Original Assignee
3M Innovative Properties Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 3M Innovative Properties Co filed Critical 3M Innovative Properties Co
Publication of EP1295181A2 publication Critical patent/EP1295181A2/en
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/12—Chemical modification
    • C08J7/16—Chemical modification with polymerisable compounds
    • C08J7/18—Chemical modification with polymerisable compounds using wave energy or particle radiation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/20—Exposure; Apparatus therefor
    • G03F7/2051—Exposure without an original mask, e.g. using a programmed deflection of a point source, by scanning, by drawing with a light beam, using an addressed light or corpuscular source

Definitions

  • This invention relates to a method of making or adding structures to an article with a multiphoton curing process.
  • Molding techniques such as injection molding, compression molding, embossing, extrusion embossing, and polymerizing within a mold may be used to fabricate a polymeric article.
  • techniques such as stamping, casting and machining may be used, while etching, sintering, and grinding are appropriate for use in forming a ceramic article.
  • These macroscopic fabrication techniques may be used to form an article or to impart a screencture to the surface of an article.
  • Relatively large three-dimensional parts can be made in a separate molding step, assembled, and attached to the surface ofthe article, but this technique is not useful for the fabrication and assembly of microscopic parts.
  • certain categories of microstructures such as undercuts, generally cannot be molded on the surface of an article.
  • the surface ofthe molded article includes a feature such as a depression or groove, it may become necessary to form a structure within the feature or along a sidewall ofthe feature.
  • Some structures may be added to the feature by placing a curable composition into the feature and curing it with light.
  • the curable composition absorbs a significant portion ofthe curing radiation, so the surface receives the greatest light intensity.
  • the surface ofthe curable composition cures first, and then the remainder of the composition cures gradually from the surface ofthe curable composition to the full depth ofthe feature.
  • the invention provides a method by which one or a few small, key components can be added in situ with a multiphoton curing process.
  • single-photon absorption scales linearly with the intensity ofthe incident radiation
  • two-photon absorption scales quadratically.
  • Higher-order absorptions scale with a related higher power of incident intensity.
  • the absorbing chromophore is excited with a number of photons whose total energy equals the energy of an excited state of a multiphoton photosensitizer, even though each photon individually has insufficient energy to excite the chromophore.
  • the exciting light is not attenuated by single- photon absorption within a curable matrix or material, so it is possible to selectively excite molecules at a greater depth within a material than would be possible via single-photon excitation.
  • the invention is a method for making a structure, including: applying a multiphoton-curable composition to a molded article, wherein the composition includes a curable species and a multiphoton photoinitiator system; at least partially curing the multiphoton-curable composition to form a structure on the article.
  • the invention is a method of adding a ultimatelycture to an article, wherein the article has a surface with at least one microscopic feature, the method including: applying a multiphoton-curable composition tothe feature, wherein the composition includes: a curable species, and a multiphoton photoinitiator system including a multiphoton photosensitizer and an electron acceptor; at least partially curing the multiphoton-curable composition to form a structure.
  • the invention is a method of adding a structure to an optical fiber, the method including: applying a multiphoton-curable composition to the optical fiber, wherein the composition includes: a curable species, and a multiphoton photoinitiator system including a multiphoton photosensitizer and an electron acceptor; at least partially curing the multiphoton-curable composition to form a structure.
  • the invention is a method for making a diffraction grating on a substrate, including applying a multiphoton-curable composition on the surface, wherein the composition includes: a curable species, and a multiphoton photoinitiator system including a multiphoton photosensitizer and an electron acceptor; and at least partially curing the multiphoton-curable composition to form a diffraction grating on the surface.
  • the invention is a method of filling a cavity with a multiphoton cured material including providing a multiphoton curable composition, wherein the composition includes a curable species and a multiphoton photoinitiator system, said multiphoton photoinitiator system including a multiphoton photosensitizer and an electron acceptor; providing a substrate with a cavity; exposing the multiphoton curable composition to a light source sufficient to cause multiphoton absorption.
  • the invention is a method of repairing a tooth, including: applying a multiphoton-curable composition to the tooth, wherein the composition includes: a curable species, and a multiphoton photoinitiator system including a multiphoton photosensitizer and an election acceptor; at least partially curing the multiphoton-curable composition.
  • FIG. 1 is a schematic representation of a multiphoton curing system.
  • FIG. 2 is a cross sectional view of a cavity in an article filled with a multiphoton curable material.
  • FIG. 3 A is an end view of a flow control device in a channel in an article.
  • FIG. 3 B is an overhead view of the flow control device of FIG. 3 A.
  • FIG. 3C is a cross-sectional view of a portion ofthe flow control device of FIG. 3 A.
  • FIG. 4 is a cross-sectional view of a diffraction grating.
  • FIG. 5 is a cross-sectional view of an undercut region in a channel in an article.
  • FIG. 6A is an end view of a flow control device in a channel in an article.
  • FIG. 6B is an overhead view ofthe flow control device of FIG. 6 A.
  • FIG. 6C is a cross-sectional view of a portion ofthe flow control device of FIG. 3A.
  • an optical system 10 for use in the invention includes a light source 12, an optical element 14, and a moveable stage 16.
  • the stage 16 is preferably moveable in three dimensions.
  • a partially completed article 18 mounted on the stage 16 includes a surface 20 and an optional surface feature 22.
  • a multiphoton-curable composition 24 is applied on the surface 20 or in the feature 22.
  • the light 26 from the light source 12 is then focused to a point P within the volume of the curable composition 24 to control the three-dimensional spatial distribution of light intensity within the composition to at least partially cure the composition 24.
  • light from a pulsed laser can be passed through a focusing optical train to focus the beam within the volume ofthe curable composition 24.
  • the focal point P can be scanned or translated in a three-dimensional pattern that corresponds to a desired shape.
  • the cured or partially cured portion ofthe curable composition 24 then creates a three-dimensional image of a desired shape.
  • the light source 12 in the system 10 may be any light source that produces multiphoton curing radiation - radiation capable of initiating a multiphoton curing process.
  • Suitable sources include, for example, femtosecond near-infrared titanium sapphire oscillators (for example, those available from Coherent under the trade designation MIRA OPTIMA 900-F) pumped by an argon ion laser (for example, those available from Coherent under the trade designation INNOVA).
  • femtosecond near-infrared titanium sapphire oscillators for example, those available from Coherent under the trade designation MIRA OPTIMA 900-F
  • an argon ion laser for example, those available from Coherent under the trade designation INNOVA.
  • any light source that provides sufficient intensity (to effect multiphoton absorption) at a wavelength appropriate for the photosensitizer (used in the photoreactive composition) can be utilized.
  • Such wavelengths can generally be in the range of about 300 to about 1500 nm; preferably, from about 600 to about 1100 nm; more preferably, from about 750 to about 850 nm.
  • Peak intensities can generally be from about 10 6 W/cm 2 .
  • the upper limit on pulse fluence is generally dictated by the ablation threshold ofthe photoreactive composition.
  • Q- switched Nd YAG lasers (for example, those available from Spectra-Physics under the trade designation QUANTA-RAY PRO), visible wavelength dye lasers (for example, those available from Spectra-Physics under the trade designation SIRAH pumped by a Spectra-Physics Quanta-Ray PRO), and Q-switched diode pumped lasers (for example, those available from Spectra-Physics under the trade designation FCBAR) can also be utilized.
  • Preferred light sources are near infrared pulsed lasers having a pulse length less than about 10 "8 second (more preferably, less than about 10 " 9 second; most preferably, less than about 10 "11 second).
  • Optical elements 14 useful in the system 10 include, for example, refractive optical elements (for example, lenses), reflective optical elements (for example, retroreflectors or focusing mirrors), diffractive optical elements (for example, gratings, phase masks, and holograms), polarizing optical elements (for example, linear polarizers and waveplates), diffusers, pockels cells, wave guides, and the like.
  • refractive optical elements for example, lenses
  • reflective optical elements for example, retroreflectors or focusing mirrors
  • diffractive optical elements for example, gratings, phase masks, and holograms
  • polarizing optical elements for example, linear polarizers and waveplates
  • diffusers for example, pockels cells, wave guides, and the like.
  • Such optical elements are useful for focusing, beam delivery, beam/mode shaping, pulse shaping, and pulse timing.
  • combinations of optical elements can be utilized, and other appropriate combinations will be recognized by those sldlled in the art.
  • the exposure system can include a scanning confocal microscope (for example, those available from BioRad under the trade designation MRC600) equipped with a 0.75 NA objective (such as, for example, those available from Zeiss under the trade designation 20X FLUAR).
  • Exposure times generally depend upon the type of exposure system used to cause image formation (and its accompanying variables such as numerical aperture, geometry of light intensity spatial distribution, the peak light intensity during the laser pulse (higher intensity and shorter pulse duration roughly correspond to peak light intensity)), as well as upon the nature ofthe multiphoton curable composition exposed.
  • Linear imaging or "writing” speeds generally can be about 5 to 100,000 microns/second using a laser pulse duration of about 10 "8 to 10 "1S second (preferably, about 10 "11 to 10 "14 second) and about 10 2 to 10 9 pulses per second (preferably, about 10 to 10 pulses per second).
  • the multiphoton curable radiation 26 induces a reaction in the curable composition that produces a material having solubility characteristics different from those ofthe unexposed curable composition.
  • the resulting pattern of cured material may then be developed by removing either the exposed or the unexposed regions with an appropriate solvent. Cured, complex, seamless tliree-dimensional structures can be prepared in this manner.
  • the resulting structures may have any suitable size and shape, but the method of the invention is particularly well suited for adding a microstructure to a microstructured surface of an article.
  • the structures may be formed on the surface of the article, or within or on a feature ofthe surface. Where such feature(s) exist on the surface of an article, for example, continuous or discontinuous patterns of depressions, protrusions, posts, or channels, the structures may be formed in the feature(s).
  • the feature(s) may be microscopic, where the term "microscopic" refers to features of small enough dimension so as to require an optic aid to the naked eye when viewed from any plane of view to determine its shape.
  • One criterion is found in Modem Optic Engineering by W. J.
  • microstructure means the configuration of features wherein at least 2 dimensions of the features are microscopic.
  • a multiphoton curable material 124 can be placed in a feature 122 in a surface 120 of an article 118.
  • the feature can be a cavity such as a cavity, depression or groove.
  • the multiphoton curable radiation 126 may be focused at any point P within the volume ofthe material to cure the material.
  • a curable composition can be easily cured from the bottom 123 ofthe feature 124 up, from the middle out, from the sidewall 125 in, or in whatever pattern is best for a particular application. For example, if a multiphoton curable material is placed in a cavity in a tooth, the curable material may be cured and hardened to form a dental filling.
  • a curable material 224 can be cured in a specific pattern to form a check valve-like flow control structure in a channel 222 in a surface 220 of an article 218.
  • the valve 230 includes a plurality of flexible extension regions 232 that extend upward from the bottom 231 ofthe channel 222. The regions 232 bend to allow fluid flow in a first direction indicated by an arrow F. Side buttresses 234 support an optional cover 240 (not shown in Fig. 3B). Ifthe fluid flow moves in a direction F ⁇ a stop bar 241 in the cover 240 limits the bending ofthe extension regions 232 to limit and/or stop flow in the direction F'.
  • a multiphoton curable composition may be applied to an aluminized mirrored layer 312 on a silicon wafer 314.
  • the multiphoton curable composition may then be cured in a stripe-like pattern to form a series of closely spaced lines 316.
  • the lines of cured material break the surface ofthe mirrored layer 312 into reflective strips interrupted by the lines 316, forming a diffraction grating 310.
  • a diffraction grating can be added to an already-fabricated mirror with little additional processing. No aluminum etching is required, and the curing process does not damage or oxidize the mirrored surface.
  • the grating construction may be used, for example, as an oscillating MEMS mirror grating in a spectrophotometer.
  • a multiphoton curable composition may be applied to a channel 362 in a surface 360 of an article 358.
  • the curable composition may be cured to form a beam 364 in the channel 362, which leaves an undercut region 366 for fluid flow.
  • the inventive method may also be used to fabricate movable parts on a molded article.
  • multiphoton curable material may be applied in a channel 422 in a surface 420 of an article 418.
  • the material may be cured to form a flapper-like flow control valve 430, which includes a central pivoting bar 432 and a flap 434.
  • the valve 430 pivots about the longitudinal axis ofthe bar 432 in retaining structures 436.
  • the flap 434 allows substantially free fluid movement.
  • a stopper bar 438 contacts a cover 440 (not shown in Fig. 6B) and moves the flap 434 into a position to restrict fluid flow.
  • Examples of other parts that may be fabricated by the method ofthe present invention include a micropump, wherein one or more valves can be added with an multiphoton curing process; an accelerometer, wherein a cantilevered beam can be added; and a channel device, wherein the top ofthe channel can be added.
  • Examples of parts that can be attached to the main body of a partially completed molded article include flapper valves, membranes, springs, bridges, cantilevers, flexures, covers, and caps.
  • Examples of parts that can be totally detached from the body of a partially- completed article include balls for ball valves, spheres, gears, hinges, and spinners.
  • a method of adding a structure can be performed on an optical fiber to add an optical device such as a lens, prism, diffuser, or diffractive element.
  • the multiphoton curable compositions that may be used to form the above- described structures include curable or non-curable species and a multiphoton photoinitiator system.
  • the multiphoton photoinitiator system includes a multiphoton photosensitizer, an electron acceptor, and an optional electron donor.
  • compositions ofthe invention can include curable species and optionally non- curable species.
  • Curable species include addition-polymerizable monomers and oligomers and addition-crosslinkable polymers (such as free-radically polymerizable or crosslinkable ethylenically-unsaturated species including, for example, acrylates, methacrylates, and certain vinyl compounds such as styrenes), as well as cationically-polymerizable monomers and oligomers and cationically-crosslinkable polymers (including, for example, epoxies, vinyl ethers, cyanate esters, etc.), and the like, and mixtures thereof.
  • addition-polymerizable monomers and oligomers and addition-crosslinkable polymers such as free-radically polymerizable or crosslinkable ethylenically-unsaturated species including, for example, acrylates, methacrylates, and certain vinyl compounds such as styrenes
  • cationically-polymerizable monomers and oligomers and cationically-crosslinkable polymers including
  • Suitable ethylenically-unsaturated species are described, for example, in U.S. Patent No. 5,545,676, and include mono-, di-, and poly-acrylates and methacrylates (for example, methyl acrylate, methyl methacrylate, ethyl acrylate, isopropyl methacrylate, n-hexyl acrylate, stearyl acrylate, allyl acrylate, glycerol diacrylate, glycerol triacrylate, ethyleneglycol diacrylate, diethyleneglycol diacrylate, triethyleneglycol dimethacrylate, 1, 3 -propanediol diacrylate, 1,3-propanediol dimethacrylate, trimethylolpropane triacrylate, 1,2,4-butanetriol trimethacrylate, 1,4- cyclohexanediol diacrylate, pentaerythritol triacrylate, pentaerythr
  • acrylated monomers such as those described in U.S. Patent No. 4,652,274, and acrylated oligomers such as those described in U.S. Patent No. 4, 642,126
  • unsaturated amides for example, methylene bis-acrylamide, methylene bis-methacrylamide, 1,6-hexamethylene bis-acrylamide, diethylene triamine tris-acrylamide and beta-methacrylaminoethyl methacrylate
  • vinyl compounds for example, styrene, diallyl phthalate, divinyl succinate, divinyl adipate, and divinyl phthalate; and the like; and mixtures thereof.
  • Suitable reactive polymers include polymers with pendant (meth)acrylate groups, for example, having from 1 to about 50 (meth)acrylate groups per polymer chain.
  • examples of such polymers include aromatic acid (meth)acrylate half ester resins such as those available under the trade designation SARBOX from Sartomer (for example, SARBOX 400, 401, 402, 404, and 405).
  • Other useful reactive polymers curable by free radical chemistry include those polymers that have a hydrocarbyl backbone and pendant peptide groups with free-radically polymerizable functionality attached thereto, such as those described in U.S. Patent No. 5,235,015. Mixtures of two or more monomers, oligomers, and/or reactive polymers can be used if desired.
  • Preferred ethylenically-unsaturated species include acrylates, aromatic acid (meth)acrylate half ester resins, and polymers that have a hydrocarbyl backbone and pendant peptide groups with free-radically polymerizable functionality attached thereto.
  • Suitable cationically-reactive species are described, for example, in U.S. Patent Nos. 5,998,495 and 6,025,406 and include epoxy resins.
  • Such materials broadly called epoxides, include monomeric epoxy compounds and epoxides ofthe polymeric type and can be aliphatic, alicyclic, aromatic, or heterocyclic. These materials generally have, on the average, at least 1 polymerizable epoxy group per molecule (preferably, at least about 1.5 and, more preferably, at least about 27).
  • the polymeric epoxides include linear polymers having terminal epoxy groups (for example, a diglycidyl ether of a polyoxyalkylene glycol), polymers having skeletal oxirane units (for example, polybutadiene polyepoxide), and polymers having pendant epoxy groups (for example, a glycidyl methacrylate polymer or copolymer).
  • the epoxides can be pure compounds or can be mixtures of compounds containing one, two, or more epoxy groups per molecule.
  • These epoxy-containing materials can vary greatly in the nature of their backbone and substituent groups.
  • the backbone can be of any type and substituent groups thereon can be any group that does not substantially interfere with cationic cure at room temperature.
  • permissible substituent groups include halogens, ester groups, ethers, sulfonate groups, siloxane groups, nitro groups, phosphate groups, and the like.
  • the molecular weight ofthe epoxy-containing materials can vary from about 58 to about 100,000 or more.
  • Useful epoxy-containing materials include those which contain cyclohexene oxide groups such as epoxycyclohexanecarboxylates, typified by 3,4- epoxycyclohexylmethyl-3 ,4-epoxycyclohexanecarboxylate, 3 ,4-epoxy-2- methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexane carboxylate, and bis(3,4- epoxy-6-methylcyclohexylmethyl) adipate.
  • cyclohexene oxide groups such as epoxycyclohexanecarboxylates, typified by 3,4- epoxycyclohexylmethyl-3 ,4-epoxycyclohexanecarboxylate, 3 ,4-epoxy-2- methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexane carboxylate, and bis(3,4- epoxy-6-methylcyclohexylmethyl) adipate.
  • epoxy-containing materials that are useful include glycidyl ether monomers ofthe formula
  • R' is alkyl or aryl and n is an integer of 1 to 6.
  • examples are glycidyl ethers of polyhydric phenols obtained by reacting a polyhydric phenol with an excess of a chlorohydrin such as epichlorohydrin (for example, the diglycidyl ether of 2,2- bis-(2,3-epoxypropoxyphenol)-propane). Additional examples of epoxides of this type are described in U.S. Patent No. 3,018,262, and in Handbook of Epoxy Resins, Lee and Neville, McGraw-Hill Book Co., New York (1967). Numerous commercially available epoxy resins can also be utilized.
  • epoxides that are readily available include octadecylene oxide, epichlorohydrin, styrene oxide, vinyl cyclohexene oxide, glycidol, glycidylmethacrylate, diglycidyl ethers of Bisphenol A (for example, those available under the trade designations EPON 828, EPON 825, EPON 1004, and EPON 1010 from Resolution Performance Products, formerly Shell Chemical Co., as well as those available under the trade designations DER 331, DER 332, and DER 334 from Dow Chemical Co.), vinylcyclohexene dioxide (for example, the compounds available under the trade designations ERL 4206 from Union Carbide Corp.), 3,4- epoxycyclohexylmethyl-3,4-epoxy cyclohexene carboxylate (for example, the compounds available under the trade designations ERL 4221, Cyracure UVR 6110 or UVR 6105 from Union Carbide Corp.), 3,4-epoxy-6
  • 1,4-butanediol diglycidyl ether of phenolformaldehyde novolak for example, those available under the trade designations DEN 431 and DEN 438 from Dow Chemical Co.
  • resorcinol diglycidyl ether for example, the compounds available under the trade designation KOPOXITE from Koppers Company, Inc.
  • bis(3,4- epoxycyclohexyl)adipate for example, those available under the trade designations ERL 4299 or UVR 6128, from Union Carbide Corp.
  • 2-(3,4-epoxycyclohexyl-5, 5- spiro-3,4-epoxy) cyclohexane-meta-dioxane for example, the compounds available under the trade designation ERL-4234 from Union Carbide Corp.
  • vinylcyclohexene monoxide 1,2-epoxyhexadecane for example, the compounds available under the trade designation UVR-6216 from Union Carbide Corp.
  • Performance Products polyglycol diepoxide (for example, HELOXY MODIFIER 32 from Resolution Performance Products), bisphenol F epoxides (for example, those available under the trade designations EPON 1138 from Resolution Performance Products or GY-281 from Ciba-Geigy Corp.), and 9,9-bis[4-(2,3-epoxypropoxy)- phenyl] fluorenone (for example, those available under the trade designation EPON 1079 from Resolution Performance Products).
  • polyglycol diepoxide for example, HELOXY MODIFIER 32 from Resolution Performance Products
  • bisphenol F epoxides for example, those available under the trade designations EPON 1138 from Resolution Performance Products or GY-281 from Ciba-Geigy Corp.
  • 9,9-bis[4-(2,3-epoxypropoxy)- phenyl] fluorenone for example, those available under the trade designation EPON 1079 from Resolution Performance Products.
  • Other useful epoxy resins comprise copolymers of acrylic acid esters of glycidol (such as glycidylacrylate and glycidylmethacrylate) with one or more copolymerizable vinyl compounds.
  • examples of such copolymers are 1:1 styrene- glycidylmethacrylate, 1 : 1 methylmethacrylate-glycidylacrylate, and a 62.5 :24: 13.5 methylmethacrylate-ethyl acrylate-glycidylmethacrylate.
  • epoxy resins are well known and contain such epoxides as epichlorohydrins, alkylene oxides (for example, propylene oxide), styrene oxide, alkenyl oxides (for example, butadiene oxide), and glycidyl esters (for example, ethyl glycidate).
  • alkylene oxides for example, propylene oxide
  • styrene oxide alkenyl oxides
  • alkenyl oxides for example, butadiene oxide
  • glycidyl esters for example, ethyl glycidate
  • Useful epoxy-functional polymers include epoxy-functional silicones such as those described in U.S. Patent No. 4,279,717, which are commercially available from the General Electric Company. These are polydimethylsiloxanes in which 1-20 mole % ofthe silicon atoms have been substituted with epoxyalkyl groups (preferably, epoxy cyclohexylethyl, as described in U.S. Patent No. 5,753,346.
  • Blends of various epoxy-containing materials can also be utilized. Such blends can comprise two or more weight average molecular weight distributions of epoxy-containing compounds (such as low molecular weight (below 200), intermediate molecular weight (about 200 to 10,000), and higher molecular weight (above about 10,000)).
  • the epoxy resin can contain a blend of epoxy-containing materials having different chemical natures (such as aliphatic and aromatic) or functionalities (such as polar and non-polar).
  • Other cationically-reactive polymers such as vinyl ethers and the like) can additionally be incorporated, if desired.
  • Preferred epoxies include aromatic glycidyl epoxies (such as the EPON resins available from Resolution Performance Products) and cycloaliphatic epoxies (such as ERL 4221 and ERL 4299 available from Union Carbide).
  • Suitable cationally-reactive species also include vinyl ether monomers, oligomers, and reactive polymers (for example, methyl vinyl ether, ethyl vinyl ether, tert-butyl vinyl ether, isobutyl vinyl ether, triethyleneglycol divinyl ether (for example, those available under the trade designation RAPI-CURE DVE-3 from International Specialty Products, Wayne, NJ), trimethylolpropane trivinyl ether (for example, those available under the trade designation TMPTVE from BASF Corp., Mount Olive, NJ), and those available under the trade designation VECTOMER divinyl ether resins from Allied Signal (for example, VECTOMER 2010, VECTOMER 2020, VECTOMER 4010, and VECTOMER 4020 and their equivalents available from other manufacturers)), and mixtures thereof.
  • VECTOMER divinyl ether resins from Allied Signal (for example, VECTOMER 2010, VECTOMER 2020, VECTOMER 4010, and VECTOMER
  • Blends in any proportion) of one or more vinyl ether resins and/or one or more epoxy resins can also be utilized.
  • Polyhydroxy-functional materials such as those described, for example, in U.S. Patent No. 5,856,373 (Kaisaki et al.)
  • epoxy- and/or vinyl ether-functional materials can also be utilized.
  • Non-curable species include, for example, reactive polymers whose solubility can be increased upon acid- or radical-induced reaction.
  • reactive polymers include, for example, aqueous insoluble polymers bearing ester groups that can be converted by photogenerated acid to aqueous soluble acid groups (for example, poly(4-tert-butoxycarbonyloxystyrene).
  • Non-curable species also include the chemically-amplified photoresists described by R. D. Allen, G. M. Wallraff, W. D. Hinsberg, and L. L. Simpson in "High Performance Acrylic Polymers for Chemically Amplified Photoresist Applications," J. Vac. Sci. Technol. B, 9, 3357 (1991).
  • THP tetrahydropyran methacrylate-based materials
  • THP-phenolic materials such as those described in U.S. Patent No. 3,779,778, t-butyl methacrylate-based materials such as those described by R. D Allen et al. in Proc. SPIE 2438. 474 (1995), and the like
  • depolymerization for example, polyphthalaldehyde-based materials
  • rearrangement for example, materials based on the pinacol rearrangements.
  • Multiphoton photosensitizers suitable for use in the multiphoton curable composition are capable of simultaneously absorbing at least two photons when exposed to radiation from an appropriate light source in the exposure system.
  • Preferred multiphoton photosensitizers have a two-photon absorption cross-section greater than that of fluorescein (that is, greater than that of 3 ', 6'- dihydroxyspiro[isobenzofuran-l(3H), 9'- [9H]xanthen]3-one).
  • the two photon absorption cross-section can be greater than about 50 x 10 "50 cm 4 sec/photon, as measured by the method described by C. Xu and W. W. Webb in J. Opt. Soc. Am. B, 13, 481 (1996) and WO 98/21521.
  • This method involves the comparison (under identical excitation intensity and photosensitizer concentration conditions) ofthe two-photon fluorescence intensity of the photosensitizer with that of a reference compound.
  • the reference compound can be selected to match as closely as possible the spectral range covered by the photosensitizer absorption and fluorescence.
  • an excitation beam can be split into two arms, with 50% ofthe excitation intensity going to the photosensitizer and 50% to the reference compound.
  • the relative fluorescence intensity ofthe photosensitizer with respect to the reference compound can then be measured using two photomultiplier tubes or other calibrated detector.
  • the fluorescence quantum efficiency of both compounds can be measured under one- photon excitation.
  • the two-photon absorption cross-section ofthe photosensitizer ( ⁇ sam ), is equal to ⁇ re f K (Isam/IrefX ⁇ sam ⁇ ref), wherein ⁇ re f is the two-photon absorption cross-section ofthe reference compound, I sam is the fluorescence intensity ofthe photosensitizer, I ref is the fluorescence intensity ofthe reference compound, ⁇ sam is the fluorescence quantum efficiency ofthe photosensitizer, ⁇ ref is the fluorescence quantum efficiency ofthe reference compound, and K is a correction factor to account for slight differences in the optical path and response ofthe two detectors.
  • K can be determined by measuring the response with the same photosensitizer in both the sample and reference arms. To ensure a valid measurement, the clear quadratic dependence ofthe two-photon fluorescence intensity on excitation power can be confirmed, and relatively low concentrations of both the photosensitizer and the reference compound can be utilized (to avoid fluorescence reabsorption and photosensitizer aggregration effects).
  • the photosensitizer is not fluorescent, the yield of electronic excited states can to be measured and compared with a known standard.
  • various methods of measuring excited state yield are known (including, for example, transient absorbance, phosphorescence yield, photoproduct formation or disappearance of photosensitizer (from photoreaction), and the like).
  • the two-photon absorption cross-section ofthe photosensitizer is greater than about 1.5 times that of fluorescein (or, alternatively, greater than about 75 x 10 "50 cm 4 sec/photon, as measured by the above method); more preferably, greater than about twice that of fluorescein (or, alternatively, greater than about 100 x 10 "50 cm 4 sec/photon); most preferably, greater than about three times that of fluorescein
  • the photosensitizer is soluble in the reactive species (if the reactive species is liquid) or is compatible with the reactive species and with any binders (as described below) that are included in the multiphoton curable composition.
  • the photosensitizer is also capable of sensitizing 2-methyl-4,6- bis(trichloromethyl)-s-triazine under continuous irradiation in a wavelength range that overlaps the single photon absorption spectrum ofthe photosensitizer (single photon absorption conditions), using the test procedure described in U.S. Pat. No. 3,729,313.
  • a standard test solution can be prepared having the following composition: 5.0 parts of a 5% (weight by volume) solution in methanol of 45,000-55,000 molecular weight, 9.0-13.0% hydroxyl content polyvinyl butyral (for example, those available under the trade designation BUTVAR B76 from Monsanto); 0.3 parts trimethylolpropane trimethacrylate; and 0.03 parts 2-methyl-4,6-bis(trichloromethyl)- s-triazine (see Bull. Chem. Soc. Japan, 42, 2924-2930 (1969)). To this solution can be added 0.01 parts ofthe compound to be tested as a photosensitizer.
  • the resulting solution can then be knife-coated onto a 0.05 mm clear polyester film using a knife orifice of 0.05 mm, and the coating can be air dried for about 30 minutes.
  • a 0.05 mm clear polyester cover film can be carefully placed over the dried but soft and tacky coating with minimum entrapment of air.
  • the resulting sandwich construction can then be exposed for three minutes to 161,000 Lux of incident light from a tungsten light source providing light in both the visible and ultraviolet range (such as that produced from a FCH 650 W quartz-iodine lamp, available from General Electric). Exposure can be made through a stencil to provide exposed and unexposed areas in the construction.
  • the cover film can be removed, and the coating can be treated with a finely divided colored powder, such as a color toner powder ofthe type conventionally used in xerography.
  • a finely divided colored powder such as a color toner powder ofthe type conventionally used in xerography.
  • the tested compound is a photosensitizer
  • the trimethylolpropane trimethacrylate monomer will be polymerized in the light- exposed areas by the light-generated free radicals from the 2-methyl-4,6- bis(trichloromethyl)-s-triazine. Since the polymerized areas will be essentially tack- free, the colored powder will selectively adhere essentially only to the tacky, unexposed areas ofthe coating, providing a visual image corresponding to that in the stencil.
  • a photosensitizer can also be selected based in part upon shelf stability considerations. Accordingly, selection of a particular photosensitizer can depend to some extent upon the particular reactive species utilized (as well as upon the choices of electron donor
  • Particularly preferred multiphoton photosensitizers include those exhibiting large multiphoton absorption cross-sections, such as Rhodamine B (that is, N-[9-(2- carboxyphenyl)-6-(diethylamino)-3H-xanthen-3-ylidene]-N-ethylethanaminium chloride and the hexafluoroantimonate salt of Rhodamine B) and the four classes of photosensitizers described, for example, by Marder and Perry et al.WO 98/21521 and WO 99/53242.
  • Rhodamine B that is, N-[9-(2- carboxyphenyl)-6-(diethylamino)-3H-xanthen-3-ylidene]-N-ethylethanaminium chloride and the hexafluoroantimonate salt of Rhodamine B
  • the four classes can be described as follows: (a) molecules in which two donors are connected to a conjugated ⁇ -electron bridge; (b) molecules in which two donors are connected to a conjugated ⁇ -election bridge which is substituted with one or more electron accepting groups; (c) molecules in which two acceptors are connected to a conjugated ⁇ -electron bridge; and (d) molecules in which two acceptors are connected to a conjugated ⁇ -election bridge which is substituted with one or more electron donating groups (where "bridge” means a molecular fragment that connects two or more chemical groups, “donor” means an atom or group of atoms with a low ionization potential that can be bonded to a conjugated ⁇ -electron bridge, and "acceptor” means an atom or group of atoms with a high electron affinity that can be bonded to a conjugated ⁇ -electron bridge).
  • photosensitizers include the following:
  • the four classes of photosensitizers described above can be prepared by reacting aldehydes with ylides under standard Wittig conditions or by using the McMurray reaction, as detailed in WO 98/21521.
  • Suitable election acceptors for the multiphoton curable compositions are capable of being photosensitized by accepting an electron from an electronic excited state ofthe multiphoton photosensitizer, resulting in the formation of at least one free radical and/or acid.
  • electron acceptors include iodonium salts (for example, diaryliodonium salts), chloromethylated triazines (for example, 2-methyl-4,6- bis(trichloromethyl)-s-triazine, 2,4,6-tris(tiichloromethyl)-s-triazine, and 2-aryl-4,6- bis(trichloromethyl)-s-triazine), diazonium salts (for example, phenyldiazonium salts optionally substituted with groups such as alkyl, alkoxy, halo, or nitro), sulfonium salts (for example, triarylsulfonium salts optionally substituted with alkyl or alkoxy groups, and optionally having 2,2
  • the electron acceptor is preferably soluble in the reactive species and is preferably shelf-stable (that is, does not spontaneously promote reaction ofthe reactive species when dissolved therein in the presence ofthe photosensitizer and an election donor compound). Accordingly, selection of a particular electron acceptor can depend to some extent upon the particular reactive species, photosensitizer, and election donor compound chosen, as described above.
  • Suitable iodonium salts include those described in U.S. Patent Nos. 5,545,676, 3,729,313, 3,741,769, 3,808,006, 4,250,053 and 4,394,403.
  • the iodonium salt can be a simple salt (for example, containing an anion such as C1-, Br-, I- or C 4 H 5 SO 3 -) or a metal complex salt (for example, containing SbF 6 -, PF 6 -, BF 4 -, tetrakis(perfluorophenyl)borate, SbF 5 OH- or AsF 6 -). Mixtures of iodonium salts can be used if desired.
  • aromatic iodonium complex salt electron acceptors include diphenyliodonium tetrafluoroborate; di(4-methylphenyl)iodonium tetrafluoroborate; phenyl-4-methylphenyliodonium tetrafluoroborate; di(4-heptylphenyl)iodonium tetrafluoroborate; di(3-nitrophenyl)iodonium hexafluorophosphate; di(4- chlorophenyl)iodonium hexafluorophosphate; di(naphthyl)iodonium tetrafluoroborate; di(4-trifluoromethylphenyl)iodonium tetrafluoroborate; diphenyliodonium hexafluorophosphate; di(4-methylphenyl)iodonium hexafluorophosphate; diphenyliodonium hexafluoroar
  • Aromatic iodonium complex salts can be prepared by metathesis of corresponding aromatic iodonium simple salts (such as, for example, diphenyliodonium bisulfate) in accordance with the teachings of Beringer et al., J. Am. Chem. Soc. 81, 342 (1959).
  • Preferred iodonium salts include diphenyliodonium salts (such as diphenyliodonium chloride, diphenyliodonium hexafluorophosphate, and diphenyliodonium tetrafluoroborate), diaryliodonium hexafluoroantimonate (for example, those available under the trade designation S ARC AT SR 1012 from Sartomer Company), and mixtures thereof.
  • diphenyliodonium salts such as diphenyliodonium chloride, diphenyliodonium hexafluorophosphate, and diphenyliodonium tetrafluoroborate
  • diaryliodonium hexafluoroantimonate for example, those available under the trade designation S ARC AT SR 1012 from Sartomer Company
  • Suitable anions, X-, for the sulfonium salts (and for any ofthe other types of electron acceptors) include a variety of anion types such as, for example, imide, methide, boron-centered, phosphorous-centered, antimony-centered, arsenic-centered, and aluminum-centered anions.
  • Suitable imide and methide anions include (C 2 F 5 SO 2 )2N-, (C 4 F 9 SO 2 )2N-, (C 8 F ⁇ 7 SO 2 ) 3 C-, (CF 3 SO 2 ) 3 C-, (CF 3 SO 2 ) 2 N-, (C 4 F 9 SO2)3C-, (CF 3 SO2)2(C4F 9 SO 2 )C-, (CF 3 S ⁇ 2)(C4F 9 S ⁇ 2)N-,
  • R f SO 2 ) 3 C " wherein R f is a perfluoroalkyl radical having from 1 to about 4 carbon atoms.
  • boron-centered anions include F 4 B " , (3,5-bis(CF3)C 6 H 3 ) 4 B-, (C 6 F 5 ) 4 B-, (p-CF 3 C 6 H 4 ) 4 B-, (m-CF 3 C 6 H 4 ) 4 B-, (p-FC 6 H 4 ) 4 B", (C 6 F 5 ) 3 (CH 3 )B-, (C 6 F 5 ) 3 (n-C 4 H 9 )B-, (p-
  • boron-centered anions generally contain 3 or more halogen-substituted aromatic hydrocarbon radicals attached to boron, with fluorine being the most preferred halogen.
  • Illustrative, but not limiting, examples ofthe preferred anions include (3,5-bis(CF3)CgH3) B", (C6F5) 4 B",
  • Suitable anions containing other metal or metalloid centers include, for example, (3,5-bis(CF 3 )C 6 H 3 ) 4 Al-, (C 6 F 5 ) 4 A1-, (C 6 F 5 ) 2 F 4 P-, (C 6 F 5 )F 5 P-, F 6 P “ , (CgF5)F5Sb “ , F ⁇ Sb “ , (HO)F 5 Sb “ , and F6As “ .
  • the anion, X- is selected from tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, hexafluoroantimonate, and hydroxypentafluoroantimonate (for example, for use with cationically-reactive species such as epoxy resins).
  • Suitable sulfonium salt electron acceptors include: triphenylsulfonium tetrafluoroborate methyldiphenylsulfonium tetrafluoroborate dimethylphenylsulfonium hexafluorophosphate triphenylsulfonium hexafluorophosphate triphenylsulfonium hexafluoroantimonate diphenylnaphthylsulfonium hexafluoroarsenate tritolysulfonium hexafluorophosphate anisyldiphenylsulfonium hexafluoroantimonate
  • Preferred sulfonium salts include triaryl-substituted salts such as triarylsulfonium hexafluoroantimonate (for example, those available under the trade designation S ARC AT SRI 010 from Sartomer Company), triarylsulfonium hexafluorophosphate (for example, those available under the trade designation S ARC AT SR 1011 from Sartomer Company), and triarylsulfonium hexafluorophosphate (for example, those available under the trade designation SARCAT KI85 from Sartomer Company).
  • triarylsulfonium hexafluoroantimonate for example, those available under the trade designation S ARC AT SRI 010 from Sartomer Company
  • S ARC AT SR 1011 for example, those available under the trade designation S ARC AT SR 1011 from Sartomer Company
  • SARCAT KI85 from Sartomer Company
  • Useful azinium salts include those described in U.S. Patent No. 4,859,572 which include an azinium moiety, such as a pyridinium, diazinium, or triazinium moiety.
  • the azinium moiety can include one or more aromatic rings, typically carbocyclic aromatic rings (for example, quinolinium, isoquinolinium, benzodiazinium, and naphthodiazonium moieties), fused with an azinium ring.
  • a quaternizing substituent of a nitrogen atom in the azinium ring can be released as a free radical upon electron transfer from the electronic excited state ofthe photosensitizer to the azinium electron acceptor.
  • the quaternizing substituent is an oxy substituent.
  • the oxy substituent, -O-T, which quaternizes a ring nitrogen atom ofthe azinium moiety can be selected from among a variety of synthetically convenient oxy substituents.
  • the moiety T can, for example, be an alkyl radical, such as methyl, ethyl, butyl, and so forth.
  • the alkyl radical can be substituted.
  • aralkyl for example, benzyl and phenethyl
  • sulfoalkyl for example, sulfomethyl radicals can be useful.
  • T can be an acyl radical, such as an -OC(O)-T 1 radical, where T can be any ofthe various alkyl and aralkyl radicals described above.
  • T 1 can be an aryl radical, such as phenyl or naphthyl. The aryl radical can in turn be substituted.
  • T 1 can be a tolyl or xylyl radical.
  • T typically contains from 1 to about 18 carbon atoms, with alkyl moieties in each instance above preferably being lower alkyl moieties and aryl moieties in each instance preferably containing about 6 to about 10 carbon atoms.
  • oxy substituent -O-T
  • azinium nuclei need include no substituent other than the quaternizing substituent. However, the presence of other substituents is not detrimental to the activity of these electron acceptors.
  • Useful triarylimidazolyl dimers include those described in U.S. Patent No. 4,963,471.
  • dimers include, for example, 2-(o-chlorophenyl)-4,5-bis(m- methoxyphenyl)- 1,1' -biimidazole; 2,2' -bis(o-chlorophenyl)-4,4' ,5 ,5 ' -tetraphenyl- 1,1' -biimidazole; and 2,5-bis(o-chlorophenyl)-4-[3 ,4-dimethoxyphenyl] -1,1'- biimidazole.
  • Preferred electron acceptors include photoacid generators, such as iodonium salts (more preferably, aryliodonium salts), chloromethylated triazines, sulfonium salts, and diazonium salts. More preferred are aryliodonium salts and chloromethylated triazines.
  • Electron donor compounds useful in the multiphoton photosensitizer system of the multiphoton curable composition are compounds (other than the photosensitizer itself) that are capable of donating an electron to an electronic excited state ofthe photosensitizer.
  • the electron donor compounds preferably have an oxidation potential that is greater than zero and less than or equal to that of p- dimethoxybenzene.
  • the oxidation potential is between about 0.3 and 1 V vs. a standard saturated calomel electrode ("S.C.E.”).
  • the electron donor compound is also preferably soluble in the reactive species and is selected based in part upon shelf stability considerations (as described above).
  • Suitable donors are generally capable of increasing the speed of cure or the image density of a photoreactive composition upon exposure to light ofthe desired wavelength.
  • electron donor compounds suitable for use with particular photosensitizers and election acceptors can be selected by comparing the oxidation and reduction potentials ofthe three components (as described, for example, in U.S.
  • Patent No. 4,859,572 Such potentials can be measured experimentally (for example, by the methods described by R. J. Cox, Photographic Sensitivity. Chapter 15, Academic Press (1973)) or can be obtained from references such as N. L. Weinburg, Ed., Technique of Electioorganic Synthesis Part II Techniques of Chemistry, Vol. V (1975), and C. K. Mann and K. K. Barnes, Electrochemical Reactions in Nonaqueous Systems (1970). The potentials reflect relative energy relationships and can be used in the manner described below to guide electron donor compound selection.
  • the photosensitizer When the photosensitizer is in an electronic excited state, an electron in the highest occupied molecular orbital (HOMO) ofthe photosensitizer has been lifted to a higher energy level (namely, the lowest unoccupied molecular orbital (LUMO) ofthe photosensitizer), and a vacancy is left behind in the molecular orbital it initially occupied.
  • the electron acceptor can accept the election from the higher energy orbital, and the electron donor compound can donate an electron to fill the vacancy in the originally occupied orbital, provided that certain relative energy relationships are satisfied.
  • the reduction potential ofthe electron acceptor is less negative (or more positive) than that ofthe photosensitizer, an electron in the higher energy orbital of the photosensitizer is readily transferred from the photosensitizer to the lowest unoccupied molecular orbital (LUMO) ofthe election acceptor, since this represents an exothermic process. Even if the process is instead slightly endothermic (that is, even if the reduction potential ofthe photosensitizer is up to 0.1 volt more negative than that ofthe electron acceptor) ambient thermal activation can readily overcome such a small barrier.
  • the reduction potential ofthe photosensitizer can be up to 0.2 V (or more) more negative than that of a second-to-react electron acceptor, or the oxidation potential ofthe photosensitizer can be up to 0.2 V (or more) more positive than that of a second-to-react electron donor compound.
  • Suitable electron donor compounds include, for example, those described by D. F. Eaton in Advances in Photochemistry, edited by B. Voman et al., Volume 13, pp. 427-488, John Wiley and Sons, New York (1986); U.S. Patent Nos. 6,025,406, and 5,545,676.
  • the electron donor compound can be unsubstituted or can be substituted with one or more non- interfering substituents.
  • Particularly preferred electron donor compounds contain an election donor atom (such as a nitrogen, oxygen, phosphorus, or sulfur atom) and an abstractable hydrogen atom bonded to a carbon or silicon atom alpha to the electron donor atom.
  • Preferred amine electron donor compounds include alkyl-, aryl-, alkaryl- and aralkyl-amines (for example, methylamine, ethylamine, propylamine, butylamine, triethanolamine, amylamine, hexylamine, 2,4-dimethylaniline, 2,3-dimethylaniline, o- , m- and p-toluidine, benzylamine, aminopyridine, N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N'-dibenzylethylenediamine, N,N' -diethyl- 1 ,3- propanediamine, N,N'-diethyl-2 -butene- 1 ,4-diamine, N,N'-dimethyl- 1,6- hexanediamine, piperazine, 4,4'-trimethylenedipiperidine, 4,4'-ethylenedipiperidine, p-N
  • Tertiary aromatic alkylamines particularly those having at least one electron- withdrawing group on the aromatic ring, have been found to provide especially good shelf stability. Good shelf stability has also been obtained using amines that are solids at room temperature. Good photographic speed has been obtained using amines that contain one or more ulolidinyl moieties.
  • Preferred amide electron donor compounds include N,N-dimethylacetamide,
  • Preferred alkylarylborate salts include Ar 3 B " (n-C 4 H 9 )N + (C 2 H 5 ) 4
  • Ar 3 B " -(sec-C 4 H 9 )N + (CH 3 ) 3 (CH 2 ) 2 CO 2 (CH 2 ) 2 CH 3 Ar 3 B--(sec-C 4 H 9 )N + (C 6 H ⁇ 3 ) 4 Ar 3 B " -(C 4 H 9 )N + (C 8 H 17 ) 4 Ar 3 B " -(C 4 H 9 )N + (CH 3 ) 4 (p-CH 3 O-C 6 H ) 3 B " (n-C 4 H 9 )N + (n-C 4 H 9 ) 4 Ar 3 B " -(C 4 H 9 )N + (CH 3 ) 3 (CH 2 ) 2 OH
  • Ar is phenyl, naphthyl, substituted (preferably, fluoro-substituted) phenyl, substituted naphthyl, and like groups having greater numbers of fused aromatic rings, as well as tetramethylammonium n-butyltriphenylborate and tetrabutylammonium n-hexyl-tris(3-fluorophenyl)borate (available under the trade designations CGI 437 and CGI 7460 from Ciba Specialty Chemicals Corporation), and mixtures thereof.
  • Suitable ether electron donor compounds include 4,4'-dimethoxybiphenyl, 1 ,2,4-trimethoxybenzene, 1,2,4,5-tetramethoxybenzene, and the like, and mixtures thereof.
  • Suitable urea electron donor compounds include N,N'-dimethylurea, N,N- dimethylurea, N,N'-diphenylurea, tetramethylthiourea, tetiaethylthiourea, tetra-n- butylthiourea, N,N-di-n-butylthiourea, N,N'-di-n-butylthiourea, N,N- diphenylthiourea, N,N'-diphenyl-N,N'-diethylthiourea, and the like, and mixtures thereof.
  • Preferred electron donor compounds for free radical-induced reactions include amines that contain one or more julolidinyl moieties, alkylarylborate salts, and salts of aromatic sulfmic acids.
  • the electron donor compound can also be omitted, if desired (for example, to improve the shelf stability ofthe photoreactive composition or to modify resolution, contrast, and reciprocity).
  • Preferred electron donor compounds for acid-induced reactions include 4- dimethylaminobenzoic acid, ethyl 4-dimethylaminobenzoate, 3- dimethylaminobenzoic acid, 4-dimethylaminobenzoin, 4- dimethylaminobenzaldehyde, 4-dimethylaminobenzonitrile, 4- dimethylaminophenethyl alcohol, and 1,2,4-trimethoxybenzene.
  • the curable and optionally non-curable species, multiphoton photosensitizers, electron donor compounds, and electron acceptors can be prepared by the methods described above or by other methods known in the art, and many are commercially available. These components can be combined under "safe light” conditions using any order and manner of combination (optionally, with stirring or agitation), although it is sometimes preferable (from a shelf life and thermal stability standpoint) to add the electron acceptor last (and after any heating step that is optionally used to facilitate dissolution of other components).
  • Solvent can be used, if desired, provided that the solvent is chosen so as to not react appreciably with the components ofthe composition. Suitable solvents include, for example, acetone, dichloromethane, and acetonitrile.
  • the multiphoton curable composition contains from about 5% to about 99.19% by weight of one or more reactive species (preferably, from about 10% to about 95%; more preferably, from about 20% to about 80%); from about 0.01% to about 10%) by weight of one or more photosensitizers (preferably, from about 0.1 % to about 5%; more preferably, from about 0.2% to about 2%); up to about 10%> by weight of one or more electron donor compounds (preferably, from about 0.1 % to about 10%; more preferably, from about 0.1 % to about 5%); and from about 0.1%) to about 10%) by weight of one or more electron acceptors (preferably, from about 0.1% to about 5%>) based upon the total weight of solids in the composition (that is, the total weight of components other than solvent).
  • adjuvants can be included in the multiphoton curable compositions, depending upon the desired end use.
  • Suitable adjuvants include solvents, diluents, resins, binders, plasticizers, pigments, dyes, inorganic or organic reinforcing or extending fillers (at preferred amounts of about 10% to 90% by weight based on the total weight ofthe composition), thixotropic agents, indicators, inhibitors, stabilizers, ultraviolet absorbers, medicaments (for example, leachable fluorides), and the like.
  • solvents diluents, resins, binders, plasticizers, pigments, dyes, inorganic or organic reinforcing or extending fillers (at preferred amounts of about 10% to 90% by weight based on the total weight ofthe composition), thixotropic agents, indicators, inhibitors, stabilizers, ultraviolet absorbers, medicaments (for example, leachable fluorides), and the like.
  • thixotropic agents indicators, inhibitors, stabilizers, ultraviolet absorbers, medicament
  • nonreactive polymeric binders in the compositions in order, for example, to control viscosity and to provide film-forming properties.
  • Such polymeric binders can generally be chosen to be compatible with the reactive species.
  • polymeric binders that are soluble in the same solvent that is used for the reactive species, and that are free of functional groups that can adversely affect the course of reaction ofthe reactive species can be utilized.
  • Binders can be of a molecular weight suitable to achieve desired film- forming properties and solution rheology (for example, molecular weights between about 5,000 and 1,000,000 daltons; preferably between about 10,000 and 500,000 daltons; more preferably, between about 15,000 and 250,000 daltons).
  • Suitable polymeric binders include, for example, polystyrene, poly(methyl methacrylate), poly(styrene)-co-(acrylonitrile), cellulose acetate butyrate, and the like.
  • Suitable nonreactive polymeric binders may be included in the compositions up to 90%>; preferably up to 75%; more preferably up to 60%) by weight ofthe total composition.
  • the resulting photoreactive compositions can be applied on a substrate, if desired, by any of a variety of application methods.
  • the compositions may be applied by coating methods such as knife, bar, reverse roll, and knurled roll coating, or by application methods such as dipping, immersion, spraying, brushing, curtain coating and the like. Alternatively, the composition can be applied drop-wise.
  • the substrate can be chosen from a wide variety of films, sheets, and other surfaces, depending upon the particular application and the method of exposure to be utilized.
  • Triethyl phosphite 300 g, 2.10 mol was added, and the reaction was heated to vigorous reflux with stirring for 48 hours under nitrogen atmosphere. The reaction mixture was cooled and the excess triethyl phosphite was removed under vacuum using a Kugelrohr apparatus. Upon heating to 100 C at 0.1 mm Hg, a clear oil resulted. Upon cooling, the desired product solidified and was suitable for use directly in the next step. The 1H NMR spectrum ofthe product was consistent with the desired product. Recrystallization from toluene yielded colorless needles.
  • Example 2 Reflective Diffraction Grating
  • a multiphoton curable composition was prepared as follows.
  • a stock solution was prepared by adding 30 g PMMA (Aldrich) to 120 g dioxane, and mixing overnight on a roller.
  • a second solution was prepared by adding 1 g of MPS I to 35 g Sartomer SR9008 , then heating and stirring to partially dissolve the photosensitizer. The second solution was added to the stock solution and allowed to mix overnight on a roller.
  • To this solution was added 35 g Sartomer SR368 and the solution allowed to mix overnight on a roller, providing masterbatch B.
  • diaryliodonium hexafluoroantimonate SRI 012, Sartomer
  • 0.1 g alkyltriarylborate salt CGI 7460, Ciba Specialties
  • the multiphoton curable composition diluted to about 4 weight % solids, was coated onto an aluminized silicon mirror using drops from a syringe to form discrete islands. These islands were then dried for 10 min at 80 C in an air oven to form films extending over areas a few mm in diameter.
  • a 40x microscope objective with focal length of 4.48 mm and numerical aperture of .65, was used to focus the laser beam at the surface ofthe aluminized mirror after passing through the dried resin film.
  • the grating pattern was produced by moving the completed aluminized mirror under the fixed laser beam to draw a series of equally spaced lines.
  • New England affiliated Technologies (NEAT), Inc., (Lawrence, MA) type 310 translation stages were mounted in a crossed configuration to allow scanning in 2 orthogonal directions, each of which was orthogonal to the laser beam.
  • the mirror was mounted on the translation stage assembly and scanned under the laser beam to polymerize the resin by means of the 2-photon interaction, forming a series of parallel lines of polymerized resin with a period of about 19.1 micrometers
  • the resin pattern was developed by rinsing first in dimethylformamide (DMF), to remove unexposed resin, and second, in isopropyl alcohol, to remove remaining residues.
  • the mirrors were then dried with a stream of nitrogen.
  • the polymerized resin lines interrupt the continuous mirror surface, forming a reflective 5 diffraction grating. Thus a diffraction grating can be added to an already-fabricated mirror with little additional processing.
  • the grating area can be of any size up to that ofthe entire mirror, and can be added in any location or orientation by choice of mounting location and stage control program content.
  • the organic solvents used to develop the polymerized pattern are o not corrosive, so there is no chance of chemically damaging the exposed aluminum thin film used for the reflective surface. No aluminum etching is required.
  • the drying temperature is too low to cause significant oxidation, and could be reduced substantially, if required, by extending the drying time.
  • the width ofthe resin lines depends on laser beam intensity, speed of motion 5 of the focal point with respect to the mirror surface, and the location of the focal point relative to the surface ofthe mirror.
  • the mirror was mounted on a pair of NEAT, Inc., type 310 translation stages operated in an x-y configuration in a plane orthogonal to the beam. These stages were used to move the mirror under the stationary laser beam at about 5.08 mm/second.
  • Neutral density filters were used to 0 adjust average beam power to about 13 mW or 50 mW. Scans at 50 mW resulted in line widths of 4.5 to 5.2 micrometers; scans at 13 mW resulted in line widths of about 3.7 micrometers.
  • the patterns written as described above visually display the iridescent appearance associated with a grating, which spreads white light into a spectrum by 5 bending longer wavelengths to a greater degree than shorter wavelengths.
  • the reflections ofthe primary beam and the first few diffraction orders were projected onto a white screen located about 71.8 cm from the mirror.
  • the above formula gives and angle of 1.90° to the first order maximum, and 3.79° to the second order maximum. Measurement on the screen gives the same angles as 1.90° and 3.79°, respectively, demonstrating that a well-behaved diffraction grating has been produced.
  • Example 2 The same equipment, materials, and techniques described in Example 2, above, have been used to fabricate a reflective diffraction grating on a micro- electromechanical system (MEMS) mirror used as an electrically-driven optical scanner.
  • MEMS micro- electromechanical system
  • This technique easily allows fabrication of mirrors at frequencies from hundreds of hertz up to tens of kilohertz, allowing for rapid acquisition of spectral data.
  • Typical mirrors used in this example had driving frequencies of from about 10 kHz to about 15 kHz.
  • the mirror and its base were etched from single crystal silicon using well-known wet anisotropic etching techniques.
  • the surface ofthe mirror was vacuum-coated with aluminum, for reflectivity and electrical conductivity.
  • the mirror base was similarly etched from a thicker silicon wafer. Here a flat-bottomed cavity was anisotropically wet etched to allow the mirror to pivot on its torsion arms when power was applied. An aluminum electrode was formed on either side ofthe cavity, running parallel to the torsion arms.
  • the wafer containing the mirror was centered on the cavity, aligned as specified, and bonded to the base with epoxy. Wiring was connected to the 2 base electrodes and the mirror electrode to allow them to be powered. Typically, the mirror was grounded, and the base electrodes alternate between ground and some bias voltage, the biased electrode attracting the grounded mirror toward itself. The bias and ground potentials were switched back and forth between the two electrodes at the resonant frequency ofthe mirror-torsion arm unit, producing a useful oscillatory amplitude. A simple drive circuit to accomplish this was mounted externally in this example, but could be incorporated almost completely into the silicon, forming an integrated circuit.
  • a 40x microscope objective with focal length of 4.48 mm and numerical aperture of .65, was used to focus the laser beam at the surface ofthe aluminized mirror after passing through the dried resin film.
  • the grating pattern was produced by moving the completed aluminized mirror under the fixed laser beam to draw a series of equally spaced lines.
  • NEAT, Inc. type 310 translation stages were mounted in a crossed configuration to allow scanning in 2 orthogonal directions, each of which was orthogonal to the laser beam.
  • the mirror was mounted on the translation stage assembly and scanned under the laser beam at 5.08 mm/second to polymerize the resin by means ofthe 2-photon interaction, forming a series of parallel lines of polymerized resin with a period of 19.1 micrometers.
  • the resin pattern was developed by rinsing first in propylene -glycol -methyl
  • a resin stock solution was prepared by talcing 30 grams of PMMA (135K molecular weight) and dissolving it in 120 grams of dichloromethane. An additional 35 grams of Sartomer SR-368 was added along with Sartomer SR-9008.
  • a second stock solution of initiator components was also made.
  • a two photon dye, bis-[4-(diphenylamino)styryl]-l,4-(dimethoxy)benzene MPS 1, 150 mg
  • diaryliodonium hexafluoroantimonate SR-1012, Sartomer, (250 mg)
  • organic borate CGI- 7460, Ciga Specialties (250 mg)
  • One ofthe cavities filled with unpolymerized resin was then irradiated using as a light source a diode-pumped Ti-sapphire laser operating at 100 MHz, 100 femtosecond pulses, 800 nm, average light intensity 109 mW, focussed using a filled 10X objective (numerical aperture of 0.25).
  • the uncured resin was cured by placing the focal point ofthe laser beam at the interface between the unpolymerized resin and the bottom ofthe cavity, and scanning the focal point in 240 lines 1.2 mm long, spaced 5 ⁇ m apart, generating a 1.2 mm square pattern.
  • the 1.2 mm square pattern was repeatedly scanned, moving the focal point 40 ⁇ m further away from the bottom ofthe cavity with each successive scan, until resin was cured up to about half the depth ofthe cavity (slightly less than 1 mm, Example A).
  • a second cavity filled with uncured resin was cured by placing the focal point ofthe laser beam at the interface between the unpolymerized resin and air (the top ofthe cavity).
  • a 1.2 mm square pattern repeatedly scanned with the focused laser as before, moving the focal point about 40 ⁇ m closer to the bottom ofthe cavity with each successive scan, until resin was cured all the way to the bottom ofthe cavity (Example B).
  • the resulting article containing cavities with partially cured resin was immersed in dimethylformamide for 2 hours to remove any unreacted resin.
  • the mold was disassembled, and the height and width ofthe resulting plug (height measured along the axis ofthe cylindrical cavity) was measured under a microscope (see table below), showing that the cavity irradiated from the bottom up was cured in the bottom half but not the top, and the cavity irradiated top to bottom was cured through the full depth ofthe cavity.
  • Examples C, D, E, F (Comparative).
  • a second mold was filled with curable resin as above.
  • curable resin in four cavities were irradiated using a He-Cd laser operating continuously at 442 nm (within the 1 -photon absorption band ofthe multiphoton photosensitizer), 2 mW, beam diameter 3 mm, such that each curable resin-filled cavity received twice the dose ofthe previous curable resin-filled cavity, starting at 71 mJ/cm 2 and ruiming to 566 J/cm 2 .
  • the resulting article containing cavities with partially cured resin were immersed in dimethylformamide for 2 hours to remove any unreacted resin.
  • the mold After rinsing with isopropyl alcohol and dried, the mold was disassembled, and the height and width of each plug (height measured along the axis ofthe cylindrical cavity) was measured under a microscope (see table below). The data shows that the comparative examples cured only from the top down, and that curing the resin in the bottom cavity occurs only after resin closer to the light source is cured first.

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  • Medicinal Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Optics & Photonics (AREA)
  • Toxicology (AREA)
  • General Chemical & Material Sciences (AREA)
  • Polymerisation Methods In General (AREA)
  • Epoxy Resins (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
EP01948900A 2000-06-15 2001-06-14 Method for making or adding structures to an article Withdrawn EP1295181A2 (en)

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US7005229B2 (en) 2002-10-02 2006-02-28 3M Innovative Properties Company Multiphoton photosensitization method
US7118845B2 (en) 2000-06-15 2006-10-10 3M Innovative Properties Company Multiphoton photochemical process and articles preparable thereby
US7381516B2 (en) 2002-10-02 2008-06-03 3M Innovative Properties Company Multiphoton photosensitization system
US6750266B2 (en) * 2001-12-28 2004-06-15 3M Innovative Properties Company Multiphoton photosensitization system
US7232650B2 (en) 2002-10-02 2007-06-19 3M Innovative Properties Company Planar inorganic device
US7030169B2 (en) * 2003-09-26 2006-04-18 3M Innovative Properties Company Arylsulfinate salts in initiator systems for polymeric reactions
US7723126B2 (en) * 2004-03-24 2010-05-25 Wisconsin Alumni Research Foundation Plasma-enhanced functionalization of inorganic oxide surfaces
WO2007073482A2 (en) * 2005-12-21 2007-06-28 3M Innovative Properties Company Method and apparatus for processing multiphoton curable photoreactive compositions
US7583444B1 (en) 2005-12-21 2009-09-01 3M Innovative Properties Company Process for making microlens arrays and masterforms
EP2468487B1 (en) 2006-05-18 2017-07-12 3M Innovative Properties Company Light extraction structures and light guides incorporating same
US8029902B2 (en) 2006-12-11 2011-10-04 Wisconsin Alumni Research Foundation Plasma-enhanced functionalization of substrate surfaces with quaternary ammonium and quaternary phosphonium groups
EP2335848B1 (de) * 2009-12-04 2014-08-20 SLM Solutions GmbH Optische Bestrahlungseinheit für eine Anlage zur Herstellung von Werkstücken durch Bestrahlen von Pulverschichten mit Laserstrahlung
JP5659189B2 (ja) * 2011-05-13 2015-01-28 富士フイルム株式会社 非共鳴２光子吸収材料、非共鳴２光子吸収記録材料、記録媒体、記録再生方法及び非共鳴２光子吸収化合物
JP5703257B2 (ja) 2011-05-13 2015-04-15 富士フイルム株式会社 非共鳴２光子吸収記録材料及び非共鳴高分子２光子吸収光情報記録媒体及び記録再生方法
JP6748883B2 (ja) * 2015-04-03 2020-09-02 株式会社スリーボンド 光遅延硬化性樹脂組成物、接合体および接着方法

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KR20030012883A (ko) 2003-02-12
KR100811018B1 (ko) 2008-03-14
JP4689936B2 (ja) 2011-06-01

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