Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
  • C08F2/46—Polymerisation initiated by wave energy or particle radiation
  • C08F2/48—Polymerisation initiated by wave energy or particle radiation by ultraviolet or visible light
  • C08F2/50—Polymerisation initiated by wave energy or particle radiation by ultraviolet or visible light with sensitising agents
• • 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
  • G03F7/004—Photosensitive materials
  • G03F7/0045—Photosensitive materials with organic non-macromolecular light-sensitive compounds not otherwise provided for, e.g. dissolution inhibitors
• • 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
  • G03F7/004—Photosensitive materials
  • G03F7/027—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds
  • G03F7/028—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds with photosensitivity-increasing substances, e.g. photoinitiators
  • G03F7/031—Organic compounds not covered by group G03F7/029
• • 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
  • G03F7/2022—Multi-step exposure, e.g. hybrid; backside exposure; blanket exposure, e.g. for image reversal; edge exposure, e.g. for edge bead removal; corrective exposure
• • 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
  • G03F7/004—Photosensitive materials
  • G03F7/038—Macromolecular compounds which are rendered insoluble or differentially wettable

Definitions

• This invention relates to photoinitiated reactions, for example curing and polymerisation reactions / and more particularly to UV curing used in photopolymer technology, as well as to photoinitiated colour forming reactions.
• the second basic form of photopolymer quantum yield enhancement is exemplified by the cationic U.V. curing systems.
• the absorbed photon generates a catalytic monomer species which is capable of catalysing polymerisations, cross-linking, or even molecular cleavage .
• This technology has been described as capable of producing "living polymers" which will continue growing as long as substrate monomer molecules are still available.
• the reactions are, however, relatively slow compared to the chain reactions of the free radical process.
• the quantum yield in terms ' of reacted molecules is theoretically near infinite, the slow reactions limit spatial resolution, by reason of diffusion of active species out of the imaged area.
• a limitation in terms of photopolymer imaging has always been the amount of time needed to deliver an adequate number of photons to the area to be .imaged.
• the delivery of a la-rge amount of random photons is easy.
• High powered lamps, simple reflectors and conveyor belts used in combination enable this aim to be achieved.
• the light needs to be collimated and delivered in a controlled fashion. To c ⁇ llimate the light output from any lamp involves a substantial loss of intensity.
• the subsequent -use of optical components and even photo tools serves to reduce the yield of available photons from even a very powerful lamp to a remarkably low level .
• a method of carrying out a photoinitiated polymerisation and/or crosslinking of a substrate which comprises providing a reactive substrate comprising a polymerisable and/or crosslinkable composition and a latent photoinitiator, activating the photoinitiator and exposing the reactive substrate composition with the resulting photoinitiator therein to photoreaction conditions wherein actinic radiation causes the composition to undergo polymerisation and/or cross1inking.
• this invention provides a method of carrying out a photoinitiated reaction which comprises applying a reactive substrate selected- from a polymerisable and/or crosslinkable composition and a colour changing substance to a support, activating a latent photoinitiator applied with the reactive substrate and subsequently exposing the reactive substrate with the resulting photoinitiator therein to photoreaction conditions wherein actinic radiation- causes the substrate to undergo polymerisation and/or crosslinking-or colour change respectively, the substrate being locally modified in its constitution as a result of its exposure to actinic radiation at at least one istage of the method, so that the resulting polymerised and/or crosslinked composition or colour changed substan ⁇ e corresponds in its distribution on the support to the locations of the modification of the substrate.
• Leu ⁇ o crystal violet is an important chromophore in this respect (latent colour formers are generally termed "leuco dyes") .
• Other leuco dyes to which the inventive principle may be applied include leucoxanthene and leucofluorans .
• the latent photoinitiator is most commonly to be a protected photoinitiator whose protection is removed in a reaction which takes place under preliminary conditions. Such preliminary conditions preferably include the use of a photoinitiator as such which, when exposed to actinic radiation, is able to interact with the latent photoinitiator to cause the latent photoinitiator to be converted to its underlying photoinitiator.
• a low energy source of actinic radiation may be employed in a first ' or preliminary photoreaction, which can be utilised in achieving an imagewise exposure of the substrate, and a high dosage of actinic radiation is applied as a flood in connection with a second photoreaction in which the substrate is polymerised and/or crosslinked.
• laser direct imaging is used in applying the low energy source of actinic radiation.
• Such method embodying this invention thus uses an amplification step, in which a second photochemical reaction is carried out subsequently to a preliminary, preferably photochemical reaction.
• a second photochemical reaction is carried out subsequently to a preliminary, preferably photochemical reaction.
• the vinyl dioxolane structure can be produced from a ketone photoinitiator starting material although other methods are available for the production of such a structure.
• the vinyl-dioxolane behaves as a ketal-protected carbonyl compound and the process generates a polyketone as the dioxolane ring is opened, generating the theoretical parent ketone for the dioxolane ring.
• the ketone used was benzophenone, a well known photoinitiator of acrylate polymerisation.
• the dioxolane ring opening reaction is applicable to formation of a whole range of ketonic functional initiator and co-initiator species ranging from such simple well known materials as benzil dimethyl ketal through to exotic materials such as di-iodo butoxy fluorone (a visible active photoinitiator used for stereolithography) .
• the resulting compounds act as "latent photoinitiators", capable of being activated by low doses of U.V. light on formation of catalytic quantities of acid from cationic initiators or by ongoing radical reactions. Examples of such compounds are:
• Di-iodobutoxy fluorone Other compounds which can be used are various benzoin ethers, as well as diethoxyacetophenone and 1- hydroxy-cycloxhexyl-phenyl ketone, and 2-hydroxy-2- methyl-l-phenyl ⁇ propan-l-one and ethers thereof.
• Such enhanced photopolymerisation method embodying this invention typically involves an initial irradiation of a film containing a cationic (acid producing) photoinitiator, acrylate and vinyl-dioxolane based latent photoinitiator. This irradiation is fast and efficient,- as the polymer formed in this step may be minimal and not cause any viscosity increase, which is a prime limit on reaction rates .
• the system can .be flood irradiated with light of wavelength long enough to avoid further photolysis of the cationic initiator, but adequate to photolyse the initiator formed from the cleavage of the dioxolane ring.
• This irradiation is not image-wise and therefore can involve far higher dosages of light in a relatively short time.
• An application for this -example is that of laser direct imaging of photoimageable coatings.
• the technology eliminates the bottleneck of having to deliver all the polymerisation energy via the laser in an imagewise fashion.
• An example of this . technology is summarised in the flow scheme of Fig. 1 of the accompanying drawings .
• cationic- acid-producing photoinitiators such as sulphonium and iodonium salts and sal -form orgonometallic compounds are utilised in achieving conversion of the latent photoinitiator although ⁇ -sulphonyloxy ketones can also be used as cationic acid-producing photoinitiators.
• the 'amount is in the range of from 0.25 to 3% by weight of the material to be acted on.
• the practical working range is from 3 to 10% by weight of the material to be acted on .
• a second procedure embodying this invention is in the field of photoimageable inks for sequential build up (SBU) technology where cationic systems are to be preferred due to their advantageous physical properties.
• This procedure demonstrates the versatility of- the method of this invention.
• One of the materials which can be made in a dioxolane ring blocked form is isopropylthioxanthone (ITX) .
• Thioxanth ⁇ nes are particularly suitable as sensitisers for iodonium salts .
• the iodonium salts themselves are generators of acid catalysts for cationic polymerisation, the possibility of their being used in a self-sensitising system is apparent and provides a means of increasing quantum yields.
• Initial irradiation of the- iodonium salt directly in an image- ' wise fashion results in production of a small amount of acid polymerisation catalyst.
• the resulting film is sensitive to an autoaccelerative reaction when flood irradiated with near visible radiation. This enhanced sensitivity opens the way for using laser direct imaging with photoimageable SBU dielectric .
• An example of this technology is summarised in the flow scheme of Fig. 2 of the accompanying drawings.
• a third example o.f the same concept relies on the radical cleavage of ' the dioxolane. If a free radical initiator sensitive only to short wavelength light is formulated together with acrylic monomers, acrylic pre- polymers, and a latent initiator, the latent initiator being sensitive to longer wavelength, the resulting mixture can be exposed to give an autoaccelerating reaction.
• LPISM Liquid Photoimageable Solder Masks
• a photoacid generating initiator cationic initiator
• a dioxolane blocked acrylate initiator permits formulation of a 100% solids LPISM.
• This system has the advantage of producing no emissions.
• Such a 100% solids formulation which can be made tack-free on exposure to acid catalysis, but remains developable, can be made by following the teaching of the present invention.
• the LPISM thus produced can be U.V. dried, being heated to. complete the solidification process and to ensure complete deblocking. Subsequently it can be re-exposed to image the formulation and still be developed and finally cured in a fashion familiar to the industry.
• the use of dioxolane blocked latent photoinitiators preserves the radical initiator during the imaging step whilst the coating is U.V. dried.
• a variety of approaches can be used to effect the
• Vinyl ethers, cycloaliphatic epoxies and oxetane compounds can be used as polymerisable solvents.
• use of such materials as cross linkers- for functionalised resins is viable.
• Use of reactive resins, and building resin molecular weight by cationic reaction can also be used.
• a vinyl ether functional resin and react it under cationic conditions with a hydroxy functional solvent, or vice versa.
• Such technology may be represented by the following:
• the technology can be applied to the field of visible active photoinitiators .
• the increased usage of these initiators means that many areas have to be configured as red light zones, these providing an exceedingly difficult environment to work in.
• Visible active formulations can be made with this ' technology so that they only become visible sensitive after U.V. irradiation. Substantial production and handling benefits ensue from this .
• the curing of thick films is limited to certain initiators which undergo photobleaching e.g. acylphosphine oxides.
• use of a low concentration of cationic initiator in conjunction with a dioxolane blocked free • radical initiator results in the ongoing, in-situ formation of free radical initiator.
• the dioxolanes are blue shifted with respect to their parent initiator, optical density can be controlled, only a small proportion of free- radical initiator being produced at any one time. This, in conjunction with the cold running of these lamps, would enable the use of this latent initiator' technology in a wide variety of fields.
• the : latent initiators described here are not confined to being unblocked by photochemical processes yielding acid moieties .
• Any blocked acid of sufficient strength for example a blocked toluene sulphonic acid, especially p-toluene sulphonic acid, will, on unblocking, catalyse the breakdown of the dioxolane ring on the latent photoinitiators .
• Examples of such compounds which can be used are the thermally unblockable blocked superacids produced by King Industries .
• a thermal unblocking variant on ' this technology can be useful for a number of the examples given here, especially the 100% solids LPISM and the improved handling for visible initiated processes
• the chemistry outlined here provides for the synthesis of a deactivated photoinitiator by a prescribed synthetic method, for example by reaction of a carbonyl group to form a vinylic functionalised dioxolane ring, for- example, by use of a leuco carbonyl group present in the form of a vinyl functionalised dioxolene ring as latent photoinitiator.
• PCB industry Primary and Secondary imaging
• Example 1 illustrates the preparation of dioxolanes which can be used in the method of this invention:
• Example 1 illustrates the preparation of dioxolanes which can be used in the method of this invention:
• the resultant reaction mixture was cooled and washed with 200ml molar sodium carbonate solution and then water.
• the organic layer was then dried over magnesium sulphate, rotary evaporated and distilled under reduced pressure .
• the purified intermediate was taken and dripped into a refluxing solution of potassium t-butoxide (22g) in tetrahydrofuran (50g) contained in a 250ml two necked round bottomed flask fitted with a dropping funnel and condenser. After adding the intermediate over a period of 1.5 hours the mixture was refluxed for a further hour. The resultant reaction mixture was extracted with ether, washed twice with water, dried over magnesium sulphate and rotary evaporated to leave a clear oil of the above captioned target substance .

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polymerisation Methods In General (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 2000
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• 2001
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