CA1326579C

CA1326579C - Ternary photoinitiator system for addition polymerization

Info

Publication number: CA1326579C
Application number: CA000583765A
Authority: CA
Inventors: Michael C. Palazzotto
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1987-12-09
Filing date: 1988-11-22
Publication date: 1994-01-25
Anticipated expiration: 2011-01-25
Also published as: AU2515188A; EP0320127B1; KR890010613A; HK1007563A1; DE3850366T2; AU616697B2; JPH02972A; US4889792A; EP0320127A3; KR0148114B1; DE3850366D1; EP0320127A2

Abstract

ABSTRACT OF THE DISCLOSURE

This invention relates to photoinitiator systems for use in addition, i.e., free radically-initiated, polymerization. This invention porvides photopolymerizable compositions comprising:
(1) at least one vinyl monomer capable of undergoing free radical polymerization, (2) a visible light or ultraviolet light responsive photoinitiator system comprising:
a) a diarylidonium salt, b) a pigment, insoluble in the photopolymerizable composition, said pigment also serving as a sensitizer, c) one or more electron donating compounds, and, optionally, (3) adjuvants.
The three component photoinitiator system of this invention can increase, by several orders of magnitude, the rate of ultraviolet light or visible light photocuring of vinyl monomers.

Description

1 32657~ F.N. 42587 CAN 3A

`~ ~I`ERNARY Pi~OTOINITIATOR SYSTEM
FOR ADDITION POLYMERI~;A~ION
~ACRGROl~D OF T~E INVENTION

1~ Technical Field This invention relates to photoinitiator systems for use in addition, i.e., free radically-initiated, polymerization.

3 2. ~iscussion of Prior ~rt Addition polymerization ~also referred ilio as free radical polymerization) of vinyl monomers by exposure thereof to radiation from the ultraviolet or visible portion of the electromagnetic spectrum is well known in the art. Polymerization of this type is also known as photopolymerization, photocuring, or curing.
Aryliodonium salts have been previously described for use as photoinitiators in addition-polymerizable compositions. References relating ito such compositions include U.S. Patent Nos. 3,729,313, 3,741,769, 3,808/006 . 4,228,232, 4,250,053 and 4,428,807; H.J. Timpe and H.
.; 25 Baumann, Wiss. Z. Tech. Hoch c _ Leuna-Merseburg, 26, 439 (1984)~ H. Bau~ann, B. Si~rehmel, ~. J. Timpe and U. Lam~el, ~, J. Prakt. Chem, 326 ~3~, 415 (1984~; and H. Baumann, U.
.,l Oertel and H. J. Timpe, Euro. Polym. J., 22, 313 (1986).
i Photopolymerizable compositions usually contain a '~f 30 photoinitiator system, a polymerizable monomer, and optionally ad~uvants. Often pigments are added to color or opacify the compositions. ~he addition of pigments usually inhibits the initiation of polymerization because of compe~itive light absorption or ligiht scattering, whicih decreases the amount of light available for absorption by '- the photoinitiator system. It would be desitable to ~e .. able to use pigments as part of a photoinitiator system in .~ .
,i, ~

,, .

'' ' ' ' ` 1 326579 ~. .

2 605~7-3526 a photopolymerizable compositlon. In the present lnventlon, ln-soluble sensitlzers can serve both as sensltizers and colorants.
~ three component system describlllg the use o~ iodonlum salts, electron donor compound, and soluble sensltlzer is descrl-bed ln Cana~ian patent applicatlon serlal nos. S62,679 and 562,881.
However, these appllcations do not suggest the use of an lnsoluble pigment as a sensltlzer.
U.S. Patent No. 4,2S7,915 discloses semiconductors in combination wlth an oxidatlon-reduction system Eor produclng images. This patent does not teach the use of lodonium salts or organlc plgments.

SUMMARY OF THE INVENTION
This lnvention provldes compositions that are photopoly-merizable by both vislble llght and ultraviolet (UV) llght. More specifically, this invention provides photopolymerizable composi-tions comprlsing:
1) at least one vinyl monomer capable of undergolng free radlcal polymerization, 2) a visible llght or ultraviolet light responslve photoinitlator system comprlslng:
a) a dlaryllodonium salt, b3 an organic or inorganlc plgment, insoluble ln the photopolymerizable composition, said pigment also serving as a sensitl~er, c) one or more electron donatlng compounds selec-ted from the group of compounds that possess a 2a 60557-3526 potentlal ~E~x~ donor) between about 0.5 and 1. 5 volts versus a saturated calomel electrode ("S.C.E."), and, optionally, 3~ ad~uvants.
Thls lnvention also provides methods for the preparat lon of photopolymerized composltlons.

' ~' .~

-: . . .. .

" , ' ; '~

- ` 1 32657q compositions of the present invention provide a very useful combination ~f cu~e speed, cure depth, and shelf life. They can be used in a variety of applications, including graphic arts imaging (e.g., for color proofing systems, curable inks, or silverless imaging), printin~
plates (e.y., projection plates or laser plates), photoresists, solder masks, coated abrasives, magnetic media, photocurable adhesives (e.g., Eor orthodontics), and photocurable composites (e.g., for automobile repair or dentistry e.g., dental restoratives).

DETAILED DESCRIPTION OF THE_ INVENTION
Light responsive photoinitiator systems for initiation of the polymerization of vinyl monomers comprise an inorganic or organic pigment, an electron donating, or donor, compound, and an electron accepting. or acceptor, compound, such as, for example, onium salts. A
~ wide variety of monomers can be photopolymerized using the j photoinitiator system of this invention. Suitable monomers for this invention contain at least one ethylenically-unsaturated double bond and are capable of undergoing addition polymerization. These monomers can also be oligomers. Suitable monomers include ~1) mono-, di- or poly- acrylates and methacrylates, such as, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ~ isopropyl methacrylate, n-hexyl acrylate, stearyl acrylate, 'J allyl acrylate, glycerol diacrylate, glycerol triacrylate, ~ ethyleneglycol diacrylate, diethylene~lycol diacrylate, ; triethyleneqlycol dimethacrylate, 1,3-propanediol diacrylate, 1,3-propanediol dimethacrylate, trimethylol-propane triacrylate, 1,2,4-butanetriol trimethacrylate, 1,4-cyclohexanediol diacrylate, pentaerythritol triacrylate, pentaerythritol teteaacrylate, pentaerythritol tetramethacrylate, sorbitol hexacrylate, bis11-(2-acryloxy~]-p-ethoxyphenyldimethylmethane, bis11-13-acryloxy-2-hydroxy~-p-propoxyphenyldimethylmethane, trishydroxyethyl-isocyan~rate trimethacrylate;

.
"
,,,~.

.
, . . .

~' ~
, (2) bis-acrylates and bis-methacrylates of polyethylene glycols of molecular weight 200-S00, copolymeriza~le mlxtures of acrylated monomers such as those descrlbed ln U.S. Patent No. 4,652,274, and acrylated ollgomers such as those described in U.S. Patent No.
4,642,126;
(3) unsaturated amldes such as, for example, acrylamide, methylene bis-acrylamlde, methylene bis methacrylamlde, 1,6-hexamethylene bis-acrylamide, diethylene triamine tris-acrylamlde, and beta-methacrylamlnoethyl methacrylate; and (4) vinyl compounds such as, for example, styrene, diallyl phtha-late, divlnyl succinate, dlvinyl adipate, and dlvlnylphthalate.
Mlxtures of two or more monomers can be used 1~ deslred.
The monomer ls combined with a three component or ter-nary photoinltlator system. The flrst component ln the photo-initiator system is a dlaryliodonium salt. The dlaryllodonium salt should be soluble in the photopolymerlzable compositlon and preferably is shelf-stable (l.e., does not spontaneously promote polymerlzatlon) when~dlssolved thereln in the presence of the plgment sensltlzer and donor. Accordingly, selectlon of a parti-cular diaryliodonlum salt depends, to some extent, upon the partl-cular monomer, pigment sensltizer and donor chosen. Diaryllo-donium salts suitable for the present inventlon are described in U.S. Patent No~. 3,729,313, 3,741,769, 3,808,006, 4,250,053 and 4,394,403. The diaryllodonlum salt can be a slmple salt (e.g., contalning an anlon such as Cl-, Br , I- or C6H5SO3-) or a metal or metallold complex salt (e.g., contalnlng an anion such as BF4-, PF6-, SbF6-, SbF50H- or AsF6-). Mlxtures of dlaryliodonlum salts can be used lf deslred.
1~

~: : .

4~ 60557-3526 .~, Preferred diaryliodonium salts include diphenyliodoniurn salts such as diphenyliodonium chlorlde, dl.phenyliodonium hexa-fluorophorphate, end dlphenyllodonlum tetraEluorooorate.

.~ , ~1 , :
i .~
.

~I ' :i .

, , 1 32657~
The second component in the photoinitiator system is the pigment sensitizer. The pigment sensitizer c~n he ~n oL-ganic or inorganic material that:
1) is generally not soluble ~solubility less than about 0.1 percent) in the photopolymerizable composition, 2) absorbs energy in a certain portion of the electromagnetic spectrum (for visible light, absorption is usually from ~bout 380 to about 750 nanometers ~nm) and for ultraviolet liyht, absorption is usually from abou~ 300 to about 380 n~), i.e. displays a band gAp energy of about 1.5 to about 4.0 electron volts, and 3) behaves as a semiconductor, i.e., is capable of undergoing photoredox reactions.
In conventional photosensitive compositions, pigments are usually viewed as a hindrance, because, by their nature, they competitively absorb light.
2~ Surprisingly, it has been found tha~ insoluble otganic and inorganic pigments actually serve as visible light and ultraviolet light photosensitizers for the light initiated polymerization of vinyl monomers when they are in combination with an aryliodonium salt and an electron donor compound. ~hus, certain pigments can actually replace soluble dyes, which are normally used as sensitizers. It is preferred that the pigment be dispersible with at least one of the other components of the pho~opolymerizable composition.
Inorganic pigments suitable for use as sensitizers in this invention are described in U.S. Patent No. 4,257,915 and include, for example, titanium dioxide, strontium titanate, barium titanate, zinc oxide, æinc sulfide, zinc selenide, cadmium sulfide, cadmium selenide, cadmium telluride. Organic pigments suitable for use as sensitizers in this inventiQn include, for example, phthalocyanine blue (pigment blue 15), copper ; .
;: ` ' 32657q polychlorophthalocyanine green (pigment green 7), co~per polybromochlorophthalocyanines (pigment green 36~, ~erylene scarlet Ivat red 29), perylene vermillion (pigment red 123), perylene maroon, perylene bordeaux, perylene dianhydride (perylene red), and others such as those described in "Pig~ents-Inorganic" and "Pigments-Organic" in ~;irk-Othmer Encyclopedia of Chemical Technology, Third ed., Volume 17, John Wiley and Sons (New York: 1982) pp.
7~8-871, semiconducting polymers ~see Ya. M. Paushkin, et al., Organic PQlymeric Semiconductors, John Wiley ~ Sons, ew York: 1974), and photoconducting polymers lsuch as described in J. M. Pearson, Pure and Appl. Chem., 49, 463-477 (1977)).
The third component in the photoinitiato~ system is the electron donor. ~ wide variety of donors can be employed. The donor should not only be soluble in the photopolymerizable composition, but should also ~eet the oxidation poten~ial ~Eox) requirements discussed in more detail below. Preferably, the donor is also selected on the basis of shelf stability. Accordingly, selection of a particular donor depends, in part, on the particular monomer, diaryliodonium salt, and pigment chosen. Donors are capable of increasing the speed of cure o~ depth of ~; cure of a composition of the invention upon exposure to light of the desired waveIength. Preferably, Eox of the donor is between abo~t 0.5 and 1.5 volts versus a saturated calomel electrode ~"S.C.E."). Values of E~x of the donor can be measured experimentally, or obtained from references such as N. L. Weinburg, Ed., Technique of Electroorganic 3Q Synthesis Part II Techniques of Chemistry, Vol. V (1975), and C~ K. Mann and K. K. ~arnes, El_ctrochemical Reactions in Nonaqueous Systems (1970).
Preferred donors include amines (including aminoaldehydes and aminosilanes), amides (including phos~horamides), ethers (including thioethers), ureas (including thioureas~, ferrocene and its derivatives, sulfinic acids and their salts, salts of ferrocyanide, . .

.

.

; a~corbic acid and its salts, dithiocarbamic acid an~ its salts, salts of xanthates, salts of ethylene diamine t~traacetic acid, and salts of tetralkyl and tetraaryl borates. The donor can be unsubstituted or suhstituted with one or more substituents that do not adversely affect the photopolymerization reaction.
Preferred amine donor compounds inclu~e alkyl-, aryl-, alkaryl- and aralkyl-amines, such as, for example, m~thylamine, ethylamine, propylamine, butylamine, triethanolamine, amylamine, hexylamine, 2,4-dimethylaniline, 2,3-dimethylaniline, o-, m- and p-toluidine, benzy~amine, aminopyridine, N,N'-dimethyl-ethylenediamine, 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,N-dimethylaminophenethanol and p-N,N-dimethylamino-b~nzonitrile; aminoaldehydes, such as, for example, p-N,N-dimethylaminobenzaldehyde, p-N,N-diethylaminobenzaldehyde, 9-julolidine carboxaldehyde, an~
4-morpholinobenzaldehyde; and aminosilanes, such as, for example, trimethylsilylmorpholine, trimethylsilylpiperdine, bis(dimethylamino)diphenylsilane, tris(dimethylamino)-methylsilane, N,N-diethylaminotrimethy]silane, tris(dimethylaminojphenylsilane, tris(methylsilyl)amine, tristdimethylsilyl)amine, bis(dimethylsilyl)amine, N,N-bis(dimethylsilyl~aniline, N-phenyl-N-dimethylsilyl-aniline and N,N-dimethyl-N dimethylsilylamine. Tertiary aro~atic alkylamines, particularly those having at least one electron-withdrawing group on the aromatic ring, have been found to provide especially good shelf stability.
Preferred amide donor compounds include N,N-dimethylacetamidet M,N-diethylacetamide, N-methyl-N-phenylacetamide, hexamethylphosphoramide, hexaethyl-phosphoramide, hexapropylphosphoramide, trimorpholino-phosphine oxide, and tripiperidinophosphine oxide.

, , ' '' ' ,:

1 32657q Suitable ether donor compounds include 4,4~-dimethoxybiphenyl, 1,2,4-trimethoxybenzene, and 1,2,4,5-tetramethoxybenzene.
Suitable urea donor compounds include N,N'-dimethylurea, N,N-di~ethylurea, N,N~-diphenyl~rea, tetramethylthiourea, tetxaethylthiourea, tetra-n-~utylthiourea, N,N-di-n-butylthiourea, N,N' di-n-but~lthiourea, N,N-diphenylthiourea, and N,N'-diphenyl-N,N'-diethylthiourea.
~ The three necessary components of the composition of this invention are present in "photochemically effective a~ounts", that is, the amount of each component must be sufficient to enable the monomer to undergo photochemical gelation or hardening upon exposure to light of the desire~
wavelellgth. Amounts of each component are independently variable and thus need not be equalt with larger amounts of diaryliodonium salt and/or electron donor compound generally providing faster cure, but shorter shelf life.
Use of too much pigment or improper preparation of the dispersion can adversely affect the cure.
Compositions of this invention can contain a wide variety o~ adjuvants depen-~ing upon the desired end use.
Classes of adjuvants suitable for this in~ention inclu~e solvents, diluents, resins, binders, plasticizers, dyes, inorganic or organic reinforcing or extending fillers~
thixotropic agents, indicators, surfactants, inhibitors, stabilizers, W absorbers, dispersing aids, and the like.
An additional component that can be added to the composition of this invention is ~ radiation-sensitive dye.
Suitable dyes include those that sensitize the photoconductivity of semiconductor pigments, particularly those that absorb visible radiation. Such dyes are discussed by Meier in Spectr~l Sensitization, Focal Press ~imited, London, 1968, pp. 101 to 110. Examples of such suitable dyes include Acriflavine CI 46000, Rose Bengal CI
45435, Acridine Orange CI 46005, Kryptocyanine, Fuchsine, Malachite Green, Eryth~osine, Eosine, Fluorescein, : .:. , ~. . ~ ::

1 32657q Phthalocyanlne, and merocyanine dyes as taught ln U.S. Patent No.
4,257,915. Amounts and types of such ad~uvants, and thelr manner of addition to a composition of the invention will be famlliar to `~ those skilled in the art.
Suitable ratios of ingredlents include the following:
for every lO0 parts by weight of the photopolymerizable composl-tion there may be present from 1 to 99 parts by weight vinyl mono-mer, from 0.001 to 50 parts by welght pigment sensitizer, from 0.005 to 10 parts by weight of diaryliodonlum salt, from 0.005 to lO parts by welght of donor compound, from 0 to 99 parts by weight of adiuvants. Preferably there is used per 100 parts by weight of the photopolymerizable composition from 5 to 60 parts by welght i vinyl monomer, 0.1 to 30 parts by welght of pigment sensltlzer, 0.1 to 5 parts by weight of diaryllodonium salt, 0.1 to 5 parts by weight of donor compound, and from 5 to 90 parts by welght of ad-l. ~uvants.

In making the photosensltive compositlons of this inven-tlon, the pigment sensitlzer, diaryllodonlum salt, donor compound, polymerlzable monomer or monomers, and optionally ad~uvants can be combined in any order and mixed until a homogeneous dispersion or mlxture ls obtained. Fillers and other ad~uvants can be added as deslred. It has been found deslrable to store the composltlons of this lnventlon away from light until it is desired to initiate polymerization by the lntentional exposure to light.
Composltlons of thls inventlon can be cured by means of a varlety of methods. It ls convenient to expose the composltions to actinlc radiation by employing light sources that emit ultra-violet or vlsible llght, such asr for example, ~uartz halogen , ~

, .

.. . . . .
. : , ga 605S7-3525 lamps, tungsten-halogen lamps, mercury arcs, car~on arcs, low-, medium-, and hlgh-pressure mercury lamps, plasma arcs, llght emlt ting diodes and lasers at a wavelength between about 300 and 1000 nanometers. Electron beam ("E-beam") lrracliatlon and other curing devices that do not depend on light emission can also be employed.
In general, heat applled during or after exposure and/or an lnert etmo phere wll l accelerat e cure .

, , . , : .; ~ ., . . ~ .

, :.

Insoluble sensitizer pigments are introduced as dispersions in place of the usual soluble org~nic sensitizers. Dispersions can be prepared by dispersing the pigment in water. While not necessary, surfactants and 5 water soluble polyvinylalcohol ~ PVA) can be used as a~ditives in the preparation of tlle dispersions. Stock dispersions can be prepared by means of a ball mill. A
photoinitiator system comprising a mixture of this dispersion, an electron donor compound, and a diaryliodonium salt, can be used to polymerize a vinyl monomtr by means of exposure to visible or ultraviolet light.
The three component photoinitiator system of this invention has increased by several orders of magnitude the rate of ultraviolet light or visible light photocuring of vinyl monomers.
This invention is further illustrated by the following examples, but the particular m~terials and amounts thereof recited in these examples, as well as other conditions and details, should not ~e construed to unduly limit this invention to the illustrative embodiments set forth herein~

EXAMPLES
In the following examples, parts-are reported as parts by weight and all percentages are giv~n as percentages by weight unless indicated otherwise. ~ll temperatures are reported in degrees ~entigrade and examples were conducted at ambient temperature (about 20-25'C) unless indicated otherwise. Monomers, diaryliodonium salts, pigments, electron donor compounds, adjuvants, resins, and the like used in the examples were commercially available unless indicated otherwise.
Light used to initiate the polymerizations was from a visible light source unless indicated otherwise.

.

. .

~,: ~ -. ,, -~, .

--ll--The following example describes the use of pigments as sensitizers to initiate free radical polymeri~ation of vinyl monomers using the three component photoinitiator system, i.e., pigment, diaryliodonium salt, and electron donor compound.
Pigments used in this example were prepared as water dispersions according to the following procedure: a c~olution containing polyvinylalcohol ~PVA) 1}2 9), cetyltrimethylammonium bromide surfactant (0.2 9, Aldcich Chemical Co., Milwaukee, WI) and water (200 g) was prepared. Two different polyvinyl alcohols, both of which are commercially available from Aldrich Chemical Co., Milwaukee, WI, were used; one had a molecular weight of 2,000 and was 75~ hydrolyzed, and the other had a ~olecular weight of 10,000 and was 88~ hydrolyzed. To the solution was added 5 g of the desired pigment. The resultant mixture was placed on a ball mill and milled until a satisfactory stock dispersion was obtained as in~3icated by visual examination of the dispersion spread on a glass slide through a IOQ X microscope. Fine particles indicated a good, suitable dispersion.
For each sample, a dilution of 1/19, volume per volume, dispersion/water was made. A~4 ml por~ion of this 25A diluted ~ixture was placed in a "Pyrex" test tube, and -acrylamide (about 0.3 g) was added thereto. Depending on the sample, either sodium p-toluenesulfinate (about 0.03 g) or diphenyliodonium chloride (about 0.03 9~ or both were added. Each sample was purged with nitrogen for two minutes before and continuously during a five minute exposure to a light source ("Kod~k~Carousel" projector, 500 watts) using a 400 nm filter between the source and sample.
Each sample was then poured into methanol (30 ml) to cause ~recipitation of any poiymer. The following table shows polymeriz~tion results of compositions of the present invention, along with comparative results. In the table, column A shows results for compositions contaiaing pigment rR ~

~12- 1 32 657 q pl~s sodium p-toluenesulfinate, column B shown results for compositions containing pigment plus diphenyliodonium chloride, and column C shows results for compositions cvntaining pigment, sodium p-toluenesulfinate, and S diphenyliodonium chloride.
In the table, N means no polymer was detected, S
means a small amount of polymer was formed, and P means a 1arge amount of polymer was formed.

ABLE I
~xample Pi~ment A B C
.
l Phthalocyanine Bluel N N P
2 Perylene Redl S N P
3 Cadmium Sulfide2 S N P
4 Poly(p-aminobenzaldehyde)2 S N P

A1PVA mole ular weight 2000, 75~ hydrolyzed, 0.2 g surfactant ~("Triton~ X-l00") added to dispersion.
~PVA, molecular weight l0000, 88% hydrolyzed.
Only the samples containing pigment underwent ~ecided polymerization.

The following example describes a coating formulation comprising a mixture of vinyl monomers, a diaryliodonium salt, an electron donor compound, and a pigment as a sensitizer and a process wherein the mix~ure is photopolymerized to provide a coated film. The sensitizer pigments of the examples are indicated in Ta~le ~ below. The example shows the increase in spee-l provided by photoinitiator systems containillg pigment sensitizer, diaryliodonium salt, electron donor compound (ternary systems) as c~mpared to photoinitiator system~ containing pigment sensitizer-diarylidonium salt or pigment ~ r~

- -13- 1 32657~

sensitizer-electron donor compound (binary systems) for the initiation of free radic~l polyme~ization.
Stock ooating formulatior~s were prepared by using ~I suitable stock dispersion of ~he pigment prepared clccorcling to the process set forth in Examples 1-~ and a~ding to it 12 g of acrylamide and 1 9 of N,N~-methylenebisacrylamide, followed by ball milling until mixing was complete. A small amount o~E surfactant, about ~ 0.05 g of "Triton X-lOO'' surfactant or "Nelk~l NF"
surfactant (GAF Corporation, New York, NY), was added to improve the coating characteristics of these formulations.
Coating samples were prepared by taking 25 9 of the above stock coating formulation and adding O.l g of the appropriate electron donor com~ound and/or diaryliodonium salt. Samples were coated onto a substrate of gelatin-subbed 3 mil polyester film (3M Co., St. Paul, MN) using a number eighteen wire wound rod. The coated ~ilm was dried first by a heat gun and then in an oven at 60`C
for three minutes. All manipulations using visible light sensitive materials were performed under red safelights and UV sensitive materials were correspondingly handled under yellow safelights. Visible light exposures were made with a Model 70 tunqsten light source ( 3M Co., st. Paul, MN~ in a commercial vacuum frame and UV exposures were made with a 2 kilowatt Berkey Ascor (Berkey Technical Company, Woodside, NY) light source with photopolymer b~llb in a commercial vacuum frame.
The resultant exp~sed, coated films were then washed with a water/methanol solvent mixture for development to remove unpolymerized material.
Polymerization in a coated film was detecte~ by exposing a film in an imagewise manner and revealing the retained image by washing of the film to remove unpolymerized materialsO Relative speed of polymerization was determined by the number of s~eps of a Stouffer 21 step wedge (Stouffer Graphio Arts, Sou~h Bend, IN) remaining after washing. In Table 2 colu~n ~ shows results for ~R Pro ~

':

' ' , ~ :

-14- l 326579 compositions containing pigment plus sodium p-toluenesulfinate, column ~ shown results for co~positions containing pigment plus diphenyliodonium chloride, and column C shows results for compositions containing pigment, S sodium p-toluenesulfinate, and diphellyliodonium chloride.
TABI.E 2 Light Number of steps Example Pigment source ~ B C
Phthalocyanine Bluel'5 Visible N L

6 Perylene Red'~5 Visible* N L 14 (p-aminobenzaldehyde)3'4'6 Visible* N N 10 8 Cadium Sul f ide l,4,5 UV L L 13 lS g Zinc Oxide2~3~6 UV L L 7 Titanium Dioxide2'3'6 UV L L 8 .

* lO second light exposure PVA, molecular weight 2000, 75~ hydrolyzed.
'PVA, molecular weight 10000, 8840 hydrolyzed.
3surf~ctant ~"Triton X~lO0") added.
4surfactant ("Nekal-NF") added.
53/20~ V/V, methanol/water used for development.
63~10, V/V, methanol/water used for development.
Results are shown in Table 2 where N means that no imags was formed and L means that an image was formed but was lost upon development. Where expos~res were made of coated films without the added diaryliodonium salt/electron donor compound, no image was detected except in the case of cadmium sulfi~e. This image was lost on washing. Coatings containing only the diaryliodonium salt/electron donor compound combination did not image under these conditions.

; ~ ..., , . :
.: .
' ; :

Claims

1. A photopolymerizable composition comprising:
a) at least one vinyl monomer capable of undergoing free-radical polymerization, and b) a photoinitiator system comprising photochemically effective amounts of i) a diaryliodonium salt, ii) an organic or inorganic pigment, insoluble in the photopolymerizable composition, which serves as a sensitizer, iii) at least one electron donor compound, said donor being different from said pigment and having a potential between about 0.5 and 1.5 volts versus a saturated calomel electrode.

2. A composition according to claim 1, wherein said diaryliodonium salt comprises a diphenyliodonium simple salt or diphenyliodonium metal complex salt.

3. A composition according to claim 1, wherein said sensitizer pigment is selected from the group consisting of phthalocyanines, porphyrins, and perylenes.

4. A composition according to claim 1, wherein said sensitizer pigment is a phthalocyanine.

5. A composition according to claim 1, wherein said sensitizer pigment is a porphyrin.

6. A composition according to claim 1, wherein said sensitizer pigment is a perylene.

7. A composition according to claim 1, wherein said sensitized pigment is selected from the group consisting of cadmium sulfide, cadmium selenide, cadmium telluride, zinc oxide, zinc sulfide, and titanium dioxide.

8. A composition according to claim 1, wherein said Eox (donor) is between about 0.5 and 1 volt versus a saturated calomel electrode.

9. A composition according to claim 1, wherein said donor is selected from the group consisting of amines, amides, ethers, ureas, ferrocene derivatives, sulfinic acids and their salts, ferrocyanide salts, ascorbic acid and its salts, dithiocarbamic acid and its salts, xanthate salts, ethylene diamine tetraacetic acid salts, tetraalkyl borate salts, tetraaryl borate salts.

10. A composition according to claim 1, wherein said donor comprises sulfinic acid salts.

11. A composition according to claim 10, wherein said donor comprises a member of the group selected from tetraalkyl and tetraaryl borate salts.

12. A composition according to claim 1, wherein said composition contains, for every 100 parts by weight of composition, about 1 to 99 parts by weight of said monomer, about 0.005 to about 10 parts by weight of said diaryliodonium salt, about 0.001 to about 50 parts by weight of said sensitizing pigment, and about 0.005 to about 10 parts by weight of said donor.

13. A composition according to claim 12, wherein said composition contains, for every 100 parts by weight of said composition, about 5 to 60 parts by weight of said monomer, about 0.1 to about 5 parts by weight each of said diaryliodonium salt, about 0.1 to about 3 parts by weight of said sensitizing pigment, and about 0.1 to about 5 parts by weight of said donor.

14. A composition according to claim 12, wherein said composition further comprises about 10% to 90% by weight of fillers, based on the total weight of said composition.

15. A composition according to claim 1, further including adjuvants.

16. An article comprising a support bearing a coating comprising the composition of claim 1.

17. An article according to claim 16 wherein said pigment is selected from the group consisting of phthalocyanines, perylenes, and cadmium sulfide.

18. A method for addition photopolymerization comprising the step of irradiating a composition according to any one of claims 1 to 15 with light having a wavelength between about 300 and about 1000 nanometers until said composition gels or hardens.