CA1200559A

CA1200559A - Acrylphosphine oxides and their use

Info

Publication number: CA1200559A
Application number: CA000409201A
Authority: CA
Inventors: Andreas Henne; Anton Hesse; Manfred Jacobi; Gunnar Schornick; Rudolf Vyvial; Klaus Holoch
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1981-08-24
Filing date: 1982-08-11
Publication date: 1986-02-11
Also published as: DK376982A; EP0073413B1; NO164837B; FI822872L; EP0073413A2; US4447520A; DE3261467D1; FI71322C; FI822872A0; DE3133419A1; NO164837C; FI71322B; JPH0457677B2; EP0073413A3; DK158043B; NO822860L; ES515178A0; JPS5877890A; DK158043C; ES8400448A1

Abstract

Abstract of the Disclosure: Acylphosphine oxides of the general formula

Description

~~559 o.z. 0050/353~2 Acyl~hosphine oxides and their use m e present invention relates to novel acylphos-phine oxides and their use as photoinitiators in photo-polymerizable materials such as coating agents, finishes, printing inks, unsaturated polyester molding materials and recording materials.
German Laid-Open Applications DOS 2,8~0,927 and DOS 2,909,994, and European Patent Applications No. 7,086 and No. 7,508,have disclosed acylphosphine oxides and their use as photoinitiators. German Laid-Open Application DC~ 2,909,994 describes acyldiphenylphosphine oxides with the aid of which even pigmented surface coat ings can be hardened with UV light. For hardening printing inks and pigmented finishes, there is, however, a need for photoinitiators which permit photo-hardening of thicker layers than in the case of the com-pounds described in German Laid-Open Application DOS

2,909,~94.
Wehave found,surprisingly,that relativelythicklayers ofpigmented finishesandofprintinginks can be hardened using acyldiphenylphosphine oxides which are methyl-substituted or ethyl-substituted in the 2-position of the phenyl rings bonded to phosphorus. Additional sub-stituents in the phenyl nucleus do not change this effect.
The present invention relates to acylphosphine oxides of the general formula (I) ~O~)SS9 Rl R3 R~ n~ (I) where Rl is methyl or ethyl, R2 is a branched or straight-chain alkyl radical of 1 to 4 carbon atoms, chlorine, alkoxy of 1 to 4 carbon atoms or hydrogen, R3 and R4 are identical or different, and are each alkyl, alkoxy or alkylthio, each of 1 to 4 carbon atoms, or chlorine, and R5 is hydrogen, chlorine, or alkoxy or alkylthio, each of 1 to 6 carbon atoms, or a branched or straight-chain alkyl radical of 1 to 12 carbon atoms. The compounds of the formula (I) mav be used as a photoinitiator.
Thus, the present invention furthermore relates to the use of the acylphosphine oxides of the general formula (I) as photoinitiators in photopolymerizable materials, for example for coating agents, finishes and printing inks, and for the production of plastic moldings based on unsaturated polyester resins, where relevant in combination with secondary or tertiary amines, other photoinitiators, or thermal polymerization initiators.
The phenyl ring substituted by Rl and R2 is prefer-ably a 2-methylphenyl or 2,5-dimethylphenyl radical, and that substituted by R3, ~4 and R5 is preferably a 2,6-dimethylphenyl, 2,4,6-trimethylphenyl, 2,3,6-trimethylphenyl, 2,6-dimethoxyphenyl, 2,6-dichlorophenyl, 2,6-bis-(methylthio)-phenyl, 2,6-dimethyl-4-tert~-butyl-phenyl or 2,6-~imethyl-4-octylphenyl radical.
Examples of the novel compounds are:

2,4,6-trimethylbenzoyl-bis-(o-tolyl)-phosphine oxide, 2,6-dimethoxybenzoyl bis-(o-tolyl)-phosphine oxide, 2,6-dichlorobenzoyl-bis-(o-tolyl)-phosphine oxide, ~()5~9 2,6-dimethyl-4-tert.-butyl-bis-(o-tolyl)-phosphine oxide, 2,6-dimethyl-4-octyl-bis-~o-tolyl)-phosphine oxide, 2,4,6-trimethylbenzoyl-bis-(2,5-dimethylphenyl)-phosphine oxide, 2,6-dimethoxybenzoyl-bis-(2,5-dimethylphenyl)-phosphine oxide, 2,4,6-trimethylbenzoyl-bis-(2,3-dimethylphenyl)-phosphine oxide, 2,6-dichlorobenzoyl-bis-(2,5-dimethylphenyl)-phosphine oxide and 2,6-dimethyl-4-tert.-butyl-bis-(2,5-dimethylphenyl)-phosphine oxide.
The novel substances may be prepared in a manner similar to that described in German Laid-Open Application DOS
2,909,994.
The acylphosphine oxides according to the invention are very reactive as photoinitiators for photopolymerizable monomers having one or more C-C multiple bonds, and mixtures thereof with one another and with conventional additives, and are particularly suitable as photoinitiators in photo-polymerizable materials for coatings, finishes, printing inks and recording materials. They are ~ar superior to the conventional photoinitiators, eg. benzil dimethyl ketal, which is disclosed in German /
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- 4 - O.Z. 005a/353~
Published Application DAS 2,261,383, in respect of yellow-ing of the resulting finishes and coatings. Using the novel compounds, thicker pigmented surface coatings may be hardened than in the case of the acyl-phosphine oxides described in German Laid-Open Applica-tion DOS 2,909,994.
The novel compounds are also very advan-tageous as photoinitiators for photohardening styrene/
polyester resins, which may contain glass fibers and other assistants.
Suitable photopolymerizable monomers are the con-ventional compounds and substances having polymerizable C~C double bonds which are activated by, for example, aryl, carbonyl, amino, amide, amido, ester, carboxyl or cyanide groups, halogen atoms or additional C-C double or triple bonds, for example vinyl ethers and vinyl esters of 3 to 10, preferably 4 to 8, carbon atoms, vinyl-aromatics, eg. styrene and vinyltoluene, acrylic and methacrylic acid and esters thereof with monohydric and polyhydric alcohols of not more than 20, preferably 1 to 8, carbon atoms, eg. methyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl me~hacrylate, butane-1,4-diol diacrylate and hexane-1,6-diol diacrylate, nitriles and amides of acrylic and methacrylic acid, maleates and fumarates of alcohols of 1 to 20, preferably 1 to 8, car-bon atoms, eg diethyl fumarate7 N-vinyl compounds, eg.
N-vinylpyrrolidone, N-vinylcaprolac-tam and N-vinylcarbaz-ole, and allyl esters, eg. diallyl phthalate.
Examples o~ suitable photopolymerizable compounds 3ss~
- 5 - o Z~ 0050/35362 of relatively high molecular weight are unsaturated pol~J-esters prepared from ~ unsaturated dicarboxylic acids, eg. maleic, fumaric or itaconic acid, mixed if desired, with sa-turated or aromatic dicarboxylic acids, eg. adi-pic, phthalic or terephthalic acid, by reacting these acids with alkanediols, egl ethylene glycol, propylene - glycol, butanediol, neopentyl glycol or oxyalkylated bisphenol A; epoxideacrylates prepared from acrylic or methacrylic acid and aromatic or aliphatic diglycidyl ethers, and urethane acrylates, for example prepared from hydroxyalkyl acrylates and polyisocyanates, and poly-ester acrylates, for example prepared from hydroxyl-containing saturated polyesters and acrylic or metha-crylic-acid.
Saturated and/or unsaturated polymers and other additives, eg. thermal polymerization inhibitors, paraf-fin, pigments, dyes, peroxides, leveling agents~
fillers, glass fibers, and stabilizers against thermal or photochemical degradation, may be added to the photo-polymerizable compounds in a conventional manner, thetype and amount of additive depending on the particular end use.
~ he composition of the photopolymerizable com-pounds ~or a particular end use, and mixtures of these compounds with the above additi~es, are familar to a skilled worl~er.
The acylphosphine oxides according to the inven-tion are employed in these mixtures in general in a concentra-tio~ of from OoOl to 15, preferably from 0.05 35~9 - 6 - O.Z. 35362 to 5, % by weight, based on the photopolymerizable material. If desired, they may be combined with accelerators which eliminate the inhibitory effec-t of atmospheric oxygen on the photopolymerization.
~ ~xamples of such accelerators or synergistic agents are secondary and/or tertiary amines, eg. methyl-diethanolamine, dimethylethanolamine, triethylamine, triethanolamine, ethyl p-dimethylaminobenzoate, benzyl-dimethylamine, dimethylaminoethyl acrylate, N-phenyl-glycine and N-methyl-N-phenylglycine, and similar com-pounds which are known to those skilled in the art.
Hardening can a~so be accelerated by using aliphatic and aromatic halides, eg. 2-chloromethylnaphthalene and l-chloro-2-chloromethylnaphthalene, and, where relevant, agents which form freeradicals and are generally used as thermal polymerization initiators, eg. peroxides, azo compounds and compounds with a labile carbon-carbon bond, these being added in amounts of not more than 15% by weight~ based on the photopolymerizable material, and being known to a s~illed worker.
The acylphosphine oxides can furthermore be used in the presence or absence of the above synergistic agents and accelerators, or in combination with other photoinitiators for photohardening coatings, finishes and printing inks, for photosensitive recording materials, eg. photopolymerizable printing plates, and in styrene/
polyester resins~ Examples of such photoini-tiato s are aromatic ke-tones, eg benzil ketals, benzoin ethers, benzoin esters, Cl-C3-alkyl-, chloro- or chloromethyl-~ 7 ~ O.Z. 0050/35352substituted thioxanthones, the acylphosphines described in German Laid-Open Application DOS 30 20 092, the acyl-phosphine oxides and acylphosphinic acid esters disclosed in German Laid-Open Applications DOS 2,830,927 and DOS
2,909,994, and aromatic disulfides and naphthalenesul-fonyl chlorides, as well as any other suitable compounds known to a skilled worker.
Sources of radiation which preferentially emit light in the absorp-tion range of the compounds according to the invention, ie. between 230 and 450 nm, are gener-ally used for triggering the polymerization of the above mixtures. Low-, medium- and high-pressure mercury ~ vapor lamps, superactinic fluorescent tubes and pulsed discharge lamps are particularly suitable. If appro-priate, the said lamps may be doped.
A particular advantage of the acylphosphine oxides according to the invention is that they can be used as photoinitiators for photopolymerization with light sources which have a relatively long wavelength and are therefore less dangerous, eg. fluorescent tubes, or for hardening by sunli~ht.
In the Examples which ~ollow, parts and percent-ages are by weight~ unless stated other~;rise. Parts by volume bear the same relation to parts by weight as that of the liter to the kilogram.
Examples of the novel compounds are given in Table 1, but the invention is not restricted to these.
The compounds listed in Table 2 are taken from German Laid Open Application DOS 2,909,994,for comparison.

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Preparation of an acylphosphine oxide:
122 parts of bis-(o-tolyl)-methox~phosphine ~rere added dropwise to 91.5 parts by weight of 2,4,6-tri-methylbenzoyl chloride in 100 parts by volume of dioxane, under reflux Thereafter, the mixture was stirred under reflux for a ~urther 5 hours and then cooled to room temperature, and the product was filtered off and recrystallized from toluene.
Yield: 116 9 parts (62% of theor~) Melting point: 155 - 159C
Analysis: calculated: C 76.6~ H 6.65% P 8.24%
found: C 75.3% H 6.8% P 7.95%

An unsaturated polyester resin was obtained by esterifying 143 parts of tetrahydrophthalic a~hydride and 175 pa~ts of maleic anhydride with 260 parts of diethylene glycol, 0.01~ of hydroquinone was added to the product, and a 64 per centstrength solution of this mixture in styrene was prepared.
For the W hardening experiments,20 parts of styrene, 30 parts of titanium dioxide (RN 57) and 1.5 parts of the photoinitiator ~rere added to 100 parts of this solution, and the finish was cast onto a glass plate with the aid of a film~casting apparatus (slot width 100 ~m).
The film was dried in air for about one min-ute7 and was then irradiated for 20 seconds with a high-pressure mercury vapor lamp (30 wat~/cm arc length, )55~
" .
~ O.Z. 0050/35302 Philips HTQ 7) which was located 15 cm abo~e the object.
The hardening was determined using the Konig pen-dulurn method (DIN 53,147), and the results are summarized in Table 3.
In a 2nd series of experiment, a thicker ].ayer of the above solution was cast onto a glass plate with the aid of a film-casting apparatus (slot width 400 ~rn), and the film was irradiated as described above.
When hardening was complete, the film was peeled off, and washed with acetone, and its thickness was determined. m ese measurements are also given in Table 3.
It can be seen from the Table that, compared with the comparative compounds I and IV, compounds 1 and 4 have a substantially superior hardening action in pig-mented polyester finishes.
~ABLE 3 W hardening of pigmented unsaturated polyester resins Initiator Koni pendulurn hardness Curable coatin~
~seconds) thickness (~m~

1.5 parts of each of the photoinitiators to be compared weredissol~ed, in each case,in arnixture cornprising 2C 56parts ofa reactionp-roduct ofbisphenol A digl~cldyl ether 55~
- 12 - O.Z 0050/35362 and acrylic acid, 44 parts of hexanediol diacrylate, 30 parts of titanium dioxide (rutile) and 3 parts of methyl-diethanolamine.
m e finish was cast onto glass plates with the aid of a film-casting apparatus (slot width lOO ~m), and the film was hardened at a belt speed of 5 m/minute, under a high-pressure mercury vapor lamp (lOO watt/cm arc length, Original Hanau Q 67 l9) which was located lO cm above the belt.
"
The hardening was determined by the Konig pen-dulum method (DIN 53,147), and the results are summar-ized in Table 4.
In a 2nd series of experiments,the above finishes were cast onto glass plates with the aid of a film-casting appartus (400 ~m), and thefilms were hardened as described above, but at a belt speed of lO m/minute.
When hardening was complete, thefilmswere peeled off, and washed with acetone, and theirthicknesses were determined. These measurements are also given in 20Table 4.

InitiatorPendulum hardness Curable coating (seconds) thickness (~m) I 55 lOO

Vwrinkled sur~ace 20 )S5S~
~ o.Z. 0050/35362 In pigmented finishes, compounds 1 and 2 give hardened layers which are 50 - 100% thicker than those obtained using comparative compounds I to V.

To measure the hardening activity, the change in temperature in the unsaturated polyester resin (UP
resin) durlng irradiation with W light was recorded by immersing a thermocouple, which was coated with a layer of wax and connected to a temperature recorder ~Tastotherm Script 3 N, standard thermocouple T ~00 from Deutschen Gulton GmbH), in a tinplate lid which was filled with 10 g of UP resin and had a diameter of 5 cm (thickness of the UP resin: 4.8 mm). m e lid was embedded in rigid polyurethane foam in order to avold heat losses durlng irradiation with UV light.
The radiation source was a UV field comprising 5 fluor-escent tubes (T~AK 40 W/05, Philips) arranged side-by-side at a distance of 8.5 cm from the surface of the UP
resin.

g 25 C-Tmax hardening temperature TmaX reached were obtained as characteristic parameters of the hardening activity from the temperature/time curves recorded. The hardening time was the time taken for the temperature of the sample to rise from25C to TmaX.
m e polyester resin with ~rhich the Examples and Comparative Examples were carried out was a 65 per cent strength s-tyrene solution of an unsaturated polyester obtained from maleic acid, o-phthalic acid, ethylene S~9 .
~ 0,Z, 0050/35362 glycol and propylene 1,2-glycol in the molar ratio 1 : 2 : 2,3 : 0.70-, and having an acid number of 50, -the solution being stabilized by 0.01% of hydroquinone.

Hardening activity of various compounds Compound Hardening activity ht250C_T . TmaX (C) I 4 minutes 45 seconds 125 II 4 minutes 38 seconds 101 III 4 minutes 53 seconds 103 IV 7 minutes 08 seconds 112 V 8 minutes 30 seconds 103 1 4 minutes 23 seconds 122 2 5 minutes 00 seconds 121

3 5 minutes 38 seconds 108 3 parts of photoinitiator were dissolved in a binder comprising 65 parts of a reaction product of bis-phenol A glycidyl ether and acrylic acid, and 35 parts of hexane-1,6-diol diacrylate. The finished mixture was knife-coated onto glass plates to give a ~0 ~m thick layer, and the plates were then passed under a high-pressure mercury vapor lamp (power: 80 W/cm of arc length), at a distance of 10 cm. The reactivity is quoted as the maximum possible conveyor belt speed at which a coating which is sufficiently hardened not to be scratched by a fingernail can still be obtained. m e results are summarized in Table 6.

ss~
- 15 - 0 Z- 0050/3~362 3% of methyldiethanolamine was added to a fin-ish prepared as described in ~xample 5. As in that Example, the finish was then kni~e-coated onto glass plates and the plates were exposed. According to the results, which are summarized in Table 6, the speed at which the compounds according to the invention effect hardening can.be increased by adding an amine accelerator.

Photo- Maximum conveyor belt speed in m/minute initiatr i~ air under an in air, with the addition inert gas of 3% of methyldiethanol-amine

Claims

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. An acylphosphine oxide which may be used as a photoinitiator and is of the formula (I) where R1 is methyl or ethyl, R2 is a branched or straight-chain alkyl radical of 1 to 4 carbon atoms, chlorine, alkoxy of 1 to 4 carbon atoms or hydrogen, R3 and R4 are identical or different, and are each alkyl, alkoxy or alkylthio, each of 1 to 4 carbon atoms, or chlorine, and R5 is hydrogen, chlorine, or alkoxy or alkylthio, each of 1 to 6 carbon atoms, or a branched or straight-chain alkyl radical of 1 to 12 carbon atoms.

2. An acylphosphine compound as claimed in claim 1, wherein the phenyl radical substituted by R1 and R2 is 2-methylphenyl or 2,5-dimethylphenyl.

3. An acylphosphine compound as claimed in claim 1, wherein the phenyl radical substituted by R3 R4 and R5 is 2,5-dimethylphenyl, 2,4,6-trimethylphenyl, 2,3,6-trimethyl-phenyl, 2,6-dimethoxyphenyl, 2,6-dichlorophenyl, 2,6-bis-(methylthio)-phenyl, 2,6-dimethyl-4-tert.-butylphenyl or 2,6-dimethyl-4-octylphenyl.

4. A process for the preparation of a photo-polymerizable material, wherein an acylphosphine compound as claimed in claim 1 is used as the photoinitiator.

5. A process as claimed in claim 4, wherein said acylphosphine compound is used in combination with a secondary or tertiary amine.

6. A process for the preparation of a photo-polymerizable coating agent, finish, printing ink or recording material, wherein from 0.1 to 15 per cent by weight of an acylphosphine compound as claimed in claim 1 is employed as the photoinitiator.

7. A process for the preparation of a photo-polymerizable plastic material based on an unsaturated polyester resin which may contain further assistants, wherein an acylphosphine compound as claimed in claim 1 is used as the photoinitiator.

8. A process as claimed in claim 5, wherein said acylphosphine compound is used in combination with a compound selected from the group comprising benzil ketals, benzoin ethers, benzoin esters, C1-C4-alkyl-, chloro- or chloro-methyl-substituted thioxanthones, aromatic disulfides, naphthalenesulfonyl chlorides, acylphosphines, acylphosphinic acid esters, acylphosphine sulfides, and acylphosphine oxides which differ from those claimed in claim 1.

9. A process as claimed in claim 6, wherein said acylphosphine compound is used in combination with a compound selected from the group comprising benzil ketals, benzoin ethers, benzoin esters, C1-C4-alkyl-, chloro- or chloromethyl-substituted thioxanthones, aromatic disulfides, naphthalene-sulfonyl chlorides, acylphosphines, acylphosphinic acid esters, acylphosphine sulfides, and acylphosphine oxides which differ from those claimed in claim 1.

10. A process as claimed in claim 7, wherein said acylphosphine compound is used in combination with a compound selected from the group comprising benzil ketals, benzoin ethers, benzoin esters, C1-C4-alkyl-, chloro- or chloromethyl-substituted thiozanthones, aromatic disulfides, naphthalene-sulfonyl chlorides, acylphosphines, acylphosphinic acid esters, acylphosphine sulfides, and acylphosphine oxides which differ from those claimed in claim 1.

11. A process for the preparation of a photo-polymerizable material as claimed in claim 5, 6 or 7, wherein said acylphosphine compound is employed in combination with a thermal polymerization initiator.

12. A process for the preparation of a photo-polymerizable material as claimed in claim 4, wherein said acylphosphine compound is employed in combination with a thermal polymerization initiator.

13. A process for the preparation of a photo-polymerizable material, wherein an acylphosphine compound as claimed in claim 2 is used as the photoinitiator.

14. A process as claimed in claim 13, wherein said acylphosphine compound is used in combination with a secondary or tertiary amine.

15. A process for the preparation of a photo-polymerizable coating agent, finish, printing ink or recording material, wherein from 0.01 to 15 per cent by weight of an acylphosphine compound as claimed in claim 2 is employed as the photoinitiator.

16. A process for the preparation of a photo-polymerizable plastic material based on an unsaturated polyester resin which may contain further assistants, wherein an acylphosphine compound as claimed in claim 2 is used as the photoinitiator.

17. A process as claimed in claim 14, wherein said acylphosphine compound is used in combination with a compound selected from the group comprising benzil ketals, benzoin ethers, benzoin esters, C1-C4-alkyl-, chloro- or chloromethyl-substituted thioxanthones, aromatic disulfides, naphthalenesulfonyl chlorides, acylphosphines, acylphosphinic acid esters, acylphosphine sulfides, and acylphosphine oxides which differ from those claimed in claim 1.

18. A process as claimed in claim 15, wherein said acylphosphine compound is used in combination with a compound selected from the group comprising benzil ketals, benzoin ethers, benzoin esters, C1-C4-alkyl-, chloro or chloromethyl-substituted thioxanthones, aromatic disulfides, naphthalenesulfonyl chlorides, acylphosphines, acylphosphinic acid esters, acylphosphine sulfides, and acylphosphine oxides which differ from those claimed in claim 1.

19. A process as claimed in claim 16, wherein said acylphosphine compound is used in combination with a compound selected from the group comprising benzil ketals, benzoin ethers, benzoin esters, C1-C4-alkyl-, chloro- or chloromethyl-substituted thioxanthones, aromatic disulfides, naphthalenesulfonyl chlorides, acylphosphines, acylphosphinic acid esters, acylphosphine sulfides, and acylphosphine oxides which differ from those claimed in claim 1.

20. A process for the preparation of a photo-polymerizable material as claimed in claim 14, 15 or 16, wherein said acylphosphine compound is employed in combina-tion with a thermal polymerization initiator.

21. A process for the preparation of a photo-polymerizable material as claimed in claim 13, wherein said acylphosphine compound is employed in combination with a thermal polymerization initiator.

22. A process for the preparation of a photo-polymerizable material, wherein an acylphosphine compound as claimed in claim 3 is used as the photoinitiator.

23. A process as claimed in claim 22, wherein said acylphosphine compound is used in combination with a secondary or tertiary amine.

24. A process for the preparation of a photo-polymerizable coating agent, finish, printing ink or recording material, wherein from 0.01 to 15 per cent by weight of an acylphosphine compound as claimed in claim 3 is employed as the photoinitiator.

25. A process for the preparation of a photo-polymerizable plastic material based on an unsaturated poly-ester resin which may contain further assistants, wherein an acylphosphine oxide as claimed in claim 3 is used as the photoinitiator.

26. A process as claimed in claim 23, wherein said acylphosphine compound is used, in combination with a compound from the group comprising benzil ketals, benzoin ehters, benzoin esters, C1-C4-alkyl-, chloro- or chloromethyl-substituted thioxanthones, aromatic disulfides, naphthalene-sulfonyl chlorides, acylphosphines, acylphosphinic acid esters, acylphosphine sulfides, and acylphosphine oxides which differ from those claimed in claim 1.

27. A process as claimed in claim 24, wherein said acylphosphine compound is used, in combination with a compound from the group-comprising benzil ketals, benzoin ethers, benzoin esters, C1-C4-alkyl-, chloro- or chloromethyl-substituted thioxanthones, aromatic disulfides, naphthalene-sulfonyl chlorides, acylphosphines, acylphosphinic acid esters, acylphosphine sulfides, and acylphosphine oxides which differ from those claimed in claim 1.

28. A process as claimed in claim 25, wherein said acylphosphine compound is used, in combination with a compound from the group comprising benzil ketals, benzoin ethers, benzoin esters, C1-C4-alkyl-, chloro- or chloromethyl-substituted thioxanthones, aromatic disulfides, naphthalene-sulfonyl chlorides, acylphosphines, acylphosphinic acid esters, acylphosphine sulfides, and acylphosphine oxides which differ from those claimed in claim 1.

29. A process for the preparation of a photo-polymerizable material as claimed in claim 23, 24 or 25, wherein said acylphosphine compound is employed in combi-nation with a thermal polymerization initiator.

30. A process for the preparation of a photo-polymerizable material as claimed in claim 22, wherein said acylphosphine compound is employed in combination with a thermal polymerization initiator.