Molecular complex compounds of acylphosphine oxide and .alpha.-hydroxy ketones as photoinitiators

Molecular complex compounds comprising a mono-, bis- or trisacylphosphine oxide compound with an .alpha.-hydroxy ketone compound are suitable as photoinitiators for the photopolymerization of free-radically polymerizable compounds.

The invention relates to molecular complex compounds comprising mono- and 
bisacylphosphine oxides with .alpha.-hydroxy ketones and to the use of 
these molecular complex compounds as photoinitiators. 
Acylphosphine oxides have been described in the literature as 
photoinitiators. For example, EP-A 7 508 reveals the preparation and use 
of some monoacylphosphine oxides. Further monoacylphosphine oxides, and 
bisacylphosphine oxides, are known from U.S. Pat. No. 5,218,009. The 
preparation and use of bisacylphosphine oxide photoinitiators is 
disclosed, for example, in the U.S. Pat. Nos. 4,737,593 and 4,792,632 and 
in GB-A2259704. Trisacylphosphine oxide compounds are revealed, for 
example, in WO-A 96/7662. .alpha.-Hydroxy ketone compounds as 
photoinitiators are cited, for example, in the U.S. Pat. Nos. 4,347,111 
and 4,672,079 and in EP-A 3002. The use of photoinitiator mixtures 
comprising acylphosphine oxides and .alpha.-hydroxy ketones is described, 
for example, in GB-A 2 259 704 or GB-A 2 292 740. 
There is a need for readily obtainable, reactive and storage-stable 
photoinitiator compounds which can be incorporated readily into 
formulations that are to be polymerized. 
It has now been found that molecular complex compounds comprising various 
photoinitiator compounds possess these properties. 
The invention therefore provides molecular complex compounds comprising a 
mono-, bis- or trisacylphosphine oxide compound with an .alpha.-hydroxy 
ketone compound. 
The molecular complex compounds can be prepared, for example, by generally 
known methods of growing crystals, for example from solution or melt 
methods. Such crystallization methods are known to the skilled worker and 
are also described in textbooks of chemistry, for example in Ullmann's 
Encyclopedia of Industrial Chemistry, Vol. A 8,127-131, Verlag Chemie, 
Weinheim-New York (1987) or Kirk-Othmer, Encyclopedia of Chemical 
Technology, Vol.7, 672-81, Verlag John Wiley & Sons, New York (1979). 
In the case of the solution process, the molecular complex compound can be 
prepared, for example, by dissolving the two components (i.e. the 
acylphosphine oxide compound and the .alpha.-hydroxy ketone compound), 
with or without heating, in appropriate solvents or solvent mixtures and 
precipitating the molecular complex compounds which form, either by adding 
a solvent in which the resulting complex compound is of lower solubility 
or by cooling the solution very slowly. 
It is judicious, for example, to cool a solution of the components which 
has been saturated at a relatively high temperature, in a vessel subject 
to uniform thermal conditioning, very slowly to a lower temperature. In 
this case the nucleation of the crystals can be initiated by rubbing on 
the wall of the vessel, for example. 
It is also possible, for example, to remove continuously the solvent from a 
saturated solution of the components, for example by evaporation, in which 
case the formation of the molecular complex crystal begins. 
The temperatures used in preparing the saturated solutions are dependent on 
the solvent or solvent mixture employed and range, for example, from room 
temperature to 150.degree. C., in particular 50-100.degree. C. 
In preparing the molecular complex compounds the two components are 
preferably employed in a molar ratio of 1:1. However, it is also possible 
to employ the components in other molar ratios, for example from 5:1 to 
1:5. In this case it is then possible, for example, for the mixture formed 
to comprise molecular complex compound and the component added in excess. 
The choice of solvent in preparing the molecular complex compounds is 
guided by the particular melting point of the components. In the present 
case, particularly suitable solvents for the different photoinitiator 
compounds are aliphatic hydrocarbons, such as hexane, pentane, heptane, 
octane and isomer mixtures of these solvents. Also possible, however, is 
the use of aromatic hydrocarbons, for example xylene or toluene, etc. 
It is advantageous to use polar additives, for example in amounts of 1-30%, 
for example 1-20%, especially 1-5%. Examples of such additives are ethyl 
acetate, methyl ethyl ketone, acetone, methyl isobutyl ketone and 
alcohols. 
Also conceivable is the use of other polar solvents, for example linear and 
cyclic ethers, such as diethyl ether, tetrahydrofuran or dioxane. 
It is also possible, for example, to use polar solvents, such as methyl 
ethyl ketone, and to precipitate the resulting complex compounds with 
water. These solvents can be employed in pure form or else may include 
water, for example as azeotrope. In other words, recycled solvents 
produced in the course of workup in an azeotropic mixture with water are 
also suitable. 
Examples of other suitable solvents are boiling-limit petroleum spirits 
with an aromatics content of about 3-10%. These solvents can be admixed, 
for example, with the polar solvents described above. Other examples of 
suitable solvent mixtures are mixtures of isooctane and ethyl acetate, but 
also those which include water, as already mentioned above, for example 
methyl ethyl ketone and water. 
The resultant molecular complex crystals are separated from the solution 
judiciously by means of customary separation measures, for example 
filtration. If the solvents used are high-boiling solvents, then in the 
course of filtration the precipitated molecular complex compounds are 
washed with a low-boiling solvent, for example hexane, in order to make it 
possible to dry the crystals. The crystals are judiciously dried at 
slightly elevated temperature and with application of a vacuum, in 
particular at 40-50.degree. C. and about 50 mbar. It may also be judicious 
to wash the crystals in order to remove impurities. This is done, for 
example, using a solvent in which the crystals are of very low solubility 
and which is miscible with the mother liquor. 
It is also possible, for example, to prepare the complex compound by adding 
the second component directly in the course of the preparation of one 
component, prior to its isolation and thus while it is still in solution, 
and to precipitate the complex compound by adding an appropriate solvent. 
In the preparation of the acylphosphine oxide compound, for example, the 
compound can be transferred after the oxidation step into an appropriate 
solvent, the .alpha.-hydroxy ketone compound added, and the molecular 
complex compound precipitated. 
It is also possible, for example, to obtain the novel molecular complex 
compounds by melting the acylphosphine oxide compounds and .alpha.-hydroxy 
ketone compounds and then slowly cooling the melt. In this case it is 
possible, for example, first to prepare the mixture of the two components 
and then to melt the mixture, although each component can also be melted 
individually and the compounds mixed in the melted state. The temperatures 
are dependent on the melting points of the respective components and are, 
for example, from about 100.degree. C. to 200.degree. C. In some cases it 
is judicious to seed the melt with crystals of the molecular complex 
compounds obtained from the solvent method. Such seeding is carried out, 
for example, after the melt has been cooled to room temperature or else at 
the melting point of the molecular complex compound. 
Melt methods of this kind for producing crystals are known to the skilled 
worker and are described, for example, in Ullmann's Encyclopedia of 
Industrial Chemistry, Vol. A 8, 121-127, Verlag Chemie, Weinheim-New York 
(1987). 
When cooling the melt, especially when cooling the melt rapidly, amorphous 
modifications of the novel molecular complex compounds, for example, can 
also be obtained. For the preparation of certain molecular complex 
compounds the rapid cooling may prove to be in-judicious, since with some 
compounds the formation of the complex is slow. In the case of rapid 
cooling, moreover, there is a greater probability of mixtures forming 
between the complex compound and one of its components. 
It is also conceivable, for example, that polymorphous crystal forms of the 
molecular complex compounds are formed, or, for example, crystals of 
molecular complex compounds which contain "guest molecules", for example 
solvent, depending on the crystallization method. However, these mixtures 
are also suitable as initiators for photopolymerization. 
The molecular complexes are in general associated by way of hydrogen bonds 
between the H atoms of the OH group of the hydroxy ketone and the oxygen 
atom which is attached to the P atom in the phosphine oxide compound. 
Preference is given to molecular complex compounds in which the mono-, bis- 
or trisacylphosphine oxide compound is a compound of the formula I 
##STR1## 
R.sub.1 and R.sub.2 independently of one another are C.sub.1 -C.sub.18 
alkyl, C.sub.2 -C,.sub.8 alkyl interrupted by one or more O atoms, 
phenyl-substituted C.sub.1 -C.sub.4 alkyl, C.sub.2 -C.sub.18 alkenyl, 
phenyl which is unsubstituted or is substituted from one to five times by 
halogen, hydroxyl, C.sub.1 -C.sub.8 alkyl and/or C.sub.1 -C.sub.8 alkoxy, 
naphthyl which is unsubstituted or substituted from one to five times by 
halogen, hydroxyl, C.sub.1 -C.sub.8 alkyl and/or C.sub.1 -C.sub.8 alkoxy, 
biphenyl which is unsubstituted or substituted from one to five times by 
halogen, hydroxyl, C.sub.1 -C.sub.8 alkyl and/or C.sub.1 -C.sub.8 alkoxy, 
or are C.sub.3 -C.sub.12 cycloalkyl, an O-, S- or N-containing 5- or 
6-membered heterocyclic ring or a group COR.sub.3 ; or 
R.sub.1 is -- OR.sub.4 or a group 
##STR2## 
or 
R.sub.1 and R.sub.2 together are C.sub.4 -C.sub.8 alkylene and, with the P 
atom to which they are attached, form a ring structure; 
R.sub.3 is C.sub.1 -C.sub.18 alkyl, C.sub.3 -C.sub.12 cycloalkyl, C.sub.2 
-C.sub.18 alkenyl, phenyl, naphthyl or biphenyl each of which is 
unsubstituted or substituted from one to four times by C.sub.1 -C.sub.8 
alkyl, C.sub.1 -C.sub.8 alkoxy, C.sub.1 -C.sub.8 alkylthio and/or halogen, 
or is an O--, S-- or N-containing 5- or 6-membered heterocyclic ring or a 
group 
##STR3## 
R.sub.4 is C.sub.1 -C.sub.8 alkyl, phenyl, naphthyl or phenyl-C.sub.1 
-C.sub.8 alkyl; 
Y is phenylene, C.sub.1 -C.sub.12 alkylene, cyclopentylene or 
cyclohexylene; 
X is C.sub.1 -C.sub.18 alkylene, C.sub.2 -C.sub.18 alkylene which is 
interrupted one or more times by --O--, --S--, --NR.sub.5 --, 
##STR4## 
or --SO.sub.2 --, or is C.sub.1 -C.sub.6 alkylene which is substituted by 
Cl, F, C.sub.1 -C.sub.4 alkoxy, COOR.sub.7, phenyl, phenyl-C.sub.1 
-C.sub.4 alkyl, naphthyl-C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 
alkylphenyl, C.sub.1 -C.sub.4 alkylnaphthyl, phenyl-C.sub.1 -C.sub.4 
alkoxy, naphthyl-C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 alkoxy-C.sub.1 
-C.sub.4 alkoxy and/or CN, or 
X is C.sub.1 -C.sub.8 alkylene which is substituted by one or two radicals 
of the formula A 
##STR5## 
X is a group of the formula A.sub.1 -A.sub.9 
##STR6## 
a and b independently of one another are 0 or 1 and the sum of d and f is a 
number from 3 to 8, neither d nor f being 0, or 
X is a group --CH.sub.2 --CH.dbd.CH--CH.sub.2 -- or --CH.sub.2 
--C.tbd.C--CH.sub.2 --, or is phenylene which is unsubstituted or 
substituted from one to three times by Cl, F, C.sub.1 -C.sub.4 alkyl 
and/or C.sub.1 -C.sub.4 alkoxy, or is xylylene, 
##STR7## 
or 
X is a group of the formula A.sub.10 -A.sub.13 
##STR8## 
Q is a single bond, CR.sub.9 R.sub.10, --O--, --S--, --NR.sub.5 --, 
--SO2--, --(CH.sub.2).sub.p -- or --CH.dbd.CH--; 
p is a number from 2-12; 
Z is O or S; 
R.sub.5 is hydrogen, C.sub.1 -C.sub.12 alkyl or phenyl; 
R.sub.6 is C.sub.1 -C.sub.4 alkyl or phenyl; 
R.sub.7 is C.sub.1 -C.sub.12 alkyl, C.sub.2 -C.sub.18 alkyl interrupted one 
or more times by --O--, or is benzyl, phenyl, cyclopentyl or cyclohexyl; 
R.sub.8 is hydrogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy or 
halogen; 
R.sub.9 is hydrogen or C.sub.1 -C.sub.4 alkyl; and 
R.sub.10 is hydrogen, methyl or ethyl. 
C.sub.1 -C,.sub.8 alkyl can be linear or branched and is, for example, 
methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec.-butyl, 
tert.-butyl, pentyl, isopentyl, hexyl, heptyl, octyl, nonyl, decyl, 
dodecyl or octadecyl. Preference is given to C.sub.1 -C.sub.12, for 
example C.sub.1 -C.sub.8 or C.sub.1 -C.sub.6, especially C.sub.1 -C.sub.4 
alkyl. 
C.sub.1 -C.sub.12, C.sub.1 -C.sub.8 and C.sub.1 -C.sub.4 alkyl can have the 
same meanings as indicated above up to the corresponding number of C 
atoms. 
C.sub.2 -C.sub.18 alkyl interrupted by one or more O atoms is interrupted, 
for example, from 1 to 5 times, for example 1 to 3 times or once or twice 
by --O--. This results as in structural units such as, for example, 
--O(CH.sub.2).sub.2 OH, --O(CH.sub.2).sub.2 OCH.sub.3, --O(CH.sub.2 
CH.sub.2 O).sub.2 CH.sub.2 CH.sub.3, --CH.sub.2 --O--CH.sub.3, --CH.sub.2 
CH.sub.2 O--CH.sub.2 CH.sub.3, --CH.sub.2 CH.sub.2 O!.sub.y --CH.sub.3, 
where y=1 to 5, --(CH.sub.2 CH.sub.2 O).sub.5 CH.sub.2 CH.sub.3, 
--CH.sub.2 --CH(CH.sub.3)--O--CH.sub.2 --CH.sub.2 CH.sub.3 or --CH.sub.2 
--CH(CH.sub.3)--O--CH.sub.2 --CH.sub.3. 
Phenyl-substituted C.sub.1 -C.sub.4 alkyl is, for example, benzyl, 
2-phenylethyl, 3-phenylpropyl, .alpha.-methylbenzyl or 
.alpha.,.alpha.-dimethylbenzyl, especially benzyl. 
Phenyl-C.sub.1 -C.sub.8 alkyl is, for example, benzyl, phenylethyl, 
.alpha.-methylbenzyl, phenylpentyl, phenylhexyl, phenyloctyl or 
.alpha.,.alpha.-dimethylbenzyl, especially benzyl. 
Phenyl-C.sub.1 -C.sub.4 alkyl has the definitions given above up to the 
appropriate number of C atoms. Preference is given to phenyl-C.sub.1 
-C.sub.4 alkyl, especially phenyl-C.sub.1 -C.sub.2 alkyl. 
C.sub.2 -C.sub.18 alkenyl can be linear or branched and there can be more 
than one unsaturated bond in the molecule. Examples are vinyl, allyl, 
methylvinyl, butenyl, butadienyl, pentenyl, hexenyl, heptenyl, octenyl, 
nonenyl, decenyl, dodecenyl or octadecenyl. 
C.sub.1 -C.sub.8 alkoxy can be linear or branched and is, for example, 
methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec.-butoxy, 
tert.-butoxy, pentoxy, isopentoxy, hexyloxy, heptyloxy or octyloxy. 
Preference is given, for example, to C.sub.1 -C.sub.6 or, in particular, 
C.sub.1 -C.sub.4 alkoxy. C.sub.1 -C.sub.6 alkoxy and C.sub.1 -C.sub.4 
alkoxy can have the same definitions as indicated above up to the 
appropriate number of C atoms. 
C.sub.1 -C.sub.4 alkoxy-C.sub.1 -C.sub.4 alkoxy is, for example, 
methoxyethoxy, methoxypropoxy, methoxybutoxy, ethoxymethoxy, ethoxyethoxy, 
ethoxypropoxy, ethoxybutoxy, propoxymethoxy, propoxyethoxy, 
propoxypropoxy, propoxybutoxy, butoxymethoxy, butoxyethoxy, butoxypropoxy 
or butoxybutoxy, especially methoxyethoxy and ethoxyethoxy. 
C.sub.1 -C.sub.8 alkylthio can be linear or branched and is, for example, 
methylthio, ethylthio, propylthio, isopropylthio, butylthio, 
tert-butylthio, hexylthio or octylthio, especially methylthio. 
Halogen is, for example, chlorine, bromine and iodine, especially chlorine. 
Substituted phenyl is substituted from one to five times, for example once, 
twice or three times, especially once or twice, on the phenyl ring. 
Substitution takes place, for example, in positions 2, 3, 4, 5, 2,4, 2,5, 
2,6, 3,4, 3,5, 2,4,6 or 3,4,5 of the phenyl ring. C.sub.1 -C.sub.8 alkyl, 
C.sub.1 -C.sub.4 alkyl-, C.sub.1 -C.sub.8 alkoxy, C.sub.1 -C.sub.8 
alkylthio and C.sub.1 -C.sub.4 alkoxy substitutents can have the 
definitions indicated above. Examples of substituted phenyl are tolyl, 
xylyl, 4-methoxyphenyl, 2,4- and 2,5-dimethoxyphenyl, ethylphenyl and 
4-alkoxy-2-methylphenyl. 
Examples of C.sub.3 -C.sub.12 cycloalkyl are cyclopentyl, cyclohexyl, 
cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl or cyclododecyl, 
preferably cyclopentyl and cyclohexyl. 
R.sub.1 and R.sub.2 as an O--, S--or N-containing 5- or 6-membered 
heterocyclic ring are, for example, furyl, thienyl, pyrrolyl, oxinyl, 
dioxinyl or pyridyl. 
If R.sub.1 and R.sub.2 together are C.sub.4 -C.sub.8 alkylene and, with the 
P atom to which they are attached, form a ring structure then this 
structure can include not just simple rings but also bridged rings, for 
example 
##STR9## 
X as C.sub.1 -C.sub.18 alkylene is linear or branched alkylene, for example 
methylene, ethylene, propylene, isopropylene, n-butylene, sec-butylene, 
isobutylene, tert-butylene, pentylene, hexylene, heptylene, octylene, 
nonylene, decylene, dodecylene, tetradecylene, heptadecylene or 
octadecylene. In particular, X is C.sub.1 -C.sub.12 alkylene, for example 
ethylene, decylene, 
##STR10## 
Interruption of X as C.sub.2 -C.sub.18 alkylene by --O--, --S--, --NR.sub.5 
--, 
##STR11## 
or --SO.sub.2 -- results, for example, in structural units such as 
--CH.sub.2 --O--CH.sub.2 --, --CH.sub.2 CH.sub.2 --O--CH.sub.2 CH.sub.2 
--, --CH.sub.2 CH.sub.2 O!.sub.y --, where y=1-9, --(CH.sub.2 CH.sub.2 
O).sub.7 CH.sub.2 CH.sub.2 --, --CH.sub.2 --CH(CH.sub.3)--O--CH.sub.2 
--CH(CH.sub.3)--, --CH.sub.2 --S--CH.sub.2 --, --CH.sub.2 CH.sub.2 
--S--CH.sub.2 CH.sub.2 --, --CH.sub.2 CH.sub.2 CH.sub.2 --S--CH.sub.2 
CH.sub.2 CH.sub.2 --, --(CH.sub.2).sub.3 --S--(CH.sub.2).sub.3 
--S--(CH.sub.2).sub.3 --, --CH.sub.2 --(NR.sub.5)--CH.sub.2 --, --CH.sub.2 
CH.sub.2 --(NR.sub.5)--CH.sub.2 CH.sub.2 --, --CH.sub.2 
--(P(O)R.sub.6)--CH.sub.2 --, --CH.sub.2 CH.sub.2 
--(P(O)R.sub.6)--CH.sub.2 CH.sub.2 --, 
##STR12## 
Examples of C.sub.1 -C.sub.8 alkylene which is substituted by one or two 
radicals of the formula A are 
##STR13## 
in which R.sub.3 is as defined above. 
Naphthyl-C.sub.1 -C.sub.4 alkyl is, for example, naphthylmethyl, 
naphthylethyl, naphthyl(1-methyl)eth-1-yl or 
naphthyl(1,1-dimethyl)eth-1-yl, especially naphthylmethyl. 
C.sub.1 -C.sub.4 alkylphenyl is, for example, tolyl, xylyl, mesityl, 
ethylphenyl or diethylphenyl, preferably tolyl or mesityl. 
C.sub.1 -C.sub.4 alkylnaphthyl is naphthyl substituted by methyl, ethyl 
and/or propyl or butyl. 
Phenyl-C.sub.1 -C.sub.4 alkoxy is, for example, benzyloxy, phenylethyloxy, 
.alpha.-methylbenzyloxy or .alpha.,.alpha.-dimethylbenzyloxy, especially 
benzyloxy. 
Naphthyl-C.sub.1 -C.sub.4 alkoxy is, for example, naphthylmethyloxy or 
naphthylethyloxy. 
Examples of groups of the formula A.sub.1 in which the sum of d and f is 
from 3 to 8 are: 
##STR14## 
Preferred groups of the formula A.sub.10 are 
##STR15## 
The preparation of acylphosphine oxide compounds of the formula I is known 
to the skilled worker and is described, for example, in EP-A 7 508, in 
U.S. Pat. Nos. 5,218,009, 4,737,593 and 4,792,632, in GB-A 2 259 704 and 
in WO-A 96/7662. 
Preference is given to compounds of the formula I in which R.sub.1 and 
R.sub.2 independently of one another are C.sub.1 -C.sub.12 alkyl, benzyl, 
phenyl which is unsubstituted or substituted from one to four times by 
halogen, especially Cl, C.sub.1 -C.sub.8 alkyl and/or C.sub.1 -C.sub.8 
alkoxy, or are cyclohexyl or COR.sub.3, or R.sub.1 is OR.sub.4 or 
##STR16## 
R.sub.3 is phenyl which is unsubstituted or substituted from one to four 
times by C.sub.1 -C.sub.8 alkyl, especially C.sub.1 -C.sub.4 alkyl, 
C.sub.1 -C.sub.8 alkoxy, C.sub.1 -C.sub.8 alkylthio, especially C.sub.1 
-C.sub.4 alkylthio, and/or halogen, especially chlorine, or is a group 
##STR17## 
R.sub.4 is C.sub.1 -C.sub.8 alkyl, especially C.sub.1 -C.sub.4 alkyl, 
phenyl or benzyl; 
X is C.sub.1 -C.sub.18 alkylene, especially C.sub.6 -C.sub.10 alkylene, or 
a group 
##STR18## 
and Y is phenylene, C.sub.2 -C.sub.12 alkylene or cyclohexylene. 
Other compounds of the formula I that are of interest are those in which 
R.sub.1 and R.sub.2 independently of one another are C.sub.1 -C.sub.8 
alkyl, phenyl which is unsubstituted or substituted from one to four times 
by C.sub.1 -C.sub.4 alkyl and/or C.sub.1 -C.sub.8 alkoxy, or are 
cyclohexyl or a group COR.sub.3, or 
R.sub.1 is a group 
##STR19## 
or --OR.sub.4 ; R.sub.3 is phenyl which is unsubstituted or substituted 
from one to four times by methyl and/or methoxy; R.sub.4 is methyl, ethyl 
or phenyl; and X is C.sub.6 -C.sub.10 alkylene or 
##STR20## 
Notable compounds of the formula I are those in which R.sub.1 is COR.sub.3, 
R.sub.2 is C.sub.1 -C.sub.18 alkyl and R.sub.3 is phenyl which is 
substituted two or three times by C.sub.1 -C.sub.4 alkyl or C.sub.1 
-C.sub.4 alkoxy. 
Also of particular interest are those compounds of the formula I in which 
R.sub.1 is COR.sub.3, R.sub.2 is phenyl which is unsubstituted or 
substituted by C.sub.1 -C.sub.4 alkyl and/or C.sub.1 -C.sub.4 alkoxy and 
R.sub.3 is phenyl which is substituted two or three times by C.sub.1 
-C.sub.4 alkyl or C.sub.1 -C.sub.4 alkoxy. 
Compounds of the formula I are of particular interest when the substitution 
of R.sub.3 as phenyl is in positions 2,6 or 2,4,6. 
Examples of compounds of the formula I which are suitable for preparing the 
molecular complex compounds are 
bis(2,6-dimethoxybenzoyl)phenylphosphine oxide, 
bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide, 
bis(2,6-dimethoxybenzoyl)-n-butylphosphine oxide, 
bis(2,6-dimethoxybenzoyl)-(2-methylprop-1-yl)phosphine oxide, 
bis(2,6-dimethoxybenzoyl)-(1-methylprop-1-yl)phosphine oxide, 
bis(2,6-dimethoxybenzoyl)-t-butylphosphine oxide, 
bis(2,6-dimethoxybenzoyl)cyclohexylphosphine oxide, 
bis(2,6-dimethoxybenzoyl)octylphosphine oxide, 
bis(2-methoxybenzoyl)(2-methylprop-1-yl)phosphine oxide, 
bis(2-methoxybenzoyl)(1-methylprop-1-yl)phosphine oxide, 
bis(2,6-diethoxybenzoyl)(2-methylprop-1-yl)phosphine oxide, 
bis(2,6-diethoxybenzoyl)(1-methylprop-1-yl)phosphine oxide, 
bis(2,6-dibutoxybenzoyl)(2-methylprop-1-yl)phosphine oxide, 
bis(2,4-dimethoxybenzoyl)(2-methylprop-1-yl)phosphine oxide, 
bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 
2,4,6-trimethylbenzoyidiphenylphosphine oxide, 
bis(2,4,6-trimethylbenzoyl)(2,4-dipentoxyphenyl)phosphine oxide, 
bis(2,6-dimethoxybenzoyl)benzylphosphine oxide, 
bis(2,6-dimethoxybenzoyl)-2-phenylpropylphosphine oxide, 
bis(2,6-dimethoxybenzoyl)-2-phenylethylphosphine oxide, 
bis(2,6-dimethoxybenzoyl)benzylphosphine oxide, 
bis(2,6-dimethoxybenzoyl)-2-phenylpropylphosphine oxide, 
bis(2,6-dimethoxybenzoyl)-2-phenylethylphosphine oxide, 
2,6-dimethoxybenzoylbenzylbutylphosphine oxide, 
2,6-dimethoxybenzoylbenzyloctylphosphine oxide, 
bis(2,4,6-trimethylbenzoyl)isobutylphosphine oxide and 
2,6-dimethoxybenzoyl-2,4,6-trimethylbenzoyl-n-butylphosphine oxide. 
The .alpha.-hydroxy ketone compounds are, in particular, compounds of the 
formula II 
##STR21## 
in which 
R.sub.11 and R.sub.12 independently of one another are hydrogen, C.sub.1 
-C.sub.6 alkyl, phenyl, C.sub.1 -C.sub.6 alkoxy, OSiR.sub.16 
(R.sub.17).sub.2 or --O(CH.sub.2 CH.sub.2 O).sub.q --C.sub.1 -C.sub.6 
alkyl, or 
R.sub.11 and R.sub.12, together with the carbon atom to which they are 
attached, form a cyclohexyl ring; 
q is a number from 1 to 20; 
R.sub.13 is OH, C.sub.1 -C.sub.16 alkoxy or --O(CH.sub.2 CH.sub.2 O).sub.q 
--C.sub.1 -C.sub.6 alkyl; 
R.sub.14 is hydrogen, C.sub.1 -C.sub.18 alkyl, C.sub.1 -C.sub.18 alkoxy, 
--OCH.sub.2 CH.sub.2 --OR.sub.15, a group CH.sub.2 .dbd.C(CH.sub.3)-- or 
##STR22## 
l is a number from 2 to 10; 
B is the radical 
##STR23## 
R.sub.15 is hydrogen, 
##STR24## 
and 
R.sub.16 and R.sub.17 independently of one another are C.sub.1 -C.sub.8 
alkyl or phenyl. 
Examples of C.sub.1 -C.sub.18 alkyl, C.sub.1 -C.sub.6 alkyl, C.sub.1 
-C.sub.4 alkyl, C.sub.1 -C.sub.18 alkoxy and C.sub.1 -C.sub.6 alkoxy have 
been indicated above. 
The preparation of the .alpha.-hydroxy ketone compounds of the formula II 
is familiar to the skilled worker and is described, for example, in the 
U.S. Pat. Nos. 4,347,111 and 4,672,079 and in EP-A 3002. 
Compounds of the formula II that are of interest are those in which 
R.sub.11 and R.sub.12 independently of one another are hydrogen, C.sub.1 
-C.sub.6 alkyl or phenyl or R.sub.11 and R.sub.12, together with the 
carbon atom to which they are attached, form a cyclohexyl ring; R.sub.13 
is OH; and R.sub.14 is hydrogen, C.sub.1 -C.sub.12 alkyl, C.sub.1 
-C.sub.12 alkoxy, especially C.sub.1 -C.sub.4 alkoxy, --OCH.sub.2 CH.sub.2 
OR.sub.15, a group 
##STR25## 
Preference is given to the compounds of the formula II in which R.sub.11 
and R.sub.12 independently of one another are methyl or ethyl or R.sub.11 
and R.sub.12, together with the carbon atom to which they are attached, 
form a cyclohexyl ring; R.sub.13 is hydrogen and R.sub.14 is hydrogen, 
C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy or --OCH.sub.2 CH.sub.2 
OH. 
Examples of compounds of the formula II which are suitable for preparing 
the molecular complex compounds are 
.alpha.-hydroxycyclohexyl phenyl ketone, 
2-hydroxy-2-methyl-1-phenylpropanone, 
2-hydroxy-2-methyl-1-(4-isopropylphenyl)propanone, 
2-hydroxy-2-methyl-1-(4-dodecylphenyl)propanone and 
2-hydroxy-2-methyl-1-(2-hydroxyethoxy)phenyl!propanone. 
Preferred molecular complex compounds are those comprising a mono- or 
bisacylphosphine oxide compound of the formula I 
##STR26## 
in which 
R.sub.1 and R.sub.2 independently of one another are C.sub.1 -C.sub.12 
alkyl, phenyl which is unsubstituted or substituted once or twice by 
C.sub.1 -C.sub.8 alkyl and/or C.sub.1 -C.sub.8 alkoxy, or are COR.sub.3 ; 
R.sub.3 is a radical 
##STR27## 
R.sub.18 is C.sub.1 -C.sub.4 alkyl, especially methyl, or C.sub.1 -C.sub.4 
alkoxy, especially methoxy; and 
R.sub.19 is hydrogen or C.sub.1 -C.sub.4 alkyl, especially methyl; 
and an .alpha.-hydroxy ketone compound of the formula II 
##STR28## 
in which 
R.sub.11 and R.sub.12 independently of one another are C.sub.1 -C.sub.4 
alkyl or R.sub.1 and R.sub.2, together with the carbon atom to which they 
are attached, form a cyclohexyl ring; and R.sub.14 is hydrogen. 
Preference is given, furthermore, to molecular complex compounds in which 
the acylphosphine oxide compound is 
bis(2,6-dimethoxybenzoyl)(2,4,4-trimethyl-pentyl)-phosphine oxide or 
2,4,6-trimethylbenzoyldiphenylphosphine oxide and the .alpha.-hydroxy 
ketone compound is a compound of the formula II in which R.sub.11 and 
R.sub.12 are C.sub.1 -C.sub.4 alkyl or R.sub.11 and R.sub.12, together 
with the C atom to which they are attached, form a cyclohexyl ring, 
R.sub.13 is OH and R.sub.14 is hydrogen. 
Also of interest are molecular complex compounds in which the acylphosphine 
oxide compound is 
bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide, 
bis(2,4,6-trimethylbenzoyl)(2,4-dihexyloxyphenyl)phosphine oxide, 
bis(2,4,6-trimethylbenzoyl)(4-ethoxyphenyl)phosphine oxide or 
2,4,6-trimethylbenzoyldiphenylphosphine oxide and the .alpha.-hydroxy 
ketone compound is .alpha.-hydroxycyclohexyl phenyl ketone or 
2-hydroxy-2-methyl-1-phenylpropan-1-one. 
Of particular interest are molecular complex compounds comprising 
bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide and 
2-hydroxy-2-methyl-1-phenylpropanone; 
bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide and 
.alpha.-hydroxycyclohexyl phenyl ketone; 
bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 
.alpha.-hydroxycyclohexyl phenyl ketone; 
bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 
2-hydroxy-2-methyl-1-phenylpropanone; 
2,4,6-trimethylbenzoyldiphenylphosphine oxide and .alpha.-hydroxycyclohexyl 
phenyl ketone; 
2,4,6-trimethylbenzoyldiphenylphosphine oxide and 
2-hydroxy-2-methyl-1-phenylpropanone; 
bis(2,4,6-trimethylbenzoyl)(4-ethoxyphenyl)phosphine oxide and 
.alpha.-hydroxycyclohexyl phenyl ketone; 
bis(2,4,6-trimethylbenzoyl)(2,4-dipentoxyphenyl)phosphine oxide and 
.alpha.-hydroxycyclohexyl phenyl ketone; 
bis(2,4,6-trimethylbenzoyl)(2,4-dihexyloxyphenyl)phosphine oxide and 
.alpha.-hydroxy-cyclohexyl phenyl ketone; 
bis(2,4,6-trimethylbenzoyl)(2,4-dipentoxyphenyl)phosphine oxide and 
2-hydroxy-2-methyl-1-phenylpropanone; 
bis(2,4,6-trimethylbenzoyl)(2-methylpropyl)phosphine oxide and 
.alpha.-hydroxycyclohexyl phenyl ketone; 
bis(2,4,6-trimethylbenzoyl)(2-methylpropyl)phosphine oxide and 
2-hydroxy-2-methyl-1-phenylpropanone; 
bis(2,6-dimethoxybenzoyl)(2-methylpropyl)phosphine oxide and 
2-hydroxy-2-methyl-1-phenylpropanone and 
bis(2,6-dimethoxybenzoyl)(2-methylpropyl)phosphine oxide and 
.alpha.-hydroxycyclohexyl phenyl ketone. 
In accordance with the invention the molecular complex compounds can be 
used as photo-initiators for the photopolymerization of ethylenically 
unsaturated compounds or of mixtures which comprise such compounds. 
This use may also be practised in combination with another photoinitiator 
and/or with other additives. 
The invention therefore also provides photopolymerizable compositions 
comprising 
(a) at least one ethylenically unsaturated photopolymerizable compound, and 
(b) as photoinitiator, at least one molecular complex compound comprising a 
mono-, bis- or trisacylphosphine oxide compound with an .alpha.-hydroxy 
ketone compound, it being possible for the composition to comprise other 
photoinitiators and/or other additives in addition to component (b). 
The unsaturated compounds may contain one or more olefinic double bonds. 
They may be of low molecular mass (monomeric) or of relatively high 
molecular mass (oligomeric). Examples of monomers containing a double bond 
are alkyl or hydroxyalkyl acrylates or methacrylates, for example methyl, 
ethyl, butyl, 2-ethylhexyl or 2-hydroxyethyl acrylate, isobornyl acrylate, 
or methyl or ethyl methacrylate. Silicone acrylates are also of interest. 
Further examples are acrylonitrile, acrylamide, methacrylamide, 
N-substituted (meth)acrylamides, vinyl esters such as vinyl acetate, vinyl 
ethers such as isobutyl vinyl ether, styrene, alkyl- and halostyrenes, 
N-vinylpyrrolidone, vinyl chloride or vinylidene chloride. 
Examples of monomers containing two or more double bonds are the 
diacrylates of ethylene glycol, propylene glycol, neopentyl glycol, 
hexamethylene glycol and bisphenol A, 
4,4'-bis-(2-acryloyloxyethoxy)diphenylpropane, trimethylolpropane 
triacrylate, pentaerythritol triacrylate or tetraacrylate, vinylacrylate, 
divinylbenzene, divinyl succinate, diallyl phthalate, triallyl phosphate, 
triallyl isocyanurate or tris(2-acryloylethyl) isocyanurate. 
Examples of relatively high molecular mass (oligomeric) polyunsaturated 
compounds are acrylicized epoxy resins, and polyesters, polyurethanes and 
polyethers which are acrylicized or contain vinyl ether or epoxy groups. 
Further examples of unsaturated oligomers are unsaturated polyester resins 
which are mostly prepared from maleic acid, phthalic acid and one or more 
diols and have molecular weights of from about 500 to 3000. In addition it 
is also possible to employ vinyl ether monomers and vinyl ether oligomers, 
and also maleate-terminated oligomers having polyester, polyurethane, 
polyether, polyvinyl ether and epoxy main chains. Combinations of vinyl 
ether group-containing oligomers and polymers as are described in WO 
90/01512 are of particular suitability. However, copolymers of vinyl ether 
and maleic acid-functionalized monomers are also appropriate. Such 
unsaturated oligomers can also be referred to as prepolymers. 
Examples of particularly suitable compounds are esters of ethylenically 
unsaturated carboxylic acids and polyols or polyepoxides, and polymers 
containing ethylencially unsaturated groups in the chain or in side 
groups, for example unsaturated polyesters, polyamides and polyurethanes 
and copolymers thereof, polybutadiene and butadiene copolymers, 
polyisoprene and isoprene copolymers, polymers and copolymers containing 
(methy)acrylic groups in side chains, and also mixtures of one or more 
such polymers. 
Examples of unsaturated carboxylic acids are acrylic, methacrylic, 
crotonic, itaconic and cinnamic acid and unsaturated fatty acids such as 
linolenic acid or oleic acid. Acrylic and methacrylic acid are preferred. 
Suitable polyols are aromatic and, in particular, aliphatic and 
cycloaliphatic polyols. Examples of aromatic polyols are hydroquinone, 
4,4'-dihydroxybiphenyl, 2,2-di(4-hydroxyphenyl)-propane, and also novolaks 
and resols. Examples of polyepoxides are those based on said polyols, 
especially aromatic polyols and epichlorohydrin. Other suitable polyols 
include polymers and copolymers which contain hydroxyl groups in the 
polymer chain or in side groups, for example polyvinyl alcohol and 
copolymers thereof or poly(hydroxyalkyl methacrylates) or copolymers 
thereof. Further suitable polyols are oligoesters containing hydroxyl end 
groups. 
Examples of aliphatic and cycloaliphatic polyols are alkylenediols, 
preferably having 2 to 12 C atoms, such as ethylene glycol, 1,2- or 
1,3-propanediol, 1,2-, 1,3- or 1,4-butanediol, pentanediol, hexanediol, 
octanediol, dodecanediol, diethylene glycol, triethylene glycol, 
polyethylene glycols having molecular weights from preferably 200 to 1500, 
1,3-cyclopentanediol, 1,2-, 1,3- or 1,4-cyclohexanediol, 
1,4-dihydroxymethylcyclohexane, glycerol, tris(.beta.-hydroxyethyl)amine, 
trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol 
and sorbitol. 
The polyols may be esterified in part or in whole with one or with 
different unsaturated carboxylic acids; in partial esters, the free 
hydroxyl groups can be modified, for example etherified or esterified with 
other carboxylic acids. 
Examples of esters are: 
Trimethylolpropane triacrylate, trimethylolethane triacrylate, 
trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, 
tetramethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 
tetraethylene glycol diacrylate, pentaerythritol diacrylate, 
pentaerythritol triacrylate, pentaerythritol tetraacrylate, 
dipentaerythritol diacrylate, dipentaerythritol triacrylate, 
dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, 
dipentaerythritol hexaacrylate, tripentaerythritol octaacrylate, 
pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, 
dipentaerythritol dimethacrylate, dipentaerythritol tetramethacrylate, 
tripentaerythritol octamethacrylate, pentaerythritol diitaconate, 
dipentaerythritol trisitaconate, dipentaerythritol pentaitaconate, 
dipentaerythritol hexaitaconate, ethylene glycol diacrylate, 
1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol 
diitaconate, sorbitol-triacrylate, sorbitol tetraacrylate, 
pentaerythritol-modified triacrylate, sorbitol tetramethacrylate, sorbitol 
pentaacrylate, sorbitol hexaacrylate, oligoester acrylates and 
methacrylates, glycerol di- and triacrylate, 1,4-cyclohexane diacrylate, 
bisacrylates and bismethacrylates of polyethylene glycol having molecular 
weights from 200 to 1500, or mixtures thereof. 
Further suitable components (a) are the amides of identical or different 
unsaturated carboxylic acids with aromatic, cycloaliphatic and aliphatic 
polyamines having preferably from 2 to 6, especially from 2 to 4 amino 
groups. Examples of such polyamines are ethylenediamine, 1,2- or 
1,3-propylenediamine, 1,2-, 1,3- or 1,4-butylenediamine, 
1,5-pentylenediamine, 1,6-hexylenediamine, octylenediamine, 
dodecylenediamine, 1,4-diaminocyclohexane, isophoronediamine, 
phenylenediamine, bisphenylenediamine, di-.beta.-aminoethyl ether, 
diethylenetriamine, triethylenetetramine, di(.beta.-aminoethoxy)- or 
di(.beta.-aminopropoxy)ethane. Other suitable polyamines are polymers and 
copolymers with or without additional amino groups in the side chain, and 
oligoamides with amino end groups. Examples of unsaturated amides are: 
methylenebisacrylamide, 1,6-hexamethylenebis-acrylamide, 
diethylenetriaminetrismethacrylamide, bis(methacrylamidopropoxy)ethane, 
.beta.-methacrylamidoethyl methacrylate and 
N-(.beta.-hydroxyethoxy)ethyl!acrylamide. 
Suitable unsaturated polyesters and polyamides are derived, for example, 
from maleic acid and diols or diamines. Some of the maleic acid may be 
replaced by other dicarboxylic acids. They can be employed together with 
ethylenically unsaturated comonomers, for example styrene. The polyesters 
and polyamides may also be derived from dicarboxylic acids and 
ethylenically unsaturated diols or diamines, in particular from relatively 
long-chain compounds containing, for example, 6 to 20 C atoms. Examples of 
polyurethanes are those built up from saturated or unsaturated 
diisocyanates and from unsaturated or saturated diols. 
Polybutadiene and polyisoprene and copolymers thereof are known. Examples 
of suitable comonomers are olefins such as ethylene, propene, butene, 
hexene, (meth)acrylate, acrylonitrile, styrene and vinyl chloride. 
Polymers containing (meth)acrylate groups in the side chain are also 
known. These may be, for example, products of the reaction of 
novolak-based epoxy resins with (meth)acrylic acid, homopolymers or 
copolymers of vinyl alcohol or hydroxyalkyl derivatives thereof which have 
been esterified using (meth)acrylic acid, or homopolymers and copolymers 
of (meth)acrylates which have been esterified using hydroxyalkyl 
(meth)acrylates. 
The photopolymerizable compounds may be employed alone or in any desired 
mixtures. Preference is given to mixtures of polyol (meth)acrylates. 
It is also possible to add binders to the compositions according to the 
invention; this is particularly judicious if the photopolymerizable 
compounds are liquid or viscous substances. The quantity of binder may be, 
for example, 5-95% by weight, preferably 10-90% by weight and, in 
particular, 40-90% by weight, based on the overall solids content. The 
binder is chosen depending on the field of application and on the 
properties required therefor, such as the facility for development in 
aqueous and organic solvent systems, adhesion to substrates and 
sensitivity to oxygen. 
Examples of suitable binders are polymers having a molecular weight of 
about 5000-2,000,000, preferably 10,000-1,000,000. Examples are homo- and 
copolymeric acrylates and methacrylates, for example copolymers of methyl 
methacrylate/ethyl acrylate/methacrylic acid, poly(alkyl methacrylates), 
poly(alkyl acrylates); cellulose esters and cellulose ethers, such as 
cellulose acetate, cellulose acetate butyrate, methylcellulose and 
ethylcellulose; polyvinylbutyral, polyvinylformal, cyclized rubber, 
polyethers, such as polyethylene oxide, polypropylene oxide and 
polytetrahydrofuran; polystyrene, polycarbonate, polyrurethane, 
chlorinated polyolefins, polyvinyl chloride, copolymers of vinyl 
chloride/vinylidene chloride, copolymers of vinylidene chloride with 
acrylonitrile, methyl methacrylate and vinyl acetate, polyvinyl acetate, 
copoly(ethylene/vinyl acetate), polymers such as polycaprolactam and 
poly(hexamethyleneadipamide), and polyesters such as poly(ethylene glycol 
terephthalate) and poly(hexamethylene glycol succinate). 
The unsaturated compounds may also be used in mixtures with 
non-photopolymerizable film-forming components. These may be, for example, 
physically drying polymers or solutions thereof in organic solvents, for 
example nitrocellulose or cellulose acetobutyrate. However, these may also 
be chemically curable or heat-curable resins for example polyisocyanates, 
polyepoxides or melamine resins. The additional use of heat-curable resins 
is important for use in so-called hybrid systems, which are 
photopolymerized in a first step and crosslinked by thermal aftertreatment 
in a second step. 
The photoinitiators according to the invention are also suitable as 
initiators for the curing of oxidatively drying systems, as are described, 
for example, in Lehrbuch der Lacke und Beschichtungen Textbook of paints 
and coatings! Volume III, 296-328, Verlag W. A. Colomb in der Heenemann 
GmbH, Berlin-Oberschwandorf (1976). 
The photopolymerizable mixtures may contain various additives in addition 
to the photoinitiator. Examples thereof are thermal inhibitors, which are 
intended to prevent premature polymerization, for example hydroquinone, 
hydroquinone derivatives, p-methoxyphenol, .beta.-naphthol or sterically 
hindered phenols such as 2,6-di(tert-butyl)-p-cresol. The shelf life in 
the dark can be increased, for example, by using copper compounds such as 
copper naphthenate, copper stearate or copper octoate, phosphorus 
compounds, for example triphenylphosphine, tributylphosphine, triethyl 
phosphite, triphenyl phosphite or tribenzyl phosphite, quaternary ammonium 
compounds, for example tetramethylammonium chloride or 
trimethylbenzylammonium chloride, or hydroxylamine derivatives, for 
example N-diethylhydroxylamine. In order to exclude atmospheric oxygen 
during the polymerization, paraffin or similar wax-like substances can be 
added; these migrate to the surface on commencement of the polymerization 
because of their low solubility in the polymer, and form a transparent 
surface layer which prevents the ingress of air. Similarly, an 
oxygen-impermeable layer may be applied. Light stabilizers which can be 
added are UV absorbers, for example those of the 
hydroxyphenylbenzotriazole, hydroxyphenylbenzophenone, oxalamide or 
hydroxyphenyl-s-triazine type. These compounds can be employed 
individually or as mixtures with or without the use of sterically hindered 
amines (HALS). 
Examples of such UV absorbers and light stabilizers are 
1. 2-(2'-Hydroxyphenyl)benzotriazoles, for example 
2-(2'-hydroxy-5'-methylphenyl)-benzotriazole, 
2-(3',5'-di-tert-butyl-2'-hydroxyphenyl)benzotriazole, 
2-(5'-tert-butyl-2'-hydroxyphenyl)benzotriazole, 
2-(2'-hydroxy-5'-(1,1,3,3-tetramethylbutyl)phenyl)-benzotriazole, 
2-(3',5'-di-tert-butyl-2'-hydroxyphenyl)-5-chlorobenzotriazole, 
2-(3'-tert-butyl-2'-hydroxy-5'-methylphenyl)-5-chlorobenzotriazole, 
2-(3'-sec-butyl-5'-tert-butyl-2'-hydroxyphenyl)benzotriazole, 
2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole, 
2-(3',5'-di-tert-amyl-2'-hydroxyphenyl)benzotriazole, 
2-(3',5'-bis(.alpha.,.alpha.-dimethylbenzyl)-2'-hydroxyphenyl)-benzotriazo 
le, a mixture of 
2-(3'-tert-butyl-2'-hydroxy-5'-(2-octyloxycarbonylethyl)phenyl)-5-chlorobe 
nzotriazole, 
2-(3'-tert-butyl-5'-2-(2-ethylhexyloxy)carbonylethyl!-2'-hydroxyphenyl)-5 
-chlorobenzotriazole, 
2-(3'-tert-butyl-2'-hydroxy-5'-(2-methoxycarbonylethyl)phenyl)-5-chloroben 
zotriazole, 
2-(3'-tert-butyl-2'-hydroxy-5'-(2-methoxycarbonylethyl)phenyl)-benzotriazo 
le, 
2-(3'-tert-butyl-2'-hydroxy-5'-(2-octyloxycarbonylethyl)phenyl)benzotriazo 
le, 
2-(3'-tert-butyl-5'-2-(2-ethylhexyloxy)carbonylethyl!-2'-hydroxyphenyl)be 
nzotriazole, 2-(3'-dodecyl-2'-hydroxy-5'-methylphenyl)benzotriazole, and 
2-(3'-tert-butyl-2'-hydroxy-5'-(2-isooctyloxycarbonylethyl)phenylbenzotria 
zole, 
2,2'-methylenebis4-(1,1,3,3-tetramethylbutyl)-6-benzotriazol-2-ylphenol!; 
the transesterification product of 
2-3'-tert-butyl-5'-(2-methoxy-carbonylethyl)-2'-hydroxyphenyl!benzotriazo 
le with polyethylene glycol 300; 
R--CH.sub.2 CH.sub.2 --COO(CH.sub.2).sub.3 !.sub.2 where 
R=3'-tert-butyl-4'-hydroxy-5'-2H-benzotriazol-2-ylphenyl. 
2. 2-Hydroxybenzophenones, for example the 4-hydroxy, 4-methoxy, 4-octoxy, 
4-decyloxy, 4-dodecyloxy, 4-benzyloxy, 4,2',4'-trihydroxy and 
2'-hydroxy-4,4'-dimethoxy derivative. 
3. Esters of substituted or unsubstituted benzoic acids, for example 
4-tert-butyl-phenyl salicylate, phenyl salicylate, octylphenyl salicylate, 
dibenzoylresorcinol, bis(4-tert-butylbenzoyl)resorcinol, 
benzoylresorcinol, 2,4-di-tert-butylphenyl 
3,5-di-tert-butyl-4-hydroxybenzoate, hexadecyl 
3,5-di-tert-butyl-4-hydroxybenzoate, octadecyl 
3,5-di-tert-butyl-4-hydroxybenzoate, 2-methyl-4,6-di-tert-butylphenyl 
3,5-di-tert-butyl-4-hydroxybenzoate. 
4. Acrylates, for example ethyl 
.alpha.-cyano-.beta.,.beta.-diphenylacrylate or isooctyl 
.alpha.-cyano-.beta.,.beta.-diphenylacrylate, methyl 
.alpha.-carbomethoxycinnamate, methyl 
.alpha.-cyano-.beta.-methyl-p-methoxycinnamate or butyl 
.alpha.-cyano-.beta.-methyl-p-methoxycinnamate, methyl 
.alpha.-carbomethoxy-p-methoxycinnamate and 
N-(.beta.-carbomethoxy-.beta.-cyanovinyl)-2-methylindoline. 
5. Sterically hindered amines, for example 
bis(2,2,6,6-tetramethylpiperidyl) sebacate, 
bis(2,2,6,6-tetramethylpiperidyl) succinate, 
bis(1,2,2,6,6-pentamethylpiperidyl) sebacate, 
bis(1,2,2,6,6-pentamethylpiperidyl) n-butyl 
3,5-di-tert-butyl-4-hydroxybenzylmalonate and succinic acid, the 
condensate of 1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and 
succinic acid, the condensate of 
N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and 
4-tertoctylamino-2,6-dichloro-1,3,5-s-triazine, 
tris(2,2,6,6-tetramethyl-4-piperidyl) nitrilotriacetate, 
tetrakis(2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetraoate, 
1,1'-(1,2-ethanediyl)bis-(3,3,5,5-tetramethylpiperazinone), 
4-benzoyl-2,2,6,6-tetramethylpiperidine, 
4-stearyloxy-2,2,6,6-tetramethylpiperidine, 
bis(1,2,2,6,6-pentamethylpiperidyl)-2-n-butyl-2-(2-hydroxy-3,5-di-tert-but 
ylbenzyl) malonate, 
3-n-octyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro4.5!decane-2,4-dione, 
bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl) sebacate, 
bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl) succinate, the condensate of 
N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and 
4-morpholino-2,6-dichloro-1,3,5-triazine, the condensate of 
2-chloro-4,6-di(4-n-butylamino-2,2,6,6-tetramethylpiperidyl)-1,3,5-triazin 
e and 1,2-bis(3-aminopropylamino)ethane, the condensate of 
2-chloro-4,6-di(4-n-butylamino-1,2,2,6,6-pentamethylpiperidyl)-1,3,5-triaz 
ine and 1,2-bis(3-aminopropylamino)ethane, 
8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro4.5!decane-2,4-di 
one, 3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidyl)pyrrolidine-2,5-dione, 
3-dodecyl-1-(1,2,2,6,6-pentamethyl-4-piperidyl)pyrrolidine-2,5-dione. 
6. Oxalamides, for example 4,4'-dioctyloxyoxanilide, 
2,2'-diethoxyoxanilide, 2,2'-dioctyloxy-5,5'-di-tert-butyloxanilide, 
2,2'-didodecyloxy-5,5'-di-tert-butyloxanilide, 2-ethoxy-2'-ethyloxanilide, 
N,N'-bis(3-dimethylaminopropyl)oxalamide, 
2-ethoxy-5-tert-butyl-2'-ethyloxanilide and its mixture with 
2-ethoxy-2'-ethyl-5,4'-di-tert-butyloxanilide and mixtures of o- and 
p-methoxy and of o- and p-ethoxy-disubstituted oxanilides. 
7. 2-(2-Hydroxyphenyl)-1.3.5-triazines, for example 
2,4,6-tris(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 
2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 
2-(2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 
2,4-bis(2-hydroxy-4-propyloxyphenyl)-6-(2,4-dimethylphenyl)-1,3,5-triazine 
, 2-(2-hydroxy-4-octyloxyphenyl)-4,6bis(4-methylphenyl)-1,3,5-triazine, 
2-(2-hydroxy-4-dodecyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin 
e, 
2-2-hydroxy-4-(2-hydroxy-3-butyloxypropyloxy)phenyl!-4,6-bis(2,4-dimethyl 
phenyl)-1,3,5-triazine, 
2-2-hydroxy-4-(2-hydroxy-3-octyloxypropyloxy)-phenyl!-4,6-bis(2,4-dimethy 
lphenyl)-1,3,5-triazine and 
2-4-dodecyl/tridecyloxy(2-hydroxypropyl)oxy-2-hydroxyphenyl!-4,6-bis(2,4- 
dimethylphenyl)-1,3,5-triazine. 
8. Phosphites and phosphonites, for example triphenyl phosphite, diphenyl 
alkyl phosphites, phenyl dialkyl phosphites, tris(nonylphenyl) phosphite, 
trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol 
diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, diisodecyl 
pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol 
diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol 
diphosphite, bisisodecyloxypentaerythritol diphosphite, 
bis(2,4-di-tert-butyl-6-methylphenyl)pentaerythritol diphosphite, 
bis(2,4,6-tri-tert-butylphenyl)pentaerythritol diphosphite, tristearyl 
sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl) 4,4'-biphenylene 
diphosphonite, 
6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenzod,g!-1,3,2-dioxaphosph 
ocin, 
6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyl-dibenzod,g!-1,3,2-dioxaphosp 
hocin, bis(2,4-di-tert-butyl-6-methylphenyl) methyl phosphite, 
bis(2,4-di-tert-butyl-6-methylphenyl) ethyl phosphite. 
The invention therefore also provides a photopolymerizable composition 
comprising as photoinitiator at least one molecular complex compound 
comprising a mono-, bis- or tris-acylphosphine oxide compound with an 
.alpha.-hydroxy ketone compound, and also a UV absorber from the class of 
the hydroxyphenyl-s-triazines and/or hydroxy-phenylbenzotriazoles and/or 
sterically hindered amines based on 2,2,6,6-tetramethylpiperidines. 
To accelerate the photopolymerization it is possible to add amines, for 
example triethanolamine, N-methyldiethanolamine, ethyl 
p-dimethylaminobenzoate or Michler's ketone. The action of the amines can 
be intensified by the addition of aromatic ketones of the benzophenone 
type. Examples of amines which can be used as oxygen scavengers are 
substituted N,N-dialkylanilines as described in EP-A-339 841. Further 
accelerators, coinitiators and autoxidizers are thiols, thioethers, 
disulfides and phosphines as described, for example, in EP-A-438 123 and 
GB-A-2 180 358. 
The photopolymerization can also be accelerated by the addition of 
photosensitizers which shift or broaden the spectral sensitivity. These 
are, in particular, aromatic carbonyl compounds such as benzophenone 
derivatives, thioxanthone derivatives, anthraquinone derivatives and 
3-acylcoumarin derivatives and 3-(aroylmethylene)thiazolines, and also 
eosine, rhodamine and erythrosine dyes. 
The curing process may be assisted, in particular, by compositions which 
are pigmented (for example with TiO.sub.2), but also by the addition of a 
component which forms free radicals under thermal conditions, for example 
an azo compound such as 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 
a triazine, diazo sulfide, pentazadiene or a peroxy compound such as a 
hydroperoxide or peroxycarbonate, for example t-butyl hydroperoxide, as 
described in EP-A 245 639, for example. 
The compositions according to the invention may also contain a 
photoreducible dye, for example xanthene, benzoxanthene, 
benzothioxanthene, thiazine, pyronine, porphyrin or acridine dyes, and/or 
a trihalomethyl compound which can be cleaved by radiation. Similar 
compositions are described in, for example, EP-A-445 624. 
Other conventional additives are--depending on the intended 
application--optical brighteners, fillers, pigments, dyes, wetting agents 
or levelling assistants. Thick and pigmented coatings can suitably be 
cured by the addition of glass microbeads or powdered glass fibres, as 
described in U.S. Pat. No. 5,013,768, for example. 
The invention also relates to compositions comprising as component (a) at 
least one ethylenically unsaturated, photopolymerizable compound which is 
emulsified or dissolved in water. 
Radiation-curable, aqueous prepolymer dispersions of this type are 
commercially available in many variations. This term is taken to mean a 
dispersion of water and at least one prepolymer dispersed therein. The 
concentration of the water in these systems is, for example, from 5 to 80% 
by weight, in particular from 30 to 60% by weight. The radiation-curable 
prepolymer or prepolymer mixture is present, for example, in 
concentrations of from 95 to 20% by weight, in particular from 70 to 40% 
by weight. The total of the percentages indicated for water and prepolymer 
in these compositions is in each case 100, to which are added the 
auxiliaries and additives in various amounts depending on the application. 
The radiation-curable, water-dispersed, film-forming prepolymers, which are 
frequently also dissolved, are, for aqueous prepolymer dispersions, 
monofunctional or polyfunctional ethylenically unsaturated prepolymers 
which are known per se, can be initiated by means of free radicals and 
contain, for example, from 0.01 to 1.0 mol of polymerizable double bonds 
per 100 g of prepolymer, and have an average molecular weight of, for 
example, at least 400, in particular from 500 to 10,000. Depending on the 
intended application, however, prepolymers having higher molecular weights 
may also be suitable. 
For example, polyesters containing polymerizable C--C double bonds and 
having a maximum acid number of 10, polyethers containing polymerizable 
C--C double bonds, hydroxyl-containing products of the reaction of a 
polyepoxide containing at least two epoxide groups per molecule with at 
least one .alpha.,.beta.-ethylenically unsaturated carboxylic acid, 
polyurethane (meth)acrylates and .alpha.,.beta.-ethylenically unsaturated 
acrylic copolymers containing acrylic radicals, as described in EP-A-12 
339, are used. Mixtures of these prepolymers may also be used. Also 
suitable are the polymerizable prepolymers described in EP-A-33 896, which 
are thioether adducts of polymerizable prepolymers having an average 
molecular weight of at least 600, a carboxyl group content of from 0.2 to 
15% and a content of from 0.01 to 0.8 mol of polymerizable C--C double 
bonds per 100 g of prepolymer. Other suitable aqueous dispersions based on 
specific alkyl (meth)acrylate polymers are described in EP-A-41 125, and 
suitable water-dispersible, radiation-curable prepolymers made from 
urethane acrylates are disclosed in DE-A-2 936 039. 
These radiation-curable, aqueous prepolymer dispersions may contain, as 
further additives, dispersion assistants, emulsifiers, antioxidants, light 
stabilizers, dyes, pigments, fillers, for example talc, gypsum, silica, 
rutile, carbon black, zinc oxide and iron oxides, reaction accelerators, 
levelling agents, lubricants, wetting agents, thickeners, matting agents, 
antifoams and other assistants which are conventional in surface-coating 
technology. Suitable dispersion assistants are water-soluble, high 
molecular weight organic compounds containing polar groups, for example 
polyvinyl alcohols, polyvinylpyrrolidone and cellulose ethers. Emulsifiers 
which can be used are nonionic emulsifiers and possibly also ionic 
emulsifiers. 
The photopolymerizable compositions contain the photoinitiator (b) 
judiciously in a quantity of from 0.05 to 15% by weight, preferably from 
0.1 to 5% by weight, based on the composition. 
In certain cases it may be of advantage, in addition to the molecular 
complex photoinitiator compound of the invention, to use other known 
photoinitiators, for example benzophenone, benzophenone derivatives, 
acetophenone, acetophenone derivatives, for example 
.alpha.-hydroxycycloalkyl phenyl ketone, dialkoxyacetophenone, 
.alpha.-hydroxy- or .alpha.-aminoacetophenone, 4-aroyl-1,3-dioxolane, 
benzoin alkyl ethers and benzil ketals, mono-acylphosphine oxides, 
bisacylphosphine oxides, ferrocenes or titanocenes. 
When the molecular complex photoinitiators according to the invention are 
employed in hybrid systems, cationic photoinitiators such as benzoyl 
peroxide, aromatic sulfonium, phosphonium or iodonium salts or 
cyclopentadienylareneiron(II) complex salts are used in addition to the 
free-radical curing agents according to the invention. 
The photopolymerizable compositions can be used for various purposes, for 
example as printing inks, as varnishes or clearcoats, as white paints, for 
example for wood or metal, as coating compositions, inter alia, for paper, 
wood, metal or plastic, as daylight-curable coatings for buildings and 
roadmarking, for photographic reproduction processes, for holographic 
recording materials, for image recording processes or for the production 
of printing plates which can be developed using organic solvents or 
aqueous-alkaline media, for the production of masks for screen printing, 
as dental filling materials, as adhesives, as pressure-sensitive 
adhesives, as laminating resins, as etch resists or permanent resists and 
as solder masks for electronic circuits, for the production of 
three-dimensional articles by bulk curing (UV curing in transparent 
moulds) or by the stereolithography process, as described, for example, in 
U.S. Pat. No. 4,575,330, for the preparation of composite materials (for 
example styrenic polyesters, which may contain glass fibres and other 
assistants) and other thick-layer compositions, for the coating or 
encapsulation of electronic components or as coatings for optical fibres. 
The molecular complex compounds according to the invention may also be used 
as initiators for emulsion polymerizations, as initiators of a 
polymerization for the fixing of ordered states of liquid-crystalline 
mono- and oligomers, and as initiators for the fixing of dyes to organic 
materials. 
In surface coatings, mixtures of a prepolymer with polyunsaturated monomers 
are often used which also contain a monounsaturated monomer. The 
prepolymer here is primarily responsible for the properties of the coating 
film, and variation thereof allows the person skilled in the art to 
influence the properties of the cured film. The polyunsaturated monomer 
functions as a crosslinking agent which renders the coating film 
insoluble. The monounsaturated monomer functions as a reactive diluent by 
means of which the viscosity is reduced without the need to use a solvent. 
Unsaturated polyester resins are mostly used in two-component systems in 
conjunction with a monounsaturated monomer, preferably styrene. For 
photoresists, specific one-component systems are frequently employed, for 
example polymaleimides, polychalcones or polyimides, as described in DE-A 
2 308 830. 
The molecular complex compounds according to the invention can additionally 
be used as free-radical photoinitiators or photoinitiating systems for 
radiation-curable powder coatings. The powder coatings can be based on 
solid resins and on monomers containing reactive double bonds, for example 
maleates, vinyl ethers, acrylates, acrylamides and mixtures thereof. A 
free-radically UV-curable powder coating can be formulated by mixing 
unsaturated polyester resins with solid acrylamides (e.g. methyl 
methacrylamidoglycolate) and with a free-radical photoinitiator according 
to the invention, as described, for example, in the paper "Radiation 
Curing of Powder Coating", Conference Proceedings, Radtech Europe 1993 by 
M. Wittig and Th. Gohmann. Similarly, free-radically UV-curable powder 
coatings can be formulated by mixing unsaturated polyester resins with 
solid acrylates, methacrylates or vinyl ethers and with a photoinitiator 
according to the invention. The powder coatings may also comprise binders 
as described, for example, in DE-A-42 28 514 and EP-A-636 669. The 
UV-curable powder coatings may also comprise white or coloured pigments. 
Thus, for example, preferably rutile titanium dioxide can be employed in 
concentrations of up to 50% by weight in order to give a cured powder 
coating having good covering power. The process normally comprises 
electrostatic or tribostatic spraying of the powder onto the substrate, 
for example metal or wood, melting of the powder by heating and, after a 
smooth film has been formed, radiation-curing of the coating using 
ultraviolet and/or visible light, for example with medium-pressure mercury 
lamps, metal halide lamps or xenon lamps. A particular advantage of the 
radiation-curable powder coatings over their heat-curable counterparts is 
that the flow time after the melting of the powder particles can be 
selectively extended in order to ensure the formation of a smooth, 
high-gloss coating. In contrast to heat-curable systems, radiation-curable 
powder coatings can be formulated without the unwanted effect of a 
reduction in their lifetime, so that they melt at relatively low 
temperatures. For this reason, they are also suitable as coatings for 
heat-sensitive substrates such as wood or plastics. In addition to the 
molecular complex photoinitiators according to the invention, the powder 
coating formulations may also include UV absorbers. Appropriate examples 
have been listed above under sections 1.-8. 
The photocurable compositions according to the invention are suitable, for 
example, as coating substances for substrates of all kinds, for example 
wood, textiles, paper, ceramic, glass, plastics such as polyesters, 
polyethylene terephthalate, polyolefins or cellulose acetate, tate, 
especially in the form of films, and also metals such as Al, Cu, Ni, Fe, 
Zn, Mg or Co and GaAs, Si or SiO.sub.2, on which it is desired to apply a 
protective coating or, by imagewise exposure, an image. 
The substrates can be coated by applying a liquid composition, a solution 
or suspension to the substrate. The choice of the solvent and the 
concentration depend predominantly on the type of composition and the 
coating process. The solvent should be inert: in other words it should not 
undergo any chemical reaction with the components and should be capable of 
being removed again after the coating operation, in the drying process. 
Examples of suitable solvents are ketones, ethers and esters, such as 
methyl ethyl ketone, isobutyl methyl ketone, cyclopentanone, 
cyclohexanone, N-methylpyrrolidone, dioxane, tetrahydrofuran, 
2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol, 
1,2-dimethoxyethane, ethyl acetate, n-butyl acetate and ethyl 
3-ethoxypropionate. Using known coating processes, the solution is applied 
evenly to a substrate, for example by spin coating, dip coating, knife 
coating, curtain coating, brushing, spraying--especially electrostatic 
spraying--and reverse roll coating. It is also possible to apply the 
photosensitive layer to a temporary, flexible support and then to coat the 
final substrate, for example a copper-laminated circuit board, by means of 
layer transfer via lamination. 
The quantity applied (layer thickness) and the nature of the substrate 
(layer support) are functions of the desired application. The range of 
coat thicknesses generally comprises values from about 0.1 .mu.m to more 
than 10 .mu.m. 
The radiation-sensitive compositions according to the invention find 
application as negative resists which have a very high photosensitivity 
and can be developed in an aqueous-alkaline medium without swelling. They 
are suitable as photoresists for electronics (galvano-resists, etch 
resists and solder resists), the production of printing plates such as 
offset printing plates or screen printing forms, and can be used for 
chemical milling or as microresists in the production of integrated 
circuits. There is a correspondingly wide range of variation in the 
possible layer supports and the processing conditions for the coated 
substrates. Examples of the layer supports for photographic information 
recording are films made of polyester, cellulose acetate or plastic-coated 
paper; for offset printing plates, specially treated aluminium; for the 
production of printed circuits, copper-faced laminates, and for the 
production of integrated circuits, silicon wafers. The layer thicknesses 
for photographic materials and offset printing plates are generally from 
about 0.5 .mu.m to 10 .mu.m, while for printed circuits they are from 0.4 
.mu.m to about 2 .mu.m. 
Following the coating of the substrates, the solvent is generally removed 
by drying to leave a layer of the photoresist on the substrate. 
The term "imagewise exposure" relates both to exposure through a photomask 
containing a predetermined pattern, for example a slide, exposure by a 
laser beam which is moved under control from a computer, for example, over 
the surface of the coated substrate, thereby generating an image, and to 
irradiation with computer-controlled electron beams. 
Following the imagewise exposure of the material and prior to developing, 
it may be advantageous to carry out a brief thermal treatment, in which 
only the exposed parts are thermally cured. The temperatures employed are 
generally 50-150.degree. C. and preferably 80-130.degree. C.; the duration 
of the thermal treatment is generally between 0.25 and 10 minutes. 
The photocurable composition can also be used in a process for the 
production of printing plates or photoresists as described, for example, 
in DE-A-40 13 358. In this process the composition is exposed before, 
simultaneously with or after the imagewise irradiation, exposure being 
carried out for a short period with visible light having a wavelength of 
at least 400 nm without a mask. 
Following exposure and the optional thermal treatment, the unexposed areas 
of the photo-resist are removed using a developer in a manner known per 
se. 
As already mentioned, the compositions according to the invention can be 
developed by aqueous-alkaline media. Suitable aqueous-alkaline developer 
solutions are, in particular, aqueous solutions of tetraalkylammonium 
hydroxides or of alkali metal silicates, phosphates, hydroxides and 
carbonates. Relatively small quantities of wetting agents and/or organic 
solvents may also be added, if desired, to these solutions. Examples of 
typical organic solvents which may be added in small quantities to the 
developing liquids are cyclohexanone, 2-ethoxyethanol, toluene, acetone 
and mixtures of such solvents. 
Photocuring is of considerable importance for printing inks, since the 
drying time of the binder is a crucial factor for the production rate of 
graphic products and should be in the order of fractions of seconds. 
UV-curable inks are important, in particular, for screen printing. 
As already mentioned, the mixtures according to the invention are also 
highly suitable for the production of printing plates, where, for example, 
mixtures of soluble, linear polyamides or styrene/butadiene or 
styrene/isoprene rubber, polyacrylates or polymethyl methacrylates 
containing carboxyl groups, polyvinyl alcohols or urethane acrylates are 
used with photopolymerizable monomers, for example acrylamides, 
methacrylamides, acrylates or methacrylates, and a photoinitiator. Films 
and plates made from these systems (wet or dry) are exposed through the 
negative (or positive) of the print original, and the uncured parts are 
subsequently washed out using a suitable solvent. 
A further area of application for photocuring is in the coating of metals, 
for example in the coating of metal sheets and tubes, cans or bottle caps, 
and the photocuring of plastic coatings, for example PVC-based wall or 
floor coverings. 
Examples of the photocuring of paper coatings are the colourless coating of 
labels, record sleeves or book covers. 
The use of the compounds according to the invention for curing shaped 
articles made from composite compositions is likewise of interest. The 
composite composition is made up of a self-supporting matrix material, for 
example a glass-fibre fabric, or else, for example, plant fibres cf. 
K.-P. Mieck and T. Reussmann in Kunststoffe 85 (1995), 366-370!, which is 
impregnated with the photocuring formulation. Shaped articles which are 
produced from composite compositions, using the compounds according to the 
invention, are of high mechanical stability and resistance. The compounds 
according to the invention can also be used as photocuring agents in 
moulding, impregnating and coating compositions, as are described, for 
example, in EP-A-7086. Examples of such compositions are fine coating 
resins on which stringent requirements are placed with respect to their 
curing activity and resistance to yellowing, or fibre-reinforced mouldings 
such as planar or longitudinally or transversely corrugated light 
diffusing panels. Processes for the production of such mouldings, for 
example hand lay-up, spray lay-up, centrifugal or filament winding 
processes, are described by, for example, P. H. Selden in 
"Glasfaserverstarkte Kunststoffe" Glass fibre-reinforced plastics!, page 
610, Springer Verlag Berlin-Heidelberg-New York 1967. Examples of articles 
which can be produced by this process are boats, chipboard or plywood 
panels coated on both sides with glass fibre-reinforced plastic, pipes, 
containers and the like. Other examples of moulding, impregnating and 
coating compositions are UP resin fine coatings for mouldings containing 
glass fibres (GRP), e.g. corrugated sheets and paper laminates. Paper 
laminates may also be based on urea or melamine resins. The fine coating 
is produced on a support (for example a sheet) prior to the production of 
the laminate. The photocurable compositions according to the invention can 
also be used for casting resins or for encapsulating articles such as 
electronic components and the like. Curing employs medium-pressure mercury 
lamps as are conventional in UV curing. However, less intense lamps are 
also of particular interest, for example those of the type TL 40W/03 or 
TL40W/05. The intensity of these lamps corresponds approximately to that 
of sunlight. It is also possible to employ direct sunlight for curing. A 
further advantage is that the composite composition can be removed in a 
part-cured, plastic state from the light source and can be shaped. 
Complete curing is carried out subsequently. 
Also important is the use of photocurable compositions for imaging 
processes and for the optical production of information carriers. In these 
applications, the coat (wet or dry) applied to the support is 
irradiated--as already described above--with UV or visible light through a 
photomask and the unexposed areas of the coat are removed by treatment 
with a solvent (=developer). The photocurable layer can also be applied by 
electrodeposition to metal. The exposed areas are crosslinked/polymeric 
and thus insoluble and remain on the support. If appropriate coloration is 
carried out, visible images are formed. If the support is a metallized 
layer, then the metal can be removed from the unexposed areas by etching 
after exposure and development or can be increased in thickness by 
electroplating. In this way, printing electronic circuits and photoresists 
can be produced. 
The photosensitivity of the compositions according to the invention 
generally ranges from the UV region (about 200 nm) up to about 600 nm. 
Suitable radiation comprises, for example, sunlight or light from 
artificial sources. Therefore, a large number of very different types of 
light source can be used. Both point sources and flat radiators (lamp 
carpets) are appropriate. Examples are carbon arc lamps, xenon arc lamps, 
medium-pressure, high-pressure and low-pressure mercury lamps, doped with 
metal halides if desired (metal halogen lamps), microwave-stimulated metal 
vapour lamps, excimer lamps, superactinic fluorescent tubes, fluorescent 
lamps, incandescent argon lamps, electronic flashlights, photographic 
flood lamps, electron beams and X-rays. The distance between the lamp and 
the substrate according to the invention which is to be coated can vary 
depending on the application and on the type and/or power of the lamp, for 
example between 2 cm and 150 cm. Also suitable, for example, are lasers in 
the visible range. 
The invention therefore also provides a method for the photopolymerization 
of compounds having ethylenically unsaturated double bonds, which 
comprises irradiating a composition according to the invention as 
described above, with light in the range from 200 to 600 nm. 
The invention also provides for the use of the above-described composition 
for the production of surface coating materials, printing inks, printing 
plates, dental compositions and resist materials and as image recording 
material, especially for holographic recordings. 
The invention likewise provides a coated substrate which is coated on at 
least one surface with a composition as described above, and to a process 
for the photographic production of relief images, in which a coated 
substrate is subjected to imagewise exposure and then the unexposed 
portions are removed with a solvent. This exposure can take place either 
through a mask or by means of a laser beam without a mask. 
The molecular complex compounds according to the invention can easily be 
incorporated into the formulations that are to be cured. 
The molecular complex compounds according to the invention in general 
contain fewer impurities than the individual components, since in the 
course of the preparation the impurities remain in solution. These 
photoinitiators are therefore also suitable for very sensitive 
applications. 
The molecular complex compounds according to the invention are of good 
stability on storage. 
In preparing the molecular complex compounds it is also possible for 
mixtures to be formed between the molecular complex crystals according to 
the invention and one of the components used for their preparation, for 
example a mixture of molecular complex crystals consistings of compounds 
of the formula I and II and crystals of the compounds of the formula I. 
These mixtures can also be employed as photoinitiators.

The examples which follow illustrate the invention in more detail. As in 
the remainder of the description and in the claims, parts or percentages 
are by weight unless stated otherwise. 
EXAMPLE 1 
Molecular Complex of 
bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine Oxide and 
.alpha.-hydroxycyclohexyl Phenyl Ketone 
To prepare seed crystals, 
bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and 
.alpha.-hydroxycyclohexyl phenyl ketone in a molar ratio of 1:1 are 
dissolved at 80.degree. C. in a mixture of isooctane and ethyl acetate 
(weight ratio 2.3:1). Nucleation is initiated at 53-55.degree. C. by 
rubbing on the glass wall using a glass rod until the crystallization 
process begins. The crystals obtained in this way are used as seed 
crystals in the first preparation of larger amounts of the molecular 
complex. 
Preparation of larger amounts of the molecular complex crystals: 
385 g of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and 
165 g of .alpha.-hydroxycyclohexyl phenyl ketone are dissolved in a 
mixture of 385 g of isooctane and 165 g of ethyl acetate at 80.degree. C. 
The mixture is cooled to 53-55.degree. C. The emulsion present is seeded 
at this temperature with the corresponding mixed-crystal modification, and 
crystallized. After filtration at 20.degree. C., the product is washed 
with the solvent mixture and is dried at about 70.degree. C. and 50 mbar, 
to give 530 g of dry crystalline product, i.e. 96% of theory. The melting 
point (determined by Differential Scanning Calorimetry) is 90.degree. C. 
The phosphorus content is 4.47%. The content of 
bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide is 71%, 
that of .alpha.-hydroxycyclohexyl phenyl ketone 29%. These values are 
determined by High Pressure Liquid Chromatography (HPLC). 
X-ray structural analysis (measured on a yellow platelet-shaped crystal 
using a four-circle diffractometer Philips PW1100, MoK.alpha..sub.1 
radiation (.lambda.=0.70926 .ANG.), calculated by direct methods using the 
program system SHELX86 (Sheldrick, Gottingen), indicates a monoclinic 
crystal system having the space group P2.sub.1 /c (International Tables 
for X-ray Crystallography, 1974, Vol. IV). 
Formula C.sub.26 H.sub.35 O.sub.7 P.C.sub.13 H.sub.16 O.sub.2 ; molecular 
weight 694.80 
The unit cell contains 4 molecules and its dimensions are as follows: 
a (.ANG.) 17.514(2); b (.ANG.) 10.518(1); c (.ANG.) 20.912(2); 
.beta. (.degree.) 97.92(1); V (.ANG..sup.3) 3815.5(8). 
The refinement calculation gives an R value of 0.047. 
EXAMPLE 2 
Molecular Complex of 
bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine Oxide and 
.alpha.-hydroxycyclohexyl Phenyl Ketone 
The seed crystals are prepared as described in Example 1. 140 g of 
bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and 60 g of 
.alpha.-hydroxycyclohexyl phenyl ketone are dissolved at 30-35.degree. C. 
in a mixture of 92 g of methyl ethyl ketone (MEK) and 11 g of water. (The 
presence of water here is not mandatory; the complex is also obtained if 
pure MEK is used). The solution is cooled to 20-23.degree. C. and seeded 
with the appropriate mixed-crystal modification. As soon as a distinct 
crystal suspension has formed, it is slowly diluted with 500 ml of water. 
Filtration at 20.degree. C. gives 220 g of a moist product which is washed 
with water and dried at about 70.degree. C. and 50 mbar, to give 200 g, 
i.e. &gt;99% of theory, of dry crystalline product having a melting point of 
91.degree. C. (DSC). The content of 
bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide is 71%, 
that of .alpha.-hydroxycyclohexyl phenyl ketone 29% (HPLC). 
EXAMPLE 3 
Molecular Complex of 
bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine Oxide and 
2-hydroxy-2-methyl-1-phenylpropan-1-one 
Seed crystals are prepared by dissolving the components in a molar ratio of 
1:1 in ethyl acetate at room temperature. Crystallization is brought about 
by adding hexane. A mixture is formed of molecular complex crystals 
consisting of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine 
oxide and 2-hydroxy-2-methyl-1-phenylpropan-1-one and crystals consisting 
of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide. This 
crystal mixture is suitable as a seed crystal in the preparation of larger 
amounts of crystals of the molecular complex. 
Preparation of larger amounts of the molecular complex crystals: 
150 g of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and 
50 g of 2-hydroxy-2-methyl-1-phenylpropan-1-one are dissolved at 
30-35.degree. C. in a mixture of 92 g of methyl ethyl ketone and 11 g of 
water. (The presence of water is not mandatory here: the complex is also 
obtained if pure MEK is used). The solution is cooled to 5.degree. C. and 
is seeded with the corresponding mixed-crystal modification. As soon as a 
distinct crystal suspension has formed, at 5.degree. C., it is diluted 
slowly with 1000 ml of water. Filtration at 20.degree. C. and drying at 
about 60.degree. C. and 50 mbar give 194 g of dry crystalline product, 
i.e. 97% of theory, having a melting point of 73.degree. C. (DSC) and a 
phosphorus contents of 4.7%. 
X-ray structural analysis (measured on a platelet-shaped colourless crystal 
using a four-circle diffractometer Philips PW1100, MoK.alpha..sub.1 
radiation (.lambda.=0.70926 .ANG.), calculated using direct methods with 
the program system SHELX86 (Sheldrick, Gottingen), indicates a monoclinic 
crystal system having the space group P2.sub.1 /n (International Tables 
for X-ray Crystallography, 1974, Vol. IV). 
Formula C.sub.26 H.sub.35 O.sub.7 P.C.sub.10 H.sub.12 O.sub.2 ; molecular 
weight 654.73. 
The unit cell contains 4 molecules, and its dimensions are as follows: 
a (.ANG.) 17.828(2); b (.ANG.) 10.365(1); c (.ANG.) 19.592(2); 
.beta. (.degree.) 95.46(1); V (.ANG..sup.3) 3603.9(8). 
The refinement calculation gives an R value of 0.042. 
EXAMPLE 4 
Molecular Complex of bis(phenyl)-2,4,6-trimethylbenzoylphosphine Oxide and 
.alpha.-hydroxycyclohexyl Phenyl Ketone 
Seed crystals are prepared by very slowly cooling a solution of 
bis(phenyl)-2,4,6-trimethyl-benzoylphosphine oxide and 
.alpha.-hydroxycyclohexyl phenyl ketone in a molar ratio of 1:1 in 
.RTM.Isopar E (mixture of branched and unbranched paraffinic hydrocarbons; 
ESSO). 
Preparation of larger amounts of the molecular complex crystals 100 g of 
bis(phenyl)-2,4,6-trimethylbenzoylphosphine oxide and 59 g of 
.alpha.-hydroxycyclohexylphenyl ketone are dissolved at 80.degree. C. in 
200 ml of .RTM.Isopar E. The resulting solution is cooled to 55.degree. 
C., during which a cloudy emulsion is formed. This emulsion is seeded at 
53-55.degree. C. with the corresponding mixed-crystal modification. The 
product crystallizes out in the form of hard, pale yellow crystals. The 
resulting suspension is cooled to room temperature at a uniform rate over 
the course of from 2 to 3 hours and then is filtered. The filter cake is 
washed first with .RTM.Isopar E and then with hexane. Drying at 50.degree. 
C. and 50 mbar gives 150 g of the product, corresponding to 94.3% of 
theory. The melting point is 69.4.degree. C. (DSC), the phosphorus content 
5.5%. 
X-ray structural analysis (measured using a four-circle diffractometer 
Philips PW1100, MoK.alpha..sub.1 radiation (.lambda.=0.70926 .ANG.), 
calculated by direct methods using the program system SHELX86 (Sheldrick, 
Gottingen), indicates a triclinic crystal system having the space group 
Pl, centrosymmetric (No.2 in International Tables for X-ray 
Crystallography, 1974, Vol. IV). 
Formula: C.sub.22 H.sub.21 O.sub.2 P.C.sub.13 H.sub.16 O.sub.2 ; molecular 
weight 552.65. 
The unit cell contains 2 molecules and its dimensions are as follows: 
a (.ANG.) 9.081; b (.ANG.) 11.436; c (.ANG.) 16.092; 
.alpha. (.degree.) 91.98; .beta. (.degree.) 101.05; .gamma. (.degree.) 
109.50; V (.ANG..sup.3) 1537.3. 
The refinement calculation gives an R value of 0.051. 
The distance between the two O atoms associated via a hydrogen bond (OH 
group of the hydroxy ketone with the O atom on the phosphorus of the 
phosphine oxide) is 2.715 .ANG.. The bond angle O--H..O is measured as 
169.degree.. 
EXAMPLE 5 
Molecular Complex of bis(phenyl)-2,4,6-trimethylbenzoylphosphine Oxide and 
.alpha.-hydroxycyclohexyl Phenyl Ketone (Melt Method) 
10 g of bis(phenyl)-2,4,6-trimethylbenzoylphosphine oxide and 5.9 g of 
.alpha.-hydroxycyclohexyl phenyl ketone are melted at 100.degree. C., 
homogenized and allowed to cool slowly to room temperature. Seeding with 
the corresponding molecular complex compound brings about spontaneous 
crystallization. 
EXAMPLE 6 
Molecular Complex of 
bis(2,4,6-trimethylbenzoyl)-2,4-dihexoxyphenylphosphine Oxide and 
.alpha.-hydroxycyclohexyl Phenyl Ketone (Melt Method) 
Seed crystals are obtained by very slowly cooling a 1:1 molar melt of 
bis(2,4,6-trimethylbenzoyl)-2,4-dihexoxyphenylphosphine oxide and 
.alpha.-hydroxycyclohexyl phenyl ketone and intensively scratching on the 
wall of the flask after the melt has cooled. 
Preparation by crystallization 
1.5 g of bis(2,4,6-trimethylbenzoyl)-2,4-dihexoxyphenylphosphine oxide and 
0.5 g of .alpha.-hydroxycyclohexyl phenyl ketone are dissolved at 
50-60.degree. C. in 10 ml of .RTM.Isopar E/ethyl ester (3:1). The 
resulting solution is cooled to 20-25.degree. C. and is seeded with seed 
crystals as described above. The solution is then stored overnight in a 
refrigerator. During this time, the product crystallizes out in the form 
of pale yellow crystals. The resulting suspension is filtered and the 
filter cake is washed first with cold Isopar.RTM. E and then with cold 
hexane. 
Drying at 40-50.degree. C. and 50 mbar gives 1 g of the product (about 50% 
of theory). The melting point is determined by the DSC method is 
67.3.degree. C. 
X-ray structural analysis (measured on a cubic crystal using a four-circle 
diffractometer Nonius CAD4 (Enraf Nonius), CuK.alpha..sub.1 radiation 
(.lambda.=1.54178 .ANG.), calculated by direct methods using the program 
system SHELX86 (Sheldrick, Gottingen), indicates a triclinic crystal 
system having the space group P-1 (International Tables for X-ray 
Crystallography, 1974, Vol. IV). 
Formula: C.sub.38 H.sub.51 O.sub.5 P.C.sub.13 H.sub.16 O.sub.2 ; molecular 
weight 823.02. 
The unit cell contains 2 molecules and its dimensions are as follows: 
a (.ANG.) 11.721 (1); b (.ANG.) 12.327(1); c (.ANG.) 17.493(1); 
.alpha. (.degree.) 105.73(1); .beta. (.degree.) 99.32(1); .gamma. 
(.degree.) 92.71(1); V (.ANG..sup.3) 2389.6(3). 
The refinement calculation gives an R value of 0.079. 
The distance between the two O atoms associated via a hydrogen bond (OH 
group of the hydroxy ketone with O atom on the phosphorus of the phosphine 
oxide) is 2.747 .ANG.. The bond angle O--H..O is measured as 169.degree.. 
EXAMPLE 7 
Curing of a White Paint 
A photocurable white paint is prepared by mixing the following components: 
______________________________________ 
67.5% Ebecryl .RTM. 830 
5.0% hexanediol diacylate 
2.5% trimethylolpropane triacrylate 
25.0% RTC-2 .RTM. Titanium dioxide and 
3.0% molecular complex compound from Example 3. 
______________________________________ 
The formulation is applied to chipboard panels using a 100 .mu.m slotted 
doctor knife. Exposure is then carried out with an 80 W/cm medium-pressure 
mercury lamp of the Canrad-Hanovia type (USA), the sample being passed 
under the lamp by belt at a speed of 5 m/min. The resulting paint film is 
fully through cured and resistant to smearing, and its pendulum hardness 
(in accordance with Konig, DIN 53157) is 146 seconds.