Photopolymerizable mixture containing improved plasticizer

This invention relates to an improvement in a photopolymerizable mixture, comprising a polymeric binder which is soluble or at least swellable in aqueous-alkaline solutions, a compound with at least two acrylic or methacrylic acid ester groups and a boiling point above 100.degree. C. which is capable of addition polymerization, a photoinitiator, and a plasticizer, the improvement being that the plasticizer is a compound corresponding to Formula I ##STR1## wherein R.sub.1 is a hydrogen or halogen atom or an alkyl group with 1 to 4 carbon atoms, R.sub.2 is a hydrogen atom, an OH group, or an alkyl group with 1 to 4 carbon atoms, R.sub.3 is a hydrogen atom or a methyl group, R.sub.4 is an alkyl or alkenyl group with 1 to 20 carbon atoms, and n is zero or a whole number from 1 to 20, and wherein R.sub.4 has at least 4 carbon atoms if n is zero or 1. The invention also relates to a light-sensitive transfer material including the photopolymerizable mixture.

The present invention relates to a photopolymerizable mixture comprising 
polymeric binders, polymerizable compounds, and photoinitiators. 
Mixtures of this type are used in the reproduction field for the 
manufacture of printing plates, photoresists, i.e. etching and 
electroplating resists, and relief images which may be colored. 
A particular group of such mixtures adapted for the production of 
photoresists is used in the form of a dry, photopolymerizable layer on a 
temporary support consisting of a transparent flexible plastic film. Under 
the influence of pressure and heat, the layer is laminated to a metal 
support which is to be imagewise modified, e.g. a copper plate, and is 
then exposed and developed to form the photoresist. Preferably, the layers 
are capable of being developed with aqueous, usually aqueous alkaline 
developer solutions. Materials of this type and methods of processing them 
are disclosed, e.g., in U.S. Pat. Nos. 3,526,504, 3,469,982, 4,088,498, 
and 4,019,972. 
If they are developed with aqueous alkaline solutions, the layers disclosed 
in the above-mentioned patents have a specially good adhesion to the 
support, in particular copper supports, and a good resistance to etching 
solutions and electroplating baths. 
The binders required for these materials, which must be soluble or at least 
swellable in aqueous alkaline solutions, frequently have the drawback that 
they impart a certain brittleness to the exposed layer. This is 
particularly true in the case of binders containing monomer units which 
impart to the polymer a higher glass transition temperature and which are 
thus preferred because they prevent cold flow of the unexposed layer. 
Binders of this type are disclosed, e.g., in U. S. Pat. No. 3,930,865. 
Monomers containing more than two polymerizable groups in the molecule, 
which otherwise are particularly advantageous because their exposure 
products have a high cross-linking density, normally also yield relatively 
brittle exposure products, especially if exposure is prolonged beyond the 
optimum exposure time. 
Generally, it can be stated that photopolymerizable layers which have a 
satisfactorily low degree of cold flow in the unexposed state and which, 
after exposure, show good adhesion to the metal support, good resistance 
to the developer, and good resistance to etching solutions and 
electroplating baths, form relatively brittle exposure products. Because 
this applies particularly to over-exposures, usually there is only a very 
narrow exposure latitude in the processing of such layers, if optimum 
combinations of properties are to be achieved. A further embrittlement may 
occur during storage or handling of the products under daylight. 
This increased brittleness of the exposed and even of the unexposed 
photoresist layers may cause considerable difficulties in the further 
processing of these layers, e.g. in the production of printed circuits. 
One of these difficulties is that the brittle resist layer tends to form 
flakes when the copper circuit boards laminated to the dry resist are cut, 
thus leading to considerable contamination and interference with the 
further processing of the material. As another drawback, the brittle 
resist overhangs tend to break off during etching in conventional spray 
etching apparatuses, or fine details of photomasks crack off in aggressive 
electroplating baths, especially in gold baths in which the current yield 
is relatively low (e.g. from 45 percent down to 25 percent). In this case, 
hydrogen is formed which may easily cause cracking of brittle resist 
masks. 
Although the described problems have not been clearly outlined before for 
this combination of layer components and processing conditions, the 
question of the brittleness of photopolymerizable layers has been studied 
in principle, and it was recommended to solve the problem by adding 
plasticizers to the layers. Thus, in U.S. Pat. No. 3,844,790, dibutyl 
phthalate and other esters of aromatic and aliphatic dicarboxylic acids, 
further glycol esters, polyglycols, alkyl and aryl phosphates, certain 
sulfonamides, and other compounds are mentioned as suitable plasticizers 
for certain types of photopolymerizable layers. These, and other similar 
plasticizers are also mentioned in U.S. Pat. No. 3,192,194, column 4, and 
in U.S. Pat. No. 3,895,949. 
All the plasticizers disclosed in these publications have certain 
disadvantages when used in photopolymerizable layers of the above type 
adapted for alkaline development. Many of them are not compatible with the 
alkali-soluble binders required and ooze out from the exposed or unexposed 
layer during storage. Others may have a good plasticizing effect and be 
compatible, but produce layers with excessive cold-flow in the unexposed 
state. Still others cause an undesirable reduction of the developer 
resistance of the exposed areas of the layer, of their resistance to 
electroplating baths, or their adhesion to the metallic support. 
It is the object of the present invention to provide new plasticizers for 
photopolymerizable mixtures and new layer combinations which do not have 
the above-mentioned drawbacks. Above all, the unexposed layer should have 
only an insignificant cold flow and its homogeneity should undergo no 
changes during storage. After exposure, the layer should have a high 
cross-linking density and thus a high resistance to developer solutions 
and electroplating baths, further a good adhesion to metal supports, 
especially copper supports, but should retain its flexibility even if 
considerably overexposed. 
The invention is based on a photopolymerizable mixture which comprises: a 
polymeric binder which is soluble or at least swellable in 
aqueous-alkaline solutions; a compound with at least two acrylic or 
methacrylic acid ester groups in the molecule and a boiling point above 
100.degree. C. which is capable of addition polymerization; a 
photoinitiator; and a plasticizer. 
In the mixture according to the present invention the plasticizer is a 
compound which corresponds to Formula I 
##STR2## 
wherein R.sub.1 is a hydrogen or halogen atom or an alkyl group with 1 to 
4 carbon atoms, 
R.sub.2 is a hydrogen atom, an OH group, or an alkyl group with 1 to 4 
carbon atoms, 
R.sub.3 is a hydrogen atom or a methyl group, 
R.sub.4 is an alkyl or alkenyl group with 1 to 20 carbon atoms, and 
n is zero or a whole number from 1 to 20, 
and wherein R.sub.4 has at least 4 carbon atoms if n is zero or 1. 
The mixture according to the present invention normally contains between 1 
and 30 percent by weight of the new plasticizers, calculated on the weight 
of the non-volatile components. Preferably, 10 to 25 percent by weight of 
plasticizer is added. If more than 30 percent by weight is added, the 
exposed areas of the layer still possess an excellent flexibility and 
other advantageous properties, but in this case the cold flow of the 
unexposed layer is already noticeable and may be annoying when the 
material is used as a dry resist film. If it is not intended to store the 
mixture over a relatively long time in the form of a rolled-up unexposed 
dry layer, i.e. if the mixture is to be stored in dissolved form, as a 
liquid resist, and is to be applied to the support only immediately prior 
to its use, this drawback is of no consequence, so that even higher 
proportions of plasticizer, up to 40 percent by weight, may be used. 
If the plasticizers contain oxyalkylene units, i.e. if n is not zero, these 
units preferably are oxyethylene units (R.sub.3 =H). The number n of 
oxyalkylene units preferably is between 1 and 6. Compounds in which n=3 
and R.sub.3 =H show a particularly high resistance to electroplating 
baths. 
The group R.sub.4 is derived from an unsaturated, or preferably, from a 
saturated, straight-chained or branched aliphatic alcohol with 1 to 20 
carbon atoms. Even if n is more than 1, the group R.sub.4 preferably has 
from 4 to 20 carbon atoms. On the other hand, of the compounds in which 
R.sub.4 contains 4 or more carbon atoms, those are preferred in which n is 
at least 1. If n is zero, the group R.sub.4 preferably contains at least 6 
carbon atoms. Examples of alcohols in which R.sub.4 is OH, and which may 
be used for the preparation of suitable plasticizers are methanol, 
isopropanol, isoamyl alcohol, n-hexanol, 2,4-dimethyl-hexanol, isooctanol, 
decanol, octadecyl alcohol and geraniol. 
Suitable hydroxybenzene carboxylic acids which may be used for the 
preparation of compounds corresponding to Formula I are, e.g., salicylic 
acid, 4-hydroxy-3-chloro-benzoic acid, 2,5-dihydroxy-4-ethyl-benzoic acid, 
2,4-dihydroxy-benzoic acid, 4-bromo-3-hydroxy-benzoic acid and 
2-hydroxy-4-chloro-6-methyl-benzoic acid. If R.sub.1 is a halogen atom, it 
preferably is chlorine or bromine. Compounds in which R.sub.1 stands for 
hydrogen or alkyl are generally preferred. 
The new plasticizers are readily compatible with the other components of 
the layer, in particular with the preferred binders and monomers referred 
to below. Even if they are stored for a relatively long time at relatively 
high temperatures, e.g. at 50.degree. C. or even 100.degree. C., they have 
no tendency to migrate from the layer. Also, no migration takes place in 
the conventionally used acid electroplating baths. By means of the 
inventive plasticizers, photopolymerizable layers are obtained which are 
excellently flexible before and especially after exposure. In combination 
with suitable binders and monomers, they yield layers which have only a 
very slight cold flow or no cold flow at all. Furthermore, it was found 
that when plasticizers according to the invention are used the resistance 
of exposed layers to electroplating baths, especially to acid gold baths, 
is surprisingly improved, as compared with layers containing no 
plasticizers, although other known plasticizers frequently decrease the 
resistance to electroplating baths. The desired combination of properties 
which normally are hard to reconcile with each other, is even maintained 
if the layer is substantially over-exposed, so that the consumer is spared 
the expensive and troublesome task of exactly determining the optimum 
exposure time for each original and each light source used. 
Compounds according to Formula I wherein n=1 or more have not yet been 
disclosed in the literature. Some of the compounds in which n=0 are known; 
thus, the 2-ethyl-hexyl ester of 4-hydroxy benzoic acid, e.g., is known as 
a plasticizer for polyamides and polyvinyl chloride. It is frequently 
mentioned in connection with N-alkyl-phenyl sulfonamide or N-alkyl toluene 
sulfonamide (e.g. in German Auslegeschrift No. 1,283,796 and in U.S. Pat. 
No. 3,395,060). These publications do not indicate, however, that the 
plasticizer is also suitable for photopolymerizable mixtures of the above 
described type. N-alkyl-toluene sulfonamide, e.g. which is described as 
being equivalent, is completely unsuitable for this purpose and 
crystallizes or exudes from the solid mixture. 
The plasticizers according to the present invention may be easily prepared 
from alcohols, by azeotropic esterification with aromatic carboxylic 
acids. The following alcohols may be used: 
(a) aliphatic monohydric alcohols with 4 to 20 carbon atoms, 
(b) polyglycol monalkyl ethers obtained by reacting aliphatic monohydric 
alcohols having from 1 to 20 carbon atoms with ethylene oxide or propylene 
oxide. 
The preparation of polyglycol monalkyl ethers from alcohols and alkylene 
oxides is known. Compounds of this type are commercially available. 
The photopolymerizable mixtures according to the present invention further 
contain polymeric, preferably thermoplastic binders which are soluble or 
at least swellable in aqueous-alkaline solutions. Polymers of this type 
contain groups which form salts in an alkaline medium, e.g. COOH, PO.sub.3 
H.sub.2, SO.sub.3 NH.sub.2, SO.sub.2 NHCO, or OH groups. Polymers 
containing carboxyl groups are preferred. Maleic acid resins, polymers of 
N-(p-toluenesulfonyl)-carbamic acid-(.beta.-methacryloxyloxy)-ethyl ester, 
and copolymers of such monomers, further styrene-maleic acid anhydride 
copolymers and in particular, acrylic and methacrylic acid copolymers may 
be used as binders. The latter compounds may contain alkyl acrylates and 
alkyl methacrylates as comonomers, of which at least some have alkyl 
groups with 4 to 15 carbon atoms, and, additionally, styrene, substituted 
styrene, acrylonitrile, benzyl acrylate, or a similar monomer forming a 
homopolymer with a glass transition temperature Tg of at least 80.degree. 
C. Such preferred binders are disclosed in U.S. Pat. Nos. 3,804,631, and 
3,930,865. The binder should have an average molecular weight of at least 
10,000, preferably of about 20,000 to 200,000. Normally, the acid number 
is between 50 and 250, preferably between 100 and 200. Terpolymers of 
methacrylic acid, an alkyl-methacrylate with 4 to 12 carbon atoms in the 
alkyl group, and styrene or substituted styrene are preferred. As a rule, 
the binder content is in the range from 20 to 80 percent by weight, 
preferably between 35 and 65 percent by weight of the non-volatile 
components of the mixture. 
Furthermore, the mixtures according to the invention comprise polymerizable 
compounds with at least 2 acrylic or methacrylic acid ester groups in the 
molecule. Compounds of this type are known in large numbers and are 
conventionally used for the preparation of photopolymerizable 
compositions. Examples of suitable compounds are, e.g.: ethylene glycol 
diacrylate, di-, tri- and polyethyleneglycol-diacrylates, 
hexanediol-(1,6)-diacrylate, tri-methylol-propane-triacrylate, 
trimethylol-ethane-diacrylate, pentaerythritol-triacrylate, 
neopentylglycol diacrylate, diglycerol diacrylate, and the corresponding 
methacrylates. Acrylic and methacrylic acid amides, e.g. 
methylene-bis-acrylamide, hexamethylene-bis-acrylamide, or 
xylylene-bis-methacrylamide, also may be used in combination with the 
esters. Acrylic and methacrylic acid esters containing at least two 
urethane groups in their molecules are preferred, because these monomers 
form exposure products which are distinguished by their good flexibility 
and adhesion to metals. The compounds also may include biuret groups and, 
if desired, carboxylic acid amide groups. Compounds of this type are 
disclosed in U.S. Pat. Nos. 4,088,498, 4,019,972, and 3,850,770. Reaction 
products of 2 moles of hydroxyalkyl acrylate or -methacrylate and 1 mole 
of a diisocyanate, e.g. hexamethylene-diisocyanate, 
2,2,4-trimethyl-hexamethylene-diisocyanate, isophoron-diisocyanate, 
dicyclohexyl-methane-diisocyanate, or tolylene-diisocyanate, are mentioned 
as examples. Aliphatic and cycloaliphatic diisocyanates with 2 to 12 
carbon atoms are generally preferred, and among these those which contain 
at least one lateral methyl group. Furthermore, those monomers are used 
with advantage which contain at least one oxyalkylene unit, preferably 
oxyethylene units, in the molecule. The reaction products of hydroxyl 
group containing acrylates and methacrylates with diisocyanates produced 
by the partial reaction of the above-mentioned simple diisocyanates, with 
diols, e.g. hexane diol, diethyleneglycol, triethylene glycol, 
pentaethylene glycol, tripropylene glycol and the like, are mentioned as 
examples. These compounds with terminal isocyanate groups may contain one 
or more diol or polyether groups. 
Polymerizable compounds obtained by reaction of the above mentioned 
preferred diisocyanates with di-, tri-, or tetra-ethylene-glycol, in a 
molar ratio from 2:1 to 1.1:1, followed by reaction of the resulting 
reaction product with 1 mole of 2-hydroxy-ethyl methacrylate per 
equivalent of isocyanate groups, are particularly, preferred. 
For the preferred application of the mixtures according to the invention in 
the preparation of dry resist films, the methacrylates are generally 
preferred. Polymerizable compounds containing two terminal polymerizable 
double bonds are particularly preferred. As a rule, the monomers are used 
in quantities ranging from 10 to 70 percent by weight, preferably from 20 
to 50 percent by weight, calculated on the weight of the non-volatile 
components of the mixture. 
A great number of substances may be used as photo-initiators. Benzoin, 
benzoin ether, multi-nuclear quinones, e.g. 2-ethyl-anthraquinone, 
acridine derivatives, e.g. 9-phenyl-acridine, 9-p-methoxyphenyl-acridine, 
9-acetyl-amino-acridine or benz(a)acridine, phenazine derivatives, e.g. 
9,10-dimethyl-benz(a)phenazine, 9-methyl-benz(a)phenazine, 
10-methoxy-benz(a)phenazine, quinoxaline derivatives, e.g. 
6,4',4"-trimethoxy-2,3-diphenyl-quinoxaline or 
4',4"-dimethoxy-2,3-diphenyl-5-aza-quinoxaline, quinazoline derivatives, 
and others are mentioned as examples. As a rule, their quantity is in the 
range from 0.1 to 10 percent of the weight of the non-volatile components 
of the mixture. 
In addition to monomers, plasticizers, photoinitiators and binders, the 
mixture according to the present invention may include a number of further 
conventional additives, such as inhibitors to prevent thermal 
polymerization of the monomers, adhesion-promoting agents, hydrogen 
donors, sensitometric regulators, dyes, colored or uncolored pigments, 
color couplers and indicators. 
Advantageously, these additives should be selected in a manner such that 
they do not excessively absorb within the actinic wave length range 
essential for the initiating process. 
The photopolymerizable mixture according to the present invention may be 
marketed in known manner as a solution or dispersion, which the consumer 
uses in particular for the preparation of etch resists. Preferably, 
however, the mixtures according to the invention are used for the 
preparation of dry resist films which consist of a ready-made photoresist 
layer on a temporary support, e.g. a transparent plastic film. Such dry 
resist films are laminated by the consumer to the support on which an 
image is to be formed by etching or electroplating and are then exposed 
and developed in situ, the temporary support being removed before 
development. 
The mixture according to the present invention is particularly suitable for 
this type of use. Alternatively, it may be manufactured as a presensitized 
copying material on a suitable support, e.g. aluminum or zinc, for the 
photomechanical production of offset or letterpress printing forms. 
Moreover, it is suitable for the production of relief images, screen 
printing stencils, color proofing films and the like. The advantages of 
the present material are effective in all cases where good and lasting 
flexibility of the exposed layer, low cold flow of the unexposed layer, 
and high resistance of the exposed layer to aggressive chemicals are of 
importance. 
The light-sensitive materials containing the mixture according to the 
present invention are prepared in known manner. Thus, a solvent may be 
added to the mixture and the resulting solution or dispersion may be 
applied to the support by casting, spraying, immersion, roller 
application, or some other method, and the resulting film dried. Thicker 
layers (e.g. of 250 .mu.m or more) may be prepared, as a self-supporting 
film, by extrusion or molding and the film is then laminated to the 
support. 
Suitable supports for the copying layers containing the mixtures according 
to the invention are metals, e.g. aluminum, zinc, copper, steel, chromium, 
brass, and other metal alloys, further supports for screen printing 
stencils, e.g. nickel or perlon gauze, and, plastic films, e.g. polyester 
films, especially surface-treated plastic films. 
The copying layers according to the invention are exposed and developed in 
the conventional manner. Suitable developers are aqueous, or preferably 
aqueous-alkaline solutions, e.g. alkali phosphate or alkali silicate 
solutions, to which, if desired, small quantities, e.g. up to 10 percent 
by weight, but preferably less than 5 percent by weight, of water-miscible 
organic solvents or wetting agents may be added. Development may be 
effected by manual treatment, or by treatment in commercial spray 
development or brush development apparatuses. 
As already mentioned, the mixtures according to the present invention may 
be used for very different purposes. As a particularly advantageous 
application, they are used for the production of photoresist or etch 
resist layers on metal supports. They are particularly suitable for use on 
copper supports. In this preferred application, the excellent adhesion and 
flexibility of the exposed areas of the layer are of advantage not only 
during development, but also during the following etching of the support 
wherein the layers display good flexibility and etch resistance. 
The mixtures may be used and handled with particular advantage in the form 
of the so-called dry resist materials mentioned above, because even dry 
layers are capable of being transferred onto metal supports and forming 
firmly adhering layers thereon. In this case, polyester films may be used 
with particular advantage as temporary supporting films.

In the following examples, some embodiments of the inventive mixture are 
described. Unless stated otherwise, percentages and proportions are by 
weight. 
EXAMPLE 1a 
A solution of: 
6.5 g of a terpolymer of n-hexylmethacrylate, methacrylic acid, and styrene 
(60:30:10) with an average molecular weight of about 35,000, 
2.8 g of a polymerizable diurethane obtained by reacting 1 mole of 
2,2,4-trimethyl-hexamethylene-diisocyanate with 2 moles of hydroxyethyl 
methacrylate, 
2.8 g of a polymerizable polyurethane, obtained by reacting 11 moles of 
2,2,4-trimethyl-hexamethylene-diisocyanate with 10 moles of anhydrous 
triethylene glycol and further reacting the resulting reaction product 
with 2 moles of hydroxyethyl-methacrylate, 
0.2 g of 9-phenyl-acridine, 
0.1 g of 3-mercapto-propionic acid-2,4-dichloro-anilide, 
0.035 g of a blue azo dye, obtained by coupling 
2,4-dinitro-6-chlorobenzene-diazonium salt with 
2-methoxy-5-acetylamino-N-cyanoethyl-N-hydroxy-ethyl-aniline, and 
2.8 g of the ester of 2,6-dihydroxy-benzoic acid with 
diethyleneglycolmono-2-ethylhexyl ether, in 
35.0 g of methylethyl ketone, and 
2.0 g of ethanol, 
is whirler-coated onto a 25 .mu.m thick, biaxially stretched and heat set 
polyethylene terephthalate film in a manner such that, after drying at 
100.degree. C., the layer weighs 28 g/m.sup.2. 
The resulting dry resist film is laminated by means of a commercial 
laminating apparatus, at 120.degree. C., to a laminated phenoplast panel 
provided with a 35 .mu.m thick copper foil and is then exposed for 8 
seconds in a commercial exposure device. The master used is a line 
original, in which the lines and the distances between lines have widths 
down to 80 .mu.m. 
After exposure, the polyester film is stripped off and the layer is 
developed within 50 seconds with a 0.8 percent Na.sub.2 CO.sub.3 solution 
in a spray developing apparatus. 
The plate is then rinsed for 30 seconds with tap water, superficially 
etched for 1 minute with a 25 percent ammonium peroxy disulfate solution 
and then consecutively electroplated in the following electrolyte baths: 
1. For 40 minutes in a copper electrolyte bath marketed by Messrs. 
Blasberg, Solingen, under the designation "Feinkornkupferplastic-Bad"; 
Current density: 2 A/dm.sup.2 ; Thickness of the metal layer produced: 
about 20 .mu.m. 
2. For 10 minutes in a nickel bath of type "Norma" marketed by Messrs. 
Blasberg, Solingen: Current density: 4 A/dm.sup.2 ; Thickness of the metal 
layer produced: 6 .mu.m, 
3. For 15 minutes in a gold bath of type "Autronex N", marketed by Messrs. 
Blasberg, Solingen: Current density: 0.6 A/dm.sup.2 ; Thickness of the 
metal layer produced: 2.5 .mu.m. 
The plate shows no undercutting or damage. 
The plate may then be decoated in a 5 percent KOH solution at 50.degree. C. 
and the bared copper areas may be etched away by conventional etching 
means. 
Even after 10-times overexposure, i.e. after an exposure time of 80 seconds 
in the above-described exposure apparatus, the above-described dry resist 
film is entirely flexible. This can be proved by manually stretching an 
about 2 cm wide and 20 cm long strip of the exposed material consisting of 
the support and the layer. At room temperature, the 10-times overexposed 
strip of dry resist film may be stretched to at least twice its original 
length without cracking or tearing of the layer. 
This flexibility is of decisive importance for many processing steps, such 
as cutting of the laminated material, etching, gold-plating and others. 
The above described dry resist film has a very low cold flow in the 
unexposed state, so that rolls can be stored for long periods of time 
without the resist layer squeezing out at the edges. 
EXAMPLES 1b to 1g 
Instead of the plasticizer used in Example 1a, either of the following 
plasticizers may be used: 
(1b) 2.8 g of the ester of 2,4-dihydroxy-benzoic acid and 
diethyleneglycolmono-2-ethylhexyl ether. Layer weight: 29 g/m.sup.2 ; 
Exposure time: 6 seconds; Processing: as described above, the same good 
resistance to electroplating baths being obtained; Flexibility: even after 
10-times overexposure the material can be stretched without tearing or 
embrittlement of the layer. 
(1c) 2.8 g of the ester of 2,6-dihydroxy-benzoic acid and 
triethyleneglycolmono-2-ethylhexyl ether. Results: as above. Layer weight: 
27 g/m.sup.2. 
(1d) 2.8 g of the ester of 2,6-dihydroxy-benzoic acid and 
tripropyleneglycolmono-2-ethylhexyl-ether. Results: as above. Layer 
weight: 27 g/m.sup.2. 
(1e) 2.8 g of the ester of 2,6-dihydroxy-benzoic acid and 
hexaethyleneglycol-mono-2-ethylhexyl- ether. Results: as above. Layer 
weight: 27 g/m.sup.2. 
(1f) 2.8 g of the ester of 4-hydroxy-toluene-2-carboxylic acid and 
diethyleneglycol-monohexyl ether. Results: as above. Layer weight: 32 
g/m.sup.2. 
(1g) 2.8 g of 4-hydroxy-toluene-2-carboxylic acid-n-hexylester. Results: as 
above. Layer weight: 32 g/m.sup.2. 
COMATIVE EXAMPLE 1h 
If a solution is prepared from 
6.5 g of the terpolymer used in Example 1a, 
2.8 g of the diurethane used in Example 1a, 
2.8 g of the polyurethane used in Example 1a, 
0.2 g of 9-phenyl-acridine, 
0.1 g of 3-mercapto-propionic acid-2,4-dichloro-anilide, 
0.035 g of the dye used in Example 1a, p1 35.0 g of methylethyl ketone, and 
2.0 g of ethanol 
(i.e. without the addition of a plasticizer), a dry resist film results 
which is relatively brittle after normal exposure time and which cracks 
and splinters when the material is manually stretched after increasing the 
exposure time by 50%. 
COMATIVE EXAMPLE 1i 
A solution is prepared from 
6.5 g of the terpolymer used in Example 1a, 
5.6 g of the diurethane used in Example 1a, 
2.8 g of the polyurethane used in Example 1a, 
0.2 g of 9-phenyl-acridine, 
0.1 g of 3-mercapto-propionic acid-2,4-dichloro-anilide, 
0.035 g of the dye used in Example 1a, 
35.0 g of methylethyl ketone and 
2.0 g of ethanol 
and is applied, in the manner described in Example 1a, to a support, a 
layer weighing 30 g/m.sup.2 being the result. After an exposure time of 
only 10 seconds, this layer becomes brittle and splinters. 
EXAMPLE 2a 
A solution of 
6.5 g of the terpolymer used in Example 1a, 
2.8 g of the diurethane used in Example 1a, 
2.8 g of the polyurethane used in Example 1a, 
0.2 g of 9-phenyl-acridine, 
0.1 g of 3-mercapto-propionic acid-2,4-dichloro-anilide, 
0.035 g of the dye used in Example 1a, and 
2.8 g of a plasticizer obtained by azeotropic esterification of 
4-hydroxy-benzoic acid with triethyleneglycol-mono-tridecyl ether 
(commercial product), 
35.0 g of methyl ethyl ketone and 
2.0 g of ethanol, 
is processed as described in Example 1a to yield a dry resist film weighing 
28 g/m.sup.2. 
After an exposure of only 8 seconds in the exposure apparatus used in 
Example 1a, an optimally exposed circuit board is obtained which yields a 
true copy of the line original after development in a 0.8 percent Na.sub.2 
CO.sub.3 solution. 
The resist remains flexible and does not crack or break even if it is 
10-times overexposed. 
EXAMPLE 2b 
The plasticizer used in Example 2a is replaced by 2.8 g of the salicylic 
acid ester of triethylene-glycol-mono-ethyl ether. Layer weight of the dry 
resist film: 29.4 g/m.sup.2 ; Exposure time: 10 seconds; Development: 70 
seconds in 0.8 percent Na.sub.2 CO.sub.3 solution. Resistance to 
electroplating baths: very good, even to gold baths (see Example 1a). 
Flexibility: even after an exposure time of 80 seconds, the resist layer 
is completely flexible and does not break or splinter if it is stretched. 
EXAMPLES 2c to 2g 
Similar results are obtained if the plasticizer used in Example 2a is 
replaced by 2.8 g of one of the following compounds: 
(2c) ester of 4-hydroxy-benzoic acid and triethyleneglycolmonobutyl-ether 
(2d) ester of 4-hydroxy-benzoic acid and 2-ethyl-hexanol 
(2e) ester of 4-hydroxy-benzoic acid and isotridecyl alcohol 
(2f) ester of 3-hydroxy-benzoic acid and 2-ethyl-hexanol 
(2g) ester of 4-hydroxy-benzoic acid and 
hexaethyleneglycolmono-2-ethylhexyl-ether. 
In all cases layers weighing around 30 g/m.sup.2 are obtained which remain 
flexible, even if the dry resist films are grossly overexposed (e.g. 160 
seconds exposure time in the exposure apparatus used in Example 1a). The 
resistance of these layers to electroplating baths is excellent. 
EXAMPLE 3a 
A solution of 
6.5 g of the terpolymer used in Example 1a, 
5.0 g of a polymerizable polyurethane obtained by reacting 2 moles of 
2,2,4-trimethyl-hexamethylene-diisocyanate with 1 mole of 
triethyleneglycol and further reacting the reaction product with 2 moles 
of hydroxyethylmethacrylate, 
2.8 g of 4-hydroxy-benzoic acid-2-ethylhexyl ester, 
0.2 g of 9-phenyl-acridine, and 
0.025 g of the dye "Disperse Red" (Color Index No. 179), in 25.0 g of 
methyl ethyl ketone and 
2.0 g of ethanol, 
is whirler-coated onto a polyester film as described in Example 1a and then 
dried in a manner such that the resulting layer weighs 52 g/m.sup.2. The 
coated film is exposed for 20 seconds through a film original comprising 
groups of lines of different widths, using the exposure apparatus 
mentioned in Example 1a. 
After 120 seconds development in a spray developing apparatus, using a 0.8 
percent sodium carbonate solution, even lines of a width of 50 .mu.m are 
resolved. A test of the resistance to electroplating baths, carried 
through with the electroplating baths used in Example 1a, yields good 
results; no undercutting or cracking of the resist lines is observed in 
the critical gold bath. 
The flexibility is very good, even after an exposure time of 160 seconds. 
The developer resistance is at least 6 minutes, even in lines only 50 .mu.m 
wide. 
EXAMPLE 3b (COMATIVE EXAMPLE) 
If the plasticizer is omitted from the composition used in Example 3a, 
relatively brittle layers, which break when bent and cannot be stretched, 
are obtained after normal exposure. The resistance to the gold bath 
described in Example 1a is not sufficient. 
EXAMPLE 3c (COMATIVE EXAMPLE) 
If the plasticizer used in Example 3a is replaced by the same quantity (2.8 
g) of the monomer used in this example, i.e. if 7.8 g of the monomer is 
used without the addition of a plasticizer, the same poor results are 
obtained as in Example 3b. 
EXAMPLE 4a 
A solution of 
6.5 g of the terpolymer used in Example 1a, 
5.0 g of the polymerizable polyurethane used in Example 3a, 
2.8 g of the 4-hydroxy-benzoic acid ester of 
triethylene-glycol-mono-2-ethylhexyl ether, 
0.2 g of 9-phenyl-acridine, and 
0.025 g of "Disperse Red" as a dye (C.I. 179), in 25.0 g of methylethyl 
ketone and 
2.0 g of ethanol, is whirler-coated onto a polyester film as described in 
Example 1a and dried in a manner such that a layer weighing 51 g/m.sup.2 
is produced. If the material is processed as described in Example 3a, 
substantially the same results are obtained in Example 3a. 
EXAMPLE 4b (COMATIVE EXAMPLE) 
Example 4a is repeated, except that the plasticizer mentioned in the 
example is replaced by the same quantity of diisodecyl-adipate, a compound 
which is commercially used as a plasticizer for polymers. After an 
exposure of only 15 seconds the layer becomes brittle. In addition, its 
adhesion to copper is poor. 
EXAMPLE 4c (COMATIVE EXAMPLE) 
Example 4a is repeated, except that the plasticizer mentioned in the 
example is replaced by the same quantity of 
(1) the polyester of adipic acid and 1,2-propane-diol, or 
(2) the polyester of adipic acid and butane-diol. 
Both compounds are commercially available plasticizers. Even after normal 
exposure (20 seconds), brittle resist layers are obtained. Moreover, the 
adhesion of the layers to copper is poor. 
EXAMPLE 5a 
A solution of 
6.5 g of the terpolymer used in Example 1a, 
5.0 g of the polymerizable diurethane used in Example 1a, 
2.8 g of 4-hydroxy-benzoic acid-nerolidyl ester, 
0.2 g of 9-phenyl-acridine, and 
0.025 g of "Disperse Red" as a dye (C.I. 179) in 25.0 g of methyl-ethyl 
ketone, and 
2.0 g of ethanol, 
is whirler-coated onto a polyester film as described in Example 1a and is 
dried in a manner such that a layer weighing 50 g/m.sup.2 results. The 
layer is processed as described in Example 3a. Even if the normal exposure 
time is exceeded by 200 percent, the exposed resist layer is sufficiently 
flexible. 
EXAMPLE 5b (COMATIVE EXAMPLE) 
Example 5a is repeated, except that the plasticizer used in Example 5a is 
replaced by the same quantity of N-ethyl-p-toluene-sulfonamide (a 
commercially available plasticizer). Immediately after preparation of the 
resist layer, the flexibility of the layer after normal and prolonged 
exposure is good, but after storing the unexposed layer for 2 or 3 days, 
signs of embrittlement are apparent after exposure. After 4 weeks storage, 
substantial portions of the plasticizer are lost by migration and the 
resist film has become useless. 
EXAMPLE 5C (COMATIVE EXAMPLE) 
Example 5a is repeated, except that the plasticizer used in Example 5a is 
replaced by the same quantity of (1) diisooctyl phthalate, or (2) 
tricresyl phosphate. Brittle layers are produced by normal exposure (20 
seconds). 
If the same quantity of (3) polyethyleneglycol with an average molecular 
weight of 1,000 is used as the plasticizer, a layer is obtained whose 
adhesion to copper is no longer sufficient. 
It will be obvious to those skilled in the art that many modifications may 
be made within the scope of the present invention without departing from 
the spirit thereof, and the invention includes all such modifications.