Note: Descriptions are shown in the official language in which they were submitted.
~lZ88~Z Hoe 7~/K 02~
The present invention relates to a photopolymerizable mix-
ture comprising polymeric binders, polymerizable compounds, and
photoinitiators .
Mixtures of thls 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 produc-
tion of photoresists is used in the form of a dry, photopolymeriz-
able layer on a temporary support consisting of a transparent flex-
ible 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 solu-
tions. Materials of this type and methods of processing them are
disclosed, e.g., in German Auslegeschrift No. 1,522,515, and
German Offenlegungsschriften Nos. 2,064,079, and 2,361,041.
If they are developed with a~ueous alkaline solu~ions, the
layers disclosed in the above mentioned Offenlegungsschriften have
a specially good adhesion to the supportt in particular copper sup-
ports, and a good resistance to etching solutions and electroplat-
ing baths.
The binders required for these materials, which must be
soluble or at least swellable in aqueous alkaline solutions, fre-
quently have the drawback that they impart a certain brittleness to
the exposed layer. This is particularly true in the case of binders
containing monomer unlts which lmpart to the polymer a hlgher
- 1 - ~
l~Z88~ Hoe 78/K 026
glass transition temperature and which are thus preferred because
they prevent cold flow of the unexposed layer. Binders of this type
aredisclosed, e.g., inU. S. PatentNo. 3,930,865.
Monomers containing more than two polymerizable groups in
the molecule, which otherwise are particularly advantageous be-
cause 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 law degree of cold flow in the unex-
posed state and which, after exposure, show good adhesion to the
metal support, good resistance to the developer, and good resis-
tance 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 lati-
tude in the processing of such layers, if optimum combinations of
properties are to be achievedO 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
Iaminated to the dry resist are cut, thus leading to considerable
contamina~ion and interference with the further processing of the
material. As another drawback, the brlttle resist overhangs tend
to break off during etching in conventional spray etching apparatuses,
-- 2 --
~ILZ88~: Hoe 78/K 026
or fine details of photomasks crack off in aggressive electroplat- -
ing baths, especially in gold baths in which the current yield is
relatively low (e . g . from 45 per cent down to 25 per cent) . In
this case, hydrogen is formed which may easily cause cracking
of brlttle resist masks.
Although the described problems have not been clearly out-
lined before for this combination of layer components and process-
ing conditions, the question of the brittleness of photopolymeriz-
able layers has been studied in principle, and it was recommend-
ed to solve the problem by adding plasticizers to the layers.
Thus, in column 14 of German Auslegeschrift No. 2,327,513, di-
butyl phthalate and other esters of aromatic and aliphatic dicarboxy-
lic acids, further glycol esters, polyglycols, alkyl and aryl phos-
phates, 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. Patent No. 3,192,194, column 4, and in German Auslege-
schrift No. 2,337,645, column 12.
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 requlred and
ooze out from the exposed or unexposed layer durin~ 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 resis-
tance of the exposed areas of the layer, of their resistance to
electroplatlng baths, or thelr adhesion to the metallic support.
~Z~38~2 Ho~ 78/K 02 6
It is the object of the present invention to provide new
plasticizers for photopolymerizable mlxtures and new layer combi-
nations which do not have the above-mentioned drawbacks. Above
all, the unexposed layer should have only an lnsignificant cold
flow and its homogeneity should undergo no changes during stor-
age. After exposure, the layer should have a high cross-linking
density and thus a high resistance to developer solutions and elec-
troplating baths, further a good adhesion to metal supports, especi-
ally copper supports, but should retain its flexibility even if
considerably overexposed.
The invention is based on a photopolymerizable mixture
which comprlses: a polymeric binder which is soluble or at least
swellable in aqueous-alkaline solutlons; a compound with at least
two acrylic or methacrylic acid ester groups in the molecule and a
boiling point above 100 C whlch is capable of addition polymeri-
zation; a photoinitiator; and a plasticizer.
In the mixture according to the present invention the plas-
ticizer is a compound which corresponds to Formula I
R H R3
2 ~
Rl~--C - o-tc - I - o _ )nR4 (I)
wherein
R1 is a hydrogen or halogen atom or an alkyl
group with 1 to 4 carbon atoms,
-- 4 --
~.~2~8~;~ H oe 7 8/K 02 6
R2 is a hydrogen atom, an OH group, or an alkyl
group with 1 to 4 carbon atoms,
R3 is a hydrogen atom or a methyl group,
R4 ls an alkyl or alkenyl group with 1 to 2 0
carbon atoms, and
n is zero or a whole number from 1 to 2 0,
and wherein R4 has at least 4 carbon atoms if n is zero or 1.
The mixture according to the present invention normally con-
tains between 1 and 3 0 per cent by weight of the new plasticizers,
calculated on the weight of the non-volatile components. Prefer-
ably, 10 to 25 per cent by weight of plasticizer is added. If
more than 30 per cent by weight is added, the exposed areas of
the layer still possess an excellent flexibility and other advantage-
ous 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 unex-
posed 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 per cent by
: ;
weight, may be used.
If the plasticizers contain oxyalkylene units, i . e . if n is
not zero, these units preferably are oxyethylene units (R3 = H).
The number n of oxyalkylene units preferably 1s between 1 and 6.
Compounds in which n = 3 and R3 = H show a particularly high
resistance to electroplating haths.
~L12~ Hoe 78/K 026
The group R4 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
R4 preferably has from 4 to 20 carbon atoms. On the other hand,
of the compounds in which R4 contains 4 or more carbon atoms,
those are preferred in which n ls at least 1. If n is zero, the
group R4 preferably contains at least 6 carbon atoms. Examples
of alcohols in which R4 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 Rl isa halogen atom, it preferably is chlorine
or bromine. Compounds in which Rl 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
C or even 100 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 whlch are excellently
-- 6 --
~2~8~Z Hoe 78fK 026
flexible before and especially after exposure. In combination with
sultable blnders and monomers, they yield layers which have only a
very slight eold flow or no cold flow at all. Furthermore, lt was found
that when plasticizers aceording to the invention are used the re-
sistance of exposed layers to electroplating baths, especially to acid
gold baths, is surprisingly improved, as compared with layers con-
taining no plasticizers, although other known plasticizers frequently
decrease the resistance to electroplating baths. The desired combina-
tion 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
determinin~ 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; thu s, the 2 -ethyl -hexyl e ster of 4 -hydroxy
benzoie acid, e.g., is known as a plasticizer for polyamides and poly-
vlnyl 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. Patent No. 3,395,0603.
These publications do not indicate, however, that the plasticizer is
also suitable for photopolymerizable mlxtures 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 plastlcizers according to the present invention may be
easily prepared from alcohols, by azeotropic esterification with aro-
matic carboxylic acids. The following alcohols may be us0d:
' ~
~2~8~2 ~Ioe 78/K 0Z6
(a) aliphatic monohydric alcohols with 4 to 20 carbon
atoms,
(b) polyglycol monoalkyl ethers obtained by reacting ali-
phatlc monohydric alcohols having from 1 to 20 carbon atoms with
ethylene oxlde or propylene oxlde.
The preparation of polyglycol monoalkyl ethers from alco-
hols and alkylene oxides is known. Compounds of this type are
commercially available.
The photopolymerizable mixtures according to the present
1 0 invention further contain polymeric, preferably thermoplastic binders
whlch are soluble or at least swellable in aqueous-alkaline solu-
tions. Polymers of this type contain groups which form salts in
an alkaline medium, e . g . COOH, PO3H2, SO3NH2, SO2NHCO, or
OH groups. Polymers containing carboxyl groups are preferred.
Maleic acid resins, polymers of N-(p-toluenesulfonyl)-carbamic
acid-(,B-methacryloyloxy)~ethyl ester, and copolymers of such mono-
mers, further styrene-maleic acid anhydride copolymers and in par-
ticular, 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 C. Such preferred binders are disclosed in U .
S. Patents Nos, 3,804,631, and 3,930,865. The binder should
have an average molecular weight of at least 10, 000, preferably
of about 2Q,000 to 200,000. Normally, the acld number ls between
-
~L~2~8~Z Hoe 78/K 02~
50 and 250, preferably between 100 and 200. Terpolymers of
methacryllc acid, an alkyl-methacrylate with 4 to 12 carbon atoms
ln the alkyl group, and styrene or substltuted styrene are preferred.
As a rule, the binder content is in the range from 20 to 80 per cent
by welght, preferably between 35 and 65 per cent by welght of the
non-volatile components of the mixture.
Furthermore, the mixtures according to the invention com-
prise 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 prepa-
ration of photopolymerizable compositions. Examples of suitable
compounds are, e . g .: ethylene glycol diacrylate, di-, tri- and
polyethyleneglycol-diacrylates, hexanediol-(l, 6)-diacrylate, tri-
methylol-propane-triacrylate, trimethylol-ethane-diacrylate, penta-
erythritol-triacrylate, neopentylglycol diacrylate, diglycerol diacryl-
ate, 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 dis-
closed in German Offenlegungs schriften No . 2, 064, 079 and No .
2,361,041, and in U.S. Patent No. 3,850,770. Reaction products
of 2 moles of hydroxyalkyl acrylate or -methacrylate and 1 mole
~Z~8132 Hoe 7~/. 0~
of a diisocyanate, e .g. hexamethylene-diisocyanate, 2, 2, 4-
trimethyl-hexamethylene-diisocyanate, isophoron-diisocyanate, di-
cyclohexyl-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. Further-
more, 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, trlpropylene glycol and the like, are men-
tioned 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 reac-
tion of the resulting reaction product with 1 mole of 2-hydroxy-
ethyl methacrylate per equivalent of isocyanate groups, are par-
ticularly preferred.
For the preferred application of the mixtures according to
the invention in the preparation of dry resist films, the methacryl-
ates 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 per cent by weight, preferably from 20 to 50 per cent by
-- 10 --
liZ8~ Hoe 7~/~ OZ~
weight, calculated on the weight of the non-volatile components
of the mixture.
A yreat number of substances may be used as photo-inltia-
tors . Benzoin, benzoin ether , multi-nuclear quinones, e . g . 2 -
ethyl-anthraquinone, acrldine derivatives, e . g . 9-phenyl-acridine,
9-p-methoxyphenyl-acridlne, 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)phena-
zine, quinoxaline derivatives, e.g. 6,4' ,4"-trimethoxy-2 ,3-di-
phenyl-quinoxaline or 4' ,4"-dimethoxy-2 ,3-diphenyl-5-aza-quin-
oxaline, quinazoline derivatives, and others are mentioned as ex-
amples. As a rule, their quantity is in the range from 0.1 to 10
per cent of the weight of the non-volatile components of the mix-
ture .
In addition to monomers, plasticizers, photoinitiators and
binders, the mixture according to the present invention may in-
clude a number of further conventional additives, such as inhibi-
tors 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 dis-
persion, which the consumer uses in particular for the preparation
of etch resLsts. Preferably, however, the mixtures according to
'11 L~8~Z Hoe 78/~ 02~
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 lami-
nated by the consumer to the support on which an image is to be
formed by etching or electroplating and are then exposed and de-
veloped in situ, the temporary support being removed before
development .
The mixture according to the present invention is particu-
larty suitable for this type of use. Alternatively, it may be manu-
factured as a presensitized copying material on a suitable support,
e . g . aluminum or zinc, for the photomechanical production of off-
set or letterpress printing forms. ~oreover, it is suitable for the
production of relief images, screen printing stencils, color proof-
ing 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-sensltive materials containing the mixture accord-
ing to the present inventlon 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 appllcation, or some other method, and the re-
sulting film dried. Thicker layers (e.g. of 250~m or more) may
be prepared, as a self-supporting film, by extrusion or molding
and the film is then laminated to the support.
~Z88~2 Hoe 78/K 02~
- Suitable supports for the copying Iayers containing the mix-
tures according to the invention are metal s, e . g . aluminum, zinc,
copper, steel, chromium, brass, and other metal alloys, further
supports for screen prlnting 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 expos ed
and developed in the conventional manner. Suitable developers are
aqueous, preferably aqueous-alkaline solutions, e.g. alkali phos-
phate or alkali silicate solutions, to which, if desired, small
quantities, e.g. up to 10 per cent by weight, but preferably less
than 5 per cent by welght, 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 mentloned, the mixtures accordlng to the pres-
ent invention may be used for very different purposes. As a par-
ticularly 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 follawing etching of the support wherein the
layers display good flexibility and etch resistance.
The mixtures may be used and handled with particular ad-
vantage in the form of the so-called dry resist materials mention-
ed abave, because even dry layers are capable of being transferred
-- 13 --
~L~288~Z Hoe 78/K 026
onto metal supports and forming firmly adhering layers thereon.
In this case, polyester fllms may be used with particular advan-
tage as temporary supporting films.
In the following examples, some embodiments of the inven-
tive mixture are described. Unless stated otherwise, percentages
and proportions are by weight.
Example 1 a
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 react-
ing 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-methacryl-
ate,
0 . 2 g of 9-phenyl-acridine,
0 .1 g of 3 -mercapto-propionic acid-2, 4-dichloro-anilide 1
0.035 g of a blue azo dye, obtained by coupling 2,4-di-
nitro-6-chlorobenzene-diazonium salt with 2-methoxy-5-acetylamino-
N-cyanoethyl-N-hydroxy-ethyl-anillne, and
2 .8 g of the ester of 2 ,6-dihydroxy-benzoic acid with di-
ethyleneglycolmono-2-ethylhexyl ether, ln
35 . 0 g of methylethyl ketone, and
2 . 0 g of ethanol,
.Z~8~Z Hoe 78~. 026
is whirler-coated onto a 25 ~m thick, biaxially stretched and heat
set polyethylene terephthalate film in a manner such that, after
drying at 100 C, the layer weighs 28 g/m
The resulting dry resist film is laminated by means of a
commercial laminating apparatus, at 120 C, to a laminated pheno-
plast panel provided with a 35~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 dis-
tances between lines have widths down to 80~m.
After exposure, the polyester film ls stripped off and the
layer is developed within 50 seconds with a 0 . 8 per cent Na2CO3
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 per cent ammonium
peroxy disulfate solution and then consecutively electroplated in
the following electrolyte baths:
I . ) For 40 minutes in a copper electrolyte bath marketed by
Messrs, Blasberg, Solingen, under the designatlon "Feinkornkupfer-
plastic-Bad", Current density: 2 A/dm2; Thickness of the metal layer
produced: about 20~m,
2.~ For 10 minutes in a nickel bath of type "Norma"~marketed
by Messrs, Blasberg, Solingen: Current density: 4 A/dm2; Thick~
ness of the metal layer produced: 6~,m,
3.) For 15 minutes in a gold bath of type "Autronex N", market-
ed by Messrs. Blasberg, Solingen: Current density: 0.6 A/dm2;
Thickness of the metal layer produced: 2 . 5 ~m .
The plate shows no undercutting or damage.
n~ r ~c
-- 15 --
~28~2 Hoe 78/K 026
The plate may then be decoated in a 5 per cent KOH solu-
tion at 50C 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 stretchlng an about 2 cm wide and 2 0 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 process-
ing steps, such as cutting of the laminated material, etching,
gold-plating and others. The above described dry resist film has
a very lc~w 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 lb to lg:
Instead of the plasticizer used in Example la, either of
the following plasticizers may be used:
lb) 2 . 8 g of the ester of 2, 4-dihydroxy-benzoic acid and di-
ethyleneglycolmono-2-ethylhexyl ether. Layer weight: 29 g/m2;
Exposure time: 6 seconds; Processing: as described above, the
same good resistance to electroplating baths being obtained;
Flexibility: even after 10-times overexposure the materlal can be
stretched without tearing or embrittlement of the layer.
-- 16 --
~1213~2 Hoe 78/~C 026
1c) 2.8 g of the ester of 2,6-dihydroxy-benzoic acid and triethyl-
eneglycolmono-2-ethylhexyl ether. Results: as above. Layer weight:
27 g/m .
ld) 2 . 8 g of the ester of 2 ,6-dihydroxy-benzoic acid and tripropyl-
eneglycolmono-2-ethylhexyl-ether. Results: as above. Layer
weight: 27 g/m2.
le) 2.8 g of the ester of 2,6-dihydroxy-benzoic acid and hexa-
ethyleneglycol-mono-2-ethylhexyl-ether. Results: as above. Layer
weight: 27 g/m2.
lf) 2.8 g of the ester of 4-hydroxy-toluene-2-carboxylic acid
and diethyleneglycol-monohexyl ether. Results: as above. Layer
weight: 3 2 g/m2 .
lg) 2 . 8 g of 4-hydroxy-toluene-2-carboxylic acid-n-hexylester.
Results: as above. Layer weight: 32 g/m2.
Com~arative Example lh
If a solution is prepared from
6 . 5 g of the terpolymer used in Example la,
2 . 3 g of the diurethane used in Example la,
2 . 8 g of the polyurethane used in Example la,
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 la,
35 . 0 g of methylethyl ketone, and
2 . 0 g of ethanol
(i.e, without the addition of a plasticizer), a dry resist film re-
sults 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%.
-- 17 --
-
8~ H oe 7 8/K U 2
Comparative Exa mpl e 1 i
A solution is prepared from
6 . 5 g of the terpolymer used in Example la,
5 . 6 g of the diurethane used in Example la,
2 . 8 g of the polyurethane used in Example la,
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 la,
35 . 0 g of methylethyl ketone and
2 . 0 g of ethanol
and is applied, in the manner described in Example la, to a sup-
port, a layer weighing 3 0 g/m2 being the result . After an expo-
sure 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 la,
2 . 8 g of the diurethane used in Example la,
2 . 8 g of the polyurethane used in Example la,
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 la, and
2.8 g of a plasticizer obtained by azeotropic esterifica-
tion of 4-hydroxy-benzoic acid with triethylene-
glycol-mono-tridecyl ether (commercial product),
3 5 . 0 g of methyl ethyl ketone and
2 . 0 g of ethanol,
-- 1~ -
~L~2~38~2 Hoe 78/K 025
is processed as described in Example la to yield a dry resist
film weighing 28 g/m .
After an exposure of only 8 seconds ln the exposure appa-
ratus used in Example la, an optimally exposed circuit board is
obtained which yields a true copy of the line original after devel-
opment in a 0 . 8 per cent Na2CO3 solution .
The resist remains flexible and does not crack or break
even if it is 1 0-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/m2; Exposure time: 10
seconds; Development: 70 seconds in 0 . 8 per cent Na2CO3 solu-
tion. Resistance to electroplating baths: very good, even to gold
baths (see Example la). 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 Ex-
ample 2a is replaced by 2 . 8 g of one of the following compounds:
2c) ester of 4-hydroxy-benzolc acid and triethyleneglycol-
monobutyl -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 hexaethyleneglycol-
mono-2 -ethylhexyl -ether .
-- 19 -
,~
8~2 Hoe 78/K 026
In all cases layers weighing around 30 g/m2 are obtained
which remain flexible, even if the dry resist films are grossly
overexposed (e. g . 160 seconds exposure time ln the exposure
apparatus used in Example la). The resistance of these layers
to electroplating baths is excellent.
Example 3a
A solution of
6.5 g of the terpolymer used in Example la,
5 . 0 g of a polymeriæable polyurethane obtained by reacting
2 moles of 2, 2, 4-trimethyl-hexamethylene-diisocya-
nate with 1 mole of triethyleneglycol and further
reactlng the reaction product with 2 moles of
hydroxyethylmethacrylate,
2 . 8 g Gf 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 la
and then dried in a manner such that the resulting layer weighs 52
g/m2. 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 la.
After 120 seconds development in a spray developing appa-
ratus, using a 0 . 8 per cent sodium carbonate solution, even lines
of a width of 5014m are resolved. A test of the resistance to
electroplating baths, carried through wlth the electroplating baths
-- 20 -
~Z1~8~2 Hoe 78/K 02&
used in Example la, yields good results; no undercutting or crack-
ing of the resist lines is observed ln 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~m wide.
Example 3b (ComParative 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 re-
sistance to the gold bath described in Example la is not sufficient.
Example 3c (ComParative 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 plasti-
cizer, the same poor results are obtained as in Example 3b.
Example 4a
A solution of
6 . 5 g of the terpolymer used in Example la,
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 . 9 g of ethanol,
-- 21 --
88~2 ~oe 78/K ~2 6
is whirler-coated onto a polyester film as described in Example la
and dried in a manner such that a layer weighing 51 g/m2 is pro-
duced. If the materlal is processed as described in Example 3a,
substantially the same results are obtalned as in Example 3a.
Example 4b (Comparative Example)
Example 4a is repeated, except that the plasticizer men-
tioned in the example is replaced by the same quantity of diiso-
decyl-adipate, a compound which is commercially used as a plas-
ticizer for polymers. After an exposure of only 15 seconds the
layer becomes brittle. In addition, its adhesion to copper is poor.
Example 4c (ComParative Exam~le)
Example 4a is repeated, except that the plasticizer men-
tioned in the example is replaced by the same quantity of
1 ) the polye ster of adipic acid and 1, 2-propane-diol, or
2) the polyester of adipic acld and butane-diol.
Both compounds are commercially available pLasticizers. Even
after normal exposure (20 seconds~, brittle resist layers are ob-
tained. Moreover, the adhesion of the layers to copper is poor.
-Example 5a
2 0 A s olution of
6.5 g of the terpolymer used in Example la,
5 . O g of the polymerizable diurethane used in Example la,
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,
-- 22 --
l~Z8l~2 Hoe 78~ 026
is whirler-coated onto a polyester film as described in Example la
and is dried in a manner such that a layer weLghing 50 g/m2 re-
sults. The layer is processed as described in Example 3a. Even
if the normal exposure time is exceeded by 200 per cent, the ex-
posed resist layer is sufficiently flexible.
Example 5b (ComParative 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 appar-
ent after exposure. After ~ weeks storage, substantial portions of
the plasticizer are lost by migration and the resist film has become
useless .
Example 5c (Comparative 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 aver~
age 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 ~he scope of the pre sent inven-
tion without departing from the spirit thereof, and the invention
includes all such modifications.
-- 23 -
