Note: Descriptions are shown in the official language in which they were submitted.
37 H oe 7 Y~
The present lnvention relates to a photopolymerizable mix-
ture comprlsing 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 reslsts, and relief images whlch 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,
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 should be capable
of being developed with aqueous, usually aqueous-alkaline devel-
oper solutions. Materials of this type and methods of processing
them are disclosed, e.g., in German Auslegeschrift No. 1,522,515,
and in German Offenlegungsschriften Nos. 2,064,079 and 2,361,041.
If they are developed with aqueous- alkaline solutions, the
layers disclosed in the above-mentioned Offenlegungsschriften have
a specially good adhesion to the support, in particular copper sup-
ports, and a good resistance to etching solutions and electroplat-
ing baths.
The binders requlred for these materlals which must be
soluble or at least swellable in aqueous-alkaline solutlons, fre-
quently have the drawback that they impart a certaln brittleness
to the exposed layer. This is particularly true in the case of
binders containing monomer unlts which impart to the polymer a
higher glass transition temperature and which are thus preferred,
- 1 -
1~;29237 Hoe 78/K 02 8
because they prevent a cold flow of the unexposed layer. Bind-
ers of this type are dlsclosed, e.g., in U. S. Patent 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, especi-
ally if exposure is prolonged beyond the optimum exposure time.
Certain compounds containing urethane groups in their
molecules have proved partlcularly suitable as monomeric or
polymerizable compounds which are readily compatible with the
above-mentioned binders and possess other properties which are
of advantage for photoresist techniques. Polymerizable compounds
of this type are disclosed in the above-mentioned German Offen-
legungsschriften. Due to their higher number of acrylic ester groups
or their relatively low molecular weight, the compounds disclosed
in German Offenlegungsschrift No. 2,064,079, which invariably
contain two urethane groups in their molecules, produce a high
cross-linking density and thus layers which tend to be brittle after
exposure. Higher molecular weight compounds of this type produce
layers which tend to have a lower light-sensitivity and lower re-
sistance to developer solutions.
The compounds containing biuret groups, which are dis-
closed in German Offenlegungsschrift No. 2,361,041, also have a
tendency towards forming relatively brittle exposure products. The
compounds with four urethane groups and one polyether group in
the molecule, which are also described in this Offenlegungsschrift,
237 11 oe 7 8/K 0 2 8
still have a certain resemblance to the compounds containing two
urethane groups.
Generally, lt can be stated that photopolymerizable layers
which have a satisfactorily low degree of cold flc~w in the unex-
posed state and which, after exposure, show good adhesion to
metal supports, good resistance to developer solutions, and good
resistance to etching solutions and electroplating baths, form
relatively brittle exposure products. Because this applies par-
ticularly to overexposures, usually there is only a very narrow
exposure latitude for processing such layers, if optimum combina-
tions of properties are to be achieved. A further embrittlement
may occur during storage or handling of the products at daylight.
This increased brittleness of the exposed and even of the
unexposed photoresist layers may cause considerable dlfficulties
in the further processing of these layers, e.g. in the production
of printed circuits. One of these difficultles is that the brlttle
resist layer tends to form flakes when the copper circuit boards
laminated to the dry resist are cut, thus leading to serious con-
taminatlon 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 appara-
tuses, or fine details of the photomasks crack off in aggressive
electroplatin~ 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 whlch may easily cause
a cracking of brlttle reslst masks.
Although the described problems have not been clearly out-
lined before for this combination of layer components and process-
Hoe 7~/K 02~3
ing conditions, the question of the brlttleness of photopolymeriz-
able layers has been studied ln prlnciple, and it was recommend-
ed to solve the problem by addlng plasticizers to the layers.
Thus, in column 14 of German Auslegeschrlft No. 2,327,513, di-
butyl phthalate and other esters of aromatic and aliphatic dicar-
boxylic acids, further glycol esters, polyglycols, alkyl and aryl
phosphates, certain sulfonamides, and other compounds are men-
tioned as suitable plastLcizers for certain types of photopolymer-
izable layers. These, and other simllar plasticizers are also
mentioned in U. S. Patent No. 3,192,194, column 4, and in Ger-
man Auslegeschrift 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. ~any of them
are not compatible w1th 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 devel-
oper resistance of the exposed areas of the layer, of their resis-
tance to electroplating baths, or their adhesion to the metallic
support .
Furthermore, it is known from German Offenlegungsschriften
Nos. 2,361,986, and 2,404,239, to add certain saturated urethane
compounds of similar structure to polymerizable urethanes or poly-
urethanes and to harden the mixtures by irradiation with ultraviolet
light. Allegedly, softer, more flexlble light hardening products
Hoe 78/K 028
are thus produced. The mixtures are used for the production of
hardenable varnlshes or for the production of printing plates. In
the latter case, no polymeric binder, and especially no alkali-
soluble binder is present in addition to the components already
mentioned. Consequently, organic solvents are used for develop-
ment. The compounds described in detail in these publications can-
not be used for the productlon of solid layers capable of aqueous-
alkaline development. Above all, the compounds are unsuitable
for the production of layers which display no cold-flow in the
unexposed state while their exposure products are sufficiently re-
sistant to developer and electroplating solutions.
It is the object of the present invention to provide a
photopolymerizable mixture which produces solid, flexible layers
capable of aqueous-alkaline development, which have a high light-
sensitivity and low cold-flow, and whose exposure products have
a good adhesion to metals, especially to copper, a high resistance
to aqueous-alkaline developer solutions, acid etching solutions,
and electroplating baths, and maintain their flexibility even after
considerable overexposure.
The object of the present invent~on is a photopolymerizable
mixture comprising a polymeric binder which is soluble or swell-
able in aqueous-alkaline solutions, a photoinitiator, and a com-
pound with at least two terminal acrylic acid or methacrylic acid
ester groups and a boiling point above 100C which is capable
of addition polymerization.
The mixture according to the present invention additionally
contains a polyurethane corresponding to the following Formula I
11;Z9~37 Hoe 78/~C 02 8
Y-~NHCOO-X-CONH-Y-)nNHCOO-Z-R1 (I)
NH
COO -Z -R
wherein
-X- is one of the following groups:
f
R2
(-CH2 -fH-S-)m 1 CH2 fH-o-
R2 R2
k 2k and
r 2r-2
Y is a saturated aliphatic or cycloaliphatic group with
2 to 12 carbon atoms,
Z is the group (-CH -CH-O)
2 I p
R3
R1 is R4 or CONH-R4,
R2 and R3 are hydrogen atoms or methyl groups,
R4 is a saturated aliphatic group with 1 to 20 carbon
atoms,
n ls zero or a whole number from 1 to 15,
m is a whole number from 2 to 4,
p is zero or a whole number from 1 to 4,
k is a whole number from 2 to 1 2,
r is a whole number from 4 to 12, and
n + p is a whole number from 1 to 1 9,
erein Rl R4 if p = 0, and R1 = CONH-R4 if n = 0
11;~9;237 ~oe 7~1/K 02~3
The mixtures according to the present invention normally
contain between 5 and 40 per cent by weight, preferably between
10 and 35 per cent by weight, calculated on the weight of their
non-volatile components, of compounds corresponding to Formula
I . Generally, from 0 . 2 to 2, preferably from 0 . 5 to 1 . 2 parts by
welght of compounds according to Formula I per part by weight of
polymerizable compounds are present in the mixtures according to
the invention.
On the average, the compounds according to Formula I con-
tain at least 4 urethane groups ln their molecules. Their average
molecular weights generally range from about 500 to 8,000, and
preferably from 900 to 6,000. The lower molecular weight com-
pounds are viscous liquids; higher molecular weight compounds
are solid.
Among the compounds corresponding to Formula I, those
are preferred in which n is a whole number between 1 and 11.
Compounds in which n = 5 or more are preferably combined with
low molecular weight polymerizable compounds. Both the polymer-
izable diurethanes obtained from 1 mole of diisocyanate and 2
moles of hydroxy alkyl methacrylate or -acrylate disclosed in Ger-
man Offenlegungsschrift No. 2,064,079, and the polymerizable
tetraurethanes obtained from 1 mole of diol or polyether diol, 2
moles of diisocyanate, and 2 moles of hydroxyalkylacrylate or
methacrylate known from German Offenlegungsschrift No. 2,361,041
are suitable for this purpose.
The compounds corresponding to Formula I may be used in
the form of the pure compounds with an exactly defined uniform
- value for n. In practice, however, they will in most cases be
37 ~i oe 7 8/K 0 2 8
ln the form of mixtures of homologous compounds whose molecular
weights and values for n will vary around a mean value, depend-
ing upon the manner of thelr preparatlon which will he described
hereinafter. If reference is made in the following to certain values
for n or to tetraurethanes, e.g. those mixtures of homologous com-
pounds are always included which have corresponding mean values
and which approximately correspond to the value stated. The
mean values for n or for the molecular weights may be calculated,
with an accuracy which is sufficient for practical purposes, from
the quantity of reaction partners used, without exactly ascertain-
ing the molecular weight of the product obtained.
The diol group X in the above generaL formula I may be
derived from a saturated or from a singly unsaturated diol. Suit-
able saturated diols are linear and branched compounds with 2 to
1 2 carbon atoms, preferably 4 to 1 2 carbon atoms .
Examples of suitable diols are: ethylene glycol, propylene
glycol, butane-diol-(1,4), but-2-enediol-t1,4), 2-ethyl-hexane-
diol-(1,6), decanediol-(1 ,10), and 1,4-bis-hydroxymethyl-
cycl ohexane .
The diol group X may further contain oxygen or sulfur atoms
in its chaln. Polyglycol groups, especially polyethylene glycol
groups with 1 to 3 ether bonds, are preferred. Triethylene glycols
are preferably used as the diol component.
The group Y which is derived from the diisocyanate used
for the preparation, is a saturated aliphatic or cycloaliphatic group
with 2 to 12, preferably 6 to 12 carbon atoms. Acyclic aliphatic
diisocyanates are preferred, in particular those with at least one
H oe 7 8/K () 2 ~
lateral methyl group . 2 ,2 ,4-trimethyl-hexamethylenediisocyanate
is a particularly advantageous compound.
Rl preferably is the same as the group R4 and R2 and R3
preferably are hydrogen atoms.
As a rule, the novel polyurethanes containing saturated
terminal groups are prepared in two steps. First, the dlol compo-
nent HO-X-OH is reacted witn the desired quantity of diisocyanate
OCN-Y-NCO. If 3 moles of diisocyanate are reacted with 2
moles of diol, an intermediate product with 2 terminal isocyanate
groups is obtained which on the average contains 3 diisocyanate
units and 2 diol units, i . e . a compound in which n = 2 . Then
the terminal isocyanate groups are caused to react with the select~
ed alcohol or ether alcohol. By this process, normally polymer
homologous mixtures are produced, i.e. mixtures of compounds in
-which the value for n varles. This applies particularly to those
mixtures in which the mean values of n are relatively high. Such
mixtures are excellently suitable for the purposes of the present
invention and may be immediately used. If it is desired to obtain
products witrh a more exactly defined or at least less varying
molecular weight, it 1s also possible for the above mentioned di-
isocyanate intermediate product to be step-wise prepared, by first
reacting 1 mole of diol with 2 moles of diisocyanate, then react-
ing the reaction product with 2 moles of diol, and so on. The
intermediate products containing two terminal hydroxyl groups are
analogously prepared, by reacting a diisocyanate with the desired
diol in excess. Then the terminal OH groups are caused to react
with an appropriate monoisocyanate.
3;~3~ H oe 7 B/K O 2 8
The mlxtures accordin~ to the present invention yielcl
photopolymerlzable layers of high light-sensltivity and good flexi-
bility which have only a very slight tendency towards cold flow
or no cold flow tendency at all. The exposure products are dis-
tinguished by high flexlbility and good resistance to aqueous-alka-
line developer solutions and to etching solutions and electroplat-
ing baths. In additlon, they have all the advantages of the known
mixtures containing alkali-soluble binders and urethane group-
containing monomers. It is particularly surprising that, by adding
the non-polymerizable polyurethanes according to the lnvention, it
is not only possible to reduce the cold flow of the unexposed layer
but also to improve the flexibility of the exposure products, as
compared with layers containing the hitherto known polymerizable
urethanes. The desired combination of properties which normally
are difficuit to reconcile with each other is even maintained if the
layer is substantially overexposed, 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.
The photopolymerizable mixtures according to the present
invention further contain polymeric, preferably thermoplastic bind-
ers 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, P03H, S03NH2, SG2NHCO,
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
monomers, further styrene-maleic acid anhydride-copolymers and
- 10 -
37 Hoe 78/K 028
in partlcu~ar, acrylic and methacrylic acld copolymers may be used
as binders. The latter compounds may contaln 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 20,000 to 200,000. Normally, the acid number is be-
tween 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 per cent by weight, preferably between 35 and 65 per cent by
weight of the non-volatlle components of the mixture.
Advantageously, the mixtures according to the present in-
vention may contain certain plasticizers which add to the substan-
tial improvement of the flexibility of the layers after exposure.
These plastici~ers which are described in detail in simultaneously
Ca~c~diR~
filed~/,application Serial No.32~,26, filed IYa~ 17~ Iq~l, are
compounds corresponding to the following Formula II
R O H R
2 3~ -O-O-(C-H-O-) R4 (ll)
OH
wherein
-- 11 --
3~7 Hoe 78/K 028
Rl ls a hydrogen or halogen atom or an alkyl
group w1th 1 to 4 carbon atoms,
R2 is a hydrogen atom, an OH group, or an
alkyl group wlth 1 to 4 carbon atoms,
R3 is a hydrogen atom or a methyl group,
R is an alkyl or alkenyl group wlth 1 to 20
carbon atoms, and
n is zero or a whole number from 1 to 20,
preferably from 1 to 4, and wherein
R4 has at least 4 carbon atoms i~ n is zero or 1.
As a rule, the plasticizers are added in a quantity of up to
30 per cent by weight, preferably between 10 and 25 per cent by
weight, calculated on the weight of the non-volatile components
of the mixture.
Furtherrnore, the mixtures according to the lnvention include
polymerizable compounds with at least 2 acrylic or methacryllc acid
ester groups in the molecule. Compounds of this type are known
in large numbers and are conventionally used for the preparation
of photopolymerizable composltions. Examples of sultable com-
pounds are, e.g.: ethylene glycol diacrylate, di-, ~ri- and poly-
ethyl eneglycol -diacrylate s, hexanediol - ( 1, 6 ) -diacrylate, trimethylol -
propane-triacrylate, trimethylol-ethane-diacrylate, pentaerythritol-
triacry late, neopentyl~lycol dlacrylate, diglycerol diacrylate, and
the correspondlng methacrylates. Acryllc and methacryllc acid
amides, e . g . methylene-bis-acrylamide, hexamethylene-bls-
acrylamide, or xylylene-bis-methacrylamide, also may be used in
combination wlth the esters. Acrylic and methacryllc acid esters
..~
-- 12 --
l~d~37 Iloe 78/K 028
containin~ at least two urethane groups in their molecules are
preferred, because these monomers form exposure products which
are dlstinguished by their good flexlbillty and adhesion to metals.
The compounds may also lnclude biuret groups and, if desired,
carboxylic acid amide groups. Compounds of this type are dis-
closed in German Offenlegungsschriften Nos . 2, 064, 079 and
2,361,G41 and in U. S. Patent No. 3,850,770. Reaction prod-
ucts 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. ~urther-
more, monomers are used with advantage which contain at least
one oxyalkylene unit, preferably oxyethylene units r in the mole-
cule. The reaction products of hydroxyl group-containing acrylates
and methacrylates with diisocyanates produced by the partial re-
action of the above-mentioned simple diisocyanates, with diols,
e.g. hexane diol, diethyleneglycol, triethylene glycol, penta-
ethylene 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 $he above-
mentioned preferred dilsocyanates with di-, tri-, or tetra-ethylene-
glycol, in a molar ratio from 2 : 1 to 1.1 : 1, followed by re-
action of the resulting reaction product with 1 mole of 2-hydroxy-
-- 13 --
3?3~ ~o~ 7~/K 028
ethyl methacrylate per equivalent of isocyanate groups, 3re par-
ticularly preferred .
For the preferred applicatlon 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 u sed in quantities ranging from 10 to
50 per cent by weight, preferably from 15 to 40 per cent by
weight, calculated on the weight of the non-volatile components
of the mixture.
A great number of substances may be used as photoinitia-
tors. 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)phena-
zine, quinoxal ine d erivative s, e . g . 6, 4 ', 4 " -trimethoxy - 2, 3 -di -
phenyl-q[uinoxaline or 4' ,4"-dimethoxy-2,3-diphenyl-5-aza-quin-
oxaline, quinazoline derivatives, and others are mentioned as
examples. 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
mixture .
In additlon to the urethanes according to Formula I, polym-
erizable compounds, photoinitiators, binders, and, if desired,
plasticizers, the mixture according to the present invention may
include a number of further conventional additives, such as inhibi-
tors to prevent thermal polymerization of the monomers, adhesion-
-- 14 --
3 ~ l oe 7 8/K 0 2 8
promoting agents, hydrogen donors, sensitometric regulators,
dyes, colored or uncolored pigments, color couplers and lndica-
tors .
Advantageously, these additives should be selected in a
manner such that they do not excessively absorb -within the
actlnic wave length range essential for the initiating process.
The photopolymerizable mixture according to the present
inventlon may be marketed in known manner as a solution or dis-
persion, which the consumer uses in partlcular for the preparation
of etch resists. Preferably, however, the mixtures according to
the invention are used for the preparation of dry resist filrns 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 mlxture according to the present invention is particu-
larly suitable for this type of use. Alternatively, it may be manu-
factured as a presensitized copylng material on a suitable support,
e . g . aluminum or zinc, for the photomechanical production of off-
set or letterpress printing forms. Moreover, 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 ex-
posed layer, low cold flow of the unexposed layer, and hlgh re-
sistance of the exposed layer to aggressive chemicals are of
i mportance .
-- 15 --
oe 78/K 028
The light-sensitive materials containing the mixture accord-
ing 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 re-
sultlng film dried. Thicker layers te.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.
Suitabl e supports for the copying layers containing the mix-
tures 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, 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 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 apparatu ses .
As already mentioned, the mixtures according $o the present
invention may be used for very different purposes. As a particu-
larly advantageous application, they are used for the production of
pho$oresist or etch resist layers on metal supports. They are
-- 16 --
11~>~ e 78/K 02~
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 durlng development,
but also during the subsequent 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 above, because even dry layers are capable of being transferr-
ed onto metal supports and forming firmly adhering layers thereon.
In this case, polyester films 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
6 . 5 g of a terpolymer of n-hexylmethacrylate,
methacrylic acid, and styrene (60: 30: 10)
w$th an average molecular weight of about
35,000,
2 . 8 g of the saturated polyurethane described below,
2 . 8 g of a polymerizable polyurethane obtained by
first reacting 2 moles of 2,2,4-trimethyl-
hexamethylene-diisocyanate with 1 mole of
anhydrous triethyleneglycol and then reacting
the resulting reaction product with 2 moles
of hydroxyethyl methacrylate,
2 . 8 g of 4-hydroxy-(2-ethyl-hexyl)-benzoate,
-- 17 --
'3~3'7 Hoe 78/K 028
0 . 2 9 of 9-phenyl-acridine,
0 .1 9 of 3 -mercapto-propionic acid-2, 4-dlchloro-
anilide, and
0 . 025 g of the dye called "Disperse Red " (Color Index
No. 179)
are dissolved in
25 . 0 g of methyl ethyl ketone and
2 . 0 g of ethanol
and the resulting solut~on is whirler-coated onto a 25 ~m thick, bi-
axially stretched and heat-set polyethylene terephthalate film in a
manner such that, after drying at 100 C, thelayer weighs 49
g/m2 .
The dry resist fllm thus produced is laminated by means of
a commercial laminating apparatus, at 120 C, to a laminated
phenoplast panel provided with a 35 ~m thick copper foil and is
then exposed for 14 seconds by means of 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~m.
After exposure, the polyester film is stripped off and the
layer is developed within 70 seconds in 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 successively electroplated in
the following electroplating baths:
1. For 40 minutes in a copper bath marketed by Messrs. Blas-
berg, Solingen, Germany, under the designation "Felnkornkupfer-
-- 18 --
7 H oe 7 8/K 0 2 8
~ f
plastic-Bad " . Current density: 2 A~dm2; Thickness of the metal
deposltlon: approximately 20~m.
2. For l0 minutes in a nickel bath of type "Norma'' marketed
by Messrs. Blasberg, Solingen. Current density: 4 A/dm2; Thick-
ness of the metal deposition: 6 ~m.
3 . For 15 minutes in a gold bath of type "Autronexi~N " market-
ed by Messrs . Blasberg, Solingen . Current Density: 0 . 6 A/dm2;
Thickness of the metal deposition: 2.5~m.
- The plate shows no undercutting or damage.
l 0 The plate then may be decoated in a 5 per cent KOH solu-
tion at 50 C and the bared copper areas may be etched away by
conventional etching means.
Even after l l -times overexposure, i. e . after an exposure
time of 160 seconds in the above-described exposure apparatus,
the above described dry resist film is completely flexible. This
can be proved by manually stretching an about 2 cm wide and 20
cm long strip of the exposed material consisting of support and
layer . At room temperature, the l l -times overexposed strip of dry
resist film can be stretched to at least twice its original length
without cracking or tearing of the layer.
This flexibility is of decisive importance for many pro-
cesslng steps, such as cutting of the laminated material, etching,
gold-plating and others. Furthermore, the above-described dry re-
sist 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.
~ro~q~e r~a r~
-- 19 --
li oc 7 ~/~; () ~ .'
E~y means of the abovc-(iescribed layer, lines of a v,1,~1th of
SO~m can be resolved wlth sharp edges, as can be easily ~oved
by exposing the material under a resolution test original 2n'3 de-
veloping it with a 0 . ~ per cent Na2CO3 solution . The dev~loper
resistance corresponds to at least 3-times the developing ti~e.
The polyurethane used in this example is prepared as
follow~:
2 moles of 2 ~2 ,4-trimethyl-hexamethylene-diisocyanat~ in
800 g of methyl ethyl ketone are filled into a three-necked ~l~sk
provided with stirrer, reflex condenser with CaC12-drying tl~e, and
dropping funnel. After adding a mixture of
1. 5 g of iron(III)-acetyl-acetonate and
2 . 0 g of diethyl cyclohexyl amine, in
50 . 0 g of methyl ethyl ketone,
-which acts as a catalyst, a solution of 1 mole of anhydrous tri-
ethyleneglycol in 50 g of methyl ethyl ketone is cautiously added
in a manner such that a constant reaction temperature of 70 + 1
C is maintained. For this purpose, a water bath is provided
which first has a temperature of 60 C, so that it heats the mix-
ture from the outside, and after the desired interior temperature
ha s been attained by the heat generated by the polyaddition re-
- action, the same bath - which now has a temperature between
about 40 C and 50 C - serves to cool the reaction mixture .
When the entire triethyleneglycol solution has been introduced, 2
mo!es of triethyleneglycol-mono-butylether are dropwise added at
70 C . After completion of the reaction, the mixture is stirred
for 2 hours at 70 C and then cooled . The resulting polyurethane
-- 2 0
37 H oe 7 8/K 0 2 8
may be added to the polymerizable mixtures either in the form of
the solution or a s a resin, after the solvent has been distilled
off. In the examples, the polyurethanes are used in the form of
the resins.
Example 2
The saturated polyurethane used in Example 1 may be re-
placed by the same quantity (2 . 8 g) of a polyurethane which is
prepared analogously by reacting
4 moles of 2, 2, 4-trimethyl-hexamethylene diisocyanate
flrst with 3 moles of triethyleneglycol (first reaction t
step) and then with 2 moles of triethyleneglycol-mono-
butylether (second reaction step).
A dry resist film is prepared in a manner analogous to that
described in Example 1. The resist layer has a weight of 53 g/
m2 and is still stretchable and flexible after 1 0-times overexpo-
sure. The resistance of the layer to the electroplating baths used
in Example 1 is excellent.
Example 3
The saturated polyurethane used in Example 1 may be re-
placed by the same quantity (2 . 8 g) of a polyurethane which is
prepared analogously to the method described in Example 1, by
reacting
2 moles of 2,2,4-trimethyl-hexamethylene-diisocyanate
flrst with 1 mole of butene-(2)-diol-(1,4) (first reaction
step) and then with 2 moles of diethyleneglycol-mono-
2-ethylhexyl ether (second reaction step).
Details of the resulting dry resist film are as follows:
-- 21
~io~ 7~/~; 0
Layer weight: 51 g/m2
Exposure time: 16 seconds
Development: 80 seconds/0.8% Na2CO3 solution
Test results: similar to those of Example 1.
Example 4
The saturated polyurethane used in Example 1 may be re-
placed by the same quantity (2 . 8 g) of a polyurethane which is
prepared by reacting
2 moles of 2, 2, 4-trimethyl-hexamethylene-diisocyanate
first with 1 mole of thiodiethyleneglycol (first reaction
step) and then with 2 moles of diethyleneglycol-mono-
2-ethylhexyl ether (second reaction step).
A dry resist film with a layer weight of 53 g/m is thus
obtained whose test results are similar to those of Example 1.
Example 5
The saturated polyurethane used in Example 1 may be re-
placed by the same quantity (2 . 8 g) of a polyurethane which is
prepared by adding
mole of 2, 2, 4-trimethyl-hexamethylene-diisocyanate
to 2 moles of triethyleneglycol (first reaction step),
and then reacting the resulting reaction product with
2 moles of octadecyl-monoisocyanate (second reaction
step) .
A dry resist film with a layer weight of 53 g/m2 is ob-
tained whose test results are similar to those of Example 1.
Exam~le 6
6 . 5 g of the terpolymer used in Example 1,
-- 22 --
1~J'~237
Hoe 78/k 028
2 . 8 g of a polymerlzable diurethane obtalned from 1
mole of 2 ,2 ,4-trimethyl-hexamethylene-diiso-
cyanate and 2 moles of hydroxy-ethyl-methyl-
acrylate,
2 . 8 g of the 4-hydroxy-benzoic acid ester of diethyl-
eneglycol-mono-n-hexyl ether,
0 . 2 g of 9-phenyl-acridine,
0 .1 g of 3 -mercapto-propionic acid-2, 4-dichloro-
anilide,
0.025 g of the dye used in Example 1,
2 . 8 g of a saturated polyurethane prepared analogously
to the method described in Example 1, by react-
ing 11 moles of 2,2,4-trimethyl-hexamethylene-
diisocyanate first with 10 moles of triethylene-
glycol (first reaction step) and then with 2 moles
of diethyleneglycol-mono-2-ethyl-hexyl ether
(second reaction step)
are dissolved ln
35 . 0 g of methyl ethyl ketone and
2 . 0 g of ethanol
and the resulting solution is processed as descrLbed in Example
1 to form a dry resist film in which the layer on the polyester
film weighs 52 g/m2 after drying.
When this dry resist film is tested as described in Exam-
ple 1, it is found that, as regards its resistance to electroplating
baths and the flexibility of the exposed and 1 0-times overexposed
resist layer, the film is similar to that obtained by Example 1.
-- 23 --
3~ ~o~ 78/~; 0~8
Example 7
The saturated polyurethane used in Example 6 may be re-
placed by the same quantity (2 . 8 g) of a polyurethane which ls
analogously prepared by reacting
2 moles of 2, 2, 4-trimethyl-hexamethylene-diisocyanate
first with 1 mole of butane-diol-(l, 4) (first reaction
step) and then with 2 moles of triethyleneglycol-mono-
butyl ether (second reaction step).
The resulting dry resist film has a layer weight of 52 g/
m2 and its test results are comparable to those of the film accord-
ing to Example 6. Even after 6-times overexposure, the flexibility
of the resist layer is still good, so that the layer does not tear
or crack when a test strip of the material is stretched.
Example 8
6 . 5 g of the terpolymer used in Example 1,
2 . 8 g of the polymerLzable polyurethane used in
Exa mple 1,
2 . 8 g of 4-hydroxy-(2-ethyl-hexyl)-benzoate,
0 .1 g of 3 -mercapto-propionic acid-2, 4-dichloro-
anilide,
0 . 2 g of 9-phenyl-acridine,
0.025 g of the dye used in Example 1, and
2 . 8 g of a saturated polyurethane obtained by react-
ing 2 moles of 2, 2, 4-trimethyl-hexamethylene-
diisocyanate with 1 mole of triethyleneglycol
(first reaction step) and then reacting the
reaction product with 2 moles of diethylene-
-- 24 --
'7i~oe 7B/K 02
glycol-mono-2-ethyl-hexyl-ether (second
reaction step),
are dlssolved in
25 . 0 g of methyl ethyl ketone and
2 . 0 g of ethanol,
and a dry reslst film with a layer weight of 52 g/m2 is prepared
from the solution as descrlbed in Example 1.
After lamination, exposure (l 5 seconds) and development
(100 seconds in an 0.8 per cent Na2CO3 solution), a resist mask
l O is obtained which is excellently resistant to the electroplating
baths used in Example l. The flexibility of the 11-times over-
exposed resist film (160 seconds exposure time) is still excel-
lent .
Example 9 (ComParative Example)
If the mixture of 2 . 8 g of the polymerizable diurethane and
2 . 8 g of the saturated polyurethane used in Example 6 is replaced
by 5 . 6 g of the polymerizable diurethane, while the other compo-
nents of the layer remaln the same, a dry resist layer weighing
52 g/m2 is obtained which has about the same light-sensitivity,
but a considerably greater tendency to become brittle by overexpo-
sure. Wlth normal exposure time, the layer is flexible; after
double the exposure time, i.e. about 30 seconds, and increasingly
with exposure times above 40 seconds, using the exposure appara-
tus mentioned in Example 1, the layer becomes brittle and no
longer can be stretched without tearing or splintering. Moreover,
the layer displays a substantially higher flowing tendency at room
temperature than the layer described in Example 6, whlch leads to
- 25 -
3~;~7
EIoe 78/K OZ8
an undeslrable squeezing out of the layer when the material is
stored 1n the form of rolls of dry resist film, e.g. rolls of 50 m
length. The layer accordlng to Example 6 shows no undesirable
squeezing out of the resist layer during storage, a fact which can
be attributed to the considerably lower cold flow of this layer.
It ~A'ill be obvious to those skilled ln the art that many
modifications may be made within the scope of the present inven-
tion without departing from the spirit thereof, and the invention
includes all such modifications.
-- 26 --
