Note: Descriptions are shown in the official language in which they were submitted.
20236~
O.Z. 0050/41049
Radiation-sensitive positive-working_mixture
The present invention relates to a radiation-
sensitive positive-working mixture whose solubility in
water or aqueous alkali increases on irradiation.
- Positive-working light-sensitive compositions,
ie. compounds or mixtures of compounds whose solubility
in a given solvent increases on irradiation, are known
per se. The compounds most fre~uently used in reproduc-
tion technology are naphthoquinonediazide~ and derivat-
ive~ thereof (cf. W. Fra~, Chemie in un~erer Zeit, 17
(1983), 10; H.W. Vollmann, Angew. Chem. 92 (1980) 95). On
irradiati~ these compounds elimin te nitrogen and
undergo a Wolff rearrangement which convert~ a hydro-
phobic diazoketone unit into a carboxyl group which
render~ the compounds mentioned, or mixture~ containing
these compound~, soluble in aqueou~ alkali.
A further clas~ of compound~ which are suîtable
for preparing posltive-working light-sensitive mixture~
are aromatic or heteroaromatic nitro compound3. Whereas
the above-described compound~ with a diazoketone struc-
ture are u-~ually present in light-sen~itiva mixture3 as
low molecular weight compound3, light-3ensitive nitro
compound~ can be used not only in t:he fo~m e~ low molecu-
lax weight compound8 (DE-A-22 07 574, US-A-4 181 531) but
also a~ polymQrs formod from monomers having an o-nitro-
carbinol ester ~tructure or copolymer~ of these monomer3
with other vinyl compounds ~cf. DE-A-21 50 691, DE-A-29
22 746 and EP-A-19 770). Here too irradiation result~ in
the ~ormation of a carboxyl group which increa~aq the
~olubility of the mixtures in a9u~ou8 alkali.
A similar principle i8 probably t work with th~
po~itive ~y~t~m~ which are d~cribed for example in
US-A-4 469 774 and which contain photochamically
cleavable benzoln es~ers in the side chain.
A further in~tance of qolubilization duo to
carboxyl groups i~ described fer example in EP-A-62 474,
EP~-99 949 or US~A~4 415 652. The mix~ure contains a
- 2 - O.Z. 0050/41049
water-insoluble binder, a mercaptocarboxylic acid and an
i~itiator system which forms free radicals on irradia-
tion. Irradiation causes a free radical graft of the
mercaptocarboxylic acid on~o the binder, thereby render-
ing the latter soluble in aqueous alkali.
In photosensitive mixtures devised according to
one of the above-described principles, only at most one
carboxyl group is formed or grafted onto the binder per
quantum of light absorbed. Usually the quantum yield is
still distinctly below 1. For this reason all cases
require long exposure times, but the solubility differen-
tiation achieved is still poor in most cases. of the
photosensitive systems mentioned, therefore, only those
which are based on ~he Wolff rearrangement of diazo-
ketone3 have become established in the marketplace, and
this only in the area of positive offset plate3 or
positive rQsists for the fabrication of integrated
circuits. In the case o~ other products, in particular
photoresist film~ for circuitboard manufacture, the long
exposure times required and the half-aqueous developers
reg~lired on account of the lac}c o~ solubility dif-
erentiation are unacceptable. The problem of how to
dispose o~ daveloper~ will become .increasingly important
in the future.
A fundamentally diferent way of increasing the
solubility of a photo~ensitive laye~ by irradiation
con~ist~ in ~electing the composition o~ ~he lay~r in
~uch a way that the average molecular weight of the
binder decreases on irradiation. To this end, group~
which are cleavabl0 by actinic light are incorporated in
the main chain of a polymer. Example~ of such systems are
polyoxymethylene polym~rs which contain acetal units
formed from o-nitrobenzaldehyde or deri~atives of
o-nitrobenzaldehyda in the maln chain. Such polymers and
light-sensitive layer~ prepared ther~from are described
for example in US-A-3 991 033 and US-A-4 189 611. In the
same way it i~ also po~ible to lncorporate acetal~ of o-
- 2~23~
- 3 - O.~. 0050/41049
nitrobenzaldehyde in the main chain of polymers which are
essen~ially polyesters formed from a dicarboxylic acid
and a difunctional alcohol (cf. US-A-4 086 210). Other
polymers which on irradiation react by cleaving the main
chain and hence reducing the molecular weight are poly-
mers which contain hexaarylbisLmida~ole units in their
main chain (cf. US-A-4 009 040).
A combination of main chain degradation and
grafting with a carboxyl group is the principle exploited
in EP-A-57 162 whera unsaturated carboxylic aeid~ are
present as well as a polymer which contains benzoin units
in the main chain. On irradiation the benzoin units split
and reduce the average molecular weight. At the same tLme
the unsaturated carboxylic acids undergo addition to the
free radicale formed at the cleavage sites and thus
likewise increase tha solubllity in aqueou~ alkali.
~ gain the positive-working photosensitive layers
based on the main chain dagradation o~ a suitable polymer
aceording to one of the prineiples deseribed above are
not suffieiently sensitive to light. In addition, a
postQxposure thermal aftertreatment i~ necessary in many
eases. For this rea~on none o~ the ~ays~ems deseribed have
beeome established in praetiee.
~ttempt3 have therefore been mada ~o utilize the
high light-sensitivity of pho~opolymerizable layers for
the produetion of positive-working layers by forming an
inhibitor of the polymerization by imagawise exposure
through an original and then polymerizing the non-
inhibited areas in a seeond, not neeessarily imagewi~e
exposure ~tep. Example~ of eompounds propo~ed ~ox the
formation of polymsrization inhibitors by irradiation ara
nitroso dlmers (ef. DE-A-25 42 151) or eertain o-nitro-
aromaties ~ef. DE-A-27 10 417 and EP-~-103 197). ~hese
systems all require an additional exposure step, ~o that
if anything the total proeess tima is inereased eompared
with other po~itive sy~temsO
The hitherto most sueces~ul attampt at inereas-
- 2~23~
4 - O.Z. 0050/41049
ing the light sensitivity of positive-working light-
sensitive layers has become known as chemical enhance-
ment. Here irradiation leads to the formation of a
catalyst which in a second, thermal step, catalyzes a
reaction which ultimately leads to an increase in the
solubility of the photosensitive layer. The catalyst is
usually a strong acid which is formed photochemically,
for example, from an organic halogen compound, in par-
ticular a halogen-containing triazine compound (cf. for
example DE-A-23 06 248), an aromatic nitro compound (cf.
for example EP-A-78 981), a diazonium salt or an aromatic
iodonium or sulfonium salt (cf. for example
DE-A-36 30 677 and US-A-4 491 628). The acid formed is
used for splitting acid-labile bonds in the second,
thermal step of the process. Depending on the acid-labile
compound used, thi~ ~plitting can lead either to the
formation of a hydrophilic group from a hydrophobic group
tcf. for example DE-A-36 20 677 and US-A-4 491 6~8) or to
a decrease in the molecular weight. Example~ of acid-
labile groups suitable for the last: case are acetal (cf.
DE-A-23 06 248, EP-A-78 981, EP-A-82 463 and US-A-
3 779 778~, orthocarboxylic ester ~cf. EP-A-78 981 and
EP-A-82 463), enol ether (c~. EP-A-6 627 and EP-A-
82 463), silyl ethar (c~. DE-~-35 44 165 and EP-A-
130 599) or silyl ester groups (cf. EP-~-130 599).
Although these mixtures make it pos~ible to achieve light
sen~itiYitie~ which in the best case~ corre3pond to those
of negative-working layers, products which are con~truc-
ted accordlng to the principle o~ chemical enhancement
have become .~mportant only within the area of resists for
fabrication o~ integrated circuits. In other fields, the
additional thenmal step required is not acceptable.
~ fur~her ~ype of a po~itive-working
light-sen~itive mixture i-~ described in EP-A-106 156.
This mixture con~ist~ of a polyconden~ate having certain
group~ in the m~in chain and unsaturated group~ at the
end of the chain in combination with a photoinitiator.
- 2~2~
- 5 - O.Z. ~050/41049
Groups mentioned for forming the main chain are aromatic
hydrocarbon, diaryl ether, diaryl sulfide, diaryl
sulfone, diarylamine, diaryl ketone and diaryl diketone
groups. End group~ are alkenyl groups or unsaturated
S carboxylic acid groups. The cause for the increase in the
solubility on irradiation is suspected to be a chain
degradation process induced by free radicals. Despite the
very high initiator content of t~pically 25% by weight,
only moderate light sensitivities are achieved.
The use of certain vinyl-containing urethane
compounds as raw materials in photos~nsitive compositions
is known per se (cf. EP-A-48 913, EP-A-54 150 and
EP-A-72 918~. In all the sy3tems in question, however,
the solubility decreases on irradiation; they are thus
negative-working systems.
The examples mentioned show that in most araas
there is still a demand for new positi~e-working light-
sensiti~e mixture~ which combin~ high light-sensitivity
~nd ease of handling, ie. in particular the absance of
additional operation~.
It i~ an ob~act of tha present invention to
develop a positive-working light-se~nsitive mixture having
the properties mentioned and to devise its underlying
reaction produc~.
We have found, surprisingly, that thi~ oh~ect is
achieved in that the solubility of mixtures of certain
ethylenically un aturated reaction produc~s containing
urea and urethane groups and compounds which contain one
or more carbo~yl groups increases on irradiation in the
presence of compound~ from which free radical3 are formed
on irradiation.
The present invention accordingly provides a
radiation-sensitive po~itive-working mixture formed from
(a) an ethylenically unsaturated reaction product
containing urea and urethana group~,
(b) at laast one organic compound containing one or mora
carboxyl groups,
` ~ 2~23~
- 6 - O.Z. OOS0/~1049
(c) an optional photoinitiator or photoinitiator system
with or without
(d) further additives and auxiliaries,
wherein component (a) is an ethylenically unsaturated
S reaction product containing urea and urethane groups
obtained by reaction of
i) at least one ethylenically monounsaturated or
polyunsaturated mono- or polyalcohol with
ii) at least one di- or polyisocyanate and
iii) at least one amino compound having a primary and/or
secondary amino group,
and
iv) one or more optional organic compounds other than
component i) having at least one hydroxyl group,
the number of NCO groups in component ii) being equal to
or less than the number of groups in components i), iii)
and iv) which are reactive therewith.
In particular embodiments of the present inven-
tionr component (a) i8 prepared u~ing as component i) an
ethylenically monounsaturated mono- or polyalcohol, an
ethylenically monounsaturated or polyunsaturated mono-
alcohol, an ethylsnically monounsaturated monoalcohol, an
~ ethylanicallyun~aturatedcarbonylcompoundcontaining
a c~rboxyl group, in par~icula.r a monohydroxyalkyl
2S acrylate or methacrylate, a~ component ii) a diisocyanate
~nd a~ component iii3 one or morQ primary and/or secon-
dary amine~. A further preferred component (a) is a
raaction pro~uct prepared using as component iii) at
least ona amino compound o the general formula
R'~N-R-XH (I)
where
R is the divalent radical of a substituted or un3ub-
~itutad alkane, arene, etherr polye~har, amine, poly-
amine, ester, polye~ter, amide or polyamide,
R' is hydro~en, alkyl, aryl, aralkyl, hydroxyalkyl,
aminoalkyl, mercaptoalXyl, a derivative thereo~ or ~he
monovalent radical H~O~(C~2)~-CHR"~m whare n i~ from 1 to
2~2~$~
_ 7 _ o.Z. OOS0/41049
3, m is from 1 to 10 and R~ is H or Cl-C4-alkyl, or an
isomer thereof,
X i5 0, S or NR"',
R"' is hydrogen, alkyl, aryl, aralkyl, hydroxyalkyl,
aminoalkyl, mercaptoalkyl or a derivative thereof,
and/or
at leas~ one amino compound of the general formula
Rl
HN / \ NR3
1 0 R2
where
Rl and R2 are identical or different and each is the
divalent radical of a sub~tituted or un~ubstituted
alkane, arene, ether, polyether, amine, polyamine, ester,
polyester, amide or pvlyamide,
R3 i~ hydrogen, alkyl, aryl, aralkyl, hydroxyalkyl,
aminoalkyl, mercaptoalkyl or a de:rivativo thereof.
A ~uitable component (b) is in particular a
carboxyl-containing compound having an average molecular
weight ~ o~ above 10,000, in particular from 15,000 to
300,00Q, and preferably an acid number of from 50 to 300,
in particular copolymer~ ~ormed ~rom an acid monomer and
at least one hydrophoblc monomer, the acid monomer being
pre~erably acryllc acid, methacrylic acid, crotonic acid
and~or itaconic acid and the hydrophobic monomer being
preferably a styrene, an acrylate or a methacrylate.
Preferred photoinitiator~ or photoinitiator
systems (c~ for the radiation-0ensitive mixture~ accord-
ing to ~h~ present lnvention are benzophonone and
d2rivati~es thereof, hQxaarylbisimidazole derivative~
alkoxypyridinium ~alts and mixtures thereof.
The pre~ent invention provide~ in particular
those radiatLon-sensitive mixtures who~e ~olubility in
water or aqueou~ alkali incraa~e~ on irradiation or
exposure to light.
The ureido containing reaation product ta) to be
u~ed according to the pra~ent in~ention i~ thu~ prepared
2~2~
- 8 - O.Z. 0050/41049
by r~acting the isocyanate component (ii) with the un-
saturated alcohol component (i) and sLmultaneously or in
stages with the amine component (iii) and with or without
a hydroxyl component (iv~ to give an unsaturated
urethane-urea compound, preferably by using the groups
which are reactive toward isocyanate in excess, in
par~icular in a ratio of from 1.5Ol to 4:1.
This reaction can be carried out without a
solvent or alternatively in an inert solvent, eg. ace-
tone, tetrahydrofuran, dioxane, dichloromethane, toluene,
methyl ethyl ketone or ethyl acetate. Other suitable
solvents are the ethylanically monounsaturated or polyun-
saturated compounds, if they are liquid.
The temperature for the reaction of the isocyan-
ate groups is in general ~ithin the range from 0 to
100C, preferably from 20 to 70C.
To ~paed up the reaction it i~ pos~ible to u~e
catalysts as described for example in Houben-Weyl,
Methoden der organischen Chemie, volume XIV/2, p. 60f,
Georg Thieme-Verlag, Stuttgart (1963) and Ullmann,
Encyclopadie der technischen Chemie, volume 19, p. 306
( 1981) . Preference iB given to tln-containing compounds
~uch as dibutyltin dilaurate, tin~II) octoate and di-
butyltin dimethoxid~.
In general, the catalyst is u~ed in an amount of
from 0.001 to 2.5~ by weight, pxeferably from 0.005 to
1.5~ by weight, ba3ed on the total amount o~ the reac-
tants.
Stabilization i8 obtained by adding in general
from 0.001 to 2~ by weight, preferably from 0.005 to
1.0~, of polymerization inhibitor~. The~e are the u~ual
compound~ u~ed for inhibiting thermal polymerization, for
example compounds of tha hydro~uinone, the hydroquinone
monoalkyl ether, the 2,6-di-t-butylphenol, tha N-nitro-
somine, the phenothiazine or th~ pho~phoraus e~ter type.
E~pecially if the reaction wa3 carri~d out
without a solvent, the product, which i~ solid or highly
2~36~
- 9 - O.Z. 0050J41049
viscous at room temperature, may be diluted before
cooling. In addition to the abovementioned solvents it is
also possible after the reaction to use alcoholic
diluents such as methanol, ethanol, isopropanol, etc.
- There now follow detailed observations concerning
the formative components for preparing the reaction
products (a) and their use in the radiation-sensitive
mixtures according to the present invention.
The reaction of components i) to iv) is prefer-
ably carried ollt using as ethylenically monounsaturated
or polyunsaturated mono- or polyalcohol (i) hydroxyl-
containing ~,~-un~aturated carbonyl compounds, allyl
alcohols, hydroxyl-functionalized allyl ethers and esters
and hydroxyalkyl vinyl ethers; particular preference is
given to hydroxyalkyl acrylates and methacrylate~ having
from 2 to 4 caxbon atom in the alkyl group, which alkyl
groups may be linear or branched and carry further
substituentq, eg. hydroxyethyl acrylate, hydroxyethyl
methacrylate, hydroxypropyl acrylate, hydroxypropyl
methacrylate, butanediol monoacrylate and butanediol
monomethacrylate.
A ~uitable isocyanate component ii) i~ any com-
pound which contains a~ least ~.wo isocyanate group3
capable o~ reac~ion with alcohols or primary or secondary
amines. Particular prefersnce is given to diisocyanato-
diphenylma~hane, diisocyanatotoluene (= toluylene diiso-
cyanate), hexamethylene diisocyanate and i~ophorone
diisocyanate, and al~o to oligomer~ thereof of the
isocyanurate ~nd biuret type.
Suitable amino compounds iii) are all primary and
secondary amines which are reactive toward isocyanate
groups. Examples are n-butylamine, n-pentylamine, n-
haxylamine, dodecylamlne, benzylamine, e~hylhexylamine,
dibutylamine, ethylisopropylamine, l-methoxy-2-aminopro-
pane, dibenzylamine, 1,5-dimethylhexylamine, dipentyl-
amine, dihe~ylamine, cyclopropylamine, cyclopQn~ylamine
and methylben~ylamine.
- 10 - O.Z. 0050/41049
Of particular suita~ility are amines of the
general formula
R'HN-R-XH
and/or
~ ~ Rl\
HN NR3
\ R2~
where, in the general formula
R'HN-R-XH
R is the divalent xadical of a substituted or
un~ubstituted alkane, for example of from 2 to lO
carbon atom~, such as -(CH2~p- where p is from 2
to 10, -CH2-C(CH3)2-CH2- or -CH(CH3)-CH2-~ of an
arene, for example phenylene, of a substituted
arene, for example -( CH2)r-C6H3(OH)- where r is
from 1 to b, preferably 2, of an ethex, for
example -(CH2-C~RIV-O)~-CH2-CHR~- where q is from
1 to S, and RIV i~ H or alkyl of ~rom 1 to 4
carbon atom~, of an amine, for example of from 2
to 20 carbon atom~, eg. -(C'H2) 3-N(CH3)-(CH2)3-~ Of
a polyamine, for example -(CH2-CHz-NH)o~ where o
is from 2 to 5, o~ an es~eI, for example of from
4 to 20 carbon atom~, eg. -(CH2)2-COO-(CH2),- where
9 i9 rom ~ to 6, -CH2-COO-CH2-CH(CH3)-, or of an
amidet for e~ampla of from 4 to 20 ~arbon atam~,
a g . - ( C H 2 ~ 2 ~ C O N H - C H 2 - O r
-(cHz)~-coNH-~cH2)5-NH~c-(cH2)2-;
R' i~ hydrogen, alkyl, or example of from 1 to 30,
preferably from 1 to 10, carbon atoms, eg.
methyl, ethyl, propyl, butyl and isomers ~hereof,
cyclohexyl, aryl, for example of from 6 to 18
carbon atom~, preferably phanylr naphthyl,
aralkyl, ~or exampla of from 7 to 20 carbon
atom~, eg. benzyl, l~phenylethyl, 1-methyl-3-
phenylpropyl, hydroxyalkyl, for example o~ from
2 ~o 10 carbon atoms, e~ hydroxyethyl, hydroxy
propyl, hydroxybutyl, aminoalkyl, for example of
~a2~$~s
~ O.Z. 0050/41049
from 2 to 10 carbon atoms, eg. aminoethyl,
aminopropyl, dimethylaminobutyl, dLmethyl
aminoneopentyl, mercaptoalkyl, for ex~mple of
from 2 to 10 carbon atoms, eg. mercaptoethyl, or
derivatives of ~hese groups - derivatives being
in the present case alkyl-l aryl-, halogen-,
carboxyl-, nitro-, nitrile-, sulfoxyl-, amino~,
alkoxy- or aryloxy-substituted groups of the
aforementioned kind - or the monovalent radical
H~O-(CH2)n-CHR"-~ where n is from 1 to 3, m is
from 1 to 10 and R" is H or Cl-C4-alkyl, or
isomers thereof as obtainable by simple addition
or polyaddition of cyclic ethsrs, eg. ethylene
oxide, propylene oxide or tetrahydrofuran, for
example hydroxyethylo~yethyl;
X is O, S or NR"', where R"' i8 hydrogen, alkyl,
for example of from 1 to 10 carbon atom~, eg.
methyl or ethyl, aryl, far example phenyl or
naphthyl, aralkyl, or exa~nple benzyl or phenyl-
ethyl, hydroxyalkyl, aminoalkyl or mercaptoalkyl,
with alkyl group3 whieh may each contain from 1
to 10 carbon atom~, or derivative~ o~ the~a
group~ of tha type men~ioned under R'.
Examples of compoundq of the general formula
R'HN-R-XH are ethylenedi2~ine, butanediamine,
neopentanediamine, polyoxypropylenediamines,
polyoxyethylenediamines, N-athylethylenediamine,
diethylenetriamine, moneisopropanolamine.
Particular preference is given to ethanolamine,
diethanolamine, diiYopropanolamine, neopentanol~
amine, ethylisopropanolamine, butylethanolamin.
and 2-mer~aptaethylamine.
Tn the general formula
Rl
HN NR3
\RZ
R1 and R2 are identical or di~ferent and each is
2~23~
- 12 - O.Z. 0050/4104g
in particular the divalent radical of a sub-
stituted or unsubstituted alkane, for example of
from 2 to 4 carbon atoms, eg. -(CH2~ t- where t is
from 1 to 4~ of an arene, for example o-
~ phenylene, or an ether, for ex mple of from 2 to
4 carbon atoms, eg. -CH2-O-CH2-;
R3 is a hydrogen, alkyl, aryl, aralkyl, hydroxy-
alkyl r aminoalkyl, mercaptoalkyl or a derivative
thereof of the type mentioned under R~. Preferred
compounds of the general ~ormu~a
~Rl
HN NR3
\ R~
are piperazine and 1-(2-hydroxyethyl)piperazine.
Similarly, it i~ al~o pos~ible to use mixtures of
the amino compound~ mentioned under iii).
Suitable organie compounds for optional inelusion
ag iY ) as having at lea~t ono hydroxyl group and being
di~farent from component i) are saturated mono- or
polyalcohols. Preference i~ given 1:o aliphatic alcohols,
particularly aliphatic monoalcohol~, eg. methanol,
ethanol or isopropanol.
(b~ Suitable organie eompound~ ~or inelu~ion as having
one or more carboxyl group~ are low moleeular weight
carboxylic acid~, for example monoearboxylie or dicar-
boxylie aeid3 eontaining from 1 to 20 ear~on atoms, eg.
adipie aeid, phthalic acid, terephthalie aeid, m~lonie
aeid, suceinie aeid or maleie aeid. A particularly
~uitable eomponen~ (b) is a earboxyl-eantaining eompound
whieh~ owing to it~ eomposition and its moleeular weight,
ha3 good ~ilm fo~ming properties. Pre~erenee is given to
polymer~ having an average moleeular weight ~ of above
10,000, praferably o~ from lS,000 to 300,000, and an aeid
number whieh i~ within the range from 50 to 300 mg of
KO~g. Pa.rtieular prefQrenee i3 givan to eopolymer~
formed from an aeid monomer, eg. ae~ylie aeid, methacry-
lie aeidt erotonie aeid or itaeonie aeid, and on~ or more
~2~
- 13 - O.Z. 0050/41049
hydrophobic comonomers, eg. styrene, ethyl acrylate,
butyl acrylate, 2-ethylhexyl acrylate or methyl meth-
acrylate. of particular suitability are also
styrene/maleic anhydride copolymers which have been
partially esterified with lower alcohols. The composition
of these copolymers is chosen in such a way that they are
compatible with component (a).
The mixing ratio of component (b) to component
(a) is chosen in such a way that the radiation-sensitive
mixtures according to the present invention are insoluble
in the developer used but become soluble therein on
irradiation. The concentrat~on range in which this is
achiaved naturally depends strongly on the composition of
component (b). In general, a favorable concentration
lS range for (b) is from 5 to 40% by weight, particularly
preferably from 10 to 30% by weight, based on ~he total
weight of the radiation-~ensitive mixture.
(c) The photoinitiators which may be included in the
radiation-sensitive mixture according to the present
invention are the photoinitiator~ and photoinitiator
~ystems which are customary and known per se for light-
~en~itive photopolymerizable recording material~. Speci-
fic examples are: benzoin, benzoin ethers, in particular
benzoin alkyl ethers, substituted ben20ins, alkyl ethers
of substituted benzoins, eg. ~-methylbenzoin alkyl
ethers, or ~-hydroxymethylbenzoin alkyl ethers; banzil~,
ben~il ketals, in particular benzil dimethyl ketal,
benzil methyl ethyl ketal or benzil mothyl benzyl ketal;
the acylphosphine oxide compounds known for use a~
ef~ective photoinitiators, eg. 2,4,6-trimethylbenæoyl-
diarylphosphine oxide; benzophenone, dexivatives of
benzophenone,4,4'-dimethylaminobenzophenonQ,deriva~ives
of Michler's kotone; anthraquinone and ~ubstituted
anthraquinones; aryl~ubstitu~ed imidazoles or
derivatives thereof, eg. 2,4,5-tria~ylimidazole dimers;
thioxanthone derivative~, the active photoini~iator
acridina or phenacine d~rivative~ and N-alkaxypyridinium
2~2~3~
- 14 - O.Z. 0050/41049
salts and derivatives thereof. Suitable photoinitiators
also include diazonium salts, eg. p-phenylamino-
~enzenPdiazonium hexafluorophosphate, iodonium salts, eg.
diphenyliodonium tetrafluoroborate, or sulfonium salts,
S eg. triphenylsulfonium hex~fluoroarsenate. Examples of
initiator systems are combinations of the aforementioned
initiators with sensitizing assi~tant~ or activators, in
particular tertiary amines. Typical examples of such
initiator systems are combinations of benzophenone or
benzophenone derivatives with tertiary amine~, such as
triethanolamine or Michlex~s ketone; or mixtures of
2,4,5-triarylimidazole dLm~rs and Michler'q keton~ or the
leuco bases of triphenylmethane dye~. The choice of
suitable photoinitiators or photoinitiator systems is
known to the skilled worker. Particularly pref~rred
photoinitiators are Michler's ketone, benzophenone,
hexaarylbisLmidazole derivatives and N-alkoxypyridinium
saltq. It is also very advantageous to use mixture~ of
said photoinitiators. The photoinitiators or photoiniti-
ator systems are in general present in the light-
sensitive recording layer in amounts of from 0.1 to 10%
by weight, based on the radiation-3ensitive mixturQ.
(d) Suitable additives and/or auxillaries (d) ~or
pos~ible inclu~ion in the radiation-~ensitive mixture
according to the present invention include for example
dyes and/or pigments, photochromic compounds and systems,
san~itometric regulator~, plaqticizers, flow control
agant~, delusterants, lubricants, basic components and
the like. Examples of dyes and/or pigments, which may
serve not only as contra~t agent~ but also to rein~orca
the layer, include inter alia Brilliant Green (C.I. 42
040), Victoria Pure Blue FGA, Victoria Pure Blue 80 (C.I.
4~ 595), Victoria Blue B ~C.I. 44 045), Rhodamine 6 G
(C.I. 45 160), triphenylmethane dyes, naphthalimide dyes
and 3'-phenyl-7-dimethylamino-2,2'-spirodi(2H-l-
benzopyran). Photochromic or color change systems which
on irradiation wi~h actinic ligh~ undergo a reversible or
2~23~
- 15 - O.Z. 0050/41049
irreversible color change without thereby interferiny
with the photopolymerization process are for example
leuco dyes together with suitable activators. Examples of
leuco dyes are the leuco bases of triphenylmethane dyes,
such a~ crystal violet leuco base and malachite green
leuco base, leuco Basic Blue, leuco pararosaniline, leuco
Patent Blue A or V; it is also possible to use Rhodamine
B base. Suitable activators for these photochromic
compounds include inter alia organic halogen compounds
which eliminate the halogen radicals on irradiation with
actinic light or hexaarylbisimidazoles. Suitable color
change systems are al~o described in DE-A-38 24 551.
Particularly suitable color change systems are tho~e
where the color inten~ity decreases on irradiation, for
example Sudan dyes, polymethine dyes or azo dyes combined
with suitable photoinitiator~. Suitable sen~itometric
regulator~ include compounds such a~ 9-nitroanthracenQ,
10,10'-bisanthrone~ phenazinium, phenoxazinium,
acridinium or phenothiazinium dye~, in particular com-
bined with mild reducing agents, lr3-dinitrobenzenes and
the like. 5uitable plasticizers are the known and cu~-
tomary low or high molecular we.Lght esters, ~uch as
phthalates or adipates, toluene3ulfonamide or tricresyl
phosphate. Sui~able ba~ic components are additions of
amine~, in particular tertiary amines, eg. triethyl~mine
or triethanolamine, or alkali metal or alkaline earth
metal hydroxides and carbonate~. The additive~ and/or
as~istants are pre3ent in the radiation-sensitive mixture
in the ef~ective amounts known and customary for th0se
~ubstance However, their amount should in general not
Qxceed 30% by weight, prefarably ~0% by weight, based on
the radiation-qen~itive mixture.
The radiation-sen~itive mixture3 according to the
pre~Qnt in~ention may contain as urther additives (d)
one or more ethylenically monounsaturated or polyun-
~aturated compounds. Ethylenically unsaturated compounds
particularly suitable ~or thi~ purpose are acrylates and
~23~
- 16 - O.Z. 0050~41049
methacrylates, eg. trlmethylolpropane triacrylate,
tripropylene glycol diacrylate, butyl acrylate or butyl
methacrylate. The ethylenically unsaturated compounds may
preferably be present in the radiation-sensitive mi~ture
in a concentration of 1-20% by weight, particularly
preferably in a concentration of 3-10% by weight, based
on the total weight of the radiation-sensitive mixture.
An addition of ethylenically unsaturated compounds will
be made in particul~r when after a first Lmagewise
exposure step and the removal o~ the irradiated material
in a developer a cros~linking reaction is to be brought
about in a second, longer exposure step in order in thi~
way to improve the mechanical stability, for example of
printing plates.
A film or coating can be prepared by dissolving
the above-de~cribed radiation-sensitive mixture in a
solvent and then applying the resulting mixture to a
permanent or temporary ~upport by casting, with or
without a doctor blade, spin coating, roller coating or
some other technique.
Suitable sol~ent~ are for example aromatic
hydrocarbons, low molecular weight ketone~, alcohol~,
ethers, esters and chlorocarbon~.
A suitable ~upport for the radiation-sensitive
coatings according to the present invantion i9 virtually
any material which is customary in printing and in the
fabrication of circuit boards for the electronic~ in-
dustry. However, an important condition i9 that the
support be inert, ie. that it ~hould not react with the
radiation-sensitive mixture used for preparinq the
coating.
Suitable ~upport material3 are for example Yteel,
aluminum alloys, mechanically, chemically or electro-
chemically roughened aluminum, silicon, polyesters and
other plastics. The layer thLckne~s here may va~y within
widP lLmits. If ~he radiation-sensitive mixturQ i~ u~ed
for axample a~ a lettQrprass or intaglio printing plate,
~23~
- 17 - O.Z. OOS0/41049
it will typically be within the range from 50 to 500 ~m,
if used as a photoresist for the fabrication of printed
circuits within the range from 20 to 100 ~m and if used
as a photoresist for structuring semiconductor materials
within the range from 0.3 to 5 ~m. If the radiation-
sensitive mixture according to the present invention is
used as an o~fset printing plate, the coating will be
prepared in such a way as to produce dry layer weights of
from 0.5 to 5 g/sqm.
The radiation-sensitive mixtures according to the
present invention are advantageous for producing printing
plates or resist patterns in a conventional manner. To
this end the light-sensitive recording layer - in the
case of photoxesist films and laminating materials after
lamination to the substrate to be protected - i.s sub-
~ected to Lmagewise exposure with actinic light, suitable
sources of which are the customary ones, such as W
fluorescent tubes, marcury hight medium or low pressure
lamps, superactinic fluorescent tubes, pulsed xenon lamps
or even W lasers, argon lasers and the like. The wave-
length emitted by the light source~; should in general be
within the range ~rom ~30 to 450 nm, preferably within
the range from 300 to 420 nm, and be adapted in par-
ticular to the characteristic absorption o~ the photo-
initiator present in the photopolymerizable recordinglayer.
Following imagewise axposure, the printing plate
or re~ist pattern i~ developad by washing out the irra-
diated areas of the recording layer with water or prefer-
ably an aqueous alkali. The procQ~s of development cantake the form of wa~hing, spraying, rubbing, brushing
etc. The recording element~ according to the present
invention here show a wida expo~ure latitude and a v2ry
low overwash sensitivity. Suitable developer~ are aqueous
alkalis which to ~e~ the be~t p~, in general pH 8-14,
preferably a pH within the range from 9 to 13, contain
alkalisle ~ub~tances, ~or example borax, disodium
~23~
- 18 - O.Z. 0050/41049
hydrogenphosphate, sodium carbonate, alkali metal hydrox-
ides or organic bases, such as di- or triethanolamine,
dissolved in water. The aqueous alkali developers may
also contain buffer salts, for example water-soluble
alkali~metal phospha~es, silicates, borates, acetates or
benzoates. Further suitable constituents of developer~
are wetting agents, preferably anionic wetting ayents,
and possibly water-soluble polymers, for example sodium
carboxymethylcellulose~ polyvinyl alcohol, polysodium
ac~ylate and the like. Although the recording elements
accordinq to the present invantion are in general washed
out with water or aqueous alkali, it is of course pos-
sible in principle, although not strictly necessary, that
the developer should also contain a small ~mount of
water-~oluble organic solvent, for example an aliphatic
alcohol, acetone or tetrahydrofuran.
The radiation-sensitive mixture~ according to the
pre~ent invention can be ~tructured for example by high-
energy radiatio~ such as electron beam~ or X-ray~, when
they show their very high ~ensiti~ity to rsdiation. If
used in this way it is generally possible to dispense
with the addition of a separate initiator system. If, by
contrast, the mixtures according to tho present invention
are to be ~tructursd by vi~ible or W light, a~ i
customary for production of printing plate~ and photo-
resists~ it i3 advisable to add suitable photoinitiator~
whose spectxal sen~itivity matches the emitted spectrum
o the light sourc2 used. These mi8tures likewise show
very high light sensitivity for positive-working ~ystems,
which corrasponds to the light sen3itivity of commercial
negative system~ of s~milar thickne4s. Thi~ high light
sen~itivity is obtained without any need for additional
operations, for example the thenmal aftertreatment which
is neces~ary with many other positive systems. Similarly,
3S the developer3 u~ed correspond to those u~ed for
negative-working layers, so that the recording layers
according to the pre~en~ invention are completely
6`~
- 19 - O.Z. 0050/41049
compatible with conven~ional systems. The radiation-
sensitive recording layers according to the present
invention are highly suitable for multiple expo~ures.
This makes it pos~ible in many applications to save
process steps. Multiple exposures are not possible with
all photopolymerizable systems, including many positive
systems, for fundamental reasons. The radiation-sensitive
mixtures according to the present invention also have the
interesting property of acting as positive systems for
short exposure time~ but as crosslinkable systems for
long expo~ure tLmes. This effect can, as described, be
reinforced by the addition of ethylenically unsaturated
pol~merizable compounds. This property can be utilized
after a first, Lmagewi~e exposure step with a short
exposure time and after removal of the irradiated areas
in a developer for initiating a cro~linking reaction in
a second, not nece~arily imagewise exposure ~tep using
a distinctly longer expo4ure time. In this way it i~
possible ~o improve the mechanical properties, for
example of printing plates.
The invention is illus~rat:ed in more detail by
the Examples which follow.
In ~he method of preparation and in the Example~,
the parts and parcentages are by weight, unles~ otherwisQ
stated.
Prepar~tion of ~he reac~ion products to be used according
to the pre~ant invention.
Me~hod o~ preparation
232.2 g of hydroxyethyl acrylate (2 mol) are
added dropwise at 21 22C to a mixturo of 444 g o~
isophorone dii~ocyanate (2 mol), 218 g of methyl ethyl
ketone, 0.1 g of dibutyltin dilaurate and 1.1 g of
di-tert-butyl-4-mothylphenol in the cour3e of 20 minutes.
Aftar 2 hours' r~ac~ion at 50-53C, the NCO content is
8.30~. A solution of 240 g o~ diisopropanolamine
(1.8 mol) in 103 g of methyl ethyl ketone i~ then added
dropwise with ice coolin~ at 16C in the course o 15
~`231~
- 20 - O.Z. OOS0/41~49
minutes. The reaction is completed by further stirring at
50C in about 2 hours. The 72.1% strength product has a
viscosity o~ 335 mPa.s (measured at 23C in a plate-cone
viscometer).
~ EXAMPLE 1
8.5 g of the reaction product prepared by the
above method of preparation, 1.5 g of a copolymer of
styrene (25%), methyl methacrylate (35%), butyl acrylate
(10%) and methacrylic acid (30%) having a K value
(according to H. Fikentscher) of 41, 700 mg of N-methoxy-
picolinium tosylate and 15 mg of Michler's ketone were
dissolved in 8 g of methyl ethyl ketone and cast onto a
23 ~m thick sheet of polyethylene terephthalate in such
a way that, after drying, the photocensitive lay~r has a
thickness of 40 ~m. The layer was covered for ~torage
with a 30 ~m thick ~heet of PE. To test the layer, the
sheet of PE was peeled off, the composite of polyethylene
terephthalate film and photosensitive layer was laminated
with the photosensitive layer next to the copper onto a
copper-clad circuit board substrate and irradiated in a
Riston~ PC printer at 60 mJ~cm2. AEter the polyethylene
terephthalate film had been peeled off, the layer was
developed in a spray washer with 1% strength sodium
carbonate solution at 30C for 150 se~onds, ~he irradi-
ated areas of the light-sensitive layer proving com-
pletely removable. The nonirradiated area3 remained
unchanged.
EX~MP~E 2
As ln Example 1, 8 g of the compound prepared in
accordance with the above method of preparation and 2
of a copolymer of methyl methacrylate (57%), ethyl
acrylats (20%) and methacrylic acid t~3%) having a K
value ~according to H. Fikentsch~r) o~ 44 in 8 ~ of
methyl e~hyl ketone were admixed with 700 mg of N-meth-
oxypicolinium tosylate and 15 mg of ~lichlsr's ketone. The
solution obtained was processed as in Example 1. Follow-
ing irradiation in a ~ ton~ PC printer at 60 mJ~cm2, the
2~2~6~i~
- 21 - O.Z. 0050/41049
irradiated areas were developable with 1% strength sodium
carbonate solution in the course of 120 seconds.
EXAMPLE 3
As in Example 1, 8.5 g of the reaction product
obtain~d as described in the abo~e method of preparation
and 1.5 g of the copolymer described in Example 1 were
dissolved in 8 g of methyl ethyl ketone and admixed with
200 mg of 2,2'-bis(o-chlorophenyl)-4,4',5,5'-tetra(p-
methoxyphenyl)bisimidazolyl, which had been predissolved
in 1 ml of methylene chloride. The solution obtained was
processed as in Example 1. Following irradiation at
150 mJ/cm2 the development time required for removing the
irradiated areas in 1% strength sodium carbonate solution
was 150 seconds.
