Note: Descriptions are shown in the official language in which they were submitted.
PROCESS FOR THE PRODUCTION OF PRINTING
FORMS OR PHOTORESISTS BY IMAGEWISE
IRRADIATION OF A PHOTOPOLYMERIZABLE
RECORDING MATERIAL
Backaround of the Invention
The present invention relates to a process
for the production of printing forms or photoresists
by imagewise irradiation of a photopolymerizable
recording material containing a polymer binder, a
compound polymerizable by free radicals, in
particular an acrylic or alkacrylic ester, and a
photoinitiator or photoinitiator combination.
DE 1,214,085 (US 3,144,331) discloses a
technique for restoring the sensitivity of
photopolymerizable recording materials comprising a
printing plate support and a photosensitive layer,
the sensitivity of which has decreased due to
, : absorption of molecular oxygen. The photosensitive
layer is exposed to 70 to 98% of the amount of
actinic radiation necessary for initiating
photopolymerization. For example, exposure takes
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place through the transparent printing plate
support, the wavelengths of the actinic radiation
used being such that only 10 to 70% of the radiation
is absorbed by the photopolymerizable layer. In
this process, one diffuse and one imagewise exposure
are in principle carried out. The diffuse or
preexposure is then followed by imagewise exposure
up to the full amount of radiation.
US 4,716,097 discloses a process in which a
photopolymerizable layer containing a dye is first
exposed to light having a wavelength above 400 nm
and an intensity of at least 1500 lumen/m2 for
approximately 60 minutes diffuse and then imagewise.
DE 2,412,571 describes a process for the
curing of a light-curable layer of a printing plate
in which blanket exposure is carried out for a short
time and is followed by imagewise exposure until the
layer in the exposed regions has been virtually
completely cured. ~he blanket exposure lasts not
more than 90% of the time necessary for curing the
polymer layer, if the same intensity of radiation
is used for both the preexposure and the
imagewise exposure.
EP 53,708 describes a process for the
production of relief copies in which the
photopolymerizable layer of a recording material is
subjected to imagewise exposure, is heated to
elevated temperatures for a short time before or
after exposure, and is then developed.
- 30 EP 284,938 describes photopolymerizable
mixtures containing (meth)acrylic esters with
urethane groups, tertiary amino groups and possibly
-2-
''
'
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urea groups in the molecule, polymer binders and a
photoreducible dye, if desired in combination with
a radiation-sensitive trihalomethyl compound, as the
photoinitiator. EP 321,827 describes similar
mixtures containing (meth)acrylic esters but no
urethane groups.
EP 364,735 describes photopolymerizable
mixtures containing
- a polymer binder,
- a compound polymerizable by free
radicals and containing at least one
polymerizable group,
- a photoreducible dye,
- a trihalomethyl compound which can be
cleaved by radiation, and
- a metallocene compound, in particular a
titanocene or zirconocene.
The metallocenes used are those carrying two
substituted or unsubstituted cyclopentadienyl
radicals and two substituted phenyl radicals as
ligands. German Patent Application P 4,007,428.5,
describes further photopolymexizable mixtures of the
above composition containing a dicyclopentadienyl-
bis-2,4,6-trifluorophenyltitanium or -zirconium as
metallocene. These mixtures have extremely high
photosensitivity.
German Patent Application P 4,011,023.0
describes an after-treatment apparatus for
imagewise-exposed printing plates comprising an
exposure station for full-area exposure of the
printing plate and a heating station. The full-area
exposure is carried out using light in the spectral
2 ~
range from 500 to 700 nm. No detailed information
about the composition of the photopolymerizable
printing plates which are processed is given.
Summary of the Invention
It is therefore an object of the invention to
provide a process for the production of printing
forms, in particular planographic printing forms, or
photoresists by imagewise exposure of a
photopolymerizable recording material which already
has very high photosensitivity and to propose
suitable processins steps, by means of which the
energy requirement during exposure of the image can
be reduced substantially, thus achieving a
correspondingly higher photosensitivity in practice.
These and other objects according to the
present invention are achieved by a process for the
production of printing forms or photoresists,
comprising the steps of imagewise irradiating a
photopolymerizable recording material comprising a
photopolymerizable layer containing a polymer
binder, an ethylenically unsaturated compound that
is polymerizable by free radicals and that contains
at least one terminal ethylenic double bond, and a
metallocene compound that forms free radicals upon
2S irradiation; heating the recording material after
the imagewise irradiation for a short time; and then
developing the recording material; wherein the
material is also blanket-exposed to visible light
having a wavelength of at least 400 nm for a short
time.
. .
,' , i ' ~ '
Other objects, features and advantages of the
present invention will become apparent from the
following detailed description. It should be
understood, however, that the detailed description
and the specific examples, while indicating
preferred embodiments of the invention, are given by
way of illustration only, since various changes and
modifications within the spirit and scope of the
invention will become apparent to those skilled in
the art from this detailed description.
Detailed Descri~tion of the Preferred Embodiments
According to the invention, a process for the
production of printing forms or photoresists by
imagewise irradiation of a photopolymerizable
recording material is proposed. The photo-
polymerizable layer contains a polymer binder, an
ethylenically unsaturated compound polymerizable by
free radicals and containing at least one terminal
ethylenic double bond, and a polymerization
initiator or initiator combination that forms free
radicals upon irradiation. The material is heated
after the imagewise irradiation for a short time and
then developed.
The process according to the invention uses
a metallocene compound as the radical-forming
polymerization initiator and entails exposing the
material before, simultaneously with, or after the
imagewise irradiation for a short time to visible
light having a wavelength of at least 400 nm without
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an original. This latter exposure is termed
"blanket-exposure" in this description
The heating and exposure without an original
can advantageously be carried out in an apparatus
such as that described in German Application
P 4,011,023Ø The sequence of the exposure steps is
as desired; preferably the material is first
subjected to imagewise exposure or irradiation, then
exposed without an original and finally heated.
lo The imagewise irradiation can preferably be
carried out by projection using standard copying
light or laser radiation. Examples of projection
light sources which can be used are mercury vapor
lamps, xenon lamps, metal ha~ide lamps, flashlight
lamps, c~rbon arc lamps and the like, it being
possible for the intensity and/or duration of
exposure to be kept low. Suitable laser light
sources are in particular lasers emitting in the
visible spectral range, for example, at 488 and 514
~0 nm. For this purpose, for example, argon ion lasers
having a relatively low output, for example, 10 to
25 mW, can advantageously be used. The dosage of
imagewise irradiation is preferably in the range
from about 5 to 50% of the dosage necessary for
complete curing of the layer without further
treatment. The remainder of the amount of energy
re~uired is supplied according to the invention by
the combination of diffuse exposure, i.e., without
an original, followed by heating.
; 30 For exposure without an original, a light
- source of relatively low output, for example, a
fluorescent lamp, is used, which emits a very high
proportion of light having a wavelength of more than
500 nm. The emission range is generally between
about 400 and 700, preferably between about 450 and
650, nm. The layer surface should generally be
exposed to an intensity of about lo to 80 lux. The
doses have to be selected so that complete curing is
effected in combination with the image exposure and
heat treatment on the image areas to be cured. It
must be ensured that the non-image areas do not
become cured by the diffuse exposure in combination
with the heating to such an extent that they are no
longer completely soluble in the developer. The
desired image differentiation can be achieved with
` an image exposure or irradiation in the above-
mentioned range of about 5 to 50% of the amount of
radiation required.
Heating is carried out as the last treatment
step before development in a manner known per se.
To this end, the completely exposed material is
heated to ~ temperature in the range from about 60
t~ 140C, preferably from about 80 to 120C, in
particular from about 90 to 110C, for approximately
seconds to 2 minutes. In most cases, the
treatment time required is in the range between
about 30 and 80 seconds. During this treatment, the
temperature must be measured when printing plates on
metal supports, in particular aluminum, are heated.
This is advantageously done on the back of the
plate, for example, using commercially-available
temperature test strips. Heating can take place by
air circulation, by contact heating or by infrared
radiation.
~ -7-
; ' ' ' "
,
:
Surprisingly, it has been found that the
process according to the invention results in tha
desired increase in sensitivity only in very
specific photopolymerizable materials. Thus, it has
been shown that adequate reexposure and reheating
achieves virtually no increase in sensitivity, if a
known photopolymerizable material is used which
contains 9-phenylacridine as the photoinitiator and
trimethylolethane triacrylate as the monomer. If,
however, a metallocene, in particular a titanocene
or zirconocene, is used as the photoinitiator, an
increase in photosensitivity by several degrees is
achieved by the same treatment.
The metallocenes used as initiators are known
as such and also as photoinitiators, for example,
from US 3,717,558, 4,590,287 and 4,707,432.
Preferably, metallocenes of elements from subgroup
IV of the periodic table of the elements, in
particular compounds of titanium and zirconium, are
uced. Compounds o~ this type are de6cribed in
EP 364,735. Of the large number of known
metallocenes, in particular titanocenes, compounds
; of the general formula
l ~ R3
Me "'
R ~ ~ R4
are preferred. In this formula,
,
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`:
2 ~
Me is a tetravalent metal atom, in
particular Ti or Zr,
Rt and R2 are identical or different
cyclopentadienyl radicals, which
maybe substituted, and
R3 and R4 are identical or different phenyl
radicals which may also be
substituted.
The cyclopentadienyl groups can be
substituted, in particular by alkyl radicals having
1 to 4 carbon atoms, chlorine atoms, phenyl or
cyclohexyl radicals or linked to one another by
alkylene groups. They are preferably unsubstituted
or substituted by alkyl radicals or chlorine atoms.
lS R3 and R4 are preferably phenyl groups which
contain at least one fluorine atom in the ortho
position relative to the bond. The other carbons
can be substituted by halogen atoms, such as F, Cl
or Br, alkyl or alkoxy groups having 1 to 4 carbon
atoms, a polyoxyalkylene group which may be
etheri~ied or esterified, or a heterocyclic group,
fox example, a pyrrolyl radical. The polyoxy-
alkylene group generally has 1 to 6 oxyalkylene
units and is preferably in the 4 position of the
phenyl radical. It can be etherified or esterified
by an alkyl or acyl radical having 1 to 18 carbon
atoms; it is in particular a polyoxyethylene group.
The relative amount of metallocene compound
is generally between about 0~01 and 10, preferably
between about 0.05 and 8, % by weight, relative to
the photopolymerizable layer.
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The photopolymerizable layer can contain a
photoreducible dye as a further photoinitiator
constituent. Suitable dyes are in particular
xanthene, benzoxanthene, benzothioxanthene,
thiazine, pyronine, porphyrin or acridine dyes.
Suitable xanthene and thiazine dyes are
described, for example, in EP 287,817. Suitable
benzoxanthene and benzothioxanthene dyes are
described in DE 2,025,291 and in ~P 321,828.
An example of a suitable porphyrin dye is
hematoporphyrin and an example of a suitable
acridine dye is acriflavinium chloride
hydrochloride.
Examples of xanthene dyes are Eosin B (C.I.
No. 45400), Eosin J (C.I. No. 45380), Eosin alcohol-
soluble (C.I. 45386), Cyanosine (C.I. No. 45410),
Rose Bengal, Erythrosine (C.I. No. 45430), 2,3,7-
trihydroxy-9-phenylxanthen-6-one and Rhodamin 6 G
(C.I. No. 45160).
Examplee of thiazine dyes are thionine (C.I.
No. 52000), Azure A (C.I. No. 52005) and ~zure C
(C.I. No. 52002).
Examples of pyronine dyes are Pyronine B
(C.I. No. 45010) and Pyronine GY (C.I. No. ~5005).
The amount of photoreducible dye is generally
between about 0.01 and 10, preferably between about
0.05 and 4, % by weight of the layer.
To increase the photosensitivity, the
photopolymerizable layers can additionally contain
compounds having trihalomethyl groups which can be
cleaved photolytically, these compounds being known
per se as free radical-forming photoinitiators for
--10--
9 ~
photopolymerizable mixtures. In particular,
compounds containing chlorine and bromine, in
particular chlorine as a halogen have proved
suitable as coinitiators of this type. The
5trihalomethyl groups can be bound to an aromatic
carbo- or heterocyclic ring directly or via a
through-conjugated, e.g., vinylogous, chain.
Preference is given to compounds having a triazine
ring in the parent structure which in turn
10preferably carries two trihalomethyl groups, in
particular to those described in EP 137,452, DE
2,718,259 and DE 2,243,621. Compounds with a
different parent structure, which absorb in the
shorter W wavelength region, for example, phenyl
15trihalomethyl sulfones or phenyl trihalomethyl
ketones, for example, phenyl tribromomethyl sulfone,
are also suitable. The halogen compounds are
generally used in an amount of about 0.01 to 10,
preferably about 0.05 to 4, % by weight of the layer.
20The photopolymerizable layers can contain, if
desired, acridine, phenazine or quinoxaline
compounds as ~urther initiator constituents. These
comp~unds are known as photoinitiators and described
in DE 2,027,467 and 2,03~,861. The total amount of
25polymerization initiators is generally about 0.05 to
20, preferably about 0.1 to 10, % by weight.
Polymerizable compounds which are suitable
for the purposes of the invention are known and
described, for example, in US 2,760,863 and
303,060,023. Preferred examples are acrylic and
methacrylic esters of di- or polyhydric alcohols,
such as ethylene glycol diacrylate, polyethylene
--11--
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glycol dimethacrylate, acrylates and methacrylates
of trimethylolethane, trimethylolpropane,
pentaerythritol and dipentaerythritol, and of
polyhydric alicyclic alcohols or N-substituted
acryl- and methacrylamides. Reaction products of
mono- or diisocyanates with partial esters of
polyhydric alcohols are also advantageously used.
Monomers of this type are described in DE 2,064,079,
2,361,041 and 2,822,190.
Polymerizable compounds containing at least
one photooxidizable and, if desired, at least one
urethane group in the molecule are particularly
preferred. Suitable photooxidizable groups are in
particular amino groups, urea groups, thio groups,
which can also be constituents of heterocyclic
rings, enol groups and carboxyl groups in
combination with olefinic double bonds. Examples of
groups of this type are triethanolamino,
triphenylamino, thiourea, imidazole, oxazole,
thiazole, acetylacetonyl, N-phenylglycine and
ascorbic acid groups. Polymerizable compounds having
primary, secondary and in particular tertiary amino
groups are preferred.
Examples of compounds containing
photooxidizable groups are acrylic and alkacrylic
esters of the formula I
R7
R(~"_n~Q~ (-C~2-CO-~a-CONH~X~ b-X2(-OOC-C~C~)C~n
R6
-12-
2 ~
in which
Q is Dl
/ \
-N-, -N-r-N-, -N N- or -5-
D2
R is an alkyl, hydroxyalkyl or aryl group,
R5 and R6 are each a hydrogen atom, an
alkyl group or alkoxyalkyl group,
R7 is a hydrogen atom, a methyl or ethyl
group,
Xl is a saturated hydrocarbon group having
2 to 12 carbon atoms,
X2 is a (c+l)-valent saturated
hydrocarbon group in which up to S
methylene groups can be replaced by
oxygen atoms,
Dt and D2 are each a saturated hydrocarbon group
having 1 to 5 carbon atoms,
;~ E is a saturated hydrocarbon group of 2 to
12 carbon atoms, a cycloaliphatic group
of 5 to 7 ring members, which, if
desired, can contain up to two N, O or
S atoms as ring members, an arylene
~ gro~p of 6 to 12 carbon atoms or a
; heterocyclic aromatic group of 5 or 6
ring members,
a is O or a number from 1 to 4,
b is O or 1,
~ c is an integer from 1 to 3,
:~ ~
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: ,: . , , : . ,
2 ~
m is, depending on the valency of Q, 2, 3
or 4, and
n is an integer from 1 to m,
it being possible for all symbols of the same
definition to be identical to or different from one
another. The compounds of this formula, and their
preparation and use are described in detail in
EP 287,818. If in the compound of the general
formula I more than one radical R or more than one
radical of the type indicated in square brackets is
bound to the central group Q, these radicals can be
different from one another.
Compounds in which all substituents of Q are
polymerizable radicals, i.e., in which m is n, are
generally preferred. In general, a is 0 in not more
than one radical, and preferably in no radical.
Preferably a is 1.
If R is an alkyl or hydroxyalkyl group, this
group generally has 2 to 8, preferably 2 to 4,
carbon atoms. The aryl radical R can generally be
substituted on one or two rings, preferably on one
ring, and may be substituted by ~lkyl or alkoxy
groups of up to 5 carbon atoms or halogen atoms.
If R5 and R6 are alkyl or alkoxyalkyl groups,
they can contain 1 to 5 carbon atoms. R7 is
preferably a hydrogen atom or a methyl group, in
particular a methyl group.
X~ is preferably a straight-chain or branched
aliphatic or cycloaliphatic radical of, preferably,
4 to 10 carbon atoms. X~ preferably has 2 to 15
carbon atoms, up to 5 of which can be replaced by
. . .
. . .
oxygen atoms. If pure carbon chains are involved,
those having 2 to 12, preferably 2 to 6, carbon
atoms are generally used. x2 can also be a
cycloaliphatic group of 5 to 10 carbon atoms, in
particular a cyclohexylene group. Dl and D2 can be
identical or different and, together with the two
nitrogen atoms, form a saturated heterocyclic ring
having 5 to 10, preferably 6, ring members.
If E is an alkylene group, it preferably has
2 to 6 carbon atoms, and as an arylene group it is
preferably a phenylene group. Preferred cyclo-
aliphatic groups are cyclohexylene groups, preferred
aromatic heterocycles are those having N or S as
hetero atoms and 5 or 6 ring members. The value of
c is preferably 1.
Further suitable compounds containing
photooxidizable groups are compounds of the formula
II
2(~_"1~ ~2-f)~- ~ ~2 ~ - N~"
R6 ¦ 2 IR7 ( I I )
OOC--CH~CN2
in which Q, R, R5, R6, R7, m and n have the
abovementioned meaning and Q can additionally be a
group
,. . . .
: ~ . . ' , - . . . : ' '
. ', - ', . .' , ': . . '
3~ ~ ~
.
-N-E'-~-
in which E'
is a group of
the formula III
-C~-C~oH-cH2-~o~ >-o-c~2-cH~H-a~2-~c (II~)
in which c has the meaning as in formula I; a' and
S b' are integers f rom 1 to 4.
The compounds of this formula, their
preparation and use are described in detail in EP
316,706.
Further suitable compounds having
photooxidizable groups are acrylic and alkacrylic
esters of the formula IV
27
Q~ x~ c~2o)a~CC~ -xl-NHCoo)~, x2-~ c~ v)
in which
Q' is -N-,
--16--
,:,
'
2 ~
Dl ~--
/ \ or D3 N-,
-N N- \ I~
D2/ z
Xl is CjH2;
or
ClH2~. IO-CON~(-%~ 00)2,-X~-OOC-C-CH2,
D3 is a saturated hydrocarbon group having
4 to 8 carbon atoms which, together
with the nitrogen atom, forms a 5- or 6-
membered ring,
Z is a hydrogen atom or a radical of the
formula
R~
O--CO~ D~ C~b--X --OOc C~2
i and k are lntegers from 1 to 12,
n' is, depending on the valency of Q', 1,
2 or 3, and
R7, X~, X2, Dl, D2, a and b have the meaning given
under formula I, it being possible for all symbols
of the same definition to be identical to or
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.
. . . : .
. .~ - .
: . . . .
; :- . - . . .
. . ,
different from one anot~er and a in at least one
substituent on the group Q being 0.
of the compounds of the formula IV, those are
preferred which contain at least one urethane group
apart from a urea group.
The symbol a in formula IV is preferably 0 or
1; i is preferably a number from 2 to 10.
The polymerizable compounds of the formula IV
are prepared analogously to the compounds of the
formula I. The compounds of the formula IV and
their preparation are described in detail in EP
355,387.
The percentages of polymerizable compounds in
the photopolymerizable layer is generally about 10 to
1580, preferably about 20 to 60, % by weight, relative
to the non-volatile components.
Examples of binders which can be used are
chlorinated polyethylene, chlorinated polypropylene,
polyalkyl (meth)acrylates, in which the alkyl group
is, for example, methyl, ethyl, n-butyl, i-butyl, n-
hexyl or 2-ethylhexyl, copolymers of the alkyl
(meth)acrylates with at least one monomer, such as
acrylonitrile, vinyl chloride, vinylidene chloride,
styrene or butadiene; polyvinyl chloride, vinyl
chloride/acrylonitrile copolymers, polyvinylidene
chloride, vinylidene chloride/acrylonitrile
copolymers, polyvinyl acetate, polyvinyl alcohol,
polyacrylonitrile,acrylonitrile/styrenecopolymers,
acrylonitrile/butadiene/styrene copolymers, poly-
styrene, polymethylstyrene, polyamides, for example,
nylon-6, polyurethanes, methyl cellulose, ethyl
"~
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~ -18-
:
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cellulose, acetyl cellulose, polyvinyl formal and
polyvinyl butyral.
Binders that are insoluble in water, soluble
in organic solvents and soluble or at least
swellable in aqueous-alkaline solutions are
particularly suitable.
Carboxyl group-containing binders, for
example, copolymers comprising (meth)acrylic acid
and/or unsaturated homologues thereof, such as
crotonic acid, copolymers of maleic anhydride or its
monoesters, reaction products of hydroxyl-containing
polymers with dicarboxylic anhydrides and mixtures
thereof, should be mentioned in particular.
Reaction products of polymers carrying groups
with acidic hydrogen, which have been completely or
partially reacted with activated isocyanates, such
as, for example, reaction products of hydroxyl-
containing polymers with aliphatic or aromatic
sulfonyl isocyanates or phosphinyl isocyanates, are
also suitable.
Hydroxyl-containing polymers are also
suitable, such as, for example, hydroxyalkyl
~meth)acrylate copolymers, allyl alcohol copolymers,
vinyl alcohol copolymers, polyurethanes or
polyesters, and epoxy resins, as long as they carry
a sufficient number of free OH groups or are
modified in such a manner that they are soluble in
aqueous-alkaline solutions. Polymers of this kind
carrying aromatically-bound hydroxyl groups can be
used, such as, for example, condensation products of
condensable carbonyl compounds, in particular
formaldehyde, acetaldehyde or acetone, with phenols
--19--
,:
.
';
or hydroxystyrene copolymers. Finally, copolymers of
(meth)acrylamide with alkyl (meth)acrylates can also
be used.
The polymers described above are particularly
suitable if they have a molecular weight between
about 500 and 200,000 or more, preferably between
about 1,000 and 100,000, and either acid numbers
between about 10 and 250, preferably between about
20 and 200, or hydroxyl numbers between about 50 and
750, preferably between about 100 and 500. The
amount of binder in the photosensitive layer is
generally about 20 to 9o, preferably about 40 to 80,
% by weight.
Depending on the intended use and the desired
properties, a wide range of substances can be
present as additives in the photopolymerizable
layers. These additives are inhibitors for
preventing thermal polymerization of the monomers,
hydrogen donors, dyes, colored and uncolored
pigments, color formers, indicators, plasticizers
and chain transfer agents. These components are
advantageously selected to have the lowest possible
absorption in the actinic radiation region important
for the initiation process.
In the context of this description, actinic
radiation is understood to mean any radiation having
an energy that corresponds at least to that of
visible light. In particular, visible light and
long-wave W radiation, but also short-wave W
radiation, laser radiation, electron and X-ray
radiation are suitable. The photosensitivity ranges
from about 300 nm to 700 nm.
-20-
~, . . .
.
Possible applications for the ~p~e~
according to the invention include the
photomechanical production of printing forms for
relief printing, offset printing, intaglio printing,
screen printing, relief copies, for example,
production of texts in braille, individual copies,
tanning images,pigment images, and the like.
Furthermore, the process can be used for the
photomechanical production of etch resists, for
example, for manufacturing name tags, printed
circuits and for chemical milling. The preparation
of planographic printing plates and the photoresist
technique are of particular importance.
Examples of suitable supports are aluminum,
steel, zinc, copper and plastic sheets, for example,
those made of polyethylene terephthalate or
cellulose acetate, and screen printing supports,
such as perlon gauze. In many cases, it is
advantageous to subject the surface of the support
20 to a pretreatment (chemically or mechanically), wit~
the aim of properly adjusting the adhesion of the
layer, to improve the lithographic properties of the
surface of the support or to reduce the reflectance
of the support in the actinic region of the copying
layer (antihalation).
It is generally advantageous to protect the
photopolymerizable materials during the
photopolymerization substantially against the effect
of oxygen in the air. In the case where the mixture
is applied in the form of thin copying layers, it is
recommended that a suitable top film which has low
permeability to oxygen be applied. This film may be
-
self-supporting and removed before development of
the copying layer. For this purpose, for example,
polyester films are suitable. The top film can also
be made of a material which is soluble in the
developer liquid or can at least be removed at the
uncured areas during the development. Examples of
materials which are suitable for this are polyvinyl
alcohol, polyphosphates, sugars, and the like. Top
coats of this type generally have a thickness of
about 0.1 to 10, preferably about 1 to 5, ~m.
For development, the materials are treated
with a suitable developer solution, for example,
with organic solvents, but preferably with a weakly
alkaline-aqueous solution, in which the unexposed
portions of the layer are removed and the exposed
areas remain on the support. The developer
solutions can con~ain a small portion, preferably
less than about 5% by weight, of water-miscible
organic solvents. They can further contain wetting
agents, dyes, salts and other additives. The
development removes the entire top coat together
with the unexposed areas of the photopolymerizable
layer.
Working examples of the invention are given
below. Parts by weight (pbw) relate to parts by
volume (pbv) as the gram relates to cubic
; centimeters. Percentages and amounts are by weight,
unless stated otherwise.
ExamPles 1-7 (comparative examPles)
-22-
2. Q ~
Electrochemically roughened and anodized
aluminum having an oxide layer of 3 gtm2 that had
been pretreated with an aqueous solution of
polyvinylphosphonic acid was used as the support for
printing plates. The support was coated with a
solution of the following composition. All these
operations were carried out under red light:
2.84 pbw of a 22.3% strength solution of a
terpolymer comprising styrene, n-hexyl
methacrylate and methacrylic acid
(10:60:30) and having an acid number of
190 in methyl ethyl ketone,
1.49 pbw of the monomer according to Table 1,
0.04 pbw of Eosin alcohol-soluble (C.I. 45386),
0.03 pbw of 2,4-bis-trichloromethyl-6-(4-
styrylphenyl)-s-triazine~ and
0.01 pbw of dicyclopentadienyl-bis(pentafluoro-
phenyl)titanium, in
22 pbw of propylene glycol monomethyl ether.
, .
The mixture was applied by spin-coating 50
that a dry weight of 2.4 to 2.8 g/m2 was obtained.
The plate was then dried for two minutes at 100C in
a through-circulation drying oven. The plate was
then coated with a 15% strength aqueous solution of
polyvinyl alcohol (12% of residual acetyl groups, K
value 4). After drying, a top coat having a weight
of 2.5 to 4 g/m2 was obtained. The printing plate
obtained was exposed to a 2 kW metal halide lamp at
a distance of 110 cm under a 13-step exposure wedge
30 at density increments of 0.15. To test the
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sensitivity of the printing plates in visible light,
a 3 mn ~chick heat-ab6orption glass filter from Schott with an
edge transmitt~nce of 4ssnm and a si lver fil~ havin~
uniform blàckening (density 1.4 ) and uniform
absorption over the effective spectral range as a
gray filter were mounted on the exposure wedge. The
plates were exposed for 10 seconds and then heated
to lOO~C for one minute. They were then developed
using a developer of the following composition:
120 pbw of sodium metasilicate x 9
H20 ~
2.13 pbw of strontium chloride,
1.2 pbw of nonionic wetting agent
(coconut fatty alcohol/poly-
oxyethylene ether having
about 8 oxyethylene units),
and
0.12 pbw of antifoam, in
4000 pbw of fully deionized water.
The plates were coated with fatty printing
ink. The fully crosslinked wedge steps given in
Table 2 were obtained.
.
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Table 1
Example No. Monomer
1 Reaction product of 1 mol of
triethanolamine with 3 mol of
isocyanatoethyl methacrylate,
2 Reaction product of 1 mol of N,N'-
bis(~-hydroxyethyl)piperidine
with 2 mol of isocyanatoethyl
methacrylate,
3 Reaction product of 1 mol of
triethanolamine with 3 mol of
glycidyl methacrylate,
4 Reaction product of 1 mol of
2,2,4-trimethylhexamethylene
diisocyanate with 2 mol of 2-
hydroxyethyl methacrylate,
Reaction product of 1 mol of
hexamethylene diisocyanate with 1
mol of 2-hydroxyethyl methacrylate
and 0.33 mol of triethanolamine,
6 Trimethylolethane triacrylate,
7 Reaction product of 1 mol of
hexamethylene diisocyanate with
0.5 mol of 2-hydroxyethyl
methacrylate and 0.25 mol of 2-
piperidinoethanol.
~'
Exam~les 8-14
The printing plates described in Examples 1
~ to 7 were produced as described there and subjected
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to imagewise exposure. They were then reexposed
over the entire area with diffuse light from a
fluorescent lamp emitting light of about 400 to 700
nm, the spectral portion below 500 nm of which was
absorbed by a filter, at a light intensity of 15 lux
for 20 seconds, followed by heating as in Examples
1 to 7 and development. The number of the wedge
steps obtained is shown in Table 2.
Table 2
_
Example No. Gray Filter Wedge Steps
I
8 yes 9 - 11
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* no image
:~ -26-
Exa~le lS
A solution of the following composition was
spin-coated onto the supports mentioned in Examples
1 to 7 under the same conditions as there, in such
5 a manner that a coating weight of 2.5 g/m2 was
obtained:
2.84 pbw of the terpolymer solution mentioned in
Example 1,
1.49 pbw of the monomer according to Example 7,
0.04 pbw of Eosin alcohol-soluble (C.I. 45386),
0.03 pbw of 2,4-bis(trichloromethyl)-6-(4-
styrylphenyl)-s-triazine, and
0.01 pbw of dicyclopentadienyl bis(2,4,6-
trifluorophenyl) titanium, in
22 pbw of propylene glycol monomethyl ether.
After applying a top coat comprising
polyvinyl alcohol, the plate was exposed in the same
manner as in EY.amples 1 to 7 for 5 seconds and then
developed. To test the sensitivity of the printing
plates in visible liaht, ~ 3 mm thick heat-absorption glass
filter from Schott with an edge transmittance of 455nm and
a silver film having uniform blackening (density 1.1)
as gray filter were mounted on the exposure ~edge.
Eight to nine fully-crosslinked wedge steps were
obtained. In a further experiment, the plate was
exposed to diffuse reexposure as mentioned in
Examples 8-14. Eleven to twelve fully-crosslinked
wedge steps were obtained.
:
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In both cases, the printing plates were
developed without leaving a residue and gave more
than 150,000 excellent prints.
Exam~le 16
A photopolymerizable printing plate produced
as in Example 7 was irradiated in a commercially-
available film exposure apparatus ~y means of an
argon ion laser (~ = 488 nm~ with 182 ~J/cm2 and
processed without reexposure as in Example 7. More
than 150,000 excellent prints were obtained.
The same plate was reexposed after laser
irradiation with 375 lux seconds as described in
Example 14. It was found that under these
conditions an irradiation energy of only 32 ~J/cm2
was required to completely cure the plat~. Again
more than 150,000 prints were obtained.
In a further experiment, reexposure using 500
1UX seconds was carried out, requiring only 18 ~J/cm2
for the laser imaging.
Exam~le 17
The coating solution from Example 7 was spin-
coated onto a biaxially-oriented 35 ~m thick
polyethylene terephthalate support so that a coating
weight of 15 g/m2 was obtained after drying. The
layer was then dried at 100C for three minutes in a
through-circulation drying oven. The layer was then
laminated onto a cleaned support composed of a
-28-
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board n~ade of an insulating materlal and clad with
a 35 um copper layer, at 115 C and 1 . 5 mlmin .
l~e layer was exposed for 30 seconds to a 2 kW metal
halide lamp ~distance 140 an) under a heat-absorption qlass
filter 455 nm, as described in Example l, using a
step wedge as the original, and reexposed followed
by heating as described in Examples 1 to 7. After
removing the polyethylene terephthalate support, the
layerwas developed for 20 seconds with 0.8~ strength
sodium carbonate solution in a spraying processor.
Eight fully-crosslinked wedge steps were obtained.
The crosslinked layer was resistant to iron(III)
chloride solution which is common in printed circuit
technology. The resistance to etching was good.
ExamPle ~8 (Com~arative Exam~le)
The following coating solution was applied to
the support described in Examples 1 to 7 and dried:
1.4 pbw of a methacrylic acid/methyl methacry-
late mixed polymer having an acid number
of 115,
1.4 pbw of trimethylolethane triacrylate,
O.2 pbw of dihydroxyethoxyhexane, and
0.05 pbw of 9-phenylacridine, in
13 pbw of 2-methoxyethanol
The plate was exposed to a 5,000 W metal
; halide lamp under a step wedge for 35 seconds,
followed by heating as in Example l. Six to seven
fully-crosslinked wedge steps were obtained. In a
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further experiment, the same plate was only exposed
for 15 seconds, subjected to diffuse reexposure
after the image exposure with 300 lux seconds and
then heated. No image was obtained. ~iffuse re-
exposure with 300 lux seconds after an unchangedimage exposure of 35 seconds likewise gave 6 to 7
fully-crosslinked wedge steps.
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