FIELD OF THE INVENTION
[0001] The present invention relates to a heat-sensitive lithographic printing plate precursor.
BACKGROUND OF THE INVENTION
[0002] Lithographic printing typically involves the use of a so-called printing master such
as a printing plate which is mounted on a cylinder of a rotary printing press. The
master carries a lithographic image on its surface and a print is obtained by applying
ink to said image and then transferring the ink from the master onto a receiver material,
which is typically paper. In conventional lithographic printing, ink as well as an
aqueous fountain solution (also called dampening liquid) are supplied to the lithographic
image which consists of oleophilic (or hydrophobic, i.e. ink-accepting, water-repelling)
areas as well as hydrophilic (or oleophobic, i.e. water-accepting, ink-repelling)
areas. In so-called driographic printing, the lithographic image consists of ink-accepting
and ink-abhesive (ink-repelling) areas and during driographic printing, only ink is
supplied to the master.
[0003] Printing masters are generally obtained by the so-called computer-to-film method
wherein various pre-press steps such as typeface selection, scanning, color separation,
screening, trapping, layout and imposition are accomplished digitally and each color
selection is transferred to graphic arts film using an imagesetter. After processing,
the film can be used as a mask for the exposure of an imaging material called plate
precursor and after plate processing, a printing plate is obtained which can be used
as a master.
[0004] A typical photosensitive printing plate precursor for computer-to-film methods comprises
a hydrophilic support and an image-recording layer which includes UV-sensitive compositions.
Upon image-wise exposure of a negative-working plate, typically by means of a film
mask in a UV contact frame, the exposed image areas become insoluble and the unexposed
areas remain soluble in an aqueous alkaline developer. The plate is then processed
with the developer to remove the diazonium salt or diazo resin in the unexposed areas.
So the exposed areas define the image areas (printing areas) of the printing master,
and such printing plate precursors are therefore called 'negative-working'. Also positive-working
materials, wherein the exposed areas define the non-printing areas, are known, e.g.
plates having a novolac/naphtoquinone-diazide coating which dissolves in the developer
only at exposed areas.
[0005] In addition to the above photosensitive materials, also heat-sensitive printing plate
precursors have become very popular. Such thermal materials offer the advantage of
daylight-stability and are especially used in the so-called computer-to-plate method
wherein the plate precursor is directly exposed, i.e. without the use of a film mask.
The material is exposed to heat or to infrared light and the generated heat triggers
a (physico-)chemical process, such as ablation, polymerization, insolubilization by
cross-linking of a polymer or by particle coagulation of a thermoplastic polymer latex,
and solubilization by the destruction of intermolecular interactions.
[0006] Thermal plates which require no processing are also known; such plates are typically
of the so-called ablative type, i.e. the differentiation between hydrophilic and oleophilic
areas is produced by heat-induced ablation of one or more layers of the coating, so
that at exposed areas a surface is revealed which has a different affinity towards
ink or fountain than the surface of the unexposed coating. A major problem associated
with ablative plates, however, is the generation of ablation debris which may contaminate
the electronics and optics of the exposure device and which needs to be removed from
the plate by wiping it with a cleaning solvent, so that ablative plates are often
not truly processless. Ablation debris which is deposited onto the plate's surface
may also interfere during the printing process.
[0007] Other thermal plates that require no processing are described in
US 5,855,173,
US 5,839,369 and
5,839,370 where a method relying on the image-wise hydrophilic-hydrophobic transition of a
ceramic such as a zirconia ceramic and the subsequent reverse transition in an image
erasure step. This image-wise transition is obtained by exposure to infrared laser
irradiation at a wavelength of 1064 nm at high power (the average power is 1 W to
50 W and the peak power lies between 6 kW and 100 kW) which induces local ablation
and formation of substoichiometric zirconia.
US 5,893,328,
US 5,836,248 and
US 5,836,249 disclose a printing material comprising a composite of zirconia alloy and µ-alumina
which can be imaged using similar exposure means to cause localized "melting" of the
alloy in the exposed areas and thereby creating hydrophobic/oleophilic surfaces. A
similar printing material containing an alloy of zirconium oxide and Yttrium oxide
is described in
US 5,870,956. The high laser power output required in these prior art methods implies the use
of expensive exposure devices.
[0008] Another type of processless plates are printing plates based on a so-called "switching"
reaction where a hydrophilic surface is irreversibly changed into an oleophilic surface
or vice versa by imagewise exposure.
EP 652 483 for example, describes a positive working printing plate based on an acid catalyzed
cleavage of acid-labile groups pendant from a polymer backbone.
EP 200 488 and
US 4 081 572 describe negative working plates where a hydrophilic / hydrophobic conversion is
obtained by a chemical reaction upon imagewise exposure to heat. Other examples of
processless plates are based on the thermally induced rupture of microcapsules and
the subsequent reaction of the microencapsulated oleophilic materials (isocyanates)
with functional (hydroxyl-)groups on cross-linked hydrophilic binders (
US 5,569,573;
EP 646 476;
W094/2395;
WO98/29258).
[0009] US 6 582 882 describes an imaging element comprising a graft copolymer having a hydrophobic backbone
and a plurality of pendant hydrophilic groups or a plurality of pendant groups comprising
hydrophilic and hydrophobic segments. Upon exposure of the imaging element to thermal
energy, the exposed areas become less soluble in a developer than the unexposed areas.
[0010] US 6 362 274 describes grafted copolymers comprising three sequences: one sequence for anchoring
on solid particles such as pigments and fillers, one hydrophobic sequence and one
hydrophilic sequence for using the copolymers in aqueous and/or organic medium. The
disclosed copolymers are of particular interest in a wide range of paint formulations;
there is no reference in the cited prior art document to lithographic printing plates.
[0011] None of the prior art discloses the heat-sensitive copolymer of the present invention
in lithographic printing plates.
SUMMARY OF THE INVENTION
[0012] It is an aspect of the present invention to provide a heat sensitive lithographic
printing plate precursor comprising on a support having a hydrophilic surface or which
is provided with a hydrophilic layer, a coating comprising an infrared light absorbing
agent and a copolymer, wherein said copolymer comprises a plurality of recurring units
X having a hydrophilic polymeric pendant group and a plurality of recurring units
Y having a hydrophobic polymeric pendant group.
[0013] It is another aspect of the present invention to provide a method for preparing a
heat-sensitive lithographic printing plate without wet processing comprising the steps
of
- (i) applying on a support having a hydrophilic surface or which is provided with a
hydrophilic layer, a coating comprising an infrared light absorbing agent and a copolymer
comprising a plurality of recurring units X having a hydrophilic polymeric pendant
group and a plurality of recurring units Y having a hydrophobic polymeric pendant
group
- (ii) image-wise exposing the coating to heat and/or infrared light.
[0014] It is another aspect of the present invention to provide a printing plate precursor
whereof the coating is capable of switching from a hydrophilic state into a hydrophobic
state or vice versa after exposure to heat and/or infrared light.
[0015] Specific embodiments of the invention are defined in the dependent claims.
DETAILED DESCRIPTION OF THE INVENTION
[0016] According to the present invention, there is provided a heat sensitive lithographic
printing plate precursor comprising on a support having a hydrophilic surface or which
is provided with a hydrophilic layer, a coating comprising an infrared absorbing agent
and a copolymer comprising a plurality recurring units X having a hydrophilic polymeric
pendant group and a plurality of recurring units Y having a hydrophobic polymeric
pendant group, said copolymer hereinafter also referred to as "double comb graftcopolymer"
or "DC-graftcopolymer".
[0017] The recurring unit X having a hydrophilic polymeric pendant group and the recurring
unit Y having a hydrophobic polymeric pendant group may be represented by the following
formula's:
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0002)
wherein a' and c' are 0 or 1,
wherein L
1 and L
2 independently represent a linking group,
wherein R
a, R
b, R
c, R
d, R
e and R
f independently represent hydrogen, an alkyl such as methyl, ethyl, propyl, isopropyl,
a cycloalkyl such as cyclopentane, cyclohexane, 1,3-dimethylcyclohexane, an aryl,
a heteroaryl, a carboxylic acid, an ester of a carboxylic acid, an amide of a carboxylic
acid, or an alkyl or aryl group which is substituted with a carboxylic acid, with
an ester of a carboxylic acid or with an amide of a carboxylic acid,
wherein b' is 0 or 1 and when b'=0, L
1 is further bound to C
1 to form a cyclic structure,
wherein d' is 0 or 1 and when d'=0, L
2 is further bound to C
2 to form a cyclic structure,
and wherein R
1 and R
2 represent respectively a hydrophilic polymeric pendant group and a hydrophobic polymeric
pendant group.
[0018] In a preferred embodiment the recurring units X and Y can be represented by the following
formula's:
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0004)
wherein e and f are 0 or 1,
wherein L
3 and L
4 independently represent a linking group,
wherein R
g, R
h, R
i and R
j independently represent hydrogen, an alkyl such as methyl, ethyl, propyl, isopropyl,
cycloalkyl such as cyclopentane, cyclohexane, 1,3-dimethylcyclohexane, aryl, or heteroaryl
group,
and wherein R
1 and R
2 represent respectively a hydrophilic polymeric pendant group and a hydrophobic polymeric
pendant group.
[0019] The linking groups L
1, L
2, L
3 and L
4 may independently represent a linking group selected form the group comprising alkylene,
arylene, heteroarylene, -O-, -CO-, -CO-O-, -O-CO-, -CS-, -O-(CH
2)
k-, -(CH
2)
k-O-, -(CH
2)
k-O-CO-, -O-CO-(CH
2)
k-, -(CH
2)
k-O-CO-(CH
2)
1-, -(CH
2)
k-COO-, -CO-O-(CH
2)
k-,-(CH
2)
k-COO-(CH
2)
1-, -(CH
2)
k-NH-, -NH-(CH
2)
k-, -(CH
2)
k-CONH-, -(CH
2)
k-CONH-SO
2-, -NH-(CH
2)
k-O-(CH
2)
1-, -CO-(CH
2)
k, -(CH
2)
k-CO-, -CO-NH-, -NH-CO-, -NH-CO-O-, -O-CO-NH, -(CH
2)
k-CO-NH-, -NH-CO-(CH
2)
k-, -NH-CO-NH-, -NH-CS-NH-, or combinations thereof; wherein k and 1 independently
represent an integer ≥ 1, preferably an integer between 1 and 8.
[0020] When b'=0 or when d'=0, the linking groups L
1 and L
2 are further bound to respectively C
1 and C
2 and are trivalent groups. In one embodiment, L
1 and L
2 include a nitrogen atom and form a cyclic structure; they are preferably independently
represented by a linking group selected from the group comprising: -CO-N<
co-, -(CH
2)
k-N<, >N-(CH
2)
k-, -(CH
2)
k-CON<-, -(CH
2)
k-CON<
SO2->N-(CH
2)
k-O-(CH
2)
1-, -CO-N<, >N-CO-, >N-CO-O-, -O-CO-N<, -(CH
2)
k-CO-N<, >N-CO-(CH
2)
k-, >N-CO-NH-, >N-CS-NH-, or combinations thereof; wherein k and l independently represent
an integer ≥ 1, preferably an integer between 1 and 8.
[0021] The hydrophilic polymeric pendant group comprises hydrophilic monomeric units which
are polymerisable by an addition polymerisation or by a condensation polymerisation.
The hydrophilic monomeric units are monomers which comprise an anionic, cationic or
non-ionic group.
[0022] Examples of suitable hydrophilic monomers are selected from the group of alkylene
oxides such as ethylene oxide, glycidol and propylene oxide, vinyl alcohol, acrylic
acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid, hydroxyalkyl
methacrylate such as hydroxyethyl methacrylate, hydroxyalkyl acrylate such as hydroxyethyl
acrylate, vinylpyrolidone, acrylamides such as hydroxyethyl acrylamide, methacrylamides
such as hydroxypropyl methacrylamide, vinyl methyl ether, vinyl sulfonate, vinylphosphonic
acid, styrene sulfonic acid, sulphoethyl methacrylate, 2-acrylamido-2-methyl-1-propanesulfonic
acid, or protonated or alkylated derivates of vinylpyridine, vinylimidazole or N-vinyl
diethylamine.
[0023] The hydrophilic polymeric pendant group may also be selected from a polysaccharide,
starch, a cellulose, a dextran, or derivate of cellulose or dextran.
[0024] The hydrophobic polymeric pendant group comprise hydrophobic monomeric units which
are polymerisable by an addition polymerisation or by a condensation polymerisation.
[0026] Examples of hydrophobic monomeric units are selected from the group comprising siloxanes
such as dimethylsiloxane, diphenylsiloxane and methylphenyl siloxane, perfluoroalkylethylene,
alkylacrylates such as butylacrylate, 2-ethylhexylacrylate and cyclohexyl acrylate,
alkyl methacrylates such as methyl methacrylate, butyl methacrylate, benzyl methacrylate,
lauryl methacrylate and stearyl methacrylate, allyl methacrylate, fluorinated alkylacrylates
such as trifluoroethylacrylate and pentafluoropropylacrylate, fluorinated alkylmethacrylates,
ethylene, isoprene, butadiene, chlorinated or brominated monomers such as vinyl chloride
or vinylidene chloride, vinyl esters such as vinyl propionate and vinyl stearate,
vinyl ethers such as vinyl propylether, styrene, styrene derivatives, acrylonitrile,
methacrylonitrile, N-alkylacrylamides and N-alkylmethacrylamides.
[0027] Typical examples of recurring monomeric units having a hydrophobic polymeric pendant
group are:
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0017)
wherein R
5 is represented by an alkyl group such as methyl, n-butyl and sec-butyl, and each
m by an integer > 3.
[0028] In a preferred embodiment the DC-graftcopolymer comprises polyethylene oxide or a
mixture of polyethylene oxide and polypropylene oxide as hydrophilic polymeric pendant
group and polydimethylsiloxane or polymethylphenyl siloxane as hydrophobic polymeric
pendant group.
[0029] The DC-graftcopolymer can be prepared by several methods. In these methods, several
intermediate products are previously prepared:
- A = a hydrophilic polymeric group comprising a terminal functional group G1;
- B = a hydrophobic polymeric group comprising a terminal functional group G2;
- C = a macromonomer formed by a chemical reaction between a monomer having a reactive
group G3 and a hydrophilic polymeric group A having a reactive group G1 wherein G1 and G3 form a covalent bound;
- D = a macromonomer formed by a chemical reaction between a monomer having a reactive
group G4 and a hydrophobic polymeric group B having a reactive group G2 wherein G1 and G4 form a covalent bound.
[0030] In a first method a macromonomer C is copolymerised with a monomer having a reactive
group G
5, and, subsequently, B is further reacted wherein G
5 and G
2 form a covalent bound.
[0031] In a second method a macromonomer D is copolymerised with a monomer having a reactive
group G
6, and, subsequently, A is further reacted wherein G
6 and G
1 form a covalent bound.
[0032] In a third method a macromonomers C and D are copolymerised. The first and second
methods are preferred, the second method is most preferred.
[0033] The reactive groups G
1 to G
6 independently represent a group including an -OH group, an amine group, an anhydride
group, an acid group, an acid chloride group or an isocyanate group. The reactive
groups are defined in such a way that a chemical reaction is possible. For example,
a reaction between an amine group as reactive group and an anhydride group as the
other reactive group. Other combination are also possible.
[0034] Examples of A are
Jeffamine M-1000, Huntsman Corporation, having the following structure:
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0018)
R6 =H (86-mol%), -CH3 (14-mol%) and R7 = CH3
Other Jeffamines monoamines such as Jeffamine M-600, M-1000 and M-2005 are suitable
examples.
[0035] Examples of B are:
A polysiloxane B having an -OH group at the end of the chain can be obtained from
several suppliers including Shinetsu, Itochu and Chisso.
The polysiloxanes include any compound which contains more than one siloxane group
-Si(R',R")-O-, wherein R' and R" are optionally substituted alkyl or aryl groups.
Preferred siloxanes are phenylalkylsiloxanes and dialkylsiloxanes, e.g. phenylmethylsiloxanes
and dimethylsiloxanes. The number of siloxane groups -Si(R',R")-O- is at least 2,
preferably at least 10, more preferably at least 20. It may be less than 100, preferably
less than 60.
[0036] Examples of C are:
Polydimethylsiloxane having a terminal methacrylate group
(PDMS-MA); Chisso M
w = 1000 g/mol, 94%,
Polydimethylsiloxane having a terminal methacrylate group with molecular weights of
5000 g/mol, 8000 g/mol, 10000 g/mol, and 160000 g/mol. Higher molecular weights than
160000 g/mol or lower molecular weights than 1000 g/mol are also suitable examples.
[0037] Examples of D are the following:
The polymers D can be synthesized by a reaction of a polysiloxane B having an -OH
group at the end of the chain with acryloyl chloride or methacryloyl chloride.
[0038] The products of polycondensation may also represent the recurring unit X comprising
the polymeric hydrophilic pendant group and recurring unit Y comprising the polymeric
hydrophobic pendant group. Polyesters and polyamides are for example obtained by a
poycondensation reaction; polyesters can be prepared from diacids and diols, or from
hydroxyacids, and polyamides can be prepared from diacids and diamines or from aminoacids.
[0039] Surprisingly, it was found that the coating of the heat-sensitive lithographic printing
plate of the present invention switches from a hydrophilic state to a hydrophobic
state upon exposure to heat and/or to infrared light. The same was observed when exposing
the copolymer of the heat-sensitive lithographic printing plate of the present invention
to heat. This conversion reaction is illustrated by an increase of the contact angle
against water. For measuring the contact angle against water, the coating is applied
,for example, onto a glass substrate by spin cast coating. The glass substrate can
be covered with more than one polymer monolayer. The contact angle against water changes
from values ranging from 20 to 65 before exposure to heat and/or infrared light, to
values ranging form 90 to 110 after the exposure.
[0040] Typically, by exposure of the coating of the heat-sensitive lithographic printing
plate of the present invention comprising a DC-graftcopolymer, with heat and/or infrared
light, hydrophobic areas are formed which are ink accepting while the unexposed areas
remain hydrophilic and define the non-image areas. Wet processing of the printing
plate is not required. Here, wet processing means a developing step wherein a liquid
such as an aqueous solution or an aqueous alkaline solution is used.
[0041] The support of the lithographic printing plate precursor has a hydrophilic surface
or is provided with a hydrophilic layer. The support may be a sheet-like material
such as a plate or it may be a cylindrical element such as a sleeve which can be slid
around a print cylinder of a printing press. Preferably, the support is a metal support
such as aluminum or stainless steel. The support can also be a laminate comprising
an aluminum foil and a plastic layer, e.g. polyester film.
[0042] A particularly preferred lithographic support is an electrochemically grained and
anodized aluminum support. The aluminium is preferably grained by electrochemical
graining, and anodized by means of anodizing techniques employing phosphoric acid
or a sulphuric acid/phosphoric acid mixture. Methods of both graining and anodization
of aluminum are very well known in the art.
[0043] By graining (or roughening) the aluminium support, both the adhesion of the printing
image and the wetting characteristics of the non-image areas are improved. By varying
the type and/or concentration of the electrolyte and the applied voltage in the graining
step, different type of grains can be obtained.
[0044] By anodising the aluminium support, its abrasion resistance and hydrophilic nature
are improved. The microstructure as well as the thickness of the Al
2O
3 layer are determined by the anodising step, the anodic weight (g/m
2 Al
2O
3 formed on the aluminium surface) varies between 1 and 8 g/m
2.
[0045] The grained and anodized aluminum support may be post-treated to improve the hydrophilic
properties of its surface. For example, the aluminum oxide surface may be silicated
by treating its surface with a sodium silicate solution at elevated temperature, e.g.
95°C. Alternatively, a phosphate treatment may be applied which involves treating
the aluminum oxide surface with a phosphate solution that may further contain an inorganic
fluoride. Further, the aluminum oxide surface may be rinsed with an organic acid and/or
salt thereof, e.g. carboxylic acids, hydrocarboxylic acids, sulphonic acids or phosphonic
acids, or their salts, e.g. succinates, phosphates, phosphonates, sulphates, and sulphonates.
A citric acid or citrate solution is preferred. This treatment may be carried out
at room temperature or may be carried out at a slightly elevated temperature of about
30 to 50°C. A further interesting treatment involves rinsing the aluminum oxide surface
with a bicarbonate solution. Still further, the aluminum oxide surface may be treated
with polyvinylphosphonic acid, polyvinylmethylphosphonic acid, phosphoric acid esters
of polyvinyl alcohol, polyvinylsulfonic acid, polyvinylbenzenesulfonic acid, sulfuric
acid esters of polyvinyl alcohol, and acetals of polyvinyl alcohols formed by reaction
with a sulfonated aliphatic aldehyde. It is further evident that one or more of these
post treatments may be carried out alone or in combination. More detailed descriptions
of these treatments are given in
GB 1084070,
DE 4423140,
DE 4417907,
EP 659909,
EP 537633,
DE 4001466,
EP A 292801,
EP A 291760 and
US 4458005.
[0046] According to another embodiment, the support can also be a flexible support, which
is provided with a hydrophilic layer, hereinafter called 'base layer'. The flexible
support is e.g. paper, plastic film, thin aluminum or a laminate thereof. Preferred
examples of plastic film are polyethylene terephthalate film, polyethylene naphthalate
film, cellulose acetate film, polystyrene film, polycarbonate film, etc. The plastic
film support may be opaque or transparent.
[0047] The base layer is preferably a cross-linked hydrophilic layer obtained from a hydrophilic
binder cross-linked with a hardening agent such as formaldehyde, glyoxal, polyisocyanate
or a hydrolyzed tetra-alkylorthosilicate. The latter is particularly preferred. The
thickness of the hydrophilic base layer may vary in the range of 0.2 to 25 µm and
is preferably 1 to 10 µm. The hydrophilic binder for use in the base layer is e.g.
a hydrophilic (co)polymer such as homopolymers and copolymers of vinyl alcohol, acrylamide,
methylol acrylamide, methylol methacrylamide, acrylate acid, methacrylate acid, hydroxyethyl
acrylate, hydroxyethyl methacrylate or maleic anhydride/vinylmethylether copolymers.
The hydrophilicity of the (co)polymer or (co)polymer mixture used is preferably the
same as or higher than the hydrophilicity of polyvinyl acetate hydrolyzed to at least
an extent of 60% by weight, preferably 80% by weight. The amount of hardening agent,
in particular tetraalkyl orthosilicate, is preferably at least 0.2 parts per part
by weight of hydrophilic binder, more preferably between 0.5 and 5 parts by weight,
most preferably between 1 parts and 3 parts by weight.
[0048] According to another embodiment the base layer may also comprise Al
2O
3 and an optional binder. Deposition methods for the Al
2O
3 onto the flexible support may be (i) physical vapor deposition including reactive
sputtering, RF-sputtering, pulsed laser PVD and evaporation of aluminium, (ii) chemical
vapor deposition under both vacuum and non-vacuum condition, (iii) chemical solution
deposition including spray coating, dipcoating, spincoating, chemical bath deposition,
selective ion layer adsorption and reaction, liquid phase deposition and electroless
deposition. The Al
2O
3 powder can be prepared using different techniques including flame pyrolisis, ball
milling, precipitation, hydrothermal synthesis, aerosol synthesis, emulsion synthesis,
sol-gel synthesis (solvent based), solution-gel synthesis (water based) and gasphase
synthesis. The particle size of the Al
2O
3 Powders can vary between 2 nm and 30 µm; more preferably between 100 nm and 2 µm.
[0049] The hydrophilic base layer may also contain substances that increase the mechanical
strength and the porosity of the layer. For this purpose colloidal silica may be used.
The colloidal silica employed may be in the form of any commercially available water
dispersion of colloidal silica for example having an average particle size up to 40
nm, e.g. 20 nm. In addition inert particles of larger size than the colloidal silica
may be added e.g. silica prepared according to Stöber as described in
J. Colloid and Interface Sci., Vol. 26, 1968, pages 62 to 69 or alumina particles or particles having an average diameter of at least 100 nm which
are particles of titanium dioxide or other heavy metal oxides.
[0051] The coating preferably also contains a compound which absorbs infrared light and
converts the absorbed energy into heat. The concentration of the IR absorbing compound
in the coating is typically between 0.25 and 10.0 wt.%, more preferably between 0.5
and 7.5 wt.%. Preferred IR absorbing compounds are dyes such as cyanine and merocyanine
dyes or pigments such as carbon black. Examples of suitable IR absorbers are described
in e.g.
EP 823327,
978376,
1029667,
1053868,
1093934;
WO 97/39894 and
00/29214. A preferred compound is the following cyanine dye :
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0019)
[0052] To protect the surface of the coating, in particular from mechanical damage, a protective
layer may also optionally be applied. The protective layer generally comprises at
least one water-soluble polymeric binder, such as polyvinyl alcohol, polyvinylpyrrolidone,
partially hydrolyzed polyvinyl acetates, gelatin, carbohydrates or hydroxyethylcellulose,
and can be produced in any known manner such as from an aqueous solution or dispersion
which may, if required, contain small amounts, i.e. less than 5% by weight, based
on the total weight of the coating solvents for the protective layer, of organic solvents.
The thickness of the protective layer can suitably be any amount, advantageously up
to 5.0 µm, preferably from 0.1 to 3.0 µm, particularly preferably from 0.15 to 1.0
µm.
[0053] Optionally, the coating may further contain additional ingredients. Preferred ingredients
are e.g. additional binders, especially sulfonamide and phthalimide groups containing
polymers, to improve the run length and chemical resistance of the plate. Examples
of such polymers are those described in
EP 933682,
EP 894622 and
WO 99/63407. Also colorants can be added such as dyes or pigments which provide a visible colour
to the coating and which remain in the coating at unexposed areas so that a visible
image is produced after exposure and processing. Typical examples of such contrast
dyes are the amino-substituted tri- or diarylmethane dyes, e.g. crystal violet, methyl
violet, victoria pure blue, flexoblau 630, basonylblau 640, auramine and malachite
green. Polymers particles such as matting agents and spacers are also well-known components
of lithographic coatings which can be used in the plate precursor of the present invention.
[0054] For the preparation of the lithographic plate precursor, any known method can be
used. For example, the above ingredients can be dissolved in a solvent mixture which
does not react irreversibly with the ingredients and which is preferably tailored
to the intended coating method, the layer thickness, the composition of the layer
and the drying conditions. Suitable solvents include ketones, such as methyl ethyl
ketone (butanone), as well as chlorinated hydrocarbons, such as trichloroethylene
or 1,1,1-trichloroethane, alcohols, such as methanol, ethanol or propanol, ethers,
such as tetrahydrofuran, glycol-monoalkyl ethers, such as ethylene glycol monoalkyl
ether, e.g. 2-methoxy-1-propanol, or propylene glycol monoalkyl ether and esters,
such as butyl acetate or propylene glycol monoalkyl ether acetate. It is also possible
to use a mixture which, for special purposes, may additionally contain solvents such
as acetonitrile, dioxane, dimethylacetamide, dimethylsulfoxide or water.
[0055] Any coating method can be used for applying one or more coating solutions to the
hydrophilic surface of the support. A multi-layer coating can be applied by coating/drying
each layer consecutively or by the simultaneous coating of several coating solutions
at once. In the drying step, the volatile solvents are removed from the coating until
the coating is self-supporting and dry to the touch. However it is not necessary (and
may not even be possible) to remove all the solvent in the drying step. Indeed the
residual solvent content may be regarded as an additional composition variable by
means of which the composition may be optimised. Drying is typically carried out by
blowing hot air onto the coating, typically at a temperature of at least 70°C, suitably
80-150°C and especially 90-140°C. Also infrared lamps can be used. The drying time
may typically be 15-600 seconds.
[0056] The printing plate precursor of the present invention can be image-wise exposed directly
with heat, e.g. by means of a thermal head, or indirectly by infrared light, preferably
near infrared light. The infrared light is preferably converted into heat by an IR
light absorbing compound as discussed above. The heat-sensitive lithographic printing
plate precursor of the present invention is preferably not sensitive to visible light.
Most preferably, the coating is not sensitive to ambient daylight, i.e. visible (400-750
nm) and near UV light (300-400 nm) at an intensity and exposure time corresponding
to normal working conditions so that the material can be handled without the need
for a safe light environment.
[0057] The printing plate precursor of the present invention can be exposed to infrared
light by means of e.g. LEDs or a laser. Most preferably, the light used for the exposure
is a laser emitting near infrared light having a wavelength in the range from about
750 to about 1500 nm, such as a semiconductor laser diode, a Nd:YAG or a Nd:YLF laser.
The required laser power depends on the sensitivity of the image-recording layer,
the pixel dwell time of the laser beam, which is determined by the spot diameter (typical
value of modern plate-setters at 1/e
2 of maximum intensity : 10-25 µm), the scan speed and the resolution of the exposure
apparatus (i.e. the number of addressable pixels per unit of linear distance, often
expressed in dots per inch or dpi; typical value : 1000-4000 dpi).
[0058] Two types of laser-exposure apparatuses are commonly used: internal (ITD) and external
drum (XTD) plate-setters. ITD plate-setters for thermal plates are typically characterized
by a very high scan speed up to 1500 m/ and may require a laser power of several Watts.
The Agfa Galileo T (trademark of Agfa Gevaert N.V.) is a typical example of a plate-setter
using the ITD-technology. XTD plate-setters for thermal plates having a typical laser
power from about 20 mW to about 500 mW operate at a lower scan speed, e.g. from 0.1
to 20 m/. The Creo Trendsetter plate-setter family (trademark of Creo) and the Agfa
Excalibur plate-setter family (trademark of Agfa Gevaert N.V.) both make use of the
XTD-technology.
[0059] The known plate-setters can be used as an off-press exposure apparatus, which offers
the benefit of reduced press down-time. XTD plate-setter configurations can also be
used for on-press exposure, offering the benefit of immediate registration in a multi-color
press. More technical details of on-press exposure apparatuses are described in e.g.
US 5,174,205 and
US 5,163,368.
[0060] The plate precursor according to the invention can, if required, then be post-treated
with a suitable correcting agent or preservative as known in the art. To increase
the resistance of the finished printing plate and hence to extend the print run, the
layer can be briefly heated to elevated temperatures ("baking"). As a result, the
resistance of the printing plate to washout agents, correction agents and UV-curable
printing inks also increases. Such a thermal post-treatment is described, inter alia,
in
DE-A 14 47 963 and
GB-A 1 154 749.
[0061] The printing plate thus obtained can be used for conventional, so-called wet offset
printing, in which ink and an aqueous dampening liquid is supplied to the plate. Another
suitable printing method uses so-called single-fluid ink without a dampening liquid.
Single-fluid inks which are suitable for use in the method of the present invention
have been described in
US 4 045 232;
US 4 981 517 and
US 6 140 392. In a most preferred embodiment, the single-fluid ink comprises an ink phase, also
called the hydrophobic or oleophilic phase, and a polyol phase as described in
WO 00/32705.
EXAMPLES
1. Materials.
1.1. Polydimethylsiloxane having a terminal methacrylate group (PDMS-MA); Chisso Mw = 1000 g/mol, 94%.
[0062] PDMS-MA is purified by the following method:
The PDMS-MA is purified by filtration over a two-layer comlumn of silica gel (20 cm)
and aluminum oxide (Al2O3) using absolute chloroform as the mobile phase.
1.2. Maleic anhydride (MSA), Merck, 98%
Purified by Sublimation under vacuum at 80°C.
1.3. Jeffamine M-1000, Huntsman Corporation.
[0063] Jeffamine M-1000 is purified as followed:
In a 250 ml round bottom flask six gram of Jeffamine monoamine M-1000 was dissolved
in 40 ml ethanol, than n-heptane was added slowly until the mixture became turbid.
The two phases were separated by means of a separation funnel. The heavy phase (mixture
of ethanol/amine) was recovered and re-precipitated in n-heptane. Then the excess
of ethanol was evaporated and the residue was dried under vacuum overnight at room
temperature. The purity of the end product was verified by Size Exclusion Chromatography.
2. Synthesis of the double comb polymers.
2.1. Step 1: copolymerization of PDMS-MA and MSA to yield poly[PDMS-MA-co-MSA].
[0064] A 250 ml two necked round bottomed flask was charged with 2-mol% of dimethyl-2,2'-azobis(2-methylpropionate)
(V-6), followed by the monomers PDMS-MA and MSA at the desired ratios (see Table 1).
Then absolute benzene was added. The content of the flask was degassed 3 times to
remove the air. The reaction was carried out under argon atmosphere at 60°C for 6-hours.
The polymer was recovered by precipitation in a mixture of methanol : diethyl ether
(1:1), this procedure was repeated until the remaining PDMS-MA was removed. The end
product (CMSA 34,35,36 and 38) was dried under vacuum at room temperature overnight.
Table 1: Concentration of the reagentia.
Poly
[PDMS-MA-co-MSA] |
PDMS-MA
g |
MSA
G |
V-6
mg |
Vbenzene
ml |
CMSA34 |
6 |
0.183 |
72.0 |
12 |
CMSA35 |
6 |
0.571 |
105 |
12 |
CMSA36 |
6 |
2.350 |
234 |
12 |
CMSA38 |
9 |
0.360 |
140 |
24 |
2.2. Step 2: synthesis of poly[PDMS-MA-co-(MSA-graft-Jeffamine)]:
[0065] The grafting reaction of Jeffamine M-1000 on poly[PDMS-MA-co-MSA] is a two step process,
involving (i) the nucleophilic addition of the amine group to a carbonyl unit of the
MSA rings to form an amic acid intermediate, and (ii) the formation of an cyclic imide
with water expellation. Since both the steps require different reaction conditions
the amic acid can be isolated and investigated. It turned out that the amic acid form
was not stable against crosslinking in bulk and at ambient conditions, hence it had
to be converted to the imide form (Figure 1 gives a schematically representation of
the reaction).
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0021)
wherein x, y and n are integers >1 and wherein R is H or methyl or a mixture of H
and methyl.
[0066] A 100 ml three-necked round bottle equipped with a stirring bar, reflux condenser,
inert-line and septum to add the monomer was used. The concentration of the reagentia
used in the synthesis, are given in Table 2.
[0067] The following procedure was used:
[0068] Poly[PDMS-MA-
co-MSA] copolymer and Jeffamine M-1000 were added and dissolved in 9 ml of xylene/DMF
(2:3) and heated at 90 °C for 24 hours. Subsequently, triethylamine (=TEA) and acetic
anhydride (=AC
2O) were added to the mixture and heated for 24 hours at 90°C. After this time the
reaction was ended and the solvent was removed by evaporation. The polymer was re-dissolved
in 15 ml of toluene and transferred in a separation funnel. 20 ml of distilled water
was added and, after shaking, the light phase was separated. The organic layer was
washed twice with 20 ml of distilled water. The solvent was removed on a rotary evaporator
and the graft polymer was dried under vacuum at room temperature for 24 hours. The
polymer was isolated as a waxy-brown material. The graft copolymers were analysed
by Size Exclusion Chromatography to confirm that the non-reacted Jeffamine was removed.
Table 2: Concentration of the reagentia.
Double comb graftcopolymers |
[PDMS-MA-co-MSA] |
Jeffamine M-1000 |
trietyl amine |
Acetic anhydride |
Vxylene/DMF |
|
|
mg |
mg |
mg |
ml |
DC18 |
CMSA34
1 g |
0.54 |
0.10 |
0.10 |
9 |
DC20 |
CMSA35
1 g |
1.14 |
0.15 |
0.18 |
9 |
DC21 |
CMSA36
1 g |
18.20 |
1.83 |
2.47 |
9 |
DC23 |
CMSA38
9 g |
2300 |
3600 |
6300 |
84 |
3. Contact angle measurements against water.
[0069] Thin films from double comb polymers DC 18, DC 20, DC 21 and DC 23 were prepared
according to the following procedure: 0.2 ml of a 1 wt% polymer solution in toluene
was spin casted on a glass substrate at 2000 revolutions/min for 1 minute. The contact
angle θ against water of the spin cast copolymer films on the glass substrate, were
determined by means of sessile drop and annealing for 2 minutes at 150°C. The results
are summarized in Table 3.
Table 3: Contact angle θ against water
Double comb graftcopolymer |
θ [°]
at room temperature |
θ [°]
annealed at 150° |
DC18 |
20 |
100 |
DC20 |
41 |
98 |
DC21 |
62 |
101 |
DC23 |
40 |
98 |
[0070] Table 3 clearly shows an increase in contact angle against water after annealing
the substrate indicating a hydrophilic / hydrophobic conversion.
4. Preparation of thermal printing plates.
[0071] Solution A containing double comb polymer DC 23 was combined with solution B containing
0,54% IR absorber (mixture of 0,27% PRO-JET 900NP + 0,27% PRO-JET 830NP, trademarks
of Avecia). This coating solution was coated on a grained and anodized aluminum substrate
heated at 40 °C and subsequently dried using a hair dryer. The compositions of the
coatings are shown in Table 4.
Table 4: Coating compositions.
Example Nr. |
Solution A : DC23 |
Solution B : 0.54%wt I.R. absorber* in toluene |
Coating µm wet thickness |
Coating after drying g/m2 |
1 |
6 ml of a 2%
DC23 |
1 ml |
20 |
0,34 DC23
0,016 I.R. |
|
in toluene |
|
|
|
2 |
2 ml of a 2%
DC23 |
2 ml |
20 |
0,4 DC23
0,054 I.R. |
|
in toluene |
|
|
|
3 |
1 ml of a 2%
DC23 |
3 ml |
20 |
0,4 DC23
0,081 I.R. |
|
in toluene |
|
|
|
* mixture of 0,27% PRO-JET 900NP + 0,27% PRO-JET 830NP |
5. Print results.
[0072] The coatings were exposed using an 830 nm IR laser (1000 mJ/cm
2 and at 4 m/s) and prints were obtained by using an off-set printer GTO 52 (available
from Heidelberger Druckmaschinen AG). The printing results are shown in Table 5. The
ink density is the optical density, measured by using a GretagMacbeth densitometer
Type D19C. The values were corrected for the paper density.
[0073] The results shows that low optical density values are obtained in the non-image areas
and high optical densities in the imaged areas.
Table 5: Printing results.
Example Nr. |
Optical density of the imaged areas after 100 prints |
Optical density of the non-image areas |
1 |
1,27 |
0,013 |
2 |
1,37 |
0,024 |
3 |
1,17 |
0,020 |
1. A heat-sensitive lithographic printing plate precursor comprising on a support having
a hydrophilic surface or which is provided with a hydrophilic layer, a coating comprising
an infrared absorbing agent and a copolymer comprising a plurality of recurring units
X and a plurality of recurring units Y, characterize in that X has a hydrophilic polymeric pendant group and Y has a hydrophobic polymeric pendant
group.
2. A heat-sensitive lithographic printing plate precursor according to claim 1 wherein
the recurring unit X is represented by the following formula:
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0022)
and the recurring unit Y is represented by the following formula:
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0023)
wherein a' and c' are 0 or 1,
wherein L
1 and L
2 independently represent a linking group,
wherein R
a, R
b, R
c, R
d, R
e and R
f independently represent hydrogen, an alkyl, cycloalkyl, aryl, heteroaryl group, a
carboxylic acid, an ester of a carboxylic acid, an amide of a carboxylic acid, or
an alkyl or aryl group which is substituted with a carboxylic acid, with an ester
of a carboxylic acid or with an amide of a carboxylic acid,
wherein, b' is 0 or 1 and when b'=0, L
1 is further bound to C
1 to form a cyclic structure,
wherein d' is 0 or 1 and when d'=0, L
2 is further bound to C
2 to form a cyclic structure,
and wherein R
1 and R
2 represent respectively a hydrophilic polymeric pendant group and a hydrophobic polymeric
pendant group.
3. A heat-sensitive lithographic printing plate precursor according to claim 2 wherein
the linking groups L1 and L2 which form a cyclic structure are linking groups including a nitrogen atom.
4. A heat-sensitive lithographic printing plate precursor according to claim 2 wherein
the recurring unit X is represented by the following formula:
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0024)
wherein e is 0 or 1,
wherein L
3 represents a linking group,
and wherein R
g and R
h independently represent hydrogen, an alkyl, cycloalkyl, aryl, or heteroaryl group.
5. A heat-sensitive lithographic printing plate precursor according to claim 2 wherein
the recurring unit Y is represented by the following formula:
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0025)
wherein f is 0 or 1,
wherein L
4 represents a linking group,
and wherein R
i and R
j independently represent hydrogen, an alkyl, cycloalkyl, aryl, or heteroaryl group.
6. A heat-sensitive lithographic printing plate precursor according to any of the preceding
claims 1 to 4 wherein the hydrophilic polymeric pendant group comprises hydrophilic
monomeric units selected from monomers comprising an anionic, a cationic or a non-ionic
group.
7. A heat-sensitive lithographic printing plate precursor according to claims 6 wherein
said hydrophilic monomer is selected from the group comprising alkylene oxides, vinyl
alcohol, acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid,
fumaric acid, hydroxyalkyl methacrylate, hydroxyalkyl acrylate, vinylpyrolidone, acrylamides,
methacrylamides, vinylphosphonic acid, styrene sulfonic acid, vinyl methyl ether;
vinyl sulfonate, sulphoethyl methacrylate, 2-acrylamido-2-methyl-1-propanesulfonic
acid, or protonated or alkylated derivates of vinylpyridine, vinylimidazole or N-vinyl
diethylamine.
8. A heat-sensitive lithographic printing plate precursor according to any of the preceding
claims 1 to 3 and 5 wherein the hydrophobic polymeric pendant group comprises hydrophobic
monomeric units selected from the group comprising siloxanes, perfluoroalkylethylene,
alkylacrylates, fluorinated alkylacrylates, chlorinated or brominated monomers, vinyl
esters, vinyl ethers, ethylene, isoprene, butadiene, styrene, styrene derivatives,
alkylmethacrylates, allyl methacrylates, fluorinated alkylmethacrylates, acrylonitrile
methacrylonitrile, N-alkylacrylamides and N-alkylmethacrylamides.
9. A heat-sensitive lithographic printing plate precursor according to claim 7 wherein
the hydrophilic monomeric units are represented by ethylene oxide or a mixture of
ethylene oxide and propylene oxide.
10. A heat-sensitive lithographic printing plate precursor according to claim 8 wherein
the hydrophobic monomeric units are represented by dimethyl siloxane or methylphenyl
siloxane.
11. A heat sensitive lithographic printing plate precursor according to any of the preceding
claims wherein the coating is capable of switching from a hydrophilic state into a
hydrophobic state or from a hydrophobic state into a hydrophilic state upon exposure
to heat and/or infrared light.
12. A method for preparing a heat-sensitive lithographic printing plate precursor comprising
the step of applying on a support having a hydrophilic surface or provided with a
hydrophilic layer, a coating comprising a copolymer wherein said copolymer comprises
a plurality of recurring units X having a hydrophilic polymeric pendant group and
a plurality of recurring units Y having a hydrophobic polymeric pendant group.
13. A method for preparing a heat-sensitive lithographic printing plate without wet processing
comprising the steps of
(i) providing a lithographic printing plate precursor according to any of the preceding
claim 1-10
(ii) image-wise exposing the coating to heat and/or infrared light.
14. A method for increasing the contact angle, measured against water, of a coating comprising
the steps of
(i) providing a lithographic printing plate precursor according to any of the preceding
claims 1 to 10
(ii) image-wise heating said coating by means of infrared light and/or heat.
15. A process of changing the surface of a lithographic printing plate from a hydrophilic
state into a hydrophobic state by an image-wise exposure to heat or infrared light
of a heat-sensitive lithographic printing plate precursor according to claim 1.
1. Eine wärmeempfindliche lithografische Druckplattenvorstufe, die auf einem Träger mit
einer hydrophilen Oberfläche oder einem mit einer hydrophilen Schicht versehenen Träger
eine Beschichtung enthält, die einen IR-Absorber und ein Copolymer mit einer Vielzahl
von Struktureinheiten X und einer Vielzahl von Struktureinheiten Y enthält, dadurch gekennzeichnet, dass X eine hydrophile polymere Seitengruppe und Y eine hydrophobe polymere Seitengruppe
enthält.
2. Wärmeempfindliche lithografische Druckplattenvorstufe nach Anspruch 1,
dadurch gekennzeichnet, dass Struktureinheit X folgender Formel entspricht :
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0026)
und Struktureinheit Y folgender Formel entspricht :
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0027)
in denen :
a' und c' 0 oder 1 bedeuten,
L1 und L2 unabhängig voneinander eine Verbindungsgruppe bedeuten,
Ra, Rb, Rc, Rd, Re und Rf unabhängig voneinander ein Wasserstoffatom, eine Alkylgruppe, eine Cycloalkylgruppe,
eine Arylgruppe, eine Heteroarylgruppe, eine Carbonsäuregruppe, eine Carbonsäureestergruppe,
eine Carbonsäureamidgruppe oder eine mit einer Carbonsäuregruppe, einer Carbonsäureestergruppe
oder einer Carbonsäureamidgruppe substituierte Alkylgruppe oder Arylgruppe bedeuten,
b' 0 oder 1 bedeutet und wenn b'=0, L1 an C1 gebunden ist, um eine cyclische Struktur zu bilden,
d' 0 oder 1 bedeutet und wenn d'=0, L2 an C2 gebunden ist, um eine cyclische Struktur zu bilden,
und R1 und R2 eine hydrophile polymere Seitengruppe bzw. eine hydrophobe polymere Seitengruppe
bedeuten.
3. Wärmeempfindliche lithografische Druckplattenvorstufe nach Anspruch 2, dadurch gekennzeichnet, dass die Verbindungsgruppen L1 und L2, die eine cyclische Struktur bilden, stickstoffhaltige Verbindungsgruppen sind.
4. Wärmeempfindliche lithografische Druckplattenvorstufe nach Anspruch 2,
dadurch gekennzeichnet, dass Struktureinheit X folgender Formel entspricht :
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0028)
in der :
e 0 oder 1 bedeutet,
L3 eine Verbindungsgruppe bedeutet und
Rg und Rh unabhängig voneinander ein Wasserstoffatom, eine Alkylgruppe, eine Cycloalkylgruppe,
eine Arylgruppe oder eine Heteroarylgruppe bedeuten.
5. Wärmeempfindliche lithografische Druckplattenvorstufe nach Anspruch 2,
dadurch gekennzeichnet, dass Struktureinheit Y folgender Formel entspricht :
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0029)
in der :
f 0 oder 1 bedeutet,
L4 eine Verbindungsgruppe bedeutet und
Ri und Rj unabhängig voneinander ein Wasserstoffatom, eine Alkylgruppe, eine Cycloalkylgruppe,
eine Arylgruppe oder eine Heteroarylgruppe bedeuten.
6. Wärmeempfindliche lithografische Druckplattenvorstufe nach einem der vorstehenden
Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die hydrophile polymere Seitengruppe hydrophile Monomereinheiten aus der Gruppe bestehend
aus Monomeren, die eine anionische, kationische oder nicht-ionische Gruppe enthalten,
enthält.
7. Wärmeempfindliche lithografische Druckplattenvorstufe nach Anspruch 6, dadurch gekennzeichnet, dass das hydrophile Monomer aus der Gruppe bestehend aus Alkylenoxiden, Vinylalkohol,
Acrylsäure, Methacrylsäure, Maleinsäure, Itakonsäure, Crotonsäure, Fumarsäure, Hydroxyalkylmethacrylat,
Hydroxyalkylacrylat, Vinylpyrolidon, Acrylamiden, Methacrylamiden, Vinylphosphonsäure,
Styrolsulfonsäure, Vinylmethylether, Vinylsulfonat, Sulfoethylmethacrylat, 2-Acrylamid-2-methyl-1-propansulfonsäure
oder protonierten oder alkylierten Derivaten von Vinylpyridin, Vinylimidazol oder
N-Vinyldiethylamin gewählt wird.
8. Wärmeempfindliche lithografische Druckplattenvorstufe nach einem der vorstehenden
Ansprüche 1 bis 3 und 5, dadurch gekennzeichnet, dass die hydrophobe polymere Seitengruppe hydrophobe Monomereinheiten aus der Gruppe bestehend
aus Siloxanen, Perfluoralkylethylen, Alkylacrylaten, fluorierten Alkylacrylaten, chlorierten
oder bromierten Monomeren, Vinylestern, Vinylethern, Ethylen, Isopren, Butadien, Styrol,
Styrol-Derivaten, Alkylmethacrylaten, Allylmethacrylaten, fluorierten Alkylmethacrylaten,
Acrylnitril, Methacrylnitril, N-Alkylacrylamiden und N-Alkylmethacrylamiden enthält.
9. Wärmeempfindliche lithografische Druckplattenvorstufe nach Anspruch 7, dadurch gekennzeichnet, dass die hydrophilen Monomereinheiten Ethylenoxid oder ein Gemisch aus Ethylenoxid und
Propylenoxid sind.
10. Wärmeempfindliche lithografische Druckplattenvorstufe nach Anspruch 8, dadurch gekennzeichnet, dass die hydrophoben Monomereinheiten Dimethylsiloxan oder Methylphenylsiloxan sind.
11. Wärmeempfindliche lithografische Druckplattenvorstufe nach einem der vorstehenden
Ansprüche, dadurch gekennzeichnet, dass die Beschichtung durch Erwärmung und/oder IR-Bestrahlung von hydrophil in hydrophob
oder von hydrophob in hydrophil geschaltet werden kann.
12. Ein Verfahren zur Herstellung einer wärmeempfindlichen lithografischen Druckplattenvorstufe,
umfassend den Schritt, in dem auf einen Träger mit einer hydrophilen Oberfläche oder
einen mit einer hydrophilen Schicht versehenen Träger eine ein Copolymer enthaltende
Beschichtung aufgetragen wird, wobei das Copolymer eine Vielzahl von Struktureinheiten
X mit einer hydrophilen polymeren Seitengruppe und eine Vielzahl von Struktureinheiten
Y mit einer hydrophoben polymeren Seitengruppe enthält.
13. Ein Verfahren zur Herstellung einer wärmeempfindlichen lithografischen Druckplatte
ohne Nassentwicklung, wobei das Verfahren folgende Schritte umfasst :
(i) Bereitstellen einer lithografischen Druckplattenvorstufe nach einem der vorstehenden
Ansprüche 1 bis 10 und
(ii)bildmäßige Erwärmung und/oder IR-Bestrahlung der Beschichtung.
14. Ein Verfahren zur Erhöhung des Kontaktwinkels einer Beschichtung mit Wasser, wobei
das Verfahren folgende Schritte umfasst :
(i) Bereitstellen einer lithografischen Druckplattenvorstufe nach einem der vorstehenden
Ansprüche 1 bis 10, und
(ii)bildmäßige Erwärmung der Beschichtung mit Infrarotlicht und/oder Wärme.
15. Ein Verfahren zur Änderung der Oberfläche einer lithografischen Druckplatte, wobei
die Oberfläche bei bildmäßiger Erwärmung oder IR-Bestrahlung einer wärmeempfindlichen
lithografischen Druckplattenvorstufe nach Anspruch 1 von hydrophil in hydrophob umgewandelt
wird.
1. Un précurseur de plaque d'impression lithographique thermosensible comprenant sur
un support ayant une surface hydrophile ou sur un support revêtu d'une couche hydrophile
un revêtement contenant un agent absorbant les rayons infrarouges et un copolymère
contenant une multitude d'unités structurales X et une multitude d'unités structurales
Y, caractérisé en ce que X comprend un groupe latéral polymère hydrophile et Y comprend un groupe latéral
polymère hydrophobe.
2. Précurseur de plaque d'impression lithographique thermosensible selon la revendication
1,
caractérisé en ce que l'unité structurale X répond à la formule suivante :
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0030)
et que l'unité structurale Y répond à la formule suivante :
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0031)
où :
a' et c' représentent 0 ou 1,
L1 et L2 représentent, indépendamment l'un de l'autre, un groupe de liaison,
Ra, Rb, Rc, Rd, Re et Rf représentent, indépendamment l'un de l'autre, un atome d'hydrogène, un groupe alkyle,
un groupe cycloalkyle, un groupe aryle, un groupe hétéroaryle, un groupe acide carboxylique,
un groupe ester d'un acide carboxylique, un groupe amide d'un acide carboxylique ou
un groupe alkyle ou un groupe aryle substitué par un groupe acide carboxylique, un
groupe ester d'un acide carboxylique ou un groupe amide d'un acide carboxylique,
b' représente 0 ou 1 et si b'=0, L1 est également lié à C1 afin de former une structure cyclique,
d' représente 0 ou 1 et si d'=0, L2 est également lié à C2 afin de former une structure cyclique,
et R1 et R2 représentent respectivement un groupe latéral polymère hydrophile et un groupe latéral
polymère hydrophobe.
3. Précurseur de plaque d'impression lithographique thermosensible selon la revendication
2, caractérisé en ce que les groupes de liaison L1 et L2 formant une structure cyclique sont des groupes de liaison azotés.
4. Précurseur de plaque d'impression lithographique thermosensible selon la revendication
2,
caractérisé en ce que l'unité structurale X répond à la formule suivante :
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0032)
où :
e représente 0 ou 1,
L3 représente un groupe de liaison et
Rg et Rh représentent, indépendamment l'un de l'autre, un atome d'hydrogène, un groupe alkyle,
un groupe cycloalkyle, un groupe aryle ou un groupe hétéroaryle.
5. Précurseur de plaque d'impression lithographique thermosensible selon la revendication
2,
caractérisé en ce que l'unité structurale Y répond à la formule suivante :
![](https://data.epo.org/publication-server/image?imagePath=2009/28/DOC/EPNWB1/EP04105542NWB1/imgb0033)
où :
f représente 0 ou 1,
L4 représente un groupe de liaison et
Ri et Rj représentent, indépendamment l'un de l'autre, un atome d'hydrogène, un groupe alkyle,
un groupe cycloalkyle, un groupe aryle ou un groupe hétéroaryle.
6. Précurseur de plaque d'impression lithographique thermosensible selon l'une quelconque
des revendications 1 à 4, caractérisé en ce que le groupe latéral polymère hydrophile comprend des unités monomères hydrophiles choisies
parmi des monomères comprenant un groupe anionique, cationique ou non ionique.
7. Précurseur de plaque d'impression lithographique thermosensible selon la revendication
6, caractérisé en ce que le monomère hydrophile est choisi parmi des oxydes d'alkylène, de l'alcool vinylique,
de l'acide acrylique, de l'acide méthacrylique, de l'acide maléique, de l'acide itaconique,
de l'acide crotonique, de l'acide fumarique, du méthacrylate d'hydroxyalkyle, de l'acrylate
d'hydroxyalkyle, de la vinylpyrolidone, des acrylamides, des méthacrylamides, de l'acide
vinylphosphonique, de l'acide styrènesulfonique, de l'oxyde de méthyle et de vinyle,
du sulfonate de vinyle, du méthacrylate de sulfoéthyle, de l'acide 2-acrylamido-2-méthyl-1-propanesulfonique
ou des dérivés protonés ou alkylés de pyridine vinylique, d'imidazole vinylique ou
de diéthylamine de N-vinyle.
8. Précurseur de plaque d'impression lithographique thermosensible selon l'une quelconque
des revendications 1 à 3 et 5, caractérisé en ce que le groupe latéral polymère hydrophobe contient des unités monomères hydrophobes choisies
parmi des siloxanes, de l'éthylène de perfluoroalkyle, des acrylates d'alkyle, des
acrylates d'alkyle fluorés, des monomères chlorés ou bromés, des esters vinyliques,
des éthers vinyliques, de l'éthylène, de l'isoprène, du butadiène, du styrène, des
dérivés de styrène, des méthacrylates d'alkyle, des méthacrylates d'allyle, des méthacrylates
d'alkyle fluorés, de l'acrylonitrile, du méthacrylonitrile, des acrylamides de N-alkyle
et des méthacrylamides de N-alkyle.
9. Précurseur de plaque d'impression lithographique thermosensible selon la revendication
7, caractérisé en ce que les unités monomères hydrophiles sont de l'oxyde d'éthylène ou un mélange d'oxyde
d'éthylène et d'oxyde de propylène.
10. Précurseur de plaque d'impression lithographique thermosensible selon la revendication
8, caractérisé en ce que les unités monomères hydrophobes sont du diméthylsiloxane ou du méthylphénylsiloxane.
11. Précurseur de plaque d'impression lithographique thermosensible selon l'une quelconque
des revendications précédentes, caractérisé en ce que le revêtement peut être commuté d'hydrophile en hydrophobe ou d'hydrophobe en hydrophile
par chauffage et/ou par exposition à des rayons infrarouges.
12. Un procédé pour la confection d'un précurseur de plaque d'impression lithographique
thermosensible, comprenant l'étape dans laquelle un revêtement contenant un copolymère
est appliqué sur un support ayant une surface hydrophile ou sur un support revêtu
d'une couche hydrophile, ledit copolymère contenant une multitude d'unités structurales
X comprenant un groupe latéral polymère hydrophile et une multitude d'unités structurales
Y comprenant un groupe latéral polymère hydrophobe.
13. Un procédé pour la confection d'une plaque d'impression lithographique thermosensible
sans développement humide, comprenant les étapes suivantes :
(i) la mise à disposition d'un précurseur de plaque d'impression lithographique selon
l'une quelconque des revendications 1 à 10 et
(ii)le chauffage et/ou l'irradiation infrarouge sous forme d'image du revêtement.
14. Un procédé servant à augmenter l'angle de contact d'un revêtement avec de l'eau, comprenant
les étapes suivantes :
(i) la mise à disposition d'un précurseur de plaque d'impression lithographique selon
l'une quelconque des revendications 1 à 10 et
(ii)le chauffage sous forme d'image du revêtement par du rayonnement infrarouge et/ou
de la chaleur.
15. Un procédé servant à modifier la surface d'une plaque d'impression lithographique,
dans lequel la surface hydrophile est rendue hydrophobe par chauffage ou par irradiation
infrarouge d'un précurseur de plaque d'impression lithographique thermosensible selon
la revendication 1.