HK1079578B

HK1079578B - On-press developable ir sensitive printing plates using binder resins having polyethylene oxide segments

Info

Publication number: HK1079578B
Application number: HK05111672.7A
Authority: HK
Inventors: 黄建兵; H．M．芒尼利; S．萨莱亚; S．P．帕普帕斯
Original assignee: 伊士曼柯达公司
Priority date: 2002-04-10
Filing date: 2003-04-10
Publication date: 2009-11-27

Description

INFRARED SENSITIVE PRINTING PLATE DEVELOPABLE ON PRESSURE USING BINDER RESIN HAVING POLYETHYLENE OXIDE FRAGMENT

Technical Field

The present invention relates to a negative printing plate which can be developed by exposure to ultraviolet, visible or infrared radiation under pressure. In particular, the invention relates to printing plates comprising a polymeric binder comprising polyoxyethylene segments.

Background

Radiation-sensitive compositions are commonly used to prepare high-efficiency printing plate precursors. There are two main ways to improve the properties of radiation-sensitive compositions and of corresponding printing plate precursors. The first approach consists in improving the properties of the radiation-sensitive component (often a negative diazo resin or a photoinitiator) in the composition. Another approach consists in modifying the physical properties of the radiation-sensitive layer using new polymeric compounds ("binders").

Recent advances in the field of printing plate precursors are radiation-sensitive compositions which can be imagewise exposed by means of a laser or laser diode. This type of exposure does not require film as an intermediate information carrier, since the laser can be controlled by a computer.

High efficiency lasers or laser diodes for commercially available image modulators emit light at wavelengths of 800-850nm and 1060-1120nm, respectively. Thus, the printing plate precursors or the initiator systems contained therein, which are to be imagewise exposed by means of the image modulator, have to be sensitive in the vicinity of this IR range. These printing plate precursors can then be operated substantially under daylight conditions which significantly facilitate their production and processing.

There are two possible methods of making printing plates using radiation-sensitive compositions. For the case of a cathode printing plate, a radiation-sensitive composition is used in which the exposed areas harden after imagewise exposure. In this development step, only the unexposed areas are removed from the substrate. For the case of an anodic printing plate, a radiation-sensitive composition is used whose exposed areas dissolve in a given developer more quickly than the unexposed areas. This process is called photosolubilisation.

The cathode work plate typically requires a pre-heating step after imagewise exposure, as described in EP0672544, EP0672954, and in US 5,491,046 and EP 0819985. These plates require a very narrow temperature range of the pre-heating step, which only partially crosslinks the image layer. In order to meet the current standards for printable copy number and resistance to press chamber actives, an additional heating step, herein referred to as a post-bake step, is performed during further cross-linking of the image layer.

U.S. Pat. No. 4,997,745 describes photosensitive compositions comprising a dye absorbing between 300 and 900nm and a trihalomethyl-s-triazine compound.

In US 5,496,903 and DE 19648313, photosensitive compositions are described which, in addition to dyes which absorb in the infrared range, also contain borate coinitiators; and further describes the use of halogenated s-triazines as additional coinitiators.

Other compositions which can be photopolymerized with an initiator system are described in U.S. Pat. No. 5,756,258, U.S. Pat. No. 5,545,676, U.S. Pat. No. 5,914,215, JP-11-038633, JP-09-034110, U.S. Pat. No. 5,763,134 and EP 0522175.

US patent US 6,245,486 discloses radiation-sensitive printing plates comprising a plate that can be developed when pressed. However, this patent requires a composition having an infrared ablatable masking layer on an ultraviolet addressable, pressure developable, free radically polymerizable negative layer.

U.S. Pat. No. 6,245,481 discloses infrared ablatable, ultraviolet photopolymerizable two layer compositions which require an infrared exposure followed by ultraviolet flood radiation.

US patent US 5,599,650 discloses uv-addressable, pressure developable negative-working printing plates based on free radical polymerization. This patent requires a radical quencher polymer, particularly one containing nitroxide groups, in the overcoat layer to facilitate developability.

U.S. Pat. No. 6,071,675 discloses a printing plate similar to U.S. Pat. No. 5,599,650. It is desirable to add dispersed solid particles to the imaging layer to improve developability or reduce tackiness upon application of pressure.

US 6,309,792 and WO00/48836 describe infrared-sensitive compositions comprising a polymeric binder, a free-radically polymerizable system and a specific initiator system. The composition of WO00/48836 requires a preheating step after exposure to fully harden the composition. The printing plate precursor must be developed with an aqueous developer.

U.S. application serial No. 09/832989 (attorney docket No. KPG 1109) describes infrared-sensitive compositions that contain leuco dyes in addition to the ingredients described in U.S. patents US 6,309,792 and WO 00/48836. U.S. application serial No. 09/832989 requires a pre-heat step after the infrared exposure and aqueous development steps for the development process.

US patent US 5,204,222 teaches a composition comprising a polymerizable component and a polymeric binder, said binder comprising a polyurethane backbone. The side chains of the polymeric binder do not contain polyoxyethylene chains.

US patent US 5,800,965 teaches a composition suitable for use in a printing blanket comprising a polyethylene glycol monomer as a polymerizable component.

U.S. patent 6,037,102 also relates to flexographic printing plates and teaches photopolymerizable compositions comprising graft copolymers with polyvinyl alcohol grafts on a Polyoxyethylene (PEO) backbone polymer.

EP 1,117,005 discloses photopolymerizable compounds which contain polyoxyethylene chains with 1 to 10 ethylene oxide units. The invention is exemplified by the use of a polymer having 1 ethylene oxide unit. With more than 10 ethylene oxide units, the resolution and water resistance of the hardened product are reduced. Binder resins with sufficiently long PEO segments are not disclosed in the present invention.

Pending U.S. patent application serial No. 09/826,300 discloses graft copolymers containing polyoxyethylene side chains, but does not teach compositions containing polymerizable components or initiators. These side chains may also include hydrophobic segments between the polyoxyethylene segments and the backbone, as well as hydrophobic segments at the ends of the polyoxyethylene side chains.

Pending U.S. patent application serial No. 10/066,874 (attorney docket number KPG 1164) discloses polyalkylene ether polymers and copolymers comprising block copolymers of polyoxyethylene and polyoxypropylene. However, the polyalkylene ether polymers and copolymers disclosed in this co-pending application do not provide sufficient differences in developability of the unexposed areas and durability of the exposed image areas.

None of the above patents or patent applications disclose the polymerizable compositions of the present invention containing a binder resin with PEO segments.

There is therefore a need in the art for a printing plate and method of making the same that does not require a pre-heat step or a development step and is met by the present invention. As a result of extensive research, it has been found that polymerizable compositions containing certain polymeric binders with Polyoxyethylene (PEO) segments are readily developable in aqueous developers, including developability with jet liquid and printing inks under pressure. Moreover, after imagewise exposure to electromagnetic radiation in the ultraviolet, visible or infrared spectral region, the exposed regions are resistant to developability and serve as durable ink-receiving image areas, without the need for a pre-development heating step. It has therefore been unexpectedly discovered that certain polymeric binders with PEO segments improve the contrast between exposed and unexposed areas by facilitating the developability of the unexposed areas, while improving the durability of the exposed image areas.

Summary of The Invention

Accordingly, it is an object of the present invention to provide a polymerizable composition comprising a polymerizable compound and a polymeric binder comprising polyoxyethylene segments.

It is another object of the present invention to provide an imageable element comprising: (a) a substrate, and (b) a polymerizable composition coated on said substrate, the composition comprising (i) a polymerizable compound and (ii) a polymeric binder comprising polyoxyethylene segments, wherein said polymeric binder is selected from the group consisting of at least one graft copolymer comprising a backbone polymer and polyoxyethylene side chains, a block copolymer having at least one polyoxyethylene block and at least one non-polyoxyethylene block, and combinations thereof. Preferably, the imageable element is exposed to radiation of one of ultraviolet, visible, and infrared.

It is another object of the present invention to provide a method of making a negative-working printing plate that is developable under pressure, the method comprising: (a) providing a substrate; (b) applying a negative layer comprising a composition on said substrate, wherein said composition comprises a polymerizable compound and a polymeric binder comprising polyoxyethylene segments; (c) irradiating the image with one of ultraviolet rays, visible rays and infrared rays; and (d) pressure development, wherein the method does not comprise a separate development step.

The present invention enables the preparation of flexographic printing plates that are developable under pressure or water developable, which can be imaged by a UV exposure frame, infrared laser plate conditioner, and computer to plate conditioner of visible light. The invention also provides laser addressable, digitally imaged printing plate precursors that are developable upon application of pressure, thus avoiding a separate development step.

Brief Description of Drawings

Figure 1 shows an electron microscope (SEM) scan of the coating of example 7 discussed herein.

Figure 2 shows an electron microscope (SEM) scan of the coating of example 9 discussed herein.

Figure 3 shows an electron microscope (SEM) scan of the coating of example 12 discussed herein.

Fig. 4 shows an electron microscope (SEM) scan of the coating of example 18 discussed herein.

Fig. 5 shows an electron microscope (SEM) scan of the coating of example 19 discussed herein.

Detailed Description

The polymerizable compounds present in the compositions of the invention preferably contain polymerizable groups selected from: an addition polymerizable ethylenically unsaturated group, a crosslinkable ethylenically unsaturated group, a ring-opening polymerizable group, an azide group, an aryldiazonium salt group, an aryldiazonium sulfonate group, and combinations thereof.

The addition polymerizable ethylenically unsaturated groups can be polymerized by free radical polymerization, cationic polymerization, or a combination thereof. The free-radically addition polymerizable ethylenically unsaturated groups are preferably selected from the group consisting of methacrylate groups, acrylate groups, and combinations thereof. The cationic addition polymerizable ethylenically unsaturated groups are preferably selected from the group consisting of vinyl ethers, vinyl aromatic compounds, including styrene and alkoxystyrene derivatives, and combinations thereof.

The crosslinkable ethylenically unsaturated group is preferably selected from the group consisting of a dimethylmaleimide group, a chalcone group and a cinnamate group.

The ring-opening polymerizable group is preferably selected from the group consisting of epoxides, propylene oxide (oxyethane), and combinations thereof.

The polymerizable compounds of the present invention are present in an amount sufficient to render the composition insoluble in an aqueous developer after radiation exposure. The weight ratio of polymerizable compound to polymeric binder is in the range of about 5:95 to about 95:5, preferably in the range of about 10:90 to about 90:10, more preferably in the range of about 20:80 to about 80:20, and most preferably in the range of about 30:70 to about 70: 30.

The polymerizable composition preferably comprises a free radical addition polymerizable composition comprising a polymerizable ethylenically unsaturated compound and a photoinitiator system that generates initiating free radicals. The polymerizable composition may also contain a copolymerizable compound comprising at least two thiol groups. Photoinitiating systems which are active in the ultraviolet, visible and/or infrared spectral regions for electromagnetic radiation may be used, corresponding to the spectral range of about 300-1400 nm. These photoinitiator systems include, for example, either trichloromethyltriazines alone or trichloromethyltriazines in combination with photosensitizers as described in U.S. Pat. No. 4,997,745; diaryliodonium salts and photosensitizers as described in U.S. patent 5,546,258; spectral sensitizers and trichloromethyl triazines for visible light activation, as described in U.S. patent 5,599,650; 3-ketocoumarins and polycarboxylic acid co-initiators for ultraviolet and visible light activation, such as anilino-N, N-diacetic acid and second co-initiators, such as diaryliodonium salts, cyclopentadienyltitanates, haloalkyl triazines, hexaarylbisimidazoles, borates and photo-oxidizers containing heterocyclic nitrogen atoms substituted with alkoxy and acyloxy groups, as described in U.S. patent No. 5,942,372; cyanine dyes, diaryliodonium salts, and coinitiators having a carboxylic acid group linked via a methylene group to N, O or an S group directly linked to an aromatic ring, as described in us patent 5,368,990; cyanine dyes for infrared radiation activation, together with trichloromethyl triazine and organic boron salts, as described in us patent 5,496,903; infrared radiation absorbers, a compound capable of generating initiating free radicals, include trichloromethyltriazines and azinium compounds and polycarboxylic acid coinitiators having a carboxylic acid group attached via a methylene group to N, O or an S group directly attached to an aromatic ring, as described in U.S. patent 6,309,792.

Preferred photoinitiator systems include ultraviolet, visible or infrared absorbers, electron acceptors capable of generating initiating radicals, and coinitiators capable of donating electrons and/or hydrogen atoms and/or capable of forming initiating radicals. The amount of radiation absorber is that amount which renders the composition insoluble in an aqueous developer after radiation exposure. Preferably, the radiation absorber is present at a concentration that imparts about 0.05 to 3mol 1^-1cm^-1Preferably about 0.1 to 1.5mol 1^-1cm^-1More preferably 0.3 to 1.0mol 1^-1cm^-1Within the molar absorbance range of (a).

Preferred IR absorbers for light/heat activation are squarylium dyes, croconium salt dyes, triarylamine dyes, thiazolium dyes, indolium dyes, oxaxolium dyes, cyanine and merocyanine dyes, polyaniline dyes, polypyrrole dyes, polythiophene dyes, chalcogeno-pyrano-arylene and bis (chalcogeno-pyrano) polymethine dyes, indolizine oxide dyes, pyrylium dyes and phthalocyanine pigments. Other useful types include azulenium and xanthene dyes, as well as carbon black, metal carbides, borides, nitrides, carbonitrides and bronze-structured oxides. Cyanine dyes are particularly preferred.

In another embodiment, the polymerizable composition preferably comprises an aryl diazonium salt or a condensate of an aryl diazonium salt and a condensable compound. The condensable compound is preferably selected from the group consisting of aldehydes, dimethoxymethyl diphenyl ether, and mixtures thereof. The polymerizable composition comprising the condensate of an aryl diazonium salt preferably further comprises a co-reactive binder.

The aryldiazonium salt condensate polymerizable composition may also comprise a free radical addition polymerizable composition comprising a polymerizable ethylenically unsaturated compound and a photoinitiator system that generates initiating free radicals, as described above. These compositions are known as diazo photopolymer blend compositions.

The polymerizable composition of the present invention comprises a polymerizable compound and a polymeric binder comprising polyoxyethylene segments, wherein the polymeric binder is selected from the group consisting of graft copolymers having a backbone polymer and Polyoxyethylene (PEO) side chains and block copolymers having PEO and non-PEO blocks.

Preferably the graft and block copolymers are amphiphilic, which implies transparency including both hydrophilic and hydrophobic segments. These amphiphilic copolymers also tend to be surface active. These PEO fragments are hydrophilic. While not being bound by any theory, the combination of hydrophobic and hydrophilic segments is believed to be important to enhance the difference between exposed and unexposed regions.

The glass transition temperature Tg of the polymeric binders useful in the present invention is preferably in the range of from about 35 to about 220 ℃, more preferably in the range of from about 45 to about 140 ℃, and most preferably in the range of from about 50 to about 130 ℃. Polymeric binders having Tg values within the above specified ranges are solid and preferably non-elastomeric. These polymeric binders may be crosslinked, but are preferably non-crosslinked. The glass transition temperature Tg of the backbone polymer of the graft copolymer and the non-PEO blocks of the block copolymer is preferably in the range of 40 to about 220 ℃, more preferably in the range of about 50 to about 140 ℃, and most preferably in the range of about 60 to about 130 ℃.

Preferably, the graft and block copolymers have a number average molecular weight in the range of about 2,000 to about 2,000,000. Preferably, the number average molecular weight (Mn) of the PEO fragments is in the range of about 500 to about 10,000, more preferably in the range of about 600 to about 8,000, and most preferably in the range of about 750 to about 4,000. When the Mn value is less than about 500, there are not enough hydrophilic segments to suitably improve the aqueous developability. However, the ink receptivity of the image area tends to decrease as the Mn value of the polyoxyethylene segment (close to 10,000) increases.

The amount of PEO segments in the graft copolymer is in the range of about 0.5 to about 60 weight percent, preferably in the range of about 2 to about 50 weight percent, more preferably in the range of about 5 to about 40 weight percent, and most preferably in the range of about 5 to about 20 weight percent. The amount of PEO segments in the block copolymer is in the range of about 5 to about 60 weight percent, preferably in the range of about 10 to about 50 weight percent, and more preferably in the range of about 10 to about 30 weight percent. At low PEO segment content in the graft and block copolymers, developability tends to decrease, while at high levels, ink receptivity in the image areas tends to decrease.

The amount of the polymeric binder is sufficient to enable the photopolymerizable composition to be dissolved or dispersed in an aqueous developer. Preferably, the amount of polymeric binder is in the range of about 10% to 90% by weight of the composition, more preferably in the range of about 30% to 70% by weight. The aqueous developability tends to increase with increasing PEO flake content in the polymeric binder. However, at too high a PEO content, the ink receptivity of the image area tends to decrease.

Preferably, the graft copolymer has a hydrophobic polymer backbone and a plurality of pendant groups represented by the formula:

-Q-W-Y

wherein Q is a bifunctional linking group; w is selected from the group consisting of a hydrophilic segment and a hydrophobic segment; y is selected from the group consisting of a hydrophilic segment and a hydrophobic segment; provided that when W is a hydrophilic segment, Y is selected from the group consisting of a hydrophilic segment and a hydrophobic segment; and Y is a hydrophilic segment when W is hydrophobic.

The term "graft" polymer or copolymer in the context of the present invention refers to a polymer having as side chains a group with a molecular weight of at least 200. These graft copolymers may be obtained, for example, by anionic, cationic, nonionic or free-radical grafting methods, or they may be obtained by polymerizing or copolymerizing monomers containing these groups. The term "polymer" in the context of the present invention refers to high and low molecular weight polymers, including oligomers, and includes homopolymers and copolymers. The term "copolymer" refers to a polymer derived from two or more different monomers. The term "backbone" in the context of the present invention refers to the chain of atoms in a polymer to which a plurality of pendant groups are attached. An example of such a backbone is an "all carbon" backbone obtained by polymerizing ethylenically unsaturated monomers.

The graft copolymer preferably comprises a repeating unit each unit of which is represented by the following formula

Wherein R is¹And R²Each independently selected from H, alkyl, aryl, aralkyl, alkaryl, COOR⁵，R⁶CO, halogen and cyano;

q is selected from:

wherein R is³Selected from H and alkyl; r⁴Selected from the group consisting of H, alkyl, halo, cyano, nitro, alkoxy, alkoxycarbonyl, acyl, and combinations thereof;

w is selected from the group consisting of a hydrophilic segment and a hydrophobic segment;

y is selected from the group consisting of a hydrophilic segment and a hydrophobic segment;

z is selected from the group consisting of H, alkyl, halogen, cyano, acyloxy, alkoxy, alkoxycarbonyl, hydroxyalkoxycarbonyl, acyl, aminocarbonyl, aryl, and substituted aryl;

with the proviso that when W is a hydrophilic segment, Y is selected from the group consisting of a hydrophilic segment and a hydrophobic segment, and with the further proviso that when W is hydrophobic, Y is a hydrophilic segment.

In one embodiment, the graft copolymer of the present invention comprises a backbone segment that is predominantly hydrophobic and a branch segment that is predominantly hydrophilic.

In a second embodiment, the graft copolymer includes a backbone segment that is predominantly hydrophobic and a branch segment that includes both hydrophobic and hydrophilic segments.

The hydrophilic segment in W in the graft copolymer of the present invention is preferably a segment represented by the formula:

or

Wherein R is⁷、R⁸、R⁹And R¹⁰Each is hydrogen; r³May be H or alkyl; and n is from about 12 to about 250. The hydrophobic moiety in W may be-R¹²-、-O-R¹²-0-，-R³N-R¹²-NR³-、-OOC-R¹²-O-or-OOC-R¹²-O-in which each R¹²Alkylene of 6 to 120 carbon atoms, haloalkylene of 6 to 120 carbon atoms, arylene of 6 to 120 carbon atoms, alkarylene of 6 to 120 carbon atoms or aralkylene of 6 to 120 carbon atoms, which may be independently straight, branched or cyclic; and R is³May be H or alkyl.

The hydrophilic segment in Y may be H, R¹⁵、OH、OR¹⁶、COOH、COOR¹⁶、O₂CR¹⁶A fragment represented by the formula:

or

Wherein R is⁷、R⁸、R⁹And R¹⁰Each is hydrogen; r³May be H or alkyl; wherein R is¹³、R¹⁴、R¹⁵And R¹⁶Each independently may be H or alkyl of 1-5 carbon atoms, and n is from about 12 to about 250. The hydrophobic moiety in Y may be a linear, branched OR cyclic alkyl group of 6 to 120 carbon atoms, a haloalkyl group of 6 to 120 carbon atoms, an aryl group of 6 to 120 carbon atoms, an alkylaryl group of 6 to 120 carbon atoms, an arylalkyl group of 6 to 120 carbon atoms, OR¹⁷、COOR¹⁷Or O₂CR¹⁷Wherein R is¹⁷Is an alkyl group of 6 to 20 carbon atoms.

In a preferred embodiment, the graft copolymer comprises repeating units represented by the formula:

wherein R is¹And R²Each independently of the others being H, alkyl, aryl, aralkyl, alkaryl, COOR⁵、R⁶CO, halogen or cyano;

wherein Q may be one of the following formulas:

and wherein R³May be H or alkyl;R⁴may independently be H, alkyl, halo, cyano, nitro, alkoxy, alkoxycarbonyl, acyl, or combinations thereof,

z is selected from H, alkyl, halogen, cyano, acyloxy, alkoxy, alkoxycarbonyl, hydroxyalkoxycarbonyl, acyl, aminocarbonyl, aryl and substituted aryl, wherein the substituent in the above substituted aryl may be alkyl, halogen, cyano, alkoxy or alkoxycarbonyl, and the alkyl group is preferably an alkyl group of 1 to 22 carbon atoms;

The segment W may be a hydrophilic segment or a hydrophobic segment, wherein the hydrophilic segment may be a segment represented by the following formula:

or

Wherein R is⁷，R⁸，R⁹And R¹⁰Each is hydrogen; r³May be H and alkyl; and n is from about 12 to about 250. The hydrophobic moiety may be-R¹²-，-O-R¹²-O-、-R³N-R¹²-NR³-、-OOC-R¹²-O-or-OOC-R¹²-O-in which each R¹²May independently be a linear, branched or cyclic alkylene group of 6 to 120 carbon atoms, a halogenated alkylene group of 6 to 120 carbon atoms, an arylene group of 6 to 120 carbon atoms, an alkylene group of 6 to 120 carbon atomsAryl or aralkylene of 6 to 120 carbon atoms; r³May be H or alkyl.

Y may be a hydrophilic or hydrophobic moiety, wherein the hydrophilic moiety may be H, R¹⁵、OH、OR¹⁶、COOH、COOR¹⁶、O₂CR¹⁶A fragment represented by the formula:

or

Wherein R is⁷，R⁸，R⁹And R¹⁰Each is hydrogen; r³May be H and alkyl; wherein each R¹³、R¹⁴、R¹⁵And R¹⁶May be H or alkyl of 1-5 carbon atoms, and n is from about 12 to about 250. The hydrophobic moiety in Y may be a linear, branched OR cyclic alkyl group of 6 to 120 carbon atoms, a haloalkyl group of 6 to 120 carbon atoms, an aryl group of 6 to 120 carbon atoms, an alkylaryl group of 6 to 120 carbon atoms, an arylalkyl group of 6 to 120 carbon atoms, OR¹⁷、COOR¹⁷Or 0₂CR¹⁷Wherein R is¹⁷And may be an alkyl group of 6 to 20 carbon atoms.

In another preferred embodiment, fragment W-Y may be represented by the formula:

-(OCH₂CH₂)_n-OCH₃

wherein n is from about 12 to about 75. In this preferred embodiment, the graft copolymer has, for example, a repeating unit represented by the following formula:

wherein n is from about 12 to about 75. More preferably, n has an average value of about 45.

In another preferred embodiment, the graft copolymer comprises a repeat unit represented by the formula:

wherein n is from about 12 to about 75, more preferably, n has an average value of about 45.

In a preferred embodiment, the backbone polymer in the graft copolymer of the present invention comprises monomer units selected from the group consisting of: acrylates, methacrylates, styrene, acrylic acid, methacrylic acid, and combinations thereof. More preferably, these monomer units are methyl methacrylate, allyl methacrylate, or a combination thereof.

The graft copolymer having a hydrophobic segment and/or a hydrophilic segment may be prepared by a method comprising the steps of:

(A) contacting the following components to produce a polymerizable graft copolymer:

(i) a compound represented by the formula:

H-W-Y

wherein W is selected from the group consisting of a hydrophilic segment and a hydrophobic segment, and Y is selected from the group consisting of a hydrophilic segment and a hydrophobic segment, with the proviso that when W is a hydrophilic segment, Y is selected from the group consisting of a hydrophilic segment and a hydrophobic segment, and with the further proviso that when W is hydrophobic, Y is a hydrophilic segment, and

(ii) a polymerizable monomer selected from the group consisting of compounds represented by the following formulae:

and

wherein each R¹Independently selected from H, alkyl, aryl, aralkyl, alkaryl, COOR⁵、R⁶CO, halogen and cyano; r⁴Selected from the group consisting of H, alkyl, halo, cyano, nitro, alkoxy, alkoxycarbonyl, acyl, and combinations thereof; and X is glycidyloxy or a leaving group selected from: halogen, alkoxy or aryloxy groups, thereby producing a polymerizable grafting monomer; and

(B) copolymerizing the polymerizable grafting monomer and one or more comonomers at a temperature and for a time sufficient to produce said graft copolymer. The contacting step is carried out in the presence of a catalyst, if desired.

Preferably, the comonomer is one or more of the following monomers: styrene, substituted styrenes, alpha-methylstyrene, acrylates, methacrylates, acrylonitrile, acrylamide, methacrylamide, vinyl halides, vinyl esters, vinyl ethers, and alpha-olefins.

The preferred polymerizable monomer may be any monomer capable of reacting with H-W-Y, and includes, for example, the following polymerizable monomers: m-isopropenyl-alpha, alpha-dimethylbenzyl isocyanate, acryloyl chloride and methacryloyl chloride. The reaction is generally carried out in the presence of a catalyst, which is preferably a base, a tin compound or a mixture thereof. In allowing the reaction of the acid catalyst, an acid catalyst such as a lewis acid or a albumin acid may be used.

Preferably, the compound represented by the formula H-W-Y may be one or more compounds represented by the following formula:

and

wherein R is⁷，R⁸，R⁹And R¹⁰Each is hydrogen; r³May be H or alkyl; y may be alkyl, acyloxy, alkoxy or carboxylate; and n is from about 12 to about 250.

The graft copolymer is typically obtained by free radical copolymerization of the graft monomer and comonomer, preferably in a weight ratio of comonomer to graft monomer of from about 99:1 to about 45: 55.

Alternatively, the graft copolymer may be prepared by: the polymerizable monomers of the present invention are first copolymerized with one or more comonomers at a temperature and for a time sufficient to produce a graftable copolymer, and the group-W-Y is then grafted onto the graftable copolymer. This grafting can be accomplished by contacting the above graftable copolymer with a compound represented by the formula:

H-W-Y

wherein W can be a hydrophilic or hydrophobic segment and Y can be a hydrophilic or hydrophobic segment, with the proviso that when W is a hydrophilic segment, Y is a hydrophilic or hydrophobic segment, and with the further proviso that when W is hydrophobic, Y is a hydrophilic segment.

The graft copolymers of the present invention may be prepared by reacting hydroxy-functional or amine-functional polyethylene glycol monoalkyl ethers with polymers having co-reactive groups including acid chloride, isocyanate and anhydride groups. The side chains may also include a hydrophobic segment between the PEO segment and the backbone, and a hydrophobic segment at the end of the PEO side chain. Other methods of making the graft copolymers of the present invention include those described in U.S. patent application serial No. 09/826,300, which is incorporated herein by reference.

The backbone polymer in the graft copolymer may be an addition polymer or a condensation polymer. The addition polymer is preferably prepared from: acrylates and methacrylates, acrylic acid and methacrylic acid, acrylamides and methacrylamides, acrylonitrile and methacrylonitrile, styrene, vinyl phenol, and combinations thereof. More preferably, the addition polymer is prepared from: styrene, methyl methacrylate, allyl acrylate and methacrylate, acrylic acid and methacrylic acid, and combinations thereof. Preferred condensation polymers are polyurethanes, epoxies, polyesters, polyamides and phenolic polymers, including phenol/formaldehyde and pyrogallol/acetone polymers.

The polymeric binder may also comprise a mixture of graft copolymers, wherein each graft copolymer comprises a backbone polymer and polyoxyethylene side chains. The backbone polymer of each graft copolymer is independently selected from the group consisting of addition polymers and condensation polymers. Preferred addition polymers are homopolymers and copolymers of monomers independently selected from the group consisting of: acrylates and methacrylates including allyl acrylate and methacrylate, acrylic acid and methacrylic acid, acrylamides and methacrylamides, acrylonitriles and methacrylonitriles, styrene, vinyl phenol, and combinations thereof. Preferred condensation polymers are independently selected from polyurethanes, epoxies, polyesters, polyamides, and phenolic polymers, including phenol/formaldehyde and pyrogallol/acetone condensation polymers.

The block copolymers of the present invention can be prepared by conventional procedures including anionic, cationic and free radical polymerization. Atom Transfer Radical Polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization can be particularly convenient methods. PEO block copolymers can be conveniently made by the ATRP method, such as M.Ranger et al, "From well-defined diblock polymers prepared by a laboratory transfer method to supra, Journal of Polymer Science, Part A: polymer Chemistry, Vol.39(2001), pp.3861-74.

At least one non-polyoxyethylene block in the block copolymer may be an addition polymer or a condensation polymer. These addition polymers are preferably homopolymers or copolymers of monomers selected from: acrylates and methacrylates including allyl acrylate and methacrylate, acrylic acid and methacrylic acid, acrylamides and methacrylamides, acrylonitrile and methacrylonitrile, styrene, and vinyl phenol. Preferred condensation polymers are polyurethanes, epoxies, polyesters, polyamides and polyureas.

In a preferred embodiment of the present invention, at least one non-polyoxyethylene block of the block copolymer does not comprise polyoxyalkylene segments. In another preferred embodiment, the at least one non-polyoxyethylene block comprises a homopolymer or a copolymer of monomers selected from the group consisting of: methyl methacrylate, allyl acrylate and methacrylate, acrylic and methacrylic acid, styrene, vinyl phenol, and combinations thereof.

The polymeric binder may comprise a mixture of block copolymers, wherein each block copolymer comprises at least one PEO block and at least one non-PEO block, as described above. In addition, the polymeric binder may include a mixture of graft and block copolymers, as described above.

In another embodiment of the present invention, the polymerizable composition comprises discrete particles. These particles may comprise a mixture of copolymers containing various possible combinations of monomer units. Preferably, these discrete particles are particles of a polymeric binder suspended in the polymerizable composition. In a particularly preferred embodiment, the polymeric binder comprises at least one graft copolymer. The diameter of these particles in the suspension may be in the range of about 60nm to about 300 nm. The presence of these discrete particles tends to improve the developability of the unexposed areas.

The substrate of the imageable element is typically an aluminum sheet. However, other materials commonly known to those skilled in the art may also be used. Suitable substrates include any sheet material conventionally used in the preparation of offset printing plates, including metals such as aluminum sheets, papers coated on one or both sides with an alpha-olefin polymer such as polyethylene; films such as cellulose acetate film, polyvinyl acetal film, polystyrene film, polypropylene film, polyester film such as polyethylene terephthalate film, polyamide film, nitrocellulose film, polycarbonate film, polyvinyl chloride film; composite films such as polyester, polypropylene or polystyrene films coated with polyethylene films; metallized paper or film; metal/paper laminates, and the like.

The surface of the plastic film may be treated with surface treatment techniques known in the art to improve adhesion between the substrate and the organic coating.

The preferred substrate is an aluminum sheet. The aluminum sheet surface may be treated with metal polishing techniques known in the art, including physical roughening, electrochemical roughening, chemical roughening, anodization, and silicate sealing, among others. If the surface is roughened, the average roughness (Ra) is preferably in the range of 0.1-0.8 μm, more preferably in the range of about 0.1 to about 0.4 μm. The preferred thickness of the aluminum sheet is in the range of about 0.005 inch to about 0.020 inch. Preferred substrates are electrochemically grained (grained) and anodized aluminum, such as is commonly used in offset printing plates.

The anode pore size for sulfuric acid anodization is typically less than 20nm, while the anode pore size for phosphoric acid anodization is typically greater than 30 nm. The use of phosphoric acid anodized large anode pore substrates is preferred over sulfuric acid anodized substrates. Other conventional anodization methods may also be used to prepare the anodized substrates of the invention, particularly methods that include the creation of anode pore sizes larger than those created by sulfuric acid anodization.

The polymeric binder may be applied to the substrate in a solution or dispersion of the coating solution of the imaging layer by any suitable coating method. An exemplary such method is to dissolve the graft copolymer in a solvent immiscible with organic water, disperse the resulting solution into an aqueous medium, apply the resulting dispersion to a substrate, and then evaporate off the solvent. Is suitable forAfter drying, the coating weight of the layer is preferably from about 0.2 to about 5.0g/m²More preferably in the range of about 0.7 to about 2.5g/m²Within the range of (1).

Preferably, the imaging is performed using an infrared laser and a radiation absorber that absorbs IR radiation. However, UV and visible laser imaging may also be used with appropriate radiation absorbers. Thus, the imageable compositions of this invention also include radiation absorbers that can be used as sensitizers to promote polymerization or as materials capable of converting electromagnetic radiation into heat.

The imageable element can also include a topcoat layer. One possible function of the topcoat is to act as an oxygen barrier layer by including an oxygen impermeable compound. The term "oxygen-impermeable compound" refers to a compound that prevents diffusion of oxygen from the atmosphere into the layer during the lifetime of radicals generated by IR exposure. The topcoat layer should be soluble, dispersible, or at least permeable to the developer. Other possible functions of the topcoat include:

(1) preventing damage, such as scratching, of the surface layer during handling prior to imagewise exposure;

(2) preventing damage to the surface of the imagewise exposed area, e.g. over exposure may lead to partial ablation; and

(3) the developability of the unexposed areas is promoted.

Preferably, the imagewise exposure step of the process of the invention is preferably with radiation in the range from about 300 to about 1400nm, preferably from about 350 to about 900 nm.

Preferably, the development with the aqueous developer does not comprise a separate development step. The printing plate can be mounted by direct pressure, wherein the non-exposed areas are removed by fountain solution (fountain solution) and/or ink, thereby avoiding a separate development step. Note that the plate for pressure development may also be developed using a suitable aqueous developer in a conventional manner. The plates disclosed herein include plates that are developable when pressed and plates that are otherwise required for the development process.

The aqueous developer composition depends on the nature of the graft copolymer composition. Conventional components of aqueous developers include surfactants, chelating agents such as salts of ethylenediaminetetraacetic acid, organic solvents such as benzyl alcohol, and alkali components such as inorganic silicates, organosilicates, hydroxides, and bicarbonates. The pH of the aqueous developer is preferably in the range of about 5 to about 14, depending on the nature of the graft copolymer composition.

After development, a post bake may optionally be employed to increase the pressing time.

In addition to the thermally imageable layer, the thermally imageable element can have other layers, such as an undercoating. Possible functions of the inner coating include:

(1) improving the developability of the imagewise unexposed areas; and

(2) the imagewise exposed areas act as a heat-insulating layer.

Such a thermally insulating polymer layer additionally prevents rapid dissipation of heat, for example via a thermally conductive aluminum substrate. This enables efficient thermal imaging over the entire thermally imageable layer, particularly in the underlying portions. In view of these functions, the undercoat layer should be soluble or at least dispersible in the developer and preferably have a relatively low thermal conductivity.

The invention is further illustrated by the following examples, which are intended to be illustrative and not limiting.

Example 1: synthesis of macromonomer 1

Methacryloyl chloride PEGME macromonomer 1

Toluene (266g) was poured into a 500mL flask, followed by N₂Poly (ethylene glycol monomethyl ether) (80g) (Mn2000) and methacryloyl chloride (4.2g) were added to the atmosphere. Then, triethylamine (4.52g) was added over 20 minutes while maintaining the reaction temperature at 30 ℃. After a further 2 hours, the temperature of the reaction mixture was raised to 50 ℃ and held at this temperature for a further 2 hours. After this time, the reaction mixture was cooled to room temperature and filtered to remove triethylamine hydrochloride, which was obtained in theoretical amount. To the filtrate was added petroleum ether to precipitate the macromonomer 1, and the macromonomer 1 was collected by filtration and dried in a vacuum oven at room temperature. The reaction is shown in the above scheme. Preferably, n has an average value of about 45.

Example 2: synthesis of graft copolymer 1

Macromer 1(7.5g), water (48g), and 1-propanol (192g) were poured into a 500mL flask, which was heated to 80 ℃. Styrene (66.9g) and azobisisobutyronitrile (0.48g) (Vazo-64 from DuPont de Nemours Co) were mixed in a separate beaker and a portion of the solution (12g) was added to the macromer solution, which became cloudy within about 10 minutes. The remaining solution was then added over 30 minutes. After an additional 3 hours, the conversion of graft copolymer 1 was about 97%, based on the percent non-volatile measurement. Styrene in graft copolymer 1: the weight ratio of macromer 1 is about 90: 10.

Example 3: preparation of developable printing plates under pressure

The solutions described in Table 1 were applied to a brushed-grained (brush-grained) and phosphoric acid anodized aluminum substrate primed with polyacrylic acid to give a dry coating weight of 2g/m²。

TABLE 1 composition of example 3 (formulation in parts by weight)

¹Sartomer 355 is a multifunctional acrylic monomer available from Sartomer co.

²The IR dye is chlorinated 2- [2- [ 2-phenylthio-3- [ (1, 3-dihydro-1, 3, 3-trimethyl-2H-indol-2-ylidene) ethylene]-1-cyclohexen-1-yl]Vinyl radical]-1, 3, 3-trimethyl-3H-indolium.

³Byk 307 is a modified polysiloxane available from Byk Chemie.

The resulting coating was then overcoated with a solution of polyvinyl alcohol (5.26 parts) and polyvinyl imidazole (0.93 parts) in isopropanol (3.94 parts) and water (89.87 parts) to give 2g/m²Dry coating weight of (c). The resulting plate was placed on a Creo Trendsetter 3244x at 250mJ/em²Imaged and then mounted directly on an AB Dick press. The plate prints more than 500 parts of pictures with good quality. The second panel was imaged with an oelec vacuum frame (5kW bulb) on 12 units at medium intensity. The plate was mounted on an ABDick printer to obtain over 500 parts of good quality pictures.

Example 4: preparation of UV-sensitive on-press developable printing plates

Example 3 was repeated except that the IR dye was removed and no topcoat was applied. The resulting plate was imaged at medium intensity for 6 units using an oelec vacuum frame (5kW bulb). The plate was mounted on an AB Dick press to obtain more than 300 parts of good quality pictures.

Example 5: preparation of visible light sensitive on-press developable printing plates

The solutions described in Table 2 were applied to brushed grained and phosphoric acid anodized aluminum substrates primed with polyacrylic acid to give a dry coating weight of 1.3g/m²。

TABLE 2 composition of example 5 (formulation in parts by weight)

¹Sartomer 355 is a multifunctional acrylic monomer available from Sartomer co.

²Diphenyliodonium chloride was obtained from Aldrich.

³Byk 307 is a modified polysiloxane available from Byk Chemie.

⁴Ketocoumarin 93 has the following structure:

the resulting coating was then overcoated as described in example 3 to give 2g/m²Dry coating weight of (c). The resulting plate was placed on an Oriel 1000W solarsilator model #81291 (Oriel Instruments, Stratford, CT) equipped with a 530 run filter at 4mW/cm²Imaging was performed for 5 seconds.

The plate was treated in a wash tank with water and 30% Varn 142W/30% Varn Par solution and then mounted directly on an AB Dick printer. The plate prints more than 500 parts of pictures with good quality.

Example 6: preparation of graft copolymer 2:

deionized water (314.8g) and sodium lauryl sulfate (2.0g) were poured into a 1L 4-necked flask under nitrogen and heated to 70 ℃. A premix of ammonium persulfate (0.65g) and deionized water (20g) was added over 15 minutes at 70 ℃. A pre-mixture of styrene (79.5g), macromer 1(10g) and acrylic acid (7.9g) was added over 3 hours at 70 ℃. After 1.5 hours, it was found that the% non-volatiles was 22.5% and theoretically 23%. The reaction mixture was cooled to room temperature with water. Ammonium hydroxide solution (8g) was added at room temperature to stabilize the latex.

Example 7: preparation of IR-sensitive printing plates

Example 3 was repeated except that the topcoat was not applied and graft copolymer 1 was replaced with graft copolymer 2 to illustrate the effect of the acid number of the binder. Fig. 1 shows a Scanning Electron Microscope (SEM) analysis of the resulting coating. As shown in fig. 1, the coating comprises discrete particles. The particles have a diameter of up to about 60 nm.

The resulting plate was placed on a Creo Trendsetter 3244x at 496mJ/cm²Imaged and then mounted on a Komori printer. The plate was then treated with Prisco liquid plate cleaner. The plate prints more than 27,500 parts of good quality pictures.

Example 8: synthesis of graft copolymer 3

Macromer 1(7.5g), water (48g), and 1-propanol (192g) were poured into a 500mL flask, which was heated to 80 ℃. Allyl methacrylate (66.9g) and Vazo-64(0.48g) were slowly added. Within 10 minutes of the monomer addition, the reaction mixture gelled. Therefore, the reaction mixture was thrown away and the process was modified as follows.

2-butanone (384.1g) and macromer 1(4.25g) were poured into a 1L 4-necked flask under nitrogen and heated to 80 ℃. A pre-mixture of allyl methacrylate (38.0g) and Vazo-64(0.3g) was added over 90 minutes at 80 ℃. After the end of the addition, another 0.13g of Vazo-64 was added. Two additional doses of Vazo-64, 0.13g each, were then added. The polymer conversion in% non-volatiles was 90%. Allyl methacrylate in graft copolymer 3: the weight ratio of macromer 1 is about 90: 10.

The resin solution was precipitated in powder form using hexane (1200g) and stirred with a high shear mixer at 3000RPM for 15-20 minutes. The solution was then filtered and the product was dried at room temperature.

Example 9: preparation of IR-sensitive on-press developable printing plates

Example 3 was repeated except that the graft copolymer 1 was replaced with graft copolymer 3 and no overcoat was applied. Figure 2 shows SEM analysis of the resulting coating. As shown in fig. 2, the coating is free of discrete particles.

The resulting plate was placed on a Creo Trendsetter 3244x at 496mJ/cm²Imaged and then mounted directly on an AB Dick press. The plate prints more than 1000 pictures of good quality.

Another plate, prepared accordingly and on a Creo Trendsetter at 361mJ/cm²Imaged, mounted on a Komori printer equipped with a hard filter layer (hard blanket) and using an Equinox ink. The plate prints more than 40,000 parts of good quality pictures.

Example 10: preparation of IR-sensitive on-press developable printing plates

Example 3 was repeated except that the brushed textured substrate was replaced with an electrochemically textured substrate with a polyvinylphosphonic acid sealed anodic oxide layer.

The resulting plate was placed on a Creo Trendsetter 3244x at 250mJ/cm²Imaged and then mounted directly on an AB Dick press. The plate prints more than 500 parts of pictures with good quality.

Example 11: synthesis of graft copolymer 4

Macromer 1(20g of 50% aqueous solution) (obtained from Aldrich and used as such), water (50g), and 1-propanol (240g) were poured into a 1000mL flask, which was heated to 80 ℃. Methyl methacrylate (89.4g) and Vazo-64(0.65g) were mixed in a separate beaker and a portion of this solution (12g) was added to the macromer solution, which became cloudy within about 10 minutes. The remaining solution was then added over 90 minutes. After an additional 3 hours, the conversion to graft copolymer 4 was about 97%, based on the percent non-volatile determination. Methyl methacrylate in graft copolymer 4: the weight ratio of macromer 1 is about 90: 10.

In another procedure, a solution of macromer 1(7.5g) dissolved in a mixture of water (48g) and 1-propanol (192g) was poured into a 500mL flask, which was heated to 80 ℃. Methyl methacrylate (66.9g) and Vazo-64(0.48g) were mixed in a separate beaker and a portion of this solution (12g) was added to the macromer solution, which became cloudy within about 10 minutes. The remaining solution was then added over 30 minutes. After an additional 3 hours, the conversion to graft copolymer 4 was about 97%, based on the percent non-volatile determination. Methyl methacrylate in graft copolymer: the weight ratio of macromer 1 is about 90: 10.

Example 12: preparation of IR-sensitive printing plates

Example 3 was repeated except that graft copolymer 1 was replaced with graft copolymer 4, which was prepared from macromer 1 available from Aldrich. Fig. 3 shows SEM analysis of the resulting coating. As shown in fig. 3, the coating is free of discrete particles.

The resulting plate was placed on a Creo Trendsetter 3244x at 100mJ/cm²Imaged and then mounted directly on an AB Dick press. However, the use of graft copolymer 4 by itself does not provide a sufficient difference in developability of the unexposed areas and durability of the exposed image areas.

Example 13: synthesis of graft copolymer 5

Macromer 1(7.0g), deionized water (60g), and n-propanol (240g) were poured into a 1L flask and heated to 83 ℃. Styrene (92.4g) and Vazo-64(0.65g) were mixed together in a separate beaker. A portion of this mixture (12g) was added and the remaining solution was added after 30 minutes over 2 hours. After an additional 3 hours, the conversion to graft copolymer 5 was about 97%, based on the percent non-volatile determination. The weight ratio of styrene to macromer 1 was 93: 7.

Example 14: preparation of IR-sensitive on-press developable printing plates

Example 3 was repeated except that the graft copolymer 1 was replaced with graft copolymer 5 and no topcoat was applied.

The resulting plate was imaged at 250mJ/cm2 on a Creo Trendsetter 3244x and then mounted directly on an AB Dick printer. The plate prints more than 400 parts of pictures of good quality.

Example 15: synthesis of macromonomer 2

Toluene (25g) was poured into a 500mL flask equipped with a toluene-filled dean Stark trap, followed by the addition of polyethylene glycol monomethyl ether (PEGME) (225g) (Mn2000) under a nitrogen atmosphere. The reaction mixture was heated to 110 ℃ and held at that temperature for 2 hours to remove any water by azeotropic distillation. Next, the mixture was cooled to 70 ℃ and dibutyltin dilaurate (0.225g) was added, followed by m-isopropenyl- α, α -dimethylbenzyl isocyanate (23.6g) (m-TMI, available from Cytec Industries, West Patterson, N.J.) at 70 ℃ over 30 minutes. After a further 2 hours at 70 ℃ the reaction is complete and evidence is given of the disappearance of the NCO groups, determined by titration and FT-IR analysis. The solution was then poured into a glass dish, and after 1 day a waxy solid material was obtained. This material was dissolved in methyl ethyl ketone (300g) followed by the addition of petroleum ether (2000g) to precipitate solid macromer 2, which was collected by filtration and dried in a vacuum oven at room temperature.

Example 16: synthesis of graft copolymer 6

Macromer 2(7.5g), water (48g), and 1-propanol (192g) were poured into a 500mL flask, which was heated to 80 ℃. In a separate beaker, styrene (66.9g) and Vazo-64(0.48g) were mixed and a portion of the solution (12g) was added to the macromer solution, which became cloudy in about 10 minutes. The remaining solution was then added over 30 minutes. After a further 3 hours, the conversion to graft copolymer 6 was about 97%, based on the% non-volatiles determined. Styrene in graft copolymer 6: the weight ratio of macromer 2 is about 90: 10.

Example 17: preparation of IR-sensitive on-press developable printing plates

Example 3 was repeated except that graft copolymer 1 was replaced with graft copolymer 6.

The resulting plate was placed on a Creo Trendsetter 3244x at 100mJ/cm²Imaged and then mounted directly on an AB Dick press. The plate prints more than 500 parts of pictures with good quality.

Example 18: preparation of IR-sensitive on-press developable printing plates without overcoat

Example 3 was repeated except that no topcoat was applied. Fig. 4 shows SEM analysis of the resulting coating. As shown in fig. 4, the coating comprises discrete particles. The particles have diameters of up to about 100-200 nm.

The resulting plate was placed on a Creo Trendsetter 3244x at 250mJ/cm²Imaged and then mounted directly on an AB Dick press. The plate prints more than 600 parts of pictures with good quality.

Example 19: preparation of developable printing plates under pressure

Example 7 was repeated except that graft copolymer 2 was replaced with a combination of graft copolymer 1(3.35 parts by weight) and graft copolymer 2(0.18 parts by weight). Fig. 5 shows SEM analysis of the resulting coating. As shown in fig. 5, the coating includes discrete particles. The particles have diameters of up to about 100-200 nm.

The resulting plate was plated on a Creo Trendsetter 3244x at 496mJ/cm²Imaged and then mounted on an AB Dick printer. The plate prints more than 1,000 parts of good quality pictures.

Another plate thus prepared and imaged was mounted on a Komori press equipped with a hard filter layer and using an Equinox ink. The plate prints more than 30,000 parts of good quality pictures.

Comparative example 1: IR-sensitive, press-developable printing plates without free radical generators Preparation of

Example 18 was repeated except that the 2- (4-methoxyphenyl) -4, 6-bis (trichloromethyl) -2-triazine in the photopolymerizable coating was omitted.

The resulting plate was placed on a Creo Trendsetter 3244x at 250mJ/cm²Imaged and then mounted directly on an AB Dick press. The coating was completely washed away and no picture was obtained because there was no image on the plate.

Although the present invention has been described in connection with specific exemplary embodiments, it should be understood that various changes, substitutions, and alterations can be made to the disclosed embodiments without departing from the spirit and scope of the invention as described in the following claims.

Claims

1. An imageable element comprising:

a substrate; and

a polymerizable composition applied to the substrate, the composition comprising a polymerizable compound and about 10 wt% to about 90 wt% of a polymeric binder;

wherein the polymeric binder is selected from the group consisting of at least one graft copolymer comprising a backbone polymer and polyoxyethylene side chains, a block copolymer having at least one polyoxyethylene block and at least one non-polyoxyethylene block, and combinations thereof;

and wherein the polymerizable composition comprises discrete particles of the graft or block copolymer.

2. The imageable element of claim 1 wherein said discrete particles are characterized by a diameter of from about 60nm to about 300 nm.

3. The imageable element of claim 1 wherein said polyoxyethylene side chains or polyoxyethylene segments of the polyoxyethylene block have a number average molecular weight of from about 500 to about 10,000.

4. The imageable element of claim 1 wherein said polymeric binder is a graft copolymer and said polyoxyethylene segments of polyoxyethylene side chains are present in an amount of from about 0.5 to about 60% by weight.

5. The imageable element of claim 1, wherein the non-polyoxyethylene blocks of said block copolymer are free of polyalkylene oxide segments.

6. The imageable element of claim 1 wherein said polymeric binder comprises at least one graft copolymer comprising a backbone polymer and polyoxyethylene side chains.

7. The imageable element of claim 1 wherein said polymeric binder comprises a mixture of at least two copolymers, wherein said copolymers independently comprise a graft copolymer comprising a backbone polymer and polyoxyethylene side chains or a block copolymer having at least one polyoxyethylene block and at least one non-polyoxyethylene block.

8. The imageable element of claim 7 wherein said polymeric binder comprises a mixture of graft copolymers that respectively comprise a backbone polymer and polyoxyethylene side chains.

9. The imageable element of claim 7 wherein said mixture of copolymers comprises at least one graft copolymer in the form of non-discrete particles.

10. The imageable element of claim 1 wherein said polymeric binder is a block copolymer and the polyoxyethylene segment of the block copolymer is present in an amount of from about 5 to about 60 weight percent.

11. The imageable element of claim 1, wherein said imageable element is sensitive to ultraviolet, visible, or infrared radiation.

12. The imageable element of claim 1 wherein said polymerizable compound comprises an addition polymerizable ethylenically unsaturated group, a crosslinkable ethylenically unsaturated group, a ring-opening polymerizable group, an azide group, an aryldiazonium salt group, an aryldiazonium sulfonate group, or a combination thereof.

13. The imageable element of claim 12 wherein said addition polymerizable ethylenically unsaturated groups can be polymerized by free radical polymerization, cationic polymerization, or a combination thereof.

14. The imageable element of claim 12 wherein said crosslinkable ethylenically unsaturated group is selected from the group consisting of dimethylmaleimide groups, chalcone groups, and cinnamate groups.

15. The imageable element of claim 12 wherein said ring-opening polymerizable group is selected from the group consisting of epoxides, propylene oxide, and combinations thereof.

16. The imageable element of claim 1 wherein the weight ratio of polymerizable compound to polymeric binder is in the range of from about 5:95 to about 95: 5.

17. The imageable element of claim 1 wherein said polymerizable composition further comprises a radiation absorber suitable for absorbing electromagnetic radiation of about 300-1400 nm.

18. The imageable element of claim 17 wherein said radiation absorber is an infrared radiation absorber.

19. The imageable element of claim 1 wherein said polymerizable composition further comprises a free radical initiator system comprising an electron acceptor and a co-initiator capable of donating electrons, donating hydrogen atoms, or capable of forming hydrocarbyl groups.

20. The imageable element of claim 1, wherein said imageable element is a printing plate precursor.

21. The imageable element of claim 20 wherein said printing plate precursor is suitable for pressure developable.

22. A polymerizable composition comprising:

a polymerizable compound, and

about 10 wt% to about 90 wt% of a polymeric binder;

wherein the polymerizable composition comprises discrete particles of the graft or block copolymer.

23. The composition of claim 22, wherein the discrete particles are characterized by a diameter of about 60nm to about 300 nm.

24. The composition of claim 22, wherein the weight ratio of polymerizable compound to polymeric binder ranges from about 5:95 to about 95: 5.

25. The composition of claim 22 wherein the polymerizable composition further comprises a radiation absorber capable of absorbing electromagnetic radiation in the range of about 300-1400 nm.

26. The composition of claim 22, wherein the polymerizable composition further comprises a free radical initiator system comprising an electron acceptor and a co-initiator capable of donating electrons, donating hydrogen atoms, or capable of forming hydrocarbyl groups.

27. The composition of claim 22, wherein the polyoxyethylene side chains or polyoxyethylene segments of the polyoxyethylene blocks have a number average molecular weight of about 500 to about 10,000.

28. The composition of claim 22, wherein the polymeric binder comprises at least one graft copolymer comprising a backbone polymer and polyoxyethylene side chains.

29. The composition of claim 22, wherein the non-polyoxyethylene block of the block copolymer is free of polyalkylene oxide segments.

30. The composition of claim 22, wherein the polymeric binder comprises a mixture of at least two copolymers, wherein the copolymers independently comprise a graft copolymer comprising a backbone polymer and polyoxyethylene side chains or a block copolymer having at least one polyoxyethylene block and at least one non-polyoxyethylene block.

31. The composition of claim 30, wherein the polymeric binder comprises a mixture of graft copolymers comprising a backbone polymer and polyoxyethylene side chains, respectively.

32. The composition of claim 30, wherein the mixture of copolymers comprises at least one graft copolymer in the form of non-discrete particles.

33. A method of making a printing plate, the method comprising:

providing a substrate;

applying a negative-working layer comprising a radiation-sensitive composition on the substrate, wherein the radiation-sensitive composition comprises a polymerizable compound and from about 10 wt.% to about 90 wt.% of a polymeric binder, wherein the polymeric binder is selected from the group consisting of at least one graft copolymer comprising a backbone polymer and polyoxyethylene side chains, a block copolymer having at least one polyoxyethylene block and at least one non-polyoxyethylene block, and combinations thereof, and wherein the radiation-sensitive composition comprises discrete particles of the graft or block copolymer;

imagewise exposing the negative layer to ultraviolet, visible or infrared radiation; and

developing the negative layer to produce a printing plate.

34. The method of claim 33, wherein the discrete particles are characterized by a diameter of about 60nm to about 300 nm.

35. The method of claim 33, wherein said imagewise exposing step is carried out using an infrared laser with infrared radiation.

36. The method of claim 33, further comprising post-baking the printing plate after the developing step.

37. The method of claim 33, wherein said developing step is performed by applying pressure.

38. The method of claim 33, wherein the polyoxyethylene side chains or polyoxyethylene segments of the polyoxyethylene blocks have a number average molecular weight of about 500 to about 10,000.

39. The method of claim 33, wherein the non-polyoxyethylene block of the block copolymer is free of polyalkylene oxide segments.

40. The method of claim 33, wherein the polymeric binder comprises a mixture of at least two copolymers, wherein the copolymers independently comprise a graft copolymer comprising a backbone polymer and polyoxyethylene side chains or a block copolymer having at least one polyoxyethylene block and at least one non-polyoxyethylene block.

41. The method of claim 40, wherein the polymeric binder comprises a mixture of graft copolymers comprising a backbone polymer and polyoxyethylene side chains, respectively.

42. The method of claim 40, wherein the mixture of copolymers comprises at least one graft copolymer in the form of non-discrete particles.

43. A method of making an imageable element comprising:

providing a substrate; and

applying a radiation-sensitive composition comprising a polymerizable compound, a radiation absorber, and from about 10 wt% to about 90 wt% of a polymeric binder onto the substrate, wherein the polymeric binder is selected from the group consisting of at least one graft copolymer comprising a backbone polymer and polyoxyethylene side chains, a block copolymer having at least one polyoxyethylene block and at least one non-polyoxyethylene block, and combinations thereof;

wherein the radiation-sensitive composition comprises discrete particles of the graft or block copolymer.

44. The method of claim 43, wherein said coating step comprises drying said radiation-sensitive composition.

45. The method of claim 43, wherein the discrete particles of the block copolymer are characterized by a diameter of about 60nm to about 300 nm.

46. The method of claim 43 wherein the polyoxyethylene side chains or polyoxyethylene segments of the polyoxyethylene blocks have a number average molecular weight of from about 500 to about 10,000.

47. The method of claim 43, wherein the non-polyoxyethylene block of the block copolymer is free of polyalkylene oxide segments.

48. The method of claim 43, wherein the polymeric binder comprises at least one graft copolymer comprising a backbone polymer and polyoxyethylene side chains.

49. The method of claim 43 wherein the polymeric binder comprises a mixture of at least two copolymers, wherein the copolymers independently comprise a graft copolymer comprising a backbone polymer and polyoxyethylene side chains or a block copolymer having at least one polyoxyethylene block and at least one non-polyoxyethylene block.

50. The method of claim 49, wherein the polymeric binder comprises a mixture of graft copolymers comprising a backbone polymer and polyoxyethylene side chains, respectively.

51. The method of claim 49, wherein the mixture of copolymers comprises at least one graft copolymer in the form of non-discrete particles.

52. The method of claim 43 wherein the imageable element is a printing plate precursor.

53. A method according to claim 52 wherein the printing form precursor is adapted to be pressure developable.

54. An imageable element comprising:

a substrate; and

a negative layer applied to the substrate, the negative layer comprising a polymerizable compound and from about 10 wt% to about 90 wt% of a polymeric binder selected from a mixture of block copolymers, wherein each block copolymer has at least one polyoxyethylene block and at least one block that is not a polyoxyethylene block, wherein the negative layer comprises discrete particles of at least one block copolymer in the mixture.