JP2894550B2 - Thermosensitive imaging elements and methods of making printing plates therewith - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a method of making a printing plate which involves the use of a heat-sensitive imaging element and which can be developed with plain water or aqueous liquids.

[0002]

BACKGROUND OF THE INVENTION A lithographic process is a method of printing from a specially manufactured surface that will have some portions of the surface capable of receiving lithographic ink while others will not receive the ink when wetted with water. is there. The ink-receiving portions form the printed image portions and the ink-reject portions form the background portions.

In photolithographic techniques, photographic materials are made image-wise receptive to oily or greasy inks on exposed (negative-working) or unexposed parts (positive-working) on a hydrophilic background. .

In the production of common lithographic printing plates, also called surface lithographic or planographic printing plates, a photosensitive composition is provided on a support which has an affinity for water or which obtains such an affinity by chemical treatment. Coating. Coatings for this purpose include photopolymer layers containing diazo compounds, hydrophilic colloids sensitized with dichromates and various synthetic photopolymers. In particular, diazo-sensitized systems are widely used.

[0005] Upon image-wise exposure of the photosensitive layer, the exposed image portions become insoluble and the unexposed portions remain soluble. The plate is then developed with a suitable liquid to remove unexposed portions of the diazonium salt or diazo resin.

[0006] Commercially available diazo-based printing plates most commonly use them as supports with hydrophilic surfaces, since anodized and roughened aluminum offers the advantage of high print resistance. . A particular disadvantage of such types of printing plates is that they require a special developer which is expensive and inconvenient for development.

[0007] EP-A 601240 discloses a diazo-based printing plate using as a lithographic base a polyester film provided with a cross-linked hydrophilic layer provided with a photosensitive diazo layer on top. I have. Such a diazo-based printing plate can be developed by rinsing it with fresh water after image-wise exposure.

[0008] Commercially available plates using a flexible support such as paper, for example, provided with a hydrophilic layer are also available. For example, Li
thocraft 10008 FOTOPLATE ^™ is a printing plate comprising a paper support and a hydrophilic layer on top of which is provided a diazo-based photosensitive layer. According to the supplier's plate instructions, the imagewise exposure of the lithographic printing plate precursor, i.e. the imaging element, the installation of the exposed imaging element on a printing machine and the L
Ithocraft 10008 Plates can be manufactured by wiping with a development desensitizer. Plate instructions also consider a method that does not use a development desensitizer. However, such methods very often result in poor lithographic performance, so in practice a development desensitizer is almost always required.

A particular disadvantage of the above-described diazo-based printing plates, which is usually independent of the type of lithographic base used, is that they must be shielded from light. In addition, diazos are of insufficient sensitivity to be exposed by commercial, economical lasers.

On the other hand, there are also known processes for making printing plates which involve the use of imaging elements which are heat-sensitive rather than light-sensitive. For example, Research Disclosure n January 1992
o. 33303 discloses a heat-sensitive imaging element comprising a crosslinked hydrophilic layer containing a thermoplastic polymer and an infrared-absorbing pigment such as carbon black on a support. Upon image-wise exposure to an infrared laser, the thermoplastic polymer particles coagulate image-wise, thereby rendering the surface of the imaging element and these portions ink-receiving without further development. A disadvantage of this method is that when some pressure is applied to the non-printed parts, the resulting printing plate is easily damaged because the parts become ink-receptive. Further, under critical conditions, the lithographic performance of such printing plates can be poor, and thus such printing plates have little lithographic printing tolerance.

[0011] FR-A-1,561,957 describes a recording material comprising at least a recording layer containing a hydrophilic binder and a hydrophobic compound dispersed in the hydrophilic binder. Upon irradiation and development, the recording material can be used as a planographic printing plate.

US Pat. No. 3,476,937 also describes a recording material comprising at least a recording layer containing a hydrophilic binder and a hydrophobic compound dispersed in the hydrophilic binder. Upon irradiation and development, the recording material can be used as a planographic printing plate.

US Pat. No. 3,580,719 discloses an imaging device containing a recording layer containing at least about 80% by weight of a common water-soluble polymer whose normal solubility in aqueous solvents is lost upon heating. Describes the element.

The last three imaging elements all have the disadvantage that the corresponding printing plates have a low printing resistance.

[0015] EP 514.145 uses a heat-sensitive imaging element comprising an imaging layer comprising core-shell particles and a light-to-heat conversion material on a lithographic base such as anodized aluminum. It describes a method for producing a printing plate. The shell of these particles is hydrophilic and makes the particles developable. The wick is hydrophobic and flows out on heating. Thus, with image-wise exposure using an infrared laser diode, the image forming layer can be rendered insoluble in the exposed areas. In the areas that have not been exposed, the imaging layer can be removed with an aqueous developing agent containing ethanolamine. Continue to bake the ingredients. Although such printing plates produce high print resistance, their development places a burden on the environment due to the use of alkanolamines.

[0016]

SUMMARY OF THE INVENTION Accordingly, one object of the present invention is to provide a heat sensitive method for producing a printing plate which can be developed in a simple and environmentally friendly manner and which can be exposed by a commercially available laser. To provide a sexual imaging element.

Another object of the present invention is to provide a heat-sensitive imaging element that can be used to obtain a printing plate having high printing resistance.

Further objects of the present invention will become clear from the description hereinafter.

The present invention provides an image forming layer comprising (i) hydrophobic thermoplastic polymer particles dispersed in a hydrophilic binder on a lithographic base hydrophilic surface; and (ii) the image forming layer. Or an image-forming element comprising a compound capable of converting light contained in a layer adjacent thereto into heat, wherein the image-forming layer further cross-links the hydrophilic binder upon heating. From 1: 100 to 20 relative to the hydrophilic binder
Imaging element characterized in that it comprises in a ratio between 0: 1.

The present invention further comprises the steps of (1) exposing the image-forming element described above image-wise and (2) developing the image-wise exposed image-forming element thus obtained using fresh water or an aqueous liquid. A method for producing a lithographic printing plate comprising the same is also provided.

[0021]

DETAILED DESCRIPTION OF THE INVENTION An imaging element for use in accordance with the present invention comprises, on a lithographic base hydrophilic surface, hydrophobic thermoplastic polymer particles dispersed in a hydrophilic binder and a hydrophilic binder upon heating. A cross-linking agent capable of cross-linking the agent. The hydrophilic binder used in connection with the present invention is preferably uncrosslinked or only slightly crosslinked. The imaging element also includes a compound that can convert light to heat. The compound is preferably included in the imaging layer, but may be provided in a layer adjacent to the imaging layer.

According to one embodiment of the present invention, the lithographic base can be anodized aluminum. A particularly preferred lithographic base is an electrochemically granulated and anodized aluminum support.
According to the present invention, an anodized aluminum support may be treated to improve the hydrophilicity of its surface. For example,
Elevated temperature of the surface of the aluminum support, eg 9
The support may be silicate treated by treatment with a sodium silicate solution at 5 ° C. Alternatively, a phosphate treatment may be applied which involves treating the aluminum oxide surface with a phosphate solution which may further contain inorganic fluoride. Further, the aluminum oxide surface may be rinsed with a citric acid or citrate solution. This treatment may be performed at room temperature or at a slightly elevated temperature of about 40-50 ° C. Other interesting treatments include rinsing the aluminum oxide surface with a bicarbonate solution. It is also clear that one or more of these post-treatments can be performed alone or in combination.

According to another aspect of the present invention, the lithographic base comprises a flexible support, such as paper or plastic film, provided with a cross-linked hydrophilic layer. Particularly suitable crosslinked hydrophilic layers are obtained from hydrophilic binders which are crosslinked with a crosslinking agent such as, for example, formaldehyde, glyoxal, polyisocyanate or hydrolyzed tetra-alkyl orthosilicate.
The latter is particularly preferred.

As the hydrophilic binder, hydrophilic (co) polymers such as vinyl alcohol, acrylamide, methylolacrylamide, methylolmethacrylamide,
Homopolymers and copolymers of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, or maleic anhydride / vinyl methyl ether copolymer can be used. Used (co)
The hydrophilicity of the polymer or (co) polymer mixture is preferably at least equal to or greater than the hydrophilicity of the polyvinyl acetate hydrolyzed to at least 60% by weight, preferably to the extent of 80% by weight. high.

The amount of crosslinking agent, especially tetraalkyl orthosilicate, is preferably at least 0.2 parts by weight, preferably between 0.5 and 5 parts by weight, per part by weight of hydrophilic binder. Is between 1.0 and 3 parts by weight.

The cross-linked hydrophilic layer in the lithographic base used according to the invention preferably also contains substances which increase the mechanical strength and the porosity of the layer. Colloidal silica can be used for this purpose. The colloidal silica used may be in the form of a commercially available aqueous dispersion of colloidal silica, for example, having an average particle size of up to 40 nm, for example 20 nm. In addition, inert particles larger in size than colloidal silica, such as J. Colloid and Interface Sc
i., Vol. 26, 1968, pages 62 to 69
It is also possible to add particles having an average diameter of at least 100 nm, which are silica or aluminum particles or particles of titanium dioxide or other heavy metal oxides produced according to the Stoeber method. The addition of these particles gives the surface of the cross-linked hydrophilic layer a uniform rough texture consisting of microscopic dimensional irregularities, which act as storage for water in the background.

The thickness of the crosslinked hydrophilic layer in the lithographic base according to the invention can vary in the range from 0.2 to 25 μm and is preferably from 1 to 10 μm.

Specific examples of cross-linked hydrophilic layers suitable for use according to this embodiment include EP-A 601 240, GB-
P-1419512, FR-P-2300354, US
-P-397660, US-P-4284705 and EP-A 514490.

As the lithographic base flexible support for this embodiment, use may be made of a plastic film, for example a polyester such as a polyethylene terephthalate film or a polyethylene naphthalate film, a cellulose acetate film, a polystyrene film, a polycarbonate film, etc. Is particularly preferred. The plastic film support may be opaque or transparent.

It is particularly preferred to use a polyester film support provided with an adhesion improving layer. Particularly suitable adhesion improving layers for use according to the invention are EP-A6
19524, EP-A 620502 and EP-A6
Comprising a hydrophilic binder and colloidal silica as disclosed in US Pat. Preferably, the amount of silica in the adhesion improving layer is between 200 mg / m ² and 750 mg / m
m ² . Further, the ratio of silica to hydrophilic binder is preferably greater than 1 and the surface area of the colloidal silica is preferably at least 300 m ² per gram, more preferably 500 m ² per gram.

According to the invention, an imaging layer is provided on top of the hydrophilic surface. Optionally, one or more intermediate layers may be provided between the lithographic base and the image forming layer. The imaging layer for the present invention comprises thermoplastic polymer particles dispersed in a hydrophilic binder and a heat-activatable crosslinker.

[0032] Hydrophilic binders suitable for use in the imaging layers according to the present invention are preferably those containing a reactive group, such as a hydroxy, amine or carboxy group. Specific examples of hydrophilic binders are synthetic homo or copolymers,
For example, polyvinyl alcohol, dimethylhydantoin
Formaldehyde resins, poly (meth) acrylic acid, poly (meth) acrylamide, hydroxyethyl poly (meth) acrylate, polyvinyl methyl ether, or natural binders such as gelatin, polysaccharides such as dextran,
Pullulan, cellulose, gum arabic, alginic acid.

[0033] The hydrophobic thermoplastic polymer particles used in connection with the present invention preferably have a glass transition temperature of at least 90 ° C, more preferably at least 100 ° C.

The hydrophobic thermoplastic polymer particles used in connection with the present invention preferably have a coagulation temperature above 50 ° C. and more preferably above 70 ° C. Coagulation results from the softening or melting of the thermoplastic polymer particles under the influence of heat. There is no particular upper limit on the coagulation temperature of the thermoplastic hydrophobic polymer particles, but this temperature must be well below the decomposition of the polymer particles. Preferably, the setting temperature is at least 10 ° C. below the temperature at which decomposition of the polymer particles occurs. When the polymer particles are subjected to temperatures above the congealing temperature, they condense to form hydrophobic agglomerates in the hydrophilic layer, and in these parts the hydrophilic layer becomes insoluble in fresh water or aqueous liquids .

Specific examples of hydrophobic polymer particles for use in connection with the present invention include, for example, polystyrene, polyvinyl chloride, polymethyl methacrylate, polyvinylidene chloride, polyacrylonitrile, polyvinyl carbazole, and the like, or copolymers thereof. And / or mixtures.
Polymethyl methacrylate is most preferably used.

The weight average molecular weight of the polymer is 5,000 to 1,
It may be in the range of 1,000,000 g / mol.

The hydrophobic particles are 0.01 μm to 50 μm,
More preferably it may have a particle size between 0.05 μm and 10 μm and most preferably between 0.05 μm and 0.5 μm.

The polymer particles are present in a dispersion in the aqueous coating solution of the imaging layer and are disclosed in US-P-3.4.
It can be produced by the method disclosed in 76.937.
Other methods particularly suitable for preparing aqueous dispersions of thermoplastic polymer particles are:-dissolving a hydrophobic thermoplastic polymer in a water-immiscible organic solvent;-dissolving the resulting solution in water or aqueous Dispersing in a medium and removing the organic solvent by evaporation.

[0039] The amount of hydrophobic thermoplastic polymer particles contained in the imaging layer is preferably greater than 35% by weight and more preferably greater than 50% by weight and most preferably greater than 65% by weight.

Suitable compounds capable of converting light into heat are preferably infrared absorbing components, provided that the absorption of the compound used is within the wavelength range of the light source used for image-wise exposure. The absorption wavelength is not particularly important. Particularly useful compounds are, for example, dyes and especially infrared dyes, carbon black, metal carbides, borides, nitrides, carbonitrides, bronze-structured oxides and oxides structurally related to the bronze family but lacking the A component. For example, WO _2.9 . It is also possible to use conductive polymer dispersions, for example those based on polypyrrole or polyaniline. The lithographic performance obtained, and especially the print resistance, depends on the heat sensitivity of the imaging element. In this regard, carbon black has been found to give very good and favorable results.

Although the light-to-heat conversion compound according to the present invention is most preferably added to the imaging layer, at least a portion of the light-to-heat conversion compound may be contained in a nearby layer. Such a layer can be, for example, a lithographic base cross-linked hydrophilic layer according to the second aspect of the lithographic base described above.

The heat-activatable crosslinkers suitable for use in the imaging layers according to the present invention are in a weight ratio of between 1: 100 and 200: 1 to the hydrophilic binder, more preferably In a ratio between 1:50 and 50: 1, most preferably 1:10.
Used in a ratio between -10: 1.

Heat-activatable crosslinkers suitable for use in the imaging layers according to the present invention are preferably capable of reacting with a hydrophilic binder, for example with one of the reactive groups mentioned above. A compound having two or more groups. The crosslinker according to the present invention may be a low molecular weight compound or may be an oligomer or a polymer. Examples of crosslinking agents suitable for use in the imaging layer according to the invention include, for example, aldehydes such as formaldehyde, hexamethoxymethylmelamine, amine-formaldehyde resins such as melamine-formaldehyde or guanamine-formaldehyde resins, dimethylol. It is a urea-formaldehyde resin, a phenol-formaldehyde resin, a compound having two or more epoxy groups, such as a polymer having an epoxy group.

For the present invention, it is also preferred to add a catalyst to the imaging layer according to the present invention. Such catalysts can accelerate the cross-linking reaction and thus reduce the overall plate making time while maintaining the high level of cross-linking required to obtain high print resistance. Particularly suitable catalysts for use in this concept are acid catalysts. It is also advantageous to use catalyst precursors to improve the selectivity of the process and to obtain the best lithographic performance. Such precursors convert to the actual catalyst on heating, ie the catalyst is at least partially produced during image-wise exposure.

Suitable precursors for the catalyst are, for example, those which release acids on heating. Specific examples of suitable acid releasing catalyst precursors are described, for example, in EP 612065, EP 61523
3, and the sulfonium compounds disclosed in US 5.326.677, especially benzylsulfonium compounds,
EP 462773, WO 81/1755, US 4.3
70.401 inorganic nitrates such as Mg
(NO _{3) 2} .6H ₂ O or organic nitrates, such as nitric acid guanidinium, ammonium nitrate, etc. pyridinium nitrate,
Compounds which release sulfonic acids as disclosed in U.S. Pat.
5-dihydrothio-thiophene-1,1-dioxides, thermally decomposable compounds disclosed in GB 1.204.495, co-crystallinity of amines and volatile organic acids disclosed in US 3.669.747 (co-cristalin) adduct, US
Aralkyl cyanoforms disclosed in 3.166.583, EP 159725 and DE 351576
Thermo-acids, U.S. Pat.
The squaric acid generating compounds disclosed in S 5.278.031, US 5.225.314 and US 5.227.
277 and the acid generating compound disclosed in RD 11511 of November 1973.

According to the method of the invention for producing a lithographic printing plate, an imaging element according to the invention is image-wise exposed and then preferably developed by rinsing it with fresh water. The resulting imaged imaging element is then preferably heated globally to obtain the best print durability.

During image-wise exposure, a compound capable of converting light to heat absorbs the light used for imagewise exposure and converts it to heat to form a thermal image-wise image in the imaging layer. Generate the pattern of As a result of this heat, the hydrophobic thermoplastic polymer particles coagulate and render the imaging layer insoluble in fresh water or aqueous liquids, but the unexposed portions remain soluble in fresh water or aqueous liquids. is there.

After development, heating the imaged imaging element, preferably globally, causes substantial cross-linking of the imaging layer and consequently reduces the abrasion resistance of the printed portion during printing. Improve. Nevertheless, print resistance suitable for many printing operations is obtained without additional overall heating.

It is particularly advantageous with respect to the present invention to apply the rubber before subjecting the imaged imaging element to a global heat treatment. This will ensure hydrophilicity in the non-printed areas, especially when anodized aluminum is used as the lithographic base. Rubber suitable for this purpose are known and include, for example Polychrome PC965 ^TM (P
olychrome).

The image-wise exposure according to the present invention is preferably an image-wise scanning exposure involving the use of a laser or LED. It is highly preferred for the present invention to use a laser that emits in the infrared (IR) and / or near infrared, that is to say in the wavelength range from 700 to 1500 nm. Lasers that emit in the near infrared are particularly preferred for use with the present invention.

Preferred imaging devices suitable for image-wise scanning exposure according to the present invention are preferably directly feedable to the imaging element surface via a lens or other light-guiding component or are at a remote location. Includes a laser output that can be transmitted from the lens to the surface of the blank imaging element using a fiber optic cable. An adjuster and associated positioning hardware keep the beam output in the correct orientation relative to the imaging element surface, scan the output over the surface, and direct the laser at a location adjacent to a selected point or portion of the imaging element. Activate. The adjuster forms an accurate negative or positive image of the original in response to an input image signal corresponding to the original document and / or picture to be copied on the imaging element. The image signal is stored as a bitmap data file on a computer. Such files are stored in a raster image processor (RI
P) or other suitable means. For example, the RIP converts input data in a page-description language or as a combination of a page-description language and one or more image data files that defines all of the features required to transfer the data on the imaging element. Can receive. The bitmap is configured to define the tone and screen number and angle in the case of amplification adjustment screening. However, the present invention, for example, EP-
A 571010, EP-A 620677 and EP-A
Particularly suitable for use in combination with the number-adjusted screening disclosed in US Pat.

The imaging device can be configured as a flatbed recorder or as a drum recorder and has imaging elements mounted on the inside or outside cylindrical surface of the drum. In a preferred drum construction, the drum (and the imaging element mounted thereon) is rotated about its axis and the light beam is moved parallel to the axis of rotation, thereby causing the imaging element to scan circumferentially. The "growing" of the image in the axial direction provides the necessary relative movement between the laser beam and the imaging element. Alternatively, moving the light beam parallel to the drum axis and increasing the angle after each pass over the imaging element causes the image on the imaging element to "grow" in the circumferential direction. In both cases, after complete scanning and development by the light beam, an image corresponding to the original will have been applied to the surface of the imaging element. In a flat-bed configuration, light rays are drawn across one axis of the buildable element and are directed along the other axis after each pass. Of course, the necessary relative movement between the light beam and the imaging element may be caused by (in addition to) the movement of the imaging element rather than the movement of the light beam.

Regardless of how the light beam is scanned, it is generally preferred (for speed reasons) to use multiple lasers and to direct their output to a single writing column. After completion of each pass over or along the imaging element, the writing column is then moved by a distance determined by the number of rays emanating from the column and by the desired resolution (ie the number of image points per unit length). Be instructed.

The invention will now be illustrated by the following examples, which are not intended to limit the invention. All parts are by weight unless otherwise indicated.

[0055]

【Example】

Example 1 Preparation of a lithographic base The foil was degreased by dipping 0.2 mm thick aluminum foil in an aqueous solution containing 5 g / l of sodium hydroxide at 50 ° C. and rinsed with demineralized water. The foil is then heated using alternating current in an aqueous solution containing 4 g / l hydrochloric acid, 4 g / l hydroboric acid and 0.5 g / l aluminum ion at a temperature of 35 ° C. and 120 ° C.
Electrochemically grained at a current density of 0A / m ^2, to form a surface topography with an average center-line roughness R _a of 0.5 [mu] m.

After rinsing with demineralized water, the aluminum foil was then etched for 180 seconds at 60 ° C. with an aqueous solution containing 300 g / l of sulfuric acid and rinsed for 30 seconds at 25 ° C. with demineralized water.

The foil is then immersed in an aqueous solution containing 200 g / l of sulfuric acid at a temperature of 45 ° C., a voltage of about 10 V and 150 A
Solution / at a current density of m ² over the anodic oxidation for about 300 seconds to form an anodic oxidation film of Al ₂ O ₃ of 3 g / m ^2, then washed with demineralized water, containing sodium bicarbonate 20 g / l At 40 ° C. for 30 seconds, then rinsed with demineralized water at 20 ° C. for 120 seconds and dried.

The lithographic base obtained was immersed in an aqueous solution containing 5% by weight of citric acid at 50 ° C. for 60 seconds, rinsed with demineralized water and dried.

Preparation of Imaging Element (Material) The following coating composition was prepared and applied to the above lithographic base in an amount of 30 g / m ² (wet coating amount).
An imaging element according to the invention was prepared by coating at 35 ° C. and drying it at 35 ° C.

Preparation of Coating Composition Polymethyl methacrylate stabilized with Hostapal ^™ B (1% based on polymer) (particle diameter 90 nm)
Into 10.8 g of a 20% dispersion of demineralized water while stirring,
4.5 g of a 15% dispersion of carbon black in water, 5
9.79g of water and 25 g 200000 g / mole weight average molecular 98% 2% water hydrolyzed polyvinyl acetate having a weight solution and 2.5g hexamethoxymethylmelamine camera 1% in water solution of Min continuously the added.

Preparation of the printing plate and the printed copy using it The obtained imaging element was subjected to an image-wise scanning exposure using an infrared laser diode emitting at 830 nm. The scanning speed was 1 m / sec, the spot size was 10 μm and 120 mW on the plate surface. The imaging element is then watered into the development section and rubber into the rubber section (Polychrome
PC965 ^™ ) was developed in a PolychromePC28E ^™ processor filled with.

The printing plate obtained was then subjected to Heidelb equipped with K + E125 ink and Rotamatic as dampening solution.
erg GTO46 Installed on offset printing press. 15,000 copies were obtained with non-ink acceptance in the non-image areas. After printing 15,000 copies, no damage to the image areas was observed.

[0063] Example 2 (Comparative) hexamethoxymethylmelamine Mela Min (crosslinking agent) was changed as not used in the coating composition was prepared as described printing plate in Example 1 . When printing is performed as in Example 1, 6000 due to damage of the image area
Only one copy could be printed.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ identification code FI G03F 7/40 501 G03F 7/40 501 (56) References JP-A-7-306528 (JP, A) JP-A-8-156413 (JP, A) JP-A-9-76637 (JP, A) JP-A-9-120164 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03F 7/004 505 B41C 1 / 055 501 G03F 7/00 503 G03F 7/033 G03F 7/20 505 G03F 7/40 501

Claims (14)

(57) [Claims] 1. An image forming layer comprising: (i) a hydrophobic thermoplastic polymer particle dispersed in a hydrophilic binder on a lithographic base hydrophilic surface; and (ii) the image forming layer or a combination thereof. An imaging element comprising a compound capable of converting light contained in an adjacent layer into heat, wherein said imaging layer further comprises a cross-linking agent capable of cross-linking said hydrophilic binder upon heating. An imaging element comprising a ratio of between 1: 100 and 200: 1 relative to the sexual binder. 2. The compound capable of converting light into heat is selected from the group consisting of infrared absorbing dyes, carbon black, metal borides, metal carbides, metal nitrides, metal carbonitrides and conductive polymer particles. An imaging element according to claim 1, which is selected. 3. The lithographic base is anodized.
An imaging element according to claim 1, comprising d) a flexible support having aluminum or a hydrophilic layer crosslinked thereon. 4. An imaging element according to claim 1, wherein said thermoplastic polymer particles have a setting temperature higher than 50 ° C. 5. The group wherein the hydrophilic binder in the image forming layer comprises polyvinyl alcohol, poly (meth) acrylic acid, poly (meth) acrylamide, hydroxyethyl poly (meth) acrylate, polyvinyl methyl ether, and polysaccharide. An imaging element according to any of the preceding claims, selected from: 6. The hydrophobic thermoplastic polymer particles are selected from the group consisting of polystyrene, polyvinyl chloride, polymethyl methacrylate, polyvinylidene chloride, polyacrylonitrile, polyvinyl carbazole and the like, or copolymers and / or mixtures thereof. An imaging element according to any one of the preceding claims. 7. The imaging element of claim 1, wherein said hydrophilic binder comprises a reactive group and said crosslinker is capable of reacting with said reactive group under the influence of heat. 8. An imaging element according to claim 7, wherein said reactive groups are selected from the group consisting of hydroxy, amine and carboxyl groups. 9. The imaging element according to claim 1, wherein said imaging layer further comprises a catalyst capable of catalyzing said cross-linking or a precursor of said catalyst which can be converted to a catalyst upon heating. element. 10. An image-forming element according to claim 1, wherein said image-forming element is exposed to fresh water or an aqueous liquid. A method for producing a lithographic printing plate comprising the step of developing using a lithographic printing plate. 11. The method of claim 10, wherein said imagewise exposure is a scanning exposure. 12. The method according to claim 11, wherein said scanning exposure is performed by a single laser or a plurality of lasers. 13. The method according to claim 10, wherein said image-wise exposed imaging element is heated globally after development. 14. The method of claim 13 wherein said imaged imaging element is treated with rubber prior to global heating.