JP2000066379A - Heat mode sensitive image forming element for manufacture of positive working printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat mode sensitive image forming element for the manufacture of a planographic printing plate having a wide development latitude, high resolution and improved scratch resistance. SOLUTION: The heat mode sensitive image forming element has a 1st layer contg. a polymer soluble in an aq. alkaline soln. but insoluble in water and <5 wt.% hydrophilic polymer soluble in the aq. alkaline soln. based on the amt. of the water-insoluble polymer on a planographic printing base having a hydrophilic surface and the upper most layer sensitive to IR and impermeable to or insoluble in the alkaline developer on the 1st layer side of the base. The 1st layer and the uppermost layer may be formed as one layer. The uppermost layer contains 30-500 mg/m2 polymer and a compd. selected from the group consisting of triarylmethane and phthalocyanine dyes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION This invention relates to heat mode imaging elements for making lithographic printing plates containing an IR sensitive top layer.

More specifically, the present invention relates to a method of increasing scratch resistance.
e) for a heat mode imaging element for the preparation of a lithographic printing plate having e).

[0003]

BACKGROUND OF THE INVENTION Lithographic printing is a method of printing from a specially made surface in which some areas can receive lithographic printing ink, while others do not receive the ink when wetted with water. It is. The areas that receive ink form the printed image areas and the ink-repellent areas form the background areas.

In the field of photolithographic printing, photographic materials are image-wise oily or greasy on a hydrophilic background, in exposed areas (negative-working) or in unexposed areas (positive-working). Receptive to ink.

[0005] Surface lithographic printing plate (surface lit)
ho plates) or planographic printing plates (pl
ananographic printing plate
In the preparation of conventional lithographic printing plates, also referred to as s), a thin layer of the photosensitive composition is coated on a support that has an affinity for water or obtains such an affinity by chemical treatment. Coatings for that purpose include photopolymer layers containing diazo compounds, dichromate-sensitized hydrophilic colloids and various synthetic photopolymers. In particular, diazo-sensitized systems are widely used.

When the photosensitive layer is image-wise exposed, the exposed image areas become insoluble and the non-exposed areas remain soluble. The plate is then developed using a suitable solution to remove the diazonium salt or diazo resin in unexposed areas.

[0007] In another case, printing plates are known that contain a photosensitive coating that, when exposed imagewise, renders the exposed areas soluble. In that case, subsequent development removes the exposed areas. A typical example of such a photosensitive coating is a quinone-diazide based coating.

Typically, the photographic material from which the printing plate is made is camera-exposed through a photographic film containing the image to be reproduced in a lithographic printing process. Such work practices are cumbersome and labor intensive. On the other hand, however, the printing plates thus obtained are of excellent lithographic quality.

Thus, there has been an attempt to obtain a printing plate directly from computer data representing the image to be reproduced, except for the need for photographic film in the above method. However, the photosensitive coating is not sensitive enough to be directly exposed using a laser. It has therefore been proposed to coat a silver halide layer over the photosensitive coating. The silver halide can then be directly exposed using a laser under computer control. The silver halide layer is subsequently developed to leave a silver image on the photosensitive coating. The silver image then serves as a mask in the overall exposure of the photosensitive coating. After overall exposure, the silver image is removed and the photosensitive coating is developed. Such a method is described, for example, in JP-A-60.
Although it is disclosed in US Pat. No. 6,617,52, it has the disadvantage of requiring complex development and an associated developer.

GB-1 492 070 discloses a method of providing a metal layer or a layer containing carbon black on a photosensitive coating. Next, the metal layer is ablated using a laser to obtain an image mask on the photosensitive layer. The photosensitive layer is then entirely exposed by UV-light through an image mask. After removing the image mask, the photosensitive layer is developed to obtain a printing plate. However, this method still has the disadvantage that the image mask must be removed by a cumbersome process before developing the photosensitive layer.

Furthermore, methods are known for making printing plates that involve the use of imaging elements that are heat-sensitive rather than light-sensitive. A particular disadvantage of the photosensitive imaging element as described above for the preparation of a printing plate is that it must be shielded from light. Furthermore, they have sensitivity problems in terms of storage stability, and they exhibit relatively low resolution. There is a clear trend in the market towards heat mode printing plate precursors.

For example, Research in January 1992
Disclosure no. No. 33303 discloses a heat mode imaging element comprising on a support a crosslinked hydrophilic layer containing thermoplastic polymer particles and an infrared absorbing pigment such as carbon black. Imagewise exposure to the infrared laser causes the thermoplastic polymer particles to coagulate imagewise, thereby rendering the surface of the imaging element ink-receptive in these areas without further development. A disadvantage of this method is that the resulting printing plate is easily damaged, since the non-printed areas can become ink-receptive if some pressure is applied thereto. Furthermore, under marginal conditions, the lithographic performance of such printing plates can be poor, and thus such printing plates have little lithographic latitude.

[0013] US-P-4 708 925 discloses an imaging element comprising a photosensitive composition containing an alkali-soluble novolak resin and an onium-salt. The composition may optionally contain an IR-sensitizer. After exposing the imaging element imagewise to UV-visible- or IR-rays and following a development step with an aqueous alkaline solution, a positive- or negative-working printing plate is obtained. The printing results of the lithographic printing plate obtained by irradiation and development of the imaging element are inferior.

[0014] EP-A-625 728 discloses an imaging element comprising a layer which is sensitive to UV- and IR-radiation and which can be positive or negative working. This layer is made of resole resin, novolak resin,
Includes potential Bronsted acids and IR-absorbing materials.
The printing results of the lithographic printing plate obtained by irradiation and development of the imaging element are inferior.

US-P-5 340 699 is EP-A
-625 728, but discloses a method for obtaining a negative working IR-laser recording imaging element. The IR-sensitive layer contains a resole resin, a novolak resin, a potential Bronsted acid and an IR-absorbing material. The printing results of the lithographic printing plate obtained by irradiation and development of the imaging element are inferior.

Further, EP-A-678 380 discloses a method of providing a protective layer on a roughened metal support under a laser-ablationable surface layer. Upon image-wise exposure, the surface layer is completely ablated as well as some portions of the protective layer. The printing plate is then treated with a cleaning liquid to remove the remainder of the protective layer, thereby exposing the hydrophilic surface layer.

EP-A-97 200 588.8 comprises on a lithographic base having a hydrophilic surface an intermediate layer containing a polymer soluble in an aqueous alkaline solution and a top layer sensitive to IR radiation. The top layer discloses a heat mode imaging element for making a lithographic printing plate wherein the volume permeated and / or solubilized by an aqueous alkaline solution decreases or increases when exposed to IR-radiation. .

GB-A-1 208 415 uses a heat-sensitive recording layer constructed with an intermediate layer such that heating as information produces information recording as a difference in water-permeability in various areas of the recording layer. The recording material, including the support, with or without the support, is heated as informed and penetrates through the water-permeable or relatively water-permeable areas of the recording layer, and Treating the recording material with an aqueous liquid configured to cause a permanent physical and / or chemical change of at least a surface portion of the support or the intermediate layer, and removing the entire recording layer A method of recording information including exposing the informationally altered underlying support or interlayer is disclosed.

EP-A-823 327 discloses a positive photosensitive composition exhibiting a difference in an alkaline developer between exposed and unexposed areas, which as a component inducing a difference in solubility. (A) Light-
It contains a heat conversion material and (b) a high molecular weight compound whose solubility in an alkaline developer can be changed mainly by changes other than chemical changes.

US-A-5 641 608 discloses a method for making an imaging pattern of a resist directly on a substrate, which method is not a photoresist but a thermo-resist, ie a light-induced A composition that undergoes a thermal-induced chemical transformation is used. A film of a thermo-resist composition applied to a surface substrate is scanned by a heat source focused on a predetermined pattern without using optical means, and a thermally induced localized composition This results in a chemical transformation of the product, which either creates a resist pattern directly or creates a latent image of a developable pattern in the film.

GB-A-1 154 568 discloses a method for recording graphic originals having contrasting light-absorbing and light-transmitting areas, in which the layer is mainly composed of gelatin and the layer is composed of gelatin. When heated sufficiently, its water-soluble or water-absorbing capacity increases and the light-absorbing substance is also distributed in the recording material, including the supported layer, in which the gelatin layer is applied to the light source of the original. Placing the gelatin layer in contact with the absorbent area and exposing the gelatin layer through the original, the light intensity and duration of the exposure being such that the area of the gelatin layer in contact with the light absorbing area of the original Although substantially unaffected by heat conduction from the light-absorbing region, the water-soluble or water-absorbing capacity of the other region of the gelatin layer may increase the absorption of the copy light by the light-absorbing material in the other region of the gelatin layer. Because of its heating as it increases It is intended.

GB-A-1 245 924 discloses information on a recording material comprising a heat-sensitive recording layer having a composition such that the solubility of a certain region of the layer in a certain solvent can be increased by heating the region of the layer. Discloses a recording method, in which the layer is heated in an informational manner, producing a record of information as the difference in solubility of the various areas of the recording layer in the solvent, and then transferring the entire layer to such a solvent. To remove or infiltrate such a solvent soluble or most soluble portion of the recording layer, wherein the recording layer is completely or predominantly one or more Characterized by comprising a heat-sensitive polymer compound of the formula:

FR-A-1 561 957 discloses a method for recording or reproducing information using electromagnetic radiation, and also discloses elements sensitive to heat-containing substances, in which case the heat is Caused by line exposure.

GB-A-1 155 035 describes a layer of polymeric material which, when a region of the layer is sufficiently heated, undergoes a modification that reduces the solubility of that region in water or an aqueous medium in that region. Discloses a method of recording information in which a recording material is used, wherein one or more substances distributed over the entire area of the layer are introduced into such a layer, Such a material can be heated by exposing the layer to the intense radiant energy absorbed by the material, the material being distributed throughout the material in a pattern determined by the information to be recorded. Exposed to intense radiant energy that is at least partially absorbed by the material, and a corresponding thermal pattern is generated in the material, whereby such information is transmitted to the various regions of the layer by water or water. It is recorded as the difference in solubility in an aqueous medium.

GB-A-1 160 221 is a hydrophobic thermoplastic in the form of particles which are solid at room temperature and which can become water-impermeable or substantially water-impermeable by the action of heat. A method of recording information using a recording material comprising a water-permeable recording layer into which a polymeric material has been introduced is disclosed, wherein the recording material is in thermal conductivity with the polymer particles, and such a material is disclosed. One or more substances distributed over the entire area of the substance have also been introduced, and such substances can be heated by exposing the material to strong electromagnetic radiation absorbed by such substances; The method exposes the recording material to an amount of electromagnetic radiation that is absorbed by the distribution material and distributed throughout the recording material in a pattern determined by the information to be recorded, generating a corresponding thermal pattern in the recording material. ,in addition Water of various regions of the Ri該 recording layer - to record such information as the difference in permeability.

EP-A-97 203 129.8 and EP-A-97 203 132.2 are lithographic bases having a hydrophilic surface and are sensitive to IR radiation,
A heat mode imaging element comprising a soluble polymer in an aqueous alkaline solution and comprising a top layer that is impermeable or insoluble therein with respect to an alkaline developer containing SiO ₂ as a silicate is disclosed.

[0027] The last three heat mode imaging elements have the disadvantage that the top layer is very sensitive to scratches. Covering the layer with a protective layer reduces the resolution and the development latitude due to the small difference in the rate of developer penetration between the exposed and unexposed areas. The solution to the problem will be worthwhile.

[0028]

OBJECTS OF THE INVENTION It is an object of the present invention to provide a heat mode imaging element for making a lithographic printing plate having a wide development latitude.

It is an object of the present invention to provide a heat mode imaging element for making a lithographic printing plate having a high resolution.

It is a further object of the present invention to provide a heat mode imaging element for making a lithographic printing plate having improved scratch resistance.

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

[0032]

SUMMARY OF THE INVENTION In accordance with the present invention, on a lithographic printing base having a hydrophilic surface, a polymer soluble in aqueous alkaline solution but insoluble in water and less than 5% by weight of aqueous polymer relative to the polymer. A first layer comprising a hydrophilic polymer that is soluble in water and an upper layer on the same side as the first layer of the lithographic base, which is IR-sensitive and impervious or insoluble with respect to an alkaline developer. The first layer and the top layer are heat mode imaging elements for making a lithographic printing plate, which can be one and the same layer; wherein the top layer is a polymer in an amount of 30 mg to 500 mg / m ² , tria A heat mode imaging element is provided which comprises a compound selected from the group consisting of a reel methane dye and a phthalocyanine dye.

[0033]

DETAILED DESCRIPTION OF THE INVENTION The top layer is also called the second layer.

The first layer preferably contains no more than 1% by weight of a hydrophilic polymer, more preferably no hydrophilic polymer.

Suitable polymers which can be used as scratch resistance improvers are preferably at least 35
Is a polymer having a glass transition temperature of greater than 400C, more preferably greater than 40C, and capable of forming a film upon drying at elevated temperatures.

Representative polymers that can be used as scratch resistance improvers are, for example, acrylates, self-crosslinking acrylates, acrylates combined with melamine-hardeners. These polymers can be added to the coating as a solution, but can also be added to the coating as a dispersion.

Another type of polymer that can be used as a scratch resistance enhancer is of the polyvinyl alcohol and modified derivative type, which is a known cure of the orthosilicate, orthotitanate, aldehyde-type compound type. It can be cured using an agent.

Other polymers that can be used as a scratch resistance improver include polymethyl methacrylate,
It is a styrene-maleic anhydride copolymer, polycarbonate, polyamide, styrene-methyl methacrylate-maleic acid terpolymer, and acrylate-styrene-maleic acid self-crosslinkable terpolymer.

One preferred type of polymer that can be used as a scratch resistance enhancer is the type of polyurethane. Polyurethanes can be obtained from the polymerization of the following polyisocyanates and polyhydric alcohols.

Simple polyhydric alcohols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4 butylene glycol, 1,5 pentanediol, 1,6 hexane Diol, diethylene glycol,
Dipropylene glycol, neopentyl glycol, triethylene glycol, p-xylylene glycol, bisphenol A, hydrogenated bisphenol A, bisphenol dihydroxypropyl ether, glycerol, trimethylolethane, trimethylolpropane, trishydroxymethylaminomethane, pentaerythritol, Dipentaerythritol, sorbitol, sucrose, degraded starch can be used. As polyhydric alcohols, the polycondensation between any of these polyhydric alcohols and a dicarboxylic acid or anhydride, such as succinic acid, three phthalic acid isomers, phthalic anhydride, adipic acid, hexahydrophthalic acid, isophthalic acid The resulting condensed polyester polyol having hydroxyl groups at both ends and a hydroxy-functional polylactone produced by a transesterification reaction of diphenyl carbonate and glycol can also be used. Another method for the preparation of hydroxy-terminated polyesters involves ring opening polymerization of ε-caprolactone in the presence of glycol.

The following compounds can be used as isocyanates: hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, diphenyl ether isocyanate, dimer acid diisocyanate,
Bicycloheptane triisocyanate, paraphenylene diisocyanate, 2,4- or 2,6-toluylene diisocyanate, 4,4-diphenylmethane diisocyanate, tolidine diisocyanate, hydrogenated xylylene diisocyanate, cyclohexane diisocyanate Notate, meta-xylylene diisocyanate, 2,6-diisocyanate methyl caproate, 4,4'-methylenebis (cyclohexyl isocyanate), methylcyclohexane 2,4 (2,6) diisocyanate, 1,3-
(Isocyanatomethyl) cyclohexane, isophorone diisocyanate, teratomethylxylylenediisocyanate, polymethylene polyphenylisocyanate, triarylmethanetriisocyanate, tris (isocyanatophenyl) thiophosphate, tetramethylxylylenediisocyanate, lysine Ester triisocyanate, 1,6,11-undecane triisocyanate, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-hexamethylene triisocyanate. . . .

The polyurethanes described above can be cured with melamine derivatives. As a preferred melamine derivative, a methylated melamine-formaldehyde reaction product can be used. For curing these systems,
The addition of a strong acid functions as a catalyst.

The urethane is preferably from 30 to 200 mg.
/ M ² .

Another preferred type of polymer that can be used as a scratch resistance enhancer is the type of cellulose and derivatives. As nitrocellulose, products obtained by esterifying cellulose with a nitrating acid having a nitrogen content of the final product of less than 12.6% can be used. Natural cellulose can be used as the cellulose.

The cellulose is preferably 30 to 120 m
It is used in an amount of g / m ² .

The triarylmethane dye is preferably 30
Amounts in the range of ~ 500 mg, more preferably 50-200 mg.
It is used in an amount of mg / m ² .

The phthalocyanine dye can be a metal-containing dye or a metal-free dye. They preferably have an amount in the range of 40-600 mg, more preferably 80-600 mg.
Used in an amount of 250 mg / m ² .

In the case of the first embodiment, the first layer and the top layer are different. A lithographic base on having a hydrophilic surface in the embodiment, is sensitive to the first layer and IR- line comprising a polymer soluble in an aqueous alkaline solution, an alkaline developer containing SiO ₂ as silicate A heat mode imaging element for making a lithographic printing plate having an uppermost layer on the same side as the first layer of the lithographic printing base, which is impermeable or insoluble therein.

The top layer according to the invention comprises an IR-dye or pigment and a binder resin. Mixtures of IR-dyes or pigments can be used, but it is preferred to use only one type of IR-dye or pigment. Preferably said I
The R-dye is an IR-cyanine dye. Particularly useful IR
The cyanine dye is a cyanine dye having at least two acid groups, more preferably at least two sulfone groups. Even more preferred are cyanine dyes having two indolenines and at least two sulfonic acid groups. Most preferred are compounds I having the structure
It is.

[0050]

Embedded image Particularly useful IR-absorbing pigments are carbon black, metal carbides, borides, nitrides, carbonitrides, bronze-
Structurally related to structural oxides and bronze groups,
Oxides without components, for example WO _2.9 . Conductive polymer dispersions, such as those based on polypyrrole or polyaniline, can also be used.
The lithographic performance obtained, and especially the printing durability, depends on the heat sensitivity of the imaging element. In this regard, it has been found that carbon black gives very good and favorable results.

IR-absorbing dyes or pigments are
Preferably from 1 to 99 parts by weight of the total amount of the sensitive top layer,
More preferably it is present in an amount of 50 to 95 parts by weight.

The top layer is preferably a water-insoluble polymer as binder, such as cellulose esters, copolymers of vinylidene chloride and acrylonitrile, poly (meth)
It can include acrylates, polyvinyl chloride, silicone resins, and the like. Preferred as a binder is a nitrocellulose resin.

The total amount of the uppermost layer is preferably 0.05 to 1
0 g / m ^2, more preferably in the range of 0.1-2 g / m ^2.

Upon image-wise exposure, in the top layer, differences in the volume permeated and / or solubilized by the aqueous alkaline solution are created with the alkaline developer of the present invention.

In the present invention, image-wise IR exposure cleans the imaged portions without solubilizing and / or damaging the non-imaged portions during development. The capacity increases to the extent.

The development using the aqueous alkaline solution is preferably carried out within an interval of 5 to 120 seconds.

Between the top layer and the lithographic base, the present invention preferentially 7.5
A first layer soluble in an aqueous alkaline developer having a pH of １４14. The layer is preferably continuous with the top layer, but there can be other layers between the top layer and the first layer. The alkali-soluble binder used in this layer is preferably a conventional positive or negative working P
Hydrophobic binders such as those used in S-plates, such as novolak polymers, polymers containing hydroxystyrene units, carboxy-substituted polymers and the like. Typical examples of these polymers are DE-A-4 007 428, D
EA-4 027 301 and DE-A-4 445
820. The hydrophobic binders used in connection with the present invention are further characterized by insolubility in water and partial solubility / swellability in alkaline solutions and / or partial solubility in water when combined with cosolvents. I have.

Furthermore, the aqueous alkali-soluble layer is preferably a visible light- and UV-light desensitizing layer. The layer is preferably thermally curable. This preferably visible- and UV-desensitized layer is between 250 nm and 650 nm.
Excluding photosensitive components that absorb in the wavelength range of, for example, diazo compounds, photoacids, photoinitiators, quinonediazides, and sensitizers. In this way, a printing plate stable in daylight can be obtained.

The first layer is preferably a low molecular weight acid, preferably a carboxylic acid, even more preferably benzoic acid,
Most preferably, it also contains 3,4,5-trimethoxybenzoic acid or benzophenone.

The ratio of the total amount of low molecular weight acid or benzophenone to polymer in the first layer is preferably 2:98.
-40: 60, more preferably 5: 95-20: 80. The total amount of the first layer is preferably 0.1 to 1
0 g / m ^2, more preferably from 0.3 to 2 g / m ^2.

In the imaging element of the present invention, the lithographic base can be anodized aluminum for all embodiments. A particularly preferred lithographic base is an electrochemically roughened, anodized aluminum support. The anodized aluminum support can be treated to increase its surface hydrophilicity. For example, an aluminum support can be silicated by treating its surface with a sodium silicate solution at an elevated temperature, for example, 95 ° C. In another case, a phosphating can be applied, which comprises treating the aluminum oxide surface with a phosphating solution, which can further contain inorganic fluoride. Further, the aluminum oxide surface can be rinsed with a citric acid or citrate solution. This treatment can be performed at room temperature or at a slightly elevated temperature of about 30-50 ° C. A further interesting treatment involves rinsing the aluminum oxide surface with a bicarbonate solution. Furthermore, the surface of aluminum oxide is coated with polyvinyl phosphonic acid, polyvinyl methyl phosphonic acid, phosphate of polyvinyl alcohol, polyvinyl sulfonic acid,
The treatment can be carried out using polyvinyl benzene sulfonic acid, a sulfate of polyvinyl alcohol, and an acetal of polyvinyl alcohol produced by a reaction with a sulfonated aliphatic aldehyde. It is further apparent that one or more of these post-treatments can be performed alone or in combination. A more detailed description of these processes is given in GB-A-1 084 070, DE-A-4.
423 140, DE-A-4 417 907, E
PA-659 909, EP-A-537 633,
DE-A-4 001 466, EP-A-292 8
01, EP-A-291760 and US-P-445
8005.

According to another mode in connection with the present invention, the lithographic base having a hydrophilic surface is, in all embodiments, a flexible support, such as a paper or plastic film provided with a cross-linked hydrophilic layer. including. Particularly suitable cross-linked hydrophilic layers can be obtained from hydrophilic binders cross-linked with cross-linking agents such as formaldehyde, glyoxal, polyisocyanate or hydrolyzed tetra-alkyl orthosilicate. The latter is particularly preferred.

As hydrophilic binders, 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. The hydrophilicity of the (co) polymer or (co) polymer mixture used is preferably the same or higher than that of the polyvinyl acetate hydrolyzed to at least 60% by weight, preferably to the extent of 80% by weight.

The amount of crosslinker, especially tetraalkyl orthosilicate, is preferably at least 0.2 parts by weight, more preferably 0.5 to 5 parts by weight, most preferably 1.0 part by weight per part by weight of hydrophilic binder. Parts to 3 parts by weight.

The lithographic base-based crosslinked hydrophilic layer used according to this embodiment preferably also contains substances which improve the mechanical strength and porosity of the layer. Colloidal silica can be used for this purpose. The colloidal silica used is, for example, up to 40 nm, for example 20 n
It can be in the form of any commercially available water-dispersion of colloidal silica having an average particle size of m. In addition, inert particles of larger dimensions than colloidal silica, for example, Colloid and Interface
Sci. , Vol. 26, 1968, pages 6
Particles having an average diameter of at least 100 nm can be added which are silica or alumina particles or particles of titanium dioxide or other heavy metal oxides prepared according to StOEber as described in 2 to 69. The introduction of these particles gives the surface of the cross-linked hydrophilic layer a uniform rough texture consisting of microscopic hills and valleys, which serves as a storage for water in the background areas.

The thickness of the crosslinked hydrophilic layer of the lithographic printing base according to this embodiment can vary within the range of 0.2 to 25 μm, preferably 1 to 10 μm.

A specific example of a cross-linked hydrophilic layer suitable for use in accordance with the present invention is described in EP-A-601 24
0, GB-P-1 419 512, FR-P-23
00354, US-P-3 971 660, US-P
-4 284 705 and EP-A 514 490.

As the lithographic printing base flexible support relating to this embodiment, a plastic film such as a substrate-based polyethylene terephthalate film, a substrate-based polyethylene naphthalate film, a cellulose acetate film, a polystyrene film, a polycarbonate film and the like can be used. Particularly preferred. The plastic film support can be opaque or transparent.

It is particularly preferable to use a polyester film support provided with an adhesion promoting layer. Particularly suitable adhesion promoting layers for use in accordance with the present invention are EP-A-619.
524, EP-A-620 502 and EP-A-6
A hydrophilic binder and colloidal silica as disclosed in US Pat. Preferably the amount of silica in the adhesion improving layer is between ^{200mg / m 2 ~750mg / m 2} . Furthermore, the ratio of silica to hydrophilic binder is preferably more than 1 and the surface area of the colloidal silica is preferably at least 300 meters ² / g, more preferably at least 500 meters ² /
g.

In the case of the second embodiment, the first and second layers are identical. In this embodiment, there is provided a heat mode imaging element for making a lithographic printing plate having a top layer on a lithographic printing base having a hydrophilic surface, wherein the top layer comprises I
Sensitive to R- line comprises a polymer soluble in an aqueous alkaline solution, an impermeable insoluble or therein which respect alkaline developer containing SiO ₂ as silicate.

The IR-sensitive layer according to the invention comprises an IR-dye or pigment and a polymer which is soluble in an aqueous alkaline solution. Mixtures of IR-dyes or pigments can be used, but it is preferred to use only one type of IR-dye or pigment. Suitable IR-dyes and pigments are those listed above in the first embodiment of the present invention.

The IR-dye is preferably present in an amount of 1 to 60 parts by weight, more preferably 3 to 60 parts by weight of the total amount of the IR-sensitive top layer.
It is present in an amount of 50 parts by weight.

The alkali-soluble polymers used in this layer are preferably hydrophobic and ink-receptive polymers such as those used in conventional positive- or negative-working PS-plates, such as carboxy-substituted polymers. More preferred are phenolic resins such as hydroxystyrene unit containing polymers or novolak polymers. Most preferred are novolak polymers. A typical example of these polymers is DE-A-400
7 428, DE-A-4 027 301 and DE-
A-4445820. The hydrophobic polymers used in connection with the present invention are further characterized by insolubility in water and at least partial solubility / swelling in alkaline solutions and / or at least partial solubility in water when combined with cosolvents. And

Furthermore, the IR-sensitive layer is preferably a visible- and UV-light desensitizing layer. Furthermore, the layer is preferably thermally curable. This preferably visible- and UV-light desensitized layer is between 250 nm and 650 nm.
Excluding light-sensitive components that absorb in the wavelength range of, for example, diazo compounds, photoacids, photoinitiators, quinonediazides, and sensitizers. In this way, a printing plate stable in daylight can be obtained.

The IR-sensitive layer is preferably a low molecular weight acid, more preferably a carboxylic acid, even more preferably benzoic acid, most preferably 3,4,5-trimethoxybenzoic acid or benzophenone, more preferably trihydroxybenzophenone. Including.

Low molecular weight acids or in the IR-sensitive layer
The ratio of the total amount of benzophenone to the polymer is preferably
Is 2:98 to 40:60, more preferably 5:95 to 3
The range is 0:70. The total amount of the IR-sensitive layer is good.
Preferably 0.1 to 10 g / m ^Two, More preferably 0.3
~ 2g / m^TwoRange.

Upon image-wise exposure, differences in the volume permeated and / or solubilized by the alkaline developer in the IR-sensitive layer are created for the alkaline developer of the present invention.

To prepare a lithographic printing plate, the heat mode imaging element is imagewise exposed and developed.

The image-wise exposure in connection with the present invention is an image-wise scanning exposure involving the use of a laser operating in the infrared or near-infrared, ie, 700-1500 nm wavelength region. Most preferred are laser diodes that emit in the near-infrared. Exposure of the imaging element can be performed using a laser having a short pixel dwell time as well as a laser having a long pixel dwell time. Preferred is 0.0
A laser with a pixel dwell time of between 05 μs and 20 μs.

After image-wise exposure, the heat mode imaging element is developed by rinsing it with an aqueous alkaline solution. The aqueous alkaline solution used in the present invention,
It is used for the development of conventional positive-acting presensitized printing plates, preferably SiO ₂ as a silicate.
And preferably has a pH of 11.5-14.
The imaged portion of the top layer thus exposed and made more permeable to the aqueous alkaline solution is cleaned, thereby obtaining a positive working printing plate.

In the case of the present invention, the composition of the developer used is also very important.

Therefore, what is particularly important for stable development for a long time is the quality such as the concentration of alkali and the concentration of silicate in the developer. Under such circumstances, the present inventors can carry out rapid high-temperature processing only when a developer having the above composition is used, the amount of replenisher to be supplemented is small, and the developer must be replaced. It has been found that stable development can be carried out over a long period of three months or more without any problem.

Preferably, the developing solution and the replenisher for the developing solution used in the present invention are mainly alkali metal silicate and alkali metal hydroxide represented by MOH or M _2.
O by an aqueous solution containing the oxide represented, wherein said developer comprises SiO ₂ concentration of 0.5 to 5 wt%. Suitable as such alkali metal silicates are, for example, sodium silicate, potassium silicate,
Lithium silicate and sodium metasilicate. On the other hand, preferred as such alkali metal hydroxides are sodium hydroxide, potassium hydroxide and lithium hydroxide.

The developer used in the present invention can simultaneously contain another alkaline reagent. Examples of such other alkaline reagents are ammonium hydroxide, sodium triphosphate, sodium diphosphate, potassium triphosphate, potassium diphosphate, ammonium triphosphate,
Inorganic alkaline reagents such as ammonium diphosphate, sodium bicarbonate, sodium carbonate, potassium carbonate and ammonium carbonate; and mono-, di- or triethanolamine, mono-, di- or trimethylamine, mono-, di- or triethylamine And organic alkaline reagents such as mono- or di-isopropylamine, n-butylamine, mono-, di- or triisopropanolamine, ethyleneimine, ethylenediimine and tetramethylammonium hydroxide.

In the case of the present invention, [SiO ₂ ] /
The molar ratio of [M ₂ O] is particularly important, it is generally 0.6 to 1.5, preferably from 0.7 to 1.3. This means that if the molar ratio is lower than 0.6, a large variation in activity is observed, whereas if it exceeds 1.5, rapid development becomes difficult, and the elution of the photosensitive layer on non-image areas or This is because the removal tends to be incomplete. Further concentration of SiO ₂ in the developer and replenisher preferably ranges from 1 to 4 wt%. Such limitation of the concentration of SiO ₂ makes it possible to provide large amounts of stable lithographic printing plates having good finishing qualities even when treated prolonged present invention.

In a particularly preferred embodiment, 1.0 to
A molar ratio [SiO 2 in the range of 1.5_Two] / [M_TwoO] and 1 to 1
4% by weight SiO_TwoMetal silicic acid having a concentration of
An aqueous salt solution is used as a developer. Such a place
Is equal to or higher than the alkali concentration of the developer
Of course, replenishers with alkaline concentrations are used
It is. To reduce the amount of replenisher to be supplied
In addition, the molar ratio of the replenisher [SiO _Two] / [M_TwoO] of the developer
Less than or equal to or developer
If the molar ratio of_TwoConcentration of
Is advantageously high.

In the developer and replenisher used in the present invention, the solubility in water at 20 ° C. was 10% by weight at the same time.
The following organic solvents can be used as needed. Examples of such organic solvents are carboxylic esters such as ethyl acetate, propyl acetate, butyl acetate, amyl acetate, benzyl acetate, ethylene glycol monobutyl acetate, butyl lactate and butyl levulinate; ethyl butyl ketone, methyl isobutyl ketone and Ketones such as cyclohexanone; ethylene glycol monobutyl ether;
Alcohols such as ethylene glycol benzyl ether, ethylene glycol monophenyl ether, benzyl alcohol, methylphenyl carbinol, n-amyl alcohol and methyl amyl alcohol; alkyl-substituted aromatic hydrocarbons such as chilesine; and methylene dichloride and monochlorobenzene Is a halogenated hydrocarbon. These organic solvents can be used alone or in combination. Particularly preferred in the present invention is benzyl alcohol. These organic solvents are generally added to the developer or replenisher therefor in amounts of up to 5% by weight, preferably up to 4% by weight.

The developer and replenisher used in the present invention can simultaneously contain a surfactant for the purpose of improving their developability. Examples of such surfactants include salts of higher alcohol (C8-C22) sulfates, such as sodium salt of lauryl alcohol sulfate,
Octyl alcohol sulfate sodium salt, lauryl alcohol sulfate ammonium salt, Tee
pol B-81 (trademark, Shell Chemica)
ls Co. And disodium alkyl sulfates; salts of aliphatic alcohol phosphates, such as sodium salt of cetyl alcohol phosphate; alkyl aryl sulfonates, such as sodium salt of dodecylbenzene sulfonate, isopropyl naphthalene sulfonate. Sodium salt, sodium salt of dinaphthalenedisulfonate and sodium salt of metanitrobenzenesulfonate; sulfonate of alkylamide, for example, C ₁₇ H ₃₃ CON (CH ₃ ) CH ₂ CH ₂
Includes SO ₃ Na and sulfonates of dibasic aliphatic acid esters, such as sodium dioctyl sulfosuccinate and sodium dihexyl sulfosuccinate. These surfactants can be used alone or in combination. Particularly preferred are sulfonates. These surfactants can generally be used in amounts of up to 5% by weight, preferably up to 3% by weight.

In order to enhance the development stability of the developer and replenisher used in the present invention, the following compounds can be used simultaneously.

Examples of such compounds are neutral salts, for example
NaCl, KCl and KBr as disclosed in JN-A-58-75 152; chelating agents such as
JN-A-58-190 952 (U.S.A.-44
EDTA and N as disclosed in US Pat.
TA, JN-A-59-121 336 (US-A-4
606 995) [Co (N
Complexes such as _{H 3) 6] C 13;} JN-A-55-25 10
IIa, II of the periodic table such as those disclosed in US Pat.
Ionizable compounds of group Ia or IIIb elements; anionic or amphoteric surfactants, for example JN-A-50-5
Sodium alkylnaphthalenesulfonate and N-tetradecyl-N, N- as disclosed in US Pat.
Dihydroxytyl betaine; US-A-4 374 9
Tetramethyldecine diol as disclosed in No. 20, non-ionic surfactants as disclosed in JN-A-60-213 943; cationic polymers;
For example, the methyl chloride quaternary product of p-dimethylaminomethyl polystyrene as disclosed in JN-A-55-95 946
de quaternary products); amphoteric polyelectrolytes, for example, JN-A-56-145
Copolymers of vinylbenzyltrimethylammonium chloride and sodium acrylate as disclosed in US Pat. No. 28; Reducing inorganic salts such as JN-A-57-192
Sodium sulfite and alkali-soluble mercapto compounds or thioether compounds such as those disclosed in US-A-4 467 027, for example thiosalicylic acid, cysteine and thioglycolic acid; inorganic lithium compounds such as JN-A- 58-59 444
Lithium chloride as disclosed in JN-A-5034 442; lithium benzoate as disclosed in JN-A-5034442; JN-A-59-7.
No. 5,255, containing organometallic surfactants containing Si, Ti, and the like; JN-A-59-842
Organoboron compounds as disclosed in US Pat. No. 41 (US-A-4500 625); quaternary ammonium salts, for example tetraalkylammonium oxides as disclosed in EP-A-101 010; Agents such as sodium dehydroacetate as disclosed in JN-A-63-226 657.

In the method for development processing of the present invention,
Any known means of replenishing the replenisher for the developer can be used. An example of such a method preferably used is JN-A-55-115039 (GB-A-
JN-A-58-953, a method for intermittent or continuous replenishment as a function of the amount and time of PS plates processed as disclosed in US Pat. No. 2,046,931).
A sensor for detecting the extent of the eluted photosensitive layer as described in US Pat. No. 49 (U.S. Pat. No. 4,537,496) is located in the central part of the development zone and is sensitive to the extent of the eluted photosensitive layer to be detected. A method comprising proportionally replenishing the replenisher; determining the impedance value of the developer solution as disclosed in GB-A-2 208 249, processing the detected impedance value by a computer and processing the replenisher solution It is a method that includes performing replenishment.

The printing plate of the present invention can be used as a seamless sleeve printing plate in a printing method. With this option, the printing plate is soldered in a cylindrical shape using a laser. Instead of applying a classically produced printing plate in the classical way, this cylindrical printing plate having the diameter of the printing cylinder as the diameter is slid over the printing cylinder. For more details on sleeves, see "Grafisc
h Nieuws ”ed. Keesing, 15, 1
995, page 4 to 6.

After the image-forming element exposed image-wise is developed using an aqueous alkaline solution and dried, the resulting plate can be used as it is as a printing plate. However, to improve the durability, the plate can be baked at a temperature of 200 ° C. to 300 ° C. for 30 seconds to 5 minutes. The imaging element can also be subjected to an overall post-exposure to UV-radiation to harden the image and increase the run length of the printing plate.

The following examples illustrate the present invention without limiting it thereto. All parts and percentages are by weight unless otherwise specified.

[0095]

EXAMPLES Example 1 (Comparative Example) Production of a Lithographic Printing Base An aluminum foil having a thickness of 0.30 mm was immersed in an aqueous solution containing 5 g / l of sodium hydroxide at 50 ° C., and deionized water was added. Degreased by rinsing. Then 3
Using alternating current at a temperature of 5 ° C. and a current density of 1200 A / m ² , 4 g / l hydrochloric acid, 4 g / l boric acid and 5 g / l
The foil was electrochemically roughened in an aqueous solution containing 1 aluminum ion to form a surface topology with an average centerline roughness Ra of 0.5 mm.

After rinsing with deionized water, then 300 g /
at 60 ° C. using an aqueous solution containing 1
The aluminum foil was etched for 0 seconds and rinsed with deionized water at 25 ° C. for 30 seconds.

The foil was then placed in an aqueous solution containing 200 g / l of sulfuric acid, at a temperature of 45 ° C., a voltage of
Anodize at a current density of A / m ² for about 300 seconds to form an anodized film of 3.00 g / m ² Al ₂ O ₃ , then wash with deionized water and contain polyvinylphosphonic acid The solution is then worked up with a solution containing aluminum trichloride and then with deionized water.
Rinse at 0 ° C. for 120 seconds and dry. Preparation of Heat Mode Imaging Element 1 A layer from a 8.6% by weight solution in tetrahydrofuran / methoxypropanol in a 55/45 ratio was first coated on the above lithographic printing base with a wet coating thickness of 14 μm. The resulting layer is 88% Alnovo
Contains 1 SPN452 and 12% 3,4,5-trimethoxybenzoic acid.

On top of this layer was then added 0.73 in 50/50 methyl ethyl ketone / methoxypropanol.
An IR-sensitive layer from a 5% by weight solution was coated with a wet coating thickness of 20 μm. This layer was dried at a temperature of at least 120 ° C. for at least 40 seconds. Resulting IR- sensitive layer of carbon black 115 mg / m ^2, nitrocellulose 11.5mg / m ^2, Solsperse 500 of 2.1 mg / m ²
0, 11.3 mg / m ² Solsperse 280
It contained Tego Wet 265 and 5.0 mg / m ² of Tego Glide 410 in 00,2.0mg / m ^2.

Example 2 A 55/4 sheet was first placed on the lithographic base described in Example 1.
A layer from a 8.6 wt% solution in tetrahydrofuran / methoxypropanol in a ratio of 5 was coated with a wet coating thickness of 14 μm. The resulting layers are 88% Alnovol SPN452 and 12% 3,4,5-
Trimethoxybenzoic acid was included.

On top of this layer was then added 1.05 in a 50/50 ratio of methyl ethyl ketone / methoxypropanol.
An IR-sensitive layer from a 20% by weight solution was coated with a wet coating thickness of 20 μm. This layer was dried at a temperature of at least 120 ° C. for at least 40 seconds. Resulting IR- sensitive layer 115 mg / m ² of carbon black, of 63.0mg / m ² ALMACRYL
XPE-1676,11.5mg / m ² nitrocellulose, Solsperse500 of 2.1 mg / m ²
0, 11.3 mg / m ² Solsperse 280
It contained Tego Wet 265 and 5.0 mg / m ² of Tego Glide 410 in 00,2.0mg / m ^2. ALMACRYL XPE-1676 ^R is I
urethane-modified polyester commercially available from MagePolymers Europe.

Example 3 First, 55/4 on the lithographic printing base described in Example 1.
A layer from a 8.6 wt% solution in tetrahydrofuran / methoxypropanol in a ratio of 5 was coated with a wet coating thickness of 14 μm. The resulting layers are 88% Alnovol SPN452 and 12% 3,4,5-
Trimethoxybenzoic acid was included.

On top of this layer was then 1.30 in a 50/50 ratio of methyl ethyl ketone / methoxypropanol.
An IR-sensitive layer from a 57% by weight solution was coated with a wet coating thickness of 20 μm. This layer was dried at a temperature of at least 120 ° C. for at least 40 seconds. Resulting IR- sensitive layer 115 mg / m ² of carbon black, of 114.1mg / m ² ALMACRY
L XPE-1676,11.5mg / m ² nitrocellulose, of 2.1mg / m ² Solsperse 5
000, 11.3 mg / m ² Solsperse 2
8000, 2.0 mg / m ² Tego Wet 26
Tego Glide 41 at 5 and 5.0 mg / m ²
0.

Example 4 A 55/4 sheet was first placed on the lithographic printing base described in Example 1.
A layer from a 8.6 wt% solution in tetrahydrofuran / methoxypropanol in a ratio of 5 was coated with a wet coating thickness of 14 μm. The resulting layers are 88% Alnovol SPN452 and 12% 3,4,5-
Trimethoxybenzoic acid was included.

On top of this layer was then added 1.05 in a 50/50 ratio of methyl ethyl ketone / methoxypropanol.
An IR-sensitive layer from a 2% by weight solution was coated with a wet coating thickness of 20 μm. This layer was dried at a temperature of at least 120 ° C. for at least 40 seconds. The resulting IR-sensitive layer is 115 mg / m ² carbon black, 43.7 mg / m ² ALMACRYL
XPE-1676,11.5mg / m ² nitrocellulose, 18.9 mg / m ² of CYMEL 303,
0.63 mg / m ² p-toluenesulfonic acid, 2.1
mg / m ² Solsperse 5000, 11.3
mg / m ² Solsperse 28000, 2.0
Tego Wet 265 and 5.0 mg in mg / m ²
/ M ² of TegoGlide 410. CY
MEL 303 ^R is commercially available methylated melamine from CYANAMID - formaldehyde crosslinking agent.

Example 5 On the lithographic printing base described in Example 1, 55/4
A layer from a 8.6 wt% solution in tetrahydrofuran / methoxypropanol in a ratio of 5 was coated with a wet coating thickness of 14 μm. The resulting layers are 88% Alnovol SPN452 and 12% 3,4,5-
Trimethoxybenzoic acid was included.

On top of this layer was then added 0.77 in 50/50 methyl ethyl ketone / methoxypropanol.
An IR-sensitive layer from a 7% by weight solution was coated with a wet coating thickness of 20 μm. This layer was dried at a temperature of at least 120 ° C. for at least 40 seconds. The resulting IR-sensitive layer is 115 mg / m ² carbon black, 20 mg / m ² nitrocellulose,
2.1 mg / m ² Solsperse 5000, 1
1.3 mg / m ² Solsperse 28000,
2.0 mg / m ² Tego Wet 265 and 5.
It contained 0 mg / m ² of TegoGlide 410.

Example 6 On a lithographic base described in Example 1, 55/4
A layer from a 8.6 wt% solution in tetrahydrofuran / methoxypropanol in a ratio of 5 was coated with a wet coating thickness of 14 μm. The resulting layers are 88% Alnovol SPN452 and 12% 3,4,5-
Trimethoxybenzoic acid was included.

On top of this layer was then added 0.92 in a 50/50 ratio of methyl ethyl ketone / methoxypropanol.
An IR-sensitive layer from a 7% by weight solution was coated with a wet coating thickness of 20 μm. This layer was dried at a temperature of at least 120 ° C. for at least 40 seconds. The resulting IR-sensitive layer is 115 mg / m ² carbon black, 50 mg / m ² nitrocellulose,
2.1 mg / m ² Solsperse 5000, 1
1.3 mg / m ² Solsperse 28000,
2.0 mg / m ² Tego Wet 265 and 5.
It contained 0 mg / m ² of TegoGlide 410.

Example 7 On the lithographic printing base described in Example 1, 55/4
A layer from a 8.6 wt% solution in tetrahydrofuran / methoxypropanol in a ratio of 5 was coated with a wet coating thickness of 14 μm. The resulting layers are 88% Alnovol SPN452 and 12% 3,4,5-
Trimethoxybenzoic acid was included.

On top of this layer is 1.17 in 50/50 methyl ethyl ketone / methoxypropanol.
An IR-sensitive layer from a 7% by weight solution was coated with a wet coating thickness of 20 μm. This layer was dried at a temperature of at least 120 ° C. for at least 40 seconds. The resulting IR-sensitive layer is 115 mg / m ² carbon black, 100 mg / m ² nitrocellulose,
2.1 mg / m ² Solsperse 5000, 1
1.3 mg / m ² Solsperse 28000,
2.0 mg / m ² Tego Wet 265 and 5.
It contained 0 mg / m ² of Tego Glide 410.

Example 8 First, a 55/4 on the lithographic base described in Example 1
A layer from a 8.6 wt% solution in tetrahydrofuran / methoxypropanol in a ratio of 5 was coated with a wet coating thickness of 14 μm. The resulting layers are 88% Alnovol SPN452 and 12% 3,4,5-
Trimethoxybenzoic acid was included.

On top of this layer is 1.17 in methyl ethyl ketone / methoxypropanol in a 50/50 ratio.
An IR-sensitive layer from a 7% by weight solution was coated with a wet coating thickness of 20 μm. This layer was dried at a temperature of at least 120 ° C. for at least 40 seconds. Resulting IR- sensitive layer of carbon black 115 mg / m ^2, nitrocellulose 11.5mg / m ^2, Solsperse 500 of 2.1 mg / m ²
0, 11.3 mg / m ² Solsperse 280
00, 100 mg / m ² HELIOGEN BLAU
D7565, 2.0 mg / m ² Tego Wet
Tego Glide at 265 and 5.0 mg / m ²
410. C. I. Pigment Blue
HELIOGEN BLAU also named 16
D7565 is a copper and chloride free phthalocyanine dye commercially available from BASF.

Example 9 The lithographic base described in Example 1 was first 55/4
A layer from a 8.6 wt% solution in tetrahydrofuran / methoxypropanol in a ratio of 5 was coated with a wet coating thickness of 14 μm. The resulting layers are 88% Alnovol SPN452 and 12% 3,4,5-
Trimethoxybenzoic acid was included.

On top of this layer is 1.17 in 50/50 methyl ethyl ketone / methoxypropanol.
An IR-sensitive layer from a 7% by weight solution was coated with a wet coating thickness of 20 μm. This layer was dried at a temperature of at least 120 ° C. for at least 40 seconds. Resulting IR- sensitive layer of carbon black 115 mg / m ^2, nitrocellulose 11.5mg / m ^2, Solsperse 500 of 2.1 mg / m ²
0, 11.3 mg / m ² Solsperse 280
00, 100 mg / m ² BASONYL BLAU
633, 2.0 mg / m ² Tego Wet 265
And 5.0 mg / m ² Tego Glide 410
Was contained. C. I. BASONYL BLAU 633, also named Basic Blue 8, is a BA
A triarylmethane dye commercially available from SF.

Heat Mode Imaging Element Scratch The above materials in Comparative Example 1 and Examples 2-9 were scratched in a "Linimark" test. In this test, a scratch is formed by moving the needle at a speed of 96 cm / min under a well-defined load. The needle has a 1.5 mm radius Robin type (type).
robin). Form 15 scratches under the following loads: 57-85-114-142-
170-113-169-225-282-338-4
00-600-800-1000 and 1200 mN.

After the formation of 15 scratches, the material is exposed.

Exposure of the Heat Mode Imaging Element All of the above materials were processed using a Creo 3244 ^™ external drum plate setter at 263 mJ / cm ² and 24
An image was formed at 00 dpi.

Development of the Imagewise Exposed Element After exposure of the imaging element, the element was developed in an aqueous alkaline developer. These developments are based on Technograph
2 at a speed of 1 m / min on an NPX-32 processor
Perform at 5 ° C, and rinse in Ozasol EP262
A (Ozasol EP262A is commercially available from Agfa) and water;
sol RC795 rubber. The resulting printing plate has an undamaged image without etching defects.

Evaluation of Scratch Resistance Fifteen scratches are examined for the width of the damage and give the corresponding rating shown in Table 1. If the depth of the scratch is down to the support, this means that the entire layer has been removed, adding an extra value. This phenomenon can be seen by the color change from black to white metallic over the scratched area. This value is 3 if the discoloration is local.
If the entire scratch is white, a value of 5 is added.

[0120]

[Table 1] The sum of all the ratings given gives the scratch resistance of the material. The lower the value, the higher the scratch resistance.

Evaluation of the lithographic quality of the material After the evaluation of the scratch resistance of the above-mentioned materials, the plates are printed on a Heidelberg GTO46 printing press using a conventional ink (K + E) and a dampening solution (Rotamatic). . The plate is evaluated for scum formation in the IR-exposed areas and excellent ink absorption in the non-imaging areas. result

[0122]

[Table 2] Print quality OK: means no visible scum formation on non-image areas and excellent ink-absorption.

The examples show that Examples 2-4 and 6-9 (Examples according to the invention) give (much) better scratch resistance than Comparative Examples 1 and 5. The main features and aspects of the present invention are as follows.

[0124] 1. On a lithographic printing base having a hydrophilic surface, a first polymer comprising a polymer soluble in an aqueous alkaline solution but insoluble in water and a hydrophilic polymer soluble in an aqueous alkaline solution of less than 5% by weight relative to the polymer.
And a top layer on the same side as the first layer of the lithographic base, which is impervious or insoluble with respect to the IR-sensitive and alkaline developer, wherein the first layer and the top layer are one and the same. A heat mode imaging element for making a lithographic printing plate, which can be a layer, wherein the top layer is selected from the group consisting of polymers, triarylmethane dyes and phthalocyanine dyes in an amount of 30 mg to 500 mg / m ^2. A heat mode imaging element characterized in that it contains a compound to be heated.

[0125] 2. 2. A heat mode imaging element for making a lithographic printing plate according to claim 1, wherein the IR-sensitive layer contains carbon black.

3. The IR-sensitive layer described above, wherein the IR-sensitive layer has a glass transition temperature of at least 35 ° C and contains a polymer capable of forming a film by drying at an elevated temperature
Or a heat mode imaging element for preparing a lithographic printing plate according to item 2.

[0127] 4. 4. A heat mode imaging element for making a lithographic printing plate according to claim 3 wherein the polymer is a polyurethane.

5. 5. A heat mode imaging element for making a lithographic printing plate according to claim 4, wherein said polyurethane is cured with melamine.

6. 4. A heat mode imaging element for making a lithographic printing plate according to any one of the above items 1 to 3, wherein the polymer is cellulose or a cellulose derivative.

7. 3. A heat mode imaging element for making a lithographic printing plate according to claim 1 or 2, wherein the top layer contains a phthalocyanine dye.

8. A heat mode imaging element for making a lithographic printing plate according to claim 1 or 2, wherein the top layer contains a triarylmethane dye.

9. 9. A heat mode imaging element for making a lithographic printing plate according to any one of the above 1 to 8, wherein the polymer soluble in the aqueous alkaline solution is a novolak polymer or a polymer containing polyhydroxystyrene units.

10. a) exposing the heat mode imaging element of any of the above items 1 to 9 imagewise to IR-rays; b) using the imagewise exposed heat mode imaging element with the alkaline developer. And dissolving the exposed areas of the first and top layers, which may be the same, and leaving the unexposed areas of the first layer undissolved.

Continued on the front page (72) Inventor Marc van Dame Belgian Bee 2640 Maltcell Septes Trat 27 Agfa-Gevuert Na Mrose Fennoutjaps (72) Inventor Giyoan Belmercille Belgian Bee 2640 Maltcell Septes Trat 27 Agfa-Gevert Na Murose Fennoutjap (72) Inventor Guido Hokie Belgium 2640 Maltcell Septes Trat 27 Agfa-Gevert Na Mullose Fennjoutjap (72) ) Inventor Jörg Jung Deutsche D-65439 Frelsheim-Hauptschoutlase 9 (72) Inventor Helmut Huberhauser Deutsche D-65232 Taunusstein Ludwigsjüthlase 1

Claims (2)

[Claims] 1. A lithographic printing base having a hydrophilic surface, comprising a polymer soluble in an aqueous alkaline solution but insoluble in water and a hydrophilic polymer soluble in an aqueous alkaline solution of less than 5% by weight with respect to the polymer. The first containing
And a top layer on the same side as the first layer of the lithographic base, which is IR-sensitive and impervious or insoluble therewith with respect to the alkaline developer, wherein the first layer and the top layer comprise one layer. A heat mode imaging element for making a lithographic printing plate, which can be the same layer, wherein the top layer is from the group consisting of a polymer, a triarylmethane dye and a phthalocyanine dye in an amount of 30 mg to 500 mg / m ^2. A heat mode imaging element comprising the compound of choice. 2. A) exposing the heat mode imaging element of claim 1 image-wise to IR-rays; b) using the image-wise exposed heat mode imaging element with the alkaline developer. And dissolving the exposed areas of the first and top layers, which may be the same, and leaving the unexposed areas of the first layer undissolved.