JP2003107689A - Heat sensitive positive-working lithographic printing plate precursor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal lithographic printing plate precursor having high sensitivity. SOLUTION: The heat sensitive lithographic printing plate precursor is composed of (i) a supporting body having a hydrophilic surface or a hydrophilic layer and (ii) a coating applied thereon having the following properties. The coating contains such an oleophilic layer that when the layer is image-wise exposed to heat or IR rays and then immersed in an aqueous alkali developer, the exposed region dissolved at a higher dissolution rate in the developer than in the unexposed region and that the oleophilic layer contains a polymer soluble with a developer and contains an organic dye in an enough amount to give visible colors to the coating. The organic dye does not decrease the dissolution rate of the unexposed region in the developer. By using the non-suppressing dye, the sensitivity of the precursor during image-wide exposure is increased.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-sensitive positive working lithographic printing plate precursor which requires an aqueous alkaline treatment.

[0002]

BACKGROUND OF THE INVENTION Lithographic printing machines use so-called printing masters, such as printing plates mounted in the cylinders of the printing machine. A print master carries a lithographic image on its surface, and a print is obtained by applying ink to the image and then transferring the ink from the master to a receiver material, which is typically paper. In conventional lithographic printing, ink and an aqueous fountain solution are used.
n solution [dampening solution (dampening
also referred to as liquid)] is applied to a lithographic image consisting of lipophilic (or hydrophobic, ie ink receptive, water repellent) areas and hydrophilic (or oleophobic, ie water receptive, ink repellent) areas. It So-called dry lithographic printing (dr
In iographic printing,
The lithographic image has ink receiving areas and ink adhesion prevention (ink a
bhesive (ink repellent) areas and only ink is supplied to the master during dry lithographic printing.

Printing masters are generally at various prepress stages, such as typeface selection, scanning, color separation, screening, trapping, layout and imposition (i.
composition is achieved digitally and each color selection is transferred to a graphic arts film using an imagesetter, the so-called computer-to-film method.
Obtained by After processing, the film can be used as a mask for the exposure of an imaging element called a plate precursor, and after plate processing a printing plate is obtained which can be used as a master.

A typical printing plate precursor for computer-to-film processes comprises an image-recording layer of a hydrophilic support and a photosensitive polymer layer, which is a UV-sensitive diazo. Including compounds, dichromate sensitized hydrophilic colloids and a wide variety of synthetic photopolymers. Particularly diazo-sensitized systems are widely used.
Image-wise exposure with a film mask, typically in a UV contact frame, causes the exposed image areas to become insoluble and the unexposed areas to remain soluble in the aqueous alkaline developer. The plate is then treated with a developer to remove the diazonium salt or diazo resin in the unexposed areas. The areas so exposed define the image areas (print areas) of the printing master, and thus such printing plate precursors are "negative-working".
rking) ". Positive working materials are also known in which the exposed areas define non-printed areas, for example:
Plates are known which have a novolac / naphthoquinone-diazide coating which dissolves in the developer only in the exposed areas.

In addition to the above photosensitive materials, heat-sensitive printing plate precursors have also become very popular. Such thermal materials
materials) provide the benefits of sunlight stability, and, in particular,
The so-called computer-to-plate method in which the plate precursor is exposed directly, i.e. without using a film mask.
used in d). This material is exposed to heat or infrared light, and the heat generated is a (physical) chemical process,
For example, it triggers ablation, polymerization, insolubilization by cross-linking of the polymer, degradation, or particle coagulation of the thermoplastic polymer latex.

WO 97/39894 and EP-A-82
3327 describes a positive working heat sensitive material comprising a hydrophilic support and a lipophilic coating provided thereon. The coating comprises a phenolic resin and a dissolution inhibitor, a compound that reduces the solubility of the phenolic resin in an aqueous alkaline developer. The interaction of the inhibitor with the phenolic resin is disrupted by exposure to heat or infrared light, so that the exposed areas of the coating dissolve faster in the developer than the unexposed areas, and A lithographic image consisting of hydrophilic (exposed) and lipophilic (non-exposed) areas is obtained. In order to further increase the difference in solubility between exposed and unexposed areas, WO99 / 21725, EP-
A-864420 and EP-A-950517 disclose the use of developer resistance means such as polysiloxane compounds which can prevent aqueous alkaline developers from penetrating the phenolic resin layer. The increased developer resistance thus obtained can be reduced by exposure to heat or infrared light, and subsequent immersion in developer yields a positive lithographic image.

The coatings of known printing plates contain colorants, also called contrast dyes or indicator dyes, to give a visible image after image-wise exposure and development. Such colorants remain in the coating in the printed areas and are removed with the coating in the non-printed areas. Most such prior art materials are characterized by low sensitivity and therefore require high power during exposure.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high sensitivity thermal lithographic printing plate precursor.

[0009]

This object is achieved by the material according to claim 1 of the claims. Preferred embodiments are defined in the dependent claims.

[0010] Colorants used as indicator dyes in the prior art materials are typically quaternary nitrogen atom or a carbonyl (-CO-), sulfinyl (-SO-) or sulfonyl (-SO ₂ - ) Is an organic molecule containing a group. Such groups are probably the hydrogen bridge f with the binder (s) present in the coating, such as a phenolic resin.
It has the effect of suppressing dissolution by Known examples of such inhibitory dyes are amino-substituted tri- or diarylmethane dyes such as crystal violet, methyl violet, violet pure blue, auramine and malachite green.

According to the invention, it has been found that the colorants used in the prior art materials can be replaced by non-inhibiting substitutes. Such colorants provide higher sensitivity even if the absorption efficiency at the wavelength of the image-wise exposure is not affected thereby.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The lithographic printing plate precursor of the present invention comprises a hydrophilic support and a coating comprising a lipophilic layer provided thereon. The printing plate precursor is positive working (p
layers that are positive-working), that is, after exposure and development, the exposed areas of the lipophilic layer are removed from the support and define hydrophilic (non-printing) areas, against which the layer was not exposed. Are not removed from the support and define lipophilic (printing) areas.

The support has a hydrophilic surface or is provided with a hydrophilic layer. The support can be a sheet-like material such as a plate or it can be a cylindrical element such as a sleeve that can slide around the printing cylinder of a printing press. Preferably the support is a metal support such as aluminum or stainless steel.

A particularly preferred lithographic support is an electrochemically polished and anodized aluminum support. The anodized aluminum support can be treated to improve the hydrophilic properties of its surface. For example, an aluminum support can be silicated by treating its surface with a sodium silicate solution at elevated temperature, eg 95 ° C. Alternatively, a phosphate treatment can be applied, which further involves treating the aluminum oxide surface with a phosphate solution that may contain an inorganic fluoride. In addition, the aluminum oxide surface can be washed with a citric acid or citrate solution. This treatment can be performed at room temperature or from about 30-
It can be carried out at a slightly elevated temperature of 50 ° C. A further interesting treatment involves washing the aluminum oxide surface with a bicarbonate solution. Still further, the aluminum oxide surface was formed by reaction with polyvinylphosphonic acid, polyvinylmethylphosphonic acid, polyvinyl alcohol phosphate, polyvinyl sulfonic acid, polyvinyl benzene sulfonic acid, polyvinyl alcohol sulfate, and sulfonated aliphatic aldehydes. It can be treated with an acetal of polyvinyl alcohol. It is further clear that one or more of these post-treatments can be carried out alone or in combination. For a more detailed description of these processes, see GB-A-1084070, D.
EA-4423140, DE-A-4417907,
EP-A-659909, EP-A-537633, D
EA-40014666, EP-A-292801, E
Shown in PA-291760 and US-P-4458005.

According to another embodiment, the support can also be a flexible support with a hydrophilic layer, hereinafter referred to as the "base layer". The flexible support is, for example, paper, plastic film, thin aluminum or a laminate thereof. Preferred examples of the plastic film are polyethylene terephthalate film, polyethylene naphthalate film, cellulose acetate film, polystyrene film, polycarbonate film and the like.
The plastic film support can be opaque or transparent.

The base layer is preferably a crosslinked hydrophilic layer obtained from a hydrophilic binder crosslinked with a curing agent such as formaldehyde, glyoxal, polyisocyanate, or hydrolyzed tetraalkyl orthosilicate. Hydrolyzed tetraalkyl orthosilicates are especially preferred. The thickness of the hydrophilic base layer is 0.2 to 2
It can be varied within a range of 5 μm, and is preferably 1 to 10 μm.

Hydrophilic binders for use in the base layer are, for example, hydrophilic (co) polymers such as vinyl alcohol, acrylamide, methylol acrylamide, methylol methacrylamide, acrylate acid,
Homopolymers and copolymers of methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, or maleic anhydride / vinyl methyl ether copolymers. (Co) polymer or (co) used
The hydrophilicity of the polymer mixture is preferably equal to or higher than the hydrophilicity of polyvinyl acetate hydrolyzed to the extent of at least 60% by weight, preferably 80% by weight.

The amount of curing agent, especially tetraalkyl orthosilicate, is preferably at least 0.2 parts by weight per part by weight of hydrophilic binder, more preferably 0.
5 to 5 parts by weight, most preferably 1 to 3 parts by weight.

The hydrophilic base layer can also contain substances that increase the mechanical strength and porosity of the layer. Colloidal silica can be used for this purpose. The colloidal silica used can be, for example, in the form of commercially available aqueous dispersions of colloidal silica having an average particle size of up to 40 nm, for example 20 nm. In addition, inert particles of larger size than colloidal silica,
For example, J. Colloid and Interfa
ce Sci. , Vol. 26,1968, pages
62 to 69 silica or alumina particles prepared according to Stoeber or particles of titanium dioxide or other heavy metal oxides of at least 100 n
Particles having an average diameter of m can be added. By incorporating these particles, the surface of the hydrophilic base layer is provided with a uniform rough texture consisting of microscopic hills and valleys, which are storage sites for water in the background area. Serve as.

Specific examples of suitable hydrophilic base layers for use according to the invention are EP-A-601240, GB-
P-1419512, FR-P-2300354, US
-P-3971660 and US-P-4284705.

It is particularly preferred to use a film support provided with an adhesion-improving layer, also called support layer.
A particularly suitable adhesion-improving layer for use according to the invention is E
P-A-619524, EP-A-620502 and E
It comprises a hydrophilic binder as disclosed in P-A-619525 and colloidal silica. Preferably, the amount of silica in the adhesion improving layer is from 200 mg / m ^{2 to} 750 mg.
/ M ² . Furthermore, 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 / gram, more preferably at least 500 m ² / gram.

The lipophilic layer contains a polymer that is soluble in the aqueous alkaline developer. A preferred polymer is a phenolic resin that is soluble in aqueous developers, preferably having a pH of 7.5-14. Suitable polymers are, for example, novolacs, resoles, polyvinylphenols and carboxy-substituted polymers. Typical examples of such polymers are DE-A-4007428, DE-A-4.
027301 and DE-A-4445820.

According to the invention, the lipophilic layer also contains an organic dye which absorbs visible light, so that a perceptible image is obtained upon image-wise exposure and subsequent development. The term "organic dye" should be understood to exclude pigments and metal ion complexes. Preferably, this dye has an absorption maximum in the visible wavelength region (380 to 750 nm). The dye can also absorb infrared light, which can be used for image-wise exposure. In another embodiment, the dye does not substantially absorb light that can be used for image-wise exposure, and in that case absorbs light used for image-wise exposure. It is advantageous to add an additional sensitizer to the possible coating. The latter sensitizers are discussed in more detail below. Although the dye absorbs visible light it is preferred that it does not sensitize the printing plate precursor, ie the coating is not more soluble in the developer upon exposure to visible light. In a preferred sunlight-stable embodiment, the coating absorbs near-ultraviolet and / or visible light present in sunlight or office lighting and thereby renders the coating more soluble in the exposed areas, a diazide or diazonium compound, photo Acids,
It does not contain photosensitive components such as photoinitiators and sensitizers.

The dyes in the material of the present invention are non-inhibiting,
That is, they do not reduce the solubility of the polymers in aqueous alkaline developers. "Reducing the solubility of the polymer" should be understood as not reducing the concentration of the dissolved polymer at equilibrium, but rather reducing the dissolution rate of the polymer in the developer. is there. As explained above, positive-working materials show a faster dissolution of the lipophilic layer in the exposed areas than in the unexposed areas. Preferably, the exposed areas are completely dissolved in the developer before the unexposed areas are attacked, whereby the unexposed areas are characterized by sharp edges and high ink receptivity. It can be concluded that the difference in solubility between exposed and unexposed areas of the coating is caused by kinetics rather than thermodynamic effects.

The ability of the dye to suppress dyes is limited to the lipophilic layer on the support.
It can be easily tested by coating one sample. That is, the reference sample contains only the polymer and the other samples contain both the polymer (in comparable amounts to the reference) and the dye. A series of unexposed samples is immersed in the aqueous alkaline developer for a period of time different for each sample. After the immersion period, the sample is removed from the developer, immediately washed with water, dried and then the dissolution of the coating in the developer is determined by comparing the weight of the sample before and after development. As soon as the coating is completely dissolved, the weight loss is no longer measured for longer immersion time periods,
That is, the curve representing weight loss as a function of immersion time is
The plateau is reached from the moment of complete dissolution of the layer, called the "dissolution time". If the dissolution time of the sample containing the dye is longer than the dissolution time of the sample without dye, the dye will obviously act as an inhibitor. If the dissolution time of the sample containing the dye is not longer than the value of the reference sample,
The dye is non-inhibiting and as a result does not reduce the solubility of the lipophilic layer in the developer.

The dye preferably has a chromophore group that absorbs visible light represented by the following formula: D-[(L) _x- (G) _y ] _{n where} D is a chromophore group and L is Is a valence linking group,
x is 0 or 1, y and n are at least 1, and
And G is an anionic group or a group that can be made anionic by immersion of the coating in an aqueous alkaline solution,
One or more solubilizing groups represented by
It has a chemical structure that is substituted by the azo. G is preferably -COOH,-.
_{OH, PO 3 H 2, -O} -PO 3 H 2, -SO 3 H, -O-
_{SO 3 H, -SO 2 -NH 2} , -SO 2 -NH-R, -SO
Selected from the group consisting of _2- NH-CO-R and salts thereof, R is an optionally substituted alkyl or an optionally substituted aryl group. L
Is, for example, -O-, -CO-O-, -O-CO-,-.
N = N-, -NR'-, -CO-NR'-, NR'-C
O—, a group comprising optionally substituted arylene or optionally substituted alkylene, R ′ is hydrogen, optionally substituted alkyl or optionally substituted. It may be aryl. When x = 0, G is directly attached to the chromophore group D. When x = 1, y can be greater than 1 and the same linking group can have more than one anionic group. Each L and G can be independently selected from the other L and G groups. Also within the scope of the invention are dyes in which one or more anionic groups G are directly attached to D and dyes in which one or more other anionic groups G are coupled to D by a linking group L. Belong to.

Suitable dyes are, for example:

[0028]

[Chemical 2]

Where i and j are independently 0 to 3,
k, l and o are independently 0 to 4, m and n are independently
0-5, p = 0-3, R₁, R₁′,
R₁″, R₂And R₂'May be replaced by
Good alkyl, optionally substituted aryl
-G, -L-G, -CN, halogen, -NO₂,-
OR_d, -CO-OR_a, -O-CO-R_a, -CO-
NR _dR_e, -NR_dR_e, -NR_d-CO-R_a, -NR_d
-CO-OR_a, -NR_d-CO-NR_dR_f, -SO₂
-OR_a, -SO₂-NR_dR_eIndependently selected from a group of
Blob or two adjacent groups R₁, R₁′, R₁″, R₂
Or R₂′ Is a carbocyclic or heterocyclic ring fused together
Form a ring and R3, R4 and R5 are hydrogen, optionally
Optionally substituted alkyl, optionally substituted
Any aryl, -CO-R_b, -CO-OR_b,
-CO-NR_fR_gAnd -L-G independently selected
Where L and G are as described above and R_a
And R_bIs an optionally substituted alkyl or
Is an optionally substituted aryl group,
R_d, R_e, R_fAnd R_gIs hydrogen, optionally substituted
Optionally alkyl or optionally substituted
Which is an aryl group.

Specific examples of such dyes are:

[0031]

[Chemical 3]

The non-inhibiting dye is present in an amount sufficient to impart a visible color to the coating. It is self-evident that the amount required depends on the extinction coefficient of the dye. Typical non-inhibiting dye concentrations in the lipophilic layer are relative to the lipophilic layer, for example:
0.25 to 10.0% by weight, more preferably 0.5 to
It can vary by 5.0% by weight.

The lipophilic layer may contain other components such as additional binders to improve the running length of the plate, eg EP-A-.
Further, the binder described in 933682 may be contained. Preferably, it also includes a compound that acts as a development accelerator, that is, a dissolution accelerator. Because they can reduce the dissolution time of the lipophilic layer,
This can be tested for the ability of the dye to suppress by the same method as described above. For example, a cyclic acid anhydride,
Phenols or organic acids can be used to improve aqueous developability. Examples of cyclic acid anhydrides are phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, as described in US Pat. No. 4,115,128.
3,6-endoxy-4-tetrahydrophthalic anhydride,
It includes tetrachlorophthalic anhydride, maleic anhydride, chloromaleic anhydride, α-phenylmaleic anhydride, succinic anhydride, and pyromellitic anhydride. Examples of phenol include bisphenol A, p-nitrophenol, p-
Ethoxyphenol, 2,4,4'-trihydroxybenzophenone, 2,3,4-trihydroxy-benzophenone, 4-hydroxybenzophenone, 4,4 ',
4 ″ -trihydroxy-triphenylmethane, and 4,4 ′, 3 ″, 4 ″ -tetrahydroxy-3,
5,3 ', 5'-tetramethyltriphenylmethane and the like are included. Examples of organic acids include those disclosed in JP-A-60-88,
As described in Japanese Patent Application Laid-Open No. 942 and Japanese Patent Application Laid-Open No. 2-96,755, sulfonic acid, sulfinic acid, alkyl sulfuric acid, phosphonic acid, phosphate and carboxylic acid are included. Specific examples of these organic acids include p-toluene sulfonic acid,
Dodecylbenzenesulfonic acid, p-toluenesulfinic acid, ethylsulfate, phenylphosphonic acid, phenylphosphinic acid, phenylphosphate, diphenylphosphate, benzoic acid, isophthalic acid, adipic acid, p-toluic acid, 3,4-dimethoxybenzoic acid, Phthalic acid, terephthalic acid, 4-cyclohexene-1,2-dicarboxylic acid,
Includes erucic acid, lauric acid, n-undecanoic acid and ascorbic acid. The amount of cyclic acid anhydride, phenol or organic acid contained in the imageable composition is preferably 0.0.
It is in the range of 5 to 20% by weight.

In a preferred embodiment, the coating is a developer resistance means.
means), ie to prevent the penetration of the aqueous alkaline developer into the lipophilic layer in the unexposed areas 1
It also contains seeds or higher substances. Such developer resisting means can be added to the lipophilic layer or can be added to the barrier layer provided over the lipophilic layer. In the latter embodiment, the solubility of the barrier layer in the developer and the permeability of the barrier layer by the developer are, for example, EP-A-8.
64420, EP-A-950517 and WO99 / 2.
It can be reduced by exposure to heat or infrared light, as described in 1725. Preferred examples of developer resistance means include water repellent polymers such as polymers comprising siloxane and / or perfluoroalkyl units. In one embodiment, the barrier layer comprises 0.5 to 25 mg / m ² , preferably 0.
5 to 15 mg / m ² , most preferably 0.5 to 10 mg
/ M ² content. When the water-repellent polymer is also ink-repellent, for example, in the case of polysiloxane,
Amounts greater than 25 mg / m ² can lead to poor ink receptivity of the unexposed areas. On the other hand, 0.5 mg / m
Amounts less than ² may result in unsatisfactory developer resistance. The polysiloxane can be a linear, cyclic or composite crosslinked polymer or copolymer. The term polysiloxane compound refers to more than one siloxane group —Si (R, R ′) — O—, where R and R ′ are optionally substituted alkyl or aryl groups. It includes any compound that it contains. Preferred siloxanes are phenylalkyl siloxanes and dialkyl siloxanes. The number of siloxane groups in the (co) polymer is at least 2, preferably at least 10,
More preferably, it is at least 20. It can be less than 100, preferably less than 60. In another aspect, the water repellent polymer is a block or graft copolymer of a poly (alkylene oxide) and a polymer comprising siloxane and / or perfluoroalkyl units. Suitable copolymers are from about 15 to
It comprises 25 siloxane units and 50 to 70 alkylene oxide groups. Preferred examples are copolymers comprising phenylmethylsiloxane and / or dimethylsiloxane and ethylene oxide and / or propylene oxide, eg all Tego Chemi.
Tego Glide 410, Tego Wet, commercially available from E., Essen, Germany.
265, Tego Protect 5001 or Si
Includes likophen P50 / X. Such a copolymer, when coated, due to its bifunctional structure, automatically locates itself at the coating-air interface, and thus even when applied as a component of the coating solution of the lipophilic layer. Acts as a surfactant to form another top layer. At the same time, such surfactants improve the quality of the coating.
It acts as an adding agent). Alternatively, the water repellent polymer can be added to the second solution and coated on top of the lipophilic layer. In that embodiment, it may be advantageous to use a solvent in the second coating solution that is incapable of dissolving the components present in the first layer, which results in a highly concentrated water repellent phase. Obtained at the top of the material.

The material can be image-wise exposed by heat, for example directly by a thermal head or indirectly by infrared light which is converted to heat by a light absorbing compound. Near infrared light is preferred. The light absorbing compound can be the non-inhibiting dye described above. The coating preferably comprises, in addition to the non-inhibiting dye, a sensitizer which is a dye or pigment having an absorption maximum in the infrared wavelength range. The concentration of the sensitizing dye or pigment in the lipophilic layer is typically 0.25 to 10.0% by weight, more preferably 0.5.
~ 7.5% by weight.

Preferred infrared absorbing compounds are pigments such as cyanine or merocyanine dyes or pigments such as carbon black. Suitable compounds include the infrared dyes listed below.

[0037]

[Chemical 4]

[0038]

Sensitizing dyes or pigments can be present in the lipophilic layer, in the barrier layer described above or in other layers, which are optionally provided. According to a highly preferred embodiment,
The dye or pigment is concentrated in or near the barrier layer, for example in the intermediate layer between the lipophilic layer and the barrier layer. According to that embodiment, the intermediate layer comprises the light absorbing compound in an amount greater than the amount of the light absorbing compound in the lipophilic layer or barrier layer. In a preferred embodiment, the barrier layer consists essentially of a water repellent polymer, i.e., does not contain an effective amount of sensitizer or other ingredients.

The printing plate precursor of the present invention can be exposed to heat or infrared light by, for example, a thermal head, LEDs or a laser. Most preferably, the light used for exposure is a near-infrared emitting laser having a wavelength in the range of about 750 to about 1500 nm, such as a semiconductor laser diode, Nd: YAG or Nd: YLF.
It is a laser. The required laser power is determined by the sensitivity of the image recording layer, the spot diameter (a typical value of a modern platesetter at 1 / e ² of maximum intensity: 10 to 25 μm), the pixel residence time of the laser beam, and the scanning speed. And the resolving power of the exposure device (ie the number of addressable pixels per unit of linear distance, often expressed in dots / inch or dpi; typical values: 1000-4000d
pi).

Two types of laser exposure devices are commonly used: internal drum (ITD) and external drum (XTD) platesetters. I for thermal plate
TD platesetters are characterized by very high scan speeds, typically up to 500 m / sec, and may require laser powers of a few watts. About 200
XTD platesetters for thermal plates with typical laser powers of mW to about 1 W are operated at lower scan speeds, eg 0.1-10 m / sec.

Known platesetters can be used as an off-press exposure device, which offers the advantage of reduced press down-time. The XTD platesetter configuration can also be used for on-press exposure, which offers the advantage of instant registration in multicolor printing presses. Further technical details of the on-press exposure device are described in eg US Pat. No. 5,174,205 and US Pat. No. 5,163,368.

In the developing step, the non-image areas of the coating are removed by immersion in an aqueous alkaline developer,
This is due to, for example, mechanical friction with a rotating brush.
It can be combined with the mechanical rubbing). After the developing step, a washing step, a rubberizing step, a drying step and / or a post-baking step can be performed.

The printing plate thus obtained has an ink and an aqueous dampening liquid.
It can be used for the conventional so-called wet offset printing, in which the liquid is fed to the plate. Other suitable printing methods are so-called single-fluid inks (s) without fountain solution.
single-fluid ink). A suitable single fluid ink for use in the method of the present invention is U
S 4,045,232, US 4,981,517 and U
S6, 140, 392. In the most preferred embodiment, the single-fluid ink comprises an ink phase, also called the hydrophobic or lipophilic phase and a polyol phase as described in WO 00/32705.

[0045]

EXAMPLE Preparation of the support The foil is degreased by immersing 0.30 mm thick aluminum foil in an aqueous solution containing 5 g / l of sodium hydroxide at 50 ° C. and washed with deionized water. did. The foil was then subjected to alternating current using an alternating current at a temperature of 35 ° C. and a current density of 1200 A / m ² in an aqueous solution containing 4 g / l hydrochloric acid, 4 g / l hydroboric acid and 5 g / l aluminum ions. Electrochemically polished to 0.5 μm average center-line roughness.
A surface topography with roughness Ra was formed.

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

The foil is then placed in an aqueous solution containing 200 g / l of sulfuric acid at a temperature of 45 ° C., a voltage of about 10 V and 1
Anodizing at a current density of 50 A / m ² for about 300 seconds to form an anodizing film of Al ₂ O ₃ 3.00 g / m ² , then washed with deionized water and containing polyvinylphosphonic acid. Work-up with a solution, then with a solution containing aluminum trichloride, with deionized water at 20 ° C. 1
Washed for 20 seconds and dried.

Testing the Inhibitory Ability of the Dye Novolak (Alnovol from Clariant
SPN452, a 40.5 wt% solution in methoxypropanol) and layers of the dyes listed in Table 1 were coated on the support. After drying for 2 minutes at 120 ° C., the sample contained 0.9 g / m ² of novolak. The sample was then immersed in Ozasol EP26 developer from Agfa at 20 ° C and the dissolution time was determined as described above. Examples 2 to 4 contained dyes according to the invention and showed shorter dissolution time values than the reference example 1 without dye. Comparative Example 5 is Re which is a suppressing dye.
It contained solin Rot F3BS, but resulted in a longer dissolution time than with the material of the invention.

[0049]

[Table 1]

[0050]

[Table 2]

Plate Precursor Material The solution of Table 2 was coated on the above support at a wet coating thickness of 22 μm and then dried at 120 ° C. for 2 minutes. This material was then treated with the following series of energy density settings (power at image plane): 79 mJ / cm ² , 9
^{9mJ / cm 2, 125mJ / cm} 2, 157mJ / cm
Creo Tren using ² and 197 mJ / cm ²
Imaged on dsetter 3244 (830 nm). The plate is then subjected to Agfa Ozasol at 25 ° C.
Processed in an Agfa Autolith PN85 processor operating at a speed of 0.84 m / min using EP26 developer and finally Agfa Ozasol.
Rubberized with RC795. Infrared sensitivity is 50%
It was defined as the energy density required to obtain 50% light absorption measured in the developed plate at the dye wavelength maxima in the exposed areas of the screen (at 200 lpi) in the dot area.

The results in Table 2 show that the non-inhibiting dye, Dye 1
~ 3 is more sensitive than inhibitor dye Resolin Rot F3BS (given by lower energy density)
To give.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) The inventor, Joan Bellmerer             Belgium Bee 2640 Maltcell Septes             Trat 27 Agfa-Gewert Na             Murose Fuennaught Shyt (72) Inventor Gert Delever             Belgium Bee 2640 Maltcell Septes             Trat 27 Agfa-Gewert Na             Murose Fuennaught Shyt F term (reference) 2H025 AA01 AA04 AB03 AC08 AD03                       BG00 CB42 CC13 DA02 DA03                       DA36 DA40 FA17                 2H096 AA06 BA09 EA04 EA23 GA08

Claims (10)

[Claims] 1. A method comprising: (i) a support having a hydrophilic surface or provided with a hydrophilic layer; and (ii) a coating provided on the support, which coating is resistant to heat or infrared light. Image-wise exposure and subsequent immersion in an aqueous alkaline developer comprising a lipophilic layer that dissolves in the developer at a higher dissolution rate in the exposed areas than in the unexposed areas, The lipophilic layer is a heat-sensitive lithographic printing plate precursor comprising a developer-soluble polymer and an amount of organic dye sufficient to impart a visible color to the coating, the organic dye being incorporated into the developer. A heat-sensitive lithographic precursor characterized in that it does not reduce the dissolution rate of the unexposed areas. 2. The organic dye has the following formula: D-[(L) _x- (G) _y ] _{n where} D is a chromophore group and L is a divalent linking group.
x is 0 or 1, y and n are at least 1, and
A lithographic printing plate precursor according to claim 1, wherein G is an anionic group or a group which can be made anionic by immersion of the coating in a developer. 3. Each G is —COOH, —OH, PO ₃ H ₂ ,
_{-O-PO 3 H 2, -SO} 3 H, -O-SO 3 H, -SO 2
_{-NH 2, -SO 2 -NH-R} , -SO 2 -NH-CO-
The lithographic printing plate precursor according to claim 2, which is independently selected from the group consisting of R and salts thereof, and R is an optionally substituted alkyl group or an optionally substituted aryl group. 4. The organic dye has the following formula: [Chemical 1] In the formula, i and j are independently 0 to 3, k, l and o are independently 0-4, m and n are independently 0 to 5, p is 0 to 3, R₁, R₁′, R₁″, R₂And R₂'Is replaced in some cases
Optionally substituted alkyl, optionally substituted
Good aryl, -G, -LG, -CN, halogen,
-NO₂, -OR_d, -CO-OR_a, -O-CO-
R_a, -CO-NR _dR_e, -NR_dR_e, -NR_d-CO-
R_a, -NR_d-CO-OR_a, -NR_d-CO-NR_d
R_f, -SO₂-OR_a, -SO₂-NR_dR_eA group of
Independently selected from two or two adjacent groups R₁, R₁′,
R₁″, R₂Or R₂′ Is a carbocycle fused together
Form a formula or heterocyclic ring, R3, R4 and R5 are hydrogen, optionally substituted
Optionally alkyl, optionally substituted ari
, -CO-R_b, -CO-OR_b, -CO-NR_f
R_gAnd independently selected from the group consisting of -L-G, here, R_aAnd R_bIs an optionally substituted alkyl
Or an optionally substituted aryl group
, R_d, R_e, R_fAnd R_gIs hydrogen, optionally substituted
Optionally alkyl or optionally substituted
An aryl group, having a chemical structure according to one of the claims
Item 4. The lithographic printing plate precursor as described in Item 3. 5. A lithographic printing plate precursor according to claim 1, wherein the lipophilic layer further comprises a compound which increases the rate of dissolution of the unexposed areas in the developer. 6. A lithographic printing plate precursor according to claim 5, wherein the compound which increases the dissolution rate of the unexposed areas is a cyclic acid anhydride, phenol or an organic acid. 7. The coating further comprises means for imparting increased developer resistance to the coating, and the developer resistance of the coating decreases upon exposure to heat or infrared light. The lithographic printing plate precursor as described in any one of 6 above. 8. A means for imparting increased developer resistance is present in the barrier layer provided on the lipophilic layer, and the solubility of the barrier layer in the developer or the developer barrier layer. The lithographic printing plate precursor of claim 7, wherein the permeability of the lithographic printing plate precursor decreases when exposed to heat or infrared light. 9. A lithographic printing plate precursor according to claim 7 or 8 wherein the means for providing increased developer resistance comprises a water repellent polymer. 10. A water repellent polymer is a polymer comprising a siloxane and / or a perfluoroalkyl unit; or a block of a polymer comprising a poly (alkylene oxide) and a siloxane and / or a perfluoroalkyl unit. The lithographic printing plate precursor according to claim 9, which is a copolymer or a graft copolymer.