JP2988886B2 - Imaging element and method of making lithographic plate using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to an imaging element for making a lithographic printing plate wherein the imaging element comprises a heat-sensitive mask on a photosensitive coating.

[0002]

BACKGROUND OF THE INVENTION Lithographic printing is a method of printing from specially prepared surfaces where some areas are capable of receiving lithographic ink but other areas will not receive the ink when wetted with water. . The ink receiving area forms a print image area,
The ink-repellent area forms the background area.

In the photolithographic technique, the exposed or unexposed areas (positive-working) on a hydrophilic background are image-receptive to oily or greasy inks. Certain photographic materials are produced.

[0004] Surface litho plates or planographic printing plates
In the manufacture of common lithographic printing plates, also referred to as s), a support having an affinity for water or obtaining such an affinity by chemical treatment is coated with a thin layer of a photosensitive composition. Coatings for this purpose include a photopolymer layer containing a diazo compound, a hydrophilic colloid sensitized with dichromate, and various synthetic photopolymers. In particular, diazo-sensitized systems are widely used.

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

[0006] Alternatively, printing plates are known which contain a photosensitive coating which becomes soluble in the areas exposed by the image-wise exposure. The exposed areas are removed in subsequent development.
A typical example of such a photosensitive coating is quinone-
It is a coating based on diazide.

[0007] Typically, the above photographic materials for making printing plates are camera-exposed through a photographic film containing the image to be reproduced in a lithographic printing process. Such an operation method is troublesome and labor-intensive.
However, on the other hand, the printing plates thus obtained have excellent lithographic quality.

[0008] Attempts have therefore been made to eliminate the need for photographic film in the above methods and to obtain printing plates directly from computer data which, in particular, represent the image to be reproduced. In particular, it has been proposed to coat a silver halide layer on top of the photosensitive coating. The silver halide can then be exposed by a laser under computer control. Subsequently, the silver halide layer is developed, leaving a silver image on top of the photosensitive coating. This silver image then acts as a mask during 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 disclosed, for example, in JP-A 60-61752, but has the disadvantage that complicated development and the associated developer are required.

GB 1.492.070 discloses a method of applying a metal layer or a layer containing carbon black on a photosensitive coating. The metal layer is then ablated by a laser to provide an image mask on the photosensitive layer. The photosensitive layer is then totally exposed by UV light through this image mask. After removal of the image mask, the photosensitive layer is developed to obtain a printing plate. However, this method has the disadvantage that the image mask must be removed by a troublesome process before developing the photosensitive layer.

[0010] As disclosed in EP-A 1136, systems are also known in which a mask is image-wise formed on a photosensitive layer by transfer of the masking material to a photosensitive coating, for example by laser transfer or senography. However, such methods are generally slow and may not meet the image resolution required to obtain high quality prints.

WO 96/02021 discloses a method for making a lithographic plate by using an original form comprising a substrate, a photosensitive layer and a light-shielding layer which can be removed image-wise by means of a laser beam. However, the sensitivity of the material could be improved.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing high quality printing plates in a convenient manner, which eliminates certain disadvantages of the prior art.

According to the present invention, a photosensitive layer having a sensitivity to light having a wavelength of 300 to 450 nm on a support having a hydrophilic surface, and the photosensitive layer making the heat-sensitive layer opaque to light having a spectral sensitivity. An image comprising a heat-sensitive layer comprising a masking dye having an absorption peak in the wavelength range of 300 to 450 nm and further comprising a compound A capable of converting light into heat in the heat-sensitive layer or a layer adjacent thereto; A masking dye which is ablative upon exposure to a laser beam in which compound A has absorptivity.
There is provided an imaging element characterized in that

The present invention further discloses a method of obtaining a lithographic printing plate using the imaging element defined above.

[0015]

DETAILED DESCRIPTION OF THE INVENTION A heat sensitive layer comprising an ablative masking dye allows development of the imaging element, thereby simultaneously either the exposed or unexposed portions of the heat sensitive layer and the photosensitive layer. Has been found to be eliminated. Thus, substantial savings in time and price are realized while maintaining a high level of lithographic performance of the resulting printing plate. The present invention is described in detail below, but does not limit the invention to any of the embodiments described below.

A. Imaging Element a.1. Thermosensitive Layer According to the present invention, a thermosensitive layer comprising an ablative masking dye that renders the thermosensitive layer opaque to light having a spectral sensitivity. used. The imaging element according to the invention further comprises a compound A capable of converting light, preferably a laser beam, into heat. This compound A is preferably also contained in the thermosensitive layer. Compound A is preferably an infrared absorbing compound, and the laser beam is preferably an infrared laser beam. More preferably, the infrared absorbing compound is an infrared absorbing dye or a conductive polymer.

The photosensitive layer is sensitive to light (ultraviolet light) having a wavelength within the wavelength range of 300 to 450 nm, and thus the masking dye is a dye having an absorption peak within the range. In a particularly preferred embodiment for the present invention, the masking dye has an extinction coefficient of at least 10 ⁴ at the absorption peak, more preferably at least 2 10 ⁴ , most preferably at least 5 10 ⁴ . Therefore, suitable UV-absorbing masking dyes have a sufficiently high extinction coefficient in the wavelength range of 300-450 nm, so that with a moderate amount of masking dye, the amount of UV light transmitted through the thermosensitive layer is no more than 10%. And more preferably not more than 3% and most preferably not more than 1%. Examples of suitable UV masking dyes are UVIN from BASF
UL D49, UVINUL E50 and UVINUL
N539, TINUVIN P from Ciba-Geigy,
I from Crompton and Knowles Limited
NTRAWITE YELLOW 2GLN, 4-dimethylaminobenzophenone, 4-phenylazophenol and the like.

The heat-sensitive layer preferably also contains at least one yellow dye, at least one magenta dye and at least one cyan dye.

The heat-sensitive layer preferably also contains a binder, preferably a water-soluble or water-swellable binder. Suitable polymeric binders include water-swellable or water-soluble binders, especially those that are swellable or soluble in alkaline aqueous media.
Examples of suitable binders are, for example, the hydrophilic polymers mentioned below for use in the interlayer and / or the alkali-soluble binders mentioned in the composition of the photosensitive layer.

It is particularly desirable that the photosensitive layer in the present invention further contains a thermally decomposable polymer, especially one which decomposes exothermically. In the latter case, the sensitivity of the thermosensitive layer is improved. A particular example of a thermally decomposable polymer that decomposes exothermically is nitrocellulose.

Typically, the thickness of the heat-sensitive layer is, for example, 0.1.
μm to about 4 μm and more preferably 0.5 μm to 1.5 μm
m.

The heat-sensitive layer according to the present invention further comprises additional other components to achieve various other desired functions, such as visual inspection which can be achieved by including a colored dye in the heat-sensitive layer. May be.

The heat-sensitive layer for use according to the invention preferably also comprises a compound A which can convert laser light into heat. It is particularly preferred to use infrared pigments or dyes for this purpose. In the present invention, an infrared dye is particularly desirable. However, other pigments, such as conductive polymer particles, metal carbides, borides, nitrides, carbonitrides (c
arbonitrides), bronze - it is also possible to use an oxide structure.

A part or all of the compound A may be added to a layer adjacent to the heat-sensitive layer, for example, an intermediate layer between the light-sensitive layer and the heat-sensitive layer.

A.2. Interlayer According to the present invention, the imaging element preferably also comprises an interlayer between the light-sensitive layer and the heat-sensitive layer. Such an interlayer must be soluble or swellable in an aqueous medium, preferably an aqueous alkaline medium. Suitable interlayers preferably contain a hydrophilic binder. Suitable hydrophilic binders include, for example, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, celluloses, sugars, gelatin, carboxyl-containing polymers such as homo- or copolymers of (meth) acrylic acid, maleic anhydride. Examples of the polymer include a base polymer and a polymer containing a phenolic hydroxy group, such as polyvinylphenols. The intermediate layer according to the present invention may contain various additional components, for example, a compound capable of converting laser light into heat is desirably added to the intermediate layer as described above.

The dry thickness of the intermediate layer is preferably between 0.5 and 5 μm.
m, more preferably between 1 and 3.5 μm.

A.3. Photosensitive layer The photosensitive layer according to the present invention may comprise a suitable photosensitive composition capable of obtaining an ink-receiving image on the hydrophilic surface of the support of the imaging element. . Examples of such photosensitive compositions as used herein comprise those comprising diazo compounds; British Patent Nos. 1,235,281 and 1,495,
No. 4,072,528, and 4,072, comprising azide compounds disclosed in U.S. Pat.
No. 527, the photo-crosslinkable photopolymers, and in particular those described in more detail below.

Among these photosensitive compositions, those comprising a diazo compound include, for example, the storage properties of the photosensitive layer; developability, eg, development latitude; image properties, eg, image quality; printing properties, eg, ink acceptance. They are preferably used because of their overall excellent properties in various properties, such as resistance and abrasion resistance; and the low environmental contamination potential of the developing agents used.

Photosensitive compositions containing a diazo compound can be roughly classified into two types, that is, a negative-working type and a positive-working type.

The negative-working photosensitive composition containing the diazo compound comprises the photosensitive diazo compound and preferably a polymeric compound. Commonly known photosensitive diazo compounds can be used, and preferred examples thereof include organic solvent-soluble salts of diazo resins, such as p-diazodiphenylamine and formaldehyde or acetaldehyde and hexafluorophosphate. And salts of these with 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid salts.

On the other hand, examples of the polymeric compounds preferably used are acrylic acid or methacrylic acid copolymers; crotonic acid copolymers; itaconic acid copolymers, maleic acid copolymers, side chains And a polyvinyl alcohol derivative having a carboxyl group in the side chain, a hydroxyalkyl (meth) acrylate having a carboxyl group in the side chain, and an unsaturated polyester resin having a carboxyl group.

As the diazo compound used in the positive-working photosensitive composition, generally known compounds can be used, and typical examples thereof are o-quinonediazides and preferably It is an o-naphthoquinonediazide compound. Particularly preferred are o-naphthoquinonediazidosulfonic acid esters or o-naphthoquinonediazidocarboxylic acid esters of various hydroxyl compounds; and o-naphthoquinonediazidosulfonamides or o-naphthoquinonediazidocarboxylic acid amides of various aromatic amine compounds. It is. Examples of such phenols include phenol, cresol, resorcinol and pyrogallol, examples of such carbonyl-containing compounds are formaldehyde, benzaldehyde and acetone. Examples of suitable hydroxyl compounds include phenol-formaldehyde resin, cresol-formaldehyde resin, pyrogallol-acetone resin and resorcin-benzaldehyde resin.

Typical examples of o-quinonediazide compounds include benzoquinone- (1,2) -diazidesulfonic acid or naphthoquinone- (1,2) -diazidesulfonic acid and phenol-formaldehyde resin or cresol-
Esters of formaldehyde resin; US Patent No. 3,6
Naphthoquinone- (1,2) disclosed in US Pat.
Esters of -diazide- (2) -5-sulfonic acid and pyrogallol-acetone resin;
Naphthoquinone- (1,
Includes esters of 2) -diazide- (2) -5-sulfonic acid and resorcin-pyrogallol-acetone copolycondensate.

Examples of other useful o-quinonediazide compounds include polyesters having a hydroxyl group at the terminal esterified with o-naphthoquinonediazidosulfonyl chloride disclosed in JP-A-50-117503; Homopolymer of p-hydroxystyrene esterified with o-naphthoquinonediazidosulfonyl chloride or a copolymer thereof with another copolymerizable monomer disclosed in JP-A-50-113305; Bisphenol-formaldehyde resin and esters of o-quinonediazide sulfonic acid disclosed in US Pat. No. 5,429,922; alkyl acrylate-acryloyloxyalkyl carbonate-hydroxyalkyl acrylate disclosed in U.S. Pat. No. 3,859,099; Polymer and o-naph chloride Quinone condensates of diazide sulfonyl; copolymerization product of styrene and phenol derivatives disclosed in Japanese Patent Publication Sho 49-17481 and o
A reaction product with quinonediazidesulfonic acid; o- and a copolymer of p-aminostyrene and a monomer copolymerizable therewith as disclosed in U.S. Pat. No. 3,759,711.
Amides with naphthoquinonediazidosulfonic acid or o-naphthoquinonediazidocarboxylic acid; and ester compounds of polyhydroxybenzophenone and o-naphthoquinonediazidosulfonyl chloride.

In order to form a photosensitive layer, these o-
The quinonediazide compound may be used alone, but is preferably used as a mixture with an alkali-soluble resin.

Suitable alkali-soluble resins include novolak type phenols, typical examples of which are phenol formaldehyde, cresol-formaldehyde resin, and phenol-cresol-phenol disclosed in Japanese Patent Publication No. 55-57841. It is a formaldehyde copolycondensation resin. More preferably, the phenolic resin is a condensate of phenol or cresol substituted with an alkyl group having 3 to 8 carbon atoms and formaldehyde disclosed in Japanese Patent Publication No. 50-125806,
For example, it is used simultaneously with t-butylphenol-formaldehyde.

Further, an alkali-soluble polymer other than the above-mentioned alkali-soluble novolak phenol resin may be optionally added to the photosensitive composition. Examples of such polymers are styrene-acrylic acid copolymer, methyl methacrylate-methacrylic acid copolymer, alkali-soluble polyurethane resin, and Japanese Patent Publication No. 52-2.
No. 8401, and an alkali-soluble vinyl resin and an alkali-soluble polybutyral resin.

The amount of the o-quinonediazide compound is preferably from 5 to 5 based on the total weight of the solid content of the photosensitive composition.
80% by weight and more preferably 10-50% by weight. On the other hand, the amount of alkali-soluble resin is preferably from 30 to 30, based on the total weight of the solids content of the photosensitive composition.
90% by weight and more preferably 50-85% by weight.

The photosensitive layer according to the present invention may be applied in the form of a multilayer structure. In addition, the photosensitive composition in the photosensitive layer or multilayer package includes other optional components, such as dyes, plasticizers, and components to provide printout quality (the ability to provide a visible image immediately after image-wise exposure). It may be.

The coating amount of the photosensitive layer applied on a hydrophilic surface of a support is preferably in the 0.1~7g / m ² and more preferably in the range of 0.5-4 g / m ^2.

The preferred photo-crosslinkable substances in the present invention are based on photo-crosslinkable polymers having a maleimide group in the side chain. To enhance their photosensitivity, sensitizers such as thioxanthones, benzophenones, Michler's ketones, anthraquinones, anthracenes,
Chrysene, p-dinitrobenzene, 2-nitrofluorene, and JP-A-62-294238, JP-A-
2-173646, JP-A-2-236552, JP
-A-3-54566 and JP-A-6-10771
The sensitizer described in 8 is added. (The term "JP-A-" as used herein means "Japanese patent application published without examination.") Photo-crosslinking having a maleimide group in one or more side chains For example, US Pat. No. 4,079,041 (J.
West German Patent No. 2,626,769; European Patent Nos. 21,019 and 3,552; Die Angewandte Makromolekular.
e Chemie, 115 (1983), pp. 163-181; JP-A-49.
-128991-JP-A-49-128993, JP
-A-50-5376 to JP-A-50-5380, J
PA-53-5298 to JP-A-53-5300,
JP-A-50-50107, JP-A-51-479
40, JP-A-52-13907, JP-A-50-
45076, JP-A-52-121700, JP-A
-50-10844, JP-A-50-45087, J
P-A-58-43951; West German Patent 2,349,
No. 948 and 2,616,276.

Among these polymers, those having an average of two or more maleimide groups in a side chain in one molecule and having an average molecular weight of 1,000 or more are preferably used in the present invention. used.

The imaging element containing any of these polymers is preferably developed with an aqueous alkaline developing agent substantially free of organic solvents from an environmental safety standpoint. Thus, these polymers are soluble or swellable in aqueous alkali. Therefore, it is preferable to obtain a polymer of these by copolymerizing a monomer having a maleimide group in a side chain with a monomer having alkali-solubility.

The alkali-soluble group is preferably an acid group having a pKa of 14 or less. Specific examples of such monomers having an alkali-soluble group include:
Vinyl compounds having a carboxyl group, such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, -CON
Vinyl monomer having an HSO ₂ group; vinyl monomer having an —SO ₂ NH— group; vinyl monomer having a phenolic hydroxyl group; vinyl monomer having a phosphoric acid group or a phosphonic acid group; Maleic acid and itaconic anhydride are included.

The monomer having an alkali-soluble group and the monomer having a maleimide group are generally used in an amount of 10/90 to
It is copolymerized at a 70/30 molar ratio, preferably at a 20/80 to 60/40 molar ratio, to easily provide a photo-crosslinkable polymer for use in the present invention. The polymer is preferably from 30 to
It has an acid number of 500, particularly preferably 50 to 300. Among such photo-crosslinking polymers, copolymers consisting of N- [2-methacryloyloxy) alkyl] -2,3-dimethylmaleimide and methacrylic or acrylic acid, such as Die Angewandte Makromolekulare Chem
Those described in ie, 128 (1984), pp. 71-91 are particularly useful. In the production of these copolymers, a vinyl monomer may be further copolymerized as a third component to give a desired multi-component copolymer. For example, an alkyl methacrylate or an alkyl acrylate whose homopolymer has a glass transition temperature higher than room temperature can be copolymerized as a third component to give a soft copolymer.

The photo-crosslinkable polymer for use in the present invention is preferably 1000 or more, more preferably 10,000 to 500,000, and even more preferably 20,000 to 300, It has a weight average molecular weight of 000.

As described above, it is desirable to add a sensitizer to the photosensitive layer having the photocrosslinkable polymer.
Triplet sensitizers having an absorption peak to ensure sufficient light absorption at 300 nm or more are preferred.

Examples of such sensitizers include benzophenone derivatives, benzanthrone derivatives, quinones, aromatic nitro compounds, naphthothiazoline derivatives, benzothiazoline derivatives, thioxanthones, naphthothiazole derivatives, ketocoumarin compounds, benzothiazole derivatives , Naphthofuranone compounds, pyrylium salts, and thiapyrylium salts.

[0049] Specific examples thereof include Michler's ketone,
N, N'-diethylaminobenzophenone, benzanthrone, (3-methyl-1,3-diazo-1,9-benz)
Anne ronpicramide, 5-nitroacenaphthene, 2-
Chlorothioxanthone, 2-isopropylthioxanthone, dimethylthioxanthone, methylthioxanthone-1-ethyl carboxylate, 2-nitrofluorenone, 2-
Dibenzylmethylene-3-methylnaphthothiazoline,
3,3-carbonyl-bis- (7-diethylaminocoumarin), 2,4,6-triphenylthiapyrylium perchlorate, 2- (p-chlorobenzoyl) naphthothiazole, and JP-B-45-8832; JP-A-52-12
9791, JP-A-62-294238, JP-A-
2-173646, JP-A-2-131236, EP 368,327, JP-A-2-236
552, JP-A-3-54566 and JP-A-6
Sensitizers described in US Pat.

Of these, JP-A-2-2365
52, JP-A-3-54566 and JP-A-6-
Preference is given to sensitizers described in US Pat. No. 107718 and one or more —COOH, —NHSO ₂ R ²⁰ , as alkali-soluble groups in one molecule described in JP-A-6-107718. -CONCHCO
R ²⁰ and / or -CONHSO ₂ R ²⁰ (wherein R ²⁰
Represents an alkyl group, an aromatic group or an alkyl-aromatic group).

The amount of the sensitizer in the photosensitive layer is generally 1 to 20% by weight, preferably 2 to 20% by weight of the total weight of the composition in the photosensitive layer.
15% by weight, and more preferably 3-10% by weight.

It may be desirable to add a diazo resin to the photosensitive layer in addition to the photocrosslinkable polymer described above.
Examples of the diazo resin include a co-condensate composed of an aromatic diazonium compound and an aldehyde. JP-B-49-48001, JP-B-50 are respectively examples of these.
-7481, JP-B-5-2227, JP-A-3-
2864, JP-A-3-240061, and JP-
The diazo resin described in A-4-274429 is included.

Among these, diazo resins having a carboxyl group in the molecule, for example, diazo resins obtained by cocondensation with an aromatic compound having at least one carboxyl group, for example, those described in JP-A-3-240061 And a diazo resin obtained by condensation with an aldehyde having a carboxyl group, such as JP
-A-2864 are preferred.

The amount of the diazo resin in the photosensitive layer is preferably from 0.1 to 30% by weight, preferably from 0.5 to 10% by weight, and more preferably from 1 to 30% by weight of the total amount of the composition in the photosensitive layer. ~ 5% by weight
It is.

Further, for example, JP-B-3-6374
0, U.S. Patent Nos. 3,376,138, 3,556,79
A polymer having one or more polymerizable groups, such as the polymer disclosed in No. 3, may be added.

The above-mentioned polymers having one or more polymerizable groups are preferably soluble or swellable in aqueous alkaline developing agents, as are polymers having a maleimide group in the side chain. Accordingly, the polymer is preferably a copolymer comprising one or more monomers having, for example, an alkali-soluble group as described above.

A.4. Support According to the present invention, the imaging element comprises a support having a hydrophilic surface. Supports suitable for use in the present invention include, for example, metal supports comprising a hydrophilic layer, preferably a cross-linked hydrophilic layer, particularly polished and anodized aluminum.
Or a support comprising a substrate such as paper or plastic film. Particularly suitable crosslinked hydrophilic layers are obtained from hydrophilic binders which are crosslinked with a crosslinking agent such as, for example, formaldehyde, glyoxal, polyisocyanate or hydrolyzed tetraalkyl orthosilicate.

As the hydrophilic binder, hydrophilic (co) polymers such as homopolymers of vinyl alcohol, acrylamide, methylolacrylamide, methylolmethacrylamide, acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate And copolymers or anhydrous / vinyl methyl ether copolymers are used. The hydrophilicity of the (co) polymer or (co) polymer mixture used is preferably the same as that of the polyvinyl acetate hydrolyzed to at least 60% by weight, preferably to the extent of 80% by weight. Or higher.

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

The cross-linked hydrophilic layer according to the invention preferably also contains substances which increase the mechanical strength and the porosity of the layer. Colloidal silica is used for this purpose. The colloidal silica used is up to 40 nm,
It may be in the form of a commercial water-dispersion of colloidal silica having an average particle size of, for example, 20 nm. In addition, inert particles larger in size than colloidal silica, such as
J. Colloid and Interface Sci., Vol. 26, 1968, page
It is possible to add particles having an average diameter of at least 100 nm, which are particles of silica or titanium dioxide or other heavy metal oxides prepared according to the Stoeber method described in s 62 to 69. The addition of these particles gives the surface of the crosslinked hydrophilic layer a uniform roughness texture consisting of microscopic irregularities, which acts as a storage for water in the background. The thickness of the crosslinked hydrophilic layer can vary from 0.2 to 25 μm and is preferably from 1 to 10 μm.

Other special examples of cross-linked hydrophilic layers suitable for use according to the invention are EP-A 601 240, GB
-P-1419512, FR-P-2300354, U
These are disclosed in SP-397660, US-P-4284705 and EP-A 514490.

As the substrate on which the hydrophilic layer is provided,
Plastic films, such as polyethylene terephthalate film on substrate, cellulose acetate film,
It is particularly preferable to use a polystyrene film, a polycarbonate film or the like. The plastic film support may be opaque or transparent.

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

B. Method of making a lithographic printing plate b.1. Imagewise exposure Imagewise exposure according to the invention emits in the infrared (IR), ie above 700 nm, preferably 700-1.
Includes the use of lasers that emit in the 500 nm wavelength range. Laser diodes emitting at around 830 nm (gallium arsenide laser diodes) or NdYAG-lasers emitting at 1060 nm are particularly suitable for use in connection with the present invention.

Suitable imaging devices suitable for image-wise exposure in accordance with the present invention are preferably applied directly to the imaging element surface via a lens or other ray-guiding component, or connect a fiber optic cable from a lens at a remote location. Including a laser output that can be used to transmit to the surface of a black imaging element. An adjuster and associated positioner keep the beam output in the correct orientation with respect to the imaging element surface, cause this output to scan over the surface, and activate the laser at a location adjacent to a selected point or portion of the imaging element. To
The adjuster forms an accurate negative or positive image of the original in response to an input image signal corresponding to the original document and / or picture to be copied on the imaging element. The image signal is stored in the computer as a bitmap data file. Such a file can be created by a raster image processor (RIP) or other suitable means.
For example, a RIP can accept input data in a page-description language, which defines all of the features that need to be transferred onto the imaging element, or a page-description language and one or more As image data file combinations. A bitmap is created to define the color hue and, in the case of amplification adjustment screening, the number of screens and angles. However, the invention relates, for example, to EP-A 571 010, EP-A
Particularly suitable for use in combination with the number-adjusted screening disclosed in 620677 and EP-A 620674.

The imaging device for use in the present invention is preferably configured as a flat bed recorder or a drum recorder having an imaging element mounted on the cylindrical outer surface of the drum. In a preferred drum configuration, the necessary relative movement between the laser beam and the imaging element rotates the drum (and the imaging element mounted thereon) about its axis and moves the beam parallel to the axis of rotation. To "grow" the image axially by causing it to scan the imaging element circumferentially
It can be obtained by: Alternatively, the light beam can be moved parallel to the drum axis and "grown" on the imaging element at increasing angles after a single pass over the imaging element. In both cases, after a full scan with light and development, an image corresponding to the original will have been applied to the surface of the imaging element. In a flat-bed configuration, light rays are directed along either axis of the imaging element, and are designated along the other axis after a single pass. Of course, the necessary relative movement between the light beam and the imaging element can be effected not by (or in addition to) the movement of the light beam, but by the movement of the imaging element.

Regardless of the method of scanning the light beam, it is generally preferred (for speed reasons) to use multiple lasers and direct their output to one writing column. A writing column is then specified, and after the completion of a single pass over or along the imaging element, the distance depends on the number of rays emanating from the column and on the desired resolution (ie, the number of image points per unit length). Number).

B.2. Global Exposure Global exposure for the present invention is performed by a light source that emits at least in the wavelength range where the photosensitive layer of the imaging element according to the present invention has spectral sensitivity. In a practical embodiment of the invention, the photosensitive layer is UV-sensitive and / or optionally sensitive to short wavelength parts of the visible spectrum, for example to green. The overall exposure is, for example, 100
This can be done with an exposure source such as a 0 W high or medium pressure mercury vapor lamp.

B.3. Development The development according to the present invention is performed with a suitable liquid capable of removing the exposed or unexposed portions of the photosensitive layer. The appropriate composition of the developer in the present invention depends on the type of photosensitive layer and is preferably such that during development the heat-sensitive layer and optionally the intermediate layer are removed simultaneously.

For morphological reasons, water-based developers are used without other organic solvents. Particularly preferred developers are aqueous alkaline solutions.

Particularly suitable developers for use with the preferred photosensitive coatings described above are as follows.

The developing agent suitably used in the present invention is an aqueous solution mainly comprising an alkali metal silicate and an alkali metal hydroxide. As such an alkali metal silicate, for example, sodium silicate, potassium silicate, lithium silicate and sodium metasilicate are preferably used. On the other hand, sodium hydroxide, potassium hydroxide and lithium hydroxide are preferred as such alkali metal hydroxides. From the standpoint of preventing the formation of insoluble precipitates, it is particularly desirable that the developing agent comprises at least 20 mol% of potassium with respect to the total amount of alkali metal in the aqueous developing solution.

The developing agent used in the present invention may simultaneously contain another alkaline reagent. Examples of such other alkaline reagents include inorganic alkaline reagents such as ammonium hydroxide, sodium tertiary phosphate, sodium dibasic phosphate, potassium tertiary phosphate, potassium dibasic phosphate, ammonium tertiary phosphate, ammonium dibasic phosphate Sodium bicarbonate, sodium carbonate, potassium carbonate and ammonium carbonate; and organic alkaline reagents such as mono-, di- or triethanolamine, mono-, di- or trimethylamine, mono-, di- or triethylamine, mono-di-. Or isopropylamine, n-
Butylamine, mono-, di- or triisopropanolamine, ethyleneimine, ethylenediimine and tetramethylammonium hydroxide are included.

The molar ratio of silicate [SiO ₂ ] to alkali metal oxide [M ₂ O] in the developing agent for use in the present invention is from 0.6 to 1.5, preferably from 0.7 to 1.5. 1.3 is particularly desirable. Further, SiO ₂ concentration in the replenisher preferably ranges from 2 to 4 wt%.

In the developing agent used in the present invention, 20
Organic solvents having a solubility in water of not more than 10% by weight at 0 ° C. can be used simultaneously if desired. Examples of such organic solvents are carboxylic esters such as ethyl acetate, propyl acetate, amyl acetate, benzyl acetate, ethylene glycol monobutyl acetate, butyl lactate and butyl levulinate; ketones such as ethyl butyl ketone, methyl isobutyl ketone And cyclohexanone; alcohols such as ethylene glycol monobutyl ether, ethylene glycol benzyl ether, ethylene glycol monophenyl ether, benzyl alcohol, methylphenylcarbinol, n-amyl alcohol and methyl amyl alcohol; alkyl-substituted aromatic hydrocarbons Hexylene; and halogenated hydrocarbons such as methylene dichloride and monochlorobenzene. These organic solvents can be used alone or in combination. In the present invention, benzyl alcohol is particularly preferred. These organic solvents are added to the developing agent in an amount not more than 5% by weight and more preferably not more than 4% by weight.

The developing agents used in the present invention can simultaneously contain a surfactant for the purpose of improving the developing properties. Examples of such surfactants include higher alcohols (C _8-
C ₂₂₎ salts of sulfuric acid esters such as sodium salt of lauryl alcohol sulfate commercially available sodium salt of octyl alcohol sulfate, ammonium salt of lauryl alcohol sulfate, Teepol B-81 (trade mark, Shell Chemicals Co., Ltd. Salts of aliphatic alkyl phosphates, such as sodium ester of cetyl alcohol phosphate; alkyl aryl sulfonates, such as sodium salt of dodecyl benzene sulfonate, isopropyl naphthalene sulfonate Naphthalene salt, sodium salt of dinaphthalenedisulfonic acid ester and sodium salt of metanitrobenzenesulfonic acid ester; Hong salts; sulfonates and dibasic aliphatic acid esters such as sodium and dihexyl sodium sulfosuccinate dioctyl sulfosuccinate, and the like. These surfactants can be used alone or in combination. Sulfonates are particularly preferred. These surfactants can generally be used in amounts not more than 5% by weight and preferably not more than 3% by weight.

In order to enhance the development stability of the developing agent, the following compounds may be used together.

Examples of such compounds include NaCl and K disclosed in Japanese Patent Publication No. 58-75152.
Neutral salts such as Br; Japanese Patent Publication No. 58-19095
No. 2 (U.S. Pat. No. 4,469,776); chelating agents such as EDTA and NTA; Japanese Patent Publication No. 59-121336 (U.S. Pat. No. 4,606,99).
Disclosed in No. _{5) [Co (NH 3) 6} ] such complex of Cl _3; Japanese Patent Publication Sho periodic table disclosed in JP 55-25100 IIa, possible ion of IIIa or IIIb group element Compounds: Anionic or amphoteric surfactants such as sodium alkylnaphthalenesulfonate and N-tetradecyl-N, N-dihydroxyethylbetaine disclosed in Japanese Patent Publication No. 50-51324; U.S. Pat. No. 4,374,920 No. 60-1394.
No. 3; a nonionic surfactant; a cationic polymer, for example, a quaternary methyl chloride product of p-dimethylaminomethylpolystyrene disclosed in Japanese Patent Publication No. 55-95946; Molecular electrolytes such as copolymers of vinylbenzyltrimethylammonium chloride and sodium sulfite disclosed in Japanese Patent Publication No. 56-142528; reducing inorganic salts such as Japanese Patent Publication No. 57-192954 (U.S. Pat. 46
7,027) and sodium-sulfite and alkali-soluble mercapto compounds or thioether compounds such as thiosalicylic acid, cysteine and thioglycolic acid; inorganic lithium compounds such as those disclosed in JP-A-58-95444. Lithium chloride; containing organolithium compounds, such as lithium benzoate disclosed in Japanese Patent Publication No. 50-34442 for objection; Si, Ti, etc. disclosed in Japanese Patent Publication No. 59-75255. Organometallic surfactants; organoboron compounds disclosed in Japanese Patent Publication No. 59-84241 (U.S. Pat. No. 4,500,625); quaternary ammonium salts, such as those disclosed in European Patent No. 101,010 Tetraalkylammonium oxide; and killing Bacterial agents such as sodium dehydroacetate.

According to the method of the present invention, the imaging element is wiped with a cleaning means, preferably a dry cleaning means, such as a cotton pad or paper towel, after the image-wise exposure and before the overall exposure. This is particularly suitable when the heat-sensitive layer comprises carbon black or a metal pigment.

According to the invention, the imaging element can also be processed image-wise and after the fully exposed imaging element has been placed on the printing cylinder of a printing machine. This is particularly suitable for imaging elements that can be processed with water or water-alcohol solutions. Such an imaging element is incorporated herein by reference EP-A 631189.
It is described in. According to a preferred embodiment, the printing machine is then started, and a dampening fluid roller supplying dampening fluid falls onto the imaging element while the printing cylinder with the imaging element mounted thereon is rotating. And then the ink roller falls there. In general, the first clean and useful prints are obtained after about 10 rotations of the printing cylinder.

According to a variant, the ink roller and the dampener roller can be dropped simultaneously or the ink roller can be dropped first.

Suitable dampening solutions which can be used in connection with the present invention are generally aqueous solutions having an acidic pH and comprising an alcohol such as, for example, isopropanol. There is no particular limitation on the fountain solution useful in the present invention, and commercially available fountain solutions, also known as fountain solutions, can be used.

According to a variant, the imaging element is first placed on the printing cylinder of a printing press and then exposed directly image-wise and totally on the printing press. After exposure,
The imaging element can be developed as described above.
Imaging elements suitable for image-wise exposure on a printing machine are those imaging elements which can be developed while being mounted on a printing cylinder of the printing machine described above.

The invention will now be further described by the following examples, which do not limit the invention. All parts are by weight unless otherwise indicated.

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【Example】

Example 1 Preparation of a lithographic base 440 g of 21.5% TiO ₂ (average particle size 0.3 to
Stirring with a dispersion containing 0.4 μm) and 2.5% polyvinyl alcohol in deionized water, 250 g of a 5% aqueous solution of polyvinyl alcohol, 105 g of a 22% aqueous emulsion of hydrolyzed tetramethyl orthomethyl silicate and 12 g Was added continuously. To this mixture is added 193 g of deionized water and the pH is adjusted to pH = 4.
Was adjusted to The resulting dispersion is coated on a polyethylene terephthalate film support (coated with a hydrophilic adhesive layer) at a wet coating thickness of 50 g / m ² , dried at 30 ° C. and then dried. 57 ° C
At a temperature of 1 week for a week. An aqueous solution of Dormacid (dextran modified with diethylaminoethyl group, commercially available from Faifer and Langen) (pH
= 5) and 30 mg / m ^{2 of} cationic wetting agent
Of Dormacid dry coating thickness. The resulting element was then heated to 57 ° C for one week.

Preparation of the Imaging Element The imaging element according to the present invention was prepared by preparing the following photosensitive composition.

Preparation of UV Sensitive Coating 120 g of a 20% dispersion of polymethyl methacrylate (particle size of 40 nm) stabilized with 63 g of cetyltrimethylammonium bromide in deionized water are stirred.
98 having a weight average molecular weight of 200,000 g / mol
5% aqueous solution of hydrolyzed polyvinyl acetate (MOWIOL 56-98, commercially available from Hoechst) and 15 g of 10% Heliogen Blue D 7
A dispersion containing 565 (commercially available from BASF) and 5% polyvinyl alcohol (MOWIOL 56-98) in water was added continuously. 46 g of a 15% solution of the condensation product of diphenylamine diazonium salt with formaldehyde (NE commercially available from PCAS)
GALUX N18) and 20 g of a 15% aqueous solution of the condensation product of methox-diphenylaminediazonium salt with formaldehyde (DIAZO No. 8 commercially available from Fairmont) were then added slowly. Finally, 30 g of an aqueous solution of a cationic fluorine-containing surfactant (3
M Fluorad FC 135) and 726 ml of water were added. The UV-sensitive composition was coated on the lithographic base described above in an amount of 35 g / m ² (wet coating amount) and then dried at 30 ° C.

Preparation of Infrared Sensitive Coatings The infrared sensitive formulations contain the following components, indicated in parts by weight, unless otherwise indicated.

Methyl-Ethyl Ketone 834.5 Novolak MLEX XL225 (commercially available from Mitsui) 12.25 Nitrocellulose E620 (commercially available from Wolf Walsroad) 12.25 (ultraviolet-absorbent 1) 25 (infrared-dye 1) 10 ( Infrared-dye 2) 50 (cyan-dye 1) 7.5 (cyan-dye 2) 14.5 (magenta-dye 1) 11 (magenta-dye 2) 6.5 (yellow-dye 1) 8 (yellow -Dye 2) 7.5

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The ultraviolet-sensitive layer was overcoated with a knife coater with an infrared-sensitive formulation to a wet coating thickness of 20 μm.

Production of a printing plate and making an original copy Scanning NdY which emits the above imaging element at 1050 nm
LF infrared laser (scan speed 1.1 m / s, spot size 15 μm and 400 mW power on imaging element surface). After this exposure, the infrared-sensitive mask disappeared where it was exposed to the laser beam. Subsequently, 10 imaging elements
9W at a distance of 70 cm from a high-pressure halogen mercury vapor lamp of 00 W
Presented for 0 seconds. Further, the image forming element is
A development step using DN-5 was performed to remove non-image portions. After development, the imaging element was placed on a GTO 46 offset printing machine. K + E as ink
Rotamati using 123W and as fountain solution
c was used. Printing was commenced and good print quality was obtained with no ink absorption in the non-image areas.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Marc van Dame Belgium 2640 Malt cell septestrat 27 Inside Agfa-Gevuert-Namrose-Fuennoutjapp (72) Inventor Thomas Nouen Belgium B 2640 Maltcell Septe Strat 27 Agfa-Gevuert Namrose Rosenenjjapp (72) Inventor Eddie Dems Belgium 2640 Maltcell Septe Strat 27 Agfa-Gevert Namrose Rosenjenjap (56) Reference Reference JP 6-95494 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03F 7/00 G03F 7/004 G03F 7/11

Claims (11)

(57) [Claims] 1. The method according to claim 1, wherein the support has a hydrophilic surface.
A heat-sensitive layer comprising a photosensitive layer having sensitivity to light having a wavelength of 450 nm and a masking dye having an absorption peak within a wavelength range of 300 to 450 nm which makes the heat-sensitive layer opaque to light having spectral sensitivity. An imaging element comprising, in the heat-sensitive layer or a layer adjacent thereto, a compound A capable of converting light into heat and further comprising a compound A capable of converting light into heat. An imaging element wherein the dye can be ablated. 2. An imaging element according to claim 1, wherein compound A is an infrared absorbing compound. Wherein the image forming element of claim 2 wherein the compound A is an infrared dye fees. 4. An imaging element according to claim 1, wherein said support comprises polished and anodized aluminum or a substrate provided with a hydrophilic layer. 5. The imaging element according to claim 1, wherein said heat-sensitive layer further comprises a thermally decomposable binder. 6. 300 on a support having a hydrophilic surface
A heat-sensitive layer comprising a photosensitive layer having sensitivity to light having a wavelength of ~ 450 nm and a masking dye having an absorption peak in a wavelength range of 300 to 450 nm which renders the heat-sensitive layer opaque to light having spectral sensitivity. Exposing the imaging element comprising a layer and further comprising a compound A capable of converting light to heat, in the thermosensitive layer or a layer adjacent thereto, image-wise with a laser, whereby the masking dye is Ablating and rendering the thermosensitive layer imagewise transparent to light whose photosensitive layer is spectrally sensitive, the imagewise exposed imaging element thus obtained is provided with Exposed entirely with light having
Thereby forming a latent image in the photosensitive layer, developing the imaging element thus obtained, thereby removing the heat-sensitive layer and the unexposed or exposed parts of the photosensitive layer. And a step of leaving an ink-receiving image of the photosensitive layer on the support. 7. The compound A is an infrared absorbing compound,
7. The method according to claim 6, wherein said laser is an infrared laser or a laser diode. 8. The method according to claim 6, wherein said developing is carried out with an aqueous alkaline liquid. 9. The method according to claim 6, wherein the imaging element is wiped with cleaning means after the image-wise exposure and before performing the overall exposure. 10. The method according to claim 6, wherein the image-forming element is processed after the image-wise and fully exposed imaging element has been placed on a printing cylinder of a printing machine. 11. The method according to claim 6, wherein the imaging element is imagewise and totally exposed while being mounted on a printing cylinder of a printing machine.