JP2001047758A - Processless printing plate having coating layer containing compound having cationic group - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material for a heat mode recording material which has high sensitivity and a high lithographic quality. SOLUTION: In regard to a thermosensible material for manufacturing a lithographic plate constituted by comprising an infrared-photosensitive lipophilic layer and a crosslinked hydrophilic layer in the sequence of the mention on a substrate, the thermosensible material is coated with a layer constituted by containing at least one kind of organic compound containing a cationic group. This organic compound is a hydrophilic polymer having one or more ammonium groups or a low-molecular-weight hydrophilic organic compound having one or more ammonium groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat mode recording material for producing a lithographic plate for use in lithographic printing.
The invention further relates to a method for forming an image of the heat mode recording material, for example by means of a laser.

[0002]

BACKGROUND OF THE INVENTION Lithographic printing is a specially prepared surface in which some areas are receptive to ink (oleophilic areas) while others will not. This is the printing method. According to so-called conventional or wet printing plates, both water or an aqueous dampening solution and ink are applied to the plate surface containing hydrophilic and lipophilic regions. The hydrophilic areas will be soaked in water or fountain solution and thereby rendered oleophobic, while the lipophilic areas will receive the ink.

When a laser heat mode recording material is used as a direct offset master for printing with oleaginous inks, the lipophilicity of the image and non-image areas
It is necessary to perform hydrophilic mapping. In the case of heat mode laser ablation, the hydrophilic or lipophilic topcoat is completely removed imagewise to obtain the required difference in ink receptivity between the image and non-image areas. It is also necessary to expose the lipophilic or hydrophilic surface under the photosensitive recording material.

[0004] For example, DE-A-2 448 325
Discloses a laser heat mode "direct negative" printing plate comprising, for example, a polyester film support provided with a hydrophilic surface layer. The disclosed heat mode recording material is imaged using an argon laser, thereby rendering the exposed areas oleophilic. An offset printing plate which can be used on a printing press without further processing is thus obtained. Because the exposed areas of the recording material are made ink-receptive,
The version is called the "direct negative" version.

Another disclosure in DE-A-2 448 325 is, for example, that of a water-soluble laser beam (Argon-488).
nm) a "direct negative" printing plate comprising a hydrophilic aluminum support coated with a coating based on an absorbing dye or a mixture of a hydrophilic polymer and a laser light absorbing dye (argon-488 nm). Further examples of heat mode recording materials for producing "direct negative" printing plates are described, for example, in U.S. Pat. No. 4,341,183, DE-A-2 60.
7 207, DD-A-213 530, DD-A-2
17 645 and DD-A-217 914. These documents disclose heat mode recording materials having a hydrophilic layer on an anodized aluminum support. The disclosed heat mode recording material is image-wise exposed using a laser. Laser exposure renders the exposed areas insoluble and ink-receptive, but the unexposed image portions remain hydrophilic and water-soluble and are removed by the dampening solution during printing, exposing the hydrophilic support. Such a plate can be used directly without processing on a printing machine.

[0006] DD-A-155 407 discloses a laser heat mode "direct negative" printing plate in which a hydrophilic aluminum oxide layer is made lipophilic by direct laser heat mode imaging. These printing plates can be used on a printing machine without further processing.

From the above, it can be seen that many proposals have been made for producing "direct negative" offset printing plates by laser heat mode recording. They have disadvantages such as low recording speed and / or poor quality of the resulting plate.

Another method of making direct lithographic plates is by laser ablation.

[0009] EP-A-580 393 discloses a lithographic printing plate which can be imaged directly by laser irradiation, the plate comprising a top first layer and a second layer below the first layer. Wherein the first layer is characterized by effective absorption of infrared radiation and the first and second layers are at least one
Shows different affinities for different printing fluids.

EP-A-683 728 describes substances capable of converting light to heat on a support having an ink-receiving surface or coated with an ink-receiving layer.
Disclosed is a heat mode recording material comprising a cured hydrophilic surface layer having a thickness no greater than μm. The lithographic properties of the material are not very good.

[0011]

OBJECTS OF THE INVENTION It is an object of the present invention to provide a material for high lithographic quality heat mode recording materials with regard to high sensitivity and, in particular, little toning and little thickening at startup.

[0012]

SUMMARY OF THE INVENTION According to the present invention, there is provided a heat-sensitive material for producing a lithographic plate comprising an IR-photosensitive lipophilic layer and a cross-linked hydrophilic layer on a support in the order described.
At least one of the heat-sensitive materials comprising a cationic group;
A heat-sensitive material is provided, characterized in that it is coated with a layer comprising at least one organic compound.

[0013]

DETAILED DESCRIPTION OF THE INVENTION Organic compounds having a cationic group for use in connection with the present invention are preferably hydrophilic and can be low molecular weight compounds, but are preferably polymers. Preferred compounds are those having one or more ammonium groups or amino groups that can be converted to ammonium groups in an acidic medium. A particularly preferred type of cationic compound is a polysaccharide modified with one or more groups containing ammonium or amino groups.

The most preferred organic compounds having a cationic group include the following groups in which at least a part of the hydroxy group is one or more of the following groups: -OR ¹ -O-CO-R ^{2 wherein} R ¹ is Represents an organic residue containing an amino or ammonium group, such as an amine-substituted alkyl, an amine-substituted alkylaryl, and the like, wherein R ² has ^one of the meanings indicated for R ¹ , or —OR ³ or -N (R ⁴ ) R ⁵ , wherein R ³ has ^one of the meanings indicated for R ¹ and each of R ⁴ and R ⁵ can be the same or different and is indicated for R ¹ Dextran or pullulan modified to have one of the meanings described above.

Pullulan is produced by a microorganism of the Aureobasidium pullulans type (Pullularia pullulans) and contains maltotriose repeat units linked by a-1,6-glycosidic bonds. It is a polysaccharide. Pullulan is generally produced on an industrial scale by fermentation of partially hydrolyzed starch or by bacterial fermentation of sucrose. Pullulan is commercially available, for example, from Shodex, Pharmacosmos.

Examples of dextrans or pullulans suitable for use in accordance with the present invention are dextrans or pullulan in which some of the hydroxyl groups have been modified with one of the groups shown in Table 1. Table 1 No. Group to be modified 1 -O-CH ₂ -CH ₂ -NH ₂ 2 -O-CO-NH-CH ₂ -CH ₂ -NH ₂ 3 -O-CO-NH-CH ₂ -CH ₂ -N _{(CH 2 -CH 2 -NH 2)} 2 4 -O-CH 2 -CH 2 -NH-CH 2 -CH 2 -NH 2 5 -O-CH 2 -CH 2 -NH-CH 2 -CHOH-CH 2 ^{_{-N + (CH 3) 3 Cl}} - 6 -O- (CH 2 -CH 2 -O) n -CH 2 -CH 2 -NH 2 ( here n represents an integer of 1 to 50) 7 -O- _{CO-NH-CH 2 -CH 2} -NH-CH 2 -CHOH-CH 2 -N + (CH 3) 3 Cl - 8 -O-CH 2 -CH 2 -N (CH 2 -CH 3) 2 .HCl 9 -O-CH ₂ -CH ₂ -N (CH ₂ -CH ₂ -NH ₂ ) ₂ 10 -O-CONH-CH ₂ -CH ₂ -N (CH ₂ -CH ₂ -NH ₂ ) ₂ 11 -O- _{CONH- (CH 2 -CH 2 -O)} n-CH 2 -CH 2 -NH 2 modified dextrans or pullulan, dextran and include alkylating agents, chloroformates, acid halides, such as carboxylic acid and Can be produced.

The organic compounds having one or more cationic groups according to the invention are preferably from 10 to 20
In an amount of 00 mg / m ² and more preferably from 20 to 10
It is supplied in an amount of 00 mg / m ² .

Various cured hydrophilic surface layers are suitable for the present invention. The hydrophilic coating preferably comprises a hydrophilic binder having free reactive groups including, for example, hydroxyl, carboxyl, hydroxyethyl, hydroxypropyl, amino, aminoethyl, aminopropyl, carboxymethyl, etc. reagent,
It is cast from an aqueous composition containing suitable crosslinkers or modifiers including aluminoformyl acetate, dimethylol urea, melamines, aldehydes, hydrolyzed tetraalkyl orthosilicate, and the like.

Suitable polymers for the hydrophilic layer include gum arabic, casein, gelatin, starch derivatives, carboxymethylcellulose and its Na salts, cellulose acetate, sodium alginate, vinyl acetate-maleic acid copolymer,
Styrene-maleic acid copolymers, polyacrylic acids and their salts, polymethacrylic acids and their salts, hydroxyethylene polymers, polyethylene glycols, hydroxypropylene polymers, polyvinyl alcohols, and at least 60% by weight and more Preferably it can be selected from the group consisting of hydrolyzed polyvinyl acetate having a degree of hydrolysis of at least 80% by weight.

Polyvinyl alcohol hydrolyzed to the extent of at least 60% by weight cured with a tetraalkyl orthosilicate, for example tetraethyl orthosilicate or tetramethyl orthosilicate, as disclosed, for example, in US Pat. No. 3,476,937. Alternatively, hydrophilic layers containing polyvinyl acetate are particularly preferred because their use in the present heat mode recording materials provides excellent lithographic printing properties.

Another suitable cured hydrophilic surface layer is EP-
A-514 990. The hydrophilic layers disclosed in this EP-application are curable reaction products of (co) polymers and aldehydes containing amine or amide functionalities with at least one free hydrogen (eg amino-modified dextran). Comprising.

The cross-linked hydrophilic binder in the heat-sensitive layer used according to this embodiment is preferably also a substance which increases the mechanical strength and porosity of the layer, for example particles of titanium dioxide or other metal oxides Metal oxide colloid particles. The addition of these particles gives the surface of the crosslinked hydrophilic layer a uniform rough texture consisting of minute irregularities. Preferably, these particles are beryllium, magnesium, aluminum, silicon, gadolinium, germanium, arsenic, indium, tin, antimony, tellurium,
Lead, bismuth or transition metal oxides or hydroxides. Particularly preferred colloidal particles are those of 20 to
Aluminum, silicon, zirconium and titanium oxides or hydroxides used at 95% by weight, more preferably 30-90% by weight of the hydrophilic layer.

The cross-linked hydrophilic layer is preferably 0.3.
It is coated at a dry thickness of ５5 μm, more preferably at a dry thickness of 0.5-3 μm.

According to the present invention, the cured hydrophilic layer may comprise additional substances, such as plasticizers, pigments, dyes and the like. The cross-linked hydrophilic layer can contain IR-absorbing compounds to further increase IR-sensitivity.

The IR-photosensitive lipophilic layer comprises a lipophilic binder and a compound capable of converting light to heat.

Suitable compounds capable of converting light into heat are preferably infrared-absorbing components which have an absorption in the wavelength range of the light source used for the image-wise exposure. Particularly useful compounds are, for example, the dyes disclosed in EP-A-908 307 and especially infrared dyes and pigments and especially infrared pigments such as carbon black, metal carbides, borides, nitrides, carbonitrides ( carbonitrides, bronze-structured oxides and oxides structurally related to the bronze group but lacking the A component, such as WO _2.9 . It is also possible to use conductive polymer dispersions, for example those based on polypyrrole or polyaniline.
The lithographic performance and especially the printing resistance obtained depend, inter alia, on the heat sensitivity of the imaging element. In this connection, it has been found that carbon black or graphite gives very good and favorable results.

[0027] Preferably, the polymer is selected from the group consisting of polyvinyl chloride, polyesters, polyurethanes, novolak, polyvinyl carbazole and the like or copolymers or mixtures thereof.

Most preferably, the polymeric binder in the recording layer is heat-sensitive, for example polymers containing nitrate groups (eg GB-P-1 316 398 and DE).
-A-2 512 038, a self-oxidizing binder cellulose nitrate), for example a polymer containing carbonate groups (for example polyalkylene carbonate), for example a polymer containing covalently bonded chlorine (for example polychlorinated). Vinyl). A substance containing an azo or azide group capable of releasing N ₂ upon heating is also preferably used.

Preferably, the lipophilic layer is 0.5-30 g /
m^Two, Preferably between 3 and 15 g / m ^TwoWith dry weight between
Coated.

The support according to the invention is preferably dimensionally stable and can be aluminum or another metal or alloy. Preferably, electrochemically and / or mechanically grained and anodized aluminum is used in the present invention.

Further in the context of the present invention, the support can be a flexible support. Flexible supports in connection with this embodiment include plastic films, such as substrated polyethylene terephthalate film, polyethylene naphthalate film, cellulose acetate film, polystyrene film, polycarbonate film, polyethylene film, polypropylene film, polyvinyl chloride film, It is particularly preferred to use a polyethersulfone film. The plastic film support may be opaque or translucent. The plastic film is preferably EP-A-619 524, EP
-A- 619 525 and EP-A-620 502
And subbing with a subbing layer as described in

In addition, paper or glass having a thickness of no more than 1.2 mm can be used.

According to the invention, the imaging element is image-wise exposed. During the exposure, the coated layer and the cross-linked hydrophilic layer can be removed in the exposed areas and the areas are converted to lipophilic areas, while the unexposed areas remain hydrophilic. This is usually a short pixel dwell time (p
pixel dwell time) (for example, 1 to 100 ns). However, when using relatively long pixel dwell times (eg, 1-20 μs), the hydrophilic layer is not removed or only partially removed by exposure. The remaining part of the hydrophilic layer can be removed by contact with fountain solution and ink on the printing press or by an additional wet or dry processing step between the IR-laser exposure and the start of the printing process.

The image-wise exposure according to the present invention is preferably an image-wise scanning exposure which involves the use of a laser or LED. Infrared or near-infrared, ie 70
Lasers operating in the wavelength range from 0 to 1500 nm are preferably used. Most preferred is a near-infrared emitting laser diode having an intensity greater than 0.1 mW / μm ² .

According to the invention, the plate is now ready for printing without additional development and can be placed on a printing press.

According to another method, the imaging element is first placed on the printing cylinder of a printing press and then image-wise exposed directly on the printing press. After exposure, the imaging element is ready for printing.

The printing plate of the present invention can also be used as a seamless sleeve printing plate in a printing method. In this case, the printing plates are joined cylindrically by a laser. This cylindrical printing plate having the diameter of the printing cylinder as the diameter is slid onto the printing cylinder instead of the conventional printing plate installation. For more details on sleeves see "Graf
isch Nieuws ", 15, 1995, page 4 to 6.

The following examples illustrate the invention but do not limit the invention. All parts and percentages are by weight unless otherwise indicated.

[0039]

EXAMPLES An IR-sensitive layer was coated on top of an aluminum substrate from a solution having the following composition with a wet coating thickness of 50 .mu.m: carbon black dispersion of the following composition, 279.3 g: Special Schwartz (Sp)
ecial Schwarz) ^TM (Degussa), 34.9 g,
Nitrocellulose E950 ^TM (Wolf Walsroad
(Wolf Walsrode)), 3.5 g, dispersant, 4.2 g, methyl ethyl ketone, 236.7 g nitrocellulose solution having the following composition, 217.8 g: nitrocellulose E950 ^™ , 21.8 g, ethyl acetate,
196.0 g Cymel solution having the following composition, 24.0 g: Cymel 301 ^™ , 4.8 g ethyl acetate, 19.2 g p-toluenesulfonic acid solution having the following composition, 8.75
g: p-toluenesulfonic acid, 0.875 g, ethyl acetate 7.
875 g.

After drying the infrared-sensitive layer, the hydrophilic layer was coated with a wet coating thickness of 20 μm from a solution having the following composition: Polyviol
WX48 ^™ (polyvinyl alcohol from Wacker) stabilized TiO ₂ in water dispersion (10% w / w polyvinyl alcohol to TiO ₂ ) (average particle size 0.3-0.5 μm) -6 .25% w / w,
70.0 g, hydrolyzed tetramethyl orthosilicate in water / ethanol-6.25 w / w%, 30.0 g, wetting agent in water-5 w / w, 1.2 g.

The pH of this solution was adjusted to 4 before coating. This layer was cured at 67 ° C./50% relative humidity for 12 hours. In this way, a control element was obtained.

Elements 1, 2, 3, 4, and 5 were made as follows.

On top of the imaging element, diethylaminoethoxylated dextran (Pfeiffer and Langen (Pfe
The hydrophilic layer was coated from a 1% w / w aqueous solution from Dormacid ^™ from Ifer & Langen). This hydrophilic layer was 0.05 g / m ² (element 1), 0.1 g / m ^2.
g / m ² (element 2), 0.25 g / m ² (element 3), 0.5
Coated to a dry thickness of 0 g / m ² (element 4), 0.75 g / m ² (element 5). Element 6 was prepared as follows: an imaging element as described in the Control Element was treated by rinsing with a cotton pad soaked in a 1% w / w aqueous solution of Dolmasid ^™ in the above solution.

The resulting imaging element is operated at a scan rate of 80 rps and a laser power of 15.5 watts, a Creo 3244 Trendsetter.
^Imaged at 2400 dpi on ^TM .

After image formation, the plate was placed on a GTO 52 printing machine using K + E800 as the ink and rotamatic as the fountain solution.

Subsequently, the printing machine was started by rotating the printing cylinder with the imaging element mounted thereon. The dampening roller of the printing machine is first lowered onto the imaging element to supply dampening fluid to the imaging element and to
After each rotation of the printing cylinder, the ink roller was lowered to supply ink. The dot area of the 50% screen at D _min and 200 lpi was measured with a Macbeth®
Measured on prints 5, 25 and 50 using D918-SB. The results are summarized in Tables 2 and 3.

[0047]

[Table 1]

[0048]

[Table 2]

From these results it is clear that the additional cationic hydrophilic coating of diethylaminoethoxylated dextran improves the lithographic properties, ie, less toning at start-up and lower streaking. .

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Giyoan Vermeersch Belgium 2640 Malt Cell Septes Trat 27 Agfa-Gevert Na Mrose Hohennenjaup

Claims (9)

[Claims] 1. A heat-sensitive material for producing a lithographic plate comprising an IR-photosensitive lipophilic layer and a cross-linked hydrophilic layer in the order described on a support, wherein the heat-sensitive material is cationic. A heat-sensitive material, wherein the heat-sensitive material is covered with a layer containing at least one organic compound containing a functional group. 2. The heat-sensitive composition according to claim 1, wherein the organic compound is a hydrophilic polymer having one or more ammonium groups or a low molecular weight hydrophilic organic compound having one or more ammonium groups. material. 3. The heat-sensitive material according to claim 2, wherein the hydrophilic polymer is a polysaccharide. 4. The heat-sensitive material according to claim 3, wherein the polysaccharide is dextran or pullulan. 5. The method of claim 1, wherein the organic compound is present in the imaging element in an amount of 0.01.
Heat-sensitive material according to claim 1 in an amount between ~2.00g / m ^2. 6. The heat-sensitive material according to claim 1, wherein the lipophilic layer is coated with a dry weight of between 0.75 and 15 g / m ² . 7. The crosslinked hydrophilic layer is beryllium,
The method according to claim 1, comprising an oxide or hydroxide of magnesium, aluminum, silicon, gadolinium, germanium, arsenic, indium, tin, antimony, tellurium, lead, bismuth, titanium or a transition metal. Thermosensitive material. 8. A heat-sensitive material according to claim 1, wherein the hydrophilic layer has a dry thickness between 0.3 and 5 μm. 9. (i) image-wise exposing the heat-sensitive material according to claim 1 to a laser beam having an intensity of more than 0.1 mW / μm ² , wherein (ii) the step (i) A method for producing a lithographic printing plate, comprising: before or after, placing the plate on a printing machine and (iii) contacting the plate with a dampening solution and ink.