JP2002200730A - Apparatus for automatically plate coating and plate cleaning - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus capable of applying a print master by effectively cleaning the master without long non-operating time of a printing machine on a substrate for recirculating a new coating of high quality. SOLUTION: An off press platemaking unit has a means for removing a lithographic image from a substrate of the print master, and a means for recoating the substrate to be recirculated with a new image recording layer. The off press cleaning and recoating of the substrate gives a short non-operating time of the printing machine. The recording substrate generates an image forming material, and can be exposed in an exposure unit which may be integrated in a digital printing machine including the exposure unit integrated in the off press or integrated within the platemaking unit by the off press and/or may be mechanically coupled thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a printing master that carries a lithographic image on a substrate.
More specifically, this apparatus coats the lithographic image from the substrate of the printing master with a new image recording layer capable of forming a lithographic image with exposure to heat or light and optional processing to remove the recycled image from the substrate. Means.

[0002]

2. Description of the Prior Art Lithographic printing methods use a so-called printing master, such as a printing plate, which is mounted on a cylinder on a printing machine. The 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 onto a receiver material, typically paper. . In conventional lithographic printing, ink and aqueous dampening solution (also called dampening solution)
Is lipophilic (or hydrophobic, ie, ink-receptive,
It is supplied to a lithographic image comprising a water-repellent region and a hydrophilic (or oleophobic, ie water-receptive, ink-repellent) region. In so-called driographic printing, the lithographic image consists of ink-accepting and ink-abhesive (ink-repellent) areas, and only ink is supplied to the master during driographic printing.

[0003] Printing masters are generally referred to as so-called computer-to-film methods.
od), in which the various pre-printing steps such as typeface selection, scanning, color separation, screening, trapping, layout and assembly are performed digitally and each color selection is performed using an image-setter. Is transferred to After processing, the film can be used as a mask for exposing the imaging material, called a plate precursor, and after plate processing, a printing plate is obtained which can be used as a master.

In recent years, the so-called computer-to-plate method has been of great interest. This method, also referred to as the direct-to-plate method, avoids the creation of a film because the digital document is transferred directly to the plate precursor by a so-called plate-setter. The following improvements are currently being investigated in the field of such computer-to-plate methods.

(I) On-press image formation. A special type of computer-to-plate method involves exposing the plate precursor while being placed on the plate cylinder of the printing press by an integrated image-setter in the printing press. This method can be referred to as "computer-to-press", and printing machines with an integrated plate-setter are sometimes referred to as digital printing machines. Review of digital printing machines is the Proceedings of th
e Imaging Science &Technology's 1997 Internationala
l Conference on Digital Printing Technologies (Non
-Impact Printing13). Computer-to-press methods are described, for example, in EP-A 770 495,
EP-A 770 496, WO 940012280, E
It is described in P-A 580 394 and EP-A 774 364. Typical plate materials used in the computer-to-press method are based on abrasion. A problem with the abrasion plate is the generation of debris that is difficult to remove and may interfere with the printing process or contaminate the exposure optics of the integrated image-setter. Other methods require wet processing with chemicals that may damage or contaminate the electronics and optics of the integrated image-setter and other equipment of the printing machine.

(Ii) On-press coating. The plate precursor usually comprises a sheet-like support and one or more practical coatings, but a composition capable of forming a lithographic surface with image-wise exposure and optional treatment is used in a printing machine plate. The computer-to-press method applied directly on the surface of the cylinder is for example GB1465532
It is described in. EP-A 101 266 describes the coating of a hydrophobic layer directly on the hydrophilic surface of a plate cylinder. After removal of the non-printed areas by abrasion, a master is obtained. However, as discussed above,
Ablation should be avoided with the computer-to-press method. US Pat. No. 5,713,287 describes a computer-to-press method in which a so-called exchangeable polymer such as, for example, tetrahydropyranyl methyl methacrylate is applied directly on the surface of the plate cylinder. The interchangeable polymer is initially water-sensitive to water-
Made insensitive. The latter method requires a curing step,
And because polymers are thermally unstable and consequently difficult to synthesize, they are very expensive.

(Iii) Thermal imaging. Many of the computer-to-press methods described above use so-called thermal or thermal materials, i.e., plate precursors or on-press-coatable compositions comprising compounds that convert absorbed light into heat. The heat generated by the image-wise exposure causes (physical) chemical processes, such as abrasion, polymerization, cross-linking insolubilization of the polymer, decomposition, or particle coagulation of the thermoplastic polymer latex, and optional treatment Later, a lithographic image is obtained.

(Iv) Practical coating development that does not require wet processing or may be treated with fresh water, ink or fountain solution is another major trend in plate making. Such materials are particularly desirable in computer-to-press methods to avoid damage or contamination of the integrated image-setter optics and electronics due to contact with the processing solution. WO 9000020
4, WO 91008108 and EP-A 580 3
Although 94 discloses such plates, they are all abrasive plates having a multilayer structure that makes them relatively unsuitable for on-press coating. Non-abrasive plates which can be treated with fresh water are for example EP-A 770 497 and E
PA 773 112. Such plates also allow for on-press processing by wiping the exposed plate with water while being placed on the printing press or with ink or fountain applied during the first run of the printing operation.

[0009] A computer-to-press method characterized by most of the above advantages is EP-A 69
8488. The lipophilic substance is transferred image-wise from the foil to the rotary printing machine cylinder by locally melting the substance with a laser beam. The flake-shaped transfer foil has a narrow width compared to the cylinder, and is transferred along a path parallel to the axis of the cylinder while being kept in close contact with the surface of the cylinder, and a complete image is formed on the surface. Create gradually. As a result, the system is rather time-consuming and requires long downtime of the printing press, thereby reducing its productivity.

[0010] EP-A 802 457 coats an aqueous liquid containing a hydrophilic binder, a compound capable of converting light into heat and hydrophobic thermoplastic polymer particles on a plate cylinder to form a uniform continuous layer. An on-press coating method formed thereon is described. With image-wise exposure, the areas of the coated layer are converted to a hydrophobic phase, thereby defining the print areas of the print master. Since the layers are treated by interaction with the fountain solution and the ink supplied to the cylinder during operation of the printing machine, the operation of the printing machine can be started immediately after exposure without any further treatment. As such, wet chemical treatment of these materials is "hidden" to the user and occurs during the first operation of the printing press. After operation of the printing press, the coating can be removed from the plate cylinder by an on-prescreening step. They are attractive because the on-press coating methods, on-press exposure and on-pre-screening of such masters can be performed without special training or experience, in contrast to conventional lithographic printing. Such printing machines generally function like desktop computer printers and require less human intervention than conventional printing machines.

A problem with the on-press coating, exposure and cleaning methods is that the wet coating and cleaning steps include the risk of damage or contamination of the integrated image-setter optics and electronics. In addition, the printing machines are used to remove paper dust, ink fog,
This method results in poor consistency and poor coating quality, which is characterized by low consistency and high frequency of coating artifacts, due to disadvantages for defect-free coating applications due to temperature or humidity fluctuations. Only by installing complex and sophisticated coating equipment on the printing press, which is difficult to achieve due to space and price constraints, the quality of the wet coating stage can be improved. Finally, during the on-press coating, exposure and cleaning phases, the printing press is not printing and the downtime of the printing press must be minimized to be economically viable.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to effectively clean a print master and apply a new high quality coating on a recycled substrate without long downtime of the printing press. It is to provide a device that makes it possible. This object is achieved by a plate making device as defined in claim 1 and a printing system comprising such a plate making device as defined in claim 7. According to the present invention, there is provided an off-set comprising means for removing a lithographic image from a used printing master substrate and means for recoating the recirculated substrate thus obtained with a new image recording layer. A press plate making apparatus is provided. One or more printing masters of a previous printing operation can be cleaned during operation of the printing press and the recirculated substrate thus obtained is used for subsequent printing press operation. The downtime of the printing press is minimal because it can be re-coated in an off-press prepress machine.

The recoated substrate produces an imaging material which can be integrated in a digital printing machine comprising on-press integrated exposure equipment, or in a prepress machine. Alternatively, it can be exposed by an off-press exposure device, which can also be mechanically connected to it. On-press exposure offers the advantage of complete registration of the master in the multi-color printing press immediately after exposure, while off-press exposure gives even shorter press downtime.

The plate-making device can be mechanically connected to the printing machine so that the used printing master and the recoated substrate can be automatically transferred between the printing machine and the plate-making device. By using the optional stacking device between the plate making device and the printing press, one plate making device can be combined with a multicolor printing machine that requires more than one print master. Such a printing system allows for a fully automated workflow of coating, exposure, printing and cleaning, where the downtime of the printing press is minimal and it can be done without special techniques.

[0015] Further advantages and embodiments of the present invention will become apparent from the following description and drawings. Preferred embodiments of the invention are disclosed in the dependent claims.

[0016]

In addition to the terms defined in the background, some related terms used herein will be understood as follows. An off-press device: a device that is not integrated in the printing press but is located close to the printing press and is mechanically connected to the printing press; this device operates while the printing press is printing You can also. On-press device: device integrated in the printing press; operation of this device is contingent on the printing press not printing. -(Mechanical) transport means: means for transferring, carrying or transporting a material such as a substrate, an imaging material or a printing master from one device to another. A color station: a unit of a printing machine used to print one color; a lithographic color station is usually a plate cylinder for carrying a print master, a blanket cylinder for transferring ink from the print master to paper, and paper. And a pressure cylinder for pressing the rubber against the blanket cylinder. -Platemaking: As discussed below in the section on substrates, the term "plate" is to be interpreted broadly, i.e. it means not only sheet-like material but also cylindrical elements.

The plate-making apparatus of the present invention can be used according to the following method: (a) Coating: An image-forming material is prepared by applying an image recording layer onto a substrate by an off-press plate-making apparatus;
The layer is a continuous layer capable of forming an image with exposure to heat or light and optional processing, (b) exposure: exposing the image recording layer to heat or light by off-press or on-press exposure equipment and optionally Making a printing master with a lithographic image by processing; (c) printing: applying ink to the lithographic image and transferring the ink from the lithographic image to paper or other receiver material by a printing machine; (d) cleaning : Removing the lithographic image from the substrate in an off-press platemaking apparatus, thereby obtaining a recycled substrate; (e) reusing the recycled substrate in the next cycle of coating, exposing and printing. Between steps (a) and (b), the imaging material is transferred from the plate-making apparatus to the printing machine after or before being exposed and optionally processed. Between steps (c) and (d), the used printing master is transferred from the printing press to the plate making apparatus.
These movements of material can be transferred manually, i.e., by an operator transporting the material from one device to another. However, according to a preferred embodiment, the movement is performed by means of movement that mechanically couples one device to another. Means for transferring material from the plate making apparatus to the printing machine are referred to herein as plate-carrying means. Moving means for transferring the used printing master from the printing machine back to the plate making device is referred to herein as a plateless means.

The exposing device can be integrated into the printing press (such an embodiment is shown in FIG. 1), or can be integrated into the plate making device (FIG. 2), or It can also be a separate device mechanically connected to the plate making device and the printing device (FIG. 3). If the imaging material is sensitive to sunlight, the plate-making device and the platemaking device are connected unless the exposure device is connected to a processing device that processes the exposed imaging material to produce a print master that is no longer sensitive to sunlight. The mechanical means of movement between the exposing device and between the exposing device and the printing machine must be lightfast.

The plate making device is preferably a single device that performs both the cleaning and the coating steps. The single device may comprise different sections for cleaning and coating, and in that case the apparatus may further comprise internal means for mechanically transferring the substrate from the cleaning section to the coating section. Is preferred. Alternatively, the plate making device may be an assembly of two separate devices, one for cleaning and one for coating. According to the latter embodiment, the recirculated substrate is manually transferred from the cleaning device to the coating device between steps (d) and (a), but preferably by moving means connecting the cleaning device to the coating device. Transferred mechanically. During such transfer, the recycled substrate is preferably shielded from the environment to avoid contamination or damage to its surface. Transfer means for transferring the substrate between steps (d) and (a) preferably shield the substrate from dust to avoid pinholes and other artifacts in the recoated image recording layer.

In a preferred embodiment according to the invention, the plate making apparatus comprises means for coating, cleaning, exposing and optionally processing, so that all of steps (a) coating, (b) exposing and (d) cleaning are the same. In the apparatus, for example, the print master was placed on the outer surface of a rotating drum and the master was cleaned by a cleaning head running on the master in the axial direction of the drum rotating in an angled direction and then recirculated. This can be done by coating the substrate with a coating head (running over the substrate in a similar direction) and finally exposing the coated layer, for example by a laser head. The cleaning head, the coating head and the laser head may be connected together to form a multi-function head in which the steps of cleaning, coating and exposing can be performed during a single pass of the multi-function head over the substrate. Further details and other means regarding coating, cleaning and exposure are provided below.

Alternatively, the plate making apparatus may contain a coating section, an exposure section and a cleaning section having internal mechanical means for transferring material between different sections of the apparatus. Such a plate making machine sorts the three materials into all categories,
That is, they can be handled at once by simultaneous operations of coating the substrate, exposing the image recording material and cleaning the print master.

The plate making device and the printing machine together form a printing system, which may optionally include one or more stacking devices. The printing machine can be a single or multi-color printing machine, which includes a plurality of color stations (the number of color stations is typically in the range of 2-6, or 12 in the case of 6-color composite printing).
). Especially when the printing machine is a multi-color printing machine, the stacking device is placed in a plate-bearing means for transferring the imaging material from the plate-making device to the printing machine, and / or
It is also very advantageous to include the printing master used in a plate-free means for transferring the used printing master back from the printing machine to the plate-making apparatus. Such a stacking device acts as a buffer for temporary storage between one device in a cycle and the next, so that the stacking device has one plate making and / or off-press exposure for all color stations. The device allows the material to be coated, exposed and / or cleaned. Or,
Placing the stacking device inside the device, not in the means of transport between the two devices, at either its entrance and / or exit,
They may be integrated.

A particularly preferred arrangement of the present invention comprises (i) a plate making apparatus (FIG. 1) connected via a stacking apparatus to a multicolor digital printing machine (containing an integrated exposure apparatus in each color station). ), (Ii) a plate-making device (FIG. 2) having an integrated exposure device (and optionally a processor) mechanically connected to the multi-color printing machine via a stacking device, and (iii) a stacking device. A plate making device (FIG. 3) connected to an exposing device (optionally with a processor) connected to the multicolor printing machine via the device.

As an example of the arrangement (i), a digital four-color printing machine for printing the basic colors cyan (C), magenta (M), yellow (Y) and black (K) is provided via a stacking device. Combine with one plate making device. A prepress machine first makes the imaging material, for example for a C color station, and transfers that material to a stacking device that temporarily stores the material while the printing machine is performing a previous printing operation. Subsequently, the material for another color selection, for example M, is coated and also stored in the stacking device. Similarly, the imaging materials for the Y and K stations are made and stored in a stacker until the previous printing press operation is completed. The used print master is then mechanically transferred to the plate making device (also preferably via an intermediate stacking device present in the unplated means) for removal and cleaning from the printing press. , And finally, the material for the next printing operation from the stacking device to each color station C, M, Y and K
, Where they are exposed by an integrated exposure device.

In arrangements (ii) and (iii), the printing system of the present invention comprises a plate making device having an integrated exposure device or being connected to a separate off-press exposure device. In such a case, the stacking device between the exposing device and the multi-color printing machine and the means for loading the plate between the exposing device and the printing machine preferably have their respective color selections transferred to the correct color station. Some information is provided, for example, driven by a microcomputer, to ensure that it is reached. In a most preferred embodiment of a printing system comprising a multi-color printing machine, one stacking device is an image recording material (or exposed material in the case of off-press exposure) produced by a plate making device and a plate making device for cleaning. Handle the used print master that needs to be transferred back to.

Before going into a detailed discussion of the various elements of this invention, it should now become apparent to those skilled in the art that many modifications of the invention are possible. Substrates The substrates used in the present invention may have some affinity for inks and / or ink-tacky fluids, such as fountain solutions. By providing an ink-receptive substrate with an ink-receptive image recording layer, or an image-recording layer that becomes ink-receptive after exposure and optional processing.
A driographic material can be obtained. Alternatively, a driographic material can be obtained by providing an ink-receptive substrate with an ink-tacky image-recording layer or an image-recording layer that becomes ink-tacky after exposure and optional processing. . Conventional lithographic materials can be obtained by providing a hydrophilic substrate with a hydrophobic image recording layer or an image recording layer that becomes hydrophobic after exposure and optional treatment. Alternatively, conventional lithographic materials can be obtained by providing a hydrophobic substrate with a hydrophilic image recording layer or an image recording layer that becomes hydrophilic after exposure and optional treatment.

[0027] According to yet another embodiment, it can be switched from one more particularly ink-friendly to another and is exposed on the substrate in the exposed and unexposed areas after exposure and optional treatment. If the substrate is coated with the remaining so-called replaceable image recording layer, the affinity of the substrate for the ink or for the ink-tacky fluid is irrelevant. In this embodiment, the printed as well as the non-printed areas are defined primarily by the coated layer and not by the substrate. Further details regarding exchangeable layers, and more particularly exchangeable polymers, are provided in the "Imaging Material" section below.

The substrate may be a sheet-like material, for example a plate, or it may be a cylindrical part, for example a sleeve,
It may be. In the latter case, the printing plates may be joined in cylindrical form, for example by means of a laser. Such a cylindrical printing plate can be slid over the printing cylinder of a printing machine instead of being placed thereon, for example, as in a conventional printing plate. Further details on sleeves are given, for example, in "Grafisch Nieuws", 15, 1995, pages 4-6.

[0029] The substrate may be an aluminum support.
A particularly preferred substrate is an electrochemically grained and anodized aluminum support. The anodized aluminum support may be treated to improve its surface hydrophilicity. For example, it may be silicate-treated by treating the surface of the aluminum support with a sodium silicate solution at an elevated temperature, for example 95 ° C. Alternatively, a phosphating treatment may be applied that involves treating the aluminum oxide surface with a phosphating solution that may further contain inorganic fluoride. Further, the aluminum oxide surface may be rinsed with a citric acid or citrate solution. This treatment can be performed at room temperature or at a slightly elevated temperature of about 30-50 ° C. Another interesting treatment involves rinsing the aluminum oxide surface with a bicarbonate solution. In addition, the reaction of the aluminum oxide surface with polyvinylphosphonic acid, polyvinylmethylphosphonic acid, polyvinyl alcohol phosphates, polyvinyl sulfonic acid, polyvinyl benzene sulfonic acid, polyvinyl alcohol sulfates, and sulfonated aliphatic aldehydes May be treated with the acetal of polyvinyl alcohols produced by the above method. It has also been demonstrated that one or more of these post-treatments can be performed alone or in combination. A more detailed description of these processes is given in GB-A-1 084 070, DE-A-442.
3 140, DE-A- 4 417 907, EP-A-
659 909, EP-A-537 633, DE-A
-4 001 466, EP-A- 292 801; E
PA-291 760 and US-P-4 4580
05.

According to another embodiment, the substrate can also be a flexible support provided with a hydrophilic layer, hereinafter referred to as "base layer". The flexible support is, for example, paper, plastic film or aluminum. Preferred examples of the plastic film are polyethylene terephthalate ethylene film,
Examples include an ethylene polynaphthalate film, a cellulose acetate film, a polystyrene film, and a polycarbonate film. The plastic film support may be opaque or transparent.

The base layer is preferably a crosslinked hydrophilic layer obtained from a hydrophilic binder crosslinked with a hardener such as, for example, formaldehyde, glyoxal, polyisocyanate or hydrolyzed tetraalkyl orthosilicate. It is. The latter is particularly preferred. The thickness of the hydrophilic base layer can vary between 0.2 and 25 μm and is preferably between 1 and 10 μm.

Hydrophilic binders for use in the base layer include, for example, hydrophilic (co) polymers such as vinyl alcohol, acrylamide, methylolacrylamide, methylolmethacrylamide, acrylic acid, methacrylic acid,
Homopolymers and copolymers of hydroxyethyl acrylate and hydroxyethyl methacrylate or maleic anhydride / vinyl methyl ether copolymer. The hydrophilicity of the (co) polymer or (co) polymer mixture used is preferably equal to or less than that of the polyvinyl acetate hydrolyzed to at least 60% by weight, preferably of the order of 80% by weight. taller than.

Hardeners, especially tetraalkyl orthosilicates,
Is preferably at least 0.2 part by weight per part by weight of hydrophilic binder, more preferably between 0.5 and 5 parts by weight, most preferably between 1 and 3 parts by weight.

[0034] The hydrophilic base layer may 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 is, for example, up to 40 nm, for example 20 nm.
It may be in the form of any commercially available aqueous dispersion of colloidal silica having an average particle size of nm. In addition, inert particles larger in size than colloidal silica, such as J. Colloid and Interface Sci., Vol. 26, 1968,
Particles having an average diameter of at least 100 nm which are silica or alumina particles or particles of titanium dioxide or other heavy metal oxides produced according to the Stoeber method as described in pages 62 to 69 may be added. The addition of these particles gives the surface of the hydrophilic base layer a uniform coarse texture consisting of microscopically sized irregularities that act as storage for water in the background area.

Particular examples of hydrophilic base layers suitable for use according to the invention are EP-A-601 240, GB-P-
1 419 512, FR-P-2 300 354, U
SP-3 971 660 and US-P-428
No. 4,705.

It is particularly preferred to use a film support provided with an adhesion improving layer, also referred to as a substrate layer.
Particularly suitable adhesion improving layers for use according to the invention are EP-A
-619 524, EP-A-620 502 and E
It comprises a hydrophilic binder and colloidal silica as disclosed in P-A-619 525. Preferably, the amount of silica in the adhesion improving layer is 200 mg / m ²
〜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. Imaging Material The imaging material comprises at least one image recording layer provided on a substrate. Preferably, only one layer is provided on the substrate. The material may be light-sensitive or heat-sensitive, the latter being preferred for sunlight stability. As a general rule, any known direct-to-plate material is suitable, especially in embodiments comprising an off-press exposure device. For materials requiring post-exposure processing, the exposure device can be coupled to the processor or the exposure device can comprise the processor. Known materials that require processing include, for example, photosensitive plates, for example, photopolymer plates and silver diffusion transfer plates, or, for example, heat-induced solubilization of the polymer layer or heat that causes cross-linking of the polymer layer. This is a heat-sensitive plate (so-called hot plate) due to the release (insolubilization) of the acid.

Highly preferred imaging materials for use in the present invention have an image recording layer such that no processing is required and the print master is obtained immediately after exposure. This is particularly advantageous in embodiments using on-press exposure. Alternatively, the material may be processed on-press, for example by applying an aqueous liquid, a fountain solution and / or an ink (so-called "hidden process").
g ").

The raw material can be based on various mechanisms. The abrasion plate typically has a layer that can be removed by high-energy infrared laser exposure, e.g., a metal layer, or a thermally unstable layer that may contain an autoxidizable polymer such as nitrocellulose. use. Typical abrasive materials are EP 628 409, WO 98/55330, US
5,401,611, DE 19 748 711, US
5,605,780, US5,691,114, WO97 /
00735, US 4,054,094 and EP 882
582. The non-abrasive untreated plate is, for example, changed from a hydrophobic state to a hydrophilic state (WO92 / 09934, EP
652 483) or vice versa (US 4,081,57).
2, EP 200,488, EP 924 065) Exchangeable polymers which can be converted image-wise (eg EP 924)
102). Another example of the untreated version is thermally induced destruction of microcapsules and subsequent functional groups (hydroxyl groups) on a hydrophilic binder cross-linked with microencapsulated lipophilic substances (isocyanates). (US 5,569,573, EP
646 476, WO94 / 2395, WO98 / 29
258).

The most preferred composition of the image forming layer is, for example, E
P 770 494, EP 770 495, EP 770
497, EP 773 112, EP 774 364, and EP 849 090 by heat-induced fusion of hydrophobic thermoplastic polymer particles in a hydrophilic binder. These substances are specially designed for on-press ("hidden") treatment with ink and / or fountain solution. The fused polymer particles define a hydrophobic print area and do not dissolve in the ink or fountain solution, while the unexposed layer readily dissolves in the ink and / or fountain solution. The components of the latter embodiment (the thermoplastic polymer latex and the hydrophilic binder) will now be described in further detail.

The hydrophobic thermoplastic polymer particles preferably have a particle size of 3
It has a solidification temperature above 5 ° C and more preferably above 50 ° C. Coagulation can result from the softening or melting of the thermoplastic polymer particles under the influence of heat. There is no specific upper limit for the solidification temperature of the thermoplastic hydrophobic polymer particles, but this temperature must be well below the decomposition of the polymer particles. Preferably, the coagulation temperature is at least 10 ° C. below the temperature at which decomposition of the polymer particles occurs. Specific examples of the hydrophobic polymer particles include, for example, polyethylene, polyvinyl chloride, poly (methyl) methacrylate, poly (ethyl meth) acrylate, polyvinylidene chloride, polyacrylonitrile, polyvinylcarbazole, polystyrene, and copolymers thereof. It is. Polystyrene is most preferably used. The weight average molecular weight of the polymer can range from 5,000 to 1,000,000 g / mol. 0.01 μm to 50 hydrophobic particles
It may have a particle size of μm, more preferably between 0.05 μm and 10 μm, and most preferably between 0.05 μm and 2 μm. The hydrophobic thermoplastic polymer particles contained in the image forming layer are preferably 20% by weight
~ 65% by weight, and more preferably 25% by weight ~
Between 55% by weight, and most preferably 30% to 4%
Between 5% by weight.

The polymer particles are present as a dispersion in the aqueous coating solution of the imaging layer and are disclosed in US Pat. No. 3,476,93.
7 can be produced.
Another method which is particularly suitable for the preparation of an aqueous dispersion of thermoplastic polymer particles is:-dissolving a hydrophobic thermoplastic polymer in a water-immiscible organic solvent;-dissolving the solution thus obtained in water or Dispersing in an aqueous medium and removing the organic solution by evaporation.

Suitable hydrophilic binders are, for example, synthetic homo or copolymers, such as polyvinyl alcohol, poly (meth) acrylic acid, poly (meth) acrylamide, hydroxyethyl poly (meth) acrylate, polyvinyl methyl ether, or natural Binders such as gelatin, polysaccharides such as dextran, pullulan, cellulose, acacia, alginic acid.

The imaging layer based on heat-induced polymer latex coalescence is preferably an infrared-sensitive layer containing one or more compounds capable of converting infrared light to heat. Particularly useful compounds are, for example, infrared dyes, carbon black, metal carbides, borides, nitrides, carbonitrides,
Bronze structured oxides and conductive polymer dispersions, for example conductive polymer dispersions based on polypyrrole, polyaniline or polythiophene. Means for applying the image recording layer on the substrate The plate-making apparatus comprises means for applying the image recording layer on the substrate. This layer is continuous, ie a uniform layer. It may be necessary to repeat the coating several times on the same substrate to get the correct coating thickness.

The coating was carried out according to EP 1 048 458
Or by heat or friction induced transfer from donor material as described in, for example, EP-A 974 44
55 and EP-A-99203682, filed Nov. 3, 1999, or by any known coating method, such as rotary coating, dip coating, bar coating, blade coating, air knife. Coating, gravure coating, reversing roll coating,
It can be applied by coating the liquid solution according to extrusion coating, slide coating and curtain coating. An overview of these coating technologies can be found in the Modern Coating and Drying Technolog
y ", EdwardCohen and Edgar B. Gutoff Editors, VCH p
ublishers, Inc, New York, NY, 1992. It is also possible to apply the coating solution to the substrate by a printing technique, for example ink jet printing, gravure printing, flexographic printing or offset printing.
EP-A No. 0020 filed on Jul. 31, 2000
Ink jet printing as described in 2700 is highly preferred.

According to the most preferred embodiment, the coating solution is sprayed onto the substrate by a head comprising a spray nozzle. The preferred values of the spray parameters are both 1
EP-A No. 992 filed on Sep. 15, 999
03064 and EP-A No. 992030065. In a preferred arrangement, the substrate is placed on the outer surface of the drum and the spray head moves axially along the substrate while the drum rotates in an angular direction.

Coating by spraying or jetting is preferred for applying a layer of the most preferred composition of the imaging layer based on heat-induced fusion of the thermoplastic polymer particles in the hydrophilic binder indicated above. Technology. Means for Exposing the Image Recording Layer to Heat or Light According to one embodiment of the present invention, the imaging material is image-wise exposed by an off-press exposure device and subsequently placed on the printing cylinder of a printing press. According to another aspect, the imaging element is exposed on-press by an integrated exposure device while being placed on the printing cylinder. The imaging material used in the present invention is exposed to heat or light, for example, by a thermal head, LEDs or laser head. Preferably,
One or more lasers are used, for example a He / Ne or Ar laser. Most preferably, the light used for exposure is not visible light so that a sun-stable material can be used, e.g., ultraviolet (laser) light or near-infrared light having a wavelength in the range of about 700 to about 1500 nm. A laser that emits infrared light, such as a semiconductor laser diode, Nd: YAG or Nd: YL
An F laser is used. The required laser power is the sensitivity of the image recording layer, the spot diameter (typical values of modern plate-setters at a maximum intensity of 1 / e ² : 10-25)
μm), the pixel stay time of the laser beam determined by
It depends on the scanning speed and the choice of the exposure device (i.e. the number of dots per inch or addressable pixels per unit of linear distance expressed in dpi; typical value: 1000-4000 dpi).

There are two types of laser-exposure devices: internal drum (ITD) and external drum (XTD)
Plate-setters are commonly used. ITD plate-setters are characterized by very high scan speeds, typically up to 500 m / s, and require several watts of laser power. XTD plate-setters having a typical laser power of about 200 mW to about 1 W are operated at relatively low scan speeds, e.g.

Known plate-setters can be used in the present invention as an off-press exposure device. This offers the advantage of reduced downtime of the printing press.
The XTD plate-setter arrangement can also be used for on-press exposure, providing the advantage of rapid registration in a multicolor printing press. More technical details of the on-press exposure device can be found, for example, in US 5,174,205 and US
5,163,368. Means for Processing the Exposed Image Recording Layer As noted above, the need for a processor depends on the choice of imaging material. The material requiring processing is preferably used in an off-press exposure device, which may be mechanically coupled to or comprise the processing device. More preferably, untreated materials or materials which can be processed on-press by supplying ink and / or fountain solution to the image recording layer are used.

As discussed in the "Imaging Material" section above, materials that rely on heat-induced coalescence of hydrophobic thermoplastic polymer particles in a hydrophilic binder may be ink and / or wet. It is a good example of enabling such a "hidden on-press treatment" with water. Such a material can be installed on a printing machine, and a dampening water roller supplying dampening water is applied on the imaging element while the printing cylinder having the imaging element mounted thereon rotates. And subsequently the ink roller drops there. Generally, after about 10 rotations of the printing cylinder, the first clean and usable print is obtained. According to another method for treating such a material, the ink roller and the fountain roller can be lowered simultaneously or the ink roller can be lowered first.

Suitable fountain solutions which can be used in connection with such materials are generally aqueous liquids having an acidic pH and comprising an alcohol such as, for example, isopropanol.

In combination with other materials, such as an abrasion imaging material, the imagewise exposed image may be obtained before or after the imaging material is installed on the printing press or at least before the printing press is started. It is advantageous to wipe the image-recording layer of the forming material with a cotton pad or sponge soaked in water (to remove abrasion debris).

In addition to the optional processing that may be necessary to obtain a lithographic image, additional post-imaging processing
For example, a fixing stage, a post-baking stage, a rubberizing stage, a rinsing stage, and the like can be used. The means for performing these steps can be integrated in the processor. Before starting the printing press, the results from (optical) measurements made on the lithographic image of the printing master are used to correct the registration of the master in a multicolor printing press or to adjust the ink keys of the printing press. Can be used for Means for Removing the Lithographic Image from the Substrate In the plate making apparatus, the ink-receiving area of the used printing master is removed from the substrate by cleaning means.
The cleaning step is preferably characterized by a low risk of deterioration of the lithographic surface of the substrate and by an effective removal of the ink-receiving areas, which can be a difficult solution. The cleaning means can be a means for treating the surface of the substrate in a scanning manner, for example a laser head for cleaning by abrasion or a cleaning head comprising a nozzle for spraying or spraying a cleaning liquid onto the substrate. Alternatively, the cleaning can be performed in an immersion tank containing a cleaning liquid for immersing the print master therein. The above means for cleaning can be combined with sonication or mechanical cleaning means. Suitable mechanical means for cleaning the substrate include, for example, means for stripping the substrate, means for rubbing the substrate which may be moistened with a cleaning liquid,
For example, a rotating brush, cloth or other absorbing means, or means for injecting water or a volatile medium, such as air, solvent or dry ice pellets.

Preferred cleaning liquids must be sufficiently effective, for example, to avoid the appearance of ghost images after several (preferably> 10, most preferably> 20) cycles of coating, exposure, printing and cleaning. Should be something. Other preferred features of the cleaning liquid are low volatile organic content to avoid environmental pollution and inertness to the hardware of the plate making device, for example, it is preferably a rubber, seal or seal used in the plate making device A liquid that does not affect other materials. Suitable cleaning liquid compositions meeting the above conditions are EP-A, filed Jan. 18, 2000
Numbers 0020176, 0020177 and 00
No. 200178.

For the cleaning of the most preferred imaging elements discussed above, comprising hydrophobic thermoplastic polymer particles in a hydrophilic binder, the cleaning liquid is preferably an emulsion of an organic liquid in an aqueous liquid. Liquid. The preparation of this emulsion is preferably carried out in a plate-making apparatus, which comprises, for example, cyclic organic compounds containing at least one double bond,
It can comprise means for mixing the organic liquid with the aqueous liquid by stirring the mixture of alcohol, water and the emulsifier to form the emulsion. Preferably, the plate making apparatus may comprise means for separating the emulsion (after use) into an organic phase and an aqueous phase, for example by heating the emulsion to induce phase separation. The recycled water thus obtained can be used for the production of a new emulsion or for rinsing the substrate after cleaning or before recoating.

The plate-making device may preferably comprise means for rinsing the substrate after the cleaning step, for example for supplying water or an aqueous solution onto the substrate, for example for spraying or spraying. The plate can then be dried, for example, with hot air, vacuum extraction or an absorbing medium, such as a cloth. Transport Means The transport means comprises a mechanism capable of transferring, carrying or transporting a substrate, imaging material or used printing master from one device to another. Such mechanisms are known in the art and are widely used in plate-handling devices. The moving means may comprise conveyor belts, grippers, suction caps, rollers, chains and the like. When transferring material that is sensitive to visible light, the transfer means is preferably lightfast, ie it can transfer the material while shielding it from light (the same specifications apply to any other material used in the present invention). It is also effective for devices).

The means for placing the plate preferably comprises a mechanism for placing the printing master on the plate cylinder. The means for carrying no printing form preferably comprises a mechanism for removing the printing master from the printing form cylinder. The plate is usually clamped to the torso, while the sleeve slides over the torso. Stacking device The stacking device acts as a buffer for temporarily storing a substrate, imaging element or printing master between one device in a cycle and the next. Various features of such a device have been discussed above. The stacking device is for mechanical movement means from the plate making device to the exposing device (which may be on-press or off-press), from the off-press exposing device to the printing machine, and from the printing machine to the plate making device. It may be used in the means.

When used in a plate-loading means of a multi-color printing press, the stacking device is preferably driven by a system which directs the correct color selection to the correct color station of the printing press at the correct time. Is done. The stacking device may comprise means for regulating and adjusting the temperature and / or humidity in the device and must be lightfast when handling photosensitive materials.

The stacking device between the off-press exposing device and the printing press or between the plate making device and the digital printing press is ready to bend and / or pierce the substrate to place the material on the printing press easily. May be included. Means for returning the substrate from bending may be included in the stacking device between the printing press and the plate making device. Such means for bending and unbending may be included in another device of the invention.

[Brief description of the drawings]

FIG. 1 schematically shows a preferred embodiment of a printing system according to the invention in which an on-press exposure device is used.

FIG. 2 schematically shows another preferred embodiment of a printing system according to the present invention in which an off-press exposure device integrated with a plate making device is used.

FIG. 3 schematically shows yet another preferred embodiment of a printing system according to the present invention in which an off-press exposure device that is not integrated with the plate making apparatus is used.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) G03F 7/30 501 G03F 7/30 501 (72) Inventor Rudy Gedewijk Belgium 2640 Malt Cell Septest Strat 27・ Agfa-Gevert-Na-Murose ・ Fennout F-term (for reference) 2H084 AA14 AA16 AA30 AA36 AA38 AE04 CC05 CC18 2H096 AA06 CA12 CA20 GA01 GA60 2H114 AA04 AA23 AA24 BA01 BA02 BA10 DA21 GA01 EA01 GA06

Claims (10)

[Claims] 1. means for applying a continuous image-recording layer capable of forming a lithographic image on a substrate by exposure to heat or light and optional treatment; and for removing the lithographic image from the substrate. An off-press plate-making apparatus comprising: 2. The method of claim 1, further comprising: means for exposing the image recording layer to heat or light; and, optionally, means for treating the exposed image recording layer. Press plate making equipment. 3. The method according to claim 1, wherein the means for applying the continuous image recording layer onto the substrate comprises a spray nozzle or an ink jet nozzle for applying the coating solution onto the substrate. The plate making device described in the above. 4. The plate-making apparatus according to claim 1, wherein the means for removing the lithographic image from the substrate comprises a spray nozzle or an ink jet nozzle for applying a cleaning liquid onto the substrate. 5. The plate making apparatus according to claim 1, further comprising means for producing an emulsion by mixing an organic liquid with an aqueous liquid. 6. The plate making apparatus according to claim 1, further comprising means for separating the emulsion into an organic phase and an aqueous phase. 7. A printing system comprising a lithographic printing machine and the plate making apparatus according to claim 1. 8. A plate-making apparatus by means of placing a plate for transferring a printing plate precursor or a printing master from a plate-making device to a printing machine and / or by means of a plate-less means for transferring a printing master from a printing machine to a plate-making device. The printing system according to claim 7, wherein is mechanically connected to the printing machine. 9. The printing system according to claim 8, wherein the printing machine is a multi-color printing machine and the means for loading the plate and / or the means for not loading the plate comprise a stacking device. 10. The printing system according to claim 9, wherein the stacking device is integrated in the plate making device.