JP2001088458A - Processless thermal printing plate with distinct nanostructure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processless thermal printing plate with a distinct nanostructure. SOLUTION: A heat-sensitive material for manufacturing a negative type (negative working) non-ablative lithographic printing plate, wherein a thermoplastic polymer bead and a compound that can convert light into heat are contained in a heat-sensitive layer supported on the surface of a hydrophilic metallic substrate and not containing a binder, is provided. The thermoplastic polymer bead has a diameter in the limits of 0.2-1.4 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a lithographic printing plate (lithogr).
Heat-sensitive material for producing aphic printing plates
material).

More specifically, the present invention provides
process that results in a lithographic printing plate showing good ink receptivity without mming
ss) heat-sensitive materials.

[0003]

BACKGROUND OF THE INVENTION Rotary pri
nting presses), the so-called master,
For example, a printing plate attached to a cylinder of a printing machine is used. The master carries an image defined by the ink-receiving area of the printing surface, and after printing with the ink applied to the surface, the ink is removed from the master by a substrate, which is typically a paper substrate. Transfer). In ordinary lithographic printing, not only ink but also an aqueous fountain solution is used.
n solution is sent to the printing surface of the master, which printing surface is referred to herein as a lithographic surface, which is lipophilic (or hydrophobic, ie ink receptive, water repellent)
It is composed of not only regions but also hydrophilic (or oleophobic, that is, water-receptive and ink-repellent) regions.

[0004] Printing masters are commonly referred to as so-called computer-to-film.
m), in which various pre-press steps, such as selection of typeface, scanning, color separation (color s) are performed.
digitally achieves color separation, screening, trapping, layout and imposition, and so on.
on) by using an image setting device (image-setter).
(arts film). After processing, the film is converted to an imaging material called a plate precursor.
1) It can be used as a mask for performing the exposure, and a plate process
After ssing), a printing plate is obtained which can be used as a master.

[0005] In recent years, so-called computer-to-plate methods have become of great interest. This method [also direct-to-plate
e) also directly transfers the digital document to the plate precursor with a so-called plate-setter, thus avoiding the production of a film. The following improvements are currently being studied in the field of such computer-to-plate methods: (i) On-press imaging.
ging). A special type of computer-to-plate method involves exposing a plate precursor to a plate cylinder of a printing press with an image setting device integrated into the printing machine. . Such a method is referred to as “computer-to-pre
ss) ", and printing presses with an integrated image setting device are sometimes referred to as digital presses.
l presses). Digital Press Commentary on Proceedings of the Imag
ing Science &Technology's
1997 International Confes
rence on Digital Printing
Technologies (Non-Impact)
Printing 13). The computer-to-press method is described, for example, in EP-A 770 49
5, EP-A 770 496, WO 9400128
0, EP-A 580 394 and EP-A 7
74 364. The most well-known image forming method is an ablation-based method. Problems associated with ablative plates can be difficult to remove without compromising the printing process, or the exposure optics of an integrated image setting device (ex.
Positive optics may be contaminated. Other methods require processing with chemicals, which can damage electronics and other equipment of the printing machine. (Ii) On-press coating (On-press)
coating). The master precursor usually comprises a sheet-like support and one or more functional coatings, but is coated with a composition capable of forming a lithographic surface by imagewise exposure and optional processing, the surface of a plate cylinder of a printing machine. A computer-to-press method of feeding directly to a computer was described.
EP-A 101 266 describes a hydrophobic layer coating which is applied directly to the hydrophilic surface of the plate cylinder. The master is obtained after removing the non-printed areas by ablation. However, as discussed above, computer-to-press methods should avoid ablation. U.S. Patent No. 5,713,287 states that
A computer-to-press method is described in which a so-called switchable polymer, such as tetrahydro-pyranylmethyl methacrylate, is applied directly to the surface of the plate cylinder. The switchable polymer is changed in imagewise exposure from the initial water-sensitive properties to the opposite of water-sensitive properties. This latter method requires a curing step, and the polymers are extremely expensive because they are thermally unstable and therefore difficult to synthesize. EP-A-802 457 describes a hybrid method of providing a functional coating on a plate support which is mounted on a cylinder of a printing machine.
Such a method also requires processing. A major problem associated with the known on-press coating method is that a wet coating device is required and this device must be integrated into the printing press. (Iii) Elimination of chemical treatment. It is another major trend in plate making to produce functional coatings that require no treatment or can be treated with fresh water. WO-900002044,
WO-91008108 and EP 580
No. 394 discloses such plates, however, they are all ablative plates. In addition, such methods typically require multiple layers of material, which makes such methods less suitable for on-press coating. Non-ablative (non)
-Ablate) versions are described, for example, in EP-A-770 497 and EP-A-773 112. Such a board is
Alternatively, the plate can be on-pressed by wiping the exposed plate with water while attached to a printing machine or by using a fountain solution during the first printing operation. (Iv) Thermal imaging (Thermal imaging)
g). In most of the computer-to-press methods described above, so-called thermal materials
reals, ie plate precursors comprising compounds that convert absorbed light into heat or on-press coatable (on-
press coatable) compositions have been used. The heat generated in the imagewise exposure is converted to a (physical) chemical process, such as ablation,
It triggers polymerization, insolubilization by polymer crosslinking, decomposition, or coagulation of particles of thermoplastic polymer latex.
As a result of such thermal pattern stenciling, a lithographic surface is subsequently formed comprising an ink receiving area and an ink repelling area.

[0006] EP-A-786 337.
The publication discloses a method for imaging a printing plate, in which the entire surface of the printing plate is charged and then the entire surface is coated with toner particles, which have the opposite charge. Thereafter, the particles are fixed in an imagewise manner or by infrared exposure to the surface of the printing plate to cause imagewise ablation to form a layer. Thereafter, the entire surface of the plate is heated to remove the unfixed parts and, optionally, to fix the unablated areas. Such a method requires cumbersome development.

[0007] A problem associated with most thermal sensitive materials disclosed in the prior art is that such materials require an internal drum imager (ie, typically a high power, short exposure) or an external drum imager. It is suitable for exposing using any of the devices (ie, long exposures at relatively low power). Providing a versatile material that can produce satisfactory results when exposed using both such types of laser devices known in the art is a challenging requirement.

[0008]

OBJECTS OF THE INVENTION It is an object of the present invention to provide a processless thermal imaging material suitable for use in the production of lithographic printing plates having excellent printing characteristics.

It is a further object of the present invention to provide a thermal imaging material suitable for use in the manufacture of a lithographic printing plate in which a thermal layer has been applied to the printing plate.

It is a further object of the present invention to provide a thermal imaging material suitable for use in making lithographic printing plates that can be used in computer-to-plate applications.

[0011] Further objects of the present invention will become clear from the description hereinafter.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a thermoplastic polymer bead and a compound capable of converting light to heat are provided in a heat-sensitive layer supported on the surface of a hydrophilic metal support and containing no binder. Negative type comprising (negative w
A heat-sensitive material is provided for making an ablative, non-ablationable lithographic printing plate, characterized in that the thermoplastic polymer beads have a diameter in the range from 0.2 μm to 1.4 μm.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The thermoplastic polymer beads have a diameter of from 0.2 μm to 1.4 μm, preferably from 0.5 to 1.2 μm. If the diameter of the thermoplastic polymer bead is smaller than the diameter, such a printing plate will show background smear, while if the diameter of the thermoplastic polymer bead is larger than the diameter, such a printing plate will be inked. Do not accept enough. Although we do not want to be bound by any explanation of such facts, we propose the following mechanism. Thermoplastic particles having a diameter which is too small adhere to the metal support too much and are not completely removed by the ink and / or fountain solution. Thermoplastic polymer beads of too large a diameter do not adhere well enough to the imaged areas of the metal support, even after solidification by infrared irradiation. Only thermoplastic polymer beads having a diameter within the claimed range exhibit a suitable balance between adsorption in the image areas and removal by ink and / or fountain solution in the non-image areas.

In addition, the hydrophobic thermoplastic polymer particles used in connection with the present invention preferably have a coagulation temperature above 50 ° C, more preferably above 70 ° C.
ntemperature). Solidification can occur as a result of the thermoplastic polymer particles softening or melting under the influence of heat. There is no particular upper limit on the coagulation temperature exhibited by the thermoplastic, hydrophobic polymer particles; however, this temperature must be well below the decomposition temperature of the polymer particles. The coagulation temperature of the polymer particles is preferably at least 10 ° C. below the temperature at which the polymer undergoes decomposition. When the polymer particles are exposed to temperatures above their coagulation temperature, they coagulate to form a hydrophobic coagulate, so that the metallic support in that portion becomes hydrophobic, ie, lipophilic.

A specific example of a hydrophobic polymer particle suitable for use in connection with the present invention is a polymer particle having a Tg of greater than 80 ° C. Such polymer particles are preferably selected from the group consisting of polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyvinyl carbazole and the like or copolymers or mixtures thereof. Most preferably, polystyrene, polyacrylate or copolymers thereof, and polyesters or phenolic resins are used.

The weight average molecular weight of such polymers may range from 5,000 to 5,000,000 g / mol.

The image forming element (imaging element)
ment) further includes a compound capable of converting light into heat. Suitable compounds capable of converting light to heat are preferably infrared-absorbing components, but the wavelength of absorption is particularly limited as long as the maximum absorbance of the compound used is within the wavelength range of the light source used for image-wise exposure. It does not matter. Particularly useful compounds are, for example, dyes, especially infrared dyes having a maximum absorbance in the range of 750 to 11 nm, and pigments, especially infrared pigments, such as carbon black, metal carbides, borides, nitrides,
Carbonitrides, oxides with a bronze structure, and oxides that are structurally related to the bronze series but do not contain the A component, such as WO _2.9 . The lithographic performance obtained, in particular the printing durability, depends inter alia on (ia) the heat sensitivity of the imaging element. In this regard, it was confirmed that very good and favorable results were obtained when carbon black was used.

In the context of the present invention, a compound that converts light into heat is added to a dispersion of a thermoplastic polymer bead.

The amount of the compound capable of converting light into heat is in the range of 0.5 to 20% by weight of the dry layer, more preferably in the range of 1 to 10% by weight.

The weight of the image forming layer is preferably in the range of 0.1 to 6 g / m ² , more preferably 0.125 to 4 g / m ² .

The lithographic substrate according to the invention preferably has an electrochemically and / or mechanically roughened surface,
ed) and anodized aluminum.

The aluminum support of the imaging element suitable for use in accordance with the present invention can be made of high purity aluminum or aluminum alloy (aluminum content of at least 95%). The thickness of the support typically ranges from about 0.13 to about 0.50 mm.

The preparation of an aluminum or aluminum alloy foil for lithographic offset printing comprises the following steps: surface roughening, anodizing and optionally sealing of said foil.

In order to obtain a lithographic printing plate capable of producing high quality prints according to the present invention, it is necessary to roughen and anodize the foil. Sealing is not required, but may further improve the printing results. 0.2 to 1.5μ for this aluminum foil
The roughness is set to indicate a CLA value in the range of m, the thickness of the anodic oxide layer is in the range of 0.4 to 2.0 μm, and post-treatment is performed using an aqueous bicarbonate solution.

In accordance with the present invention, roughening of the aluminum foil can be performed according to methods well known in the art. By roughening the surface of the aluminum substrate using mechanical, chemical or electrochemical surface roughening or a combination thereof, a satisfactory adhesion between the aluminum support and the silver halide emulsion layer is achieved. Good water retention properties can be obtained in the areas which can be obtained and form non-printing areas on the plate surface.

The use of the electrochemical surface-roughening method makes it possible to form a uniform surface roughness having a very fine and even grain which is generally desired for use in a lithographic printing plate, even if the average surface area is large. Therefore, such a method is preferable.

Before the surface roughening, a degreasing treatment for mainly removing grease-like substances from the surface of the aluminum foil is preferably performed.

Therefore, the aluminum foil may be subjected to a degreasing treatment using a surfactant and / or an aqueous alkaline solution.

After the roughening, a chemical etching step is preferably performed using an aqueous solution containing an acid. The chemical etching is preferably performed at a temperature of at least 30 ° C, more preferably at least 40 ° C, most preferably at least 50 ° C.

After the aluminum foil is subjected to surface roughening and optional chemical etching, anodic oxidation is performed, which can be performed as follows.

The aluminum foil having the roughened surface is immersed in a solution containing an acid as an anode, and an electric current is applied to the foil. Electrolyte concentrations of 1 to 70% by weight can be used within a temperature range of 0-70 ° C. 1-
The current density of the anode may be changed at 1-50 A / dm ² and the voltage may be changed within a range of 1-100 V so as to obtain an Al ₂ O ₃ .H ₂ O film weight of 8 g / m ² . Next, the anodized aluminum foil may be rinsed with deionized water at a temperature in the range of 10-80 ° C.

The anodized aluminum support can be subjected to a treatment for improving the hydrophilicity of its surface. For example, a silicate treatment may be performed by treating the surface of the aluminum support with a sodium silicate solution at a high temperature, for example, at a temperature of 95 ° C.
Alternatively, a phosphating treatment involving treating the surface of the aluminum oxide with a phosphate solution, which may further include an inorganic fluoride, can be applied. Furthermore, it is possible to rinse the aluminum oxide surface with a citric acid or citrate solution. Such a treatment can be carried out at room temperature or at a slightly elevated temperature of about 30 to 50 ° C. A further treatment of interest is that which involves rinsing the aluminum oxide surface with a bicarbonate solution. Further, the aluminum oxide surface is reacted with polyvinyl phosphonic acid, polyvinyl methyl phosphonic acid, polyvinyl alcohol phosphate, polyvinyl sulfonic acid, polyvinyl benzene sulfonic acid, polyvinyl alcohol sulfate, and polyvinyl alcohol with sulfonated aliphatic aldehyde. It is also possible to treat using the obtained acetal. Further, it is clear that one or more of such post-processing may be performed alone or in combination. A more detailed description of such processing is given in GB-A-1.
084 070, DE-A-4 423 140,
DE-A-4 417 907, EP-A-659
909, EP-A- 537 633, DE-A-
4 001466, EP-A-292 801 and EP
-A- 291 760 and U.S. Pat. No. 4,458.
005.

The features of the invention as specified in the appended claims will be understood as set forth hereinafter. The term "image" is used herein in connection with lithographic printing, i.e., "a pattern composed of lipophilic and hydrophilic regions"
It is. The material obtained according to the invention is negative-working (meaning that the area becomes lipophilic upon exposure and thus becomes ink-receptive upon said exposure). In the context of the present invention, a "negative" feature can be considered to correspond to a "non-abervable" feature, since in the case of ablative material a positive image (where the exposed areas are hydrophilic and The functional layer is completely removed from the underlying (hydrophilic) metallic support by imagewise exposure so as to obtain an ink-repellent ink. In fact, analysis of the exposed areas of the material obtained by the method of the present invention shows that the layers or stacks of layers are not removed by imagewise exposure,
It was shown to have changed to a hydrophobic surface (supported by a metal support). The unexposed areas are hydrophilic.

According to the invention, the heat-sensitive layer can be applied as a dry powder (by rubbing in the dry powder onto a metal support). Alternatively, a dry coating method can be used, for example, the powder can be sputter-coated on the metal support. Preferably, the heat-sensitive layer comprises an aqueous dispersion containing 1 to 30% by weight of a thermoplastic hydrophobic polymer bead, more preferably 5 to 2% of a thermoplastic hydrophobic polymer bead.
It is applied to the metal support as a dispersion containing 0% by weight. The dispersion can be applied by various coating techniques, such as dipping.

According to the present invention, the imaging element is subjected to imagewise exposure. During the exposure, the exposed areas change to hydrophobic, ie lipophilic, areas.

The image formation is performed by direct thermal recording
ct thermal recording), and in this direct thermal recording, the heat transfer is heat radiation,
Heat conduction or inductive heat transport
t transport). The hydrophobic polymer particles solidify in the heated region to form a hydrophobic region.

The image formation can also be performed by irradiation using high-intensity light. In this case, the thermosensitive material should include a compound capable of converting light to heat.

The imagewise exposure in the context of the present invention is preferably carried out with a laser or L.A. E. FIG. D. (Light Emitting Diode) imagewise scanning exposure. Preferably, a laser operating in the infrared or near infrared, i.e. at a wavelength in the range 700-1500 nm, is used. Laser diodes that emit near-infrared light are most preferred.

The plate is now ready for printing according to the invention without additional development and can be mounted on a printing machine.

According to a further method, the imaging element is first mounted on a printing cylinder of a printing press and then subjected to image-wise exposure directly on the printing press. This image forming element can be used in printing after exposure.

The printing plate of the present invention can also be used as a seamless sleeve printing plate (seamless sleeve pri
It is also possible to use it in the printing process as an ending plate). In such an option, the printing plate is soldered in a cylindrical form using a laser. This cylinder printing plate has a print cylinder (print cylinder)
nder) and slide it into the print cylinder instead of mounting a normal printing plate. More details on sleeves can be found in Grafisch Nieuws, 1
5, 1995, pp. 4-6.

The present invention will be described with reference to the following examples, but the present invention is not limited thereto. All parts and percentages are by weight unless otherwise indicated.

[0043]

EXAMPLE A surface of an aluminum support is electrochemically roughened using hydrochloric acid, anodized in sulfuric acid, and then treated with polyvinylphosphonic acid. The resulting hydrophilic surface is further treated with a hydrophobic thermoplastic polymer bead and a compound of formula I

[0044]

Embedded image

Coating is carried out using a dispersion containing an infrared-absorbing dye according to the above.

The dispersion contains 10% of polymer beads and 0.5% of dye I. 0.09 μm particle diameter
From 2.6 to 2.6 μm. Polymer beads having various particle sizes were applied to the aluminum support. Material 1: the diameter of the polystyrene particles is 90 nm.
The layer thickness after drying is varied in the range from 400 mg / m ² to 800 mg / m ² . The coating solution is composed of 2-4% of the dispersion and water. The coated layer was dried at a temperature of 50 ° C. for 10 minutes. Material 2: The diameter of the polystyrene bead is 0.8 μm. Layer thickness after drying is from 130 mg / m ² to 1300 mg
/ M ² . 12.3 Coating solution
Consist of 8-24.76% of the dispersion and water. The coated layer was dried at a temperature of 50 ° C. for 10 minutes. Material 3: The diameter of the polystyrene bead is 1.5 μm. Layer thickness after drying is from 244 mg / m ² to 2440 mg
/ M ² . 23.2 coating solution
Consist of 4-46.43% of the dispersion and water. The coated layer was dried at a temperature of 50 ° C. for 10 minutes. Material 4: The diameter of the polystyrene bead is 2.6 μm. Layer thickness after drying is from 130 mg / m ² to 1300 mg
/ M ² . 12.3 Coating solution
Consist of 8-24.76% of the dispersion and water. The coated layer was dried at a temperature of 50 ° C. for 10 minutes.

Thereafter, the aluminum support covered with such a heat-sensitive layer was exposed using a diode laser of 830 nm [Isomet-spot size 1].
Pixel dwell time of 1 μm-3.2 m / s; ie, 3.4 μs pixel dwell time
e)]. Image plane power
er) was changed as follows: 148 mW, 220 m
W and 295 mW were used.

The obtained printing element (printing e)
elements were printed on a conventional offset press using conventional inks and fountain solution. The printing was started without any processing between the imaging and the press start, resulting in a good print with good image quality when using material 2. When using Material 1, background smear was present and when using Materials 3 and 4, the ink-up was not sufficient.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Frank Roewett Belgium Bee 2640 Malt Cell Septes Trat 27 Agfa-Gevuert Na Mrose Fennoutjaps (72) Inventor Rafael Samiin Belgium Be 2640 Malt Cell・ Septes Trat 27 ・ Aghua-Gevuert Na Mrose Rosenenjoutsjap (72) Inventor Marc van Dame Belgium 2640 Maltcell Septestrat 27 ・ Agfa-Gevert Na Mrose Rosenenjjassap

Claims (8)

[Claims] 1. A negative non-ablative material comprising a thermoplastic polymer bead and a compound capable of converting light to heat in a binder-free thermosensitive layer supported on the surface of a hydrophilic metal support. A heat-sensitive material for producing a lithographic printing plate, wherein the thermoplastic polymer bead has a thickness of 0.2 μm to 1.4 μm.
A heat-sensitive material characterized by having a diameter in the range: 2. The heat-sensitive material according to claim 1, wherein the thermoplastic polymer bead is a polystyrene, a polyacrylate homo- and / or copolymer, a polyester, or a phenol resin. 3. The heat-sensitive material according to claim 1, wherein the heat-sensitive layer contains a dye whose maximum absorbance is located in an infrared region. 4. The method according to claim 1, wherein the infrared absorbing dye is 750 to 1
The heat-sensitive material according to claim 3, which exhibits a maximum absorbance in a range of 100 nm. 5. The heat-sensitive material according to claim 1, wherein the support is aluminum having been subjected to surface roughening and anodizing. 6. A method for producing a negative-working non-absorptive printing plate, comprising the steps of: forming an image on the image-forming element according to claim 1 using an infrared laser; Improving the adhesion between the bead and the surface of the support,-removing the unexposed bead in the area where the image has not been formed from the surface of the metal support under the influence of ink and / or fountain solution; Method with steps. 7. The method of claim 6, wherein said metal support is mounted on a cylinder of a rotary printing press. 8. The method according to claim 6, wherein the metal support is a sleeve or a cylinder of a rotary printing machine.