Method of manufacturing offset plates

FIELD: printing industry.

SUBSTANCE: method of manufacturing offset plates by changing the wetting properties of parts of the working surface of the plates, transformation of the properties is carried out by changing the chemical composition of the working surfaces, made from silicon nitride, aluminium nitride and silicon carbide by acting on the selected parts with a stream of accelerated particles.

EFFECT: possibility to simplify and accelerate the process of manufacture, increase resolution and durability of the plates.

7 cl, 1 dwg

The invention relates to a process of making printing plates for offset printing by changing the wettability properties of the printing form.

From the description to European application EP 262475 B1 [1] well-known printing machine, provided with a printed form, on which subject the print image can be displayed using the corresponding hydrophobic and hydrophilic areas. To ensure switching between hydrophilic, respectively, hydrophobic, a condition in separate zones on the printed form provided ferroelectric material, which can locally polarize, respectively, be depolarized. Thus, hydrophilization, respectively prehydrolysis, the printing form is carried out using the mechanism of polarization (respectively depolarization), which means to perform inside the printing machine. However, the disadvantage of this method is that the effect is based on having a large radius of action of the electrostatic forces of attraction and in accordance with this resolution subject to printing images with limited long range electrostatic forces of attraction.

From the description of the U.S. patent US 3678852 [2] known printing plate, which is covered with an amorphous semiconductor. Amorphous state of the semiconductor can be changed with the help of the laser beam from disordered amorphous state to a more ordered crystalline state. In the crystalline state of the semiconductor surface is more rough, so changing the state of the semiconductor surface causes the liquid in the area of the rough surface is better kept than in the smooth amorphous zones. Resolution of the printing plate made according to this method, limited to the minimum size of the crystalline zones.

There is also known a method of making an offset printing plate by direct laser writing on the pre-chuvstvennyh plate plates with a copy layer of the composition on the basis of ordinationand, which is carried out by CO₂a laser with a wavelength of 1.06 μm by the method of linear scan when the power of the recording beam 5 W and a linear speed of 1.5 m/s, followed by exposure of the copying layer within 3-5 min metal halide lamps with the subsequent manifestation of copies, hydrophilization, reprisal and the coating forms a protective solution (USSR Author's certificate SU 1419921, CL VS 1/10 [3]). The disadvantage of this method is the complexity of the technological process and relatively low resolution.

Closest to the claimed is a method of making an offset printing plate by forming printing and spacing of the elements on the plate the plate is e from polyester fabric with a metallic coating (EN 2079413 [4]). When forming the printing elements carried out by sublimation metallized coating to polyester substrates in areas of exposure by a laser beam wavelength of 1.06 μm, so that the remaining parts of metallized coatings serve as spacing elements. Gap elements printed forms processed 5...10%aqueous solution of sodium acid meta-9-water with a pH of 10...13. In this process, use powerful lasers with a wavelength of 1.06 or 10.6 μm, for example, yttrium aluminium garnet or CO₂. Laser radiation is modulated in accordance with control commands from the computing machine. As the plates using a film with polyester base with a thickness of 0.05 to 0.30 mm...and sprayed it with metallic coating, such as titanium, stainless steel, aluminum of a thickness of from 0.25 to 1.50 μm.

The use of solid-state laser provides the image recording with the diameter of the point from 5 μm or more. The reduce resistance of the obtained forms reaches about 60,000 prints.

The disadvantage of this method is not sufficiently high resolution, due to the fact that it is impossible to focus the laser beam into a small spot size and high energy density required for sublimation of metallized coatings. In addition, due to the fact that as the plate is plate using the film with polyester base with a thickness of 0.05 to 0.30 mm...and sprayed it with metallic coating, the durability of this form is relatively small. Moreover exposed working surface of the tool needs further treatment with aqueous solutions.

The inventive method of making printing plates for offset printing is aimed at simplifying and speeding up the production process, resolution enhancement and durability and providing reusable forms.

This result is achieved in that the method of making printing plates for offset printing is implemented by modifying the properties of wettability areas of the working surface of the printing form, and conversion of properties carried out by changing the chemical composition of the working surface by exposure to selected areas of a stream of accelerated particles.

This result is achieved by the fact that the blank printing plate is made in the form of a substrate and a deposited as a working surface.

This result is achieved by the fact that caused as a working surface coating carry a thickness of 5-200 nm.

This result is achieved by the fact that, as the material of the working surface of the mold using a coating of silicon nitride, aluminum nitride, silicon carbide.

This result is achieved by the fact that as of accelerated particles using protons (or ions H ₂⁺).

This result is achieved by the fact that, as the accelerated particles helium ions are used.

This result is achieved by the fact that, as the accelerated particles used hydrogen atoms, or helium.

This result is achieved because of the impact on selected plots provide a stream of accelerated particles with energies from 100 eV to 5 Kev.

Changing the properties of wettability areas of the working surface (layer) printed forms by changing the chemical composition of the working surface by exposure to selected areas of a stream of accelerated particles and turning on the irradiated areas of the coating of silicon nitride in the silicon oxide or nitride coating of aluminum in aluminum oxide, which greatly simplifies and accelerates the production process forms with simultaneous resolution enhancement. Indeed, the process of the working surface (active layer) of the workpiece to achieve the changes of surface properties occurs in one stage, is processed at the same time the entire surface of the workpiece and through the use of as a means of flow effects of accelerated particles is provided by the high (several microns) resolution.

This feature of the proposed method for the manufacture of printed forms is that it produces is presented so after irradiation accelerated particles printed forms ready to use without symptoms or any additional processing.

The most appropriate blank printing plate made in the form of the substrate and deposited on it as a working surface. This allows you to use for the background of cheaper and sturdy enough construction materials and reuse the substrate by removing the worn-out working layer containing the image and application of a new coating with subsequent exposure to a stream of accelerated particles. Experiments have shown that most appropriately applied as the working surface of the floor to perform layer with a thickness of 5-200 nm. If you perform a coating thickness of less than 5 nm, the coating is difficult to make solid. If you perform a coating thickness of more than 200 nm, it does not improve the properties and resource molds, and leads only to their appreciation. Also experimentally, it was found that the most suitable materials for use as the working surface forms are silicon nitride, aluminum nitride, silicon carbide. On the one hand, they provide a sufficient lifetime of the produced offset forms, because they have a high wear resistance, and on the other hand, facilitate the process of their manufacture, as easily change their properties under the influence of a stream of accelerated particles due to the changing chemical composition of the coating. These change the of properties allow the use of these coatings after exposure in part offset forms without symptoms. As determined experimentally, as the accelerated particles that transform chemical composition and related properties wettability of the material of the working surface of the workpiece, can be used ions of hydrogen or helium or hydrogen atoms, or helium. The use of heavier ions or atoms is possible, but impractical, since in this case, the process changes the chemical composition of the coating is less effective and a lesser depth at the same time he is accompanied by a significant sputtering of the coating material. Impact on selected areas should be implemented by the stream of accelerated particles with energies from 100 to 150 eV to 5 Kev. If the energy of the particles in the stream is less than 100 eV, the changes in the chemical composition of the working surface (and hence wettability) will not. If the energy of the particles in the stream is greater than 5 Kev, under the influence of a stream of accelerated particles can occur not only change the chemical composition of the working surface, but also its significant heating, which is undesirable.

The essence of the invention is illustrated by examples of its implementation and drawing, which schematically shows the sequence of operations impact of the stream of accelerated particles on the working surface of the workpiece offset forms W is the patterns.

Example 1. In General, the method of manufacturing offset form as follows. On a substrate 1 (see drawing), which may be made of aluminum or another metal, plastic, polyester, etc. with sufficient thickness, providing the required strength characteristics, is applied by vacuum deposition working layer 2 of various two - or polyhydric substances. As such mainly can be used compounds of silicon or aluminum, and some other chemical elements nitrogen, carbon and other chemical elements. The most suitable materials for use as the working surface forms are silicon nitride, aluminum nitride, silicon carbide. The resulting billet is placed in a working chamber containing a source of accelerated particles, and creates a vacuum of ~10^-2-10^-7PA. As the accelerated particles can be used protons, helium ions, hydrogen atoms, or helium. The workpiece is irradiated with the flow 3 of accelerated particles with the desired (pre-defined) value of energy through the template (mask) 4. Template (mask) can be placed directly on the workpiece, i.e. it can be in contact with the upper layer of the irradiated substance, or to be at some distance from him. Under the influence of flow 3 accelerated the s of the particles may change the chemical composition of the working surface on the exposed parts of 5 by substitution of nitrogen atoms or carbon atoms of oxygen in the surface layers of nitride or carbide layer, i.e. in the working layer is a certain figure, which has properties other than the surrounding matrix, not exposed to accelerated particles.

The desired range of values of the energy for the process is determined by calculation or experimentally.

During the experimental determination of the energy of accelerated particles, necessary for optimal process, carry out a few preliminary experiments. For this purpose, the prepared workpiece with a working layer from a material of the desired thickness is irradiated through a pattern with a stream of accelerated particles with different energies and receive dose dependence of changes required properties. For this purpose, the substrate is put a layer of the source substances and carry out exposure with a fixed dose, and then examine its properties. Then the dose increase, and again explore the properties. For example, take as a starting material of silicon nitride and explore the fullness of his conversion to silicon oxide, and determine the change in contact angle in water or in water with 10% alcohol content. Naturally, with the increase of irradiation dose increasing number of nitrogen atoms or carbon will be replaced by oxygen atoms up to complete conversion into the oxide. The relevant sections of the printing form when pectine will make coloring paper. Focusing on the print quality of the data and selects the optimum exposure dose. On the basis of dose dependencies determine the dose required to achieve a given level of required properties.

In some cases it is advisable to use computational, and experimental methods for the determination of the optimal values of the particle energy required to implement the method. First, the calculated value of the energy of the particles is determined approximately, and then confirmed by preliminary experiments. This allows you to save time and money necessary to select the type and energy of accelerated particles for use in the process.

Irradiation of prepared blanks may be implemented using one or more patterns having a through hole, or by scanning over the surface of the workpiece intensity modulated beam of accelerated particles.

Example 2. The method is implemented according to the General scheme described in example 1. On a substrate made of aluminum, size 15×15 mm, thickness of 0.5 mm by a vacuum sputtering was applied layer of silicon nitride with a thickness of 150 nm. Then, to provide the material layer through the pattern with the corresponding figure, the workpiece was allucination protons with an energy of 2 Kev for 240 minutes As a result, the layer in the irradiated areas changed material is silicon nitride to silicon oxide.

Example 3. The method was implemented according to the General scheme outlined in examples 1 and 2 with the use of various substances as a working layer and different types of accelerated particles. For convenience the results are summarized in table.

1. Method of making printing plates for offset printing by changing the properties of wettability areas of the working surface of the printing form, characterized in that the conversion of properties carried out by changing the chemical composition of the working surface made of silicon nitride, aluminum nitride, silicon carbide, through the impact on selected areas of a stream of accelerated particles.

2. The method according to claim 1, characterized in that the blank printing plate is made in the form of the substrate and deposited on it as a working surface.

3. The method according to claim 1, characterized in that applied as the working surface coating carry a thickness of 5-200 nm.

4. The method according to claim 1, characterized in that as accelerated particles using protons.

5. The method of claim 1, characterized in that as the accelerated particles helium ions are used.

6. The method according to claim 1, characterized in that as the accelerated particles used hydrogen atoms, or helium.

7. The method according to claim 1, characterized in that the impact on selected plots provide a stream of accelerated particles with energies from 100 eV to 5 Kev.