A process for intaglio printing ink blocking

Abstract

The present application relates to the technical field of intaglio printing, and particularly relates to an intaglio printing anti-ink bleeding process. The process comprises the following steps: selecting an intaglio roller, the intaglio roller comprises a substrate layer and a metal chromium layer in sequence from inside to outside; the surface of the intaglio roller comprises a graphic part provided with graphic cells, and the part of the surface of the intaglio roller other than the graphic part is a non-graphic part; an oleophobic coating is arranged on the metal chromium layer located at the non-graphic part, and no oleophobic coating is arranged on the metal chromium layer located at the graphic part, to obtain a modified intaglio roller; the modified intaglio roller is used as an intaglio printing plate. In the present application, during printing, the ink will not be attached due to the oleophobic characteristics of the non-graphic part and the rotation of the intaglio roller, but the rotation of the intaglio roller will drive the ink at the graphic part to the printing surface, effectively reducing the ink aggregation between the outer layer of the intaglio roller and the doctor blade, and thus the ink bleeding phenomenon caused by the large particles blocked outside the doctor blade edge.

Description

Technical Field

[0001] This invention relates to the field of gravure printing technology, and more particularly to a gravure printing anti-ink mixing process. Background Technology

[0002] Gravure printing, as a printing method, occupies an important position in the printing industry due to its advantages such as thick ink layers, vibrant colors, high saturation, high plate durability, stable print quality, and fast printing speed. However, gravure printing also has some quality problems, mainly including: back adhesion and solvent residue, scalpel lines, missing highlight dots, ink spot contamination, and color difference. Among these, scalpel lines and ink mixing are the most frequent problems.

[0003] There are many reasons for ink bleed, such as: In terms of the printing process, there is always friction between the ink, doctor blade, and printing plate during printing. As the printing plate travels in the ink trough for a long time, the printing plate and doctor blade will wear down. Due to various reasons, large particles will gradually accumulate in the ink. When these ink particles are blocked at the doctor blade edge, they leave traces on the printing plate and are then transferred to the substrate, forming ink bleed. In addition, the ink path (the distance from the doctor blade point to the transfer point) in gravure printing is shorter, and the ink's leveling properties cannot compensate for defects at the doctor blade edge, which can also cause ink bleed.

[0004] Since the "short ink path" problem in gravure printing cannot be fundamentally solved, then improving the ink is key to solving the knife line issue. An effective measure is to increase the ink's solubility and leveling properties, but currently there is no ink that can fully meet these requirements.

[0005] Regarding printing plates, generally, the innermost layer of the printing plate is a thicker cast iron layer, followed by a copper-plated layer. The pattern after color separation is electro-engraved on the copper-plated surface of the printing roller. To enhance the wear resistance and corrosion resistance of the printing plate, an additional layer of chromium plating is required. The hardness of the chromium layer is generally 750~1000HV, and for special requirements, it can be above 1000HV. Currently, the domestic gravure printing industry generally considers 800HV to be sufficient. The reasons for ink bleeding caused by printing plates are as follows: 1. According to the plate-making process requirements, chromium plating must be polished. If the polishing is insufficient, the chromium layer surface will be rough, and ink bleeding will occur when the printing is used; 2. To meet the requirements of the pattern design, some parts of the plate may have excessively deep dots, and the hardness of the edges may be too high, which can easily damage the doctor blade and cause ink bleeding during printing; 3. The density and lightness transition of the dots, as well as poor dot smoothness, can all produce knife lines; 4. During use, wear between the printing plate and the doctor blade can also cause ink bleeding. Currently, there are no technical means to solve the problem of ink mixing caused by printing plates in terms of preventing ink mixing. Summary of the Invention

[0006] The present invention aims to solve the above problems by providing a gravure printing anti-ink mixing process.

[0007] The technical solution to the problem of this invention is to provide a gravure printing anti-ink mixing process, comprising the following steps: S1. Select an printing roller, wherein the printing roller comprises a substrate layer and a chromium metal layer in sequence from the inside to the outside; the surface of the printing roller includes a graphic portion having graphic holes, and the portion of the printing roller surface other than the graphic portion is a non-graphic portion; S2. An oleophobic coating is provided on the chromium layer located in the non-image area, and no oleophobic coating is provided on the chromium layer located in the image area, to obtain the modified printing roller; S3. Use the modified printing roller as a printing plate for gravure printing.

[0008] This application combines an oleophobic coating with gravure printing, addressing ink bleed caused by the printing plate itself. By improving the performance of the printing roller in gravure printing, this problem is reduced. Specifically, an oleophobic material is applied to the outer layer of the printing plate cylinder, avoiding the electroplated and engraved image areas, forming an oleophobic coating on the chromium layer of the printing plate's outer wall. During gravure printing, the ink is not adhered to the roller due to the oleophobic coating's properties, and because the image areas are not coated with the oleophobic material, the roller rotation does not affect the transfer of ink from the image areas to the printing plate. The doctor blade then only removes excess ink from the image areas, preventing excessive ink thickness that could lead to ink smearing or smudging. This effectively reduces ink accumulation between the outer layer of the printing roller and the doctor blade, preventing large ink particles from being blocked at the blade's edge and causing ink bleed.

[0009] In principle, the selection and application method of the oleophobic coating are unrestricted. For example, in some embodiments, a low surface energy material can be directly sprayed onto the chromium layer in the non-graphic area. Optional low surface energy materials include at least one of perfluorodecyltrichlorosilane, perfluorooctyltrichlorosilane, perfluorodecyltriethoxysilane, perfluoromethyltriethoxysilane, perfluorodecyl thiol, perfluorodecanoic acid, and perfluorooctanoic acid. Furthermore, in some embodiments, to improve the bonding strength of the low surface energy material on the chromium layer, the chromium layer in the non-graphic area can be first activated to obtain hydroxyl groups, and then a fluorosilane material can be applied. Stable O-Si bonds are obtained through the reaction of the active hydroxyl groups with the fluorosilane.

[0010] However, in practical application, the inventors found that the oleophobic coating obtained by the above method still had a short service life under long-term printing and ink-scraping operations, requiring frequent shutdowns for maintenance and replenishment of the oleophobic coating, resulting in low printing efficiency. Therefore, the inventors sought a new oleophobic coating.

[0011] As a preferred embodiment of the present invention, the oleophobic coating comprises a fluorinated diamond-like carbon film.

[0012] In this application, the fluorinated diamond-like carbon film is based on a specific selection of the metallic chromium layer. The diamond-like carbon film (DLC) is a type of film containing sp... 3 and sp 2 Amorphous carbon-based coatings with carbon hybrid bonds are produced, and chromium, being a strong carbide element, can promote the graphitization transformation of amorphous carbon coatings, thereby reducing the internal stress of the coating and improving its mechanical properties, including hardness. Simultaneously, the chromium metal interface layer can form a significant mechanical interlocking structure with the amorphous carbon, which is beneficial to the interfacial bonding strength between the two. Based on this, a fluorinated diamond-like carbon film is selected to provide oleophobic properties, resulting in an oleophobic coating with high bonding strength to the metallic chromium layer, scratch resistance, and long service life.

[0013] There are many ways to deposit fluorinated diamond-like carbon films, including at least one of the following: DC sputtering, radio frequency sputtering, magnetron sputtering, pulsed laser deposition, ion beam deposition, cathode vacuum arc deposition, dual-frequency glow discharge deposition, and short-frequency-radio frequency plasma chemical vapor deposition. Preferably, the fluorinated diamond-like carbon film is deposited using magnetron sputtering. This method offers a large deposition area, good controllability, and is suitable for deposition in non-image areas.

[0014] There are many ways to achieve deposition only in non-image areas and not in image areas. These include physically masking the image areas, introducing a laser beam to activate the non-image areas to make them more susceptible to adsorption of sputtered atoms or molecules, and precisely adjusting the magnetic and electric fields to control the trajectory and guide the sputtered atoms or molecules to deposit directionally in the non-image areas. From the perspective of cost control and ease of operation, physical masking is preferred in this invention, with the image areas having a masking layer. After magnetron sputtering is completed, the masking layer can be removed. The choice of masking layer is not limited; for example, it can be a protruding plate adapted to the image area cells, metal, quartz glass fiber cloth, flexible ceramics, carbon fiber / quartz ceramic composite materials, etc.

[0015] The protruding plates adapted to the mesh of the graphic section can be obtained through hot pressing: Mixing slurry: Non-plastic lean ceramic powder is uniformly mixed with hot paraffin wax to form a flowable slurry. Injection into the graphic section: Under certain pressure, the mixed wax-containing slurry is injected into the graphic section. Cooling and solidification: After the slurry cools and solidifies in the graphic section, demolding is performed. At this point, the ceramic powder has initially formed the desired shape through the binding effect of paraffin wax. Trimming and dewaxing: The demolded green body may need appropriate trimming to remove excess burrs or uneven parts. Then, the green body is embedded in an adsorbent (such as pre-fired Al2O3 powder) for heated dewaxing. Sintering and forming: The dewaxed green body undergoes sintering treatment, causing a tight bond between the ceramic particles, thus obtaining the final ceramic product.

[0016] As a preferred embodiment of the present invention, the magnetron sputtering process is as follows: the sputtering target includes a carbon-containing material, the source gas includes an inert gas and a gas capable of dissociating into fluorine plasma, and the radio frequency power is 60~250W.

[0017] In this invention, the carbon-containing material is selected from high-purity carbon targets with a purity of 99.99%; more preferably, it is graphite with a purity of 99.99%.

[0018] As a preferred embodiment of the present invention, the inert gas is argon.

[0019] As a preferred embodiment of the present invention, the gas capable of dissociating into fluorine plasma is selected from at least one of trifluoromethane and carbon tetrafluoride.

[0020] As a preferred embodiment of the present invention, the flow rate ratio of the inert gas to the gas capable of dissociating into fluorine plasma is 1:(0.5~1.5); for example, it can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5; preferably 1:1.

[0021] As a preferred embodiment of the present invention, the radio frequency power is 150~200W. The inventors discovered through experiments that the radio frequency power affects the deposition rate of fluorinated diamond-like carbon films and is directly related to the film surface roughness and bond structure. With increasing radio frequency power, the oil contact angle first increases and then decreases, exhibiting a larger oil contact angle within the 150~200W radio frequency power range; for example, it can be 150W, 160W, 170W, 180W, 190W, or 200W; preferably 180W.

[0022] This application applies to adding an oleophobic coating to existing printing rollers, and also to adding an oleophobic coating during the printing roller manufacturing process. During the printing roller manufacturing process, further control of the formation of the metallic chromium layer will result in better bonding strength between the fluorinated diamond-like carbon layer and the metallic chromium layer. Preferably, the metallic chromium layer is deposited on the substrate layer using a dual-glow plasma surface alloying process. This method not only yields a metallic chromium layer with sufficient hardness but also generates a gradient distribution layer under thermal diffusion, forming a good metallurgical bond with the substrate layer and perfectly serving as a connecting bridge between the substrate layer and the diamond-like carbon film.

[0023] Fluorinated diamond-like carbon films possess oleophobic and hydrophobic properties. The principle behind this is that changes in the surface tension of the film alter its wettability with liquids. Since oil has a relatively low surface tension, the oleophobic properties of fluorinated diamond-like carbon films are not as strong as their hydrophobic properties. The inventors have been able to achieve a contact angle of around 105°, and further improvements in oleophobicity are needed from other aspects.

[0024] As a preferred embodiment of the present invention, the oleophobic coating comprises a polymer film with side-linked perfluoroalkyl groups. The polymer film with side-linked perfluoroalkyl groups can be directly deposited on the chromium layer, or it can be further deposited on the fluorinated diamond-like carbon film after the fluorinated diamond-like carbon film has been deposited. The latter is preferred, as it provides a longer service life for the oleophobic coating: even after the polymer film with side-linked perfluoroalkyl groups wears down, the fluorinated diamond-like carbon film can still provide oleophobic protection. Furthermore, using the polymer film with side-linked perfluoroalkyl groups as the primary oleophobic layer provides a higher oil contact angle, while the fluorinated diamond-like carbon film strengthens the connection between the chromium layer and the polymer film with side-linked perfluoroalkyl groups, avoiding problems such as low connection strength and mismatched mechanical properties caused by incompatibility between the metal and the polymer.

[0025] As a preferred embodiment of the present invention, the polymer membrane with side-linked perfluoroalkyl groups is selected from at least one of fluorinated polythiophene membrane, fluorinated polypyrrole membrane, fluorinated polyaniline membrane, and fluorinated polymethyl methacrylate membrane.

[0026] There are many ways to set up a polymer film with side-linked perfluoroalkyl groups. As a preferred embodiment of the present invention, the polymer film with side-linked perfluoroalkyl groups is deposited by electrochemical polymerization process.

[0027] As a preferred embodiment of the present invention, the electrochemical polymerization process is as follows: firstly, a fluorocarbon chain is introduced onto the polymer monomer to obtain a modified monomer; then, using the non-graphic part as the working electrode, the polymer film with side-linked perfluoroalkyl groups is obtained by electrochemical polymerization in an electrochemical cell containing the modified monomer.

[0028] As a preferred embodiment of the present invention, during electrochemical polymerization, the process is carried out at a constant potential of 1.5~2.0V for 350~450s. The constant potential can be 1.5V, 1.6V, 1.7V, 1.8V, 1.9V, or 2.0V, preferably 1.8V. The time can be 350s, 360s, 370s, 380s, 390s, 400s, 410s, 420s, 430s, 440s, or 450s, preferably 400s.

[0029] As a preferred embodiment of the present invention, after constant potential, the device continues to scan within the range of -0.5 to 1.0V for 5 to 15 cycles to further polymerize. The number of cycles can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 cycles, but is preferably 10 cycles.

[0030] During electrochemical polymerization, to prevent electrochemical polymerization from also occurring on the graphic portion, a masking layer is preferably provided on the surface of the graphic portion, as a preferred embodiment of the present invention. The masking layer can be removed after the electrochemical polymerization is completed. The choice of masking layer is not limited; for example, it can be a raised plate adapted to the cells of the graphic portion, quartz fiber cloth, flexible ceramics, carbon fiber / quartz ceramic composite materials, polyurethane coatings, epoxy resin coatings, polyurea coatings, etc.

[0031] The beneficial effects of this invention are: 1. In this application, by providing an oleophobic coating on the non-image area of ​​the printing roller and not providing an oleophobic coating on the image area, the ink will not be adhered by the rotation of the printing roller due to the oleophobic properties of the non-image area during gravure printing. However, this will not affect the rotation of the printing roller to carry the ink from the image area to the printing plate. At this time, the doctor blade only scrapes off the excess ink from the image area, so that the ink in the image area of ​​the finished product is not too thick, which would cause problems such as ink stripping and smudging. This effectively reduces the ink accumulation between the outer layer of the printing roller and the doctor blade, which would lead to the formation of large particles that are blocked outside the blade and cause ink bleeding.

[0032] 2. This application can be directly modified on existing printing rollers without the need to manufacture new printing rollers, making the operation simple and cost-effective.

[0033] 3. In some embodiments, the oleophobic coating of this application includes a fluorinated diamond-like carbon film, which has good mechanical properties and good bonding strength with the metallic chromium layer, thereby improving the service life of the oleophobic coating.

[0034] 4. In some embodiments, the oleophobic coating of this application further includes a polymer film with side-linked perfluoroalkyl groups, which further improves the oleophobic effect of the oleophobic coating without affecting the bonding strength. Detailed Implementation

[0035] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described, but the present invention is not limited to these embodiments.

[0036] Example 1 A gravure printing anti-ink mixing process includes the following steps: S1. Select an printing roller with graphic cells on its surface. The entire printing roller consists of a cast iron layer, a copper plating layer, and a chromium plating layer, arranged sequentially from the inside out. The portion of the printing roller with graphic cells forms the graphic area, and the remaining portion forms the non-graphic area.

[0037] S2. After applying a layer of silicone oil for lubrication on the graphic layer, insert a convex ceramic plate that matches the graphic. Apply an oleophobic coating to the chromium layer on the non-graphic area: Place the printing roller in a plasma cleaner and bombard its surface with air plasma (13.56MHz, 18w) for 10 minutes to activate hydroxyl groups. Prepare a fluorosilane solution using anhydrous ethanol as solvent and perfluorooctyltrichlorosilane as solute. Immerse the activated printing roller in the fluorosilane solution for 15 minutes, allowing the active hydroxyl groups to react with the perfluorooctyltrichlorosilane monomer. Then remove the roller and rinse with anhydrous ethanol until no fluorosilane residue remains. Finally, remove the convex ceramic plate from the graphic layer and rinse sequentially with anhydrous ethanol and deionized water until no silicone oil residue remains. The modified printing roller is obtained.

[0038] S3. Use the modified printing roller as the printing plate for gravure printing.

[0039] Example 2 A gravure printing anti-ink mixing process includes the following steps: S1. Select an printing roller with graphic cells on its surface. The entire printing roller consists of a cast iron layer, a copper plating layer, and a chromium plating layer, arranged sequentially from the inside out. The portion of the printing roller with graphic cells forms the graphic area, and the remaining portion forms the non-graphic area.

[0040] S2. After applying a layer of silicone oil for lubrication on the graphic layer, insert a convex ceramic plate that matches the graphic. Apply an oleophobic coating to the chromium layer on the non-graphic area: polish the non-graphic area to a roughness Ra≤10mm, then ultrasonically clean it with deionized water. Deposit a fluorinated diamond-like carbon film using magnetron sputtering: RF frequency 13.56Hz, vacuum evacuated to 4.0×10⁻⁶. -3 Below Pa, the sputtering target was 99.99% pure graphite with a pitch of 45 mm. The source gas was a mixture of argon and trifluoromethane at flow rates of 2 sccm and 2 sccm respectively. The working pressure was 2 Pa, and the RF power was 180 W. Etching lasted 30 min, followed by deposition for 100 min, resulting in a fluorinated diamond-like carbon film. Finally, the raised ceramic plate on the pattern layer was removed, and the film was rinsed sequentially with anhydrous ethanol and deionized water until no silicone oil residue remained. The modified printing roller was obtained.

[0041] S3. Use the modified printing roller as the printing plate for gravure printing.

[0042] Example 3 This embodiment is basically the same as embodiment 2, except that the radio frequency power is 60W.

[0043] Example 4 This embodiment is basically the same as embodiment 2, except that the radio frequency power is 250W.

[0044] Example 5 A gravure printing anti-ink mixing process includes the following steps: S1. Select an printing roller with graphic cells on its surface. The entire printing roller consists of a cast iron layer, a copper plating layer, and a chromium plating layer, arranged sequentially from the inside out. The portion of the printing roller with graphic cells forms the graphic area, and the remaining portion forms the non-graphic area.

[0045] S2. After applying a layer of silicone oil for lubrication on the graphic layer, insert a convex ceramic plate that matches the graphic. Apply an oleophobic coating to the chromium layer on the non-graphic area: First, polish the non-graphic area to a roughness Ra ≤ 10 mm, then ultrasonically clean it with deionized water. Deposit a fluorinated diamond-like carbon film using magnetron sputtering: RF frequency 13.56 Hz, vacuum evacuated to 4.0 × 10⁻⁶ mm. -3 The sputtering target was 99.99% pure graphite with a pitch of 45 mm. The source gas was a mixture of argon and trifluoromethane with flow rates of 2 sccm and 2 sccm, respectively. The working pressure was 2 Pa, the RF power was 180 W, the etching time was 30 min, and the deposition time was 100 min to obtain a fluorinated diamond-like carbon film.

[0046] Next, 0.1 mol of 3-thiophene malonic acid and 0.4 mol of sodium hydroxide were added to 500 mL of acetonitrile, and the mixture was stirred and heated to 70 °C for 1 h to deprotonate the 3-thiophene malonic acid and form carboxylate ions. Then, 0.1 mol of perfluorohexylsulfonyl fluoride was slowly added, and the reaction was continued for 3 h after the addition was complete. After the reaction was completed, the mixture was cooled to room temperature to obtain a fluorinated thiophene monomer. Using an ink roller with a fluorinated diamond-like carbon film deposited as the working electrode, Ag / AgCl as the reference electrode, and a platinum electrode as the counter electrode, the mixture was placed in an electrochemical cell containing 1 mmol / L of the fluorinated thiophene monomer in a pH 6.76 buffer solution (0.1 mol / L NaH2PO4 and 0.1 mol / L Na2HPO4). After maintaining a constant potential of 1.8 V for 400 s, the mixture was removed, cleaned, and dried with nitrogen to obtain a fluorinated polythiophene film modified with a fluorinated diamond-like carbon film.

[0047] Finally, the raised ceramic plate on the image layer is removed, and the roller is rinsed sequentially with anhydrous ethanol and deionized water until no silicone oil residue remains. The modified printing roller is obtained.

[0048] S3. Use the modified printing roller as the printing plate for gravure printing.

[0049] Example 6 This embodiment is basically the same as embodiment 5, except that the electrochemical polymerization is different.

[0050] Specifically, the process involved using an printing roller with a fluorinated diamond-like carbon film as the working electrode, Ag / AgCl as the reference electrode, and a platinum electrode as the counter electrode. The roller was placed in an electrochemical cell containing a pH 6.76 buffer solution (0.1 mol / L NaH2PO4 and 0.1 mol / L Na2HPO4) with 1 mmol / L of fluorinated thiophene monomer. After maintaining a constant potential of 1.8 V for 400 s, a cyclic voltammetric scan was performed for 10 cycles at a scan rate of 100 mV / s within the range of -0.5 to 1.0 V. The roller was then removed, cleaned, and dried with nitrogen to obtain a fluorinated diamond-like carbon film modified with a fluorinated polythiophene film.

[0051] Example 7 A gravure printing anti-ink mixing process includes the following steps: S1. Select an printing roller with graphic cells on its surface. The entire printing roller consists of a cast iron layer, a copper plating layer, and a chromium plating layer, arranged sequentially from the inside out. The portion of the printing roller with graphic cells forms the graphic area, and the remaining portion forms the non-graphic area.

[0052] S2. After applying a layer of silicone oil for lubrication on the graphic layer, insert a convex ceramic plate that matches the graphic. An oleophobic coating is applied to the chromium layer in the non-graphic area: 0.1 mol of 3-thiophene malonic acid and 0.4 mol of sodium hydroxide are added to 500 mL of acetonitrile, and the mixture is stirred and heated to 70 °C for 1 h to deprotonate the 3-thiophene malonic acid, forming carboxylate ions; then 0.1 mol of perfluorohexylsulfonyl fluoride is slowly added, and the reaction continues for 3 h after the addition is complete. After the reaction is complete, the mixture is cooled to room temperature to obtain a fluorinated thiophene monomer. Using an printing roller as the working electrode, Ag / AgCl as the reference electrode, and a platinum electrode as the counter electrode, the roller was placed in an electrochemical cell containing 1 mmol / L of fluorinated thiophene monomer in a pH 6.76 buffer solution (0.1 mol / L NaH₂PO₄ and 0.1 mol / L Na₂HPO₄). After maintaining a constant potential of 1.8 V for 400 s, the roller was removed, cleaned, and dried with nitrogen to obtain a printing roller modified with a fluorinated polythiophene film. Finally, the raised ceramic plate on the image layer was removed, and the roller was rinsed sequentially with anhydrous ethanol and deionized water until no silicone oil residue remained. The modified printing roller was obtained.

[0053] S3. Use the modified printing roller as the printing plate for gravure printing.

[0054] Example 8 A gravure printing anti-ink mixing process includes the following steps: S1. Select an printing roller that has already undergone copper plating and engraving on the cast iron layer. The portion of the printing roller with graphic cells forms the graphic area, and the remaining portion forms the non-graphic area. Chromium plating: Chromium plating is performed using a double-glow equipment: the target material is a chromium target with a purity of 99.99%, the target spacing is 17mm, and the vacuum is drawn to 5.0×10. -3Pa, then argon gas is introduced, the working pressure is 35 Pa, etching is performed for 10 min, and deposition is performed for 100 min to obtain a metallic chromium layer.

[0055] S2. After applying a layer of silicone oil for lubrication on the graphic layer, insert a convex ceramic plate that matches the graphic. Apply an oleophobic coating to the chromium layer on the non-graphic area: polish the non-graphic area to a roughness Ra≤10mm, then ultrasonically clean it with deionized water. Deposit a fluorinated diamond-like carbon film using magnetron sputtering: RF frequency 13.56Hz, vacuum evacuated to 4.0×10⁻⁶. -3 Below Pa, the sputtering target was 99.99% pure graphite with a pitch of 45 mm. The source gas was a mixture of argon and trifluoromethane at flow rates of 2 sccm and 2 sccm respectively. The working pressure was 2 Pa, and the RF power was 180 W. Etching lasted 30 min, followed by deposition for 100 min, resulting in a fluorinated diamond-like carbon film. Finally, the raised ceramic plate on the pattern layer was removed, and the film was rinsed sequentially with anhydrous ethanol and deionized water until no silicone oil residue remained. The modified printing roller was obtained.

[0056] S3. Use the modified printing roller as the printing plate for gravure printing.

[0057] Comparative Example 1 A printing roller with graphic cells on its surface is selected. The entire printing roller consists of a cast iron layer, a copper plating layer, and a chromium plating layer, arranged sequentially from the inside out. The portion of the printing roller with graphic cells forms the graphic area, and the remaining portion forms the non-graphic area.

[0058] Comparative Example 2 S1. Select an printing roller that has already been copper-plated and engraved on a cast iron layer. The part of the printing roller with graphic holes forms the graphic part, and the remaining part forms the non-graphic part.

[0059] S2. After applying a layer of silicone oil for lubrication on the graphic layer, insert a convex ceramic plate that matches the graphic. Apply an oleophobic coating to the copper plating layer on the non-graphic areas: polish the non-graphic areas to a roughness Ra≤10mm, then ultrasonically clean with deionized water. Deposit a fluorinated diamond-like carbon film using magnetron sputtering: RF frequency 13.56Hz, vacuum evacuated to 4.0×10⁻⁶. -3 Below Pa, the sputtering target was 99.99% pure graphite with a pitch of 45 mm. The source gas was a mixture of argon and trifluoromethane at flow rates of 2 sccm and 2 sccm respectively. The working pressure was 2 Pa, and the RF power was 180 W. Etching lasted 30 min, followed by deposition for 100 min, resulting in a fluorinated diamond-like carbon film. Finally, the raised ceramic plate on the pattern layer was removed, and the film was rinsed sequentially with anhydrous ethanol and deionized water until no silicone oil residue remained. The modified printing roller was obtained.

[0060] S3. Use the modified printing roller as the printing plate for gravure printing.

[0061] Detection Ink bleed test: The printing rollers obtained in the examples and comparative examples were used in a gravure printing machine and printed continuously for 3 days at a speed of 300 m / min. The results were then observed to see if ink bleed was observed on the final printed products.

[0062] Non-image area ink contact angle: The contact angle between the non-image area surface of the printing roller and the ink is measured using a contact angle meter.

[0063] Bond strength: The bonding force between the film and the substrate was tested by scratch test. A WS-92 acoustic emission scratch tester was used with a Rockwell hardness C indenter (R=0.2mm) to scratch the substrate. The loading speed was 100N / min and the termination load was 100N. The minimum pressure, i.e. the critical load, at which the coating peeled off from the substrate (a chromium layer for the example and a copper plating layer for Comparative Example 2) was recorded.

[0064] The test results are shown in Table 1 below.

[0065] Table 1.

[0066] As shown in Table 1, comparing the examples and Comparative Example 1, it can be seen that this application can solve the ink migration problem in gravure printing by providing an oleophobic coating only on the non-image area of ​​the printing roller. Comparing Examples 1 and 2, and Comparative Example 2, it can be seen that providing a fluorinated diamond-like carbon film on a chromium layer not only achieves a better oleophobic effect but also improves the bonding strength of the coating on the substrate, thus increasing its anti-ink migration lifespan. Comparing Examples 2, 5, and 7, it can be seen that further electrochemically depositing a polymer film with side-linked perfluoroalkyl groups on the fluorinated diamond-like carbon film can further improve the oleophobic effect without reducing the bonding strength.

[0067] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A gravure printing anti-ink mixing process, characterized in that: Includes the following steps: S1. Select an printing roller, wherein the printing roller comprises a substrate layer and a chromium metal layer in sequence from the inside to the outside; the surface of the printing roller includes a graphic portion having graphic holes, and the portion of the printing roller surface other than the graphic portion is a non-graphic portion; S2. An oleophobic coating is provided on the chromium layer located in the non-image area, and no oleophobic coating is provided on the chromium layer located in the image area, to obtain the modified printing roller; The oleophobic coating includes a fluorinated diamond-like carbon film and a polymer film with side-linked perfluoroalkyl groups further disposed on the fluorinated diamond-like carbon film. The fluorinated diamond-like carbon film is deposited using a magnetron sputtering process: the sputtering target includes a carbon-containing material, the source gas includes an inert gas and a gas capable of dissociating fluorine plasma, and the radio frequency power is 60~250W; The polymer film with side-linked perfluoroalkyl groups was deposited using an electrochemical polymerization process: First, a fluorocarbon chain was introduced onto the polymer monomer to obtain a modified monomer; then, using the non-image area as the working electrode, the polymer film with side-linked perfluoroalkyl groups was obtained by electrochemical polymerization in an electrochemical cell containing the modified monomer; during electrochemical polymerization, the process was carried out at a constant potential of 1.5~2.0V for 350~450s; after the constant potential, the process continued to scan within the range of -0.5~1.0V for 5~15 cycles; S3. Use the modified printing roller as a printing plate for gravure printing.

2. The gravure printing anti-ink mixing process according to claim 1, characterized in that: The polymer membrane with side-linked perfluoroalkyl groups is selected from at least one of fluorinated polythiophene membrane, fluorinated polypyrrole membrane, fluorinated polyaniline membrane, and fluorinated polymethyl methacrylate membrane.

3. The gravure printing anti-ink mixing process according to claim 1, characterized in that: The graphic section is equipped with a masking layer.

4. The gravure printing anti-ink mixing process according to claim 1, characterized in that: The chromium layer is deposited on the substrate layer using a dual-glow plasma surface alloying process.

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