Liquid-like flexographic printing plate capable of achieving 3D printing and preparation method of liquid-like flexographic printing plate

Abstract

The invention discloses a liquid-like flexographic printing plate capable of 3D printing and a preparation method of the liquid-like flexographic printing plate. The liquid-like flexographic printing plate is prepared from 60-90 wt% of a resin matrix, 1-10 wt% of liquid-like molecules, 1-5 wt% of a photoinitiator and 0-30 wt% of an auxiliary agent, the liquid-like molecules are one of polydimethylsiloxane, perfluoropolyether, polyisobutene and polyethylene glycol which are terminated by a single functional group. According to the flexible printing plate with the DLP photocuring 3D printing liquid-like property, the mode that resin matrixes (an acrylate group, a polyurethane group and an epoxy group) are combined with liquid-like molecules is adopted for the flexible printing plate, the surface of the flexible printing plate has the excellent static oleophylic and dynamic oleophobic characteristics, and by reasonably regulating and controlling the structure and distribution of the liquid-like molecules, the surface of the flexible printing plate has the excellent static oleophylic and dynamic oleophobic properties. The ink transfer capacity of the printing plate is enhanced, the printing quality is improved, and ink residues are reduced.

Description

Technical Field

[0001] The present invention belongs to the field of flexographic plate making, and relates to a flexible printing plate (flexo plate), specifically to a flexible printing plate based on the surface of PDMS-like liquid and a preparation method thereof. Background Art

[0002] Flexographic printing is a printing technology widely used in packaging, labeling, and corrugated paper printing. Its main feature is that the printing plate has a certain elasticity and can adapt to different substrates. Traditional flexo plates usually use photosensitive resin materials and are made through multiple steps such as exposure, development, cleaning, and drying. However, this traditional plate-making method has many limitations:

[0003] (1) The plate-making process is complex and the production efficiency is low: The preparation of traditional flexo plates requires multiple processes, including ultraviolet exposure, development, plate washing, and post-curing. The whole process is time-consuming and laborious, and the plate-making cycle is long. (2) It is difficult to clean the printing plate and its service life is limited: During the printing process, the ink is easily attached to the surface of the printing plate. After long-term use, it needs to be frequently cleaned, otherwise it will affect the printing quality. And due to the relatively high surface energy of traditional resin-based flexo plates, it is difficult to clean them, which easily leads to printing downtime. (3) The ink transfer is limited, affecting the printing quality: Due to the surface characteristics of traditional flexo plate materials, the wettability and transfer efficiency of the ink on the printing plate are limited, which may lead to ink accumulation or unevenness, affecting the printing accuracy. (4) It is difficult to achieve high-precision patterns: The micro-structure processing accuracy of traditional flexo plates is limited, and it is difficult to achieve high-fidelity replication of ultra-fine graphics and complex patterns.

[0004] In recent years, the development of materials science has prompted researchers to explore more functional printing plate materials. Among them, the liquid-like surface technology has attracted wide attention. The liquid-like surface is the surface of a solid material with liquid-like properties, which exhibits the characteristics of static lipophilicity and dynamic oleophobicity. This surface characteristic makes it have many advantages in printing applications: (1) Excellent ink wettability: Under static conditions, the ink can be evenly spread on the liquid-like surface, improving the ink coverage and consistency during the printing process. (2) High ink transfer efficiency: During the dynamic printing process, the liquid-like surface can reduce the ink residue and improve the ink transfer efficiency, making the printing dots clearer and the colors more saturated. (3) Strong self-cleaning ability: Due to the dynamic oleophobic property, the ink is not easily attached to the printing plate, reducing the pollution of the printing plate, lowering the cleaning frequency, and improving the printing production efficiency. (4) High durability: The chemical stability of the liquid-like surface is strong and it is not easily aged due to ink erosion or mechanical friction, improving the service life of the flexo plate. This characteristic makes the liquid-like surface an ideal printing plate surface material, which can effectively improve the quality and efficiency of flexographic printing.

[0005] With the development of 3D printing technology, it has become possible to directly manufacture printing plates using digital means. For example, stereolithography 3D printing can build three-dimensional structures layer by layer with high precision. If digital light processing (DLP) technology can be applied to the direct preparation of flexographic plates, it is expected to simplify the plate-making process, reduce costs, and improve plate-making accuracy. In addition, flexographic printing has high requirements for ink transfer efficiency and plate durability. Existing plate materials are difficult to balance ink affinity and easy cleanability. Therefore, it is necessary to develop a new type of flexographic plate whose surface material is easy to adhere to ink when stationary, but can quickly release ink during dynamic printing contact, thereby improving printing transfer efficiency and facilitating cleaning. Summary of the Invention

[0006] In order to improve the ink transfer efficiency of flexographic plates, reduce the frequency of plate cleaning, lower production and maintenance costs, extend the service life of plates, enhance environmental protection and printing adaptability, the present invention provides a 3D-printable liquid-like flexographic printing plate and its preparation method. The present invention uses DLP technology to prepare flexographic plates with a special material combination (including resin and linear polymer molecules capped with monofunctional groups), so that its surface has the characteristics of static oil affinity and dynamic oil repellency, thereby improving ink transfer efficiency, self-cleaning ability and printing suitability.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] A 3D-printable liquid-like flexographic printing plate is prepared from 60-90 wt% of a resin matrix, 1-10 wt% of liquid-like molecules (capped with monofunctional groups), 1-5 wt% of a photoinitiator, and 0-30 wt% of an additive, wherein:

[0009] The resin matrix is one or a mixture of polyurethane acrylate, epoxy acrylate, polyester acrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, 2-phenoxyethyl acrylate, methoxy-capped polyurethane acrylate, ethoxylated bisphenol A diacrylate, bisphenol A diglycidyl ether, ethoxylated bisphenol A diglycidyl ether, bisphenol F diglycidyl ether;

[0010] The liquid-like molecules are one of monofunctional group-capped polydimethylsiloxane, perfluoropolyether, polyisobutene, polyethylene glycol, with a molecular weight of 100-100,000, and the monofunctional group is one of hydroxyl, amino, epoxy, vinyl, acyl chloride, urethane group, carboxyl group;

[0011] The photoinitiator is one of acrylate system, polyurethane system and epoxy resin system, preferably one of trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, triarylsulfonium hexafluorophosphate, and iodonium salt;

[0012] The auxiliary agent is one or a mixture of two of plasticizer and stabilizer.

[0013] A preparation method of the above-mentioned 3D-printable liquid-like flexographic printing plate includes the following steps:

[0014] Step 1: Prepare a resin composition for DLP photocuring: Add a resin matrix, liquid-like molecules, a photoinitiator, and an auxiliary agent, first mix and stir, and then remove air bubbles under vacuum;

[0015] Step 2: Pour the resin composition prepared in Step 1 into the resin tank of a DLP 3D printer, and perform layer-by-layer exposure and curing molding according to the designed flexographic model, controlling the layer thickness to be 10-100 microns, the exposure time to be 1-20 seconds per layer, and the light intensity to be 1-30 mW / cm 2 ;

[0016] Step 3: After printing is completed, take out the formed flexographic substrate from the printer, wash off the residual uncured resin on the surface, and then perform global secondary curing on the printing plate under an ultraviolet lamp, controlling the global secondary curing time to be 5-60 minutes.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The present invention provides a flexible printing plate based on the surface of PDMS liquid-like material. This flexographic plate combines a resin matrix and PDMS liquid-like material (the specific structure is as Figure 1 shown), enabling its surface to have excellent static oil affinity and dynamic oil repellency characteristics. By reasonably regulating the structure and distribution of PDMS, the ink transfer ability of the printing plate is enhanced, the printing quality is improved, and ink residue is reduced. Specifically, it is manifested as:

[0019] (1) Liquid-like surface characteristics: Static oil affinity (as Figure 2 shown), dynamic oil repellency (as Figure 3 shown), improving ink wettability and transfer performance;

[0020] (2) High adaptability: Applicable to different types of inks (such as water-based inks, solvent-based inks, UV inks, etc.);

[0021] (2) High resolution: Support the printing of fine patterns at the 10-20 μm level, ensuring printing quality;

[0022] (4) High wear resistance: PDMS enhances the durability of flexographic plates, enabling them to remain stable in high-load printing environments;

[0023] (5) High environmental friendliness: Reduces ink waste and cleaning agent consumption, meeting the standards of green printing.

[0024] 2. The improvements and main performance indicators of the flexible printing plate of the present invention compared with traditional flexographic plates are shown in Tables 1 and 2 as follows:

[0025] Table 1

[0026]

[0027] Table 2

[0028]

[0029] Description of the Drawings

[0030] Figure 1 is a schematic diagram of the structure of the liquid-like flexographic plate;

[0031] Figure 2 is the static contact angle of the oil-based ink on the surface of the PDMS-like liquid;

[0032] Figure 3 is a sliding photo of the oil-based ink on the surface of the liquid-like substance;

[0033] Figure 4 is a confocal laser scanning microscope photo of the liquid-like flexographic plate;

[0034] Figure 5 is a printed product of the liquid-like flexographic plate. Detailed Embodiments

[0035] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings, but are not limited thereto. Any modifications or equivalent replacements of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered within the protection scope of the present invention.

[0036] The present invention provides a 3D-printable liquid-like flexographic printing plate, which is prepared from 60-90 wt% of a resin matrix, 1-10 wt% of liquid-like molecules (monofunctional group terminated), 1-5 wt% of a photoinitiator, and 0-30 wt% of an auxiliary agent, wherein:

[0037] The resin matrix is one or a mixture of several of polyurethane acrylate, epoxy acrylate, polyester acrylate, 1,6 - hexanediol diacrylate, trimethylolpropane triacrylate, 2 - phenoxyethyl acrylate, methoxy - terminated polyurethane acrylate, ethoxylated bisphenol A diacrylate, bisphenol A diglycidyl ether, ethoxylated bisphenol A diglycidyl ether, and bisphenol F diglycidyl ether to provide the necessary mechanical strength.

[0038] The liquid - like molecules (monofunctional - terminated) are one of polydimethylsiloxane with monofunctional termination (hydroxyl, amino, epoxy, vinyl, acyl chloride, urethane group, carboxyl), perfluoropolyether, polyisobutene, and polyethylene glycol, with a molecular weight of 100 - 100,000, enabling the formation of a stable liquid - like surface.

[0039] The selection of the photoinitiator is crucial for the speed and curing depth of the photocuring reaction. In the present invention, the photoinitiator is one of the acrylate system, epoxy resin system, and polyurethane system, preferably one of TPO (Diphenyl(2,4,6 - trimethylbenzoyl)phosphine oxide, trimethylbenzoyl - diphenylphosphine oxide), Irgacure 819 (Phenylbis(2,4,6 - trimethylbenzoyl)phosphine oxide, phenyl bis(2,4,6 - trimethylbenzoyl)phosphine oxide), Irgacure 2959 (2 - Hydroxy - 2 - methylpropiophenone, 2 - hydroxy - 4'-(2 - hydroxyethoxy)-2 - methylpropiophenone), Triarylsulfonium Hexafluorophosphate (hexafluorophosphate triarylsulfonium salt), and Iodonium Salt (iodonium salt).

[0040] The additive is one or a mixture of two of a plasticizer and a stabilizer to optimize the performance of the flexographic plate, and the mass ratio of the plasticizer to the stabilizer is 1:1 - 10.

[0041] The present invention also provides a preparation method of the above - mentioned 3D - printable liquid - like flexographic printing plate, and the method comprises the following steps:

[0042] Step 1: Prepare a resin composition for DLP photocuring: Add the resin matrix, liquid - like molecules (monofunctional - terminated), photoinitiator, epoxy resin system, and additive, first mix and stir for 10 - 60 min, and then perform vacuum treatment for 10 - 60 min to remove air bubbles.

[0043] Step 2: Pour the resin composition prepared in Step 1 into the resin tank of a DLP 3D printer, and perform layer-by-layer exposure curing and forming according to the designed flexographic plate model. The printing parameters such as layer thickness (10 - 100 microns), exposure time (1 - 20 seconds per layer), and light intensity (1 - 30 mW / cm 2 ) are optimized according to the resin formula.

[0044] Step 3: After printing is completed, take out the formed flexographic plate substrate from the printer, ultrasonically clean the residual uncured resin on the surface using solvents such as ethanol and isopropyl alcohol, and then perform global secondary curing (post-curing) of the printing plate under an ultraviolet lamp for 5 - 60 minutes to fully cure the resin substrate and improve its mechanical properties and solvent resistance.

[0045] The present invention utilizes a DLP photocuring 3D printing flexible printing plate with liquid-like properties. This flexographic plate adopts a combination of a resin matrix (acrylate-based, polyurethane-based, epoxy-based) and liquid-like molecules, enabling its surface to have excellent static lipophilic and dynamic oleophobic characteristics. By reasonably regulating the structure and distribution of the liquid-like molecules, the ink transfer ability of the printing plate is enhanced, the printing quality is improved, and ink residue is reduced. The specific advantages are as follows:

[0046] 1. Improve ink transfer efficiency: Through the static lipophilic and dynamic oleophobic characteristics of the liquid-like surface, the wettability and transfer efficiency of the ink are improved, ink accumulation is reduced, making the printing dots clearer and the colors more uniform.

[0047] 2. Reduce the frequency of printing plate cleaning and lower production and maintenance costs: Due to the dynamic oleophobic characteristics of the liquid-like surface, the ink is not easily adhered to the surface of the printing plate during the printing process, thereby reducing ink residue, improving the self-cleaning ability, and reducing the frequency of downtime for cleaning.

[0048] 3. Prolong the service life of the printing plate: The liquid-like surface has excellent chemical resistance and mechanical friction resistance, which can reduce the erosion of the ink on the printing plate, enabling the printing plate to maintain good printing quality during long-term use and prolonging its service life.

[0049] 4. Enhance environmental protection: Reduce the usage amount of chemical solvents required for cleaning the printing plate during the traditional printing process, reduce the emission of volatile organic compounds (VOCs), and better meet the requirements of green and environmental-friendly printing processes.

[0050] 5. Improve printing adaptability: The flexographic plate with a liquid-like surface is suitable for different types of inks (such as water-based inks, solvent-based inks, UV inks, etc.) and can maintain stable printing performance on different substrates, improving the consistency and adaptability of printing.

[0051] 6. The application of DLP technology in the direct preparation of flexographic plates is expected to simplify the plate-making process, reduce costs, and improve plate-making accuracy.

[0052] Example 1:

[0053] This example provides a kind of liquid-like flexographic printing plate applicable to solvent-based inks and UV inks. The specific preparation method is as follows:

[0054] (1) Prepare a resin composition for DLP photocuring. Add polyurethane acrylate matrix (70 wt%), epoxy acrylate (20 wt%), monohydroxy-terminated polydimethylsiloxane molecule (1 wt%, molecular weight 6000), photoinitiator TPO (1 wt%), plasticizer (4 wt%), stabilizer (4 wt%), mix and stir for 30 min, and then remove air bubbles under vacuum for 30 min.

[0055] (2) Pour the above resin into the resin tank of a DLP 3D printer, and perform layer-by-layer exposure curing molding according to the designed flexographic model. Printing parameters: layer thickness: 50 microns, exposure time: 10 seconds per layer, light intensity: 10 mW / cm 2 .

[0056] (3) After printing is completed, take out the formed flexographic matrix from the printer, use ethanol to ultrasonically clean the residual uncured resin on the surface, and then perform global secondary curing (post-curing) on the printing plate under ultraviolet light for 30 min. High-precision patterns are obtained by DLP printing as Figure 4 shown, and the printed products are as Figure 5 shown.

[0057] Example 2:

[0058] This example provides a kind of liquid-like flexographic printing plate applicable to solvent-based inks and UV inks. The specific preparation method is as follows:

[0059] (1) Prepare a resin composition for DLP photocuring. Add bisphenol A diglycidyl ether (70 wt%), epoxy acrylate (10 wt%), perfluoropolyether molecule with a single epoxy group at the end (2 wt%, molecular weight 10000), photoinitiator Iodonium Salt (2 wt%), stabilizer (16 wt%), mix and stir for 40 min, and then remove air bubbles under vacuum for 20 min.

[0060] (2) Pour the above resin into the resin tank of a DLP 3D printer, and perform layer-by-layer exposure curing molding according to the designed flexographic model. Printing parameters: layer thickness: 30 microns, exposure time: 5 seconds per layer, light intensity: 15 mW / cm 2 .

[0061] (3) After printing is completed, take out the formed flexographic matrix from the printer, use ethanol to ultrasonically clean the residual uncured resin on the surface, and then perform global secondary curing (post-curing) on the printing plate under ultraviolet light for 40 min.

[0062] Example 3:

[0063] This example provides a liquid-like flexographic printing plate suitable for water-based inks. The specific preparation method is as follows:

[0064] (1) Prepare a resin composition for DLP photocuring. Add ethoxylated bisphenol A diacrylate (70 wt%), polyurethane acrylate (20 wt%), polyethylene glycol molecule (5 wt%, molecular weight 5000), photoinitiator Irgacure 819 (1 wt%), plasticizer (2%), stabilizer (2%), mix and stir for 30 min, and then remove air bubbles under vacuum for 20 min.

[0065] (2) Pour the above resin into the resin tank of a DLP 3D printer, and perform layer-by-layer exposure and curing molding according to the designed flexographic model. Printing parameters: layer thickness: 20 microns, exposure time: 10 seconds per layer, light intensity: 20 mW / cm 2 .

[0066] (3) After printing is completed, take out the formed flexographic substrate from the printer, use isopropyl alcohol to ultrasonically clean the residual uncured resin on the surface, and then perform global secondary curing (post-curing) on the printing plate under ultraviolet light for 30 min.

[0067] Example 4:

[0068] This example provides a liquid-like flexographic printing plate suitable for solvent-based inks and UV inks. The specific preparation method is as follows:

[0069] (1) Prepare a resin composition for DLP photocuring. Add polyurethane acrylate matrix (60 wt%), monohydroxy-terminated polydimethylsiloxane molecule (10 wt%, molecular weight 10000), photoinitiator TPO (1 wt%), plasticizer (26 wt%), stabilizer (3 wt%), mix and stir for 30 min, and then remove air bubbles under vacuum for 30 min.

[0070] (2) Pour the above resin into the resin tank of a DLP 3D printer, and perform layer-by-layer exposure and curing molding according to the designed flexographic model. Printing parameters: layer thickness: 50 microns, exposure time: 10 seconds per layer, light intensity: 10 mW / cm 2 .

[0071] (3) After printing is completed, take out the formed flexographic substrate from the printer, use ethanol to ultrasonically clean the residual uncured resin on the surface, and then perform global secondary curing (post-curing) on the printing plate under ultraviolet light for 30 min.

[0072] Example 5:

[0073] This embodiment provides a kind of liquid-like flexographic printing plate applicable to solvent-based ink and UV ink. The specific preparation method is as follows:

[0074] (1) Prepare the resin composition for DLP photocuring. Add polyurethane acrylate matrix (70 wt%), epoxy acrylate (20 wt%), monohydroxy-terminated polydimethylsiloxane molecule (8 wt%, molecular weight 6000), photoinitiator TPO (2 wt%). After mixing and stirring for 30 min, remove air bubbles under vacuum for 30 min.

[0075] (2) Pour the above resin into the resin tank of the DLP 3D printer, and perform layer-by-layer exposure and curing according to the designed flexographic model. Printing parameters: layer thickness: 50 microns, exposure time: 15 seconds per layer, light intensity: 10 mW / cm 2 .

[0076] (3) After printing, take out the formed flexographic substrate from the printer, use ethanol ultrasonic cleaning to remove the uncured resin remaining on the surface, and then perform global secondary curing (post-curing) on the printing plate under ultraviolet light for 30 min.

Claims

1. A 3D printable liquid-like flexographic printing plate, characterized in that The liquid-like flexographic printing plate is prepared from 60-90wt% of a resin matrix, 1-10wt% of liquid-like molecules, 1-5wt% of a photoinitiator and 0-30wt% of an auxiliary agent, wherein the liquid-like molecules are one of monofunctional end-capped polydimethylsiloxane, perfluoropolyether, polyisobutylene and polyethylene glycol.

2. The 3D printable liquid-like flexographic printing plate according to claim 1, characterized in that The resin matrix is ​​one or a mixture of polyurethane acrylate, epoxy acrylate, polyester acrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, 2-phenoxyethyl acrylate, methoxy-terminated polyurethane acrylate, ethoxylated bisphenol A diacrylate, bisphenol A diglycidyl ether, ethoxylated bisphenol A diglycidyl ether, and bisphenol F diglycidyl ether.

3. The 3D printable liquid-like flexographic printing plate according to claim 1, characterized in that The molecular weight of the liquid-like molecules is 100 to 100,000.

4. The 3D printable liquid-like flexographic printing plate according to claim 1, characterized in that The monofunctional group is one of hydroxyl, amino, epoxy, vinyl, acyl chloride, carbamate and carboxyl.

5. The 3D printable liquid-like flexographic printing plate according to claim 1, characterized in that The photoinitiator is one of an acrylate system, a polyurethane system and an epoxy resin system.

6. The 3D printable liquid-like flexographic printing plate according to claim 1, characterized in that The photoinitiator is one of trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, triarylsulfonium hexafluorophosphate, and iodonium salt.

7. The 3D printable liquid-like flexographic printing plate according to claim 1, characterized in that The auxiliary agent is one of a plasticizer and a stabilizer or a mixture of the two.

8. A method for preparing a 3D printable liquid-like flexographic printing plate according to any one of claims 1 to 7, characterized in that The method comprises the following steps: Step 1: prepare a resin composition for DLP photocuring: add a resin matrix, liquid-like molecules, a photoinitiator, and an auxiliary agent, mix and stir, and then vacuum to remove bubbles; Step 2: pour the resin composition prepared in step 1 into the resin tank of the DLP 3D printer, and perform exposure and curing layer by layer according to the designed flexographic model; Step 3: After printing is completed, remove the formed flexographic substrate from the printer, clean the uncured resin remaining on the surface, and then perform global secondary curing on the printing plate under ultraviolet light.

9. The method for preparing a 3D printable liquid-like flexographic printing plate according to claim 8, characterized in that In step 2, the layer thickness is controlled to be 10 to 100 microns, the exposure time is 1 to 20 seconds per layer, and the light intensity is 1 to 30 mW / cm 2 .

10. The method for preparing a 3D printable liquid-like flexographic printing plate according to claim 8, characterized in that In step three, the global secondary curing time is controlled to be 5 to 60 minutes.

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