High-saturation color printing process for release paper

Abstract

The invention discloses a high-saturation color printing process for release paper, which comprises the following steps: carrying out surface corona treatment on a release paper substrate, coating a bottom coating on the treated release paper substrate, and carrying out first drying and curing; and performing multi-time color register printing on the prime coat by adopting high-saturation color ink to form a color image-text layer. According to the high-saturation color printing process for the release paper, accurate surface corona treatment is carried out on the release paper base material, the surface molecular structure of the release paper base material is effectively changed, the surface energy is increased, a good foundation is provided for subsequent coating and printing, a base coating can be firmly attached, and the color printing quality is improved. Therefore, high-saturation printing of the color ink is guaranteed, printed images and texts are bright and full in color and extremely high in color reducibility and definition, and the product requirement for extremely high printing quality can be met.

Description

Technical Field

[0001] This invention relates to the field of release paper printing technology, and more particularly to a high-saturation color printing process for release paper. Background Technology

[0002] In terms of release paper surface treatment, previous methods often failed to effectively alter the molecular structure of the release paper substrate surface, resulting in insufficient surface energy. This made it difficult for subsequent base coatings to adhere well, thus affecting the printing effect of colored inks. The printed images and text were prone to problems such as dull colors and poor adhesion, failing to present highly saturated and vibrant colors.

[0003] Traditional primer coating materials and coating processes often result in suboptimal film-forming properties, adhesion, and flexibility, failing to bond well with the release paper substrate and colored inks. Furthermore, the lack of precise parameter control during coating makes it difficult to manage coating dryness, frequently leading to uneven coating. All of these negatively impact the printing quality of colored inks, resulting in insufficient smoothness and limited color gradation in the printed images.

[0004] Traditional inks have limited pigment content, failing to provide vibrant and saturated colors, and thus struggling to meet the requirements of high-saturation color printing. Furthermore, their limited printing methods prevent flexible selection based on different product needs, resulting in suboptimal printing accuracy and color reproduction. Moreover, the lack of effective inter-color drying measures during multi-color printing processes easily leads to ink mixing and smudging, severely impacting the clarity and color saturation of color images and text.

[0005] Traditional protective varnishes perform poorly in terms of curing speed, hardness, and abrasion resistance, failing to effectively protect the colored graphic layer and making it susceptible to environmental corrosion. Improper coating thickness control during application can result in either incomplete coverage of the colored graphic layer or excessive coating, increasing cost and drying difficulty. Inappropriate curing process parameters can also lead to incomplete or over-curing of the protective varnish, affecting its protective performance and flexibility.

[0006] Therefore, it is necessary to provide a new high-saturation color printing process for release paper to solve the above-mentioned technical problems. Summary of the Invention

[0007] To solve the above-mentioned technical problems, the present invention provides a high-saturation color printing process for release paper.

[0008] This invention provides a high-saturation color printing process for release paper, comprising the following steps:

[0009] S1. Perform surface corona treatment on the release paper substrate to make its surface tension reach 40-48 dynes;

[0010] S2. Apply a base coating to the treated release paper substrate and perform the first drying and curing.

[0011] S3. High-saturation colored inks are used to perform multiple color printing on the base coating layer to form a colored graphic layer;

[0012] S4. Apply a protective varnish to the colored graphic layer and perform a second drying and curing process.

[0013] S5. Cool and rewind the release paper after printing.

[0014] Preferably, in step S1, the power of the corona treatment is 2.5 to 3.5 kW, and the treatment speed is 50 to 120 m / min.

[0015] Preferably, in step S2, the primer coating is a water-based acrylic resin coating with a dry coating weight of 1.5–3.0 g / m³. 2 The first drying and curing temperature is 90-110℃, and the time is 15-30 seconds.

[0016] Preferably, in step S3, the high-saturation colored ink is a solvent-based ink or an energy-curing ink with a high pigment toner content, and its viscosity range is 25 to 35 seconds.

[0017] Preferably, in step S3, the multiple color printing is carried out using offset printing or flexographic printing, with 2 to 4 printing times, and each printing is followed by inter-color drying at 60 to 80°C.

[0018] Preferably, in step S4, the protective varnish is a UV-curable varnish or a water-based abrasion-resistant varnish; when a UV-curable varnish is used, the second drying and curing is performed using a UV lamp with a power of 120-200 W / cm and a curing speed of 30-70 m / min.

[0019] Preferably, in step S5, the cooling and winding process involves using a cooling roller to cool the release paper to below 35°C before winding, with the winding tension controlled between 15 and 25 N.

[0020] Compared with related technologies, the high-saturation color printing process for release paper provided by this invention has the following beneficial effects:

[0021] This invention provides a high-saturation color printing process for release paper. By precisely treating the release paper substrate with corona discharge, its surface molecular structure is effectively altered, increasing surface energy and providing a solid foundation for subsequent coating and printing. This ensures the strong adhesion of the base coating, guaranteeing high-saturation printing of the color inks. The printed images and text are vibrant, rich in color, and exhibit extremely high color reproduction and clarity, meeting the demands of products with extremely high printing quality requirements. The process involves precise setting and strict control of parameters for each step. From the power and speed of the corona discharge treatment, to the coating dryness, drying and curing temperature and time of the base coating, to the ink viscosity, printing pressure and speed, inter-color drying during the printing process, and the coating thickness and curing parameters, cooling temperature, and winding tension of the protective varnish, all are clearly specified. This refined parameter control ensures the stability of the entire printing process, significantly reducing quality problems during production and improving product consistency and yield.

[0022] The selected water-based acrylic resin primer coating material possesses excellent overall performance, bonding tightly with the release paper substrate and color inks; the color inks with high pigment toner content provide vibrant colors; and the UV-curable varnish or water-based abrasion-resistant varnish, selected according to different needs, effectively protects the color graphic layer. The selection of these high-quality materials further enhances the quality and lifespan of the printed products.

[0023] In terms of production efficiency and cost control, reasonable settings for processing speed and drying / curing time improve production efficiency and reduce production costs while ensuring processing results and printing quality. At the same time, precise coating control avoids material waste, making the entire printing process highly economical. Attached Figure Description

[0024] Figure 1 The flowchart of the high-saturation color printing process for release paper provided by the present invention. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] In the specific implementation process, such as Figure 1 As shown, a high-saturation color printing process for release paper.

[0027] This invention provides a high-saturation color printing process for release paper, comprising the following steps:

[0028] S1: Surface corona treatment of release paper substrate:

[0029] Equipment Preparation: The corona treatment equipment features precise power regulation and stable speed control. The electrode structure of the corona treatment equipment ensures uniform corona discharge, effectively treating the surface of the release paper substrate.

[0030] Parameter settings: Set the corona treatment power to 2.5–3.5 kW. Within this power range, a sufficiently strong corona discharge can be generated to alter the molecular structure of the release paper substrate surface, increasing its surface energy. If the power is too low, the desired treatment effect cannot be achieved, and the surface tension of the release paper may not meet the requirements; while if the power is too high, it may damage the release paper substrate and affect its physical properties.

[0031] The processing speed is set to 50–120 m / min. A faster processing speed can improve production efficiency, but it is necessary to ensure that the corona treatment can fully act on the surface of the release paper within a unit of time. When the processing speed is too slow, although the treatment effect may be more ideal, it will reduce the overall production efficiency and increase the production cost; when the processing speed is too fast, it may lead to uneven treatment and insufficient surface tension in some areas.

[0032] Processing Procedure: Place the release paper substrate smoothly onto the conveyor of the corona treatment equipment, ensuring the substrate remains flat during transport to avoid wrinkles or shifting. Start the corona treatment equipment and continuously process the release paper substrate according to the set power and speed. During the process, closely observe the equipment's operating status and the surface condition of the release paper substrate to ensure stable processing.

[0033] Effect Testing: The surface tension of the release paper substrate after corona treatment is tested using a surface tension tester. The surface tension should reach 40–48 dynes to ensure that the subsequent primer coating can adhere well to the release paper substrate, providing a foundation for high-saturation color printing. If the surface tension does not meet the requirements, the corona treatment parameters need to be readjusted and the treatment repeated until the standard is met.

[0034] S2: Apply a primer coating to the treated release paper substrate and perform the first drying and curing.

[0035] Primer coating material selection: Water-based acrylic resin was selected as the primer coating material. Water-based acrylic resin has good film-forming properties, adhesion, and flexibility, and can form a good bond with the release paper substrate and subsequent colored inks. At the same time, water-based coatings are environmentally friendly and pollution-free.

[0036] Coating process: The primer coating is applied using precision coating equipment. The parameters of the coating equipment are adjusted according to the specifications of the release paper and production requirements to ensure that the dry weight of the coating is controlled between 1.5 and 3.0 g / m³. 2If the dry weight of the coating is too small, the thickness of the base coat will be insufficient, failing to provide adequate adhesion and smoothness, thus affecting the printing effect of the colored inks. If the dry weight of the coating is too large, the coating may be too thick, which can easily lead to problems such as cracking and peeling, and will also increase production costs.

[0037] During the coating process, it is essential to maintain the cleanliness and stable operation of the coating equipment to ensure that the primer coating is evenly applied to the surface of the release paper substrate. The parameters of the coating equipment can be adjusted by real-time monitoring of the coating thickness and uniformity to guarantee coating quality.

[0038] First drying and curing: The release paper with the primer coating is fed into the drying and curing equipment for the first drying and curing. The drying and curing temperature is set to 90-110℃, and the time is 15-30 seconds. The water-based acrylic resin can be fully dried and cured to form a primer coating with certain strength and adhesion.

[0039] If the drying and curing temperature is too low or the time is too short, the primer coating will not be completely dried and cured, affecting its adhesion to the release paper substrate and colored inks. Conversely, if the temperature is too high or the time is too long, the primer coating may become brittle and yellow, affecting its performance and appearance. During the drying and curing process, it is essential to ensure a uniform temperature distribution within the equipment and avoid localized overheating or underheating to guarantee the quality stability of the primer coating.

[0040] S3: High-saturation colored inks are used to perform multiple color printing on the base coating layer to form a colored graphic layer.

[0041] Selection of High-Saturation Color Inks: Solvent-based inks or energy-curing inks with high pigment toner content are recommended for high-saturation color printing. Inks with high pigment toner content provide more vibrant and richer colors, meeting the requirements of high-saturation color printing. Solvent-based inks have good flowability and drying properties, allowing for rapid film formation on the base coat; energy-curing inks offer advantages such as fast curing speed and high printing accuracy. The choice can be made based on actual production needs.

[0042] Ink viscosity adjustment: Adjust the viscosity of high-saturation color inks to 25-35 seconds. Ink viscosity is one of the important factors affecting print quality. If the viscosity is too low, the ink is prone to problems such as running and spreading during the printing process, resulting in blurry images; if the viscosity is too high, it will make it difficult for the ink to transfer on the printing plate, affecting the uniformity of printing and color saturation. The viscosity of the ink can be adjusted by adding an appropriate amount of thinner or thickener to achieve the optimal printing state.

[0043] Printing method selection: Multiple-color printing can be performed using either offset or flexographic printing. Offset printing offers advantages such as high printing precision and excellent color reproduction, making it suitable for products with high print quality requirements. Flexographic printing, on the other hand, features fast printing speed and low cost, making it suitable for large-scale production. The appropriate printing method should be selected based on the specific requirements of the product and the production scale.

[0044] Printing cycles and inter-color drying: 2-4 color printing passes are performed, with each pass undergoing inter-color drying at 60-80℃ after printing. Multiple color printing passes allow for a rich variety of color effects, creating highly saturated colored images and text through the layering and mixing of different colored inks. The purpose of inter-color drying is to ensure that the inks from each print dry and solidify quickly, preventing ink mixing and smudging during subsequent printing processes, and guaranteeing the clarity and color saturation of the colored images and text.

[0045] During the printing process, parameters such as printing pressure and speed must be strictly controlled to ensure that the ink is evenly transferred to the base coating with each print. At the same time, the quality of the printing plate must be checked regularly, and ink residue and impurities on the plate must be cleaned promptly to ensure the stability and consistency of the printing process.

[0046] S4: Apply a protective varnish to the colored graphic layer and perform a second drying and curing process.

[0047] Protective varnish selection: Choose either UV-curable varnish or water-based abrasion-resistant varnish based on the product's usage environment and requirements. UV-curable varnishes offer advantages such as fast curing speed, high hardness, and good abrasion resistance, forming a robust protective film in a short time to effectively protect the colored graphic layer from external environmental erosion. Water-based abrasion-resistant varnishes are environmentally friendly and odorless, making them suitable for products with high environmental protection requirements.

[0048] Coating Process: Use suitable coating equipment to evenly apply the protective varnish onto the colored graphic layer. During coating, it is crucial to control the coating thickness to ensure the protective varnish completely covers the colored graphic layer, while avoiding excessive coating, which increases costs and hinders drying. The coating thickness can be controlled by adjusting parameters of the coating equipment, such as coating speed and blade pressure.

[0049] Second drying and curing: When using UV-curable varnish: use a UV lamp for curing. The UV lamp power should be set to 120–200 W / cm, and the curing speed to 30–70 m / min. Within this parameter range, the UV-curable varnish can rapidly absorb UV energy, undergo a polymerization reaction, and cure into a film. Too low a UV lamp power or too fast a curing speed may result in incomplete curing of the protective varnish, affecting its protective performance; too high a UV lamp power or too slow a curing speed may cause over-curing of the protective varnish, leading to a brittle film and reduced flexibility and abrasion resistance. During the UV curing process, ensure that the release paper surface is uniformly exposed to UV light to avoid uneven curing.

[0050] When using water-based abrasion-resistant varnish: it should be placed in a drying equipment for drying and curing. The drying temperature and time should be set reasonably according to the characteristics of the water-based abrasion-resistant varnish and production requirements. Generally, the drying temperature is 80-100℃ and the time is 20-40 seconds to ensure that the water-based abrasion-resistant varnish can be fully dried and cured to form a protective film with good abrasion resistance and chemical resistance.

[0051] S5: Cool and rewind the release paper after printing.

[0052] Cooling process: Cooling rollers are used to cool the released paper after printing. The cooling rollers contain a cooling medium, such as cooling water or cooling oil, which carries away the heat from the release paper through heat exchange, rapidly reducing its temperature to below 35°C. This cooling process prevents the release paper from deforming or sticking due to excessive temperature during winding, ensuring the quality and performance of the release paper.

[0053] During the cooling process, it is crucial to control the temperature and cooling rate of the cooling rollers to ensure uniform cooling of the release paper. Excessive cooling roller temperature will result in poor cooling; conversely, excessively low temperature may cause condensation on the release paper surface, affecting its quality. Simultaneously, the cooling rate must be moderate to avoid excessive internal stress in the release paper due to overly rapid cooling, which could lead to cracks.

[0054] Rewinding Process: The cooled release paper is rewound using a rewinding device. The rewinding tension is controlled between 15 and 25 N. Appropriate rewinding tension ensures neat rewinding of the release paper and prevents loose or collapsed rolls. If the rewinding tension is too low, the release paper will not be tightly rewound and is prone to unraveling during transportation and storage; if the rewinding tension is too high, the release paper may be overstretched, leading to dimensional deformation or surface wrinkles. During the rewinding process, the rewinding tension and quality should be monitored in real time, and the parameters of the rewinding device should be adjusted promptly according to the actual situation. Simultaneously, attention should be paid to the flatness and concentricity of the rewinding shaft to ensure uniform and stable rewinding of the release paper.

[0055] Quality control and testing:

[0056] Printing Quality Inspection: After each printing step, a rigorous quality inspection is conducted. High-precision color testing instruments are used to check the color saturation and color difference of the colored graphics to ensure they meet design requirements. Simultaneously, visual inspection and observation with a magnifying glass are used to check for clarity, missing strokes, smudges, and other defects in the colored graphics.

[0057] Physical performance testing: The physical performance of the printed release paper is tested, including surface tension, adhesion, abrasion resistance, and chemical resistance. Surface tension testing uses a surface tension tester to ensure that the surface tension of the release paper meets the requirements for subsequent processing and use. Adhesion testing can be performed using the cross-cut test or pull-out test to evaluate the adhesion strength between the base coating, colored graphic layer, and protective varnish layer and the release paper substrate. Abrasion resistance testing uses an abrasion testing machine to simulate the friction conditions of the release paper during actual use and test its abrasion resistance performance. Chemical resistance testing involves immersing the release paper sample in different chemical reagents and observing whether discoloration or peeling occurs on its surface to assess its resistance to chemical substances.

[0058] Process Monitoring and Recording: A process monitoring system is established throughout the entire printing process to record and monitor parameters at each step in real time. This includes the power and speed of corona treatment, the dry weight of the primer coating, drying and curing temperature and time, printing pressure and speed, ink viscosity, the coating thickness and curing parameters of the protective varnish, cooling temperature, and winding tension. By monitoring and analyzing these parameters, problems in the production process can be identified and adjusted promptly, ensuring the stability of the printing process and the consistency of product quality.

[0059] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A high-saturation color printing process for release paper, characterized in that, Includes the following steps: S1. Perform surface corona treatment on the release paper substrate to make its surface tension reach 40-48 dynes; S2. Apply a base coating to the treated release paper substrate and perform the first drying and curing. S3. High-saturation colored inks are used to perform multiple color printing on the base coating layer to form a colored graphic layer; S4. Apply a protective varnish to the colored graphic layer and perform a second drying and curing process. S5. Cool and rewind the release paper after printing.

2. The high-saturation color printing process for release paper according to claim 1, characterized in that: In step S1, the power of the corona treatment is 2.5 to 3.5 kW, and the treatment speed is 50 to 120 m / min.

3. The high-saturation color printing process for release paper according to claim 1, characterized in that: In step S2, the primer coating is a water-based acrylic resin coating with a dry coating weight of 1.5–3.0 g / m². 2 The first drying and curing temperature is 90-110℃, and the time is 15-30 seconds.

4. The high-saturation color printing process for release paper according to claim 1, characterized in that: In step S3, the high-saturation colored ink is a solvent-based ink or an energy-curing ink with a high pigment toner content, and its viscosity range is 25 to 35 seconds.

5. The high-saturation color printing process for release paper according to claim 1, characterized in that: In step S3, the multiple color printing is carried out using offset printing or flexographic printing, with 2 to 4 printing times, and each printing is followed by color drying at 60 to 80°C.

6. The high-saturation color printing process for release paper according to claim 1, characterized in that: In step S4, the protective varnish is a UV-curable varnish or a water-based abrasion-resistant varnish; when a UV-curable varnish is used, the second drying and curing is performed using a UV lamp with a power of 120-200 W / cm and a curing speed of 30-70 m / min.

7. The high-saturation color printing process for release paper according to claim 1, characterized in that: In step S5, the cooling and winding process involves using a cooling roller to cool the release paper to below 35°C before winding it up, with the winding tension controlled between 15 and 25 N.

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