A printing process based on mirror silver ink undercoating and four-color overprinting and application thereof

Abstract

The present application relates to a kind of printing process based on mirror surface silver ink undercoating and four-color overprint and its application, printing process includes the following steps: pre-press document processing: mirror surface silver ink corresponding layout is set to overprint mode, make four-color graphics and text not hollow silver bottom area;Mirror surface silver ink printing: using low particle size mirror surface silver ink on the printing material is carried out full plate solid printing to form silver ink layer, and make silver ink layer dry;Wherein, the overall particle size of low particle size mirror surface silver ink≤7.5 μm, printing density is 0.70-0.85;Four-color overprint: four-color printing is carried out on the silver ink layer after drying, using deep ink thin printing mode to control ink layer thickness, to keep mirror surface metal effect.Such, it can be while retaining strong mirror surface metal gloss Realize full and clear color presentation, effectively improve overprint production stability.

Description

Technical Field

[0001] This invention relates to the field of printing technology, and in particular to a printing process based on mirror silver ink underprinting and four-color overprinting and its application. Background Technology

[0002] As the packaging and printing industry accelerates its move towards high-end and high-quality products, the market demand for metallic finishes on printed materials continues to rise. Currently, mainstream metallic effect printing processes mainly involve hot stamping, lamination, and float silver ink printing, but all have significant drawbacks: hot stamping is costly, has low production efficiency, and struggles to achieve high-precision registration; while float silver ink can produce a mirror-like metallic effect, it suffers from poor surface adhesion, difficulties in subsequent processing such as varnishing / lamination, and is prone to defects like masking of the metallic effect, misregistration, and ink peeling when overprinted with four-color inks. Therefore, the industry urgently needs to develop a new printing efficiency-enhancing process that combines a high-gloss mirror effect, excellent color reproduction, and good processing adaptability. Summary of the Invention

[0003] Therefore, it is necessary to provide a printing process based on mirror silver ink base and four-color overprinting that combines metallic effect and color reproduction effect, has stable overprinting process and good post-processing adaptability, and its application.

[0004] A printing process based on mirror silver ink base and four-color overprinting, the printing process includes the following steps: Prepress file processing: Set the printing plate corresponding to the mirror silver ink to overprint mode so that the four-color text and images do not cut out the silver background area; Mirror silver ink printing: Low-particle-size mirror silver ink is used to form a solid silver ink layer on the substrate and then dried; the overall particle size of the low-particle-size mirror silver ink is ≤7.5μm and the printing density is 0.70-0.85. Four-color overprinting: Four-color printing is performed on the dried silver ink layer, and the ink layer thickness is controlled by a deep ink thin printing method to maintain the mirror metallic effect.

[0005] In one embodiment, the mirror silver ink includes mirror aluminum silver paste, plant-based resin binder, photoinitiator, and functional additives.

[0006] In one embodiment, the prepress document processing step further includes: setting the screen ruling to 300 LPI and the dot shape to circular; setting the screen angle to C: 15°, M: 75°, Y: 0°, K: 45°, and mirror silver spot color: 45°.

[0007] In one embodiment, the silver ink layer is dried by UV curing or natural drying, with the natural drying time being no less than 4 hours; when the silver ink layer is cured by UV, the UV lamp power is set to 160W; when natural drying is used, the ambient temperature is controlled at 23±2℃ and the humidity at 55%±5%.

[0008] In one embodiment, the printing color sequence of the four-color overprinting is K→C→M→Y; the thickness of each color ink layer is controlled as follows: K: 1.75±0.05, C: 1.40±0.05, M: 1.45±0.05, Y: 1.05±0.05.

[0009] In one embodiment, a tack reducer of ≤3% of the total ink mass is added to the four-color ink to reduce the ink viscosity; Under the conditions of 30℃, 400r / min rotation speed, and CB-50T viscosity meter testing, the viscosity control range of the inks is as follows: yellow ink 6.0~7.5Pa·s, magenta ink 8.5~9.0Pa·s, cyan ink 8.0~9.5Pa·s, and black ink 8.5~9.0Pa·s.

[0010] In one embodiment, the water tank parameters are controlled as follows during the printing process: water: dampening solution: IPA = 88:2:10; ink parameters are controlled as follows: conductivity 750~770 µs / cm, pH value 5.1~5.3, and opacity 10~12.

[0011] In one embodiment, after four-color overprinting is completed, the printing process further includes a post-processing step: applying an inline water-based varnish, a reverse process, or a lamination to the printed matter.

[0012] In one embodiment, the substrate is specifically 250g single-sided coated paper, 157g double-sided coated paper, or white cardboard. In one embodiment, when using a UV printing scheme, both mirror silver ink printing and four-color overprinting are completed in one integrated PU1 printing unit; when using a conventional offset printing scheme, mirror silver ink printing is done using a Heidelberg printing press, and four-color overprinting is done using a 705 printing press.

[0013] A printed matter, said printed matter being prepared using a printing process based on mirror silver ink underprinting and four-color overprinting as described in any of the above embodiments.

[0014] The aforementioned printing process based on mirror silver ink underprinting and four-color overprinting solves the problems of traditional metal printing processes, such as difficulty in simultaneously achieving a mirror metallic texture and color reproduction, instability in the overprinting process due to misregistration and ink peeling, and poor adaptability to subsequent processing such as varnishing and lamination. It can achieve full and clear color presentation while retaining a strong mirror metallic luster, effectively improving the stability of overprinting production. Moreover, the finished product is compatible with various post-processing treatments such as water-based varnish, reverse engineering, and lamination, thus broadening the application range of printed products.

[0015] Compared with the prior art, the present invention also has the following advantages: 1. Balancing metallic luster and color reproduction: By using the sequence of "solid base of mirror silver + overprinting of four-color thin ink", the high reflectivity of silver ink is utilized, combined with the high transparency of four-color thin ink, so that light can penetrate the colored ink layer and be reflected by the silver base, which not only achieves rich colors, but also retains a strong metallic texture, solving the problem that the metallic texture is covered by a thick ink layer in traditional processes.

[0016] 2. Significantly Improved Printing Stability and Post-Processing Adaptability: This invention uses high-reflectivity mirror silver ink as the base layer, which has strong adhesion and a smooth surface after drying. By strictly controlling registration, ink-water balance, and adopting the principle of "deep ink, thin printing," misregistration and ink peeling are effectively prevented, providing a good foundation for subsequent UV coating, lamination, and other processes, and expanding the post-processing possibilities of the product.

[0017] 3. Wide applicability and high efficiency: The process of this invention is compatible with UV printing and ordinary offset printing, and is suitable for a variety of substrates such as coated paper and white cardboard. It does not require expensive hot stamping equipment and can achieve high-quality metal-enhanced printing on ordinary multi-color offset printing machines, combining cost advantages and production efficiency. Attached Figure Description

[0018] Figure 1 This is an illustration of the printing process of a printing technology based on mirror silver ink base and four-color overprinting according to an embodiment of the present invention. Figure 2 This is a printing effect diagram of a printing process based on mirror silver ink base and four-color overprinting according to an embodiment of the present invention. Detailed Implementation

[0019] To facilitate understanding of the present invention and to make the above-mentioned objects, features, and advantages of the present invention more apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention, and preferred embodiments are shown in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention. The present invention can be implemented in many other ways different from those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention; therefore, the present invention is not limited to the specific embodiments disclosed below. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0020] A printing process based on mirror silver ink base and four-color overprinting, the printing process includes the following steps: S1: Prepress file processing: Set the plate corresponding to the mirror silver ink to overprint mode so that the four-color text and images do not cut out the silver background area; By setting the plate corresponding to the mirror silver ink to overprint mode, the four-color plates are prevented from being cut out on the silver background; the four-color graphics are set to normal output mode.

[0021] For example, the prepress file processing steps also include: setting the screen ruling to 300 LPI, the dot shape to a circular screen; and setting the screen angles to C: 15°, M: 75°, Y: 0°, K: 45°, and for the mirror silver spot color: 45°. Thus, using a 300 LPI circular screen with a fixed set of screen angles significantly improves the detail of the image and text, avoids issues like screen collisions and pattern blurring between the four-color dots and the mirror silver spot color dots, resulting in smooth color transitions while ensuring a uniform and consistent metallic luster on the silver base, thus enhancing the overall refinement and visual depth of the printed material. Setting the screen ruling to 300 LPI, the dot shape to a circular screen, and the screen angles to C: 15°, M: 75°, Y: 0°, K: 45°, and for the spot color: 45° ensures the harmony between image detail and metallic luster.

[0022] S2: Mirror silver ink printing: Low-particle-size mirror silver ink is used to form a solid silver ink layer on the substrate and then dried; the overall particle size of the low-particle-size mirror silver ink is ≤7.5μm and the printing density is 0.70-0.85. By selecting high-reflectivity mirror silver ink as the base layer, its adhesion is strong, and the surface is smooth after drying. Using low-particle-density mirror silver ink with an overall particle size ≤7.5μm for full-page solid printing results in a denser and more uniform arrangement of fine silver particles, forming a highly smooth and highly reflective mirror base. This effectively improves the uniformity of the metallic mirror gloss, avoiding issues such as rough particles and mottled reflections. Controlling the printing density within the range of 0.70~0.85 avoids both insufficient reflectivity and weak metallic texture caused by an excessively thin silver ink layer, and incomplete drying, overprinting wrinkling, and ink peeling caused by an excessively thick ink layer. Combined with complete drying of the silver ink layer, the adhesion of the silver base is significantly improved, and the surface structure is stable, providing a smooth and reliable substrate for subsequent four-color thin ink overprinting. This effectively reduces the mixing and peeling defects between the upper colored ink and the silver base, while ensuring that the reflectivity of the underlying silver layer is not damaged, laying the foundation for simultaneously achieving clear color reproduction and a strong mirror metallic effect.

[0023] For example, the mirror silver ink includes mirror aluminum silver paste, plant-based resin binder, photoinitiator, and functional additives. The mirror silver ink is formed by compounding mirror aluminum silver paste, plant-based resin binder, photoinitiator, and functional additives. The aluminum silver paste ensures a high-reflectivity mirror effect, the plant-based resin binder enhances the adhesion of the silver ink to the substrate surface, the photoinitiator is compatible with rapid UV curing, and various functional additives optimize ink leveling and drying performance, resulting in a smooth and compact silver ink layer. This avoids defects such as silver layer peeling and uneven mirror effect at the ink raw material level, providing a stable base for the upper four-color overprinting.

[0024] For example, the silver ink layer can be dried by UV curing or natural drying, with natural drying lasting no less than 4 hours. When UV curing is used, the UV lamp power is set to 160W. When natural drying is used, the ambient temperature is controlled at 23±2℃ and the humidity at 55%±5%. This dual-mode system of UV curing and natural drying adapts to different production conditions. The 160W UV lamp can quickly and completely cure the silver ink layer, shortening the production cycle. Natural drying is limited to a minimum of 4 hours, preferably at 23±2℃, ensuring the silver ink layer is thoroughly dry and preventing issues such as color mixing, ink peeling, and insufficient adhesion when overprinting four colors on an undried silver base, thus enhancing the stability of the overprinting process.

[0025] For example, the substrate is specifically 250g single-sided coated paper, 157g double-sided coated paper, or white cardboard; For example, a high-reflectivity, low-particle-size mirror silver ink is selected, whose main components include mirror aluminum silver paste, plant-based resin binder, photoinitiator, functional additives, etc. The overall particle size of the ink is ≤7.5μm, and 100% solid printing is performed on the surface of the substrate; the printing density is controlled at 0.70-0.85; UV curing or natural drying is used to ensure that the ink layer is completely dry; among which, the natural drying time is not less than 4 hours.

[0026] S3: Four-color overprinting: Four-color printing is performed on the dried silver ink layer, using a deep ink thin printing method to control the ink layer thickness in order to maintain the mirror metallic effect.

[0027] Four-color (CMYK or XCMYK) printing is performed on a completely dry mirror silver ink layer; the printing color sequence is K→C→M→Y; following the principle of "deep ink, thin printing," the thickness of the four-color ink layers is controlled. For example, the printing color sequence of the four-color overprinting is K→C→M→Y; the thickness of each color ink layer is controlled as follows: K: 1.75±0.05, C: 1.40±0.05, M: 1.45±0.05, Y: 1.05±0.05, so that it remains thin while satisfying color reproduction, so as to avoid covering the mirror effect of the underlying layer. By adopting a fixed printing color sequence of K→C→M→Y and precisely limiting the thickness of each color ink layer, following the logic of printing dark ink thinly, the thickness of dark black, cyan, and magenta is moderately controlled, while the yellow ink layer is the thinnest. This ensures complete CMYK color reproduction while minimizing the obstruction of the underlying silver mirror surface by the colored inks, achieving a balanced color saturation and high-gloss metallic texture, and further reducing the registration deviation and smudging problems caused by thick ink.

[0028] To reduce the risk of ink peeling, a tack reducer is added to the four-color inks to lower their viscosity. In one embodiment, a tack reducer of ≤3% of the total ink mass is added to the four-color inks to reduce the ink viscosity. Thus, adding no more than 3% tack reducer precisely lowers the ink viscosity to a specified range, reducing the peeling force between the upper four-color ink layer and the lower silver ink layer. This reduces the likelihood of ink peeling and ink loss defects during printing, stabilizes the overprinting yield, and allows for standardized control of ink viscosity under uniform testing conditions, resulting in higher consistency in printing effects across different batches. For example, under conditions of 30℃, 400r / min rotation speed, and CB-50T viscometer testing, the ink viscosity control range is: yellow ink 6.0~7.5Pa·s, magenta ink 8.5~9.0Pa·s, cyan ink 8.0~9.5Pa·s, and black ink 8.5~9.0Pa·s. Table 1 shows the viscosity before and after adding the tack reducer in a specific embodiment. Table 1. Effect of adding detackifiers on viscosity reduction of four-color inks

[0029]

[0030] For example, commercial ink tack removers such as Toyo TPP-043, Tiannv 8045, and Hanghua UV-08 can be selected. Alternatively, a self-made tack reducer can be made using a compound system of aluminum stearate and polymerized linseed oil. The amount added should be controlled at 1% to 3% of the total ink mass. This can adjust the viscosity of the four-color inks to the corresponding range in Table 1, effectively preventing peeling of overprinted inks.

[0031] In one embodiment, the water tank parameters are controlled during printing as follows: water: dampening solution: IPA (isopropyl alcohol) = 88:2:10; ink parameters are controlled as follows: conductivity 750~770 µs / cm, pH value 5.1~5.3, and opacity 10~12. By using a fixed ratio of dampening solution and strictly controlling the conductivity, pH value, and opacity parameters, a stable water-ink balance is achieved during the printing process. This avoids excessive water causing silver ink blooming or insufficient water causing ink buildup and smudged printing plates, ensuring uniform solid silver, accurate reproduction of four-color halftone dots, reducing registration defects, and improving overall process controllability.

[0032] In one embodiment, after four-color overprinting, the printing process further includes post-processing steps: applying inline water-based varnish, reverse processing, or lamination to the printed material. Thus, after four-color overprinting, various post-finishing processes such as water-based varnish, reverse processing, and lamination can be directly performed. Thanks to the excellent adhesion of the underlying silver ink, bubbling, delamination, and peeling will not occur during post-processing, expanding the deep processing options for printed materials, meeting the diverse surface treatment needs of high-end packaging, and enhancing product added value.

[0033] In one embodiment, when using a UV printing solution, both mirror silver ink printing and four-color overprinting are completed in an integrated PU1 printing unit; when using a conventional offset printing solution, mirror silver ink printing uses a Heidelberg printing press, and four-color overprinting uses a 705 printing press. This allows for both high-speed inline UV mass production and low-cost production using existing conventional offset printing equipment, demonstrating strong equipment adaptability and flexibility to different factory production conditions.

[0034] The aforementioned printing process based on mirror silver ink underprinting and four-color overprinting solves the problems of traditional metal printing processes, such as difficulty in simultaneously achieving a mirror metallic texture and color reproduction, instability in the overprinting process due to misregistration and ink peeling, and poor adaptability to subsequent processing such as varnishing and lamination. It can achieve full and clear color presentation while retaining a strong mirror metallic luster, effectively improving the stability of overprinting production. Moreover, the finished product is compatible with various post-processing treatments such as water-based varnish, reverse engineering, and lamination, thus broadening the application range of printed products.

[0035] A printed matter, said printed matter being prepared using a printing process based on mirror silver ink underprinting and four-color overprinting as described in any of the above embodiments.

[0036] Compared with the prior art, the present invention also has the following advantages: 1. Balancing metallic luster and color reproduction: By using the sequence of "solid base of mirror silver + overprinting of four-color thin ink", the high reflectivity of silver ink is utilized, combined with the high transparency of four-color thin ink, so that light can penetrate the colored ink layer and be reflected by the silver base, which not only achieves rich colors, but also retains a strong metallic texture, solving the problem that the metallic texture is covered by a thick ink layer in traditional processes.

[0037] 2. Significantly Improved Printing Stability and Post-Processing Adaptability: This invention uses high-reflectivity mirror silver ink as the base layer, which has strong adhesion and a smooth surface after drying. By strictly controlling registration, ink-water balance, and adopting the principle of "deep ink, thin printing," misregistration and ink peeling are effectively prevented, providing a good foundation for subsequent UV coating, lamination, and other processes, and expanding the post-processing possibilities of the product.

[0038] 3. Wide applicability and high efficiency: The process of this invention is compatible with UV printing and ordinary offset printing, and is suitable for a variety of substrates such as coated paper and white cardboard. It does not require expensive hot stamping equipment and can achieve high-quality metal-enhanced printing on ordinary multi-color offset printing machines, combining cost advantages and production efficiency.

[0039] The present application will be further described below with reference to specific embodiments.

[0040] Example 1: UV printing process, substrate: 250g single-sided coated cardstock Prepress file processing: Set the mirror silver spot color plate to overprint mode, and do not cut out the silver background area for the four-color graphics; add a screen ruling of 300 LPI, and select round dots; set the screen angles as follows: C: 15°, M: 75°, Y: 0°, K: 45°, and mirror silver spot color: 45°.

[0041] Mirror silver ink printing: Mirror silver ink with an overall particle size ≤7.5μm (components include mirror aluminum silver paste, plant-based resin binder, photoinitiator and functional additives) is selected and printed solidly on 250g single-sided coated cardstock with a printing density controlled at 0.75; UV curing is completed using a 160W UV lamp to form a dry silver ink layer.

[0042] Four-color overprinting: The PU1 printing unit is used to complete the four-color overprinting in one unit, with the printing color sequence K→C→M→Y; the thickness of each ink layer is: K: 1.75±0.05, C: 1.40±0.05, M: 1.45±0.05, Y: 1.05±0.05; 2% of the total ink mass of Toyo TPP-043 tack remover is added to the four inks. Under the conditions of 30℃, 400r / min and CB-50T viscometer, the viscosity of yellow ink is 6.0~7.5Pa·s, magenta ink is 8.5~9.0Pa·s, cyan ink is 8.0~9.5Pa·s, and black ink is 8.5~9.0Pa·s.

[0043] Water and ink control for printing: Water tank ratio: dampening solution: isopropanol (IPA) = 88:2:10; conductivity 750~770µs / cm, pH value 5.1~5.3, opacity 10~12; workshop ambient temperature 21~25℃, relative humidity 50%~60%.

[0044] Post-processing: After printing, apply water-based varnish.

[0045] Finished product: The mirror-like metallic luster is uniform and bright; all four colors are richly reproduced; the cross-cut adhesion test shows a 5B rating; there is no ink peeling or bubbling during lamination; production efficiency is high. Printing effect is as follows... Figure 1 and Figure 2 Figure 1 is a schematic diagram of the metallic silver plate corresponding to Embodiment 1 of the present invention. It is a solid outline plate of mirror silver spot color made before printing, which is used to form the silver ink base layer for full-page printing. Figure 2 is a CMYK + mirror silver printing finished product effect diagram obtained by using mirror silver ink base and four-color overprinting process in Embodiment 1 of the present invention. It can simultaneously present a uniform mirror metallic texture and high-fidelity color graphics.

[0046] Example 2: Ordinary offset printing process, substrate: 157g coated paper Prepress file processing: Set the mirror silver spot color plate to overprint mode, and do not cut out the silver background area for the four-color graphics; add a screen ruling of 300 LPI, and select round dots; set the screen angles as follows: C: 15°, M: 75°, Y: 0°, K: 45°, and mirror silver spot color: 45°.

[0047] Mirror silver ink printing: Mirror silver ink with an overall particle size ≤7.5μm (components include mirror aluminum silver paste, plant-based resin binder, photoinitiator, and functional additives) is selected and printed solidly on 157g coated paper with a printing density controlled at 0.78. It is then naturally dried for 4.5 hours at 23±2℃ and 55%±5% humidity to obtain a fully dried silver ink layer. The mirror silver printing process uses a Heidelberg printing press.

[0048] Four-color overprinting: Four-color overprinting was carried out using a 705 printing press, with the printing color sequence K→C→M→Y; the thickness of each ink layer was: K: 1.75±0.05, C: 1.40±0.05, M: 1.45±0.05, Y: 1.05±0.05; 2.5% of the total ink mass of Tiannv 8045 tack remover was added to the four-color inks. Under the conditions of 30℃, 400r / min, and CB-50T viscometer, the viscosity of the four-color inks fell within the viscosity range corresponding to the addition in Table 1.

[0049] Water and ink control for printing: Water tank ratio: dampening solution: isopropanol (IPA) = 88:2:10; conductivity 750~770µs / cm, pH value 5.1~5.3, opacity 10~12; workshop ambient temperature 21~25℃, relative humidity 50%~60%.

[0050] Post-processing: Lamination is performed after printing.

[0051] Finished product effect: The mirror-like reflection is uniform and without mottles, and the color graphics are clear and layered; there is no misregistration or ink peeling during overprinting, and no delamination or peeling during post-processing lamination. It can be adapted to mass production in conventional offset printing workshops.

[0052] Comparative Example

[0053] When using traditional floating silver ink as a base and then printing four colors, the metallic feel of the finished product is significantly weakened due to the relatively thick ink layer of the four colors; and because the floating silver ink has poor adhesion, bubbling and peeling occur during the lamination process.

[0054] In comparison, the process of this invention has significant advantages in terms of preserving the metallic texture and adaptability to post-processing.

[0055] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be noted that the terms "in one embodiment," "for example," and "as in another example" in this application are intended to illustrate the application and are not intended to limit the application.

[0056] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A printing process based on mirror silver ink base and four-color overprinting, characterized in that, The printing process includes the following steps: Prepress file processing: Set the printing plate corresponding to the mirror silver ink to overprint mode so that the four-color text and images do not cut out the silver background area; Mirror silver ink printing: Low-particle-size mirror silver ink is used to form a solid silver ink layer on the substrate and then dried; the overall particle size of the low-particle-size mirror silver ink is ≤7.5μm and the printing density is 0.70-0.

85. Four-color overprinting: Four-color printing is performed on the dried silver ink layer, and the ink layer thickness is controlled by using a deep ink thin printing method to maintain the mirror metallic effect.

2. The printing process according to claim 1, characterized in that, The mirror silver ink comprises mirror aluminum silver paste, plant-based resin binder, photoinitiator, and functional additives.

3. The printing process according to claim 1, characterized in that, The prepress document processing steps also include: setting the screen ruling to 300 LPI, the dot shape to circular; and setting the screen angle to C: 15°, M: 75°, Y: 0°, K: 45°, and mirror silver spot color: 45°.

4. The printing process according to claim 1, characterized in that, The silver ink layer is dried by UV curing or natural drying, with the natural drying time being no less than 4 hours. When the silver ink layer is cured by UV, the UV lamp power is set to 160W. When natural drying is used, the ambient temperature is controlled at 23±2℃ and the humidity at 55%±5%.

5. The printing process according to claim 1, characterized in that, The printing color sequence of the four-color overprinting is K→C→M→Y; the thickness of each color ink layer is controlled as follows: K: 1.75±0.05, C: 1.40±0.05, M: 1.45±0.05, Y: 1.05±0.

05.

6. The printing process according to claim 5, characterized in that, Add a tack reducer of ≤3% of the total ink mass to the four-color ink to reduce ink viscosity; Under the conditions of 30℃, 400r / min rotation speed, and CB-50T viscosity meter testing, the viscosity control range of the inks is as follows: yellow ink 6.0~7.5Pa·s, magenta ink 8.5~9.0Pa·s, cyan ink 8.0~9.5Pa·s, and black ink 8.5~9.0Pa·s.

7. The printing process according to claim 1, characterized in that, During the printing process, the water tank parameters are controlled as follows: water: dampening solution: IPA = 88:2:10; the ink parameters are controlled as follows: conductivity 750~770 µs / cm, pH value 5.1~5.3, and opacity 10~12.

8. The printing process according to claim 1, characterized in that, After completing the four-color overprinting, the printing process also includes post-processing steps: applying inline water-based varnish, reverse process, or lamination to the printed matter.

9. The printing process according to claim 1, characterized in that, The printing substrate is specifically 250g single-sided coated paper, 157g double-sided coated paper, or white cardboard. And / or, when using the UV printing solution, both mirror silver ink printing and four-color overprinting are completed in one PU1 printing unit; when using the ordinary offset printing solution, mirror silver ink printing is done using a Heidelberg printing press, and four-color overprinting is done using a 705 printing press.

10. A printed matter, characterized in that, The printed matter is prepared using the printing process described in any one of claims 1 to 9, which is based on mirror silver ink base and four-color overprinting.

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