A method of flexographic printing of a tactile ink

Abstract

A method for inline offset flexographic printing of tactile ink involves using an offset color printing unit to print a base color on the surface of a paper packaging box, followed by two or more flexographic printing steps to print the tactile ink onto the paper packaging box, resulting in a tactile ink thickness of ≥6μm on the packaging box surface. After finishing the paper packaging box using this method, the surface exhibits a matte gloss effect, and a subtle velvety feel can be detected by touch, enhancing the packaging box's aesthetics. Compared to single-pass printing of tactile ink, this invention uses a two-step flexographic printing process, improving the leveling effect of the tactile ink on the paper packaging box surface, increasing the ink thickness, and effectively reducing the accumulation of tactile ink during printing due to increased ink thickness and viscosity. Inline production results in less product deformation, smoother subsequent processes, and improved efficiency and product yield in later stages.

Description

Technical Field

[0001] This invention relates to the field of packaging printing, and in particular to a method for offset flexographic inline printing of tactile inks for tobacco packaging boxes. Background Technology

[0002] Currently, the main surface finishing techniques for printed paper packaging boxes are varnishing and lamination. These techniques aim to enhance the gloss of the box surface and prevent scratches on the printed graphics. Existing varnishing processes can be performed inline on multi-color printing presses or applied separately after the graphics printing. However, this approach suffers from a limited range of surface finishing effects. Therefore, tactile inks have been developed to enhance the velvety feel of the printed paper box surface.

[0003] Based on the classification of printing plates, traditional printing can be divided into four types: letterpress printing, gravure printing, screen printing, and offset printing. Currently, most tactile ink printing processes utilize screen printing and gravure printing. When tactile ink printing is required on offset products, a combination of offset printing followed by gravure or screen printing is necessary. This involves two processes and requires two sets of printing equipment, resulting in significant manpower and equipment investment. Furthermore, screen printing for tactile ink products suffers from numerous printing defects, such as significant paper deformation after multiple processes, leading to unsatisfactory hot stamping, embossing, and die-cutting effects; screen clogging is also common, resulting in low production efficiency. Tactile inks with a good velvet feel are water-based and hot-air drying inks, making them prone to clogging when using screen or gravure printing, resulting in low production efficiency and high quality risks.

[0004] CN108059874A discloses a tactile effect ink and its surface finishing process for paper packaging boxes. The tactile effect ink is printed on the surface of the paper packaging box, including the following steps: 1) printing a base color on the surface of the paper packaging box; using offset printing or other printing methods known to those skilled in the art; 2) printing patterns and text on the surface of the paper packaging box obtained in step 1); 3) applying the aforementioned tactile effect ink to the surface of the paper packaging box obtained in step 2) using a UV offset printing machine; 4) drying and curing the tactile effect ink obtained in step 3) using an ultraviolet curing device. This process is prone to issues such as leveling deviations in the applied tactile effect ink, incomplete surface printing, insufficient ink layer thickness, and ink piling if the tactile ink finishing area has halftone patterns or perforated lines with a width less than 0.5 mm.

[0005] Currently, printing professionals primarily improve the leveling properties of tactile inks by adjusting their formulations, thereby meeting the demands of offset and flexographic printing. For example, CN202210049384.0 discloses an offset tactile oil and its preparation method, which utilizes glycol ethers and surfactants to improve the leveling properties of the tactile oil on offset printing presses and shorten drying time. Because most offset printing units in China typically only have one flexographic printing unit, and the investment cost for customized configurations of printing equipment is high, technical personnel have developed a technical bias that "improving existing offset printing equipment and processes is difficult." Summary of the Invention

[0006] The technical problem this invention aims to solve is as follows: Based on the special requirement of tobacco paper packaging boxes for a thick and substantial feel, and combined with the company's printing technology and equipment (the offset printing press is equipped with two sets of flexographic printing presses), the applicant proposes an improved solution for the process of offset flexographic inline printing of tactile inks. This solution overcomes the technical difficulties of leveling deviation and thin ink layer in existing offset flexographic inline printing of tactile inks, and provides a method for offset flexographic inline printing of tactile inks that is simple to operate, has a good decorative effect, and does not require fine engraving in the tactile finishing area.

[0007] The technical solution adopted by this invention to solve its technical problem is:

[0008] A method for offset flexographic inline printing of tactile ink involves using an offset color printing unit to print a base color on the surface of a paper packaging box, and then using a flexographic printing unit to print tactile ink on the paper packaging box in two or more passes, so that the thickness (D) of the tactile ink on the surface of the packaging box is ≥6μm.

[0009] Traditional tactile inks, produced using screen printing or gravure printing, can achieve a thickness of 7-11 μm. In contrast, traditional offset flexographic printing uses varnish, typically 2-3 μm thick. A single pass of tactile ink can only reach about 3 μm. If the tactile ink is too thick, ink buildup occurs, failing to achieve the desired substantial feel for tobacco packaging. Therefore, to ensure product quality, the applicant has improved the existing offset flexographic tactile ink process by applying it in two or more passes to the paper packaging. The tactile ink is printed on the box, thereby improving the adhesion thickness of the tactile ink and solving the technical problems of ink accumulation or incomplete printing of single sets of tactile ink in existing offset flexographic inline printing. It can achieve printing effects comparable to traditional screen printing or gravure printing of tactile ink (including the thickness of the printed tactile ink and the appearance of the product, such as thickness, matte gloss, etc.). However, compared with the traditional offset base color + screen / gravure printing of tactile ink process, it simplifies the printing process, shortens the printing cycle, and makes it easier for operators to check the product colors, significantly improving production efficiency.

[0010] Preferably, a flexographic printing press is used to print tactile ink on the paper packaging box in 2 to 4 passes.

[0011] The thickness (D) of the tactile ink on the surface of the packaging box is 6~11μm.

[0012] A method for in-line offset flexographic printing of tactile inks includes the following steps:

[0013] 1) Use an offset printing press color printing unit to print the base color on the surface of the paper packaging box and then dry it;

[0014] 2) The substrate after color printing in step 1) is transferred to the first flexographic printing unit for the first printing of tactile ink. The amount of tactile ink used for the first printing is 1 / 2D to 2 / 3D of the total amount, and then dried.

[0015] 3) The substrate from step 2) is then transferred to the second flexographic printing unit for reprinting tactile ink. The amount of tactile ink used for the reprint is 1 / 3D to 1 / 2D of the total amount. Then it is dried.

[0016] A further improvement involves using a resin plate for the tactile ink printing, with the tactile effect finishing area on the plate being solid.

[0017] In a further improvement, in steps 2) and 3), the tactile ink finishing area only includes coarse perforated lines or solids with a width greater than or equal to 0.5 mm. The method also includes, in step 4), after reprinting the tactile ink, the UV gloss finishing area (i.e., the area that does not require tactile ink finishing) is then printed with UV gloss using a screen with a mesh size greater than or equal to 450 mesh (preferably, a screen with a mesh size of 450~550 mesh). The UV gloss finishing area includes halftone patterns and / or fine lines with a width less than 0.5 mm, thereby avoiding the effect of ink accumulation at the perforated areas of the resin plate when printing fine lines or halftones on a flexographic printing press, which would reduce the aesthetic appearance of the paper packaging box.

[0018] In one exemplary embodiment, the viscosity of the initial tactile ink and the re-printed tactile ink is 100~120s (measured at room temperature using a Zahn cup No. 4).

[0019] The flexographic printing press unit includes a conveying device, a doctor blade, an anilox roller, a printing plate roller with a resin plate, and an impression cylinder. The conveying device is installed below the impression cylinder to convey the substrate onto the impression cylinder. The doctor blade and printing plate roller are installed on both sides of the anilox roller, and the printing plate roller is installed above the impression cylinder. The doctor blade transfers tactile ink through the anilox roller onto the resin plate covering the printing plate roller. Then, under the action of the impression cylinder, the tactile ink on the resin plate is transferred to the substrate. The doctor blade includes a blade holder and a blade. The blade holder is a frame with an ink storage cavity inside, and the blade is fixed on the blade holder facing the ink storage cavity. An ink inlet / outlet device communicating with the ink storage cavity is provided on the back of the blade holder. The ink inlet / outlet device includes an ink inlet pipe, an ink outlet pipe, and a suction pump. The ink inlet pipe is connected to multiple ink inlets located at the bottom of the ink storage chamber via a four-way connector. The diameter of the four-way connector decreases from the main pipe of the ink inlet pipe to the first branch pipe in the middle of the ink storage chamber to the second branch pipes at both ends of the ink storage chamber, preferably in a 3:2:1 ratio. For example, the diameter of the four-way connector connected to the main pipe of the ink inlet pipe is ∅30mm, the diameter of the four-way connector connected to the first branch pipe in the middle of the ink storage chamber is ∅20mm, and the diameter of the four-way connector connected to the second branch pipe at both ends of the ink storage chamber decreases. The second branch pipe connected to both ends of the ink storage chamber has a diameter of ∅10mm. This allows the pressure of the tactile ink flowing from the main pipe to the first branch pipe connected to the ink storage chamber to be greater than the pressure of the second branch pipe connected to both ends of the ink storage chamber. This causes the tactile ink to flow from the middle to both ends and smoothly return to the oil storage tank from the outlets at both ends, facilitating the uniform distribution of ink within the ink storage chamber. One end of the ink discharge pipe is connected to the ink outlet located at the top of the ink storage chamber, and the other end is connected to a suction pump or ink storage tank via a connecting pipe.

[0020] The anilox roller is a linear spiral anilox roller, that is, the cells of the anilox roller are in the shape of a spiral groove. The anilox roller has a line count of 100 to 120 lines and an ink load of 16 to 20 grams. It is not easy for the plate to dry out and improves the transfer effect.

[0021] The beneficial effects of this invention's method for in-line offset flexographic printing of tactile inks are as follows:

[0022] 1) Compared to the traditional separate printing process of printing tactile ink on the surface of paper packaging boxes using offset printing followed by gravure printing or screen printing, this invention reduces one printing step (screen printing or gravure printing), lowers production costs, shortens delivery time, better meets customer delivery needs, achieves energy saving and emission reduction, is more environmentally friendly, saves investment in gravure or screen printing equipment for tactile ink, improves the effective utilization rate and production efficiency of offset printing equipment, and reduces the labor intensity of workers; at the same time, compared to the single-pass printing process of tactile ink, this invention performs step-by-step offset printing in two or more passes through a flexographic printing press, resulting in less heat exposure and deformation of the paper, smoother paper feeding during post-processing, better hot stamping, embossing, and die-cutting effects, and improved leveling effect of tactile ink on the surface of paper packaging boxes, resulting in higher and more stable product quality, lower quality risk, and effectively avoiding the accumulation of tactile ink due to high ink viscosity during the printing process;

[0023] 2) Products produced in the production line have less deformation, and subsequent processes are smoother, which improves the efficiency of subsequent processes and the output rate of products;

[0024] 3) After finishing paper packaging boxes using the offset flexographic inline printing tactile ink method of the present invention, the surface of the packaging box presents a matte gloss effect, and the surface of the packaging box can be felt with a slight velvet texture when touched, which improves the aesthetics of the packaging box.

[0025] 4) Print tactile ink in multiple steps, and then use a high mesh (mesh ≥ 450 mesh) screen to print UV gloss on the gloss finishing area with halftone patterns or fine line patterns with a width of less than 0.5mm. This improves the fineness and aesthetics of the product, and solves the problem that tactile ink cannot show the exquisite halftone layer and fine lines in small hollow areas. Attached Figure Description

[0026] Figure 1 —Comparative images of products printed using the methods described in Comparative Example 1, Comparative Example 2, and Example 1, wherein (a) —Product image printed in Comparative Example 1; (b) —Product image printed in Comparative Example 2; (c) —Product image printed in Example 1;

[0027] Figure 2 —A magnified comparison image of the white crane portion of the printed product using the methods described in Example 2 and Example 1;

[0028] Figure 3 —This is a structural diagram of the offset resin plate used in the method of offset flexographic printing of tactile ink in Example 1, wherein (a) —the overall front view of the resin plate, (b) —an enlarged schematic diagram of a printing unit of the resin plate, 1. the hollow area, 2. the solid area.

[0029] Figure 4—A front view of a doctor blade used in Example 1, which describes a method for in-line offset flexographic printing of tactile inks.

[0030] Figure 5 —A rear view of a squeegee used in an offset flexographic inline printing method for tactile inks, as described in Example 1;

[0031] Among them, 3, knife holder, 4, blade, 5, ink storage chamber, 6, four-way valve, 7, ink inlet, 8, ink outlet, 9, suction pump, and 10, ink storage tank;

[0032] Figure 6 —A structural diagram of the offset printing resin plate used in Example 2, a method for in-line offset flexographic printing of tactile ink;

[0033] Figure 7 —A structural diagram of the screen printing varnish plate used in Example 2, a method for in-line offset flexographic printing of tactile ink;

[0034] Figure 8 —A product image printed using a method for in-line offset flexographic printing of tactile inks as described in Example 2;

[0035] Figure 9 —A magnified comparison image of the white crane portion of the printed product produced by the method described in Examples 1 and 2;

[0036] Figure 10 —A product image printed using a method for printing tactile inks using offset flexographic inline printing as described in Example 3. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] The tactile ink used in this invention is a water-based UV offset printing flocking tactile ink purchased from Huizhou Fuliante New Materials Co., Ltd., with product model SG-339-1.

[0039] Comparative Example 1

[0040] A method for offset flexographic inline printing of tactile inks involves using an offset color printing press to print a base color on the surface of a paper packaging box. The printed product (taking a premium third-generation cigarette packaging box as an example) exhibits... Figure 1 - (a) is shown.

[0041] Comparative Example 2

[0042] A method for in-line offset flexographic printing of tactile ink involves using an offset color printing unit to print a base color on the surface of a paper packaging box, followed by a flexographic printing unit to print tactile ink onto the paper packaging box in a single pass. The amount of tactile ink used is 6μm. The printed product (taking a premium third-generation cigarette packaging box as an example) shows... Figure 1 - (b) is shown. Example 1

[0043] Reference Figure 1 - (c) A method for in-line offset flexographic printing of tactile inks according to this embodiment includes the following steps:

[0044] 1) Use an offset printing press color printing unit to print the base color on the surface of the paper packaging box and then dry it;

[0045] 2) The substrate after color printing in step 1) is transferred to the first flexographic printing unit for the first printing of tactile ink. The amount of tactile ink used for the first printing is 4μm, which is 2 / 3 of the total amount D 6μm, and then dried.

[0046] 3) The substrate from step 2) is then transferred to the second flexographic printing unit for reprinting of tactile ink. The amount of tactile ink used for the reprint is 2μm, which is 1 / 3D of the total amount D 6μm. Then it is dried.

[0047] In steps 2-3), the specific drying operation is as follows: the drying system of hot air, infrared and UV lamps is turned on at the same time, and the cold air is increased in the paper collection section.

[0048] Reference Figure 3 The printing plate for the tactile ink is a resin plate, and the tactile effect areas on the printing plate are solid. For example, in this embodiment, the border, "Baisha Tobacco," and other elements in the resin plate of the printed premium third-generation cigarette packaging box are solid.

[0049] The areas featuring "baisha and its patterns" and "crane patterns" are hollowed out. The tactile ink finishing area only includes thick hollowed-out lines with a width of 0.5mm or greater and solid areas; the rest are solid. Figure 3 The white part is the cut-out area, with a depth of about 0.8mm, and the black part is the solid area. The tactile ink is printed onto the paper packaging box through the solid area.

[0050] The viscosity of the initial tactile ink and the reprinted tactile ink is 100s (measured at room temperature using a Zahn cup No. 4).

[0051] See Figure 4 and Figure 5The flexographic printing press unit includes a conveying device, a doctor blade, an anilox roller, a printing plate roller with a resin plate, and an impression cylinder. The conveying device is installed below the impression cylinder to convey the substrate onto the impression cylinder. The doctor blade and printing plate roller are installed on both sides of the anilox roller, and the printing plate roller is installed above the impression cylinder. The doctor blade transfers tactile ink through the anilox roller onto the resin plate covering the printing plate roller. Then, under the action of the impression cylinder, the tactile ink on the resin plate is transferred to the substrate. The doctor blade includes a blade holder and a blade. The blade holder is a frame with an ink storage cavity inside, and the blade is fixed on the blade holder facing the ink storage cavity. An ink inlet / outlet device communicating with the ink storage cavity is provided on the back of the blade holder. The ink feeding device includes an ink feed pipe, an ink discharge pipe, and a suction pump. The ink feed pipe is connected to multiple ink inlets located at the bottom of the ink storage chamber via a four-way connector. The diameter of the main pipe of the four-way connector and the ink feed pipe is ∅30mm. The diameter of the first branch pipe in the middle of the ink storage chamber is ∅20mm. The diameter of the second branch pipe at both ends of the ink storage chamber is ∅10mm. This design ensures that the pressure of the tactile ink flowing from the main pipe to the first branch pipe connected to the ink storage chamber is greater than the pressure of the second branch pipe connected to both ends of the ink storage chamber. This allows the tactile ink to flow from the middle to both ends and smoothly return to the oil storage tank from the outlets at both ends, facilitating uniform distribution of the ink within the ink storage chamber. One end of the ink discharge pipe is connected to the ink outlet located at the top of the ink storage chamber, and the other end is connected to the suction pump or the ink storage tank via a connecting pipe.

[0052] The anilox roller is a linear spiral anilox roller, meaning the cells of the anilox roller are grooved spirally, which makes the plate less prone to drying and improves the transfer effect. The applicant improved the structure of the flexographic printing unit, increasing the resin plate cleaning frequency from 1000 impressions / cycle to 12000 impressions / cycle compared to the original offset printing unit.

[0053] Products printed using the offset flexographic inline printing method for tactile inks in this embodiment (taking a premium third-generation cigarette box as an example) are as follows: Figure 1 - (c) is shown.

[0054] and Figure 1 -(a) compared to, Figure 1 -(b) and Figure 1 - (c) Products printed with tactile inks have a more matte finish and a subtle velvety feel when touched.

[0055] Compare again Figure 1 -(b) and Figure 1 -(c) Figure 1 - (b) The product surface in the picture has ink buildup, and the edges of the hollowed-out pattern are not printed properly (as shown in the picture, the tip of the crane's wing, "Baisha and its pattern", and the border; see the attached document for details). Figure 3The phenomenon shown is the hollowed-out area in the resin plate. Figure 2 The printed sample of Comparative Example 2 shown below shows ink marks on the head and wingtips of the crane, indicating that the printing at the edges of the stencil pattern is incomplete and ink has accumulated. Figure 1 - (c) The product surface is smooth and clean, with a substantial feel. By printing tactile ink in two layers, the tactile ink spreads more evenly on the paper packaging box after offset printing, preventing ink buildup. See details... Figure 2 The enlarged view above clearly shows the outline of the crane's head and wingtips, with no ink buildup. The method of this invention dries the tactile ink between the two printing processes, avoiding adhesion caused by incomplete drying during printing or re-sticking due to a soft resin feel after complete drying. This improves the adhesion strength of the second tactile ink. The two tactile inks overlap, resulting in a more uniform distribution of tactile ink on the surface of the paper packaging box. This solves the technical problem of low opacity and poor leveling properties of tactile inks affecting the effect of offset printing on printed materials such as cigarette packaging boxes that require a heavy feel.

[0056] The method of offset flexographic inline printing of tactile inks in this embodiment, compared with traditional screen printing or gravure printing, reduces production costs, shortens printing cycles and product delivery times, and can better meet customer delivery requirements; it improves the effective utilization rate and production efficiency of offset printing equipment; offset flexographic inline printing of tactile inks reduces paper heat exposure and deformation, makes paper feeding smoother during post-processing, and improves the effects of hot stamping, embossing, and die-cutting, thereby improving product quality and product quality stability, and increasing output by 4-5%.

[0057] Compared to the traditional offset printing process of base color and screen printing ink, after offset printing the base color and then screen printing the tactile ink, it is necessary to compare it with the customer's standard sample on the offset printing machine to see if the offset base color needs adjustment. The offset flexographic inline printing method for tactile ink allows for direct proofreading after offset printing, which is convenient for operators to check the hue and improves printing efficiency. It also greatly reduces the batch color deviation products caused by the inability to detect color deviation problems of offset base color in the non-inline screen printing of tactile ink in time.

[0058] The applicant applied the offset flexographic inline printing method for tactile inks of this embodiment to actual production for one year. Compared with the original combined offset and screen printing process, the main improvements include:

[0059] 1. Improvement in output rate when using offset flexographic inline printing with tactile inks

[0060] (1) In 2022, the output rate of inline printing was 98.19%, which is 4.39% higher than the output rate of non-inline printing of 93.8% in 2021.

[0061] 2. Improved production efficiency and cost savings in each step of the offset flexographic inline printing tactile ink process.

[0062] (1) In 2022, the efficiency of offset flexographic printing tactile inks was 52,100 impressions / shift. In 2021, the average efficiency of offset + screen printing non-linear printing tactile inks was 31,100 impressions / shift, representing an efficiency increase of 67.5%.

[0063] (2) The use of offset flexographic printing for tactile inks directly eliminates the screen printing process, saving 1270.99 screen printing shifts per year based on production volume.

[0064] (3) In 2022, the production efficiency of the embossing process for offset flexographic inline printing tactile ink products was 30,300 impressions / shift. The average production efficiency of the embossing process for offset + screen printing non-inline printing tactile ink products last year was 22,900 impressions / shift, representing an efficiency increase of 32.3%.

[0065] (4) In 2022, the production efficiency of the die-cutting process for offset flexographic inline printing tactile ink products was 29,000 impressions / shift, while in 2021, the average production efficiency for offset + screen printing non-inline printing tactile ink products was 23,000 impressions / shift, representing an efficiency increase of 36.09%.

[0066] (5) In 2022, the production efficiency of the inspection process for offset flexographic inline printing tactile ink products was 438,000 units / shift, while in 2021, the average production efficiency of offset + screen printing non-inline printing tactile ink products was 284,000 units / shift, representing an efficiency increase of 51%.

[0067] 3. The production of tactile inks using offset printing + screen printing non-linear printing requires printing a clear varnish to increase the adhesion of the tactile ink on the screen. However, by using offset flexographic inline printing tactile ink production process, the clear varnish is not required, directly saving the cost of the clear varnish. Example 2

[0068] This embodiment of a method for in-line offset flexographic printing of tactile inks includes the following steps:

[0069] 1) Use an offset printing press color printing unit to print the base color on the surface of the paper packaging box and then dry it;

[0070] 2) The substrate after color printing in step 1) is transferred to the first flexographic printing unit for initial printing of tactile ink. The amount of tactile ink used for the initial printing is 4μm, that is, 2 / 3 of the total amount D (6μm). The tactile ink finishing area only includes solid or coarse hollow lines with a width greater than or equal to 0.5mm, and then it is dried.

[0071] 3) The substrate from step 2) is then transferred to the second flexographic printing press for reprinting tactile ink. The amount of tactile ink used for the reprint is 2μm, which is 1 / 3 of the total amount D 6μm. The tactile ink finishing area only includes solid areas or coarse hollow lines with a width greater than or equal to 0.5mm. Then it is dried.

[0072] 4) The substrate from step 3) is transferred to a 500-mesh screen printing machine to print a layer of UV varnish. The UV varnish finishing area includes dots and lines with a width of less than or equal to 0.5 mm. The substrate is then dried.

[0073] Reference Figure 6 The printing plate for the tactile ink is a resin plate, and the tactile effect areas on the printing plate are solid. For example, in this embodiment, the border, "Baisha Tobacco," and other elements in the resin plate of the printed premium third-generation cigarette packaging box are solid.

[0074] The "baisha and its pattern" are solid, except for the crane in this pattern, which is openwork. Everything else is solid. Figure 4 The white part is the cut-out area, with a depth of about 0.8mm, and the black part is the solid area. The tactile ink is printed onto the paper packaging box through the solid area.

[0075] Reference Figure 7 The UV gloss varnish decoration on the varnish plate includes the dot pattern on the packaging box and lines with a width of less than 0.5mm. After the tactile ink is printed again, a high mesh (mesh count ≥ 450 mesh) screen UV gloss varnish is used for printing. This avoids the effect of ink accumulation at the cutout areas of the resin plate affecting the overall decoration when printing finer lines or dots on a flexographic printing press, thus reducing the aesthetic appearance of the paper packaging box.

[0076] The viscosity of the initial tactile ink and the reprinted tactile ink is 100s (measured at room temperature using a Zahn cup No. 4).

[0077] The flexographic printing unit is the same as in Example 1. Its tactile ink printing uses a resin plate with the following structure: Figure 6 As shown, the screen printing plate used for UV gloss varnish printing has the following structure: Figure 7 As shown.

[0078] The products printed by the method described in Example 2 are as follows: Figure 8 As shown, compared with the product printed by the method described in Example 1, the fineness of offset flexographic printing followed by screen printing of varnish is higher, especially in the presence of fine lines and fine meshes in the printed pattern, such as the head and wing patterns of the crane and the border lines of the cigarette packaging box printed in this example, which have a line width of less than 0.5mm, thus meeting the requirements for high-precision products.

[0079] Enlarged views of parts of Examples 2 and 1 are shown below. Figure 9 As shown, the two have very similar appearances. Figure 9 In the printed sample of Example 2 shown below, the background areas corresponding to the cranes are all printed with UV varnish, and the cranes corresponding to the background areas are relatively... Figure 9 The printed sample of Example 1 shown above (its tactile ink printing uses a resin plate, the structure of which is as follows) Figure 3 - (b) shows that the difference is small. The main difference is that the outline of the pattern lines is more distinct and clear, and has a more three-dimensional sense of layering. Comparing the outer edge of the crane pattern in the printed sample of Example 1, it was found that the resin plate with the hollowed-out thick lines has a slight ink piling phenomenon at the thick line border. However, the outer edge of the crane pattern in the printed sample of Example 2 achieves the thick feel of tactile ink, while avoiding the ink piling phenomenon of hollowed-out resin plate printing tactile ink in the halftone or fine lines. The printing method of this example fully satisfies the reproduction of halftone dots and fine lines in the tactile oil finishing area. Example 3

[0080] This embodiment of a method for in-line offset flexographic printing of tactile inks includes the following steps:

[0081] 1) Use an offset printing press color printing unit to print the base color on the surface of the paper packaging box and then dry it;

[0082] 2) The substrate after color printing in step 1) is transferred to the first flexographic printing unit for the first printing of tactile ink. The amount of tactile ink used for the first printing is 3μm, which is 1 / 3 of the total amount D 9μm, and then dried.

[0083] 3) The substrate from step 2) is then transferred to the second flexographic printing unit for reprinting of tactile ink. The amount of tactile ink used for the reprint is 3μm, which is 1 / 3 of the total amount D 9μm. Then it is dried.

[0084] 4) The substrate from step 3) is then transferred to the third flexographic printing unit for reprinting of tactile ink. The amount of tactile ink used for the reprint is 3μm, which is 1 / 3 of the total amount D 9μm. Then it is dried.

[0085] The flexographic printing unit is the same as in Example 1.

[0086] The products printed by the method described in Example 3 are as follows: Figure 10 As shown. Compared with the printed product produced by the method described in Example 1, the product has a heavier feel, a stronger velvet texture, and a higher aesthetic appeal. Example 4

[0087] This embodiment of a method for in-line offset flexographic printing of tactile inks includes the following steps:

[0088] 1) Use an offset printing press color printing unit to print the base color on the surface of the paper packaging box and then dry it;

[0089] 2) The substrate after color printing in step 1) is transferred to the first flexographic printing unit for the first printing of tactile ink. The amount of tactile ink used for the first printing is 4μm, which is half of the total amount D 8μm, and then dried.

[0090] 3) The substrate from step 2) is then transferred to the second flexographic printing unit for reprinting of tactile ink. The amount of tactile ink used for the reprint is 4μm, which is half of the total amount D 8μm. Then it is dried.

[0091] The flexographic printing press and resin plate are the same as in Example 1. Example 5

[0092] This embodiment of a method for in-line offset flexographic printing of tactile inks includes the following steps:

[0093] 1) Use an offset printing press color printing unit to print the base color on the surface of the paper packaging box and then dry it;

[0094] 2) The substrate after color printing in step 1) is transferred to the first flexographic printing unit for initial printing of tactile ink. The amount of tactile ink used for the initial printing is 4μm, which is half of the total amount D 8μm. The area decorated by the initial printing of tactile ink includes coarse hollow lines with a width of 0.5mm or more, and then dried.

[0095] 3) The substrate from step 2) is then transferred to the second flexographic printing unit for reprinting tactile ink. The amount of tactile ink used for reprinting is 4μm, which is half of the total amount D 8μm. The area decorated by reprinting tactile ink includes coarse cutout lines with a width of 0.5mm or greater, and then dried.

[0096] 4) Apply UV gloss varnish to the dots and lines with a width of 0.5mm or less on the original offset printing resin plate using a 500-mesh screen and let it dry.

[0097] This invention discloses a method for offset flexographic inline printing of tactile ink, wherein the viscosity of the initial tactile ink and the subsequent tactile ink can be 105s, 110s, or 120s; the changes in the above technical features can be understood and implemented by those skilled in the art through textual description, and therefore will not be further illustrated with drawings.

[0098] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0099] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

Claims

1. A method for in-line offset flexographic printing of tactile inks, characterized in that, The base color is printed on the surface of the paper packaging box using an offset printing machine color printing unit, and then the flexographic printing unit is used to print tactile ink on the paper packaging box in two or more passes, so that the thickness of the tactile ink on the surface of the packaging box is ≥6μm. Includes the following steps: 1) Use an offset printing press color printing unit to print the base color on the surface of the paper packaging box and then dry it; 2) The substrate after color printing in step 1) is transferred to the first flexographic printing unit for the first printing of tactile ink. The amount of tactile ink used for the first printing is 1 / 2D to 2 / 3D of the total amount, and then dried. 3) The substrate from step 2) is then transferred to the second flexographic printing unit for reprinting of tactile ink. The amount of tactile ink used for the reprint is 1 / 3D to 1 / 2D of the total amount. Then it is dried. In steps 2) and 3), the tactile ink finishing area only includes coarse cut lines or solid areas with a width of 0.5 mm or greater; 4) After reprinting the tactile ink, use a screen UV gloss varnish with a mesh size of 450 or greater to print the UV gloss varnish finishing area. The UV gloss varnish finishing area includes halftone patterns and / or fine line patterns with a width of less than 0.5mm. The flexographic printing press unit includes a conveying device, a doctor blade, an anilox roller, a printing plate roller fitted with a resin plate, and an impression cylinder. The conveying device is installed below the impression cylinder to convey the substrate onto the impression cylinder. The doctor blade and printing plate roller are installed on both sides of the anilox roller, and the printing plate roller is installed above the impression cylinder. The doctor blade transfers tactile ink through the anilox roller onto the resin plate fitted with the printing plate roller. Then, under the action of the impression cylinder, the tactile ink on the resin plate is transferred onto the substrate. The doctor blade includes a blade holder and a blade. The blade holder is a frame with an ink storage cavity inside, and the blade is fixed on the blade holder facing the ink storage cavity. An ink inlet / outlet device communicating with the ink storage cavity is provided on the back of the blade holder. The ink inlet / outlet device includes an ink feed pipe, an ink outlet pipe, and a suction pump. The ink feed pipe is connected to multiple ink inlets located at the bottom of the ink storage cavity via a four-way connector. One end of the ink outlet pipe is connected to an ink outlet located at the top of the ink storage cavity, and the other end is connected to the suction pump or an ink tank via a connecting pipe. The anilox roller is a linear spiral anilox roller with a line count of 100-120 and an ink load of 16-20 grams.

2. The method for in-line offset flexographic printing of tactile ink as described in claim 1, characterized in that, The thickness of the tactile ink on the surface of the packaging box is 6~9μm.

3. The method for in-line offset flexographic printing of tactile ink as described in claim 1, characterized in that, The method uses a flexographic printing press to print tactile ink on the paper packaging box in two or three passes.

4. The method for in-line offset flexographic printing of tactile ink as described in claim 3, characterized in that, The printing plate for the tactile ink is a resin plate, and the tactile effect decoration area on the printing plate is solid.

5. The method for in-line offset flexographic printing of tactile ink as described in claim 2, characterized in that, The viscosity of the initial printing tactile ink and the reprinting tactile ink is 100~120s.

6. The method for in-line offset flexographic printing of tactile ink as described in claim 1, characterized in that, The diameter of the main pipe of the four-way connector and the ink inlet pipe is ∅30mm, the diameter of the first branch pipe of the four-way connector and the middle of the ink storage cavity is ∅20mm, and the diameter of the second branch pipes at both ends of the four-way connector and the ink storage cavity is ∅10mm.

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