Control method for accurate ink-jet coloring of corrugated color box

Abstract

The invention relates to the technical field of ink-jet printing, and discloses a control method for accurate ink-jet coloring of a corrugated color box, which comprises the following steps of: analyzing printing data by a control system, and judging a printing area as an edge detail area and a color filling area according to the activation density of a nozzle; as for the edge detail area, reactive curing powder is immediately sprayed after reactive printing ink is sprayed, and instantaneous curing is achieved; and aiming at the color filling area, a step of spraying a competitive volatilization inhibitor is added between spraying of the reactive ink and spraying of the reactive curing powder so as to realize delayed curing. By adopting differentiated curing strategies for the printing area, the marginal definition is ensured by utilizing instantaneous curing in the marginal detail area, and printing ink leveling is promoted by utilizing delayed curing in the color filling area so as to obtain high color uniformity; therefore, the technical problem that high-definition edges and high-uniformity color blocks are difficult to realize on the corrugated board at the same time is solved, and the printing quality is further improved.

Description

Technical Field

[0001] This invention relates to the field of inkjet printing technology, specifically to a method for controlling precise inkjet coloring of corrugated color boxes. Background Technology

[0002] As a widely used packaging material, the surface coloring quality of corrugated boxes directly affects the product's appearance. Existing inkjet coloring technology, when applied to corrugated cardboard, generally faces an inherent technical contradiction: a conflict exists between achieving sharp, clear pattern edges and achieving uniform, flat color filling areas.

[0003] For the edge details of a pattern, to achieve high definition, the sprayed ink droplets must maintain their geometric shape on the substrate surface, avoiding disordered diffusion and penetration. However, existing technologies, such as direct inkjet printing, cause the ink to smudge and spread at the line edges due to capillary action on porous corrugated cardboard, resulting in ink accumulation or blurring and reducing the sharpness of the pattern.

[0004] Conversely, for large areas of color filling, achieving high uniformity requires adjacent ink droplets to flow, merge, and level sufficiently before curing to eliminate printing streaks and color spots caused by gaps or overlaps between ink dots. However, existing technologies, such as rapid hot air or UV curing using post-curing methods, often cure the ink droplets before they have leveled, leading to uneven color distribution or color differences within the color blocks. While pre-coating before inkjet printing can improve ink spreading characteristics to some extent, it increases production steps and material costs, thus reducing production efficiency and failing to fundamentally resolve the contradiction of curing control.

[0005] Therefore, existing technologies lack a control method that can dynamically adjust the curing rate according to the different regional characteristics (edges or fills) of the printed content in the same printing job. As a result, when inkjet printing on corrugated color boxes, it is impossible to simultaneously ensure the clarity of the pattern edges and the uniformity of the color fill area, which has become a technical bottleneck restricting the improvement of print quality. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a control method for precise inkjet coloring of corrugated boxes, which solves the technical problem that existing technologies cannot simultaneously achieve high definition of pattern edges and high uniformity of color filling areas when inkjet coloring corrugated cardboard due to the single curing control strategy.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for controlling precise inkjet coloring of corrugated color boxes, comprising the following steps:

[0008] S1. Monitor and analyze the nozzle activation density in the print data stream sent to the inkjet head in real time to determine whether the current printing area is an edge detail area or a color filling area.

[0009] S2. When it is determined in step S1 that the current printing area is an edge detail area, an instant curing operation is performed, the instant curing operation including:

[0010] Reactive ink is sprayed onto the surface of the corrugated box, and reactive curing powder is sprayed simultaneously. During the instant curing operation, no competing volatile inhibitors are sprayed.

[0011] S3. When it is determined in step S1 that the current printing area is a color-filled area, a delayed curing operation is performed, the delayed curing operation including:

[0012] The reactive ink is sprayed onto the surface of the corrugated box, followed by the spraying of the competitive volatilization inhibitor onto the wetted surface of the reactive ink, and then the reactive curing powder is sprayed on, utilizing the volatilization process of the competitive volatilization inhibitor to form a reaction delay window.

[0013] Preferably, the reactive ink comprises an aqueous epoxy resin emulsion with a first reactive functional group, wherein the first reactive functional group is an epoxy group, the reactive curing powder is a micro powder, the micro powder comprises a second reactive functional group capable of chemically reacting with the first reactive functional group, wherein the second reactive functional group is an amino group, and the competitive volatilization inhibitor is propylene glycol methyl ether.

[0014] Preferably, in step S1, the step of determining whether the current printing area is an edge detail area or a color fill area specifically involves:

[0015] This is achieved by counting the number of nozzles activated per unit length in real time and comparing the number of nozzles with a number threshold used to distinguish the edge detail area from the color fill area.

[0016] When the number of nozzles is less than or equal to the number threshold, it is determined to be the edge detail area;

[0017] When the number of nozzles is greater than the number threshold, it is determined to be the color filling area.

[0018] Preferably, in the instant curing operation of step S2, the spray volume of the reactive ink is 5-12 pL / drop, and the spraying amount of the reactive curing powder is 0.8-1.5 g / m³. 2 .

[0019] Preferably, in the delayed curing operation of step S3, the spray volume of the reactive ink is 18-35 pL / drop, and the spray amount of the competitive volatile inhibitor is 0.2-0.8 g / m³.2 The spraying amount of the reactive curing powder is 1.2-2.5 g / m². 2 .

[0020] Preferably, the aqueous epoxy resin emulsion is an aqueous bisphenol A epoxy resin emulsion, and the reactive ink is made of 15.0-25.0 parts by weight of aqueous bisphenol A epoxy resin emulsion, 5.0-10.0 parts of pigment, 1.0-2.0 parts of nonionic surfactant and 70.0-80.0 parts of deionized water.

[0021] Preferably, the micropowder uses isophorone diamine as its core, and the core is coated with a coating layer formed of polyvinyl alcohol.

[0022] Preferably, the preparation steps of the reactive curable powder include:

[0023] A fluidized bed coating process is used to atomize and spray a polyvinyl alcohol coating solution onto isophorone diamine powder in a fluidized state at a temperature of 55-70℃. After spraying, fluidized drying is continued to obtain the reactive curing powder.

[0024] Preferably, the distance between the inkjet head that sprays the reactive ink and the printhead that sprays the competitive volatile inhibitor is 10-20 mm, and the distance between the printhead that sprays the competitive volatile inhibitor and the powder spray head that sprays the reactive curing powder is 15-30 mm.

[0025] Preferably, the method for controlling the precise inkjet coloring of corrugated color boxes further includes a post-processing step:

[0026] After the instant curing operation or the delayed curing operation is completed, a vacuum suction device is used to remove the reactive curing powder that has not participated in the reaction from the surface of the corrugated box.

[0027] In summary, the present invention has at least one of the following beneficial technical effects:

[0028] 1. This invention distinguishes between edge detail areas and color fill areas by real-time analysis of the printing data stream, and performs two different operation processes, instant curing or delayed curing, accordingly. Through differentiated control strategies, corresponding curing control can be applied to different types of printing areas in a single printing task, thereby synergistically improving the clarity of the pattern outline and the color uniformity of large-area color blocks. This solves the contradiction that existing technologies cannot simultaneously meet the requirements of rapid curing for printing edge details to ensure clarity and delayed curing for printing color fill areas to ensure uniformity.

[0029] 2. This invention targets the edge detail areas of corrugated color boxes. By performing an instant curing operation, the reactive ink and reactive curing powder come into direct contact and undergo an immediate chemical reaction. The immediate chemical reaction is completed before the ink droplets diffuse and penetrate. By fixing the shape of the ink droplets on the surface of the corrugated cardboard, the edge ink accumulation caused by disordered ink spread is eliminated, ensuring the sharpness of the edges of printed patterns or text.

[0030] 3. This invention targets the color-filling area of ​​corrugated color boxes. By performing a delayed curing operation and utilizing the controlled volatilization of competitive volatilization inhibitors, a temporary reaction delay window is constructed between the ink and the curing powder. During the reaction delay window, adjacent liquid ink droplets are allowed to flow and merge sufficiently to form a smooth liquid film, avoiding printing streaks caused by uneven curing speed, thereby improving the color uniformity and finished product quality of large-area coloring areas. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, examples, comparative examples, and test examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Preparation Examples 1-2:

[0033] Preparation Example 1: Preparation of Reactive Inks

[0034] Preparation of reactive ink A:

[0035] Formula (by weight):

[0036] Waterborne bisphenol A epoxy resin emulsion: 15.0 parts; phthalocyanine blue: 5.0 parts; octylphenol polyoxyethylene ether: 1.0 part; deionized water: 80.0 parts.

[0037] Preparation method:

[0038] Add 80.0 parts by weight of deionized water to a reaction vessel equipped with jacketed cooling and high-speed dispersion functions, and start stirring;

[0039] While stirring, add 1.0 part by weight of octylphenol polyoxyethylene ether and 5.0 parts by weight of phthalocyanine blue pigment in sequence;

[0040] The dispersion speed was increased to 4000 rpm and the dispersion was carried out continuously for 90 minutes. During this period, the system temperature was controlled below 40℃ by jacket cooling to obtain a uniform and stable pigment slurry.

[0041] Then, reduce the rotation speed to 400 rpm and slowly add 15.0 parts by weight of water-based bisphenol A epoxy resin emulsion. After the addition is complete, continue stirring for 30 minutes.

[0042] The resulting mixture was filtered through a filter with an absolute precision of 1µm to obtain reactive ink A.

[0043] Preparation of reactive ink B:

[0044] Formula (by weight):

[0045] Waterborne bisphenol A epoxy resin emulsion: 20.0 parts; phthalocyanine blue: 7.5 parts; octylphenol polyoxyethylene ether: 1.5 parts; deionized water: 75.0 parts.

[0046] Preparation method:

[0047] Add 75.0 parts by weight of deionized water to a reaction vessel equipped with jacketed cooling and high-speed dispersion functions, and start stirring;

[0048] While stirring, add 1.5 parts by weight of octylphenol polyoxyethylene ether and 7.5 parts by weight of phthalocyanine blue pigment in sequence;

[0049] The dispersion speed was increased to 4000 rpm, and the dispersion was carried out continuously for 90 minutes. During this period, the system temperature was controlled below 40℃ by jacket cooling to obtain a uniform and stable pigment slurry.

[0050] Then, reduce the rotation speed to 400 rpm and slowly add 20.0 parts by weight of water-based bisphenol A epoxy resin emulsion. After the addition is complete, continue stirring for 30 minutes.

[0051] The resulting mixture was filtered through a filter with an absolute precision of 1µm to obtain reactive ink B.

[0052] Preparation of reactive ink C:

[0053] Formula (by weight):

[0054] Waterborne bisphenol A epoxy resin emulsion: 25.0 parts; Phthalocyanine blue: 10.0 parts; Octylphenol polyoxyethylene ether: 2.0 parts; Deionized water: 70.0 parts.

[0055] Preparation method:

[0056] Add 70.0 parts by weight of deionized water to a reaction vessel equipped with jacketed cooling and high-speed dispersion functions, and start stirring;

[0057] While stirring, add 2.0 parts by weight of octylphenol polyoxyethylene ether and 10.0 parts by weight of phthalocyanine blue pigment in sequence;

[0058] The dispersion speed was increased to 4000 rpm and the dispersion was carried out continuously for 90 minutes. During this period, the system temperature was controlled below 40℃ by jacket cooling to obtain a uniform and stable pigment slurry.

[0059] Then, reduce the rotation speed to 400 rpm and slowly add 25.0 parts by weight of water-based bisphenol A epoxy resin emulsion. After the addition is complete, continue stirring for 30 minutes.

[0060] The resulting mixture was filtered through a filter with an absolute precision of 1µm to obtain reactive ink C.

[0061] Preparation Example 2: Preparation of Reactive Curing Powder

[0062] The reactive curing powders A, B, and C prepared in the following steps will be respectively loaded into the powder hopper of the curing powder spraying device. During the printing process, the control system will instruct the spray head to spray specific types of curing powder according to the set process parameters. Temperature control involved in the preparation process is completed by a fluidized bed coating machine equipped with a precise temperature control unit.

[0063] Preparation of polyvinyl alcohol coated solution:

[0064] 5.0 parts by weight of polyvinyl alcohol powder were slowly added to 95.0 parts by weight of deionized water under stirring. The mixture was heated to 90-95°C and kept at this temperature with stirring for 2 hours until the polyvinyl alcohol was completely dissolved, forming a transparent and homogeneous solution. The solution was then cooled to room temperature for later use, yielding a 5% polyvinyl alcohol coated solution.

[0065] Preparation of reactive curable powder A:

[0066] A bottom-spray fluidized bed coating machine is used;

[0067] Weigh 1000g of isophorone diamine powder as the core material and place it in the material chamber of the fluidized bed;

[0068] Start the air intake fan and adjust the air intake volume until the IPDA powder is in a stable and uniform fluidized state;

[0069] Set the air inlet temperature to stabilize the bed temperature at 55℃;

[0070] Start the peristaltic pump and spray the prepared polyvinyl alcohol coating solution into the fluidized bed through the atomizing nozzle at a rate of 20 g / min, for a total of 1000 g of coating solution.

[0071] After spraying, stop the liquid supply and continue fluidized drying at a bed temperature of 55°C for 60 minutes to remove residual moisture;

[0072] After drying, turn off the equipment, remove the material, and pass it through a 200-mesh sieve to obtain reactive solidified powder A.

[0073] Preparation of reactive curing powder B:

[0074] A bottom-spray fluidized bed coating machine is used;

[0075] Weigh 1000g of isophorone diamine powder as the core material and place it in the material chamber of the fluidized bed;

[0076] Start the air intake fan and adjust the air intake volume until the IPDA powder is in a stable and uniform fluidized state;

[0077] Set the air inlet temperature to stabilize the bed temperature at 62℃;

[0078] Start the peristaltic pump and spray the prepared polyvinyl alcohol coating solution into the fluidized bed through the atomizing nozzle at a rate of 20 g / min, for a total of 1000 g of coating solution.

[0079] After spraying, stop the liquid supply and continue fluidized drying at a bed temperature of 62°C for 50 minutes to remove residual moisture;

[0080] After drying, turn off the equipment, remove the material, and pass it through a 200-mesh sieve to obtain reactive solidified powder B.

[0081] Preparation of reactive curable powder C:

[0082] A bottom-spray fluidized bed coating machine is used;

[0083] Weigh 1000g of isophorone diamine powder as the core material and place it in the material chamber of the fluidized bed;

[0084] Start the air intake fan and adjust the air intake volume until the IPDA powder is in a stable and uniform fluidized state;

[0085] Set the air inlet temperature to stabilize the bed temperature at 70℃;

[0086] Start the peristaltic pump and spray the prepared polyvinyl alcohol coating solution into the fluidized bed through the atomizing nozzle at a rate of 20 g / min, for a total of 1000 g of coating solution.

[0087] After spraying, stop the liquid supply and continue fluidized drying at a bed temperature of 70°C for 40 minutes to remove residual moisture;

[0088] After drying, turn off the equipment, remove the material, and pass it through a 200-mesh sieve to obtain reactive solidified powder C.

[0089] Examples 1-3:

[0090] Examples 1-3 are carried out in a complete coloring apparatus of the present invention, which consists of an inkjet device, a curing powder spraying device, a temperature control device, a control system and a suction device.

[0091] Specifically, along the conveying direction of the corrugated cardboard, the coloring unit sequentially integrates a piezoelectric inkjet head (part of the inkjet unit), a printhead for spraying competitive volatile inhibitors, a powder spraying head (part of the curing powder spraying unit), and a suction device located at the rear of the printing station. The entire printing process is carried out in a constant temperature environment regulated by a temperature control device.

[0092] The core of this invention lies in the control system, which is connected to the printing data stream and can analyze the nozzle activation density in real time. Based on the quantity threshold, it comprehensively controls the selected ink type (i.e., ink concentration), the amount of ink sprayed in a single stroke, the characteristics of the selected curing powder, and the start / stop and spraying / coating amount of each printhead and powder spraying head, thereby accurately executing the following steps.

[0093] Example 1:

[0094] This embodiment uses reactive ink A prepared in Preparation Example 1 and reactive curing powder A prepared in Preparation Example 2, and the printing substrate is type B three-layer corrugated cardboard.

[0095] The printing device parameters are set as follows:

[0096] The distance between the printhead that sprays reactive ink and the printhead that sprays competitive volatile inhibitor is 10 mm;

[0097] The distance between the nozzle for spraying competitive volatile inhibitors and the nozzle for spraying reactive curing powder is 15 mm.

[0098] The control method for precise inkjet coloring of corrugated color boxes shall be performed according to the following steps:

[0099] The control system analyzes the print data in real time, using the number of active nozzles per unit length (100) as a threshold. When the number of nozzles counted in real time is ≤100, it is determined to be an edge detail area; when the number of nozzles counted in real time is >100, it is determined to be a color fill area.

[0100] When the control system determines that the current printing area is an edge detail area, it performs an instant curing operation:

[0101] Control the inkjet head to eject reactive ink A at a volume of 5 pL / drop;

[0102] Simultaneously, the powder spraying head is controlled to spray reactive curing powder A at a rate of 0.8 g / m³. 2 .

[0103] During this process, the nozzle that sprays the competitive volatile inhibitor does not work.

[0104] When the control system determines that the current printing area is a color-filled area, it performs a delayed curing operation:

[0105] First, control the inkjet head to eject reactive ink A at a volume of 18 pL / drop;

[0106] Subsequently, propylene glycol methyl ether was sprayed from a nozzle controlling the spraying of a competitive volatilization inhibitor at a spraying rate of 0.2 g / m³. 2 ;

[0107] Then, control the powder spraying head to spray reactive curing powder A at a spraying rate of 1.2 g / m³. 2 .

[0108] Post-processing steps:

[0109] After the printed corrugated box is passed under a vacuum suction device, the unreacted reactive curing powder on the surface is removed, resulting in printed sample 1.

[0110] Example 2:

[0111] This embodiment uses reactive ink B prepared in Preparation Example 1 and reactive curing powder B prepared in Preparation Example 2, and the printing substrate is type B three-layer corrugated cardboard.

[0112] The printing device parameters are set as follows:

[0113] The distance between the printhead that sprays reactive ink and the printhead that sprays competitive volatile inhibitor is 15 mm;

[0114] The distance between the nozzle for spraying competitive volatile inhibitors and the nozzle for spraying reactive curing powder is 22 mm.

[0115] The control method for precise inkjet coloring of corrugated color boxes shall be performed according to the following steps:

[0116] The control system analyzes the print data in real time, using the number of active nozzles per unit length (100) as a threshold. When the number of nozzles counted in real time is ≤100, it is determined to be an edge detail area; when the number of nozzles counted in real time is >100, it is determined to be a color fill area.

[0117] When the control system determines that the current printing area is an edge detail area, it performs an instant curing operation:

[0118] Control the inkjet head to eject reactive ink B at a volume of 8 pL / drop;

[0119] Simultaneously, the powder spraying head is controlled to spray reactive curing powder B at a rate of 1.1 g / m³. 2 .

[0120] During this process, the nozzle that sprays the competitive volatile inhibitor does not work.

[0121] When the control system determines that the current printing area is a color-filled area, it performs a delayed curing operation:

[0122] First, control the inkjet head to eject reactive ink B at a volume of 26 pL / drop;

[0123] Subsequently, propylene glycol methyl ether was sprayed from a nozzle controlling the spraying of a competitive volatilization inhibitor at a spraying rate of 0.5 g / m³. 2 ;

[0124] Then, control the powder spraying head to spray reactive curing powder B at a spraying rate of 1.8 g / m³. 2 .

[0125] Post-processing steps:

[0126] After the printed corrugated box is passed under a vacuum suction device, the unreacted reactive curing powder on the surface is removed, resulting in printed sample 2.

[0127] Example 3

[0128] This embodiment uses the reactive ink C prepared in Preparation Example 1 and the reactive curing powder C prepared in Preparation Example 2, and the printing substrate is a type B three-layer corrugated cardboard.

[0129] The printing device parameters are set as follows:

[0130] The distance between the printhead that sprays reactive ink and the printhead that sprays competitive volatile inhibitor is 20 mm;

[0131] The distance between the nozzle for spraying competitive volatile inhibitors and the nozzle for spraying reactive curing powder is 30 mm.

[0132] The control method for precise inkjet coloring of corrugated color boxes shall be performed according to the following steps:

[0133] The control system analyzes the print data in real time, using the number of active nozzles per unit length (100) as a threshold. When the number of nozzles counted in real time is ≤100, it is determined to be an edge detail area; when the number of nozzles counted in real time is >1100, it is determined to be a color fill area.

[0134] When the control system determines that the current printing area is an edge detail area, it performs an instant curing operation:

[0135] Control the inkjet head to eject reactive ink C at a volume of 12 pL / drop;

[0136] Simultaneously, the reactive curing powder C is sprayed from the powder spray head at a rate of 1.5 g / m². 2 .

[0137] During this process, the nozzle that sprays the competitive volatile inhibitor does not work.

[0138] When the control system determines that the current printing area is a color-filled area, it performs a delayed curing operation:

[0139] First, control the inkjet head to eject reactive ink C at a volume of 35 pL / drop;

[0140] Subsequently, propylene glycol methyl ether was sprayed from a nozzle that controlled the spraying of a competitive volatilization inhibitor at a spraying rate of 0.8 g / m³. 2 ;

[0141] Then, control the powder spraying head to spray reactive curing powder C at a spraying rate of 2.5 g / m³. 2 .

[0142] Post-processing steps:

[0143] After the printed corrugated box is passed under a vacuum suction device, the unreacted reactive curing powder on the surface is removed, resulting in printed sample 3.

[0144] Comparative Examples 1-3:

[0145] Comparative Example 1:

[0146] Compared to Example 1, the difference lies in that the control system of the present invention does not perform region determination on the printing data stream, and uniformly executes the instant curing operation in Example 1 on all printing areas (including edge detail areas and color fill areas). That is, during the entire printing process, only the printhead of the inkjet device and the powder spraying head of the curing powder spraying device are working, while the printhead spraying the competitive volatile inhibitor is not working at all. The resulting sample is recorded as Comparative Sample 1.

[0147] Comparative Example 2:

[0148] Compared to Example 1, the difference lies in that the control system of the present invention does not perform region determination on the printing data stream, and uniformly executes the delayed curing operation in Example 1 on all printing areas (including edge detail areas and color fill areas). That is, throughout the entire printing process, the printhead of the inkjet device, the printhead spraying competitive volatile inhibitor, and the powder spraying head of the curing powder spraying device all operate according to the settings of the delayed curing operation, and the resulting sample is recorded as comparative sample 2.

[0149] Comparative Example 3:

[0150] Compared to Example 1, the difference lies in that the ink supply system of the inkjet device is loaded with a conventional water-based pigment ink that does not contain epoxy resin. During the printing process, only the printhead of the inkjet device is working; the curing powder spraying device, the printhead spraying competitive volatile inhibitor, and the suction device are not working at all. No chemical curing treatment is performed on the printed ink. The resulting sample is designated as Comparative Sample 3.

[0151] Test Example 1-2:

[0152] To verify the technical effects of the present invention, performance tests were conducted on the printed samples obtained in Examples 1-3 and Comparative Examples 1-3.

[0153] Test Example 1: Edge Sharpness Test

[0154] This test case aims to quantitatively evaluate the edge sharpness of patterns on different printed samples.

[0155] The testing method is as follows:

[0156] Using the process methods of Examples 1-3 and Comparative Examples 1-3, test patterns containing parallel line arrays with a designed width of 0.1 mm were printed on Type B three-layer corrugated cardboard.

[0157] After all printed samples have been left to stand at room temperature for 24 hours to ensure complete curing or drying, the printed lines are measured using a VHX-7000 digital microscope.

[0158] In the linear array pattern of each sample, 10 different measurement positions were randomly selected to measure the actual printed width of each line, and all 10 measurement values ​​were recorded;

[0159] Calculate the arithmetic mean of the 10 measurements as the average measured linewidth of the sample.

[0160] Calculate the linewidth expansion rate using the following formula:

[0161] Linewidth expansion rate (%) = [(Average measured linewidth - Design linewidth) / Design linewidth] × 100%;

[0162] The smaller the line width expansion rate, the less noticeable the edge diffusion of the printed lines, and the higher the edge clarity.

[0163] The test results are recorded in Table 1 below.

[0164] Table 1: Edge Sharpness Test Results

[0165] sample Average measured line width (mm) Line width expansion rate (%) Printed Sample 1 0.1112 11.2 Printed Sample 2 0.1085 8.5 Printed Sample 3 0.1138 13.8 Comparative Sample 1 0.1079 7.9 Comparative Sample 2 0.1856 85.6 Comparative sample 3 0.2523 152.3

[0166] As shown in the test data in Table 1, this invention can control the edge sharpness of the printed pattern by applying differentiated coloring to the corrugated box surface in different zones. Differentiated coloring in different zones is achieved based on the control system's real-time determination of the printing area and precise selection of the subsequent curing path. The control system analyzes the printing data stream and, based on whether the number of activated nozzles exceeds a threshold, divides the printing area into edge detail areas and color filling areas, and instructs the inkjet unit and the curing powder spraying unit to execute different curing processes.

[0167] When the control system determines that the current printing area is an edge detail area, it performs an instant curing operation. At this time, after the inkjet printhead sprays reactive ink, the spray head of the curing powder spraying device immediately sprays reactive curing powder. The epoxy resin in the ink undergoes a rapid contact chemical reaction with the amine curing agent in the curing powder. The contact chemical reaction is completed before the ink droplets spread and penetrate the porous corrugated cardboard surface, thus fixing the ink droplet shape in its original position. The final printed samples 1, 2, and 3 all exhibit low linewidth expansion.

[0168] The linewidth expansion rate of Comparative Sample 2 was higher than that of Printed Samples 1, 2, and 3. This is because a delayed curing process was used in all areas (including edge detail areas). The delayed curing process, an artificially introduced reaction delay, allows the ink sufficient time to flow and spread, resulting in the inability to maintain the geometry of the edge lines. Comparative Sample 3, on the other hand, did not use any reactive components, and the curing powder spraying and suction devices were not operational. Conventional water-based inks experienced uncontrolled capillary penetration on the corrugated cardboard, leading to the most severe linewidth expansion. The comparative results confirm that the area determination and differentiated curing method described in this invention is the direct cause of achieving edge sharpness.

[0169] Test Example 2: Color Fill Area Uniformity Test

[0170] This test case aims to quantitatively evaluate the color uniformity of the color-filled areas on different printed samples.

[0171] The testing method is as follows:

[0172] Using the process methods of Examples 1-3 and Comparative Examples 1-3, pure blue test patterns with a size of 5cm×5cm were printed on Type B three-layer corrugated cardboard.

[0173] After all printed samples were left to stand at room temperature for 24 hours to ensure complete curing or drying, colorimetric measurements were performed using a portable spectrophotometer of model Ci64.

[0174] Nine measurement points were evenly distributed across the surface of each color patch sample using a 3x3 grid. First, the CIE Lab value of the center point was measured and set as the baseline.

[0175] Subsequently, the CIE Lab values ​​of the remaining 8 points were measured in sequence, and the color difference (ΔE) between these 8 points and the center reference point was calculated according to the CIEDE2000 formula.

[0176] The maximum value among the eight color difference values ​​is recorded as the color non-uniformity index (ΔE) of the sample. max ).

[0177] ΔE max The smaller the value, the higher the color consistency within the color block and the better the uniformity of the color filling area.

[0178] The test results are recorded in Table 2 below.

[0179] Table 2: Test Results of Uniformity of Color Filling Area

[0180] sample <![CDATA[Maximum color difference (ΔE max ).]]> Printed Sample 1 1.15 Printed Sample 2 0.92 Printed Sample 3 1.31 Comparative Sample 1 6.87 Comparative Sample 2 1.45 Comparative sample 3 8.52

[0181] The test data in Table 2 show that the control method for precise inkjet coloring of corrugated color boxes described in this invention can achieve color uniformity in the color-filling area of ​​the corrugated color box. Achieving color uniformity in the color-filling area of ​​the corrugated color box is achieved by the control system determining the printing area and instructing relevant components in the coloring device to execute a specific delayed curing process. When the control system determines that the printing area is a color-filling area, the operating logic of the coloring device ensures that the ink obtains the necessary leveling time before final curing.

[0182] In the color filling area, the control system instructs the inkjet unit to eject relatively large ink droplets, followed by an instruction to a dedicated printhead to eject propylene glycol methyl ether as a competitive evaporation inhibitor. This competitive evaporation inhibitor forms a momentary high-concentration vapor layer on the ink droplet surface. Because the vapor pressure of this high-concentration vapor layer is lower than that of water, it slows down the evaporation rate of moisture in the ink. This reduced evaporation rate prolongs the transition time of the ink from liquid to solid, allowing adjacent ink droplets sufficient time to merge, flow, and redistribute, thus forming a physically continuous and smooth liquid film on the corrugated cardboard surface. Subsequently, the curing powder sprayed by the curing powder spraying unit comes into contact with the liquid film, undergoing a chemical cross-linking reaction that fixes the leveled color layer. The resulting printed samples 1, 2, and 3 all exhibit low maximum color difference values.

[0183] Comparative Sample 1, due to its instant curing across all areas, resulted in ink droplets reacting immediately with the curing powder upon contact with the substrate. The individual ink droplet morphology was instantly solidified, failing to form a uniform color film, leading to visual mottled appearance and a high color difference value in measurements. While Comparative Sample 2 also achieved a lower color difference value, this came at the cost of sacrificing edge sharpness (as shown in Test Example 1), demonstrating the limitations of a single curing mode. Comparative Sample 3 used conventional water-based ink without any curing or leveling control; the curing powder spraying device and suction device were not involved. The uneven penetration and drying of the ink on the porous substrate resulted in the highest color difference value. Comparative data confirms that the differentiated curing strategy based on area determination described in this invention is fundamental to simultaneously achieving edge sharpness and color uniformity in the filled area.

Claims

1. A control method for precise inkjet coloration of a corrugated color box, characterized by, The method comprises the following steps: S1, real-time monitoring and analyzing the nozzle activation density in the print data stream sent to the inkjet head, and determining whether the current printing area is an edge detail area or a color filling area; S2, when it is determined in step S1 that the current printing area is an edge detail area, performing a transient curing operation, the transient curing operation comprising: spraying reactive ink on the surface of the corrugated color box, and synchronously spraying reactive curing powder, during the performance of the transient curing operation, no competitive volatile inhibitor is sprayed; S3, when it is determined in step S1 that the current printing area is a color filling area, performing a delayed curing operation, the delayed curing operation comprising: spraying the reactive ink on the surface of the corrugated color box, then spraying the competitive volatile inhibitor on the wet surface of the reactive ink, and then spraying the reactive curing powder, using the volatilization process of the competitive volatile inhibitor to form a reaction delay window.

2. The control method for precise inkjet coloration of a corrugated color box according to claim 1, characterized in that, The reactive ink comprises an aqueous epoxy resin emulsion with a first reactive functional group, the first reactive functional group is an epoxy group, the reactive curing powder is a micro powder, the micro powder comprises a second reactive functional group capable of chemical reaction with the first reactive functional group, the second reactive functional group is an amino group, and the competitive volatile inhibitor is propylene glycol methyl ether.

3. The control method for precise inkjet coloration of a corrugated color box according to claim 1, characterized in that, In step S1, the step of determining whether the current printing area is an edge detail area or a color filling area comprises: by real-time statistics of the number of activated nozzles per unit length, and comparing the number of nozzles with a number threshold value as the basis for distinguishing the edge detail area and the color filling area; when the number of nozzles is less than or equal to the number threshold value, it is determined as the edge detail area; when the number of nozzles is greater than the number threshold value, it is determined as the color filling area.

4. The control method for precise inkjet coloration of a corrugated color box according to claim 1, characterized in that, In the instant curing operation of step S2, the jetted volume of the reactive ink is 5-12 pL / drop, and the spray amount of the reactive curing powder is 0.8-1.5 g / m 2 .

5. The control method for precise inkjet coloration of a corrugated color box according to claim 1, characterized in that, In the said delayed curing operation of step S3, the reactive ink is jetted with a volume of 18-35 pL / drop, the competitive volatilization inhibitor is sprayed with a quantity of 0.2-0.8 g / m 2 , and the reactive curing powder is sprayed with a quantity of 1.2-2.5 g / m 2 .

6. The control method for precise inkjet coloration of a corrugated color box according to claim 2, characterized in that, The aqueous epoxy resin emulsion is an aqueous bisphenol A epoxy resin emulsion, and the reactive ink is prepared from 15.0-25.0 parts by weight of the aqueous bisphenol A epoxy resin emulsion, 5.0-10.0 parts by weight of pigment, 1.0-2.0 parts by weight of non-ionic surfactant, and 70.0-80.0 parts by weight of deionized water.

7. The control method for precise inkjet coloration of a corrugated color box according to claim 2, characterized in that, The micro powder takes isophorone diamine as the core, and the outer surface of the core is coated with a coating layer formed by polyvinyl alcohol.

8. The control method for precise inkjet coloration of a corrugated color box according to claim 7, characterized in that, The preparation steps of the reactive curing powder comprise: using fluidized bed coating process, at a temperature of 55-70℃, polyvinyl alcohol coating solution is atomized and sprayed onto isophorone diamine powder in a fluidized state, and after spraying is completed, fluidized drying is continued, thereby obtaining the reactive curing powder.

9. The control method for precise inkjet coloration of a corrugated color box according to claim 1, characterized in that, The distance between the inkjet head for spraying the reactive ink and the nozzle for spraying the competitive volatile inhibitor is 10-20mm, and the distance between the nozzle for spraying the competitive volatile inhibitor and the powder spraying head for spraying the reactive curing powder is 15-30mm.

10. The control method for precise inkjet coloration of a corrugated color box according to claim 1, characterized in that, The control method for precise inkjet coloration of corrugated color boxes further comprises a post-processing step: after the completion of the transient curing operation or the delayed curing operation, using a vacuum suction device to remove the reactive curing powder on the surface of the corrugated color box which does not participate in the reaction.