Method for reducing imprint after carton laser code burning

Abstract

The invention relates to the technical field of carton printing and laser marking, and particularly discloses a method for reducing imprint after carton laser code burning, which comprises the following steps: step 1, preparing carbon-free black ink: uniformly mixing blue ink, yellow ink and red ink according to the mass ratio of 33.3% to obtain the carbon-free black ink; and 2, preparing common carbon black ink: adding 15-20% of high-pigment carbon black into the resin system to prepare the common carbon black ink. According to the method for reducing imprint after laser code burning of the paper box, non-carbon black ink formed by mixing 33.3% of blue ink, 33.3% of yellow ink and 33.3% of red ink is mixed with common carbon black ink according to the proportion of 1: 0.2, the compatibility design of a phenolic resin modification system is combined, the relative content of high-pigment carbon black in the ink is greatly reduced, and the imprint after laser code burning of the paper box is reduced by matching the code burning parameters of 2000mm / s speed and 70% power of a 40WCOC laser machine. The residual amount after laser code burning is only 15%, the total amount of residues is reduced, and even if the content is heavy, black imprint cannot be generated on paper boxes stacked up and down due to residue transfer.

Description

Technical Field

[0001] This invention relates to the field of paper box printing and laser marking technology, specifically a method for reducing the pressure of laser marking on paper boxes. Background Technology

[0002] In the production of paper box packaging in the pharmaceutical, food and cosmetic fields, laser coding has been widely used as a core technology to achieve one code per box for traceability management. Currently, most paper boxes on the market that use laser coding have the coding position designed on the four sides of the paper box to avoid appearance problems that may occur during subsequent stacking. However, some brands adjust the coding position to the top or bottom of the paper box in order to improve the overall aesthetics of the outer box, adapt to the coding direction of the packaging line, or improve production efficiency.

[0003] In actual production, after laser coding is completed on the top or bottom of paper boxes printed with conventional carbon black ink, the ink layer is damaged by the laser, resulting in a large amount of black residue. The suction devices currently equipped on production lines are limited by their structural design and suction parameters, making it impossible to effectively remove these residues adhering to the surface of the paper boxes. This causes the residues to continuously adhere to the coding area. Furthermore, when the contents of the paper boxes are heavy, during subsequent warehousing and transportation, the residues at the top and bottom of the stacked boxes will come into contact and transfer due to gravity, forming obvious black imprints on the surface of the paper boxes. These imprints not only severely damage the appearance of the paper boxes and affect the overall aesthetics of the product, but may also cover the key traceability information formed by the coding, making information reading difficult and even preventing traceability verification. This hinders the quality traceability management of pharmaceuticals, food, and cosmetics, and also reduces consumer acceptance of the product in the market, negatively impacting the brand image. Summary of the Invention

[0004] The purpose of this invention is to provide a method to reduce the embossing after laser coding of paper boxes, in order to solve the problem mentioned in the background art that after laser coding is completed on the top or bottom of paper boxes printed with conventional carbon black ink, the ink layer will be damaged by the laser, resulting in a large amount of black residue, which cannot be removed by the online suction device. If the contents are too heavy, black embossing will occur on the top and bottom of the paper boxes after stacking, affecting the appearance of the paper boxes and the readability of key information.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for reducing the printing pressure after laser coding of paper boxes, comprising step 1: preparing carbon-free black ink: mixing blue ink, yellow ink and red ink at a mass ratio of 33.3% each to obtain carbon-free black ink; Step 2: Preparation of ordinary carbon black ink: Add 15%-20% high-pigment carbon black to the resin system to prepare ordinary carbon black ink; Step 3: Mix the carbon-free ink obtained in Step 1 with the ordinary carbon black ink obtained in Step 2. The resin systems of both the carbon-free ink and the ordinary carbon black ink are phenolic resin modified with rosin or rosin derivatives and then boiled with drying vegetable oil. Step 4: Print the mixed ink obtained in Step 3 onto the surface of the paper box, apply acrylic resin varnish on the printed ink layer, and use a combination of oxidative film formation and natural penetration to dry the varnish. Step 5: Using a 4-pound slider, rub the ink layer of the coated paper box back and forth at a frequency of 43 times / min for a total of 600 rubs to verify that the ink does not peel off. Step 6: Laser coding: A CO2 laser coding machine with a rated power of 40W is used to laser code the paper box at a speed of 2000mm / s and 70% power to simulate the automatic machine coding process. Step 7: Residual amount test: After the coding is completed, gently stroke the coding area back and forth with non-woven fabric, observe and record the amount of black ink residue on the non-woven fabric; Step 8: Determine the ink ratio: Based on hue, density, abrasion resistance, and laser coding residue, select the mixing ratio of carbon-free ink and ordinary carbon black ink for use in paper box production; The selected mixing ratio is carbon-free ink: ordinary carbon black ink = 1:0.2. Under this ratio, the solid black density is 1.65, the LAB value is L: 14.59, a: 1.57, b: 0.89, and the ink residue after laser coding is 15%.

[0006] By adopting the above technical solution, through mixing carbon-free ink and ordinary carbon black ink and optimizing the process, the residual amount after laser coding is reduced to 15%, while ensuring that the ink's abrasion resistance, hue and density meet the standards, ensuring that the coded information is clear and readable, and the process is compatible with existing equipment and easy to apply in industrial applications.

[0007] Preferably, the amount of high-pigment carbon black added to the ordinary carbon black ink in step 2 is 15%-20%.

[0008] By adopting the above technical solution, the amount of high-pigment carbon black added is limited to 15%-20%, which can ensure the contrast between the information in the coding area and the background to meet the reading requirements, while avoiding the surge in residue due to excessive carbon black, thus balancing the readability of information and the requirement of low residue.

[0009] Preferably, in step 3, the carbon-free ink and ordinary carbon black ink are mixed in a system that is compatible and does not separate into layers.

[0010] By adopting the above technical solution, it is ensured that there is no layering after the two inks are mixed, the stability of the mixed ink system is guaranteed, the fluctuation of printing quality caused by layering is avoided, and the consistency of subsequent process effects is ensured.

[0011] Preferably, the drying vegetable oil in step 3 is flaxseed oil.

[0012] By adopting the above technical solution, the drying vegetable oil is identified as linseed oil, which enhances the compatibility of the resin system with the two inks, optimizes the film-forming properties of the ink, and improves the adhesion and abrasion resistance of the printed layer.

[0013] Preferably, in step 6, the laser coding is performed using a simulated automatic machine for wire coding.

[0014] By adopting the above technical solution, laser coding simulates the working conditions of an automatic machine, making the test conditions consistent with actual production, ensuring that the method can be directly applied to industrial production, and improving the practicality of the technical solution.

[0015] Preferably, the nonwoven fabric is gently stroked back and forth three times in step 7.

[0016] By adopting the above technical solution, the nonwoven fabric is limited to three gentle strokes, and the residual amount test operation is standardized to ensure the comparability of residual amount data under different ratios, providing a reliable basis for screening the optimal ratio.

[0017] Preferably, the optimal ink mixing ratio in step 8 is a mass ratio of carbon-free ink to ordinary carbon black ink of 1:0.2.

[0018] By adopting the above technical solution, the optimal ratio of 1:0.2 is determined. At this ratio, the residual amount is low, the density of solid black and the hue meet the standards, and the imprinting problem is accurately solved while ensuring the optimal appearance of the paper box and the information readability performance.

[0019] Compared with the prior art, the beneficial effect of the present invention is that it reduces the printing pressure after laser coding on paper boxes. First, this invention significantly reduces the relative content of high-pigment carbon black in the ink by mixing carbon-free ink (33.3% each of blue, yellow, and red ink) with ordinary carbon black ink at a ratio of 1:0.2, combined with the compatibility design of the phenolic resin modification system. With the coding parameters of a 40W CO2 laser machine at a speed of 2000mm / s and 70% power, the residual amount after laser coding is only 15%, which is far lower than the 60% residual amount of pure carbon black ink. This improvement reduces the total amount of residue from the source. Even if the contents are heavy, stacked cartons will not produce black imprints due to residue transfer. Secondly, the abrasion resistance test of 600 rubs with a 4-pound slider without peeling and the acrylic resin varnish coating process ensure the durability of the mixed ink layer. The clear black solid density and LAB value prove that the ink hue of this ratio is close to that of pure carbon black ink, which meets the visual requirement of jet black. Moreover, the contrast of the laser-engraved information is sufficient, avoiding the difficulty of reading information caused by the reduction of carbon black, and taking into account the dual requirements of low residue and high performance. Finally, the resin system of the ink used in this invention is based on phenolic resin modification and linseed oil boiling, which is compatible with existing printing equipment. Its laser coding parameters and varnish drying method are all standard industry configurations, and mass production can be achieved without adding new equipment, thereby improving the product appearance qualification rate and ensuring the reliability of traceability information. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process flow of the present invention; Figure 2 This is a schematic diagram of the ink residue test in Example 1 of the present invention; Figure 3 This is a schematic diagram of the ink residue test in Example 2 of the present invention; Figure 4 This is a schematic diagram of the ink residue test in Example 3 of the present invention; Figure 5 This is a schematic diagram of the ink residue test in Example 4 of the present invention; Figure 6 This is a schematic diagram of the ink residue test in Example 5 of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0022] Please see Figures 1-6 The present invention provides a technical solution: a method for reducing the embossing effect after laser coding of paper boxes; Example 1: 100% Carbon-Free Black Ink Raw material preparation: Take 1 kg each of blue ink, yellow ink and red ink, and ensure that the three inks are all from the same series of printing inks; prepare 500 mL of acrylic resin varnish, as well as a CO2 laser coding machine with a rated power of 40W, a 4-pound slider abrasion resistance testing device, and 80 g / m² degreased non-woven fabric. Preparation of carbon black-free ink: Blue ink, yellow ink and red ink are added to a mixing tank at a mass ratio of 33.3% each, and stirred at a speed of 1200 r / min for 8 minutes. After mixing evenly, carbon black-free ink is obtained. This ink does not contain any carbon black components. Printing and varnish coating: The carbon-free ink was printed onto the top of 10 medicine boxes using an offset printing machine. The area of ​​the coding area was 2cm × 1.5cm. After printing, acrylic resin varnish was immediately coated evenly on the surface of the ink layer using a coater. The coating thickness was controlled at 4μm. The boxes were then placed in an environment with a temperature of 25℃ and a relative humidity of 55% and dried for 5 hours through a combination of oxidative film formation and natural penetration. Abrasion resistance test: Using a 4-pound slider, the dried paper box ink layer was rubbed back and forth at a frequency of 43 times / min for a total of 600 rubs. After the test, no visible peeling of the ink layer was observed, and there was no exposed ink layer on the surface of the paper box. Laser coding: Start the CO2 laser coding machine, set the rated power to 40W, coding speed to 2000mm / s, and power output to 70%, and simulate the automatic machine's coding conditions to code the coding area on the top of the carton; Residual ink test: After coding, the coded area was gently stroked back and forth three times with degreased nonwoven fabric. The amount of black ink residue on the nonwoven fabric was observed and recorded. The results showed that the residual amount was 10%. Figure 2 As shown, 10 cardboard boxes were stacked in 5 layers, with 2 boxes in each layer. After 24 hours, they were disassembled. No black imprint was produced, but the ink hue was too light. Its LAB values ​​were: L: 15.89, a: 2.56, b: 0.23. The black solid density was 1.65, and the contrast of some of the burned-in code information was insufficient.

[0023] Example 2: Carbon black-free ink: ordinary carbon black ink = 1:0.2 Raw material preparation: Prepare 1 kg of carbon-free black ink, and 33.3% each of blue ink, yellow ink, and red ink; Prepare 0.2 kg of ordinary carbon black ink. The resin system is phenolic resin modified with rosin and boiled with linseed oil, containing 18% high-pigment carbon black; the rest of the equipment and materials are the same as in Example 1. Preparation of mixed ink: 1 kg of carbon black-free ink and 0.2 kg of ordinary carbon black ink were put into a mixing tank and stirred at 1500 r / min for 10 minutes. After mixing evenly, a compatible mixed ink was obtained. The ink was observed to have no layering or clumping. Printing and varnishing: The printing and varnishing steps are the same as in Example 1. After drying, the surface of the ink layer is smooth. Abrasion resistance test: The test was conducted under the conditions of Example 1. After 600 rubs, the ink layer did not peel off, indicating that the abrasion resistance was qualified. Laser coding: The laser coding parameters are the same as in Example 1. The information is clearly identifiable after coding. Residual amount test: After gently rubbing the non-woven fabric 3 times, if... Figure 3 As shown, the residual black ink content is 15%; Ten cardboard boxes were stacked in five layers for 24 hours, and there were no black embossing marks on the top and bottom boxes. The measured density of the black solid was 1.65, and the LAB values ​​were L: 14.59, a: 1.57, and b: 0.89. The hue was jet black, meeting the requirements for appearance and information recognition.

[0024] Example 3: Carbon black-free ink: ordinary carbon black ink = 1:0.5 Raw material preparation: Prepare 1 kg of carbon-free black ink, and 33.3% each of blue ink, yellow ink, and red ink; Prepare 0.5 kg of ordinary carbon black ink containing 16% high-pigment carbon black. The resin system is the same as in Example 2, and the rest of the equipment and materials are the same as in Example 1. Preparation of mixed ink: Mix 1 kg of carbon black-free ink with 0.5 kg of ordinary carbon black ink and stir for 9 minutes. The system is compatible and does not separate into layers. Printing and varnishing: The printing and varnishing steps are the same as in Example 1. After drying, the ink layer has good adhesion. Abrasion resistance test: After 600 cycles of friction with a 4-pound slider, the ink layer did not peel off, and the abrasion resistance met the requirements; Laser coding: Coding is performed at 40W power, 2000mm / s speed, and 70% power output, resulting in clear information; Residual amount test: After gently rubbing the non-woven fabric 3 times, if... Figure 4 As shown, the residual black ink content is 50%; Ten cardboard boxes were stacked in five layers for 24 hours, and a slight black dent appeared on the top of the bottom cardboard box. The measured density of the black solid was 1.75, with LAB values ​​of L: 14.46, a: 1.78, and b: 1.57. The hue was too dark, and the high residual amount affected the appearance of the stack.

[0025] Example 4: Carbon-free ink: Ordinary carbon black ink = 1:1 Raw material preparation: Prepare 1 kg of carbon-free black ink, and 33.3% each of blue ink, yellow ink, and red ink; Prepare 1 kg of ordinary carbon black ink containing 20% ​​high-pigment carbon black, and use the same resin system as in Example 2; the rest of the equipment and materials are the same as in Example 1. Preparation of mixed ink: Mix 1 kg of carbon black-free ink with 1 kg of ordinary carbon black ink and stir for 12 minutes. After the mixture is evenly mixed, the ink is dark black. Printing and varnish application: The printing and varnish application steps are the same as in Example 1. After drying, the ink layer shows no abnormalities. Abrasion resistance test: After 600 cycles of friction, the ink layer did not peel off, indicating that the abrasion resistance is qualified; Laser coding: The coding is performed according to the parameters in Example 1, and the information is readable; Residual amount test: After gently rubbing the non-woven fabric 3 times, if... Figure 5 As shown, the residual black ink content is 55%; Ten cardboard boxes were stacked in five layers for 24 hours, and obvious black embossing appeared on the top of the bottom three layers of cardboard boxes. The measured density of the black solid color was 2.12, and the LAB values ​​were L: 6.90, a: -0.24, b: -0.51. The hue was too dark, and the high residual amount led to prominent imprinting problems.

[0026] Example 5: 100% Ordinary Carbon Black Ink Raw material preparation: Prepare 1 kg of ordinary carbon black ink containing 15% high-pigment carbon black. The resin system is phenolic resin modified with rosin derivatives and then boiled with linseed oil. The other equipment and materials are the same as in Example 1.

[0027] Ink usage: Print directly using the above-mentioned ordinary carbon black ink; no mixing is required. Printing and varnishing: The printing and varnishing steps are the same as in Example 1. After drying, the ink layer is pure black. Abrasion resistance test: After 600 cycles of friction with a 4-pound slider, the ink layer did not peel off, indicating that the abrasion resistance is qualified; Laser coding: The coding is performed according to the parameters in Example 1, and the information is clear; Residual amount test: After gently rubbing the non-woven fabric 3 times, if... Figure 6 As shown, the residual black ink content is 60%; Ten cardboard boxes were stacked in five layers for 24 hours. All the boxes had severe black embossing on the top and bottom, and some of the embossing obscured the burned code information. The measured density of the black solid material was 1.90, and the LAB values ​​were L: 10.86, a: 0.74, and b: 1.82. Although the hue was jet black, the residual amount was too high and could not meet the requirements for stacking.

[0028] Based on the test results of the above embodiments, the density test at the solid black area is as follows: Table 1: Density at solid black areas Considering hue, density, abrasion resistance, and laser coding effect, Example 2 uses a carbon-free black to ordinary black ink ratio of 1:0.2, which meets the experimental requirements. Through the compatible mixing of carbon-free black ink and ordinary carbon black ink, the total amount of residue during laser coding is significantly reduced from 60% to 15% while ensuring hue and density. The protective film formed by the acrylic resin varnish reduces excessive damage to the ink layer during laser coding and prevents residue from being transferred to other cartons due to pressure during stacking, thus eliminating black embossing at the source. The following test method is used to detect the amount of residual ink, as shown in the table below: Table 2: Ink Residue Detection The optimal ratio was selected through residual amount testing. In Example 2, the ratio of carbon black-free ink to ordinary carbon black ink was 1:0.2. After laser coding, the residual amount was only 15%, which is much lower than that of pure ordinary carbon black ink. In Example 5, the residual amount was 60%. Actual stacking verification showed that there was no black imprint on the top and bottom of the cardboard box under this ratio. This effectively avoids the problem of imprinting and affecting the appearance caused by the excessive weight of the contents inside the cardboard box, improves the appearance qualification rate of the cardboard box, and avoids the damage to the appearance caused by imprinting, thus meeting the requirements of traceability code reading.

[0029] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for reducing the embossing effect after laser coding on paper boxes, characterized in that, include: Step 1: Preparation of carbon-free black ink: Mix blue ink, yellow ink and red ink at a mass ratio of 33.3% each to obtain carbon-free black ink; Step 2: Preparation of ordinary carbon black ink: Add 15%-20% high-pigment carbon black to the resin system to prepare ordinary carbon black ink; Step 3: Mix the carbon-free ink obtained in Step 1 with the ordinary carbon black ink obtained in Step 2. The resin systems of both the carbon-free ink and the ordinary carbon black ink are phenolic resin modified with rosin or rosin derivatives and then boiled with drying vegetable oil. Step 4: Print the mixed ink obtained in Step 3 onto the surface of the paper box, apply acrylic resin varnish on the printed ink layer, and use a combination of oxidative film formation and natural penetration to dry the varnish. Step 5: Using a 4-pound slider, rub the ink layer of the coated paper box back and forth at a frequency of 43 times / min for a total of 600 rubs to verify that the ink does not peel off. Step 6: Laser coding: A CO2 laser coding machine with a rated power of 40W is used to laser code the paper box at a speed of 2000mm / s and 70% power to simulate the automatic machine coding process. Step 7: Residual amount test: After the coding is completed, gently stroke the coding area back and forth with non-woven fabric, observe and record the amount of black ink residue on the non-woven fabric; Step 8: Determine the ink ratio: Based on hue, density, abrasion resistance, and laser coding residue, select the mixing ratio of carbon-free ink and ordinary carbon black ink for use in paper box production; The selected mixing ratio is carbon-free ink: ordinary carbon black ink = 1:0.

2. Under this ratio, the solid black density is 1.65, the LAB value is L: 14.59, a: 1.57, b: 0.89, and the ink residue after laser coding is 15%.

2. The method for reducing the embossing effect after laser coding of paper boxes according to claim 1, characterized in that: The amount of high-pigment carbon black added to the ordinary carbon black ink in step 2 is 15%-20%.

3. The method for reducing the embossing effect after laser coding of paper boxes according to claim 1, characterized in that: In step 3, the carbon-free ink and ordinary carbon black ink are mixed, and the system is compatible and does not separate.

4. The method for reducing the embossing effect after laser coding of paper boxes according to claim 1, characterized in that: The drying vegetable oil mentioned in step 3 is flaxseed oil.

5. The method for reducing the embossing effect after laser coding of paper boxes according to claim 1, characterized in that: In step 6, the laser coding is simulated by an automatic machine for coding the wire.

6. The method for reducing the embossing effect after laser coding of paper boxes according to claim 1, characterized in that: The nonwoven fabric stroking method in step 7 is to stroke back and forth 3 times.

7. The method for reducing the embossing effect after laser coding of paper boxes according to claim 1, characterized in that: The optimal ink mixing ratio in step 8 is a mass ratio of carbon-free ink to ordinary carbon black ink of 1:0.2.

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