Method for improving color gathering of heat shrink film

Abstract

The invention discloses a method for improving color gathering of a heat shrink film, and relates to the technical field of heat shrink film printing. According to the method, the shrinkage ratio of each segment is accurately calculated by measuring the reference perimeter of a low-shrinkage area and the segment perimeter of a high-shrinkage area of a bottle body; making a T ruler strip based on an association rule of a shrinkage ratio and a dot ratio, and positioning a to-be-compensated area through a thermal shrinkage test; and in combination with a color density partition compensation coefficient and an exclusive compensation formula, dot accurate compensation is realized. According to the method, independent testing and debugging for each color are not needed, the full-color system can be adapted only through a single reference compensation curve, the operation process is remarkably simplified, and the production efficiency is improved; the color gathering phenomenon of high-deformation areas of the bottle body can be effectively eliminated, the color consistency of labels in all the areas is guaranteed, and the method is suitable for large-scale production of heat shrinkage film labels of bottle products.

Description

Technical Field

[0001] This invention relates to the field of heat shrink film printing technology, specifically to a method for improving color aggregation in high deformation areas of heat shrink film by combining shrinkage ratio calculation with dot compensation. Background Technology

[0002] Heat shrink film, with its heat-shrink lamination properties, has been widely used as a packaging label for various bottle products, achieving a decorative packaging effect that tightly adheres to the bottle body. However, during the heat shrinkage process, areas such as the bottle shoulder and mouth experience concentrated material shrinkage due to structural design, forming high-deformation areas. The printed colors in these areas will accumulate due to material shrinkage, resulting in a visually deeper color and an abnormally increased color density. This creates a significant hue difference compared to the low-deformation areas such as the middle and bottom of the bottle, severely compromising the overall aesthetics and color consistency of the product packaging.

[0003] Existing solutions for uneven color in heat shrink film generally employ a crude approach of adjusting the overall printing color density, failing to consider the differences in shrinkage rates across different areas of the bottle, resulting in poor color compensation. Furthermore, existing solutions require repeated testing and adjustments for each printing color individually, leading to cumbersome procedures, long debugging cycles, and low production efficiency, failing to meet the demands of industrial-scale production. Therefore, there is an urgent need to develop a highly accurate, easy-to-operate, and highly efficient reverse compensation technology to completely solve the color aggregation problem in high-deformation areas of heat shrink film, ensuring overall color consistency on the label. Summary of the Invention

[0004] This invention aims to overcome the shortcomings of the prior art and provide a method to improve the color aggregation of heat shrink film. The core objective is to solve the problem of color accumulation and uneven hue caused by the concentrated shrinkage in the high deformation area of ​​the bottle; to achieve accurate and consistent label color in all areas of the bottle (high deformation area and low deformation area); to simplify the operation process, shorten the debugging cycle, reduce production costs, and improve production efficiency to meet the needs of large-scale production.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: 1. A method for improving the color cohesion of heat-shrinkable film, characterized by comprising the following steps: S1. Select the bottle type to be shrunk and measure the reference circumference in a flat, low-shrinkage area in the middle or bottom of the bottle. ; S2. Measure the perimeter of the high-shrinkage area segment by segment along the axial direction of the bottle at preset intervals from the self-shrinkage initiation point. , i=1,2,...,n; S3, according to the formula Calculate the shrinkage ratio S of each segment. i; S4. Based on the color density of the low - shrinkage area, according to the calculated shrinkage ratio S i , design and manufacture a T - scale bar in the way that the dot - area percentage decreases correspondingly with the shrinkage ratio increasing by a certain determined ratio; S5. Determine the compensation coefficient K according to the color density D, and calculate the dot - area percentage Mi after compensation for each part through the reference compensation curve formula The value of the compensation coefficient K is as follows: when D > 1.2, K≈0.9; when 0.7 < D ≤ 1.2, K = 1.0; when 0.3 < D ≤ 0.7, K≈1.15; when D ≤ 0.3, K≈0.5; is the dot - area percentage of the low - shrinkage area; S6. Print the colors of each corresponding part of the heat - shrinkable film according to the dot - area percentage after compensation.

[0006] Preferably, the reference compensation curve in step S6 is established based on black or the main color and applied to all printing channels of colors.

[0007] Preferably, the preset interval in step S2 is 5mm, the shrinkage starting point is at the beginning of the bottle shoulder, and the measurement end point is at the end of the bottleneck.

[0008] Preferably, the low - shrinkage area in step S4 is the middle part of the bottle body or the flat area at the bottom. Preferably, the shrinkage ratio in step S4 is in the range of 0% - 22%, and no artificial lightening treatment is required.

[0009] Preferably, the value of the compensation coefficient K in each color - density interval in step S5 is obtained by printing the T - scale bar in step S4 on the heat - shrinkable film with different color densities and then thermally shrinking and fitting it on the bottle body for testing. During the test, the final required dot - area percentage of the part with the maximum shrinkage ratio is obtained by adjusting the dot - area percentage of the part with the maximum shrinkage ratio multiple times. The final required dot - area percentage should ensure that the color of the part with the maximum shrinkage ratio after thermal shrinkage is consistent with that of the low - shrinkage area. Then, based on the reference compensation curve formula calculate the value of the compensation coefficient k in this density interval.

[0010] Adopting the above technical solutions, the present invention has the following remarkable beneficial effects: 1. High compensation accuracy: By segmentally measuring the perimeter of the high - shrinkage area and calculating the local shrinkage ratio, accurate positioning of areas with different deformation degrees is achieved. Combining the color - density - partition compensation coefficient and the exclusive compensation formula, the dot - area percentage is adjusted specifically, completely eliminating the color aggregation phenomenon in the high - deformation area, ensuring that the label colors in all areas of the bottle body are uniformly consistent, and significantly improving the aesthetics and standardization degree of product packaging.

[0011] 2. Improved production efficiency: By establishing a mathematical model of "shrinkage ratio - compensation amount", all printing colors can be adapted by calibrating the baseline compensation curve with only black or the main color. There is no need to measure the bottle, make T-strips and adjust them separately for each color. This greatly simplifies the operation process, shortens the production preparation cycle, reduces production costs and meets the needs of large-scale production.

[0012] 3. Wide adaptability: It introduces a color density zoning compensation coefficient, and sets differentiated compensation coefficients for different shades of color (high density, medium density, low density) to ensure that all colors can maintain visual consistency after shrinkage, adapting to the printing needs of multiple color systems and with a wide range of application scenarios.

[0013] 4. High practicality: The threshold range of 0%~22% shrinkage ratio that does not require additional processing is clearly defined, reducing unnecessary debugging steps. At the same time, parameters such as segmented measurement interval and compensation coefficient are clearly defined, the operation is highly repeatable, and it is easy to promote and apply in industrial applications. Attached Figure Description

[0014] Figure 1 This is a schematic diagram showing the perimeter of various parts of the bottle body to be shrunk and the corresponding calculated shrinkage ratio.

[0015] Figure 2 This is a schematic diagram showing the color pattern of a T-shaped strip printed on a heat-shrinkable film and then heat-shrinkable on the bottle. Detailed Implementation

[0016] Example: Color enhancement of dark green heat shrink film 1. Parameter preset Select the bottle type to be shrunk, and use the flat area in the middle of the bottle as the low-shrinkage area. Measure the reference circumference of this area. =190.3mm.

[0017] 2. Perimeter measurement of high contraction areas in segments Starting at the bottle shoulder and ending at the bottle neck, the perimeter of each segment of the high-shrinkage area was measured at 5mm intervals along the bottle's axial direction. And record all measurement data (the specific measurement results are shown in Figure 1).

[0018] 3. Shrinkage ratio calculation According to the formula Calculate the shrinkage ratio S of each segment. i The calculation results show that the shrinkage ratio of the high shrinkage area measured in this study ranges from 0.15% to 39.5% (the specific shrinkage ratio distribution is shown in Figure 1).

[0019] 4. Making T-shaped strips Based on the 100% actual dot ratio of the low shrinkage area (middle of the bottle), T-strips for testing were made according to the rule that "for every 2.5% increase in shrinkage ratio, the dot ratio decreases by 2% accordingly"; however, no additional lightening treatment was applied to the segments with shrinkage ratios of 0% to 22%.

[0020] In this embodiment, taking the part with a shrinkage ratio of 39.5% as an example, its dot ratio on the T-strip is 68.4%.

[0021] 5. T-strip printing and heat shrinkage test The completed T-shaped labels were printed in dark green (color density D=1.3, Lab values ​​L=52, a=-82, b=29) onto heat-shrink film. The heat-shrink film was then subjected to standard heat-shrink treatment to adhere it to the bottle to be shrunk. Observation revealed that in areas with a shrinkage ratio of 0%~22%, the color difference ΔE≤1.2, and color aggregation was not visible to the naked eye, requiring no further compensation; in areas with a shrinkage ratio of 22%~40%, the color difference ΔE>1.2, and color aggregation was clearly identifiable to the naked eye (as shown in Figure 2), requiring targeted dot compensation.

[0022] For example, even if the dot ratio of a part with a shrinkage ratio of 39.5% has been reduced to 68.4%, its color is still relatively darker than that of the low-shrinkage area after heat shrinkage. Therefore, the dot ratio of this part needs to be further adjusted. After multiple tests, when the dot ratio is adjusted to 65%, the color of this part is basically consistent with the color of the low-shrinkage area after shrinkage. Thus, it can be known that the final dot ratio required for this part is 65%.

[0023] Then, based on the final required dot ratio of 65% for this part and the dot ratio of 100% for the low-shrinkage area in this embodiment, the formula of the benchmark compensation curve is used. The calculated value of the compensation coefficient k in this density range is approximately 0.9. Therefore, it can be determined that the compensation coefficient K ≈ 0.9 when D > 1.2 in the medium-high color density range.

[0024] 6. Calculation of compensation for service outlets Given a compensation coefficient K≈0.9 for the dark green color (color density D=1.3) in this embodiment, and considering the shrinkage ratio S of each high-shrinkage segment... i Through the benchmark compensation curve formula Calculate the target dot ratio for each area. The compensated dot ratio for a typical high-shrinkage segment (shrinkage ratio 39.5%) is 64%. Use this method to calculate the dot ratio for all areas requiring compensation (areas with shrinkage ratios ranging from 22% to 40%). The calculated compensated target dot ratios are shown in the table below.

[0025]

[0026] 7. Final printing and effect verification Based on the calculated target dot ratio, dark green was printed on the heat-shrink film to correspond to the different parts of the bottle. After printing, the heat-shrink film underwent standard heat shrink treatment, and the Lab value of each part was measured after being attached to the bottle. The test results showed that the color difference ΔE of all areas of the bottle was ≤1.2, and the hue difference between areas was indistinguishable to the naked eye, fully meeting the color consistency requirements of the product packaging.

[0027] As can be seen from this embodiment, the method of the present invention can accurately solve the color aggregation problem in the high deformation area of ​​heat shrink film, and the operation process is simple and the compensation efficiency is high, making it suitable for large-scale production scenarios.

Claims

1. A method for improving the color cohesion of heat-shrinkable film, characterized in that, Includes the following steps: S1. Select the bottle type to be shrunk and measure the reference circumference in a flat, low-shrinkage area in the middle or bottom of the bottle. ; S2. Measure the perimeter of the high-shrinkage area segment by segment along the axial direction of the bottle at preset intervals from the self-shrinkage initiation point. , i=1,2,...,n; S3, according to the formula Calculate the shrinkage ratio S of each segment. i ; S4. Based on the color density of the low-shrinkage region, and according to the calculated shrinkage ratio S i T-strips are designed and manufactured by decreasing the mesh ratio accordingly for each increment of the shrinkage ratio. S5. Determine the compensation coefficient K according to the color density D, and perform compensation through the reference compensation curve formula to calculate the dot percentage Mi after compensation for each part; the value of the compensation coefficient K is: when D > 1.2, K ≈ 0.9; when 0.7 < D ≤ 1.2, K = 1.0; when 0.3 < D ≤ 0.7, K ≈ 1.15; when D ≤ 0.3, K ≈ 0.5; is the dot percentage of the low shrinkage area; S6. Print the colors of the corresponding parts of the heat shrink film according to the compensated dot ratio.

2. The method for improving the color of heat-shrinkable film according to claim 1, characterized in that, The baseline compensation curve in step S5 is established based on black or the primary color and is applied to the printing channels of all colors.

3. The method for improving the color cohesion of heat-shrinkable film according to claim 1, characterized in that, The preset interval in step S2 is 5mm, the shrinkage start point is the beginning of the bottle shoulder, and the measurement end point is the end of the bottle neck.

4. The method for improving the color cohesion of heat-shrinkable film according to claim 1, characterized in that, The low-shrinkage area mentioned in step S4 is the flat area in the middle or bottom of the bottle.

5. The method for improving the color cohesion of heat-shrinkable film according to claim 1, characterized in that, The shrinkage ratio in step S4 is in the range of 0% to 22%, so no artificial shallowing treatment is required.

6. The method for improving heat-shrinkable color polymerization according to claim 1, characterized in that: The compensation coefficient K for each color density range in step S5 is obtained by printing the ruler strip of step S4 (T) onto a heat-shrinkable film with different color densities and then heat-shrinking and bonding it to the bottle. During the test, the dot ratio of the part with the largest shrinkage ratio is adjusted multiple times to obtain the final required dot ratio of that part. This final required dot ratio should ensure that the color of the part with the largest shrinkage ratio is consistent with that of the low-shrinkage area after heat shrinking. Then, the final required dot ratio and the dot ratio of the low-shrinkage area are used as the basis for the compensation curve formula. Calculate the value of the compensation coefficient k in this density range.

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