A test method for gloss varnish texture

Abstract

This invention relates to the fields of pharmaceuticals, food, and cosmetics, and discloses a method for testing the particle texture of varnishes, comprising the following steps: S1. Preparing the sample to be tested; S2. Acquiring a microscopic image; S3. Image processing and analysis; S4. Calculating the proportion of the highlight area. This method for testing the particle texture of varnishes, by acquiring a microscopic image of the sample surface and using image processing technology to calculate the specific value of the "proportion of the highlight area," transforms the subjective sensory evaluation, which originally relied on human observation and tactile touch, into an objective and repeatable numerical indicator. This fundamentally solves the industry problem of inconsistent evaluation results due to subjective differences among different testers, providing a unified and traceable objective standard for product quality control and judgment. Compared to indirect and highly variable assessments using macroscopic physical quantities such as friction coefficient and smoothness, this method directly acts on the microstructure itself that forms the particle texture.

Description

Technical Field

[0001] This invention relates to the fields of pharmaceuticals, food, and cosmetics, specifically a method for testing the glossy texture of granules. Background Technology

[0002] In the packaging and printing industry, especially in fields with special requirements for the appearance and feel of high-end packaging such as pharmaceuticals, food, and cosmetics, a surface treatment technology called "Reverse Effect" is widely used. The principle of this technology is to use two varnishes with different surface tensions (usually one is a base coat and the other is a reverse varnish) and a specific printing process. During the drying and curing process of the coating, due to incompatibility or differences in shrinkage, a granular structure of varying size and density is formed at the micro level, thereby creating a unique frosted and granular texture in terms of visual and tactile senses, enhancing the texture and added value of the product. However, controlling this grainy texture is a major challenge in the production process. The size and uniformity of the grains directly determine the sensory characteristics of the packaging box surface, such as smoothness and gloss. Currently, the industry mainly relies on two methods to evaluate this grainy texture: Subjective sensory evaluation: This method relies on visual observation and touch by quality inspectors or customers. It is greatly affected by individual experience and subjective differences, and lacks objective and unified evaluation standards. This can lead to inconsistent evaluation conclusions for the same sample, causing problems for production quality judgment, customer acceptance and market feedback. Indirect instrument measurement: In order to seek objective data, existing technologies attempt to use physical testing instruments for indirect evaluation, such as: Friction coefficient tester: It indirectly reflects the surface roughness (granularity) by measuring the static friction coefficient and dynamic friction coefficient of the sample surface. However, the data obtained by this method fluctuates greatly, is not sensitive enough to subtle changes in particle size, and the test results are affected by multiple factors such as pressure, speed, and test surface, making it difficult to accurately and stably correspond to specific differences in particle morphology. Smoothness tester: It assesses surface smoothness by measuring the time required for a certain volume of air to pass through the gap between the sample surface and the measuring head ring. However, this method is also a macroscopic and indirect physical property test, and cannot directly quantify key characteristics such as the size and area ratio of micro particles. In summary, the existing technology lacks a method that can directly, objectively, and quantitatively measure and evaluate the surface graininess formed by reverse varnish. The uncertainty of subjective evaluation and the inaccuracy of indirect measurement bring significant obstacles to the production stability control, quality standardization, and process optimization of this special effect process. Therefore, developing a test method that can accurately and reliably characterize the strength and morphology of varnish graininess has become an urgent technical problem to be solved in this field. Summary of the Invention

[0003] The purpose of this invention is to provide a testing method for the particle appearance of varnish, in order to solve the problems mentioned in the background art, such as the reliance on subjective evaluation, lack of objective and unified standards, and the inaccuracy of existing indirect instrument measurement methods, which make it difficult to directly quantify the microscopic particle characteristics, thus making it difficult to accurately evaluate and effectively control the particle appearance effect of reverse varnish.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for testing the graininess of varnish, comprising the following steps: S1. Preparation of the test sample: Reverse varnish printing is performed on the substrate to obtain a test sample with a grainy surface; S2. Acquire a microscopic image: Acquire a microscopic image of the particle-like surface of the sample under test at a magnification of 100x; S3. Image processing and analysis: Thresholding is performed on the microscopic image using image processing software to distinguish and extract the highlight areas in the image; S4. Calculate the proportion of the highlight area: Calculate the proportion of the area of ​​the highlight area to the total area of ​​the microscopic image to obtain the highlight area proportion. The value of the highlight area proportion is used to characterize the strength of the graininess. The smaller the proportion, the stronger the graininess and the more dispersed the grains.

[0005] Preferably, in step S1, reverse varnish printing includes: A water-based base coat, a reverse printing ink, and a reverse varnish are sequentially applied to the substrate. The water-based base coat is composed of a water-based acrylic emulsion.

[0006] By adopting the above technical solution and using water-based acrylic emulsion as the base oil, a stable coating foundation can be provided, which exhibits good incompatibility with subsequent reverse inks and varnishes, thereby promoting the formation of a grainy texture.

[0007] Preferably, the substrate is 300g white cardboard.

[0008] Using the above technical solution, 300g white cardboard is used as the standard substrate. It has sufficient thickness, stiffness and surface flatness to stably support the printed coating, reduce the interference of the substrate itself on the test results, and ensure the standardization and repeatability of the test.

[0009] Preferably, in step S3, the image processing software is IMAGEJ.

[0010] Using the above technical solution, IMAGEJ software is an open-source and powerful image processing and analysis tool. Its thresholding and particle analysis functions are mature and reliable, and it can accurately and efficiently extract and analyze the highlight region features in microscopic images.

[0011] Preferably, the method further includes S5: The calculated proportion of the highlight area is compared with a preset evaluation standard to determine whether the graininess of the sample meets the requirements.

[0012] By adopting the above technical solution, the calculated quantitative data is compared with the preset standard, which enables an objective and rapid determination of the particle effect and transforms subjective sensory evaluation into an executable quality control standard.

[0013] Preferably, the evaluation criterion is: when the proportion of the highlight area is less than 5%, it is judged to be qualified in terms of graininess.

[0014] Using the above technical solution, this quantitative standard (less than 5%) is established based on the high consistency between the test results of the examples and traditional sensory evaluation (e.g., examples 1 and 2 are qualified, and example 3 is unqualified), providing a clear and unified numerical boundary for whether the production process is qualified or not.

[0015] Preferably, the method further includes performing a friction coefficient test and a smoothness test on the sample to be tested before performing step S2.

[0016] By adopting the above technical solution, adding friction coefficient and smoothness tests before image analysis can provide supplementary data on the macroscopic physical properties of the sample surface, which helps to comprehensively evaluate surface characteristics from multiple dimensions and corroborate the microscopic quantitative indicator of "highlight area ratio".

[0017] Preferably, when evaluating in conjunction with the proportion of the highlight area, the comprehensive standard for qualified graininess includes: a dynamic friction coefficient greater than 0.12, a smoothness of less than 55 seconds, and a highlight area proportion of less than 5%.

[0018] By adopting the above technical solution, this comprehensive standard combines quantitative indicators of macroscopic physical properties (friction coefficient, smoothness) and microscopic morphology (proportion of highlight area), providing a more comprehensive and reliable comprehensive evaluation system for graininess, and can more accurately judge whether the graininess effect is excellent.

[0019] Preferably, the reverse varnish is applied by an anilox roller, and the coating amount of the anilox roller is 18 g / m².

[0020] By adopting the above technical solution, the coating amount of the reverse varnish is standardized to 18g / m², which can ensure the consistency of process parameters in the sample preparation stage, thereby reducing the impact of coating amount fluctuation on the final graininess and ensuring the stability and comparability of the test method starting point (i.e., the sample).

[0021] Compared with the prior art, the beneficial effect of the present invention is: the test method for the graininess of the varnish: 1. By acquiring microscopic images of the sample surface and using image processing technology to calculate the specific value of "highlight area ratio", the subjective sensory evaluation that originally relied on human eye observation and tactile touch is transformed into an objective and repeatable digital indicator. This fundamentally solves the industry problem of inconsistent evaluation results caused by subjective differences among different testers, and provides a unified and traceable objective standard for product quality control and judgment. 2. Compared with indirect and highly variable evaluations using macroscopic physical quantities such as friction coefficient and smoothness, this method directly targets the microstructure that forms the graininess. Through thresholding, it accurately separates and quantifies the area of ​​the highlight region in the image that represents the graininess. Test results show that the "highlight region ratio" obtained by this method is highly consistent with the intuitive observation effect of the sample under a magnifying glass and the tactile evaluation, thus reflecting the true strength and morphological characteristics of the graininess more accurately and directly. 3. Parameterizing the assessment of particle texture provides clear quantitative targets for quality control in the production process. This helps companies conduct rapid and stable online or offline testing during production, promptly identify the impact of process fluctuations on the final result, and effectively guide the adjustment, optimization, and standardization of the production process, thereby improving the stability and consistency of product quality. 4. It combines conventional sample preparation, standard optical microscopic observation, and mature image processing software for analysis. The equipment and technologies involved are common in industrial and laboratory environments. The operation process is clear, the learning cost is low, and it is easy to promote and apply in quality inspection departments and R&D centers in the packaging and printing and related industries. Attached Figure Description

[0022] Figure 1 This is a layered diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the image processing interface of the present invention; Figure 3 This is a schematic diagram of the Results window showing the image processing results of this invention; Figure 4 This is a magnified image of particle distribution under a microscope, representing an embodiment of the present invention. Figure 5 This is a schematic diagram of the highlight area of ​​IMAGE J in various embodiments of the present invention. Detailed Implementation

[0023] 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.

[0024] Please see Figures 1-5 The present invention provides a technical solution: a test method for the particle texture of varnish.

[0025] Example 1: Sample Preparation Substrate: 300g white cardboard.

[0026] Printing method: The "full UV" printing process is adopted. First, the initial printing and coating of water-based base oil (composed of water-based acrylic emulsion) are completed on a regular printing press. Then, the reverse ink and reverse varnish are printed and coated on a UV printing press.

[0027] Key process parameters: The reverse varnish is applied using an anilox roller with a coating amount of 18g / ㎡; the ink content of the reverse ink is controlled between 65-70%.

[0028] Drying method: After the base coat dries once, the subsequent reverse ink and reverse varnish are applied to create a distinct grainy texture.

[0029] Results of traditional method testing: Smoothness: Test results ranged from 1.7 to 12.2 seconds.

[0030] Friction coefficients: static friction coefficient is 0.25-0.36, dynamic friction coefficient is 0.11-0.12.

[0031] Magnifying glass observation: Under a 100x magnifying glass, the particle boundaries are clear and continuous, and the particles are evenly dispersed.

[0032] Subjective feel: Strong tactile sensation, with a noticeable grainy texture.

[0033] Test of the method of this invention: Obtain 100x magnification microscopic images of the granular surface of the above samples, and at 1920 nm. Saved at 1440 pixels.

[0034] Import the image into the IMAGEJ image processing software and use its thresholding function to distinguish and mark the highlight areas (corresponding to the light reflection areas between particles) in the image from the background (particle body).

[0035] The software's "Analyze Particles" function calculates the proportion of the highlight area to the total area of ​​the entire image, i.e., the "highlight area ratio".

[0036] Test results: The measured proportion of the highlight area was 4.69%. After image processing, it was found that the highlight area was mainly composed of relatively complete continuous lines, which is consistent with the effect of "dispersed particles and clear boundaries" observed under a magnifying glass. Moreover, the "proportion of highlight area" value was small, which confirms the evaluation of strong tactile feel.

[0037] Example 2: Sample Preparation Substrate: 300g white cardboard.

[0038] Printing method: The process of "ordinary printing + UV reverse varnishing" is adopted. First, printing is completed on an ordinary printing press and water-based base oil (the composition is water-based acrylic emulsion) is applied. Then, reverse varnish is applied on a UV machine.

[0039] Key process parameters: The reverse varnish uses an anilox roller with a coating amount of 18g / ㎡; the reverse ink volume is controlled at 70-72%.

[0040] Drying method: Same as in Example 1.

[0041] Results of traditional method testing: Smoothness: The test result was 12.7-14.5 seconds.

[0042] Friction coefficients: static friction coefficient is 0.16-0.30, dynamic friction coefficient is 0.12-0.14.

[0043] Magnifying glass observation: Under a 100x magnifying glass, the particles are relatively clear, but compared to Example 1, the particle distribution is relatively concentrated.

[0044] Subjective feel: Medium tactile feel.

[0045] Test of the method of this invention: Following the same steps as in Example 1, microscopic images were acquired and analyzed using IMAGEJ software.

[0046] Test results: The measured proportion of the highlight area was 4.86%. After image processing, it was shown that the highlight area was a combination of dots and lines. This value was slightly higher than that in Example 1, indicating that the area of ​​the highlight area was slightly larger, which corresponds to the result of "relatively concentrated particles" and "medium" feel evaluation observed under a magnifying glass.

[0047] Example 3: Sample Preparation Substrate: 300g white cardboard.

[0048] Printing method: "Ordinary printing + UV reverse varnishing" process.

[0049] Key process parameters: The reverse varnish uses an anilox roller with a coating amount of 13g / ㎡ (different from 18g in Examples 1 and 2); the reverse ink volume is controlled at 50-55%.

[0050] Drying method: Same as in Examples 1 and 2.

[0051] Results of traditional method testing: Smoothness: The test result was 60-70 seconds, which is much higher than that of Examples 1 and 2.

[0052] Friction coefficient: static friction coefficient is 0.15-0.18, dynamic friction coefficient is 0.15-0.17, the dynamic friction coefficient is higher than that in Examples 1 and 2.

[0053] Magnifying glass observation: Under a 100x magnifying glass, the particle boundaries are not clear and the distribution is relatively concentrated.

[0054] Subjective feel: Weak tactile sensation, indistinct graininess.

[0055] Test of the method of this invention: Following the same steps as in Example 1, microscopic images were acquired and analyzed using IMAGEJ software.

[0056] Test results: The proportion of the highlight area was measured to be 10.98%. After image processing, it was found that the highlight area was mainly dotted. This value was significantly higher than that of Examples 1 and 2, indicating that the area of ​​the highlight area on the sample surface was relatively large, that is, the particle structure was not prominent. This is completely consistent with the observation results of "unclear and concentrated particle boundaries" under the magnifying glass and the evaluation of "weak" feel.

[0057] Comparative Analysis and Conclusions of Examples: As can be seen from the above three examples, the "highlight area ratio" values ​​obtained by the method of the present invention (Example 1: 4.69%, Example 2: 4.86%, Example 3: 10.98%) can accurately and quantitatively distinguish the different levels of graininess produced under different process parameters. This value is highly consistent with traditional subjective evaluation (feel: strong, medium, weak) and visual observation results under a magnifying glass (particle dispersion, boundary clarity), and can clearly distinguish process differences (such as the significant difference in effect between 13g and 18g of varnish coating).

[0058] Based on the results of the combined embodiments, a quantitative evaluation standard can be established: when tested using the method of the present invention, if the obtained "highlight area ratio" is less than 5%, the dynamic friction coefficient is greater than 0.12, the smoothness is less than 55 seconds, and the particles are clearly dispersed and the boundaries are clear when observed under a magnifying glass, the particle effect of the reverse varnish printing can be judged to be qualified and excellent. This verifies the effectiveness and practicality of the method of the present invention as an objective and accurate quantitative testing means in guiding production and quality control.

[0059] Example 4: Actual measurement using IMAGEJ: Detailed testing steps: Step 1: Image Preprocessing Convert to 8-bit grayscale: Image > Type > 8-bit, simplify the image; Step 2: Image segmentation and thresholding; The goal is to clearly separate the particles from the background.

[0060] Click `Image`>`Adjust`>`Threshold`.

[0061] Drag the slider to turn all the particles to be measured white against a black background. Drag the threshold slider to 175 and click `Apply` to generate a black and white image. The highlight areas will become clearer. Figure 2 Step 3: One-click analysis Click Analyze > AnalyzeParticles In the pop-up window, set the parameters: Size: Sets the minimum area of ​​the particles, which can filter out noise; Circularity: Generally set to 0.00-1.00, indicating that it accepts particles of all shapes.

[0062] Check Exclude on edges and Display results.

[0063] Click OK, and the results will automatically appear in the Results window, such as... Figure 3 ; Final step: The last value is read from %Area in the area reading. The result is interpreted as the proportion of the highlight area in the whole image in terms of graininess. The smaller the highlight area, the larger the reverse graininess, the more dispersed the grains, and the more obvious the texture. The IMAGEJ analysis results are consistent with previous experience. The data of Example 3 are quite different from those of Examples 1 and 2, and are close to the effect under a magnifying glass. 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 testing the graininess of varnish, characterized in that: Includes the following steps: S1. Preparation of the test sample: Reverse varnish printing is performed on the substrate to obtain a test sample with a grainy surface; S2. Acquire a microscopic image: Acquire a microscopic image of the particle-like surface of the sample under test at a magnification of 100x; S3. Image processing and analysis: Thresholding is performed on the microscopic image using image processing software to distinguish and extract the highlight areas in the image; S4. Calculate the proportion of the highlight area: Calculate the proportion of the area of ​​the highlight area to the total area of ​​the microscopic image to obtain the highlight area proportion. The value of the highlight area proportion is used to characterize the strength of the graininess. The smaller the proportion, the stronger the graininess and the more dispersed the grains.

2. The method for testing the graininess of varnish according to claim 1, characterized in that: In step S1, reverse varnish printing includes: A water-based base coat, a reverse printing ink, and a reverse varnish are sequentially applied to the substrate. The water-based base coat is composed of a water-based acrylic emulsion.

3. The method for testing the graininess of varnish according to claim 1, characterized in that: The substrate is 300g white cardboard.

4. The method for testing the graininess of varnish according to claim 1, characterized in that: In S3, the image processing software is IMAGEJ.

5. The method for testing the graininess of varnish according to claim 1, characterized in that: The method further includes S5: The calculated proportion of the highlight area is compared with a preset evaluation standard to determine whether the graininess of the sample meets the requirements.

6. The method for testing the graininess of varnish according to claim 5, characterized in that: The evaluation criterion is: when the highlight area accounts for less than 5%, the graininess is considered acceptable.

7. The method for testing the graininess of varnish according to claim 1, characterized in that: The method further includes performing friction coefficient testing and smoothness testing on the sample to be tested before performing step S2.

8. The method for testing the graininess of varnish according to claim 7, characterized in that: When evaluating in conjunction with the proportion of the highlight area, the comprehensive standard for acceptable graininess includes: a dynamic friction coefficient greater than 0.12, a smoothness of less than 55 seconds, and a highlight area proportion of less than 5%.

9. The method for testing the graininess of varnish according to claim 1, characterized in that: The reverse varnish is applied by an anilox roller, with a coating amount of 18 g / m².

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