Process for quantitative image analysis of liquid breakthrough of barrier coatings

Abstract

A method for quantifying liquid breakthrough of a barrier coating comprises: a) providing a system for acquiring and analyzing images of a wetted substrate; b) loading the wetted substrate on a holder; c) illuminating the wetted substrate with a lighting system; d) acquiring at least one image of the wetted substrate with an imaging system; e) transforming the at least one image of the wetted substrate with an analysis unit to provide at least one transformed image and quantifying liquid breakthrough of the barrier coating based on the at least one transformed image; and f) providing an output, wherein the output comprises a value identifying an amount or percentage of the liquid on the wetted substrate and / or a generated image illustrating the amount or percentage of the liquid on the wetted substrate.

Description

[0001] PROCESS FOR QUANTITATIVE IMAGE ANALYSIS OF LIQUID BREAKTHROUGH OF BARRIER COATINGS

[0002] FIELD OF THE INVENTION

[0003] This invention relates generally to processes for identifying and quantifying liquid breakthrough of barrier coatings using image analysis.

[0004] BACKGROUND

[0005] Barrier coatings are an important commercial product used to protect food, products, and other materials. Barrier coatings for paper substrates include, for example, fluorocarbon pulp treatment, extruded polyethylene coatings, and waterborne coatings. Sustainability goals are driving the industry towards solvent free and thinner coatings. However, meeting sustainability goals without compromising performance of coatings remains a challenge.

[0006] Evaluating the performance of these coatings is necessary to determine whether the coatings perform adequately. The performance of a barrier coating is one of the most important performance evaluation metrics used by consumers and researchers. Liquid resistance, such as, for example, water or oil and grease resistance, is a key performance criterion in the food and packaging industry.

[0007] For example, grease breakthrough of paper coatings is typically observed or measured by a human. The identification and quantification of grease breakthrough is often difficult to quantify accurately, reproducibly, and / or quickly as the process takes a significant amount of time.

[0008] There is a need for a process that can more accurately and reproducibly detect liquid breakthrough of barrier coatings to identify and quantify the performance of the barrier coating. SUMMARY OF THE INVENTION

[0009] The invention relates to a method for quantifying liquid breakthrough of a barrier coating, comprising: a) providing a system for acquiring and analyzing images, comprising: i) an imaging system for acquiring one or more images of a wetted substrate; ii) a lighting system comprising at least one light source for illuminating the wetted substrate; iii) a holder for holding the wetted substrate in a position to be illuminated by the at least one light source; iv) an analysis unit configured to transform the one or more images and quantitatively analyze the one or more transformed images for grease breakthrough of the barrier coating, b) loading the wetted substrate on the holder, wherein the wetted substrate comprises a stain comprising oil or grease; c) illuminating the wetted substrate with the lighting system; d) acquiring at least one image of the wetted substrate with the imaging system; e) transforming the at least one image of the wetted substrate with the analysis unit, wherein transforming the at least one image of the wetted substrate comprises processing the at least one image of the wetted substrate with an algorithm selected from the group consisting of image thresholding, wavelet transformation, morphological transformation, color detection, pattern detection, clustering, and combinations thereof, to provide at least one transformed image and quantifying grease breakthrough of the barrier coating based on the at least one transformed image; and f) providing an output, wherein the output comprises a value identifying an amount or percentage of the oil or grease on the wetted substrate and / or a generated image illustrating the amount or percentage of the oil or grease on the wetted substrate.

[0010] BRIEF DESCRIPTION OF THE FIGURES

[0011] Figure 1 is a schematic drawing of a system for acquiring and analyzing images according to an embodiment of the present invention.

[0012] Figure 2 is a schematic drawing of the position of a light source with respect to a wetted substrate according to an embodiment of the invention.

[0013] Figure 3 is a series of images demonstrating the transformation of an image analyzed by an image analysis system according to an embodiment of the present invention.

[0014] Figure 4 is a parity plot comparing the percentage breakthrough of grease counted by a human observer and the percentage breakthrough of grease as quantified by the process according to an embodiment of the present invention.

[0015] Figure 5 A and FIG. 5B are acquired and transformed images, respectively, of a wetted substrate analyzed by an image analysis system according to an embodiment of the present invention.

[0016] DETAILED DESCRIPTION

[0017] The inventors have found a process for reproducibly and accurately identifying and quantifying liquid breakthrough of a barrier coating.

[0018] As used herein, the term “barrier coating” refers to a film or coating designed to prevent a liquid, such as, for example, oil or grease, from passing through. Preferably, the barrier coating is formed on a substrate, such as, for example, a paper or cardboard substrate. Such barrier coatings are known in the art and are often used to protect food or products. The barrier coatings may include commercially available coatings.

[0019] As used herein, the term “wetted substrate” refers to a substrate that has been contacted with liquid, such as, for example, contacted with water or stained by oil or grease. For example, the wetted substrate may comprise an absorbent material such as paper or may comprise any other material on which a liquid that penetrates a barrier coating may be observed. The substrate may comprise a metal, plastic, wood, glass, composite, fiberglass, paper, fabric, leather, or other substrate. For testing, it is preferred that the substrate has a flat or planar surface.

[0020] As used herein, the term “breakthrough” refers to the passage of the liquid through the barrier coating. For example, a barrier coating designed to prevent penetration of water may be tested for water breakthrough. Similarly, a barrier coating designed to prevent penetration of oil or grease may be tested for grease breakthrough. Any combination of liquid and barrier coating may be analyzed by the process of the present invention to detect breakthrough of the liquid. The analysis is similar for each combination of liquid and barrier coating.

[0021] In one embodiment, the barrier coating is tested for grease breakthrough. Grease breakthrough is a measure of a barrier coatings resistance to grease or oil. To test for grease breakthrough, a barrier coating is typically placed on top of a substrate that will absorb or show oil or grease that penetrates the barrier coating. Oil or grease is placed on top of the barrier coating and, after a predetermined amount of time has passed, the substrate is observed to determine whether the oil and grease has penetrated through the barrier coating, and if so, how much oil or grease has penetrated the barrier coating. The oil or grease may be applied directly to the surface of the barrier coating, or the oil or grease may be applied to a pad or other article placed on top of the barrier coating. A weight may be applied to the top of the oil or grease to apply pressure and accelerate the testing process. To analyze liquid breakthrough of a barrier coating, a system for analyzing and quantifying grease breakthrough is provided. A schematic drawing of a system for analyzing and quantifying defects 100 is shown in FIG. 1. The system 100 comprises an imaging system 10, a lighting system 20, a holder 30 for holding a wetted substrate 35, and an analysis unit 40.

[0022] Imaging system 10 is configured to acquire one or more images of the wetted substrate 35. The imaging system 10 may be configured to acquire images for a plurality of channels, wherein each of the plurality of channels comprises a predetermined range of wavelengths. For example, each of the channels may consist of wavelengths associated with a single color of light in the visible spectrum (e.g., red = 620 to 780 nm, orange = 585 to 620 nm, etc.). Alternatively, each channel may consist of a predetermined range of wavelengths (e.g., channel 1 = 400 to 500 nm, channel 2 = 500 to 600 nm, etc.). In yet another example, one channel may comprise the visible light spectrum and a second channel may comprise either the ultraviolet spectrum or infrared spectrum. In another example, one channel may comprise wavelengths in the near-infrared range (800 to 1000 nm) and a second channel may comprise wavelengths longer infrared wavelengths (e.g., 1000 to 1500 nm).

[0023] To identify and quantify the liquid breakthrough, the imaging system may be configured to acquire images in channels most relevant to the color of the defect. For example, when analyzing a wetted substrate using liquid having a different color than the substrate, the imaging system 10 may then be configured to acquire at least one image in a channel comprising wavelengths associated with the color of the liquid. A second channel may be used as a control. If the liquid absorbs or reflects ultraviolet or infrared radiation differently than the substrate, the imaging system 10 may be configured to acquire at least one image in the ultraviolet and / or infrared spectra. The imaging system 10 may comprise, for example, a camera, a thermal imaging system, an ultraviolet imaging system, or an image sensor. The imaging system 10 may further comprise a filter for preferentially or selectively transmitting or blocking predetermined wavelengths of light, such as, for example, at least one channel of a predetermined wavelength. For example, when the imaging system 10 is configured to detect in the ultraviolet spectrum, a filter may be used to block channels of visible light. For example, when using the infrared spectrum, filters may be used to block visible wavelengths and allow transmission of infrared wavelengths.

[0024] The lighting system 20 comprises at least one light source for illuminating the wetted substrate 35. The lighting system 20 may be configured to emit radiation in the visible light spectrum, the infrared spectrum, the ultraviolet spectrum, and combinations thereof. Preferably, the lighting system is configured to emit radiation in wavelengths associated with at least one of the plurality of channels used by the imaging system 10. At least one light source may comprise a single light source or a plurality of light sources. When a single light source is used, the light source may comprise a ring light or a diffuser to provide uniform illumination to the wetted substrate 35. When a plurality of light sources are used, the light sources may be arranged to provide uniform lighting. The plurality of light sources may also be controlled individually or within a predetermined group to control the lighting of the wetted substrate 35. Preferably, the lighting system 20 is configured to allow for adjustments to the intensity of the light, the angle of incidence on the wetted substrate 35, or wavelength of light emitted.

[0025] The substrate holder 30 is used to hold the wetted substrate 35 for imaging by the imaging system 10. The holder 30 is configured to hold the wetted substrate in a position to be illuminated by the lighting system 20 as it is imaged. The holder 30 may be configured to hold a single wetted substrate 35 or a plurality of wetted substrates. The holder 30 may be stationary or adapted to allow samples to be automatically loaded / unloaded.

[0026] Preferably, at least one of the imaging system 10 and the holder 30 is adjustable so that the position of the wetted substrate 35 can be changed relative to the imaging system 10. For example, as shown in FIG. 1, the imaging system 10 may be mounted on an arm 101 attached to a vertical support 102. The arm 101 may be configured to be adjustable such that the distance between the imaging system 10 and the holder 30 can be selected. Alternatively, the arm 101 may be moveable between more than one position. In another alternative, the holder 30 may be adjustable to raise or lower the holder 30 using base 103, or the angle of the holder with respect to a fixed position may be adjusted.

[0027] Preferably, at least one of a the lighting system 20 and the holder 30 is adjustable relative to each other such that the position of the wetted substrate 35 can be changed relative to the lighting system 20. For example, the lighting system 20 may be height or angle adjustable relative to the holder 30 to change the angle of incidence, a, of the light 25 as shown in FIG. 2. For example, the lighting system 20 may be adjustable to allow for a shallower or steeper angle of incidence on the wetted substrate 35. Additionally, the lighting system 20 may be adjustable to allow for rotation of the lighting system 20 around the wetted substrate 35 such that the angle of incidence, a, is the same, but the light is directed on the wetted substrate 35 from a different angle, e.g., from the side rather than the front of the wetted substrate 35. To reduce potential influence by outside lighting, the system 100 may be covered or enclosed (not shown) such that only light from the lighting system 20 is used to acquire the images.

[0028] The system 100 further comprises an analysis unit 40 configured to transform images acquired by the imaging system 10 into transformed images. The analysis unit 40 further quantitatively analyzes the transformed images to identify and / or quantify the amount or percentage of liquid breakthrough of the barrier coating, as shown by the amount or percentage of liquid on the wetted substrate 35. The analysis unit 40 may comprise, for example, a computer, workstation, notebook computer, tablet computer, or smartphone. The analysis unit 40 may comprise an application or program adapted to transform and analyze the images from the imaging system 10. Information obtained and / or generated by the system 100 may be stored locally within the analysis unit 40, a server, cloud storage, or media storage device.

[0029] The analysis unit 40 is preferably configured to transform acquired images by processing the acquired images with an algorithm selected from image thresholding, wavelet transformation, morphological transformation, color detection, pattern detection, contrast detection, clustering, and combinations therefore. The transformed images may then be analyzed by the analysis unit 40 to identify and / or quantify the liquid on the wetted substrate 35 and to provide an output of the analysis. Preferably, the output comprises a value signifying the quantity / percentage of liquid breakthrough and / or an image or data set identifying the location, size, and / or quantity / percentage of the liquid breakthrough.

[0030] Preferably, the analysis unit 40 comprises or is connected to a display comprising a graphical user interface (GUI). The GUI is preferably configured to display the output of the analysis unit 40. For example, the GUI may display a value quantifying the amount or percentage of liquid present on the wetted substrate 35. Alternatively, the GUI may display a transformed image identifying the location, size, and / or number / percentage of the wetted area on the wetted substrate.

[0031] The method of identifying and quantifying liquid breakthrough of a barrier coating according to the present invention comprises providing the system for acquiring and analyzing images, loading a wetted substrate on the holder, illuminating the wetted substrate with the lighting system, acquiring at least one image of the wetted substrate with the imaging system, transforming the at least one image of the wetted substrate with the analysis unit to provide at least one transformed image and identifying and quantifying oil or liquid on the wetted substrate based on the at least one transformed image, and providing the output. Preferably, the liquid is selected from water or oil / grease.

[0032] In one embodiment, the analysis is configured to process the acquired image by transforming the acquired image by morphological transformation to identify the breakthrough area. The transformation of the acquired image may further comprise increasing the contrast levels in the image, transforming or straightening the perspective of the image, reducing the noise in the image, and combinations thereof.

[0033] Examples

[0034] A system having a similar arrangement as shown in FIG. 1 was prepared using a camera as the imaging system, a lighting system to illuminate the substrate with white light, and a customizable sample holder to hold a wetted substrate for imaging and analysis.

[0035] All or a subset of the acquired images were then transformed using an image analysis algorithm that transformed the acquired images. The image analysis algorithm identified and quantified the amount or percentage of liquid on the wetted substrate.

[0036] Grease Resistance Test

[0037] A barrier coated paper substrate was subjected to grease resistance testing. A 1 inch diameter cloth soaked with an oil was placed on top of a barrier coated paper substrate, which was then placed on a piece of graph paper on a glass surface. A 50 g brass weight was placed on top of the cloth and allowed to remain for a predetermined time period. The graph paper was then removed and analyzed using the system according to the present method and by a human tester. The human tester was able to provide a subjective quantification of the area affected by the grease by counting the number of squares covered with grease on the graph paper. Using the inventive system, images were acquired, analyzed and quantified to provide a reproducible and accurate value of the area stained by the grease.

[0038] A sequence of images showing the transformations applied by the inventive system is shown in FIG. 3. The initial acquired image is shown in frame A of FIG. 3. The corners of the image are identified in frame B, and that information is used to transform the perspective of the image as shown in frame C. Noise is reduced as shown in frame D. The image is then subjected to a processing algorithm to conduct a morphological transform, as shown in frame E, to produce the transformed image in frame F. As shown in the final transformed image in frame F, the shape and entire extent of the grease transferred to the paper has been identified by the analysis unit and a reproducible and quantifiable value of the defect was obtained. A parity plot comparing the percentage of grease breakthrough counted by a human observer and the percentage breakthrough identified and quantified by the image analysis process of the inventive process is shown in FIG. 4. A representative sample of an acquired image and a transformed image is shown in FIGS. 5 A and 5B, respectively.

Claims

WHAT IS CLAIMED IS:

1. A method for quantifying liquid breakthrough of a barrier coating, comprising: a) providing a system for acquiring and analyzing images, comprising i) an imaging system for acquiring one or more images of a wetted substrate; ii) a lighting system comprising at least one light source for illuminating the wetted substrate; iii) a holder for holding the wetted substrate in a position to be illuminated by the at least one light source; iv) an analysis unit configured to transform the one or more images and quantitatively analyze the one or more transformed images for liquid breakthrough of the barrier coating, b) loading the wetted substrate on the holder, wherein the wetted substrate comprises liquid that passed through a barrier coating; c) illuminating the wetted substrate with the lighting system; d) acquiring at least one image of the wetted substrate with the imaging system; e) transforming the at least one image of the wetted substrate with the analysis unit, wherein transforming the at least one image of the wetted substrate comprises processing the at least one image of the wetted substrate with an algorithm selected from the group consisting of image thresholding, wavelet transformation, morphological transformation, color detection, pattern detection, clustering, and combinations thereof, to provide at least one transformed image and quantifying liquid breakthrough of the barrier coating based on the at least one transformed image; and f) providing an output, wherein the output comprises a value identifying an amount or percentage of the liquid on the wetted substrate and / or a generated image illustrating the amount or percentage of the liquid on the wetted substrate.

2. The method according to claim 1, wherein the imaging system is configured to acquire images at a plurality of channels, wherein each of the plurality of channels comprises a predetermined range of wavelengths, wherein the plurality of channels comprise channels selected from at least one of the visible light spectrum, the infrared spectrum, and the ultraviolet spectrum.

3. The method according any one of the preceding claims, wherein at least one of the imaging system and the holder is adjustable to vary at least one parameter selected from an angle between the imaging system and the holder, a distance between the imaging system and the holder, and a relative position between the imaging system and the holder, and acquiring at least one image of the wetted substrate with the imaging system comprises adjusting a relative position between the imaging system and the holder to acquire at least two images of the wetted substrate at different positions.

4. The method according to any one of the preceding claims, wherein at least one of the lighting system and the holder is adjustable to vary at least one parameter selected from an angle between the lighting system and the holder, a distance between the lighting system and the holder, and a relative position between the lighting system and the holder, and acquiring at least one image of the wetted substrate with the imaging system comprises adjusting a relative position between the lighting system and the holder to acquire at least two images of the wetted substrate at different positions.

5. The method according to any one of the preceding claims, wherein the at least one light source comprises a ring light or a diffuse light source.

6. The method according to any one of the preceding claims, wherein the at least one light source emits light in at least one spectrum selected from the visible light spectrum, the infrared spectrum, and the ultraviolet spectrum.

7. The method according to any one of the preceding claims, wherein the imaging system further comprises at least one filter, wherein the at least one filter preferentially transmits light of a wavelength in one of the plurality of channels or preferentially blocks light of a wavelength in one of the plurality of channels.

8. The method according to any one of the preceding claims, further comprising displaying the output on a graphical user interface (GUI).

9. The method according to any one of the preceding claims, wherein transforming the at least one image of the wetted substrate comprises morphological transformation.

10. The method according to any one of the preceding claims, further comprising preparing the wetted substrate by placing a barrier coating on a top surface of a substrate, applying a liquid to a top surface of the barrier coating, and allowing the liquid to penetrate the barrier coating for a predetermined period of time to form the wetted substrate.

11. The method according to any one of the preceding claims, wherein the liquid is selected from water, oil or grease.

12. The method according to claim 11, wherein the liquid is selected from oil or grease.

13. The method according to any one of the preceding claims, wherein the wetted substrate comprises an absorbent material.

14. The method according to claim 13, wherein the absorbent material is paper.

15. The method according to any one of the preceding claims, wherein the barrier coating comprises a barrier coating formed on paper.

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