Method for quantitative image analysis of liquid breakthrough of barrier coatings

Abstract

A method for quantifying a liquid breakthrough of a barrier coating is disclosed, the method comprising: a) providing a system for acquiring and analyzing an image of a wetted substrate; b) loading the wetted substrate on a holder; c) irradiating the wetted substrate with an illumination 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 a 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 showing the amount or percentage of the liquid on the wetted substrate.

Description

Technical Field

[0001] The present invention generally relates to methods for identifying and quantifying liquid breakthrough of barrier coatings using image analysis. Background Art

[0002] Barrier coatings are important commercial products used to protect food, products, and other materials. Barrier coatings for paper substrates include, for example, fluorocarbon pulp treatments, extruded polyethylene coatings, and water-based coatings. Sustainability goals are driving the industry toward solvent-free and thinner coatings. However, meeting sustainability goals without compromising coating performance remains a challenge.

[0003] Evaluating the performance of these coatings is essential to determining whether they are performing adequately. Barrier coating performance is one of the most important performance metrics used by consumers and researchers. Resistance to liquids, such as water or oil and grease, is a key performance criterion in the food and packaging industries.

[0004] For example, grease breakthrough of paper coatings is typically observed or measured by humans. Identification and quantification of grease breakthrough is often difficult to quantify accurately, reproducibly, and / or quickly because the process is time-consuming.

[0005] A method is needed that can more accurately and reproducibly detect liquid breakthrough of a barrier coating to identify and quantify the properties of the barrier coating. Summary of the Invention

[0006] The present invention relates to a method for quantifying liquid breakthrough of a barrier coating, the method comprising:

[0007] a) providing a system for acquiring and analyzing images, the system comprising:

[0008] i) an imaging system for acquiring one or more images of the wetted substrate;

[0009] ii) an illumination system comprising at least one light source for illuminating the wetted substrate;

[0010] iii) a holder for holding the wetted substrate in a position to be irradiated by the at least one light source;

[0011] iv) an analysis unit configured to transform the one or more images and perform a quantitative analysis on the transformed one or more images for grease breakthrough of the release coating,

[0012] b) loading the wetted substrate onto the holder, wherein the wetted substrate comprises an oily or greasy stain;

[0013] c) illuminating the wet substrate with the illumination system;

[0014] d) acquiring at least one image of the wetted substrate with the imaging system;

[0015] e) transforming the at least one image of the wet substrate with the analysis unit, wherein transforming the at least one image of the wet substrate comprises processing the at least one image of the wet substrate with an algorithm selected from the group consisting of image thresholding, wavelet transform, morphological transform, color detection, pattern detection, clustering, and combinations thereof to provide at least one transformed image, and quantifying grease breakthrough of the release coating based on the at least one transformed image; and

[0016] f) providing an output, wherein the output comprises a value identifying the amount or percentage of the oil or grease on the wet substrate and / or a generated image showing the amount or percentage of the oil or grease on the wet substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of a system for acquiring and analyzing images according to an embodiment of the present invention.

[0018] Figure 2 is a schematic diagram of the position of a light source relative to a wetted substrate according to an embodiment of the present invention.

[0019] Figure 3 is a series of images illustrating image transformations analyzed by an image analysis system according to an embodiment of the present invention.

[0020] Figure 4 is a parity graph comparing the percent breakthrough of grease counted by a human observer with the percent breakthrough of grease quantified by the method according to an embodiment of the present invention.

[0021] Figure 5A and Figure 5B An acquired image and a transformed image, respectively, of a wetted substrate analyzed by an image analysis system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present inventors have discovered a method for reproducibly and accurately identifying and quantifying liquid breakthrough of a barrier coating.

[0023] As used herein, the term "barrier coating" refers to a film or coating designed to prevent the passage of liquids, such as oil or grease. Preferably, the barrier coating is formed on a substrate, such as a paper or cardboard substrate. Such barrier coatings are known in the art and are commonly used to protect food or products. Barrier coatings may include commercially available coatings.

[0024] As used herein, the term "wetted substrate" refers to a substrate that has been in contact with a liquid, such as water or stained with oil or grease. For example, the wetted substrate may include an absorbent material, such as paper, or any other material through which a liquid is observed to penetrate the barrier coating. The substrate may include metal, plastic, wood, glass, composites, fiberglass, paper, fabric, leather, or other substrates. For testing, it is preferred that the substrate have a flat or planar surface.

[0025] As used herein, the term "breakthrough" refers to the passage of a liquid through a barrier coating. For example, a barrier coating designed to prevent water penetration can be tested for water breakthrough. Similarly, a barrier coating designed to prevent oil or grease penetration can be tested for grease breakthrough. Any combination of liquid and barrier coating can be analyzed by the methods of the present invention to detect liquid breakthrough. The analysis for each combination of liquid and barrier coating is similar.

[0026] In one embodiment, the release coating is tested for grease breakthrough. Grease breakthrough is a measure of the release coating's resistance to grease or oil. To test for grease breakthrough, the release coating is typically placed on top of a substrate that will absorb or show oil or grease that penetrates the release coating. The oil or grease is placed on top of the release coating, and after a predetermined amount of time, the substrate is observed to determine whether the oil or grease has penetrated the release coating, and if so, how much oil or grease has penetrated the release coating. The oil or grease can be applied directly to the surface of the release coating, or it can be applied to a pad or other article placed on top of the release coating. A weight can be applied to the top of the oil or grease to apply pressure and speed up the testing process.

[0027] To analyze liquid breakthrough of barrier coatings, a system for analyzing and quantifying grease breakthrough is provided. Figure 1 A schematic diagram of a system 100 for analyzing and quantifying defects is shown in FIG. The system 100 comprises an imaging system 10 , an illumination system 20 , a holder 30 for holding a wet substrate 35 , and an analyzing unit 40 .

[0028] The imaging system 10 is configured to acquire one or more images of the wet substrate 35. The imaging system 10 can be configured to acquire images of multiple channels, wherein each of the multiple channels includes a predetermined range of wavelengths. For example, each channel can be composed of wavelengths associated with monochromatic light in the visible spectrum (e.g., red = 620nm to 780nm, orange = 585nm to 620nm, etc.). Alternatively, each channel can be composed of wavelengths in a predetermined range (e.g., channel 1 = 400nm to 500nm, channel 2 = 500nm to 600nm, etc.). In yet another example, one channel can include the visible spectrum and a second channel can include the ultraviolet spectrum or the infrared spectrum. In another example, one channel can include wavelengths in the near infrared range (800nm ​​to 1000nm) and a second channel can include wavelengths longer than the infrared wavelength (e.g., 1000nm to 1500nm).

[0029] To identify and quantify liquid breakthrough, the imaging system can be configured to acquire images in the channel most relevant to the color of the defect. For example, when analyzing a wet substrate using a liquid that has a different color than the wetted substrate, imaging system 10 can be configured to acquire at least one image in a channel that includes wavelengths associated with the liquid's color. A second channel can be used as a control. If the liquid absorbs or reflects ultraviolet or infrared radiation differently than the substrate, imaging system 10 can be configured to acquire at least one image in the ultraviolet and / or infrared spectrum.

[0030] Imaging system 10 may include, for example, a camera, a thermal imaging system, an ultraviolet imaging system, or an image sensor. Imaging system 10 may further include an optical filter configured to preferentially or selectively transmit or block light of predetermined wavelengths, such as at least one channel of predetermined wavelengths. For example, when imaging system 10 is configured to detect in the ultraviolet spectrum, an optical filter may be used to block channels of visible light. For example, when using the infrared spectrum, an optical filter may be used to block visible wavelengths and allow transmission of infrared wavelengths.

[0031] The illumination system 20 includes at least one light source for illuminating the wetted substrate 35. The illumination system 20 can be configured to emit radiation in the visible spectrum, infrared spectrum, ultraviolet spectrum, and combinations thereof. Preferably, the illumination system is configured to emit radiation at a wavelength associated with at least one of the multiple channels used by the imaging system 10. The at least one light source can include a single light source or multiple light sources. When a single light source is used, the light source can include a ring light or a diffuser to provide uniform illumination of the wetted substrate 35. When multiple light sources are used, the light sources can be arranged to provide uniform illumination. The multiple light sources can also be controlled individually or in predetermined groups to control the illumination of the wetted substrate 35. Preferably, the illumination system 20 is configured to allow adjustment of the intensity of the light, the angle of incidence on the wetted substrate 35, or the wavelength of the emitted light.

[0032] The substrate holder 30 is used to hold a wet substrate 35 for imaging by the imaging system 10. The holder 30 is configured to hold the wet substrate in a position to be illuminated by the illumination system 20 when the wet substrate is imaged. The holder 30 can be configured to hold a single wet substrate 35 or a plurality of wet substrates. The holder 30 can be stationary or adapted to allow for automated loading / unloading of samples.

[0033] 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, Figure 1 As shown, the imaging system 10 can be mounted on an arm 101 attached to a vertical support 102. The arm 101 can be configured to be adjustable so that the distance between the imaging system 10 and the holder 30 can be selected. Alternatively, the arm 101 can be moved between more than one position. In another alternative, the holder 30 can be adjusted to raise or lower the holder 30 using a base 103, or the angle of the holder can be adjusted relative to a fixed position.

[0034] Preferably, at least one of the lighting system 20 and the holder 30 is adjustable relative to each other so that the position of the wetted substrate 35 can be changed relative to the lighting system 20. For example, the lighting system 20 can be adjusted in height or angle relative to the holder 30 to change the incident angle α of the light 25, such as Figure 2 As shown. For example, the illumination system 20 can be adjusted to make the angle of incidence on the wet substrate 35 shallower or steeper. In addition, the illumination system 20 can be adjusted to allow the illumination system 20 to be rotated around the wet substrate 35 so that the angle of incidence α is the same, but the light is directed onto the wet substrate 35 from a different angle, such as from the side of the wet substrate 35 rather than the front. To reduce the potential impact of external lighting, the system 100 can be covered or encapsulated (not shown) so that only light from the illumination system 20 is used to acquire the image.

[0035] The system 100 further includes an analysis unit 40 configured to transform the image acquired by the imaging system 10 into a transformed image. The analysis unit 40 further quantitatively analyzes the transformed image to identify and / or quantify the amount or percentage of liquid breakthrough of the barrier coating, as indicated by the amount or percentage of liquid wetting the substrate 35. The analysis unit 40 may include, for example, a computer, a workstation, a laptop, a tablet computer, or a smartphone. The analysis unit 40 may include an application or program suitable for transforming and analyzing the image from the imaging system 10. The information obtained and / or generated by the system 100 may be stored locally in the analysis unit 40, a server, a cloud storage device, or a media storage device.

[0036] The analysis unit 40 is preferably configured to transform the acquired image by processing the acquired image using an algorithm selected from the group consisting of image thresholding, wavelet transform, morphological transform, color detection, pattern detection, contrast detection, clustering, and combinations thereof. The transformed image can then be analyzed by the analysis unit 40 to identify and / or quantify the liquid on the wetting substrate 35 and provide an output of the analysis. Preferably, the output includes a value indicating the number / percentage of liquid breakthroughs and / or an image or data set identifying the location, size, and / or number / percentage of liquid breakthroughs.

[0037] Preferably, the analysis unit 40 includes or is connected to a display including 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 wet substrate 35. Alternatively, the GUI may display a transformed image identifying the location, size, and / or number / percentage of wetted areas on the wet substrate.

[0038] The method for identifying and quantifying liquid breakthrough of a barrier coating according to the present invention comprises providing a system for acquiring and analyzing an image, loading a wet substrate onto a holder, illuminating the wet substrate with an illumination system, acquiring at least one image of the wet substrate with an imaging system, transforming the at least one image of the wet substrate with an analysis unit to provide at least one transformed image, identifying and quantifying oil or liquid on the wet substrate based on the at least one transformed image, and providing an output. Preferably, the liquid is selected from water or oil / grease.

[0039] In one embodiment, the analysis is configured to process the acquired image to identify the breakthrough region by transforming the acquired image using a morphological transformation. The transformation of the acquired image may further include increasing contrast in the image, transforming or straightening the perspective of the image, reducing noise in the image, and combinations thereof.

[0040] Example

[0041] The samples were prepared using a camera as an imaging system, an illumination system for illuminating the substrate with white light, and a customizable sample holder for holding the wet substrate for imaging and analysis. Figure 1 A similarly arranged system is shown.

[0042] All or a subset of the acquired images are then transformed using an image analysis algorithm that transforms the acquired images.The image analysis algorithm identifies and quantifies the amount or percentage of liquid wetting the substrate.

[0043] Grease resistance test

[0044] A paper substrate coated with a release layer was tested for grease resistance. A 1-inch diameter cloth soaked in oil was placed on top of the release-coated paper substrate, which was then placed on a piece of graph paper on a glass surface. A 50g brass weight was placed on top of the cloth and allowed to remain there for a predetermined period of time. The graph paper was then removed and analyzed by a human tester using a system according to the present method. The human tester was able to provide a subjective quantification of the area affected by grease by counting the number of grease-covered squares on the graph paper. The system of the present invention was used to acquire, analyze, and quantify images to provide reproducible and accurate values ​​for the area stained with grease.

[0045] Figure 3 A series of images showing the transformations applied by the system of the present invention are shown in FIG. The image initially acquired at Figure 3 The image is shown in frame A. The corners of the image are identified in frame B, and this information is used to transform the image's perspective, as shown in frame C. Noise is reduced, as shown in frame D. The image is then subjected to a processing algorithm for morphological transformation, 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 full extent of the grease transferred to the paper have been identified by the analysis unit, and a reproducible and quantifiable value for the defect has been obtained. Figure 4 A parity diagram comparing the percentage of oil breakthrough counted by a human observer with the percentage of breakthrough identified and quantified by the image analysis method of the present invention is shown in FIG. Figure 5A and Figure 5B Representative samples of the acquired and transformed images are shown in , respectively.

Claims

1. A method for quantifying liquid breakthrough of a barrier coating, the method comprising: a) providing a system for acquiring and analyzing images, said system comprising i) an imaging system for acquiring one or more images of the wetted substrate; ii) an illumination 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 analyzing unit configured to transform the one or more images and perform a quantitative analysis of the transformed one or more images for liquid breakthrough of the barrier coating, b) loading the wetted substrate onto the holder, wherein the wetted substrate comprises liquid that has passed through the release coating; c) illuminating the wetted substrate with the illumination system; d) acquiring at least one image of the wetted substrate with the imaging system; e) transforming the at least one image of the wet substrate with the analysis unit, wherein transforming the at least one image of the wet substrate comprises processing the at least one image of the wet substrate with an algorithm selected from the group consisting of image thresholding, wavelet transform, morphological transform, 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 the amount or percentage of the liquid on the wetted substrate and / or a generated image showing the amount or percentage of the liquid on the wetted substrate.

2. The method of 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 comprises channels selected from at least one of a visible spectrum, an infrared spectrum, and an ultraviolet spectrum.

3. The method of any one of the preceding claims, wherein at least one of the imaging system and the holder is adjustable to change at least one parameter selected from the group consisting of 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 wet substrate with the imaging system comprises adjusting the relative position between the imaging system and the holder to acquire at least two images of the wet substrate at different positions.

4. The method according to any one of the preceding claims, wherein at least one of the illumination system and the holder is adjustable to change at least one parameter selected from the group consisting of an angle between the illumination system and the holder, a distance between the illumination system and the holder, and a relative position between the illumination system and the holder, and acquiring at least one image of the wet substrate with the imaging system comprises adjusting the relative position between the illumination system and the holder to acquire at least two images of the wet 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 spectrum, the infrared spectrum and the ultraviolet spectrum.

7. The method of 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 certain wavelength in one of the plurality of channels or preferentially blocks light of a certain wavelength in one of the plurality of channels.

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

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

10. The method of any one of the preceding claims, further comprising preparing the wetted substrate by placing a release coating on a top surface of a substrate, applying a liquid to the top surface of the release coating, and allowing the liquid to penetrate the release 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 of claim 11, wherein the liquid is selected from oil or grease.

13. The method of any preceding claim, wherein the wetted substrate comprises an absorbent material.

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

15. The method of any preceding claim, wherein the release coating comprises a release coating formed on paper.

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