WO2023014393A1

WO2023014393A1 - Laminate bond strength

Info

Publication number: WO2023014393A1
Application number: PCT/US2021/071089
Authority: WO
Inventors: Matan Schneider; Irit LEVI; Gil Fisher
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2021-08-03
Filing date: 2021-08-03
Publication date: 2023-02-09

Abstract

An example method of determining the bond strength between two layers of a laminated print media comprises advancing a laminated print media proximate a roller. The laminated print media has a plurality of layers including an uppermost layer, and the roller includes a protrusion. The laminated print media is advanced proximate the roller such that the protrusion of the roller makes an indentation in the uppermost layer of the laminated print media. A property of the indentation is measured. A measure of the bond strength between two layers of the laminated print media is determined based on the measured property of the indentation in the uppermost layer.

Description

LAMINATE BOND STRENGTH

BACKGROUND

[0001] A laminated print media is formed from multiple individual substrate layers pressed together to form the print media. A laminated print media is therefore a composite material. The properties of the composite material depend on the number of layers and the properties of each layer.

BRIEF DESCRIPTION OF DRAWINGS

[0002] Examples of the disclosure will now be described with reference to the accompanying drawings, in which:

[0003] Figure 1 is a flowchart of an example method to determine a measure of the bond strength between two layers of a laminated print media;

[0004] Figure 2 is a flowchart of an example method that may be used with the method of Figure 1;

[0005] Figure 3 is a simplified schematic of an example indentation formed by an indenter roller;

[0006] Figure 4 is a simplified schematic of an example laminated print media including a stack of layers and having an indentation formed in an uppermost surface thereof;

[0007] Figure 5 is a simplified schematic of an example apparatus for measuring a property of a laminated print media;

[0008] Figure 6 is a simplified schematic of an example indenter roller; and

[0009] Figure 7 is a flowchart of an example method to determine a measure of adhesion between two layers of a substrate.

DETAILED DESCRIPTION

[0010] Print medias are used to form containers or packaging, for example by folding and assembling a blank. Such print medias can be laminated, meaning that they are formed by joining multiple layers together in a stack. A laminated print media is therefore a composite material. The individual layers can have different compositions and therefore different properties such as tensile strength. A laminated print media may have overall properties that are improved relative to the properties of the individual layers, e.g. example improved strength, stability, elasticity etc. Good adhesion between the individual layers means that the print media can reliably be inferred to withstand forces to which it will be subject during its intended use. For example, for a laminated print media that is intended for use as packaging in the food industry, good adhesion between its layers reduces the risk of the packaging coming into contact with any food contained therein which could lead to the food being deemed unfit for consumption. Good adhesion between layers is also an indication that any packaging formed from the laminated print media can survive downstream processes such as packaging, shipping, and storage.

[0011] Some examples herein relate to determining a measure of the bond strength between two layers of a laminated print media. The bond strength is a measure of adhesion in that it is directly correlated with the force to take apart any two layers. The laminated print media includes an uppermost layer and a lowermost layer. In some examples, the laminated print media includes an intermediate layer or a plurality of intermediate layers between the uppermost and lowermost layers. Therefore, a laminated print media includes a plurality of layers (including an uppermost and a lowermost layer) arranged in a stack. According to the examples herein, a measure of the bond strength is determined between any two layers. In an example, the measure of bond strength is determined between the uppermost layer and an intermediate layer. In another example, the measure of bond strength is determined between two intermediate layers. In yet another example, the measure of bond strength is determined between an intermediate layer and the lowermost layer. To determine the measure of bond strength, the laminated print media is advanced past a roller which includes a protrusion. The protrusion projects away from an outer surface of the roller. As such, the protrusion may be termed a projection or protuberance. Examples of a protrusion include a stud, knob, impresser, or, bulge etc. The protrusion forms an indentation in the uppermost surface of the laminated print media and the indentation is subsequently analysed. Based on a property of the indentation, a measure of the bond strength is determined. In some examples, this includes determining a quantity from the measured property. For example, the measured property may be the depth of the indentation and the projected area, elastic modulus and/or hardness is be determined from the indentation, these properties indicating the strength of bond between the layers of the print media. The bond strength is used as an indicator of the reliability, durability, and/or quality of the laminated print media. The bond strength between any two layers is affected by various factors including, for example, the ambient temperature, thickness (or depth) of the print media as a whole and/or the thickness of the individual layers themselves, the number of layers, the composition of each layer, and the velocity at which one layer was applied to the other. However, the examples herein allow the bond strength between any two layers to be determined for any laminated print media. The laminated print media is subsequently graded (e.g. as pass or fail) based on a comparison between the determined property of the indentation and a stored property (e.g. a target value of the property). In some examples, determining the measure of the bond strength includes grading the laminated print media as pass or fail.

[0012] Figure 1 is an example method 100 of determining a measure of the bond strength between two layers of a laminated print media. At block 102, a laminated print media having a plurality of layers including an uppermost layer is advanced proximate a roller including a protrusion. The protrusion forms an indentation in the uppermost layer of the laminated print media. At block 104, a property of the indentation is measured. In one example, the property is measured by a sensor, such as an optical sensor or any other sensor. The size and/or shape of the indentation formed in the uppermost layer may correspond to the size and/or shape of the protrusion that made the indentation. For example, the shape of the protrusion may be a portion of a sphere, such as a spherical cap. Consequentially, the shape of the indentation is a portion of a sphere. As such, the indentation may have a depth and a radius and a circumference (e.g. a circumferential edge), any of which may be measured at block 104 of the method. The geometry of the indentation is substantially the same as the geometry of the protrusion that made the indentation, but the geometrical values may not be equal since the entire volume of the protrusion may not protrude into the laminate. Put another way, a portion of the volume of the protrusion may protrude into the laminate such that the geometrical values of the indentation (e.g. its radius etc.) are all slightly less than their corresponding values for the protrusion. This will be further explained with reference to Figure 4.

[0013] At block 106, a measure of the bond strength between two layers of the laminated print media is determined based on the property of the indentation in the uppermost layer. In one example, blocks 104 and 106 are performed by an imaging apparatus, e.g., a camera. In these examples the imaging apparatus generates an image of the indentation that is subsequently analysed to determine the bond strength of the laminate based on a property of the indentation determined from the image. In one example, an imaging apparatus is to generate an image of the indentation and subsequently analyse the image to determine a property of the indentation. In another example, an imaging apparatus is to generate the image and a separate processor analyses the image to determine a property of the indentation. For the image analysis, any clear deformities or non-uniformities in the uppermost layer (e.g. distortion or ripping) may indicate poor adhesion between any of the layers of the laminated print media. In this way, although the indentation is formed in the uppermost layer of the laminated print media, its properties are used as a reliable indicator of the adhesion between any two layers of the laminated print media. An imaging apparatus or processor may determine the depth of the indentation from the image, even a 2D image, to determine the depth of penetration into the uppermost layer of the laminated print media. In such examples, a depth that is greater than a predetermined threshold is an indicator of high residual strain. The residual strain is a measure of how far through the substrate layers the impact, as a result of the protrusion, has propagated. A low residual strain is considered indicative of good bonding between the print media’s layers. The depth may be directly proportional to the residual strain and therefore low depth is considered indicative of good bonding. An imaging apparatus or processor may also determine the size of the indentation from the image or from the radius of the indentation determined from the image. As for the depth, the size of the indentation is used as an indicator of the bond strength since a poor quality of bonding between layers corresponds to a large size of indentation. In some examples the measured property of the indentation is a property of the edge of the indentation, such as the length of the edge. Like the size of the indentation, the length of the edge is proportional to the depth and therefore a shorter edge (for example, a shorter circumference in the case of a spherical indentation) indicates good bond strength in the underlying layers. Therefore, in some examples, an imaging apparatus may generate an image of the indentation, and the imaging apparatus or a processor may determine, from the image, if the indentation is too large, or the edge too long, or the indentation too deep, etc. for the laminated print media to be of sufficient quality.

[0014] However, in some examples the property is measured by a sensor, such as an optical sensor or an acoustic sensor. Therefore, in some examples the sensor comprises an optical emitter such as a laser diode or light-emitting diode. An optical emitter may emit visible light or non-visible light. In other examples, the sensor comprises an acoustic (or audio signal) emitter such as an ultrasonic emitter. Such an acoustic emitter may emit acoustic waves of any frequency. In these examples the method includes emitting, by the sensor, a signal, such as an optical beam or an acoustic signal as described above, toward the indentation and receiving, at the sensor, a signal reflected from the indentation. In such examples, a property of the indentation is determined based on the reflected signal. For example, the time in between emission and receipt of the emitted signal is proportional to the depth of the indentation. However, in other examples, another property of the received (or reflected) signal is used, and a property other than the depth is determined. In one example, a sensor is to perform a measurement of the indentation and determine a property of the indentation. In another example, a sensor is to measure the indentation and a separate processor is to determine a property of the indentation based on the measurement of the sensor. As stated above, the measured property includes the depth, radius, size, or edge length (e.g. circumference) of the indentation. Any of these properties may be directly measured by the sensor or determined by a processor based on a measurement from the sensor. As will now be described with reference to Figure 2, in some examples, the measured property is compared to a stored value, or is used to determine another quantity that is compared to a stored value.

[0015] Figure 2 shows an example method 200 that can be used in conjunction with the method 100. At block 202 the method includes measuring a property of the indentation, as described above with respect to block 104 of the method 100. In the Figure 2 example, at block 204 the measured property is compared to a stored value. The stored value may include a target value of the property that is indicative of a good bond strength between substrate layers. According to the method 200, if the measured property is within a range including the stored value, the measure of the bond strength is determined as acceptable and the laminated print media is graded as a pass (block 206). Otherwise, it is graded as a fail (block 208). In other examples, the comparison includes determining if the measured property is greater than, or less than, a predetermined value. Whether the measured property being greater than, or less than, any given value indicates good bond strength depends on the property being measured. In some examples, any of the blocks of the method 200 are performed by a computer (or a processor) and therefore, the measure of the bond strength of the laminated print media can be performed automatically.

[0016] In some examples, grading the laminated print media as a pass comprises determining whether the measured property is within a predetermined range, less than a predetermined value, or greater than a predetermined value. In these examples the laminated print media is graded as pass/fail based on whether it meets a certain condition (within the range or less than/greater than a predetermined value). In other examples, however, the method 200 grades the laminated print media according to a different method, such as according to a sliding scale. In these examples, a grade of greater than a predetermined value corresponds to the laminated print media being graded as a pass. For example, the laminated print media may be assigned a value between 1 and 5 with any value greater than 3 constituting a pass. The value may be assigned according to the deviation between the measured property and a stored property, with the smaller the deviation corresponding to a higher assigned value, in one example.

[0017] In other examples, determining the measure of the bond strength may include deriving or calculating a further property of the indentation from the property that was measured at block 104 or 202. In some examples, the depth is measured and the projected area is determined based on the depth. In some further examples, the elastic modulus is determined based on the projected area. In yet other examples, a measure of hardness is determined based on the projected area and elastic modulus. These quantities will be explained in further detail with reference to Figure 3. In any example however, the determined quantities (e.g. projected area and/or elastic modulus and/or measure of hardness) may be compared to stored values to grade the laminated print media as pass or fail as described above with reference to blocks 204-208 of the method 200.

[0018] In one example, the roller includes a plurality of protrusions. In such examples, advancing the laminated print media proximate the roller causes a plurality of indentations to be formed in the uppermost layer of the laminated print media, with each indentation being formed by a respective protrusion. Consequentially, the method includes measuring a property of each indentation and determining an average of the measured properties. The measure of the bond strength between is then based on the determined average. In some examples, the plurality of protrusions includes protrusions of the same size and/or shape. In other examples, the plurality of protrusions includes protrusions of different sizes and/or shapes. These latter examples allow one roller to be calibrated for laminated print medias of various thicknesses and compositions.

[0019] In some examples, the laminated print media is advanced between the roller having the protrusion and an opposing roller. In these examples, the two rollers form a nip. In these examples, the method includes adjusting the distance between the rollers based on the thickness of the laminated print media. The two rollers may be caused to rotate in opposite directions and/or at the same rotational speed. The laminated print media may be advanced toward the roller at the same speed at which the roller is caused to rotate.

[0020] Figure 3 shows an example indentation 300 formed in an uppermost layer 305 of a laminated print media to illustrate some properties of the indentation 300. The indentation 300 was formed by a protrusion 302 of a roller 303. The protrusion 302 is shaped as a spherical cap and therefore has a radius R. The indentation 300 also has a radius L and a depth d. The depth d is the distance by which the protrusion 302 penetrated into the uppermost layer 305 to form the indentation 300. In this example, the protrusion 302 did not penetrate the uppermost payer 305 up to its centre and therefore there is a difference (R - d) between the radius of the protrusion 302 and the depth of the indentation 300.

[0021] Based on the depth d of the indentation 300 a number of further quantities may be determined. For example, the projected area A_p of the indentation 300 is given by:

A_p = TTL² with the radius L of the indentation 300, being given by:

L = (2dR - d²)^1/2.

Therefore, in one example, the depth d of the indentation 300 is measured and, from this quantity, the radius L of the indentation 300 and/or the projected area A_p is determined. In some examples, therefore, the depth d and/or the radius L and/or projected area A_p of the indentation 300 is used to determine a measure of the bond strength. As discussed above with reference to Figure 2, these quantities may be compared to stored values to determine the measure of the bond strength between two layers of the laminated print media.

[0022] In another example, the elastic modulus E of the laminated print media is determined from the measured depth. More specifically, the elastic modulus E may be determined from the projected area A_p. The elastic modulus E is given by:

E = 2TTSA_P, where S is the stiffness constant of the uppermost layer 305 of the laminated print media in which the indentation 300 is formed. In yet another example, a measure of the hardness is determined from the elastic modulus E and the projected area A_p. One example measure of hardness, H, is given by: H = E / Ap.

The quantity H may be referred to as the “Meyer hardness.” As discussed above with reference to Figure 2, in some examples, the elastic modulus E and/or the measure of hardness H are compared to stored values to determine the measure of the bond strength between two layers of the laminated print media. For example, there is an inverse correlation between bond strength and the determined elastic modulus such that if the determined elastic modulus is less than a predetermined threshold the laminated print media has acceptable bond strength between its layers. There is a direct correlation between bond strength and hardness such that if the determined hardness is greater than a predetermined threshold the laminated print media has acceptable bond strength between its layers.

[0023] As stated above, in some examples the measured property of the indentation 300 is a property of the edge of the indentation 300. In the Figure 3 example, the edge is a circumferential edge due to the spherical shape of the protrusion. The circumferential edge has a length C given by:

C = TTL.

Since L is related the depth d of the indentation 300, the length of the circumferential edge may be determined from the measured depth d in some examples. In other examples, the circumferential length C of the indentation 300 is directly measured.

[0024] Therefore, in one example the measured property is a depth and is compared to a stored depth. The laminated print media is graded as a pass if the measured depth is within a predetermined range including the stored depth, or if the measured depth is less than a largest acceptable depth. Otherwise, it is graded as a fail. In another example, the measured property is a depth and the projected area is determined from the depth, e.g. according to the formula above. The projected area is then compared to a stored projected area. The laminated print media is graded as a pass if the projected area is within a predetermined range including the stored projected area, or if the projected are is less than a largest acceptable projected area. Otherwise, it is graded as a fail. In another example, the measured property is a depth and the length of the edge is determined from the depth, e.g. according to the formula above, or the measured property is the length of the edge. The edge length is then compared to a stored edge length. The laminated print media is graded as a pass if the edge length is within a predetermined range including the stored edge length, or if the edge length is less than a largest acceptable edge length. Otherwise, it is graded as a fail. In another example, the measured property is a depth and the elastic modulus is determined, e.g. from the projected area as above. The determined elastic modulus is then compared to a stored elastic modulus. The laminated print media is graded as a pass if the elastic modulus is within a predetermined range including the stored elastic modulus, or if the elastic modulus is less than a largest acceptable elastic modulus. Otherwise, it is graded as a fail. In yet another example, the measured property is a depth and a hardness is determined, e.g. from the projected area and elastic modulus as above. The determined hardness is then compared to a stored hardness. The laminated print media is graded as a pass if the hardness is within a predetermined range including the stored hardness, or if the hardness is greater than a lowest acceptable hardness. Otherwise, it is graded as a fail.

[0025] Figure 4 shows an example laminated print media 400 including a plurality of layers 401-406 arranged in a stack. In this example the plurality of layers includes an uppermost layer 401 , a lowermost layer 406 (or base layer 406), and intermediate layers 402-405. Figure 4 illustrates, by the dotted line, a region of influence following the application of force by the protrusion (as indicated by the arrow). This region may be referred to as a stress field. If the adhesion between any two adjacent layers of the laminated print media 400 is poor (in a region of the stress field) then this will affect the properties of the indentation formed in the uppermost layer 401. The bond strength between any two adjacent layers, including between the lowermost layer 406 and the adjacent intermediate layer 405 or between two adjacent intermediate layers 402-405 or between the uppermost layer 401 and the adjacent intermediate layer 402, can be inferred from the protrusion in the uppermost layer 401. In other words, if any portion of the internal volume of the print media 400 is inadequately bonded, this can be determined from a property of the indentation in the uppermost layer 401. This is due to the applied force (the arrow in Figure 4) from the protrusion propagating to the lower layers of the print media 400 (e.g. in the dotted region). Therefore, if any layers, even lower layers, are inadequately bonded, this has a corresponding effect on the uppermost layers’ resilience to the force applied by the protrusion.

[0026] According to one example, layer 403 includes a printing fluid such as an ink, layer 402 includes a primer, and layer 401 includes a polymer (such as polyethylene terephthalate). In other words, the laminated print media 400 may be for use in the food industry where the uppermost plastic layer 401 is to prevent food from contacting any of the underlying layers of the laminated print media 400. [0027] Figure 5 shows an example apparatus 500 for measuring a property of a laminated print media 503. The laminated print media 503 includes a plurality of layers, for example as described with respect to Figure 4. The apparatus 500 may include a print apparatus or a printing system, such as a printer. The apparatus 500 may include a laminator to combine layers of a print media to form a laminated print media. The apparatus 500 includes an indenter roller 501. The indenter roller 501 has a protrusion 502 (shown in the exploded view) which is to contact an uppermost surface of the laminated print media 503. For example, the indenter roller 501 is to contact the uppermost surface of an uppermost layer of the laminated print media 503 (e.g. layer 401 of the Figure 4 example). The protrusion 502 is to at least partially indent the uppermost surface of the laminated print media 503 when the protrusion contacts the uppermost surface. The apparatus 500 also includes a sensor 504. The sensor 504 is an optical sensor or any other sensor. The sensor 504 is to measure a property of the indentation in the uppermost surface of the laminated print media 503. A measure of the strength of adherence between two layers of the laminated print media 503 may be determined based on the property.

[0028] In an example, the sensor 504 is to emit a signal toward the indentation and to receive a reflected signal from the indentation. In these examples, the sensor 504 determines a property of the indentation based on the reflected signal. In one example, the sensor 504 is to measure the depth of the indentation. Based on the measured depth, the sensor 504 in some examples is to determine an edge length, projected area, elastic modulus and/or hardness. In other examples, the sensor 504 is to measure a property other than the depth of the indentation such as the edge length or projected area. In some examples, the sensor 504 is an imaging apparatus to generate an image of the indentation.

[0029] In some examples, the apparatus 500 is to advance the laminated print media 503 toward the indenter roller 501 and/or past the sensor 504, as indicated by the arrow. In these examples, the apparatus 500 includes a conveyor to advance the laminated print media 503. In an example, the apparatus 500 is to cause the indenter roller 501 to rotate to form the indentation in the laminated print media 503. In other examples, the indenter roller 501 may be translatably movable (e.g. in a vertical direction) to bring the protrusion 502 into contact with the laminated print media 503 in a stamp-like manner.

[0030] Figure 6 shows a portion of an example indenter roller 600. The indenter roller 600 of this example has a plurality of protrusions of different sizes. The plurality in this example includes a first set of protrusions 601 and a second set of protrusions 602. Each protrusion in the first and second sets are spaced apart along an axial direction of the indenter roller 600 at the same radial position, in this example. The protrusions in the first set 601 are of a first size. The protrusions in the second set 602 are of a second, larger, size. Each protrusion 601 , 602 is to contact the uppermost surface of the laminated print media forming a plurality of indentations is formed in the laminated print media, each indentation corresponding to a respective protrusion. Therefore, as for the protrusions 601, 602, the indentations will be of different sizes. In other examples, the indenter roller 600 includes protrusions of different shapes, or different shapes and sizes. In some examples, to determine a measure of the bond strength, or strength of adherence between any two layers of the laminated print media, the same property of each indentation is measured, and the values are averaged. The measure of bond strength is then determined based on the calculated average, for example by comparing it to a stored value as discussed above. Referring again to Figure 5, in some examples, the indenter roller 501 includes an indenter roller 600 as depicted in Figure 6.

[0031] Using an indenter roller comprising a plurality of protrusions means that one roller is calibrated for different print media thicknesses. For example, even if the exact thickness of a laminated print media is not determined, a plurality of different sized and/or shaped indentations can be formed in an uppermost surface of the laminated print media. Then, the depth of each indentation may be measured. If all indentations of a particular size exhibit uniformly low depth, e.g. the lowest depth of the plurality, then those correspondingly sized protrusions can be considered as calibrated to that particular laminated print media. The protrusions forming the indentations having the lowest depth also exhibit the lowest residual strain. In these examples, the indentation, or indentations, indicating the lowest residual strain are used for the analysis to determine the bond strength.

[0032] Figure 7 is an example method 700 of determining a measure of adhesion between two layers of a composite substrate having a plurality of layers arranged in a stack. The method 700 includes, at block 702, contacting an outermost surface of the substrate with an indenter roller. The indenter roller includes a protrusion. At block 704, through contact between the protrusion and the outermost surface of the substrate, a depression is formed in the outermost surface of the substrate. At block 706, a property of the depression is measured. In some examples, the property is a depth of the depression. In other examples, the property is a shape and/or size of the depression. In other examples, the property is another dimension of the depression, such as its circumference. At block 708 a measure of adhesion between any two layers, e.g. a first layer and a second layer of the composite substrate, is determined based on the property of the depression. As discussed above, from the measured property, another quantity is determined in some examples. In these examples, a measure of adhesion is determined based on the other quantity. In one example, the projected area is determined from the measured depth. In another example, an elastic modulus is determined from the projected area. In yet another example a hardness is determined from the projected area and elastic modulus. In these examples, the quantity (depth, projected area, elastic modulus, hardness etc.) is compared to a stored value and the measure of hardness is determined based on the comparison, as discussed above.

[0033] The outermost layer is an uppermost layer in some examples. In other examples, the outermost layer is a lowermost, or base, layer. According to some examples, the substrate includes a plurality of intermediate layers in between two outermost layers. In these examples, the depression is formed in one of the outermost layers. The first and second layers are intermediate layers in the stack in some examples. In other examples, one of the first and second layers is an outermost layer in the stack, the other being an intermediate layer. Therefore, according to the method 700, a measure of adhesion between two intermediate layers, or between an intermediate layer and an outermost layer, can be determined.

[0034] Examples in the present disclosure can be provided as methods, systems or machine readable instructions, such as any combination of software, hardware, firmware or the like. Such machine readable instructions may be included on a computer readable storage medium (including but is not limited to disc storage, CD-ROM, optical storage, etc.) having computer readable program codes therein or thereon.

[0035] The present disclosure is described with reference to flow charts and/or block diagrams of the method, devices and systems according to examples of the present disclosure. Although the flow diagrams described above show a specific order of execution, the order of execution may differ from that which is depicted. Blocks described in relation to one flow chart may be combined with those of another flow chart. It shall be understood that each flow and/or block in the flow charts and/or block diagrams, as well as combinations of the flows and/or diagrams in the flow charts and/or block diagrams can be realized by machine readable instructions.

[0036] The machine readable instructions may, for example, be executed by a general purpose computer, a special purpose computer, an embedded processor or processors of other programmable data processing devices to realize the functions described in the description and diagrams. In particular, a processor or processing apparatus may execute the machine readable instructions. Thus functional modules of the apparatus and devices may be implemented by a processor executing machine readable instructions stored in a memory, or a processor operating in accordance with instructions embedded in logic circuitry. The term ‘processor’ is to be interpreted broadly to include a CPU, processing unit, ASIC, logic unit, or programmable gate array etc. The methods and functional modules may all be performed by a single processor or divided amongst several processors.

[0037] Such machine readable instructions may also be stored in a computer readable storage that can guide the computer or other programmable data processing devices to operate in a specific mode.

[0038] Such machine readable instructions may also be loaded onto a computer or other programmable data processing devices, so that the computer or other programmable data processing devices perform a series of operations to produce computer-implemented processing, thus the instructions executed on the computer or other programmable devices realize functions specified by flow(s) in the flow charts and/or block(s) in the block diagrams.

[0039] Further, the teachings herein may be implemented in the form of a computer software product, the computer software product being stored in a storage medium and comprising a plurality of instructions for making a computer device implement the methods recited in the examples of the present disclosure.

[0040] While the method, apparatus and related aspects have been described with reference to certain examples, various modifications, changes, omissions, and substitutions can be made without departing from the spirit of the present disclosure. It is intended, therefore, that the method, apparatus and related aspects be limited only by the scope of the following claims and their equivalents. It should be noted that the above-mentioned examples illustrate rather than limit what is described herein, and that those skilled in the art will be able to design many alternative implementations without departing from the scope of the appended claims.

[0041] The word “comprising” does not exclude the presence of elements other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims. [0042] The features of any dependent claim may be combined with the features of any of the independent claims or other dependent claims.

Claims

1. A method of determining a measure of the bond strength between two layers of a laminated print media, the method comprising: advancing a laminated print media, the laminated print media having a plurality of layers including an uppermost layer, proximate a roller including a protrusion such that the protrusion makes an indentation in the uppermost layer of the laminated print media; measuring a property of the indentation; and determining a measure of the bond strength between two layers of the laminated print media based on the measured property of the indentation in the uppermost layer.

2. The method of claim 1 , wherein the property of the indentation is the depth of the indentation.

3. The method of claim 1 , wherein the property of the indentation is the size and/or length of an edge of the indentation.

4. The method of claim 2, wherein determining a measure of the bond strength further comprises determining an elastic modulus of the laminated print media based on the depth of the indentation, and the method further comprises: comparing the elastic modulus to a stored elastic modulus; and determining whether the elastic modulus is within a predetermined range containing the stored elastic modulus or is less than the stored elastic modulus.

6. The method of claim 3, wherein determining a measure of the bond strength further comprises determining a measure of hardness of the laminated print media based on the depth, and the method further comprises: comparing the measure of hardness to a stored hardness; and determining whether the measure of hardness is within a predetermined range containing the stored hardness or is greater than the stored hardness.

7. The method of claim 1 , wherein the roller includes a plurality of protrusions and wherein the method comprises advancing the laminated print media proximate the roller such that each protrusion makes a corresponding indentation in the uppermost layer; the method comprising: measuring a property of each indentation; determining the average of the measured properties; and determining a measure of the bond strength between two layers of the laminated print media based on the average.

8. An apparatus for measuring a property of a laminated print media having a plurality of layers, the apparatus comprising: an indenter roller including a protrusion to contact an uppermost surface of the laminated print media to at least partially indent the uppermost surface to form an indentation in the uppermost surface; and a sensor to measure a property of the indentation in the uppermost surface of the laminated print media, wherein a measure of the strength of adherence between two layers of the laminated print media may be determined based on the property.

9. The apparatus of claim 8, wherein the sensor is to emit a signal toward the indentation and to receive a reflected signal from the indentation, wherein the measure of the strength of adherence is determined based on then reflected signal.

10. The apparatus of claim 8, wherein the indenter roller includes a plurality of protrusions.

11. The apparatus of claim 10, wherein the plurality of protrusions includes a protrusion of a first size and a protrusion of a second, larger, size, each protrusion being to contact the laminated print media to at least partially indent the uppermost surface to form an indentation therein, wherein the sensor is to measure a property of each indentation.

12. A method of determining a measure of adhesion between two layers of a composite substrate having a plurality of layers arranged in a stack, the method comprising: contacting, with an indenter roller including a protrusion, an outermost surface of the composite substrate; 17 forming, through contact between the protrusion and the outermost surface of the substrate, a depression in the outermost surface of the substrate; measuring, a property of the depression; and determining a measure of adhesion between first and second layers of the plurality of layers based on the property of the depression.

13. The method of claim 12, further comprising: measuring, the depth of the depression; determining, based on the depth, an elastic modulus for the substrate; comparing the determined elastic modulus to a target elastic modulus; and determining the measure of adhesion based on the comparison.

14. The method of claim 12, wherein one of the first and second layers is an outermost layer of the substrate.

15. The method of claim 12, wherein the plurality of layers includes a base layer, an uppermost layer, and wherein the first and second layers are intermediate layers between the base layer and the uppermost layer.