Laser-marked articles having machine-readable codes

Abstract

A material sheet marked on its outer surface in a predetermined pattern using a pulsed laser. The sheet material is a layered material having an outer and inner edge separated by a core. There is a first layer containing a first material starting from the outer edge and extending into the core, and a second layer containing a second material within the core. The outer surface further has patches, which are areas of the outer surface where the second material is placed on the outer surface, and at least a portion of the laser marks are placed on the patches.

Description

[Technical Field]

[0001] The present invention relates to laser-marked sheet materials having machine-readable codes such as barcodes and QR codes, and articles containing such sheet materials. The present invention also relates to laser-marked sheet materials having machine-readable codes and a transparent / decorative outer layer, and articles containing such sheet materials. [Background technology]

[0002] Short-pulse laser decoration utilizes energy from nano, pico, and femto short-pulse lasers across various wavelengths and energies to mark decorative patterns onto articles such as products and / or packaging. Any and all other decorative techniques that can be applied to products and / or packaging (i.e., labels, screen printing, digital printing, etc.) can be used in conjunction with laser marking to achieve a variety of decorative and functional effects. The laser technology used in short-pulse laser marking is, importantly, a high-throughput technique that uses a fixed laser source, in which the laser beam is directed onto the product or packaging to be marked by electronically / mechanically controlled mirrors (i.e., "Garbo" sets) and lenses (i.e., F-theta and similar lenses). These mirrors and lenses steer the laser beam across the surface of the article (this steering is also called "scanning") so that the laser can impart images, such as digital images (e.g., from computer files such as PDF files), to the surface of the packaging or product. This technique has a further advantage over other decorative techniques in that the use of digital images allows for the customization and personalization of the decoration.

[0003] There is great interest in the possibilities presented by laser-marked articles, such as by short-pulse laser marking. For example, replacing adhesive labels on polymer containers is not only economically beneficial but also ecologically beneficial. Removing adhesive labels from polymer containers, for example, reduces the total weight of the packaging material, which reduces the amount of petroleum-derived material per package, reduces the weight of the packaging, and thereby requires less fuel for transportation. Furthermore, since it is often necessary to remove adhesive labels before recycling due to potential impurities that can be incorporated into the recycling stream, the absence of adhesive labels makes it possible to recycle polymer containers more easily.

[0004] Laser marking of small items (i.e., golf balls, etc.) and / or small areas on items (i.e., date codes, address labels on finished packages) is known. While lasers are improving, and newer lasers have a variety of energies and wavelengths, these marking processes can still be slow and expensive. Furthermore, they lack the ability to mark small characters requiring high precision, such as small font text consisting of alphanumeric characters (i.e., instructions for use, ingredient lists). For example, date codes are marked on packages by relatively simple lasers, but these use single lines of large, inaccurate, or unevenly spaced spots (in the range of 250 μm to over 800 μm in diameter) and relatively large font characters. This is equivalent to printing stick figures that, while suitable for some purposes, are difficult for consumers to read and nearly impossible for machines to read. More specifically, single lines of large, inaccurate, or unevenly spaced spots cannot currently be used to mark high-precision small font text or machine-readable graphics, such as UPC or QR codes, on items. More specifically, even when UPC, QR, DataMatrix, or other machine-readable codes are printed on polymer articles with external decorative coatings such as pearl essence, the external coatings can scatter light, making it difficult to read these codes. Therefore, some decorative items present very specific problems with respect to machine-readable codes.

[0005] The current state of the art of laser marking devices and processes generally includes a laser that generates a laser beam and a scanner that directs the beam onto the surface of the article to be marked. The scanner may use a set of mirrors directed onto the surface of the article by a galvo set or may use a polygon scanner. Devices that utilize a galvo set include “raster” marking processes and “vector” marking processes. These are either fast but have low precision and resolution or slow but have high precision and resolution. A combination of high speed and high precision does not exist in the prior art. This problem is particularly prominent when marking a large area on an article, such as when laser marking is used as a complete alternative to other decorative techniques where all the text and / or graphics provided on at least one surface of the article (many of which are required for regulatory purposes) are provided via laser marking. Marking of a large area can be facilitated by a polygon scanner, but these lack flexibility in terms of changing the image.

[0006] In the raster laser marking process, individual laser marks are placed in a grid, and the image is marked row by row and point by point by the laser. Each of the pulses is “gate-controlled” such that the pulse is emitted only for the dark pixels of the image and not for the bright pixels of the image (or vice versa). Each of the pulses is gate-controlled individually, and the pulse energy of each pulse can be varied to produce a grayscale. The state-of-the-art raster marking process is effectively limited to lasers with a repetition rate of approximately 100 kHz, considering the practical limit of an update rate of approximately 10 us when signaling the on / off function of the laser (i.e., “gating”), and can only be made faster by increasing the pulse interval, which may sacrifice the fine details required for marking small font text and graphics.

[0007] The vector marking process can run at frequencies above 100 kHz because the pulse is typically gate-open while the laser beam is "directed" (by a mirror) to the shape of the vector line to be marked. Vector-marked items, including text, are often recognizable because the marked line is typically one pulse width (unless filled in), and the pulses converge near corners where the surface velocity of the laser beam slows down as it bends the corner. However, it has been found that the accuracy of mark placement by vector marking is compromised when the surface velocity of the laser beam is very high.

[0008] High-speed laser marking can be achieved using polygon scanners (for example, the High Throughput Raster Processing Polygon scanner system from Next Scan Technology (Evergem, Belgium)), which can be optimized for high speed and high accuracy. Polygon scanner systems use rotating polygon mirrors for column scanning. These scanners are typically used for full-surface processing of regular patterns. Specifically, the field of view is typically square, which is relatively large depending on the printing standard, and repeating patterns are marked repeatedly on subsequent items. The square field of view configuration of these scanners may not be suitable for accurate marking of small letters, alphanumeric characters, logos, pictures, etc.

[0009] While high speed is important for high throughput, high precision is crucial for the legibility of laser-marked patterns, which is important when marking text (i.e., for human readability) and when marking machine-readable codes such as barcodes, UPC codes, and QR codes (i.e., for machine readability). The quality of the laser marks and the precision of their position on the object are both important for the legibility of the laser-marked patterns.

[0010] Furthermore, it has been found that when laser-marked machine-readable codes are marked on the inner layers of multilayer sheet materials, machine readability is impaired even when the outer layers of the sheet material are transparent. The addition of decorative additives such as effect pigments to the outer transparent layer can further exacerbate this problem. [Overview of the project] [Problems that the invention aims to solve]

[0011] Therefore, there is still a need for laser-marked sheet materials containing machine-readable laser-marked codes, and articles formed from such sheet materials. Furthermore, there is a need for laser-marked sheet materials having a transparent / decorative outer layer, and articles formed from such sheet materials containing machine-readable laser-marked codes. [Means for solving the problem]

[0012] The present invention provides solutions to one or more of the shortcomings of the prior art, as well as other advantages. This specification, claims, and drawings describe various features and embodiments of the present invention, including a pulsed laser-marked material sheet, the material sheet having an outer and inner edge separated by a core, and having a first layer starting from the outer edge and extending into the core for less than about 60 microns. There is a second layer starting where the first layer ends, at least about 2.5 microns from the outer edge, and beginning no more than 60 microns from the outer edge. The first layer is substantially free of pigments and laser marking additives, and optionally, the first layer contains decorative additives selected from the group consisting of pearlescent, iridescent, shimmering, metallic (aluminum, copper, gold flake), matting / frosting agents, dyes and toners, and combinations thereof. The laser marking additive in the second layer may be TiO2 or an IR laser marking additive. If the laser marking additive is TiO2, the second layer has an average concentration of TiO2 in the range of about 5.00% to about 12.00% by weight, preferably about 5.75% to about 10.00% by weight, more preferably about 6.00% to about 9.50% by weight, and even more preferably about 7.00% to about 8.50% by weight. If the laser marking additive is an IR laser marking additive, the second layer has an average concentration of the IR laser marking additive in the range of about 0.005% to about 2.00% by weight, preferably about 0.0075% to about 1.80% by weight, more preferably about 0.010% to about 1.60% by weight, and even more preferably about 0.020% to about 1.50% by weight. Preferably, the material sheet is a polymer.

[0013] In one embodiment, the first material of the material sheet is L * a * , b *The material is either colored or dark as measured by the laser mark, resulting in insufficient contrast with the laser mark. In a further embodiment, the second material is lightly colored or white, providing good contrast with the laser mark. Preferably, the material sheet forms an article which may be a garbage bag, bottle, pouch, tube, film, laminate, bag, wrap, drum, jar, cup, or cap. In one embodiment of the present invention, the laser marking on the sheet material includes a UPC, QR, data matrix, or other machine-readable code, and the L of the laser-marked code relative to the unmarked portion of the patch material is greater than 40. In another embodiment of the present invention, the laser marking is on a patch. In yet another embodiment of the present invention, the laser marking on the material sheet is a UPC, QR, data matrix, or other machine-readable code, and the machine-readable code has a score of 1.5 or higher according to ISO / IEC 15416 (2016) (for one-dimensional barcodes) and ISO / IEC 15415 (2011) (for two-dimensional barcode specifications). Preferably, the machine-readable code is on a patch.

[0014] In yet another embodiment of the present invention, laser marking by a pulsed laser includes a predetermined positional pattern, each containing marks or gaps in a grid pattern, wherein the predetermined pattern contains alphanumeric characters in the form of text with font sizes in the range of 6pt to 10pt or 11pt to 16pt. The grid pattern has a plurality of positions positioned in two or more columns, the two or more columns being substantially parallel, and each adjacent pair of positions in the plurality of positions along any one of the two or more columns being separated by an X distance, and each adjacent pair in the two or more columns being separated by a Y distance. When the font size is 6pt to 10pt, the Y distance is at least 1.2 times, preferably 1.5 times, more preferably 1.7 times, and even more preferably 2 times, the X distance. When the font size is in the range of 11pt to 16pt, the Y distance is at least 2 times, preferably 2.5 times, more preferably 3 times, and even more preferably 4 times, the X distance.

[0015] In another embodiment of the present invention, there is a material sheet to be marked by a pulsed laser, the material sheet forming an article having an outer surface and an outer surface region, the outer surface region having a patch surface and a patch having a patch surface area of ​​less than about 49.00%, preferably less than about 40.00%, more preferably less than about 25.00%, and even more preferably less than about 10.00% of the outer surface region. Furthermore, the average concentration of the laser marking additive on the patch surface within the patch surface area is greater than about 2.50% of the average concentration of the laser marking additive on the outer surface outside the patch surface area.

[0016] In another embodiment, a sheet material forms an article, laser marking forms a machine-readable code, and the laser-marked machine-readable code is placed on a patch. The present invention offers many advantages over the prior art because laser marking can be another method of visual communication that can mark an article without requiring consumer-readable alphanumeric characters, text, paragraphs, and conventional labels. Specifically, the process and articles of the present invention can mark ingredient lists, instructions for use, UPC codes, etc., in a fast and cost-effective manner without using labels and adhesives. The present invention further solves problems associated with decorative items. More specifically, decorative outer layers and / or additives on the outside of an article can interfere with the laser marking and / or machine readability of symbols and codes such as UPC codes and QR codes on those articles. For example, a transparent outer layer can provide a visual effect of depth and, by further adding pearlescent additives to the outside, can result in a beautiful shampoo bottle, but it can also interfere with light transmission, making it difficult for machines such as UPC code readers to read the laser-marked code beneath the surface of the bottle.

[0017] The present invention further solves problems associated with decorative / colored articles. More specifically, an article having a decorative outer surface, such as a colored surface that provides a ΔL of less than 40 for a laser marking area on its surface, can be laser marked on a patch that provides a ΔL greater than 40.

[0018] The ability to laser-mark such text, symbols, and codes offers cost savings, is environmentally friendly (fewer unnecessary stickers on packaging and / or no need for coatings), and allows for instantaneous changes to the message communicated to consumers. For example, if an ingredient is changed in a formulation, the change can be made via a computer command to the laser device, and the new ingredient label can be marked on the product immediately. No new label / coating is required. [Brief explanation of the drawing]

[0019] [Figure 1] This is an article according to the present invention, marked with alphanumeric characters in a grid pattern. [Figure 2] This is a schematic diagram of the raising apparatus according to this disclosure. [Figure 3] This disclosure presents a grid pattern, where the positions of adjacent parallel columns are stacked. [Figure 4] This disclosure presents a grid pattern, where the positions within adjacent parallel rows are offset. [Figure 5] These are alphanumeric characters marked with a grid pattern according to the present invention. [Figure 6A] These are alphanumeric characters in a grid pattern marked according to the present invention. [Figure 6B] These are alphanumeric characters in a grid pattern, marked according to the process of prior art. [Figure 7A] This is a schematic diagram of the two-layer sheet material according to the present invention. [Figure 7B] This is a schematic diagram of a two-layer sheet material including a patch according to the present invention. [Figure 7C] This is a schematic diagram of a two-layer sheet material including a patch according to the present invention. [Figure 8] This is a schematic diagram of a multilayer material sheet of the material according to the present invention. [Figure 9] This is a revised version of Figure 5, which illustrates the mis-marked percentage calculation. [Modes for carrying out the invention]

[0020] Goods As used herein, “article” refers to individual objects such as objects for consumer use, including containers suitable for containing materials or compositions. Articles can be containers, and non-limiting examples include bottles, tubes, films, laminates, bags, wraps, drums, jars, cups, caps, etc. Compositions contained in such containers may be any of a variety of compositions, including, but not limited to, detergents (e.g., laundry detergents, fabric softeners, dishwashers, skincare products, and haircare products), beverages, powders, paper (e.g., tissues, wipes), diapers, beauty care compositions (e.g., cosmetics, lotions), pharmaceuticals, oral care products (e.g., toothpaste, mouthwash), etc. Containers may be used to store, transport, and / or dispense the materials and / or compositions contained therein. Articles can be made from any of a variety of common materials, including: PET, PETG, HDPE, PP, PVOH, LDPE, LLDPE, steel, glass, aluminum, cellulose, pulp, paper, etc.

[0021] As used herein, “sheet material” refers to any structure whose thickness is substantially less than its length and width. Sheet materials include flexible sheet materials such as films and laminates, as well as rigid materials such as bottle walls that can be formed by blow-molding preforms or parisons. Films and laminates may be rolled up to form tubes or other containers.

[0022] "Blow molding" refers to a manufacturing process that forms plastic articles containing hollow cavities, such as bottles, which are preferably suitable for containing a composition. The blow molding process typically begins by melting, or at least partially melting, or thermally softening (plasticizing) a thermoplastic material and forming it into a parison (when using extrusion blow molding) or a preform (when using injection blow molding or injection stretch blow molding), which can be formed by molding or forming steps such as extrusion or injection molding through a die head. A parison, or preform, is a tubular plastic part with a hole at one end through which compressed gas can pass. The parison, or preform, is typically sandwiched in a mold and air is injected, and depending on the configuration, the parison, or preform, is mechanically stretched (so-called "stretch blow molding"). The parison, or preform, may be preheated before air is injected. Under pressure, the thermoplastic is extruded and conforms precisely to the shape of the mold that will contain it. Once the plastic has cooled and hardened, the mold is opened and the part is removed. Generally, there are three main types of blow molding: extrusion blow molding (EBM), injection blow molding (IBM), and injection stretch blow molding (ISBM).

[0023] As used herein, “layer” refers to a striped region within a sheet material that includes at least a portion substantially parallel to the outer surface of the sheet material. Exemplary embodiments of sheet materials include co-extruded materials for forming films, and co-blown materials such as parisons used in forming bottles, co-injection materials used in forming bottle preforms, and layered materials for bottle manufacturing such as overmolded preforms. As used herein, “layer” does not include painted, ink-printed, or coated materials or labels, including in-mold labels.

[0024] Figure 1 shows an article 10 having a predetermined feature 17 laser-marked as a grid 16. The predetermined feature 17 can be consumer-readable, machine-readable, or both. The predetermined feature 17 can be, for example, alphanumeric characters, a company logo, a drawing, artwork, a UPC, or a QR code. In this example, the marked position 12 constitutes the alphanumeric character 14, which in this case is the digit 2, "2". The unmarked positions 11 in the grid 16 are shown for illustrative purposes only and do not appear on the final marked article 10. The article 10 is shown as a container and has an opening 11 and a neck 13 that provides access to an internal space 15.

[0025] Furthermore, article 10 has an outer surface 18 having an outer surface area defined by the article surface boundary 111. Patch 110 has a patch surface area defined by the square boundary of patch 110 and is shown as part of the outer surface 18 of article. Patch 110 can be any geometric shape known to those skilled in the art. The surface area of ​​patch 110 and the outer surface 18 of article are determined by standard mathematical principles known to those skilled in the art (length × width for rectangles, half the base × height for right triangles, and πr for circles). 2It can be calculated by (etc.). The surface area of ​​patch 110 should be less than about 49.00%, preferably less than about 40.00%, more preferably less than about 25.00%, and even more preferably less than about 10.00% of the outer surface area of ​​the outer surface 18 of the article. The laser marking additive in the second layer may be TiO2 or an IR laser marking additive. If the laser marking additive is TiO2, the second layer has an average concentration of TiO2 in the range of about 2.50% to about 10.00% by weight, preferably about 2.75% to about 8.00% by weight, more preferably about 2.90% to about 7.00% by weight, and even more preferably about 3.00% to about 6.50% by weight. If the laser marking additive is an IR laser marking additive, the second layer has an average concentration of the IR laser marking additive in the range of about 0.005% to about 2.00% by weight, preferably about 0.0075% to about 1.80% by weight, more preferably about 0.010% to about 1.60% by weight, and even more preferably about 0.020% to about 1.50% by weight. A machine-readable code may be placed on the patch.

[0026] The patch may be integrated with the sheet material. The sheet material may be a layered material (Figure 7a), and the patch may be formed by a surface sublayer pressed against the outer surface of the sheet material. In one embodiment, the sheet material is a multilayer co-extruded material, and the patch is formed by a projection in the die head, which deflects one or more of the outer layers to one side, exposing the next layer. Alternatively, a separate flow of material can be added to a portion of the extruded sheet. In another embodiment, the article formed from the sheet material is a bottle formed from a blow-molded co-extruded parison, in which a projection in the die head deflects one or more of the outer layers to one side, exposing the next layer. Alternatively, a separate flow of material can be added to a portion of the parison. In another embodiment, the article formed from the sheet material is a bottle formed from a blow-molded co-injection bottle preform, and the patch is formed by a delta of relative pressure between the core and the outer layer, with the core exposed on the surface of the finished preform. In another embodiment, the article formed from a sheet material is a bottle formed from a blow-molded co-injection-molded bottle preform, and the patch is formed by molding a portion of the finished preform, transferring the article to another cavity, where an additional shot is injection-molded on at least a portion of the first shot.

[0027] While not bound by any theory, certain decorative surfaces may be difficult to mark with a laser because the laser mark itself may not form a hue and contrast with the surface of the item. High-speed laser marking processes (such as CV bitmaps) may not provide a large variation in the color / darkness of the laser mark itself. It is known to impart grayscale to laser-marked images (also called "dithering"), but this requires a relatively low-speed laser marking process (i.e., a raster). High-speed laser marking processes generally require pulsed lasers in which the energy per pulse does not change substantially from pulse to pulse. High-speed laser marking can provide that a group of pulses has approximately the same energy. High-speed laser marking can provide that all pulses used to mark a given given pattern or image have approximately the same energy.

[0028] It is also known that pulsed lasers can produce either dark or bright marks depending on the energy per pulse provided by the laser. For example, when laser marking on a plastic material, the laser may cause foaming of the material, thereby producing bright marks, or the laser may cause carbonization or reduction / oxidation of the laser marking additive, thereby producing dark marks. Thus, high-speed laser marking can produce either bright or dark marks, but it may not be possible to vary the shading of the marks throughout the process of marking a given predetermined pattern, and all marks may be dark or all marks may be bright.

[0029] Humans can typically see finer contrasts than machines that read machine-readable codes. For example, UPC codes are generally graded by devices such as the Axicon 15500 verifier that operates using visible light at 660 nm. Thus, by having small patch areas on the surface with higher contrast, it becomes possible to mark a machine-readable code on the surface while the remaining part of the bottle maintains its decorative appearance. By making the patch surface area approximately equal in size and / or shape to the machine-readable code, it becomes less noticeable to consumers that there is no decorative coating on the patch.

[0030] To make the laser marking legible, it may be practical to have a difference in lightness between the outer surface that matches the laser-marked image and the outer surface that is away from the laser-marked image. If the laser marking does not provide sufficient contrast on the first material, it may be preferable to place the laser marking on a second material. It may be particularly preferable to place a laser marking containing a machine-readable code that requires higher contrast than human-readable text on the patch material. The laser marking may be a dark mark, and the second material may be a light material (i.e., having an L value greater than 90), or the laser marking may be a light mark, and the second material may be a dark material (i.e., L < 90). It will be understood that any of the color metrics including L, a, b, and E can be used to represent the color and contrast of the laser-marked image and the material away from the laser-marked image. * value), or the laser marking may be a light mark, and the second material may be a dark material (i.e., L * < 90). L * , a * , b * , and E * In the CIELAB color space framework, the difference in lightness can be characterized by L measured by the 95% delta color value measurement described herein. The outer surface is the L of the outer surface that matches the laser-marked image

[0031] of the outer surface that matches the laser-marked image. * of the outer surface that matches the laser-marked image.* From the absolute value of L, the outer surface away from the laser-marked image. * It can have a ΔL obtained by subtracting [X]. For human readability, ΔL may preferably be greater than about [X]. For machine readability, ΔL may preferably be greater than about [X].

[0032] The outer surface that matches the laser-marked image may have a first color, and the outer surface that is away from the laser-marked image may have a second color. The first and second colors are measured by the 95% delta color value measurement described herein. The first and second colors are L * a * , and b * Using the values, the equation ΔE = [(L * X -L * Y ) 2 +(a * X -a * Y ) 2 +(b * X -b * Y ) 2 ] 1 / 2 The color difference can be calculated by the formula, where X represents the value taken on the outer surface that coincides with the laser-marked image, and Y represents the value taken on the outer surface that is away from the laser-marked image. The ΔE between the outer surface that coincides with the laser-marked image and the outer surface that is away from the laser-marked image may be greater than 10 for human readability. The ΔE between the outer surface that coincides with the laser-marked image and the outer surface that is away from the laser-marked image may be greater than 40 for machine readability.

[0033] Optionally, the outer surface is the outer surface that matches the laser-marked image. * From the absolute value of, the outer surface a away from the laser-marked image *It is possible to have Δa after subtracting . For human readability, Δa may preferably be greater than about [[X]]. For machine readability, Δa may preferably be greater than about [[X]]. Using the 95% delta color value measurement described herein, a * It is possible to measure the variable a. * This relates to the red / green color components of a color.

[0034] Optionally, the outer surface is the outer surface b that matches the laser-marked image. * From the absolute value of, the outer surface b away from the laser-marked image * It is possible to have a Δb obtained by subtracting [X]. For human readability, Δb may preferably be greater than about [X]. For machine readability, Δb may preferably be greater than about [X]. Using the 95% delta color value measurement described herein, b * It is possible to measure variable b. * This relates to the blue / yellow color component of the color.

[0035] Figure 7A shows a two-layer sheet material 126 having an outer edge 122 and an inner edge 123 defining the core 124. The distance from the outer edge 122 to the inner edge 123 is the sheet thickness. The sheet thickness may be about 10.0 microns to about 2.00 mm, preferably about 20.0 microns to about 1.50 mm, and more preferably about 50 microns to about 750 mm. The core 124 has an outer layer 120 and an inner layer 121. The outer layer is decorative and contains colorants / pigments and does not contain laser marking additives in an essential way, while the inner layer 121 contains laser marking additives. The laser marking additive in the inner layer 121 may be TiO2 or an IR laser marking additive. When the laser marking additive is TiO2, the inner layer 121 has an average concentration of TiO2 in the range of about 5.00% to about 12.00% by weight, preferably about 5.75% to about 10.00% by weight, more preferably about 6.00% to about 9.50% by weight, and even more preferably about 7.00% to about 8.50% by weight. When the laser marking additive is an IR laser marking additive, the inner layer 121 has an average concentration of the IR laser marking additive in the range of about 0.005% to about 2.00% by weight, preferably about 0.0075% to about 1.80% by weight, more preferably about 0.010% to about 1.60% by weight, and even more preferably about 0.020% to about 1.50% by weight.

[0036] Figures 7B and 7C show a two-layer sheet material 126 having an outer edge 122 and an inner edge 123 defining a core 124. The distance from the outer edge 122 to the inner edge 123 is the sheet thickness. The sheet thickness may be about 10.0 microns to about 2.00 mm, preferably about 20.0 microns to about 1.50 mm, and more preferably about 50 microns to about 0.750 mm. The core 124 has an outer layer 120 and an inner layer 121. The outer layer is decorative and essentially does not contain laser marking additives, while the inner layer 121 contains laser marking additives. Figures 7B and 7C further show a patch 127. Figure 7B shows a patch 127 defined by the inner layer 121 protruding through the outer edge 122. Figure 7C shows a patch 127 defined by the inner layer 121 located behind the gap of the outer edge 122. When the sheet material 126 is blow-molded into an article as described above, it is very common for the patch 127 to be formed in the pre-molded or parison, as shown in Figure 7B, and then the patch 127 appears after the blow molding process, as shown in Figure 7B.

[0037] Figure 8 shows a multilayer sheet material 136 having an outer edge 137 and an inner edge 138 defining a core 135. The sheet material 136 is shown together with an optional protective layer 134, which may be, for example, a varnish. The protective layer 134 may be added to the sheet material 136 either before or after laser marking of the sheet material 136. The sheet material 136 comprises an outer layer 130 and two inner layers 131 and 132. It is understood that there may be three or more inner layers. The outer layer 130 is a decorative layer that may contain a colorant, while the inner layer 131 is essentially colorant-free. The outer layer 130 is a decorative layer that is essentially laser marking additive-free, while the inner layer 131 has a laser marking additive. The laser marking additive in the second layer may be TiO2 or an IR laser marking additive. When the laser marking additive is TiO2, the inner layer 131 has an average concentration of TiO2 in the range of about 5.00% to about 12.00% by weight, preferably about 5.75% to about 10.00% by weight, more preferably about 6.00% to about 9.50% by weight, and even more preferably about 7.00% to about 8.50% by weight. When the laser marking additive is an IR laser marking additive, the inner layer 131 has an average concentration of the IR laser marking additive in the range of about 0.005% to about 2.00% by weight, preferably about 0.0075% to about 1.80% by weight, more preferably about 0.010% to about 1.60% by weight, and even more preferably about 0.020% to about 1.50% by weight.

[0038] The thickness of the outer layer may be any suitable thickness. Often, decorative outer layers are made thinner than other layers as a means of reducing costs (i.e., the cost of colorants). The thickness of the outer layer, measured from the outer edge of the material sheet, is about 5 to 60 microns, preferably about 10 to 55 microns, and more preferably about 15 to 50 microns. The second layer or inner layer begins where the first layer ends. The inner layer 131 may be of any suitable thickness. Often, the inner layer is made thicker than other layers as a means of reducing costs (i.e., by including recycled material in the inner layer). The inner layer may begin from about 5 microns from the outer edge and no more than 60 microns from the outer edge. The second layer or inner layer should be at least about 5 microns thick, preferably about 10 microns thick, and more preferably about 15 microns thick. It is understood that there may be three or more inner layers, as shown in Figure 8. If only two layers exist, namely an outer layer and a second / inner layer, the second / inner layer can be the total thickness of the material sheet.

[0039] The outer layer may further contain decorative additives selected from the group consisting of glitter, iridescent or pearlescent pigments such as coated mica or glass flakes, aluminum flakes, coated aluminum flakes, copper flakes, and transparent toners / dyes and matte / frost pigments such as silica and uncoated synthetic mica, as well as combinations thereof. The laser marking additive in the second layer may be TiO2 or an IR laser marking additive. If the laser marking additive is TiO2, the second layer has an average concentration of TiO2 in the range of about 2.50% to about 10.00% by weight, preferably about 2.75% to about 8.00% by weight, more preferably about 2.90% to about 7.00% by weight, and even more preferably about 3.00% to about 6.50% by weight. If the laser marking additive is an IR laser marking additive, the second layer has an average concentration of the IR laser marking additive in the range of about 0.005% to about 2.00% by weight, preferably about 0.0075% to about 1.80% by weight, more preferably about 0.010% to about 1.60% by weight, and even more preferably about 0.020% to about 1.50% by weight.

[0040] Articles according to the present invention may be formed from a single thermoplastic material or resin, or, in one or more embodiments, from two or more materials that are different from each other. Two or more materials may constitute layers within the article. If the article has different layers, the materials constituting each layer may be the same as or different from any other layer. For example, articles may be made of polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), polystyrene (PS), polycarbonate (PC), polyvinyl chloride (PVC), polyethylene naphthalate (PEN), polycyclohexylenedimethylene terephthalate (PCT), glycol-modified PCT copolymer (PCTG), copolyester of cyclohexanedimethanol and terephthalic acid (PCTA), polybutylene terephthalate (PBCT), acrylonitrile styrene (AS), styrene butadiene copolymer (SBC), or polyolefins, such as low-density polyethylene. The article may include one or more layers of thermoplastic resin selected from the group consisting of polyethylene (LDPE), linear low-density polyethylene (LLPDE), high-density polyethylene (HDPE), propylene (PP), and combinations thereof. The article may also include cellulosic materials such as pulp or paper.Cellulosic materials may be included together with an additional second material, the additional second material may be a second cellulosic material, or it may include a thermoplastic material or a resin containing a water / solvent-based coating.

[0041] For example, recycled thermoplastics and / or cellulosic materials such as polyethylene terephthalate (PCRPET), high-density polyethylene (PCRHDPE), low-density polyethylene (PCRLDPE), polyethylene terephthalate (PIRPET), high-density polyethylene (PIRHDPE), and low-density polyethylene (PIRLDPE), as well as post-consumer recycled (PCR) materials, post-industrial recycled (PIR) materials, and regrinded materials may also be used.

[0042] Thermoplastic materials may include monomers derived from renewable resources and / or monomers derived from non-renewable resources (e.g., petroleum) or combinations thereof. For example, thermoplastic resins may include polymers made entirely from bio-derived monomers, or polymers made partly from bio-derived monomers and partly from petroleum-derived monomers.

[0043] Pigments, colorants, and laser-absorbing additives may be added to any of the materials in the layers of the article of the present invention. A suitable selection of laser wavelengths in combination with the pigments / colorants / additives may provide suitable marking of the article. If the contrast or speed of the marking is insufficient, these pigments / colorants / additives can promote the absorption of laser energy and thereby function as laser-absorbing additives. Laser-absorbing additives known to those skilled in the art can promote the formation of laser marks, making the laser markings sharper, easier to read by users and machines, and increasing the rate at which they can be marked on articles. These laser-absorbing additives generally absorb laser energy specific to the laser wavelength and subsequently initiate a color change into the surrounding matrix (via local heating causing carbonization, foaming, etc.), or the laser-absorbing additive itself undergoes a chemical or physical change. Titanium dioxide (TiO2) and carbon black are pigments commonly used to opaque containers to protect their contents from the effects of light and can also function as laser-absorbing additives / marking additives depending on the wavelength of the laser used. Examples of additional laser-absorbing additives, referred to herein as "IR laser marking additives," include tin oxide (ATO), ATO-coated substrates such as mica, Sb2O3, indium tin oxide, tin oxide, iron oxide, zinc oxide, carbon black, graphite carbon, bismuth oxide, mixed metal oxides, metal nitrides, doped metal nitrides, metal carbides, metal borides, tungsten oxides, doped tungsten oxides, non-plate-shaped micron and submicron zero-valent metals including aluminum, molybdenum, and copper, as well as alloys, metal phosphates such as copper phosphate, and mixtures thereof. Examples of IR laser marking laser-absorbing additives are commonly sold under the trade name "Iriotec" by Merck KGaA in Darmstadt, Germany, and under the trade name LASERSAFE® by Eckart GmbH in Hartenstein, Germany.

[0044] Laser and Raising Equipment To mark articles according to the present invention, pulsed lasers, such as short-pulse lasers, may be used. Lasers for use in the present invention are commercially available and include nanosecond, picosecond, and femtosecond lasers. These short-pulse lasers can emit pulses applied at high energy density and high repetition rates, and the high energy and high repetition rate are important to enable laser marking of articles at high speed. The laser marks themselves include marks made on articles such as products or packages by oxidation, reduction, ablation, etching, foaming, and carbonization.

[0045] Any suitable laser can be used to mark article 10. Figure 2 shows an embodiment of a lathing apparatus 200 equipped with a laser 20 useful for marking articles according to the present invention. The lathing apparatus 200 includes a laser 20 which can be any laser capable of generating sufficient energy to mark an article, such as a UV laser having an output in the range of 1W to 60W and a laser wavelength of 355 nanometers, or an IR marking laser having an output in the range of 1W to 300W, and even 500W, and a laser wavelength of 1064 nanometers. Such lasers are available from various suppliers, including the IPG ULPN-355-10-1-3-M marker or YLPN-1-1x350-50-3M MOPA module available from IPG Photonics (Oxford, MA, United States). Other forms and types of lasers are also possible, and different output ranges and settings may be used. The raising device may include an optical system that can be used, if necessary, to direct the laser beam and / or modify the laser beam by changing the energy density and / or spot size of the laser beam 28.

[0046] Frequency, or repetition rate, measured in Hz, is the number of laser pulses a single laser can deliver per second. For example, a 1 MHz laser delivers 1,000,000 pulses / second, and a laser with a repetition rate of 100 kHz delivers 100,000 pulses / second. The repetition rate can be important for processing certain lazing jobs (i.e., high-speed laser marking) in a short amount of time. More pulses available per unit time correlate almost linearly (inversely) to the time required to mark a given column for a particular job.

[0047] Pulse energy is the amount of energy contained in a single laser pulse and is typically measured in μJ or mJ. Typically, pulse energy is in the range of 5 μJ to 2000 μJ (2 mJ), preferably 7 μJ to 1000 μJ, and more preferably 10 μJ to 300 μJ. The average output of the laser is then given as pulse energy × repetition rate. Average power = pulse energy (J) * Repeat rate (Hz or 1 / second).

[0048] The peak power is equal to the pulse energy divided by the pulse duration, which can be less than 100 nanoseconds, less than 50 nanoseconds, less than 20 nanoseconds, less than 10 nanoseconds, or less than 1 nanosecond. Therefore, the pulse energy and pulse duration are linearly related to the peak power. Shorter pulse durations achievable with nanosecond, picosecond, and femtosecond lasers enable very high peak power, which is useful for marking objects.

[0049] In the lathing apparatus 200 depicted in Figure 2, the laser 20 projects a laser beam 28 onto an X-mirror 22 rotated by an X-Garbo 21. The X-mirror 22 and X-Garbo 21 collectively form an X-Garbo set. The laser beam 28 is then projected onto a Y-mirror 24 rotated by a Y-Garbo 23. The Y-mirror 24 and Y-Garbo 23 collectively form a Y-Garbo set. The X-mirror 22 and Y-mirror 24 cooperate to direct the laser beam 28 to a position on the article 27 where a desired mark 29 should be marked. The laser beam 28 typically passes through a lens 26 before reaching the article 27. The distance from the lens 26 to the article 27 is the focal length 25.

[0050] The combined optical system of a laising device may function to sweep a laser beam across the surface of an article in a series of passes. The laser beam may sweep across the article along a first row of a grid in the X direction, directed by an X-mirror while emitting (or omitting) pulses. The combination of the sweeping speed of the laser beam across the surface of the article, also called the surface velocity of the laser beam, and the repetition rate of the laser pulses determines the spacing of the marks along the X direction. X interval * Repetition rate = surface velocity

[0051] The laser may emit one or more pulses while sweeping across the article at a given position, thereby resulting in marked positions (or more), or the laser may omit pulses while sweeping across the article at a given position, thereby resulting in unmarked positions (i.e., voids). The laser beam may sweep across the article at a constant surface velocity while emitting and / or omitting pulses. The surface velocity or sweep velocity is defined above. The laser beam may then sweep across the article along a second row of the grid (such as a row adjacent to the first row) while emitting (or omitting) pulses. The laser beam may sweep across the first and second rows in the same or opposite directions. For example, the laser beam may sweep across the first row "from left to right" and then sweep across the subsequent / adjacent row "from right to left".

[0052] Those skilled in the art will understand that for an article to be marked, the laser energy must be absorbed by the material of the article. The laser energy can be absorbed by the substrate of the article or by laser-absorbing additives incorporated into the article. The wavelength of the laser may coincide with the absorption band, bandgap energy, or surface plasmon / plasma resonance frequency in the UV-vis-NIR-IR spectrum of at least one of the substrates or laser-absorbing additives incorporated into the article. For example, a pulsed laser utilizing 355 nm (UV) may be absorbed by TiO2 added to the article, and 532 nm (green) may be absorbed by precious metal nanoparticles such as gold, silver, and copper. Other laser wavelengths, such as 1030 nm to 1064 nm or 9 to 12 μm (infrared), may be absorbed by PET, which may be the substrate of the article. Other combinations of laser wavelengths and the substrates or laser-absorbing additives of the article exist and are construed herein.

[0053] Laser marking Articles of the present invention are typically marked by processes of foaming, carbonization, ablation, etching, reduction, oxidation, and / or phase change. The term foaming refers to the process by which a laser beam melts and vaporizes a portion of a material, creating bubbles that are trapped within the molten resin and, upon cooling, diffusely reflect light. Foaming generally results in brighter markings in the laser-marked area, and this method is most commonly used for dark-colored materials such as plastics or translucent materials. The term "translucent," as used herein, means that the material, layer, article, or portion of an article being measured has a total luminous transmittance greater than 0% and less than or equal to 90%. The term "opaque," as used herein, means that the material, layer, article, or portion of an article being measured has a total luminous transmittance of about 0%. Total luminous transmittance is measured according to ASTM D1003.

[0054] Carbonization-based marking is a process that produces a strong dark contrast on lighter surfaces and is commonly used on carbon-containing polymers or biopolymers or natural materials such as leather and wood and pulp-based materials. When carbonizing a material, a laser heats the surface of the material (generally to a minimum of 100°C) and emits oxygen, hydrogen, or a combination of decomposition products. Carbonization generally leads to a dark mark with a higher carbon content than the original material, making it a good choice for lighter-colored articles, although the contrast is rather minimal on darker materials.

[0055] Reduction and oxidation involve laser energy altering the oxidation state of at least one component of an article, such as a laser-absorbing additive or opacifying pigment, resulting in discoloration or a change in color that is visible as a mark. For example, though not bound by theory, the energy imparted from a UV laser could accelerate the reduction of TiO2 to form titanium dioxide, where the oxidation state of titanium is reduced to less than +4, thereby resulting in a color change from white / colorless to blue, and from dark blue to black.

[0056] There are additional methods for marking objects. For example, annealing is a unique laser process that can be used on metals and other materials. The energy from the laser beam creates an oxidation process beneath the surface of the material, which results in a change of color on the material's surface.

[0057] Coloring is another marking process that can be achieved as a result of chemical reactions that occur on a material when energy from a laser beam is applied. The change in color will depend on the composition of the material being colored. For example, light-colored plastic materials often change color during the laser etching process, resulting in darker markings from the resulting soot particles.

[0058] Laser engraving is another process that involves removing material from the surface of a workpiece as it is melted and evaporated by a laser beam, which creates an indentation on the engraved surface. Removing material is sometimes referred to as etching or ablation. Laser etching is the process in which a laser beam removes the top layer of a substrate or a coating previously applied to the substrate of an article. Contrast results from the different colors of the topcoat and substrate, or from the different topography and texture of the etched area versus the adjacent area. Common materials that are laser-marked by removing material include anodized aluminum, coated metals, foils and films, or laminates. The term "etching," when used as a noun herein, refers to the cavity formed when material is removed from a surface. As a verb, the terms "etch" and "to etch" refer to the action of removing material from a surface. Etching can be done mechanically, chemically, and thermally (e.g., with a laser). There are no specific limits on the maximum or minimum etching depth, but the etching depth is typically in the range of approximately 0.01 mm to approximately 2.0 mm, including any depth within the range of, for example, 0.010 mm, 0.075 mm, 0.100 mm, 0.200 mm, 0.300 mm, 0.400 mm, 0.500 mm, 1.0 mm, 1.5 mm, etc.

[0059] Bleaching or photobleaching (sometimes called color fading) is a photochemical change in which a chromophore (such as in a pigment or dye) or fluorophore molecule permanently loses its intrinsic color and / or can no longer fluoresce. This is caused by the breaking of covalent bonds or nonspecific reactions between the chromophore / fluorophore and surrounding molecules, and laser marking may also be involved.

[0060] Spot size relates to the focal region where the laser beam contacts an object. "Spot size" is the diameter of a circular spot. While the spot is circular, it is possible to achieve an elliptical spot by controlling the laser beam optics relative to the object. Spot size can be modified by focusing or defocusing the laser beam, but the "fluence" (energy per unit area) within the spot decreases as the spot is expanded or defocused. Theoretically, the minimum spot size achievable with any laser is the wavelength of the laser itself. In practice, the minimum spot size achievable with a pulsed laser is about 7–20 μm. Spot sizes can range from about 10 μm to about 150 μm, preferably about 20 μm to about 100 μm, more preferably about 30 μm to about 80 μm, and even more preferably about 40 μm to about 60 μm. As discussed in the background art, the spot size for conventional laser marking (e.g., using a CO2 laser), such as date codes, is at least 250 μm and can exceed 800 μm. Another way to think about spot size in the context of marking is to compare it to the size of a paintbrush a painter uses to create a picture. Smaller spot sizes are used when very fine detail is desired. Larger areas to be covered may prefer larger spot sizes. However, laser marking mechanisms require a minimum fluence to achieve the desired mark, and therefore, a balance between pulse energy, pulse duration, pulse overlap, and spot size is crucial.

[0061] The geometric shape of the mark spacing can contribute to the cycle time and fluence (or energy per unit area) provided to the article. For example, the spacing between marks may be such that the marks do not overlap at all, or have 0% overlap. With 0% overlap, each individual laser pulse contributes to the energy provided to mark the article. If the laser does not have sufficient pulse energy or peak power to achieve the desired marks, the pulse spacing can be reduced to a point where the spots overlap in either the X and Y directions, or both. Overlapping the spots involves providing two or more laser pulses to the area of ​​the article where the spots overlap, which provides a higher fluence or energy per unit area to that part of the article. In addition, pulse spacing is a major lever for cycle time. If the laser has a fixed repetition rate or pulse frequency, it is desirable to spread the pulses as much as possible while still achieving the desired mark type and mark contrast in order to achieve the lowest process time (also called cycle time). In one embodiment of the present invention, the pulses do not overlap.

[0062] Pulse duration is the length of time a pulse continuously remains above half its maximum value. Shorter pulses can produce higher peak power at a typical average power output. This is because average power = pulse energy (J). * This is because the repetition rate is (Hz or 1 / second). The peak power is equal to the pulse energy divided by the pulse duration. Therefore, if the pulse duration is significantly shorter, the resulting peak pulse power will be significantly higher. This peak power enables improved carbonization, foaming, oxidation, reduction, etc., on the target being marked. Short-pulse lasers utilize this phenomenon to mark articles, enabling marking mechanisms that are typically not found with longer-pulse lasers.

[0063] Changing the laser power / fluence output when creating laser marks can also be manipulated during marking to produce a grayscale, also known as dithering. Such a process is a known aspect of the raster process in laser marking. While not bound by theory, such dithering during laser marking is also thought to increase process time, in that each laser pulse must be signaled to emit a different power / fluence. In one embodiment of the present invention, the laser pulse is of constant power. Constant power can be maintained while the laser is marking within an entire row, or even while the laser is marking between rows across the entire marked pattern.

[0064] Go board pattern As used herein, “grid” or “bitmap grid” is interpreted to mean a regular, periodic array of positions that may contain multiple marks. The periodicity of the array includes periodicity in both the X and Y directions. Multiple marks in the grid may or may not be present at each position in the grid. That is, marks may or may not be formed at a position in the grid (i.e., voids). As mentioned, the lazing apparatus sweeps a laser beam across an article while either laser pulses are being emitted from the laser or no pulses are being emitted. Marked positions occur when the laser pulses at a given position, and unmarked positions occur when the laser does not pulse at a given position. A laser beam can be swept across an article at a constant surface velocity while the laser repetition rate is constant. Therefore, the periodicity of the position will be regular (i.e., X-distance) in the direction the laser beam is swept across the article (i.e., the X-direction), even if the marked positions are not spaced equally, considering the possibility of unmarked positions. For unmarked positions, the distance between any marked positions along the same direction (i.e., the X-direction) can be an integer (i.e., 2x, 3x or greater) of the smallest distance measured between marks in that direction (i.e., the X-direction).

[0065] A laser beam can be swept across articles in subsequent rows. The laser beam can be swept from left to right or right to left, and as it moves from row to row, it can be swept in the same direction (e.g., like a carriage return on a typewriter in a raster process), or it can be swept in alternating directions as it moves from row to row. A major contributing factor to reducing cycle time is sweeping the laser beam in alternating directions as it moves from row to row. Rows can be approximately parallel to each other. The distance between adjacent rows is the Y distance. The positions of adjacent rows can be directly above / below each other, or offset relative to each other. An offset equal to the X distance is understood to result in a realignment of the positions between rows.

[0066] Alphanumeric characters are letters or numbers; for example, in English, letters are A-Z, including uppercase and lowercase letters, and universal numbers are 0-9 and combinations thereof. Alphanumeric characters are not limited to any particular style or font. Chinese, Japanese (e.g., kanji, katakana), Russian, Arabic, and other languages ​​have different alphanumeric characters that can be used for marking.

[0067] Those skilled in the art will understand that the size of printed, or in this case, marked, alphanumeric characters is measured by their font. The smallest font generally accepted as consumer-readable on a marked article is about 6pt. Font sizes can be increased to very large sizes, but when marking the faces of consumer packaging, fonts larger than 20, for example, are impractical as a few characters may fill the entire package. The “faces” of consumer packaging are typically the front or back of the package, and these faces typically have different markings. For example, the product name and general product description (shampoo, conditioner, soap, etc.) are typically found on the front, while the ingredient list, UPC code, and instructions for use are usually found on the back. In the case of cylindrical packaging, a virtual vertical face can be drawn downwards from the bottle, with the front on one side of the virtual face and the back on the opposite side.

[0068] As discussed earlier, laser marks may not overlap to reduce the time required to mark a given pattern (i.e., "time to mark"). Time to mark can be further reduced by spacing the marks in either or both the X and / or Y directions, although increasing this spacing may lead to poor legibility of any alphanumeric characters constituting a given pattern. For example, increasing the X distance allows for a faster surface velocity of the laser beam across the surface of the article when marking a given row (at a constant repetition rate). Increasing the Y distance allows for fewer reversals in the process of marking a given pattern.

[0069] Surprisingly, for certain predetermined patterns, it has been found that increasing the Y distance (fewer inversions) can have a greater impact on reducing the time to marking than increasing the X distance (faster surface velocity). Conventional raster marking processes include equal X and Y spacing, but the Y distance is greater than the X distance. The X distance is preferably in the range of about 0.005 mm to about 0.500 mm, more preferably about 0.010 mm to about 0.100 mm, and even more preferably about 0.040 mm to about 0.075 mm. The Y distance is preferably in the range of about 0.010 mm to about 2.0 mm, more preferably about 0.050 mm to about 0.150 mm, and even more preferably about 0.060 mm to about 0.075 mm.

[0070] If the predetermined alphanumeric characters have a font size in the range of 6pt to 10pt, the Y distance may be at least 1.2 times, preferably 1.5 times, more preferably 1.7 times, and even more preferably 2 times, the X distance. If the predetermined alphanumeric feature part has a font size in the range of 11pt to 16pt, the Y distance is at least 2 times, preferably 2.5 times, more preferably 3 times, and even more preferably 4 times, the X distance.

[0071] Figures 3, 4, and 5 all show various depictions of a grid. More specifically, Figure 3 is a grid 39 illustrating the X direction 30, Y direction 32, X distance 31, and Y distance 33. Potential marking positions 36 are depicted by empty circles that make up the grid. Furthermore, in Figure 3, positions 36 between parallel columns 38 are "stacked" when the angle 35 between the position in the adjacent column 34 drawn in the Y direction between two potential marking positions and the X direction 30 is approximately 90 degrees. In other words, when using vectors to connect adjacent marks from an array to form a parallelogram (i.e., a unit cell), positions are stacked when the interior angles of the parallelogram are approximately 90 degrees. If the interior angles of the parallelogram are different from 90 degrees (i.e., 120 degrees and 60 degrees), the positions are offset. The X distance is measured from the center of one position to the center of an adjacent position in the X direction.

[0072] Those skilled in the art will understand that a grid of unit cells has four axes of symmetry: horizontal, vertical, and two diagonals. The laser marking considered herein can be performed along any of these four axes. For simplicity, the vertical and horizontal directions shown in Figure 5 will be described. Figure 5 can be rotated 45 degrees so that the diagonals are vertical and horizontal. Again, as shown in Figure 5, laser marking occurs across one row, and then the laser moves up or down to the row above or below, marking in the opposite direction.

[0073] Figure 4 shows another grid 49, illustrating an offset 44 with an offset distance 47 between adjacent parallel columns 48. The offset 44 is defined by an angle 45 between a position 46 in one column 48 and the nearest position 46 in the adjacent column 48, and the offset 44 exists when the angle 45 is greater than or less than 90 degrees. Figure 4 further shows the X direction 40, the X distance 41, the Y direction 42, and the Y distance 43.

[0074] Figure 5 shows alphanumeric characters 52 marked on a grid 50. The alphanumeric character is the number "2," and is marked by the laser-marked position 54, in contrast to the unmarked position 56. When multiple alphanumeric characters, such as words, sentences, or paragraphs, are printed, characters that share the same column of text will also share the same horizontal column 53 of laser marking. That is, the laser device moves across a column, marking the necessary positions for each alphanumeric character, and then leaving the necessary number of unmarked positions between the characters, thereby forming a column where the markings are associated with multiple characters within that column. In this way, words, sentences, and paragraphs can be marked and are clearly legible to consumers or machines.

[0075] Horizontal columns 53 and vertical columns 55 define the grid 50. The distance between a marked position 54 and an unmarked position 56 in the horizontal column 53 defines the X distance 51. Furthermore, the distance between a marked position 54 and an unmarked position 56 in the vertical column 55 defines the Y distance 57. It is important to note that the X distance 51 and the Y distance 57 are defined with respect to the horizontal orientation (53) and vertical orientation (55), respectively, of the marked indicia, in this case the number "2". However, the marked position 54 can be marked in the horizontal direction 59 or the vertical direction 58. More specifically, when marking in the horizontal direction 59, the laser moves across the horizontal column 53, either marking each position (54 and 56, respectively) or leaving them unmarked. Next, the laser moves down or up by one Y distance and begins to travel across another column above or below the previously marked column. Similarly, when marking in the vertical direction 58, the laser moves up or down the vertical column 55, either marking or leaving each position (54 and 56, respectively) unmarked. The laser then moves across one X distance and begins to travel up or down the vertical column adjacent to the previously marked vertical column.

[0076] The aspect ratio of a number or letter is the ratio of its height to its width. The aspect ratio of the number "2" shown in Figure 5 is greater than 1 because its height is greater than its width. It is easy to see that marking the number "2" vertically 58 requires fewer inversions than marking it horizontally 59. This means that marking this indicia can be faster when sweeping the laser beam while marking vertically 58. Many considerations are made when deciding whether to mark horizontally or vertically. However, when considering the relative spacing and font size of alphanumeric characters, the X distance 51 and Y distance 57 are always defined horizontally and vertically, respectively, with respect to the indicia being marked.

[0077] The periodicity of the positions constituting the grid includes periodicity in the X direction and periodicity in the Y direction. The X and Y directions can be approximately orthogonal to each other. As depicted in Figures 3 and 4, the grid 39 and 49 can take the form of being evenly spaced along consecutive parallel rows, respectively. The direction parallel to consecutive parallel rows is denoted as the X direction (30, 40), and the direction approximately perpendicular to the X direction is denoted as the Y direction (32, 42). The distance between adjacent positions along any parallel row (e.g., in the X direction) is considered the X distance (31, 41), and the distance between adjacent parallel rows is considered the Y distance (33, 43).

[0078] The grid 39 can be a stacked grid as depicted in Figure 3. In a stacked grid, the positions where a mark can be placed along the first column are directly above the positions along the second column that are directly below the first column. In other words, the angle 35 formed between the column segment connecting the first position along the first column to an adjacent position along the first column and the column segment connecting the first position to its nearest position along the second column is 90 ° In a stacked grid, the distance between adjacent positions along the X-axis is equal to the X-distance of 31, and the shortest distance between adjacent positions along adjacent X-axis is the Y-distance of 33.

[0079] The grid can be an offset grid as depicted in Figure 4. In an offset grid 49, the positions where marks can be placed along the first X-axis are not directly above the positions along the second X-axis that are directly below the first X-axis. In other words, the angle 45 formed between the column segment connecting the first position along the first X-axis to an adjacent position along the first X-axis and the column segment connecting the first position to its nearest position along the second X-axis is 90 ° It is either greater than or less than [a certain value].

[0080] Those skilled in the art will understand that the X and Y directions can be selected to some extent arbitrarily for a given pattern. For example, Figure 6B depicts an embodiment of "2" produced by laser marking, where the X direction is perpendicular to the marked "2" 61. Those skilled in the art will understand that the X direction can easily be horizontal to the marked "2" 61.

[0081] Those skilled in the art will understand that the grid pattern (e.g., 39 and 49) and the regular spacing between adjacent positions assume a flat surface of the article. If the surface of the article is curved, the spacing may change with the curvature of the surface.

[0082] The X distance can be the same across all parallel rows that make up a grid. That is, the X distance does not change along the X direction of a given row, nor does it change between rows of a grid containing a given pattern. Alternatively, a given pattern may contain multiple regions where the X spacing within each region is the same but differs between regions. For example, one X distance may be used consistently when marking alphanumeric characters, while different X distances may be used when marking machine-readable codes such as UPC codes. Similarly, the Y distance may not change within a given pattern, or it may change between regions within a given pattern. The surface velocity of the laser beam and / or the marking direction (i.e., up / down or left / right) may also differ between regions. For example, it should be noted that articles laser-marked using a vector marking process generally exhibit variable position / mark spacing along one of their marked directions as the laser accelerates (moving marks further apart) and / or decelerates (moving marks closer together) along the process of marking the article. Laser marking can be performed at a constant speed while the laser is marking. The laser beam moves, stopping after completing one row along the X direction, then moving up or down along the Y direction to the next row, and then starting to mark the new row at a constant speed. This speed can also be the same throughout the entire marking of a given pattern. Articles marked with a CV bitmap grid marking process can be distinguished from articles marked with a vector marking process by the regular periodicity of the marks and, in many cases, by the absence of contours or "boundaries" defining the marked areas (see, for example, boundary 63 in Figure 6B).

[0083] Figures 6A and 6B illustrate the difference between laser marking via bitmap grid marking using the CV bitmap process 6A of the present invention and the prior vector marking process 6B, in which the alphanumeric characters 60 and 61 (i.e., the digit "2") are laser marked. The alphanumeric character 60 has clean, sharp edges and is substantially better defined with very little stray marking. Figure 6B is very contrasting, with mostly undefined edges and a considerable number of stray markings 62 outside the boundary of the alphanumeric character 61. Both characters 60 and 61 were marked in approximately the same amount of time.

[0084] High-speed laser marking of human / machine-readable text, symbols, and codes. As described above, the present invention enables laser marking of human- and machine-readable text, symbols, and codes. For example, the present invention provides human- and machine-readable text, symbols, and codes on articles having a decorative / colored outer layer. Furthermore, according to the present invention, it is possible to perform laser marking of text, symbols, codes, etc., even when performing laser marking at high speeds. High-speed laser marking can include laser marking using pulses of substantially equal energy, and the present invention further enables both human and machine readability of laser-marked text and codes on decorative items.

[0085] Existing raster processes are slow but relatively accurate. Vector laser marking processes are faster and more accurate at low speeds, but inaccurate at high speeds, potentially resulting in illegible markings that are difficult for consumers or machines to read. Laser marking methods such as polygon scanners and CV bitmap scanning can offer higher speeds with better precision compared to other marking processes.

[0086] Figure 6B illustrates the potential effects of performing a vector-type process at high speed when marking text containing alphanumeric characters, including misplacement of marks within a column. This figure shows many misaligned rows, where either starting the marking too early or too late can result in jagged outlines of alphanumeric characters, blurred overall appearance, and illegibility (e.g., an "8" being indistinguishable from a "0"). In contrast, the process and resulting pattern created by a constant surface velocity (CV) bitmap path are shown in Figure 6A. The surface velocity of the laser beam across the surface of an article in current CV bitmap processes is far faster than that achievable in currently available laser marking processes such as raster and vector marking processes. Current processes are typically good examples of surface velocities on the order of 1–2 m / s or less. The CV bitmap process of the present invention provides surface velocities exceeding 8 m / s, and even 10 m / s, 15 m / s, 18 m / s, 22.5 m / s, 32.5 m / s, 45 m / s, 60 m / s or more, and even 90 m / s or more.

[0087] The sweep path of the laser beam across the surface of the object can also contribute to reducing cycle time. Conventional raster laser marking processes sweep the laser beam across the rows in either a right-to-left or left-to-right direction, also known as unidirectional, and then "jump" the laser beam back (like a typewriter's carriage return) after marking each row to start the subsequent rows. In this way, subsequent rows can be easily aligned (i.e., stacked) and the grid positions can be aligned based on this identical starting point. To eliminate the jump distance and reduce the time between each marked row, the CV bitmap process may use a "bidirectional" process in which marking can be performed alternately in both directions (i.e., marking is performed from left to right in the first row and from right to left in the subsequent rows).

[0088] The inversion of the laser beam after completing the row can also contribute to reducing cycle time. The inversion can be symmetrical or asymmetrical. An asymmetrical inversion may be preferable when the laser beam is sweeping across the surface of the article at high speeds.

[0089] The choice of marking direction can affect job cycle time, especially when marking features with high (or low) aspect ratios. The aspect ratio of a feature is generally considered to be the ratio of its height to its width. When the height and width are nearly equal, the aspect ratio is close to 1, and the impact of choosing the marking direction relative to the feature dimensions (on job cycle time) may be minimal. However, for features with high aspect ratios (e.g., height >> width) or low aspect ratios (e.g., width >> height), job cycle time can be reduced by choosing the marking direction relative to the feature dimensions. For example, the marking direction may be chosen to be approximately parallel to the longer dimension of the feature (i.e., the major axis), or it may be chosen to be approximately parallel to the shorter dimension of the feature (i.e., the minor axis) (see Figure 5 again). While many factors affect job cycle time, aligning the marking direction with the major axis of the feature is thought to reduce the number of inversions required when marking the feature, thereby reducing job cycle time.

[0090] The choice of marking direction can also affect job cycle time at very high surface velocities. At very high surface velocities, reversal time can increase to a point where it dominates job cycle time. By selecting the marking direction to be approximately parallel to the longer dimension of the feature, reversal can be minimized, thereby reducing job cycle time. As discussed earlier, the X and Y distances can differ, and this difference can contribute to reducing the job cycle. Loss of image clarity in feature areas such as alphanumeric characters can be compensated for by decreasing the X distance while increasing the Y distance.

[0091] Accuracy metrics As described above, the precision of laser mark placement can contribute to both the human readability of the marked text or image and the machine readability of the marked code. Numerous precision metrics can be used to characterize the precision of laser mark placement, which are detailed below.

[0092] Precision metrics generally depend on determining the arrangement of marked positions. The precision of laser marks can be determined relative to a given pattern, a grid, or relative to each other. While the arrangement of marks can be determined using image analysis, those skilled in the art will understand that any means of determining the arrangement (e.g., pencils and graph paper) can be used.

[0093] Microscopy Images for image analysis can be generated by microscopy. Stereoscopic microscopes such as the motorized Zeiss SteREO Discovery.V20 (Carl Zeiss Microscopy, LLC, Thornwood, NY) equipped with a color camera such as the Axiocam 305 (5-megapixel CMOS, Carl Zeiss Microscopy, LLC, Thornwood, NY) are used to image the target letters, digits, and images of the sample using reflected light illumination achieved by LED ring lights and light sources such as the Cold-light source CL 6000 LED lamp (Carl Zeiss Microscopy, LLC, Thornwood, NY). Typical light intensities of 80-100% of the maximum light intensity are used. Individual laser markings combined to form the target letters, digits, or images are resolved using a suitable magnification, combined with a zoom magnification such as 10x-345x, using an objective lens such as the Achromat S 1.5x FWD 28mm (Carl Zeiss Microscopy, LLC, Thornwood, NY). As an example, for characters, numbers, or images with a font size of 10pt, the total magnification is approximately 40x. After the target character enters the camera's field of view, the character, number, or image is focused using manual skill, or preferably using an autofocus module via a user interface platform (Zen V2.6 Blue Edition or higher with Zen Autofocus module, Carl Zeiss Microscopy, LLC, Thornwood, NY, etc.). Before collecting the image of the character, number, or image, the imaging settings are optimized by using the automatic exposure option from the user interface platform along with the lamp intensity. The image is collected in the highest possible resolution format, such as ZVI, and then exported as a TIFF file with a resolution of approximately 2464 × 2056 pixels. Furthermore, the marked columns of the character, number, or artwork should be approximately parallel to the horizontal boundary of the image.If necessary, multiple images taken at higher magnification can be precisely stitched together to encompass the entire area of ​​letters, numbers, or images.

[0094] Image analysis Images from the microscope appear gray, but are captured in color. The images are converted to grayscale using the NTSC protocol. Suitable image analysis software is required to perform this step and several other image processing steps. Analysis functions implemented in MATLAB, available from The Mathworks, Inc. (Natick, MA), are referenced in this description of the method.

[0095] Microscopy and subsequent image analysis may be performed on one or more predetermined patterns, parts of predetermined patterns, or individual images within a predetermined pattern, such as graphics or alphanumeric characters. If image analysis is performed on a part of a predetermined pattern, that part (such as individual graphics or alphanumeric characters) must be isolated from any surrounding images, characters, or artwork before analysis. A mask may be drawn around the character or image in the predetermined pattern. The mask isolates the character or image from other partial characters, numbers, barcodes, artwork, smudges, or other defects that may occur in the image.

[0096] Image analysis first relies on identifying the laser marks that make up the image. Laser marks can be identified by any reasonable means, for example, by repeatedly thresholding a grayscale image from a microscope. The starting threshold is set to capture only a few pixels that fall within some of the markings. The threshold then gradually changes to capture the continuously increasing area of ​​the markings. Progressive thresholding continues from the starting threshold to the stopping threshold. The stopping threshold can be determined automatically, for example, by using MATLAB's "multithresh" function (i.e., Otsu's method). Progressive thresholding can be advantageous in analysis because areas of the markings may overlap and / or merge, and the background may not be perfectly uniform. The direction of threshold progression (i.e., light to dark, or dark to light) can be used to identify dark markings against a relatively light background, or light markings against a relatively dark background. In the presented embodiment, dark marks against a relatively light background are identified.

[0097] Next, when the region reaches a certain size, connected components can be used to identify individual marks. The connected component algorithm is executed with each new threshold to group contact pixels into blobs. When a blob reaches 50% of the mark's area, it is identified as a mark. The center coordinates of a mark are found using the centroid method, which is implemented in MATLAB's "regionprops" function. The center is then used to determine the spacing between adjacent marks in a column (e.g., X distance) and the spacing between adjacent columns of a mark (e.g., Y distance) (see below).

[0098] Determine the observed X and Y distances and their standard deviations. The precision of marked text, images, or codes can be represented by a grid pattern based on the observed X and Y distances of the grid, as well as their standard deviations. While these parameters can be determined using image analysis, those skilled in the art will understand that any means can be used to determine these distances and standard deviations. One means of determining these values ​​by image analysis involves the use of "Delaunay triangles." In the Delaunay triangle method, the center coordinates of the marks are passed to MATLAB's "Delaunay Triangle" function, which creates a triangulation based on their center points. The edges of the Delaunay triangle never intersect, and the center points are connected by their nearest neighbors.

[0099] The X-distance is taken as the distance between adjacent marked positions along a given column in a grid. Adjacent marked positions along a given column result in horizontal edges in the Delaunay triangulation data structure. These horizontal edges can be separated from other edges in the triangulation by calculating the angle of the edges. Horizontal edges in a grid column are within + / - 10 degrees of the horizontal edges of the image. Since the grid consists of periodic intervals of positions along the columns, the X-intervals should be relatively consistent (e.g., have a low standard deviation). In this analysis, horizontal edges with a length greater than twice the programmed distance can be excluded from consideration as indicating non-adjacent positions. The observed X-distance determined when analyzing images such as alphanumeric characters is taken as the average length of the horizontal edges between adjacent marks for all marks / columns in a given image or character. The X-distance for multiple characters in a macroscopic image can then be further averaged to provide the average X-distance for a given marking condition and a given image or given pattern. Table 1 shows the observed X-distances for the letters / numbers associated with the UPC codes presented for a series of marking conditions.

[0100] The Y-distance can be determined as the vertical distance between adjacent columns. In a Delaunay triangulation, a horizontal edge can be part of two adjacent triangles. Each base edge gives each triangle two vertices, and a third vertex is the nearest neighbor mark in either the adjacent column above or below the base edge.

[0101] For each base edge, the vertical distance to the nearest mark above and below the base edge is determined. Only the minimum of these two distances (i.e., the closest) is recorded. Using only the minimum distance helps ensure that columns are adjacent and helps prevent double counting of columns. The mean and standard deviation of these vertical distances across a given image are then taken as the mean Y distance and standard deviation of the image. The top and bottom columns of letters / numbers are not used as the base of the measured triangle because they have only one adjacent column. The Y distances of multiple images in a given pattern or part thereof can then be further averaged to provide the mean Y distance and standard deviation of a given given pattern or part thereof (e.g., a given alphanumeric string).

[0102] displacement Another way to parameterize the precision of laser marking when using a grid is by percentage displacement. As shown in Figure 6B, an inaccurate laser marking process can result in substantial displacement or overhang of marks or gaps within a row, leading to a blurry image (such as alphanumeric characters) with jagged contours. Displacement within a row can be represented using any of a number of means, including simple visual inspection. For example, such means may include simply observing a character (or other element of a given pattern) and assessing whether it is legible given prior knowledge of the intended marked pattern (e.g., alphanumeric characters). Displacement can also be quantified. Importantly, human- and machine-readable patterns generally have a "smooth" contour (as opposed to the jagged contours shown in Figure 6B). In other words, for user-readable and machine-readable patterns, the leftmost and rightmost marked positions within a given column or marked portion of a column are generally not substantially displaced (in the X direction) with respect to the X distance from the leftmost and rightmost marked positions (each) within the adjacent columns (above and below).

[0103] In this displacement quantification, the starting point of each marked portion within a given column of letter or pattern elements is considered the leftmost mark, and the ending point of each marked portion within the column is considered the rightmost mark. The starting and ending points for each marked portion within a column are determined relative to the corresponding starting and ending points (each) of the adjacent columns above and below it. A column under consideration is determined to be "displaced" to the left of the letter / pattern element if the starting points of both the column above and below it are to the left of the starting point of the measured column, and a column under consideration is determined to be "displaced" to the right if the ending points of both the column above and below it are to the right of the ending point of the measured column. The horizontal distance from the starting (and ending) point of the column to the starting (and ending) points of the column above and below is determined, and the displacement is taken as the shorter of these two distances. Leftward displacement is the displacement determined by the starting point, and rightward displacement is the displacement determined by the ending point. A marked portion within a column may contain no displacement, contain leftward or rightward displacement, or contain both leftward and rightward displacement. The top and bottom rows containing the images to be analyzed (i.e., alphanumeric characters) are omitted from the analysis because they do not have two adjacent rows. One means of identifying the start and end points of each row is to use the aforementioned Delaunay triangulation analysis to determine the X distance, Y distance, and standard deviation.

[0104] The "% displacement" for a given image, such as alphanumeric characters, is the sum of the displacements for the columns containing the characters, divided by the number of columns that make up the characters. % displacement = (total displacement within the character) / (number of columns within the character) * 100

[0105] For a given pattern containing multiple alphanumeric characters as text, the "A%D" or average % displacement is simply the sum of the % displacements for each character in the sample set divided by the number of characters in the sample, "n".

[0106] mismarked percentage Another way to quantify precision is by the percentage of mismarked locations, i.e., "mismarked %". Referring here to Figure 9, which is a modified version of Figure 5 for illustrative purposes. Figure 5 shows the alphanumeric character "2" marked in a grid pattern according to the present invention. There are approximately 130 marked locations 54. In Figure 9, there are 8 gaps 101 where there should be marked locations. Furthermore, there are 4 marked locations 100 where there should be gaps. As is clear, both the gaps where there should be marked locations and the marked locations where there should be gaps are mismarked mistakes, and therefore they are added together and compared to the number of marked locations. In the example of Figure 9, there are 12 (8+4) mistakes out of a total of 130 desired marked locations. Mismarked % = number of mistakes divided by the number of desired marked locations and multiplied by 100, ((12 / 130) * 100) = 9.23%. Figure 6B shows the significantly mismarked alphanumeric characters ("2") where the mismarked percentage exceeds 20%.

[0107] The "average % mismarked" for a given pattern containing text is simply the sum of the mismarked percentages for each alphanumeric character divided by the number of alphanumeric characters. To achieve the desired readability of text composed of alphanumeric characters, the average % mismarked for alphanumeric characters is less than about 20%, preferably less than about 15%, more preferably less than about 10%, and even more preferably less than about 5%. The average is calculated using the following criteria for both the calculation of % precision and the provision of the standard deviation: The character font must be 6pt or larger, and there must be at least 10 marked columns per character.

[0108] 95% Delta Color Value Measurement Method To measure the 95% delta color value measurement of a visual effect placed on an article, the sample containing the visual effect to be analyzed must be identified. This can preferably be done by visually locating the visual effect to be analyzed in an area of ​​low curvature or an area that can be properly flattened using pressure or a frame on the article. The sample is prepared by cutting a rectangular piece from the article so that the sample is nearly flat. To obtain the sample, first cut the piece from the article wall using sharp scissors (or other cutting means that do not destroy the sample piece itself). Carefully cut the sample to the desired dimensions using a sharp single edge, such as a GEM polytetrafluoroethylene (PTFE) coated stainless steel razor blade, available from Electron Microscopy Sciences (1560 Industry Road, Hatfield, PA 19440) (item number 71970). The center of the sample must include both the marked and unmarked areas. Scan the sample and analyze a circular region of interest (C-ROI) from the center of the sample. The C-ROI should contain at least 50,000 pixels. The pixel count can be calculated using the following formula.

[0109]

number

[0110] At least 10% of the circular area of ​​the sample must consist of a marked area, and at least 10% of the circular area of ​​the sample must consist of an unmarked area. The sample can be of any suitable size, as long as it is larger than a circle positioned at the center of the sample having the required diameter. The C-ROI should be free of any cutting edge artifacts and visible blemishes.

[0111] Since the visual perception of translucent samples can be influenced by the background color, it is best practice to evaluate the samples on white and black backgrounds. The samples are scanned separately with a white backing, then a black backing, for example, the backing being half white and half black of the 2856 Byko-chart Brushout 5DX card available from BYK-Gardner (Germany), or for the white backing being L * >91, -5 * <5 and -3 * <3 has a spatially consistent appearance, and the black backing is L * <8, -2 * <2 and -2 * It may consist of equivalents having a spatially consistent appearance of <2. The backing is placed on the opposite surface of the article from which the scan image is collected. The sample is conditioned for 2 hours at approximately 23°C ± 2°C and approximately 50% ± 2% relative humidity before analysis.

[0112] ​​​​As described herein, a flatbed scanner capable of scanning the minimum value of 24-bit color at 1200 dpi and having manual control of color management (a preferred scanner is the Epson PERFECTION V750 / V850 Pro or equivalent from Epson America Inc. (Long Beach, CA)) is obtained and calibrated. The scanner is interfaced to a computer running color calibration software capable of calibrating the scanner against a color reflective IT8 target using a corresponding reference file compliant with ANSI method IT8.7 / 2-1993 (a preferred color calibration software is MONACO EZCOLOR or I1STUDIO, available from X-Rite Grand Rapids, MI, or an equivalent). The color calibration software constructs an International Color Consortium (ICC) color profile for the scanner, which is used to color-correct the output image using an image analysis program that supports the application of ICC profiles (a preferred program is PHOTOSHOP or an equivalent, available from Adobe Systems Inc. (San Jose, CA)). Next, the color-corrected image is subjected to the following color analysis by CIE L * a * b * Convert to a color space (a suitable image color analysis software is MATLAB version 9.12, available from Mathworks, Inc. (Natick, MA)).

[0113] Before calibration and image acquisition, turn on the scanner for 30 minutes. Automatic color correction or color management options included in the scanner software should be turned off (deselected). If automatic color management cannot be disabled, the scanner is not suitable for this application. Create and export the scanner's ICC color profile following the procedure recommended by the color calibration software. The scanning surface must be free from dirt, dust, streaks, and other elements that could distort the image.

[0114] Two scans of the sample are performed for analysis. One scan is performed on each side of the sample. A scan that completely includes the sample is obtained and imported into 24-bit color image analysis software with a resolution of at least 1200 dpi (approximately 47.2 pixels / mm) in reflection mode. An ICC color profile is assigned to the image to generate a color-corrected sRGB image. Prior to analysis, this calibrated image is saved in an uncompressed format such as a TIFF file to preserve the calibrated R, G, and B color values.

[0115] Open the sRGB color calibration image in color analysis software such as MATLAB, and then select CIE L * a * b * Convert to a color space. This is done as follows: First, the sRGB data is scaled to the range [0, 1] by dividing each value by 255. Second, when the following operation is performed for all three channels (R, G, and B), the sRGB channels (represented by uppercase R, G, B, or comprehensively "V") are linearized (represented by lowercase r, g, b, or comprehensively "v").

[0116]

number

[0117] Next, the linear r, g, and b values ​​are multiplied by the matrix to obtain the XYZ tristimulus values ​​according to the following formula.

[0118]

number

[0119] Next, the XYZ tristimulus values ​​are rescaled by multiplying those values ​​by 100, and then, using the D65 reference white, CIE1976 L as defined in CIE 15:2004 Section 8.2.1.1. * a * b * Convert to a value.

[0120] CIE L * a * b * The images are analyzed by drawing the contour of the sample in each image. This can be done manually or using automated thresholding, assuming sufficient contrast between the sample and the aforementioned backing. The sample contour is used to create a binary image where the inside of the contour is the foreground and the outside of the contour is the background. From the binary image, the centroid of the sample, also known as the geometric center of the shape, can be found using standard image processing methods such as the "regionprops" function in MATLAB. The center of the shape is used as the center of the C-ROI. The C-ROI should cover approximately the same area of ​​the sample on both the marked and unmarked sides of the item.

[0121] L of each pixel within the C-ROI * a * , and b * The value is L of all other pixels within the C-ROI. * a * , and b * The value is compared to AΔL. * And ΔE are calculated for each comparison. These are derived using the following formulas.

[0122]

number

[0123] These ΔL * And the cumulative histogram of ΔE values ​​is ΔL *And it is divided by the sum of the ΔE measurements. Therefore, the last bin value is 1, which represents 100% of the delta measurements. The bin size of the cumulative histogram is set to equal 0.1. The largest bin value less than 95% is recorded as the "95% bin value" for the sample in order to ignore any residual noise in the image.

[0124] For the results shown in Table X, the diameter of the C-ROI was approximately 0.2 inches or 254 pixels, and the scanner resolution was 1200 DPI. This resulted in 50,670 pixels for analysis. Results are reported for each sample scanned using white and black backing.

[0125] A series of thermoplastic resin chips containing suitable grades of pigment TiO2 are prepared using a single-screw or twin-screw extruder at concentrations of 0.5, 0.75, 1, 1.5, 2, 3, 5, 7.5, and 10%. Flat parts such as plaques or chips are manufactured using injection molding machines, such as those available from BOY Machines, Inc. (Exton, PA 19341 USA). Pigment TiO2 is best selected from grades that include coatings to enable compatibility with the resin and ensure good dispersibility and homogeneity throughout the part. Examples of pigment TiO2 intended for use with polyolefins include TIOXIDE® TR48 (Venator, Wynyard Park, UK) and Ti-Pure® R-103 (The Chemours Company FC LLC, Wilmington, Delaware USA). Since many examples of pigment TiO2 have surface coatings, the percentage of powder added in the extrusion process may differ slightly from what is expected. For this reason, the %TiO2 content of the chip is confirmed by inductively coupled plasma emission spectroscopy (ICP-OES), and the measured values ​​are used for Raman spectroscopy as described herein.

[0126] Samples from 0.5, 0.75, 1, 1.5, 2, 3, 5, 7.5, and 10% TiO2 standard tips are cut into smaller pieces using ceramic scissors and a knife. The scissors and knife are washed between samplings. Blank resin samples (the same resin used for the TiO2 standard) and TiO2 standard samples are prepared (n=1 to n=3). Approximately 0.05 to 0.1 g of sample is transferred to a pre-washed 15 mL TFM UltraWAVE tube (Milestone Srl, Bergamo, Italy) and weighed. Each sample is combined with a digesting agent such as nitric acid, hydrochloric acid, and fluoroboric acid. The sample is then completely digested by heating to a final temperature of 250 to 260°C using an UltraWAVE Microwave Digestion System. The sample is then transferred to a 50 mL polypropylene tube, combined with an internal standard, and diluted to 50 mL with deionized water. The resulting test solution is visually checked to confirm complete digestion of the sample, ensuring that the solution yields a clear solution free of particulate matter. The clear solution is analyzed for Ti by ICP-OES. Working standards are prepared by combining appropriately diluted reference standards (Inorganic Ventures, Christiansburg, Virginia, USA) covering the target concentration range (45 ppm to 145 ppm Ti) with a selected internal standard (Y). The final composition of these working standards is matched to the prepared sample in terms of acid content for matrix matching purposes. The analytical results of these working standards provide the data necessary to create calibration curves for titanium quantification. The prepared standards and test samples are analyzed using an ICP-OES analyzer such as the Agilent 5110 ICP-OES (Agilent Technologies, Inc., Santa Clara, CA, USA) using multiple wavelengths to demonstrate appropriate selectivity using one wavelength selected for reporting purposes (Ti 336 nm) and yttrium (Y 371 nm) used as the internal standard.

[0127] Method for determining %TiO2 within a specific layer Standards of thermoplastic resins with varying amounts of TiO2 are analyzed by Raman spectroscopy using a Raman microscope such as the Renishaw Virsa® Raman analyzer (Renishaw plc., Gloucestershire, United Kingdom), which is equipped with a continuous 785 nm laser, a fiber-optic coupled probe including an electric x / y / z stage, a live video camera, a halogen or LED light source for white light sample observation, and a 20x / 0.40 NA LE Plan Nikon microscope objective lens. The sample surface is localized using live white light video images before data acquisition. Spectrum acquisition is achieved by two-dimensional (2D) mapping by scanning the sample in x and y directions relative to the incident laser beam, or by scanning a standard line in the x or y direction. 300 μm 2 A minimum of 300 Raman spectra covering the above area are obtained for each calibration standard. For each collected spectrum, the area of ​​the intrinsic TiO2 Raman peak that does not interfere with the Raman peak from the host resin is determined, and the obtained value is divided by the area of ​​the intrinsic Raman peak from the host resin. For HDPE, as an example, for each collected spectrum, %TiO2 is determined by calculating the area of ​​the TiO2 Raman peak centered at approximately 417 cm⁻¹¹ and dividing it by the spectral signature area of ​​HDPE between 1390 and 1504 cm⁻¹¹. The calibration curve is generated by calculating the average value of all normalized TiO2 and plotting the result against the %TiO2 determined from the ICP-OES method. This calibration formula is used to determine the %TiO2 in a particular layer of the article.

[0128] To determine the %TiO2 in a specific layer of an article, a properly flat cross-section of the sample for viewing the internal structure of a potentially layered article is prepared by a method known to those skilled in the art of microscopy. Preferred methods include slicing parallel to the layer using a sharp single-edge razor blade (cutting perpendicular to the thickness direction of the layer is unacceptable), cryogenic fracture of the article (removing a small area, clamping it with forceps, placing it in a liquid nitrogen bath, and fracturing it if brittle), and / or low-energy broad-beam cryogenic ion milling, such as using a Hitachi IM4000Plus Ion Milling System (Hitachi High-Tech America, Inc., Dallas, Texas). The cross-section of the sample is visualized in real time using a white-light video camera. Two-dimensional (2D) chemical mapping of the cross-section is obtained by scanning the cross-section in the thickness direction by focusing a laser beam on or below the cross-sectional surface and collecting data points every 5 μm, preferably every 1 μm, with a detector exposure time of a maximum of 10 seconds and a laser power of 20 mW or less on the sample, appropriately adjusted to maximize the Raman signal while preventing detector saturation or sample burning. In this way, spectral data is collected over a region having a width of approximately half the total cross-sectional thickness dimension (i.e., if the film thickness is 200 μm, the region to be analyzed should be 200 μm in the thickness direction × 100 μm in the orthogonal direction, as observed through a microscope). Full Raman spectral data at each pixel in the dataset is corrected against cosmic rays and a baseline corrected before image generation. Hyperspectral Raman images highlighting the TiO2 distribution from spectral features inherent to the host resin, such as TiO2HDPE, are generated using suitable software such as Renishaw WiRE® 5 software. The layers and layer thicknesses are determined by techniques known to those skilled in the art. The concentration of %TiO2 in different layers of the article is obtained by selecting at least 300 Raman spectra from evenly spaced intrinsic positions within a square / rectangle across each interface of the cross-section containing TiO2.For HDPE, as an example, for each collected spectrum, %TiO2 is determined by calculating the area of ​​the TiO2 peak centered at approximately 417 cm⁻¹ and dividing it by the spectral signature area of ​​HDPE in the range of 1390–1504 cm⁻¹. A calibration curve is used to obtain the average %TiO2 within individual layers of the article.

[0129] Method for determining the overall grade of barcode symbols For the verification of linear barcodes, seven verification parameters specified by ISO / IEC 15416(2016) (decoding, symbol contrast, minimum reflectance, minimum edge contrast, modulation, defects, and decodeability) are measured using an ISO / IEC compliant barcode verifier such as the Axicon 15500 (Axicon Auto ID Limited, Oxfordshire, UK). "Barcode" is synonymous with the term "symbol" as defined in ISO / IEC 15416(2016). Each of these parameters is assigned a grade from 0 to 4 according to ISO / IEC 15416(2016), where 0 represents failure and 4 represents the highest quality. At least 10 scans collecting reflectance profiles across the full width of the barcode are measured using an ISO / IEC compliant barcode verifier. The scan reflectance profile grade for each scan reflectance profile shall be the lowest grade of any parameter evaluated for that profile. The overall grade of a barcode symbol is calculated by the arithmetic mean of each grade in the scanned reflectance profile. The overall grade of a barcode symbol is reported to the nearest tenth of a digit. For linear barcode symbols, the measurement may be performed using any combination of aperture, wavelength of light, and angle of incident light as recommended by ISO / IEC.

[0130] For the verification of two-dimensional barcode symbols, including two-dimensional multi-line barcode symbols and two-dimensional matrix symbols, grading is performed according to ISO / IEC 15415 (2011) using an ISO / IEC compliant 2D barcode symbol verifier such as the Axicon 15500 (Axicon Auto ID Limited, Oxfordshire, UK). Each parameter receives a grade from 0 to 4, where 0 represents failure and 4 represents the highest quality. The parameter with the lowest grade becomes the overall grade of the 2D symbol. For two-dimensional barcode symbols, measurements can be performed using any combination of aperture diameter, wavelength of light, and angle of incident light recommended by ISO / IEC.

[0131] Unless otherwise specified, all percentages are weight percentages based on the weight of the composition. Unless specifically stated otherwise, all ratios are weight ratios. All numerical ranges include narrower ranges, and the upper and lower range limits are interchangeable in creating further ranges that are not explicitly defined. The number of significant figures does not limit the indicated quantity or the precision of the measurement. All measurements are understood to be taken at approximately 25°C and under ambient conditions, where “ambient conditions” means conditions at approximately 1 atmosphere and approximately 50% relative humidity.

[0132] The dimensions and values ​​disclosed herein should not be understood as being strictly limited to the exact numerical values ​​listed. Instead, unless otherwise specified, each such dimension is intended to mean both the listed value and the functionally equivalent range encompassing that value. For example, a dimension disclosed as "40 mm" is intended to mean "approximately 40 mm."

[0133] All documents referenced herein, including any patents or patent applications that are cross-referenced or related, and any patent applications or patents for which this application claims priority or benefit thereof, are incorporated herein by reference in their entirety unless expressly excluded or particularly limited. No citation of any document shall be deemed prior art to any invention disclosed or claimed herein, nor shall it be deemed to teach, suggest or disclose any such invention, either alone or in combination with any one or more other references. Furthermore, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in any document incorporated by reference, the meaning or definition given to that term in this document shall prevail.

[0134] While specific embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended that all such changes and modifications within the scope of the invention be covered in the appended claims.

Claims

1. A material sheet marked on its outer surface in a predetermined pattern with a pulsed laser, wherein the sheet material is a layered material having an outer edge and an inner edge separated by a core, having a first layer containing a first material starting from the outer edge and extending into the core, and having a second layer containing the second material within the core, the outer surface further including patches, the patches including regions of the outer surface on which the second material is disposed, and at least a portion of the laser marks is disposed on the patches.

2. The sheet material according to claim 1, wherein the patch does not include a coating and a label.

3. The sheet material according to claim 1 or 2, wherein the sheet material is a polymer.

4. The sheet material according to any one of claims 1 to 3, wherein the first material comprises a coloring agent.

5. The first material has an L value of less than 80. ＊ The sheet material according to claim 4, having the following characteristics.

6. The sheet material according to claim 5, wherein the first material is colored, and the sheet material further comprises laser marks on the first material, wherein the DL of the laser mark area on the first material is less than 40.

7. The aforementioned patch has a value of 90 L ＊ A sheet material according to claim 6, having a value.

8. The sheet material according to claim 6, wherein the patch is white.

9. The sheet material according to any one of claims 1 to 8, wherein the laser mark of the predetermined pattern on the patch includes a machine-readable code.

10. The sheet material according to claim 9, wherein the machine-readable code is a linear barcode symbol and has an overall symbol grade of 1.5 or higher based on verification in accordance with ISO / IEC 15416 (2016).

11. The sheet material according to claim 9, wherein the machine-readable code is a two-dimensional barcode symbol and has one or more grades based on verification in accordance with ISO / IEC 15415 (2011).

12. The sheet material according to claim 9, further comprising laser marks of a predetermined pattern including alphanumeric text.

13. The sheet material according to claim 12, wherein the predetermined pattern including alphanumeric text is arranged on the first material.

14. The sheet material according to claim 12, wherein the predetermined pattern of the laser mark is a grid pattern having a plurality of positions positioned in two or more rows, the two or more rows are substantially parallel, each adjacent pair of positions along any of the two or more rows is separated by an X distance, and each adjacent pair in the two or more rows is separated by a Y distance.

15. The sheet material according to claim 14, wherein the alphanumeric text has a font size in the range of 6pt to 10pt, and when the font size is 6pt to 10pt, the Y distance is at least 1.2 times the X distance.

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