Method for protecting a printed substrate or a substrate to be printed

Abstract

Method for protecting a printed substrate, comprising the following steps: - printing on the substrate at least two printed protective zones having a height greater than the height of said printing in the print zone, such that the printed protective zones provide protection for the print zone against contact via the face of the substrate, and - curing and / or drying the printed protective zones.

Description

[0001] PROCEDURE FOR PROTECTING A PRINTED SUBSTRATE

[0002] DESCRIPTION

[0003] The present invention is applicable to digital printing and substrate processing systems that require protection from contact with any other parts, especially, but not exclusively, in the period following printing. Protection may be required on any surface of the substrate. The substrate may have any shape. In the case of flat substrates, the surface to be protected may be the top and / or bottom surface. Protection may be necessary to prevent contact of the substrate with the freshly printed area of ​​other substrates printed in the same process, or to prevent contact with other elements of the production line. Therefore, the substrate could be, for example, a sanitary substrate where, from a certain point in its processing, direct contact with the transport elements of the production line must be avoided.However, the present invention has special application in the field of digital printing where there is a subsequent stage, immediately after digital printing, of stacking the substrates.

[0004] In digital printing systems with stacking, after applying the print to the substrate and curing and / or drying it, the substrates are stacked one on top of the other, with the new printed substrate, which can be identical to the one below, being stacked on top, and so on. The printed area on the upper surface of a lower substrate comes into contact with the lower surface of the upper substrate. Any possible form of contamination due to contact between substrates can occur from one surface to the other. For example, substances contained in the printed ink, even if completely fixed, can migrate to the contact surface, or simply substances, particles, or dirt from the unprinted surface can migrate to the printed area.

[0005] Contamination or migration will depend on the type of inks and materials used. In the case of printed substrates used as food packaging, migration that may occur during stacking from the printed side to the unprinted side of another substrate could subsequently cause the compounds that migrated to the inside of the packaging to migrate into the food inside during use. The range of materials whose components must not leach into food is very broad: plastic, glue, paper and cardboard, varnish, aluminum, colored dyes, etc. Contamination can also occur, for example, through soiling due to contact between surfaces.

[0006] It is an objective of the present invention to disclose means for providing a solution to the aforementioned pollution problem.

[0007] More specifically, the present invention discloses a method for protecting a printed substrate, preferably belonging to a food and / or health product, comprising the following steps:

[0008] - printing on the substrate of at least one printed protection zone, the printed protection zone protruding a height above the substrate greater than that of a printed area to be protected, such that the printed protection zone or zones provide protection to a printed and / or unprinted area against contact,

[0009] - curing and / or drying of the printed protective areas

[0010] - and, preferably, stored or stacked between two substrates, preferably the same as the said substrate, in such a way that the printed protection zone prevents the said printed zone from coming into contact with the said two substrates.

[0011] The substrate may have a printed area that has been previously printed, may be printed simultaneously, or the printed area may be printed after the application of the protective areas. Therefore, with regard to the procedural steps, the term “printed area” in the present invention shall be understood as either “previously printed (decorative) area” or “area (of decorative printing) to be printed.”

[0012] The substrates between which the substrate is stored or stacked can be of a similar nature. For example, the substrates can be identical or similar, differing or not in the designs printed on them.

[0013] Preferably, at least two protective printed areas are used, and even more preferably, more than two. Printing different protective areas allows for a layout that adequately protects the printed (decorative) area with a minimum of material.

[0014] Printed protective zones should preferably be taller than the material of the printing area. In this way, the protective zones protrude from the printing area.

[0015] In summary, the present invention proposes the printing of "printed protective zones" that offer protection because they protrude more than the printed areas (or printed decoration) from which it is desired to prevent the migration of unwanted elements to substrate surfaces that will come into contact with a food product (e.g., a food or food substance) or a medical substance (e.g., a drug, a cosmetic, or a medical substance). By protruding further, the protruding printed protective zone ("printed protective zone") protects the printed decorative area, either from the substrate on which it is located and / or from adjacent substrates in a stack. Preferably, the composition of the material (or "ink") of the printed protective zone is different from the material (or "ink") of the printed area.

[0016] Therefore, the height that the printed protection zone protrudes from the printed (decorative) zone, the distribution of the printed protection zone, and the flexibility of the substrate should preferably be chosen to prevent a substrate placed on top of another in a stack from coming into contact with the aforementioned printing zone.

[0017] Preferably, the protective zones create a distribution of raised areas that prevent contact between the printed area and another substrate placed on top of it. More preferably, the protective zones are distributed around the printed area, most preferably along the entire outer perimeter of the printed area. In a particularly preferred embodiment, the protective zone(s) are distributed, continuously or discontinuously, around the outer perimeter of the printed area. When the protective zone(s) are placed on top of the printed area, they may be distributed along the entire printed area, preferably in such a way as to create a distribution of raised points that prevent contact between another substrate and the printed area.

[0018] In certain applications, especially when the protective zones do not interfere with the printed area, i.e., they are not placed on top of it, preferably, the overall thickness of the printed protective zone is greater than the thickness of the printing material deposited in the printed area.

[0019] The protective area(s) may be applied to the same surface as the printed area and / or to an opposite surface, whether printed or unprinted. In any case, the protective area(s) shall be located on or outside the printed or unprinted area, preferably surrounding it. When the protective area is located on an opposite, unprinted surface, it is understood that the protective area is located “on the printed area” when it coincides with the projection of the printed area on the opposite surface, “outside it,” and “preferably surrounding the printed area” when it is located outside said projection and surrounding it, respectively.

[0020] These protective areas can be printed using different printing technologies, such as gravure printing, spray printing, or inkjet printing, among others. In a preferred embodiment, they are printed using inkjet printing.

[0021] The decorative prints (printed area) can be printed using various printing technologies, such as gravure printing, spray printing, or inkjet printing, among others. In a preferred embodiment, this is printed using inkjet printing.

[0022] Preferably, both the protective areas and the decorative prints can feature the same printing technologies.

[0023] Also, preferably, the protective areas and the decorative prints can feature different printing technologies. In a particularly preferred embodiment, both the protective area and the printed area (decorative print) are printed using inkjet printing.

[0024] The present invention, to solve the aforementioned problem, proposes printing and curing or drying a material at strategic points on the substrate, forming a protective pattern. The printed protective zones, by protruding from the printed area, act as separators that prevent contamination or migration to or from the printed area. The separators can be applied in liquid form, through printing, and subsequently solidified by curing and / or drying. The separators can be applied during the same printing process, or before or after printing the printed area.

[0025] Ideally, the printed areas should not affect the material's subsequent functionality, but they must prevent unwanted contamination. The printed protective areas can form a "mask" that can be touched. A series of printed protective areas creates raised zones that prevent unwanted contact. For example, when printing on corrugated cardboard sheets for food industry packaging, several repeated designs are typically printed on the same sheet. In this case, it is possible to print protective areas between these designs using a material that creates a certain height relative to the substrate. This ensures that, when stacked, the upper substrate does not come into contact with the printed areas, but rather with the protective zones.The material used to print the protective areas may not exhibit migration, or may exhibit a lower degree of migration than the printed (decorative) area. However, the type of material used to print the protective areas that create a gap between substrates does not necessarily have to be specifically low-migration. If the selected areas where the protective areas are printed are areas that will later be discarded, it is irrelevant whether the material is high- or low-migration. Likewise, if the pattern of printed protective areas is distributed in such a way that any migration it might produce is below acceptable limits, it would not be necessary to use low-migration products. It is also advantageous for the material of the protective area(s) to be more resistant and / or have a higher coefficient of friction than the material of the printed area.For example, when both the printed area and the protective area(s) are printed using inkjet printing, the material used to print the protective area(s) preferably has a higher viscosity than the ink(s) used to print the printed area. This higher viscosity—possibly with adjustments to the printing parameters—allows the printer to generate larger droplets that extend beyond the printed area. For instance, the material used for the protective area could be a finishing varnish, which has a higher viscosity than a decorative ink that also possesses properties that confer high resistance, either due to the type of polymers or the presence of specific solids, etc.

[0026] Preferably, the printed protection zones are all the same height, which facilitates the creation of the aforementioned protection pattern.

[0027] In applications for protection against contamination that may occur during stacking, preferably, the printed protection zones generate a network of raised points that prevent another substrate, stacked above or below, from coming into contact, among others, with the printed area.

[0028] One advantage associated with the distribution or network of protruding points is that it can be easier, since the entire surface of the substrates is not in contact, to subsequently extract these substrates when unstacking, as no "vacuum" force, or force due to electrostatic charges, or any other type of force is generated between the surfaces of the substrates when trying to move them.

[0029] Another advantage of the distribution or network of protective dots or zones, especially when the protective material is more resistant and / or has a higher coefficient of friction than the ink in the printing area, is that these zones prevent one substrate from sliding over another while the substrate stack is being formed or while substrates are being removed from the stack. In short, the present invention will not only protect against contamination but also against insufficient friction between substrates during stacking or unstacking. This problem of insufficient friction arises due to the low coefficient of friction that certain inks can exhibit once cured. It should be noted, in these cases, that the upper substrate will rest on the network of raised dots created by the printed protective zones.When designing the distribution and height of the printed protective zones, it must be taken into account that the upper substrate may flex between these zones. The network of raised dots or printed protective zones, according to the present invention, may exhibit more severe patterns than others, that is, a greater density of dots and / or their extent, depending on the weight of the stack that each specific substrate must support.

[0030] In certain embodiments, it will be possible for all protective zones to be located outside the printing area. Furthermore, if these zones are located in areas that will be discarded after stacking or transport, they need not be made of low-migration material and can be made of high-migration material.

[0031] It is also possible for at least one printed protective zone to be printed on or over the print area. In these cases, it is highly recommended that the material of the printed protective zone be transparent or a color integrated with the print area at the points where the protective zone is printed. For example, the printed protective zone could be the same color as the print area at those points. It is also highly recommended that this printed protective zone be made of a low-migration material. Therefore, for certain applications, the protective zone material may be transparent and / or pigment-free. In general, materials for the protective zone should be chosen that do not exhibit migration of unwanted substances from the protective zone to another substrate, preferably a stacked one.The consideration of which substances are undesirable will depend on the particular application (e.g., food, cosmetic or pharmaceutical industry).

[0032] However, it is also possible for the printed protective zones within the print area to be made of the same material as the print itself, even if that material is not low-migration. For example, higher zones may be incorporated to form the protective pattern or part of it. In these cases, migration or contamination will be restricted to the areas defined by the printed protective zones. This can be useful in applications where a certain level of contamination / migration is acceptable.

[0033] As indicated, preferably, the procedure of the present invention may comprise a subsequent placement of an element on the printed substrate, such that said element rests above the printed protection areas. Said element may be another printed substrate, for example, a substrate the same as or identical to the aforementioned printed substrate with the protection areas.

[0034] The substrate can be shaped and / or filled to create packaging, preferably food-grade. More preferably, these shaping and / or filling processes are carried out after the aforementioned stacking.

[0035] Preferably, the present invention carries out the printing process of the protection areas and / or the decoration itself by means of digital inkjet printing.

[0036] The present invention, preferably in a particularly advantageous embodiment, utilizes inkjet printing technology for both decorative and protective printing. The advantageous use of inkjet technology for both the decorative and protective printing processes allows for cost savings in terms of resources and time, thanks to the uniformity of the process. For example, the printed area (decorative printing) and the protective area can be printed on the same printer, using different printheads for each.

[0037] The present invention finds preferential application when the substrate is a food packaging material, in addition to other fields in which protection must be given to possible contamination and / or migration during manufacturing processes, such as materials for medical, cosmetic or pharmaceutical use.

[0038] In summary, the present invention discloses the use of a process according to the invention (in any of its variations) for the manufacture of food and / or sanitary packaging. Preferably, the substrate forms food packaging. Also preferably, the substrate is printed on only one side. In this application, it is additionally advantageous to eliminate the possible migration of unwanted substances from decoratively printed surfaces to surfaces that will be in contact with food.

[0039] In the present invention, the term “sanitary” encompasses the pharmaceutical, medical, and cosmetic fields.

[0040] For better understanding, drawings of possible embodiments of the object of the present invention are attached as an explanatory, but not limiting, example.

[0041] Figure 1 schematically shows a substrate plan in which printing areas and printed protection areas have been marked.

[0042] Figure 2 is an elevation of Figure 1 in which the different heights of the printed and printed protection areas can be observed.

[0043] Figure 3 shows two substrates, produced after cutting the substrate of Figures 1 and 2, and stacked one on top of the other.

[0044] Figure 4 schematically shows a plan view of a substrate in which printing areas and printed protection areas have been marked, with the protection areas on the opposite face to the printing area.

[0045] Figure 5 is an elevation of Figure 4 in which the different heights of the printed and printed protection areas can be observed.

[0046] Figure 6 shows two substrates, produced after cutting the substrate of Figures 4 and 5, and stacked one on top of the other.

[0047] Figure 1 shows a substrate 1, for example, a corrugated cardboard substrate from a roll, on which a repeating pattern is printed within the printing area 2. Subsequently, the substrate 1 is cut along the dotted line, and the substrate cuts are stacked for transport to subsequent cutting, folding, etc. operations. This would cause the underside of each substrate cut to come into contact with the printed area of ​​the cut below during stacking. To prevent contamination, a series of printed protective zones 3 are also printed, with a height greater than that of the printed area 2. When the elements are stacked on top of each other, as shown in Figure 3, the taller printed protective zones prevent the underside of the upper cut 1' from contacting the printed area 2 of the substrate cut 1 located inside.

[0048] The printed protective zones 3 in the example shown fall outside the printed zone 2. If, in subsequent operations, the substrate is to be trimmed to the limits of the printed zone 2, the printed protective zones 3 will be discarded from the final packaging. Therefore, these printed protective zones 3 can be made of any material, including materials that could contaminate the cut of the substrate 1' immediately above, since the contaminated area of ​​the upper substrate 1' will also be cut and discarded. However, during stacking, the printed protective zones 3, due to their greater height, prevent the printed zone 2 of the lower substrate 1 from making contact with the back of the substrate 1' immediately above.

[0049] If the printed protective zones 3 are not to be discarded in the final packaging, they can be made of low-migration materials, allowing the material / ink of the printed zones 2 to be non-migratory. It is also possible for all or part of the printed protective zones 3 to be located within the printed area. In this case, it may be preferable for the material to be transparent or a color integrated into the design printed on the substrate.

[0050] Figure 4 shows another possible embodiment in which a substrate 1 prints a repetitive pattern within the printing area 2. Subsequently, substrate 1 is cut along the intermediate dotted line, and the substrate cuts are stacked for transport to subsequent cutting, folding, etc. operations. This causes the underside of each substrate cut to come into contact with the printed area of ​​the cut below during stacking, generating contact contamination. To prevent this, a pattern of printed protective zones 3, taller than the printed area 2, is printed on the opposite side of the printing area. When the elements are stacked on top of each other, as shown in Figure 6, the taller printed protective zones 3' prevent the underside of the upper cut 1 from contacting the printed area 2 of the substrate cut 1 located inside.

[0051] Although the invention has been presented and described with reference to embodiments thereof, it is understood that these are not limiting to the invention. Therefore, numerous construction details or other aspects may vary and may become apparent to those skilled in the art after interpreting the material disclosed in this description, claims, and drawings. Thus, all variations and equivalents will be included within the scope of the present invention if they can be considered to fall within the broader scope of the following claims.

Claims

CLAIMS 1. A method for protecting a printed or unprinted substrate, characterized in that it comprises the following steps: - printing on the substrate of at least one printed protection zone, the printed protection zone protruding a height with respect to the substrate, said height being greater than the height of a printed zone that is to be protected, in such a way that the printed protection zone or zones exert a protection of a printed and / or unprinted zone against contacts - curing and / or drying of the printed protective areas.

2. A process, according to the preceding claim, characterized in that the substrate belongs to a food and / or health product.

3. A method according to any of the preceding claims, characterized in that it comprises an additional step of stacking the substrate between two substrates adjacent to said substrate, such that the printed protection zone prevents said printed zone from coming into contact with said two substrates.

4. A method, according to any of the preceding claims, characterized in that at least two printed protection zones are printed on the substrate.

5. A method, according to any of the preceding claims, characterized in that the printed protective areas all protrude equally from the substrate.

6. A method, according to any of the preceding claims, characterized in that the printed protective zones generate a network of protruding protective zones that prevent another substrate stacked above or below from coming into contact with the printed area.

7. A method according to any of the preceding claims, characterized in that the entire printed protection zone or zones are located outside the area of impression.

8. A method, according to any of the preceding claims, characterized in that at least one printed protection zone is printed in the printing area.

9. A method, according to any of the preceding claims, characterized in that said printed protective area is made of a transparent material or of the same color as the printed area.

10. A method, according to any of the preceding claims, characterized in that said printed protection zone is made of a low migration material.

11. A method, according to any of the preceding claims, characterized in that the stacking comprises the subsequent placement of an element on the printed substrate, such that said element is located above the printed protection zone or zones.

12. Method, according to the preceding claim, characterized in that said element is another printed substrate.

13. Method, according to the preceding claim, characterized in that said printed substrate which rests on top of the printed protection areas rests on said printed protection areas in a non-printed area.

14. A method according to any of the preceding claims, characterized in that the printing of the protective areas and / or the decoration itself is carried out by digital inkjet printing.

15. Use of a procedure according to any of the above claims in the manufacturing process of food and / or sanitary packaging.

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