Liner-free label

Abstract

The present invention relates to a method of manufacturing a direct heat-sensitive linerless label web (100) comprising a facestock (110) and a water-based acrylic pressure sensitive adhesive coating (120) wherein the facestock (110) comprises a base layer (113) and a direct heat-sensitive printable coating (115) wherein the method comprises: providing the facestock (110), the base layer (113) comprising a water-based acrylic pressure sensitive adhesive coating (120) comprising a water-based acrylic pressure sensitive adhesive coating (115), the water-based acrylic pressure sensitive adhesive coating (120) comprising a water-based acrylic pressure sensitive adhesive coating (115); applying a water-based acrylic adhesive coating (121) comprising a free and / or non-free surfactant, the total amount of surfactant excluding the surface-active polymerization agent being 0% by weight to less than 0.6% by weight, calculated based on the total dry weight of the water-based acrylic adhesive coating, and the total amount of the surfactant being 0% by weight to less than 0.6% by weight, calculated based on the total dry weight of the water-based acrylic adhesive coating. And thermally drying the water-based acrylic adhesive coating (121) into a water-based acrylic pressure sensitive adhesive coating (120). The invention also relates to a direct heat-sensitive linerless label web and to the use of a direct heat-sensitive linerless label (100) in on-demand printing.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a direct thermal linerless label roll. The present invention also relates to a direct thermal linerless label roll. The present invention also relates to the use of a direct thermal linerless label roll in on-demand printing. Background Art

[0002] Linerless labels with direct thermal facestock are used for a variety of purposes, such as for on-demand printing. However, it is well known that conventional linerless labels can cause problems over time, especially in simple and low-cost on-demand printers. These problems can be caused by the pressure-sensitive adhesive being exposed without a protective release liner, resulting in sticky adhesive contamination onto the internal mechanisms of the printer, causing printer jams and requiring additional repairs.

[0003] Furthermore, some pressure sensitive adhesives have traditionally been difficult to use with linerless labels containing direct thermal facestock. Thus, there remains a need for an improved yet simple direct thermal linerless label product, and an improved method for making a direct thermal linerless label product that provides consistent and trouble-free performance. Summary of the invention

[0004] One object of the present specification is to provide a method for making a direct thermal linerless label web comprising a pressure sensitive adhesive. In addition, one object of the present specification is to provide a direct thermal linerless label web comprising a pressure sensitive adhesive.

[0005] The various aspects of the invention are characterized by what is stated in the independent claims. Some preferred embodiments are disclosed in the dependent claims. These and other embodiments are disclosed in the description and the drawings.

[0006] Traditionally, direct thermal linerless label rolls can have a very limited shelf life, which creates additional challenges in logistics and handling or conversion before they can actually be used as printed labels. Improvements to these issues have been primarily achieved by improving the thermal layer or changing the base layer.

[0007] Surprisingly, it was found that surfactants added after the polymerization process can shorten the shelf life of direct thermal linerless labels comprising water-based acrylic pressure sensitive adhesives and lead to several challenges associated with the direct thermal linerless labels and methods of making the same.

[0008] For example, the drying process of linerless label webs containing water-based acrylic adhesives can be improved while reducing bleeding of the product simply by using an adhesive formulation containing minimal amounts of free surfactant.

[0009] Bleeding is a complex phenomenon that can depend on the effectiveness of adhesive transfer to the facestock, the level of anchoring of the adhesive, the curing and / or drying stage of the direct thermal linerless label web, and the coat weight of the adhesive layer. However, an adhesive formulation comprising a water-based acrylic adhesive with a lower amount of added surfactant was found to be one of the key features for reducing bleed.

[0010] Furthermore, surprisingly, the print quality of aged direct thermal linerless labels was significantly improved by reducing the amount of surfactant (eg, wetting agent) in the adhesive.

[0011] Furthermore, surprisingly, by using a water-based acrylic adhesive with minimal wetting agent content, dusting-related issues were reduced. The best results were obtained by using a water-based acrylic adhesive with a facestock with reduced mineral content. Thus, while facestock and silicone are typically the primary source of dusting, by minimizing bleed-through, dusting-related issues for direct thermal printers can also be minimized. Since the amount of adhesive residue in the printer is minimized, the adhesive residue may not be able to collect dust, and thus the dust that is formed may not be able to remain in the printer.

[0012] Thus, thanks to the novel technical solution, several problems associated with direct thermal linerless label rolls in on-demand printers, such as bleed-through, can be avoided or at least greatly reduced. Furthermore, the shelf life of direct thermal linerless label rolls can be extended, thereby simplifying their logistics and handling before final use. Furthermore, the print quality of aged direct thermal linerless labels can be greatly improved.

[0013] Direct thermal linerless label rolls according to this specification may include:

[0014] A) A face material having a first side and a second side, the face material comprising

[0015] - grass roots, and

[0016] - Direct thermal printable coating,

[0017] as well as

[0018] B) a water-based acrylic pressure-sensitive adhesive coating on the second side of the facestock, the water-based acrylic pressure-sensitive adhesive coating being obtained from a water-based acrylic adhesive coating comprising free and / or non-free surfactants, wherein

[0019] The total amount of surfactant, excluding the surface active polymerizing agent, is from 0 wt % to 0.6 wt % based on the dry weight of the water-based acrylic adhesive coating.

[0020] The first side of the face stock may be a top side of the face stock and the second side of the face stock may be a bottom side of the face stock.

[0021] The surfactant may include a surface active polymerizing agent which is used in the polymerization process of the water-based acrylic adhesive coating.

[0022] The surface-active polymerizing agent may include one or more reactive surface-active polymerizing agents and / or one or more non-reactive surface-active polymerizing agents.

[0023] The reactive surface active polymerizing agent is capable of reacting with the acrylic monomers during the polymerization process. Due to the reactive surface active polymerizing agent (if used), there may be no free surfactant left in the system after the polymerization process.

[0024] Therefore, the water-based acrylic adhesive may include a non-free surfactant. The amount of non-free surfactant (including surfactant polymerizing agent) may be at least 0.8 wt %, preferably at least 1 wt % (by dry weight), determined by the dry weight of the water-based acrylic adhesive coating. The non-free surfactant (if substituted for the free surfactant) may provide many benefits to the formed water-based acrylic adhesive coating. For example, the non-free surfactant may be substantially uniformly dispersed in the formed PSA layer, thereby improving the quality of the direct thermal linerless label web.

[0025] After the polymerization process, one or more surfactants may be applied as additives to the resulting adhesive coating. These surfactants may include wetting agents, which may increase diffusion and penetration properties by reducing surface tension. However, the water-based acrylic adhesive according to the present specification may not contain the wetting agent.

[0026] In one embodiment, the water-based acrylic adhesive coating contains from 0 wt % to equal to or less than 2 wt % (by dry weight) of free surfactant. The water-based acrylic adhesive coating preferably contains equal to or less than 1.5 wt % (by dry weight), more preferably equal to or less than 1.0 wt % (by dry weight), most preferably equal to or less than 0.6 wt % (by dry weight) of free surfactant. In this embodiment, the free surfactant includes free surfactant polymerizer and surfactant added after the polymerization process. In an advantageous embodiment, the amount of free surfactant in the water-based acrylic adhesive is less than 0.6 wt % (by dry weight), more preferably less than 0.5 wt % (by dry weight), and most preferably equal to or less than 0.3 wt % (by dry weight).

[0027] In one embodiment, the total amount of free surfactant (excluding surfactant polymerizing agent) calculated based on the dry weight of the water-based acrylic adhesive coating is less than 0.6 wt%, preferably less than 0.5 wt%, more preferably 0 wt% to 0.3 wt%, and most preferably 0 wt% to 0.2 wt%. The technical effect is that the formed water-based acrylic adhesive coating can be easily dried to a pressure-sensitive adhesive. In addition, the print quality of aged direct thermal linerless labels can be greatly improved. In addition, the bleeding of direct thermal linerless labels can be avoided or at least reduced.

[0028] If used, the total amount of wetting agent may be less than 0.3 wt %, preferably in the range of 0 wt % to 0.2 wt %, based on the total dry weight of the water-based acrylic adhesive coating. In one embodiment, the water-based acrylic adhesive coating comprises equal to or less than 0.2 wt % of wetting agent, such as in the range of 0.01 wt % to 0.2 wt %, based on the total dry weight of the water-based acrylic adhesive coating. More preferably, the total amount of wetting agent in the water-based acrylic adhesive coating is equal to or less than 0.1 wt %, such as in the range of 0.0 wt % to 0.1 wt %, based on the total dry weight of the water-based acrylic adhesive coating. The technical effect is that the print quality of aged direct thermal linerless labels can be significantly improved. In addition, bleeding of direct thermal linerless labels can be avoided, which can also reduce dusting related problems in printers.

[0029] In one advantageous embodiment, the water-based acrylic adhesive coating contains equal to or less than 0.6 wt% (by dry weight) of free surfactant and at least 0.8 wt% (by dry weight) of non-free surfactant. In this embodiment, since the reactive surfactant polymerizing agent forms the non-free surfactant, the amount of free surfactant in the water-based acrylic adhesive coating can be reduced. In addition, since the amount of non-free surfactant in the formed water-based acrylic adhesive is increased and the amount of free surfactant is relatively small, the surfactant can be dispersed approximately uniformly in the formed water-based acrylic adhesive. Therefore, the quality of the formed linerless label web can be significantly improved.

[0030] Therefore, in one embodiment, the amount of non-free surfactant in the water-based acrylic adhesive coating is greater than the amount of free surfactant. In order to further improve the quality of the direct thermal linerless label web containing the water-based acrylic adhesive, in one embodiment, the amount of non-free surfactant in the water-based acrylic adhesive is at least 10% greater than the amount of free surfactant. More preferably, the amount of non-free surfactant in the water-based acrylic adhesive is at least 20% greater than the amount of free surfactant. Most preferably, the amount of non-free surfactant in the water-based acrylic adhesive is at least 30% greater than the amount of free surfactant.

[0031] In one embodiment, the adhesive comprises the wetting agent, and at least one wetting agent is preferably selected from the following group:

[0032] - dioctyl sulfosuccinate (DOSS) wetting agent, and

[0033] -Ethylene glycol.

[0034] In one embodiment, the surfactant added to the formed water-based acrylic adhesive after the polymerization process may also include an emulsifier, for example, an emulsified silicone additive may be added to the water-based acrylic adhesive.

[0035] The water-based acrylic adhesive coating can be an aqueous polymer emulsion. The aqueous polymer emulsion can be derived from a component comprising an acrylate monomer, a vinyl aromatic compound and a surface-active polymerizing agent. The surface-active polymerizing agent can be composed of a non-reactive surface-active polymerizing agent and / or a reactive surface-active polymerizing agent. The surface-active polymerizing agent can include a reactive surface-active polymerizing agent or be composed of a reactive surface-active polymerizing agent.

[0036] The facestock may further include a topcoat layer on the direct thermal printable coating, wherein the topcoat layer preferably has a thickness of 0.5 g / m 2 Up to 3g / m 2 The top coating protects the top surface of the facestock and / or printed matter from friction or other external stresses.

[0037] The direct thermal linerless label web may also include a release layer on top of the facestock. Non-thermally cured release coatings (e.g., UV-curable silicones) are preferred because curing of these layers does not heat the thermal material of the direct thermal linerless label web. The release layer may be used to reduce friction with the printer printhead and minimize wear on the printhead. Additionally, the print quality of the linerless label web may be improved in some cases due to reduced friction and minimized wear on the printhead.

[0038] The surface material may also include an intermediate layer disposed between the base layer and the directly thermally printable coating. In this embodiment, the gram weight of the intermediate layer is 0.9 g / m 2 Up to 7g / m 2 In the range of 1g / m 2 Up to 5g / m 2 In one embodiment, the total amount of mineral pigment in the middle layer may be equal to or less than 4 g / m 2 , preferably equal to or less than 3g / m 2 , and / or the mineral pigment content in the intermediate layer may be less than 85% by weight, preferably equal to or less than 75% by weight.

[0039] The coating weight of the water-based acrylic pressure-sensitive adhesive coating may be 10 g / m 2 Up to 25g / m 2 .

[0040] In one embodiment, the total coverage of the water-based acrylic pressure-sensitive adhesive coating is in the range of 10% to 90% based on the total area of ​​the second side.

[0041] In one embodiment, the pressure sensitive adhesive coating comprises the emulsified silicone additive in an amount ranging from 1 wt % to 6 wt %, preferably ranging from 2 wt % to 4 wt %, based on the total dry weight of the adhesive coating.

[0042] Thus, in one embodiment, the water-based acrylic pressure-sensitive adhesive coating may include an emulsified silicone additive. In this embodiment, the emulsifier may maintain the silicone additive as a stable aqueous dispersion. The emulsified silicone additive may include a silicone component, such as silicone oil (polydimethylsiloxane), at least one emulsifier, and water. The water-based acrylic pressure-sensitive adhesive including the silicone additive, wherein the water-based acrylic pressure-sensitive adhesive has a reduced wetting agent content, may be more easily cut mechanically in such devices and leave less adhesive residue on the cutting blade or edge.

[0043] As described above, by reducing bleed, dusting related problems in the printer may also be reduced. In one embodiment, to minimize the dusting tendency of the linerless label web, the total mineral content of the direct thermal linerless label web may be in the range of 0 to 20 weight percent, calculated based on the total dry weight of the direct thermal linerless label web.

[0044] Preferably, in order to improve the print quality in a cost-effective manner, the grammage of the direct thermal printable coating is 1 g / m 2 Up to 5g / m 2 within the range.

[0045] A method of manufacturing a direct thermal linerless label web may include the following steps:

[0046] -Provide surface materials,

[0047] - Apply a coating of water-based acrylic adhesive, and

[0048] - thermally drying the adhesive coating to form a pressure-sensitive adhesive coating,

[0049] The result is a direct thermal linerless label roll.

[0050] The water-based acrylic adhesive coating can be applied directly to the face stock. Alternatively, the water-based acrylic adhesive coating can first be applied to a carrier material, dried on the carrier material, and then transferred to the face stock.

[0051] In one embodiment, the direct thermal linerless label web is composed of the following components:

[0052] - A surface material comprising at least:

[0053] - grass roots,

[0054] - Direct thermal printable coating,

[0055] -optionally, a top coating on the direct thermal printable coating, and

[0056] - optionally, an intermediate layer disposed between the base layer and the directly thermally printable coating,

[0057] -optionally, a release coating on the facestock, and

[0058] - Adhesive coating.

[0059] The substrate can be an uncoated base paper or film material. For environmental reasons, the substrate is preferably paper.

[0060] As described above, the water-based acrylic adhesive may contain free and non-free surfactants. The free surfactant may include surfactants added to the adhesive after the polymerization process, such as wetting agents. The free surfactant may additionally or alternatively contain, for example, residual surfactants from the polymerization process.

[0061] A total amount of at least 0.7% by weight of wetting agent is considered to be an essential ingredient to obtain a good adhesive layer. Surprisingly, by removing the wetting agent from the adhesive formulation, or at least reducing the wetting agent content, the drying process of the adhesive coating can be improved, thereby expanding the operating window. In addition, the print quality can be significantly improved. In addition, the runnability of the printer can be improved.

[0062] Surprisingly, the print quality of aged direct thermal linerless label webs can be improved by adjusting the adhesive formulation. Furthermore, surprisingly, the component that was found to affect the print quality of aged direct thermal linerless labels was the wetting agent. By selecting the type of wetting agent and / or the correct dosage of the wetting agent, the inventors were able to significantly increase the shelf life of the direct thermal linerless labels. Furthermore, the selected adhesive has a significant impact on the shelf life of the direct thermal linerless labels.

[0063] Furthermore, thanks to this novel technical solution, adhesive build-up on the printer roller and / or the cutting blade can be significantly reduced. This effect can be further improved by adding silicone additives to the adhesive composition.

[0064] Dust and bleed interfere with the labelling process, reduce the quality of direct thermal printing and can eventually lead to printhead damage. Therefore, by minimising dust and bleed of direct thermal linerless labels, long-term trouble-free printing of paper-based direct thermal linerless labels can be achieved. Dust and bleed of direct thermal linerless label rolls can be minimised thanks to the solution according to this specification.

[0065] Depending on the printer model in question, dust or particle residues or contaminants in the label material can have several different adverse effects on the printer mechanism. For example, dust can reduce the thermal contact of the printhead with the label material, which can reduce print quality. This can lead to hot spots in the printer head and / or the need to compensate by using higher printhead energies, which again shortens the life of the printer. Sticky adhesive residues are often generated, especially when the label material is cut against a manual or motorized cutter mechanism to separate the printed individual labels. These residues can then weaken the cutting mechanism itself or be slowly transported and accumulate on other internal parts of the printer. Thanks to novel solutions, the anchoring effect of the adhesive on the face stock can be significantly improved. In addition, surprisingly, water-based adhesives can be dried easily to PSA.

[0066] Thanks to the novel solution, a linerless label roll for an on-demand linerless label printer may be obtained in a cost-effective manner, which linerless labels may have improved properties for the on-demand printer and for labelling purposes.

[0067] Additionally, it is easier to achieve a high-quality, cost-effective and environmentally friendly product while improving print quality and reducing the dusting and bleed tendency of direct thermal linerless label rolls.

[0068] Additionally, the method can allow drying of adhesive, such as on a facestock, without causing undesirable and premature color changes in the thermal coating of a direct thermal linerless label web. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1a The S of linerless labels (roll stock) is shown by way of example. x , S y cross section,

[0070] Figure 1b The S of the surface material is shown by way of example x , S y cross section,

[0071] Figure 2 A schematic diagram of a label printer that can be used for a linerless label roll according to the present disclosure is shown by way of example.

[0072] Figure 3 By way of example, the method steps according to one embodiment are shown.

[0073] Figure 4 By way of example, the method steps according to one embodiment are shown.

[0074] Figure 5 One embodiment of the manufacturing method and apparatus is shown by way of example.

[0075] Figure 6 Details of a manufacturing method and apparatus according to one embodiment are shown by way of example.

[0076] Figure 7 Details of a manufacturing method and apparatus according to one embodiment are shown by way of example.

[0077] Figure 8 One embodiment of the manufacturing method and apparatus is shown by way of example, and

[0078] Figure 9a -b and Fig.10a -d shows photos of experimental tests.

[0079] The accompanying drawings are schematic and are intended to illustrate the general principles of the disclosed technical solutions. Therefore, the illustrations in the accompanying drawings are not necessarily to scale or imply an exact layout of the system components. DETAILED DESCRIPTION

[0080] The solution will be described in more detail below with reference to some embodiments, but these embodiments should not be considered limiting.

[0081] In this specification, reference is made to the accompanying drawings having the following reference numerals and symbols:

[0082] S x , S y , S z 3D coordinates,

[0083] MD Machine direction, first direction,

[0084] CD Transverse, Secondary Direction,

[0085] 100 Linerless Label Rolls,

[0086] 110 face material,

[0087] 111 The first side, i.e. the top side,

[0088] 112 The second side, i.e. the bottom side,

[0089] 113 substrate, such as paper,

[0090] 114 middle layer,

[0091] 115 Direct thermal printable coating,

[0092] 116 Top coating of surface material,

[0093] 120 Adhesive coating (PSA),

[0094] 121 Adhesive coating,

[0095] 130 Release coating,

[0096] 150 No bonding area,

[0097] 200 Linerless Labels, Tags,

[0098] 240 label printer,

[0099] 401 Set the surface material.

[0100] 402 Apply water-based adhesive,

[0101] 403 Set no-adhesive zone,

[0102] 404 Ensures the predetermined moisture level,

[0103] 405 The adhesive coating is dried,

[0104] 406 Transferring the adhesive to the face material,

[0105] 407 Winding the material into linerless rolls,

[0106] 560 Drying unit,

[0107] 561 Drying device,

[0108] 570 Linerless Label Roll,

[0109] 580, a coating unit for applying an adhesive,

[0110] 590 Moisture hydration unit for ensuring a predetermined moisture level,

[0111] 611 Carrier materials,

[0112] 611b Coil material,

[0113] 612 face uncoiler,

[0114] 650 Cooling cylinder,

[0115] 660 roll gap, and

[0116] 690 Unit to remove adhesive.

[0117] In this specification, the term "includes / comprising" may be used as an open term, but also includes the closed term "consisting of..." Therefore, unless otherwise specified, the word "includes / comprising" may be understood as "includes / comprising or consists of...".

[0118] For the purposes of this specification and claims, unless otherwise indicated, all ranges include any combination of the highest and lowest points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

[0119] The temperature unit is expressed in degrees C, which is equivalent to °C.

[0120] Unless otherwise stated, percentage values ​​referring to amounts of materials are percentages by weight (wt %).

[0121] Unless otherwise stated, all percentage values ​​relating to amounts of material refer to dry weight.

[0122] The term "surfactant" refers to a surface active agent. Surfactants can include free surfactants and non-free surfactants.

[0123] The surfactant may include one or more surface active polymerizing agents. The surfactant may include one or more wetting agents. The surfactant may include one or more emulsifiers.

[0124] The term "surface active polymerizing agent" refers to a surfactant used in the polymerization process of a water-based acrylic adhesive. The surface active polymerizing agent may be a non-reactive surfactant. Preferably, the surface active polymerizing agent is a reactive surface active polymerizing agent. The reactive surface active polymerizing agent polymerizes at least primarily with the monomers, and a large amount of free surfactant may not remain in the formed adhesive coating. The reactive surface active polymerizing agent may include a reactive double bond, through which it can copolymerize with the monomers during the polymerization process.

[0125] The term "wetting agent" refers to a surfactant that is added to the formed water-based acrylic adhesive after the polymerization process to adjust the surface interaction properties and, for example, reduce the surface tension of the water-based adhesive. The wetting agent may be a non-reactive surfactant. The water-based acrylic adhesive may or may not contain a wetting agent.

[0126] In this specification, the term "emulsifier" refers to a surfactant added to the formed water-based acrylic adhesive after the polymerization process to adjust the interaction characteristics of certain particles. If the water-based acrylic adhesive contains a silicone additive, the emulsifier can be part of the silicone additive.

[0127] The term "coil" refers to a continuous sheet of material. Coils are typically processed by moving on rollers. Between processing stages, the coil may be stored and / or transported in roll form.

[0128] In this specification, the term "linerless label web" refers to a continuous direct thermal web including a facestock 110 and a pressure sensitive adhesive 120, from which linerless labels 200, i.e., individual labels, can be separated. Conventional linerless label webs may not have the same challenges as direct thermal linerless label webs due to the direct thermal coating therein and the typical end use in on-demand printing.

[0129] In this specification, unless otherwise specified, the terms "label", "linerless label" and "adhesive label" refer to a single direct thermal label product 200 separated from a direct thermal linerless label web 100 to be applied to an article. The label 200 can be attached to the article by using an adhesive. Therefore, in this application, unless otherwise specified, the terms "label", "linerless label" and "adhesive label" refer to a product including a direct thermal face material 110 and a pressure-sensitive adhesive coating 120.

[0130] The term “linerless label (web)” refers to the label 200 and / or the linerless label web 100 .

[0131] The term "machine direction" refers to the direction in which the coil is manufactured. The machine direction may also refer to the circumferential direction of the roll. In addition, the longitudinal direction of the coil is referred to as the machine direction. In this application, the term "first direction" refers to the machine direction.

[0132] The terms "cross-sectional direction", "cross-machine direction" and "lateral direction" refer to a direction transverse to the machine direction. In the present application, the term "second direction" refers to the lateral direction.

[0133] The term "face stock" refers to the substrate of the label, also referred to as face stock or face material. In the present application, the face stock includes a base layer, a direct thermal printable coating, and an intermediate layer between the base layer and the direct thermal printable coating. In an advantageous embodiment, the base layer is uncoated paper.

[0134] In the present application, the term "adhesive coating" refers to a coating comprising a water-based acrylic adhesive. The adhesive coating may also contain, for example, silicone additives.

[0135] The terms "adhesive layer" and "adhesive coating" refer to a layer of adhesive, which may be a continuous or non-continuous layer. The adhesive layer may include areas of adhesive, such as adhesive stripes and / or adhesive dots.

[0136] The term "PSA" means pressure sensitive adhesive.

[0137] Surface material

[0138] Figure 1b The S of the surface material is shown by way of example x , S y Cross section. The facestock 110 is the layer that is adhered to the surface of the article by the adhesive coating during labeling.

[0139] The surface material 110 includes a first side 111 and a second side 112 (eg Figure 1a-1b ). The top side (first side 111) of the linerless label (web) can be printed by using heat. The second side 112 is the adhesive side.

[0140] The face material 110 of the direct thermal linerless label web has at least two layers. The face material includes or consists of the following parts:

[0141] - a base layer 113, which can be a base paper or a film material,

[0142] - Direct thermal coating 115,

[0143] - optionally, an intermediate layer 114, which is left between the direct thermal coating 115 and the base layer, and

[0144] - Optionally, a top coating 116 .

[0145] The top coating 116 on the direct thermal coating 115 can be used to protect the thermal coating 115. At least during the manufacturing process of the direct thermal linerless label web, the top coating can protect the direct thermal coating. The top coating can protect the top surface of the face material and / or the printed matter from friction or other external stresses. However, in one embodiment, the face material does not have the top coating 116.

[0146] The top coating layer (if used) may comprise at least one of the following: starch, polyvinyl alcohol (PVA), latex, and wax. Preferably, the top coating layer comprises polyvinyl alcohol (PVA) and / or wax. These polymers may provide better protection for the direct thermal printable coating. In addition, the wax may improve the friction properties of the linerless label web. The top coating layer may further help reduce dusting of the linerless label web.

[0147] In addition to or as an alternative to the top coating 116, the face stock can include one or more back coatings, for example, on the second side 112 of the face stock 110. The back coating can contain, for example, polyvinyl alcohol or be based on, for example, polyvinyl alcohol. The back coating can improve the anchoring of the adhesive 120, 121 to the face stock 110. In one embodiment, the face stock does not have such a back coating, but the water-based pressure sensitive adhesive 120 is directly in contact with the base layer without any additional coating between the PSA and the base layer.

[0148] The linerless label (web) 100, 200 may also include one or more barrier layers to prevent chemicals from migrating through the surface of the first side 111 of the face material or the surface of the second side 112 of the face material, or other interfaces of the linerless label (web) 100, 200. In one embodiment, the linerless label web does not have the additional barrier layer.

[0149] Advantageously, for cost and environmental reasons, the base layer has a grammage of 38 g / m 2 Up to 82g / m 2 The weight of the surface material 110 is preferably at least 45 g / m 2 , more preferably at least 50 g / m 2 In addition, the weight of the surface material is preferably less than 80g / m 2 , more preferably equal to or less than 75g / m 2 For example, the weight can be 45g / m 2 Up to 80g / m 2 In the range of or within 50g / m 2 Up to 75g / m 2 The grammage is particularly suitable for linerless labels comprising a direct thermal printable coating and for use in on-demand linerless label printers. The grammage can be measured according to standard ISO536.

[0150] The facestock 110 may have a static sensitivity of less than 100° C., preferably in the range of 75° C. to 95° C. The static sensitivity as well as the dynamic sensitivity need to be low enough so that the product does not darken before printing (e.g., during transportation). However, the static and dynamic sensitivities should be high enough so that the linerless labels (webs) 100, 200 can be thermally printed.

[0151] The face material 110 may have a caliper thickness in the range of 60 μm to 85 μm measured according to ISO 534. If the face material is too thin, the linerless label (web) 100, 200 may be difficult to handle. For example, if the face material is very thin, the stiffness of the linerless label web may be too low, resulting in the linerless label web being too loose. Therefore, the linerless label (web) may be difficult to manufacture and / or may cause problems when used with a linerless label printer.

[0152] As previously mentioned, the base layer of the face material 110 may include or consist of paper. Alternatively, the base layer of the face material 110 may include or consist of a film material. The film material may be made of polyethylene (PE), polypropylene (PP) or biaxially oriented polypropylene (BOPP). In addition, other suitable materials, such as different types of polyesters, such as polyethylene terephthalate (PET) or polyethylene are also feasible.

[0153] Preferably, the substrate comprises or consists of paper. Advantageously, the substrate consists of uncoated paper.

[0154] The face material 110 may include paper containing natural fibers as its main raw material. Natural fibers refer to any plant material containing cellulose. The natural fibers may be wood-based. The wood-based natural fibers may come from softwood trees, such as spruce, pine, fir, larch, Douglas fir or hemlock, and / or from hardwood trees, such as birch, aspen, poplar, alder, eucalyptus or acacia, or from a mixture of softwood and hardwood.

[0155] If used, paper preferably comprises wood-based natural fibers. Wood-based natural fibers are preferably the main fiber material of paper. Face material 110 may include cellulose fibers from hardwood and / or softwood. A mixture of hardwood and softwood may be used to improve the internal bonding strength of face material 110.

[0156] The base layer can be a so-called wood-free paper. Wood-free refers to chemical pulp, such as Kraft pulp. According to one embodiment, due to the high quality requirements of the surface material, the pulp used to make the surface material does not contain any kind of mechanical pulp. The paper 113 of the surface material 110 can be a wood-free paper containing fibers (e.g., fibers from softwood and / or hardwood).

[0157] The base layer 113, such as an uncoated base paper, may further include at least one mineral filler selected from the group consisting of clay, calcined clay, kaolin, natural ground calcium carbonate, precipitated calcium carbonate, talc, calcium sulfate, and titanium dioxide. The total amount of mineral fillers in the base layer 113 may be less than 18% by weight, preferably less than 13% by weight, more preferably less than 8% by weight, and most preferably less than 5% by weight, such as between 0% by weight and 4% by weight, based on the total weight of the base layer 113. Mineral fillers can reduce the cost of manufacturing the product. However, mineral fillers may also reduce the strength properties of the face material 110. In addition, if the base layer contains too much filler, some properties of the face material 110 may be compromised. For example, mineral fillers may increase the dusting of the face material, which may cause blocking and other problems in on-demand printers. If the amount of mineral fillers in the base layer is very low, the dusting tendency of the direct thermal linerless label web can be reduced.

[0158] The fiber content of the uncoated base paper can be equal to or greater than 50% by weight, preferably at least 60% by weight, and more preferably at least 70% by weight to increase the strength of the linerless label web. In addition, increasing the natural fiber content and reducing the mineral filler content can reduce dusting of the on-demand printer substrate.

[0159] Paper can be certified by FSC TM The face stock can therefore include or consist of environmentally friendly materials. Therefore, the new linerless labels (roll stock) may be more environmentally friendly than some other types of face stock materials.

[0160] Whether the base layer is fiber-based or film-based, the composition of the intermediate layer 114 (if disposed between the base layer and the direct thermal printable coating) is important in influencing the amount of dust when the linerless label material is cut and separated into labels in a thermal printer. It appears that the composition of the intermediate layer 114 has an effect on how the internal pressure is propagated into the label material layers during the cutting operation of the cutter. The composition of the intermediate layer appears to prevent dust generation not only in the intermediate layer itself, but also in other layers of the label material. In the case of a film-based base layer, the structure of the intermediate layer 114 appears to minimize the spread of compressive stresses generated in the cutter from the cut line more widely into the label material, thereby affecting the smaller area around the cut line.

[0161] The base paper can be calendered with a calender or supercalender to obtain a high-density surface.

[0162] The base layer 113 may be coated to form an intermediate layer 114 between the base layer 113 and the direct thermal coating 115. The intermediate layer 114, if used, may have a coating weight of 0.9 to 7 g / m per side. 2 In the range of 1g / m 2 Up to 5g / m2 In the range of 1.3 g / m 2 Up to 4g / m 2 The most preferred range is 1.6 g / m 2 Up to 3g / m 2 Due to the intermediate layer, the quality of the direct thermal coating can be improved. In addition, the amount of expensive direct thermal coating required to obtain good printability can be reduced.

[0163] The intermediate layer (if used) may include at least one mineral pigment. Preferably, the amount of mineral pigment in the intermediate layer is very low. The mineral pigment content of the uncoated base paper may be equal to or less than 18% by weight, more preferably equal to or less than 16% by weight, to reduce the dusting tendency of the product. Instead of mineral pigments, or in addition to mineral pigments, the intermediate layer may also include non-mineral pigments. In addition, based on the total weight of the intermediate layer, the amount of binder in the intermediate layer (if used) may be at least 15% by weight, for example, in the range of 20% to 50% by weight, preferably in the range of 25% to 45% by weight, more preferably in the range of 30% to 42% by weight, and most preferably in the range of 33% to 40% by weight. The pigment particles may be bonded together using a binder to form a uniform coating. In addition, the intermediate layer 114 may have the effect of reducing heat transfer from the heat-sensitive coating to the base paper 113. This may enable the formation of enhanced or high-resolution print content.

[0164] Facestock: Examples of Direct Thermal Printable Coatings

[0165] The face stock 110 includes a direct thermal printable coating 115. Therefore, the face stock 110 can be referred to as a direct thermal printable face stock.

[0166] The direct thermal printable coating 115 is arranged to provide thermal printability to the face material 110. The direct thermal printable coating is arranged to form a thermosensitive reactive layer that changes color during thermal printing. The thermosensitive coating comprises a reactive component. The thermosensitive coating may comprise a matrix. The matrix may comprise a dye and a developer.

[0167] The solid heat-sensitive coating matrix is ​​heated to a temperature higher than its activation temperature and / or melting point by the thermal print head. The dye of the heat-sensitive coating may include a leuco dye. The leuco dye is arranged to react with an acid and become a colored form. The heat-sensitive coating may contain a dye, a developer, a sensitizer, a binder and a stabilizer.

[0168] The developer may be arranged to co-react with the dye above the activation temperature during thermal printing. The reaction of the dye with the developer is arranged to cause color formation. The developer may include a sulfonylurea, a zinc salt of a substituted salicylic acid, or a phenol, such as bisphenol S (BPS). The thermal coating may preferably be free of BPA, free of bisphenol (BP), and / or free of phenol to improve chemical safety.

[0169] Sensitizers can be used in the thermosensitive coating to reduce the melting point of the dye and / or developer. The dye and developer are set to react when heated to a temperature higher than the melting point of the thermosensitive coating matrix. The melting point of the matrix can depend on the melting point values ​​of its components. The thermal threshold of the thermosensitive coating is the melting point of the component of the thermosensitive coating with the lowest melting point. The sensitizer of the thermosensitive coating can be set to reduce the melting point of the dye and / or developer. This has the effect of proving the accuracy of the melting point and / or optimizing the temperature of the color change and / or promoting the mixing of the dye and the developer.

[0170] Optionally, the thermal coating may contain a stabilizer. The dye in the thermal paper may be unstable and tend to return to its original colorless crystalline form. For example, the thermal paper may be sensitive to external conditions of heat and humidity. In order to stabilize the metastable glass formed by the leuco dye, developer and sensitizer, a stabilizer may be added to the mixture. The stabilizer has the effect of inhibiting the recrystallization of the dye and developer and / or stabilizing the printed content.

[0171] The binder of the thermosensitive coating can have the effect of promoting the thermosensitive coating to adhere to the base substrate or pre-coating. The binder can contain double bonds. The binder can include polyvinyl alcohol (PVA) or latex, for example, styrene butadiene latex (SB) or styrene acrylic (SA).

[0172] The sensitivity of a thermal coating refers to how well it responds to a given amount of heat or energy. Sensitivity is a determining factor in choosing the right thermal coating or thermal paper. It can be described by a graph that plots image density or optical density (OD) versus the amount of heat or energy transferred. Optical density is a measure of the relationship between incident and reflected light. An optical density of about 1.1 typically appears completely black to the human eye. Therefore, lower optical densities correspond to different shades of gray. Thermal coatings and thermal papers are often characterized using static and dynamic sensitivity.

[0173] Static sensitivity indicates the temperature at which the thermal paper starts to form an image (i.e. change color). Thermal paper with low static sensitivity starts to form an image only at high temperatures, for example, at a temperature above 90°C. On the other hand, thermal paper with medium static sensitivity starts to form an image at a lower temperature, for example, at a temperature between 80°C and 90°C. Thermal paper with high static sensitivity starts to react even at a lower temperature, for example, at a temperature of 65-80°C or 70-80°C.

[0174] The dynamic sensitivity of thermal paper actually indicates the printing speed that the thermal paper is capable of. This is particularly important for choosing the right thermal paper for a specific thermal printer, because the higher the dynamic sensitivity of the paper, the faster the printer can run without changing any settings. Dynamic sensitivity is usually expressed as mJ / mm 2 Therefore, thermal papers with low dynamic sensitivity require higher print head temperatures and / or longer exposure times, i.e. slower printing speeds, to obtain high optical density of the image. On the other hand, high dynamic sensitivity enables faster printing even at lower print head temperatures.

[0175] Dynamic sensitivity is difficult to measure using a single, unambiguous value (e.g. mJ / mm 2 The total energy level transferred into the paper (in units of energy level) is divided into low, medium and high categories, because the total energy level transferred into the paper does not directly correspond to a specific temperature reached in the thermosensitive coating. The heat capacity of the thermal paper is related to, for example, the thickness of the paper and the presence of different materials or layers of materials. Therefore, different amounts of energy may be required to heat papers with different thicknesses to the same temperature. Different paper thicknesses or thermal conductivities of different layers may result in different temperature levels in the thermosensitive coating.

[0176] For example, at an optical density of 1.1 (total black to the human eye), very different energy levels may be required to achieve this full color change in the thermal coating. High dynamic sensitivity thermal paper may be at less than 15mJ / mm 2 Such optical density has been achieved at energy levels of 20 mJ / mm2, and medium dynamic sensitivity may require about 20 mJ / mm2 2 , for example 15-25mJ / mm 2 For the same print darkness, thermal papers with low dynamic sensitivity may even require more than 25mJ / mm 2 Each of these papers may still be exposed to much lower energy levels (e.g., less than 10 mJ / mm 2 ) begins to show some color changes.

[0177] A combination of high static sensitivity with high dynamic sensitivity may be preferred, allowing fast printing with an economical and simple linerless printer. The surface temperature of the labeled item is unlikely to exceed 65-70°C, which allows the use of some thermal papers with moderate static sensitivity, and more preferably thermal papers with high static sensitivity close to the maximum surface temperature of the labeled item. On the other hand, long-term stability is not an issue in these short-term applications, so more economical thermal papers can be used that are not specifically designed for archival or long-term stability. This high static and dynamic sensitivity of the thermal coating / thermal paper may pose a challenge to the manufacture of direct thermal printable linerless labels, as it limits the maximum temperature to which the direct thermal facestock material can be exposed during the manufacturing process of the linerless label product to prevent unwanted and premature color changes in the thermal coating.

[0178] Waterborne polymer emulsion

[0179] The water-based acrylic adhesive coating 121 may be based on an aqueous (ie, water-based) polymer emulsion. The aqueous polymer emulsion may be based on an acrylic polymer.

[0180] Water-based polymer emulsions are relatively low in cost, easy to apply, and contain relatively few volatile organic compounds (VOCs). In addition, water-based polymer emulsions are suitable for food applications. Water-based polymer emulsions can be suitable for direct contact with food and have been approved.

[0181] The aqueous polymer emulsion may comprise an acrylic-based copolymer. The term "copolymer" refers to a polymer prepared from more than one different type of monomer.

[0182] In one embodiment, the amount of the acrylic acid-based copolymer may be 40 to 65 wt %, or 45 to 60 wt %, based on the weight of the emulsion.

[0183] The aqueous polymer emulsion may be an acrylic-based copolymer, which may be derived from components including those listed below:

[0184] 1) Acrylate monomer,

[0185] 2) a vinyl aromatic compound, and

[0186] 3) Surfactant, i.e. surface active polymerizing agent.

[0187] Additionally, the components may include a chain transfer agent.

[0188] Generally speaking, acrylate monomers may be based on an acrylic structure consisting of a vinyl group and either a carboxylate end or a nitrile end.

[0189] In one embodiment, the aqueous polymer emulsion comprises the following amounts of acrylate monomers (by dry weight): 0 to 5 wt % acrylic acid, 0 to 5 wt % methacrylic acid, 0 to 5 wt % beta-carboxyethyl acrylate, 0 to 15 wt % methyl acrylate, and 0 to 90 wt % 2-ethylhexyl acrylate. With these amounts of acrylate monomers, an improved aqueous polymer emulsion can be provided for the adhesive coating 121. In an advantageous embodiment, the amount of 2-ethylhexyl acrylate is at least 50 wt %.

[0190] The aqueous polymer emulsion may contain a total of 85 to 99 weight percent (by dry weight) of monomers including acrylate monomers and vinyl aromatic compounds. The aqueous polymer emulsion may contain 0.1 to 10 weight percent (by dry weight) of vinyl aromatic compounds. The vinyl aromatic compound may include or consist of alpha-methylstyrene or styrene. Such acrylic-based copolymers may improve the performance of linerless label webs.

[0191] The polymerization may be carried out in the presence of one or more surface active polymerization agents. The surface active polymerization agent may include reactive surfactants and / or non-reactive surfactants.

[0192] Generally speaking, the role of the surfactant in the polymerization process is to form micelles and emulsify the monomers. For this purpose, it is best to use a surfactant that has a hydrophilic part and a hydrophobic part. The surfactant can emulsify and disperse the polymer particles.

[0193] The reactive surface active polymerizing agent may contain a component that can act as an internal crosslinking agent during the polymerization process. The component may have a polymerizable double bond. Therefore, the reactive surface active polymerizing agent can react with the acrylic monomer. Therefore, the reactive surface active polymerizing agent may contain an active double bond through which it can copolymerize with the monomer.

[0194] According to one embodiment, at least one reactive surface-active polymerizing agent is an anionic surfactant.

[0195] For example, the polymer emulsion may contain 0.1 to 5 wt% (by dry weight) of the surfactant polymerizing agent. In an advantageous embodiment, the polymer emulsion contains 0.5 to 4 wt% (by dry weight) of the surfactant polymerizing agent, more preferably 1 to 3 wt% (by dry weight) of the surfactant polymerizing agent, and most preferably 1.5 to 2.5 wt% (by dry weight) of the surfactant polymerizing agent. In an advantageous embodiment, the surfactant polymerizing agent is at least mainly polymerized with the monomer, and only free surfactant may remain in the water-based acrylic adhesive 121.

[0196] Therefore, due to the reactive surfactant polymerizing agent (if used), there may be no free surfactant left in the system after the polymerization process. Alternatively, a small amount of residual free surfactant may remain in the system after the polymerization process. Since the amount of free surfactant after the polymerization process is very small, the amount of free surfactant in the formed water-based adhesive coating will also be reduced. Therefore, the formed water-based acrylic adhesive coating can be easily dried to form a pressure-sensitive adhesive.

[0197] In addition to or in place of reactive surfactants, the surfactant may include non-reactive surfactants. However, reactive surfactants may be preferred because non-reactive surfactants may remain free during the polymerization process and thus they may cause some problems with the formed linerless label web.

[0198] The aqueous polymer emulsion may include a chain transfer agent. For example, the polymer emulsion may include 0.005 to 0.5 wt % (by dry weight) of a chain transfer agent. The chain transfer agent may be used to control the average polymer chain length of the acrylic copolymer. With the chain transfer agent, adhesion properties may be improved. In one embodiment, the chain transfer agent is n-dodecyl mercaptan (n-DDM) or tert-dodecyl mercaptan (t-DDM).

[0199] Adhesive coating

[0200] According to the present specification, the adhesive coating is a water-based acrylic adhesive coating.

[0201] As noted above, in one embodiment, no free surfactant (ie, free surface-active polymerizing agent) may be present in the polymer emulsion after the polymerization process.

[0202] However, before the formed water-based acrylic adhesive is applied to the surface material, one or more additional surfactants are usually added to the aqueous polymer emulsion. For example, 1-2% by weight of a wetting agent is considered to be an essential component of a water-based acrylic adhesive because the wetting agent can increase the spreading and penetration properties by reducing the surface tension. Wetting agents are not unfamiliar to those skilled in the art.

[0203] Therefore, before the formed water-based acrylic adhesive is applied and dried into the pressure-sensitive adhesive coating 120, some surfactant may be added as an additive to the aqueous polymer emulsion.

[0204] In an advantageous embodiment, the total content of free surfactants is equal to or less than 1 wt% (by dry weight), preferably equal to or less than 0.6 wt% (by dry weight), more preferably equal to or less than 0.5 wt% (by dry weight), and most preferably equal to or less than 0.3 wt% (by dry weight), based on the total dry weight of the water-based acrylic adhesive 120, 121. Reducing the content of free surfactants may have a technical effect, so that the surfactant is substantially evenly dispersed in the formed adhesive, and the formation of separate hydrophilic islands may be avoided or at least reduced. Therefore, the formed PSA composition may not experience undesirable peeling, i.e., delamination. The acrylic adhesive composition including a reduced free surfactant content can have the following effects: increasing (i.e., improving) the initial adhesion of the label, especially when the surface to be labeled is polar. Polar surfaces include glass, steel, and PET.

[0205] Therefore, as mentioned above, the use of reduced free surfactant content can improve peel adhesion. High peel adhesion is very important for the stability of the label on the substrate. High peel adhesion can prevent the label (corner) from detaching in humid conditions, during transportation and during consumer use of the labeled item.

[0206] In one embodiment, the surfactant added as an additive to the adhesive coating may include a wetting agent. Surprisingly, a water-based acrylic adhesive with no wetting agent or a minimal amount of wetting agent can provide many benefits at various stages of the manufacturing process, the conversion stage, and the end-use stage. In addition, these effects can be improved by optimizing the coating thickness.

[0207] The amount of wetting agent used can be equal to or less than 0.3 wt %, preferably equal to or less than 0.2 wt %, more preferably equal to or less than 0.1 wt %, or even as low as 0 wt %, based on the total dry weight of the water-based acrylic adhesive coating. Most preferably, the adhesive coating is completely free of wetting agent. Surprisingly, if the amount of wetting agent used exceeds 0.3 wt % (calculated by dry weight), especially if its amount exceeds 0.5 wt % or 0.6 wt % (by dry weight of the adhesive coating), it will lead to reduced drying efficiency and decreased print quality. The greater the amount used, the faster the print quality changes. Therefore, the more wetting agent, the worse the print quality.

[0208] In one embodiment, the water-based acrylic adhesive contains a wetting agent. In this embodiment, the wetting agent is preferably anionic or nonionic, most preferably anionic. By using a small amount of wetting agent less than 0.3 wt %, preferably equal to or less than 0.2 wt %, the uniformity of the PSA layer can be improved without reducing other properties too much.

[0209] Fig.10aShown is an example of print quality on a direct thermal linerless label aged for 12 weeks at 0.2 wt% wetting agent. Fig.10b An example of print quality after aging for 12 weeks at a wetting agent level of 0.5 wt% is shown. It is clear that the higher the wetting agent level, the worse the print quality. At levels of at least 0.3 wt%, the print quality of the linerless label stock starts to deteriorate after only two to three weeks of aging.

[0210] Fig.10c Shown is an example of print quality at a wetting agent level of 1.3 wt % and after aging for 7 weeks. Fig.10d An example of print quality after 9 weeks of aging is shown for a wetting agent dosage of 1.3 wt%. At dosages above 0.3 wt%, print quality may change noticeably after the 9th week; at dosages around 1 wt%, print quality may already change noticeably after the 7th week.

[0211] In order to improve the drying of the water-based acrylic adhesive and improve the print quality of the aged direct thermal linerless label web, the total content of free surfactant (excluding the surfactant polymerizing agent) in the water-based acrylic adhesive coating may be in the range of 0 to equal to or less than 0.6 wt% (on a dry weight basis), preferably equal to or less than 0.5 wt%, more preferably equal to or less than 0.4 wt%, most preferably equal to or less than 0.3 wt%, such as in the range of 0.01 to 0.5 wt% (on a dry weight basis). Since the water-based acrylic adhesive coating contains a very small amount of free surfactant, the water-based acrylic adhesive coating can be dried very easily to form a pressure-sensitive adhesive. In addition, due to the small amount of free surfactant, the print quality of the aged direct thermal linerless label web can be improved.

[0212] The adhesive coating may include a tackifier. Tackified acrylic adhesives can be used to provide strong adhesion to surfaces. Tackifiers are optional components. If a tackifier is used, it is preferably added in the form of an aqueous dispersion. In one embodiment, the tackifier is selected from rosin esters, terpene resins, phenol resins, rosin resins and rosin derivative resins, petroleum resins, and ketone resins. Compatibility between the tackifier (if used) and the adhesive coating may be an important factor in improving the performance of the adhesive coating. In one embodiment, the tackifier is selected from rosin resins and rosin derivative resins. These tackifiers can be used to improve the adhesion and viscosity of pressure sensitive adhesives.

[0213] The adhesive coating may include an emulsified silicone additive. Due to the emulsifier or emulsified silicone additive, the silicone additive does not float in the water, but rather the silicone additive can be mixed ("dissolved") in the water-based solution. The silicone additive in the adhesive coating 120, 121 can improve the ease of cutting the label material, especially for on-demand linerless label printers. In addition, due to the improved cutting ease, the silicone additive in the adhesive coating 120, 121 can also reduce the amount of dust in the on-demand printer.

[0214] The water-based acrylic adhesive may or may not contain a silicone additive. If the adhesive layer contains silicone, the amount of the emulsified silicone additive in the adhesive layer may be equal to or greater than 1 weight percent, more preferably equal to or greater than 1.5 weight percent, and most preferably equal to or greater than 2 weight percent, calculated based on the dry weight of the adhesive coating. This gram weight can provide improved usability for the printer for the linerless label. In addition, the amount of the emulsified silicone additive may be equal to or less than 6 weight percent, more preferably equal to or less than 5 weight percent, and most preferably equal to or less than 4 weight percent, calculated based on the dry weight of the adhesive coating. Therefore, a low-cost solution with good adhesive properties can be obtained. The amount of the emulsified silicone additive in the adhesive layer may be, for example, in the range of 1 weight percent to 6 weight percent, or in the range of 2 weight percent to 4 weight percent, calculated based on the dry weight of the adhesive coating. If a silicone additive is used, the silicone additive may be added to the adhesive coating by adding a silicone emulsion to an acrylic water-based adhesive to form an adhesive coating 121. The silicone emulsion may change the properties of the adhesive, thereby greatly reducing the immediate adhesion to the metal blade that moves quickly during the printer / labeling process.

[0215] Pressure sensitive adhesive coating

[0216] During the manufacturing process of the linerless labels (webs) 100, 200, the adhesive coating 121 is dried to become the pressure-sensitive adhesive coating 120. Thus, the obtained linerless labels (webs) have the pressure-sensitive adhesive coating on their surfaces.

[0217] The labels 200 and linerless label webs 100 disclosed herein include a pressure sensitive adhesive coating 120 disposed on the second side 112 of the facestock 110. The pressure sensitive adhesive coating 120 may also be referred to as a self-adhesive coating.

[0218] The pressure sensitive adhesive coating 120 may include one or more water-based adhesive layers. If the PSA coating 120 includes more than one layer of adhesive, the adhesive coating may have improved smoothness. For example, if the first adhesive coating includes any pores, these pores may be filled with the second adhesive coating.

[0219] The PSAs may be permanent adhesives, or may be removable or repositionable, or even ultra-removable. The PSAs may have operating temperatures from ambient to cryogenic temperatures.

[0220] The pressure sensitive adhesive can be used for permanent linerless labels (rolls) or removable linerless labels (rolls). For removable linerless labels (rolls), the maximum tack value measured on glass according to FINAT test method FTM9 can be between 0.5N and 6N. The value can be a particularly suitable performance value for the pressure sensitive adhesive coating 120 of the direct thermal linerless labels (rolls) 100, 200 for fast food restaurants.

[0221] For permanent linerless labels (rolls) with acrylic adhesive, the maximum tack value measured on glass according to FINAT test method FTM9 may be equal to or greater than 2N, more preferably equal to or greater than 8N, and most preferably equal to or greater than 10N. The value may be a particularly suitable performance value for the pressure-sensitive adhesive coating 120 of direct thermal linerless labels (rolls) 100, 200 for industrial food or retail labeling. In addition, a value equal to or greater than 10N may be a particularly suitable performance value for the pressure-sensitive adhesive coating 120 of direct thermal linerless labels (rolls) 100, 200 for logistics and warehouses.

[0222] Water-based adhesives can provide better sustainability, involving fewer fossil raw materials and fewer volatiles during manufacturing and end-use. In addition, it may be easier to achieve good anchoring levels on the face material 110 disclosed herein with a water-based PSA, even without using any additional primer. In addition, the reduction in the amount of wetting agent can further improve the anchoring level. In one embodiment, the water-based pressure-sensitive adhesive 120 is directly in contact with the face material 110, such as in contact with the base layer of the face material, without any other coating between the PSA and the face material. This is particularly advantageous when no wetting agent is used or the amount of wetting agent is reduced.

[0223] Water-based adhesives according to this specification can be designed to obtain approval for direct or indirect food contact (food safe), which is a requirement for certain food-related labeling end-use areas.

[0224] The pressure sensitive adhesive according to the present specification can be applied at high coating speeds. Preferably, the adhesive is applied at a speed of 10-30 g / m 2The adhesive coating 120 may be free of plasticizers, and may be used on thermal papers (including economy grade) without problems of premature image development or image fading. Thus, the adhesive coating 120 may be free of plasticizers. This may have several advantages, as plasticizers may migrate into the product and cause problems. For example, food safety may be compromised.

[0225] Water-based acrylic PSAs may have many advantages over other types of PSAs. Water-based acrylic PSAs may be very environmentally friendly. In addition, the viscosity of the product may be improved due to the water-based acrylic adhesive. In addition, hot melt adhesives may accumulate more easily into the cutting machine than water-based acrylic adhesives and further increase the amount of dust in the machine. In addition, the peel value of acrylic-based adhesives is generally different from the peel value of hot melt-based adhesives.

[0226] Furthermore, acrylic adhesives may have a longer open time, so a linerless label (web) containing a water-based acrylic PSA may be removed after a few seconds or minutes if desired. In contrast, hot melt adhesives are generally not removable from surfaces, even if they are attached to the wrong surface. Therefore, the removability of a water-based acrylic adhesive may be better than that of a hot melt adhesive.

[0227] In addition, water-based acrylic adhesives, for example, having a wetting agent content of less than 0.3 wt. % in the adhesive coating 120, 121 can significantly reduce adhesive accumulation on rollers and other parts of the web guide of a linerless printer. Reducing the amount of free surfactant can protect linerless label printers, for example, because the adhesive can dry properly and thus adhere firmly to the surface material. The reduction in the wetting agent content can significantly reduce adhesive accumulation on the cutter blade of an on-demand printer, especially when the total amount of wetting agent is less than 0.3 wt. % (by dry weight), preferably equal to or less than 0.2 wt. % (by dry weight). In addition, dust accumulation on the cutter blade of an on-demand printer can be reduced.

[0228] The pressure-sensitive adhesive layer 120 may have a thickness of 10 to 30 g / m 2 Preferably, the coating weight of the adhesive layer 120 is equal to or less than 25 g / m 2 (dry coating weight), more preferably equal to or less than 21 g / m 2 Thus, an adhesive layer which is good enough to adhere a linerless label to the surface of an article can be obtained without being too expensive.

[0229] The pressure-sensitive adhesive coating 120 of the produced linerless label (roll) 100, 200 can have a thickness of at least 10 μm, preferably at least 12 μm or at least 14 μm, and most preferably equal to or greater than 16 μm. The coating weight of the PSA may need to be high enough to fill the pores of the surface. Therefore, the thickness of the PSA may depend on the surface to be coated. In addition, the amount of PSA needs to be high enough to adhere the label to the surface of the object. Advantageously, the thickness of the pressure-sensitive adhesive coating 120, 121 is equal to or less than 40 μm, preferably equal to or less than 30 μm, more preferably equal to or less than 25 μm, and most preferably equal to or less than 20 μm. The thickness of the adhesive layer can be, for example, between 12 and 25 microns. Therefore, an adhesive layer that is good enough to adhere a linerless label to the surface of an article can be obtained without being too expensive.

[0230] The linerless label adhesive coating according to the present specification can be used to minimize adhesive accumulation on the cutting blades, rollers and web paths in linerless printers. Therefore, the labels can be easily cut so that the adhesive does not adhere to the printer but remains on the face stock.

[0231] In one embodiment, reducing the amount of wetting agent to less than 0.3 weight percent, preferably equal to or less than 0.2 weight percent, can help prevent adhesive accumulation on the blades and rollers of the linerless label printer 240, and can also prevent or at least reduce some problems associated with dusting. The accumulation of adhesive and dust can lead to a shortened printer service cycle. Therefore, the printer service cycle can be improved. In addition, reducing the amount of wetting agent to less than 0.3 weight percent, preferably less than 0.2 weight percent, can improve the drying step, so that the adhesive coating according to the present specification can be used on thermal paper (including economical thermal paper) without the problem of premature image development or image fading.

[0232] Furthermore, it may be easier to achieve good anchoring on the substrate using water-based acrylic PSAs, even without the use of any additional primer in some cases.

[0233] Adhesive coating

[0234] The adhesive coating may be a continuous layer or a discontinuous layer.

[0235] Thus, the adhesive coating of the linerless label web may be a continuous adhesive layer, wherein the adhesive coating does not have any non-adhesive areas.

[0236] Alternatively, the adhesive coating of the linerless label web can be a discontinuous adhesive layer. The discontinuous adhesive layer can include adhesive areas and non-adhesive areas. Advantageously, the adhesive coating includes one or more adhesive areas and one or more non-adhesive areas.

[0237] The adhesive coating may include or consist of, for example, adhesive stripes and / or adhesive dots and / or other shaped adhesive areas.

[0238] The adhesive coating may include, for example, at least one of the following:

[0239] - straight continuous strips,

[0240] - consecutive bars that alternate in position, and

[0241] - Small patterned patches of glue.

[0242] Adhesive coatings 120, 121 may be, for example, Figure 6 and 7 The performance of the linerless label web 100 in an on-demand printer and the manual handling of the printed labels may be significantly improved by arranging the adhesive coatings 120, 121 in strips in the longitudinal direction (i.e., the first direction) of the label web 100. The adhesive strips may be in the form of straight continuous strips or in the form of alternating continuous strips.

[0243] Patterned coatings may be particularly advantageous when used with lower amounts of wetting agents (e.g., from less than 0.3 wt. % to 0 wt. %). Thus, bleed-through may be reduced or avoided while significantly improving print quality.

[0244] In one embodiment, the total coverage of the adhesive coating may be equal to or less than 90%, preferably equal to or less than 80%, calculated based on the total area of ​​the second side of the facestock. In addition, the total coverage of the pressure-sensitive adhesive coating may be equal to or greater than 10%, more preferably equal to or greater than 30%, and most preferably equal to or greater than 40%, calculated based on the total area of ​​the second side of the facestock. The total coverage of the adhesive coating according to the present specification can prevent adhesive seepage in the label roll and help keep the printer mechanism free of adhesive and dust.

[0245] For certain end uses, it may be necessary to leave a continuous non-adhesive area / strip 150 near the longitudinal edges of the label web 100. These non-adhesive areas / strips 150 near or on the longitudinal edges may correspond to a minimum of 10%, or a minimum of 20%, of the total width of the label web 100. The non-adhesive areas on the outer edges of the labels can prevent any seepage of adhesive in the label roll and help the printer mechanism to stay clean. The non-adhesive areas can be arranged symmetrically or almost symmetrically on the two longitudinal edges of the label web 100. Thus, it can simplify the movement of the label in the printer and / or help to be able to grip the label with fingers without contacting the sticky PSA. Whether the width of the non-adhesive area 150 is selected to be symmetrical or asymmetrical, the narrowest area on any longitudinal edge of the label web 100 may correspond to a minimum of 10% of the total width of the label web 100.

[0246] The width of the non-adhesive area / strip 150 near (or on) the longitudinal edge of the label web 100 may be in the range of 10 to 25 mm. This provides a good compromise between tack and manual handling and, most importantly, good long-term performance for compact, on-demand linerless printers. The non-adhesive area 150 on the outer edge of the label may also prevent any seepage of adhesive in the label roll and help keep the printer mechanism clean. It should be noted that in some embodiments, the non-adhesive area may contain a residual amount of adhesive coating.

[0247] Due to the use of a water-based acrylic adhesive coating according to the present specification, many advantages can be obtained. The adhesive coating can be easily cut mechanically, and less adhesive remains on the cutting blade or edge. Therefore, this can reduce the accumulation of the adhesive coating on the linerless label printer. The accumulation of the adhesive may cause more dust-related problems, because the dust will adhere to the printer together with the adhesive, thus resulting in a shortened printer service cycle. Therefore, problems related to dusting can also be reduced. In addition, the acrylic water-based adhesive can be an environmentally friendly adhesive and can be used for example for food materials. In addition, the acrylic water-based adhesive can have a longer open time, so if necessary, the linerless label (roll) containing the water-based acrylic PSA can be removed after a few seconds or minutes.

[0248] Release coating

[0249] The direct thermal linerless label (roll stock) may have a release coating 130 on the first side 111 of the face stock 110, ie, the top of the face stock 110, such as Figure 1a shown.

[0250] The linerless label web 100 having the pressure sensitive adhesive 120 on one side (bottom side) thereof and the release coating 130 on the other side (top side) thereof can be self-wound around itself without the tendency of adjacent layers of the label web 100 to interfere with each other. Thermal printing of the linerless labels (webs) 100, 200 can be performed through the release coating 130.

[0251] The release coating 130 can be directly on the direct thermal coating. Alternatively, the release coating can be on the top coating 116 of the facestock.

[0252] The release coating 130 can be a silicone-based or non-silicone-based release coating. Preferably, the release coating comprises or consists of a silicone-based release coating. Non-thermally curable release coatings are preferred, such as UV-curable silicones, because the curing of these layers does not heat the heat-sensitive material in the directly thermally printable facestock 110. Therefore, the release coating can be a UV-curable silicone, which has the advantage of being cured on top of the heat-sensitive facestock without heating.

[0253] The release coating 130 may include one or more layers of the release coating 130. Due to the release coating, the adhesion may be low enough so that the adhesive layer may be easily peeled off from the facestock material when the linerless label product roll is unrolled.

[0254] The release coating 130 can also provide a lower level of friction to the print head of the on-demand printer and / or other mechanical parts of the on-demand printer, thereby minimizing wear of these parts and minimizing the accumulation of adhesive residues. Therefore, in one example, the release layer 130 is used to reduce friction to the print head of the printer.

[0255] Linerless Labels

[0256] The label 200 (also referred to as a linerless label or label product) is a piece of material to be applied to an article. Articles of different shapes and materials can be used with the label 200. The label 200 containing a pressure-sensitive adhesive may be referred to as a pressure-sensitive adhesive label. A pressure-sensitive adhesive label is also referred to as a self-adhesive label.

[0257] The label 200 comprising a PSA can be adhered to most surfaces through the adhesive layer without the use of adjuvants (such as solvents) or the use of heat to strengthen the bond. In that case, the adhesive itself is pressure sensitive. Alternatively, the adhesive can be activatable so as to be pressure sensitive. When pressure is applied to the label at ambient temperature (e.g., between 15°C and 35°C), or for cold applications even at freezing temperatures below 0°C, the PSA forms a bond so that the label adheres to the item to be labeled. Examples of pressure-sensitive adhesives include water-based (aqueous) PSAs, solvent-based PSAs, and hot melt PSAs.

[0258] There are different kinds of labels on the market. The label can be a linerless label 200. The label can be a so-called shrink label, in which a heat-shrinkable polymeric facestock material is sewn and wrapped or sleeved onto the article to which the label is attached and shrinks around the article. Shrinkable labels can additionally contain some pressure-sensitive adhesive, or can be produced without a pressure-sensitive adhesive at all or even without a seam adhesive. In addition, the label can be an activatable linerless label, in which the adhesive can be activated to be pressure-sensitive, for example using additional heat, moisture or other activation means.

[0259] In the present application, the pressure sensitive adhesive is a water-based acrylic PSA. The PSA may be inherently pressure sensitive and need not be separately activated before being able to be dispensed onto the article to be labeled. Furthermore, the label may be a linerless label that adheres to the labeled article primarily by means of a pressure sensitive adhesive that at least partially covers the bottom side of the label. The linerless label (roll) of the present invention is of tape type, in other words, it can be wound on itself in the form of a roll without an additional release liner.

[0260] Labels can be used in a wide range of marking applications and end-use areas, such as marking food, home and personal care products, industrial products, pharmaceutical and health care products, beverage and wine bottles, other consumables, etc. Labels can provide information about the labeled product, such as product specifications. Information, such as the print on the label, can include human-readable information, such as images, logos, text and / or machine-readable information, such as barcodes, QR (Quick Response) codes.

[0261] An important subcategory of labels using directly thermally printable face stock materials are the so-called Variable Information Print (VIP) labels. These labels are at least partially printed before they are assigned to the items to be labeled and carry product-specific information on the individual items to be labeled. For example, VIP labels are used on retail weighing scales for fruits, vegetables, meat and other items sold by weight. Other labels that are printed individually as needed are different types of logistics labels - containing transport or product-specific information, bus or train tickets or other tickets, etc.

[0262] In one advantageous example, the linerless label consists of:

[0263] - Direct thermal surface material,

[0264] - a release coating on the first side 111 of the facestock, and

[0265] - A water based acrylic adhesive on the second side 112 of the facestock.

[0266] Linerless Label Rolls and Linerless Label Rolls

[0267] As discussed herein, linerless label web 100 refers to a structure including a continuous face stock 110 and an adhesive 120 disposed on one side of the face stock 110. The linerless label web 100 is typically processed by moving on a roll. Between processing stages, the label web 100 can be stored and shipped as a roll. From the linerless label web 100, individual labels 200 can be cut.

[0268] The width of the linerless label roll before being cut into customer rolls is usually several times the width of the final customer roll. Before it is cut into customer rolls, the width of the roll can be, for example, 1 to 3 meters. Afterwards, the wider roll width of the machine roll produced in the manufacturing process can be cut into a suitable customer roll width, for example a width of at least 10 mm, preferably 20 to 100 mm, or 40 to 100 mm. A fairly common width is between 40-60 mm.

[0269] The PPS10 roughness of the linerless label (web) may be in the range of 0.9 μm to 1.5 μm, preferably in the range of 0.9 μm to 1.3 μm, and most preferably in the range of 0.9 μm to 1.2 μm, which is determined from the top surface of the linerless label (web) according to ISO standard ISO 8791-4. For example, for using a facestock comprising paper, if the paper is too rough, the life of the print head may be excessively shortened.

[0270] The brightness of a linerless label (roll stock) can be higher than 85% (R457) when measured according to standard ISO2469. Therefore, a linerless label may look good. In addition, the high brightness may create contrast between symbols / letters. Therefore, if the lettering includes machine-readable letters, these letters can be easily read due to the brightness.

[0271] The opacity of the linerless label (web) may be higher than 80%, for example in the range of 80 to 90, when measured according to standard ISO 2471. Due to the opacity, the surface of the linerless label is not too transparent to be readable by machine or human eyes.

[0272] When measured according to standard ISO1924 / 2, the tensile strength of the linerless label (web) in the machine direction (i.e., the first direction) can be higher than 40N / 15mm, preferably higher than 45N / 15mm. Therefore, the dimensional stability of the linerless label (web) can be improved, which can have a positive impact on the manufacturing process and the printing process.

[0273] When measured according to standard ISO1924 / 2, the tensile strength of the linerless label (web) in the transverse direction (ie the second direction) can be higher than 28N / 15mm. Due to the strength, the dimensional stability of the linerless label can be improved, which affects the manufacturing process and the printing process.

[0274] The stiffness of the linerless label web can be in the range of 0.15 mNm to 0.30 mNm, which is determined in the machine direction MD of the linerless label web. The stiffness of the linerless label web can be measured according to ISO standard ISO 2494. Due to the stiffness range, the stiffness of the linerless label web will not be too low, which may cause the linerless label web to be too loose. Therefore, when used with a linerless label printer, the linerless label web may not cause too much trouble. In addition, due to the stiffness, the function of the cutter in the linerless printer and the ease of the cutting process therein can be improved, which can further reduce the dusting caused by the cutting process. Therefore, the combination of the stiffness, the intermediate layer and the acrylic adhesive can significantly reduce the accumulation of dust and adhesive on the cutting blade of the on-demand printer. In one embodiment, the stiffness of the linerless label web is in the range of 0.05 mNm to 0.20 mNm, which is determined in the transverse direction of the linerless label web.

[0275] The linerless labels (webs) 100, 200 may include at least one characteristic selected from the following group, preferably including all characteristics of the following group:

[0276] - The facestock has at least two layers, including a base layer and a direct thermal coating layer.

[0277] The facestock has a static sensitivity below 100° C., preferably below 95° C. but above 65° C. This ensures that thermal printing can be performed at relatively low energy levels and high speeds in thermal printers, while preventing the thermal paper from undergoing undesired activation during manufacturing and logistics.

[0278] - The coating weight of the adhesive layer 120 is 10-25 g / m 2 range (dry coating weight) to ensure both: good anchorage to thermal paper and good adhesion to different types of surfaces.

[0279] - The adhesive layer 120, 121 comprises an acrylic-based PSA. The wetting agent content of the adhesive layer may be less than 0.3% by weight. Such acrylic-based adhesives are more environmentally friendly and also provide a more suitable time build-up of final tack, helping to reduce contamination of the printer. Furthermore, such acrylic adhesives may have a longer open time, so that a linerless label (roll stock) comprising a water-based acrylic PSA may be removed after a few seconds or minutes if desired.

[0280] -Problems associated with exudation can be avoided or reduced.

[0281] -Problems associated with dust generation can be avoided or reduced.

[0282] - The adhesive layer 120, 121 has at least one adhesive area and may have at least one non-adhesive area. This ensures suitable label properties for each given end use and also helps to reduce contamination of the printer.

[0283] Linerless Label Printer

[0284] The general attributes of an on-demand compact printer are discussed to illustrate the requirements for label products. In the labeling process, a linerless label web 100 is printed by a printer having variable information, and a printer's cutter cutter cuts the label web 100 into appropriate label lengths for attachment to a product.

[0285] Labelling is done manually or automatically. A challenge for linerless label printers is that adhesive and dust accumulate on, for example, the cutter blade, resulting in a shortened printer service cycle. In the worst case, the adhesive is applied perfectly but the printer service cycle becomes too short to be used.

[0286] Figure 2 An example of a label printer 240 that can be used with a linerless label web 100 according to the present disclosure is shown. The label printer 240 may be referred to as a linerless label printer or a linerless printer. These terms refer to a printer that is arranged to print linerless labels. The label printer 240 may be referred to as an on-demand label printer to emphasize that the printer can be used to print labels individually as needed.

[0287] Commercial environments that use such on-demand label printers usually require very compact size and ease of use of those printer devices, with minimal need for maintenance. This is due to direct thermal printable linerless labels, which come with a thermal printable coating on their own. This differs from other non-direct thermal printing methods, which for example use separate thermal print ribbons that need to be loaded into the printer and replaced after respective use.

[0288] Furthermore, the number of individual components is chosen to have a minimum complexity. Preferably, the printer is also made to be very easy to use and with a minimum need for any settings and adjustments, for example.

[0289] The main functional components inside such a compact linerless label printer may include a mechanism for conveying the label web 100 through the printer, a thermal print head for printing individual labels onto the label web 100, and a mechanism for separating individual labels from the label web 100 and providing them for manual dispensing.

[0290] The mechanism for conveying the label web 100 from the unwinding of the web from the label roll through all the different parts of the printer and finally outputting the individual labels is usually a series of guide rollers and guide surfaces. In order to minimize both the size and complexity of such an apparatus, most of the rollers are free running and perhaps only one or only a few of them are motorized to pull the label web 100 forward during printing. These rollers or surfaces may not use any special friction reducing coatings to achieve a cost-effective structure. The pulling rollers may also include simple plastic or rubber rollers without any special coatings and only have a rough surface to ensure traction. Typically, a single printer model is also designed to accept label rolls of different widths, using simple adapters to center the rollers relative to the web track. This simple, effective and economical printer design places stringent requirements on the linerless label web 100 to ensure smooth customer service. Typical challenges involve the pressure sensitive label web 100 sticking to its various components inside the printer and preventing the smooth forward traction of the label web 100, and / or the accumulation of adhesive residues on the printer components over long periods of use causing the above problems and requiring the cleaning of the printer components.

[0291] Thermal printheads in compact printers of this type are typically selected to use lower print energies, i.e. less thermal energy can be transferred to the thermal layer of the linerless label web 100. This is preferred in applications where short run labels are to be printed in a simple and economical manner. Even if the printheads can be adjusted for higher energy levels or temperatures, it is best to run them at lower settings to maximize the life of the thermal head / printer. It may also be that if a higher activation is required for the linerless labels, the print speed needs to be reduced due to the performance limitations of the printer.

[0292] To print, the thermal linerless label web 100 may be drawn through the gap between the thermal head and the platen roller. The printer sends an electrical current to the heating element of the thermal head, which generates heat. The heat activates the heat-sensitive coloring layer of the thermal paper, which changes color to black where heated. This printing mechanism is known as a thermal printing system or direct thermal printing system. The heating elements are typically arranged in a row of closely spaced dots. The print energy (temperature and / or exposure time) can be adjusted, but such adjustments are often tedious, and preferably, a direct thermal printable label material should be selected to work without the need to fine-tune the printer's characteristics. If more print energy is required, this generally means that the print speed will be slowed, allowing the print temperature to affect the label for a longer time, thus transferring more energy to the web. Therefore, the performance of the print head has an impact on the selection of thermal facestock material for linerless label products to ensure good print quality even at lower print energy / heat levels and higher print speeds.

[0293] The mechanism provided on the output side of the printer for separating the individual printed labels from the continuous linerless label web 100 may include various types of motorized cutting blades or cutters, or in many cases simply a non-movable serrated cutting blade. The latter requires the user to manually tear the label web 100 against the serrated or toothed blade. In any case, the user needs to manually grab the printed labels output by the printer. When a non-motorized or non-assisted cutting mechanism is used, the user needs to grasp the label fairly firmly to manually separate it from the continuous web. This again places a demand on the label material so that it does not stick unnecessarily to the printer's cutting mechanism or the user's fingers, and the user needs to be able to easily position the label to its first labeling position.

[0294] Given the use of water-based acrylic adhesives in such printers, water-based acrylic adhesives have a lower initial tack, meaning that after unwrapping from the label roll, the PSA has a lower immediate tack when being guided through the printer compared to, for example, hot melt PSAs. This, together with the other characteristics of the label, helps to minimize the build-up of adhesive residues inside the printer. The final tack is only developed after the label has been dispensed and remains on the labeled item for a long time. The label may even be removable for a period of time (minutes) before a more permanent type of tack is established. The specific properties of the PSA naturally depend on the exact formulation of the adhesive and the surface material to be labeled.

[0295] The linerless label products disclosed herein are contemplated for end uses where the label life is short and manual handling is required, with repositionability and / or removability, and a lean sustainable and economical construction.

[0296] The linerless label according to the present description is particularly suitable for use with an on-demand linerless label printer. It can therefore reduce the problems caused by cut-through of said printer, i.e. the linerless label being cut by the blade of the linerless label printer. The novel solution prevents the adhesive coating 120 from accumulating on the blade of the linerless label printer, which would result in a shortened printer service cycle. With this novel solution, adhesive accumulation on the printer blade can be significantly reduced. Furthermore, adhesive accumulation on the platen roller and other parts of the linerless label printer can be significantly reduced.

[0297] Therefore, multiple requirements are placed on linerless label products in order to provide cost-effective, efficient and trouble-free operation in a user-friendly and sustainable manner.

[0298] Manufacturing method

[0299] A method of manufacturing a direct thermal linerless label web 100 including a facestock 110 may include the following steps:

[0300] - providing a face material 110 having a direct thermal printable coating,

[0301] - applying a coating of water-based acrylic adhesive 121, and

[0302] The adhesive coating 121 is thermally dried to form a pressure-sensitive adhesive coating 120 .

[0303] Figure 3-4 Some example methods are shown. The adhesive coating can be applied directly to the face material 110. In one embodiment, the adhesive layer can be effectively dried on the face material due to the reduced amount of wetting agent. Therefore, a separate carrier material may not be required. However, in one embodiment, the adhesive coating can be applied to the carrier material 611 and then the pressure sensitive adhesive coating 120 can be transferred from the carrier material to the face material 110.

[0304] The machine speed of the process may be, for example, 100-600 m / min.

[0305] according to Figure 4 The advantageous embodiment shown provides a method for manufacturing a linerless label web 100 including a direct thermal printable coating and a pressure sensitive adhesive. The method may include:

[0306] - providing a face material including a direct thermal printable coating (step 401),

[0307] - applying an adhesive coating 121 to the face material (step 402),

[0308] - optionally, providing the face material with alternating bonded and non-bonded areas (step 403),

[0309] - optionally, ensuring that the non-adhesive area 150 has a predetermined moisture level (step 404), and

[0310] - Thermally drying the adhesive coating 121 to form the pressure sensitive adhesive 120 (step 405).

[0311] Steps 402-404 of the method may be performed simultaneously or stepwise. Step 404 may also refer to maintaining or arranging the non-adhesive area 150 with moisture.

[0312] Example of adhesive coating steps

[0313] A coating unit 580 may be provided for applying the adhesive coating 121 to the face material 110 .

[0314] The adhesive coating 121 may be applied to the facestock 110 using a contact coating method, such as roller or curtain coating, foam coating, or spray coating. The adhesive coating 121 may be applied by direct gravure coating.

[0315] Alternatively, a coating unit 580 may be provided for applying the adhesive 121 to the carrier material. The coating step may include a contact coating method, such as roller coating or curtain coating, foam coating or spray coating.

[0316] As discussed, the adhesive coatings 120, 121 may or may not be patterned.

[0317] Patterned adhesive refers to the case where the adhesive covers less than 100% of the second side 112 of the surface of the face material. For example, the adhesive may cover 10% to 90% of the total area of ​​the face material 110. The adhesive can be arranged as strips, for example, along the longitudinal direction (i.e., the first direction) of the label web 100. Alternatively, the adhesive can be arranged in dots or other similar non-continuous areas, for example. Due to these solutions, contamination of the printer components by the adhesive can be reduced. In addition, from an economic and environmental point of view, it is advantageous to provide the label web 100, 200 with adhesive only on the label portion necessary to provide the required adhesion.

[0318] Thus, the adhesive layer may be a continuous layer. Alternatively, the adhesive layer may be a discontinuous layer having

[0319] 1) adhesive areas, such as adhesive dots and / or adhesive strips, and / or other types of adhesive areas, and

[0320] 2) No bonding area.

[0321] In one embodiment, the patterned adhesive is provided by first applying an adhesive coating 121 to 100% of the area of ​​the face material 110 by means of a coating unit 580. Afterwards, some of the adhesive coating 121 can be removed from the face material 110, thereby providing the face material 110 with alternating adhesive areas and non-adhesive areas 150 in the transverse direction of the face material 110. The adhesive removal is performed before the adhesive is dried in at least one drying unit 560. The adhesive removal can be performed by a unit 590. Thus, the area from which the adhesive is subsequently removed is wetted by the water contained in the adhesive. In this embodiment, the adhesive can be removed from the face material with a blade, such as a nylon blade. The blade has the effect that when removing the adhesive, the blade simultaneously provides pressure to the face material 110, thereby pushing moisture, i.e. the water contained in the adhesive, into the face material 110.

[0322] Figure 6A detailed view of a method and apparatus according to one embodiment is provided. The adhesive coating 121 is applied to 100% of the area of ​​the facestock 110 by the coating unit 580. Thereafter, some of the adhesive coating 121 may be removed from the facestock 110, thereby providing the facestock 110 with adhesive areas and non-adhesive areas 150 alternating in the transverse direction of the facestock 110. A unit 690 is provided to remove the adhesive coating 121, thereby providing the facestock 110 with adhesive strips, Figure 6 The enlarged dashed line is shown as a black block 121. Figure 6 The gray droplets of show the adhesive coating removed from the facestock 110. The adhesive removed from the facestock 110 can be collected and returned to the coating unit, as shown by the curved arrow between unit 690 and coating unit 580.

[0323] Alternatively, if a patterned adhesive is used, this can be provided by applying the adhesive coating 121 only partially to the face stock 110, thereby providing the face stock 110 with alternating bonded areas 121 and non-bonded areas 150 in the transverse direction of the face stock 110. This is shown in Figure 7 The bonding area, i.e. the strip of adhesive 121, is Figure 7 In order to prevent the thermal paper from activating when the adhesive dries, moisture can be provided to the non-adhesive area 150 of the face material 110 before the adhesive coating 121 dries to the pressure sensitive adhesive 120. The moisture can be provided by the unit 590, which in this case is, for example, a water sprayer. The water sprayer can be configured to spray water only onto the non-adhesive area 150, such as Figure 7 As indicated by the grey arrow in .

[0324] Thus, downstream of the coating unit 580, the apparatus may include:

[0325] -like Figure 6 The unit 590 for removing adhesive is shown, and / or

[0326] -like Figure 5 Humidification unit 690 is shown.

[0327] Ensure that the adhesive-free area 150 (e.g. Figure 7 Having a predetermined level of moisture in the adhesive (as shown in ) produces the following effect: the moisture will evaporate when the adhesive is dried, which evaporation prevents the temperature of the thermal paper from rising to a value that would cause the thermal paper to activate.

[0328] Drying Steps Example

[0329] The adhesive coating layer 121 may be dried in the at least one drying unit 560 .

[0330] During the drying process, the solids content of the adhesive coating increases. For direct thermal linerless labels, a correct drying process is probably the most important stage in achieving a high-performance product.

[0331] Adhesive haze is a test that determines how dry the adhesive layer is during the drying step. Well-dried direct thermal linerless labels can improve print performance and reduce the product's tendency to bleed.

[0332] Wetting agents can be added to optimize the surface tension of the adhesive. Wetting agents are particularly useful for improving spreading and penetration properties by reducing the surface tension of the adhesive. Wetting agents can also improve the mechanical stability of the coating. Thus, wetting agents can be added to improve mechanical stability so that it can be run on a high shear coater without generating grit. In addition, wetting agents can be used to achieve good leveling and flow properties to obtain a uniform film.

[0333] However, surprisingly, by minimizing the amount of wetting agent, even to 0% by weight, certain properties of direct thermal linerless labels can be significantly improved without affecting their runnability. For example, in the absence of a wetting agent, surfactants (particularly non-free surfactants) can be substantially uniformly dispersed in the formed adhesive, thereby improving the ease of the drying process and improving the quality of the formed linerless label web. For example, print quality can be significantly improved because the amount of free surfactant in a water-based acrylic adhesive is minimized.

[0334] Traditionally, direct thermal printable coatings of facestock have prevented the use of water-based adhesives for linerless labels. Thermal coatings are activated using heat. This can hinder the drying and / or heating of water-based adhesives on thermal paper, as heating can cause activation and darkening of the thermal paper or cause less severe but undesirable visual changes. Partially or fully activated brown or black thermal paper surfaces hinder the provision of high-quality visible printing thereon. Drying with lower temperatures and lower coating weights (i.e., less mass to be dried) is feasible, but will at least result in inefficiency and longer drying times and / or drying chamber or oven size (length) if the drying process parameters are not selected very carefully.

[0335] It should be noted that a certain coating thickness (coating weight) is required to obtain a water-based PSA as a uniform, defect-free layer on the facestock 110. Simply reducing the adhesive coating thickness below a certain value in an effort to promote drying at a lower temperature without increasing the drying time may result in unsatisfactory PSA quality and performance. Low coating weights may have a negative impact on the adhesion of the PSA on the labeling surface. In particular, if good adhesion is required while removability and / or repositionability are required, a higher PSA coating weight is required, which is particularly prominent in the case of water-based adhesives. Due to the solution according to the present specification, the adhesive coating is easier to completely dry than with traditional methods. Therefore, it is possible to achieve good PSA quality and performance, but prevent overheating of the heat-sensitive coating.

[0336] In one embodiment, reducing the wetting agent content helps to dry the adhesive coating in a controlled manner. By using a wetting agent amount of less than 0.3 wt %, preferably equal to or less than 0.2 wt %, or even as low as 0 wt %, water will not penetrate the coating as easily, and the ease of the drying process will be improved. Reducing the amount of free surfactant (such as wetting agent) can improve the drying process because the non-free surfactant can be more evenly dispersed in the formed adhesive layer, thereby avoiding the formation of isolated hydrophilic islands.

[0337] The apparatus may include at least one drying unit 560 for drying the adhesive coating 121. The drying unit may include at least one drying device 561. As a result of the drying, the pressure-sensitive adhesive 120 is obtained.

[0338] Adhesive 121 is dried to evaporate moisture from the water-based adhesive. Drying includes heating. Heating can be achieved by at least one of the following methods: infrared heating, microwave heating, or blowing. Preferably, adhesive 121 is dried by air drying or by air drying together with another type of drying. Another type of drying can include infrared energy and / or microwave energy. This ensures an appropriate preheating level of the adhesive to begin evaporating moisture from the adhesive layer, but prevents the top surface of the adhesive layer from forming a skin, which would prevent moisture from escaping deeper into the adhesive layer.

[0339] The drying stage of the machine including the drying unit may have a total length of 20 to 40 meters.

[0340] If the adhesive coating 121 is dried on the face stock 110, the temperature of the drying unit 560 may be between 60° C. and 90° C., or even higher than 100° C. and above 100° C. in some cases. Preferably, the drying temperature is at least 75° C. to ensure that the water-based adhesive becomes completely dry and provides maximum adhesive properties, such as adhesion. The face stock 110 including the adhesive coating 121 thereon may be arranged to travel through the drying unit 560. Thus, a linerless label web 100 is formed.

[0341] When exiting thermal drying, the temperature of the linerless label web 100 may be set 5 to 15°C lower than the activation temperature of the direct thermal printable coating. From an economic point of view, it may be preferred to set the temperature of the linerless label web 100 when exiting thermal drying as close as possible to the activation temperature of the direct thermal printable coating. In addition, for example, a low wetting agent content may also reduce the drying cost of the product.

[0342] After the adhesive has dried, the facestock 110 having the pressure sensitive adhesive thereon, ie, the linerless label web 100 , may be wound onto a roll 570 of linerless label web 100 .

[0343] According to one embodiment, the adhesive for linerless label webs is dried separately on a carrier material 611 before the adhesive is adhered to the face stock of the label. This avoids problems caused by heat sensitivity and enables the use of environmentally friendly water-based adhesives in such linerless labels. For such uses, even lower grade and more economical materials can be used because the adhesive is dried separately using a separate carrier material 611 (e.g., a metal tape or mesh).

[0344] If used, the carrier material 611 can be a tape, such as a silicone tape, a plastic tape, such as a nylon tape, or a metal tape, such as a steel tape. Alternatively, the carrier material 611 can be a batch of web materials. In this embodiment, the adhesive coating 121 is applied to the carrier material 611 in a first step 402. Then, in a second step 405, the adhesive coating 121 is dried / cured into a PSA 120 on the carrier material 611 by conveying the carrier through a dryer. In a third step 406, the dried water-based adhesive 120 is transferred to the face stock 110 of the label web 100. Finally, in a fourth step 407, the face stock with the pressure-sensitive adhesive is wound into a roll of linerless label web 100. In this embodiment, the drying / curing of the adhesive coating 121 occurs on a separate carrier material 611, so the heat-sensitive coating of the face stock is not exposed to temperatures exceeding the activation temperature of the heat-sensitive coating.

[0345] An example method of manufacturing a method using a support material is Figure 8 According to Figure 8In the embodiment schematically described in , the carrier material is arranged as an endless belt. In addition to the endless belt, the carrier material can also be arranged as a batch of reusable roll materials (not shown in the figure). The device including the carrier material can include an unwinder 612 for the face material 110. After drying, the adhesive 120 can be adhered to the face material 110. The unrolled face material 110 on the belt 611 and the dried water-based adhesive can be attached in the roller gap 660 to form the linerless label roll 100. The formed linerless label roll 100 can be wound into a roll 570. The device can also include a cooling cylinder 650. The cooling cylinder can be located before the position where the dried water-based adhesive layer is adhered to the face material 110.

[0346] The formed linerless label web 100 is arranged to be wound onto a linerless label web roll 570. The label web roll 570 can be stored and / or transported for later processing. The label web roll 570 can be further processed at other locations.

[0347] Due to the present invention, many advantages can be obtained. For example, at least the following advantages can be obtained:

[0348] 1) Water-based acrylic PSAs with a wetting agent content of less than 0.3 wt % (preferably equal to or less than 0.2 wt %) can reduce problems associated with bleed-through in on-demand printers.

[0349] 2) Reliable adhesion / tack of the adhesive can be obtained for all those different types of surfaces to which labels will be manually dispensed or applied, for example, during preparation of an order (e.g., in a kitchen) or when labeling various items for an order (e.g., cups, boxes, wraps, bags, or other packaging).

[0350] 3) Easy repositionability can be achieved so that the label is first applied to a first surface and then repositioned to another surface. For example, the label may first be used as a note in the kitchen and then affixed to a finished dish.

[0351] 4) Easy removability can be achieved, such as customer removal of a label used as a package closure or seal.

[0352] 5) Permanent final tack of the label can be achieved in applications where a lower initial tack is advantageous to reduce adhesive build-up in the printer, but a permanent type of tack of the label is preferred after dispensing onto the item to be labeled.

[0353] 6) Chemistry suitable for direct or indirect food contact can be obtained.

[0354] 7) Sustainability can be obtained to support the shorter life of such labels, i.e. their chemistry will not impose an undue burden on the environment or require any special waste management procedures compared to other wastes generated in the processes and activities in which such labels are used.

[0355] The invention relates in particular to linerless labels to be cut by a blade of a linerless label printer. With conventional linerless labels, dust and adhesive quickly begin to accumulate on the blade of a linerless label printer, which shortens the service life of the printer. Sometimes, linerless labels with perfect adhesives, except for the above-mentioned defects, may not be used at all, because the printer service life becomes too short. Due to the novel invention, dust and adhesive accumulation on the blade, platen roller and other parts of a linerless label printer can be significantly reduced. In addition, the print quality of aged direct thermal linerless labels can be greatly improved.

[0356] Experimental testing

[0357] Example 1

[0358] A water-based acrylic adhesive coating was prepared. Surfactants were used such that the total amount of wetting agent in the adhesive coating was between 0% and 1.3%, based on the total dry weight of the adhesive coating.

[0359] According to the test results, the wetting agent has a significant effect on the drying and printing quality. When the amount of the wetting agent does not exceed 0.3% by weight, the results are the best.

[0360] Surprisingly, if the amount of wetting agent exceeds 0.2 wt %, such as exceeds 0.3 wt %, and in particular if the amount exceeds 0.5 wt %, such as exceeds 0.6 wt % (based on the dry weight of the adhesive coating), the print quality will be reduced. Therefore, the more wetting agent, the worse the print quality. In addition, the wetting agent also reduces the drying efficiency of the adhesive coating.

[0361] According to the test results, the performance of direct thermal linerless labels with a wetting agent content of less than 0.6% by weight, especially equal to or less than 0.3% by weight, is significantly better than other similar products with a wetting agent content of more than 0.6% by weight.

[0362] Figures 10a to 10d Some test points are shown.

[0363] Fig.10a Shown are test spots printed with a wetting agent level of 0.2 wt% after 12 weeks of aging. Fig.10b Shown are test spots printed with a wetting agent level of 0.5 wt% after 12 weeks of aging. Fig.10c Shown are test spots printed with a wetting agent level of 1.3 wt% after 7 weeks of aging. Fig.10dShown are test spots printed with a wetting agent level of 1.3 wt% after 9 weeks of aging.

[0364] It can also be seen from the photo that the test point with a wetting agent dosage of 0.2 wt% ( Fig.10a ) is significantly better than the test point with a wetting agent dosage of 0.5 wt% ( Fig.10b ). These samples were printed on direct thermal linerless labels after aging for 12 weeks.

[0365] In addition, if the amount of wetting agent was 1.3 wt%, the print quality was very poor after only 7 weeks of aging ( Fig.10c -d).

[0366] Surprisingly, if the amount of wetting agent used is less than 0.3 wt. %, such as equal to or less than 0.2 wt. %, only very little change may occur within 12 weeks after the linerless label web is formed.

[0367] If the wetting agent dosage was 0.5 wt%, the quality would be significantly reduced after the 9th week.

[0368] Furthermore, if the amount of the wetting agent exceeds 1 wt %, such as 1.3 wt %, the print quality will quickly deteriorate.

[0369] The worst results occurred after 12 weeks. After 12 weeks, all test points ( Fig.10b The print quality of the test points with less than 0.3 wt % of wetting agent, such as 0.2 wt % ( Fig.10a ), the print quality was excellent even after 12 weeks.

[0370] Furthermore, wetting agents also have a significant effect on oozing out. By using less than 0.5 wt. %, such as equal to or less than 0.3 wt. %, and most preferably using adhesives without wetting agents, oozing out can be avoided or at least reduced. FIG. 11 a shows a test point containing a wetting agent, wherein the amount of wetting agent used is greater than 0.5 wt. %, and FIG. 11 b shows a test point without a wetting agent.

[0371] The difference in print quality is clear. The test results further confirm the good functionality of the new linerless label stock with no or reduced wetting agent. In addition, there is a clear difference in the bleed tendency between the standard material with wetting agent and the new product with reduced wetting agent.

[0372] Example 2

[0373] An adhesive coating containing a small amount of a wetting agent and a silicone additive is formed by mixing a silicone emulsion with an acrylic water-based adhesive. The adhesive coating comprises an emulsified silicone additive and a water-based acrylic adhesive. The total amount of the silicone additive in the adhesive coating varies between 0% and 6% based on the total dry weight of the adhesive coating.

[0374] According to the test results, 1 wt% of the emulsified silicone additive in the adhesive improves the adhesive properties. The best results were found when the amount of the emulsified silicone additive exceeded 2 wt%. For cost reasons, the silicone content was kept between 1 wt% and 6 wt%, i.e. the maximum amount of silicone was 6 wt%.

[0375] Linerless labels containing emulsified silicone additives performed significantly better than their counterparts without the emulsified silicone additives.

[0376] The amount of cutting depends on the amount of silicone additive, so that best results are obtained when the amount of silicone additive is between 2 wt % and 6 wt %, calculated on the total dry weight of the adhesive coating.

[0377] Therefore, the adhesive coating with reduced wetting agent usage and added silicone additive is suitable for use with acrylic water-based adhesives. In addition, labels containing adhesive coatings containing silicone additives are firmly attached to the surface of the labeled product every time.

[0378] The invention is not limited to the examples presented in the drawings and the above description but may be modified within the scope of the appended claims.

Claims

1. A method for manufacturing a direct thermal linerless label roll (100), the direct thermal linerless label roll (100) comprising: - a face material (110) having a first side (111) and a second side (112), and - a water-based acrylic pressure sensitive adhesive coating (120) on the second side of the facestock, Surface materials (110) include: - a base layer (113), and - a directly thermally printable coating (115), Wherein, the method comprises: - Provide surface material (110), - applying a water-based acrylic adhesive coating (121) comprising free and / or non-free surfactants, in, - Based on the total dry weight of the water-based acrylic adhesive coating, excluding the surfactant polymerizing agent, The total amount of surfactant is 0 wt% to less than 0.6 wt%, as well as - thermally drying the water-based acrylic adhesive coating (121) to form a water-based acrylic pressure-sensitive adhesive coating (120), in, Applying a water-based acrylic adhesive coating (121) directly to the face material, or A water-based acrylic adhesive coating (121) is first applied to the carrier material and then transferred to the face material. Thereby a direct thermal linerless label web is obtained comprising a water-based acrylic pressure sensitive adhesive coating (120) on the second side of the facestock.

2. A direct thermal linerless label web (100) obtainable by the method according to claim 1.

3. A direct thermal linerless label roll (100), comprising: A) A face material (110) having a first side (111) and a second side (112), the face material (110) comprising: - a base layer (113), and - a directly thermally printable coating (115), as well as B) a water-based acrylic pressure-sensitive adhesive coating (120) on the second side of the facestock, the water-based acrylic pressure-sensitive adhesive coating (120) being obtained from a water-based acrylic adhesive coating comprising free and / or non-free surfactants, Wherein, based on the total dry weight of the water-based acrylic adhesive coating, excluding the surfactant polymerizing agent, the total amount of the surfactant is 0 wt % to less than 0.6 wt %.

4. A method or direct thermal linerless label web as claimed in any preceding claim wherein: Based on the total dry weight of the water-based acrylic adhesive coating, excluding the surface-active polymerizing agent, the amount of free surfactant is equal to or less than 0.3 wt %, preferably in the range of 0 wt % to 0.2 wt %.

5. The method or direct thermal linerless label web as claimed in claim 4, wherein: Based on the total dry weight of the water-based acrylic adhesive coating, excluding the surface active polymerizing agent, the amount of free surfactant is equal to or less than 0.1 wt %, preferably in the range of 0 wt % to 0.1 wt %.

6. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The amount of the wetting agent in the surfactant is equal to or less than 0.3 wt %, such as in the range of 0.01 wt % to 0.2 wt %, based on the total dry weight of the water-based acrylic adhesive coating (121).

7. The method or direct thermal linerless label web of claim 6, wherein: The amount of the wetting agent is equal to or less than 0.1 wt %, such as in the range of 0 wt % to 0.1 wt %, calculated based on the total dry weight of the water-based acrylic adhesive coating ( 121 ).

8. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The surfactant includes non-free surfactant.

9. The method or direct thermal linerless label web of claim 8, wherein: The amount of non-free surfactant including the surface active polymerizing agent is at least 0.8 wt % (on a dry weight basis) of the water-based acrylic adhesive coating.

10. The method or direct thermal linerless label web as claimed in claim 8 or 9, wherein: The amount of the non-free surfactant is at least 10% greater than the amount of the free surfactant, based on the total dry weight of the water-based acrylic adhesive coating, including the surface active polymerizing agent.

11. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The total amount of free surfactant including the surface active polymerizing agent is equal to or less than 2 wt% (on a dry weight basis) determined based on the water-based acrylic adhesive coating.

12. The method or direct thermal linerless label web of claim 11, wherein: The total amount of free surfactant including the surface active polymerizing agent determined on the water-based acrylic adhesive coating is equal to or less than 1.5 wt % (on a dry weight basis), preferably equal to or less than 1.0 wt % (on a dry weight basis).

13. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The water-based acrylic adhesive coating (121) is a water-based polymer emulsion derived from components including acrylate monomers, vinyl aromatic compounds and at least one surface-active polymerizing agent.

14. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The surface active polymerizing agent includes at least one reactive surface active polymerizing agent.

15. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The water-based acrylic adhesive coating is a non-tackified water-based acrylic adhesive coating.

16. The method or direct thermal linerless label web of any one of claims 1 to 14, wherein: The water-based acrylic adhesive coating contains a tackifier, The amount of the tackifier is preferably greater than 0 wt % and less than 35 wt % based on the total dry weight of the water-based acrylic adhesive coating (121).

17. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The total coverage of the adhesive coating is in the range of 10% to 90% based on the total area of ​​the second side (112) of the face material.

18. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The coating weight of the water-based acrylic pressure-sensitive adhesive coating (120) is 10 g / m 2 Up to 25g / m 2 (by dry weight).

19. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The pressure sensitive adhesive coating comprises an emulsified silicone additive in an amount ranging from 1 wt % to 6 wt %, preferably ranging from 2 wt % to 4 wt %, based on the total dry weight of the adhesive coating (121).

20. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The total mineral content of the direct thermal linerless label web is in the range of 0 to 20 weight percent, calculated based on the total dry weight of the direct thermal linerless label web.

21. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The weight of the coating that can be directly printed by thermal printing is 1g / m 2 Up to 5g / m 2 within the range.

22. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The facestock further comprises a topcoat layer on the direct thermal printable coating, wherein the topcoat layer preferably has a 2 Up to 3g / m 2 Weight within the range.

23. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The surface material further comprises an intermediate layer (114) arranged between the base layer (113) and the coating layer (115) capable of direct thermal printing, wherein the intermediate layer has a gram weight of 0.9 g / m 2 Up to 7g / m 2 In the range of 1g / m 2 Up to 5g / m 2 within the range.

24. A method or direct thermal linerless label web as claimed in any preceding claim wherein: The direct thermal linerless label web also includes a release layer located on top of the facestock.

25. The method or direct thermal linerless label web of claim 24, wherein: The release layer on top of the facestock comprises a non-thermosetting release coating, such as UV-curable silicone.

26. Use of a direct thermal linerless label web as claimed in any one of the preceding claims 2 to 25 in print on demand.

Images