Heat-sensitive recording material

Abstract

The present invention relates to a heat-sensitive recording material comprising: a carrier substrate having a first surface and a second surface opposite the first surface; the pigment layer is arranged on the first surface or the second surface of the bearing substrate, and the pigment layer contains at least one coloring substance; and a heat-sensitive layer disposed on the colorant layer and at least partially covering the colorant layer wherein the heat-sensitive layer is configured to become translucent by local heating so that the colorant layer below becomes visible. The heat-sensitive layer contains a first material comprising at least one fatty acid and / or at least one fatty amide. The heat-sensitive layer contains a second material comprising at least one fatty acid metal salt. The first material has a first melting temperature TS1, and the second material has a second melting temperature TS2. The first melting temperature TS1 is lower than the second melting temperature TS2.

Description

Technical Field

[0001] According to a first aspect, the present invention relates to a thermal recording material, comprising: a substrate having a first surface and a second surface opposite to the first surface; a colorant layer disposed on the first or second surface of the substrate, the colorant layer containing at least one coloring substance; and a thermal layer disposed on the colorant layer and at least partially covering the colorant layer, the thermal layer being configured to become translucent by local heating, thereby making the underlying colorant layer visible.

[0002] The heat-sensitive layer contains a first material, which contains at least one fatty acid and / or at least one fatty acid amide, and the heat-sensitive layer also contains a second material, which contains at least one fatty acid metal salt. The first material has a first melting temperature T. S1 The second material has a second melting temperature T S2 First melting temperature T S1 Below the second melting temperature T S2 .

[0003] According to a second aspect, the present invention relates to a method for manufacturing a thermal recording material, comprising the following steps: providing a substrate having a first side and a second side opposite to the first side; applying a pigment layer suspension to the first or second side of the substrate, the pigment layer suspension containing at least one coloring substance; drying the pigment layer suspension to obtain a pigment layer disposed on the first or second side of the substrate; and applying a coating suspension to the pigment layer, the coating suspension containing a first material, the first material containing at least one fatty acid and / or at least one fatty amide, and the coating suspension containing a second material, the second material containing at least one fatty acid metal salt, the first material having a first melting temperature T. S1 The second material has a second melting temperature T S2 First melting temperature T S1 Below the second melting temperature T S2 ; and drying the coating suspension to obtain a heat-sensitive layer disposed on the pigment layer.

[0004] According to a third aspect, the present invention relates to a thermal recording material that can be manufactured by the method of the second aspect.

[0005] According to a fourth aspect, the present invention relates to the use of the thermal recording material of the first or third aspect as receipt paper rolls, adhesive label rolls, ticket rolls, or printing paper for mechanical printers or writing pens. Background Technology

[0006] Thermal recording materials, also known as thermal paper, are used in various applications such as retail receipts.

[0007] In the prior art, thermal recording materials for direct thermal printing, also known as thermal labels, are known. Specifically for direct thermal printing, thermal recording materials can be divided into two categories.

[0008] The first type of thermal recording material contains a thermal recording material and forms a printed image through a localized thermo-induced chemical reaction within a pigment layer. This chemical reaction is, for example, a reaction between a colorant such as a leuco dye and a color developer such as bisphenol A or a non-phenol substitute. Typically, the pigment layer further contains a thermosensitive solvent, which may include, for example, long-chain fatty alcohols, amides, esters, or carboxylic acids, and melts upon heating, thereby achieving a color-forming reaction between the colorant and the color developer. Furthermore, the pigment layer may contain a thermosensitive sensitizer.

[0009] The second type of thermal recording material contains thermal recording material and forms a printed image by means such as localized heating using a direct thermal printer, making the thermal top layer translucent, thereby revealing the underlying pigment layer. This technology is described and interpreted differently in the prior art, and such thermal recording materials are obtained through various thermal top layer compositions, porosities, and materials optimized for direct thermal printing. This will be further explained in detail below.

[0010] In the second type of thermal recording material, the thermal top layer should cover the underlying pigment layer as much as possible. This is mainly achieved through light scattering (especially light scattering achieved through scattering particles) and light absorption. Compared with the underlying pigment layer, the contrast of the thermal top layer should be as high as possible to produce printed images that can be read by the human eye and / or machines such as scanners, such as black / white or yellow / blue images.

[0011] In the second type of thermal recording material, the thermal top layer should have sufficiently high thermal sensitivity to become translucent when locally heated, especially by existing direct thermal printers. Ideally, both the first and second types of recording materials should be usable with existing direct thermal printers, while printer settings (especially printhead temperature and printer speed) should be comparable.

[0012] This invention relates to the aforementioned second type of thermal recording material.

[0013] GB997289 describes a recording material for direct thermal printing, the recording material comprising a carrier material, an ink layer and a thermal top layer, wherein the thermal top layer becomes translucent by local heating of the direct thermal printer, thereby allowing the underlying ink layer to be seen and forming a printed image.

[0014] US6043193 describes a thermal recording material comprising a substrate and an opaque recording layer applied to the substrate, the opaque recording layer containing hollow beads dispersed in a hydrophilic binder, wherein the beads have an average diameter of 0.2µm to 1.5µm and a void volume of 40% to 90%.

[0015] US6133342 describes a thermal recording material containing a colorant and an opaque polymer material whose opacity changes in a substantially irreversible manner when heated, thereby making the colorant more visible.

[0016] WO2015 / 119964A1 discloses a multilayer aligned film for printing, comprising an extruded outer layer, an extruded inner pigment layer, and an extruded image reproduction layer located between the outer layer and the inner pigment layer. The image reproduction layer includes a void layer with a collapsible layer structure, wherein a plurality of voids are dispersed within the void layer, formed by aligning multiple layers. The extruded image reproduction layer and the collapsible layer structure are in a substantially opaque, non-collapsed state to obscure the underlying pigment layer.

[0017] US2010 / 245524A describes a thermal recording material comprising: a thermal substrate containing an opaque polymer, the thermal substrate being sensitive to heating and pressure, and the opaque polymer becoming transparent when heated to a predetermined temperature and subjected to predetermined pressure; and a colorant disposed relative to the substrate in such a way that it is obscured by the opaque polymer before the application of predetermined heat and pressure, and becomes visible after the application.

[0018] US2011 / 172094A discloses a recording material comprising: a support for which a surface is impregnated with a colorant or coating containing a pigment or dye; and a layer containing core-shell structured polymer particles, the core-shell structure being a hollow structure that scatters visible light when dry, wherein each particle has a first polymer inner shell with a Tg of 40°C to 130°C and a second polymer outer shell with a Tg of -55°C to 50°C, the Tg of the polymer outer shell being lower than that of the polymer inner shell.

[0019] US2011 / 251060A describes a thermal recording material composed of a dye and a flexible support substrate. The thermal recording material further includes a thermal layer disposed on the dye, comprising a binder, various organic hollow spherical pigments, and a thermal solvent; the thermal layer may include a barrier layer and a protective layer.

[0020] WO2012 / 145456A1 describes a thermal recording material optimized for existing direct thermal printing, the thermal recording material comprising: a substrate having a planar structure and containing at least one colored surface; and a layer disposed on the substrate containing core-shell structured polymer particles, the polymer particles having a first polymer shell with a calculated Tg value of 40°C to 130°C and an opacity reducer with a melting point of 45°C to 200°C, and containing at least one void after drying, the opacity reducer comprising 1% to 90% by weight of the polymer particles.

[0021] WO2013 / 152287A1 describes a thermal recording material having a bilayer uniaxially oriented film, comprising: a first layer containing an opaque polymer based on β-nucleated polypropylene; and a second layer containing a dark pigment.

[0022] US2015 / 049152A describes a thermal recording material comprising a thermal layer disposed on a colored solid substrate. The thermal layer contains single-phase scattering polymer particles, each particle having a center and a surface. The refractive index of the center differs from that of the surface, and each particle has a continuous refractive index gradient. The thermal layer further contains heat-deformable particles and a binder.

[0023] EP2993054A1 describes a roll-shaped thermal recording material comprising at least one first layer and a second layer at least partially covering the first layer. The first layer has a concentrated pigment at least facing the second layer, and the second layer has a hollow pigment that can be melted by localized heat treatment to form a written image. The thermal recording material is characterized in that, in addition to the hollow pigment, the second layer further contains one or more fatty acids and one or more thermal sensitizers.

[0024] EP1778499A1 discloses a recording material that differs from EP2993055A1 only in the type of coloring of the second layer. The written content becomes visible under ultraviolet light, not visible light. The protective layer helps improve printability and environmental resistance, particularly resistance to plasticizers, oils, greases, and water splashes.

[0025] EP2993055A1 describes a roll-shaped thermal recording material comprising at least one first layer and a second layer at least partially covering the first layer. The first layer has a concentrated pigment at least facing the second layer, and the second layer has a hollow pigment that can be melted by localized heat treatment to form a written image. The thermal recording material is characterized by including at least one protective layer that at least partially covers the second layer.

[0026] According to the description in this article, the physical process of generating printed images can be divided into two different methods.

[0027] In the first method, a printed image is formed by locally heating a thermal top layer with a direct thermal printer to make it translucent, wherein the top layer contains fusible hollow pigment. In the second method, a printed image is formed by locally heating a thermal top layer with a direct thermal printer to make it translucent, wherein the top layer comprises softenable or soluble hollow pigment.

[0028] According to the article, a gray recording material that meets the requirements can be obtained. This recording material has the following characteristics: whiteness of 56% with UV component and whiteness of 52% without UV component; optical density of 0.33 ODU before printing and optical density of 1.22 ODU after printing; and contrast ratio of 0.89 ODU (thermal printhead: 300 dpi, 16 mJ / mm). 2 ).

[0029] The relevant divisional application EP3517309A1 describes the characteristics of the top layer in particular detail. The top layer contains hollow sphere pigments that can be manipulated to form written images and at least one fatty acid, which is stearic acid and / or palmitic acid, or stearamide and / or methylstearamide.

[0030] US2017 / 337851A discloses a recording material comprising a peel-off backing layer, an optional adhesive layer, a label base layer, a heat-insulating layer disposed on the label base layer, and an ink layer disposed on the heat-insulating layer. The ink layer contains at least one colorant and includes a cover layer disposed on the printed ink layer and a top coating layer disposed on the cover layer. The cover layer has an acrylic-based composition containing light-scattering particles that make the cover layer opaque in a first state and transparent in a second state. The printhead is at least heated or pressurized to change the cover layer from the first state to the second state, thereby making the at least one colorant in the ink layer visible through the cover layer.

[0031] WO2019 / 183471A1 discloses a recording medium including a substrate, the substrate being contained at first scattering particles having a melting point, and including a first solid light scattering layer. The first solid light scattering layer is disposed as close as possible to a plurality of second solid scattering particles. The second melting point of the second solid scattering particles is lower than the first melting point of the second solid scattering particles. The first light scattering layer is a porous layer, and the second scattering particles are disposed between the first solid scattering particles during the solid melting process to fill the spaces between the recording medium.

[0032] WO2019 / 219391A1 describes a thermal recording material comprising: a substrate with at least one side being black or colored; and a thermally responsive layer disposed on the black or colored side of the substrate. The thermally responsive layer contains at least one cellulose ester nanoparticle.

[0033] WO2021 / 055719A1 describes a thermosensitive or pressure-sensitive recording material, comprising an opaque material layer and a pigment disposed on a first surface of the opaque material layer, wherein the opaque material layer covers the pigment. The opaque material, in its opaque state, contains a plurality of opaque polymer particles having irregular and / or unusual shapes, with voids formed between these particles, and having different shapes and / or sizes. Furthermore, the opaque material is configured to transition from an opaque state to a transparent state upon application of sufficiently high temperature and / or pressure, thereby exposing the pigment beneath the opaque material.

[0034] WO2021 / 062230A1 discloses a recording medium including a substrate; a first light scattering layer supported by the substrate and containing first scattering particles having a first melting point; and a plurality of second scattering particles located near the first light scattering layer, the second scattering particles having a second melting point lower than the first melting point. The first light scattering layer is a porous layer, and the second scattering particles are configured to fill the spaces between the first scattering particles upon melting. The first scattering particles include porous particles.

[0035] EP3957489A1 discloses a thermal recording material, including a substrate and a fused layer disposed on one side of the substrate or paper substrate, or both thereof.

[0036] All existing thermal recording materials of this kind require improvement, particularly in their functionality, sustainability, and cost-effective manufacturing. In particular, the first type of thermal recording materials mentioned above must use chromogenic agents. These chromogenic agents are often harmful to health and efforts need to be made to eliminate them.

[0037] Specifically, for thermal recording materials, it is particularly necessary to maintain or further enhance their protection against external influences such as pressure, friction, humidity, liquids, and moisture. Furthermore, for existing thermal recording materials, their functionality, properties, and cost-effective manufacturing performance should be maintained (ideally even improved) in the following aspects: sensitivity or optical density; water resistance / abrasion resistance; and the deposition characteristics of thermal recording materials at the thermal printhead of a thermal printer. Since such deposition can negatively impact the long-term operation of thermal printers (printing volumes exceeding 10,000 meters), it should be eliminated or its occurrence minimized where possible.

[0038] Furthermore, existing Class II thermal recording materials often contain organic pigments, especially hollow sphere pigments. These pigments, acting as microplastics or nanoplastics, often lead to serious environmental pollution. Therefore, the use of such organic pigments, especially hollow sphere pigments, should be avoided in thermal recording materials. Summary of the Invention

[0039] definition

[0040] One object of the present invention is to provide a thermal recording material having balanced application-related properties and achieving a practical printing density (optical density) comparable to or better than that of existing thermal recording materials, while simultaneously ensuring high durability of the printed image, especially when the surface of the thermal recording material comes into contact with hydrophobic substances such as plasticizers, oils, and greases from the film material.

[0041] Another object of the present invention is to provide a thermal recording material that can maintain the required functional characteristics (especially high relative print contrast) relevant to the application, even when stored for a longer period of time and / or under extreme climatic conditions (high temperature and / or high humidity) after printing (image retention performance) or before printing (rewrite / write performance).

[0042] Another objective of this invention is to improve the deposition characteristics of thermal recording materials at the thermal printhead of a thermal printer.

[0043] A recent surprising discovery suggests that the aforementioned shortcomings of the prior art can be addressed by using at least one fatty acid and / or at least one fatty amide as a component in the thermosensitive layer of the thermosensitive recording material, which has a lower melting point. S1 The first material, and at least one fatty acid metal salt is used as the T with a high melting point. S2 The second material.

[0044] The corresponding fatty acids, fatty amides, and fatty acid metal salts are harmless to health and biodegradable, thus avoiding the generation of microplastic waste during the degradation of thermal recording materials. This improves the environmental compatibility of the corresponding thermal recording materials.

[0045] The corresponding fatty acids, fatty amides, and fatty acid metal salts used in this thermal recording material serve as lubricants. Since these lubricants also function as sensitizers and release agents, this significantly enhances the material's advantages. Thus, the present invention achieves the aforementioned effects without using different categories of substances.

[0046] Furthermore, the fatty acids, fatty amides, and fatty acid metal salts used in this thermal recording material ensure that the thermal recording material produces favorable deposition characteristics at the thermal printhead of the thermal printer, and ensure that no deposition occurs that would negatively affect the long-term operation of the thermal printer (printing volume exceeding 10,000 meters), or that only a small amount of such deposition occurs.

[0047] The present invention also aims to optimize the thermal printing properties of thermal recording materials, particularly by eliminating the use of organic pigments, especially hollow sphere pigments, so that the thermal recording materials do not generate harmful microplastic waste during degradation, thereby improving the environmental compatibility of thermal recording materials.

[0048] Thermal recording materials

[0049] According to a first aspect, the aforementioned objective is achieved by a thermal recording material comprising: a substrate having a first surface and a second surface opposite to the first surface; a colorant layer disposed on the first or second surface of the substrate, the colorant layer containing at least one coloring substance; and a thermally sensitive layer disposed on and at least partially covering the colorant layer, the thermally sensitive layer being configured to become translucent by localized heating, thereby making the underlying colorant layer visible. The thermally sensitive layer contains a first material containing at least one fatty acid and / or at least one fatty acid amide. The thermally sensitive layer contains a second material containing at least one fatty acid metal salt. The first material has a first melting temperature T. S1 The second material has a second melting temperature T S2 First melting temperature T S1 Below the second melting temperature T S2 .

[0050] By combining fatty acids or fatty amides as the first material with fatty acid metal salts as the second material, the use of organic pigments, especially hollow sphere pigments, in the thermal layer can be avoided. This prevents or reduces the release of microplastics during the degradation of the thermal recording material, thus giving it high environmental compatibility.

[0051] Specifically, this thermal recording material (especially the thermal layer) contains no organic pigments, and especially no hollow sphere pigments.

[0052] Furthermore, compared to existing recording materials, the corresponding thermal recording material of the present invention achieves comparable, and in particular superior, image quality after printing. Image quality is characterized by the following parameters: whiteness conforming to ISO 2470-1:1:2016-09 standard; contrast between printed and unprinted areas; optical density and / or image retention performance after storage of the thermal recording material.

[0053] This thermal recording material has a colorant layer containing coloring substances.

[0054] The coloring substance gives the pigment layer a color that is black, red, green, or blue, or any color that can be obtained by mixing red, green, and blue. The coloring substance, in particular, gives the pigment layer a color that is not white.

[0055] The side of the pigment layer facing the heat-sensitive layer is particularly black, red, green, or blue, or any color obtainable by mixing red, green, and blue. The coloring substance, in particular, gives the pigment layer a color other than white.

[0056] The thermal recording material has a thermal layer that at least partially covers the pigment layer, so that the color of the pigment layer or the color of the side of the pigment layer facing the thermal layer is not visible under normal conditions because the thermal layer above is opaque. Only when the thermal layer becomes translucent due to localized heating can the pigment layer or the side of the pigment layer facing the thermal layer be seen, thus forming a printed image on the thermal recording material.

[0057] By using fatty acid metal salts in the heat-sensitive layer as having a second melting temperature T S2 The second material can in particular ensure improved interlayer adhesion and enhanced wettability of polar components, thereby avoiding loss of opacity due to undesirable heating methods such as environmental influences or sunlight exposure, while simultaneously achieving favorable deposition characteristics.

[0058] The heat-sensitive layer contains no chemical colorants or chemical colorants.

[0059] The heat-sensitive layer contains no dyes, especially no coloring and / or black dyes.

[0060] According to one embodiment, the first melting temperature T S1 Compared to the second melting temperature T S2 The temperature should be at least 1°C, preferably at least 2°C, more preferably at least 5°C, and most preferably at least 10°C.

[0061] Specifically, the first material contains a first melting temperature T S1 The second material is stearamide at 108°C, and contains a second melting temperature T. S2 Calcium stearate at 125°C and / or second melting temperature T S2 Zinc stearate at 124°C.

[0062] According to one embodiment, the at least one fatty acid of the first material is selected from the group consisting of betaine, stearic acid and / or palmitic acid, and / or the at least one fatty amide of the first material is selected from the group consisting of behenamide, mustardamide, stearamide, oleamide, palmitamide and / or lauramide, preferably stearamide.

[0063] Behenic acid has a melting point of 80°C, and behenic acid from Croda is particularly used (Behenic acid 86 / 89.9%-BE-(HU), CAS No.: 112-85-6). Stearic acid has a melting point of 72°C, and stearic acid from Sigma Aldrich is particularly used (CAS No.: 57-11-4). Palmitic acid has a melting point of 65°C, and palmitic acid from Carl Roth is particularly used (palmitic acid ≥98% purity, CAS No.: 57-10-3). Behenamide has a melting point of 112°C, and behenamide from TCI Europe NV is particularly used (behenamide, CAS No.: 3061-75-4). Mustardamide has a melting point of 83°C, and mustardamide from TCI Europe NV is particularly used (mustardamide, CAS No.: 112-84-5). Stearamides, in particular, have a melting point of 108°C, and stearamide from TCI Europe NV (stearamide, CAS No.: 124-26-5) is used in particular. Oleamides, in particular, have a melting point of 74°C, and oleamide from TCI Europe NV (oleamide, CAS No.: 301-02-0) is used in particular. Palmitamides, in particular, have a melting point of 108°C, and palmitamide from Cayman Chemical Company (hexadecamide, CAS No.: 629-54-9) is used in particular. Lauramides, in particular, have a melting point of 104°C, and lauramide from TCI Europe NV (lauramide, CAS No.: 1120-16-7) is used in particular.

[0064] The melting points were determined, in particular, by differential scanning calorimetry (DSC) using equipment from Netzsch-Gerätebau GmbH (Selb). The samples were heated in an aluminum crucible placed in a nitrogen atmosphere. The crucible had a cold-welded perforated lid. The heating temperature was 25°C to 200°C, and the heating rate was 10 K / min. The melting points were determined based on the peak and trough points or endothermic peaks of the corresponding melting processes.

[0065] According to one embodiment, the content of the first material in the thermosensitive layer is 1% to 90% by weight of the total dry weight of the thermosensitive layer, preferably 30% to 80% by weight.

[0066] According to one embodiment, the at least one fatty acid metal salt of the second material is selected from the group consisting of calcium stearate, magnesium stearate, zinc stearate and mixtures thereof, preferably calcium stearate and / or zinc stearate.

[0067] Calcium stearate has a melting point of approximately 125°C, and more particularly in the range of 125°C to 127°C. Among these, calcium stearate from Sigma Aldrich (CAS No.: 1592-23-0) with a calcium content of 6.6% to 7.4% and a melting point of 127°C is particularly suitable. Calcium stearate from Carl Roth (CAS No.: 1592-23-0) with a calcium stearate content of over 95% and a melting point of 126°C is also particularly suitable.

[0068] Magnesium stearate has a melting point of approximately 71°C, and more particularly in the range of 100°C to 125°C. Among these, magnesium stearate from Sigma Aldrich (CAS No.: 557-04-0) with a melting point of 125°C is particularly suitable. Calcium stearate from Carl Roth (CAS No.: 557-04-0) with a magnesium stearate content of over 95% and a melting point of 100°C is also particularly suitable.

[0069] Magnesium stearate has a melting point of approximately 124°C, and more particularly in the range of 124°C to 126°C. Zinc stearate (CAS No.: 557-05-1) from Thermo Fisher Scientific, with a melting point of 126°C, is particularly suitable.

[0070] Melting points were determined by differential scanning calorimetry (DSC) using a Netzsch-Gerätebau GmbH DSC 200 F3 Maia® instrument. The samples were heated in an aluminum crucible with a cold-welded perforated lid within a nitrogen atmosphere. Heating temperatures ranged from 25°C to 200°C at a rate of 10 K / min. Melting points were determined based on the peak-to-minimum or endothermic peak of the corresponding melting process.

[0071] According to one embodiment, the content of the at least one fatty acid metal salt of the second material in the thermosensitive layer is greater than 10% by weight of the total dry weight of the thermosensitive layer.

[0072] According to one embodiment, the content of the second material in the thermosensitive layer is 10.1% to 90% by weight of the total dry weight of the thermosensitive layer, preferably 25% to 40% by weight.

[0073] The content of the second material in the thermosensitive layer is particularly 10.5% to 60% by weight of the total dry weight of the thermosensitive layer, preferably 11.0% to 60% by weight, more preferably 11.5% to 60% by weight, even more preferably 12.0% to 60% by weight, even more preferably 12.5% ​​to 60% by weight, even more preferably 13.0% to 60% by weight, even more preferably 12.5% ​​to 60% by weight, even more preferably 13.5% to 60% by weight, even more preferably 14.0% to 60% by weight, even more preferably 14.5% to 60% by weight, even more preferably 15.0% to 60% by weight, even more preferably 15.5% to 60% by weight, even more preferably 16.0% to 60% by weight, even more preferably 16.5% to 60% by weight, even more preferably 17.0% to 60% by weight, and even more preferably... The preferred weight percentage is 17.5%~60%, further preferred is 18.0%~60%, further preferred is 18.5%~60%, further preferred is 19.0%~60%, further preferred is 19.5%~60%, further preferred is 20.0%~60%, further preferred is 20.5%~60%, further preferred is 21.0%~60%, further preferred is 21.5%~60%, further preferred is 22.0%~60%, further preferred is 22.5%~60%, further preferred is 23.0%~60%, further preferred is 23.5%~60%, further preferred is 24.0%~60%, further preferred is 24.5%~60%, and most preferably is 25%~60%.

[0074] The content of the second material in the thermosensitive layer is particularly 10.5% to 59% by weight of the total dry weight of the thermosensitive layer, preferably 11.0% to 58% by weight, more preferably 11.5% to 57% by weight, even more preferably 12.0% to 56% by weight, even more preferably 12.5% ​​to 55% by weight, even more preferably 13.0% to 54% by weight, even more preferably 12.5% ​​to 53% by weight, even more preferably 13.5% to 52% by weight, even more preferably 14.0% to 51% by weight, even more preferably 14.5% to 50% by weight, even more preferably 15.0% to 49% by weight, even more preferably 15.5% to 48% by weight, even more preferably 16.0% to 47% by weight, even more preferably 16.5% to 46% by weight, even more preferably 17.0% to 45% by weight, and even more preferably... The preferred weight percentage is 17.5%~44%, further preferred is 18.0%~43%, further preferred is 18.5%~42%, further preferred is 19.0%~41%, further preferred is 19.5%~40%, further preferred is 20.0%~39%, further preferred is 20.5%~38%, further preferred is 21.0%~37%, further preferred is 21.5%~36%, further preferred is 22.0%~35%, further preferred is 22.5%~34%, further preferred is 23.0%~33%, further preferred is 23.5%~32%, further preferred is 24.0%~31%, further preferred is 24.5%~30%, and most preferably is 25%~29%.

[0075] According to one embodiment, the content of the first material and the second material in the thermosensitive layer is 30% to 95% by weight of the total dry weight of the thermosensitive layer, preferably 40% to 90% by weight, and most preferably 50% to 85% by weight.

[0076] Within the aforementioned weight range of the first material and the second material, the weight of the first material is particularly at least 25%.

[0077] Both the first and second materials exist, in particular, in the form of mixtures.

[0078] According to one embodiment, the thermal layer does not contain organic pigments, especially hollow sphere pigments.

[0079] The heat-sensitive layer is particularly free of styrene / acrylate copolymer hollow sphere pigments and / or styrene / butadiene solid sphere pigments.

[0080] By avoiding the use of organic pigments, especially hollow sphere pigments, it can be ensured that no microplastic waste is generated during the degradation of thermal recording materials.

[0081] According to one embodiment, the heat-sensitive layer contains at least one binder, wherein the binder is selected from the group consisting of water-soluble starch, starch derivatives, bio-latex based on EcoSphere starch, methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, gelatin, casein, partially or fully saponified polyvinyl alcohol, chemically modified polyvinyl alcohol, ethylene / vinyl alcohol copolymer, sodium polyacrylate, styrene / maleic anhydride copolymer, ethylene / maleic anhydride copolymer, styrene / butadiene copolymer, acrylamide / (meth)acrylate copolymer, acrylamide / acrylate / methacrylate terpolymer, polyacrylate, poly(meth)acrylate, acrylate / butadiene copolymer, polyvinyl acetate, acrylonitrile / butadiene copolymer, and mixtures thereof.

[0082] According to one embodiment, the content of the at least one adhesive in the heat-sensitive layer is 2% to 40% by weight of the total dry weight of the heat-sensitive layer, preferably 5% to 20% by weight.

[0083] According to one embodiment, the heat-sensitive layer contains at least one pigment, wherein the pigment is selected from the group consisting of: synthetic and naturally derived inorganic pigments, preferably clay, precipitated or natural calcium carbonate, alumina, aluminum hydroxide, silica, precipitated and pyrolytic silica (such as Aerodisp type silica), diatomaceous earth, magnesium carbonate, talc, kaolin, titanium dioxide, bentonite; organic pigments, such as hollow pigments having styrene / acrylate copolymer walls, urea / formaldehyde condensates and mixtures thereof, preferably calcium carbonate, aluminum hydroxide and / or pyrolytic silica.

[0084] According to one embodiment, the content of the at least one pigment in the thermosensitive layer is 2% to 50% by weight of the total dry weight of the thermosensitive layer, preferably 5% to 20% by weight.

[0085] The pigments in the thermal layer can be the same as or different from those in the colorant layer. The advantage of using such pigments is that they can fix the chemical melts produced during the thermal printing process onto its surface. Pigments can also be used to control the surface whiteness and opacity of the thermal layer, as well as its printability with existing printing inks.

[0086] Suitable pigments are especially synthetic and natural inorganic pigments, as well as organic pigments. Preferred inorganic pigments include clay, precipitated or natural calcium carbonate, alumina, aluminum hydroxide, silica, precipitated and pyrolytic silica (such as Aerodisp type silica), diatomaceous earth, magnesium carbonate, talc, kaolin, titanium dioxide, and bentonite. These pigments can be used individually or in any mixture.

[0087] Calcium carbonate, aluminum hydroxide, and pyrolytic silica are preferred because they give thermal recording materials particularly advantageous application-related properties in terms of subsequent printability with commercially available printing inks.

[0088] The heat-sensitive layer may also contain carbon black, and / or dyes / colored pigments.

[0089] According to one embodiment, the thermal layer contains an optical brightener, particularly a stilbene-based brightener, for controlling the whiteness of the surface of the thermal recording material of the present invention.

[0090] According to one embodiment, the heat-sensitive layer particularly contains an oil-absorbing white inorganic pigment.

[0091] Oil-absorbing white inorganic pigments especially contain natural or calcined kaolin, silica, bentonite, calcium carbonate, aluminum hydroxide (especially boehmite) and mixtures thereof.

[0092] The content of the oil-absorbing white inorganic pigment in the heat-sensitive layer is preferably 2% to 50% by weight of the total dry weight of the heat-sensitive layer, and more preferably 5% to 20% by weight.

[0093] According to one embodiment, the heat-sensitive layer contains at least one crosslinking agent, wherein the crosslinking agent is selected from the group consisting of polyaldehydes such as glyoxal, dialdehyde starch, and glutaraldehyde, which may be mixed with boron salts (such as borax); salts or esters of glyoxylic acid; crosslinking agents based on zirconium carbonate; polyamide-polyamine epichlorohydrin (PAE) resin; adipic acid dihydrazide (AHD); boric acid or its salts; polyamines; epoxy resins; formaldehyde oligomers; cyclourea; hydroxymethylurea; melamine / formaldehyde oligomers; and mixtures thereof.

[0094] In order to give the thermal recording material specific application-related performance characteristics, the binder contained in the thermal layer is preferably present in the thermal layer in a cross-linked form, wherein the binder achieves the optimal degree of cross-linking by performing a drying step in the presence of a cross-linking agent during the coating process.

[0095] The crosslinking agents used can be: glyoxal, dialdehyde starch, glutaraldehyde, and other polyaldehydes that can be combined with borates (borax); salts or esters of glyoxylic acid; crosslinking agents based on zirconium carbonate; polyamide-polyamine epichlorohydrin (PAE) resins; adipic acid dihydrazide (AHD); boric acid or its salts; polyamines; epoxy resins; formaldehyde oligomers; cyclourea; hydroxymethylurea; melamine / formaldehyde oligomers; and so on. These crosslinking agents can be used individually or in any mixture.

[0096] For food compliance reasons, ammonium zirconium carbonate and polyamide polyamine epichlorohydrin (PAE) resins are particularly preferred.

[0097] Self-crosslinking polymer adhesives such as polyvinyl alcohol or acrylate modified in a special way contain groups that can crosslink through reaction, so they can achieve crosslinking without any crosslinking agent.

[0098] According to one embodiment, the content of the at least one crosslinking agent in the thermosensitive layer is 0.01% to 25.0% by weight of the total dry weight of the thermosensitive layer, preferably 0.05% to 10.0% by weight.

[0099] According to one embodiment, the heat-sensitive layer contains at least one auxiliary agent, wherein the auxiliary agent is selected from the group consisting of rheology modifiers such as thickeners and / or surfactants.

[0100] According to one embodiment, the auxiliary agent is selected from the group consisting of: viscosity modifiers, preferably dicyandiamide, polyethylene glycol and / or urea as viscosity reducers, or preferably alginate, carboxymethyl cellulose and / or acrylate as viscosity enhancers; dispersants, preferably polyphosphates, sodium tripolyphosphate, sodium pyrophosphate and / or polycarboxylates; defoamers; wet strength agents, preferably melamine / formaldehyde resin, urea-formaldehyde resin, formalin and / or glyoxal; preservatives, preferably antibacterial additives and / or antifungal additives; lubricants, preferably polyethylene glycol; pH adjusters, preferably sodium hydroxide and / or ammonia; dyes; optical brighteners; conductive agents; mixtures thereof; and polyacrylamide, especially anionic modified polyacrylamide.

[0101] According to one embodiment, the content of the auxiliary agent in the total dry weight of the heat-sensitive layer ranges from 0.01% to 5% by weight, preferably from 0.1% to 2% by weight.

[0102] Thus, the technical advantage achieved is that it enables favorable optimization of the applicability and / or characteristics of the heat-sensitive layer.

[0103] According to one embodiment, the at least one rheology modifier is selected from the group consisting of:

[0104] a) Polyols, especially sugar alcohols and their derivatives, selected from the group consisting of diglycerides, triglycerides, glucose, fructose, maltose, lactose, mannose, ribose, xylose, D-mannitol, triacetin, pentaerythritol, dipentaerythritol, erythritol, xylitol, sorbitol, glycerol, mannitol, maltitol and mixtures thereof;

[0105] b) Diol, selected from the group consisting of methylpentanediol, 1,2-propanediol, 1,4-butanediol, 2-hydroxy-1,3-propanediol, 3-methyl-1,3-butanediol, 3,3-dimethyl-1,2-butanediol and mixtures thereof;

[0106] c) Ethylene glycol, selected from the group consisting of polyethylene glycol 300, polyethylene glycol 400, polyethylene glycol 2000, alkoxylated polyethylene glycol, and mixtures thereof;

[0107] d) Caprolactam, cyclotrimethylolpropane, resin esters, mustardamide, and mixtures thereof;

[0108] e) Fatty acids, especially stearic acid, and / or fatty amides, especially mustardamide, stearamide and / or palmitamide and mixtures thereof.

[0109] The mixture of subgroups a) to e) is included.

[0110] According to one embodiment, the surfactant is a natural surfactant, most preferably a saponin and / or phospholipid.

[0111] Surfactants particularly include water-soluble nonionic ethoxylated alcohols, especially those with a solid content between 4% and 15%. The surfactant preferably has RO(CH2CH2O). X The chemical formula H is given, in which the substituent R is chosen as isoC. 13 H 27 The subscript x is 8 or higher; or, the substituent R is selected as isoC. 10 The subscript x is selected from the group including 5, 6, 7, 8 or 11.

[0112] According to one embodiment, the content of natural surfactant is 0.05% to 3% by weight of the total dry weight of the heat-sensitive layer, preferably 0.1% to 1.0% by weight.

[0113] According to one embodiment, the basis weight of the thermal layer is 1~8 g / m². 2 Especially 2~6g / m 2 .

[0114] According to one embodiment, the thickness of the thermal layer is 1~10µm, especially 2~8µm.

[0115] Buick (Bekk) smoothness

[0116] According to one embodiment, the smoothness of the substrate on the side where the pigment layer is applied is greater than 30s, preferably greater than 50s, as measured according to ISO 5267:1995-03.

[0117] According to one embodiment, the colorant layer on the side where the heat-sensitive layer is applied has a smoothness greater than 50s, preferably greater than 100s, and most preferably greater than 150s, as measured according to ISO 5267:1995-03.

[0118] According to one embodiment, the heat-sensitive layer, on the side where the colorant layer is not located, has a smoothness greater than 100s, particularly preferably greater than 250s, as measured according to ISO 5267:1995-03.

[0119] According to one embodiment, the smoothness of the substrate on the side where the pigment layer is applied, measured according to ISO 5267:1995-03, is 20~400s, preferably 30~300s, and particularly preferably 50~200s.

[0120] According to one embodiment, the colorant layer on the side where the heat-sensitive layer is applied has a smoothness of 50 to 400 s, particularly preferably 100 to 250 s, and most preferably 150 to 250 s, as measured according to ISO 5267:1995-03.

[0121] According to one embodiment, the smoothness of the heat-sensitive layer on the side where the colorant layer is not located, as measured according to ISO 5267:1995-03, is preferably 100 to 1000 s, and more preferably 250 to 800 s.

[0122] In particular, each layer applied to the supporting substrate has a Buick smoothness on its top surface, i.e., the surface where the supporting substrate is not located, measured according to ISO 5267:1995-03, that is, the same as or higher than that of the layer below it.

[0123] In particular, the smoothness of each layer applied to the support substrate, measured according to ISO 5267:1995-03, is at least 5% higher (percentage increase) on its top surface, i.e. the surface where the support substrate is not located, compared to the layer below it.

[0124] In particular, the Buick smoothness of each layer applied to the support substrate, measured according to ISO 5267:1995-03, is at least 5 seconds higher (in absolute value) on its top surface, i.e. the surface where the support substrate is not located, compared to the corresponding layer below it.

[0125] Since a smoother underlying substrate results in better overall smoothness and thus better sensitivity of the final product, it is advantageous to make the substrate itself relatively smooth and to maintain this smoothness in all other layers.

[0126] Supporting base

[0127] According to one embodiment, the substrate is selected from the group consisting of paper, single-sided coated paper, and double-sided coated paper.

[0128] According to one embodiment, the base weight of the supporting substrate is 30~100g / m². 2Preferred concentration: 40~80g / m 2 .

[0129] According to one embodiment, the thermal recording material is characterized in that a starch layer (also known as a starch coating) and / or its modifiers are directly disposed on at least one side of a support substrate, preferably on both sides of the support substrate.

[0130] The preferred application rate of the starch coating is 0.1 g / m². 2 ~3g / m 2 0.2g / m 2 ~1.5g / m 2 .

[0131] The advantage of applying a starch coating to the side of the substrate where the colorant layer is located is that it seals the substrate, thereby improving the adhesion of the colorant layer and reducing or preventing the colorant layer from penetrating into the substrate.

[0132] The advantage of applying a starch coating to the side of the substrate without a colorant layer is that it reduces or prevents the colorant layer from penetrating the substrate.

[0133] The smoothness of the starch-containing layer, as measured according to ISO 5267:1995-03, is preferably greater than 20s, more preferably greater than 50s, and most preferably 50~200s.

[0134] Pigment layer

[0135] According to one embodiment, the coloring substance in the colorant layer contains at least one pigment and / or one dye.

[0136] Pigments and / or dyes include, in particular, various organic and inorganic pigments, dyes, and / or carbon black. These pigments and / or dyes can be used individually or in any mixture.

[0137] In a preferred embodiment, the thermal recording material of the present invention is further characterized in that the at least one dye is selected from the group consisting of bleachable dyes, hydrophobic dyes, hydrophobic dyes and / or magnetic dyes.

[0138] The content of each of the pigment, dye and / or carbon black in the colorant layer is preferably 2 to 50% by weight of the total dry weight of the colorant layer, and more preferably 10 to 35% by weight.

[0139] According to one embodiment, the colorant layer contains a binder.

[0140] Preferably, water-soluble starch, starch derivatives, EcoSphere-based starch-based bio-latex, methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, gelatin, casein, partially or fully saponified polyvinyl alcohol, chemically modified polyvinyl alcohol, ethylene / vinyl alcohol copolymer, sodium polyacrylate, styrene / maleic anhydride copolymer, ethylene / maleic anhydride copolymer, styrene / butadiene copolymer, acrylamide / (meth)acrylate copolymer, acrylamide / acrylate / methacrylate terpolymer, polyacrylate, poly(meth)acrylate, acrylate / butadiene copolymer, polyvinyl acetate, and / or acrylonitrile / butadiene copolymer are used as binders. These binders can be used individually or in any mixture.

[0141] The binder content in the colorant layer is preferably 2% to 40% by weight of the total dry weight of the colorant layer, and more preferably 10% to 30% by weight.

[0142] The preferred basis weight of the pigment layer is 1~10 g / m³. 2 Especially 3~8g / m 2 .

[0143] The thickness of the pigment layer is preferably 1~10µm, especially 2~8µm.

[0144] protective layer

[0145] According to one embodiment, the thermal recording material has a protective layer disposed on the thermal layer.

[0146] In other words, the protective layer is located on the side opposite to the colorant layer on the heat-sensitive layer.

[0147] According to one embodiment, the Buick smoothness of the protective layer, measured according to ISO 5267:1995-03, is at least 500s, preferably at least 750s, and particularly preferably at least 1000s.

[0148] Preferably, the smoothness of the protective layer, measured according to ISO 5267:1995-03 standard, is no greater than 2000s, and more preferably no greater than 1600s.

[0149] According to one embodiment, the protective layer contains at least a pigment and / or at least a binder and / or at least a lubricant and / or at least a crosslinking agent and / or at least a rheology modifier.

[0150] In another embodiment, the protective layer contains no single pigment, or contains no multiple pigments.

[0151] If at least one pigment is present in the protective layer, the content of the at least one pigment in the protective layer is less than 5% by weight in the total dry weight of the protective layer, and in particular, greater than 0% by weight but less than 5% by weight.

[0152] In a preferred embodiment, the content of the at least one pigment in the protective layer is: less than 4% by weight, particularly greater than 0% by weight to less than 4% by weight; or less than 3% by weight, particularly greater than 0% by weight to less than 3% by weight; or less than 2% by weight, particularly greater than 0% by weight to less than 2% by weight; or less than 1% by weight, particularly greater than 0% by weight to less than 1% by weight; or less than 0.5% by weight, particularly greater than 0% by weight to less than 0.5% by weight; or less than 0.2% by weight, particularly greater than 0% by weight to less than 0.2% by weight; or less than 0.1% by weight, particularly greater than 0% by weight to less than 0.1% by weight; or less than 0.01% by weight, particularly greater than 0% by weight to less than 0.01% by weight. Alternatively, the protective layer contains no pigment except for unavoidable impurities or unavoidable trace amounts, or contains no pigment at all. All of the above amounts are relative to the dry weight of the protective layer.

[0153] If the manufacturing plant (of pigment-containing coatings) has previously treated or currently needs to treat pigments (such as the previous application of pigment-containing layers, such as pigment-containing insulation layers, colorant layers, or heat-sensitive layers), then unavoidable pigment impurities or unavoidable trace amounts of pigment may enter the protective layer, for example, due to the manufacturing process.

[0154] According to the inventors' observations, the less pigment contained in the protective layer, the higher the smoothness can be set, which is beneficial to the sensitivity or optical density of thermal recording materials. However, this invention is not limited by this theory. Surprisingly, it has been shown that for some applications, reducing the pigment content in the protective layer does not impair its protective effect. Furthermore, it has been shown that doing so can actually increase or improve relative print contrast.

[0155] Preferably, the at least one pigment is selected from organic and / or inorganic pigments.

[0156] Suitable inorganic pigments include synthetic and naturally derived inorganic pigments, preferably clay, precipitated or natural calcium carbonate, alumina, aluminum hydroxide, silica, precipitated and pyrolytic silica (such as Aerodisp type silica), diatomaceous earth, magnesium carbonate, talc, kaolin, titanium dioxide, and bentonite. In addition, organic pigments, such as hollow pigments with styrene / acrylate copolymer walls or urea / formaldehyde condensates, can also be used. These pigments can be used individually or in any mixture.

[0157] Preferably, the protective layer is characterized in that it contains at least one component selected from the following: an adhesive; a lubricant / release agent, especially based on waxes or fats, fatty acids, salts of fatty acids or polysiloxanes (especially metal salts); a crosslinking agent, especially a boron-free crosslinking agent; and / or a rheology modifier.

[0158] The protective layer preferably contains at least one binder, more preferably water-soluble starch, starch derivatives, bio-latex based on EcoSphere starch, methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, partially or fully saponified polyvinyl alcohol, chemically modified polyvinyl alcohol (such as polyvinyl alcohol modified with acetoacetyl, diacetone, carboxyl or silanol groups), styrene / maleic anhydride copolymer, styrene / butadiene copolymer, acrylamide / (meth)acrylate copolymer, acrylamide / acrylate / methacrylate terpolymer, polyacrylate, poly(meth)acrylate, acrylate / butadiene copolymer, polyvinyl acetate and / or acrylonitrile / butadiene copolymer. Such binders can be used individually or in any mixture.

[0159] The binder preferably contains polyvinyl alcohol, and most preferably polyvinyl alcohol with a saponification degree of 88% or higher.

[0160] The adhesive content in the protective layer is preferably 40% to 90% by weight of the total dry weight of the protective layer, and more preferably 50% to about 80% by weight.

[0161] In order to give the thermal recording material specific application-related performance characteristics, the binder contained in the protective layer is preferably present in the protective layer in a cross-linked form, wherein the binder achieves the optimal degree of cross-linking by performing a drying step in the coating process in the presence of a cross-linking agent.

[0162] Crosslinking agents can be: glyoxal, dialdehyde starch, glutaraldehyde, and other polyaldehydes that can be combined with borates (borax); salts or esters of glyoxylic acid; crosslinking agents based on zirconium carbonate; polyamide-polyamine epichlorohydrin (PAE) resins; adipic acid dihydrazide (AHD); boric acid or its salts; polyamines; epoxy resins; formaldehyde oligomers; cyclourea; hydroxymethylurea; melamine / formaldehyde oligomers; and so on. These crosslinking agents can be used individually or in any mixture.

[0163] Among them, boron-free crosslinking agents are preferred.

[0164] For food compliance reasons, ammonium zirconium carbonate and polyamide polyamine epichlorohydrin (PAE) resins are particularly preferred.

[0165] Self-crosslinking polymer adhesives such as polyvinyl alcohol or acrylate modified in a special way contain groups that can crosslink through reaction, so they can achieve crosslinking without any crosslinking agent.

[0166] The crosslinking agent content is preferably 0.01% to 25.0% by weight of the total dry weight of the protective layer, and more preferably 0.05% to 15.0% by weight.

[0167] The protective layer preferably contains at least one lubricant.

[0168] Such lubricants are preferably: fatty acid metal salts, such as zinc stearate, calcium stearate or behenate; synthetic waxes, such as synthetic waxes in the form of fatty amides, such as stearamide, behenamide, fatty alkanolamide (such as stearylmethamide); paraffin waxes with different melting points; ester waxes with different molecular weights; polyethylene waxes, polypropylene waxes with different hardness; and / or natural waxes, such as carnauba wax, montan wax or soybean wax.

[0169] The lubricant is preferably a lubricant based on wax or fat, fatty acid or fatty acid salt (especially metal salt).

[0170] The lubricant content is preferably 1% to about 30% by weight of the total dry weight of the protective layer, and more preferably about 2% to about 20% by weight.

[0171] The protective layer preferably contains at least one release agent.

[0172] The release agent is preferably a polysiloxane-based release agent, such as the release agent disclosed in US2006 / 0063013A1, the entire contents of which are incorporated herein by reference.

[0173] The release agent content is preferably about 1% to about 30% by weight of the total dry weight of the protective layer, and more preferably about 2% to about 20% by weight.

[0174] The protective layer preferably contains at least one rheology modifier.

[0175] Thickeners and surfactants are preferred rheology modifiers. The material selection for the heat-sensitive layer is entirely applicable to the protective layer; details in this regard can be found in the relevant descriptions above.

[0176] Preferably, the protective layer contains at least one lubricant / release agent, at least one adhesive, and at least one crosslinking agent.

[0177] In order to control the surface whiteness of the thermal recording material of the present invention, an optical brightener may be incorporated into the protective layer, preferably a stilbene-based brightener.

[0178] Preferably, the basis weight of the protective layer is 0.01 g / m³. 2 ~3.5g / m 2Within the range, it is preferred to be greater than 0.05 g / m 2 ~2.5g / m 2 Within the specified range, 0.1 g / m is particularly preferred. 2 ~1.5g / m 2 Within the range.

[0179] Surprisingly, it turns out that for certain requirements, reducing the base weight of the protective layer does not compromise its protective effect. In fact, it can even increase or improve relative print contrast.

[0180] The thickness of the protective layer is preferably 0.3µm to 6.0µm, especially 0.5µm to 2.0µm.

[0181] Preferably, the protective layer has a "non-stick effect," particularly for the adhesive layer on the back of the thermal recording material, and / or for the pressure-sensitive adhesive, especially the pressure-sensitive adhesive on the back of the thermal recording material.

[0182] Thus, the technical advantage achieved is that this thermal recording material can be used as a substrate-free (also known as "lined") thermal recording material.

[0183] Thus, the technical advantage achieved is particularly that the thermal recording material can roll itself without a backing (i.e., so-called "backingless" or "bottomless"), and when the self-rolled thermal recording material is unrolled again, the thermal recording material does not exhibit any performance degradation in terms of paper and application-related properties.

[0184] Thus, the technological advantages achieved also include: further reduction in manufacturing costs; greater straight length per roll; no need to spend effort on handling backing paper; and the ability to transport more labels within the same freight volume.

[0185] Adhesive layer

[0186] According to one embodiment, the thermal recording material has an adhesive layer disposed on a first or second surface of a support substrate opposite to the colorant layer, wherein the adhesive layer contains at least one adhesive, preferably a heat-activated adhesive, and more preferably a pressure-sensitive adhesive.

[0187] When a starch coating is present, the starch coating is located between the supporting substrate and the adhesive layer.

[0188] The adhesive layer preferably contains at least one adhesive, which is preferably a heat-activated adhesive, especially a pressure-sensitive adhesive. The adhesive, preferably a heat-activated adhesive and especially a pressure-sensitive adhesive, is particularly preferably a rubber- and / or acrylate-based adhesive.

[0189] Preferably, the protective layer has a "non-stick effect" for rubber- and / or acrylate-based adhesives.

[0190] According to one embodiment, the basis weight of the adhesive layer is 1~40 g / m². 2 Especially 12~25g / m 2 .

[0191] Release layer

[0192] According to one embodiment, the thermal recording material has a release layer disposed on the thermal recording layer, particularly a siliconized release layer.

[0193] The smoothness of the siliconized release layer, measured according to ISO 5267:1995-03, is preferably greater than 400s, more preferably greater than 800s, and most preferably 800~2000s.

[0194] When a protective layer is present on the thermal layer, especially the protective layer as described above, the silicide release layer is preferably located on the protective layer.

[0195] In other preferred embodiments, the thermal recording material is preferably characterized by the formation of a diffusion layer between the silane release layer and the underlying layer (preferably the thermal layer). This diffusion layer is preferably formed by at least a portion of the silane release layer diffusing into the top region of the underlying layer. The amount of silane release layer diffusing into the top region of the underlying layer is preferably 5% to 50% by weight, more preferably 6% to 45% by weight, and particularly 7% to 40% by weight. Such diffusion layers are described, for example, in EP3221153A1.

[0196] The siliconized release layer is preferably provided in the presence of the aforementioned adhesive layer.

[0197] The advantage of having a siliconized release layer on the thermal layer and an adhesive layer on the substrate side not located by the colorant layer is that the thermal recording material can be used as a "backdrop-less" ("unlined") thermal recording material.

[0198] Thus, the technical advantage achieved is particularly that the thermal recording material can roll itself up without a support (i.e., "shieldless"), and when the self-rolled thermal recording material is unrolled again, the properties of the thermal recording material will not be significantly degraded.

[0199] Thus, the technological advantages achieved also include: further reduction in manufacturing costs; greater straight length per roll; no need to spend effort on handling backing paper; and the ability to transport more labels within the same freight volume.

[0200] When a silicide release layer is provided, the layer immediately below the silicide release layer preferably contains at least one flake pigment.

[0201] The at least one flake pigment is preferably selected from the group consisting of kaolin, Al(OH)3, and / or talc. Kaolin is particularly preferred, and most especially preferred is easily spreadable kaolin. Such products may be, for example, products under the trade name Kaolin ASP 109 (BASF GmbH, Germany).

[0202] The main advantage of using such flake pigments (especially kaolin) is that they can achieve silanization of the heat-sensitive layer or the layer located immediately below the silanized release layer with extreme efficiency.

[0203] Flake pigments should be understood as having a diameter-to-thickness ratio of approximately 7 to 40:1, preferably approximately 15 to 30:1.

[0204] The particle size of the flake pigment is preferably adjusted such that at least about 70%, preferably at least about 85%, of the particles have a particle size of about 2µm (as determined by a settling particle size analyzer). The pH of the aqueous solution of the flake pigment is preferably 6 to 8.

[0205] The content of the at least one flake pigment in the heat-sensitive layer or the layer immediately below the siliconized release layer is preferably about 5% to about 60% by weight of the total dry weight of the corresponding layer, and more preferably about 15% to about 55% by weight.

[0206] When the protective layer is located immediately below the siliconized release layer, the content of the flake pigment is the same as the pigment content in the protective layer.

[0207] In other preferred embodiments, the thermal recording material is preferably characterized in that the silanized release layer contains at least one siloxane, preferably a poly(organo)siloxane, especially an acrylic / (organo)siloxane copolymer.

[0208] In another embodiment, the silanized release layer contains a mixture of at least two siloxanes. Preferably, a mixture of at least two acrylic / (organo)siloxane copolymers is used.

[0209] Particularly preferred embodiments of the siloxane are the siloxanes under the trade names TEGO®RC902 and TEGO®RC711 (Evonik GmbH, Germany).

[0210] In another embodiment, the thermal recording material is preferably characterized in that the silicified release layer contains at least one siloxane / acrylate copolymer, and is preferably formed by the condensation of at least one polysiloxane acrylate.

[0211] In a preferred embodiment, the silanized release layer is a thermosetting release layer. This release layer is formed in the presence of a platinum catalyst.

[0212] The silanized release layer is preferably an anhydrous layer. Furthermore, the silanized release layer preferably does not contain any platinum catalyst.

[0213] The siliconized release layer preferably contains an initiator, and more particularly a photoinitiator. This initiator is used to achieve free radical curing of the polysiloxane.

[0214] Among them, TEGO® photoinitiator A18 (Evonik GmbH, Germany) is particularly preferred.

[0215] The siliconized release layer may preferably contain other additives, such as matting agents and / or adhesion additives.

[0216] The preferred basis weight of the silicide release layer is 0.3~5.0 g / m³. 2 Especially 1.0~3.0g / m 2 .

[0217] The thickness of the silicide release layer is preferably 0.3~6.0µm, especially 0.5~2.0µm.

[0218] Insulation layer

[0219] According to one embodiment, a heat insulation layer is provided between the supporting substrate and the colorant layer.

[0220] According to another embodiment, the colorant layer serves as both a colorant layer and a heat insulation layer.

[0221] Such heat-insulating layers, or colorant layers that function as both colorant and heat-insulating layers, can reduce heat conduction of thermal recording materials, thereby improving the local heating efficiency of direct thermal printers and increasing thermal printing speed. In this way, the top layer can become translucent more quickly under heating, thus improving sensitivity.

[0222] This reduces the amount of dye required, making it easier to deink and separate the dye from the substrate, thereby improving the recycling rate of the corresponding recycling process, especially waste paper recycling.

[0223] The smoothness of the insulation layer or the color layer that serves as both a color layer and an insulation layer, as measured according to ISO 5267:1995-03, is preferably greater than 50s, more preferably greater than 100s, and most preferably 100~250s.

[0224] The heat insulation layer, or the colorant layer that serves as both a colorant layer and a heat insulation layer, preferably contains heat insulation material.

[0225] Preferably, the thermal conductivity of the thermal recording material is lower when it contains an insulating layer or a colorant layer that functions as both a colorant layer and an insulating layer, compared to the case where the colorant layer does not contain an insulating layer or functions as both a colorant layer and an insulating layer.

[0226] The insulation material preferably contains kaolin, and more preferably calcined kaolin and mixtures thereof.

[0227] The content of the insulation material in the insulation layer is preferably 20% to 80% by weight of the total dry weight of the insulation layer, and more preferably 40% to 60% by weight.

[0228] When the colorant layer serves as both a colorant layer and a heat insulation layer, the content of the heat insulation material in the heat insulation layer is preferably 30% to 70% by weight of the total dry weight of the colorant layer that serves as both a colorant layer and a heat insulation layer, and more preferably 40% to 60% by weight.

[0229] The preferred basis weight of the insulation layer is 1~5 g / m³. 2 Especially 2~4g / m 2 .

[0230] The thickness of the insulation layer is preferably 1~10µm, especially 2~8µm.

[0231] When the colorant layer serves as both a colorant layer and a heat insulation layer, the preferred basis weight of the colorant layer is 1~10 g / m³. 2 Especially 3~8g / m 2 .

[0232] When the colorant layer serves as both a colorant layer and a heat insulation layer, the thickness of the colorant layer is preferably 1~12µm, especially 4~8µm.

[0233] parameter

[0234] According to one embodiment, as defined in the definition section, the relative printing contrast of the thermal layer is at least 50%, preferably at least 55%, and more preferably at least 60%.

[0235] The relative print contrast ratio (DK, unit: %) is calculated according to Formula 1, based on the optical density (OD) of the thermally printed area (i.e., the optical density of the printed pattern (ODs)) and the optical density (OD0) of the unprinted area, where s represents the printed area and 0 represents the unprinted area. The deviation of the calculated percentage value is ≤ ±2 percentage points.

[0236] Relative print contrast (%) = ((ODs – OD0) / ODs) × 100

[0237] (Equation 1)

[0238] In the first optical density (OD) measurement method, especially with the X-Rite SpectroEye densitometer and 12.79 mJ / mm², 2 The energy level is measured. The measurement uncertainty of the OD value is ≤2%.

[0239] Specifically, in this first method, a 6cm wide thermal recording material strip was thermally printed using a GeBE PrinterLab GPT-10000 test printer (GeBE Elektronik und Feinwerktechnik GmbH, Germany) equipped with a Kyocera printhead. The printhead resolution was 305 dpi, the resistance was 1146 ohms, the applied voltage was 24V, the printed content was a checkerboard pattern with 10 energy levels, the printing speed was approximately 100mm / s, and the contact pressure was 19N. Each square of the printed pattern corresponds to an area of ​​80×80 dots.

[0240] In this second optical density (OD) measurement method, a 6 cm wide strip of thermal recording material was thermally printed using a GeBE PrinterLabGPT-10000 test printer (GeBE Elektronik und Feinwerktechnik GmbH, Germany) equipped with a Kyocera printhead. The printhead resolution was 305 dpi, the resistance was 1146 ohms, and the applied voltage was 24 V. The printed content was a checkerboard pattern without different energy levels. The printing speed was approximately 100 mm / s, and the contact pressure was 19 N. The selected energy level achieved an optical density of 1.20 ± 0.05. The area of ​​each square in the printed pattern corresponds to 80 × 80 dots. The optical density (OD) of the printed and unprinted areas was measured using an X-Rite SpectroEye densitometer, with a measurement uncertainty of ≤2%. The deviation of the percentage calculation was ±2 percentage points.

[0241] According to one embodiment, after a storage period of four weeks according to the image retention performance storage test described in this specification, the image retention performance of the thermal layer is at least 95%, preferably at least 96%, more preferably at least 97%, even more preferably at least 98%, more preferably at least 99%, and most preferably 100% of the initial image retention performance of the thermal layer.

[0242] Under the present disclosure, the image retention performance storage test is as follows: After printing with thermal recording material, it is stored in the dark for four weeks sandwiched between two glass plates at a storage temperature of 60°C and a storage pressure of 1350 N / m. 2 The relative humidity is 50%.

[0243] According to the storage test protocol of this disclosure, the image retention performance of the thermal recording material is determined according to Equation 1, based on the relative print contrast before and after four weeks of storage. After determining the two relative print contrast values, they are substituted into Equation 2 as shown below. The deviation of the percentage calculation value is ≤ ±2 percentage points.

[0244] Image retention performance or write performance (%) = (Relative print contrast after storage / Relative print contrast before storage) × 100

[0245] (Equation 2)

[0246] Image retention performance is determined, in particular, by analyzing the printed and unprinted areas of the printed thermal recording material strip.

[0247] According to one embodiment, after a four-week storage period according to the write performance storage test described in this specification, the write performance of the thermal layer is at least 95% of the initial write performance of the thermal layer, preferably at least 96%, more preferably at least 97%, even more preferably at least 98%, even more preferably at least 99%, and most preferably 100%.

[0248] Under the present disclosure, the write performance storage test was conducted as follows: Unprinted thermal recording material was stored in the dark for four weeks sandwiched between two glass plates at a storage temperature of 60°C and a storage pressure of 1350 N / m. 2 The relative humidity was 50%. After storage, the unprinted thermal recording material was allowed to naturally return to room temperature before printing was performed according to the second method described above to determine its optical density. Specifically, the optical density (OD) of the printed and unprinted areas was measured first, and then the relative printing contrast was determined based on Equation 2, which relates to the optical density value before storage.

[0249] According to one embodiment, the surface whiteness of this thermal recording material, measured according to ISO 5267:1995-03 standard, is 35-60%, particularly 45-50%.

[0250] Higher print-to-print contrast can improve readability and other application-related features.

[0251] Surface whiteness (paper whiteness) can be measured using an Elrepho 3000 spectrophotometer according to ISO 2470-2 (2008) standard.

[0252] According to one embodiment, the thermal recording material is characterized in that the contrast between the thermal layer region that becomes translucent due to localized heating and the thermal layer region that does not become translucent due to localized heating is 40-80%, particularly 50-70%.

[0253] This contrast can be calculated based on the difference in optical density between the background and the text. Optical density (OD) is measured, for example, using a densitometer.

[0254] According to one embodiment, the thermal recording material is preferably characterized by a deposition characteristic of at least "Level 2" in a long-term thermal printer test (10,000 meters) printing a checkerboard pattern with 10 energy levels. After completing the 10,000-meter printing test with a commercially available thermal printer (model: Zebra ZD420), the deposition condition at the thermal printhead is visually inspected, and its deposition characteristics are evaluated according to the following scoring system: "Level 0" = no deposition; "Level 1" = slight deposition; "Level 2" = moderate deposition; "Level 3" = severe deposition. Commercially available thermal recording materials do not exhibit deposition ("Level 0").

[0255] According to one embodiment, the thermal recording material is preferably characterized in that it has a thermal recording capacity of 12.79 mJ / mm². 2 The optical density (OD) measured at the energy level is at least 1.35.

[0256] Methods, products obtained by the process, and uses

[0257] According to the second aspect, the above objective is achieved by a method for manufacturing a thermal recording material. This method includes the following steps:

[0258] A support substrate is provided, the support substrate having a first surface and a second surface opposite to the first surface;

[0259] A pigment layer suspension is applied to the first or second surface of the substrate, wherein the pigment layer suspension contains at least one coloring substance.

[0260] The pigment layer suspension is dried to obtain a pigment layer disposed on the first or second surface of the substrate.

[0261] A paint suspension is applied to a pigment layer, wherein the paint suspension contains a first material, the first material containing at least one fatty acid and / or at least one fatty amide, and the paint suspension also contains a second material, the second material containing at least one fatty acid metal salt, and the first material has a first melting temperature T. S1 The second material has a second melting temperature T S2 First melting temperature T S1 Below the second melting temperature T S2 ;as well as

[0262] The coating suspension is dried to obtain a heat-sensitive layer on the pigment layer.

[0263] Preferably, the thermal recording material of the present invention is obtained by sequentially applying suspensions (especially aqueous suspensions) containing each layer of starting material onto a supporting substrate. The dry weight of the applied suspensions (especially aqueous suspensions) accounts for 8-50% by weight, preferably 10-40% by weight, and is applied by a curtain coating method using a coating system with an operating speed of at least 200 m / min, especially at least 900 m / min.

[0264] This method is particularly advantageous, both from an economic perspective and because of its ability to achieve uniform application across the entire load-bearing substrate.

[0265] If the dry content drops below 8% by weight, a large amount of moisture must be removed quickly using a gentle drying method, which negatively impacts the coating speed and reduces efficiency. Conversely, if the value exceeds 60% by weight, more technical effort is required to ensure the stability of the coating curtain during the coating process and the drying of the applied film, enabling the machine to operate at extremely high speeds.

[0266] In the curtain coating process, a coating dispersion is used to form a freely falling curtain. This coating dispersion in the form of a thin film (curtain) is "splashed" onto the substrate by free falling to achieve the application of the coating dispersion onto the substrate. DE10196052TI discloses the use of the curtain coating process in the manufacture of information recording materials, in which a multi-layer recording layer is manufactured by applying a curtain composed of a multi-layer coating dispersion film onto a substrate.

[0267] Furthermore, in embodiments of the method of the present invention, a "double-curtain" method can be adopted. That is, one layer is applied immediately after another, with the interval between the two layers being so short that the previous layer is not yet dry when the next layer is applied. Accordingly, these two layers are preferably applied in a "wet layer on top of wet layer" manner.

[0268] All descriptions related to curtain coating processes can be similarly applied to double curtain coating processes.

[0269] The advantage of using a double-coat process with a "wet layer on wet layer" method is that it can enhance the adhesion between the two layers and, in particular, avoid the need to use tackifiers between the two layers.

[0270] In a preferred embodiment of the method of the present invention, the viscosity of the degassed aqueous suspension of the coating is about 100 to about 1000 mPas (Brookfield viscometer, 100 rpm, 20°C). If this value is less than about 100 mPas or greater than about 1000 mPas, the flowability of the coating compound within the coating equipment will be poor. The viscosity of the degassed aqueous suspension of the coating is particularly preferably about 200 to about 500 mPas. In a double-coat process, the viscosity of the two successively applied layers should gradually decrease from bottom to top. Improper viscosity adjustment increases the likelihood of buildup and wetting problems at the contact points between the coating layers.

[0271] In a preferred embodiment, to optimize the process, the surface tension of the coating suspension can be adjusted to approximately 25 to approximately 70 mN / m, preferably to approximately 35 to approximately 60 mN / m, according to the surface tension measurement standard of the bubble pressure method (ASTM D 3825-90) described below. By measuring the dynamic surface tension of the coating and precisely adjusting its dynamic surface tension by selecting a suitable surfactant and determining the required amount of surfactant, the control of the coating process can be improved.

[0272] Dynamic surface tension was measured using a bubble pressure surface tension meter. This involved first forming a bubble in a liquid using a capillary tube, and then measuring the maximum internal pressure of that bubble. According to the Yang-Laplace equation, the internal pressure p (Laplace pressure) of a spherical bubble depends on its radius of curvature r and surface tension σ:

[0273] When a bubble forms at the distal end of a capillary immersed in a liquid, the curvature initially increases and then decreases, resulting in maximum pressure. The curvature is at its maximum when the radius of curvature equals the capillary radius, thus maximizing the pressure.

[0274] The pressure curve and the location of maximum pressure during the bubble pressure measurement process are obtained as follows:

[0275] First, a reference measurement is performed using a liquid with known surface tension (usually water) to determine the capillary radius. Once the radius is known, the surface tension can be calculated based on the maximum pressure pmax. Since the capillary is immersed in the liquid, the hydrostatic pressure p0, determined by the immersion depth and liquid density, must be subtracted from the pressure measurement (modern measuring instruments perform this automatically). Therefore, for the immersion pressure method, the following formula can be obtained:

[0276] The obtained measurements represent the surface tension at a specific surface age. Surface age refers to the time from the initial formation of bubbles to the reaching of maximum pressure. By varying the bubble formation rate, the relationship between surface tension and surface age can be determined, thus allowing the plotting of the corresponding surface tension versus time curve.

[0277] This relationship is crucial for the use of surfactants. In many processes, the diffusion and adsorption rates of surfactants are too low to reach the equilibrium value of interfacial tension.

[0278] The formation of each layer can be completed online or offline during a separate coating process.

[0279] To ensure that each layer described in detail above has the Buick smoothness as described above, it is particularly preferable to perform the following method steps.

[0280] Preferably, the substrate is first smoothed with a first roller to achieve high smoothness on one or both sides, thus giving the substrate an inherent advantage. Before entering the first coating unit, it is preferable to further satin-finish it using an downstream calender, which can further improve smoothness and / or contribute to achieving a good surface condition.

[0281] As described above, if a starch coating is to be applied, it is preferable to first apply the starch coating using a laminating machine, and then apply the colorant layer using a scraping machine.

[0282] By applying starch to the back, it is particularly advantageous to prevent paint leakage caused by the scraper.

[0283] Alternatively, the colorant layer can be applied directly using a laminating machine. However, this method is inferior to using a doctor blade coater in terms of subsequent smoothness. Doctor blade coaters provide a good initial smoothness of the material, which is crucial for the dynamic sensitivity of the final product, and there is a correlation between final smoothness and dynamic sensitivity.

[0284] Another conceivable approach is to apply the pigment layer using a laminating machine or even a curtain coating machine. While this would result in the loss of the advantage of achieving a smooth surface, this can be compensated for, in particular, by laminating using a calender. However, since lamination would damage the hollow sphere structure, this approach is only feasible when hollow sphere pigments are not used.

[0285] When an insulation layer is installed, it can be applied using the same method described above.

[0286] When a siliconized layer is applied, it can be done in the same way as described above.

[0287] The above method is applicable to protective layers. Alternatively, the protective layer can also be applied by printing. In terms of process technology and technical characteristics, protective layers that can be cured by photochemical radiation are particularly suitable. The term "photochemical radiation" refers to ionizing radiation such as ultraviolet light or electron beams.

[0288] The heat-sensitive layer is preferably applied using a curtain coating process as described above.

[0289] When the substrate is coated, especially paper, the resulting curling should be corrected.

[0290] This correction is preferably achieved using a liquid coating system (LAS). In this system, a water film is first applied to the side with less coating, and then allowed to dry. This process restores the surface to its smooth state. The application of the water film causes slight changes to the surface.

[0291] A preferred surface protection solution is a steam humidifier. Because steam humidifiers use steam, rather than water, they prevent surface damage. This solution is ideal for applications with the highest surface quality requirements.

[0292] Another option is a mist humidifier that sprays water mist.

[0293] All of the above types of layers can be either single-layer or multi-layer.

[0294] The embodiment of the thermal recording material in the first aspect is also the embodiment of the method for manufacturing the thermal recording material in the second aspect, and vice versa.

[0295] According to the third aspect, the above objective is achieved by a thermal recording material that can be manufactured by the method of the second aspect.

[0296] The embodiments of the thermal recording material in the first aspect and the method of manufacturing the thermal recording material in the second aspect are also embodiments of the thermal recording material that can be manufactured by a method in the third aspect.

[0297] According to a fourth aspect, the present invention relates to the use of the thermal recording material of the first or third aspect as receipt paper rolls, adhesive label rolls, ticket rolls, or printing paper for mechanical printers or writing pens.

[0298] The embodiments of the thermal recording material in the first aspect and the embodiments of the thermal recording material manufacturing method in the second aspect are also embodiments for the purpose of the fourth aspect. Detailed Implementation

[0299] In the exemplary embodiments described in detail below, various thermal recording materials or thermal papers are manufactured by forming a composite structure on a supporting substrate by applying a coating suspension, and such thermal recording materials or thermal papers are inspected by various measurement methods.

[0300] In all embodiments, the basis weight of the paper made from hardwood and softwood pulp was 41 g / m³. 2 Or 58g / m 2 The paper substrate is used as the carrier substrate.

[0301] Measurement methods

[0302] Optical density (OD) measurement method 1:

[0303] Thermal printing was performed on thermal recording material (6cm wide strips) using a GeBE PrinterLab GPT-10000 test printer (GeBEElektronik und Feinwerktechnik GmbH, Germany) equipped with a Kyocera printhead. The printhead resolution was 305 dpi, the resistance was 1146 ohms, the applied voltage was 24V, and the printed content was a checkerboard pattern with 10 energy levels. The printing speed was approximately 100mm / s, and the contact pressure was 19N. Each square of the printed pattern corresponds to an area of ​​80×80 dots. The optical density (OD), measured using an X-Rite SpectroEye density meter, was 12.79 mJ / mm². 2 The measurement is performed at energy levels. It is estimated that the measurement uncertainty of the OD value is ≤2%.

[0304] Optical density (OD) measurement method 2:

[0305] Thermal printing was performed on thermal recording material (6 cm wide strips) using a GeBE PrinterLab GPT-10000 test printer (GeBEElektronik und Feinwerktechnik GmbH, Germany) equipped with a Kyocera printhead. The printhead resolution was 305 dpi, the resistance was 1146 ohms, and the applied voltage was 24 V. The printed content was a checkerboard pattern without different energy levels. The printing speed was approximately 100 mm / s, and the contact pressure was 19 N. The selected energy level (determined based on preliminary test results (see Method 1)) achieved an optical density of 1.20 ± 0.05. Each square of the printed pattern corresponded to an area of ​​80 × 80 dots. The optical density (OD) of the printed and unprinted areas was measured using an X-Rite SpectroEye densitometer. The measurement uncertainty of the OD value was estimated to be ≤ 2%. As described below, the deviation of the percentage calculation value is ± 2 percentage points.

[0306] Measurement of relative print contrast:

[0307] The relative print contrast is calculated according to Formula 1, based on the optical density value (ODs) of the thermally printed area and the optical density value (OD0) of the unprinted area (OD0), where s represents the printed area and 0 represents the unprinted area:

[0308] Relative print contrast (%) = ((ODs – OD0) / ODs) × 100

[0309] (Equation 1)

[0310] Measurement of surface whiteness:

[0311] Surface whiteness was measured using an Elrepho 3000 spectrophotometer according to ISO 2470-2 (2008) standard.

[0312] Measurement of Buick smoothness:

[0313] Buick smoothness is measured according to standard DIN 53107 (2016).

[0314] Measurement of sedimentation characteristics:

[0315] Deposition characteristics at the thermal printhead were evaluated by printing a checkerboard pattern with 10 energy levels using a commercially available thermal printer (model: Zebra ZD420) during a long-duration thermal printer test (10,000 meters). After completing the 10,000-meter printing test, the deposition condition at the thermal printhead was visually inspected, and its deposition characteristics were evaluated according to the following scoring system: "Level 0" = no deposition; "Level 1" = slight deposition; "Level 2" = moderate deposition; "Level 3" = severe deposition. Commercially available thermal recording materials showed no deposition ("Level 0").

[0316] Measurement of plasticizer (Omni Foil) resistance:

[0317] After printing two thermal recording materials according to optical density (OD) measurement method 2, plasticized plastic wrap (PVC film containing 20-25% dioctyl adipate) was placed on them in contact with each other. The two thermal recording materials were then carefully wound into a roll to prevent wrinkling or air trapping. After winding, they were stored for 16 hours. One roll was stored at room temperature (20-22°C), and the other at 40°C. After removing the plastic wrap, the optical density of the printed and unprinted areas was measured, and the image retention or write performance was determined according to Equation 2, which relates to the corresponding optical density values ​​before plasticizer exposure.

[0318] Image retention performance or write performance (%) = (Relative print contrast after storage / Relative print contrast before storage) × 100

[0319] (Equation 2)

[0320] Measurement of adhesive resistance:

[0321] After printing two thermal recording materials according to Method 2, their optical density (OD) was measured according to the method described in this instruction manual. One was affixed with Tesa transparent self-adhesive tape (Tesafilm® Crystal Clear, #57315), and the other with Tesa packaging tape (#04204). Care was taken during affixing to prevent wrinkling or air trapping. After storing at room temperature (20~22°C) for seven days, the optical density (OD) of the printed and unprinted areas was measured through the respective tapes. The relative printing contrast (Equation 1) was determined based on the relationship between the OD values ​​and the corresponding optical density values ​​of samples not stored fresh after tape application (Equation 2).

[0322] Measurement of resistance to hydrophobic and hydrophilic reagents:

[0323] After printing according to Method 2, sunflower seed oil (Nestle, 100% pure Thomy sunflower seed oil), lard (LARU GmbH), hand cream (lanolin hand cream), sweat (obtained according to DIN EN ISO 105-E04), milk (3.5% fat content), ethanol (40% aqueous solution), and water (tap water) were applied to the printed and unprinted areas respectively by dropping / finger-tip application. After 30 minutes of exposure, the reagents were removed by brief contact with standard kitchen paper towels, and the paper samples were stored at room temperature (20~22°C). After a specific storage period (see Table 1), the optical density (OD) of the printed and unprinted areas was measured, and the relative printing contrast (Equation 1) was determined according to the relationship between the OD values ​​and the corresponding optical density values ​​before reagent application (Equation 2).

[0324] Measurement of the shelf life of thermal recording materials:

[0325] After printing a thermal recording material according to Method 2, its optical density (OD) was measured as per this instruction manual (OD before storage). Subsequently, this thermal recording material and an unprinted thermal recording material were stored simultaneously at 60°C in the dark for four weeks. During storage, the thermal recording material was sandwiched between two glass plates at a storage pressure of 1350 N / m³. 2 The relative humidity is 50%.

[0326] After storage, the material was allowed to naturally return to room temperature, and then the unprinted thermal recording material strip was printed according to Method 2 (=residual write performance). Subsequently, the optical density (OD) of the printed and unprinted areas was measured, and the relative print contrast was determined according to Equation 2, which relates the OD values ​​to the corresponding OD values ​​before storage. Furthermore, the printed and unprinted areas of the printed thermal recording material strip were also measured (=residual image retention performance), and the relative print contrast was determined according to Equation 2, which relates the OD values ​​to the corresponding OD values ​​before storage.

[0327] Thermal recording materials are made into self-adhesive labels.

[0328] First, an adhesive layer is applied to the back of an A4 sheet of paper. This involves applying an adhesive dispersion to the back of the A4 paper (thermal recording material) that carries the thermal layer on the front using a squeegee, and then drying it in a hot air dryer at a temperature up to 70°C. To protect the adhesive layer during subsequent processing, a silicone release paper is laminated onto it. Care is taken during lamination to prevent air from getting trapped or wrinkling.

[0329] In the case of an "adhesive liner sandwich structure" where the adhesive layer is sandwiched between two layers of release paper, one of the two layers of release paper is removed first, and then the adhesive layer (the sticky side) is pressed onto the back of the A4 thermal paper to prevent air from being trapped or wrinkling.

[0330] During label manufacturing, it is irrelevant whether the thermal recording layer is applied on the opposite side of the adhesive layer after the adhesive layer is applied. For the insulation layer or colorant layer, the application order is particularly important: apply the insulation layer or colorant layer first, and then apply the thermal recording layer.

[0331] When making self-adhesive labels, a commercially available removable adhesive based on acrylate (R5000N, AveryFasson) is used.

[0332] Adhesive migration test of thermal labels

[0333] After printing and measuring (optical density (OD)) a strip of thermal recording material according to Method 2, it was stored together with an unprinted strip of thermal recording material at 60°C in the dark for four weeks. During storage, the thermal recording material was sandwiched between two glass plates at a storage pressure of 1350 N / m³. 2 The relative humidity is 50%.

[0334] After storage, the material was allowed to return to room temperature naturally, and then the unprinted thermal recording strip was printed according to Method 2 (Optical Density (OD) Measurement (= Residual Write Performance)). Subsequently, the printed and unprinted areas were measured, and the relative print contrast was determined according to Equation 2, which relates the printed thermal recording strip to the corresponding optical density value before storage.

[0335] In addition, the printed and unprinted areas of the thermal recording material strip after printing were measured (= residual image retention performance), and the relative printing contrast was determined according to Equation 1 based on its relationship with the corresponding optical density value before storage (Equation 2).

[0336] Manufacturing of thermal recording materials

[0337] The layered formulations of the following layers are adjusted by adding water to the corresponding dry content (DQ) as follows: heat insulation layer (30%); colorant layer (26%); heat-sensitive layer (20%); protective layer (10%).

[0338] The raw materials used are applied in the form of dispersions or solutions with the following dry contents: styrene / acrylate copolymer (21%); styrene / butadiene latex (48%); carbon black (45%); sodium metaborate tetrahydrate (2%); stearamide wax (22%); silica (28%); zinc stearate (35%); calcium stearate (35%); polyvinyl alcohol (high viscosity) (10%); calcined kaolin (45%); precipitated calcium carbonate (58%); ammonium zirconium carbonate (9%); polyamide polyamine epichlorohydrin (10%); polyvinyl alcohol (low viscosity) (7%); kaolin (75%).

[0339] All quantities expressed as weight percentages are in the dry state (otro).

[0340] On a laboratory scale, aqueous suspensions of pigments, thermal layers, and protective layers for forming thermal recording materials were sequentially applied to a paper substrate using a bar coater. After each application, the material was dried in a hot air dryer (40 cm distance) at 90–110°C for 1–3 minutes.

[0341] Examples of embodiments 1a, 2a, 3a, 4 and comparative example V1 are shown.

[0342] In exemplary embodiments 1a, 2a, 3a, 4 and comparative example V1, the heat insulation layer is applied to the paper substrate by a laminator at a speed of 800 m / min within a paper machine. The colorant layer and the thermally sensitive layer are applied sequentially and / or simultaneously by a double-curtain coater to the paper substrate already coated with the heat insulation layer within a coating machine. The protective layer is applied to the thermally sensitive layer by a curtain coater at a speed of 900 m / min within a coating machine. After each application, the corresponding coated paper substrate is dried in a conventional manner, and this drying process does not adversely affect the surface whiteness of the thermally sensitive layer or the whiteness of the paper of the thermally sensitive recording material of the present invention.

[0343] The compositions of illustrative embodiments 1a, 2a, 3a, 4 and comparative example V1 are shown below.

[0344] Example of implementation method 1a

[0345] Example of implementation method 2a

[0346] Example of implementation method 3a

[0347] Example of Implementation Method 4

[0348] Comparative Example 1

[0349] Examples of implementation methods 1b, 1c, 2b, 2c, 3b, 3c

[0350] In illustrative embodiments 1b, 1c, 2b, 2c, 3b, and 3c, the pigment layer and the thermal layer are applied to the paper substrate sequentially and / or simultaneously at a speed of 900 m / min by a single-curtain coater and / or a double-curtain coater within a coating machine. Subsequently, the protective layer is applied to the thermal layer by a curtain coater within a coating machine at a speed of 900 m / min. After each application, the corresponding coated paper substrate is dried in a conventional manner, and this drying process does not adversely affect the surface whiteness of the thermal layer or the whiteness of the paper, etc., of the thermal recording material of the present invention.

[0351] The components of exemplary implementation methods 1b, 1c, 2b, 2c, 3b, and 3c are shown below.

[0352] Example of implementation method 1b

[0353] Example of implementation method 1c

[0354] Example of implementation method 2b

[0355] Example of implementation method 2c

[0356] Example of implementation method 3b

[0357] Example of implementation method 3c

[0358] Examples of implementation methods 1d, 1f, 1g, 1h

[0359] In the illustrated embodiments 1d, 1f, 1g, and 1h, the starch base coating (0.5g / m 2Inside the paper machine, a laminator applies the coating to both sides of the paper substrate at a speed of 800 m / min. Subsequently, in the coating machine, a coating unit applies the pigment layer to the starch-coated paper substrate at a speed of 600 m / min. Inside the coating machine, the thermal layer and protective layer are applied sequentially and / or simultaneously at a speed of 900 m / min to the ink- and starch-coated paper substrates by a single-curtain coating unit and / or a double-curtain coating unit. After each application, the corresponding coated paper substrate is dried using conventional methods. This drying process does not adversely affect the surface whiteness of the thermal layer or the whiteness of the paper, etc., of the thermal recording material of this invention.

[0360] The composition of 1d, 1f, 1g, and 1h in illustrative embodiments is shown below.

[0361] Example of implementation method 1d

[0362] Example of implementation method 1f

[0363] Example of implementation method 1g

[0364] Example of implementation method 1h

[0365] Example of implementation method 1e

[0366] In illustrative embodiment 1e, the pigment layer and the thermal layer are applied to the paper substrate sequentially and / or simultaneously at a speed of 900 m / min by a single-curtain coater and / or a double-curtain coater within a coating machine. Subsequently, the protective layer is applied to the thermal layer by a curtain coater within the coating machine at a speed of 900 m / min. After each application, the corresponding coated paper substrate is dried in a conventional manner, and this drying process does not adversely affect the surface whiteness of the thermal layer or the whiteness of the paper, etc., of the thermal recording material of the present invention.

[0367] The components of exemplary implementation 1e are shown below.

[0368] Example of implementation method 1e

[0369] Furthermore, it should be emphasized that a protective layer may be optionally applied outside the heat-sensitive layer in all illustrated embodiments. This protective layer is selected from protective layers 1, 2, 3, and 4 shown below.

[0370] Protective layer 1

[0371] Protective layer 2

[0372] Protective layer 3

[0373] Protective layer 4

[0374] result

[0375] In embodiments 1a-1h, 2a-2c, 3a-3c, 4 and comparative example V1, the measurement results of the above parameters are summarized in Tables 1, 2a, 2b and 3 below.

[0376] Table 1

[0377] * Only the smoothness of the printed area is considered.

[0378] In all exemplary embodiments 1 to 3c and 4 of the present invention, the heat-sensitive layer uses stearamide as the first material and fatty acid metal salt, especially zinc stearate, as the second material.

[0379] In Comparative Example V1 (not of this invention), the heat-sensitive layer contains stearamide as a first material, but does not contain fatty acid metal salts as a second material or as a lubricant or release agent, especially not zinc stearate.

[0380] In exemplary embodiments 1a, 2a, 3a, and 4, the thermal recording material includes a heat-insulating layer disposed on a substrate, a colorant layer disposed on the heat-insulating layer, and a thermally sensitive layer disposed on the colorant layer. In exemplary embodiments 1b-1h and 2b-2c, the thermal recording material includes a colorant layer disposed directly on the substrate and a thermally sensitive layer disposed on the colorant layer. In exemplary embodiments 1a-1h, 2b-2c, 3b-3c, and 4, the basis weight, material composition, and weight percentage of each layer are different.

[0381] As can be seen from Table 1, by replacing the hollow sphere pigment in the existing thermal marking layer with fatty acids or fatty amides as the first material and fatty acid metal salts as the second material, satisfactory or good printing parameters can be achieved in all cases for the following reasons: in all embodiments employing Method 1, an optical density value of at least 1.35 can be achieved; in all embodiments, a relative printing contrast value of at least 60% can be achieved; in all embodiments, a surface whiteness value of at least 30% can be achieved; and in all cases, Buick smoothness greater than 250s and greater than 100s can be achieved before and after printing, respectively.

[0382] However, the assessment results of the depositional characteristics differed.

[0383] In Comparative Example V1, although the heat-sensitive layer contains stearamide as the first material, it does not contain fatty acid metal salts as the second material or as a lubricant or release agent, especially not zinc stearate. Accordingly, as shown in Table 1, Comparative Example V1 has the disadvantage of heavy deposition (deposition grade = 3), while Embodiments 1a to 3c have the advantage of no deposition (deposition grade = 0).

[0384] In Example 4, although the heat-sensitive layer contains stearamide as the first material, it contains only a very small percentage (3.9% by weight) of a fatty acid metal salt, particularly zinc stearate, as the second material (i.e., as a lubricant or release agent). Accordingly, as shown in Table 1, the deposition characteristics observed in Example 4 (deposition grade = 1) are better than those in Comparative Example V1, but not as good as those in Example 1a to 3c, which have the advantage of no deposition (deposition grade = 0).

[0385] It is important to emphasize that in all exemplary embodiments 1a-3c, the weight percentage of the fatty acid metal salt used as the second material is greater than 10% by weight, while in exemplary embodiments 3a-3c, this weight percentage is only slightly greater than 10% by weight. In exemplary embodiments 1a-2c, the weight percentage of the fatty acid metal salt used as the second material is much greater than 10% by weight. Accordingly, compared with exemplary embodiments 3a-3c (deposition level = 1), exemplary embodiments 1a-2c exhibit the best deposition characteristics (deposition level = 0).

[0386] As shown in Tables 2a and 2b below, the exemplary embodiments 1a-3c and 4, as well as comparative example V1, all ensure resistance to the hydrophilic and hydrophobic reagents studied.

[0387] Table 2a

[0388] *Percentage of residual image retention performance / write performance calculated according to Equation 2 (%)

[0389] Table 2b

[0390] *Percentage of residual image retention performance / write performance calculated according to Equation 2 (%)

[0391] As can be seen from Tables 2a and 2b, all examples exhibited an effective resistance of more than 90% against various hydrophilic and hydrophobic reagents.

[0392] Table 3

[0393] As can be seen from Table 3, all embodiments exhibited effective storage stability and effective resistance in the adhesive migration test: the storage stability (image retention performance) of the thermal recording material after printing was greater than 95%, and the storage stability (write performance) of the thermal recording material before printing was 100%.

[0394] In summary, it can be considered that, compared with existing thermal application materials, by using fatty acids or fatty amides with lower melting points as the first material of the thermal recording layer and fatty acid metal salts with higher melting points as the second material of the thermal recording layer, it is possible to at least ensure that the printed image has stable image properties and at least ensure stable resistance to hydrophilic and hydrophobic reagents.

[0395] More importantly, compared to existing recording materials, by using fatty acids or fatty amides with lower melting points as the first material of the thermal recording layer and fatty acid metal salts with higher melting points as the second material of the thermal recording layer, the deposition characteristics of direct thermal printing can be improved, and the use of environmentally harmful organic pigments, especially hollow sphere pigments, can be avoided.

Claims

1. A thermal recording material, comprising: A supporting substrate having a first surface and a second surface opposite to the first surface; A colorant layer is disposed on the first or second surface of the supporting substrate, wherein the colorant layer contains at least one coloring substance; and A thermally sensitive layer is disposed on the pigment layer and at least partially covers the pigment layer, wherein the thermally sensitive layer is configured to become translucent by localized heating, thereby making the underlying pigment layer visible. The feature is that: the heat-sensitive layer contains a first material, the first material containing at least one fatty acid and / or at least one fatty amide; the heat-sensitive layer contains a second material, the second material containing at least one fatty acid metal salt. The first material has a first melting temperature T. S1 The second material has a second melting temperature T S2 The first melting temperature T S1 Below the second melting temperature T S2 .

2. The thermal recording material according to claim 1, characterized in that, First melting temperature T S1 Compared to the second melting temperature T S2 The temperature should be at least 1°C lower, preferably at least 2°C lower, more preferably at least 5°C lower, and most preferably at least 10°C lower.

3. The thermal recording material according to claim 1 or 2, characterized in that, The at least one fatty acid in the first material is selected from the group consisting of betaine, stearic acid and / or palmitic acid, and / or the at least one fatty amide in the first material is selected from the group consisting of behenamide, mustardamide, stearamide, oleamide, palmitamide and / or lauramide, preferably stearamide.

4. The thermal recording material according to any one of the preceding claims, characterized in that, The content of the first material in the thermosensitive layer is 1% to 90% by weight of the total dry weight of the thermosensitive layer, preferably 30% to 80% by weight.

5. The thermal recording material according to any one of the preceding claims, characterized in that, The at least one fatty acid metal salt of the second material is selected from the group consisting of calcium stearate, magnesium stearate, zinc stearate and mixtures thereof, preferably calcium stearate and / or zinc stearate.

6. The thermal recording material according to any one of the preceding claims, characterized in that, The content of at least one fatty acid metal salt of the second material in the thermosensitive layer is greater than 10% by weight in the total dry weight of the thermosensitive layer.

7. The thermal recording material according to claim 6, characterized in that, The content of the second material in the thermosensitive layer is 10.1% to 90% by weight of the total dry weight of the thermosensitive layer, preferably 25% to 40% by weight.

8. The thermal recording material according to any one of the preceding claims, characterized in that, The heat-sensitive layer contains at least one binder, wherein the binder is selected from the group consisting of water-soluble starch, starch derivatives, bio-latex based on EcoSphere starch, methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, gelatin, casein, partially or fully saponified polyvinyl alcohol, chemically modified polyvinyl alcohol, ethylene / vinyl alcohol copolymer, sodium polyacrylate, styrene / maleic anhydride copolymer, ethylene / maleic anhydride copolymer, styrene / butadiene copolymer, acrylamide / (meth)acrylate copolymer, acrylamide / acrylate / methacrylate terpolymer, polyacrylate, poly(meth)acrylate, acrylate / butadiene copolymer, polyvinyl acetate, acrylonitrile / butadiene copolymer, and mixtures thereof.

9. The thermal recording material according to any one of the preceding claims, characterized in that, The heat-sensitive layer contains at least one pigment, wherein the pigment is selected from the group consisting of: synthetic and naturally derived inorganic pigments, preferably clay, precipitated or natural calcium carbonate, alumina, aluminum hydroxide, silica, precipitated and pyrolytic silica (such as Aerodisp type silica), diatomaceous earth, magnesium carbonate, talc, kaolin, titanium dioxide, bentonite; organic pigments, such as hollow pigments having styrene / acrylate copolymer walls, urea / formaldehyde condensates and mixtures thereof, preferably calcium carbonate, aluminum hydroxide and / or pyrolytic silica.

10. The thermal recording material according to any one of the preceding claims, characterized in that, The heat-sensitive layer contains at least one crosslinking agent, wherein the crosslinking agent is selected from the group consisting of polyaldehydes such as glyoxal, dialdehyde starch, and glutaraldehyde, which may be mixed with boron salts (such as borax); salts or esters of glyoxylic acid; crosslinking agents based on zirconium carbonate; polyamide-polyamine epichlorohydrin (PAE) resin; adipic acid dihydrazide (AHD); boric acid or its salts; polyamines; epoxy resins; formaldehyde oligomers; cyclourea; hydroxymethylurea; melamine / formaldehyde oligomers; and mixtures thereof.

11. The thermal recording material according to any one of the preceding claims, characterized in that, The thermal recording material has a protective layer disposed on the thermal layer.

12. The thermal recording material according to any one of the preceding claims, characterized in that, The thermal recording material has an adhesive layer disposed on a first or second surface of the substrate opposite to the pigment layer, wherein the adhesive layer contains at least one adhesive, preferably a heat-activated adhesive, and more preferably a pressure-sensitive adhesive.

13. The thermal recording material according to any one of the preceding claims, characterized in that, The thermal recording material is defined according to this specification and, in particular, has a strength of 12.79 mJ / mm². 2 The optical density measured at this energy level is at least 1.

35.

14. The thermal recording material according to any one of the preceding claims, characterized in that, The surface whiteness of the recorded material, measured according to ISO 5267:1995-03 standard, is 35-60%, particularly 45-50%.

15. A method for manufacturing a thermal recording material, comprising the following steps: A support substrate is provided, the support substrate having a first surface and a second surface opposite to the first surface; A pigment layer suspension is applied to the first or second surface of the supporting substrate, wherein, The colorant layer suspension contains at least one coloring substance; The pigment layer suspension is dried to obtain a pigment layer disposed on the first or second surface of the supporting substrate; A paint suspension is applied to the pigment layer, wherein the paint suspension contains a first material, and the first material contains at least one fatty acid and / or at least one fatty amide. The coating suspension contains a second material, which contains at least one fatty acid metal salt; the first material has a first melting temperature T. S1 The second material has a second melting temperature T. S2 The first melting temperature T S1 Below the second melting temperature T S2 ;as well as The coating suspension is dried to obtain a heat-sensitive layer disposed on the pigment layer.

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