Direct thermal print media having a coating of side chain crystalline polymeric material

Abstract

A direct thermal printing medium comprising side-chain crystalline materials is disclosed. The printing medium is substantially free of bisphenol A substances and retains its color for an extended period when exposed to light and / or temperatures ranging from, for example, -15°C to 45°C.

Description

[0001] Priority Statement This invention claims priority to U.S. Patent Application No. 18 / 958,742, filed November 25, 2024, the entire contents of which are incorporated herein by reference. Background Technology

[0002] Direct thermal printing uses a thermal medium to create an image by selectively heating the medium, typically on a pixel-by-pixel or line-by-line basis. Heating produces color changes, most commonly from light to dark, which creates text, graphics, or images. Thermal exposure from a direct thermal printer activates chemicals in or on the medium, causing color changes and producing the desired print. Summary of the Invention

[0003] In one embodiment, a thermal printing medium is provided, the thermal printing medium comprising: a transparent or translucent substrate; a thermal layer on a first surface of the substrate, the thermal layer comprising: a thermal polymer; and an adhesive that adheres the thermal polymer to the first surface; a colored adhesive layer on a second surface of the substrate; and a removable release liner in contact with the colored adhesive layer; wherein, in response to heat exposure at a selected location on the printing medium at a temperature above a predetermined threshold temperature, the thermal layer irreversibly becomes transparent or translucent at the selected location, thereby revealing the color of the colored adhesive at the selected location.

[0004] In some embodiments, the second surface is opposite to the first surface.

[0005] In some embodiments, the thermosensitive polymer is selected from side-chain crystalline (SCC) polymers or side-chain liquid crystal polymers (SCLCP).

[0006] In some embodiments, the thermosensitive layer irreversibly becomes transparent or translucent at the selected location due to a change in the crystallinity of the thermosensitive polymer.

[0007] In some embodiments, the thermal layer covers about 80% to about 100% of the first surface of the substrate.

[0008] In some embodiments, the thermally sensitive layer has optical transparency sufficient to obscure the colored adhesive before the heat exposure. In some embodiments, the thermally sensitive layer has optical transparency of about 2% to about 5% before the heat exposure and about 90% to about 95% after the heat exposure.

[0009] In some embodiments, the colored adhesive is applied to about 80% to about 100% of the second surface of the substrate.

[0010] In some embodiments, the coloring adhesive comprises water-based ink. In a variation of this embodiment, the coloring adhesive comprises carbon black in an amount sufficient to allow the dark color to be visible through the transparent or translucent substrate and the heat-sensitive layer at the selected location after the heat-sensitive layer has become transparent or translucent at the selected location.

[0011] In some embodiments, the coloring adhesive contains about 1% to about 25% pigment by weight of the coloring adhesive.

[0012] In some embodiments, the transparent or translucent substrate comprises polyethylene terephthalate (PET), biaxially oriented polypropylene (BOPP), cast polypropylene (CPP), cast polypropylene (PE), polypropylene (PP), ethylene vinyl acetate (EVA), or ethylene vinyl alcohol (EVOH), or combinations thereof. In a variation of this embodiment, the transparent or translucent substrate is a polymer film. In some embodiments, the polymer film comprises PET or BOPP.

[0013] In some embodiments, the thermosensitive polymer is an SCC polymer.

[0014] In some embodiments, the melting point (T) of the SCC polymer is... m The temperature range is from about 40°C to about 300°C. In some embodiments, the melting point (T0) of the SCC polymer is... m The temperature range is from approximately 40°C to approximately 100°C.

[0015] In some embodiments, the SCC polymer is approximately 20% by weight (w / w) to approximately 50% by weight of the coating on the substrate.

[0016] In some embodiments, the SCC polymer and the adhesive are mixed in water at a ratio ranging from about 10:1 to about 1:10 and then coated onto the substrate.

[0017] In some embodiments, the SCC polymer is an acrylate. In some embodiments, the SCC polymer contains a plurality of C... 16 -C 30 Polyalkyl acrylates with alkyl side chains. In some embodiments, the number-average molecular weight of the SCC polymer is from about 60,000 Daltons to 120,000 Daltons.

[0018] In some embodiments, the adhesive comprises anionic acrylates. In some embodiments, the adhesive comprises hydroxyalkyl acrylates.

[0019] In some embodiments, the thermal printing medium described herein may further include a varnish outer coating superimposed on the thermal layer. In some embodiments, the varnish outer coating comprises a water-based acrylic emulsion. In some embodiments, the varnish outer coating is a transparent outer coating. In some embodiments, the varnish outer coating further comprises paraffin wax and / or carnauba wax.

[0020] In some embodiments, the thermal printing media described herein retains its color for at least one year when exposed to light (e.g., ultraviolet (UV) light) and / or temperatures ranging from -15°C to 45°C. In some embodiments, the thermal printing media described herein retains its color for at least three months, six months, one year, or two years when exposed to light (e.g., ultraviolet (UV) light) and / or temperatures ranging from -15°C to 45°C or from -30°C to approximately 55°C.

[0021] In one embodiment, a method for preparing the thermal printing media described herein is provided, the method comprising: receiving a substrate; coating a thermal layer comprising a thermal polymer and an adhesive over a first surface of the substrate covering approximately 80% to approximately 100%; coating a colored adhesive over a second surface of the substrate opposite the first surface covering approximately 80% to approximately 100%; placing a removable release liner in contact with the colored adhesive; and optionally overlaying a varnish outer coating onto the thermal layer.

[0022] In some embodiments, the method further includes contacting the printable medium with a direct thermal printhead to provide the printed medium.

[0023] In some embodiments, the method further includes removing the pad and applying the printed medium onto the surface.

[0024] In an additional embodiment, a thermal printing medium is provided, comprising: a substrate; a coloring layer on a first surface of the substrate; a thermal layer superimposed on the coloring layer, the thermal layer comprising: a thermal polymer; an adhesive adhering the thermal polymer to the coloring layer; an adhesive on a second surface of the substrate opposite to the first surface; and a removable release liner in contact with the adhesive; wherein, in response to heat exposure at a selected location on the printing medium at a temperature above a predetermined threshold, the thermal layer irreversibly becomes transparent or translucent at the selected location, thereby revealing the color of the coloring layer at the selected location. The thermal layer irreversibly becomes transparent or translucent at the selected location within a temperature range of about 65°C to about 150°C; wherein the thermal polymer comprises a plurality of components having a length range of C... 16 To C 30 The polyalkyl acrylate is prepared from a monomer with a side chain; wherein the number average molecular weight of the thermosensitive polymer is from about 60,000 Daltons to about 120,000 Daltons; and wherein the thermosensitive layer covers the surface of the colored layer by about 80% to about 100%.

[0025] In an additional embodiment, a thermal printing medium is provided, comprising: a substrate; a thermal layer superimposed on a first surface of the substrate, the thermal layer comprising: a thermal polymer; an adhesive adhering the thermal polymer to the first surface; and pigment; an adhesive layer on a second surface of the substrate opposite to the first surface; and a release liner in contact with the adhesive; wherein, in response to heat exposure at a selected location on the printing medium at a temperature above a predetermined threshold temperature, the thermal layer irreversibly becomes transparent or translucent at the selected location, thereby revealing the color of the pigment at the selected location. The thermal layer irreversibly becomes transparent or translucent at the selected location within a temperature range of about 65°C to about 150°C; wherein the thermal polymer comprises a plurality of components having a length range of C... 16 To C 30 The polyalkyl acrylate is prepared from a monomer with a side chain; wherein the number average molecular weight of the thermosensitive polymer is from about 60,000 Daltons to about 120,000 Daltons; and wherein the thermosensitive layer covers about 80% to about 100% of the substrate. Attached Figure Description

[0026] The accompanying drawings (in which the same reference numerals refer to the same or functionally similar elements throughout the individual views) are incorporated in and form part of this specification together with the following detailed description, and serve to further illustrate embodiments including the concepts of the claimed apparatus, methods and devices, and to explain the various principles and advantages of these embodiments.

[0027] Figure 1 A first configuration of a thermal printing medium according to an embodiment of the present disclosure is shown.

[0028] Figure 1A It shows Figure 1 The printed thermal medium of the embodiment shown.

[0029] Figure 2 A second configuration of a thermal printing medium according to an embodiment of the present disclosure is shown.

[0030] Figure 2A It shows Figure 2 The printed thermal medium of the embodiment shown.

[0031] Figure 3 A third configuration of a thermal printing medium according to an embodiment of the present disclosure is shown.

[0032] Figure 3A It shows Figure 3 The printed thermal medium of the embodiment shown.

[0033] Figure 4 A thermal printing medium configured as a sheet is shown according to an embodiment of the present disclosure.

[0034] Figure 5 A thermal printing medium configured as a roll is shown according to an embodiment of the present disclosure.

[0035] Figure 6 A thermal printing medium configured as a thermal printing self-adhesive label web is shown according to an embodiment of the present disclosure.

[0036] Figure 7 Results from Example 1 are shown, based on embodiments of the present disclosure.

[0037] Figure 8 Results from Example 1 are shown, based on embodiments of the present disclosure.

[0038] Figure 9 Results from Example 4, based on embodiments of the present disclosure, are shown.

[0039] Figure 10 The results of using varnish are shown according to embodiments of the present disclosure.

[0040] Figure 11 Showing from Figure 3 The results of the implementation shown.

[0041] Those skilled in the art will understand that the elements in the figures are shown for simplicity and clarity and are not necessarily drawn to scale. For example, some elements in the figures may be exaggerated relative to others to help improve the understanding of embodiments of this disclosure.

[0042] The components of the apparatus and methods have been indicated by conventional symbols in the accompanying drawings where appropriate, showing only those specific details relevant to understanding embodiments of this disclosure, so as not to obscure the description with details that would be readily apparent to those skilled in the art who would benefit from the description herein. Detailed Implementation

[0043] Direct thermal printing eliminates the need for ink, toner, or ribbons, thus reducing environmentally harmful waste. However, currently used direct thermal printing substrates incorporate thermochromic developers that contain, for example, environmentally harmful bisphenols. In contrast, the printing media described herein utilizes water-based pigments incorporated into the binder layer and does not contain harmful bisphenols.

[0044] Another problem with many common thermal printing media is that prints produced by the thermal printing process fade after a certain period of time, rendering the printed media unreadable. The thermal printing media discussed in this article are robust and retain printed images or text for a much longer period compared to many common thermal printing media.

[0045] The thermal printing media described herein comprises an opaque thermal layer superimposed on a transparent or translucent substrate. Further, the thermal printing media described herein includes a coloring layer initially obscured by the opaque thermal layer. In some cases, this coloring layer may be formed from pigments mixed into an adhesive on the opposing surface of the transparent or translucent substrate. When a specific portion of the thermal printing media described herein is heated with a thermal printer (e.g., in the shape of an image or alphanumeric character), heat from the printhead melts the thermal layer in the heated area, irreversibly changing the thermal layer from opaque to transparent or translucent, thereby revealing the color of the coloring adhesive, which is subsequently visible through the transparent or translucent substrate and the thermal layer. Therefore, the printing media described herein has a different layered structure compared to currently used thermal printing media.

[0046] Because the color change does not occur within the coloring layer, pigments that are durable and resistant to extreme environmental effects can be selected. Similarly, the opaque layer can maintain its transparency or translucency more or less indefinitely, and when exposed to elevated temperatures, it maintains its transparency or translucency for a significantly longer period than conventional thermal printing media would retain their color. Furthermore, conventional thermal printing media may change color over time when exposed to sunlight or elevated temperatures, thus reducing the expected readability lifetime of conventional thermal labels. Some exemplary embodiments of this disclosure demonstrate a much superior readability lifetime, including when exposed to sunlight or elevated temperatures, such as in a vehicle passenger compartment.

[0047] definition All numerical representations, such as volume and mass, are approximations, which are varied (+) or (-) in increments of 1.0 or 0.1, depending on the context. It should be understood that, although not always explicitly stated, all numerical representations are preceded by the term "approximately".

[0048] As used herein, unless the context clearly indicates otherwise, the singular indefinite articles "a" and "an" (meaning "a kind of, one") and the definite article "the" (meaning "the, the subject") include plural referents.

[0049] The terms “substantially,” “basically,” “about,” “approximately,” or any other version thereof are defined as close to what is understood by one of ordinary skill in the art, and in one non-limiting embodiment, the term is defined as within 10% of such defined quantity, parameter, or feature, in another embodiment within 5%, in another embodiment within 1%, in another embodiment within 0.5%, which should be understood by one of skill in the scientific context in which the term is used.

[0050] As used herein, the terms “comprising,” “containing,” and “including” are intended to mean that the compositions, preparations, and / or methods disclosed herein include the listed elements but do not exclude other elements.

[0051] Number-average molecular weight (M) n ) is the statistical average molecular weight of all polymer chains in the sample, and is defined as: Where M i It is the molecular weight of the chain, and N i It is the number of chains with that molecular weight. Mn can be predicted by the polymerization mechanism and measured by determining the number of molecules in a sample of a given weight.

[0052] "Optical transparency" refers to the ratio of transmitted light flux to incident light flux, and is a measure of the transmittance of light through a thermosensitive polymer.

[0053] Pigments are finely ground solid particles that provide color and opacity to inks. Typically, pigments include colored, black, white, or fluorescent organic or inorganic solids that are insoluble in or unaffected by the substrate or medium in which they are incorporated.

[0054] "Thermosensitive layer" and "thermosensitive polymer" refer to materials that undergo physical changes (e.g., melting) when exposed to a threshold temperature, thereby altering their optical transparency.

[0055] As used herein, “the thermal layer irreversibly becomes transparent or translucent at a selected location” means that after the thermal polymer in the thermal layer has undergone a change in optical transparency during direct thermal printing, the thermal polymer will not revert to its initial optical transparency during the duration of use of the printing medium (e.g., from about 1 month to about 2 years or longer), or under conditions that the printing medium is typically exposed to (such as temperature and / or incident light). In other words, the thermal layer has irreversibly become transparent or translucent at a selected location.

[0056] In one embodiment, the thermal printing medium of this invention includes a transparent or translucent substrate on which a thermal layer is superimposed on a first surface. For example, about 80% to 100% or about 50% to 80% of the first surface of the substrate is covered by the thermal layer. In some embodiments, about 100% of the first surface of the substrate is covered by the thermal layer. In another embodiment, the thermal printing medium of this invention includes a transparent or translucent substrate on which a colored adhesive is superimposed on a second surface of the transparent or translucent substrate opposite the first surface, wherein the first surface has already been covered with a thermal layer. For example, about 80% to 100% or about 50% to 80% of the second surface of the substrate is covered by the colored adhesive. In some embodiments, about 100% of the second surface of the substrate is covered by the colored adhesive.

[0057] In some embodiments herein, the thermosensitive polymer is a homopolymer or a mixture of copolymers, and is a reaction product of various monomers having alkyl side chains optionally functionalized with hydroxyl, ester, amide, N-alkylamino, N,N-dialkylamino, or ether groups. In some embodiments, the length of the alkyl side chain ranges from C0. 16 Alkyl to C 30 Alkyl, C 16 Alkyl to C 28 Alkyl, C 16 Alkyl to C 26 Alkyl or C16 Alkyl to C 24 alkyl.

[0058] The side chains in the thermosensitive polymer are selected to form crystalline regions and may contain, for example, -(CH2). n - and / or -((CH2) m -O-)n groups. The side chain is preferably straight-chain to facilitate crystallization. For crystallizable side chains containing -(CH2) groups... n -Thermosensitive polymers with -(CH2) groups, where n can range from about 6 to about 35, or from about 16 to about 30. For thermosensitive polymers containing -(CH2) groups in their crystallizable side chains... m Thermosensitive polymers with -O-)n groups, where m can range from about 1 to about 35, or from about 10 to about 30. In some embodiments, m and n are selected, and the spacing between side chains, as well as the length and type of side chains, are selected to provide a thermosensitive polymer with a desired melting point.

[0059] The spacing between side chains, as well as the length and type of side chains, are selected to provide a thermosensitive polymer with a melting point in the range of about 40°C to about 100°C. As the spacing between side chains increases, the tendency for the side chains to crystallize tends to decrease. As the flexibility of the side chains increases, the tendency for the side chains to crystallize tends to decrease. As the length of the side chains increases, the tendency for the side chains to crystallize tends to increase. In some embodiments, the length of the crystallizable side chains can be about two to about ten times the average distance between the crystallizable side chains in the thermosensitive polymer. Examples of thermosensitive polymers include, but are not limited to, poly(1-olefin), poly(alkyl acrylate), poly(alkyl methacrylate), poly(alkyl vinyl ether), and / or poly(alkyl styrene), or any combination thereof.

[0060] The thermal printing media described herein are printable at various temperatures ranging from about 40°C to about 110°C, about 40°C to about 100°C, about 40°C to about 80°C, or about 40°C to about 65°C, and the melting temperature of the thermal polymer is tunable depending on the selection of the length of the alkyl side chain. For example, containing C 26 Alkyl-side-chain acrylate homopolymers can provide a melting point of approximately 80°C for thermosensitive polymers, containing C 30 alkyl-side-chain acrylate homopolymers can provide a melting temperature of approximately 80°C for thermosensitive polymers.

[0061] The ability to overlay a substrate with a heat-sensitive layer also depends on the viscosity of the polymer emulsion used to coat the substrate. The viscosity of the polymer emulsion containing the heat-sensitive polymer can range from about 500 cps to 3500 cps. The emulsion may contain water, isopropanol, n-propanol, 2-(2-butoxyethoxy)ethanol, ethers (e.g., ethylene glycol monobutyl ether, diethylene glycol monobutyl ether), or any combination thereof.

[0062] By selecting an appropriate number-average molecular weight and an appropriate side chain length, the melting temperature (T0) of the thermosensitive polymer can be controlled. m The thermal polymer used herein for thermal printing media can be variably configured. In some embodiments, the number-average molecular weight of the thermal polymer used herein ranges from about 60,000 Daltons to 120,000 Daltons, or from about 80,000 Daltons to about 100,000 Daltons. Therefore, the thermal printing media herein can develop color at different temperatures, thereby allowing compatibility with a variety of printers and printing settings, ideally without compromising print quality.

[0063] In some examples, the proportion (by weight) of the thermosensitive polymer in the coating superimposed on a transparent or translucent substrate is about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, or about 75%. In some embodiments, about 20% to about 75%, about 20% to about 50%, or about 25% by weight (w / w) to about 60% by weight of the coating superimposed on the transparent or translucent substrate is composed of a thermosensitive polymer, providing optical transparency (e.g., optical transparency of about 1% to about 10%) that can mask colored adhesives. In some embodiments, the thermosensitive layer is substantially free of additives selected from cavitation agents, β-nucleating agents, crystallizable solvents, or colorants. Without being bound by any theory, it is believed that the thermosensitive polymer used herein undergoes an irreversible change in crystallinity, thereby making the printed area transparent or translucent (e.g., optical transparency of about 80% to about 100%), thus revealing the colored printed area.

[0064] The thermosensitive polymer is prepared as an emulsion in a suitable solvent and added to a mixture of the adhesive and water to provide a final coating solution, which is then layered onto the substrate. In some embodiments, the adhesive is a hydroxyalkyl acrylate in an aqueous emulsion. Other adhesives, such as acrylic dispersions, acrylic emulsions, water-dilutable epoxy esters, and styrene-acrylic emulsions, can also be used. The ratio of the thermosensitive polymer to the adhesive can be variably configured to provide low initial optical transparency. Figure 7 Examples are provided of the effects of variations in the polymer:binder (P / B) ratio on the optical transparency of the thermal layer. In some embodiments, the P / B ratio ranges from about 1:10 to 10:1. In some embodiments, the P / B ratio is 10, 5, 3.5, 2.5, 2.0, or 1. In some embodiments, the binder is in the form of about 25% to 30% by weight in the emulsion or solution, for example, an aqueous solution of acrylate (e.g., hydroxyalkyl acrylate). The optical transparency of the thermal layer is initially about 1% to about 10%, and after thermal printing, the optical transparency of the thermal layer is about 90% to about 100%.

[0065] The weight percentage of solids in the mixture used for overlaying the substrate (i.e., the mixture of the thermosensitive polymer emulsion and the adhesive) can be an amount that allows for the formation of at least about 80% of a continuous film for the overlay substrate. If the weight percentage of solids in the mixture used for overlaying the substrate is too high, the flood coating may be flake-like, resulting in uneven deposition of the thermosensitive layer on the substrate, thus affecting the quality of direct thermal imaging / printing. In some embodiments, the weight percentage of solids in the mixture used for overlaying the substrate ranges from about 30% to about 50% by weight, or from about 40% to about 45% by weight, of the mixture comprising the thermosensitive polymer, adhesive, and solvent. After the thermosensitive layer is overlayed onto the substrate, the substrate is dried to remove most of the solvent.

[0066] Additional components, such as surfactants / wetting agents, humectants (e.g., polyethylene glycol), thickeners, and / or defoamers, may be included in the mixture of thermosensitive polymers and adhesives superimposed on the substrate.

[0067] Although thermosensitive polymers have been described above in the context of side-chain crystalline polymers, this paper also envisions side-chain liquid crystal polymers (SCLCPs) that can be tuned to desired melting temperatures and used in the thermal printing media described herein.

[0068] Containing pigments (e.g., water-based pigments) in the layer initially covered by the thermal layer advantageously avoids the use of thermochromic inks previously used in thermal printing media and which may contain bisphenol-based substances. Therefore, in some embodiments, the thermal printing media of the present invention does not contain environmentally harmful bisphenol-based substances. Non-limiting examples of water-based pigments include carbon black, Neo Colors manufactured by Matsui, plant-derived pigments, or metal-based pigments. The pigment loading in the binder ranges from about 1% to about 25% by weight, about 1% to about 20% by weight, or about 2% to about 10% by weight of the colored binder. While separate layers can be used (as will be disclosed in more detail later), it is advantageous to provide a colored layer by including the pigment in a label adhesive layer applied to the side of a transparent substrate opposite to the side having the thermal layer. The adhesive may be a pressure-sensitive adhesive, such as an acrylic adhesive. The pigment is mixed in an aqueous solution of the adhesive (e.g., an acrylic adhesive). Other examples of adhesives include, but are not limited to, acrylic copolymers, polyisobutylene rubber, silicone, styrene block copolymers, acrylic / vinyl acetate copolymers, and polyurethane / acrylic copolymers. Examples of commercially available adhesives include Butofan® NS 166 (aqueous polymer dispersion of styrene / butadiene copolymer), Acronal® DS 3598 NA (acrylic copolymer dispersion), Robond® PS-7735 and PS-68HV (water-based acrylics), Rhoplex® N-619 (acrylic emulsion), Alberdingk® AC 75025 VP (acrylic polymer emulsion), Alberdingk® AC 7514 (dispersion of acrylate copolymers), Alberdingk® AC 75013 (polyurethane and acrylate dispersions), Covinax® 289-01 DEV (acrylic copolymer), and Covinax® 386-07 (vinyl-modified acrylic copolymer). Pigments can be surface-treated or pre-dispersed in water (with surfactants / stabilizers and / or in combination with polymer dispersion additives or binder resins) to reduce agglomeration, and then mixed into the aqueous solution of the binder.Examples of commercially available black pigments include: NeoBlack® (Matsui) – an aqueous carbon black concentrate, resin-free; AquaBlack® 5106 (Chromascape) – non-resin-based, surfactant-based; AquaBlack® 8386 (Chromascape) – a modified acrylic resin, low in surfactants; Raven® 900 (Birla Carbon) – a surface-modified powder; BlackShield® 11B760 (DyStar) – a non-resin-based aqueous dispersion; and BlackShield® 11B701 (DyStar) – an acrylic resin, aqueous dispersion.

[0069] The adhesive layer contacts a removable backing (release liner) that can be removed during or after printing. In some embodiments, the coloring adhesive contains carbon black in an acrylate. In some embodiments, the coloring adhesive contains a solution of Neo Colors manufactured by Matsui in an acrylate. In some embodiments, the adhesive is environmentally friendly and substantially formaldehyde-free. In some embodiments, the adhesive is an acrylate, a cyanoacrylate, or an epoxide.

[0070] For example, the release liner can be a wood-free paper double-laminated with polyethylene and coated with silicone.

[0071] Figure 1 A cross-section of a thermal printing medium 100 according to a first embodiment is shown. The substrate 130 is transparent or translucent. In some embodiments, the substrate is a polymer film comprising polyethylene terephthalate (PET), biaxially oriented polypropylene (BOPP), cast polypropylene (CPP), polyethylene (PE), polypropylene (PP), ethylene vinyl acetate (EVA), or ethylene vinyl alcohol (EVOH), or any combination thereof. In some embodiments, the substrate 130 is a polymer film comprising PET or BOPP. A thermal layer 140 is disposed on a first surface of the substrate 130. The thermal layer 140 may cover the entire first surface of the substrate 130, or may cover about 80% to about 100% of the first surface of the substrate 130. The thermal layer may comprise an SCC polymer as described above, such as having C 16 To C 30Alkyl acrylate with alkyl side chains. The pigment is incorporated into the adhesive. The colored adhesive 120 is disposed on the second surface of the substrate 130 opposite the first surface. The pigment can be a water-based pigment without bisphenols as described above, and can be incorporated into a pressure-sensitive adhesive (such as an acrylate). If the thermosensitive layer is opaque and light-colored in its initial state (or has a light-colored appearance due to light scattering), the pigment is dark, and preferably black. After direct thermal imaging, the portions of the thermosensitive layer will appear as... Figure 1A The image becomes transparent, revealing the color of the colored adhesive, i.e., the printed image. The colored adhesive 120 may cover the entire second surface of the substrate 130, or may cover about 80% to about 100% of the second surface of the substrate 130. Patterned adhesive placement or partial coverage can be made, but this can only simultaneously reduce the intended printable area of ​​the medium—in the example described in this section, the medium cannot be printed using the methods described in this disclosure in areas of the substrate where no colored adhesive has been applied. A removable release liner 110 is placed in contact with the colored adhesive 120. As shown by dashed lines, the thermal polymer layer 140 is optionally overlaid with a varnish 150. When the thermal layer 140 is overlaid with the varnish layer 150, the varnish layer 150 remains transparent, while the thermal layer 140 is initially opaque and becomes translucent or transparent in the imaging area after direct thermal printing.

[0072] The substrate 130 can be coated using a flow coating method, or in alternative embodiments, a heat-sensitive layer can be applied by spraying or by flexo coating. The colored adhesive 120 can be transferred onto the substrate 130 using a gravure coater, slot coater, or roller coater.

[0073] exist Figure 1 In an alternative design to the first embodiment shown, instead of incorporating color into the adhesive, a colored layer can be provided on the second surface of the substrate between the substrate and the adhesive layer.

[0074] Figure 1A Showing the target Figure 1 The cross-section of the thermal printing medium in the embodiment of the invention, wherein the imaging area in the thermal layer is transparent or semi-transparent.

[0075] Figure 2A cross-section of a thermal printing medium 200 according to a second embodiment is shown. Using, for example, a gravure coater, slot coater, or roller coater, a pigment 240 is deposited on the first surface of a substrate 230. The pigment may be a water-based pigment free of bisphenol A, as described above. The substrate comprises a material selected from the group consisting of: paper, paperboard, cardboard, cotton, flax, jute, ramie, industrial hemp, or rayon, polyamide, polyester, polyacrylate, polyurethane, or ethylene-based fibers, cellulosic fiber-based and non-cellulosic fiber blends; polymer resins; and composites of polymer resins with cellulosic or non-cellulosic fiber materials; and combinations thereof. In a variation of this embodiment, the substrate is paper. Figure 1 In different implementations, the substrate 230 does not need to be transparent or translucent because the coloring layer is disposed between the thermosensitive layer and the substrate, rather than on the other side of the substrate. The pigment layer 240 may cover the entire first surface of the substrate 230, or may cover about 80% to about 100% of the first surface of the substrate 230. The pigment may be a water-based pigment as described herein. The thermosensitive layer 250 is stacked on the pigment layer 240 by flow coating or flexible coating. The thermosensitive layer may contain an SCC polymer as described above, such as having C 16 To C 30 Alkyl acrylate with alkyl side chains. As shown by the dashed lines, the thermal layer 250 is optionally overlaid with a varnish 260. When the thermal layer 250 is overlaid with the varnish layer 260, the varnish layer 260 remains transparent, while the thermal layer 250 is initially opaque and becomes translucent or transparent in the imaging area after direct thermal printing.

[0076] After direct thermal imaging, the various parts of the thermally sensitive layer will appear as follows: Figure 2A The image becomes transparent or translucent, revealing the color of the pigment, i.e., the printed image. Using, for example, a gravure coater, slot coater, or roller coater, an adhesive layer 220 is applied to the second surface of the substrate 230 opposite the first surface. For example, the adhesive may include acrylate or other adhesives described herein. The adhesive layer 220 is brought into contact with the removable release liner 210.

[0077] Figure 2A Showing the target Figure 2 The cross-section of the thermal printing medium in the embodiment of the invention, wherein the imaging area is transparent.

[0078] Figure 3A cross-section of a thermal printing medium 300 according to a third embodiment is shown. A layer 340 is superimposed on a first surface of a substrate 330, the layer comprising a thermal polymer mixed with pigment. The layer 340 is superimposed on the substrate 330 by flow coating or flexible coating. In this embodiment, the layer 340 may be opaque or light-colored (e.g., light gray). The thermal polymer may be an SCC polymer as described above, such as having C 16 To C 30 Alkyl acrylate with alkyl side chains. The pigment can be a water-based pigment as described above. After direct thermal imaging, the portions of the thermosensitive layer will appear as... Figure 3A The image becomes transparent, revealing the color of the pigment, i.e., the printed image. Substrate 330 comprises a material selected from the group consisting of: paper, cardboard, hardboard, cotton, flax, jute, ramie, industrial hemp, or rayon, polyamide, polyester, polyacrylate, polyurethane, or ethylene-based fibers, cellulosic fiber-based and non-cellulosic fiber blends; polymer resins; and composites of polymer resins with cellulosic or non-cellulosic fiber materials; and combinations thereof. In a variation of this embodiment, the substrate is paper. In a third embodiment, substrate 330 may have an initial color, preferably dark or black, which may be the inherent color of the material, or the color may be obtained by dyeing the substrate or otherwise including pigments in the substrate. Alternatively, the substrate may have an initial neutral color. Layer 340 may cover the entire first surface of substrate 330, or may cover about 80% to about 100% of the first surface of substrate 330. As shown by the dashed lines, layer 340 is optionally superimposed with a varnish layer 350. When layer 340 is superimposed with varnish layer 350, varnish layer 150 remains transparent, while layer 340 is initially opaque and becomes translucent or transparent in the imaging area after direct thermal printing.

[0079] An adhesive layer 320 is coated on the second surface of the substrate 330, opposite to the first surface. The adhesive layer 320 is brought into contact with the removable release liner 310.

[0080] Figure 3A Showing the target Figure 3 The cross-section of the thermal printing medium in the embodiment of the invention, wherein the imaging area is colored.

[0081] Figure 4 It shows Figure 1 , Figure 1A , Figure 2 , Figure 2A , Figure 3 or Figure 3AA top view of a sheet 400 of thermal printing material according to any of the embodiments described herein, the sheet comprising a substrate 410 and a thermal layer 415 disposed in a printable region 420. The thermal printing sheet 400 may have a size ratio consistent with a letter-size sheet; however, this disclosure contemplates embodiments in which the thermal printing medium includes any side-length ratio. This disclosure further contemplates embodiments in which the thermal layer 415 of the sheet 400 occupies the entire surface of the substrate 410, asymmetrical portions of the substrate 410, and / or any configuration of non-printable boundaries on the sheet 400. In an alternative embodiment, the substrate 410 has a layer 415 superimposed thereon, wherein the layer 415 further comprises pigment. In another alternative embodiment, the substrate 410 has a pigment layer thereon, the pigment layer overlaid with the thermal layer 415. In various embodiments, an optional varnish is superimposed on the thermal layer 415.

[0082] Figure 5 It shows Figure 1 , Figure 2 or Figure 3 The roll 500 of thermal printing material in any of the embodiments described herein includes a substrate 410 and a thermal layer in a printable region 420. The roll 500 is configured as a continuous substrate strip 410 wound around a spool. According to some embodiments, the roll 500 of thermal printing material is suitable for applications using thermal roll printers for printing media such as receipts, tickets, and other forms with a constant width and variable length. Although shown with non-printable boundaries, this disclosure contemplates embodiments where the printable region 420 extends to the edge of the substrate 410. Optionally, if the label is intended to be torn or broken, the roll 500 may include lines of weakness 450 between the labels. These can be achieved by various methods, such as partial cutting using a laser, punching, folding, embossing, or other methods. If the roll is intended for use with a printer with a cutter, this feature may be included (if alignment between the cut line and the weak point line is maintained) or omitted.

[0083] Figure 6 It shows Figure 1 , Figure 2 or Figure 3A roll 500 of thermally printed label 440, comprising a substrate 410, a thermal layer 415 disposed in a printable area 420, and a backing 430, is described in any of the embodiments described herein. The roll 500 of thermally printed label 440 is configured as a web of label 440, the web being temporarily adhered to the backing 430, the backing including, in some examples, a peel surface allowing the label 440 to be easily removed for application to a body product. Label 440 includes an adhesive backing on the surface of substrate 410 opposite the printable area 420, the label being temporarily adhered to the backing and then to the body product. Although shown as having non-printable boundaries, this disclosure contemplates embodiments in which the printable area 420 of each label 440 extends to the edge of substrate 410. The roll 500 may include weak-point lines 450 between labels. The scope of this disclosure further includes embodiments in which the webs of the labels are configured as fan-shaped folded stacks.

[0084] The thermal printing media described herein has a total thickness of about 0.05 mm to about 0.3 mm and includes a substrate film, an adhesive or colored adhesive, a removable pad, and an optional varnish layer.

[0085] In some embodiments, the thickness of the heat-sensitive layer ranges from about 0.02 mm to about 0.05 mm, the thickness of the transparent substrate ranges from about 0.02 mm to about 0.2 mm, and the thickness of the colored adhesive layer ranges from about 0.01 mm to about 0.05 mm. In some embodiments, when a colored adhesive is used, such as in... Figure 1 and Figure 1A In the first embodiment, to ensure uniform color and adhesion, the weight percentage of pigment in the colored adhesive ranges from about 1% to about 25%. The thickness of the colored adhesive layer ranges from about 0.01 mm to about 0.02 mm.

[0086] In some embodiments, the thickness of the heat-sensitive layer ranges from about 0.02 mm to about 0.05 mm, the thickness of the pigment layer on the substrate is less than about 0.01 mm, the thickness of the substrate is from about 0.02 mm to about 0.2 mm, and the thickness of the adhesive is from about 0.01 mm to about 0.05 mm. In some embodiments, such as in Figure 2 and Figure 2A In a second embodiment, the pigment layer on the substrate should be thinner than the thermosensitive layer to ensure appropriate opacity. In some of these embodiments, the ratio of the thickness of the pigment layer to the thickness of the thermosensitive layer is approximately 1:10.

[0087] In some embodiments, the substrate in the thermal printing medium described herein has a thickness suitable for supporting other layers, but thin enough to ensure the flexibility of the thermal printing medium. In some embodiments, the substrate thickness is not less than about 0.02 mm. In some embodiments, the substrate thickness ranges from about 0.02 mm to about 0.2 mm.

[0088] In some embodiments, the thermal layer should not be too thick to avoid affecting the melting of the thermal polymer during direct thermal printing and negatively impacting print quality. For example, if the thickness of the thermal layer exceeds 0.05 mm, the image print quality may be degraded. Therefore, in some embodiments, the thickness of the thermal layer ranges from about 0.02 mm to about 0.05 mm.

[0089] Figure 7 , Figure 8 , Figure 9 , Figure 10 and Figure 11 The experimental results are shown, and a discussion of these results can be found in the Examples section below.

[0090] Example Using a Zebra ZT610 printer, in direct thermal printing mode, 2ip (range 2-14ip), 203dpi resolution, depth range of 15 to 30, and printhead heating element temperature range of approximately 50°C to approximately 300°C, or approximately 180°C to approximately 200°C.

[0091] Example 1 Approximately 50% by weight of C 16 and C 18 An SCC polymer emulsion of acrylate is blended into Ottopol® 25-30 acrylic resin (30% aqueous solution) to obtain a mixture, which is then laminated onto a substrate (commercially available clear PET film). The opposing surfaces of the substrate are coated with a pressure-sensitive acrylic adhesive, i.e., black acrylic adhesive tape, which is then brought into contact with a silicone-coated paper release liner (PT25 NB manufactured by Lintec).

[0092] To achieve the appropriate opacity for the SCC coating, the ratio of SCC polymer emulsion to acrylic adhesive resin (P / B) was varied. In this experiment, the weight percentage of SCC polymer in the mixture ranged from approximately 24% to approximately 44%.

[0093] Figure 7 Results from the experiment are shown. Opacity is measured as optical density (OD) cyan value. An AP / B ratio of approximately 2.5 to approximately 10 provides higher opacity (less visible black).

[0094] Change the thickness of the thermal SCC layer. Figure 8 Results are shown from SCC adhesive mixtures with a P / B ratio of 10.0 flow-coated at different thicknesses of 0.4 mil (or 0.01 mm), 0.65 mil (or 0.017 mm), or 1.5 mil (or 0.038 mm). Figure 8 As shown, higher thickness increases opacity (less visible black).

[0095] In addition, a varnish can be applied over the thermal SCC layer to protect it, reduce peeling, and ensure that the coating remains intact during direct thermal printing.

[0096] Example 2 A colored water-based dispersion (e.g., NeoColors manufactured by Matsui) is mixed into a water-based pressure-sensitive adhesive (e.g., Covinax 289-01 DEV) at a ratio (e.g., about 1% to 25% by weight of pigment). The colored adhesive is then transferred onto a release liner using a gravure coater, slot coater, and / or roller coater. A clear film is then overlaid on the colored adhesive, such that the first surface of the clear film is in contact with the colored adhesive.

[0097] Approximately 50% by weight of C 16 and C 18 Thin film of SCC polymer emulsion of acrylate (T m The emulsion polymer is mixed with 30% by weight of Ottopol® 25-30 acrylic adhesive resin in an aqueous adhesive solution (approximately 48-49°C). The number average molecular weight of the emulsion polymer falls within the range of 80,000 to 100,000 Daltons. The mixture of SCC polymer and adhesive is flow-coated onto the opposite surfaces of the transparent film.

[0098] Adjust the ratio of SCC polymer emulsion to acrylic adhesive resin and the thickness of the flow coating to provide suitable optical transparency to mask colored backgrounds while maintaining the ability to image using a thermal printer.

[0099] When printing directly with thermal ink, the heat from the thermal printer melts the SCC coating according to the image being printed, making the SCC coating transparent, thereby revealing the color layer of the colored adhesive through the transparent film.

[0100] Example 3 A water-based ink (e.g., Matsui NeoColors WB dispersion) is mixed into an aqueous solution of 30% by weight of Ottopol® 25-30 acrylic binder. The colored mixture is then flexibly coated in a thin layer onto a base substrate (e.g., paper (Z-Select 4000T), polypropylene (PolyPro 4000T), or polyester (Z-Xtreme 4000T)) to provide a colored coated base substrate. Alternatively, a resin (or wax, wax / resin) containing pigment can be pre-printed into the base substrate in solid squares via thermal transfer.

[0101] Approximately 50% by weight of C 16 and C 18 SCC polymer emulsion of acrylate (T) m The emulsion polymer (at approximately 48-49°C) is added to 30% by weight of an aqueous solution of Ottopol® 25-30 acrylic resin adhesive. The number average molecular weight of the emulsion polymer falls within the range of 80,000 to 100,000 Daltons. The mixture of SCC polymer and adhesive is then applied in a thin lamination to overlay a colored, coated base substrate.

[0102] The ratio of SCC polymer emulsion to acrylic adhesive resin and the thickness of the opaque coating are adjusted to provide suitable opacity to cover a colored background, but such that the opaque coating can appear transparent or translucent when imaged with a thermal printer.

[0103] When printing directly with thermal ink, the heat from the thermal printer melts the SCC coating, making it transparent and revealing the color of the coated base substrate.

[0104] Example 4 Approximately 50% by weight of C 16 and C 18 Thin film of SCC polymer emulsion of acrylate (T m An aqueous solution of 30% Ottopol® 25-30 acrylic adhesive resin (approximately 48-49°C) is mixed in and flow-coated over a single-layer matte black stripe #67100B-20KT. The number average molecular weight of the emulsion polymer falls in the range of 80,000 to 100,000 Daltons.

[0105] Adjust the ratio of SCC polymer emulsion to acrylic adhesive resin and the thickness of the flow coating to provide suitable opacity (e.g., optical transparency of about 1% to about 10%) to cover the black background while maintaining the ability to image with a thermal printer.

[0106] When printing directly with thermal ink, the heat from the thermal printer melts the SCC coating, making it transparent and revealing the black layer. Figure 9 The results from this experiment are shown.

[0107] Figure 10 Results from some additional experiments are shown, in which varnish was superimposed on a heat-sensitive layer.

[0108] Figure 11 Results from an experiment in which pigment was incorporated into a thermal layer are shown. During direct thermal printing, heat from the thermal printer melts the thermal polymer, making it transparent and revealing the black pigment.

[0109] Specific embodiments have been described in the foregoing description. However, those skilled in the art will understand that various modifications and alterations can be made without departing from the scope of this disclosure as defined in the following claims. Therefore, this specification and drawings should be considered illustrative rather than restrictive, and all such modifications are intended to be included within the scope of the teachings of this invention. Furthermore, the described embodiments / examples / specific implementations should not be construed as mutually exclusive, but should be understood as being combinable if such combinations are permitted in any way. In other words, any feature disclosed in any of the foregoing embodiments / examples / specific implementations may be included in any of the other foregoing embodiments / examples / specific implementations.

[0110] Benefits, advantages, solutions to problems, and any elements that may lead to or make any benefit, advantage, or solution appear more apparent should not be construed as key, claimed, or essential features or elements of any or all claims. The claimed apparatus, method, and device are defined solely by the appended claims, including any amendments made during the pending period of this application and all equivalents of those published claims.

[0111] Furthermore, in this document, relational terms such as first, second, top, and bottom are used only to distinguish one entity or action from another, and do not necessarily require or imply any actual such relationship or order between such entities or actions. The terms “comprising,” “having,” “including,” “containing,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article of manufacture, or apparatus that comprises, has, includes, or contains a list of elements may include not only those elements but also other elements not expressly listed or inherent to such process, method, article of manufacture, or apparatus. Elements preceded by “comprising…a,” “having…a,” “including…a,” or “containing…a” do not, without further constraints, exclude the presence of additional identical elements in a process, method, article of manufacture, or apparatus that comprises, has, includes, or contains said elements. An apparatus or structure “configured” in a certain way is configured at least in that way, but may also be configured in ways not listed.

[0112] This abstract is provided to allow the reader to quickly determine the nature of the technical disclosure. It is understood that this document is not intended to interpret or limit the scope or meaning of the claims. Furthermore, as can be seen from the foregoing description, various features have been grouped together in various embodiments for the purpose of simplifying the disclosure. This approach of the disclosure should not be construed as reflecting that the claimed embodiments require more features than are expressly listed in each claim. Rather, as reflected in the following claims, the subject matter of the invention may reside in fewer than all features of a single disclosed embodiment. Therefore, the following claims are hereby incorporated into the specification, wherein each claim is, in itself, a separately claimed subject matter.

Claims

1. A thermal printing medium, the thermal printing medium comprising: Transparent or translucent substrate; A thermally sensitive layer, comprising, on a first surface of the substrate: Thermosensitive polymers; as well as An adhesive that bonds the heat-sensitive polymer to the first surface; A colored adhesive layer, the colored adhesive layer being disposed on the second surface of the substrate; as well as A removable release liner that contacts the colored adhesive layer; In response to heat exposure at a selected location on the printing medium at a temperature above a predetermined threshold, the thermal layer irreversibly becomes transparent or translucent at the selected location, thereby revealing the color of the colored adhesive at the selected location.

2. The thermal printing medium according to claim 1, wherein, The thermosensitive polymer is selected from side-chain crystalline (SCC) polymers or side-chain liquid crystal polymers (SCLCP).

3. The thermal printing medium according to claim 1, wherein, The irreversible transformation of the thermosensitive layer to transparency or translucency at a selected location is due to a change in the crystallinity of the thermosensitive polymer.

4. The thermal printing medium according to claim 1, wherein, At least one of the heat-sensitive layers coats about 80% to about 100% of a first surface of the substrate, or a colored adhesive coats about 80% to about 100% of a second surface of the substrate.

5. The thermal printing medium according to claim 1, wherein, The heat-sensitive layer has sufficient optical transparency to shield the colored adhesive before thermal exposure.

6. The thermal printing medium according to claim 5, wherein, The thermally sensitive layer has an optical transparency of about 2% to about 5% before thermal exposure and about 90% to about 95% after thermal exposure.

7. The thermal printing medium according to claim 1, wherein, The coloring adhesive contains water-based inks.

8. The thermal printing medium according to claim 1, wherein, The coloring adhesive contains carbon black in an amount sufficient to allow the dark color to be visible through the transparent or translucent substrate and the heat-sensitive layer at a selected location after the heat-sensitive layer becomes transparent or translucent at that location.

9. The thermal printing medium according to claim 1, wherein, The coloring binder contains about 1% to about 25% pigment.

10. The thermal printing medium according to claim 1, wherein, The heat-sensitive polymer is an SCC polymer, and the SCC polymer accounts for about 20% to about 50% by weight (w / w) of the coating on the substrate.

11. The thermal printing medium according to claim 1, wherein, The heat-sensitive polymer is an SCC polymer, and the SCC polymer and the adhesive are mixed in water at a ratio of about 10:1 to about 1:10 and coated onto the substrate.

12. The thermal printing medium according to claim 1, wherein, The thermosensitive polymer is an SCC polymer, and the SCC polymer contains a plurality of C... 16 -C 30 Alkyl polyacrylates with alkyl side chains.

13. The thermal printing medium according to claim 1, wherein, The thermosensitive polymer is an SCC polymer, and the number-average molecular weight of the SCC polymer is from about 60,000 Daltons to about 120,000 Daltons.

14. The thermal printing medium according to claim 1, wherein, The adhesive contains at least one of anionic acrylates or hydroxyalkyl acrylates.

15. The thermal printing medium according to claim 1, wherein the thermal printing medium further comprises a varnish outer coating, the varnish layer preferably comprising a water-based acrylic emulsion, the varnish outer coating being superimposed on the thermal layer.

16. The thermal printing medium according to claim 1, wherein, Thermal printing media retain their color for at least one year when exposed to light and / or temperatures ranging from -15°C to 45°C.

17. A method for preparing the thermal printing medium according to claim 1, the method comprising: Receive substrate; A heat-sensitive layer comprising a heat-sensitive polymer and an adhesive is coated on approximately 80% to approximately 100% of the first surface of the substrate; A colored adhesive is applied to about 80% to about 100% of the second surface of the substrate opposite to the first surface; Place the removable peel pad into contact with the colored adhesive; as well as Optionally, a varnish outer coating is superimposed on the heat-sensitive layer.

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