Primer with improved reflection and heat insulation properties for a microcapsule imaging system

Abstract

The primer layer (104) with improved reflectivity and heat insulation properties is provided for use in the microencapsulated thermal imaging sheet (100). The primer layer having a polymer binder, white fine particles in an amount of about 3 to about 60% by weight based on the total weight of the primer layer, a primer substrate (102), and hollow fine particles improves the reflectivity, color development, color density, and heat insulation of the microcapsule (108) imaging sheet containing it. The black backcoat (105) applied to the substrate on the opposite side of the primer layer further enhances the Dmax and E of the microcapsule imaging sheet and prevents premature exposure of the microcapsule imaging sheet in the laminated media. 10 ​

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Application No. 17 / 833,735, filed on June 6, 2022, which is hereby incorporated by reference in its entirety.

[0002] The present disclosure generally relates to the field of microcapsule imaging systems, and more specifically, to primers for use in microcapsule imaging systems.

Background Art

[0003] Since the 1980s, single - sheet self - contained full - color microcapsule imaging systems (e.g., Cycolor) have been developed. In these imaging systems, an imaging sheet containing a layer of microcapsules with a photocurable or photo - softening composition and a leuco dye in the internal phase is image - wise exposed to actinic radiation. Typically, the photosensitive composition includes a photopolymerizable, polyfunctional acrylate, a photoinitiator, and a color former. Generally, the microcapsules are image - wise cured by actinic radiation, and when the exposed imaging sheet is passed through a pressure roller, the microcapsules can rupture image - wise and release the internal phase encapsulated therein. The leuco dye thus released migrates to and reacts with a developer material to form a continuous - tone full - color image with a color density (or grayscale) modulated by exposure energy (time or pulse width), intensity (pulse amplitude), and / or pulse frequency. Such self - contained single - sheet imaging systems are available for lightweight, portable, high - speed printing applications.

Summary of the Invention

Problems to be Solved by the Invention

[0004] General microcapsule imaging systems have several drawbacks. For example, very high pressures are required to rupture the microcapsules, which causes inefficient dye release, a decrease in color density (Dmax), and slow color development. These problems may be partially solved by using larger microcapsules, but as the size of the microcapsules increases, the image resolution and ease of handling decrease dramatically.

[0005] Furthermore, white substrates are often used to improve the color density of the image area (and to improve the whiteness of non-imaging areas). However, the reflectivity of most commercially available white substrates, especially thin (≤50um) substrates, is insufficient. Large light losses (e.g., leakage) through the substrate cause unacceptably low color density and chroma. For example, the reflectivity (%) of commercially available white PET (e.g., MELINEX® 339 (manufactured by Dupont Teijin Films LP, Chester, Virginia), 50um) is only about 85%. That is, about 15% of the incident light or color leaks out of the substrate and is not reflected to the viewer's eyes. Relatedly, substrates with low reflectivity tend to have low hiding power. When an image sheet with low hiding power is placed on a highly colored background, the viewer's eyes will see an image "contaminated" by the color and pattern of the background. An image sheet with high reflectivity and hiding power is particularly beneficial for image quality when used to improve resolution by using a black extinction layer on the opposite side of the substrate (relative to the microcapsule imaging layer) and to prevent light leakage that prematurely exposes the second imaging sheet directly below in the media stack.

[0006] Furthermore, to mitigate the slow color development described above, some technologies require a heating step to increase the color development rate after the microcapsules are crushed under pressure. The heating step requires the consumption of a large amount of energy (or battery power), which is further exacerbated by the dissipation of wasted heat through the substrate, especially when a thick sticker and release liner are applied to the back of the image sheet.

[0007] Also, in some techniques, to improve the adhesion of microcapsules to the substrate, a primer coating is applied between the substrate and the microcapsule layer. However, primer coatings are often soft and sticky and adhere to the coater's facing roller or the back surface of the substrate during rewinding. This reduces the coating quality and yield. To prevent these problems, a release coating can be applied to the back surface of the substrate or the interleaving, but these solutions require additional processing steps, materials, and costs. Further, the release coating on the back surface of the substrate can cause the sticker to peel off from the image sheet.

[0008] Against this background, there is significant commercial interest in primer layers that address some or all of the aforementioned problems. The primer layer according to the present disclosure provides significant improvements in Dmax of the primer coating, color development speed (fresh Dmax), Dmin stability, energy consumption, printing speed, hiding power, blister and blocking resistance, ease of handling, ease of processing, cost, and yield without requiring a trade-off in the adhesion quality between the image sheet and the sticker.

Means for Solving the Problems

[0009] In one aspect, which can be combined with any other aspect or embodiment, the present disclosure relates to a primer layer for a microcapsule imaging sheet comprising a polymer binder, one or more fine particles (e.g., white fine particles) constituting about 3 to about 60% by weight of the total weight of the primer layer, and a substrate. In some embodiments, the primer layer further comprises polymer hollow fine particles constituting about 1 to about 30% by weight of the total weight of the primer layer.

[0010] In some embodiments, the white fine particles have a refractive index of about 1.5 to about 3.0. In some embodiments, the fine particles are selected from the group consisting of TiO2, BaSO4, CaSO4, CaCO3, BN, Al2O3, and Ca3(PO4)2. In some embodiments, the white fine particles are TiO2. In some embodiments, the white fine particles have an average particle diameter of about 50 nm to about 2000 nm. In some embodiments, the white fine particles have an average particle diameter of about 100 nm to about 300 nm. In some embodiments, the concentration of the white fine particles is about 10 to about 50% by weight based on the total weight of the primer layer. In some embodiments, the white fine particles include TiO2 and basic fine particles. In some embodiments, the basic fine particles are selected from CaCO3, Al2O3, or Ca3(PO4)2.

[0011] In some embodiments, the polymer binder includes a latex polymer having a glass transition temperature (Tg) of about -70°C to about 40°C. In some embodiments, the polymer binder includes a latex polymer having a Tg of about -20°C to about 20°C. In some embodiments, the polymer binder is selected from the group consisting of acrylic polymers or copolymers, styrene copolymers, butadiene copolymers, vinyl chloride copolymers, vinylidene chloride copolymers, epoxy copolymers, ethylene copolymers, propylene copolymers, vinyl acetate copolymers, polyesters, polyurethanes, polylactones, polyamides, polyvinylpyrrolidone, and blends or copolymers thereof.

[0012] In some embodiments, the polymer hollow fine particles include a polymer shell and an air core. In some embodiments, the polymer hollow fine particles include a polymer shell containing a polymer selected from the group consisting of polyacrylic acid, polymethacrylate, polystyrene, polyvinyl acetate, polyolefin, polyamide, polyester, polyurea, polyurethane, melamine formaldehyde, phenol resin, and blends or copolymers thereof. In some embodiments, the polymer shell of the hollow fine particles is crosslinked or filled with an inorganic filler such as silica.

[0013] In some embodiments, the polymeric hollow microparticles have an average particle diameter of from about 200 nm to about 2000 nm or from about 500 nm to about 2000 nm. In some embodiments, the polymeric hollow microparticles have an average particle diameter of from about 100 nm to about 1000 nm, or from about 300 nm to about 1000 nm. In some embodiments, the air core has an average diameter of from about 50 nm to about 1000 nm. In some embodiments, the air core has an average diameter of from about 100 nm to about 400 nm. In some embodiments, the polymeric hollow microparticles have a dry specific gravity of from about 0.1 g / cm 3 to about 0.7 g / cm 3 . In some embodiments, the polymeric hollow microparticles are present at a concentration of from about 5 to about 30 weight percent based on the total weight of the primer layer.

[0014] In some embodiments, the polymeric hollow microparticles comprise a blend of a first polymeric hollow microparticle having a first average particle diameter and a second polymeric hollow microparticle having a second average particle diameter.

[0015] In some embodiments, the primer layer has a thickness of from about 1 μm to 10 μm. In some embodiments, the primer layer has a thickness of from about 2 μm to about 5 μm.

[0016] In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to a microcapsule imaging sheet comprising a primer layer according to any of the above embodiments and a photosensitive microcapsule layer in contact with the primer layer. In some embodiments, the microcapsule imaging sheet comprises a first substrate, a primer layer according to any of the above embodiments in contact with a first surface of the first substrate, and a photosensitive microcapsule layer comprising photosensitive microcapsules in contact with the first substrate, the primer layer, or both the primer layer and the first substrate.

[0017] In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to a microcapsule imaging sheet that includes a primer layer on a first surface of a substrate and a backcoat on a second surface of the substrate to improve image resolution and energy efficiency. In some embodiments, the microcapsule layer is coated on the primer layer. In some embodiments, the backcoat includes hollow microparticles and reflective microparticles that are essentially the same as those within the primer layer. In some embodiments, the backcoat is deposited on the second surface of the substrate by vapor deposition, sputtering, spraying, or wet coating. In some embodiments, the backcoat is blackened with a pigment such as a black dye or carbon black to further improve resolution and eliminate the risk of light leaking through the imaging sheet and prematurely exposing the imaging sheet below in the stack.

[0018] In some embodiments, the microcapsule imaging sheet is a full-color imaging sheet that includes photosensitive microcapsules that include red-sensitive, green-sensitive, and blue-sensitive microcapsules.

[0019] In some embodiments, the photosensitive microcapsules include a polymer shell and a core that includes a leuco dye, a photoinitiator, and a polymerizable or crosslinkable monomer or oligomer. In some embodiments, the leuco dye is one or more of a cyan, magenta, yellow, or black leuco dye. In some embodiments, the photoinitiator is a red-sensitive, green-sensitive, or blue-sensitive photoinitiator or sensitizer such as a cyanine borate or a semi-cyanine borate. In some embodiments, the photoinitiator consists essentially of, consists of, or includes an ultraviolet-sensitive or near-infrared-sensitive photoinitiator or sensitizer such as ketocoumarin, isopropylthioxanthone (ITX), and squarylium dyes.

[0020] In some embodiments, the microcapsule imaging sheet further includes (i) a microcapsule layer and / or a primer layer, and (ii) a developer layer that contacts the developer substrate. In some embodiments, the microcapsules are blended with a developer composition and coated as a single layer on the primer layer.

[0021] In some embodiments, the backcoat includes a black pigment or dye and a polymer binder. In some embodiments, the backcoat includes 1 to 30 wt% black pigment or dye based on the total weight of the backcoat. In some embodiments, the backcoat includes 3 to 20 wt% black pigment or dye based on the total weight of the backcoat. In some embodiments, the black pigment is carbon black.

[0022] In some embodiments, the backcoat further includes hollow polymer microparticles. In some embodiments, the backcoat further includes one or more microparticles (e.g., white microparticles) selected from the group consisting of TiO2, BaSO4, CaSO4, BN, CaCO3, Al2O3, Ca3(PO4)2.

[0023] In another aspect that can be combined with any other aspect or embodiment, the present disclosure is a method of making an imaging sheet, comprising: (i) coating a first surface of a first substrate with a primer layer according to any of the embodiments disclosed herein to produce a first substrate coated with a primer; (ii) contacting the primer layer of the first substrate coated with the primer with a microcapsule layer to produce a first substrate coated with microcapsules; (iii) contacting the first substrate coated with microcapsules with a developer layer to produce a first substrate coated with a developer; and (iv) contacting the developer layer of the first substrate coated with the developer with a second substrate to produce an imaging sheet.

[0024] In another aspect that can be combined with any other aspect or embodiment, the present disclosure provides a method of making an imaging sheet, the method comprising: (i) coating a first surface of a first substrate with a primer layer as described in any of the embodiments disclosed herein to produce a first substrate coated with a primer; (ii) contacting the primer layer of the first substrate coated with the primer with a microcapsule layer to produce a first substrate coated with microcapsules; (iii) contacting a second substrate with a developer layer to produce a second substrate coated with a developer; and (iv) contacting the developer layer of the second substrate coated with the developer with the microcapsule layer of the first substrate coated with microcapsules to produce an imaging sheet.

[0025] In some embodiments, a second primer layer is disposed between the second substrate and the developer layer.

[0026] In some embodiments, the method further comprises (v) contacting a second surface of the first substrate with a backcoat, the second surface of the first substrate being opposite the first surface of the first substrate. In some embodiments, the contacting in (v) is performed by physical vapor deposition, sputtering, chemical vapor deposition, lamination, or spin coating.

[0027] In another aspect that can be combined with any other aspect or embodiment, the present disclosure provides an imaging or printing method comprising exposing an imaging sheet comprising a primer layer and a microcapsule layer comprising microcapsules according to any of the embodiments disclosed herein to heat, pressure, or radiation, the microcapsules comprising a primer shell and an internal phase comprising a leuco dye, and the exposure being sufficient to release the leuco dye from the microcapsules within the microcapsule layer to generate an image.

[0028] Additional aspects and / or embodiments of the present invention are provided in the detailed description of the present technology described below without limitation. The following detailed description is exemplary and explanatory but not limiting.

[0029] Various objectives, aspects, features, and advantages of the present disclosure will become clearer and better understood by referring to the detailed description in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 3E

Figure 3F

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Figure 6

Best Mode for Carrying Out the Invention

[0031] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present technology. Certain exemplary embodiments of the present technology may be practiced without some or all of these specific details. In other instances, specific process operations are not described in detail but would be understood by those of ordinary skill in the art.

[0032] Photosensitive microcapsule layer Referring to FIGS. 1A and 1B, in some embodiments, a microcapsule imaging sheet 100 according to the present disclosure includes a photosensitive microcapsule layer 106. The photosensitive microcapsules 108 include a polymer shell and a core within the polymer shell, the core including a photosensitizer or photoinitiator, a photocurable monomer or oligomer, and a dye precursor (e.g., a leuco dye), which can impart color to the microcapsule imaging sheet upon release under pressure and subsequent heat, specific pH conditions, reactive chemical species (e.g., Lewis acids), or exposure to a developer. The shell may function as an oxygen barrier to ensure high photosensitivity of the photosensitive core and avoid premature mixing of the photoinitiator with the dye precursors of various colors, thereby enabling successful color separation and reproduction. In some embodiments, the photocurable monomer may be replaced with a softening or photodegradable composition.

[0033] The developer may be present, for example, in a developer layer 110a that contacts a developer substrate 114, which is configured to be separately disposed so as to contact the microcapsule layer 106, or may be present as a developer particle layer 110b within discrete developer fine particles 112. In some embodiments, the developer may be mixed with the microcapsules and coated as a single layer (not shown). When released from the microcapsules 108, the dye precursor (e.g., a leuco dye) undergoes a chemical conversion and transitions from a colorless state to a colored state (e.g., magenta, cyan, yellow, or black). Useful developers include, but are not limited to, acid clay, salicylic acid derivatives, phenolic resins and novolak resins, particularly those grafted or copolymerized with salicylic acid derivatives, and zinc complexes thereof.

[0034] The photosensitive microcapsule layer may include one or more types of microcapsules. For example, a positive-acting full-color microcapsule imaging sheet may include three types of microcapsules: red-sensitive microcapsules containing a red-sensitive photoinitiator and a cyan leuco dye, green-sensitive microcapsules containing a green-sensitive photoinitiator and a magenta leuco dye, and blue-sensitive microcapsules containing a blue-sensitive photoinitiator and a yellow leuco dye. For example, in a positive-acting imaging sheet, when exposed to white light, all three types of microcapsules are cured and no color is formed after the color development step. When completely exposed to red light, the red-sensitive microcapsules are cured, so the cyan leuco dye is not released in the development step. As a result, red is reproduced in the exposed area. In contrast, when completely exposed to a combination of blue and green light (cyan light), the corresponding magenta and yellow leuco dyes are not released, and cyan is reproduced in the exposed area. Intermediate-tone colors of various color densities may also be reproduced in areas exposed to various lights of various energies and / or intensities.

[0035] In some embodiments, the dye precursor is a cyan, magenta, yellow, or black leuco dye. By way of non-limiting example, representative leuco dyes include, but are not limited to, PERGASCRIPT® RedI6B, BlueI-2G or Blue-63 from BASF, Blue220, Blue203, Red500, Red40, or Black305 from Yamada, JYDY-1, JYDR-2, JYDR-3, JYDB-1 or JYDB-2 from Wuxi Jiayida New Materials, Red-16, O-C6, or O-C8 from Synmedia Chemicals, or ODB-2 from Anyang General Chemicals.

[0036] In some embodiments, the photoinitiator is a cyanine borate, a semi-cyanine borate, or a ketocoumarin that is sensitive to blue, green, or red light. For a panchromatic imaging system, red, green, and blue photoinitiators with a narrow spectral sensitivity bandwidth of less than 100 nm are preferred. In some embodiments, the photoinitiator consists essentially of, or consists of, a UV-sensitive or near-infrared-sensitive photoinitiator or sensitizer such as ketocoumarin, isopropylthioxanthone (ITX), and squarylium dyes. In some embodiments, a UV initiator or an infrared initiator is used in the false-color imaging system. In some embodiments, the photosensitive microcapsule 108 may include a polymer shell that is softenable by actinic radiation and a core that includes a dye precursor (e.g., a leuco dye). In this scenario, the core may be photo-softenable or decomposable. In this case, a negative-acting image is obtained in which the exposed areas / capsules are colored after being developed with a developer. In some embodiments, the microcapsule further includes a monomer or oligomer (e.g., a polymerizable or crosslinkable monomer or oligomer) selected from polyfunctional acrylates and methacrylates, polyfunctional vinyl ethers, polyfunctional allyls or vinylbenzenes, and their oligomers, dendrimers, or blends. Polyfunctional acrylates are particularly useful for their excellent light speed, compatibility with leuco dyes and developers, and outdoor weather resistance. Exemplary polyfunctional acrylates include, but are not limited to, pentaerythritol triacrylate (PETA-3), pentaerythritol tetraacrylate (PETA-4), dipentaerythritol hexaacrylate (DPHA), dipentaerythritol pentaacrylate (DPPA), trimethylolpropane triacrylate (TMPTA), 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), and neopentyl glycol diacrylate (NPGDA).

[0037] substrate The primer layer 104 according to the present disclosure is coated on the substrate 102. The substrate may be any suitable material having sufficient thickness, flexibility, reflectivity (e.g., hiding power), and durability against recording and printing media (e.g., images). In some embodiments, the substrate is white or transparent. By way of non-limiting example, in some embodiments, the substrate is polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, polyolefin, cyclic olefin copolymer (COC), cellulose acetate, or a copolymer, blend, or composite thereof. A series of PET substrates are readily commercially available (e.g., white PET films MELINEX® 329, 339, 394, 331, 534, and the transparent PET film MYLAR® from DuPont Teijin Films LP of Chester, Virginia, and Mitsubishi's HOSTAPHAN®).

[0038] The substrate can have any suitable thickness. In some embodiments, the substrate has a thickness of about 3.5 μm to about 150 μm, about 12.5 μm to about 100 μm, or about 25 μm to about 75 μm. In some embodiments, the substrate may be surface-treated, for example, by corona, plasma, or an underlayer to improve the adhesion between the substrate and the primer or backcoat. In some embodiments, one side of the substrate may be pretreated with an antistatic layer to reduce the accumulation of undesirable electrostatic charges during coating or printing. In some embodiments, one side of the substrate may be pretreated with a release layer, such as a polysiloxane or wax layer, to improve media transport during printing and / or media blocking resistance during conversion and packaging. Primer layer

[0039] In various embodiments, the microcapsule imaging sheet according to the present disclosure includes a primer layer 104. The primer layer is disposed between the substrate and the microcapsule layer and improves performance characteristics such as adhesion, image resolution, capsule rupture efficiency, or fresh Dmax (maximum optical density) achievable immediately after pressure generation, energy efficiency, and light speed. In some embodiments, the thickness of the primer layer is from about 0.5 μm to about 10 μm, from about 1 μm to about 8 μm, or from about 2 μm to about 5 μm. In some embodiments, the primer layer may include a polymer binder, white fine particles, and a substrate. In some embodiments, the primer layer may further include polymer hollow fine particles. In some embodiments, the primer layer may further include basic fine particles.

[0040] Polymer binder The primer layer according to the present disclosure includes one or more polymer binders. The one or more polymer binders are present at any suitable concentration and have any suitable molecular weight to impart favorable adhesion, flexibility, blocking resistance, and film quality (e.g., uniform thickness) to the primer layer, and may be any suitable polymer material.

[0041] In some embodiments, the one or more polymer binders include, consist essentially of, or can consist of one or more polymers selected from the group consisting of acrylic polymers or copolymers, styrene copolymers, butadiene copolymers, vinyl chloride copolymers, vinylidene chloride copolymers, ethylene copolymers, propylene copolymers, vinyl acetate copolymers, epoxy copolymers, polyesters, polyurethanes, polylactones, polyamides, polyolefins, polyvinylpyrrolidone, and blends or copolymers thereof. In some embodiments, the one or more polymer binders are latex polymers, or blends thereof.

[0042] In some embodiments, one or more polymer binders may have a weight average molecular weight of from about 5,000 g / mol to about 10,000,000 g / mol. In some embodiments, one or more polymer binders include, consist essentially of, or consist of a latex binder having a molecular weight in the range of 100,000 g / mol to several million g / mol and a particle size in the range of about 0.05 μm to about 1.0 μm. In some embodiments, useful latexes may have a minimum film formation temperature (MFFT) or glass transition temperature (Tg) of less than 50 °C, less than 30 °C, or less than 20 °C. In some embodiments, a crosslinkable latex may be used to improve the cohesive strength of the primer layer.

[0043] In some aspects, one or more polymer binders may have a weight average molecular weight of at least about 5,000 g / mol, at least about 10,000 g / mol, at least about 5,000,000 g / mol, at least about 10,000,000 g / mol, or at most about 5,000,000 g / mol.

[0044] In some embodiments, one or more polymer binders may be present in the primer layer, alone or in combination, at a concentration, by weight percent based on the weight of the total primer layer, of from about 5 wt% to about 80 wt%, preferably from about 10 wt% to about 70 wt%, more preferably from about 20 wt% to about 60 wt%, and even more preferably from about 30 wt% to about 50 wt%.

[0045] In some embodiments, one or more polymer binders may be present in the primer layer at a concentration, by weight percent relative to the weight of the total primer layer, of about 5 wt% or more, about 10 wt% or more, about 80 °C or more, about 90 °C or more, or about 100 °C or more, about 90 °C or less, or about 80 °C or less, either alone or in combination. In some embodiments, one or more polymer binders may have a glass transition temperature (Tg) of about -100 °C to about 100 °C or less, about -70 °C to about 60 °C, about -30 °C to about 30 °C. In some embodiments where a latex binder is used, the latex may have a minimum film formation temperature (MFFT) of less than 60 °C, such as less than 20 °C, to ensure acceptable film properties after coating.

[0046] Fine particles In some embodiments, the polymer binder layer according to the present disclosure includes one or more fine particles, such as white fine particles having a high refractive index or reflectivity. The white fine particles can be any suitable composition, size, and concentration for enhancing the reflectivity and / or hiding power of the primer layer.

[0047] In some embodiments, one or more fine particles may include one or more of TiO2, BaSO4, CaSO4, CaCO3, silica, BN, Al2O3, Ca3(PO4)2, Ca(HPO4), ZrO2, ZnO, or any other suitable metal oxide, transition metal oxide, sulfate, carbonate, or phosphate material. In some embodiments, the white fine particles are one or more selected from the group consisting of TiO2, BaSO4, CaSO4, BN, Al2O3, CaCO3, and Ca3(PO4)2. In some embodiments, the white fine particles include TiO2, consist essentially of TiO2, or consist of TiO2.

[0048] In some embodiments, one or more fine particles may have an average particle diameter between about 0.1 μm and about 5 μm, between about 0.14 μm and about 2 μm, or between about 0.2 μm and about 1 μm.

[0049] In some embodiments, one or more of the microparticles may have an average particle diameter of about 0.1 μm or more, about 0.11 μm or more, about 0.12 μm or more, about 0.13 μm or more, about 0.14 μm or more, about 0.15 μm or more, about 0.2 μm or more, about 0.3 μm or more, about 0.4 μm or more, about 0.5 μm or more, about 0.6 μm or more, about 0.7 μm or more, about 0.8 μm or more, about 0.9 μm or more, about 1 μm or more.

[0050] In some embodiments, one or more of the microparticles comprise, consist essentially of, or consist of a single white microparticle composition (e.g., TiO2), or two or more white microparticle compositions (e.g., TiO2 and Al2O3).

[0051] In some embodiments, one or more of the microparticles may further comprise one or more basic microparticles including, but not limited to, Al2O3, CaCO3, or Ca3(PO4)2. In some embodiments, one or more basic microparticles are included as a buffer for the primer layer to neutralize or absorb any acidic chemical substances that may diffuse or migrate from other layers (e.g., the developer layer), thereby improving the stability of Dmin. In some embodiments, one or more basic microparticles are selected from the group consisting of CaCO3, Al2O3, Ca3(PO4)2.

[0052] In some embodiments, one or more of the microparticles may have only one average diameter (e.g., a monomodal size distribution). In some embodiments, one or more of the microparticles may have a bimodal or trimodal size distribution (e.g., other differences in average diameter may be achieved depending on the difference between any two of the average diameters specified in the examples above, e.g., one white microparticle with an average diameter of about 0.1 μm to about 2 μm, and one white microparticle with an average diameter of about 0.2 μm to about 0.5 μm).

[0053] In some embodiments, one or more filler microparticles with a smaller particle size, such as silica or CaCO3, may be used to further improve the packing density of the primer layer. The useful particle size range of the filler microparticles can be from about 0.01 μm to about 1 μm, from about 0.02 μm to about 0.5 μm, or from about 0.05 μm to 0.2 μm.

[0054] In some embodiments, one or more microparticles may be present in the primer layer at a concentration, by weight %, based on the weight of the entire primer layer, of from about 10 wt% to about 50 wt%, from about 15 wt% to about 40 wt%, or from about 20 wt% to about 35 wt%, either alone or in combination.

[0055] In some embodiments, one or more microparticles may be present in the primer layer at a concentration, by weight %, based on the weight of the entire primer layer, either alone or in combination. In some embodiments, one or more microparticles have a refractive index of about 1.5 or greater, preferably about 2.0 or greater, more preferably about 2.4 or greater, or any range or value therebetween.

[0056] In some embodiments, one or more microparticles have a refractive index of from about 1.4 to about 3, from about 2 to about 3, or any range or value therein. In some embodiments, low refractive index filler microparticles such as silica or CaCO3 may be present in the primer layer at a concentration, by weight %, based on the weight of the entire primer layer, of from about 0.1 wt% to about 15 wt%, preferably from about 1 wt% to about 10 wt%.

[0057] Polymer hollow microparticles In some embodiments, the primer layer according to the present disclosure includes one or more polymer hollow microparticles. The polymer hollow microparticles may have any suitable composition, size (average diameter), or specific gravity, may be present at any suitable concentration, and improve the heat insulation properties of the primer layer while obtaining an acceptable reflectance (e.g., hiding power), blocking resistance, adhesiveness, blister resistance, and film quality compared to conventional primer layers that do not include any polymer hollow microparticles.

[0058] In some embodiments, the one or more polymeric hollow microparticles can include, consist essentially of, or consist of a polymer shell and a core. In some embodiments, the core is an air core or a precursor thereof, for example, a highly water-swollen gel that forms an air core when water is removed during or after coating.

[0059] In some embodiments, the one or more polymeric hollow microparticles include a polymer shell that comprises a polymer selected from the group consisting of polyacrylate, polymethacrylate, polystyrene, polyester, melamine formaldehyde condensate, polyolefin, polyurea, polyurethane, and blends or copolymers thereof. In some embodiments, the polymer shell is crosslinked. In some embodiments, the polymer shell may include an inorganic network such as silica formed, for example, by a sol-gel process. Exemplary polymeric hollow microparticles may be made according to the disclosures found in C.J. McDonald et al., 99 Adv. Colloid & Interface Sci. 181-213 (2002) (DOI: 10.1016 / S0001-8686(02)00034-9) and W. Wichaita et al., 58 Indus. Eng’g Chem. Res. 20880-20901 (2019) (DOI: 10.1021 / acs.iecr.9b02330), which are hereby incorporated by reference in their entirety.

[0060] In some embodiments, the one or more polymeric hollow microparticles have an average diameter or D of from about 0.1 μm to about 2 μm, from about 0.1 μm to about 1 μm, from about 0.3 μm to about 5.0 μm, or from about 0.5 μm to about 2 μm. 50 In some embodiments, the air core of the polymeric hollow microparticle has a diameter of from about 0.1 μm to about 1.0 m, or from about 0.15 μm to about 1 μm. Preferably, the hollow microparticle or its core has a narrow particle size distribution. A series of polymeric hollow microparticles may be readily available, for example, from Dow Chemicals and Taiwan Hopax Chemicals.

[0061] In some embodiments, one or more polymeric hollow microparticles have an average diameter or D of about 0.1 μm or greater, about 0.2 μm or greater, about 0.3 μm or greater, about 0.4 μm or greater, about 0.5 μm or greater, about 0.6 μm or greater, about 0.7 μm or greater, about 0.8 μm or greater, about 0.9 μm or greater, about 1 μm or greater, about 1.5 μm or greater, about 2 μm or greater, about 2.5 μm or greater, about 3 μm or greater, about 3.5 μm or greater, about 4 μm or greater, about 4.5 μm or greater, about 5 μm or greater, about 10 μm or greater, or any range or value therebetween. 50 It may have.

[0062] In some embodiments, one or more polymeric hollow microparticles have an average diameter D of about 5 μm or less, about 4.5 μm or less, about 4 μm or less, about 3.5 μm or less, about 3 μm or less, about 2.5 μm or less, about 2 μm or less, about 1.5 μm or less, about 1 μm or less, about 0.9 μm or less, about 0.8 μm or less, about 0.7 μm or less, about 0.6 μm or less, about 0.5 μm or less, about 0.4 μm or less, about 0.3 μm or less, about 0.2 μm or less, or any range or value therein. 50 It may have.

[0063] In some embodiments, one or more polymeric hollow microparticles comprise, consist essentially of, or consist of a single polymeric hollow microparticle composition (e.g., NTR-50 (D 50 = about 0.16 μm)), or two or more polymeric hollow microparticle compositions (e.g., Hopax NTR-50 (D 50 = 0.16 μm), Hopax NTR-100 (D 50 = about 0.82 μm), Dow ROPAQUE™ ULTRA-E (D 50 = about 0.35 μm), Dow ROPAQUE™ TH-1000 (D 50 = about 1.0 μm), etc.).

[0064] In some embodiments, the one or more polymeric hollow microparticles may be present in the primer layer, alone or in combination, in a concentration, by weight percent relative to the weight of the total primer layer, of from about 2 wt% to about 30 wt%, from about 5 wt% to about 25 wt%, more preferably from about 10 wt% to about 25 wt%.

[0065] Backcoat Referring to FIG. 1C, in some embodiments, an opaque backcoat 105 is coated on the second surface of the substrate 102, and the first surface is coated with the primer layer 104. Such embodiments can not only improve image resolution, fresh Dmax, and energy efficiency, but also eliminate the risk of light leakage through the upper imaging sheet that causes premature exposure of the media stack underlying image sheet. In some embodiments, the opaque backcoat comprises essentially the same components as those within the primer layer (e.g., white microparticles, filler microparticles, or hollow polymer microparticles), having either the same composition or size as those disclosed above, or being present at any of the concentrations disclosed above relative to the total weight of the backcoat. For example, in some embodiments, the backcoat comprises hollow polymer microparticles. In some embodiments, the backcoat further comprises one or more microparticles (e.g., TiO2, silica, BaSO4, CaSO4, BN, CaCO3, Al2O3, AIN, and Ca3(PO4)2). In some embodiments, the backcoat comprises a binder (e.g., a polymer binder).

[0066] In some embodiments, the backcoat further comprises a quenching dye or pigment for incident light. In some embodiments, the quenching dye or pigment is a pigment such as a black dye or carbon black. Examples of commercially available carbon blacks include, but are not limited to, NW-KAB85 (manufactured by Taiwan Nanotechnology Corp. (D 50 = 0.15 μm)).

[0067] The backcoat may be of any thickness suitable for easy handling of the media sheet and ensuring acceptable extinction of the initial light. In some embodiments, the thickness of the backcoat is from about 2 μm to about 30 μm, from about 3 μm to about 20 μm, or from about 5 μm to about 15 μm.

[0068] In some embodiments, the backcoat may have a thickness of about 1 μm or more, about 1.5 μm or more, about 2 μm or more, about 2.5 μm or more, about 3 μm or more, about 3.5 μm or more, about 4 μm or more, about 4.5 μm or more, about 5 μm or more, about 6 μm or more, about 7 μm or more, about 8 μm or more, about 9 μm or more, about 10 μm or more, about 15 μm or more, about 20 μm or more, about 25 μm or more, about 30 μm or more, or any range or value therebetween.

[0069] In some embodiments, the backcoat may have a thickness of about 50 μm or less, about 45 μm or less, about 40 μm or less, about 35 μm or less, about 30 μm or less, about 25 μm or less, about 20 μm or less, about 15 μm or less, about 10 μm or less, about 5 μm or less, or any range or value therebetween.

[0070] In some embodiments, the backcoat contains a black pigment or dye at a concentration of from about 0.1 wt% to about 50 wt%, from about 1 wt% to about 30 wt%, or from about 3 wt% to about 20 wt%, or any range or value therebetween, based on the total weight of the backcoat.

[0071] In some embodiments, the backcoat contains a black pigment or dye at a concentration of about 0.1 wt% or more, about 0.2 wt% or more, about 0.3 wt% or more, about 0.4 wt% or more, about 0.5 wt% or more, about 0.6 wt% or more, about 0.7 wt% or more, about 0.8 wt% or more, about 0.9 wt% or more, about 1 wt% or more, about 2 wt% or more, about 3 wt% or more, about 4 wt% or more, about 5 wt% or more, about 6 wt% or more, about 7 wt% or more, about 8 wt% or more, about 9 wt% or more, about 10 wt% or more, about 15 wt% or more, about 20 wt% or more, about 25 wt% or more, or any range or value therebetween, based on the total weight of the backcoat.

[0072] In some embodiments, the backcoat comprises a black pigment or dye at a concentration of about 60 wt% or less, about 55 wt% or less, about 50 wt% or less, about 45 wt% or less, about 40 wt% or less, about 35 wt% or less, about 30 wt% or less, about 25 wt% or less, about 20 wt% or less, about 15 wt% or less, about 10 wt% or less, or any range or value therein, based on the total weight of the backcoat.

[0073] In some embodiments, the backcoat is deposited on the second surface of the substrate by vapor deposition, sputtering, spraying, or wet coating. In some embodiments, the backcoat may not include a polymer binder. In some embodiments, the backcoat may not include a black pigment or dye. In some embodiments, the backcoat may include a vapor coating or sputter coating of a metal, metal nitride, metal oxide, metal carbide, or metal boride film (such as Al, Cr, Ag, Ni, Au, Cu, Ti, and combinations thereof, etc.) on the second surface of the substrate (such as the first substrate).

[0074] The foregoing terms are considered to be well understood by one of ordinary skill in the art, but the following definitions are set forth to facilitate the description of the presently disclosed subject matter.

[0075] The term "a" or "an" may refer to one or more of that entity, i.e., it can refer to multiple referents. Therefore, the terms "a" or "an", "one or more", and "at least one" are used interchangeably herein. Additionally, a reference to an element by the indefinite article "a" or "an" does not exclude the possibility that more than one of the elements exists, unless the context clearly requires that only one of the elements exists.

[0076] Throughout this specification, references to "one embodiment", "an embodiment", "one aspect", or "an aspect" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Further, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0077] As used herein, the terms "about" or "approximately" preceding a numerical value indicate adding or subtracting a range of 10% of the value.

[0078] As will be understood by those skilled in the art, for any or all purposes, particularly from the perspective of providing a written description, all ranges disclosed herein also include any and all possible sub-ranges and combinations of those sub-ranges. It can be readily recognized that the listed ranges are made sufficiently descriptive and enable the division of the same range into at least equal halves, thirds, fourths, fifths, tenths, etc. By way of non-limiting example, each range discussed herein can be readily decomposed into a lower third, a middle third, and an upper third, etc. As will also be understood by those skilled in the art, all language such as "up to", "at least", "greater than", "less than", etc. includes the recited number and then refers to a range that can be decomposed into sub-ranges as described above. Finally, as will be understood by those skilled in the art, ranges include each individual member.

[0079] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms defined in commonly used dictionaries shall be interpreted to have a meaning that coincides with their meaning in the context of the present application and related technologies, and it will be further understood that they should not be interpreted in an idealized or overly formal sense unless explicitly defined herein. Although not explicitly defined below, such terms should be interpreted according to their common meaning.

[0080] For the purposes of the present disclosure, the term "color density" or "color optical density" refers to the ability of a medium to reflect light, and the greater the light reflection of a dye at a specific color, the higher the color optical density (i.e., the stronger the color). The smaller the light reflection of the dye, the lower the color density (i.e., the less intense the color).

[0081] For the purposes of the present disclosure, the term "maximum color density" (or "Dmax") refers to the maximum color density achieved by a dye after a given development time as measured by a Konica Minolta reflection spectrophotometer FD-5. For example, Dmax, フレッシュ or fresh Dmax refers to the maximum color density of a developed image sheet measured immediately after development, and Dmax,t refers to the maximum color density of a developed image sheet measured after it has been conditioned for a certain period (t).

[0082] For the purposes of the present disclosure, the term "leuco dye" refers to a chemical dye that can alternate between two chemical forms, one of which is colorless. The conversion from the colorless to the colored form may be reversible or irreversible and may be induced by a Lewis acid or base, or a change in temperature, pH, irradiation, or redox state. Useful developers include, but are not limited to, phenols, phenolic resins, salicylic acid, oxalic acid, phthalic acid, organic phosphonic acids, organic sulfonic acids, and their zincated derivatives. Zincated salicylic acid derivatives and novolak resins are particularly useful due to their high color development rate and the color fastness of the dyes formed therefrom.

[0083] Method for producing an imaging sheet

[0084] In some other embodiments that can be combined with any other embodiment or implementation form, the present disclosure includes: (i) coating the first surface of the first substrate with a primer layer described in any of the embodiments disclosed herein to produce a first substrate coated with a primer; (ii) contacting the primer layer of the first substrate coated with the primer with a microcapsule layer to produce a first substrate coated with microcapsules; (iii) contacting the first substrate coated with microcapsules with a developer layer to produce a first substrate coated with a developer; and (iv) contacting the developer layer of the first substrate coated with the developer with a second substrate to produce an imaging sheet. The present disclosure relates to a method for producing an imaging sheet including these steps.

[0085] In some embodiments, the second primer layer may be disposed between the second substrate and the developer layer.

[0086] In some embodiments, the method of making the imaging sheet further includes (v) contacting the second surface of the first substrate by backcoating, wherein the second surface of the first substrate is on the opposite side of the first surface of the first substrate. In some embodiments, the contacting in (v) is performed by physical vapor deposition, sputtering, chemical vapor deposition, lamination, or spin coating.

[0087] Method of using a primer layer and an imaging sheet containing the same In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to a method of using a primer layer according to any of the above-described embodiments. In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to a method of using an imaging sheet according to any of the above-described embodiments.

[0088] For example, in some embodiments, the method of imaging or printing includes exposing an imaging sheet comprising a primer layer according to any of the embodiments disclosed herein and a microcapsule layer according to any of the embodiments disclosed herein to heat, pressure, or radiation, the exposure being sufficient to release a leuco dye from the microcapsules within the microcapsule layer to generate an image.

[0089] In some embodiments, the present disclosure relates to a method of improving one or more properties of an imaging sheet, including the step of including (or adding to) the imaging sheet a primer layer according to any of the embodiments disclosed herein. In some embodiments, the one or more properties include one or more of Dmax, fresh Dmax, Dmax,t, Dmin, image resolution, hiding power, blocking resistance, adhesion, reflection optical density, and heat insulation performance.

[0090] Unless otherwise explicitly indicated, all specific embodiments, features, and terms are intended to include both the recited embodiments, features, or terms and their equivalents.

[0091] Refer in detail to the various specific embodiments contemplated by the present disclosure. Although various embodiments are described herein, it is understood that the present technology is not limited to the described embodiments. On the contrary, the present case is intended to cover alternatives, modifications, and equivalents that may be included within the spirit and scope of the technology defined by the appended claims.

Example

[0092] Materials and Methods

Table 1-1

Table 1-2

Table 2

[0093] Preparation of Photosensitive Microcapsules The photosensitive microcapsules were prepared using the materials listed in Table 2 by the process described below.

[0094] 1. 220 parts of water and 8 parts of Versa TL502 sulfonated polystyrene (dry) were added to a 1000 ml stainless steel beaker and mixed thoroughly.

[0095] 2. 10 parts of pectin (methyl polygalacturonate) was slowly sieved into the mixture and stirred overnight at room temperature (500 - 1000 rpm).

[0096] 3. The pH was adjusted to 7.5 with 10% sodium carbonate and the mixing speed was increased to 1750 rpm.

[0097] 4. The internal phase as shown in Table 2 was added over a period of 15 - 30 seconds, the resulting mixture was stirred for 30 minutes, 11 parts of DETA (diethylenetriamine) in a 9.1% aqueous solution (adjusted to pH 7.0) was added, and after reacting at 25°C for 30 minutes, it was reacted at 40°C for 1 hour.

[0098] 5.19.9 parts of CYMEL® 385 and 40 g of water (adjusted to pH 6.0) were added, and the mixture was further reacted at 70 °C for 2 hours.

[0099] 6. 15.23 parts of sodium sulfate, an aqueous solution of 34.3%, was added and stirred for 10 minutes. Then, 1.97 parts of CYMEL 385® and 10 parts of water were added, and the mixture was further reacted at 70 °C for 1 hour.

[0100] 7. The mixing speed was reduced to 600 rpm, the pH was adjusted to 9.5 using a 20% NaOH solution, and the resulting reaction mixture was stirred overnight at room temperature.

[0101] The microcapsules thus prepared were extensively washed with water and centrifuged to remove excess water-soluble polymer and additives in the aqueous phase. The particle size (D 50 ) of the purified and washed microcapsules was approximately 6 μm as measured with a HORIBA LA-960 particle size analyzer.

[0102] Preparation of control microcapsule sheet - Microcapsule coating on PET (MELINEX® 339) without primer or backcoat

Table 3

[0103] The coating solution shown in Table 3 was adjusted to a solid content of 33 wt% by adding water and thoroughly dispersed using a low-shear mixer. Then, it was coated on a 2 mil white PET substrate (MELINEX® 339) with a Myrad bar and dried in an oven at 80 °C for 10 minutes. The thickness of the dried coating was approximately 8 μm as measured with a Mitutoyo thickness gauge.

[0104] Preparation of color developer coating To prepare the color former coating, the composition shown in Table 4 was coated onto a 1 mil clear PET film with a Myrad bar and dried in an oven at 80 °C for 10 minutes to achieve a target dry coating thickness of approximately 13 μm.

Table 4

[0105] Preparation of Control Image Sheet - Image Sheet without Primer or Backcoat The microcapsule film and developer film prepared as described above were laminated using a Tamerica roll laminator TCC2700 with temperature, pressure, and speed settings of 100 °C, 3.621 Kgf / 170 mm, and 0.368 m / min, respectively, to form various photosensitive imaging sheets as described in the following examples.

[0106] Example 1. Influence of Primer Coating on Blocking Resistance, Reflectance, Hiding Power, Adhesion, and Blistering To test the relative effect of the hollow microparticles present in the primer layer, the primer formulation contained 30 wt% TiO2 microparticles (DuPont's TIPURE™ 6431), 5 wt% PVA205, 0 - 10 wt% hollow microparticles NTR - 50 (D 50 = 0.25 μm, manufactured by Hopax Chemicals), and 55 - 60 wt% M35 latex as a buffer. The primer formulation was coated onto a MELINEX® 339 substrate with a Myrad rod. For comparison, a primer layer containing 5 wt% (dry) silica CAB - O - SIL® 1015 was also prepared. The thickness of each coating was from 6.3 μm to 6.7 μm.

[0107] In the blocking test, each sample was pressed against the back of a MELINEX® 339 substrate for 24 hours at 10 kg / 100 cm 2 , 40 °C, and 85% relative humidity, and the proportion of the test area with observable damage marks was recorded.

[0108] To test the hiding power, the upper surface of MELINEX® 339 was coated with a primer layer containing hollow microparticles NTR-50 at various concentrations, and the optical density was measured against a black surface. The lower the reflection optical density, the higher the hiding power, and the color of a black background with an optical density of about 2.0 is hidden.

[0109] As shown in Table 5, all samples with primer coating showed a dramatic increase in hiding power or a decrease in reflection optical density (black outer diameter 0.0 - 0.02 or reflectance 95.5 - 100%) compared to the control without primer coating. Also, all samples coated with a primer coating containing 5 - 10 wt% of NTR-50 showed a dramatic improvement in blocking resistance or a decrease in the proportion of areas with observable damage marks after the blocking test compared to those containing only silica particles, which are additives commonly used to improve the blocking resistance of coatings.

Table 5

[0110] Also, all coatings showed excellent water resistance (blister test) and adhesion to PET339 (tape test).

[0111] Example 2. Primer layer with reduced thickness A primer layer identical to that described in Example 1 was prepared, except that the film thickness was reduced to 2.9 ± 0.3 mμm. To obtain an image with high color density, it is necessary to diffuse the leuco dye released from the microcapsules into the developer layer as much as possible to convert the leuco dye from the leuco form to the color form. A thin and impermeable primer layer is highly preferred to reduce the risk of unwanted dye diffusion or absorption into the primer layer on the opposite side of the microcapsule layer of the imaging sheet having the following structure (PET / primer layer / microcapsule layer / developer layer / PET). A thin primer layer composition was prepared, and the composition contained 0.4 to 1.1 wt% hydroxypropyl methylcellulose (HPMC) (DuPont METHOCEL™ K15M) as a thickener to improve coating quality and various M35 latex concentrations (up to 100 wt% of the composition) as a buffer. Next, the thin primer layer composition was coated on MELINEX® 339. The samples were subjected to the adhesion, hiding power, and blocking tests described above (see Example 1).

[0112] As shown in Table 6, all the films made from the HPMC-containing primer formulations showed excellent coating quality, adhesion, blister resistance, and hiding power even after reducing the thickness of the primer layer to 2.9 ± 0.3 μm (measured against a black background with an optical density > 2.0, reflected black optical density ≤ 0.01 or reflectance ≥ 97.7%). All four primer layers of Example 2 also showed a significant improvement in blocking resistance, and the proportion of the area with observable damage marks after the blocking test decreased significantly from < 30% (see Examples 1-2) to < 10%.

Table 6

[0113] Example 3. Primer layers with various particulate concentrations (30 - 37 wt%) A primer layer was prepared in the same manner as described in Example 2, except that the concentration of TiO2 (TIPURE (trademark) 6431) was increased from 30 wt% to 37 wt% and the concentration of M35 latex was changed as a buffer solution (making the composition 100 wt%). The coating thickness was 2.5 μm to 3.2 μm with MELINEX (registered trademark) 339. The samples were subjected to the same hiding power, blocking resistance, adhesiveness, and blister resistance tests as described above (see Examples 1 and 2).

[0114] As shown in Table 7, all the prepared primer layers exhibited excellent hiding power (black reflectance optical density ≤ 0.01, or reflectance ≥ 97.7% compared to a black reflectance optical density of 0.07 for bare PET MELINEX (registered trademark) 339, or a reflectance of 85.1%), suggesting that a higher concentration of TiO2 particles enabled the production of a highly reflective primer layer with a low thickness of 2.5 μm. This high reflectance means a fast light speed because the reflected light functions as an additional light source for exposing the microcapsules. The color intensity of the developed image is also improved because more light of the appropriate color is reflected into the observer's eyes during image evaluation.

Table 7

[0115] Referring to Table 7, in the blocking resistance test, it is shown that each primer layer exhibits good blocking resistance, with less than 5% of the loaded area showing very faint marks. Primer layers with TiO2 of ≥ 32.5 wt% tend to adhere slightly less to the edges of the PET339 substrate without a release liner or coating, and the film only slightly blurred at the edges of the loaded weight. All primer layers showed acceptable adhesion (i.e., passed the adhesion test) regardless of the TiO2 concentration. Also, all primer layers showed good blister resistance in the presence of two different test solutions of 0.01 wt% water each of deionized water and AEROSOL OT (trademark) (sodium dioctyl sulfosuccinate) and TRITON (registered trademark) X-114 nonionic detergent (Sigma-Aldrich Inc., St. Louis, Missouri).

[0116] Example 4. Influence of Concentration and Size of Hollow Particles To test the influence of the size and concentration of hollow particles on film performance, five primer layers with different hollow particles (of different sizes and concentrations) were prepared as described in Example 3, except that the types and concentrations of hollow particles shown in Table 8 were used. Their hiding power is also shown in Table 8, as indicated by the reflectance optical density measured against a black substrate (OD = 2.0, black).

Table 8

[0117] As shown in Table 8, the hollow particles NTR-50 and NTR-100 (D 50The primer layer having a particle size of 0.9 μm showed excellent hiding power compared to the bare MELINEX® 339 substrate, as evidenced by a low reflectance optical density (or high reflectance of 97.7%), regardless of the size and concentration of the hollow particles. Furthermore, all primer layers showed acceptable blocking resistance. The primer layer containing 10 wt% or 14.3 wt% of NTR-100 showed slightly better blocking resistance than a similar primer layer containing NTR-50 particles.

[0118] All films passed the dry adhesion test, and the primer layer showed acceptable adhesion to the MELINEX® 339 substrate, regardless of the size and concentration of the hollow particles. However, the primer layer containing NTR-50 hollow particles showed slightly better film quality when visually observed at the same concentration compared to a similar primer layer containing NTR-100 hollow particles.

[0119] Example 5. Influence of the size of mixed hollow particles on the quality and performance of the primer Blocking resistance, hiding power, adhesion, blister resistance

[0120] To test the influence of bimodal size distribution hollow particles on the hiding power, blocking resistance, adhesion, and blister resistance of the primer layer, primer layer formulations were prepared according to Table 9, with each primer layer containing NTR-50 (D 50 = 0.25 μm) and NTR-100 (D 50 = 0.9 μm) and made at a total concentration of 10.0 wt%, but with different NTR-50:NTR-100 ratios. All primer coatings of Example 5 contained 0.8 wt% of HPMC-K15M and were coated on MELINEX® 339 with a target dry thickness of approximately 2.8 μm according to the same procedure described in Example 4.

[0121] As shown in Table 9, all of the primer coatings of Example 5 exhibited good adhesion to the PET substrate, and the samples with hollow microparticles showed excellent blocking resistance and hiding power compared to the samples without hollow microparticles (see Example 5-0). All of the primer coatings showed acceptable coating quality, but the coating with a high concentration of larger-sized microparticles (NTR-100) had slightly inferior coating uniformity.

Table 9

[0122] Also, it was observed that all of the primer formulations showed good blister resistance as judged from the size of the water stain observed after exposure to an aqueous solution containing 0.5 wt% each of deionized water, AEROSOLOT (trademark), and TRITON (registered trademark) X-114. Primer formulations containing blends of hollow microparticles of different sizes (e.g., Examples 5-3 and 5-4, NTR-50 / NTR-100 = 8 / 2 to 7 / 3) showed excellent reflectance, film quality, and blister resistance while showing desirable coating quality and and blocking resistance.

[0123] Heat insulation performance To test the heat insulation characteristics of the primer layer containing hollow microparticles, the primer formulations of Example 5-0 (without hollow microparticles), 5-1 (10 wt% NTR-50), and 5-5 (5 wt% NTR-50 and 5 wt% NTR-100) were used. The temperature difference between the upper and lower surfaces of the imaging sheet containing the primer layer was measured as a function of the heating time at a preset jig temperature of 70°C using an apparatus as shown in Figure 2A, and thermal probes were placed above and below the imaging sheet.

[0124] Referring to FIG. 2B, the temperature difference between the upper and lower parts of the primer layer is significantly increased by the addition of hollow microparticles, and further increased by the addition of a blend of hollow microparticles. Comparing with the difference of about 3.5 °C after 26 seconds and about 5.4 °C after 29 seconds for the primer layer without hollow microparticles and the bare MELINEX® 339 substrate respectively, in the primer layer containing hollow microparticles, the temperature difference reaches a maximum of about 17 °C after about 20 seconds. As shown in FIG. 2B, the presence of hollow microparticles significantly increases both the rate of temperature rise and the equilibrium temperature of the upper surface of the primer layer (or the lower surface of the image layer if the image layer is coated on top of the primer).

[0125] The actual temperature differences between the upper and lower probes for each sample are shown in FIGS. 3A - 3F. The slight periodic deviation in the temperature of the upper probe is due to the cycling of the heater by relay control (shutting off the heater at 70 °C). Consistent with the results shown in FIG. 2B, the equilibrium temperature difference between the upper and lower probes is greatest in the primer layer with a blend of NTR - 50 / NTR - 100 hollow microparticles (Example 5 - 5, 8.3 °C, FIG. 3F), followed by the primer layer with only NTR - 50 hollow microparticles (Example 5 - 1, 6.7 °C, FIG. 3E), which is much higher than the temperature differences observed in the formulation without hollow microparticles (Example 5 - 0, 2.5 °C, FIG. 3D) or the formulation without a primer layer (2.7 °C, FIG. 3C). FIGS. 3A and 3B overlay the temperature - time plots for all upper probe readings and all lower probe readings respectively.

[0126] Therefore, when hollow microparticles are present in the primer layer, the loss of thermal energy from the primer layer (e.g., leakage to the substrate) is effectively minimized. Furthermore, primer layers with blends of different hollow microparticle sizes appear to provide better insulation and heating efficiency than primer layers with a single hollow microparticle size.

[0127] Example 6. Influence of jig temperature and hollow microparticle composition on color development To test the influence of processing parameters (e.g., jig temperature) and the hollow particle composition (e.g., the ratio of NTR-50 to NTR-100) on color development, according to Examples 5-1 and 5-4, with NTR-50:NTR-100 ratios of 10 / 0 and 7 / 3 respectively, containing 10 wt% hollow particles, a primer layer (2 - 3 μm, 1 - pass corona treatment), a magenta capsule layer (thickness 8 μm, D 50 microcapsules with D of 5 - 6 μm were coated with 15 phm PERGASCRIPT® Red I6B to produce a microcapsule imaging sheet. A control experiment (Example 6-0) was prepared using the primer layer of Example 5-0 without any hollow particles. The obtained microcapsule imaging sheet was laminated with a developer sheet (15 μm developer RD9870 / 15% Novolac 586 on 1 mil transparent PET) at room temperature under low pressure. The prepared media were developed using a developing jig at various pre-set temperatures (60 °C, 70 °C, 80 °C).

[0128] Referring to Figure 4A here, the fresh Dmax of the media with Primer 5-1 (10% NTR-50 in the primer) increases from about 2.25 to about 2.35 as the jig temperature (60 °C to 80 °C) increases. After cooling to room temperature, Dmax continues to increase for about 1 hour, and the final Dmax value reaches from 2.35 (60 °C) to about 2.43 (80 °C). Assuming that Dmax 1 hour after jig development represents the maximum conversion of the leuco dye, the dye conversion immediately after jig development is calculated to be from 93.6% (60 °C) to 94.7% (80 °C).

[0129] Referring to FIG. 4B, the primer particulate composition can further improve the initial dye conversion and obtain a higher fresh Dmax. FIG. 4B shows that the Dmax for the control media with a primer without hollow particulates is about 2.2, while the media with primer layers according to Example 5-1 (NTR-50 only) and Example 5-4 (NTR-50:NTR-100 is about 7:3) showed significant improvements in fresh Dmax (about 2.37 and 2.48, respectively). This approximately 10% increase in Dmax, without being bound by a specific theory, is thought to be due to the improved heat insulation achieved by the hollow particulates, in order to prevent the loss of thermal energy from the active dye development region.

[0130] Example 7. Influence of the primer composition on color density and color development To test the influence of the primer layer composition on color development and color density, a microcapsule imaging layer containing a magenta leuco dye as shown in Table 1 was coated on a primer layer derived from a composition containing various concentrations of NTR-50, NTR-100, and TIPURE™ 6431 as shown in Table 10. This microcapsule sheet was laminated with a developer sheet having the composition described in Table 4. The jig temperature was maintained at 60° C. for color development, and the maximum color density was measured immediately after pressure development (Dmax, fresh), 4 hours after development (Dmax, 4 hours), and 12 hours after development (Dmax, 12 hours). The results are shown in Table 10 and FIGS. 5A - 5B.

Table 10

[0131] Figure 5A shows the optical image of the newly developed imaging sheet corresponding to the Dmax and flash values shown in Table 10 and Figure 5B. On the other hand, Figure 5B shows the color development (optical density) immediately after development (Dmax (fresh)), after 4 hours (Dmax, 4 hours), and after 12 hours (Dmax, 12 hours). As shown in Figures 5A - 5B and Table 10, the primer layer containing 22.8 wt% TiO2, 16.0 wt% NTR - 50, and 4.0 wt% NTR - 100 provided higher Dmax (fresh), Dmax (4 hours), and Dmax (12 hours) than the microcapsule layer directly coated on the substrate (MELINEX® 339), or the primer layer containing only M35 or M35 + TiO2. Therefore, TiO2 and The addition of hollow microparticles significantly improves the fresh Dmax and final Dmax values. Without being bound by a particular theory, when 22 - 23 wt% TiO2 (Example 7 - 1) is present in the primer layer, (1) due to the high reflectivity, more colors can be detected by the viewer's eyes, and / or (2) it is considered that the increase in the elastic modulus of the medium or the improvement of the capsule rupture efficiency due to the stress concentration at the microcapsule - primer interface occurs. The addition of hollow microparticles NTR - 50 and NTR - 100 (Example 7 - 2) further significantly improved Dmax, especially the newly developed Dmax. Without being bound by a particular theory, the presence of hollow microparticles is considered to have significantly improved the thermal efficiency of the medium and thus Dmax even at a low jig temperature of 60°C.

[0132] Example 8. Influence of the black backcoat on the early exposure of the second imaging sheet in the media stack A primer coating containing 30 (dry) parts of NW-WNQ11 TiO2 dispersion (solid content 54.73%), 11.05 (dry) parts of MK-WD42515 CaCO3 dispersion (solid content 33.16%), 37.80 (dry) parts of M35 latex, 20.0 (dry) parts of ROPAQUE (trademark) ULTRA-E hollow microparticles (solid content 29.89%), 0.15 (dry) parts of TAMOL (trademark) 165A, 0.75 (dry) parts of CELLOSIZE (trademark) QP-52000H, 0.05 (dry) parts of SILWET (registered trademark) L-7604, and 0.1 (dry) parts of FOAMSTAR (registered trademark) ST2410 was coated on the first surface of MELINEX (registered trademark) 339 to a dry thickness of 2.4 + 0.1 μm.

[0133] On the second surface of MELINEX (registered trademark) 339 (opposite side of the primer coating substrate), a backcoat containing 30.0 (dry) parts of NW-WNQ11 TiO2 dispersion (54.73% solid content), 3 (dry) parts of CAB-O-SPERSE (registered trademark) 1015A fumed silica dispersion (11.9% solid content), 0 - 10 (dry) parts of NW-KAB85 carbon black dispersion (27% solid content), 35.55 - 41.55 (dry) parts of PRIMAL (trademark) AC-261T (51.24% solid content), 20.0 (dry) parts of ROPAQUE (trademark) ULTRA-E hollow microparticles (solid content 29.89%), 0.15 (dry) parts of TAMOL (trademark) 165A, 1.0 (dry) parts of CELLOSIZE (trademark) QP-52000H, 0.05 (dry) parts of SILWET (registered trademark) L-7604, and 0.1 (dry) parts of FOAMSTAR (registered trademark) ST2410 was coated on the first surface of MELINEX (registered trademark) 339 to a dry thickness of 5.0 + 0.1 μm.

[0134] A microcapsule imaging layer was coated on the primer layer, and the resulting microcapsule sheet was laminated with a developer sheet as described in Example 7 to obtain an imaging media sheet. Next, two imaging sheets were stacked with the developer sheet facing up, and then the stack was irradiated with 14.3 mW / cm 2Through a neutral density step wedge equipped with a green LED, it was exposed from the upper media sheet for 1 to 30 seconds. Then, the lower media sheet was developed using a pressure jig, and the optical density of each step was recorded as shown in FIG. 6 and Table 11.

[0135] Referring to FIG. 6 and Table 11, the control media sheet without a backcoat is E 10 (The exposure energy required to lose 10% of the optical density of the lower media sheet) is about 0.3 mJ / cm 2 At, with an exposure time of 1 second, it was exposed early through the upper media sheet. In fact, the lower media sheet has an exposure time of 30 seconds and is actually completely overexposed. For the backcoat with 30 wt% TiO2 (Example 8-1), the E 10 of the lower media sheet increased slightly to about 0.4 mJ / cm 2 , but it was still easily exposed early through the upper media sheet. For the backcoat containing 30 wt% TiO2 and 4 wt% black pigment (NW-KAB85), E 10 increased significantly to 154 mJ / cm 2 at an exposure time of 30 seconds. For the backcoat containing 30 wt% TiO2 and 10 wt% black pigment (NW-KAB85), E 10 further increased significantly to >271 mJ / cm 2 at an exposure time of 30 seconds. The lower media sheet basically has no early exposure when a backcoat containing more than 4 to 7 wt% black pigment and 30 wt% TiO2 is applied to the second surface of the substrate during the exposure of the upper media sheet. As shown in Table 11, the Dmax of the media sheet containing a black backcoat increases as the concentration of the black pigment increases.

Table 11

[0136] Example 9. Influence of primer and backcoat on the resolution of the imaging sheet To investigate the influence of the primer and the backcoat on the resolution of the imaging sheet, the same primer coating and backcoat as those described in Example 8 were used. For the backcoat, 35.8 (dry) parts of M35 latex (instead of PRIMAL™ AC-261T) were used as the binder, and 20 parts (dry) of carbon black and 20 parts (dry) of TiO2 were used in the backcoat. The same green-sensitive microcapsule layer as that used in Example 8 was coated on bare MELINEX® 339 (capsule sheet 9-1), MELINEX® 339 with primer (capsule sheet 9-2), and MELINEX® 339 with both primer and backcoat (capsule sheet 9-3). The obtained microcapsule sheets were laminated with the same developer sheet as in Example 8 at 90 °C, 3.621 Kgf / 170 mm, and 0.368 m / min using a Tamerica roll laminator TCC2700 to form the media sheets of Examples 9-1, 9-2, and 9-3 (corresponding to capsule sheets 9-1, 9-2, and 9-3, respectively).

[0137] The green photosensitive media sheet was exposed through a collimated light unit (model ESPCOL60-W) at 0.8 mW / cm 2 for 1.7 to 4.0 seconds via a PET photomask with black and white lines of different line widths from 20 μm to 1000 μm. The exposed media sheet was developed as described in the previous example, and the widths of the developed lines are shown in Tables 12A and 12B.

Table 12A

Table 12B

[0138] As is clear from Table 12A, the presence of the primer layer showed a significant improvement in many aspects of media performance, as exemplified in Examples 1 to 7, but it made the printing of thin black lines more difficult (Example 9-2). By adding a black backcoat (Example 9-3), the demerits caused by the primer layer can be compensated for. In fact, the media sheet with both the primer and the black backcoat showed a significantly improved suitability for printing thin black lines up to 28 μm (Example 9-3) compared to 36.0 μm and 40 μm of the control (Example 9-1) and that with only the primer coating (Example 9-2), respectively.

[0139] Table 12B shows the influence of the primer and the black backcoat on the suitability for printing thin white lines. Although the sample with only the primer layer (Example 9-2) had the narrowest suitability for printing white lines, the addition of the black backcoat (Example 9-3) showed overall optimal white line printing line width control because it could best reproduce the line width of the photomask in a wider line width range.

[0140] The compositions and methods illustratively described herein can be preferably implemented even in the absence of any element or elements, limitation or limitations not specifically disclosed herein. Thus, for example, terms such as "comprising", "including", "containing", etc. shall be understood in a broad sense without limitation. Further, the terms and expressions used herein are used as terms of explanation and not of limitation, and there is no intention to exclude any equivalents of the features shown and described or parts thereof by the use of such terms and expressions. It is recognized that various changes are possible within the scope of the claimed disclosure. Accordingly, although the present disclosure is specifically disclosed by preferred embodiments and any features, it should be understood that changes and modifications to the disclosure disclosed herein may be claimed by those skilled in the art, and such corrections and modifications are considered to be within the scope of the present disclosure.

[0141] Specifically intended is that, unless the context specifically indicates otherwise, the various features of the invention described herein can be used in any combination. Further, this disclosure also contemplates that, in some embodiments, any feature or combination of features described herein may be excluded or omitted. By way of illustration, when this specification states that a composite includes components A, B, and C, it is specifically intended that any one of A, B, or C, or combinations thereof, can be omitted and excluded, either singly or in any combination.

[0142] This disclosure is described herein in a broad and encompassing manner. Each of the respective groups of the narrower species and subgenera that fall within the general disclosure also forms part of the compositions and methods. This includes general descriptions of compositions or methods with provisos or negative limitations that exclude any subject matter from the genus, whether or not the extracted material is specifically described herein. The technology is not limited to the specific embodiments described in this application, and these embodiments are intended as representative examples of the individual aspects of the technology. As will be apparent to those skilled in the art, many changes and modifications of the technology can be made without departing from its spirit and scope. In addition to those listed herein, functionally equivalent compositions, methods, and devices within the scope of the technology will be apparent to those skilled in the art from the foregoing description. Such changes and modifications are intended to fall within the scope of the technology. It should be understood that the technology is not limited to specific methods, reagents, compounds, or compositions, which can, of course, be varied. It should also be understood that the terms used herein are for the purpose of describing only specific embodiments and are not intended to be limiting.

[0143] Those skilled in the art will readily understand that this disclosure is well adapted to carry out the objectives and obtain the mentioned objectives and advantages, as well as those inherent therein. Changes and other uses thereof will occur to those skilled in the art. These changes are encompassed within the spirit of the disclosure and are defined by the scope of the claims that define the non-limiting embodiments of the disclosure.

[0144] In addition, when a feature or aspect of the present disclosure is described from the perspective of a Markush group, one of ordinary skill in the art will recognize that the present disclosure is thereby described from the perspective of any individual member or subgroup of members of the Markush group.

Claims

1. A polymer binder, white fine particles constituting about 3 to about 60% by weight of the total weight of the primer layer, and a substrate, a primer layer for a microcapsule imaging sheet containing the same.

2. The primer layer according to claim 1, further comprising polymer hollow fine particles constituting about 1 to about 30% by weight of the total weight of the primer layer.

3. The primer layer according to claim 1 or claim 2, wherein the white fine particles have a refractive index of about 1.5 to about 3.

0.

4. The white fine particles are TiO ２ , BaSO ４ , CaSO ４ , CaCO ３ , Al ２ O ３ , and Ca ３ (PO ４ ) ２ The primer layer according to any one of claims 1 to 3, selected from the group consisting of

5. The white fine particles are TiO ２ The primer layer according to any one of claims 1 to 4, wherein the primer layer is as described above.

6. The white fine particles are TiO ２ and basic fine particles, and the primer layer according to any one of claims 1 to 5.

7. The basic fine particles are CaCO ３ , Al ２ O ３ , or Ca ３ (PO ４ ) ２ The primer layer according to claim 6, wherein the primer layer is the above.

8. The primer layer according to any one of claims 1 to 7, wherein the white fine particles have an average particle diameter of about 50 nm to about 2000 nm.

9. The primer layer according to any one of claims 1 to 8, wherein the white fine particles have an average particle diameter of about 100 nm to about 300 nm.

10. The primer layer according to any one of claims 1 to 9, wherein the concentration of the white fine particles is about 10 to about 50% by weight based on the total weight of the primer layer.

11. The primer layer according to any one of claims 1 to 10, wherein the polymer binder contains a latex polymer having a glass transition temperature of about -70°C to about 40°C.

12. The primer layer according to any one of claims 1 to 11, wherein the polymer binder contains a latex polymer having a glass transition temperature of about -20°C to about 20°C.

13. The primer layer according to any one of claims 1 to 12, wherein the polymer binder is selected from the group consisting of acrylic polymers or copolymers, styrene copolymers, butadiene copolymers, vinyl chloride copolymers, vinylidene chloride copolymers, epoxy copolymers, ethylene copolymers, propylene copolymers, vinyl acetate copolymers, polyesters, polyurethanes, polylactones, polyamides, polyvinylpyrrolidone, and blends or copolymers thereof.

14. The primer layer according to claim 2, wherein the polymer hollow fine particles include a polymer shell and an air core.

15. The primer layer according to claim 2, wherein the polymeric hollow microparticles comprise a polymer shell containing a polymer selected from the group consisting of polyacrylic acid, polymethacrylate, polystyrene, polyvinyl acetate, polyolefin, polyamide, polyester, polyureas, polyurethane, melamine formaldehyde, phenolic resin, and blends or copolymers thereof.

16. The primer layer according to claim 2, wherein the polymeric hollow microparticles have an average particle diameter of about 200 nm to about 2000 nm.

17. The primer layer according to claim 14, wherein the air core has a diameter of about 50 nm to about 1000 nm.

18. The primer layer according to claim 14, wherein the air core has a diameter of about 100 nm to about 400 nm.

19. The polymer hollow fine particles have a dry specific gravity of about 0.1 g / cm ３ to about 0.7 g / cm ３ The primer layer according to claim 2.

20. The primer layer according to claim 2, wherein the polymeric hollow microparticles are present at a concentration of about 5 to about 30% by weight based on the total weight of the primer layer.

21. The primer layer according to claim 14, wherein the polymeric hollow microparticles comprise a blend of first polymeric hollow microparticles having a first average particle diameter and second polymeric hollow microparticles having a second average particle diameter.

22. The primer layer according to any one of claims 1 to 21, wherein the primer layer has a thickness of about 1 μm to about 10 μm.

23. The primer layer according to any one of claims 1 to 22, wherein the primer layer has a thickness of about 2 μm to about 5 μm.

24. A first substrate, The primer layer according to any one of claims 1 to 23, which is in contact with a first surface of the first substrate, A microcapsule imaging sheet comprising a photosensitive microcapsule layer in contact with the primer layer.

25. The microcapsule imaging sheet according to claim 24, wherein the microcapsule imaging sheet is a full-color imaging sheet comprising photosensitive microcapsules including red-sensitive, green-sensitive, and blue-sensitive microcapsules.

26. The photosensitive microcapsules, A polymer shell, A core containing a leuco dye, a photoinitiator, and a polymerizable or crosslinkable monomer or oligomer, The microcapsule imaging sheet according to claim 24 or claim 25.

27. The microcapsule imaging sheet according to claim 26, wherein the leuco dye is one or more of cyan, magenta, yellow, or black leuco dyes.

28. The microcapsule imaging sheet according to claim 26 or claim 27, wherein the photoinitiator is a red-sensitive, green-sensitive, or blue-sensitive cyanine borate or semi-cyanine borate.

29. The microcapsule imaging sheet according to any one of claims 24 to 28, further comprising (i) the microcapsule layer and / or the primer layer, and (ii) a developer layer in contact with a developer substrate.

30. The microcapsule imaging sheet according to any one of claims 24 to 29, further comprising a backcoat on a second surface of the first substrate, wherein the first surface of the first substrate is coated with the primer layer.

31. The microcapsule imaging sheet according to claim 30, wherein the backcoat comprises a black pigment or dye and a polymer binder.

32. The microcapsule imaging sheet according to claim 30 or claim 31, wherein the backcoat comprises 1 to 30% by weight of a black pigment or dye based on the total weight of the backcoat.

33. The microcapsule imaging sheet according to claim 32, wherein the backcoat comprises 3 to 20% by weight of a black pigment or dye based on the total weight of the backcoat.

34. The microcapsule imaging sheet according to any one of claims 31 to 33, wherein the black pigment is carbon black.

35. The microcapsule imaging sheet according to any one of claims 31 to 34, wherein the backcoat further comprises hollow polymer microparticles.

36. The backcoat is TiO ２ , silica, BaSO ４ , CaSO ４ , BN, CaCO ３ , Al ２ O ３ , AlN, and Ca ３ (PO ４ ) ２ The microcapsule imaging sheet according to any one of claims 30 to 35, further comprising fine particles selected from the group consisting of

37. A method for producing an imaging sheet, comprising: (i) coating a first surface of a first substrate with a primer layer according to any one of claims 1 to 23 to produce a first substrate coated with the primer; and (ii) contacting the primer layer of the first substrate coated with the primer with a microcapsule layer to produce a first substrate coated with microcapsules. (iii) contacting a first substrate coated with the microcapsules with a developer layer to produce a first substrate coated with a developer; (iv) contacting the developer layer of the first substrate coated with the developer with a second substrate to produce an imaging sheet. A method comprising:

38. A method for producing an imaging sheet, comprising: (i) coating a first surface of a first substrate with a primer layer according to any one of claims 1 to 23 to produce a first substrate coated with a primer; (ii) contacting the primer layer of the first substrate coated with the primer with a microcapsule layer to produce a first substrate coated with microcapsules; (iii) contacting a second substrate with a developer layer to produce a second substrate coated with a developer; (iv) contacting the developer layer of the second substrate coated with the developer with the microcapsule layer of the first substrate coated with the microcapsules to produce an imaging sheet. A method comprising:

39. The method according to claim 37 or claim 38, wherein a second primer layer is disposed between the second substrate and the developer layer.

40. (v) further comprising contacting a second surface of the first substrate with a backcoat, wherein the second surface of the first substrate is on the opposite side of the first surface of the first substrate. The method according to any one of claims 37 to 39.

41. The method according to claim 40, wherein the contacting in (v) is performed by physical vapor deposition, sputtering, chemical vapor deposition, lamination, or spin coating.

42. A method of imaging or printing, comprising: exposing an imaging sheet comprising a primer layer according to any one of claims 1 to 23 and a microcapsule layer comprising microcapsules to heat, pressure, or radiation, wherein the microcapsules comprise a polymer shell and an internal phase comprising a leuco dye, the exposure being sufficient to release the leuco dye from the microcapsules in the microcapsule layer to generate an image. A method.

43. A method for improving one or more properties of an imaging sheet, comprising: including the step of adding the primer layer according to any one of claims 1 to 23 to the imaging sheet, wherein the one or more properties include one or more of Dmax, fresh Dmax, Dmax,t, Dmin, image resolution, hiding power, blocking resistance, adhesiveness, reflective optical density, and heat insulation performance, a method.

Images