Microcapsule imaging system containing a non-photopolymerizable reactive diluent

Abstract

Microcapsules (208, 209) comprising a polymer shell (116) and an internal phase (118) containing a non-photopolymerizable reactive diluent are provided for use in a microcapsule imaging sheet. An imaging sheet is provided that includes microcapsules (209) containing a non-photopolymerizable reactive diluent and exhibits improved color development (Dmax), color change resistance (yellowing), mechanical properties (e.g., peel strength), and temperature latitude of the imaging sheet containing a leuco dye.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Application No. 17 / 833,731, 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 microcapsules having an internal phase containing a non - photopolymerizable reactive diluent for use in microcapsule imaging systems.

Background Art

[0003] Since the 1980s, single - sheet self - contained full - color microcapsule imaging systems (e.g., CYCOLOR® manufactured by Mead, Inc., in Miamisburg, Ohio) have been developed. In such 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, functional 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 encapsulated internal phase 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, conventional leuco dyes have insufficient temperature latitude, especially at low temperatures. To increase color density, microcapsules contain a high concentration of leuco dyes. However, at low storage or operating temperatures, the leuco dyes tend to precipitate, resulting in a degradation of image quality. Furthermore, conventional imaging sheets have a high internal phase viscosity and poor mobility of leuco dyes even under low energy exposure or low degrees of polymerization of the internal phase, resulting in insufficient color rendering of intermediate tones. As a result, the resulting image has a high contrast ratio and loses details in the intermediate tones. Additionally, at maximum color density (Dmax), the leuco dyes tend to spread over a wide area, but spread slowly, resulting in a degradation of image resolution, especially with respect to the sharpness of edges.

[0005] Some of the above problems can be avoided by adding a non-polymerizable, inert solvent or diluent (e.g., dibutyl phthalate, dioctyl phthalate, trioctyl phosphate, trioctyl trimellitate, bisoctyl adipate, dioctyl sebacate, etc.) to improve the solubility of the leuco dyes and reduce the viscosity of the internal phase. However, the presence of an additional liquid solvent in the imaging sheet can cause non-uniform image quality, degradation of film integrity, or delamination.

[0006] The inventors have discovered that using a non-photopolymerizable but reactive solvent or diluent (e.g., an epoxide compound) addresses the problems of low-temperature latitude, mid-tone color rendition, and slow color development speed. The epoxide group cannot be photopolymerized by a radical-type photoinitiator in the internal phase. Upon pressure generation in the exposed image sheet, the epoxide released from the ruptured microcapsules reacts with the phenolic or carboxylic acid groups of the developer to crosslink. This improves the image resolution, edge sharpness, film integrity, and mechanical properties. The color development speed by the developer is usually faster than or equivalent to the speed of the epoxide crosslinking reaction. Therefore, high color density or high color development speed can be achieved without typical trade-offs in image quality and film integrity.

Means for Solving the Problems

[0007] In one aspect that can be combined with any other aspect or embodiment, the present disclosure relates to a photosensitive microcapsule for a microcapsule imaging sheet, comprising an internal phase including a polymer shell, a leuco dye, a non-photopolymerizable diluent configured to react with a leuco dye developer, a photoinitiator, and a polymerizable or crosslinkable monomer or oligomer, preferably a polyfunctional monomer or oligomer.

[0008] In some embodiments, the leuco dye developer includes a Lewis acid, an acidic clay, or one or more compounds containing a phenolic or carboxylic acid group, or a metal complex thereof. In some embodiments, the leuco dye developer includes a novolak resin, a salicylic acid derivative, a zincate derivative thereof, or a combination, copolymer, blend, complex, or metal complex derivative thereof.

[0009] In some embodiments, the diluent comprises an epoxide compound. In some embodiments, the epoxide compound comprises two or more epoxide moieties. In some embodiments, the diluent comprises a diepoxide or a triepoxide compound. In some embodiments, the epoxide compound comprises at least one selected from the group consisting of triglycidyl trimethylolpropane (TMPTGE), epoxidized oil containing epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, dicyclopentadiene diepoxide, alicyclic diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and diglycidyl ester of 1,2-cyclohexanedicarboxylic acid.

[0010] In some embodiments, the diluent is present at a concentration of about 3 wt% to about 20 wt% based on the total weight of the internal phase. In some embodiments, the diluent is present at a concentration of about 3 wt% to about 10 wt% based on the total weight of the internal phase.

[0011] In some embodiments, the diluent has a water solubility of about 5 wt% or less. In some embodiments, the diluent has a water solubility of about 1 wt% or less.

[0012] In some embodiments, when the diluent is measured using a Brookfield viscometer at 100 rpm, it has a viscosity of about 300 cps or less at 25°C. In some embodiments, when the diluent is measured using a Brookfield viscometer at 100 rpm, it has a viscosity of about 100 cps or less at 25°C.

[0013] In some embodiments, the internal phase further comprises a co-initiator, an oxygen scavenger, or a self-oxidizer. Suitable oxygen scavengers include, but are not limited to, N,N,-dialkyl derivatives such as ethyl 4-(dimethylamino)benzoate, N,N-dimethylaminodiisopropylbenzene (DIDMA), and N,N,-dimethylethyl acrylate. Suitable self-oxidizers include, but are not limited to, organic disulfides such as mercaptobenzothiazole disulfide (MTBS) and 2-ethoxymercaptobenzothiazole disulfide.

[0014] In some embodiments, the polymerizable or crosslinkable monomer or oligomer comprises a functional polyfunctional acrylate.

[0015] In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to an imaging sheet comprising: (i) microcapsules comprising a polymer shell and an internal phase comprising a leuco dye, a non-photopolymerizable diluent configured to react with the leuco dye developer, a photoinitiator, and a polymerizable or crosslinkable monomer or oligomer; (ii) a first substrate in contact with the microcapsules; and (iii) a leuco dye developer. In some embodiments, the first substrate is in contact with the microcapsules.

[0016] In some embodiments, the leuco dye developer comprises a Lewis acid, an acidic clay, or one or more compounds comprising a carboxylic acid group or a phenol group, or metal complexes thereof. In some embodiments, the leuco dye developer is a novolak resin, a phenol resin, salicylic acid, or a combination, copolymer, blend, composite, or metal complex derivative thereof. In some embodiments, the metal is zinc.

[0017] In some embodiments, the imaging sheet further includes a second substrate that contacts the leuco dye developer. In some embodiments, one of the first and second substrates is opaque. In some embodiments, the opaque substrate is white. In some embodiments, the first substrate is opaque or white.

[0018] In some embodiments, the first substrate further includes a primer layer that contacts the microcapsules. In some embodiments, the primer layer includes fine particles. In some embodiments, the fine particles include at least one selected from the group consisting of CaCO3, CaSO4, BaSO4, silica, TiO2, Al2O3, BN, Ca3(PO4)2, and their hydrophobically treated derivatives.

[0019] In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to microcapsules for a microcapsule imaging sheet including a polymer shell and an internal phase including a non-photopolymerizable diluent configured to react with a leuco dye developer.

[0020] In some embodiments, the diluent includes an epoxide compound. In some embodiments, the epoxide compound includes two or more epoxide moieties. In some embodiments, the diluent includes a diepoxide or a triepoxide compound. In some embodiments, the epoxide compound includes at least one selected from the group consisting of triglycidyl trimethylolpropane (TMPTGE), epoxidized oils including epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, dicyclopentadiene diepoxide, alicyclic diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and diglycidyl ester of 1,2-cyclohexanedicarboxylic acid.

[0021] In some embodiments, the diluent is present at a concentration of about 50 wt% to about 100 wt% based on the total weight of the internal phase. In some embodiments, the diluent is present at a concentration of about 90 wt% to about 100 wt% based on the total weight of the internal phase.

[0022] In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to (i) diluent microcapsules comprising a polymer shell and an internal phase comprising a non-photopolymerizable diluent configured to react with a leuco dye developer, (ii) photosensitive microcapsules comprising a polymer shell and an internal phase comprising a leuco dye, a photoinitiator, and a polymerizable or crosslinkable monomer or oligomer, (iii) a first substrate in contact with the microcapsules, and (iv) an imaging sheet comprising a leuco dye developer.

[0023] In some embodiments, the leuco dye developer comprises a Lewis acid or acidic clay, or comprises one or more compounds having a phenol group or a carboxylic acid group.

[0024] In some embodiments, the diluent comprises an epoxide compound. In some embodiments, the epoxide compound comprises two or more epoxide moieties. In some embodiments, the diluent comprises a diepoxide or a triepoxide compound. In some embodiments, the epoxide compound comprises at least one selected from the group consisting of triglycidyl trimethylolpropane (TMPTGE), epoxidized oils including epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, dicyclopentadiene diepoxide, alicyclic diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and 1,2-cyclohexanedicarboxylic acid diglycidyl ester.

[0025] In some embodiments, the diluent is present at a concentration of about 50 wt% to about 100 wt% based on the total weight of the internal phase. In some embodiments, the diluent is present at a concentration of about 90 wt% to about 100 wt% based on the total weight of the internal phase of the diluent microcapsules.

[0026] In some embodiments, the leuco dye developer is a novolak resin, a phenolic resin, salicylic acid, or a combination thereof, a copolymer, a blend, a composite, or a metal complex derivative. In some embodiments, the metal is zinc.

[0027] In some embodiments, the imaging sheet further comprises a second substrate in contact with the leuco dye developer. In some embodiments, one of the first and second substrates is opaque. In some embodiments, the opaque substrate is white.

[0028] In some embodiments, the first substrate further comprises a primer layer in contact with the microcapsules. In some embodiments, the primer layer contains fine particles. In some embodiments, the fine particles include at least one selected from the group consisting of CaCO3, CaSO4, BaSO4, silica, BN, Al2O3, TiO2, Ca3(PO4)2, their hydrophobically treated derivatives, and any combination thereof.

[0029] In some embodiments, the internal phase of the photosensitive microcapsules further comprises a non-photopolymerizable diluent configured to react with the leuco dye developer. In some embodiments, the diluent contains an epoxide compound. In some embodiments, the epoxide compound contains two or more epoxide moieties. In some embodiments, the diluent contains a diepoxide or a triepoxide compound. In some embodiments, the epoxide compound includes at least one selected from the group consisting of triglycidyl trimethylolpropane (TMPTGE), an epoxide oil containing epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, dicyclopentadiene diepoxide, an alicyclic diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and 1,2-cyclohexanedicarboxylic acid diglycidyl ester.

[0030] In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to a microcapsule composition comprising one or more microcapsules described in any of the embodiments disclosed herein and a carrier in which the one or more microcapsules are dispersed.

[0031] In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to a method for producing an imaging sheet, comprising: (i) contacting a first substrate with a microcapsule layer to produce a first substrate coated with microcapsules; (ii) contacting the microcapsule layer of the first substrate coated with microcapsules with a developer layer to produce a first substrate coated with a developer; and (iii) contacting the developer layer of the first substrate coated with the developer with a second substrate to produce an imaging sheet.

[0032] In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to a method for producing an imaging sheet, comprising: (i-a) contacting a first substrate with a primer layer to produce a first substrate coated with a primer; (i-b) contacting the primer layer of the first substrate coated with the primer with a microcapsule layer to produce a first substrate coated with microcapsules; (ii) contacting the microcapsule layer of the first substrate coated with microcapsules with a developer layer to produce a first substrate coated with a developer; and (iii) contacting the developer layer of the first substrate coated with the developer with a second substrate to produce an imaging sheet.

[0033] In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to a method of making an imaging sheet, the method comprising: (i) making a first substrate coated with microcapsules as described in any of the embodiments disclosed herein (e.g., contacting a first substrate or a first substrate coated with a primer with a microcapsule layer); (ii) contacting a second substrate with a developer layer to make a second substrate coated with a developer; and (iii) contacting the microcapsule layer of the first substrate coated with microcapsules with the developer layer of the second substrate coated with a developer to make an imaging sheet.

[0034] In some embodiments, a primer layer according to any of the embodiments disclosed herein is disposed (i) between the second substrate and the developer layer, (ii) between the second substrate and the developer layer, or between the first substrate and the microcapsule layer, or (iii) between the second substrate and the developer layer and between the first substrate and the microcapsule layer.

[0035] In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to a method of adjusting one or more properties of an imaging sheet, the method comprising including (or adding to) the imaging sheet one or more microcapsules as described in any one 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, temperature latitude, dynamic range, color change resistance (yellowing), and edge sharpness. BRIEF DESCRIPTION OF THE DRAWINGS

[0036]

Figure 1

Figure 2

[0037] 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 will be understood by those skilled in the art.

[0038] Referring to FIG. 1A, in some embodiments, a microcapsule imaging sheet 100 according to the present disclosure includes a microcapsule layer 106 disposed on a first substrate 102 and containing microcapsules 108 (e.g., photosensitive and / or non-photosensitive microcapsules), which may optionally include a primer layer 104 in contact with the first substrate and / or the microcapsule layer 106. The microcapsule layer may be in contact with a developer layer 110a disposed on a second substrate 114, which is configured to be separately disposed so as to be in contact with the microcapsule layer 106.

[0039] Alternatively, as shown in FIG. 1B, the microcapsule layer 106 may be overcoated with the developer layer 110b. The resulting microcapsule / developer imaging sheet can be used as is or laminated with a second substrate 114, which may be pre-coated with an adhesive layer (not shown). Alternatively, the microcapsule layer composition may be mixed with the developer layer composition and coated as a single layer (not shown).

[0040] Referring to FIG. 1C, the microcapsules 108 may be photosensitive microcapsules, which include a polymer shell 116 and a core (or internal phase) 118 encapsulated therein, which can be softened or cured by actinic radiation. The internal phase 118 contains a dye (e.g., a leuco dye), which imparts color to the microcapsule imaging sheet upon release under pressure and upon simultaneous or subsequent exposure to heat, specific pH conditions, reactive chemical species, or a developer. When released from the microcapsules 108, the dye (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).

[0041] The internal phase 118 of the photosensitive microcapsules may further contain one or more photoinitiators, one or more polyfunctional functional monomers or oligomers, and one or more non-photopolymerizable reactive diluents. The non-photopolymerizable reactive diluent can be configured to react with a Lewis acid, a phenol group, or a carboxylic acid group (e.g., within the developing layer), and their metal complexes, especially their zincated derivatives, but should not react with photoinitiators, sensitizers, co-initiators, oxygen scavengers, self-oxidants, chain transfer agents, and / or monomers or oligomers that may be present in the internal phase 118. Suitable oxygen scavengers include, but are not limited to, N,N,-dialkyl derivatives such as ethyl 4-(dimethylamino)benzoic acid, N,N-dimethylaminodiisopropylbenzene (DIDMA), and N,N,-dimethylethyl acrylate. Suitable self-oxidants include, but are not limited to, organic disulfides such as mercaptobenzothiazole disulfide (MTBS) and alkoxymercaptobenzothiazole disulfide, 2-ethoxymercaptobenzothiazole disulfide.

[0042] The photosensitive microcapsules 108 may include a polymer shell and a photosensitive core, which can be photocured by polymerizing or crosslinking the monomers / oligomers contained therein. In some embodiments, the photocurable monomer may be replaced with a softening or photodegradable composition.

[0043] The polymer shell can be formed, for example, by interfacial or in-situ polymerization / crosslinking, simple or complex coacervation processes, phase separation, or combinations thereof. In some embodiments, suitable polymer shells include, but are not limited to, polyureas, polythioureas, polyurethanes, polythiourethanes, polyallophanates, polycarbamates, polysulfones, melamine-formaldehyde or urea-formaldehyde condensates, gelatin-gum arabic complexes, gelatin-carboxymethylcellulose complexes, and copolymers, interpolymer complexes, blends or composites thereof. In some embodiments, water-insoluble polymers that are incompatible with the internal phase or non-swelling / insoluble in the internal phase are preferred as shell materials because they tend to exhibit favorable barrier properties against moisture and / or oxygen.

[0044] The shell provides desirable oxygen barrier properties to ensure the high photosensitivity of the photosensitive core and avoid premature mixing of the photoinitiator with various colored dye precursors, thereby guaranteeing successful color separation and reproduction.

[0045] In some embodiments, the photocurable core comprises a dye (e.g., a leuco dye), a photoinitiator or sensitizer, and a polymerizable or crosslinkable monomer or oligomer. In some embodiments, the core comprises a polyfunctional monomer or oligomer. In some embodiments, the monomer or oligomer is selected from polyfunctional acrylates and methacrylates, polyfunctional vinyl ethers, polyfunctional allyls or vinylbenzenes, and their oligomers, dendrimers or blends. Polyfunctional acrylates are suitable due to 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). In some embodiments, the leuco dye is one or more of a cyan, magenta or yellow leuco dye.

[0046] The microcapsule layer may include one or more types of microcapsules. For example, the microcapsules may be sensitive to red visible light, green visible light, or blue visible light. The microcapsule layer may include red-sensitive, green-sensitive, or blue-sensitive microcapsules, in which case the microcapsule imaging sheet is considered a "full-color" imaging sheet. In some embodiments, the dye is a cyan, magenta, yellow or black leuco dye. As a non-limiting example, a representative magenta leuco dye, PERGASCRIPT® Red I6B (CAS: 50292-95-0, Synamedia-chem), may be included. In some embodiments, the photoinitiator is a blue-sensitive ketocoumarin, cyanine borate or semicyanine borate.

[0047] Referring now to FIG. 2, in some embodiments, the non-photopolymerizable reactive diluent is present in another microcapsule in which the internal phase does not contain a dye, a photoinitiator, or a polyfunctional oligomer. In such embodiments, the microcapsule layer 206 may include at least two different types of microcapsules, a dye microcapsule 208 and a diluent microcapsule 209. In some embodiments, the dye microcapsule may include the above-described components and features (e.g., a polymer shell, a leuco dye, a photoinitiator, a polyfunctional monomer or oligomer), and a non-photopolymerizable reactive diluent. In some embodiments, the dye microcapsule may include the above-described components and features (e.g., a polymer shell, a leuco dye, a photoinitiator, a polyfunctional monomer or oligomer) except for the non-photopolymerizable reactive diluent. In some embodiments, the diluent microcapsule comprises a polymer shell and an internal phase containing a non-photopolymerizable reactive diluent.

[0048] In some embodiments, the diluent microcapsule may be non-photosensitive, while the dye microcapsule may be photosensitive. In some embodiments, when the diluent is present in a microcapsule separate from the photosensitive dye microcapsule, the mechanical properties (e.g., peel strength) of the imaging sheet 200 and the discoloration resistance of the imaging sheet (e.g., lower yellow Dmin) are improved, but the improvement in temperature latitude may be relatively small compared to embodiments in which the diluent and the dye are present in the same microcapsule.

[0049] In some embodiments, the microcapsule imaging system includes photosensitive diluent microcapsules that include a shell, a non-photopolymerizable diluent, a photoinitiator or sensitizer, and a polyfunctional monomer.

[0050] In some embodiments according to FIG. 2, the first substrate 202, any primer layer 204, photosensitive dye microcapsules 208, diluent microcapsules 209, developer layer 210a, developer fine particles 210b, and second substrate 214 are the same as those described for the embodiments of FIGS. 1A and 1B.

[0051] In some embodiments, the imaging sheet is exposed from the developer side. In some embodiments, the imaging sheet is exposed from the microcapsule side. In some embodiments, the microcapsule sheet is first exposed, and then the developer sheet is laminated with the microcapsule sheet exposed under pressure to form a sandwich sheet with the developed image therein. In some embodiments, the microcapsule sheet is peeled off from the sandwich structure described above to leave a color image on the developer sheet.

[0052] Microcapsule layer The microcapsule layer includes photosensitive microcapsules having a polymer shell and an internal phase (or core). In some embodiments, the internal phase of the microcapsules includes a leuco dye, a photoinitiator, one or more polyfunctional monomers or oligomers, and one or more non-photopolymerizable reactive diluents.

[0053] In some embodiments, the microcapsule layer includes (i) photosensitive dye microcapsules including a polymer shell and an internal phase including a leuco dye, a photoinitiator, and a polyfunctional monomer or oligomer but not including a non-photopolymerizable reactive diluent, and (ii) non-photosensitive diluent microcapsules including a polymer shell and an internal phase consisting essentially of, or consisting of, a non-photopolymerizable reactive diluent.

[0054] In some embodiments, the dye microcapsules are photosensitive, while the diluent microcapsules are non - photosensitive, i.e., the core is not softened or cured by actinic radiation. In some embodiments, both the dye and diluent microcapsules are photosensitive, in which case the core is softened or cured by actinic radiation.

[0055] In some embodiments, the microcapsule layer contains dye microcapsules at a concentration, measured by dry weight relative to the total dry weight of the microcapsule layer, of at least about 50 wt%, at least about 70 wt%, at least about 80 wt%, at least about 85 wt%, at least about 90 wt%, or any range or value therebetween.

[0056] In some embodiments, the microcapsule layer contains one or more diluent microcapsules at a concentration, measured by dry weight relative to the total dry weight of the microcapsule layer, of at least about 1 wt%, at least about 2 wt%, at least about 3 wt%, at least about 4 wt%, at least about 5 wt%, at least about 6 wt%, at least about 7 wt%, at least about 8 wt%, at least about 9 wt%, at least about 10 wt%, at least about 11 wt%, at least about 12 wt%, at least about 13 wt%, at least about 14 wt%, at least about 15 wt%, at least about 16 wt%, at least about 17 wt%, at least about 18 wt%, at least about 19 wt%, at least about 20 wt%, at least about 25 wt%, at least about 30 wt%, or any range or value therebetween.

[0057] In some embodiments, the diluent microcapsules may contain two or more diluents. In some embodiments, the diluent microcapsules may contain a first diluent and a second diluent, and the weight ratio of the first diluent microcapsules to the second diluent microcapsules is about 1:10, 1:9, 1:8, 1:7, 2:7, 3:7, 4:7, 1:6, 1:5, 2:5, 3:5, 4:5, 1:4, 3:4, 1:3, 2:3, 1:2, 1:1, 2:1, 3:2, 3:1, 4:3, 4:1, 5:4, 5:3, 5:2, 5:1, 6:1, 7:4, 7:3, 7:2, 7:1, 8:1, 9:1, 10:1, or any range or value therein.

[0058] In some embodiments, the microcapsule layer may contain two or more diluent microcapsules. In some embodiments, the microcapsule layer may contain a first diluent microcapsule and a second diluent microcapsule, and the weight ratio of the first diluent microcapsules to the second diluent microcapsules is about 1:10, 1:9, 1:8, 1:7, 2:7, 3:7, 4:7, 1:6, 1:5, 2:5, 3:5, 4:5, 1:4, 3:4, 1:3, 2:3, 1:2, 1:1, 2:1, 3:2, 3:1, 4:3, 4:1, 5:4, 5:3, 5:2, 5:1, 6:1, 7:4, 7:3, 7:2, 7:1, 8:1, 9:1, 10:1, or any range or value therein.

[0059] In some embodiments, the microcapsules have a D 10 particle size of at least about 1 μm (10% of the microparticles are smaller than 1 μm), at least about 1.5 μm, or at least about 2 μm.

[0060] In some embodiments, the microcapsules have a D 50 particle size of at least about 2 μm (50% of the microparticles are smaller than 2 μm), at least about 3 μm, or at least about 4 μm. In some embodiments, the microcapsules have a D of about 15 μm or less, about 12 μm or less, or about 10 μm or less. 50It has a microparticle size. The pressure required to break the microcapsules decreases dramatically as the microparticle size increases. D less than about 2 μm 50 Microcapsules having a microparticle size are difficult to break at pressures readily available in portable printers, particularly handheld printers. Furthermore, a minimum shell thickness is often required to ensure adequate barrier properties to prevent premature damage to the internal phase or leakage from the microcapsules, so D 50 the smaller it is, the lower the payload of the internal phase in which the leuco dye dissolves. As a result, small microcapsules tend to result in imaging systems with a low maximum color density (Dmax).

[0061] In contrast, D 50 microcapsules having a D greater than about 15 μm can be more easily crushed during media handling and processing. Thus, imaging systems containing microcapsules having a D 50 greater than about 15 μm often exhibit higher Dmin (minimum color density of non-imaging or white areas) and lower resolution images.

[0062] Polymer shell In some embodiments, the microcapsules (e.g., dye microcapsules or diluent microcapsules) include a polymer shell that is either photosensitive or non - photosensitive. The polymer shell can be formed by processes including, but not limited to, interfacial polymerization or in situ polymerization / cross - linking, simple or complex coacervation processes, phase separation, or combinations thereof. Suitable polymer shells include, but are not limited to, polyureas, polythioureas, polyurethanes, polythiourethanes, polyallophanates, polycarbamates, polysulfones, melamine - formaldehyde or urea - formaldehyde condensates, gelatin - gum arabic complexes, gelatin - carboxymethylcellulose, or pectin complexes, as well as copolymers, interpolymer complexes, blends, or composites thereof. In some embodiments, water - insoluble polymers that are incompatible with the internal phase or non - swellable / insoluble in the internal phase are suitable as shell materials because they tend to exhibit excellent barrier properties against moisture and / or oxygen.

[0063] Leuco dye In some embodiments, the internal phase of the microcapsules contains a leuco dye. In some embodiments, the dye is a cyan, magenta, yellow, or black leuco dye. As non-limiting examples, representative magenta leuco dyes include PERGASCRIPT® Red I6B (CAS: 50292-95-0, Synamedia-chem), COPIKEM 35 (CAS: 50292-91-6), BASF's BlueI-2G and Blue-63, Yamada's Blue220, Blue203, Red500, Red40 or Black305, Wuxi Jiayida New Materials' JYDY-1, JYDR-2, JYDR-3, JYDB-1, or JYDB-2, Synmedia Chemicals' Red-16, O-C6, or O-C8, or Anyang General Chemicals' ODB-2. Further suitable examples of leuco dyes are disclosed, for example, in Chemistry and Applications of Leuco Dyes (R. Muthyala ed., 1997), which is incorporated herein by reference.

[0064] In some embodiments, the leuco dye is present in the internal phase at a concentration by weight of at least about 1 wt%, at least about 2 wt%, at least about 3 wt%, at least about 4 wt%, at least about 5 wt%, at least about 6 wt%, at least about 7 wt%, at least about 8 wt%, at least about 9 wt%, at least about 10 wt%, at least about 11 wt%, at least about 12 wt%, at least about 13 wt%, at least about 14 wt%, at least about 15 wt%, at least about 16 wt%, at least about 17 wt%, at least about 18 wt%, at least about 19 wt%, at least about 20 wt%, at least about 25 wt%, at least about 30 wt%, at least about 35 wt%, at least about 40 wt%, at least about 45 wt%, at least about 50 wt%, or any range or value therebetween, based on the total weight of the internal phase.

[0065] In some embodiments, the leuco dye is present in the internal phase at a weight-based concentration of 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, or a range or value therebetween, based on the total weight of the internal phase.

[0066] In some embodiments, the leuco dye is present in the internal phase at a weight-based concentration of about 1 wt% to about 50 wt%, about 5 wt% to about 40 wt%, or about 10 wt% to about 30 wt%, based on the total weight of the internal phase.

[0067] Photoinitiator In some embodiments, the one or more photoinitiators include one or more borate initiators of a general structure, [Chemical formula] where D + is a cationic chromophore such as cyanine, squaraine (e.g., squarylium), thiopyrylium, or triarylmethane. In some embodiments, R 1 , R 2 , R 3 , and R 4 are each independently a substituted or unsubstituted alkyl group, arylalkyl group, or aryl group. In some embodiments, R 1 is an alkyl group or arylalkyl group, and R 2 , R 3 , and R 4 are aryl groups. In some embodiments, the one or more photoinitiators include one or more of ketocoumarin, benzophenone, thioxanthone, and Norrish type I, II, and III photoinitiators, and combinations thereof.

[0068] In some embodiments, one or more photoinitiators are present in the internal phase at a concentration by weight of about 0.01 wt% or more, about 0.02 wt% or more, about 0.03 wt% or more, about 0.04 wt% or more, about 0.05 wt% or more, 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 1.0 wt% or more, about 2.0 wt% or more, about 3.0 wt% or more, about 4.0 wt% or more, about 5.0 wt% or more, about 10.0 wt% or more, or any range or value therebetween, based on the total weight of the internal phase.

[0069] In some embodiments, one or more photoinitiators are present in the internal phase at a concentration by weight of about 10.0 wt% or less, about 5.0 wt% or less, about 4.0 wt% or less, about 3.0 wt% or less, about 2.0 wt% or less, about 1.0 wt% or less, about 0.5 wt% or less, about 0.4 wt% or less, about 0.3 wt% or less, about 0.2 wt% or less, about 0.1 wt% or less, about 0.05 wt% or less, about 0.04 wt% or less, about 0.03 wt% or less, about 0.02 wt% or less, about 0.01 wt% or less, or any range or value therebetween, based on the total weight of the internal phase.

[0070] In some embodiments, one or more photoinitiators are present in the internal phase at a concentration by weight of about 0.01 wt% to about 10.0 wt%, about 0.01 wt% to about 5.0 wt%, about 0.01 wt% to about 1.0 wt%, about 0.01 wt% to about 0.5 wt%, about 0.01 wt% to about 0.1 wt%, about 0.01 wt% to about 0.05 wt%, about 0.05 wt% to about 10.0 wt%, about 0.1 wt% to about 10.0 wt%, about 0.1 wt% to about 10.0 wt%, about 0.5 wt% to about 10.0 wt%, about 1.0 wt% to about 10.0 wt%, about 5.0 wt% to about 10.0 wt%, about 0.05 wt% to about 5.0 wt%, about 0.1 wt% to about 1.0 wt%, or any range or value included therein, based on the total weight of the internal phase.

[0071] Monomer or oligomer In some embodiments, the internal phase of the microcapsules (e.g., dye microcapsules) contains one or more monomers or oligomers. In some embodiments, the monomers or oligomers are polymerizable or crosslinkable. In some embodiments, the monomers or oligomers are photo-softenable or photo-curable. In some embodiments, the one or more monomers include polyfunctional monomers. In some embodiments, the monomers or oligomers may include acrylic or methacrylic esters of polyhydric alcohols, acrylate or methacrylate-terminated epoxy resins, acrylate or methacrylate-terminated polyesters or polyurethanes, vinylbenzene, vinyl ether, or maleimide-terminated oligomers or polymers, as well as copolymers, blends, or combinations thereof. By way of non-limiting example, in some embodiments, the one or more monomers or oligomers include trimethylolpropane triacrylate (TMPTA), pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hydroxypentaacrylate (DPHPA), tris(2-hydroxyethyl) isocyanurate triacrylate, 1,2,4-butanetriol trimethacrylate, 1,4-cyclohexanediol diacrylate, 1,4-benzenediol dimethacrylate, diethylenetriamine tris-methacrylamide, vinyl esters (e.g., vinyl succinate), divinyl adipate, divinyl phthalate, divinyl terephthalate, divinylbenzene, or any combination thereof. In some embodiments, the monomers or oligomers include polyfunctional acrylates.

[0072] In some embodiments, one or more monomers or oligomers are present in the internal phase at a concentration by weight of at least about 30 wt%, at least about 35 wt%, at least about 40 wt%, at least about 45 wt%, at least about 50 wt%, at least about 55 wt%, at least about 60 wt%, at least about 65 wt%, at least about 70 wt%, at least about 75 wt%, at least about 80 wt%, at least about 85 wt%, at least about 90 wt%, or any range or value therebetween, based on the total weight of the internal phase.

[0073] In some embodiments, one or more monomers or oligomers are present in the internal phase at a concentration by weight of about 90 wt% or less, about 85 wt% or less, about 80 wt% or less, about 75 wt% or less, about 70 wt% or less, about 65 wt% or less, 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, or any range or value therebetween, based on the total weight of the internal phase.

[0074] In some embodiments, one or more monomers or oligomers are present in the internal phase at a concentration by weight of about 40 wt% to about 90 wt%, about 50 wt% to about 85 wt%, or about 60 wt% to about 80 wt%, based on the total weight of the internal phase.

[0075] Diluent In some embodiments, instead of an inert solvent or diluent, a reactive diluent (e.g., an epoxide) that is non-photopolymerizable is used to increase the temperature latitude, midtone color rendering, peel strength, and color development rate. In some embodiments, the diluent is an epoxide compound. In some embodiments, the epoxide compound contains at least 1, at least 2, at least 3, at least 4, at least 5, or at least 6 epoxide groups, preferably about 2 to 6 epoxide groups. By way of non-limiting example, the diluent may include triglycidyl trimethylolpropane (TMPTGE), epoxidized oils including epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, dicyclopentadiene diepoxide, alicyclic diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 1,2-cyclohexanedicarboxylic acid diglycidyl ester, or any combination thereof.

[0076] In some embodiments, the epoxide groups are not photopolymerized by a radical-type photoinitiator that may be present in the internal phase. In some embodiments, the epoxide compound is configured to react with a Lewis acid, a phenol group, or a carboxylic acid group, and / or their metal complexes, particularly zinc complexes. Thus, upon pressure development of the exposed image sheet, the epoxide released from the ruptured microcapsules reacts with the Lewis acid, phenol, or carboxylic acid group of the developer to crosslink. This results in high image resolution and sharp edges, improving the integrity and mechanical properties of the media film.

[0077] The phenolic groups of the color developer are generally sensitive to thermal oxidation or photooxidation and tend to exhibit a high degree of yellow background color (high yellow Dmin or discoloration) upon aging. By reaction with the epoxide released from the microcapsules, the phenolic groups are converted to non-yellowing phenoxy groups, effectively reducing the yellow Dmin or discoloration degree after aging. The color development rate by the developer is usually faster than or equivalent to the rate of the epoxide cross-linking reaction. Therefore, a high color development rate with high color saturation or high color fastness can be achieved without sacrificing image quality and physical and mechanical properties.

[0078] In some embodiments, the diluent comprises one or more epoxide compounds at an appropriate concentration to improve temperature latitude, Dmax, color rendition of midtones, image resolution, and sharpness of edges. If the concentration of the diluent is too high, the photopolymerization / cross-linking of the internal phase becomes insufficient, and as a result, an image with a "dirty" background (poor Dmin) may be generated. In contrast, if the concentration of the epoxide is too low, the improvement of temperature latitude, Dmax, midtone color, resolution, and edge sharpness may not be significant.

[0079] In some embodiments, one or more diluents (e.g., epoxide compounds) are present in the internal phase at a concentration by weight of at least about 0.1 wt%, at least about 0.5 wt%, at least about 1 wt%, at least about 2 wt%, at least about 3 wt%, at least about 4 wt%, at least about 5 wt%, at least about 6 wt%, at least about 7 wt%, at least about 8 wt%, at least about 9 wt%, at least about 10 wt%, at least about 11 wt%, at least about 12 wt%, at least about 13 wt%, at least about 14 wt%, at least about 15 wt%, at least about 16 wt%, at least about 17 wt%, at least about 18 wt%, at least about 19 wt%, at least about 20 wt%, or any range or value therebetween.

[0080] In some embodiments, one or more diluents (e.g., epoxide compounds) are present in the internal phase at a concentration by weight of 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 19 wt% or less, about 18 wt% or less, about 17 wt% or less, about 16 wt% or less, about 15 wt% or less, about 14 wt% or less, about 13 wt% or less, about 12 wt% or less, about 11 wt% or less, about 10 wt% or less, about 9 wt% or less, about 8 wt% or less, about 7 wt% or less, about 6 wt% or less, about 5 wt% or less, about 4 wt% or less, about 3 wt% or less, about 2 wt% or less, about 1 wt% or less, or any range or value therebetween, based on the total weight of the internal phase.

[0081] In some embodiments, one or more diluents (e.g., epoxide compounds) are present in the internal phase at a concentration by weight of about 0.5 wt% to about 40 wt%, about 2 wt% to about 30 wt%, about 3 wt% to about 20 wt%, or about 3 wt% to about 12 wt%, or any range or value therebetween, based on the total weight of the internal phase.

[0082] To ensure successful encapsulation and good barrier properties of the shell after encapsulation, the epoxide compound should exhibit high compatibility with multifunctional monomers (e.g., acrylates) present in the internal phase and low solubility (less than about 5 wt%, preferably insoluble) in the aqueous phase used in the microencapsulation process. In some embodiments, a salting-out agent (e.g., NaCl and / or Na2SO4) may be included in the microencapsulation process to further reduce the solubility of the epoxide in the aqueous phase.

[0083] In some embodiments, the diluent has a water solubility of about 10.0 wt% or less, about 5.0 wt% or less, about 4.0 wt% or less, about 3.0 wt% or less, about 2.0 wt% or less, about 1.0 wt% or less, about 0.5 wt% or less, about 0.4 wt% or less, about 0.3 wt% or less, about 0.2 wt% or less, about 0.1 wt% or less, or any range or value therebetween.

[0084] In some embodiments, the diluent (e.g., an epoxide compound) has a viscosity at 25°C of about 1000 cps or less, about 900 cps or less, about 800 cps or less, about 700 cps or less, about 600 cps or less, about 500 cps or less, about 400 cps or less, about 300 cps or less, about 200 cps or less, about 100 cps or less, about 90 cps or less, about 80 cps or less, about 70 cps or less, about 60 cps or less, about 50 cps or less, about 40 cps or less, about 30 cps or less, or any range or value therebetween. In some embodiments, the viscosity of the diluent is measured at room temperature using a Brookfield viscometer (Spindle S31) at 100 rpm.

[0085] In some embodiments, the diluent (e.g., an epoxide compound) has a weight average molecular weight of about 1,000 g / mol or less, about 900 g / mol or less, about 800 g / mol or less, about 700 g / mol or less, about 600 g / mol or less, about 500 g / mol or less, about 400 g / mol or less, about 300 g / mol or less, or any range or value therebetween.

[0086] In some embodiments, the diluent has a weight average molecular weight of about 200 g / mol or more, about 250 g / mol or more, about 300 g / mol or more, about 350 g / mol or more, about 400 g / mol or more, about 450 g / mol or more, about 500 g / mol or more, or any range or value therebetween.

[0087] In some embodiments, the diluent has a weight average molecular weight of about 100 g / mol to about 3,000 g / mol, about 200 g / mol to about 2,000 g / mol, about 200 g / mol to about 1,000 g / mol, about 200 g / mol to about 800 g / mol, or any range or value therein.

[0088] The first and second substrates In some embodiments, the microcapsules are coated on a first substrate. The first substrate may include, for example, any coated paper and / or its pigment derivatives. In some embodiments, the first substrate is white or transparent. In some embodiments, the first substrate includes at least one of polyester (e.g., polyethylene terephthalate ("PET"), polyethylene naphthalate ("PEN"), etc.), cellulose-based polymers (e.g., cellulose triacetate), polycarbonate, polyolefins including cyclic polyolefins, or combinations, blends, composites, laminates, or copolymers thereof. By way of non-limiting example, the first substrate can be selected from commercially available films including, but not limited to, HOSTAPHAN® polyester film (Mitsubishi Polyester Films), MELINEX® (DuPont Teijin Films (trademark)), and MYLAR® polyester film (DuPont Teijin Films (trademark)).

[0089] The substrate can have any suitable thickness. In some embodiments, the first substrate has a thickness of about 3 μm, about 3.5 μm, about 4 μm, about 4.5 μm, about 5 μm, about 10 μm, about 20 μm, about 30 μm, about 40 μm, about 50 μm, about 60 μm, about 70 μm, about 80 μm, about 90 μm, about 100 μm, about 150 μm, about 200 μm, about 250 μm, about 300 μm, about 350 μm, about 400 μm, about 450 μm, about 500 μm, or any range or value therebetween. In some embodiments, the thickness of the first substrate is about 12 μm to about 150 μm, or about 25 μm to about 100 μm.

[0090] In some embodiments, the developer is coated on a first substrate. The second substrate may include, for example, any coated paper and / or their pigment derivatives. In some embodiments, the first substrate includes at least one of polyester (e.g., polyethylene terephthalate (“PET”), polyethylene naphthalate (“PEN”), etc.), cellulose-based polymers (e.g., cellulose triacetate), polycarbonate, polyolefins including cyclic polyolefins, or combinations, blends, composites, laminates, or copolymers thereof. As a non-limiting example, the first substrate may include commercially available films such as HOSTAPHAN® polyester film (Mitsubishi Polyester Films), MELINEX® (DuPont Teijin Films (trademark)), and MYLAR® polyester film (DuPont Teijin Films (trademark)).

[0091] The second substrate may be disposed in contact with the microcapsule layer such that the developer layer contacts the microcapsule layer with the developer disposed thereon. The second substrate may have any suitable thickness. In some embodiments, the second substrate has a thickness of about 3 μm, about 3.5 μm, about 4 μm, about 4.5 μm, about 5 μm, about 10 μm, about 20 μm, about 30 μm, about 40 μm, about 50 μm, about 60 μm, about 70 μm, about 80 μm, about 90 μm, about 100 μm, about 150 μm, about 200 μm, about 250 μm, about 300 μm, about 350 μm, about 400 μm, about 450 μm, about 500 μm, or any range or value therebetween. In some embodiments, the thickness of the second substrate is about 3.5 μm to about 150 μm, or about 10 μm to about 100 μm.

[0092] In some embodiments, at least one of the first and second substrates is an opaque or white substrate. As used herein, the term "opaque" means that the total light transmittance (TLT) measured in accordance with ASTM D1003 is less than 20%, less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, less than 4%, less than 3%, less than 2%, or less than 1%. The term "white substrate" means a substrate having a whiteness index of at least about 90%, at least about 92%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, at least about 99.5%, or more, as measured in accordance with ASTM E313-79. In some embodiments, the second substrate has a whiteness index of 100% as measured by ASTM E313-79.

[0093] In some embodiments, the microcapsule layer is coated on an opaque substrate and the developer is coated on a transparent substrate. In some embodiments, the initial light passes through the (upper) developer layer and cures the (lower) microcapsules. After development, the leuco dye diffuses to the developer layer and forms a color image therein. The opposite configuration having an upper microcapsule and a lower developer layer can also be used, but in some embodiments having this configuration, the cured microcapsules may have a slight, unclear coloration and may appear as a mottled image.

[0094] Developer layer In some embodiments, the imaging sheet according to the present disclosure includes a developer layer that contacts a second substrate. The developer layer may be disposed in contact with the microcapsule layer, for example, by laminating after being applied to the second substrate. In some embodiments, the developer layer may be overcoated on the microcapsule layer, and the resulting overcoat sheet may be used as is without the second substrate. In some embodiments, the overcoated developer / microcapsule sheet may be further overcoated with a durable protective coating or laminated with a second substrate and optionally an additional adhesive layer. In some embodiments, the composition of the developer layer can be premixed with the composition of the microcapsule layer and coated as a single layer on the first substrate.

[0095] In some embodiments, the developer layer includes one or more leuco dye developers. By way of non-limiting example, the developer may include Lewis acids, silicic acids, salicylic acid derivatives, benzoic acid derivatives, novolak resins, and metal complexes thereof, particularly zinc complexes, or copolymers including blends, composites, grafts and block copolymers, or combinations thereof. For example, the developer may include acid clay, zinc salicylate 3,5-bis(α-methylbenzyl)salicylate (e.g., N-054-W, SANKO Co., Ltd.), zinc salicylate 3,5-di-t-butylsalicylate, zinc salicylate 3,5-dioctylsalicylate, HRJ4542 (Schenectady Chemical), or novolak resin developers such as RD9870, RD9870A, RD9880, RD9880U, RF-118 (Xinxiang Richful Lube Additive Co., Ltd.).

[0096] The developer layer may have any suitable thickness. For example, the developer layer may have a thickness of at least about 1 μm, at least about 2 μm, at least about 3 μm, at least about 4 μm, at least about 5 μm, at least about 6 μm, at least about 7 μm, at least about 8 μm, at least about 9 μm, at least about 10 μm, at least about 15 μm, at least about 20 μm, at least about 25 μm, at least about 30 μm, at least about 35 μm, at least about 40 μm, at least about 45 μm, at least about 50 μm, or any range or value therebetween. In some embodiments, the developer layer has a thickness of about 1 μm to about 30 μm, about 2 μm to about 20 μm, or about 3 μm to about 15 μm.

[0097] The developer may be present in the developer layer at a concentration by weight of about 50% by weight or more, about 55% by weight or more, about 60% by weight or more, about 65% by weight or more, about 70% by weight or more, about 75% by weight or more, about 80% by weight or more, about 85% by weight or more, about 90% by weight or more, about 95% by weight or more, about 96% by weight or more, about 97% by weight or more, about 98% by weight or more, about 99% by weight or more, or any range or value therebetween, based on the dry weight of the developer layer. In some embodiments, the developer layer may include a filler such as a polymer binder and silica.

[0098] Primer layer In some embodiments, the microcapsule imaging sheet according to the present disclosure includes a primer layer. The primer layer may be a film that contacts the first substrate and / or the microcapsule layer. In some embodiments, the primer layer may include a polymer binder and white fine particles. In some embodiments, the primer layer may further include polymer hollow fine particles.

[0099] In some embodiments, the one or more polymer binders consist of, consist essentially of, or are selected from one or more polymers including acrylic polymers or copolymers, styrene copolymers, butadiene copolymers, vinyl chloride copolymers, vinylidene chloride copolymers, ethylene copolymers, propylene copolymers, vinyl acetate copolymers, polyesters, polyurethanes, polylactones, polyamides, and blends or copolymers thereof. In some embodiments, the one or more polymer binders are latex polymers, or blends or copolymers thereof.

[0100] In some embodiments, the primer layer according to the present disclosure includes one or more fine particles (e.g., white fine particles). The white fine particles can be of any suitable composition, size, and concentration for enhancing the reflectivity and / or hiding power of the primer layer.

[0101] In some embodiments, the one or more white fine particles may include one or more of TiO2, BaSO4, CaSO4, CaCO3, BN, Al2O3, Ca3(PO4)2, ZrO2, ZnO, or any other suitable metal oxide, transition metal oxide, sulfate, carbonate, or phosphate material, or hydrophobic treatment derivatives thereof. In some embodiments, the white fine particles are one or more selected from the group consisting of TiO2, BaSO4, CaSO4, CaCO3, Al2O3, and Ca3(PO4)2, and hydrophobic derivatives thereof. In some embodiments, the white fine particles include TiO2, consist essentially of TiO2, or consist of TiO2.

[0102] The foregoing terms are believed 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.

[0103] The terms "a" or "an" may refer to one or more of that entity, i.e., they 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 may be present, unless the context clearly requires that only one of the elements exists.

[0104] References throughout this specification 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.

[0105] As used herein, the term "about" or "approximately" preceding a numerical value indicates plus or minus a range of 10% of the value.

[0106] 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. The listed ranges can be readily recognized as enabling an explanation sufficient to divide the same range into at least equal halves, thirds, fourths, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be easily decomposed into a lower third, middle third, 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, a range includes each individual member.

[0107] Unless otherwise defined, all terms (including technical and scientific terms) used herein shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms defined as in a commonly used dictionary 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.

[0108] For the purposes of the present disclosure, the term "color density" refers to the reflected optical density of the developed dye or the ability to reflect light from the media sheet, measured by the Konica Minolta reflection spectrophotometer FD-5, where the greater the light reflection of the dye, the higher the optical density of the color (i.e., the darker the color). The smaller the light reflection of the dye, the lower the color density (i.e., the less intense the color).

[0109] 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 change from the colorless leuco form to the colored dye form can be reversible or irreversible and can be induced by changes in temperature, pH, irradiation, or redox state.

[0110] For the purposes of the present disclosure, "maximum color density" (or "Dmax") and "minimum color density" (or "Dmin") refer to the maximum color density achieved by a dye after a given development time as measured by a Konica Minolta reflection spectrophotometer FD-5 (e.g., "Dmax , "Fresh" 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 the developed image sheet has been conditioned for a period of time t. The term "minimum color density" (or "Dmin") refers to the minimum reflectance color optical density measured in the non-image area.

[0111] For the purposes of the present disclosure, the term "opaque" means that the total light transmittance (TLT) measured according to ASTM D1003 is less than 20%, less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, less than 4%, less than 3%, less than 2%, or less than 1%.

[0112] For the purposes of the present disclosure, the term "white substrate" means a substrate having a whiteness index of at least about 90%, at least about 92%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, at least about 99.5%, or more as measured according to ASTM E313-79. In some embodiments, the second substrate has a whiteness index of 100% as measured by ASTM E313-79.

[0113] A composition comprising microcapsules containing a non-photopolymerizable diluent In another aspect, the present disclosure relates to a composition comprising microcapsules according to any of the embodiments discussed above. For example, the microcapsule composition may include microcapsules for a microcapsule imaging sheet, the microcapsules including a polymer shell and an internal phase including a non-photopolymerizable diluent configured to react with a leuco dye developer, and a carrier in which the microcapsules are dispersed. In some embodiments, the internal phase of the microcapsules further includes a leuco dye. In some embodiments, the internal phase of the microcapsules further includes a photoinitiator. In some embodiments, the internal phase of the microcapsules further includes a polymerizable or crosslinkable monomer or oligomer.

[0114] In some embodiments, the microcapsules may include photosensitive microcapsules including a polymer shell and an internal phase including a leuco dye, a photoinitiator, a polymerizable or crosslinkable monomer or oligomer. In some embodiments, the microcapsules may include diluent microcapsules including a polymer shell and an internal phase including a non-photopolymerizable diluent configured to react with a leuco dye developer. In some embodiments, the microcapsules include photosensitive microcapsules, diluent microcapsules, or any combination thereof.

[0115] In some embodiments, the carrier is water. In some embodiments, the carrier includes an organic solvent, water, or any combination thereof. In some embodiments, the organic solvent is methanol, ethanol, acetone, or any other suitable solvent.

[0116] Method for producing an imaging sheet In another aspect, the present disclosure relates to a method of making an imaging sheet including the step of contacting a first substrate with a microcapsule layer to produce a first substrate coated with microcapsules, the microcapsule layer including microcapsules according to any of the embodiments discussed above. In some embodiments, the first substrate is contacted with a primer layer according to any of the embodiments described above to produce a first substrate coated with a primer. In some embodiments, the first substrate coated with a primer is contacted with the microcapsule layer to produce a first substrate coated with microcapsules, the microcapsule layer including microcapsules according to any of the embodiments described above.

[0117] For example, the microcapsule layer includes microcapsules for a microcapsule imaging sheet and a carrier, the microcapsules including a polymer shell and an internal phase including a non-photopolymerizable diluent configured to react with a leuco dye developer, the microcapsules being dispersed within the carrier. In some embodiments, the internal phase of the microcapsules further includes a leuco dye. In some embodiments, the internal phase of the microcapsules further includes a photoinitiator. In some embodiments, the internal phase of the microcapsules further includes a polymerizable or crosslinkable monomer or oligomer. In some embodiments, the microcapsules may include photosensitive microcapsules including a polymer shell and an internal phase including a leuco dye, a photoinitiator, a polymerizable or crosslinkable monomer or oligomer. And, in some embodiments, the microcapsules may include diluent microcapsules including a polymer shell and an internal phase including a non-photopolymerizable diluent configured to react with a leuco dye developer. And, in some embodiments, the microcapsules include photosensitive microcapsules, diluent microcapsules, or any combination thereof. In some embodiments, the microcapsules are present in a composition as disclosed above, the microcapsules being dispersed within the carrier.

[0118] In some embodiments, a method of making an imaging sheet includes contacting a first substrate coated with microcapsules with a developer layer to produce a first substrate coated with a developer. In some embodiments, the first substrate coated with the developer is contacted with a second substrate to produce an imaging sheet. In some embodiments, the developer layer is coated on the second substrate to produce a second substrate coated with a developer before contacting the first substrate coated with microcapsules to produce an imaging sheet. In some embodiments, the second substrate coated with the developer and the first substrate coated with microcapsules contact each other such that the developer layer contacts the microcapsule layer. In some embodiments, a primer may be disposed between the second substrate and the developer layer.

[0119] Method of Using Microcapsules and Imaging Sheet In another aspect that can be combined with any other aspect or embodiment, the present disclosure relates to a method of using microcapsules according to any of the above 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 embodiments.

[0120] For example, in some embodiments, a method of imaging or printing includes exposing an imaging sheet comprising microcapsules according to any of the above embodiments to heat, pressure, or radiation, the exposure releasing a non-photopolymerizable diluent configured to react with a leuco dye developer from the leuco dye and / or polymer shell and being sufficient to produce an image.

[0121] In some embodiments, the present disclosure relates to a method of adjusting (e.g., improving) one or more properties of an imaging sheet, including adding the microcapsules of the present disclosure to the imaging sheet. In some embodiments, the one or more properties include one or more of Dmax, fresh Dmax, Dmax,t, Dmin, image resolution, temperature latitude, dynamic range, colorfastness (yellowing resistance), and edge sharpness.

[0122] Unless otherwise explicitly indicated, all specific embodiments, features, and terms are intended to include both the recited embodiments, features, or terms and their equivalents.

[0123] Here, specific embodiments contemplated by the present disclosure will be referred to in detail. Although various embodiments are described herein, it is understood that the technology is not limited to the described embodiments. On the contrary, this 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.

Examples

[0124] Example 1. Influence of non-photopolymerizable epoxide compounds on the temperature latitude, dynamic range, and edge sharpness of microcapsule imaging sheets To achieve high Dmax with fast color development and high temperature latitude, it is necessary to increase the solubility of the leuco dye in the internal phase of the microcapsules and keep the viscosity of the dye solution as low as possible over a wide temperature range. To achieve a wide dynamic range of gray-scale color rendering, it is also necessary to keep the viscosity of the partially cross-linked internal phase as low as possible. However, a dye solution with low viscosity has a large spread of the dye, especially in the Dmax region, resulting in a decrease in edge sharpness.

[0125] As shown in Table 1, the "conventional" internal phase consisting of a mixture of two polyfunctional acrylates TMPTA / HDDA (7:3) tends to cause phase separation of common leuco dyes at concentrations of 10 phm (parts per 100 monomers) and 15 phm within 3 days after solvation.

Table 1

[0126] To improve the Dmax, dynamic range, and temperature latitude, low-viscosity epoxide compounds such as triglycidyl trimethylolpropane ether (TMPTGE) and DER 732 were evaluated as non-photopolymerizable reactive diluents for the internal phase of the photosensitive microcapsules. Table 2 compares the viscosities of the "conventional" internal phase monomers (TMPTA and HDDA) with the viscosities observed for epoxide compounds such as TMPTGE (triepoxide) and DER 732 (diepoxide).

Chemical formula

Table 2

[0127] As shown in Tables 1 and 2, including an epoxide compound diluent in the internal phase may improve the solubility of the leuco dye and achieve a wide dynamic range. It was hypothesized that the colorfastness and edge sharpness may also be improved by adding an epoxide compound to the internal phase. This is probably due to (1) reducing the risk of ring closure of the dye to return the dye to the leuco dye by the reaction of the epoxide with the carboxylic acid group of the developed (ring-opened) leuco dye, and / or (2) crosslinking the developer resin and reducing the diffusion rate of the dye by the reaction of the epoxide with the novolak resin of the developer.

[0128] Example 2. Influence of polyfunctional epoxide on the temperature latitude of photosensitive microcapsule imaging media The green-sensitive imaging sheet was produced according to the formulation and process described below.

Table 3-1

Table 3-2

[0129] The photosensitive microcapsules were produced using the materials in Table 3 according to the following procedure.

[0130] 1. 220 parts of water and 8 parts of Versa TL502 sulfonated polystyrene (dry) were added to a stainless-steel beaker and mixed thoroughly.

[0131] 2. 10 parts of pectin (methyl polygalacturonate) were slowly sifted into the mixture and stirred overnight at room temperature (500 - 1000 rpm).

[0132] 3. The pH was adjusted to 7.5 with 10% sodium carbonate, and the mixing speed was increased to 1750 rpm.

[0133] 4. The internal phase as shown in Table 4 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 (pH adjusted to 7.0) were added, and after reacting at 25°C for 30 minutes, it was reacted at 40°C for 1 hour.

[0134] 5. A solution containing 19.9 parts of CYMEL® 385 and 40 parts of water (adjusted to pH 6.0) was added, and the mixture was reacted at 70°C for an additional 2 hours.

[0135] 6. 15.23 parts of sodium sulfate, an aqueous solution of 34.3%, were added, the mixture was stirred for 10 minutes, 1.97 parts of CYMEL® 385 and 10 parts of water were added, and the mixture was reacted at 70 ℃ for an additional 1 hour.

[0136] 7. The mixing speed was reduced to 600 rpm, the pH was adjusted to 9.5 using 20% NaOH solution, and the resulting reaction mixture was stirred overnight at room temperature.

Table 4

[0137] The coating solution shown in Table 5 was adjusted to a solid content of 33 wt% with water, thoroughly dispersed using a low-shear mixer, coated onto a 2-mil white PET (MELINEX® 339) substrate with a Myrad bar, and dried in an oven at 80 °C for 10 minutes. The thickness of the dried coating, as measured with a Mitutoyo thickness gauge, was approximately 8 microns.

Table 5

[0138] The developer composition as shown in Table 6 was coated onto a 1-mil transparent PET film with a Myrad bar, dried in an oven at 80 °C for 10 minutes, and the target dried coating thickness was set to approximately 7 μm.

Table 6

[0139] The microcapsules and developer film thus prepared were laminated using a Tamerica roll laminator TCC2700 with the temperature, pressure, and speed set to 100 °C, 3.621 Kgf / 170 mm, and 0.368 m / min, respectively, to form various photosensitive imaging sheets. The prepared media were developed with Dmax and Dmin measured using a pressure developing jig at 80 °C and a Konica Minolta reflection-type spectrophotometer FD-5.

Table 7

[0140] As shown in Table 7, the Dmax data reveals that the Dmax (both for newly developed and post-heated at 80 °C for 10 minutes) and the temperature latitude of the microcapsules containing the epoxy diluent (Examples 2-2 to 2-5) are generally superior to those of the control capsules (Example 2-1) containing only the acrylic monomers TMPTA / HDDA (7:3). The microcapsule layer containing the microcapsules of Example 2-2 contains TMPTA / HDDA / TMPTGE (63 / 27 / 10) in the internal phase and appears to provide the highest Dmax and the best temperature latitude among the tested internal phases, maintaining approximately 93.1% and 80.4% of its Dmax (80 °C, 10 minutes) respectively after storage overnight at 4 °C and -10 °C. In fact, in this internal phase, even the low-temperature Dmax values are approximately 20% (-10 °C adjustment) to approximately 40% (4 °C adjustment) better than the room-temperature Dmax of the control samples (Example 2-1) without TMPTGE or DER732.

[0141] As is also clear from Table 7, the microcapsules containing the highest concentration of DER732 in the internal phase (Example 2-5) appear to result in a higher Dmin in the non-image area, while those containing a low concentration of DER732 showed a slightly lower Dmin. Without being bound by a particular theory, incorporating the epoxy diluent may have improved the solubility of the leuco dye into the internal phase even at a low temperature of -10 °C. Also, the viscosity of the resulting internal phase decreased. As a result, both the color development rate indicated by the fresh Dmax and the temperature latitude indicated by the Dmax after low-temperature storage were significantly improved. However, if the concentration of the low-molecular-weight epoxy DER732 in the internal phase (Example 2-5) is too high, the barrier properties of the microcapsule shell may deteriorate through one or more mechanisms such as plasticization of the shell, interference with the interfacial polymerization / crosslinking shell formation process, and micropore formation within the shell. As a result, Examples 2 to 5 show a very high Dmin.

[0142] Example 3: Preparation of a microcapsule imaging system containing photosensitive microcapsules and non-photosensitive microcapsules containing polyfunctional epoxides.

[0143] Preparation of Photosensitive Microcapsules To test the effect of incorporating photosensitive and non - photosensitive microcapsules containing polyfunctional epoxides into the same microcapsule imaging system, the compositions and processes of Example 2 were used, except that the internal phase of Table 8 was used for microencapsulation.

Table 8

[0144] Non - photosensitive microcapsules containing a polymer shell and an internal phase containing one or more epoxide compounds were prepared according to the procedure described above for photosensitive microcapsules, but 1.97 parts of CYMEL® 385 and 10 parts of water in Step 6 were omitted, and the internal phase of the microcapsules (Step 4) was replaced with the compositions (3A - 3D) shown in Table 9 below.

Table 9

[0145] All the photosensitive and non - photosensitive microcapsules prepared according to the above method were extensively washed with water and centrifuged to remove the excess water - soluble polymers and additives present in the aqueous phase. The size distribution of the microcapsules (Table 10) was measured using a HORIBA Partica LA - 960 laser scattering particle size distribution analyzer. As shown in Table 10, all the microcapsules investigated had equivalent particle sizes and particle size distributions.

Table 10

[0146] Table 11 shows the composition of the microcapsule stock fluids of green-sensitive microcapsules (Microcapsule 3, control) and four diluent microcapsules containing an epoxy compound (Microcapsules 3A - 3D). Microcapsule coatings containing various types and concentrations of epoxy microcapsules were prepared by mixing the control fluid containing Microcapsule 3 with fluids of various concentrations containing Microcapsules 3A - 3D. Each coating solution was adjusted to 30 wt% solids by adding water and then coated onto a 2 mil white PET (MELINEX® 339) substrate using a Myrad bar. Thereafter, the coated substrate was dried in an oven at 80 °C for 10 minutes, aiming for a dry coating thickness of approximately 8 μm as measured with a Mitutoyo thickness gauge.

Table 11

[0147] The same developer coating as used in Example 2 was prepared, but the dry coating thickness was approximately 9 μm as measured with a Mitutoyo thickness gauge.

[0148] To produce imaging sheets containing photosensitive microcapsules and non-photosensitive epoxy microcapsules, the microcapsule film and the developer film prepared by the above procedure were laminated using a Tamerica roll laminator TCC2700 with the temperature, pressure, and speed set at 100 °C, 3.621 Kgf / 170 mm, and 0.368 m / min, respectively, to form various imaging sheets (control, 3A1 - 3A8, Table 12, 3B1 - 3B8, Table 13, 3C1 - 3C8, Table 14, and 3D1 - 3D8, Table 15).

[0149] The color development characteristics of the various imaging sheets were determined by exposing the imaging sheets through a Kodak Q60 mask equipped with a white light LED exposure unit at 9.5 mW / cm 2 for 1 second and developing the image sheet using a pressure jig. The results are shown in Tables 12 - 15 below.

[0150] For each exposed imaging sheet, the various characteristics reported in Tables 12 - 15 are defined as follows.

[0151] E 10 : Energy required to reduce Dmax by 10%

[0152] E 90 : Energy required to reduce Dmax by 90%

[0153] Dmin, M : Average (magenta) color density of the fully exposed area measured immediately after exposure, pressure development, and post - heating by a heating roller at 100°C

[0154] Aged Dmin, M : Dmin, after conditioning in an environmental chamber (40°C / 85%RH) for 2 days M

[0155] Dmax, M : Average (magenta) density achieved in the unexposed area measured immediately after exposure, pressure development, and post - heating by a heat roller at 100°C

[0156] Normalized Dmax, M = Dmax, M / (proportion of control capsules used)

[0157] ΔY (yellow discoloration): Increase in yellow color density after exposing the sample in a white light box (37,000 lux) for 7 days after conditioning in a 40°C / 85%RH chamber for 2 days.

[0158] Peel strength: Average interlayer peel force (180°) in the Dmax area (unexposed area).

[0159] For all imaging sheets, Dmin, M , Dmax, Mand ΔY were measured with a spectrocolorimeter FD-5 (Konica Minolta). The peel strength in the Dmax region (width 25.4 mm) was measured with an Instron Peel Tester, Model 3367 at a peel rate of 30 mm / min after conditioning the developed samples under ambient conditions for 4 days.

Table 12

Table 13

Table 14

Table 15

[0160] As shown in Table 12, incorporation of high-concentration non-photosensitive epoxide-containing microcapsules 3A (2% - 16%) results in a decrease in yellowing (ΔY) of approximately 50% (0.29 - 0.13) and an increase in interlayer peeling resistance (peel strength) of approximately 69% (0.062 - 1.05 N / 25 mm). In contrast, E 10 and E 90 , and the maximum (Dmax, M ) and minimum (Dmin, M ) color densities achievable in the non-exposed and fully exposed regions did not essentially change regardless of the microcapsule 3A concentration. In fact, the normalized Dmax (normalized by the actual dye loading) is an indicator of the coloring power of the leuco dye used and increases with the addition of ESPO microcapsules 3A.

[0161] These phenomena are also observed with microcapsules 3B. As shown in Table 13, addition of microcapsules 3B (2% - 16%) improves the peel strength and coloring power of the leuco dye and reduces yellow discoloration. Furthermore, the addition of microcapsules 3B results in a change in photosensitivity (E 10 and E 90Unexpected improvements were observed. Similarly, Tables 14 and 15 show that an increase in the concentration of microcapsules 3C and 3D causes an improvement in peel strength, an increase in photosensitivity (E 10 and E 90 ), and a decrease in yellow discoloration (ΔY).

[0162] Without being bound by a particular theory, it is believed that after the epoxide compound is pressure-induced to release from the microcapsules, it reacts with the phenol groups in the developer layer and crosslinks, thereby significantly improving the peeling force and reducing the yellowing (ΔY). The epoxide compound also acts as a solvent or diluent to improve the diffusion of the dye into the developer layer, causing an increase in the normalized Dmax or coloring efficiency of the leuco dye.

[0163] Example 4. Preparation of a Microcapsule Imaging System Containing Photosensitive Microcapsules Containing a Polyfunctional Epoxide in the Inner Phase Preparation of Photosensitive Microcapsules Containing a Polyfunctional Epoxide in the Inner Phase and an Imaging Sheet Containing the Same

[0164] Except that the inner phase shown in Table 5 was replaced with that shown in Table 16 (in the case of microcapsules 4-1 and 4-2), the photosensitive microcapsules containing epoxidized soybean oil in the inner phase were prepared by the same microencapsulation process as described in Example 2 for preparing green photosensitive microcapsules.

Table 16

[0165] The microcapsules thus prepared were extensively washed with water and centrifuged to remove excess water-soluble polymers and additives present in the aqueous phase. The particle size (D 50 ) of the purified and washed microcapsules, as measured by a HORIBA LA-960 particle size analyzer, was 6.44 μm for microcapsule 4-1 and 5.42 μm for 4-2.

[0166] The imaging sheet containing photosensitive microcapsules 4-1 and 4-2 was produced by laminating the microcapsule coating composition shown in Table 17 below with the developer coating composition shown in Table 6. The solid content of all the microcapsule liquids was adjusted to 30% by weight with water before coating on a 2-mil white PET (MELINEX® 339) substrate with a Myrad bar, then dried in an oven at 80 °C for 10 minutes, and targeted a dry coating thickness of about 8 μm measured with a Mitutoyo thickness gauge.

Table 17

[0167] The imaging sheet was exposed for 1 second at 9.5 mW / cm 2 through a Kodak Q60 mask equipped with a white light LED exposure unit and developed with a pressure jig. The results are shown in Table 18.

Table 18

[0168] As shown in Table 18, as a result of substituting about 5 to about 10% by weight (weight ratio) of the polyfunctional acrylate in the internal phase with the non-photosensitive reactive diluent ESBO, the yellowing after aging significantly decreased and the peel strength of the laminated image sheet increased. Different from the examples of microcapsules 3A to 3D in which the polyfunctional epoxide was separately encapsulated in non-photosensitive microcapsules instead of photosensitive microcapsules, microcapsules 4-1 and 4-2 showed 10 (energy required to reduce the image optical density (OD) by 10%) decrease and dynamic range (E 90 -E 10 ) increase. Therefore, higher set light sensitivity and wider gray scale images can be achieved by using about 5% to about 10% of the diluent ESBO.

[0169] Without being bound by a specific theory, the presence of the non-photosensitive diluent ESBO effectively reduces the viscosity of the internal phase (and the cage effect), increases the quantum efficiency of the photoinitiator or the self-oxidizer / deoxygenator, and thus 10 may reduce E. Furthermore, the presence of ESBO effectively reduces the gel effect, especially in the later stages of photopolymerization / crosslinking, and increases the solubility of the leuco dye in the internal phase. The improved solubility increases E 90 (the energy required to reduce the image outer diameter by 90%) and broadens the dynamic range of grayscale color rendering.

[0170] Table 19 shows the exposure temperature latitude of the imaging sheets of Example 4-1 (5 wt% ESBO) and 4-2 (10 wt% ESBO). The imaging sheets were sealed in aluminum-coated PET barrier bags and conditioned at room temperature, 1.5 °C, and -26 °C for 64 hours. Next, the aged imaging sheets were reconditioned at room temperature for about 10 minutes and then exposed for 1 second through a Kodak Q60 mask equipped with a white light LED exposure unit (9.5 mW / cm 2 ) and developed immediately with a pressure jig. The obtained Dmax of magenta was measured immediately after development.

Table 19

[0171] As shown in Table 19, when about 5 to about 10 wt% of the polyfunctional acrylate in the internal phase of the microcapsules is replaced with ESBO, the stability of Dmax is significantly improved, and the photospeed is improved in a relatively wide temperature range from room temperature to -26 °C. The control imaging sheet showed a decrease of 14.7% to 16.7% in Dmax and an increase of 82.1% to 89.2% in E 90 , indicating a decrease in both the color density and the photospeed after low-temperature conditioning. However, when about 5% to about 10% of the non-photopolymerizable ESBO was incorporated into the internal phase of the photosensitive microcapsules, Dmax decreased by only 5.4% to 8.7%, and E 90 increased by only about 2.7% to 58.1%.

[0172] Without being bound by a particular theory, the observed improvement in exposure latitude at low temperatures realized by the incorporation of a polyfunctional epoxide (e.g., ESBO) may be due to an improvement in the solubility of the leuco dye in the internal phase and / or a decrease in the viscosity of the internal phase at low temperatures, particularly sub-freezing temperatures.

[0173] The compositions and methods exemplified herein can be suitably practiced 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. are to be understood broadly and without limitation. Further, the terms and expressions used herein are used as terms of description and not of limitation, and there is no intention to exclude any equivalents of the features shown and described or portions thereof. It is recognized that various modifications are possible within the scope of the claimed disclosure. Accordingly, although the disclosure is specifically disclosed by preferred embodiments and any features, it should be understood that modifications and variations of the disclosure disclosed herein may be claimed by those skilled in the art and that such modifications and variations are considered to be within the scope of the disclosure.

[0174] Specifically, it is intended that, unless the context specifically indicates otherwise, the various features of the invention described herein can be used in any combination. Further, the disclosure also contemplates that, in some embodiments, any feature or combination of features described herein may be excluded or omitted. By way of example, if the specification states that an imaging sheet comprises components A, B, and C, it is specifically intended that any one of A, B, or C, or combinations thereof, can be omitted or excluded, either singly or in any combination.

[0175] This disclosure is described broadly and generically herein. Each of the subgroups of specific species and subgenera that fall within the general disclosure also form 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 illustrations of 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 will, of course, be subject to change. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0176] Those skilled in the art will readily appreciate that the 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.

[0177] In addition, when a feature or aspect of the disclosure is described from the perspective of a Markush group, those skilled in the art will recognize that the disclosure is also described from the perspective of any individual member or subgroup of members of the Markush group thereby.

Claims

1. A polymer shell, a leuco dye, a non-photopolymerizable diluent configured to react with the leuco dye developer, a photoinitiator, a polymerizable or crosslinkable monomer or oligomer, and an internal phase, comprising a photosensitive microcapsule for a microcapsule imaging sheet.

2. The photosensitive microcapsule according to claim 1, wherein the leuco dye developer comprises a Lewis acid, an acidic clay, or one or more compounds containing a phenol group or a carboxylic acid group, or a metal complex thereof.

3. The photosensitive microcapsule according to claim 1 or 2, wherein the leuco dye developer comprises a novolak resin, a salicylic acid derivative, a zincate derivative thereof, or a combination, copolymer, blend, or composite thereof.

4. The photosensitive microcapsule according to any one of claims 1 to 3, wherein the diluent comprises an epoxide compound.

5. The photosensitive microcapsule according to claim 4, wherein the epoxide compound contains two or more epoxide moieties.

6. The photosensitive microcapsule according to claim 4 or 5, wherein the diluent comprises a diepoxide or a triepoxide compound.

7. The photosensitive microcapsule according to any one of claims 4 to 6, wherein the epoxide compound comprises at least one selected from the group consisting of triglycidyl trimethylolpropane (TMPTG), an epoxide oil containing epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, dicyclopentadiene diepoxide, an alicyclic diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and 1,2-cyclohexanedicarboxylic acid diglycidyl ester.

8. The photosensitive microcapsule according to any one of claims 1 to 7, wherein the diluent is present at a concentration of about 3% by weight to about 20% by weight based on the total weight of the internal phase.

9. The photosensitive microcapsule according to any one of claims 1 to 8, wherein the diluent is present at a concentration of about 3% by weight to about 10% by weight based on the total weight of the internal phase.

10. The photosensitive microcapsule according to any one of claims 1 to 9, wherein the internal phase further comprises a co-initiator, an oxygen scavenger, or an auto-oxidant.

11. The photosensitive microcapsule according to any one of claims 1 to 10, wherein the diluent has a water solubility of about 5% by weight or less.

12. The photosensitive microcapsule according to any one of claims 1 to 11, wherein the diluent has a water solubility of about 1% by weight or less.

13. The photosensitive microcapsule according to any one of claims 1 to 12, wherein the diluent has a viscosity of about 300 cps or less at 25 ° C when measured using a Brookfield viscometer at 100 rpm.

14. The photosensitive microcapsule according to any one of claims 1 to 13, wherein the diluent has a viscosity of about 100 cps or less at 25 ° C when measured using a Brookfield viscometer at 100 rpm.

15. The photosensitive microcapsule according to any one of claims 1 to 14, wherein the polymerizable or crosslinkable monomer contains a polyfunctional acrylate.

16. A polymer shell, A leuco dye, A non-photo-polymerizable diluent configured to react with a leuco dye developer, A photoinitiator, An internal phase containing a polymerizable or crosslinkable monomer or oligomer, and a microcapsule, A first substrate in contact with the microcapsule, An imaging sheet containing a leuco dye developer.

17. The imaging sheet according to claim 16, wherein the first substrate is in contact with the microcapsule.

18. The imaging sheet according to claim 16, wherein the leuco dye developer contains a Lewis acid, or an acidic clay, or one or more compounds having a phenol group or a carboxylic acid group.

19. The imaging sheet according to any one of claims 16 to 18, wherein the leuco dye developer is a novolak resin, a phenol resin, salicylic acid, or a combination, copolymer, blend, composite or metal complex derivative thereof.

20. The imaging sheet according to claim 19, wherein the metal is zinc.

21. The imaging sheet according to any one of claims 16 to 19, further comprising a second substrate in contact with the leuco dye developer.

22. The imaging sheet according to claim 21, wherein one of the first and second substrates is opaque.

23. The imaging sheet according to claim 21, wherein the opaque substrate is white.

24. The imaging sheet according to claim 22 or claim 23, wherein the first substrate is opaque or white.

25. The imaging sheet according to any one of claims 16 to 24, wherein the first substrate further includes a primer layer that contacts the microcapsules.

26. The imaging sheet according to claim 25, wherein the primer layer contains fine particles.

27. The fine particles are CaCO ３ , CaSO ４ , BaSO ４ , silica, BN, TiO ２ , Al ２ O ３ , Ca ３ (P.O. ４ ) ２ 27. The imaging sheet of claim 26 comprising at least one selected from the group consisting of: and hydrophobically treated derivatives thereof.

28. A polymer shell and A microcapsule for a microcapsule imaging sheet, including an internal phase containing a non-photopolymerizable diluent configured to react with a leuco dye developer.

29. The microcapsule according to claim 28, wherein the diluent contains an epoxide compound.

30. The microcapsule according to claim 29, wherein the epoxide compound contains two or more epoxide moieties.

31. The microcapsule according to claim 29 or claim 30, wherein the diluent contains a diepoxide or a triepoxide compound.

32. The microcapsule according to claim 30 or claim 31, wherein the epoxide compound contains at least one selected from the group consisting of triglycidyl trimethylolpropane (TMPTG), epoxidized oil containing epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, dicyclopentadiene diepoxide, alicyclic diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and diglycidyl ester of 1,2-cyclohexanedicarboxylic acid.

33. The microcapsule according to any one of claims 28 to 32, wherein the diluent is present at a concentration of about 50% by weight to about 100% by weight based on the total weight of the internal phase.

34. The microcapsule according to any one of claims 28 to 33, wherein the diluent is present at a concentration of about 90% by weight to about 100% by weight based on the total weight of the internal phase.

35. A polymer shell and A diluent microcapsule including a polymer shell and an internal phase containing a non-photopolymerizable diluent configured to react with a leuco dye developer, and A polymer shell and A photosensitive microcapsule including a polymer shell, a leuco dye, a photoinitiator, and an internal phase containing a polymerizable or crosslinkable monomer or oligomer, and A first substrate in contact with the diluent microcapsule and the photosensitive microcapsule, and A leuco dye developer, and an imaging sheet.

36. The imaging sheet according to claim 35, wherein the leuco dye developer contains a Lewis acid or an acidic clay, or contains one or more compounds having a phenol group or a carboxylic acid group.

37. The imaging sheet according to claim 35 or 36, wherein the diluent contains an epoxide compound.

38. The imaging sheet according to claim 37, wherein the epoxide compound contains two or more epoxide moieties.

39. The imaging sheet according to claim 37 or 38, wherein the diluent contains a diepoxide or a triepoxide compound.

40. The imaging sheet according to any one of claims 37 to 39, wherein the epoxide compound contains at least one selected from the group consisting of triglycidyl trimethylolpropane (TMPTG), an epoxidized oil containing epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, dicyclopentadiene diepoxide, an alicyclic diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and diglycidyl ester of 1,2-cyclohexanedicarboxylic acid.

41. The imaging sheet according to any one of claims 35 to 40, wherein the diluent is present at a concentration of about 50 wt% to about 100 wt% based on the total weight of the internal phase.

42. The imaging sheet according to any one of claims 35 to 41, wherein the diluent is present at a concentration of about 90 wt% to about 100 wt% based on the total weight of the internal phase of the diluent microcapsules.

43. The imaging sheet according to any one of claims 35 to 42, wherein the leuco dye developer is a novolak resin, a phenol resin, salicylic acid, or a combination, copolymer, blend, complex, or metal complex derivative thereof.

44. The imaging sheet according to claim 43, wherein the metal is zinc.

45. The imaging sheet according to any one of claims 35 to 44, further comprising a second substrate in contact with the leuco dye developer.

46. The imaging sheet according to claim 45, wherein one of the first and second substrates is opaque.

47. The imaging sheet according to claim 46, wherein the opaque substrate is white.

48. The imaging sheet according to any one of claims 35 to 47, wherein the first substrate further includes a primer layer that contacts the microcapsules.

49. The imaging sheet according to claim 48, wherein the primer layer contains fine particles.

50. The microparticles are CaCO ３ , CaSO ４ , BaSO ４ , silica, BN, TiO ２ , Al ２ O ３ , Ca ３ (PO ４ ) ２ The imaging sheet according to claim 49, comprising at least one selected from the group consisting of those hydrophobic-treated derivatives and any combination thereof.

51. The imaging sheet according to any one of claims 35 to 50, wherein the internal phase of the photosensitive microcapsules further includes a non-photopolymerizable diluent configured to react with a leuco dye developer.

52. The imaging sheet according to claim 51, wherein the diluent contains an epoxide compound.

53. The imaging sheet according to claim 52, wherein the epoxide compound contains two or more epoxide moieties.

54. The imaging sheet according to claim 52 or claim 53, wherein the diluent contains a diepoxide or a triepoxide compound.

55. The imaging sheet according to any one of claims 52 to 54, wherein the epoxide compound contains at least one selected from the group consisting of triglycidyl trimethylolpropane (TMPTG), epoxidized oil containing epoxidized soybean oil, epoxidized castor oil, epoxidized linseed oil, dicyclopentadiene diepoxide, alicyclic diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and diglycidyl ester of 1,2-cyclohexanedicarboxylic acid.

56. One or more microcapsules according to any one of claims 1 to 15 or claims 28 to 34, and a carrier, A microcapsule composition in which the one or more microcapsules are dispersed in the carrier.

57. (i) A step of bringing a first substrate into contact with a microcapsule layer to produce a first substrate coated with microcapsules; (ii) A step of bringing the microcapsule layer of the first substrate coated with the microcapsules into contact with a developer layer to produce a first substrate coated with a developer; (iii) A method including a step of bringing the developer layer of the first substrate coated with the developer into contact with a second substrate to produce an imaging sheet.

58. (i-a) A step of bringing a first substrate into contact with a primer layer to produce a first substrate coated with a primer; Step (i - b) of contacting the primer layer of the first substrate coated with the primer with the microcapsule layer to produce a first substrate coated with microcapsules; Step (ii) of contacting the microcapsule layer of the first substrate coated with the microcapsules with the developer layer to produce a first substrate coated with the developer; A method comprising: Step (iii) of contacting the developer layer of the first substrate coated with the developer with a second substrate to produce an imaging sheet.

59. Step (i) of producing a first substrate coated with the microcapsules according to Claim 57 or Claim 58; Step (ii) of contacting a second substrate with the developer layer to produce a second substrate coated with the developer; A method comprising: Step (iii) of contacting the microcapsule layer of the first substrate coated with the microcapsules with the developer layer of the second substrate coated with the developer to produce an imaging sheet.

60. The method according to any one of Claims 57 to 59, wherein the primer layer is disposed between the second substrate and the developer layer or between the first substrate and the microcapsule layer.

61. The method according to any one of Claims 57 to 59, wherein the primer layer is disposed between the second substrate and the developer layer and between the first substrate and the microcapsule layer.

62. A method for adjusting one or more properties of an imaging sheet, comprising including one or more microcapsules according to any one of Claims 1 to 15 or Claims 28 to 34 in the imaging sheet.

63. The method according to Claim 62, wherein the one or more properties include one or more of Dmax, fresh Dmax, Dmax,t, Dmin, image resolution, temperature latitude, dynamic range, colorfastness, and edge sharpness.

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