Microcapsule imaging system comprising non-photopolymerizable reactive diluent

Abstract

The present disclosure provides microcapsules (208, 209) comprising a polymeric outer shell (116) and an inner phase (118), the inner phase comprising a non-photopolymerizable reactive diluent, for use in a microcapsule imaging sheet. Imaging sheets comprising microcapsules (209) include non-photopolymerizable reactive diluents and exhibit improvements in color development (Dmax), discoloration (yellowing) resistance, mechanical properties (e.g., peel strength), and temperature tolerance in imaging sheets comprising leuco dyes.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 17 / 833,731, filed on June 6, 2022, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to the field of microcapsule imaging systems, and more particularly to microcapsules having an internal phase comprising a non-photopolymerizable reactive diluent for use in microcapsule imaging systems. Background Art

[0004] Since the 1980s, single-sheet, self-contained, full-color microcapsule imaging systems have been developed (e.g., manufactured by Mead Corp. of Miamisburg, Ohio). ). In such imaging systems, an imaging sheet comprising a microcapsule layer comprising a photohardenable or photosoftenable composition and a leuco dye in an internal phase is image-wise exposed to actinic radiation. Typically, the photosensitive composition comprises a photopolymerizable multifunctional acrylate, a photoinitiator, and a color former. In general, the microcapsules are image-wise hardened by actinic radiation, and when the exposed imaging sheet passes through a pressure roller, the microcapsules can be image-wise broken to release the internal phase encapsulated therein. The leuco dye thus released migrates to the developer material and reacts to form a continuous tone full-color image, whose color density (or grayscale) is regulated by the exposure energy (time or pulse width), intensity (pulse amplitude) and / or pulse frequency. This independent single sheet imaging system can be used for lightweight, portable, high-speed printing applications. Summary of the invention

[0005] There are several disadvantages to typical microcapsule imaging systems. For example, conventional leuco dyes have poor temperature tolerance, especially at low temperatures. In order to increase color density, high concentrations of leuco dyes are contained in microcapsules. However, at low storage or operating temperatures, leuco dyes tend to precipitate, resulting in poor image quality. In addition, conventional imaging sheets exhibit poor mid-tone reproduction because the fluidity of leuco dyes is poor even at low energy exposure or low internal phase polymerization degree, given the high viscosity of the internal phase. Therefore, the resulting image has high contrast and loss of mid-tone details. In addition, at maximum color density (Dmax), leuco dyes tend to diffuse widely but slowly, resulting in reduced image resolution, especially edge definition.

[0006] Some of the above problems can be avoided by adding non-polymeric inert solvents or diluents (e.g., dibutyl phthalate, dioctyl phthalate, trioctyl phosphate, trioctyl trimellitate, dioctyl adipate, dioctyl sebacate, etc.) to improve the solubility of the leuco dye and reduce the internal phase viscosity. However, the presence of additional liquid solvents in the imaged sheeting may result in uneven image quality, poor film integrity, and delamination.

[0007] The present inventors have found that the use of non-photopolymerizable but reactive solvents or diluents (e.g., epoxy compounds) can solve the problems of low temperature tolerance, mid-tone reproduction and slow color development speed. The epoxy groups cannot be photopolymerized by free radical photoinitiators in the internal phase. When the exposed image sheet is pressure developed, the epoxide released from the ruptured microcapsules reacts with the phenol or carboxyl groups of the developer and crosslinks. This leads to improved image resolution, edge definition, film integrity and mechanical properties. The speed of color development by the developer is generally faster or comparable to the speed of the epoxide crosslinking reaction. Therefore, high color saturation or high color development rate can be achieved without the need to make typical trade-offs in terms of image quality and film integrity.

[0008] In one aspect that may be combined with any other aspect or embodiment, the present disclosure relates to a photosensitive microcapsule for a microcapsule imaging sheet, the photosensitive microcapsule comprising: a polymer shell; an internal phase, the internal phase comprising: a leuco dye; a non-photopolymerizable diluent, the non-photopolymerizable diluent being configured to react with a leuco dye developer; a photoinitiator; and a polymerizable or cross-linkable monomer or oligomer, preferably a multifunctional monomer or oligomer.

[0009] In some embodiments, the leuco dye developer comprises a Lewis acid, an acid clay, or one or more compounds comprising a phenolic group or a carboxylic acid group, or a metal complex thereof. In some embodiments, the leuco dye developer comprises a novolac resin, a salicylic acid derivative, a zincate derivative thereof, or a combination, copolymer, blend, composite, or metal complex derivative thereof.

[0010] In some embodiments, the diluent includes an epoxy compound. In some embodiments, the epoxy compound includes two or more epoxide moieties. In some embodiments, the diluent includes a diepoxide or a triepoxide. In some embodiments, the epoxy 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 diepoxides; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; and 1,2-cyclohexanedicarboxylic acid diglycidyl ester.

[0011] In some embodiments, the diluent is present at a concentration of about 3 wt.% to about 20 wt.% relative to 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.% relative to the total weight of the internal phase.

[0012] In some embodiments, the diluent has a water solubility of less than or equal to about 5 wt. %. In some embodiments, the diluent has a water solubility of less than or equal to about 1 wt. %.

[0013] In some embodiments, the diluent has a viscosity of less than or equal to about 300 cps at 25°C, as determined using a Brookfield viscometer at 100 rpm. In some embodiments, the diluent has a viscosity of less than or equal to about 100 cps at 25°C, as determined using a Brookfield viscometer at 100 rpm.

[0014] In some embodiments, the internal phase further comprises a coinitiator, an oxygen scavenger or an auto-oxidant. 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 auto-oxidants include, but are not limited to, organic disulfides such as mercaptobenzothiazole disulfide (MTBS) and 2-ethoxymercaptobenzothiazole disulfide.

[0015] In some embodiments, the polymerizable or cross-linkable monomer or oligomer comprises a multifunctional acrylate.

[0016] In another aspect that may be combined with any other aspect or embodiment, the present disclosure is directed to an imaging sheeting comprising: (i) a microcapsule comprising: a polymer shell; and an internal phase, the internal phase of the microcapsule comprising: a leuco dye; a non-photopolymerizable diluent configured to react with a leuco dye developer; a photoinitiator; and a polymerizable or cross-linkable monomer or oligomer; (ii) a first substrate in contact with the microcapsule; and (iii) a leuco dye developer. In some embodiments, the first substrate is in contact with the microcapsule.

[0017] In some embodiments, the leuco dye developer comprises a Lewis acid, an acidic clay, one or more compounds comprising a carboxylic acid group or a phenolic group, or a metal complex thereof. In some embodiments, the leuco dye developer is a novolac resin, a phenolic resin, salicylic acid, or a combination, copolymer, blend, composite or metal complex derivative thereof. In some embodiments, the metal is zinc.

[0018] 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 substrate and the second substrate is opaque. In some embodiments, the opaque substrate is white. In some embodiments, the first substrate is opaque or white.

[0019] In some embodiments, the first substrate further comprises a primer layer in contact with the microcapsule. In some embodiments, the primer layer comprises microparticles. In some embodiments, the microparticles comprise at least one selected from the group consisting of: CaCO 3 、CaSO 4 ,BaSO 4 , silicon dioxide, TiO 2 、Al 2 O 3 , BN, Ca 3 (PO 4 ) 2 and their hydrophobically treated derivatives.

[0020] In another aspect that may be combined with any other aspect or embodiment, the present disclosure is directed to a microcapsule for a microcapsule imaging sheeting, the microcapsule comprising: a polymer shell; and an internal phase comprising a non-photopolymerizable diluent configured to react with a leuco dye developer.

[0021] In some embodiments, the diluent includes an epoxy compound. In some embodiments, the epoxy compound includes two or more epoxide moieties. In some embodiments, the diluent includes a diepoxide or a triepoxide. In some embodiments, the epoxy 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 diepoxides; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; and 1,2-cyclohexanedicarboxylic acid diglycidyl ester.

[0022] In some embodiments, the diluent is present at a concentration of about 50 wt.% to about 100 wt.% relative to 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.% relative to the total weight of the internal phase.

[0023] In another aspect that may be combined with any other aspect or embodiment, the present disclosure is directed to an imaging sheet comprising: (i) a diluent microcapsule comprising: a polymer shell; and an internal phase comprising a non-photopolymerizable diluent configured to react with a leuco dye developer; and (ii) a photosensitive microcapsule comprising: a polymer shell; an internal phase, the internal phase comprising: a leuco dye; a photoinitiator; and a polymerizable or cross-linkable monomer or oligomer; (iii) a first substrate in contact with the microcapsule; and (iv) a leuco dye developer.

[0024] In some embodiments, the leuco dye developer comprises a Lewis acid, an acid clay, or one or more compounds comprising a phenolic group or a carboxylic acid group.

[0025] In some embodiments, the diluent includes an epoxy compound. In some embodiments, the epoxy compound includes two or more epoxide moieties. In some embodiments, the diluent includes a diepoxide or a triepoxide. In some embodiments, the epoxy 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 diepoxides; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; and 1,2-cyclohexanedicarboxylic acid diglycidyl ester.

[0026] In some embodiments, the diluent is present at a concentration of about 50 wt.% to about 100 wt.% relative to the total weight of the inner phase. In some embodiments, the diluent is present at a concentration of about 90 wt.% to about 100 wt.% relative to the total weight of the inner phase of the diluent microcapsule.

[0027] In some embodiments, the leuco dye developer is a novolac resin, a phenolic resin, salicylic acid, or a combination, copolymer, blend, composite or metal complex derivative thereof. In some embodiments, the metal is zinc.

[0028] 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 substrate and the second substrate is opaque. In some embodiments, the opaque substrate is white.

[0029] In some embodiments, the first substrate further comprises a primer layer in contact with the microcapsule. In some embodiments, the primer layer comprises microparticles. In some embodiments, the microparticles comprise at least one selected from the group consisting of: CaCO 3 、CaSO 4 ,BaSO4 , silicon dioxide, BN, Al 2 O 3 、TiO 2 , Ca 3 (PO 4 ) 2 , their hydrophobically treated derivatives, and any combination thereof.

[0030] In some embodiments, the inner phase of the photosensitive microcapsule further comprises a non-photopolymerizable diluent configured to react with a leuco dye developer. In some embodiments, the diluent comprises an epoxy compound. In some embodiments, the epoxy compound comprises two or more epoxide moieties. In some embodiments, the diluent comprises a diepoxide or a triepoxide. In some embodiments, the epoxy 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 diepoxides; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; and 1,2-cyclohexanedicarboxylic acid diglycidyl ester.

[0031] In another aspect that may be combined with any other aspect or embodiment, the present disclosure is directed to a microcapsule composition comprising: one or more microcapsules according to any embodiment disclosed herein; and a carrier, wherein the one or more microcapsules are dispersed in the carrier.

[0032] In another aspect that may be combined with any other aspect or embodiment, the present disclosure is directed to a method of preparing an imaging sheeting, the method comprising: (i) contacting a first substrate with a microcapsule layer to produce a microcapsule-coated first substrate; (ii) contacting the microcapsule layer of the microcapsule-coated first substrate with a developer layer to produce a developer-coated first substrate; and (iii) contacting the developer layer of the developer-coated first substrate with a second substrate to produce an imaging sheeting.

[0033] In another aspect that may be combined with any other aspect or embodiment, the present disclosure is directed to a method of preparing an imaging sheeting, the method comprising: (ia) contacting a first substrate with a primer layer to produce a primer-coated first substrate; (ib) contacting the primer layer of the primer-coated first substrate with a microcapsule layer to produce a microcapsule-coated first substrate; (ii) contacting the microcapsule layer of the microcapsule-coated first substrate with a developer layer to produce a developer-coated first substrate; and (iii) contacting the developer layer of the developer-coated first substrate with a second substrate to produce an imaging sheeting.

[0034] In another aspect that may be combined with any other aspect or embodiment, the present disclosure is directed to a method of preparing an imaging sheet, the method comprising: a method of preparing an imaging sheet, the method comprising: (i) producing a microcapsule-coated first substrate according to any embodiment disclosed herein (e.g., contacting a first substrate or a primer-coated first substrate with a microcapsule layer); (ii) contacting a second substrate with a developer layer to produce a developer-coated second substrate; (iii) contacting the microcapsule layer of the microcapsule-coated first substrate with the developer layer of the developer-coated second substrate to produce an imaging sheet.

[0035] In some embodiments, the primer layer according to any embodiment disclosed herein is located (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.

[0036] In another aspect that may be combined with any other aspect or embodiment, the present disclosure is directed to a method of improving one or more properties of an imaging sheeting, the method comprising including (or adding) one or more microcapsules according to any one of the embodiments disclosed herein in the imaging sheeting. In some embodiments, the one or more properties include one or more of the following: Dmax; fresh Dmax; Dmax,t; Dmin; image resolution; temperature tolerance; dynamic range; anti-discoloration (yellowing); and edge definition. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1A is a schematic diagram of an embodiment of an imaging sheeting having photosensitive microcapsules according to the present disclosure, the photosensitive microcapsules comprising a leuco dye and a non-photopolymerizable reactive diluent within the same microcapsule.

[0038] Figure 1B is a schematic diagram of an embodiment of an imaging sheeting having photosensitive microcapsules according to the present disclosure, wherein the photosensitive microcapsules have a leuco dye and a non-photopolymerizable reactive diluent within the same microcapsule.

[0039] Figure 1C is a schematic diagram (cross-sectional side view) of a microcapsule according to the present disclosure.

[0040] Figure 2A is a schematic diagram of an embodiment of an imaging sheeting having separate photosensitive leuco dye microcapsules and non-photosensitive diluent microcapsules according to the present disclosure.

[0041] Figure 2B is a schematic diagram of a microcapsule imaging sheet having separate photosensitive leuco dye microcapsules and non-photosensitive diluent microcapsules according to the present disclosure. DETAILED DESCRIPTION

[0042] In the following description, many specific details are set forth in order to provide a thorough understanding of the technology of the present invention. Specific exemplary embodiments of the technology of the present invention may be implemented in the absence of some or all of these specific details. In other cases, some process operations are not described in detail, but will be understood by those skilled in the art.

[0043] refer to Figure 1A In some embodiments, the microcapsule imaging sheet 100 according to the present disclosure includes a microcapsule layer 106, which includes microcapsules 108 (e.g., photosensitive microcapsules and / or non-photosensitive microcapsules) disposed on a first substrate 102, and the first substrate 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 placed separately in contact with the microcapsule layer 106.

[0044] Alternatively, if Figure 1B As shown, the microcapsule layer 106 can be overcoated with a developer layer 110b. The resulting microcapsule / developer imaging sheet can be used as is or laminated with a second substrate 114, which can be pre-coated with an adhesive layer (not shown). Alternatively, the microcapsule layer composition can be mixed with the developer layer composition and applied as a single layer (not shown).

[0045] refer to Figure 1C , the microcapsule 108 can be a photosensitive microcapsule comprising a polymer shell 116 and a core (or inner phase) 118 encapsulated therein, which can be softened or hardened by actinic radiation. The inner phase 118 contains a dye (e.g., a leuco dye) that imparts color to the microcapsule imaging sheet after release under pressure and simultaneous or subsequent exposure to heat, certain pH conditions, reactive chemicals, or a developer. After being released from the microcapsule 108, the dye (e.g., a leuco dye) undergoes a chemical transformation from a colorless state to a colored state (e.g., magenta, cyan, yellow, or black).

[0046] The inner phase 118 of one or more photosensitive microcapsules may further include one or more photoinitiators, one or more multifunctional monomers or oligomers, and one or more non-photopolymerizable reactive diluents. The non-photopolymerizable reactive diluent may be configured to react with Lewis acids, phenolic groups or carboxylic acid groups (e.g., in the developer layer) and their metal complexes, particularly their zincated derivatives, but may not react with photoinitiators, sensitizers, co-photoinitiators, scavengers, auto-oxidizers, chain transfer agents and / or monomers or oligomers that may be present in the inner phase 118. Suitable 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 auto-oxidizers include, but are not limited to, organic disulfides such as mercaptobenzothiazole disulfide (MTBS) and alkoxymercaptobenzothiazole disulfide, including 2-ethoxymercaptobenzothiazole disulfide.

[0047] The photosensitive microcapsule 108 may include a polymer shell and a photosensitive core that can be photohardened by polymerizing or cross-linking the monomers / oligomers contained therein. In some embodiments, the photohardenable monomers may be replaced with photosoftenable or photodegradable compositions.

[0048] The polymer shell can be formed by, for example, interfacial or in-situ polymerization / crosslinking, simple or complex coagulation processes, phase separation or a combination thereof. In certain embodiments, suitable polymer shells include, but are not limited to, polyureas, polythioureas, polyurethanes, polythiourethanes, polyalophanates, polyurethanes, polysulfones, melamine-formaldehyde or urea-formaldehyde condensates, gelatin-gum arabic complexes, gelatin-carboxymethyl cellulose complexes, and copolymers, interpolymer complexes, blends or complexes thereof. In certain embodiments, water-insoluble polymers that are incompatible with or do not swell / insoluble in the internal phase are preferred as shell materials because they tend to exhibit favorable barrier properties for moisture and / or oxygen.

[0049] The outer shell provides the required oxygen barrier properties to ensure high photosensitivity of the photosensitive core and avoids any premature mixing of the photoinitiator and dye precursors of the various colors, thus ensuring successful color separation and reproduction.

[0050] In some embodiments, the photohardenable 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 multifunctional monomer or oligomer. In some embodiments, the monomer or oligomer is selected from multifunctional acrylates and methacrylates, multifunctional vinyl ethers, multifunctional allyl or vinyl benzenes, and oligomers, dendrimers, or blends thereof. Multifunctional acrylates are suitable for use due to their excellent photosensitive speed, compatibility with leuco dyes and developers, and outdoor weatherability. Exemplary multifunctional 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.

[0051] The microcapsule layer may contain 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 contain 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. By way of non-limiting example, a representative magenta leuco dye may include Red I6B (CAS: 50292-95-0, Synamedia-chem) In some embodiments, the photoinitiator is a blue-sensitive ketocoumarin, cyanine borate, or hemicyanine borate.

[0052] Now referring to Fig. 2, in some embodiments, non-photopolymerizable reactive diluent is present in separate microcapsules, wherein the internal phase does not include dye, photoinitiator or multifunctional oligomer.In such embodiments, microcapsule layer 206 can include at least two different types of microcapsules: dye microcapsules 208 and diluent microcapsules 209.In some embodiments, the dye microcapsules can include components and features discussed above (e.g., polymer shell, leuco dye, photoinitiator, multifunctional monomer or oligomer) and non-photopolymerizable reactive diluent.In some embodiments, the dye microcapsules can include components and features discussed above (e.g., polymer shell, leuco dye, photoinitiator, multifunctional monomer or oligomer), but do not include non-photopolymerizable reactive diluent.In some embodiments, the diluent microcapsule includes a polymer shell and an internal phase that includes non-photopolymerizable reactive diluent.

[0053] In some embodiments, the diluent microcapsules may be non-photosensitive and the dye microcapsules may be photosensitive. In some embodiments, the presence of the diluent in a separate microcapsule from the photosensitive dye microcapsules provides improvements in mechanical properties (e.g., peel strength) of the imaging sheeting 200 and resistance to discoloration (e.g., lower yellow Dmin) of the imaging sheeting, but may provide relatively small improvements in temperature latitude, compared to embodiments where the diluent and dye are present in the same microcapsule.

[0054] In some embodiments, a microcapsule imaging system comprises a photosensitive diluent microcapsule comprising a shell, a non-photopolymerizable diluent, a photoinitiator or sensitizer, and a multifunctional monomer.

[0055] In some embodiments according to FIG. 2 , the first substrate 202, the optional primer layer 204, the photosensitive dye microcapsules 208, the diluent microcapsules 209, the developer layer 210a, the developer particles 210b and the second substrate 214 are Figure 1A and Figure 1B The same as described in the embodiment.

[0056] 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 exposed microcapsule sheet under pressure to form an interlayer sheet with the image developed therein. In some embodiments, the microcapsule sheet is peeled from the interlayer structure to leave a color image on the developer sheet.

[0057] Microcapsule layer

[0058] The microcapsule layer comprises photosensitive microcapsules having a polymer shell and an inner phase (or core). In some embodiments, the inner phase of the microcapsule comprises a leuco dye, a photoinitiator, one or more multifunctional monomers or oligomers, and one or more non-photopolymerizable reactive diluents.

[0059] In some embodiments, the microcapsule layer comprises: (i) photosensitive dye microcapsules, which include a polymer shell and an inner phase, which includes a leuco dye, a photoinitiator and a multifunctional monomer or oligomer, but does not include a non-photopolymerizable reactive diluent; and (ii) non-photosensitive diluent microcapsules, which include a polymer shell and an inner phase, which includes, is essentially composed of, or is composed of a non-photopolymerizable reactive diluent.

[0060] In some embodiments, the dye microcapsules are photosensitive, while the diluent microcapsules are non-photosensitive - that is, the core neither softens nor hardens by actinic radiation. In some embodiments, both the dye and diluent microcapsules are photosensitive, wherein the core softens or hardens by actinic radiation.

[0061] In some embodiments, the microcapsule layer comprises 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.

[0062] In some embodiments, the microcapsule layer comprises 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.

[0063] In some embodiments, the diluent microcapsules may include two or more types of diluents. In some embodiments, the diluent microcapsules may include a first diluent and a second diluent in a weight ratio of the first diluent microcapsules to the second diluent microcapsules: 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 therebetween.

[0064] In some embodiments, the microcapsule layer may include two or more types of diluent microcapsules. In some embodiments, the microcapsule layer may include a first diluent microcapsule and a second diluent microcapsule in a weight ratio of the first diluent microcapsule to the second diluent microcapsule: 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 therebetween.

[0065] In some embodiments, the microcapsules have a D of at least about 1 μm (10% of the particles are less than 1 μm), at least about 1.5 μm, or at least about 2 μm. 10 granularity.

[0066] In some embodiments, the microcapsules have a D of at least about 2 μm (50% of the particles are smaller than 2 μm), at least about 3 μm, or at least about 4 μm. 50 In some embodiments, the microcapsules have a particle size of no greater than about 15 μm, no greater than about 12 μm, or no greater than about 10 μm. 50 Particle size. As the particle size increases, the pressure required to break the microcapsules decreases dramatically. 50 Microcapsules with a D value of 0.10 are difficult to break by pressures that are easily accessible with portable printers, especially handheld printers. In addition, since a minimum shell thickness is generally required to ensure adequate barrier properties to protect the inner phase from premature damage or leakage from the microcapsule, a smaller D value is more likely to break. 50 This means a lower effective loading of the internal phase in which the leuco dye is dissolved. Therefore, small microcapsules tend to result in a lower maximum color density (Dmax) of the imaging system.

[0067] In contrast, a D of greater than about 15 μm 50 Microcapsules with a D of greater than about 15 μm may be more easily crushed during media handling and processing. 50 Imaging systems of microcapsules usually exhibit higher Dmin (minimum color density in the non-imaged or white area) and poorer resolution images.

[0068] Polymer housing

[0069] In certain embodiments, microcapsules (for example, dye microcapsules or diluent microcapsules) comprise photosensitive or non-photosensitive polymer shells.Polymer shells can be formed by methods including but not limited to interface or in-situ polymerization / crosslinking, simple or complex coagulation processes, phase separation or its combination.Suitable polymer shells include but are not limited to polyureas, polythioureas, polyurethanes, polythiourethanes, polyalophanates, polyurethanes, polysulfones, melamine-formaldehyde or urea-formaldehyde condensates, gelatin-gum arabic complexes, gelatin-carboxymethyl cellulose, or pectin complexes, and copolymers, interpolymer complexes, blends or their complexes.In certain embodiments, water-insoluble polymers that are incompatible with or insoluble in the internal phase / insoluble in the internal phase are suitable as shell materials because they often show excellent barrier properties for moisture and / or oxygen.

[0070] Leuco dye

[0071] In some embodiments, the inner phase of the microcapsule comprises a leuco dye. In some embodiments, the dye is a cyan, magenta, yellow, or black leuco dye. By way of non-limiting example, a representative magenta leuco dye may include Red I6B (CAS: 50292-95-0, Synamedia-chem); COPIKEM 35 (CAS: 50292-91-6); Blue I-2G and Blue-63 from BASF; Blue 220, Blue 203, Red 500, Red40 or Black 305 from Yamada; JYDY-1, JYDR-2, JYDR-3, JYDB-1 or JYDB-2 from WuXi Jiayida New Materials; Red-16, O-C6 or O-C8 from Synmedia Chemicals; or ODB-2 from Anyang General Chemicals. Other suitable examples of leuco dyes are disclosed in, for example, Chemistry and Applications of Leuco Dyes (R. Muthyala, ed., 1997), which is hereby incorporated by reference.

[0072] In some embodiments, the leuco dye is present in the internal phase at a concentration (by weight relative to the total weight of the internal phase) 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.

[0073] In some embodiments, the leuco dye is present in the internal phase at a concentration (by weight relative to the total weight of the internal phase) of no greater than about 50 wt.%, no greater than about 45 wt.%, no greater than about 40 wt.%, no greater than about 35 wt.%, no greater than about 30 wt.%, no greater than about 25 wt.%, or any range or value therebetween.

[0074] In some embodiments, the leuco dye is present in the internal phase at a concentration (by weight relative to the total weight of the internal phase) of about 1 wt.% to about 50 wt.%, about 5 wt.% to about 40 wt.%, or about 10 wt.% to about 30 wt.%.

[0075] Photoinitiator

[0076] In some embodiments, the one or more photoinitiators include one or more borate initiators having the general structure

[0077]

[0078] Where D + is a cationic chromophore such as a cyanine, a squaraine (e.g., a squarylium), a thiopyranium, or a triarylmethane. 1 , R 2 , R 3 and R 4 Each is independently a substituted or unsubstituted alkyl, arylalkyl or aryl group. In some embodiments, R 1 is an alkyl or arylalkyl group, and R 2 , R 3 and R 4is an aryl group. In some embodiments, the one or more photoinitiators include one or more of ketocoumarins, benzophenones, thioxanthones, and Norrish I, II, and III type photoinitiators and combinations thereof.

[0079] In some embodiments, one or more photoinitiators are present in the internal phase at a concentration (by weight relative to the total weight of the internal phase) of greater than or equal to about 0.01 wt.%, greater than or equal to about 0.02 wt.%, greater than or equal to about 0.03 wt.%, greater than or equal to about 0.04 wt.%, greater than or equal to about 0.05 wt.%, greater than or equal to about 0.1 wt.%, greater than or equal to about 0.2 wt.%, greater than or equal to about 0.3 wt.%, greater than or equal to about 0.4 wt.%, greater than or equal to about 0.5 wt.%, greater than or equal to about 1.0 wt.%, greater than or equal to about 2.0 wt.%, greater than or equal to about 3.0 wt.%, greater than or equal to about 4.0 wt.%, greater than or equal to about 5.0 wt.%, greater than or equal to about 10.0 wt.%, or any range or value therebetween.

[0080] In some embodiments, one or more photoinitiators are present in the internal phase at a concentration (by weight relative to the total weight of the internal phase) of less than or equal to about 10.0 wt.%, less than or equal to about 5.0 wt.%, less than or equal to about 4.0 wt.%, less than or equal to about 3.0 wt.%, less than or equal to about 2.0 wt.%, less than or equal to about 1.0 wt.%, less than or equal to about 0.5 wt.%, less than or equal to about 0.4 wt.%, less than or equal to about 0.3 wt.%, less than or equal to about 0.2 wt.%, less than or equal to about 0.1 wt.%, less than or equal to about 0.05 wt.%, less than or equal to about 0.04 wt.%, less than or equal to about 0.03 wt.%, less than or equal to about 0.02 wt.%, less than or equal to about 0.01 wt.%, or any range or value therebetween.

[0081] In some embodiments, the one or more photoinitiators are present in the internal phase at a concentration (by weight relative to the total weight of the internal phase) 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 0.0 .05wt.% to about 10.0wt.%, about 0.1wt.% to about 10.0wt.%, about 0.1wt.% to about 10.0wt.%, about 0.5wt.% to about 10.0wt.%, about 1.0wt.% to about 10.0wt.%, about 5.0wt.% to about 10.0wt.%, about 0.05wt.% to about 5.0wt.%, about 0.1wt.% to about 1.0wt.%, or any range or value therebetween.

[0082] Monomer or oligomer

[0083] In certain embodiments, the internal phase of microcapsule (for example, dye microcapsule) comprises one or more monomers or oligomers.In certain embodiments, monomer or oligomer is polymerizable or cross-linkable.In certain embodiments, monomer or oligomer is light-softenable or light-hardenable.In certain embodiments, one or more monomers include multifunctional monomers.In certain embodiments, monomer or oligomer can include acrylate or methacrylate of polyol, acrylate or methacrylate end-capped epoxy resin, acrylate or methacrylate end-capped polyester or polyurethane, vinylbenzene, vinyl ether or maleimide end-capped oligomer or polymer, and copolymer, blend or combination thereof. By way of non-limiting example, in some embodiments, 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 trimethylacrylamide, vinyl esters (e.g., divinyl succinate), divinyl adipate, divinyl phthalate, divinyl terephthalate, divinylbenzene, or any combination thereof. In some embodiments, the monomer or oligomer comprises a multifunctional acrylate.

[0084] In some embodiments, one or more monomers or oligomers are present in the internal phase at a concentration (by weight relative to the total weight of the internal phase) 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.

[0085] In some embodiments, one or more monomers or oligomers are present in the internal phase at a concentration (by weight relative to the total weight of the internal phase) of not more than about 90 wt.%, not more than about 85 wt.%, not more than about 80 wt.%, not more than about 75 wt.%, not more than about 70 wt.%, not more than about 65 wt.%, not more than about 60 wt.%, not more than about 55 wt.%, not more than about 50 wt.%, not more than about 45 wt.%, not more than about 40 wt.%, not more than about 35 wt.%, not more than about 30 wt.%, or any range or value therebetween.

[0086] In some embodiments, one or more monomers or oligomers are present in the internal phase at a concentration (by weight relative to the total weight of the internal phase) of about 40 wt.% to about 90 wt.%, about 50 wt.% to about 85 wt.%, or about 60 wt.% to about 80 wt.%.

[0087] Thinner

[0088] In some embodiments, a non-photopolymerizable but reactive diluent (e.g., an epoxide) is used instead of an inert solvent or diluent to increase temperature tolerance, mid-tone reproduction, peel strength, and color development rate. In some embodiments, the diluent is an epoxy compound. In some embodiments, the epoxy compound contains at least 1, at least 2, at least 3, at least 4, at least 5, or at least 6 epoxy groups, preferably about 2 to 6 epoxy 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 diepoxides; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; 1,2-cyclohexanedicarboxylic acid diglycidyl ester, or any combination thereof.

[0089] In some embodiments, the epoxy groups are not photopolymerizable by free radical photoinitiators that may be present in the internal phase. In some embodiments, the epoxy compound is configured to react with Lewis acids, phenolic groups or carboxyl groups, and / or metal complexes thereof (particularly zinc complexes). Thus, when the exposed image sheet is pressure developed, the epoxide released from the ruptured microcapsules will react and crosslink with the Lewis acid, phenolic or carboxylic acid groups of one or more developers. This can achieve high image resolution and edge definition, as well as improved dielectric film integrity and mechanical properties.

[0090] The phenolic groups of dye developers are generally sensitive to thermal or photooxidation and tend to show a high degree of yellow background color (high yellow Dmin or discoloration) after aging. The reaction with the epoxide released from the microcapsules converts the phenolic groups to non-yellowing phenoxy groups and effectively reduces the degree of yellow Dmin or discoloration after aging. The speed of color development by the developer is generally faster or comparable to the speed of the epoxide cross-linking reaction. Therefore, high color saturation or high color development speed and high resistance to discoloration can be achieved without sacrificing image quality and physical and mechanical properties.

[0091] In some embodiments, the diluent includes one or more epoxy compounds at a suitable concentration to improve temperature latitude, Dmax, mid-tone reproduction, image resolution, and edge definition. Too high a diluent concentration may result in insufficient internal phase photopolymerization / cross-linking, resulting in an image with a "dirty" background (poor Dmin). In contrast, if the concentration of the epoxy is too low, the improvements in temperature latitude, Dmax, mid-tones, resolution, and edge definition may not be significant.

[0092] In some embodiments, one or more diluents (e.g., epoxy compounds) are present in the internal phase at a concentration (by weight relative to the total weight of the internal phase) 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.

[0093] In some embodiments, one or more diluents (e.g., epoxy compounds) are present in the internal phase at a concentration (by weight relative to the total weight of the internal phase) of not more than about 40 wt.%, not more than about 35 wt.%, not more than about 30 wt.%, not more than about 25 wt.%, not more than about 20 wt.%, not more than about 19 wt.%, not more than about 18 wt.%, not more than about 17 wt.%, not more than about 16 wt.%, not more than about 15 wt.%, not more than about 14 wt.%, not more than about 13 wt.%, not more than about 12 wt.%, not more than about 11 wt.%, not more than about 10 wt.%, not more than about 9 wt.%, not more than about 8 wt.%, not more than about 7 wt.%, not more than about 6 wt.%, not more than about 5 wt.%, not more than about 4 wt.%, not more than about 3 wt.%, not more than about 2 wt.%, not more than about 1 wt.%, or any range or value therebetween.

[0094] In some embodiments, one or more diluents (e.g., epoxy compounds) are present in the internal phase at a concentration (by weight relative to the total weight of the internal phase) 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.

[0095] To ensure successful encapsulation and good barrier properties of the encapsulated shell, the epoxy compound should exhibit high compatibility with the multifunctional monomers (e.g., acrylates) present in the internal phase, as well as 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 Na 2 SO 4 ) to further reduce the solubility of the epoxide in the aqueous phase.

[0096] In some embodiments, the diluent has a water solubility of less than or equal to about 10.0 wt.%, less than or equal to about 5.0 wt.%, less than or equal to about 4.0 wt.%, less than or equal to about 3.0 wt.%, less than or equal to about 2.0 wt.%, less than or equal to about 1.0 wt.%, less than or equal to about 0.5 wt.%, less than or equal to about 0.4 wt.%, less than or equal to about 0.3 wt.%, less than or equal to about 0.2 wt.%, less than or equal to about 0.1 wt.%, or any range or value therebetween.

[0097] In some embodiments, the diluent (e.g., epoxy compound) has a viscosity 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 at 25° C. In some embodiments, the viscosity of the diluent is measured at room temperature using a Brookfield viscometer (Spindle S31) at 100 rpm.

[0098] In some embodiments, the diluent (e.g., epoxy compound) has a weight average molecular weight of less than or equal to about 1,000 g / mol, less than or equal to about 900 g / mol, less than or equal to about 800 g / mol, less than or equal to about 700 g / mol, less than or equal to about 600 g / mol, less than or equal to about 500 g / mol, less than or equal to about 400 g / mol, less than or equal to about 300 g / mol, or any range or value therebetween.

[0099] In some embodiments, the diluent has a weight average molecular weight of greater than or equal to about 200 g / mol, greater than or equal to about 250 g / mol, greater than or equal to about 300 g / mol, greater than or equal to about 350 g / mol, greater than or equal to about 400 g / mol, greater than or equal to about 450 g / mol, greater than or equal to about 500 g / mol, or any range or value therebetween.

[0100] 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 therebetween.

[0101] The first substrate and the second substrate

[0102] In some embodiments, the microcapsules are coated on a first substrate. The first substrate may include, for example, any coated paper and / or a dyed derivative thereof. In some embodiments, the first substrate is white or transparent. In some embodiments, the first substrate comprises at least one of: polyester (e.g., polyethylene terephthalate ("PET"), polyethylene naphthalate ("PEN"), etc.), cellulose-based polymers (e.g., cellulose triacetate), polycarbonate, polyolefin (including cyclic polyolefin), or a combination, blend, composite, laminate or copolymer thereof. By way of non-limiting example, the first substrate may be selected from commercially available films, including but not limited to Polyester film (Mitsubishi Polyester Film), (DuPont Teijin Films TM )and Polyester film (DuPont TeijinFilms TM ).

[0103] The substrate can have any suitable thickness. In some embodiments, the first substrate has the following thickness: 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 from about 12 μm to about 150 μm, or about 25 μm to about 100 μm.

[0104] In some embodiments, the developer is coated on the second substrate. The second substrate may include, for example, any coated paper and / or a dyed derivative thereof. In some embodiments, the first substrate comprises at least one of a polyester (e.g., polyethylene terephthalate ("PET"), polyethylene naphthalate ("PEN"), etc.), a cellulose-based polymer (e.g., cellulose triacetate), a polycarbonate, a polyolefin (including a cyclic polyolefin), or a combination, blend, composite, laminate, or copolymer thereof. By way of non-limiting example, the first substrate may comprise a commercially available film such as Polyester film (Mitsubishi Polyester Film), (DuPont TeijinFilms TM )and Polyester film (DuPont Teijin Films TM ).

[0105] The second substrate on which the developer is arranged can be placed in contact with the microcapsule layer so that the developer layer contacts the microcapsule layer. The second substrate can have any suitable thickness. In some embodiments, the second substrate has the following thickness: 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 from about 3.5 μm to about 150 μm, or about 10 μm to about 100 μm.

[0106] In some embodiments, at least one of the first substrate and the second substrate is an opaque or white substrate. As used herein, the term "opaque" means having a total light transmittance (TLT) of 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%, as measured according to ASTM D1003. 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.

[0107] In some embodiments, a layer of microcapsules is coated on an opaque substrate and a developer is coated on a transparent substrate. In some embodiments, the initial light passes through the (top) developer layer and hardens the (bottom) microcapsules. After development, the leuco dye diffuses into the developer layer and forms a color image therein. The opposite configuration with a top microcapsule and a bottom developer layer can also be used, but in some embodiments with this configuration, the hardened microcapsules are slightly colored and fuzzy and may present a mottled image to the observer.

[0108] Developer layer

[0109] In some embodiments, imaging sheets according to the present disclosure include a developer layer in contact with a second substrate. The developer layer can be in contact with the microcapsule layer by, for example, laminating after being applied to the second substrate. In some embodiments, the developer layer can be externally coated on the microcapsule layer, and the resulting externally coated sheet can be used as is in the absence of a second substrate. In some embodiments, the externally coated developer / microcapsule sheet can be further coated with a durable protective coating or laminated with a second substrate (optionally with an additional adhesive layer). In some embodiments, the composition of the developer layer can be pre-mixed with the composition of the microcapsule layer and applied to the first substrate as a single layer.

[0110] In some embodiments, the developer layer includes one or more leuco dye developers. By way of non-limiting example, the developer may include Lewis acid, silicic acid, salicylic acid derivatives, benzoic acid derivatives, novolac resins and metal complexes thereof (particularly zinc complexes), or blends, composites, copolymers (including graft copolymers and block copolymers) or combinations thereof. For example, one or more developers may include: acid clay, 3,5-bis(α-methylbenzyl) zinc salicylate (e.g., N-054-W, SANKO Co., Ltd.), 3,5-di-tert-butyl zinc salicylate, 3,5-dioctyl zinc salicylate, HRJ4542 (Schenectady Chemical), or novolac resin developers (such as RD9870, RD9870A, RD9880, RD9880U, RF-118, etc. (Xinxiang Richful Lube Additive Co., Ltd.)).

[0111] The developer layer can have any suitable thickness. For example, the developer layer can 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 from about 1 μm to about 30 μm, about 2 μm to about 20 μm, or about 3 μm to about 15 μm.

[0112] The developer may be present in the developer layer at a concentration (by weight relative to the dry weight of the developer layer) of about 50 wt.%, about 55 wt.%, about 60 wt.%, about 65 wt.%, about 70 wt.%, about 75 wt.%, about 80 wt.%, about 85 wt.%, about 90 wt.%, about 95 wt.%, about 96 wt.%, about 97 wt.%, about 98 wt.%, about 99 wt.%, or any range or value therebetween. In some embodiments, the developer layer may include a polymer binder and a filler, such as silica.

[0113] Primer layer

[0114] In some embodiments, the microcapsule imaging sheet according to the present disclosure includes a primer layer. The primer layer can be a film in contact with the first substrate and / or the microcapsule layer. In some embodiments, the primer layer can include a polymer binder and white particles. In some embodiments, the primer layer can further include polymer hollow particles.

[0115] In some embodiments, the one or more polymer binders may comprise, consist essentially of, or consist of one or more polymers selected from the group consisting of acrylic polymers or copolymers, styrene copolymers, butadiene copolymers, vinyl chloride copolymers, vinylidene chloride copolymers, ethylene copolymers, propylene copolymers, vinyl acetate copolymers, 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.

[0116] In some embodiments, the primer layer according to the present disclosure includes one or more particles (eg, white particles). The white particles can be of any suitable composition, size, and concentration for enhancing the reflectivity and / or hiding power of the primer layer.

[0117] In some embodiments, the one or more white particles may include one or more of the following: TiO 2 ,BaSO 4 、CaSO 4 、CaCO 3 , BN, Al 2 O 3 , Ca 3 (PO 4 ) 2 、ZrO 2, ZnO, or any other suitable metal oxide, transition metal oxide, sulfate, carbonate, or phosphate material, or its hydrophobic treated derivative. In some embodiments, the white particles are one or more selected from the group consisting of: TiO 2 ,BaSO 4 、CaSO 4 、CaCO 3 、Al 2 O 3 , and Ca 3 (PO 4 ) 2 , and hydrophobic derivatives thereof. In some embodiments, the white particles comprise TiO 2 , consisting essentially of, or consisting of.

[0118] While the foregoing terms are believed to be well understood by those of ordinary skill in the art, the following definitions are set forth to facilitate explanation of the presently disclosed subject matter.

[0119] The term "a" or "an" may refer to one or more of the entity, i.e., may refer to multiple referents. Thus, the terms "a" or "an", "one or more" and "at least one" are used interchangeably herein. In addition, reference to an "element" by the indefinite article "a" or "an" does not exclude the possibility that more than one element is present, unless the context clearly requires the presence of one and only one element.

[0120] References throughout this specification to "one embodiment," "an embodiment," "one aspect," or "an aspect" mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in at least one embodiment of the present disclosure. Thus, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout this specification do not necessarily all refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0121] As used herein, the term "about" or "approximately" when preceding a numerical value indicates a range of plus or minus 10% of the value.

[0122] As will be appreciated by those skilled in the art, for any and all purposes, particularly in accordance with the provision of written specifications, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily considered to fully describe and enable the same range to be decomposed into at least equal halves, one-third, one-quarter, one-fifth, one-tenth, etc. As a non-limiting example, each range discussed herein can be easily decomposed into lower third, middle third, and upper third, etc. It will also be understood by those skilled in the art that all language (such as "until", "at least", "greater than", "less than", etc.) includes the number and refers to such a range, which can then be decomposed into subranges as described above. Finally, as will be appreciated by those skilled in the art, ranges include each individual member.

[0123] Unless otherwise defined, all terms used herein (including technical terms and scientific terms) have the same meanings as those generally understood by those of ordinary skill in the art to which the present invention belongs. It should be further understood that terms (such as those defined in common dictionaries) should be interpreted as having the same meanings as those in the context of the present application and related fields, and unless clearly defined as such herein, should not be interpreted in an idealized or overly formal sense. Although not clearly defined below, such terms should be interpreted according to their common meanings.

[0124] For the purposes of this disclosure, the term "color density" refers to the reflective optical density of a developed dye or the ability to reflect light from a media sheet, as measured by a reflective densitometer FD-5 from Konica Minolta, wherein the stronger the light reflectance of the dye, the higher the color optical density (i.e., the darker the color). The lower the light reflectance of the dye, the lower the color density (i.e., the lighter the color).

[0125] For the purposes of this disclosure, the term "leuco dye" refers to a chemical dye that can alternate between two chemical forms, one of which is colorless. The transition from the colorless leuco form to the colored dye form can be reversible or irreversible and can be induced by changes in temperature, pH, radiation, or redox state.

[0126] For purposes of this disclosure, the terms "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 reflectance densitometer FD-5 from Konica Minolta, (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 measured after conditioning the developed image sheet for a period of time t). The term "minimum color density" (or "Dmin") refers to the minimum reflected color optical density measured in a non-image area.

[0127] For purposes of this disclosure, the term "opaque" means having a total light transmittance (TLT) of 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%, as measured according to ASTM D1003.

[0128] For the purposes of this 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.

[0129] Compositions comprising microcapsules containing non-photopolymerizable diluents

[0130] In another aspect, the present disclosure relates to a composition comprising a microcapsule according to any of the embodiments discussed above. For example, a microcapsule composition may comprise a microcapsule for a microcapsule imaging sheet, the microcapsule comprising: a polymer shell; and an internal phase comprising a non-photopolymerizable diluent configured to react with a leuco dye developer; and a carrier, wherein the microcapsules are dispersed in the carrier. In some embodiments, the internal phase of the microcapsule further comprises a leuco dye. In some embodiments, the internal phase of the microcapsule further comprises a photoinitiator. In some embodiments, the internal phase of the microcapsule further comprises a polymerizable or cross-linkable monomer or oligomer.

[0131] In some embodiments, the microcapsule may include a photosensitive microcapsule comprising a polymer shell; and an internal phase comprising a leuco dye; a photoinitiator; and a photopolymerizable or cross-linkable monomer or oligomer. In some embodiments, the microcapsule may include a diluent microcapsule comprising a polymer shell; and an internal phase comprising a non-photopolymerizable diluent configured to react with a leuco dye developer. In some embodiments, the microcapsule includes a photosensitive microcapsule, a diluent microcapsule, or any combination thereof.

[0132] In some embodiments, the carrier is water. In some embodiments, the carrier comprises an organic solvent, water, or any combination thereof. In some embodiments, the organic solvent is methanol, ethanol, acetone, or any other suitable solvent.

[0133] Method for preparing imaging sheeting

[0134] In another aspect, the present disclosure is directed to a method of preparing an imaging sheeting, the method comprising: contacting a first substrate with a microcapsule layer to produce a microcapsule-coated first substrate, the microcapsule layer comprising 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 discussed above to produce a primer-coated first substrate. In some embodiments, the primer-coated first substrate is contacted with a microcapsule layer to produce a microcapsule-coated first substrate, the microcapsule layer comprising microcapsules according to any of the embodiments discussed above.

[0135] For example, the microcapsule layer may include microcapsules for microcapsule imaging sheeting, the microcapsules comprising: a polymer shell; and an internal phase, the internal phase comprising a non-photopolymerizable diluent configured to react with a leuco dye developer; and a carrier, wherein the microcapsules are dispersed in the carrier. In some embodiments, the internal phase of the microcapsule further comprises a leuco dye. In some embodiments, the internal phase of the microcapsule further comprises a photoinitiator. In some embodiments, the internal phase of the microcapsule further comprises a polymerizable or crosslinkable monomer or oligomer. In some embodiments, the microcapsules may include photosensitive microcapsules, which include a polymer shell; and an internal phase comprising a leuco dye; a photoinitiator; and a photopolymerizable or crosslinkable monomer or oligomer. In some embodiments, the microcapsules may include diluent microcapsules, which include a polymer shell; and an internal phase comprising 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. In some embodiments, the microcapsules are present in a composition as disclosed above, wherein the microcapsules are dispersed in a carrier.

[0136] In some embodiments, the method of producing an imaging sheet includes contacting a microcapsule-coated first substrate with a developer layer to produce a developer-coated first substrate. In some embodiments, the developer-coated first substrate 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 developer-coated second substrate, which is then contacted with the microcapsule-coated first substrate to produce the imaging sheet. In some embodiments, the developer-coated second substrate and the microcapsule-coated first substrate are contacted with each other so that the developer layer contacts the microcapsule layer. In some embodiments, a primer may be located between the second substrate and the developer layer.

[0137] Methods of using microcapsules and imaging sheets

[0138] In another aspect that may be combined with any other aspect or embodiment, the present disclosure relates to a method of using the microcapsules according to any of the above-discussed embodiments. In another aspect that may be combined with any other aspect or embodiment, the present disclosure relates to a method of using the imaging sheeting according to any of the above-described embodiments.

[0139] For example, in some embodiments, a method of imaging or printing comprises exposing an imaging sheeting comprising microcapsules according to any of the above-discussed embodiments to heat, pressure, or radiation, wherein the exposure is sufficient to release a leuco dye and / or a non-photopolymerizable diluent configured to react with a leuco dye developer from the polymer shell to produce an image.

[0140] In some embodiments, the present disclosure is directed to a method of adjusting (e.g., to improve) one or more properties of an imaging sheeting, the method comprising adding microcapsules of the present disclosure to the imaging sheeting. In some embodiments, the one or more properties include one or more of the following: Dmax; fresh Dmax; Dmax,t; Dmin; image resolution; temperature latitude; dynamic range; resistance to discoloration (yellowing); and edge definition.

[0141] Unless expressly indicated otherwise, all specified embodiments, features, and terms are intended to include the listed embodiments, features, or terms and their equivalents.

[0142] Reference will now be made in detail to some specific embodiments contemplated by the present disclosure. Although various embodiments are described herein, it should be understood that it is not intended to limit the present invention technology to the described embodiments. In contrast, it is intended to cover alternatives, modifications and equivalents that may be included in the spirit and scope of the technology defined by the appended claims.

[0143] Examples

[0144] Example 1. Effect of non-photopolymerizable epoxy compounds on temperature tolerance, dynamic range and edge definition in microencapsulated imaging sheets

[0145] In order to achieve high Dmax and high temperature tolerance for rapid color development, the solubility of the leuco dye in the microcapsule internal phase should be high, and the viscosity of the dye solution should be as low as possible over a wide temperature range. In order to achieve a wide dynamic range for grayscale reproduction, the viscosity of the partially cross-linked internal phase should also be as low as possible. However, due to the high degree of dye diffusion (especially in the Dmax zone), low viscosity dye solutions will also result in low edge definition.

[0146] As shown in Table 1, a "conventional" internal phase comprising a mixture of two multifunctional acrylates, TMPTA / HDDA (7:3), tends to result in phase separation of typical leuco dyes at 10 phm (one percent monomer) and 15 phm concentrations within three days after solvation.

[0147] Table 1. Solubility of three typical leuco dyes in TMPTA / HDDA (7:3)

[0148]

[0149] To improve Dmax, dynamic range, and temperature latitude, low viscosity epoxy compounds such as triglycidyl trimethylolpropane ether (TMPTGE) and DER 732 were evaluated as non-photopolymerizable reactive diluents for the internal phase of photosensitive microcapsules. Table 2 compares the viscosity of "traditional" internal phase monomers (TMPTA and HDDA) with the viscosity observed for epoxy compounds (e.g., TMPTGE (triepoxide) and DER 732 (diepoxide)).

[0150]

[0151] Table 2. Viscosity of TMPTA, HDDA, TMPTGE and DER 732

[0152]

[0153] As shown in Tables 1 and 2, it is possible to improve the solubility of leuco dyes and achieve a wide dynamic range by including an epoxy diluent in the internal phase. It is hypothesized that colorfastness and edge sharpness may also be improved by adding the epoxy compound to the internal phase, presumably via: (1) the epoxide reacts with the carboxyl groups of the developed (ring-opened) leuco dye to reduce the risk of dye ring closure (which would reverse the dye back to a leuco dye); and / or (2) the epoxide reacts with the novolac resin of the developer to crosslink the developer resin and reduce the dye diffusion rate.

[0154] Example 2. Effect of Multifunctional Epoxides on the Temperature Tolerance of Photosensitive Microcapsule Imaging Media

[0155] Green-sensitive imaging sheets were prepared according to the formulation and method described below:

[0156] Table 3. List of materials used

[0157]

[0158]

[0159] Microencapsulation method for preparing photosensitive microcapsules

[0160] Using the materials in Table 3, prepare photosensitive microcapsules according to the following procedure:

[0161] 1. Add 220 parts water and 8 parts Versa TL502 sulfonated polystyrene (dry) to a stainless steel beaker and mix thoroughly.

[0162] 2. Slowly sift 10 parts of pectin (methyl polygalacturonate) into the mixture and stir overnight at room temperature (500-1000 rpm).

[0163] 3. Adjust pH to 7.5 with 10% sodium carbonate and increase mixing speed to 1750 rpm.

[0164] 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, and 11 parts of a 9.1% aqueous solution of DETA (diethylenetriamine) (pH adjusted to 7.0) was added and allowed to react at 25°C for 30 minutes, followed by one hour at 40°C.

[0165] 5. Add 19.9 parts 385 and 40 parts of a solution of water (pH adjusted to 6.0), and the mixture was reacted at 70°C for a further 2 hours.

[0166] 6. Add 15.23 parts of 34.3% sodium sulfate aqueous solution and stir the mixture for 10 minutes. Add 1.97 parts 385 and 10 parts of water, and the mixture was allowed to react at 70°C for a further hour.

[0167] 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 at room temperature overnight.

[0168] Table 4. Internal phase of green sensitive microcapsules (Example 2)

[0169]

[0170] Control microcapsule sheet-PET( Preparation of microcapsule coating on 339)

[0171] The coating fluid as shown in Table 5 was adjusted to 33 wt.% solids with water and dispersed thoroughly using a low shear mixer and coated on a 2-mil. white PET ( 339) substrate and dried in an oven at 80°C for 10 minutes. The dry coating thickness was about 8 microns as measured by a Mitutoyo thickness gauge.

[0172] Table 5. Composition of microcapsule fluid (Example 2)

[0173]

[0174]

[0175] Preparation of developer coating

[0176] The developer composition shown in Table 6 was coated on 1-mil. clear PET film using a Myrad rod and dried in an 80°C oven for 10 minutes with a target dry coating thickness of about 7 μm.

[0177] Table 6. Composition of developer coating (Example 2)

[0178]

[0179] Preparation and Development of Image Sheet (Example 2)

[0180] The microcapsules and developer films thus prepared were laminated together using a Tamerica roll laminator TCC2700 (temperature, pressure and speed were set at 100°C, 3.621 Kgf / 170 mm and 0.368 m / min, respectively) to form various photosensitive imaging sheets. The prepared media were developed at 80°C using a pressure development fixture, and Dmax and Dmin were measured by a reflection densitometer FD-5 from Konica Minolta.

[0181] Table 7. Effect of Epoxides on Temperature Tolerance of Green-sensitive Microcapsules

[0182]

[0183] As shown in Table 7, the Dmax data show that the Dmax (both freshly developed and after heating at 80°C for 10 min) and temperature latitude of the microcapsules (Examples 2-2 to 2-5) containing the epoxide diluent are generally better than 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 (containing TMPTA / HDDA / TMPTGE (63 / 27 / 10) in the internal phase) appears to provide the highest Dmax and best temperature latitude of the internal phase tested, and maintains about 93.1% and 80.4% of its Dmax (80°C, 10 min) after storage overnight at 4°C and -10°C, respectively. In fact, for this internal phase, even the low temperature Dmax values ​​are about 20% (-10°C condition) to about 40% (4°C condition) better than the room temperature Dmax of the control sample (Example 2-1) without TMPTGE or DER732.

[0184] As can also be seen from Table 7, the microcapsules containing the highest concentration of DER 732 in the inner phase (Examples 2-5) appear to result in higher Dmin in the non-image area, although those microcapsules containing lower concentrations of DER 732 show slightly lower Dmin. Without being bound by any particular theory, the introduction of the epoxide diluent may improve the solubility of the leuco dye in the inner phase, even at temperatures as low as -10°C. The viscosity of the resulting inner phase is also reduced. As a result, both the color development rate (as indicated by the fresh Dmax) and the temperature latitude (as indicated by the Dmax after low temperature storage) are significantly improved. However, the presence of an excessively high concentration of low molecular weight epoxide DER 732 in the inner phase (Examples 2-5) may result in a deterioration of the barrier properties of the microcapsule shell through one or more mechanisms, including plasticization of the shell, interference with the interfacial polymerization / crosslinking shell formation process, and micropore formation in the shell. Therefore, Examples 2-5 exhibit an abnormally high Dmin.

[0185] Example 3: Preparation of a microcapsule imaging system comprising photosensitive microcapsules and non-photosensitive microcapsules containing multifunctional epoxides.

[0186] Preparation of photosensitive microcapsules

[0187] To test the effect of incorporating photosensitive and non-photosensitive microcapsules containing multifunctional epoxides into the same microcapsule imaging system, the composition and method of Example 2 were used, except that the internal phase of Table 8 was used for microencapsulation.

[0188] Table 8. Internal phase of the green sensitive microcapsules of Example 3

[0189]

[0190] Preparation of non-photosensitive microcapsules of epoxide diluent (Example 3)

[0191] Non-photosensitive microcapsules comprising a polymer shell and an internal phase containing one or more epoxy compounds were prepared according to the above procedure for photosensitive microcapsules, except that 1.97 parts of 385 and 10 parts of water, and the internal phase of the microcapsules (step 4) was replaced with the compositions (3A-3D) shown in Table 9 below.

[0192] Table 9. Internal phase composition of non-photosensitive microcapsules containing epoxy compounds (in dry fraction)

[0193]

[0194] Particle size of photosensitive and non-photosensitive microcapsules (Example 3)

[0195] All photosensitive and non-photosensitive microcapsules prepared according to the above method were washed thoroughly with water and centrifuged to remove excess water-soluble polymers and additives present in the aqueous phase. The microcapsule size distribution was measured using a HORIBA Partica LA-960 laser scattering particle size distribution analyzer (Table 10). As indicated in Table 10, all microcapsules examined had comparable particle sizes and particle size distributions.

[0196] Table 10. Particle size distribution of microcapsules (Example 3)

[0197] Microcapsule Type <![CDATA[D 10 (μm)]]> <![CDATA[D 50 (μm)]]> <![CDATA[D 90 (μm)]]> Green photosensitive microcapsule 3 (control) 4.41 6.74 10.18 Epoxide Capsules 3A 4.11 6.49 10.00 Epoxide Capsules 3B 5.65 8.75 13.13 Epoxide Capsules 3C 4.75 7.19 10.87 Epoxy Capsule 3D 5.29 8.21 12.53

[0198] Preparation of microcapsule coating

[0199] Table 11 shows the composition of the microcapsule stock solutions of green sensitive microcapsules (microcapsules 3, control) and four kinds of diluent microcapsules containing epoxy compounds (microcapsules 3A-3D). Microcapsule coatings containing various types and concentrations of epoxy microcapsules were prepared by mixing the control fluid containing microcapsules 3 with fluids containing microcapsules 3A-3D at different concentrations. Each coating fluid was adjusted to 30 wt.% solids by adding water and then coated on 2-mil white PET ( The coated substrate was then dried in an oven at 80° C. for 10 minutes with a target dry coating thickness of about 8 μm as measured by a Mitutoyo thickness gauge.

[0200] Table 11. Composition of microcapsule fluid

[0201]

[0202] Preparation of developer coating and imaging sheet

[0203] A developer coating identical to that used in Example 2 was prepared except that the dry coating thickness was about 9 μm as measured by a Mitutoyo thickness gauge.

[0204] In order to prepare imaging sheets containing photosensitive microcapsules and non-photosensitive epoxide microcapsules, the microcapsule films and developer films prepared according to the above procedure were laminated together using a Tamerica roll laminator TCC2700 (temperature, pressure and speed were set to 100°C, 3.621Kgf / 170mm and 0.368m / 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).

[0205] The imaged sheets were exposed to light at 9.5 mW / cm2 using a Kodak Q60 mask using a white light LED exposure unit. 2 The color development characteristics of various imaged sheets were determined by exposing them for 1 sec and developing them using a pressure fixture. The results are shown in Tables 12-15 below.

[0206] For each exposed imaged sheeting, the various properties reported in Tables 12-15 are defined as follows:

[0207] E 10 : The energy required to reduce Dmax by 10%

[0208] E 90 : The energy required to reduce Dmax by 90%

[0209] Dmin, M : Average (magenta) color density of the fully exposed area measured immediately after exposure, pressure development and heating at 100°C by a heating roller

[0210] Aging Dmin, M : Dmin after conditioning in an environmental chamber (40°C / 85%RH) for 2 days, M

[0211] Dmax, M : Average (magenta) density achieved in the non-exposed area measured immediately after exposure, pressure development and heating at 100°C by a heat roller

[0212] Normalized Dmax, M =Dmax, M / (fraction of control capsules used)

[0213] ΔY (yellowing): Increase in yellow density after conditioning the sample in a 40° C. / 85% RH room for 2 days and then exposing it to a white light box (37,000 lux) for 7 days.

[0214] Peel strength: average peel force (180°) of the Dmax area (unexposed area).

[0215] For all imaged sheets, Dmin, M ; Dmax, M Both ΔY were measured by densitometer FD-5 (Konica Minolta). After the developed samples were conditioned for 4 days under ambient conditions, the peel strength in the Dmax area (25.4 mm wide) was measured using an Instron peel tester model 3367 at a peel rate of 30 mm / min.

[0216] Table 12. Imaged sheet properties as a function of microcapsule 3A (ESBO) content

[0217]

[0218] Table 13. Microcapsules 3B (ESBO: GE-30=20:80) content changes in imaging sheet properties

[0219]

[0220]

[0221] Table 14. Imaging sheet properties as a function of microcapsule 3C (EP-4221) content

[0222]

[0223] Table 15. Imaging sheet properties as a function of microcapsule 3D (EP-3510) content

[0224]

[0225] As shown in Table 12, incorporation of higher concentrations of non-photosensitive epoxy-containing microcapsules 3A (2% to 16%) can reduce yellowing (ΔY) by about 50% (from 0.29 to 0.13) and increase peel resistance (peel strength) by about 69% (from 0.062 to 1.05 N / 25 mm). In contrast, regardless of the concentration of microcapsules 3A, photosensitivity, E 10 and E 90 and the maximum achievable values ​​(Dmax, M ) and minimum (Dmin, M ) The color density remains essentially unchanged. In fact, the normalized Dmax (normalized by the actual dye loading), an indicator of the coloring power of the leuco dye used, increases with the addition of ESPO microcapsules 3A.

[0226] These phenomena were also observed for microcapsule 3B. As shown in Table 13, the addition of microcapsule 3B (2% to 16%) improved the peel strength and tinting strength of the leuco dye while reducing the yellowing. In addition, the photosensitivity (E 10 and E 90 Similarly, Tables 14 and 15 show that increasing concentrations of microcapsules 3C and 3D lead to improvements in peel strength, photosensitivity (E 10 and E 90 ) and a decrease in yellowing (ΔY).

[0227] Without being bound by any particular theory, it is believed that after pressure-induced release from the microcapsules, the epoxy compound reacts and crosslinks with the phenolic groups in the developer layer, significantly improving the peel force and reducing the yellowing (ΔY). The epoxy compound also acts as a solvent or diluent to improve the diffusion of the dye into the developer layer, resulting in an increase in the normalized Dmax or coloring efficiency of the leuco dye.

[0228] Example 4. Preparation of microcapsule imaging system comprising photosensitive microcapsules containing multifunctional epoxides in the internal phase

[0229] Preparation of photosensitive microcapsules containing multifunctional epoxides in the internal phase and imaging sheets containing the photosensitive microcapsules

[0230] Photosensitive microcapsules containing epoxidized soybean oil in the internal phase were prepared by the same microencapsulation method as discussed in Example 2 for preparing green photosensitive microcapsules, except that the internal phase shown in Table 5 was replaced with the internal phase shown in Table 16 (for microcapsules 4-1 and 4-2).

[0231] Table 16. Composition of the inner phase for photosensitive epoxide-containing microcapsules

[0232]

[0233] The thus prepared microcapsules were washed thoroughly with water and centrifuged to remove excess water-soluble polymer and additives present in the aqueous phase. For microcapsules 4-1 and 4-2, the particle size (D 50 ) are 6.44μm and 5.42μm respectively.

[0234] Imaging sheets containing photosensitive microcapsules 4-1 and 4-2 were prepared by laminating the microcapsule coating compositions shown in Table 17 below with the developer coating compositions shown in Table 6. The solid content of all microcapsule fluids was adjusted to 30 wt.% solids by adding water and then coated on 2-mil white PET ( 339) substrate and then dried in an 80°C oven for 10 minutes, with a target dry coating thickness of about 8 μm as measured by a Mitutoyo thickness gauge.

[0235] Table 17. Microcapsule coating fluid composition for photosensitive microcapsules 4-1 and 4-2

[0236]

[0237] The imaged sheet was passed through a Kodak Q60 mask with a white light LED exposure unit at 9.5 mW / cm 2 The exposure was 1 sec and the film was developed by a pressure fixture. The results are shown in Table 18.

[0238] Table 18. Imaging sheet properties as a function of ESBO content in photosensitive microcapsules

[0239]

[0240] As shown in Table 18, replacing about 5% to about 10% (by weight) of the multifunctional acrylate in the internal phase with the non-photosensitive reactive diluent ESBO results in a significant reduction in yellowing after aging and an increase in the peel strength of the laminated image sheet. Unlike the examples of microcapsules 3A-3D (in which the multifunctional epoxide is encapsulated in a non-photosensitive microcapsule instead of a photosensitive microcapsule), microcapsules 4-1 and 4-2 show that E 10 The reduction in the energy required to reduce the optical density (OD) of an image by 10% and the dynamic range (E 90 -E 10 ). Therefore, a higher initial sensitivity and a wider grayscale image can be achieved by using about 5% to about 10% of the diluent ESBO.

[0241] Without being bound by any particular theory, the presence of the non-photosensitive diluent ESBO can effectively reduce the viscosity (and cage effect) of the internal phase, thereby providing a higher quantum efficiency of the photoinitiator or auto-oxidant / oxygen scavenger, and thus providing a lower E 10 In addition, the presence of ESBO also effectively reduced the gel effect and increased the solubility of the leuco dye in the internal phase, especially in the later stages of photopolymerization / cross-linking. 90(the energy required to reduce the image OD by 90%) and a wider dynamic range for grayscale reproduction.

[0242] The exposure temperature latitude of the imaged sheets of Examples 4-1 (5 wt.% ESBO) and 4-2 (10 wt.% ESBO) is shown in Table 19. The imaged sheets were sealed in aluminized PET barrier bags and conditioned at room temperature, 1.5°C, and -26°C for 64 hours. The aged imaged sheets were then reconditioned at room temperature for about 10 minutes and exposed to light by a white light LED exposure unit (9.5 mW / cm 2 ) was exposed to light for 1 sec and immediately developed by a pressure fixture. The resulting magenta Dmax was measured immediately after development.

[0243] Table 19. Temperature tolerance with changes in ESBO content in photosensitive microcapsules

[0244]

[0245] 1 % ΔDmax after aging = [(Dmax, room temperature - Dmax, aging) / Dmax, room temperature] × 100

[0246] 2 %ΔE 90 =[(E 90，老化 -E 90，室温 ) / E 90，室温 ]×100;E 90 =Dmax The exposure energy required to lose 90% of the exposure energy.

[0247] As shown in Table 19, replacing about 5% to about 10% by weight of the multifunctional acrylate in the internal phase of the microcapsules with ESBO significantly improved the stability of Dmax and improved the photospeed over a relatively wide temperature range (between room temperature and -26°C). The control imaged sheeting showed a 14.7% to 16.7% reduction in Dmax and an E 90 The 82.1% to 89.2% increase in Dmax indicated that both color density and photospeed decreased after low temperature conditioning. However, incorporating about 5% to about 10% of non-photopolymerizable ESBO into the internal phase of the photosensitive microcapsules reduced Dmax by only 5.4% to 8.7% and increased Emax by 1. 90 The increase was only about 2.7% to 58.1%.

[0248] Without being bound by any particular theory, the observed improvement in exposure latitude at low temperatures achieved by incorporating a multifunctional epoxide (e.g., ESBO) may be attributed to improved solubility of the leuco dye in the internal phase and / or a reduction in viscosity in the internal phase at low temperatures, particularly sub-zero temperatures.

[0249] The compositions and methods exemplarily described herein can be appropriately implemented in the absence of any one or more elements, one or more restrictions not specifically disclosed herein. Therefore, for example, the terms "comprise", "include", "contain" etc. should be understood in an extended manner and without limitation. In addition, the terms and expressions adopted herein have been used as descriptive and non-restrictive terms, and any equivalents of the features shown and described or parts thereof are not intended to be excluded when using such terms and expressions. It is recognized that various modifications are possible within the scope of the disclosure claimed. Therefore, it should be understood that although the disclosure has been specifically disclosed by preferred embodiments and optional features, modifications and changes of the disclosure implemented therein disclosed herein may be adopted by those skilled in the art, and such modifications and changes are considered to be within the scope of the disclosure.

[0250] Unless the context indicates otherwise, it is expressly intended that the various features of the invention described herein may be used in any combination. In addition, the present disclosure also contemplates that, in some embodiments, any feature or combination of features shown herein may be excluded or omitted. For example, if the specification states that the imaging sheeting comprises components A, B, and C, it is specifically intended that any one or combination of A, B, or C may be omitted and abandoned, alone or in any combination.

[0251] The disclosure has been described extensively and non-patently herein. Each narrower species and subgenus grouping falling within the non-patent disclosure also constitutes a part of the composition or method. This includes a non-patent description of the composition or method, with conditions or negative restrictions, so that any subject matter is removed from the class, regardless of whether these excluded materials are explicitly mentioned in this article. The technology of the present invention is not limited to the specific embodiments described in this application, which are intended to be representative illustrations of various aspects of the technology of the present invention. Without departing from the spirit and scope of the technology of the present invention, many modifications and changes can be made to the technology of the present invention, which is clear to those skilled in the art. Functionally equivalent combinations, methods and equipment within the scope of the technology of the present invention, in addition to those enumerated herein, will be clear to those skilled in the art from the aforementioned description. Such modifications and changes are intended to fall within the scope of the technology of the present invention. It should be understood that the technology of the present invention is not limited to specific methods, reagents, compounds or compositions, and of course, these methods, reagents, compounds or compositions can vary. It should also be understood that the terms used herein are only used for the purpose of describing specific embodiments and are not intended to be restrictive.

[0252] It will be readily appreciated by those skilled in the art that the present disclosure is well suited to achieve the objectives and advantages mentioned, as well as those inherent therein. Modifications and other uses thereof will be made by those skilled in the art. Such modifications are encompassed within the spirit of the present disclosure and are limited by the scope of the claims, which illustrate non-limiting embodiments of the present disclosure.

[0253] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

Claims

1. A photosensitive microcapsule for a microcapsule imaging sheet, the photosensitive microcapsule comprising: polymer housing; and Internal phase, which includes: Leuco dyes; a non-photopolymerizable diluent configured to react with the leuco dye developer; a photoinitiator; and A polymerizable or cross-linkable monomer or oligomer. 2 . The photosensitive microcapsule according to claim 1 , wherein the leuco dye developer comprises a Lewis acid, an acid clay, or one or more compounds comprising a phenol group or a carboxylic acid group, or a metal complex thereof.

3. The photosensitive microcapsule according to claim 1 or claim 2, wherein the leuco dye developer comprises a novolac resin, a salicylic acid derivative, a zincate derivative thereof, or a combination, copolymer, blend or composite thereof. 4 . The photosensitive microcapsule according to claim 1 , wherein the diluent comprises an epoxy compound. The photosensitive microcapsule according to claim 4 , wherein the epoxy compound comprises two or more epoxide moieties.

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

7. The photosensitive microcapsule according to any one of claims 4 to 6, wherein the epoxy 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 diepoxides; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; and diglycidyl 1,2-cyclohexanedicarboxylate.

8. The photosensitive microcapsule according to any one of claims 1 to 7, wherein the diluent is present in a concentration of about 3 wt.% to about 20 wt.% relative to 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 in a concentration of about 3 wt.% to about 10 wt.% relative to 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 less than or equal to about 5 wt.%.

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

13. The photosensitive microcapsule according to any one of claims 1 to 12, wherein the diluent has a viscosity of less than or equal to about 300 cps at 25°C, as determined 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 less than or equal to about 100 cps at 25°C, as determined using a Brookfield viscometer at 100 rpm. 15 . The photosensitive microcapsule according to claim 1 , wherein the polymerizable or cross-linkable monomer comprises a multifunctional acrylate.

16. An imaging sheet, comprising: A microcapsule comprising: polymer housing; and Internal phase, which includes: Leuco dyes; a non-photopolymerizable diluent configured to react with the leuco dye developer; Photoinitiator; and polymerizable or cross-linkable monomers or oligomers; a first substrate in contact with the microcapsules; as well as Leuco dye developer.

17. The imaging sheeting of claim 16, wherein the first substrate is in contact with the microcapsules.

18. The imaging sheeting of claim 16, wherein the leuco dye developer comprises a Lewis acid or an acid clay or one or more compounds having a phenolic group or a carboxylic acid group.

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

20. The imaged sheeting of claim 19, wherein the metal is zinc.

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

22. The imaging sheeting of claim 21, wherein one of the first substrate and the second substrate is opaque.

23. The imaged sheeting of claim 21, wherein the opaque substrate is white.

24. The imaging sheeting of claim 22 or claim 23, wherein the first substrate is opaque or white.

25. The imaging sheeting of any one of claims 16 to 24, wherein the first substrate further comprises a primer layer in contact with the microcapsules.

26. The imaged sheeting of claim 25, wherein the primer layer comprises microparticles.

27. The imaging sheeting of claim 26, wherein the microparticles comprise at least one selected from the group consisting of CaCO3, CaSO4, BaSO4, silica, BN, TiO2, Al2O3, Ca3(PO4)2, and hydrophobically treated derivatives thereof.

28. A microcapsule for a microcapsule imaging sheet, the microcapsule comprising: polymer housing; and An internal phase comprising a non-photopolymerizable diluent configured to react with the leuco dye developer.

29. The microcapsule of claim 28, wherein the diluent comprises an epoxy compound.

30. The microcapsule of claim 29, wherein the epoxy compound comprises two or more epoxide moieties.

31. A microcapsule according to claim 29 or claim 30, wherein the diluent comprises a diepoxide or a triepoxide.

32. A microcapsule according to claim 30 or claim 31, wherein the epoxy 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 diepoxides; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; and diglycidyl 1,2-cyclohexanedicarboxylate.

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

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

35. An imaging sheet, comprising: A diluent microcapsule, wherein the diluent microcapsule comprises: polymer housing; and an internal phase comprising a non-photopolymerizable diluent configured to react with the leuco dye developer; and Photosensitive microcapsules, the photosensitive microcapsules comprising: polymer housing; and Internal phase, which includes: Leuco dyes; a photoinitiator; and polymerizable or cross-linkable monomers or oligomers; a first substrate, the first substrate being in contact with the diluent microcapsules and the photosensitive microcapsules; as well as Leuco dye developer.

36. The imaging sheeting of claim 35, wherein the leuco dye developer comprises a Lewis acid or an acid clay or comprises one or more compounds having a phenolic group or a carboxylic acid group.

37. The imaged sheeting of claim 35 or claim 36, wherein the diluent comprises an epoxy compound.

38. The imaged sheeting of claim 37, wherein the epoxy compound comprises two or more epoxide moieties.

39. The imaged sheeting of claim 37 or claim 38, wherein the diluent comprises a diepoxide or a triepoxide.

40. The imaging sheeting of any one of claims 37 to 39, wherein the epoxy compound comprises at least one selected from the group consisting of triglycidyl trimethylol propane (TMPTGE); epoxidized oils including epoxidized soybean oil; epoxidized castor oil; epoxidized linseed oil; dicyclopentadiene diepoxide; alicyclic diepoxides; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; and diglycidyl 1,2-cyclohexanedicarboxylate.

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

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

43. The imaging sheeting of any one of claims 35 to 42, wherein the leuco dye developer is a novolac, a phenolic resin, salicylic acid, or a combination, copolymer, blend, composite or metal complex derivative thereof.

44. The imaged sheeting of claim 43, wherein the metal is zinc.

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

46. ​​The imaging sheeting of claim 45, wherein one of the first substrate and the second substrate is opaque.

47. The imaged sheeting of claim 46, wherein the opaque substrate is white.

48. The imaging sheeting of any one of claims 35 to 47, wherein the first substrate further comprises a primer layer in contact with the microcapsules.

49. The imaged sheeting of claim 48, wherein the primer layer comprises microparticles.

50. The imaging sheeting of claim 49, wherein the microparticles comprise at least one selected from the group consisting of CaCO3, CaSO4, BaSO4, silica, BN, TiO2, Al2O3, Ca3(PO4)2, hydrophobically treated derivatives thereof, and any combination thereof.

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

52. The imaged sheeting of claim 51, wherein the diluent comprises an epoxy compound.

53. The imaged sheeting of claim 52, wherein the epoxy compound comprises two or more epoxide moieties.

54. The imaged sheeting of claim 52 or claim 53, wherein the diluent comprises a diepoxide or a triepoxide.

55. The imaging sheeting of any one of claims 52 to 54, wherein the epoxy compound comprises at least one selected from the group consisting of triglycidyl trimethylol propane (TMPTGE); epoxidized oils including epoxidized soybean oil; epoxidized castor oil; epoxidized linseed oil; dicyclopentadiene diepoxide; alicyclic diepoxides; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; and diglycidyl 1,2-cyclohexanedicarboxylate.

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

57. A method of preparing an imaged sheeting, the method comprising: (i) contacting a first substrate with a microcapsule layer to produce a microcapsule-coated first substrate; (ii) contacting the microcapsule layer of the microcapsule-coated first substrate with a developer layer to produce a developer-coated first substrate; as well as (iii) contacting the developer layer of the developer-coated first substrate with a second substrate to produce an imaged sheet.

58. A method of preparing an imaged sheeting, the method comprising: (ia) contacting a first substrate with a primer layer to produce a primer-coated first substrate; (ib) contacting the primer layer of the primer-coated first substrate with a microcapsule layer to produce a microcapsule-coated first substrate; (ii) contacting the microcapsule layer of the microcapsule-coated first substrate with a developer layer to produce a developer-coated first substrate; as well as (iii) contacting the developer layer of the developer-coated first substrate with a second substrate to produce an imaged sheet.

59. A method of preparing an imaged sheeting, the method comprising: (i) producing a first substrate coated with microcapsules according to claim 57 or claim 58; (ii) contacting the second substrate with the developer layer to produce a developer-coated second substrate; as well as (iii) contacting the microcapsule layer of the microcapsule-coated first substrate with the developer layer of the developer-coated second substrate to produce an imaged sheet.

60. A method according to any one of claims 57 to 59, wherein a primer layer is located between the second substrate and the developer layer or between the first substrate and the microcapsule layer.

61. A method according to any one of claims 57 to 59, wherein a primer layer is located between the second substrate and the developer layer and between the first substrate and the microcapsule layer.

62. A method of adjusting one or more properties of an imaged sheeting, the method comprising including in the imaged sheeting one or more microcapsules of any one of claims 1 to 15 or claims 28 to 34.

63. The method of claim 62, wherein the one or more characteristics include one or more of: Dmax; freshness Dmax; Dmax,t; Dmin; image resolution; temperature tolerance; dynamic range; resistance to discoloration; and edge sharpness.

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