Crosstalk reduction in microcapsule imaging systems.

Abstract

Microcapsules are provided for use in microcapsule imaging sheets, which include a color-filtering shell and a core containing a leuco dye or dye precursor, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material. Imaging sheets containing such microcapsules reduce unwanted crosstalk among microcapsules of various colors and significantly improve the color fidelity of reproduced images.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Patent Application No. 18 / 074,412, filed December 2, 2022, the entire text of which is incorporated herein by reference.

[0002] The present disclosure relates generally to the field of microcapsule imaging systems, and more particularly to microcapsules having color filtering shells for use in such systems. [Background technology]

[0003] Single-sheet, self-contained, full-color microcapsule imaging systems (e.g., CYCOLOR®, manufactured by Mead Corporation, Miamisburg, Ohio) have been developed since the 1980s. In these imaging systems, an imaging sheet containing a layer of microcapsules whose internal phase contains a photohardenable or photosoftenable material or composition and a leuco dye is exposed to actinic radiation in an imagewise fashion. Typically, the photosensitive composition contains a photopolymerizable multifunctional acrylate, a photoinitiator, and a color former. Generally, the microcapsules are hardened imagewise by the actinic radiation, and when the exposed imaging sheet passes through a pressure roller, the microcapsules rupture imagewise, releasing the encapsulated internal phase. The released leuco dye migrates to and reacts with a developer material to form a continuous-tone, full-color image with color density (or grayscale) modulated by the exposure energy (time or pulse width), intensity (pulse amplitude), and / or pulse frequency. Such self-contained single-sheet imaging systems are useful for lightweight, portable, high-speed printing applications.

[0004] Such photohardening microcapsule imaging systems typically produce positive images, while photosoftening microcapsule imaging systems or alternative techniques produce negative images.

[0005] In addition to single-sheet self-contained systems, microcapsule imaging systems may also include two separate sheets: a microcapsule sheet and a dye developer sheet. A positive image may be obtained by imagewise exposing the microcapsule sheet to light to form a latent image, followed by rupturing the microcapsules and transferring the released leuco dye to the developer sheet, where it is developed. Summary of the Invention

[0006] The image quality of photosensitive imaging systems, including the microcapsule imaging system described above, depends largely on the spectral sensitivities of the three microcapsules and the emission spectrum of the light source used. For example, in a full-color microcapsule imaging system using red (R), green (G), and blue (B) photoinitiators, such as cyanine borate initiators, with R, G, and B light sources (e.g., R-LEDs, G-LEDs, and B-LEDs or OLEDs used in LED or OLED displays, or R, G, and B light transmitted through color filtering in LCD displays), the absorption spectra of the B and G photoinitiators overlap significantly in the 440-500 nm range. Similarly, the absorption spectra of the G and R photoinitiators overlap significantly in the 540-600 nm range. The R, G, and B emission spectra of the light sources from OLED or LCD displays also overlap significantly. Therefore, when the image forming sheet is exposed to light with wavelengths within the overlapping range, multiple types of capsules are cured, which may cause crosstalk.

[0007] For example, if multiple types of microcapsules are cured when the system is written with only one light source, or if one type of microcapsule is cured with multiple light sources, crosstalk of any photoreactions can occur, degrading the fidelity of the color reproduction process. This can result in the color of the printed image being contaminated with unwanted color(s), significantly degrading the color gamut. Therefore, to achieve high-quality color reproduction, photosensitizers / photoinitiators with narrow, well-separated spectral sensitivities and light sources with narrow, well-separated emission spectra that appropriately match the spectral sensitivities of the corresponding photosensitizers / photoinitiators are highly desirable.

[0008] Unfortunately, most photoinitiators or photosensitizers exhibit very broad spectral sensitivities, and most modulatable light sources, including self-emissive OLEDs and backlit LCDs with R, G, and B color filters, exhibit very broad emission spectra. When microencapsulated imaging media with typical spectral sensitivities are printed with such broadband light sources, severe crosstalk is observed. Semiconductor light-emitting devices, including LEDs and lasers, exhibit relatively narrow emission spectra. Unfortunately, for printing applications, it is difficult to achieve an acceptable λ range. max There are very limited options on the market for LEDs and lasers that offer the required size and power efficiency, and the cost is often prohibitive.

[0009] On the other hand, finding a set of R, G, and B photoinitiators with narrow-band absorption spectra is also extremely difficult. In fact, cyanine borate photoinitiators have been chosen for microcapsule imaging systems primarily due to their high thermal stability, quantum efficiency, and relatively narrow absorption spectrum. However, even with cyanine borate photoinitiators, serious crosstalk was still observed. Most other known photosensitizers and photoinitiators have much broader absorption spectra and poorer quantum efficiency than the commonly used cyanine borate photoinitiators.

[0010] Even if all three well-matched photoinitiator-light source pairs were identified, the requirements for high quantum efficiency of the photosensitizer / initiator and high light source power for high-speed printing applications would make the task extremely difficult and costly, if not impossible. Therefore, there remains an unmet need for an effective and low-cost solution to reduce or eliminate crosstalk for high-quality printing.

[0011] The present disclosure relates to improved full-color microcapsule imaging systems that utilize photosensitive microcapsules with color-filtering shells, or shells capable of filtering out unwanted wavelengths of incident light. The color-filtering shells significantly reduce unwanted crosstalk among microcapsules of various colors, significantly improving the color fidelity of reproduced images. The microcapsules described herein are particularly beneficial for digital imaging systems because they significantly reduce the need to select a light source with an emission wavelength that perfectly matches the spectral sensitivity of the photosensitizer / photoinitiator used within the microcapsules. Fine-tuning the emission spectrum of light sources such as LEDs and OLEDs, or the absorption spectrum of photosensitizers / photoinitiators, while maintaining quantum efficiency, is difficult, if not impossible, to achieve. The present disclosure provides an effective, low-cost solution for significantly reducing unwanted crosstalk and improving the color image fidelity of microcapsule imaging systems.

[0012] According to one aspect, which may be combined with any other aspect or embodiment, the present disclosure relates to photosensitive microcapsules for use in microcapsule imaging sheets, the photosensitive microcapsules comprising a color filtering shell and a core comprising a leuco dye or dye precursor, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material.

[0013] In some embodiments, the photocurable material comprises a photopolymerizable or crosslinkable monomer or oligomer, hi some embodiments, the polymerizable or crosslinkable monomer or oligomer is selected from multifunctional acrylates or methacrylates, multifunctional vinyl ethers, multifunctional allyl or vinyl benzenes, and oligomers, dendrimers, or blends thereof.

[0014] In some embodiments, the multifunctional acrylate is 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), or neopentyl glycol diacrylate (NPGDA).

[0015] In some embodiments, the photosoftenable material comprises a photodegradable or photodepolymerizable polymer.

[0016] In some embodiments, the leuco dye is a cyan, magenta, yellow, black leuco dye, or any combination thereof. In some embodiments, the photoinitiator is a red-sensitive, green-sensitive, or blue-sensitive cyanine borate, semicyanine borate, or ketocoumarin. In some embodiments, the photoinitiator is a cyanine borate, semicyanine borate, triarylmethane dye, squarylium dye, or thiopyrylium dye. In some embodiments, the photoinitiator or photosensitizer comprises an ultraviolet-sensitive, blue-sensitive, green-sensitive, red-sensitive, or near-infrared-sensitive photoinitiator or sensitizer.

[0017] In some embodiments, the photosensitive microcapsules are sensitive to a particular color or a particular range of the radiation spectrum, and the shell contains one or more color filtering dyes or pigments that allow wavelengths corresponding to that color or range of the radiation spectrum to penetrate to the core, but selectively absorb or filter out all or a portion of radiation outside the particular color or range. In some embodiments, one or more of the color filtering dyes or pigments are bleachable. In some embodiments, one or more of the color filtering dyes or pigments are thermally or photobleachable.

[0018] In some embodiments, the particular color or range is red, green, blue, cyan, magenta, or yellow, hi some embodiments, the emission spectrum ranges from about 330 nm to about 900 nm.

[0019] In some embodiments, one or more of the color filtering dyes or pigments includes a functional group for reacting with one or more shell-forming materials, in some embodiments, the functional group is -OH, -SH, -NH, -N-HR, -CHOH, -CHOR, -CHO, -CONH, -CONHR 、 In some embodiments, the functional group is selected from the group consisting of urea, thiourea, isocyanate, thioisocyanate, epoxide, and precursors thereof, where R is alkyl, aryl, arylalkyl, alkylaryl, or heteroatom derivatives thereof, particularly those with short chain lengths. In some embodiments, the functional group is selected from the group consisting of -OH, -SH, -NH, -N-HR, -CONH, -NCO, -NCS-, -CHOH, -CHOR, -CHO, and precursors thereof, where R is alkyl, aryl, arylalkyl, alkylaryl, or heteroatom derivatives thereof.

[0020] In some embodiments, one or more shell-forming materials are included in the internal or oil phase and form a shell by interfacial polymerization or crosslinking during the microencapsulation process. In some embodiments, one or more shell-forming materials are included in the internal and / or external phase and form a shell by interfacial polymerization or crosslinking during the microencapsulation process. In some embodiments, the one or more shell-forming materials included in the oil or internal phase are selected from the group including polyfunctional isocyanates, thioisocyanates, and epoxides, or precursors thereof.

[0021] In some embodiments, one or more shell-forming materials are included in the external or aqueous phase and form a shell during the microencapsulation process by interfacial or in situ polymerization, or by crosslinking, phase separation, or coacervation. In some embodiments, the one or more shell-forming materials in the external or aqueous phase are water-soluble compounds containing reactive functional groups, including, but not limited to, -OH, -SH, -NH, -N-HR, -COOH, -CHOR, -CHO, or precursors thereof, where R is alkyl, aryl, arylalkyl, alkylaryl, or heteroatom derivatives thereof, particularly those with short chain lengths (e.g., alkyl chains containing one to four carbons). In some embodiments, the one or more shell-forming materials are selected from the group including urea, amines, urea formaldehyde, melamine formaldehyde, poly(N-methylolacrylamide), gelatin, gum arabic, pectin, carboxylate methylcellulose, and oligomers, copolymers, or blends thereof.

[0022] In some embodiments, the color filtering shell comprises one or more of a color filtering dye or pigment, hi some embodiments, the color filtering dye is heat-bleachable or photo-bleachable.

[0023] In some embodiments, the photoinitiator or photosensitizer is red-sensitive and the color filtering shell is magenta, yellow, or a combination thereof. In some embodiments, the photoinitiator or photosensitizer is green-sensitive and the color filtering shell is cyan, yellow, or any combination thereof. In some embodiments, the photoinitiator or photosensitizer is blue-sensitive and the color filtering shell is magenta, cyan, or any combination thereof. In some embodiments, the photoinitiator or photosensitizer is infrared-sensitive and the color filtering shell is cyan, magenta, yellow, or any combination thereof.

[0024] In some embodiments, the color filtering dye or pigment is a magenta (green absorbing) and / or cyan (red absorbing) dye or pigment for blue photosensitive microcapsules.

[0025] In some embodiments, the color filtering dye or pigment is a yellow (blue absorbing) and / or cyan (red absorbing) dye or pigment for green-sensitive microcapsules. In some embodiments, the color filtering dye or pigment is Yellow Pigment 155 or CI Direct Yellow 86.

[0026] In some embodiments, the color filtering dye or pigment is a yellow (blue absorbing) and / or magenta (green absorbing) dye or pigment for red-sensitive microcapsules. In some embodiments, the color filtering dye or pigment is Pigment Violet 19 or CI Dispersed Red 60.

[0027] In some embodiments, one or more of the color filtering dyes or pigments present in the microcapsules is in an amount of about 0.01 to about 3 phi (parts per 100 parts of internal phase or parts per 100 parts of core by weight), hi some embodiments, one or more of the color filtering dyes or pigments present in the microcapsules is in an amount of about 0.05 to about 1.0 phi.

[0028] In some embodiments, when the photosensitive microcapsules are green- or red-sensitive, the one or more color filtering dyes or pigments comprise a yellow (blue-absorbing) color filtering dye or pigment having a total absorption optical density of about 0.005 to about 0.3, preferably about 0.05 to about 0.2, in the range of about 450 to about 500 nm. Depending on the extinction coefficient, the concentration of the dye or pigment used in the shell is about 0.05 to about 2 phi, preferably about 0.1 to about 1 phi.

[0029] In some embodiments, when the photosensitive microcapsules are blue- or red-sensitive microcapsules and the one or more color filtering dyes or pigments are magenta (green-absorbing) color filtering dyes or pigments, the absorption optical density is about 0.005 to about 0.3, preferably about 0.05 to about 0.2, in the range of about 550 to about 600 nm. Depending on the extinction coefficient, the concentration of the dye or pigment used in the shell is about 0.05 to about 2 phi, preferably about 0.1 to about 1 phi.

[0030] In some embodiments, the photosensitive microcapsules have an average diameter or D of about 4.0 μm to about 9.0 μm. 50 In some embodiments, the photosensitive microcapsules have an average diameter or D of about 5.0 μm to about 6.5 μm. 50 In some embodiments, the core does not include any color filtering dyes or pigments.

[0031] In some embodiments, the core further comprises a radical inhibitor, retarder, or antioxidant, hi some embodiments, the radical inhibitor, antioxidant, or retarder is selected from the group comprising phenols, anilines, N-oxides of hindered amines, CuO, copper dithiocarbamates, copper or manganese carboxylates, and thiuram (thiocarbamoyl) derivatives, such as those of the formula: [ka] In the formula, R 1 , R 2 , R 3 , and R 4 are each independently an alkyl group having 1 to 8 carbon atoms or a phenyl group.

[0032] In some embodiments, the radical inhibitor is alkyl gallate, butylated hydroxyanisole, 3,5-di-t-butylbutyl-4-hydroxytoluene, vitamin E, 3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-ol (IRGANOX® E201), triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate (IRGANOX® 245), 3-{[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoyl]oxy}-2,2-bis({[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoyl]oxy}methyl)propyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate (IRGANOX® 1010), 1,2-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazine (IRGANOX® MD 1024), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene (IRGANOX® 1076), 2,2'-thiobis(6-tert-butyl-p-cresol) (IRGANOX® 1081), N,N'-hexane-1,6-diylbis(3-3,5-di-tert-butyl-4-hydroxyphenyl-propionamide) (IRGANOX® 1098), 3,5-bis(1,1-dimethylethyl) -4-Hydroxybenzenepropanoic acid thiodi-2,1-ethanediyl ester (IRGANOX® 1035), benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-C7-C9 branched alkyl ester (IRGANOX® 1135), 3,3',3',5,5',5'-hexa-tert-butyl-a,a',a'-(mesitylene-2,4,6-triyl)tri-p-cresol (IRGANOX® 1330), (1,1-di-tert.and a phenol radical inhibitor selected from the list including 1,3,5-tris[4-hydroxy-3,5-bis(2-methyl-2-propanyl)benzyl]-1,3,5-triazinane-2,4,6-trione (IRGANOX® 3114), 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol (IRGANOX® 565), and other IRGANOX® primary antioxidants.

[0033] In some embodiments, the radical inhibitor is an N-oxide of a hindered amine, and the hindered amine is selected from the list including bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate (Tinuvin 770 DF), bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate (ADK STAB LA-72), tetrakis(2,2,6,6-tetramethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate (ADK STAB LA-57), and bis(1-undecanoxy-2,2,6,6-tetramethylpiperidin-4-yl)carbonate (ADK STAB LA-81).

[0034] In some embodiments, the radical inhibitor, retarder, or antioxidant is present at a concentration of about 0.1 to about 1.0 parts per 100 parts of monomer of the internal phase by weight. In some embodiments, the radical inhibitor, retarder, or antioxidant is present at a concentration of about 0.05 to 0.8 parts per 100 parts of monomer of the internal phase by weight. In some embodiments, the radical inhibitor, retarder, or antioxidant is present at a concentration of about 0.3 to about 0.8 phi. In some embodiments, the radical inhibitor, retarder, or antioxidant is present at a concentration of about 0.1 to 0.6 phi.

[0035] In some embodiments, the core further comprises a coinitiator, an oxygen scavenger, or an autoxidizer.

[0036] In another aspect, there is provided a microcapsule imaging sheet comprising: a first substrate; and a photosensitive microcapsule layer in contact with a first surface of the first substrate, the photosensitive microcapsules comprising a color filtering shell that may further comprise a color filtering dye or pigment; and a core that comprises a leuco dye, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material.

[0037] In some embodiments, the photocurable material comprises a photopolymerizable or crosslinkable monomer or oligomer. In some embodiments, the polymerizable or crosslinkable monomer or oligomer is selected from multifunctional acrylates or methacrylates, multifunctional vinyl ethers, multifunctional allyl or vinyl benzenes, and oligomers, dendrimers, or blends thereof. In some embodiments, the multifunctional acrylate is 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), or neopentyl glycol diacrylate (NPGDA).

[0038] In some embodiments, the photosoftenable material comprises a photodegradable or photodepolymerizable polymer.

[0039] In some embodiments, the microcapsule imaging sheet is a full-color imaging sheet comprising photosensitive microcapsules, such as including red-sensitive, green-sensitive, and blue-sensitive microcapsules.

[0040] In some embodiments, the photosensitive microcapsule sheet further comprises a developer. In some embodiments, the photosensitive microcapsule sheet further comprises a separate developer layer. In some embodiments, the separate developer layer is overcoated or laminated onto the photosensitive microcapsule layer.

[0041] In some embodiments, any one of the microcapsule imaging sheets described herein further comprises (i) a microcapsule layer, and / or (ii) a developer layer in contact with the developer substrate.

[0042] In some embodiments, any one of the microcapsule imaging sheets described herein further comprises an adhesive layer between the developer layer and the microcapsule layer.

[0043] In some embodiments, any one of the microcapsule imaging sheets described herein further comprises a primer layer between the microcapsule layer and the first substrate.

[0044] In some embodiments, the developer substrate is polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, polyolefin, cyclic olefin copolymer (COC), cellulose acetate, or copolymers, blends, or composites thereof.

[0045] In some embodiments, the developer layer comprises a Lewis acid, an acidic clay, or one or more compounds containing phenolic or carboxylic acid groups, or a metal complex thereof. In some embodiments, the developer layer comprises a novolac resin, a salicylic acid derivative thereof, a zincate derivative thereof, or a combination, copolymer, blend, or composite thereof.

[0046] In some embodiments, the first substrate is polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, polyolefin, cyclic olefin copolymer (COC), cellulose acetate, or copolymers, blends, or composites thereof.

[0047] In some embodiments, the microcapsule imaging sheeting has increased or improved color gamut and / or fidelity of color reproduction of the original image.

[0048] In another aspect, there is provided a method of preparing an imaging sheet according to any one of the imaging sheets described herein, the method comprising: (i) coating a first surface of a first substrate with a microcapsule layer to produce a microcapsule-coated first substrate; and (ii) contacting the microcapsule-coated first substrate with a developer layer to produce the imaging sheet.

[0049] In another aspect, there is provided a method of preparing an imaging sheet according to any one of the imaging sheets described herein, the method comprising: (i) coating a first surface of a first substrate with a developer layer to produce a developer-coated first substrate; and (ii) contacting the developer-coated first substrate with a microcapsule layer to produce the imaging sheet.

[0050] In another aspect, there is provided a method of preparing an imaging sheet according to any one of the imaging sheets described herein, the method comprising coating a first surface of a first substrate with a mixture of developer and photosensitive microcapsules to produce an imaging sheet. In some embodiments, the method further comprises contacting the first substrate coated with the microcapsule / developer mixture with a second substrate.

[0051] In another aspect, there is provided a method of preparing an imaging sheet according to any one of the imaging sheets described herein, the method comprising: (i) coating a first surface of a first substrate with a microcapsule layer to produce a microcapsule-coated first substrate; (ii) coating a second substrate with a developer layer to produce a developer-coated second substrate; and (iii) contacting the developer layer of the developer-coated second substrate with the microcapsule layer of the microcapsule-coated first substrate to produce the imaging sheet.

[0052] In another aspect, a method of imaging or printing is provided, the method comprising: exposing an imaging sheet according to any one of the imaging sheets described herein to heat or radiation in an imagewise manner, the exposure being sufficient to selectively immobilize the leuco dye in the exposed or cured microcapsules in the microcapsule layer to form a latent image; and developing the latent image with pressure and / or heat to release the leuco dye to react with a developer to form an image. In some embodiments, the radiation is ultraviolet light, visible light, near-infrared light, or infrared light.

[0053] In another aspect, a method of imaging or printing is provided, the method comprising: exposing an image-wise imaging sheet according to any one of the imaging sheets described herein to heat or radiation, the exposure being sufficient to harden or soften microcapsules in the microcapsule layer to form a latent image; and developing the latent image with pressure and / or heat to release a leuco dye or dye precursor to form an image. In some embodiments, the radiation is ultraviolet light, visible light, near-infrared light, or infrared light.

[0054] Other aspects and / or embodiments of the present invention are provided, without limitation, in the detailed description of the technology set forth below, which is exemplary and explanatory but not intended to be limiting.

[0055] Various objects, aspects, features and advantages of the present disclosure will become more apparent and be better understood by reference to the following detailed description read in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0056] [Figure 1A] 1 shows the absorption spectra of illustrative examples of color filtering pigments / dyes described herein, including a representative green photoinitiator and the yellow color filtering (blue absorbing) pigment, Pigment Yellow 155. [Figure 1B] 1 shows the absorption spectra of illustrative examples of color filtering pigments / dyes described herein, including a representative red photoinitiator and the absorption spectrum of Pigment Violet 19, a magenta / violet color filtering (blue and green absorbing) pigment. [Figure 2A] 1 is a schematic diagram of an imaging sheet with green-sensitive microcapsules with a color filtering sheet, showing the sheet before development. [Figure 2B] 1 is a schematic diagram of an imaging sheet with green-sensitive microcapsules with a color filtering sheet, the figure showing the sheet after development. [Figure 3A] The chemical structure of Pigment Yellow 155, the pigment used in Example 2, is shown below. [Figure 3B] The chemical structure of Pigment Violet 19, the pigment used in Example 2, is shown below. [Figure 4]The normalized reflected optical density (OD) of the developed image is shown as a function of blue light energy. 1-1 is the yellow OD curve of the blue-sensitive image sheet of Example 1-1 (Control-B), which contains a yellow leuco dye (CAS: 123521-47-1) in the microcapsule core. 1-2 is the magenta OD curve of the green-sensitive image sheet of Example 1-2 (Control-G), which contains a magenta leuco dye (CAS: 50292-95-0) in the microcapsule core. 2-1, 2-2, and 2-3 are the magenta OD curves of the green-sensitive image sheets of Examples 2-1, 2-2, and 2-3, which contain a magenta leuco dye in the core and Pigment Yellow 155 in the shell at 0.244 phi, 0.488 phi, and 0.733 phi, respectively. [Figure 5] The normalized reflected optical density (OD) of the developed image is shown as a function of green light energy. 1-2 is the magenta OD curve of the green-sensitive image sheet of Example 1-2 (Control-G). 1-3 is the cyan OD curve of the red-sensitive image sheet of Example 1-3 (Control-R), which contains a cyan leuco dye (CAS: 114090-18-5) in the microcapsule core. 2-4, 2-5, and 2-6 are the cyan OD curves of the red-sensitive image sheets of Examples 2-4, 2-5, and 2-6, which contain a cyan leuco dye in the core and 0.188 phi, 0.376 phi, and 0.556 phi of Pigment Violet 19 in the shell, respectively. [Figure 6]The normalized reflective optical density (OD) of the developed image is shown as a function of green light energy. 1-2 is the magenta OD curve of the green-sensitive image sheet of Example 1-2 (Control-G). 1-3 is the cyan OD curve of the red-sensitive image sheet of Example 1-3 (Control-R). 2-4, 2-5, and 2-6 are the cyan OD curves of the red-sensitive image sheets of Examples 2-4, 2-5, and 2-6, which contain 0.188 phi, 0.376 phi, and 0.556 phi of Pigment Violet 19 in the shell, respectively. 2-1, 2-2, and 2-3 are the magenta OD curves of the green-sensitive image sheets of Examples 2-1, 2-2, and 2-3, which contain 0.244 phi, 0.488 phi, and 0.733 phi of Pigment Yellow 155 in the shell, respectively. [Figure 7A] The normalized reflective optical density (OD) of the developed image is shown as a function of blue light energy. 1-1 is the yellow OD curve of the blue-sensitive image sheet of Example 1-1 (Control-B). 2-3, 3-1, and 3-2 are the magenta OD curves of the green-sensitive image sheets of Examples 2-3, 3-1, and 3-2, which contain 0.15 phm, 0.3 phm, and 0.6 phm of antioxidant IRGANOX® 1035 in the core, respectively, and 0.733 phm of Color Filtering Yellow 155 in the shell. [Figure 7B] The normalized reflective optical density (OD) of the developed image is shown as a function of green light energy. 1-1 is the yellow OD curve of the blue-sensitive image sheet of Example 1-1 (Control-B). Curves 2-3, 3-1, and 3-2 are the magenta OD curves of the green-sensitive image sheets of Examples 2-3, 3-1, and 3-2. Curves 2-6, 3-3, and 3-4 are the cyan OD curves of Examples 2-6, 3-3, and 3-4, which contain 0.15 phm, 0.3 phm, and 0.6 phm of antioxidant IRGANOX® 1035 in the core, respectively, and 0.566 phm of Color Filtering Violet 19 in the shell. DETAILED DESCRIPTION OF THE INVENTION

[0057] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present technology. Certain exemplary embodiments of the present technology may be implemented without some or all of these specific details. In other instances, certain process operations are not described in detail, but would be understood by one of ordinary skill in the art.

[0058] Disclosed herein is an improved full-color microcapsule imaging system in which the photosensitive microcapsules are provided with a color filtering shell or a shell capable of filtering out incident light of unwanted wavelengths.

[0059] In some embodiments, the microcapsule imaging systems described herein may include any or all of the following combinations of microcapsules: 1. Red (λ1) photosensitive microcapsules comprising a cyan leuco dye contained within a photocurable core and a color filtering shell for filtering out non-red (non-λ1) light, such as ultraviolet, blue and / or green light. 2. Green (λ2) photosensitive microcapsules comprising a magenta leuco dye contained within a photocurable core and a color filtering shell for filtering out non-green (non-λ2) light, such as ultraviolet, blue and / or red light. 3. Blue (λ3) photosensitive microcapsules comprising a yellow leuco dye contained within a photocurable core and a color filtering shell that filters out non-blue (non-λ3) light, such as ultraviolet, green and / or red light.

[0060] The above red (R), green (G), and blue (B) light / colors, as well as cyan (C), magenta (M), and yellow (Y) colors are listed as examples because they are typically used in complementary color imaging systems. In a pseudocolor imaging system, various light sources (λ1, λ2, and λ3), including ultraviolet and near-infrared light, may be used as long as they are sufficiently separated from each other to ensure good color separation.

[0061] Microcapsules with color-filtering shells described herein significantly reduce unwanted crosstalk among microcapsules of various colors, thereby significantly improving the color fidelity of reproduced images. This is particularly advantageous for digital imaging systems, because the microcapsules described herein significantly reduce the need to select a light source with an emission wavelength that perfectly matches the spectral sensitivity of the photosensitizer / photoinitiator used in the microcapsules. Fine-tuning the emission spectrum of a light source, such as an LED or OLED, or the absorption spectrum of a photosensitizer / photoinitiator while maintaining quantum efficiency is difficult. The microcapsules described herein provide an effective, low-cost solution for reducing unwanted crosstalk and improving the color image fidelity of imaging systems.

[0062] The image quality of a photosensitive imaging system depends heavily on the spectral sensitivities of the three microcapsules and the emission spectrum of the light source used. As discussed above, the absorption spectra of commonly used red (R), green (G), and blue (B) photoinitiators, such as cyanine borate photoinitiators, have significant overlap, as do the emission spectra of broadband light sources (e.g., the R-OLED, G-OLED, and B-OLED used in OLED displays, as well as the R, G, and B light transmitted through color filtering in LED displays). For these photoinitiators, the absorption spectra of the B and G photoinitiators overlap significantly in the 440-500 nm range. Similarly, the absorption spectra of the G and R photoinitiators also overlap significantly in the 540-600 nm range. Therefore, exposing an imaging sheet to light with overlapping wavelengths can result in crosstalk due to the curing of multiple types of capsules.

[0063] To further illustrate the impact of crosstalk on image quality, particularly the fidelity of the color reproduction process, a microcapsule-imaging sheet containing three types of microcapsules, each containing one of three photoinitiators (R-, G-, and B-sensitive) and one of three complementary cyan (C), magenta (M), and yellow (Y) leuco dyes, is exposed or written to with one of three light sources (e.g., R-, G-, or B-OLED or LED). In an ideal scenario, after being written to with red (λ1) light, only the R-sensitive microcapsules are cured, and the release of the encapsulated C leuco dye is reduced as a function of the red energy received by the red-sensitive microcapsules. The G- and B-sensitive microcapsules should remain intact and free of any photoreaction upon R light exposure. The M and Y leuco dyes encapsulated in G and B photosensitive microcapsules, respectively, can be freely released into the dye developer layer to reproduce the red image of the source image if the M and Y leuco dyes are carefully selected and the ratio of the two dyes is properly balanced. Similarly, when the imaging sheet is exposed to green (λ2) light, only the green image of the source image is reproduced. Similarly, when the imaging sheet is exposed to blue (λ3) light, only the blue image of the source image is reproduced.

[0064] For example, if the system is written with only one light source and multiple types of microcapsules are cured, any crosstalk in the light reactions can degrade the fidelity of the color reproduction process: the colors of the printed image will be contaminated with unwanted color(s), significantly reducing the color gamut.

[0065] As discussed above, one approach to improving the fidelity of the color reproduction process is to utilize photosensitizers / photoinitiators with narrow and well-separated spectral sensitivities and light sources with narrow and well-separated emission spectra that adequately match the spectral sensitivities of the corresponding photosensitizers / photoinitiators. Such techniques are conducive to high-quality color reproduction. However, most photosensitizers / photoinitiators exhibit very broad spectral sensitivities, and most readily available modulatable light sources exhibit very broad or non-uniform emission spectra. There are only a limited number of commercially available narrow-band LEDs or lasers with reasonably acceptable λmax, size, and power efficiency, which often make them cost-prohibitive for printing applications, especially portable printing applications. Furthermore, with the exception of cyanine borate photoinitiators, it is extremely difficult, if not impossible, to find a set of R, G, and B photoinitiators with a reasonably narrow absorption spectrum. Finally, such systems require high quantum efficiency of the photosensitizers / photoinitiators and high light source power, making implementation for any high-speed printing application difficult and expensive.

[0066] Photosensitive Microcapsules As described herein, photosensitive microcapsules comprise a color filtering shell and a core containing a leuco dye or dye precursor, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material.

[0067] Specifically, in one or more embodiments, the photosensitive microcapsules are sensitive to a particular color or range of the radiation spectrum, and the shell contains one or more color filtering dyes or pigments that allow wavelengths corresponding to that color or range of the radiation spectrum to be transmitted to the core, but selectively absorb or filter out all or a portion of radiation outside the particular color or range. In some embodiments, the particular color or range is red, green, blue, cyan, magenta, or yellow. In some embodiments, the emission spectrum ranges from about 330 nm to about 900 nm, including about 330 nm, about 350 nm, about 375 nm, about 400 nm, about 425 nm, about 450 nm, about 475 nm, about 500 nm, about 525 nm, about 550 nm, about 575 nm, about 600 nm, about 625 nm, about 650 nm, about 675 nm, about 700 nm, about 725 nm, about 750 nm, about 775 nm, about 800 nm, about 825 nm, about 850 nm, about 875 nm, and 900 nm.

[0068] Color filtering shells can be prepared by adding one or more color filtering dyes or pigments during the shell-forming step(s) of the microencapsulation process. For example, water-soluble or dispersible color filtering dyes or pigments can be introduced into the aqueous phase during the formation of the front wall by absorption or interfacial polymerization / crosslinking and / or coacervation processes, grafting or embedding the dye / pigment onto or within the front wall. Alternatively, the dye or pigment can be introduced during the formation of the second wall by in situ polymerization and / or phase separation processes. Color filtering dyes or pigments with reactive functional groups, such as -NH-, -NH2, -OH, -SH, -COOH, -CONH-, -CONH2, -CSNH-, and -CSNH2, that react or graft with the shell-forming material are particularly useful. Unreacted or unembedded color filtering dyes or pigments in the aqueous phase can be removed, for example, by repeatedly centrifuging and washing the resulting microcapsules.

[0069] Figures 1A and 1B show the spectra of two representative aqueous color filtering pigment dispersions used in the present invention. As shown in Figure 1A, the yellow color filtering pigment absorbs incident light below 500 nm very effectively, with absorbance rapidly decreasing to zero at approximately 550 nm. Incorporating such a yellow pigment into the shell of green-sensitive microcapsules effectively reduces the risk of unwanted photocuring reactions caused by broadband blue light sources. Depending on the concentration of yellow pigment present in the shell, photosensitivity to green light exposure may remain substantially unchanged or may be slightly reduced, as evidenced by the absorption spectrum of the green photoinitiator used. As shown in Figure 1B, incorporating a magenta / violet pigment into the shell of red-sensitive microcapsules effectively reduces the risk of unwanted photocuring reactions caused by broadband green and / or blue light sources.

[0070] The color-filtering shells described herein filter out some or all of the unwanted wavelengths of light while allowing the appropriate wavelengths of light to pass through and trigger the photoreaction within the core. For example, a green-sensitive microcapsule with a shell containing a magenta leuco dye, a green-sensitive photoinitiator, and a yellow dye or pigment as the color-filtering material will block unwanted blue light (the complementary color of yellow) within the shell and allow green light to pass through to cure the core. Similarly, replacing the yellow dye or pigment in the shell with a cyan dye or pigment will block unwanted red light (the complementary color of cyan). Furthermore, using both yellow and cyan dyes / pigments in the shell of a green-sensitive microcapsule will block both unwanted blue and red light.

[0071] In this way, the color-filtering dyes / pigments in the shell prevent the core from being cured by an incorrect light source, even if the photosensitizer / photoinitiator in the core may have some sensitivity to the incorrect light source. As demonstrated in the examples, this resulted in a significant reduction in unwanted crosstalk and a significant improvement in the color fidelity of the color printing process. Furthermore, after developing the image-forming sheet, for example, by pressure and / or heat, the color of the color-filtering dyes or pigments is immobilized by the shell network, effectively hiding their color(s) beneath the printed image in the developer layer, making them virtually invisible (see Figures 2A and 2B).

[0072] 2A and 2B are schematic diagrams of an imaging sheet comprising green photosensitive microcapsules with a color-filtering shell. 2A shows the sheet before development, and 2B shows the sheet after exposure and development. Illustrated in FIGS. 2A and 2B are a transparent substrate 1, a developer layer 2, a microcapsule layer 3 comprising photosensitive microcapsules 3a, an opaque substrate 4, a photosensitive microcapsule shell 5 comprising a color-filtering yellow and / or cyan dye or pigment (depicted by triangular elements), a core 6 comprising a green photosensitive photoinitiator G, an acrylic monomer A, and a magenta leuco dye M, a ruptured microcapsule 7, a cured capsule 8 in which the magenta leuco dye is immobilized within the capsule, a developer layer 9 comprising magenta leuco dye M and acrylic monomer A transferred or diffused from the ruptured microcapsule 7, and an observer 10. In some embodiments, a microencapsulated imaging sheet according to the present disclosure comprises a photosensitive microcapsule layer 3 comprising photosensitive microcapsules 3a on a substrate 4. The photosensitive microcapsules 3a comprise a shell 5 containing a color-filtering dye or pigment Δ (e.g., a yellow and / or cyan dye / pigment dye) and a curable core 6 containing (i) a dye (e.g., a leuco dye, such as a magenta leuco dye) that imparts color to the microencapsulated imaging sheet upon release and development under pressure and / or heat, (ii) a photoinitiator such as a green-photosensitive cyanine borate, and (iii) a multifunctional monomer such as trimethylolpropane triacrylate (TMPTA). The developer may be present, for example, in a developer layer 9 configured to contact the microcapsule layer 3 separately. Alternatively, the developer may be premixed with the microcapsules and coated as a single layer on the substrate 4. In some embodiments, after the imagewise exposure step, the microcapsule layer may be contacted with the developer layer and thereby developed. The developed microcapsule layer may be discarded after the image is transferred to the developer layer and developed (two-sheet imaging system).

[0073] Upon imagewise exposure, the microcapsules are selectively hardened or softened, and the encapsulated dye (e.g., leuco dye) is selectively released from the ruptured microcapsules 7 during a pressure / heat development step, undergoing a chemical change and transitioning from a colorless state to a colored state (e.g., magenta, cyan, or yellow).

[0074] In some embodiments, one or more of the color filtering dyes or pigments includes a functional group for reacting with one or more shell-forming materials, in some embodiments, the functional group is -OH, -SH, -NH, -N-HR, -CHOH, -CHOR, -CHO, -CONH, -CONHR 、 The functional group is selected from the group consisting of urea, thiourea, isocyanate, thioisocyanate, epoxide, and precursors thereof, where R is alkyl, aryl, arylalkyl, alkylaryl, or heteroatom derivatives thereof, particularly those with short chain lengths. In some embodiments, the functional group is selected from the group consisting of -OH, -SH, -NH, -N-HR, -CONH, -NCO, -NCS-, -CHOH, -CHOR, -CHO, and precursors thereof, where R is alkyl, aryl, arylalkyl, alkylaryl, or heteroatom derivatives thereof, particularly those with short chain lengths. In some embodiments, the color filtering dye or pigment containing the functional group is water-soluble or dispersible, contained in the aqueous phase (external phase), and incorporated into or onto the shell of the microcapsule by absorption or interfacial reaction.

[0075] In some embodiments, one or more shell-forming materials are included in the internal or oil phase and form a shell by interfacial polymerization or crosslinking during the microencapsulation process. In some embodiments, one or more shell-forming materials are included in the internal and / or external phase and form a shell by interfacial polymerization or crosslinking during the microencapsulation process. In some embodiments, the one or more shell-forming materials included in the oil or internal phase are selected from the group including polyfunctional isocyanates, thioisocyanates, and epoxides, or precursors thereof.

[0076] In some embodiments, one or more shell-forming materials are included in the external or aqueous phase and form a shell during the microencapsulation process by interfacial or in situ polymerization or crosslinking, phase separation, or coacervation. In some embodiments, the one or more shell-forming materials in the external or aqueous phase are water-soluble compounds containing reactive functional groups, including, but not limited to, -OH, -SH, -NH, -N-HR, -COOH, -CHOR, -CHO, or precursors thereof, where R is alkyl, aryl, arylalkyl, alkylaryl, or heteroatom derivatives thereof, particularly those with short chain lengths. In some embodiments, the one or more shell-forming materials are selected from the group including urea, amines, urea formaldehyde, melamine formaldehyde, poly(N-methylolacrylamide), gelatin, gum arabic, pectin, carboxylate methylcellulose, and oligomers, copolymers, or blends thereof.

[0077] In some embodiments, the photoinitiator or photosensitizer is red-sensitive and the color filtering shell is magenta, yellow, or a combination thereof. In some embodiments, the photoinitiator or photosensitizer is green-sensitive and the color filtering shell is cyan, yellow, or any combination thereof. In some embodiments, the photoinitiator or photosensitizer is blue-sensitive and the color filtering shell is magenta, cyan, or any combination thereof. In some embodiments, the photoinitiator or photosensitizer is infrared-sensitive and the color filtering shell is cyan, magenta, yellow, or any combination thereof.

[0078] In some embodiments, the color filtering shell comprises one or more color filtering dyes or pigments. In some embodiments, the color filtering dyes are thermally bleachable or photobleachable. For blue-sensitive microcapsules, the color filtering dyes or pigments may be magenta (green-absorbing) and / or cyan (red-absorbing) dyes or pigments. For green-sensitive microcapsules, the color filtering dyes or pigments are yellow (blue-absorbing) and / or cyan (red-absorbing) dyes or pigments. In some embodiments, the color filtering dyes or pigments are Pigment Yellow 155 or CI Direct Yellow 86. For red-sensitive microcapsules, the color filtering dyes or pigments are yellow (blue-absorbing) and / or magenta (green-absorbing) dyes or pigments for red-sensitive microcapsules. In some embodiments, the color filtering dyes or pigments are Pigment Violet 19 or CI Disperse Red 60.

[0079] Illustrative examples of suitable color filtering dyes or pigments include, but are not limited to, cyanine or semicyanine dyes, quinacridone dyes, and perylene dyes. Cyan, magenta, and yellow dyes or pigments used in inkjet printing are particularly suitable. These are readily available from suppliers such as Cabot, Kolorjet Chemicals, Sun Chemicals, and Kao Collins, Inc. Reviews of dyes / pigments for inkjet printing include P. Gregory, "High-Technology Applications of Organic Colorants," Plenum Press, New York, 1991; P. Gregory, "Colorants For Electronic Printers," in JAG Drake Ed., "Chemical Technology In Printing And Imaging Systems," Royal Soc. Chem. (1993); W. Bauer, J. Ritter, "Tailoring Dyes for Ink Jet Applications," American Ink Maker 73, 42-49 (1995); R.W. Kenyon, "Dyes for Ink Jet Printing, Innovations in Modern Color Chemistry," SCI, London, 1994; W. Bauer, B. Baumgart and W. Zoller, "Magenta Dyes for Inkjet Applications," in "Recent Progress in Ink Jet Technologies II," Chapter 6, IS&T, 1999; R. Senthilkumar, "Dyes for Ink Jet Printing of Textiles" (2016), and D.M. Marmion, "Handbook of US Colorants For Foods, Drugs And Cosmetics" John Wiley & Sons (1984).

[0080] In some embodiments, one or more of the color filtering dyes or pigments present in the microcapsules is in an amount of about 0.01 to about 3 phi (parts per 100 parts of internal phase or parts per 100 parts of cores by weight), including about 0.01, about 0.02, about 0.03, about 0.04, about 0.05, about 0.06, about 0.07, about 0.08, about 0.09, about 0.10, about 0.20, about 0.30, about 0.40, about 0.50, about 0.60, about 0.70, about 0.80, about 0.90, about 1.0, about 1.5, about 2.0, about 2.5, and about 3.0 parts per 100 parts of cores. In some embodiments, one or more of the color filtering dyes or pigments present in the microcapsules is in an amount of about 0.05 to about 1.0 phi.

[0081] In some embodiments, when the photosensitive microcapsules are green- or red-sensitive microcapsules and the one or more color filtering dyes or pigments include a yellow (blue-absorbing) color filtering dye or pigment, the total absorption optical density of the one or more yellow (blue-absorbing) color filtering dyes / pigments in the range of about 450 nm to about 500 nm is about 0.005 to about 0.3. In some embodiments, the total optical density of the one or more yellow (blue-absorbing) color filtering dyes / pigments in the range of about 450 nm to about 500 nm is about 0.05 to about 0.2.

[0082] In some embodiments, when the photosensitive microcapsules are green-sensitive and the one or more color filtering dyes or pigments include a cyan (red-absorbing) color filtering dye or pigment, the total absorption optical density of the one or more cyan (red-absorbing) color filtering dyes / pigments in the range of about 600 nm to about 650 nm is about 0.005 to about 0.3. In some embodiments, the total optical density of the one or more cyan (red-absorbing) color filtering dyes / pigments in the range of about 600 nm to about 650 nm is about 0.05 to about 0.2.

[0083] In some embodiments, when the photosensitive microcapsules are blue-sensitive or red-sensitive microcapsules and the one or more color filtering dyes or pigments include a magenta (green-absorbing) color filtering dye or pigment, the total absorption optical density of the one or more magenta (green-absorbing) color filtering dyes or pigments in the range of about 500 nm to about 600 nm is about 0.005 to about 0.3. In some embodiments, the total optical density of the one or more magenta (green-absorbing) color filtering dyes or pigments in the range of about 500 nm to about 600 nm is about 0.05 to about 0.2.

[0084] It should be noted that the above red (R), green (G), and blue (B) light / colors, as well as cyan (C), magenta (M), and yellow (Y) colors, are given as non-limiting examples because they are typically used in complementary color imaging systems. In a pseudocolor imaging system, various light sources (λ1, λ2, and λ3), including ultraviolet and near-infrared light, can be used, but these light sources must be sufficiently separated from each other to ensure good color separation.

[0085] In some embodiments, the photosensitive microcapsules have an average diameter or D of about 4.0 μm to about 9.0 μm. 50 In some embodiments, the photosensitive microcapsules have an average diameter or D of about 5.0 μm to about 6.5 μm, including about 4.0, about 4.5, about 5.0, about 5.5, about 6.0, about 6.5, about 7.0, about 7.5, about 8.0, about 8.5, and about 9.0 μm. 50 It has.

[0086] Furthermore, the inventors of the present disclosure have discovered that incorporating a color filtering dye / pigment within the core of a microcapsule results in color contamination. Without wishing to be bound by theory, it is believed that the soluble or dispersible dye / pigment within the core is released into the developer layer simultaneously with the leuco dye(s) and monomer(s) during pressure / heat development, and that unless the color filtering dye / pigment is effectively decolorized after development, its color will be noticeable to the observer. Indeed, the presence of a color filtering dye or pigment within the core can inappropriately broaden the spectral sensitivity of the microcapsule and potentially cause crosstalk in the microcapsule imaging system, especially if the color filtering dye or pigment itself exhibits sensitivity to unwanted wavelength ranges, for example, via energy or electron transfer mechanisms. In some embodiments, the core does not contain (i.e., is devoid of) any color filtering dye or pigment.

[0087] As described herein, photosensitive microcapsules comprise a color filtering shell and a core containing a leuco dye, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material.

[0088] When encapsulated in one or more color-filtering shells, each photosensitive microcapsule comprises a core containing a leuco dye, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material. In some embodiments, the leuco dye is a cyan, magenta, yellow, black leuco dye, or any combination thereof. By way of non-limiting example, representative magenta leuco dyes may include PERGASCRIPT® Red I6B (CAS: 50292-95-0, Synamedia-chem), COPIKEM 35 (CAS: 50292-91-6), BASF's Blue I-2G and Blue-63, Yamada's Blue 220, Blue 203, Red 500, Red 40, or Black 305, WuXi Jiayida New Materials' JYDY-1, JYDR-2, JYDR-3, JYDB-1, or JYDB-2, Synmedia Chemicals' Red-16, O-C6, or O-C8, or Anyang General Chemicals' ODB-2. Other suitable examples of leuco dyes are disclosed, for example, in CHEMISTRY AND APPLICATIONS OF LEUCO DYES (R. Muthyala ed., 1997).

[0089] Suitable photoinitiators or photosensitizers include borate complexes which may be represented by the following general structural formula: [ka] In the formula, D + is a cationic chromophore such as a cyanine, semicyanine, squarine (e.g., squarylium), thiopyrylium, or triarylmethane. 1 , R 2 , R 3 , and R 4 are each independently a substituted or unsubstituted alkyl group, arylalkyl group, or aryl group. In some embodiments, R 1 is an alkyl group or an arylalkyl group, and R 2 , R 3, and R 4 is an aryl group. In some embodiments, the one or more photoinitiators include one or more of ketocoumarins, benzylidene ketones, benzophenones, thioxanthones, acylphosphine oxides, metallocene derivatives, and other Norrish Type I, II, and III photoinitiators, and combinations thereof.

[0090] The photoinitiator may be a red-, green-, or blue-sensitive cyanine borate, semicyanine borate, or ketocoumarin. In some embodiments, the photoinitiator is a cyanine borate, semicyanine borate, triarylmethane dye, squarylium dye, or thiopyrylium dye. In some embodiments, the photoinitiator or photosensitizer comprises an ultraviolet-, blue-, green-, red-, or near-infrared-sensitive photoinitiator or sensitizer.

[0091] The photocurable material may include a photopolymerizable or crosslinkable monomer or oligomer. In some embodiments, the polymerizable or crosslinkable monomer or oligomer is selected from multifunctional acrylates or methacrylates, multifunctional vinyl ethers, multifunctional allyl or vinyl benzenes, and their oligomers, dendrimers, or blends. The multifunctional acrylate may be 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), or neopentyl glycol diacrylate (NPGDA). The photosoftenable material may include a photodegradable or photodepolymerizable polymer.

[0092] In some embodiments, the core further comprises a radical inhibitor, retarder, or antioxidant. In some cases, a retarder or radical inhibitor is used to slow the photosensitivity of certain types of R, G, or B photosensitive microcapsules to further reduce the degree of crosstalk of the microcapsules with the color filtering shell.

[0093] The radical inhibitor, antioxidant, or retarder may be selected from the group comprising phenols, anilines, N-oxides of hindered amines, CuO, copper dithiocarbamates, copper or manganese carboxylates, and thiuram (thiocarbamoyl) derivatives, such as those of the following formula, or combinations thereof: [ka] R in the formula 1 , R 2 , R 3 , and R 4 are independently an alkyl group having 1 to 8 carbon atoms or a phenyl group.

[0094] The radical inhibitors were alkyl gallates, butylated hydroxyanisole, 3,5-di-t-butylbutyl-4-hydroxytoluene, vitamin E, 3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-ol (IRGANOX® E201), triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate (IRGANOX® 245), 3 -{[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoyl]oxy}-2,2-bis({[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoyl]oxy}methyl)propyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate (IRGANOX® 1010), 1,2-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazine (IRGANOX® MD 1024), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene (IRGANOX® 1076), 2,2'-thiobis(6-tert-butyl-p-cresol) (IRGANOX® 1081), N,N'-hexane-1,6-diylbis(3-3,5-di-tert-butyl-4-hydroxyphenyl-propionamide) (IRGANOX® 1098), 3,5-bis(1,1-dimethylethyl) -4-Hydroxybenzenepropanoic acid thiodi-2,1-ethanediyl ester (IRGANOX® 1035), benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-C7-C9 branched alkyl ester (IRGANOX® 1135), 3,3',3',5,5',5'-hexa-tert-butyl-a,a',a'-(mesitylene-2,4,6-triyl)tri-p-cresol (IRGANOX® 1330), (1,1-di-tert.The phenol radical inhibitor may be selected from the list including 1,3,5-tris[4-hydroxy-3,5-bis(2-methyl-2-propanyl)benzyl]-1,3,5-triazinane-2,4,6-trione (IRGANOX® 3114), 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol (IRGANOX® 565), and other IRGANOX® primary antioxidants.

[0095] The radical inhibitor may be an N-oxide of a hindered amine, the hindered amine being selected from the list including bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate (Tinuvin 770 DF), bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate (ADK STAB LA-72), tetrakis(2,2,6,6-tetramethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate (ADK STAB LA-57), and bis(1-undecanoxy-2,2,6,6-tetramethylpiperidin-4-yl)carbonate (ADK STAB LA-81).

[0096] The radical inhibitor, retarder, or antioxidant may be present at a concentration of about 0.01 to about 1 part per 100 parts of core by weight, including about 0.01, about 0.05, about 0.10, about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, and about 1.0 per 100 parts of monomer of the internal phase by weight. In some embodiments, the radical inhibitor, retarder, or antioxidant is present at a concentration of about 0.3 to 0.5 parts per 100 parts of monomer of the internal phase by weight.

[0097] In some embodiments, the radical inhibitor, retarder, or antioxidant is present at a concentration of about 0.1 to about 1.0 parts per 100 parts of monomer of the internal phase by weight. In some embodiments, the radical inhibitor, retarder, or antioxidant is present at a concentration of about 0.05 to 0.8 parts per 100 parts of monomer of the internal phase by weight. In some embodiments, the radical inhibitor, retarder, or antioxidant is present at a concentration of about 0.3 to about 0.8 phi. In some embodiments, the radical inhibitor, retarder, or antioxidant is present at a concentration of about 0.1 to 0.6 phi.

[0098] The core may further comprise, alone or in any combination, one or more of a coinitiator, an oxygen scavenger, or an autoxidizer. For example, a coinitiator, an oxygen scavenger, or an autoxidizer may be used to accelerate the photosensitivity of certain types of R, G, or B photosensitive microcapsules, further reducing the degree of crosstalk of the microcapsules with the color filtering shell.

[0099] Microcapsule image forming sheet Also described herein is a microcapsule imaging sheet comprising a first substrate and a photosensitive microcapsule layer in contact with a first surface of the first substrate, the photosensitive microcapsules comprising a color filtering shell and a core comprising a leuco dye, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material.

[0100] The photosensitive microcapsule layer may comprise 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 photosensitive microcapsule layer may comprise red-sensitive, green-sensitive, or blue-sensitive microcapsules, in which case the microencapsulated imaging sheet is considered a "full-color" imaging sheet.

[0101] In some embodiments, the photosensitive microcapsule layer or sheet further comprises a developer. In some embodiments, the photosensitive microcapsule layer or sheet further comprises a separate developer layer. In some embodiments, the separate developer layer is overcoated or laminated onto the photosensitive microcapsule layer.

[0102] In some embodiments, any one of the microcapsule imaging sheets described herein further comprises an adhesive layer between the developer layer and the microcapsule layer.

[0103] In some embodiments, any one of the microcapsule imaging sheets described herein further comprises a primer layer between the microcapsule layer and the first substrate.

[0104] The microcapsule imaging sheeting described herein has increased or improved color gamut and / or fidelity of color reproduction of the original image.

[0105] Base material The microcapsules described herein can be coated onto a substrate (e.g., a first substrate or a second substrate). The substrate can be any suitable material having sufficient thickness, flexibility, reflectivity (e.g., hiding power), and durability to record a print medium (e.g., an image). In some embodiments, the substrate is white or transparent. The substrate can be polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, polyolefin, cyclic olefin copolymer (COC), cellulose acetate, or copolymers, blends, or composites thereof. For example, a commercially available PET substrate is MELINEX® 339 ("PET339") manufactured by DuPont Teijin Films. Other useful commercially available PET films include, but are not limited to, HOSTAPHAN® polyester film (Mitsubishi Polyester Film), MELINEX® (Dupont Teijin Films™), and MYLAR® polyester film (Dupont Teijin Films™). The substrate may be in contact with the microcapsule layer, the developer layer, or both.

[0106] The substrate may have any suitable thickness, hi some embodiments, the substrate has a thickness of 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 therein.

[0107] Developer layer In some embodiments, imaging sheets according to the present disclosure include a developer layer in contact with the microcapsule layer and / or developer substrate. The developer layer can be applied to a second substrate and then placed in contact with the microcapsule layer, for example, by lamination. In some embodiments, the developer layer can be overcoated onto the microcapsule layer, and the resulting overcoated sheet can be used directly without a second substrate. In some embodiments, the overcoated developer sheet / microcapsule sheet can be further overcoated with a durable protective coating or laminated to a second substrate. In some embodiments, the developer layer composition can be premixed with the microcapsule layer composition and coated as a single layer on the first substrate.

[0108] In some embodiments, an imaging system according to the present disclosure includes two separate sheets: a photosensitive microcapsule sheet and a developer sheet. The microcapsule sheet is imagewise exposed, contacted with the developer sheet, and then developed under pressure / heat. After the leuco dye is transferred to the developer sheet, the microcapsule sheet is discarded.

[0109] In some embodiments, the developer substrate is polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, polyolefin, cyclic olefin copolymer (COC), cellulose acetate, or copolymers, blends, or composites thereof.

[0110] In some embodiments, the developer layer includes one or more leuco dye developers. Non-limiting examples of developers include Lewis acids, silicic acids, salicylic acid derivatives, benzoic acid derivatives, novolac resins, and their metal complexes, particularly zinc complexes, or blends, composites, copolymers, including graft and block copolymers, or combinations thereof. For example, the developer(s) may include acid clay, zinc 3,5-bis(alpha-methylbenzyl)salicylate (e.g., N-054-W, SANKO Co., Ltd.), zinc 3,5-di-t-butylsalicylate, zinc 3,5-dioctylsalicylate, HRJ 4542 (Schenectady Chemical), or novolac resin developers such as RD9870, RD9870A, RD9880, RD9880U, and RF-118 (Xinxiang Richful Lube Additive Co., Ltd.). In some embodiments, the developer layer comprises a Lewis acid, an acidic clay, or one or more compounds containing phenolic or carboxylic acid groups, or a metal complex thereof. In some embodiments, the developer layer comprises a novolak resin, a salicylic acid derivative, a zincate derivative thereof, or a combination, copolymer, blend, or composite thereof.

[0111] The developer layer may have any suitable thickness. For example, the developer layer may have a thickness of at least about 1 μm, at least about 2 μm, at least about 3 μm, at least about 4 μm, at least about 5 μm, at least about 6 μm, at least about 7 μm, at least about 8 μm, at least about 9 μm, at least about 10 μm, at least about 15 μm, at least about 20 μm, at least about 25 μm, at least about 30 μm, at least about 35 μm, at least about 40 μm, at least about 45 μm, at least about 50 μm, or any range or value therein. In some embodiments, the developer layer has a thickness of about 1 μm to about 30 μm, about 2 μm to about 20 μm, or about 3 μm to about 15 μm.

[0112] The developer may be present in the developer layer at a concentration by weight based on the dry weight of the developer layer of about 50 wt.% or more, about 55 wt.% or more, about 60 wt.% or more, about 65 wt.% or more, about 70 wt.% or more, about 75 wt.% or more, about 80 wt.% or more, about 85 wt.% or more, about 90 wt.% or more, about 95 wt.% or more, about 96 wt.% or more, about 97 wt.% or more, about 98 wt.% or more, about 99 wt.% or more, or any range or value therein. In some embodiments, the developer layer may include a polymer binder and a filler such as silica, acid clay, CaSO4, BaSO4, and TiO2.

[0113] method In another aspect, there is provided a method of preparing an imaging sheet according to any one of the imaging sheets described herein, the method comprising: (i) coating a first surface of a first substrate with a microcapsule layer to produce a microcapsule-coated first substrate; and (ii) contacting the microcapsule-coated first substrate with a developer layer to produce the imaging sheet.

[0114] In another aspect, there is provided a method of preparing an imaging sheet according to any one of the imaging sheets described herein, the method comprising: (i) coating a first surface of a first substrate with a developer layer to produce a developer-coated first substrate; and (ii) contacting the developer-coated first substrate with a microcapsule layer to produce the imaging sheet.

[0115] In another aspect, there is provided a method of preparing an imaging sheet according to any one of the imaging sheets described herein, the method comprising coating a first surface of a first substrate with a mixture of developer and photosensitive microcapsules to produce an imaging sheet. In some embodiments, the method further comprises contacting the first substrate coated with the microcapsule / developer mixture with a second substrate. In some embodiments, the method further comprises contacting the first substrate coated with the microcapsule / developer mixture with a protective overcoat.

[0116] In another aspect, there is provided a method of preparing an imaging sheet according to any one of the imaging sheets described herein, the method comprising: (i) coating a first surface of a first substrate with a microcapsule layer to produce a microcapsule-coated first substrate; (ii) coating a second substrate with a developer layer to produce a developer-coated second substrate; and (iii) contacting the developer layer of the developer-coated second substrate with the microcapsule layer of the microcapsule-coated first substrate to produce the imaging sheet.

[0117] In another aspect, a method of imaging or printing is provided, the method comprising: exposing an image-wise imaging sheet of any one of the imaging sheets described herein to heat or radiation, the exposure being sufficient to selectively immobilize or migrate the leuco dye within the microcapsules by hardening or softening the microcapsules to form a latent image; and developing the latent image by applying pressure and / or heat to form an image. In some embodiments, the exposure radiation is ultraviolet light, visible light, near-infrared light, or infrared light. In some embodiments, the exposure radiation is ultraviolet light, visible light, near-infrared light, or infrared light. In some embodiments, the exposure or development heat is obtained from a thermal printhead.

[0118] In some embodiments, a process for making photosensitive microcapsules is provided. Exemplary embodiments for making photosensitive microcapsules are provided in the Examples. The process includes providing an aqueous phase, contacting the aqueous phase with an internal phase containing a leuco dye or dye precursor, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material to provide a mixture, contacting the mixture with a dispersion containing a color filtering dye or pigment, and forming photosensitive microcapsules by interfacial or in situ polymerization or crosslinking, phase separation, or coacervation during the microencapsulation process.

[0119] While the foregoing terms are believed to be well understood by those of ordinary skill in the art, the following definitions are provided to facilitate explanation of the subject matter of the present disclosure.

[0120] The term "a" or "an" may refer to one or more of that entity, i.e., it can refer to multiple referents. Thus, the terms "a," "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 of the element is present, unless the context clearly requires that only one of the element is present.

[0121] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0122] As used herein, the terms "about" or "approximately," when preceding a numerical value, indicate a range of plus or minus 10% of that value.

[0123] As will be understood by those skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of those subranges. Any recited range can be readily recognized as fully descriptive and allowing for equal division of that same range into at least one half, one third, one quarter, one fifth, one tenth, etc. As a non-limiting example, each range discussed herein can be readily divided into a lower third, a middle third, an upper third, etc. As will also be understood by those skilled in the art, all terms such as "up to," "at least," "greater than," "less than," etc., are inclusive of the stated numbers and refer to ranges that can be subsequently divided into subranges as discussed above. Finally, as will be understood by those skilled in the art, a range includes each individual component.

[0124] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs. Furthermore, terms such as those defined in commonly used dictionaries should be interpreted to have a meaning consistent with their meaning in the context of this application and related art, and should not be interpreted in an idealized or overly formal sense unless expressly defined herein. Unless expressly defined below, such terms should be interpreted according to their common meaning.

[0125] For purposes of this disclosure, the term "color density" refers to the light absorption ability of a dye; the greater the light absorption of a dye, the higher the color density (i.e., the darker the color); the lower the light absorption of a dye, the lower the color density (i.e., the lighter the color).

[0126] For purposes of this disclosure, "maximum color density" (or "D max ") refers to the maximum color density achieved by the dye after a given development time (e.g., after about 1 hour, about 2 hours, about 4 hours, about 8 hours, about 12 hours, about 24 hours, etc.).

[0127] For purposes of this disclosure, "fresh color density" or "fresh D max The term "" refers to the color density achieved by the dye immediately after the microcapsules are ruptured (e.g., at the onset of color development) (e.g., within 1 second, or within a few seconds to a few minutes, e.g., between about 1 second, about 2 seconds, about 5 seconds, or about 10 seconds to about 1 minute, about 2 minutes, about 3 minutes, about 4 minutes, or about 5 minutes).

[0128] For 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 change from the colorless to the colored form may be reversible or irreversible and can be triggered by changes in temperature, pH, irradiation, and / or redox state.

[0129] Unless expressly indicated otherwise, all specified embodiments, features, and terms are intended to include both the stated embodiment, feature, or term and their equivalents.

[0130] Reference will now be made in detail to specific embodiments contemplated by the present disclosure. While various embodiments have been described herein, it will be understood that the present disclosure is not intended to limit the present technology to the described embodiments. Rather, the present disclosure is intended to cover alternatives, modifications, and equivalents that may be included within the spirit and scope of the present technology as defined by the appended claims. [Example]

[0131] Example 1. Preparation of control red, green, and blue photosensitive microcapsules and microcapsule-based self-contained imaging sheets Table 1 below lists the materials used in the examples below. [Table 1]

[0132] Preparation of photosensitive microcapsules Photosensitive microcapsules were prepared using the materials in Table 2 according to the following procedure. 1. 220 parts water and 8 parts Versa TL502 sulfonated polystyrene (dry) were added to a beaker and mixed thoroughly. 2. 10 parts of pectin (polygalacturonic acid methyl ester) was slowly sieved into the mixture and stirred (500-1000 rpm) overnight at room temperature. The pH was adjusted to 7.5 with 3.10% sodium carbonate and the mixing speed was increased to 1750 rpm. 4. The internal phase shown in Table 2 was added over 15 to 30 seconds. After stirring the resulting mixture for 30 minutes, 11 parts of a 9.1% aqueous solution of DETA (diethylenetriamine) (adjusted to pH 7.0) was added and the mixture was allowed to react at 25°C for 30 minutes, then at 40°C for 1 hour. 5. A solution containing 19.9 parts CYMEL® 385 and 40 parts water (adjusted to pH 6.0) was added and allowed to react at 70° C. for a further 2 hours. 6.3 15.23 parts of a 4.3% aqueous solution of sodium sulfate was added and the mixture was stirred for 10 minutes, after which 1.97 parts of CYMEL® 385 and 10 parts of water were added and the mixture was stirred for 70 minutes. o C and allowed to react for an additional hour. 7. The mixing speed was reduced to 600 rpm, the pH was adjusted to 9.5 using 20% ​​NaOH solution, and the resulting reaction mixture was stirred overnight at room temperature. [Table 2-1] [Table 2-2]

[0133] Preparation of color developer coating Developer compositions as shown in Table 3 were coated onto 1 mil clear PET film with a Maillard bar and dried in an oven at 80°C for 10 minutes to a target dry coating thickness of approximately 8 μm as measured with a Mitutoyo film thickness gauge. [Table 3]

[0134] Preparation of microcapsule coatings The coating solutions of R / G / B photosensitive microcapsules (Examples 1-1, 1-2, and 1-3) shown in Table 4 were adjusted to a solids content of 33 wt.% with DI water and coated onto 2 mil white PET (MELINEX®) using a Myrad bar to a target dry coating thickness of approximately 8 μm as measured with a Mitutoyo film thickness gauge. The coating was dried in an oven at 80° C. for 10 minutes. [Table 4-1] [Table 4-2]

[0135] Preparation of an imaging sheet comprising a photosensitive microcapsule layer and a development layer The microcapsules and developer film thus prepared were laminated together in a Tamerica roll laminator TCC2700 at a temperature of 100°C, a pressure of 3.621 Kgf / 170 mm, and a speed of 0.368 m / min to form various photosensitive imaging sheets.

[0136] Example 2. Preparation of photosensitive microcapsules with color-filtering shells and self-contained imaging sheets based on the microcapsules Self-contained imaging sheets containing various concentrations of color filtering pigments on or within the shell were prepared using the same procedure as in Example 1, except that in step 4 of the microencapsulation procedure, (i) the resulting mixture was stirred for 30 minutes, (ii) an aqueous pigment dispersion as shown in Table 5 and Figure 5 was thoroughly mixed with 10 parts DI water and added to the mixture, and (iii) 11 parts of a 9.1% aqueous solution of DETA (diethylenetriamine) (adjusted to pH 7.0) was added, and the resulting mixture was allowed to react at 25°C for 30 minutes, followed by 40°C for 1 hour. [Table 5]

[0137] *phi: parts per 100 parts of inner phase or parts per 100 parts of core by weight The chemical structures of Pigment Yellow 155 and Pigment Violet 19 are shown in Figures 3A and 3B, respectively.

[0138] All microcapsules prepared in this manner were thoroughly washed with water and centrifuged to remove excess water-soluble polymer and additives in the aqueous phase. As can be clearly seen from Table 6, all purified / washed microcapsules have similar particle sizes as measured by a HORIBA LA-960 laser scattering particle size analyzer. No aggregation of the microcapsules was observed. [Table 6]

[0139] Reduction of blue light induced crosstalk in green photosensitive imaging sheets The blue-sensitive imaging sheet of Example 1-1 (Control-B), and the green-sensitive imaging sheets of Example 1-2 (Control-G) and Examples 2-1, 2-2, and 2-3 with yellow color filtering shells containing different concentrations of Pigment Yellow 155, were placed directly on top of a Visionox OLED panel (Model No. G1392FH101GG-003) and exposed for 20 seconds through an RGB grayscale image with levels 0 to 255 (level 0 being the darkest and level 255 being the brightest). The exposed imaging sheets were developed using a pressure fixture, and the normalized reflected optical density of the developed images as a function of relative blue energy output (blue HD curve) is shown in Figure 4.

[0140] As can be seen from Figure 4, the green-sensitive imaging sheets (Examples 1-2, 2-1, 2-2, and 2-3) can also be cured by blue light from an OLED panel, but their photosensitivity is significantly lower than that of the blue-sensitive imaging sheets (Example 1-1, Control-B). It is also clear from Figure 4 that the imaging sheet of Example 1-2 (Control-G) exhibited significant crosstalk upon exposure to blue light. Control-B (Example 1-1) was fully cured and yellow-D min A blue energy level of approximately 130 is required to reach this level. Exposure to such high blue energy levels also partially cured the imaged sheet of Control-G (Example 1-2), resulting in a reduction in magenta OD of approximately 30%. Figure 4 also clearly shows that incorporating Pigment Yellow 155 into the shells of the green-sensitive microcapsules (Examples 2-1, 2-2, and 2-3) resulted in a significant increase in the blue energy required to cure the green-sensitive microcapsules. For microcapsules containing Pigment Yellow 155 at ≥ 0.488 phi, no reduction in magenta density was observed after exposing the imaged sheet to a blue energy level of approximately 130. The color filtering shell containing Pigment Yellow 155 appeared to be very effective in reducing blue-induced crosstalk in the green-sensitive microcapsules.

[0141] Yellow color filtering shell containing various concentrations of Pigment Yellow 155 provides green photosensitivity (E 10 and E 90 ) and D max and D min The impact on the [Table 7]

[0142] D min , D max , E 10 , and E 90 is defined as follows: D min: Average minimum reflected color (cyan, magenta, or yellow) density in fully exposed area D max : Average maximum color (cyan, magenta, or yellow) density developed in unexposed areas E 10 (Level): Total Density (D max -D min ) energy level required to reduce by 10% (0-255) E 90 (Level): Total Density (D max -D min ) by 90%.

[0143] All optical densities are based on exposure, pressure development, and 100 o Immediately after post-heating with the heated roller of C, the density was measured by a spectrodensitometer FD-5 (Konica Minolta, MO, ISO-E).

[0144] Table 7 shows that a color filtering shell containing Pigment Yellow 155 at ≤0.488 phi yields a magenta D min , Yellow D min , Magenta D max , green E 10 and E 90 Microcapsules containing high concentrations (≥0.733 phi) of Pigment Yellow 155 (a yellow pigment commonly used in inkjet printing) in the shell exhibited no significant (or even within experimental error) effect on nearly all optical functions, including Yellow D. min and green E 10 Without being bound by theory, it is believed that too high a concentration of yellow pigment may degrade the crosslinkability and / or oxygen barrier properties of the shell, resulting in a decrease in E 10 This may cause an increase in the initial velocity of light (i.e., a decrease in the initial velocity of light).

[0145] Table 7 also shows that no cure was observed for all green-sensitive imaging sheets after full exposure to the highest level of red light, an effect attributed to the very limited overlap between the red emission spectrum of the OLED used and the absorption spectrum of the green photoinitiator.

[0146] Reduction of green light induced crosstalk in red-sensitive imaging sheets As can be seen from Figure 5, the red-sensitive imaging sheets (Examples 1-3, 2-4, 2-5, and 2-6) containing a cyan leuco dye (CAS: 114090-18-5) were curable by green light from an OLED panel, but their photosensitivity was significantly lower than that of the green-sensitive imaging sheets (Example 1-2, Control-G) containing a magenta leuco dye (CAS: 50292-95-0). Figure 5 also reveals that the imaging sheet of Example 1-3 (Control-R) exhibited significant crosstalk upon green light exposure. Control-G (Example 1-2) was fully cured to produce magenta leuco dye (CAS: 50292-95-0). minA green energy level of approximately 130-140 is required to reach the magenta Dmin. However, similar to the blue-green crosstalk discussed above, green light-induced curing of the red-sensitive microcapsules (crosstalk of the red-sensitive imaging sheet due to green light exposure) was also observed at such high green energy levels. The Control-R imaging sheet (Examples 1-3) was also partially cured, resulting in a decrease in cyan OD of approximately 30% when the green exposure energy was high enough to reach the magenta Dmin. Figure 5 also reveals that incorporating Pigment Violet 29 (a magenta pigment commonly used in inkjet printing) into the shells of the red-sensitive microcapsules (Examples 2-4, 2-5, and 2-6) resulted in a significant increase in the green energy required to cure the red-sensitive microcapsules. Microcapsules containing Pigment Violet 29 at ≥ 0.376 phi (Examples 2-5 and 2-6) showed little loss of cyan density even after exposing the imaged sheet to a green energy level of about 130, high enough to fully cure the green microcapsules and reach magenta Dmin. The color filtering shell containing Pigment Violet 29 also appeared to be very effective for reducing green-induced crosstalk in red-sensitive microcapsules.

[0147] Figure 6 shows the OD curves of Examples 1-2 (Control-G), 1-3 (Control-R), and Examples 2-1 through 2-6 as a function of green light exposure. As is evident from Figure 6, the yellow color filtering shells (Examples 2-1, 2-2, and 2-3) had the highest Pigment Yellow 155 content (0.733 phi) in the shell, yet still exhibited the highest magenta OD of all four green-sensitive imaging sheets. min As a result, the incorporation of yellow pigment into the green-sensitive microcapsule shells effectively reduced the blue-induced crosstalk of the green-sensitive microcapsules, as shown in Figure 4, although it did not affect the green crosstalk of the red-sensitive microcapsules.

[0148] The red sensitivity (E) of the red-sensitive imaging sheet containing cyan leuco dye (CAS: 114090-18-5) 10 and E 90 ) and D max and D min The effect of the magenta color filtering shell on the

[0149] As can be seen from Table 8, the color filtering shell containing Pigment Violet 29 at ≤0.556 phi yields Cyan D min , Magenta D min , Cyan D max , and red E 90 Microcapsules containing high concentrations (≥0.556 phi) of Pigment Violet 29 (a magenta pigment commonly used in inkjet printing) in the shell (Examples 2-6) showed no significant (or even within experimental error) effect on nearly all optical functions, including magenta D. min and Red E 10 The red-sensitive imaging sheets showed a slight increase in ρ, likely due to the high pigment loading, which may be due to a deterioration in crosslinking and / or oxygen barrier properties of the shell. Also, note from Table 8 that all red-sensitive imaging sheets showed no cure even after full exposure to the highest level of blue light. This is primarily due to the blue emission spectrum of the OLED used not overlapping with the absorption spectrum of the red photoinitiator. [Table 8]

[0150] Example 3 Green and Red Photosensitive Microcapsules Containing Color Filtering Pigments in the Shell and High Concentration of Radical Quenchers in the Core The compositions of the internal phases of the green- and red-sensitive microcapsules and the procedures for preparing the microcapsules and imaging sheets were the same as those described in Examples 1 and 2, except that a high concentration (0.3-0.6 parts per 100 parts of monomer or phm) of antioxidant IRGANOX® 1035 manufactured by BASF was added to the microcapsule core as a radical quencher or polymerization retarder / inhibitor. Except for the concentration of IRGANOX® 1035, the formulations of the internal phases of the green-sensitive microcapsules in Examples 3-1 and 3-2 were the same as those of Examples 2-3. Similarly, except for the concentration of IRGANOX® 1035, the formulations of the internal phases of the red-sensitive microcapsules in Examples 3-3 and 3-4 were the same as those of Examples 1-3. The differences in formulation and the D of the microcapsules prepared accordingly were analyzed. 50 The particle sizes are shown in Table 9. Microcapsule-based imaging sheets were prepared using the procedure described in Example 2, and the characteristic optical functions of the imaging sheets are shown in Tables 10 and 11 and Figures 7 and 8. [Table 9] [Table 10] [Table 11]

[0151] As can be seen from Tables 9, 10, and 11, increasing the concentration of the radical quencher IRGANOX® 1035 in the core from 0.15 phm to 0.60 phm significantly increased the particle size, D min , and D max However, in the case of green-sensitive microcapsules containing 0.733 phi of color filtering Yellow 155 in the shell, E 10 6.1 to 8.1% increase in E (a decrease in the speed of light due to the onset of hardening of the microcapsules) 90HD curves with higher contrast ratios were obtained, accompanied by a 4.5-12.5% ​​decrease in E (due to the increased speed of light required to reach a nearly complete hardening state of the microcapsules). Similarly, for red-sensitive microcapsules containing 0.566 phi color filtering Violet 19 in the shell, E 10 and an increase of 5.9 to 31.4% in E 90 The resulting HD curves have significantly higher contrast ratios, with a 6.5-14.6% reduction in crosstalk. The significant reduction in unwanted crosstalk is evident from the HD curves shown in Figures 7A and 7B.

[0152] The blue-sensitive imaging sheet of Example 1-1 (Control-B) and the green-sensitive imaging sheets of Examples 2-3, 3-1, and 3-2, containing 0.15, 0.3, and 0.6 phm, respectively, of IRGANOX® 1035 as a radical quencher in the core and 0.733 phm of Yellow 155 in the shell, were exposed to blue light from a Visionox OLED panel as described in Example 2. As shown in Figure 7A, at a blue energy level of approximately 130-140, the blue-sensitive Control-B (Example 1-1) reached a yellow Dmin. However, at the same level of blue exposure energy, the two green-sensitive imaging sheets, i.e., Examples 2-3 and 3-1, showed similar OD reductions, while the imaging sheet of Example 3-2, containing the highest density (0.60 phm) of IRGANOX®, did not show any OD reduction until the blue energy level was increased above approximately 150. From both Table 10 and Figure 7A, increasing the concentration of IRGANOX® 1035 from 0.15 phm to 0.60 phm resulted in a decrease in the Magenta D max and D min It is clear that the blue crosstalk of the green-sensitive imaging sheet was significantly reduced without any significant trade-off.

[0153] The effect of IRGANOX® 1035 concentration in the core of red-sensitive imaging sheets (Examples 2-6, 3-3, and 3-4) with 0.566 phm of color filtering Violet 19 in the microcapsule shell on green crosstalk can also be clearly seen in Figure 7B and Table 11. Also, the addition of 0.60 phm of IRGANOX® 1035 in the core of red-sensitive microcapsules resulted in a Cyan D max and D min Green crosstalk was significantly reduced without any trade-off.

[0154] Example 4. Green and Red Photosensitive Imaging Sheets Containing Color Filtering Pigments in Microcapsule Cores For Examples 4-1 and 4-2, the formulations and procedures for preparing the self-contained imaging sheets of Examples 3-2 (green-sensitive) and 3-4 (red-sensitive) were repeated, except that the color filtering pigments Yellow 155 (0.733 phi) and Violet 19 (0.566 phi), respectively, were ground, dispersed in the internal phase, and encapsulated. The results are shown in Table 12. [Table 12]

[0155] As can be clearly seen from Table 12, the green photosensitive imaging sheet containing Yellow 155 color filtering pigment in the shell (Example 3-2) exhibited significantly lower yellow D than the imaging sheet containing the same yellow pigment in the core (Example 4-1). min and sharper contrast ratio (smaller E 90 -E 10 If a higher concentration of yellow pigment is transferred to the developer layer during the development step and is contained within the core, the result is yellow D min Furthermore, the presence of pigment in the core increases D min Or the speed of light to reach the fully cured state of the internal phase is slowed (E 90Without being bound by theory, it is believed that the pigment contained within the shell tends to be immobilized within the highly cross-linked shell, resulting in the formation of Yellow D, as shown in the schematic diagram in Figure 2. min In addition, since the pigment is not in contact with the monomer in the internal phase, there is little effect on the polymerization or crosslinking of the multifunctional monomer in the core.

[0156] Also, the red-sensitive imaging sheet of Example 3-4, which incorporates Violet 19 pigment in the shell, exhibits a lower magenta D than the imaging sheet of Example 4-2, which has a color filtering pigment dispersed in the core. min and a clear contrast ratio was observed.

[0157] The compositions and methods illustratively described herein may suitably be practiced in the absence of any element(s), limitation(ies) not specifically disclosed herein. Thus, for example, terms such as "comprising," "including," and "containing" are to be understood broadly and without limitation. Furthermore, the terms and expressions employed herein are used as terms of description rather than limitation, and the use of such terms and expressions is not intended to exclude any equivalents of the features shown and described or portions thereof. It will be recognized that various modifications are possible within the scope of the claimed disclosure. Thus, while the present disclosure has been specifically disclosed by preferred embodiments and optional features, it will be understood that modifications and variations of the disclosure embodied herein may occur to those skilled in the art, and such modifications and variations are deemed to be within the scope of the present disclosure.

[0158] It is specifically contemplated that the various features of the invention described herein can be used in any combination, unless the context dictates otherwise. Furthermore, the present disclosure also contemplates that in some embodiments, any feature or combination of features described herein can be excluded or omitted. To illustrate, if the specification states that a composite comprises components A, B, and C, it is specifically contemplated that any of A, B, or C, or combinations thereof, alone or in any combination, can be omitted or eliminated.

[0159] The present disclosure has been described broadly and generically herein. Each of the narrower species and subtaxa falling within the generic disclosure also form part of the composition or method. This includes a generic description of a composition or method with a provisos or negative limitation excluding any subject matter from that genus, regardless of whether the excluded material is specifically set forth herein. The present technology is not limited with respect to the specific embodiments described in this application, which are intended as representative illustrations of individual aspects of the technology. Many modifications and variations of the present technology can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent compositions, methods, and devices within the scope of the present technology, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing description. Such modifications and variations are intended to be within the scope of the present technology. It is understood that the present technology is not limited to specific methods, compounds, or compositions, as these may, of course, vary. It is also understood that the terminology employed herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0160] Those skilled in the art will readily appreciate that the present disclosure is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. Modifications therein and other uses will occur to those skilled in the art. These modifications are encompassed within the spirit of the disclosure and are defined by the scope of the claims which describe non-limiting embodiments of the disclosure.

[0161] Additionally, when features or aspects of the disclosure are described in terms of a Markush group, 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 image forming sheet, comprising: A color filtering shell; a core comprising a leuco dye or dye precursor, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material;

2. 10. The photosensitive microcapsule of claim 1, wherein the photoinitiator or photosensitizer is red-sensitive and the color of the color-filtering shell is magenta, yellow, or any combination thereof.

3. 10. The photosensitive microcapsule of claim 1, wherein the photoinitiator or photosensitizer is green-sensitive and the color of the color-filtering shell is cyan, yellow, or any combination thereof.

4. 10. The photosensitive microcapsule of claim 1, wherein the photoinitiator or photosensitizer is blue-sensitive and the color of the color-filtering shell is magenta, cyan, or any combination thereof.

5. 10. The photosensitive microcapsule of claim 1, wherein the photoinitiator or photosensitizer is infrared-sensitive and the color of the color-filtering shell is cyan, magenta, yellow, or any combination thereof.

6. The photosensitive microcapsules of claim 1 , wherein the photocurable material comprises a photopolymerizable or crosslinkable monomer or oligomer.

7. 7. The photosensitive microcapsule of claim 6, wherein the polymerizable or crosslinkable monomer or oligomer is selected from polyfunctional acrylates or methacrylates, polyfunctional vinyl ethers, polyfunctional allyl or vinyl benzenes, and oligomers, dendrimers, or blends thereof.

8. The photosensitive microcapsules of claim 1 , wherein the photosoftenable material comprises a photodegradable or photodepolymerizable polymer.

9. 2. The photosensitive microcapsules of claim 1, wherein the leuco dye is a cyan, magenta, yellow, black leuco dye, or any combination thereof.

10. 2. The photosensitive microcapsule of claim 1, wherein the photoinitiator is a cyanine borate, a semicyanine borate, a triarylmethane dye, a squarylium dye, or a thiopyrylium dye.

11. 10. The photosensitive microcapsule of claim 1, wherein the photoinitiator or photosensitizer comprises an ultraviolet-sensitive, blue-sensitive, green-sensitive, red-sensitive, or near-infrared-sensitive photoinitiator or sensitizer.

12. 10. The photosensitive microcapsule of claim 1, wherein the photosensitive microcapsule is sensitive to a particular color or a particular range of the radiation spectrum, and the shell contains one or more color filtering dyes or pigments that allow wavelengths corresponding to the color or range of the radiation spectrum to be transmitted to the core, but selectively absorb or filter out all or a portion of radiation outside the particular color or range.

13. 13. The photosensitive microcapsules of claim 12, wherein one or more of the color filtering dyes or pigments is bleachable, heat bleachable or photo bleachable.

14. 13. The photosensitive microcapsule of claim 12, wherein one or more of the color filtering dyes or pigments includes a functional group for reacting with one or more shell-forming materials.

15. The functional groups are —OH, —SH, —NH ２ , -N-HR, -CONH ２ , -NCO, -NCS-, -CH ２ OH, -CH ２ 15. The photosensitive microcapsule of claim 14, wherein R is selected from the group consisting of -OR, -CHO, and precursors thereof, and R is alkyl, aryl, arylalkyl, alkylaryl, or heteroatom derivatives thereof.

16. 15. The photosensitive microcapsule of claim 14, wherein the one or more shell-forming materials are contained in the internal and / or external phase and form the shell by interfacial polymerization or crosslinking during the microencapsulation process.

17. 15. The photosensitive microcapsule of claim 14, wherein the one or more shell-forming materials are included in the external phase and form a shell by in situ polymerization or crosslinking, phase separation, or coacervation during the microencapsulation process.

18. 10. The photosensitive microcapsules of claim 1, wherein the one or more of the color filtering dyes or pigments present in the microcapsules is in an amount by weight of about 0.01 to about 3 parts per 100 parts of core, or about 0.01 to about 3 parts per 100 parts of internal phase.

19. 2. The photosensitive microcapsules of claim 1, wherein when the photosensitive microcapsules are green- or red-sensitive microcapsules and the one or more color filtering dyes or pigments are yellow (blue-absorbing) color filtering dyes or pigments, the absorption optical density of the yellow 0 (blue-absorbing) color filtering shell is from about 0.005 to about 0.3, preferably from about 0.05 to about 0.2, in the range of 450 to 500 nm.

20. 2. The photosensitive microcapsules of claim 1, wherein when the photosensitive microcapsules are blue- or red-sensitive microcapsules and the one or more color filtering dyes or pigments are magenta (green-absorbing) color filtering dyes or pigments, the absorption optical density of the magenta (green-absorbing) color filtering shell is from about 0.005 to 0.3, preferably from about 0.05 to about 0.2, in the range of 550 to 600 nm.

21. 10. The photosensitive microcapsule of claim 1, wherein the core does not contain any color filtering dyes or pigments.

22. The photosensitive microcapsule of claim 1 , wherein the core further comprises a radical inhibitor, retarder, or antioxidant.

23. The radical inhibitor, antioxidant, or retarder is selected from the group comprising phenols, anilines, N-oxides of hindered amines, CuO, copper dithiocarbamates, copper or manganese carboxylates, and thiuram (thiocarbamoyl) derivatives having the following chemical formula: 【Chemistry 1】 In the formula, R １ , R ２ , R ３ , and R ４ and are independently an alkyl group having 1 to 8 carbon atoms or a phenyl group.

24. 10. The photosensitive microcapsule of claim 1, wherein the radical inhibitor, retarder, or antioxidant is present in a concentration of about 0.1 to about 1.0 parts per 100 parts of monomer of the internal phase by weight.

25. 25. The photosensitive microcapsule of claim 24, wherein the radical inhibitor, retarder, or antioxidant is present in a concentration of about 0.3 to 0.8 parts per 100 parts of monomer of the internal phase by weight.

26. The photosensitive microcapsule of claim 1 , wherein the core further comprises a coinitiator, an oxygen scavenger, or an autoxidizer.

27. a first substrate; a photosensitive microcapsule layer comprising photosensitive microcapsules in contact with the first surface of the first substrate; The photosensitive microcapsules are A color filtering shell; a core comprising a leuco dye, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material.

28. 28. The microcapsule imaging sheet according to claim 27, wherein the microcapsule imaging sheet is a full-color imaging sheet comprising photosensitive microcapsules including red-photosensitive microcapsules, green-photosensitive microcapsules, and blue-photosensitive microcapsules.

29. 28. The microcapsule imaging sheet of claim 27, wherein the photosensitive microcapsule layer further comprises a developer.

30. 30. The microcapsule imaging sheet of claim 27, wherein the photosensitive microcapsule layer further comprises a separate developer layer.

31. 28. The microcapsule imaging sheet of claim 27, further comprising a developer layer in contact with (i) the microcapsule layer, and / or (ii) the developer substrate.

32. 32. The microcapsule imaging sheet of claim 31, wherein the developer substrate is polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, polyolefin, cyclic olefin copolymer (COC), cellulose acetate, or a copolymer, blend, or composite thereof.

33. 1. A method of imaging or printing, comprising:

28. Imagewise exposing the imaging sheet of claim 27 to heat or radiation, exposing, wherein the exposure is sufficient to harden or soften the microcapsules in the microcapsule layer to produce a latent image; developing said latent image by pressure and / or heat to release said leuco dye or dye precursor to form an image.

Images