CROSSTALK REDUCTION OF MICROCAPSULE IMAGING SYSTEM
20240184198 ยท 2024-06-06
Assignee
Inventors
Cpc classification
G03F7/002
PHYSICS
G03F7/105
PHYSICS
C09B67/0097
CHEMISTRY; METALLURGY
International classification
G03F7/00
PHYSICS
Abstract
Microcapsules including a color-filtering shell and a core comprising a leuco dye or dye precursor, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material are provided for use in microcapsule imaging sheets. The imaging sheets including such microcapsules reduce undesirable crosstalk among the microcapsules of various colors and provide significantly improved color fidelity of the image thus reproduced.
Claims
1. A photosensitive microcapsule for a microcapsule imaging sheet, 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.
2. 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. 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. 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. The photosensitive microcapsule of claim 1, wherein the photoinitiator or photosensitizer is IR-sensitive and the color of the color-filtering shell is cyan, magenta, yellow or any combination thereof.
6. The photosensitive microcapsule of claim 1, wherein the photohardenable material comprises a photopolymerizable or crosslinkable monomer or oligomer.
7. The photosensitive microcapsule of claim 6, wherein the polymerizable or crosslinkable monomer or oligomer is selected from a multifunctional acrylate or methacrylate, multifunctional vinyl ether, multifunctional allyl or vinylbenzene, and the oligomer, dendrimer or a blend thereof.
8. The photosensitive microcapsule of claim 1, wherein the photosoftenable material comprises a photodegradable or photo-depolymerizable polymer.
9. The photosensitive microcapsule of claim 1, wherein the leuco dye is a cyan, magenta, yellow, black leuco dye, or any combination thereof.
10. The photosensitive microcapsule of claim 1, wherein the photoinitiator is a borate of cyanine, semi-cyanine borate, triarylmethane, squarylium or thiopyrylium dyes.
11. The photosensitive microcapsule of claim 1, wherein the photoinitiator or photosensitizer comprises a UV-sensitive, blue-sensitive, green-sensitive, red-sensitive or near-IR-sensitive photoinitiator or sensitizer.
12. The photosensitive microcapsule of claim 1, wherein the photosensitive microcapsule is sensitive to a specific color or a specific range of radiation spectrum, and the shell comprises one or more of a color-filtering dye or pigment that allows a wavelength corresponding to the color or a range of radiation spectrum to pass through to the core but selectively absorbs or filters off all or a portion of the radiation outside of the specific color or range.
13. The photosensitive microcapsule of claim 12, wherein the one or more of color-filtering dye or pigment is bleachable, including thermally bleachable or photo-bleachable.
14. The photosensitive microcapsule of claim 12, wherein the one or more of color-filtering dye or pigment comprises a functional group to react with one or more shell-forming materials.
15. The photosensitive microcapsule of claim 14, wherein the functional group is selected from a group comprising OH, SH, NH.sub.2, NHR, CONH.sub.2, NCO, NCS, CH.sub.2OH, CH.sub.2OR, CHO, and their precursors, wherein R is alkyl, aryl, arylalkyl, alkylaryl or their heteroatom derivatives.
16. The photosensitive microcapsule of claim 14, wherein the one or more shell-forming materials are included in the internal phase and/or external phase and form a shell by interfacial polymerization or crosslinking during the microencapsulation process.
17. 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. The photosensitive microcapsule of claim 1, wherein the one or more of a color-filtering dye or pigment present in the microcapsule is in amount of from about 0.01 to about 3 parts per hundred core or parts per hundred internal phase by weight.
19. The photosensitive microcapsule of claim 1, wherein when the photosensitive microcapsules are green-sensitive or red-sensitive microcapsules and the one or more color-filtering dye or pigment is a yellow (blue-absorbing) color-filtering dye or pigment, the absorption optical density of the yellow (blue-absorbing) color-filtering shell is from about 0.005 to about 0.3 in the 450 to 500 nm range, preferably from about 0.05 to about 0.2.
20. The photosensitive microcapsule of claim 1, wherein when the photosensitive microcapsules are blue-sensitive or red-sensitive microcapsules and the one or more color-filtering dye or pigment is a magenta (green-absorbing) color-filtering dye or pigment, the absorption optical density of the magenta (green-absorbing) color-filtering shell is from about 0.005 to 0.3 in the 550 to 600 nm range, preferably from about 0.05 to about 0.2.
21. The photosensitive microcapsule of claim 1, wherein the core does not comprise any color-filtering dye or pigment.
22. The photosensitive microcapsule of claim 1, wherein the core further comprises a radical inhibitor, retarder or antioxidant.
23. The photosensitive microcapsule of claim 22, wherein the radical inhibitor, antioxidant, or retarder is selected from a group comprising phenols, anilines, N-oxide of hindered amines, CuO, copper dithiocarbanate, copper or manganese carboxylates, and thiuram (thiocarbanoyl) derivatives, including ##STR00004## wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is independently an alkyl group having the carbon number of 1 to 8 or a phenyl group.
24. The photosensitive microcapsule of claim 1, wherein the radical inhibitor, retarder or antioxidant is present in a concentration of from about 0.1 to about 1.0 parts per hundred monomers in the internal phase by weight.
25. The photosensitive microcapsule of claim 24, wherein the radical inhibitor, retarder or antioxidant is present in a concentration of from about 0.3 to 0.8 parts per hundred monomers in the internal phase by weight.
26. The photosensitive microcapsule of claim 1, wherein the core further comprises a co-initiator, an oxygen scavenger or an auto-oxidizer.
27. A microcapsule imaging sheet, comprising: a first substrate; and a photosensitive microcapsule layer comprising photosensitive microcapsules in contact with a first surface of the first substrate, wherein the photosensitive microcapsules comprise: a color-filtering shell; and a core comprising a leuco dye, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material.
28. The microcapsule imaging sheet of claim 27, wherein the microcapsule imaging sheet is a full-color imaging sheet comprising photosensitive microcapsules including red-sensitive, green-sensitive, and blue-sensitive microcapsules.
29. The microcapsule imaging sheet of claim 27, wherein the photosensitive microcapsule layer further comprises a developer.
30. The microcapsule imaging sheet of claim 27, wherein the photosensitive microcapsule layer further comprises a separate developer layer.
31. The microcapsule imaging sheet of claim 27, further comprising a developer layer in contact with: (i) the microcapsule layer; and/or (ii) a developer substrate.
32. The microcapsule imaging sheet of claim 31, wherein the developer substrate is a polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, polyolefins, cyclic olefin copolymers (COC), cellulose acetates, or a copolymer, blend or composite thereof.
33. A method of imaging or printing, the method comprising: image-wise exposing an imaging sheet according to claim 27 to heat or radiation, wherein the exposing is sufficient to harden or soften the microcapsules in the microcapsule layer to produce a latent image; and developing the latent image by pressure and/or heat to release the leuco dye or dye precursor and form an image.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] Various objects, aspects, features, and advantages of the disclosure will become more apparent and better understood by referring to the detailed description taken in conjunction with the accompanying figures.
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DETAILED DESCRIPTION
[0064] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present technology. Particular exemplary embodiments of the present technology may be implemented without some or all of these specific details. In other instances, certain process operations have not been described in detail but would be understood by the skilled person in the art.
[0065] Disclosed herein is improved full-color microcapsule imaging system in which the photosensitive microcapsules comprise a color-filtering shell or a shell capable of filtering off incipient light of undesirable wavelengths.
[0066] In some embodiments, the microcapsule imaging system described herein may comprise any or all of the combinations of the microcapsules listed below: [0067] 1. A red (?.sub.1)-sensitive microcapsule comprising a cyan leuco dye in the photo-harden-able core and a color filtering shell to filter off non-red (non-?.sub.1) light such as UV, blue and/or green light. [0068] 2. A green (?.sub.2)-sensitive microcapsule comprising a magenta leuco dye in the photo-harden-able core and a color filtering shell to filter off non-green (non-?.sub.2) light such as UV, blue and/or red light. [0069] 3. A blue (?.sub.3)-sensitive microcapsule comprising a yellow leuco dye in the photo-harden-able core and a color filtering shell to filter off non-blue (non-?.sub.3) light such as UV, green and/or red light.
[0070] The red (R), green (G) and blue (B) lights/colors and cyan (C), magenta (M) and yellow (Y) colors mentioned above are given as one of the examples since they are typically used in a complementary-color imaging system. In a false-color imaging system, various light source (?.sub.1, ?.sub.2, and ?.sub.3) including UV and near IR light may be used as long as they are well separated from one another to ensure a good color separation.
[0071] The microcapsules comprising the color-filtering shell described herein greatly reduce undesirable crosstalk among the microcapsules of various color and significantly improve the color fidelity of the image thus reproduced. This is particularly advantageous for digital imaging systems since the microcapsules described herein greatly reduce the need to select light sources of emission wavelengths perfectly matched to the spectrum sensitivities of the photosensitizers/initiators used in the microcapsules. Fine-tuning the emission spectra of the light sources such as LEDs or OLEDs or the absorption spectra of the photosensitizers/initiators while maintaining their quantum efficiency is challenging. The microcapsules described herein provide an effective and low-cost solution to reduce undesirable crosstalk and improve color image fidelity of imaging systems.
[0072] The image quality of a photosensitive imaging system is heavily dependent on the spectra sensitivities of the three microcapsules and the emission spectra of the light sources used. As discussed above, there is significant overlap in the absorption spectra of commonly used red (R)- and green (G)- and blue (B)-sensitive photoinitiators, such as cyanine borate photoinitiators as well as overlaps of emission spectra of broad band light sources (e.g., R-, G- and B-OLED used in a OLED display and R-, G-, B-light passing through color filters in LCD displays). For such photoinitiators, there is significant overlap of the absorption spectra of B- and G-photoinitiators in the 440?500 nm range. Similarly, there is also significant overlap of the absorption spectra of G- and R-photoinitiators in the 540?600 nm range. As such, exposing the imaging sheet with a light of wavelength in the overlap range causes crosstalk by hardening more than one types of capsules.
[0073] To further illustrate the impact of crosstalk on the image quality, particularly the fidelity of the color reproduction process, a microcapsule imaging sheet comprising three types of microcapsules, each containing one of three (R-sensitive, G-sensitive and B-sensitive) photoinitiators and three complementary cyan (C), magenta (M) and yellow (Y) leuco dyes, respectively, is exposed or written with one of the three light sources (e.g., R-, G-, or B-OLED or LED). In the ideal scenario, after being written by a red (Xi) light, only the R-sensitive microcapsules are hardened and the release of C-leuco dye encapsulated therein is reduced as a function of the red energy received by the red-sensitive microcapsules. The G-sensitive and B-sensitive microcapsules should remain intact and be free of any photoreactions by the R-light exposure. The corresponding M- and Y-leuco dyes enclosed in the G- and B-sensitive microcapsules, respectively, can be released freely to 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 well balanced. Similarly, exposing the imaging sheet with a green (?.sub.2) light, only the green image of the source image is reproduced. And, exposing the imaging sheet with a blue ?.sub.3 light, only the blue image of the source image is reproduced.
[0074] The fidelity of the color reproduction process can deteriorate if any crosstalk of the photoreactions occurs, e.g., if more than one type of microcapsules is hardened when the system is written by only one light source. The color of the printed image is then contaminated by unwanted color(s) and the color gamut is significantly deteriorated.
[0075] As discussed above, one approach for improving the fidelity of the color reproduction process is to utilize photosensitizers/initiators of a narrow and well-separated spectra sensitivity and light sources of narrow bandwidth and well-separated emission spectra appropriately matched to the spectrum sensitivity of the corresponding photosensitizers/initiators. Such a technique aids in a high-quality color reproduction. However, most photosensitizers/initiators exhibit very broad spectra sensitivities and most readily available modulate-able light sources exhibit either very broad or mismatched emission spectra. There are only few limited choices of commercially available narrow-band LEDs or lasers with reasonably acceptable ?max, size and power efficiency and the cost is often very high for printing applications, particularly for portable printing applications. Also, it is extremely difficult, if not impossible, to find a set of R- and G- and B-photoinitiators with a reasonably narrow band absorption spectrum, aside from cyanine borate photoinitiators. Lastly, such systems require high quantum efficiency of the photosensitizers/initiators and high-power output of light sources that tend to make any high-speed printing application difficult to implement and costly.
Photosensitive Microcapsules
[0076] As described herein the photosensitive microcapsules comprise a color-filtering shell, and a core comprising a leuco dye or dye precursor, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material.
[0077] Specifically, in one or more embodiments, the photosensitive microcapsule is sensitive to a specific color or a specific range of radiation spectrum, and the shell comprises one or more of a color-filtering dye or pigment that allow a wavelength corresponding to the color or a range of radiation spectrum to pass through to the core but selectively absorb or filter off all or a portion of the radiation outside of the specific color or range. In some embodiments, the specific color or range is red, green, blue, cyan, magenta or yellow. In some embodiments, the range of radiation spectrum is 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.
[0078] The color-filtering shells may be prepared by adding one or more color-filtering dyes or pigments during the shell formation step(s) of microencapsulation processes. For example, a water soluble or dispersible color-filter dye or pigment may be introduced into the aqueous phase during the pre-wall formation by adsorption or interfacial polymerization/crosslinking and/or coacervation processes to graft or embed the dyes/pigments on or in the pre-wall. Alternatively, the dyes or pigments may be introduced during the second wall formation by in-situ polymerization and/or phase separation processes. A color filtering dye or pigment with a reactive functional group, such as NH, NH.sub.2, OH, SH, COOH, CONH, CONH.sub.2, CSNH, CSNH.sub.2 and the like, to react or graft with the shell formation materials is particularly useful. The unreacted or un-embedded color-filtering dyes or pigments in the aqueous phase were removed by for example, repetitive centrifuging and washing the resultant microcapsules.
[0079]
[0080] The color filtering shell described herein filters off part of or all of the light of unwanted wavelengths but allows the light of the right wavelength to pass through and trigger the photoreactions in the core. For example, a green-sensitive microcapsule comprising a magenta leuco dye, a green sensitive photoinitiator and a shell comprising a yellow dye or pigment as the color filtering material will screen off the unwanted blue light (the complementary light of yellow color) in the shell and allow green light to pass through and harden the core. Similarly, by replacing the yellow dye or pigment in the shell by a cyan dye or pigment, the unwanted red light (the complementary light of cyan color) is screened off. And, if both yellow and cyan dyes/pigments are used in the shell of the green-sensitive microcapsule, both the unwanted blue and red light are screened off.
[0081] As such, the color-filtering dyes/pigments in the shell protects the core from being hardened by a wrong light source even if the photosensitizer/initiator in the core may be somewhat sensitive to the wrong light. As demonstrated in the Examples, this resulted in a significant reduction of undesirable crosstalk and greatly improved the color fidelity of the color printing process. Moreover, the color of the color-filtering dyes or pigments are hardly seen after the imaging sheet is developed by, for example, pressure and/or heat, since they are immobilized by the network of the shell, and their color(s) are effectively hidden underneath the printed images in the developer layer (see
[0082]
[0083] Upon image-wise exposure, the microcapsules are selectively hardened or softened. The dye (e.g., a leuco dye) enclosed in the microcapsules are selectively released from the ruptured microcapsule 7 in the pressure/heat development step, and undergoes a chemical transformation, transitioning from a colorless state to a color state (e.g., magenta, cyan, or yellow).
[0084] In some embodiments, the one or more of color-filtering dye or pigment comprises a functional group to react with one or more shell-forming materials. In some embodiments, the functional group is selected from a group comprising OH, SH, NH.sub.2, NHR, CH.sub.2OH, CH.sub.2OR, CHO, CONH.sub.2, CONHR, urea, thiourea, isocyanate, thioisocyanate, epoxide, and their precursors, wherein R is alkyl, aryl, arylalkyl, alkylaryl or their heteroatom derivatives, particularly those with a short chain length. In some embodiments, the functional group is selected from a group comprising OH, SH, NH.sub.2, NHR, CONH.sub.2, NCO, NCS, CH.sub.2OH, CH.sub.2OR, CHO, and their precursors, wherein R is alkyl, aryl, arylalkyl, alkylaryl or their heteroatom derivatives, particularly those with a short chain length. In some embodiments, the color-filtering dye or pigment comprising the functional group is water soluble or dispersible and is included in the aqueous phase (the external phase) and incorporated into or onto the shell of the microcapsules by adsorption or interfacial reactions.
[0085] In some embodiments, the one or more shell-forming materials are included in the internal phase or oil phase and form a shell by interfacial polymerization or crosslinking during the microencapsulation process. In some embodiments, the one or more shell-forming materials are included in the internal phase 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 phases are selected from a group comprising multifunctional isocyanate, thioisocyanate, and epoxide, or their precursors.
[0086] In some embodiments, the one or more shell-forming materials are included in the external phase or aqueous phase and form a shell by interfacial or in-situ polymerization or crosslinking, phase separation, or coacervation during the microencapsulation process. In some embodiments, the one or more shell-forming materials in the external phase or aqueous phase are water-soluble compounds comprising reactive functional groups including but are not limited to, OH, SH, NH.sub.2, NHR, COOH, CH.sub.2OR, CHO or their precursors, wherein R is alkyl, aryl, arylalkyl, alkylaryl or their heteroatom derivatives, particularly those with a short chain length. In some embodiments, the one or more shell-forming materials are selected from a group comprising urea, amine, urea formaldehyde, melamine formaldehyde, poly(N-methylol acrylamide), gelatin, gum arabic, pectin, carboxylate methyl cellulose and their oligomers, copolymers or blends thereof.
[0087] In some embodiments, the photoinitiator or photosensitizer is red-sensitive and the color of the color filtering shell is magenta, yellow or their combinations. In some embodiments, the photoinitiator or photosensitizer is green-sensitive and the color of the color-filtering shell is cyan, yellow, or any combination thereof. In some embodiments, the photoinitiator or photosensitizer is blue-sensitive and the color of the color-filtering shell is magenta, cyan, or any combination thereof. In some embodiments, the photoinitiator or photosensitizer is IR-sensitive and the color of the color-filtering shell is cyan, magenta, yellow or any combination thereof.
[0088] In some embodiments, the color-filtering shell comprises one or more of a color-filtering dye or pigment. In some embodiments, the color-filtering dye is thermo- or photo-bleachable. For blue sensitive microcapsules, the color-filtering dye or pigment may be a magenta (green-absorbing) and/or cyan (red-absorbing) dye or pigment. For the green-sensitive microcapsules, the color-filtering dye or pigment is a yellow (blue-absorbing) and/or cyan (red-absorbing) dye or pigment. In some embodiments, color-filtering dye or pigment is Yellow Pigment 155 or CI Direct Yellow 86. For red-sensitive microcapsules, the color-filtering dye or pigment is a yellow (blue-absorbing) and/or magenta (green-absorbing) dye or pigment for the red-sensitive microcapsules. In some embodiments, the color-filtering dye or pigment is Pigment Violet 19 or CI Dispersed Red 60.
[0089] Illustrative examples of suitable color-filtering dye or pigments include, but are not limited to, cyanine or semicyanine dyes, quinacridone dyes, perelene dyes. Cyan, magenta and yellow dyes or pigments used in inkjet printing are particularly suitable. They are readily available from suppliers such as Cabot, Kolorjet Chemicals, Sun Chemicals, and Kao Collins, Inc. Reviews of inkjet printing dyes/pigments include P. Gregory, High-Technology Applications of Organic Colorants, Plenum Press, New York, 1991; P. Gregory, Colorants For Electronic Printers, in J.A.G. 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).
[0090] In some embodiments, the one or more of a color-filtering dye or pigment present in the microcapsule is in amount of from about 0.01 to about 3 phi (parts per hundred internal phase or parts per hundred core 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 hundred core. In some embodiments, the one or more of a color-filtering dye or pigment present in the microcapsule is in amount of from about 0.05 to about 1.0 phi.
[0091] In some embodiments, when the photosensitive microcapsules are green-sensitive or red-sensitive microcapsules and the one or more color-filtering dye or pigment comprises a yellow (blue-absorbing) color-filtering dye or pigment, the total absorption optical density of the one or more yellow (blue-absorbing) color-filtering dye/pigment in the about 450 nm to about 500 nm range is from about 0.005 to about 0.3. In some embodiments, the total optical density of the one or more yellow (blue-absorbing) color-filtering dye/pigment in the about 450 nm to about 500 nm range is from about 0.05 to about 0.2.
[0092] In some embodiments, when the photosensitive microcapsules are green-sensitive and the one or more color-filtering dye or pigment comprises a cyan (red-absorbing) color-filtering dye or pigment, the total absorption optical density of the one or more cyan (red-absorbing) color-filtering dye/pigment in the about 600 nm to about 650 nm range is from about 0.005 to about 0.3. In some embodiments, the total optical density of the one or more cyan (red-absorbing) color-filtering dye/pigment in the about 600 nm to about 650 nm range is from about 0.05 to about 0.2.
[0093] In some embodiments, when the photosensitive microcapsules are blue-sensitive or red-sensitive microcapsules and the one or more color-filtering dye or pigment comprises a magenta (green-absorbing) color-filtering dye or pigment, the total absorption optical density of the one or more magenta (green-absorbing) color-filtering dye or pigment in the about 500 nm to about 600 nm range is from about 0.005 to about 0.3. In some embodiments, the total optical density of the one or more magenta (green-absorbing) color-filtering dye or pigment in the about 500 nm to about 600 nm range is from about 0.05 to about 0.2.
[0094] It is worth noting that the red (R), green (G) and blue (B) lights/colors and cyan (C), magenta (M) and yellow (Y) colors mentioned above are given as non-limiting examples since they are typically used in a complementary-color imaging system. In a false-color imaging system, various light sources (?.sub.1, ?.sub.2, and ?.sub.3) including UV and near IR lights may be used as long as they are well separated from one another to ensure good color separation.
[0095] In some embodiments, the photosensitive microcapsule has an average diameter or D.sub.50 from about 4.0 ?m to about 9.0 ?m, 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 ?m. In some embodiments, the photosensitive microcapsule has an average diameter or D.sub.50 from about 5.0 ?m to about 6.5 ?m.
[0096] Further, the inventors of the present disclosure discovered that incorporating a color-filtering dye/pigment in the core of the microcapsules resulted in a contaminated color. Without wishing to be bound by theory, it is believed that a soluble or dispersed dye/pigment in the core was released at the same time as the leuco dye(s) and monomer(s) upon pressure/heat development to the developer layer, and its color would be seen by the viewer unless the color-filtering dye/pigment can be bleached effectively after the development. In fact, the presence of a color-filtering dye or pigment in the core may also undesirably broaden the spectrum sensitivity of the microcapsules and cause crosstalk of the microcapsule imaging system particularly if the color-filtering dye or pigment itself also exhibits some degree of photosensitivity in the unwanted wavelength range via for example, an energy or electron transfer mechanism. In some embodiments, the core does not comprise (that is, lacks) any color-filtering dye or pigment.
[0097] As described herein the photosensitive microcapsules comprise a color-filtering shell; and a core comprising a leuco dye, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material.
[0098] Enclosed by the color-filtering shell or shells, each photosensitive microcapsule comprises a core comprising 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, a representative magenta leuco dye may include PERGASCRIPT? Red I6B (CAS: 50292-95-0, Synamedia-chem); COPIKEM 35 (CAS: 50292-91-6), Blue I-2G and Blue-63 from BASF, Blue 220, Blue 203, Red 500, Red 40 or Black 305 from Yamada, JYDY-1, JYDR-2, JYDR-3, JYDB-1, or JYDB-2 from WuXi Jiayida New Materials, Red-16, O-C6, or O-C8 from Synmedia Chemicals, or ODB-2 from Anyang General Chemicals. Additional suitable examples of leuco dyes are disclosed in, e.g., CHEMISTRY AND APPLICATIONS OF LEUCO DYES (R. Muthyala ed., 1997).
[0099] Suitable photoinitiators or photosensitizers include borate complexes which may be represented by the general structure:
##STR00002##
wherein D.sup.+ is a cationic chromophore, such as a cyanine, semicyanine, squaraine (e.g., squarylium), thiopyrylium, or triarylmethane. In some embodiments, R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are each independently a substituted or unsubstituted alkyl, arylalkyl, or aryl group. In some embodiments, R.sup.1 is an alkyl or arylalkyl group, and R.sup.2, R.sup.3, and R.sup.4 are aryl groups. In some embodiments, the one or more photoinitiators comprise one or more of ketocoumarins, benzylidene ketones, benzophenones, thioxanthones, acrylphosphine oxides, metallocene derivatives and other Norrish Type I, II and III photoinitiators, and combinations thereof.
[0100] The photoinitiator may be a red-sensitive, green-sensitive, or blue-sensitive cyanine borate, semi-cyanine borate, or ketocoumarin. In some embodiments, the photoinitiator is a borate of cyanine, semi-cyanine borate, triarylmethane, squarylium or thiopyrylium dye. In some embodiments, photoinitiator or photosensitizer comprises a UV-sensitive, blue-sensitive, green-sensitive, red-sensitive, or near-IR-sensitive photoinitiator or sensitizer.
[0101] The photohardenable material may comprise a photopolymerizable or crosslinkable monomer or oligomer. In some embodiments, the polymerizable or crosslinkable monomer or oligomer is selected from a multifunctional acrylate or methacrylate, multifunctional vinyl ether, multifunctional allyl or vinylbenzene, and the oligomer, dendrimer or blend thereof. The multifunctional acrylate may be pentaerythritol triacrylate (PETA-3), pentaerythritol tetra-acrylate (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 comprise a photodegradable or photo-depolymerizable polymer.
[0102] In some embodiments, the core further comprises a radical inhibitor, retarder, or antioxidant. In some instances, a retarder or radical inhibitor is used to slow down the photospeed of a particular type of the R-, G- or B-photosensitive microcapsules to reduce even further the degree of crosstalk of the microcapsules with a color-filtering shell.
[0103] The radical inhibitor, antioxidant, or retarder may be selected from a group comprising phenols, anilines, N-oxide of hindered amines, CuO, copper dithiocarbamate, copper or manganese carboxylates, and thiuram (thiocarbanoyl) derivatives, or combinations thereof, such as
##STR00003##
wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is independently an alkyl group having the carbon number of 1 to 8 or a phenyl group.
[0104] The radical inhibitor may be a phenol radical inhibitor selected from a list comprising alkyl gallate, butyl hydroxy anisole, 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-4hydroxyphenyl)propanoyl]-oxy}methyl)-propyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate (IRGANOX? 1010), 1,2-Bis(3,5-di-tert-butyl-4-hydroxyhvdrocinnamoyl)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-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl esters (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-butyl)-4-hydroxyphenyl)methyl) ethylphosphonate) (IRGANOX? 1425), 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.
[0105] The radical inhibitor may be a N-oxide of hindered amine, wherein the hindered amine is selected from the list comprising bis(2,2,6,6,-tetramethyl-4-piperidyl)sebaceate (Tinuvin 770 DF), bis(1,2,2,6,6pentamethyl-4-piperidyl) sebacate (ADK STAB LA-72), tetrakis(2,2,6,6-tetramethyl-4-piperidyl) butane-1,2,3, Atetracarboxylate (ADK STAB LA-57), and bis(1-undecanoxy-2,2,6,6-tetramethylpiperidin-4-yl)carbonate (ADK STAB LA-81).
[0106] The radical inhibitor, retarder or antioxidant may be present in a concentration of from about 0.01 to about 1 part per hundred 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 4, about 0.6, about 0.7, about 0.8, about 0.9, and about 1.0 per hundred monomers in the internal phase by weight. In some embodiments, the radical inhibitor, retarder or antioxidant is present in a concentration of from about 0.3 to 0.5 part per hundred monomers in the internal phase by weight.
[0107] In some embodiments, the radical inhibitor, retarder or antioxidant is present in a concentration of from about 0.1 to about 1.0 parts per hundred monomers in the internal phase by weight. In some embodiments, the radical inhibitor, retarder or antioxidant is present in a concentration of from about 0.05 to 0.8 parts per hundred monomers in the internal phase by weight. In some embodiments, the radical inhibitor, retarder or antioxidant is present in a concentration of from about 0.3 to about 0.8 phi. In some embodiments, the radical inhibitor, retarder or antioxidant is present in a concentration of from about 0.1 to 0.6 phi.
[0108] The core may further comprise one or more of a co-initiator, an oxygen scavenger or an auto-oxidizer, alone or in any combination. For instance, a co-initiator, oxygen scavenger or auto-oxidizer may be used to accelerate the photospeed of a particular type of the R-, G- or B-photosensitive microcapsules to further reduce the degree of crosstalk of the microcapsules with a color-filtering shell.
Microcapsule Imaging Sheet
[0109] Also described herein is a microcapsule imaging sheet, comprising: a first substrate; and a photosensitive microcapsule layer comprising photosensitive microcapsules in contact with a first surface of the first substrate, wherein the photosensitive microcapsules comprise a color-filtering shell and a core comprising a leuco dye, a photoinitiator or photosensitizer, and a photohardenable or photosoftenable material.
[0110] The photosensitive microcapsule layer may comprise one or more types of microcapsules. For instance, 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.
[0111] 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.
[0112] In some embodiments, any one of the microcapsule imaging sheet described herein further comprises an adhesive layer between the developer layer and the microcapsule layer.
[0113] In some embodiments, any one of the microcapsule imaging sheet described herein further comprises a primer layer between the microcapsule layer and the first substrate.
[0114] The microcapsule imaging sheets described herein have an increase or improved color gamut and/or fidelity of color reproduction of the original image.
Substrates
[0115] The microcapsules described herein may be coated onto a substrate (e.g., a first or second substrate). The substrate may be any suitable material with sufficient thickness, flexibility, reflectivity (e.g., hiding power), and durability to record printed media (e.g., images). In some embodiments, the substrate is white or transparent. The substrate may be a polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, polyolefins, cyclic olefin copolymers (COC), cellulose acetates, or a copolymer, blend or composite thereof. For example, a commercially available PET substrate is MELINEX? 339 made by Dupont Teijin Films (PET339). Other useful commercially-available PET films include, but not limited to, HOSTAPHAN? polyester films (Mitsubishi Polyester Film), MELINEX? (DuPont Teijin Films?), and MYLAR? polyester films (DuPont Teijin Films?). The substrate may be in contact with the microcapsule layer, the developer layer, or both.
[0116] The substrate may have any suitable thickness. In some embodiments, the substrate has a thickness of about 10 ?m, about 20 ?m, about 30 ?m, about 40 ?m, about 50 ?m, about 60 ?m, about 70 ?m, about 80 ?m, about 90 ?m, about 100 ?m, about 150 ?m, about 200 ?m, about 250 ?m, about 300 ?m, about 350 ?m, about 400 ?m, about 450 ?m, about 500 ?m, or any range or value therein between.
Developer Layer
[0117] In some embodiments, imaging sheets according to the present disclosure include a developer layer that is contact with the microcapsule layer and/or the developer substrate. The developer layer may be placed in contact with the microcapsule layer by for example, lamination after being applied to the second substrate. In some embodiments, the developer layer may be over-coated onto the microcapsule layer and the resultant over-coated sheet is used as is without the second substrate. In some embodiments, the over-coated developer/microcapsule sheet may be further over-coated with a durable protective coating or laminated with a second substrate. In some embodiments, the composition of the developer layer may be pre-mixed with the composition of the microcapsule layer and coated as a single layer onto the first substrate.
[0118] In some embodiments, imaging systems according to the present disclosure comprise two separate sheets, a photosensitive microcapsule sheet and a developer sheet. The microcapsule sheet is image-wise exposed, brought to contact with the developer sheet, and subsequently developed with pressure/heat. The microcapsule sheet is discarded after the leuco dyes are transferred to the developer sheet.
[0119] In some embodiments, the developer substrate is a polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, polyolefins, cyclic olefin copolymers (COC), cellulose acetates, or a copolymer, blend or composite thereof.
[0120] In some embodiments, the developer layer comprises one or more leuco dye developers. By way of non-limiting example, the developers may comprise 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 instance, the developer(s) may comprise: acid clay, zinc 3,5-bis(alpha-methylbenzyl)salicylate (e.g., N-054-W, SANKO Co., Ltd.), zinc 3,5-di-t-butyl salicylate, zinc 3,5-dioctyl salicylate, HRJ 4542 (Schenectady Chemical), or novolac resin developers such as RD9870, RD9870A, RD9880, RD9880U, RF-118, etc. (Xinxiang Richful Lube Additive Co., Ltd.). In some embodiments, the developer layer comprises a Lewis acid, an acid clay, or one or more compounds comprising a phenol group or carboxylic acid group, or metal complex thereof. In some embodiments, developer layer comprises a novolac resin, a salicylic acid derivative, a zincate derivative thereof, or a combination, copolymer, blend, or composite thereof.
[0121] The developer layer may have any suitable thickness. For instance, the developer layer may have a thickness of at least about 1 ?m, at least about 2 ?m, at least about 3 ?m, at least about 4 ?m, at least about 5 ?m, at least about 6 ?m, at least about 7 ?m, at least about 8 ?m, at least about 9 ?m, at least about 10 ?m, at least about 15 ?m, at least about 20 ?m, at least about 25 ?m, at least about 30 ?m, at least about 35 ?m, at least about 40 ?m, at least about 45 ?m, at least about 50 ?m, or any range or value therein. In some embodiments, the developer layer has a thickness from about 1 ?m to about 30 ?m, about 2 ?m to about 20 ?m, or about 3 ?m to about 15 ?m.
[0122] The developer may be present in the developer layer at a concentration by weight, relative to the dry weight of the developer layer, of greater than or equal to about 50 wt. %, greater than or equal to about 55 wt. %, greater than or equal to about 60 wt. %, greater than or equal to about 65 wt. %, greater than or equal to about 70 wt. %, greater than or equal to about 75 wt. %, greater than or equal to about 80 wt. %, greater than or equal to about 85 wt. %, greater than or equal to about 90 wt. %, greater than or equal to about 95 wt. %, greater than or equal to about 96 wt. %, greater than or equal to about 97 wt. %, greater than or equal to about 98 wt. %, greater than or equal to about 99 wt. %, or any range or value therein between. In some embodiments, the developer layer may comprise a polymeric binder and a filler such as silica, acid clay, CaSO.sub.4, BaSO.sub.4, and TiO.sub.2.
Methods
[0123] Provided in another aspect is 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 an imaging sheet.
[0124] Provided in another aspect is 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 an imaging sheet.
[0125] Provided in another aspect is 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 microcapsule/developer mixture-coated first substrate with a second substrate. In some embodiments, the method further comprises contacting the microcapsule/developer mixture-coated first substrate with a protective overcoat.
[0126] Provided in another aspect is 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 an imaging sheet.
[0127] Provided in another aspect is a method imaging or printing, the method comprising image-wise exposing an imaging sheet according to any one of the imaging sheets described herein to heat or radiation, wherein the exposing is sufficient to selectively immobilize or mobilize the leuco dyes in the microcapsules by hardening or softening the microcapsules to produce an latent image; and developing the latent image by pressure and/or heat to form an image. In some embodiments, the exposing radiation is UV, visible, near IR or IR light. In some embodiments, the exposing radiation is UV, visible, near IR or IR light. In some embodiments, the exposing or development heat is from a thermal print head.
[0128] In some embodiments, a process of making a photosensitive microcapsule 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 comprising 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 comprising a color-filtering dye or pigment, and forming a photosensitive microcapsule by interfacial or in-situ polymerization or crosslinking, phase separation, or coacervation during the microencapsulation process.
[0129] While the foregoing terms are believed to be well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate explanation of the presently disclosed subject matter.
[0130] The term a or an may refer to one or more of that entity, i.e. can refer to plural referents. As such, the terms a or an, one or more and at least one are used interchangeably herein. In addition, reference to an element by the indefinite article a or an does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there is one and only one of the elements.
[0131] Reference throughout this specification to one embodiment, an embodiment, one aspect, or an aspect means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases in one embodiment or in an embodiment in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.
[0132] As used herein, the terms about or approximately when preceding a numerical value indicates the value plus or minus a range of 10% of the value.
[0133] As will be understood by one 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 subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as up to, at least, greater than, less than, and the like, include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member.
[0134] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the present application and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. While not explicitly defined below, such terms should be interpreted according to their common meaning.
[0135] For purposes of the present disclosure, the term color density refers to a dye's ability to absorb light, where the greater the dye's light absorption, the higher the color density (i.e., the more intense the color). The lower the dye's light absorption, the lower the color density (i.e., the less intense the color).
[0136] For purposes of this disclosure, the term maximum color density (or D.sub.max) refers to the maximum color density achieved by a dye after a given development time (e.g., after about 1 hr., about 2 hrs., about 4 hrs., about 8 hrs., about 12 hrs., about 24 hrs., etc.).
[0137] For purposes of this disclosure, the term fresh color density or fresh D.sub.max refers to the color density achieved by a dye immediately (e.g., within one second or a few seconds to several minutes, e.g., between about 1 second, about 2 seconds, about 5 seconds, or about ten seconds to about 1 minute, about 2 minutes, about 3 minutes, about 4 minutes, or about 5 minutes) upon microcapsule rupture (e.g., at the onset of color development).
[0138] For purposes of this disclosure, the term leuco dye refers to a chemical dye which can alternate between two chemical forms, one of which is colorless. The transformation from colorless to color form may be reversible or irreversible and may be induced by changes in temperature, pH, irradiation, and/or redox state.
[0139] Unless explicitly indicated otherwise, all specified embodiments, features, and terms intend to include both the recited embodiment, feature, or term and equivalents thereof.
[0140] Reference will now be made in detail to specific embodiments contemplated by the present disclosure. While various embodiments are described herein, it will be understood that the disclosure is not intended to limit the present technology to the described embodiments. On the contrary, the present disclosure is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the technology as defined by the appended claims.
EXAMPLES
Example 1. Preparation of Control Red-, Green- and Blue-Sensitive Microcapsules and Self-Containing Imaging Sheets Based on the Microcapsules
[0141] Table 1 below lists the materials used in the following Examples.
TABLE-US-00001 TABLE 1 Materials used in Example 1 Chemical Name Description Versa TL502 Sulfonated polystyrene from Nouryon Corp. CYMEL? 385 Methylated high imino melamine resin with a low degree of alkylation from Allnex Corp. NW-YOT05 Yellow (Pigment Yellow 155) water-based ink dispersion (D50 of 0.14 um) from Taiwan Nanotechnology Corporation. NW-MEA12 Magenta (Pigment Violet 19) water-based ink dispersion (D50 of 0.14 um) from Taiwan Nanotechnology Corporation. DESMODUR? N 100 Aliphatic polyisocyanate from Covestro Corp. AEROSOL? OT Sodium bis (2-ethylhexyl) sulfosuccinate surfactant from Cytec Corp. TRITON? X-114 Nonionic surfactant from Dow Corp. IRGANOX? 1035 Phenolic antioxidant and heat stabilizer from BASF GSB1202 Spacer particle from Guidewin Corp. (D.sub.50 = 11.44 ?m) CELLOSIZE? QP- Hydroxyethyl cellulose from Dow Corp. 52000H SIL WET? L-7001 Silicone surfactant from Momentive Performance Materials SIL WET? L-7604 Silicone surfactant from Momentive Performance Materials JONCRYL? 7256 Latex binder from BASF TAMOL? 731 DP A hydrophobic copolymer dispersant from Dow Corp. PVA1799 Polyvinyl alcohol from Sinochem Corp. CAB-O-SPERSE? An aqueous dispersion of CAB-O-SIL? L-90 (fumed silica) from 1015A Cabot Corp. Eastman AQ? 55S Water-dispersible polyester resin from Eastman
Preparation of Photosensitive Microcapsules
[0142] Photosensitive microcapsules were prepared using materials in Table 2, according to the following procedure: [0143] 1. Into a beaker, 220 parts of water and 8 parts of Versa TL502 sulfonated polystyrene (dry) were added and thoroughly mixed. [0144] 2. 10 parts of pectin (polygalacturonic acid methyl ester) was slowly sifted into the mixture and stirred overnight at room temperature (500?1000 rpm). [0145] 3. The pH was adjusted to 7.5 with 10% sodium carbonate, and the mixing speed was increased to 1750 rpm. [0146] 4. The internal phase as shown in Table 2 was added over a period of 15-30 seconds. The resultant mixture was stirred for 30 minutes, and 11 parts of a 9.1% aqueous solution (pH adjusted 7.0) of DETA (diethylene triamine) were added and allowed to react for 30 minutes at 25? C., followed by an hour at 40? C. [0147] 5. A solution comprising 19.9 parts of CYMEL? 385 and 40 parts of water (pH adjusted to 6.0) was added, and the mixture was allowed to react at 70? C. for an additional 2 hours. [0148] 6. 15.23 parts of a 34.3% aqueous of sodium sulfate were added, and the mixture was stirred for 10 minutes, 1.97 parts of CYMEL? 385 and 10 parts of water were added, and the mixture was allowed to react at 70? C. for an additional 1 hour. [0149] 7. The mixing speed was reduced to 600 rpm, the pH was adjusted to 9.5 using a 20% NaOH solution, and the resultant reaction mixture was stirred overnight at room temperature.
TABLE-US-00002 TABLE 2 Internal Phase of Photosensitive Sensitive Microcapsule Controls Example 1-1 Example 1-2 Example 1-3 (Control-B) (Control-G) (Control-R) Blue- Green- Red- sensitive sensitive sensitive Ingredients (Dry Parts) Microcapsule Microcapsule Microcapsule Yellow Leuco Dye (C.sub.32H.sub.36O.sub.5) CAS: 20.00 123521-47-1) from Aether industries, India Blue-sensitive photoinitiator 3-Ethyl-2-[(1- 0.15 Ethyl-3,3-dimethyl-1,3-dihydro-2H-indol-2- ylidene)-methyl]benzothiazolium (sec- Butyl)triphenylborate Magenta Leuco Dye (CAS: 50292-95-0 from 30.00 Synmedia-chem) Green photoinitiator: (1-heptyl-2-[3-(1- 0.075 heptyl-3,3-dimethyl-1,3-dihydro-2H-indol- 2-ylidene)-propenyl]-3,3-dimethyl-3H- indolium isobutyl triphenyl borate) Cyan Leuco Dye (CAS: 114090-18-5 from 13.00 NAGASE) Red-sensitive photoinitiator: 1-Heptyl-2-[5- 0.05 (1-heptyl-3,3-dimethyl-1,3-dihydro-2H- indol-2-ylidene)-penta-1,3-dienyl]- 3,3dimethyl-3H-indolium(sec- Butyl(triphenylborate) TMPTA (trimethylolpropane triacrylate) 90.00 TPGDA (tripropylene glycol diacrylate) 10.00 (EMBT) 6,6-diethoxy 0.50 mercaptobenzothiazole disulfide THEED (N,N,N,N-tetrakis(2- 0.20 hydroxyethyl)ethylenediamine) DIDMA (2,6-diisopropyl-N,N- 3.00 dimethylaniline) IRGANOX? 1035 0.15 DESMODUR? N 100 8.00 DBTDL (dibutyltin dilaurate) 0.05
Preparation of Color Developer Coating
[0150] The developer composition as shown in Table 3 was coated on a 1 mil, transparent PET film with a Myrad bar and dried in an 80? C. oven for 10 minutes with a target dry coating thickness of about 8 ?m as measured by a Mitutoyo thickness gauge.
TABLE-US-00003 TABLE 3 Composition of Developer Coating Ingredient Dry parts Resin Developer RD9870A (Richful, China) 98.00 CAB-O-SPERSE? 1015A (Cabot, USA) 0.86 PVA1799 (Sinochem, China) 1.14
Preparation of Microcapsule Coatings
[0151] The coating fluids of the R/G/B photosensitive microcapsules (Examples 1-1, 1-2 and 1-3) as shown in Table 4 were adjusted to 33 wt. % solid by D.I. water and coated on a 2 mil, white PET (MELINEX?) with a Myrad bar with a target dry coating thickness of about 8 ?m as measured by a Mitutoyo thickness gauge. The coatings were dried in an 80? C. oven for 10 minutes.
TABLE-US-00004 TABLE 4 Compositions of Microcapsule Coating Fluids Ingredient Dry parts Blue or Green or Red sensitive microcapsule (45% solid) 100.00 GSC1202 (50% solid) (Particle size, D.sub.50 = 11.44 um) 2.50 Calcium Carbonate (33% solid) (Particle size, D.sub.50 = 0.12 5.00 ?m) CELLOSIZET? QP-52000H 0.51 AEROSOL? OT 0.05 TRITON? X-114 0.20 SILWET? L*-7001 0.20 SILWET? L*-7604 0.20 TAMOL? 731 DP 2.00 JONCRYL? FLX 5040 6.00 Eastman AQ? 55S 8.00
Preparation of Imaging Sheets Comprising a Photosensitive Microcapsule Layer and a Develop Layer
[0152] The microcapsule and the developer films thus prepared were laminated together with a Tamerica roll laminator TCC2700 with the temperature, pressure and speed settings of 100? C., 3.621 Kgf/170 mm and 0.368 m/min, respectively to form various photosensitive imaging sheets.
Example 2. Preparation of Photosensitive Microcapsule with a Color-Filtering Shell and Self-Containing Imaging Sheets Based on the Microcapsules
[0153] The self-containing imaging sheets comprising various concentration of color-filtering pigment on or in the shell were prepared using the same procedures as those of Example 1 except that in step 4 of the microencapsulation procedure: (i) the resultant mixture was stirred for 30 minutes, (ii) the water-based pigment dispersions as shown in Table 5 and
TABLE-US-00005 TABLE 5 Color-filtering pigments Grafted or Embedded in or on Microcapsule Shells Pigment Green- Red- Dispersion Used sensitive sensitive (dry phi)* Example Capsules Capsules NW-YOT05 1-2 (Control-G) 0.000 (phi) (Pigment Yellow 2-1 0.244 (phi) 155) 2-2 0.488 (phi) 2-3 0.733 (phi) NW-MEA12 1-3 (Control-R) 0.000 (phi) (Pigment Violet 2-4 0.188 (phi) 19) 2-5 0.376 (phi) 2-6 0.556 (phi) *phi: Parts per hundred internal phase or parts per hundred core by weight
[0154] The chemical structures of Pigment Yellow 155 and Pigment Violet 19 are shown in
[0155] All the microcapsules thus prepared were washed extensively with water and centrifuged to remove the excess of the water-soluble polymers and additives in the aqueous phase. As can be seen clearly from Table 6, all the purified/washed microcapsules show similar particle sizing as measured by HORIBA LA-960 (Laser Scattering Particle Size Distribution Analyzer). No aggregation of microcapsules was observed either.
TABLE-US-00006 TABLE 6 Particle Size of Microcapsules As Purified D.sub.10 D.sub.50 D.sub.90 Sample (?m) (?m) (?m) 1-1 (Control-B) 4.93 7.44 11.15 1-2 (Control-G) 3.75 5.78 8.55 1-3 (Control-R) 3.32 5.59 8.83 2-1 (Green-sensitive) 3.54 5.63 8.52 2-2 (Green-sensitive) 3.67 6.07 9.48 2-3 (Green-sensitive) 3.76 6 9.18 2-4 (Red-sensitive) 3.49 5.87 9.26 2-5 (Red-sensitive) 3.34 5.64 9.06 2-6 (Red-sensitive) 3.3 5.61 8.96
Reduction of Blue-Light Induced Crosstalk of Green-Sensitive Imaging Sheets
[0156] 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 comprising yellow color-filtering shells of various concentration of the yellow pigment 155 were placed directly on a Visionox OLED panel (Model No. G1392FH101GG-003) and exposed for 20 sec through a 0-255 level (where level 0 is the darkest and level 255 is the brightest) RGB gray-scale image. The exposed imaging sheet was developed by a pressure fixture and the normalized reflective optical densities of the developed images as a function of the relative blue energy output (the Blue H-D curves) are shown in
[0157] As can be seen from
[0158] The effect of the yellow color-filtering shell comprising various concentration of yellow pigment 155 on the green photosensitivity (E.sub.10 and E.sub.90) and D.sub.max and D.sub.min is shown in Table 7.
TABLE-US-00007 TABLE 7 Effect of Yellow Color-Filtering Shell on the Photo- Functions of Green-Sensitive Imaging Sheets Yellow 155 Green Green added to the Magenta Yellow Magenta E.sub.10 E.sub.90 Red Example shell (phi) D.sub.min D.sub.min D.sub.max (Level) (Level) Exposure 1-2 0 0.03 0 2.08 36 105 No (Control-G) reaction 2-1 0.244 0.03 0.06 2.16 40 98 No (+11.1%) (?7.3%) reaction 2-2 0.488 0.02 0.11 2.06 40 105 No (+11.1%) (0%) reaction 2-3 0.733 0.03 0.2 2.12 49 112 No (+36.1%) (+6.6%) reaction The definitions of D.sub.min, D.sub.max, E.sub.10, and E.sub.90 are as below: D.sub.min: The average minimum reflective color (cyan, magenta or yellow) density in the fully exposed area D.sub.max: The average maximum color (cyan, magenta or yellow) density developed in the non-exposed area E.sub.10 (Level): Energy level (0-255) required to reduce total density (D.sub.max ? D.sub.min) by 10% E.sub.90 (Level): Energy level (0-255) required to reduce total density (D.sub.max ? D.sub.min) by 90%.
[0159] All the optical density were measured by spectrodensitometer FD-5 (Konica Minolta, MO, ISO-E) immediately after exposure, pressure development and post-heating through a heating roller at 100? C.
[0160] Table 7 shows that the color-filtering shell comprising ?0.488 phi of Pigment Yellow 155 did not show any noticeable impact (or within experimental error) on almost all photo-functions including magenta D.sub.min, yellow D.sub.min, magenta D.sub.max, Green E.sub.10 and E.sub.90. The microcapsules comprising a high concentration (?0.733 phi) of Pigment Yellow 155 (a yellow pigment commonly used in inkjet printing) in the shell showed slight increases in yellow D.sub.min and green-E.sub.10. Without being bound by theory, it is believed that too high a concentration of the yellow pigment might cause a deterioration of the crosslinking and/or the barrier property of the shell against oxygen and result in an increase in E.sub.10 (that is, a decrease in the onset photospeed).
[0161] Table 7 also shows that no hardening of all the green-sensitive imaging sheet was observed after they were fully exposed with the highest level of red light. This effect is attributable to the very limited overlap of the red emission spectrum of OLED used and the absorption spectrum of the green-photoinitiator.
Reduction of Green-Light Induced Crosstalk of Red-Sensitive Imaging Sheets
[0162] As can be seen from
[0163]
[0164] The effect of magenta color-filtering shell on the red-photosensitivity (E.sub.10 and E.sub.90) and D.sub.max and D.sub.min of red-sensitive imaging sheets comprising a cyan leuco dye (CAS: 114090-18-5) is shown in Table 8.
[0165] As can be seen from Table 8, the color-filtering shell comprising ?0.556 phi of Pigment Violet 29 did not show significant impact (or within experimental error) on almost all photo-functions including cyan D.sub.min, magenta D.sub.min, cyan D.sub.max, and red-E.sub.90. The microcapsules (Examples 2-6) comprising a high concentration (?0.556 phi) of Pigment Violet 29 (a magenta pigment commonly used in inkjet printing) in the shell showed slight increases in magenta D.sub.min and Red-E.sub.10, potentially because of the deterioration of the crosslinking and/or the barrier property of the shell against oxygen by the high loading of the pigment. It is also noted from Table 8 that no hardening of all the red-sensitive imaging sheet was observed after they were fully exposed with the highest level of blue light, mainly because the blue emission spectrum of OLED used does not overlap with the absorption spectrum of the red-photoinitiator.
TABLE-US-00008 TABLE 8 Effect of Magenta Color-Filtering Shell on the Photo-functions of Red-Sensitive Imaging Sheets Violet 29 Red- Red- Blue- added to the Cyan Magenta Cyan E.sub.10 E.sub.90 light Example shell (phi) D.sub.min D.sub.min D.sub.max (level) (level) Exposure 1-3 0.000 0.03 0.00 1.89 42 114 No (Control-R) Reaction 2-4 0.188 0.04 0.05 1.92 50 114 No (+19.0%) (0%) Reaction 2-5 0.376 0.06 0.11 1.98 50 118 No (+19.0%) (+3.5%) Reaction 2-6 0.556 0.07 0.13 1.97 51 123 No (+21.4%) (+7.9%) Reaction
Example 3 Green- and Red-Sensitive Microcapsules Comprising a Color-Filtering Pigment in the Shell and a High Concentration of Radical Quencher in the Core
[0166] The compositions of the internal phase of the green- and red-sensitive microcapsules and the procedures for the making of microcapsules and imaging sheets are the same as those described in Examples 1 and 2 except that a high concentration (0.3-0.6 parts per hundred monomer or phm) of antioxidant IRGANOX? 1035 from BASF were added as a radical quencher or polymerization retarder/inhibitor into the cores of microcapsules. Except for the concentration of IRGANOX? 1035, the formulation of the internal phase of the green-sensitive microcapsules of Examples 3-1 and 3-2 are the same as that of Examples 2-3. Similarly, except for the concentration of IRGANOX? 1035, the formulation of the internal phase of the red-sensitive microcapsules of Examples 3-3 and 3-4) are the same as that of Example 1-3. The differences in the formulations and the D.sub.50 particle size of the microcapsules prepared accordingly are shown in Table 9. Imaging sheets based on the microcapsules were prepared using the procedures as described in Example 2 and the characteristic photo-function of the imaging sheets are shown in Tables 10 and 11 and
TABLE-US-00009 TABLE 9 Microcapsules Comprising Antioxidant IRGANOX? 1035 in the Core and Color Filtering Pigment in the Shell Example Example Example Example Example Example 2-3 3-1 3-2 2-6 3-3 3-4 Green- Green- Green- Red- Red- Red- Ingredients sensitive sensitive Sensitive Sensitive Sensitive Sensitive IRGANOX? 0.15 0.30 0.60 0.15 0.30 0.60 1035 in Internal Phase (phm) Color-Filtering Pigment in the Shell Yellow 155 (phi) 0.733 0.733 0.733 Violet 19 (phi) 0.556 0.556 0.556 Average Capsule 6.00 5.89 5.91 5.61 4.97 6.28 Size (D.sub.50), ?m
TABLE-US-00010 TABLE 10 Effect of Antioxidant IRGANOX? 1035 in the Core on the Photo-functions of Green-Sensitive Imaging Sheets Comprising 0.733 Phi of Yellow 155 in the Shell Yellow 155 Irganox 1035 Green Green Red- in the in the Magenta Yellow Magenta E.sub.10 E.sub.90 light Example shell (phi) core (phm) Dmin Dmin Dmax (Level) (Level) Exposure 2-3 0.733 0.15 0.03 0.2 2.12 49 112 No reaction 3-1 0.733 0.3 0.04 0.21 2.11 53 107 No (+8.1%) (?4.5%) reaction 3-2 0.733 0.6 0.04 0.19 2.1 52 98 No (+6.1%) (?12.5%) reaction
TABLE-US-00011 TABLE 11 Effect of Antioxidant IRGANOX? 1035 in the Core on the Photo-functions of Red-sensitive Imaging Sheets Comprising 0.566 Phi of Violet 19 in the Shell Violety 19 Irganox 1035 Red Red Blue- in the in the Cyan Magenta Cyan E.sub.10 E.sub.90 light Example shell (phi) core (phm) Dmin Dmin Dmax (Level) (Level) Exposure 2-6 0.556 0.15 0.07 0.13 1.97 51 123 No reaction 3-3 0.556 0.3 0.08 0.14 1.91 54 115 No (+5.9%) (?6.5%) reaction 3-4 0.556 0.6 0.06 0.13 1.92 67 105 No (+31.4%) (?14.6% reaction
[0167] As evident from Tables 9, 10 and 11, the increase of the concentration of the radical quencher IRGANOX? 1035 from 0.15 phm to 0.60 phm in the core did not show any noticeable impact on particle size of the microcapsules, D.sub.min and D.sub.max. However, for the green-sensitive microcapsules comprising 0.733 phi of color-filtering Yellow 155 in the shell, it resulted in a H-D curve of a higher contrast ratio with a 6.1-8.1% increase in E.sub.10 (a decrease in photospeed for the onset of the hardening of the microcapsules) and a 4.5-12.5% decrease in the E.sub.90 (an increase in the photospeed to reach the almost fully-hardened state of the microcapsules). Similarly, for the red-sensitive microcapsules comprising 0.566 phi of color-filtering Violet 19 in the shell, it resulted in a H-D curve of an even more significantly higher contrast ratio with a 5.9-31.4% increase in E.sub.10 and a 6.5-14.6% decrease in the E.sub.90. The significant alleviation of undesirable crosstalk is evident from the H-D curves shown in
[0168] 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 comprising 0.15, 0.3 and 0.6 phm, respectively of IRGANOX? 1035 as the radical quencher in the core and 0.733 phi of Yellow 155 in the shell were exposed with the blue light from a Visionox OLED panel as described in Example 2. As shown in
[0169] The effect the IRGANOX? 1035 concentration in the core of the red-sensitive imaging sheets (Examples 2-6, 3-3 and 3-4) with 0.566 phi of color-filtering Violet 19 in the microcapsule shell on the green crosstalk can also be clearly seen in
Example 4. Green- and Red-Sensitive Imaging Sheets Comprising a Color-Filtering Pigment in the Microcapsule Core
[0170] The formulations and procedures of making the self-containing imaging sheets of Examples 3-2 (green-sensitive) and 3-4 (red-sensitive) were repeated except that the color-filtering pigment Yellow 155 (0.733 phi) and Violet 19 (0.566 phi) were ground and dispersed in the internal phase and encapsulated for Example 4-1 and 4-2, respectively. The results are shown in Table 12.
TABLE-US-00012 TABLE 12 Effect of Color-Filtering Dyes/Pigments in the Core Versus in The Shell Green- Yellow 155 Yellow 155 Irganox 1035 Green Green Red- Sensitive in Shell in Core in Core Magenta Yellow Magenta E.sub.10 E.sub.90 Light Example (phi) (phi) (phm) Dmin Dmin Dmax (Level) (Level) Exposure 3-2 0.733 0.6 0.04 0.19 2.1 52 98 No reaction 4-1 0.733 0.6 0.04 0.28 2.12 59 119 No reaction Red- Violet 19 Violet 19 Irganox 1035 Red Red Blue- Sensitive in Shell in Core in Core Cyan Magenta Cyan E.sub.10 E.sub.90 light Example (phi) (phi) (phm) Dmin Dmin Dmax (Level) (Level) Exposure 3-4 0.566 0.6 0.06 0.13 1.92 67 105 No reaction 4-2 0.566 0.6 0.05 0.29 1.9 53 124 No reaction
[0171] As it can be seen clearly from Table 12 that the green-sensitive imaging sheet (Examples 3-2) comprising the yellow 155 color-filtering pigment in the shell show a significantly lower yellow D.sub.min and a sharper contrast ratio (a smaller E.sub.90-E.sub.10) than those of the imaging sheets comprising the same yellow pigment in the core (Example 4-1). It is evident that a higher concentration the yellow pigments were transferred to the developer layer in the development step and resulted in a higher yellow D.sub.min when it is included in the core. Moreover, the presence of the pigment in the core also resulted in a slower photospeed (a higher E.sub.90) to reach the D.sub.min or the fully cured state of the internal phase. Without being bound by the theory, it is believed that the pigments included in the shell tend to be immobilized in the highly crosslinked shell and resulted in a lower yellow D.sub.min as illustrated in the schematic drawing of
[0172] A lower magenta D.sub.min and a sharper contrast ratio were also observed for the red-sensitive imaging sheet of Example 3-4 in which the Violet 19 pigment was incorporated in the shell than those of the imaging sheets of Example 4-2 in which the color filtering pigment was dispersed in the core.
[0173] The compositions and methods illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. Thus, for example, the terms comprising, including, containing, etc. shall be read expansively and without limitation. Additionally, the terms and expressions employed herein have been used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof. It is recognized that various modifications are possible within the scope of the disclosure claimed. Thus, it should be understood that although the present disclosure has been specifically disclosed by preferred embodiments and optional features, modification and variation of the disclosure embodied therein herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this disclosure.
[0174] Unless the context indicates otherwise, it is specifically intended that the various features of the invention described herein can be used in any combination. Moreover, the disclosure also contemplates that in some embodiments, any feature or combination of features set forth herein can be excluded or omitted. To illustrate, if the specification states that a complex comprises components A, B and C, it is specifically intended that any of A, B or C, or a combination thereof, can be omitted and disclaimed singularly or in any combination.
[0175] The disclosure has been described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the compositions or methods. This includes the generic description of the compositions or methods with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein. The present technology is not to be limited in terms of the particular embodiments described in this application, which are intended as representative illustrations of individual aspects of the present technology. Many modifications and variations of this 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 descriptions. Such modifications and variations are intended to fall within the scope of the present technology. It is to be understood that this present technology is not limited to particular methods, compounds or compositions, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
[0176] One skilled in the art would 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 set forth non-limiting embodiments of the disclosure.
[0177] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.