Methods and compositions for the formation of highly reflective materials

Abstract

Methods and compositions for the formation of highly reflective layers through thermal decomposition of reflective inks are provided. The methods comprise the steps of providing a target substrate for coating applying the reflective ink to the target substrate, and curing the reflective ink on the target substrate to form the reflective layer. Also provided are reflective ink compositions.

Description

Patent Application 3611-00-029W01METHODS AND COMPOSITIONS FOR THE FORMATION OF HIGHEY REFEECTIVE MATERIALSCross-reference to Related Application

[0001] This application claims the benefit of U.S. Application No. 63 / 762,560, filed on February 24, 2025, the disclosure of which is incorporated herein by reference in its entirety.Field of the Invention

[0002] The present disclosure relates generally to novel methods of producing reflective metal coatings on target substrates through the thermal decomposition of novel reflective inks. The disclosure also relates to novel reflective ink formulations and to methods of using the ink formulations to prepare reflective materials containing metallic layers with highly reflective surfaces.Background of the Invention

[0003] Traditional reflective coating processes are extremely energy intensive and create several chemical residues that create environmental concerns from metal ions and metallic impurities in the process effluents as well as potentially carcinogenic organic moieties that are used in the coating process. Furthermore, traditional coating processes such as chemical vapor deposition are expensive.

[0004] Reflective materials have become indispensable in diverse sectors, providing safety and visibility in low-light conditions. These materials are a crucial key component of high-visibility clothing, preventing accidents and enhancing the overall safety of individuals working in hazardous environments or engaging in outdoor activities.Reflective materials, commonly utilized in safety apparel such as high- visibility safety vests, are designed to enhance visibility in low-light conditions. Unlike self-illuminatingsources, these materials do not generate light independently; instead, they reflect light from external sources back toward the source. This retroreflective property ensures that the wearer or object is visible in dim environments, thereby reducing the risk of accidents.

[0005] Today, reflective materials are also used in modern computing and display technologies, for example in the development and deployment of systems relating to “virtual reality” or “augmented reality” experiences. A virtual reality, or “VR”, scenario typically involves the presentation of digital or virtual image information without transparency to any actual real- world visual input. On the other hand, an augmented reality, or “AR”, scenario typically involves presentation of digital or virtual image information as an augmentation to visualization of the real world around the user. Further, reflective materials are used across numerous industries, including transportation, apparel, construction, and emergency services.

[0006] Silver and aluminum coatings are widely used in the reflective coating industry owing to their high reflectance, thermal endurance, and cost effectiveness. Most common methods of depositing reflective metal layers as described in the prior art include electron beam evaporation, chemical vapor deposition, physical vapor deposition methods, and the like. For example, U.S. Patent Publication No. 2007 / 0281136 Al to Hampden-Smith reports silver-based nanoparticle ink formulations for inkjet printed surfaces that find utility in reflective applications. U.S. Patent Publication No. 2004 / 0233463 Al to Hersch reports a method of combining reflective metallic ink and a transparent ink for application of system and security documents, certificates, and the like. U.S. Patent No. 6,078,425 to Wolfe reports durable multilayer reflective coatings that were generated by vapor depositing a reflective silver layer that was protected by a passivating layer of nickel and / or chromium.

[0007] Most widely applied methods of generating reflective metal coatings, such as chemical vapor deposition, electron beam evaporation, and the like, are energy intensive and require a high operating temperature. As a result, these processes are incompatible with target substrates that are unstable at high temperatures, and they also result in higher operating costs. It would therefore be highly desirable in the market for reflective surfaces to have a simple ink composition that can be coated on various surfaces at lower temperature without compromising the reflectivity of the resulting surface.

[0008] Much effort is therefore currently being directed toward the generation of highly-reflective surfaces at lower temperatures and with minimal processing. Recently, low temperature sol-gel mediated coating techniques have been published for preparing dense films. Bahuguna et. al. (2016) Research Journal of Chemical Science 6:65-72.

[0009] There is still, however, a need for improved methods for generating reflective surfaces through thermal decomposition, including methods that do not rely on substantiative high operating temperature and energy intensive limitations to form reflective surfaces.Summary of the Invention

[0010] In some aspects, the techniques described herein relate to a method for forming a reflective material including steps of: providing a target substrate; providing a reflective ink; applying the reflective ink to the target substrate; and curing the reflective ink to form a reflective layer on the target substrate; wherein the reflective ink includes a silver salt, a solvent, and a film-forming reagent.

[0011] In some aspects, the techniques described herein relate to a reflective ink including: a silver salt, a solvent, and a film- forming reagent.Brief Description of the Drawin s

[0012] FIG. 1 provides the compositional details of ink formulation 1.

[0013] FIGs. 2A and 2B graphically illustrate decomposition trend of a metal-organic decomposition (MOD) reflective ink and its isomers as a function of temperature.

[0014] FIGs. 3A-3C illustrate the spectrum analysis and reflectance behavior of a coated reflective layer after 40 minutes at cured temperature of 140 °C and 180 °C.

[0015] FIG. 4 shows a scanning electron microscopic (SEM) image of a reflective layer that was prepared using with a silver complex reflective ink.

[0016] FIG. 5 shows the characteristics of the reflective coated interfaces at the curing temperature of 180 °C after 180 minutes mass loss for samples that are cured at different temperatures of 140 °C, 180 °C, and 240 °C.

[0017] FIG. 6 shows a comparison of the reflectance of a reflective layer prepared using a composition of the disclosure according to the disclosed methods and a reflective standard.Detailed Description of the Invention

[0018] The current disclosure addresses the need for improved methods and compositions for preparing reflective layers through low-temperature thermal decomposition of reflective inks.

[0019] The disclosure also provides reflective materials comprising a target substrate and a reflective layer on the target substrate. In these reflective materials, the reflective layer is preferably formed by applying a reflective ink composition of the disclosure to a target substrate.

[0020] Traditional methods of generating reflective metal coating, such as chemical vapor deposition, electron beam evaporation etc. are energy exhaustive as they have high operating temperature. As a result, the above-mentioned processes suffer from low temperature substrate incompatibility and higher operating cost. In contrast to traditional approaches, it would be highly desirable for the reflective market to have a simple ink composition that can be coated on various surfaces at lower temperature without compromising the reflectivity.

[0021] Disclosed herein are novel ink formulations specially designed for producing highly reflective layers upon thermal decomposition after coating on a suitable target substrate. The reflective inks used to form the reflective layers preferably comprise silver salts, and they form the reflective layers upon curing at an elevated temperature, preferably at, or below, 250 °C.

[0022] The reflective layers that are generated according to the methods and compositions disclosed herein can have significantly higher reflectivity than those prepared according to known techniques. Reflectances of the reflective layers can be measured according to standard methods, for example as illustrated in the Examples section.Methods for Formation of Reflective Lavers through Thermal Decomposition

[0023] According to one aspect, the current disclosure provides novel methods for forming a reflective layer. These methods can include, for example, the steps of providing a target substrate, applying a reflective ink to the target substrate, and curing the reflective ink into a reflective layer on the target substrate.

[0024] The target surface used in the methods can be any suitable surface that is compatible with the treatment steps. The target surface is typically an exposed surface ofa suitable substrate. Where the reflective ink is converted to a reflective layer by a heat treatment, the target surface is preferably capable of being heated to a temperature that is sufficient to convert the reflective ink to the reflective layer in a reasonable time. Since the temperature necessary to form a reflective layer from the reflective inks typically used in these methods is low, however, most materials are suitable for use in these methods. For example, in some embodiments, the target substrate is a heat-sensitive substrate. The target surface should also be suitably adherent for the reflective ink, so in some embodiments, the target substrate is an adherent substrate. Finally, the target substrate is also preferably not sensitive to the components of the reflective ink compositions used in the process, for example any of the solvents or any other reactive agents present in the reflective ink.

[0025] Exemplary target substrates can be organic substrates or inorganic substrates, for example, glass, metal, or silicon substrates. More specifically, target substrates can comprise, without limitation, polyimide, epoxy with glass reinforcement, buildup films with no reinforcement, glass, silicon, passivated metals, bare metals, ceramics, engineered plastics, or three-dimensional (3D)-printablc materials. An exemplary buildup film is Ajinomoto Build-up Film® (ABF).

[0026] In some embodiments, the target substrate can be associated with a heat source, so that the target substrate can be heated to, or above, a threshold temperature for forming the reflective layer prior to application of the reflective ink to the target substrate. In some embodiments, the target substrate is in direct physical contact with the heat source. In other embodiments, the target substrate is heated through space by a heat source that is not in direct physical contact with the target substrate. Examples of heat sources include an IR lamp, an oven, or a heated platen.

[0027] As described above, the disclosed methods include the step of curing the reflective ink to form a reflective layer. In some embodiments, the curing step involves heating the reflective ink on the target substrate to a specific temperature. More specifically, the target substrate can be heated to a temperature of at least about 80° C. In some embodiments, the reflective ink on the target substrate is heated to a temperature of about 250 °C or less, of about 230 °C or less, of about 210 °C or less, of about 200 °C or less, of about 190 °C, of about 180 °C or less, of about 170 °C or less, of about 160 °C, of about 150 °C or less, of about 140 °C or less, of about 130 °C or less, of about 120 °C orless, of about 110 °C or less, or even of about 90 °C or less. The temperature used in the disclosed methods reflects the temperature required to convert the reflective ink to a reflective layer.

[0028] In some embodiments, the reflective ink is cured by photo activation, for example by irradiation of the reflective ink on the target substrate. More specifically, the irradiating step can be performed by exposing the reflective ink to a light source at a wavelength from about 100 nm to about 1500 nm. In some embodiments, the irradiating step can be performed by exposing the reflective ink to a light source such as a Xenon lamp, an IR lamp, or a laser at a wavelength from about 100 nm to about 1000 nm. In some embodiments, the irradiating step can be performed by exposing the reflective ink to a light source at a wavelength from about 100 nm to about 700 nm. In some embodiments, the irradiating step can be performed by exposing the reflective ink to a light source at a wavelength from about 100 nm to about 500 nm. In some embodiments, the irradiating step can be performed by exposing the reflective ink to a light source at a wavelength from about 100 nm to about 300 nm. In some embodiments, the irradiating step can be performed by exposing the reflective ink to a light source at a wavelength of about 100 nm, about 200 nm, about 300 nm, about 400 nm, about 500 nm, about 600 nm, about 700 nm, about 800 nm, about 900 nm, or about 1000 nm.

[0029] In some embodiments, the reflective ink is applied by slot die coating, spin coating, roll-to-roll printing, including gravure, flexography, rotary screen printing, screen printing, aerosol jet printing, inkjet printing, airbrushing, Mayer rod coating, flood coating, 3D printing, dispenser, or electrohydrodynamic printing. More specifically, the ink can be applied by inkjet printing, dip coating, or spray coating. In preferred embodiments, the ink is applied by bar coating.

[0030] In some embodiments, the reflective ink is applied and / or cured under ambient pressure. In other embodiments, the reflective ink is applied and / or cured under a reduced pressure.

[0031] The reflective layer formed on the target substrate can in some embodiments be at least about 0.003 pm thick, at least about 0.005 pm thick, at least about 0.01 pm thick, at least about 0.02 pm thick, at least about 0.05 pm thick, at least about 0.1 pm thick, at least about 0.2 pm thick, at least about 0.5 pm thick, at least about 1 pm thick, at least about 2 pm thick, at least about 3 pm thick, at least about 4 pm thick, at least about 5 pmthick, at least about 8 pm thick, at least about 10 pm thick, at least about 20 pm thick, or even thicker. In some embodiments, the reflective layer formed on the target substrate can be no more than about 200 pm thick, no more than about 100 pm thick, no more than about 50 pm thick, no more than about 20 ptm thick, no more than about 10 pirn thick, no more than about 8 ptm thick, no more than about 5 ptm thick, no more than about 2 pirn thick, no more than about 1 pim thick, no more than about 0.5 pim thick, no more than about 0.2 pim thick, not more than about 0.1 pim thick, no more than about 0.05 pim thick, no more than about 0.02 pim thick, no more than about 0.01 pun thick, or even thinner. In some embodiments, the reflective layer formed on the target substrate can be from about 0.003 pim thick to about 0.1 pim thick, from about 0.003 pim thick to about 0.5 pim thick, from about 0.003 pim thick to about 1 pim thick, from about 0.003 pim thick to about 5 pim thick, from about 0.5 pim thick to about 10 pim thick, or from about 1 pim thick to about 5 pim thick. The thickness of the reflective layer formed on the target substrate can in some embodiments have a deviation in thickness of no more than about 30%, no more than about 20%, no more than about 10%, or even no more than about 5%.Reflective Ink Compositions

[0032] Reflective ink compositions suitable for use in forming reflective layers according to the methods described herein include any ink composition that is capable of forming a highly reflective layer on a target substrate rapidly, ideally at low temperature, and ideally under ambient atmospheric conditions. Such compositions, which will also be referred to as “reflective inks” or “inks”, are preferably metal complex reflective inks (or metal-organic decomposition (MOD) reflective inks). Some of these inks are known in the art but have not previously been used for these purposes.

[0033] The reflective ink compositions of the instant disclosure preferably comprise a silver salt. More specifically, the reflective ink compositions comprise a silver decanoate. For example, the silver decanoate can be a silver salt of versatic acid, which may also be referred to as silver versatate or Ag-V. Exemplary ink compositions comprising silver salts have been described in PCT International Publication No. WO2013 / 096664A1, which is incorporated herein by reference in its entirety. Further metal complex ink compositions comprising silver metal precursors are described, for example, in PCT International Publication Nos. WO2Q15 / 160938A1, WO2023 / 168452A2,WO2024 / 145547A1 , and WO2025 / 1 5932A1, each of which is incorporated herein by reference in its entirety.

[0034] In specific embodiments, the reflective ink composition comprises a silver salt, a solvent, and a film-forming reagent. More specifically, the silver salt can be a silver decanoate, the solvent can be a terpene, terpenoid, or combination thereof, and the filmforming agent can be a di alkyl phthalate.

[0035] In some embodiments, the silver decanoate can be or can comprise any of the silver decanoates disclosed in PCT International Publication No. WO2023 / 168452A2 or WO2024 / 145547A1, each of which is incorporated herein by reference in its entirety.

[0036] In some embodiments, the dialkyl phthalate can be diethyl phthalate, dibutyl phthalate, di(2-ethylhexyl) phthalate, diisononyl phthalate, or diisodecyl phthalate.

[0037] In some embodiments, the terpene can be a purified terpene or the terpenoid can be a purified terpenoid.

[0038] In some embodiments, the terpene can be a pinene or a limonene.

[0039] In some embodiments, the terpenoid can be a terpineol.

[0040] In some embodiments, the solvent can comprise a limonene and a terpineol, and more specifically, the limonene can be a purified limonene and the terpineol can be a purified terpineol.

[0041] For example, in some specific embodiments the solvent can comprise a-terpineol, and in some embodiments, the film-forming agent can comprise di-butyl phthalate. In some specific embodiments, the reflective ink composition can further comprise a cosolvent, for example, the reflective ink composition can comprise an ethylene glycol such as ethylene glycol monopropyl ether. In some specific embodiments, the reflective ink composition can further comprise a polymer, for example the reflective ink composition can comprise polystyrene.

[0042] In some embodiments, the metal complex reflective ink composition is a particle-free reflective ink composition. A particle-free reflective ink composition is preferably one that does not include any particles at a diameter of greater than about 10 nm. In some embodiments, a particle-free ink composition is one that has less than about 1% particles, preferably less than about 0.1% particles.

[0043] The reflective ink compositions used in the instant methods preferably possess low viscosity, so that they are compatible with a broad range of application techniques,including slot die coating, spin coating, roll-to-roll printing, including gravure, flexography, rotary screen printing, screen-printing, aerosol jet printing, inkjet printing, airbrushing, Mayer rod coating, flood coating, 3D printing, and electrohydrodynamic printing. In particular, the inks may be compatible with inkjet printing, dip coating, and spray coating. Preferably, the inks are compatible with bar coating. The ink compositions preferably remain stable at room temperature for months without particle precipitation. They are also preferably stable to the process by which they are applied to the target substrate, so they do not form significant amounts of a reflective layer until they are in full contact with the target substrate.

[0044] As just described, the reflective ink composition of the instant methods preferably have a desired viscosity. In some embodiments, the desired viscosity is measured using a micro VISC viscometer. In some embodiments, the reflective ink composition has a viscosity from about 50 centipoise to about 1000 centipoise. In some embodiments, the reflective ink composition has a viscosity from about 5 centipoise to about 50 centipoise. In some embodiments, the reflective ink composition has a viscosity from about 10 centipoise to about 40 centipoise. In some embodiments, the reflective ink composition has a viscosity from about 20 centipoise to about 30 centipoise. In some embodiments, the reflective ink composition has a viscosity from about 18 centipoise to about 20 centipoise. In some embodiments, the reflective ink composition has a viscosity of about 18, about 19, or about 20 centipoise. In some embodiments, the reflective ink composition has a viscosity of at least about 5 centipoise, about 10 centipoise, about 20 centipoise, about 30 centipoise, about 40 centipoise, about 50 centipoise, about 60 centipoise, about 70 centipoise, about 80 centipoise, about 90 centipoise, about 100 centipoise, about 200 centipoise, about 300 centipoise, about 400 centipoise, about 500 centipoise, about 600 centipoise, about 700 centipoise, about 800 centipoise, or about 900 centipoise. In some embodiments, the reflective ink composition has a viscosity of at most about 1000 centipoise, about 900 centipoise, about 800 centipoise, about 700 centipoise, about 600 centipoise, about 500 centipoise, about 400 centipoise, about 300 centipoise, about 200 centipoise, about 100 centipoise, about 90 centipoise, about 80 centipoise, about 70 centipoise, about 60 centipoise, about 50 centipoise, about 40 centipoise, about 30 centipoise, about 20 centipoise, or about 10 centipoise.

[0045] In some embodiments, the viscosity of the reflective ink composition is adjusted based upon the amount of dissolving agent used. In some embodiments, the viscosity of the complex is adjusted based upon the type of dissolving agent used. For example, in embodiments where the dissolving agent comprises limonene and terpineol, an increase in the percentage of terpineol in the reflective ink composition can increase the viscosity of the ink. In some embodiments, the viscosity of silver complex can be tuned from less than 5 centipoise with a large proportion of limonene to 50 centipoise with a large portion of terpineol. Unless otherwise indicated, all viscosity values are for samples at room temperature.

[0046] In some embodiments, the ink compositions of the instant methods have a concentration of about 0.1-50 weight percent metal salt of the ink composition. In some embodiments, the ink compositions of the instant methods have a concentration of about 0.1-40 weight percent metal salt of the ink composition. In some embodiments, the ink compositions have a concentration of about 1-30 weight percent metal salt of the ink composition. In some embodiments, the ink compositions have a concentration of about 1-20 weight percent metal salt of the ink composition. In some embodiments, the ink compositions have a concentration of about 1-10 weight percent metal salt of the ink composition. In some embodiments, the ink compositions have a concentration of about 5-15 weight percent metal salt of the ink composition. In some embodiments, the ink compositions have a concentration of about 0.1 weight percent, about 0.2 weight percent, about 0.3 weight percent, about 0.4 weight percent, about 0.5 weight percent, about 0.6 weight percent, about 0.7 weight percent, about 0.8 weight percent, about 0.9 weight percent, about 1 weight percent, about 2 weight percent, about 3 weight percent, about 4 weight percent, about 5 weight percent, about 6 weight percent, about 7 weight percent, about 8 weight percent, about 9 weight percent, about 10 weight percent, about 11 weight percent, about 12 weight percent, about 13 weight percent, about 14 weight percent, about 15 weight percent, about 16 weight percent, about 17 weight percent, about 18 weight percent, about 19 weight percent, or about 20 weight percent metal of the ink composition.

[0047] In some embodiments, the ink compositions of the instant methods have a concentration of at least about 0.1 weight percent, about 0.2 weight percent, about 0.3 weight percent, about 0.4 weight percent, about 0.5 weight percent, about 0.6 weight percent, about 0.7 weight percent, about 0.8 weight percent, about 0.9 weight percent, 1weight percent, about 2 weight percent, about 3 weight percent, about 4 weight percent, about 5 weight percent, about 6 weight percent, about 7 weight percent, about 8 weight percent, about 9 weight percent, about 10 weight percent, about 11 weight percent, about 12 weight percent, about 13 weight percent, about 14 weight percent, about 15 weight percent, about 16 weight percent, about 17 weight percent, about 18 weight percent, about 19 weight percent, or about 20 weight percent metal salt of the ink composition. In some embodiments, the ink compositions have a concentration of at most about 40 weight percent, about 39 weight percent, about 38 weight percent, about 37 weight percent, about 36 weight percent, about 35 weight percent, about 34 weight percent, about 33 weight percent, about 32 weight percent, 31 weight percent, about 30 weight percent, about 29 weight percent, about 28 weight percent, about 27 weight percent, about 26 weight percent, about 25 weight percent, about 24 weight percent, about 23 weight percent, about 22 weight percent, about 21 weight percent, about 20 weight percent, about 19 weight percent, about 18 weight percent, about 17 weight percent, about 16 weight percent, about 15 weight percent, about 14 weight percent, about 13 weight percent, or about 12 weight percent metal salt of the ink composition.

[0048] In some embodiments, the ink compositions of the instant methods have a concentration of about 0.1-50 weight percent metal complex of the ink composition. In some embodiments, the ink compositions of the instant methods have a concentration of about 0.1 -40 weight percent metal complex of the ink composition. In some embodiments, the ink compositions have a concentration of about 1-30 weight percent metal complex of the ink composition. In some embodiments, the ink compositions have a concentration of about 1-20 weight percent metal complex of the ink composition. In some embodiments, the ink compositions have a concentration of about 1-10 weight percent metal complex of the ink composition. In some embodiments, the ink compositions have a concentration of about 5-15 weight percent metal complex of the ink composition. In some embodiments, the ink compositions have a concentration of about 0.1 weight percent, about 0.2 weight percent, about 0.3 weight percent, about 0.4 weight percent, about 0.5 weight percent, about 0.6 weight percent, about 0.7 weight percent, about 0.8 weight percent, about 0.9 weight percent, 1 weight percent, about 2 weight percent, about 3 weight percent, about 4 weight percent, about 5 weight percent, about 6 weight percent, about 7 weight percent, about 8 weight percent, about 9 weight percent,about 10 weight percent, about 11 weight percent, about 12 weight percent, about 13 weight percent, about 14 weight percent, about 15 weight percent, about 16 weight percent, about 17 weight percent, about 18 weight percent, about 19 weight percent, or about 20 weight percent metal complex of the ink composition.

[0049] In some embodiments, the ink compositions of the instant methods comprise an adhesion promoter. Exemplary adhesion promoters are described in PCT International Publication No. WO2023 / 168452A2 and in WO2024 / 145547A1, the disclosures of which are incorporated by reference herein for all purposes.Curing the Reflective Layer

[0050] The methods of the instant disclosure include the step of curing or baking the reflective layer at an elevated temperature after the reflective ink has been applied to a target substrate. In addition to converting the reflective ink to a reflective metallic layer, the curing or baking step can remove undesirable volatile components from the reflective layer. Such residual agents can include, for example, volatile solvents or other volatile components of the reflective ink. In some cases, such residual agents can compromise the structural or functional properties of the reflective layer, and the curing or baking step may accordingly improve those properties by release of the residual agent.

[0051] For example, in some embodiments, the curing step is performed at a temperature of about 250 °C or less. In some embodiments, the curing step is performed at a temperature of about 240 °C or less, about 230 °C or less, about 220 °C or less, about 210 °C or less, about 200 °C or less, about 190 °C or less, about 180 °C or less, about 170 °C or less, about 160 °C or less, about 150 °C or less, about 140 °C or less, about 130 °C or less, about 120 °C or less, about 110 °C or less, about 100 °C or less, about 90 °C or less, about 80 °C or less, or about 70 °C or less. In some embodiments, the curing step is performed using a heat source. Examples of heat sources include an IR lamp, oven, or a heated substrate.

[0052] In some embodiments, the curing or baking step is performed for at least 5 minutes, at least 10 minutes, at least 20 minutes, at least 30 minutes, at least 60 minutes, or even longer. In some embodiments, the curing or baking step is performed for no more than 60 minutes, no more than 30 minutes, no more than 20 minutes, no more than 10 minutes, no more than 5 minutes, or even shorter.

[0053] In some embodiments, the curing step is performed by exposing the reflective ink on the target substrate to a light source at a wavelength from about 100 nm to about 1500 nm. In some embodiments, the curing step is performed by exposing the reflective ink to a light source such as a Xenon lamp, an IR lamp, or a laser at a wavelength from about 100 nm to about 1000 nm. In some embodiments, the curing step is performed by exposing the reflective ink to a light source at a wavelength from about 100 nm to about 700 nm. In some embodiments, the curing step is performed by exposing the reflective ink to a light source at a wavelength from about 100 nm to about 500 nm. In some embodiments, the curing step is performed by exposing the reflective ink to a light source at a wavelength from about 100 nm to about 300 nm. In some embodiments, the curing step is performed by exposing the reflective ink to a light source at a wavelength of about 100 nm, about 200 nm, about 300 nm, about 400 nm, about 500 nm, about 600 nm, about 700 nm, about 800 nm, about 900 nm, or about 1000 nm.

[0054] In some embodiments, the curing step is performed by a combination of heating the reflective ink, for example at any of the above-listed temperatures, and exposing the reflective ink to a light source, for example at any of the above-listed wavelengths.

[0055] It will be readily apparent to one of ordinary skill in the relevant arts that other suitable modifications and adaptations to the compositions and methods described herein may be made without departing from the scope of the invention or any embodiment thereof. Having now described the present invention in detail, the same will be more clearly understood by reference to the following Examples, which are included herewith for purposes of illustration only and are not intended to be limiting of the invention.EXAMPLESPreparation of a reflective ink composition

[0056] A particle free ink composition has been developed utilizing a silver complex that decomposes at low temperature and produces a highly reflective layer.

[0057] In one exemplary preparation, the reflective ink composition was prepared as follows:Step.1 : 2.045 g of silver neodecanoate (40.9 wt.%) was added to a mixture of 2.115 g a-tcipincol (42.3 wt.%), 0.5 g of ethylene glycol monopropyl ether (10 wt.%), and 0.34 g of di-butyl phthalate (6.8 wt.%).Step.2: The resulting mixture was stirred on a hotplate at 75 °C, at 800 RPM for one hour.Step. 3: The final ink, with a yellow-dispersion appearance was filtered through 0.45 pm PTFE filter, which resulted in a clear, translucent ink with solid content of 14%, and viscosity of 5 cP.Step 4: The ink was stored under ambient conditions protected from light.Formation of Highly Reflective Laver Through Thermal Decomposition of a Silver Metallo-organic Ink

[0058] The ink is bar coated on RK Printcoat Industries, with bar 9 (specialties) on Premiere microscope glass slide (3” x 2”) and cured in the oven (Binder), with temperature ramping from room temperature to 180 °C, which takes about thirty minutes. A highly reflective surface was generated at the glass side of the coated film. The reflectivity of the surface was measured using a Cary 5000 UV-Vis NIR Spectrophotometer and was found to be >90% in the range from 450-800 nm.

[0059] FIG. 1 provides the compositional details of ink formulation 1. The formulation could be printed on suitable substrates using standard inkjet technologies to form reflective silver films at relatively low temperatures. The reflective ink composition can be spray-coated, spin-coated, or bar coated on a target substrate, as described above.

[0060] FIGs. 2A and 2B graphically illustrate decomposition trend of a metal-organic decomposition (MOD) ink formed from various silver decanoate salts as a function of temperature. The silver salts were silver versatate (AgV), silver 2-butyLhexanoate (Ag-2BHA), and silver 2,2-diethyl-hexanoate (Ag-2,2DEHA).

[0061] FIGs. 3A-3C illustrates the spectrum analysis and reflectance behavior of a coated reflective surface at cured temperature of 140 °C and 180 °C after 40 minutes.

[0062] FIG. 4 shows a scanning electron microscopic (SEM) image of a reflective layer that was prepared by coating a target surface with a silver complex reflective ink.

[0063] FIG. 5 shows the characteristics of the reflective coated interfaces at the curing temperature of 180 °C after 180 minutes mass loss for samples that are cured at different temperatures of 140 °C, 180 °C, and 240 °C.

[0064] As shown in this figure, the remaining mass plateaus at approximately 15% in each case. The plateau is reached in approximately 1 hour at 140 °C, in approximately 30 minutes at 180 °C, and in approximately 15 minutes at 240 °C.Alternative Ink Formulations with Silver-Neodecanoate

[0065] In another reflective ink embodiment, 0.04 g of 37,000 molecular weight polystyrene (0.8 wt.%) was added into the mixture of 2.075 g a-terpineol (41.5 wt.%), 0.5 g of ethylene glycol monopropyl ether (10 wt.%), and 0.34 g of di-butyl phthalate (6.8 wt.%). The resulting mixture was stirred on hotplate at 75 °C, at 800 RPM for one hour. The solution was cooled down to room temperature and 2.045 g of silver neodecanoate (40.9 wt.%) was added to the mixture and stirred on the hotplate for one hour at 50 °C at 700 RPM. The final ink, with a yellow-dispersion appearance was filtered through 0.45 pm PTFE filter resulting a translucent ink with silver content of 14%, and viscosity of 5 centipoise. The ink is stable for months when stored under ambient conditions protected from light.

[0066] The ink was bar coated using RK Printcoat Industries (K Control Coater model 101.) coater, with bar 9 (rdspecialties) on microscope glass slide (3” x 2”) and cured in the oven (Binder), with temperature ramping from room temperature to 180 °C, which takes about thirty minutes. After this time period a highly reflective surface was generated on the glass side of the coating. The reflectivity of the surface was measured using a Cary 5000 UV-Vis NIR Spectrophotometer with Thorlabs silver mirror as a reference. As shown in FIG. 6, an overlay of the reflectance spectra of silver ink coated film (El-Reflective Ink) and the Thorlabs reference (ThorLabs P01 Silver Reference) indicates that the film generated from the silver ink has exceptionally high reflectance that outperforms the standard Thorlabs mirror. The reflectance was found to be >90% in the range from 450-800 nm.

[0067] All patents, patent publications, and other published references mentioned herein are hereby incorporated by reference in their entireties as if each had been individually and specifically incorporated by reference herein.

[0068] While specific examples have been provided, the above description is illustrative and not restrictive. Any one or more of the surfaces of the previously described embodiments can be combined in any manner with one or more surfaces of any other embodiments in the present invention. Furthermore, many variations of the invention will become apparent to those skilled in the art upon review of the specification. The scope of the invention should, therefore, be determined by reference to the appended claims, along with their full scope of equivalents.

Claims

What is Claimed is:

1. A reflective ink comprising:a silver salt,a solvent, anda film-forming reagent.

2. The reflective ink of claim 1, wherein the silver salt is a silver decanoate.

3. The reflective ink of claim 1, wherein the solvent is a terpene or a terpenoid.

4. The reflective ink of claim 1, wherein the film-forming reagent is a dialkyl phthalate.

5. The reflective ink of claim 1, wherein the reflective ink comprises a silver decanoate, a terpene or a terpenoid, and a dialkyl phthalate.

6. The reflective ink of claim 1, further comprising a cosolvent.

7. The reflective ink of claim 6, wherein the cosolvent is an ethylene glycol.

8. The reflective ink of claim 1, further comprising a polymer.

9. The reflective ink of claim 8, wherein the polymer is a polystyrene.

10. A method for forming a reflective material comprising steps of:providing a target substrate;providing a reflective ink;applying the reflective ink to the target substrate; andcuring the reflective ink to form a reflective layer on the target substrate; wherein the reflective ink comprises a silver salt, a solvent, and a film- forming reagent.

11. The method of claim 10, wherein the silver salt is a silver decanoate.

12. The method of claim 10, wherein the solvent is a terpene or a terpenoid.

13. The method of claim 10, wherein the film-forming reagent is a dialkyl phthalate.

14. The method of claim 10, wherein the reflective ink comprises a silver decanoate, a terpene or a terpenoid, and a dialkyl phthalate.

15. The method of claim 10, wherein the reflective ink further comprises a cosolvent.

16. The method of claim 15, wherein the cosolvent is an ethylene glycol.

17. The method of claim 10, wherein the reflective ink further comprises a polymer.

18. The method of claim 17, wherein the polymer is a polystyrene.

19. The method of claim 10, wherein the curing is performed at a temperature of about 80° C or more.

20. The method of claim 10, wherein the curing is performed at a temperature of about 250° C or less.

21. The method of claim 10, wherein the reflective ink is applied to the target substrate by bar coating.

22. The method of claim 10, wherein the reflective ink is applied to the target substrate in an ambient atmosphere.

23. The method of claim 10, wherein the target substrate is a heat- sensitive substrate.

24. The method of claim 10, wherein the reflective layer has a thickness of from about 0.003 pm to about 5 pm.

25. The method of claim 10, wherein the target substrate is a glass substrate, a metal substrate, or a silicon substrate.

26. A reflective material prepared using the method of any one of claims 10-25.

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