WO2010117371A1

WO2010117371A1 - Energy activated film and method of making the same

Info

Publication number: WO2010117371A1
Application number: PCT/US2009/040268
Authority: WO
Inventors: Makarand P. Gore; Christopher O. Oriakhi
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2009-04-10
Filing date: 2009-04-10
Publication date: 2010-10-14

Abstract

A method for forming an energy activated film (28) is disclosed herein. An ink (20), including a plurality of particles (18) therein, is deposited. At least one component (18, 22) of the ink (20) is configured to absorb electromagnetic radiation including a wavelength within a selected band of wavelengths. The selected band including wavelength ranges from 10 nm to 50 nm from a peak component absorption wavelength. At least a portion of the deposited ink (20) is exposed to electromagnetic radiation having a wavelength within the selected band of wavelengths. The electromagnetic radiation emanates from a light source (26) configured to generate electromagnetic radiation having a wavelength ranging from 10 nm to 55 nm from the peak component absorption wavelength of the ink (20).

Description

ENERGY ACTIVATED FILM AND METHOD OF MAKING THE SAME

BACKGROUND The present disclosure relates generally to energy activated films and a method of making the same.

Metallic inks often include a metal dispersed in an ink vehicle. One attribute of such a metallic ink is its electrical conductivity. As such, metallic ink may be used as a coating material for electrical devices, such as, for example, solar cells, flat panel displays, touch screens, printed circuit boards, flexible circuit boards, thin films, plastic films, radio frequency identification (RFID) tags, organic semiconductors, and organic light-emitting diodes (OLEDs). Another attribute of metallic ink is its tendency to shine (i.e., reflect light) when exposed to light. Thus, metallic inks may be useful in printing processes for forming printed images exhibiting a metallic luster (e.g., decorative applications, such as greeting cards, scrap books, brochures, sign boards, business cards, certificates, and other like applications).

BRIEF DESCRIPTION OF THE DRAWINGS Features and advantages of embodiments of the present disclosure will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though perhaps not identical, components. For the sake of brevity, reference numerals or features having a previously described function may or may not be described in connection with other drawings in which they appear. Fig. 1 is a schematic flow diagram of an embodiment of a method for forming an energy activated film;

Fig. 2 is a schematic diagram of an embodiment of a system for forming the energy activated film; Fig. 3 is a semi-schematic perspective view of an embodiment of the energy activated film; and

Figs. 4A and 4B are microscope images of a deposited inkjet ink that was not exposed to electromagnetic radiation (Fig. 4A); and that was exposed to electromagnetic radiation (Fig. 4B).

DETAILED DESCRIPTION

Embodiments of the method disclosed herein advantageously enable the efficient deposition and processing of metallic or metalloid films. The films are formed from inks having one or more components that absorb electromagnetic radiation (i.e., EM radiation or light) within a narrow waveband. A light source is selected such that it emits electromagnetic radiation having wavelengths within a narrow waveband that corresponds with the narrow waveband of the ink absorption component(s). It is believed that the corresponding narrow wavebands advantageously increase the curing efficiency of the film by eliminating side effects of and energy losses due to undesirable wavelengths (e.g., wavelengths that do not contribute to the curing of the film). Furthermore, the narrow wavebands enable low energy curing of the ink, thereby reducing or eliminating deleterious effects (e.g., burning through a substrate) that may result when a broad range of wavelengths is exposed to a substrate. The narrow wavebands of the ink component(s) and the light source result in a film exhibiting desirable characteristics. For example, the electrical properties (e.g., conductivity), the mechanical properties (e.g., hardness), the physicochemical properties (e.g., homogeneity), and the optical properties (e.g., reflectivity) of the film disclosed herein are believed to be enhanced when compared to other unexposed metallic films. It is further believed that the specific absorption of radiation causes the plurality of particles within the resulting film to aggregate and fuse together, thereby reducing amorphousness within the film.

It is to be understood that the terms "light", "radiation" or "electromagnetic radiation" as used herein are meant to describe any electromagnetic radiation in the ultraviolet (UV), visible, near infrared (IR), or IR bands.

As used herein, the terms "narrow waveband", "absorption band" or "band" refer to light wavelengths, radiation, and/or absorption corresponding with a range of wavelengths. The narrow waveband of an absorption component in the ink disclosed herein are the wavelengths at which absorption occurs, and the narrow waveband of a light source is generally selected to exclude wavelengths that are outside of the absorption band of one or more components of an ink. When the phrase "at about" a stated value is used to describe the narrow waveband (e.g., waveband at about 405 nm) or when the phrase "the [stated value] waveband" (e.g., the 405 nm waveband) is used, it is meant that the referenced waveband includes the stated wavelength (e.g., a peak absorption wavelength (405 nm)) and at least ± 10 nm or at most ± 50 nm from the stated value. The waveband may also be referred to herein as having "a center." In such instances, the waveband includes the stated wavelength (e.g., 405 nm) and at most ± 50 nm from the stated value. One non-limiting example of this waveband includes the 405 nm wavelength as the center and wavelengths at ± 25 nm from the stated center value. In other non-limiting examples, the 405 nm waveband includes wavelengths ranging from 355 nm to 455 nm, the 650 nm waveband includes wavelengths ranging from 600 nm to 700 nm, and the 780 nm waveband includes wavelengths ranging from 730 nm to 830 nm. Such wavelengths are considered to be "within" the identified waveband.

The term wavelength generally refers to the stated value. However, when discussing the wavelength of a laser diode, the term wavelength includes the stated value ± 5 nm. Other sources of radiation, such as light emitting diodes or lamps, have at least one intense band with a selected wavelength and a width of ± 25 nm from the selected wavelength. Referring now to Fig. 1 , an embodiment of the method for forming the film is disclosed. Generally, the method includes depositing an ink including a plurality of particles therein (as shown at reference numeral 100), and exposing at least a portion of the deposited ink to radiation (as shown at reference numeral 102). At least one component of the ink is configured to absorb radiation having a wavelength within a selected band of wavelengths (i.e., ranging from 10 nm to 50 nm from a peak component absorption wavelength), and the exposure radiation has a wavelength within the selected band of wavelengths. In particular, the exposure radiation is emanated from a light source that is configured to generate radiation having a wavelength ranging from 10 nm to 55 nm from the peak component absorption wavelength of the ink. It is to be understood that the ink components, the deposition and exposure processes, and the resulting film will be discussed further in reference to Figs. 2 and 3.

Fig. 2 illustrates the system 10 for forming the radiation exposed film 28 disclosed herein. The system 10 generally includes a printer 12, an ink 20, a substrate 24, and a light source 26.

The printer 12 may be any suitable printer, including, but not limited to, offset printers, screen printers, inkjet printers (e.g., thermal, piezoelectric, continuous inkjet printers, etc.), laser printers, 3D printers, stereolithography printers, digital press printers, or any other suitable printer. Other examples of suitable printing processes may be found in The Printing Ink Manual, 5^th Ed., Lecah, R. H.; Pierce, R. J., Eds., Kluwer Academic, Norwell, 2004, ISBN 0948905816. Specific examples of techniques for applying the ink 20 on a substrate 24 include offset lithography, flexographic printing, gravure printing, letter press printing, screen printing, toner printing, spin coating, spray coating, roller printing or coating, painting, or other like processes. In an embodiment, an inkjet printer includes one or more reservoirs 16 for holding the ink 20 and print heads 14 operatively connected thereto for dispensing the ink 20.

The ink 20 is a precursor of the ultimately formed film 28. The ink 20 generally includes an ink vehicle having at least particles 18 dispersed therein. The ink vehicle may include solvent(s), surfactant(s), binder(s), or other additives (e.g., biocides, etc.) It is to be understood that the binders may be conductive or non-conductive polymers prior to curing. The ink 20 may be a nano-dispersion of one or more metals that contain dispersing agents, polymers or surfactants. It is to be understood that the term "dispersion" refers to particles of any size in a liquid, such as colloids, dispersions, suspensions, and the like.

Non-limiting examples of suitable ink components include cellulose acetate, trisodium citrate, acrylate polymers, Disperbyk® 190 (BYK chemie), carboxymethyl cellulose, polyols, poly-n-vinylpyrrolidone, tetraethylorthosilicate, butanol, propanol, acacia gum (gum Arabic), N-vinylcaprolactum, hexamethyl disilazane, and 4- aminothiophenol. Other ink 20 dispersing agents, polymers and/or surfactants may also be used. Examples of such other components are discussed in U.S. Patent App. Pub. No. 2006/0254387; U.S. Patent App. Pub. No. 2006/0261316; U.S. Patent App. Pub. No. 20080032047; U.S. Patent App. Pub. No. 20070166558; U.S. Patent App. Pub. No. 2007/0283848; U.S. Patent App. Pub. No. 20080060549;

U.S. Patent App. Pub. No. 20080108218; U.S. Patent App. Pub. No. 20080044634; and U.S. Patent App. Pub. No. 20080113195, the contents of which are incorporated herein by reference. Specific examples of such other components include polyvinylpyrrolidone, glycol or glycol mixtures (such as propylene glycol, ethylene glycol, etc.), amine based compounds having the formula C_xH_2x+INH₂

(where X is 8 to 16), alkanoic (saturated fatty) acids (such as lauric acid, oleic acid, etc.), Surfynol® 465, Triton® X-100, thiols containing more than twelve carbon atoms, and any combinations of the previously listed components.

The ink 20 includes at least one component that is selected to absorb radiation having wavelengths within the selected narrow waveband. In some instances, the absorbing component is the particles 18, and in other instances, the absorbing component is a separate absorber 22 that is added to the ink 20 having the particles 18 therein. It is to be understood that the particles 18 are selected such that they are capable of being converted to a film 28 upon irradiation with energy (from light source 26) that is absorbed by the particles 18 themselves or that is transferred to the particles 18 from the absorber 22. Both of these embodiments will be discussed further hereinbelow.

In any of the embodiments disclosed herein, the particles 18 are included at least as colorants in the ink 20. Non-limiting examples of suitable particles 18 are silver particles, particles of metal alloys (where the metals are selected from, for example, Ag, Au, Fe, Sn, Ti, Mn Ni, Rh, Ru, Mo, Ta, Ti, Pt, or Pd), metal oxide particles (e.g., iron oxide particles), metal coated oxide particles (e.g., particles of iron oxide coated with Ag, Au or Pt), zinc particles, cadmium selenide particles, or metal coated silica particles (e.g., silica particles coated with Ag or Au). It is to be understood that the previous list of particles is non-limiting, and that other particles may be suitable for use in the embodiments disclosed herein.

In an embodiment, the particles 18 are nanoparticles having at least one average dimension (a non-limiting example of which is the diameter) that is less than 200 nm. As a non-limiting example, the nanoparticles 18 are generally spherical, and the at least one average dimension ranges from about 2 nm to about 120 nm. Other examples of suitable ranges for the dimension include from about 2 nm to about 40 nm, or from about 50 nm to about 200 nm. It is to be understood that, depending upon the synthesis conditions used, from about 5% to about 10% of the nanoparticulate distribution in the ink 20 may consist of nano-cube, nano- rod, nano-needle or nano-wire morphology. Any known synthesis technique may be utilized. Furthermore, the synthesis may be tailored to yield a desired particle size range. For example, particle size distributions of various ranges (e.g., 20 - 60 nm, 60 - 90 nm, or 80 - 160 nm) can be achieved.

In still another embodiment, the particles 18 are selected such that they are in a zero valence state.

As previously mentioned, in one embodiment, the particles 18 function as both an absorber (i.e., a substance that absorbs a particular wavelength or range of wavelengths) and a contrast agent (i.e., a material that, in response to receiving or absorbing radiation, alters its chemical and/or physical structure and produces an optically detectable change, for example, contrast or color). In this embodiment, the particles 18 are selected such that they absorb light of wavelengths within the desirably narrow waveband. As such, in some embodiment, the addition of the separate absorber 22 is not desirable.

In another embodiment, the previously mentioned absorber 22 is added to the ink 20. This absorber 22 is selected to absorb the radiation having wavelength(s) within the selected narrow waveband and transfer such absorbed energy to the particles 18 to initiate the desirable contrast and/or color change. When the absorber 22 is included in the ink 20, a suitable concentration of the particles 18 ranges from about 1 wt.% to 90 wt.% of the total ink weight, and a suitable concentration of the absorber 22 ranges from 1 wt.% to 5 wt.% of the total ink weight.

Non-limiting examples of other suitable absorbers 22 include porphyrin dyes, phthalocyanine dyes, napthalocyanine dyes, squaranine dyes, diazo dyes, and diazo metal complex dyes. Absorbers 22 that have modifying groups as described in U.S. Patent No. 6,015,896 and U.S. Patent No. 6,025,486 (both of which are incorporated herein by reference) are suitable for use in the embodiments disclosed herein. Such modifying groups may be present on the ring, the atom or the ion at the center of a naphthalocyanine or a phthalocyanine complex. Examples of some suitable naphthalocyanine and phthalocyanine dyes are shown below:

where M is a metal or hydrogen; Pc is a phthalocyanine nucleus; Ri, R₂, W₁, and W₂, are each independently selected from H or optionally substituted alkyls, aryls, or aralkyls; R3 is an aminoalkyl group; L is a divalent organic linking group; x, y and t are each independently selected from a value in the range of 0.5 to 2.5; and (x+y+t) ranges from 3 to 4;

where M is a metal or hydrogen; Pc is a phthalocyanine nucleus; R¹ is H or an optionally substituted alkyl, aryl, or aralkyl; L¹ is a divalent organic linking group; Z is an optionally substituted piperazinyl group; q is 1 or 2; x and y are each independently selected from a value ranging from 0.5 to 3.5; and (x+y) ranges from 2 to 5;

where M is a metal;

Another suitable example is silicon naphthalocyanine (SiNc) with trihexyloxy substituents. Still further, some commercial dyes previously used for recording of low density optical media at 650 nm and 780 nm are useful as absorbers 22. Examples of such commercial dyes include those used in conventional DVD or CD recording, such as IRGAPHOR® Ultragreen MX, IRGAPHOR® LASERVIOLET, IRGAPHOR® 1699 (all of which are commercially available from Ciba, Tarrytown, NY). Other commercially available dyes suitable for use as the absorber 22 include PRO-JET™ 800NP, PRO-JET™ 830NP, and PRO-JET™ 900NP (all of which are available from Fujifilm Imaging Colorants Inc., Wilmington, DE), as well as YKR 3070 (available from Yamamoto Chemicals, Japan).

Non-limiting examples of other absorbers 22 with absorption at or near 405 nm that are suitable for use in the ink 20 include curcumin; crocetin; porphyrin and derivatives thereof (e.g., etioporphyhn 1 (CAS 448-71 -5), octaethyl porphyrin (CAS 2683-82-1 ), and deuteroporphyrin IX 2,4 bis ethylene glycol (D630-9), available from Frontier Scientific); azo dyes (e.g., Mordant Orange (CAS 2243-76-7), Methyl Yellow (CAS 60-11 -7), 4-phenylazoaniline (CAS 60-09-3), and Alcian Yellow (CAS 61968-76-1 )); C.I. Solvent Yellow 93; C.I. Solvent Yellow 163; 1 ,3-dimethyl-5-[2-(1 - methyl-pyrrolidin-2-ylidene)-ethylidene]-pyrimidine-2,4,6-trione; 1 ,3-dimethyl-5-[2- (3-methyl-oxazolidin-2-ylidene)-ethylidene]-pyrimidine-2,4,6-trione; or the like. Still other suitable examples include 1 -(2-chloro-5-sulfophenyl)-3-methyl-4- (4~sulfophenyl)azo-2-pyrazolin-5-one disodium salt (λ_max = 400 nm); ethyl 7- diethylaminocoumahn-3-carboxylate (λ_max = 418 nm) (CAS 28705-46-6); 3,3'- diethylthiacyanine ethylsulfate (λ_max = 424 nm) (CAS 2602-17-7); 3-a I IyI -5-(3-ethy I - 4-methyl-2-thiazolinylidene) rhodanine (λ_max = 430 nm) (CAS 203785-75-5), (each of which is available from Organica Feinchemie GmbH Wolfen), or mixtures thereof. Non-limiting specific examples of suitable aluminum quinoline complexes that may be used as absorber 238 include ths(8-hydroxyquinolinato)aluminum (CAS 2085-33-8) and derivatives such as tris(5-cholor-8- hydroxyquinolinato)aluminum (CAS 4154-66-1 ); 2-(4-(1 -methyl-ethyl)-phenyl)-6- phenyl-4H-thiopyran-4-ylidene)-propanedinitril-1 ,1 -dioxide (CAS 174493-15-3); 4,4'-[1 ,4-phenylenebis(1 ,3,4-oxadiazole-5,2-diyl)]bis N,N-diphenyl benzeneamine (CAS 184101 -38-0); bis-tetraethylammonium-bis(1 ,2-dicyano-dithiolto)-zinc(ll) (CAS 21312-70-9); or 2-(4,5-dihydronaphtho[1 ,2-d]-1 ,3-dithiol-2-ylidene)-4,5- dihydro-naphtho[1 ,2-d]1 ,3-dithiole, all of which are available from Syntec GmbH.

Still other examples of suitable absorbers 22 include enol-diene metal complex dyes. Such dyes may have any of the following sub-structures:

where Ri, R2, R3, and R₄, or R, R', and R" are each independently selected from aryl groups, alkyl groups, amino groups, sulfonyl groups, and amino alkyl groups, and where M is a metal. It is to be understood than any metal is suitable, and in one embodiment, the metal is a transition metal (e.g., copper, nickel, palladium, zinc, zirconium, gadolinium, titanium, europium, cerium, iron II, iron III, or any other transition metal listed in the periodic table of the elements).

As shown in Fig. 1 , the ink 20 is deposited, via the printer 12, onto the surface of the substrate 24. It is to be understood that any suitable substrate 24 may be used. Non-limiting examples of suitable substrates 24 include paper (e.g., labels, tickets, receipts, or stationery), coated porous or swellable media, photo media, an overhead transparency, or the like. Other examples of suitable media include polymer substrates, such as polyethylene, polycarbonate, polyethylene terephthalate (PET), polyethylene(napthalenedicarboxylate) (PEN), or polyimides. Still other examples of substrates 24 include composite materials, such as glass epoxy-amine polymers.

The printer 12 is generally configured to print the ink 20 in any desirable pattern (e.g., text, indicia, graphics, circuit patterns, etc.). The printer 12 may receive control signals and data indicative of the pattern from a source (e.g., a computer, portable storage memory device, etc.).

After the ink 20 is printed in the desirable pattern, it is exposed to electromagnetic radiation having wavelengths within the selected narrow waveband. The light source 26 emanates electromagnetic radiation having wavelengths ranging from 10 nm to 55 nm from the peak absorption of the absorbing component of the ink 10 (i.e., the particles 18 or the absorber 22). As such, the light source 26 emits radiation having wavelengths within the narrow waveband at which the absorbing component absorbs.

Non-limiting examples of suitable light sources 26 include lasers, light emitting diodes and mercury lamps with cut off filters. Table 1 illustrates a number of suitable semiconductor light sources that may be used in the embodiments disclosed herein.

Table 1 : Examples of suitable light sources

LED Sources

Laser Sources

In one non-limiting example, the waveband of the absorbing component 18 or 22 in the ink 20, and the waveband of the corresponding light source 26 each ranges from 380 nm to 430 nm. In another non-limiting example, the waveband of the absorbing component/particles 18 is the 780 nm waveband, and the waveband of the near infra red light source 26 is the 780 nm waveband. In yet another non- limiting example, the waveband of absorbing component/absorber 22 is the 675 nm waveband, and the waveband of the visible red laser light source 26 is the 650 nm waveband.

The EM radiation emanated from the light source 26 photo-thermally cures the ink 20 to which it is exposed. The emitted radiation causes the particles 18 to aggregate and fuse together to form a substantially homogeneous film 28. Since wavelengths inside the absorption waveband are substantially absorbed by the deposited ink 20, it is believed that all of the energy of the radiation from the light source 26 is concentrated and effectively used in curing the deposited ink 20. As such, it is believed that a low energy light source 26 may be used to effectively cure the ink 20 to form the film 28. In conventional light process technologies without using the absorber 22 or absorbing particles 18, a light or laser power of >10000 mWatts and energy density of >5000 millijoules/cm² is required for adequate processing of films, which also requires an excess of 110⁰C in temperature. In one example of the embodiments disclosed herein, the light source 26 is 1000 mW or less, and delivers energy of 10 to 900 milli joules/cm² to the deposited ink 20. In another example, the energy density is less than 1 joule/cm².

A non-limiting example of the film 28 is shown in Fig. 3. As discussed in reference to Fig. 2, the precursor of the film 28 is the ink 20, which, in this embodiment, is deposited and cured in a pattern to form circuitry. The film 28 includes the cured ink vehicle (i.e., a matrix) having the aggregated and fused particles 18 substantially homogeneously dispersed therein.

The films 28 disclosed herein may advantageously be used in a variety of applications, including, but not limited to, flex circuit preparation, printed circuit board manufacturing, conductive security antenna printing, decorative printing, and metal printing.

To further illustrate the embodiment(s) of the present disclosure, an example is given herein. It is to be understood that this example is provided for illustrative purposes and is not to be construed as limiting the scope of the disclosed embodiment(s).

EXAMPLE

InkJet inks were prepared using the formulation shown in Table 2, with readily available silver dispersions, such as CCI-300 (available from Cabot Corporation, Albuquerque, NM), SW-101 (available from Sumitomo Electric Industries, Japan), or CRSN2442 (available from SunChemical, England). It is to be understood that other inks may by synthesized using known procedures. The dispersions were modified by the addition of an absorber that absorbs at the 405 nm waveband or at the 780 nm waveband.

Table 2: Ink Compositions (amounts are in wt/wt ratio)

Ag Particles 20% w/w Dispersion Content 2.00% 10

Glycerine 5.00% 5 lsopropyl alcohol (IPA) 2.00% 2

2-Pyrrolidone 7.00% 7

Neopentyl alcohol 2.00% 2

Proxel GXL 0.20% 0.2

Surfynol 465 0.50% 0.5

Water 81.30% 73.0

Absorber (in Ink 1 , Absorber = lndocyanine Green and in Ink 2, Absorber = S0512^*) 0.3% 0.3

Total 100.00% 100

^*Absorber S0512 is available from Few Chemicals Gmbh, Germany

The inks were deposited via inkjet printers as coatings and lines onto photo- paper and Teslin® media. The coated films were exposed to laser light of the 405 nm waveband or the 780 nm waveband at 0.5 m/sec and from 5 to 50 mW power to cure the deposited ink and form films. Although this process is dynamic, the results shown herein were from an average of five microseconds of exposure time per area of about 100 square microns. The waveband to which the deposited inks were exposed was selected to match the waveband at which the particular absorber absorbs.

The Teslin® media used includes a polymer that deforms at about 130⁰C. It was observed that there was no substantial deformation in the Teslin® support, even when the bulk film temperature reaches >200°C for a short time. This particular property may be particularly useful in the preparation of electronics on plastics and glass epoxy boards, etc. As such, it is believed that in the embodiments disclosed herein, the film processing temperature may exceed the substrate/support deformation temperature by about 50⁰C or less for a short duration (e.g., less than a millisecond). In some instances, the deposited ink may be exposed to even higher processing temperatures. This may be accomplished, at least in part, because heating is localized when the laser matches the ink absorbance and when an absorber is included in the ink. Heating and cooling of the ink/film is substantially instantaneous, and thus there is no substantial heat transfer from the ink/film to the substrate. The radiative losses are proportional to the fourth exponent of temperature, so the metallic film cools off very fast (in milliseconds). Furthermore, low melting films are often organic, with low heat transfer coefficient.

Resistance and reflectivity were measured using a HP digital multimeter, and by judgment of darkness by visual observations of the photo images.

Figs. 4A and 4B illustrate micrographs of Ink 2 both before and after exposure to the laser treatment. As depicted, the film exposed to the corresponding absorbing waveband is more homogeneous and has higher reflectivity than the unexposed film. The resistance measurements (Ohm/cm) are shown in Table 3 below. As depicted, the resistance of the films after laser treatment was significantly decreased, thus illustrating that the films disclosed herein have increased conductivity. Table 3: Resistance Measurements: Ohm/cm (with track width measurements in parenthesis)

Before Laser After Laser

Treatment Treatment

Ink 1 (Track 1 350μ) 850 Ohm/cm ⁷⁰ Ohm/cm

Ink 1 (Track 2 700μ) 850 Ohm/cm 56 Ohm/cm

Ink 2 (Track 1 250μ) 73 Ohm/cm ³-² Ohm/cm

Ink 2 (Track 2 700μ) 32.6 Ohm/cm 1.2 Ohm/cm

While several embodiments have been described in detail, it will be apparent to those skilled in the art that the disclosed embodiments may be modified. Therefore, the foregoing description is to be considered exemplary rather than limiting.

Claims

What is claimed is:

1. A method for forming an energy activated film (28), the method comprising: depositing an ink (20) including a plurality of particles (18) therein, at least one component (18, 22) of the ink (20) configured to absorb electromagnetic radiation including a wavelength within a selected band of wavelengths, the selected band including wavelengths ranging from 10 nm to 50 nm from a peak component absorption wavelength; and exposing at least a portion of the deposited ink (20) to electromagnetic radiation having a wavelength within the selected band of wavelengths, the electromagnetic radiation emanating from a light source (26) configured to generate radiation having a wavelength ranging from 10 nm to 55 nm from the peak component absorption wavelength of the ink (20).

2. The method as defined in claim 1 , further comprising selecting nanoparticles having an average diameter less than 200 nm as the plurality of particles (18) and as the at least one component (18, 22) of the ink (20) configured to absorb the electromagnetic radiation including the wavelength within the selected band of wavelengths.

3. The method as defined in claim 1 wherein the ink (20) further includes an absorber (22) as the at least one component (18, 22) of the ink (20) configured to absorb the electromagnetic radiation including the wavelength within the selected band of wavelengths.

4. The method as defined in any of the preceding claims wherein exposing photo-thermally cures the at least the portion of the deposited ink (20) at an energy density of less than 1 joule/cm² to form the energy activated film (28).

5. The method as defined in any of the preceding claims wherein the selected band of wavelengths includes wavelengths ranging from 25 nm to 50 nm from the peak component absorption wavelength.

6. The method as defined in any of the preceding claims, further comprising selecting the plurality of particles (18) such that each particle (18) is in a zero valence state.

7. The method as defined in any of the preceding claims wherein depositing is accomplished via inkjet printing.

8. The method as defined in any of the preceding claims wherein specific absorption of electromagnetic radiation accomplished as a result of the exposing step causes the plurality of particles (18) to aggregate and fuse together.

9. The method as defined in any of the preceding claims wherein the energy activated film (28) is substantially more homogeneous.

10. The method as defined in any of the preceding claims wherein the ink is deposited on a substrate, and wherein during exposing, the substrate is exposed to a temperature that is equal to or less than 50⁰C of a deformation temperature of the substrate for less than one millisecond, and the ink is heated to a temperature higher than the substrate exposure temperature.

11. An energy activated film (28), comprising: a cured ink matrix formed from a metallic dispersion (20); aggregated and fused particles (18) substantially homogeneously dispersed throughout the cured ink matrix; and at least one component (18, 22) within the metallic dispersion (20) and within the cured ink matrix, the at least one component (18, 22), when in the metallic dispersion (20), configured to absorb electromagnetic radiation having a wavelength within a selected band of wavelengths ranging from 10 nm to 50 nm from a peak component absorption wavelength, the adsorbed electromagnetic radiation initiating the aggregation and fusing of the particles (18).

12. The energy activated film (28) as defined in 11 wherein the at least one component (18, 22) is an absorber (22) selected from porphyrin dyes, phthalocyanine dyes, napthalocyanine dyes, squaranine dyes, diazo dyes, and diazo metal complex dyes.

13. The energy activated film (28) as defined in any of claims 11 or 12 wherein the particles (18) are selected from silver nanoparticles, metal oxide nanoparticles, zinc nanoparticles, cadmium selenide nanoparticles, nanoparticles of metal alloys, nanoparticles of metal coated oxides, and nanoparticles of metal coated silica, and wherein the particles (18) are the at least one component (18, 22).

14. A system (10) for forming the energy activated film (28) of any of claims 10 through 13, comprising: a printer (12) configured to print an ink (20) on a substrate (24), the ink (20) being the metallic dispersion that includes a plurality of particles (18) and the at least one component (18, 22) configured to absorb the electromagnetic radiation having the wavelength within the selected band of wavelengths; and a light source (26) positioned to irradiate the deposited ink (20) with electromagnetic radiation having a wavelength ranging from 10 nm to 55 nm from the peak component absorption wavelength of the deposited ink (20).

15. The system as defined in claim 14 wherein the printer (12) is an inkjet printer.