Material having a metal layer and a process for preparing this material

Abstract

A method for preparing a metal layer comprising: a) preparing a liquid composition comprising at least one precursor of at least one metal, at least one solvent of the precursor and at least one photo-initiator, the concentration of the precursor being at least 0.6% by weight relative to the weight of the liquid composition; b) depositing the liquid composition on a substrate forming a liquid composition deposited on a substrate; c) irradiating with a UV, Vis and IR source the liquid composition deposited on a substrate obtained at step b) forming a metal layer comprising or consisting of the metal; d) obtaining a metal layer. The present invention also relates to a material comprising a substrate and a metal layer, the metal layer being in contact with said substrate, the metal layer consisting of particles of metal in spatial contact together thereby forming a continuous metal layer of particles.

Claims

1. A method for preparing a metal layer, said method comprising: a) preparing a liquid composition comprising at least one precursor of at least one metal, at least one solvent of said precursor and at least one photo-initiator, wherein the concentration of the precursor is of at least 0.6% by weight relative to the weight of the liquid composition; b) depositing said liquid composition on a substrate thereby forming a liquid composition deposited on a substrate; c) irradiating with a UV, Vis and IR source the liquid composition deposited on a substrate obtained at step b) thereby forming a metal layer comprising or consisting of said metal; d) obtaining a metal layer.

2. The method according to claim 1, wherein said irradiating step c) is performed in the presence of a UV source providing an intensity sufficient to induce photoreduction of the precursor and to form metal particles thereby forming a continuous metal layer.

3. The method according to claim 1, wherein said irradiating step c) is performed in the presence of a UV source providing a fluence of at least 500 mW/cm.sup.2 in the range from 300 to 450 nm, on the liquid composition.

4. The method according to claim 1, wherein said irradiating step c) is performed during a time sufficient to induce the photoreduction of the precursor to form metal particles.

5. The method according to claim 1, wherein said metal layer forms a metal mirror surface.

6. The method according to claim 1, wherein said electronically conducting metal is selected from Ag, Au, Pd, Pt Cu, Cr, Zn, and any mixture thereof.

7. The method according to claim 1, wherein said metal layer comprises silver particles or nanoparticles.

8. The method according to claim 1, wherein said metal layer has a thickness of from 1 nanometer to 5000 micrometers.

9. The method according to claim 1, wherein said substrate is selected from the group consisting of silica; textile; metal substrates, wood, terephthalate, plastic materials, and any mixture thereof.

10. The method according to claim 1, wherein said liquid composition is deposited by spin coating, dip coating, spray coating, doctor blade coating, web coating, cup coating, slot/die coating, lip coating, roll-to-roll, printing, an ink deposit technique, ink printing, screenprinting, laser printing, microgravure, reverse microgravure, photolithography, serigraphic technique, spraying process or any combination thereof.

11. A material having a metal layer said material being obtainable by a method according to claim 1.

12. A material comprising a substrate and a metal layer, said metal layer being in contact with said substrate, said metal layer consisting of particles of metal in spatial contact together thereby forming a continuous metal layer of particles.

13. The material according to claim 12, wherein said substrate is a transparent substrate, said metal layer forms a reflective surface in contact with said transparent substrate.

14. The material according to claim 12, wherein said particles of metal present a decreasing disorder in the particles organization and coalescence from the substrate side to the opposite side of said metal layer.

15. A method for conducting heat or electricity wherein said method comprises contacting a metal layer of at least one material according to claim 12; with heat or electricity and conducting heat or electricity, respectively, though said metal layer.

Description

[0165] In the figures:

[0166] FIG. 1 represents schematically an embodiment wherein a material 1 comprises a substrate 10 a metal layer 20 comprising metal particles 22 and in which the disorder of metal particles 22 increases from the substrate side 15 to atmosphere side 25 or in other words the order of metal particles 22 increases from atmosphere side 25 to substrate side 15.

[0167] FIG. 2 represents results obtained by EDXS analysis according to example 1.

[0168] FIGS. 3 to 5 represent XPS spectra obtained according to example 1.

[0169] Other aims, characteristics, and advantages of the invention will appear clearly to the skilled person in the art upon reading the explanatory description which makes reference to the examples which are given simply as illustrations and which in no way limit the scope of the invention.

[0170] The examples make up an integral part of the present invention and any characteristic which appears novel with respect to any prior state of the art from the description taken its entirety, including examples, makes up an integral part of the invention in its function and in its generality.

[0171] Thus, every example has a general scope.

[0172] In the examples, all percentages are given by weight, unless indicated otherwise, temperature is expressed in degree Celsius unless indicated otherwise. Also pressure and temperatures are atmospheric pressure and room temperature (around 20 C. and 101 325 Pa), unless indicated otherwise.

EXAMPLES

Example 1: Preparation of the Metal Film on Glass Substrate

[0173] Silver nitrate (AgNO.sub.3) with a high purity (>99%), ethanol (purity 96%) and H.sub.2O distilled were purchased from Sigma-Aldrich and used as received. 2-Hydroxy-2-methylpropiophenone [CAS: No. 7473-98-5] was obtained from Aldrich.

[0174] The photochemical reactions were carried out with a Hamamatsu Lightningcure LC8 (HgXe L8252) device fitted with a 365 nm-elliptical reflector. The experimental set up used to shape up the actinic beam delivered to the sample a maximum fluence of 800 mW/cm.sup.2 in the 300-450 nm range.

[0175] Scanning electron microscopy (SEM) was used to characterize the metal film of silver particles. SEM samples were visualised directly on the glass slide. Measurements were carried out using a Philips CM200 instrument with LaB6 cathode at 200 kV.

[0176] The atomic force microscopy (AFM) investigations were performed on a Nanoscope V multimode AFM (Brucker) operating in tapping mode at ambient conditions. A 2 nm radius of curvature Si ultrasharp tip (SNL) with a Si.sub.3N.sub.4 cantilever of 0.37 N.Math.m.sup.1 nominal spring constant was used with a lateral scan rate of 1 to 2 Hz at 512 lines.

[0177] X-ray photoelectron spectroscopy (XPS) analysis was performed on a VG Scienta (Uppsala, Sweden) SES 200-2 x-ray photoelectron spectrometer under ultra-high vacuum (P<10-9 mbar). The spectrometer resolution at the Fermi level is about 0.4 eV. The depth analyzed extends up to about 8 nm. The monochromatized AlKa source (1486.6 eV) was operated at a power of 420 W (30 mA and 14 kV) and the spectra were acquired at a take-off angle of 90 (angle between the sample surface and photoemission direction). During acquisition, the pass energy was set to 100 eV for high-resolution and 500 eV for wide scan spectra. CASAXPS software (Casa Software Ltd, Teignmouth, UK, www.casaxps.com) was used for all peak fitting procedures.

[0178] The photosensitive formulation chromophore (0.5 wt. %) and H.sub.2O (2 g) was prepared in a flask covered with aluminium foil to protect it from light. Magnetic stirring was carried out at 40 C. for 10 min and after the heating was stopped and the metal precursor Ag.sup.+ (5 wt. %) was added (silver nitrate). This step ensures complete dissolution of the metal precursor and chromophore.

[0179] The reactive formulation was deposited by spin coating on a very thin layer on a substrate (glass slide).

[0180] The sample was set on a horizontal stand and irradiated at 1 W/cm.sup.2 for 1 min. In parallel with the photochemical reaction, the solvent evaporated progressively under the effect of its vapour tension. After irradiation, a metal layer was formed on the surface of the substrate. The metal layer generated onto the substrate exhibited remarkable stability on the air and strong adhesion on the substrate. On the substrate side (side where the metal layer is in contact with the substrate), a metallic reflective surface having a mirror aspect can be observed through the glass substrate. On the substrate side, objects can be reflected on the formed metal layer thereby forming a metallic mirror surface. On the atmosphere side a metal surface can be observed.

[0181] Different samples were prepared according to the same method.

[0182] Characterisation

[0183] The metal layers were characterized by AFM in order to study the roughness and the thickness of the deposited film on the glass substrate.

[0184] The AFM characterisations carried out in tapping mode, showed a film with high roughness on the air side.

[0185] The thickness of the thin film was about 1 m.

[0186] Additional examination of the nanostructures by SEM was carried out on the surface of the metal films (air side).

[0187] The image obtained showed a dispersion of Ag aggregates particles on the surface of the sample air side with a diameter ranging from some nm to 1-2 m. Chemical analysis by energy-dispersive X-ray spectroscopy (EDXS) confirmed the presence of high signal corresponding to silver and very smalls corresponding to carbon and oxygen; the last two ones were mainly related to same traces of the photosensitiser (chromophore) used to the reaction (FIG. 2).

[0188] XPS analysis was carried out to study the surface chemistry of the silver films. The XPS spectra obtained on the surface of a sample exposed 1 minute to UV light (FIGS. 3, 4 and 5) confirmed the results obtained by EDXS analysis i.e. only Ag, C and O are detected, the last two ones being assigned to the traces of the degradation products of the chromophore. The Ag 3d spectrum (368.31 eV) clearly revealed the presence of Ag (0) at the surface. Table 1, shows the position of the Ag 3d (FIG. 3), C1s (FIG. 4) and O1s (FIG. 5) peaks and the atomic concentrations.

[0189] The presence of the same three elements (Ag, C, O) was confirmed, and the Ag 3d spectrum showed only the peak corresponding to Ag(0) (368.31 eV). Since no other silver forms were visible, the reduction of Ag.sup.+ can be postulated to be complete.

TABLE-US-00001 TABLE 1 XPS fitting and the relative atomics concentrations lock Id Name Position Area/(RSF*T*MFP) % At Conc Ag3d Ag 3d5/2 368.31 22.6452 43.83 C1s CC CH 284.70 17.4157 33.71 C1s CO2 288.24 2.99687 5.80 C1s Sat 291.53 0.904551 1.75 O1s CO2 531.32 7.69785 14.90

Example 2: Preparation of a Water Photosensitive Formulation

[0190] 0.3% chromophore Darocur 1173 are added to 5 grams of distillated H.sub.2O. Magnetic stirring was carried out at ambient temperature for 10 min for homogenization. To this mixture, 3% by weight of AgNO.sub.3 were added. The mixing is maintained until complete dissolution of the AgNO.sub.3 about 3 min. The formulation is kept off from any light.

[0191] 3 drops of this formulation are disposed on a glass substrate and coated with thin layer by the solution and then irradiated under UV lamp during 35 sec at a power of 1100 mW/cm.sup.2. The glass substrate is only slightly washed with H.sub.2O before utilization.

[0192] A metal layer forming a metal mirror on the glass substrate side is obtained and very well attached to the substrate. Moreover on the other side, air side the metal layer is rough.

[0193] The metal layer is of submicrometric thickness.

[0194] The resistance is R=0.2 and depending directly on the thickness and photonic and chemical conditions.

[0195] The atomic force microscopy (AFM) as described in example 1.

[0196] Once the irradiation was stopped, the Ag films were characterized by AFM in order to study the roughness of the as-synthesized silver layers. The AFM characterisations carried out in tapping mode, showed well dispersed nanostructures. The topography is fairly irregular. The roughness was visualized on the AFM images (topography and phase).

[0197] X-Ray Photoelectron Spectroscopy (XPS) Characterisation

[0198] XPS analysis was performed as described in Example 1. The intensity area was determined using integrated peak areas of each component and taking into account the transmission factor of spectrometer, means free path, and sensibility factor of each atom.

[0199] XPS analysis was carried out to study the surface chemistry of these thin layers. The main element is Ag. Some other elements are also present (O, C). C and O come by the photolysis products of the chromophore. The spectrum of Ag 3d 5/2 (368.21 eV) supported the position of the peak corresponding to silver Ag(0).

[0200] Scanning Electron Microscopy SEM Characterization of Sample with Water

[0201] The SEM investigations were performed on a FEI Quanta 400 Scanning electron microscope. Images were recorded by SEM on the surface of the silver layer as it is. The images showed a good dispersion of particles obtained on the surface of the sample with a diameter ranging from 100 nm to 1 m. Chemical analysis by energy-dispersive X-ray spectroscopy (EDXS) confirms the presence of signals corresponding to silver, carbon and oxygen; the last two ones are related to the photolysis products of the chromophore. The Au signal is from the gold metallization of the sample before characterization (preparation necessary for the analyze)

[0202] Several diameters of AgNPs agglomerates were measured: D1=0.85 m; D2=0.48 m; D3=0.41 m.

Example 3: Preparation of a Water/Ethanol Photosensitive Formulation

[0203] 0.5% chromophore Darocur 1173 are added to 5 grams solvent EtOH/H.sub.2O 50/50 was prepared in a flask covered with aluminium foil to protect it from light. Magnetic stirring was carried out at ambient temperature for 15 min in the case of EtOH/H.sub.2O 50/50. To this mixture, 5% by weight of AgNO.sub.3 were added. The mixing is maintained until complete dissolution of the AgNO.sub.3 about 30 min at ambient temperature.

[0204] 1 drop of the reactive formulation was placed on the glass slide on a horizontal stand and a thin layer was coated. The sample was then irradiated under UV lamp during 30 sec at about 1100 mW/cm2.

[0205] A metal layer forming a metal mirror on the glass substrate side is obtained and very well attached to the substrate. Moreover on the other side, air side the metal layer is rough (according to Scanning electron microscopy SEM characterization).

[0206] The X-ray photoelectron spectroscopy (XPS) characterisation of this sample was as follows:

TABLE-US-00002 Sample Area/ % At Identifier Block Id Name Position (RSF*T*MFP) Conc MA 11 Ag3d Ag3d5/2 368.30 71.4411 44.20 C1s CC CH 284.30 52.9185 32.74 C1s CO 287.64 7.87792 4.87 C1s CO 285.31 6.02964 3.73 O1s CO 530.85 17.1302 10.60 O1s NO3 532.46 4.67682 2.89 N1s NO3 406 1.55978 0.97

Example 4: Preparation with an Ethanol Photosensitive Formulation

[0207] 0.5% chromophore Darocur 1173 are added to 5 grams solvent EtOH in a flask covered with aluminium foil to protect it from light. Magnetic stirring was carried out at ambient temperature for 15 min. To this mixture, 5% by weight of AgNO.sub.3 were added and mixed for 60 min at ambient temperature.

[0208] 1 drop of the reactive formulation was placed on the glass slide on a horizontal stand and a thin layer was coated. The sample was then irradiated under UV lamp during 25 sec at about 1100 mW/cm2.

[0209] A metal layer forming a metal mirror on the glass substrate side is obtained and very well attached to the substrate. Moreover on the other side, air side the metal layer is rough (according to Scanning electron microscopy SEM characterization).

[0210] X-ray photoelectron spectroscopy (XPS) characterisation of this sample was as follows:

TABLE-US-00003 Sample Area/ % At Identifier Block Id Name Position (RSF*T*MFP) Conc MA 12 Ag3d Ag3d5/2 368.30 52.0201 31.36 C1s CC CH 284.36 58.7022 35.39 C1s CO 287.67 9.03432 5.45 C1s CO 285.58 7.87922 4.75 O1s CO 530.89 16.1924 9.76 O1s NO3 532.23 16.5315 9.97 N1s NO3 406.20 5.49999 3.32

Example 5: Preparation of a Water/Ethanol Photosensitive Formulation with Gold (Au)

[0211] 0.5% chromophore Darocur 1173 were added to 5 grams of a mixture of solvents EtOH/H.sub.2O 10/90 in a flask covered with aluminium foil to protect it from light. Magnetic stirring was carried out at ambient temperature for 30 min. To this mixture, 2% by weight of HAuCl.sub.4 were added. The mixing is maintained until complete dissolution of the HAuCl.sub.4, about 5 min at ambient temperature (20 C.).

[0212] 3 drops of the reactive formulation was placed on the glass slide on a horizontal stand and a thin layer was coated. The sample was then irradiated under UV lamp during 1 min 30 sec at about 650 mW/cm2 UVA.

[0213] The resistance is about R=0.5 and depending directly on the thickness and photonic and chemical conditions.