DE102008001580A1 - Producing transparent conductive layer, by subjecting substrate e.g. glass to plasma treatment, applying dispersion from transparent conductive oxide nanoparticles on substrate, and partially removing solvent/dispersant from obtained layer - Google Patents

Abstract

The method comprises subjecting a substrate such as glass or plastic to a plasma treatment, applying a dispersion from transparent conductive oxide (TCO) nanoparticles on the substrate, partially removing solvent or dispersant from the obtained layer by annealing at 20-200[deg] C for a time period of 1 second to 60 minutes, and subsequently irradiating the obtained layer with a carbon dioxide (CO 2)-laser energy. The dispersion contains indium-tin oxide nanoparticles and is applied on the substrate by inkjet-printings, flexographic printings, pad-printings, spin coating and spraying. The method comprises subjecting a substrate such as glass or plastic to a plasma treatment, applying a dispersion from transparent conductive oxide (TCO) nanoparticles on the substrate, partially removing solvent or dispersant from the obtained layer by annealing at 20-200[deg] C for a time period of 1 second to 60 minutes, and subsequently irradiating the obtained layer with a carbon dioxide (CO 2)-laser energy. The dispersion contains indium-tin oxide nanoparticles and is applied on the substrate by inkjet-printings, flexographic printings, pad-printings, spin coating, spraying, dipping, knife-coating, offset printings, screen printings, thermo-transfer printings, gravure printings, flooding, aerosol jet deposition process or pouring. The obtained layer is irradiated with the CO 2-laser energy with a wavelength of 10.6 mu m and/or with an average output of 1 W to 3 kW and/or a scan line between the next adjacent lines of 0.01-2 mm described by scanning. During scanning, an intersection plane of the focused laser beam is moved with the plane of the obtained layer on the intersection plane with a speed of 50-150000 mm/s. An independent claim is included for a transparent conductive layer.

Description

The present invention relates to a process for producing transparent conductive layers based on transparent, conductive oxide (TCO) nanoparticles, in particular indium tin oxide (ITO) nanoparticles by CO ₂ laser irradiation, and the layers obtained by this process.

• – Widerstandsfähigkeit gegen Beanspruchung durch kratzende, scharfkantige Gegenstände oder Materialien, charakterisiert z. B. durch die Stifthärte nach Wolff-Wilborn oder durch die Bleistifthärte nach DIN EN 13523-4: 2001 ;
• – Haftung auf dem Substrat, ermittelt z. B. durch den Kreuzschnitt- oder Tape-Test nach DIN EN ISO 2409 ;
• – Zunahme des Flächenwiderstandes unter wiederholter, in einer definierten Anzahl Biegezyklen und einem definiertem Biegeradius ausgedrückten Biegebeanspruchung der Schicht, um einen begrenzten Faktor.

An electrically-mechanically stable layer is understood in the following to mean a layer which has the following properties:

• - Resistance to stress from scratching, sharp-edged objects or materials, characterized z. B. by the pencil hardness to Wolff-Wilborn or by the pencil hardness after DIN EN 13523-4: 2001 ;
• - adhesion to the substrate, determined z. B. by the cross-cut or tape test after DIN EN ISO 2409 ;
• Increasing the sheet resistance under repeated bending stress of the layer expressed in a defined number of bending cycles and a defined bending radius by a limited factor.

This increase is with a device after Königer et al. measured and is described at Königer and Münsted in Measurement Science and Technology , The increase in surface resistance decreases with increasing bending radius.

Under Sheet resistance is hereafter the ohmic resistance understood that on a coating with a uniform Layer thickness is obtained when a square area of any Contacted size on two opposite edges and the current as a function of the (DC) voltage is measured. The sheet resistance is measured in Ω and marked with Ω / ☐. The determination of the Sheet resistance can also be determined by other methods, such as z. B. the four-point measurement.

Under resistivity is hereinafter the ohmic resistance understood by multiplying the sheet resistance with the layer thickness [in cm] is obtained and a measure of the ohmic properties of the conductive material itself represents. The resistivity is in Ω · cm specified.

Under Transmission is hereafter the permeability of a transparent body for light of wavelength 550 nm understood.

The Transmission of a coated substrate is in proportion to the transmission in air in percentages.

transparent Layers with high ohmic conductivity have surface resistances of at most 10000 Ω / □ and a transmission of at least 40% and are used in all modern displays, eg. As LCD (liquid crystal display), plasma displays, OLEDs, and z. B. also required in organic solar cells to the by the photovoltaic effect excited electrical currents to be able to use with little loss.

in the The state of the art becomes conductive layers, for example produced by flame spraying or in a vacuum by sputtering techniques. A Structuring is not possible or only very expensive. It is generally made by applying various etching techniques receive.

conductive Layers are also produced on the basis of nanoparticles, wherein These must be thermally treated, according to the state the technology, for example, in a furnace process to the desired To achieve conductivity. The thermal aftertreatment of coatings of metallic nanoparticles, for example from silver particles, can also be done by laser irradiation.

For conductive layers that are transparent in the visible range, ITO has proven to be the most suitable material for applications in modern electronics. ITO layers on flexible polyethylene terephthalate (PET) substrates are produced in the prior art in sputtering or vapor deposition processes, the z. B. at DC Paine, H.-Y. Yeom and B. Yaglioglu in "Flexible Flat Panel Displys", pp. 79-98 , and S. Ray, R. Banerjee et al. in J. Appl. Phys. 54 (1983), 3497-3501 , are described in detail.

For continuous production processes are these coating techniques however, expensive, since they are carried out in a vacuum have to. There is also a textured coating of substrates only by a masking or by lithography process possible where ITO is wasted. The coating using printable ITO nanoparticle dispersions although a direct structuring by means of printing process under waiver on a litigation under vacuum, but it resulted the demand for an improvement of the specific resistance.

in the State of the art are investigations to improve the conductivity of ITO nanoparticle coatings on flexible polymer substrates by means of UV treatment is known in which the ITO nanoparticle dispersions modified with a UV-curing binder. This however, may affect the dispersion of the nanoparticles and increase the resistivity.

on the other hand For example, coatings of ITO nanoparticles become more economically viable Conductances thermally treated, with the nanoparticles fused or sintered.

The thermal aftertreatment of ITO nanoparticle coatings on flexible polymer substrates, however, because of their limited Thermal stability is difficult to solve Problem dar. For example, surface resistances below 1000 Ω / □ of ITO nanoparticle layers on PET substrates and at the same time transmissions of at least 80% In the visible range, the coatings must annealed from ITO nanoparticles at temperatures above 500 ° C become. For continuous production processes, for example Roll-to-roll production processes, for coating However, flexible transparent polymer substrates are the temperatures limited to values around 200 ° C, otherwise the polymer substrates will suffer and / or the coatings show cracks even at low bending stresses from the substrate.

thermal After treatment by laser irradiation at the same time more transparent and conductive coatings of non-metallic nanoparticles knows However, the prior art is not.

all A common prior art method is that the nanoparticles with each other and / or with other components or the substrate be sintered or fused. So there in the nano-layer Heat energy is generated, is so far always on it Pay attention that the heat transfer into the substrate does not become so large that in the substrate transformations of chemical (eg, decomposition) or physical type (eg, melting) be set. Especially with sensitive substrates like the Most plastic films is the temperature at which such unwanted Processes in the substrate occur, generally so low that not enough heat energy in the nanoparticulate Layer can be produced that optimizes the nanoparticles Sink or merge circumference. It is technical teaching so far, that the resistivity of conductive layers is lower the more comprehensive the nanoparticles sinter and / or merge.

task The present invention was therefore to provide a method which reduces the thermal load of the substrate and thus overcomes the disadvantages of the prior art. It was the same task, a layer with improved electrical-mechanical To provide stability.

These Task is solved by a process for producing transparent conductive Layers with the characterizing features of claim 1 solved.

• (1) Bereitstellung einer Dispersion aus TCO Nanopartikeln, anschließend
• (2) Aufbringen der nach Schritt (1) erhaltenen Dispersion auf ein Substrat, und zumindest teilweises Entfernen des Lösungsmittels oder Dispersionsmittels, anschließend
• (3) Bestrahlen der nach Schritt (2) erhaltenen Beschichtung mit CO₂-Laser Energie

umfasst.The subject matter of the present invention is therefore a process for producing transparent conductive layers, which comprises the steps

• (1) providing a dispersion of TCO nanoparticles, subsequently
• (2) applying the dispersion obtained after step (1) to a substrate, and at least partially removing the solvent or dispersant, subsequently
• (3) irradiating the coating obtained after step (2) with CO ₂ laser energy

includes.

The inventive method has the advantage that short interaction times are achieved and thus the thermal Loading of the substrate compared to methods in the state of Technology is greatly reduced. The invention Procedure is also inline-capable, synonymous So that this in a continuous production process for substrates with transparent conductive layers can be used, for example in a roll-to-roll process.

Therefore is also the subject of the present invention, a transparent conductive layer associated with the invention Procedure is obtained.

As well the subject of the present invention is an electronic component, having the layer according to the invention, as well as the use of the electronic according to the invention Component in an OLED (Organic Light Emitting Diodes), electroluminescent module, Display, photovoltaic element, touch-sensitive Screen, so-called touch panel, resistance heating element, infrared protection film, antistatic housing, chemical sensor, electromagnetic Sensor, FKD (liquid crystal display), so-called LCD, electrophoretic display.

The Invention will be explained in more detail below.

It may be advantageous to use in step (1) of the process according to the invention a dispersion which contains indium tin oxide nanoparticles. The preparation of such a dispersion is for example in the patent applications DE 10 2006 005 019.3 . DE 10 2006 005 025.8 , and DE 10 2006 005 026.6 , the publication DE 198 40 527 A1 , as well as the European patent application EP 06018493.4 disclosed. ITO nanoparticle dispersions, also nanocomposites based on ITO with, for example, polyvinylpyrrolidone, have the advantage that in the Step (3) of the method according to the invention, the majority of the CO ₂ laser energy is absorbed or reflected by the ITO nanoparticles, thus the energy input into the substrate is further reduced and therefore also sensitive and / or less expensive, less heat-resistant substrates can be used.

In It can be advantageous for the process according to the invention after step (1) and before step (2), the substrate in one further step (1A) to undergo a plasma treatment. These Possibility has the advantage of obtaining a substrate can be with the obtained after step (1) dispersion is more wettable.

It can be a hydrogen, oxygen, inert gas plasma, or a plasma from a mixture of these gases with one fed by microwaves Power from 1 to 5 kW, preferably from 2 to 3 kW at one pressure be used from 50 to 1100 hPa. The inert gas can be nitrogen, Argon, helium, neon, or a mixture of these inert gases selected become. Preferably, an under ambient conditions Air ignited plasma can be used. The plasma treatment can in step (1A) for a period of 1 to 60 s, preferably from 10 to 40 s, more preferably made from 25 to 35 s become.

Prefers can in step (2) of the method according to the invention dispersion by inkjet printing, flexo printing, pad printing, spin coating, spraying, dipping, knife coating, offset printing, screen printing, Thermal transfer printing, gravure printing, flood, Aerosil Jet Deposition Process of the company optomec, (optomec inc., Albuquerque, New Mexico) or pouring onto the substrate.

Thereby is a structuring, at least partially structuring up the substrate possible. Preferably, the dispersion applied once or several times and / or continuously or batchwise become. The environmental conditions are from the requirements of Dependent on and depending on how the dispersion is applied may be different.

Advantageously, in step (2) of the method according to the invention a substrate can be used which contains or is glass or plastic. Preference is given to using transparent materials, particularly preferably quartz glass, borosilicate display glass, alkali-free borosilicate display glass, white glass, window glass, float glass, polyester, polyamide, polyimide, polyacrylate, polycarbonate (PC), polyethersulfone (PES), polyetheretherketone (PEEK), polyvinyl chloride (PVC ), Polyethylene (PE), polypropylene (PP), polyacetal (POM), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polyhydroxybutyrate (PHB), polyamide 6, polyamide 6.6, polyamide 11, polyamide 12, Kapton ^® polymethyl methacrylate (PMMA) or a combination of these materials. Most preferably, these materials or a combination of these materials can be used in the form of films and / or laminates.

Preferably, in step (2) of the method according to the invention, a substrate can be used which is transparent or nearly transparent to the wavelength or the wavelengths of the CO ₂ laser used in step (3)

It may also be advantageous before step (3) of the invention Process the solvent or dispersant the coating obtained after step (2) at a temperature from 20 ° C to 200 ° C, preferably from 150 ° C to 200 ° C, more preferably from 180 ° C to 200 ° C during from 1 s to 60 min by annealing. Especially preferably, the solvent or dispersant for a period of 20 minutes at a temperature of 200 ° C, removed from the dispersion or solution become. The solvent or dispersant may be, for example by entry of electromagnetic energy or by contact of the Substrates with a hot plate, in a roll-to-roll process preferably by contact with at least one heated roll or calender removed. Furthermore, the solution or dispersing agent by irradiation with IR, VIS, or UV light, for example, by halogen lamps or emitting in the IR range Laser, in a tempering furnace, or by purging with heated Air or inert gas are removed. Particularly preferably, the Solvent or dispersing agent by at least one method which are integrated in a roll-to-roll process can. Up to 99% of the solvent or dispersant can preferably removed from the coating obtained after step (2) become. The fraction of solution or solvent removed by the annealing Dispersing agent may be by measuring methods known to those skilled in the art be determined, for example by gravimetric methods. To the tempering may have a layer thickness of 0.05 to 100 μm, preferably from 0.1 to 75 μm, more preferably from 0.5 to 50 microns, more preferably from 1 to 30 microns to be obtained.

In the method according to the invention, it may be advantageous if in step (3) the coating with CO ₂ laser energy with a wavelength of 10.6 microns and / or 9.4 microns, preferably 10.6 microns, and / or with a average power of 1 W to 3 kW, preferably from 5 W to 500 W, more preferably from 8 W to 30 W, most preferably from 10 W to 20 W, and / or continuously and / or pulsed, at least once irradiated by scanning, wherein the CO ₂ laser energy acts on the material of the coating in the cutting volume of the focused laser beam with the coating for a period of 0.01 .mu.s to 1000 .mu.s. Methods of measuring average power are known to those skilled in the art.

The advantage is that, due to the short duration of the action of the CO ₂ laser energy, no or much less heat is transferred to the substrate than with methods according to the prior art.

Preferably, in the method according to the invention, the coating can be repeatedly irradiated with CO ₂ laser energy from 1 to 5000 times by scanning.

If, in step (3), the coating obtained in step (2) is irradiated with pulsed CO ₂ laser energy, a pulse duration of 0.01 μs to 1000 μs may be advantageous in the method according to the invention. Pulse durations of from 5 μs to 1000 μs, more preferably from 10 μs to 900 μs, further preferably from 10 μs to 750 μs, particularly preferably from 20 μs to 500 μs, very particularly preferably from 30 μs to 400 μs, may preferably be used.

In continuously operated laser sources durations can during CO ₂ laser energy is entered in the step (2) coating obtained, may be advantageous from 0.1 to 1000 microseconds. With particular preference, these time periods can be from 10 to 900 μs for continuously operated beam sources, more particularly preferably from 50 to 750 μs, furthermore particularly preferably from 100 to 500 μs, very particularly preferably from 250 to 400 μs.

In It can be advantageous for the process according to the invention be when scanning the cut surface of the focused Laser beam with the plane of the coating obtained after step (2) at this level, at a speed called the scan speed, from 50 to 150000 mm / s is moved. Preferably, this speed of 1000 to 35000 mm / s, more preferably from 4500 to 15000 mm / s, very particularly preferably from 3000 to 10,000 mm / s.

It may also be advantageous in step (3) when scanning a Track spacing between those described by scanning next use adjacent lines of 0.01 to 2 mm, depending on the laser beam diameter on the workpiece or dimension of the beam in the direction perpendicular to the scanning direction. Preferably, a track pitch of 0.02 to 1.5 mm, more preferably from 0.05 to 1.25 mm, most preferably from 0.05 to 1 mm. The cut surface may be circular or elliptical, preferably elliptical be chosen, with the major axis of the ellipse oriented perpendicular to the feed direction of the laser beam. Also a rectangular, preferably square, cut surface can be beneficial.

In The process according to the invention can be carried out in step (3) are advantageously scanned meandering. Further preferred may be manually or through a small process control system scanned, which was particularly preferably implemented by a PC Software can be controlled. Furthermore preferred several lasers are used which are simultaneously or temporally staggered different or the same lines on the coating obtained in step (2) depart. If several lasers are used, track spacing, Speeds, and / or cut surfaces equal or different, preferably in each case the same.

The Steps (1), (1A), (2), (3) of the invention Processes can be repeated as often as desired, preferably once become.

object The present invention is also a transparent conductive Layer using the method according to the invention is obtained.

The Layer according to the invention can have a sheet resistance from 10 to 10,000 Ω / □, preferably from 10 to 100 Ω / □, furthermore preferably from 50 to 250 Ω / □, preferred from 250 to 1500 Ω / □ and from 1500 to 10000 Ω / □.

Preferably the layer according to the invention can increase the sheet resistance under bending stress, if in step (2), a flexible substrate is inserted around a Factor from 1.0 to 10 times after 50 bending cycles at a bending radius of 5 mm and an amplitude of 30 mm, measured according to Königer, preferably by a factor of 1 to 5 times, especially preferably from 1 to 3 times.

The According to the invention, as already stated, have different layer thicknesses after annealing in the step (2), preferably from 0.05 to 50 μm. Therefore can the sheet resistance depending on the use of the invention electronic component, the inventive Layer, advantageously selected.

If the electronic component according to the invention comprising the layer according to the invention is used in an OLED or FKD, this sheet resistance can be from 10 to 100 Ω / □ when used in an electroluminescent module of 50 to 250 Ω / □ when used in a touchpad from 250 to 1500 Ω / □, or in a sensor from 1500 to 10000 Ω / ☐.

Furthermore the layer according to the invention may have a transmission of at least 40%, preferably of at least 80%, more preferably of at least 90%. Most preferably, the inventive Layer have a transmission of at least 95%.

The layer according to the invention can according to a tape test according to DIN EN ISO 2409 measured adhesion preferably from 0% to 65%, equivalent to Gt 0 to Gt 4, preferably from 0% to 35%, equivalent to Gt 0 to Gt 3, more preferably from 0% to 15%, equivalent to Gt 0 to Gt 2 , very particularly preferably from 0% to 5%, meaning Gt 0 to Gt 1.

The layer according to the invention may preferably be made by means of a Scratch Hardness Tester from Erichsen, Model 291, according to test methods DIN 13523-4 measured pencil hardness of 8 B to 6 H, preferably from F to 6 H, more preferably from 3 H to 6 H.

The inventive method and the invention Layer are explained in more detail below using an example.

Example 1.

A PET film was first set in air for 30 seconds Environmental conditions ignited plasma exposed to the To improve wettability with the ITO nanoparticle dispersion, and then fixed on a heatable glass plate.

• – 35 Gew.-% ITO Nanopartikel mit Primärpartikeln einer Größe unter 20 nm, und
• – 65 Gew.-% Ethanol als Lösungs- oder Dispersionsmittel,

durch Rakeln mittels Erichsen Coatmaster Model 509 C in einer Dicke von etwa 100 μm aufgebracht. Die so erhaltene Beschichtung wurde bei einer Temperatur von 200°C an Luft für eine Dauer von 20 min getempert und eine Schichtdicke von 3 μm erhalten.Subsequently, a dispersion containing on the PET film

• 35% by weight of ITO nanoparticles with primary particles smaller than 20 nm, and
• 65% by weight of ethanol as solvent or dispersing agent,

applied by doctoring with Erichsen Coatmaster Model 509 C in a thickness of about 100 microns. The coating thus obtained was annealed at a temperature of 200 ° C in air for a period of 20 minutes and a layer thickness of 3 microns obtained.

1 shows a scanning electron micrograph (SEM) image of this coating.

Subsequently was the coating with a continuous CO2 Laser with a wavelength of 10.6 μm and a Power of 9 W irradiated. The diameter of the circular beam cross-section was 1 mm, the scan speed 4500 mm / s and the track pitch 0.05 mm.

2 shows an SEM image of the resulting layer according to the invention, which has a sheet resistance of (750 ± 50) Ω / □, a transmission of over 75%, and a Königer measured increase in sheet resistance by a factor of 2.4 after 50 bending cycles at a bending radius of 5 mm and an amplitude of 30 mm, which is equivalent to the increase of sheet resistance to approximately (1800 ± 50) Ω / □.

3 Figure 4 shows the behavior of the kinked increase in sheet resistance as a function of the number of bending cycles of the inventive layer (graph a) compared to the increase in sheet resistance of a layer of sputtered ITO on the same substrate obtained in the prior art (Graph (FIG. b)).

The layer according to the invention showed a DIN EN ISO 2409 determined adhesion coefficients of 1 and one according to test methods DIN 13523-4 measured pencil hardness of 3 H on.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102006005019 [0025]
• - DE 102006005025 [0025]
• - DE 102006005026 [0025]
• - DE 19840527 A1 [0025]
• EP 06018493 [0025]

Cited non-patent literature

• - DIN EN 13523-4: 2001 [0002]
• - DIN EN ISO 2409 [0002]
• - Königer et al. [0003]
• - Königer and Münsted in Measurement Science and Technology [0003]
• - DC Paine, H.-Y. Yeom and B. Yaglioglu in Flexible Flat Panel Displys, pp. 79-98 [0011]
• - S. Ray, R. Banerjee et al. in J. Appl. Phys. 54 (1983), 3497-3501 [0011]
• - DIN EN ISO 2409 [0048]
• - DIN 13523-4 [0049]
• - DIN EN ISO 2409 [0057]
• - DIN 13523-4 [0057]

Claims (15)

A process for producing transparent conductive layers, comprising the steps of (1) providing a dispersion of TCO nanoparticles, then (2) applying the dispersion obtained after step (1) to a substrate, and at least partially removing the solvent or dispersant, then (3) Irradiating the obtained after step (2) coating with CO ₂ laser energy. Method according to claim 1, characterized in that that after step (1) and before step (2), the substrate in a further step (1A) is subjected to a plasma treatment. Method according to claim 1, characterized in that that in step (1) a dispersion is used, the indium tin oxide Contains nanoparticles. Method according to claim 1, characterized in that that in step (2) the dispersion by inkjet printing, flexographic printing, Pad printing, spin coating, spraying, dipping, knife coating, offset printing, screen printing, thermal transfer printing, gravure printing, Flooding, Aerosil jet deposition process, or pouring on the substrate is applied. Method according to claim 1, characterized in that that in step (2) the substrate is selected, the glass or plastic contains or is. Method according to claim 1, characterized in that in that before step (3) the solvent or dispersant from the coating obtained after step (2) at a temperature from 20 ° C to 200 ° C for a period of time from 1 s to 60 min by annealing. A method according to claim 1, characterized in that in step (3) the coating with CO ₂ laser energy at a wavelength of 10.6 microns, and / or with an average power of 1 W to 3 kW, and / or a track pitch is irradiated between the next adjacent lines described by the scanning of 0.01 to 2 mm, and / or when scanning the cut surface of the focused laser beam with the plane of the obtained after step (2) coating on this plane at a speed of 50 to 150,000 mm / s is moved. Transparent conductive layer with a method according to at least one of claims 1-7 becomes. A layer according to claim 8 having a sheet resistance from 10 to 10,000 Ω / □. Layer according to claim 8 or 9 with a transmission of at least 40%. Layer according to at least one of the claims 8-10 with a tape test according to DIN EN ISO 2409 measured adhesion coefficients from Gt 0 to Gt 4. Layer according to at least one of the claims 8-11 with one according to test method DIN 13523-4 measured pencil hardness from 8 B to 6 H. Layer according to at least one of the claims 8-12 with an increase in sheet resistance under bending stress, if used in step (2) a flexible substrate is added by a factor of 1.0 to 10 times after 50 flex cycles a bending radius of 5 mm and an amplitude of 30 mm, measured according to King, at an amplitude of 30 mm. Electronic component, one layer after at least one of claims 8-13. Use of the electronic component according to claim 14 in an OLED, electroluminescent module, photovoltaic element, touch-sensitive screen, resistance heating element, Infrared protection film, antistatic housing, chemical Sensor, electromagnetic sensor, FKD, LCD, electrophoretic Display.