KR20170092568A - Electrically conductive compositions, process and applications - Google Patents

Abstract

An electroconductive composition based on electroconductive particles, the use of said electroconductive composition in a method of making an electroconductive mesh, and a fabricated conductive mesh, and a touch panel display comprising an electroconductive mesh on the substrate.

Description

[0001] ELECTRICALLY CONDUCTIVE COMPOSITIONS, PROCESS AND APPLICATIONS [0002]

The present invention relates to electrically conductive compositions based on electrically conductive particles and their use in electrically conductive meshes. The electrically conductive composition according to the present invention can be used for a touch screen.

The touch screen sensor senses the position of an object (e.g. a finger or stylus) applied to the surface of the touch screen display or the position of an object located near the surface of the touch screen display. These sensors sense the position of an object along the surface of the display, for example in the plane of a flat rectangular display. Examples of touch screen sensors include capacitive sensors, resistive sensors, and projected capacitive sensors. Such sensors include electrically conductive elements that overlay the display. These elements are combined with electronic components that use electrical signals to contact the display or to probe the elements to determine the location of an object in the vicinity.

In the field of touch screen sensors, there is a need to have improved control over the electrical properties of the touch screen sensor without compromising the optical quality of the display. In general, optical quality can be expressed in terms of visible light transmittance, haze, and sensor visibility. The quality is determined by observing the sensor when it is assembled on the touch screen by the human eye. Typically, in a metal mesh touch sensor, the transparent micropatterned conductive region includes a metal mesh structure, which is used as a touch screen sensor. The geometry of the micropatterned mesh structure includes, but is not limited to, the width and height of the mesh traces (sometimes referred to as "lines ") used for the micropattern, the density of the lines, Can be defined with the same parameters. The micropattern usually has a line width of less than 5 μm (these fine lines are not visible to the human eye), a trace height of less than 5 μm, and an open area fraction of 95% to 99.99%. The space between the mesh lines (transparent area) is usually from a few hundred microns to several millimeters. In this way, very high transparency of the touch screen sensor can be achieved. The micropatterned mesh structure may be, for example, a diamond shape, a hexagonal shape, or a random shape. The electrical conductivity of a touch screen sensor is related to the density of the line and the geometry of the line.

In one form of metal mesh technology, a mesh pattern is first formed on the substrate surface, the mesh pattern consisting of grooves having suitable widths and heights. The grooves are then filled with an electrically conductive composition. After any residual composition in the filling process is removed from the substrate surface during the cleaning step, the electrically conductive composition in the mesh groove is cured or sintered at elevated temperature to form a solid conductive metal mesh structure. The ease of cleaning and the amount of residual composition on the surface are very important factors in determining product yield loss due to visual defects on the surface caused by excessive residue.

The metal mesh structure may be made from a highly electrically conductive metal or metal alloy consisting of metal particles of micron or submicron size. Silver particles are often used to form conductive mesh lines to ensure high conductivity of the mesh structure. However, the surface of the cured silver line usually has a high reflectance and can be detected by the human eye. This visibility impairs the optical quality of the touch screen sensor and, consequently, the display comprising the touch screen sensor, and thus is one of the major drawbacks of this technology.

It is known to paint a dark overlay of a black ink coating on top of a conductive metal mesh line to reduce the reflectivity of the surface of the metal mesh structure. Thereby, there will be additional process steps to extend the overall process and thus increase process time and cost. Also, the added step can result in additional yield loss.

Another solution known in the prior art is the addition of a black dye material (e. G. Carbon black or organic black dye) to the conductive composition to reduce the surface reflectance of the cured metal mesh surface. However, this may result in an uneven color appearance on the film surface if the dye is not evenly distributed. Also, due to the insulating nature of the organic black dye material and the lower conductivity of the carbon black, the conductivity of the cured metal mesh will decrease.

Thus, there remains a need to provide an electrically conductive composition that has the ability to cure or sinter at relatively low temperatures, has sufficient adhesion to the substrate after curing or sintering, high electrical conductivity, and low reflectivity. It is also desired that the residual composition can be simply removed from the substrate surface outside the grooves before curing.

The present invention provides a method of forming a composite particle comprising: a) a first particle having an aspect ratio of at least 1 and less than 2.0 and being selected from spherical particles, faceted particles, pyramidal particles and mixtures thereof; Or a mixture of the first particles and second particles that are non-spherical particles having an aspect ratio greater than 2.0; b) a resin; And c) at least one organic solvent.

The present invention also relates to a process for producing a transparent electroconductive mesh comprising the electroconductive composition according to the invention, and to the resulting electroconductive mesh structure.

The invention also encompasses the use of electrically conductive mesh structures in touch sensor technology.

Finally, the present invention comprises a touch panel display comprising an electrically conductive mesh on a substrate comprising a cured or sintered composition according to the present invention.

The present invention is described in more detail in the following paragraphs. Each aspect described above may be combined with any other aspect or aspect as opposed to being explicitly stated. In particular, any feature that is shown as being preferred or advantageous may be combined with any other feature or feature that is shown as being advantageous or advantageous.

In the context of the present invention, unless the context clearly indicates otherwise, the terms used should be construed in accordance with the following definitions.

As used herein, the singular forms "a," "an," and "the" include both singular and plural referents unless the context clearly dictates otherwise.

As used herein, the terms "comprising," "comprises," and "comprising" are intended to be inclusive, And do not exclude the inclusion of a generic or open, additional, unrecited member, element, or method step.

The description of numerical endpoints includes all numbers and fractions included in each range as well as the endpoints described.

All percentages, parts, ratios and the like mentioned herein are by weight unless otherwise indicated.

When an amount, concentration, or other value or parameter is expressed in the form of a range, a preferred range, or a desirable upper limit value and a desired lower limit value, any range obtained by combining any lower limit or desired value with any upper limit or desired value, It should be understood that the scope is specifically disclosed without considering whether it is explicitly mentioned in this context.

All references cited herein are incorporated herein by reference in their entirety.

Unless otherwise defined, all terms used to describe the invention, including technical and chemical terms, have the meaning commonly understood by one of ordinary skill in the art to which this invention pertains. By way of further guidance, the following definitions are included to better understand the teachings of the present invention.

The present invention provides a method of forming a composite particle comprising: a) a first particle having an aspect ratio of at least 1 and less than 2.0, the particle being selected from spherical particles, particles having facets and mixtures thereof; Or a mixture of the first particles and second particles that are non-spherical particles having an aspect ratio greater than 2.0; b) a resin or a mixture of resins; And c) at least one organic solvent.

The electrically conductive compositions according to the present invention provide the ability to cure or sinter at relatively low temperatures. The cured or sintered compositions according to the present invention have sufficient adhesion to the substrate, high electrical conductivity and low reflectance. In addition, the residual composition can be simply removed from the substrate surface outside the grooves before curing.

Each essential component of the electrically conductive composition according to the present invention is described in detail below.

Electrically conductive particle

The electroconductive composition according to the present invention comprises a first particle having an aspect ratio of at least 1 and less than 2.0 and being selected from spherical particles, particles having facets, pyramidal particles and mixtures thereof; Or a mixture of said first particles and second particles which are non-spherical particles having an aspect ratio of greater than 2.0.

The particles according to the present invention are characterized by the shape and size of the particles. The particle size is measured by a particle size analyzer and the particle shape is analyzed by a scanning electron microscope. In summary, the detector array detects scattered laser light from the particles. The theoretical calculations are performed to fit the measured distribution of the scattered light intensity. During the fitting process, the particle size distribution is deduced and therefore the values D10, D50, D90, etc. are calculated. The particles according to the invention have a D50 of 10 nm to 500 nm and a D90 of 1 μm or less.

The term "aspect ratio" as used herein means an image projection attribute that describes the proportional relationship between the width of the particle and its height. The particle shape is observed by SEM and the dimensions are measured and an average value of the aspect ratio is provided.

As used herein, the aspect ratio refers to the average aspect ratio of 50, preferably 100 particles of each filler, measured according to the following method of measurement.

The aspect ratios used herein are related to the ratio between sizes at different dimensions of the three-dimensional object, more specifically the ratio of the longest side to the shortest side, e.g., height to width. Thus, since the ball-shaped or spherical particles have an aspect ratio of about 1, they have a tendency to have an aspect ratio of more than 10, since they have comparable small diameters or thicknesses in relation to their length or length and width have. The aspect ratio can be determined by scanning electron microscope (SEM) measurement. As the software, "Analysis pro" from Olympus Soft Imaging Solutions GmbH may be used. The magnification is from x 250 to x 1000 and the aspect ratio is the median value obtained by measuring the length and width of at least 50, preferably 100, particles in the photograph. For relatively large and thin fillings, SEM measurements can be obtained at an oblique angle of 45 DEG of the sample.

The electrically conductive first and second particles according to the present invention are selected from the group consisting of metals, metal alloys, metal-containing composites, non-metal particles and mixtures thereof, preferably silver, gold, platinum, Nickel, aluminum, zinc, iron, copper-nickel, silver-copper, silver-nickel, copper-aluminum, silver plated copper, silver plated glass, silver plated graphite, silver plated fiber, graphite, carbon black, , And more preferably the electroconductive particles are silver particles.

Silver particles are desirable due to their ideal balance between conductivity and price.

The first particle

In one embodiment, the electrically conductive composition according to the present invention comprises electrically conductive first particles having an aspect ratio of at least 1 and less than 2.0, and the aspect ratio is measured as described above. The first particle has a spherical or angular or pyramidal shape. The first particle may contain only one shape from a spherical, angled, or pyramidal shape. Alternatively, the first particle may also be a mixture of any two shapes or a mixture of all three shapes.

The first particles according to the invention preferably have an average particle size of from 5 nm to 1 [mu] m, more preferably from 5 nm to 500 nm and even more preferably from 5 nm to 200 nm.

The width of the grooves in the metal mesh application is usually less than 5 μm for large touch sensors and less than 2.5 μm for small sensors. In order to successfully fill in the grooves to form conductive lines, it is necessary to control the composition according to the invention such that the particle size is smaller than the width of the grooves. Thus, the preferred size range is ideal for metal mesh applications. Additionally, silver particles with smaller particle sizes have a darker color compared to silver particles with larger particle sizes. Particularly, particles with a size between 5 nm and 200 nm have a darker color than larger particles, which is advantageous in reducing the reflectance of the conductive mesh pattern, and thus less visible to the human eye.

The composition according to the invention comprises first particles in an amount of 5% to 85% by weight, preferably 60% to 75% by weight of the total weight of the composition.

If the composition comprises a first particle that is less than 5% by weight of the total weight of the composition, this may result in lower conductivity. On the other hand, if the composition comprises first particles that are greater than 85% by weight of the total weight of the composition, this may lead to poor adhesion and too high viscosity, because the solvent or resin binder is not sufficient. An ideal range of 60-75 weight percent of the total weight of the composition provides rheology and mechanical properties and ideal conductivity suitable for metal mesh applications.

The spherical and / or angled and / or pyramidal particles in the adhesive composition according to the invention improve the optical properties, meaning they reduce the overall reflectance. In addition, spherical and / or angled surfaces and / or pyramidal particles improve the removal of residual adhesive outside the grooves.

The second particle

In one embodiment, an electrically conductive composition according to the present invention comprises an electrically conductive first particle and a mixture of electrically conductive second particles that are non-spherical particles having an aspect ratio greater than 2.0.

If the conductive composition comprises only the second (non-spherical) particles, excellent conductivity can be achieved, but the optical properties will not be ideal since the reflectance of the composition will be very high.

To improve the balance between conductivity and optical properties, particles having an aspect ratio of at least 1 and less than 2 may be used in combination with non-spherical particles having an aspect ratio of greater than 2. Also, the use of mixtures of non-spherical and spherical and / or angular surfaces and / or pyramidal particles can improve the physical properties of the cured composition, especially the adhesion of the cured mesh structure to the substrate.

The second particle having an aspect ratio of greater than 2.0 is defined as a non-spherical particle. Non-spherical particles according to the present invention may have, for example, a flaky or rod-like shape. The non-spherical particles according to the present invention preferably have an aspect ratio of greater than 10.0.

Higher aspect ratios provide lower filtration thresholds, resulting in improved conductivity. A lower filtration threshold due to the high aspect ratio (which means that it forms a continuous contact between silver particles and possibly silver particles to start forming an electrically continuous path) is the fundamental reason for conductivity. Also, in this application, the filling of the denser grooves contributes to improved conductivity. Finally, the lower contact resistance between the particles is another factor for better conductivity.

The non-spherical particles according to the present invention preferably have an average particle size of 10 nm to 2 占 퐉, and more preferably 10 nm to 1 占 퐉.

The width of the grooves used in the metal mesh application according to the present invention is less than 5 占 퐉 for a large touch sensor and less than 2.5 占 퐉 for a small touch sensor. In order to successfully fill the grooves with conductive particles and to obtain conductive lines, the particle size must be optimized and controlled. Thus, the selected particle size range of the present invention is ideal for metal mesh applications.

When the conductive composition according to the present invention comprises a mixture of first and second particles, the second particles are present in an amount of 10% to 85% by weight, preferably 30% to 70% by weight, of the total weight of the composition And the first particles are present in an amount of 5 to 40% by weight of the total weight of the composition.

A selected combination of first and second particles provides ideal conductivity with a comparable color. A larger amount of second particles is preferred. The greater the amount of the first particles in the composition, the less the conductivity of the composition will be. However, the color L * value is inverse trend. The greater the amount of the first particles in the composition, the darker the color is seen. Thus, in order to provide a comparable color L * < 60% and good conductivity (VR < 5E-05 ohm.cm), it is preferred that the composition contains a larger amount of second particles.

In a highly preferred embodiment, the weight ratio of the second particle to the first particle is from 6: 1 to 1: 2, more preferably from 3: 1 to 1: 1.

Suzy

The electrically conductive composition according to the present invention comprises a resin or a mixture of resins. The resin used in the present invention should have good solubility in the solvent used in the composition. In addition, the resin should have good solvent release properties during curing or sintering at elevated temperatures to ensure complete drying at relatively low temperatures. The resins used in the present invention should have good compatibility with the selected particles. The resin should also have good mechanical and rheological properties to facilitate the grooving process. As a binder material in the middle of the particles, the resin should have good conductivity. Finally, the resin should have good adhesion to substrates used with polyethylene terephthalate (PET).

Preferably, the resin used in the composition according to the invention is selected from the group consisting of halogenated thermoplastic resins, phenoxy resins, polyester resins, thermoplastic polyurethanes, polyacrylates, silicones and mixtures thereof, The resin is selected from the group consisting of polyvinyl dichloride, polyvinyl dichloride copolymer, phenoxy resin PKHH and mixtures thereof, more preferably polyvinyl dichloride and polyvinyl dichloride copolymers and mixtures thereof &Lt; / RTI &gt;

Thermoplastic resins suitable for use herein include vinyl copolymers, polyesters, polyurethanes, and others. In certain embodiments, the thermoplastic resin suitable for use herein comprises a halogenated thermoplastic resin.

In certain embodiments, a composition according to the present invention comprises a polyvinyl dichloride copolymer comprising a first monomer and a second monomer, wherein the first monomer is selected from the group consisting of vinyl acetate, vinyl alcohol, vinyl chloride, vinylidene chloride, Styrene and the second monomer is selected from the group consisting of a second vinyl acetate, a second vinyl alcohol, a second vinyl chloride, a second vinylidene chloride, a second styrene, an acrylate and a nitride.

In certain embodiments, the first monomer is vinylidene chloride and the second monomer is vinyl chloride, acrylonitrile, or alkyl acrylate.

In certain embodiments, the first monomer is vinylidene chloride and the second monomer is vinyl chloride (e.g., polyvinylidene chloride). In certain embodiments, the first monomer is vinylidene chloride and the second monomer is an alkyl acrylate.

According to certain embodiments, the compositions according to the present invention optionally comprise one or more thermosetting resins selected from the group consisting of epoxy-functionalized resins, acrylates, cyanate esters, silicon, oxetanes, maleimides, .

A wide variety of epoxy-functionalized resins, for example liquid-type epoxy resins based on bisphenol A, solid-type epoxy resins based on bisphenol A, liquid-type epoxy resins based on bisphenol F, Polyfunctional epoxy resins based on novolac resins, dicyclopentadiene-type resins, naphthalene-type epoxy resins and mixtures thereof are suitable for use herein.

Examples of suitable epoxy-functionalized resins for use in the present invention include aliphatic alcohols, hydrogenated bisphenol A, diepoxides of bifunctional cycloaliphatic glycidyl esters of hexahydrophthalic anhydride, and mixtures thereof .

Acrylates suitable for use in the present invention are well known in the art.

Examples of (meth) acrylates suitable for use in the present invention include compounds having formula (I)

(I)

Wherein R is H or methyl and X is (a) an alkyl group having from 8 to 24 carbon atoms, or (b)

Where R is H or methyl, R 'is independently selected from H or methyl, and x is an integer from 2 to 6.

Preferably, (meth) acrylate is selected from the group consisting of tridecyl methacrylate, 1,6-hexanediol dimethacrylate, 1,10-decanediol diacrylate, 1,10-decanediol dimethacrylate, 12-dodecanediol diacrylate, 1,12-dodecanediol dimethacrylate, and mixtures thereof.

Cyanate esters suitable for use in the present invention are well known in the art.

Cyanate ester monomers suitable for use in the present invention contain two or more rings that form a cyanate (-O-C = N) group, which cyclotrimerizes upon heating to form a substituted triazine ring. The curing reaction is referred to as addition polymerization because no leaving group or volatile by-products are formed during the curing of the cyanate ester monomer. Preferably, the polycyanate ester monomers that can be used in the present invention are 1,1-bis (4-cyanatophenyl) methane, 1,1-bis (4-cyanatophenyl) (4-cyanatophenyl) propane, bis (4-cyanatophenyl) -2,2-butane, 1,3- Bis (4-cyanato-3,5-dimethylphenyl) methane, tris (4-cyanatophenyl) ethane, cyanated novolak, 1, 3-bis 4-cyanatophenyl-1- (1-methylethylidene) benzene, cyanated phenol-dicyclopentadiene adducts, and mixtures thereof. The polycyanate ester monomers used in the present invention can be easily prepared by reacting a halogenated cyano group with a suitable divalent or polyhydric phenol in the presence of an acid acceptor.

Silicones suitable for use in the present invention are well known in the art.

Silicone-based adhesive formulations suitable for use in the present invention include a substantially stoichiometric mixture of polysiloxane (s) end-capped with a hydride and polysiloxane (s) end-capped with vinyl. The polysiloxane with a terminal end of the hydride, which is exemplified for use herein, is a polydimethylsiloxane endblocked with a hydride. The vinyl-terminated polysiloxane, which is exemplified for use herein, is a polydimethylsiloxane having a divinyl terminated group.

Also suitable resins for use in the present invention are oxetanes containing monomers and / or oligomers.

The electrically conductive composition according to the present invention comprises a resin that is 1 wt% to 10 wt%, preferably 1 wt% to 8 wt%, and more preferably 2 wt% to 6 wt% of the total weight of the composition.

Very poor adhesion is provided when the composition comprises less than 1% by weight of the total weight of the composition. On the other hand, if the composition comprises a resin that is greater than 10% by weight of the total weight of the composition, this may lead to poor conductivity, which is not ideal for metal mesh applications.

Preferably, the volume ratio of the conductive particles and the resin is 1.5 to 3.5, preferably 2.0 to 3.0.

The volume ratio is calculated based on the weight of the conductive particles and resin added to the composition. Since the density of particles and resin is known, volume = weight / density.

This volume ratio range is ideal, and it meets the conductivity requirements (<5E-05 ohm.cm).

menstruum

The electrically conductive composition according to the present invention comprises at least one organic solvent. A wide variety of known organic solvents may be used in the present invention. As a solvent for use in the present invention, this is not particularly limited so long as it has good compatibility with both the resin and the conductive particles used in the composition according to the present invention. Preferred solvents should have a relatively low evaporation rate at room temperature and a relatively high evaporation rate at the curing temperature to ensure adequate binder shrinkage and sufficient curing during drying to ensure adequate processing time.

Suitable organic solvents for use in the present invention are preferably dipropylene glycol methyl ether (DPM), 3-methoxy-3-methyl-1-butanol (MMB), butyl glycol acetate (BGA), diethylene glycol, ethylene (DBE-3), a mixture of dimethyl adipate and dimethyl glutarate (DBE-3), succinic acid dimethyl ester (DBE-4), glutaraldehyde Is selected from the group consisting of acid dimethyl ester (DBE-5), dimethyl adipate (DBE-6), propylene glycol methyl acetate (PMA), butyl carbitol (BC), butyl carbitol acetate (BCA) And more preferably selected from the group consisting of DBE-9, DPM, PMA, BC, BGA, and mixtures thereof.

The electrically conductive composition according to the present invention comprises at least one organic solvent which is 10% to 50%, preferably 15% to 40%, more preferably 20% to 35% by weight of the total weight of the composition . The amount of solvent herein is meant to include the total sum of solvent and possible co-solvent.

The term secondary-solvent refers to the additional solvent that comes in with the other reagent and composition, or the solvent used to provide, for example, particle dispersion.

If the amount of solvent and co-solvent is too high in the composition, the effective solids content will decrease in the composition, which results in a thinner film after curing and thus, a poorer conductivity. On the other hand, if the composition is insufficiently solvent, the composition can have a very high viscosity, which can lead to work-ability problems during the manufacturing process.

additive

In addition to the above-mentioned components, the electrically conductive composition according to the present invention may further comprise additives in an amount of 0.01 wt% to 5 wt%, preferably 0.05 wt% to 2 wt% of the total weight of the composition.

The additive may be selected from the group consisting of rheology modifiers, conductivity modifiers, pigments, and mixtures thereof.

In particular, when the composition according to the present invention contains only the first particles, the conductive modifier is a highly preferred additive. A large amount of the first particles in the composition according to the invention can in some cases reduce the conductivity of the composition. Therefore, it is desirable to use additional conductivity modifiers to improve the conductivity of the composition.

The conductive modifier is different from the electrically conductive particles (different from the first and second particles). Examples of suitable conductivity modifiers for use in the present invention include organic acid-containing compounds such as diacids, for example glutaric acid; Phosphate-containing organic compounds such as phosphoric acid 2-hydroxyethyl methacrylate ester; Metal complexes, and organometallic compounds such as silver acetylacetonate, palladium methacrylate.

Examples of pigments suitable for use in the present invention include dyes such as Clariant RLSN, Clariant GLX; Inorganic materials such as carbon black, nickel oxide, cobalt oxide, silver oxide; Is an organometallic compound such as acetylacetonate and palladium methacrylate.

In particular, when the composition according to the present invention contains only the first particles, the rheological modifier is a highly preferred additive. Since the use of the first particles in the composition increases the adhesion and / or adhesion of the composition and thus reduces its rheological profile. Therefore, adjustment of the rheology of the composition is necessary.

Examples of rheological modifiers suitable for use in the present invention include, for example, Disperbyk-111, Disperbyk-180, Disperbyk-145, and BYK-Chemie from BYK- W980.

In one preferred embodiment, the electrically conductive composition according to the present invention comprises a first electrically conductive particle having an aspect ratio of at least 1 and less than 2.0 and selected from spherical particles, particles having facets, pyramidal particles and mixtures thereof, And at least one organic solvent.

In another preferred embodiment, the electroconductive composition according to the present invention has an aspect ratio of at least 1 and less than 2.0 and comprises a first particle selected from spherical particles, particles having facets, pyramidal particles and mixtures thereof and an aspect ratio of more than 2.0 And particles, resin, and at least one organic solvent that is a mixture of second particles that are non-spherical particles having an average particle size of about &lt; RTI ID = 0.0 &gt;

In one preferred embodiment, the electrically conductive composition according to the present invention comprises a first electrically conductive particle having an aspect ratio of at least 1 and less than 2.0 and selected from spherical particles, particles having facets, pyramidal particles and mixtures thereof; Suzy; And at least one organic solvent and at least one conductivity modifier.

In one preferred embodiment, the electrically conductive composition according to the present invention comprises a first electrically conductive particle having an aspect ratio of at least 1 and less than 2.0 and selected from spherical particles, particles having facets, pyramidal particles and mixtures thereof; Suzy; And at least one organic solvent and at least one rheological modifier.

In one preferred embodiment, the electrically conductive composition according to the present invention comprises a first electrically conductive particle having an aspect ratio of at least 1 and less than 2.0 and selected from spherical particles, particles having facets, pyramidal particles and mixtures thereof, At least one organic solvent, at least one conductivity modifier, and at least one rheological modifier.

In another preferred embodiment, the electroconductive composition according to the present invention has an aspect ratio of at least 1 and less than 2.0 and comprises a first particle selected from spherical particles, particles having facets, pyramidal particles and mixtures thereof and an aspect ratio of more than 2.0 At least one organic solvent, and at least one conductivity modifier, which is a mixture of the first particles and the second particles that are non-spherical particles having a specific surface area of less than about 200 nm.

In another preferred embodiment, the electroconductive composition according to the present invention has an aspect ratio of at least 1 and less than 2.0 and comprises a first particle selected from spherical particles, particles having facets, pyramidal particles and mixtures thereof and an aspect ratio of more than 2.0 At least one organic solvent, at least one conductivity modifier, and at least one rheological modifier, which is a mixture of second particles that are non-spherical particles having at least one non-spherical particle.

The electrically conductive composition according to the present invention can be prepared by several methods by mixing all the components together.

In one embodiment, the composition is prepared by mixing all of the particles, resin, organic solvent (s) and any necessary additives using a high shear mixer until the composition is homogeneous.

The electrically conductive composition according to the present invention can be cured and / or sintered.

The general temperature for sintering the silver particles is at least 180 ° C. However, due to the plastic substrate used in the touch screen, the sintering temperature can not be too high due to the nature of the plastic substrate material. Therefore, a low curing temperature is required. The process according to the invention enables curing at 150 DEG C through the selection of suitable conductive particles. When a conductive modifier is used in the composition, the temperature may be even lower. The standard hardening or sintering profile according to the invention is 30 minutes at 150 占 폚.

Alternatively, or in addition, ultraviolet radiation may be used in the curing process.

In yet another aspect,

Forming a mesh pattern on the substrate surface consisting of grooves having a width greater than 0 [mu] m and a width less than 5 [mu] m,

Filling the grooves with the conductive composition according to the present invention,

- cleaning the residual composition from the substrate surface, and

- curing or sintering the composition

To a method of making a transparent electrically conductive mesh.

The mesh pattern according to the present invention can be formed on the substrate surface by various techniques. Suitable techniques for use herein are, for example, an imprinting process, a soft lithography process and a laser patterning process. The imprinting process is the most preferred method.

The substrate suitable for use in the present invention is preferably comprised of polyethylene terephthalate (PET), polymethylmethacrylate, polyethylene, polypropylene, polycarbonate, epoxy resin, polyimide, polyamide, polyester or glass , And preferably the substrate is polyethylene terephthalate.

In the cleaning step, the residual composition is removed from the substrate by wiping with a wiper and a solvent. It is important that as little residue as possible remains on the surface of the substrate after the charging and cleaning steps. The pyramidal particles and / or pyramidal particles are preferred to the non-spherical / flaky particles because the flake particles tend to adhere more to the surface of the substrate and are more difficult to remove.

According to the present invention, it is preferred to carry out the curing or sintering at a temperature of less than 150 ° C, or even less than 130 ° C.

As the excess adhesive is removed from the outside of the groove, the composition according to the present invention improves the efficiency of the cleaning step.

In another aspect, the present invention relates to an electrically conductive mesh made by the method described above.

The electrically conductive composition according to the present invention has a volume resistivity of less than 5E-5 Ohms.cm, preferably less than 3E-5 Ohms.cm after drying and curing. The volume resistivity is measured using a standard four-wire resistance measurement method using an Agilent 34401A multimeter. Once the resistance value of the sample is measured and the dimensions of the sample are measured, the volume resistivity of the sample can be calculated accordingly.

The electrically conductive composition according to the present invention has a reflectance value of less than 65%, preferably less than 60% after drying and curing, as measured by CIELAB color space measurement using a Datacolor 650 instrument L *. L * represents the brightness of the color. The lightness reflected from the sample surface for the present invention is preferably as low as possible.

The electrically conductive mesh according to the present invention has at least a level 5B adhesion between the mesh and the substrate when measured by ASTM standard cross-cut tape test according to Test Method D 3359-97.

The electroconductive mesh according to the present invention may be applied to a flexible or rigid touch panel or OLED display or a smart window or a transparent heater or a thin film photovoltaic or dye sensitized photovoltaic or organic photovoltaic or electromagnetic interference shielding or electrostatic discharge It is suitable for use in membrane switches.

Accordingly, another aspect of the present invention is to provide a touch panel display comprising an electrically conductive mesh on a substrate comprising a cured or sintered composition according to the present invention.

Example

The example compositions were prepared by mixing the particles, resin, organic solvent (s) and any necessary additives using a high shear mixer until the composition became substantially homogeneous.

A resin PVDC copolymer (Saran F-310 from DOW) and solvent DBE-9 (Sigma-Aldrich) are used in all compositions. The silver to resin volume ratio remains constant at 2.43 (also in the comparative example). All samples are cured at &lt; RTI ID = 0.0 &gt; 150 C &lt; / RTI &gt; Volume resistivity and surface L * measurements are performed according to the method described above.

Unless otherwise defined, additives are added to a given weight percent of the total weight of the composition.

Unless defined otherwise, the substrate used in the examples is a PET substrate. Adhesion of the cured mesh structure to the PET substrate was tested by a standard cross hatch test (the test method described above).

The amount of the residual composition on the surface of the substrate may be determined by visual inspection and / or SEM.

Example  One

Composition 1-6 according to the present invention

Composition 1 contains spherical silver particles with shaped particles having facets, with an average particle size of about 0.3 占 퐉. As a result, the L * value of the cured mesh structure is reduced to about 62% and the volume resistivity is acceptable. In addition, it is found that there are fewer residual particles in the substrate after cleaning than in Comparative Example 2. [

Composition 2 contains a mixture of silver particles with an aspect ratio of 6: 1 (average particle size is about 0.3 占 퐉) and spherical silver particles (average particle size is about 100 nm). As a result, the L * value of the cured film mesh structure is reduced to about 65% and the volume resistivity is slightly lower than composition 3. In addition, it is found that there are fewer particles remaining after cleaning than in Comparative Example 2. [

Composition 3 contains a mixture of spherical silver particles with an average particle size of about 0.3 [mu] m and spherical silver particles with an average particle size of about 100 nm at 3: 1 weight ratio. As a result, the L * value of the cured mesh structure is reduced to about 62% and the volume resistivity is still less than 5E-5 ohm cm. In addition, it is found that there are fewer particles remaining after cleaning than in Comparative Example 2. [

Composition 4 contains a conductive promoter (2-hydroxyethyl methacrylate phosphate) of 0.2 wt .-% (in total composition) in addition to the basic constituents as in Composition 3 above. It is found that there is little change in the L * value, but the volume resistivity decreases from 1.27E-5 to 7.7E-6 ohm cm. Thus, the conductivity was improved with low reflectivity of the mesh structure being maintained. In addition, it is found that there are fewer particles remaining after cleaning than in Comparative Example 2. [

Composition 5 contains, in addition to the basic constituents of Composition 6, a black dye GLX from Clariant of 0.2 wt .-% (in total composition). The L * value decreased from 60.74% to 58.82%, while the volume resistivity increased from 7.7E-6 to 1.27E-5 ohm cm, which is still within application requirements. In addition, it is found that there are fewer particles remaining after cleaning than in Comparative Example 2. [

Composition 6 contains, in addition to the basic constituents of Composition 5, palladium methacrylate in an amount of 0.5 wt .-% (in the total composition). L * was found to decrease from about 62% to 56% and the volume resistivity is still within the application requirements. In addition, it is found that there are fewer particles remaining after cleaning than in Comparative Example 2. [

Example  2

Composition 7-9 according to the present invention

Example  3

Comparative Example-Composition 10

F-310 binder resin polyvinylidene chloride (PVDC) from Dow Chemicals is dissolved in the DBE-9 solvent at 30% solids weight percent (30 wt.% PVDC and 70 wt.% DBE -9). The solution is then used as a master resin solution. The silver particles used are non-spherical particles (N300 from Tokusen) with an aspect ratio greater than 30 (average particle size is about 0.3 [mu] m). The silver dispersion contains 90 wt.% Silver particles and 10 wt .-% DBE-9. Thus, an additional solvent (DBE-9) is added to adjust the final solids weight percent and viscosity. The high-to-low volume ratio is kept constant at 2.43.

The conductivity of the cured mesh structure is high enough, but the reflectance is too high and the mesh structure is grayish white to be visible to the eye. It is also found that during the processing of the metal mesh structure, the residue on the substrate surface needs to be carefully removed and cleaned. Otherwise, the residual particles will appear as visible defects and are detrimental to the final product yield.

Example  4

Comparative Example - Composition 11 - 15

The Savinyl RLSN black dye prepared by Clariant is added to the composition of Comparative Composition 7 in an amount of 0.1 wt .-%, 0.5 wt .-%, 1 wt .-% and 2 wt .-% . The measured L * and volume resistivities are listed in the following table.

Although the L * value may reach about 65.5%, the volume resistivity increases correspondingly to a too high value > 5E-5 ohm.cm. In addition, the residues during the processing of the metal mesh structure do not change the difficulty of cleaning the particles.

Claims (15)

a) a first particle having an aspect ratio of at least 1 and less than 2.0 and being selected from spherical particles, faceted particles, pyramidal particles and mixtures thereof;
or
A mixture of the first particles and the second particles that are non-spherical particles having an aspect ratio greater than 2.0
Electroconductive particles selected from the group consisting of;
b) a resin; And
c) at least one organic solvent
&Lt; / RTI &gt; 2. The method of claim 1, wherein the electrically conductive particles are selected from the group consisting of metals, metal alloys, metal-containing composites, non-metal particles and mixtures thereof; Silver, platinum, copper, nickel, aluminum, zinc, iron, copper-nickel, silver-copper, silver-nickel, copper-aluminum, silver-plated copper, silver- , Graphite, carbon black, carbon nanotubes, and mixtures thereof; More preferably the electroconductive particles are silver. 3. The method according to claim 1 or 2, wherein the spherical or angled or pyramidal particles have an average particle size of from 5 nm to 1 [mu] m, preferably from 5 nm to 500 nm and more preferably from 5 nm to 200 nm &Lt; / RTI &gt; 4. The composition according to any one of claims 1 to 3, wherein the non-spherical particles preferably have an aspect ratio of greater than 10.0. 5. The composition according to any one of claims 1 to 4, wherein the non-spherical particles have an average particle size of from 10 nm to 2 μm, preferably from 10 nm to 1 μm. 6. The method according to any one of claims 1 to 5,
- a first particle which is from 5% to 85% by weight, preferably from 60% to 75% by weight of the total weight of the composition, or
- second particles of from 10% to 85% by weight, preferably from 30% to 70% by weight of the total weight of the composition, and from 5% to 40% by weight of the total weight of the composition,
&Lt; / RTI &gt; 7. The composition according to any one of claims 1 to 6, wherein the weight ratio of the second particle to the first particle is from 6: 1 to 1: 2, preferably from 3: 1 to 1: 1. 8. A composition according to any one of claims 1 to 7, wherein the resin is selected from the group consisting of a halogenated thermoplastic resin, a phenoxy resin, a polyester resin, a thermoplastic polyurethane, a polyacrylate, silicon and mixtures thereof Selected; More preferably selected from the group consisting of PVDC polymers, PVDC copolymers, phenoxy resins, polyacrylates, and mixtures thereof; Most preferably a PVDC polymer and a PVDC copolymer and mixtures thereof. 9. A composition according to any one of claims 1 to 8, which comprises from 1% to 10%, preferably from 1% to 8% and more preferably from 2% to 6% by weight of the total weight of the composition A composition comprising a resin. 10. The composition according to any one of claims 1 to 9, wherein the volume ratio of particles and resin is from 1.5 to 3.5, preferably from 2.0 to 3.0. 11. The process according to any one of claims 1 to 10, wherein at least one organic solvent is selected from the group consisting of dipropylene glycol methyl ether (DPM), 3-methoxy-3-methyl-1-butanol (MMB) (BGA), diethylene glycol, ethylene glycol monobutyl ether, DBE, DBE-9, DBE-3, DBE-4, DBE-5, DBE-6, propylene glycol methyl acetate (PMA), butyl carbitol ), Butyl carbitol acetate (BCA), and mixtures thereof. Forming a mesh pattern on the substrate surface, the mesh pattern having a width greater than 0 [mu] m and a width less than 5 [mu] m;
- filling the grooves with the composition of any one of claims 1 to 11,
- cleaning the residual composition from the substrate surface,
- curing or sintering the composition
&Lt; / RTI &gt; 13. The method of claim 12, wherein the curing or sintering is performed at a temperature of less than 150 &lt; 0 &gt; C. An electrically conductive mesh produced by the method of claim 12 or 13. 13. A touch panel display comprising an electrically conductive mesh on a substrate comprising the cured or sintered composition of any one of claims 1-11.