TWI681409B - Electrically conductive compositions, process and applications - Google Patents

Abstract

The present invention relates to electrically conductive compositions based on electrically conductive particles, use of said electrically conductive composition in a method for preparing electrically conductive meshes and the manufactured conductive meshes, as well as a touch panel displays comprising an electrically conductive mesh on a substrate.

Description

Conductive composition, method and application

The present invention relates to a conductive composition mainly made of conductive particles in a conductive mesh and its use. The conductive composition of the present invention can be used in touch screens.

Background of the invention

The touch screen sensor detects the position of an object (such as a finger or pen tip), which is applied to the surface of a touch screen display or an object located near the surface of the touch screen display. These sensors detect the position of the 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. The sensor includes conductive elements overlayed on the display. These components are combined with electronic parts that use electronic signals to detect the component in order to determine the location of an object that is close to or in contact with the display.

In the field of touch screen sensors, there is a need for improved control of the electrical properties of touch screen sensors without affecting the optical quality of the display. In general, optical quality can be expressed in terms of visible light transmittance, turbidity, and sensor visibility. The quality is determined by the human eye observing the sensors assembled in the touch screen. Typically, in a metal mesh touch sensor, the transparent micro-patterned conductive region includes a metal mesh structure, which is used as a touch screen sensor. Parameters can be used to define the geometry of the micropatterned mesh structure, such as but not limited to the width of the mesh trace (sometimes referred to as "lines") used in micropatterns and The height, the density of the line and the uniformity of the line density. The micropattern usually has a line width of less than 5 μm (the fine (Invisible to the informant), the intersection line height less than 5μm and the open area fraction between 95% and 99.99%. The space (transparent area) between the mesh lines is usually between hundreds of microns and several millimeters. This method can achieve a very high transparency of the touch screen sensor. The micro-patterned mesh structure may be, for example, rhombic, hexagonal, or random. The electrical conductivity of the touch screen sensor is related to the density of the wire and the geometry of the wire.

In one of the metal mesh technical forms, a mesh pattern containing grooves is first formed on a substrate surface, and the grooves have a suitable width and height. The trench is then filled with a conductive composition. Removing any remaining components in the filling process from the surface of the substrate in the cleaning step, and then curing or sintering the conductive composition in the mesh trench at an elevated temperature to form the solid conductive metal mesh structure . The ease of cleaning and the amount of residual components on the surface are very important factors used to determine the loss of product yield. Surface visual defects due to excessive residues.

The metal mesh structure can be made of a highly conductive metal or metal alloy, which contains micron or sub-micron size metal particles. Silver particles are generally used to form the conductive mesh wire to ensure high conductivity of the mesh structure. However, the surface of the solidified silver wire usually has a high reflectivity and can be detected by the human eye. This visibility will damage the optical quality of the touch screen sensor, and of course the result is also related to the display including the touch screen sensor, so it is one of the key shortcomings of this technology.

It is known that a dark coating of black ink applied on top of the conductive metal mesh line can be painted to reduce the reflectivity of the surface of the metal mesh structure. Doing so will have additional processing steps to extend the overall process, thus increasing processing time and cost. The additional steps can also lead to additional production losses.

Another known solution in the prior art is to add a black dye substance (ie carbon black or organic black dye) to the conductive composition to reduce the surface reflectance of the surface of the cured metal mesh. However, if the dye is not evenly distributed, it may cause uneven color on the surface of the film Exterior. In addition, since the insulating properties of the organic black dye material and the conductivity of carbon black are lower than silver, the conductivity of the cured metal mesh will be reduced.

Therefore, there is still a need to provide a conductive composition that has the ability to be cured or sintered at a relatively low temperature, and has sufficient adhesion to the substrate, high electrical conductivity, and low reflectance after curing or sintering. In addition, it is desirable that the residual composition outside the trench can be simply removed from the substrate surface before curing.

Summary of the invention

The present invention relates to a conductive composition, which includes: a) conductive particles selected from first particles having an aspect ratio equal to or greater than 1 and less than 2.0, wherein the first particles are Selected from spherical particles, faceted particles, pyramidal particles, and mixtures thereof; or a mixture of the first particles and second particles, wherein the second particles have an aspect ratio greater than 2.0 Non-spherical particles; b) a resin; and c) at least one organic solvent.

The present invention further relates to a method for preparing a transparent conductive mesh, which includes the conductive composition of the present invention and the obtained conductive mesh structure.

In addition, the invention includes the use of the conductive mesh structure in touch sensor technology.

Finally, the present invention includes a touch panel display including a conductive mesh on a substrate, wherein the mesh includes a cured or sintered composition according to the present invention.

The invention is described in more detail in the following paragraphs. Each aspect so described may be combined with any other aspect or aspects unless explicitly indicated to the contrary. In particular, any accused Features that are preferred or advantageous can be combined with any other feature or features that are referred to as preferred or advantageous.

In the context of the present invention, the terms used should be interpreted according to the following definitions, unless the context indicates otherwise.

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

The terms ``comprising,'' ``comprises,'' and ``comprised of'' as used herein refer to ``including,'' ``includes,'' or ``containing,'' `` "Contains" is synonymous, which includes inclusive or open-ended and does not exclude additional, unlisted components, elements or method steps.

The numerical endpoint records include all numbers and fractions contained within individual ranges, as well as the endpoints cited by them.

Unless otherwise stated, all percentages, parts, ratios and others mentioned herein are based on weight.

When the quantity, concentration or other value or parameter is expressed in the form of a range, a preferred range, or a preferred upper limit value and a preferred lower limit value, it should be understood that by any upper limit or preferred value and any lower limit or preferred Any range obtained by the value is specifically disclosed, regardless of whether the obtained range is clearly mentioned in the context.

All references in this specification are incorporated by reference in their entirety.

Unless otherwise defined, all terms including technical and scientific terms used in the disclosure of the present invention have the meaning generally understood by those of ordinary skill in the technical field to which the present invention belongs. By means of further guidance, the definitions of terms are included in the teaching of the present invention and can be better understood.

The present invention provides a conductive composition, which includes: a) conductive particles selected from first particles having an aspect ratio equal to or greater than 1 and less than 2.0, wherein the first particles are selected From spherical particles, faceted particles and mixtures thereof; or a mixture of the first particles and second particles, wherein the second particles 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 conductive composition of the present invention provides the ability to be cured or sintered at relatively low temperatures. The cured or sintered composition of the present invention has sufficient adhesion to the substrate, high electrical conductivity, and low reflectance. In addition, the residual composition outside the trench can be simply removed from the substrate surface before curing.

The main components of the conductive composition of the present invention are described in detail below.

Conductive particles

The conductive composition of the present invention includes conductive particles selected from first particles having an aspect ratio equal to or greater than 1 and less than 2.0, wherein the first particles are selected from spherical particles, polyhedral particles, and cones Particles and mixtures thereof; or a mixture of the first particles and second particles, wherein the second particles are non-spherical particles having an aspect ratio greater than 2.0.

The particle of the present invention is characterized by the shape and size of the particle. The particle size is measured by a particle size analyzer and the particle shape is analyzed by a scanning electron microscope. The detector array detects short scattered laser lights from the particles. A theoretical calculation is performed to fit the measured scattered light intensity distribution. Inferring the particle size distribution during the fitting process, and calculating D10, D50, D90 and other values accordingly. The particles of the invention have a D50 from 10 nm to 500 nm and a D90 below 1 μm.

The term "aspect ratio" refers herein to an image projection attribute, which describes the proportional relationship between the particle width and its height. Observe the particle shape and measure the dimension with SEM to provide the average of the aspect ratio.

The aspect ratio herein refers to an average aspect ratio of 50, preferably 100, and each filler particle is determined according to the following measurement method.

The aspect ratio used herein refers to the ratio between the dimensions of the three-dimensional object in different dimensions, more specifically the ratio of the longest side to the shortest side, such as height and width. Spherical (ball-shaped) or spherical particles therefore have an aspect ratio of about 1, while fibers, needles or flakes often have an aspect ratio greater than 10 because they are related to their length or relative to their length and width Smaller diameter (diameter) or thickness (thickness). The aspect ratio can be determined by scanning electron microscope (SEM) measurements. The software can use "Analysis pro" of Olympus Soft Imaging Solutions GmbH. The magnification is between X250 and X1000, and the aspect ratio is the average value obtained by measuring the width and length of at least 50 and preferably 100 particles in the image. In the case of relatively large and flaky fillers, SEM measurements can be obtained from the 45° tilt angle of the sample.

The conductive first and second particles of the present invention are selected from the group consisting of metals, metal alloys, metal-containing composites, non-metallic particles and mixtures thereof, preferably selected from silver , Gold, platinum, copper, 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 In the group consisting of carbon black, carbon nanotubes and mixtures thereof, the conductive particles are preferably silver particles.

Silver particles are preferred because of the ideal balance between conductivity and price.

First particle

In a specific embodiment, the conductive composition of the present invention includes conductive first particles having an aspect ratio equal to or greater than 1 and less than 2.0, which is determined in the above-described manner. The first particles have a spherical or multi-faceted or tapered shape. The first particles may contain only one of spherical or multi-sided or conical shapes. Alternatively, the first particles may be a mixture of any two shapes or a mixture of all three shapes.

The first particles of the present invention preferably have an average particle diameter from 5 nm to 1 μm, more It is preferably from 5 nm to 500 nm, and even more preferably from 5 nm to 200 nm.

For metal mesh applications, the width of the trench is usually less than 5 μm for large-size touch sensors and less than 2.5 μm for small sensors. In order to successfully fill the trench to form a conductive line, the particle size in the composition of the present invention needs to be controlled to be smaller than the width of the trench. Therefore, the preferred size range is ideal for metal mesh applications. In addition, silver particles with a smaller particle size have a darker color than silver particles with a larger particle size. In particular, those with a particle size from 5 nm to 200 nm have a darker color than those with larger particles, which is beneficial to reduce the reflectivity of the conductive mesh pattern, and thus the visibility of the human eye is low.

The composition of the present invention includes the first particles, based on the weight of the total weight of the composition from 5% to 85%, preferably from 60% to 75%.

If the composition includes less than 5% of the first particles based on the total weight of the composition, it may cause low conductivity. On the other hand, if the composition includes first particles greater than 85% by weight of the total weight of the composition, it may result in poor adhesion and excessive viscosity because there is not enough solvent or resin binder . The ideal range of 60-75% based on the total weight of the composition provides the ideal conductivity and suitable rheological and mechanical properties of the metal mesh application.

The spherical and/or multi-faceted and/or cone-shaped particles in the adhesive composition of the present invention improve optical properties, which means that they reduce the overall reflectance. In addition, the spherical and/or multi-faceted and/or cone-shaped particles improve the removal of residual adhesive outside the groove.

Second particle

In a specific embodiment, the conductive composition of the present invention includes a mixture of conductive first particles and conductive second particles, wherein the second particles are non-spherical particles having an aspect ratio greater than 2.0.

If the conductive composition includes only second (non-spherical) particles, it will be achieved Excellent conductivity, but its optical properties will not be ideal, because the reflectance of the composition will be very high.

To improve the balance between conductive and optical properties, particles with an aspect ratio equal to or greater than 1 and less than 2 may be used in combination with non-spherical particles with an aspect ratio greater than 2. The use of a mixture of non-spherical and/or multi-faceted and/or cone-shaped particles may also improve the physical properties of the cured composition, especially the adhesion of the cured mesh structure to the substrate.

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

A higher aspect ratio provides a lower percolation threshold that produces good conductivity. The lower penetration threshold (which means the loading of silver particles to start the continuous contact between the silver particles and the possible formation of electrically continuous paths), because the high aspect ratio is the root cause of conduction. The denser filling of the trench in this application also helps to improve conductivity. Finally, the lower contact resistance between particles is another factor for better conductivity.

The non-spherical particles of the present invention preferably have an average particle diameter from 10 nm to 2 μm, more preferably from 10 nm to 1 μm.

The trench width used in the metal mesh application of the present invention is less than 5 μm for large-size touch sensors and less than 2.5 μm for small touch sensors. In order to successfully fill the trench with the conductive particles to obtain a conductive line, the particle size must be optimized and controlled. Therefore, the selected particle size range of the present invention is ideal for this metal mesh application.

When the conductive composition of the present invention includes a mixture of first particles and second particles, the second particles are present from 10% to 85% by weight of the total weight of the composition, preferably from 30% to 70 %, and the first particle is stored from 5 to 40% based on the weight of the total weight of the composition in.

The selected combination of the first and second particles provides an ideal conductivity with comparable colors. A higher amount of second particles is preferred. The greater the amount of first particles in the composition, the more the conductivity of the composition will decrease. However, the color L* value is in the opposite trend. The more the first particles in the composition, the darker the color. Therefore, in order to provide a good conductivity with a comparable color L*<60% (VR<5E-05 ohm.cm), it is preferred that the composition contains a higher amount of second particles.

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

Resin

The conductive composition of the present invention includes 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 when cured or sintered at elevated temperatures to ensure complete drying at relatively low temperatures. The resin 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 filling process of the trench. As an in-between binder material, the resin should have good conductivity. Finally, the resin should have good adhesion to substrates such as polyethylene terephthalate (PET).

Preferably, the resin used in the composition of the present invention is selected from the group consisting of halogenated thermoplastic resins, phenoxy resins, polyester resins ), thermoplastic polyurethanes (thermoplastic polyurethanes), polyacrylates (polyacrylates), silicones (silicones) and mixtures thereof; preferably selected from the group consisting of polyvinyl dichloride (polyvinyl dichloride), polydichloride Ethylene copolymer, phenoxy resin PKHH, and mixtures thereof; more preferably selected from polydimethy Groups composed of vinyl chloride and polyvinyl chloride copolymers and their mixtures.

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

In some embodiments, the composition of the present invention includes a polyvinyl chloride copolymer, which includes a first monomer and a second monomer, wherein the first monomer system is selected from vinyl acetate (vinyl acetate) ), vinyl alcohol (vinyl alcohol), vinyl chloride (vinyl chloride), vinylidene chloride (vinylidene chloride) and styrene (styrene), and the second single system is selected from the second acetic acid The group consisting of vinyl ester, second vinyl alcohol, second vinyl chloride, second vinylidene chloride, second styrene, acrylate and nitride.

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

In some embodiments, the first monomer is vinylidene chloride and the second monomer is vinyl chloride (eg, polyvinyl chloride). In some embodiments, the first monomer is vinylidene chloride and the second monomer is alkyl acrylate.

According to some specific embodiments, the composition of the present invention may optionally further include one or more thermosetting resins selected from the group consisting of epoxy-functionalized resin, Acrylates, cyanates, silicone resins, oxetanes, maleimides and mixtures thereof.

A wide variety of epoxy functional resins are suitable for use in this article, such as liquid epoxy resins based on bisphenol A, solid epoxy resins based on bisphenol A, and liquid epoxy resins based on bisphenol F Epoxy resin, multifunctional epoxy resin mainly based on phenol-novolac resin, dicyclopentadiene-type resin, naphthalene-type epoxy resin and mixtures thereof.

Exemplary epoxy functional resins suitable for use in the present invention include diepoxides Dicycloepoxides of cycloaliphatic alcohol, hydrogenated bisphenol A, difunctional cycloaliphatic glycidyl esters of hexahydropeptide and mixtures thereof.

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

其中R為H或甲基，且X係選自於(a)具有自8至24個碳原子之烷基基團，或(b)

其中R為H或甲基，R‘為獨立地選自於H或甲基且x為自2至6之整數。較佳(甲基)丙烯酸酯係選自於由下列所組成之組群：2-甲基-2-丙烯酸十三烷基酯(tridecylmethacrylate)、1,6-己二醇二甲基丙烯酸酯(1,6-hexanediol dimethacrylate)、1,10-癸二醇二丙烯酸酯(1,10-decanediol diacrylate)、1,10-癸二醇丙烯酸二甲酯(1,10-decanediol dimethacrylate)、1,12-十二烷二醇二丙烯酸酯(1,12-dodecanediol diacrylate)、1,12-十二烷二醇丙烯酸二甲酯(1,12-dodecanediol dimethacrylate)及其混合物。 Suitable (meth)acrylate examples for use in the present invention include compounds having the general structure I as follows:

Where R is H or methyl, and X is selected from (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. Preferred (meth)acrylates are selected from the group consisting of tridecylmethacrylate, 1,6-hexanediol dimethacrylate ( 1,6-hexanediol dimethacrylate), 1,10-decanediol diacrylate (1,10-decanediol diacrylate), 1,10-decanediol dimethacrylate, 1,12 -1,12-dodecanediol diacrylate, 1,12-dodecanediol dimethacrylate and mixtures thereof.

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

The cyanate monomer suitable for use in the present invention contains two or more rings forming cyanate (-O-C=N) groups, which are cyclotrimerized by heating to form substituted The triazabenzene ring. Because no detached groups or volatile by-products are formed during the curing of the cyanate ester monomer, the curing reaction is called addition polymerization. The polycyanate monomer system which may be preferably used in the present invention is selected from the group consisting of: 1,1-bis(4-cyanoxyphenyl)methane, 1,1-bis(4 -Cyanoxyphenyl)ethane, 2,2-bis(4-cyanoxyphenyl)propane, bis(4-cyanoxyphenyl)-2,2-butane, 1,3-bis-2 -(4-cyanooxyphenyl)propylbenzene, bis(4-cyanooxyphenyl) ether, 4,4'-dicyanooxydiphenyl, bis(4-cyanooxy-3,5- Dimethylphenyl) methane, tris(4-cyanooxyphenyl)ethane, cyanated novolak, 1,3-bis 4-cyanooxyphenyl-1-(1-methyl Ethylene)benzene, cyanated phenol-dicyclopentadiene adduct (cyanated phenol-dicyclopentadiene adduct) and mixtures thereof. The polycyanate monomer used in the present invention may be prepared by reacting a suitable binary or polyhydric phenol with a cyanogen halide in the presence of an acid acceptor.

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

Silicone resin-based adhesive formulations suitable for use in the present invention include a substantially stoichiometric mixture of hydride-terminated polysiloxane and vinyl-terminated polysiloxane . The hydride-terminated polysiloxanes used in the examples herein are hydride-terminated polydimethylsiloxanes. The exemplified vinyl-terminated polysiloxanes used herein are divinyl-terminated polydimethylsiloxanes.

The resin suitable for the present invention may also be oxycyclobutane containing monomers and/or oligomers.

The conductive composition of the present invention includes a resin from 1% to 10% by weight of the total weight of the composition, preferably from 1% to 8%, more preferably from 2% to 6%.

When the composition includes less than 1% resin based on the total weight of the composition, there will be poor adhesion. On the other hand, if the composition includes a resin greater than 10% by weight of the total weight of the composition, it will cause poor conductivity, which is not ideal for the application of the metal mesh.

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

The volume ratio is calculated based on the weight of resin and conductive particles added to the composition. Because the density of the particles and resin is known, volume = weight/density. This volume ratio range is ideal, and it meets conductivity requirements (<5E-05 ohm.cm).

Solvent

The conductive composition of the present invention includes at least one organic solvent. A wide variety of known organic solvents can be used in the present invention. The solvent used in the present invention is not particularly limited as long as it has good compatibility with both the resin and the conductive particles used in the composition of the present invention. The preferred solvent should have a relatively low evaporation rate at room temperature to ensure sufficient processing time and relatively high evaporation rate at the curing temperature to ensure sufficient curing and sufficient adhesive shrinkage during the drying process.

The organic solvent suitable for use in the present invention is preferably selected from dipropylene glycol methyl ether (DPM), 3-methoxy-3-methyl-1-butanol (3-methoxy-3 -methyl-1-butanol) (MMB), butyl glycol acetate (BGA), diethylene glycol, ethylene glycol mono butyl ether , DBE, a mixture of dimethyl glutarate and dimethyl succinate (DBE-9), dimethyl adipate and dimethyl glutarate ( Mixture of dimethyl glutarate (DBE-3), succinic acid dimethyl ester (DBE-4), glutaric acid dimethyl ester (DBE-5), adipic acid dimethyl Dimethyl adipate (DBE-6), propylene glycol methyl acetate (PMA), butyl carbitol (BC), butyl carbitol acetate (butyl carbitol acetate) (BCA) and mixtures thereof are more preferably selected from the group consisting of DBE-9, DPM, PMA, BC, BGA and mixtures thereof.

The conductive composition of the present invention includes at least one weight based on the total weight of the composition The organic solvent counts from 10% to 50%, preferably from 15% to 40%, more preferably from 20% to 35%. The amount of solvent herein is meant to include the sum of the solvent and possible co-solvents.

The term co-solvent means an additional solvent that enters the composition with other reagents, or a solvent used to provide particle dispersion, for example.

If the amount of the solvent and the co-solvent in the composition is too high, the effective solid content in the composition will decrease, resulting in a thinner film after curing, thus providing poor conductivity. On the other hand, if there is not enough solvent in the composition, the composition may have an excessively high viscosity, which may cause a problem of processing ability during the manufacturing process.

additive

In addition to the above components, the conductive composition of the present invention may further include additives from 0.01% to 5% by weight of the total weight of the composition, preferably from 0.05% to 2%.

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

Conductive modifiers are highly preferred additives, especially when the composition of the present invention includes only the first particles. The high amount of the first particles in the composition of the present invention may reduce the conductivity of the composition in some cases. Therefore, it is preferable to use an additional conductivity modifier to improve the conductivity of the composition.

The conductive modifier is different from the conductive particles (different from the first and second particles). Examples of conductive modifiers suitable for use in the present invention are: acids containing compounds such as organic diacids, such as glutaric acid; phosphate compounds containing organic compounds, Such as phosphoric acid 2-hydroxyethyl methacrylate ester; metal containing complexes and organometalic compounds (such as silver acetone) (silver acetlyacetonate), palladium methacrylate.

Examples of pigments suitable for the present invention are pigment materials such as: dyes, such as Clariant RLSN, Clariant GLX; inorganic materials, such as carbon black, nickel oxide, cobalt oxide, silver oxide; organic metal compounds , Such as silver acetylacetonate and palladium methyl acrylate.

Rheology modifiers are highly preferred additives, especially when the composition of the present invention includes only the first particles. Because the use of the first particles in the composition increases the adhesion and/or adhesion of the composition, it reduces its rheology profile. Therefore, it is necessary to adjust the rheology of the composition.

Examples of rheology modifiers suitable for use in the present invention are: Disperbyk-111, Disperbyk-180, Disperbyk-145 and BYK-W980 of BYK-Chemie.

In a preferred embodiment, the conductive composition of the present invention contains: first conductive particles having an aspect ratio equal to or greater than 1 and less than 2.0, wherein the first particles are selected from spherical particles, polyhedral particles, Cone-shaped particles and their mixtures; a resin; and at least one organic solvent.

In another preferred embodiment, the conductive composition of the present invention contains conductive particles mixed with first particles and second particles, wherein the first particles have an aspect ratio equal to or greater than 1 and less than 2.0, wherein The first particles are selected from spherical particles, polyhedral particles, cone-shaped particles and mixtures thereof, and the second particles are non-spherical particles and particles with an aspect ratio greater than 2.0, a resin and at least one organic solvent.

In a preferred embodiment, the conductive composition of the present invention contains: first conductive particles having an aspect ratio equal to or greater than 1 and less than 2.0, wherein the first particles are selected from spherical particles, polyhedral particles, Cone-shaped particles and their mixtures; a resin; and at least one organic solvent and at least one conductive modifier.

In a preferred embodiment, the conductive composition of the present invention contains: First conductive particles having an aspect ratio equal to or greater than 1 and less than 2.0, wherein the first particles are selected from spherical particles, polyhedral particles, cone-shaped particles and mixtures thereof; a resin; at least one organic solvent and at least first-class Change modifier.

In a preferred embodiment, the conductive composition of the present invention contains: first conductive particles having an aspect ratio equal to or greater than 1 and less than 2.0, wherein the first particles are selected from spherical particles, polyhedral particles, Cone-shaped particles and their mixtures; a resin; at least one organic solvent, at least one conductive modifier and at least a first-class modifier.

In another preferred embodiment, the conductive composition of the present invention contains conductive particles mixed with first particles and second particles, wherein the first particles have an aspect ratio equal to or greater than 1 and less than 2.0, wherein The first particles are selected from spherical particles, polyhedral particles, cone-shaped particles and mixtures thereof, and the second particles are non-spherical particles and particles having an aspect ratio greater than 2.0, a resin, at least one organic solvent and at least A conductive modifier.

In another preferred embodiment, the conductive composition of the present invention contains conductive particles mixed with first particles and second particles, wherein the first particles have an aspect ratio equal to or greater than 1 and less than 2.0, wherein The first particles are selected from spherical particles, polyhedral particles, cone-shaped particles and mixtures thereof, and the second particles are non-spherical particles and particles having an aspect ratio greater than 2.0, a resin, at least one organic solvent, at least A conductive modifier and at least a first-class modifier.

The conductive composition of the present invention can be prepared in several ways by mixing all the ingredients together.

In a specific embodiment, the composition is manufactured using a high shear mixer to mix all particles, resin, organic solvent, and any necessary additives until the composition is uniform.

The conductive composition of the present invention can be cured and/or sintered.

The normal temperature for sintering the silver particles is higher than 180°C. However, due to the plastic substrate used in the touch screen, the sintering temperature cannot be too high due to the nature of the plastic substrate material. Therefore, it must be a low curing temperature. By selecting suitable conductive particles, the process of the present invention can be cured at 150°C. If a conductive modifier is used in the composition, the temperature can be lowered. The standard curing or sintering profile of the present invention is 30 minutes at 150°C.

Alternatively or additionally UV rays can also be used in the curing process.

In another aspect, the invention relates to a method for preparing a transparent conductive mesh, which includes the following steps:-forming a mesh pattern composed of grooves on the surface of the substrate, the The trench has a width greater than 0 μm and less than 5 μm,-the trench is filled with the conductive composition of the present invention,-the remaining composition on the substrate surface is removed, and-the composition is cured or sintered.

According to the present invention, the mesh pattern can be formed on the surface of a substrate by various techniques. Techniques suitable for use in this document, such as the imprinting process, soft lithography method, and laser patterning method. The impression process is the best method.

The substrate suitable for use in the present invention is preferably selected from the group consisting of polyethylene terephthalate (PET), polymethyl methacrylate, polyethylene, polypropylene, polycarbonate , Epoxy resin, polyimide, polyamide, polyester or glass, the preferred substrate is polyethylene terephthalate.

In the cleaning step, wipe with a wiper and a solvent to remove the remaining composition from the substrate. It is important to keep as little residue as possible on the substrate surface after the filling and cleaning steps. Spherical and/or multi-faceted and/or cone-shaped particles are more aspherical/flake particles than Good, because flake particles tend to adhere more to the substrate surface and are more difficult to remove.

According to the invention, the curing or sintering is preferably carried out at a temperature of less than 150°C, or even less than 130°C.

The composition of the present invention improves the efficiency of the cleaning step, and the excess adhesive outside the groove is removed.

In an additional aspect, the present invention relates to a conductive mesh, which is prepared by the above method.

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

After drying and curing, the conductive composition of the present invention has a reflective lightness value L* of less than 65%, preferably less than 60%, which is determined by CIELAB color space measurement using a Datacolor 650 instrument. L* indicates the brightness of the color. For the present invention, the brightness of the sample surface reflection is preferably as low as possible.

The conductive mesh of the present invention has an adhesion of at least 5B between the mesh and the substrate, which is measured by the ASTM standard cross-cut tape test according to Test Method D 3359-97.

The conductive mesh of the present invention is suitable for flexible or rigid touch panels or OLED displays or smart windows or transparent heaters or thin-film photovoltaics or dye sensitized photovoltaics Or organic photoelectric or electromagnetic interference shielding (electromagnetic interference shielding) or electrostatic discharge (electrostatic discharge) or membrane switches (membrane switches).

Therefore, according to a further aspect of the present invention, there is provided a touch panel display including a conductive mesh on a substrate, wherein the mesh includes the cured or sintered composition according to the present invention.

Examples

The composition of this example is prepared by mixing particles, resin, organic solvent, and any necessary additives using a high shear mixer until the composition is substantially uniform.

Resin polyvinylidene chloride (PVDC) copolymer (Saran F-310 from DOW) and solvent DBE-9 (Sigma-Aldrich) were used in all compositions. The volume ratio of silver to resin is maintained fixed at 2.43 (the same is true in the comparative example). All samples were cured at 150°C for 30 minutes. Measurement of volume resistivity and surface L* is done according to the above method.

Unless otherwise defined, the additive is added as a given percentage based on the weight of the total weight of the composition.

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

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

Example 1 Composition 1-6 of the present invention:

Composition 1 includes spherical silver particles plus polyhedral particles having an average particle diameter of about 0.3 μm. As a result, the L* value of the cured mesh structure further decreased to about 62%, which had an acceptable volume resistivity. In addition, it was found that compared with Comparative Example 2, there were fewer residual silver particles in the substrate after cleaning.

Composition 2 includes a mixture of polyhedral silver particles (average particle size about 0.3 μm) and spherical silver particles (average particle size about 100 nm) in a weight ratio of 6:1. As a result, the L* value of the cured film mesh structure further decreased to about 65%, which had a volume resistivity slightly lower than that of Composition 3. In addition, it was found that compared with Comparative Example 2, there were fewer residual silver particles after cleaning.

Composition 3 includes multi-faceted silver particles with a weight ratio of 3:1 (average particle diameter about 0.3 μm) And spherical silver particles (average particle size about 100nm) mixture. As a result, the L* value of the cured mesh structure further decreased to about 62%, which has a volume resistivity still less than 5E-5 ohm cm. In addition, it was found that compared with Comparative Example 2, there were fewer residual silver particles after cleaning.

The composition 4 includes the composition 3 as described above except for the essential components (accounting for the total composition) 0.2 wt.-% of the conductivity promoter (2-hydroxyethyl methyl acrylate phosphate). It was found that there was almost no change in the L* value, but the volume resistivity decreased from 1.27E-5 to 7.7E-6 ohm cm. Therefore, while maintaining the reflectivity of the mesh structure, the conductivity is improved. In addition, it was found that compared with Comparative Example 2, there were fewer residual silver particles after cleaning.

Composition 5 includes the above-mentioned composition 6 except for the essential components, 0.2 wt.-% (total composition) of the black dye GLX from Clariant. It was found that 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 in the application requirements. In addition, it was found that compared with Comparative Example 2, there were fewer residual silver particles after cleaning.

Composition 6 includes 0.5 wt.-% (based on the total composition) of palladium methyl acrylate as the above-mentioned composition 5 except for the essential components. It was found that the L* value was reduced from 62% to 56%, while the volume resistivity is still in the application requirements. In addition, it was found that compared with Comparative Example 2, there were fewer residual silver particles after cleaning.

Example 2 Composition of the invention 7-9

Example 3 Comparative Example-Composition 10

The adhesive resin polyvinylidene chloride (polyvinylidene chloride) (PVDC) Saran F-310 (from Dow Chemicals) was dissolved in DBE-9 solvent, which is 30% by weight solids (30wt.-% PVDC and 70wt. -% DBE-9). Subsequently, this solution was used as the main resin solution. The silver particles used were non-spherical particles (N300 from Tokusen) with an aspect ratio greater than 30 (average particle size about 0.3 μm). The silver dispersion contains 90 wt.-% silver particles and 10 wt.-% DBE-9. Add additional solvent (DBE-9) to adjust the final solid weight percentage and viscosity. The volume ratio of silver to resin was kept fixed at 2.43.

Although the conductivity of the cured mesh structure is high enough, the reflectivity is too high so that the mesh structure is off-white and visible to the naked eye. It is also known that during the manufacturing process of the metal mesh structure, the residual silver particles on the surface of the substrate need to be carefully removed and cleaned. Otherwise, the residual particles will appear as visible defects and are not conducive to the yield of the final product.

Example 4 Comparative Example-Composition 11-15

Savyl RLSN black dye (manufactured by Clariant) was added to Comparative Composition 7 in an amount of 0.1 wt.-%, 0.5 wt.-%, 1 wt.-% and 2 wt.-% based on the total weight of the composition. The The measured L* and volume resistivity are listed in the table below.

Although the L* value can reach approximately 65.5%, the volume resistivity correspondingly increases by an excessively high value >5E-5 ohm.cm. Moreover, the difficulty in cleaning residual silver particles during the manufacturing of the metal mesh structure has not changed.

Claims (25)

A conductive composition comprising: a) conductive particles selected from first particles having an aspect ratio equal to or greater than 1 and less than 2.0, wherein the first particles are selected from spheres Spherical particles, faceted particles, pyramidal particles and mixtures thereof; or a mixture of the first particles and second particles, wherein the second particles are non-spherical with an aspect ratio greater than 2.0 Particles; b) a halogenated thermoplastic resin; and c) at least one organic solvent. The composition according to item 1 of the patent application scope, wherein the conductive particles are selected from the group consisting of metals, metal alloys, metal-containing composites, non-metallic particles, and mixtures thereof. The composition according to item 2 of the patent application scope, wherein the conductive particles are selected from silver, gold, platinum, copper, 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, carbon nanotubes and their mixtures. The composition according to item 2 of the patent application scope, wherein the conductive particles are silver. The composition according to item 1 of the patent application scope, wherein the spherical or multi-faceted or cone-shaped particles have an average particle diameter of from 5 nm to 1 μm. The composition according to item 5 of the patent application scope, wherein the spherical or multi-faceted or cone-shaped particles have an average particle diameter of from 5 nm to 500 nm. The composition according to item 1 of the patent application scope, wherein the second non-spherical particles have an aspect ratio greater than 10.0. The composition according to item 1 of the patent application scope, wherein the second non-spherical particles have an average particle diameter of from 10 nm to 2 μm. The composition according to item 8 of the patent application range, wherein the second non-spherical particles have an average particle diameter of from 10 nm to 1 μm. The composition according to any one of items 1 to 9 of the patent application scope, wherein the composition includes the first particles in an amount of from 5% to 85% by weight of the total weight of the composition, or The amount of the second particles is from 10% to 85% by weight of the total weight of the composition and the amount of the first particles is from 5% to 40% by weight of the total weight of the composition. The composition according to item 10 of the patent application scope, wherein the composition includes the first particles in an amount of from 60% to 75% by weight of the total weight of the composition, or the amount of second particles in the composition The weight of the total weight is from 30% to 70% and the amount of the first particles is from 5% to 40% based on the weight of the total weight of the composition. The composition according to any one of items 1 to 9 of the patent application range, wherein the weight ratio of the second particles to the first particles is from 6:1 to 1:2. The composition according to item 12 of the patent application scope, wherein the weight ratio of the second particles to the first particles is from 3:1 to 1:1. The composition according to any one of items 1 to 9 of the patent application scope, which further includes phenoxy resins, polyester resins, and thermoplastic polyurethane polyurethanes), polyacrylates, silicones, and mixtures thereof. The composition according to item 14 of the patent application scope, which further comprises a resin, wherein the resin is selected from the group consisting of phenoxy resins, polyacylates and mixtures thereof . The composition according to item 1 of the patent application scope, wherein the halogenated resin is selected from the group consisting of polydichloroethylene (PVDC) polymer and polydichloroethylene (PVDC) copolymer and mixtures thereof group. The composition according to any one of items 1 to 9 of the patent application scope, wherein the composition includes a resin in an amount of from 1% to 10% by weight of the total weight of the composition. The composition according to any one of items 1 to 9 of the patent application scope, wherein the volume ratio of the particles to the resin is from 1.5 to 3.5. The composition according to item 18 of the patent application scope, wherein the volume ratio of the particles to the resin is from 2.0 to 3.0. The composition according to any one of items 1 to 9 of the patent application scope, wherein the at least one organic solvent is selected from the group consisting of: dipropylene glycol methyl ether (dipropylene glycol methyl ether) ( DPM), 3-methoxy-3-methyl-1-butanol (MMB), butyl glycol acetate (BGA), diethylene glycol, ethylene glycol mono butyl ether, DBE, DBE-9, DBE-3, DBE-4, DBE-5, DBE-6, Propylene glycol methyl acetate (PMA), butyl carbitol (BC), butyl carbitol acetate (BCA) and mixtures thereof. The composition according to item 20 of the patent application scope, wherein the at least one organic solvent is selected from the group consisting of: DBE-9, dipropylene glycol methyl ether (DPM), propylene glycol Propylene glycol methyl acetate (PMA), butyl carbitol (BC), butyl carbitol acetate (BCA) and mixtures thereof. A method for preparing a conductive mesh includes the following steps: forming a mesh pattern composed of grooves on the surface of the substrate, the grooves having greater than 0 μm and less than 5 μm For the width, fill the trench with the composition described in any one of claims 1 to 21, remove the remaining composition on the substrate surface, and cure or sinter the composition. The method according to item 22 of the patent application scope, wherein the curing or sintering is performed at a temperature of less than 150°C. A conductive mesh prepared by the method according to item 22 or item 23 of the patent application scope. A touch panel display includes one conductive mesh on a substrate, wherein the mesh includes the composition according to any one of items 1 to 21 of the patent application range that is cured or sintered.