TW201620623A - Process for blackening a transparent electrically conductive film - Google Patents

Abstract

A process for blackening an electrically conductive metal network that includes: (a) providing a transparent electrically conductive film comprising a metal network; and (b) treating the metal network with a blackening composition comprising (i) an organic solvent, (2) a chalcogen selected from the group consisting of sulfur, tellurium, selenium, and combinations thereof, and (iii) an amine.

Description

Treatment for blackening a transparent conductive film

This invention relates to the preparation of transparent, electrically conductive films.

The transparent conductive film can be formed by depositing a conductive metal on a transparent substrate. In some cases, the metal may be deposited on the substrate in a network such that the transparent cells are defined by a network of metal traces. In other cases, the metal may be deposited in the form of crossed metal fibers or wires. For example, when a conductive network is placed on the viewing side of the display screen, reflections of visible light from the metal surface of the conductive element can visually impair the image being viewed through the film.

The blackening process has been described to reduce the reflectivity of the conductive elements by depositing a dark layer on a metal surface (e.g., a sulfide layer on a silver network). However, the blackening process can undesirably increase the sheet resistance of the metal network. Some blackening treatments also introduce complexity in the manufacturing process for films. It would be beneficial to have a blackening process that is economical and minimizes any increase in sheet resistance.

Described is a process for blackening a conductive metal network comprising: (a) providing a transparent conductive film comprising a metal network; and (b) processing a metal network using a blackening composition, The composition comprises (i) an organic solvent, (ii) a chalcogen element selected from the group consisting of sulfur, antimony, selenium, and combinations thereof, and (iii) an amine. The term "blackening" Often referred to as the use of a chemical composition to treat a metal surface to add a colored layer (usually a metallic one of its own colored compounds), thereby darkening the overall appearance and reducing the amount of light reflected from the surface. The actual color of the coating on the metal can be black, or it can be other colors that appear darker than the color of the untreated metal. When a transparent conductive film is used in an application in which the film is placed on the viewing side of an electronic display such as a computer monitor or video screen, the blackening visual effect is reduced by light reflected from the metal surface. A gray appearance and restores the appearance to the appearance that would be seen if the conductive film did not exist.

In a particular embodiment, the amine can be an aliphatic amine. For example, the aliphatic amine can be a monohydroxy aliphatic amine. The amount of the amine in the blackening composition may vary from 0.01 wt.% to 5 wt.%, from 0.1 wt.% to 1.0 wt.%, or from 0.1 wt.% to 0.5 wt.%, wherein all weights The percentage is based on the weight of the blackening composition. The chalcogen element can be sulfur. Sulfur may be in the form of colloidal sulfur. The amount of the chalcogen element in the blackening composition may vary from 0.01 wt.% to 0.5 wt.%, from 0.02 wt.% to 0.2 wt.%, or from 0.025 wt.% to 0.1 wt.%, wherein All weight percentages are based on the weight of the blackening composition.

The blackening composition can be in the form of a solution or a colloidal dispersion. The metal network can comprise a pattern of conductive traces formed from metal nanoparticles that define at least a portion of the unit transparent to visible light.

The blackening process described herein is beneficial in several respects. This treatment is effective in blackening all surfaces of the conductive metal network (i.e., the surface facing the film substrate and the surface opposite to the film substrate). The chemicals used are relatively safe compared to the treatment with more toxic blackening compositions. The treatment is carried out under relatively mild conditions (e.g., room temperature for the coating step) and no subsequent washing steps are required to remove residual blackening agent. Importantly, the handling minimizes the increase in electrical film resistance of the conductive network.

The details of one or more embodiments of the invention are set forth in the claims Other features, objectives, and advantages of the present invention will be apparent from the description and claims. point.

The blackening process blackens the conductive metal network while minimizing an increase in the sheet resistance. The treatment comprises treating the network with a blackening composition comprising (i) an organic solvent, (ii) a chalcogen element selected from the group consisting of sulfur, antimony, selenium, and combinations thereof, and (iii) an amine. By including an amine in the composition, an increase in one of the sheet resistances is less than an increase in the use of a comparable composition lacking one of the amines.

Transparent conductive film

The transparent conductive film comprises a film having a conductive metal network disposed on a transparent substrate or a freestanding conductive metal network without a supporting substrate. The substrate may comprise a polymeric film or sheet such as polyester, polyamide, polyimide, polycarbonate, polyolefin, poly(meth)acrylate, copolymer, and multilayer film. The glass can also be a useful substrate for one of the transparent conductive networks. The substrate can be rigid or flexible for a roll-to-roll process, and is preferably selected to be compatible with the solvent used in the blackening composition.

The conductive metal network can be a transparent, conductive network of one of the metal traces. The network of metal traces can continuously conduct electricity and define cells that are transparent to visible light (ie, visible radiation). The shape of the network and the units defined by the network (eg, patterns) may be regular, irregular, or random. A useful network can be self-assembled into a conductive metal (eg, silver) nanoparticle that is self-assembled into a transparent, conductive network of traces and cells, as described in U.S. Patent No. 7,601,406, incorporated herein by reference. form. Such networks include traces formed from at least partially bound metal nanoparticles to provide electrical conductivity. A useful network includes the network sold under the trademark "SANTE" by Cima NanoTech, St. Paul, Minnesota (MN).

Other useful conductive networks include webs deposited from conductive inks using a print process A network formed by exposure and subsequent development of a pattern of radiation by a silver halide emulsion, and a network formed by the deposition of conductive particles into a pre-formed pattern of grooves in the surface of a substrate. Other conductive metal networks include metal networks formed from crossed metal fibers or wires. In some cases, the transparent conductive network can have enhanced electrical conductivity provided by electroplating or electroless plating of an alkaline conductive metal network.

Blackening composition

The blackening composition may comprise sulfur, an aliphatic amine, and a solvent. Sulfur can be used in the form of colloidal sulfur (i.e., elemental sulfur having a colloidal particle size). Useful sulfur concentrations in the composition can range from 0.01 to 0.5 weight percent, or from 0.02 to 0.2 weight percent, or from 0.025 to 0.1 weight percent. As shown in the examples, a higher sulfur concentration provides more blackening. A member of the family of sulfur-based chalcogen elements, which also contains selenium and tellurium, either of which may be included in the blackening composition. A combination of sulfur, selenium and/or tellurium can likewise be used.

The amine can be an aliphatic amine such as octylamine or monohydroxyamine. Examples of the hydroxylamine include ethanolamine and aminobutanol. Combinations of two or more amines can likewise be used. The amine concentration in the composition may range from 0.01 to 5.0 weight percent, or from 0.1 to 1.0 weight percent, or from 0.1 to 0.5 weight percent.

The solvent may be a blend of an organic solvent or an organic solvent, and is selected to be compatible with the substrate for the transparent conductive film, compatible with the treatment, and capable of dispersing or dissolving other components in the blackening composition. . Examples of the solvent include methyl ethyl ketone, ethanol, and toluene. Dispersions (e.g., colloidal suspensions of small particles in a solvent) are preferred for slower and more controlled blackening, particularly if the metallic conductive network is porous. The solution is preferably used for faster blackening. The blackening composition may contain dispersed and decomposed chalcogen elements (e.g., sulfur) depending on the solvent.

The degree of blackening can be controlled by the amount of the composition applied, the concentration of the chalcogen element in the composition, and one or more of the selected solvents.

deal with

The transparent conductive film can be treated with a blackening composition using several known coating techniques including dip coating, flow coating, spray coating, pressure coating, and rod coating.

After application of the composition, the film can be dried and heated to an elevated temperature (eg, 80 to 200 degrees C) for a time ranging from 10 seconds to 10 minutes. The temperature and time selected should be compatible with any substrate used to support the conductive network.

Batch processing can be used, or continuous processing (eg, reel-type film transport) can be used.

Instance

testing method

Thin film resistance (Rs) was measured using a Loresta-GP MCP T610 4-point probe (Chesapeake, Mitsubishi Chemical, Va.).

A non-blackened film is used as a reference to visually characterize the color. A scale of 0 to 5 is used, where 0 corresponds to no blackening, 1 corresponds to light blackening, and 5 corresponds to very black. "Front color" is the color observed from the surface of a film having a conductive network. "Backside color" is the color observed from the surface of the film opposite the conductive network (ie, viewed through the substrate).

The ingredients shown in Table 1 were mixed with methyl ethyl ketone (MEK) until an ultrasonic homogenizer was used uniformly to form a dispersion. These components were obtained from Sigma Aldrich, St. Louis, Missouri (MO). The uniform dispersion is coated on a transparent, conductive film (SANTE® FS200 touch film) with a silver nanoparticle network of traces and cells on a PET substrate, available from Westmanami Technologies, St. Paul, Minnesota In this case, the substrate uses a Mayer rod to give a wet thickness of 40 microns. The dispersion is applied to the surface of the film having a conductive network. The coated film was dried at 150 deg. C for 30 seconds. The film thus formed was tested and the results are shown in Table 1.

A number of embodiments of the invention have been described. However, it should be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

Claims (14)

A process for blackening a conductive metal network, comprising: (a) providing a transparent conductive film comprising a metal network; and (b) processing the metal network using a blackening composition, The composition comprises (i) an organic solvent, (ii) a chalcogen element selected from the group consisting of sulfur, antimony, selenium, and combinations thereof, and (iii) an amine. The treatment of claim 1 wherein the amine comprises an aliphatic amine. The treatment of claim 2 wherein the aliphatic amine comprises a monohydroxy aliphatic amine. The treatment of claim 1, wherein the chalcogen element is sulfur. The treatment of claim 4, wherein the sulfur is in the form of colloidal sulfur. The treatment of claim 1 wherein the blackening composition is in the form of a solution. The treatment of claim 1 wherein the blackening composition is in the form of a colloidal dispersion. The treatment of claim 1, wherein the amount of the chalcogen element is changed from 0.01 wt.% to 0.5 wt.% based on the weight of the blackening composition. The treatment of claim 1 wherein the amount of chalcogenide varies from 0.02 wt.% to 0.2 wt.% based on the weight of the blackening composition. The treatment of claim 1 wherein the amount of chalcogenide varies from 0.025 wt.% to 0.1 wt.% based on the weight of the blackening composition. The treatment of claim 1 wherein the amount of the amine varies from 0.01 wt.% to 5.0 wt.% based on the weight of the blackening composition. The treatment of claim 1 wherein the amount of the amine varies from 0.1 wt.% to 1.0 wt.% based on the weight of the blackening composition. The treatment of claim 1 wherein the amount of the amine varies from 0.1 wt.% to 0.5 wt.% based on the weight of the blackening composition. The processing of claim 1, wherein the metal network comprises a transparent surface defined by visible light At least a portion of the unit is bonded to one of the conductive traces formed by the metal nanoparticles.