TRANSPARENT CONDUCTIVE FILM WITH PATTERNED

METALLIC WIRE MESH

FIELD OF THE DISCLOSURE

[0001] The disclosure relates to nanomaterials, and more specifically, to conductive nanostructures on transparent films.

BACKGROUND

[0002] Transparent conductive films are of great interest for many applications ranging from touch screen displays to electromagnetic interference shielding, from photovoltaic cells to de-icing applications. Indium tin oxide (ITO) has been the material of choice for many of these applications due its high optical transparency, good electrical conductance, and high chemical and environmental stability. However, ITO has poor mechanical stability, high raw material cost, and significant absorption loss in the UV and IR portion of the spectrum. Extensive search has been devoted for alternative materials, such as carbon-based materials, conductive polymers, metal nanowires, and graphene, to realize flexible transparent conductive films with good light transmission, and high conductivity. Some of these materials provide mechanical stability and low cost. However, each system has one or more drawbacks such as, but not limited to, surface roughness, low optical transmissivity and low electrical conductivity.

[0003] Metallic meshes can provide increased optical transmissivity and electrical conductance along with a wide transmission spectrum without bandgap limitations. Metallic wire networks have been utilized in many of the aforementioned applications, e.g., but not limited to, electromagnetic interference shielding, window de-icers, heat reflectors, and transparent electrodes. On the other hand, creating a metallic mesh invisible to the human eye requires fabrication of meshes with submicrometer linewidths. This has so far been possible only with expensive fabrication tools, thereby inhibiting the use of metallic wires in a wide range of applications.

[0004] Thus, what is needed are improved transparent conductive films for high optical transmissivity and electrical conductance that can be produced using low cost fabrication tools at a large scale. SUMMARY

[0005] It has been discovered that conductive mesh nanostructures on transparent films can yield electrically conductive films with high optical transmissivity, including nanostructures that can be reliably formed using techniques scalable to high volume manufacturing. This discovery has been exploited to develop the present disclosure, which, at least in part provides examples of conductive mesh nanostructures, films that contain such mesh nanostructures, and techniques for manufacturing such films.

[0006] In general, the disclosure relates to conductive mesh nanostructures on transparent films. The present disclosure, in some aspects, relates to large area fabrication of transparent films having planar meshes of continuous wires with submicrometer line widths. In some examples, the transparent films are produced using Rolling Mask Lithography (RML). The film can have high conductivity and high transparency and can be fabricated for large area products and flexible devices in a roll-to-roll fashion. The RML process can allow for patterning the mesh with a mesh design for a specific target application. For example, the transparency, optical haze, and/or electrical specifications can be designed for the target application. This disclosure explains methods and mesh pattern configurations which can be combined with optical coatings to improve relevant optical and electrical specifications.

[0007] The transparent films, in some examples, include an array, or arrays, of conductive mesh which provides high broadband optical radiation (e.g., but not limited to, visible light) transmission, high electromagnetic interference (EMI) shielding effectiveness and high electrical conductivity. The effectiveness of each application, e.g., but not limited to, EMI shielding effectiveness, transparent antenna, heater etc., is determined, at least in part, by the properties of the mesh pattern, e.g., but not limited to, metallic mesh stripe width, periodicity, thickness etc. In some cases, the mesh can have multiple uses in more than one of these applications. Each application or combination of applications can utilize an optimized mesh, designed with relevant specifications to that application(s).

[0008] Metallic meshes can provide high optical transmissivity and electrical conductance along with a wide transmission spectrum without bandgap limitations. The resulting transparent film can have low optical haze and low diffraction, e.g., but not limited to, the strength of diffraction orders can be reduced by selecting appropriate dimensions of the metallic wires in the mesh. This disclosure describes mesh designs that can have low optical haze and/or high clarity with a low sheet resistance (e.g., but not limited to, about 10 Q/sq or less).

[0009] Another example is combining multi-layer coatings to improve the optical performance. The coatings can be below and/or above the mesh layer and can be designed to provide improvement in scattering cross-section, haze and anti -refl ection and combination of these properties.

[0010] Additionally, a mesh pattern with anisotropic electrical conductivity can be used. The mesh can be designed to give high conductivity in a particular direction of the current flow across the substrate film, specified by the application. This can be accomplished by increasing the density of wires along the particular direction of the current relative to other directions, which can improve the optical transparency while providing higher electrical performance.

[0011] In general, in an aspect, the invention features an electrically conductive film comprising a conductive material network deposited in a pattern on a substrate, wherein the substrate is transmissive for optical wavelengths.

[0012] Examples may include one or more of the following features. The sheet resistance of the film can be about 20 Q/sq or less. The sheet resistance can be about 10 Q/sq or less. The conductive material can be a metallic material. The metallic material can have an electrical resistivity of about 10 pQcm or more, and the conductive film can have a sheet resistance of about 40 Q/sq or less. The conductive material deposited in a pattern can include a metallic wire network including multiple wires having a width of about 0.1 micrometer or more and about 10 micrometer or less in width, and about 10 micrometer or less in thickness.

[0013] The wires can have a width of about 0.1 micrometer or more and about 5 micrometer or less, and a thickness of about 5 micrometer or less. The wires can have a width and a thickness both of about 0.2 micrometer or more both of about 1 micrometer or less. The wires can have a thickness of about 400 nm or more and a width of about 500 nm or more. The wires that are connected over a distance of about one millimeter or more can be connected by at least two wires deposited perpendicular to the primary direction of the disconnected wires. The wires can include connected and disconnected wires, wherein a first portion of the wires are connected with a second portion of the plurality of wires over a distance of about one millimeter or more, where a closest separation between the connected wires can be smaller than a closest separation between disconnected wires. The conductive film can be used for heating. The conductive film can include a planar layer of material overlaying the substrate.

[0014] The planar layer can include a conductive material. The planar layer can include a metallic material. The metallic material can be coated with an anti -reflective coating layer to provide a reflectance of about 30% reflectance or less (e.g., but not limited to, about 20% or less, about 10% or less, about 5% or less) from the metallic film (at least one operative wavelength). The planar layer can include an electrically conductive oxide. The planar layer of material overlaying the substrate can be an anti- reflective coating layer. The anti -reflective coating layer can provide a reflectance of about 15% reflectance or less (e.g., but not limited to, about 10% or less) from the planar substrate (at least one operative wavelength).

[0015] The conductive film can include a second planar layer of material, the second planar layer of material being composed of a different material from the first planar layer of material. The conductive film can decrease a haze parameter by about 10% or more. Haze can be measured using a hazemeter, e.g., but not limited to, according to an ASTM standard (e.g., but not limited to, ASTM D1003). The conductive film can include a layer of material overlying the conductive material. The layer of material overlying the conductive material can be an anti -reflective coating. The anti-reflective coating can reduce a haze parameter by about 10% or more. The conductive film can be applied onto a wire mesh design as described. The disconnected wires can be connected over a distance which passes electromagnetic waves having a portion of RF frequencies and a portion of polarizations. The pattern can be optimized to eliminate diffraction peaks. The conductive film can function as a frequency-selective surface for RF signals. The pattern can include curved segments. A density of the pattern in one direction can be higher than a density of the pattern in the other (e.g., but not limited to, orthogonal) direction. The conductive film can function as a RF notch filter. The conductive film can function as a RF band-pass filter. The conductive film can function as a frequency-selective surface for RF signals over a range of incidence angles between about 0 degrees and about 70 degrees from normal incidence. The conductive film can function as a high pass filter for RF signals wherein signals below a cut-off frequency are transmitted. [0016] In general, in another aspect, the disclosure features a method of making an electrically conductive film including providing a substrate; coating the substrate in a conductive material, coating the conductive material in a photoresist material, contacting the photoresist material with a cylindrical mask having a pattern, causing relative motion between the cylindrical mask and the photoresist material such that the cylindrical mask rotates on an axis oriented to maintain contact of the cylindrical mask and the photoresist material, exposing the photoresist material to a light source arranged within the cylindrical mask such that light emitted from the light source can be transmitted through the a portion of the cylindrical mask contacting the photoresist material, developing the exposed photoresist material to expose the underlying conductive material, and etching the exposed conductive material.

[0017] Examples may include one or more of the following features. The pattern can be a regular array of rectangles. The regular array can have a pitch of about 300 pm or less (e.g., but not limited to, in a range from 20 pm to 200 pm)

[0018] In general, in another aspect, the invention features a thermally reflective film comprising a plurality of cylindrical features (e.g., but not limited to, interlaced circles) forming a repeating pattern extending from a substrate, wherein the plurality of features are composed of a semi-conducting material and the substrate can be transmissive for optical wavelengths.

[0019] Examples may include one or more of the following features. The thermally reflective film wherein the cylindrical features extend from the substrate by a height in a range from about 100 nm to about 500 nm. The cylindrical features can extend from the substrate by a height in a range from about 200 nm to about 500 nm. The cylindrical features can extend from the substrate by a height in a range from about 300 nm to about 500 nm. The cylindrical features extend from the substrate by a height in a range from about 100 nm to about 400 nm. The cylindrical features can extend from the substrate by a height in a range from 200 nm to about 400 nm. The cylindrical features can extend from the substrate by a height in a range from about 300 nm to about 400 nm.

[0020] The pattern can have a pitch in a range from about 200 nm to about 1000 nm. The pattern can have a pitch in a range from about 200 nm to about 800 nm. The pattern can have a pitch in a range from about 200 nm to about 600 nm. The pattern can have a pitch in a range from about 200 nm to about 400 nm. The pattern can have a pitch in a range from about 300 nm to about 800 nm. The pattern can have a pitch in a range from about 400 nm to about 600 nm. The pattern can have a pitch in a range from about 400 nm to about 1000 nm.

[0021] In general, in another aspect, the invention features a system for producing an electrically conductive film comprising a rolling mask lithography printer comprising a roller having a light source arranged within a cylindrical mask; an actuator connected to the cylindrical mask capable of moving the cylindrical mask in at least one spatial dimension; a means of supplying a substrate into contact with the rolling mask lithography printer; a means of depositing a photoresist material on the substrate; a means of depositing a metallic material on the substrate; a means of depositing a developer material on the substrate; and a controller, comprising at least one processer, comprising instructions stored on a non-transitory storage medium, wherein the instructions when executed by the at least one processor perform the method of: coating the substrate in a conductive material; coating the conductive material in a photoresist material; contacting the photoresist material with a cylindrical mask having a pattern; causing relative motion between the cylindrical mask and the photoresist material such that the cylindrical mask rotates on an axis oriented to maintain contact of the cylindrical mask and the photoresist material; exposing the photoresist material to a light source arranged within the cylindrical mask such that light emitted from the light source can be transmitted through the a portion of the cylindrical mask contacting the photoresist material; developing the exposed photoresist material to expose the underlying conductive material; and etching the exposed conductive material.

[0022] Among other advantages, examples of the conductive transparent mesh exhibit reduced optical haze, reduced diffraction and/or higher transmission compared to similar conductive mesh without the coatings disclosed. Examples exhibit improved electrical conductivity without comprising optical transmissivity compared to conventional transparent conductors. For example, nanoweb patterns with non- uniform conductivity can exhibit such advantages.

[0023] In some examples, meshes comprise nanoweb patterns with high RF transparency, e.g., but not limited to, either through bandpass, or polarization dependent transparency. [0024] In certain implementations, nanoweb meshes are produced using certain mask designs (for lithographic fabrication) that improve the fabrication process, e.g., but not limited to, by improving yield, and/or defect density

[0025] Other advantages are also possible. For example, in certain heater applications, the coatings on a nanoweb can enable reduced haze and diffraction compared to any other technology that provides similar conductivity, and enable operating at low voltages. For instance, for certain automotive applications, materials disclosed herein can achieve manufacturer specified operating voltages (e.g., but not limited to, 12V).

[0026] In some examples, e.g., but not limited to, for antenna applications, the materials disclosed herein has sufficiently high conductivity for use in antennas while still being transparent at optical and/or other frequencies.

[0027] Other advantages will be apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The foregoing and other objects of the present disclosure, the various features thereof, as well as the disclosure itself may be more fully understood from the following description, when read together with the accompanying drawings in which:

[0029] FIG. 1 A is a schematic representation of a conductive film having a mesh on the surface of a substrate;

[0030] FIG. IB is a schematic representation of a cross-section of the conductive film;

[0031] FIG. 1C is a schematic representation of an example rolling mask lithography system for forming a patterned conductive film;

[0032] FIG. ID is a schematic representation of a portion of the example rolling mask lithography system shown in FIG. 1C;

[0033] FIG. 2A is a schematic representation of a cross section of an exemplary conductive film without a coating layer;

[0034] FIG. 2B is a schematic representation of a cross-section of an exemplary conductive film with a single coating layer;

[0035] FIG. 2C is a schematic representation of a cross-section of an exemplary conductive film with two coating layers; [0036] FIG. 2D is a schematic representation of a cross-section of another exemplary conductive film with two coating layers;

[0037] FIG. 2E is a schematic representation of a cross-section of an exemplary conductive film with multiple layers;

[0038] FIG. 2F is a schematic representation of a cross-section of another exemplary conductive film with multiple layers;

[0039] FIG. 3A is a graphical representation of an exemplary simulated optical transmission heat-map, with surface contour plots of sheet resistance, Rsh, (red) and Haze (black) for varying mesh thickness and mesh width;

[0040] FIG. 3B is a graphical representation of another exemplary simulated optical transmission heat-map, with surface contour plots of sheet resistance, Rsh, (red) and Haze (black) for varying mesh thickness and mesh width;

[0041] FIG. 4A is a graphical representation of another exemplary simulated haze heat map with surface contour plots of sheet resistance, Rsh, (white) and Haze (black) for varying mesh thickness and mesh pitch;

[0042] FIG. 4B is a table of simulated values of haze, Rsh, and optical transmittance values for mask designs with varying pitch;

[0043] FIG. 5A is graphical representation of an exemplary simulated haze heat map with surface contour plots of sheet resistance, Rsh, (red) and Haze (black) for varying mesh thickness and mesh pitch for an exemplary mesh composed of bare silver on glass;

[0044] FIG. 5B is graphical representation of another exemplary simulated haze heat map with surface contour plots of sheet resistance, Rsh, (red) and Haze (black) for varying mesh thickness and mesh pitch for an exemplary mesh composed of coated silver on glass;

[0045] FIG. 6A is a schematic illustration depicting two exemplary conductive transparent films;

[0046] FIG. 6B is a graphical representation of an exemplary simulated transmission heat map comparing the thickness of the first coating to the thickness of the second coating for the exemplary conductive transparent film delineated in FIG. 6A;

[0047] FIG. 6C is a graphical representation of an exemplary simulated haze heat map comparing the thickness of the first coating to the thickness of the second coating for the exemplary conductive transparent film delineated in FIG. 6A; [0048] FIG. 7A is a schematic illustration depicting an exemplary linear mesh design for RF transparency and high optical transparency;

[0049] FIG. 7B is a table of simulated values of haze, Rsh, and optical transmittance values for a linear mesh design;

[0050] FIG. 8A is a schematic illustration depicting a portion of a linear mesh design;

[0051] FIG. 8B is a graphical representation comparing the reflection (%) of an incident TE polarized wave to the angle of incidence;

[0052] FIG. 8C is a graphical representation comparing the reflection (%) of an incident TM polarized wave to the angle of incidence;

[0053] FIG. 9A is a graphical representation comparing an exemplary simulated normalized transmission of an incident wave to the frequency of the incident wave as a function of angle of incidence;

[0054] FIG. 9B is a graphical representation comparing another exemplary simulated normalized transmission of an incident wave to the frequency of the incident wave as a function of angle of incidence;

[0055] FIG. 9C is a graphical representation comparing a further exemplary simulated normalized transmission of an incident wave to the frequency of the incident wave as a function of angle of incidence;

[0056] FIG. 9D is a graphical representation comparing another exemplary simulated normalized transmission of an incident wave to the frequency of the incident wave as a function of angle of incidence;

[0057] FIG. 10A is a schematic illustration depicting an exemplary mesh pattern having a regular square pattern;

[0058] FIG. 10B is a graphical representation of a simulated diffraction pattern graph generated using a regular square mesh pattern;

[0059] FIG. 11 A is a graphical representation of an exemplary mesh pattern having an interconnected circular pattern;

[0060] FIG. 1 IB is a graphical representation of a simulated diffraction pattern graph generated using an interconnected circular mesh pattern;

[0061] FIG. 12A is a schematic representation of an exemplary mesh design;

[0062] FIG. 12B is a schematic representation of another exemplary mesh design;

[0063] FIG. 12C is a schematic representation of a further exemplary mesh design; [0064] FIG. 12D is a table of simulated values of haze, Rsh, and optical transmittance values for varying mask designs;

[0065] FIG. 13 A is a graphical representation depicting a simulated electric field distribution for a normally incident wave through an exemplary stacked configuration of a masking layer, a photoresist layer, and a substrate;

[0066] FIG. 13B is a graphical representation depicting a simulated electric field distribution for a normally incident wave through another exemplary stacked configuration of a masking layer, a photoresist layer, and a substrate;

[0067] FIG. 13C is a graphical representation depicting a simulated electric field distribution for a normally incident wave through a further exemplary stacked configuration of a masking layer, a photoresist layer, and a substrate;

[0068] FIG. 14A is a schematic representation of two mask patterns for producing a mesh with pairs of wires;

[0069] FIG. 14B is a graphical representation of an exemplary microscopy image depicting a mesh including interconnected wires at 6kx magnification;

[0070] FIG. 14C is a graphical representation of an exemplary microscopy image depicting the mesh including interconnected wires at 400x magnification;

[0071] FIG. 15A is a schematic illustration depicting a cross section of an exemplary mask centered on a single trench;

[0072] FIG. 15B is a schematic illustration of an exemplary mask pattern having an offset rectangular array with varying pitch;

[0073] FIG. 15C is a schematic illustration of another exemplary mask pattern having an offset rectangular array with varying pitch;

[0074] FIG. 15D is a schematic illustration of a further exemplary mask pattern having an offset rectangular array with varying pitch;

[0075] FIG. 15E is a schematic illustration depicting a mask pattern having an offset rectangular array for creating pairs of wires;

[0076] FIG. 16A is a schematic illustration depicting an exemplary arrangement of a mask contacting a photoresist layer which contacts a substrate;

[0077] FIG. 16B is a graphical representation depicting a simulated electric field distribution for a normally incident wave through a cross section of an exemplary stacked configuration of a mask layer, a photoresist layer, a conductor layer, and a substrate layer; [0078] FIG. 16C is a graphical representation depicting a simulated electric field distribution for a normally incident wave through a cross section of an exemplary stacked configuration of a mask layer, a photoresist layer, a conductor layer, and a substrate layer;

[0079] FIG. 16D is a graphical representation depicting a simulated electric field distribution for a normally incident wave through a cross section of an exemplary stacked configuration of a mask layer, a photoresist layer, a conductor layer, and a substrate layer;

[0080] FIG. 17A is a schematic illustration depicting an exemplary conductive transparent film having an enshrouding layer;

[0081] FIG. 17B is a table of reference values of transmission and haze;

[0082] FIG. 17C is a graphical representation of an exemplary simulated normalized transmission to the enshrouding layer covering thickness;

[0083] FIG. 17D is a graphical representation of an exemplary simulated normalized haze to the enshrouding layer covering thickness;

[0084] FIG. 17E is a graphical representation comparing reference lines and simulated normalized transmission and the enshrouding layer covering thickness; [0085] FIG. 17F is a graphical representation comparing reference lines and simulated normalized haze and the enshrouding layer covering thickness;

[0086] FIG. 18A is a schematic illustration of an exemplary mesh pattern and simulated diffraction patterns resulting from the mesh pattern at varying mesh wire width;

[0087] FIG. 18B is a schematic illustration of another exemplary mesh pattern and simulated diffraction patterns resulting from the mesh pattern at varying mesh wire width;

[0088] FIG. 18C is a schematic illustration of a further exemplary mesh pattern and simulated diffraction patterns resulting from the mesh pattern at varying mesh wire width;

[0089] FIG. 19A is a schematic representation of an exemplary honeycomb mesh pattern;

[0090] FIG. 19B is a graphical representation showing a Fourier Transform of the exemplary honeycomb mesh pattern;

[0091] FIG. 20A is a schematic representation of an exemplary randomized honeycomb mesh pattern; [0092] FIG. 20B is a graphical representation showing a Fourier Transform of the exemplary randomized honeycomb mesh pattern;

[0093] FIG. 21 A is a schematic representation of an exemplary doubly randomized honeycomb mesh pattern; and

[0094] FIG. 21B is a graphical representation showing a Fourier Transform of the exemplary doubly randomized honeycomb mesh pattern.

[0095] In the figures, like symbols indicate like elements.

DETAILED DESCRIPTION

[0096] The disclosures of these patents, patent applications, and publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art as known to those skilled therein as of the date of the disclosure described and claimed herein. The instant disclosure will govern in the instance that there is any inconsistency between the patents, patent applications, and publications and this disclosure.

[0097] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art nanomaterials to which this disclosure belongs. The initial definition provided for a group or term herein applies to that group or term throughout the present specification individually or as part of another group, unless otherwise indicated.

[0098] As understood herein, optical wavelength are wavelengths within the optical spectrum, typically in one or more of the infrared, visible or ultraviolet spectra, for example wavelengths between about lOnm and about 1pm.

[0099] It will be appreciated that any substrate, material or arrangement that is transmissive in the optical spectrum will, for example, appear substantially clear to an observer perceiving light transmitted through the substrate, although in reality an amount of absorption, scattering, reflection etc., will occur. “Transmissive” is used herein in the sense of more transmission of one or more operative wavelengths than not for at least some incident angles, for example at least 50% transmission, in some cases at least 60%, 70%. 80%, 90%, 95% or 99% transmission for at least some incident angles.

[0100] As used herein, the articles "a" and "an" refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element. Furthermore, use of the term "including" as well as other forms, such as "include," "includes," and "included," is not limiting.

[0101] As used herein, the term "about" will be understood by persons of ordinary skill in the art and will vary to some extent on the context in which it is used. As used herein when referring to a measurable value such as an amount, a temporal duration, and the like, the term "about" is meant to encompass variations of ±20% or ±10%, including ±5%, ±1%, and ±0.1% from the specified value, as such variations are appropriate to perform the disclosed methods.

[0102] The present disclosure relates to large area fabrication of two-dimensional meshes of continuous wires which can be done with sub-micrometer line widths using Rolling Mask Lithography (RML). This high transmission "Nanoweb" metal mesh can have increased conductivity and transparency over alternative technologies and can be fabricated for large area products and flexible devices in roll-to-roll fashion. The RML process allows for patterning the Nanoweb with the mesh design optimized for the target application transparency, haze and/or electrical specifications. This disclosure explains methods and mesh pattern configurations which can be combined with optical coatings to improve relevant optical and electrical specifications.

[0103] Nanoweb consists of array/arrays of metallic meshes, which provides high broadband light transmission, strong EMI shielding effectiveness and good electrical conductivity. The effectiveness of each application, e.g., EMI shielding effectiveness, transparent antenna, heater etc., is determined by the properties of the Nanoweb mesh pattern, e.g., but not limited to, metallic mesh stripe width, periodicity, thickness etc. In some cases, Nanoweb can have multiple uses in more than one of these applications. Each application or combination of applications require an optimized Nanoweb mesh, designed with relevant specifications to that application(s).

[0104] A mesh pattern can be deposited on a transparent film to enable filtering of radiation (e.g., but not limited to, optical radiation, e.g., but not limited to, visible light). For example, the conductive transparent film can perform high and/or low pass filtering, and/or bandpass filtering characteristics. FIG. 1 A is a diagram that schematically illustrates a section of a conductive transparent film 100 having a mesh 102 on the surface of a substrate 104. An example coordinate axis is included for reference. The characteristics of the conductive transparent film 100 and components thereof can depend on the application, though general characteristics and specific examples are discussed.

[0105] In the example of FIG. 1, the mesh 102 is an electrically conductive film constructed of perpendicular rows and columns of conductive material (e.g., but not limited to, wires) on the surface of the substrate 104. The conductive material can be a conductor (e.g., but not limited to, a metal), or a semiconductor (e.g., but not limited to, metalloid) material, which permits electrical signals to propagate along the mesh 102 without significant loss. The mesh 102 can be constructed from overlain, or woven, individual wires or the mesh 102 can be constructed using printing techniques, e.g., but not limited to, additive or subtractive, to form a unitary structure.

[0106] In general, the substrate 104 is a transparent, or semi-transparent, material which provides high (e.g., but not limited to, about 85% or more) transparency through a spectrum of electromagnetic wavelengths such as optical wavelengths (e.g., but not limited to, between 100 nanometers (nm) and 800 nm) and IR (e.g., but not limited to, between 800 nm and 1000 nm) wavelengths. In some implementations, the substrate 104 material is a flexible material (e.g., but not limited to, low flexural rigidity). In alternative implementations, the substrate 104 material is a rigid or semirigid material (e.g., but not limited to, high flexural rigidity).

[0107] Haze is an optical phenomenon which can be associated with glossy surfaces or optically transmissive materials. There are two types of haze that can occur in materials: reflection haze occurs when radiation (e.g., but not limited to, visible light) is reflected from a material, and transmission haze occurs when radiation passes through a material. The material of the substrate 104 has low haze (e.g., but not limited to, about 10% or less reflection and/or transmission haze, e.g., about 5% or less, about 2% or less, about 1% or less).

[0108] The rows and columns of the mesh 102 form a regular pattern, e.g., but not limited to, a rectangular pattern, having a pitch 106. The pitch 106 is the distance which defines the spacing, e.g., periodicity, of the pattern of the mesh 102. A high periodicity, for the mesh 102 can decrease visual turbidity range, e.g., but not limited to, haze, of the conductive transparent film 100 while maintaining about the same substrate 104 transparency. In some implementations, the pitch 106 is in a range from about 1 micrometers (pm) to about 1000 pm, or alternatively in a range from about 20 pm to about 300 pm. In some implementations, other patterns are achieved such as, but not limited to, non-regular patterns, asymmetric patterns, wavy patterns, circular patterns, interlaced circular patterns, sinusoidal patterns, and off-set patterns.

[0109] In some implementations, the conductive transparent film 100 is constructed to include multiple layers of mesh 102. For example, the conductive transparent film 100 can include, but is not limited to, two or more, three or more, or four or more layers of mesh 102. In such implementations the multiple layers of mesh 102 are separated, e.g., not in contact. The multiple layers of mesh 102 can be separated in space normal to the planar surface of the substrate 104, e.g., along the z- axis. A conductive transparent film 100 configuration including more than one layer of mesh 102 can be termed a “stacked” configuration.”

[0110] FIG. IB is a diagram that schematically illustrates a cross section of the conductive transparent film 100. The cross section of FIG. IB is taken along line A in FIG. 1A. The columns of the mesh 102 are shown contacting and extending from the upper surface (e.g., along the z axis) of the substrate 104. The individual rows and columns of the mesh 102 have a thickness 110 and a width 112. The dimensions of the rows and columns of the mesh 102 can be common to every row or column, or can vary between groups of columns and/or rows, or individually. The wire parameters (material (conductivity), thickness and width), and mesh design parameters are optimized to give higher transmission and lower haze vs. conductivity for the same filling ratio. In some implementations, the thickness 110 and/or the width 112 is in a range from about 50 nanometers (nm) to about 2000 nm (e.g., but not limited to, about 50 nm to about 1500 nm, about 50 nm to about 1200 nm, about 50 nm to about 800 nm, about 50 nm to about 500 nm, about 50 nm to about 200 nm, about 200 nm to about 2000 nm, about 800 nm to about 2000 nm, about 1200 nm to about 2000 nm, or about 1500 nm to about 2000 nm), or in a range from about 500 nm to about 2000 nm.

[0111] The wire parameters of the mesh 102, e.g., but not limited to, material, conductivity, thickness 110, and width 112, and mesh 102 design parameters (e.g., but not limited to, pattern) can be designed to produce increased transmission and decreased haze against conductivity for the same filling ratio (e.g., but not limited to, ratio of the open area of a unit cell of the mesh to the total area of a unit cell). As an example, 500 nm to 2 pm wide wires provide higher conductivity than 50 nm to 200 nm width for the same filling ratio and same aspect ratio (e.g., but not limited to, ratio of thickness 110 to width 112). As a second example, higher periodicity for the mesh 102 on a same substrate 104 of the same or similar transparency decreases haze. An optimum pitch 106 range is between about 20 pm to about 300 pm.

[0112] The mesh 102 can be deposited or constructed on the same substrate 104 using any method known in the art capable of producing the optimum mesh 102 characteristics for the application. For example, lithography methods such as, but not limited to, photolithography can be utilized. One method of fabrication of the mesh 120 is Rolling Mask Lithography (RML).

[0113] In RML, a photoresist coating is applied to a layer of conducting material on a substrate. A cylindrical rolling soft mask including a continuous mesh pattern through which curing light, e.g., but not limited to, UV light, is emitted is rolled over the photoresist layer. The curing light is applied to the photoresist layer to cure the mesh pattern in the photo resist. A developer is applied to the deposited material and uncured photo resist and the underlying conducting material is removed.

[0114] An example roll-to-roll RML system 150 is shown in FIG. 1C and FIG. ID. System 150 includes a resist coating station 152, a cylindrical rolling mask 156 with a UV source 156 therein, a develop station 158, and a rinse station 160. Rollers 170 move a continuous substrate (e.g., a plastic film) beneath the various stations of system 150 from left to right as shown. An electronic control module 162 controls the operation of the system. Resist coating station 152 deposits a photoresist material 153 on the substrate 151 to form a continuous layer 153’ of photoresist. As the substrate moves past cylindrical rolling mask 156, the photo resist layer 153’ is selectively exposed to UV light 157 from source 156 through a pattern 155 of the mask 154.

[0115] After patterning the resist layer 153’, a layer of a conductive material is deposited over the patterned resist. The conductive material is deposited onto the surface of the substrate 151 in regions where the photoresist has been removed from the substrate, and it is otherwise deposited on the photoresist material. Photoresist liftoff removes the residual resist from the substrate surface, along with the conductive material deposited onto the resist. The result is a patterned layer of the conductive material on the substrate.

[0116] In some examples, an etch process is used. For example, the substrate can be pre-coated with a layer of the conductive material prior to the lithography step.

The result of the lithography step, in this instance, is a patterned resist that exposes portions of the conductive material leaving other portions of the conductive material covered by the photoresist. An etch step is then used to etch exposed portions of the conductive material while the covered conductive material remains shielded by the photoresist. Thereafter, residual resist can be removed leaving a patterned layer of the conductive material on the substrate.

[0117] In general, the mask can include patterns having an aspect ratio equal to or higher than 1. The mask can include patterns of width of at least about 200 nm and depth of least about 200 nm. The mask can include patterns of width of at least about 300 nm and depth of least about 300 nm. The mask can include patterns of width smaller than about 600 nm, and of depth smaller than about 800 nm. The mask can include patterns that creates mesh lines that are larger than about 300 nm in width. The mask can include patterns that creates mesh lines that are smaller than about 1 pm in width. The mask can include patterns having that are connected in T-shape.

[0118] The mask can include patterns or combinations of patterns which form connected and disconnected line patterns in a specified direction. The specified direction and the distance between successive connected line patterns can be arranged and optimized to fabricate mesh 102 with anisotropic electrical conductivity and/or bandpass characteristic for incident electromagnetic waves. Disconnected line patterns can be connected in pairs or large number wire elements to prevent loss of conduction due to local defects in fabrication.

[0119] The mask can include patterns that are closely packed, e.g., low pitch, to create one or more structures in the mesh 102, for example, but not limited to, contact pads. As an example, a mask with smaller than about 3 pm separation creates an opening in the photoresist capable of creating features, e.g., but not limited to, contact pads, with larger than about 3 pm feature size.

[0120] The conductive transparent film 100 can be constructed in a range of total areas based on the construction methods. Conductive transparent film 100 produced using RML can have a total square area in a range from about 1 square centimeter (sqcm) to about 100 sqcm. In some implementations, the conductive transparent film 100 has a total square area in a range from about 10 sqcm to about 10,000 sqcm. In some implementations, the conductive transparent film 100 has a total square area in a range from about 0.1 square meters (sqm) to about 10 sqm. In some implementations, the conductive transparent film 100 has a total square area in a range from about 1 square meters (sqm) to about 100 sqm.

[0121] FIG. 2 A depicts a cross section of the conductive transparent film 200 having a mesh 202 extending from a substrate 204, as in FIG. IB. A transparent conductive film that consists of metallic mesh can include at least one coating layer. In some implementations, one or more of the coatings is electrically conductive. As one example, an electrically conductive layer can be a transparent conductive oxide, such as indium tin oxide (ITO).

[0122] FIG. 2B depicts an implementation in which the conductive transparent film 200 has a first coating material 208 deposited on top of the mesh 202 wire’s only. The area between the wires remains free of coating material 208.

[0123] FIG. 2C depicts an implementation in which the conductive transparent film 200 has a second coating material 210 deposited on top of the mesh 202 and first coating material 208. In some implementations, the coating material used in the conductive transparent film 200 is a metallic conductive coating material, such as silver, copper, chromium, or nickel, or alloys thereof, such as NiCu, or NiCr.

[0124] In some implementations, the conductive transparent film 100 includes additional materials to alter one or more optical or electric characteristics. For example, one or more additional layers of coating material can be applied to the conductive transparent film 100 over, under, or encapsulating, the mesh 102. The coating layer can have one or more functions, including anti -refl ection, and/or haze suppression. In some implementations, the coating layer is deposited below, on top of, coating, or encapsulating, the mesh 102. FIGS. 2A-2F are diagrams that schematically illustrate various examples of different coating schemes in which at least one coating layer is applied to a conductive transparent film 200.

[0125] The electrically conductive layer can be a metallic film having a thickness in a range from about 4 nm to about 30 nm (e.g., but not limited to, about 8 nm to about 30 nm, about 12 nm to about 30 nm, about 16 nm to about 30 nm, about 20 nm to about 30 nm, about 24 nm to about 30 nm, about 4 nm to about 24 nm, about 4 nm to about 20 nm, about 4 nm to about 16 nm, about 4 nm to about 12 nm, or about 4 nm to about 8 nm). In some implementations, the conductive layer includes a dielectric coating. The dielectric coating refractive index and thickness is optimized to provide enhanced optical transmission. In some implementations, the conductive layer includes metallic nanowires (e.g., but not limited to, gold nanowires), carbon nanotubes, or a combination of the two. The conductive layer can be below the mesh 102 or can be deposited on top.

[0126] In some implementations, the conductive film includes a combination of connected and disconnected wires. The connected and disconnected wires can be arranged in a chosen direction. The chosen direction and the distance between neighboring wires, e.g., pitch, can be arranged and optimized to have chosen transmission characteristic, e.g., but not limited to, a high pass, a low pass, or a bandpass, for incident RF electromagnetic waves.

[0127] FIG. 2D depicts an implementation in which the conductive transparent film 200 has a second coating material 210 extending between the gaps of the mesh 202 and coating the substrate 204 beneath.

[0128] FIG. 2E depicts an implementation in which the conductive transparent film 200 has a third coating material 212 encapsulating the second coating material 210 and extending between the gaps of the mesh 202 and to contact and coat the substrate 204 beneath.

[0129] FIG. 2E depicts an implementation in which the conductive transparent film 200 has a fourth coating material 214 and a fifth coating material 216 layered between the substrate 204 and the mesh 202. In such implementations, the mesh 202 does not contact the substrate 204. The mesh 202 can be deposited in any manner described herein onto the coating material covering the substrate 204, e.g., as in the fourth coating material 214 and fifth coating material 216.

EXAMPLES

[0130] Reference will now be made to specific examples illustrating the disclosure. It is to be understood that the examples are provided to illustrate exemplary examples and that no limitation to the scope of the disclosure is intended thereby.

[0131] Example 1 - Mesh Designs For Haze, Transmission And Conductivity Control

[0132] FIGS. 3 A and 3B are simulated transmission heat maps comparing mesh 102 thickness (pm) along the y-axis to mesh 102 width (pm) along the x-axis. A transmission color scale is inset adjacent the chart in FIGS. 3A and 3B. The transmission color scale adjacent FIG. 3 A represents normalized transmission (as a % of input) at a given coordinate between 0.92 and 0.97. The transmission color scale adjacent FIG. 3B represents normalized transmission at a given coordinate between about 0.98 and about 0.995. [0133] FIGS. 3A and 3B include a set of haze contour lines 302 indicating lines of constant haze and a set of sheet resistance (Rsh) contour lines 304 indicating lines of constant sheet resistance. The value of the haze and sheet resistance is inset to the respective contour lines. The value of the haze contour lines 302 increases with increasing width at a given thickness. The value of the sheet resistance contour lines 304 generally increases with increasing thickness and width.

[0134] The transmission heat map of FIG. 3A was simulated with a 30 pm mesh pitch and the transmission heat map of FIG. 3B was simulated with a 150 pm mesh pitch. The dashed area of FIGS. 3A and 3B represent the ranges of thickness and width of the wires of the mesh of conductive transparent film that have been previously constructed and correspond to areas of high conductivity of the constructed conductive transparent film.

[0135] Example 2 - Haze and Conductivity Control On Mesh Designs

[0136] FIG. 4A is a simulated haze heat map for constant filling ratio of 1 :50

(e.g., but not limited to, 95% transmission). FIG. 4A compares mesh 102 thickness (pm) along the y-axis to pitch 106 (pm), e.g., period, along the x-axis. A haze color scale is inset adjacent the chart in FIG. 4 A. The haze color scale represents normalized haze (as a % of input) at a given coordinate between 0 and 0.2.

[0137] FIG. 4 A includes a set of haze contour lines 402 indicating lines of constant haze and a set of sheet resistance contour lines 404 indicating lines of constant sheet resistance. The value of the haze and sheet resistance is inset to the respective contour lines. The value of the haze contour lines 402 decreases with increasing pitch 106 at a given thickness. The value of the sheet resistance contour lines 404 is constant at a given thickness. Due to the relative increase in haze with periodicity, larger pitch values enable haze values of 0.03 to 0.04, as shown in the dotted oval outline.

[0138] FIG. 4B is a table of simulated values of haze, Rsh, and optical transmittance values for mask designs with varying pitch 106 values. The table was generated assuming a mesh 102 thickness of 800 nm. The results of columns 406, 408, 410, 412, and 414 were generated with a pitch 106 of 30 pm, 45 pm, 90 pm, 200 pm, and 100 pm, respectively. [0139] Example 3 - Haze Improvement Enables Lower Sheet Resistance At Fixed Transparency

[0140] In general, sheet resistance increases with mesh 102 wire thickness 110 and width 112. Transparency remains for increased thickness 110, and drops with increased wire width 112. For a selected transparency, i.e. width 112, coatings can be selected which enable low haze values (e.g., but not limited to, about 0.01 or less) with increased thickness 110 and lower sheet resistance.

[0141] FIGS. 5A and 5B are simulated haze heat maps comparing mesh 102 thickness (pm) along the y-axis to mesh 102 width (pm) along the x-axis. A haze color scale is inset adjacent the chart in FIGS. 5A and 5B. The haze color scale adjacent FIG. 5 A represents haze at a given coordinate between 1 and 17 x 10' ³ . The haze color scale adjacent FIG. 5B represents normalized haze at a given coordinate between 1 and 10 x 10' ³ .

[0142] FIGS. 5A and 5B include a set of haze contour lines 502 indicating lines of constant haze and a set of sheet resistance (haze) contour lines 504 indicating lines of constant sheet resistance. The value of the haze and sheet resistance is inset to the respective contour lines. The value of the haze contour lines 502 increases with increasing width at a given thickness. The value of the sheet resistance contour lines 504 generally increases with increasing thickness and width.

[0143] The haze heat map of FIGS. 5A and 5B were simulated with a 150 pm pitch. FIG. 5 A was generated by simulating a metallic mesh 102 constructed from silver deposited on a glass substrate 104. FIG. 5B was generated by simulating a metallic mesh 102 constructed from silver deposited on a glass substrate 104 and coated with a first coating.

[0144] FIG. 5B depicts similar haze values for lower sheet resistance going from 30 at point 506 to 4 at point 508.

[0145] Example 4 - Improved Haze For Encapsulated Mesh With Multi-Layer Coatings Preserving High Transmission

[0146] A conductive transparent film 600 was simulated have a mesh 602 constructed from silver deposited on a glass substrate 604 including an encapsulating layer 606. A second conductive transparent film 612 was simulated have a mesh 602 constructed from silver (Ag) deposited on a glass substrate 604 including an encapsulating layer 606, a first coating 608 covering the mesh 602 and glass substrate 604, and a second coating 610 covering the first coating 608. The encapsulating layer 606 covers the second coating 610. The mesh 602 in conductive transparent film 600 and second conductive transparent film 612 has a width (D) of 600 nm, a thickness (H) of 500 nm, and a pitch (P) of 30 pm. FIG. 6A schematically illustrates the conductive transparent film 600 above the second conductive transparent film 612. [0147] The encapsulating layer 606 is simulated as silicon oxide having a refractive index of 1.5. The first coating 608 is simulated as having a thickness in a range from about 0 to about 100 nm with a refractive index of about 2. The second coating 610 is simulated as having a thickness in a range from about 0 to about 150 nm with a refractive index of about 1.75.

[0148] FIG. 6B is a simulated transmission heat map comparing the thickness of the first coating 608 (nm) along the y-axis to the thickness of the second coating 610 (nm) along the x-axis. A transmission color scale is inset adjacent the chart in FIG. 6B representing transmission at a given coordinate between 0.9 and 0.98.

[0149] FIG. 6C is a simulated haze heat map comparing the thickness of the first coating 608 (nm) along the y-axis to the thickness of the second coating 610 (nm) along the x-axis. A haze color scale is inset adjacent the chart in FIG. 6C representing haze at a given coordinate between 0.38 and 0.068.

[0150] FIGS. 6B and 6C include dotted circles indicating a region of thickness values for the first coating 608 and the second coating 610 in which both high transmission (e.g., but not limited to, more than .96) and low haze (e.g., but not limited to, less than 0.048) are achieved.

[0151] Example 5 - Mesh Design For Heater With 77 GHz Pass

[0152] In some implementations, a conductive film includes anisotropic conductivity. In such implementations, the conductive film is constructed of a combination of connected and disconnected wires in a specified direction. The specified direction and the distance between successive connected wires can be arranged to enable high and low conductance across the conductive film surface. The specified direction can be overlapped with current flow to decrease resistive losses and/or increase overall transparency of the film. Disconnected wires can be connected in pairs, or alternatively a large number wire elements can be connected to prevent loss of conduction due to local defects. [0153] FIG. 7A schematically illustrates a linear mesh 702 design for RF transparency and high (e.g., but not limited to, about 95% or more) optical transparency. A conductive transparent film 700 is shown having a mesh 702 constructed on a substrate 704 as a series of parallel wires 703 running vertically (e.g., along the z-axis) in FIG. 7A. Pairs of wires 703 are spaced apart by 20 pm, and the pairs have a pitch of 60 pm, as shown in the exploded area inset adjacent FIG. 7 A. The pairs of wires 703 include a series of conductive connections 706 running horizontally, e.g., perpendicular to the wires, e.g., along the y-axis, connecting the pairs of wires 703 of the mesh 702.

[0154] In some implementations, the mesh 702 includes spanning connections 712 connecting pairs of wires 703 perpendicular to the wires 703. In some implementations, the wires 703 are disconnected for several millimeters, e.g., the spanning connections 712 are spaced several millimeters apart. This provides high- pass transmission of radio waves having a polarization perpendicular to the wires 703 where the frequency band for transmission depends on the overall distance between disconnected wires 703. The wires 703connected in pairs by the conductive connections 706 prevent loss of conduction due to local defects in the mesh 702. The mesh 702 pattern can also be designed to connect two or more (e.g., but not limited to, three wires 703, four wires 703, five wires 703, or more).

[0155] FIG. 7B is a table of simulated values of haze, Rsh, and optical transmittance values for a linear mesh design, such as the designs of FIG. 7 A. The table was generated assuming a wire 703 thickness of 400 nm and 800 nm width. The results of columns 708, and 710 were generated with a pitch between pairs of wires 703 of 30 pm, and 20 pm, respectively.

[0156] FIG. 8 A schematically illustrates a portion of the linear mesh 802 design of FIG. 7A, having a wire 803 thickness of 500 nm and 800 nm width. The wires 803 are connected by a conductive connection 806. The pitch between pairs of wire 803 is 60 pm. The spacing between connections is 200 pm.

[0157] The mesh 802 design of FIG. 8 A, was used to simulate reflection of transverse electric (TE) and transverse magnetic (TM) polarized waves at 77 GHz from the conductive transparent film 800.

[0158] FIG. 8B is a chart showing the reflection (%) of an incident TE-polarized wave along the y-axis to the angle of incidence (deg) along the x-axis. The conductive transparent film 800 achieves a reflection of a TE polarized wave at 0 degrees angle of incidence of more than 99.4% (at 77 GHz), to 99.9% at an 80 degree angle of incidence.

[0159] FIG. 8C is a chart showing the reflection (%) of an incident TM-polarized wave along the y-axis to the angle of incidence (deg) along the x-axis. The conductive transparent film 800 achieves a reflection of 0.5% of a TM polarized wave at 0 degrees angle of incidence, to less than 0.1% at an 80 degree angle of incidence.

[0160] Example 6 - Angle independent Frequency Selective Surface (FSS) using

Mesh

[0161] A conductive transparent film can be produced in which a portion of the RF spectrum is transmitted (e.g., but not limited to, an FSS system). In some FSS system implementations, the remaining RF spectrum is blocking. High transmittance and high frequency selectivity can be achieved by constructing the conductive transparent film with a material having a high conductance, for example less than about 10 Q/sq, e.g., but not limited to, about 3 Q/sq. In the present example, the FSS system is constructed including a mesh with circular patterning.

[0162] An example FSS is shown in FIGS. 9A through 9C. The FSS system including a mesh with circular patterning establishes a resonant structure. The pattern periodicity 5 mm in length and is implemented on a 1 mm thick glass substrate. In the results of FIGS. 9A through 9C a relative permittivity and loss tangent of 2.65 and 0.003 for the substrate, respectively. A polarization-independent and wide-angle response was achieved.

[0163] FIGS. 9A and 9B are charts comparing the simulated normalized transmission of an incident wave along the y-axis to the frequency (GHz) of the incident wave along the x-axis as a function of angle of incidence (Theta). FIGS. 9A and 9B include lines 900, 902, and 904 corresponding to an angle of incidence (Theta) of 0 degrees, 45 degrees, and 90 degrees respectively. FIG. 9A depicts the transmission response of the FSS system for an incident electromagnetic wave having TE polarization. FIG. 9B depicts the transmission response of the FSS system for an incident electromagnetic wave having TM polarization.

[0164] FIG. 9A depicts a transmission peak for all three angles of incidence around 8.5 GHz with a narrow band pass (e.g., peak width) compared to FIG. 9B. FIG. 9B depicts the transmission response of the FSS system for an incident electromagnetic wave having TM polarization. A transmission peak is shown for all three angles of incidence around 8.5 GHz with a broad band pass (e.g., peak width) and increased transmission for high angles of incidence (e.g., but not limited to, 75 degrees) compared to FIG. 9A.

[0165] A conductive transparent film can be produced in which multiple portions of the RF spectrum are transmitted (e.g., but not limited to, a multiband FSS system). In the present example, the multiband FSS system is constructed including a mesh with concentric squares. The multiband FSS system can transmit selected regions of the RF spectrum by tuning the width and the separation between concentric squares. [0166] FIGS. 9C and 9D are charts comparing the simulated normalized transmission of an incident wave along the y-axis to the frequency (GHz) of the incident wave along the x-axis as a function of angle of incidence (Theta). FIGS. 9C and 9D include lines 906, 908, and 910 corresponding to an angle of incidence (Theta) of 0 degrees, 45 degrees, and 90 degrees respectively. FIG. 9C depicts the transmission response of the FSS system for an incident electromagnetic wave having TE polarization. FIG. 9D depicts the transmission response of the FSS system for an incident electromagnetic wave having TM polarization.

[0167] FIG. 9C depicts a transmission peak for all three angles of incidence around 5.5 GHz, 8 GHz, and 10 GHz with a narrow band pass (e.g., peak width) compared to FIG. 9D. FIG. 9D depicts the transmission response of the multiband FSS system for an incident electromagnetic wave having TM polarization. FIG. 9D depicts a transmission peak for all three angles of incidence around 5.5 GHz, 8 GHz, and 10 GHz with a broad band pass (e.g., peak width) and increased transmission for high angles of incidence (e.g., but not limited to, 75 degrees) compared to FIG. 9C.

[0168] Example 7 - Mesh Patterns For Diffraction Control

[0169] An electrically conductive film including a combination of connected and disconnected wires in a specified direction can enable optical diffraction control. The specified direction and the distance between successive connected wires can be selected according to application and diffraction pattern.

[0170] FIG. 10A shows an exemplary mesh pattern 1000 having a regular square pattern. FIG. 10B is a simulated diffraction pattern graph 1004 generated using the mesh pattern 1000 of FIG. 10 A. Two perpendicular lines are shown extending to the radius of the graph 1004. FIG. 10B includes an inset graph 1006 which is an exploded view of the central region of the adjacent graph 1004. A diffraction peak 1008 is shown at the intersection of the perpendicular lines.

[0171] FIG. 11 A shows an exemplary mesh pattern 1100 having an interconnected circular pattern. Specifically, the mesh includes interconnected circular segments. The result is an array of small cells and large cells. FIG. 1 IB is a simulated diffraction pattern graph 1104 generated using the mesh pattern 1100 of FIG. 11 A. The diffraction pattern is shown originating from the center of the diffraction pattern graph 1104. The central area of the diffraction pattern graph 1104 has the highest values.

[0172] Example 8 - Different Mesh Designs With Varying Sheet Resistance And Transparency

[0173] The mesh pattern design of a conductive transparent film changes the optical transmittance, haze, and Rsh. FIGS. 12A, 12B, and 12C schematically illustrate three exemplary mesh designs. FIG. 12A is an exemplary mesh design depicting an offset square pattern. FIG. 12B is an exemplary mesh design depicting a paired wire pattern, such as the paired wire pattern of FIG. 7. FIG. 12C is an exemplary mesh design depicting an interconnected circular pattern, such as the interconnected circular pattern of FIG. 11 A. The interconnected circular pattern of FIG. 12C includes a maximal circular diameter of 110 pm.

[0174] FIG. 12D is a table of simulated values of haze, Rsh, and optical transmittance values for varying mask designs, such as the designs of FIGS. 12A- 12C. Table columns 1200, 1202, and 1204 were generated using the offset square pattern of FIG. 12A having a pitch of 45 pm, 90 pm, and 200 pm, respectively. Table column 1206 was generated using the paired wire pattern of FIG 12B having a paired wire pitch of 40 pm. Table column 1208 was generated using the interconnected circular pattern of FIG 12C.

[0175] Example 9 - Different Mesh Designs With Varying Sheet Resistance And Transparency

[0176] The lithography mask design impacts the exposure regions beneath the mask thereby controlling the transmission parameters of the mesh produced with the lithography mask. FIGS. 13A, 13B, and 13C depict the electric field distribution for a normally incident wave during the development of the photo resists layer when the conductive transparent film is exposed to light through the lithography mask. Exposed and non-exposed regions are shown.

[0177] The designs of FIGS. 13A, 13B, and 13C show differences between exposed and non-exposed regions for respective designs. The fabrication of mesh features via photolithography can be controlled by the lithography mask design. [0178] FIGS. 13A, 13B, and 13C are heat map charts depicting the relative field strength of an electromagnetic wave through a cross section of a mask layer 1300, a photoresist layer 1302, and a substrate layer 1304. Lines at approximate y-axis values denote the division between respective layers. Each of FIGS. 13A, 13B, and 13C has a respective heat map bar chart adjacent to the chart depicting the relative strength of the electromagnetic wave at a given coordinate.

[0179] The mask patterns 1306, 1308, and 1310 are the mask patterns used to generate the heat maps of FIGS. 13A, 13B, and 13C, respectively. The mask patterns 1306, 1308, and 1310 have a depth and a width. The mask pattern 1308 has a depth of 300 nm and a width of 300 nm (e.g., square). The mask pattern 1310 has a depth of 550 nm and a width of 400 nm (e.g., a high aspect ratio).

[0180] FIGS. 13A, 13B, and 13C compare the vertical position (y) compared to the horizontal (x) position of the cross section. FIG. 13 A compares the vertical position (y) to the horizontal (x) in nanometers, while FIGS. 13B and 13C compare the vertical position (y) to the horizontal (x) in micrometers.

[0181] FIGS. 13A, 13B, and 13C each depict an unexposed region 1312, 1314, and 1316, respectively. The unexposed region 1312, 1314, and 1316 are regions of low electromagnetic exposure. The width of the unexposed region 1312, 1314, and 1316 can be used to control the approximate width of the finished wire pattern.

[0182] Mask patterns having larger depth and width values provide increases the width of the exposure pattern, e.g., unexposed region 1312, 1314, and 1316. In some implementations, wires produced using mask patterns similar to mask patterns 1306, 1308, and 1310 have a width under 1 pm. Increasing wire width increases conductivity.

[0183] Mask patterns having a high aspect ratio (e.g., but not limited to, about 1 : 1 or more) increases the contrast between exposed and non-exposed regions. Said another way, mask patterns having a high aspect ratio increases the difference of electromagnetic field strength in a small x position range. For example, the unexposed region 1316 produces an electromagnetic field having a local field strength maximum of 0.5 at 0.0 pm and a maximum of 1.5 at the exposed region, e.g., but not limited to, a factor of 3 difference in the field strength.

[0184] Example 10 - T-Shaped Mask To Fabricate Mesh With Line-Pairs

[0185] In some implementations, a mask pattern having a T-shape is utilized to fabricate a mesh with pairs of wires, such as the pairs of wires of FIG. 7 A. FIG. 14A illustrates two mask patterns for producing a mesh with pairs of wires. Mask pattern 1402 features mask lines intersecting at a right angle in the center (circled) of the pattern 1402. Mask pattern 1404 features a central mask line and two mask lines extending at opposing directions which intersect the mask line at staggered points (circled).

[0186] FIGS. 14B and 14C are SEM microscopy images depicting a mesh 1406 including interconnected wires. FIG. 14B depicts an image of the mesh 1406 including a scale bar of 5 pm, while FIG. 14C depicts an image of the mesh 1406 including a scale bar of 75 pm.

[0187] Example 11 - Masks To Fabricate Varying Mesh Patterns

[0188] The parameters of a mask pattern can be designed to create a mesh pattern sharing the characteristics of the mask pattern. The mask include trenches having a width and depth and are arranged in a pattern to create the mask pattern. For example, FIG. 15A shows a cross section of an exemplary mask centered on a single trench 1500. The trench 1500 has a width of 400 nm wide and a 550 nm depth.

[0189] Trenches can be manufactured into the mask in varying patterns, including mesh pattern disclosed herein. FIG. 15B schematically illustrates a mask pattern 1502 having an offset rectangular array with a pitch of 45 pm. FIG. 15C schematically illustrates a mask pattern 1504 having an offset rectangular array with a pitch of 90 pm. FIG. 15D schematically illustrates a mask pattern 1508 having an offset rectangular array with a pitch of 200 pm. In some implementations, the mask pattern 1508 achieves a haze of around 1%.

[0190] FIG. 15E schematically illustrates a mask pattern 1506 having an offset rectangular array creating pairs of wires. The mask pattern 1506 can be designed for heater applications including increased transparency (e.g., but not limited to, about 95 % or more) and higher conductivity in one direction, e.g., anisotropic conductivity. [0191] Example 12 - Field Pattern Of Close-Packed Mask Pattern To Enable Large Opening In The Photoresist

[0192] The pitch of the mask pattern used to produce a conductive transparent film affects the opening created in a photoresist layer. FIG. 16A schematically illustrates an example arrangement of a mask 1602 contacting a photoresist layer 1604 which contacts a substrate 1606. The mask 1602 includes trenches 1608 arranged at a given pitch. The example arrangement of mask 1602 was used to generate simulated heat maps of FIGS. 16B, 16C, and 16D, respectively.

[0193] FIGS. 16B, 16C, and 16D are relative field strength heat map charts depicting an electromagnetic wave through a cross section of a mask layer 1610, a photoresist layer 1612, a liftoff resist (LOR) layer 1614, and a substrate layer 1616. Lines at approximate y-axis values denote the division between respective layers. Each of FIGS. 16B, 16C, and 16D has a respective heat map bar chart adjacent to the chart depicting the relative strength of the electromagnetic wave at a given coordinate. The mask layer 1610 includes a trench 1618 having a depth and a width according to the dimensions of shown on the x and y axes. FIGS. 16B, 16C, and 16D compare the vertical position (y, pm) compared to the horizontal (x, pm) position of the cross section.

[0194] The pitch of the trenches 1618 of mask layer 1610 was varied in each simulation. FIG. 16B corresponds to a trench 1608 pitch of 3 pm. FIG. 16C corresponds to a trench 1608 pitch of 2 pm, and FIG. 16D corresponds to a trench 1608 pitch of 1.5 pm.

[0195] FIGS. 16A, 16B, and 16C each depict an unexposed region 1620, 1622, and 1624, respectively. The unexposed region 1620, 1622, and 1624 are regions of low electromagnetic exposure. The pitch of the trenches 1618 in a mask layer 1610 affects the unexposed regions 1620, 1622, and 1624 and can be used to control the approximate width of the finished wire pattern. As evident from FIG. 16D, a mask trench pitch of 1.5 pm can provide a continuous or near continuous opening instead of individual wires due to the proximity of adjacent wires. Such a mask can be used to make large area contact pads by creating large openings that connect wires.

[0196] Example 13 - AR Coating With Coating For Haze Reduction

[0197] The parameters of a mesh pattern can be designed to increase haze suppression. In some implementations, the parameters of the mesh wires is constructed a width, depth, and pitch to increase haze suppression. For example, FIG. 17A depicts a conductive transparent film 1700 having a gold (Au) mesh 1702 enshrouded in an encapsulating layer 1706. The wires of the mesh 1702 have a width (D), a thickness (H), and a pitch (P). The encapsulating layer 1706 contacts a first coating layer 1708 which is deposited on a glass substrate 1704 to a thickness ti, thereby separating the encapsulating layer 1706 from the substrate 1704.

[0198] The encapsulating layer 1706 has a thickness of t2 between adjacent wires. The mesh 1702 is covered by the encapsulating layer 1706 by a thickness t2c. The encapsulating layer 1706 separates the mesh 1702 from the first coating layer 1708 by a thickness equal to about t2 - t2c.

[0199] FIG. 17B is a table showing the transmission and haze for a reference glass substrate, e.g., glass substrate 1704.

[0200] FIGS. 17C and 17D are simulated line charts comparing normalized transmission and haze (%), respectively, along the y-axis to t2c (nm) along the x-axis. A transmission peak 1712 and a haze minimum 1714 are show.

[0201] FIGS. 17E and 17F are simulated line charts comparing references values (e.g., lines 1716 and 1724) for a glass substrate and normalized transmission and haze (%)(e.g., lines 1718 and 1722), respectively, along the y-axis to t2c (nm) along the x- axis.

[0202] Example 14 - Different Structures For Diffraction Control

[0203] In some implementations, varying the mesh pattern provides varying diffraction patterns.

[0204] FIG. 18 A, from the left, depicts an exemplary “interlaced circles” mesh pattern, and three simulated diffraction patterns resulting from the mesh patterns at a mesh wire width of 6 pm, 8 pm, 10 pm, respectively.

[0205] FIG. 18B, from the left, depicts an exemplary “random amplitude” mesh pattern, and three simulated diffraction patterns resulting from the mesh patterns at a mesh wire width of 6 pm, 8 pm, 10 pm, respectively.

[0206] FIG. 18C, from the left, depicts an exemplary “interlaced circles” mesh pattern, and three simulated diffraction patterns resulting from the mesh patterns at a mesh wire width of 6 pm, 8 pm, 10 pm, respectively. [0207] The mesh paterns of FIGS. 18B and 18C are series of horizontal and vertical sine waves. Randomness is added to either the amplitude (e.g., FIG. 18B) or the pitch (e.g., FIG. 18C) of the waves.

[0208] In general, the diffraction patterns increase in spread (e.g., but not limited to, overall width, increasing diffusion) from left to right (e.g., but not limited to, from 6 pm to 10 pm).

[0209] In some implementations, randomness is added to both the amplitude and the pitch. As a non-limiting example, increasing randomness by 10% means the actual value (e.g., the amplitude or the pitch) for each individual period of a sine wave is a random number within 10% of a base parameter. Increasing the randomness value (e.g., but not limited to, values about 10 % or more) further increases the spread of the diffraction pattern.

[0210] An example of a honeycomb mesh is delineated in FIG. 19A. A Fourier Transform of the honeycomb mesh shown in FIG. 19A is shown in FIG. 19B. The honeycomb mesh pattern includes segments each having the same length forming closed, hexagonal cells. The diffraction pattern exhibits the six-fold symmetry of the honeycomb pattern in the six dominant diffraction spikes in a symmetric star pattern. [0211] An example of a randomized honeycomb mesh pattern is delineated in FIG. 20A. A Fourier Transform of the honeycomb mesh shown in FIG. 20A is shown in FIG. 20B, delineating the diffraction profile from the honeycomb mesh. In this mesh pattern, a honeycomb mesh such as in FIG. 19A is used as a starting point and each point in the mesh is displaced from its starting position by an amount, such as a fraction (e.g., but not limited to, a quarter, a third, a half) of the average periodicity of the starting honeycomb mesh. The loss of the six-fold symmetry is evident from the diffraction patern when comparing FIG. 20B with FIG. 19B.

[0212] An example of a doubly randomized honeycomb mesh pattern is delineated in FIG. 21 A. A Fourier Transform of the doubly randomized honeycomb mesh shown in FIG. 21 A is shown in FIG. 2 IB. In this pattern, the lines connecting the mesh points in FIG. 20A are also converted into randomized curves with sine waves of varying period and amplitude. The resulting mesh pattern shown in FIG. 21A is a referred to as doubly randomized honeycomb mesh. Such a mesh can have a superior isotropic diffraction patern and can reduce (e.g., eliminate) directional diffraction such as a lens-flare. The diffraction pattern shown in FIG. 2 IB shows increased homogeneity compared to both FIG. 19B and FIG. 20B. [0213] In some examples, each segment of the mesh can have an associated period and amplitude while the period and/or amplitude varies between different mesh segments. Alternatively, or additionally, segments can have a period and/or amplitude that varies along its length.

[0214] It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other implementations will be apparent to those of skill in the art upon reading and understanding the above description. Although the present disclosure has been described with reference to specific example implementations, it will be recognized that the disclosure is not limited to the implementations described but can be practiced with modification and alteration within the scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense. Although various features of the approach of the present disclosure have been presented separately (e.g., in separate figures), the skilled person will understand that, unless they are presented as mutually exclusive, they may each be combined with any other feature or combination of features of the present disclosure

[0215] While this specification contains many details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular examples. Certain features that are described in this specification in the context of separate implementations can also be combined. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple examples separately or in any suitable subcombination.

[0216] Those skilled in the art will recognize, or be able to ascertain, using no more than routine experimentation, numerous equivalents to the specific examples described specifically herein. Such equivalents are intended to be encompassed in the scope of the following claims.