KR20140118405A - Method for Coating Film with Ag Nano Wire in a Manner Capable of Regulating Electric Properties - Google Patents

Abstract

The present invention relates to a coating method of a silver nanowire capable of adjusting electrical properties, and more specifically to a coating method of a silver nanowire for which a coated film has the demanded electrical properties by changing process conditions in the process of coating silver nanowire ink regarding a film base material. The coating method of a silver nanowire comprises: a step of determining a coating gap of a coater; a step of adjusting speed of moving line or tensile stress of a base material film according to the electrical properties of the demanded-coated film; a step of moving the film along a film moving path in which a gradient is adjusted according to viscosity of a silver nanowire ink composition; and a step of drying the coated film by dividing into at least two steps.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of coating a silver nanowire,

The present invention relates to a silver nanowire coating method capable of adjusting electrical characteristics, and more particularly, to a method for coating silver nanowire ink on a film substrate, To a method of coating silver nanowires.

Transparent electrodes can be made by ITO (Indium Tin Oxide) films as electronic components, which generally have a transparency of 80% or more and a conductivity of 500 Ω / sqm or less. However, the ITO film is weak in bending, and indium itself has been developed as a substitute electrode corresponding to rare metals. Graphene), carbon nanotubes and silver nanowires (Ag-Nano_Wire) have been proposed as substitute electrodes for ITO electrodes. Silver nanoparticle surfaces are made up of several crystal planes and can be made in a word form by inducing isotropic growth using their reactivity differences. Silver nanowires have a resistance value of 80 to 120 Ω, which is lower than that of ITO films having a thickness of 200 to 400 Ω, which is advantageous for enlarging the size and can be applied to a printing method and can be applied to a flexible display .

Prior art relating to the formation of a transparent conductive film using silver nanowires is disclosed in Patent Publication No. 2011-0071526 'Nanowire and its manufacturing method and transparent conductive film using the same. In the prior art, a silver nanowire is prepared by dissolving silver nitrate and an ionic liquid in a solvent that performs a reducing action, and an ink composition prepared by mixing a urethane aqueous dispersion, a dispersion stabilizer, ultrapure water, and an alcohol, Discloses a method of manufacturing a transparent conductive film.

Another prior art related to the formation of transparent electrodes using nanowires is disclosed in Korean Patent Publication No. 2012-0092294, 'Transparent electrodes using nanowires and a manufacturing method thereof'. The prior art relates to a transparent electrode for forming a silver nanowire network with minimized contact resistance characteristics, comprising the steps of: preparing a nanowire dispersion solution; Coating the silver nanowire dispersion solution on a substrate; And photo-sintering the silver nanowires coated on the substrate to make the contact sites between the silver nanowires weld to each other.

The prior art or known technique does not disclose a coating method according to the electrical characteristics of the silver nanowire ink composition. Silver nanowire ink compositions can be prepared in a variety of ways and need to be coated in new ways for the formation of transparent electrodes. The present invention is intended to propose a novel coating method not disclosed in the prior art or the known art, and has the following purpose.

It is an object of the present invention to provide a method of coating silver nanowires that enables adjustment of electrical characteristics.

According to a preferred embodiment of the present invention, a method of coating silver nanowires comprises: determining a coating gap of a coater; Adjusting the speed of the transfer line or the tension of the base film according to the electrical characteristics of the film to be coated; Transporting the film along an inclined film transport path according to the viscosity of the nanowire ink composition; And coating the coated film in at least two stages.

According to another preferred embodiment of the present invention, the coater is a slot die coater and the tension is controlled by a roll-to-roll method.

According to another preferred embodiment of the present invention, the slope is from 0 to 15 degrees with respect to the ground, with the conveyance path from which the drying starts from the coater.

According to another preferred embodiment of the present invention, the drying step comprises blowing at ambient temperature.

According to yet another preferred embodiment of the present invention, the method of coating silver nanowires is such that the gradient between the coater from which coating is initiated by at least silver nanowire ink composition and the transport path where drying is initiated is 0 to 15 degrees , And air blow drying at room temperature.

The coating method according to the present invention has the advantage that the entire silver nanowire-coated film exhibits uniform electrical characteristics. Further, the coating method according to the present invention has an advantage in that it makes it possible to adjust electric characteristics such as electrical resistance of a coated film, for example. In addition, the process according to the present invention is advantageous in that it can be coated to a certain thickness and thus the properties of the film coated in various forms can be controlled.

1A schematically shows an embodiment of a coating method according to the invention.
Fig. 1b schematically shows an embodiment of an apparatus to which the coating method according to the invention is applied.
Figure 2 shows the results of coating with an inclination of 0 to 5 degrees and an inclination of 45 degrees.
FIG. 3 shows the result of the coating process according to the present invention in which only the heat drying without the blow drying and the blow drying is performed.
4 is a graph showing a change in resistance value according to the feeding speed.
5A, 5B and 5C are graphical representations of changes in resistance value according to coating thickness, in which FIG. 5A shows polyacryl, FIG. 5B shows polyethylene terephthalide and FIG. 5C shows glass.
Fig. 6 shows an embodiment of the coating result according to the tension change.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the accompanying drawings, but the present invention is not limited thereto. In the following description, components having the same reference numerals in different drawings have similar functions, so that they will not be described repeatedly unless necessary for an understanding of the invention, and the known components will be briefly described or omitted. However, It should not be understood as being excluded from the embodiment of Fig.

FIG. 1A schematically shows an embodiment of a coating method according to the invention, and FIG. 1B schematically shows an embodiment of an apparatus to which a coating method according to the invention is applied.

Referring to FIGS. 1A and 1B, a coating method according to the present invention includes: preparing a silver nano-coating composition (S11); (S12) determining the required physical properties of the coating film to be coated; A step S13 of setting a gap of the coater; Adjusting the slope of the transport path of the base film (S14); Adjusting the feed speed and tension of the base film (S15); Transferring the base film (S16); Coating (S17) with a thickness determined by the coater; And drying the coated film (S18).

Silver nanowires can be any silver nanowires known in the art and can be silver nanowires that can be applied, for example, to an LCD or touch screen panel (TSP). The ink composition should be prepared for the coating of the nanowire (S11). Silver nanowire ink compositions may include, for example, silver nanowires, distilled water, alcohol or acrylic polyesters or various types of dispersants, and the method according to the invention is not limited by the type of silver nanowire ink composition.

Once the nanowire ink composition is prepared, the required properties of the coating film can be determined (S12). The required physical properties may be, for example, the type of base film, electrical resistance, coating thickness or roughness, and may be appropriately set in accordance with the application field of the transparent electrode. The required physical properties can be a prerequisite for controlling the coating method. But may be the general properties required in this field, such as known or improved electrical properties or thin coating thickness in this field. Therefore, it can be understood that the method according to the present invention is applied for improving the general properties of the coating film. The base film may be a transparent resin such as a polyimide (PI), polyacrylic, polyurethane, polyepoxy, polyol, polycarbonate or polycellulose resin film, But is not limited thereto. Also, the viscosity of the silver nanowire ink composition may be from 1 cps to 3000 cps, but the present invention can be applied regardless of the viscosity of the silver nanowire ink composition.

The coating of the base film can be made in the R2R (Roll to Roll) manner for the continuous coating and can be a slot die coater for uniform coating as shown in FIG. 1B. The slot die coater 11 is designed so that the ink composition is discharged on a die so as to have a uniform flow distribution in the width direction so that the coating surface is flattened by the shear force between the die lip and the roller Coating method. The slot die coater 11 applied to the coating method according to the present invention can be operated, for example, by a solution tank, a pulsating dosing pump or a piston pump, and the coating gap is suitable by the method according to the invention . According to the present invention, the coating thickness may be 1 to 20 占 퐉 before drying, and the coating thickness of the dried final coated film may be 10 to 200 nm. Under such conditions, the coater gap can be adjusted to be 10 to 150 mu m. For a given coating thickness and feed rate, the coater gap was found to affect the resistance value of the coating film. For example, when the thickness of the coated surface is 6 to 8 占 퐉 and the film transporting speed is 40 to 60 mm / sec, when the coater gap is 60 to 80 占 퐉, the resistance value becomes 85 to 98 ohm / The resistance value was found to be 50 to 56 ohm / sq. On the other hand, as the coater gap becomes larger in a certain range, the resistance value becomes larger.

When the coater gap is set (S13), the inclination can be adjusted. The inclination refers to an angle formed by the film transfer line with the ground surface and specifically refers to a path between the first roller 12 coated by the slot die coater 11 and the third roller 14 completed drying, 12) to the drying chamber (15). According to the invention, the slope can be from 0 to 15 degrees, preferably from 0 to 10 degrees, and most preferably from 0 to 5 degrees, relative to the ground. It is advantageous that the inclination degree of the transfer line is practically 0 degree. In particular, in the case of an ink composition having a low viscosity, the smaller the degree of inclination, the easier the control of physical properties. However, according to the present invention, it is advantageous that the inclination is 0 to 15 degrees due to various reasons, but at least the slope between the drying chamber corresponding to the slot die coater 11 and the completion of natural drying is 0 Lt; RTI ID = 0.0 > 15 < / RTI >

When the inclination is adjusted (S14), the speed and tension of the transfer line can be adjusted (S15). The speed of the transfer line can be controlled by the rotational speed of the first roller 12, the second and third rollers 13 and 14, and the tension means the tension of the base film F. [ The rotational speed or tension may be adjusted in any manner known in the art.

According to the present invention, if the thickness of the wet coating is 5 to 10 mu m and the coater gap is 50 to 70 mu m, the conveying speed can be 50 to 200 mm and the resistance value can be adjusted to be 120 to 200 ohm / sq . As the feedrate increases over a range of coater thicknesses and coater gaps, the tensile strength increases as well. If the coating thickness is the same and the conveying speed is increased, the speed at which the ink composition is discharged from the slot line coater 11 must be increased accordingly.

On the other hand, the tension of the base film was found to affect such things as resistance, transparency or surface roughness. For example, transparency can be increased if the tension is increased in a certain range. It is advantageous that the tension of the base film is determined in consideration of the stretchability of the base film. For example, as the stretchability of the base film increases, the tensile force applied to the base film increases, which may improve the physical properties of the coating film. According to the present invention, tension control may not be performed separately unless specifically required. For example, the physical properties of the coating film can be controlled through controlling the rotational speed or the drying condition, and the physical properties can be controlled by controlling the tension when the physical properties are difficult to control by such parameters. Therefore, tension control of the coating film may not be achieved unless it is a special case.

When the speed of the transfer line is determined (S15), the base film F is transferred (S16) by the rotation of the first roller 12, the second and third rollers 13 and 14 and the slot die coater 11 The silver nanowire ink composition may be coated on the substrate film to a predetermined thickness (S17). The slope is then transferred along the controlled transfer line and the drying process can proceed (S18).

According to the present invention, the drying process includes blow drying at a room temperature or a constant temperature range. The constant temperature range refers to a temperature of, for example, 50 degrees or less, preferably 15 to 40 degrees and most preferably 20 to 35 degrees. And air blow drying is a film coated with a blowing fan or an air knife to generate air movement at a certain speed. The air blast drying may be performed in a natural state or by a method of introducing air from the outside such as using an air knife. Specifically, the coated film can be moved above the transport line to be transported, for example, with an air movement of 0.5 to 10 m / sec at an air speed of 0.5 to 10 m / sec above the transport line using an air knife Can be generated. The pressure in the air knife can be, for example, 1.5 to 5 atm. The movement of the air can be adjusted so that the air is moved through the area at least 5 mm above the surface of the transfer line. The adjustment of the moving range of the air is intended to prevent an unnecessary flow of the ink composition due to the movement of the air. The blowing drying time is not particularly limited, and may be, for example, immediately after coating by the coater 11, before entering the drying chamber, or at a specific position of the transferring line.

Thermal drying can be performed on the air-dried coated film. The thermal drying can be performed in the drying chamber 15 where a constant temperature range is maintained. The drying of the drying chamber may be carried out in a plurality of stages and the drying by blowing may be performed in parallel. Specifically, drying in the drying chamber may be performed at a temperature of 60 ° C in the first stage, 80 ° C in the second stage, 100 ° C in the third stage, 80 ° C in the fourth stage and 60 ° C in the fifth stage, Step drying can be performed. Drying chamber drying can be made so that each step is made at a uniform time based on the time that the coating can be completely dried, or the time of the initial and later steps is long and the time of the intermediate step is short. Drying chamber drying may be carried out while allowing the transfer of the coating film, and each step may be, for example, 5 to 30 minutes, but is not limited thereto. The drying substantially in the drying chamber 15 can be carried out by any method in which the coated surface can be completely dried, and according to the present invention, the drying in the drying chamber can be carried out for 1 to 30 minutes in which the drying is performed. Drying of the blast furnace enables a uniform coating surface to be achieved while at the same time improving electrical characteristics.

The drying step (S18) may be carried out in various ways and the present invention is not limited to the embodiments shown.

An embodiment of the coating method according to the present invention will be described below.

For the examples, a silver nanowire ink composition containing 1.0 wt% of silver nanowire and 5 wt% of polyester resin and having alcohol and distilled water as a dispersion medium was prepared. The viscosity of the nanowire ink composition was adjusted to be 1 cps, 10 cps and 100 cps, respectively.

A transparent polyethylene terephthalate (PET) based film was coated on the surface of a transparent polyethylene terephthalate (PET) base film at an angle of inclination of 0 to 100 mm at a coating gap of 60 탆, a conveying speed of 50 mm / s, a coating thickness of 10 탆, Lt; RTI ID = 0.0 > 5 C. < / RTI > A silver nanowire ink composition having a viscosity of 10 cps was used.

Coating films were prepared for each of 1 cps, 10 cps, and 100 cps under the same conditions as in Example 1, but drying was performed while maintaining a temperature of 45 degrees.

For the silver nanowire ink composition having a viscosity of 1 cps under the same conditions as in Example 1, the coating film was adjusted while controlling the transfer speed to 60 mm / s, 120 mm / s and 150 mm / s, respectively. The resistance values measured after drying for 60 mm / s, 120 mm / s and 150 mm / s were 133 ~ 137 ohm / sq, 139 ~ 148 ohm / sq and 175 ~ 184 ohm / sq respectively.

Coating was carried out in the same manner as in Example 1, and the transporting speed was 60 mm / s and the coating thickness was adjusted to 20 μm, 10 μm and 6.7 μm, respectively. The resistance values measured after drying for each coating thickness were 40 ~ 44 ohm / sq, 82 ~ 88 ohm / sq and 126 ~ 134 ohm / sq, respectively.

The coating was carried out in the same manner as in Example 1, except that the base film was made of polyethylene terephthalate (PET) and the coating thickness was 15 탆, 10 탆 and 7 탆, respectively. The resistance values measured after drying for each coating thickness were 32-36 ohm / sq, 50-53 ohm / sq and 92-96 ohm / sq, respectively.

The substrate was coated with a glass plate by a plate-to-plate method and the feeding rate was adjusted to 50 mm / sec. The same silver nanowire ink composition and drying conditions as in Example 1 were applied Coating was carried out such that the coating thickness was 20 탆, 15 탆 and 10 탆, respectively. For each coating thickness, the resistance values measured after drying were 20 ~ 22 ohm / sq, 27 ~ 31 ohm / sq and 42 ~ 48 ohm / sq.

The coating thickness was set to 7 탆 and 10 탆, respectively, and coating was carried out with coater gaps of 60 탆 and 80 탆, respectively. Resistance values measured after drying for a coating thickness of 7 占 퐉 and coating gaps of 60 占 퐉 and 80 占 퐉 were 88 to 92 ohm / sq and 92 to 96 ohm / sq, respectively, and the coating thickness was 10 占 퐉 and the coating gap was 60 占 퐉 and 80 占 퐉 The resistance values measured after drying were 52 ~ 55 ohm / sq and 50 ~ 53 ohm / sq, respectively.

Coating was carried out under the same conditions as in Example 1, but the tensile strength was increased to 10%.

Comparative Example

Under the same conditions as in Example 1, only the slope was adjusted to 45 degrees, and coating was carried out.

The results shown for each example are summarized.

result

Fig. 2 is a photograph showing the results of coating according to Example 1 and Comparative Example 1. Fig.

As can be seen from FIG. 2, when the inclination is 0 to 5 degrees, the coating can be uniformly performed, thereby improving the transmittance, reducing the haze, reducing the resistance variation and preventing the occurrence of stains occurring in a specific UV region . This advantage is increased as the viscosity is lowered.

FIG. 3 shows the result of the coating process according to the present invention in which only the heat drying without the blow drying and the blow drying is performed.

And FIG. 3 shows the case where only the thermal drying is performed without the blow drying, and the case where only the blow drying is performed without the thermal drying. It can be seen that the electrical properties of the coating film are determined by blow drying, regardless of heat drying.

5A, 5B and 5C are graphs showing changes in resistance value according to the coating thickness. Fig. 5A is a polyacrylic, Fig. 5B is a graph showing a change in resistance value according to a polyethylene terephthalate And Fig. 5C are respectively for glass, and Fig. 6 is an embodiment of the coating result according to the tension change.

It can be seen that the resistance value is increased with an increase in the conveying speed in a certain range and the resistance value is decreased when the coating thickness is increased. In general, an increase in the coating thickness can lead to a decrease in the resistance value. In the method according to the present invention, the change in the resistance value with the variation of the coating thickness is maintained at a constant level according to the base film, so that the coating thickness can be determined according to the appropriately required level. On the other hand, the change of the tensile force improves the physical properties of the coating film, for example, the transparency is increased, so that the tension of the base film can be appropriately controlled by the method according to the present invention.

The coating method according to the present invention has the advantage that the entire silver nanowire-coated film exhibits uniform electrical characteristics. Further, the coating method according to the present invention has an advantage in that it makes it possible to adjust electric characteristics such as electrical resistance of a coated film, for example. In addition, the process according to the present invention is advantageous in that it can be coated to a certain thickness and thus the properties of the film coated in various forms can be controlled.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention . The invention is not limited by these variations and modifications, but is limited only by the claims appended hereto.

11: Slot die coater
12, 13, 14: rollers
15: drying room

Claims (5)

A method of coating silver nanowires on a base film,
Determining a coating gap of the coater;
Adjusting the speed of the transfer line or the tension of the base film according to the electrical characteristics of the film to be coated;
Transporting the film along an inclined film transport path according to the viscosity of the nanowire ink composition; And
Wherein the coated film comprises at least two steps of drying. The method according to claim 1, wherein the coater is a slot die coater and the tension is controlled by a roll-to-roll method. The method according to claim 1, wherein the slope is 0 to 15 degrees with respect to the ground surface of the conveying path where drying is started from the coater. The method according to claim 1, wherein the drying step comprises blowing at room temperature. Wherein the gradient between the coater where at least the silver nanowire ink composition is coated and the transport path where drying is initiated is from 0 to 15 degrees and comprises a room temperature blow drying step.

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