CN102063951A - Transparent conductive film and manufacturing method thereof - Google Patents

Abstract

The invention provides a transparent conductive film, which comprises a transparent substrate and a conductive metal, wherein nanoimprinting technology is used to press out grooves for embedding conductive metal particles and grids for light transmission on the transparent substrate, By designing the line width and depth of the groove and the proportion of the entire transparent conductive film, a transparent conductive film with high light transmittance and good conductivity is obtained. At the same time, since the conductive metal part is embedded in the transparent substrate, it is not easy to fall off and oxidize, and flexible materials can be used as the transparent substrate to develop a transparent conductive film that can be used in more occasions. At the same time, the invention also provides a manufacturing method of the transparent conductive film.

Description

A kind of transparent conductive film and preparation method thereof

technical field

The invention relates to a transparent conductive film and a manufacturing method thereof, in particular to an embedded transparent conductive film and a manufacturing method thereof.

Background technique

Transparent conductive films are widely used in fields such as touch liquid crystal panels, organic light emitting diodes (OLEDs), and electromagnetic shielding. At present, the more common transparent conductive films are ITO film and metal film. The former is to form a layer of indium-tin oxide film (ITO) on the surface of transparent glass or plastic substrate by evaporation or sputtering. Transparent conductive material, the latter is formed on the surface of a transparent glass or plastic substrate by metal plating or vapor deposition to form a metal film on the entire surface, and then process it by photolithography to etch the metal layer into fine metal particles. grid.

However, although the ITO film has excellent light transmittance, its electrical conductivity is average, and it is not suitable for high-demand fields such as electrical and aviation. Although the metal film has better conductivity, most of the metal film needs to be removed when processing the metal film, so there are disadvantages of waste and high production cost.

In recent years, some scientists have proposed a method of forming grid-like metal wires directly on the surface of a transparent substrate. One of them is to mix and emulsify raw materials such as silver nanoparticles, organic solvents, surfactants and aqueous solvents. When this ink is coated on the surface of a transparent substrate, due to the polarity, surface energy and volatility of the solvent The difference can automatically form a silver network structure of any shape on the surface of the substrate, and it will become a transparent conductive film after sintering. The surface resistance value of the transparent conductive film published by this technology is about 4-270Ω/sq, and the visible light transmittance is about 75-86%.

However, the shape, size and position distribution of the mesh metal silver wires obtained by this method are completely dependent on the characteristics of the solvent itself, and the controllability is very poor, and it is easy to cause some areas to be overly dense, while some areas are very sparse, making transparent and conductive Both the uniformity of light transmission and the uniformity of conductivity of the film are affected. In addition, for all transparent conductive films made of conductive metal lines on the surface of the film, the metal layer is easy to oxidize and fall off, which greatly affects the service life of the transparent conductive film.

Contents of the invention

In view of the above problems, the present invention proposes a transparent conductive film and a manufacturing method thereof. The transparent conductive film uses the method of nanoimprinting to form regular submicron patterns on the surface, and fill conductive metal in these submicron patterns to form conductive metal lines, so as to strictly control the configuration position and size of the metal lines, so that the While the conductivity and light transmittance of the transparent conductive film are significantly improved, it can also be controllably designed according to different application scenarios. In addition, since the metal wires are embedded inside the film, its stability and oxidation resistance are also improved.

A kind of transparent conductive film that proposes according to the object of the present invention comprises a transparent substrate and a conductive metal, and the transparent substrate includes a conductive region and a light-transmitting region, the conductive region is a network line-shaped groove connected to each other, and the light-transmitting region is the network line A grid surrounded by a grid-shaped groove; the conductive metal is filled in the grid-shaped groove of the conductive area, wherein the ratio of the area of the groove to the area of the grid is less than 5%.

According to the purpose of the present invention, a transparent conductive film is proposed, wherein the grid of the light-transmitting area is a regular polygonal grid, and its side length is less than 200um.

According to the purpose of the present invention, a transparent conductive film is proposed, wherein the transparent substrate is a flexible transparent material, and its light transmittance is greater than 85%.

According to the purpose of the present invention, a transparent conductive film is proposed, wherein the groove aspect ratio of the conductive region is greater than 1:1.

A kind of preparation method of transparent conductive film proposed according to the object of the present invention comprises the following steps:

Embossing process: using a metal punch to emboss a grid pattern on a transparent substrate, wherein the edge of the grid is a groove, and the ratio of the area of the groove to the area of the grid is less than 5%;

Metallization process: Metallize the transparent substrate to fill the groove with conductive metal;

Polishing process: remove excess conductive metal on the surface of the transparent substrate, and only retain the conductive metal in the groove, thereby forming a transparent conductive film.

A kind of preparation method of transparent conductive film proposed according to the purpose of the present invention, wherein said metallization process is a wet coating process, comprising:

Continuous coating method is used to coat the nano-silver paste mixed with hydrophobic solvent on the surface of the transparent substrate;

According to the self-leveling effect, the silver paste is deposited in the groove;

Heat and bake to make the silver paste condense and form a metal wire grid in the groove.

A method for making a transparent conductive film proposed according to the object of the present invention, wherein a hydrophobic layer is coated on a transparent substrate to accelerate the accumulation of nano-silver paste in the groove.

According to the object of the present invention, a method for manufacturing a transparent conductive film is proposed, wherein the metallization process is an electroforming process or a sputtering process, and a conductive metal is grown in a groove of a transparent substrate through electroforming or sputtering.

A kind of preparation method of transparent conductive film that proposes according to the object of the present invention, wherein also comprise the preparation technology of metal convex film, this preparation process comprises:

Photolithography process: use scanning lithography or tile lithography to etch a grid pattern on the surface of the photoresist, the edge of the grid is a groove, and the depth-to-width ratio of the groove is greater than 1:1;

Electrode plating: Metallize the photoresist with groove pattern by vacuum sputtering or electroless plating, so that the entire surface of the photoresist, including the groove part, forms an electrode layer;

Electroformed motherboard: The photoresist dry plate with a conductive layer is placed in the electroforming tank for electrodeposition of metal ions, which are gradually deposited on the electrode layer to form a thin metal plate of a certain thickness;

Degumming: separate the metal thin plate from the photoresist dry plate, remove the photoresist, and form a convex grid pattern structure on the metal plate.

According to the object of the present invention, a method for making a transparent conductive film is proposed, wherein the embossing process is roll-to-roll roller embossing.

According to the object of the present invention, a method for manufacturing a transparent conductive film is proposed, wherein the polishing process is one of mechanical polishing, chemical electrolysis or chemical corrosion.

In the above-mentioned transparent conductive film and its manufacturing method, a groove for embedding conductive metal is pressed on the surface of the transparent substrate by using nano-imprint technology, and a groove is obtained by designing the line width and depth of the groove and the proportion of the entire transparent conductive film. A transparent conductive film with high light transmittance and good conductivity. At the same time, since the conductive metal part is embedded in the transparent substrate, it is not easy to fall off and oxidize, and flexible materials can be used as the transparent substrate, and a transparent conductive film that can be applied in more occasions has been developed.

The present invention will be described in detail below with specific embodiments in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is a schematic diagram of a transparent conductive film of the present invention;

Fig. 2 is a schematic diagram of the transparent substrate in Fig. 1;

Fig. 3 is the cross-sectional view on A-A direction among Fig. 1;

Fig. 4 is the flow chart of convex film preparation of the present invention;

Fig. 5 is a flow chart of making the transparent conductive film of the present invention.

Detailed ways

Please refer to FIG. 1 and FIG. 2 together. FIG. 1 is a schematic diagram of the transparent conductive film of the present invention, and FIG. 2 is a schematic diagram of the transparent substrate in FIG. 1 . As shown in the figure, the transparent conductive film 100 includes a transparent substrate 110 and a conductive metal 120 . The transparent substrate 110 includes a conductive area 111 and a light-transmitting area 112. The conductive area 111 is a network of grooves connected to each other. The conductive metal 120 is filled in the conductive area 111. The light-transmitting area 112 is a grid surrounded by a network of grooves. . The conductive metal 120 can be a silver particle wire formed by sintering silver paste, or a conductive wire formed by depositing other metals such as copper, nickel, aluminum, etc. in the conductive region 111 by electroforming or sputtering. The light transmittance and conductivity of the transparent conductive film 100 will be analyzed respectively below.

For light transmittance: under normal circumstances, the conductive region 111 is opaque after filling the conductive metal 120, so the actual light transmittance of the transparent conductive film 100 is determined by the area size of the conductive region 111 and the light transmittance of the transparent substrate 110 itself Decide. That is, the smaller the ratio of the area of the conductive region 111 to the area of the transparent region, the higher the light transmittance of the transparent conductive film 100 . Usually, the area ratio of the conductive region 111 to the light-transmitting region 112 is 5%, and when the light transmittance of the transparent substrate 110 itself is 90%, the light transmittance of the transparent conductive film 100 can reach more than 85%. In order to obtain higher light transmittance, we choose that the ratio of the area of the grooves in the conductive region 111 to the area of the entire grid is less than 5%, and the light transmittance of the transparent substrate 110 is greater than 90%. In particular, when the mesh of the light-transmitting region 112 is a regular polygon, the area ratio of the conductive region 111 and the light-transmitting region 112 can be calculated by the following formula:

P＝1-a ² /(a+L*tan180/n) ² (1)

In the formula (1): a is the side length of the regular polygon, L is the width of the conductive region 111, and n is the number of sides of positive deformation.

Taking a regular hexagonal grid as an example, when the side length of the grid is 35um and the light transmittance is 90%, the line width of the metal conductive wire is about 3um.

Regarding conductivity: the conductivity of the transparent conductive film mainly depends on the electrical properties and cross-section of the conductive metal 120 , please refer to FIG. 3 , which is a cross-sectional view along the direction A-A in FIG. 1 . As shown, the cross section of the conductive metal 120 is determined by the width and depth of the conductive region 111 . Since the width is affected by the light transmittance, it is impossible to make it very wide. Therefore, the depth of the conductive region 111 needs to be designed relatively deep to increase the cross-section of the conductive metal 120 . Preferably, we design the aspect ratio to be greater than 1:1. Taking metal silver as an example, when the width is 3um, the surface impedance of the transparent conductive film 100 can reach a range greater than 3.5Ω/sq.

In practical applications, we can flexibly design the width and depth of the network cable according to the balance between the conductivity and light transmittance of the transparent conductive film, as well as the limitations of the used occasions. In addition, for some application fields that require high overall conductivity of the surface of the transparent light guide film, such as in the touch screen with built-in contacts, or in some electromagnetic shielding applications, it is necessary to design high-density conductive mesh lines, so the mesh The size design is below 200um.

The manufacturing method of the transparent conductive film of the present invention will be described in detail below.

In the present invention, when the above-mentioned transparent conductive film is produced, the method of nanoimprinting is used to form the mesh grooves on the surface of the transparent conductive film. In particular, when the transparent substrate is a flexible material, the transparent conductive film can be produced at high speed by a roll-to-roll roll embossing method. Therefore, before the film is formed, the convex film needs to be prepared first.

Please refer to FIG. 4 . FIG. 4 is a flowchart of the preparation of the convex film of the present invention. As shown in the figure, the preparation of the convex film includes: using scanning lithography or tile lithography to etch a grid pattern on the surface of the photoresist, the edge of the grid is a groove, and the depth and width of the groove are The ratio is greater than 1:1;

Metallize the photoresist with a groove pattern by vacuum sputtering or electroless plating, so that the entire surface of the photoresist, including the groove part, forms an electrode layer;

The photoresist dry plate with the conductive layer is placed in the electroforming tank, and the electrodeposition of metal ions is carried out, and a metal thin plate of a certain thickness is gradually deposited on the conductive layer;

The metal thin plate is separated from the photoresist dry plate, and the photoresist is removed to form a convex grid pattern structure on the metal plate.

Among them, when the grid is a regular quadrilateral, the method of scanning lithography is adopted, and the light spot of 0.5um is selected to expose the surface of the photoresist twice vertically and horizontally. The advantage of this etching method is that the etching speed is fast, And it is easy to etch a deep grain pattern.

When the grid is other polygons, the method of tiled projection exposure is adopted. Now the exposure figure is preset on the diaphragm, and then the surface of the photoresist is exposed with this figure to directly form a grid with a regular polygon pattern, and through mechanical Auxiliary, splicing the single-exposure graphics into a whole to realize the etching of the grid. The advantage of this etching method is that the exposure pattern is controllable, but the mechanical precision is relatively high.

Please refer to FIG. 5 again. FIG. 5 is a flow chart of making the transparent conductive film of the present invention. As shown in the figure, the method mainly includes three major processes: first, the embossing process, through a metal punch with a grid pattern on the surface, to apply pressure to the surface of the transparent substrate, while applying pressure, heating or UV curing can be used Transfer the pattern on the surface of the convex mold to the transparent substrate to form a grid pattern with mesh lines as grooves. Wherein the edge of the grid pattern is a groove, and the ratio of the area of the groove to the area of the grid is less than 5%.

The second is the metallization process. The purpose of this process is to fill the conductive metal in the groove of the conductive area so that it fills or overflows the groove. Specifically, the metallization process can be performed by the following methods:

The first method may be a wet coating process. The method includes:

Using continuous coating method, coating the nano-silver paste mixed with hydrophobic solvent on the surface of the transparent substrate, the diameter of silver particles in the nano-silver paste is about 50nm-70nm, and the specific gravity of the hydrophobic solvent is between 10%-20%;

According to the self-leveling effect, the silver paste will be automatically deposited in the groove, or a 10% hydrophobic layer can be coated on the surface of the transparent substrate. The thickness of the hydrophobic layer is controlled within 200nm, making it much smaller than the depth of the groove. In combination with the hydrophobic agent contained in the silver paste, it can accelerate the accumulation of silver particles to the grooves, and ensure that the silver particles are filled in the grooves after continuous coating;

Heat and bake to make the silver paste condense, and finally form a metal wire grid in the groove.

The advantage of this method is that the process is simple, the operation is convenient, and it can cooperate with the continuous coating method of roll-to-roll (Roll to Roll) to produce large-scale at high speed. But the disadvantage is that the adhesion of the silver paste is not good, it is easy to fall off, and the uniformity of the coating is not good, and it is easy to make the silver paste gather more in some places, while it is relatively sparse in some places.

The second method is an electroforming process or a sputtering process. On the transparent substrate, the metal conductive layer is deposited by electroforming process or vacuum sputtering process. Since the inner two sides of the groove are deposited simultaneously, the metal filling speed in the groove is faster than the metal deposition speed on the pattern surface. twice as fast. For example, for a groove line width of 2um, the surface metal thickness is about 1um when the groove is filled.

The advantage of this method is that the process is relatively mature, the metal deposition is uniform, and a variety of metals such as copper, nickel, aluminum, etc. can be selected as conductive metals for deposition, and the adhesion is strong and not easy to fall off. The disadvantage is that the surface is all attached to metal, which is easy to cause waste, and it takes a long time to make it not suitable for large-scale production.

The last is the polishing process. This step is mainly to remove the redundant metal layer on the surface and retain the conductive metal in the groove of the conductive area to improve the overall light transmittance of the transparent light guide film. The polishing process may adopt one of mechanical polishing, chemical electrolysis or chemical corrosion.

In summary, the present invention provides a transparent conductive film, which utilizes nanoimprint technology to press out grooves for embedding conductive metals on the surface of a transparent substrate. By designing the line width and depth of the grooves and occupying the entire By adjusting the specific gravity of the transparent conductive film, a transparent conductive film with high light transmittance and good conductivity is obtained. At the same time, since the conductive metal part is embedded in the transparent substrate, it is not easy to fall off and oxidize, and flexible materials can be used as the transparent substrate to develop a transparent conductive film that can be used in more occasions.

From the above detailed description of the preferred embodiments, it is hoped that the characteristics and spirit of the present invention can be described more clearly, and the scope of the claims of the present invention is not limited by the preferred embodiments disclosed above. On the contrary, the intention is to cover various modifications and equivalent arrangements within the scope of the appended claims of the present invention.

Claims (10)

1. A transparent conductive film, comprising a transparent substrate and a conductive metal, characterized in that: the transparent substrate comprises a conductive region and a light-transmitting region, the conductive region is a mesh-like groove connected to each other, and the light-transmitting region is the mesh line A grid surrounded by a grid-like groove; the conductive metal is filled in the wire-like groove of the conductive region, wherein the ratio of the area of the groove to the area of the grid is less than 5%. 2 . The transparent conductive film according to claim 1 , wherein the grid in the light-transmitting region is a regular polygonal grid with a side length of less than 200 um. 3 . 3 . The transparent conductive film according to claim 1 , wherein the transparent substrate is a flexible transparent material with a light transmittance greater than 85%. 4 . 4. The transparent conductive film according to claim 1, wherein the groove aspect ratio of the conductive region is greater than 1:1. 5. A preparation method of transparent conductive film, is characterized in that, comprises the steps: Embossing process: using a metal punch to emboss a grid pattern on a transparent substrate, wherein the edge of the grid is a groove, and the ratio of the area of the groove to the area of the grid is less than 5%; Metallization process: Metallize the transparent substrate to fill the groove with conductive metal; Polishing process: remove excess conductive metal on the surface of the transparent substrate, and only retain the conductive metal in the groove, thereby forming a transparent conductive film. 6. The preparation method of transparent conductive film as claimed in claim 5, is characterized in that: described metallization process is wet coating process, comprises: Continuous coating method is used to coat the nano-silver paste mixed with hydrophobic solvent on the surface of the transparent substrate; According to the self-leveling effect, the silver paste is deposited in the groove; Heat and bake to make the silver paste condense and form a metal wire grid in the groove. 7. The manufacturing method of the transparent conductive film according to claim 6, characterized in that: coating a layer of hydrophobic layer on the transparent base to accelerate the aggregation of the nano-silver paste into the groove. 8. The manufacturing method of the transparent conductive film according to claim 5, characterized in that: the metallization process is an electroforming process or a sputtering process, and through electroforming or sputtering, a metal layer is grown in the groove of the transparent substrate. conductive metal. 9. The manufacture method of transparent conductive film as claimed in claim 5, is characterized in that: also comprise the preparation process of convex film, this preparation process comprises: Using scanning lithography or tiled projection lithography to etch a grid pattern on the surface of the photoresist, the edge of the grid is a groove, and the depth-to-width ratio of the groove is greater than 1:1; Metallize the photoresist with a groove pattern by vacuum sputtering or electroless plating, so that the entire surface of the photoresist, including the groove part, forms an electrode layer; The photoresist dry plate with the conductive layer is placed in the electroforming tank, and the electrodeposition of metal ions is carried out, and a metal thin plate of a certain thickness is gradually deposited on the conductive layer; The metal thin plate is separated from the photoresist dry plate, and the photoresist is removed to form a convex grid pattern structure on the metal plate. 10 . The method for manufacturing a transparent conductive film according to claim 5 , wherein the embossing process is planar embossing or roll-to-roll roller embossing. 11 .

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