CN117736554A

CN117736554A - Transparent conductive film

Info

Publication number: CN117736554A
Application number: CN202211107511.4A
Authority: CN
Inventors: 萧仲钦; 练修成; 蔡家扬; 萧启帆
Original assignee: Cambrios Film Solutions Xiamen Corp
Current assignee: Cambrios Film Solutions Xiamen Corp
Priority date: 2022-09-13
Filing date: 2022-09-13
Publication date: 2024-03-22
Also published as: JP2024041019A

Abstract

The present invention provides a transparent conductive film comprising: a substrate; a metal nanowire layer disposed on the substrate; the water-blocking protective layer is provided with water-absorbing particles and is arranged on the metal nanowire layer; wherein the transparent conductive film is measured at 2750cm using FTIR ^‑1 ‑3000cm ^‑1 The wavenumber region has a first absorption peak at 3000cm ^‑1 ‑3750cm ^‑1 The wave number region has a second absorption peak, the maximum of the first absorption peak and the second absorption peakThe peak intensity ratio is 0.18 to 0.50, and the haze value of the transparent conductive film is 1.7% or less. The transparent conductive film of the invention can solve the problems of intolerance to bending and visibility of the transparent conductive film in the prior art, and can be properly applied to a touch sensor because of the performances of bending, high water resistance and the like.

Description

Transparent conductive film

Technical Field

The invention relates to a transparent conductive film, in particular to a bendable transparent conductive film containing nano silver wires and having high water blocking performance.

Background

Conventionally, a transparent conductive film including a nano silver wire layer can be applied to a touch sensing electrode of a touch sensor.

For example, the TWI675895 patent discloses a transparent conductive sheet having at least: a conductive layer made of a metal material and an adhesive layer in contact with the conductive layer are used as the conductive substance. The adhesive layer contains an acrylic copolymer containing a hydrophilic acrylic monomer as a comonomer component, and at least one migration inhibitor selected from the group consisting of a moisture absorber and a metal ion scavenger.

Thus, the transparent conductive sheet of the TWI675895 patent can suppress occurrence of disconnection or short circuit due to migration of the metal material constituting the conductive layer.

However, since the position of the touch sensing electrode is present in the visible region of the touch panel, in the known technology such as the TWI675895 patent, the hydrophilic monomer concentration of the adhesive layer is generally higher than 15%, which affects the visibility (including the visible light transmittance and the haze) of the electrode. In addition, the moisture absorbent, the metal ion scavenger, and the like contained in the adhesive layer also affect the visibility of the electrode, and adversely affect the visibility of the entire touch panel.

Disclosure of Invention

In addition, the thickness of the adhesive layer is also related to the visibility of the overall touch electrode. Therefore, it is an urgent problem to be solved how to maintain the electrical properties of the conductive film and maintain excellent visibility while having a bending-resistant function.

In order to solve the above problems, a transparent conductive film according to an aspect of the present invention comprises: a substrate; a metal nanowire layer disposed on the substrate; a water-blocking protective layer having water-absorbing particles and arrangedOn the metal nanowire layer; wherein the transparent conductive film is detected at 2750cm by using Fourier transform infrared spectroscopy (FTIR, fourier-transform infrared spectroscopy) ^-1 -3000cm ^-1 The wavenumber region has a first absorption peak at 3000cm ^-1 -3750cm ^-1 The wave number region has a second absorption peak, the ratio of the maximum peak intensity of the first absorption peak to the second absorption peak (second absorption peak/first absorption peak) is 0.18 to 0.50, and the haze value of the transparent conductive film is 1.7% or less.

In an embodiment, a ratio of the spectrum integration area of the first absorption peak to the spectrum integration area of the second absorption peak is 0.618-1.410.

In an embodiment, the transparent conductive film includes a plurality of electrodes formed of metal nanowires.

In an embodiment, the line spacing between the plurality of electrodes is 30-200 μm.

In an embodiment, the transparent conductive film has a linear resistance change rate of less than 10% after being electrified for y hr at a linear distance of x μm under a test condition of direct current and voltage of 5V and high temperature and high humidity environment of 85 ℃/85%, wherein x and y conform to the following relation: y=0.53179x+364.47977.

In an embodiment, the transparent conductive film has a linear resistance change rate of less than 10% after being electrified for 400hr under the test conditions of direct current and voltage of 5V and high temperature and high humidity environment of 85 ℃/85%.

In an embodiment, the transparent conductive film has a visible light transmittance of 92 to 97%.

In an embodiment, the transparent conductive film has a yellowness (b) of 0.5 or less.

In an embodiment, the thickness of the water-blocking protective layer is 1-15 μm.

In an embodiment, the water-absorbing particles account for 1-5% of the water-blocking protective layer by volume.

The transparent conductive film can solve the problems of intolerance to bending and visibility of the transparent conductive film in the prior art, and can be properly applied to a touch sensor because the transparent conductive film has the performances of bending, high water resistance and the like.

Drawings

FIG. 1 is a schematic diagram of a transparent conductive film according to an embodiment of the present invention;

FIG. 2 is an FTIR spectrum of the transparent conductive film of reference example and examples 1, 4, 7;

fig. 3 is a silver migration test chart of reference example and example 1;

FIG. 4 is a flow chart of the preparation of a silver migration test sample;

fig. 5 is a graph of line spacing versus lifetime for a silver migration test sample.

[ reference numerals ]

1. Substrate board

2. Metal nanowire layer

3. Water-blocking protective layer

10. Transparent conductive film

4. Water-absorbent particles

5. Copper layer

6. Photoresist

S1 to S10 steps

Detailed Description

Other advantages and effects of the present invention will become apparent to those skilled in the art from the disclosure of the present specification, which is accomplished by the following description of the embodiments of the invention with specific examples. The invention is capable of other and different embodiments and its several details are capable of modification and variation in various respects, all without departing from the spirit of the present invention.

As used in the specification and in the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

The term "or" as used in the specification and the appended claims is intended to have a meaning of "including" and/or "unless the context clearly dictates otherwise.

The term "a-B" as used in the specification and the appended claims includes the meaning of "above a and below B" unless the context indicates otherwise. For example, the term "30 to 150 μm" includes the meaning of "30 μm or more and 150 μm or less".

Transparent conductive film

First, referring to fig. 1, a transparent conductive film 10 according to an embodiment of the present invention will be described. As shown in fig. 1, the transparent conductive film 10 includes: a substrate 1, a metal nanowire layer 2 and a water-blocking protective layer 3. The metal nanowire layer 2 is arranged on the substrate 1, and the water-blocking protective layer 3 is arranged on the metal nanowire layer 2.

The material of the substrate 1 may be any one selected from the group consisting of polyethylene terephthalate (polyethylene terephthalate, PET), cyclic olefin copolymer (Cyclic olefin copolymer, COP), colorless polyimide (Colorless Polyimide, CPI), polyethylene naphthalate (Polyethylene naphthalate, PEN), polycarbonate (PC), and polyether sulfone (PES). The thickness of the substrate 1 may be 15 to 125. Mu.m, preferably 25 to 100. Mu.m, and more preferably 30 to 50. Mu.m. Here, if the thickness of the substrate 1 is less than 15 μm, the process is not easy to operate, the tension is not well controlled, the film breakage is easily caused, and the process difficulty is increased; on the other hand, if the thickness of the substrate 1 is larger than 125 μm, the overall optical properties and flexibility are affected.

Next, as far as the metal nanowire layer 2 is concerned, which comprises metal nanowires covered by a cover layer, nanowires of any metal may be used, including but not limited to: silver, gold, copper, nickel, and gold-plated silver. Among them, silver nanowires are preferred from the standpoint of cost and conductivity, and can be manufactured in the manner described in U.S. Pat. nos. 8454721B2 and 9672950B2, which are incorporated herein by reference in their entirety. The cover layer may be an acrylate resin having an adhesive polymer material, such as epoxy, urethane, polyester, and polyether acrylic resins, for the purpose of fixing the nano silver wire to form the metal nanowire layer 2. The thickness of the metal nanowire layer 2 is preferably 20 to 120nm, more preferably 30 to 100nm, and most preferably 40 to 90nm, and the thickness of the metal nanowire layer 2 can be measured by SEM cross-section analysis after slicing a metal nanowire sample. The metal nanowire layer 2 with the thickness range can achieve a preferable conductive effect by matching with a water-blocking protection layer which is described below.

Furthermore, the material of the water-blocking protective layer 3 is mainly composed of a polymer material having a specific water permeability section, such as acryl glue, silica gel, polyolefin glue, polyurethane glue, rubber, epoxy glue, and the like. The water-blocking protective layer 3 contains water-absorbing particles 4, and the volume percentage of the water-absorbing particles 4 in the water-blocking protective layer 3 is preferably 1-5%, and the relative volume of the water-absorbing particles is not limited if the water-blocking protective layer can have both the water-absorbing effect and the visibility requirement. The water-absorbent particles 4 may contain an amide polymer of polyolefin, including, but not limited to, polyimide block copolymer modified polyethylene, and the like. The polyimide block copolymer modified polyethylene has a main colloidal structure comprising 95-99% of polyolefin segments, and the water-absorbing functional group is an amine group capable of binding water. Surprisingly, the water-absorbent particles 4 used in the present invention can achieve the effect of simultaneously absorbing water by only 1 to 5% by volume of the water-blocking protective layer 3 to avoid disconnection and short circuit caused by migration of metal (e.g., silver) ions and simultaneously having excellent overall visibility.

Compared with the prior art, the embodiment of the invention can effectively avoid the problems of poor overall optical properties, particularly over-high haze value by controlling the proportion of the water absorbing particles to be less than 5 volume percent of the water blocking protective layer. If the proportion of the water-absorbent particles is greater than 5% by volume of the water-blocking protective layer, the adhesion between the protective layer and the metal nanowire layer may be reduced, so that the overall structure of the transparent conductive film may be peeled off during bending, and thus open circuit may be generated. If the proportion of the water-absorbent particles is less than 1% by volume of the water-blocking protective layer, the desired water-absorbing effect cannot be obtained.

In addition, the thickness of the water-blocking protective layer is also related to the integral property of the transparent conductive film, and if the thickness of the water-blocking protective layer is increased, the adhesion between layers can be improved and the peeling can be avoided; however, if the thickness of the water blocking protective layer is too thick, the overall optical properties of the transparent conductive film may be affected. Therefore, the thickness of the water blocking protective layer is preferably 1 to 15. Mu.m, more preferably 5 to 15. Mu.m, particularly preferably 5 to 10. Mu.m. If the thickness of the water-blocking protective layer is smaller than 1 μm, the metal of the metal nanowire layer is oxidized, so that the conductivity is affected; on the other hand, if the thickness of the water blocking protective layer is greater than 15 μm, the contact resistance becomes high, and the transmission of the electrical signal is hindered.

In addition, the thickness of the water blocking protective layer is considered, and the water blocking protective layer is considered together with the filling ratio of the water-absorbent particles so as not to affect the visibility (for example, haze) of the transparent conductive film. Specifically, when the thickness of the water blocking protective layer is less than 1 μm, there may be a case where the water blocking protective effect cannot be sufficiently exerted; on the other hand, when the thickness of the water blocking protective layer is greater than 15 μm, the performance of the overall optical properties of the transparent conductive film may be affected.

Examples

Hereinafter, the present invention will be described specifically with reference to examples and comparative examples.

Reference example

PET (U483 manufactured by Toray Co., ltd.) was used as a material of the substrate, and the thickness of the substrate was 50. Mu.m. Then, a nano silver wire layer was coated on the substrate, and the thickness of the nano silver wire layer was 40nm. In the reference example, the transparent conductive film of the reference example was formed without the water blocking protective layer applied.

Determination of optical Properties

The visible light transmittance (T%), haze (Haze) and yellowness (b) of the transparent conductive film can be measured using well-known measurement methods. For example, the light transmittance and Haze of the transparent conductive film can be measured by a transmission method using a desktop type penetration Haze meter (manufactured by BYK Gardner company, haze-guard plus), respectively; the yellowness (b) can be calculated by an ultraviolet/visible light spectrometer (manufactured by PerkinElmer corporation, lambda 650) with a 150mm integrating sphere and then by an equation of CIE standard observer functions. In the present invention, the transparent conductive film needs to have a haze of 1.7% or less, preferably 92 to 97% in visible light transmittance (T%), and preferably 0.5 or less in yellowness (b).

Next, according to the content of the water-absorbent particles and the thickness of the water-blocking protective layer in table 1 below, a water-blocking protective layer was further coated on the nano silver wire layer of the reference example to produce transparent conductive films of examples 1 to 7 and comparative examples 1 to 2; the water-blocking protective layers of the examples and the comparative examples are acrylic adhesives, and contain specific content of polyimide block copolymer modified polyethylene as water-absorbent particles. Thereafter, the transparent conductive films of reference examples, examples 1 to 7 and comparative examples 1 to 2 were subjected to measurement of optical properties, and the results were collated in table 1 below.

TABLE 1

First, as can be seen from table 1, the transparent conductive film of the reference example had the lowest haze (0.46%) without the water blocking protective layer applied. However, since nano silver itself has a congenital problem of electrolytic dissociation, particularly, a phenomenon of silver ion migration (silver migration) occurs easily under the condition of power on and moisture, thereby causing a decrease in the reliability of nano silver. Therefore, the transparent conductive film of the reference example has a short lifetime (see silver migration test described later), and it is necessary to further apply a water blocking protective layer without affecting optical properties as much as possible.

Next, as shown in table 1, after the water blocking protective layer was coated, the water blocking protective layer had a large influence on haze and yellowness, although the water blocking protective layer had little influence on the visible light transmittance. From examples 1 to 6, it was found that the thickness of the water-blocking protective layer was 5 to 15 μm at a low (about 1.+ -. 0.5 vol%) or medium (about 2.5.+ -. 0.5 vol%) water-absorbing particles, and that the migration of silver ions was suppressed even when the water-blocking protective layer was acceptable (haze value of 1.7% or less and yellowness of 0.5 or less).

Further, as can be seen from Table 1, when the water-absorbent particles content was large (about 5.+ -. 0.5 vol%), the thickness of the water-blocking protective layer was 10 μm or 15 μm (see comparative examples 1 to 2), and a sharp increase in haze value (greater than 1.7%) was found, and a phenomenon of yellowness of greater than 0.5 was also observed in comparative example 2, so that comparative examples 1 to 2 were not preferred. This phenomenon is because the polarity of-CH group and-NH group in the water-absorbent particles is incompatible, and the content of the water-absorbent particles in comparative examples 1 to 2 is too high and the water-blocking protective layer is too thick, which causes an increase in intermolecular hydrogen bonds, so that the arrangement of molecules is disordered, and further haze and yellowness are rapidly increased. From these results, it was found that the water-blocking protective layer having a thickness of 15 μm can have a haze value (1.7% or less) which is desirable in the present invention under the conditions that the water-absorbing particles content is 1.+ -. 0.5 to 2.5.+ -. 0.5% by volume; however, when the water-blocking protective layer has a thickness of 10 μm or 15 μm under the condition that the content of the water-absorbent particles is 5.+ -. 0.5% by volume, the haze value required in the present invention cannot be satisfied.

Next, further discussion is made regarding the above phenomenon, please refer to fig. 2 and tables 2 and 3. Fig. 2 is FTIR spectra of transparent conductive films of reference examples and examples 1, 4, and 7. Further, after normalizing the absorption spectrum intensities, the respective peak intensity values can be calculated from fig. 2, and the respective spectrum integration areas can be calculated from fig. 2 by the integrated absorption spectrum method; the results are shown in tables 2 and 3 below.

TABLE 2

As shown in FIG. 2, since the water-blocking protective layer was not applied in the reference example, no-CH group characteristic peak and-NH group characteristic peak were observed from the water-absorbent particles. As shown in FIG. 2, examples 1, 4 and 7 can be each about 2945cm ^-1 Is observed at a position of-CH group characteristic peak, and is about 3450cm ^-1 Is observed at the position of the-NH group characteristic peak. The maximum intensity of the-CH group characteristic peaks of examples 1, 4 and 7 was 0.922 to 0.999, and there was no difference between the examples; in contrast, the maximum intensity of the-NH group characteristic peak is 0.173 to 0.378, which varies greatly from one example to another.

In FIG. 2, the characteristic peak of-CH group (2750 cm ^-1 -3000cm ^-1 First absorption peak in wavenumber region) and-NH group characteristic peak (3000 cm ^-1 -3750cm ^-1 The second absorption peak in the wavenumber region) represents the water absorption capacity, the larger the maximum peak intensity ratio (also simply referred to as the intensity ratio), the better the water absorption capacity. In the invention, the maximum peak intensity ratio of the first absorption peak to the second absorption peak is 0.18-0.50, and if the intensity ratio is smaller than 0.18, the water absorption/blocking effect cannot be achieved because the number of N-H bonds is too low; in contrast, if the intensity ratio is greater than 0.50, the optical properties may be degraded, and even in the case where the thickness of the water-blocking protective layer is low (for example, 5 μm), the haze may be greater than 2%, which is disadvantageous for further application of the transparent conductive film.

Specifically, the main component of the water absorbing particles used in the invention is composed of polyimide, wherein polyimide is an organic polymer material containing imide rings (-CO-NH-CO-) and the molecular chain of the polyimide contains a large amount of aromatic groups (such as benzene rings, imide bonds and the like). Therefore, the polyimide material has high water absorption characteristics in addition to excellent thermal stability and mechanical, electrical and chemical properties.

As shown in fig. 2 and table 3 below, even when the ratio of the spectrum integration area of the first absorption peak to the spectrum integration area of the second absorption peak (spectrum integration area of the second absorption peak/spectrum integration area of the first absorption peak) is 0.618 to 1.410, an appropriate balance between the water absorption property and the optical property can be achieved.

TABLE 3 Table 3

Next, the present invention was demonstrated to be able to suppress the occurrence of the nanosilver migration mechanism by the following sample manufacturing method.

Sample manufacturing method

First, according to the flow chart of fig. 4, samples for silver migration test were prepared based on the reference example and example 1, respectively. Specifically, the sample preparation includes patterning process (S1-S6) of nano silver and copper pad and windowing process (S7-S10) of copper.

S1: a metallic copper layer 5 having a thickness of about 200nm was sputtered on the metallic nano layer (nano silver wire layer) 2 of the transparent conductive film of the reference example. A metallic copper layer 5 having a thickness of about 200nm was sputtered on the water blocking protective layer (not shown) of the transparent conductive film of example 1.

S2: subsequently to S1, a photoresist 6 is coated on the respective copper layer 5.

S3: and S2, performing an exposure and development process by using a first photomask to define a circuit and an electrode pattern of the nano silver wire layer and the copper pad (layer).

S4: and S3, performing copper etching by using a copper etching solution to finish the manufacture of copper circuits and electrodes.

S5: and S4, carrying out nano silver etching by using silver etching liquid to finish the manufacture of the nano silver wire electrode.

S6: and S5, stripping and removing the photoresist by using a stripping liquid to finish the patterning process of the nano silver wire layer and the copper pad (layer).

S7: and S6, coating a photoresist 6' on the transparent conductive film after the patterning of the nano silver and the copper pad.

S8: and S7, performing an exposure and development process by using the second photomask to define a copper window pattern.

S9: subsequently, S8, copper etching is performed using the copper etching solution.

S10: and finally, stripping and removing the photoresist 6' after the step S9 by using a stripping liquid, namely completing the copper windowing process, and obtaining a sample for silver migration test.

Placing each silver migration test sample in a high-temperature high-humidity (85 ℃/85%) environment, and applying Direct Current (DC) and voltage of 5 volts to track the change of the nano silver wire resistance in the nano silver wire layer with time under the test condition; wherein the width of the nano silver wire electrode is 100 μm, and the interval (wire pitch) between the nano silver wire electrodes is 50 μm. The results of the silver migration test are shown in fig. 3 and 5. The line distance between the nano silver wire electrodes can be adjusted between 30 and 200 mu m.

Fig. 3 is a silver migration test chart of reference example and example 1. As shown in fig. 3, the transparent conductive film of the reference example had a line resistance change rate of more than 10% after being energized for about 45 hours (hr); in contrast, the transparent conductive film of example 1 had a line resistance change rate of more than 10% after about 450 hours of energization. From this, it was found that the transparent conductive film of example 1 was stretched by approximately 10 times under severe silver migration test conditions (DC direct current and voltage of 5V, high temperature and high humidity environment of 85 ℃/85%), and the lifetime (time point from the increase of the line resistance change rate to more than 10%) from 45 hours to 450 hours, as compared with the transparent conductive film of the reference example. In addition, the transparent conductive film of example 1 had a linear resistance change rate of only about 8% after 400 hours of energization.

Further, as shown in FIG. 5, since the line width of the electrode generally does not affect migration of silver ions, the test was conducted under conditions of a fixed line width of 100 μm and line pitches (Gap Distance) of 30 μm, 50 μm, 100 μm and 200 μm, respectively, and the resistance change rates at 380hr, 390hr, 420hr and 470hr, respectively, were smaller than 10% when the test was passed. Thus, it can be seen that the line spacing is linear with lifetime (Life time), which can be expressed as y=0.53179x+364.47977 (x=gap distance, y=life time).

From the above results, the transparent conductive film of the present invention has greatly improved reliability by covering the water-blocking protective layer, and can further improve the stability of the nano silver wire layer in the performance of electronic products.

The transparent conductive film can be applied to a touch sensing electrode of a touch sensor. In addition, the method can be applied to flat/flexible touch display, organic photovoltaic (OPV, organic photovoltaic), OLED lighting, smart window and other products possibly containing transparent conductive films.

In summary, the transparent conductive film and the application thereof of the present invention have at least the following excellent technical effects:

1. the transparent conductive film of the present invention has a bendable effect and maintains interlayer adhesion without impairing the conductivity of the conductive layer.

2. The transparent conductive film of the invention can inhibit migration of silver ions in a severe environment, has excellent visual effect in a state of not reducing conductivity, and has more obvious haze characteristics.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the claims, and embodiments in which technical means disclosed in different embodiments are appropriately combined are also included in the technical scope of the present invention.

Claims

1. A transparent conductive film, comprising:

a substrate;

a metal nanowire layer disposed on the substrate; and

The water-blocking protective layer is provided with water-absorbing particles and is arranged on the metal nanowire layer; wherein,

for the transparent conductive film, FTIR detection was used at 2750cm ^-1 -3000cm ^-1 The wavenumber region has a first absorption peak at 3000cm ^-1 -3750cm ^-1 The wave number region has a second absorption peak, the ratio of the maximum peak intensity of the first absorption peak to the second absorption peak (second absorption peak/first absorption peak) is 0.18 to 0.50, and the haze value of the transparent conductive film is 1.7% or less.

2. The transparent conductive film according to claim 1, wherein a ratio of a spectrum integration area of the first absorption peak to a spectrum integration area of the second absorption peak is 0.618 to 1.410.

3. The transparent conductive film according to claim 1, wherein the transparent conductive film comprises a plurality of electrodes formed of metal nanowires.

4. The transparent conductive film according to claim 3, wherein a line distance between the plurality of electrodes is 30 to 200 μm.

5. The transparent conductive film according to claim 4, wherein the transparent conductive film has a line resistance change rate of less than 10% when the transparent conductive film is energized for y hours at a line distance of x μm under a test condition of direct current and a voltage of 5V in a high temperature and high humidity environment of 85 ℃/85%, wherein x, y satisfies the following relationship: y=0.53179x+364.47977.

6. The transparent conductive film according to claim 1, wherein the change rate of the line resistance of the transparent conductive film is lower than 10% after the transparent conductive film is energized for 400 hours under a test condition of direct current and a voltage of 5V, a high temperature and high humidity environment of 85 ℃/85%.

7. The transparent conductive film according to claim 1, wherein the transparent conductive film has a visible light transmittance of 92 to 97%.

8. The transparent conductive film according to claim 1, wherein the transparent conductive film has a yellowness of 0.5 or less.

9. The transparent conductive film according to claim 1, wherein the water blocking protective layer has a thickness of 1 to 15 μm.

10. The transparent conductive film according to claim 1, wherein the water-absorbent particles account for 1 to 5% by volume of the water-blocking protective layer.