A Method for Preparing a Regulable Cracking Template

Abstract

The present invention discloses a method for preparing a controllable crack template. A crack solution is prepared by adding egg yolk liquid to egg white liquid. After cleaning and hydrophilizing a transparent substrate, the crack solution is scraped onto the treated transparent substrate and heated and dried to form a crack template. The present invention regulates the crack block width by regulating the crack solution (egg white liquid + egg yolk liquid), and obtains a crack template with smaller crack blocks than those prepared from egg white liquid in the prior art. Moreover, by regulating the amount of added egg yolk liquid, the size of the crack block width can be further controlled, thereby improving the performance of the transparent conductive electrode fabricated using the crack template.

Description

Technical Field

[0001] The present invention belongs to the technical field of transparent conductive electrodes, and particularly relates to a preparation method of a controllable crack template. Background Art

[0002] Transparent conductive electrodes (TCEs) are widely used in various optoelectronic devices, such as touch displays, solar cells, light emitting diodes (LEDs), electromagnetic shielding, transparent heaters, smart windows, and electronic skins.

[0003] Currently, indium tin oxide (ITO) is the commonly used transparent electrode material. However, due to its own brittleness, scarcity of indium raw materials, high cost, and complex preparation process, the ITO electrode cannot adapt to the development of the next-generation flexible optoelectronic devices. Therefore, in recent years, researchers have proposed a variety of new flexible materials to replace ITO, such as conductive polymer films, graphene films, metal nanowires, and metal networks.

[0004] Among them, metal networks usually have low resistance, good bending resistance, and can independently adjust the optical transmittance and resistivity, and are considered to be the most promising new generation of transparent electrode materials. The inventor has been researching the preparation of metal network transparent electrodes by the crack template method since 2010. Cracking, also known as reticulation, is a phenomenon that occurs when the crack liquid is heated and the stress distribution is uneven, resulting in crack formation and the connection of cracks into a network, which is commonly found in life and nature. The existing preparation process of sub-micron metal network transparent electrodes by the crack template method includes four steps: 1. Synthesize and deposit the template / sacrificial layer; 2. Dry and crack to obtain the crack template; 3. Deposit the metal film (sputtering, thermal evaporation, or electroplating); 4. Finally, remove the crack template; the above template / sacrificial layer is made of materials such as TiO2, epoxy resin, nail polish, or egg white solution. Among them, the egg white solution is mainly composed of proteins, which can form a film well, is green, pollution-free, and easy to clean, so it is an excellent material for preparing the template / sacrificial layer. Since the cracking materials used in the above crack template method are simple and easy to obtain, the technology is mature, green and environmentally friendly, the cost is low, the lithography technology is not involved in the process, the transparent electrodes of the crack template do not have a periodic distribution, there is no optical diffraction phenomenon, and there is no moiré fringe, completely solving the moiré interference phenomenon of regular metal networks. Therefore, the metal network transparent electrodes prepared by the crack template method have good application prospects.

[0005] However, the crack templates prepared by the prior art have the problem of too large crack block widths, and the crack templates also have the problem of uneven crack block widths due to the randomness of cracking, that is, the uniformity of the crack block widths is poor; and the light transmittance and sheet resistance of the transparent conductive electrode are mainly affected by the size of the crack block widths. Therefore, the above problems affect the optoelectronic performance of the transparent conductive electrode, thus restricting the application of the crack template method and making it inapplicable to the preparation of devices that require a relatively high carrier concentration, such as solar cells; in addition, when using the existing crack template method to prepare a transparent conductive electrode for displays and touchscreens, due to the large and uneven crack block widths, there may be a situation where there is no metal wire between the display and touch pixel walls (100*100μm), and thus it will not conduct. Moreover, the poor uniformity of the crack block widths also leads to uneven optoelectronic performance of the produced transparent conductive electrodes, thereby reducing the product qualification rate and causing material and industrial waste. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing an adjustable crack template. By this method, the crack block width in the prepared crack template can be adjusted, and the crack block width is relatively small.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] A method for preparing an adjustable crack template includes the following steps:

[0009] (1) Add egg yolk liquid to egg white liquid and mix well to make it evenly distributed in the egg white liquid to obtain a crack liquid.

[0010] (2) Clean and hydrophilize the transparent substrate.

[0011] (3) Coat the crack liquid on the surface of the transparent substrate to obtain a crack film, and then dry the crack film and let it crack naturally to form a crack template.

[0012] The ratio of the egg yolk liquid to the egg white liquid is 3.5 - 13 g: 1 L.

[0013] The principle of the present invention is as follows: First, clean and hydrophilize the surface of the transparent substrate to improve the hydrophilicity of the substrate. Then, mix the egg yolk liquid and the egg white liquid well to obtain a crack liquid, and coat the mixed crack liquid on the surface of the transparent substrate and dry it to form a crack template; during this process, since the crack liquid loses moisture in the air, the film shrinks and stress concentration occurs, thus generating cracks; among them, the egg yolk will be evenly distributed in the egg white liquid in the form of tiny particles, and it and the egg white liquid are evenly coated on the surface of the transparent substrate, which can significantly affect the size of the crack blocks, obtaining a crack template with a smaller crack block width compared to not adding egg yolk liquid. Moreover, as the proportion of the egg yolk liquid in the crack liquid increases, the crack block width becomes smaller, realizing the adjustability of the crack template.

[0014] In the solution of the present invention, the ratio of the egg yolk liquid to the egg white liquid includes but is not limited to 3.5 - 13 g: 1 L. As long as the egg yolk liquid is added to the egg white liquid, the purpose of regulating the crack template can be achieved.

[0015] In a specific embodiment of the present invention, the material of the transparent substrate is selected from any material that can be used as a transparent substrate, such as glass, PET, PP, PVC, PC, etc.

[0016] The hydrophilic treatment is to clean with a plasma cleaner for 50 - 100 s, and the power of the plasma cleaner is 180 - 220 W.

[0017] In a preferred solution, the cleaning treatment is specifically as follows: ultrasonically clean the transparent substrate with dishwashing liquid for 10 - 15 minutes, ultrasonically clean with ethanol for 10 - 15 minutes, ultrasonically clean with deionized water for 10 - 15 minutes, and then blow it dry with nitrogen; the power of the above ultrasonic is 100 W.

[0018] In step (3), the method of coating the crack liquid on the transparent substrate includes but is not limited to knife coating, slot coating, spin coating, etc. All methods that can achieve the coating of the crack liquid on the transparent substrate are within the scope of the present invention.

[0019] In step (3), the ways to crack the crack liquid include natural drying cracking, heating drying cracking, vacuum pumping to accelerate cracking, etc.

[0020] Preferably, in step (3), the crack film is heated and dried at 60 - 70 °C for 7 - 10 min with a heating table to make it crack and form a crack template.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) On the basis of the existing method of preparing a crack template with egg white liquid, the present invention regulates the crack template by regulating the crack liquid, that is, uniformly mixing different ratios of egg yolk liquid into the egg white liquid, to regulate the size of the crack blocks in the crack template, and the width of the crack blocks is relatively small. Moreover, the width of the crack blocks in the crack template prepared by the method of the present invention has good uniformity.

[0023] (2) The transparent conductive electrode produced by the crack template prepared by the method of the present invention can significantly reduce the sheet resistance on the basis of maintaining a high light transmittance. Therefore, the method of the present invention expands the application of the crack template method, enabling it to be used for preparing transparent conductive electrodes for devices that require a relatively high carrier concentration and for displays and touch screens.

[0024] (3) The egg white liquid and egg yolk liquid used in the present invention are both non-toxic, easy to obtain, green and pollution-free; the method of the present invention has a simple process, low cost, and is easy to industrialize. Brief Description of the Drawings

[0025] Figure 1 is the preparation flow chart of the adjustable crack template of the present invention;

[0026] Figure 2 is the 5-fold magnification optical microscope image of the crack template in Example 1.

[0027] Figure 3 is the 20-fold magnification optical microscope image of the crack template in Example 1.

[0028] Figure 4 is the 5-fold magnification optical microscope image of the crack template in Example 2.

[0029] Figure 5 is the 20-fold magnification optical microscope image of the crack template in Example 2.

[0030] Figure 6 is the 5-fold magnification optical microscope image of the crack template in Example 3.

[0031] Figure 7 is the 20-fold magnification optical microscope image of the crack template in Example 3.

[0032] Figure 8 is the 5-fold magnification optical microscope image of the crack template in Comparative Example 1, where a and b are images of two different fields of view.

[0033] Figure 9 is the 20-fold magnification optical microscope image of the crack template in Comparative Example 1, where c and d are images of two different fields of view. Detailed Description of the Invention

[0034] The present invention will be further described below through specific examples.

[0035] Example 1

[0036] As Figure 1 shown, a method for preparing an adjustable crack template includes the following steps:

[0037] (1) Add 0.15 g of egg yolk liquid to 40 mL of egg white liquid, and through ultrasonic mixing, make the egg yolk liquid evenly distributed in the egg white liquid to obtain a crack liquid;

[0038] (2) Use sodium-calcium glass as the transparent substrate material. First, perform a cleaning treatment: ultrasonically clean with dishwashing liquid for 15 minutes, ultrasonically clean with ethanol for 15 minutes, ultrasonically clean with deionized water for 15 minutes, and then dry it with nitrogen;

[0039] Then perform a hydrophilic treatment: place it in a plasma cleaner for 60 s, and the power of the plasma cleaner is 180 - 220 W;

[0040] (3) Uniformly scrape and coat the crack solution on the processed soda-lime glass to obtain a cracked film, and then heat and dry it at 60 °C for 8 min to cause the cracked film to crack and form a crack template.

[0041] Detect the prepared crack template:

[0042] As Figure 2 shown, use an optical microscope to magnify 5 times for observation, and it can be seen that the measured width of the cracked block is 57.177 μm; as Figure 3 shown, use an optical microscope to magnify 20 times for observation, and it can be seen that the measured width of the crack line is 1.246 μm; moreover, as the size of the cracked block width becomes smaller, the uniformity of the cracked block width and the crack line width is better.

[0043] Example Two

[0044] The method of this example is the same as that of Example One, except that the crack solution in this example is 0.3 g of egg yolk solution fully mixed into 40 mL of egg white solution.

[0045] Detect the prepared crack template: As Figure 4 shown, the crack template after coating the crack solution (egg white solution plus 0.3 g of egg yolk solution) and drying, under an optical microscope magnified 5 times, it can be seen that the measured width of the cracked block is 38.01 μm; Figure 5 For the figure magnified 20 times under an optical microscope, it can be seen that the measured width of the crack line is 1.003 μm; moreover, as the size of the cracked block width becomes smaller, the uniformity of the cracked block width and the crack line width is better.

[0046] Example Three

[0047] The method of this example is the same as that of Example One, except that the crack solution in this example is 0.5 g of egg yolk solution fully mixed into 40 mL of egg white solution.

[0048] Detect the prepared crack template: As Figure 6 shown, the crack template after coating the crack solution (egg white solution plus 0.5 g of egg yolk solution) and drying, under an optical microscope magnified 5 times, it can be seen that the measured width of the cracked block is 30.751 μm; Figure 7 For the figure magnified 20 times under an optical microscope, it can be seen that the measured width of the crack line is 0.919 μm; moreover, as the size of the cracked block width becomes smaller, the uniformity of the cracked block width and the crack line width is better.

[0049] Comparative Example One

[0050] The method of the comparative example is the same as that of Example One, except that the crack solution in the comparative example is 40 mL of pure egg white solution.

[0051] As Figure 8 shown in a and b, the cracked template without egg yolk solution was observed under an optical microscope magnified 5 times, and it can be seen that the uniformity of the width of the cracked blocks therein is poor. The measured widths of the cracked blocks are 148.101 μm, 151.888 μm, and 260.762 μm respectively, and the sizes of the three cracked block widths vary greatly; as Figure 9 shown in c and d, the cracked template without egg yolk solution was observed under an optical microscope magnified 20 times, and it can be seen that the measured widths of the cracked lines are 1.690 μm and 2.468 μm respectively.

[0052] From the results of the above Examples 1-3 and Comparative Example 1, it can be seen that the cracked blocks in the cracked template with egg yolk solution are significantly smaller than those in the cracked template without egg yolk solution; moreover, as the proportion of egg yolk solution in the cracking solution increases, the width of the cracked blocks becomes smaller, thus realizing the controllability of the cracked template.

[0053] Furthermore, transparent conductive electrodes were prepared by sputtering using the cracked templates of Example 1, Example 2, and Comparative Example 1, and their transmittance and sheet resistance are shown in the following table.

[0054] Cracked template Transmittance (%) Sheet resistance (Ω / sq) Example 1 79.6 6 Example 2 80.0 4 Comparative Example 1 86.3 40

[0055] It should be noted that the above embodiments are only further descriptions of the present invention, rather than limitations. For example, in addition to using calcium-sodium glass for the substrate of the prepared sample, other inexpensive transparent substrate materials (PET, PC, PVC, PP, etc.) can also be used. The amount of egg yolk solution added to the egg white solution is not limited to 0.15 g, 0.3 g, and 0.5 g in the above embodiments, and the drying method can also be natural drying or vacuum drying; within the scope of the technical solution, other specific parameter values can also achieve the purpose of the present invention. Therefore, any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing a controllable crack template, characterized in that, It includes the following steps: (1) Add the egg yolk liquid to the egg white liquid and mix well to make it evenly distributed in the egg white liquid to obtain a cracked liquid; the ratio of the egg yolk liquid to the egg white liquid is 3.5 - 13 g:1 L; (2) Conduct a cleaning treatment and a hydrophilic treatment on the transparent substrate; (3) Coat the cracked liquid on the surface of the transparent substrate to obtain a cracked film, and then dry the cracked film and let it crack naturally to form a cracked template.

2. The method for preparing a crack template according to claim 1, wherein The material of the transparent substrate is selected from one of glass, PET, PP, PVC, and PC.

3. The method for preparing a crack template according to claim 2, characterized in that, The hydrophilic treatment is to clean with a plasma cleaner for 50 - 100 s, and the power of the plasma cleaner is 180 - 220 W.

4. The method for preparing the crack template according to claim 3, wherein The cleaning treatment is as follows: ultrasonically clean the transparent substrate with dishwashing liquid for 10 - 15 minutes, ultrasonically clean it with ethanol for 10 - 15 minutes, ultrasonically clean it with deionized water for 10 - 15 minutes, and then blow it dry with nitrogen.

5. The method for preparing a crack template according to claim 4, characterized in that, In step (3), the method of coating the cracked liquid on the transparent substrate is knife coating, slot coating, or spin coating.

6. The method for preparing a crack template according to claim 5, characterized in that, In step (3), the ways to make the cracked liquid crack include natural drying cracking, heating drying cracking, and vacuum pumping to accelerate cracking.

7. The method for preparing a crack template according to claim 6, characterized in that, In step (3), use a heating table to heat and dry the cracked film at 60 - 70 °C for 7 - 10 minutes to make it crack and form a cracked template.

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