A method for preparing polarizers doped with metal nanowires

Abstract

This invention relates to a method for preparing a polarizer doped with metal nanowires, comprising: preparing an aqueous latex solution containing doped metal nanowire microcapsules; casting the aqueous latex solution containing doped metal nanowire microcapsules onto a rotary drum casting machine to obtain a cast film containing doped metal nanowires; subjecting the cast film to stretching and curing processes sequentially to obtain a stretched cast film; and pressing the stretched cast film onto a first optical base film and a second optical base film on a laminating machine to form a polarizer doped with metal nanowires. This invention features a metal wire grid polarizer that polarizes across various wavelengths, including infrared, visible, and ultraviolet light, and also allows for large-area thin-film fabrication. Furthermore, it is compatible with existing polarizer manufacturing technologies and equipment.

Description

Technical Field

[0001] This invention relates to the field of optical thin film technology, and in particular to a method for preparing a polarizer doped with metal nanowires. Background Technology

[0002] Polarizing films are optical functional thin-film materials. Iodine-based polarizing films, which have been industrialized, are widely known for their extensive use in liquid crystal displays and polarized glasses. When natural light is incident, half of the light is transmitted and the other half is absorbed. In addition, metal wire grid polarizing films have special applications in instruments in the infrared, microwave, and terahertz bands, and are also well-known to professional researchers.

[0003] Iodine-based polarizers are structurally composed of two cellulose triacetate (TAC) films sandwiching a polyvinyl alcohol (PVA) film that has been impregnated with iodine solution and then stretched through casting. Zhang Zihan et al. proposed an invention patent, "A Nano-Silver Wire-Based Polarizer and Its Manufacturing Method" (CN111240081A). Compared with existing iodine-based polarizers, the nano-silver wire polarizer has advantages such as high temperature and humidity resistance and colorfastness.

[0004] However, as mentioned earlier, non-iodine-based silver nanowire polarizers are expected to enable the large-area thin-film production of metal wire grid polarizers, allowing thin-film polarizers to be used in more wavelengths beyond the visible light spectrum. Therefore, the industrialization of metal nanowire polarizers has a very promising market prospect. Summary of the Invention

[0005] In response to the problems raised in the prior art, the present invention provides a method for preparing a polarizer doped with metal nanowires.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a polarizer doped with metal nanowires includes:

[0008] Preparation of latex aqueous solution doped with metal nanowire microcapsules;

[0009] A latex aqueous solution doped with metal nanowire microcapsules is cast into a film on a rotary drum casting machine to obtain a cast film doped with metal nanowires.

[0010] The cast film is subjected to stretching and curing processes in sequence to obtain a cast stretched film;

[0011] On a laminating machine, a cast stretch film is pressed between a first optical base film and a second optical base film to form a polarizer with doped metal nanowires.

[0012] As a preferred technical solution, microcapsules encapsulating metal nanowires are prepared;

[0013] Metal nanowire microcapsules were added to polyvinyl alcohol latex to obtain a polyvinyl alcohol latex aqueous solution doped with metal nanowire microcapsules.

[0014] As a preferred technical solution, the encapsulated metal nanowire microcapsules are spherical or elliptical, and the diameter of the encapsulated metal nanowire microcapsules is 50-500 μm.

[0015] As a preferred technical solution, the encapsulated metal nanowire microcapsules comprise metal nanowires and a solvent, wherein the diameter of the metal nanowires is 0.01-0.2 micrometers; the metal nanowires are one or more of silver, gold, copper, nickel, iron, and aluminum.

[0016] As a preferred technical solution, 78-83 wt% pure water and 17-22 wt% polyvinyl alcohol are placed in a high-temperature and high-pressure autoclave and stirred at 130°C for 24 hours; wherein the solid content of polyvinyl alcohol includes: 5-8 wt% glycerol, 0.5-1 wt% cationic surfactant, and 5-15 wt% metal nanowires;

[0017] Stop stirring and let stand at 90℃ for 48 hours to defoam, thus preparing a polyvinyl alcohol latex aqueous solution doped with metal nanowire microcapsules.

[0018] As a preferred technical solution, the metal nanowire microcapsules are discretely distributed in polyvinyl alcohol latex, and the metal nanowires inside the metal nanowire microcapsules are arranged in a discrete distribution.

[0019] As a preferred technical solution, a cast film of doped metal nanowires is prepared by extrusion coating on a roller casting machine and then wound up, with the thickness of the cast film being 50–75 μm.

[0020] As a preferred technical solution, after the cast film is placed on a stretching machine for unidirectional stretching, the nano-silver wire microcapsules are shaped into a spindle. The arrangement of the metal nano-wire microcapsules in the cast film after unidirectional stretching is in a sequential arrangement, and the metal nanowires in the metal nano-wire microcapsules are in a sequential arrangement.

[0021] The uniaxially stretched cast film is placed in a drying tunnel chamber for shaping and curing to obtain a cast stretched film.

[0022] As a preferred technical solution, an adhesive is coated on both sides of the cast stretch film;

[0023] The cast and stretched film coated with adhesive is placed on a laminating machine, which is used to press the cast and stretched film between the first optical base film and the second optical base film to form a polarizer with doped metal nanowires. As a preferred technical solution, the transmittance of the first optical base film and the second optical base film is greater than 85%.

[0024] As a preferred technical solution, both the first optical base film and the second optical base film are one or more combinations of TAC film, PET film, SRF film, PMMA film, COC film or COP film.

[0025] This application also provides a polarizer manufactured using the above-described preparation method, comprising:

[0026] A first optical base film and a second optical base film are disposed opposite to each other;

[0027] The polarizing film contains microcapsules encapsulating metal nanowires and is positioned between the first optical base film and the second optical base film.

[0028] The beneficial effects achieved by the technical solution adopted in this invention are as follows: The polarizer prepared by this invention is composed of two polarizer surface treatment films sandwiching a polymer material casting and stretching film doped with metal nanowires.

[0029] 1. The metal nanowires are encapsulated in a microcapsule manner to stretch the entire microcapsule into an elongated ellipsoid so that the silver nanowires are oriented along the long axis, while also preventing the metal nanowires from becoming misaligned.

[0030] 2. Polyvinyl alcohol-doped metal nanowire casting film does not require the iodine solution dyeing process. The resulting metal nanowire polarizer has a semi-transparent appearance and a light transmission axis. When natural light is incident, half of the light is transmitted and half is absorbed.

[0031] 3. The fabricated metal nanowire polarizer has the characteristics of metal wire grid polarizers that can polarize in all bands such as infrared, visible and ultraviolet light, and also has the characteristics of being able to be made into a large-area thin film. Furthermore, it is compatible with existing polarizer manufacturing technology and production equipment. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, forming part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0033] Figure 1 This is a flowchart of the method for preparing a polarizer using doped metal nanowires disclosed in an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the polarizer structure of the doped metal nanowires disclosed in an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the microcapsule structure for encapsulating metal nanowires disclosed in an embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of the doped metal nanowire casting film structure disclosed in an embodiment of the present invention;

[0037] Figure 5 This is a schematic diagram of the doped metal nanowire casting and stretching film structure disclosed in an embodiment of the present invention.

[0038] Explanation of reference numerals in the attached figures:

[0039] 10. Polyvinyl alcohol; 11. Microcapsules encapsulating metal nanowires; 111. Urea-formaldehyde resin capsule wall; 112. Silver nanowire core; 13. Cast film; 14. Cast stretch film;

[0040] First optical base film 21; second optical base film 22; adhesive 23. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0042] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0043] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] This embodiment provides a method for preparing a polarizer doped with metal nanowires, based on... Figure 1 ,include:

[0046] Prepare a latex aqueous solution doped with metal nanowire microcapsules 11;

[0047] A latex aqueous solution containing doped metal nanowire microcapsules 11 is placed on a rotary drum casting machine to cast a film, thereby obtaining a cast film 13 doped with metal nanowires.

[0048] The cast film 13 is sequentially stretched and cured to prepare a cast stretched film 14, namely a polarizing element film, also known as a polarizing mirror.

[0049] On a laminating machine, a cast and stretched film 14 is pressed between a first optical base film 21 and a second optical base film 22 to form a polarizer with doped metal nanowires. Figure 2 .

[0050] Preferably, microcapsules 11 encapsulating metal nanowires are prepared;

[0051] Metal nanowire microcapsules 11 were added to polyvinyl alcohol 10 latex solution to obtain polyvinyl alcohol 10 latex aqueous solution doped with metal nanowire microcapsules.

[0052] Specifically, to prepare the metal nanowire-encapsulated microcapsules 11, in a preferred embodiment, urea and formaldehyde solution (37%) were added to a reaction vessel at a molar ratio of 1:2 and stirred. After the urea was completely dissolved, the pH of the solution was slowly adjusted to approximately 8.5 with triethanolamine, and the temperature was increased to 75°C at a heating rate of 5°C / min and maintained for 1 hour to obtain a transparent and viscous urea-formaldehyde prepolymer. Sodium chloride, a curing agent, was slowly added to the above solution, and after dissolution, 1 / 5 of the volume fraction of the prepolymer (Wt) of silver nanowires (Wt) were added. 环己醇 =2%)-cyclohexanol dispersion, with the surfactant Span-85 (Wt) added 环己醇 =0.65%), add hydrochloric acid-potassium chloride acidic catalyst in batches, after half an hour, control the pH to 3-4, stir for 1 hour, raise the temperature to 60℃, and end the reaction after 1 hour. Wash the reactants with deionized water 5-6 times, and filter to obtain metal nanowire-encapsulated microcapsules 11.

[0053] Preferably, the metal nanowire microcapsules 11 are circular or elliptical, and the diameter of the metal nanowire microcapsules 11 is 50-500 μm.

[0054] Specifically, during the microcapsule synthesis process, a dispersion of metal nanowires is added to form spherical or near-spherical microcapsules 11 encapsulating the metal nanowires. The microcapsules contain stress buffer release areas that can withstand the stretching process without the metal nanowires being broken.

[0055] Preferably, the metal nanowire microcapsule 11 comprises metal nanowires and a solvent, wherein the diameter of the metal nanowires is 0.01-0.2 micrometers; the metal nanowires are one or more combinations of silver, gold, copper, nickel, iron, and aluminum.

[0056] In a preferred embodiment, according to Figure 3 The metal nanowire microcapsule 11 includes a urea-formaldehyde resin capsule wall 111 and a silver nanowire core 112.

[0057] Preferably, the capsule wall material for manufacturing the microcapsules is one of urea-formaldehyde resin, phenol-formaldehyde resin, melamine-formaldehyde resin, urea-formaldehyde resin, gelatin-arabinose gel, or gelatin-carboxymethyl cellulose sodium.

[0058] Preferably, 78-83 wt% purified water and 17-22 wt% polyvinyl alcohol are placed in a high-temperature and high-pressure autoclave and stirred at 130°C for 24 hours; wherein the solid content of polyvinyl alcohol includes: 5-8 wt% glycerol, 0.5-1 wt% cationic surfactant, and 5-15 wt% metal nanowires.

[0059] Stop stirring and let stand at 90℃ for 48 hours to defoam, thus preparing a polyvinyl alcohol latex aqueous solution doped with metal nanowire microcapsules.

[0060] Specifically, the polyvinyl alcohol 10 latex aqueous solution doped with metal nanowire microcapsules is prepared by adding 78-83% purified water, 17-22% polyvinyl alcohol 10 PVA-2499 or PVA-2699, 5-8% glycerol (glycerol) in the solid content of polyvinyl alcohol 10, 0.5-1% cationic surfactant (such as hexadecyltrimethylammonium bromide), and 5%-10% microcapsules encapsulating metal nanowires with a diameter of 0.01-0.2 micrometers in the high-temperature and high-pressure reactor. The mixture is stirred at 130°C for 24 hours, then allowed to stand at 90°C for 48 hours to defoam, thus preparing the polyvinyl alcohol 10 latex aqueous solution doped with metal nanowire microcapsules.

[0061] Preferably, the metal nanowire microcapsules 11 are discretely distributed in the polyvinyl alcohol 10 latex solution, and the metal nanowire microcapsules 11 are arranged in a sequential manner.

[0062] Specifically, the metal nanowire microcapsules are randomly and discretely distributed in the polyvinyl alcohol 10 latex solution and are roughly parallel to the stretching direction of the cast film 13, thereby enabling the polymer film doped with metal nanowires to function as a metal wire grid polarizer.

[0063] Preferably, a cast film 13 doped with metal nanowires is prepared by extrusion coating on a roller casting machine and then wound up, with the thickness of the cast film 13 being 50–75 μm.

[0064] In a preferred embodiment, according to Figure 4 Polyvinyl alcohol 10-doped metal nanowire cast film 13 was prepared by extrusion coating on a roller casting machine. By adjusting the extrusion nozzle gap, the heating temperature and rotation speed of the drum, etc., a polyvinyl alcohol 10-doped metal nanowire cast film 13 with a thickness of 50-75 micrometers was produced.

[0065] Preferably, the cast film 13 is placed on a stretching machine for unidirectional stretching treatment, and the encapsulated silver nanowire microcapsules are shaped into a spindle shape. Figure 5 The metal nanowire microcapsules 11 encapsulating the metal nanowire microcapsules 11 are arranged in a sequential manner within the cast film 13 after uniaxial stretching treatment.

[0066] The uniaxially stretched cast film 13 is placed in a drying tunnel box for shaping and curing to obtain a cast stretched film 14.

[0067] Specifically, the polarizer is stretched on a stretching machine in the polarizer production line and then shaped and cured in a drying tunnel box. The stretching can be either dry or wet. Unlike existing polarizer manufacturing processes, the polyvinyl alcohol 10-doped metal nanowire cast film 13 does not require an iodine solution dyeing process.

[0068] In a preferred embodiment, according to Figure 5 For example, if the metal nanowires being wrapped are made of silver, on a TN dry production line with a polarizing film, the polyvinyl alcohol 10-doped silver nanowire cast film 13 is unwound, and the cast film 13 is heated and stretched by 4 to 6 times to obtain a cast film 14 with a thickness of about 25 to 30 μm. The polyvinyl alcohol 10-doped silver nanowire cast film 14 is then conveyed into a drying tunnel box for curing, shaping, and winding to obtain the finished silver nanowire cast film 14.

[0069] Preferably, adhesive 23 is applied to both sides of the cast stretch film 14;

[0070] The cast and stretched film 14 after being coated with adhesive 23 is placed on a film laminating machine. The laminating machine is used to press the cast and stretched film 14 between the first optical base film 21 and the second optical base film 22 to form a polarizer with doped metal nanowires.

[0071] Preferably, both the first optical base film 21 and the second optical base film 22 are cellulose triacetate protective films.

[0072] In a preferred embodiment, a polyvinyl alcohol 10-doped silver nanowire cast and stretched composite film is manufactured. On a TN polarizer production line, the polyvinyl alcohol 10-doped silver nanowire cast and stretched film 14 is unwound, an adhesive is first coated on both sides of the film, and then a cellulose triacetate protective film is laminated on both sides on a laminating machine. Finally, the film is wound up to obtain a polyvinyl alcohol 10-doped silver nanowire cast and stretched composite polarizer product.

[0073] Preferably, the transmittance of both the first optical base film 21 and the second optical base film 22 is greater than 85%.

[0074] Preferably, the first optical base film 21 and the second optical base film 22 are both TAC film, PET film, or one or more combinations of SRF film, PMMA film, COC film or COP film.

[0075] The principle of a polyvinyl alcohol 10-doped metal nanowire polarizer: The polyvinyl alcohol 10-doped metal nanowire cast and stretched composite film polarizer appears as a semi-transparent gray film. The microcapsules encapsulating the metal nanowires can be simplified as being randomly and discretely distributed within the cast film 13. After unidirectional stretching (4-6 times), the microcapsules are stretched into a spindle shape (spherical or ellipsoidal). Due to the stress buffer release region within the microcapsules, the metal nanowires are not broken during stretching but are roughly oriented along the stretching direction. When light is incident perpendicularly through the polyvinyl alcohol 10-doped metal nanowire thin layer, light polarized along the stretching direction is easily absorbed by the metal nanowires, while light polarized perpendicular to the stretching direction is easily transmitted; that is, the direction perpendicular to the stretching direction is the transmission axis. This is because the roughly oriented metal nanowires function as a metal wire grating polarizer. Although it does not have the uniform grating constant of a metal wire grating polarizer, the non-uniform distribution of the metal nanowires results in a range of grating constant values, making the polarizer more adaptable to a wider wavelength range.

[0076] Metal nanowires are an emerging material for transparent conductive films. Researchers in this field are focusing on coating metal nanowires to minimize their anisotropy in conductivity, i.e., minimizing the anisotropy in their orientation. However, this embodiment takes the opposite approach, aiming for maximum anisotropy in the orientation of the metal nanowires. Clever design of the coating extrusion port, coating speed, and liquid flow angle have already enabled anisotropy in the orientation of the metal nanowires. Furthermore, after the cast film 13 is stretched several times, this anisotropy is inevitably amplified. Therefore, in this embodiment, the polyvinyl alcohol 10-doped metal nanowire cast and stretched film 14 functions as a metal wire grid polarizer.

[0077] Compared to existing iodine-based polarizers, polyvinyl alcohol 10-doped metal nanowire polarizers may fall short or even be significantly inferior in optical properties such as polarization degree. However, in non-liquid crystal display devices, such as ultraviolet, infrared, terahertz, and microwave fields, the requirements for polarizers do not require very high polarization degrees. Therefore, polyvinyl alcohol 10-doped silver nanowire polarizers are an effective solution for achieving large-area thin-film fabrication of metal wire grid polarizers, and have great potential in non-visible light band devices. Since the polyvinyl alcohol 10-doped metal nanowire polarizer fabricated in this invention has a similar structure to that of iodine-based polarizers, the final product naturally has a similar film thickness and cannot achieve the effect of reducing the thickness of the polarizer.

[0078] Example 2

[0079] This embodiment provides a polarizer manufactured using the preparation method described in Example 1, according to... Figure 2 ,include:

[0080] The first optical base film 21 and the second optical base film 22 are disposed opposite to each other.

[0081] A polarizing film is formed by encapsulating metal nanowire microcapsules 11 within the polarizing film. After being coated with adhesive 23 on both sides, the film is positioned between a first optical base film 21 and a second optical base film 22. The resulting polarizer has a semi-transparent appearance, a transmission axis, and the ability to transmit half of the light and absorb the other half when natural light is incident. It also exhibits polarization across various wavelengths, including infrared, visible, and ultraviolet light. Furthermore, it can be fabricated into large-area thin films and is compatible with existing polarizer manufacturing technologies and equipment.

[0082] The above provides a detailed description of a method for preparing a polarizer using doped metal nanowires according to embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing a polarizing sheet doped with metal nanowires, characterized by, include: Preparation of latex aqueous solution doped with metal nanowire microcapsules; The latex aqueous solution containing the doped metal nanowire microcapsules was placed on a rotary drum casting machine to cast a film, thereby obtaining a cast film doped with metal nanowires. The cast film is subjected to stretching and curing processes in sequence to obtain a cast stretched film; The cast and stretched film is pressed between the first optical base film and the second optical base film on a laminating machine to form a polarizer with doped metal nanowires.

2. The production method according to claim 1, characterized by, The preparation of a latex aqueous solution doped with and encapsulating metal nanowire microcapsules includes: Preparation of microcapsules encapsulating metal nanowires; The metal nanowire microcapsules were added to a polyvinyl alcohol latex solution to obtain a polyvinyl alcohol latex aqueous solution doped with metal nanowire microcapsules.

3. The preparation method according to claim 2, characterized in that, The encapsulated metal nanowire microcapsules are spherical or elliptical, and the diameter of the encapsulated metal nanowire microcapsules is 50-500 μm.

4. The production method according to claim 2, characterized by, The encapsulated metal nanowire microcapsules comprise metal nanowires and a solvent, wherein the diameter of the metal nanowires is 0.01-0.2 micrometers; and the metal nanowires are one or more of silver, gold, copper, nickel, iron, and aluminum.

5. The preparation method according to claim 2, characterized in that, Adding the encapsulated metal nanowire microcapsules to a polyvinyl alcohol latex solution yields a polyvinyl alcohol latex aqueous solution doped with metal nanowire microcapsules, comprising: 78-83 wt% purified water and 17-22 wt% polyvinyl alcohol are placed in a high-temperature and high-pressure autoclave and stirred at 130°C for 24 hours; wherein the solid content of the polyvinyl alcohol includes: 5-8 wt% glycerol, 0.5-1 wt% cationic surfactant, and 5-15 wt% metal nanowires. Stop stirring and let stand at 90℃ for 48 hours to defoam, thus preparing a polyvinyl alcohol latex aqueous solution doped with metal nanowire microcapsules.

6. The preparation method according to claim 2, characterized in that, Adding the encapsulated metal nanowire microcapsules to a polyvinyl alcohol latex solution yields a polyvinyl alcohol latex aqueous solution doped with metal nanowire microcapsules, comprising: The encapsulated metal nanowire microcapsules are discretely distributed in polyvinyl alcohol latex, and the metal nanowires within the encapsulated metal nanowire microcapsules are arranged in a discrete distribution.

7. The preparation method according to claim 1, characterized in that, The latex aqueous solution containing the doped metal nanowire microcapsules is cast into a film on a rotary drum casting machine to obtain a cast film of doped metal nanowires, comprising: A cast film of doped metal nanowires is prepared by extrusion coating on a roller casting machine and then wound up. The thickness of the cast film is 50~75mm.

8. The method of claim 1, wherein, The cast film is sequentially subjected to stretching and curing processes to obtain a cast stretched film, including: After the cast film is placed on a stretching machine for uniaxial stretching, the metal nanowire microcapsules are deformed into a spindle shape, and the metal nanowire microcapsules are arranged in a sequential manner in the cast film after uniaxial stretching, and the metal nanowires in the metal nanowire microcapsules are arranged in a sequential manner. The uniaxially stretched cast film is placed in a drying tunnel box for shaping and curing to obtain a cast stretched film.

9. The method of claim 1, wherein, The cast and stretched film is pressed between a first optical base film and a second optical base film on a laminating machine to form a polarizer with doped metal nanowires, comprising: The cast stretch film is coated with an adhesive on both sides; The cast stretch film coated with the adhesive is placed on a laminating machine, which is used to press the cast stretch film between the first optical base film and the second optical base film to form a polarizing sheet doped with metal nanowires.

10. The method of claim 9, wherein, The light transmittance of the first optical base film and the second optical base film is greater than 85%.

11. The preparation method according to claim 9, characterized in that, The first optical base film and the second optical base film are one or more than two combinations of TAC film, PET film, or SRF film, PMMA film, COC film, or COP film.

12. A polarizing plate produced by the production method according to any one of claims 1 to 11, characterized by Comprise: The first optical base film and the second optical base film are oppositely arranged; The polarizing film is provided with metal nanowire microcapsules, and the polarizing film is arranged between the first optical base film and the second optical base film.

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