A method for preparing a metal nanowire polarizer

Abstract

The present invention relates to a method for preparing a metal nanowire polarizer, comprising: providing a stretchable base film, and unwinding the stretchable base film; coating an alcohol-based metal nanowire ink on one side surface of the stretchable base film, and then placing it in a drying box to dry the alcohol-based metal nanowire ink to obtain a composite stretchable film; placing the composite stretchable film on a heating and stretching device for unidirectional stretching to 4-7 times to obtain a metal nanowire stretched film of directional arrangement; coating one side of the metal nanowire stretched film coated with alcohol-based metal nanowire ink, coating a polymer resin ultraviolet light curing glue, and then drying and curing treatment, and rolling up to obtain a metal nanowire polarizer. The polarizer prepared in the present invention has the effect that a metal wire grid polarizer can be polarized in each band of visible light and non-visible light, and can be produced in a large area of ​​thin film and can realize ultra-thin polarizer, and has strong practicality.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing and application of new optical functional film materials, and in particular to a method for preparing a metal nanowire polarizer. Background Art

[0002] Polaroids are thin film materials with optical functions. Iodine-based polaroids that have been industrialized are widely used in fields such as liquid crystal displays and polarized glasses. When natural light is incident, half of the light is transmitted and the other half is absorbed. However, this type of polaroid only has the function of a polaroid in the visible light band. In addition, metal wire grid polaroids have special applications in instruments in infrared, microwave and terahertz bands, and are also well known to professional researchers. However, metal wire grid polaroids cannot be made into thin films over a large area and are expensive, which makes the cost of devices other than visible light that require metal wire grid polaroids very high.

[0003] The structure of the iodine-based polarizer is a film composed of two triacetyl cellulose (TAC) films sandwiched by a polyvinyl alcohol (PVA) film that has been impregnated with iodine solution and then stretched by casting. Zhang Zihan et al. proposed the invention patent of "A nano silver wire-based polarizer and its production method" (CN111240081A). Compared with the existing iodine-based polarizer, the nano silver wire polarizer has the advantages of high temperature and humidity resistance and discoloration resistance.

[0004] But as mentioned earlier, non-iodine-based nanosilver wire polarizers are expected to enable metal wire grid polarizers to be produced into large-area thin films, allowing thin-film polarizers to be used in more bands beyond visible light. Therefore, the industrialization of metal nanowire polarizers has considerable market prospects. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a method for preparing a metal nanowire polarizer.

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

[0007] A method for preparing a metal nanowire polarizer, comprising:

[0008] Providing a stretchable base film, and unwinding the stretchable base film;

[0009] Coating an alcohol-based metal nanowire ink on one surface of the stretchable base film, and then placing the base film in a drying oven to dry the alcohol-based metal nanowire ink to obtain a composite stretchable film;

[0010] Placing the composite stretchable film on a heating stretching device and uniaxially stretching it to 4-7 times to obtain a directional metal nanowire stretched film;

[0011] The side of the oriented metal nanowire stretched film coated with alcohol-based metal nanowire ink is coated with polymer resin UV-curable glue, which is then dried and cured, and rolled up to obtain a metal nanowire polarizer.

[0012] As a preferred technical solution, the stretchable base film is a PETG film, the thickness of the PETG film is 60-100 μm, and the width is 30-300 cm.

[0013] As a preferred technical solution, an alcohol-based metal nanowire ink is provided, wherein the solid content of the metal nanowires in the alcohol-based metal nanowire ink is 0.5 to 5 wt %;

[0014] The alcohol-based metal nanowire ink is coated on one side of the stretchable base film by a wire rod, a row brush, or a multi-channel slit coating head installed on a coating line;

[0015] The temperature in the drying box is set to be lower than the softening temperature of the stretchable base film to dry the alcohol-based metal nanowire ink coated on the stretchable base film. The transmittance of the obtained composite stretchable film is 15-25%.

[0016] As a preferred technical solution, the spacing between the liquid outlet units of the wire rod, or the row brush, or the multi-channel slit coating head is less than 10 μm.

[0017] As a preferred technical solution, the temperature in the heating and stretching device is set to be within the softening temperature range of the stretchable base film;

[0018] Based on the dry stretching process, the composite stretchable film is uniaxially stretched to 4-7 times, and the transmittance of the obtained directional metal nanowire stretched film is more than 40%.

[0019] As a preferred technical solution, a polymer resin UV-curable glue is coated on one side of the oriented metal nanowire stretched film coated with the alcohol-based metal nanowire ink by a slit coating machine or a micro-concave coating machine;

[0020] The temperature in the drying box is set to be lower than the softening temperature of the stretchable base film to dry the polymer resin UV curing glue.

[0021] As a preferred technical solution, the directional metal nanowire stretched film after drying the polymer resin UV-curable glue is placed in a UV curing device to cure the dried polymer resin UV-curable glue to obtain an optical protective film.

[0022] As a preferred technical solution, the thickness of the optical protective film is 10 to 1000 nm.

[0023] As a preferred technical solution, the metal nanowires are one or more combinations of silver, gold, copper, nickel, iron, aluminum, zinc, and magnesium.

[0024] As a preferred technical solution, the metal nanowire has a diameter of 10 to 200 nm and a length of 1 to 20 μm.

[0025] The technical solution adopted in the present invention achieves the beneficial effects as follows: the metal nanowire polarizer prepared by the present invention can have the optical properties and functions of the metal wire grid polarizer, and can realize large-area thin film and ultra-thin metal wire grid polarizer, and has practicality. At the same time, the polarizer is expected to be applied to polarization devices in multiple bands of ultraviolet light, infrared light, terahertz, and microwaves, and greatly reduce the manufacturing cost of related devices, especially has application prospects in OLED flexible display devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments, which constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions explain the present invention and do not constitute improper limitations on the present invention. In the drawings:

[0027] Figure 1 A flow chart of a method for preparing a metal nanowire polarizer disclosed in one embodiment of the present invention;

[0028] Figure 2 A structural diagram of a metal nanowire polarizer disclosed in one embodiment of the present invention;

[0029] Figure 3 A structural diagram of a metal nanowire polarizer disclosed in one embodiment of the present invention;

[0030] Figure 4 This is a structural diagram of a metal nanowire polarizer disclosed in one embodiment of the present invention.

[0031] Description of reference numerals:

[0032] Stretchable base film 10; metal nanowires 20; directional metal nanowire stretched film 30; optical protective film 40. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. In the description of the present invention, it should be noted that the term "or" is usually used in the sense of including "and / or", unless the content clearly indicates otherwise.

[0034] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] according to Figure 1 The present invention provides a method for preparing a metal nanowire polarizer, comprising:

[0037] Step 101, providing a stretchable base film 10, and flattening the stretchable base film 10;

[0038] Step 102, coating the alcohol-based metal nanowire 20 ink on one side of the stretchable base film 10, and then placing it in a drying box to dry the alcohol-based metal nanowire 20 ink to obtain a composite stretchable film;

[0039] Step 103, placing the composite stretchable film on a heating stretching device for uniaxial stretching to 4-7 times, to obtain a directional metal nanowire stretched film 30;

[0040] Step 104 , coating the side of the oriented metal nanowire stretched film 30 coated with the alcohol-based metal nanowire 20 ink with a polymer resin UV-curable glue, then drying and curing the film, and rolling it up to obtain a metal nanowire polarizer.

[0041] A method for preparing a metal nanowire polarizer proposed in this specification is a method for manufacturing a large-area thin-film metal nanowire polarizer based on the existing polarizer structure and existing technical process equipment. The structure of the polarizer includes a stretchable base film 10; a metal aligned nanowire layer located on the stretchable base film 10; an optical protective layer located on the metal nanowire 20 layer, which can enhance the adhesion and weather resistance of the metal nanowires 20 and the stretchable base film 10. The polarizer has a translucent appearance and a light transmission axis. When natural light is incident, half of the light is transmitted and half of the light is absorbed. This metal nanowire polarizer has the characteristics of metal wire grid polarizers that are polarized in various bands such as infrared light, visible light and ultraviolet light, and has the characteristics of being able to be industrialized in large-area thin films. At the same time, it is compatible with the technical processes and production equipment for the manufacture of existing polarizers.

[0042] In one embodiment of this specification, step 101 specifically includes:

[0043] The stretchable base film 10 is a PETG film, and the thickness of the PETG film is 60-100 μm and the width is 30-300 cm.

[0044] Specifically, PETG, whose full English name is Poly (ethyleneterephthalateco-1,4-cylclohexylenedimethylene terephthalate), is a transparent, non-crystalline copolyester. The PETG sheet has outstanding toughness and high impact strength. In a preferred embodiment, the stretchable base film 10PETG is unrolled on the nano silver wire transparent conductive film production line, and the PETG base film has a thickness of 75μm and a width of 60cm.

[0045] In one embodiment of this specification, step 102 specifically includes:

[0046] Providing an alcohol-based metal nanowire 20 ink, wherein the solid content of the metal nanowire 20 in the alcohol-based metal nanowire 20 ink is 0.5-5wt%;

[0047] The alcohol-based metal nanowire 20 ink is coated on one side surface of the stretchable base film 10 by a wire rod, a row brush, or a multi-channel slit coating head installed by a coating line;

[0048] The temperature in the drying box is set to be lower than the softening temperature of the stretchable base film 10 to dry the alcohol-based metal nanowire 20 ink coated on the stretchable base film 10. The transmittance of the obtained composite stretchable film is 15-25%.

[0049] Specifically, the alcohol-based ink is a metal nanowire 20 dispersion liquid that can evenly disperse the metal nanowires 20 without agglomeration, and the solid content of the metal nanowires 20 is 0.5-5wt%. The directional coating of the alcohol-based metal nanowire 20 ink is to coat the alcohol-based metal nanowire 20 ink onto one side surface of the stretchable base film 10 by a wire rod installed on a coating line, or a row brush, or a multi-hole slit coating head, and the metal nanowires 20 in the ink coming out of the coating head tend to be preferentially oriented along the outflow direction, and then the ink drying step is performed.

[0050] In a preferred embodiment, on a drying device of a nanosilver wire transparent conductive film production line, the alcohol-based ink is dried at 50°C, which is lower than the softening temperature of the PETG film of 65°C, to obtain a composite stretchable film, i.e., a nanosilver wire anisotropic transparent conductive film, with a sheet resistance of about 0.5 ohms per square along the direction in which the ink flows out from the coating head, and a sheet resistance of about 1 ohm per square along the direction perpendicular to the direction in which the ink flows out from the coating head, and the transmittance of the composite stretchable film is about 20%.

[0051] In one embodiment of the present specification, the spacing between the liquid outlet units of the wire rod or the row brush, or the multi-channel slit coating head is less than 10 μm.

[0052] In a preferred embodiment, on a nano silver wire transparent conductive film production line, a PETG film with a thickness of 75 μm and a width of 60 cm is unwound, and an alcohol-based nano silver wire ink is directionally coated from a coating head to one side of the surface of the stretchable base film 10 PETG by a coating machine, and the nano silver wire ink has a solid content of 3wt%, an average diameter of 50nm, and an average length of 5μm. It should be noted that, in general, the stretchable base film 10 is a PET film that is not stretchable, and the nano silver wire transparent conductive film must have both high transmittance and low sheet resistance. The typical parameters are a transmittance of 80% and a sheet resistance of 10 ohms per square. The nano silver wire polarizer must have a high degree of polarization and a high transmittance, so the sheet resistance must be smaller, so the amount of nano silver wire ink applied must be relatively excessive.

[0053] In one embodiment of this specification, step 103 specifically includes:

[0054] The temperature in the heating and stretching device is set to be within the softening temperature range of the stretchable base film 10;

[0055] Based on the dry stretching process, the composite stretchable film is uniaxially stretched to 4-7 times, and the light transmittance of the obtained directional metal nanowire stretched film 30 is more than 40%.

[0056] Specifically, the stretching process is carried out within the softening temperature range of the stretchable base film 10. For the PETG film, the stretching temperature range is 65 to 75°C. The process adopts dry stretching and is carried out in a constant temperature drying tunnel furnace. In a preferred embodiment, in a constant temperature tunnel furnace equipped with a multi-roll unidirectional stretching machine, the anisotropic transparent conductive film is unidirectionally stretched in the softening temperature range of 65 to 75°C of the PETG base film. The stretching direction is exactly the direction of small square resistance. The stretching multiple is 6 times, and a directional metal nanowire stretched film 30 with a film thickness of 25μm, a width of 20cm, and a transmittance of about 40% is obtained. Figure 2 In addition, the structure before stretching is an anisotropic transparent conductive film of silver nanowires, and the directional metal nanowire stretched film 30 obtained after stretching increases the anisotropy and can produce a polarizer effect.

[0057] In one embodiment of the present specification, step 104 specifically includes:

[0058] Applying polymer resin UV-curable glue to the side of the oriented metal nanowire stretched film 30 coated with the alcohol-based metal nanowire 20 ink by a slit coating machine or a micro-concave coating machine;

[0059] The temperature in the drying box is set to be lower than the softening temperature of the stretchable base film 10 to dry the polymer resin UV-curable glue.

[0060] Specifically, on the production line of the nano silver wire transparent conductive film, a polymer resin UV-curable glue is coated on one side of the stretched metal nanowire stretched film 30 with the metal nanowire 20 layer by a slit coating machine or a micro-concave coating machine, and then dried at a temperature lower than the softening temperature of the base film. In a preferred real-time method, the drying temperature of the PETG film glue is below 65° C. The amount of glue applied is preferably sufficient to effectively cover the nano silver wire layer, and the thickness is greater than 50 nm.

[0061] In one embodiment of the present specification, the oriented metal nanowire stretched film 30 after drying the polymer resin UV-curable glue is placed in a UV curing device to cure the dried polymer resin UV-curable glue to obtain an optical protective film 40.

[0062] Specifically, the directional metal nanowire stretched film 30 after drying the polymer resin UV-curable glue is placed in a UV curing device, the polymer resin UV-curable glue is cured to obtain an optical protective layer, and finally rolled up to obtain a metal nanowire polarizer.

[0063] In one embodiment of the present specification, the thickness of the optical protective film 40 is 10-1000 nm.

[0064] The metal nanowires 20 in this specification are one or more combinations of silver, gold, copper, nickel, iron, aluminum, zinc, and magnesium. In the embodiment, nanosilver wires are preferably used, with a diameter of 10-200 nm and a length of 1-20 μm.

[0065] It should be noted that in the specification, short and thick metal nanowires 20 with a relatively rigid length-to-thickness ratio of about 100 are preferably used, and metal nanowires 20 with a length-to-thickness ratio of thousands are not suitable, because metal nanowires 20 with a large length-to-thickness ratio are easy to bend and not easy to be straightened. In addition, the amount of alcohol-based metal nanowire 20 ink applied should be such that after the ink is dried, the conductivity of the obtained composite stretchable film is anisotropic, and the conductivity along the direction of the ink flowing out from the coating head is more than twice the conductivity along the direction perpendicular to the outflow direction, and the light transmittance of the obtained transparent composite stretchable film is only about 20%. After the base film is stretched 4-7 times along the direction of the ink flowing out from the coating head, the light transmittance of the obtained metal nanowire polarizer becomes about 40% or more. These conditions are used as the criterion for determining the amount of metal nanowire 20 ink applied.

[0066] The principle of the metal nanowire polarizer of this specification: the metal nanowire polarizer appears as a translucent black-gray film in appearance. The technology can be simplified as follows: the metal nanowire 20 is first directional coated on one side of the stretchable base film 10, initially having a certain orientation, and then stretched unidirectionally with a stretching multiple of 4-7 times. Then, the metal nanowires 20 in the stretched film are mostly roughly oriented along the stretching direction, and then coated with a polymer resin to protect the metal nanowires 20. When light is incident on a thin layer of the metal nano-polarizer 40, light with a polarization direction along the stretching direction is easily absorbed by the metal nanowire 20, and light with a polarization direction perpendicular to the stretching direction is easily transmitted, that is, the perpendicular stretching direction is the direction of the light transmission axis. This is because the roughly oriented metal nanowires 20 have the polarizer function of a metal wire grid. Although they do not have a consistent grating constant like a metal wire grid polarizer, the uneven distribution of a small part of the metal nanowires 20 results in a range of values ​​for the grating constant, which is more conducive to the polarizer adapting to a wider wavelength range.

[0067] Metal nanowires 20 are emerging materials for transparent conductive films. The research direction of researchers in this field is how to coat the metal nanowires 20 so that the difference in conductive anisotropy is as small as possible, that is, the difference in orientation anisotropy of the metal nanowires 20 is as small as possible. However, the content mentioned in this specification goes the other way, that is, the difference in orientation anisotropy of the metal nanowires 20 is as large as possible. The clever design of the coating extrusion port, coating speed, liquid flow angle, etc., can make the orientation anisotropy of the metal nanowires 20, and after the base film is stretched several times, this anisotropy will inevitably be amplified, so it is beyond doubt that this directional arrangement of metal nanowire stretched film 30 has the function of a metal wire grid polarizer.

[0068] Compared with existing iodine-based polarizers, metal nanowire polarizers may be inferior or even far behind in optical indicators such as polarization degree, but in the field of non-liquid crystal display devices, such as ultraviolet light, infrared light, terahertz, microwave, millimeter wave, centimeter wave and other fields, the requirements for polarizers do not need to have too high a polarization degree. One of the research directions in the field of polarizer technology is to make polarizers ultra-thin, but it is difficult to thin the sandwich structure of existing iodine-based polarizers. Therefore, metal nanowire polarizers are an effective solution to achieve large-area thin-film and ultra-thin metal wire grid polarizers. They have great potential in non-visible light band devices and have more advantageous application prospects in OLED flexible display devices.

[0069] The above is a detailed introduction to a method for preparing a metal nanowire polarizer in an embodiment of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for general technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for preparing a metal nanowire polarizer, characterized in that: include: Providing a stretchable base film, and unrolling the stretchable base film; the stretchable base film is a PETG film, the PETG film has a thickness of 60-100 mm and a width of 30-300 cm; The method comprises coating an alcohol-based metal nanowire ink on one side of the stretchable base film, and then placing the base film in a drying oven to dry the alcohol-based metal nanowire ink to obtain a composite stretchable film; specifically comprising: Providing an alcohol-based metal nanowire ink, wherein the solid content of the metal nanowires in the alcohol-based metal nanowire ink is 0.5-5wt%, and the aspect ratio of the metal nanowires is 100; The alcohol-based metal nanowire ink is coated on one side of the stretchable base film by a wire rod, a row brush, or a multi-porous slit coating head installed on a coating line; the spacing between the liquid outlet units of the wire rod, the row brush, or the multi-porous slit coating head is less than 10 mm; The temperature in the drying box is set to be lower than the softening temperature of the stretchable base film, so as to dry the alcohol-based metal nanowire ink coated on the stretchable base film, and the transmittance of the obtained composite stretchable film is 15-25%; Placing the composite stretchable film on a heating and stretching device for uniaxial stretching to 4-7 times to obtain a directional metal nanowire stretch film; comprising: setting the temperature in the heating and stretching device to within the softening temperature range of the stretchable base film; Based on the dry stretching process, the composite stretchable film is uniaxially stretched to 4-7 times, and the light transmittance of the obtained directional metal nanowire stretched film is more than 40%; The side of the oriented metal nanowire stretched film coated with the alcohol-based metal nanowire ink is coated with a polymer resin ultraviolet light curing glue, followed by drying and curing treatment, and then rolled up to obtain a metal nanowire polarizer.

2. The method according to claim 1, characterized in that The side of the oriented metal nanowire stretched film coated with the alcohol-based metal nanowire ink is coated with a polymer resin ultraviolet light curing glue, and then dried and cured, and rolled up to obtain a metal nanowire polarizer, including: The polymer resin UV-curable glue is coated on the side of the oriented metal nanowire stretched film coated with the alcohol-based metal nanowire ink by a slit coater or a micro-concave coater; The temperature in the drying box is set to be lower than the softening temperature of the stretchable base film, so as to dry the polymer resin UV-curable glue.

3. The method according to claim 2, characterized in that The side of the oriented metal nanowire stretched film coated with the alcohol-based metal nanowire ink is coated with a polymer resin ultraviolet light curing glue, and then dried and cured, and rolled up to obtain a metal nanowire polarizer, including: The oriented metal nanowire stretched film after the polymer resin UV-curable glue is dried is placed in a UV curing device to cure the dried polymer resin UV-curable glue to obtain an optical protective film.

4. The method according to claim 3, characterized in that The optical protective film has a thickness of 10 to 1000 nm.

5. The method according to any one of claims 1 to 4, characterized in that: The metal nanowires are one or more combinations of silver, gold, copper, nickel, iron, aluminum, zinc, and magnesium.

6. The method according to claim 5, characterized in that The metal nanowire has a diameter of 10 to 200 nm and a length of 1 to 20 mm.

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