Polarizing film and method for producing same

Abstract

The invention provides a preparation method of a polarizing film. The preparation method comprises the following steps: S1, providing a flat substrate; s2, preparing a liquid crystal polymer and metal nanorod liquid mixed material system; s3, performing uniform liquid crystal alignment on the substrate by adopting a light-operated liquid crystal alignment technology; s4, coating a substrate with the material system; and S5, the substrate is cured through irradiation of UV light, so that liquid crystal molecules are cross-linked with one another, and a layer of thin film is formed. The invention further provides the polarizing film, and the polarizing film is obtained through the preparation method of the polarizing film. According to the polarizing film and the preparation method thereof, the polarizing film is prepared by using the metal nano material, and compared with iodine molecules, the prepared polarizing film is smaller in thickness and higher in high-temperature and high-humidity resistance; compared with a dichroic dye, the conductive performance is better, and the polarization performance is stronger. And the compatibility problem of the thickness, the polarization degree and the transmittance is effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical films, and in particular to a polarizing film and a preparation method thereof. Background Art

[0002] Polarizers with light transmission and shielding properties are the basic components of liquid crystal displays (LCDs) and are widely used in display devices such as liquid crystal displays and organic light-emitting diodes. The core of polarizers is polarizing film, which is a transparent film with dichroic properties. It allows light vibrations parallel to the transmission axis to pass through, while light perpendicular to this direction is absorbed. This phenomenon is called polarization of light; the light that passes through is light with the same vibration direction, which is called polarized light; the reflected light is absorbed because it becomes perpendicular to the transmission axis of the polarizing film after reflection.

[0003] At present, polarizing films only have two types of mass-produced products: high-molecular iodine polyvinyl alcohol type and dichroic dye type. The main materials of iodine polyvinyl alcohol type polarizing films are polyvinyl alcohol (PVA) and iodine. Among them, PVA is mainly composed of light atoms such as carbon, hydrogen and oxygen. It has high transparency and high ductility, as well as good iodine adsorption and film-forming properties. Iodine polyvinyl alcohol type polarizing films can easily obtain high polarization and high transmittance, that is, high depolarization ratio, but the film thickness is large, and iodine volatilization is prone to occur in high temperature environments, thus losing the polarizing effect.

[0004] Liquid crystal polarizing film is widely used in dichroic dye type polarizing film. Liquid crystal polarizing film uses a mixture of liquid crystal polymer and dichroic dye (organic dye) as the material system. The substrate is aligned through the light-controlled alignment technology to induce the orientation of liquid crystal molecules, thereby driving the dichroic dye molecules in the material system to be oriented, so that the light vibrating parallel to the long axis direction of the dichroic dye molecules is absorbed, and the light vibrating perpendicular to the long axis direction is transmitted, realizing the polarization function. However, the polarization of this polarizing film is usually worse than that of iodine-based polyvinyl alcohol type polarizing film, and the depolarization ratio is relatively low. Summary of the invention

[0005] The object of the present invention is to provide a polarizing film and a preparation method thereof, so as to solve the problem that the polarizing film is incompatible with thin thickness and high polarization degree and high transmittance.

[0006] The technical solution for achieving the purpose of the present invention is as follows: The present invention provides a method for preparing a polarizing film, characterized in that it comprises:

[0007] S1, providing a flat substrate;

[0008] S2, preparing a material system of a liquid crystal polymer mixed with a metal nanorod liquid;

[0009] S3, performing uniform liquid crystal alignment on the substrate using a light-controlled liquid crystal alignment technology;

[0010] S3, coating the material system onto the substrate;

[0011] S4, curing the substrate by irradiating with UV light, so that the liquid crystal molecules are cross-linked to form a thin film.

[0012] In one embodiment of the present invention, the metal nanorod solution includes metal nanorods, and the metal nanorods are aluminum nanorods.

[0013] In one embodiment of the present invention, the length of the aluminum nanorods is 90 nm to 110 nm, and the width is 10 nm to 100 nm.

[0014] In one embodiment of the present invention, in step S3, the hydrogen radicals of the liquid crystal polymer act as initiators to drive the aluminum nanorods to align.

[0015] In one embodiment of the present invention, step S2 includes: coating a layer of alignment film on the substrate, irradiating the substrate with polarized ultraviolet light to cause a photochemical reaction in the polymer in the alignment film to generate anisotropy, thereby inducing the orientation of liquid crystal molecules in the liquid crystal polymer.

[0016] In one embodiment of the present invention, the content of liquid crystal molecules in the liquid crystal polymer used in step S2 is 18% to 22%, and the concentration of the metal nanorod solution is 0.4 mg / ml to 0.6 mg / ml.

[0017] In one embodiment of the present invention, step S2 includes: taking 45g-55g of the liquid crystal polymer and 15g-150g of the metal nanorod solution, mixing the liquid crystal polymer and the metal nanorod solution in proportion, and irradiating them with infrared light.

[0018] The present invention also provides a polarizing film, which is obtained by the polarizing film preparation method as described above.

[0019] In one embodiment of the present invention, the thickness of the polarizing film is 5 μm to 10 μm.

[0020] The beneficial effects of the present invention and the prior art are as follows: in the polarizing film and the preparation method thereof of the present invention, the polarizing film is prepared by using metal nanomaterials, and the thickness of the polarizing film prepared is smaller than that of iodine molecules; compared with dichroic dyes, the conductivity is better and the polarization is stronger, which effectively solves the compatibility problem between thickness, polarization degree and transmittance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1FIG. 4 is a schematic diagram of a first arrangement of aluminum nanorods and liquid crystal molecules of a polarizing film according to an embodiment of the present invention.

[0022] Figure 2 FIG. 4 is a schematic diagram of a second arrangement of aluminum nanorods and liquid crystal molecules in a polarizing film according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0024] The present invention provides a method for preparing a polarizing film, comprising:

[0025] S1, providing a flat substrate 11;

[0026] S2, preparing a material system of a liquid crystal polymer mixed with a metal nanorod liquid;

[0027] S3, using a light-controlled liquid crystal alignment technology to perform uniform liquid crystal alignment on the substrate 11;

[0028] S3, coating the material system onto the substrate 11;

[0029] S4, curing the substrate 11 by irradiating with UV light, so that the liquid crystal molecules 12 are cross-linked to form a thin film.

[0030] In the polarizing film and preparation method of the present invention, the polarizing film is prepared by using metal nanomaterials. Compared with iodine molecules, the polarizing film is thinner and has stronger resistance to high temperature and humidity; compared with dichroic dyes, the conductivity is better and the polarization is stronger, which effectively solves the compatibility problem between thickness, polarization degree and transmittance.

[0031] In this embodiment, the metal nanorod solution includes metal nanorods, and the metal nanorods are aluminum nanorods 13. It should be noted that gold, silver, copper, and aluminum are all good conductor materials. Considering that gold and silver are expensive, aluminum is cheap and has corrosion resistance, good thermal stability, and strong light absorption ability, and is an ideal polarizing material, so aluminum nanorods 13 are selected in this embodiment.

[0032] In this embodiment, the length of the aluminum nanorod 13 is 90nm to 110nm, and the width is 10nm to 100nm. Those skilled in the art can set the length to 90nm, 92nm, 95nm, 98nm, 100nm, 102nm, 104nm, 106nm, 108nm, 110nm, etc. according to actual conditions, and no unique limitation is made here; those skilled in the art can set the width to 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc. according to actual conditions, and no unique limitation is made here.

[0033] Specifically, the temperature of the laboratory is first controlled at 20°C to 25°C, the length of the aluminum nanorod 13 is selected to be 100nm, and the width is from 10nm to 100nm, with a gradient of 10nm, and an infrared spectrometer is used to perform infrared testing, measure the extinction coefficient of each aluminum nanorod solution, and record the value. The experiment shows that when the width of the aluminum nanorod 13 is about 40nm, the extinction coefficient of the aluminum nanorod 13 reaches a peak value, that is, the absorption effect of the incident light is the best. Therefore, the aluminum nanorod 13 with a length of 100nm and a width of 40nm is preferred.

[0034] In this embodiment, the content of the liquid crystal molecules 12 in the liquid crystal polymer is 18% to 22%, and the concentration of the aluminum nanorod solution is 0.4 mg / ml to 0.6 mg / ml. Those skilled in the art can set the content of the liquid crystal molecules 12 to 18%, 19%, 20%, 21%, 22%, etc. according to actual conditions, and this is not a sole limitation; those skilled in the art can set the concentration of the aluminum nanorod solution to 0.4 mg / ml, 0.45 mg / ml, 0.5 mg / ml, 0.55 mg / ml, 0.6 mg / ml, etc. according to actual conditions, and this is not a sole limitation.

[0035] Further, take 45g to 55g of liquid crystal polymer and 15g to 150g of aluminum nanorod solution, mix the liquid crystal polymer and the metal nanorod solution in proportion, and irradiate with infrared light. Those skilled in the art can set the weight of the liquid crystal polymer to 45g, 46g, 47g, 48g, 49g, 50g, 51g, 52g, 53g, 54g, 55g, etc. according to actual conditions, which is not limited here; those skilled in the art can set the weight of the aluminum nanorod solution to 15g, 20g, 25g, 30g, 35g, 40g, 45g, 50g, 55g, 60g, 70g, 80g, 90g, 100g, 115g, 120g, 130g, 140g, 150g, etc. according to actual conditions, which is not limited here.

[0036] Specifically, the liquid crystal polymer used in the experiment has a liquid crystal molecule 12 content of 20%, and the aluminum nanorod solution concentration is 0.5 mg / ml. Take 50g of liquid crystal polymer and 15g to 150g of aluminum nanorod solution, mix the liquid crystal polymer and the aluminum nanorod solution in a certain proportion, and irradiate with infrared rays, measure the maximum transmission light intensity and the minimum projection light intensity of the material system when the mass ratio of the two is 3:1, 2.5:1, 2:1, 1.5:1...1:3, respectively, bring the calculation formula of the depolarization ratio into the calculation formula of the depolarization ratio to calculate the depolarization ratio under each material system ratio, and use MATLAB software to fit the change curve of the depolarization ratio and the material system ratio. It can be concluded from the image that when the mass ratio of the material system is about 1.5:1, the depolarization ratio can reach 44dB, which is close to the optimal mass ratio of the material system.

[0037] Afterwards, a liquid crystal polarizing film is prepared according to the above preferred data. Preparation method: (1) The liquid crystal polymer and the aluminum nanorod solution are mixed and stirred in a ratio of 1.5:1 to form a material system for making a liquid crystal polarizing film; (2) The substrate 11 is uniformly aligned with the liquid crystal by using a light-controlled liquid crystal alignment technology; specifically, a layer of alignment film is coated on the substrate 11, and the substrate 11 is irradiated with polarized ultraviolet light to make the polymer in the alignment film undergo a photochemical reaction to generate anisotropy, thereby inducing the orientation of the liquid crystal molecules 12; (3) The material system is coated on the substrate 11 in a certain thickness by scraping or spin coating; (4) The substrate 11 is cured by UV light irradiation to make the liquid crystal molecules 12 cross-linked to form a thin film, which is the liquid crystal polarizing film.

[0038] In this embodiment, after the liquid crystal molecules 12 are aligned, the hydrogen radicals of the liquid crystal polymer act as initiators to drive the aluminum nanorods 13 to be aligned. Generally, the length direction of the aluminum nanorods 13 is parallel to the length direction of the liquid crystal molecules 12. Figure 1 At this time, the incident light parallel to the length direction of the liquid crystal molecules 12 is absorbed, and the incident light perpendicular to the length direction of the liquid crystal molecules 12 is transmitted. In this way, polarized light vibrating in a certain direction can be obtained, realizing the polarization function.

[0039] It is understood that the functional groups in the liquid crystal polymer can be modified to convert hydrogen radicals into methyl radicals, which can induce the length direction of the aluminum nanorods 13 to be perpendicular to the length direction of the liquid crystal molecules 12, such as Figure 2 At this time, the incident light parallel to the length direction of the liquid crystal molecules 12 is transmitted, and the incident light perpendicular to the length direction of the liquid crystal molecules 12 is absorbed.

[0040] The present invention further provides a polarizing film. The polarizing film of this embodiment is obtained by the above-mentioned method for preparing the polarizing film.

[0041] In this embodiment, the polarizing film based on the aluminum nanorods 13 and the liquid crystal polymer material system has a thickness of 5 μm to 10 μm. Those skilled in the art can set the thickness to 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc. according to actual conditions, and this is not limited here.

[0042] In this document, unless otherwise specified or 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 an indirect connection 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 can be understood according to specific circumstances.

[0043] In this document, the directions or positional relationships indicated by terms such as "up", "down", "front", "back", "left", "right", "top", "bottom", "inside", "outside", "vertical", and "horizontal" are based on the directions or positional relationships shown in the accompanying drawings and are only for the clarity of expressing the technical solutions and the convenience of description, and therefore should not be understood as limitations of the present invention.

[0044] In this document, the terms "comprises," "comprising," or any other variations thereof, are intended to cover a non-exclusive inclusion of elements other than those listed and may also include additional elements not expressly listed.

[0045] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a polarizing film, characterized in that: include: S1, providing a flat substrate; S2, preparing a material system of a liquid crystal polymer mixed with a metal nanorod liquid; S3, performing uniform liquid crystal alignment on the substrate using a light-controlled liquid crystal alignment technology; S4, coating the material system onto the substrate; S5, curing the substrate by irradiating with UV light, so that the liquid crystal molecules are cross-linked to form a thin film.

2. The method for preparing a polarizing film according to claim 1, characterized in that: The metal nanorod solution comprises metal nanorods, and the metal nanorods are aluminum nanorods.

3. The method for preparing a polarizing film according to claim 2, characterized in that: The aluminum nanorod has a length of 90nm to 110nm and a width of 10nm to 100nm.

4. The method for preparing a polarizing film according to claim 2, characterized in that: In step S3, hydrogen radicals of the liquid crystal polymer serve as initiators.

5. The method for preparing a polarizing film according to claim 1, characterized in that: The step S3 comprises: coating a layer of alignment film on the substrate, irradiating the substrate with polarized ultraviolet light, so that the polymer in the alignment film undergoes a photochemical reaction to generate anisotropy.

6. The method for preparing a polarizing film according to claim 1, characterized in that: The content of liquid crystal molecules in the liquid crystal polymer used in step S2 is 18% to 22%, and the concentration of the metal nanorod solution is 0.4 mg / ml to 0.6 mg / ml.

7. The method for preparing a polarizing film according to claim 6, characterized in that: The mass ratio of the liquid crystal polymer to the metal nano solution is 3:1 to 1:

3.

8. A polarizing film, characterized in that: The polarizing film is obtained by the method for preparing the polarizing film according to any one of claims 1 to 7.

9. The polarizing film according to claim 8, characterized in that: The thickness of the polarizing film is 5 μm to 10 μm.

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