Composite color liquid crystal polymer reflecting film for mobile phone back shell and preparation method of composite color liquid crystal polymer reflecting film

Abstract

The invention discloses a composite color liquid crystal polymer reflecting film for a mobile phone back shell and a preparation method thereof, and relates to the technical field of liquid crystal polymers, the composite color liquid crystal polymer reflecting film is a liquid crystal polymer film based on selective Bragg reflection and having a cholesteric phase structure, and the film selectively reflects left-hand or right-hand circularly polarized light. When a reflection band is located in a visible region, the film presents a structural color, the color has angle dependence, the film realizes a composite color through a one-time coating process, the liquid crystal polymer film contains a diacrylate liquid crystal compound and a chiral additive, and the reflection band of the liquid crystal polymer film can be located in an ultraviolet region, a visible region and a near-infrared region. The color and the function of the composite color are determined by adjusting the position and the intensity of the reflection spectrum band. According to the composite color liquid crystal polymer reflecting film for the mobile phone back shell and the preparation method thereof, the composite color can be realized through one-time coating, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of liquid crystal polymers, in particular to a composite color liquid crystal polymer reflective film for a mobile phone back shell and a preparation method thereof. Background Art

[0002] With the development of science and technology, the requirements for the decoration and functions of the back shells of mobile phones and other electronic devices are becoming increasingly diversified. The existing liquid crystal film has certain limitations in reflecting light. For example, the double-layer coating to achieve composite colors has complex processes and low yields, which cannot well meet the requirements of mobile phone back shells for multi-functions and rich colors. To this end, in response to the above problems, a composite color liquid crystal polymer reflective film for mobile phone back shells and its preparation method are designed to better meet the actual use needs. Summary of the invention

[0003] The purpose of the present invention is to provide a composite color liquid crystal polymer reflective film for mobile phone back shell and its preparation method, so as to solve the problems of complex process and low yield of double-layer coating to achieve composite color proposed in the above background technology.

[0004] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a composite color liquid crystal polymer reflective film for a mobile phone back cover, the composite color liquid crystal polymer reflective film is based on selective Bragg reflection, and has a liquid crystal polymer film with a cholesteric phase structure, the film selectively reflects left-handed or right-handed circularly polarized light, and presents a structural color when the reflection band is in the visible region, and the color has angle dependence, and the film realizes composite color through a one-time coating process, and the liquid crystal polymer film contains a diacrylate liquid crystal compound and a chiral additive.

[0005] Furthermore, the reflection band of the liquid crystal polymer film may be located in the ultraviolet region, the visible light region and the near infrared region, and the color and function of the composite color can be determined by adjusting the position and intensity of the reflection band.

[0006] Furthermore, the diacrylate liquid crystal compounds regulate the phase change behavior of the liquid crystal compounds by introducing different side groups and chiral functional groups, thereby broadening the liquid crystal phase change temperature range and lowering the freezing point of the liquid crystal compounds.

[0007] Furthermore, in the method for preparing a composite color liquid crystal polymer reflective film for a mobile phone back cover, during the preparation process, four different liquid crystal film preparation principles are controlled, including controlling light intensity, light irradiation time, polymerization temperature and polymerization time to prepare the main formula of the coating liquid.

[0008] Furthermore, the preparation process also includes the preparation of auxiliary agents.

[0009] Furthermore, the liquid crystal polymer film is pilot-coated on a pilot coating line by precisely controlling various parameters, and is subjected to relevant test characterizations, including but not limited to reflection spectrum testing, color characteristic testing, and mechanical property testing.

[0010] Furthermore, the liquid crystal polymer film can be used for the reflection of blue light related to the colorful back cover of mobile phones and eye protection.

[0011] Furthermore, the preparation process of the liquid crystal polymer film involves the synthesis of liquid crystal compounds and chiral additives, the proportioning of the liquid crystal mixture, the addition of various chemical additives and the pilot line coating operation.

[0012] Further, the method includes the steps of synthesizing a liquid crystal compound and a chiral additive, wherein different side groups and chiral functional groups are introduced during the synthesis of the liquid crystal compound to regulate the phase change behavior of the liquid crystal compound;

[0013] The method comprises a proportioning step of a liquid crystal mixture, during which the diacrylate liquid crystal and the chiral additive are reasonably proportioned;

[0014] The method includes the steps of adding various chemical additives, including but not limited to photoinitiators, leveling agents, adhesion promoters and other additives used to assist coating and optimize film performance;

[0015] The method comprises a pilot line coating step, on which the coating operation is performed by precisely controlling parameters such as light intensity, light irradiation time, polymerization temperature and polymerization time.

[0016] Furthermore, when preparing the main formula of the coating liquid, control is performed based on four principles: thermochromism, photochromism, polymerization-induced molecular migration and polymerization-induced phase separation, so as to obtain a coating liquid with desired properties.

[0017] Compared with the prior art, the beneficial effects of the present invention are: the composite color liquid crystal polymer reflective film for the back cover of a mobile phone and its preparation method solve the problems of adhesion, crystal domain size and shrinkage holes of the liquid crystal film, and can achieve composite colors in one coating, thereby improving production efficiency. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the 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.

[0019] The invention provides a technical solution: a composite color liquid crystal polymer reflective film for a mobile phone back shell, the film selectively reflects left-handed or right-handed circularly polarized light, presents structural color when the reflection spectrum band is in the visible region, and the color has angle dependence, and the film realizes composite color through a one-time coating process, the liquid crystal polymer film comprises a diacrylate liquid crystal compound and a chiral additive, the reflection spectrum band of the liquid crystal polymer film can be located in the ultraviolet region, the visible light region and the near-infrared region, the color and function of the composite color are determined by adjusting the position and intensity of the reflection spectrum band, and the diacrylate liquid crystal compound regulates the phase change behavior of the liquid crystal compound by introducing different side groups and chiral functional groups, thereby broadening the liquid crystal phase change temperature range and reducing the freezing point of the liquid crystal compound.

[0020] A method for preparing a composite color liquid crystal polymer reflective film for a mobile phone back cover. During the preparation process, four different liquid crystal film preparation principles are controlled, including controlling light intensity, light irradiation time, polymerization temperature and polymerization time to prepare the main formula of the coating liquid. The preparation process also includes the preparation of additives. The liquid crystal polymer film is subjected to pilot coating on a pilot coating line by precisely controlling various parameters, and is subjected to relevant test characterization, the test characterization includes but is not limited to reflection spectrum test, color characteristic test and mechanical property test. The liquid crystal polymer film can be applied to the blue light reflection related to the colorful and eye protection of the mobile phone back cover. The preparation process of the liquid crystal polymer film involves the synthesis of liquid crystal compounds and chiral additives, the ratio of liquid crystal mixtures, the addition of various chemical additives and the pilot line coating operation, including liquid crystal The invention relates to a method for synthesizing compounds and chiral additives, wherein different side groups and chiral functional groups are introduced into the synthesis of liquid crystal compounds to regulate the phase change behavior of liquid crystal compounds; a method for proportioning a liquid crystal mixture, wherein the diacrylate liquid crystal and the chiral additive are reasonably proportioned during the proportioning process; a method for adding various chemical additives, wherein the added additives include but are not limited to photoinitiators, leveling agents, adhesion promoters and other additives for assisting coating and optimizing film performance; a method for coating on a pilot line, wherein the coating operation is performed on the pilot coating line by precisely controlling parameters such as light intensity, light irradiation time, polymerization temperature and polymerization time, and when preparing the main formula of the coating liquid, the coating liquid is controlled based on four principles: thermochromism, photochromism, polymerization-induced molecular migration and polymerization-induced phase separation, so as to obtain a coating liquid with the desired properties.

[0021] The synthesis steps of liquid crystal compounds are as follows: first, atom transfer radical polymerization is used to react diacrylate with a chiral catalyst to generate a polymer containing chiral carbon atoms. Then, by changing the reaction conditions, such as the type of catalyst, reaction temperature, reaction time, etc., polymers with different side groups and chiral functional groups can be obtained. Finally, through the refining and purification process, a liquid crystal compound with good crystal morphology and optical properties is obtained. High-purity diacrylate is selected as the main monomer. Before use, the diacrylate needs to be strictly dried to remove the water and impurities that may be contained therein, because these impurities may interfere with the polymerization reaction. For example, the diacrylate can be purified by vacuum distillation under the protection of inert gas. It is very important to select a suitable chiral catalyst. Common chiral catalysts include metal-ligand complexes, such as catalysts based on metal ions such as copper and ruthenium and chiral ligands. These chiral catalysts need to be accurately weighed and stored and used in anhydrous and oxygen-free environment to ensure their activity. Select a suitable solvent to dissolve the diacrylate and the chiral catalyst. Commonly used solvents include toluene and tetrahydrofuran (THF ), etc., the solvent needs to be dehydrated and deoxygenated. For example, toluene can be dried with sodium-potassium alloy and then distilled to obtain an anhydrous and oxygen-free solvent to ensure that the polymerization reaction is carried out in a pure environment. The diacrylate and the chiral catalyst are added to the pretreated solvent in a certain molar ratio. The molar ratio of the diacrylate to the chiral catalyst is usually between 100:1 and 1000:1. The specific ratio depends on the activity of the catalyst and the molecular weight of the desired polymer. As the reaction proceeds, the viscosity of the solution gradually increases. The reaction progress is tracked by monitoring the viscosity change of the reaction system and the monomer conversion rate (which can be determined by gas chromatography or nuclear magnetic resonance and the like). The reaction time is generally between 12 and 72 hours. For example, for a target polymer with a smaller molecular weight, the reaction time may be between 12 and 24 hours, while for a polymer with a larger molecular weight, the reaction time may be as long as 48 to 72 hours. When the reaction temperature is lowered, the polymerization reaction rate will slow down, which may lead to a narrower molecular weight distribution of the polymer. For example, when the reaction temperature is lowered from 60°C to 40°C, the molecular weight of the generated polymer may be more uniform, and the formation of the chiral structure may be more selective.

[0022] Increasing the reaction temperature will speed up the reaction rate, but may lead to an increase in side reactions. For example, at higher temperatures, chain transfer reactions or polymer degradation reactions may occur, thus affecting the structure and properties of the polymer. By systematically changing the reaction temperature, such as testing at intervals of 10°C in the range of 40-100°C, the optimal temperature conditions can be found to synthesize polymers with specific side groups and chiral functional groups. Prolonging the reaction time: Prolonging the reaction time within a certain range can make the polymerization reaction more complete and improve the conversion rate of the monomer. For example, extending the reaction time from 24 hours to 48 hours may increase the molecular weight of the polymer and make the chiral structure more perfect. Shortening the reaction time: In some cases, when it is necessary to control the molecular weight of the polymer to be lower, the reaction time can be shortened. At the same time, a shorter reaction time may produce polymer intermediates with unique structures, which may have special liquid crystal properties after further processing.

[0023] Mixing steps of liquid crystal mixture: When preparing the liquid crystal mixture, factors such as the molecular weight, solubility, and compatibility of the liquid crystal compound need to be considered. By optimizing these factors, a liquid crystal mixture with good liquid crystal properties can be obtained. In addition, the chiral additives need to be selected and optimized to ensure that they can effectively affect the phase change behavior of the liquid crystal compound;

[0024] Adding steps of additives: When adding chemical additives, you can choose the appropriate type of additives according to actual needs and performance requirements. For example, you can choose photoinitiators to improve photosensitivity, leveling agents to improve coating fluidity, and adhesion promoters to enhance adhesion. By adding additives reasonably, you can further optimize the performance of the coating solution;

[0025] Pilot line coating steps: During the pilot stage, the coating parameters can be adjusted in real time by online monitoring of various performance indicators during the coating process, such as viscosity, solid content, coating thickness, etc., to ensure the consistency and stability of the coating quality. At the same time, by precisely controlling parameters such as light intensity, light irradiation time, polymerization temperature and polymerization time, the physical properties of the coating liquid can be optimized to meet the requirements of subsequent applications;

[0026] Test characterization: After coating is completed, a series of performance tests are required, such as reflectance spectrum test, color characteristic test and mechanical property test, to ensure that the coating liquid has good optical properties, color stability and mechanical properties.

[0027] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A composite color liquid crystal polymer reflective film for a mobile phone back cover, the composite color liquid crystal polymer reflective film is based on selective Bragg reflection, and has a liquid crystal polymer film with a cholesteric phase structure, characterized in that: The film selectively reflects left-handed or right-handed circularly polarized light, presents structural color when the reflection band is in the visible region, and the color is angle-dependent. The film achieves composite color through a one-time coating process, and the liquid crystal polymer film contains a diacrylate liquid crystal compound and a chiral additive.

2. The composite color liquid crystal polymer reflective film for a mobile phone back cover according to claim 1, characterized in that: The reflection band of the liquid crystal polymer film can be located in the ultraviolet region, the visible light region and the near infrared region. The color and function of the composite color are determined by adjusting the position and intensity of the reflection band.

3. The composite color liquid crystal polymer reflective film for a mobile phone back cover according to claim 2, characterized in that: Diacrylate liquid crystal compounds regulate the phase change behavior of liquid crystal compounds by introducing different side groups and chiral functional groups, thereby broadening the liquid crystal phase change temperature range and lowering the freezing point of the liquid crystal compounds.

4. A method for preparing a composite color liquid crystal polymer reflective film for a mobile phone back cover as claimed in any one of claims 1 to 3, characterized in that: During the preparation process, the main formula of the coating liquid is prepared by controlling four different liquid crystal film preparation principles, including controlling light intensity, light irradiation time, polymerization temperature and polymerization time.

5. The method for preparing a composite color liquid crystal polymer reflective film for a mobile phone back cover according to claim 4, characterized in that: The preparation process also includes the preparation of auxiliary agents.

6. The method for preparing a composite color liquid crystal polymer reflective film for a mobile phone back cover according to claim 4, characterized in that: The liquid crystal polymer film is pilot-coated on the pilot coating line by precisely controlling various parameters and undergoes relevant test characterization, including but not limited to reflection spectrum testing, color characteristic testing, and mechanical property testing.

7. The method for preparing a composite color liquid crystal polymer reflective film for a mobile phone back cover according to claim 4, characterized in that: Liquid crystal polymer film can be used for the colorful back cover of mobile phones and the reflection of blue light related to eye protection.

8. The method for preparing a composite color liquid crystal polymer reflective film for a mobile phone back cover according to claim 4, characterized in that: The preparation process of liquid crystal polymer film involves the synthesis of liquid crystal compounds and chiral additives, the proportion of liquid crystal mixture, the addition of various chemical additives and pilot line coating operations.

9. The method for preparing a composite color liquid crystal polymer reflective film for a mobile phone back cover according to claim 4, characterized in that: The method comprises the steps of synthesizing a liquid crystal compound and a chiral additive, wherein different side groups and chiral functional groups are introduced during the synthesis of the liquid crystal compound to regulate the phase change behavior of the liquid crystal compound; The method comprises a proportioning step of a liquid crystal mixture, during which the diacrylate liquid crystal and the chiral additive are reasonably proportioned; The method includes the steps of adding various chemical additives, including but not limited to photoinitiators, leveling agents, adhesion promoters and other additives used to assist coating and optimize film performance; The method comprises a pilot line coating step, on which the coating operation is performed by precisely controlling parameters such as light intensity, light irradiation time, polymerization temperature and polymerization time.

10. The method for preparing a composite color liquid crystal polymer reflective film for a mobile phone back cover according to claim 4, characterized in that: When preparing the main formula of the coating liquid, control is performed based on four principles: thermochromism, photochromism, polymerization-induced molecular migration and polymerization-induced phase separation to obtain a coating liquid with desired properties.