Liquid crystal microcapsule film with multiple responsiveness as well as preparation method and application of liquid crystal microcapsule film

Abstract

The invention relates to the technical field of liquid crystal microcapsule materials, and discloses a liquid crystal microcapsule film with multiple responsiveness and a preparation method and application thereof. The liquid crystal microcapsule film with multiple responsiveness comprises a PVA (polyvinyl alcohol) film and a large number of flat ellipsoid cholesteric liquid crystals which are uniformly dispersed in the PVA film, wherein the particle size of the cholesteric liquid crystal is 5.5 to 7.0 [mu] m; each cholesteric liquid crystal and PVA wrapping the cholesteric liquid crystal form a microcapsule structure. According to the liquid crystal microcapsule film disclosed by the invention, the spiral structure of the oblate ellipsoid-shaped liquid crystal microcapsule is subjected to controllable structural color change in an ultraviolet irradiation or temperature change process by virtue of a special preparation method and in combination with regulation and control on the proportion of the polymerizable monomer and the chiral agent, so that the liquid crystal microcapsule film has the composite characteristics of temperature and ultraviolet response; the sensitive response capability can be shown under multiple environment conditions, and the method can be widely applied to anti-counterfeiting films, intelligent labels and adjustable display materials.

Description

Technical Field

[0001] This application relates to the technical field of liquid crystal microcapsule materials, and particularly relates to a liquid crystal microcapsule film with multiple responsiveness, a preparation method thereof, and an application thereof. Background Art

[0002] Cholesteric liquid crystals (CLCs) are rod-shaped molecules organized in a helical manner. When the periodic length (referred to as the helical pitch) is within the visible light range, they exhibit structural colors, and the color of the reflected light can be adjusted by changing the helical pitch. They have both the fluidity of a liquid and the orderliness of a crystal, showing extremely rich self-assembled structures and unique physical and chemical properties. Despite many advantages, however, the fluidity of cholesteric liquid crystals makes them unstable, making it impossible to fabricate devices on a large scale. In the processing of traditional liquid crystal functional materials, an external alignment layer is relied on to induce the alignment of liquid crystal materials to improve the stability of liquid crystal materials. However, this will result in impurities and uneven thickness of liquid crystal materials, ultimately leading to uneven properties of liquid crystal functional materials.

[0003] By microencapsulating liquid crystal molecules, the problem of poor stability can be avoided. Cholesteric microcapsules consist of a liquid crystal core and a polymer shell, and usually exhibit a spherical geometry. The cholesteric phase in the core can maintain a fluid state, and the liquid crystal molecules are oriented under the induction of a surfactant, so that the orientation of the cholesteric phase can be efficiently induced. On the one hand, the polymer shell can enhance the stability of the material, maintain the stability of the structure under pressure, and improve the durability of the liquid crystal.

[0004] Preparing liquid crystal microcapsules by ultrasonic emulsification to encapsulate cholesteric liquid crystals is a very novel method. The microcapsules consist of an internal liquid crystal core and a polymer shell. This microcapsule structure has advantages in liquid crystal orientation induction and stability, and the formed film has good mechanical properties and fascinating structural colors. However, most existing studies have modified the microcapsule shell by adding polymerizable substances, but ignored the influence of the change of the core material on the microcapsules, resulting in the common problem of single response mode in existing liquid crystal microcapsule films, and it is impossible to achieve multiple responses to light, heat, and humidity simultaneously. There is an urgent need to develop new technologies to solve these problems. Summary of the Invention

[0005] This application provides a liquid crystal microcapsule film with multiple responsiveness, a preparation method thereof, and an application thereof, aiming to solve the technical problem that existing liquid crystal microcapsule films only respond to a single stimulus source (such as temperature, light, etc.) and are difficult to have the ability to respond to multiple stimulus sources simultaneously.

[0006] To achieve the above object, this application adopts the following technical solutions.

[0007] In the first aspect of the present application, a liquid crystal microcapsule film with multiple responsiveness is provided. The liquid crystal microcapsule film includes a PVA film and a large number of cholesteric liquid crystals in the shape of oblate ellipsoids uniformly dispersed inside the PVA film.

[0008] Among them, the particle size of the cholesteric liquid crystal is 5.5 - 7.0 μm; each cholesteric liquid crystal and the PVA wrapping the cholesteric liquid crystal form a microcapsule structure.

[0009] Preferably, by weight, the raw materials of the cholesteric liquid crystal include the following components:

[0010] Liquid crystal raw materials, including 76 - 93 wt% of rod-shaped liquid crystals, 5 - 20 wt% of liquid crystal polymerizable monomers, and 2 - 4 wt% of chiral agents;

[0011] Photoinitiator, and its dosage is 1 wt% of the dosage of the liquid crystal raw materials.

[0012] Preferably, the rod-shaped liquid crystal is 5CB;

[0013] The liquid crystal polymerizable monomer is C6M;

[0014] The chiral agent is R5011;

[0015] The photoinitiator includes any one of benzoin dimethyl ether, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, or 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone.

[0016] In the second aspect of the present application, a preparation method of the above liquid crystal microcapsule film with multiple responsiveness is provided, including:

[0017] S1, Weigh the liquid crystal monomer, liquid crystal polymerizable monomer, chiral agent, and photoinitiator according to the ratio, heat to the clearing point and mix evenly to obtain cholesteric liquid crystals;

[0018] S2, Add the cholesteric liquid crystals into the aqueous solution of polyvinyl alcohol, and through ultrasonic emulsification, disperse the cholesteric liquid crystal microspheres in the PVA solution to obtain an emulsion containing liquid crystal microcapsules;

[0019] S3, Add the emulsion into a petri dish and dry at room temperature to remove water to obtain a liquid crystal microcapsule film with multiple responsiveness.

[0020] Preferably, the preparation method further includes:

[0021] S4, Apply a mask with a light-transmitting pattern to the liquid crystal microcapsule film with multiple responsiveness, and perform patterning treatment through ultraviolet irradiation to obtain a liquid crystal microcapsule film with a pattern.

[0022] Among them, the wavelength of the ultraviolet light is 365 nm, and the light intensity is 4 - 10 mW / cm 2 ; the irradiation time is 20 - 40 s.

[0023] Preferably, the concentration of the polyvinyl alcohol aqueous solution is 10%;

[0024] The volume of the liquid cholesteric liquid crystal is 1% of the volume of the polyvinyl alcohol aqueous solution.

[0025] Preferably, in step S2, the ultrasonic emulsification includes: first stirring the mixture of the cholesteric liquid crystal and the polyvinyl alcohol aqueous solution on a magnetic stirrer at a rotation speed of 2000 r / min for 2 - 4 h for pretreatment, and then performing ultrasonic emulsification on the pretreated liquid crystal solution with an ultrasonic emulsifier.

[0026] More preferably, the ultrasonic power of the ultrasonic emulsifier is set to 5%, and the emulsification time is 3 s / mL.

[0027] In the third aspect of the present application, there is provided an application of the above-mentioned liquid crystal microcapsule film with multiple responsiveness in the fields of intelligent display, anti-counterfeiting, and temperature sensing.

[0028] In the fourth aspect of the present application, there is provided an anti-counterfeiting film with dual temperature and light responsiveness, which includes the above-mentioned liquid crystal microcapsule film with multiple responsiveness.

[0029] Compared with the prior art, the beneficial effects of the present application are as follows:

[0030] Through a special preparation method, the liquid crystal microcapsule film of the present application combines the regulation of the ratio of polymerizable monomers and chiral agents, so that the helical structure of the oblate ellipsoidal liquid crystal microcapsules undergoes controllable structural color changes during ultraviolet light irradiation or temperature changes, and can accurately regulate the color of the liquid crystal microcapsules under different conditions (such as ultraviolet light irradiation, temperature or humidity changes), thus having the composite characteristics of temperature and ultraviolet light response, and can show sensitive response capabilities under multiple environmental conditions. It can be widely applied to anti-counterfeiting films, intelligent labels, and adjustable display materials.

[0031] The present application adopts a combination of the liquid crystal emulsion method and ultraviolet light curing. First, by adjusting the ultrasonic emulsification time and power, a liquid crystal microcapsule emulsion with uniform particle size and stable distribution is obtained, and then a structurally stable liquid crystal microcapsule film is prepared through a process combining solvent evaporation into film and photopolymerization. The preparation method of the present application has a simple process, does not require complex equipment or high-temperature reactions, can complete the preparation of the liquid crystal microcapsule film under normal temperature conditions, and has good repeatability; during the preparation process, by precisely controlling the formula and polymerization conditions of the liquid crystal microcapsules, the color and structural characteristics of each batch of films can be ensured to be consistent, thereby realizing the standardized production of products. Description of the Drawings

[0032] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments described in the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0033] Figure 1 It is the ultraviolet spectrum diagram and physical diagram of the liquid crystal microcapsule film of the present application before and after ultraviolet light irradiation;

[0034] Figure 2 It is the physical diagram of the change of the liquid crystal microcapsule film of the present application under different ultraviolet light intensities;

[0035] Figure 3 It is the physical diagram of the change of the liquid crystal microcapsule film of the present application under different humidity conditions;

[0036] Figure 4 It is the physical diagram of the change of the liquid crystal microcapsule film of the present application at different temperatures;

[0037] Figure 5 It is the application example diagram of the liquid crystal microcapsule film of the present application. Detailed implementation manners

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0039] In the following description of this embodiment, terms such as "include", "comprise", "have" and "contain" are all open-ended terms, that is, they are intended to include but not limited to.

[0040] In the following description of this embodiment, the term "and / or" is used to describe the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and both A and B exist simultaneously. Where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are an "or" relationship.

[0041] In the following description of this embodiment, the term "at least one" means one or more, and "a plurality" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0042] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms "a" and "the" used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0043] Those skilled in the art should understand that in the following description of the embodiments of this application, the sequence numbers do not mean the sequence of execution. Some or all of the steps can be executed in parallel or sequentially. The execution sequence of each process should be determined by its function and internal logic and should not constitute any limitation to the implementation process of the embodiments of this application.

[0044] Those skilled in the art should understand that the numerical ranges in the embodiments of this application should be understood as specifically disclosing each intermediate value between the upper and lower limits of the range. The intermediate value within any stated value or stated range and each smaller range between any other stated value or intermediate value within the stated range are also included in this application. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0045] Unless otherwise specified, the technical / scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs. Although this application only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0046] In a first aspect, this application provides a liquid crystal microcapsule film with multiple responsiveness. The liquid crystal microcapsule film includes a PVA film and a large number of cholesteric liquid crystals in the shape of oblate ellipsoids uniformly dispersed inside the PVA film. Among them, the particle size of the cholesteric liquid crystal is 5.5 - 7.0 μm; each cholesteric liquid crystal and the PVA wrapping the cholesteric liquid crystal form a microcapsule structure.

[0047] In this application, by weight, the raw materials of the cholesteric liquid crystal include the following components:

[0048] The liquid crystal raw material comprises 76-93 wt% of rod-shaped liquid crystal, 5-20 wt% of liquid crystal polymerizable monomer, and 2-4 wt% of chiral agent;

[0049] The photoinitiator is used in an amount of 1 wt% of the amount of the liquid crystal raw material.

[0050] In this application, the rod-shaped liquid crystal is used as the liquid crystal matrix material, preferably 5CB (4-cyano-4'-pentylbiphenyl);

[0051] The liquid crystal polymerizable monomer is a rod-shaped liquid crystal with photopolymerization performance. When it undergoes a polymerization reaction without ultraviolet light irradiation, it serves as a part of the liquid crystal matrix material; under ultraviolet light irradiation, it undergoes a polymerization reaction to form a polymer network; the liquid crystal polymerizable monomer is preferably C6M (1,4-bis[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene).

[0052] The chiral agent is used to control the pitch of the liquid crystal matrix material inside the liquid crystal microcapsule, preferably the chiral dopant R5011;

[0053] The photoinitiator is used to initiate the polymerization reaction of the liquid crystal polymerizable monomer under ultraviolet light irradiation, including any one of benzoin dimethyl ether, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, or 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone; in this application, the photoinitiator is preferably Irgacure 651.

[0054] In this application, PVA is used as a surfactant. It can not only serve as a shell to wrap the cholesteric liquid crystal droplets to form liquid crystal microcapsules and induce the orientation of liquid crystal molecules; but also serve as a film-forming substance to form a film.

[0055] In this application, the liquid crystal polymerizable monomer is used as the filling material of the inner core of the liquid crystal microcapsule. Before polymerization, the liquid crystal polymerizable monomer such as C6M acts as the liquid crystal part and can be regarded as a rod-shaped liquid crystal; after ultraviolet light irradiation and polymerization, it forms a polymer network and loses the function of the liquid crystal, resulting in a decrease in the overall liquid crystal content and an increase in the chiral agent content in the liquid crystal microcapsule, causing a change in the pitch of the liquid crystal inside the liquid crystal microcapsule, and finally causing a change in the color of the liquid crystal microcapsule, resulting in a change in the color of the liquid crystal microcapsule film.

[0056] In this application, by regulating the ratio of the liquid-crystalline polymerizable monomer and the chiral agent, the helical structure of the oblate ellipsoidal liquid-crystal microcapsules undergoes controllable structural color changes during ultraviolet light irradiation and temperature variation processes, enabling the liquid-crystal microcapsule film to possess the composite characteristics of temperature and ultraviolet light response and exhibit a sensitive response ability under multiple environmental conditions. On the one hand, with different chiral agent contents, the liquid-crystal microcapsule film of this application presents different colors; on the other hand, when the chiral agent content remains unchanged, under ultraviolet light irradiation, the liquid-crystalline polymerizable monomer polymerizes, resulting in a passive change in the chiral agent content and also causing a change in the color of the liquid-crystal microcapsule film. In addition, as the temperature rises, the color of the liquid-crystal microcapsule film of this application changes. When the temperature rises to the clearing point of the liquid crystal, the structural color disappears, leading to a change in the color of the liquid-crystal microcapsule film; while when the temperature drops below the clearing point, the structural color appears and the film returns to its original color. Among them, the reflection spectral range of the dynamic color change of the liquid-crystal microcapsule film of this application is 400nm - 700nm.

[0057] In this application, the thickness of the liquid-crystal microcapsule film with multiple responsiveness is preferably 20 - 30μm, more preferably 25μm.

[0058] In the second aspect of this application, there is provided a preparation method of the above-mentioned liquid-crystal microcapsule film with multiple responsiveness, including:

[0059] S1, weighing liquid-crystal monomers, liquid-crystalline polymerizable monomers, chiral agents, and photoinitiators according to the ratio, heating to the clearing point and mixing evenly to obtain a cholesteric liquid crystal;

[0060] S2, adding the cholesteric liquid crystal into an aqueous solution of polyvinyl alcohol, and through ultrasonic emulsification, dispersing the cholesteric liquid crystal microspheres in the PVA solution to obtain an emulsion containing liquid-crystal microcapsules;

[0061] In this application, a pipette is used to measure and add the cholesteric liquid crystal into the aqueous PVA solution, and the mixture is stirred on a magnetic stirrer at a rotation speed of 2000r / min for 2 - 4h for pretreatment, and then the pretreated liquid-crystal solution is ultrasonically emulsified with an ultrasonic emulsifier. Among them, preferably, the ultrasonic power of the ultrasonic emulsifier is set to 5%, and the emulsification time is 3s / mL.

[0062] In this application, through ultrasonic emulsification, a large number of cholesteric liquid crystal microspheres are formed and evenly dispersed in the aqueous PVA solution to form an emulsion containing liquid-crystal microcapsules. Among them, the liquid-crystal microcapsules have cholesteric liquid crystal microspheres as the inner core and PVA wrapping the cholesteric liquid crystal microspheres as the outer shell. Among them, preferably, the concentration of the aqueous PVA solution is 10%; preferably, the volume of the cholesteric liquid crystal is 1% of the volume of the aqueous polyvinyl alcohol solution.

[0063] S3. Add the emulsion into a petri dish and dry it at room temperature to remove the moisture, obtaining a liquid crystal microcapsule film with multiple responsiveness.

[0064] In this application, the emulsion containing liquid crystal microcapsules is added into a plastic petri dish and dried in a fume hood for 24 hours. As the moisture in the emulsion continuously volatilizes, the liquid crystal microcapsules gradually change from spherical to elliptical, resulting in a gradually enlarged reflection area at the center. The reflection of color changes from scattering to opaque color, and the liquid crystal microcapsules are gradually flattened and produce structural color, obtaining a liquid crystal microcapsule film with multiple responsiveness.

[0065] As a preference, the liquid crystal microcapsule film with multiple responsiveness of this application can be patterned on its surface by ultraviolet curing, further increasing its application scope. Specifically, the patterning steps are as follows:

[0066] S4. Apply a mask with a light-transmitting pattern to the liquid crystal microcapsule film with multiple responsiveness and perform patterning treatment by ultraviolet irradiation to obtain a liquid crystal microcapsule film with a pattern.

[0067] In this application, in the pattern area where the mask is light-transmitting, after ultraviolet irradiation, the photoinitiator initiates the polymerization reaction of some liquid crystalline polymerizable monomers to generate a polymer network. As the liquid crystalline polymerizable monomers decrease, the chiral agent content increases, causing a change in the pitch of the liquid crystal inside the liquid crystal microcapsules, resulting in a change in the color of the liquid crystal microcapsules and showing the pattern.

[0068] Among them, it is preferred that the wavelength of the ultraviolet light is 365 nm and the light intensity is 4 - 10 mW / cm 2 ; the irradiation time is 20 - 40 s.

[0069] This application combines the liquid crystal emulsion method with ultraviolet curing. By adjusting the ultrasonic emulsification time and power, a liquid crystal microcapsule emulsion with uniform particle size and stable distribution is obtained, and then a liquid crystal microcapsule film with stable structure is prepared through a process combining solvent evaporation film formation and photopolymerization. The preparation method of this application has a simple process, does not require complex equipment or high-temperature reactions, can complete the preparation of the liquid crystal microcapsule film under normal temperature conditions, and has good repeatability; during the preparation process, by precisely controlling the formula and polymerization conditions of the liquid crystal microcapsules, the color and structural characteristics consistency of each batch of films can be ensured, thus realizing the standardized production of products. In addition, the materials used in this application have low cost and wide sources, and are suitable for large-scale industrial production.

[0070] The liquid crystal microcapsule film of this application has the composite characteristics of temperature and ultraviolet light response, can show sensitive response ability under multiple environmental conditions, and can be used to prepare intelligent displays, anti-counterfeiting or temperature sensing devices.

[0071] The present application also provides an anti-counterfeiting film with dual temperature and light responses, which includes the above-mentioned liquid crystal microcapsule film with multiple responses.

[0072] As a preference, by using the liquid crystal microcapsule film with multiple responses of the present application as the bottom layer film, another layer or multiple layers of films are formed on its surface to prepare a composite film. Exemplarily, the composite film of the present application is prepared by the following method:

[0073] Step 1: Weigh liquid crystal monomers, liquid crystal polymerizable monomers, chiral agents and photoinitiators according to the ratio, heat to the clearing point and mix evenly to obtain cholesteric liquid crystal; add it to the aqueous solution of polyvinyl alcohol, and through ultrasonic emulsification, disperse the cholesteric liquid crystal microspheres in the PVA solution to obtain emulsion A containing liquid crystal microcapsules; add the emulsion A to a petri dish and dry it at room temperature to remove water to obtain a liquid crystal microcapsule film with multiple responses as the bottom layer film; among them, the cholesteric liquid crystal includes: liquid crystal raw materials, including 76-93 wt% of rod-shaped liquid crystal, 5-20 wt% of liquid crystal polymerizable monomers, and 2-4 wt% of chiral agents; the photoinitiator is used in an amount of 1 wt% of the amount of liquid crystal raw materials.

[0074] Step 2: Weigh liquid crystal monomers and chiral agents according to the ratio, heat to the clearing point and mix evenly to obtain cholesteric liquid crystal; add it to the aqueous solution of polyvinyl alcohol, and through ultrasonic emulsification, disperse the cholesteric liquid crystal microspheres in the PVA solution to obtain emulsion B containing liquid crystal microcapsules; among them, the cholesteric liquid crystal includes: liquid crystal raw materials, including 96-98 wt% of rod-shaped liquid crystal and 2-4 wt% of chiral agents.

[0075] Step 3: Add emulsion B to the surface of the bottom layer film and dry it at room temperature to remove water to obtain a composite film.

[0076] The following further illustrates the present application through examples.

[0077] In the examples of the present application, the specific raw materials used are:

[0078] Rod-shaped liquid crystal 5CB;

[0079] Chiral agent R5011

[0080] Polyvinyl alcohol PVA

[0081] Photoinitiator Irgacure-651

[0082] Liquid crystal polymerizable monomer C6M

[0083] The chemical formulas of the above raw materials are shown as follows:

[0084]

[0085] Example 1

[0086] This embodiment provides a method for preparing a liquid crystal microcapsule film with multiple responsiveness, including:

[0087] S1, Weigh 0.86 g of 5CB, 0.04 g of R5011, 0.1 g of C6M, and 0.01 g of Irgacure-651. By using a vortex oscillator and a hot air blower, make them reach the clearing point under high-temperature oscillation and mix evenly quickly to obtain a cholesteric liquid crystal.

[0088] S2, Use a pipette to measure 50 μL of cholesteric liquid crystal and add it to 5 mL of a 10 wt% aqueous PVA solution. Stir on a magnetic stirrer at a speed of 2000 r / min for 3 hours for pretreatment; Subsequently, set the ultrasonic power of the ultrasonic emulsifier to 5% and the emulsification time to 3 s / mL, and perform ultrasonic emulsification on the pretreated liquid to obtain a PVA solution containing a large number of liquid crystal microcapsules;

[0089] S3, Add the PVA solution containing liquid crystal microcapsules to a plastic petri dish and place it in a fume hood to dry for 24 hours until the moisture in the emulsion is completely removed. The liquid crystal microcapsules are compressed into a flattened ellipsoidal shape due to the evaporation of water, presenting an opaque structural color, and obtaining a liquid crystal microcapsule film with multiple responsiveness.

[0090] Example 2

[0091] The difference between Example 2 and Example 1 is that the dosage of R5011 is 0.03 g, and the rest are the same as in Example 1.

[0092] Example 3

[0093] The difference between Example 3 and Example 1 is that the dosage of R5011 is 0.023 g, and the rest are the same as in Example 1.

[0094] Example 4

[0095] This embodiment provides a method for preparing a patterned liquid crystal microcapsule film, including:

[0096] S1 - S3 are the same as in Example 1;

[0097] S4, Cover the liquid crystal microcapsule film with multiple responsiveness with a mask engraved with a small animal pattern, and irradiate it with a UV lamp with a wavelength of 365 nm at a light intensity of 10 mW / cm 2 for 20 s to complete the patterned preparation.

[0098] This embodiment respectively prepares a liquid crystal microcapsule film with a kitten pattern, a liquid crystal microcapsule film with a fawn pattern, and a liquid crystal microcapsule film with the letters USTB.

[0099] Example 5

[0100] This embodiment provides a method for preparing a composite liquid crystal microcapsule film, including:

[0101] S1, Weigh 0.86 g of 5CB, 0.04 g of R5011, 0.1 g of C6M, and 0.01 g of Irgacure-651. Through a vortex oscillator and a hot air blower, make them reach the clearing point under high-temperature oscillation and quickly mix evenly to obtain a cholesteric liquid crystal. Measure 50 μL of it with a pipette and add it to 5 mL of a 10 wt% PVA aqueous solution. Stir on a magnetic stirrer at a speed of 2000 r / min for 3 hours for pretreatment. Subsequently, set the ultrasonic power of the ultrasonic emulsifier to 5% and the emulsification time to 3 s / mL, and perform ultrasonic emulsification on the pretreated liquid to obtain a first emulsion;

[0102] S2, Weigh 0.97 g of 5CB and 0.03 g of R5011. Through a vortex oscillator and a hot air blower, make them reach the clearing point under high-temperature oscillation and quickly mix evenly to obtain a cholesteric liquid crystal. Measure 50 μL of it with a pipette and add it to 5 mL of a 10 wt% PVA aqueous solution. Stir on a magnetic stirrer at a speed of 2000 r / min for 3 hours for pretreatment. Subsequently, set the ultrasonic power of the ultrasonic emulsifier to 5% and the emulsification time to 3 s / mL, and perform ultrasonic emulsification on the pretreated liquid to obtain a second emulsion;

[0103] S3, First add the first emulsion to a plastic culture dish, place it on a hot stage and keep it in the dark and warm for 30 minutes to form a first layer; then add the second emulsion and heat it in the dark for 30 minutes to form a composite film. Take the composite film off the hot stage and cool it to room temperature, and the film shows a blue structural color. Cover the composite film with a mask and irradiate it with a UV lamp with a wavelength of 365 nm at a light intensity of 10 mW / cm 2 for 20 s to complete the patterning preparation, so that a pattern appears on the first layer, and a composite liquid crystal microcapsule film with a kitten pattern is obtained.

[0104] Perform performance evaluation on the films prepared in Examples 1-5 of this application, specifically as follows:

[0105] Take the liquid crystal microcapsule films with multiple responsiveness prepared in Examples 1-3, and irradiate them with a UV lamp with a wavelength of 365 nm at a light intensity of 10 mW / cm 2 for 20 s. The physical pictures and UV spectra of the three films before and after UV irradiation are as Figure 1 shown.

[0106] From Figure 1It can be seen that the liquid crystal microcapsule film of Example 1 is blue, the liquid crystal microcapsule film of Example 2 is green, and the liquid crystal microcapsule film of Example 3 is red. After ultraviolet irradiation, the colors of the three films show a blue shift, and the colors change before and after irradiation.

[0107] After ultraviolet irradiation, for the liquid crystal microcapsule film with a chiral agent content of 4% in Example 1, its structural color changes from blue to colorless and transparent, and the reflection peak changes from 406 nm to beyond 400 nm; for the film with a chiral agent content of 3.0% in Example 2, the structural color changes from green to blue, and the reflection peak changes from 504 nm to 448 nm; for the film with a chiral agent content of 2.3% in Example 3, the structural color changes from red to yellow, and the reflection peak changes from 620 nm to 562 nm. By observing the ultraviolet spectrum, it can be obtained that regardless of the content of the chiral agent, the reflection peak shifts by about 50 nm after polymerization. And the colors of the film before and after polymerization correspond one-to-one with the cholesteric phase, which can be used as a basis to regulate the film color to meet actual needs. Through the change of color before and after ultraviolet irradiation, a light-responsive anti-counterfeiting effect can be achieved.

[0108] Take 3 identical samples of the liquid crystal microcapsule film with a kitten pattern prepared in Example 4 and place them under different ultraviolet light intensities to test the time for the pattern to disappear. Among them, the ultraviolet light intensities from top to bottom are 4 mW / cm 2 , 5 mW / cm 2 , 6 mW / cm 2 . Record the color change of the film every 5 seconds. The test results are as Figure 2 shown.

[0109] From Figure 2 it can be seen that for the patterned liquid crystal microcapsule film of this application, a reaction occurs under ultraviolet light resulting in a color change, and the disappearance speed of the pattern accelerates with the increase of light intensity, which has the characteristic of light response.

[0110] Take the liquid crystal microcapsule film with a fawn pattern prepared in Example 4 and test it under 100% humidity conditions. As Figure 3 shown, compared with the obvious color in the dry state, the liquid crystal microcapsule film becomes a semi-transparent scattering state under 100% humidity conditions, indicating that the liquid crystal microcapsule film responds to changes in humidity.

[0111] Take the composite liquid crystal microcapsule film prepared in Example 5 and place it on a hot stage and slowly heat it to observe its changes. The temperature starts from 28 °C and gradually increases in a gradient of 2 °C until the film color completely disappears, and the final temperature is 38 °C. During the heating process, the appearance and disappearance of the pattern are gradually observed. When the temperature is 34 °C, the pattern of the film is the most obvious, as Figure 4 shown.

[0112] The liquid crystal microcapsule film with the letters "USTB" prepared in Example 4 was used as an anti-counterfeiting film. After being exposed to the sun for a period of time, the green pattern "USTB" in the anti-counterfeiting film gradually disappeared and finally completely disappeared after 90 s, and the pattern did not recover after the sunlight irradiation was stopped, as Figure 5 shown. This anti-counterfeiting film can be used for the protection of valuable items. Placing the product in the sun can quickly detect the authenticity of the product.

[0113] Although this specification has described the present application in detail with general descriptions and specific embodiments, based on the present application, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present application all fall within the scope of protection required by the present application.

Claims

1. A liquid crystal microcapsule film with multiple responsiveness, characterized in that: The liquid crystal microcapsule film includes a PVA film and a large amount of cholesteric liquid crystals in an oblate ellipsoid shape uniformly dispersed inside the PVA film; The particle size of the cholesteric liquid crystal is 5.5-7.0 μm; each cholesteric liquid crystal and the PVA encapsulating the cholesteric liquid crystal form a microcapsule structure.

2. The liquid crystal microcapsule film according to claim 1, characterized in that: The raw materials of the cholesteric liquid crystal include the following components by weight: Liquid crystal raw materials, including 76-93wt% of rod-shaped liquid crystal, 5-20wt% of liquid crystal polymerizable monomer, and 2-4wt% of chiral agent; The amount of the photoinitiator used is 1wt% of the amount of the liquid crystal raw material used.

3. The liquid crystal microcapsule film according to claim 2, characterized in that: The rod-shaped liquid crystal is 5CB; The liquid crystal polymerizable monomer is C6M; The chiral agent is R5011; The photoinitiator includes any one of benzoin dimethyl ether, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone or 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone.

4. The method for preparing a liquid crystal microcapsule film with multiple responsiveness according to claim 2, characterized in that: include: S1, weighing liquid crystal monomer, liquid crystal polymerizable monomer, chiral agent and photoinitiator according to the ratio, heating to a clearing point and mixing them evenly to obtain cholesteric liquid crystal; S2, adding cholesteric liquid crystal to a polyvinyl alcohol aqueous solution, dispersing cholesteric liquid crystal beads in the PVA solution by ultrasonic emulsification, and obtaining an emulsion containing liquid crystal microcapsules; S3, adding the emulsion into a culture dish, drying at room temperature to remove moisture, and obtaining a liquid crystal microcapsule film with multiple responsiveness.

5. The preparation method according to claim 4, characterized in that: Also includes: S4, applying a mask having a light-transmitting pattern to the liquid crystal microcapsule film having multiple responsiveness, and performing patterning treatment by ultraviolet light irradiation to obtain a liquid crystal microcapsule film having a pattern; The wavelength of ultraviolet light is 365nm and the light intensity is 4-10mW / cm 2 ; The irradiation time is 20 to 40 seconds.

6. The preparation method according to claim 4, characterized in that: The concentration of the polyvinyl alcohol aqueous solution is 10%; The volume of the liquid cholesteric liquid crystal is 1% of the volume of the polyvinyl alcohol aqueous solution.

7. The preparation method according to claim 4, characterized in that: In step S2, the ultrasonic emulsification includes: firstly stirring the mixed solution of cholesteric liquid crystal and polyvinyl alcohol aqueous solution on a magnetic stirrer at a speed of 2000 r / min for 2 to 4 hours for pretreatment, and then ultrasonic emulsifying the pretreated liquid crystal solution with an ultrasonic emulsifier.

8. The preparation method according to claim 7, characterized in that: The ultrasonic power of the ultrasonic emulsification instrument was set to 5%, and the emulsification time was 3 s / mL.

9. Application of the liquid crystal microcapsule film with multi-responsiveness as claimed in any one of claims 1 to 3 in the fields of intelligent display, anti-counterfeiting and temperature sensing.

10. An anti-counterfeiting film with dual response to temperature and light, characterized in that: The invention comprises the liquid crystal microcapsule film with multi-responsiveness as described in any one of claims 1 to 3.

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