CN113429775A - UV (ultraviolet) photocuring liquid crystal structure color film and preparation method thereof - Google Patents
UV (ultraviolet) photocuring liquid crystal structure color film and preparation method thereof Download PDFInfo
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- C08J2429/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
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Abstract
The UV photocuring liquid crystal structure color film is characterized in that a cholesteric liquid crystal material is uniformly dispersed in a mixed system of polyvinyl alcohol and polyethylene glycol diacrylate, and then the liquid crystal structure color film with the polymer dispersed liquid crystal characteristic is formed through UV photocuring. The invention also provides a preparation method of the UV photocuring liquid crystal structure color film. The UV photocuring liquid crystal structure color film has better liquid crystal dispersion encapsulation performance and color presentation effect by optimizing the network structure of the PDLC liquid crystal structure color film, and has the characteristics of high curing speed, energy conservation, environmental protection and the like. The UV photocuring liquid crystal structure color film has the advantages of simple preparation process, low cost and the like.
Description
Technical Field
The invention relates to a liquid crystal structure color material, in particular to a UV photocuring liquid crystal structure color film and a preparation method thereof.
Background
The fact that a plurality of animals and plants can adjust body colors according to environmental stimuli to achieve the purposes of camouflage and communication is found in nature, the interesting phenomena stimulate researchers to deeply research a bionic color response system, and Cholesteric Liquid Crystal (CLC) structural color materials show great potential in this respect. CLC molecules can self-assemble to form a periodic ordered structure, the helical axis perpendicular to the orientation direction has a corresponding helical pitch, and when the helical pitch of the CLC is equivalent to the wavelength of visible light, the CLC can present a color of a specific wavelength due to its selective Bragg reflection. The Chinese invention application specification with the publication number CN 109143712A, CN 109161385A, CN 110187581A discloses the CLC material film and a preparation method thereof.
The CLC must be in its mesogenic region to achieve the structural color effect, and good fluidity limits its application range and value. The CLC is limited in a polymer matrix through microencapsulation and phase separation technology, so that the CLC can be protected from adverse environmental influence and corresponding color expression characteristics are reserved. The microencapsulation technology has the characteristics of higher phase separation degree, simple and convenient process and the like, and the Chinese patent application publication No. CN 106890607A, CN 108786676A discloses a preparation method of the microencapsulated liquid crystal. However, the CLC is not directly used for obtaining a liquid crystal structural color film after microencapsulation, and further treatment is required.
Polymer Dispersed Liquid Crystal (PDLC) systems consist of a continuous polymer matrix with cholesteric liquid crystal droplets dispersed therein, and optical films with special applications can be obtained by techniques such as solvent phase separation, UV curing, thermal crosslinking, and the like. The method has simple film forming process, can retain the color expression characteristic of the liquid crystal, and is convenient for the device application of the film. Chinese patent application publication No. CN 110376783A, CN 111607037A, CN 106632772 discloses a method for preparing a polymer dispersed liquid crystal light-adjusting film. However, the existence of the polymer and the network structure thereof can also interfere with the ideal arrangement of the liquid crystal molecules, and cause a strong light scattering phenomenon, thereby influencing the color generation effect of the liquid crystal structural color.
Disclosure of Invention
The technical problem to be solved by the invention is to provide the UV photocuring liquid crystal structure color film and the preparation method thereof, and the UV photocuring liquid crystal structure color film has better liquid crystal dispersion encapsulation property and color presentation effect by optimizing the network structure of the PDLC liquid crystal structure color film, and has the characteristics of high curing speed, energy conservation, environmental protection and the like. The technical scheme is as follows:
the UV photocuring liquid crystal structure color film is characterized in that a cholesteric liquid crystal material is uniformly dispersed in a mixed system of polyvinyl alcohol and polyethylene glycol diacrylate, and then the liquid crystal structure color film with the polymer dispersed liquid crystal characteristic is formed through UV photocuring.
The invention also provides a preparation method of the UV photocuring liquid crystal structure color film, which is characterized by comprising the following steps:
(1) mixing a polyvinyl alcohol aqueous solution with a cholesteric liquid crystal material under a preset temperature condition, uniformly stirring, and cooling to room temperature to obtain a white sol emulsion;
(2) adding a polyethylene glycol diacrylate aqueous solution containing a photoinitiator into the white sol emulsion, and uniformly stirring at room temperature to obtain polymer dispersed liquid crystal hydrogel;
(3) transferring the polymer dispersed liquid crystal hydrogel onto the surface of a printing stock to form a polymer dispersed liquid crystal hydrogel layer;
(4) and curing the polymer dispersed liquid crystal hydrogel layer under the irradiation of ultraviolet light to obtain the UV photocuring liquid crystal structural color film.
The room temperature is 20-30 ℃.
In the preferable step (1), after adding the polyvinyl alcohol into the deionized water, heating to 90-95 ℃ and continuously stirring at a constant speed of 1500rpm for 30-60 minutes to obtain a uniform polyvinyl alcohol aqueous solution; and then adding the cholesteric liquid crystal material into a polyvinyl alcohol aqueous solution under the condition of a preset temperature, mechanically stirring uniformly at a high speed of 1500-.
More preferably, the polyvinyl alcohol used in step (1) is PVA1788 or PVA1799, and the mass percent of the polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 10-20%.
More preferably, the preset temperature in the step (1) is 10-15 ℃ higher than the clearing point temperature of the cholesteric liquid crystal material.
More preferably, in the step (1), the cholesteric liquid crystal material is added, then the heat preservation and the stirring are continued for 5 to 12 hours, and then the temperature is gradually reduced to the room temperature, wherein the temperature reduction rate is 30 to 100 ℃/min, and the white sol emulsion is obtained.
Preferably, the cholesteric liquid crystal material is formed by mixing nematic liquid crystal and chiral dopant according to the proportion of 5-50% of nematic liquid crystal mass fraction and 95-50% of chiral dopant mass fraction. The cholesteric liquid crystal materials with different proportions correspond to different color information. More preferably, the nematic liquid crystal is one or a mixture of more of 4-cyano-4 '-pentylbiphenyl, 4-cyano-4' -hexylbiphenyl, 4-cyano-4 '-heptylbiphenyl and 4-cyano-4' -octylbiphenyl. More preferably, the chiral dopant is one or a mixture of more of cholesteryl acetate, cholesteryl valerate, cholesteryl heptanoate, cholesteryl n-octanoate, cholesteryl nonanoate, cholesteryl decanoate and cholesteryl carbonate. When the composition of the cholesteric liquid crystal material is changed, the color information of the structural color of the liquid crystal is changed accordingly.
Preferably, the addition amount of the cholesteric liquid crystal material is 1-6 times of the weight of polyvinyl alcohol, so that the high solid content of the cholesteric liquid crystal material in a white sol emulsion system is ensured. The system viscosity of the white sol emulsion is usually 1 to 6 pas.
In the preferable step (2), the polyethylene glycol diacrylate and the deionized water are uniformly stirred, the photoinitiator is added, and the polyethylene glycol diacrylate aqueous solution containing the photoinitiator is obtained after uniform mixing; and (2) adding a polyethylene glycol diacrylate aqueous solution containing a photoinitiator into the white sol emulsion obtained in the step (1), and then stirring at a constant speed for 1-2 hours at room temperature to obtain the polymer dispersed liquid crystal hydrogel.
Preferably, the photoinitiator used in step (2) is 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1- [4- (2-hydroxyethoxy) -phenyl ] -2-hydroxy-2-methyl-1-propanone or 2-methyl-1- (4-methylthiophenyl) -2-morphinyl-1-propanone.
More preferably, in the aqueous solution of polyethylene glycol diacrylate containing the photoinitiator in the step (2), the mass fraction of the polyethylene glycol diacrylate is 30-60%, and the mass fraction of the photoinitiator is 1-5%.
Preferably, the mass of the polyethylene glycol diacrylate contained in the aqueous polyethylene glycol diacrylate solution containing the photoinitiator in the step (2) is 1 to 3 times that of the polyvinyl alcohol contained in the white sol emulsion.
Preferably, in the step (3), the polymer-dispersed liquid crystal hydrogel is pretreated before being transferred onto the surface of the printing material; the pretreatment is to add deionized water or ethanol to dilute and adjust the solid content of the polymer dispersed liquid crystal hydrogel system, so that the solid content of the polymer dispersed liquid crystal hydrogel system is 30-60%.
The method for transferring the polymer dispersed liquid crystal hydrogel onto the surface of the printing stock in the step (3) can be in the modes of coating, spraying, silk-screen printing, gravure printing and the like. The substrate may be paper, fabric or a plastic film. The polymer dispersed liquid crystal hydrogel layer may be formed to cover the entire surface of the substrate, or may be formed to cover a part of the surface of the substrate to form a pattern layer. The polymer dispersed liquid crystal hydrogel layer is generally uniform in thickness. The surface of the substrate may be either flat or curved.
In the step (4), the polymer dispersed liquid crystal hydrogel layer can be vertically irradiated in a short distance by adopting a UV lamp to finish curing. Preferably, in the step (4), the wavelength of the UV lamp is 365nm, the light source power is 12W, and the photocuring time is 3-15 min.
Compared with the prior art, the invention has the following beneficial effects:
(1) the UV photocuring liquid crystal structure color film has the advantages of simple preparation process, low cost and the like, and can solve the technical bottleneck of processing the liquid crystal structure color film by microencapsulation in the prior art;
(2) the polyvinyl alcohol and polyethylene glycol diacrylate polymer system can improve the network crosslinking density of the polymer dispersed liquid crystal hydrogel, can obviously improve the packaging effect of the polymer system on dispersed liquid crystal after photocrosslinking reaction occurs, and the formed UV photocuring liquid crystal structure color film has stronger scratch resistance;
(3) the UV photocuring method is adopted to prepare the liquid crystal structure color film, has the characteristics of high curing speed, energy conservation, environmental protection and the like, and has great technical advantages in preparing the liquid crystal structure color film;
(4) the liquid crystal structure color film can be widely applied to the surface of a common base material, and has a dynamic color display effect along with the temperature change.
Detailed Description
Example 1
In this embodiment, the method for preparing the UV light-cured liquid crystal structure color film includes the following steps:
(1) adding 0.32 part of polyvinyl alcohol (PVA 1788) into 2.9 parts of deionized water, heating to 95 ℃, and continuously stirring at a constant speed of 1000rpm for 30 minutes (heating in a water bath manner) to obtain a uniform polyvinyl alcohol aqueous solution (the mass percent of the polyvinyl alcohol in the polyvinyl alcohol aqueous solution is about 10%); adding the cholesteric liquid crystal material into a polyvinyl alcohol aqueous solution under a preset temperature condition (the polyvinyl alcohol aqueous solution is continuously stirred and cooled to the temperature of 55-60 ℃, and the cholesteric liquid crystal material is added), mechanically stirring uniformly at a high speed of 2000rpm, and cooling to room temperature to obtain a white sol emulsion;
in the step (1), adding the cholesteric liquid crystal material, continuing to keep the temperature and stirring for 8 hours, and then gradually cooling to room temperature at a cooling rate of 50 ℃/min to obtain white sol emulsion;
the cholesteric liquid crystal material in the step (1) is formed by mixing 0.37 part of 4-cyano-4' -pentylbiphenyl and 0.91 part of cholesterol carbonate, the liquid crystal temperature interval is 23.8-37.2 ℃, and the appearance color is green under the room temperature condition;
(2) stirring 0.64 parts of polyethylene glycol diacrylate and 0.64 parts of deionized water uniformly, adding 0.02 part of photoinitiator (1- [4- (2-hydroxyethoxy) -phenyl ] -2-hydroxy-2-methyl-1-acetone), and mixing uniformly to obtain a polyethylene glycol diacrylate aqueous solution containing the photoinitiator; adding a polyethylene glycol diacrylate aqueous solution containing a photoinitiator into the white sol emulsion obtained in the step (1), and then stirring at a constant speed for 2 hours at room temperature to obtain polymer dispersed liquid crystal hydrogel;
(3) transferring the polymer dispersed liquid crystal hydrogel onto the surface of a printing stock to form a polymer dispersed liquid crystal hydrogel layer;
the method for transferring the polymer dispersed liquid crystal hydrogel onto the surface of the printing stock in the step (3) is coating, wherein the printing stock is paper;
(4) and curing the polymer dispersed liquid crystal hydrogel layer under the irradiation of ultraviolet light to obtain the UV photocuring liquid crystal structural color film.
In the step (4), the polymer dispersed liquid crystal hydrogel layer is vertically irradiated by a UV lamp in a short distance to complete curing. In the step (4), the wavelength of the UV lamp is 365nm, the power of the light source is 12W, and the photocuring time is 8 min.
In the preparation method of the UV photocuring liquid crystal structure color film, the parts of the raw materials are parts by mass.
In the UV photocuring liquid crystal structure color film, the crosslinking yield of the polyethylene glycol diacrylate reaches about 90%, the stability of the liquid crystal structure color film structure can be kept in a humid environment or water, and the maximum swelling rate in water is 8%. The pencil hardness of the UV photocuring liquid crystal structure color film is tested to be 4H according to GB/T6739-2006 Pencil hardness determination of paint film by a colored paint and varnish pencil method.
Example 2
In this embodiment, the method for preparing the UV light-cured liquid crystal structure color film includes the following steps:
(1) adding 0.28 part of polyvinyl alcohol (PVA 1799) into 2.0 parts of deionized water, heating to 95 ℃, and continuously stirring at a uniform speed of 1500rpm for 30 minutes (heating in a water bath manner) to obtain a uniform polyvinyl alcohol aqueous solution (the mass percent of the polyvinyl alcohol in the polyvinyl alcohol aqueous solution is about 12%); adding the cholesteric liquid crystal material into a polyvinyl alcohol aqueous solution under a preset temperature condition (the polyvinyl alcohol aqueous solution is continuously stirred and cooled to the temperature of 58-63 ℃, and the cholesteric liquid crystal material is added), mechanically stirring uniformly at a high speed of 2500rpm, and cooling to room temperature to obtain a white sol emulsion;
in the step (1), adding the cholesteric liquid crystal material, continuing to keep the temperature and stirring for 10 hours, and then gradually cooling to room temperature at a cooling rate of 30 ℃/min to obtain white sol emulsion;
the cholesteric liquid crystal material in the step (1) is formed by mixing 0.49 part of 4-cyano-4' -pentylbiphenyl, 0.59 part of cholesterol carbonate and 0.60 part of cholesterol pelargonate, the liquid crystal temperature range is 25.8-46.6 ℃, and the appearance color is green under the room temperature condition;
(2) stirring 0.56 part of polyethylene glycol diacrylate and 0.9 part of deionized water uniformly, adding 0.03 part of photoinitiator (1-hydroxycyclohexyl phenyl ketone), and mixing uniformly to obtain a polyethylene glycol diacrylate aqueous solution containing the photoinitiator; adding a polyethylene glycol diacrylate aqueous solution containing a photoinitiator into the white sol emulsion obtained in the step (1), and then stirring at a constant speed for 1.5 hours at room temperature to obtain polymer dispersed liquid crystal hydrogel;
(3) pretreating the polymer dispersed liquid crystal hydrogel (the pretreatment is to add deionized water for dilution to adjust the solid content of a polymer dispersed liquid crystal hydrogel system, so that the solid content of the polymer dispersed liquid crystal hydrogel system is 45 percent), and transferring the polymer dispersed liquid crystal hydrogel onto the surface of a printing stock to form a polymer dispersed liquid crystal hydrogel layer;
the method for transferring the polymer dispersed liquid crystal hydrogel onto the surface of the printing stock in the step (3) is coating, wherein the printing stock is paper;
(4) and curing the polymer dispersed liquid crystal hydrogel layer under the irradiation of ultraviolet light to obtain the UV photocuring liquid crystal structural color film.
In the step (4), the polymer dispersed liquid crystal hydrogel layer is vertically irradiated by a UV lamp in a short distance to complete curing. In the step (4), the wavelength of the UV lamp is 365nm, the power of the light source is 12W, and the photocuring time is 10 min.
In the preparation method of the UV photocuring liquid crystal structure color film, the parts of the raw materials are parts by mass.
In the UV photocuring liquid crystal structure color film, the crosslinking yield of the polyethylene glycol diacrylate reaches about 88 percent, the stability of the liquid crystal structure color film structure can be kept in a humid environment or water, and the maximum swelling rate in water is 10 percent. The pencil hardness of the UV photocuring liquid crystal structure color film is tested to be 5H according to GB/T6739-2006 Pencil hardness determination of paint film by a colored paint and varnish pencil method.
Example 3
In this embodiment, the method for preparing the UV light-cured liquid crystal structure color film includes the following steps:
(1) adding 0.28 part of polyvinyl alcohol (PVA 1788) into 1.2 parts of deionized water, heating to 95 ℃, and continuously stirring at a constant speed of 500rpm for 60 minutes to obtain a uniform polyvinyl alcohol aqueous solution (the mass percent of the polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 19%); adding the cholesteric liquid crystal material into a polyvinyl alcohol aqueous solution under a preset temperature condition (the polyvinyl alcohol aqueous solution is continuously stirred and cooled to 50-55 ℃, and the cholesteric liquid crystal material is added), mechanically stirring uniformly at a high speed of 3000rpm, and cooling to room temperature to obtain a white sol emulsion;
in the step (1), adding the cholesteric liquid crystal material, continuing to keep the temperature and stirring for 10 hours, and then gradually cooling to room temperature at a cooling rate of 60 ℃/min to obtain white sol emulsion;
the cholesteric liquid crystal material in the step (1) is formed by mixing 0.50 part of 4-cyano-4' -pentylbiphenyl and 0.62 part of cholesterol carbonate, the liquid crystal temperature interval is 20.1-37.0 ℃, and the appearance color is red under the room temperature condition;
(2) stirring 0.50 part of polyethylene glycol diacrylate and 0.8 part of deionized water uniformly, adding 0.03 part of photoinitiator (2-hydroxy-2-methyl-1-phenyl-1-acetone), and mixing uniformly to obtain a polyethylene glycol diacrylate aqueous solution containing the photoinitiator; adding a polyethylene glycol diacrylate aqueous solution containing a photoinitiator into the white sol emulsion obtained in the step (1), and then stirring at a constant speed for 2 hours at room temperature to obtain polymer dispersed liquid crystal hydrogel;
(3) pretreating the polymer dispersed liquid crystal hydrogel (the pretreatment is to add ethanol for dilution to adjust the solid content of a polymer dispersed liquid crystal hydrogel system, so that the solid content of the polymer dispersed liquid crystal hydrogel system is 48 percent), and transferring the polymer dispersed liquid crystal hydrogel onto the surface of a printing stock to form a polymer dispersed liquid crystal hydrogel layer;
the method for transferring the polymer dispersed liquid crystal hydrogel onto the surface of the printing stock in the step (3) is coating, and the printing stock is a plastic film;
(4) and curing the polymer dispersed liquid crystal hydrogel layer under the irradiation of ultraviolet light to obtain the UV photocuring liquid crystal structural color film.
In the step (4), the polymer dispersed liquid crystal hydrogel layer is vertically irradiated by a UV lamp in a short distance to complete curing. In the step (4), the wavelength of the UV lamp is 365nm, the light source power is 12W, and the photocuring time is 6 min.
In the preparation method of the UV photocuring liquid crystal structure color film, the parts of the raw materials are parts by mass.
In the UV photocuring liquid crystal structure color film, the crosslinking yield of the polyethylene glycol diacrylate reaches about 90%, the stability of the liquid crystal structure color film structure can be kept in a humid environment or water, and the maximum swelling rate in water is 10%. The pencil hardness of the UV photocuring liquid crystal structure color film is tested to be 5H according to GB/T6739-2006 Pencil hardness determination of paint film by a colored paint and varnish pencil method.
Example 4
In this embodiment, the method for preparing the UV light-cured liquid crystal structure color film includes the following steps:
(1) adding 0.28 part of polyvinyl alcohol (PVA 1799) into 2.3 parts of deionized water, heating to 90 ℃, and continuously stirring at a constant speed of 1000rpm for 50 minutes (heating in a water bath manner) to obtain a uniform polyvinyl alcohol aqueous solution (the mass percent of the polyvinyl alcohol in the polyvinyl alcohol aqueous solution is about 11%); adding the cholesteric liquid crystal material into a polyvinyl alcohol aqueous solution under a preset temperature condition (the polyvinyl alcohol aqueous solution is continuously stirred and cooled to 50-55 ℃, and the cholesteric liquid crystal material is added), mechanically stirring uniformly at a high speed of 3000rpm, and cooling to room temperature to obtain a white sol emulsion;
in the step (1), adding the cholesteric liquid crystal material, continuing to keep the temperature and stirring for 10 hours, and then gradually cooling to room temperature at a cooling rate of 40 ℃/min to obtain white sol emulsion;
the cholesteric liquid crystal material in the step (1) is formed by mixing 0.50 part of 4-cyano-4' -pentylbiphenyl and 0.62 part of cholesterol carbonate, the liquid crystal temperature interval is 25.6-38.4 ℃, and the appearance color of the cholesteric liquid crystal material is blue at room temperature;
(2) stirring 0.42 part of polyethylene glycol diacrylate and 0.6 part of deionized water uniformly, adding 0.02 part of photoinitiator (1- [4- (2-hydroxyethoxy) -phenyl ] -2-hydroxy-2-methyl-1-acetone), and mixing uniformly to obtain a polyethylene glycol diacrylate aqueous solution containing the photoinitiator; adding a polyethylene glycol diacrylate aqueous solution containing a photoinitiator into the white sol emulsion obtained in the step (1), and then stirring at a constant speed for 1 hour at room temperature to obtain polymer dispersed liquid crystal hydrogel;
(3) transferring the polymer dispersed liquid crystal hydrogel onto the surface of a printing stock to form a polymer dispersed liquid crystal hydrogel layer;
the method for transferring the polymer dispersed liquid crystal hydrogel onto the surface of the printing stock in the step (3) is coating, wherein the printing stock is paper;
(4) and curing the polymer dispersed liquid crystal hydrogel layer under the irradiation of ultraviolet light to obtain the UV photocuring liquid crystal structural color film.
In the step (4), the polymer dispersed liquid crystal hydrogel layer is vertically irradiated by a UV lamp in a short distance to complete curing. In the step (4), the wavelength of the UV lamp is 365nm, the power of the light source is 12W, and the photocuring time is 10 min.
In the preparation method of the UV photocuring liquid crystal structure color film, the parts of the raw materials are parts by mass.
In the UV photocuring liquid crystal structure color film, the crosslinking yield of the polyethylene glycol diacrylate reaches about 92%, the stability of the liquid crystal structure color film structure can be kept in a humid environment or water, and the maximum swelling rate in water is 8%. The pencil hardness of the UV photocuring liquid crystal structure color film is tested to be 5H according to GB/T6739-2006 Pencil hardness determination of paint film by a colored paint and varnish pencil method.
Claims (10)
1. The UV photocuring liquid crystal structure color film is characterized in that a cholesteric liquid crystal material is uniformly dispersed in a mixed system of polyvinyl alcohol and polyethylene glycol diacrylate, and then the liquid crystal structure color film with the polymer dispersed liquid crystal characteristic is formed through UV photocuring.
2. The method for preparing a UV light-curable liquid crystal structure color film according to claim 1, comprising the steps of:
(1) mixing a polyvinyl alcohol aqueous solution with a cholesteric liquid crystal material under a preset temperature condition, uniformly stirring, and cooling to room temperature to obtain a white sol emulsion;
(2) adding a polyethylene glycol diacrylate aqueous solution containing a photoinitiator into the white sol emulsion, and uniformly stirring at room temperature to obtain polymer dispersed liquid crystal hydrogel;
(3) transferring the polymer dispersed liquid crystal hydrogel onto the surface of a printing stock to form a polymer dispersed liquid crystal hydrogel layer;
(4) and curing the polymer dispersed liquid crystal hydrogel layer under the irradiation of ultraviolet light to obtain the UV photocuring liquid crystal structural color film.
3. The method for preparing a UV-curable liquid crystal structural color film according to claim 2, wherein: in the step (1), adding polyvinyl alcohol into deionized water, heating to 90-95 ℃, and continuously stirring at a constant speed of 500-1500rpm for 30-60 minutes to obtain a uniform polyvinyl alcohol aqueous solution; and then adding the cholesteric liquid crystal material into a polyvinyl alcohol aqueous solution under the condition of a preset temperature, mechanically stirring uniformly at a high speed of 1500-.
4. The method for preparing a UV-curable liquid crystal structural color film according to claim 3, wherein: the polyvinyl alcohol adopted in the step (1) is PVA1788 or PVA1799, and the mass percent of the polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 10-20%.
5. The method for preparing a UV light-curable liquid crystal structural color film according to claim 2 or 3, wherein: the preset temperature in the step (1) is 10-15 ℃ higher than the clearing point temperature of the cholesteric liquid crystal material;
and (2) adding the cholesteric liquid crystal material in the step (1), keeping the temperature, stirring for 5-12 hours, and then gradually cooling to room temperature at the cooling rate of 30-100 ℃/min to obtain the white sol emulsion.
6. The method for preparing a UV light-curable liquid crystal structural color film according to claim 2 or 3, wherein: the cholesteric liquid crystal material is formed by mixing nematic liquid crystal and chiral dopant according to the proportion of 5-50% of nematic liquid crystal mass fraction and 95-50% of chiral dopant mass fraction;
the nematic liquid crystal is one or a mixture of more of 4-cyano-4 '-pentylbiphenyl, 4-cyano-4' -hexylbiphenyl, 4-cyano-4 '-heptylbiphenyl and 4-cyano-4' -octylbiphenyl;
the chiral dopant is one or a mixture of more of cholesteryl acetate, cholesteryl valerate, cholesteryl heptanoate, cholesteryl n-octanoate, cholesteryl nonanoate, cholesteryl decanoate and cholesteryl carbonate;
the addition amount of the cholesteric liquid crystal material is 1-6 times of the weight of polyvinyl alcohol.
7. The method for preparing a UV-curable liquid crystal structural color film according to claim 2, wherein: in the step (2), uniformly stirring the polyethylene glycol diacrylate and the deionized water, adding the photoinitiator, and uniformly mixing to obtain a polyethylene glycol diacrylate aqueous solution containing the photoinitiator; and (2) adding a polyethylene glycol diacrylate aqueous solution containing a photoinitiator into the white sol emulsion obtained in the step (1), and then stirring at a constant speed for 1-2 hours at room temperature to obtain the polymer dispersed liquid crystal hydrogel.
8. The method for preparing a UV light-curable liquid crystal structural color film according to claim 2 or 7, wherein: the photoinitiator adopted in the step (2) is 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-acetone, 1- [4- (2-hydroxyethoxy) -phenyl ] -2-hydroxy-2-methyl-1-acetone or 2-methyl-1- (4-methylthiophenyl) -2-morphinyl-1-acetone;
in the step (2), the mass fraction of the polyethylene glycol diacrylate in the aqueous solution of the polyethylene glycol diacrylate containing the photoinitiator is 30-60%, and the mass fraction of the photoinitiator is 1-5%.
9. The method for preparing a UV light-curable liquid crystal structural color film according to claim 2 or 7, wherein: the mass of the polyethylene glycol diacrylate contained in the polyethylene glycol diacrylate aqueous solution containing the photoinitiator in the step (2) is 1-3 times that of polyvinyl alcohol contained in the white sol emulsion.
10. The method for preparing a UV-curable liquid crystal structural color film according to claim 2, wherein: in the step (3), before the polymer dispersed liquid crystal hydrogel is transferred to the surface of a printing stock, the polymer dispersed liquid crystal hydrogel is pretreated; the pretreatment is to add deionized water or ethanol for dilution to adjust the solid content of the polymer dispersed liquid crystal hydrogel system, so that the solid content of the polymer dispersed liquid crystal hydrogel system is 30-60%;
the method for transferring the polymer dispersed liquid crystal hydrogel onto the surface of the printing stock in the step (3) is coating, spraying, silk-screen printing or gravure printing; the substrate is paper, fabric or plastic film.
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