A white-background and black-letter liquid crystal writing board and its preparation method

Abstract

The present invention discloses a white-background black-character liquid crystal writing board and a preparation method thereof, which includes a transparent PET film with a nanocomposite network plated on one side, a cholesteric liquid crystal layer containing an azo photosensitive molecular mixture, and an opaque PET black film with a nanocomposite network plated on one side, which are connected in sequence from top to bottom. The addition of azo photosensitive molecules causes the semi-helical liquid crystal composite system to generate a texture opposite to that of ordinary cholesteric liquid crystals, so that when an electric field is applied, the liquid crystal transforms into a planar texture, and the planar texture can achieve white light reflection and present white; the locally pressed area is a focal conic texture, and the liquid crystal presents a transparent state, and the black color at the bottom can be displayed. The final writing result is to achieve white background and black characters.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid crystal writing boards, and particularly relates to a white-background black-letter liquid crystal writing board and a preparation method thereof. Background Art

[0002] The statements herein only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Existing liquid crystal writing boards are mostly of the green light reflection type, and their handwriting is green. The reflection wave width of the liquid crystal thin layer of this kind of liquid crystal writing board is relatively narrow, which limits the improvement of its contrast and handwriting brightness, and further limits the application range of the liquid crystal writing board.

[0004] There are few types of white-background black-letter liquid crystal writing boards on the existing market, and the technology is not mature. There are generally problems of low contrast and large driving voltage. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a white-background black-letter liquid crystal writing board and a preparation method thereof.

[0006] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0007] In the first aspect, the present invention provides a liquid crystal composite system, which comprises the following components in parts by weight: 50-80 parts of cholesteric liquid crystal, 3-10 parts of polymerizable monomer mixture, 15-25 parts of azo photosensitive molecule, and 1-5 parts of ultraviolet light initiator;

[0008] The cholesteric liquid crystal is composed of the following components in parts by weight: 0-50 parts of CB11CB liquid crystal, 0-50 parts of CB7CB, 10-50 parts of 5CB, 5-15 parts of chiral molecular dopant, and the contents of CB11CB and CB7CB are not both 0 at the same time;

[0009] The azo photosensitive molecule is selected from

[0010]

[0011] two, three, four or five of them.

[0012] Adding a chiral molecule containing an epoxy isoprene substituent makes the prepared cholesteric liquid crystal have a semi-helical structure. After the molecular arrangement rotates 180 degrees, it rotates back to the original position in the opposite direction, and can produce an opposite texture in cooperation with a unique azo photosensitive molecule; if only one is selected, its influence on the texture is weak, and multiple azo photosensitive molecules produce a synergistic effect, making the texture transformation more complete.

[0013] The preparation methods of the azo photosensitive molecules (2), (3), and (5) are:

[0014] 1. Dissolve the aromatic primary amine in an acidic aqueous solution containing added nitrite, react to obtain an aqueous solution A of aromatic diazonium salt;

[0015] 2. Dissolve the corresponding aromatic coupling component in an alkane organic solvent to obtain solution B;

[0016] 3. Mix the above solutions A and B, heat under the condition of 90 °C, stir, and carry out a coupling reaction;

[0017] 4. After the reaction is completed, separate the product and recover the solvent.

[0018] The preparation method of the azo photosensitive molecules (1) and (4) is as follows:

[0019]

[0020] Among them, R1 and R2 can be alkyl, alcohol, or halogen.

[0021] The addition of the azo photosensitive molecule makes the semi-helical liquid crystal composite system produce a texture opposite to that of the ordinary cholesteric liquid crystal. When an electric field is applied, the liquid crystal changes to a planar texture, and the planar texture can achieve white light reflection and present white; the locally pressurized area is a focal conic texture, and the liquid crystal presents a transparent state, and the black at the bottom can be displayed. The final writing result is to achieve white background and black characters.

[0022] In some embodiments, the mass ratio of the azo photosensitive molecules described in formula (1), formula (2), formula (3), formula (4), and formula (5) is 0 - 30:0 - 30:0 - 30:0 - 30:0 - 30, and the masses of various azo photosensitive molecules are not 0 at the same time.

[0023] Preferably, the mass ratio of the azo photosensitive molecules described in formula (1), formula (2), formula (3), formula (4), and formula (5) is 20 - 30:10 - 25:20 - 25:3 - 10:5 - 15.

[0024] In some embodiments, the chiral molecular dopant is selected from

[0025]

[0026]

[0027] The preparation method of the chiral molecular dopant is:

[0028] It is prepared by using tetrahydrofuran and an alkane compound with corresponding substituents as raw materials, zinc oxide as a catalyst, and tert-butyl peroxide as an initiator, and reacting at 100-110 °C for 10 h. Among them, the amount of substance of zinc oxide is 15% of the amount of substance of tetrahydrofuran; the amount of substance of tert-butyl peroxide is 10% of the amount of substance of tetrahydrofuran; the amount of substance of the corresponding alkane compound is 3 times the amount of substance of tetrahydrofuran.

[0029] A chiral molecule containing an epoxy isoprene substituent is added, and the substituent undergoes a complexation reaction with the added azo photosensitive molecule, changing the magnitude of the intermolecular force. The two produce a synergistic effect, making the prepared cholesteric liquid crystal a semi-helical structure. After the molecular arrangement rotates 180 degrees, it rotates back to the original position in the opposite direction, generating an opposite texture.

[0030] Preferably, the mass ratio of the chiral molecular dopants described in formula (6), formula (7), formula (8) and formula (9) is 0-10:0-10:0-10:0-10, and the masses of the four chiral molecular dopants are not all 0 at the same time.

[0031] More preferably, the mass ratio of the chiral molecular dopants described in formula (6), formula (7), formula (8) and formula (9) is 1-4:1-4:1-4:1-3.

[0032] In some embodiments, the polymerizable monomer mixture is composed of the following components in parts by weight: 1-10 parts of p-methylstyrene, 0-10 parts of 2-vinyl butyl ether, 0-5 parts of isopentenyl mercaptan, 1-3 parts of cobalt butenoate, and the contents of 2-vinyl butyl ether and isopentenyl mercaptan are not 0.

[0033] A small amount of metal-based polymerizable organic matter is added to the polymerizable monomer. Its addition can promote the compatibility of the polymerizable monomer system, is beneficial to the stability of the polymer and the increase of the molecular weight of the polymer, and the entire polymerization system also plays a role in stabilizing the texture to a certain extent.

[0034] In some embodiments, the ultraviolet light initiator is an aromatic ketone molecule.

[0035] Preferably, the ultraviolet light initiator is selected from

[0036]

[0037] one or a combination thereof.

[0038] The preparation method of the ultraviolet light initiator is:

[0039] An alkyne having structure (I) and N-fluorobis(phenylsulfonyl)amide having structure (II) are dispersed in a dichloromethane solvent, an appropriate amount of copper acetate catalyst and an oxidizing agent are added, and an aromatic ketone compound having structure (III) can be obtained by stirring at 80 - 120 °C:

[0040]

[0041] The molar ratio of the alkyne, N-fluorobis(phenylsulfonyl)amide, and copper acetate is: 1:1.5 - 3:2.2 - 3.

[0042] The obtained aromatic ketone compound having structure (III) is reacted with the corresponding aliphatic chain under the catalysis of palladium acetate in an inert gas and reacted at 70 - 90 °C for 3 - 5 h to obtain the aromatic ketone type ultraviolet light initiator.

[0043] The molar ratio of the aromatic ketone compound and the aliphatic chain is: 1:1.2 - 1.5.

[0044] An aromatic ketone type ultraviolet light initiator is used, which has a wider absorption wavelength range. Compared with common photoinitiators, it has stronger initiation activity for this polymerization system, more active free radicals, and better photoinitiation effect.

[0045] In a third aspect, the present invention provides a white background and black characters liquid crystal film, which is sequentially a transparent PET film, a liquid crystal layer, and a non-transparent PET black film from one side to the other side, and the three form a sandwich structure;

[0046] The liquid crystal layer is formed by ultraviolet polymerization of the liquid crystal composite system.

[0047] In some embodiments, a nano-composite network is provided on one side of both the transparent PET film and the non-transparent PET black film. The material of the nano-composite network is a mixture of silver nanowires, titanium dioxide nanowires, zinc oxide nanowires, and multi-walled carbon nanotubes, and a gallium zinc oxide film is plated on the silver nanowires. Traditional transparent conductive materials mostly use ITO, but ITO is brittle and toxic. Using flexible materials such as silver nanowires and multi-walled carbon nanotubes can effectively increase the bending resistance of the writing board. Combining with zinc oxide nanowires and titanium dioxide nanowires can effectively increase the thermal stability and heat conduction ability of the system.

[0048] Depositing a gallium zinc oxide film on the silver nanowires can effectively improve the chemical stability and thermal stability of the silver nanowires.

[0049] Using the uneven surface of the electrode, under pressure conditions, the liquid crystal can be oriented by the irregular surface, causing it to change from a planar texture to a twisted nematic texture. At the same time, compared with common ITO electrodes, the composite network conductive film composed of silver nanowires and graphene has advantages such as high light transmittance, low resistance, and excellent flexibility.

[0050] Preferably, the mass ratio of silver nanowires, titanium dioxide nanowires, zinc oxide nanowires, and multi-walled carbon nanotubes is 80-100:5-20:5-20:0.2-1.

[0051] Preferably, the silver nanowires have a length of 30-60 μm and a diameter of 20-60 nm;

[0052] Or, the titanium dioxide nanowires have a length of 5-20 μm, a diameter of 5-20 nm, and a Mohs hardness of 5.5-6;

[0053] Or, the zinc oxide nanowires have a length of 10-30 μm and a diameter of 5-20 nm;

[0054] Or, the multi-walled carbon nanotubes have an outer diameter of 10-30 nm and an inner diameter of 2-10 nm.

[0055] The multi-walled carbon nanotubes have a Young's modulus of 1-5 TPa and a flexural strength of 10-15 GPa.

[0056] The zinc oxide nanowires have a Mohs hardness of 5.5-6.

[0057] In some embodiments, the surfaces of the transparent PET film and the non-transparent PET black film are embossed with anti-glare textures.

[0058] Preferably, the anti-glare texture is a moth-eye structure. Embossing a moth-eye structure anti-glare texture on the surface of the PET film can provide good anti-blue light performance.

[0059] The transparent PET film and the non-transparent PET black film have a thickness of 35-80 μm and a resistivity of 600-900 Ω / m.

[0060] In some embodiments, a polyimide insulating film is attached to the conductive layer side of both the transparent PET film and the non-transparent PET black film;

[0061] The polyimide insulating film material is composed of the following components in parts by weight: 5-10 parts of polyimide, 0-5 parts of AlBi, 0-5 parts of GaN, and 0-5 parts of BSb;

[0062] The inorganic filler has a particle size of 2-20 nm.

[0063] Instead of using ordinary insulating glue, on the basis of a traditional polyimide insulating film, inorganic fillers are filled inside to form a composite system, which plays a role in increasing light transmittance on the basis of insulation, improving the contrast, and making the white background with black characters more obvious.

[0064] In some embodiments, the thicknesses of the transparent PET film, the liquid crystal layer, and the non-transparent PET black film are 60 - 160 μm, 5 - 50 μm, and 60 - 160 μm in sequence.

[0065] In some embodiments, an absorbing layer is provided on the non-transparent PET black film, and the absorbing layer is a detachable black ink sticker. The thickness of the ink sticker is 60 - 100 μm.

[0066] The color of the background can be changed according to needs to achieve combinations of various writing situations, such as white background with black characters, white background with yellow characters, white background with green characters, etc.

[0067] In a third aspect, the present invention provides a method for preparing the white-background black-character liquid crystal film, including the following steps:

[0068] Mix a cholesteric liquid crystal, a mixture of polymerizable monomers, an azo photosensitive molecule, and a UV initiator in proportion, and ultrasonically mix them evenly in the dark to obtain a liquid crystal composite system;

[0069] Fix the transparent PET film and the non-transparent PET black film relative to each other, then pour the liquid crystal composite system between the two films, and form a composite film by extrusion;

[0070] Finally, perform UV polymerization to obtain the liquid crystal film.

[0071] In some embodiments, it further includes the step of depositing a nano-composite network on one side surface of the transparent PET film and the non-transparent PET black film;

[0072] Specifically: First, deposit a gallium zinc oxide film on the surface of silver nanowires;

[0073] Mix silver nanowires, titanium dioxide nanowires, zinc oxide nanowires, and multi-walled carbon nanotubes in proportion to obtain a nano-particle mixture;

[0074] After the nano-particle mixture is fully dispersed, print it on one side of the transparent PET film and the non-transparent PET black film.

[0075] In a fourth aspect, the present invention provides a white-background black-character liquid crystal writing board assembled from the white-background black-character liquid crystal film.

[0076] The beneficial effects obtained by one or more of the above embodiments of the present invention are as follows:

[0077] The addition of azo photosensitive molecules causes the semi-helical liquid crystal composite system to produce a texture opposite to that of ordinary cholesteric liquid crystals. When an electric field is applied, the liquid crystal transforms into a planar texture, and the planar texture can achieve white light reflection and present white; the locally pressurized area is a focal conic texture, and the liquid crystal presents a transparent state, allowing the black color at the bottom to be displayed. The final writing result is white characters on a black background.

[0078] A small amount of metal-polymerizable organic matter is added to the polymerizable monomer. Its addition can promote the compatibility of the polymerizable monomer system, is beneficial to the stability of the polymer and the increase of the molecular weight of the polymer, and the entire polymerization system also plays a role in stabilizing the texture to a certain extent.

[0079] An aromatic ketone ultraviolet light initiator is used. Its absorption wavelength range is wider. Compared with common light initiators, its initiation activity for this polymerization system is stronger, the free radicals are more active, and the photo-initiation effect is better. Detailed implementation mode

[0080] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0081] The present invention will be further described below in conjunction with embodiments.

[0082] Example 1

[0083] Step 1) First, use an anti-glare texture roller to fully extrude the upper and lower surfaces of the transparent PET film and the non-transparent PET black film.

[0084] Step 2) First, deposit a thin film on the silver nanowires by chemical deposition using gallium zinc oxide; take 80 parts of silver nanowires, 5 parts of titanium dioxide nanowires, 5 parts of zinc oxide nanowires, and 0.5 part of multi-walled carbon nanotubes by weight to obtain a nanoparticle mixture; then, after fully dispersing the nanoparticle mixture by mechanical dispersion method, use a nanomaterial deposition inkjet printer to deposit the nanoparticles on one side of the transparent PET film and the black PET film to form a nanocomposite network.

[0085] Step 3) First, weigh 5 parts of polyimide, 3 parts of AlBi, 2 parts of GaN, and 2 parts of BSb by mass to obtain an insulating layer material mixture; then dissolve the mixture in a solvent, which is a mixture of tetrahydrofuran and cyclohexane, and the mixing ratio of the two is 1:1; the mass fraction of the insulating material is 25%; on the conductive layer side of one of the transparent or black PET films, uniformly coat the prepared insulating material solution on its conductive surface, and then dry and cure.

[0086] Step 4) First, prepare a chiral molecular dopant using chiral molecules. The chemical structural formulas of the chiral molecular substances are as follows:

[0087]

[0088] The mass parts of each of the above components are as follows:

[0089]

[0090]

[0091] Then, take 30 parts of CB11CB, 20 parts of CB7CB, 30 parts of 5CB, and 10 parts of the chiral molecular dopant by weight, mix them, and ultrasonically oscillate for 10 h at 40 °C to obtain a tilted helical cholesteric liquid crystal; then, weigh 5 parts of p-methylstyrene, 5 parts of 2-vinyl butyl ether, 2 parts of isopentenyl mercaptan, and 3 parts of cobalt butenoate by weight to obtain a polymerizable monomer mixture; then, weigh an aromatic ketone molecule as an ultraviolet light initiator. The chemical structural formulas of the aromatic ketone molecules are as follows:

[0092]

[0093] The mass parts of each of the above components are as follows:

[0094] (10) (11) (12) (13) 0.2 parts 0.3 parts 0.5 parts 0.2 parts

[0095] Then, weigh an azo photosensitive molecule. The chemical structural formulas of the azo photosensitive molecules are as follows:

[0096]

[0097]

[0098] The mass parts of each of the above components are as follows:

[0099] (1) (2) (3) (4) (5) 3 parts 5 parts 0 parts 2 parts 2 parts

[0100] Then, weigh 70 parts of the cholesteric liquid crystal, 5 parts of the polymerizable monomer mixture, 20 parts of the azo photosensitive molecule mixture, and 2 parts of the ultraviolet light initiator by weight. Under light-shielded conditions, oscillate the obtained mixture for 10 min and ultrasonically treat it for 1 h, repeating multiple times until it is uniformly mixed;

[0101] Step 5) Place the PET transparent film with a nanocomposite network coated on one side and the conductive layer side of the PET non-transparent black film with a nanocomposite grid coated on one side opposite to each other, pour the uniformly mixed liquid crystal composite system into the gap between the two films, and form a composite film by extrusion.

[0102] Then, ultraviolet polymerization is carried out. The polymerization process and conditions are as follows: under 30°C, irradiated with 4mW of 365nm ultraviolet light for 15 minutes; under 40°C, irradiated with 4mW of 365nm ultraviolet light for 15 minutes; under 50°C, irradiated with 4mW of 365nm ultraviolet light for 15 minutes.

[0103] Step 6) Cut the liquid crystal film prepared in step 5) into the required size.

[0104] Example 2

[0105] Step 1) First, use an anti-glare texture roller to fully extrude the upper and lower surfaces of the transparent PET film and the non-transparent PET black film.

[0106] Step 2) First, deposit a thin film on the silver nanowires using gallium zinc oxide by chemical deposition method; take 90 parts of silver nanowires, 15 parts of titanium dioxide nanowires, 15 parts of zinc oxide nanowires, and 0.8 part of multi-walled carbon nanotubes by weight to obtain a nanoparticle mixture; then, after fully dispersing the nanoparticle mixture by mechanical dispersion method, use a nano-material deposition inkjet printer to deposit the nanoparticles on one side of the transparent PET film and the black PET film to form a nano-composite network.

[0107] Step 3) First, weigh 7 parts of polyimide, 2 parts of AlBi, 2 parts of GaN, and 2 parts of BSb by mass to obtain an insulating layer material mixture; then dissolve the mixture in a solvent, which is a mixture of tetrahydrofuran and cyclohexane, and the mixing ratio of the two is 1:1; the mass fraction of the insulating material is 25%; on the conductive layer side of one of the transparent or black PET films, uniformly coat the prepared insulating material solution on its conductive surface, and then dry and cure it.

[0108] Step 4. First, prepare a chiral molecular dopant using chiral molecules. The chemical structural formulas of each chiral molecule are:

[0109]

[0110]

[0111] The mass fractions of the above components are:

[0112] (6) (7) (8) (9) 2 parts 1 part 2 parts 2 parts

[0113] Then, take 30 parts of CB11CB, 20 parts of CB7CB, 30 parts of 5CB, and 5 parts of chiral molecular dopant by weight, mix them, and ultrasonically oscillate at 40 °C for 10 h to obtain a tilted helical cholesteric liquid crystal; then weigh 4 parts of p-methylstyrene, 6 parts of 2-vinyl butyl ether, 6 parts of isopentenyl mercaptan, and 2 parts of cobalt butenoate by weight to obtain a polymerizable monomer mixture; then weigh aromatic ketone molecules as ultraviolet light initiators, and the chemical structural formulas of each aromatic ketone molecule are:

[0114]

[0115] The mass parts of each of the above components are:

[0116]

[0117]

[0118] Then weigh azo photosensitive molecules, and the chemical structural formulas of each azo photosensitive molecule are:

[0119]

[0120] The mass parts of each of the above components are:

[0121] (1) (2) (3) (4) (5) 20 parts 20 parts 5 parts 5 parts 5 parts

[0122] Then weigh 65 parts of cholesteric liquid crystal, 6 parts of polymerizable monomer mixture, 15 parts of azo photosensitive molecule mixture, and 1 part of ultraviolet light initiator by weight. Under dark conditions, oscillate the obtained mixture for 10 min and ultrasonically treat it for 1 h, and repeat multiple times until it is evenly mixed;

[0123] Step 5) Place the PET transparent film with a nano-composite network plated on one side and the PET non-transparent black film with a nano-composite grid plated on one side with the conductive layer sides facing each other, pour the evenly mixed liquid crystal composite system into the gap between the two films, and form a composite film by extrusion.

[0124] Then carry out ultraviolet polymerization, and the polymerization process and conditions are: irradiate with 4 mW of 365 nm ultraviolet light at 30 °C for 15 minutes; irradiate with 4 mW of 365 nm ultraviolet light at 40 °C for 15 minutes; irradiate with 4 mW of 365 nm ultraviolet light at 50 °C for 15 minutes.

[0125] Step 6) Cut the liquid crystal film prepared in Step 5) into the required size.

[0126] Example 3

[0127] Step 1) First, use an anti-glare texture roller to fully extrude the upper and lower surfaces of the transparent PET film and the non-transparent PET black film.

[0128] Step 2) First, deposit a thin film on the silver nanowires by chemical deposition using zinc gallium oxide; take 90 parts by weight of silver nanowires, 10 parts of titanium dioxide nanowires, 10 parts of zinc oxide nanowires, and 1 part of multi-walled carbon nanotubes and mix them to obtain a nanoparticle mixture; then, after fully dispersing the nanoparticle mixture by mechanical dispersion method, use a nanomaterial deposition inkjet printer to deposit the nanoparticles on one side of a transparent PET film and a black PET film to form a nanocomposite network.

[0129] Step 3) First, weigh 7 parts by mass of polyimide, 3 parts of AlBi, 3 parts of GaN, and 3 parts of BSb to obtain an insulating layer material mixture; then dissolve the mixture in a solvent, where the solvent is a mixture of tetrahydrofuran and cyclohexane with a mixing ratio of 1:1; the mass fraction of the insulating material is 25%; on the conductive layer side of one of the transparent or black PET films, uniformly coat the prepared insulating material solution on its conductive surface, and then dry and cure it.

[0130] Step 4. First, prepare a chiral molecular dopant using chiral molecules. The chemical structural formulas of the chiral molecular substances are:

[0131]

[0132] The mass parts of the above compounds are:

[0133] (6) (7) (8) (9) 4 parts 4 parts 8 parts 5 parts

[0134] Then, take 40 parts by weight of CB11CB, 40 parts of CB7CB, 45 parts of 5CB, and 7 parts of chiral molecular dopant and mix them, and ultrasonically oscillate at 40 °C for 10 h to obtain a tilted helical cholesteric liquid crystal; then, weigh 5 parts of p-methylstyrene, 6 parts of 2-vinyl butyl ether, 6 parts of isopentenyl mercaptan, and 3 parts of cobalt butenoate to obtain a polymerizable monomer mixture; then, weigh an aromatic ketone molecule as an ultraviolet light initiator. The chemical structural formulas of the aromatic ketone molecules are:

[0135]

[0136]

[0137] The mass parts of the above molecules are:

[0138] (10) (11) (12) (13) 1 part 1 part 1 part 1 part

[0139] Then, weigh an azo photosensitive molecule. The chemical structural formulas of the azo photosensitive molecules are:

[0140]

[0141] The mass parts of the above molecules are:

[0142]

[0143]

[0144] Then, weigh 70 parts by weight of cholesteric liquid crystal, 7 parts of polymerizable monomer mixture, 20 parts of azo photosensitive molecule mixture, and 1.5 parts of ultraviolet initiator. Under light-shielded conditions, oscillate the obtained mixture for 10 min and ultrasonicate for 1 h, repeating multiple times until it is uniformly mixed;

[0145] Step 5) Place the PET transparent film with a nanocomposite network plated on one side and the PET non-transparent black film with a nanocomposite grid plated on one side opposite to each other with the conductive layer sides facing each other. Pour the uniformly mixed liquid crystal composite system into the gap between the two films and form a composite film by extrusion.

[0146] Then, perform ultraviolet polymerization. The polymerization process and conditions are as follows: irradiate with 4 mW of 365 nm ultraviolet light at 30 °C for 15 minutes; irradiate with 4 mW of 365 nm ultraviolet light at 40 °C for 15 minutes; irradiate with 4 mW of 365 nm ultraviolet light at 50 °C for 15 minutes.

[0147] Step 6. Cut the liquid crystal film prepared in Step 5 into the required size.

[0148] Example 4

[0149] Step 1) First, use an anti-glare texture roller to fully extrude the upper and lower surfaces of the transparent PET film and the non-transparent PET black film.

[0150] Step 2) First, deposit a thin film on the silver nanowires by chemical deposition using gallium zinc oxide; take 95 parts by weight of silver nanowires, 5 parts of titanium dioxide nanowires, 5 parts of zinc oxide nanowires, and 1 part of multi-walled carbon nanotubes and mix them to obtain a nanoparticle mixture; then, after fully dispersing the nanoparticle mixture by mechanical dispersion, use a nanomaterial deposition inkjet printer to deposit the nanoparticles on one side of the transparent PET film and the black PET film to form a nanocomposite network.

[0151] Step 3) First, weigh 8 parts of polyimide, 3 parts of AlBi, 3 parts of GaN, and 3 parts of BSb by mass to obtain an insulating layer material mixture; then, dissolve the mixture in a solvent, where the solvent is a mixture of tetrahydrofuran and cyclohexane with a mixing ratio of 1:1; the mass fraction of the insulating material is 25%; on the conductive layer side of one of the transparent or black PET films, uniformly coat the prepared insulating material solution on its conductive surface, and then dry and cure it.

[0152] Step 4) First, prepare a chiral molecular dopant using chiral molecules. The chemical structural formulas of the chiral molecules are as follows:

[0153]

[0154] The mass parts of the above compounds are as follows:

[0155] (6) (7) (8) (9) 3 parts 4 parts 4 parts 6 parts

[0156] Then, take 40 parts of CB11CB, 45 parts of CB7CB, 30 parts of 5CB, and 7.5 parts of the chiral molecular dopant by weight, mix them, and ultrasonically oscillate for 10 h at 40 °C to obtain a tilted helical cholesteric liquid crystal; then, weigh 7 parts of p-methylstyrene, 3 parts of 2-vinyl butyl ether, 2 parts of isopentenyl mercaptan, and 1 part of cobalt butenoate by weight to obtain a polymerizable monomer mixture; then, weigh aromatic ketone molecules as a UV initiator. The chemical structural formulas of the aromatic ketone molecules are as follows:

[0157]

[0158] The mass parts of the above molecules are as follows:

[0159] (10) (11) (12) (13) 4 parts 2 parts 1 part 2 parts

[0160] Then, weigh azo photosensitive molecules. The chemical structural formulas of the azo photosensitive molecules are as follows:

[0161]

[0162]

[0163] The mass parts of the above molecules are as follows:

[0164] (1) (2) (3) (4) (5) 25 parts 25 parts 25 parts 5 parts 9 parts

[0165] Then, weigh 70 parts of the cholesteric liquid crystal, 7 parts of the polymerizable monomer mixture, 20 parts of the azo photosensitive molecule mixture, and 1.5 parts of the UV initiator by weight. Under light-shielded conditions, oscillate the obtained mixture for 10 min and ultrasonically treat it for 1 h, and repeat multiple times until it is uniformly mixed;

[0166] Step 5) Place the PET transparent film with a nanocomposite network coated on one side and the conductive layer side of the PET non-transparent black film with a nanocomposite grid coated on one side opposite to each other, pour the uniformly mixed liquid crystal composite system into the gap between the two films, and form a composite film by extrusion.

[0167] Then, ultraviolet polymerization is carried out. The polymerization process and conditions are as follows: irradiated with 4 mW of 365 nm ultraviolet light for 15 minutes at 30 °C; irradiated with 4 mW of 365 nm ultraviolet light for 15 minutes at 40 °C; irradiated with 4 mW of 365 nm ultraviolet light for 15 minutes at 50 °C.

[0168] Step 6) Cut the liquid crystal film prepared in step 5) into the required size.

[0169] Example 5

[0170] Step 1) First, use an anti-glare texture roller to fully extrude the upper and lower surfaces of the transparent PET film and the non-transparent PET black film.

[0171] Step 2) First, deposit a thin film on the silver nanowires using gallium zinc oxide by chemical deposition method; take 85 parts of silver nanowires, 15 parts of titanium dioxide nanowires, 15 parts of zinc oxide nanowires, and 0.3 part of multi-walled carbon nanotubes by weight to obtain a nanoparticle mixture; then, after fully dispersing the nanoparticle mixture by mechanical dispersion method, use a nanomaterial deposition inkjet printer to deposit the nanoparticles on one side of the transparent PET film and the black PET film to form a nano-composite network.

[0172] Step 3) First, weigh 9 parts of polyimide, 4 parts of AlBi, 4 parts of GaN, and 4 parts of BSb by mass to obtain an insulating layer material mixture; then dissolve the mixture in a solvent, and the solvent is a mixture of tetrahydrofuran and cyclohexane, and the mixing ratio of the two is 2:1; the mass fraction of the insulating material is 25%; on the conductive layer side of one of the transparent or black PET films, uniformly coat the prepared insulating material solution on its conductive surface, and then dry and cure.

[0173] Step 4) First, prepare a chiral molecular dopant using chiral molecules. The chemical structural formulas of each chiral molecule are as follows:

[0174]

[0175] The mass fractions of the above compounds are as follows:

[0176] (6) (7) (8) (9) 11 parts 5 parts 10 parts 5 parts

[0177] Then, take 50 parts of CB11CB, 20 parts of CB7CB, 20 parts of 5CB, and 8 parts of chiral molecular dopant by weight and mix them. Ultrasonically oscillate at 40 °C for 10 h to obtain a tilted helical cholesteric liquid crystal; then, weigh 8 parts of p-methylstyrene, 4 parts of 2-vinyl butyl ether, 5 parts of isopentenyl mercaptan, and 2 parts of cobalt butenoate by weight to obtain a polymerizable monomer mixture; then, weigh aromatic ketone molecules as ultraviolet light initiators. The chemical structural formulas of each aromatic ketone molecule are as follows:

[0178]

[0179] The mass fraction of the above-mentioned molecules is as follows:

[0180] (10) (11) (12) (13) 0 parts 3 parts 2 parts 5 parts

[0181] Then weigh the azo photosensitive molecules. The chemical structural formulas of the azo photosensitive molecules are as follows:

[0182]

[0183] The mass fraction of the above-mentioned molecules is as follows:

[0184] (1) (2) (3) (4) (5) 25 parts 9 parts 25 parts 5 parts 15 parts

[0185] Then weigh 70 parts by weight of cholesteric liquid crystal, 7 parts of polymerizable monomer mixture, 20 parts of azo photosensitive molecule mixture, and 1.5 parts of ultraviolet initiator. The obtained mixture is shaken for 10 min and ultrasonicated for 1 h under light-shielded conditions, and repeated multiple times until it is uniformly mixed;

[0186] Step 5) Place the side with the conductive layer of the PET transparent film with a unidirectionally deposited nano-composite network and the PET non-transparent black film with a unidirectionally deposited nano-composite grid opposite to each other. Pour the uniformly mixed liquid crystal composite system into the gap between the two films and form a composite film by extrusion. Then carry out ultraviolet polymerization. The polymerization process and conditions are as follows: irradiate with 4 mW of 365 nm ultraviolet light for 15 minutes at 30 °C; irradiate with 4 mW of 365 nm ultraviolet light for 15 minutes at 40 °C; irradiate with 4 mW of 365 nm ultraviolet light for 15 minutes at 50 °C.

[0187] Step 6) Cut the liquid crystal film prepared in Step 5) into the required size.

[0188] Example 6

[0189] Step 1) First, use an anti-glare texture roller to fully extrude the upper and lower surfaces of the transparent PET film and the non-transparent PET black film.

[0190] Step 2) First, deposit a thin film on the silver nanowires using gallium zinc oxide by chemical deposition; take 80 parts by weight of silver nanowires, 10 parts of titanium dioxide nanowires, 10 parts of zinc oxide nanowires, and 0.3 parts of multi-walled carbon nanotubes and mix them to obtain a nanoparticle mixture; then, after fully dispersing the nanoparticle mixture by mechanical dispersion method, use a nano-material deposition inkjet printer to deposit the nanoparticles on one side of the transparent PET film and the black PET film to form a nano-composite network.

[0191] Step 3) First, weigh 10 parts of polyimide, 5 parts of AlBi, 5 parts of GaN, and 5 parts of BSb according to mass parts to obtain an insulating layer material mixture; then dissolve the mixture in a solvent, where the solvent is a mixture of tetrahydrofuran and cyclohexane, and the mixing ratio of the two is 2:1; the mass parts of the insulating material is 25%; on one side of the conductive layer of one of the transparent or black PET films, uniformly coat the prepared insulating material solution on its conductive surface, and then dry and cure it.

[0192] Step 4) First, prepare a chiral molecular dopant using chiral molecules. The chemical structural formulas of the chiral molecular substances are:

[0193]

[0194] The mass parts of the above compounds are:

[0195] (6) (7) (8) (9) 10 parts 15 parts 11 parts 6 parts

[0196] Then, take 50 parts of CB11CB, 20 parts of CB7CB, 20 parts of 5CB, and 12 parts of the chiral molecular dopant and mix them. Ultrasonically oscillate for 10 h at 40 °C to obtain a tilted helical cholesteric liquid crystal; then weigh 8 parts of p-methylstyrene, 4 parts of 2-vinyl butyl ether, 5 parts of isopentenyl mercaptan, and 2 parts of cobalt butenoate according to weight parts to obtain a polymerizable monomer mixture; then weigh aromatic ketone molecules as the ultraviolet light initiator. The chemical structural formulas of the aromatic ketone molecules are:

[0197]

[0198]

[0199] The mass parts of the above molecules are:

[0200] (10) (11) (12) (13) 3 parts 2 parts 1 part 5 parts

[0201] Then weigh azo photosensitive molecules. The chemical structural formulas of the azo photosensitive molecules are:

[0202]

[0203] The mass parts of the above molecules are:

[0204] (1) (2) (3) (4) (5) 30 parts 10 parts 25 parts 5 parts 15 parts

[0205] Then weigh 80 parts of the cholesteric liquid crystal, 10 parts of the polymerizable monomer mixture, 30 parts of the azo photosensitive molecule mixture, and 2 parts of the ultraviolet light initiator according to weight parts. Under dark conditions, oscillate the obtained mixture for 10 min and ultrasonicate for 1 h, and repeat multiple times until it is uniformly mixed;

[0206] Step 5) Place the side with the nanocomposite network-coated PET transparent film and the side with the conductive layer of the PET non-transparent black film coated with a nanocomposite grid opposite to each other, pour the uniformly mixed liquid crystal composite system into the gap between the two films, and form a composite film by extrusion.

[0207] Then, carry out ultraviolet polymerization. The polymerization process and conditions are as follows: irradiate with 4 mW of 365 nm ultraviolet light for 15 minutes at 30 °C; irradiate with 4 mW of 365 nm ultraviolet light for 15 minutes at 40 °C; irradiate with 4 mW of 365 nm ultraviolet light for 15 minutes at 50 °C.

[0208] Step 6) Cut the liquid crystal film prepared in Step 5) into the required size.

[0209] The products of the embodiments of the present invention were tested for performance, and the results are shown in Table 1 below:

[0210] Table 1

[0211]

[0212] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A liquid crystal composite system, characterized in that: Comprising the following components in parts by weight: 50 - 80 parts of cholesteric liquid crystal, 3 - 10 parts of polymerizable monomer mixture, 15 - 25 parts of azo photosensitive molecule, and 1 - 5 parts of ultraviolet initiator; The cholesteric liquid crystal consists of the following components in parts by weight: 10 - 50 parts of CB11CB liquid crystal, 0 - 50 parts of CB7CB, 0 - 50 parts of 5CB, 5 - 15 parts of chiral molecular dopant, and the contents of CB7CB and 5CB are not both 0 at the same time; The azo photosensitive molecule is selected from （1）； （2）； （3）； （4）； Or, (5) two, three, four, or five of them.

2. The liquid crystal composite system according to claim 1, characterized in that: The mass ratio of the azo photosensitive molecules represented by formula (1), formula (2), formula (3), formula (4), and formula (5) is 0 - 30:0 - 30:0 - 30:0 - 30:0 - 30, and the masses of various azo photosensitive molecules are not all 0 at the same time.

3. The liquid crystal composite system according to claim 2, characterized in that: The mass ratio of the azo photosensitive molecules represented by formula (1), formula (2), formula (3), formula (4), and formula (5) is 20 - 30:10 - 25:20 - 25:3 - 10:5 - 15.

4. The liquid crystal composite system according to claim 1, characterized in that: The chiral molecular dopant is selected from （6）； （7）； （8）； （9）。 5. The liquid crystal composite system according to claim 4, characterized in that: The mass ratio of the chiral molecular dopants represented by formula (6), formula (7), formula (8), and formula (9) is 0 - 10:0 - 10:0 - 10:0 - 10, and the masses of the four chiral molecular dopants are not all 0 at the same time.

6. The liquid crystal composite system according to claim 5, characterized in that: The mass ratio of the chiral molecular dopants represented by formula (6), formula (7), formula (8), and formula (9) is 1 - 4:1 - 3:1 - 4:1 - 3.

7. The liquid crystal composite system according to claim 1, characterized in that: The polymerizable monomer mixture consists of the following components in parts by weight: 0 - 10 parts of p-methylstyrene, 0 - 10 parts of 2-vinyl butyl ether, 0 - 5 parts of isopentenyl mercaptan, 1 - 3 parts of cobalt butenoate, and the contents of 2-vinyl butyl ether and isopentenyl mercaptan are not 0.

8. The liquid crystal composite system according to claim 1, characterized in that: The ultraviolet initiator is an aromatic ketone molecule.

9. The liquid crystal composite system according to claim 8, characterized in that: The ultraviolet initiator is selected from （10）； （11）； （12）； Or, (13) one of them or a combination thereof.

10. A white background black character liquid crystal film, characterized in that: From one side to the other side are a transparent PET film, a liquid crystal layer, and an opaque PET black film in sequence, and the three form a sandwich structure; The liquid crystal layer is formed by ultraviolet polymerization of the liquid crystal composite system according to any one of claims 1 - 9.

11. The white background black character liquid crystal film according to claim 10, characterized in that: On one side of both the transparent PET film and the opaque PET black film, a nano composite network is provided, and the material of the nano composite network is a mixture of silver nanowires, titanium dioxide nanowires, zinc oxide nanowires, and multi-walled carbon nanotubes, and a gallium zinc oxide film is plated on the silver nanowires.

12. The white background black character liquid crystal film according to claim 11, characterized in that:The mass ratio of silver nanowires, titanium dioxide nanowires, zinc oxide nanowires, and multi-walled carbon nanotubes is 80 - 100:5 - 20:5 - 20:0.2 - 1.

13. The white-background and black-character liquid crystal film according to claim 11, wherein: The length of the silver nanowires is 30 - 60 μm, and the diameter is 20 - 60 nm; Or, the length of the titanium dioxide nanowires is 5 - 20 μm, the diameter is 5 - 20 nm, and the Mohs hardness is 5.5 - 6; Or, the length of the zinc oxide nanowires is 10 - 30 μm, and the diameter is 5 - 20 nm; Or, the outer diameter of the multi-walled carbon nanotubes is 10 - 30 nm, and the inner diameter is 2 - 10 nm.

14. The white-background and black-character liquid crystal film according to claim 10, wherein: Anti-glare textures are pressed on the surfaces of the transparent PET film and the opaque PET black film.

15. The white-background and black-character liquid crystal film according to claim 14, wherein: The anti-glare texture is a moth-eye structure.

16. The white-background and black-character liquid crystal film according to claim 14, wherein: On the conductive layer side of both the transparent PET film and the opaque PET black film, a polyimide insulating film is attached; The material of the polyimide insulating film consists of the following components in parts by weight: 5-10 parts of polyimide, 0-5 parts of AlBi, 0-5 parts of GaN, and 0-5 parts of BSb; The particle size of AlBi is 2-20 nm, the particle size of GaN is 2-20 nm, and the particle size of BSb is 2-20 nm.

17. The white-background and black-character liquid crystal film according to claim 10, wherein: The thicknesses of the transparent PET film, the liquid crystal layer, and the non-transparent PET black film are 60-160 μm, 5-50 μm, and 60-160 μm in sequence.

18. The white-background and black-character liquid crystal film according to claim 17, wherein: An absorbing layer is provided on the non-transparent PET black film, and the absorbing layer is a removable black ink sticker; the thickness of the ink sticker is 60-100 μm.

19. A method for preparing the white-background and black-character liquid crystal film according to any one of claims 10-18, wherein: It includes the following steps: Mix the cholesteric liquid crystal, the polymerizable monomer mixture, the azo photosensitive molecule, and the ultraviolet initiator in proportion, and ultrasonically mix them evenly in the dark to obtain a liquid crystal composite system; Fix the transparent PET film and the non-transparent PET black film relatively, then pour the liquid crystal composite system between the two films, and form a composite film by extrusion; Finally, perform ultraviolet polymerization to obtain a liquid crystal film.

20. The method for preparing the white-background and black-character liquid crystal film according to claim 19, wherein, It also includes the step of depositing a nano-composite network on one side surface of the transparent PET film and the non-transparent PET black film: First, deposit a gallium zinc oxide film on the surface of the silver nanowire; Mix the silver nanowire, the titanium dioxide nanowire, the zinc oxide nanowire, and the multi-walled carbon nanotube in proportion to obtain a nano-particle mixture; After the nano-particle mixture is fully dispersed, print it on one side of the transparent PET film and the non-transparent PET black film.

21. A white-background and black-character liquid crystal writing board, wherein: It is assembled from the white-background and black-character liquid crystal film according to any one of claims 10-18.

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