TW202340432A - A liquid crystal film and preparation method and application thereof - Google Patents

Abstract

The invention discloses a liquid crystal film and a preparation method and application thereof. The liquid crystal film is prepared by coating cholesteric liquid crystal, the cholesteric liquid crystal includes 12-38% of achiral polymerizable monomer, 2-5% of chiral polymerizable monomer, 0.03-3% of initiator, 1-3% of auxiliary and 60-80% of solvent. During preparation, the alignment coating solution is first coated on the support, and the release material is obtained by drying and rubbing alignment. Then, the liquid crystal coating solution is coated on the release material, and the liquid crystal film can be obtained after drying and curing. In this invention, the alignment layer formed by the alignment coating solution has the effect of inducing alignment, and the liquid crystal film obtained therefrom has a liquid crystal layer with a specific structure. The Bragg reflection occurs and has a multicolored color effect. Therefore, the liquid crystal film can be further used to prepare multicolored shells, such as mobile phone back covers, tablet back covers and so on.

Description

Liquid crystal film and preparation method and application thereof

The invention belongs to the technical field of polymer materials. Specifically, it is a liquid crystal film and its preparation method and application.

With the popularity of electronic products in public life, people are gradually pursuing the appearance design of products. Whether it is mobile phones, tablets, laptops and other electronic devices, the appearance characteristics of the product need to satisfy the aesthetic concepts of most consumers to the greatest extent. . At present, in order to attract consumers' attention, electronic products have also appeared in many differentiated designs in appearance. Taking the back cover of mobile phones as an example, there are various effects such as matte, shiny and colorful effects, which can improve the appearance of mobile phones. Among them, glossy and colorful effects are favored by consumers because of their strong visual impact.

We know that the back cover of mobile phones is mainly made of metal, glass and engineering plastics. Although metal materials have a shiny effect, when used as a mobile phone back cover, they have disadvantages such as difficulty in coloring and electromagnetic shielding properties. Although glass material has no magnetic field interference, it is fragile under the action of external force and has poor fall resistance and wear resistance. Engineering plastics, such as the existing composite board back cover, not only have the advantages of metal and glass materials, but can also achieve a colorful appearance through coating. Therefore, they are deeply loved by young consumers.

In the prior art, the invention patent with the announcement number CN107357056A discloses a colorful plate and a preparation method thereof. The colorful plate includes a stacked cholesterol liquid crystal layer and a reflective plate, wherein the cholesterol liquid crystal layer has a layer arranged stacked along the first direction. There are multiple layers of liquid crystal molecules, and the cholesterol liquid crystal layer has at least one gradient area. The pitch between adjacent liquid crystal molecular layers corresponding to the gradient area gradually changes along the second direction, and the first direction and the second direction are perpendicular. The above-mentioned gradient pitch can make the surface of the cholesterol liquid crystal layer present a microstructure with a required size, so that when the light is reflected by the reflective plate and passes through the above-mentioned cholesterol liquid crystal layer, the above-mentioned microstructure can make the reflected light have a reflection wavelength at the microstructure. Difference, due to the series of unequal wavelengths contained in the reflected light, the colorful board shows the effect of color change, which in turn enables the colorful board to present a colorful visual effect.

In addition, the utility model with announcement number CN214381674U discloses a shell composed of a matrix, a liquid crystal optical film layer and a reflective layer. The matrix is made of polycarbonate (PC) and polymethylmethacrylate (polymethylmethacrylate). , PMMA) composite sheet; its liquid crystal optical film layer contains oriented liquid crystal. On the one hand, the incident light entering the liquid crystal optical film layer can be reflected by the reflective layer, thereby improving the overall brightness and gloss of the shell; on the other hand, the The oriented liquid crystal displays a certain main color after reflecting the light, and the wavelength of the reflected light changes with the change of the incident angle of the incident light, so that when the user observes at different angles, the liquid crystal optical film layer observed appears The color of the casing will be red-shifted or blue-shifted as the viewing angle changes, ultimately giving the whole casing a colorful effect; its reflective layer can improve the brightness and gloss of the casing, and can cooperate with the liquid crystal optical film layer to make the casing The body presents a bright and colorful effect. It can be seen that this patent discloses the combination of a liquid crystal optical film layer and a reflective layer, and uses the combination of the reflective layer and the liquid crystal layer to achieve a colorful effect. However, since the optical film in this patent is composed of a liquid crystal optical film layer and a multi-layer reflective layer, it greatly increases the thickness of the back cover of the mobile phone, which is not conducive to the lightweight of the back cover of the mobile phone, thus making the consumer experience worse. In addition, due to the existence of multi-layer reflective layers, the production cost of the back cover of the mobile phone will also be increased and the preparation cycle will be greatly extended.

The object of the present invention is to provide a liquid crystal film, which is prepared by coating cholesterol liquid crystal. The cholesterol liquid crystal is made of achiral polymerizable monomers and chiral polymerizable monomers as main raw materials, and is further supplemented with initiators and auxiliaries. Made from agents and solvents. In order to make the liquid crystal film have a more regularly arranged multi-layer liquid crystal lattice structure, the present invention also provides a method for preparing a liquid crystal film, that is, first forming an alignment layer that can induce orientation on a support, and then coating the liquid crystal coating liquid on the alignment layer. On the layer, the liquid crystal film thus obtained undergoes Bragg reflection due to the liquid crystal layer with a specific structure and has a magic color effect. Therefore, the liquid crystal film can be further used to prepare magic color shells, such as mobile phone back covers and tablet back covers. Cover and so on.

The present invention is realized through the following technical solution: a liquid crystal film, which is prepared by coating a liquid crystal coating liquid. The liquid crystal coating liquid is cholesterol liquid crystal. In terms of mass percentage, the cholesterol liquid crystal includes achiral polymerizable monomer 12 ~38%, chiral polymerizable monomer 2~5%, initiator 0.03~3%, additives 1~3% and solvent 60~80%.

The achiral polymerizable monomer includes a bifunctional polymerizable monomer and a monofunctional polymerizable monomer, wherein the bifunctional polymerizable monomer satisfies the following structural formula (1): (1) In the structural formula (1), m and n respectively represent any natural number from 4 to 8, and R ₁ represents a hydrogen atom, methyl, ethyl, methoxy, ethoxy, phenyl, and benzyl. Or ester group; The monofunctional polymerizable monomer satisfies the following structural formula (2): (2) In structural formula (2), R ₂ represents a hydrogen atom, methyl group, ethyl group, methoxy group, ethoxy group, phenyl group, benzyl group or ester group.

Chiral polymerizable monomers include but are not limited to CN, CB15, S811, R1011 or chiral agents satisfying the following structural formula (3), (3).

Further, initiators include but are not limited to azo, peroxy and redox types. It can also be divided into water-soluble initiators (such as inorganic persulfates, hydrogen peroxide, water-soluble azo initiators, etc.) and oil-soluble (soluble in monomers or organic solvents) organic initiators according to their solubility properties. The polymerizable liquid crystal composition (cholesterol liquid crystal) of the present invention preferably contains at least one polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator. As a thermal polymerization initiator, benzoyl peroxide, 2,2'-azobisisobutyronitrile, etc. can be used. In addition, as photopolymerization initiators, benzoin ethers, benzophenones, acetophenones, benzoyl ketals, and sulfide initiators can be used. Ketones etc.

Auxiliaries can be flame retardants, defoaming agents, and hardening accelerators. Among them, flame retardants are mainly halogen-free flame retardants, which can be phosphorus-based flame retardants, nitrogen-based flame retardants, intumescent flame retardants, etc., and further can be tricresyl phosphate, triphenyl phosphate, triisophosphate Propyl phenyl ester, tributyl phosphate, trioctyl phosphate, tolyl diphenyl phosphate, melamine, etc. The preferred defoaming agent is organosilicon defoaming agent. This type of defoaming agent has high silicone oil activity in H ₂ O and ordinary oils. Its basic characteristics are stable chemical properties, wide range of use, low volatility, non-toxic, and It has outstanding defoaming ability, etc. It can be specifically polydimethylsiloxane, ethylene glycol siloxane, hydroxy silicone oil, fluorosiloxane, etc. In order to ensure the mechanical strength of the formed liquid crystal layer and the stability of the liquid crystal orientation, the hardening accelerator can be selected from: phenol group, silanol group, thiol group, phosphate group, sulfonic acid group, carboxyl group, carboxylic acid anhydride group, etc. Compounds, of which compounds having a phenol group or a silanol group are preferred. Specific examples of compounds having a phenol group include cyanophenol, nitrophenol, methoxyphenoxyphenol, thiophenoxyphenol, 4-benzylphenol, and the like; compounds having a silanol group Examples of the compound include trimethylsilanol, triethylsilanol, 1,4-bis(hydroxydimethylsilyl)benzene, triphenylsilanol, diphenylsilanediol, and the like.

The solvent is an organic solvent, selected from one or more of toluene, xylene, cumene, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, acetone, butanone, dipentanone, cyclopentanone, etc. species.

The technical solution of the present invention also includes: a method for preparing a liquid crystal film, which includes coating an alignment coating liquid on a support, drying and rubbing alignment to prepare a release material, and then coating the above liquid crystal coating liquid on the release material, and drying and After curing, a liquid crystal film is produced.

In terms of mass percentage, the alignment coating liquid includes 8% to 15% of liquid crystal guide agent, 60% to 85% of solvent and 3% to 8% of other components.

Further, the liquid crystal guiding agent is water-soluble polyvinyl alcohol and/or its derivatives. Its derivatives include: polyvinyl formal, polyvinyl acetal, polyvinyl butyral, polyvinyl phthalate, etc.

The solvent is mainly water, and may also contain other solvents, including but not limited to at least one of alcohols, esters, ketones, benzene, and ketoamide solvents. For example: alcohols such as methanol and ethanol; toluene, xylene, cumene, mesitylene; ester solvents such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate; acetone, methyl ethyl ketone, Ketone solvents such as methyl isobutyl ketone, cyclohexanone, and cyclopentanone; ether solvents such as tetrahydrofuran, 1,2-dimethoxyethane, and anisole; N,N-dimethylformamide , N-methyl-2-pyrrolidinone and other amide solvents; propylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, γ-butyrolactone, chlorobenzene, etc. They may be used alone or in a mixture of two or more types. In the present invention, one type of alcohol solvent may be preferably used or two or more types may be mixed and used.

Surfactants can improve the coating properties of the alignment layer solution and the liquid crystal coating solution. In the present invention, the surfactants include but are not limited to nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. , silicone surfactants, polyalkylene oxide surfactants or fluorosurfactants.

When using the above alignment coating liquid to prepare release materials, first, apply the alignment coating liquid on a support with a thickness of 80 to 300 μm. After coating, it is sent to a drying equipment and heated at 80 to 100°C for 3 to 10 minutes. Form an alignment film on the body, and then continue to rub and align the film. For example, use paper, gauze, felt, rubber, nylon or polyester fiber to rub the surface of the alignment film in a certain direction to obtain an aligned alignment layer. The alignment layer and the support form a release material.

Among them, the support body is a film formed by extrusion of thermoplastic resin, which can be polyester resin, polycarbonate resin, polystyrene resin, polyacrylate resin, polymethacrylate resin, polyurethane resin, polyethylene resin and polyethylene resin. One or a mixture of several vinyl chloride resins, preferably polyethylene terephthalate resin (PET).

The coating method of the alignment coating liquid can adopt the existing known rod coating method, applicator method, spin coating method, roll coating method, direct gravure coating method, reverse gravure coating method, flexographic coating method, inkjet method, and die coating method. , capcoating, dip coating, slot coating, etc. In actual operation, the support body is continuously transported in the transportation direction, and then the alignment coating liquid is applied to the support body using any of the above coating methods.

The drying equipment can adopt existing known methods such as hot air heating, near infrared heating, far infrared heating and microwave heating.

After preparing the release material in the above manner, apply the above-mentioned liquid crystal coating liquid on the release material, and then dry, cool and temper the release material coated with the liquid crystal coating liquid in sequence. When drying, The drying temperature is set to 70-80°C, 80-90°C and 90-100°C along the conveying direction; the cooling temperature is 20-40°C; the tempering temperature is set to 90-100°C, 80-100°C along the conveying direction. 90℃ and 70～80℃. After tempering treatment, the liquid crystal coating liquid forms a liquid crystal coating on the alignment layer, making the liquid crystals more orderly.

The curing is performed under UV light irradiation of 250-370 nm for 10-20 seconds. The initiator in the liquid crystal coating can be excited to further initiate the polymerization of the liquid crystal monomer, causing the liquid crystal coating to cross-link and solidify, thereby obtaining a liquid crystal layer with a multi-layered liquid crystal lattice structure with a certain hardness.

The liquid crystal film meets the following indicators: Thickness: ±8%; Light transmittance: ≥85%; Haze: ≤3%; Core wavelength tolerance: ±5nm; Reflectivity: ≥40%.

The technical solution of the present invention also includes: applying the liquid crystal film in the preparation of the magic color shell, laminating the above-mentioned liquid crystal film and the base material to prepare the magic color laminating board, and then removing the release material to prepare the magic color lamination board. Color shell.

In the preparation process of the magic shell, the base material can be PC/PMMA composite board, PC board or PMMA board, and meet the following indicators: reflectivity: ≥50%; light transmittance: ≥75%; haze: < 2%; hardness: 500g/F; flame retardant performance: no puncture within 60 seconds of burning. When laminating, the above-mentioned liquid crystal film can be glued through a gluing roller (gluing roller speed 2 to 8 m/min, gluing gap 100 to 200 microns), so that the liquid crystal layer of the liquid crystal film can be laminated to the substrate, and LED lamp curing and mercury lamp curing (LED lamp power 30~50%, mercury lamp temperature 70~90℃, mercury lamp current 27~37A), make a fantasy laminate board, and then peel off the release material, you can get only the A colorful shell composed of substrate and liquid crystal layer.

Compared with the existing technology, the present invention has the following advantages and beneficial effects:

(1) The present invention provides a preparation process for a liquid crystal film. First, an alignment coating liquid is coated on a support to form an alignment layer, and then the liquid crystal coating liquid is coated on the alignment layer to form a liquid crystal film. The induced orientation of the alignment layer is utilized. The resulting liquid crystal layer has a more regular multi-layered liquid crystal lattice structure, eliminating the need to add a reflective layer or other alignment layers to achieve a bright phantom effect.

(2) In the present invention, an aligned alignment layer is formed by coating the alignment coating liquid on the support, drying, and rubbing the alignment, and then coating the liquid crystal coating liquid on the alignment layer to form a liquid crystal layer with a phantom effect. Actual preparation At this time, the release method can be used to transfer the liquid crystal layer to the substrate to obtain a colorful shell. The preparation process is simple and the operation is convenient. Both the alignment coating liquid and the liquid crystal coating liquid can be realized by continuous winding coating, which is easy to produce on a large scale. large-scale mass production and improve production efficiency.

(3) When preparing the liquid crystal film in the present invention, drying, cooling and tempering are used to dry the release material coated with the liquid crystal coating liquid. Through the control of specific temperatures in the above-mentioned process flow, especially the tempering temperature The step control can make the liquid crystal coating liquid coated on the alignment layer more orderly when forming the liquid crystal coating, and provide guarantee for the phantom effect of subsequent products.

(4) In the present invention, the liquid crystal coating liquid is cholesterol liquid crystal. Under the action of the alignment layer, the molecules in cholesterol are arranged in a layered manner. The molecules in each layer are arranged in parallel, and there is a slight angle between the arrangement directions of each layer ( About 1/6° to 1/3°), the molecules in each layer are generally arranged in a spiral shape, so that after a certain number of layers, the molecules are arranged in the same direction as the first layer, forming a periodic spiral structure. The distance that the molecular helix in cholesterol liquid crystal rises during one rotation is called the pitch P. Since the molecules of each layer of cholesterol liquid crystal are arranged in different directions, only the reflected light of two layers of liquid crystals with the same arrangement direction has interference conditions. That is, two layers of liquid crystal with molecular arrangement directions 180° apart (the distance is half of the pitch P) form a Bragg reflection structure. The wavelength of the reflected light satisfies the following formula: λ = 2npsinθ, where λ is the wavelength of the reflected light, θ is the angle between the incident light and the surface of the liquid crystal layer, n is the refractive index of the liquid crystal, and P is the pitch of the cholesterol liquid crystal. Inversely proportional to the concentration of chiral molecules. When in use, as the user's observation angle changes, θ changes, and the angle of the incident light is the same as the angle of the reflected light. Therefore, as an observer, as the observation angle continues to tilt, the light reflected into the observer's eyes will gradually From long waves to short waves, this means a change in color. This phenomenon of color change with changing viewing angles is called "angle-changing".

For the liquid crystal layer of the present invention, since the molecules of each layer of cholesterol liquid crystal are arranged in a multi-layered structure and form a Bragg reflection structure, when the angle of the observer changes, the color can change significantly and continuously, thereby producing a phantom. In the actual production process, the pitch P of the cholesterol liquid crystal can also be adjusted by changing the composition ratio of the cholesterol liquid crystal, and then the wavelength λ of the reflected light can be controlled, thereby obtaining the phantom effect of the desired color and further meeting user needs.

(5) The liquid crystal film involved in the present invention has a simple structure and can achieve high transmittance and phantom effects with a single liquid crystal layer. Compared with the existing colorful shell formed by a (multi-layer) reflective layer and a liquid crystal layer, it is much more transparent. The preparation cycle of the shell is shortened and the production cost is reduced.

(6) The present invention is suitable for use as casings for electronic products, especially portable electronic products such as mobile phone back covers, notebook computers, and tablet computers. The structure is light and thin, easily favored by users, and the appearance is bright and colorful, which can satisfy users' needs. The pursuit of appearance effect. During preparation, a layer of liquid crystal (cholesterol liquid crystal film) prepared from an alignment coating solution is directly attached to a substrate with high reflectivity and high transmittance to achieve a bright and colorful effect of the shell.

Example 1: Liquid crystal film I. Alignment coating liquid I and liquid crystal coating liquid I were prepared according to the following formulas: Alignment coating liquid I: 15% polyvinyl alcohol, 80% methanol and water, and 5% fluorine-containing surfactant. Liquid crystal coating liquid I: 10% of the monomer that satisfies the formula (a) (its m and n are 4 respectively, and R ₁ is a hydrogen atom), 8% of the monomer that satisfies the formula (b) (its R ₂ is a methyl group), CN 3%, 2,2'-azobisisobutyronitrile 0.15%, tricresyl phosphate 1%, polydimethylsiloxane 1%, trimethylsilanol 1% and toluene 76%.

Coat the above-mentioned alignment coating liquid I on PET with a thickness of 100 μm according to the gravure coating method. After coating, send it to the hot air drying equipment and heat it at 80-85°C for 5 minutes to form an alignment film on the PET film. Use gauze to clean the PET film. Perform friction alignment to form an alignment layer, and obtain a release material. The performance indicators of the release material are as shown in Table 1 below. The above-mentioned liquid crystal coating liquid I is coated on the alignment layer of the release material according to the gravure coating method, and the coated release material is sent to a multi-stage oven. In the first drying box, the drying temperatures are set to 70~75°C, 80~85°C and 95~100°C respectively along the conveying direction; then it passes through the cooling box for cooling to a temperature of 20~22°C; finally, it enters the second drying box. The second drying box is tempered and dried again. The tempering temperature is set to 90~100℃, 80~90℃ and 70~80℃ along the conveying direction. After tempering treatment, it is then irradiated with 350nm ultraviolet light. Curing 15s, curing capacity is 350mj/cm ² . The liquid crystal coating is cured by polymerization and cross-linking, and forms a liquid crystal layer, that is, liquid crystal film I. The performance indicators of liquid crystal film I are shown in Table 2 below. Table 1 Performance indicators of release materials parameters indicator Test method Thickness tolerance ±1um GB/T 33051 Transmittance ≥90% JIS K7361 test method Haze ≤2% JIS K7361 test method Dyne value ≥34dyne Arcotest dyne pen Table 2 Performance indicators of liquid crystal film I parameters indicator Test method thickness 103um GB/T 33051 Transmittance 92% JIS K7361 Haze 1.1% JIS K7361 Core wavelength tolerance ±3nm UH4150 Reflectivity 45% UH4150

Example 2: Liquid crystal film II. Alignment coating liquid II and liquid crystal coating liquid II were prepared according to the following formulas: Alignment coating liquid II: 8% polyvinyl alcohol, 85% methanol and water, and 7% anionic surfactant. Liquid crystal coating liquid II: 15% of the monomer satisfying formula (a) (its m and n are 6 respectively, R ₁ is methoxy), 20% of the monomer satisfying formula (b) (its R ₂ is methyl) , 2% chiral agent satisfying formula (c), 0.05% benzoin ether initiator, 0.05% tricresyl phosphate, 0.05% hydroxyl silicone oil, 0.05% trimethylsilanol and 62.8% toluene.

Coat the above-mentioned alignment coating liquid II on PET with a thickness of 80 μm according to the gravure coating method. After coating, send it to the hot air drying equipment and heat it at 95-100°C for 8 minutes to form an alignment film on the PET film. Use gauze to clean the PET film. Conduct friction alignment to form an alignment layer, and obtain a release material. The performance indicators of the release material are shown in Table 1. The above-mentioned liquid crystal coating liquid II is coated on the alignment layer of the release material according to the gravure coating method, and the coated release material is sent to a multi-stage oven. In the first drying box, the drying temperatures are set to 75-80°C, 80-85°C and 90-95°C respectively along the conveying direction; then it passes through the cooling box for cooling to a temperature of 35-40°C; and finally enters the second drying box. The second drying box is tempered and dried again. The tempering temperature is set to 90~100℃, 80~90℃ and 70~80℃ along the conveying direction. After tempering treatment, it is then irradiated with 350nm ultraviolet light. Curing 20s, curing capacity is 350mj/cm ² . The liquid crystal coating is cured by polymerization and cross-linking, and forms a liquid crystal layer, namely liquid crystal film II. The performance indicators of liquid crystal film II are shown in Table 3 below. Table 3 Performance indicators of liquid crystal film II parameters indicator Test method thickness 83um GB/T 33051 Transmittance 93% JIS K7361 Haze 1.0% JIS K7361 Core wavelength tolerance ±3nm UH4150 Reflectivity 46% UH4150

Example 3: Liquid crystal film III. Alignment coating liquid III and liquid crystal coating liquid III were prepared according to the following formulas: Alignment coating liquid III: 10% polyvinyl alcohol, 82% methanol and water, and 8% fluorine-containing surfactant. Liquid crystal coating liquid III: 25% of the monomer satisfying formula (a) (where m is 4, n is 6, and R ₁ is methyl), and 5% of the monomer satisfying formula (b) (where R ₂ is phenyl) , R1011 5%, benzoyl peroxide 1%, tricresyl phosphate 1%, 1,4-bis(hydroxydimethylsilyl)benzene 0.5% and ethyl acetate 62.5%.

Coat the above-mentioned alignment coating liquid III on PET with a thickness of 120 μm according to the gravure coating method. After coating, send it to a hot air drying equipment and heat it at 95 to 100°C for 3 minutes to form an alignment film on the PET film. Use gauze to clean the PET film. Conduct friction alignment to form an alignment layer, and obtain a release material. The performance indicators of the release material are shown in Table 1. The above-mentioned liquid crystal coating liquid III is coated on the alignment layer of the release material according to the gravure coating method, and the coated release material is sent to a multi-stage oven. In the first drying box, the drying temperatures are set to 70~75°C, 85~90°C and 95~100°C respectively along the conveying direction; then it passes through the cooling box for cooling to a temperature of 30°C; and finally enters the second drying box. Dry box, temper and dry again. The tempering temperature is set to 90~100℃, 80~90℃ and 70~80℃ along the conveying direction. After tempering treatment, it is then cured under 370nm ultraviolet light for 10 seconds. , curing capacity is 350mj/cm ² . The liquid crystal coating is cured by polymerization and cross-linking, and forms a liquid crystal layer, namely liquid crystal film III. The performance indicators of liquid crystal film III are shown in Table 4 below. Table 4 Performance indicators of liquid crystal film III parameters indicator Test method thickness 124um GB/T 33051 Transmittance 93% JIS K7361 Haze 1.0% JIS K7361 Core wavelength tolerance ±3nm UH4150 Reflectivity 45% UH4150

Example 4: Liquid crystal film IV. Alignment coating liquid IV and liquid crystal coating liquid IV were prepared according to the following formulas: Alignment coating liquid IV: 11% polyvinyl alcohol, 85% ethanol and water, and 4% cationic surfactant. Liquid crystal coating liquid IV: 6% of the monomer satisfying formula (a) (its m and n are 5 respectively, R ₁ is phenyl), 6% of the monomer satisfying formula (b) (its R ₂ is ethyl), Chiral agent satisfying formula (c) is 5%, 2,2'-azobisisobutyronitrile 1.5%, polydimethylsiloxane 0.5%, cyanophenol 1% and xylene 80%.

Coat the above-mentioned alignment coating liquid IV on PET with a thickness of 150 μm according to the gravure coating method. After coating, send it to the hot air drying equipment and heat it at 85-90°C for 6 minutes to form an alignment film on the PET film. Use gauze to clean the PET film. Conduct friction alignment to form an alignment layer, and obtain a release material. The performance indicators of the release material are shown in Table 1. The above-mentioned liquid crystal coating liquid IV is coated on the alignment layer of the release material according to the gravure coating method, and the coated release material is sent to a multi-stage oven. In the first drying box, the drying temperatures are set to 70~75°C, 80~85°C and 90~95°C respectively along the conveying direction; then it passes through the cooling box for cooling to a temperature of 35°C; and finally enters the second drying box. Dry box, temper and dry again. The tempering temperature is set to 90~100℃, 80~90℃ and 70~80℃ along the conveying direction. After tempering treatment, it is then cured under 370nm ultraviolet light for 10 seconds. , curing capacity is 350mj/cm ² . The liquid crystal coating is cured by polymerization and cross-linking, and forms a liquid crystal layer, that is, liquid crystal film IV. The performance indicators of liquid crystal film IV are shown in Table 5 below. Table 5 Performance indicators of liquid crystal film IV parameters indicator Test method thickness 154um GB/T 33051 Transmittance 93% JIS K7361 Haze 1.0% JIS K7361 Core wavelength tolerance ±2nm UH4150 Reflectivity 45% UH4150

Example 5: Liquid crystal film V. Alignment coating liquid V and liquid crystal coating liquid V were prepared according to the following formulas: Alignment coating liquid V: 12% polyvinyl alcohol, 80% methanol and water, and 8% fluorine-containing surfactant. Liquid crystal coating liquid V: 15% of the monomer that satisfies the formula (a) (its m and n are 4 respectively, and R ₁ is a hydrogen atom), 10% of the monomer that satisfies the formula (b) (its R ₂ is a methyl group), Chiral agent satisfying formula (c) 4%, benzophenone initiator 0.05%, tricresyl phosphate 1%, polydimethylsiloxane 0.5%, trimethylsilanol 1.45% and toluene 68% .

Coat the above-mentioned alignment coating liquid V on PET with a thickness of 300 μm according to the gravure coating method. After coating, send it to the hot air drying equipment and heat it at 95 to 100°C for 10 minutes to form an alignment film on the PET film. Use gauze to clean the PET film. Conduct friction alignment to form an alignment layer, and obtain a release material. The performance indicators of the release material are shown in Table 1. The above-mentioned liquid crystal coating liquid V is coated on the alignment layer of the release material according to the gravure coating method, and the coated release material is sent to a multi-stage oven. In the first drying box, the drying temperature is set to 75~80℃, 90℃ and 100℃ respectively along its conveying direction; then it passes through the cooling box for cooling, and the temperature is 38℃; finally it enters the second drying box, and again Tempering and drying, the tempering temperature is set to 90~95℃, 80~85℃ and 70~75℃ along the conveying direction. After tempering treatment, it is then cured under 370nm ultraviolet light for 10 seconds. The curing ability is 350mj/ ^cm2 . The liquid crystal coating is solidified by polymerization and cross-linking, and forms a liquid crystal layer, namely liquid crystal film V. The performance indicators of liquid crystal film V are shown in Table 6 below. Table 6 Performance indicators of liquid crystal film V parameters indicator Test method thickness 303um GB/T 33051 Transmittance 92% JIS K7361 Haze 1.2% JIS K7361 Core wavelength tolerance ±3nm UH4150 Reflectivity 45% UH4150

Example 6: Liquid crystal film VI. Alignment coating liquid VI and liquid crystal coating liquid VI were prepared according to the following formulas: Alignment coating liquid VI: 15% polyvinyl alcohol, 80% methanol and water, and 5% fluorine-containing surfactant. Liquid crystal coating liquid VI: 17% of the monomer satisfying the formula (a) (its m and n are 4 respectively, R ₁ is a hydrogen atom), 10% of the monomer satisfying the formula (b) (its R ₂ is a methoxy group) , S811 4%, 2,2'-azobisisobutyronitrile 1%, fluorosiloxane 1%, nitrophenol 1% and toluene 66%.

Coat the above-mentioned alignment coating liquid VI on PET with a thickness of 270 μm according to the gravure coating method. After coating, send it to a hot air drying equipment and heat it at 95 to 100°C for 10 minutes to form an alignment film on the PET film. Use gauze to clean the PET film. Conduct friction alignment to form an alignment layer, and obtain a release material. The performance indicators of the release material are shown in Table 1. The above-mentioned liquid crystal coating liquid VI is coated on the alignment layer of the release material according to the gravure coating method, and the coated release material is sent to a multi-stage oven. In the first drying box, the drying temperatures are set to 75~80°C, 90°C and 100°C respectively along the conveying direction; then it passes through the cooling box for cooling to a temperature of 35°C; finally it enters the second drying box and again Tempering and drying, the tempering temperature is set to 90~95℃, 80~85℃ and 70~75℃ along the conveying direction. After tempering treatment, it is then cured under 350nm ultraviolet light for 15s. The curing ability is 350mj/ ^cm2 . The liquid crystal coating is cured by polymerization and cross-linking, and forms a liquid crystal layer, that is, liquid crystal film VI. The performance indicators of liquid crystal film VI are shown in Table 7 below. Table 7 Performance indicators of liquid crystal film VI parameters indicator Test method thickness 273um GB/T 33051 Transmittance 92% JIS K7361 Haze 1.2% JIS K7361 Core wavelength tolerance ±3nm UH4150 Reflectivity 45% UH4150

Embodiment 7: The back cover of the Symphony mobile phone is glued with the above-mentioned liquid crystal film I through a rubber roller. The speed of the rubber roller is 6m/min, and the glue gap is 100 microns. After the glue is applied, the liquid crystal film and PC/PMMA composite board (performance index As shown in Table 8 below, of course, PC or PMMA can also be used for lamination, and LED lamp curing and mercury lamp curing are performed. The LED lamp power is 50%, the mercury lamp temperature is 80°C, and the mercury lamp current is 35A. Remove the support body. That is, a colorful mobile phone back cover composed of a composite of liquid crystal film and PC/PMMA is obtained (the performance indicators are shown in Table 9 below). Table 8 Performance indicators of PC/PMMA composite boards parameters indicator Test method Reflectivity ≥50% UH4150 test method Transmittance ≥75% JIS K7361 test method Haze <2% JIS K7361 test method hardness 500g/F JIS K5600 test method Flame retardant properties No puncture within 60 seconds of burning IEC 60695 test method Table 9 Performance indicators of the Symphony back cover parameters indicator Test method Transfer adhesion 5B GB9286-98 Haze 1.5% JIS K7361 Core wavelength tolerance ±3nm UH4150 Reflectivity 41% UH4150

The structure of liquid crystal film I can be seen in Figure 1. It can be seen from Figure 1 that the molecules in each layer of liquid crystal film I are arranged in a multi-layered structure, which can form a Bragg reflection structure. When the angle of the observer changes, the color can change significantly. The continuous changes produce a phantom effect. The phantom effect of the phantom mobile phone back cover prepared by the liquid crystal film I is shown in Figure 2. It can be seen from Figure 2 that under different visual angles, observers can observe different phantom effects presented by the mobile phone back cover. For example, in Figure 2, the back cover of the mobile phone appears red at 0°, yellow at 45°, and green at 70°.

For pictures of liquid crystal film I, please refer to the photo shown in Figure 3. Liquid crystal film I shows different gradient colors with different angles of incident light, and also has a certain light transmittance. For example, the liquid crystal film shown in a has a gradient from green to yellow to red along the direction of the arrow. The liquid crystal film shown in b has a gradient from orange to red along the direction of the arrow. For pictures of the colorful mobile phone back covers made from the liquid crystal film I, please refer to the photos shown in Figure 4. For the same colorful mobile phone back covers (a total of 7 identical mobile phone back covers from left to right), the photos are taken from different angles. We took photos of three groups A, B, and C in order. As can be seen from Figure 3, the colors of the back covers of the 7 same mobile phones taken at the same angle are all different. At the same time, when the shooting angle changes, the color of the back cover of the corresponding mobile phone changes. The covers are all in gradient color.

Comparative ratio: This comparative example is a comparative example with Example 1 and Example 7. The only difference is that no alignment coating liquid is used. During the preparation process, the same process method and parameter standards as in Example 1 and Example 7 are used. The liquid crystal coating liquid is coated on PET to prepare a liquid crystal film with a corresponding liquid crystal layer. Finally, a mobile phone back cover is prepared in the same manner.

Comparing the back cover of this mobile phone with the colorful mobile phone back cover prepared in Example 7, the experimenter can find that the back cover of the mobile phone in the comparative example also shows a certain color change when the angle of incident light changes. , but the color change is relatively simple, usually one color jumps directly to another color, there is no presentation of multiple colors during the gradient process, and there is no phantom effect on the back cover of the phantom mobile phone in Embodiment 7. Therefore, for the observer, It also has no obvious visual impact.

The above are only preferred embodiments of the present invention and do not impose any formal restrictions on the present invention. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention fall within the scope of the present invention. within the scope of protection.

a, b: arrow A, B, C: Group

Figure 1 is a structural diagram of a liquid crystal film. Figure 2 is a schematic diagram of different visual phantom effects on the back cover of a phantom mobile phone. Figure 3 is a picture of the liquid crystal film. Figure 4 is a comparison picture of the back cover of the Symphony phone.

Claims (10)

A liquid crystal film, wherein: it is prepared by coating a liquid crystal coating liquid. The liquid crystal coating liquid is cholesterol liquid crystal. In terms of mass percentage, the cholesterol liquid crystal includes 12 to 38% of achiral polymerizable monomers and chiral polymerizable monomers. Polymerized monomers 2 to 5%, initiators 0.03 to 3%, additives 1 to 3% and solvents 60 to 80%. The liquid crystal film according to claim 1, wherein: the achiral polymerizable monomer includes a bifunctional polymerizable monomer and a monofunctional polymerizable monomer, wherein the bifunctional polymerizable monomer satisfies the following structure Formula 1): (1) In the structural formula (1), m and n respectively represent any natural number from 4 to 8, and R ₁ represents a hydrogen atom, methyl, ethyl, methoxy, ethoxy, phenyl, and benzyl. Or ester group; The monofunctional polymerizable monomer satisfies the following structural formula (2): (2) In structural formula (2), R ₂ represents a hydrogen atom, methyl group, ethyl group, methoxy group, ethoxy group, phenyl group, benzyl group or ester group. The liquid crystal film according to claim 1, wherein: the chiral polymerizable monomer includes CN, CB15, S811, R1011 or a chiral agent satisfying the following structural formula (3), (3). A method for preparing a liquid crystal film, which includes: coating an alignment coating liquid on a support, drying and rubbing alignment to prepare a release material, and then coating the release material with the liquid crystal coating liquid described in claim 1, drying and solidifying Finally, a liquid crystal film is produced. The preparation method of a liquid crystal film according to claim 4, wherein: in terms of mass percentage, the alignment coating liquid includes 8 to 15% of a liquid crystal guide agent, 60 to 85% of a solvent, and 3 to 8% of other components. The preparation method of a liquid crystal film according to claim 5, wherein the liquid crystal guiding agent is water-soluble polyvinyl alcohol and/or its derivatives. The preparation method of a liquid crystal film as described in claim 4, wherein: the release material coated with the liquid crystal coating liquid is dried, cooled and tempered in sequence, and during drying, the drying temperature is along its conveying direction. The cooling temperature is set to 70~80℃, 80~90℃ and 90~100℃ in sequence; the cooling temperature is 20~40℃; the tempering temperature is set to 90~100℃, 80~90℃ and 70~80℃ along the conveying direction. . The preparation method of a liquid crystal film as described in claim 4, wherein: the curing is cured under ultraviolet light irradiation of 250 to 370 nm for 10 to 20 seconds. The preparation method of a liquid crystal film as described in claim 4, wherein: the liquid crystal film meets the following indicators: Thickness: ±8%; Light transmittance: ≥85%; Haze: ≤3%; Core wavelength tolerance: ±5nm; Reflectivity: ≥40%. An application of a liquid crystal film in the preparation of a colorful shell, wherein: the liquid crystal film as described in claim 1 is bonded to a base material to prepare a colorful laminating board, and then the release material is removed to obtain Colorful shell.