CN113885245A

CN113885245A - Liquid crystal dimming film with high mechanical property, low driving voltage and high contrast and preparation method thereof

Info

Publication number: CN113885245A
Application number: CN202111289944.1A
Authority: CN
Inventors: 杨槐; 狐竣梅; 胡威; 高延子; 任云霄; 许建军
Original assignee: Peking University
Current assignee: Peking University
Priority date: 2021-11-02
Filing date: 2021-11-02
Publication date: 2022-01-04

Abstract

The invention discloses a liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast and a preparation method thereof, wherein the size and the shape of a mesh are changed by introducing a methacrylate monomer containing hydroxyl to improve the cohesive force and the contrast of polymer dispersed liquid crystal, fluorine is introduced into a system to reduce the voltage rise phenomenon caused by introducing the hydroxyl, and finally the liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast is obtained by compounding the two, and the size of the mesh can be controlled by introducing a cross-linking agent, so that the driving voltage and the contrast are controlled; therefore, a new way is provided for improving the mechanical properties of the formal and trans-form light-adjusting films. The invention is suitable for the technical field of liquid crystal material preparation, and is suitable for preparing a liquid crystal dimming film with high mechanical property, low driving voltage and high contrast.

Description

Liquid crystal dimming film with high mechanical property, low driving voltage and high contrast and preparation method thereof

Technical Field

The invention belongs to the technical field of functional liquid crystal material preparation, and particularly relates to a liquid crystal dimming film with high mechanical property, low driving voltage and high contrast and a preparation method thereof.

Background

The Polymer Dispersed Liquid Crystal (PDLC) is a novel electric control light modulation material. In the PDLC film, liquid crystal molecules are dispersed in the form of droplets in a polymer matrix.

The light control principle of the PDLC: when no electric field is applied, because the director of the liquid crystal molecules is randomly distributed, the difference is generated between the refractive index of the liquid crystal microdroplet and the refractive index of the polymer matrix, and the film is in a strong light scattering state; when an electric field is applied, because a liquid crystal material with positive dielectric anisotropy is generally used in the PDLC film, the director of liquid crystal molecules is rearranged along the direction of the electric field, so that the refractive index of liquid crystal microdroplets is matched with the refractive index of a polymer matrix again, and the film is in a transparent state; therefore, PDLC can regulate and control the orientation of liquid crystal molecules by applying an electric field at two ends of the film, continuously regulate the light transmittance of the film and realize reversible switching between a transparent state and a scattering state.

At present, the mechanical property is a key parameter for calculating the PDLC film for practical application. The formal electrically controlled light adjusting film is in a transparent state when an electric field is applied, so that the molecules of the liquid crystal material are always in a certain alignment state, and the state needs a polymer network for stabilization. The research for improving the mechanical property has mainly focused on the surface treatment of the substrate material by using the silane coupling agent, but the method is relatively complex and is not beneficial to large-scale treatment application, and the addition amount is limited, so that the improvement of the mechanical property is limited. The research of the trans-form electric control liquid crystal dimming film is still stopped at the laboratory stage.

The trans-electric control light adjusting film is in a transparent state when no electric field is applied, so the molecules of the liquid crystal material are in a certain orientation state certainly, and the state needs a polymer network for stabilization, so the prior trans-electric control light adjusting film system is mainly a Polymer Stabilized Liquid Crystal (PSLC) system, and the preparation method focuses on polymer stabilized negative liquid crystal, dual-frequency liquid crystal (DFLC) and cholesteric liquid crystal (ChLC), however, the PSLC system has low network content (usually about 3-5 wt%), so the bonding strength between two layers of substrates of the obtained film is low, the stability is poor, and the practical application is difficult.

At present, no system for improving the mechanical properties of the polymer dispersed liquid crystal film while reducing the driving voltage and improving the contrast by using the composite system has been reported.

Disclosure of Invention

The invention aims to provide a liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast;

the invention also aims to provide a preparation method of the liquid crystal light-adjusting film with high mechanical property, low driving voltage and high contrast, which firstly introduces a methacrylate monomer containing hydroxyl to improve the mechanical property and the contrast in the traditional acrylate system, and then continuously introduces a methacrylate monomer containing fluorine to reduce the driving voltage, thereby providing a new way for improving the mechanical properties of formal and trans light-adjusting films.

In order to achieve the purpose, the invention adopts the following technical scheme:

a liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast is prepared from a component A, a component B, a component C and a component D;

wherein the component A, the component B, the component C and the component D are selected from the following materials in percentage by mass,

by way of limitation, the liquid crystal material is a positive liquid crystal material or a negative liquid crystal material.

As a second limitation, the methacrylate monomer is at least one of cyclohexyl methacrylate, propylene glycol methyl ether acetate, isoamyl acrylate, isobornyl methacrylate, isobutyl methacrylate, unsaturated polyester, epoxy acrylate, urethane acrylate, polyester acrylate, epoxy acrylate, polyenylthiol system, polyether acrylate, aqueous acrylate, vinyl ether.

As a third limitation, the hydroxyl-containing methacrylate monomer is at least one of 4-hydroxybutyl acrylate, hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, hydroxypropyl methacrylate.

As a fourth limitation, the fluorine-containing methacrylate monomer is at least one of trifluoroethyl methacrylate, pentafluoropropyl methacrylate, 2, 3-dihydroxypropyl 2-methyl-2-acrylate, 2- (perfluorooctyl) ethyl methacrylate, and heptafluorobutyl acrylate.

As a fifth limitation, the crosslinking agent is at least one of polyethylene glycol diacrylate (molecular weight 200), polyethylene glycol diacrylate (molecular weight 400), polyethylene glycol diacrylate (molecular weight 575), polyethylene glycol diacrylate (molecular weight 600), polyethylene glycol diacrylate (molecular weight 700), polyethylene glycol diacrylate (molecular weight 1000), diethylene glycol diacrylate, 1,4 butylene glycol diacrylate, Bis-EMA 15;

the photoinitiator is at least one of benzophenone, benzoin dimethyl ether, chloro-thioxanthone, 2, 4-diethyl thioxanthone, isopropyl thioxanthone and 2-hydroxy-2, 2-methyl-1-phenyl acetone.

As a sixth limitation, the spacer has a particle diameter of 2 to 300 μm;

the spacer is a polymer film with the thickness of 5-500 mu m.

The preparation method of the liquid crystal dimming film with high mechanical property, low driving voltage and high contrast adopts the first method or the second method, wherein,

first, method

The first method is carried out according to the following steps:

s1, weighing and mixing the component A, the component B and the component C respectively according to a proportion, and fully oscillating to form isotropic liquid;

s2, pouring the obtained isotropic liquid into a liquid crystal box on a hot stage at the temperature of 18-50 ℃, wherein the thickness of the liquid crystal box is controlled by a spacer;

s3, preserving heat of the liquid crystal box on a 18-50 ℃ hot stage for 1-10 min, then preserving heat at 20-30 ℃ for 1-10 min, irradiating for 1.0-30.0 min by 10-400 nm ultraviolet light, and then preserving for 0.5-7 h in an environment without ultraviolet light irradiation until the liquid crystal box is completely cured; obtaining the liquid crystal dimming film with high mechanical property, low driving voltage and high contrast;

second, method two

P1, weighing and mixing the component A, the component B and the component C respectively according to a proportion, and fully oscillating to form isotropic liquid;

p2, adding spacer particles into the obtained isotropic liquid, and pressing the isotropic liquid into a liquid crystal film by using a plastic film on a heating table at the temperature of 18-50 ℃;

and P3, preserving the heat of the pressed liquid crystal film on a hot table at 18-50 ℃ for 1-10 min, then preserving the heat at 20-30 ℃ for 1-10 min, irradiating for 1.0-30.0 min by 10-400 nm ultraviolet light, and then, preserving for 0.5-7 h in an environment without ultraviolet light irradiation until the liquid crystal film is completely cured to obtain the liquid crystal light-adjusting film with high mechanical property, low driving voltage and high contrast.

By way of limitation, the liquid crystal box is made of a glass substrate plated with an ITO conductive film; the plastic film is a plastic film plated with an ITO conductive film.

Due to the adoption of the technical scheme, compared with the prior art, the invention has the technical progress that:

(1) according to the invention, the size and the shape of the mesh are changed by introducing the methacrylate monomer containing hydroxyl to improve the cohesive force and the contrast of the polymer dispersed liquid crystal, and the methacrylate monomer containing fluorine is introduced to reduce the voltage rise caused by introducing the hydroxyl into the system, so that the liquid crystal dimming film with high mechanical property, low driving voltage and high contrast is obtained by compounding the methacrylate monomer containing fluorine and the fluorine, and the mesh size can be controlled by introducing the cross-linking agent, so that the driving voltage and the contrast are controlled; therefore, a new way is provided for improving the mechanical properties of the formal and trans-form light-adjusting films;

(2) the photoinitiator is introduced to generate free radicals under specific polymerization conditions to initiate polymerization of the polymerization monomers;

(3) the invention can be used for preparing both rigid liquid crystal dimming film and flexible liquid crystal dimming film, the threshold of the driving voltage is 5V-100V, the contrast is 15-200, and the light transmittance can be adjusted between 0.3% -82% by adjusting the voltage, wherein the bonding strength between two substrates of the rigid liquid crystal dimming film is 80-500N/cm²。

The invention is suitable for the technical field of liquid crystal material preparation, and is suitable for preparing a liquid crystal dimming film with high mechanical property, low driving voltage and high contrast.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

In the drawings:

FIG. 1 is a scanning electron micrograph of polymer dispersed liquid crystal films prepared in comparative example and example 1;

FIG. 2a is a graph showing electro-optic response curves of polymer dispersed liquid crystal films prepared in comparative example and example 1;

FIG. 2b is a schematic drawing of the mechanical stretching of the polymer dispersed liquid crystal film prepared in comparative example and example 1;

FIG. 3 is a scanning electron micrograph of a polymer dispersed liquid crystal film prepared in example 3;

FIG. 4a is a graph showing the electro-optic response of the polymer dispersed liquid crystal film prepared in example 3;

FIG. 4b is a schematic diagram of the mechanical stretching of the polymer dispersed liquid crystal film prepared in example 3;

FIG. 5 is a scanning electron micrograph of a polymer dispersed liquid crystal film prepared in example 5;

FIG. 6a is a graph showing the electro-optic response of the polymer dispersed liquid crystal film prepared in example 5;

FIG. 6b is a schematic diagram of the mechanical stretching of the polymer dispersed liquid crystal film prepared in example 5;

FIG. 7 is a scanning electron micrograph of a polymer dispersed liquid crystal film prepared in example 7;

FIG. 8a is a graph showing the electro-optic response of the polymer dispersed liquid crystal film prepared in example 7;

FIG. 8b is a schematic drawing of the mechanical stretching of the polymer dispersed liquid crystal film prepared in example 7.

Detailed Description

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for purposes of illustration and explanation only and are not intended to limit the present invention.

Example 1 preparation method of liquid crystal light-adjusting film with high mechanical property, low driving voltage and high contrast

This example was carried out in the following sequence of steps:

p11, weighing and mixing the component A, the component B and the component C according to the proportion in the table 1 respectively, and stirring and fully shaking at 20 ℃ to form isotropic liquid;

TABLE 1

The total mass of each component in table 1 is 8 kg;

p12, adding the spacer particles of Table 1 to the resulting isotropic liquid, then at T₁₁On a hot bench at 35 ℃, the isotropic liquid added with the spacing particles is clamped between two plastic films plated with indium tin oxide industrial transparent conductive films by a roll-to-roll processing mode, the isotropic liquid is pressed to form a liquid crystal film,

p13, preparing the pressed liquid crystal film at T₁₂Hot bench heat preservation t of 35 ℃₁₁Keeping the temperature t at 20 ℃ after 5min₁₂6min, passing 365nm and light intensity of 8mw/cm²Ultraviolet light irradiation t₁₃And (3) standing for 10min in an environment without ultraviolet irradiation for 3h until the curing is completed, so as to obtain the liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast.

The prepared liquid crystal light modulation film is soaked in a cyclohexane solution and placed for 14 days, E8 nematic liquid crystal is soaked out of the liquid crystal light modulation film, the surface appearance of the liquid crystal light modulation film is observed by using a scanning electron microscope, and as shown in figure 1, the appearance of meshes is uniform and the size is small. This results in a lower driving voltage and a higher contrast ratio for the system. The cyclohexane solution can be replaced by acetone solution, ethanol solution or dichloromethane solution.

The liquid crystal comprehensive parameter instrument is used for testing the change curve of the transmittance of the liquid crystal dimming film along with the voltage (1kHz) at the wavelength of 632nm at 25 ℃, the result is shown in figure 2a, and the graph shows that the driving voltage of an experimental group introduced with hydroxyl is greatly reduced compared with the driving voltage of a control group, and the contrast is increased.

The effective area of the obtained liquid crystal light-adjusting film is tested by a mechanical universal tensile testing machine to obtain the bonding strength of the liquid crystal light-adjusting film under 2cm multiplied by 2cm, and the result is shown in figure 2b, so that the experimental group has higher bonding force and better mechanical property compared with the control group.

The liquid crystal material of component A used in this example was E8 from Merck liquid crystal materials, Germany.

Example 2 preparation method of liquid crystal light-adjusting film with high mechanical property, low driving voltage and high contrast

In this example, the amount of the raw materials used and the types of other raw materials were the same as in example 1 except that the spacer having a thickness of 20 μm was used as the component D, and the difference from example 1 was also in the difference in the preparation process.

This example was carried out in the following sequence of steps:

s11, weighing and mixing the component A, the component B and the component C according to the proportion in the table 1 respectively, and stirring and fully oscillating at 20 ℃ to form isotropic liquid;

s12, will getTo isotropic liquid at T₂₁Pouring the mixture into a liquid crystal box made of a glass substrate plated with an ITO conductive film on a 35 ℃ hot table, and making a component D into two spacing pads which are placed at two ends of the liquid crystal box for controlling the thickness;

s13, placing the liquid crystal box in T₂₂Hot bench heat preservation t of 35 ℃₂₁Keeping the temperature t at 20 ℃ after 5min₂₂6min, passing 365nm and light intensity of 8mw/cm²Ultraviolet light irradiation t₂₃Standing for 3min, and standing for 6h in an environment without ultraviolet irradiation until complete curing; the liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast is obtained.

Preparation method of comparative example liquid crystal light-adjusting film

This example was carried out in the following sequence of steps:

q1, weighing and mixing the component A, the component B and the component C according to the proportion in the table 2 respectively, and stirring and fully shaking at room temperature to form isotropic liquid;

TABLE 2

The total mass of each component in table 2 is 8 kg;

q2, adding the spacer particles of Table 2 to the resulting isotropic liquid, and then adding the spacer particles at T₀₁On a 35 ℃ hot bench, the isotropic liquid added with the spacing particles is clamped between two plastic films plated with indium tin oxide industrial transparent conductive films by a roll-to-roll processing mode, and the isotropic liquid is pressed to form a liquid crystal film;

q3, preparing the pressed liquid crystal film at T₀₂Hot bench heat preservation t of 35 ℃₀₁Keeping the temperature t at 20 ℃ after 5min₀₂6min, passing 365nm and light intensity of 8mw/cm²Ultraviolet light irradiation t₀₃And (3) standing for 10min in an environment without ultraviolet irradiation for 3h until the curing is completed, so as to obtain the liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast.

Soaking the prepared liquid crystal dimming film in a cyclohexane solution, standing for 14 days, soaking the E8 nematic liquid crystal from the liquid crystal dimming film, and observing the surface appearance of the liquid crystal dimming film by using a scanning electron microscope, as shown in figure 1, it can be seen that liquid crystal droplets are uniformly distributed and have a small particle size of 2-3 μm after hydroxyl is introduced.

The liquid crystal comprehensive parameter instrument is used for testing the change curve of the transmittance of the liquid crystal dimming film along with the voltage (1kHz) at the wavelength of 632nm at 25 ℃, and the result is shown in figure 2a, so that the experimental group has higher cohesive force and better mechanical property compared with the control group.

Example 3 preparation method of liquid crystal light-adjusting film with high mechanical property, low driving voltage and high contrast

This example was carried out in the following sequence of steps:

p31, weighing and mixing the component A, the component B and the component C according to the proportion in the table 3 respectively, and stirring and fully shaking at 30 ℃ to form isotropic liquid;

TABLE 3

The total mass of each component in table 3 is 8 kg;

p32, adding the spacer particles of Table 1 to the resulting isotropic liquid, then at T₃₁On a 18 ℃ hot bench, the isotropic liquid added with the spacing particles is clamped between two plastic films plated with indium tin oxide industrial transparent conductive films by a roll-to-roll processing mode, the isotropic liquid is pressed to form a liquid crystal film,

p33, preparing the pressed liquid crystal film at T₃₂Heat preservation t on 18 deg.C hot bench₃₁Keeping the temperature t at 30 ℃ after 1min₃₂10min, light intensity of 8mw/cm at 400nm²Ultraviolet light irradiation t₃₃1min, thenAnd then placing the film for 7 hours in the environment without ultraviolet irradiation until the film is completely cured, thus obtaining the liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast.

The prepared liquid crystal light adjusting film is soaked in a cyclohexane solution and is placed for 14 days, and E8 nematic liquid crystal is soaked out of the film. The surface topography of the film was observed using a scanning electron microscope, as shown in fig. 3, it can be seen from the figure that the meshes are three-dimensional interpenetrating networks and the topography changes. This is due to the hydrogen bonding effect resulting from the increased content of the hydroxyl-containing acrylate monomer.

The liquid crystal comprehensive parameter instrument is utilized to test the change curve of the transmittance of the film along with the voltage (1kHz) at the wavelength of 632nm at 25 ℃, and the result is shown in figure 4a, and the graph shows that the driving voltage is lower, the on-state transmittance is higher, the off-state transmittance is lower, the contrast is higher, and the electro-optical performance is better.

The bonding strength of the effective area of the film under 2cm multiplied by 2cm is tested by utilizing a mechanical universal tensile testing machine, and the result is shown in figure 4b, and the content of the hydroxyl is increased, the bonding force is increased, and the mechanical property is enhanced.

Example 4 preparation method of liquid crystal light-adjusting film with high mechanical property, low driving voltage and high contrast

In this example, the liquid crystal material of component A was E7 from Merck liquid crystal materials, Germany, and the spacer with a thickness of 5 μm was used for component D, and the amounts of the raw materials and the types of the other raw materials were the same as those in example 3, except that the preparation process was different.

This example was carried out in the following sequence of steps:

s41, weighing and mixing the component A, the component B and the component C according to the proportion in the table 3, and stirring and fully oscillating at 30 ℃ to form isotropic liquid;

s42, placing the obtained isotropic liquid at T₄₁Pouring the mixture into a liquid crystal box made of a glass substrate plated with an ITO conductive film on a 18 ℃ hot table, and making a component D into two spacing pads which are placed at two ends of the liquid crystal box for controlling the thickness;

s43, placing the liquid crystal box in T₄₂Heat preservation t on 18 deg.C hot bench₄₁Keeping the temperature t at 30 ℃ after 1min₄₂10min, light intensity of 8mw/cm at 400nm²Ultraviolet light irradiation t₄₃Standing for 1min, and standing for 7h in an environment without ultraviolet irradiation until complete curing; the liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast is obtained.

Example 5 preparation of liquid Crystal light-adjusting film with high mechanical Properties, Low Driving Voltage and high contrast

The present embodiment may also be performed according to the following sequence of steps:

p51, weighing and mixing the component A, the component B and the component C according to the proportion in the table 4 respectively, and stirring and fully oscillating at 25 ℃ to form isotropic liquid;

TABLE 4

The total mass of each component in table 4 is 8 kg;

p52, adding the spacer particles of Table 4 to the resulting isotropic liquid, then at T₅₁On a hot table at 50 ℃, the isotropic liquid added with the spacing particles is clamped between two plastic films plated with indium tin oxide industrial transparent conductive films by a roll-to-roll processing mode, and the isotropic liquid is pressed to form a liquid crystal film;

p53, preparing the pressed liquid crystal film at T₅₂Heat preservation t on hot bench at 50 ℃₅₁Keeping the temperature t at 25 ℃ after 10min₅₂1min, passing 365nm and light intensity of 8mw/cm²Ultraviolet light irradiation t₅₃And standing for 30min in an environment without ultraviolet irradiation for 0.5h until complete curing is achieved, so that the liquid crystal dimming film with high mechanical property, low driving voltage and high contrast is obtained.

The prepared liquid crystal light adjusting film is soaked in a cyclohexane solution and is placed for 14 days, and E8 nematic liquid crystal is soaked out of the film. The surface morphology of the film was observed by a scanning electron microscope, as shown in FIG. 5, it can be seen that the further increase in the hydroxyl group content morphology changes from a mesh structure to a polymer skeleton structure, and the mesh becomes larger.

The transmittance of the film was measured by a liquid crystal comprehensive parameter instrument according to the curve of voltage (1kHz) at a wavelength of 632nm at 25 ℃ and the result is shown in FIG. 6a, which shows that the driving voltage is increased and the comprehensive electro-optic performance is better with higher contrast.

The bonding strength of the effective area of the film under 2cm multiplied by 2cm is tested by utilizing a mechanical universal tensile testing machine, the result is shown in figure 6b, and the figure shows that the combined action of introduced hydroxyl and fluorine jointly ensures high mechanical property.

Example 6 preparation of liquid Crystal light-adjusting film with high mechanical Properties, Low Driving Voltage and high contrast

In this example, the raw materials used were the same as in example 5 except that the liquid crystal material of component A was E48 from Merck liquid crystal materials, Germany, and a spacer having a thickness of 500 μm was used for component D, except that the preparation process was different.

This example was carried out in the following sequence of steps:

s61, weighing and mixing the component A, the component B and the component C according to the proportion in the table 4 respectively, and stirring and fully oscillating at 20 ℃ to form isotropic liquid;

s62, placing the obtained isotropic liquid at T₆₁Pouring a liquid crystal box made of a glass substrate plated with an ITO conductive film on a 50 ℃ hot bench, and making a component D into two spacing pads which are placed at two ends of the liquid crystal box for controlling the thickness;

s63, placing the liquid crystal box in T₆₂Heat preservation t on hot bench at 50 ℃₆₁Keeping the temperature t at 20 ℃ after 10min₆₂1min, passing 365nm and light intensity of 8mw/cm²Ultraviolet light irradiation t₆₃30min, then standing for 0.5h in an environment without ultraviolet irradiation until complete curing; the liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast is obtained.

Example 7 preparation of high mechanical Properties, Low drive Voltage and high contrast liquid Crystal light films

p71, weighing and mixing the component A, the component B and the component C according to the proportion in the table 5 respectively, and stirring and fully oscillating at 28 ℃ to form isotropic liquid;

TABLE 5

The total mass of each component in table 5 is 8 kg;

p72, adding the spacer particles of Table 5 to the resulting isotropic liquid, then at T₇₁On a 35 ℃ hot bench, the isotropic liquid is clamped between two plastic films plated with indium tin oxide industrial transparent conductive films in a roll-to-roll processing mode, and the isotropic liquid is pressed into a liquid crystal film;

p73, preparing the pressed liquid crystal film at T₇₂Hot bench heat preservation t of 35 ℃₇₁Keeping the temperature t at 28 ℃ after 8min₇₂4min, 10nm passing light intensity of 8mw/cm²Ultraviolet light irradiation t₇₃And standing for 10min in an environment without ultraviolet irradiation for 5h until complete curing is achieved, so that the liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast is obtained.

The prepared liquid crystal light adjusting film is soaked in a cyclohexane solution and is placed for 14 days, and E8 nematic liquid crystal is soaked out of the film. The surface topography of the film was observed using a scanning electron microscope, as shown in FIG. 7, from which it can be seen that the mesh was dense and small in size, 0.5-1.5 microns.

The transmittance of the film was measured by a liquid crystal comprehensive parameter instrument according to the change curve of voltage (1kHz) at a wavelength of 632nm at 25 ℃ as shown in FIG. 8a, and it was found that the driving voltage was high but the contrast was high. This is because intermolecular forces are generated upon addition of hydroxyl groups, so that the viscosity increases. The mesh is dense and uniform so that a high contrast ratio is maintained.

The bonding strength of the effective area of the film under 2cm x 2cm is tested by using a mechanical universal tensile testing machine, the result is shown in figure 8b, and the mechanical property is improved after hydroxyl and fluorine are introduced.

Example 8 preparation of high mechanical Properties, Low Driving Voltage and high contrast liquid Crystal light films

In this example, except that the liquid crystal material of the component A was GXP-6908 from Nicoti Hua liquid crystal Material Ltd, and the component D was a spacer with a thickness of 5 μm, the used raw materials were the same in percentage by weight and the types of other raw materials as those of example 1, except that the preparation process was different.

This example was carried out in the following sequence of steps:

s81, weighing and mixing the component A, the component B and the component C according to the proportion in the table 5 respectively, and stirring and fully oscillating at 23 ℃ to form isotropic liquid;

s82, placing the obtained isotropic liquid at T₈₁Pouring the mixture into a liquid crystal box made of a glass substrate plated with an ITO conductive film on a 35 ℃ hot table, and making a component D into two spacing pads which are placed at two ends of the liquid crystal box for controlling the thickness;

s83, placing the liquid crystal box in T₈₂Hot bench heat preservation t of 35 ℃₈₁Keeping the temperature t at 23 ℃ after 8min₈₂4min, 10nm passing light intensity of 8mw/cm²Ultraviolet light irradiation t₈₃Standing for 10min, and standing for 3h in the absence of ultraviolet irradiation until completely cured; the liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast is obtained.

Example 9 preparation of high mechanical Properties, Low Driving Voltage and high contrast liquid Crystal light films

The preparation process of this example is the same as that of example 1, except that the raw materials are selected and the proportions of the raw materials are different, as shown in table 6.

TABLE 6

The total mass of each component in table 6 is 8 kg;

in this embodiment, the liquid crystal material used is SLC-1717 from Yongsheng Huaqing liquid crystal materials, Inc.

Example 10 preparation of liquid Crystal light-modulating film with high mechanical Properties, Low Driving Voltage and high contrast

The preparation process of this example is the same as that of example 2, except that the raw materials are selected and the ratio of the raw materials is different, as shown in table 7.

TABLE 7

The total mass of each component in table 7 was 8 kg;

in this embodiment, the liquid crystal material used is SLC-7011 from Yongsheng Huaqing liquid crystal materials, Inc.

Example 11 preparation of high mechanical Properties, Low drive Voltage and high contrast liquid Crystal light films

The preparation process of this example is the same as that of example 1, except that the raw materials are selected and the ratio of the raw materials is different, as shown in table 8.

TABLE 8

Components	Categories	Name (R)	Proportion/wt%
				A	Liquid crystal display device	TEB30A		15
B1	Methacrylate monomer	Vinyl ethers	70
				B2	Hydroxyl group-containing methacrylate monomer	Hydroxyethyl methacrylate		5
B3	Fluorine-containing methacrylate monomer	Heptafluorobutyl acrylate							5
				B4	Crosslinking agent	Bis-EMA15	5
C	Initiator	Chlorothiathrones	7
				D	Spacer particles		300 micron glass bead	0.01

The total mass of each component in table 8 is 8 kg;

in this embodiment, the liquid crystal material used is TEB30A from permanent huaqing liquid crystal materials ltd.

Example 12 preparation of liquid Crystal light-modulating film with high mechanical Properties, Low Driving Voltage and high contrast

The preparation process of this example is the same as that of example 2, except that the raw materials are selected and the proportions of the raw materials are different, as shown in table 9.

TABLE 9

The total mass of each component in table 9 was 8 kg;

the liquid crystal material of component A used in this example was E7 from Merck liquid crystal materials, Germany.

Example 13 preparation of high mechanical Properties, Low drive Voltage and high contrast liquid Crystal light films

The preparation process of this example is the same as that of example 1, except that the raw materials are selected and the proportions of the raw materials are different, as shown in table 10.

Watch 10

The total mass of each component in table 10 was 8 kg;

the liquid crystal material of component A used in this example was E44 from Merck liquid crystal materials, Germany.

Comparative examples, the a-component liquid crystal materials of examples 1-13, are merely illustrative, and in fact the a-component liquid crystal material may be a positive liquid crystal or a negative liquid crystal, including but not limited to nematic liquid crystal materials, cholesteric liquid crystal materials, smectic liquid crystal materials, etc., wherein the liquid crystal monomers in the components include but are not limited to one or more of the following molecules:

wherein II and III are alkyl containing 1-16 carbon atoms, alkoxy containing 1-16 carbon atoms, siloxane containing 1-16 carbon atoms, cyano, ester, halogen, hydroxyl, isothiocyanato, nitro or fluoro; VI, VII is an aromatic ring (such as a1, 4-benzene ring, a 2-5-pyrimidine ring and a1, 2, 6-naphthalene ring) or an alicyclic cycloalkane (such as trans-1, 4-cyclohexane), wherein x and y are 0-4 respectively; VIII and IX are side groups of VI and VII, and are halogen, cyano or methyl, wherein a and b are 0-4 respectively; wherein, IV is ester group, alkynyl, alkyl, direct connection, nitrogen-nitrogen double bond or ether bond.

The nematic liquid crystal material can be selected from the liquid crystal materials sold in the market, such as E48 and ZLI-1275 of Merck liquid crystal materials of Germany, GXP-6908, GXP-6917, GXP-6928 and GXP-6930 of Nicoti China liquid crystal materials of China, but not limited to these materials.

If cholesteric liquid crystals are selected, the chiral additives include, but are not limited to, one or more of the following molecules, such as cholesteryl pelargonate, CB15, C15, S811, R811, S1011, R1011, and the like.

The compositions and chemical structures of the comparative examples and the liquid crystal materials E8 described in examples 1 to 8 are as follows:

the molecular formula of the component B1 used in the comparative examples, examples 1-8 was:

the molecular formula of the B2 component is as follows:

the molecular formula of the B3 component is as follows:

the molecular formula of the B4 component is as follows:

the PEGDA series can differ in chain length by many such as PEGDA 4006001000;

the molecular formula of the component C is as follows:

comparative examples, examples 1-13 the selection of materials for the B1, B2, B3, B4, C components is also illustrative only, and in fact the B1 component may be at least one of isoamyl acrylate, isobornyl methacrylate, isobutyl methacrylate, unsaturated polyesters, epoxy acrylates, urethane acrylates, polyester acrylates, epoxy acrylates, polyenethiol systems, polyether acrylates, waterborne acrylates, vinyl ethers; the component B2 can be at least one of 4-hydroxybutyl acrylate, hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate and hydroxypropyl methacrylate as a hydroxyl-containing methacrylate monomer; the B3 component can be at least one of trifluoroethyl methacrylate, pentafluoropropyl methacrylate, 2-methyl-2-propenoic acid-2, 3-dihydroxypropyl ester, 2- (perfluorooctyl) ethyl methacrylate and heptafluorobutyl acrylate, and the B4 component can be at least one of polyethylene glycol diacrylate (molecular weight 200), polyethylene glycol diacrylate (molecular weight 400), polyethylene glycol diacrylate (molecular weight 575), polyethylene glycol diacrylate (molecular weight 600), polyethylene glycol diacrylate (molecular weight 700), polyethylene glycol diacrylate (molecular weight 1000), diethylene glycol diacrylate, 1, 4-butanediol diacrylate and Bis-EMA 15; the component C can be at least one of benzophenone, benzoin dimethyl ether, chloro-thioxanthone, 2, 4-diethyl thioxanthone, isopropyl thioxanthone and 2-hydroxy-2, 2-methyl-1-phenyl acetone.

In the examples of the present invention, it is customary for the person skilled in the art to calculate the percentage of only the components participating in the reaction, i.e. component a, component B and component D, and not the total percentage of the C component not participating in the reaction.

The final products prepared in examples 2,4, 6, 8,9-13 were tested to have similar properties as in examples 1, 3, 5, 7, i.e., high mechanical properties, low driving voltage and high contrast.

In the invention, the thickness of the spacer and the particle size of the spacer can be changed according to actual needs, and different thicknesses of the spacer and different particle sizes of the spacer can lead to different thicknesses of the dimming film. Specifically, the thickness of the spacer is controlled to be 5 to 500 μm, and the particle diameter of the spacer is controlled to be 2 to 300. mu.m.

Claims

1. A liquid crystal light adjusting film with high mechanical property, low driving voltage and high contrast is characterized by being prepared from a component A, a component B, a component C and a component D;

2. the high mechanical property, low driving voltage and high contrast liquid crystal dimming film according to claim 1, wherein said liquid crystal material is a positive liquid crystal material or a negative liquid crystal material.

3. The high mechanical properties, low driving voltage and high contrast liquid crystal dimming film according to claim 1 or 2, wherein the methacrylate monomer is at least one of cyclohexyl methacrylate, propylene glycol methyl ether acetate, isoamyl acrylate, isobornyl methacrylate, isobutyl methacrylate, unsaturated polyester, epoxy acrylate, urethane acrylate, polyester acrylate, epoxy acrylate, polyenethiol system, polyether acrylate, water-based acrylate, vinyl ether.

4. The high mechanical properties, low driving voltage and high contrast liquid crystal dimming film according to claim 1 or 2, wherein the hydroxyl group-containing methacrylate monomer is at least one of 4-hydroxybutyl acrylate, hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate and hydroxypropyl methacrylate.

5. The high mechanical properties, low driving voltage and high contrast liquid crystal dimming film according to claim 1 or 2, wherein said fluorine-containing methacrylate monomer is at least one of trifluoroethyl methacrylate, pentafluoropropyl methacrylate, 2-methyl-2-propenoic acid-2, 3-dihydroxypropyl ester, 2- (perfluorooctyl) ethyl methacrylate and heptafluorobutyl acrylate.

6. The high mechanical property, low driving voltage and high contrast liquid crystal dimming film according to claim 1 or 2, wherein the crosslinking agent is at least one of polyethylene glycol diacrylate (molecular weight 200), polyethylene glycol diacrylate (molecular weight 400), polyethylene glycol diacrylate (molecular weight 575), polyethylene glycol diacrylate (molecular weight 600), polyethylene glycol diacrylate (molecular weight 700), polyethylene glycol diacrylate (molecular weight 1000), diethylene glycol diacrylate, 1,4 butylene glycol diacrylate, Bis-EMA 15;

7. The high mechanical properties, low driving voltage and high contrast liquid crystal light adjusting film according to claim 1 or 2, wherein the spacer has a particle diameter of 2 to 300 μm;

the spacer is a polymer film with the thickness of 5-500 mu m.

8. A method for preparing a high mechanical property, low driving voltage and high contrast liquid crystal light adjusting film according to any one of claims 1 to 7, characterized by using the first method or the second method, wherein,

first, method

The first method is carried out according to the following steps:

second, method two

9. The method according to claim 8, wherein the liquid crystal cell is a cell made of a glass substrate coated with an ITO conductive film; the plastic film is a plastic film plated with an ITO conductive film.