A method for producing a brightness enhancement film and a brightness enhancement film

Abstract

The application relates to a brightening sheet preparation method and a brightening sheet. The preparation method comprises the following steps: S1, preparing a brightening film and a polarizing sheet; S2, preparing a liquid crystal alignment layer on one side of the brightening film or one side of the polarizing sheet; and S3, roll-to-roll compounding the brightening film and the polarizing sheet. In S2, the liquid crystal alignment layer changes the transmission axis by changing the polarization direction of polarized light. The application has the effects of improving the production efficiency and yield of the brightening sheet and improving the utilization rate of the substrate.

Description

Technical Field

[0001] This application relates to the field of liquid crystal displays, and in particular to a method for preparing a brightness enhancement film and the brightness enhancement film itself. Background Technology

[0002] LCD screens are widely used in various display fields due to their low space occupancy and low energy consumption. Among them, brightness enhancement film is a technology that can improve the surface brightness of LCD screens.

[0003] In related technologies, brightness enhancement films are composed of polarizing films and brightness enhancement films. When preparing brightness enhancement films, the brightness enhancement film roll is first cut into sheets, then the sheets are rotated 90° and multiple sheets are spliced ​​together, then rewound into a roll of brightness enhancement film, and finally combined with polarizing films in roll-to-roll composite production. The above method requires additional cutting and splicing processes, which will reduce production efficiency, and the splicing will cause a decrease in utilization and yield. Summary of the Invention

[0004] In order to improve the production efficiency and yield of brightening films, as well as the utilization rate of substrates, this application provides a method for preparing brightening films and a brightening film.

[0005] In a first aspect, this application provides a method for preparing a brightness enhancement film, which adopts the following technical solution:

[0006] A method for preparing a brightness enhancement film includes the following steps:

[0007] S1. Preparation of brightness enhancement film and polarizer;

[0008] S2. A liquid crystal alignment layer is formed on the bonding side of the brightness enhancement film or the bonding side of the polarizer.

[0009] S3. The brightening film and polarizer are rolled together in a roll-to-roll composite process.

[0010] In S2, the liquid crystal alignment layer changes the transmission axis by altering the polarization direction of the polarized light.

[0011] By adopting the above technical solution, the light transmission axis of the brightness enhancement film is parallel to the length direction of the roll material, while the light transmission axis of the polarizer is parallel to the width direction of the roll material. Therefore, a liquid crystal alignment layer is added. By utilizing the characteristics of liquid crystal, the light transmission axis of the brightness enhancement film or the light transmission axis of the polarizer can be changed so that the light transmission axes of the brightness enhancement film and the polarizer are parallel to each other. Thus, roll-to-roll composite production of brightness enhancement films can be achieved without additional cutting and splicing. At the same time, since there is no cutting and splicing, the yield of brightness enhancement films and the utilization rate of substrates will be improved.

[0012] Preferably, in step S2, if the liquid crystal alignment layer is located on the brightness enhancement film, step S2 includes the following steps:

[0013] S21. Synthesize azobenzene compounds via diazotization-coupling reaction;

[0014] S22. Azobenzene compounds are esterified with acrylic acid or acryloyl chloride to obtain azobenzene monomers.

[0015] S23. Mix the azobenzene monomer with the predetermined comonomer in a predetermined solvent;

[0016] S24. Add an initiator and carry out a free radical polymerization reaction to form a liquid crystal polymer under conditions of oxygen concentration ≤ 5 ppm and heating at a predetermined temperature;

[0017] S25. Dissolve the liquid crystal polymer in a predetermined solvent to form a liquid crystal polymer solution of a predetermined concentration;

[0018] S26. A liquid crystal polymer solution is coated on the side of the brightening film to be bonded to form a liquid crystal polymer coating.

[0019] S27. The internal stress of the liquid crystal polymer coating is removed to form a liquid crystal alignment layer.

[0020] By adopting the above technical solution and following the chemical path of "diazotization-coupling reaction → esterification reaction → free radical polymerization", polymers with specific molecular weights and liquid crystal properties are synthesized, thus enabling the preparation of a liquid crystal alignment layer on the brightness enhancement film.

[0021] Preferably, if the liquid crystal alignment layer is located on the polarizer, then step S2 includes the following steps:

[0022] S201. Mix liquid crystal molecules and polymer precursor in a predetermined ratio in a predetermined solvent, and simultaneously add a predetermined amount of photoinitiator to form a liquid crystal molecule solution.

[0023] S202. A liquid crystal molecular solution is coated on the side of the polarizer to be bonded to form a liquid crystal molecular coating film.

[0024] S203. A liquid crystal molecular coating is photocured to form a liquid crystal primary polymer film.

[0025] S204. The liquid crystal primary polymer film is subjected to ordered arrangement of liquid crystal molecules to form a liquid crystal alignment layer.

[0026] By adopting the above technical solution, the polarization performance can be controlled by the orientation of liquid crystal molecules. The system is "liquid crystal molecules are dispersed in polymer precursors, and then the polymer precursors are cross-linked into a network by photocuring". The essence is physical dispersion and photocross-linking curing, so a liquid crystal orientation layer can be prepared on the polarizer.

[0027] Preferably, in step S24, before heating, the chamber containing the mixed solution is alternately subjected to vacuuming and inert gas filling, and the process is repeated multiple times. After vacuuming to a predetermined pressure, the reaction vessel is held at pressure for a predetermined time, and the pressure holding time gradually increases with the number of cycles. After inert gas filling to atmospheric pressure, the gas is released for a predetermined time, and the inert gas flow rate gradually decreases with the number of cycles. After the last cycle, inert gas is filled at a flow rate lower than the last inert gas flow rate.

[0028] By adopting the above technical solution and using multiple cycles of treatment, the reaction vessel is kept at normal pressure and the oxygen concentration is below 5 ppm, while preventing solvent evaporation.

[0029] Preferably, in step S27, the liquid crystal polymer coating is annealed at 80-120°C for 1-2 hours to remove internal stress.

[0030] By adopting the above technical solution, since the coating in S26 is a "freshly synthesized liquid crystal polymer solution", the solvent evaporation and polymer molecule stacking during the film formation process are prone to generating mechanical internal stress. Therefore, annealing at 80-120℃ only requires the molecular chains to move slightly through the heat effect to relax the stress, thereby removing the internal stress.

[0031] Preferably, in step S27, the internal stress removal treatment of the liquid crystal polymer coating is performed by solvent vapor annealing. This step involves a double-layer reaction vessel, which has a working inner cavity and a vacuum insulation cavity. The working inner cavity is equipped with a suspension frame, an evaporating dish, a temperature control base, and a magnetic stirrer. The temperature control base is used to change the temperature of the evaporating dish, and the magnetic stirrer is used to stir the solvent in the evaporating dish. The working inner cavity is connected to an exhaust valve and a vent pipe, and the outer wall of the vacuum insulation cavity is equipped with a cooling pipe. Therefore, step S27 includes the following steps:

[0032] S271. Fix the brightening film onto the hanging frame;

[0033] S272. Inject the predetermined solvent into the evaporating dish;

[0034] S273. Inject cooling water into the cooling pipe and pre-cool the evaporating dish using the temperature control base;

[0035] S274. Heat and stir the solvent to increase the vapor saturation gradient until it reaches 70% saturation.

[0036] S275. Turn off the heating and allow the steam saturation gradient to decrease;

[0037] S276. Introduce dry nitrogen gas at a predetermined temperature into the working chamber at a predetermined flow rate and purge for a predetermined time.

[0038] By adopting the above technical solution and using solvent vapor annealing, both production efficiency and stress relief rate are taken into account, while the production environment temperature is relatively low.

[0039] Preferably, after step S276, the brightening film is heat-cured at 80-100°C for 5-10 minutes.

[0040] By adopting the above technical solution, the characteristics of the brightness enhancement film are taken into account, and the stress relief rate is improved at a lower cost.

[0041] Preferably, in step S204, the liquid crystal primary polymer film is annealed at 60-100°C for 30-90 minutes to achieve the orderly arrangement of liquid crystal molecules.

[0042] By adopting the above technical solution, thermal energy is used to further arrange the liquid crystal molecules in an orderly manner, while simultaneously driving the fine-tuning of the polymer network, allowing the two to interact more fully and ultimately optimizing the polarization rotation performance.

[0043] Preferably, between S202 and S203, a step of pre-aligning the liquid crystal molecules in the liquid crystal molecule coating is added, wherein the alignment treatment is implemented by one of polarization light induction, electric field induction, magnetic field induction, polarization light combined electric field induction, and polarization light combined magnetic field induction.

[0044] By adopting the above technical solution, the orientation of the liquid crystal is induced before photocuring. After annealing, the interaction between molecules and the network can be optimized, internal stress can be relieved, and the orientation order and transmittance uniformity can be improved.

[0045] Secondly, this application provides a brightness enhancement film, which adopts the following technical solution:

[0046] A brightness enhancement film, comprising a product manufactured using the aforementioned brightness enhancement film preparation method.

[0047] By adopting the above technical solution, roll-to-roll composite production of brightening sheets can be achieved without additional cutting and splicing. At the same time, since there is no cutting and splicing, the yield of brightening sheets and the utilization rate of substrates will be improved.

[0048] In summary, this application includes at least one of the following beneficial technical effects:

[0049] 1. The light transmission axis of the brightness enhancement film is parallel to the length direction of the roll material, while the light transmission axis of the polarizer is parallel to the width direction of the roll material. Therefore, a liquid crystal alignment layer is added. By utilizing the characteristics of liquid crystal, the light transmission axis of the brightness enhancement film or the light transmission axis of the polarizer can be changed so that the light transmission axes of the brightness enhancement film and the polarizer are parallel to each other. Thus, roll-to-roll composite production of brightness enhancement films can be achieved without additional cutting and splicing. At the same time, since there is no cutting and splicing, the yield of brightness enhancement films and the utilization rate of substrates will be improved.

[0050] 2. By following the chemical pathway of "diazotization-coupling reaction → esterification reaction → free radical polymerization", polymers with specific molecular weights and liquid crystal properties are synthesized, thus enabling the preparation of a liquid crystal alignment layer on the brightness enhancement film;

[0051] 3. By utilizing the directional control of liquid crystal molecules to regulate polarization performance, the system is "liquid crystal molecules dispersed in a polymer precursor, and then the polymer precursor is cross-linked into a network through photocuring". Essentially, it is a combination of physical dispersion and photo-crosslinking curing, thus enabling the preparation of a liquid crystal oriented layer on a polarizer. Attached Figure Description

[0052] Figure 1 This is a schematic flowchart of the method for preparing the brightening film in the embodiments of this application.

[0053] Figure 2 This is a schematic diagram of the layer structure of the brightness enhancement film with added liquid crystal alignment layer in the embodiments of this application.

[0054] Figure 3 This is a schematic diagram of the layer structure of a polarizer with a liquid crystal alignment layer added in an embodiment of this application. Detailed Implementation

[0055] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail.

[0056] This application discloses a method for preparing a brightness enhancement film.

[0057] Reference Figure 1 The method for preparing the brightening film includes the following steps:

[0058] S1. Preparation of brightness enhancement film and polarizer;

[0059] S2. A liquid crystal alignment layer is formed on the bonding side of the brightness enhancement film or the bonding side of the polarizer.

[0060] S3. The brightening film and polarizer are rolled together in a roll-to-roll composite process.

[0061] In S2, the liquid crystal alignment layer changes the transmission axis by altering the polarization direction of the polarized light.

[0062] The key to achieving roll-to-roll lamination of the brightness enhancement film and the polarizer lies in the setting of the liquid crystal alignment layer. This is because, in the initial state, that is, before the substrate has undergone any processing, the light transmission axis of the brightness enhancement film is parallel to the length direction of the roll, and the light transmission axis of the polarizer is parallel to the width direction of the roll. Therefore, the light transmission axes of the brightness enhancement film and the polarizer are perpendicular to each other.

[0063] However, thanks to the characteristics of liquid crystals, the light transmission axis of the brightness enhancement film with a liquid crystal alignment layer changes. Similarly, the light transmission axis of the polarizer with a liquid crystal alignment layer also changes. In this way, the light transmission axes of the brightness enhancement film with a liquid crystal alignment layer and the polarizer can be parallel to each other. Likewise, the light transmission axes of the polarizer with a liquid crystal alignment layer and the brightness enhancement film can also be parallel to each other. Therefore, roll-to-roll composite production of brightness enhancement films can be achieved without additional cutting and splicing. At the same time, since there is no cutting and splicing, the yield of brightness enhancement films and the utilization rate of substrates are improved.

[0064] The aforementioned brightening film is an APF brightening film. Specifically, the brightening film can be made by laminating two polymer materials with different refractive indices (such as PET and PEN) through multiple layers, or it can be formed into a multi-layer film structure in one step through co-extrusion. In large-scale production, multi-layer co-extrusion technology has become the dominant manufacturing process due to its significant advantages in efficiency, number of layers, interface quality and optical performance. Lamination and lamination are more often used in specific application scenarios or as a supplement to the co-extrusion process.

[0065] In S2, if the liquid crystal alignment layer is located on the brightness enhancement film, then S2 specifically includes the following steps:

[0066] S21. Synthesize azobenzene compounds via diazotization-coupling reaction;

[0067] S22. Azobenzene compounds are esterified with acrylic acid or acryloyl chloride to obtain azobenzene monomers.

[0068] S23. Mix the azobenzene monomer with the predetermined comonomer in a predetermined solvent;

[0069] S24. Add an initiator and carry out a free radical polymerization reaction to form a liquid crystal polymer under conditions of oxygen concentration ≤ 5 ppm and heating at a predetermined temperature;

[0070] S25. Dissolve the liquid crystal polymer in a predetermined solvent to form a liquid crystal polymer solution of a predetermined concentration;

[0071] S26. A liquid crystal polymer solution is coated on the side of the brightening film to be bonded to form a liquid crystal polymer coating.

[0072] S27. The internal stress of the liquid crystal polymer coating is removed to form a liquid crystal alignment layer.

[0073] In S22, the choice between acrylic acid and acryloyl chloride depends on the specific requirements: if low cost and esterification of conventional alcohols are desired, acrylic acid is more suitable; if rapid reaction, high purity, or treatment of difficult-to-react alcohols are required, acryloyl chloride is more advantageous, but attention should be paid to operating conditions and safety.

[0074] In step S23, to optimize and ensure the performance of the liquid crystal, the comonomers are preferably methyl methacrylate and n-substituted maleimide monomers. However, in other embodiments, monomers such as styrene, acrylonitrile, and vinyl acetate can also be used. Under the premise that the comonomers are methyl methacrylate and n-substituted maleimide monomers, the solvent in this step is preferably tetrahydrofuran. Similarly, in other embodiments, the solvent can also be 1,4-dioxane, toluene, or chlorobenzene.

[0075] In S24, the initiator is preferably azobisisobutyronitrile (AIBN). In other embodiments, AMBN (2,2'-azobis(2-methylbutyronitrile)) or ACVA (4,4'-azobis(4-cyanopentanoic acid)) can also be used. The condition of oxygen concentration ≤ 5 ppm is usually achieved under the protection of an inert gas, such as nitrogen, helium, or argon, to remove oxygen and prevent it from interfering with the polymerization process. The heating condition is usually achieved at a temperature of 60-80°C. The purpose of heating is to activate the initiator to decompose and generate free radicals. 60-80°C is the optimal condition for balancing the initiator decomposition rate, liquid crystal phase stability, and oxygen suppression effect.

[0076] In step S24, the condition of achieving an oxygen concentration of ≤5ppm must be met before heating. Specifically, the chamber containing the mixed solution in this step will be alternately evacuated and filled with inert gas, and this process will be repeated multiple times. As mentioned above, the chamber containing the mixed solvent is provided by a three-necked flask. The main port of the three-necked flask is sealed with a mechanical stirrer. The left side port is equipped with a vacuum pressure gauge and a vacuum pump interface, which is connected to a vacuum pump. The right side port is equipped with an inert gas inlet pipe and a bubbler, which is connected to a gas flow meter and an inert gas cylinder.

[0077] The aforementioned cyclic treatment method involves evacuating to a predetermined pressure, holding the pressure in the reaction vessel for a predetermined time (the holding time gradually increases with the number of cycles), then purging with inert gas to atmospheric pressure and dissipating the gas for a predetermined time (the inert gas flow rate gradually decreases with the number of cycles). After the final cycle, inert gas is introduced at a flow rate lower than the last inert gas flow rate. Specifically, taking three cycles as an example, in the first cycle, the pressure is first evacuated to 10 mbar, then held for 1 minute, followed by inert gas introduction at a flow rate of 1 L / min until atmospheric pressure is reached, and then allowed to stand for 30 seconds to allow gas diffusion. In the second cycle, the pressure is first evacuated to 1 mbar, then held for 2 minutes, followed by inert gas introduction at a flow rate of 0.8 L / min until atmospheric pressure is reached, and then allowed to stand for 30 seconds. In the third cycle, the pressure is first evacuated to 0.1 mbar, then held for 3 minutes, followed by inert gas introduction at a flow rate of 0.5 L / min until atmospheric pressure is reached, and then the flow rate is reduced to 0.2 L / min to maintain dynamic protection.

[0078] In S25, the solvent is preferably chloroform, and the concentration of the solution is 10%-20% (w / w).

[0079] In S26, the liquid crystal polymerization solution is applied to some areas of the brightness enhancement film to form a liquid crystal polymerization coating using a slit coating method. Specifically, refer to... Figure 2 The side for bonding is the side where the release film is removed from the brightness enhancement film, which is the other side of the protective film on the brightness enhancement film. Specifically, the layer structure of the brightness enhancement film consists of a liquid crystal alignment layer, an APF brightness enhancement film, and a protective film. As for the complete preparation of the brightness enhancement film, a release film is applied to the side of the liquid crystal alignment layer away from the APF brightness enhancement film.

[0080] In S27, the reason for needing to remove internal stress is that during the film formation process of liquid crystal polymerization solution, solvent evaporation and polymer molecule stacking easily generate mechanical internal stress. Considering both stress relief rate and industrialization difficulty, the following two methods are preferred. The first is thermal annealing. Specifically, the liquid crystal polymerization coating is annealed at 80-120℃ for 1-2 hours to remove internal stress. The principle of this method is that the molecular chains move slightly through the heat effect, relaxing the stress and thus removing internal stress.

[0081] The second type is solvent vapor annealing, which involves a double-layer reaction vessel. The double-layer reaction vessel is made of glass and has a working inner cavity and a vacuum insulation cavity. The working inner cavity is a chamber treated with a brightening film, while the vacuum insulation cavity is made to have a pressure of less than 0.1 Pa during the equipment manufacturing process to reduce the rate at which heat is transferred from the working inner cavity to the outside.

[0082] The working chamber is equipped with a hanging rack, an evaporating dish, a temperature control base, and a magnetic stirrer. The temperature control base is used to change the temperature of the evaporating dish, and the magnetic stirrer is used to stir the solvent in the evaporating dish. The working chamber is also connected to an exhaust valve and a vent pipe. The outer wall of the vacuum insulation chamber is equipped with a cooling pipe. The purpose of the cooling pipe is to further prevent the outer wall of the double-layer reaction vessel from overheating, thereby achieving safe production.

[0083] When solvent vapor annealing is used, S27 includes the following steps:

[0084] S271. Fix the brightening film onto the hanging frame;

[0085] S272. Inject the predetermined solvent into the evaporating dish;

[0086] S273. Inject cooling water into the cooling pipe and pre-cool the evaporating dish using the temperature control base;

[0087] S274. Heat and stir the solvent to increase the vapor saturation gradient until it reaches 70% saturation.

[0088] S275. Turn off the heating and allow the steam saturation gradient to decrease;

[0089] S276. Introduce dry nitrogen gas at a predetermined temperature into the working chamber at a predetermined flow rate and purge for a predetermined time.

[0090] In S272, the solvent is a chloroform / THF mixed solvent (7:3), where 7:3 is the volume ratio.

[0091] In S273, the temperature of the cooling water is 10°C to prevent overheating of the outer wall and condensation on the outer wall. The purpose of preventing condensation is to ensure the accuracy of liquid crystal observation. At the same time, the pre-cooling treatment allows the evaporating dish to be pre-cooled to 25°C to prevent the solvent from evaporating too early.

[0092] In S274, the magnetic stir bar and temperature control base are activated to heat and stir the solvent. The vapor saturation varies as follows: 0-5 min, vapor saturation reaches 20%; 5-15 min, vapor saturation reaches 60%; 15-30 min, vapor saturation reaches 70%.

[0093] In S275, the temperature control base is closed and the exhaust valve is opened to allow the steam saturation to decrease gradually. The steam saturation changes as follows: 0-1 min, steam saturation decreases from 70% to 50%; 1 min-3 min, steam saturation decreases from 50% to 30%; 3 min-7 min, steam saturation decreases from 30% to 10%; 7 min-12 min, steam saturation decreases from 10% to 0, in order to achieve gradient pressure reduction and prevent stress rebound.

[0094] In S276, the nitrogen flow rate is 10 L / min, the nitrogen temperature is 40℃, and the purging time is 5 min to achieve drying and curing, thereby locking in a low-stress state.

[0095] In summary, thermal annealing or solvent vapor annealing can be used to eliminate the internal stress of liquid crystal polymer coatings. Thermal annealing requires 1-2 hours and has a stress relief rate of 95%, while solvent vapor annealing requires 10-30 minutes and has a stress relief rate of 90%.

[0096] In other embodiments, mechanical stretching-relaxation or plasma treatment can also be used to eliminate internal stress.

[0097] After completing the aforementioned S276, if production costs are not a concern or are not a major concern, a curing process can be performed to improve the stress relief rate. Specifically, considering that the liquid crystal alignment layer is set on the brightness enhancement film, a thermal curing method is used to achieve this. The curing conditions are 80-100℃ for 5-10 minutes. The reason is that for silver-based APF brightness enhancement films, UV curing will cause silver oxidation and deterioration.

[0098] In summary, the core of forming a liquid crystal alignment layer on a brightness enhancement film is to construct a liquid crystal polymer film layer. This is achieved through a chemical pathway of "diazotization-coupling reaction → esterification reaction → free radical polymerization" to synthesize a polymer with specific molecular weight and liquid crystal properties.

[0099] In S2, if the liquid crystal alignment layer is located on the polarizer, then S2 includes the following steps:

[0100] S201. Mix liquid crystal molecules and polymer precursor in a predetermined ratio in a predetermined solvent, and simultaneously add a predetermined amount of photoinitiator to form a liquid crystal molecule solution.

[0101] S202. A liquid crystal molecular solution is coated on the side of the polarizer to be bonded to form a liquid crystal molecular coating film.

[0102] S203. A liquid crystal molecular coating is photocured to form a liquid crystal primary polymer film.

[0103] S204. The liquid crystal primary polymer film is subjected to ordered arrangement of liquid crystal molecules to form a liquid crystal alignment layer.

[0104] In S201, the liquid crystal molecules are cholesteric liquid crystals, the polymer precursor is a UV-curable acrylate polymer, the liquid crystal molecules account for 70%-90% by mass, the solvent is toluene, and the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone, the content of which is generally 1%-3% of the polymer precursor mass.

[0105] In other embodiments, the polymer precursor may also be an epoxy resin polymer or a polyurethane acrylate polymer. The key consideration in choosing which type to use is that the polymer precursor must ensure the feasibility of mixing and coating through physical properties (viscosity, solubility), control the network structure through chemical properties (reactivity, crosslinking density), match existing equipment through process compatibility (curing method, adhesion), and finally achieve a high-performance composite material through interaction with the liquid crystal (compatibility, orientation stability).

[0106] In step S202, the liquid crystal molecular solution is applied using a slit coating method to form a liquid crystal molecular coating film on the side of the polarizer to be bonded. For details, refer to... Figure 3 The side for bonding is the side of the polarizer where the protective film has been removed, which is the other side of the release film on the brightness enhancement film. Specifically, the layer structure of the polarizer is, in sequence, a liquid crystal alignment layer, a TAC film, a PVA film, another TAC film, and a release film. As for the complete fabrication of the polarizer, a protective film is covered on the side of the liquid crystal alignment layer away from the TAC film.

[0107] In S203, ultraviolet light is used for curing.

[0108] In S204, the liquid crystal primary polymer film is annealed at 60-100℃ for 30-90 minutes to achieve the orderly arrangement of liquid crystal molecules. The thermal energy is used to further arrange the liquid crystal molecules in an orderly manner, while driving the fine adjustment of the polymer network, so that the two interact more fully and ultimately optimize the polarization rotation performance.

[0109] To further improve the orientation order and transmittance uniformity of the liquid crystal alignment layer, a pre-alignment treatment can be performed on the liquid crystal molecules in the liquid crystal molecular coating between S202 and S203, that is, before photocuring. Specifically, polarized light induction, electric field or magnetic field induction, or a combination of polarized light and electric field or magnetic field induction can be used. That is, polarized light induction can be performed first, followed by electric field or magnetic field induction, or electric field or magnetic field induction can be performed first, followed by polarized light induction.

[0110] In summary, the core of forming a liquid crystal alignment layer on a polarizer is to utilize the orientation of liquid crystal molecules to regulate polarization performance. The system consists of "liquid crystal molecules (such as cholesteric type) dispersed in a polymer precursor (acrylate)," and the polymer precursor is cross-linked into a network (physically encapsulating and fixing the liquid crystal molecules) through "ultraviolet light curing." Essentially, it is a combination of physical dispersion and photocrosslinking curing, which does not require changing the chemical structure of the liquid crystal molecules. It only needs to utilize their orientation characteristics, and therefore there are no complex chemical reactions.

[0111] The implementation principle of the brightness enhancement film preparation method in this application embodiment is as follows: the light transmission axis of the brightness enhancement film is parallel to the length direction of the roll material, while the light transmission axis of the polarizer is parallel to the width direction of the roll material. Therefore, a liquid crystal alignment layer is added. By utilizing the characteristics of liquid crystal, the light transmission axis of the brightness enhancement film or the light transmission axis of the polarizer can be changed so that the light transmission axes between the brightness enhancement film and the polarizer are parallel to each other. Thus, roll-to-roll composite production of brightness enhancement films can be achieved without additional cutting and splicing. At the same time, since there is no cutting and splicing, the yield of brightness enhancement films and the utilization rate of substrates will be improved.

[0112] This application also discloses a brightness enhancement film.

[0113] The brightness enhancement film is made using the aforementioned preparation method. Therefore, the brightness enhancement film includes a brightness enhancement film, a polarizer, and a liquid crystal alignment layer. With the help of the liquid crystal alignment layer, roll-to-roll composite production of the brightness enhancement film can be achieved without additional cutting and splicing. At the same time, since there is no cutting and splicing, the yield of the brightness enhancement film and the utilization rate of the substrate will be improved.

[0114] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for producing a brightness enhancement sheet, characterized by: The method comprises the following steps: ​ S1, preparing a brightness enhancement film and a polarizer; S2, preparing a liquid crystal alignment layer on the side of the brightness enhancement film or the side of the polarizer to be bonded; S3, performing roll-to-roll compounding of the brightness enhancement film and the polarizer; In S2, the liquid crystal alignment layer changes the polarization direction of polarized light to change the light transmission axis; In S2, if the liquid crystal alignment layer is on the brightness enhancement film, S2 comprises the following steps: S21, synthesizing an azobenzene compound through diazotization-coupling reaction; S22, performing esterification reaction of the azobenzene compound and acrylic acid or acryloyl chloride to obtain an azobenzene monomer; S23, mixing the azobenzene monomer and a predetermined comonomer in a predetermined solvent; S24, adding an initiator, and performing free radical polymerization under the condition of oxygen concentration ≤ 5ppm and heating at a predetermined temperature to form a liquid crystal polymer; S25, dissolving the liquid crystal polymer in a predetermined solvent to form a liquid crystal polymer solution with a predetermined concentration; S26, coating the liquid crystal polymer solution on the side of the brightness enhancement film to be bonded to form a liquid crystal polymer coating film; S27, removing the internal stress of the liquid crystal polymer coating film to form a liquid crystal alignment layer; In S27, the internal stress removal treatment of the liquid crystal polymer coating film is performed by solvent vapor annealing, and the steps involve a double-layer reaction container, the double-layer reaction container has a working inner cavity and a vacuum heat insulation cavity, a hanging rack, an evaporation dish, a temperature control base and a magnetic stirring rod are arranged in the working inner cavity, the temperature control base is used to change the temperature of the evaporation dish, the magnetic stirring rod is used to stir the solvent in the evaporation dish, an exhaust valve and an air inlet pipe are arranged on the working inner cavity in communication, and a cooling pipe is arranged on the outer wall of the vacuum heat insulation cavity, and S27 comprises the following steps: S271, fixing the brightness enhancement film on the hanging rack; S272, injecting a predetermined solvent into the evaporation dish; S273, injecting cooling water into the cooling pipe, and pre-cooling the evaporation dish by the temperature control base; S274, heating and stirring the solvent to increase the vapor saturation degree gradient until reaching 70% saturation; S275, turning off the heating, and decreasing the vapor saturation degree gradient; S276, introducing dry nitrogen gas at a predetermined temperature into the working inner cavity at a predetermined flow rate, and purging for a predetermined time; After S276, the brightness enhancement film is heat cured at 80-100°C for 5-10 minutes.

2. The brightness enhancement sheet production method according to claim 1, characterized by: In S24, before heating, the chamber where the mixed solution is located is alternately subjected to vacuumizing treatment and inert gas filling treatment and is cycled multiple times, wherein the reaction container is kept at a predetermined pressure after vacuumizing treatment for a predetermined time, the pressure keeping time gradually increases with the number of cycles, the inert gas filling treatment is kept at atmospheric pressure for a predetermined time after the inert gas filling treatment, and the inert gas filling flow rate gradually decreases with the number of cycles, and finally, the inert gas is filled at a flow rate lower than the flow rate of the last inert gas filling.

3. A method for producing a brightness enhancing sheet, characterized by: The method comprises the following steps: S1, preparing a brightness enhancement film and a polarizer; S2, preparing a liquid crystal alignment layer on the side of the brightness enhancement film or the side of the polarizer to be bonded; S3, performing roll-to-roll compounding of the brightness enhancement film and the polarizer; In S2, the liquid crystal alignment layer changes the polarization direction of polarized light to change the light transmission axis; The S2 includes the following steps if the liquid crystal alignment layer is located on the polarizer: S201, mixing liquid crystal molecules and polymer precursors in a predetermined proportion in a predetermined solvent, and adding a predetermined amount of a photoinitiator to form a liquid crystal molecule solution; S202, coating the liquid crystal molecule solution on one side of the polarizer for lamination to form a liquid crystal molecule coating film; S203, performing a photo-curing treatment on the liquid crystal molecule coating film to form a liquid crystal initial polymerization film; S204, performing an ordered arrangement treatment of liquid crystal molecules on the liquid crystal initial polymerization film to form a liquid crystal alignment layer; In the S204, the liquid crystal initial polymerization film is annealed at 60-100°C for 30-90 minutes to achieve the ordered arrangement of the liquid crystal molecules; Between the S202 and the S203, a step of performing a pre-alignment treatment on the liquid crystal molecules in the liquid crystal molecule coating film is added, and the alignment treatment is achieved by one of polarization light induction, electric field induction, magnetic field induction, polarization light combined electric field induction, and polarization light combined magnetic field induction.

4. A brightening sheet, characterized by: The brightness enhancement film is prepared by the method of any one of claims 1-3.

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