Roll-to-roll preparation method and device for liquid crystal dimming film

Abstract

The invention discloses a roll-to-roll preparation method of a liquid crystal dimming film. The roll-to-roll preparation method comprises the following steps: providing a first base film; coating the first base film with a liquid crystal dimming material to form a liquid crystal dimming coating; a second base film is provided, the second base film and the first base film are attached to form a semi-finished product film, and the liquid crystal dimming coating is located between the first base film and the second base film; providing a first light source, and rapidly curing the two sides of the base film; and providing a second light source to cure the semi-finished product film. The invention discloses a roll-to-roll preparation device for a liquid crystal dimming film. The roll-to-roll preparation device comprises a laminating device, and first light sources are arranged on the two sides of the laminating device. According to the technical scheme, the liquid crystal dimming material can be precisely controlled.

Description

Technical Field

[0001] The present invention relates to the field of liquid crystal dimming films, and more specifically, to a roll-to-roll preparation method and a preparation device for liquid crystal dimming films. Background Art

[0002] A liquid crystal dimming film is an intelligent dimming material based on liquid crystal technology. By changing the orientation of liquid crystal molecules through an electric field, the arrangement control of liquid crystal molecules and the adjustment of light transmittance are achieved.

[0003] A liquid crystal dimming film is composed of two layers of transparent conductive films and an intermediate polymer liquid crystal layer. The polymer liquid crystal layer is formed by curing a prepolymer and a liquid crystal. In the power-off state, the liquid crystal molecules are disorderly arranged, resulting in the inability of light to penetrate, presenting a milky white opaque state; after power-on, the liquid crystal molecules are rearranged under the action of an electric field, enabling light to pass through and presenting a transparent state.

[0004] Liquid crystal dimming films can be applied to fields such as architectural glass, automotive windshields, commercial projections, and medical devices. For example, in architecture, it can be used as an intelligent curtain or a heat insulation film; in automobiles, it can be used as a privacy protection film or a sunshade film.

[0005] Due to the wide application prospects of liquid crystal dimming films, the academic community has conducted extensive research on the preparation methods and performance control of liquid crystal dimming films. Among the preparation methods of liquid crystal dimming films, the Polymerization-induced phase separation (PIPS) method is a relatively common method. In this method, the prepolymer and the liquid crystal material are fully mixed in a certain proportion, and then an appropriate polymerization method is selected depending on the reaction characteristics of the prepolymer. Common polymerization means include free radical polymerization, polycondensation reaction, photo-thermal initiation polymerization, etc. The reaction will increase the molecular weight of the prepolymer until it reaches the critical molecular size. At this time, the miscibility of the two substances in the system decreases, phase separation occurs, and the liquid crystal molecules precipitate in the form of micron-sized droplets to form a liquid crystal dimming film.

[0006] However, the academic research mainly focuses on performance regulation. Regarding the research on factors such as ultraviolet curing intensity and curing temperature involved in the preparation method, the purpose is also to control performance, focusing on the control of single-piece production process factors. There is little research on the roll-to-roll production process that can achieve large-scale batch production.

[0007] One of the problems to be solved in the roll-to-roll manufacturing process is how to control the coating amount of the liquid crystal light modulating material in the roll-to-roll manufacturing process, which is an important technical problem in the industry. If the coating amount of the liquid crystal light modulating material is insufficient, the conductive base film will be wasted, and more importantly, the coating of the liquid crystal light modulating film will be uneven. If the coating amount of the liquid crystal light modulating material is excessive, it will result in waste of the liquid crystal light modulating material, and more seriously, it will cause overflow of the liquid crystal light modulating material, increase the cleaning and post-treatment costs, and contaminate the processing device, thereby increasing the maintenance cost of the device.

[0008] In the traditional roll-to-roll process, the above-mentioned overflow problem is often solved by means of dynamic speed adjustment and coating liquid supply control. However, the dynamic speed adjustment affects the light curing time, resulting in deviation of the performance of the liquid crystal light modulating film from the control. Using coating liquid supply control affects the liquid crystal coating amount and also causes deviation of the performance of the liquid crystal light modulating film from the control.

[0009] Therefore, for liquid crystal light modulating films, there is a lack of a technical solution that can solve the problem of tight control of liquid crystal light modulating materials. Summary of the Invention

[0010] To solve the above technical problems, on the one hand, the present invention provides a roll-to-roll manufacturing method for liquid crystal light modulating films.

[0011] The present invention provides a roll-to-roll manufacturing method for liquid crystal light modulating films, including the following steps: Provide a first base film; Coat a liquid crystal light modulating material on the first base film to form a liquid crystal light modulating coating; Provide a second base film, and bond the second base film to the first base film to form a semi-finished film, with the liquid crystal light modulating coating located between the first base film and the second base film; Provide a first light source to quickly cure both sides of the base film; Provide a second light source to cure the semi-finished film.

[0012] Preferably, the first light source and the second light source are ultraviolet light sources or visible light sources, the first light source is a light emitting diode light source, and the second light source is a mercury lamp, a xenon lamp, a deuterium lamp, a laser light source or a light emitting diode light source.

[0013] Preferably, the time for the quick curing is not more than 10 seconds.

[0014] Preferably, the time for the quick curing is not more than 1 second.

[0015] Preferably, the spot size of the first light source does not exceed 5 mm.

[0016] Preferably, the first light source is a point light source or a line light source.

[0017] Preferably, the liquid crystal light modulating material comprises a liquid crystal, a polymer and an ionic liquid.

[0018] Preferably, the liquid crystal light modulating material comprises a liquid crystal, a polymer and a light stabilizer, and the polymer comprises at least one free radical initiating resin and at least one cationic initiating resin.

[0019] On the other hand, the present invention also provides a roll-to-roll preparation device for a liquid crystal light modulating film.

[0020] A roll-to-roll preparation device for a liquid crystal light modulating film, the roll-to-roll preparation device comprising a laminating device, and first light sources are arranged on both sides of the laminating device.

[0021] Preferably, the first light source is a light emitting diode light source, the light emitting diode light source is a linear light source, and the width of the linear light source does not exceed 5 mm.

[0022] Compared with the prior art, the present invention has the following beneficial effects: By installing light emitting diode light sources on both sides for rapid curing, it is possible to accurately control the coating amount of the liquid crystal light modulating material without the need to monitor and adjust the coating parameters and curing parameters at any time during roll-to-roll coating, and to avoid the situation of glue overflow.

[0023] The heat release of the light emitting diode is small compared with light sources such as mercury lamps, so that the performance and quality of the liquid crystal light modulating film are controllable. The light source is close to the edge, and the influence on the performance and quality of the liquid crystal light modulating film is small, which also makes it easy to cut later.

[0024] Compared with the existing coating control technology, the preparation method of the present invention is simple and has good controllability. Compared with the existing preparation device, the device of the present invention only needs to add light emitting diode light sources to the edge of the original preparation device, has basically no influence on the original equipment, and is convenient to install. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of a preparation device of the prior art, wherein, 100 - first base film, 200 - second base film, 300 - coating device, 400 - liquid crystal light modulating coating, 500 - coating platform, 600 - laminating device, 700 - curing device. The coating device coats the liquid crystal light modulating material on the first base film, and the coating platform is used to bear the weight. The laminating device laminates the first base film and the second base film. The curing device cures the semi-finished film, which is the area where the second light source is located.

[0026] Figure 2 It is a schematic structural diagram of the preparation device of the liquid crystal light modulating film of the present invention. 800 - first light source.

[0027] The structures in the attached drawings are schematic, and some are not absolutely necessary. For example, the coating platform is not absolutely necessary. When the coating device uses a pressure nozzle, the coating platform can be removed. Some forms are not straight as shown schematically. For example, the shape of the coating device can be arbitrary. The distance between the coating device and the laminating device can be very close, which depends on the actual needs. Figure 1 The coating device and the laminating device can be very close to each other, which depends on the actual needs. Detailed implementation manners

[0028] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined purpose, the following is described in conjunction with embodiments.

[0029] Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] The preparation techniques of liquid crystal dimming films include the phase separation method, the hole method, and the microcapsule method. The hole method and the microcapsule method have complex processes, so the mainstream method is the phase separation method. The phase separation method is further divided into the polymerization-induced phase separation method, the solvent-induced phase separation method, and the thermal-induced phase separation method. The solvent-induced method requires at least removing the solvent, which has an adverse impact on the environment. The thermal-induced method requires heating, which increases energy consumption. Therefore, the mainstream method is the polymerization-induced phase separation method. It can be seen that the improvement and selection of the preparation method develop from high complexity and high energy consumption to automation and low energy consumption.

[0031] When controlling the coating liquid in the roll-to-roll process, the main problem lies in the balance between glue overflow and insufficient glue coating. Comparatively speaking, since the coating liquid generally has good fluidity, the most likely problem is glue overflow. The core of controlling glue overflow in traditional processes lies in "prevention + real-time correction", that is, through various pre-designed and post-designed means, to determine whether the glue exceeds the preset range, and according to factors such as the frequency received by the sensor, to perform real-time parameter correction. The parameter correction includes controlling the transfer speed of the base film and the discharging speed of the coating liquid at the coating outlet such as the slit to control the coating amount of the coating liquid.

[0032] Prior design, such as precisely testing the annual and surface tension of the coating solution and its corresponding relationship with temperature, involves extremely complex work. If the fluid exhibits non-Newtonian shear force at different temperatures and viscosities, not only may more preparations be required for measurement accuracy, but the difficulty of parameter adjustment during real-time correction also increases further. Prior design also includes determining the discharging efficiency under different pressures according to the shape and size of the discharging port of the equipment device. Post-design includes adding optical sensors or other sensors to detect glue overflow. Adding sensors increases the complexity of the system, and optical sensors are insensitive to transparent liquids. For the production of liquid crystal dimming films, when curing occurs, the liquid crystal dimming film will not be completely transparent, which further requires higher sensitivity of optical sensors.

[0033] For real-time correction, adjusting the speed of the base film through rollers or other mechanical structures is a common method. However, in the production process of liquid crystal dimming films, adjusting the speed of the base film means that the process speed of the ultraviolet curing section is also adjusted, making the curing process of the liquid crystal dimming film inconsistent and resulting in unstable product performance.

[0034] Therefore, in the preparation of liquid crystal dimming films by traditional roll-to-roll processes, there is a technical problem that the technical solutions are too complex.

[0035] The present invention provides a roll-to-roll preparation method for liquid crystal dimming films, comprising the following steps: Providing a first base film; Coating a liquid crystal dimming material on the first base film to form a liquid crystal dimming coating; Providing a second base film, laminating the second base film with the first base film to form a semi-finished film, and the liquid crystal dimming coating is located between the first base film and the second base film; Providing a first light source to rapidly cure both sides of the base film; Providing a second light source to cure the semi-finished film.

[0036] In traditional roll-to-roll processes, regarding the control of the amount of coating solution, since insufficient glue coating can be quickly solved by increasing the amount of coating solution, the actual technical problem to be solved is how to solve glue overflow, which is in line with the actual coating situation. When using the "prevention + real-time correction" method to solve the glue overflow problem, on the one hand, as a preventive measure, it may be inaccurate and have errors, such as the inherent accuracy of the optical detector; on the other hand, as a detection method itself, it cannot provide a solution, and other methods need to be introduced additionally to solve the problem. Therefore, the present invention adopts a brand-new method. By applying light sources to both sides of the base film and forming a "pocket" with the laminating device, pocket-type coating is realized, so that the coating solution, that is, the liquid crystal dimming material, can only be coated in one direction, avoiding glue overflow.

[0037] Preferably, the first light source and the second light source are ultraviolet light sources or visible light sources. The first light source is a light-emitting diode light source, and the second light source is a mercury lamp, a xenon lamp, a deuterium lamp, a laser light source or a light-emitting diode light source.

[0038] Preferably, the time for rapid curing is not more than 10 seconds.

[0039] Preferably, the time for rapid curing is not more than 1 second.

[0040] Preferably, the spot size of the first light source does not exceed 5 mm.

[0041] For the present invention, rapid curing is necessary. The advantage of the roll-to-roll preparation process is that it can achieve mass production, so speed is the advantage of roll-to-roll. Therefore, for the roll-to-roll process of the liquid crystal dimming film, the ability of rapid curing needs to be provided to achieve rapid curing. Since the laminating device is mostly a roller device and quickly leaves after laminating the first base film and the second base film, rapid curing is required to achieve pocket coating. Specifically, to achieve rapid curing, a higher power can be used, or the curing formula of the liquid crystal dimming material can be changed. The first light source of the present invention uses a light-emitting diode light source, which has significantly lower heat dissipation performance compared with a mercury lamp. When rapid curing is carried out, the influence of edge curing on the performance of the whole film is minimized. When a mercury lamp is used as the first light source, the thermal effect will cause a great influence of edge curing on the performance of the whole film, and this thermal effect may also have an adverse effect on the film. Regarding the spot size of the light source, a smaller spot should be used, which also helps to reduce the influence of edge curing on the performance of the whole film. Preferably, the spot size does not exceed 5 mm, and spots of 3 mm or 1 mm can also be selected. Another advantage of a smaller spot is that less edge cutting is required during later cutting, increasing the utilization rate and reducing losses.

[0042] Preferably, the first light source is a point light source or a line light source. For the point light source of the present invention, the specific shape of the spot is not limited. It can be circular, square, triangular or any other shape. For spots of any shape, the spot size refers to the maximum distance between any two points of the spot. It can be understood that when the spot is circular, the size is the diameter of the spot. When the spot is square, the spot is the length of the diagonal. The line light source of the present invention refers to a strip light source. Regardless of its internal structure, light is emitted through a linear light source externally. For the line light source, the size is the width of the line light source. The line light source can be planar or curved. The present invention preferably uses a line light source, and preferably the line light source is installed on both sides of the laminating device.

[0043] Preferably, the liquid crystal light modulating material comprises a liquid crystal, a polymer and an ionic liquid. The weight percentage of the ionic liquid in the total mass of the liquid crystal light modulating layer is preferably not higher than 2%. The ionic liquid is one selected from salts composed of organic cations and inorganic anions, salts composed of inorganic cations and organic anions, or salts composed of organic cations and organic anions; the organic cation of the ionic liquid is an imidazole-based, pyridine-based, pyrrolidine-based, piperidine-based, pyrazole-based, triazole-based, quaternary ammonium-based, quaternary phosphonium-based or thiazole-based organic cation; the organic anion or inorganic anion is a trifluoromethanesulfonate, bis(trifluoromethanesulfonyl)imide, hexafluorophosphate, tetrafluoroborate, methylsulfonate, acetate, trifluoroacetate, bis(fluorosulfonyl)imide, methyl sulfate, methyl carboxylate, chloride, bromide, iodide, fluoride, nitrate, sulfate, bisulfate, phosphate, decanoate or dicyanamide anion.

[0044] Preferably, the liquid crystal light modulating material comprises a liquid crystal, a polymer and a light stabilizer, and the polymer comprises at least one free radical initiating resin and at least one cationic initiating resin. The free radical initiating resin comprises at least one of an acrylic resin or an allyl resin, and the cationic initiating resin comprises at least one epoxy resin. The free radical initiating resin further contains a free radical initiator, and the cationic initiating resin further contains a cationic initiator. The weight percentage of the light stabilizer in the liquid crystal light modulating layer is preferably not higher than 0.05%.

[0045] The roll-to-roll preparation method of the present invention can be applied to various liquid crystal light modulating materials, including conventional liquid crystal light modulating materials and also including the liquid crystal light modulating materials independently developed by the inventors. It includes liquid crystal light modulating materials containing ionic liquids and also includes liquid crystal light modulating materials containing light stabilizers and cationic initiating resins.

[0046] On the other hand, the present invention also provides a roll-to-roll preparation device for a liquid crystal light modulating film.

[0047] A roll-to-roll preparation device for a liquid crystal light modulating film, the roll-to-roll preparation device is provided with a laminating device, and first light sources are arranged on both sides of the laminating device. The first light source of the present invention is one or several groups of light sources, which are composed of one or more minimum light sources. The second light source of the present invention is also one or several groups of light sources. The minimum light source of the present invention refers to the smallest unit that can be obtained commercially. When multiple minimum units are combined, they can be regarded as a group of light sources. First light sources are arranged on both sides of the laminating device of the present invention. It is easy to understand that there is one or several groups of light sources on each side, preferably one group of light sources. Generally, as a light-emitting diode light source, each light-emitting unit is a point light source, and it can be composed of point light sources or line light sources according to requirements. The present invention preferably uses a line light source, and the line light source can be fixed on both sides of the laminating device.

[0048] The laminating device of the preparation device of the present invention is divided into an upper laminating device and a lower laminating device. Referring to the appendix Figure 2 , a group of first light sources on one side of the upper laminating device are listed. It can be understood that there is another group of first light sources on the other side of the upper laminating device. Although Figure 2 not shown, it can be understood that the first light sources can also be provided on both sides of the lower laminating device.

[0049] Preferably, the first light source is a light-emitting diode light source, and the light-emitting diode light source is a linear light source, and the width of the linear light source does not exceed 5 millimeters.

[0050] The above description of the disclosed embodiments enables those skilled in the art of the present technology to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The present invention will not be limited to the embodiments shown herein, but only needs to conform to the principles and characteristics disclosed herein.

Claims

1. A roll-to-roll preparation method of a liquid crystal dimming film, characterized in that, It includes the following steps: Provide a first base film; Coat a liquid crystal light - modulating material on the first base film to form a liquid crystal light - modulating coating; Provide a second base film, and bond the second base film to the first base film to form a semi - finished film, with the liquid crystal light - modulating coating located between the first base film and the second base film; Provide a first light source to rapidly cure both sides of the base film; Provide a second light source to cure the semi - finished film.

2. The roll-to-roll preparation method according to claim 1, wherein, The first light source and the second light source are ultraviolet light sources or visible light sources. The first light source is a light - emitting diode light source, and the second light source is a mercury lamp, a xenon lamp, a deuterium lamp, a laser light source or a light - emitting diode light source.

3. The roll-to-roll preparation method according to claim 1, wherein The time for the rapid curing is not more than 10 seconds.

4. The roll-to-roll preparation method according to claim 1, wherein The time for the rapid curing is not more than 1 second.

5. The roll-to-roll preparation method according to claim 1, characterized in that, The spot size of the first light source does not exceed 5 mm.

6. The roll-to-roll preparation method according to claim 1, wherein The first light source is a point light source or a line light source.

7. The roll-to-roll preparation method according to claim 1, wherein The liquid crystal light - modulating material contains liquid crystal, polymer and ionic liquid.

8. The roll-to-roll preparation method according to claim 1, wherein The liquid crystal light - modulating material contains liquid crystal, polymer and light stabilizer. The polymer includes at least one free - radical initiating resin and at least one cationic initiating resin.

9. A roll-to-roll preparation device for a liquid crystal dimming film, characterized in that, The roll - to - roll preparation device contains a bonding device, and the two sides of the bonding device are provided with a first light source.

10. The roll-to-roll manufacturing apparatus according to claim 9, wherein, The first light source is a light - emitting diode light source. The light - emitting diode light source is a line light source, and the width of the line light source does not exceed 5 mm.

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