Low driving wide temperature stable high liquid crystal content pdlc film and preparation method thereof

Abstract

This invention belongs to the field of polymer-dispersed liquid crystal (PDLC) optoelectronic functional materials technology, specifically referring to a low-drive, wide-temperature stable, high-liquid-content PDLC thin film and its preparation method. The technical solution is a low-drive, wide-temperature stable, high-liquid-content PDLC thin film and its preparation method, comprising the following components: 22.44g~23.46g of polymer matrix and 74g~78g of liquid crystal; the polymer matrix comprises the following components: 14g~16g of epoxy acrylate prepolymer CN131, 2g~3g of monofunctional reactive diluent OPPEA, 1g~2g of monofunctional reactive diluent IBOA, 2g~3g of trifunctional crosslinking agent TMPTA, and photoinitiator PI184. 0.44g~0.46g; the liquid crystal is QYPDLC-901 nematic liquid crystal, and the mass fraction of the QYPDLC-901 nematic liquid crystal is 70%~80%; the present invention achieves stable dispersion of high liquid crystal content of 70%~80%, breaking through the limitation of the optimal liquid crystal content of 60%~70% in traditional PDLC, while avoiding the problem of phase separation runaway under high content, and significantly improving the electro-optic performance of the film.

Description

Technical Field

[0001] This invention belongs to the field of polymer dispersed liquid crystal (PDLC) optoelectronic functional materials technology, specifically referring to low-drive, wide-temperature stable, high liquid crystal content PDLC thin films and their preparation methods. Background Technology

[0002] Polymer dispersed liquid crystal (PDLC) is a novel optoelectronic functional material composed of a polymer matrix and liquid crystal microdroplets dispersed therein. Its core principle is to control the orientation of liquid crystal molecules by applying an external electric field, so that the refractive index of the liquid crystal microdroplets and the polymer matrix is ​​matched or mismatched, thereby realizing the reversible switching between transparent and hazy states of the thin film. It has broad application prospects in fields such as intelligent dimming, display devices, and privacy protection.

[0003] However, traditional PDLC films suffer from three major drawbacks in practical applications, which severely limit their industrialization and adaptation to high-end scenarios: 1. High driving voltage: The threshold voltage of traditional PDLC films is usually greater than 10V and the saturation voltage is greater than 15V. They cannot be directly compatible with existing 3.3V, 5V and 12V low voltage power supply systems. If they are to be adapted, an additional boost circuit is required, which not only increases the cost and size of the devices, but also reduces the stability of the system.

[0004] 2. Performance runaway under high liquid crystal content: Liquid crystal content is a key factor affecting the electro-optic performance of PDLC thin films. The optimal liquid crystal content of traditional PDLC is only 60%~70%. When the liquid crystal content exceeds 70%, polymerization-induced phase separation runaway is likely to occur, leading to the aggregation and fusion of liquid crystal droplets, forming a dual continuous phase structure. This results in a sharp drop in film contrast and a deterioration in light-shielding performance, making it impossible to achieve stable output of high electro-optic performance.

[0005] 3. Poor high-temperature stability: In high-temperature environments above 60°C, the orientation stability of liquid crystal molecules in traditional PDLC films decreases, and the polymer matrix is ​​prone to thermal deformation, which leads to a sharp deterioration in the electro-optical properties of the film (such as transmittance, response time, and driving voltage), making it difficult to adapt to scenarios with strict requirements for wide-temperature performance, such as automotive, outdoor, and extreme temperature industrial environments.

[0006] Currently, there is no existing technology that can simultaneously solve the above three major defects and achieve synergistic optimization of high liquid crystal content, low driving voltage, wide temperature stability, and high contrast in PDLC thin films and their preparation methods. Therefore, developing a PDLC thin film with low driving voltage, wide temperature stability, and high liquid crystal content to fill the technological gap in the industry has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes a low-drive, wide-temperature stable, high-liquid-content PDLC thin film and its preparation method.

[0008] The technical solution adopted in this invention is as follows: This invention provides a low-drive, wide-temperature stable, high-liquidity PDLC film, comprising the following components: 22.44g~23.46g of polymer matrix and 74g~78g of liquid crystal; the polymer matrix comprises the following components: 14g~16g of epoxy acrylate prepolymer CN131, 2g~3g of monofunctional reactive diluent OPPEA, 1g~2g of monofunctional reactive diluent IBOA, 2g~3g of trifunctional crosslinking agent TMPTA, and 0.44g~0.46g of photoinitiator PI184; the liquid crystal is QYPDLC-901 nematic liquid crystal, and the mass fraction of the QYPDLC-901 nematic liquid crystal is 70%~80%.

[0009] Furthermore, the clearing point of the QYPDLC-901 nematic liquid crystal is 106°C, the birefringence of the QYPDLC-901 nematic liquid crystal is Δn=0.264, and the positive dielectric anisotropy of the QYPDLC-901 nematic liquid crystal is Δε≈18.

[0010] This solution also discloses a method for preparing low-drive, wide-temperature stable, high-liquid-content PDLC thin films, which mainly includes the following steps: Step 1: Mix epoxy acrylate prepolymer CN131, monofunctional reactive diluent OPPEA, monofunctional reactive diluent IBOA and trifunctional crosslinking agent TMPTA, add 2% by mass of photoinitiator PI184, stir in the dark until dissolved, and obtain polymer matrix. Step 2: Add QYPDLC-901 nematic liquid crystal to the polymer matrix and stir evenly in the dark to obtain a liquid crystal mixture; Step 3: Apply the liquid crystal mixture between two ITO conductive glass sheets, and support the two ITO conductive glass sheets with a gasket control box. Cure with ultraviolet light for 3 minutes to obtain a PDLC film.

[0011] Furthermore, the wavelength of the ultraviolet light is 365nm, and the intensity of the ultraviolet light is 12.8mW / cm². The ultraviolet light is used to suppress microdroplet aggregation and bicontinuous phase formation under high liquid crystal content, thereby achieving uniform phase separation.

[0012] Furthermore, the threshold voltage of the PDLC film is ≤3V, the saturation voltage of the PDLC film is ≤7V, and the PDLC film maintains stable electro-optical switching characteristics within the temperature range of 25~90℃.

[0013] Furthermore, the thickness of the gasket control box is 15μm-25μm.

[0014] Furthermore, the QYPDLC-901 nematic liquid crystal has a mass fraction of 77%.

[0015] The beneficial effects achieved by the present invention using the above structure are as follows: 1. Overcoming the limitations of high liquid crystal content: This invention achieves stable dispersion of high liquid crystal content of 70%~80%, breaking through the limitation of the optimal liquid crystal content of 60%~70% in traditional PDLC, while avoiding the problem of phase separation runaway under high content, and significantly improving the electro-optic performance of the film.

[0016] 2. Low driving voltage characteristics: The PDLC thin film prepared by this invention has a threshold voltage as low as 2.9V and a saturation voltage of only 7V. It can be directly compatible with 3.3V, 5V and 12V low voltage power supply systems without the need for additional boost circuits, which reduces device cost and size and improves system stability.

[0017] 3. Excellent performance with wide temperature range: The film has stable electro-optical properties in a wide temperature range of 25~90℃. At a high temperature of 90℃, the maximum transmittance can be maintained at 93% of the room temperature, and the threshold voltage only rises by 0.4V. This completely solves the defect of the traditional PDLC's rapid performance drop at high temperatures, making it suitable for wide temperature application scenarios such as automotive and outdoor applications.

[0018] 4. Simple and controllable preparation process: The low light intensity slow curing process is adopted, the reaction is mild, the equipment requirements are low, no complicated production equipment is required, it is compatible with existing PDLC production lines, it is easy to achieve large-scale mass production, and the production cost is reduced.

[0019] 5. Excellent overall performance: The film has a rise time of 4.2ms in the on state and a fall time of 47ms in the off state. It has high transmittance in the on state, low light leakage in the off state, and the best contrast ratio. It can meet the dimming needs of different scenarios and has a wide range of applications. Detailed Implementation

[0020] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention. However, the scope of protection of the present invention is not limited to these embodiments. All changes or equivalent substitutions that do not depart from the concept of the present invention are included within the scope of protection of the present invention.

[0021] Example 1 The low-drive, wide-temperature stable, high-liquid-content PDLC film has the following raw material ratio: 77g liquid crystal; 15g epoxy acrylate prepolymer CN131; 3g monofunctional reactive diluent OPPEA; 2g monofunctional reactive diluent IBOA; 3g trifunctional crosslinking agent TMPTA; and 0.46g photoinitiator PI184. The liquid crystal is QYPDLC-901 nematic liquid crystal, with a mass fraction of 77%.

[0022] Preparation process: Step 1: Take 15g of epoxy acrylate prepolymer CN131, 3g of monofunctional reactive diluent OPPEA, 2g of monofunctional reactive diluent IBOA, and 3g of trifunctional crosslinking agent TMPTA. Mix them evenly, then add 0.46g of photoinitiator PI184 (2% by mass). Stir in the dark for 40 minutes to obtain a uniform prepolymer solution. Step 2: Add 77g of QYPDLC-901 nematic liquid crystal to the prepolymer solution, stir in the dark for 20min to ensure uniform dispersion of the liquid crystal, and obtain a liquid crystal mixture; Step 3: Coat the liquid crystal mixture between two ITO conductive glass sheets, use a spacer to control the thickness to 20μm, place it under 365nm ultraviolet light, and cure it for 3min with a light intensity of 12.8mW / cm² to obtain a PDLC film.

[0023] The performance of the PDLC film prepared in this embodiment was tested, and the test results are as follows: • Liquid crystal quality fraction: 78%; • Threshold voltage: 2.8V, saturation voltage: 6.8V; • Response time: 4.0ms rise, 45ms fall; • Operating temperature: 25~90℃, maximum transmittance at 90℃ is 92% of room temperature, threshold voltage is 3.2V; • Liquid crystal droplets: uniformly dispersed, without phase fusion and bicontinuous phase structure, with low interfacial energy.

[0024] Example 2 The low-drive, wide-temperature stable, high-liquid-content PDLC film has the following raw material ratio: 78g liquid crystal; 14g epoxy acrylate prepolymer CN131; 4g monofunctional reactive diluent OPPEA; 1g monofunctional reactive diluent IBOA; 3g trifunctional crosslinking agent TMPTA; and 0.44g photoinitiator PI184. The liquid crystal is QYPDLC-901 nematic liquid crystal, and the mass fraction of the QYPDLC-901 nematic liquid crystal is 77%.

[0025] Preparation process: Step 1: Take 14g of epoxy acrylate prepolymer CN131, 4g of monofunctional reactive diluent OPPEA, 1g of monofunctional reactive diluent IBOA, and 3g of trifunctional crosslinking agent TMPTA. Mix them evenly, then add 0.44g of photoinitiator PI184 (2% by mass). Stir for 30 minutes in the dark to obtain a uniform prepolymer solution. Step 2: Add 78g of QYPDLC-901 nematic liquid crystal to the prepolymer solution, stir in the dark for 20min to ensure uniform dispersion of the liquid crystal, and obtain a liquid crystal mixture; Step 3: Coat the liquid crystal mixture between two ITO conductive glass sheets, use a spacer to control the thickness to 15μm, place it under 365nm ultraviolet light, and cure it for 3min with a light intensity of 12.8mW / cm² to obtain a PDLC film.

[0026] The performance of the PDLC film prepared in this embodiment was tested, and the test results are as follows: • Liquid crystal quality fraction: 78%; • Threshold voltage: 2.8V, saturation voltage: 6.8V; • Response time: 4.0ms rise, 45ms fall; • Operating temperature: 25~90℃, maximum transmittance at 90℃ is 92% of room temperature, threshold voltage is 3.2V; • Liquid crystal droplets: uniformly dispersed, without phase fusion and bicontinuous phase structure, with low interfacial energy.

[0027] Example 3 The low-drive, wide-temperature stable, high-liquid-content PDLC film has the following raw material ratio: 74g liquid crystal; 16g epoxy acrylate prepolymer CN131; 2g monofunctional reactive diluent OPPEA; 2g monofunctional reactive diluent IBOA; 2g trifunctional crosslinking agent TMPTA; and 0.44g photoinitiator PI184. The liquid crystal is QYPDLC-901 nematic liquid crystal, and the mass fraction of the QYPDLC-901 nematic liquid crystal is 77%.

[0028] Preparation process: Step 1: Take 16g of epoxy acrylate prepolymer CN131, 2g of monofunctional reactive diluent OPPEA, 2g of monofunctional reactive diluent IBOA, and 2g of trifunctional crosslinking agent TMPTA. Mix them evenly, then add 0.44g of photoinitiator PI184 (2% by mass). Stir in the dark for 60 minutes to obtain a uniform prepolymer solution. Step 2: Add 74g of QYPDLC-901 nematic liquid crystal to the prepolymer solution, stir in the dark for 20min to ensure uniform dispersion of the liquid crystal, and obtain a liquid crystal mixture; Step 3: Coat the liquid crystal mixture between two ITO conductive glass sheets, use a spacer to control the thickness to 25μm, place it under 365nm ultraviolet light, and cure it for 3min with a light intensity of 12.8mW / cm² to obtain a PDLC film.

[0029] The performance of the PDLC film prepared in this embodiment was tested, and the test results are as follows: • Liquid crystal quality fraction: 78%; • Threshold voltage: 3.0V, saturation voltage: 7.0V; • Response time: 4.0ms rise, 48ms fall; • Operating temperature: 25~90℃, maximum transmittance at 90℃ is 94% of room temperature, threshold voltage is 3.4V; • Liquid crystal droplets: uniformly dispersed, without phase fusion and bicontinuous phase structure, with low interfacial energy.

[0030] Example 4 Effect verification To verify the performance advantages of the PDLC film of the present invention, the PDLC film prepared in Example 1 of the present invention was compared with a traditional PDLC film under the same test conditions (cell thickness 20 μm, test temperature 25℃, 90℃). The test results are shown in the table below: As can be seen from the above comparative test results, the PDLC film prepared by the present invention is significantly superior to the traditional PDLC film in terms of liquid crystal content, driving voltage, wide temperature stability, and response time. It completely solves the technical bottleneck of traditional PDLC and has significant technical advantages and application value.

[0031] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-drive, wide-temperature stable, high-liquid-content PDLC thin film, characterized in that, The product comprises the following components: 22.44g~23.46g of polymer matrix and 74g~78g of liquid crystal; the polymer matrix comprises the following components: 14g~16g of epoxy acrylate prepolymer CN131, 2g~3g of monofunctional reactive diluent OPPEA, 1g~2g of monofunctional reactive diluent IBOA, 2g~3g of trifunctional crosslinking agent TMPTA, and 0.44g~0.46g of photoinitiator PI184; the liquid crystal is QYPDLC-901 nematic liquid crystal, and the mass fraction of QYPDLC-901 nematic liquid crystal is 70%~80%.

2. The low-drive, wide-temperature stable, high-liquid-content PDLC thin film according to claim 1, characterized in that: The clearing point of the QYPDLC-901 nematic liquid crystal is 106℃, the birefringence of the QYPDLC-901 nematic liquid crystal is Δn=0.264, and the positive dielectric anisotropy of the QYPDLC-901 nematic liquid crystal is Δε≈18.

3. A method for preparing a low-drive, wide-temperature-stable, high-liquid-content PDLC thin film, wherein the low-drive, wide-temperature-stable, high-liquid-content PDLC thin film is prepared according to claim 2, characterized in that... The main steps include the following: Step 1: Mix epoxy acrylate prepolymer CN131, monofunctional reactive diluent OPPEA, monofunctional reactive diluent IBOA and trifunctional crosslinking agent TMPTA, add 2% by mass of photoinitiator PI184, stir in the dark until dissolved, and obtain polymer matrix. Step 2: Add QYPDLC-901 nematic liquid crystal to the polymer matrix and stir evenly in the dark to obtain a liquid crystal mixture; Step 3: Apply the liquid crystal mixture between two ITO conductive glass sheets, and support the two ITO conductive glass sheets with a gasket control box. Cure with ultraviolet light for 3 minutes to obtain a PDLC film.

4. The method for preparing a low-drive, wide-temperature stable, high-liquid-content PDLC thin film according to claim 3, characterized in that: The wavelength of the ultraviolet light is 365nm, and the intensity of the ultraviolet light is 12.8mW / cm². The ultraviolet light is used to suppress microdroplet aggregation and bicontinuous phase formation under high liquid crystal content, thereby achieving uniform phase separation.

5. The method for preparing a low-drive, wide-temperature stable, high-liquid-content PDLC thin film according to claim 3, characterized in that: The threshold voltage of the PDLC film is ≤3V, the saturation voltage of the PDLC film is ≤7V, and the PDLC film maintains stable electro-optical switching characteristics within the temperature range of 25~90℃.

6. The method for preparing a low-drive, wide-temperature stable, high-liquid-content PDLC thin film according to claim 3, characterized in that: The thickness of the gasket control box is 15μm-25μm, and the gasket control box is made of polyester material.

7. The method for preparing a low-drive, wide-temperature stable, high-liquid-content PDLC thin film according to claim 1, characterized in that: The QYPDLC-901 nematic liquid crystal has a mass fraction of 77%.

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