Preparation process of PVA (Polyvinyl Alcohol) film

Abstract

The invention discloses a preparation technology of a PVA film in the technical field of polaroids. The preparation technology comprises the steps of washing, swelling, dyeing, stretching, color fixing and drying. Nanoparticles and a photochemical cross-linking agent are added in the swelling treatment step; in the dyeing treatment step, ultrasonic vibration of 40 kHz to 50 kHz is adopted in a potassium iodide dyeing solution, so that the dyeing uniformity is improved; in the stretching treatment step, dynamic multidirectional stretching is utilized, and the stretching temperature is combined to balance the mechanical property and the optical property of the film; in the color fixing process, an ultraviolet light chemical treatment step is combined, and meanwhile, nano coating deposition is carried out on the surface of the dried PVA film; by introducing a dynamic multidirectional stretching technology and an ultrasonic-assisted dyeing process, ordered arrangement of iodine molecules in the film is ensured, the polarization efficiency and polarization degree of the film are greatly improved, meanwhile, good optical uniformity and stability are kept, and the requirement of high-end display equipment for the precise polarization effect is met.

Description

Technical Field

[0001] The invention relates to a preparation process of a PVA film, and belongs to the technical field of polarizers. Background Art

[0002] At present, PVA film is widely used in display technology and optics, especially in polarizers, liquid crystal displays, polarized glasses and other products. Although the traditional PVA film preparation process has made some progress, it still faces a series of challenges.

[0003] First, the stability and adjustability of polarization performance are insufficient. Existing film preparation methods often rely on simple dyeing and stretching processes. The arrangement of iodine molecules in the film is not uniform enough, resulting in the inability to always maintain the polarization degree and polarization efficiency at an ideal level. Secondly, the PVA film in the traditional process has poor anti-aging performance and is easily affected by environmental factors such as ultraviolet rays, humidity and temperature, resulting in degradation of the optical and physical properties of the film and a short service life. Therefore, the existing technical solutions cannot achieve the ideal effect in improving the polarization performance and anti-aging ability of the film at the same time. There is an urgent need for a new PVA film preparation process that can effectively solve these technical problems and meet the growing demand for high-performance polarizers and optical films. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art. In the existing PVA film preparation process for polarizers, it is impossible to simultaneously improve the polarization performance and anti-aging ability of the film.

[0005] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions: Provided is a preparation process for a PVA film, including washing, swelling, dyeing, stretching, fixing, and drying; Also includes: In the swelling treatment step, nanoparticles and a photochemical crosslinking agent are added; In the dyeing process, ultrasonic vibration of 40kHz to 50kHz is used in the potassium iodide dyeing solution to improve dyeing uniformity; The stretching step utilizes dynamic multi-directional stretching in combination with stretching temperature to balance the mechanical properties and optical properties of the film; The color fixing process is combined with an ultraviolet light chemical treatment step, and at the same time, a nano-coating is deposited on the surface of the dried PVA film.

[0006] Furthermore, the nanoparticles are at least one of TiO2 and ZnO, and the added ratio is 0.1%-0.5% of the total mass of the original PVA film.

[0007] Furthermore, in the staining solution, the concentration of iodine is 0.01 mol / L to 0.05 mol / L, and the concentration of potassium iodide is 0.05 mol / L to 0.15 mol / L.

[0008] Furthermore, in the dyeing step, the dyeing time is 5-20 minutes.

[0009] Furthermore, the stretching temperature is set to 80-120°C.

[0010] Furthermore, the dynamic multi-directional stretching has a stretching ratio of 1.5-3 times and is performed in an orthogonal stretching manner.

[0011] Furthermore, in the color fixing process, a color fixing solution containing polysiloxane is used, wherein the concentration is set to 1-5%, and the concentration of fluoride is 0.1-0.3%.

[0012] Furthermore, in the ultraviolet light chemical treatment step, the wavelength of the ultraviolet light is 365nm and the treatment time is 30-60 seconds.

[0013] Furthermore, the drying process uses a multi-stage oven, the temperature of the first stage is 60°C-80°C, and the temperature of the second stage is 100°C-120°C.

[0014] Furthermore, the nano coating is at least one of silicon dioxide SiO2 and Al2O3, the coating thickness is 50-100nm, and chemical vapor deposition is performed by a mixed gas of argon and oxygen, and the gas flow ratio is 3:1.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention ensures the orderly arrangement of iodine molecules in the film by introducing dynamic multi-directional stretching technology and ultrasonic-assisted dyeing process, thereby greatly improving the polarization efficiency and polarization degree of the film, while maintaining good optical uniformity and stability, meeting the needs of high-end display devices for precise polarization effects; at the same time, nanoparticles and photochemical cross-linking treatment are added in the swelling and fixing steps, which significantly enhances the UV resistance and moisture and heat resistance of the PVA film, thereby effectively extending the service life of the film. Combined with the application of transparent nano-coating, this process further improves the surface protection performance of the film, enabling it to maintain excellent optical properties and structural stability for a long time in high humidity, high UV and harsh environments.

[0016] 2. The present invention adopts low-concentration dyeing liquid and ultraviolet chemical treatment technology in the dyeing and fixing process to ensure that the film maintains the transmittance to the maximum extent while improving the polarization performance; by optimizing the concentration of iodine and potassium iodide and the dyeing time, the degradation of optical performance caused by excessive dyeing is avoided, so that while improving the polarization degree, the high transmittance of the film is maintained to meet the needs of high-transparency applications; in addition, the nanoparticles and photochemical cross-linking agents introduced in the process not only improve the film's UV resistance, but also enhance the film's resistance to moisture and heat, which enables the PVA film to maintain long-term stable optical properties and structural strength in an environment with high humidity, ultraviolet rays and large temperature changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Shown is a schematic diagram of the overall process of the present invention; DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0019] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances. Example

[0020] Provided is a preparation process for a PVA film, including: washing, swelling, dyeing, stretching, fixing, and drying; During the water washing process, the original PVA membrane was placed in a water washing tank and washed with deionized water at room temperature of 30°C for 5 minutes to remove impurities and dissolved substances on the membrane surface.

[0021] The washed PVA film is immersed in a swelling solution, the solution temperature is controlled at 50-80°C, the swelling time is 15 minutes, and nanoparticles and photochemical crosslinkers are added to the swelling solution, wherein the nanoparticles are selected from at least one of TiO2 and ZnO, and the addition ratio is 0.1%-0.5% of the total mass of the PVA film. The photochemical crosslinker is ethylene glycol diacrylate, and the concentration is set to 2%-5%. The anti-aging ability and physical properties of the film are improved through the dispersion of nanoparticles and the chemical action of the crosslinker.

[0022] The color states produced by different amounts of TiO2 and ZnO and different parameters are shown in the following table:

[0023] According to the table above, TiO2 is mainly used to improve the UV resistance, and has little effect on the transparency of the film, but may appear slightly turbid at high concentrations; ZnO has UV resistance and antibacterial capabilities, and may make the film appear slightly yellow after addition, which is suitable for scenes with less stringent requirements on color. The composite addition of TiO2 and ZnO needs to balance the UV resistance and moisture resistance, while adjusting the mechanical and optical properties of the film.

[0024] After the swelling treatment is completed, the PVA film is placed in a dyeing tank. The dyeing solution is prepared by mixing 0.01mol / L to 0.05mol / L iodine and 0.05mol / L to 0.15mol / L potassium iodide. Ultrasonic vibration of 40kHz to 50kHz is applied to the dyeing solution. The dyeing time is 5-20 minutes. The effect of ultrasound can enhance the permeability of the dyeing solution, so that the iodine molecules are evenly distributed inside the PVA film and form a stable bond.

[0025] Different dye dosages are shown in the following table

[0026] After the dyed PVA film is cleaned to remove surface residues, it enters the stretching process. The stretching temperature is set to 80-120°C, and the stretching ratio is 1.5 to 3 times. The orthogonal dynamic stretching method is used to adjust the arrangement direction of the iodine molecules in the film to balance the mechanical and optical properties of the film; mechanical stretching produces molecular alignment, thereby arranging the main chains of the PVA molecules in the same direction.

[0027] The stretched film then enters the color fixing treatment. First, it is immersed in a color fixing solution containing 1%-5% polysiloxane and 0.1%-0.3% fluoride for chemical fixation. Then, the film is photochemically treated with ultraviolet light with a wavelength of 365nm for 30-60 seconds to further enhance the binding stability of iodine molecules and the film's anti-ultraviolet performance.

[0028] After the color fixation is completed, the PVA film is subjected to multi-stage oven drying treatment. The temperature of the first stage is set at 60-80℃, the temperature of the second stage is set at 100-120℃, and the drying time is controlled at 20-40 minutes to ensure that the moisture content of the film meets the requirements.

[0029] Finally, a transparent nano-coating is deposited on the surface of the dried PVA film by plasma enhanced chemical vapor deposition technology. The coating material is silicon dioxide or aluminum oxide, the coating thickness is controlled at 50-100nm, and the reaction gas is a mixture of argon and oxygen. The gas flow ratio is set to 3:1, thereby giving the PVA film additional protective performance and environmental adaptability. Example

[0030] The original PVA film was placed in deionized water for washing to remove impurities and dissolved substances on the surface of the film; the flow rate of deionized water was 5L / min, the washing time was set to 5 minutes, and the water temperature was controlled at room temperature; after washing, the PVA film was immersed in a swelling solution containing nanoparticles and a photochemical crosslinker; the nanoparticles used in the swelling solution were titanium dioxide, and the addition amount was 0.3% of the mass of the original PVA film, and ethylene glycol diacrylate was added as a photochemical crosslinker, and the concentration of the crosslinker was 3%; the temperature of the swelling solution was set to 60°C, and the processing time was 20 minutes. During this period, an ultrasonic agitator was used to ensure that the nanoparticles were evenly dispersed to avoid particle aggregation.

[0031] The swollen PVA film is transferred to the dyeing tank for dyeing. 0.03 mol / L of iodine and 0.1 mol / L of potassium iodide are used in the dyeing solution; the dyeing time is set to 10 minutes, the dyeing temperature is maintained at 30°C, and an ultrasonic vibration device is used to ensure dyeing uniformity; ultrasonic vibration helps iodine molecules and potassium iodide to penetrate more evenly into the PVA film, improving the dyeing effect; the dyed PVA film is washed and stretched. The stretching temperature is set to 100°C, the stretching ratio is 2 times, and the orthogonal stretching method is adopted. The stretching operation lasts about 5 minutes to ensure that the iodine molecules in the film are evenly arranged along the longitudinal and transverse directions of the film, thereby optimizing the polarization effect.

[0032] The stretched PVA film was immersed in a color fixing solution composed of 1% polysiloxane and 0.2% fluoride. The temperature of the color fixing solution was kept at room temperature, and the immersion time was 15 minutes. The film was transferred to the UV photochemical treatment area for UV irradiation with a wavelength of 365nm and an irradiation time of 45 seconds. This process can further stabilize the arrangement of iodine molecules in the film and enhance the film's UV resistance. The fixed PVA film was dried in a multi-stage oven; the temperature of the oven was set to two stages: the first stage was 70°C, the second stage was 110°C, and the total drying time was 30 minutes to ensure that the moisture of the film was completely removed.

[0033] On the surface of the dried PVA film, a transparent nano-coating is deposited by plasma enhanced chemical vapor deposition technology. The coating material is silicon dioxide, the coating thickness is controlled at 80nm, the reaction gas is a mixture of argon and oxygen, and the gas flow ratio is set to 3:1; the deposition process lasts for 25 minutes to ensure that the coating is evenly covered on the surface of the film, providing additional protection and UV resistance.

[0034] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A process for preparing a PVA film, comprising: Washing, swelling, dyeing, stretching, fixing, and drying; characterized in that it also includes: In the swelling treatment step, nanoparticles and a photochemical crosslinking agent are added; In the dyeing process, ultrasonic vibration of 40kHz to 50kHz is used in the potassium iodide dyeing solution to improve dyeing uniformity; The stretching step utilizes dynamic multi-directional stretching in combination with stretching temperature to balance the mechanical properties and optical properties of the film; The color fixing process is combined with an ultraviolet light chemical treatment step, and at the same time, a nano-coating is deposited on the surface of the dried PVA film.

2. The process for preparing the PVA film according to claim 1, characterized in that: The nanoparticles are at least one of TiO2 and ZnO, and the added ratio is 0.1%-0.5% of the total mass of the original PVA film.

3. The process for preparing the PVA film according to claim 1, characterized in that: In the staining solution, the concentration of iodine is 0.01 mol / L to 0.05 mol / L, and the concentration of potassium iodide is 0.05 mol / L to 0.15 mol / L.

4. The process for preparing the PVA film according to claim 1, characterized in that: In the dyeing step, the dyeing time is 5-20 minutes.

5. The process for preparing the PVA film according to claim 1, characterized in that: The stretching temperature is set at 80-120°C.

6. The process for preparing the PVA film according to claim 1, characterized in that: The dynamic multi-directional stretching has a stretching ratio of 1.5-3 times and is performed in an orthogonal stretching manner.

7. The process for preparing the PVA film according to claim 1, characterized in that: In the color fixing process, a color fixing solution containing polysiloxane is used, wherein the concentration is set to 1-5%, and the concentration of fluoride is 0.1-0.3%.

8. The process for preparing the PVA film according to claim 1, characterized in that: In the ultraviolet light chemical treatment step, the wavelength of the ultraviolet light is 365nm and the treatment time is 30-60 seconds.

9. The process for preparing the PVA film according to claim 1, characterized in that: The drying process uses a multi-stage oven, the temperature of the first stage is 60°C-80°C, and the temperature of the second stage is 100°C-120°C.

10. The process for preparing the PVA film according to claim 1, characterized in that: The nano coating is at least one of silicon dioxide SiO2 and Al2O3, the coating thickness is 50-100nm, and is chemically vapor deposited by a mixed gas of argon and oxygen, with a gas flow ratio of 3:1.

Images