Preparation method of PVA (Polyvinyl Alcohol) polarizing film base film with adjustable dyeing characteristic

Abstract

The invention discloses a preparation method of a PVA polarizing film base film with adjustable dyeing characteristics, and the preparation method comprises the following steps: S1, dissolving PVA for a film, a plasticizer, a surfactant and an antioxidant in a solvent to prepare a PVA casting film stock solution; s2, defoaming and filtering the PVA casting film stock solution through an extruder, extruding the PVA casting film stock solution through a mouth mold, and carrying out tape casting on a liquid film extruded through the mouth mold to prepare a formed film; and S3, performing heat treatment on the molded film, and rolling the molded film into the base film of the polarizing film. According to the preparation method of the PVA polarizing film base film with the adjustable dyeing characteristic, the dyeing characteristic of the PVA polarizing film base film can be adjusted, and a PVA optical film with better dyeing performance can be obtained through the preparation method and can be used for producing polaroids with higher quality.

Description

Technical Field

[0001] The invention belongs to the technical field of optical components, and in particular relates to a method for preparing a PVA polarizing film base film with adjustable dyeing properties. Background Art

[0002] Polarizers made by dyeing and stretching polyvinyl alcohol optical films are widely used in display panels of televisions, computer monitors, mobile phones, car navigation and wearable electronic devices. As display panels evolve from LCD to OLED, higher and higher requirements are placed on the quality of polyvinyl alcohol optical films. How to improve the quality of polyvinyl alcohol optical films, reduce the number of optical defects, and increase the qualified rate of finished products has become the most important goal of technological progress in the industry.

[0003] At present, the production method of polyvinyl alcohol optical film is: adding polyvinyl alcohol into water, dissolving and adding plasticizer and auxiliary agent under high temperature and high pressure, and obtaining polyvinyl alcohol film through casting method, drying and heat treatment.

[0004] In many years of production practice, we have found that the films produced have problems such as slow dyeing and reddish or bluish tones in downstream use. For example, in the dyeing process, simply adjusting the amount of dichroic dyes (iodine and iodine compounds) and the dyeing process may lead to problems such as decreased transmittance and poor weather resistance. Invention patent CN107417941A mentions wet heat treatment of PVA film, but only mentions it for improving tensile properties. Invention patent CN105738977A mentions heat treatment with hot air and silicone oil bath to reduce wrinkles and product defects during processing. Invention patent CN111732749A uses segmented heat treatment to adjust the difference in transverse and longitudinal swelling of the film to reduce defects in downstream production. The above-mentioned documents all mentioned the regulation of PVA film during the heat treatment process, but the goals of each regulation did not involve adjusting the chromaticity parameters of the polarizer product.

[0005] Therefore, an effective method is needed to prepare a polyvinyl alcohol optical base film with adjustable dyeing properties to solve the problem from the source. Summary of the invention

[0006] The purpose of the present invention is to overcome the above problems existing in the prior art and provide a method for preparing a PVA polarizing film base film with adjustable dyeing properties. The dyeing properties of the PVA polarizing film base film are adjustable. The preparation method can obtain a PVA optical film with better dyeing properties, which can be used to produce higher quality polarizers.

[0007] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0008] A method for preparing a PVA polarizing film base film with adjustable dyeing properties, the method comprising the following steps:

[0009] S1: dissolving PVA for film, plasticizer, surfactant and antioxidant in a solvent to prepare PVA film casting stock solution;

[0010] S2: Degassing and filtering the PVA film casting stock solution through an extruder, and then extruding it through a die. The liquid film extruded through the die is cast to prepare a formed film;

[0011] S3: After heat treatment, the formed film is rolled up into a polarizing film base film.

[0012] Furthermore, the degree of polymerization of the PVA for the membrane is 1200-3000; further, the degree of polymerization of the PVA for the membrane is 1500-3000.

[0013] Furthermore, the alcoholysis degree of the PVA for membrane is not less than 98%; further, the alcoholysis degree of the PVA for membrane is not less than 99%.

[0014] Furthermore, in step S2, the specific process of tape casting is as follows: the liquid film first flows through a tape casting roller to be dried to form a thin film, and the thin film is then pre-dried by a plurality of drying rollers;

[0015] Further, the temperature of the casting roller is 70-99°C, and the temperature of the drying roller is 40-99°C; further, the temperature of the casting roller is 85-95°C, and the temperature of the drying roller is 50-95°C;

[0016] The number of the drying rollers is greater than 5, and the temperature of each drying roller is different.

[0017] Furthermore, in step S3, during the heat treatment process, the heat treatment temperature is 90-130° C., and the heat treatment time is 60-180 s.

[0018] Furthermore, the preparation method further comprises the following steps:

[0019] S4: Testing

[0020] The polarizing film base film prepared in step S3 is swollen, dyed, washed, stretched, washed again, and dried to prepare a polarizing film, and the monomer B value of the prepared polarizing film is measured;

[0021] The heat treatment temperature in the heat treatment process in step S3 is marked as T, and the heat treatment time is marked as t. Then, according to the monomer B value of the polarizing film at multiple heat treatment temperatures and heat treatment times, a mathematical model for representing the relationship between the monomer B value of the polarizing film and the heat treatment temperature and the heat treatment time is fitted. The fitted mathematical model of the monomer B value of the polarizing film is as follows:

[0022] Monomer B value = a 1 +a 2 ×T+a 3 ×t;

[0023] Among them, a 1 、a 2 、a 3 Both represent fitting coefficients, a 1 、a 2 、a 3 are all constants;

[0024] T is 90-130℃, t is 60-180s.

[0025] Furthermore, in step S3, the heat treatment is performed in an oven, and during the heat treatment process, a heat treatment gas is introduced into the oven.

[0026] Furthermore, the heat treatment gas is air, nitrogen, helium or argon.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention provides a method for preparing a PVA polarizing film base film with adjustable dyeing properties. By controlling the thermal history of the PVA polarizing film base film in the heat treatment stage during the production process, the polyvinyl alcohol molecules are made to form a certain crystalline state, which determines the dyeing rate and the corresponding ratio of iodine tri- and iodine penta-anions, thereby obtaining polarizers with different parameters.

[0029] 2. In the present invention, by regulating the heat treatment temperature, when the heat treatment temperature is lower than 60°C, the crystal growth rate is too low, and when the heat treatment temperature is higher than 150°C, the crystal nucleation rate is too low, and suitable crystals cannot be formed. Combined with the distribution law of the crystal state of polyvinyl alcohol molecules in the heat treatment stage, the heat treatment temperature is set to 90-130°C.

[0030] 3. In the present invention, the monomer B value of the prepared polarizing film is determined by changing the heat treatment temperature and the heat treatment time. Through the fitting results of multiple sets of experimental data, the monomer B value of the polarizing film is related to the heat treatment temperature and the heat treatment time of the heat treatment stage in the production process of the polarizing film base film. Through the fitting results of multiple sets of experimental data, the monomer B value = a 1 +a 2 ×T+a 3 ×t, that is, the monomer B value changes with the change of heat treatment temperature and heat treatment time, which is reflected in the process as the change of dyeing degree and chromaticity of the PVA polarizing film base film. Then, the dyeing degree and chromaticity of the PVA polarizing film base film can be adjusted according to actual production needs.

[0031] 4. In the present invention, by synchronously adjusting the heat treatment temperature and the heat treatment time, the performance of the polarizer product can be optimized without changing the process conditions of the polarizer production line; it can avoid the downstream manufacturers from adjusting the dyeing solution ratio, the physical size of the dyeing tank, the processing line speed, etc., and has good economic value. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] The present invention provides a method for preparing a PVA polarizing film base film with adjustable dyeing properties, and the preparation method comprises the following steps:

[0034] S1: dissolving PVA for film, plasticizer, surfactant and antioxidant in a solvent to prepare PVA film casting stock solution;

[0035] In step S1, the degree of polymerization of the selected film-forming PVA is 1200-3000, preferably 1500-3000; when the degree of polymerization is lower than 1200, the weather resistance of the prepared PVA polarizing film base film is poor, and when the degree of polymerization is higher than 4000, the film-forming PVA is not easily dissolved and the film preparation is difficult;

[0036] The alcoholysis degree of the selected membrane PVA is greater than 98%, and more preferably greater than 99%; this is because if the alcoholysis degree is lower than 98%, it will affect the polarization performance of the polarizer produced downstream;

[0037] In this step, the raw materials used for the plasticizer, surfactant and antioxidant used are all commonly used raw materials in the production of PVA polarizing film base film;

[0038] S2: Degassing and filtering the PVA film casting stock solution through an extruder, and then extruding it through a die to form a liquid film. The liquid film extruded through the die is cast to prepare a formed film;

[0039] The specific process of tape casting is as follows: the liquid film first flows through the casting roller to be dried to form a thin film, and the thin film is then pre-dried by several drying rollers; the number of drying rollers is greater than 5, and the temperature of each drying roller is different;

[0040] During the casting process, the casting roller temperature is 85-95°C, more preferably 89-93°C; since the casting roller temperature is lower than 85°C, it is not conducive to the evaporation of water in the PVA casting solution, and when the casting roller temperature is higher than 95°C, the difference between the two sides of the film formed after drying by the casting roller is too large;

[0041] The temperature of the drying roller is 50-95°C, more preferably 55-95°C, and the temperatures of the multiple drying rollers are independently taken from 55-95°C;

[0042] If the drying roller temperature is lower than 50°C, it is not conducive to reducing the moisture content of the film after drying by the drying roller;

[0043] If the drying roller temperature is higher than 95°C, the film adhesion after drying by the drying roller will deteriorate and defects may occur;

[0044] S3: After heat treatment, the formed film is rolled up into a polarizing film base film;

[0045] Wherein, in step S3, the heat treatment temperature is 90-130°C, and the heat treatment time is 60-180s;

[0046] In addition, the preparation method may further include a test step for the polarizing film prepared via the polarizing film base film, specifically:

[0047] S4: Testing

[0048] The polarizing film base film prepared in step S3 is swollen, dyed, washed, stretched, washed again, and dried to prepare a polarizing film, and the monomer B value of the polarizing film prepared through the polarizing film base film is measured;

[0049] In step S3, the heat treatment temperature in the heat treatment process of the formed film is marked as T, and the heat treatment time is marked as t. Then, according to the monomer B value of the polarizing film prepared by the polarizing film base film under the heat treatment temperatures and heat treatment times of the multiple formed films, a mathematical model for representing the monomer B value of the polarizing film and the heat treatment temperature and heat treatment time in the heat treatment process of the formed film is fitted. The fitted mathematical model of the monomer B value of the polarizing film is as follows:

[0050] Monomer B value = a 1 +a 2 ×T+a 3 ×t;

[0051] Among them, a 1 、a 2 、a 3 Both represent fitting coefficients, a 1 、a 2 、a 3 are all constants;

[0052] T is 90-130℃, t is 60-180s;

[0053] In step S3, the heat treatment is performed in an oven. During the heat treatment, a heat treatment gas is introduced into the oven. The heat treatment gas is air, nitrogen, helium or argon with a certain dew point. Specifically, the heat treatment gas is air, nitrogen, helium or argon containing a certain water vapor partial pressure.

[0054] During the experiment, the thermal history of the PVA optical base film during the heat treatment stage was controlled to make the polyvinyl alcohol molecules form a certain crystalline state. Specifically, when the crystallinity reaches a certain level and the grain size distribution is in a certain state, a state in which the crystalline region and the amorphous region alternate at a certain length interval can be formed. In this state, the PVA optical base film swells and stretches when immersed in water, the PVA chain segments in the amorphous region stretch, and the crystalline region remains unchanged, forming a parallel cage-like and bamboo-like structure; further complexing with iodine-based dichroic dyes can obtain a polarizing film with polarization properties; after bonding the protective layer, a polarizer is obtained;

[0055] However, experiments have shown that when the heat treatment temperature is lower than 60°C, the crystal growth rate is too low, and when the heat treatment temperature is higher than 150°C, the crystal nucleation rate is too low, and both cannot form suitable crystals; and when the heat treatment time is too low, it will also lead to problems such as insufficient crystallinity of PVA.

[0056] Therefore, combined with the research on heat treatment temperature and heat treatment time, the heat treatment temperature was set to 90-130 °C, and the heat treatment time was set to 60-180 s;

[0057] Within the range of heat treatment temperature and heat treatment time, by regulating the heat treatment time and heat treatment temperature, the appropriate crystal state of the polyvinyl alcohol molecules can be obtained according to actual production needs. The crystal state can affect the microstructure during swelling and stretching, and regulate the complexation of iodine-based dichroic dyes, thereby preparing a PVA optical film that is beneficial to the dyeing effect.

[0058] The following are specific examples. In the following examples, unless otherwise specified, all raw materials can be obtained from commercial sources.

[0059] Example 1

[0060] A total of 3500 kg of PVA polymer, sodium dodecylbenzene sulfonate, glycerol and an antioxidant mixture were put into a reactor with 6500 L of deionized water, and dissolved by stirring at 135°C and 0.2 MPa for 1 hour to obtain a PVA casting solution with a solid content of 35%; the formed PVA casting solution was degassed and filtered by an extruder and extruded from a die, and dried by a casting roller at 95°C to increase the solid content to 70% to form a film, which was then dried by 7 drying rollers and then placed in an oven for heat treatment at 90°C for 120 seconds to obtain a polarizing film base film with a thickness of 60 μm.

[0061] Among them, the roller temperature of the 7 drying rollers is 58-82°C, that is, the roller temperature of the 7 drying rollers shows an overall decreasing trend along the film transmission direction. Specifically, when the film is transmitted on the drying rollers, the roller temperatures of the drying rollers passed by are 82°C, 64°C, 70°C, 60°C, 67°C, 58°C, and 60°C respectively;

[0062] That is, the seven drying rollers passed in sequence are numbered from 1 to 7, the temperature of the drying rollers with odd numbers is higher, and the temperature of the drying rollers with even numbers is lower, and the temperature shows an overall decreasing trend; specifically, the temperature of the drying roller with even numbers is lower than the temperature of the two adjacent drying rollers with odd numbers.

[0063] Example 2

[0064] This example was prepared by the same method and conditions as Example 1, except that:

[0065] The heat treatment conditions were changed to 110 °C, 120 s;

[0066] Example 3

[0067] This example was prepared by the same method and conditions as Example 1, except that:

[0068] The heat treatment conditions were changed to 130 °C, 120 s;

[0069] Example 4

[0070] This example was prepared by the same method and conditions as Example 1, except that:

[0071] The heat treatment conditions were changed to 130 °C, 90 s;

[0072] Example 5

[0073] This example was prepared by the same method and conditions as Example 1, except that:

[0074] The heat treatment conditions were changed to 130°C, 60s.

[0075] Example 6

[0076] This example was prepared by the same method and conditions as Example 1, except that:

[0077] The heat treatment conditions were changed to 90°C, 180s.

[0078] Example 7

[0079] This example was prepared by the same method and conditions as Example 1, except that:

[0080] The heat treatment conditions were changed to 130°C, 180s.

[0081] Example 8

[0082] This example was prepared by the same method and conditions as Example 1, except that:

[0083] The casting roll temperature was 85°C.

[0084] Experimental Example 1

[0085] Experiments were conducted on the polarizing film base films prepared in Examples 1-9, and the relevant experimental procedures and test methods are as follows:

[0086] 1. Softening point determination

[0087] After the sample has been subjected to environmental equilibrium treatment at 25±2℃ and 50±10% relative humidity for 24 hours, refer to and use a device that complies with GB / T4507-1999 "Asphalt Softening Point Determination Method (Ring and Ball Method)", flatten the sample film and fix it on a brass ring, use water as the medium, and increase the temperature at 5℃ / min until the steel ball contacts the surface of the lower bottom plate, and record the temperature at this time;

[0088] 2. Swelling degree

[0089] The sample was treated in an environment of 25±2℃ and 50±10% relative humidity for 24h. Wash and dry a 60ml flat weighing bottle and weigh it. 0 , put it in a dryer for later use. Take 500ml of water and pour it into a 1000ml beaker, and put the beaker into a 30℃ water bath to maintain a constant temperature. Take a 10cm×20cm sample PVA film, cut it into 1cm wide strips, immerse the entire strip sample in a beaker filled with 30℃ water, and soak for 30 minutes. After the soaking time is up, filter the sample and water in the beaker with a dust-free cloth. Wrap the sample with a dust-free cloth, put it in a centrifuge, and dehydrate it at 3000 speed for 5 minutes. Take it out, untie the dust-free cloth, use tweezers to move the sample into a flat weighing bottle, cover the bottle cap, and weigh it and record it as m 1 Place the weighing bottle in a 120℃ oven (leave a small gap on the lid) and dry for 2 hours. Take it out, cover the weighing bottle and place it in a dryer. Cool it to room temperature and take it out. Weigh it and record it as m. 2 .

[0090]

[0091] Take the average value of the parallel tests as the test result, rounded to the integer before the decimal point, and the difference between the two values ​​of the parallel test results shall not exceed 3%.

[0092] 3. Evaluation method of dyeing effect

[0093] The polarizer production process is simulated, and the sample is prepared using a uniaxial stretching device in a solution tank. The sample is swollen, dyed, washed, stretched, washed, and dried to obtain a polarizing film for polarization testing. The range of process parameters for simulating polarizer sample preparation is shown in Table 1.

[0094] Table 1

[0095]

[0096] 4. Polarization test and chromaticity

[0097] Use a spectrophotometer with polarization test function to measure the monomer transmittance, polarization degree, vertical transmittance spectrum, and monomer B* value of the sample.

[0098] The measured vertical transmittance curve is usually U-shaped, low in the middle and high on both sides. According to the vertical transmittance curve, a horizontal line of T = 0.5% is drawn, and the two intersection points of the longer wavelength side (about 700nm) and the shorter wavelength side (about 500nm) are found, which are called the red light cutoff wavelength and the blue light cutoff wavelength. This value can quantitatively reflect the degree of red and blue light leakage of the sample in the vertical state.

[0099] According to the above test method, the test results are shown in Table 2.

[0100] Table 2

[0101]

[0102]

[0103] It can be seen from the data in Table 2 that in Examples 1-3, at the same heat treatment time, the monomer transmittance of the prepared polarizing film increases and the monomer B value decreases by increasing the heat treatment temperature. Therefore, in order to deal with the quality problems of insufficient transmittance and reddish-yellow hue of the polarizing film, the heat treatment temperature can be increased and the heat treatment time can be increased. In Examples 3-5, at the same heat treatment temperature, the heat treatment time is reduced, and the monomer transmittance of the prepared polarizing film decreases and the monomer B value increases. Therefore, in order to deal with the quality problems of insufficient polarization degree and bluish hue of the polarizing film, the heat treatment time can be reduced and the heat treatment temperature can be reduced. In Examples 6-7, the further extension of the heat treatment time corresponds to a decrease in the monomer B value, but the range of change is reduced. Example 8 shows that, compared with Example 1, adjusting the temperature of the casting roller has less effect on the final result.

[0104] The results in Table 2 show that by regulating the heat treatment time and temperature, the internal crystal state of the prepared polarizing film base film is adjusted, the dyeing characteristics of the film are changed, and finally the dyeing degree and chromaticity of the polarizing film are changed without adjusting the dyeing process. Specifically, increasing the heat treatment time and heat treatment temperature will increase the crystallinity of PVA and increase the crystal size. The macroscopic physical properties are manifested as an increase in softening point and a decrease in swelling degree. The process is manifested as dyeing becomes difficult, the transmittance of the polarizer increases, the polarization degree decreases, the monomer B value decreases, the blue light cutoff wavelength increases, and the red light cutoff wavelength decreases.

[0105] Experimental Example 2

[0106] The relevant data in Table 2 in Experimental Example 1 are analyzed and processed, and a mathematical model for representing the relationship between the monomer B value of the polarizing film and the heat treatment temperature and the heat treatment time is fitted. The fitted mathematical model of the monomer B value of the polarizing film is shown in Table 3;

[0107] Table 3

[0108]

[0109]

[0110] The mathematical model of the fitted monomer B value of the polarizing film can reflect the changing law of the monomer B value, that is, changing the heat treatment time and the heat treatment temperature can change the dyeing characteristics of the polarizing film; specifically, by increasing the heat treatment time and raising the heat treatment temperature, the monomer B value of the polarizing film decreases; by reducing the heat treatment time and lowering the heat treatment temperature, the monomer B value of the polarizing film increases.

[0111] The mathematical model provides the variation trend of the monomer B value with the heat treatment time and temperature, thus providing a reference for the subsequent adjustment of the dyeing characteristics of the polarizing film.

[0112] Therefore, the present invention provides a method for preparing a PVA polarizing film base film with adjustable dyeing properties. In order to deal with the quality problems of polarizing films with insufficient transmittance and reddish-yellow hue, the heat treatment process in the production process of the polarizing film base film can be solved by increasing the heat treatment time and increasing the heat treatment temperature; and in order to deal with the problems of insufficient polarization degree and bluish hue of the polarizing film, the heat treatment process in the production process of the polarizing film base film can be solved by reducing the heat treatment time and reducing the heat treatment temperature.

[0113] The present invention provides a method for preparing a PVA polarizing film base film with adjustable dyeing properties. By adjusting the heat treatment temperature and the heat treatment time, the performance of the polarizing film product can be optimized without changing the process conditions of the polarizing film production line. The downstream manufacturers can avoid making unfavorable adjustments such as high costs and reduced production efficiency in dyeing solution ratios, dyeing tank physical dimensions, and processing line speeds. The preparation method has good economic value.

[0114] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0115] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a PVA polarizing film base film with adjustable dyeing properties, characterized in that: The preparation method comprises the following steps: S1: dissolving PVA for film, plasticizer, surfactant and antioxidant in a solvent to prepare PVA film casting stock solution; S2: Degassing and filtering the PVA film casting stock solution through an extruder, and then extruding it through a die. The liquid film extruded through the die is cast to prepare a formed film; S3: After heat treatment, the formed film is rolled up into a polarizing film base film.

2. The method for preparing a PVA polarizing film base film with adjustable dyeing properties according to claim 1, characterized in that: The polymerization degree of the PVA for the membrane is 1200-3000.

3. The method for preparing a PVA polarizing film base film with adjustable dyeing properties according to claim 1, characterized in that: The polymerization degree of the PVA for the membrane is 1500-3000.

4. The method for preparing a PVA polarizing film base film with adjustable dyeing properties according to claim 1, characterized in that: The alcoholysis degree of the PVA used for the membrane is not less than 98%.

5. The method for preparing a PVA polarizing film base film with adjustable dyeing properties according to claim 1, characterized in that: In step S2, the specific process of tape casting is as follows: the liquid film first flows through a tape casting roller for drying to form a thin film, and the thin film is then pre-dried by a number of drying rollers.

6. The method for preparing a PVA polarizing film base film with adjustable dyeing properties according to claim 5, characterized in that: The casting roller temperature is 85-95°C; The temperature of the drying rollers is 50-95°C; The number of the drying rollers is greater than 5, and the temperature of each drying roller is different.

7. The method for preparing a PVA polarizing film base film with adjustable dyeing properties according to claim 1, characterized in that: In step S3, during the heat treatment process, the heat treatment temperature is 90-130° C. and the heat treatment time is 60-180 seconds.

8. The method for preparing a PVA polarizing film base film with adjustable dyeing properties according to claim 1, characterized in that: The preparation method also includes the following steps: S4: Testing The polarizing film base film prepared in step S3 is swollen, dyed, washed, stretched, washed again, and dried to prepare a polarizing film, and the monomer B value of the prepared polarizing film is measured; The heat treatment temperature in the heat treatment process in step S3 is marked as T, and the heat treatment time is marked as t. Then, according to the monomer B value of the polarizing film at multiple heat treatment temperatures and heat treatment times, a mathematical model for representing the relationship between the monomer B value of the polarizing film and the heat treatment temperature and the heat treatment time is fitted. The fitted mathematical model of the monomer B value of the polarizing film is as follows: Monomer B value = a1 + a2 × T + a3 × t; Among them, a1, a2, and a3 all represent fitting coefficients, and a1, a2, and a3 are all constants; T is 90-130℃, t is 60-180s.

9. The method for preparing a PVA polarizing film base film with adjustable dyeing properties according to claim 1, characterized in that: In step S3, heat treatment is performed in an oven, and during the heat treatment process, heat treatment gas is introduced into the oven.

10. The method for preparing a PVA polarizing film base film with adjustable dyeing properties according to claim 9, characterized in that: The heat treatment gas is air, nitrogen, helium or argon.

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