Preparation method of polarizing film and polarizing film and polaroid obtained by same

Abstract

The invention provides a preparation method of a polarizing film and the polarizing film and a polaroid obtained by the preparation method. The preparation method comprises the following steps: swelling, dyeing, cross-linking and extending a PVA base film, wherein a solution used in at least one step of swelling, dyeing, cross-linking or extending contains organic aromatic boric acid. In the preparation process of the polarizing film, the organic aromatic boric acid is introduced, so that the polyene reaction of the polarizing film can be inhibited, the stability of the polarizing film is improved, meanwhile, the stability of iodine molecules in the polarizing film can be improved through the introduction of aromatic groups in the organic aromatic boric acid, and the water blocking capacity and the ultraviolet blocking capacity of the polarizing film can also be improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical film, and particularly relates to a preparation method of a polarizing film and a polarizing film and a polarizing sheet obtained by the method. BACKGROUND

[0002] The polarizing sheet is a key optical element for controlling the polarization direction of light waves in display devices, and its core function depends on the molecular orientation and dyeing treatment of polyvinyl alcohol (PVA) film. In OLED (Organic Light-Emitting Diode) display technology, the role of the polarizing sheet is more critical: OLED itself has the self-luminous feature, but needs to eliminate the interference of ambient light reflection (especially in outdoor scenes) through the polarizing sheet to improve the contrast ratio and visibility. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application aims to provide a preparation method of a polarizing film and a polarizing film and a polarizing sheet obtained by the method.

[0004] To achieve the object of the present application, the following technical solutions are used:

[0005] In a first aspect, the present application provides a preparation method of a polarizing film, which comprises: swelling, dyeing, cross-linking and stretching a PVA base film, and a solution used in at least one of the steps of swelling, dyeing, cross-linking or stretching contains an organic aromatic boric acid.

[0006] By introducing the organic aromatic boric acid in the preparation process of the polarizing film, the organic aromatic boric acid can condense and polymerize with the hydroxyl groups carried by PVA, inhibit the polyene reaction of PVA, and increase the stability of PVA; at the same time, the aromatic ring carried by the organic aromatic boric acid can complex with iodine, increasing the stability of iodine molecules; and the aromatic ring has hydrophobicity and the property of absorbing ultraviolet light, so that the introduction of the organic aromatic boric acid in the preparation method can not only increase the water resistance of the polarizing film, but also endow the polarizing film with ultraviolet blocking ability.

[0007] In a second aspect, the present application provides a polarizing film prepared by the preparation method of the first aspect.

[0008] In a third aspect, the present application provides a polarizing sheet comprising the polarizing film of the second aspect.

[0009] Compared with the prior art, the present application has the following beneficial effects:

[0010] In the process of preparing the polarizing film, the organic aromatic boric acid is introduced to inhibit the polyene reaction of the polarizing film, increase the stability of the polarizing film, and the aromatic group in the organic aromatic boric acid can increase the stability of iodine molecules in the polarizing film, and the water resistance and ultraviolet blocking capacity of the polarizing film. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 The product molecular structure schematic diagram formed by the reaction of the PVA and the 2-functional boric acid;

[0012] Figure 2 The product molecular structure schematic diagram formed by the reaction of the PVA and the 3-functional boric acid;

[0013] Figure 3 The product molecular structure schematic diagram formed by the reaction of the PVA and the 4-functional boric acid;

[0014] Figure 4 The structure schematic of the polarizing sheet in some preferred embodiments of the present application Figure 1 ;

[0015] Figure 5 The structure schematic of the polarizing sheet in some preferred embodiments of the present application Figure 2 ;

[0016] 1-First protective layer; 2-Polarizing film; 3-Second protective layer; 4-First pressure-sensitive adhesive layer; 5-Release film layer; 6-Hard coating layer; 7-Phase difference film; 8-Second pressure-sensitive adhesive layer;

[0017] Figure 6 The OM photo of the device made of Comparative Example 1 observed by using the super-depth microscope (Keyence VHX-700) with 100 times magnification;

[0018] Figure 7 The FIB section photo of the corroded part of the device made of Comparative Example 1;

[0019] Figure 8 The transmittance curve comparison chart of the polarizing sheets provided by Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0020] The technical solutions of the present application are further illustrated by the specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as specific limitation to the present application.

[0021] In the RA test (reliability performance testing) of the middle-sized OLED, a high test temperature is required, but the polarizing sheet included in the OLED is prone to polyene reaction at high temperature, resulting in discoloration, and the stability of the crosslinking of PVA and boric acid decreases at high humidity, and the stability of iodine molecules (I3 - and I5 - ) to boric acid is insufficient, and at the same time, since the polarizing sheet does not have ultraviolet blocking function, ultraviolet light easily damages the organic light-emitting layer, resulting in reduced service life, therefore, the present application provides a preparation method of a polarizing film, which can inhibit the polyene reaction of PVA in the polarizing film at high temperature, and at the same time, can endow the polarizing film with ultraviolet blocking performance and water blocking performance, and increase the iodine dyeing capacity of PVA.

[0022] One of the purposes of the present application is to provide a preparation method of a polarizing film, the preparation method comprising: swelling, dyeing, crosslinking and stretching a PVA base film, the solution used in at least one of the swelling, dyeing, crosslinking or stretching steps contains an organic aromatic boric acid, preferably the swelling solution used in at least the swelling step contains an organic aromatic boric acid, and the specific preparation method is as follows:

[0023] S1. Swelling treatment of the PVA base film in a swelling tank can improve the stability and dyeing effect of the PVA base film; preferably the swelling solution used in the swelling tank is an organic aromatic boric acid solution.

[0024] S2. Dyeing: the swelled PVA base film is immersed in a dyeing tank containing dyeing solution for dyeing;

[0025] S3. Stretching: after dyeing, the PVA film can be cleaned in a cleaning tank and then stretched in a stretching tank.

[0026] The following is a specific description:

[0027] For the PVA base film, the PVA base film described in the present application can be any PVA film layer that can be processed to obtain a polarizing film, and its thickness can be any thickness, for example, it can be 5-250 μm, such as 5 μm, 10 μm, 20 μm, 25 um, 50 μm, 100 μm, 200 μm, 250 μm, etc.

[0028] For swelling, swelling is a key pretreatment step in the preparation of polarizing film, PVA base film is immersed in a specific swelling solution, PVA is swelled, the molecular chain spacing is increased, the internal structure is relaxed, the subsequent iodine ion adsorption dyeing and extension orientation are facilitated, the effect of swelling directly affects the orientation degree of PVA molecular weight, dye adsorption capacity and the like, the process of swelling is not limited too much in the application, any method capable of realizing the function of swelling can be applied to the application, and only the specific method of swelling is exemplarily listed here:

[0029] After the cleaned PVA base film is placed in the swelling tank containing the organic aromatic boric acid solution, the swelling treatment can improve the stability and dyeing effect of the PVA base film.

[0030] In the swelling process, the organic aromatic boric acid is introduced, the organic aromatic boric acid can condense and polymerize with the hydroxyl groups carried by PVA, inhibit the polyene reaction of PVA, and increase the stability of PVA; at the same time, the aromatic ring carried by the organic aromatic boric acid can complex with iodine, increase the stability of iodine molecules; and the aromatic ring has hydrophobicity and ultraviolet absorption properties, therefore, the introduction of the organic aromatic boric acid in the preparation method can not only increase the water resistance of the polarizing film, but also endow the polarizing film with ultraviolet blocking ability.

[0031] In some preferred embodiments, the concentration of the organic aromatic boric acid solution is 2-8wt%, such as 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt% and the like, in the swelling treatment process, the organic aromatic boric acid and the polyhydroxy structure of the polarizing film can carry out preliminary crosslinking reaction, which can improve the structural stability of the polarizing film and the dyeing effect of the subsequent dyeing step.

[0032] In some preferred embodiments, the functionality of the organic aromatic boric acid is ≥2, such as 2 functionality, 3 functionality or 4 functionality and the like.

[0033] In the application, the boric acid group (-B(OH)2) contained in the organic aromatic boric acid can condense with the hydroxyl group (-OH) carried on the PVA to generate a boric acid ester group, therefore, the polyene reaction of PVA can be inhibited, and the stability of PVA can be increased.

[0034] The product molecular structure schematic diagram formed by the reaction of PVA with 2-functional boric acid is shown in Figure 1 , the structure schematic diagram formed by the reaction with 3-functional boric acid is shown in Figure 2 , and the structure schematic diagram formed by the reaction with 4-functional boric acid is shown in Figure 3As can be seen from the figure, the organic aromatic boric acid can react with the hydroxyl group of PVA to form a chemical bond connection, can inhibit the polyene reaction of PVA, increase the stability of PVA, at the same time, the aromatic ring carried by the organic aromatic boric acid can be complexed with iodine to increase the stability of iodine molecules; and the aromatic ring has hydrophobicity and ultraviolet absorption characteristics, therefore, the introduction of the organic aromatic boric acid in the preparation method can not only increase the water resistance of the polarizing film, but also can endow the polarizing film with ultraviolet blocking ability.

[0035] The present application preferably uses a multifunctional organic aromatic boric acid, which can realize cross-linking with PVA to form a hydrophobic microzone, increase the hydrophobicity of PVA, and at the same time, can improve the complex coordination ability with iodine molecules or iodine ions through the hyperconjugation effect of the organic aromatic ring on iodine molecules, thereby realizing the improvement of the water resistance and stability of the (middle-size) polarizing plate.

[0036] In some preferred embodiments, the organic aromatic boric acid is selected from at least one of the following compounds:

[0037]

[0038]

[0039]

[0040] In some preferred embodiments, potassium iodide can also be added to the organic aromatic boric acid solution, and the concentration can be 0.1-0.5wt%, for example, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt% and the like. Adding a small amount of potassium iodide in the swelling process can provide iodine ion reserves for the subsequent dyeing step, so that PVA can preliminarily adsorb a small amount of iodine in the swelling stage, thereby shortening the overall process time.

[0041] In some preferred embodiments, the swelling temperature is 40-80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 80℃ and the like. Swelling at 40-80℃ can accelerate the penetration of the swelling solution, but the temperature should be avoided to exceed the glass transition temperature of PVA to inhibit the deformation or dissolution of the film.

[0042] In some preferred embodiments, the swelling time is determined according to the thickness of the PVA base film and the concentration of the swelling solution, and can be 1-5min, for example, 1min, 2min, 3min, 4min, 5min, which can ensure that the PNA film is completely immersed and no bubbles are attached.

[0043] In some preferred embodiments, after the swelling, the thickness of the PVA base film increases, and the surface of the base film appears wet but without obvious signs of dissolution. Generally, the thickness of the film preferably increases by 20-50%, such as 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0044] For dyeing: the dyeing step is one of the core steps of the preparation of the polarizing film, and the purpose is to allow the polyvinyl alcohol (PVA) base film to selectively adsorb iodine molecules (or dichroic dyes) to form a dichroic material with a specific polarization direction; through dyeing, the PVA molecular chain can orient the iodine molecules during the subsequent stretching process, so as to realize the absorption and transmission of light with a specific polarization direction, and endow the polarizing film with functional characteristics.

[0045] In some preferred embodiments, the dyeing solution generally contains iodine, which can improve the contrast, transmittance and polarization degree of the PVA film. When dyeing, the hydroxyl groups on the PVA molecular chain can form complexes with iodine molecules (I3 - and I5 - ). The formed complexes have dichroism, and during the subsequent stretching process, the iodine molecules will be rearranged along the stretching direction to form a highly ordered polarizing structure. The uniformity of dyeing and the amount of iodine adsorption directly affect the polarization degree, transmittance and durability of the polarizing film. The iodine ions contained in the dyeing solution can ensure the electrostatic balance and promote the combination of iodine molecules with PVA.

[0046] In some preferred embodiments, the concentration of iodine molecules contained in the dyeing solution is 1-5 g / L, such as 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, etc.; and the concentration of potassium iodide is preferably 10-20 g / L, such as 10 g / L, 12 g / L, 14 g / L, 15 g / L, 16 g / L, 18 g / L, 20 g / L, etc.

[0047] In some preferred embodiments, the dyeing solution can further contain a certain amount of boric acid and / or organic aromatic boric acid, and preferably contains organic aromatic boric acid. The introduction of organic aromatic boric acid during dyeing can adjust the pH value of the dyeing solution, inhibit the hydrolysis of PVA, and stabilize the iodine molecules.

[0048] In some preferred embodiments, the temperature of the dyeing solution is generally 20-60°C, such as 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc., and is preferably 30-40°C. The immersion time is generally 30-120 s, such as 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, 110 s, 120 s, etc.

[0049] In some preferred embodiments, in this invention, before extension, the film can be washed (crosslinked) with water. Preferably, the washing method includes placing the PVA base film in a washing tank, removing residues from the PVA base film by washing, and also controlling the degree of crosslinking of PVA molecules, thereby optimizing the polarization performance, durability and mechanical strength of the polarizing film.

[0050] In some preferred embodiments, the washing process can be performed using only high-purity deionized water to remove iodine, potassium iodide, or other residues from the staining solution. Alternatively, a cross-linking system solution can be introduced after washing. This cross-linking system solution may include boric acid and / or organic aromatic boric acid, preferably organic aromatic boric acid, which can form borate ester bonds between PVA molecular chains, enhancing the hydrogen bond network, etc. This invention does not impose excessive limitations; any method that meets the requirements of washing can be applied to this invention.

[0051] Stretching is a physical process that highly orienteds PVA molecular chains along a specific direction, causing iodine molecules to arrange themselves in an orderly manner between the chains, thereby forming a polarized structure with significant dichroism. In this invention, the PVA film, after being washed with water, is immediately immersed in a stretching tank for stretching. The stretching solution used in the tank may contain organic aromatic boric acid. In this invention, some organic aromatic boric acid may be introduced again during the stretching process to increase the stability of the PVA.

[0052] In some preferred embodiments, the extension factor is 3-6 times that of the PVA base film, such as 3 times, 3.5 times, 4 times, 4.5 times, 5 times, 5.5 times, 6 times, etc.

[0053] The present invention preferably uses high-magnification extension to improve the orientation of macromolecules and polyiodine substances, so that the misaligned particles are aligned in the same direction and produce polarization properties.

[0054] In some preferred embodiments, the extended temperature is 40-60°C, such as 40°C, 42°C, 45°C, 48°C, 50°C, 52°C, 55°C, 58°C, 60°C, etc.

[0055] In some preferred embodiments, the residence time of the PVA base film in the stretching tank is 1-10 min, preferably 1 min, 2 min, 3 min, 5 min, 6 min, 8 min, 10 min, etc.

[0056] In some preferred embodiments, the solvent used in the extended solution includes not only water, but also preferably alcohol solvents, and more preferably ethanol solvents, which enable better dissolution of organoboron.

[0057] In some preferred embodiments, the preparation method further includes color correction and drying after stretching.

[0058] In some preferred embodiments, the preparation method of the polarizing film preferably comprises: PVA unwinding-swelling-dyeing-water washing (crosslinking)-stretching-color compensation-drying, and optionally, water washing before swelling, in particular:

[0059] Water washing: the PVA base film is placed in a water washing tank, and the plasticizer in the PVA base film is removed by water washing;

[0060] Color compensation: the stretched PVA film is immersed in a color compensation tank for color compensation;

[0061] Drying: the color-compensated PVA film is cut and then dried to obtain the polarizing film.

[0062] In the present application, for PVA unwinding, the PVA base film is continuously and stably conveyed by the unwinding equipment during the preparation process, and the subsequent process is carried out. The present application does not limit the unwinding equipment and the unwinding method, and any unwinding equipment and unwinding method that can achieve the purpose of continuous and stable conveying of the present application can be applied to the present application. Here, only exemplary enumeration is made, the unwinding equipment can include single-station unwinding machine, double-station unwinding machine or optical-grade unwinding machine, and the unwinding method includes active unwinding or passive unwinding, which is not limited too much here.

[0063] In the present application, color compensation and drying are not limited too much, and any method that can achieve the above steps can be applied to the present application. The present application only exemplarily enumerates here.

[0064] For color compensation, the adsorption of iodine molecules can be locally supplemented to correct the unevenness of the polarizing performance caused by uneven distribution of the solution, thickness difference of the film or mechanical damage during the dyeing process, so as to ensure that the degree of polarization, transmittance and optical consistency of the final polarizing film meet the standards.

[0065] During color compensation, it can be carried out in the color compensation tank, and the immersion time in the color compensation liquid is preferably 10-30s, such as 10s, 15s, 20s, 25s, 30s, etc. The color compensation liquid is preferably the same as the dyeing liquid, or has a slightly higher concentration to enhance the compensation effect.

[0066] For drying, the purpose is to remove the residual moisture on the surface and inside of the film, to solidify the cross-linking structure between the PVA molecular chains, to stabilize the adsorption state of iodine molecules, so as to obtain a polarizing film with excellent polarizing performance, mechanical strength and durability. Generally, drying is divided into 3-5 temperature zones, including an inlet zone, generally at 60-80℃, for example, it can be 60℃, 65℃, 70℃, 75℃, 80℃, etc., a middle zone, generally at 80-100℃, for example, it can be 80℃, 85℃, 90℃, 95℃, 100℃, etc., and an outlet zone, generally at 100-120℃, for example, 100℃, 105℃, 110℃, 115℃, 120℃, etc. The drying time is generally 2-10 min, for example, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, preferably 3-5 min. The present application does not make too much repetition here.

[0067] The second object of the present application is to provide a polarizing film prepared by the preparation method according to the first object.

[0068] The third object of the present application is to provide a polarizing sheet comprising the polarizing film according to the second object.

[0069] In some preferred embodiments, the polarizing sheet further comprises a first protective layer and a second protective layer, and a pressure sensitive adhesive layer and a release film layer; wherein:

[0070] The first protective layer and the second protective layer are respectively located on both sides of the polarizing film, the pressure sensitive adhesive layer is located on the side of any protective layer away from the polarizing film, and the release film layer is located on the side of the pressure sensitive adhesive layer away from the polarizing film.

[0071] In some preferred embodiments, as shown in Figure 4 The polarizing sheet comprises a first protective layer 1, a polarizing film 2, a second protective layer 3, a first pressure sensitive adhesive layer 4 and a release film layer 5 arranged in sequence.

[0072] In some preferred embodiments, as shown in Figure 5 The polarizing sheet comprises a hard coating layer 6, a first protective layer 1, a polarizing film 2, a second protective layer 3, a first pressure sensitive adhesive layer 4, a phase difference film 7, a second pressure sensitive adhesive layer 8 and a release film layer 5 arranged in sequence.

[0073] The present application can also provide a preparation method of a polarizing sheet, comprising:

[0074] After the polarizing film is prepared, protective layers are respectively compounded on both sides, dried, compounded with a release film, and wound. In some preferred embodiments, the protective film can be a TAC film (Triacetate Cellulose), and the release film can be a PE film (Polyethylene film) or a PET film (Polyethylene terephthalate film).

[0075] The following is explained and illustrated by specific examples:

[0076] Preparation Example 1

[0077] The present preparation example provides a preparation method of a polarizing film as follows:

[0078] (1) Water washing: the PVA base film is placed in a water washing tank for water washing;

[0079] (2) Swelling: the washed PVA base film is placed in a swelling tank containing an organic aromatic boric acid for swelling treatment, the temperature is 50°C, and the time is 3 min;

[0080] The organic aromatic boric acid is The concentration is 5%, the solvent is deionized water, and 10% ethanol is added;

[0081] (3) Dyeing: the swollen PVA base film is immersed in a dyeing tank containing a dyeing solution for dyeing, the concentration of iodine in the dyeing solution is 0.01 mol / L, the concentration of potassium iodide is 0.1 mol / L, the temperature is 50°C, and the time is 1 min;

[0082] (4) Water washing (cross-linking): after the dyeing is completed, the PVA film is washed by a cleaning tank containing deionized water;

[0083] (5) Stretching: the washed PVA film enters a stretching tank for stretching, the stretching tank contains 5% boric acid, the temperature is 50°C, the time is 4 min, and the stretching multiple is 5 times;

[0084] (6) Color compensation: color compensation is performed using a dyeing solution, and the time is 20 s;

[0085] (7) Drying: after the color compensation is completed, drying is performed, the inlet zone is 70°C, the middle zone is 90°C, the outlet zone is 110°C, and the time is 4 min;

[0086] (8) Winding to obtain a polarizing film.

[0087] Preparation Examples 2-7

[0088] The present preparation example provides a preparation method of a polarizing film.

[0089] The difference from the preparation example 1 is that, in the present preparation example, the organic aromatic boric acid used is

[0090]

[0091] Preparation Example 8-9

[0092] The present preparation example provides a preparation method of a polarizing film.

[0093] The difference from Preparation Example 1 is that in the present preparation example, the concentration of the organic aromatic boric acid used is 2% (Preparation Example 8), 8% (Preparation Example 9).

[0094] Comparative Preparation Example 1

[0095] The present comparative preparation example provides a preparation method of a polarizing film.

[0096] The difference from Preparation Example 1 is that in the present comparative preparation example, the organic aromatic boric acid is replaced by boric acid, and the concentration remains unchanged.

[0097] Examples 1-9

[0098] The present examples provide a preparation method of a polarizing sheet, as follows:

[0099] A TAC film (purchased from Fuji Photo Film Co., Ltd., Japan) with a thickness of 25 μm is compounded on one side of the polarizing film provided in Examples 1-9, and a TAC film (purchased from Fuji Photo Film Co., Ltd., Japan) with a thickness of 25 μm, an optical compensation layer (purchased from Fuji Photo Film Co., Ltd., Japan), a pressure-sensitive adhesive (purchased from Soken) with a thickness of 20 μm, and a release film (purchased from Mitsubishi Chemical, Japan) with a thickness of 50 μm are successively compounded on the other side, to obtain a polarizing sheet.

[0100] Comparative Example 1

[0101] The present comparative example provides a preparation method of a polarizing sheet.

[0102] The difference from Example 1 is that in the present comparative example, the polarizing film used is the polarizing film provided in Comparative Preparation Example 1.

[0103] Performance test

[0104] The samples provided in the examples and comparative examples are subjected to performance test, in the following manner:

[0105] (1) Reliability test:

[0106] i. A device is prepared by successively stacking from bottom to top: an SCF layer (purchased from Doyo, 160 μm), a BP layer (purchased from Nittobo, 88 μm), a display panel, a polarizing sheet, an OCA layer (purchased from 3M), and a lens layer (purchased from AGC), and the prepared device is placed in an environment with a temperature of 85°C and a humidity of 85% for 240 h, and whether there is corrosion around the module and in the hole area TP circuit is observed.

[0107] Figure 6 OM photos of the device made by Comparative Example 1 were observed by using a super-depth-of-field microscope (Keyence VHX-700) with 100 times magnification. As can be seen from the figure, Comparative Example 1 has been corroded, and FIB analysis (instrument: Thermo Scientific Helios 400) was performed on the corrosion points, and the results are shown in Figure 7 Figure 7 FIB section photos of the corroded part of the device made by Comparative Example 1 are shown in Figure 7 As can be seen from the figure, the aluminum film layer in the Ti / Al / Ti film layer in the film layer has been corroded.

[0108] However, the devices made by Examples 1-9 were not corroded.

[0109] ii. An Al film 300 nm thick was plated on a glass substrate by using a pvd process, then the release film of the polarizer was removed, and the pressure-sensitive adhesive layer was attached to the Al film. The devices were tested under HAST (110°C, 85% RH, 24h) conditions, double 85 conditions for 480h, and 6595 conditions for 480h, to check whether the Al film was corroded;

[0110] The devices provided by Examples 1-9 were not corroded, while the device provided by Comparative Example 1 treated by swelling with boric acid was severely corroded, i.e., the polarizer provided by the present application can inhibit the occurrence of polyene reaction and increase the stability of the polarizing film.

[0111] iii. The devices were prepared according to i, and the prepared devices were tested under HAST (110°C, 85% RH, 24h) conditions, double 85 conditions for 480h, and 6595 conditions for 480h, to check whether the TP lines of the module four corners and the hole area were corroded, and the test results were as follows:

[0112] The devices provided by Examples 1-9 were not corroded, while the device provided by Comparative Example 1 treated by swelling with boric acid was severely corroded, i.e., the polarizer provided by the present application can inhibit the occurrence of polyene reaction and increase the stability of the polarizing film.

[0113] (2) Absorption spectrum test: The transmittance curves of the polarizing films provided by Examples 1 and Comparative Example 1 were tested by a UV-Vis absorption spectrum instrument.

[0114] Figure 8 The transmittance curves of the polarizing films provided by Examples 1 and Comparative Example 1 are shown in the figure. As can be seen from the figure, the transmittance of the polarizing film provided by Comparative Example 1 at 400 nm, 410 nm, and 420 nm was 0.24, 0.34, and 0.38, respectively; while the transmittance of the polarizing film provided by Example 1 at 400 nm, 410 nm, and 420 nm was less than 0.02, 0.03, and 0.05, respectively, i.e., the polarizing film provided by the present application has ultraviolet blocking ability.​

[0115] (3) Water resistance: The water vapor transmission rate of the polarizing plate provided by Examples 1-9 and Comparative Example 1 was tested according to the test standard GB / T 21529-2008, and the water vapor transmission rate was used to represent the water resistance of the polarizing film.

[0116] The water vapor transmission rate of the polarizing plate provided by Examples 1-9 was 50-70 g / m 2 ·24h, and the water vapor transmission rate of the polarizing plate provided by Comparative Example 1 was 80-100 g / m 2 ·24h. According to the comparison of the data, the polarizing plate provided by the present application has certain water resistance.

[0117] The applicant declares that the process method of the present application is illustrated by the above examples, but the present application is not limited to the above process steps, that is, it does not mean that the present application must rely on the above process steps to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of the selected material of the present application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a polarizing film, characterized in that, The preparation method includes: swelling, dyeing, crosslinking and stretching a PVA base film, wherein the solution used in at least one of the steps of swelling, dyeing, crosslinking or stretching contains organic aromatic boric acid.

2. The preparation method according to claim 1, characterized in that, In the preparation method, the swelling solution used for swelling contains organic aromatic boric acid.

3. The preparation method according to claim 1, characterized in that, In the swollen solution, the concentration of the organic aromatic boric acid is 2-8 wt%.

4. The preparation method according to claim 1, characterized in that, The functionality of the organic aromatic boric acid is ≥2.

5. The preparation method according to claim 4, characterized in that, The organic aromatic boric acid is selected from at least one of the following compounds:

6. The preparation method according to any one of claims 1-5, characterized in that, The swelling temperature is 40-80℃, and the time is 1-5 minutes.

7. The preparation method according to any one of claims 1-5, characterized in that, The preparation method also includes color correction and drying after stretching.

8. A polarizing film prepared by any one of claims 1-7.

9. A polarizer, characterized in that, The polarizer includes the polarizing film as described in claim 8.

10. The polarizer according to claim 9, characterized in that, The polarizer further includes a first protective layer and a second protective layer, as well as a pressure-sensitive adhesive layer and a release film layer; wherein: The first protective layer and the second protective layer are located on opposite sides of the polarizing film, the pressure-sensitive adhesive layer is located on the side of either protective layer away from the polarizing film, and the release film layer is located on the side of the pressure-sensitive adhesive layer away from the polarizing film.

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