A high-durability polarizing film and its high-speed production method

Abstract

This invention relates to the field of polarizer technology, and discloses a high-durability polarizer and its high-speed production method. This high-speed production method refers to an extension bonding process, including steps such as swelling, dyeing, washing, stretching, polarizer drying, protective layer bonding, and adhesive coating. In the dyeing step, the dyeing solution in the dyeing solution tank is a dyeing solution containing a dichroic substance and 0.5–1 wt% of dyeing auxiliaries. The washing and stretching steps contain borate, and the polarizer drying temperature is 100°C. The dichroic substance consists of four dichroic azo dyes. The high-durability polarizer produced by this invention meets the durability test requirements of 105°C × 2000h and even 115°C × 1000h. This method can significantly increase the machine speed of polarizer extension bonding, thereby further increasing the production capacity of polarizers.

Description

Technical Field

[0001] This invention relates to the field of polarizer technology, and in particular to a high-durability polarizer that can be produced quickly and its manufacturing process. Background Technology

[0002] Polarizing films are made by laminating a polarizing film substrate with other functional films using pressure-sensitive adhesive. The polarizing film substrate is formed by bonding stretched PVA (polarizer) and a protective layer. The polarizers in the polarizing film substrate play a decisive role in the weather resistance of the polarizing film. Currently, polarizer processing technology is divided into two main categories based on different dyeing media: dye-based and iodine-based. Iodine-based polarizing films on the market rarely achieve a weather resistance level of 105℃×1000h, while dye-based polarizing films, due to the use of dichroic azo dyes, can achieve a weather resistance level of 100℃×500hr. However, with the increasingly widespread application of automotive displays, displays in various fields are developing towards larger sizes and greater diversity, leading to increasingly higher requirements for the weather resistance of polarizing films. The demand for dry temperature and humidity control is also increasing, requiring weather resistance testing performance of polarizing films at 105℃ or even 115℃.

[0003] Currently, in the polarizer manufacturing industry, the production of dye-based polarizers mostly uses a wet stretching process for PVA film. The addition of chemicals in the bath significantly affects the stretching speed and quality. Too little or too much chemical addition leads to reduced weather resistance, resulting in large optical fluctuations after weathering. The stretching speed also greatly affects the optical and display effects of the polarizer, often causing uneven dyeing due to increased stretching speed. These two factors limit the production speed of polarizer substrates, thus constraining the production capacity of enterprises. Summary of the Invention

[0004] The purpose of this invention is to provide a method for producing high-durability polarizers that can be manufactured at high speed. The high-durability polarizers meet the durability test requirements of 105℃×2000h or even 115℃×1000h. This invention provides at least one beneficial option or creates conditions to solve one or more technical problems existing in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] A high-speed production method for high-durability polarizing films, with a stretching and lamination speed of over 9.5 m / min, includes the following steps: 1) Swelling: Immersing a PVA film in pure water to swell and clean its surface contaminants; 2) Dyeing: Immersing the swollen and softened PVA film in a dyeing tank containing dichroic substances to achieve dyeing treatment; 3) Cleaning: Cleaning the excess dye solution carried on the surface of the dyed PVA film; 4) Stretching: Immersing the PVA film with cleaned surface dye in a stretching tank solution for stretching, causing the dye molecules to align oriented within the PVA film during stretching, while simultaneously completing cross-linking; 5) Polarizing film drying: Placing the stretched PVA film into a drying unit to obtain a polarizing film; 6) Protective layer lamination: Laminating the dried polarizing film to two protective layers using an adhesive medium, followed by baking to form the polarizing film substrate; 7) Adhesive coating: Laminating the polarizing film substrate with pressure-sensitive adhesive and a functional film or release film to obtain polarizing films with different properties.

[0007] In step 2), the dyeing tank contains 3-5 wt% of dichroic material and 0.5-1 wt% of dyeing auxiliaries. The dichroic material is composed of four different colored azo dyes.

[0008] In step 3), the washing tank liquid contains 0.1 to 0.5 wt% borate.

[0009] In step 4), the stretching step, the liquid in the stretching tank contains 1-3 wt% boride.

[0010] The boride is borax or boric acid.

[0011] More preferably, in step 3), the temperature of the solution in the washing tank is 35-55°C, and the washing time is 30-120 seconds.

[0012] More preferably, in step 4), the temperature of the solution in the stretching tank is 45–65°C, and the stretching ratio is 5.5–7 times.

[0013] More preferably, in step 4), during the stretching step, the solution in the tank contains 2.5 to 4 wt% of a fixing agent, and the temperature of the solution in the tank is 28 to 45°C.

[0014] In step 5), the polarizer drying process, the drying temperature is 60-110℃ and the drying time is 120-300 seconds.

[0015] More preferably, in step 6) the protective layer bonding step, the two protective layers of the polarizer are cellulose triacetate, and the adhesive medium is polyvinyl alcohol adhesive or UV adhesive.

[0016] More preferably, in step 6) the protective layer bonding step, the temperature of the baking unit after the polarizer and the protective layer are bonded is 70-120°C, and the baking time is 150-600 seconds.

[0017] More preferably, in step 7), the components of the pressure-sensitive adhesive are: 20-60% pressure-sensitive acrylic copolymer, 0.1-30% tackifier, 10-79% solvent, 0.01-10% crosslinking agent, and 0.01-5% silane coupling agent, by weight percentage.

[0018] More preferably, in step 7), the functional film is a phase difference compensation film.

[0019] The present invention also provides a high-durability polarizer produced by the high-speed production method of the high-durability polarizer described above.

[0020] The present invention employing the above-described technical solution has at least the following beneficial effects.

[0021] This invention employs a specific concentration of boride in the washing and stretching stages of polarizer preparation, which greatly improves the stability and efficiency of PVA film in removing excess dye from the surface and in the directional arrangement of dye molecules during the stretching process. This allows the polarizer to achieve high durability and high polarization while increasing the machine speed. This method can increase the process speed of the polarizer base plate to 12m / min, achieving a leap in polarizer production capacity. Attached Figure Description

[0022] Figure 1 The diagram shown is a schematic diagram of the high weather-resistant polarizer structure in Embodiment 1 of the present invention.

[0023] Figure 2 The diagram shown is a schematic diagram of the high weather-resistant polarizer structure in Embodiment 2 of the present invention. Detailed Implementation

[0024] To facilitate a better understanding of the essence of the present invention by those skilled in the art, the specific embodiments of the present invention are described in detail below. Example 1

[0025] like Figure 1 As shown, a high-durability polarizer has the following composite structure from top to bottom: a protective film 1, a first polarizer protective layer 2, a polarizer element 4, a second polarizer protective layer 5, a pressure-sensitive adhesive layer 6, and a release film layer 7. Adhesive 3 is provided on the upper and lower sides of the polarizer element 4, respectively.

[0026] The manufacturing steps for the aforementioned high-durability polarizer are as follows.

[0027] 1) Swelling: The PVA membrane is soaked in pure water to perform swelling treatment and surface cleaning.

[0028] 2) Dyeing: Immerse the swollen and softened PVA film in a dyeing tank containing dichroic substances. The concentration of dichroic azo dye in the dyeing tank is controlled at 5wt%, and the concentration of auxiliary dye is controlled at 1wt%, to obtain the dyeing treatment.

[0029] In this embodiment, the dichroic azo dye is a mixture of four dyes. The concentrations of dye 1, 2, 30 wt%, 3, and 4 are 10 wt%, respectively, with the total dye content being 100%. The structural formulas of the four dichroic azo dyes can be found in the applicant's earlier Chinese invention patent application, publication number CN115728857A.

[0030] 3) Washing: The excess dye solution on the surface of the PVA film after dyeing is washed away. The washing tank liquid contains 0.3wt% boric acid, the tank solution temperature is 40℃, and the washing time is 35s.

[0031] 4) Stretching: The PVA film with cleaned surface dye is immersed in a stretching tank solution for stretching, which causes the dye molecules to align in an orientation within the PVA film during stretching, and cross-linking is completed at the same time. The stretching tank solution contains 3wt% boride, the tank solution temperature is 65℃, and the stretching ratio is 7 times. In the later stage of the stretching step, the tank solution contains 4wt% fixing agent, and the tank solution temperature is 28℃, which makes the dye molecules more stably arranged inside the polarizer.

[0032] 5) Polarizing drying: The stretched PVA film is placed in the drying unit to obtain a polarizing film; the polarizing drying temperature is 60℃ and the drying time is 280 seconds.

[0033] 6) Protective layer bonding: The polarizers that have finished drying are bonded to the two protective layers through an adhesive medium, and then baked to form the polarizer base plate; the first and second polarizer protective layers are made of cellulose triacetate, the adhesive medium is polyvinyl alcohol adhesive, the baking temperature is 70℃, and the baking time is 400 seconds.

[0034] 7) Apply adhesive: Apply pressure-sensitive adhesive to the surface of the polarizer base plate to bond it with the release film layer.

[0035] Actual production testing has shown that the high-durability polarizer manufacturing process provided in this embodiment meets the production requirements for a stretching and composite speed of 9.5~10m / min.

[0036] In this embodiment, the components of the pressure-sensitive adhesive are: 60wt% pressure-sensitive acrylic copolymer, 1wt% tackifier, 38wt% solvent, 0.5wt% crosslinking agent, and 0.5wt% silane coupling agent. Example 2

[0037] Reference Figure 2 As shown, a high-durability polarizer has a structure that is basically the same as that of Example 1, except that it is composite with a phase difference compensation film 8.

[0038] The manufacturing steps of the high-durability polarizer in this embodiment are as follows.

[0039] 1) Swelling: The PVA membrane is soaked in pure water to perform swelling treatment and surface cleaning.

[0040] 2) Dyeing: The swollen and softened PVA film is immersed in a dyeing bath containing a dichroic substance. The concentration of the dichroic azo dye in the dyeing bath is controlled at 3 wt%, and the concentration of the dyeing auxiliary agent is controlled at 0.5 wt%, resulting in an immersion dyeing treatment. In this embodiment, the dichroic azo dye is a mixture of four dyes. The concentrations of dye 1, dye 2, dye 3, and dye 4 are 5 wt%, 30 wt%, and 35 wt%, respectively, with the total dye content being 100%. The structural formulas of the four dichroic azo dyes can be found in the applicant's earlier Chinese invention patent application, publication number CN115728857A.

[0041] 3) Washing: The excess dye solution on the surface of the PVA film after dyeing is washed away. The washing tank liquid contains 0.1wt% boric acid, the tank solution temperature is 40℃, and the washing time is 60s.

[0042] 4) Stretching: The PVA film with cleaned surface dye is immersed in a stretching tank solution for stretching, which causes the dye molecules to align in an orientation within the PVA film during stretching and completes cross-linking. The stretching tank solution contains 1.5 wt% boride, the tank solution temperature is 45℃, and the stretching ratio is 7 times. In the later stage of the stretching step, the tank solution contains 2.5 wt% fixing agent, and the tank solution temperature is 35℃, which makes the dye molecules more stably arranged inside the polarizer.

[0043] 5) Polarizing drying: The stretched PVA film is placed in the drying unit to obtain a polarizing film; the polarizing drying temperature is 100℃ and the drying time is 150 seconds.

[0044] 6) Protective layer bonding: The polarizers that have finished drying are bonded to the two protective layers through an adhesive medium, and then baked to form the polarizer base plate; the first and second polarizer protective layers are made of cellulose triacetate, the adhesive medium is polyvinyl alcohol adhesive, the baking temperature is 120℃, and the baking time is 150 seconds.

[0045] 7) Apply adhesive: Apply acrylic resin pressure-sensitive adhesive to the surface of the polarizer plate and composite phase difference compensation film; continue to apply pressure-sensitive adhesive under the phase difference compensation film to bond with the release film layer.

[0046] Actual production testing has shown that the high-durability polarizer manufacturing process provided in this embodiment meets the production requirements of a stretching and composite speed of 11~12m / min.

[0047] In this embodiment, the components of the pressure-sensitive adhesive are: 60wt% pressure-sensitive acrylic copolymer, 1wt% tackifier, 38wt% solvent, 0.5wt% crosslinking agent, and 0.5wt% silane coupling agent.

[0048] Comparative Example 1.

[0049] A polarizer is prepared by the following steps.

[0050] 1) Swelling: The PVA membrane is soaked in pure water to perform swelling treatment and surface cleaning.

[0051] 2) Dyeing: The swollen and softened PVA film is immersed in a dyeing tank containing dichroic substances. The concentration of dichroic azo dye in the dyeing tank is controlled at 2 wt%, and the concentration of auxiliary dye is controlled at 0.3 wt%, thus obtaining the immersion dyeing treatment.

[0052] In this comparative example, the dichroic azo dye is a mixture of four dyes. The concentrations of dye 1, dye 2, dye 3, and dye 4 are 5 wt%, 30 wt%, and 35 wt%, respectively, with the total dye content being 100%. The structural formulas of the four dichroic azo dyes can be found in the applicant's earlier Chinese invention patent application, publication number CN115728857A.

[0053] 3) Washing: Remove excess dye from the surface of the dyed PVA film. The washing tank contains 2-4 wt% boric acid, the tank temperature is 40℃, and the washing time is 60 seconds.

[0054] 4) Stretching: The PVA film with cleaned surface dye is immersed in a stretching tank solution for stretching, which causes the dye molecules to align in an orientation within the PVA film during stretching and simultaneously completes cross-linking. The stretching tank solution contains 4-7 wt% boride, the tank solution temperature is 45-65℃, and the stretching ratio is 6 times. In the later stage of the stretching step, the tank solution contains 2.5-4 wt% fixing agent, and the tank solution temperature is 28-35℃, which makes the dye molecules more stably arranged inside the polarizer.

[0055] 5) Polarizing drying: The stretched PVA film is placed in the drying unit to obtain a polarizing film; the polarizing drying temperature is 60℃ and the drying time is 260 seconds.

[0056] 6) Protective layer bonding: The polarizers that have finished drying are bonded to the two protective layers through an adhesive medium, and then the polarizers are baked to form the polarizer base plate. The first and second polarizer protective layers are made of cellulose triacetate, the adhesive medium is polyvinyl alcohol adhesive, the baking temperature is 70-80℃, and the baking and drying time is 600 seconds.

[0057] 7) Applying adhesive: Apply an acrylic resin pressure-sensitive adhesive to the surface of the polarizer substrate and then laminate the phase lag compensation film. Continue applying pressure-sensitive adhesive below the phase lag compensation film to ensure adhesion to the release film layer. The pressure-sensitive adhesive components are: 60wt% pressure-sensitive acrylic copolymer, 1wt% tackifier, 38wt% solvent, 0.5wt% crosslinking agent, and 0.5wt% silane coupling agent.

[0058] Actual production testing showed that the polarizer manufacturing process provided by this comparative example can only meet the production requirements of a stretching and composite speed of 6~6.5m / min.

[0059] Comparative Example 2.

[0060] The high-durability polarizer prepared in this comparative example is basically the same as that in Example 1, except that the dichroic azo dyes used in the dyeing step are 20 wt% dye 1, 40 wt% dye 2 and 40 wt% dye 4, with a dye concentration of 1% to 2 wt%; the washing tank liquid contains 0 wt% boric acid; the stretching tank liquid contains 4 to 7 wt% borides, and the stretching composite speed is 6 to 6.5 m / min.

[0061] Comparative Example 3.

[0062] The high-durability polarizer prepared in this comparative example is basically the same as that in Example 1, except that the dichroic azo dyes used in the dyeing step are 20 wt% dye 1, 40 wt% dye 2 and 40 wt% dye 4, with a concentration of 1% to 2 wt%; the washing tank liquid contains 2 to 4 wt% boric acid; the stretching tank liquid contains 4 to 7 wt% borides, and the stretching composite speed is 6 to 6.5 m / min.

[0063] To better demonstrate the progressiveness of the present invention, the performance of the polarizers prepared in Examples 1-2 and Comparative Examples 1-3 were compared and tested below. The results are shown in Tables 1 and 2.

[0064] Table 1. Comparison of optical performance.

[0065] As can be seen from Table 1, the polarizers prepared in the various embodiments of the present invention have higher polarization, and maintain high polarization even after increasing the production speed. Compared with Comparative Example 1, Comparative Examples 2 and 3 have much lower polarization at the same production speed.

[0066] Table 2. Weather resistance comparison table.

[0067] As can be seen from the weathering results in Table 2, the examples, due to the use of specific boride addition amounts in the washing and stretching tanks, still met the 105℃×2000h weathering test requirements even after increasing the production speed of the polarizer substrate, without significant yellowing. Compared with Comparative Examples 2 and 3, the polarizer of the present invention exhibits excellent weathering performance; furthermore, the high-durability polarizer prepared by the present invention still achieves good weathering performance under high-speed production conditions.

[0068] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Parts not described in the specific embodiments are all prior art or common knowledge.

[0070] It should also be noted that the detailed description of preferred embodiments and included examples in the description of this invention facilitate a better understanding of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In case of any discrepancy, the definitions in this specification shall prevail.

[0071] In this invention, the term "prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof, as used in this invention, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus comprising the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0072] In this invention, when a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described in this invention, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0073] Furthermore, the indefinite articles “a” and “an” preceding the elements or components of this invention do not impose any limitation on the quantity requirement (i.e., the number of times) of the elements or components. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers to the singular form.

Claims

1. A high-speed production method for high-durability polarizing films, characterized in that, The tensile composite speed is between 9.5 m / min and 12 m / min, and includes the following steps: 1) Swelling: The PVA film is soaked in pure water to perform swelling treatment and surface cleaning. 2) Dyeing: The swollen and softened PVA film is immersed in a dyeing bath containing a dichroic substance to obtain the dyeing treatment; 3) Washing: Clean the surface of the PVA film after the dyeing process to remove any excess dye solution. 4) Stretching: The PVA film with the surface dye cleaned is immersed in the stretching tank solution for stretching, so that the dye molecules are oriented and aligned inside the PVA film during stretching, and cross-linking is completed at the same time. 5) Polarizing drying: The stretched PVA film is placed in a drying unit to dry, thus obtaining a polarizing film; 6) Protective layer bonding: The polarizers that have finished drying are bonded to two protective layers through an adhesive medium, and then baked to form the polarizer base plate. 7) Coating: The polarizer substrate is coated with pressure-sensitive adhesive and then laminated with a functional film or release film to obtain polarizers with different properties. In step 2), the dyeing tank contains 3-5 wt% of dichroic substance and 0.5-1 wt% of dyeing auxiliaries. The dichroic substance is composed of four different colored azo dyes. In step 3), the washing tank liquid contains 0.1~0.5wt% boride; In step 4), the stretching step, the liquid in the stretching tank contains 1-3 wt% boride; The boride is borax or boric acid.

2. The high-speed production method of a high-durability polarizer according to claim 1, characterized in that, In step 3), the temperature of the solution in the washing tank is 35-55℃, and the washing time is 30-120s.

3. The high-speed production method of a high-durability polarizer according to claim 1, characterized in that, In step 4), the temperature of the solution in the stretching tank is 45-65°C, and the stretching ratio is 5.5-7 times.

4. The high-speed production method of a high-durability polarizer according to claim 1, characterized in that, In step 4), during the stretching step, the solution in the tank contains 2.5-4 wt% of a fixing agent, and the temperature of the solution in the tank is 28-45°C.

5. The high-speed production method of a high-durability polarizer according to claim 1, characterized in that, In step 5), the polarizer drying process, the drying temperature is 60-110℃ and the drying time is 120-300 seconds.

6. The high-speed production method of a high-durability polarizer according to claim 1, characterized in that, In step 6), the protective layer bonding step, the two protective layers of the polarizer are cellulose triacetate, and the adhesive medium is polyvinyl alcohol adhesive or UV adhesive.

7. The high-speed production method of a high-durability polarizer according to claim 1, characterized in that, In step 6), the temperature of the baking unit after the polarizer and the protective layer are bonded is 70-120°C, and the baking time is 150-600 seconds.

8. A high-speed production method for a high-durability polarizer according to claim 1, characterized in that, In step 7), the components of the pressure-sensitive adhesive are: 20-60% pressure-sensitive acrylic copolymer, 0.1-30% tackifier, 10-79% solvent, 0.01-10% crosslinking agent, and 0.01-5% silane coupling agent, by weight percentage.

9. A high-speed production method for a high-durability polarizer according to claim 1, characterized in that, In step 7), the adhesive coating step, the functional film is a phase difference compensation film.

10. A high-durability polarizer produced by a high-speed production method for high-durability polarizers as described in any one of claims 1-9.

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