Polarizer for brightening sheet roll material compounding and preparation method of brightening sheet

Abstract

The invention discloses a polaroid for brightening sheet roll material compounding. The polaroid comprises a first release film, pressure-sensitive glue, a first cellulose triacetate layer, a polyvinyl alcohol layer, a second cellulose triacetate layer, a special functional layer and a second release film, the polyvinyl alcohol layer is positioned between the first cellulose triacetate layer and the second cellulose triacetate layer; the first release film covers the surface of one side of the first cellulose triacetate layer through pressure-sensitive glue; the special functional layer is coated on the surface of one side of the second cellulose triacetate layer, the second release film covers the special functional layer, and the special functional layer is prepared from an azobenzene side chain type liquid crystal polymer or a polymer stable liquid crystal material. According to the invention, the direct on-line roll-to-roll composite production of the polaroid roll material and the brightness enhancement film roll material is realized, additional manual slitting, splicing and material receiving procedures are not needed, and the product yield and the production efficiency are greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of brightening sheets, and in particular to a polarizing sheet used for brightening sheet roll compounding and a method for preparing the brightening sheet. Background Art

[0002] Brightness enhancement film is a technology that can significantly improve the surface brightness of liquid crystal displays, usually by 10%-30%. Brightness enhancement film is mainly composed of polarizer and brightness enhancement film. However, in the existing production process, the roll-to-roll composite production method of brightness enhancement film has certain limitations.

[0003] At present, the mainstream production method on the market is to cut the polarizer roll into sheets first, then splice multiple sheets together by manual film splicing, rewind them into a roll of polarizer, and finally perform roll-to-roll composite production with the brightening film roll. This production method has the following problems:

[0004] 1) Additional manual operations are required, resulting in reduced production efficiency;

[0005] 2) Defects are prone to occur at the joints, affecting product quality and thus reducing product yield;

[0006] 3) The presence of splicing film leads to a decrease in product cutting utilization and increases material waste.

[0007] Therefore, developing a polarizer that can be directly produced by roll-to-roll composite production is of great significance for improving production efficiency and reducing costs. Summary of the invention

[0008] The purpose of the present invention is to provide a polarizer for composite brightening film rolls and a method for preparing a brightening film. By optimizing the structural design and production process, direct roll-to-roll composite production of polarizer rolls and brightening film rolls is realized without the need for additional manual slitting, splicing and material collection processes, thereby greatly improving product yield and production efficiency.

[0009] In order to achieve the above purpose, the following technical solutions are adopted:

[0010] A polarizer for composite brightening sheet roll material, comprising a first release film, pressure-sensitive adhesive, a first triacetyl cellulose layer, a polyvinyl alcohol layer, a second triacetyl cellulose layer, a special functional layer, and a second release film; the polyvinyl alcohol layer is located between the first triacetyl cellulose layer and the second triacetyl cellulose layer; the first release film is covered on one side surface of the first triacetyl cellulose layer via pressure-sensitive adhesive; the special functional layer is coated on one side surface of the second triacetyl cellulose layer, and the second release film is covered on the special functional layer, the preparation material of the special functional layer is azobenzene side chain liquid crystal polymer or polymer stabilized liquid crystal material, and the special functional layer is used to change the polarization direction of polarized light.

[0011] Furthermore, the preparation method of the azobenzene side chain liquid crystal polymer comprises:

[0012] S1: synthesizing an azobenzene compound through a diazotization-coupling reaction, and performing an esterification reaction with an acrylic ester compound to obtain an azobenzene monomer;

[0013] S2: mixing the synthesized azobenzene monomer and other comonomers in a solvent, adding an initiator, and performing a free radical polymerization reaction under nitrogen protection to form a liquid crystal polymer;

[0014] S3: dissolving the synthesized liquid crystal polymer in an organic solvent, and coating the obtained solution on one surface of the second triacetyl cellulose layer by spin coating to form a uniform thin film, and then annealing the thin film.

[0015] Furthermore, in S2, other copolymer monomers include methyl methacrylate and n-substituted maleimide monomer, and the solvent used is tetrahydrofuran.

[0016] Furthermore, in S2, the initiator is azobisisobutyronitrile, and the reaction temperature of the free radical polymerization reaction is 60-80°C.

[0017] Furthermore, in said S3, the synthesized liquid crystal polymer is dissolved in chloroform and prepared into a solution with a concentration of 10%-20%; in said S3, the temperature of annealing the film is 80-120° C., and the annealing time is 1-2 hours.

[0018] Furthermore, the preparation method of the polymer-stabilized liquid crystal material includes:

[0019] S1: mixing cholesteric liquid crystal and ultraviolet light-cured acrylate polymer in a solvent in a predetermined mass ratio, and adding a photoinitiator;

[0020] S2: Spin-coating the mixed solution obtained in S1 onto one side of the second triacetyl cellulose layer, and curing it with ultraviolet light to cross-link the polymers to form a network;

[0021] S3: Put the sample obtained in S2 into an oven for annealing.

[0022] Furthermore, in S1, the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone, and the content of the photoinitiator is 1%-3% of the mass of the UV-curable acrylate polymer.

[0023] Furthermore, in S3, the annealing treatment is performed at a temperature of 60-100° C. and for a time of 30-90 min.

[0024] Also provided is a method for preparing a brightness enhancement film, comprising the above-mentioned polarizer, and directly performing roll-to-roll compounding of a polarizer roll and a brightness enhancement film roll.

[0025] By adopting the above scheme, the beneficial effects of the present invention are:

[0026] 1) Improve production efficiency: Eliminate the steps of slitting, splicing and rewinding, and directly carry out roll-to-roll composite production, which greatly shortens the production cycle and improves production efficiency;

[0027] 2) Reduce costs: Reduce manual operations and equipment investment, save additional labor costs and related equipment costs;

[0028] 3) Improve product yield: Avoid possible defects at the joints, improve the overall quality and consistency of the product, and significantly improve product yield;

[0029] 4) Improve material utilization: Since there is no need for splicing, material waste caused by cutting at the joints is reduced, and material utilization is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure of the present invention. DETAILED DESCRIPTION

[0031] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0032] Reference Figure 1 As shown, the present invention provides a polarizer for composite brightening sheet roll material, comprising a first release film, pressure-sensitive adhesive, a first triacetyl cellulose layer, a polyvinyl alcohol layer, a second triacetyl cellulose layer, a special functional layer, and a second release film; the polyvinyl alcohol layer is located between the first triacetyl cellulose layer and the second triacetyl cellulose layer; the first release film is covered on one side surface of the first triacetyl cellulose layer through the pressure-sensitive adhesive; the special functional layer is coated on one side surface of the second triacetyl cellulose layer, and the second release film is covered on the special functional layer, and the preparation material of the special functional layer is azobenzene side chain liquid crystal polymer or polymer stabilized liquid crystal material, and the special functional layer is used to change the polarization direction of polarized light.

[0033] Continue to refer to Figure 1As shown, in this embodiment, the polarizer is composed of a release film, a pressure-sensitive adhesive (PSA), triacetyl cellulose (TAC), polyvinyl alcohol (PVA), triacetyl cellulose (TAC), a special functional layer and a release film, wherein the sandwich structure of triacetyl cellulose (TAC), polyvinyl alcohol (PVA) and triacetyl cellulose (TAC) realizes the polarization function of the polarizer, the pressure-sensitive adhesive (PSA) is coated on the surface of the triacetyl cellulose (TAC) on one side, and the special functional layer is coated on the surface of the triacetyl cellulose (TAC) on the other side, and the composite release films on both sides are used to protect the main structure of the polarizer, wherein,

[0034] Polyvinyl alcohol (PVA) layer: It can make the polarization direction of light passing through the film layer vibrate along a fixed direction, changing natural light into linearly polarized light. It is the core functional layer of the polarizer;

[0035] Triacetyl cellulose (TAC) layer: Polyvinyl alcohol easily absorbs moisture and deteriorates, and becomes ineffective. The triacetyl cellulose (TAC) layers on both sides can block the passage of moisture and protect the polyvinyl alcohol functional layer;

[0036] Pressure-sensitive adhesive (PSA) layer: This layer enables the polarizer to be firmly attached to the surface of the display by means of pressure;

[0037] Special functional layer: Azobenzene side chain liquid crystal polymer or polymer stabilized liquid crystal material can be used to change the polarization direction of polarized light;

[0038] Release film layer: can reduce the damage of external force to the functional layers of the polarizer.

[0039] In one embodiment, the preparation method of the azobenzene side chain liquid crystal polymer includes:

[0040] S1: synthesizing an azobenzene compound through a diazotization-coupling reaction, and performing an esterification reaction with an acrylic ester compound to obtain an azobenzene monomer;

[0041] S2: mixing the synthesized azobenzene monomer and other comonomers in a solvent, adding an initiator, and performing a free radical polymerization reaction under nitrogen protection to form a liquid crystal polymer;

[0042] S3: dissolving the synthesized liquid crystal polymer in an organic solvent, and coating the obtained solution on one side of the second triacetyl cellulose layer by spin coating to form a uniform thin film, and then annealing the thin film (for eliminating internal stress of the film).

[0043] In this embodiment, the special functional layer uses azobenzene side chain type liquid crystal polymer, wherein, in S2, other copolymer monomers include methyl methacrylate and n-substituted maleimide monomer, and the solvent used is tetrahydrofuran. The addition of methyl methacrylate can improve the transparency and mechanical properties of the polymer, making it more suitable for optical materials, the introduction of n-substituted maleimide monomer can enhance the heat resistance and chemical stability of the polymer, so that it can still maintain good performance under high temperature or chemical environment, and tetrahydrofuran is used as a solvent, which can effectively dissolve the monomer and initiator, making the reaction system more uniform, thereby improving the efficiency and yield of the polymerization reaction.

[0044] At the same time, in S2, the initiator is azobisisobutyronitrile, and the reaction temperature of the free radical polymerization reaction is 60-80°C. The initiator uses azobisisobutyronitrile (AIBN), which is an efficient free radical initiator that can decompose at a relatively low temperature to produce free radicals, thereby quickly starting the polymerization reaction, which enables the reaction to be carried out under mild conditions, avoiding side reactions or polymer degradation that may be caused by high temperature; and the polymerization reaction is carried out in the temperature range of 60-80°C (this temperature belongs to mild conditions, compared with the reaction system with higher temperature, it can reduce energy consumption, and reduce equipment and operation requirements), which can better control the molecular weight and molecular weight distribution of the polymer, so as to obtain a polymer with uniform and stable performance. This is crucial for the optical and mechanical properties of special functional layers (such as liquid crystal polymers). In summary, AIBN is selected as an initiator, and free radical polymerization is carried out in the temperature range of 60-80°C, which can efficiently start the polymerization reaction while ensuring the performance of the polymer and the economy of production. This choice not only improves production efficiency, but also optimizes the performance of the polymer, making it more suitable for the functional layer of the polarizer.

[0045] In addition, in said S3, the synthesized liquid crystal polymer is dissolved in chloroform and prepared into a solution with a concentration of 10%-20%; in said S3, the temperature for annealing the film is 80-120° C., and the annealing time is 1-2 hours.

[0046] Chloroform is a relatively cheap and easily available solvent. Using this solvent can reduce material costs. The solution is configured in a concentration range of 10%-20% to ensure that the solution has moderate viscosity, which is convenient for uniform coating, while ensuring the thickness uniformity and optical performance consistency of the film. Finally, annealing can eliminate the internal stress generated in the film during the coating and drying process, reduce the warping and cracking of the film, and improve the mechanical stability and optical uniformity of the film.

[0047] In one embodiment, the method for preparing the polymer-stabilized liquid crystal material comprises:

[0048] S1: mixing cholesteric liquid crystal and ultraviolet light-cured acrylate polymer in a solvent in a predetermined mass ratio, and adding a photoinitiator;

[0049] S2: Spin-coating the mixed solution obtained in S1 onto one side of the second triacetyl cellulose layer, and curing it with ultraviolet light to cross-link the polymers to form a network, so as to stabilize the liquid crystal molecules therein;

[0050] S3: Put the sample obtained in S2 into an oven for annealing.

[0051] Among them, in S1, liquid crystal molecules (such as cholesteric liquid crystals) and polymer precursors (such as UV-cured acrylate polymers) are uniformly mixed in a solvent (such as toluene) in a certain proportion (such as 70%-90% of liquid crystal molecules), and the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone, and the content of the photoinitiator is 1%-3% of the mass of the UV-cured acrylate polymer.

[0052] In addition, in S3, the annealing treatment temperature is 60-100°C and the time is 30-90 minutes. This can further interact the liquid crystal molecules and the polymer network, optimize the orientation of the liquid crystal molecules, and improve the polarization rotation performance. By adjusting the ratio of liquid crystal and polymer, changing the type or content of the photoinitiator, optimizing the annealing conditions, etc., the material properties can be adjusted to achieve a 90° polarization rotation.

[0053] In addition, a method for preparing a brightening film is provided, including the above-mentioned polarizer. Based on this method, the polarizer roll and the brightening film roll can be directly put on-line for roll-to-roll composite production without the need for additional manual slitting, splicing and material collection processes, thereby greatly improving the product yield and production efficiency.

[0054] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A polarizer for composite brightening film rolls, comprising a first release film, a pressure-sensitive adhesive, a first triacetyl cellulose layer, a polyvinyl alcohol layer, a second triacetyl cellulose layer, a special functional layer, and a second release film; the polyvinyl alcohol layer is located between the first triacetyl cellulose layer and the second triacetyl cellulose layer; the first release film is covered on one side of the first triacetyl cellulose layer through the pressure-sensitive adhesive; the special functional layer is coated on one side of the second triacetyl cellulose layer, and the second release film is covered on the special functional layer, characterized in that: The special functional layer is prepared from azobenzene side chain type liquid crystal polymer or polymer stabilized liquid crystal material, and the special functional layer is used to change the polarization direction of polarized light.

2. The polarizer for brightening sheet roll compounding according to claim 1, characterized in that: The preparation method of the azobenzene side chain liquid crystal polymer comprises: S1: synthesizing an azobenzene compound through a diazotization-coupling reaction, and performing an esterification reaction with an acrylic ester compound to obtain an azobenzene monomer; S2: mixing the synthesized azobenzene monomer and other comonomers in a solvent, adding an initiator, and performing a free radical polymerization reaction under nitrogen protection to form a liquid crystal polymer; S3: dissolving the synthesized liquid crystal polymer in an organic solvent, and coating the obtained solution on one surface of the second triacetyl cellulose layer by spin coating to form a uniform thin film, and then annealing the thin film.

3. The polarizer for brightening sheet roll compounding according to claim 2, characterized in that: In S2, other copolymer monomers include methyl methacrylate and n-substituted maleimide monomer, and the solvent used is tetrahydrofuran.

4. The polarizer for brightening sheet roll compounding according to claim 2, characterized in that: In S2, the initiator is azobisisobutyronitrile, and the reaction temperature of the free radical polymerization reaction is 60-80°C.

5. The polarizer for composite brightening sheet roll material according to claim 2, characterized in that: In the step S3, the synthesized liquid crystal polymer is dissolved in chloroform to prepare a solution with a concentration of 10%-20%. In the step S3, the temperature for annealing the film is 80-120° C. and the annealing time is 1-2 hours.

6. The polarizer for brightening sheet roll compounding according to claim 1, characterized in that: The preparation method of the polymer-stabilized liquid crystal material comprises: S1: mixing cholesteric liquid crystal and ultraviolet light-cured acrylate polymer in a solvent in a predetermined mass ratio, and adding a photoinitiator; S2: Spin-coating the mixed solution obtained in S1 onto one side of the second triacetyl cellulose layer, and curing it with ultraviolet light to cross-link the polymers to form a network; S3: Put the sample obtained in S2 into an oven for annealing.

7. The polarizer for brightening sheet roll compounding according to claim 6, characterized in that: In S1, the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone, and the content of the photoinitiator is 1%-3% of the mass of the UV-curable acrylate polymer.

8. The polarizer for brightening sheet roll compounding according to claim 6, characterized in that: In S3, the annealing treatment is performed at a temperature of 60-100° C. and for a time of 30-90 min.

9. A method for preparing a brightness enhancement film, comprising the polarizer according to any one of claims 1 to 8, characterized in that: The polarizer roll and the brightness enhancement film roll are directly rolled to roll.

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