Preparation method of biaxially-oriented micro-foaming diffusion film

Abstract

A preparation method of a biaxially oriented micro-foaming diffusion film comprises the following steps: S1, mixing polyester chips and an olefin foaming agent according to a mass ratio of (15-17): 1, and carrying out melt blending and extrusion granulation in a single screw extruder to obtain core layer foaming agent master batches; s2, mixing polyester chips, core layer foaming agent master batches and TiO2 particles according to the mass ratio of (100-90): (1-2): 1, and performing melt blending and extrusion granulation in a single-screw extruder to obtain core layer master batches; s3, uniformly mixing polyester chips, matte particles and cross-linked microspheres according to a mass ratio of (1-2): (4-6): 1 to obtain surface master batches; and S4, after crystallizing and drying the core layer master batch and the surface layer master batch, respectively feeding the core layer master batch and the surface layer master batch into a main extrusion machine of a three-layer co-extrusion extruder and an auxiliary extrusion machine of the three-layer co-extrusion extruder, carrying out three-layer co-extrusion sheet casting and two-way asynchronous stretching forming, and then dragging and rolling to obtain the two-way stretching micro-foaming diffusion film.

Description

Technical Field

[0001] This invention relates to a method for preparing a diffusion membrane. Background Technology

[0002] In recent years, the rapid development of liquid crystal display (LCD) technology has led to significant progress in the flat panel display industry. Among the optical components of LCDs, the diffusion film is a key element, and its performance directly affects the brightness uniformity and overall quality of the display screen. Currently, commonly available diffusion films are mainly composed of polyethylene terephthalate (PET) substrate and light diffusing agents. The scattering and diffusion of light is achieved by coating the substrate surface with light-diffusing particles of different refractive indices.

[0003] However, existing diffusion film technologies still have some problems. Traditional diffusion films are mainly produced through coating, which requires two coating processes, resulting in high processing costs, significant material waste, and environmental pollution from the use of adhesives. Furthermore, diffusion films produced by coating are easily scratched, the diffusion coating is prone to peeling off, and uneven distribution of diffusion particles can lead to uneven film brightness. Adding light-diffusing inorganic particles to the matrix can cause a shift in color coordinates due to their absorption effect on the blue light band. The uniformity of inorganic filler dispersion in the polymer matrix is ​​difficult to control, easily forming micron-sized aggregates, resulting in uneven light scattering distribution and regional degradation of film transmittance.

[0004] To address these issues, the industry has been seeking novel diffusion film technologies. Microcellular diffusion films, as an emerging type of diffusion film, have become a research hotspot due to their unique structure and performance characteristics. Microcellular diffusion films typically have a multi-layered structure, with the top and bottom layers usually made of PET material, and the middle layer made of foamed material. This structural design holds promise for solving some of the problems of traditional diffusion films, such as improving the light transmittance and haze while reducing gloss. However, how to effectively control the size and distribution of microbubbles to improve the diffusion effect while ensuring the performance of the diffusion film remains a key focus and challenge of current research. Summary of the Invention

[0005] To overcome the above-mentioned shortcomings of existing diffusion films, the present invention provides a method for preparing a biaxially stretched microcellular diffusion film, which can achieve a balance between high transmittance and high haze.

[0006] The technical solution of this invention to solve its technical problem is: a method for preparing a biaxially stretched microcellular diffusion membrane, comprising the following steps: S1. Polyester chips and olefin-based foaming agents are mixed at a mass ratio of 15-17:1, melt-blended and extruded into granules in a single-screw extruder to obtain core layer foaming agent masterbatch; The glass transition temperature of the olefin-based blowing agent is ≥140℃. The melt flow index is ≥20g / 10min (230℃ / 2.16kg). That is, under the standard test conditions of 230℃ and 2.16kg load, the melt of this olefin-based blowing agent passes through a standard capillary mold at a mass of not less than 20 grams every 10 minutes.

[0007] S2. Polyester chips, core layer foaming agent masterbatch and TiO2 particles are mixed at a mass ratio of 100-90:1-2:1, melt-blended and extruded in a single screw extruder to obtain core layer masterbatch.

[0008] S3. Mix polyester chips, matte particles and cross-linked microspheres at a mass ratio of 1-2:4-6:1 to obtain surface masterbatch.

[0009] S4. After the core layer masterbatch and the surface layer masterbatch are crystallized and dried, they are fed into the main extruder and the auxiliary extruder of the three-layer co-extrusion extruder, respectively. The extrusion speed ratio of the main extruder and the auxiliary extruder is 5:4. After three-layer co-extrusion casting, bidirectional asynchronous stretching and forming, the bidirectional stretched micro-foamed diffusion film is obtained by traction and winding. It includes an intermediate layer formed by the core layer masterbatch and a surface layer formed by the surface layer masterbatch located on both sides of the intermediate layer.

[0010] Preferably, in step S3, the matte particles are TiO2 particles, and the cross-linked microspheres are PMMA cross-linked microspheres, PS microspheres, or PS-DVB microspheres.

[0011] Preferably, in step S4, the longitudinal stretching temperature is 80-90℃ and the stretching ratio is 3.0-3.4 times during bidirectional asynchronous stretching; the transverse stretching temperature is 110-120℃ and the stretching ratio is 3.3-3.4 times.

[0012] The beneficial effects of this invention are that by adding TiO2 to the intermediate layer and optimizing the selection and amount of foaming agent, a balance between high light transmittance and high haze is achieved. Detailed Implementation

[0013] The present invention will be further described in detail below with reference to specific embodiments.

[0014] Example 1: A method for preparing a biaxially stretched microcellular diffusion membrane, comprising the following steps: S1. PET polyester chips and Opteon 1100 from The Chemours Company are mixed at a mass ratio of 15:1, melt-blended and extruded in a single-screw extruder to obtain core layer foaming agent masterbatch.

[0015] S2. PET polyester chips, core layer foaming agent masterbatch, and TiO2 particles are mixed at a mass ratio of 95:1.5:1, melt-blended and extruded in a single-screw extruder to obtain core layer masterbatch. The TiO2 particles have a particle size of 1-2 μm.

[0016] S3. PET polyester chips, matte particles, and cross-linked microspheres are mixed evenly at a mass ratio of 1.5:5:1 to obtain a surface masterbatch. The matte particles are TiO2 particles with a particle size of 1-2 μm, and the cross-linked microspheres are PMMA cross-linked microspheres with a particle size of 1-2 μm.

[0017] S4. After the core layer masterbatch and surface layer masterbatch are crystallized and dried, they are fed into the main extruder and the auxiliary extruder of a three-layer co-extrusion extruder, respectively. The extrusion speed ratio of the main extruder to the auxiliary extruder is 5:4. After three-layer co-extrusion casting, biaxial asynchronous stretching, and winding, the biaxially stretched micro-foamed diffusion film is obtained, which includes an intermediate layer formed by the core layer masterbatch and a surface layer formed by the surface layer masterbatch located on both sides of the intermediate layer. During biaxial asynchronous stretching, the longitudinal stretching temperature is maintained at 80-90℃, and the stretching ratio is maintained at 3.0-3.4 times; the transverse stretching temperature is maintained at 110-120℃, and the stretching ratio is maintained at 3.3-3.4 times.

[0018] Example 2: A method for preparing a biaxially stretched microcellular diffusion membrane, comprising the following steps: S1. PET polyester chips and Honeywell International Inc.'s Solstice LBA are mixed at a mass ratio of 16.5:1, melt-blended and extruded in a single-screw extruder to obtain core layer foaming agent masterbatch.

[0019] S2. PET polyester chips, core layer foaming agent masterbatch, and TiO2 particles are mixed at a mass ratio of 90:2:1, melt-blended and extruded in a single-screw extruder to obtain core layer masterbatch. The TiO2 particles have a particle size of 2-3 μm.

[0020] S3. PET polyester chips, matte particles, and cross-linked microspheres are mixed evenly at a mass ratio of 2:5.5:1 to obtain a surface masterbatch. The matte particles are TiO2 particles with a particle size of 1-2 μm, and the cross-linked microspheres are PS cross-linked microspheres with a particle size of 2-3 μm.

[0021] S4. After the core layer masterbatch and surface layer masterbatch are crystallized and dried, they are fed into the main extruder and the auxiliary extruder of a three-layer co-extrusion extruder, respectively. The extrusion speed ratio of the main extruder to the auxiliary extruder is 5:4. After three-layer co-extrusion casting, biaxial asynchronous stretching, and winding, the biaxially stretched micro-foamed diffusion film is obtained, which includes an intermediate layer formed by the core layer masterbatch and a surface layer formed by the surface layer masterbatch located on both sides of the intermediate layer. During biaxial asynchronous stretching, the longitudinal stretching temperature is maintained at 80-90℃, and the stretching ratio is maintained at 3.0-3.4 times; the transverse stretching temperature is maintained at 110-120℃, and the stretching ratio is maintained at 3.3-3.4 times.

[0022] Example 3: A method for preparing a biaxially stretched microcellular diffusion membrane, comprising the following steps: S1. PET polyester chips and Dow Chemical Company's INFUSE 9507 are mixed at a mass ratio of 16:1, melt-blended and extruded in a single-screw extruder to obtain core layer foaming agent masterbatch.

[0023] S2. PET polyester chips, core layer foaming agent masterbatch, and TiO2 particles are mixed at a mass ratio of 100:1:1, melt-blended and extruded in a single-screw extruder to obtain core layer masterbatch. The TiO2 particles have a particle size of 2-3 μm.

[0024] S3. PET polyester chips, matte particles, and cross-linked microspheres are mixed evenly at a mass ratio of 1:4:1 to obtain a surface masterbatch. The matte particles are TiO2 particles with a particle size of 2-3 μm, and the cross-linked microspheres are PS-DVB cross-linked microspheres with a particle size of 2-3 μm.

[0025] S4. After the core layer masterbatch and surface layer masterbatch are crystallized and dried, they are fed into the main extruder and the auxiliary extruder of a three-layer co-extrusion extruder, respectively. The extrusion speed ratio of the main extruder to the auxiliary extruder is 5:4. After three-layer co-extrusion casting, biaxial asynchronous stretching, and winding, the biaxially stretched micro-foamed diffusion film is obtained, which includes an intermediate layer formed by the core layer masterbatch and a surface layer formed by the surface layer masterbatch located on both sides of the intermediate layer. During biaxial asynchronous stretching, the longitudinal stretching temperature is maintained at 80-90℃, and the stretching ratio is maintained at 3.0-3.4 times; the transverse stretching temperature is maintained at 110-120℃, and the stretching ratio is maintained at 3.3-3.4 times.

[0026] Example 4: A method for preparing a biaxially stretched microcellular diffusion membrane, comprising the following steps: S1. PET polyester chips and Dow Chemical Company's INFUSE 9007 are mixed at a mass ratio of 15.5:1, melt-blended and extruded in a single-screw extruder to obtain core layer foaming agent masterbatch.

[0027] S2. PET polyester chips, core layer foaming agent masterbatch, and TiO2 particles are mixed at a mass ratio of 92:1.2:1, melt-blended and extruded in a single-screw extruder to obtain core layer masterbatch. The TiO2 particles have a particle size of 2-3 μm.

[0028] S3. PET polyester chips, matte particles, and cross-linked microspheres are mixed evenly at a mass ratio of 1.1:6:1 to obtain a surface masterbatch. The matte particles are TiO2 particles with a particle size of 2-3 μm, and the cross-linked microspheres are PS cross-linked microspheres with a particle size of 1-2 μm.

[0029] S4. After the core layer masterbatch and surface layer masterbatch are crystallized and dried, they are fed into the main extruder and the auxiliary extruder of a three-layer co-extrusion extruder, respectively. The extrusion speed ratio of the main extruder to the auxiliary extruder is 5:4. After three-layer co-extrusion casting, biaxial asynchronous stretching, and winding, the biaxially stretched micro-foamed diffusion film is obtained, which includes an intermediate layer formed by the core layer masterbatch and a surface layer formed by the surface layer masterbatch located on both sides of the intermediate layer. During biaxial asynchronous stretching, the longitudinal stretching temperature is maintained at 80-90℃, and the stretching ratio is maintained at 3.0-3.4 times; the transverse stretching temperature is maintained at 110-120℃, and the stretching ratio is maintained at 3.3-3.4 times.

[0030] Example 5: A method for preparing a biaxially stretched microcellular diffusion membrane, comprising the following steps: S1. PET polyester chips and SOFTLON from Sekisui Chemical Co., Ltd. Mix them at a mass ratio of 17:1, melt blend them in a single screw extruder, and then extrude and granulate them to obtain core layer foaming agent masterbatch.

[0031] S2. PET polyester chips, core layer foaming agent masterbatch, and TiO2 particles are mixed at a mass ratio of 93:1.7:1, melt-blended and extruded in a single-screw extruder to obtain core layer masterbatch. The TiO2 particles have a particle size of 1-2 μm.

[0032] S3. PET polyester chips, matte particles, and cross-linked microspheres are mixed evenly at a mass ratio of 1.8:4.5:1 to obtain a surface masterbatch. The matte particles are TiO2 particles with a particle size of 2-3 μm, and the cross-linked microspheres are PMMA cross-linked microspheres with a particle size of 1-2 μm.

[0033] S4. After the core layer masterbatch and surface layer masterbatch are crystallized and dried, they are fed into the main extruder and the auxiliary extruder of a three-layer co-extrusion extruder, respectively. The extrusion speed ratio of the main extruder to the auxiliary extruder is 5:4. After three-layer co-extrusion casting, biaxial asynchronous stretching, and winding, the biaxially stretched micro-foamed diffusion film is obtained, which includes an intermediate layer formed by the core layer masterbatch and a surface layer formed by the surface layer masterbatch located on both sides of the intermediate layer. During biaxial asynchronous stretching, the longitudinal stretching temperature is maintained at 80-90℃, and the stretching ratio is maintained at 3.0-3.4 times; the transverse stretching temperature is maintained at 110-120℃, and the stretching ratio is maintained at 3.3-3.4 times.

Claims

1. A method for preparing a biaxially stretched microcellular diffusion membrane, characterized in that... Includes the following steps: S1. Polyester chips and olefin-based foaming agents are mixed at a mass ratio of 15-17:1, melt-blended and extruded into granules in a single-screw extruder to obtain core layer foaming agent masterbatch; Among them, the glass transition temperature of olefin-based foaming agents is ≥140℃, and the melt index is ≥20g / 10min (230℃ / 2.16kg); S2. Polyester chips, core layer foaming agent masterbatch and TiO2 particles are mixed at a mass ratio of 100-90:1-2:1, melt-blended and extruded in a single screw extruder to obtain core layer masterbatch; S3. Mix polyester chips, matte particles and cross-linked microspheres evenly at a mass ratio of 1-2:4-6:1 to obtain surface masterbatch; S4. After the core layer masterbatch and the surface layer masterbatch are crystallized and dried, they are fed into the main extruder and the auxiliary extruder of the three-layer co-extrusion extruder, respectively. The extrusion speed ratio of the main extruder and the auxiliary extruder is 5:

4. After three-layer co-extrusion casting, bidirectional asynchronous stretching and forming, the bidirectional stretched micro-foamed diffusion film is obtained by traction and winding. It includes an intermediate layer formed by the core layer masterbatch and a surface layer formed by the surface layer masterbatch located on both sides of the intermediate layer.

2. The method for preparing the biaxially oriented microcellular diffusion membrane as described in claim 1, characterized in that: In step S3, the matte particles are TiO2 particles, and the cross-linked microspheres are PMMA cross-linked microspheres, PS cross-linked microspheres, or PS-DVB cross-linked microspheres.

3. The method for preparing the biaxially stretched microcellular diffusion membrane as described in claim 1, characterized in that: In step S4, the longitudinal tension temperature during bidirectional asynchronous stretching is 80-90℃, and the stretching ratio is 3.0-3.4 times; the transverse tension temperature is 110-120℃, and the stretching ratio is 3.3-3.4 times.