Optical diffusion film with high light transmittance and high haze and preparation method thereof

Abstract

This invention discloses an optical diffusion film with high light transmittance and high haze. The raw materials, by mass percentage, comprise: 88.5%–97.5% matrix material, 2%–10% light diffusing agent, and 0.5%–1.5% antioxidant. The matrix material is one or more of polystyrene, polycarbonate, or polyethylene terephthalate. The light diffusing agent is monodisperse calcium carbonate particles with a grain size primarily concentrated in the range of 800–1200 nm, with particles exceeding this range accounting for less than 10%. This invention involves mixing the light diffusing agent with a small amount of matrix material and a small amount of antioxidant, followed by extrusion granulation to obtain a filler masterbatch. The filler masterbatch is then mixed with the remaining matrix material and antioxidant, and the mixture is cast into a film / sheet or extruded into a film / sheet to obtain an optical diffusion film with high light transmittance and high haze. This optical diffusion film exhibits light transmittance and haze exceeding 85%, solving the technical challenge of simultaneously improving the light diffusivity and transmittance of light diffusion films.

Description

Technical Field

[0001] This invention belongs to the field of optics, specifically relating to an optical diffusion film with high transmittance and high haze and its preparation method. Background Technology

[0002] In the fields of optical display and lighting, light-diffusing films / sheets are widely needed to diffuse light from "point light sources" such as LEDs, thereby forming "area light sources." Currently, the common approach is to use a faceted light guide plate combined with a light-diffusing film. The light-diffusing film uses polystyrene, polymethyl methacrylate, or polyethylene terephthalate as the base material, with silicon microspheres or polyester microspheres added to the film or its surface. Light diffusion is achieved through light scattering (refractive + reflective) by the microspheres. However, this method presents a trade-off between light diffusion (i.e., haze) and transmittance; good light diffusion (high haze) results in low transmittance, and vice versa. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an optical diffusion film with high transmittance and high haze, which addresses the shortcomings of the prior art. Both transmittance and haze exceed 85%, thus solving the technical problem that it is difficult to simultaneously improve the light diffusion and transmittance of the light diffusion film.

[0004] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows:

[0005] An optical diffusion film with high light transmittance and high haze comprises the following raw materials by mass percentage: 88.5% to 97.5% matrix material, 2% to 10% light diffusing agent, and 0.5% to 1.5% antioxidant; wherein the matrix material is one or more of polystyrene (PS), polycarbonate (PC), or polyethylene terephthalate (PET), and the light diffusing agent is monodisperse calcium carbonate particles.

[0006] According to the above scheme, PS is high-transparency optical-grade PS, usually called GPPS, with a number-average molecular weight between 30,000 and 120,000; PC is high-transparency, high-diffusion, glare-free, and shadow-free optical-grade PC, with a number-average molecular weight between 10,000 and 20,000; PET is high-transparency film-grade PET, with a number-average molecular weight between 15,000 and 30,000.

[0007] According to the above scheme, the antioxidant is selected from one or more of antioxidant 1010, antioxidant 168, antioxidant 626, antioxidant S-9228, etc.

[0008] The preparation method of the above-mentioned optical diffusion film with high transmittance and high haze specifically includes the following steps:

[0009] (1) Weigh out 88.5%–97.5% of the matrix material, 2%–10% of the light diffusing agent, and 0.5%–1.5% of the antioxidant by mass percentage; divide the 88.5%–97.5% matrix material into two parts, A and B, with matrix material A being 0.5%–6.5% and matrix material B being 82%–97%; divide the 0.5%–1.5% antioxidant into two parts, A and B, with antioxidant A being 0.05%–0.15% and antioxidant B being 0.45%–1.35%; wherein, the mass percentages of matrix material A, matrix material B, antioxidant A, and antioxidant B are all calculated as their proportions in the total amount of raw materials;

[0010] (2) The light diffusing agent, matrix material A and antioxidant A are mixed and stirred at room temperature using a mixer, and then extruded and granulated by a twin-rotor continuous mixing extruder to obtain filler masterbatch; wherein, the mass percentage of calcium carbonate in the filler masterbatch is 60% to 80%;

[0011] (3) The filler masterbatch, matrix material B and antioxidant B are mixed evenly with a mixer at room temperature, and then cast into a film / sheet or extruded into a film / sheet; the cast or extruded film / sheet is cut to obtain an optical diffusion film with high light transmittance and high haze.

[0012] According to the above scheme, in step (2), the filler masterbatch is preferably short rod-shaped, with a diameter of 2-3 mm and a length of 1-3 mm.

[0013] According to the above scheme, in step (2), the extrusion temperature is generally in the range of 175 to 250°C, and the screw speed is adjusted between 300 and 700 rpm according to the material state. Specifically, when the matrix material is PS, the extruder temperature is set at 175 to 180°C; when the matrix material is PC, the extruder temperature is set at 245 to 250°C; and when the matrix material is PET, the extruder temperature is set at 235 to 240°C.

[0014] According to the above scheme, in step (3), when the base material is PS, the casting or extrusion temperature is set at 190-240℃; when the base material is PC, the casting or extrusion temperature is set at 250-280℃; when the base material is PET, the casting or extrusion temperature is set at 240-270℃.

[0015] According to the above scheme, in step (3), the thickness of the film / sheet can vary depending on the application field and the substrate material, and is generally between 0.1 and 3 mm.

[0016] According to the above scheme, the monodisperse calcium carbonate particles have a grain size mainly concentrated in the range of 800–1200 nm, with particles exceeding this range accounting for less than 10%, and particles larger than 1.5 μm accounting for less than 2%, and the grains exhibit good crystallinity. The preparation method of these monodisperse calcium carbonate particles includes the following steps:

[0017] S1. Calcium carbonate slurry is prepared using calcination, digestion, and carbonation processes. The calcination process involves selecting limestone with uniform grain size (preferably 0.05–5 mm) as raw material and using a calcination temperature matching the grain size (preferably 850–1000℃ depending on the grain size) to obtain quicklime. The digestion process involves digesting quicklime with hot water at 80–90℃ and aging it to obtain lime milk (raw slurry). Carbonation involves adjusting the solid content of the lime milk to 5%–15%, then introducing carbon dioxide for carbonation. The initial carbonation temperature is 45–70℃, the CO2 content is 20%–40%, and carbonation continues until the slurry pH reaches 8.0–10.0, at which point carbonation is complete, yielding calcium carbonate slurry.

[0018] S2. After the calcium carbonate slurry obtained in S1 is allowed to stand, the supernatant is removed to achieve thickening, and a calcium carbonate thick slurry with a solid content of 20% to 40% is obtained.

[0019] S3. Add the calcium carbonate slurry obtained in S2 to the inorganic and organic crystal remodeling agents, and then perform the reaction under ultrasonic conditions (power density 100-300 W / 1000 cm³). 3 The calcium carbonate was dispersed and reconstituted at 140–200℃ for 1.5–4 hours to obtain a monodisperse calcium carbonate suspension with specified particle size and morphology.

[0020] S4. Cool the monodisperse calcium carbonate suspension obtained in S3 to 50-70℃, add a surface modifier, maintain this temperature range and continue stirring for 20-40 minutes to obtain a surface-modified calcium carbonate suspension.

[0021] S5. The surface-modified calcium carbonate suspension obtained in S4 is dehydrated by pressure filtration to obtain a calcium carbonate filter cake. The moisture content of the filter cake is controlled to not exceed 40%.

[0022] S6. The calcium carbonate filter cake obtained in S5 is dried by methods such as belt drying and flash evaporation to control the moisture content to be less than 0.1%, so as to obtain monodisperse calcium carbonate particles with an activation degree higher than 99%. The activation degree is tested according to the national standard GB / T 19281-2014.

[0023] Further, the inorganic crystal form remodeling agent is selected from one or more of sodium silicate, sodium chloride, aluminum chloride, zinc sulfate, etc.; the organic crystal form remodeling agent is selected from one or more of ethanol, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, disodium ethylenediaminetetraacetate, etc.; the total amount of the inorganic crystal form remodeling agent and the organic crystal form remodeling agent is 0.5% to 5% of the dry weight of calcium carbonate.

[0024] Further, the surface modifier is a mixture of amphiphilic polystyrene-polyethylene glycol block copolymer and polyethylene glycol stearate or pentaerythritol stearate, and the amount used is 2% to 5% of the dry weight of calcium carbonate. When the matrix material is PS, the surface modifier is composed of amphiphilic polystyrene-polyethylene glycol block copolymer and polyethylene glycol stearate in a mass ratio of 1:1 to 1:2; when the matrix material is PC, the surface modifier is composed of amphiphilic polystyrene-polyethylene glycol block copolymer and pentaerythritol stearate in a mass ratio of 1:2 to 1:4; when the matrix material is PET, the surface modifier is composed of amphiphilic polystyrene-polyethylene glycol block copolymer and pentaerythritol stearate in a mass ratio of 1:4 to 1:6. The molecular weight of the amphiphilic polystyrene-polyethylene glycol block copolymer is between 40,000 and 120,000 g / mol.

[0025] The technical concept of this invention is as follows:

[0026] This invention uses polystyrene, polycarbonate, or polyethylene terephthalate as the matrix material. These materials have refractive indices close to those of calcium carbonate, reducing total internal reflection caused by the refractive index difference at the calcium carbonate / matrix interface. Simultaneously, this invention uses well-crystallized monodisperse calcium carbonate particles with a grain size concentrated in the 800–1200 nm range as a light diffusing agent, dispersed within the matrix material to create a diffusion effect on visible light. Furthermore, the calcium carbonate undergoes surface treatment during the preparation of the light diffusing agent, ensuring good dispersion within the matrix material and good interfacial bonding, avoiding abrupt refractive index changes due to interfacial voids. By controlling the mass percentage of the matrix material in the optical diffusion film to 88.5%–97.5%, the light diffusing agent to 2%–10%, and the antioxidant to 0.5%–1.5%, this invention ultimately achieves an optical diffusion film with a transmittance and haze exceeding 85%.

[0027] In preparing the light-diffusing agent (monodispersed calcium carbonate particles), this invention selects limestone with uniform grain size as raw material and uses a calcination temperature matching the grain size to obtain quicklime with moderate and uniform activity. This quicklime is then digested and carbonized to obtain a calcium carbonate slurry. During this process, the limestone with uniform grain size is calcined to adjust its activity, preventing partial under-burning and over-burning caused by mottled grains. Furthermore, the good uniformity and moderate activity of the quicklime facilitate control of the digestion reaction, resulting in a homogeneous lime slurry with controllable properties. This allows for control of the subsequent carbonation process, ultimately yielding a calcium carbonate slurry. The calcium carbonate slurry undergoes a grain surface reconstruction process after thickening. By adding inorganic and organic surface reconstruction agents and maintaining the temperature at a certain level, grain surface reconstruction is promoted, resulting in more complete crystals, smoother particle surfaces, and reduced surface energy, thus facilitating dispersion. The inorganic surface reconstruction agent promotes crystal development, repairs defects, and makes the crystal more complete. The organic surface reconstruction agent regulates the surface potential of the particles, controls the mutual repulsion of the grains in water, and avoids adhesion during the crystal repair process. This invention controls the average particle size of calcium carbonate particles to 800–1200 nm by controlling the surface reconstruction temperature and time. After surface modification and drying, the resulting calcium carbonate powder is ensured to be highly monodisperse. This type of calcium carbonate particle size falls within the visible light wavelength range. Utilizing the birefringence of calcium carbonate, visible light transmitted through it is decomposed into two beams of light with unequal speeds and different propagation directions. After passing through n calcium carbonate particles, this decomposes into 2n beams of light with different propagation directions. By controlling the size and interface of the calcium carbonate grains, reflection is reduced, thereby simultaneously achieving high transmittance and high haze.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The optical diffusion film of the present invention has a transmittance and haze of over 85%, which solves the technical problem that it is difficult to improve the light diffusion and transmittance of the optical diffusion film at the same time, and the production cost is also significantly lower than that of existing products. Attached Figure Description

[0030] Figure 1 Scanning electron microscope image of the light diffusing agent prepared in Example 1;

[0031] Figure 2 Scanning electron microscope image of the light diffusing agent prepared in Example 2;

[0032] Figure 3 Scanning electron microscope image of the light diffusing agent prepared in Example 3;

[0033] Figure 4 Scanning electron microscope image of the light diffusing agent prepared in Example 4;

[0034] Figure 5 Scanning electron microscope image of calcium carbonate prepared for Comparative Example 1;

[0035] Figure 6 Scanning electron microscope image of calcium carbonate prepared for Comparative Example 2;

[0036] Figure 7 Scanning electron microscope image of calcium carbonate prepared for Comparative Example 3;

[0037] Figure 8 Scanning electron microscope image of calcium carbonate prepared for Comparative Example 4. Specific implementation methods

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] In the following examples, PS was purchased from Formosa Chemicals & Fibre (Ningbo) Co., Ltd., model GP550N; PC was purchased from Idemitsu Kosan Co., Ltd. of Japan, model LC1500; PET was purchased from Sinopec Yizheng Chemical Fiber Co., Ltd., model FG720; antioxidants 1010, 168 and 626 were purchased from BASF; and antioxidant S-9228 was purchased from Dover Corporation of the United States.

[0040] In the following examples, the CAS number of the polyethylene glycol stearate is 9004-99-3, and the CAS number of the pentaerythritol stearate is 115-83-3.

[0041] In the following examples, the amphiphilic polystyrene-polyethylene glycol block copolymer (PS-b-PEG) was prepared by atom transfer radical polymerization (ATRP). First, using styrene (St) as a monomer, CBr4 as a polymerization telomer, and azobisisobutyronitrile (AIBN) as an initiator, a polystyrene (PS-Br) telomer was synthesized via a free radical polymerization reaction, wherein the degree of polymerization of PS-Br was 300–1000. Then, using ethylene glycol (EG) as a monomer, PS-Br as a macromolecular initiator, and CuCl / pby as a catalyst system, the block copolymer PS-b-PEG was synthesized via ATRP, wherein the molar ratio of EG, PS-Br, CuCl, and pby was 100:1:2:6, the reaction temperature was 90–130°C, and the reaction time was 4–24 h.

[0042] Example 1

[0043] An optical diffusion film with high light transmittance and high haze comprises the following raw materials by mass percentage: 91% matrix material, 8% light diffusing agent, and 1% antioxidant; wherein the matrix material is PS, the light diffusing agent is monodisperse calcium carbonate particles, and the antioxidant is antioxidant 168.

[0044] The preparation method of the above-mentioned optical diffusion film with high transmittance and high haze specifically includes the following steps:

[0045] (1) Weigh out 91% of the matrix material, 8% of the light diffusing agent, and 1% of the antioxidant according to the above mass percentages and raw material specifications; then, divide the matrix material into two parts, labeled as matrix material A and matrix material B; wherein, the mass percentage of matrix material A is 3%, the mass percentage of matrix material B is 88%, and the sum of the two is 91%; and divide the antioxidant into two parts, labeled as antioxidant A and antioxidant B, wherein the mass percentage of antioxidant A is 0.1%, the mass percentage of antioxidant B is 0.9%, and the sum of the two is 1%;

[0046] (2) The light diffusing agent, matrix material A, and antioxidant A are mixed and blended at room temperature using a mixer. The mixture is then extruded and granulated using a twin-rotor continuous mixing extruder. The temperatures of each section of the extruder (i.e., the feeding section, the compression section, and the homogenization section) are set to 175℃, 180℃, and 180℃, respectively. The screw speed is adjusted between 300 and 700 rpm according to the viscosity of the material during extrusion, with the goal of ensuring smooth extrusion. Short rod-shaped filler masterbatch with a diameter of 2-3 mm and a length of 1-3 mm is obtained. At this point, the mass percentage of calcium carbonate in the filler masterbatch is approximately 72%.

[0047] (3) The filler masterbatch, matrix material B and antioxidant B are placed in a mixer and stirred evenly at room temperature. The mixture is then cast into a film using a casting machine. The temperatures of each section of the casting machine are set to 190℃, 220℃, 220℃, 200℃ and 230℃. The winding speed of the casting roller is 1.0m / min, the speed of the traction roller is 1.1m / min, and the film thickness is 260μm. After cutting, the optical diffusion film with high light transmittance and high haze is obtained.

[0048] The specific steps for preparing the monodisperse calcium carbonate particle light diffusing agent are as follows:

[0049] S1. Calcium carbonate slurry is prepared using a calcination, digestion, and carbonation process. The calcination process involves using high-purity limestone with a grain size of 0.2–0.5 mm as raw material, calcining at 900℃ for 2 hours to obtain quicklime with ideal activity. The digestion process involves digesting the calcined quicklime with water at 80℃ to obtain lime slurry, which is then aged for 48 hours to remove impurities and obtain lime slurry (raw slurry). The carbonation process involves adding water to the lime slurry to adjust the solid content to 15%, then introducing carbon dioxide for carbonation. The initial carbonation temperature is 45℃, the CO2 content is 40%, and carbonation continues until the slurry pH reaches 8.0–8.5, at which point carbonation is terminated to obtain calcium carbonate slurry.

[0050] S2. After the calcium carbonate slurry obtained in S1 is allowed to stand, the supernatant is removed to achieve thickening, resulting in a calcium carbonate slurry with a solid content of 20%.

[0051] S3. Add 1.0% aluminum chloride, 0.5% polyvinylpyrrolidone, 2.0% polyvinyl alcohol, and 0.3% sodium dodecyl sulfate to the calcium carbonate slurry obtained in S2, at a power density of 300 W / 1000 cm³. 3 Dispersion and reconstruction were carried out under ultrasonic conditions at 200℃ for 1.5h to obtain a monodisperse calcium carbonate suspension;

[0052] S4. Cool the monodisperse calcium carbonate suspension obtained in S3 to 70℃, add 2% PS-b-PEG and 3% polyethylene glycol stearate by dry weight of calcium carbonate, keep at 70℃ and stir for 20 min to complete the surface modification of calcium carbonate and obtain the surface-modified calcium carbonate suspension.

[0053] S5. The surface-modified calcium carbonate suspension obtained in S4 is dehydrated by pressure filtration to obtain a calcium carbonate filter cake with a moisture content of less than 40%.

[0054] S6. The calcium carbonate filter cake obtained in S5 is dried by methods such as belt drying or flash drying until the moisture content is below 0.1%. At this point, it becomes monodisperse calcium carbonate particles. Figure 1 As shown, the calcium carbonate particles are cubic in shape, with a particle size distribution concentrated in the range of 800-1200 nm. Particles exceeding this range account for less than 10%, and particles larger than 1.5 μm account for less than 2%. The interfaces between particles are clear, with distinct edges and corners, and good dispersibility. Its activation degree was tested to be 99.5%.

[0055] Example 2

[0056] This embodiment provides an optical diffusion film with high light transmittance and high haze, the raw materials of which include, by mass percentage: 92.5% matrix material, 7% light diffusing agent, and 0.5% antioxidant; wherein, the matrix material is PS, the light diffusing agent is monodisperse calcium carbonate particles, and the antioxidant is antioxidant 1010.

[0057] The method for preparing the high transmittance and high haze optical diffusion film described in this embodiment differs from that in Example 1 in that: the mass percentage of matrix material A is 4.5%, the mass percentage of matrix material B is 88%; the mass percentage of antioxidant A is 0.05%, the mass percentage of antioxidant B is 0.45%; and the calcium carbonate filling rate in the filler masterbatch is approximately 60%.

[0058] The preparation method of the monodisperse calcium carbonate particle light diffusing agent described in this embodiment differs from that in Example 1 in that: in step S1, the digestion temperature is 85℃, the solid content of the raw pulp used for carbonation is 10%, the carbonation initiation temperature is 50℃, and the CO2 content is 33%; in step S3, 0.5% sodium silicate, 0.2% sodium chloride, 0.6% aluminum chloride, and 1.0% sodium dodecylbenzenesulfonate by dry weight of calcium carbonate are added as crystal remodeling agents, and the ultrasonic power density is 280W / 1000cm³. 3 The holding temperature was 180℃, and the holding time was 4 hours. In step S4, 1.5% PS-b-PEG and 1.5% polyethylene glycol stearate (by dry weight of calcium carbonate) were added as modifiers, and the mixture was stirred at 65℃ for 30 minutes. The resulting monodisperse calcium carbonate particles were as follows: Figure 2 As shown, the calcium carbonate particles are polyhedral in shape, with a particle size distribution concentrated in the range of 800–1200 nm. Particles exceeding this range account for less than 10%, and particles larger than 1.5 μm account for less than 2%. The interfaces between particles are clear, and the dispersion is good. The activation degree is 99.9%.

[0059] Example 3

[0060] This embodiment provides an optical diffusion film with high light transmittance and high haze, the raw materials of which include, by mass percentage: 94% matrix material, 5% light diffusing agent, and 1% antioxidant; wherein, the matrix material is PET, the light diffusing agent is monodisperse calcium carbonate particles, and the antioxidant is antioxidant S-9228.

[0061] The method for preparing the high transmittance and high haze optical diffusion film described in this embodiment specifically includes the following steps:

[0062] (1) Weigh out 94% of the matrix material, 5% of the light diffusing agent, and 1% of the antioxidant according to the above mass percentages and raw material specifications; then, divide the matrix material into two parts, labeled as matrix material A and matrix material B; wherein, the mass percentage of matrix material A is 2%, the mass percentage of matrix material B is 92%, and the sum of the two is 91%; and divide the antioxidant into two parts, labeled as antioxidant A and antioxidant B, wherein the mass percentage of antioxidant A is 0.1%, the mass percentage of antioxidant B is 0.9%, and the sum of the two is 1%;

[0063] (2) The light diffusing agent, matrix material A and antioxidant A are mixed and blended at room temperature using a mixer, and then extruded and granulated using a twin-rotor continuous mixing extruder. The temperatures of each section of the extruder are set to 235℃, 240℃ and 240℃, and the screw speed is adjusted between 300 and 700 rpm according to the viscosity of the material during extrusion, with the goal of smooth extrusion. Short rod-shaped filler masterbatch with a diameter of 2 to 3 mm and a length of 1 to 3 mm is obtained. At this time, the mass percentage of calcium carbonate in the filler masterbatch is about 70%.

[0064] (3) The filler masterbatch, matrix material B and antioxidant B are placed in a mixer and stirred evenly at room temperature. The mixture is then cast into a film using a casting machine. The temperatures of each section of the casting machine are set to 240℃, 260℃, 260℃, 250℃ and 270℃. The winding speed of the casting roller is 0.9m / min, the speed of the traction roller is 1.0m / min, and the film thickness is 300μm. After cutting, the high transmittance and high haze optical diffusion film is obtained.

[0065] The preparation method of the monodisperse calcium carbonate particle light diffusing agent described in this embodiment differs from that in Example 1 in the following ways: In step S1, high-purity limestone with a grain size of 2.0–5.0 mm is selected as the raw material, the calcination temperature is 1000℃, the solid content of the raw slurry used for carbonation is 12%, the carbonation initiation temperature is 60℃, and the CO2 content is 30%; In step S3, 1.2% zinc sulfate, 0.8% sodium silicate, 1.4% polyethylene glycol, and 1.6% hexadecyltrimethylammonium bromide by dry weight of calcium carbonate are added as crystal remodeling agents, and the ultrasonic power density is 250 W / 1000 cm³. 3 The holding temperature was 200℃, and the holding time was 3 hours. In step S4, 0.5% PS-b-PEG and 2% pentaerythritol stearate (by dry weight of calcium carbonate) were added as modifiers, and the mixture was stirred at 50℃ for 40 minutes. The resulting monodisperse calcium carbonate particles were as follows: Figure 3 As shown, the calcium carbonate particles are cubic in shape, with a particle size distribution concentrated in the range of 800-1200 nm. Particles exceeding this range account for less than 10%, and particles larger than 1.5 μm account for less than 2%. The interfaces between particles are clear, with distinct edges and corners, and good dispersibility. Its activation degree is 99.6%.

[0066] Example 4

[0067] This embodiment provides an optical diffusion film with high light transmittance and high haze, the raw materials of which include, by mass percentage: 88.5% matrix material, 10% light diffusing agent, and 1.5% antioxidant; wherein, the matrix material is PC, the light diffusing agent is monodisperse calcium carbonate particles, and the antioxidant is antioxidant 626.

[0068] The method for preparing the high transmittance and high haze optical diffusion film described in this embodiment specifically includes the following steps:

[0069] (1) Weigh out 88.5% of the matrix material, 10% of the light diffusing agent, and 1.5% of the antioxidant according to the above mass percentages and raw material specifications; then, divide the matrix material into two parts, labeled as matrix material A and matrix material B; wherein, the mass percentage of matrix material A is 2.4%, the mass percentage of matrix material B is 86.6%, and the sum of the two is 89%; and divide the antioxidant into two parts, labeled as antioxidant A and antioxidant B, wherein the mass percentage of antioxidant A is 0.15%, the mass percentage of antioxidant B is 1.35%, and the sum of the two is 1.5%;

[0070] (2) The light diffusing agent, matrix material A, and antioxidant A are mixed and blended at room temperature using a mixer. The mixture is then extruded and granulated using a twin-rotor continuous mixing extruder. The temperatures of each section of the extruder are set to 245℃, 250℃, and 250℃. The screw speed is adjusted between 300 and 700 rpm according to the viscosity of the material during extrusion, with the goal of ensuring smooth extrusion. Short rod-shaped filler masterbatch with a diameter of 2-3 mm and a length of 1-3 mm is obtained. At this point, the mass percentage of calcium carbonate in the filler masterbatch is approximately 80%.

[0071] (3) The filler masterbatch, matrix material B and antioxidant B are placed in a mixer and stirred evenly at room temperature. The mixture is then cast into a film using a casting machine. The temperatures of each section of the casting machine are set to 250℃, 270℃, 270℃, 250℃ and 280℃. The winding speed of the casting roller is 3.0m / min, the speed of the traction roller is 3.1m / min, and the film thickness is 110μm. After cutting, the optical diffusion film with high light transmittance and high haze is obtained.

[0072] The difference between the preparation steps of the monodisperse calcium carbonate particle light diffusing agent in this embodiment and those in Example 1 is as follows: In step S1, high-purity limestone with a crystal size of 0.05-0.2 mm is selected as the raw material, the calcination temperature is 850℃, the solid content of the raw slurry used for carbonation is 5%, the carbonation initiation temperature is 70℃, the CO2 content is 20%, and carbonation is stopped when the pH of the slurry reaches 9.0-9.5; In step S3, 0.2% sodium chloride, 0.1% ethanol, and 0.2% disodium ethylenediaminetetraacetate (EDTA) by dry weight of calcium carbonate are added as crystal remodeling agents, and the ultrasonic power density is 200 W / 1000 cm³. 3 The holding temperature was 140℃, and the holding time was 4 hours. In step S4, 0.5% PS-b-PEG and 1.5% pentaerythritol stearate by dry weight of calcium carbonate were added as modifiers, and the mixture was stirred at 60℃ for 30 minutes. The resulting monodisperse calcium carbonate particles were as follows: Figure 4As shown, the calcium carbonate particles are polyhedral, with a particle size distribution concentrated in the range of 800–1200 nm. Particles exceeding this range account for less than 10%, and particles larger than 1.5 μm account for less than 2%. The interfaces between particles are clear, with distinct edges and corners, and good dispersibility. Its activation degree is 99.5%.

[0073] Example 5

[0074] This embodiment provides an optical diffusion film with high light transmittance and high haze, the raw materials of which include, by mass percentage: 97% matrix material, 2% light diffusing agent, and 1% antioxidant; wherein, the matrix material is PET, the light diffusing agent is monodisperse calcium carbonate particles, and the antioxidant is antioxidant S-9228.

[0075] The method for preparing the high transmittance and high haze optical diffusion film described in this embodiment differs from that in Example 3 in that: the mass percentage of matrix material A is 0.5%, and the mass percentage of matrix material B is 96.5%; the mass percentage of antioxidant A is 0.1%, and the mass percentage of antioxidant B is 0.9%; the calcium carbonate filling rate in the filler masterbatch is approximately 80%.

[0076] The preparation method of the monodisperse calcium carbonate particle light diffusing agent described in this embodiment is the same as that in Example 3.

[0077] Comparative Example 1

[0078] The only difference between Comparative Example 1 and Example 1 is that no crystal remodeling agent was added during the preparation of the light diffusing agent; all other steps were the same as in Example 1. The microstructure of the prepared light diffusing agent is as follows: Figure 5 As shown, the particles have rough surfaces, aggregate in short columnar shapes, and have poor dispersibility.

[0079] Comparative Example 2

[0080] The only difference between Comparative Example 2 and Example 1 is that, in the preparation of the light diffusing agent, ultrasonic treatment was not performed after adding the crystal remodeling agent; all other steps were the same as in Example 1. The microstructure of the prepared light diffusing agent is as follows: Figure 6 As shown, the particles have smooth surfaces but are severely aggregated and have poor dispersibility.

[0081] Comparative Example 3

[0082] The only difference between Comparative Example 3 and Example 2 is that, in the preparation of the light diffusing agent, the grain surface remodeling agent is 0.5% sodium dodecylbenzenesulfonate and 2.0% sodium dodecyl sulfate by dry weight of calcium carbonate; all other steps are the same. The microstructure of the prepared light diffusing agent is as follows: Figure 7 As shown, the particle surface is rough, and the particles are irregularly aggregated, resulting in poor dispersibility.

[0083] Comparative Example 4

[0084] The only difference between Comparative Example 4 and Example 2 is that in the preparation of the light diffusing agent, the grain surface remodeling agent is 0.5% sodium silicate and 1.5% aluminum chloride by dry weight of calcium carbonate; all other steps are the same. The microstructure of the prepared light diffusing agent is as follows: Figure 8 As shown, the particle surface is smooth, but the particles are bonded together, forming short columnar and near-spherical particle aggregates with poor dispersibility.

[0085] Comparative Example 5

[0086] The only difference between Comparative Example 5 and Example 4 is that the surface modifier used in the preparation of the light diffusing agent is stearic acid saponification solution, which is commonly used in existing production technologies. The preparation steps of this stearic acid saponification solution are as follows: Sodium hydroxide (10% of the weight of stearic acid) and water (9 times the weight of stearic acid) are placed in a saponification tank, and the solution is stirred and heated to 75-80°C. After all the sodium hydroxide has completely dissolved and the solution temperature reaches the target value, commercially available stearic acid is added to the saponification tank, and the temperature is maintained at 75-80°C. The mixture is stirred until the saponification reaction is complete. The other steps of Comparative Example 5 are the same as those of Example 4.

[0087] The performance test results of the optical diffusion film products prepared in the above embodiments and comparative examples are shown in Table 1. The transmittance and haze were tested according to the national standard GB / T 2410-2008. This invention uses the haze meter method, and the instrument used is a BYK transmission haze meter, model AT4775.

[0088] Table 1 Performance Test Results

[0089]

[0090]

[0091] As shown in Table 1, pure PS, pure PET, and pure PC films, while possessing transmittance exceeding 90%, exhibit haze of less than 2%, meeting the basic characteristics of pure films. In contrast, the light diffusion film prepared in this invention boasts transmittance and haze exceeding 85%. The comparative example, due to the poor dispersibility and crystallinity of the calcium carbonate used, resulted in an uneven diffusion film with defects such as white spots, uneven dispersibility of the diffusing agent, and a whitish film appearance, thus exhibiting transmittance and haze far below 85%. This invention strictly controls the size and dispersibility of calcium carbonate crystals, as well as the interface between calcium carbonate and the matrix material, reducing reflection and thereby simultaneously achieving high transmittance and high haze.

[0092] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. An optical diffusion film with high light transmittance and low haze, characterized in that, The raw materials, by mass percentage, comprise: 88.5%~97.5% matrix material, 2%~10% light diffusing agent, and 0.5%~1.5% antioxidant; wherein the matrix material is one or more of polystyrene, polycarbonate, or polyethylene terephthalate; the light diffusing agent is monodisperse calcium carbonate particles with a grain size mainly concentrated in the range of 800~1200 nm, and the proportion exceeding this range is less than 10%; The method for preparing the monodisperse calcium carbonate particles includes the following steps: (1) Add inorganic crystal reconstruction agent and organic crystal reconstruction agent to calcium carbonate slurry with solid content of 20%~40%, and disperse and reconstruct it under ultrasonic conditions at 140~200℃ for 1.5~4 h to obtain monodisperse calcium carbonate suspension; (2) Cool the obtained monodisperse calcium carbonate suspension to 50~70℃, add surface modifier, keep warm and stir to obtain surface-modified calcium carbonate suspension; (3) The obtained surface-modified calcium carbonate suspension is dehydrated by pressure filtration to obtain calcium carbonate filter cake. The moisture content of the filter cake is controlled to not exceed 40%. (4) The obtained calcium carbonate filter cake is dried until the moisture content is less than 0.1% to obtain monodisperse calcium carbonate particles with an activation degree of more than 99%; The inorganic crystal form reconstructing agent is selected from one or more of sodium silicate, sodium chloride, aluminum chloride, and zinc sulfate; the organic crystal form reconstructing agent is selected from one or more of ethanol, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, and disodium ethylenediaminetetraacetate; and the surface modifier is a mixture of amphiphilic polystyrene-polyethylene glycol block copolymer and polyethylene glycol stearate or pentaerythritol stearate.

2. The optical diffusion film with high light transmittance and high haze according to claim 1, characterized in that, The polystyrene is optical grade with a number average molecular weight between 30,000 and 120,000; the polycarbonate is optical grade with a number average molecular weight between 10,000 and 20,000; the polyethylene terephthalate is film-grade PET with a number average molecular weight between 15,000 and 30,000; the antioxidant is selected from one or more of antioxidant 1010, antioxidant 168, antioxidant 626, and antioxidant S-9228.

3. The method for preparing an optical diffusion film with high transmittance and high haze as described in claim 1, characterized in that, Specifically, the steps include the following: (1) Weigh out 88.5%~97.5% of matrix material, 2%~10% of light diffusing agent, and 0.5%~1.5% of antioxidant by mass percentage; divide the 88.5%~97.5% matrix material into two parts A and B, with matrix material A being 0.5%~6.5% and matrix material B being 82%~97%; divide the 0.5%~1.5% antioxidant into two parts A and B, with antioxidant A being 0.05%~0.15% and antioxidant B being 0.45%~1.35%; wherein, the mass percentages of matrix material A, matrix material B, antioxidant A, and antioxidant B are all calculated based on their proportion in the total amount of raw materials; (2) The light diffusing agent, matrix material A, and antioxidant A are mixed and stirred at room temperature using a mixer, and then extruded and granulated using a twin-rotor continuous mixing extruder to obtain filler masterbatch; wherein the mass percentage of calcium carbonate in the filler masterbatch is 60%~80%; (3) The filler masterbatch, matrix material B and antioxidant B are stirred and mixed evenly at room temperature using a mixer, and then cast into a film / sheet or extruded into a film / sheet; the cast or extruded film / sheet is cut to obtain an optical diffusion film with high light transmittance and high haze.

4. The method for preparing an optical diffusion film with high transmittance and high haze according to claim 3, characterized in that, In step (2), the extrusion temperature is in the range of 175~250℃, and the screw speed is adjusted between 300~700 rpm according to the material state; the filler masterbatch is short rod-shaped with a diameter of 2~3 mm and a length of 1~3 mm.

5. The method for preparing an optical diffusion film with high transmittance and high haze according to claim 4, characterized in that, When the matrix material is polystyrene, the extrusion temperature is set at 175~180℃; when the matrix material is polycarbonate, the extrusion temperature is set at 245~250℃; when the matrix material is polyethylene terephthalate, the extrusion temperature is set at 235~240℃.

6. The method for preparing an optical diffusion film with high transmittance and high haze according to claim 3, characterized in that, In step (3), when the matrix material is polystyrene, the casting or extrusion temperature is set at 190~240℃; when the matrix material is polycarbonate, the casting or extrusion temperature is set at 250~280℃; when the matrix material is polyethylene terephthalate, the casting or extrusion temperature is set at 240~270℃; and the film / sheet thickness is between 0.1~3 mm.

7. The method for preparing an optical diffusion film with high transmittance and high haze according to claim 3, characterized in that, The monodisperse calcium carbonate particles have a crystal size mainly concentrated in the range of 800~1200 nm, with particles outside this range accounting for less than 10%, particles larger than 1.5 µm accounting for less than 2%, and the crystals are well crystallized.

8. The method for preparing an optical diffusion film with high transmittance and high haze according to claim 3, characterized in that, The method for preparing the monodisperse calcium carbonate particles includes the following steps: S1. Calcium carbonate slurry is prepared using a calcination, digestion, and carbonation process. The calcination process involves selecting limestone with uniform grain size as raw material and calcining it to obtain quicklime. The digestion process involves digesting the quicklime with hot water at 80-90℃ and aging it to obtain lime slurry. The carbonation process involves adjusting the solid content of the lime slurry to 5%-15%, then introducing carbon dioxide for carbonation. The initial carbonation temperature is 45-70℃, the CO2 content is 20%-40%, and carbonation continues until the slurry pH reaches 8.0-10.0, at which point carbonation is terminated to obtain calcium carbonate slurry. S2. After the calcium carbonate slurry obtained in S1 is allowed to stand, the supernatant is removed to achieve thickening, resulting in a calcium carbonate slurry with a solid content of 20% to 40%. S3. Add the calcium carbonate slurry obtained in S2 to the inorganic and organic crystal form remodeling agents, and then react the mixture at a power density of 100~300 W / 1000cm³. 3 Dispersion and reconstruction were carried out under ultrasonic conditions at 140~200℃ for 1.5~4 h to obtain monodisperse calcium carbonate suspension; S4. Cool the monodisperse calcium carbonate suspension obtained in S3 to 50~70℃, add a surface modifier, keep warm and stir to obtain a surface-modified calcium carbonate suspension; S5. The surface-modified calcium carbonate suspension obtained in S4 is dehydrated by pressure filtration to obtain a calcium carbonate filter cake. The moisture content of the filter cake is controlled to not exceed 40%. S6. The calcium carbonate filter cake obtained in S5 is dried until the moisture content is less than 0.1%, resulting in monodisperse calcium carbonate particles with an activation degree higher than 99%.

9. The method for preparing an optical diffusion film with high transmittance and high haze according to claim 8, characterized in that, The total amount of the inorganic crystal form remodeling agent and the organic crystal form remodeling agent is 0.5% to 5% of the dry weight of calcium carbonate.

10. The method for preparing an optical diffusion film with high transmittance and high haze according to claim 3, characterized in that, The amount of the surface modifier is 2% to 5% of the dry weight of calcium carbonate; when the matrix material is polystyrene, the surface modifier is composed of amphiphilic polystyrene-polyethylene glycol block copolymer and polyethylene glycol stearate in a mass ratio of 1:1 to 1:2; when the matrix material is polycarbonate, the surface modifier is composed of amphiphilic polystyrene-polyethylene glycol block copolymer and pentaerythritol stearate in a mass ratio of 1:2 to 1:4; when the matrix material is polyethylene terephthalate, the surface modifier is composed of amphiphilic polystyrene-polyethylene glycol block copolymer and pentaerythritol stearate in a mass ratio of 1:4 to 1:6.

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