A high heat-resistant foamed light diffusion sheet, its preparation method and application

Abstract

This invention relates to a high heat-resistant foamed light-diffusing sheet material, comprising a GPPS foamed diffusion layer and protective layers located on the upper and lower surfaces of the GPPS foamed diffusion layer. The GPPS foamed diffusion layer is prepared from the following components in parts by weight: 97-99 parts GPPS resin, 0.5-2 parts foaming agent masterbatch, and 0.2-1 parts light-diffusing agent. The protective layer is prepared from the following components in parts by weight: 80-95 parts GPPS resin, 5-20 parts fumaric anhydride chemically grafted PPO, and 0.02-1 parts weather-resistant agent. The protective layer of this invention uses GPPS resin as the base material, which has good adhesion to the GPPS foaming diffusion layer. At the same time, fumaric anhydride chemically grafted PPO is introduced. The heat distortion temperature of fumaric anhydride chemically grafted PPO is as high as 150°C. The introduction of fumaric anhydride chemically grafted PPO significantly improves the heat distortion temperature of the protective layer, which can greatly improve the heat resistance of the GPPS protective layer. Moreover, fumaric anhydride chemically grafted PPO has good compatibility with GPPS resin and is basically miscible, which significantly improves the adhesion between the protective layer and the GPPS foaming diffusion layer.

Description

Technical Field

[0001] This invention relates to the field of light diffusion materials technology, and in particular to a high heat-resistant foamed light diffusion sheet, its preparation method, and its application. Background Technology

[0002] Light-diffusing materials are materials that allow light to pass through while effectively diffusing it. They can transform point or line light sources into line or surface light sources, exhibiting a large scattering angle, good light guiding properties, and uniform light transmission. Therefore, they are widely used in liquid crystal displays, LED lighting, and imaging display systems. Their main function is to fully scatter incident light, achieving a softer and more uniform illumination effect. Light-diffusing materials are generally made with a transparent resin matrix, by adding a certain proportion of light-diffusing agents and other additives. Commonly used transparent substrates include polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (GPPS), and polypropylene (PP).

[0003] Currently, PMMA or GPPS diffuser plates are the most commonly used light diffusion materials in the LCD display field. From a cost perspective, GPPS material is the most economical and practical choice. With product upgrades, higher performance requirements are placed on GPPS light diffusion plates. For example, to meet the requirements of portability and lightweight design, foaming technology can achieve a lightweight effect. However, after foaming, the material has defects such as poor aging resistance and unstable transmittance and haze. Although this can be improved by adding light diffusing agents, the improvement effect is limited. Furthermore, GPPS material has poor light uniformity, and adding excessive light diffusing agents significantly affects the material's transmittance. Additionally, GPPS material itself has poor heat resistance, posing a risk to products used for extended periods. Although a protective layer can be laminated to both the top and bottom surfaces of the GPPS light diffusion plate, the adhesion strength between the foamed light diffusion plate substrate and the protective layer will decrease. Furthermore, in current GPPS light diffusion sheet production, the foaming agent is directly added to the extruder. The extruder temperature is typically unstable. If the extruder screw temperature is high, the temperature at which most of the foaming agent decomposes and produces gas is below the extrusion temperature. Therefore, in most cases, gas is generated before the foaming agent is fully dispersed, leading to excessive localized bubbles, melt rupture, uneven cell diameter distribution, fewer cells, and brittleness in the foamed sheet. It can also cause the sheet to yellow. Conversely, if the extruder screw temperature is too low, insufficient melt plasticization will also result in bubble rupture, and the foaming efficiency of the foaming agent will decrease. Therefore, it is necessary to develop a high-heat-resistant foamed light diffusion sheet that meets heat resistance requirements without affecting the existing GPPS light diffusion sheet system. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a high heat-resistant foamed light diffusion board, its preparation method, and its application. The GPPS foamed diffusion layer of this high heat-resistant foamed light diffusion board utilizes a pre-formulated masterbatch method for the foaming agent, solving the problems of uneven foaming caused by the low melt strength of GPPS resin and the accumulation of bubbles at the interface between layers due to melt extrusion. The protective layer uses GPPS resin as the substrate, exhibiting good adhesion to the GPPS foamed diffusion layer. Simultaneously, fumaric anhydride-grafted PPO is introduced. Fumaric anhydride-grafted PPO has a high heat distortion temperature of up to 150℃ and good compatibility with GPPS resin. The introduction of fumaric anhydride-grafted PPO significantly improves the heat resistance of the GPPS protective layer and has little impact on transmittance even with a significant increase in material haze.

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

[0006] The present invention provides a high heat-resistant foamed light-diffusing sheet material, which includes a GPPS foamed diffusion layer and a protective layer located on the upper and lower surfaces of the GPPS foamed diffusion layer. The GPPS foamed diffusion layer is prepared from the following components in parts by weight: 97-99 parts GPPS resin, 0.5-2 parts foaming agent masterbatch, and 0.2-1 parts light-diffusing agent.

[0007] The protective layer is prepared from the following components in parts by weight: 80-95 parts GPPS resin, 5-20 parts fumaric anhydride chemically grafted PPO, and 0.02-1 parts weathering agent.

[0008] The GPPS foaming diffusion layer of this invention uses a pre-made foaming agent masterbatch method. The foaming agent masterbatch is mixed with resin and added to an extruder. The foaming agent masterbatch gradually generates bubbles in the resin, resulting in uniform foaming, stable melt strength, and a sheet with small pore size distribution, uniform dispersion, and good toughness. It also avoids decomposition and yellowing due to localized overheating, solving the problems of uneven foaming caused by low GPPS resin melt strength and bubble accumulation at the interface between layers due to melt extrusion. The protective layer of this invention uses GPPS resin as the base material, exhibiting good adhesion to the GPPS foaming diffusion layer. Simultaneously, fumaric anhydride is chemically grafted onto PPO. The heat distortion temperature of chemically grafted PPO with fumaric anhydride is as high as 150℃. The introduction of chemically grafted PPO with fumaric anhydride significantly increases the heat distortion temperature of the protective layer, which can greatly improve the heat resistance of the GPPS protective layer. Moreover, chemically grafted PPO with fumaric anhydride has good compatibility with GPPS resin and is basically miscible, which significantly improves the adhesion between the protective layer and the GPPS foamed diffusion layer. The protective layer of this invention is mainly composed of GPPS resin and chemically grafted PPO with fumaric anhydride. The protective layer formed after the two are blended has little impact on the transmittance of the GPPS foamed diffusion layer, and can also significantly improve the haze of the material, which is beneficial to the overall uniformity of the light diffusion plate.

[0009] As a further improvement to the above-described scheme of the present invention, the refractive index of the GPPS resin is 1.58-1.60, and the refractive index of the fumaric anhydride chemically grafted PPO is 1.57-1.59. The refractive indices of the GPPS resin and the fumaric anhydride chemically grafted PPO are similar, resulting in a smaller impact of the prepared protective layer on the material's transparency.

[0010] As a further improvement to the above-described scheme of the present invention, the melt flow rate of the GPPS resin at 200°C and 5kg is ≤6g / 10min. Since the foaming agent is pre-formulated as a masterbatch, the selection of GPPS resin is advantageous. More preferably, the melt flow rate of the GPPS resin at 200°C and 5kg is ≤3g / 10min. A lower melt flow rate implies higher melt strength, better ensuring the uniformity of foaming. More preferably, the heat distortion temperature of the GPPS resin exceeds 90°C at 0.45MPa.

[0011] As a further improvement to the above-described scheme of the present invention, both the GPPS foamed diffusion layer and the protective layer further include the following components in parts by weight: 0-0.5 parts of other additives; the remaining additives include lubricants and antioxidants. Preferably, the lubricant is at least one of stearate, PE wax, polysiloxane, and ethylene bis-fatty acid amide, and the antioxidant is a high-temperature resistant and hydrolysis-resistant phosphite antioxidant. More preferably, the lubricant is a stearate lubricant or ethylene bis-fatty acid amide with a high decomposition temperature, which has less impact on the permeability of GPPS resin, reduces the shearing of materials inside the screw, and provides a good dispersion effect for the light diffusing agent.

[0012] As a further improvement to the above-described solution of the present invention, the foaming agent masterbatch is prepared from the following components in parts by weight: 80-90 parts foaming agent, 10-20 parts dispersant, and 0.1 parts antioxidant. Preferably, in the foaming agent masterbatch, the dispersant is a fatty acid polyethylene glycol ester with a melting point of 66°C, and the antioxidant is a high-temperature resistant and hydrolyzable phosphite antioxidant.

[0013] As a further improvement to the above-mentioned solution of the present invention, the preparation process of the foaming agent masterbatch is as follows: foaming agent, dispersant, and antioxidant are added to a mixer in proportion and melt-mixed, and then granulated by an extruder to obtain the foaming agent masterbatch. Preferably, the mixing temperature is 80°C and the extrusion temperature after melt mixing in the mixer is 100-120°C; this allows the dispersant to melt and play a role in dispersing and carrying the foaming agent, while preventing the foaming agent from melting and decomposing, thus preventing premature action of the foaming agent and reducing the foaming effect.

[0014] And / or, the light diffusing agent is at least one of nano-barium sulfate, organosilicon, and silica. Preferably, the particle size of the light diffusing agent is 0.1-5 μm. More preferably, the light diffusing agent in the GPPS foamed diffusion layer is 0.3-0.5 parts by weight. Lower particle size of the light diffusing agent results in better diffusion, but has a greater impact on the light transmittance of the board; larger particle size reduces the light diffusing effect. Since the introduction of fumaric anhydride chemical grafting of PPO in this invention increases the haze of the material to some extent, and the haze also increases after foaming, a light diffusing agent with a smaller particle size can be selected, and the amount added can be appropriately reduced.

[0015] As a further improvement to the above-described solution of the present invention, the foaming agent is at least one selected from azo foaming agents, sulfonyl hydrazine foaming agents, nitrosyl foaming agents, and bicarbonate foaming agents. Preferably, the foaming agent is an azo foaming agent with a decomposition temperature of 180℃-220℃, which matches the processing temperature of GPPS and can increase foaming efficiency and foaming uniformity.

[0016] As a further improvement to the above-described scheme of the present invention, the weathering agent comprises a hindered amine light stabilizer and / or a UV absorber. Preferably, the weathering agent comprises a hindered amine light stabilizer and a UV absorber, wherein the ratio of the hindered amine light stabilizer to the UV absorber is 1:(0.5-1.5). More preferably, the ratio of the hindered amine light stabilizer to the UV absorber is 1:1.

[0017] As a further improvement to the above-described scheme of the present invention, the hindered amine light stabilizer includes, but is not limited to, one or a combination of two of HALS944 and HALS770. Preferably, the ultraviolet absorber is a benzotriazole light stabilizer, which includes, but is not limited to, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and / or 2-(2'-hydroxy-3',5'-bis(a,a-dimethylbenzyl)phenyl)benzotriazole.

[0018] As a further improvement to the above-mentioned solution of the present invention, the weather-resistant agent in the GPPS foam diffusion layer is 0.06 parts by weight.

[0019] As a further improvement to the above-mentioned solution of the present invention, the thickness ratio of the GPPS foam diffusion layer to the protective layer is 1:0.10-0.30.

[0020] This invention proposes a method for preparing a high heat-resistant foamed light-diffusing sheet material as described above, characterized by the following steps: The raw materials of each component of the GPPS foamed diffusion layer and the raw materials of each component of the protective layer are mixed evenly in proportion, and then added to a co-extrusion extruder through different feed ports. After melt extrusion, the high heat-resistant foamed light-diffusing sheet material is obtained. The extruder is a single-screw extruder or a twin-screw extruder, the extruder temperature is 180-220℃, and the screw speed is 200-500 rpm.

[0021] This invention proposes the application of a high heat-resistant foamed light-diffusing sheet material as described above in a backlight display device.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The GPPS foam diffusion layer of the present invention uses a pre-made foaming agent masterbatch. The foaming agent masterbatch is mixed with resin and then added to an extruder. The foaming agent masterbatch gradually generates bubbles in the resin, resulting in uniform foaming and stable melt strength. The manufactured board has a small pore size distribution, uniform dispersion, and good toughness. It will not decompose and turn yellow due to excessively high local temperature. This solves the problems of uneven foaming caused by low melt strength of GPPS resin and the accumulation of bubbles at the interface between layers due to melt extrusion.

[0024] 2. The protective layer of this invention uses GPPS resin as the base material, which has good adhesion to the GPPS foamed diffusion layer. Simultaneously, fumaric anhydride-grafted PPO is introduced. The heat distortion temperature of fumaric anhydride-grafted PPO is as high as 150℃. The introduction of fumaric anhydride-grafted PPO significantly increases the heat distortion temperature of the protective layer, greatly improving the heat resistance of the GPPS protective layer. Furthermore, fumaric anhydride-grafted PPO and GPPS resin have good compatibility and are essentially miscible, significantly improving the adhesion between the protective layer and the GPPS foamed diffusion layer. The protective layer of this invention is mainly composed of GPPS resin and fumaric anhydride-grafted PPO. The protective layer formed after the two are blended has little impact on the transmittance of the GPPS foamed diffusion layer and can also significantly improve the haze of the material, reducing the use of light diffusing agents and contributing to the overall uniformity of the light diffusion plate.

[0025] 3. The light diffusion plate material of the present invention has a light transmittance of more than 40% and a haze of more than 90%. Both the GPPS foam diffusion layer and the protective layer use GPPS resin as the matrix, which has good adhesion. Furthermore, it solves the problems of poor heat resistance and short life of traditional GPPS light diffusion plates while controlling costs. Detailed Implementation

[0026] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0028] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0029] (1) GPPS resin

[0030] GPPS1#: INEOS Styron's GPPS1050 has a melt flow rate of 2.8 g / 10 min at 200°C and a 5 kg load.

[0031] GPPS2#: INEOS Styron's GPPS1600 has a melt flow rate of 6 g / 10 min at 200°C and a 5 kg load.

[0032] (2) The grade of chemically grafted PPO with fumaric anhydride is CS-1, produced by Cosmax Chemical, with a heat distortion temperature of 150℃ (0.45MPa).

[0033] (3) Foaming agent

[0034] Foaming agent #1: Azodicarbonamide, Aladdin, decomposition temperature 200℃.

[0035] Foaming agent #2: Benzenesulfonyl hydrazine, Aladdin, decomposition temperature 100℃.

[0036] (4) Light diffusing agent

[0037] Nano silica HDK H2000, Wacker Chemie, Germany, 40μm.

[0038] Organosilicon light diffusing agent DF20A0, Changxing Chemical, 2μm.

[0039] (5) Weather resistant agent: HALS770, Sunosun, Xinxiu Chemical.

[0040] (6) Ultraviolet absorber UV-P, brand name RIASORB, manufactured by RIASORB.

[0041] (7) Antioxidant: Daohua 9228, commercially available.

[0042] (8) Lubricant: PETS AP, Italian brand.

[0043] (9) Dispersant: Polyethylene glycol fatty acid ester, commercially available.

[0044] (10) Antioxidants: Phosphite antioxidants, commercially available.

[0045] It should be noted that the light stabilizers, antioxidants, lubricants, and other additives used in the various embodiments and comparative examples of this invention are the same.

[0046] Unless otherwise specified, the reagents and equipment used in this invention are conventional reagents and equipment in this technical field.

[0047] Example 1

[0048] This embodiment provides a high heat-resistant foamed light diffusion sheet, which includes a GPPS foamed diffusion layer and protective layers located on the upper and lower surfaces of the GPPS foamed diffusion layer. In this embodiment, the thickness of the GPPS foamed diffusion layer is 1.2 mm, and the thickness of the two protective layers is the same, both being 0.15 mm. The thickness ratio of the GPPS foamed diffusion layer to the protective layers is 1:0.125.

[0049] In this embodiment, the GPPS foam diffusion layer comprises the following components in parts by weight: 99 parts GPPS1#, 0.5 parts foaming agent masterbatch, 0.3 parts light diffusing agent1#, 0.2 parts antioxidant, and 0.3 parts lubricant. The foaming agent masterbatch comprises the following components in parts by weight: 80 parts foaming agent1#, 20 parts fatty acid polyethylene glycol ester, and 0.1 parts phosphite antioxidant.

[0050] In this embodiment, the protective layer comprises the following components in parts by weight: 90 parts GPPS1#, 10 parts fumaric anhydride chemically grafted PPO, 0.03 parts HALS770, 0.03 parts UV absorber UV-P, 0.2 parts antioxidant, and 0.3 parts lubricant.

[0051] The preparation method of a high heat-resistant foamed light diffusion board in this embodiment includes the following steps:

[0052] Preparation of foaming agent masterbatch: Add the raw materials of each component of the foaming agent masterbatch into a mixer in proportion and melt-mix them. The mixing temperature is 80℃ and the temperature of the extrusion after melting and blending from the mixer is 100-120℃. Then, granulate the mixture through an extruder to obtain carrier-free foaming agent masterbatch.

[0053] Preparation of high heat-resistant foamed light diffusion board: The raw materials of each component of GPPS foamed diffusion layer and the raw materials of each component of protective layer are mixed evenly by high speed according to the proportion. Then, they are added into the co-extrusion extruder through different feeding ports. After melt extrusion, the high heat-resistant foamed light diffusion board is obtained. After the board is extruded, it can pass through rollers to obtain the predetermined texture on the upper and lower protective layers.

[0054] In this embodiment, the extruder is a single-screw extruder or a twin-screw extruder, the extruder temperature is 180-220℃, and the screw speed is 200-500rpm.

[0055] Example 2

[0056] This embodiment proposes a high heat-resistant foamed light diffusion plate and its preparation method, which adopts the same implementation method as Example 1. The difference from Example 1 is that in this embodiment, the weight of the foaming agent masterbatch in the GPPS foamed diffusion layer is 1 part.

[0057] Example 3

[0058] This embodiment proposes a high heat-resistant foamed light diffusion plate and its preparation method, which adopts the same implementation method as Example 1. The difference from Example 1 is that in this embodiment, the weight of the foaming agent masterbatch in the GPPS foamed diffusion layer is 1.5 parts.

[0059] Example 4

[0060] This embodiment proposes a high heat-resistant foamed light diffusion plate and its preparation method, which adopts the same implementation method as Example 1. The difference from Example 1 is that in this embodiment, the weight of the foaming agent masterbatch in the GPPS foamed diffusion layer is 2 parts.

[0061] Example 5

[0062] This embodiment proposes a high heat-resistant foamed light diffusion plate and its preparation method. It adopts the same implementation method as Example 1. The difference from Example 1 is that in this embodiment, light diffusion agent 2# is used instead of light diffusion agent 1# in the GPPS foamed diffusion layer.

[0063] Example 6

[0064] This embodiment proposes a high heat-resistant foamed light diffusion plate and its preparation method, which adopts the same implementation method as Example 1. The difference from Example 1 is that in this embodiment, the weight of light diffusion agent 1# in the GPPS foamed diffusion layer is 0.2 parts.

[0065] Example 7

[0066] This embodiment proposes a high heat-resistant foamed light diffusion plate and its preparation method. It adopts the same implementation method as Example 1. The difference from Example 1 is that in this embodiment, the weight of light diffusing agent 1# in the GPPS foamed diffusion layer is 1 part.

[0067] Example 8

[0068] This embodiment proposes a high heat-resistant foamed light diffusion plate and its preparation method. It adopts the same implementation method as Example 1. The difference from Example 1 is that in this embodiment, the weight of the foaming agent masterbatch in the GPPS foamed diffusion layer is 1 part, and foaming agent 2# is used to replace foaming agent 1# in the foaming agent masterbatch.

[0069] Example 9

[0070] This embodiment proposes a high heat-resistant foamed light diffusion plate and its preparation method. It adopts the same implementation method as Example 1. The difference from Example 1 is that in this embodiment, GPPS2# is used instead of GPPS1# in the GPPS foam diffusion layer and the foam layer.

[0071] Example 10

[0072] This embodiment proposes a high heat-resistant foamed light diffusion plate and its preparation method. It adopts the same implementation method as Example 1. The difference from Example 1 is that in this embodiment, the weight parts of GPPS 1# in the protective layer are 95 parts and the weight parts of fumaric anhydride chemically grafted PPO are 5 parts.

[0073] Example 11

[0074] This embodiment proposes a high heat-resistant foamed light diffusion plate and its preparation method. It adopts the same implementation method as Example 1. The difference from Example 1 is that in this embodiment, the weight parts of GPPS 1# in the protective layer are 80 parts and the weight parts of fumaric anhydride chemically grafted PPO are 20 parts.

[0075] Example 12

[0076] This embodiment proposes a high heat-resistant foamed light diffusion sheet and its preparation method. It adopts the same implementation method as Embodiment 1. The difference from Embodiment 1 is that in this embodiment, the thickness of the GPPS foamed diffusion layer is 1 mm, the thickness of the two protective layers is the same and both are 0.25 mm, and the thickness ratio of the GPPS foamed diffusion layer to the protective layer is 1:0.25.

[0077] Example 13

[0078] This embodiment proposes a high heat-resistant foamed light diffusion plate and its preparation method, which adopts the same implementation method as Example 1. The difference from Example 1 is that in this embodiment, the weight parts of HALS770 and UV-P in the protective layer are 0.01 parts.

[0079] Example 14

[0080] This embodiment proposes a high heat-resistant foamed light diffusion plate and its preparation method, which adopts the same implementation method as Example 1. The difference from Example 1 is that in this embodiment, the weight parts of HALS770 and UV-P in the protective layer are 0.5 parts.

[0081] Comparative Example 1

[0082] This comparative example presents a foamed light diffusion sheet, which includes a GPPS foamed diffusion layer and protective layers located on the upper and lower surfaces of the GPPS foamed diffusion layer. In this comparative example, the thickness of the GPPS foamed diffusion layer is 1.2 mm, and the two protective layers are of the same thickness, both being 0.15 mm. The thickness ratio of the GPPS foamed diffusion layer to the protective layers is 1:0.125.

[0083] In this comparative example, the GPPS foam diffusion layer comprises the following components by weight: 99 parts GPPS1#, 0.01 parts foaming agent masterbatch, 0.3 parts light diffusing agent1#, 0.2 parts antioxidant, and 0.3 parts lubricant.

[0084] The foaming agent masterbatch includes the following components by weight: 80 parts foaming agent 1#, 20 parts fatty acid polyethylene glycol ester, and 0.1 parts phosphite antioxidant.

[0085] In this comparative example, the protective layer comprises the following components by weight: 90 parts GPPS1#, 10 parts fumaric anhydride chemically grafted PPO, 0.03 parts HALS770, 0.03 parts UV absorber UV-P, 0.2 parts antioxidant, and 0.3 parts lubricant.

[0086] The preparation method of the foamed light diffusion board of this comparative example includes the following steps: the raw materials of each component of the GPPS foamed diffusion layer and the raw materials of each component of the protective layer are mixed evenly by high speed according to the proportion, and then added into the co-extrusion extruder from different feeding ports. After melt extrusion, the high heat-resistant foamed light diffusion board is obtained. After the board is extruded, it can pass through rollers to obtain the predetermined texture on the upper and lower protective layers.

[0087] In this embodiment, the extruder is a single-screw extruder or a twin-screw extruder, the extruder temperature is 180-220℃, and the screw speed is 200-500rpm.

[0088] Comparative Example 2

[0089] This comparative example presents a foamed light diffusion plate and its preparation method, which adopts the same implementation method as Comparative Example 1. The difference from Comparative Example 1 is that in this comparative example, the weight of the foaming agent masterbatch in the GPPS foamed diffusion layer is 6 parts.

[0090] Comparative Example 3

[0091] This comparative example presents a foamed light diffusion plate and its preparation method, which adopts the same implementation method as Comparative Example 1. The difference from Comparative Example 1 is that in this comparative example, the weight parts of the foaming agent masterbatch in the GPPS foamed diffusion layer are 0.5 parts and the weight parts of the light diffusion agent 1# are 2 parts.

[0092] Comparative Example 4

[0093] This comparative example presents a foamed light diffusion plate and its preparation method, which adopts the same implementation method as Comparative Example 1. The difference from Comparative Example 1 is that in this comparative example, the weight of the foaming agent masterbatch in the GPPS foam diffusion layer is 0.5 parts; in the protective layer, the weight of GPPS1# is 100 parts and no fumaric anhydride chemically grafted PPO is added.

[0094] Comparative Example 5

[0095] This comparative example presents a foamed light diffusion plate and its preparation method, which adopts the same implementation method as Comparative Example 1. The difference from Comparative Example 1 is that in this comparative example, the weight of the foaming agent masterbatch in the GPPS foam diffusion layer is 0.5 parts; in the protective layer, the weight of GPPS1# is 60 parts, and the weight of fumaric anhydride chemically grafted PPO is 40 parts.

[0096] Comparative Example 6

[0097] This comparative example presents a foamed light diffusion sheet and its preparation method, which adopts the same implementation method as Comparative Example 1. The difference from Comparative Example 1 is that: in this comparative example, the thickness of the GPPS foamed diffusion layer is 0.7 mm, the thickness of the protective layer is 0.4 mm, the thickness ratio of the GPPS foamed diffusion layer to the protective layer is 1:0.57; and in the GPPS foamed diffusion layer, the weight part of the foaming agent masterbatch is 0.5 parts.

[0098] Comparative Example 7

[0099] This comparative example presents a foamed light diffusion sheet and its preparation method, which adopts the same implementation method as Comparative Example 1. The difference from Comparative Example 1 is that: in this comparative example, the thickness of the GPPS foamed diffusion layer is 0.7 mm, the thickness of the protective layer is 0.4 mm, and the thickness ratio of the GPPS foamed diffusion layer to the protective layer is 1:0.57; and in the GPPS foamed diffusion layer, the weight part of foaming agent 1# is 0.4 parts, and it is not pre-prepared into masterbatch, but directly mixed with GPPS resin and added to the extruder for extrusion.

[0100] Test case

[0101] The light diffusion plates prepared in Examples 1-14 and Comparative Examples 1-7 were tested for light transmittance, haze, heat distortion temperature, light aging resistance, and density. The test results are shown in Table 1. The test methods are as follows:

[0102] Transmittance and haze testing: Transmittance and haze were tested according to GB2410-80 standard using Shenguang WGT-S transmittance and haze meter.

[0103] Heat distortion temperature: The Vicat softening temperature was obtained by testing with Instron HV6X HDT & Vicat according to GB / T 1633 test standard, with a heating rate of 120℃ / h.

[0104] Light aging resistance: Tested according to ISO 4892.2 standard: 0.51W / m2, including 102min drying, 18min spraying, continuous irradiation for 10 cycles, for a total of 200 hours;

[0105] Density: The density of the sample was determined in accordance with ISO 1183 standard.

[0106] Table 1

[0107]

[0108] According to the test results in Table 1, Examples 1-14 of the present invention all have good light transmittance and haze, significantly improved heat resistance, and low material density and good weather resistance.

[0109] As can be seen from Examples 1-4, the addition of foaming agent masterbatch within the range can reduce the density of foamed boards, and the boards are relatively stable with good permeability and haze, and the boards do not yellow.

[0110] As can be seen from the comparison of Examples 1-14 and Comparative Example 1, if the foaming agent content is too low, the foaming efficiency will be reduced, which will easily result in fewer foamed pores, leading to a decrease in both the haze and transparency of the material.

[0111] As can be seen from Comparative Example 2, excessive foaming agent content can also cause the foaming agent to be difficult to disperse, resulting in uneven foaming and affecting the transmittance and haze of the light diffusion plate.

[0112] As can be seen from Examples 5-7 and Comparative Example 3, adding too much light diffusing agent will make it difficult to disperse light and increase haze, which will seriously affect the light transmittance of the board.

[0113] As can be seen from Examples 1-14 and Comparative Example 4, the introduction of fumaric anhydride chemically grafted PPO can significantly improve the heat distortion temperature of the material and solve the problem of low heat resistance and easy deformation of GPPS light diffusion plates.

[0114] As can be seen from Examples 9-11 and Comparative Example 5, when the content of PPO chemically grafted with fumaric anhydride is too high, the heat distortion temperature of the material is high, but it has a significant impact on the transparency.

[0115] As can be seen from Examples 1-14 and Comparative Example 6, the higher the thickness of the GPPS heat-resistant protective layer, the lower the thickness of the foam diffusion layer, the heavier the overall weight of the board, and the permeability of the board will also be affected.

[0116] As can be seen from Examples 1-14 and Comparative Example 7, if the foaming method of directly adding foaming agent is used, the extruded board has low transparency and the material is prone to yellowing. Due to uneven foaming, the pores are prone to breakage, and the density of the board is also too high.

[0117] It should be noted that when a component is said to be "installed on" another component, it can be directly on the other component or it may be in a component that is centered on it. When a component is said to be "set on" another component, it can be directly set on the other component or it may also be in a component that is centered on it. When a component is said to be "fixed to" another component, it can be directly fixed to the other component or it may also be in a component that is centered on it.

[0118] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0119] 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.

[0120] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, 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. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A high heat-resistant foamed light-diffusing sheet material, comprising a GPPS foamed diffusion layer and protective layers located on the upper and lower surfaces of the GPPS foamed diffusion layer, characterized in that, The GPPS foamed diffusion layer is prepared from the following components in parts by weight: 97-99 parts GPPS resin, 0.5-2 parts foaming agent masterbatch, and 0.2-1 parts light diffusing agent. The protective layer is prepared from the following components in parts by weight: 80-95 parts GPPS resin, 5-20 parts fumaric anhydride chemically grafted PPO, and 0.02-1 parts weathering agent. The GPPS resin has a melt flow rate ≤6g / 10min at 200℃ and 5kg; the GPPS resin has a refractive index of 1.58-1.60, and the fumaric anhydride-grafted PPO has a refractive index of 1.57-1.59; the foaming agent masterbatch is prepared from the following components in parts by weight: 80-90 parts foaming agent, 10-20 parts dispersant, and 0.1 parts antioxidant; the preparation process of the foaming agent masterbatch is as follows: the foaming agent, dispersant, and antioxidant are added to a mixer in proportion and melt-mixed, and then granulated by an extruder to obtain the foaming agent masterbatch; the light diffusing agent is at least one of nano barium sulfate, organosilicon, and silicon dioxide.

2. The high heat-resistant foamed light-diffusing sheet material according to claim 1, characterized in that, Both the GPPS foam diffusion layer and the protective layer further include the following components in parts by weight: 0-0.5 parts of other additives; the other additives include lubricants and antioxidants.

3. The high heat-resistant foamed light-diffusing sheet material according to claim 1, characterized in that, The foaming agent is at least one of azo foaming agents, sulfonyl hydrazine foaming agents, nitroso foaming agents, and bicarbonate foaming agents.

4. The high heat-resistant foamed light-diffusing sheet material according to claim 1, characterized in that, The weathering agent includes hindered amine light stabilizers and / or ultraviolet absorbers.

5. The high heat-resistant foamed light-diffusing sheet material according to claim 1, characterized in that, The thickness ratio of the GPPS foam diffusion layer to the protective layer is 1:0.10-0.

30.

6. A method for preparing a high heat-resistant foamed light-diffusing sheet material as described in any one of claims 1-5, characterized in that, Includes the following steps: After the raw materials of each component of the GPPS foamed diffusion layer and the raw materials of each component of the protective layer are mixed evenly in proportion, they are added into the co-extrusion extruder through different feeding ports. After melt extrusion, the high heat-resistant foamed light diffusion board is obtained.

7. The application of a high heat-resistant foamed light-diffusing sheet material as described in any one of claims 1-5 in a backlight display device.

Images