Lightweight structure of light diffusion plate and preparation method thereof

Abstract

The application discloses a light diffusion plate foaming light-weight structure and a preparation method thereof. The structure comprises upper surface layer, first foaming layer, second foaming layer and lower surface layer connected in sequence. The thickness of the first foaming layer is less than that of the second foaming layer, and the average cell diameter of the first foaming layer is less than that of the second foaming layer. The application adopts the combination of the first foaming layer with small cell diameter and thin thickness and the second foaming layer with large cell diameter and thick thickness, improves the structure of the foaming light diffusion plate, and makes the density of the foaming light diffusion plate as low as 0.3 g / cm 3 , which is 50% lower than 0.85 g / cm 3 of the prior art, and the cost is significantly reduced, so that the application has obvious advantages in market competition. The average density, light transmittance and haze of the light diffusion plate can be regulated by adjusting the thickness or the average cell diameter of the first foaming layer and the second foaming layer.

Description

Technical Field

[0001] This invention belongs to the field of light diffusion plate technology, specifically relating to a lightweight foamed light diffusion plate structure and its preparation method. Background Technology

[0002] A light diffuser plate utilizes chemical or physical methods to alter the path of light when it encounters two media with different refractive indices (densities). This is achieved by adding inorganic or organic light diffusers to substrates such as PMMA, PC, PS, PP, and HIPS, or by artificially adjusting the arrangement of micro-structures on the substrate surface to cause light to refract, reflect, and scatter in different directions. This alters the light's path, resulting in sufficient scattering of incident light and creating an optical diffusion effect. Light diffusers are widely used in LCD displays, LED lighting, and imaging systems. Their primary function is to fully scatter incident light, achieving a softer and more uniform illumination effect.

[0003] Currently disclosed patents and technologies for foamed light diffuser panels utilize foamed pores as the light diffusion medium, improving haze and increasing light diffusion efficiency. However, these are limited by the availability of only one type of foamed pore size and panel thickness, thus affecting light transmittance and haze. When the thickness remains constant, decreasing the density leads to two possibilities: 1. The number of foamed pores increases, but the pores become finer; 2. The number of foamed pores remains the same, but the pores become larger. It is well known that when the pores become more numerous and finer, light passing through these pores undergoes more refraction, thus reducing transmittance and resulting in decreased brightness of the final display screen. Conversely, when the thickness remains constant, larger pores and lighter weight also lead to increased transmittance, but decreased light haze, thus failing to meet the required diffusion rate (90-94%). Currently mass-produced light diffuser foamed panels only achieve a density of 0.8-0.85 g / cm³. 3 Between these ranges, the light transmittance can only reach 40-50%, and if the density is below 0.8 g / cm³, the light transmittance will be even lower. 3 The light transmittance will drop below 40% or the haze will be below 90%, failing to meet current industry standards. With rising raw material prices and squeezed profit margins, how to further reduce product costs while maintaining light transmittance and light diffusion performance is an urgent problem to be solved. Summary of the Invention

[0004] To address the shortcomings and deficiencies of existing technologies, the present invention aims to provide a lightweight foamed light diffuser structure and its preparation method. To reduce the cost of light diffusers, it is necessary to change the number of light-permeable pores to reduce light scattering and loss. Experiments have shown that, with constant thickness, when the density decreases and the pore size increases, the number of pores decreases, resulting in higher light transmittance but lower haze; conversely, when the thickness remains constant, when the density decreases and the pore size decreases, the number of pores increases, resulting in lower light transmittance but higher haze. These two changes in light diffusion or haze are detrimental to meeting industry requirements for light diffusers but beneficial for weight reduction in already industrialized foamed light diffusers. Therefore, the present invention, based on the aforementioned, incorporates one or more thin layers of fine-pore foaming to achieve excellent light diffusion and suitable light transmittance, while effectively reducing the weight of the light diffuser.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] According to one aspect of the present invention, a lightweight structure for a multi-layered light diffuser plate with different pore sizes is provided. The structure includes an upper surface layer (1), a first foam layer (2), a second foam layer (3), and a lower surface layer (4) connected sequentially. The thickness of the first foam layer (2) is less than the thickness of the second foam layer (3), and the average pore diameter of the first foam layer (2) is less than the average pore diameter of the second foam layer (3). Both the upper and lower surface layers serve as protective layers to protect the core layer (foam layer). The first foam layer increases light diffusion, and the second foam layer increases light transmittance and reduces the average density of the foamed light diffuser plate.

[0007] Preferably, the total thickness of the light diffusion plate is 1–5 mm, and the average density is 0.3–0.85 g / cm³. 3 .

[0008] Preferably, the thickness of the upper surface layer (1) and the lower surface layer (4) is 0.01-0.05 mm; the thickness of the first foam layer (2) is 0.2-1 mm, and the average diameter of the foam cells is 0.03-0.08 mm; the thickness of the second foam layer (3) is 0.78-3.9 mm, and the average diameter of the foam cells is 0.3-0.8 mm.

[0009] Preferably, a first foam layer (2) is further included between the second foam layer (3) and the lower surface layer (4). That is, the foamed light diffusion plate changes from a four-layer structure to a five-layer structure, and the core layer changes from the original two-layer structure of one first foam layer and one second foam layer to a three-layer structure of one first foam layer, one second foam layer, and then another first foam layer.

[0010] Preferably, in the above five-layer foamed light diffusion plate, the thickness of the upper surface layer (1) and the lower surface layer (4) is 0.01-0.05 mm; the thickness of the first foam layer (2) is 0.1-0.5 mm, and the average diameter of the foam cells is 0.03-0.08 mm; the thickness of the second foam layer (3) is 0.78-3.9 mm, and the average diameter of the foam cells is 0.3-0.8 mm.

[0011] Preferably, a second foam layer (3) is further included between the upper surface layer (1) and the first foam layer (2). That is, the foamed light diffusion plate changes from a four-layer structure to a five-layer structure, and the core layer changes from the original two-layer structure of one first foam layer and one second foam layer to a "two-one-two" three-layer structure of one second foam layer, one first foam layer, and one second foam layer.

[0012] Preferably, in the above five-layer foamed light diffusion plate, the thickness of the upper surface layer (1) and the lower surface layer (4) is 0.01-0.05 mm; the thickness of the first foam layer (2) is 0.2-1 mm, and the average diameter of the foam cells is 0.03-0.08 mm; the thickness of the second foam layer (3) is 0.39-1.95 mm, and the average diameter of the foam cells is 0.3-0.8 mm.

[0013] According to another aspect of the present invention, a method for preparing the above-mentioned lightweight foamed light diffuser structure is provided, the method comprising: preparing the lightweight foamed light diffuser structure using a screw extruder combined with an in-mold composite process of a distributor.

[0014] Preferably, the main raw materials of the foamed layer include a transparent polymer material and a foaming agent.

[0015] Preferably, the transparent polymer material is any one of polystyrene (PS), polypropylene (PP), polycarbonate (PC), or polyethylene terephthalate (PET). When the transparent polymer material is polystyrene, the raw material further includes toughening agent SEBS or transparent TPE or TPR; when the transparent polymer material is polycarbonate, the raw material further includes toughening agent MBS.

[0016] Preferably, when the raw material includes a toughening agent, the toughening agent is added at a ratio of 1 to 20 wt% of the raw material.

[0017] Preferably, the first foaming layer uses expandable microsphere foaming agent or endothermic and / or exothermic foaming agent with a particle size of 0.003 to 0.005 mm, and the amount of foaming agent used is 0.5 to 2 wt% of the raw material of this layer.

[0018] Preferably, when the first foaming layer uses an endothermic and / or exothermic foaming agent, a nucleating agent is also used to induce the formation of a fine pore structure with a pore size of less than 0.08 mm and to control the size of the foam pores.

[0019] Preferably, the nucleating agent is calcium carbonate or silicon dioxide, and the amount of nucleating agent used is 0.1 to 3 wt% of the raw material in this layer.

[0020] Preferably, the second foaming layer uses an endothermic and / or exothermic foaming agent with a particle size of 0.05 to 0.09 mm, and the amount of foaming agent is 0.7 to 6 wt% of the raw material of this layer. In order to ensure that the pore size reaches 0.3 to 0.8 mm, a nucleating agent cannot be used in the second foaming layer to avoid making the pore size too small.

[0021] Preferably, the endothermic foaming agent is sodium bicarbonate, and the exothermic foaming agent is azodicarbonamide.

[0022] Preferably, the die back pressure of the in-mold composite process is 2–25 MPa, and the die temperature is 160–230°C. Different pressures result in different pressure drops; higher pressures lead to a faster pressure drop and smaller cell sizes. Different pressures can be used to adjust the cell size. A die temperature between 160–230°C allows the material to develop good viscoelasticity during processing, and the desired cell diameter can be obtained by adjusting the die pressure drop.

[0023] The three screw extruders are respectively the main extruder No. 3 for the second foaming layer (coarse pores), No. 1 for the surface layer (non-foamed layer), and No. 2 for the first foaming layer (fine pores). After being layered and compounded by a distributor, the materials with different pore sizes extruded by the three screw extruders, along with the non-foamed surface layer, can obtain three structural layers. These layers are then extruded through a flat die to form... Figure 1 , Figure 2 and Figure 3 The three light diffusion plate structures shown are illustrated. Each of the three screw extruders includes seven heating zones (zones 1-7) from the feeding end to the discharge end. The heating temperature of zone 1 is 150–160°C, zone 2 is 160–170°C, zone 3 is 180–190°C, zone 4 is 190–205°C, zone 5 is 190–170°C, zone 6 is 160–170°C, and zone 7 is 150–160°C. The heating temperature of the filter zone is 150–160°C, the distributor zone is 150–160°C, and the die head assembly zone is 150–200°C. It should be noted that if PC material is used, the temperature of each zone should be increased by 30°C.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) This invention improves the structure of the foamed light diffuser by combining two types of foam layers: one with a small average cell diameter and a thin foam layer, and the other with a large average cell diameter and a thick foam layer. This allows the density of the foamed light diffuser to be as low as 0.3 g / cm³ while ensuring that its performance meets existing technical standards. 3 Compared to the existing technology of 0.85g / cm 3 With a price reduction of over 50%, costs are significantly lowered, giving it a clear advantage in market competition.

[0026] (2) The lightweight foamed light diffuser structure and its preparation method of the present invention can control the average density, light transmittance and haze of the light diffuser by adjusting the thickness of the first foam layer and the second foam layer or the average diameter of their pores. The average density of the foamed light diffuser obtained is 0.3 to 0.85 g / cm³. 3 Light transmittance is 40-60%, and haze is 92-96%. Attached Figure Description

[0027] To more clearly illustrate the implementation of this solution, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this solution. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the light diffusion plate in Example 1.

[0029] Figure 2 This is a schematic diagram of the light diffusion plate in Example 2.

[0030] Figure 3 This is a schematic diagram of the light diffusion plate in Comparative Example 3. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The raw materials involved in the present invention can all be purchased directly from the market. For process parameters not specifically specified, conventional techniques can be referred to.

[0032] Example 1

[0033] like Figure 1As shown, this embodiment provides a lightweight foamed light diffuser structure, comprising an upper surface layer (1), a first foam layer (2), a second foam layer (3), and a lower surface layer (4) connected in sequence. The thickness of the first foam layer (2) is less than the thickness of the second foam layer (3), and the pore diameter of the first foam layer (2) is less than the pore diameter of the second foam layer (3). The upper and lower surface layers serve as protective layers to protect the core layer (foam layer). The first foam layer (fine pores) increases light diffusion, and the second foam layer (coarse pores) increases light transmittance and reduces the average density of the foamed light diffuser.

[0034] In this embodiment, the foamed light diffuser is a four-layer structure board with a core layer consisting of a first foamed layer and a second foamed layer between the upper and lower surface layers. Specifically, the total thickness of the foamed light diffuser in this embodiment is 1-5 mm, the thickness of the upper surface layer (1) and the lower surface layer (4) is 0.01-0.05 mm; the thickness of the first foamed layer (2) is 0.2-1 mm, and the average diameter of the foam cells is 0.03-0.08 mm; the thickness of the second foamed layer (3) is 0.78-3.9 mm, and the average diameter of the foam cells is 0.3-0.8 mm.

[0035] The average density of the foamed light diffuser plate in this embodiment can be controlled within the range of 0.3–0.85 g / cm³. 3 The light transmittance can be controlled between 40% and 60%, and the haze can be controlled between 92% and 96%. Specifically, the average density, light transmittance, and haze of the light diffusion plate can be adjusted by adjusting the thickness of the first foaming layer and the second foaming layer or the diameter of their pores, so as to obtain the desired foamed light diffusion plate.

[0036] Table 1. Haze and transmittance of light diffusion plates with different total thicknesses and average densities in this embodiment.

[0037]

[0038]

[0039] Example 2

[0040] like Figure 2As shown, this embodiment provides a lightweight foamed light diffuser structure. The structure includes an upper surface layer (1), a first foam layer (2), a second foam layer (3), a first foam layer (2), and a lower surface layer (4) connected in sequence. The thickness of the first foam layer (2) is less than the thickness of the second foam layer (3), and the pore diameter of the first foam layer (2) is less than the pore diameter of the second foam layer (3). The upper and lower surface layers are protective layers that protect the core layer (foam layer). The first foam layer (fine pores) increases light diffusion, and the second foam layer (coarse pores) increases light transmittance and reduces the average density of the foamed light diffuser.

[0041] In this embodiment, the foamed light diffuser plate is changed from a four-layer structure to a five-layer structure. Three foam layers are set between the upper and lower surface layers. The core layer is changed from the original two-layer structure of one first foam layer and one second foam layer to a three-layer structure of one first foam layer, one second foam layer, and one first foam layer. Specifically, the total thickness of the foamed light diffuser plate in this embodiment is 1 to 5 mm. The thickness of the upper surface layer (1) and the lower surface layer (4) is 0.01 to 0.05 mm. The thickness of the first foam layer (2) is 0.1 to 0.5 mm, and the average diameter of the foam cells is 0.03 to 0.08 mm. The thickness of the second foam layer (3) is 0.78 to 3.9 mm, and the average diameter of the foam cells is 0.3 to 0.8 mm.

[0042] The average density of the foamed light diffuser plate in this embodiment can be controlled within the range of 0.3–0.85 g / cm³. 3 The light transmittance can be controlled between 40% and 60%, and the haze can be controlled between 92% and 96%. Specifically, the average density, light transmittance, and haze of the light diffusion plate can be adjusted by adjusting the thickness of the first foaming layer and the second foaming layer or the diameter of their pores, so as to obtain the desired foamed light diffusion plate.

[0043] Table 2. Haze and transmittance of light diffusion plates with different total thicknesses and average densities in this embodiment.

[0044] Total thickness (mm) <![CDATA[Average density (g / cm 3 )]]> Haze (%) Light transmittance (%) 1.0 0.4 92.5 55.2 2.0 0.4 93.1 51.1 3.0 0.4 93.6 44.6 4.0 0.4 94.8 40.2 5.0 0.4 95.3 40.1 1.0 0.6 92.1 56.1 2.0 0.6 92.8 52.3 3.0 0.6 93.5 45.1 4.0 0.6 94.6 41.5 5.0 0.6 95.2 40.3 1.0 0.8 92.0 58.1 2.0 0.8 92.5 54.1 3.0 0.8 93.1 47.5 4.0 0.8 94.5 42.1 5.0 0.8 95.1 41.1

[0045] Example 3

[0046] like Figure 3As shown, this embodiment provides a lightweight foamed light diffuser structure. The structure includes an upper surface layer (1), a second foamed layer (3), a first foamed layer (2), a second foamed layer (3), and a lower surface layer (4) connected in sequence. The thickness of the first foamed layer (2) is less than the thickness of the second foamed layer (3), and the pore diameter of the first foamed layer (2) is less than the pore diameter of the second foamed layer (3). The upper and lower surface layers are protective layers that protect the core layer (foamed layer). The first foamed layer (fine pores) increases light diffusion, and the second foamed layer (coarse pores) increases light transmittance and reduces the average density of the foamed light diffuser.

[0047] In this embodiment, the foamed light diffuser plate is changed from a four-layer structure to a five-layer structure. Three foam layers are set between the upper and lower surface layers. The core layer is changed from the original two-layer structure of one first foam layer and one second foam layer to a three-layer structure of one second foam layer, one first foam layer, and one second foam layer. Specifically, the total thickness of the foamed light diffuser plate in this embodiment is 1 to 5 mm. The thickness of the upper surface layer (1) and the lower surface layer (4) is 0.01 to 0.05 mm. The thickness of the first foam layer (2) is 0.2 to 1 mm, and the average diameter of the foam cells is 0.03 to 0.08 mm. The thickness of the second foam layer (3) is 0.39 to 1.95 mm, and the average diameter of the foam cells is 0.3 to 0.8 mm.

[0048] The average density of the foamed light diffuser plate in this embodiment can be controlled within the range of 0.3–0.85 g / cm³. 3 The light transmittance can be controlled between 40% and 60%, and the haze can be controlled between 92% and 96%. Specifically, the average density, light transmittance, and haze of the light diffusion plate can be adjusted by adjusting the thickness of the first foaming layer and the second foaming layer or the diameter of their pores, so as to obtain the desired foamed light diffusion plate.

[0049] Table 3. Haze and transmittance of light diffusion plates with different total thicknesses and average densities in this embodiment.

[0050]

[0051]

[0052] Example 4

[0053] This embodiment provides a method for preparing a lightweight foamed light diffuser plate. The method includes: preparing the lightweight foamed light diffuser plate using a screw extruder combined with an in-mold composite process with a distributor. A four-layer foamed light diffuser plate consists of a top surface layer, a first foamed layer, a second foamed layer, and a bottom surface layer connected in sequence; a five-layer foamed light diffuser plate consists of a top surface layer, a first foamed layer, a second foamed layer, a first foamed layer, and a bottom surface layer connected in sequence, or a top surface layer, a second foamed layer, a first foamed layer, a second foamed layer, and a bottom surface layer connected in sequence.

[0054] The surface layer of the foamed light diffuser can be made using materials and processes conventional in the art. The main raw materials of the foam layer include a transparent polymer material and a foaming agent. The transparent polymer material can be any one of polystyrene (PS), polypropylene (PP), polycarbonate (PC), or polyethylene terephthalate (PET). When the transparent polymer material is polystyrene, the raw materials also include a toughening agent SEBS or transparent TPE or TPR; when the transparent polymer material is polycarbonate, the raw materials also include a toughening agent MBS; when the transparent polymer material is polypropylene or polyethylene terephthalate, no toughening agent is required. When the foam layer raw materials include a toughening agent, the addition ratio of the toughening agent is 1-20 wt% of the raw materials.

[0055] The first foaming layer uses an expandable microsphere foaming agent or an endothermic and / or exothermic foaming agent with a particle size of 0.003–0.005 mm, and the amount of foaming agent used is 0.5–2 wt% of the raw materials of this layer. When the first foaming layer uses an expandable microsphere foaming agent, no additional nucleating agent is required; when the first foaming layer uses an endothermic and / or exothermic foaming agent, a nucleating agent is also used to induce the formation of a fine pore structure with a pore size of less than 0.08 mm and to control the size of the pores. The nucleating agent is calcium carbonate or silicon dioxide, and the amount of nucleating agent used is 0.1–3 wt% of the raw materials of this layer.

[0056] The second foaming layer uses an endothermic and / or exothermic foaming agent with a particle size of 0.05–0.09 mm, and the amount of foaming agent is 0.7–6 wt% of the raw material of this layer. In order to ensure that the pore size reaches 0.3–0.8 mm, nucleating agents cannot be used in the second foaming layer to avoid making the pore size too small.

[0057] The endothermic foaming agent is sodium bicarbonate, and the exothermic foaming agent is azodicarbonamide.

[0058] The die back pressure in the in-mold composite process is 2–25 MPa, and the die temperature is 160–230°C. Different pressures result in different pressure drops; higher pressures lead to a faster pressure drop and smaller cell sizes. Different pressures can be used to adjust the cell size. A die temperature between 160–230°C allows the material to develop good viscoelasticity during processing, and the desired cell diameter can be obtained by adjusting the die pressure drop.

[0059] The three screw extruders are respectively the main extruder No. 3 for the second foaming layer, No. 1 for the surface layer, and No. 2 for the first foaming layer. After being layered and compounded by a distributor, the materials with different pore sizes extruded by the three screw extruders, along with the non-foamed surface layer, can obtain three structural layers. These layers are then extruded through a flat die to form... Figure 1 , Figure 2 and Figure 3 The three light diffusion plate structures shown are illustrated. Each of the three screw extruders includes seven heating zones (zones 1-7) from the feeding end to the discharge end. The heating temperature of zone 1 is 150–160°C, zone 2 is 160–170°C, zone 3 is 180–190°C, zone 4 is 190–205°C, zone 5 is 190–170°C, zone 6 is 160–170°C, and zone 7 is 150–160°C. The heating temperature of the filter zone is 150–160°C, the distributor zone is 150–160°C, and the die head assembly zone is 150–200°C. It should be noted that if PC material is used, the temperature of each zone should be increased by 30°C.

[0060] In this embodiment, the foaming layer uses polystyrene and toughening agent SEBS as raw materials, with the toughening agent added at a ratio of 1-20 wt% of the raw materials; the first foaming layer uses sodium bicarbonate, an endothermic foaming agent with a particle size of 0.003-0.005 mm, at a dosage of 0.5-2 wt% of the raw materials of this layer, and uses silica nucleating agent to induce the formation of fine pore structures with a pore size of less than 0.080 mm and control the size of the pores, at a dosage of 0.1-3 wt% of the raw materials of this layer; the second foaming layer uses azodicarbonamide, an exothermic foaming agent with a particle size of 0.05-0.09 mm, at a dosage of 0.7-6 wt% of the raw materials of this layer. To ensure that the pore size reaches 0.3-0.8 mm, nucleating agent cannot be used in the second foaming layer to avoid making the pore size too small.

[0061] The preparation method of the foamed light diffusion plate in this embodiment includes the following steps:

[0062] 1. Mix the raw materials of each layer according to the proportions, stir evenly in the mixer and set aside.

[0063] 2. Select the appropriate mold according to the five-layer extrusion process, install the extruder head, and check and confirm that the extrusion equipment and all rotating parts are in good condition.

[0064] 3. Set the temperature controller to the working temperature and heat the barrel mold. After the temperature reaches the set value, continue to maintain the temperature for half an hour.

[0065] 4. Of the three extruders, one corresponds to the upper and lower surface layers, one corresponds to the first foaming layer connected to the upper and lower surface layers respectively, and the other corresponds to the second foaming layer. Feed the thoroughly mixed material of each layer into the corresponding feed port. Replace the filter screens of each extruder, turn on the metering pumps sequentially, rotate the screw motors, and set parameters such as metering pump pressure, feeding rate, and main motor speed to allow the plastic material to pass through the barrel and be plasticized. The extruders then extrude the material and clean the die lips. Adjust the metering pump, main motor speed, pressure, and other parameters to begin extrusion.

[0066] 5. After the materials in the three extruders are melted, they are extruded into the mold for composite, and the composite board is extruded through the mold outlet to obtain a five-layer foamed light diffusion board sheet.

[0067] In this embodiment, the surface layer can be prepared using materials and processes conventional in the art.

[0068] In this embodiment, the screw extruder for preparing the first foamed layer includes seven heating zones from the feeding end to the discharge end: zone one, zone two, zone three, zone four, zone five, zone six, and zone seven. The heating temperature of zone one is 150–160°C, the heating temperature of zone two is 160–170°C, the heating temperature of zone three is 180–190°C, the heating temperature of zone four is 190–205°C, the heating temperature of zone five is 190–170°C, the heating temperature of zone six is ​​160–170°C, and the heating temperature of zone seven is 150–160°C. The heating temperature of the filter area is 150–160°C, the heating temperature of the distributor is 150–160°C, and the heating temperature of the die head device is 150–200°C. The screw extruder for preparing the second foamed layer includes seven heating zones from the feeding end to the discharge end: zone 1, zone 2, zone 3, zone 4, zone 5, zone 6, and zone 7. The heating temperature in zone 1 is 150–160℃, zone 2 is 160–170℃, zone 3 is 180–190℃, zone 4 is 190–205℃, zone 5 is 190–170℃, zone 6 is 160–170℃, and zone 7 is 150–160℃. The heating temperature in the filter zone is 150–160℃, the distributor zone is 150–160℃, and the die assembly zone is 150–200℃. The die back pressure for the in-mold compounding process is 2–25 MPa, and the die temperature is 160–230℃. A die temperature between 160 and 230°C can enable the material to form good viscoelasticity during processing, and the expected cell diameter can be obtained by matching the pressure drop of the die.

[0069] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A lightweight structure for foaming a light diffusion plate, characterized in that, The structure includes an upper surface layer (1), a first foam layer (2), a second foam layer (3), and a lower surface layer (4) connected in sequence. The thickness of the first foam layer (2) is less than the thickness of the second foam layer (3), and the average diameter of the pores in the first foam layer (2) is less than the average diameter of the pores in the second foam layer (3). The total thickness of the light diffusion plate is 1–5 mm, and the average density is 0.3–0.80 g / cm³. 3 ; The thickness of the upper layer (1) and the lower layer (4) is 0.01-0.05 mm; the thickness of the first foam layer (2) is 0.2-1 mm, and the average diameter of the foam cells is 0.03-0.08 mm; the thickness of the second foam layer (3) is 0.78-3.9 mm, and the average diameter of the foam cells is 0.3-0.8 mm.

2. The lightweight structure of a light diffusion plate foaming according to claim 1, characterized in that, The second foam layer (3) and the lower surface layer (4) are further separated by a first foam layer (2).

3. The lightweight structure of a light diffusion plate foaming according to claim 1, characterized in that, A second foam layer (3) is also included between the upper surface layer (1) and the first foam layer (2).

4. The lightweight structure of a light diffusion plate foaming according to claim 2, characterized in that, The thickness of the upper layer (1) and the lower layer (4) is 0.01-0.05 mm; the thickness of the first foam layer (2) is 0.1-0.5 mm, and the average diameter of the foam cells is 0.03-0.08 mm; the thickness of the second foam layer (3) is 0.78-3.9 mm, and the average diameter of the foam cells is 0.3-0.8 mm.

5. The lightweight structure of a light diffusion plate foaming according to claim 3, characterized in that, The thickness of the upper layer (1) and the lower layer (4) is 0.01-0.05 mm; the thickness of the first foam layer (2) is 0.2-1 mm, and the average diameter of the foam cells is 0.03-0.08 mm; the thickness of the second foam layer (3) is 0.39-1.95 mm, and the average diameter of the foam cells is 0.3-0.8 mm.

6. A method for preparing a lightweight foamed light diffusion plate structure according to any one of claims 1 to 5, characterized in that, The lightweight foamed structure of the light diffusion plate is prepared by using a screw extruder combined with a distributor or an in-mold composite process.

7. The method for preparing a lightweight foamed light diffusion plate structure according to claim 6, characterized in that, The main raw materials of the first foam layer and the second foam layer include a transparent polymer material and a foaming agent; the transparent polymer material is any one of polystyrene, polypropylene, polycarbonate or polyethylene terephthalate. When the transparent polymer material is polystyrene, the raw material also includes a toughening agent SEBS or transparent TPE or TPR; when the transparent polymer material is polycarbonate, the raw material also includes a toughening agent MBS; the addition ratio of the toughening agent is 1 to 20 wt% of the raw material.

8. The method for preparing a lightweight foamed light diffusion plate structure according to claim 7, characterized in that, The first foaming layer uses expandable microspheres or endothermic and / or exothermic foaming agents with a particle size of 0.003–0.005 mm, and the amount of foaming agent is 0.5–2 wt% of the raw materials of this layer; the second foaming layer uses endothermic and / or exothermic foaming agents with a particle size of 0.050–0.090 mm, and the amount of foaming agent is 0.7–6 wt% of the raw materials of this layer; the die back pressure of the in-mold composite process is 2–25 MPa, and the die temperature is 160–230 °C.

Images