A novel microstructure on a plastic surface and its molding process

Abstract

This invention discloses a novel microstructure for a plastic surface and its molding process, comprising: adding injection molding material into a barrel, plasticizing and metering it; closing the mold and preheating the mold cavity surface to a first preset temperature, wherein the first preset temperature is greater than the Tg temperature of the injection molding material; filling the injection molding material in the barrel into the mold cavity to form an injection molded part; after filling, switching to a holding pressure state to hold the injection molded part under pressure; after holding the pressure, opening the cooling channel and cooling the mold and the injection molded part to a second preset temperature; opening the mold and ejecting the injection molded part. Compared with the prior art, the process of this invention can produce microstructures with full shapes and compact arrangement to achieve diffuse reflection of incident light, and has high molding efficiency and low cost.

Description

Technical Field

[0001] This invention relates to the field of molding technology for microstructures on the surface of plastic products, and in particular to a novel microstructure on the surface of plastic products and its molding process. Background Technology

[0002] A camera uses an optical lens to receive light reflected from the subject to create an image, thus recording the dynamic and static effects of the subject. To prevent the optical lens from receiving invalid light and stray light from the surrounding environment, which could affect the imaging effect, a structure is usually placed on the light-incident side of the camera to reflect or absorb invalid or stray light. This structure is usually made of plastic and has an overall trumpet shape to diffuse the light on the light-incident side of the camera module, preventing it from entering the optical lens.

[0003] Existing funnel-shaped plastic products typically involve injection molding followed by flocking to create a flocked layer on the light-facing surface to absorb or reflect incoming light. However, this process requires specialized equipment, increasing production costs. Furthermore, the incompatibility between flocking and molding equipment results in separate processes, leading to low production efficiency. Additionally, the flocked layer, composed primarily of fluff or fibers, is prone to dust accumulation over time, potentially causing dust to enter the optical lens and making cleaning difficult. Moreover, the tiny structure of the fluff and fibers can lead to shedding, affecting the lens's imaging capabilities. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a novel microstructure of plastic surface and its molding process, so as to solve the problems of high processing cost and low processing efficiency of flocking process in the prior art, as well as the easy shedding and dust accumulation of flocking.

[0005] To achieve the above objectives, one technical solution of the present invention provides a molding process for a novel microstructure on a plastic surface, comprising the following steps:

[0006] Add injection molding material into the barrel, plasticize it, and complete the metering process;

[0007] The mold is closed and the surface of the mold cavity is preheated to a first preset temperature, wherein the first preset temperature is greater than the Tg temperature of the injection molding material;

[0008] The injection molding material inside the barrel is filled into the mold cavity to form an injection molded part;

[0009] After filling is complete, switch to pressure holding mode to hold pressure on the injection molded part;

[0010] After the pressure holding is completed, the cooling channel is opened and the mold and injection molded parts are cooled to the second preset temperature;

[0011] Open the mold and eject the injection molded part.

[0012] Furthermore, before the steps of adding injection molding material into the barrel, plasticizing, and completing metering, the following steps are also included:

[0013] The barrel temperature and hot runner temperature of the mold are set, and the barrel and hot runner are preheated at the set barrel temperature and hot runner temperature; wherein, the barrel has a nozzle section, a fourth heating section, a third heating section, a second heating section, a first heating section and a discharge port section arranged in sequence, and the temperatures of the corresponding nozzle section, fourth heating section, third heating section, second heating section, first heating section and discharge port section are set to 295~315℃, 295~315℃, 290~310℃, 280~300℃, 270~290℃ and 260~280℃ respectively, and the hot runner temperature is 290~330℃.

[0014] Furthermore, in the step of adding injection molding material into the barrel, plasticizing, and completing metering, multi-stage metering is used when metering the injection molding material. During the metering process, the screw speed inside the barrel is 60*(1±20%) rpm, and the back pressure is 40*(1±20%) kgf / cm². 2 After the metering is completed, the screw is released and retracted. The retraction distance is 5±3mm and the retraction speed is 15*(1±20%)mm / s.

[0015] Furthermore, in the step of closing the mold and heating the surface of the mold cavity to a first preset temperature, a multi-stage mold closing method is adopted. During mold closing, the front mold and the rear mold of the mold move relative to each other to the first mold closing position under the first mold closing pressure, and then switch to the second mold closing pressure and move relative to each other until the mold closing is completed. The first mold closing pressure is greater than the second mold closing pressure, and the mold closing speed of the front mold and the rear mold decreases during relative movement. The first mold closing pressure is 230*30%*(1±20%)TON.

[0016] Furthermore, in the step of closing the mold and heating the surface of the mold cavity to a first preset temperature, the first preset temperature is 135-145°C and the heating power is 8-15KW.

[0017] Furthermore, in the step of filling the injection molding material in the barrel into the mold cavity to form the injection molded part, a segmented filling method is adopted. During filling:

[0018] The filling pressure for the first stage of filling is 2300*(1±20%) kgf / cm³. 2The filling speed is 20*(1±20%)mm / s, and the filling time is from the metering completion position to the first filling position or the maximum filling time is reached. The first filling position is 52±3mm, and the maximum filling time is 3*(1±20%)s.

[0019] The filling pressure for the second stage of filling is 2300*(1±20%) kgf / cm². 2 The filling speed is 45*(1±20%)mm / s, and the filling time is from the first filling position to the second filling position or until the maximum filling time is reached. The second filling position is 12±3mm.

[0020] The filling pressure for the third stage of filling is 2300*(1±20%) kgf / cm³. 2 The filling speed is 25*(1±20%)mm / s, and the filling time is from the second filling position to the pressure holding switching position or the maximum filling time is reached, wherein the pressure holding switching position is 6±3mm.

[0021] Furthermore, in the step of switching to the holding pressure state after filling and holding pressure on the injection molded part, segmented holding pressure is adopted. During holding pressure:

[0022] The holding speed in the first pressure holding stage is 25*(1±15%) mm / s, the holding time is 1.3*(1±20%) s, and the holding pressure is 1000*(1±15%) kgf / cm². 2 ;

[0023] The holding speed in the second holding stage is 25*(1±15%) mm / s, the holding time is 2*(1±20%) s, and the holding pressure is 900*(1±15%) kgf / cm². 2 .

[0024] Furthermore, in the step of opening the cooling channel and cooling the mold and injection part to the second preset temperature after the pressure holding is completed, the cooling time is 30*(1±20%)s, and the second preset temperature is 85~95℃.

[0025] Furthermore, in the step of opening the mold and ejecting the injection molded part, a multi-stage mold opening is adopted. During the mold opening, the opening speed of the front mold and the rear mold during relative movement first increases and then decreases until the maximum mold opening position, after which the injection molded part is ejected and demolded by ejector pins.

[0026] To achieve the above objectives, another technical solution of the present invention provides a novel microstructure for a plastic surface, wherein the novel microstructure is formed using the molding process for novel microstructures for plastic surfaces as described above.

[0027] This invention preheats the mold and its cavity surface to a first preset temperature higher than the Tg temperature of the injection molding material before filling, and continues to heat the mold and cavity surface at the first preset temperature during the injection molding process. This allows the injection molding material to fully fill the cavity, increasing the fullness and height of the microstructure after molding. This microstructure can diffusely reflect light, reducing glare. Simultaneously, a laser process is used to form a microstructure molding area on the inner wall of the molding mold cavity, allowing the microstructure to be molded into a single piece with the main body of the plastic product in a single process. The structure is stable, the surface is not prone to dust accumulation, it is easy to clean, and there is no need to consider equipment compatibility issues. This results in high molding efficiency and low cost. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a funnel-shaped plastic product using the novel microstructure of the present invention.

[0029] Figure 2 This is a schematic diagram of a novel microstructure on a plastic surface.

[0030] Figure 3 This is a flowchart illustrating the molding process of a novel microstructure on a plastic surface according to an embodiment of the present invention.

[0031] Figure 4 This is a comparison chart of the temperature change curves of the mold during the molding process of the novel microstructure and the temperature change curves of the traditional process.

[0032] Figure 5 The image shows the radius of curvature of the surface after scanning the bottom contour of the novel microstructure using a white light interferometer.

[0033] Figure 6 The size of the pit was measured after scanning the bottom contour of the novel microstructure using a white light interferometer.

[0034] Figure 7 The roughness curve of the pits was measured after scanning the bottom contour of the novel microstructure using a white light interferometer.

[0035] Figure 8 These are microstructure morphology images of the novel microstructures on the surface, magnified 5 to 50 times using a metallographic microscope.

[0036] Figure 9 The structural dimensions of the plastic surface prepared according to the present invention were measured using an image measuring instrument with a repeatability of 0.1 μm.

[0037] Figure 10 Dimensional diagram of the microstructure obtained by traditional process.

[0038] Figure 11 To obtain the maximum profile curve of the microstructure surface using the Zhongtu profilometer.

[0039] Figure 12 This is a schematic diagram for modeling and simulating diffuse reflection in a novel microstructure. Detailed Implementation

[0040] The novel microstructure molding process for plastic surfaces of this invention is used to mold microstructures on the surface of plastic products (especially funnel-shaped plastic products for the light-incident side of camera modules), resulting in microstructures with full structures that meet design dimensions. This allows for diffuse reflection of incident light, reducing glare and preventing ineffective and stray light from entering the camera module. It is understood that although this embodiment primarily describes the molding of microstructures on funnel-shaped plastic products, it is not limited to this and can also be applied to the processing of other plastic products and even metal products that require microstructure molding to obtain microstructures with full structures that meet design dimensions.

[0041] like Figure 1 and Figure 2 The diagram shows the plastic product and the structure of the novel microstructure obtained by the molding process of the novel microstructure on the plastic surface of the present invention. The plastic product has a main body 21 connected to a camera module, and a light-transmitting hole 21a coaxial with the optical axis of the camera module is formed on the main body 21. The main body 21 has an inward-facing light-facing surface 22a (i.e., facing the axial direction of the light-transmitting hole or the optical axis direction of the camera module) and a backlighting surface 22b facing away from the light-facing surface 22a. The surface microstructure is integrally formed on the light-facing surface 22a to reflect the light incident on the light-facing surface 22a multiple times. In this embodiment, the surface microstructure is integrally formed with the plastic product. During the molding process, the main body 21 of the plastic product is formed by conventional injection molding, and the surface microstructure is formed by rapid cooling and heating. The two processes can be integrated into the same mold. In specific molding, the molding temperature of the process stage can be adjusted to achieve compatibility between the two processes, thereby simplifying the process flow and reducing the difficulty of processing the plastic product and the microstructure.

[0042] Specifically, the novel microstructure includes a substrate 11 and a microstructure layer formed on the substrate 11. The substrate 11 has a first surface and a second surface facing away from each other. The microstructure layer is formed on the first surface and has a certain roughness to diffusely reflect light incident on it, thereby reflecting away invalid and stray light. In this embodiment, both the substrate 11 and the microstructure layer are injection molded from plastic raw materials (such as PC), and the microstructure layer is integrally molded on the substrate 11. This allows the substrate 11 and the microstructure layer to be realized using the same mold in the same process flow, thereby reducing process costs and improving process efficiency. The microstructure layer includes at least one first microstructure region 12 and at least one second microstructure region 13. The first microstructure region 12 and the second microstructure region 13 are integrally formed on the substrate 11 and have different roughnesses. When light is incident, by setting the first microstructure region 12 and the second microstructure region 13, the light can exhibit irregular reflection on the first microstructure region 12 and the second microstructure region 13, thereby increasing the number of light reflections and improving the diffuse reflection effect.

[0043] The mold is designed and processed according to the specific structure, size, and arrangement of the novel microstructure to form a cavity with a novel microstructure forming region within the mold. In this embodiment, the mold cavity has a first forming surface corresponding to the inner surface (i.e., microstructure layer) of the formed novel microstructure and a second forming surface corresponding to the outer surface (i.e., substrate 11) of the formed novel microstructure. The first forming surface is laser-formed with a first microstructure forming region corresponding to the first microstructure region 12 and / or a second microstructure forming region corresponding to the second microstructure region 13, to correspondingly form the first microstructure region 12 and / or the second microstructure region 13. Please refer to... Figure 3 This is a flowchart of the molding process for the novel microstructure on the plastic surface of the present invention. The molding process for the novel microstructure on the plastic surface of the present invention is used to integrally mold the novel microstructure on the light-facing surface of a plastic product, and specifically includes the following steps:

[0044] S1: Set the molding temperature and hot runner temperature and preheat.

[0045] Based on the material and heat-melting properties of the injection molding raw material, the barrel temperature and hot runner temperature of the mold are set, and the barrel and hot runner are preheated at the set barrel and hot runner temperatures. In this embodiment, according to the flow and plasticizing process of the injection molding raw material, the barrel is sequentially divided into a nozzle section, a fourth heating section, a third heating section, a second heating section, a first heating section, and a discharge port section. Since the injection molding raw material used in the product molded in this embodiment is plastic, the molding temperatures corresponding to the nozzle section, the fourth heating section, the third heating section, the second heating section, the first heating section, and the discharge port section of the barrel are set to 295~315℃, 295~315℃, 290~310℃, 280~300℃, 270~290℃, and 260~280℃, respectively, and the molding temperature of the hot runner is set to 290~330℃, so that the injection molding raw material can be rapidly plasticized and flowed in the barrel and hot runner.

[0046] S2: Plasticize and meter the injection molding raw materials.

[0047] Specifically, injection molding material is added into the barrel from the feed port section. The injection molding material entering the barrel is plasticized by heating components (such as heating plates, heating coils, etc.) set outside the barrel. The injection molding material is then transferred by the screw inside the barrel. During the transfer process, the injection molding material is metered according to the volume of injection molding material required to mold a complete product.

[0048] In this embodiment, multi-segment metering is used when metering the injection molding raw material, and the metering parameters for each segment are switched based on the location. Specifically, a three-segment metering method is adopted:

[0049] In the first metering stage, the screw rotation speed inside the barrel is 60*(1±20%) rpm, and the back pressure of the screw is 40*(1±20%) kgf / cm². 2 After the screw moves backward from its starting position to the first metering position, the screw speed and back pressure parameters are quickly switched to the metering parameters required for the second metering stage; the first metering position is 15±3mm away from the starting position of the screw.

[0050] In the second metering stage, the screw rotation speed inside the barrel is 60*(1±20%) rpm, and the back pressure of the screw is 40*(1±20%) kgf / cm². 2 After the screw continues to move backward from the first metering position to the second metering position, the screw speed and back pressure parameters are quickly switched to the metering parameters required for the third metering stage; the second metering position is 50±3mm away from the starting position of the screw.

[0051] The third metering stage, also known as the metering completion stage, involves the screw inside the barrel rotating at 60*(1±20%) rpm and the back pressure of the screw at 40*(1±20%) kgf / cm². 2 After the screw continues to move backward from the second metering position to the third metering position (i.e., the metering completion position), the screw is controlled to retract. The metering completion position is 58±3mm from its starting position, the retraction distance is 5±3mm, and the retraction speed is 15*(1±20%)mm / s. After retraction, the screw is 73±3mm from its starting position, which is also the starting position of the filling stage described below.

[0052] In this embodiment, a three-stage metering method is adopted, which can effectively increase the accuracy and stability of injection molding material metering, thereby improving molding precision. Understandably, in other embodiments, the screw speed and back pressure can be adjusted in a timely manner according to molding precision and efficiency requirements to quickly complete metering; alternatively, a single-stage metering method can be used, where the screw is immediately retracted after one complete movement to improve metering efficiency.

[0053] S3: Close the mold and preheat the mold and cavity surfaces to the first preset temperature.

[0054] After the front and rear molds are closed, the mold cavity surface is preheated to a first preset temperature. Heating can be achieved using heating elements or coils on the mold, or by using a heating pipe to exchange heat with the mold through fluid flow. The first preset temperature is higher than the Tg temperature of the injection molding material. In this embodiment, depending on the type of injection molding material, the first preset temperature is preferably 135–145°C, and the heating power is 8–15 kW, to quickly heat the mold to the first preset temperature in a short time, thereby improving molding efficiency.

[0055] In this embodiment, during mold closing, a multi-stage mold closing method is used to close the front and rear molds. The mold moves relative to each other at a first closing pressure until it reaches a first closing position, then switches to a second closing pressure and moves relative to each other until mold closing is complete. The first closing pressure is greater than the second closing pressure, and the closing speed of the front and rear molds decreases during relative movement. The first closing pressure is 230 * 30% * (1 ± 20%)TON. Specifically, a five-stage mold closing method is used.

[0056] In the first mold closing stage, the front mold and the rear mold move relative to each other to the first mold closing position with a second mold closing pressure of 230*(1±20%)TON and a mold closing speed of 40-50%; the first mold closing position is the position where the corresponding surfaces of the front mold and the rear mold are 350±3mm apart.

[0057] In the second mold closing stage, the front mold and the rear mold move relative to each other to the second mold closing position with a second mold closing pressure of 230*(1±20%)TON and a mold closing speed of 35-45%; the second mold closing position is the position where the corresponding surfaces of the front mold and the rear mold are 200±3mm apart.

[0058] In the third mold closing stage, the front mold and the rear mold move relative to each other to the third mold closing position with a second mold closing pressure of 230*(1±20%)TON and a mold closing speed of 25-35%; the third mold closing position is the position where the corresponding surfaces of the front mold and the rear mold are 150±3mm apart.

[0059] In the fourth mold closing stage, the front mold and the rear mold move relative to each other to the fourth mold closing position with a second mold closing pressure of 230*(1±20%)TON and a mold closing speed of 20-30%; the third mold closing position is the position where the corresponding surfaces of the front mold and the rear mold are 80±3mm apart.

[0060] In the fifth mold-closing stage, which is also the final mold-locking stage, the front mold and the rear mold move relative to each other at a closing speed of 20-30% to the mold-locking position; the mold-locking position is where the corresponding surfaces of the front mold and the rear mold are 3±3mm apart. In this embodiment, to avoid pressure during contact between the front mold and the rear mold in the fifth mold-closing stage, this stage is divided into a high-pressure stage and a low-pressure stage. In the high-pressure stage, the front mold and the rear mold move relative to each other at a second mold-closing pressure of 230*(1±20%)TON to the low-pressure switching position, and then immediately move relative to each other at a first mold-closing pressure of 230*30%*(1±20%)TON to the mold-locking position to increase the mold-closing stability of the front mold and the rear mold; the low-pressure switching position is where the corresponding surfaces of the front mold and the rear mold are 30±3mm apart.

[0061] In this embodiment, a five-stage mold closing method is adopted. During the relative movement of the front and rear molds, the mold closing speed gradually decreases and the mold closing pressure switches from high pressure to low pressure. That is, when the front and rear molds are far apart, a higher mold closing speed and pressure are used to close the molds quickly. When the front and rear molds are close, a lower mold closing speed and pressure are used. At this time, the guide pillars of the front and rear molds begin to contact. The lower mold closing speed reduces mechanical vibration when the front and rear molds contact, thereby increasing the stability of the mold closing and reducing the risk of damage from collisions between the front and rear molds, thus increasing the service life of the mold. It is understood that in other embodiments, the number of mold closing stages, mold closing speed, and pressure of the front and rear molds can be determined according to the distance and stroke of the front and rear molds to adapt to the injection molding of corresponding structural products.

[0062] S4: Filling injection molding material.

[0063] Once the mold is preheated to the first preset temperature and the injection material in the barrel has been metered, the screw is controlled to move to fill the injection material in the barrel into the mold cavity to form an injection molded part.

[0064] In this embodiment, a segmented filling method is adopted during filling, and the injection molding material is filled with a certain filling pressure and filling speed. The filling speed first increases and then decreases to quickly fill the injection molding material into the cavity. Specifically, a five-stage mold closing method is adopted, and when switching from the filling stage to the holding pressure stage, position is prioritized.

[0065] The first filling stage has a filling pressure of 2300*(1±20%) kgf / cm³. 2 The filling speed is 20*(1±20%)mm / s. The screw squeezes the injection molding material from the metering completion position (specifically, the position after the screw releases after metering) to the first filling position; the first filling position is 52±3mm (that is, the distance between the screw and its final position).

[0066] In the second stage of filling, the filling pressure is 2300*(1±20%) kgf / cm². 2 The filling speed is 45*(1±20%)mm / s, and the screw fills the injection molding material from the first filling position to the second filling position; the second filling position is 12±3mm.

[0067] In the third stage of filling, the filling pressure is 2300*(1±20%) kgf / cm³. 2 The filling speed is 25*(1±20%)mm / s. The screw fills the injection molding material from the second filling position to the pressure holding switching position, wherein the pressure holding switching position is 6±3mm.

[0068] During the filling process, the mold and cavity surface are maintained at the first preset temperature until the filling and even the pressure holding are completed, so that the injection molding material can be fully filled into the cavity, thereby increasing the fullness and height of the molded microstructure. In turn, the microstructure can diffusely reflect light, ensuring that the molding size of the new microstructure meets the design requirements.

[0069] In this embodiment, a three-stage filling method is adopted, with the filling speed initially slow, then fast, and then slowing down again. During the filling process, the filling speed is relatively slow in the first stage to ensure the plasticized injection molding material is filled smoothly, preventing defects such as air bubbles, material jetting, and spirals. In the second stage, the filling speed is relatively fast to quickly inject the injection molding material into the cavity, ensuring that resistance is overcome and the material is fully filled, thus preventing material shortages. Finally, in the third stage, the filling speed is reduced again to a slower pace until the pressure-holding switching position is reached, avoiding overflow and indentations at the mold-closing point between the front and rear molds. Understandably, in other embodiments, the number of filling stages, filling position, and filling speed can also be adaptively adjusted according to parameters such as the volume and resistance of the injection molding material.

[0070] In this embodiment, position is used as the highest priority for the switching signal between the filling stage and the holding pressure stage. That is, when the screw moves to the holding pressure switching position, filling is stopped immediately and the mold is quickly switched to the holding pressure state. In this way, the injection molding material can be fully filled and problems such as material shortage can be avoided. However, when position is the priority, the mold also has a maximum filling time, which is 3*(1±20%)s. Under the limitation of the maximum filling time, since the mold is in a high temperature and high pressure state, in order to ensure the safety of processing, when the maximum filling time is reached, the mold will be controlled to quickly switch to the holding pressure state even if the screw has not moved to the holding pressure switching position. This also ensures the continuity of the molding process.

[0071] Understandably, in some other embodiments, time can also be set to the highest priority, that is, whether the filling time has been reached or not can be used as the switching signal from the filling stage to the holding stage. Once the time is reached, the system can quickly switch to the holding state, thus ensuring the efficiency and continuity of the molding process.

[0072] S5: Pressure holding for injection molded parts.

[0073] Once the injection molding material is filled, the process can be quickly switched to the holding pressure state to hold the injection molded part within the mold. In this embodiment, during holding pressure, a segmented holding pressure method is adopted, and the injection molded part is held for a certain period of time with a certain holding pressure and holding speed to control the amount of product deformation. Furthermore, a small amount of injection molding material continues to be injected during the holding pressure process to fill the shrinkage space during the cooling and solidification of the injection molded part, thereby ensuring the molding quality of the product. Specifically, a two-stage holding pressure method is used:

[0074] In the first pressure holding stage, the pressure holding speed is 25*(1±15%) mm / s, the pressure holding time is 1.3*(1±20%) s, and the pressure holding pressure is 1000*(1±15%) kgf / cm². 2.

[0075] In the second pressure holding stage, the pressure holding speed is 25*(1±15%) mm / s, the pressure holding time is 2*(1±20%) s, and the pressure holding pressure is 900*(1±15%) kgf / cm². 2 .

[0076] In this embodiment, a two-stage pressure holding method is adopted to hold the injection molded part in stages. This extends the pressure holding time curve and ensures that the injection molded part will not crack. It is understood that in other embodiments, the number of pressure holding stages can also be specifically set according to the structure of the molded product to ensure the molding quality.

[0077] S6: Cool the mold and injection molded parts to the second preset temperature.

[0078] After the pressure holding is completed, the cooling channel is opened to cool the mold and injection parts to the second preset temperature, ensuring that the product can be successfully demolded. The cooling channel can use a fluid (gas, liquid, etc.) circulation method to cool the mold and injection parts. Through the circulation of the fluid, heat exchange is carried out with the mold and injection parts to quickly cool them down. In this embodiment, the cooling time is 30*(1±20%)s, and the second preset temperature is 85~95℃.

[0079] S7: Open the mold and eject the injection molded part.

[0080] After the mold and injection molded parts have cooled to the second preset temperature, the mold is opened to demold the injection molded parts, thus completing the integrated molding of the plastic product and the new microstructure.

[0081] In this embodiment, during mold opening, a multi-stage mold opening method is used to open the front and rear molds. The front and rear molds open at a certain opening speed, which first increases and then decreases until the maximum opening position, at which point the injection molded part is ejected and demolded by ejector pins. Specifically, a five-stage mold opening method is used:

[0082] In the first mold opening stage, the front mold and the rear mold move relative to each other at a mold opening speed of 15-25% to the first mold opening position; the first mold opening position is the position where the corresponding surfaces of the front mold and the rear mold are 35±3mm apart.

[0083] In the second mold opening stage, the front mold and the rear mold move relative to each other at a mold opening speed of 30-40% to the second mold opening position; the second mold opening position is the position where the corresponding surfaces of the front mold and the rear mold are 85±3mm apart.

[0084] In the third mold opening stage, the front mold and the rear mold move relative to each other at a mold opening speed of 35-45% to the third mold opening position; the third mold opening position is the position where the corresponding surfaces of the front mold and the rear mold are 160±3mm apart.

[0085] In the fourth mold opening stage, the front mold and the rear mold move relative to each other at a mold opening speed of 40-50% to the fourth mold opening position; the fourth mold opening position is the position where the corresponding surfaces of the front mold and the rear mold are 400±3mm apart.

[0086] In the fifth mold opening stage, also known as the mold opening limit stage, the front mold and the rear mold move relative to each other at a mold opening speed of 20-30% to the fifth mold opening position (i.e., the mold opening limit position); the fifth mold opening position is the position where the corresponding surfaces of the front mold and the rear mold are 450±3mm apart.

[0087] In this embodiment, a five-stage mold opening method is adopted. During the relative movement of the front and rear molds, the mold opening speed gradually increases and then gradually decreases. That is, at the beginning of mold opening, to avoid deformation of the product due to airflow pulling during rapid separation of the front and rear molds, a relatively small mold opening speed is used to separate the front and rear molds, ensuring the shape and quality of the product. After the front and rear molds separate, a larger mold opening speed is used to quickly move the front and rear molds away from each other, shortening the mold opening time. Finally, when the front and rear molds are about to reach the maximum mold opening distance, a smaller mold opening speed is used again to move them to their limit positions, reducing the mechanical vibration of the injection molding machine. Understandably, in other embodiments, the number of mold opening stages and the mold opening speed of the front and rear molds can be determined according to the distance and stroke of the front and rear molds to adapt to the injection molding of products with corresponding structures.

[0088] When the front mold and the rear mold are opened to their limit positions, the ejector pins are provided with ejection space to eject the product. When ejecting the product, the ejector pins perform at least one ejection action. Taking one ejection action as an example, the ejector pins first extend to the first ejection position and hold for a certain period of time, and then extend to the second ejection position for a certain period of time to demold the product.

[0089] The novel microstructure molding process for plastic surfaces of the present invention involves preheating the mold and its cavity surface to a first preset temperature greater than the Tg temperature of the injection molding material before filling the injection molding material, and continuously heating the mold and cavity surface at the first preset temperature during the injection molding material filling process. This allows the injection molding material to fully fill the cavity, increasing the fullness and height of the molded microstructure. Furthermore, the microstructure can be molded into a single piece as the main body of the plastic product in a single process, resulting in stable structural molding, easy surface cleaning and minimal dust accumulation. Moreover, it eliminates the need to consider equipment compatibility issues, achieving high molding efficiency and low cost.

[0090] Example

[0091] The present invention will be described below using the process of its specific implementation as an example. In specific implementation, it is preferred to use PC raw materials to integrally injection mold the plastic product and the microstructure of its inner surface.

[0092] S101: Set the molding temperature and hot runner temperature and preheat.

[0093] The molding temperatures of the nozzle section, fourth heating section, third heating section, second heating section, first heating section and discharge port section of the barrel are set to 305℃, 305℃, 300℃, 290℃, 280℃ and 270℃ respectively, and the molding temperature of the hot runner is set to 310℃.

[0094] S102: Plasticize and meter the injection molding raw materials.

[0095] Set the screw speed to 60 rpm and the back pressure to 40 kgf / cm. 2 PC raw material particles are added into the barrel. The first and second measurements are performed at 15mm and 50mm from the initial position of the screw, respectively. After the measurement is completed at the 58mm position, the screw is released at a release speed of 15m / s and then released 5mm. At this time, the screw stops at the 73mm position, which is the starting position of the screw movement in the filling stage.

[0096] S103: Close the mold and preheat the mold and cavity surfaces to the first preset temperature.

[0097] Close the front and rear molds of the mold:

[0098] In the first mold closing stage, the mold is closed with a second mold closing pressure of 230TON and a mold closing speed of 45% until the distance between the front mold and the rear mold is 350mm.

[0099] In the second mold-closing stage, the mold is closed with a second mold-closing pressure of 230TON and a mold-closing speed of 40% until the distance between the front mold and the rear mold is 200mm.

[0100] In the third mold-closing stage, the mold is closed with a second mold-closing pressure of 230TON and a mold-closing speed of 30% until the distance between the front mold and the rear mold is 150mm.

[0101] In the fourth stage of mold closing, the mold is closed with a second mold closing pressure of 230TON and a mold closing speed of 25% until the distance between the front mold and the rear mold is 80mm.

[0102] In the fifth mold closing stage, the mold is first closed with a second mold closing pressure of 230TON and a mold closing speed of 25% until the distance between the front mold and the rear mold is 30mm. Then, the mold is closed with a first mold closing pressure of 230*30%TON and a mold closing speed of 25% until the distance between the front mold and the rear mold is 2.4mm, thus completing the mold closing.

[0103] Then, the mold and cavity are heated to 145°C or higher using a heating power of 10KW.

[0104] S104: Filling injection molding material.

[0105] The PC injection molding material inside the barrel is filled into the mold cavity. During filling:

[0106] The first stage of filling is carried out at a filling pressure of 2300 kgf / cm³. 2 The filling speed is 20mm / s, filling from the 73mm position to the 52mm position.

[0107] The second filling stage uses a filling pressure of 2300 kgf / cm³. 2 The filling speed is 45 mm / s, filling from the 52 mm position to the 12 mm position.

[0108] The third stage of filling is carried out at a filling pressure of 2300 kgf / cm³. 2 The filling speed is 25mm / s. After filling from the 12mm position to the 6mm position, quickly switch to the pressure holding stage.

[0109] S105: Pressure holding for injection molded parts.

[0110] Hold pressure on the injection molded part:

[0111] In the first pressure holding stage, the holding speed is 25 mm / s, the holding time is 1.3 s, and the holding pressure is 1000 kgf / cm². 2 .

[0112] In the second pressure holding stage, the holding speed is 25 mm / s, the holding time is 2 seconds, and the holding pressure is 900 kgf / cm². 2 .

[0113] S106: Cool the mold and injection molded parts to the second preset temperature.

[0114] After the pressure holding is completed, cool the mold and injection molded parts to below 90°C.

[0115] S107: Open the mold and eject the injection molded part.

[0116] Open the front and rear molds of the mold:

[0117] In the first mold-opening stage, the mold is opened at a speed of 20% until the distance between the front mold and the rear mold is 35mm.

[0118] In the second mold-opening stage, the mold is opened at a speed of 35% until the distance between the front mold and the rear mold is 85mm.

[0119] In the third mold-opening stage, the mold is opened at a speed of 40% until the distance between the front mold and the rear mold is 160mm.

[0120] In the fourth stage of mold opening, the mold is opened at a speed of 45% until the distance between the front mold and the rear mold is 400mm.

[0121] In the fifth mold opening stage, the mold is opened at a speed of 25% until the distance between the front mold and the rear mold is 450mm.

[0122] The ejector pin is then controlled to push the molded part out 40mm and hold for 1.2s, then continue pushing it forward to 57mm and hold for 1.2s to complete the molding of the plastic product. This process is repeated to execute the next injection molding cycle.

[0123] Please refer to Figure 4 This is a comparison chart of the temperature change curves of the molding die at each stage of the molding process in this embodiment and the temperature change curves of the traditional process. Figures 5-7 The image shows the surface radius, pit size, and roughness measured after scanning the bottom surface of the microstructure using a white light interferometer. Figures 8-9 The morphology, structural dimensions, and microstructures shown Figure 11 The maximum profile curve of the microstructure surface shown is compared with... Figure 10 Compared with the microstructure morphology obtained by the conventional process shown in the figure, the microstructure obtained in this embodiment has a more compact arrangement of protrusions, smaller gaps, and a fuller shape.

[0124] Figure 12 To model and simulate the diffuse reflection of the novel microstructure obtained in this embodiment, it can be seen that parallel light will undergo multiple reflections after hitting the surface of the microstructure, but very little light will enter the lens below.

Claims

1. A novel molding process for microstructures on plastic surfaces, characterized in that, Includes the following steps: Add injection molding material into the barrel, plasticize it, and complete the metering; The mold is closed and the surface of the mold cavity is preheated to a first preset temperature, wherein the first preset temperature is greater than the Tg temperature of the injection molding material; The injection molding material inside the barrel is filled into the mold cavity to form an injection molded part; After filling is complete, switch to pressure holding mode to hold pressure on the injection molded part; After the pressure holding is completed, the cooling channel is opened and the mold and injection molded parts are cooled to the second preset temperature; Open the mold and eject the injection molded part; During the filling process, the mold and cavity surface are maintained at the first preset temperature until the pressure holding is completed.

2. The molding process for the novel microstructure on the plastic surface according to claim 1, characterized in that, Before the steps of adding injection molding material into the barrel, plasticizing, and completing metering, the following steps are also included: The barrel temperature and hot runner temperature of the mold are set, and the barrel and hot runner are preheated at the set barrel temperature and hot runner temperature; wherein, the barrel has a nozzle section, a fourth heating section, a third heating section, a second heating section, a first heating section and a discharge port section arranged in sequence, and the temperatures of the corresponding nozzle section, fourth heating section, third heating section, second heating section, first heating section and discharge port section are set to 295~315℃, 295~315℃, 290~310℃, 280~300℃, 270~290℃ and 260~280℃ respectively, and the hot runner temperature is 290~330℃.

3. The molding process for the novel microstructure on the plastic surface according to claim 1, characterized in that, In the steps of adding injection molding material into the barrel, plasticizing, and metering, multi-stage metering is used when metering the injection molding material. During the metering process, the screw speed inside the barrel is 60*(1±20%) rpm, and the back pressure is 40*(1±20%) kgf / cm². 2 After the metering is completed, the screw is released and retracted. The retraction distance is 5±3mm and the retraction speed is 15*(1±20%)mm / s.

4. The molding process for the novel microstructure on the plastic surface according to claim 1, characterized in that, In the step of closing the mold and heating the surface of the mold cavity to a first preset temperature, a multi-stage mold closing method is adopted. During mold closing, the front mold and the rear mold of the mold move relative to each other to the first mold closing position under the first mold closing pressure, and then switch to the second mold closing pressure and move relative to each other until the mold closing is completed. The first mold closing pressure is greater than the second mold closing pressure, and the mold closing speed of the front mold and the rear mold decreases during relative movement. The first mold closing pressure is 230*30%*(1±20%)TON.

5. The molding process for the novel microstructure of the plastic surface according to claim 1, characterized in that, In the step of closing the mold and heating the surface of the mold cavity to a first preset temperature, the first preset temperature is 135~145℃ and the heating power is 8~15KW.

6. The molding process for the novel microstructure of the plastic surface according to claim 1, characterized in that, In the step of filling the injection molding material in the barrel into the mold cavity to form the injection molded part, a segmented filling method is adopted. During filling: The filling pressure for the first stage of filling is 2300 * (1 ± 20%) kgf / cm³. 2 The filling speed is 20*(1±20%) mm / s, and the filling time is from the metering completion position to the first filling position or the maximum filling time is reached. The first filling position is 52±3mm, and the maximum filling time is 3*(1±20%)s. The filling pressure for the second stage of filling is 2300 * (1 ± 20%) kgf / cm³. 2 The filling speed is 45*(1±20%)mm / s, and the filling time is from the first filling position to the second filling position or until the maximum filling time is reached. The second filling position is 12±3mm. The filling pressure for the third stage of filling is 2300 * (1 ± 20%) kgf / cm³. 2 The filling speed is 25*(1±20%) mm / s, and the filling time is from the second filling position to the pressure holding switching position or the maximum filling time is reached. The pressure holding switching position is 6±3mm.

7. The molding process for the novel microstructure of the plastic surface according to claim 1, characterized in that, In the step of switching to the holding pressure state after filling and holding pressure on the injection molded part, a segmented holding pressure method is adopted. During the holding pressure process: The holding rate in the first pressure holding stage is 25*(1±15%) mm / s, the holding time is 1.3*(1±20%) s, and the holding pressure is 1000*(1±15%) kgf / cm². 2 ; The holding speed in the second holding stage is 25*(1±15%) mm / s, the holding time is 2*(1±20%) s, and the holding pressure is 900*(1±15%) kgf / cm². 2 .

8. The molding process for the novel microstructure of the plastic surface according to claim 1, characterized in that, In the step of opening the cooling channel and cooling the mold and injection part to the second preset temperature after the pressure holding is completed, the cooling time is 30*(1±20%)s and the second preset temperature is 85~95℃.

9. The molding process for the novel microstructure on the plastic surface according to claim 1, characterized in that, In the step of opening the mold and ejecting the injection molded part, a multi-stage mold opening is adopted. When the mold is opened, the opening speed of the front mold and the rear mold moves relative to each other, first increasing and then decreasing until the maximum opening position is reached, after which the injection molded part is ejected and demolded by ejector pins.

10. A novel microstructure on a plastic surface, characterized in that, The novel microstructure is formed using the molding process for novel microstructures on plastic surfaces as described in any one of claims 1 to 9.

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