Light guide plate and preparation method thereof

Abstract

The invention relates to the technical field of optical display, and provides a preparation method of a light guide plate, polycarbonate plastic particles are used as raw materials, and an injection molding process of the light guide plate comprises the following steps: mounting a special mold for the light guide plate on an injection molding machine; drying the polycarbonate plastic particles at the temperature of 90-100 DEG C for 4 hours; the dried particles are conveyed to a mold charging barrel through a closed circulating system, and dust is synchronously removed; the high-quality polycarbonate material is adopted, so that the light guide effect is stable, and the light transmittance is high; through optimization of technological parameter setting, common defects such as yellowing, sink marks and internal stress of the product are reduced; by optimizing a drying and conveying system, it is ensured that raw materials are clean and dry, and product consistency is improved; the adjustable range of injection molding parameters is wide, and the requirements of different mold structures and product sizes are met; the finished product has high surface smoothness without subsequent polishing treatment, so that the processing cost is reduced; and the method is high in process stability and suitable for industrial large-scale continuous production.

Description

Technical Field

[0001] The present invention relates to the field of optical display, and more particularly to a light guide plate and a preparation method thereof. Background Art

[0002] The light guide plate is made of optical-grade acrylic / PC sheet material. Light guide points are printed on the bottom surface of the optical-grade acrylic sheet using laser engraving, V-shaped cross-grid engraving, and UV screen printing technology. The optical-grade acrylic sheet absorbs the light emitted from the lamp and stays on the surface of the optical-grade acrylic sheet. When the light hits each light guide point, the reflected light spreads in all directions, breaking the reflection conditions and emitting from the front of the light guide plate. The various light guide points of varying density and size ensure uniform illumination of the light guide plate.

[0003] Existing light guide plates are mostly made of PMMA or PC. During the injection molding process, defects such as bubbles, yellowing, and sink marks are prone to occur, affecting the product's appearance and service life. Therefore, a light guide plate injection molding process with controllable molding conditions and stable product quality is urgently needed. Summary of the Invention

[0004] The purpose of the present invention is to provide a light guide plate and a preparation method thereof, and to achieve the purpose of a product with a smooth surface, dense interior and excellent optical properties by optimizing injection molding process parameters.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a light guide plate, using polycarbonate plastic particles as raw materials, and the injection molding process thereof comprises the following steps:

[0007] Step S1: Installing the light guide plate mold on the injection molding machine;

[0008] Step S2: drying the polycarbonate plastic particles at 90° C.-100° C. for 4 hours;

[0009] Step S3: transporting the dried particles to the mold barrel through a closed circulation system and simultaneously removing dust;

[0010] Step S4: heating the material to 260°C-310°C in the barrel to convert the plastic particles into a viscous melt;

[0011] Step S5: injecting the melt into the mold cavity through the nozzle by a screw at an injection pressure of 180MPa-200MPa, and setting the mold temperature to 110℃-130℃ for the male mold and 65-75℃ for the female mold;

[0012] Step S6: maintaining a holding pressure of 70-200 MPa for 1-3 hours;

[0013] Step S7: Cooling water is introduced to cool the mold, and the semi-finished product is ejected after the melt solidifies;

[0014] Step S8: Cut the gate, inspect the product for defects and then package it.

[0015] Furthermore, in the present invention, a box-type dryer is used for drying in step S2.

[0016] Furthermore, in the present invention, a centralized closed air circulation conveying system is used in step S3, and the system has a dust removal device to remove dust generated during the conveying process.

[0017] Furthermore, in the present invention, the barrel heating temperature in step S4 is 300° C., and the residence time of the melt in the barrel does not exceed the critical value of thermal degradation of the material.

[0018] Furthermore, in the present invention, in step S5, the mold temperature is set to 120° C. for the male mold and 70° C. for the female mold.

[0019] Furthermore, in the present invention, the injection time is 0.45-1 second, and the holding time is 1-3 seconds.

[0020] Furthermore, in the present invention, the injection speed is 20-150 rpm, preferably 150 mm / s, and the storage speed is 60-100 rpm.

[0021] Furthermore, in the present invention, the temperature of the cooling water in step S7 is 15° C.-25° C., and the cooling time is set at a ratio of 0.5 min / mm according to the thickness of the light guide plate.

[0022] Furthermore, in the present invention, the injection position is 17-33 mm, the material storage position is 28 mm, and the ejection position is 55 mm.

[0023] The present invention also provides a light guide plate, which is manufactured by the above-mentioned manufacturing method.

[0024] Beneficial effects of the present invention:

[0025] The present invention adopts high-quality polycarbonate material, which has a stable light-guiding effect and high light transmittance. By optimizing the process parameter settings, common defects such as yellowing, shrinkage, and internal stress of the product are reduced. By optimizing the drying and conveying system, the raw materials are ensured to be clean and dry, and the consistency of the product is improved. The injection molding parameters have a wide adjustable range to meet the requirements of different mold structures and product sizes. The finished product has a high surface finish and does not require subsequent polishing, which reduces processing costs. The process is highly stable and is suitable for industrial-scale continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] Figure 1 Flowchart of the method for preparing a light guide plate of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] like Figure 1 As shown, this embodiment provides a method for preparing a light guide plate, using polycarbonate plastic particles as raw materials, and the injection molding process includes the following steps:

[0031] Step S1: Install the light guide plate mold on the injection molding machine, ensuring that the mold is tightly closed and the cooling system operates normally.

[0032] Step S2: Dry the PC particles at 95° C. for 4 hours using a box-type dryer to remove moisture adsorbed by the material.

[0033] Step S3: A centralized closed air circulation conveying system is used to transfer the dried particles to the injection molding machine hopper, and the fine powder in the conveying process is removed by a built-in dust removal device.

[0034] Step S4: The temperature of the material barrel is set at 260°C to 310°C, preferably 300°C, to prevent the material temperature from being too high and yellowing. Segmented heating is used to avoid local overheating or decomposition, so as to convert the plastic particles into a viscous melt. The residence time of the melt in the barrel does not exceed the critical value of thermal degradation of the material.

[0035] Step S5: The melt is injected into the mold cavity through the nozzle by a screw at an injection pressure of 180MPa-200MPa, with an injection time of 0.6 seconds and an injection speed of 150mm / s to prevent yellowing of the product due to excessive shear heat during molding, while ensuring rapid and uniform filling of the mold cavity.

[0036] Step S6: Maintaining a holding pressure of 70-200 MPa for 1-3 hours to compensate for the shrinkage of the melt during cooling. Excessive pressure can easily lead to burrs and internal stress concentration in the product, while too little pressure can lead to insufficient filling, resulting in glue shortage or shrinkage marks.

[0037] Step S7: The mold temperature is set at 120°C for the male mold and 70°C for the female mold to ensure smooth glue flow during molding. High mold temperature is used to reduce glue viscosity and prevent excessive viscosity during molding, which may cause yellowing of the product. Circulating cooling water maintains a constant temperature to ensure that the light guide plate surface is free of warping or internal stress concentration. The cooling water temperature is 15°C-25°C, and the cooling time is set at a ratio of 0.5 min / mm based on the thickness of the light guide plate. After the melt solidifies, the semi-finished product is ejected, and the molded product is smoothly ejected to prevent surface scratches or deformation.

[0038] Step S8: manually or automatically cutting the gate and cleaning the edge burrs.

[0039] Preferably, this embodiment also includes checking whether the product has defects such as deformation, discoloration, shrinkage, bubbles, etc. Finally, the qualified light guide plates are dust-free packaged and stored in the finished product warehouse.

[0040] In this embodiment, preferably, the injection position is 17-33 mm, the material storage position is 28 mm, and the ejection position is 55 mm. The injection position is reasonably set according to the total mass of the plastic part and the agglomerate, the type of plastic, the mold structure, etc.

[0041] Example 2

[0042] This embodiment provides a light guide plate, which is manufactured by the light guide plate manufacturing method in Example 1. The light guide plate manufactured in this embodiment has an optical uniformity deviation of ≤1.5%, a light transmittance ≥92%, a yellowing index ΔYI <0.8, and has the characteristics of a smooth surface, no bubbles, few shrinkage marks, and good optical uniformity.

[0043] The light guide plate prepared in this embodiment was tested for red light, blue light, green light, yellow light and white light. The brightness of each color was tested at 7 different positions. The experimental data of the finished product is shown in the following table:

[0044]

[0045]

[0046] In the description of the present invention, unless otherwise specified, “plurality” means two or more; it should be understood that terms such as “opening”, “upper”, “lower”, “thickness”, “top”, “middle”, “length”, “inner”, “around”, etc., indicating orientation or positional relationship, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0047] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a light guide plate, characterized in that: Using polycarbonate plastic particles as raw materials, the injection molding process includes the following steps: Step S1: Installing the light guide plate mold on the injection molding machine; Step S2: drying the polycarbonate plastic particles at 90° C.-100° C. for 4 hours; Step S3: transporting the dried particles to the mold barrel through a closed circulation system and simultaneously removing dust; Step S4: heating the material to 260°C-310°C in the barrel to convert the plastic particles into a viscous melt; Step S5: injecting the melt into the mold cavity through the nozzle by a screw at an injection pressure of 180MPa-200MPa, and setting the mold temperature to 110℃-130℃ for the male mold and 65-75℃ for the female mold; Step S6: maintaining a holding pressure of 70-200 MPa for 1-3 hours; Step S7: Cooling water is introduced to cool the mold, and the semi-finished product is ejected after the melt solidifies; Step S8: Cut the gate, inspect the product for defects and then package it.

2. The method for preparing a light guide plate according to claim 1, wherein: In step S2, a box-type dryer is used for drying.

3. The method for preparing a light guide plate according to claim 1, wherein: In step S3, a centralized closed air circulation conveying system is used, and the system is equipped with a dust removal device to remove dust generated during the conveying process.

4. The method for preparing a light guide plate according to claim 1, wherein: The barrel heating temperature in step S4 is 300° C., and the residence time of the melt in the barrel does not exceed the critical value of thermal degradation of the material.

5. The method for preparing a light guide plate according to claim 1, wherein: In step S5, the mold temperature is set to 120°C for the male mold and 70°C for the female mold.

6. The method for preparing a light guide plate according to claim 1, wherein: The injection time is 0.45-1 second, and the holding time is 1-3 seconds.

7. The method for preparing a light guide plate according to claim 1, wherein: The injection speed is 20-150 rpm, preferably 150 mm / s, and the storage speed is 60-100 rpm.

8. The method for preparing a light guide plate according to claim 1, wherein: The temperature of the cooling water in step S7 is 15° C.-25° C., and the cooling time is set at a ratio of 0.5 min / mm according to the thickness of the light guide plate.

9. The method for preparing a light guide plate according to claim 1, wherein: The injection position is 17-33mm, the storage position is 28mm, and the ejection position is 55mm.

10. A light guide plate, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 9.

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