Thermoplastic resin substrate for curved mirror and preparation method thereof

Abstract

The present invention relates to a thermoplastic resin substrate for a curved mirror, a preparation method thereof, a curved mirror comprising the same, and a head-up display. The preparation method comprises the following steps: A) heating the mold of an injection molding machine to 130-190°C o C and closing the mold, B) injecting molten thermoplastic resin into the mold cavity, C) applying a pressure of 300-700 bar to the cavity and maintaining it for a period of more than 5 seconds, D) stopping the pressure and reducing the temperature of the mold to 60-100 within 10-50 seconds. o C., and E) opening the mold and removing the formed thermoplastic resin substrate, wherein a gap of 0.3-1 mm is maintained at the parting surface of the mold cavity before pressure is applied to the cavity. The thermoplastic resin substrate according to the present invention has a large size, high dimensional stability, and low surface roughness, and can be used in future enhanced head-up displays to achieve large-area, long-distance projection and high-precision imaging, thereby meeting the driving safety and comfort requirements of future automobiles.

Description

Technical Field

[0001] The present invention belongs to the field of thermoplastic resin processing, and in particular relates to a thermoplastic resin substrate for a curved mirror and a preparation method thereof. Background Art

[0002] Head-up displays (HUDs) in cars serve two primary purposes. The first is safety, as they reduce driver distraction and improve safety. The second is a more comfortable driving experience. Furthermore, HUDs place all information directly within the driver's line of sight, enabling faster recognition and understanding of critical situations. With improved feedback on driving and vehicle conditions, important information is less likely to be missed.

[0003] The main types of head-up displays currently in use on the market are combined head-up displays (HUDs) and windshield-mounted HUDs. Windshield-mounted HUDs are increasingly being recognized and adopted by domestic and international automakers, becoming a standard feature.

[0004] Ordinary front windshield head-up displays can meet the imaging distance requirements of 2-3 meters and the projection area requirements of 40cm*20cm.

[0005] However, the projection distance and display image size of current windshield-mounted head-up displays (HUDs) cannot meet the requirements of increasingly complex road environments. These requirements include longer projection distances and longer, wider display images to provide drivers with a more comfortable field of view while also providing more information. The next generation of augmented reality HUDs can move virtual information directly into the driver's line of sight and insert full-color graphics into the real road view, producing an image approximately 130 cm wide and over 60 cm high at a distance of 7.5 meters or even greater from the driver's field of view.

[0006] In addition, the requirements for the surface roughness and surface accuracy of curved mirrors have increased accordingly, and the original preparation and processing methods are no longer suitable for the accuracy requirements of the new generation of curved mirrors.

[0007] Large-sized curved mirrors with high dimensional stability and low surface roughness can achieve the goal of projecting larger images at longer distances. Compared with the thermoplastic resin substrates commonly used for small-sized curved mirrors, the preparation of thermoplastic resin substrates for such large-sized curved mirrors brings the following technical challenges:

[0008] 1. As the size of the concave mirror is greatly increased, the surface area of the concave mirror increases by about 3 times. Such a large-size design is more prone to stress deformation than the original small-size design;

[0009] 2. Since the head-up display will be installed inside the dashboard and close to the engine, high and low temperature fluctuations may cause dimensional changes due to thermal expansion and contraction;

[0010] 3. The larger the surface area of the concave mirror, the higher the process requirements for processing polycarbonate (PC) parts with low surface roughness.

[0011] US 2014 / 0356551 A1 discloses a thermoplastic molded article with high surface quality, which is produced by combining an injection molding process with dynamic temperature control of the mold and by means of a reinforced thermoplastic molding composition.

[0012] JP55161621A discloses a concave plate formed by using a convex mold with a surface roughness of 0.1S or less under direct pressure at a mold temperature of 20-40°C lower than the thermal deformation point of the resin. of Al or Cr to produce a concave mirror.

[0013] However, the existing technology has not yet been able to provide a large-sized curved mirror with high dimensional stability and low surface roughness.

[0014] Therefore, the key to developing a new generation of augmented reality head-up displays is to prepare large-scale curved mirrors with high dimensional stability and low surface roughness. Furthermore, it is necessary to prepare substrates for large-scale curved mirrors with high dimensional stability and low surface roughness. Summary of the Invention

[0015] An object of the present invention is to provide a substrate for a large-sized curved mirror having high dimensional stability and low surface roughness.

[0016] Another object of the present invention is to provide a large-sized curved mirror with high dimensional stability and low surface roughness.

[0017] Therefore, according to a first aspect of the present invention, there is provided a method for preparing a thermoplastic resin substrate for a curved mirror, comprising the following steps:

[0018] A) Heat the mold of the injection molding machine to a temperature within the range of 130-190°C and close the mold.

[0019] B) injecting molten thermoplastic resin into the mold cavity,

[0020] C) applying a pressure of 300-700 bar to the cavity and maintaining it for a period of more than 5 seconds,

[0021] D) ceasing the application of pressure to the cavity and reducing the temperature of the mold to a temperature in the range of 60-100°C, and

[0022] E) opening the mold and taking out the molded thermoplastic resin substrate,

[0023] Before applying pressure to the cavity, a gap of 0.3-1 mm is retained at the parting surface of the mold cavity.

[0024] According to a second aspect of the present invention, there is provided a thermoplastic resin substrate prepared according to the method of the first aspect of the present invention.

[0025] According to a third aspect of the present invention, there is provided a thermoplastic resin substrate for a curved mirror, characterized in that:

[0026] The length is 300-400mm, the width is 150-300mm, and the thickness is 3-6mm.

[0027] Surface roughness ≤10nm,

[0028] Dimensional stability:

[0029] a) Surface aspect peak PV < 25 μm (at 25°C);

[0030] b) After storage at 100°C for 4 hours, the surface difference peak value PV is less than 25 μm.

[0031] According to a fourth aspect of the present invention, there is provided a curved mirror comprising the thermoplastic resin substrate according to the third aspect of the present invention.

[0032] According to a fifth aspect of the present invention, there is provided a head-up display comprising the curved mirror according to the fourth aspect of the present invention.

[0033] The thermoplastic resin substrate according to the present invention has large size, high dimensional stability, low surface roughness and high rigidity, and can be used in future enhanced head-up displays to achieve large-area, long-distance projection and high-precision imaging, thereby meeting the requirements of future automobiles for driving safety and comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Hereinafter, the present invention will be exemplarily described with reference to the accompanying drawings, in which:

[0035] Figure 1 A schematic diagram of a mold that can be used to implement the method of the present invention is shown, wherein a: fixed mold; b: movable mold; c: press frame; d: runner; e: oil cylinder; f: cavity; g: parting line.

[0036] Figure 2 A schematic diagram of the injection-compression molding principle is shown, where (i): the mold is in the open state; (ii): the cavity is formed; (iii): injection into the mold; (iv): compression molding; (v): mold opening and part removal. Specific implementation plan

[0037] Various aspects of the invention as well as further objects, features and advantages will appear more fully hereinafter.

[0038] Therefore, according to a first aspect of the present invention, there is provided a method for preparing a thermoplastic resin substrate for a curved mirror, comprising the following steps:

[0039] A) Heat the mold of the injection molding machine to a temperature within the range of 130-190°C and close the mold.

[0040] B) injecting molten thermoplastic resin into the mold cavity,

[0041] C) applying a pressure of 300-700 bar to the cavity and maintaining it for a period of more than 5 seconds,

[0042] D) ceasing the application of pressure to the cavity and reducing the temperature of the mold to a temperature in the range of 60-100°C, and

[0043] E) opening the mold and taking out the molded thermoplastic resin substrate,

[0044] Before applying pressure to the cavity, a gap of 0.3-1 mm is retained at the parting surface of the mold cavity.

[0045] The inventors of the present invention have conducted extensive research with the aim of providing a thermoplastic resin substrate for a curved mirror having the following characteristics:

[0046] The length is 300-400mm, the width is 150-300mm, and the thickness is 3-6mm.

[0047] Surface roughness ≤10nm,

[0048] Dimensional stability:

[0049] a) Surface aspect peak PV < 25 μm (at 25°C);

[0050] b) After storage at 100°C for 4 hours, the surface difference peak value PV is less than 25 μm.

[0051] The method according to the present invention solves the problem of dimensional stability of large-sized curved mirrors by combining the thermoplastic resin used, the compression injection molding process and the rapid cooling and heating mold temperature control processing technology, so that the stress distribution of the curved mirror during molding is more uniform, the dimensional stability is greatly improved, and the surface finish of the curved mirror is also greatly improved.

[0052] Preferably, the thermoplastic resin is a mineral-filled polycarbonate or a mineral-filled polycarbonate-polyethylene terephthalate blend.

[0053] Preferably, the mineral is selected from talc or quartz.

[0054] Preferably, the amount of the mineral is 10-30% by weight relative to the total weight of the thermoplastic resin.

[0055] For mineral-filled polycarbonate-polyethylene terephthalate (PET) blends, preferably, the weight ratio of polycarbonate to polyethylene terephthalate (PET) is in the range of 90:10 to 60:40.

[0056] Preferably, the thermoplastic resin has a low linear thermal expansion coefficient, which is between 0.4*10 -4 -0.6*10 -4 / K range.

[0057] Preferably, the thermoplastic resin has a low molding shrinkage, which is less than 0.6%.

[0058] Preferably, the thermoplastic resin has high temperature resistance, for example, its heat distortion temperature (HDT) measured at 1.82 MPa is greater than 105°C, preferably in the range of 110-130°C.

[0059] Injection compression molding process:

[0060] Injection compression molding is a combined molding technology of injection molding and compression molding, also known as two-stage injection molding.

[0061] Injection compression molding can be performed using an existing injection molding machine.

[0062] The operation of injection compression molding is mainly divided into two steps, namely injection into mold and compression molding.

[0063] Injection into the mold: The mold is first closed. It is best not to completely close the movable and fixed molds, but to leave a certain distance between them. Because the core part of the mold has no steps, the molten material in the cavity will not leak even if the mold is not completely closed.

[0064] Compression molding: When the screw advances to 50%-100% of the plasticizing capacity, the second mold closing process is performed, completely closing the movable and fixed mold plates. The molten material in the mold cavity is compressed by the movable mold to achieve the precise shape of the cavity. After the plastic part solidifies and the pressure on the mold disappears, the mold is opened and the part is ejected.

[0065] The following combination Figure 1 and Figure 2 The injection compression molding is briefly described. It should be understood that these figures are only for illustration and are not intended to limit the method of the present invention.

[0066] Figure 1A schematic diagram of a mold that can be used to implement the method of the present invention is shown, wherein a: fixed mold; b: movable mold; c: press frame; d: runner; e: oil cylinder; f: cavity; g: parting line.

[0067] Figure 2 The figure shows a schematic diagram of the injection compression molding principle, where (i): the mold is in the open state; (ii): the cavity is formed; (iii): injection into the mold; (iv): compression molding; (v): mold opening and part removal.

[0068] Figure 2 (i) Shows the mold in the open state.

[0069] Figure 2 (ii) shows the movable mold b advancing and stopping a certain distance from the fixed mold a. Then, driven by the hydraulic cylinder e, the press frame c advances and presses against the fixed mold a. This creates a cavity f with variable thickness between the movable mold b, the fixed mold a, and the press frame c.

[0070] Figure 2 (iii) shows that the resin melt is injected into the mold cavity f through the runner d.

[0071] Figure 2 (iv) shows that after the resin melt is injected into the cavity f or during the injection process, the movable mold b is completely closed to complete the compression of the melt.

[0072] Figure 2 (v) shows that after a certain period of cooling, the movable mold b is opened and the part is removed.

[0073] The time for heating the mold of the injection molding machine to a temperature within the range of 130-190° C. is not particularly limited and can generally be determined according to the heating method of the mold, for example, within the range of 10-200 seconds.

[0074] Preferably, a gap of 0.6 mm is retained at the parting surface of the mold cavity before pressure is applied to the cavity.

[0075] Preferably, the gap at the parting surface of the mold cavity does not exceed 0.1 mm, preferably 0 mm, when the application of pressure to the cavity is stopped.

[0076] Preferably, in step B, the holding pressure of the screw when injecting the molten thermoplastic resin into the mold cavity is in the range of 50-150 bar, preferably 60-140 bar, thereby making the cavity pressure distribution more uniform and minimizing product deformation.

[0077] Preferably, in step B, the temperature of the molten thermoplastic resin is in the range of 270-310°C.

[0078] Preferably, in step C, the pressure is in the range of 300-600 bar.

[0079] Preferably, the holding time is in the range of 5-50 s, more preferably 10-40 s.

[0080] In step D, the time for lowering the mold of the injection molding machine to a temperature within the range of 60-100° C. is not particularly limited and can generally be determined according to the cooling method of the mold, for example, within the range of 10-150 seconds.

[0081] In some embodiments, the thermoplastic resin used is a mineral-filled polycarbonate / polyethylene terephthalate blend, and in step A, the mold is heated to a temperature in the range of 130-160°C, and in step D, the temperature of the mold is lowered to a temperature in the range of 80-90°C.

[0082] In some embodiments, the thermoplastic resin used is a mineral-filled polycarbonate, and in step A, the mold is heated to a temperature in the range of 140-190°C, and in step D, the temperature of the mold is lowered to a temperature in the range of 90-100°C.

[0083] Preferably, the core of the mold has good machinability and corrosion resistance, and also has good polishability. For example, the core is made of mold steel labeled 1.2343 or 1.2343+ and processed by high-speed milling, surface hardening, and surface fine polishing.

[0084] Preferably, the surface hardness of the core of the mold reaches above 50HRC.

[0085] Preferably, the surface polishing level of the core of the mold reaches above 10 nm.

[0086] According to a second aspect of the present invention, there is provided a thermoplastic resin substrate prepared according to the method of the first aspect of the present invention.

[0087] In some embodiments, the thermoplastic resin substrate has the following characteristics:

[0088] The length is 200-500mm, the width is 100-350mm, and the thickness is 3-6mm.

[0089] Surface roughness ≤10nm,

[0090] Dimensional stability:

[0091] a) Surface aspect peak PV < 25 μm (at 25°C);

[0092] b) After storage at 100°C for 4 hours, the surface difference peak value PV is less than 25 μm.

[0093] According to a third aspect of the present invention, there is provided a thermoplastic resin substrate for a curved mirror, characterized in that:

[0094] The length is 300-400mm, the width is 150-300mm, and the thickness is 3-6mm.

[0095] Surface roughness ≤10nm,

[0096] Dimensional stability requirements:

[0097] a) Surface aspect peak PV < 25 μm (at 25°C);

[0098] b) After storage at 100°C for 4 hours, the surface difference peak value PV is less than 25 μm.

[0099] According to a fourth aspect of the present invention, there is provided a curved mirror comprising the thermoplastic resin substrate according to the third aspect of the present invention.

[0100] In addition to the thermoplastic resin substrate according to the third aspect of the present invention, the curved mirror further comprises at least one reflective film provided on the substrate, wherein the reflective film is selected from the group consisting of aluminum film, copper film and inorganic non-metallic film.

[0101] The inorganic non-metallic film may be an inorganic non-metallic film commonly used in the field of curved mirror preparation.

[0102] The reflective film can be coated by a common method in the art, such as evaporation or sputtering.

[0103] The thickness of the reflective film may be in the range of 30-300 nm.

[0104] In some embodiments, the resulting curved mirror has a reflectivity of ≥85% for visible light in the range of 420-680 nm.

[0105] According to a fifth aspect of the present invention, there is provided a head-up display comprising the curved mirror according to the fourth aspect of the present invention.

[0106] The terms “include” and “comprising” used in the present application encompass the case where the application further includes or comprises other elements not explicitly mentioned as well as the case where the application consists of the mentioned elements.

[0107] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention belongs. When the definition of a term in this specification conflicts with the meaning commonly understood by those skilled in the art to which the invention belongs, the definition described in this article shall prevail.

[0108] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as modified by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth herein are approximations that can vary depending upon the desired properties sought to be obtained.

[0109] Example

[0110] The following will further illustrate the concept and technical effects of the present invention in conjunction with the embodiments so that those skilled in the art can fully understand the purpose, features and effects of the present invention. It should be understood that some embodiments are only illustrative and do not constitute a limitation on the scope of the present invention.

[0111] Description of the main raw materials used:

[0112] PC-1: ordinary polycarbonate, from Covestro Polymers (China) Co., Ltd.;

[0113] PC-2: filled polycarbonate / PET blend, UT235M from Covestro Polymers (China) Co., Ltd.

[0114] PC-3: Filled polycarbonate, DS801 from Covestro Polymers (China) Co., Ltd.

[0115] The following are the performance data of the raw materials used:

[0116]

[0117] CLTE*: Coefficient of linear thermal expansion, measured according to ISO 11359-1, -2.

[0118] MVR**: Melt flow rate, measured using ISO 1133.

[0119] Tensile modulus and tensile strength: tested using ISO 527-1, -2.

[0120] Molding shrinkage: tested using acc. ISO 2577.

[0121] Description of experimental equipment used:

[0122] Injection molding machine: Engel 650 injection compression molding machine.

[0123] Mold temperature controller: Single ATT H2-200-48 mold temperature controller.

[0124] Injection mold: From Covestro Polymers (China) Co., Ltd., designed according to the 318mm*140.7mm*4mm concave reflector.

[0125] Mould structure:

[0126] 1. The mold is a two-plate mold, with the mirror core and hot runner mechanism on the fixed side, and the compression mechanism and ejection mechanism on the moving side.

[0127] 2. The compression mechanism uses a compression frame structure, with a hydraulic cylinder controlling the forward and backward movement of the compression frame, with a maximum movement distance of 5mm. The hydraulic cylinder can provide 40 tons of clamping force to seal the mold cavity. This compression mechanism is used in conjunction with the injection molding machine's injection program to perform the injection molding operation.

[0128] 3. The mold core is made of 1.2343 mold steel, which has excellent machining performance and corrosion resistance, and also has excellent polishing performance. The polishing grade of the core surface can reach above 10nm.

[0129] 4. Harden the surface of the polished core to make the surface hardness of the steel reach 50HRC. This way, the steel can resist the abrasion of the polished surface by the plastic melt during the molding process.

[0130] 5. There are rapid cooling and heating water circuits in the cores of the movable mold and the fixed mold, which can meet the high temperature and high pressure conditions of 200℃ / 22bar.

[0131] Optical detection method:

[0132] (1) Using a structured light scanner to measure the PV value of the curved mirror;

[0133] (2) Use white light interferometer to measure the roughness of the curved mirror surface;

[0134] (3) Lamda 750 spectrophotometer was used to measure the reflectivity of visible light in the range of 420-680 nm.

[0135] Comparative Example 1 (CE1)

[0136] The PC-1 resin was placed in a dehumidifying dryer and dried at 120° C. for 4 hours to reduce the moisture content of the PC-1 resin to below 0.01 wt %.

[0137] A mold designed for a thermoplastic resin substrate with a thickness of 7 mm was selected.

[0138] The injection molding machine mold is first heated to 100-110°C. The mold is initially closed, maintaining a 0.6mm gap at the parting line. Molten PC-1 resin at 280-300°C is then injected into the mold cavity, with the screw maintaining a holding pressure of 65 bar. A pressure of 600 bar is applied to the cavity and maintained for 30 seconds, at which point the gap at the parting line is 0 mm. Pressure is then removed and the cavity temperature is cooled to 80-90°C over 20 seconds. The mold is then opened and the molded thermoplastic resin substrate is removed.

[0139] The parameters during substrate preparation are summarized in Table 1.

[0140] The removed substrate was baked at 100° C. for 4 hours and then blown with an ion air gun for 5 seconds.

[0141] Optical tests were performed on the substrates before and after baking, and the results are summarized in Table 2.

[0142] Then at a temperature between 40-105°C and 2*10E -3 -3*10E -3 Vacuum deposition was started, and the film layer was a metallic aluminum film with a thickness of 150nm. After the evaporation was completed, a curved mirror was obtained.

[0143] Comparative Example 2 (CE2)

[0144] Comparative Example 2 was carried out with reference to Comparative Example 1, except that a mold designed for a thermoplastic resin substrate with a thickness of 4 mm was selected and the holding pressure of the screw was 130 bar.

[0145] The parameters in the substrate preparation process are summarized in Table 1.

[0146] The optical test results of the obtained substrate and curved mirror are summarized in Table 2.

[0147] Comparative Example 3 (CE3)

[0148] Comparative Example 3 was carried out with reference to Comparative Example 1, except that a mold designed for a thermoplastic resin substrate with a thickness of 4 mm was selected.

[0149] The parameters in the substrate preparation process are summarized in Table 1.

[0150] The optical test results of the obtained substrate and curved mirror are summarized in Table 2.

[0151] Example 1 (E1)

[0152] First, the PC-2 resin was placed in a dehumidifying dryer and dried at 120° C. for 4 hours to reduce the moisture content of the PC-2 resin to below 0.01% by weight.

[0153] A mold designed for a thermoplastic resin substrate with a thickness of 4 mm was selected.

[0154] The injection molding machine mold is first heated to 140-160°C. The mold is initially closed, maintaining a 0.6mm gap at the parting line. PC-2 resin, molten at 270-290°C, is then injected into the mold cavity with a screw pressure of 130 bar. A pressure of 600 bar is applied to the cavity and maintained for 30 seconds, at which point the gap at the parting line is 0 mm. Pressure is then removed and the cavity temperature is allowed to cool to 80-90°C over 40 seconds. The mold is then opened and the molded thermoplastic resin substrate is removed.

[0155] The removed substrate was baked at 100° C. for 4 hours and then blown with an ion air gun for 5 seconds.

[0156] Optical tests were performed on the substrates before and after baking, and the results are summarized in Table 2.

[0157] Then at a temperature between 40-105°C and 2*10E -3 -3*10E -3 Vacuum deposition was started, and the film layer was a metallic aluminum film with a thickness of 150nm. After the evaporation was completed, a curved mirror was obtained.

[0158] The optical test results are summarized in Table 2.

[0159] Example 2 (E2)

[0160] Example 2 was carried out with reference to Example 1, except that the holding pressure of the screw was 65 bar.

[0161] The parameters in the substrate preparation process are summarized in Table 1.

[0162] The optical test results of the obtained substrate and curved mirror are summarized in Table 2.

[0163] Comparative Example 4 (CE4)

[0164] The PC-2 resin was placed in a dehumidifying dryer and dried at 120° C. for 4 hours to reduce the moisture content of the PC-2 resin to below 0.01 wt %.

[0165] A mold designed for a thermoplastic resin substrate with a thickness of 4 mm was selected.

[0166] First, heat the injection molding machine mold to 140-160°C and fully close the mold. Then, inject melted PC-2 resin at 270-290°C into the mold cavity, maintaining a screw pressure of 65 bar. Hold the resin in the cavity for 30 seconds. Then, raise the cavity temperature to 80-90°C over 40 seconds. The mold is then opened and the molded thermoplastic resin substrate is removed.

[0167] The parameters during substrate preparation are summarized in Table 1.

[0168] The removed substrate was baked at 100° C. for 4 hours and then blown with an ion air gun for 5 seconds.

[0169] Optical tests were performed on the substrates before and after baking, and the results are summarized in Table 2.

[0170] Then at a temperature between 40-105°C and 2*10E -3 -3*10E -3 Vacuum deposition was started, and the film layer was a metallic aluminum film with a thickness of 150nm. After the evaporation was completed, a curved mirror was obtained.

[0171] Comparative Example 5 (CE5)

[0172] Example 5 was compared with Example 1, except that a mold designed for a thermoplastic resin substrate with a thickness of 7 mm was selected and the holding pressure of the screw was 65 bar.

[0173] The parameters in the substrate preparation process are summarized in Table 1.

[0174] The optical test results of the obtained substrate and curved mirror are summarized in Table 2.

[0175] Example 3 (E3)

[0176] Before the PC-3 resin is melted and injected into the mold, the PC-3 resin is placed in a dehumidifying dryer and dried at 120° C. for 4 hours to reduce the moisture content of the PC-3 resin to below 0.01 wt %.

[0177] A mold designed for a thermoplastic resin substrate with a thickness of 4 mm was selected.

[0178] The injection molding machine mold is first heated to 160-180°C, initially closed, and a 0.6mm gap is maintained at the parting line. PC-3 resin, molten at 280-300°C, is then injected into the mold cavity, with the screw maintaining a holding pressure of 130 bar. A pressure of 600 bar is applied to the cavity and maintained for 30 seconds, at which point the gap at the parting line is 0 mm. Pressure is then removed, and the cavity temperature is allowed to cool to 90-100°C over 60 seconds. The mold is then opened and the molded thermoplastic resin substrate is removed.

[0179] The parameters during substrate preparation are summarized in Table 1.

[0180] The removed substrate was baked at 100° C. for 4 hours and then blown with an ion air gun for 5 seconds.

[0181] Optical tests were performed on the substrates before and after baking, and the results are summarized in Table 2.

[0182] Then at a temperature between 40-105°C and 2*10E -3 -3*10E -3 Vacuum deposition was started, and the film layer was a metallic aluminum film with a thickness of 150nm. After the evaporation was completed, a curved mirror was obtained.

[0183] The optical test results are summarized in Table 2.

[0184] Example 4 (E4)

[0185] Example 4 was carried out with reference to Example 3, except that the holding pressure of the screw was 65 bar.

[0186] The parameters in the substrate preparation process are summarized in Table 1.

[0187] The optical test results of the obtained substrate and curved mirror are summarized in Table 2.

[0188] Comparative Example 6 (CE6)

[0189] Before the PC-3 resin is melted and injected into the mold, the PC-3 resin is placed in a dehumidifying dryer and dried at 120° C. for 4 hours to reduce the moisture content of the PC-3 resin to below 0.01 wt %.

[0190] A mold designed for a thermoplastic resin substrate with a thickness of 4 mm was selected.

[0191] First, heat the injection molding machine mold to 160-180°C and fully close the mold. Then, inject melted PC-3 resin at 280-300°C into the mold cavity, maintaining a screw pressure of 65 bar. Hold the resin in the cavity for 30 seconds. Then, cool the cavity temperature to 90-100°C over 60 seconds, open the mold, and remove the molded thermoplastic resin substrate.

[0192] The parameters during substrate preparation are summarized in Table 1.

[0193] The removed substrate was baked at 100° C. for 4 hours and then blown with an ion air gun for 5 seconds.

[0194] Optical tests were performed on the substrates before and after baking, and the results are summarized in Table 2.

[0195] Then at a temperature between 40-105°C and 2*10E -3 -3*10E -3 Vacuum deposition was started, and the film layer was a metallic aluminum film with a thickness of 150nm. After the evaporation was completed, a curved mirror was obtained.

[0196]

[0197]

[0198] A comparison between Example 1 (E1) and Example 2 (E2) shows that the surface shape of the curved mirror produced using the mineral-filled PC / PET blend is not easily affected by molding process parameters. For example, even with significant changes in the holding pressure, the surface shape of the curved mirror changes very little. This demonstrates that the filled-grade PC blend has a wide molding processing window and can ensure excellent dimensional stability during mass production.

[0199] A comparison between Example 3 (E3) and Example 4 (E4) shows that the surface shape of the curved mirror produced using filler-grade PC is not easily affected by molding process parameters. For example, even with significant changes in the holding pressure, the surface shape of the curved mirror changes very little. This demonstrates that filler-grade PC has a wide molding processing window and can ensure excellent dimensional stability during mass production.

[0200] Although some aspects of the present invention have been shown and discussed, it will be appreciated by those skilled in the art that changes can be made to the above aspects without departing from the principles and spirit of the invention. Therefore, the scope of the invention will be defined by the claims and their equivalents.

Claims

1. A method for preparing a thermoplastic resin substrate for a curved mirror, comprising the following steps: A) Heat the mold of the injection molding machine to a temperature within the range of 130-190°C and close the mold. B) injecting molten thermoplastic resin into the mold cavity, C) applying a pressure of 300-700 bar to the cavity and maintaining it for a period of 5-50 seconds, D) ceasing the application of pressure to the cavity and reducing the temperature of the mold to a temperature in the range of 60-100°C, and E) opening the mold and taking out the molded thermoplastic resin substrate, Before applying pressure to the cavity, a gap of 0.3-1 mm is retained at the parting surface of the mold cavity. The thermoplastic resin is a mineral-filled polycarbonate material or a mineral-filled polycarbonate-polyethylene terephthalate blend, and the amount of the mineral is 10-30% by weight relative to the total weight of the thermoplastic resin. The thickness of the substrate is 3-6 mm.

2. The method according to claim 1, characterized in that The mineral is selected from talc or quartz.

3. The method according to claim 1, characterized in that The thermoplastic resin is a mineral-filled polycarbonate-polyethylene terephthalate blend, and the weight ratio of polycarbonate to polyethylene terephthalate (PET) is in the range of 90:10-60:

40.

4. The method according to any one of claims 1 to 3, characterized in that The thermoplastic resin has a -4 -0.6*10 -4 Linear thermal expansion coefficient in the range of / K.

5. The method according to any one of claims 1 to 3, characterized in that The thermoplastic resin has a molding shrinkage of less than 0.6%.

6. The method according to any one of claims 1 to 3, characterized in that The thermoplastic resin has a HDT measured at 1.82 MPa greater than 105°C.

7. The method according to any one of claims 1 to 3, characterized in that The thermoplastic resin has a HDT measured at 1.82 MPa in the range of 110-130°C.

8. The method according to any one of claims 1 to 3, characterized in that The gap at the parting surface of the mold cavity does not exceed 0.1 mm when the application of pressure to the cavity is stopped.

9. The method according to any one of claims 1 to 3, characterized in that The gap at the parting surface of the mold cavity is 0 mm when the application of pressure to the cavity is stopped.

10. The method according to any one of claims 1 to 3, characterized in that In step B, the holding pressure of the screw is in the range of 50-150 bar when the molten thermoplastic resin is injected into the mold cavity.

11. The method according to any one of claims 1 to 3, characterized in that In step C, the pressure is in the range of 300-600 bar.

12. The method according to any one of claims 1 to 3, characterized in that The thermoplastic resin used was a mineral-filled polycarbonate / polyethylene terephthalate blend. In step A, the mold was heated to a temperature in the range of 130-160°C. In step D, the temperature of the mold was lowered to a temperature in the range of 80-90°C.

13. The method according to any one of claims 1 to 3, characterized in that The thermoplastic resin used is mineral-filled polycarbonate. In step A, the mold is heated to a temperature in the range of 140-190°C. In step D, the temperature of the mold is lowered to a temperature in the range of 90-100°C.

14. The method according to any one of claims 1 to 3, characterized in that The core of the mold is made of 1.2343 or 1.2343+ mold steel.

15. The method according to any one of claims 1 to 3, characterized in that The surface hardness of the core of the mold reaches above 50HRC.

16. The method according to any one of claims 1 to 3, characterized in that The surface polishing level of the core of the mold reaches above 10nm.

17. A thermoplastic resin substrate produced by the method according to any one of claims 1 to 16.

18. The thermoplastic resin substrate according to claim 17, wherein The length is 200-500mm, the width is 100-350mm, and the thickness is 3-6mm. Surface roughness ≤10nm, Dimensional stability: a) Surface aspect peak value PV < 25 μm (at 25°C); b) After storage at 100°C for 4 hours, the surface difference peak value PV is less than 25 μm.

19. The thermoplastic resin substrate according to claim 17, wherein Length 300-400mm, width 150-300mm, thickness 3-6mm Surface roughness ≤10nm, Dimensional stability: a) Surface aspect peak value PV < 25 μm (at 25°C); b) After storage at 100°C for 4 hours, the surface difference peak value PV is less than 25 μm.

20. A curved mirror comprising the thermoplastic resin substrate according to claim 17.

21. The curved mirror according to claim 20, characterized in that It also includes at least one reflective film arranged on the substrate, and the reflective film is selected from aluminum film, copper film and inorganic non-metallic film.

22. A head-up display comprising the curved mirror according to claim 20 or 21.

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