Composite membrane as well as preparation method and application thereof

Abstract

The invention provides a composite film and a preparation method and application thereof, and relates to the technical field of composite films, the composite film comprises a reflecting layer and a backlight layer, and the reflecting layer and the backlight layer are attached to each other; the reflecting layer comprises one of a polycarbonate reflecting film, a PET (Polyethylene Terephthalate) reflecting film or a PP (Propene Polymer) reflecting film; the backlight layer comprises a backlight flame-retardant film, the composite film has good insulativity and flame retardance, the film face is thinned, the problem that in the prior art, when an iron backboard frame is used, the weight is large is solved, and the risks of electric leakage and electric shock of the iron backboard frame are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of composite membranes, and in particular to a composite membrane and a preparation method and application thereof. Background Art

[0002] Currently, most of the large-size LCD (liquid crystal display) backlights on the market, such as TV (television), MNT (monitor), etc., use iron bottom frames (such as Figure 6 However, the use of an iron bottom frame has many disadvantages. The iron bottom frame is heavy and expensive, and is prone to rust and oxidation. In addition, the iron bottom frame is conductive and has dangerous hidden dangers such as leakage and breakdown.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] One of the purposes of the present invention is to provide a composite film to solve at least one of the technical problems existing in the prior art. The composite film provided by the present invention is formed by a composite of a reflective layer and a backlight layer. The reflective film plays a role of reflecting light and can be used as a reflective layer. The backlight flame retardant film has backlight and flame retardant effects and can be used as a light-shielding flame retardant layer. The composite film has good insulation and flame retardancy, and realizes thinning of the film surface, solves the problem of heavy weight when using an iron backplane frame in the prior art, and reduces the risk of leakage and electric shock of the iron backplane frame.

[0005] The second object of the present invention is to provide a method for preparing a composite film. The present invention adopts a composite process to composite a polycarbonate reflective film and a backlight flame retardant film by multi-layer co-extrusion to prepare a composite film. The preparation process is simple, and the prepared composite film product is lightweight and has good insulation and flame retardancy.

[0006] The third object of the present invention is to provide an application of a composite film in the preparation of a flame-retardant polycarbonate reflective composite backboard for backlighting.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] In a first aspect, the present invention provides a composite film, comprising:

[0009] A reflective layer and a backlight layer, wherein the reflective layer and the backlight layer are bonded to each other;

[0010] The reflective layer includes one of a polycarbonate reflective film, a PET reflective film or a PP reflective film;

[0011] The backlight layer includes a backlight flame-retardant film.

[0012] Furthermore, a conductive paint is printed on the backlight flame retardant film by printing;

[0013] Preferably, the thickness of the conductive paint is 0.6-0.8um;

[0014] Preferably, the conductive paint is arranged in a grid pattern.

[0015] Furthermore, the constituent materials of the polycarbonate reflective film include: first polycarbonate particles, reflective masterbatch, transparent polyester resin and foaming aid;

[0016] Preferably, the constituent materials of the polycarbonate reflective film include, based on 100 parts by weight: 30-50 parts of first polycarbonate particles, 25-50 parts of reflective masterbatch, 5-20 parts of transparent polyester resin and 2-5 parts of foaming aid;

[0017] Preferably, the transparent polyester resin includes at least one of PMMA, PE, PA and PBT;

[0018] Preferably, the foaming aid comprises at least one of expansion particles and glass microspheres;

[0019] The expanded particles include Expencel R 980DU100 and Expensel R At least one of 980DU200; preferably, the glass microspheres include 3M R S38HS, 3M R K46, 3M R S60 and 3M R At least one of S60HS;

[0020] Preferably, the particle size of the glass microspheres is 30-100 um.

[0021] Furthermore, the reflective masterbatch comprises components of second polycarbonate particles, crystalline polyester resin, titanium dioxide and an optional antioxidant.

[0022] Furthermore, the components of the reflective masterbatch include, based on 100 parts by weight: 20-40 parts of second polycarbonate particles, 20-40 parts of crystalline polyester resin, 20-40 parts of titanium dioxide, and 0.1-0.2 parts of antioxidant;

[0023] Preferably, the crystalline polyester resin includes at least one of PBT, PE and ABS;

[0024] Preferably, the titanium dioxide includes at least one of rutile titanium dioxide and anatase titanium dioxide;

[0025] Preferably, the titanium dioxide is produced by chlorination method;

[0026] Preferably, the antioxidant comprises IrgafosR 168. Irgafos R 1010 and Irgafos R At least one of 1076.

[0027] Furthermore, the constituent materials of the backlight flame retardant film include polycarbonate, siloxane copolymer polycarbonate, flame retardant and additives;

[0028] Preferably, the constituent materials of the backlight flame retardant film include, by weight: 35-45 parts of polycarbonate with a melt index of 8-12, 35-45 parts of polycarbonate with a melt index of 15-18, 15-25 parts of siloxane copolymer polycarbonate, 0.1-1 parts of flame retardant and 0.5-1.5 parts of auxiliary agent;

[0029] Preferably, the siloxane copolymer polycarbonate is prepared by the following steps:

[0030] Mixing bisphenol A, siloxane, triethylamine, sodium gluconate and a solvent to obtain a mixed solution, introducing phosgene into the mixed solution, and then adding p-cumylphenol to react to obtain the siloxane copolymer polycarbonate;

[0031] Preferably, the molar ratio of the bisphenol A, the siloxane, the phosgene and the p-cumylphenol is 1:0.015-0.02:1.5-2:0.03-0.05.

[0032] In a second aspect, the present invention provides a method for preparing the composite film, wherein the composite film is prepared by a multi-layer co-extrusion method using constituent materials of a polycarbonate reflective film and constituent materials of a backlight flame-retardant film.

[0033] Furthermore, the composite film is prepared by using a double-layer co-extrusion extruder, and the double-layer co-extrusion extruder is preferably a single-screw double-layer co-extrusion extruder.

[0034] Furthermore, the reflective masterbatch is prepared by the following steps:

[0035] The second polycarbonate particles, crystalline polyester resin, titanium dioxide and antioxidant in a prescribed amount are mixed and granulated to obtain the reflective masterbatch;

[0036] Preferably, a twin-screw granulator is used to granulate and prepare the reflective masterbatch.

[0037] In a third aspect, the present invention provides a use of the composite film in preparing a flame-retardant polycarbonate reflective composite back panel for backlighting.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The composite film provided by the present invention is prepared by combining a reflective layer and a backlight layer, wherein the reflective film is a reflective surface and plays a role of reflecting light, and the backlight layer is a backlight bottom frame and plays a role of backlight and flame retardancy. Wherein, the reflective layer includes one of a polycarbonate reflective film, a PET reflective film or a PP reflective film, and the polycarbonate reflective film, the PET reflective film and the PP reflective film all have excellent insulation properties. Combined with the backlight flame retardant film, the composite film can replace the original iron backplane frame, reduce the weight of the backlight, achieve thinning of the film surface, and simplify the assembly process. At the same time, because the composite film has excellent insulation and flame retardancy, the risk of leakage and electric shock of the traditional iron bottom frame is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 A physical picture of a composite film provided by an embodiment of the present invention;

[0042] Figure 2 A physical picture of a composite film provided by an embodiment of the present invention;

[0043] Figure 3 A physical picture of a composite film provided by an embodiment of the present invention;

[0044] Figure 4 A schematic diagram of a composite film printed with conductive paint provided in an embodiment of the present invention;

[0045] Figure 5 Schematic diagram for testing the resistance value of printed conductive paint;

[0046] Figure 6 It is a schematic diagram of an iron bottom frame in the prior art.

[0047] Icon: 100-polycarbonate reflective film; 200-backlit flame retardant film. DETAILED DESCRIPTION

[0048] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear, however, in the case of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-limiting.

[0049] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] A first aspect of the present invention provides a composite film, the composite film comprising:

[0051] A reflective layer and a backlight layer, wherein the reflective layer and the backlight layer are bonded to each other;

[0052] The reflective layer includes one of a polycarbonate reflective film, a PET reflective film or a PP reflective film;

[0053] The backlight layer includes a backlight flame-retardant film.

[0054] In the present invention, the reflective layer and the backlight layer are composited to obtain the reflective film, which is a reflective surface and plays a role of reflecting light, and the backlight layer is a backlight bottom frame and plays a role of backlight and flame retardancy. Among them, the reflective layer includes one of a polycarbonate reflective film, a PET reflective film or a PP reflective film, and the polycarbonate reflective film, the PET reflective film and the PP reflective film all have excellent insulation properties. Combined with the backlight flame retardant film, the composite film can replace the original iron backplane frame, reduce the weight of the backlight, achieve thinning of the film surface, and simplify the assembly process. At the same time, because the composite film has excellent insulation and flame retardancy, it reduces the leakage and electric shock risks of the traditional iron bottom frame.

[0055] Furthermore, the constituent materials of the polycarbonate reflective film include: first polycarbonate particles, reflective masterbatch, transparent polyester resin and foaming aid.

[0056] In the present invention, a composite film is prepared by compounding a polycarbonate reflective film and a backlight flame retardant film, such as Figure 1 , 2 , 3, and 4, Figure 2 , 3 , 4 are all physical pictures of composite membranes, Figure 1Schematic diagram of the structure of the composite film, the composite film is composed of a polycarbonate reflective film 100 and a backlight flame retardant film 200. The thickness of the composite film is greater than or equal to 0.4 mm, and has good stiffness, insulation and flame retardancy. The polycarbonate reflective film is used as the reflective surface to reflect light, and the backlight flame retardant film is used as the backlight bottom frame to play the role of backlight and flame retardancy. Among the constituent materials of the polycarbonate (polycarbonate) reflective film, polycarbonate (polycarbonate) is used as the matrix, and the polycarbonate reflective film is obtained by adding additives such as reflective masterbatch, transparent polyester resin, and foaming aid. Polycarbonate (polycarbonate) has strong insulation and heat resistance (its temperature resistance range can reach -40℃-120℃), the reflective masterbatch has a high reflectivity, and the transparent polyester resin can further increase the reflectivity of the film product, and has the advantages and effects of improving the hardness and wear resistance of the PC reflective film. The foaming aid has a microbubble structure, and the microbubbles are filled with air, and the refractive index is lower than that of the polycarbonate layer. Therefore, the two form high and low refractive layers, which play an effect of increasing the reflectivity of the film product. The present invention utilizes the blending of polymers with different refractive indices to increase the overall refractive index difference, thereby further increasing the reflectivity; the present invention compounds the polycarbonate reflective film and the backlight flame-retardant film, thereby reducing the backlight weight and achieving thinning of the film surface.

[0057] Preferably, the constituent materials of the polycarbonate reflective film include, based on 100 parts by weight: 30-50 parts of first polycarbonate particles, 25-50 parts of reflective masterbatch, 5-20 parts of transparent polyester resin and 2-5 parts of foaming aid;

[0058] Wherein, based on 100 parts by total weight of the polycarbonate reflective film constituent materials, the addition amount of the first polycarbonate particles (first polycarbonate particles) is 30-50 parts, for example, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 46 parts, 47 parts, 48 ​​parts, 49 parts, 50 parts, etc.;

[0059] Based on the total weight of the polycarbonate reflective film constituent materials as 100 parts, the addition amount of the reflective masterbatch is 25-50 parts, for example, it can be 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 46 parts, 47 parts, 48 ​​parts, 49 parts, 50 parts, etc.;

[0060] Based on 100 parts by total weight of the polycarbonate reflective film constituent materials, the added amount of the transparent polyester resin is 5-20 parts, for example, it can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, etc.

[0061] Based on 100 parts by total weight of the polycarbonate reflective film constituent materials, the added amount of the foaming aid is 2-5 parts, for example, 2 parts, 3 parts, 4 parts, 5 parts, etc.

[0062] Preferably, the transparent polyester resin includes at least one of PMMA, PE, PA and PBT;

[0063] Preferably, the foaming aid comprises at least one of expansion particles and glass microspheres;

[0064] The expanded particles include Expencel R 980DU100 and Expensel R At least one of 980DU200;

[0065] The glass microspheres include 3M R S38HS, 3M R K46, 3M R S60 and 3M R At least one of S60HS;

[0066] Preferably, the particle size of the glass microspheres is 30-100 um.

[0067] In the present invention, the glass microspheres selected as the foaming aid have a microbubble structure, or the expanded particles selected as the foaming aid also produce a microbubble structure. The microbubble structure of the hollow glass microspheres or the microbubble structure produced by the expanded particles form bubbles of different sizes in the membrane. The microbubbles are filled with air, and the refractive index is 1, which forms a high-low refractive layer with the polycarbonate layer with a refractive index of 1.59 on the surface, which has the effect of increasing the reflectivity. The present invention uses the blending of polymers with different refractive indices to increase the overall refractive index difference, thereby further increasing the reflectivity.

[0068] Specifically speaking about the expanded particles, since the expanded particles are characterized by being micron-sized particles at room temperature, their volume expands by more than 10 times at high temperature, and they shrink to their original size after cooling. The melting point of the expanded particles is much higher than that of polycarbonate, and their volume expands several times in the single-screw high-temperature melting chamber. After melt extrusion, they are evenly dispersed in the reflective film. After calendering and cooling, the high-temperature expanded particles will cool and shrink, and then form a micro-bubble structure with different bubble diameters in the film. At the same time, the generated pores are fine and uniform. The micro-bubbles can scatter light and reduce the refractive index inside the film. They form high and low refractive layers with the high refractive index polycarbonate layer on the surface, forming a high and low refractive index difference, which has the effect of increasing the reflectivity.

[0069] Furthermore, the reflective masterbatch comprises components of second polycarbonate particles, crystalline polyester resin, titanium dioxide and an optional antioxidant.

[0070] In the present invention, the Vicat softening temperature of polycarbonate is 145-150°C, the heat resistance is strong, and the dimensional stability is better. The reflective masterbatch is prepared from high-purity titanium dioxide, a polycarbonate matrix and an additive, and mainly improves the reflective effect of the material. The titanium dioxide in the reflective masterbatch can improve the reflectivity of the material, and the crystalline polyester resin in the reflective masterbatch can improve the crystal structure of the material, which is beneficial to improve the reflectivity of light, and at the same time can improve the product blending effect, improve the whiteness of the masterbatch, and thus improve the reflectivity of the product; the function of the antioxidant is to effectively prevent the thermal degradation of the polymer during the high-temperature extrusion process, and provide the polymer with additional long-term protection.

[0071] Furthermore, the components of the reflective masterbatch include, based on 100 parts by weight: 20-40 parts of second polycarbonate particles, 20-40 parts of crystalline polyester resin, 20-40 parts of titanium dioxide, and 0.1-0.2 parts of antioxidant;

[0072] Based on 100 parts by total weight of the raw materials for preparing the reflective masterbatch, the addition amount of the second polycarbonate particles (second polycarbonate particles) is 20-40 parts, for example, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, etc.;

[0073] Based on 100 parts by total weight of the raw materials for preparing the reflective masterbatch, the addition amount of the crystalline polyester resin is 20-40 parts, for example, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, etc.;

[0074] Based on 100 parts of the total weight of the raw materials for preparing the reflective masterbatch, the addition amount of titanium dioxide is 20-40 parts, for example, it can be 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, etc.;

[0075] Based on 100 parts by total weight of the raw materials for preparing the reflective masterbatch, the added amount of the antioxidant is 0.1-0.2 parts, for example, 0.1 parts, 0.2 parts, etc.

[0076] Preferably, the crystalline polyester resin includes at least one of PBT, PE and ABS;

[0077] Preferably, the titanium dioxide includes at least one of rutile titanium dioxide and anatase titanium dioxide;

[0078] Preferably, the titanium dioxide is produced by chlorination method;

[0079] In the present invention, the type of titanium dioxide includes at least one of CITIC Titanium Rutile CR210 / CR211 / CR510, Nantai Anatase NA100, and Yuxing A1. The titanium dioxide may further preferably be rutile prepared by the chlorination process, which has a higher reflectivity.

[0080] Preferably, the antioxidant comprises Irgafos R 168. Irgafos R 1010 and Irgafos R At least one of 1076.

[0081] Furthermore, the constituent materials of the backlight flame retardant film include polycarbonate, siloxane copolymer polycarbonate, flame retardant and additives;

[0082] Preferably, the constituent materials of the backlight flame retardant film include, by weight: 35-45 parts of polycarbonate with a melt index of 8-12, 35-45 parts of polycarbonate with a melt index of 15-18, 15-25 parts of siloxane copolymer polycarbonate, 0.1-1 parts of flame retardant and 0.5-1.5 parts of auxiliary agent;

[0083] Preferably, the siloxane copolymer polycarbonate is prepared by the following steps:

[0084] Mixing bisphenol A, siloxane, triethylamine, sodium gluconate and a solvent to obtain a mixed solution, introducing phosgene into the mixed solution, and then adding p-cumylphenol to react to obtain the siloxane copolymer polycarbonate;

[0085] Preferably, the molar ratio of the bisphenol A, the siloxane, the phosgene and the p-cumylphenol is 1:0.015-0.02:1.5-2:0.03-0.05.

[0086] In the present invention, the backlight flame-retardant film is a black backlight flame-retardant film, which has light-shielding and flame-retardant effects, and is prepared with reference to CN202210749276.4.

[0087] Furthermore, a conductive paint is printed on the backlight flame retardant film by printing;

[0088] Preferably, the thickness of the conductive paint is 0.6-0.8um, for example, 0.6um, 0.7um, 0.8um, etc.;

[0089] In the present invention, the backlight flame-retardant film is used as the back side of the composite film product, and conductive paint is printed on the back side, so that the overall product can meet the requirements of safety regulations and realize product lightness.

[0090] Preferably, the conductive paint is arranged in a grid pattern.

[0091] In the present invention, conductive paint is printed by printing, and a grid design is used so that the overall product back frame can pass the EU safety regulations. Since the conductive paint is coated on the backlight layer, the different matching of the reflective layer has little effect on the conductive paint data.

[0092] The second aspect of the present invention provides a method for preparing the composite film, wherein the composite film is prepared by a multi-layer co-extrusion method using constituent materials of a polycarbonate reflective film and constituent materials of a backlight flame-retardant film.

[0093] In the present invention, polyester materials such as polycarbonate are used, and a composite process is utilized to composite a polycarbonate reflective film and a backlight flame retardant film by multi-layer co-extrusion. The prepared reflective composite film with flame retardant properties realizes thinning of the film surface, lightweight design, and simplification of the assembly process.

[0094] Furthermore, the composite film is prepared by using a double-layer co-extrusion extruder, and the double-layer co-extrusion extruder is preferably a single-screw double-layer co-extrusion extruder.

[0095] Furthermore, the reflective masterbatch is prepared by the following steps:

[0096] The second polycarbonate particles, crystalline polyester resin, titanium dioxide and antioxidant in a prescribed amount are mixed and granulated to obtain the reflective masterbatch;

[0097] Preferably, a twin-screw granulator is used to granulate and prepare the reflective masterbatch.

[0098] In the present invention, a twin-screw granulator is used to manufacture the reflective masterbatch. Since the structure of the twin-screw is more complex, the two screws can shear the raw materials evenly, and can better complete the mixing, shearing and extrusion of the raw materials, so the granulation effect is better, the dispersion of titanium dioxide can be improved, and the product performance can be guaranteed.

[0099] The present invention provides a third aspect of an application of the composite film in preparing a flame-retardant polycarbonate reflective composite backboard for backlighting.

[0100] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0101] It should be noted that in the following embodiments and application examples, the material for preparing the backlight flame retardant film is selected from Example 1 of CN202210749276.4, and the preparation method of siloxane copolymer polycarbonate is prepared by referring to Example 1 of CN202210749276.4.

[0102] Example 1

[0103] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame-retardant film.

[0104] The constituent materials of the polycarbonate reflective film include, by 100 parts by weight:

[0105] 50 parts of reflective masterbatch, 10 parts of transparent polyester resin (PMMA), 4 parts of expanded particles (Expencel R 980DU100), the balance being polycarbonate particles;

[0106] The components of the reflective masterbatch include, based on 100 parts by weight, 33.3 parts of polycarbonate particles, 33.3 parts of crystalline polyester resin (specifically, PBT particles), 33.3 parts of titanium dioxide (specifically, CITIC Titanium Rutile CR210), 0.1 parts of antioxidant (specifically, Irgafos R 168).

[0107] Example 2

[0108] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame-retardant film. The difference from the embodiment 1 is that the transparent polyester resin is 5 parts, and the rest is the same as the embodiment 1.

[0109] Example 3

[0110] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame-retardant film. The difference from the embodiment 1 is that the transparent polyester resin is 15 parts, and the rest is the same as the embodiment 1.

[0111] Example 4

[0112] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame-retardant film. The difference from Embodiment 1 is that the reflective masterbatch is 45 parts, and the rest is the same as Embodiment 1.

[0113] Example 5

[0114] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame-retardant film. The difference from Embodiment 1 is that the reflective masterbatch is 36 parts, and the rest is the same as Embodiment 1.

[0115] Example 6

[0116] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame-retardant film. The difference from the embodiment 1 is that the expanded particles are 5 parts, and the rest is the same as the embodiment 1.

[0117] Example 7

[0118] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame-retardant film. The difference from the embodiment 1 is that there are 2 portions of expanded particles, and the rest is the same as the embodiment 1.

[0119] Example 8

[0120] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame retardant film. The difference from Embodiment 1 is:

[0121] The transparent polyester resin is PA, and the rest is consistent with the embodiment.

[0122] Example 9

[0123] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame retardant film. The difference from Embodiment 1 is:

[0124] The polycarbonate particles are 50 parts, the reflective masterbatch is 25 parts, the transparent polyester resin is 20 parts, and the expanded particles are 5 parts. The specific selection of agents is consistent with that in Example 1.

[0125] Example 10

[0126] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame retardant film. The difference from Embodiment 1 is:

[0127] The components of the reflective masterbatch include 40 parts of polycarbonate particles, 39.8 parts of crystalline polyester resin, 20 parts of titanium dioxide, and 0.2 parts of antioxidant (specifically, Irgafos R 168).

[0128] Embodiment 11

[0129] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame retardant film. The difference from Embodiment 1 is:

[0130] The components of the reflective masterbatch include 20 parts of polycarbonate particles, 40 parts of crystalline polyester resin, 39.8 parts of titanium dioxide, and 0.2 parts of antioxidant (specifically, Irgafos R 168).

[0131] Example 12

[0132] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame retardant film. The difference from Embodiment 1 is:

[0133] Expansion particles are Expencel R 980DU200, transparent polyester resin is PBT;

[0134] In the reflective masterbatch component, the crystalline polyester resin is PE, the titanium dioxide is Nantai Anatase NA100, and the antioxidant is Irgafos R 1076.

[0135] Embodiment 13

[0136] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame retardant film. The difference from Embodiment 1 is:

[0137] The foaming aid is glass microspheres 3M R S38HS, particle size is 50 um, and the rest is consistent with Example 1.

[0138] Embodiment 14

[0139] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame retardant film, and the difference from Embodiment 13 is:

[0140] The foaming aid is glass microspheres with a particle size of 30 um, and the rest is consistent with Example 13.

[0141] Embodiment 15

[0142] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame retardant film, and the difference from Embodiment 13 is:

[0143] The foaming aid is glass microspheres with a particle size of 100 um, and the rest is consistent with Example 13.

[0144] Example 16

[0145] This embodiment provides a composite film, which is composited by a polycarbonate reflective film and a backlight flame retardant film, and the difference from Embodiment 13 is:

[0146] The foaming aid is glass microspheres from 3M R S60HS, and the rest is the same as Example 13.

[0147] Examples 17-32

[0148] Embodiment 17-32 provides a method for preparing a composite film, comprising the following steps:

[0149] 1. Granulate the reflective masterbatch using a twin-screw granulator: sequentially place the polycarbonate particles, crystalline polyester resin, titanium dioxide and antioxidant in the formula amounts of Examples 1-16 into a screw granulator for mixing and granulation to prepare the reflective masterbatch in Application Examples 1-16;

[0150] 2. The preparation method of siloxane copolymer polycarbonate is prepared by referring to Example 1 of CN202210749276.4.

[0151] 3. A single-screw double-layer co-extruder is used to prepare a composite film. The single-screw double-layer co-extruder has two independent extruders, each of which has an independent heating system and a single screw. The constituent materials of the polycarbonate reflective film (reflective masterbatch, transparent polyester resin and foaming aid) and the constituent materials of the backlight flame retardant film are added to the two independent extruders from two feeding ports according to the formula amount. The discharge ports of the two independent extruders are connected to the co-extrusion head, and the two molten materials enter the co-extrusion head through the two discharge ports respectively to prepare the composite film in Application Example 1-16.

[0152] Embodiment 33

[0153] This embodiment provides a method for preparing a composite film, which further includes the following steps:

[0154] A grid-type conductive paint (the conductive paint model is Imperial Ink MRX-HF 30720GMG GOLD) is printed on the backlight flame-retardant film of the composite film prepared in Example 17, and the thickness of the conductive paint layer is 0.6 um.

[0155] Embodiment 34

[0156] This embodiment provides a method for preparing a composite film, which differs from Embodiment 33 in that:

[0157] The thickness of the conductive paint layer is 0.7um.

[0158] Embodiment 35

[0159] This embodiment provides a method for preparing a composite film, which differs from Embodiment 33 in that:

[0160] The thickness of the conductive paint layer is 0.8um.

[0161] Embodiment 36

[0162] This embodiment provides a method for preparing a composite film, which differs from Embodiment 33 in that:

[0163] The thickness of the conductive paint layer is 0.2um.

[0164] Embodiment 37

[0165] This embodiment provides a method for preparing a composite film, which differs from Embodiment 33 in that:

[0166] The thickness of the conductive paint layer is 2um.

[0167] Comparative Example 1

[0168] This comparative example provides a composite membrane, which is different from Example 1 in that:

[0169] No transparent polyester resin is added to the components of the polycarbonate reflective film, and the rest is the same as in Example 1.

[0170] Comparative Example 2

[0171] This comparative example provides a composite membrane, which is different from Example 1 in that:

[0172] No expanded particles were added to the components of the polycarbonate reflective film, and the rest was the same as in Example 1.

[0173] Comparative Example 3

[0174] This comparative example provides a composite membrane, which is different from Example 1 in that:

[0175] No crystalline polyester resin is added to the components of the reflective masterbatch, and the rest is consistent with Example 1.

[0176] Comparative Examples 4-6

[0177] Comparative Examples 4-6 provide a method for preparing a composite film, wherein the reflective masterbatch is prepared using the raw materials in the formula amounts in Comparative Examples 1-3 in sequence, and then the composite film is prepared using the raw materials in the formula amounts in Comparative Examples 1-3 in sequence. The preparation method is consistent with Example 17.

[0178] Test Example 1

[0179] Test sample: The composite film was prepared by the method of Example 17. Composite films of different thicknesses can be prepared by adjusting the extrusion amount of the corresponding single-screw extruder. The specific thickness and test results are shown in Table 1 below.

[0180] Table 1

[0181]

[0182]

[0183] It can be seen from the data in the table that the reflectivity of the composite film is related to the reflective film layer. The thicker the reflective film, the higher the reflectivity. In addition, the thickness of the backlight flame retardant film should be greater than or equal to 50um. If the thickness of the backlight flame retardant film is too thin, it will transmit light, resulting in light energy loss, causing a decrease in reflectivity and affecting product performance.

[0184] Test Example 2

[0185] Test samples: composite films prepared in Examples 17-32 and composite films prepared in Comparative Examples 4-6, wherein the composite films prepared in Examples 17-18 and composite films prepared in Comparative Examples 4-6 have a total thickness of 0.5 mm, and the thickness of the backlight flame retardant film is 50 um.

[0186] Test method:

[0187] Reflectivity

[0188] Test instrument name: UV-visible-near infrared spectrometer;

[0189] Instrument model: Cary5000;

[0190] Heat Deflection Temperature:

[0191] Test standard ASTM D648;

[0192] Testing instrument: XRW-300 thermal deformation tester produced by Beijing AVIC Dingli Instrument Equipment Co., Ltd.

[0193] Leakage detection:

[0194] Test equipment: Full digital display withstand voltage tester MS2670BN;

[0195] Test method: IEC60243-1-2013;

[0196] Test conditions: normal temperature and humidity, 2700VDS, 60s.

[0197] Flame retardant test:

[0198] Test equipment: Touch screen horizontal and vertical combustion instrument JL-CZF-5.

[0199] The test results are shown in Table 2 below.

[0200] Table 2

[0201]

[0202]

[0203] From the data in Table 1, we can see that the thickness of the reflective film in the composite film will affect the reflectivity, and the addition of polyester will affect the temperature resistance and flame retardancy of the product. The more polyester is added, the worse the temperature resistance and flame retardancy will be. The more PC is added, the better the flame retardancy and temperature resistance will be.

[0204] Test Example 3

[0205] The conductive paint resistance value of the composite film prepared in Examples 33-37 was tested by using a resistance test device (Fluke multimeter: F101), such as Figure 5 As shown, the probe measurement distance is 1 cm, and the test results are shown in Table 3 below.

[0206] Conductive paint layer thickness (um) Resistance value(Ω) Embodiment 33 0.6 8.2 Embodiment 34 0.7 6.4 Embodiment 35 0.8 5.3 Embodiment 36 0.2 50 Embodiment 37 2 Less than 1

[0207] From the data in the table, it can be seen that the coating thickness of the conductive paint layer is about 0.6-0.8um, and the resistance value is about 5-8Ω. The greater the thickness, the smaller the resistance value. The results of Example 37 show that when the coating thickness of the conductive paint layer is 2um, the resistance value can reach below 1Ω, but the material cost is too high and does not meet the actual needs. The results of Example 36 show that when the thickness is too thin, the resistance value is 50Ω, which is relatively high. The conductive paint on the composite film provided by the embodiment of the present invention does not debond or lose ink.

[0208] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite film, characterized in that The composite film comprises: a reflective layer and a backlight layer, wherein the reflective layer and the backlight layer are bonded to each other; The reflective layer includes one of a polycarbonate reflective film, a PET reflective film or a PP reflective film; The backlight layer includes a backlight flame-retardant film.

2. The composite membrane according to claim 1, characterized in that Printing conductive paint on the backlight flame retardant film by printing; Preferably, the thickness of the conductive paint is 0.6-0.8um; Preferably, the conductive paint is arranged in a grid pattern.

3. The composite membrane according to claim 1, characterized in that The constituent materials of the polycarbonate reflective film include: first polycarbonate particles, reflective masterbatch, transparent polyester resin and foaming aid; Preferably, the constituent materials of the polycarbonate reflective film include, based on 100 parts by weight: 30-50 parts of first polycarbonate particles, 25-50 parts of reflective masterbatch, 5-20 parts of transparent polyester resin and 2-5 parts of foaming aid; Preferably, the transparent polyester resin includes at least one of PMMA, PE, PA and PBT; Preferably, the foaming aid comprises at least one of expansion particles and glass microspheres; The expanded particles include Expencel R 980DU100 and Expensel R At least one of 980DU200; Preferably, the glass microspheres include 3M R S38HS, 3M R K46, 3M R S60 and 3M R At least one of S60HS; Preferably, the particle size of the glass microspheres is 30-100 um.

4. The composite membrane according to claim 3, characterized in that The components of the reflective masterbatch include second polycarbonate particles, crystalline polyester resin, titanium dioxide and an optional antioxidant.

5. The composite membrane according to claim 4, characterized in that The components of the reflective masterbatch include, based on 100 parts by weight: 20-40 parts of second polycarbonate particles, 20-40 parts of crystalline polyester resin, 20-40 parts of titanium dioxide and 0.1-0.2 parts of antioxidant; Preferably, the crystalline polyester resin includes at least one of PBT, PE and ABS; Preferably, the titanium dioxide includes at least one of rutile titanium dioxide and anatase titanium dioxide; Preferably, the titanium dioxide is prepared by a chlorination method; Preferably, the antioxidant comprises Irgafos R 168. Irgafos R 1010 and Irgafos R At least one of 1076.

6. The composite membrane according to claim 1, characterized in that The constituent materials of the backlight flame retardant film include polycarbonate, siloxane copolymerized polycarbonate, flame retardant and additive; Preferably, the constituent materials of the backlight flame retardant film include, by weight: 35-45 parts of polycarbonate with a melt index of 8-12, 35-45 parts of polycarbonate with a melt index of 15-18, 15-25 parts of siloxane copolymer polycarbonate, 0.1-1 parts of flame retardant and 0.5-1.5 parts of auxiliary agent.

7. The method for preparing the composite film according to any one of claims 1 to 6, characterized in that: The composite film is prepared by a multi-layer co-extrusion method using constituent materials of a polycarbonate reflective film and constituent materials of a backlight flame-retardant film.

8. The method for preparing a composite film according to claim 7, characterized in that: The composite film is prepared by a double-layer co-extrusion extruder, and the double-layer co-extrusion extruder is preferably a single-screw double-layer co-extrusion extruder.

9. The method for preparing a composite film according to claim 7, characterized in that: The reflective masterbatch is prepared by the following steps: The second polycarbonate particles, crystalline polyester resin, titanium dioxide and antioxidant in a prescribed amount are mixed and granulated to obtain the reflective masterbatch; Preferably, a twin-screw granulator is used to granulate and prepare the reflective masterbatch.

10. Use of the composite film according to any one of claims 1 to 6 in preparing a flame-retardant polycarbonate reflective composite back sheet for backlighting.

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