WO2021120246A1 - Reflective film and preparation method therefor - Google Patents

Abstract

The present invention relates to a reflective film which is characterized in that the reflective film is provided with an ABA three-layer structure, wherein layer A is a supporting layer, layer B is a reflective layer, the tensile strength of the reflective film at the temperature of 90ºC-130ºC is greater than or equal to 50 MPa, and the elongation at break of the reflective film is greater than or equal to 40%. Further provided is a preparation method for the reflective film.

Description

Reflective film and preparation method thereof

Related application

This application claims the priority of the Chinese patent application filed on December 16, 2019 with the application number 201911293825.6 and titled "Reflective Film and Its Preparation Method", which is hereby incorporated by reference in its entirety.

Technical field

The invention relates to the field of thin film materials, in particular to a reflective film and a preparation method thereof.

Background technique

The backlight module is one of the key components of a liquid crystal display panel (LCD panel). Since the liquid crystal itself does not emit light, the function of the backlight module is to supply sufficient brightness and uniformly distributed light sources to enable it to display images normally. The backlight module is mainly assembled by light source, lampshade, reflective film, light guide plate, diffuser plate, brightness enhancement film and outer frame.

At present, the backlight module is assembled manually, which has low efficiency and high cost. Among them, due to the traditional reflective film, the diaphragm is thin and fragile, and a slight error in the placement of the diaphragm will affect the display image effect, which is not conducive to the automatic assembly of the backlight module. Therefore, there is an urgent need for a reflective film that can be automatically assembled.

Summary of the invention

In view of this, the present invention provides a reflective film that can be automatically assembled.

A reflective film comprising a three-layer structure with ABA, wherein layer A is a support layer, layer B is a reflective layer, and the tensile strength of the reflective film at a temperature of 90°C-130°C is greater than or equal to 50Mpa, and The elongation at break is greater than or equal to 40%.

Compared with the prior art, the tensile strength of the reflective film of the present invention at a temperature of 90°C to 130°C is greater than or equal to 50Mpa, and the elongation at break is greater than or equal to 40%. Therefore, the reflective film has excellent plasticity, and it can be designed into a special shape to match the light source. Compared with the conventional reflective film that has poor plasticity and needs to manually fold the reflective film into a target special shape, the reflective film described in the present application can be directly formed into the desired target shape, which can be automated to a certain extent, while improving The utilization rate of the light source, the assembly efficiency, the improvement of the display effect, and the promotion of economic benefits.

The present invention also provides a method for preparing the above reflective film, which includes the following steps: providing a first mixture and a second mixture respectively;

The first mixture and the second mixture are added to an extruder, and then a three-layer structure prefabricated film is obtained through a three-layer co-extrusion method, wherein the material of the reflective layer in the middle of the prefabricated film is the second mixture, The material of the support layer on the upper and lower layers is the first mixture; and

Stretching and setting to obtain the reflective film.

The preparation method is simple to operate and easy to industrialize.

Description of the drawings

Fig. 1 is a schematic diagram of the structure of the reflective film of the present invention.

In the figure, 11 denotes a reflective layer; 12 and 13 denotes a support layer; 111 denotes an incompatible resin; 112 denotes a cell; 113 denotes a second inorganic particle; 121 denotes a first inorganic particle.

Detailed ways

The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

Please refer to FIG. 1, the present invention provides a reflective film, the reflective film includes an ABA three-layer structure, wherein the A layer is the support layer 12/13, and the B layer is the reflective layer 11. The tensile strength of the reflective film at a temperature of 90°C to 130°C is greater than or equal to 50Mpa, and the elongation at break is greater than or equal to 40%. Therefore, the reflective film has plasticity and can be processed into various shapes. It should be noted that the above-mentioned temperature conditions mean that at any test temperature from 90°C to 130°C, the performance can be satisfied, and there is no need to satisfy the above-mentioned tensile strength and fracture at all test temperatures in this range. Conditions for elongation.

Based on the consideration that the deformation rate of the film is within a controllable range, preferably, the longitudinal heat shrinkage (MD) of the reflective film at a temperature of 90°C-105°C is less than or equal to 0.5%, and the transverse heat shrinkage (TD) is less than or equal to 0.2%.

The material of the support layer 12/13 includes the first polyester resin, the first inorganic particles 121 and the toughening resin. The first polyester resin includes at least one of polyethylene terephthalate (PET) and polybutylene terephthalate. The first inorganic particles 121 include at least one of calcium carbonate, silicon dioxide, titanium dioxide, and barium sulfate. The toughening resin imparts toughness to the reflective film, and can have good tensile strength and elongation at break. The toughening resin is maleic anhydride (MAH) grafted polyethylene, maleic anhydride (MAH) grafted styrene-ethylene-butylene-styrene block copolymer (SEBS), glycidyl methacrylate (GMA) One of grafted polyolefin elastomers (POE). The MAH grafted polyethylene may be MAH grafted high density polyethylene (HDPE) or MAH grafted linear low density polyethylene (LDPE).

The mass fraction of the first polyester resin in the support layer 12/13 is 97%-98.9%. The mass fraction of the first inorganic particles 121 is 1%. The mass fraction of the toughening resin is 0.1%-2%. The reason for the selection is: in order to ensure a more excellent toughening effect, the mass fraction of the toughening resin is not less than 0.1%. However, considering that the addition amount is too high, the effect of the toughening agent has a certain degree of saturation. After reaching the saturation, the increase in the addition amount and the improvement of the toughening effect are not obvious, and too high a toughening agent will reduce the reflectivity of the reflective film. The mass fraction of tough resin is not more than 2%. Preferably, the mass fraction of the first polyester resin in the support layer 12/13 is 97.5%-98.5%; the mass fraction of the first inorganic particles 121 is 1%; the toughening The mass fraction of resin is 0.5%-1.5%.

A plurality of uniform cells 112 are distributed in the reflective layer 11. The material of the reflective layer 11 includes a second polyester resin, a second inorganic particle, and an incompatible resin. The second polyester resin includes at least one of polyethylene terephthalate and polybutylene terephthalate.

The incompatible resin refers to a resin that is incompatible with the second polyester resin, and includes polyolefin resin. Since the incompatible resin is incompatible with the second polyester resin, voids can be generated around the incompatible resin during the stretching process, thereby forming the bubbles in the reflective layer 11孔112. At this time, it can be considered that the incompatible resin 111 is substantially located in the center of the cell 112. In order to facilitate the formation of the cells 112, the incompatible resin 111 is preferably at least one of polypropylene, polymethylpentene, and cycloolefin copolymer with a low critical surface tension. The particle size of the incompatible resin 111 is not limited, and is preferably 0.2 μm to 0.3 μm. The existence of the cells 112 can improve the reflectivity of the reflective film. The pore size of the cell 112 is not limited, and is preferably 0.3 μm to 5 μm.

The second inorganic particles include at least one of titanium dioxide, barium sulfate, calcium carbonate, and aluminum oxide. Preferably, the second inorganic particles are titanium dioxide, because titanium dioxide has good physical and chemical stability, high refractive index, good shielding properties, and can provide higher reflectivity.

The thickness of the reflective film is not limited enough. Preferably, the thickness of the reflective film is 100 micrometers to 300 micrometers.

The invention also provides a method for preparing a reflective film, which includes the following steps:

S1, providing a first mixture and a second mixture respectively;

S2, adding the first mixture and the second mixture to an extruder, and then obtaining a three-layer prefabricated film by a three-layer co-extrusion method, wherein the material of the reflective layer 11 in the middle of the prefabricated film is the first The second mixture, the material of the support layer 12/13 in the upper and lower layers is the first mixture; and

S3, stretching and setting to obtain the reflective film, the reflective film obtained therein.

In step S1, the first mixture includes a first polyester resin, a first inorganic particle, and a toughening resin. The second mixture includes a second polyester resin, a second inorganic particle, and an incompatible resin. The specific components are as described above, and will not be repeated here. It can be granulated by twin-screw mixing, that is, the first mixture particles and the second mixture particles are formed. In order to better mix the components, the intrinsic viscosity of the first polyester resin and the second polyester resin is 0.65dL/g-0.75dL/g.

In step S2, three-layer co-extrusion can be used to melt, plasticize, and cast the cast sheet to form a prefabricated film with a three-layer structure.

In step S3, the prefabricated film is longitudinally stretched, transversely stretched, and heat-set to obtain the reflective film. Among them, in the stretching process, the longitudinal stretch ratio and the transverse stretch ratio are controlled between 3.0-3.60. Preferably, the longitudinal stretch ratio and the transverse stretch ratio are controlled at 3.3. Finally, the reflective film can be rolled and packaged.

Hereinafter, various embodiments will be used to illustrate the reflective film and the manufacturing method of the reflective film of the present invention.

Example 1

A reflective film with an ABA three-layer structure, in which layer A is a support layer and layer B is a reflective layer. The supporting layer includes 98.9% PET resin, 1% silica particles, and 0.1% toughening resin. The reflective layer includes 60% PET resin (intrinsic viscosity 0.68 dL/g), 20% polymethylpentene, and 20% titanium dioxide. The thickness of the resulting reflective film is 188 μm, wherein the thickness of the two supporting layers accounted for 18% of the total thickness, and the thickness of the reflective layer accounted for 82% of the total thickness.

Example 2-Example 17

See Table 1 and Table 2 for the raw materials and ratios of each layer of the reflective film of each embodiment.

In order to better illustrate the beneficial effects of the reflective film of the present invention, the present invention also provides Comparative Example 1.

Comparative example 1

Adopting DJX188 model PET reflective film of Ningbo Changyang Technology Co., Ltd. The PET reflective film is prepared without introducing toughening resin.

The following performance tests were performed on the reflective films of Example 1 to Example 17, and Comparative Example 1.

Reflectance test: According to GB/T3979-2008 standard, using ColorQuest XE spectrophotometer (manufactured by Hunterlab), under the condition of D65 light source, through integrating sphere d/8° structure to test the reflectance, the reflectance data is 400nm- 700nm, the reflectance value of every 10nm wavelength, take the reflectance value of 550nm wavelength.

Tensile strength and elongation at break test: in accordance with the GB/T1040-2006 standard, using the INSTRON universal material testing machine produced by the United States Instron, after stabilizing for 1 min in a 90℃-130℃ incubator, test the reflection film Tensile strength and elongation at break. It should be noted that when testing, only select one temperature for testing. The tests in Table 3 are just to illustrate the effect of this technology, and two test temperatures are selected.

Thermal shrinkage test: cut the reflective film sample into 10cm×10cm size, three pieces each, according to GB/T 13542.4-2009, put the reflective film sample in an oven at 85℃ for half an hour, and measure the thermal shrinkage of the reflective film sample Before and after dimensional data, the thermal shrinkage rate was calculated, and the average value of the thermal shrinkage rates of the three reflective films was used as the thermal shrinkage rate value.

The test results are shown in Table 3.

Table 1 Raw material list

Code	raw material name
A	Polyethylene terephthalate
B	Polybutylene terephthalate
C	Maleic anhydride (MAH) grafted high density polyethylene (HDPE)
D	MAH grafted linear low density polyethylene (LDPE)
E	MAH grafted styrene-ethylene-butylene-styrene block copolymer (SEBS)
F	Glycidyl methacrylate (GMA) grafted POE

Table 2

Table 3 Table of the performance test results of the plastic high-brightness reflective film obtained in Examples 1-17 and Comparative Example 1

It can be seen from Table 2 and Table 3 that comparing Examples 1-5, it can be seen that the above-mentioned reflective film stretch ratio adopts 3.2-3.4 parameters, which has better overall performance, and the most preferred stretch ratio is 3.3; Comparative Example 3 and Examples 6-8, the toughening resin is preferably maleic anhydride (MAH) grafted high-density polyethylene (HDPE); comparative examples 9-12, when the obtained reflective film is excellent in plasticity, the preferred ratio of the toughening resin is 0.5 %-1.5%. Comparing Examples 13-17, considering that a reflective film with high reflectivity (reflectivity above 96%) can be obtained, the content of incompatible resin is preferably 10%-20%, and the content of inorganic particles is preferably 15%-20% to ensure high The optimized ratio of the raw materials for reflectivity has better overall performance, among which Example 13 is the most excellent. Specifically, it can be selected according to actual needs, whether it requires higher brightness of the reflective film or higher requirements for plasticity. By improving the ratio, the present invention can greatly improve the plasticity of the reflective film compared with ordinary reflective films, and also has excellent high-temperature resistance mechanical properties.

The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the various technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, All should be considered as the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the present invention, and their description is relatively specific and detailed, but they should not be understood as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (13)

1. A reflective film, characterized in that the reflective film has an ABA three-layer structure, wherein layer A is a support layer, layer B is a reflective layer, and the tensile strength of the reflective film at a temperature of 90°C to 130°C is greater than or equal to 50Mpa, and the elongation at break is greater than or equal to 40%.
2. The reflective film according to claim 1, wherein the longitudinal thermal shrinkage rate of the reflective film at a temperature of 90°C-105°C is less than or equal to 0.5%, and the transverse thermal shrinkage rate is less than or equal to 0.2%.
3. The reflective film of claim 1, wherein the material of the support layer includes a first polyester resin, a first inorganic particle, and a toughening resin.
4. The reflective film of claim 3, wherein the first polyester resin comprises at least one of polyethylene terephthalate and polybutylene terephthalate, and the first polyester resin An inorganic particle includes at least one of calcium carbonate, silicon dioxide, titanium dioxide, and barium sulfate, and the toughening resin is maleic anhydride grafted polyethylene, maleic anhydride grafted styrene-ethylene-butene-benzene One of ethylene block copolymer and glycidyl methacrylate grafted polyolefin elastomer.
5. The reflective film of claim 3, wherein the mass fraction of the first polyester resin in the support layer is 97%-98.9%, and the mass fraction of the first inorganic particles is 1%, the mass fraction of the toughening resin is 0.1%-2%.
6. The reflective film of claim 1, wherein the material of the reflective layer includes a second polyester resin, a second inorganic particle, and an incompatible resin.
7. The reflective film of claim 6, wherein the second polyester resin comprises at least one of polyethylene terephthalate and polybutylene terephthalate, and the non- The compatible resin includes a polyolefin resin, and the second inorganic particles include at least one of titanium dioxide, barium sulfate, calcium carbonate, and aluminum oxide.
8. The reflective film of claim 6, wherein the mass fraction of the second polyester resin in the reflective layer is 60%-80%, and the mass fraction of the incompatible resin is 5%-20%, the mass fraction of the second inorganic particles is 5%-20%.
9. The reflective film of claim 1, wherein the thickness of the reflective film is 100 micrometers to 300 micrometers.
10. The reflective film of claim 1, wherein the reflective layer includes a plurality of cells.
11. A method for preparing a reflective film according to any one of claims 1-10, characterized in that it comprises the following steps:

    Provide the first mixture and the second mixture respectively;

    The first mixture and the second mixture are added to an extruder, and then a three-layer prefabricated film is obtained by a three-layer co-extrusion method, wherein the material of the reflective layer in the middle of the prefabricated film is the second mixture, The material of the support layer on the upper and lower layers is the first mixture; and

    Stretching and setting to obtain the reflective film.
12. 11. The method for preparing a reflective film according to claim 11, wherein in the stretching and setting step, the longitudinal and transverse stretch ratios are in the range of 3.0-3.6.
13. The method for preparing a reflective film according to claim 11, wherein the first mixture includes a first polyester resin, a first inorganic particle, and a toughening resin, and the second mixture includes a second polyester resin, Second inorganic particles and incompatible resins.

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