A high reflectivity electromagnetic shielding film and preparation process

Abstract

The invention discloses an electromagnetic shielding film with high reflectivity and a preparation process. The electromagnetic shielding film with high reflectivity comprises a first release protective film, a white insulating layer, a shielding layer, a conductive layer and a second release protective film; wherein the insulating layer covers the first release protective film, the shielding layer covers the insulating layer, the conductive layer covers the shielding layer, and the second release protective film covers the conductive layer. The electromagnetic shielding film with high reflectivity of the invention has high reflectivity and high electromagnetic shielding effect.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic shielding films, and in particular to an electromagnetic shielding film with high reflectivity and a preparation process thereof. Background Art

[0002] Electromagnetic shielding film is a kind of electromagnetic shielding material. It is currently mainly used in key electronic components PCB, FPC and related components. It is one of the important raw materials of FPC. With the rapid development of electronic products, consumers have increasingly stringent requirements for the quality and thinness of electronic products. The trend of high frequency and high speed of electronic products is becoming more and more obvious. The use of FPC in its internal structure is increasing to improve the internal assembly density, resulting in more serious electromagnetic interference between electronic components. This objectively increases the demand for electromagnetic shielding film. This demand is reflected in the increase in the use of electromagnetic shielding film on the one hand, and the requirement for improved performance of electromagnetic shielding film on the other hand.

[0003] When used in observation windows of electronic devices, such as CRT monitors, LCD monitors, LED monitors, OLED monitors and other digital display screens, traditional electromagnetic shielding films are black. In order to increase the reflectivity of the electromagnetic shielding film, white ink is generally printed again on the black shielding film, which increases the preparation process and increases the thickness of the electromagnetic shielding film, thereby increasing the production cost.

[0004] Therefore, it is urgent to develop an electromagnetic shielding film with high reflectivity and high electromagnetic shielding performance. Summary of the invention

[0005] Based on the problems existing in the background technology, the present invention provides an electromagnetic shielding film with high reflectivity and a preparation process. The electromagnetic shielding film has high reflectivity and high electromagnetic shielding effect.

[0006] The present invention is implemented by the following technical solutions:

[0007] An electromagnetic shielding film with high reflectivity, characterized in that it comprises a first release protective film, an insulating layer, a shielding layer, a conductive layer and a second release protective film;

[0008] The insulating layer covers the first release protective film, the shielding layer covers the insulating layer, the conductive layer covers the shielding layer, and the second release protective film covers the conductive layer.

[0009] Furthermore, the thickness of the insulating layer is 3-10 μm, and the insulating layer is obtained by coating with white ink.

[0010] Furthermore, the white ink comprises the following raw materials by weight: 25-45 parts of rubber, 10-15 parts of flame retardant, 3-5 parts of curing agent, 0.05-0.1 parts of ion capture agent, 0.1-0.5 parts of antioxidant, 0.1-0.5 parts of accelerator, 15-30 parts of resin, 20-40 parts of white dye and 150-240 parts of diluent.

[0011] Further, the rubber is one of the nitrile rubber N23;

[0012] The flame retardant is OP935;

[0013] The curing agent is DDS;

[0014] The ion capture agent is IXE-100;

[0015] The antioxidant is G200 or L1010;

[0016] The accelerator is EVERRNOX-10;

[0017] The resin is one of epoxy resin 901 or epoxy resin 128;

[0018] The white dye is a 1:1 mixture of titanium dioxide and zirconium oxide;

[0019] The diluent is one of 2-butanone or ethylene glycol methyl ether.

[0020] Furthermore, the shielding layer has a thickness of 0.1-5 μm, and the material comprises a first metal and a second metal, the mass ratio of the first metal to the second metal is 1:1, wherein the first metal is one of nickel, titanium, and chromium, and the second metal is one of gold or silver.

[0021] Furthermore, the thickness of the conductive layer is 3-30 μm, and the conductive layer is obtained by coating a thermosetting conductive adhesive.

[0022] Furthermore, the thermosetting conductive coating is composed of 15-35 parts of conductive powder and 50-70 parts of epoxy resin by weight;

[0023] Wherein, the conductive powder is one of aluminum powder, zinc powder, copper powder and nickel powder;

[0024] The particle size of the conductive powder is 1-15 μm.

[0025] Furthermore, the first release protective film and the second release protective film have a thickness of 10-50 μm and are a type of polyimide film or polyester film.

[0026] A preparation process of an electromagnetic shielding film with high reflectivity comprises the following steps:

[0027] Step 1: Mix the prepared rubber, flame retardant, curing agent, ion scavenger, antioxidant, accelerator, resin, white dye and diluent, and disperse them in a high-speed disperser for 3-10 hours at a speed of 800-1200 r / min, maintaining a temperature of 25-30°C. After dispersion, filter with a 1-5 μm filter to obtain white ink;

[0028] Step 2: using a corona machine to corona treat the first release protective film;

[0029] Step 3: coating white ink on the treated first release protective film and drying it to obtain an insulating layer;

[0030] Step 4: forming a metal film layer on the insulating layer by vacuum sputtering the first metal and the second metal to obtain a shielding layer;

[0031] Step 5: Evenly mix the conductive powder and epoxy resin, use a high-speed disperser to disperse for 1-1.5 hours, rotate at 800-1200 r / min, maintain the temperature at 25-30°C, and obtain a thermosetting conductive adhesive after dispersion;

[0032] Step 6: Apply the thermosetting conductive adhesive on the shielding layer and dry it to obtain a conductive layer;

[0033] Step 7: Lay the second release protective layer on the conductive layer and roll it up to obtain an electromagnetic shielding film with high reflectivity.

[0034] Furthermore, in step three and step six, tunnel oven drying is adopted, and the tunnel oven is divided into six sections, and the temperature of each section is 60°C, 80°C, 120°C, 160°C, 160°C, and 60°C respectively; the air inlet frequency of each section is 25Hz, 20Hz, 20Hz, 20Hz, 20Hz, and 25Hz respectively; and the exhaust air frequency is 40Hz.

[0035] Furthermore, the high-speed disperser in step 1 also includes a real-time detection system for the mixing degree of white ink;

[0036] The white ink mixing degree real-time detection system comprises:

[0037] An image acquisition module for acquiring an image of the stirred white ink mixture;

[0038] The computing module intercepts the image of the white ink mixture liquid collected by the camera and generates a detection area;

[0039] The control module compares the calculation result obtained by the operation module with the mixing index threshold value, determines whether the stirring of the white ink mixture meets the requirements, and then controls the working state of the stirrer according to the result.

[0040] Furthermore, the white ink mixing degree real-time detection system performs the following operations:

[0041] S1, a 4M180-CL high-speed camera in the image acquisition module acquires images of the white ink mixture;

[0042] S2, the calculation module calculates and processes the pixel values ​​of the collected white ink mixture image to obtain the pixel value distribution of the mixture image;

[0043] S3. Calculate the collected mixture uniformity index Q:

[0044]

[0045] y i is the pixel value of each pixel in the detection area, is the mean value of pixels in the detection area, and m is the number of pixels in the detection area.

[0046] S4. Set the white ink mixture uniformity index threshold value to A, and transmit the white ink mixture uniformity index Q obtained by the calculation module to the control module. The control module compares the Q value with the uniformity index threshold value A. If it is greater than the threshold value A, it is detected that the uniformity does not meet the requirements, and the control module does not send a stop stirring signal to the agitator. If it is less than or equal to the threshold value A, it is detected that the uniformity meets the requirements, and the control module sends a stop stirring signal to the agitator.

[0047] Beneficial effects of the present invention:

[0048] The electromagnetic shielding film with high reflectivity of the present invention comprises a first release protective film, an insulating layer, a shielding layer, a conductive layer and a second release protective film. The electromagnetic shielding film with high reflectivity of the present invention has an electromagnetic shielding efficiency of more than 90dB at 10-3000MHZ, and has excellent heat resistance and acid and alkali resistance, and can meet a bending life of more than 80,000 times. Compared with the black shielding film of the traditional process, the present invention uses white ink coating on the insulating layer, so that the entire electromagnetic shielding film has a high reflectivity. It can be seen from the reflection test results that the electromagnetic shielding film prepared by the method of the present invention can have a reflective effect of 85%, which provides a new idea for the application of electromagnetic shielding film on the observation window of electronic equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings are used to provide further explanation of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0050] Figure 1 It is a schematic diagram of the structure of the electromagnetic shielding film with high reflectivity of the present invention;

[0051] In the figure: 1-first release protective film, 2-insulating layer, 3-shielding layer, 4-conductive layer, 5-second release protective film. DETAILED DESCRIPTION

[0052] The technical scheme of the present invention is further described in detail below in conjunction with specific examples, but the protection scope of the present invention is not limited to the following examples. If no specific conditions are specified in the examples, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0053] Figure 1 The schematic diagram of the structure of the electromagnetic shielding film with high reflectivity of the present invention comprises a first release protective film 1, an insulating layer 2, a shielding layer 3, a conductive layer 4 and a second release protective film 5; the insulating layer is covered on the first release protective film, the shielding layer is covered on the insulating layer, the conductive layer is covered on the shielding layer, and the second release protective film is covered on the conductive layer. The insulating layer is obtained by coating with white ink. The preparation material of the shielding layer includes a first metal and a second metal. The conductive layer is obtained by coating with a thermosetting conductive adhesive, and the thermosetting conductive coating is composed of a conductive powder and an epoxy resin.

[0054] The first release protective film and the second release protective film are made of polyimide film with a thickness of 20 μm.

[0055] The thickness of the insulating layer is 8 μm, the thickness of the shielding layer is 3 μm, and the thickness of the conductive layer is 10 μm.

[0056] Example 1

[0057] In this embodiment, the white ink in the insulating layer includes the following components by weight: 35 parts of nitrile rubber N23, 12 parts of flame retardant OP935, 4 parts of curing agent DDS, 0.08 parts of ion capture agent IXE-100, 0.3 parts of antioxidant L1010, 0.3 parts of accelerator EVERRNOX-10, 20 parts of epoxy resin 901, 15 parts of titanium dioxide (white dye), 15 parts of zirconium oxide (white dye) and 200 parts of 2-butanone (diluent).

[0058] In this embodiment, the first metal in the shielding layer is nickel, the second metal is silver, and the mass ratio of the first metal to the second metal is 1:1.

[0059] In this embodiment, the thermosetting conductive coating in the conductive layer includes 25 parts of aluminum powder (conductive powder, with a particle size of 10 μm) and 60 parts of epoxy resin 901 by weight.

[0060] The preparation process of high reflectivity electromagnetic shielding film is as follows:

[0061] Step 1: Mix the prepared rubber, flame retardant, curing agent, ion scavenger, antioxidant, accelerator, resin, white dye and diluent, and disperse them in a high-speed disperser for 8 hours at a speed of 800 r / min and a temperature of 25°C. After dispersion, filter with a 3 μm filter to obtain white ink;

[0062] Step 2: Use a corona machine to corona treat the first release protective film, the corona treatment power is 10KW, and the corona value is 38-42mN / m;

[0063] Step 3: Apply white ink on the treated first release protective film and dry it in a tunnel oven. The tunnel oven is divided into six sections, and the temperatures of each section are 60°C, 80°C, 120°C, 160°C, 160°C, and 60°C respectively; the air inlet frequency of each section is 25Hz, 20Hz, 20Hz, 20Hz, 20Hz, and 25Hz respectively; the exhaust frequency is 40Hz, and an insulating layer is obtained;

[0064] Step 4: Form a metal film on the insulating layer by vacuum sputtering the first metal and the second metal to obtain a shielding layer. The specific vacuum sputtering steps are: put the first metal and the second metal into a sputtering machine for fixation and cleaning, and the sputtering machine is vacuum degassed. When the vacuum level reaches 10 -3 When the pressure of argon gas is 2Pa, the first metal is sputtered on the insulating layer to form a first metal film, the second metal is sputtered on the first metal film to form a second metal film, and finally the first metal is sputtered on the surface of the second metal film to form a final metal film, i.e., a shielding layer. The deceleration speed of the first metal and the second metal is 0.5m / min;

[0065] Step 5: Evenly mix the conductive powder and epoxy resin, use a high-speed disperser to disperse for 1.5 hours, rotate at 800 r / min, maintain the temperature at 25°C, and obtain a thermosetting conductive adhesive after dispersion;

[0066] Step 6: Apply the thermosetting conductive adhesive on the shielding layer and dry it in a tunnel oven. The tunnel oven is divided into six sections. The temperatures of each section are 60°C, 80°C, 120°C, 160°C, 160°C, and 60°C respectively; the air inlet frequency of each section is 25Hz, 20Hz, 20Hz, 20Hz, 20Hz, and 25Hz respectively; the exhaust frequency is 40Hz to obtain a conductive layer;

[0067] Step 7: Lay the second release protective layer on the conductive layer and roll it up to obtain an electromagnetic shielding film with high reflectivity.

[0068] Example 2

[0069] In this embodiment, the white ink in the insulating layer includes the following components by weight: 30 parts of nitrile rubber N23, 10 parts of flame retardant OP935, 3 parts of curing agent DDS, 0.05 parts of ion capture agent IXE-100, 0.2 parts of antioxidant L1010, 0.2 parts of accelerator EVERRNOX-10, 20 parts of epoxy resin 901, 10 parts of titanium dioxide (white dye), 10 parts of zirconium oxide (white dye) and 180 parts of 2-butanone (diluent).

[0070] In this embodiment, the first metal in the shielding layer is copper, the second metal is silver, and the mass ratio of the first metal to the second metal is 1:1.

[0071] In this embodiment, the thermosetting conductive coating in the conductive layer includes 20 parts of aluminum powder (conductive powder, with a particle size of 10 μm) and 55 parts of epoxy resin 901 by weight.

[0072] The preparation process of high reflectivity electromagnetic shielding film is as follows:

[0073] Step 1: Mix the prepared rubber, flame retardant, curing agent, ion scavenger, antioxidant, accelerator, resin, white dye and diluent, and disperse them in a high-speed disperser for 8 hours at a speed of 800 r / min and a temperature of 25°C. After dispersion, filter with a 3 μm filter to obtain white ink;

[0074] Step 2: Use a corona machine to corona treat the first release protective film, the corona treatment power is 10KW, and the corona value is 38-42mN / m;

[0075] Step 3: Apply white ink on the treated first release protective film and dry it in a tunnel oven. The tunnel oven is divided into six sections, and the temperatures of each section are 60°C, 80°C, 120°C, 160°C, 160°C, and 60°C respectively; the air inlet frequency of each section is 25Hz, 20Hz, 20Hz, 20Hz, 20Hz, and 25Hz respectively; the exhaust frequency is 40Hz, and an insulating layer is obtained;

[0076] Step 4: The first metal and the second metal are vacuum sputtered on the insulating layer to form a metal film to obtain a shielding layer. The specific vacuum sputtering steps are: the first metal and the second metal are placed in a sputtering machine for fixing and cleaning, and the sputtering machine is vacuum degassed. When the vacuum level reaches 10 -3 When the pressure of argon gas is 2Pa, the first metal is sputtered on the insulating layer to form a first metal film, the second metal is sputtered on the first metal film to form a second metal film, and finally the first metal is sputtered on the surface of the second metal film to form a final metal film, i.e., a shielding layer. The deceleration speed of the first metal and the second metal is 0.5m / min;

[0077] Step 5: Evenly mix the conductive powder and epoxy resin, use a high-speed disperser to disperse for 1.5 hours, rotate at 800 r / min, maintain the temperature at 25°C, and obtain a thermosetting conductive adhesive after dispersion;

[0078] Step 6: Apply the thermosetting conductive adhesive on the shielding layer and dry it in a tunnel oven. The tunnel oven is divided into six sections. The temperatures of each section are 60°C, 80°C, 120°C, 160°C, 160°C, and 60°C respectively; the air inlet frequency of each section is 25Hz, 20Hz, 20Hz, 20Hz, 20Hz, and 25Hz respectively; the exhaust frequency is 40Hz to obtain a conductive layer;

[0079] Step 7: Lay the second release protective layer on the conductive layer and roll it up to obtain an electromagnetic shielding film with high reflectivity.

[0080] Comparative Example 1

[0081] In this comparative example, the white ink in the insulating layer includes the following components by weight: 35 parts of nitrile rubber N23, 12 parts of flame retardant OP935, 4 parts of curing agent DDS, 0.08 parts of ion capture agent IXE-100, 0.3 parts of antioxidant L1010, 0.3 parts of accelerator EVERRNOX-10, 20 parts of epoxy resin 901, 30 parts of titanium dioxide (white dye) and 200 parts of 2-butanone (diluent).

[0082] In this comparative example, the first metal in the shielding layer is nickel, the second metal is silver, and the mass ratio of the first metal to the second metal is 1:1.

[0083] In this comparative example, the thermosetting conductive coating in the conductive layer includes 25 parts of aluminum powder (conductive powder, with a particle size of 10 μm) and 60 parts of epoxy resin 901 by weight.

[0084] The preparation process of high reflectivity electromagnetic shielding film is as follows:

[0085] Step 1: Mix the prepared rubber, flame retardant, curing agent, ion scavenger, antioxidant, accelerator, resin, white dye and diluent, and disperse them in a high-speed disperser for 8 hours at a speed of 800 r / min and a temperature of 25°C. After dispersion, filter with a 3 μm filter to obtain white ink;

[0086] Step 2: Use a corona machine to corona treat the first release protective film, the corona treatment power is 10KW, and the corona value is 38-42mN / m;

[0087] Step 3: Apply white ink on the treated first release protective film and dry it in a tunnel oven. The tunnel oven is divided into six sections, and the temperatures of each section are 60°C, 80°C, 120°C, 160°C, 160°C, and 60°C respectively; the air inlet frequency of each section is 25Hz, 20Hz, 20Hz, 20Hz, 20Hz, and 25Hz respectively; the exhaust frequency is 40Hz, and an insulating layer is obtained;

[0088] Step 4: Form a metal film on the insulating layer by vacuum sputtering the first metal and the second metal to obtain a shielding layer. The specific vacuum sputtering steps are: put the first metal and the second metal into a sputtering machine for fixation and cleaning, and the sputtering machine is vacuum degassed. When the vacuum level reaches 10 -3 When the pressure of argon gas is 2Pa, the first metal is sputtered on the insulating layer to form a first metal film, the second metal is sputtered on the first metal film to form a second metal film, and finally the first metal is sputtered on the surface of the second metal film to form a final metal film, i.e., a shielding layer. The deceleration speed of the first metal and the second metal is 0.5m / min;

[0089] Step 5: Evenly mix the conductive powder and epoxy resin, use a high-speed disperser to disperse for 1.5 hours, rotate at 800 r / min, maintain the temperature at 25°C, and obtain a thermosetting conductive adhesive after dispersion;

[0090] Step 6: Apply the thermosetting conductive adhesive on the shielding layer and dry it in a tunnel oven. The tunnel oven is divided into six sections. The temperatures of each section are 60°C, 80°C, 120°C, 160°C, 160°C, and 60°C respectively; the air inlet frequency of each section is 25Hz, 20Hz, 20Hz, 20Hz, 20Hz, and 25Hz respectively; the exhaust frequency is 40Hz to obtain a conductive layer;

[0091] Step 7: Lay the second release protective layer on the conductive layer and roll it up to obtain an electromagnetic shielding film with high reflectivity.

[0092] Comparative Example 2

[0093] In this comparative example, the white ink in the insulating layer includes the following components by weight: 35 parts of nitrile rubber N23, 12 parts of flame retardant OP935, 4 parts of curing agent DDS, 0.08 parts of ion capture agent IXE-100, 0.3 parts of antioxidant L1010, 0.3 parts of accelerator EVERRNOX-10, 20 parts of epoxy resin 901, 30 parts of zirconium oxide (white dye) and 200 parts of 2-butanone (diluent).

[0094] In this comparative example, the first metal in the shielding layer is nickel, the second metal is silver, and the mass ratio of the first metal to the second metal is 1:1.

[0095] In this comparative example, the thermosetting conductive coating in the conductive layer includes 25 parts of aluminum powder (conductive powder, with a particle size of 10 μm) and 60 parts of epoxy resin 901 by weight.

[0096] The preparation process of high reflectivity electromagnetic shielding film is as follows:

[0097] Step 1: Mix the prepared rubber, flame retardant, curing agent, ion scavenger, antioxidant, accelerator, resin, white dye and diluent, and disperse them in a high-speed disperser for 8 hours at a speed of 800 r / min and a temperature of 25°C. After dispersion, filter with a 3 μm filter to obtain white ink;

[0098] Step 2: Use a corona machine to corona treat the first release protective film, the corona treatment power is 10KW, and the corona value is 38-42mN / m;

[0099] Step 3: Apply white ink on the treated first release protective film and dry it in a tunnel oven. The tunnel oven is divided into six sections, and the temperatures of each section are 60°C, 80°C, 120°C, 160°C, 160°C, and 60°C respectively; the air inlet frequency of each section is 25Hz, 20Hz, 20Hz, 20Hz, 20Hz, and 25Hz respectively; the exhaust frequency is 40Hz, and an insulating layer is obtained;

[0100] Step 4: Form a metal film on the insulating layer by vacuum sputtering the first metal and the second metal to obtain a shielding layer. The specific vacuum sputtering steps are: put the first metal and the second metal into a sputtering machine for fixing and cleaning, and vacuum degas the sputtering machine. When the vacuum level reaches 10 -3 When the pressure of argon gas is 2Pa, the first metal is sputtered on the insulating layer to form a first metal film, the second metal is sputtered on the first metal film to form a second metal film, and finally the first metal is sputtered on the surface of the second metal film to form a final metal film, i.e., a shielding layer. The deceleration speed of the first metal and the second metal is 0.5m / min;

[0101] Step 5: Evenly mix the conductive powder and epoxy resin, use a high-speed disperser to disperse for 1.5 hours, rotate at 800 r / min, maintain the temperature at 25°C, and obtain a thermosetting conductive adhesive after dispersion;

[0102] Step 6: Apply the thermosetting conductive adhesive on the shielding layer and dry it in a tunnel oven. The tunnel oven is divided into six sections. The temperatures of each section are 60°C, 80°C, 120°C, 160°C, 160°C, and 60°C respectively; the air inlet frequency of each section is 25Hz, 20Hz, 20Hz, 20Hz, 20Hz, and 25Hz respectively; the exhaust frequency is 40Hz to obtain a conductive layer;

[0103] Step 7: Lay the second release protective layer on the conductive layer and roll it up to obtain an electromagnetic shielding film with high reflectivity.

[0104] Comparative Example 3

[0105] In this comparative example, the insulating layer ink in the insulating layer includes the following components by weight: 35 parts of nitrile rubber N23, 12 parts of flame retardant OP935, 4 parts of curing agent DDS, 0.08 parts of ion capture agent IXE-100, 0.3 parts of antioxidant L1010, 0.3 parts of accelerator EVERRNOX-10, 20 parts of epoxy resin 901 and 200 parts of 2-butanone (diluent).

[0106] In this comparative example, the first metal in the shielding layer is nickel, the second metal is silver, and the mass ratio of the first metal to the second metal is 1:1.

[0107] In this comparative example, the thermosetting conductive coating in the conductive layer includes 25 parts of aluminum powder (conductive powder, with a particle size of 10 μm) and 60 parts of epoxy resin 901 by weight.

[0108] The preparation process of high reflectivity electromagnetic shielding film is as follows:

[0109] Step 1: Mix the prepared rubber, flame retardant, curing agent, ion capture agent, antioxidant, accelerator, resin, white dye and diluent, and disperse them in a high-speed disperser for 8 hours at a speed of 800 r / min and a temperature of 25°C. After dispersion, filter with a 3 μm filter to obtain an insulating layer ink;

[0110] Step 2: Use a corona machine to corona treat the first release protective film, the corona treatment power is 10KW, and the corona value is 38-42mN / m;

[0111] Step 3: Apply an insulating layer ink on the treated first release protective film and dry it in a tunnel oven. The tunnel oven is divided into six sections, and the temperatures of each section are 60°C, 80°C, 120°C, 160°C, 160°C, and 60°C respectively; the air inlet frequency of each section is 25Hz, 20Hz, 20Hz, 20Hz, 20Hz, and 25Hz respectively; the exhaust frequency is 40Hz, and an insulating layer is obtained;

[0112] Step 4: Form a metal film on the insulating layer by vacuum sputtering the first metal and the second metal to obtain a shielding layer. The specific vacuum sputtering steps are: put the first metal and the second metal into a sputtering machine for fixing and cleaning, and vacuum degas the sputtering machine. When the vacuum level reaches 10 -3When the pressure of argon gas is 2Pa, the first metal is sputtered on the insulating layer to form a first metal film, the second metal is sputtered on the first metal film to form a second metal film, and finally the first metal is sputtered on the surface of the second metal film to form a final metal film, i.e., a shielding layer. The deceleration speed of the first metal and the second metal is 0.5m / min;

[0113] Step 5: Evenly mix the conductive powder and epoxy resin, use a high-speed disperser to disperse for 1.5 hours, rotate at 800 r / min, maintain the temperature at 25°C, and obtain a thermosetting conductive adhesive after dispersion;

[0114] Step 6: Apply the thermosetting conductive adhesive on the shielding layer and dry it in a tunnel oven. The tunnel oven is divided into six sections. The temperatures of each section are 60°C, 80°C, 120°C, 160°C, 160°C, and 60°C respectively; the air inlet frequency of each section is 25Hz, 20Hz, 20Hz, 20Hz, 20Hz, and 25Hz respectively; the exhaust frequency is 40Hz to obtain a conductive layer;

[0115] Step 7: Lay the second release protective layer on the conductive layer and roll it up to obtain an electromagnetic shielding film with high reflectivity.

[0116] Test example

[0117] Performance Testing

[0118] Electromagnetic shielding effectiveness: Refer to SJ20524-1995 material shielding effectiveness measurement method, the frequency range is 10-3000MHZ, test peak shielding performance (in dB), the results are shown in Table 1.

[0119] Table 1

[0120] Test frequency 10MHZ 30MHZ 100MHZ 300MHZ 1000MHZ 3000MHZ Example 1 93 94 97 92 95 92 Example 2 93 93 95 92 93 92 Comparative Example 1 91 93 93 90 92 93 Comparative Example 2 92 92 91 91 93 91 Comparative Example 3 90 91 93 92 90 91

[0121] Insulation resistance: Press the electromagnetic shielding film onto the FPC board cover film surface. After peeling off the release film, place 2 small steel sheets on the surface with a spacing of 1 cm between the steel sheets. Use a multimeter to test the resistance between the steel sheets.

[0122] Thermal shock resistance: Using the tin-bleaching test method, the electromagnetic shielding film is pressed onto the FPC and cured, and then tin-bleaching is performed at 288°C for 10 seconds, 5 times.

[0123] Surface hardness: After the electromagnetic shielding film is pressed onto the FPC and cured, a pencil hardness tester is used to perform a hardness test.

[0124] Solvent resistance: After the electromagnetic shielding film is pressed onto the FPC and cured, the sample is immersed in a solvent (ethanol, isopropanol, butanone) for ultrasonic cleaning at room temperature for 10 minutes. The sample is taken out and dried to observe the surface appearance, and a 100-grid peeling test is performed with 3M tape.

[0125] Acid and alkali resistance: After the electromagnetic shielding film is pressed onto the FPC and cured, the sample is immersed in a solution (2N hydrochloric acid, 10% sodium hydroxide, 10% sulfuric acid solution) for ultrasonic cleaning at room temperature for 10 minutes. The sample is taken out and dried to observe the surface appearance, and a 100-grid peeling test is performed with 3M tape.

[0126] Salt spray resistance: After the electromagnetic shielding film is pressed onto the FPC and cured, it is placed in a salt spray test box with a 5% sodium chloride aqueous solution at 35°C for 72 hours.

[0127] Bending resistance (flexibility test): in accordance with GB / T2679.5-1995, the conditions are r = 0.38mm, 135°).

[0128] Reflective effect test: Use BTR-1 visible light transmittance / reflectivity and haze tester to test the reflective effect of electromagnetic shielding film.

[0129] The above test results are shown in Table 2

[0130] Table 2

[0131] Test items Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Insulation resistance qualified qualified qualified qualified qualified Thermal shock resistance qualified qualified qualified qualified qualified Surface hardness 2H No damage 2H No damage 2H No damage 2H No damage 2H No damage Solvent resistance qualified qualified qualified qualified qualified Acid and alkali resistance qualified qualified qualified qualified qualified Salt spray resistant qualified qualified qualified qualified qualified Bending resistance ≥80000 times ≥80000 times ≥80000 times ≥80000 times ≥80000 times Reflective effect 85％ 85％ 40％ 40％ /

[0132] It can be seen from the data in Tables 1 and 2 that the white dye in the white ink used in Examples 1 and 2 contains titanium dioxide and zirconium oxide. The reflective effect is more than doubled compared to Comparative Examples 1 and 2 which only contain one white dye. The electromagnetic shielding film prepared in Comparative Example 3 which does not add white dye does not have a reflective effect.

[0133] Example 3

[0134] The high-speed disperser in step 1 of the preparation process of the electromagnetic shielding film with high reflectivity also includes a real-time detection system for the mixing degree of white ink;

[0135] The white ink mixing degree real-time detection system comprises:

[0136] An image acquisition module for acquiring an image of the stirred white ink mixture;

[0137] The computing module intercepts the image of the white ink mixture liquid collected by the camera and generates a detection area;

[0138] The control module compares the calculation result obtained by the operation module with the mixing index threshold value, determines whether the stirring of the white ink mixture meets the requirements, and then controls the working state of the stirrer according to the result.

[0139] Furthermore, the white ink mixing degree real-time detection system performs the following operations:

[0140] S1, a 4M180-CL high-speed camera in the image acquisition module acquires images of the white ink mixture;

[0141] S2, the calculation module calculates and processes the pixel values ​​of the collected white ink mixture image to obtain the pixel value distribution of the mixture image;

[0142] S3. Calculate the collected mixture uniformity index Q:

[0143]

[0144] y i is the pixel value of each pixel in the detection area, is the mean value of pixels in the detection area, and m is the number of pixels in the detection area.

[0145] S4. Set the white ink mixture uniformity index threshold value to A, and transmit the white ink mixture uniformity index Q obtained by the calculation module to the control module. The control module compares the Q value with the uniformity index threshold value A. If it is greater than the threshold value A, it is detected that the uniformity does not meet the requirements, and the control module does not send a stop stirring signal to the agitator. If it is less than or equal to the threshold value A, it is detected that the uniformity meets the requirements, and the control module sends a stop stirring signal to the agitator.

[0146] The beneficial effects of the above invention: the real-time detection system for white ink mixing degree in the present invention can intelligently control the stirring time, avoiding uneven mixing of the white ink due to too short stirring time, substandard performance of the coated insulation layer, or waste of resources due to too long stirring time.

[0147] Finally, it should be noted that the above-mentioned embodiments only express several implementation methods of the present invention and are not intended to limit the invention. For those skilled in the art, any modification, equivalent replacement, improvement, etc. made without departing from the concept of the present invention should be included in the protection scope of the invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An electromagnetic shielding film with high light reflectivity, characterized in that: It includes a first release protective film, an insulating layer, a shielding layer, a conductive layer and a second release protective film; The insulating layer covers the first release protective film, the shielding layer covers the insulating layer, the conductive layer covers the shielding layer, and the second release protective film covers the conductive layer; The thickness of the insulating layer is 3-10 μm, and the insulating layer is obtained by coating with white ink; The white ink contains the following raw materials by weight: 25-45 parts of rubber, 10-15 parts of flame retardant, 3-5 parts of curing agent, 0.05-0.1 parts of ion capture agent, 0.1-0.5 parts of antioxidant, 0.1-0.5 parts of accelerator, 15-30 parts of resin, 20-40 parts of white dye and 150-240 parts of diluent; White dye is a 1:1 mixture of titanium dioxide and zirconium oxide.

2. The electromagnetic shielding film with high light reflectivity according to claim 1, characterized in that: The rubber is one of the nitrile rubber N23; The flame retardant is OP935; The curing agent is DDS; The ion capture agent is IXE-100; The antioxidant is G200 or L1010; The accelerator is EVERRNOX-10; The resin is one of epoxy resin 901 or epoxy resin 128; The diluent is one of 2-butanone or ethylene glycol methyl ether.

3. The electromagnetic shielding film with high light reflectivity according to claim 1, characterized in that: The shielding layer has a thickness of 0.1-5 μm, and the material comprises a first metal and a second metal, the mass ratio of the first metal to the second metal is 1:1, wherein the first metal is one of nickel, titanium, and chromium, and the second metal is one of gold or silver.

4. The electromagnetic shielding film with high light reflectivity according to claim 1, characterized in that: The thickness of the conductive layer is 3-30 μm, and the conductive layer is obtained by coating a thermosetting conductive adhesive.

5. The electromagnetic shielding film with high light reflectivity according to claim 4, characterized in that: The thermosetting conductive coating is composed of 15-35 parts of conductive powder and 50-70 parts of epoxy resin by weight; Wherein, the conductive powder is one of aluminum powder, zinc powder, copper powder and nickel powder; The particle size of the conductive powder is 1-15 μm.

6. The electromagnetic shielding film with high light reflectivity according to claim 1, characterized in that: The first release protective film and the second release protective film have a thickness of 10-50 μm and are a type of polyimide film or polyester film.

7. A process for preparing an electromagnetic shielding film with high reflectivity as claimed in claims 1 to 6, characterized in that: The following steps are involved: Step 1: Mix the prepared rubber, flame retardant, curing agent, ion scavenger, antioxidant, accelerator, resin, white dye and diluent, and disperse them in a high-speed disperser for 3-10 hours at a speed of 800-1200 r / min and a temperature of 25-30°C. After dispersion, filter with a 1-5 μm filter to obtain white ink; Step 2: using a corona machine to corona treat the first release protective film; Step 3: coating white ink on the treated first release protective film and drying it to obtain an insulating layer; Step 4: Form a metal film layer on the insulating layer by vacuum sputtering the first metal and the second metal to obtain a shielding layer; Step 5: Evenly mix the conductive powder and epoxy resin, use a high-speed disperser to disperse for 1-1.5 hours, rotate at 800-1200 r / min, maintain the temperature at 25-30°C, and obtain a thermosetting conductive adhesive after dispersion; Step 6: Apply the thermosetting conductive adhesive on the shielding layer and dry it to obtain a conductive layer; Step 7: Lay the second release protective layer on the conductive layer and roll it up to obtain an electromagnetic shielding film with high reflectivity.

8. The electromagnetic shielding film with high light reflectivity according to claim 7, characterized in that: In steps three and six, tunnel oven drying is adopted. The tunnel oven is divided into six sections. The temperature of each section is 60°C, 80°C, 120°C, 160°C, 160°C, and 60°C respectively; the air inlet frequency of each section is 25Hz, 20Hz, 20Hz, 20Hz, 20Hz, and 25Hz respectively; and the exhaust air frequency is 40Hz.

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