A release film for lamination and its preparation method

Abstract

This invention discloses a release film for lamination and its preparation method, belonging to the field of electronic products. From top to bottom, it comprises: a first release layer, a first adhesive layer, a resist layer, a second adhesive layer, and a second release layer. Both the first and second release layers are poly-4-methyl-1-pentene; the first and second adhesive layers are polyolefins or modified polyolefins; and the resist layer is polyester or modified polyolefin. The release film for lamination of this invention can replace the high-cost TPX series release films, comprehensively utilizing the release properties of TPX and the stiffness of polyester, achieving a perfect balance between operability and lamination characteristics.

Description

Technical Field

[0001] This invention relates to a high-temperature release film for lamination and its preparation method, belonging to the field of electronic products. Background Technology

[0002] Flexible printed circuit boards (FPCBs) are indispensable materials in electronic products and are currently widely used in computers and their peripherals, communication products, and consumer electronics. During FPCB manufacturing, a cover film is laminated onto the copper foil, and reinforcing plates are heat-pressed onto the terminals. During this pressing process, a release film is placed on both the top and bottom of the FPCB to protect the board surface from the press and to ensure it conforms to the shape of the circuitry during heat pressing. Furthermore, the release film prevents the FPCB from sticking to the press during both heat pressing and cooling.

[0003] With the rise of the electric vehicle industry in China, a special type of FPCB (Fused Printed Circuit Board) has emerged specifically for electric vehicle batteries. This involves thicker nickel sheets, larger step differences, and narrower but longer individual circuit boards, exceeding 1 meter in length. This places new demands on the release film used in hot pressing, requiring it to be free from warping and wrinkles, have good filling properties, and possess good stiffness. Traditional FPCB release films are generally designed for boards 300-500mm in length, and they present several problems when used for battery panel lamination, such as shrinkage, wrinkles, insufficient stiffness, and poor filling. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a release film for lamination and its preparation method. The release film of the present invention does not produce shrinkage and wrinkles during lamination, has good release properties, a certain degree of stiffness, and good lamination conformability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A release film for lamination comprises, from top to bottom: a first release layer, a first adhesive layer, a barrier layer, a second adhesive layer, and a second release layer; wherein the first release layer and the second release layer are both poly-4-methyl-1-pentene; the first adhesive layer and the second adhesive layer are polyolefins or modified polyolefins; and the barrier layer is a polyester or a modified polyolefin.

[0007] Furthermore, a first fiber filament is disposed above the first release layer, and a second fiber filament is disposed above the second release layer. The first fiber filament and the second fiber filament are perpendicular in direction, and the first fiber filament and the second fiber filament are polyester fiber filaments.

[0008] Furthermore, the total thickness of the release film for lamination is 20-400 μm, the thickness of the first release layer and the second release layer is 5-30 μm, the thickness of the first adhesive layer and the second adhesive layer is 3-20 μm, and the thickness of the adhesive barrier layer is 20-200 μm.

[0009] Furthermore, the first adhesive layer and the second adhesive layer are prepared from the following raw materials: 15%-50% poly-4-methyl-1-pentene, 15%-40% maleic anhydride-grafted polypropylene, and 10%-50% polypropylene, the percentages being by mass.

[0010] Furthermore, the adhesive barrier layer is prepared from the following raw materials: 30%-60% polybutylene terephthalate, 20%-40% maleic anhydride-grafted polypropylene, and 10%-30% polyethylene, with the percentages being by mass.

[0011] This invention also provides a method for preparing a release film for lamination, comprising the following steps:

[0012] Place the poly-4-methyl-1-pentene granules in a feeding hopper and insert a vacuum feeding pump;

[0013] After mixing and stirring the various materials used for the adhesive layer, put them into the conveying bucket and insert the vacuum feeding pump;

[0014] The materials used for the adhesive barrier layer are connected to a dryer and a regular feeder, respectively. After passing through an automatic weighing system, they are automatically weighed and mixed, and then enter the storage tank of the extruder before entering the extruder.

[0015] Set the three screws, distributor, and die of the extruder to the predetermined temperature values, wait for the equipment to fully heat up, and maintain the temperature for 2-3 hours before starting the machine;

[0016] Start the machine to start the large and small screws, which will rotate slowly and gradually reach the preset parameter values. Then start the vacuum feed pump to feed the material.

[0017] The large and small screws convey the molten material through the distributor of the casting machine and into the die head, where it is distributed in proportion to form a whole film;

[0018] The cast film is deposited onto a rough steel roller, cooled, and pressed by a rubber roller to form a film. It is then pulled by subsequent rollers and measured by an online thickness gauge to finally form a film with uniform thickness.

[0019] Cut into specific widths online and then roll up.

[0020] Furthermore, for the extruder used to process the poly-4-methyl-1-pentene granules for the release layer, a screw with an aspect ratio of 30-38 is selected, and the processing temperature is set sequentially according to the zones: zone 1 is 180-250℃, zone 2 is 240-290℃, zone 3 is 280-320℃, zone 4 is 280-320℃, and the flow channel is 250-280℃.

[0021] Furthermore, for the extruder used to process the adhesive layer material, a screw with a length-to-diameter ratio of 25-30 is selected, and the temperature is set sequentially according to the zones: Zone 1 is 120-180℃, Zone 2 is 180-250℃, Zone 3 is 230-280℃, Zone 4 is 230-280℃, and the flow channel is 230-280℃.

[0022] Furthermore, the distributor is set to a temperature of 250-280℃; the casting T-die head temperature is set to a range of 240-280℃ according to the temperature control point; material feeding and production begin after each section of the equipment reaches the set temperature value.

[0023] Furthermore, the extrusion ratio of the release layer, adhesive layer, and resist layer is controlled at 2:1:7 to 3:2:5, and the linear speed is controlled at 13-20 m / min.

[0024] A manufacturing process for a release film for lamination includes the following steps:

[0025] A1. Place the poly-4-methyl-1-pentene granules in the conveying bucket A and insert the vacuum feed pump;

[0026] A2. After mixing and stirring all the materials used for the adhesive layer, put them into the conveying bucket C and insert the vacuum feeding pump.

[0027] A3. Connect the materials used for the adhesive barrier layer to the dryer and the ordinary feeder respectively. After passing through the automatic weighing system, the materials are automatically weighed and mixed, and then enter the storage tank of the extruder, and then enter the extruder.

[0028] A4. Set the three screws, distributor, and die of the extruder to the preset temperature values, wait for the equipment to fully heat up, and maintain the temperature for 2-3 hours before starting the machine;

[0029] A5. Start the machine to allow the large and small screws to start rotating slowly and gradually reach the preset parameter values, and start the vacuum feed pump to feed the material;

[0030] A6. The large and small screws convey the molten material through the distributor of the casting machine and into the die head. After being distributed in proportion, it forms a whole film.

[0031] A7. The cast film is fed onto a rough steel roller, cooled, and pressed by a rubber roller to form a film. It is then pulled by subsequent rollers and measured by an online thickness gauge to finally form a film with uniform thickness.

[0032] A8. Cut into specific widths online and rewind.

[0033] Beneficial effects

[0034] The release film for lamination of this invention is a non-coated release agent release film with stable and reliable performance. Compared with existing TPX release films, it has greater advantages in the lamination of automotive battery circuit boards, and is suitable for laminating circuit boards with relatively narrow single sheets, relatively long lengths, and large local thickness differences. The release film of this invention does not produce shrinkage wrinkles during lamination, has good release properties, a certain degree of stiffness, and good lamination conformability. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the release film for lamination according to the present invention;

[0036] The meanings of the reference numerals in the figure are as follows: 1. First release layer, 2. First adhesive layer, 3. Resistant layer, 4. Second adhesive layer, 5. Second release layer. Detailed Implementation

[0037] Example 1

[0038] A release film for lamination, characterized in that it comprises, from top to bottom: a first release layer 1, a first adhesive layer 2, a barrier layer 3, a second adhesive layer 4, and a second release layer 5; wherein the first release layer 1 and the second release layer 5 are both poly-4-methyl-1-pentene; the first adhesive layer 2 and the second adhesive layer 4 are polyolefins or modified polyolefins; and the barrier layer 3 is a polyester or a modified polyolefin.

[0039] The release film for pressing is produced by a casting machine with three screws plasticizing and a distributor, and is formed in one step with a total thickness of 20-400um.

[0040] The first and second release layers use poly-4-methyl-1-pentene, which can be one or a mixture of several of the following brands from Mitsui Chemicals: MX004, MX002, MX002O, RT18, RT31, DX845, DX231, DX820, DX310, MBZ230, and DX560M; the thickness of each is 5-30 μm.

[0041] The first and second adhesive layers are selected from poly-4-methyl-1-pentene, polypropylene, polyethylene, acrylic acid-grafted polypropylene, methyl methacrylate-grafted polypropylene, maleic anhydride-grafted polypropylene, dibutyl maleate-grafted polyethylene, maleic anhydride-grafted high-density polyethylene, and styrene-butadiene-styrene block copolymer-modified polypropylene, with a thickness of 3-20 μm. The present invention preferably uses poly-4-methyl-1-pentene, polypropylene, and their modified copolymers.

[0042] The adhesive barrier layer is selected from one of polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyester elastomer, maleic anhydride-grafted polypropylene, maleic anhydride-grafted polyethylene, polypropylene, polyethylene, and styrene-butadiene-styrene block copolymer. The thickness of the adhesive barrier layer 3 is 20-200 μm. Preferred materials in this invention are polybutylene terephthalate, maleic anhydride-grafted polypropylene, and polyethylene.

[0043] Example 2

[0044] Based on Example 1, in this example, a first fiber filament is disposed above the first release layer 1, and a second fiber filament is disposed above the second release layer 5. The first and second fiber filaments are perpendicular in direction; the first and second fiber filaments are polyester fiber filaments. By setting two layers of fiber filaments with perpendicular directions, the release layer of the present invention can have higher strength and toughness, and the tensile strength of the release film can be increased.

[0045] Example 3

[0046] A release film for lamination, characterized in that it comprises, from top to bottom: a first release layer 1, a first adhesive layer 2, a barrier layer 3, a second adhesive layer 4, and a second release layer 5; wherein the first release layer 1 and the second release layer 5 are both poly-4-methyl-1-pentene; the first adhesive layer 2 and the second adhesive layer 4 are mixtures of polyolefin and modified polyolefin; and the barrier layer 3 is a mixture of polyester and modified polyolefin. A first fiber filament is disposed above the first release layer 1, and a second fiber filament is disposed above the second release layer 5, the directions of the first fiber filament and the second fiber filament being perpendicular; the first fiber filament and the second fiber filament are polyester fibers.

[0047] The release film for pressing is produced by a casting machine with three screws plasticizing and a distributor, and is formed in one step with a total thickness of 20-400um.

[0048] The first and second release layers use poly-4-methyl-1-pentene, which can be one or a mixture of several of the following brands from Mitsui Chemicals: MX004, MX002, MX002O, RT18, RT31, DX845, DX231, DX820, DX310, MBZ230, and DX560M; the thickness of each is 5-30 μm.

[0049] The first and second adhesive layers are selected from one or a mixture of several of the following: poly-4-methyl-1-pentene, polypropylene, polyethylene, acrylic acid-grafted polypropylene, methyl methacrylate-grafted polypropylene, maleic anhydride-grafted polypropylene, dibutyl maleate-grafted polyethylene, maleic anhydride-grafted high-density polyethylene, and styrene-butadiene-styrene block copolymer-modified polypropylene, with a thickness of 3-20 μm. The present invention preferably uses poly-4-methyl-1-pentene, polypropylene, and their modified copolymers. The first and second adhesive layers may also have the following formulation: poly-4-methyl-1-pentene 15%-50%, maleic anhydride-grafted polypropylene 15%-40%, and polypropylene 10%-50%. Percentages are by mass.

[0050] The adhesive barrier layer is selected from one or a mixture of several of the following: polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyester elastomer, maleic anhydride-grafted polypropylene, maleic anhydride-grafted polyethylene, polypropylene, polyethylene, and styrene-butadiene-styrene block copolymer. The thickness of the adhesive barrier layer 3 is 20-200 μm. Preferred materials in this invention are polybutylene terephthalate, maleic anhydride-grafted polypropylene, and polyethylene. The adhesive barrier layer may also have the following formulation: 30%-60% polybutylene terephthalate, 20%-40% maleic anhydride-grafted polypropylene, and 10%-30% polyethylene. Percentages are by weight.

[0051] Example 4

[0052] The manufacturing process of the release film of the present invention includes the following steps:

[0053] A1. Place the poly-4-methyl-1-pentene granules in the conveying bucket A and insert the vacuum feed pump;

[0054] A2. After mixing and stirring all the materials used for the adhesive layer, put them into the conveying bucket C and insert the vacuum feeding pump.

[0055] A3. Connect the materials used for the adhesive barrier layer to the dryer and the ordinary feeder respectively. After passing through the automatic weighing system, the materials are automatically weighed and mixed, and then enter the storage tank of the extruder, and then enter the extruder.

[0056] A4. Set the three screws, distributor, and die of the extruder to the preset temperature values, wait for the equipment to fully heat up, and maintain the temperature for 2-3 hours before starting the machine;

[0057] A5. Start the machine to allow the large and small screws to start rotating slowly and gradually reach the preset parameter values, and start the vacuum feed pump to feed the material;

[0058] A6. The large and small screws convey the molten material through the distributor of the casting machine and into the die head. After being distributed in proportion, it forms a whole film.

[0059] A7. The cast film is fed onto a rough steel roller, cooled, and pressed by a rubber roller to form a film. It is then pulled by subsequent rollers and measured by an online thickness gauge to finally form a film with uniform thickness.

[0060] A8. Cut into specific widths online and rewind.

[0061] The manufacturing process of the release film of the present invention involves the following steps, with the main parameters set during production:

[0062] B1. For the extruder used to process the poly-4-methyl-1-pentene granules for the release layer, select a screw with an aspect ratio of 30-38, and set the processing temperature according to the zones in sequence: Zone 1: 180-250℃, Zone 2: 240-290℃, Zone 3: 280-320℃, Zone 4: 280-320℃, and the flow channel temperature: 250-280℃.

[0063] B2. For the extruder used to process the adhesive layer material, select a screw with a length-to-diameter ratio of 25-30, and set the temperature according to the zones in sequence: Zone 1: 120-180℃, Zone 2: 180-250℃, Zone 3: 230-280℃, Zone 4: 230-280℃, and the flow channel: 230-280℃.

[0064] B3. For extruders processing polyester and modified polyolefin mixtures with a barrier layer, select screws with a length-to-diameter ratio of 25-30, and set the temperature sequentially according to the zones: Zone 1: 160-230℃, Zone 2: 230-280℃, Zone 3: 230-280℃, Zone 4: 230-280℃, and the flow channel: 230-280℃.

[0065] B4. Set the distributor temperature to 250-280℃; set the casting T-die temperature to 240-280℃ according to the temperature control points; start feeding and production after each section of the equipment reaches the set temperature value.

[0066] B5. The extrusion ratio of the release layer (feeding barrel A), adhesive layer (feeding barrel C) and adhesive barrier layer (feeding barrel B) is controlled at 2:1:7-3:2:5, and the linear speed is controlled at 13-20m / min.

[0067] B6. The temperature of the extrusion cooling roller is controlled between 30-90℃. Proper temperature control ensures the flatness of the surface finish. The parameters used in steps B1-B6 are the same parameters set during the production process (A1-A8).

[0068] To more effectively verify this invention, the following comparative experiments were conducted for analysis and comparison:

[0069] The extruders used in each group have the following screw length-to-diameter ratios: 35 for the release layer and adhesive layer, and 28 for the barrier layer. The temperature of the extrusion cooling rollers is controlled at 60℃.

[0070] Table 1 Production Temperature Settings:

[0071]

[0072]

[0073] Table 2 shows the composition of raw materials used in each layer, as detailed below:

[0074] Table 3 shows the structure used by the products in each group:

[0075]

[0076] Note: The structure of Group 4 is release layer / resistance layer / release layer. The release layer uses poly-4-methyl-1-pentene MX004 as its raw material, and the resist layer uses a mixture of MX004, polypropylene, and polyethylene.

[0077] Table 4 Comparison of the properties of the release film of the present invention and the prior art.

[0078]

[0079] Side A is the rubber pressure roller surface, and side B is the cast steel roller surface.

[0080] Heat shrinking involves cutting the film into MD*TD = 300mm*250mm pieces, baking it at 180℃ for 30 minutes, and then cooling it. The dimensional change rate before and after baking is then tested.

[0081] The test data above reflects that, regarding the surface tension, since the release layer uses TPX, it also reflects the characteristics of the TPX material itself, with a surface tension of 24 mN / m.

[0082] Regarding adhesive resistance, as the outer layer gradually thickens, the adhesive resistance performance of Groups 1 to 2 deteriorates, but all meet the requirement of <0.07mm, which is considered good adhesive resistance performance; Group 4 shows conventional characteristics and meets the general characteristics requirements of the industry.

[0083] In terms of dimensional expansion and contraction, groups 1 to 3 all showed shrinkage in the MD and TD directions, with all changes within 1%, while group 4 exceeded 1%. Group 4 may have poor pressing flatness and wrinkling problems for certain boards.

[0084] Based on the current comparison of membrane characteristic data, the embodiments of the present invention all show certain advantages over the prior art group 4.

[0085] Table 5 Test of Release Film Lamination Vehicle Panel

[0086]

[0087] Note: △ indicates "poor", ○ indicates "good", and ◎ indicates "excellent".

[0088] The lamination of release films of different thicknesses onto automotive boards reveals that increasing the thickness of the poly-4-methyl-1-pentene release layer significantly improves release performance, while conversely, it negatively impacts adhesive resistance. In Group 1, using a relatively thin 15µm release layer results in insufficient thickness, leading to decreased release performance and issues such as FPCB residue and damage. Furthermore, the thinness causes significant shrinkage differences between the inner and outer layers of the release film, preventing timely air expulsion during lamination and resulting in wrinkles in the release film, ultimately forming permanent creases on the FPCB.

[0089] The release layers of Groups 2 and 3 are 20µm and 25µm respectively. Due to their sufficient thickness, the release performance meets the requirements. At the same time, the formulation ratio and thickness of the resist layer are well matched with the release layer, preventing severe asynchronous shrinkage during hot pressing and thus avoiding pressing wrinkles. The resist performance also meets the requirements. However, it should be noted that as the release layer thickness increases, the resist performance deteriorates.

[0090] Group 4, used for the comparative test, consisted of FPCBs with normal board material lamination. While they exhibited no issues with release properties, due to inherent design limitations, uneven internal and external shrinkage occurred during the lamination of long boards, easily leading to unevenness in the release film and wrinkles during lamination, resulting in permanent creases on the FPCB automotive board. Furthermore, due to the limited release layer thickness, the adhesive resistance was also unsatisfactory, failing to meet expectations.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and equivalent substitutions can be made without departing from the principle of the present invention, and the technical solutions obtained by these improvements and equivalent substitutions should also fall within the protection scope of the present invention.

Claims

1. A method for producing a lamination release film, characterized by, The pressing release film comprises from top to bottom: a first release layer (1), a first adhesive layer (2), a glue blocking layer (3), a second adhesive layer (4), and a second release layer (5); the first release layer (1) and the second release layer (5) are both poly-4-methyl-1-pentene; the first release layer (1) is provided with a first fiber filament on top, the second release layer (5) is provided with a second fiber filament on top, the first fiber filament and the second fiber filament are perpendicular, and the first fiber filament and the second fiber filament are polyester filaments; the first adhesive layer (2) and the second adhesive layer (4) are prepared from the following raw materials: poly-4-methyl-1-pentene 15%-50%, maleic anhydride grafted polypropylene 15%-40%, and polypropylene 10%-50%, with the percentages being mass percentages; the glue blocking layer (3) is prepared from the following raw materials: polybutylene terephthalate 30%-60%, maleic anhydride grafted polypropylene 20%-40%, and polyethylene 10%-30%, with the percentages being mass percentages. The preparation method of the pressing release film comprises the following steps: Put the poly-4-methyl-1-pentene pellets into a feeding barrel and insert a vacuum feeding pump; Mix and stir the various materials for the adhesive layer, then put them into the feeding barrel and insert a vacuum feeding pump; Connect the materials for the glue blocking layer to a drying machine and a common suction machine respectively, automatically weigh and stir and mix them through an automatic weighing system, then put them into the storage barrel of an extruder, and then into the extruder; The pressing release film is produced by a casting machine with three plasticizing screws through a distributor; the extruder for processing the poly-4-methyl-1-pentene pellets for the release layer is selected to have a screw with a length-diameter ratio of 30-38; the extruder for processing the adhesive layer materials is selected to have a screw with a length-diameter ratio of 25-30; the extruder for processing the mixture of the glue blocking layer polyester and modified polyolefin is selected to have a screw with a length-diameter ratio of 25-30; the three screws of the extruder, the distributor, and the die head are set to predetermined temperature values; wait for the equipment to be fully warmed up and maintain the temperature for 2-3 hours before starting the machine; Start the machine to start the large and small screws, slowly rotate, and gradually reach the preset parameter values, and start the vacuum feeding pump to feed; The molten materials conveyed by the large and small screws pass through the distributor of the casting machine and enter the die head, are proportionally distributed, and then form an integrated film; The cast film is cooled on a steel roller with roughness on the surface, is pressed by a rubber roller to form a film, is then pulled by subsequent rollers, is measured by an online thickness gauge, and finally forms a film with uniform thickness; The film is cut into a specific width online and is wound.

2. The production method of lamination release film according to claim 1, characterized by, The total thickness of the pressing release film is 20-400 um, the thickness of the first release layer (1) and the second release layer (5) is 5-30 um, the thickness of the first adhesive layer (2) and the second adhesive layer (4) is 3-20 um, and the thickness of the glue blocking layer (3) is 20-200 um.

3. The method of claim 1, wherein the lamination of the release film is performed by using a vacuum laminator. The extruder for processing the poly-4-methyl-1-pentene pellets of the release layer is sequentially provided with processing temperatures in regions, and the temperature is set to 180-250 ℃ in region 1, 240-290 ℃ in region 2, 280-320 ℃ in region 3, 280-320 ℃ in region 4, and 250-280 ℃ in the flow channel.

4. The method of claim 1, wherein the lamination of the release film is performed by using a vacuum laminator. The extruder for processing the adhesive layer material is sequentially provided with temperatures in regions, and the temperature is set to 120-180 ℃ in region 1, 180-250 ℃ in region 2, 230-280 ℃ in region 3, 230-280 ℃ in region 4, and 230-280 ℃ in the flow channel.

5. The method of claim 1, wherein the lamination of the release film is performed by using a vacuum laminator. The temperature of the distributor is set to 250-280 ℃; the temperature of the casting T-shaped die is set according to temperature control points, and is sequentially set in the range of 240-280 ℃; after the temperature of each section of the equipment reaches the set temperature value, the feeding production is started.

6. The method of claim 1, wherein the lamination of the release film is performed by using a vacuum laminator. The extrusion amount proportion of the release layer, the adhesive layer and the glue-blocking layer is controlled to be 2:1:7-3:2:5, and the linear speed setting is controlled to be 13-20 m / min.

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