CN116552082A

CN116552082A - Multilayer release film and method for manufacturing multilayer release film

Info

Publication number: CN116552082A
Application number: CN202310567912.6A
Authority: CN
Inventors: 夏超华; 高曦
Original assignee: Suzhou New Guangyi Electronics Co ltd
Current assignee: Suzhou New Guangyi Electronics Co ltd
Priority date: 2023-05-19
Filing date: 2023-05-19
Publication date: 2023-08-08

Abstract

The invention discloses a multilayer release film, which comprises a release layer, an intermediate layer and a heat-resistant layer; the release layer is arranged on the outer layer of the multilayer release film, the material of the release layer comprises polyolefin resin, the melting point of the polyolefin resin is more than 200 ℃, and the value range of the dyne value of the polyolefin resin is 15-30; the heat-resistant layer is arranged on the outer layer of the multilayer release film and is opposite to the release layer, the material of the heat-resistant layer comprises polyester resin, the melting point of the polyester resin is higher than 200 ℃, the value range of the dyne value of the polyester resin is 35-55, and the elongation at break of the polyester resin is higher than 50%; the middle layer is arranged between the release layer and the heat-resistant layer, two sides of the heat-resistant layer are respectively contacted with the release layer and the heat-resistant layer, and the middle layer comprises polyolefin resin of the release layer and polyester resin of the heat-resistant layer. The multilayer release film has excellent tensile resistance and can prevent the warpage of the multilayer release film.

Description

Multilayer release film and method for manufacturing multilayer release film

Technical Field

The present invention relates to a multilayer release film and a method for manufacturing the same, and more particularly, to a multilayer release film for flexible circuit board (FPC) processing and a method for manufacturing the same.

Background

The flexible circuit board (FPC) can greatly reduce the volume and weight of electronic products, and the convenience of circuit board installation is improved. The flexible circuit board is mainly formed by hot pressing and bonding materials such as metal conductor foil, thermosetting adhesive, insulating base film and the like. However, there are many problems in the process of hot-pressing the above materials, on one hand, the heat-softened thermosetting adhesive overflows from the insulating base film and covers the surrounding metal conductor foil, so that the subsequent gold plating or gold melting treatment of the surface of the metal conductor foil cannot be performed, and the subsequent welding of components is hindered; on the other hand, the high temperature and high pressure environment of FPC processing also very easily causes the bonding of insulating base film and the pressfitting panel of hot press, causes flexible circuit board damage or produces the fold. In order to solve the above problems, a release film is placed between a pressing panel of a hot press and a flexible circuit board, and the release film is peeled off after the pressing process is completed. In the processing process, the release film can play roles of glue overflow resistance, protection, wrinkle resistance, easy stripping and the like.

The release film with the structure comprises an upper layer, a middle layer and a lower layer which are sequentially arranged, wherein the upper layer and the lower layer are mainly made of poly-4-methyl-1-pentene (4-methylpentene-1), and the release film is also called TPX. TPX has excellent heat resistance and good stripping performance, so that the release film is not easy to deform in the heating process and is stripped smoothly. However, such release films still have the following problems:

Firstly, TPX materials are brittle, are easy to crack in the stretching process, have poor pressure bearing performance and cannot meet the production conditions of partial FPC. In particular, roll-to-Roll technology is commonly used in the production of FPCs, specifically to the fact that the FPC stock and release film are attached to each other in a "Roll-to-Roll" manner. In the Roll-to-Roll process, the release film with TPX material on both surfaces is easy to break, and the production efficiency of the FPC is greatly affected.

Secondly, the TPX material has high melting point and large specific heat, so that a large amount of energy is consumed when the TPX material is used for producing and processing the release film, the production cost is increased, and the energy conservation and emission reduction are not facilitated.

Again, TPX is a relatively expensive raw material and has a relatively low cost, and is mainly supplied by japan corporation, and is easily "stuck", and the release film is closely related to the development of the electronic industry in China. Therefore, TPX is high in cost, mainly depends on foreign imported raw materials, is not suitable for large-scale popularization and use, and is unfavorable for the development of the electronic industry in China.

The present invention has been made in view of the above technical problems.

Disclosure of Invention

The invention discloses a multilayer release film, which comprises a release layer, an intermediate layer and a heat-resistant layer; the release layer is arranged on the outer layer of the multilayer release film, the material of the release layer comprises polyolefin resin, the melting point of the polyolefin resin is more than 200 ℃, and the value range of the dyne value of the polyolefin resin is 15-30; the heat-resistant layer is arranged on the outer layer of the multilayer release film and is opposite to the release layer, the material of the heat-resistant layer comprises polyester resin, the melting point of the polyester resin is higher than 200 ℃, the value range of the dyne value of the polyester resin is 35-55, and the elongation at break of the polyester resin is higher than 50%; the middle layer is arranged between the release layer and the heat-resistant layer, two sides of the heat-resistant layer are respectively contacted with the release layer and the heat-resistant layer, and the middle layer comprises polyolefin resin of the release layer and polyester resin of the heat-resistant layer.

Further, the polyolefin-based resin is selected from one or a combination of two or more of TPX, ETFE, PTFE.

Further, the polyester resin is selected from one or a combination of two or more of PBT, PET, PC.

Further, the ratio of the thickness of the heat-resistant layer to the thickness of the release layer is 1.1-5.

Further, the ratio of the thickness of the heat-resistant layer to the thickness of the release layer is 1.5-3.

Further, the heat-resistant layer comprises a first heat-resistant surface and a second heat-resistant surface which is arranged opposite to the first heat-resistant surface, and the second heat-resistant surface is in contact with the middle layer; regarding the surface properties of the first heat resistant surface, a stylus having a tip radius of 2 μm and a cone angle of 60 ° was used by the method based on ISO 4287-1997, and the maximum height roughness Rz measured under the conditions of a measurement force of 0.75mN, a cutoff value λs=2.5 μm, and λc=0.8 mm was in the range of 5 μm to 50 μm, and the average width RSm of the roughness profile unit was in the range of 30 μm to 300 μm.

Further, regarding the surface properties of the second heat resistant surface, a stylus having a tip radius of 2 μm and a cone angle of 60 ° was used by the method based on ISO 4287-1997, and the maximum height roughness Rz measured under the conditions of a measurement force of 0.75mN, a cutoff value λs=2.5 μm, and λc=0.8 mm was in the range of 0.8 μm to 24 μm, and the average width RSm of the roughness profile unit was in the range of 50 μm to 600 μm.

Further, the maximum height roughness Rz of the first heat resistant surface is in the range of 20 μm to 40 μm.

Further, the thickness of the release layer is 10 μm to 50 μm.

Further, the thickness of the release layer is 20-40 μm.

Further, the thickness of the intermediate layer is 10 μm to 200 μm.

Further, the material of the intermediate layer may be selected from ethylene, an α -olefin- (meth) acrylate copolymer, a mixture of polybutylene terephthalate and 1, 4-cyclohexanedimethanol copolymerized polyethylene terephthalate, and a mixture of an α -olefin polymer and an α -olefin- (meth) acrylate copolymer such as ethylene.

Further, the ratio of the thickness of the heat-resistant layer to the maximum height roughness Rz of the first heat-resistant surface is in the range of 1.2 to 5.

Further, the ratio ranges from 1.5 to 3.

The above summary does not include an exhaustive list of all aspects of the invention. It is contemplated that the present invention includes all systems and methods that can be practiced by all suitable combinations of the various aspects summarized above, as well as those disclosed in the detailed description below, and particularly pointed out in the claims filed with this patent application. Such a combination has particular advantages not specifically set forth in the above summary.

Drawings

Embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements. It should be noted that references to "an" or "an" embodiment in this disclosure are not necessarily to the same embodiment.

FIG. 1 shows a schematic view of a multilayer release film of the present invention;

FIG. 2 shows a schematic view of a multilayer release film of the present invention in a side view;

fig. 3 shows a schematic view of a part of the process steps in the production process of the multilayer release film of the present invention.

Detailed Description

In this section, several embodiments of the present invention will be explained with reference to the accompanying drawings. Whenever the shape, relative position and other aspects of the components described in the embodiments are not explicitly defined, the scope of the present invention is not limited to only the illustrated components, which are shown for illustrative purposes only. In addition, while numerous details are set forth, it should be understood that some embodiments of the invention may be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Spatially relative terms, such as "under … …," "under … …," "lower," "above … …," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or elements or feature or features as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below … …" may encompass both an orientation of above … … and below … …. The device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof.

The terms "or" and/or "as used herein should be interpreted as inclusive or meaning any one or any combination. Thus, "A, B or C" or "A, B and/or C" means "any one of the following: a, A is as follows; b, a step of preparing a composite material; c, performing operation; a and B; a and C; b and C; A. b and C. An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive.

The structure of the release film comprises a release layer 101, an intermediate layer 102 and a heat-resistant layer 103.

Release layer

The release layer 101 is disposed on the outer layer or outer side of the release film, and is a film layer that contacts the surface of the FPC during the FPC production process. The thickness of the release layer of the release film is 10-50 μm, and further, the thickness of the release layer is 20-40 μm. When the thickness of the release layer is more than the lower limit value of the data range, the mechanical strength of the release layer can be improved, and the fracture of the release layer in the heating and pressurizing process can be reduced. When the thickness of the release layer is less than the upper limit value of the data range, the use amount of release layer materials can be reduced, and the cost is reduced.

The release layer of the present invention may optionally contain a polyolefin resin, and examples thereof include poly-4-methyl-1-pentene resin (TPX, also called polymethylpentene resin), ethylene-tetrafluoroethylene copolymer (ETEF), polytetrafluoroethylene (PTEF), and the like. The composition of the release layer of the present invention may include one type of polyolefin-based resin, and may also include a combination of two or more polyolefin-based resins.

The polyolefin resin of the release layer of the present invention has a dyne value of 15 to 30, and a low dyne value means a small adhesiveness, and the release layer of the present invention can be formed using the above polyolefin resin to improve the release performance of the release film.

Among the above materials, the release layer of the present invention is preferably TPX, which has good heat resistance and peelability, and when the release layer is preferably TPX, the release performance and thermal stability of the release film can be improved.

In addition, the melting point of the polyolefin-based resin of the release layer of the present invention is more than 200 ℃. Because in the FPC preparation process, the FPC needs to be heated and pressurized, so that the bonding firmness between the metal wiring, the bonding pad and the insulating base film on the FPC is improved. The polyolefin resin can ensure that the shape and the physical state of the release layer cannot change in the process of heating and pressurizing the FPC, and avoid the heat deformation of the release layer to transfer flaws such as wrinkles to the surface of the FPC while ensuring the release property of the release layer.

As an alternative embodiment, the release layer of the release film of the present invention may contain, in addition to the above-mentioned polyolefin resin, various auxiliaries such as an antioxidant, a slip aid, an anti-sticking agent, an antistatic agent, a pigment, a stabilizer, a fluororesin, an epoxy rubber, titanium oxide, calcium carbonate, talc, and the like.

The release layer of the release film of the present invention provides good peeling properties so that the release film can be easily peeled from the surface of the FPC after the hot pressing process is completed.

Heat-resistant layer

The heat-resistant layer 103 is a film layer that contacts the hot-press panel of the hot press during hot-press of FPC production.

The heat-resistant layer of the present invention may be formed of a polyester resin, for example, one or more of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polytrimethylene terephthalate (PTT), polyethylene terephthalate (PHT) and Syndiotactic Polystyrene (SPS), as the component of the heat-resistant layer.

The melting point of the polyester resin is more than 200 ℃. In the preparation process of the FPC, the FPC is required to be heated and pressurized so as to improve the bonding firmness between the metal wiring and the bonding pad on the FPC and the insulating base film. The polyester resin can ensure that the shape and the physical state of the heat-resistant layer cannot change in the process of heating and pressurizing the FPC, and the heat-resistant layer is prevented from being adhered to the hot pressing plate due to heating.

The lower limit value of the dyne value of the polyester resin of the present invention includes 30, 35, 40, and the upper limit value of the dyne value of the polyester resin of the present invention includes 50, 55, 60, and when the dyne value of the polyester resin selected for the heat-resistant layer is below the upper limit value, the adhesion between the heat-resistant layer and the autoclave plate can be reduced, and the heat-resistant layer is prevented from adhering to the autoclave plate after the completion of the hot pressing. The heat-resistant layer is usually a film layer in contact with a conveying device such as a hot platen, a conveyor belt, and a conveyor roller. When the dyne value of the polyester resin selected for the heat-resistant layer is above the lower limit value, dislocation between the heat-resistant layer and the surface of other objects in the transportation and conveying processes can be avoided, and the control precision of the production and processing of the release film is improved.

The polyolefin resin selected for the release layer has better release performance, but is crisp in texture and easy to crack and wrinkle in the processing or stripping process. The elongation at break of the polyester resin selected for the heat-resistant layer is more than 50%, alternatively, the elongation at break of the polyester resin selected for the heat-resistant layer is more than 100%, and alternatively, the elongation at break of the polyester resin is more than 150%. When the elongation at break of the heat-resistant layer is above the above value, the heat-resistant layer has better mechanical property and can bear larger mechanical pressure and tensile length, so that the release film disclosed by the invention is ensured not to be mechanically damaged in the processing, transporting and using processes, the breakage of the release layer caused by the brittle property of the release layer is avoided, and the yield of the release film and the FPC is improved.

The thickness of the heat-resistant layer is set according to the thickness of the release layer. The thickness of the release layer is set as a, the thickness of the heat-resistant layer is set as b, and the ratio of the thickness b of the heat-resistant layer to the thickness a of the release layer is 1.1-5, further 1.5-4, and further 2-3. When the ratio of the thickness of the heat-resistant layer to the thickness of the release layer is above the lower limit value of the numerical range, the stretching resistance of the release film can be further improved, the mechanical property of the release film is increased, the breakage of the release film is reduced, and the number of folds generated on the release layer in the heating and pressurizing process is reduced.

Because the heat-resistant layer is directly contacted with the hot-pressing plate, the film layer temperature is always higher than that of the release layer, and because the heat-resistant layer and the release layer are made of different materials, the thermal deformation coefficients of the heat-resistant layer and the release layer are different, under the condition, the heat-resistant layer and the release layer are obviously different from each other in deformation in the length direction caused by heating, and the difference can lead to warping of the multilayer release film, so that the processing efficiency and the yield of the FPC are affected. The ratio of the thickness of the heat-resistant layer to the thickness of the release layer is set above the lower limit value, so that on one hand, the mass of the heat-resistant layer relative to the material of the release layer can be increased, and under the condition that the specific heat capacity of the heat-resistant layer is unchanged and the received heat is unchanged, the increase of the mass of the heat-resistant layer can reduce the temperature rise of the heat-resistant layer, thereby reducing the deformation of the heat-resistant layer and reducing the deformation difference of the heat-resistant layer and the release layer under the heated state. On the other hand, the thicker heat-resistant layer can improve the rigidity of the release film, and the improvement of the rigidity can further reduce the possibility of warping of the multilayer release film.

The ratio of the thickness of the heat-resistant layer to the thickness of the release layer is set below the upper limit value, so that the thickness of the heat-resistant layer is reduced to save cost, and in addition, in the process of embossing one surface of the heat-resistant layer through the embossing roller, the concave-convex surface of the embossing roller, which is used for endowing roughness, can be directly embossed on the other surface of the heat-resistant layer, so that the production efficiency of the release film is improved.

The heat resistant layer of the present invention includes a first heat resistant surface 1031 that contacts the heat press plate during the heat press of the FPC and a second heat resistant surface 1032 that is disposed opposite to the first heat resistant surface and contacts the intermediate layer. The term "opposed arrangement" as used herein includes a positional relationship in which two layered structures, objects, and surfaces are stacked and arranged on each other, which are not on the same plane, and a positional relationship between two or more different surfaces of the same layered structure, object, and surface, and is not limited as long as the two layered structures, objects, and surfaces are not on the same plane, and have a relative positional relationship, whether or not other objects are interposed between such structures, objects, and surfaces, and angles of each other.

Regarding the surface properties of the first heat resistant surface, using a stylus having a tip radius of 2 μm and a cone angle of 60 ° using a method based on ISO 4287-1997, the lower limit value of the maximum height roughness Rz measured under the conditions of a measurement force of 0.75mN, a cutoff value λs=2.5 μm, λc=0.8 mm may be 0.8 μm, 1.2 μm, 1.6 μm, 2.4 μm; the upper limit value of the maximum height roughness Rz may be 15 μm, 18 μm, 21 μm, 24 μm. As an alternative embodiment, the maximum height roughness Rz of the first heat resistant surface of the release film heat resistant layer of the present invention ranges from 0.8 μm to 24 μm, alternatively from 1.2 μm to 18 μm, further alternatively from 2.4 μm to 15 μm. Rz is defined as the maximum height roughness and characterizes the peak-to-valley spacing of the surface relief of the material in terms of unit sampling range.

When the maximum height roughness Rz of the first heat resistant surface is above the lower limit value, the first heat resistant surface is not easy to adhere to the hot pressing plate, and the release property between the heat resistant layer and the hot pressing plate is improved. When the maximum height roughness Rz of the first heat resistant surface is below the upper limit value, the roughness of the parameter range can be better endowed from the process, and meanwhile, the surface of the first heat resistant surface is ensured to have certain flatness.

The ratio of the thickness (in μm) of the heat-resistant layer to the value (in μm) of the maximum height roughness Rz of the first heat-resistant surface is defined as an imprint ratio, and in the case of the release film of the present invention, the imprint ratio ranges from 1.2 to 5, further, the imprint ratio ranges from 1.3 to 4, and still further, the imprint ratio ranges from 1.5 to 3. The roughness is usually formed on the first heat resistant surface by means of embossing roller rolling, i.e. the roughness provided on the surface of the embossing roller is transferred to the surface of the first heat resistant surface, thereby forming the roughness on the first heat resistant surface. When the embossing ratio of the release film is above the lower limit values 1.2, 1.3 and 1.5, the thickness of the heat-resistant layer is larger than the maximum height roughness Rz of the first heat-resistant surface, and meanwhile, as the heat-resistant layer adopts a ductile material, perforation of the heat-resistant layer caused in the rolling process of the embossing roller can be avoided. When the embossing ratio of the release film is below the upper limit values 5, 4 and 3, the roughness of the release film compared with the first heat resistant surface is in a proper range and is not too thick, so that the roughness of the first heat resistant surface can be generated by rolling, the concave-convex of the first heat resistant surface can be smoothly embossed on the second heat resistant surface, and by adopting the arrangement, the roughness can be generated on the first heat resistant surface and the second heat resistant surface at the same time through one rolling process in the process of processing the heat resistant layer, and the production efficiency is improved.

Since the raw material is heated in the production process of the release film, the intermediate layer of the release film has a certain fluidity in this heated state. The heat-resistant layer and the middle layer are pressed together by arranging the concave-convex parts on the second heat-resistant surface, and at the moment, the flowing middle layer substance can fill the concave-convex parts on the second heat-resistant surface, so that the contact area between the middle layer and the second heat-resistant surface is increased, and the adhesion between the middle layer and the second heat-resistant surface is more fastened. Regarding the properties of the second heat resistant surface, using a stylus having a tip radius of 2 μm and a cone angle of 60 ° using a method based on ISO 4287-1997, the lower limit value of the average width RSm of the roughness profile unit measured under the conditions that the measurement force is 0.75mN, the cutoff value λs=2.5 μm, and λc=0.8 mm may be 10 μm, 30 μm, 60 μm; the upper limit of the RSm value may be 300 μm, 400 μm, 500 μm. The average width RSm of the roughness curve outline unit of the second heat resistant surface of the release film heat resistant layer is 10-500 μm, alternatively 30-400 μm, and further alternatively 60-300 μm.

The average width RSm of the roughness profile elements reflects the spacing of the embossments on the second heat resistant surface. When RSm is larger than the upper limit value, the interval between the irregularities on the second heat resistant surface is larger, which corresponds to less irregularities per unit area, and in this case, the effect of increasing the contact surface area between the heat resistant layer and the intermediate layer by providing roughness to increase adhesion is smaller. If RSm is smaller than the lower limit value, the interval between the concave-convex parts of the second heat-resistant surface is smaller, the number of concave-convex parts in unit area is larger, and when the heat-resistant surface and the intermediate layer are laminated, the material of the intermediate layer in a relatively flowing state cannot sufficiently fill the gaps between the concave-convex parts on the second heat-resistant surface, but rather, the adhesion between the second heat-resistant surface and the intermediate layer is reduced. When the average width RSm of the roughness curve outline unit of the second heat resistant surface is between the lower limit and the upper limit disclosed by the invention, the adhesion performance between the second heat resistant surface and the middle layer can be in an optimal state, and separation between the heat resistant layer and the middle layer in the peeling process of the release film is avoided.

Intermediate layer

The middle layer is a film layer positioned between the release layer and the heat-resistant layer, and the middle layer is a single layer or multiple layers.

The copper foil of the existing FPC board is mostly adhered on the insulating base film through thermosetting glue, then the circuit wiring is formed through steps of exposure, development and the like, and gaps are formed between the wiring and the bonding pads of each circuit. In the hot pressing process of the FPC, the thermosetting adhesive between the insulating base film and the copper foil is heated, the fluidity is increased, part of thermosetting adhesive can overflow from between the insulating base film and the copper foil and is attached to the copper foil, and the surface of the copper foil is uneven. If the thermosetting adhesive is attached to the bonding pad and other positions, the electronic components are easy to be subjected to cold joint and off-joint, and defective products are caused.

The interlayer of the release film has certain fluidity after being heated, and under the action of the interlayer in the hot pressing process of the FPC, the multilayer release film can fill up gaps between the circuit wires and the bonding pads, and can cover the circuit wires and the bonding pads at the same time, so that the flowing thermosetting adhesive is prevented from being adhered to the circuit wires or the bonding pads after overflowing. In addition, the interlayer of the invention also plays a role of adhering the release layer and the heat-resistant layer arranged on two sides of the interlayer, and avoids the release layer or the heat-resistant layer possibly generated when the release film is covered or peeled off from the interlayer.

The thickness of the intermediate layer of the present invention is 10 μm to 200. Mu.m, further, the thickness of the intermediate layer is 20 μm to 180. Mu.m, further, the thickness of the intermediate layer is 30 μm to 150. Mu.m. When the thickness of the intermediate layer is more than the lower limit value, the effect of filling the gap of the FPC after heating can be fully exerted, and the anti-overflow glue performance is improved. When the thickness of the middle layer is lower than the upper limit value, the heat conducting performance of the release film can be improved, so that the heat of the hot pressing plate can be rapidly conducted to the FPC plate, and the production efficiency is improved.

The material of the intermediate layer comprises the material of the release layer and the material of the heat-resistant layer, and the compatibility between the same materials is better, and the material adopted by the intermediate layer comprises the same material as the release layer and the heat-resistant layer, so that the adhesion performance between the intermediate layer and the release layer and between the intermediate layer and the heat-resistant layer can be improved, and the release layer, the heat-resistant layer and the intermediate layer are prevented from being stripped. Specifically, the material of the intermediate layer of the present invention includes a polyolefin-based resin and a polyester-based resin.

Optionally, the material of the middle layer also comprises engineering plastic resin such as polyethersulfone, polyphenylene sulfide and the like. Alternatively, the material of the intermediate layer may further include ethylene, an α -olefin- (meth) acrylate copolymer, a mixture of polybutylene terephthalate and 1, 4-cyclohexanedimethanol copolymerized polyethylene terephthalate, and a mixture of an α -olefin polymer and an α -olefin- (meth) acrylate copolymer of ethylene or the like. For example, a mixture of ethylene and ethylene-methyl methacrylate copolymer (EMMA), a mixture of polypropylene (PP) and ethylene-methyl methacrylate copolymer (EMMA), a mixture of polybutylene terephthalate (PBT) and polypropylene (PP) and ethylene-methyl methacrylate copolymer (EMMA), and the like.

When the material of the intermediate layer includes the above, the melting point thereof is relatively low, and therefore, the better the fluidity of the intermediate layer in the heated state. On the one hand, the better fluidity can further improve the adhesive resistance of the release film. On the other hand, in the processing process of the release film, the interlayer plays a role of lining the heat-resistant layer when embossing and rolling is carried out on the heat-resistant layer, and at the moment, the softer and higher the fluidity of the interlayer, the roughness concave-convex on the first heat-resistant surface of the heat-resistant layer can be fully embossed, so that the adhesiveness between the interlayer and the heat-resistant layer is further improved.

The multilayer release film disclosed by the invention has the advantages of taking the stripping performance and the tensile performance in the hot pressing process into consideration, and simultaneously, the warp of the release film can be reduced, the separation among film layers is reduced, and the time and the material cost are greatly reduced.

Method for preparing multilayer release film

As shown in fig. 3, the method for preparing the release film of the present invention includes: the materials of the release layer 101, the intermediate layer 102 and the heat-resistant layer 103 are respectively added into a coextrusion device, such as a multi-die coextrusion device, the layers are respectively extruded and molded by the coextrusion device, and the film layers are stacked in the order of the release layer, the intermediate layer and the heat-resistant layer.

Next, the stacked film layers are laminated using two press rolls 201, 202, respectively, wherein the first press roll 201 is in contact with the release layer for applying a compressive resultant force to the release layer, and the second press roll 202 is in contact with the heat-resistant layer for applying a compressive resultant force to the heat-resistant layer, and under the pressure opposite to the release layer and the heat-resistant layer, the release layer, the intermediate layer and the heat-resistant layer can be laminated to each other, thereby forming a structure of a multilayer release film.

The first press roller 201 of the present invention is a rubber roller. The rubber roller can provide certain buffer performance, avoids breaking and wrinkling of the release layer under the action of stress, so that a smooth and complete release layer surface is obtained, and the FPC surface is ensured not to be defective due to flaws on the release layer surface.

The second press roll 202 of the present invention is a rigid roll. For the multilayer release film, the rigid roller can conveniently endow the heat-resistant layer with the concave-convex to form roughness, and due to the fact that the rigid roller is matched with the rubber roller, the concave-convex which is endowed to the first heat-resistant surface of the heat-resistant layer by the rigid roller can be well stamped to the second heat-resistant surface under the condition that the rubber roller is used as a gasket due to the fact that the texture of the rubber roller is softer, so that the roughness is arranged on the second heat-resistant surface, the contact area between the middle layer and the second heat-resistant surface is increased, and the adhesiveness between the middle layer and the second heat-resistant surface is improved.

The temperature control method for the rigid roller and the rubber roller comprises the steps of arranging a waterway, a resistance wire and other temperature control devices on the inner sides of the rigid roller and/or the rubber roller, controlling the temperature of the surfaces of the rigid roller and the rubber roller through controlling parameters such as water temperature in the waterway or current on the resistance wire, and the like, and the method for controlling the surface temperature of the rigid roller/the rubber roller is not limited. The surface temperature of the rigid roller and the rubber roller is usually called as cooling temperature because the surface temperature of the rigid roller and the rubber roller is usually lower than the processing temperature of the release film material and plays a role in cooling the release film material.

As an embodiment of the method for producing a multilayer release film of the present invention, the temperature of the rubber roll in contact with the release layer is 20 ℃ or higher, optionally 25 ℃ or higher, further optionally 30 ℃ or higher, and at the same time, the temperature of the rubber roll is 120 ℃ or lower, optionally 100 ℃ or lower, further optionally 80 ℃ or lower. The temperature of the rubber roller ranges from 20 ℃ to 120 ℃, alternatively from 25 ℃ to 100 ℃, and further alternatively from 30 ℃ to 80 ℃. When the temperature of the rubber roller is above the lower limit value, the influence of the room temperature on the temperature of the rubber roller can be eliminated as far as possible, and if the temperature of the rubber roller is too low, the rubber roller can be heated at the room temperature under the condition of higher room temperature, so that the temperature control of the rubber roller is not facilitated. Meanwhile, the higher cooling temperature can avoid folds and bubbles on the surface of the release layer caused by overlarge difference between the cooling temperature of the rubber roller and the production temperature of the release layer. When the temperature of the rubber roller is below the upper limit value, the cooling speed of the multilayer release film can be increased, the production efficiency is increased, and because the rubber roller is directly contacted with the release layer of the release film, when the temperature of the rubber roller is below the upper limit value, the molecular chains of the polymer material of the release layer tend to be arranged in a disordered way, the brittleness property of the release layer is reduced, and the possibility of cracking and wrinkling of the release layer in the production and use processes is reduced.

As an embodiment of the method for producing a multilayer release film of the present invention, the temperature of the rigid roller in contact with the heat-resistant layer is higher than the temperature of the rubber roller in contact with the release layer. Specifically, the temperature of the rigid roller in contact with the heat-resistant layer is 60 ℃ or higher, alternatively 70 ℃ or higher, and further alternatively 80 ℃ or higher. The temperature of the rigid roller is below 150 ℃, alternatively below 120 ℃, and further alternatively below 100 ℃. The temperature of the rigid rolls ranges from 60 ℃ to 150 ℃, alternatively from 70 ℃ to 120 ℃, and further alternatively from 80 ℃ to 100 ℃. The release layer and the heat-resistant layer of the multilayer release film are made of different materials, the thermal expansion coefficients of the materials of the release layer and the heat-resistant layer are different to a certain extent, and the thermal expansion coefficient of the polyester resin is generally larger than that of the polyolefin resin, so that the release film disclosed by the invention can possibly generate warping problem due to expansion caused by heat and contraction caused by cold in the subsequent application process. When the temperature of the rigid roller is above the lower limit value, the cooling time is increased, and as part of molecular chains of the high polymer material are rearranged in the cooling process to form an ordered structure, the rearranged molecular chains of the heat-resistant layer material in the cooling process can be more dominant by increasing the cooling time of the heat-resistant layer, so that the thermal expansion coefficient of the heat-resistant layer is close to that of the release layer, and the warping of the release film is further slowed down. When the temperature of the rigid roller is below the upper limit value, the cooling efficiency can be improved, and the energy consumption can be reduced.

In the process of manufacturing the multilayer release film, the rubber roller and the rigid roller move at a linear speed of 10-50 m/min, alternatively 15-45 m/min, and further alternatively 20-30 m/min. When the linear speed of the roller is lower than the upper limit value, the heat-resistant layer can be kept at a higher temperature for a longer time, which is favorable for orderly rearranging molecular chains of the heat-resistant layer material and reducing the warping of the release film. When the linear velocity of the roller is above the lower limit value, the production efficiency can be improved. The linear speeds of the rubber roll and the rigid roll are kept consistent, that is, the lengths of the release layer and the heat-resistant layer of the multilayer release film are kept consistent after the rolling process. When the temperature continues to decrease, the heat-resistant layer has a larger thermal expansion coefficient than the release layer, so that the change in length of the heat-resistant layer is also larger than that of the release layer, and in this case, the multilayer release film is liable to warp, and the usability of the product is reduced.

After the main production process of the release film is completed, the following steps comprise: the multilayer release film is wound for convenient storage. The multilayer release film is wound in a mode that the release layer is arranged outside and the heat-resistant layer is arranged inside, and in the winding mode, the length of the heat-resistant layer is relatively smaller than that of the release layer, so that the warping of the multilayer release film can be reduced. This is because, for the multilayer release film of the present invention, although the coefficient of thermal expansion of the heat-resistant layer is generally greater than that of the release layer, the coefficient of thermal expansion of the heat-resistant layer is generally smaller than that of the intermediate layer, and the thickness of the intermediate layer is generally thicker, so that, in the case of cooling the release film, the intermediate layer contracts more than the heat-resistant layer, resulting in warping of the release film. In the production method of the release film, the release film is wound in a mode that the release layer is arranged outside and the heat-resistant layer is arranged inside when the release film is wound, so that the middle layer is arranged on the periphery of the heat-resistant layer, the length of the middle layer is physically prolonged, the length difference between the middle layer and the heat-resistant layer is reduced, and therefore warping of the release film can be reduced.

Implementation examples and evaluation

Implementation example 1:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 6 μm, the thickness of the heat-resistant layer is 30 μm, wherein the maximum height roughness Rz of the first heat-resistant surface is 10 μm, and the imprinting ratio is 3.

Implementation example 2:

the multilayer release film is characterized in that the release layer is made of PTEF, the heat-resistant layer is made of PET, the thickness of the middle layer is 100 mu m, and the middle layer is made of a mixture of PTEF and PET. The thickness of the release layer is 10 mu m, the thickness of the heat-resistant layer is 13 mu m, wherein the maximum height roughness Rz of the first heat-resistant surface is 20 mu m, and the imprinting ratio is 0.65.

Implementation example 3:

the multi-layer release film is characterized in that the release layer is made of ETEF, the heat-resistant layer is made of PC, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 20 mu m, the thickness of the heat-resistant layer is 40 mu m, wherein the maximum height roughness Rz of the first heat-resistant surface is 20 mu m, and the imprinting ratio is 2.

Implementation example 4:

the multilayer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PET, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 30 μm, and the thickness of the heat-resistant layer is 80 μm, wherein the maximum height roughness Rz of the first heat-resistant surface is 20 μm, and the imprinting ratio is 4.

Implementation example 5:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 40 μm, and the thickness of the heat-resistant layer is 60 μm, wherein the maximum height roughness Rz of the first heat-resistant surface is 10 μm, and the imprinting ratio is 6.

Implementation example 6:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 25 μm, and the thickness of the heat-resistant layer is 100 μm, wherein the maximum height roughness Rz of the first heat-resistant surface is 20 μm, and the imprinting ratio is 5.

Implementation example 7:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 60 μm, the thickness of the heat-resistant layer is 72 μm, wherein the maximum height roughness Rz of the first heat-resistant surface is 20 μm, and the imprinting ratio is 3.6.

Implementation example 8:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 30 μm, and the thickness of the heat-resistant layer is 15 μm, wherein the maximum height roughness Rz of the first heat-resistant surface is 10 μm, and the imprinting ratio is 1.5.

Implementation example 9:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 30 μm, and the thickness of the heat-resistant layer is 24 μm, wherein the maximum height roughness Rz of the first heat-resistant surface is 20 μm, and the imprinting ratio is 1.2.

Implementation example 10:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 30 μm, and the thickness of the heat-resistant layer is 210 μm, wherein the maximum height roughness Rz of the first heat-resistant surface is 20 μm, and the imprinting ratio is 10.5.

Evaluation of the degree of correlation of the imprinting ratio with the imprinting effect of the second heat-resistant surface:

selecting an embossing roller, bonding a release layer by using a rubber roller, bonding a first heat resistant surface of a heat resistant layer by using a steel roller, rolling the co-extruded release layer, the intermediate layer and the heat resistant layer at a linear speed of 15m/min, wherein the temperature of the rubber roller is 30 ℃, the temperature of the steel roller is 90 ℃, and then respectively endowing the first heat resistant surface with the maximum height roughness Rz described in the embodiment. After the preparation was completed, the release film sample was allowed to stand at room temperature for 24 hours, the heat-resistant layer was peeled off from the intermediate layer, and the roughness of the second heat-resistant surface of the heat-resistant layer in contact with the intermediate layer was measured. The second heat resistant surface is considered to have an imprint if the maximum height roughness Rz of the second heat resistant surface is 0.8 μm or more, and is considered to have no imprint if the maximum height roughness of the second heat resistant surface is less than 0.8 μm. If perforations appear on the heat resistant layer, they are recorded as perforations.

Evaluation of the warpage angle:

taking a release film sample sheet with the size of 10cm x 10cm, standing at the room temperature of 20 ℃ for 72 hours, and photographing the release film sample sheet from the side direction to obtain the side profile of the sample sheet. At this time, the highest point of the profile of the sample wafer is connected with the center point of the sample wafer, and the included angle between the connecting line and the horizontal plane is calculated, and the included angle is the warping angle of the sample wafer. If the warpage angle of the release film sample is 3 ° or less, the requirements of industrial applications can be satisfied, and the warpage performance of the sample is considered to pass.

TABLE 1

According to the above test results, when the imprint ratio between the thickness of the heat-resistant layer and the maximum height roughness Rz of the first heat-resistant surface is 1.2 to 5, the irregularities can be directly imprinted to the second heat-resistant surface while imparting the irregularities on the first heat-resistant surface, and perforation of the heat-resistant layer can be avoided.

According to the test result, when the thickness ratio between the heat-resistant layer and the release layer is more than 1.1, the warping angle of the release film sample is less than 3 degrees, the warping performance is good, and the industrial application can be met.

Implementation example 11:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 10 mu m, the thickness of the heat-resistant layer is 30 mu m, the Rz of the second heat-resistant surface of the heat-resistant layer is 0.8 mu m, and the RSm is 30 mu m.

Implementation example 12:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 10 mu m, the thickness of the heat-resistant layer is 30 mu m, the Rz of the second heat-resistant surface of the heat-resistant layer is 3 mu m, and the RSm is 20 mu m.

Implementation example 13:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 10 mu m, the thickness of the heat-resistant layer is 30 mu m, the Rz of the second heat-resistant surface of the heat-resistant layer is 5 mu m, and the RSm is 1000 mu m.

Implementation example 14:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 10 mu m, the thickness of the heat-resistant layer is 30 mu m, the Rz of the second heat-resistant surface of the heat-resistant layer is 8 mu m, and the RSm is 100 mu m.

Implementation example 15:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 10 mu m, the thickness of the heat-resistant layer is 30 mu m, the Rz of the second heat-resistant surface of the heat-resistant layer is 12 mu m, and the RSm is 200 mu m.

Implementation example 16:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 10 mu m, the thickness of the heat-resistant layer is 30 mu m, the Rz of the second heat-resistant surface of the heat-resistant layer is 15 mu m, and the RSm is 300 mu m.

Implementation example 17:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 10 mu m, the thickness of the heat-resistant layer is 30 mu m, the Rz of the second heat-resistant surface of the heat-resistant layer is 24 mu m, and the RSm is 200 mu m.

Implementation example 18:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 10 mu m, the thickness of the heat-resistant layer is 30 mu m, the Rz of the second heat-resistant surface of the heat-resistant layer is 20 mu m, and the RSm is 300 mu m.

Implementation 19:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 10 mu m, the thickness of the heat-resistant layer is 30 mu m, the Rz of the second heat-resistant surface of the heat-resistant layer is 0.5 mu m, and the RSm is 500 mu m.

Implementation example 20:

the multi-layer release film is characterized in that the release layer is made of TPX, the heat-resistant layer is made of PBT, the thickness of the intermediate layer is 100 mu m, and the intermediate layer is made of a mixture of PBT and TPX. The thickness of the release layer is 10 mu m, the thickness of the heat-resistant layer is 30 mu m, the Rz of the second heat-resistant surface of the heat-resistant layer is 30 mu m, and the RSm is 100 mu m.

Peel force test of heat-resistant layer:

the peel force between the heat-resistant layer and the intermediate layer was tested, and the multilayer release film was first cut into strips of 50mm width. The peel force test method refers to national standard GB/T2792-2014 of the people's republic of China, and the specific test method comprises the following steps: one side of the multilayer release film of the embodiment 11-20 is fixed on a plane clamp through viscose under the condition that the standard test environment temperature is 23 ℃ and the relative humidity is 50%, the free end of the heat-resistant layer far away from the plane clamp is clamped by a tension meter with the model of PFG-2504, the tension meter is fixed on a displacement device, the displacement device can carry out uniform motion at the speed of 5.0+/-0.2 mm/s with the tension meter, the heat-resistant layer of 30mm is peeled altogether, the value of the tension meter is read under the condition that the motion of the tension meter reaches uniform speed, and the motion angle of the tension meter and the middle layer form an angle of 180 degrees, namely the peeling angle is 180 degrees. Each sample was subjected to three tests and averaged to calculate the peel force (in gf) between the heat-resistant layer and the intermediate layer of this example.

If the peel force obtained by the above test is greater than 30gf, it is considered that there is a large adhesion between the heat-resistant layer and the intermediate layer, and separation of the heat-resistant layer and the intermediate layer during use can be effectively avoided.

TABLE 2

According to table 2, when the maximum height roughness Rz of the second heat resistant surface has a value of 0.8 μm to 24 μm and the average width of the roughness profile unit is 50 μm to 600 μm, the flowing intermediate layer can infiltrate into the gaps between the irregularities of the second heat resistant surface during the preparation of the multilayer release film, increasing the contact area, improving the firmness of the adhesion between the heat resistant layer and the intermediate layer, and improving the usability.

21 st to 30 th implementation examples:

the temperature of the chill roll used to prepare the multilayer release film of the present invention was varied. Wherein the temperature of the rubber roller is controlled at 20 ℃, the linear speed is 15m/min, the material of the release layer is TPX, the material of the heat-resistant layer is PBT, the material of the intermediate layer comprises a mixture of PBT and TPX, the thickness of the prepared intermediate layer is 100 mu m, the thickness of the release layer is 10 mu m, and the thickness of the heat-resistant layer is 30 mu m. The temperature of the rigid rolls in the production process was changed, and the rigid roll temperatures of examples 21 to 30 were set to 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 120 ℃ and 150 ℃ respectively.

The warpage degree of the sample wafer is evaluated by the warpage angle evaluation method.

TABLE 3 Table 3

Sequence number	Rigid roll temperature	Sample warpage angle
			21	20℃	9.3°
22	30℃	8.7°
			23	40℃	6.5°
24	50℃	5.1°
			25	60℃	2.7°
26	70℃	2.8°
			27	80℃	2.3°
28	90℃	1.9°
			29	120℃	1.5°
30	150℃	1.3°

According to Table 3, the higher the temperature of the rigid roll, the longer the cooling time of the heat-resistant layer, and the more the ordered arrangement of the molecular chains of the polymer material was. When the temperature of the rigid roller is 60-150 ℃, the thermal deformation difference between the heat-resistant layer and the release layer of the produced multilayer release film is small, the warping degree of the embodiment is small, and the multilayer release film has industrial applicability.

The present invention is not limited to the specific materials, structures, and processes, and parameters shown, but should be construed as falling within the scope of the present invention as long as similar technical solutions and similar effects can be achieved. For the parameter ranges disclosed in the present specification and the parameter ranges described in the claims, since there are various objective and subjective factors such as measurement errors, feeding errors, formulation design, etc., and the present invention is limited to the disclosure of the present specification, it should be considered that: the parameter ranges with the upper and lower limit deviation values within 30% and capable of realizing the same or similar functions as the corresponding parameter ranges belong to the protection scope of the invention.

Claims

1. A multilayer release film comprises a release layer, an intermediate layer and a heat-resistant layer;

the release layer is arranged on the outer layer of the multilayer release film, the release layer is made of polyolefin resin, the melting point of the polyolefin resin is higher than 200 ℃, and the value range of the dyne value of the polyolefin resin is 15-30;

the heat-resistant layer is arranged on the outer layer of the multilayer release film and is opposite to the release layer, the material of the heat-resistant layer comprises polyester resin, the melting point of the polyester resin is more than 200 ℃, the value range of the dyne value of the polyester resin is 35-55, and the elongation at break of the polyester resin is more than 50%;

the middle layer is arranged between the release layer and the heat-resistant layer, two sides of the heat-resistant layer are respectively in contact with the release layer and the heat-resistant layer, and the material of the middle layer comprises polyolefin resin of the release layer and polyester resin of the heat-resistant layer.

2. The multilayer release film of claim 1, wherein:

the polyolefin-based resin is selected from one or a combination of two or more of TPX, ETFE, PTFE.

3. The multilayer release film of claim 2, wherein:

The polyester resin is selected from one or more than two of PBT, PET, PC.

4. The multilayer release film of claim 1, wherein:

the ratio of the thickness of the heat-resistant layer to the thickness of the release layer is 1.1-5.

5. The multilayer release film of claim 2, wherein:

the ratio of the thickness of the heat-resistant layer to the thickness of the release layer is 1.5-3.

6. The multilayer release film according to any one of claims 4 to 5, wherein:

the heat-resistant layer comprises a first heat-resistant surface and a second heat-resistant surface which is arranged opposite to the first heat-resistant surface, and the second heat-resistant surface is in contact with the middle layer;

as for the surface properties of the first heat resistant surface, a stylus having a tip radius of 2 μm and a cone angle of 60 ° was used by the method based on ISO4287-1997, and the maximum height roughness Rz measured under the conditions of a measurement force of 0.75mN, a cutoff value λs=2.5 μm, and λc=0.8 mm was in the range of 5 μm to 50 μm, and the average width RSm of the roughness profile unit was in the range of 30 μm to 300 μm.

7. The multilayer release film of claim 6, wherein:

regarding the surface properties of the second heat resistant surface, a stylus having a tip radius of 2 μm and a cone angle of 60 ° was used by the method based on ISO4287-1997, and the maximum height roughness Rz measured under the conditions of a measurement force of 0.75mN, a cutoff value λs=2.5 μm, and λc=0.8 mm was in the range of 0.8 μm to 24 μm, and the average width RSm of the roughness profile unit was in the range of 50 μm to 600 μm.

8. The multilayer release film of claim 7, wherein:

the maximum height roughness Rz of the first heat resistant surface is in the range of 20-40 mu m.

9. The multilayer release film according to any one of claims 4 to 5, wherein:

the thickness of the release layer is 10-50 mu m.

10. The multilayer release film of claim 9, wherein:

the thickness of the release layer is 20-40 mu m.

11. The multilayer release film according to any one of claims 4 to 5, wherein:

the thickness of the intermediate layer is 10-200 mu m.

12. The multilayer release film of claim 11, wherein:

the material of the intermediate layer may also be selected from ethylene, alpha-olefin- (meth) acrylate copolymers, a mixture of polybutylene terephthalate and 1, 4-cyclohexanedimethanol copolymerized polyethylene terephthalate, and a mixture of alpha-olefin polymers and alpha-olefin- (meth) acrylate copolymers of ethylene and the like.

13. The multilayer release film of claim 7, wherein:

the ratio of the thickness of the heat-resistant layer to the maximum height roughness Rz of the first heat-resistant surface is 1.2-5.

14. The multilayer release film of claim 13, wherein:

the ratio ranges from 1.5 to 3.