Polyester film for mlcc high-smooth release film and method for manufacturing the same

Abstract

The application discloses a polyester film for MLCC high-smooth release film and a preparation method thereof. The polyester film for MLCC high-smooth release film comprises a front surface facing a release agent layer and a back surface opposite to the front surface. The front surface is provided with a first online coating layer, and the back surface is provided with a second online coating layer. The outer side of the second online coating layer is further coated with an offline protective coating layer. The offline protective coating layer is composed of 50-60 parts by weight of polymethyl methacrylate, 5-10 parts by weight of dimethyl terephthalate, 10-20 parts by weight of methyl triethoxysilane and 5-10 parts by weight of calcium phosphate particles. The polyester film for MLCC high-smooth release film can realize higher smoothness of both front and back surfaces through the combination of online coating and offline coating, meanwhile, the opening property of the back surface is ensured, and the surface adhesion damage of the ceramic green sheet is avoided.

Description

Technical Field

[0001] This invention relates to the technical field of release films for stacked ceramic blanks used in the manufacture of surface mount capacitors, and more particularly to a polyester film for high-smoothness release films of MLCCs and its preparation method. Background Technology

[0002] Multilayer ceramic capacitors (MLCCs), also known as surface mount capacitors, are manufactured by uniformly coating a ceramic paste onto a release film surface, then printing electrodes on the ceramic layer, and finally stacking, pressing, and sintering the printed ceramic layers. The release film, serving as an intermediate carrier layer, is virtually indispensable in each process step. The ceramic blank needs to be wound and temporarily stored along with the release film several times before being unwound and stacked. Therefore, the surface quality and winding performance of the release film have a significant impact on the final quality of the surface mount capacitor.

[0003] The applicant's previous application, CN 110239185 A, disclosed a MLCC release film base film, its functional masterbatch, and a preparation method. The functional masterbatch in the surface layer of the MLCC release film base film includes 90%–99.5% PET, 0.1%–0.4% nano-graphite, and 0.1%–9.9% inorganic fillers. This prior art MLCC release film base film has low surface roughness and a smoother surface. Furthermore, after coating the surface with an organosilicon coating, the repulsion effect between the coating and the inorganic fillers is significantly reduced at the locations where the inorganic fillers are present. The base film with the organosilicon coating exhibits excellent peelability and smoothness, which can well meet the needs of MLCC processing technology.

[0004] Furthermore, the applicant's previous application, CN 113683806 A, discloses an improved release film for manufacturing stacked ceramic blanks, comprising a substrate layer and a release agent layer. The substrate layer comprises a polyester film, with a first online coating on one side of the polyester film to which the release agent layer is attached, and a second online coating on the other side. This invention online coats a first online coating, which is compatible with the release agent layer, on one side of the substrate layer of the release film, and an online coating with anti-adhesion properties on the other side. This allows the polyester film to fulfill its function for manufacturing stacked ceramic blanks with only a single-layer structure, thereby simplifying the process and reducing costs.

[0005] Because existing surface mount capacitors require the ceramic preforms to be wound and temporarily stored along with the release liner before being unwound and stacked, the front (working) side of the MLCC release liner typically needs to have high smoothness to facilitate the separation of the ceramic preform from the release liner. Conversely, the back side, opposite the working side, needs to have greater openness to prevent the back of the wound release liner from sticking to the ceramic preform and becoming difficult to separate. Therefore, typically, the front side of the MLCC release liner is coated with a release agent, while the back side is usually rougher to improve openness. However, the rough back side, when in contact with the ceramic preform in the wound state, may damage the surface quality of the ceramic preform. This contradiction leads to high requirements for the smoothness of both sides of the MLCC release liner, while also requiring a certain degree of openness on the back side.

[0006] The technical solution disclosed in CN 113683806 A, mentioned in the background section, involves forming online coatings on both sides of a polyester film serving as a substrate layer. The online coating on the front side has good smoothness, while the online coating on the back side contains inorganic particles to improve openness. The advantage of this prior art is its simple process. However, a disadvantage is that the inorganic particles in the online coating on the back side can affect the surface quality of the polyester film during stretching. During stretching, the particles can create pores, resulting in insufficient uniformity of the online coating on the back side, inconsistent overall surface roughness, and varying smoothness and openness. This can lead to adhesion damage to the ceramic blank surface during unfolding. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a polyester film for high smoothness release film of MLCC and a method for preparing the same, so as to reduce or avoid the problems mentioned above.

[0008] To address the aforementioned technical problems, this invention proposes a polyester film for high-smoothness release film of MLCCs, comprising a front side facing the release agent layer and a back side opposite to the front side. The front side has a first online coating layer, and the back side has a second online coating layer. The outer side of the second online coating layer is further coated with an offline protective coating, which is composed of 50-60 parts by weight of polymethyl methacrylate, 5-10 parts by weight of dimethyl terephthalate, 10-20 parts by weight of methyltriethoxysilane, and 5-10 parts by weight of calcium phosphate particles.

[0009] Preferably, the first online coating is formed by online coating and curing of acrylic adhesive, polyethyleneimine, ethyl acrylate, polyethylene oxide, melamine, and ethylene-vinyl acetate copolymer.

[0010] Preferably, the mass ratio of each component of the first online coating is 100: (3~5): 100: (10~15): (5~10): (10~15).

[0011] Preferably, the second online coating is formed by online coating and curing of acrylic adhesive, calcium acetate particles, zinc sulfide particles, polydimethylsiloxane, ethyl acrylate, and sodium bicarbonate particles.

[0012] Preferably, the mass ratio of each component of the second online coating is 100: (4~8): (5~10): (30~60): (20~40): (3~6).

[0013] In addition, the present invention also proposes a method for preparing a polyester film for a high-smoothness release film of MLCC, comprising the following steps: using polyester chips as raw material, obtaining a thick sheet through melt extrusion, preheating and then longitudinally stretching it into a stretched sheet, then transversely stretching, shaping, cooling, and winding; wherein, after obtaining the thick sheet and before longitudinal stretching, the components of the first online coating and the second online coating are uniformly mixed to form a first primer and a second primer, preheated to 120°C, and then the first primer and the second primer are applied online to both sides of the thick sheet, and then longitudinally stretched and transversely stretched to prepare a polyester film with the first online coating and the second online coating; or, after longitudinal stretching and before transverse stretching, the components of the first online coating and the second online coating are uniformly mixed to form a first primer and a second primer, preheated to 120°C, and then the first primer and the second primer are applied online to both sides of the stretched sheet, and then longitudinally stretched and transversely stretched to prepare a polyester film with the first online coating and the second online coating.

[0014] Preferably, the preparation method further includes the following steps: polyester chips are weighed using an electronic scale, preheated and dried at 160℃~180℃ and mixed; then the mixture is added to a twin-screw extruder, the temperature of the twin-screw extruder is adjusted to 270℃~280℃, and after melting, filtered to extrude a thick sheet; the thick sheet is preheated at 50℃~90℃, placed in an infrared heating zone at 300℃~500℃, and longitudinally stretched at a linear speed of 40~150m / min, with a longitudinal stretching ratio of 3.0~4.5, to obtain a stretched sheet; the stretched sheet is preheated at 90℃~120℃, and transversely stretched at 100℃~160℃, with a transverse stretching ratio of 3.0~4.5; then shaped at 160℃~240℃, and cooled at 100℃~50℃, and finally the polyester film for MLCC high-smoothness release film is obtained.

[0015] Preferably, the preparation method further includes the step of coating an offline protective coating on the outside of the second online coating by offline coating, wherein the offline protective coating is composed of 50-60 parts by weight of polymethyl methacrylate, 5-10 parts by weight of dimethyl terephthalate, 10-20 parts by weight of methyltriethoxysilane, and 5-10 parts by weight of calcium phosphate particles.

[0016] Preferably, the preparation method further includes the following steps: the components constituting the offline protective coating are added to 50-200 parts by weight of diethyl ether and 50-100 parts by weight of deionized water at a ratio of 100 parts by weight, and then uniformly mixed. The mixture is then coated on the outer surface of the online matte coating by offline coating and cured at 90-100°C for 30-60 minutes to obtain the offline protective coating.

[0017] The polyester film for high-smoothness release film of MLCC of the present invention combines online coating and offline coating, which can achieve high smoothness on both sides, while ensuring the opening of the back side and avoiding adhesion and damage to the surface of the ceramic blank. Attached Figure Description

[0018] The accompanying drawings are intended only to illustrate and explain the present invention and do not limit the scope of the invention.

[0019] in, Figure 1 The diagram shown is a structural schematic of a polyester film for high-smoothness release film of MLCC according to a specific embodiment of the present invention.

[0020] Figure 2 The diagram shown is a structural schematic of a manufacturing apparatus for a polyester film for high-smoothness release film of MLCCs according to a specific embodiment of this application. Detailed Implementation

[0021] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments are now described with reference to the accompanying drawings. Identical components are denoted by the same reference numerals.

[0022] Based on the deficiencies of the prior art described in the background section, this invention proposes an improved polyester film for high-smoothness release film of MLCCs and its preparation method. Specifically, as follows... Figure 1 The diagram shows a structural schematic of a polyester film for high-smoothness release film of MLCC according to a specific embodiment of the present invention. The polyester film 1 for high-smoothness release film of MLCC of the present invention includes a front side facing the release agent layer 20 (shown by dashed lines in the figure) and a back side opposite to the front side. The front side has a first online coating layer 2, and the back side has a second online coating layer 3. An offline protective coating layer 4 is further coated on the outer side of the second online coating layer 3.

[0023] The first online coating 2 and the second online coating 3 can be any existing online coating suitable for the front and back functions of the MLCC release film, or they can be online coatings such as those disclosed in CN 113683806 A. For example, the first online coating 2 can be formed by online coating and curing of acrylic adhesive, polyethyleneimine, ethyl acrylate, polyethylene oxide, melamine, and ethylene-vinyl acetate copolymer. Specifically, the mass ratio of each component of the first online coating 2 is 100:(3~5):100:(10~15):(5~10):(10~15). The acrylic adhesive can be, for example, SAA1451 acrylic adhesive produced by Xi'an Aerospace Sanwo Chemical Co., Ltd., with a solid content of 40%~45% by mass. The ethylene-vinyl acetate copolymer can be the Evaflex 550 copolymer produced by Mitsui Chemicals, Inc. of Japan, in which the mass percentage of vinyl acetate polymer is 14%.

[0024] The second online coating 3 can be formed by online coating and curing of acrylic adhesive, inorganic filler with a particle size of 0.5 micrometers to 10 micrometers, polyethyleneimine, ethyl acrylate, polyethylene oxide, melamine, and ethylene-vinyl acetate copolymer. Specifically, the mass ratio of each component of the second online coating 3 is 100:(1~2):(3~5):100:(10~15):(5~10):(10~15). The acrylic adhesive can be, for example, SAA1451 acrylic adhesive produced by Xi'an Aerospace Sanwo Chemical Co., Ltd., with a solid content of 40% to 45% by mass. The ethylene-vinyl acetate copolymer can be Evaflex 550 ethylene-vinyl acetate copolymer produced by Mitsui Chemicals, Ltd. of Japan, containing 14% vinyl acetate polymer by mass. The inorganic filler is selected from one or a combination of silicon dioxide, calcium carbonate, barium sulfate, titanium dioxide, mica, and kaolin.

[0025] In another specific embodiment of this application, the thickness of the polyester film 1 is 10-200 μm, the thickness of the first online coating 2 is preferably 0.1-1 μm, the thickness of the second online coating 3 is preferably 10-20 μm, and the thickness of the offline protective coating 4 is preferably 3-5 μm.

[0026] The polyester film 1 can be made of materials with the same composition as those described in the prior art CN 113683806 A. For example, in one specific embodiment, the polyester film 1 is made of the following components in parts by weight: 80-99% PET, 0.1-0.4% nano-graphite, 0.2-0.5% nano-boron nitride, and 5-10% polycarbonate. In a preferred embodiment, the PET is in powder form, with an intrinsic viscosity of 0.65-0.75±0.01 dL / g and a colorimetric b value of -3 to +1.

[0027] To meet broader needs, the polyester film 1 of the present invention can also be a polyester film formed from one or more polycarboxylic acids containing diacids and their esterifying derivatives, and one or more polyols containing diols; or a polyester film formed from hydroxycarboxylic acids and their esterifying derivatives; or a polyester film formed from cyclic esters. The polyester film can be manufactured according to existing known methods. For example, the polyester in the polyester film can be formed by polycondensation of diacids and diols. For example, the dicarboxylic acid components include, but are not limited to, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 3,4'-diphenyl ether dicarboxylic acid, hexahydrophthalic acid, 2,7-naphthalenedicarboxylic acid, phthalic acid, 4,4'-methylenebisbenzoic acid, oxalic acid, malonic acid, succinic acid, methylsuccinic acid, glutaric acid, adipic acid, 3-methyl adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, 1,11-undecanedicarboxylic acid, 1,10-decanedicarboxylic acid, undecanediic acid, 1,12-dodecanedicarboxylic acid, hexadecanediic acid, docosanodiic acid, tetradecanediic acid, dimer acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,1-cyclohexanediacetic acid, fumaric acid, maleic acid, and hexahydrophthalic acid. Furthermore, it can be used alone or in combination with two or more other acids. For example, the diol components include, but are not limited to, ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, glycol-diethylene glycol, diethylene glycol, triethylene glycol, poly(ethylene ether) glycol, and poly(butylene ether) glycol. Alcohols, branched diols, hexanediol or combinations thereof or their derivatives, 1,4-cyclohexanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-2,4-pentanediol, neopentanediol, 2-methyl-1,4-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,5-ethyl-1,3-hexanediol, 2,2-diethyl-1,3-propanediol, 1,3-hexanediol. Alternatively, they can be used alone or in combination of two or more.

[0028] The polyester in the polyester film of the present invention can also be formed by hydroxycarboxylic acids and their esterifying derivatives, or by cyclic esters. For example, the hydroxycarboxylic acid components include, but are not limited to: lactic acid, citric acid, malic acid, tartaric acid, glycolic acid, 3-hydroxybutyric acid, p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, 4-hydroxycyclohexanecarboxylic acid, etc. The esterifying derivatives of the hydroxycarboxylic acids include, but are not limited to: dimethyl terephthalate, dimethyl isophthalate, dimethyl 2,6-naphthalenedicarboxylate, dimethyl 3,4'-diphenyl ether dicarboxylate, dimethyl hexahydrophthalate, dimethyl 2,7-naphthalenedicarboxylate, dimethyl phthalate, dimethyl 4,4'-methylenebisbenzoate, dimethyl oxalate, dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl azelaate, dimethyl 1,3-cyclohexanedicarboxylate, and dimethyl 5-sulfoisophthalate. Furthermore, they can be used alone or in combination. For example, the cyclic esters include, but are not limited to: ε-caprolactone, β-propiolactone, β-methyl-β-propiolactone, δ-valerolactone, glycolide, lactide, etc. Additionally, they can be used alone or in combination.

[0029] The polyester in the polyester film of the present invention is preferably polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, poly(1,4-cyclohexanediol) terephthalate, polyethylene naphthalate, polybutylene naphthalate, polypropylene naphthalate and copolymers thereof, and particularly preferably polyethylene terephthalate (PET) and copolymers thereof.

[0030] The polyester in the polyester film of the present invention, taking PET as an example, is preferably prepared by esterification or transesterification of terephthalic acid or dimethyl terephthalate and ethylene glycol to produce diethyl terephthalate, and industrially manufactured by polycondensation using a catalyst under high temperature and vacuum. In one specific embodiment, esterification can be carried out using terephthalic acid, ethylene glycol, cyclohexanediol, a catalyst, and a heat stabilizer as raw materials; or esterification can be carried out using terephthalic acid, ethylene glycol, isophthalic acid, a catalyst, and a heat stabilizer as raw materials. In another specific embodiment, the catalyst is any compound selected from Ti / Si non-heavy metal catalysts and antimony trioxide, and its addition amount is 0.01-0.09% of the polyester mass. In another specific embodiment, the heat stabilizer is a phosphoric acid compound, and its addition amount is 0.0003-0.030% of the polyester mass; the phosphoric acid compound includes any one of phosphoric acid, phosphorous acid, polyphosphoric acid, trimethyl phosphate, triphenyl phosphate, and triethyl phosphate. Another specific embodiment of the polyester preparation method is as follows: 5.0 kg of terephthalic acid, 2.2 kg of ethylene glycol, and 1.10 g of germanium dioxide are added to a 20 L general-purpose polymerization reactor. Esterification reaction is carried out at 230~265 °C and 0.2~0.3 MPa (gauge pressure). When the water output reaches 1200 ml, the pressure is released to atmospheric pressure, and 1.025 g of triethyl phosphate is added. The mixture is stirred at atmospheric pressure for 10 minutes, the temperature is raised to 280 °C and the pressure is lowered to below 100 Pa. After the reaction is completed in 1~3 hours, the mixture is extruded, granulated, and dried to obtain polyester chips. Then, polyester films with structures such as online coatings are further prepared from the polyester chips.

[0031] Furthermore, as shown in the figure, the polyester film for the high-smoothness release film of MLCC in this application adds an offline protective coating 4 to the outside of the second online coating 3 by offline coating. The offline protective coating 4 can not only provide sufficient protection, but also fill the areas of uneven thickness caused by the stretching of the second online coating 3, thereby covering the stretching holes caused by inorganic particles in the second online coating 3 during stretching, so that the thickness and roughness of the entire finished film layer are consistent, improving the smoothness of the product surface and avoiding the problem of adhesion damage to ceramic blanks caused by local smoothness differences.

[0032] In one specific embodiment, the polyester film of the present invention can be prepared by the following steps.

[0033] For example, polyester chips are used as raw material. Thick sheets are obtained through melt extrusion, preheated, and then longitudinally stretched into stretched sheets. These stretched sheets are then transversely stretched, shaped, cooled, and wound to obtain a polyester film. Of course, since online coating is required during the polyester film preparation process, the components of the first online coating 2 and the second online coating 3 can be mixed and coated onto the thick sheet after obtaining it but before longitudinal stretching. Then, after longitudinal and transverse stretching, a polyester film with an online coating is obtained. Alternatively, the components of the first online coating 2 and the second online coating 3 can be mixed and coated onto the stretched sheet after longitudinal stretching but before transverse stretching. Then, after transverse stretching, a polyester film with an online coating is obtained. Subsequently, an offline protective coating 4 is applied to the outside of the second online coating 3 using an offline coating method.

[0034] In another specific embodiment, the second online coating 3 can be formed by online coating and curing of acrylic adhesive, calcium acetate particles, zinc sulfide particles, polydimethylsiloxane, ethyl acrylate, and sodium bicarbonate particles. Specifically, the mass ratio of each component of the online coated matte coating 2 is 100:(4~8):(5~10):(30~60):(20~40):(3~6). The acrylic adhesive can be, for example, SAA1451 acrylic adhesive produced by Xi'an Aerospace Sanwo Chemical Co., Ltd., with a solid content of 40%~45% by mass. The particle size of the calcium acetate particles, zinc sulfide particles, and sodium bicarbonate is 100~500 nm.

[0035] In another specific embodiment, the offline protective coating 4 can be composed of 50-60 parts by weight of polymethyl methacrylate, 5-10 parts by weight of dimethyl terephthalate, 10-20 parts by weight of methyltriethoxysilane, and 5-10 parts by weight of calcium phosphate particles (particle size 100-500 nm). The components constituting the offline protective coating 4 can be added to 50-200 parts by weight of diethyl ether and 50-100 parts by weight of deionized water at a ratio of 100 parts by weight, mixed uniformly, and then coated onto the outer surface of the second online coating 3 by offline coating. After curing at 90-100°C for 30-60 minutes, the offline protective coating 4 of the present invention can be obtained.

[0036] The following reference Figure 2 The manufacturing equipment further illustrates the preparation method of the polyester film for high-smoothness release film of MLCC in this application, wherein, Figure 2 The diagram shown is a structural schematic of a manufacturing apparatus for a polyester film for high-smoothness release film of MLCCs according to a specific embodiment of this application.

[0037] As shown in the figure, the manufacturing equipment for the polyester film used in the high-smoothness release film of MLCCs of this application, in accordance with the film stretching process, includes, in sequence, a slicing preheating and drying equipment 100, a twin-screw extruder 200, a longitudinal stretching mechanism 300, a transverse stretching mechanism 400, a heat setting mechanism 401, a cooling mechanism 402, and a first take-up roller 500. Downstream of the first take-up roller 500 is an offline protective coating coating mechanism 700. To cure the offline protective coating, the downstream of the offline protective coating coating mechanism 700 further includes an infrared heating device 701 for infrared irradiation curing of the offline protective coating. Additionally, the manufacturing equipment of this application may further include a second take-up roller 800 for winding the prepared polyester film for the high-smoothness release film of MLCCs. After being wound into a roller shape by the second take-up roller 800, it can be packaged for transportation, sales, etc.

[0038] The online coating mechanism 600 is disposed between the twin-screw extruder 200 and the longitudinal stretching mechanism 300; alternatively, as shown by the dotted line in the figure, the online coating mechanism 600 may also be disposed between the longitudinal stretching mechanism 300 and the transverse stretching mechanism 400. The online coating mechanism 600 includes a first coating roller 601 for forming a first online coating 2 on one side surface and a second coating roller 602 for forming a second online coating 3 on the other side surface.

[0039] The preparation method of the polyester film for high-smoothness release film of MLCC in this embodiment includes the following steps.

[0040] Polyester chips are weighed using an electronic scale and then preheated and dried in a chip preheating and drying equipment 100 at 160℃~180℃. The mixture is then added to a twin-screw extruder 200, and the temperature of the extruder is adjusted to 270℃~280℃. After melting, the mixture is filtered and extruded into thick sheets. These sheets are preheated at 50℃~90℃ and then enter the infrared heating zone of a longitudinal stretching mechanism 300 at a heating temperature of 300℃~500℃. They are then longitudinally stretched at a linear speed of 40~150 m / min, with a longitudinal stretching ratio of 3.0~4.5, to obtain stretched sheets. The stretched sheets are preheated at 90℃~120℃ and then enter a transverse stretching mechanism 400 at 100℃~160℃, with a transverse stretching ratio of 3.0~4.5. The film is then set at 160°C to 240°C in the heat setting mechanism 401, cooled at 100°C to 50°C in the cooling mechanism 402, and finally wound up by the first take-up roller 500 to obtain the polyester film for high smoothness release film of MLCC of this application.

[0041] The coating can be applied online after extruding the thick sheet but before longitudinal stretching. Alternatively, it can be applied online after longitudinal stretching but before transverse stretching. The specific steps are as follows: the components of the first online coating 2 and the second online coating 3 are uniformly mixed to form the corresponding first primer and second primer liquid, respectively, preheated to 80°C, and then the first primer liquid and the second primer liquid are applied to both sides of the thick sheet or stretched sheet.

[0042] Furthermore, in Figure 2 In the specific embodiment shown, an offline protective coating 4 can also be coated on the outside of the second online coating layer 3 by offline coating. The specific steps are as follows: the raw material components of the offline protective coating are uniformly mixed to obtain an offline protective coating primer. The mixed offline protective coating primer is uniformly coated onto the surface of the second online coating layer 3, and finally cured by heating with an infrared heating device 701 to form an offline protective coating, thereby obtaining the polyester film for MLCC high-smoothness release film of this application, and finally taken into rolls by the second take-up roller 800.

[0043] The following is a detailed description of the preparation process of a polyester film for a high-smoothness release film of MLCC according to a specific embodiment of the present invention.

[0044] PET chips are preheated and dried at 160℃~180℃ and then fed into a twin-screw extruder. The temperature of the twin-screw extruder is adjusted to 270℃~280℃. After melting, the chips are filtered and extruded into thick sheets. The components of the first online coating 2 and the second online coating 3 of this application are uniformly mixed to form corresponding first and second base coat solutions, respectively. These solutions are preheated to 80℃, and then coated on both sides of the thick sheet. The thick sheet is then preheated at 50℃~90℃ and placed in an infrared heating zone at 300℃~500℃. It is then longitudinally stretched at a linear speed of 40~150m / min, with a longitudinal stretching ratio of 3.0~4.5, to obtain a stretched sheet. The stretched sheet is then preheated at 90℃~120℃ and transversely stretched at 100℃~160℃, with a transverse stretching ratio of 3.0~4.5. The film is then set at 160℃~240℃, cooled at 100℃~50℃, and finally wound up. The components constituting the offline protective coating are added to 50 parts by weight of ether and 50 parts by weight of deionized water at a ratio of 100 parts by weight, and mixed evenly. This mixture is then applied offline to the outer surface of the online matte coating and cured at 90-100℃ for 30 minutes to obtain the polyester film for high-smoothness release film of MLCCs of this application.

[0045] Polyester film: PET, thickness 10μm

[0046] First online coating: 0.1μm thickness

[0047] Second online coating: 10μm thickness

[0048] Offline protective coating: 3μm thick

[0049] The following is a detailed description of the preparation process of a polyester film for a high-smoothness release film of MLCCs according to another specific embodiment of the present invention.

[0050] PETG chips are preheated and dried at 160℃~180℃ and then fed into a twin-screw extruder. The temperature of the twin-screw extruder is adjusted to 270℃~280℃. After melting, the chips are filtered and extruded into thick sheets. These sheets are then preheated at 50℃~90℃ and placed in an infrared heating zone at 300℃~500℃. They are then longitudinally stretched at a linear speed of 40~150 m / min, with a longitudinal stretching ratio of 3.0~4.5, to obtain stretched sheets. The components of the first online coating 2 and the second online coating 3 of this application are uniformly mixed to form corresponding first and second primer solutions. These are preheated to 80℃, and then the first and second primer solutions are applied to both sides of the stretched sheet. The stretched sheet is preheated at 90℃~120℃ and then transversely stretched at 100℃~160℃, with a transverse stretching ratio of 3.0~4.5. The film is then set at 160℃~240℃, cooled at 100℃~50℃, and finally wound up. The components constituting the offline protective coating are added to 50 parts by weight of ether and 50 parts by weight of deionized water at a ratio of 100 parts by weight, and mixed evenly. This mixture is then applied offline to the outer surface of the online matte coating and cured at 90-100℃ for 30 minutes to obtain the polyester film for high-smoothness release film of MLCCs of this application.

[0051] Polyester film: PET, thickness 200μm

[0052] First online coating: 15μm thickness

[0053] Second online coating: 20μm thickness

[0054] Offline protective coating: 5μm thick

[0055] The table below shows the surface parameters obtained after coating a 100 μm thick ordinary PET substrate with the first online coating components of Examples 1-3 and Comparative Example 4 in parts by weight.

[0056] First Online Coating acrylic adhesives 100 100 100 100 First Online Coating Polyethyleneimine 3 4 5 0 First Online Coating Ethyl acrylate 100 100 100 100 First Online Coating Polyethylene oxide 10 12 15 20 First Online Coating melamine 5 8 10 15 First Online Coating Ethylene-vinyl acetate copolymer 10 12 15 0 Surface roughness Ra, nm Surface roughness Ra, nm 17.3 17.2 17.4 26.5

[0057] The table below shows the surface parameters obtained by testing the second online coating components of Examples 5-7 and Comparative Example 8 after coating a 100 μm thick ordinary PET substrate.

[0058] Second online coating acrylic adhesives 100 100 100 100 Second online coating Inorganic packing 1 1.5 2 0 Second online coating Polyethyleneimine 3 4 5 0 Second online coating Ethyl acrylate 100 100 100 100 Second online coating Polyethylene oxide 10 12 15 20 Second online coating melamine 5 8 10 15 Second online coating Ethylene-vinyl acetate copolymer 10 12 15 0 Surface roughness Ra, nm Surface roughness Ra, nm 765.2 770.8 778.5 27.4

[0059] The table below shows the surface parameters obtained by testing the second online coating components of Examples 9-11 and Comparative Example 12 after coating a 100 μm thick ordinary PET substrate.

[0060] Second online coating acrylic adhesives 100 100 100 100 Second online coating Calcium acetate granules 1 4 8 10 Second online coating Zinc sulfide granules 5 8 10 2 Second online coating polydimethylsiloxane 30 45 60 50 Second online coating Ethyl acrylate 20 30 40 50 Second online coating Sodium bicarbonate granules 3 4 6 0 Second online coating Thickness μm 10 15 20 15 Surface roughness Ra, nm Surface roughness Ra, nm 750.1 748.2 765.6 32.4

[0061] The table below shows the surface parameters obtained by testing after applying the weight parts of the offline protective coating to the surface of the second online coating in Examples 6, 10, 11, and Comparative Example 12. In this table, Example 13 corresponds to Example 6, Example 14 corresponds to the second online coating in Example 10, and Comparative Example 15 corresponds to Example 11, and Comparative Example 16 corresponds to the second online coating in Example 12.

[0062] Offline protective coating polymethyl methacrylate 50 60 55 55 Offline protective coating Dimethyl terephthalate 5 10 15 3 Offline protective coating Methyltriethoxysilane 10 20 15 8 Offline protective coating Calcium phosphate granules 5 10 3 12 Offline protective coating Thickness μm 3 5 4 4 Surface roughness Ra, nm Surface roughness Ra, nm 690.1 710.3 330.7 310.8

[0063] The table below shows the surface parameters obtained by testing after applying the weight parts of the offline protective coating to the surface of the second online coating in Examples 5, 6, 7, and Comparative Example 8. In this table, Example 17 corresponds to the second online coating of Example 5, Example 18 corresponds to the second online coating of Example 6, and Comparative Example 19 corresponds to Example 7 and Comparative Example 20 corresponds to the second online coating of Comparative Example 8.

[0064] Offline protective coating polymethyl methacrylate 50 60 55 55 Offline protective coating Dimethyl terephthalate 5 10 15 3 Offline protective coating Methyltriethoxysilane 10 20 15 8 Offline protective coating Calcium phosphate granules 5 10 3 12 Offline protective coating Thickness μm 3 5 4 4 Surface roughness Ra, nm Surface roughness Ra, nm 760.2 768.9 350.4 320.1

[0065] The table below shows the test results of the adhesion between the back side of the polyester film used for high-smoothness release film of MLCC and the surface of the ceramic blank.

[0066] Example 13 X Example 14 X Comparative Example 15 O Comparative Example 16 O Example 17 X Example 18 X Comparative Example 19 O Comparative Example 20 O

[0067] The polyester film for high-smoothness release film of MLCC of the present invention combines online coating and offline coating, which can achieve high smoothness on both sides, while ensuring the opening of the back side and avoiding adhesion and damage to the surface of the ceramic blank.

[0068] Those skilled in the art should understand that although the present invention has been described with reference to multiple embodiments, not every embodiment contains only one independent technical solution. This description is provided merely for clarity; those skilled in the art should understand the specification as a whole and consider the technical solutions involved in each embodiment as being able to be combined with each other to form different embodiments to understand the scope of protection of the present invention.

[0069] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes, modifications, and combinations made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A polyester film for high-smoothness release film of MLCCs, comprising a front side facing a release agent layer and a back side opposite to the front side, the front side having a first in-line coating layer and the back side having a second in-line coating layer, characterized in that, The first online coating is formed by online coating and curing of acrylic adhesive, polyethyleneimine, ethyl acrylate, polyethylene oxide, melamine, and ethylene-vinyl acetate copolymer; the mass ratio of each component of the first online coating is 100:(3~5):100:(10~15):(5~10):(10~15); the second online coating is formed by online coating and curing of acrylic adhesive, calcium acetate particles, zinc sulfide particles, polydimethylsiloxane, ethyl acrylate, and sodium bicarbonate particles; The mass ratio of the components of the second online coating is as follows: acrylic adhesive: calcium acetate particles: zinc sulfide particles: polydimethylsiloxane: ethyl acrylate: sodium bicarbonate = 100: (4~8): (5~10): (30~60): (20~40): (3~6); an offline protective coating is further applied to the outside of the second online coating. The offline protective coating is composed of 50-60 parts by weight of polymethyl methacrylate, 5-10 parts by weight of dimethyl terephthalate, 10-20 parts by weight of methyltriethoxysilane, and 5-10 parts by weight of calcium phosphate particles. The thickness of the offline protective coating is 3-5 μm.

2. The polyester film for high-smoothness release film of MLCC as described in claim 1, characterized in that, The particle size of the calcium acetate particles, zinc sulfide particles, and sodium bicarbonate particles is 100–500 nm, and the particle size of the calcium phosphate particles is 100–500 nm.

3. The polyester film for high-smoothness release film of MLCC as described in claim 1, characterized in that, The thickness of the polyester film is 10-200 μm, the thickness of the first online coating is 0.1-1 μm, and the thickness of the second online coating is 10-20 μm.

4. A method for preparing a polyester film for high-smoothness release film of MLCCs, comprising the following steps: using polyester chips as raw material, obtaining a thick sheet through melt extrusion, preheating and longitudinally stretching it into a stretched sheet, then transversely stretching, shaping, cooling, and winding; wherein, After longitudinal stretching and before transverse stretching, the components of the first online coating and the second online coating are uniformly mixed to form a first primer and a second primer, respectively, and preheated to 120°C. Then, the first primer and the second primer are applied online to both sides of the stretched sheet, respectively. After transverse stretching, a polyester film with the first online coating and the second online coating is obtained. The first online coating is characterized by being formed by online coating and curing of acrylic adhesive, polyethyleneimine, ethyl acrylate, polyethylene oxide, melamine, and ethylene-vinyl acetate copolymer. The mass ratio of the components of the first online coating is 100:(3-5):100:(10-15):(5-10):(10-15). The online coating is formed by online coating and curing of acrylic adhesive, calcium acetate particles, zinc sulfide particles, polydimethylsiloxane, ethyl acrylate, and sodium bicarbonate particles; the mass ratio of each component of the second online coating is 100:(4~8):(5~10):(30~60):(20~40):(3~6) for acrylic adhesive:calcium acetate particles:zinc sulfide particles:polydimethylsiloxane:ethyl acrylate:sodium bicarbonate. The preparation method further includes the step of coating an offline protective coating on the outside of the second online coating by offline coating, wherein the offline protective coating is composed of 50-60 parts by weight of polymethyl methacrylate, 5-10 parts by weight of dimethyl terephthalate, 10-20 parts by weight of methyltriethoxysilane, and 5-10 parts by weight of calcium phosphate particles; the thickness of the offline protective coating is 3-5 μm.

5. The preparation method according to claim 4, characterized in that, The components constituting the offline protective coating are added to 50-200 parts by weight of ether and 50-100 parts by weight of deionized water at a ratio of 100 parts by weight, and then uniformly mixed. The mixture is then applied to the outer surface of the online matte coating by offline coating and cured at 90-100°C for 30-60 minutes to obtain the offline protective coating.

6. The preparation method according to claim 4, characterized in that, The preparation method further includes the following steps: polyester chips are weighed using an electronic scale, preheated and dried at 160℃~180℃ and mixed, then the mixture is added to a twin-screw extruder, the temperature of the twin-screw extruder is adjusted to 270℃~280℃, after melting, filtered, and extruded into thick sheets; the above thick sheets are preheated at 50℃~90℃, and then placed in an infrared heating zone at 300℃~500℃, and longitudinally stretched at a linear speed of 40~150m / min, with a longitudinal stretching ratio of 3.0~4.5, to obtain stretched sheets; the stretched sheets are preheated at 90℃~120℃, and transversely stretched at 100℃~160℃, with a transverse stretching ratio of 3.0~4.5; then shaped at 160℃~240℃, and then cooled at 100℃~50℃, and finally the polyester film for MLCC high smoothness release film is obtained.

7. The preparation method according to any one of claims 4 to 6, characterized in that, The particle size of the calcium acetate particles, zinc sulfide particles, and sodium bicarbonate particles is 100–500 nm, and the particle size of the calcium phosphate particles is 100–500 nm.

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