Release film for multilayer ceramic capacitor

Abstract

A release film for multilayer ceramic capacitor, the release film comprises a back coating layer, a substrate layer, a plating film layer and a release layer, one side of the substrate layer is provided with the back coating layer, the other side is provided with the plating film layer, the plating film layer is provided with the release layer, the surface roughness Ra of the connecting surface of the substrate layer and the plating film layer is less than or equal to 50 nm, the Rp is less than or equal to 500 nm, the transverse thermal expansion coefficient of the substrate is less than or equal to 99*10 ‑6 K ‑1 -6, the surface roughness Ra of the connecting surface of the plating film layer and the release layer is less than or equal to 20 nm, and the Rp is less than or equal to 200 nm. The method of evaporation plating is used to plate the silicon dioxide plating film layer on the surface of the release film substrate of the multilayer ceramic capacitor, the pit filling effect is realized, and the roughness of the substrate layer is greatly reduced.

Description

Technical Field

[0001] This invention relates to a release film, and more particularly to a release film for multilayer ceramic capacitors. Background Technology

[0002] In recent years, with the rapid popularization of new energy vehicles and 5G communication, the demand for multilayer ceramic capacitors has been increasing. Multilayer ceramic capacitors have the characteristic of temporarily storing electrical energy and are an indispensable electronic component in electronic circuits. They can stabilize current flow. A mobile phone can contain hundreds of multilayer ceramic capacitors, and a new energy vehicle can contain thousands.

[0003] To increase the size and capacitance of multilayer ceramic capacitors, it is desirable to reduce the thickness of the ceramic sheets and stack them into multiple layers. Most ceramic sheets currently in use have a thickness of approximately 2 to 25 μm. Furthermore, advanced technologies have developed ceramic films with thicknesses below 2 μm.

[0004] However, as the ceramic sheet becomes thinner, the peeling force when separating the ceramic sheet from the release layer of the release film increases, leading to frequent new problems of poor peeling. Therefore, a release film with a lower release force than conventional release films is needed. General-purpose release films used for traditional labels, etc., have low release forces, but their release properties are insufficient in the production of thin-layer ceramic sheets. There is a demand for release films with low force. However, even if a release film with low peel force is designed for ceramic sheets of a specific composition, the release force between the ceramic sheet and the release layer of the release film will change when the sheet thickness varies. Therefore, the release layer composition of the release film must be designed to be optimally suited to the specific composition of the ceramic sheet each time.

[0005] Furthermore, as the thickness of the ceramic sheet decreases, not only do the rough protrusions on the release film surface and the unevenness of the release layer surface have a greater impact on the ceramic sheet thickness. When the thickness decreases, the release film supporting the ceramic sheet needs to have higher flatness. Currently, the release layer thickness is generally around 0.2 μm, while the surface roughness (SRz) of ordinary polyester films is generally above 0.5 μm. This makes it impossible to apply the required amount of release agent to the protrusions, leading to potential incomplete coating and even poor ceramic sheet peeling or breakage. Additionally, when the release film surface has high protrusions, the convex shape of the release film surface is transferred to the ceramic sheet as a concave shape due to the protrusions. This partial concavity on the ceramic sheet constitutes a shape defect. This defect becomes more pronounced as the ceramic sheet thickness decreases, and the high protrusions on the film surface cause concave transfer marks on the ceramic sheet, resulting in inaccurate ceramic sheet thickness. Furthermore, when the aforementioned concave transfer marks become stronger, they are likely to transform into penetrating pinholes rather than simple indentations. In the worst case, the ceramic sheet may tear when peeled from the release film. Using ceramic sheets with pinholes in multilayer ceramic capacitors will result in short-circuit and insulation resistance failures, which are fatal defects. This necessitates that the base film of the release film for multilayer ceramic capacitors must have an extremely low roughness level, and due to the requirements of the drying process, the base film must also have excellent thermal stability and be free from flatness issues such as tension lines and orange peel texture.

[0006] Furthermore, release layers primarily composed of curable silicone resin are highly susceptible to electrical charge, resulting in significant charge transfer during ceramic sheet peeling. This can lead to the adsorption of dust and other foreign matter during release film production, severely impacting product quality. Simultaneously, with increasingly stringent requirements for desiliconization in the semiconductor industry, the silicon transfer issues associated with traditional silicone release agents have a substantial impact on product applications.

[0007] Similarly, in the manufacturing process of multilayer ceramic capacitors, when the ceramic paste is coated onto the release film, the solvent of the ceramic paste needs to be spread evenly on the release film. This requires the release film surface to have high surface energy, easy spreadability, and solvent resistance. During the ceramic paste coating process, easy spreadability determines whether the ceramic sheet can be evenly and flatly formed into a film; while solvent resistance ensures that the release layer is not affected by the paste solvent, and there will be no poor peeling of the ceramic sheet due to release layer detachment.

[0008] As ceramic sheets become increasingly thinner, polyester films require increasingly lower roughness levels. However, in the production of low-roughness films, the low surface roughness makes them prone to scratches and other problems. Furthermore, they are difficult to wind up neatly and can cause slippage and other production difficulties.

[0009] In summary, with the development of the high-tech era, the ceramic sheets of multilayer ceramic capacitors are continuously becoming thinner. The most important technical requirements for release films used in multilayer ceramic capacitors currently include high flatness, low roughness, easy peeling, easy solvent spreading, good solvent resistance, antistatic properties, good thermal stability, no silicone transfer, and easy winding. Among these, flatness is the most urgent area for improvement in the technical performance of release films for multilayer ceramic capacitors. Currently, the main method to improve flatness is by modifying the PET substrate, using smooth particles of different sizes to improve roughness. However, improving substrate performance often requires highly sophisticated equipment, and improving the substrate formulation has limited effect on improving roughness; further improvements in flatness are needed. Summary of the Invention

[0010] To overcome the shortcomings of existing technologies, this invention provides a release film for multilayer ceramic capacitors. By using an evaporation deposition method, a silicon dioxide coating layer is deposited on the surface of the multilayer ceramic capacitor release film substrate to achieve a pit-filling effect and greatly reduce the roughness of the substrate layer.

[0011] The technical solution adopted by this invention to solve its technical problem is:

[0012] A release film for a multilayer ceramic capacitor includes a back coating layer, a substrate layer, a plating layer, and a release layer. The substrate layer has a back coating layer on one side and a plating layer on the other side. The release layer is disposed on the plating layer. The surface roughness of the interface between the substrate layer and the plating layer is Ra≤50nm and Rp≤500nm, and the transverse thermal expansion coefficient of the substrate is ≤99×10⁻⁶. - 6 K -1 The surface roughness of the interface between the coating layer and the release layer is Ra≤20nm and Rp≤200nm.

[0013] The release film for the aforementioned multilayer ceramic capacitor has a silicon dioxide coating layer with a coating thickness not exceeding 500 nm.

[0014] The release film for the aforementioned multilayer ceramic capacitor has a substrate layer thickness of 19μm to 50μm, and the substrate selected is a biaxially oriented polyethylene terephthalate film.

[0015] The release film for the multilayer ceramic capacitor described above has a substrate layer with a two-layer (A and B) structure. The surface of layer A is a low-roughness surface with a thickness of 0.3–2 μm, and the surface of layer B is a corona-electrode surface. Two types of inert particles of different sizes are added to the structure of layer A, while no inert particles are added to the structure of layer B.

[0016] In the release film for the aforementioned multilayer ceramic capacitor, the A layer structure contains 50% particles of 30nm to 300nm, 50% particles of 500nm to 800nm, and a total particle addition of 5000ppm to 50000ppm.

[0017] The release film for the aforementioned multilayer ceramic capacitor has a layer A structure containing a combination of particles with diameters of 30 nm and 800 nm.

[0018] The release film for the aforementioned multilayer ceramic capacitor, wherein the inert particles in the A layer structure are any one or more combinations of titanium oxide, silicon oxide, barium sulfate, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, polystyrene resin, acrylic resin, urea resin, and melamine resin.

[0019] The release film for the aforementioned multilayer ceramic capacitor has a back coating layer that is a resin layer with antistatic effect. The added antistatic agent is one of quaternary ammonium salt antistatic agent, polythiophene antistatic agent, graphene antistatic agent or carbon nanotube antistatic agent, and the amount of antistatic agent added is 2-5%. The resin main body of the back coating layer is one of melamine resin, polyurethane resin or acrylic resin.

[0020] The release film for the aforementioned multilayer ceramic capacitor is a polyacrylate-based non-silicone release layer with a thickness of 0.05 μm to 0.3 μm.

[0021] The beneficial effects of this invention are:

[0022] (1) This invention deposits a silicon dioxide film on the low-roughness surface of the substrate layer using electron beam evaporation. In addition to its good flexibility, the silicon dioxide film can achieve a smoothing and pit-filling effect on the surface of the substrate layer, greatly reducing the surface roughness and improving the smoothness. The original surface roughness level of the substrate layer is reduced from Ra≤50nm, Rp≤500nm to Ra≤20nm, Rp≤200nm. At the same time, since it is a coating process, unlike the leveling effect of silicone resin, it can greatly ensure the adhesion between coatings and ensure the adhesion of the release layer on the coating surface.

[0023] (2) The release layer uses polyacrylate release agent, which is different from traditional silicone release agent. It does not contain any silicon element and there is no silicon transfer phenomenon, so it can be widely used in the semiconductor industry. At the same time, polyacrylate non-silicone release layer has good solvent resistance and will not cause poor peeling of ceramic sheets due to missed coating; it has a high surface energy, and the ceramic slurry can be spread quickly and has good flatness; the release force is low and adjustable, and it can be used for peeling ceramic sheets of different thicknesses.

[0024] (3) The use of the back coating increases the friction between the release layer and the back of the substrate during winding, while preventing scratches and adhesion, thus solving the problem of slippage during winding.

[0025] (4) The polyester film substrate has low surface roughness, especially low maximum surface protrusion height, which can be well applied to the preparation of high-end multilayer ceramic capacitors and can be used to prepare ultra-thin ceramic sheets.

[0026] (5) The polyester film substrate has a low transverse thermal expansion coefficient, which solves thermal performance problems such as tension lines, thermal wrinkles, and orange peel texture. Detailed Implementation

[0027] The substrate layer of this invention has a two-layer (A and B) structure. Layer A contains inert particles of two different particle sizes, while layer B contains no inert particles. Layer A contains 50% particles of 30nm-300nm and 50% particles of 500nm-800nm, preferably a combination of 30nm and 800nm ​​particles, with a total particle content of 5000ppm-50000ppm. Layer A has a thickness of 0.3-2μm. The surface of layer A is a low-roughness surface, while the surface of layer B is a corona-treated surface. This two-layer (A and B) substrate layer structure effectively controls surface roughness and adhesion. Layer A, with its combination of two particle sizes, exhibits good particle uniformity, minimizing roughness to the greatest extent possible. The use of a corona-treated layer improves the adhesion of the back coating.

[0028] The substrate layer uses biaxially oriented polyethylene terephthalate (PET) film. PET substrates have high strength, good folding resistance, and excellent heat resistance, making them the best support for ceramic slurry casting.

[0029] The antistatic agent added to the back coating of this invention is one of the following: quaternary ammonium salt antistatic agent, polythiophene antistatic agent, graphene antistatic agent, or carbon nanotube antistatic agent. Preferably, a carbon nanotube antistatic agent is used, which has permanent antistatic properties. The addition of the antistatic agent can solve the problem of large electrostatic adsorption forces generated by the substrate, reducing and preventing the adsorption of foreign matter such as dust.

[0030] The resin used for the back coating is primarily melamine resin, polyurethane resin, or acrylic resin. Using a resin layer as the back coating effectively reduces slippage during winding, significantly improving production efficiency and product winding quality.

[0031] The back coating resin is prepared by online coating, with an antistatic agent addition of 2%-5%. Online coating significantly reduces product costs.

[0032] The silica coating can be applied using any known coating method, such as sputtering, chemical vapor deposition, electron beam evaporation, and ion beam deposition, either alone or in combination. This invention preferably uses electron beam evaporation for silica coating. Silica is deposited on a low-roughness surface of the substrate using electron beam evaporation at a deposition rate of 1 nm / min to 50 nm / min, a deposition time of 20 min to 25 min, and a coating thickness not exceeding 500 nm. Electron beam evaporation of silica film, in addition to its good flexibility, can achieve a smoothing and pit-filling effect on the substrate surface, significantly reducing the surface roughness and improving flatness. The original surface roughness level of the substrate is reduced from Ra≤50nm, Rp≤500nm to Ra≤20nm, Rp≤200nm. Furthermore, because it is a coating process, unlike the leveling effect of silicone resins, it greatly ensures the adhesion between coating layers, guaranteeing the adhesion of the release layer to the coating surface.

[0033] The method for coating the polyacrylate non-silicone release layer of the present invention is as follows:

[0034] S1. Preparation of acrylate monomer coating solution;

[0035] S2. Apply the coating liquid to the low-roughness surface of the substrate layer (A layer surface);

[0036] S3.120℃ dry and cure for 1 min;

[0037] S4.50℃ for 24 hours

[0038] The solvents used in the above-mentioned acrylate monomer coating solution are selected from one or more solvents such as butyl acetate, ethyl acetate, butanone, isopropanol, toluene, and heptane.

[0039] The main monomers in the acrylate monomer coating solution are of three types: A, B, and C (Arakawa Chemical's non-silicone release agent RL902 / RL903 / RL909). Among them, RL902 corresponds to low peel strength, RL903 corresponds to medium peel strength, and RL909 corresponds to heavy peel strength. The peel strength can be adjusted by combining different ratios.

[0040] Acrylic monomer coating liquid main agent: curing agent mass ratio 5:1.

[0041] The coating method can be any known coating method. For example, kiss coating, bath coating, stencil coating, reverse coating, microgravure coating, Meyer bar coating, gravure coating, roller brush coating, spray coating, air knife coating, immersion coating, and curtain coating can be used alone or in combination.

[0042] The thickness of the polyacrylate release layer is 0.05μm-0.3μm.

[0043] The polyacrylate monomer release layer, after curing, possesses a robust molecular structure, enabling excellent solvent resistance. Simultaneously, its high surface energy facilitates the spreading and coating of ceramic slurries.

[0044] The present invention will be further described below with reference to the embodiments.

[0045] Example 1

[0046] A biaxially oriented polyethylene terephthalate (PET) film with an AB double-layer structure was produced, with one side being a corona-treated surface and the other a low-roughness surface. The A layer structure contained 5000 ppm of particles, comprising 50% 30 nm silica particles and 50% 800 nm silica particles. A carbon nanotube-type antistatic back coating was applied online to the corona-treated surface (B layer surface). Silica was deposited on the low-roughness surface (A layer surface) of the substrate layer using electron beam evaporation for 25 min, resulting in a coating thickness of 100 nm.

[0047] Preparation and coating of polyacrylate non-silicone release layer: An acrylate monomer coating solution was prepared, containing 50 kg of isopropanol, 50 kg of ethyl acetate, and 5 kg of acrylate monomer main agent (Arakawa Chemical), with a ratio of RL903:RL903:RL909 = 4.8:0.1:0.1. 1 kg of curing agent RA2000 was added and stirred for 30 min to obtain the acrylate non-silicone release coating solution. The acrylate non-silicone release layer was coated onto a silica film using a microgravure coating method. The drying temperature was 120℃, and the drying time was 1 min. After drying and curing, it was aged at 50℃ for 24 h.

[0048] Example 2

[0049] A biaxially oriented polyethylene terephthalate (PET) film with an AB double-layer structure was produced, with one side being a corona-treated surface and the other a low-roughness surface. The A-layer structure contained 5000 ppm of particles, with 50% being 30 nm silica particles and 50% being 800 nm silica particles. A carbon nanotube-type antistatic back coating was applied online to the corona-treated surface. Silica was deposited on the low-roughness surface (A-layer surface) of the substrate layer using electron beam evaporation for 25 min, resulting in a coating thickness of 100 nm. An acrylate monomer coating solution was prepared, comprising 50 kg of isopropanol and 50 kg of ethyl acetate as solvents, 5 kg of acrylate monomer main agent (Arakawa Chemical) with a ratio of RL902:RL903:RL909 = 4:0.9:0.1, and 1 kg of curing agent RA2000. The mixture was stirred for 30 min. An acrylate non-silicone release layer was coated onto the silica coating layer using a microgravure coating method, drying at 120°C for 1 min. After drying and curing, it is aged at 50℃ for 24 hours.

[0050] Example 3

[0051] A biaxially oriented polyethylene terephthalate (PET) film with an AB double-layer structure was produced, with one side being a corona-treated surface and the other a low-roughness surface. The A-layer structure contained 5000 ppm of particles, with 50% being 30 nm silica particles and 50% being 800 nm silica particles. A carbon nanotube-type antistatic back coating was applied online to the corona-treated surface. Silica was deposited on the low-roughness surface (A-layer surface) of the substrate layer using electron beam evaporation for 25 min, resulting in a coating thickness of 100 nm. An acrylate monomer coating solution was prepared, comprising 50 kg of isopropanol and 50 kg of ethyl acetate as solvents, 5 kg of acrylate monomer main agent (Arakawa Chemical) with a ratio of RL902:RL903:RL909 = 3:1.9:0.1, and 1 kg of curing agent RA2000. The mixture was stirred for 30 min. An acrylate non-silicone release layer was coated onto the silica coating layer using a microgravure coating method, drying at 120°C for 1 min. After drying and curing, it is aged at 50℃ for 24 hours.

[0052] Example 4

[0053] A biaxially oriented polyethylene terephthalate (PET) film with an AB double-layer structure was produced, with one side being a corona-treated surface and the other a low-roughness surface. The A-layer structure contained 5000 ppm of particles, with 50% being 30 nm silica particles and 50% being 800 nm silica particles. A carbon nanotube-type antistatic back coating was applied online to the corona-treated surface. Silica was deposited on the low-roughness surface (A-layer surface) of the substrate layer using electron beam evaporation for 25 min, resulting in a coating thickness of 100 nm. An acrylate monomer coating solution was prepared, comprising 50 kg of isopropanol and 50 kg of ethyl acetate as solvents, 5 kg of acrylate monomer main agent (Arakawa Chemical) with a ratio of RL902:RL903:RL909 = 3:0.9:1.1, and 1 kg of curing agent RA2000. The mixture was stirred for 30 min. An acrylate non-silicone release layer was coated onto the silica coating layer using a microgravure coating method, drying at 120°C for 1 min. After drying and curing, it is aged at 50℃ for 24 hours.

[0054] Example 5

[0055] A biaxially oriented polyethylene terephthalate (PET) film with an AB double-layer structure was produced, with one side being a corona-treated surface and the other a low-roughness surface. The A-layer structure contained 5000 ppm of particles, with 50% being 30 nm silica particles and 50% being 800 nm silica particles. A carbon nanotube-type antistatic back coating was applied online to the corona-treated surface. Silica was deposited on the low-roughness surface (A-layer surface) of the substrate layer using electron beam evaporation for 25 min, resulting in a coating thickness of 100 nm. An acrylate monomer coating solution was prepared, comprising 50 kg of isopropanol and 50 kg of ethyl acetate as solvents, 5 kg of acrylate monomer main agent (Arakawa Chemical) with a ratio of RL902:RL903:RL909 = 2:1.9:0.1, and 1 kg of curing agent RA2000. The mixture was stirred for 30 min. An acrylate non-silicone release layer was coated onto the silica coating layer using a microgravure coating method, drying at 120°C for 1 min. After drying and curing, it is aged at 50℃ for 24 hours.

[0056] Example 6

[0057] A biaxially oriented polyethylene terephthalate (PET) film with an AB double-layer structure was produced, with one side being a corona-treated surface and the other a low-roughness surface. The A-layer structure contained 50,000 ppm of particles, comprising 50% 30nm silica particles and 50% 800nm ​​silica particles. A carbon nanotube-type antistatic back coating was applied online to the corona-treated surface. Silica was deposited on the low-roughness surface (A-layer surface) of the substrate layer using electron beam evaporation for 25 minutes, resulting in a coating thickness of 100nm. An acrylate monomer coating solution was prepared, comprising 50 kg of isopropanol and 50 kg of ethyl acetate as solvents, 5 kg of acrylate monomer main agent (Arakawa Chemical) with a ratio of RL902:RL903:RL909 = 4.8:0.1:0.1, and 1 kg of curing agent RA2000. The mixture was stirred for 30 minutes. An acrylate non-silicone release layer was coated onto the silica coating layer using a microgravure coating method, drying at 120°C for 1 minute. After drying and curing, it is aged at 50℃ for 24 hours.

[0058] Example 7

[0059] A biaxially oriented polyethylene terephthalate (PET) film with an AB double-layer structure was produced, with one side being a corona-treated surface and the other a low-roughness surface. The A-layer structure contained 5000 ppm of particles, with 50% being 300 nm silica particles and 50% being 500 nm silica particles. A carbon nanotube-type antistatic back coating was applied online to the corona-treated surface. Silica was deposited on the low-roughness surface (A-layer surface) of the substrate layer using electron beam evaporation for 25 min, resulting in a coating thickness of 100 nm. An acrylate monomer coating solution was prepared, comprising 50 kg of isopropanol and 50 kg of ethyl acetate as solvents, 5 kg of acrylate monomer main agent (Arakawa Chemical) with a ratio of RL902:RL903:RL909 = 4.8:0.1:0.1, and 1 kg of curing agent RA2000. The mixture was stirred for 30 min. An acrylate non-silicone release layer was coated onto the silica coating layer using a microgravure coating method, drying at 120°C for 1 min. After drying and curing, it is aged at 50℃ for 24 hours.

[0060] Comparative Example 1

[0061] Biaxially oriented polyethylene terephthalate (PET) films with an AB double-layer structure were produced, with one side being a corona-treated surface and the other a low-roughness surface. The A-layer structure contained 5000 ppm of particles, comprising 50% 30nm silica particles and 50% 800nm ​​silica particles. No back coating was applied. Silica was deposited on the low-roughness surface (A-layer surface) of the substrate layer using electron beam evaporation for 25 minutes, resulting in a coating thickness of 100 nm. An acrylate monomer coating solution was prepared, comprising 50 kg of isopropanol and 50 kg of ethyl acetate as solvents, 5 kg of acrylate monomer main agent (Arakawa Chemical) with a ratio of RL902:RL903:RL909 = 4.8:0.1:0.1, and 1 kg of curing agent RA2000. The mixture was stirred for 30 minutes. An acrylate non-silicone release layer was coated onto the silica film using a microgravure coating method, drying at 120°C for 1 minute. After drying and curing, it is aged at 50℃ for 24 hours.

[0062] Comparative Example 2

[0063] A biaxially oriented polyethylene terephthalate (PET) film with an AB double-layer structure was produced, with one side being a corona-treated surface and the other a low-roughness surface. The A-layer structure contained 5000 ppm of particles, with 50% being 30 nm silica particles and 50% being 800 nm silica particles. A carbon nanotube-type antistatic back coating was applied online to the corona-treated surface. Silica was deposited on the low-roughness surface (A-layer surface) of the substrate layer using electron beam evaporation for 25 min, resulting in a coating thickness of 100 nm. An acrylate monomer coating solution was prepared, comprising 50 kg of isopropanol, 50 kg of ethyl acetate, 5 kg of silicone release agent (Bluestar Elken 7413), and 0.1 kg of catalyst 93B, and stirred for 30 min. A silicone release layer was applied to the silica coating using a microgravure coating method, drying at 120 °C for 1 min. After drying and curing, the film was aged at 50 °C for 24 h.

[0064] Comparative Example 3

[0065] A biaxially oriented polyethylene terephthalate (PET) film with an AB double-layer structure was produced, with one side being a corona-treated surface and the other a low-roughness surface. No particles were added to the A layer. A carbon nanotube-type antistatic back coating was applied online to the corona-treated surface. An acrylate monomer coating solution was prepared, comprising 50 kg of isopropanol and 50 kg of ethyl acetate as solvents, 5 kg of acrylate monomer main agent (Arakawa Chemical), with a ratio of RL902:RL903:RL909 = 4.8:0.1:0.1, and 1 kg of curing agent RA2000. The mixture was stirred for 30 min. An acrylate non-silicone release layer was applied to the low-roughness surface of the substrate using a microgravure coating method, drying at 120°C for 1 min. After drying and curing, the film was aged at 50°C for 24 h.

[0066] Main testing methods:

[0067] (1) Center surface roughness (Ra), maximum protrusion height of center surface (Rp)

[0068] A contact surface roughness tester (Mitutoyo SJ210) was used, with a cutoff value of 0.8 mm. The average roughness (SRa) of the center surface and the maximum protrusion height (Rp) of the center surface were determined by surface analysis software installed in the roughness tester. Three measurements were performed at different measurement points, and the average values ​​were calculated for each measurement.

[0069] (2) Release force

[0070] A ceramic slurry was prepared by diluting 100 parts by weight of barium titanate (BaTiO3, particle size: 300nm) powder, 5 parts by weight of polyvinyl butyral resin, 3 parts by weight of dioctyl phthalate and 1 part by weight of dispersant in a mixed solvent of toluene and ethanol (weight ratio = 1:1) at room temperature for 30 minutes.

[0071] Take the prepared ceramic slurry and use an automatic coating machine to coat the prepared ceramic slurry onto the release layer surface of the release film sample with a wet film thickness of 10 μm. After coating, place it in a forced-air drying oven to dry. After drying, the ceramic sheet release film is obtained.

[0072] Take the prepared sample and place it at a temperature of 23℃±2℃ and a relative humidity of 50%±5% for 20 to 30 minutes. After the placement time is reached, use a utility knife to cut the prepared ceramic sheet and release film into strips of 25mm×150mm size.

[0073] Peel tests were conducted using a tensile testing machine, and the peel force values ​​of the measured specimens were recorded, expressed as gf / 25mm. Five sets of specimens were measured for each sample.

[0074] Release film 90° peel force: The average peel force value of all release test specimens is the 90° peel force of the release film.

[0075] (3) Residual adhesion rate

[0076] Polyester tape (Nitto Denko, NIT-31B) was pressed onto a cold-rolled stainless steel plate specified by J using a 5kg pressure roller, held for 30 seconds, and then peeled off at 180°. The force was measured and taken as the base adhesive force (f0).

[0077] Next, a new polyester tape was pressed onto the release layer surface of the sample film using a 5kg pressure roller and held for 30 seconds, then the polyester tape was peeled off. The peeled polyester tape was then bonded to a stainless steel plate under the same conditions, and the peel strength of the bonded portion was measured and defined as the residual adhesive strength (f). The residual adhesive strength was calculated using the obtained basic adhesive strength (f0) and residual adhesive strength (f) using the following formula: Residual Adhesion Rate (%) = (f / f0) × 100%

[0078] Table 1. Performance Test Table of Release Films in Examples and Comparative Examples

[0079]

[0080] In the embodiments, this invention discloses several typical application examples. Examples 1-5 adjust the monomer ratio of the non-silicone release agent to regulate the release force, demonstrating the performance level of precise control over the release force; Example 6 changes the amount of particles added in the A layer structure of the substrate layer. Increasing the particle amount improves the roughness level and decreases the SRa value; Example 7 changes the particle size in the A layer structure of the substrate layer, making the small and large particle sizes more similar. Under this combination, the roughness performance slightly deteriorates, and the SRa value increases. The release films for multilayer ceramic capacitors shown in Examples 1-7 exhibit excellent performance and can be applied to the casting and coating of ceramic slurries.

[0081] Comparative Example 1 lacked a back coating, resulting in poor winding performance, making it impossible to wind up the film and thus hindering industrial production.

[0082] Comparative Example 2 uses an organosilicon release agent, which exhibits significant silicon transfer and reduces the wettability and solvent resistance of the ceramic slurry. This may cause coating problems during ceramic slurry coating and affect the production of multilayer ceramic sheets.

[0083] The substrate layer of Comparative Example 3 did not use the AB structure with added functional particles, nor did it adopt the silicon dioxide coating process. The surface roughness of the film material was relatively large, which was far from meeting the production requirements of high-end multilayer ceramic capacitors.

Claims

1. A release film for a multilayer ceramic capacitor, characterized in that: The release film comprises a back coating layer, a substrate layer, a coating layer, and a release layer. The substrate layer has a back coating layer on one side and a coating layer on the other side. A release layer is disposed on the coating layer. The surface roughness Ra ≤ 50 nm and Rp ≤ 500 nm at the interface between the substrate layer and the coating layer. The transverse thermal expansion coefficient of the substrate is ≤ 99 × 10⁻⁶. -6 K -1 The surface roughness of the interface between the coating layer and the release layer is Ra≤20nm and Rp≤200nm. The coating layer is a silicon dioxide coating layer with a coating thickness of no more than 500 nm. The release layer is a polyacrylate-based non-silicone release layer with a thickness of 0.05 μm to 0.3 μm.

2. The release film for multilayer ceramic capacitors according to claim 1, characterized in that: The thickness of the substrate layer is 19μm~50μm, and the substrate selected is a biaxially oriented polyethylene terephthalate film.

3. The release film for multilayer ceramic capacitors according to claim 2, characterized in that: The substrate layer has a two-layer structure, A and B. The surface of layer A is a low-roughness surface with a thickness of 0.3~2μm, and the surface of layer B is a corona-electrode surface. Two types of inert particles of different sizes are added to the structure of layer A, while no inert particles are added to the structure of layer B.

4. The release film for multilayer ceramic capacitors according to claim 3, characterized in that: Within the A-layer structure: 50% of the particles are 30nm~300nm, 50% are 500nm~800nm, and the total particle addition is 5000ppm~50000ppm.

5. The release film for multilayer ceramic capacitors according to claim 4, characterized in that: The particles within the A-layer structure are a combination of particles with diameters of 30 nm and 800 nm.

6. The release film for multilayer ceramic capacitors according to claim 3, characterized in that: The inert particles in the A-layer structure are any one or more combinations of titanium oxide, silicon oxide, barium sulfate, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, polystyrene resin, acrylic resin, urea resin, and melamine resin.

7. The release film for multilayer ceramic capacitors according to claim 1, characterized in that: The back coating is a resin layer with antistatic effect. The added antistatic agent is one of quaternary ammonium salt antistatic agent, polythiophene antistatic agent, graphene antistatic agent or carbon nanotube antistatic agent. The amount of antistatic agent added is 2~5%. The resin main body of the back coating is one of melamine resin, polyurethane resin or acrylic resin.

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