Release film and preparation method thereof

Abstract

The release film according to one aspect of the present invention comprises: a substrate layer comprising a polyester; and a release layer formed by coating at least one surface of the base material layer with a release coating composition, the release coating composition comprising a silicon composition and a polymer composition, according to the present invention, by adjusting the content of the silicon composition and the content of the polymer composition, the release film having excellent coating properties and peeling properties of a ceramic slurry and having good peeling stability even in a high-temperature / high-humidity environment, and the method for preparing the release film can be provided.

Description

Technical Field

[0001] The present invention relates to a release film, and more specifically, to a release film and a method for preparing the same, which have excellent coatability and peelability with respect to a ceramic slurry and also have peel stability in a high-temperature / high-humidity environment. Background Art

[0002] Generally, a release film is a film having a structure in which a polyester-based film is used as a base material and a release layer is provided on the base material, and the release film is also used as a film for forming a thin ceramic green sheet for a dielectric of a multilayer ceramic capacitor or the like.

[0003] Such a ceramic green sheet is formed by coating and drying a slurry containing a ceramic component (such as barium titanate) and a binder resin on a release film. After printing electrodes on the prepared ceramic green sheet and peeling off the release film, a multilayer ceramic capacitor is prepared through a preparation process of lamination, stamping, firing, and external electrode coating. Therefore, a release film for forming a ceramic green sheet directly coated with a slurry is required to have excellent coatability and peelability with respect to the ceramic slurry.

[0004] Accordingly, in a release film for preparing a ceramic green sheet, a silicon composition having a low surface energy is used in the release layer for good peelability. However, when using a silicon composition, due to the low surface energy, the ceramic slurry is not uniformly coated on the release film, or defects such as pinholes are generated in the ceramic slurry coating layer. After processing a multilayer ceramic capacitor (MLCC), problems of inducing a short circuit defect and reducing the breakdown voltage (BDV) occur.

[0005] To solve such problems, a non-silicon resin (a polymer resin containing a long-chain alkyl having a relatively higher surface energy than the silicon composition) and a low-silicon resin (applying a low-molecular-weight silicon additive) are used in the release layer, but due to the high surface energy, there are problems of weak adsorption and penetration of moisture and an increase in peel force in a high-temperature / high-humidity environment.

[0006] Therefore, in a release film for forming a ceramic green sheet, it should have excellent coatability and peelability with respect to a ceramic slurry, as well as peel stability in a high-temperature / high-humidity environment. Summary of the Invention

[0007] Technical problems to be solved by the present invention

[0008] The present invention is proposed to solve the above-described problems and meet the existing requirements. The technical problem to be solved by the present invention is to provide a release film and a method for preparing the same, which have excellent coatability and peelability with respect to a ceramic slurry and also have peel stability in a high-temperature / high-humidity environment.

[0009] The above and other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments.

[0010] Technical solution

[0011] The object is achieved by a release film, which comprises: a substrate layer containing polyester; and a release layer formed by coating a release coating composition on at least one side of the substrate layer, wherein the release coating composition contains a silicon composition and a polymer composition; the ratio (B / A) of the content (A) of the silicon composition to the content (B) of the polymer composition satisfies the following formula 1.

[0012] Formula 1

[0013] 0.2 ≤ B / A ≤ 10.0

[0014] Preferably, the ratio (Y / X) of the peeling force (X) of the release layer from the green ceramic sheet under the conditions of a temperature of 25°C and a relative humidity of 50% to the peeling force (Y) of the release layer from the green ceramic sheet under the conditions of a temperature of 60°C and a relative humidity of 90% satisfies the following formula 2.

[0015] Formula 2

[0016] 1.0 ≤ Y / X ≤ 2.0

[0017] Preferably, the peeling force (X) of the release layer from the green ceramic sheet under the conditions of a temperature of 25°C and a relative humidity of 50% can be 3 gf / in to 10 gf / in, and the peeling force (Y) of the release layer from the green ceramic sheet under the conditions of a temperature of 60°C and a relative humidity of 90% can be 3 gf / in to 20 gf / in.

[0018] Preferably, the silicon composition may contain vinyl polysiloxane and hydrogen polysiloxane.

[0019] Preferably, the ratio (A2 / A1) of the content (A1) of vinyl polysiloxane to the content (A2) of hydrogen polysiloxane satisfies the following formula 3.

[0020] Formula 3

[0021] 0.05 ≤ A2 / A1 ≤ 0.50

[0022] Preferably, the weight average molecular weight of vinyl polysiloxane and hydrogen polysiloxane can be 4000 to 300000.

[0023] Preferably, the polymer composition may contain a polymer compound and a carbodiimide compound.

[0024] Preferably, the ratio (B2 / B1) of the content (B1) of the polymer compound to the content (B2) of the carbodiimide compound satisfies the following formula 4.

[0025] Formula 4

[0026] 0.05 ≤ B2 / B1 ≤ 0.50

[0027] Preferably, the polymer compound may include at least one selected from ester resins, acrylic resins, and urethane resins.

[0028] Preferably, the acid value of the polymer compound may be 10 mgKOH / g or more.

[0029] Preferably, the weight-average molecular weight of the carbodiimide compound may be 2000 or more.

[0030] Preferably, the release coating composition may further include 0.1 ppm to 20.0 ppm of a platinum chelate catalyst.

[0031] Preferably, the arithmetic mean roughness (Ra) of the outer surface of the release layer may be 100 nm or less, and the maximum protrusion height (Rt) may be 3 μm or less.

[0032] Preferably, the surface energy of the release layer may be 20 dynes / cm to 35 dynes / cm.

[0033] Preferably, the HT115 microhardness of the release layer surface may be 18 to 25.

[0034] In addition, the above object is achieved by a release film for preparing a ceramic green sheet, and the above release film is used for preparing a ceramic green sheet.

[0035] In addition, the above object is achieved by a method for preparing a release film, the method for preparing the release film including: a first step of preparing a release coating composition; a second step of preparing an unstretched sheet by melt-extruding a polyester composition; a third step of uniaxially stretching the unstretched sheet in the longitudinal direction to prepare a uniaxially stretched polyester film; a fourth step of coating the release coating composition for forming a release layer on at least one surface of the uniaxially stretched polyester film; a fifth step of re-stretching the uniaxially stretched polyester film coated with the release coating composition in the transverse direction to prepare a biaxially stretched release film; and a sixth step of heat-treating the biaxially stretched release film.

[0036] Preferably, the release coating composition includes a silicon composition and a polymer composition, the silicon composition includes an alkenyl polysiloxane and a hydrogen polysiloxane, and the polymer composition includes a polymer compound and a carbodiimide compound. The ratio (B / A) of the content (A) of the silicon composition to the content (B) of the polymer composition, the ratio (A2 / A1) of the content (A1) of the alkenyl polysiloxane to the content (A2) of the hydrogen polysiloxane, and the ratio (B2 / B1) of the content (B1) of the polymer compound to the content (B2) of the carbodiimide compound may respectively satisfy the following Formula 1, Formula 3, and Formula 4.

[0037] Formula 1

[0038] 0.2 ≤ B / A ≤ 10.0

[0039] Formula 3

[0040] 0.05 ≤ A2 / A1 ≤ 0.50

[0041] Formula 4

[0042] 0.05 ≤ B2 / B1 ≤ 0.50

[0043] Preferably, the ratio (Y / X) of the peeling force (X) of the release layer from the green ceramic sheet at a temperature of 25°C and a relative humidity of 50% to the peeling force (Y) from the green ceramic sheet at a temperature of 60°C and a relative humidity of 90% can satisfy the following Formula 2.

[0044] Formula 2

[0045] 1.0 ≤ Y / X ≤ 2.0.

[0046] Beneficial effects

[0047] According to the release film and its preparation method of the present invention, by adjusting the content ratio of the silicon composition and the polymer composition constituting the release layer, the ceramic slurry has excellent coatability and peelability. At the same time, a high-hardness coating is formed by the silicon composition with a large molecular weight to prevent the adsorption and penetration of moisture, thereby having good peel stability and other effects in a high-temperature / high-humidity environment.

[0048] In addition, according to the release film and its preparation method of the present invention, the residual adhesion rate is excellent and the adhesion between the base material layer and the release layer is improved, so there are effects such as no smears being generated.

[0049] However, the effects of the present invention are not limited to the above-mentioned effects, and those skilled in the art can clearly understand other effects not mentioned according to the following description. Brief Description of the Drawings

[0050] Figure 1 is a schematic cross-sectional view of the release film of one aspect of the present invention.

[0051] Figure 2 is a flowchart showing the preparation method of the release film of another aspect of the present invention.

[0052] Description of the Reference Numerals

[0053] 1: Base material layer

[0054] 2: Release layer

[0055] 10: Release film Detailed implementation manners

[0056] Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily implement it. The present invention can be implemented in various different forms and is not limited to the embodiments described herein.

[0057] Unless otherwise defined, all technical terms and scientific terms used in this specification have the same meanings as those commonly understood by those of ordinary skill in the technical field to which the present invention belongs. In case of conflict, this specification including the definitions shall prevail. In addition, although methods and materials similar or identical to those described in this specification can be used in the implementation or testing of the present invention, suitable methods and materials are described in this specification.

[0058] In this specification, the terms "~-based resin", "~-based polymer" or / and "~-based copolymer" refer to a broad concept that includes "~ resin", "~ polymer", "~ copolymer", or / and "derivatives of ~ resin, polymer, or copolymer". In addition, in this specification, the term "polymer or copolymer crosslinked by these resins" refers to "polymer or copolymer crosslinked by the aforementioned resins".

[0059] In this specification, the term "compound" refers to a broad concept that includes "single-atom molecules", "oligomers", and "macromolecular compounds including homopolymers and copolymers".

[0060] In this specification, unless otherwise specifically stated to the contrary, the term "comprising" may also include other components rather than excluding other components.

[0061] In this specification, the term "its combination" refers to a mixture or combination of one or more of the components already described.

[0062] In this specification, the term "and / or" refers to any combination and all combinations of one or more of the related items described. In this specification, the term "or" means "and / or". In this specification, the expression "at least one" or "one or more" before a component means supplementing the list of all components and does not mean supplementing a single component described above.

[0063] In this specification, unless otherwise stated, all percentages, fractions, ratios, etc. are by weight. In addition, when an equivalent, concentration, or other value or parameter is given in the form of a range, a preferred range, or a list of a preferred upper limit value and a preferred lower limit value, it should be understood that all ranges formed by any pair of an arbitrary range upper limit value or a preferred value and an arbitrary range lower limit value or a preferred value are specifically disclosed, regardless of whether these ranges are disclosed individually.

[0064] When a numerical range is recited herein, unless otherwise specified, the range is intended to include its endpoints and all integers and fractions within the range. The scope of the present invention is not intended to be limited to the specific values recited when defining the range.

[0065] In this specification, unless otherwise specifically specified, the unit "parts by weight" refers to the weight ratio between components, and the unit "parts by mass" refers to the value obtained by converting the weight ratio between components into solids.

[0066] In this specification, each constituent element is a concept that includes both single and multiple elements.

[0067] Figure 1 is a cross-sectional schematic view of a release film according to an aspect of the present invention. Referring to Figure 1 , a release film 10 according to an aspect of the present invention includes: a substrate layer 1; and a release layer 2 disposed on at least one surface of the substrate layer 1.

[0068] Generally, in a release film for ceramic green sheet forming, in order to achieve good peelability, a silicon composition with a low surface energy is used. However, when using a silicon composition, due to the low surface energy, the ceramic slurry is not uniformly coated on the release film, or defects such as pinholes are generated in the ceramic slurry coating layer. After processing a multilayer ceramic capacitor (MLCC), a short circuit (Short) defect may be induced and a problem of reducing the breakdown voltage (BDV) may occur. To solve the above problems, a non-silicon resin (a polymer resin containing a long-chain alkyl group with a relatively higher surface energy than the silicon composition) and a low-silicon resin (a low-molecular-weight silicon additive) are used. However, due to the high surface energy, there are problems such as weak adsorption and penetration of moisture and an increase in the peel force in a high-temperature / high-humidity environment. To improve these problems, the inventors of the present invention propose a release film having the following configuration. Hereinafter, each configuration will be described in detail.

[0069] 1. Substrate layer 1

[0070] The substrate layer 1 is preferably in the form of a substrate film or a substrate sheet, more preferably in the form of a substrate film. As an example, a substrate film containing polyester can be used for the substrate layer 1.

[0071] In one embodiment, the substrate layer 1 preferably contains at least one selected from polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, more preferably contains polyethylene terephthalate (PET).

[0072] As an example, the polyester resin forming the base material layer 1 can be obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic diol. At this time, as the aromatic dicarboxylic acid, isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, or hydroxycarboxylic acid (for example, p-hydroxybenzoic acid, etc.) can be used. In addition, as the aliphatic diol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanedimethanol, or neopentyl glycol can be used. The polyester resin forming the base material layer 1 can use two or more of the above-mentioned dicarboxylic acid components and diol components in combination, and can also be a copolymer containing a third component.

[0073] In one embodiment, the base material layer 1 preferably uses a uniaxially or biaxially oriented film having high transparency and excellent productivity and processability.

[0074] 2. Release layer 2

[0075] The release layer 2 is a cured layer formed by coating and drying a release coating composition on at least one surface of the base material layer 1, wherein the release coating composition contains a silicon composition and a polymer composition.

[0076] In one embodiment, preferably, the ratio (B / A) of the content (A) of the silicon composition to the content (B) of the polymer composition in the release coating composition forming the release layer 2 satisfies the following formula 1.

[0077] Formula 1

[0078] 0.2 ≤ B / A ≤ 10.0

[0079] In addition, preferably, the ratio (Y / X) of the peel strength (X) of the release layer 2 from the green ceramic sheet at a temperature of 25°C and a relative humidity of 50% to the peel strength (Y) from the green ceramic sheet at a temperature of 60°C and a relative humidity of 90% satisfies the following formula 2.

[0080] Formula 2

[0081] 1.0 ≤ Y / X ≤ 2.0

[0082] In the release coating composition, when the ratio (B / A) of the content (A) of the silicon composition to the content (B) of the polymer composition is less than 0.1, the hydrophobicity of the release layer 2 is sufficient. Therefore, the release stability under high-temperature / high-humidity environments is good and satisfies the value of Formula 2, but the coatability of the ceramic slurry is insufficient, and the adhesion between the release layer 2 and the substrate layer 1 is insufficient, resulting in the problem of scratches (SMEAR). When the ratio (B / A) of the content (A) of the silicon composition to the content (B) of the polymer composition exceeds 10.0, the slurry coatability is good and no scratches are generated, but due to the insufficient hydrophobicity of the release layer 2, the moisture resistance is insufficient. Therefore, the change amount of the release force based on humidity increases, resulting in the problem that the ratio (Y / X) of the release force (X) from the green ceramic sheet at a temperature of 25°C and a relative humidity of 50% to the release force (Y) from the green ceramic sheet at a temperature of 60°C and a relative humidity of 90% exceeds 2.0.

[0083] In addition, when the value of Formula 2 is 1.0, there is no difference in the release force between the release layer and the green ceramic sheet under normal temperature and high-temperature / high-humidity conditions. Therefore, it is most preferred. On the contrary, when the value of Formula 2 exceeds 2.0, the change amount of the release force based on humidity is excessive, and there is a problem of reduced moisture resistance.

[0084] In addition, the release force (X) of the release layer from the green ceramic sheet at a temperature of 25°C and a relative humidity of 50% is preferably 3 gf / in to 10 gf / in, and the release force (Y) of the release layer from the green ceramic sheet at a temperature of 60°C and a relative humidity of 90% is preferably 3 gf / in to 20 gf / in. When the release force under the conditions of 25°C / 50% and 60°C / 90% is less than 3 gf / in, due to the insufficient adhesion to the green sheet slurry coated on the release layer 2, problems such as the green sheet warping from the release layer or premature release at an undesired time point may occur. When the release force under the conditions of 25°C / 50% exceeds 10 gf / in or the release force under the conditions of 60°C / 90% exceeds 20 gf / in, it is difficult to release the green sheet from the release layer, so process problems may occur.

[0085] In one embodiment, the silicon composition preferably includes vinyl polysiloxane and hydrogen polysiloxane. In addition, preferably, the ratio (A2 / A1) of the content (A1) of the vinyl polysiloxane constituting the silicon composition to the content (A2) of the hydrogen polysiloxane satisfies the following Formula 3.

[0086] Formula 3

[0087] 0.05 ≤ A2 / A1 ≤ 0.50

[0088] When the ratio (A2 / A1) of the content (A1) of the alkenylpolysiloxane to the content (A2) of the hydrogenpolysiloxane is less than 0.05, there is a problem that the residual adhesion rate decreases due to the transfer of the unreacted and residual silicon component. When it exceeds 0.50, the pot life of the coating liquid decreases, and there is a problem that the peel strength of the green ceramic sheet increases due to the residual functional groups.

[0089] In one embodiment, the weight-average molecular weight of the alkenylpolysiloxane and the hydrogenpolysiloxane is preferably from 4,000 to 300,000. When the weight-average molecular weight of the alkenylpolysiloxane and the hydrogenpolysiloxane is less than 4,000, there is a problem of insufficient moisture resistance due to insufficient hydrophobicity, and thus the value (Y / X) of the above formula 2 exceeds 2. When it exceeds 300,000, there is a problem of difficulty in ensuring the coating appearance.

[0090] In one embodiment, the polymer composition preferably contains a polymer compound and a carbodiimide compound. Additionally, preferably, the ratio (B2 / B1) of the content (B1) of the polymer compound to the content (B2) of the carbodiimide compound satisfies the following formula 4.

[0091] Formula 4

[0092] 0.05 ≤ B2 / B1 ≤ 0.50

[0093] When the ratio (B2 / B1) of the content (B1) of the polymer compound to the content (B2) of the carbodiimide compound is less than 0.05, since the curing reaction of the polymer compound and the carbodiimide compound is insufficient, a dense coating is not formed, and there is a problem that the value (Y / X) of the above formula 2 exceeds 2.0. When it exceeds 0.50, there is a problem that the peel strength of the release layer 2 of the green ceramic sheet increases due to the unreacted and residual functional groups.

[0094] In one embodiment, the polymer compound preferably contains at least one selected from ester resins, acrylic resins, and urethane resins. Additionally, the acid value of the polymer compound is preferably 10 mgKOH / g or more, and the weight-average molecular weight of the carbodiimide compound is preferably 2,000 or more. When the acid value of the polymer compound is less than 10 mgKOH / g or the weight-average molecular weight of the carbodiimide compound as a curing agent is less than 2,000, the curing reaction of the polymer compound and the carbodiimide compound is insufficient, and thus a dense release layer 2 is not formed. As a result, moisture easily penetrates into the interior of the coating and causes poor moisture resistance, and there is a problem that the value (Y / X) of the above formula 2 exceeds 2.0.

[0095] In one embodiment, the release coating composition for forming the release layer 2 may further contain a platinum chelating catalyst, and the content of the platinum chelating catalyst is preferably 0.1 ppm to 20.0 ppm. For the entire release layer 2, when the concentration of the platinum chelating catalyst is less than 0.1 ppm, the curing reaction is insufficient, resulting in problems such as a decrease in the residual adhesion rate due to the transfer of unreacted and residual silicon components and insufficient adhesion between the release layer 2 and the substrate layer 1, leading to scratches (SMEAR). When the platinum chelating catalyst exceeds 20.0 ppm, there are problems such as a reduction in the shelf life of the release coating composition and deterioration of the coating appearance of the release layer 2.

[0096] In addition, the release coating composition for forming the release layer may be combined with auxiliary agents such as reaction regulators, adhesion enhancers, and antistatic agents within the scope that does not damage the gist of the present invention.

[0097] In one embodiment, the arithmetic mean roughness (Ra) of the outer surface of the release layer 2 is preferably 100 nm or less, and the maximum protrusion height (Rt) is preferably 3 μm or less. When the arithmetic mean roughness (Ra) of the outer surface of the release layer 2 exceeds 100 nm, thickness non-uniformity of the green sheet occurs during the green sheet processing. When the maximum protrusion height (Rt) of the release layer 2 exceeds 3 μm, defects such as pinhole defects occur on the green sheet during the green sheet processing.

[0098] The coatability and peelability of the ceramic green sheet slurry, which are the core characteristics of the present invention, and the peel stability in a high-temperature / high-humidity environment can be achieved only when the content ratio of the silicon composition to the polymer composition (Formula 1), the content ratio of the vinyl polysiloxane to the hydrogen polysiloxane (Formula 3), the content ratio of the polymer compound to the carbodiimide compound (Formula 4), the acid value of the polymer compound, the molecular weight of the silicon composition, and the molecular weight of the carbodiimide compound all meet the constitution of the present invention. Such core characteristics are manifested by the surface energy of the release layer 2 and the HT115 microhardness of the release layer 2 measured by a ultra microhardness tester.

[0099] In one embodiment, the surface energy of the release layer 2 is preferably 20 dynes / cm to 35 dynes / cm. When the surface energy of the release layer 2 is within the above range, the coatability and peelability of the ceramic green sheet slurry are good. More specifically, when the surface energy of the release layer 2 is less than 20 dynes / cm, there is a problem of poor coatability of the ceramic green sheet slurry. When the surface energy of the release layer 2 exceeds 35 dynes / cm, there is a problem of poor peelability of the ceramic green sheet slurry.

[0100] Moreover, in one embodiment, the HT115 microhardness of the release layer 2 measured by a ultra microhardness tester is preferably 18 to 25. When within the above range, the release stability in a high temperature / high humidity environment is good. More specifically, when the HT115 microhardness of the release layer 2 measured by a ultra microhardness tester is less than 18, due to the failure to form a dense coating of the release layer 2, the release stability in a high temperature / high humidity environment is poor. When the microhardness exceeds 25, although a dense coating of the release layer 2 is formed, there is a problem of poor peelability of the green sheet slurry due to residual functional groups.

[0101] In one embodiment, the residual adhesion rate of the release layer 2 is preferably 90% or more. When the residual adhesion rate of the release layer 2 is less than 90%, due to insufficient curing of the release layer 2, the release agent may transfer to the green sheet, and due to the poor adhesiveness of the ceramic sheet, poor quality may occur during the processing of multilayer ceramic capacitors (MLCC).

[0102] Figure 2 It is a flowchart showing a method for preparing a release film according to another aspect of the present invention.

[0103] Referring to Figure 1 and Figure 2 , the method for preparing a release film according to another aspect of the present invention may include: a first step S201 of preparing a release coating composition; a second step S202 of preparing an unstretched sheet by melt-extruding a polyester composition; a third step S203 of uniaxially stretching the unstretched sheet in the longitudinal direction to prepare a uniaxially stretched polyester film; a fourth step S204 of coating at least one surface of the uniaxially stretched polyester film with the release coating composition for forming a release layer; a fifth step S205 of stretching the uniaxially stretched polyester film coated with the release coating composition again in the transverse direction to prepare a biaxially stretched release film; and a sixth step S206 of heat-treating the biaxially stretched release film.

[0104] First, the first step S201 is a step of preparing a release coating composition, in which a silicon composition and a polymer composition are mixed and stirred to form a release coating composition. In one embodiment, the silicon composition preferably contains vinyl polysiloxane and hydrogen polysiloxane, and the polymer composition preferably contains a polymer compound and a carbodiimide compound. At this time, the specific material composition and content thereof are the same as those described in the above release film and will not be elaborated here.

[0105] Next, the second step S202 is a step of preparing an unstretched sheet by melt-extruding a polyester composition. It is a step of melt-extruding a polyester composition at a temperature of 250°C to 300°C using a co-extrusion device having an extruder, and then cooling and curing the molten resin using a T-die and a casting drum to obtain an unstretched sheet.

[0106] Next, the third step S203 is a step of uniaxially stretching the unstretched sheet in the longitudinal direction to prepare a uniaxially stretched polyester film. Preferably, after heating the unstretched sheet to a temperature above the glass transition temperature of the polyester resin by a heating unit (referred to as roll heating and infrared heater heating), the unstretched sheet is stretched 3 to 5 times using the peripheral speed difference of two or more rolls.

[0107] Next, the fourth step S204 is a step of coating a release coating composition on at least one surface of the uniaxially stretched polyester film. The release layer can be formed by an in-line coating method, which is a method of coating the release coating composition on the film surface during the film-forming process of the polyester film. In addition, the method of coating the release coating composition on the polyester film can be carried out by one method among gravure, comma, Mayer bar, die lip, die head, or spraying. However, it is not limited thereto, and it can be carried out by all coating methods that can be used in the technical field. In addition, in this specification, although the in-line coating method is described as an example, it is not limited thereto, and an off-line coating method of coating on the prepared substrate film can also be used.

[0108] Next, the fifth step S205 is a step of stretching the uniaxially stretched polyester film coated with the release coating composition in the transverse direction again to prepare a biaxially stretched release film. Preferably, using a tenter (which uses movable clips to stretch in the width direction), in an oven where a plurality of preheating zones and stretching zones are respectively formed, the uniaxially stretched polyester film coated with the release coating composition in the fourth step is preheated to a temperature within +50°C of the glass transition temperature of the polyester resin, and then stretched 3 to 5 times in the transverse direction within the same temperature range. When stretched transversely, the release coating composition dries and cures to form a release layer.

[0109] Next, the sixth step S206 is a step of heat-treating the biaxially stretched release film, which is a step of heat-treating to ensure the dimensional stability and orientation relaxation of the film stretched in the above-mentioned tenter. Heat treatment is carried out in a plurality of heat treatment zones formed in the same tenter and at a temperature condition below the melting point of the polyester +30°C. At this time, in order to ensure high dimensional stability and molding characteristics during the heat treatment process, the orientation relaxation and transverse uniform orientation of the biaxially stretched release film are achieved.

[0110] As described above, the method for preparing a release film according to one aspect of the present invention can easily prepare a release film while reducing production costs.

[0111] Hereinafter, the structure of the present invention and the effects obtained therefrom will be described in detail with reference to examples and comparative examples. However, the examples are provided to describe the present invention in more detail, and the scope of the present invention is not limited to the examples.

[0112] [Example]

[0113] Example 1

[0114] Preparation example 1: Preparation of release coating composition

[0115] 90 parts by weight of alkenyl polysiloxane (CAS No. 87244-72-2, weight-average molecular weight of 5000), 10 parts by weight of hydrogen polysiloxane (CAS No. 68037-59-2, weight-average molecular weight of 5000), 18 parts by weight of urethane resin (CAS No. 9009-54-5, acid value of 40 KOH mg / g), and 2 parts by weight of carbodiimide compound (Nippon Carbide Industries Co., weight-average molecular weight of 4000) were put into water and stirred for 30 minutes. After preparing a composition with a solids content of 2 wt%, a platinum chelate catalyst (Dow Chemical Company, Shin-Etsu Chemical Co., Ltd.) was added to make it reach 5 ppm to prepare a release coating composition.

[0116] Preparation example 2: Preparation of unstretched polyethylene terephthalate film

[0117] Polyethylene terephthalate resin pellets were dried under reduced pressure at a temperature of 135 °C and a pressure of 1.3 hPa for 6 hours, and then supplied to an extruder. In the extruder, the polyethylene terephthalate resin pellets dried under reduced pressure were melt-extruded into a sheet at a temperature of about 280 °C, and rapidly cooled and solidified on a metal roll with a surface temperature maintained at 20 °C to prepare an unstretched polyethylene terephthalate film.

[0118] Preparation example 3: Preparation of release film

[0119] The unstretched polyethylene terephthalate film prepared in Preparation Example 2 was longitudinally stretched 3 times by the difference in peripheral speed ratio between rolls to prepare a uniaxially stretched polyester film. Then, the release coating composition prepared in Preparation Example 1 was coated on one side of the uniaxially stretched polyester film, and then the uniaxially stretched polyester film coated with the release coating composition was clamped with clips and stretched transversely. It was stretched 4 times transversely and hot air was applied to prepare a biaxially stretched release film, and it was heat-treated to prepare a final release film.

[0120] Example 2

[0121] In the release coating composition of Example 1, 70 parts by weight of alkenyl polysiloxane (CAS No. 87244-72-2, weight-average molecular weight of 5000) and 30 parts by weight of hydrogen polysiloxane (CAS No. 68037-59-2, weight-average molecular weight of 5000) were used. Except for this, a release film was prepared in the same manner as in Example 1.

[0122] Example 3

[0123] In the release coating composition of Example 1, 14 parts by weight of a urethane resin (CAS No. 9009-54-5, acid value 40 KOH mg / g) and 6 parts by weight of a carbodiimide compound (Nippon Carbide Industries Co., Ltd., weight average molecular weight 4000) were used. Other than this, a release film was prepared in the same manner as in Example 1.

[0124] Example 4

[0125] In the release coating composition of Example 1, 45 parts by weight of an alkenyl polysiloxane (CAS No. 87244-72-2, weight average molecular weight 5000), 5 parts by weight of a hydrogen polysiloxane (CAS No. 68037-59-2, weight average molecular weight 5000), 63 parts by weight of a urethane resin (CAS No. 9009-54-5, acid value 40 KOH mg / g) and 7 parts by weight of a carbodiimide compound (Nippon Carbide Industries Co., Ltd., weight average molecular weight 4000) were used. Other than this, a release film was prepared in the same manner as in Example 1.

[0126] Example 5

[0127] In the release coating composition of Example 1, 18 parts by weight of an alkenyl polysiloxane (CAS No. 87244-72-2, weight average molecular weight 5000), 2 parts by weight of a hydrogen polysiloxane (CAS No. 68037-59-2, weight average molecular weight 5000), 90 parts by weight of a urethane resin (CAS No. 9009-54-5, acid value 40 KOH mg / g) and 10 parts by weight of a carbodiimide compound (Nippon Carbide Industries Co., Ltd., weight average molecular weight 4000) were used. Other than this, a release film was prepared in the same manner as in Example 1.

[0128] Example 6

[0129] In the release coating composition of Example 1, 9.9 parts by weight of an alkenyl polysiloxane (CAS No. 87244-72-2, weight average molecular weight 5000), 1.1 parts by weight of a hydrogen polysiloxane (CAS No. 68037-59-2, weight average molecular weight 5000), 98.1 parts by weight of a urethane resin (CAS No. 9009-54-5, acid value 40 KOH mg / g) and 10.9 parts by weight of a carbodiimide compound (Nippon Carbide Industries Co., Ltd., weight average molecular weight 4000) were used. Other than this, a release film was prepared in the same manner as in Example 1.

[0130] Comparative Example

[0131] Comparative Example 1

[0132] In the release coating composition of Example 1, 98 parts by weight of vinyl polysiloxane (CAS No. 87244-72-2, weight average molecular weight of 5000) and 2 parts by weight of hydrogen polysiloxane (CAS No. 68037-59-2, weight average molecular weight of 5000) were used. In addition, a release film was prepared in the same manner as in Example 1.

[0133] Comparative Example 2

[0134] In the release coating composition of Example 1, 60 parts by weight of vinyl polysiloxane (CAS No. 87244-72-2, weight average molecular weight of 5000) and 40 parts by weight of hydrogen polysiloxane (CAS No. 68037-59-2, weight average molecular weight of 5000) were used. In addition, a release film was prepared in the same manner as in Example 1.

[0135] Comparative Example 3

[0136] In the release coating composition of Example 1, 19.5 parts by weight of urethane resin (CAS No. 9009-54-5, acid value of 40 KOH mg / g) and 0.5 parts by weight of carbodiimide compound (Nippon Carbide Industries Co., weight average molecular weight of 4000) were used. In addition, a release film was prepared in the same manner as in Example 1.

[0137] Comparative Example 4

[0138] In the release coating composition of Example 1, 12 parts by weight of urethane resin (CAS No. 9009-54-5, acid value of 40 KOH mg / g) and 8 parts by weight of carbodiimide compound (Nippon Carbide Industries Co., weight average molecular weight of 4000) were used. In addition, a release film was prepared in the same manner as in Example 1.

[0139] Comparative Example 5

[0140] In the release coating composition of Example 1, 4.5 parts by weight of urethane resin (CAS No. 9009-54-5, acid value of 40 KOH mg / g) and 0.5 parts by weight of carbodiimide compound (Nippon Carbide Industries Co., weight average molecular weight of 4000) were used. In addition, a release film was prepared in the same manner as in Example 1.

[0141] Comparative Example 6

[0142] In the release coating composition of Example 1, 9 parts by weight of an alkenyl polysiloxane (CAS No. 87244-72-2, weight average molecular weight of 5000), 1 part by weight of a hydrogen polysiloxane (CAS No. 68037-59-2, weight average molecular weight of 5000), 117 parts by weight of a urethane resin (CAS No. 9009-54-5, acid value of 40 KOHmg / g), and 13 parts by weight of a carbodiimide compound (Nippon Carbide Industries Co., weight average molecular weight of 4000) were used. In addition, a release film was prepared in the same manner as in Example 1.

[0143] Comparative Example 7

[0144] In the release coating composition of Example 1, a urethane resin with an acid value of 5 KOHmg / g was used instead of the urethane resin (CAS No. 9009-54-5, acid value of 40 KOHmg / g). In addition, a release film was prepared in the same manner as in Example 1.

[0145] Comparative Example 8

[0146] In the release coating composition of Example 1, a carbodiimide compound with a weight average molecular weight of 1000 was used instead of the carbodiimide compound (Nippon Carbide Industries Co., weight average molecular weight of 4000). In addition, a release film was prepared in the same manner as in Example 1.

[0147] Comparative Example 9

[0148] In the release coating composition of Example 1, a platinum chelate catalyst (Dow Chemical Company, Shin-Etsu Chemical Co., Ltd.) with a concentration of 0.05 ppm was used instead of the platinum chelate catalyst with a concentration of 5 ppm. In addition, a release film was prepared in the same manner as in Example 1.

[0149] The values of Formula 1, Formula 3, and Formula 4 representing the components, contents, and their content relationships of the release coating compositions of the above Examples 1 to 6 and Comparative Examples 1 to 9 are shown in Table 1 below.

[0150] Table 1

[0151]

[0152] Using the release films of the above Examples 1 to 6 and Comparative Examples 1 to 9, the physical properties were measured through the following Experimental Examples, and the results are shown in Table 2 below.

[0153] [Experimental Example]

[0154] (1) Evaluation of the coatability of the green sheet slurry

[0155] 100 parts by weight of barium titanate (BaTiO3 , a powder with a particle size of 100 nm), 5 parts by weight of polyvinyl butyral resin (BL-10, Sekisui Chemical Co., Ltd.), 3 parts by weight of dioctyl phthalate (LG Chem Petrochemical Co., Ltd.) and 1 part by weight of a dispersant (DISPERBYK-180, BYK Co.) were diluted in 10 parts by weight of a mixed solvent of toluene and ethanol (weight ratio = 1:1) to prepare a green sheet slurry.

[0156] The prepared green sheet slurry was coated to a thickness of 10 μm on each release film sample and dried to prepare a green sheet. Then, the coated surface of the prepared green sheet was visually confirmed, and the case without pinholes was evaluated as "good", and the case with pinholes was evaluated as "bad".

[0157] (2) Measurement of the peel strength of the green sheet

[0158] After the green sheet prepared in Experimental Example 1 was stored at 25°C / 50% (temperature / humidity) and 60°C / 90% (temperature / humidity) conditions separately for 1 hour, it was cut into a size of 25 mm × 150 mm, and the peel strength was measured. At this time, the peel strength was measured using an AR-1000 device of ChemInstrument Co., Ltd. three times at a peel angle of 180° and a peel speed of 0.3 mpm, and the average value was obtained.

[0159] (3) Measurement of the surface energy of the release layer

[0160] After dropping distilled water and diiodomethane on the release surface of the release film, the contact angle of the release layer surface was measured using a contact angle measuring instrument (DSA-100, manufactured by KRUSS Co.). Then, the measured contact angle value was substituted into the Owens Wendt model to calculate the surface energy.

[0161] (4) Evaluation of the residual adhesion rate

[0162] For the release layer of the release film, a standard adhesive tape (No. 31B, Nitto Co.) was extruded back and forth once with a 2 kg tape roller (ASTM D-1000-55T), and after it was adhered to the release layer surface, the percentage of the peel strength of the peeled adhesive tape (the first peel strength) and the peel strength of the adhesive tape not in contact with the release layer surface (the second peel strength) (the first peel strength / the second peel strength) was used to calculate the residual adhesion rate. At this time, the peel strength was measured using an AR-1000 device of ChemInstrument Co., Ltd. at a peel angle of 180° and a peel speed of 0.3 mpm.

[0163] (5) Measurement of the microhardness of HT115

[0164] Indentation was performed on the release layer surface of the release film using a 115° triangular pyramid indenter with an electromagnetic force of 1.00 gf. The HT115 microhardness of the release layer was measured through the depth and area of the obtained indentation. At this time, the HT115 microhardness was measured 5 times using a super microhardness tester (model: DUH-W201S) manufactured by Shimadzu Corporation of Japan, and the average value was obtained.

[0165] (6) Scratch (SMEAR) evaluation

[0166] After rubbing the release layer surface of the release film back and forth vigorously with the thumb 5 times, it was evaluated whether scratches (the phenomenon that the surface of the coating was pushed like oil) occurred. At this time, the case where no scratches occurred was evaluated as "good", and the case where scratches occurred was evaluated as "bad".

[0167] Table 2

[0168]

[0169] As shown in Table 2 above, it can be confirmed that the release films of Examples 1 to 6 that satisfy the constitution of the present invention all have excellent coatability, peelability, peel stability in a high-temperature / high-humidity environment, and residual adhesion rate of the ceramic green sheet slurry, and no scratches are generated.

[0170] In contrast, it can be seen that the release films of Comparative Examples 1 to 9 have poor coatability, peelability, peel stability in a high-temperature / high-humidity environment, residual adhesion rate, or scratches of the ceramic green sheet slurry.

[0171] More specifically, it can be seen that in Comparative Example 1 where the value of Formula 3 is less than 0.05, the residual adhesion rate decreased due to the transfer of unreacted and residual silicon components, and it can be seen that in Comparative Example 2 where the value of Formula 3 exceeds 0.50, the peel force of the ceramic green sheet increased due to residual functional groups, so that the peel force (X) under the conditions of 25°C / 50% and the peel force (Y) under the conditions of 60°C / 90% are both outside the scope of the present invention.

[0172] In addition, it can be seen that in Comparative Example 3 where the value of Formula 4 is less than 0.05, the moisture resistance decreased because the value of Formula 2 exceeded 2.0, and it can be seen that in Comparative Example 4 where the value of Formula 4 exceeds 0.5, the peel force of the ceramic green sheet increased due to residual functional groups, so that the peel force (X) under the conditions of 25°C / 50% is outside the scope of the present invention.

[0173] In addition, it can be confirmed that, compared with other embodiments and comparative examples, since Comparative Example 5 contains the most silicon composition, the amount of hydrophobic components is large. As a result, the peel stability in a high-temperature / high-humidity environment is good, but the coatability of the slurry is poor and the polymer compound is insufficient, resulting in a decrease in substrate adhesion and the generation of scratches. On the contrary, compared with other embodiments and comparative examples, since Comparative Example 6 contains a polymer composition, the slurry coatability is good and no scratches are generated, but due to the insufficient amount of hydrophobic components, the peel stability in a high-temperature / high-humidity environment is poor.

[0174] In addition, it can be seen that in Comparative Example 7 where the acid value of the polymer compound is less than 10 mgKOH / g and Comparative Example 8 where the weight-average molecular weight of the carbodiimide compound is less than 2000, since the value of Formula 2 exceeds 2.0, the moisture resistance decreases.

[0175] In addition, it can be seen that in Comparative Example 9 where the content of the platinum chelate catalyst is insufficient, the residual adhesion rate decreases and scratches are generated.

[0176] From the experimental results of Examples 1 to 6 and Comparative Examples 1 to 9 of the present invention described above, it can be seen that the release films of Examples 1 to 6 that satisfy the constitution of the present invention have excellent coatability, peelability of the ceramic green sheet slurry, and excellent peel stability under high-temperature / high-humidity conditions in the application of ceramic green sheet forming.

[0177] As described above, the preferred embodiments of the present invention have been described in detail, but the scope of the rights of the present invention is not limited thereto. Various modifications and improvement forms made by those skilled in the art using the basic concepts of the present invention defined in the appended claims also fall within the scope of the rights of the present invention.

Claims

1. A release film, wherein: include: a substrate layer comprising polyester, and A release layer, formed by coating a release coating composition on at least one side of the substrate layer, wherein the release coating composition comprises a silicon composition and a polymer composition; The ratio (B / A) of the content (A) of the silicon composition to the content (B) of the polymer composition satisfies the following formula 1, Formula 1 0.2≤B / A≤10.

0.

2. The release film according to claim 1, wherein: The ratio (Y / X) of the peeling force (X) to the peeling force (Y) of the release layer satisfies the following formula 2, wherein the peeling force (X) is the peeling force of the release layer from the ceramic green sheet at a temperature of 25° C. and a relative humidity of 50%, and the peeling force (Y) is the peeling force of the release layer from the ceramic green sheet at a temperature of 60° C. and a relative humidity of 90%, Formula 2 1.0≤Y / X≤2.

0.

3. The release film according to claim 1, wherein: The peeling force (X) of the release layer from the ceramic green sheet at a temperature of 25°C and a relative humidity of 50% is 3 gf / in to 10 gf / in, and the peeling force (Y) of the release layer from the ceramic green sheet at a temperature of 60°C and a relative humidity of 90% is 3 gf / in to 20 gf / in.

4. The release film according to claim 1, wherein: The silicon composition includes alkenyl polysiloxane and hydrogenated polysiloxane.

5. The release film according to claim 4, wherein: The ratio (A2 / A1) of the content (A1) of the alkenyl polysiloxane to the content (A2) of the hydrogen polysiloxane satisfies the following formula 3, Formula 3 0.05≤A2 / A1≤0.

50.

6. The release film according to claim 4, wherein: The weight average molecular weight of the alkenyl polysiloxane and the hydrogen polysiloxane is 4,000 to 300,000.

7. The release film according to claim 1, wherein: The polymer composition comprises a polymer compound and a carbodiimide compound.

8. The release film according to claim 7, wherein: The ratio (B2 / B1) of the content (B1) of the polymer compound to the content (B2) of the carbodiimide compound satisfies the following formula 4, Formula 4 0.05≤B2 / B1≤0.

50.

9. The release film according to claim 7, wherein: The polymer compound includes at least one selected from ester resins, acrylic resins, and urethane resins.

10. The release film according to claim 7, wherein: The acid value of the polymer compound is 10 mgKOH / g or more.

11. The release film according to claim 7, wherein: The weight average molecular weight of the carbodiimide compound is 2,000 or more.

12. The release film according to claim 1, wherein: The release coating composition further includes 0.1 ppm to 20.0 ppm of a platinum chelate catalyst.

13. The release film according to claim 1, wherein: The arithmetic average roughness (Ra) of the outer surface of the release layer is less than 100 nm, and the maximum protrusion height (Rt) is less than 3 μm.

14. The release film according to claim 1, wherein: The surface energy of the release layer is 20 dyne / cm to 35 dyne / cm.

15. The release film according to claim 1, wherein: The HT115 microhardness of the release layer surface is 18 to 25.

16. A release film for preparing a ceramic green sheet, wherein: A release film according to any one of claims 1 to 15 for use in preparing a ceramic green sheet.

17. A method for preparing a release film, in, include: The first step is to prepare a release coating composition; The second step is to prepare an unstretched sheet by melt-extruding the polyester composition; The third step is to uniaxially stretch the unstretched sheet in the longitudinal direction to prepare a uniaxially stretched polyester film; The fourth step is to apply a release coating composition for forming a release layer on at least one side of the uniaxially stretched polyester film; A fifth step is to stretch the uniaxially stretched polyester film coated with the release coating composition again in the transverse direction to prepare a biaxially stretched release film; and The sixth step is to heat-treat the biaxially stretched release film.

18. The method for preparing a release film according to claim 17, wherein: The release coating composition comprises a silicon composition and a polymer composition. The silicon composition comprises alkenyl polysiloxane and hydrogen polysiloxane, The polymer composition comprises a polymer compound and a carbodiimide compound. The ratio (B / A) of the content (A) of the silicon composition to the content (B) of the polymer composition, the ratio (A2 / A1) of the content (A1) of the alkenyl polysiloxane to the content (A2) of the hydrogen polysiloxane, and the ratio (B2 / B1) of the content (B1) of the polymer compound to the content (B2) of the carbodiimide compound satisfy the following formulas 1, 3, and 4, respectively. Formula 1 0.2≤B / A≤10.0, Formula 3 0.05≤A2 / A1≤0.50, Formula 4 0.05≤B2 / B1≤0.

50.

19. The method for preparing a release film according to claim 17, wherein: The ratio (Y / X) of the peeling force (X) to the peeling force (Y) of the release layer satisfies the following formula 2, wherein the peeling force (X) is the peeling force of the release layer from the ceramic green sheet at a temperature of 25° C. and a relative humidity of 50%, and the peeling force (Y) is the peeling force of the release layer from the ceramic green sheet at a temperature of 60° C. and a relative humidity of 90%, Formula 2 1.0≤Y / X≤2.0.

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