Release film

Abstract

A release film comprising a polyester film substrate and a release layer, wherein a surface layer of the substrate is made of a polyester containing an antimony compound, an alkaline-earth metal compound, and a phosphorus compound, the surface layer has an intrinsic viscosity of 0.55 or greater, the surface layer has an antimony atom content of 120 ppm or less, the surface of the release layer has a surface free energy of 15-25 mJ / m2, the surface of the release layer has a region surface average roughness (Sa) of 7 nm or less and a maximum projection height of 100 nm or less, and the release layer has a thickness of 0.005-1.2 μm, the release layer being formed from a release-layer formation composition containing an ultraviolet-curable compound.

Description

Release film

[0001] The present invention relates to a release film for molding resin sheets, and more particularly to a release film used when molding thin resin sheets.

[0002] Conventionally, release films, which use a polyester film as a base material and laminate a release layer on top of it, have been used as process films for molding resin sheets such as adhesive sheets, cover films, polymer films, and optical lenses.

[0003] Furthermore, in recent years, there has been a demand for release films used in the manufacturing of semiconductor products. Additionally, these release films are also in demand for use in the production of ceramic green sheets.

[0004] The aforementioned release film is also used as a process film for molding ceramic green sheets, which require high smoothness for multilayer ceramic capacitors, ceramic substrates, and other applications. In recent years, with the miniaturization and increase in capacitance of multilayer ceramic capacitors, there has been a trend towards thinner ceramic green sheets. Ceramic green sheets are molded by coating a slurry containing ceramic components such as barium titanate and a binder resin onto a release film and drying it. After printing electrodes onto the molded ceramic green sheet and peeling it off the release film, the ceramic green sheets are laminated, pressed, fired, and external electrodes are applied to manufacture a multilayer ceramic capacitor.

[0005] When molding a ceramic green sheet onto the surface of a polyester film substrate's release layer, the wettability and smoothness of the release film during ceramic slurry application, as well as the peelability when removing the ceramic green sheet from the release film, become crucial. Poor smoothness can lead to problems such as pinhole formation, uneven thickness, and sheet defects in the ceramic green sheet obtained after slurry application and drying.

[0006] In recent years, ceramic green sheets have become thinner, and there is a growing demand for ceramic green sheets with a thickness of 1.0 μm or less, more specifically, 0.2 μm to 1.0 μm. As a result, the requirements for smoothness in release films have increased even further.

[0007] Similarly, when using a flexible resin film as a dielectric in a film capacitor process, poor smoothness can lead to problems such as pinhole formation, uneven thickness, and sheet defects in the resin sheet.

[0008] As a release film with excellent smoothness, Patent Document 1 specifies that the number of protrusions of 1 μm or more is 1 per meter. ２ A release film is disclosed, characterized in that a release layer is provided on the following film.

[0009] Furthermore, Patent Document 2 discloses a method for manufacturing a biaxially oriented polyester film, characterized by lateral stretching in a stent oven where the number of dust particles is below a certain number.

[0010] Japanese Patent Publication No. 2007-237497 Japanese Patent Publication No. 2009-012242

[0011] However, the technology described in Patent Document 1 is a technique for suppressing protrusions of 1 μm or more, and in recent ceramic green sheets and film capacitors with thicknesses of 0.2 μm to 1.0 μm, it is necessary to suppress protrusions that are shorter than those previously described.

[0012] Furthermore, the biaxially oriented polyester film described in Patent Document 2 requires essential cleaning of the inside and outside of the coating machine and the stent oven. The number of protrusions on the film produced before cleaning is high, and the number of protrusions may vary depending on the location and cleaning conditions. Moreover, the protrusions that can be reduced by cleaning are limited to those caused by PET chips and foreign matter from disturbances adhering to or incorporated into the release layer surface. It is impossible to reduce the protrusions present in the polyester film substrate itself.

[0013] The inventors discovered that reducing the amount of antimony compound used during the manufacturing of the surface layer of a polyester film substrate suppresses the formation of protrusions on the surface of the polyester film substrate.

[0014] Based on these findings, further research revealed that by reducing the amount of antimony compound used in the production of the polyester film substrate surface layer, while adjusting the polymerization time or performing additional solid-phase polymerization, it is possible to suppress the formation of protrusions and achieve high longitudinal breaking strength and low thermal shrinkage stability of the polyester film substrate. This led to the completion of the present invention.

[0015] The present invention typically encompasses the following embodiments.

[0016] [1] A release film having a polyester film substrate and a release layer, wherein the polyester film substrate comprises a surface layer (layer A) and a smooth-slip layer (layer B) containing polyester resin and lubricant particles, wherein the surface layer is made of polyester containing an antimony compound, an alkaline earth metal compound and a phosphorus compound, the intrinsic viscosity of the surface layer is 0.55 or more, the antimony atom content of the surface layer is 120 ppm or less, and the surface free energy of the surface of the release layer is 15 to 25 mJ / m ２ The release film is characterized in that the average surface roughness (Sa) of the surface of the release layer is in the range of 7 nm or less, the maximum protrusion height is in the range of 100 nm or less, the thickness of the release layer is 0.005 μm to 1.2 μm, and the release layer is formed from a release layer forming composition, the release layer forming composition contains an ultraviolet-curable compound.

[0017] [2] The number of antimony element-containing protrusions present on the surface of the surface layer of the polyester film substrate is 0.020 per cm. ２ The release film described in [1] below.

[0018] [3] The release film according to [1] or [2], wherein the release layer forming composition has a cation-curable binder a.

[0019] [4] The release film according to any one of [1] to [3], wherein the release layer forming composition has a release agent b.

[0020] [5] The release film according to any one of [1] to [4], wherein the cation-curable binder a contains at least one compound selected from compounds having an alicyclic epoxy group or an oxetanyl group.

[0021] [6] The release film according to any one of [1] to [5], wherein the release agent b contains a cation-curable polydimethylsiloxane.

[0022] [7] The release film according to any one of [1] to [6], wherein the release layer-forming composition contains a cation-curable binder a and a release agent b, and the content of the release agent b is 0.01 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the solid content of the binder a and the release agent b.

[0023] [8] The release film according to any one of [1] to [7], wherein the intrinsic viscosity of the surface layer is 0.55 to 0.62 dl / g.

[0024] [9] The release film according to any one of [1] to [8], wherein the number of protrusions containing antimony element present on the surface of the surface layer is 0.020 pieces / cm ２ or less.

[0025]

[10] The release film according to any one of [1] to [9], wherein the release film is for manufacturing a ceramic green sheet or a resin sheet.

[0026] The release film of the present invention is a release film having a release layer on one surface of a base film, and the number of protrusions derived from an antimony compound on the surface of the release layer is controlled.

[0027] The present invention can provide a release film capable of coating a resin sheet-forming slurry without defects, without deteriorating the high breaking strength and thermal shrinkage in the longitudinal direction of the release film, and particularly capable of forming a ceramic green sheet without defects.

[0028] Further, the release film of the present invention can prevent pinholes, partial thickness variations, etc., even when a ceramic green sheet or a resin sheet is thinned.

[0029] In this specification, the phrase "contains" is used to include the phrases "essentially consist of" and "consist of".

[0030] In the numerical ranges described stepwise in this specification, the upper or lower limit of a numerical range in a given step may be arbitrarily combined with the upper or lower limit of a numerical range in that paragraph or in another step. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of a numerical range may be replaced with a value shown in the example or a value that can be uniquely derived from the example.

[0031] In this specification, numbers enclosed in "~" represent a numerical range that includes the numbers before and after "~" as the lower and upper limits, respectively. For example, "1 to 10 mass%" is synonymous with "1 mass% or more, and 10 mass% or less."

[0032] In this specification, with respect to numerical ranges, "~" means greater than or equal to the leftmost number and less than or equal to the rightmost number. For example, "0.5~10 mass%" and "0.5 mass%~10 mass%" both mean "0.5 mass% or more and 10 mass% or less." Also, with respect to numerical ranges, "greater than or equal to" means "the same as or greater than," and "less than or equal to" means "the same as or less than."

[0033] A release film may consist of a polyester film that serves as a base material (hereinafter also simply referred to as a base film) and a release layer laminated on the surface of the film. The laminated biaxially oriented polyester film of the present invention is a base film for release films.

[0034] (Laminated biaxially oriented polyester film for release film) The base film of the present invention includes at least a surface layer (hereinafter also referred to as layer A) and a smooth-slip layer (hereinafter also referred to as layer B). The surface layer is one outermost layer of the base film, and the smooth-slip layer is the other outermost layer. In addition to the surface layer and the smooth-slip layer, the base film preferably includes an intermediate layer (hereinafter also referred to as layer C) between the surface layer and the smooth-slip layer. Therefore, the layer configuration in the thickness direction of the base film can be A / B or A / C / B. The release layer is formed on the surface layer to constitute the release film. Therefore, the layer configuration in the thickness direction of the release film can be release layer / A / B or release layer / A / C / B. Since the intermediate layer is less expensive than the surface layer and the smooth-slip layer, including the intermediate layer can reduce the thickness of the surface layer and the smooth-slip layer, making the base film less expensive.

[0035] The thickness ratio of the surface layer may be 30% to 50% of the total layer. The thickness of the surface layer may be 3.6 μm to 50 μm, preferably 4.5 μm to 40 μm. The thickness of the smooth layer may be 3.6 μm to 50 μm, preferably 4.5 μm to 40 μm. The thickness of the intermediate layer may be 3.6 μm to 50 μm, preferably 4.5 μm to 40 μm. The thickness of the base film may be 12 μm to 100 μm, preferably 15 μm to 80 μm. The film thickness is not particularly limited and can be measured by known methods, but it can be observed and measured using an optical interference film thickness gauge or by observing the cross-section with a scanning electron microscope or transmission electron microscope.

[0036] The base film of the present invention is a laminated biaxially oriented polyester film for release films, having a surface layer for lamination of a release layer, and a smooth layer containing lubricant particles and a polyester resin, wherein the surface layer contains a polyester resin containing an antimony compound, an alkaline earth metal compound, and a phosphorus compound, the intrinsic viscosity of the surface layer is 0.55 dl / g or more, and the antimony element content of the surface layer may be 120 ppm or less.

[0037] The antimony compound contained in the surface layer can be used alone or in combination of two or more types. The antimony compound may be an antimony salt of an aliphatic carboxylic acid. The antimony salt of the aliphatic carboxylic acid may be antimony trioxide, antimony pentoxide, antimony acetate, etc., and antimony trioxide is preferred in terms of polycondensation reactivity, the color of the resulting polymer, and its low cost.

[0038] The antimony compound content in the surface layer may be such that the antimony element content in the surface layer is 120 ppm or less. The antimony element content is preferably 110 ppm or less, and more preferably 90 ppm or less. The antimony element content in the surface layer can be determined using an ICP emission spectrometer. Specifically, it can be determined by the method described in the examples.

[0039] The alkaline earth metal compounds contained in the surface layer can be used individually or in combination of two or more. Magnesium compounds are preferred among the alkaline earth metal compounds. Magnesium compounds may be saturated aliphatic carboxylates, unsaturated aliphatic carboxylates, aromatic carboxylates, halogen-containing carboxylates, hydroxycarboxylates, sulfates, nitric acid, phosphoric acid, phosphonic acid, hydrogen phosphate, hydrogen sulfide, sulfite, thiosulfate, hydrochloric acid, hydrobromic acid, chloric acid, bromate, inorganic salts, organic sulfonates, organic sulfates, chelate compounds, and oxides of magnesium metal. From the viewpoint of ease of handling and availability, saturated aliphatic carboxylates of magnesium metal are preferred, and magnesium acetate is more preferred.

[0040] The content of alkaline earth metal compounds in the surface layer can be as follows: 200 ppm or less, 160 ppm or less, 100 ppm or less, 80 ppm or less, 60 ppm or less, 5 to 200 ppm, 5 to 160 ppm, etc., with 5 to 100 ppm being preferred, 5 to 80 ppm being more preferred, and 5 to 60 ppm being even more preferred. The content of alkaline earth metal elements in the surface layer can be determined by an ICP emission spectrometer. Specifically, it can be determined by the method described in the examples.

[0041] The phosphorus compound contained in the surface layer can be used alone or in combination of two or more. Examples of the phosphorus compound include phosphoric acid, phosphorous acid, phosphonic acid, and their derivatives. Specific examples include phosphoric acid, trimethyl phosphate, tributyl phosphate, triphenyl phosphate, monomethyl phosphate, dimethyl phosphate, monobutyl phosphate, dibutyl phosphate, phosphorous acid, trimethyl phosphite, tributyl phosphite, methylphosphonic acid, dimethyl methylphosphonate, diethyl ethylphosphonate, dimethyl ethylphosphonate, dimethyl phenylphosphonate, diethyl phenylphosphonate, diphenyl phenylphosphonate, etc. Among these, trimethyl phosphate, diethyl ethylphosphonate, and / or phosphoric acid are preferred, and trimethyl phosphate is more preferred.

[0042] The content of the phosphorus compound in the surface layer can be an amount such that the phosphorus element content in the surface layer is 50 ppm or less, 40 ppm or less, 30 ppm or less, etc. An amount of 1 to 50 ppm is preferred, an amount of 1 to 40 ppm is more preferred, and an amount of 1 to 30 ppm is even more preferred.

[0043] The number of foreign substances having a major diameter of 1 μm or more contained in the surface layer can be 20 pieces / mm ２ or less. The foreign substances having a major diameter of 1 μm or more can be catalyst residues, dust, etc. mixed in the surface layer. The number of foreign substances having a major diameter of 1 μm or more is preferably 15 pieces / mm ２ or less, more preferably 10 pieces / mm ２ or less, and even more preferably 6 pieces / mm ２ or less. In the present invention, the amount of such foreign substances can be reduced by reducing the amount of the antimony compound used in the production process of the polyester resin constituting the surface layer.

[0044] The number of protrusions containing antimony element present on the surface of the surface layer can be identified by observing the surface layer with a confocal microscope. Specifically, it can be identified by the method described in the examples.

[0045] The number of protrusions containing antimony element present on the surface of the surface layer is 0.020 pieces / cm ２ or less, 0.015 pieces / cm ２ or less, 0.012 pieces / cm ２Below, 0.001 to 0.020 pieces / cm ２ , 0.001~0.015 pieces / cm ２ , 0.001~0.012 pieces / cm ２ , 0.003~0.020 pieces / cm ２ , 0.003~0.015 pieces / cm ２ , 0.003~0.012 pieces / cm ２ This can range from 0.005 to 0.020 particles / cm². ２ Preferably, 0.005 to 0.015 pieces / cm ２ More preferably, 0.005 to 0.012 pieces / cm ２ This is even more preferable. The number of protrusions containing antimony elements is determined by observing the surface of the surface layer with a scanning white-light interference microscope (magnification 10x), processing the obtained microscope image with the surface analysis software VS-Viewer Version 10.0.3.0 built into the microscope, and measuring the number of protrusions with a height of 0.1 μm or more. Elemental analysis is then performed on the areas where protrusions with a height of 0.1 μm or more were measured using a digital microscope equipped with a laser analysis function, and the number of protrusions with a height of 0.1 μm or more in which antimony elements were detected is measured. The number of measured protrusions is then measured over an observation area (210 mm × 297 mm: area approximately 623.7 cm²). ２ It can be obtained by dividing by ). Specifically, it can be identified by the method described in the examples.

[0046] The antimony content in the surface layer may be 120 ppm or less. Preferably, the antimony content is 110 ppm or less, and more preferably 90 ppm or less. The antimony content in the surface layer can be determined using an ICP emission spectrometer. Specifically, it can be determined by the method described in the examples. A preferred antimony content is 5 ppm or more. If the content is lower, polymerization may not proceed, and the release film may not exhibit its intended performance as a substrate.

[0047] The alkaline earth metal element content in the surface layer can be 200 ppm or less, 160 ppm or less, 100 ppm or less, 80 ppm or less, 60 ppm or less, 5 to 200 ppm, 5 to 160 ppm, etc., with 5 to 100 ppm being preferred, 5 to 80 ppm more preferred, and 5 to 60 ppm even more preferred. Alkaline earth metal elements may form foreign matter in the surface layer. The alkaline earth metal element content in the surface layer can be determined by an ICP emission spectrometer. Specifically, it can be determined by the method described in the examples.

[0048] The phosphorus content in the surface layer can be 50 ppm or less, 40 ppm or less, 30 ppm or less, etc., with 1 to 50 ppm being preferred, 1 to 40 ppm more preferred, and 1 to 30 ppm even more preferred. The phosphorus content in the surface layer can be determined by an ICP emission spectrometer. Specifically, it can be determined by the method described in the examples.

[0049] A sample (10 g) obtained by scraping the surface layer was dissolved in a p-chlorophenol / tetrachloroethane mixture (80 ml), and the resulting solution was filtered under reduced pressure using a membrane filter. The filtered filter was then dried, and the number of particles on the resulting dried filter was measured per 1 mm of the membrane filter. ２ The number of particles per unit may be 400 or less. Hereinafter, the dissolving solution will also be simply referred to as the "dissolving solution," and the drying filter as the "drying filter." The number of particles on the drying filter is as follows: 1 mm of membrane filter ２ The number of winning tickets is preferably 350 or less, more preferably 300 or less, and even more preferably 200 or less.

[0050] Here, the p-chlorophenol / tetrachloroethane mixture consists only of p-chlorophenol and tetrachloroethane, with a mass ratio of 3 parts p-chlorophenol to 1 part tetrachloroethane. The membrane filter has an average pore size of 0.5 μm, is made of polytetrafluoroethylene, is circular with a diameter of 47 mm, and has a thickness of 90 μm. The membrane filter may be, for example, the T050A047A manufactured by ADVANTEC.

[0051] In this invention, the number of such particles can be reduced by reducing the amount of antimony compound used in the manufacturing process of the polyester resin constituting the surface layer. The number of particles on the dry filter can be determined by observing the dry filter at a magnification of 1,000x using a scanning electron microscope (SEM). Specifically, it can be determined by the method described in the examples.

[0052] The antimony element content of the particles filtered on the dry filter may be 10 mg or less per 1 kg of surface layer. Preferably, the antimony element content is 6 mg or less per 1 kg of surface layer, more preferably 5 mg or less, and even more preferably 4 mg or less. The antimony element content may be 0.1 to 10 mg, 0.1 to 6 mg, 0.1 to 5 mg, 0.1 to 4 mg, etc., per 1 kg of surface layer. The antimony element content of the particles filtered on the dry filter can be determined by measuring the amount of Sb element per 10 g of surface layer using fluorescent X-rays on the particles on the dry filter, and then converting this to the amount per 1 kg of polyester film. Specifically, it can be determined by the method described in the examples.

[0053] In the particles filtered on the dry filter, the proportion of particles containing antimony may be 30% or less. Preferably, the proportion of particles containing antimony on the dry filter is 28% or less, more preferably 25% or less, and even more preferably 20% or less. The proportion of particles containing antimony can be determined by performing elemental analysis of the particles on the dry filter using a scanning electron microscope (SEM) at a magnification of 1,000x, counting the number of particles in which Sb is detected (Sb-containing particles), and calculating the proportion (%) of Sb-containing particles by dividing the number of particles in which Sb is detected by the total number of particles on the dry filter. Specifically, it can be determined by the method described in the examples.

[0054] The number of particles filtered out on the dry filter is per 1 mm of filter. ２The number of particles per filter may be 500 or less, preferably 400 or less, more preferably 350 or less, and even more preferably 200 or less. The number of particles filtered out on the dry filter can be determined by observing the dry filter at a magnification of 1,000x using a scanning electron microscope (SEM) and measuring the number of particles. Specifically, it can be determined by the method described in the examples.

[0055] The intrinsic viscosity of the surface layer and the base film may be 0.55 dl / g or higher, respectively. The intrinsic viscosity can be controlled by adjusting the polymerization conditions of the polyester resin constituting the surface layer (polymerization time, addition of solid-phase polymerization, etc.). The intrinsic viscosity may be 0.56 dl / g or higher, 0.57 dl / g or higher, 0.58 dl / g or higher, 0.55 to 0.62 dl / g, 0.56 to 0.62 dl / g, 0.57 to 0.62 dl / g, or 0.58 to 0.62 dl / g. When the intrinsic viscosity is within the above range, it is advantageous in that the breaking strength of the base film is increased and the thermal shrinkage rate of the base film is reduced. The intrinsic viscosity can be determined in accordance with JIS K 7367-5. The measurement is performed by using a mixed solvent of phenol (6 parts by weight) and 1,1,2,2-tetrachloroethane (4 parts by weight) on a sample obtained by scraping the surface layer or on a substrate film, at a temperature of 30°C. Specifically, it can be determined by the method described in the examples.

[0056] The longitudinal thermal shrinkage rate of the base film under the heat conditions of 150°C for 30 minutes may be 1.4% or less. The longitudinal thermal shrinkage rate can be controlled by adjusting the intrinsic viscosity of the polyester resin constituting the surface layer. The longitudinal thermal shrinkage rate is preferably 1.0% or less, and more preferably 0.9% or less. When the longitudinal thermal shrinkage rate is within the above range, excellent dimensional stability at high temperatures is achieved. In the manufacture of internal electrodes for capacitors, a conductive paste is applied to a release film, dried to form a conductive layer, and the internal electrodes are printed on the conductive layer. Therefore, a small longitudinal thermal shrinkage rate of the base film at high temperatures contributes to suppressing thermal shrinkage of the release film, etc., making it easier to print and form the internal electrodes with high precision. The longitudinal thermal shrinkage rate can be determined by heat-treating a base film with a width of 10 mm and a longitudinal length of 220 mm in a hot air oven at 150°C for 30 minutes and comparing the longitudinal dimensions before and after heat treatment. Specifically, it can be determined by the method described in the examples.

[0057] The longitudinal breaking strength of the base film can be 170 MPa or more, 180 MPa or more, or 190 MPa or more. A breaking strength of 170 to 300 MPa is preferred, 180 to 280 MPa is more preferred, and 190 to 260 MPa is even more preferred. Having a longitudinal breaking strength within this range is advantageous because it reduces the likelihood of defects such as cracking, tearing, folding, or ripping during the processing and use of the base film. The longitudinal breaking strength can be determined by measurement in accordance with JIS K 7127. Specifically, it can be determined by the method described in the examples.

[0058] The surface layer may be a film made of polyester resin (preferably polyethylene terephthalate). Therefore, the surface layer may contain polyester resin (preferably polyethylene terephthalate). The polyester resin content in the surface layer may be 70 to 100% by mass, 80 to 100% by mass, etc., preferably 90 to 100% by mass, and more preferably 95 to 100% by mass.

[0059] Polyester resin, the raw material for the surface layer, can be produced by a direct reaction between dicarboxylic acid and glycol, a transesterification method in which alkyl esters of dicarboxylic acid (e.g., dialkyl esters (e.g., dimethyl ester, diethyl ester, dibutyl ester)) are transesterified with glycol followed by polycondensation, or by polycondensation of diglycol esters of dicarboxylic acid. For example, polyethylene terephthalate can be produced by an esterification or transesterification reaction of terephthalic acid or dimethyl terephthalate with ethylene glycol to produce an oligomer mixture such as bis(2-hydroxyethyl) terephthalate, which can then be produced by melt polymerization using a catalyst under high temperature and vacuum. In addition, the molten polymer can be solid-phase polymerized at a temperature below its melting point. By performing solid-phase polymerization after melt polymerization, the generation of foreign matter with a major diameter of 1 μm or more and antimony-based foreign matter (particles containing antimony elements) can be suppressed while increasing the intrinsic viscosity and lowering the acid value.

[0060] Dicarboxylic acids can be used individually or in combination of two or more. Dicarboxylic acids may be aromatic dicarboxylic acids, aliphatic dicarboxylic acids, etc., with aromatic dicarboxylic acids being preferred.

[0061] Aromatic carboxylic acids can be terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid (e.g., 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid), 4,4'-biphenyldicarboxylic acid, 4,4'-biphenylsulfondicarboxylic acid, 4,4'-biphenyletherdicarboxylic acid, 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid, pamoic acid, anthracenedicarboxylic acid, etc. Terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid are preferred, with terephthalic acid being more preferred.

[0062] Aliphatic dicarboxylic acids can be saturated aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, tetradecanedicarboxylic acid, hexadecanedicarboxylic acid, 1,3-cyclobutanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, and dimer acid; or unsaturated aliphatic dicarboxylic acids such as fumaric acid, maleic acid, and itaconic acid.

[0063] Diols can be used individually or in combination of two or more. Diols may be aliphatic glycols, aromatic glycols, etc., with aliphatic glycols being preferred.

[0064] Diols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediethanol, 1,10-decamethylene glycol, and 1,12-dodecanediol. These may be alkylene glycols such as polyethylene glycol, polytrimethylene glycol, polytetramethylene glycol, etc.; aliphatic glycols such as polyethylene glycol, polytrimethylene glycol, polytetramethylene glycol, etc.; and aromatic glycols such as hydroquinone, 4,4'-dihydroxybisphenol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4-bis(β-hydroxyethoxyphenyl)sulfone, bis(p-hydroxyphenyl)ether, bis(p-hydroxyphenyl)sulfone, bis(p-hydroxyphenyl)methane, 1,2-bis(p-hydroxyphenyl)ethane, bisphenol A, bisphenol C, 2,5-naphthalenediol, and glycols obtained by adding ethylene oxide to these glycols, with ethylene glycol being preferred.

[0065] The surface layer may be polyethylene terephthalate film, polytrimethylene terephthalate film, polybutylene terephthalate film, or polyethylene-2,6-naphthalate film, with polyethylene terephthalate film being preferred. Therefore, the polyester resin constituting the surface layer may be polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, or polyethylene-2,6-naphthalate, with polyethylene terephthalate being preferred.

[0066] The polyester resin constituting the surface layer is preferably a polyester resin in which the main dicarboxylic acid component is terephthalic acid, or a polyester resin in which the main diol component is ethylene glycol, and more preferably a polyester resin (polyethylene terephthalate) in which the main dicarboxylic acid component is terephthalic acid and the main diol component is ethylene glycol.

[0067] Here, the main dicarboxylic acid component means that, when the total dicarboxylic acid component in the polyester resin is set to 100 mol%, the dicarboxylic acid or its ester component is 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 100 mol%.

[0068] Furthermore, the term "main diol component" means that, when the total diol component in the polyester resin is considered to be 100 mol%, the diol component is 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, and even more preferably 100 mol%.

[0069] Polymerization catalysts may be used in melt polymerization for the production of polyester resins. Polymerization catalysts may be used individually or in combination of two or more types. Antimony compounds are preferred as polymerization catalysts. Antimony compounds may be used individually or in combination of two or more types. Antimony compounds may be antimony salts of aliphatic carboxylic acids. Antimony salts of aliphatic carboxylic acids may be antimony trioxide, antimony pentoxide, or antimony acetate, and antimony trioxide is preferred in terms of polycondensation reactivity, the color of the resulting polymer, and its low cost. Catalysts other than antimony compounds include alkaline earth metal compounds, manganese compounds, cobalt compounds, aluminum compounds, titanium compounds, titanium / silicon composite oxides, and germanium compounds. Catalysts other than antimony compounds may be used as long as they do not cause problems with the surface layer properties.

[0070] When manufacturing polyester resins, it is preferable to add alkaline earth metals. Alkaline earth metal compounds can be used individually or in combination of two or more. Magnesium compounds are preferred among the alkaline earth metal compounds. Magnesium compounds can be saturated aliphatic carboxylates, unsaturated aliphatic carboxylates, aromatic carboxylates, halogen-containing carboxylates, hydroxycarboxylates, sulfates, nitric acid, phosphoric acid, phosphonic acid, hydrogen phosphate, hydrogen sulfide, sulfite, thiosulfate, hydrochloric acid, hydrobromic acid, chloric acid, bromate, inorganic salts selected from these, organic sulfonates, organic sulfates, chelate compounds, and oxides of magnesium metal. From the viewpoint of ease of handling and availability, saturated aliphatic carboxylates of magnesium metal are preferred, and magnesium acetate is more preferred.

[0071] When manufacturing polyester resins, it is preferable to add a phosphorus compound as a heat stabilizer. The phosphorus compound may be used alone or in combination of two or more. Examples of phosphorus compounds include phosphoric acid, phosphorous acid, phosphonic acid, and their derivatives. Specific examples include phosphoric acid, trimethyl phosphate, tributyl phosphate, triphenyl phosphate, monomethyl phosphate, dimethyl phosphate, monobutyl phosphate, dibutyl phosphate, phosphorous acid, trimethyl phosphorous acid, tributyl phosphorous acid, methylphosphonic acid, dimethyl methylphosphonate, diethyl ethylphosphonate, dimethyl phenylphosphonate, dimethyl phenylphosphonate, diethyl phenylphosphonate, and diphenyl phenylphosphonate. Among these, trimethyl phosphate, diethyl ethylphosphonate, and / or phosphoric acid are preferred, with trimethyl phosphate being more preferred.

[0072] When manufacturing polyester resin, various compounds and additives may be added, as long as they do not cause problems with the properties of the resulting surface layer.

[0073] An example of the manufacturing process for the polyester resin constituting the surface layer is as follows. Note that the polyester resin described below is polyethylene terephthalate. The present invention may be a method for manufacturing a biaxially oriented polyester film for the surface layer constituting a release film, comprising the following steps 1 to 3.

[0074] [Step 1] A step to obtain a polyester resin by melt polymerization using terephthalic acid as the dicarboxylic acid component, ethylene glycol as the diol component, and an antimony compound as the main polymerization catalyst.

[0075] [Step 2] Optionally, a step to obtain a polyester resin by solid-phase polymerization of the polyester resin obtained in Step 1 at 197 to 225°C for 5 to 10 hours.

[0076] [Step 3] A step of stretching the polyester resin obtained in Step 1 or 2 to obtain a biaxially oriented polyester film for the surface layer that constitutes the release film.

[0077] Melt polymerization may be carried out by a batch polymerization method or a continuous polymerization method. In either method, the esterification reaction or transesterification reaction may be carried out in one step, but it is preferable to carry it out in multiple steps. In the melt polymerization reaction, the number and size of reactors and the manufacturing conditions of each step can be selected as appropriate without limitation, and it may be carried out in one step or in multiple steps, preferably in 2 to 5 steps, more preferably in 3 to 4 steps, and even more preferably in 3 steps. The melt polymerization reaction is preferably carried out in a continuous reactor. A continuous reactor is a method in which the reaction vessel for the esterification reaction or transesterification reaction and the melt polymerization reaction vessel are connected by piping, and raw materials are continuously fed into each reaction vessel, transferred to the melt polymerization reaction vessel via piping, and resin is withdrawn from the melt polymerization reaction vessel without allowing each reaction vessel to be emptied.

[0078] The process for the continuous polymerization method is as follows:

[0079] 1) Slurry preparation step: The dicarboxylic acid component and the diol component are introduced into the slurry preparation tank to prepare the slurry. The proportion of these components in the slurry is not particularly limited as long as the slurry has sufficient fluidity to be transported to the esterification reaction tank. Furthermore, from an economic standpoint, it is preferable to reuse the diol component recovered in the polycondensation step as a slurry raw material.

[0080] Furthermore, in this invention, recycled raw materials such as dicarboxylic acid components and diol components obtained by chemical decomposition recovery methods may be used.

[0081] 2) Esterification reaction step The slurry obtained above is introduced into two or more esterification reaction vessels connected in series and subjected to an esterification reaction to obtain an oligomer compound in which diols are condensed on both terminal carboxyl groups of the dicarboxylic acid component. The esterification reaction is preferably carried out while removing the water produced by the reaction from the system using a distillation column.

[0082] The number and size of reaction vessels in the esterification reaction process can be selected as appropriate without limitation. Furthermore, the manufacturing conditions for each step can be selected as appropriate depending on the type and amount of polycondensation catalyst and additives for improving electrostatic adhesion, as well as the number and size of reaction vessels.

[0083] For example, if there are three esterification reactors, the temperature of the first esterification reactor may be 240 to 270°C, the pressure may be 100 to 160 kPa in absolute pressure, and the average residence time may be 2 to 5 hours. When solid-phase polymerization is not used, the average residence time is preferably 3.5 to 5 hours, and more preferably 3.9 to 5 hours.

[0084] The temperature of the second and third esterification reaction vessels may be 250 to 280°C, the pressure 0 to 100 kPa in absolute pressure, and the average residence time 0.1 to 2.5 hours. When solid-phase polymerization is not used, the average residence time for the second esterification reaction is preferably 1.4 to 2.5 hours, more preferably 1.5 to 2.5 hours, and the average residence time for the third esterification reaction is preferably 1.0 to 2.5 hours, more preferably 1.1 to 2.5 hours.

[0085] Ultimately, it is desirable that the esterification reaction rate reaches 60% or more, preferably 70% or more. Furthermore, the esterification reaction vessel may be one that incorporates a weir or the like to create a multi-stage reaction within a single vessel.

[0086] In the esterification process, it is preferable to supply additional diol components from the second esterification reactor onward. If the entire amount of diol components is supplied during slurry preparation, there is a problem that the composition of diol components in the polyester resin may fluctuate or the esterification reaction rate may decrease when continuous production is carried out over a long period of time. By supplying additional diol components from the second esterification reactor onward, this problem can be suppressed.

[0087] In the esterification step, phosphorus compounds, alkali metal compounds, alkaline earth metal compounds, etc., may be added. The timing of the addition can be anytime between before the esterification reaction and the start of the polycondensation reaction, but in the continuous polymerization method, it is preferable to add them in the third esterification reaction vessel or later.

[0088] When producing polyester resin by batch polymerization or continuous polymerization, methods for adding antimony compounds include powder, ethylene glycol slurry, or ethylene glycol solution, but adding it as an ethylene glycol solution is preferred. The timing of addition may be either before the esterification and transesterification reactions, or between the completion of the transesterification and esterification reactions and the start of the polycondensation reaction.

[0089] 3) Polycondensation reaction step The oligomer compound that has undergone the esterification reaction is subsequently transferred to a polycondensation reaction vessel and subjected to a polycondensation reaction. The number and size of the reaction vessels in the polycondensation reaction step are not limited and can be selected as appropriate. Furthermore, the manufacturing conditions for each step can be selected as appropriate depending on the type and amount of the polycondensation catalyst and additives, the number and size of the reaction vessels, etc. For example, if there are three polycondensation reaction vessels, the temperature of the first polycondensation reaction vessel may be 260 to 290°C, the pressure may be 2 to 8 kPa, and the average residence time may be 0.1 to 1 hour. When solid-phase polymerization is not used, the average residence time of the first polycondensation is preferably 0.8 to 1 hour, and more preferably 0.9 to 1 hour.

[0090] The temperature of the second double condensation reaction vessel may be 270 to 290°C, the pressure 0.5 to 1.5 kPa, and the average residence time 0.1 to 2 hours. When solid-phase polymerization is not used, the average residence time for the second double condensation is preferably 1.0 to 2 hours, and more preferably 1.1 to 2 hours.

[0091] The temperature of the third double condensation reactor may be 270 to 290°C, the pressure 0.01 to 0.5 kPa, and the average residence time 0.1 to 2 hours. When solid-phase polymerization is not used, the average residence time for the third double condensation is preferably 1.0 to 2 hours, and more preferably 1.1 to 2 hours.

[0092] It is preferable that the degree of increase in intrinsic viscosity achieved in each of these polycondensation reaction steps be smoothly distributed. Since diol components are distilled off during the polycondensation reaction step, it is preferable to recover, purify, and reuse them. This recovery and purification can be carried out in a distillation column, similar to the esterification reaction step.

[0093] The intrinsic viscosity of the polyester resin produced by melt polymerization is preferably 0.52 to 0.59 dl / g, and more preferably 0.52 to 0.55 dl / g. Having the intrinsic viscosity of the polyester resin within this range is advantageous because it suppresses the formation of foreign matter.

[0094] Further solid-phase polymerization of the polyester resin obtained by melt polymerization is preferable because it reduces the number of antimony element-containing protrusions and increases the longitudinal tensile strength of the base film.

[0095] Solid-phase polymerization can be carried out on polyester resin in the form of powder or granules. These granules include chips, pellets, flakes, and powders, but pellets are preferred.

[0096] Solid-phase polymerization can be carried out by heating a granular polyester resin at a temperature below the melting point of the polyester resin under the flow of an inert gas or under reduced pressure. It is preferable to carry out the solid-phase polymerization under reduced pressure. The solid-phase polymerization process may be carried out in one step or in multiple steps.

[0097] It is preferable that the granular polyester resin supplied to the solid-phase polymerization process is first heated to a temperature lower than the temperature at which solid-phase polymerization is performed to crystallize it before being supplied to the solid-phase polymerization process. The crystallization process is preferably carried out by heating the granular polyester at a temperature of 70 to 90°C for 3 to 5 hours to dry it, and then heating it to a temperature of 120 to 200°C, preferably 130 to 150°C, for 1 to 4 hours.

[0098] 4) Stretching Process The polyester resin is stretched to form a film. Stretching can improve chemical resistance, heat resistance, mechanical strength, etc. It is preferable to co-extrude a polyester resin for the surface layer, a polyester resin for the smooth layer, and, if the base film has an intermediate layer, a polyester resin for the intermediate layer, to form a two- or three-layer laminated sheet, or to form each polyester resin into a sheet (for example, melt-extrude the polyester resin into a sheet at 250 to 320°C and then solidify it), then laminate these sheets together to form a two- or three-layer laminated sheet, and then stretch these laminated sheets. A base film can be obtained by stretching the laminated sheet. Stretching can be carried out by known methods. For example, a method can be used in which the laminated sheet is sequentially or simultaneously biaxially stretched longitudinally and transversely at 70°C to 140°C, and then heat-treated at 160 to 240°C to obtain a base film. Typically, the stretching ratio can be selected from a range of 1.1 to 10 times in both the longitudinal (longitudinal) and transverse (width) directions. The stretching ratio in the longitudinal direction is preferably 2.5 to 5.0 times, more preferably 2.8 to 5.0 times, and even more preferably 3.0 to 5.0 times. The stretching ratio in the width direction is preferably 2.5 to 5.0 times, more preferably 2.8 to 5.0 times, and even more preferably 3.0 to 5.0 times. When the stretching ratio is within the above range, it is advantageous in that the thickness unevenness of the resulting base film is suppressed, and the heat resistance and mechanical strength are excellent. In this invention, the stretching ratio is defined as the actual stretching ratio of the base film. This stretching ratio can be determined by measuring the mass change rate per unit area before and after each stretching process, or by marking the unstretched film with a grid of stretching ratio markers.

[0099] The surface layer may contain particles, but from the viewpoint of reducing surface irregularities, it is preferable that it does not contain particles with an average particle diameter of 1.0 μm or more. Examples of particles include inorganic particles such as titanium dioxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, and calcium fluoride, as well as organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles. The particles may be used individually or in combination of two or more types. As particles, titanium dioxide, calcium carbonate, and silica are preferred due to their high versatility. The average particle diameter of the particles is preferably 1 nm or more and less than 1.0 μm.

[0100] The base film may have a slip-free layer on the outermost layer opposite the surface layer. The slip-free layer contains lubricant particles and polyester resin. The slip-free layer may be a film made of polyester resin (preferably polyethylene terephthalate). The slip-free layer may contain lubricant particles and polyester resin (preferably polyethylene terephthalate). The content of polyester resin in the slip-free layer may be 70-90% by mass, 80-90% by mass, 70-95% by mass, 80-95% by mass, 90-95% by mass, 70-100% by mass, 80-100% by mass, 90-100% by mass, 95-100% by mass, etc.

[0101] The smooth layer may be a biaxially oriented polyethylene terephthalate film, polytrimethylene terephthalate film, polybutylene terephthalate film, or polyethylene-2,6-naphthalate film, with polyethylene terephthalate film being preferred. Therefore, the polyester resin constituting the smooth layer may be polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, or polyethylene-2,6-naphthalate, with polyethylene terephthalate being preferred. A crosslinking agent may be used in combination with the polyester resin to make it stronger. In this case, known crosslinking agents such as isocyanate resins and melamine resins can be used.

[0102] Examples of lubricant particles contained in the smooth layer include inorganic particles such as titanium dioxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, and calcium fluoride, as well as organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles. From the viewpoint of the film's slipperiness and ease of air release, at least one particle selected from calcium carbonate particles or silica particles is preferred as the lubricant particle.

[0103] The lower limit of the particle size of the lubricant particles contained in the smooth layer is preferably 5 nm, more preferably 10 nm, and even more preferably 15 nm. A particle size of 5 nm or more is preferable as it satisfies the slipperiness requirements and does not risk causing winding misalignment. The upper limit of the particle size in the smooth layer is preferably 100 nm, more preferably 90 nm, and even more preferably 80 nm. A particle size of 100 nm or less is preferable as it reduces the surface roughness of the smooth layer and does not risk transferring large surface roughness to the release layer. The particle size of the lubricant particles can be 5 to 100 nm, 5 to 90 nm, 5 to 80 nm, 10 to 100 nm, 10 to 90 nm, 10 to 80 nm, 15 to 100 nm, 15 to 90 nm, or 15 to 80 nm.

[0104] The amount of lubricant particles contained in the smooth layer may be 5,000 to 15,000 ppm, 3,000 to 15,000 ppm, or 500 to 10,000 ppm.

[0105] The smooth layer may be formed by applying a coating solution containing a solvent, particles, and resin to a polyester film and drying it. Examples of solvents include organic solvents such as toluene, water, or a mixture of water and a water-soluble organic solvent. Preferably, from an environmental standpoint, a so-called water-based solvent, such as water alone or water mixed with a water-soluble organic solvent, is preferred.

[0106] The smoothing layer may contain surfactants to improve leveling properties during application and to defoam the coating solution. The surfactant can be cationic, anionic, or nonionic, but silicone-based, acetylene glycol-based, or fluorine-based surfactants are preferred. These surfactants should be included in the coating layer in an amount that does not cause abnormalities in the appearance of the coating due to excessive addition.

[0107] The smooth layer can be formed by depositing it on the surface layer in the case of an A / B layer configuration, or on the intermediate layer in the case of an A / C / B layer configuration, using a known method. Conventional methods such as co-extrusion or lamination can be used for film formation. Alternatively, a multilayer coater die can be used to apply a coating solution for surface layer formation and a coating solution for smooth layer formation to the intermediate layer, thereby forming the surface layer and the smooth layer.

[0108] The base film may or may not have an intermediate layer between the surface layer and the smooth-slip layer.

[0109] To reduce the cost of the base film, the intermediate layer may use, for example, a resin obtained by recycling release film. When using a recycled resin, the proportion of this resin to the polyester resin is preferably 5 to 50% by mass. The intermediate layer may be a film made of biaxially oriented polyester resin (preferably polyethylene terephthalate). The intermediate layer may contain polyester resin (preferably polyethylene terephthalate). The polyester resin content in the smooth layer may be 70 to 90% by mass, 80 to 90% by mass, 70 to 95% by mass, 80 to 95% by mass, 90 to 95% by mass, 70 to 100% by mass, 80 to 100% by mass, 90 to 100% by mass, 95 to 100% by mass, etc.

[0110] The polyester constituting the intermediate layer is not particularly limited, and a film made from polyester commonly used as an intermediate layer in release films can be used. Preferably, it is a crystalline linear saturated polyester consisting of an aromatic dibasic acid component and a diol component, and for example, polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, or copolymers mainly composed of these resin components are more preferable. In particular, a polyester film formed from polyethylene terephthalate is especially preferable. The polyethylene terephthalate preferably has 90 mol% or more, more preferably 95 mol% or more of repeating units of ethylene terephthalate, and may also have small amounts of other dicarboxylic acid components and diol components copolymerized. From a cost standpoint, it is preferable to have one manufactured only from terephthalic acid and ethylene glycol. In addition, known additives, such as antioxidants, light stabilizers, ultraviolet absorbers, and crystallizers, may be added within a range that does not hinder the effect of the base film.

[0111] (Release layer) The surface free energy of the release layer surface of the present invention is 15 to 25 mJ / m ２ The surface roughness (Sa) of the release layer surface is in the range of 7 nm or less, the maximum protrusion height is in the range of 100 nm or less, and the thickness of the release layer is 0.005 μm to 1.2 μm. The release layer is formed from a release layer forming composition, and the release layer forming composition contains an ultraviolet-curable compound. The ultraviolet-curable compound may be a cationic-curable binder a.

[0112] The present invention has a release layer on the surface of the polyester film substrate according to this specification, thereby suppressing the formation of protrusions. Furthermore, with the release layer of the present invention, the effects of the polyester film substrate can be enjoyed even when the release layer is laminated. Therefore, the release film of the present invention can also achieve high tensile strength in the longitudinal direction and low stability of thermal shrinkage.

[0113] In the present invention, the release layer is a layer formed by the curing of a release layer forming composition, and the release layer forming composition contains an ultraviolet-curable compound. In one embodiment, the ultraviolet-curable compound is a cationic-curable binder a, and for example, the release layer forming composition preferably contains a cationic-curable binder a and a release agent b.

[0114] By including a cationic curing binder a, a crosslinked coating film with a high modulus of elasticity can be formed. Increasing the modulus of elasticity of the release layer is preferable because it prevents the release layer from deforming and following the peeling process, thus reducing the risk of damage to the ceramic green sheet.

[0115] By curing the release layer using photocationic polymerization, it is possible to produce a substrate with a low volume shrinkage rate of the release film.

[0116] Furthermore, because the release film of the present invention has a substrate with high tensile strength in the longitudinal direction, the film tension can be increased during release processing, and the film transport speed can be increased. Therefore, it is possible to select a resin containing an ultraviolet-curable compound that has a faster curing reaction than thermosetting resins.

[0117] Other substances besides the resin and additives mentioned above can be added, as long as they do not impair the function of the present invention. In this invention, it is thought that the structure of the cationically curable substance changes after it has cured in the coating layer. However, it is extremely difficult to accurately describe the changed structure itself resulting from the cationically curable substance. Therefore, as stated above, "the release layer forming composition contains a cationically curable binder a and a release agent b."

[0118] (Cation-curable binder a) The release layer forming composition contains a cation-curable binder a. Preferably, the cation-curable binder a contains a compound having two or more alicyclic epoxy groups in one molecule as a cation-curable substance. Compounds having two or more alicyclic epoxy groups in one molecule are preferred because the initiation reaction in cation curing (ring-opening reaction of cyclic ether) is fast, allowing cation curing to proceed efficiently, increasing the crosslinking density of the release layer, and suppressing erosion by organic solvents. Preferably, the number of alicyclic epoxy groups contained in one molecule is two or more. Having two or more alicyclic epoxy groups is preferable because it allows for crosslinking structures between molecules, increasing the crosslinking density of the release layer and improving solvent resistance.

[0119] As the compound containing two or more alicyclic epoxy groups in one molecule of the binder a, aliphatic, aromatic, and alicyclic compounds can be suitably used. The alicyclic epoxy group ring may be introduced at any position in the terminal, side chain, or main chain. The compound used may be a monomer, oligomer, or polymer, but monomers are particularly preferred in order to increase the crosslinking density and suppress erosion of the release layer by organic solvents. Using monomers is preferable because it increases the number of crosslinking points per unit mass, thereby increasing the crosslinking density.

[0120] As the compound having two or more alicyclic epoxy groups in one molecule, commercially available products can also be used. Examples of commercially available products include Cyclomer® M100, Celoxide® 2000 (both manufactured by Daicel Corporation, monofunctional), Celoxide® 2021P, 2081 (both manufactured by Daicel Corporation, bifunctional), Epolid® GT401 (manufactured by Daicel Corporation, tetrafunctional), EHPE® 3150 (manufactured by Daicel Corporation, polyfunctional), and KR-470 and X-40-2669, manufactured by Daicel Corporation and Shin-Etsu Chemical Co., Ltd., respectively.

[0121] Examples of alicyclic epoxy compounds included in binder a include those incorporating an ester skeleton, alkyl skeleton, dicyclopentadiene skeleton, fluorene skeleton, ε-caprolactone skeleton, siloxane skeleton, cyclic siloxane, etc., but other skeletons may also be present. The compound used may be a monomer, oligomer, or polymer, but for the same reasons as described above, it is particularly preferable to use a monomer in order to increase the crosslinking density and suppress erosion of the release layer by organic solvents.

[0122] The release layer forming composition may contain two or more alicyclic epoxy compounds in one molecule, in addition to a compound having an oxetanyl group (sometimes referred to as a compound having an oxetane ring). In one embodiment, it may contain at least one compound selected from alicyclic epoxy compounds or compounds having an oxetane ring. Preferably, the cationic curable binder a contains at least one compound selected from alicyclic epoxy compounds or compounds having an oxetanyl group.

[0123] Compounds containing an oxetane ring undergo a faster growth reaction in cationic curing than compounds containing two or more alicyclic epoxy groups in one molecule. Therefore, by using them in combination with compounds containing two or more alicyclic epoxy groups in one molecule, the crosslinking density of the release layer can be further increased, improving solvent resistance. There are no particular restrictions on the number of functional groups in a compound containing an oxetane ring (the number of compounds containing an oxetane ring contained in one molecule); it may be one or two or more, but two or more is preferable because it allows for the formation of a crosslinked structure.

[0124] Examples of compounds containing an oxetane ring in the release layer forming composition include those incorporating an ester skeleton, alkyl skeleton, dicyclopentadiene skeleton, fluorene skeleton, ε-caprolactone skeleton, siloxane skeleton, etc., but other skeletons may also be present. The compound used may be a monomer, oligomer, or polymer, but for the same reasons as described above, it is particularly preferable to use a monomer in order to increase the crosslinking density and suppress erosion of the release layer by organic solvents.

[0125] As the oxetane ring compound mentioned above, commercially available products can also be used. Examples of commercially available products include OXT221, OXT-121 (both manufactured by Toagosei Co., Ltd.), ETERNACOL® OXTP, OXBP (both manufactured by Ube Industries, Ltd.).

[0126] The content of a compound having two or more alicyclic epoxy groups in one molecule in binder a is preferably 50 parts by mass or more and 100 parts by mass or less, and more preferably 75 parts by mass or more and 99 parts by mass or less, when the total mass of binder a is 100 parts by mass. A content of 50 parts by mass or more is preferable because it can increase the crosslinking density of the release layer and suppress erosion of the release layer without sufficient curability even with a thick film thickness.

[0127] The molecular weights of the compounds having two or more alicyclic epoxy groups in one molecule and the compounds having an oxetane ring are preferably 100,000 or less, more preferably 10,000 or less, and most preferably 1,000 or less. A molecular weight of 100,000 or less is preferable because it prevents the viscosity of the coating solution from becoming excessively high, and a uniform film is formed after coating and drying on the film. However, if the molecular weight is too low, care must be taken because the boiling point is low, which may cause some of the resin to volatilize when the diluting solvent dries. Specifically, a boiling point of 130°C or higher is preferable.

[0128] The release layer of the present invention preferably contains 80% to 99.9% by mass of binder a, which is a cationic curable substance, relative to the total solid content of the release layer. More preferably, it contains 90% to 99.9% by mass, and even more preferably, 93% to 99.9% by mass. Containing 80% by mass or more of binder a is preferable because it allows for a high crosslinking density to be obtained through a cationic polymerization reaction, thereby suppressing erosion of the release layer by organic solvents. In this case, the total solid content of the release layer is calculated by considering the sum of the solid content of cationic curable binder a and release agent b as 100 parts by mass, since it is difficult to accurately calculate the trace amount of acid generator that remains in the release layer after decomposition during the drying process or under active energy ray irradiation.

[0129] (Acid Generator) In the present invention, it is preferable to use an acid generator in the release layer to promote the cationic polymerization reaction. It is preferable to use a photoacid generator or a thermal acid generator as the acid generator, and more preferably a photoacid generator that generates acid under active energy ray irradiation is preferable because it can reduce the amount of heat during processing. Although it is possible to increase the crosslinking density of the release layer and obtain a release layer with high solvent resistance by using general acids such as sulfonic acid or carboxylic acid, a high processing temperature is required, which may cause the surface of the release layer to become rough due to thermal shrinkage of the raw material and a decrease in smoothness. In addition, metal salt-based, phosphate ester-based, and block-type acid generators in which the acid portion is blocked can also be used, but for the reasons mentioned above, it is most preferable from the viewpoint of the amount of heat during processing.

[0130] While there are no particular limitations on the photoacid generator, and general-purpose agents can be used, it is preferable from the viewpoint of reactivity to use a salt consisting of an onium ion and a non-nucleophilic anion. Alternatively, organometallic complexes such as iron arene complexes or carbocation salts such as tropylium may be used, as well as anthracene derivatives or phenols substituted with electron-withdrawing groups, such as pentafluorophenol.

[0131] When a salt consisting of the onium ion and a non-nucleophilic anion is used as a photoacid generator, iodonium, sulfonium, and ammonium can be used as the onium ion. The organic group of the onium ion is not particularly limited, but triaryl, diaryl (monoalkyl), monoaryl (dialkyl), and trialkyl groups may be used, and benzophenone or 9-fluorene may be introduced, or other organic groups may be used. As the non-nucleophilic anion, hexafluorophosphorate, hexafluoroantimonate, hexafluoroborate, and tetra(pentafluorophenyl)borate are preferred from the viewpoint of reactivity. In addition, tetra(pentafluorophenyl)gallium ions or anions obtained by replacing the fluorine anion of the aforementioned nucleophilic anion with any number of perfluoroalkyl groups or organic groups may be used, or other anionic components may be used.

[0132] Examples of commercially available photoacid generators include CPI® 100P, 101A, 210S, 300 (all manufactured by Sunapro Co., Ltd.), IRGACURE® 250, 270, 290 (all manufactured by BASF Corporation), UV9380C (manufactured by Momentive Performance Materials), CAT-7605 (manufactured by Shin-Etsu Chemical Co., Ltd.), UV CATA211, 243 (manufactured by Arakawa Chemical Industries, Ltd.), WPI-116, 124 (both manufactured by Wako Pure Chemical Industries, Ltd.), and SP-150, 170 (both manufactured by ADEKA Corporation).

[0133] While there are no particular limitations on the type of thermal acid generator used, it is preferable to use one with a low decomposition temperature, as this can suppress thermal shrinkage and a decrease in the smoothness of the raw material. Examples of commercially available products include San-Aid® SI-300, SI-360, SI-45, SI-60, SI-80, SI-100, SI-B2A, SI-B3A, and SI-B3 (all manufactured by Sanshin Chemical Industry Co., Ltd.).

[0134] Two or more types of acid generators may be used in combination. In this case, using a photoacid generator and a thermal acid generator in combination is preferable because the acid can be generated by the heat during drying and irradiation with active energy rays, allowing the reaction to proceed more efficiently.

[0135] When using the aforementioned photoacid generator, the activity of the acid generator can be enhanced by adding a sensitizer, further increasing the crosslinking density of the release layer. While there are no particular limitations on the sensitizer, and general types can be used, anthracene derivatives and naphthalene derivatives are preferred. One or more types of sensitizers may be used.

[0136] The amount of acid generator added to the coating solution is preferably 0.1 to 10 parts by mass, when the total mass of binder a and release agent b, which consist of a cationic curable substance contained in the release layer, is 100 parts by mass. More preferably, it is 0.5 to 8 parts by mass. Even more preferably, it is 1 to 5 parts by mass. An amount of 0.1 parts by mass or more is preferable because it prevents insufficient acid generation and thus avoids the risk of curing defects. An amount of 10 parts by mass or less is preferable because it ensures an appropriate amount of acid is generated, thereby suppressing the transfer of acid to the molded ceramic green sheet.

[0137] The amount of sensitizer added is preferably 0.1 to 5 times the mass of the photoacid generator. More preferably, it is preferably 0.1 to 2 times. A value greater than 0.1 times is preferable because a sufficient sensitizing effect can be obtained. A value less than 5 times is preferable because it does not inhibit the absorption of the active energy rays of the photoacid generator, and there is no risk of insufficient production of acid.

[0138] (Release agent b) In the present invention, release agent b (additive for imparting release properties) used in the release layer can be a silicone-based additive or a non-silicone-based additive such as a long-chain alkyl-based, olefin-based, or fluorine-based additive, but from the viewpoint of release properties, it is preferable to use a silicone-based additive.

[0139] Silicone-based additives refer to materials based on polyorganosiloxanes, in which organic groups are attached to siloxane bonds. They are not particularly limited as long as the effects of the present invention can be obtained, and general materials can be used. Acrylic resins and alkyd resins having polyorganosiloxanes in their side chains can also be used. Among polyorganosiloxanes, polydialkylsiloxanes can be suitably used, and among these, polydimethylsiloxane is more preferably used, and polydimethylsiloxane having functional groups in part is even more preferable. Having functional groups is preferable because it facilitates intermolecular interactions such as hydrogen bonding with cationic curable materials, making it difficult for the material to transfer to the ceramic green sheet. Preferably, the release agent b contains cationic curable polydimethylsiloxane.

[0140] The functional groups introduced into polydimethylsiloxane are not particularly limited; they can be reactive or non-reactive. Furthermore, the functional groups may be introduced at one end, both ends, or on the side chains of the polydimethylsiloxane. They may also be introduced at one or more positions.

[0141] Reactive functional groups that can be introduced into polydimethylsiloxane include cyclic ether groups, hydroxyl groups, mercapto groups, carboxyl groups, methacryloyl groups, and acryloyl groups. While not particularly limited, cyclic ether groups are preferred, and in particular, the inclusion of cationic curable functional groups such as glycidyl ether groups, alicyclic epoxy groups, and oxetane rings is preferable because they are incorporated into the crosslinking structure of the cationic curable substance, making migration to the ceramic green sheet difficult. Among these, the inclusion of alicyclic epoxy groups is most preferred because it exhibits excellent compatibility with the binder component, making it easier to achieve peelability. Non-reactive functional groups that can be used include polyether groups, alkyl groups, fluoroalkyl groups, long-chain alkyl groups, ester groups, amide groups, and phenyl groups.

[0142] The silicone additive used in the present invention is not particularly limited and existing products can be used. For example, commercially available silicones having reactive functional groups include X-22-170DX, X-22-3710, X-22-176DX, X-22-167B (all manufactured by Shin-Etsu Chemical Co., Ltd.), BYK-UV3500, BYK-UV3505, BYK-UV3575 (all manufactured by Big Chemie Japan Co., Ltd.). Commercially available silicone additives having cationic curable functional groups include X-22-173BX, X-22-173DX, X-22-4741, and X-22-9002 (all manufactured by Shin-Etsu Chemical Co., Ltd.). Among these, commercially available silicones having alicyclic epoxy groups, such as X-22-169B, KF-102, X-62-7629, X62-7660, and X-62-7622 (all manufactured by Shin-Etsu Chemical Co., Ltd.), UV9300, UV9315, and UV9430 (all manufactured by Momentive Performance Materials), and Silikolys® UV Poly 200, 201, 215, and RCA200 (all manufactured by Arakawa Chemical Industries, Ltd.), can be suitably used.

[0143] The fluorine-based additive is not particularly limited and existing products can be used. For example, those having perfluoro groups or perfluoroether groups can be suitably used. Commercially available products include Megafac® (manufactured by DIC Corporation), Optool® (manufactured by Daikin Industries Ltd.), and F-Clear® (manufactured by Kanto Denka Kogyo Co., Ltd.).

[0144] As long-chain alkyl additives, resins modified with long-chain alkyl can be used, and those having an alkyl group with approximately 8 to 20 carbon atoms in the side chain, such as polyvinyl alcohol or acrylic resin, are preferred. Polymers in which (meth)acrylic acid ester is the main repeating unit, and which contain a long-chain alkyl group with 8 to 20 carbon atoms in the transesterified portion, can also be suitably used. Examples of commercially available products include P-Royl® 1010, P-Royl® 1050, P-Royl® 1070 (all from Lion Specialty Chemicals), and Tesfine® 305, Tesfine® 314 (both from Hitachi Chemical Co., Ltd.).

[0145] The olefin-based additive is not particularly limited and can be any common type. For example, polybutadiene and cycloolefin resins can be suitably used. Commercially available products include NISSO-PB B series, G series, JP series (hereinafter referred to as NISSO-PB), and ARTON® (manufactured by JSR Corporation).

[0146] Furthermore, two or more of the above-mentioned release agents may be used in mixture form, but preferably at least one of the release agents is a silicone-based additive, more preferably a silicone having a cationic curable functional group, and more preferably a silicone having an alicyclic epoxy group. It is preferable that at least one of the release agents is a silicone-based additive because it results in a release layer with excellent release properties.

[0147] In the present invention, the release layer preferably contains release agent b in an amount of 0.1% by mass or more and 20% by mass or less relative to the total solid content of the release layer. More preferably, it is 0.5% by mass or more and 10% by mass or less, and even more preferably, 0.5% by mass or more and 5% by mass or less. A higher amount than 0.1% by mass is preferable because it imparts release properties without the risk of worsening the peelability of the ceramic green sheet. A lower amount than 20% by mass is preferable because it suppresses the decrease in intermolecular interaction with the cationic curable substance (e.g., cationic curable binder a), and eliminates the risk of migration to the ceramic green sheet. In this case, the total solid content of the release layer is expressed as the sum of the solid content of the binder component and the release agent, because it is difficult to accurately calculate the trace amount of the acid generator that remains in the release layer after decomposition during the drying process or under active energy ray irradiation.

[0148] The release layer in this invention may contain particles with a particle size of 1 μm or less, but from the viewpoint of pinhole generation, it is preferable not to contain particles or other materials that form protrusions.

[0149] In the release layer of the present invention, additives such as adhesion enhancers and antistatic agents may be added, as long as they do not hinder the effects of the present invention. Furthermore, in order to improve adhesion to the substrate, it is also preferable to pre-treat the surface of the polyester film with an anchor coat, corona treatment, plasma treatment, atmospheric pressure plasma treatment, etc., before applying the release coating layer.

[0150] (Characteristics of the release layer) In the present invention, the thickness of the release layer can be set according to its intended use and is not particularly limited. From the viewpoint of the number of protrusions on the surface of the surface layer, the polyester film of the present invention has an intrinsic viscosity of 0.55 or more, and the antimony atom content of the surface layer is 120 ppm or less, so the number of Sb protrusions on the surface of the surface layer of the substrate is 0.020 per cm. ２ The number of particles becomes less than or equal to 1, allowing for a thinner design of the release layer thickness. Preferably, the release coating layer after curing is in the range of 0.005 to 1.2 μm, more preferably 0.005 to 0.8 μm, and even more preferably 0.005 to 0.5 μm.

[0151] In particular, when a release layer is provided on the surface layer A of a polyester film having a surface layer A that substantially does not contain inorganic particles, it is preferable that the thickness of the release layer be even thinner, as this can reduce the cost of the coating material and is therefore more economical. Specifically, a thickness of 0.005 to 0.4 μm is preferable, and a thickness of 0.005 to 0.3 μm is more preferable. A thickness of the release layer greater than 0.005 μm is preferable because it provides sufficient peeling performance. Furthermore, a thickness of less than 1.0 μm is preferable because it is less likely to cause curling defects, provides sufficient curability, and suppresses erosion of the release layer by organic solvents.

[0152] From the viewpoint of preventing breakage during mold release layer processing, the mold release film of the present invention has high breaking strength in the longitudinal direction, so the mold release layer can be designed to be thicker, reducing the risk of breakage. Preferably, the mold release coating layer after curing is in the range of 0.005 to 0.5 μm, more preferably 0.005 to 0.8 μm, and even more preferably 0.005 to 1.2 μm.

[0153] The surface of the release layer of the release film of the present invention is preferably flat in order to prevent defects from occurring in the ceramic green sheet coated and molded thereon, and the average surface roughness (Sa) of the region is preferably 7 nm or less. Furthermore, it is even more preferable that the maximum protrusion height (P) of the release layer surface satisfies the above Sa and is 100 nm or less. It is particularly preferable that the average surface roughness (Sa) of the region is 5 nm or less and the maximum protrusion height is 80 nm or less.

[0154] In the present invention, the surface layer of the substrate, that is, the surface on which the release layer is laminated on the substrate, is made of polyester containing an antimony compound, an alkaline earth metal compound, and a phosphorus compound, the intrinsic viscosity of the surface layer is 0.55 or higher, and the antimony atom content of the surface layer is 120 ppm or less, so that the maximum protrusion height of the release layer can be made 50 nm or less.

[0155] Furthermore, the maximum protrusion height of the release layer can be reduced to 40 nm or less, for example, to 30 nm or less.

[0156] Similarly, with the substrate of the present invention, the surface roughness of the release layer region can be reduced to 5 nm or less.

[0157] If the surface roughness of the region is 7 nm or less and the maximum protrusion height is 100 nm or less, then when forming the ceramic green sheet, defects such as pinholes will not occur, resulting in a good yield, which is preferable. A smaller average surface roughness of the region (Sa) is preferable, but it may be 0.1 nm or more, or 0.3 nm or more. Similarly, a smaller maximum protrusion height (P) is preferable, but it may be 1 nm or more, or 3 nm or more.

[0158] By using the polyester film substrate of the present invention, the average surface roughness (Sa) and maximum protrusion height (P) of the release layer can be brought within the range of the present invention. Furthermore, the present invention can exhibit high tensile strength in the longitudinal direction of the release film, for example, enabling faster winding and unwinding of the film during the manufacturing of the release film than conventional methods. In addition, because the thermal shrinkage stability of the release film can be achieved at low temperatures, the dimensional stability of the release film can be maintained even under high-temperature processing conditions when manufacturing ceramic green sheets or resin sheets.

[0159] The surface free energy (γs) of the release layer surface is 15 to 25 mJ / m ２ For example, the surface free energy is 16-25 mJ / m ２ Therefore, 17-24 mJ / m ２ That's fine.

[0160] Surface free energy is 15 mJ / m ２ A value of 25 mJ / m is preferable because it makes it less likely for repellency to occur when applying the ceramic slurry, allowing for uniform application. ２ The following range is preferable as it does not risk reducing the release properties of the ceramic green sheet. By setting it within the above range, it is possible to provide a release film that does not repel during coating and has excellent release properties.

[0161] The release film of the present invention preferably has a peeling force of 0.5 mN / mm or more and 2.5 mN / mm or less when peeling off the ceramic green sheet. More preferably, it has a peeling force of 0.8 mN / mm or more and 2.0 mN / mm or less. A peeling force of 0.5 mN / mm or more is preferable because the peeling force is not too light and there is no risk of the ceramic green sheet lifting up during transport. A peeling force of 2.5 mN / mm or less is preferable because there is no risk of the ceramic green sheet being damaged during peeling.

[0162] The release film of the present invention preferably has a curl of 3 mm or less, and more preferably 1 mm or less, after being heated at 100°C for 15 minutes without tension. Of course, it is also preferable that there is no curl at all. A curl of 3 mm or less is preferable because it reduces curl when molding the ceramic green sheet and printing electrodes, thereby improving printing accuracy.

[0163] (Method for forming a release layer) In the present invention, the method for forming a release layer is not particularly limited, and a coating solution obtained by dissolving or dispersing a composition containing a release resin or the like is applied to one side of a polyester film substrate, the solvent is removed by drying, the film is heated and dried, and then cured by irradiation with active energy rays or heat.

[0164] When curing using a photoacid generator, the heating temperature is preferably 50°C or higher and 110°C or lower, and more preferably 60°C or higher and 100°C or lower. The heating time is preferably 30 seconds or less, and more preferably 20 seconds or less. When the temperature is 110°C or lower, the thermal load on the film is suppressed, making it less likely for defects in appearance such as thermal shrinkage of the film to occur, and reducing the risk of uneven thickness in the ceramic green sheet, which is preferable. When the temperature is 100°C or lower, the thermal load on the film is further reduced, allowing processing without impairing the flatness of the film, and further reducing the risk of uneven thickness in the ceramic green sheet, which is particularly preferable. When the temperature is higher than 50°C, the diluting solvent used during coating dries sufficiently, eliminating the risk of process contamination, which is preferable.

[0165] For reacting cationic curable substances using a photoacid generator, the active energy rays used can include ultraviolet light, electron beams, and X-rays, but ultraviolet light is preferred due to its ease of use. The amount of ultraviolet light to be irradiated should be 10 to 1000 mJ / cm² in terms of integrated light intensity. ２ Preferably, and more preferably, 15 to 500 mJ / cm² ２ Therefore, 15-100 mJ / cm² ２ A more preferable option is 10 mJ / cm. ２ This is preferable because it allows the resin to harden sufficiently. 1000 mJ / cm ２ The following method is preferable because it allows for an improvement in processing speed, thus enabling the economical production of release films.

[0166] In the present invention, the surface tension of the coating liquid when applying the release layer is not particularly limited, but is preferably 30 mN / m or less. By setting the surface tension as described above, the wettability after coating is improved, and the surface irregularities of the coating film after drying can be reduced.

[0167] In the present invention, the coating liquid used when applying the release coating layer is not particularly limited, but it is preferable to add a solvent with a boiling point of 90°C or higher. Adding a solvent with a boiling point of 90°C or higher prevents bumping during drying, levels the coating film, and improves the smoothness of the coating film surface after drying. The amount of solvent added is preferably about 10 to 80% by mass of the total coating liquid.

[0168] Any known coating method can be applied to the above coating liquid. For example, conventional methods such as roll coating methods including gravure coating and reverse coating, bar coating methods such as wire bar coating, die coating, spray coating, and air knife coating can be used.

[0169] The release film of the present invention can be applied to release films for resin sheet manufacturing, such as for ceramic green sheet manufacturing, release sheets, protective adhesive layers for seals, film capacitors, and surface protection for printed circuit boards.

[0170] The following describes in more detail one embodiment of the present invention with reference to examples, but the present invention is not limited thereto. The method for specifying various physical properties in the examples is described below.

[0171] (Determination of Sb, Mg, and P elements in the surface layer) A sample (0.5 g) obtained by scraping the surface layer was dissolved in 15 ml of 60% nitric acid and 2 ml of ultrapure water to prepare the sample for measurement. Subsequently, the content (ppm) of Sb, Mg, and P elements relative to the mass of the polyester film was determined using an ICP emission spectrometer (Agilent 5900 ICP OES).

[0172] (Number of antimony element-containing protrusions (Sb protrusions) present on the surface of the surface layer) The base film and the release film with the release layer are sized according to the standard paper dimensions of A4 size of the Japanese Industrial Standards (210 mm x 297 mm: area approximately 623.7 cm²) ２ A section was cut from the sample and used as a sample. The entire area of ​​this sample was visually inspected for foreign matter using the crossed nicol method. Next, each foreign matter detected in the sample was measured from the surface of the surface layer of the sample using a scanning white-light interference microscope (device: Hitachi High-Tech Science Corporation "VertScan" (registered trademark) VS1540) with a 10x objective lens in Phase mode. The obtained microscope image was processed using the surface analysis software VS-Viewer Version 10.0.3.0 built into the microscope under the following conditions to obtain the height of the foreign matter at the surface of the surface layer.

[0173] (Image processing conditions) Image processing was performed in the following order.

[0174] - Interpolation: Full interpolation - Filtering: Gaussian (cutoff 100) - Surface correction: 4th order Furthermore, particle analysis processing was performed under the following conditions, and the number of particles (number of particles) displayed on the "Particle Analysis" screen, which is detected at a height threshold of 25 nm (height threshold setting value: 0.025 μm), was measured.

[0175] (Particle analysis conditions) The protrusion analysis process was performed under the following conditions.

[0176] - Analysis type: Protrusion analysis - Image correction: None - Processing height threshold: 0.025 μm Reference height: Zero plane (average plane) Of the protrusions (foreign matter) detected in this analysis, the presence or absence of antimony elements was measured by the following component analysis at locations where protrusions with a height of 0.1 μm or more on the surface of the surface layer were observed.

[0177] (Component analysis of protrusions) Areas where protrusions with a height of 0.1 μm or more were observed were subjected to elemental analysis using a digital microscope (KEYENCE, VHX) equipped with a laser elemental analysis head (KEYENCE, EA-300). The number of protrusions (Sb protrusions) in which antimony element (Sb element) was detected was counted. The number of counted protrusions was measured across the surface observation area (210 mm x 297 mm: area approximately 630 cm²). ２ Divide by ) and the 1 cm present on the film surface ２ The number of protrusions containing antimony element per unit was calculated.

[0178] (Surface layer dissolution) The sample (10 g) obtained by scraping the surface layer was washed with water and dried, and then dissolved in a p-chlorophenol / tetrachloroethane mixture (a solution consisting only of p-chlorophenol and tetrachloroethane, with a mass ratio of p-chlorophenol 3:tetrachloroethane 1) to obtain a dissolution.

[0179] (Filtration of surface layer solution) The surface layer solution was filtered using a membrane filter (Advantec PTFE membrane filter, part number: T050A430A), and the filtered filter was dried to obtain a dried filter. The membrane filter is made of polytetrafluoroethylene, has an average pore size of 0.5 μm, and is circular with a diameter of 47 mm (147.6 mm). ２ ) and its thickness was 90 μm.

[0180] (Total number of particles filtered out by filtration of the dissolution) The dry filter was observed using a scanning electron microscope (SEM) at a magnification of 1,000x, and the number of particles was measured.

[0181] (Number of antimony-containing particles filtered out by filtration of the dissolution and their proportion to the total number of particles) Using a scanning electron microscope (SEM) at a magnification of 1,000x, elemental analysis was performed on the particles on the dry filter, and the number of particles in which Sb was detected (Sb-containing particles) was counted. The proportion (%) of Sb-containing particles was calculated by dividing the number of particles in which Sb was detected by the total number of particles.

[0182] (Amount of Sb element in particles filtered out by filtration of the dissolution) The amount of Sb element per 10 g of surface layer was determined by measuring the particles on the dry filter with fluorescent X-rays, and this was converted to the amount per 1 kg of surface layer (mg).

[0183] (Intrinsic viscosity of surface layer and base film) The intrinsic viscosity was measured (dl / g) in accordance with JIS K 7367-5. For the measurement, a sample obtained by scraping the surface layer or the base film was used, along with a mixed solvent of phenol (6 parts by mass) and 1,1,2,2-tetrachloroethane (4 parts by mass), at a temperature of 30°C.

[0184] (Thermal shrinkage rate of the base film in the longitudinal direction) A sample of the base film was taken with a width of 10 mm in the width direction and a length of 220 mm. Marks were made at 200 mm intervals along the longitudinal direction of the sample, and the interval between the marks was measured (L0). Then the sample was placed between sheets of paper and placed in a hot air oven controlled to a temperature of 150°C for 30 minutes. After removing the sample, the interval between the marks was measured (L), and the thermal shrinkage rate was calculated using the following formula.

[0185] Thermal shrinkage rate (%) = {(L0 - L) / L0} × 100 (Breaking strength of the base film) Breaking strength is the stress required for the base film to break. Specifically, a tensile force is gradually applied to the base film, and the force at which the base film breaks is determined. This value is then converted to stress per unit area (unit: MPa) and expressed as such. Breaking strength was measured in accordance with JIS K 7127, specifically by the following method. That is, a film test piece with a width of 12.7 mm and a length of 200 mm was sampled, the film test piece was set in a tensile testing machine (for example, AG-X manufactured by Shimadzu Corporation), and stretched at a chuck distance of 100 mm and a pull-up speed of 100 mm / min in an environment of 23°C and 65% RH. The breaking strength was calculated from the measured elongation at the time of breakage of the film test piece and the load required for breakage.

[0186] (Surface evaluation of the base film for release film applications) The number of Sb protrusions on the surface of the surface layer is 0.015 per cm. ２ Substrate films with fewer than [number] particles were considered acceptable and are marked with "○" in Table 3. On the other hand, those that did not meet this condition were considered unacceptable and are marked with "×" in Table 4. If a film is unacceptable, unevenness may occur when the substrate film is wound onto the roller, or, for example, when the substrate film is used in the manufacture of multilayer ceramic chip capacitors (MLCCs), the frequency of unevenness occurring on the printed surface during printing of internal electrodes may increase.

[0187] (Strength evaluation of base film for release film application) Base film that has a thermal shrinkage rate in the longitudinal direction of the above-mentioned base film of 1.4% or less and a breaking strength of 180 MPa or more is considered acceptable and is indicated as "〇" in Table 3. On the other hand, those that do not meet these conditions are considered unacceptable and are indicated as "×" in Table 3.

[0188] If the film is unsuitable, breakage, cracking, etc. may occur during the manufacturing or use of the base film, or, for example, large dimensional changes may occur during heating when the base film is used in the manufacture of multilayer ceramic chip capacitors (MLCCs) to form dielectric sheets and internal electrodes.

[0189] (Overall evaluation of base film for release film application) If the surface evaluation and strength evaluation both passed, the overall evaluation was considered a pass and was indicated with "〇" in Table 4. On the other hand, if either or both of the surface evaluation and strength evaluation failed, the overall evaluation was considered a fail and was indicated with "×" in Table 4.

[0190] (Surface Free Energy) Under conditions of 25°C and 50% RH, droplets of water (droplet volume 1.8 μL), diiodomethane (appropriate liquid volume 0.9 μL), and ethylene glycol (appropriate liquid volume 0.9 μL) were prepared on the release surface of the release film using a contact angle meter (Kyowa Interface Science Co., Ltd.: Fully Automatic Contact Angle Meter DM-701), and the contact angles were measured. The contact angles were taken 10 seconds after dropping each liquid onto the release film. The contact angle data for water, diiodomethane, and ethylene glycol obtained by the above method were calculated using the "Kitazaki-Hata" theory to determine the dispersion component γsd, polar component γsp, and hydrogen bonding component γsh of the surface free energy of the release film, and the sum of these components was defined as the surface free energy γs. This calculation was performed using the calculation software within the contact angle meter software (FAMAS).

[0191] (Surface Roughness) The values ​​were measured using a non-contact surface shape measurement system (VertScan R550H-M100) under the following conditions. The average surface roughness (Sa) of the region was taken as the average of 5 measurements, and the maximum protrusion height (P) was measured 7 times, and the maximum value of the 5 measurements after excluding the maximum and minimum values ​​was used.

[0192] (Measurement conditions) Measurement mode: WAVE mode Objective lens: 10x 0.5x Tube lens Measurement area: 936 μm x 702 μm (Analysis conditions) Surface correction: 4th order correction Interpolation process: Full interpolation (Evaluation of peelability of ceramic green sheet) A composition consisting of the following materials was stirred and mixed, and dispersed for 60 minutes using zirconia beads with a diameter of 0.5 mm using a bead mill to obtain a ceramic slurry.

[0193] Toluene 38.3 parts by mass Ethanol 38.3 parts by mass Barium titanate (HPBT-1, manufactured by Fuji Titanium Co., Ltd.) 64.8 parts by mass Polyvinyl butyral (Seslec BM-S, manufactured by Sekisui Chemical Co., Ltd.) 6.5 parts by mass DOP (dioctyl phthalate) 3.3 parts by mass Next, the release surface of the obtained release film sample was coated with an applicator so that the dried slurry had a thickness of 0.8 μm, and dried at 60°C for 1 minute to form a ceramic green sheet on the release film. The obtained release film with ceramic green sheet attached was statically removed using a static eliminator (SJ-F020, manufactured by Keyence Corporation), and then peeled using a peel tester (VPA-3, manufactured by Kyowa Interface Science Co., Ltd.) at a peel angle of 90 degrees, a peel temperature of 25°C, and a peel speed of 10 m / min. For the peeling process, double-sided adhesive tape (Nitto Denko, No. 535A) was attached to a SUS plate provided with the peel test machine. The release film was then fixed on top of the tape, with the ceramic green sheet side adhering to the double-sided tape, and the release film was peeled off by pulling it. The average peeling force for peeling distances of 20 mm to 70 mm was calculated from the obtained measurements and defined as the peeling force. A total of five measurements were taken, and the average value of the peeling force was used for evaluation. The obtained peeling force values ​​were judged according to the following criteria.

[0194] ○: 0.5 mN / mm or more, 1.0 mN / mm or less △: Greater than 1.0 mN / mm, 2.5 mN / mm or less ×: Greater than 2.5 mN / mm (Manufacturing Example 1) <Production of Polyester Resin (Melting Polymerization)> (Slurry Preparation) In a slurry preparation tank, terephthalic acid and ethylene glycol were continuously supplied in a ratio of 46.4 parts by mass of ethylene glycol to 100 parts by mass of terephthalic acid, and stirred under nitrogen flow to prepare a slurry.

[0195] (Esterification Reaction) A continuous esterification reactor consisting of a three-stage complete mixing tank with a stirrer, distillation column, raw material inlet, and product outlet was used as the esterification reactor. Along with the slurry prepared above, an ethylene glycol solution of antimony trioxide (antimony trioxide concentration: 12 g / L) was supplied to the first esterification reactor, and the esterification reaction was carried out at an absolute pressure of 126 kPa, a temperature of 258°C, and an average residence time of 3.3 hours.

[0196] The reaction solution was removed from the first esterification reactor to maintain a constant liquid level and then added to the second esterification reactor. Ethylene glycol was added to the second esterification reactor at an average rate of 230 kg / hour through another inlet, and the esterification reaction was carried out under atmospheric pressure at a temperature of 261°C and an average residence time of 1.3 hours.

[0197] The reaction solution was removed from the second esterification reactor to maintain a constant liquid level and then added to the third esterification reactor. In the third esterification reactor, equal amounts of ethylene glycol solution containing magnesium acetate, ethylene glycol solution containing sodium acetate, and ethylene glycol solution containing trimethyl phosphate were added from separate inlets, and the esterification reaction was carried out under atmospheric pressure at a temperature of 260°C with an average residence time of 0.9 hours.

[0198] (Polycondensation reaction) The reaction solution was removed from the third esterification reaction tank so that the liquid level remained constant, and then introduced into the first polycondensation reaction tank of a three-stage continuous polycondensation reactor. The first polycondensation reaction was carried out at a pressure of 5.6 kPa, a temperature of 278°C, and an average residence time of 0.7 hours.

[0199] The reaction solution was removed from the first polycondensation reactor to maintain a constant liquid level and then added to the second polycondensation reactor. The second polycondensation reaction was carried out at a pressure of 0.75 kPa, a temperature of 282°C, and an average residence time of 0.9 hours.

[0200] The reaction mixture was removed from the second double condensation reaction vessel so that the liquid level of the second double condensation material remained constant, and then added to the third double condensation reaction vessel. The vacuum (pressure) was adjusted so that the intrinsic viscosity of the reaction product was 0.53 dl / g at a temperature of 282°C and an average residence time of 0.9 hours. The pressure ranged from 0.08 to 0.15 kPa.

[0201] The polyester resin obtained through the above process was extruded into strands, cooled in water, and then cut into pellets.

[0202] <Production of Polyester Resin 1 (Melting Polymerization and Solid-Phase Polymerization)> The polyester resin obtained by melt polymerization was placed in a solid-phase polymerization apparatus. After drying at a temperature of 90°C for 3.5 hours, it was crystallized at a temperature of 130°C for 4.5 hours. Next, the temperature was gradually increased from 197°C to 220°C, and solid-phase polymerization was carried out at a pressure of 40 Pa for 7 hours to obtain polyester resin 1 with an intrinsic viscosity of 0.617 dl / g.

[0203] <Production of Polyester Resins 2-6> Polyester resins 2-6 were obtained in the same manner as polyester resin 1, except that the supply amount of antimony trioxide ethylene glycol solution was changed to match the Sb content (ppm) shown in Table 3, the esterification reaction time and polycondensation reaction time were changed to the times shown in Table 1, and solid-phase polymerization was not performed.

[0204] <Manufacturing of Recycled PET1> Used PET film having a silicone-based release layer on one side and containing 600 ppm of calcium carbonate with a particle size of 1.0 μm was put through a single-screw mill and pulverized at a speed of 100 kg / hour through a 4 mm perforated screen to obtain pulverized film. The obtained pulverized film was fed into a twin-screw extruder to obtain Recycled PET1. The intrinsic viscosity of Recycled PET1 was 0.56 dl / g and the Si concentration was 200 ppm.

[0205] <Manufacturing of Polyethylene Terephthalate / Calcium Carbonate Masterbatch (MB1)> The above polyester resin 4 and calcium carbonate particles with an average particle size of 1.0 μm were melted and kneaded in a twin-screw extruder to produce a masterbatch with a calcium carbonate particle concentration of 20,000 ppm.

[0206] <Manufacturing of Laminated Film X1> After drying polyester resin 1, recycled PET 1, and MB 1, each was melted at 285°C. Using separate melt extruders (290°C), each molten material was filtered in two stages using a filter made of sintered stainless steel fibers with a 95% cut diameter of 15 μm and a filter made of sintered stainless steel particles with a 95% cut diameter of 15 μm. Next, the filtered molten materials were combined in a feed block to laminate a surface layer (layer A), a smooth layer (layer B), and an intermediate layer (layer C), and extruded (casted) into a sheet at a speed of 45 m / min. By electrostatic adhesion and cooling on a casting drum at 30°C, an unstretched laminated polyethylene terephthalate sheet (laminated PET sheet) with an intrinsic viscosity of 0.56 dl / g was obtained. At this time, layer A was formed using only polyester resin 1, and layer B was formed using polyester resin 1 7 The layers were formed by blending 5% by mass of polyester resin 1 and 25% by mass of MB1, and the C layer was formed by blending 60% by mass of polyester resin 1 and 40% by mass of recycled PET 1. The thickness ratio of the layers was adjusted so that A layer / C layer / B layer = 40% / 40% / 20% based on calculations using the discharge rate of each extruder. The electrostatic adhesion conditions at this time were as follows: the electrode material was tungsten, cylindrical (wire) with a diameter of 0.2 mm and a length of 0.5 m, with a constant current control of 5 mA, an electrode tension of 5 kg, and an electrode renewal rate of 5 m / hour.

[0207] Next, the obtained unstretched laminated PET sheet was heated with an infrared heater and then stretched 3.5 times in the longitudinal direction by the speed difference between the rolls at a roll temperature of 80°C. After that, it was guided to a tenter and stretched 4.2 times in the transverse direction at 140°C. Next, it was heat-treated at 210°C in a heat-setting zone. After that, a 2.3% relaxation treatment was performed in the transverse direction at 170°C to obtain a mill roll (width 5.0 m) of laminated biaxially oriented polyethylene terephthalate film (laminated biaxially oriented PET film) with a thickness of 25 μm.

[0208] The obtained mill rolls were moved to a slitter and treated with an anti-static device (Kasuga Electric Co., Ltd., high-density anti-static treatment system) and a web cleaner (Shinko Co., Ltd., ultrasonic cleaner system). After cutting to a width of 1400 mm, a core material with resin-impregnated paper attached, with an inner diameter of 6 inches, a wall thickness of 12 mm, a moisture content of 8%, a surface roughness (SRa = 4.3 nm, SRp = 41.4 nm), and a flattening compressive strength of 200 kg / 100 mm, was wound 8000 m in length at a maximum speed of 400 m / min using a contact roll with a rubber hardness of 60 degrees, a contact pressure of 200 kg / m, and a tension of 15 MPa to obtain a laminated biaxially oriented PET film roll. Laminated biaxially oriented PET film (base film) was cut from the obtained roll and subjected to various evaluations. The evaluation results are shown in Tables 2 to 4.

[0209] <Manufacturing of Laminated Films X2-8> Laminated biaxially oriented PET films were manufactured in the same manner as in Example 1, except that the layer configuration, layer thickness ratio, and the types and ratios of constituent resins of layers A-C were changed as shown in Table 2, and subjected to various evaluations. The evaluation results are shown in Tables 2-4.

[0210]

[0211]

[0212]

[0213]

[0214] The base films using polyester resins 1 to 3 in each layer showed excellent results in both surface evaluation and strength evaluation (manufacturing examples 1 to 5), confirming their suitability as release sheets useful for forming dielectric sheets and printing internal electrodes in MLCC manufacturing. On the other hand, the base films using polyester resins 4 to 6 in each layer lacked performance in either surface evaluation or strength evaluation, failing to achieve a balance between surface performance and strength performance (comparative manufacturing examples 1 to 3), confirming that there is significant room for improvement as release sheets used in forming dielectric sheets and printing internal electrodes in MLCC manufacturing.

[0215] (Example 1) A coating solution with the following composition was applied to the surface layer A of the laminated film X1 using reverse gravure so that the release layer thickness after drying was 400 nm, and it was dried at 120°C for 15 seconds, with an integrated light intensity of 50 mJ / cm². ２ A release film for manufacturing ultrathin ceramic green sheets was obtained by irradiating it with ultraviolet light (Heraus LC6B, H-bulb). The surface roughness, surface free energy, ceramic slurry coating properties, and ceramic release properties of the obtained release film were evaluated, and favorable evaluation results were obtained. The composition and evaluation results for the release film are shown in Tables 5A and 6.

[0216] 36.00 parts by mass methyl ethyl ketone 27.00 parts by mass toluene 26.85 parts by mass n-heptane 9.5 parts by mass epoxy compound (alicyclic epoxy group-containing monomer, active ingredient ≥97%, manufactured by Daicel Corporation, trade name Celoxide® 2021P) 0.5 parts by mass release agent (alicyclic epoxy group-modified polydimethylsiloxane Poly215, solids content 100%, manufactured by Arakawa Chemical Industries, Ltd.) 0.15 parts by mass acid catalyst (UV cation initiator CATA211, manufactured by Arakawa Chemical Industries, Ltd., trade name CATA211®, solids content 18%) (Example 2) A release layer was formed in the same procedure as in Example 1, except that a release layer was provided on surface layer A of laminated film X2. The composition and evaluation results for the release film are shown in Tables 5A and 6.

[0217] (Example 3) The release layer was formed using the same procedure as in Example 1, except that a release layer was provided on the surface layer A of the laminated film X3. The composition and evaluation results of the release film are shown in Tables 5A and 6.

[0218] (Example 4) The release layer was formed using the same procedure as in Example 1, except that a release layer was provided on the surface layer A of the laminated film X4. The composition and evaluation results of the release film are shown in Tables 5A and 6.

[0219] (Example 5) The release layer was formed using the same procedure as in Example 1, except that a release layer was provided on the surface layer A of the laminated film X5. The composition and evaluation results of the release film are shown in Tables 5A and 6.

[0220] (Examples 6-10) The release layer was formed using the same procedure as in Example 1, except that the thickness of the release layer was changed to the value shown in Table 5A. The composition and evaluation results for the release film are shown in Tables 5A and 6.

[0221] (Examples 11-14) The release layer was formed in the same procedure as in Example 1, except that the content of the cation-curable resin and release agent in the coating solution of Example 1 was changed to the values ​​shown in Table 5A or Table 5B.

[0222] The composition and evaluation results for the release film are shown in Tables 5A, 5B, and 6.

[0223] (Example 15) A release layer was formed in the same manner as in Example 1, except that the release agent in the coating solution of Example 1 was changed to the following composition. The composition and evaluation results for the release film are shown in Tables 5B and 6.

[0224] (Alicyclic epoxy group modified polydimethylsiloxane Poly215: Alicyclic epoxy group modified polydimethylsiloxane RCA200 = 90:10) (Alicyclic epoxy group modified polydimethylsiloxane Poly215, 100% solids, manufactured by Arakawa Chemical Industries, Ltd.) (Alicyclic epoxy group modified polydimethylsiloxane RCA200, 100% solids, manufactured by Arakawa Chemical Industries, Ltd.) (Example 16) A release layer was formed in the same manner as in Example 1, except that the cation-curable resin of the coating solution in Example 1 was changed to the following composition. The composition and evaluation results for the release film are shown in Tables 5B and 6.

[0225] (Alicyclic epoxy monomer C2021P: difunctional oxetane group-containing monomer oxetane OXT-121 = 80:20) (Alicyclic epoxy group-containing monomer, active ingredient ≥97%, manufactured by Daicel Corporation, trade name Celoxide (registered trademark) 2021P) (Difunctional oxetane group-containing monomer, active ingredient ≥95%, manufactured by Toagosei Co., Ltd., trade name OXT-121) (Example 17) A release layer was formed in the same manner as in Example 1, except that the cation-curable resin of the coating solution in Example 1 was changed to the following composition. The composition and evaluation results for the release film are shown in Tables 5B and 6.

[0226] (Alicyclic epoxy monomer C2021P: difunctional oxetane group-containing monomer oxetane OXT-221 = 80:20) (Alicyclic epoxy group-containing monomer, active ingredient ≥97%, manufactured by Daicel Corporation, trade name Celoxide (registered trademark) 2021P) (Difunctional oxetane group-containing monomer, active ingredient ≥98%, manufactured by Toagosei Co., Ltd., trade name OXT-221) (Example 18) A release layer was formed in the same manner as in Example 1, except that the cation-curable resin of the coating solution in Example 1 was changed to the following composition. The composition and evaluation results for the release film are shown in Tables 5B and 6.

[0227] (Alicyclic epoxy group-containing cyclic siloxane monomer, 100% active ingredient, manufactured by Shin-Etsu Chemical Co., Ltd., KR-470) (Example 19) A release layer was formed in the same manner as in Example 1, except that the cationic curable resin of the coating solution in Example 1 was changed to the following composition. The composition and evaluation results for the release film are shown in Tables 5B and 6.

[0228] (Alicyclic epoxy group-containing linear siloxane difunctional monomer, 100% active ingredient, manufactured by Shin-Etsu Chemical Co., Ltd., X-40-2669) (Comparative Example 1) A release layer was formed in the same manner as in Example 1, except that a release layer was provided on the surface layer A of the laminated film X7. Many antimony-induced protrusions were observed.

[0229] The composition and evaluation results for the release film are shown in Tables 5B and 6.

[0230] (Comparative Example 2) A release layer was formed in the same manner as in Example 1, except that a release layer was provided on the surface layer A of the laminated film X8. The longitudinal breaking strength was low, raising concerns that breakage may occur during the processing of the release layer or, for example, when the release film is used in the manufacture of a multilayer ceramic chip capacitor (MLCC) to form a dielectric sheet and internal electrodes.

[0231] The composition and evaluation results for the release film are shown in Tables 5B and 6.

[0232] (Comparative Example 3) A release layer was formed in the same manner as in Example 1, except that the release agent from the coating solution of Example 1 was removed. The result was poor release properties.

[0233] The composition and evaluation results for the release film are shown in Tables 5B and 6.

[0234] (Comparative Example 4) A release layer was formed using the same procedure as in Example 1, except that a release layer was provided on the surface layer A of the laminated film X6. Many antimony-induced protrusions were observed.

[0235] The composition and evaluation results for the release film are shown in Tables 5B and 6.

[0236]

[0237]

[0238]

[0239] The present invention relates to a release film for molding resin sheets, and more particularly to a release film used when molding thin resin sheets.

Claims

1. A release film having a polyester film substrate and a release layer, wherein the polyester film substrate is a polyester film comprising a surface layer and a smooth-slip layer containing polyester resin and lubricant particles, the surface layer is made of polyester containing an antimony compound, an alkaline earth metal compound and a phosphorus compound, the intrinsic viscosity of the surface layer is 0.55 or more, the antimony atom content of the surface layer is 120 ppm or less, and the surface free energy of the surface of the release layer is 15 to 25 mJ / m ２ The release film is characterized in that the average surface roughness (Sa) of the surface of the release layer is in the range of 7 nm or less, the maximum protrusion height is in the range of 100 nm or less, the thickness of the release layer is 0.005 μm to 1.2 μm, the release layer is formed from a release layer forming composition, and the release layer forming composition contains an ultraviolet-curable compound.

2. The number of antimony element-containing protrusions present on the surface of the surface layer of the polyester film substrate is 0.020 per cm. ２ The release film according to claim 1, which is as follows:

3. The release film according to claim 1, wherein the release layer forming composition has a cation-curable binder a.

4. The release film according to claim 1, wherein the release layer forming composition has a release agent b.

5. The release film according to claim 3, wherein the cationic curable binder a contains at least one compound selected from compounds having an alicyclic epoxy group or an oxetanyl group.

6. The release film according to claim 4, wherein the release agent b comprises a cationically curable polydimethylsiloxane.

7. The release film according to claim 1, wherein the release layer forming composition comprises a cationic curable binder a and a release agent b, and the content of the release agent b is 0.01 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the solid content of the cationic curable binder a and the release agent b.

8. The release film according to claim 1, wherein the intrinsic viscosity of the surface layer is 0.55 to 0.62 dl / g.

9. The number of antimony element-containing protrusions present on the surface of the surface layer is 0.020 per cm. ２ The release film according to claim 1, which is as follows:

10. The release film according to claim 1, wherein the release film is a release film for manufacturing ceramic green sheets or resin sheets.

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