Release film

Abstract

The present invention relates to a resin-sheet-molding release film, and provides a release film for use in molding a thin layer of resin sheet. The present invention provides a release film including a polyester film base material and a release layer. The polyester film base material is provided with a surface layer and a slippery layer containing a polyester resin and lubricant particles. The surface layer is composed of a 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. The intrinsic viscosity of the surface layer is 0.55 or more. The antimony atom content of the slippery layer is 120 ppm or less. The surface free energy of the surface of the release layer is 15 to 35 mJ / m2. The area surface average roughness (Sa) of the surface of the release layer is 7 nm or less. The maximum projection height is in a range of 100 nm or less. The release layer is formed from a release layer forming composition. The composition contains an ultraviolet curable compound in an amount of 50 mg / m2 or less.

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 manufacturing resin sheets such as adhesive sheets, cover films, polymer films, and optical lenses. Furthermore, in recent years, there has been a demand for release films used in the manufacture of semiconductor products. In addition, release films are also in demand for use as release films in the manufacture of ceramic green sheets.

[0003] 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.

[0004] 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.

[0005] 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. Similarly, for films used in film capacitor processes that utilize flexible resin films as dielectrics, poor smoothness can lead to problems such as pinhole formation, uneven thickness, and sheet defects in the resin sheet.

[0006] 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.

[0007] Furthermore, reference 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 level.

[0008] Patent Document 1: Japanese Unexamined Patent Publication No. 2007-237497 Patent Document 2: Japanese Unexamined Patent Publication No. 2009-012242

[0009] 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 even lower protrusions compared to conventional methods.

[0010] 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.

[0011] Further, the release film for ceramic green sheet manufacturing processes of Patent Document 2 can suppress fine protrusions within a 100 μm×100 μm square area, but it cannot eliminate coarse protrusions such as antimony-based PET polymerization catalysts or PET chips. It has been found that when a thin ceramic green sheet is coated using a release film provided with the present release layer, there is a problem that voids are formed. In addition, when the release layer is provided with a large thickness to fill in coarse protrusions, there has been a problem that curling occurs due to curing shrinkage of the release layer.

[0012] The present inventors discovered that when the amount of the antimony compound used is reduced during production of the surface layer of a polyester film substrate, the formation of protrusions on the surface layer of the polyester film substrate is suppressed.

[0013] Based on such findings, further research has been conducted, and it has been found that by reducing the amount of the antimony compound used during production of the surface layer of the polyester film substrate, and adjusting the polymerization time or additionally performing solid-phase polymerization, it is possible to achieve suppression of protrusion formation, high breaking strength in the longitudinal direction of the polyester film serving as the substrate, and low-level stability of heat shrinkage, thereby completing the present invention.

[0014] When release processing is performed using a conventional substrate, the number of protrusions derived from antimony compounds on the surface of the release layer is large, and it has been difficult to obtain a smooth release surface. However, the polyester film serving as the substrate of the present invention achieves a release layer surface in which the number of protrusions derived from antimony compounds on the release layer surface is controlled even when release layer processing is performed in the same manner as for conventional substrates.

[0015] The polyester film serving as the substrate of the present invention has a different surface shape compared to conventional polyester films. For this reason, the present inventors have found that depending on the release layer-forming composition, when an existing release layer formation technique is applied, there is a possibility that leveling properties become insufficient, or coating defects such as coating streaks and waviness that occur during release layer coating processing may occur. Accordingly, in the present invention, the invention has been completed by focusing on an embodiment in which the release layer-forming composition contains an ultraviolet-curable compound.

[0016] The present invention typically encompasses the following embodiments: [1] A release film having a polyester film substrate and a release layer, wherein the polyester film substrate is a biaxially oriented polyester film comprising a surface layer (sometimes referred to as surface layer A) and a smooth-slip layer (sometimes referred to as surface 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 35 mJ / m ２ Yes, a release film in which the average surface roughness (Sa) of the surface of the release layer is 7 nm or less, and the maximum protrusion height is 100 nm or less. [2] The number of antimony element-containing protrusions present on the surface of the surface layer of the polyester film substrate is 0.020 pieces / cm ２ The release film described in [1] below. [3] The release layer forming composition comprises a cationic curable polydimethylsiloxane (a), and the release layer forming composition contains 1 mg / m² of cationic curable polydimethylsiloxane (a). ２ 50mg / m or more ２The release film according to [1] or [2], comprising the following components in the amounts specified. [4] The release film according to [3], wherein the cationic curable polydimethylsiloxane (a) contains a compound having an alicyclic epoxy group. [5] The release film according to any one of [1] to [4], wherein the intrinsic viscosity of the surface layer is 0.55 to 0.62 dl / g. [6] The release film according to any one of [1] to [5], wherein the release layer contains a radical curable substance having one or more radical curable functional groups selected from (meth)acryloyl groups and alkenyl groups. [7] The release film according to any one of [1] to [6], wherein the release layer contains a polyfunctional (meth)acrylate having 2 or more (meth)acryloyl groups per molecule. [8] The release film according to any one of [1] to [7], wherein the release layer contains urethane acrylate having 4 or more functional groups per molecule. [9] The release film according to any one of [1] to [5], wherein the release film is a release film for producing ceramic green sheets, for producing semiconductor products, for producing optical members, or for producing resin sheets.

[0017] The release film of the present invention has a release layer on one surface of a base film, and is a release film in which the number of protrusions derived from an antimony compound on the surface of the release layer is controlled. The present invention can provide a release film that allows coating of a resin sheet-forming slurry without defects without deteriorating the high breaking strength in the longitudinal direction and heat shrinkability of the release film, and particularly can form a ceramic green sheet without defects. Furthermore, the release film of the present invention can prevent pinholes, partial thickness variation and the like even when, for example, a ceramic green sheet or a resin sheet is formed into a thin film. In addition, in the embodiment where the release layer-forming composition contains an ultraviolet curable compound, the present invention can improve leveling properties and form a highly smooth release layer, and further can suppress coating defects such as coating streaks and waviness that may occur during coating processing of the release layer-forming composition.

[0018] In this specification, the term "comprise" is used with the intention of encompassing the phrase "consist essentially of" and the phrase "consist of".

[0019] 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.

[0020] In this specification, numbers enclosed in "~" signify 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." 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, both "0.5 to 10 mass%" and "0.5 mass% to 10 mass%" mean "0.5 mass% or more and 10 mass% or less." Furthermore, 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."

[0021] 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.

[0022] (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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] The phosphorus compounds contained in the surface layer can be used individually 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 ethylphosphonate, 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.

[0030] The content of the phosphorus compound in the surface layer may 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.

[0031] The number of foreign substances with a major diameter of 1 µm or more contained in the surface layer is 20 pieces / mm ２ or less. Foreign substances with a major diameter of 1 µm or more may be catalyst residues, dust or the like mixed in the surface layer. The number of foreign substances with a major diameter of 1 µm or more is 15 pieces / mm ２ or less is preferred, 10 pieces / mm ２ or less is more preferred, 6 pieces / mm ２ or less is even more preferred. In the present invention, the amount of such foreign substances can be reduced by reducing the usage amount of the antimony compound in the production step of the polyester resin constituting the surface layer. The number of foreign substances with a major diameter of 1 µm or more can be identified by observing the surface layer with a confocal microscope. Specifically, it can be identified by the method described in the Examples.

[0032] The number of protrusions containing an 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 ２ or less, 0.001 to 0.020 pieces / cm ２ , 0.001 to 0.015 pieces / cm ２ , 0.001 to 0.012 pieces / cm ２ , 0.003 to 0.020 pieces / cm ２ , 0.003 to 0.015 pieces / cm ２ , 0.003 to 0.012 pieces / cm ２ or the like, 0.005 to 0.020 pieces / cm ２ is preferred, 0.005 to 0.015 pieces / cm ２ is more preferred, 0.005 to 0.012 pieces / cm ２This 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.

[0033] The antimony content of the surface layer is 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 by an ICP emission spectrometer. Specifically, it can be determined by the method described in the examples. Preferably, the antimony content is 5 ppm or more. If it is less than that, polymerization will not proceed, and the performance as a base material for the release film may not be exhibited. The antimony content of the surface layer may be 30 ppm or more, 40 ppm or more, or 50 ppm or more. It is thought that by including a certain amount of antimony compound, protrusions containing antimony elements will appear on the surface of the surface layer, thereby improving the adhesion between the base material and the release layer. For example, it is presumed that by including antimony elements within the scope of the present invention, at least a part of the protrusions will fit into the release layer according to the present invention, thereby improving adhesion.

[0034] 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.

[0035] 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.

[0036] 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 Preferably, the number of particles per sheet is 350 or less, more preferably 300 or less, and even more preferably 200 or less. Here, the p-chlorophenol / tetrachloroethane mixture consists only of p-chlorophenol and tetrachloroethane, with a mass ratio of p-chlorophenol 3: tetrachloroethane 1. 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, T050A047A manufactured by ADVANTEC. 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.

[0037] 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.

[0038] 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.

[0039] The number of particles filtered out on the dry filter is per 1 mm of filter. ２ The 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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%.

[0053] 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%.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] [Step 1] A step to obtain a polyester resin by melt polymerization using terephthalic acid as the main component of the dicarboxylic acid and ethylene glycol as the main component of the diol, with an antimony compound as the main polymerization catalyst. [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. [Step 3] A step to obtain a biaxially oriented polyester film for the surface layer constituting the release film by stretching the polyester resin obtained in Step 1 or 2.

[0060] 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.

[0061] The process for the continuous polymerization method is as follows:

[0062] 1) Slurry preparation step: The dicarboxylic acid component and the diol component are introduced into a 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. In this invention, recycled raw materials such as dicarboxylic acid components and diol components obtained by chemical decomposition recovery may also be used.

[0063] 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. The number and size of reaction vessels in the esterification reaction step are not limited and can be selected as appropriate. In addition, the manufacturing conditions for each step can be appropriately selected depending on the type and amount of polycondensation catalyst and additives for improving electrostatic adhesion, the number and size of reaction vessels, etc. For example, if there are three esterification reaction vessels, the temperature of the first esterification reaction vessel 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. 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. Ultimately, it is desirable that the esterification reaction rate reaches 60% or more, preferably 70% or more. Furthermore, as the esterification reaction vessel, a multi-stage reaction within a single vessel may be used, with a weir or the like installed inside.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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. The temperature of the second polycondensation reaction vessel may be 270 to 290°C, the pressure may be 0.5 to 1.5 kPa, and the average residence time may be 0.1 to 2 hours. When solid-phase polymerization is not used, the average residence time for the second polycondensation is preferably 1.0 to 2 hours, and more preferably 1.1 to 2 hours. The temperature of the third polycondensation reaction vessel 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 polycondensation is preferably 1.0 to 2 hours, and more preferably 1.1 to 2 hours. It is preferable that the degree of increase in intrinsic viscosity achieved in each of these polycondensation reaction steps is smoothly distributed. Since diol components are distilled off in 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.

[0068] 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.

[0069] 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.

[0070] Solid-phase polymerization can be carried out on polyester resin in the form of powder or granules. The term "powder or granules" refers to chips, pellets, flakes, or powder, but pellets are preferred.

[0071] 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. 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 will be carried out 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 usually 120 to 200°C, preferably 130 to 150°C, for 1 to 4 hours.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] The base film may or may not have an intermediate layer between the surface layer and the smooth-slip layer.

[0083] 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.

[0084] 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.

[0085] (Release layer) The release layer of the release film of the present invention has a surface free energy of 15 to 35 mJ / m² on the surface of the release layer. ２ Yes, the average surface roughness (Sa) of the surface of the release layer is within the range of 7 nm or less, and the maximum protrusion height is within the range of 100 nm or less.

[0086] [Aspect of the release layer 1] In one aspect, the release layer is formed from a release layer forming composition, the composition containing 1 mg / m² of an ultraviolet curing compound. ２ From 50 mg / m² ２ It contains the following amounts. In the present invention, the release layer is laminated on surface layer A. In the present invention, the release layer is a layer formed by curing the release layer forming composition, and the release layer forming composition contains 50 mg / m² of UV-curable compound. ２ It contains the following amount: preferably 40 mg / m². 2 The following is the case: 30 mg / m² 2It may be less than or equal to 20 mg / m2. On the other hand, the release layer forming composition may contain an ultraviolet curing compound at a concentration of 0.1 mg / m2 or more, for example, 0.5 mg / m2 or more, 3 mg / m2 or more, or 5 mg / m2 or more. If the concentration is 0.1 mg / m2 or more, the leveling properties of the release layer are maintained, the coat appearance is excellent, and a highly smooth release layer can be obtained. Furthermore, a concentration of 0.1 mg / m2 or more is preferable because it also provides excellent peelability.

[0087] Preferably, the release layer and the release layer forming composition contain a cationic curable polydimethylsiloxane (a). Having these characteristics in the release layer suppresses the occurrence of pinholes in ultrathin resin sheets requiring high smoothness, such as ceramic green sheets, and enables the formation of resin sheets with uniform film thickness. More specifically, the present invention can suppress curing defects due to oxygen inhibition in the release layer and achieve high crosslinking of the release layer. The present invention, achieving these effects, can, for example, improve the solvent resistance of the release layer surface. Improved solvent resistance of the release layer surface suppresses erosion of the release layer by organic solvents used during molding of ceramic green sheets and printing of internal electrodes, resulting in high release properties. Furthermore, with the release layer of the present invention, the effects of the base polyester film can be enjoyed even when the release layer is laminated. Therefore, the release film of the present invention can also achieve high longitudinal breaking strength and low thermal shrinkage stability. By curing the release layer by photocationic polymerization, it is possible to produce a substrate with a low volume shrinkage rate of the release film. Furthermore, in embodiments in which the release layer forming composition includes an ultraviolet-curable compound, leveling properties are improved and a highly smooth release layer can be formed, and coating defects such as coating streaks and waviness that may occur during the coating process of the release layer forming composition can be suppressed.

[0088] The release layer in the resin sheet molding release film of the present invention is a layer formed by curing a release layer forming composition, and the release layer forming composition contains cationic curable polydimethylsiloxane (a). Since the cationic curable polydimethylsiloxane (a) undergoes a crosslinking reaction through a cationic curing reaction, it does not cause curing defects due to oxygen inhibition and becomes a release layer with excellent solvent resistance. Therefore, there is no risk of the release layer being corroded by organic solvents used during ceramic green sheet molding, internal electrode printing, etc., and a release layer with excellent peelability can be obtained.

[0089] Furthermore, the inventors have found that in a release layer containing cationically curable polydimethylsiloxane (a), the amount of cationically curable polydimethylsiloxane (a) is important for achieving a release layer with high smoothness. The amount of cationically curable polydimethylsiloxane (a) in the release layer is 1 mg / m². ２ 50mg / m or more ２ It is contained in the following amounts. For example, 3 mg / m² ２ 50mg / m or more ２ It is contained in the following amounts: 4 mg / m² ２ 50mg / m or more ２ It may be contained in the following amounts: 5 mg / m² ２ 50mg / m or more ２ It is contained in the following amount: 5.5 mg / m² ２ 50mg / m or more ２ It may be contained in the following amounts. By satisfying these conditions, for example, leveling properties can be improved and a highly smooth release layer can be formed, and furthermore, coating defects such as coating streaks and waviness that may occur during the coating process of the release layer forming composition can be suppressed. Herein, in another aspect of the present invention, cationic curable polydimethylsiloxane (a) is contained in the release layer at 90 mg / m2 or less and 50 mg / m2 2 Amounts exceeding 60 mg / m³, for example. 2 Less than 50mg / m 2 It may be included in amounts exceeding 90 mg / m². 2 Less than 50mg / m 2 If the quantity is greater than 50 mg / m³, the release layer should contain 50 mg / m³. ２The smoothness of the release layer may be slightly inferior compared to the configuration containing the following amounts, but the above content can be applied depending on the type of resin sheet formed on the release layer. Therefore, when higher resolution properties are required, 50 mg / m² of cation-curable polydimethylsiloxane (a) can be added to the release layer. ２ It is contained in the following amounts. For example, it is more preferable that it be 40 mg / m2 or less, and even more preferable that it be 30 mg / m2 or less. Also, for example, the amount of cation-curable polydimethylsiloxane (a) may be 20 mg / m2 or less.

[0090] If the content of cation-curable polydimethylsiloxane (a) in the release layer is 50 mg / m2 or less, aggregation of polydimethylsiloxane (a) during the process of forming the release layer, for example, the drying process, can be suppressed, there is no risk of generating many protrusions outside the scope of the present invention, and the effects of the present invention can be achieved. In one embodiment, the release layer and the release layer forming composition may also contain components other than cation-curable polydimethylsiloxane (a). In this case as well, although judgment should not be made based on a specific theory, in the present invention, polydimethylsiloxane (a) can segregate on the surface of the release layer during processing of the release layer, and if the content is 50 mg / m2 or less, aggregation is less likely to occur, and a release layer with high smoothness can be formed. The lower the content of polydimethylsiloxane (a) according to the present invention, the less likely aggregation is to occur, but if the content in the release layer is 0.1 mg / m2 or more, the leveling properties of the release layer are maintained, the coat appearance is excellent, and a release layer with high smoothness can be obtained. Furthermore, a concentration of 0.1 mg / m2 or more is preferable because it also provides excellent release properties. For example, the content of polydimethylsiloxane (a) may be 0.5 mg / m2 or more. In the present invention, the release layer forming composition contains cationic curable polydimethylsiloxane (a). In addition, in the release layer formed by the curing of the release layer forming composition, compounds (cured products) derived from cationic curable polydimethylsiloxane (a) are present. In this specification, compounds derived from (a) present in the release layer may also be simply referred to as cationic curable polydimethylsiloxane (a).

[0091] In the present invention, cationic curable polydimethylsiloxane (a) refers to a polydimethylsiloxane having a cationic curable functional group. A cationic curable functional group is a reactive functional group that exhibits cationic curability, and examples include vinyl ether groups, oxetanyl groups, epoxy groups, and alicyclic epoxy groups. Among these, it is preferable from the viewpoint of reactivity to have at least one functional group selected from oxetanyl groups, epoxy groups, and alicyclic epoxy groups, and it is most preferable to have an alicyclic epoxy group. Having such a functional group is preferable because it forms a crosslinked structure by the cationic curing reaction, resulting in a release layer with excellent solvent resistance and excellent release properties.

[0092] The number of cationic curable functional groups in cationic curable polydimethylsiloxane (a) is limited to one or more. For example, having two or more cationic curable functional groups is preferable because it facilitates the cationic curing reaction and results in a release layer with high crosslink density. The position of the cationic curable functional groups is not particularly limited, and they are generally located on the side chains or terminals of the polydimethylsiloxane. The structure of the polydimethylsiloxane can be linear or branched, and it can be used without problems even if it has functional groups other than cationic curable functional groups.

[0093] Cationic curable polydimethylsiloxane (a) can preferably be a commercially available product. Examples include Silicolease® UV POLY200, UV POLY201, UV POLY215, UV RCA200, UV RCA251 from Arakawa Chemical Industries, Ltd., X-62-7622, ​​X-62-7629, X-62-7660, KF-101, KF-105, X-22-343, X-22-169AS, X-22-169B, X-22-163, X-22-173BX, X-22-173DX, X-22-9002 from Shin-Etsu Chemical Co., Ltd., and UV9440E, UV9430 from Momentive Performance Materials, Inc.

[0094] The weight-average molecular weight of the cationic curable polydimethylsiloxane (a) is preferably 1,000 to 500,000, and more preferably 5,000 to 100,000. A weight-average molecular weight of 1,000 or more is preferable because the cationic curing reaction proceeds easily and the release properties are excellent. A weight-average molecular weight of 500,000 or less is preferable because the viscosity does not become too high, the coating properties are excellent, and the release layer has high flatness.

[0095] The release layer forming composition of the present invention may also contain other resins in addition to the cationic curable polydimethylsiloxane (a). In this case, the thickness of the release layer can be reduced. In the present invention, since the release layer is provided on the surface layer A of a substrate film that is substantially free of inorganic particles, even if the thickness of the release layer is thin, an extremely smooth release layer can be obtained. For example, a cationic curable resin (b) other than cationic curable polydimethylsiloxane (a) may be included. In this case, the release layer forming composition contains a total of 50 mg / m² of cationic curable polydimethylsiloxane (a) and cationic curable resin (b) in the release layer. ２ It contains the following amounts. Even in such cases, leveling performance is improved, coating defects such as coating streaks and undulations that occur during the release layer coating process are suppressed, and the proportion of film area that can be used for the ceramic green sheet can be increased. When coating streaks and undulations occur, there is a difference in the thickness of the release layer compared to the normal area, and when peeling the ceramic green sheet, the streaks may become the starting point, potentially causing peeling errors such as cutting and tearing of the ceramic green sheet.

[0096] Furthermore, 50 mg / m² of UV-curing compound is added. ２ As described below, by including it in an amount closer to 0.1 mg / m2, although the mechanism has not been identified, it is possible to suppress the incorporation of extremely small foreign matter present in the base film, release process, etc., into the release layer. Therefore, there is no risk of protrusions caused by foreign matter forming on the surface of the release layer, and a release layer with the smooth surface described above can be obtained.

[0097] In the case of a release layer cured from a composition containing an ultraviolet-curable compound, such as a cation-curable polydimethylsiloxane (a), the thickness of the release layer is preferably 0.001 μm or more and less than 0.050 μm. A thickness of 0.001 μm or more is preferable because it provides excellent release properties. A thickness of less than 0.050 μm is preferable because it prevents aggregation of the release layer forming composition and results in a smooth release layer. In this invention, when cation-curable polydimethylsiloxane (a) is the main component, the composition contains 50 parts by mass or more, for example more than 50 parts by mass, preferably 70 parts by mass or more, for example 80 parts by mass or more, per 100 parts by mass of the resin solids content of the release layer, and in one embodiment, it contains 90 parts by mass or more. Alternatively, the entire resin solids content of the release layer may substantially consist of cation-curable polydimethylsiloxane (a).

[0098] When the release layer, i.e., the release layer forming composition, contains a cation-curable polydimethylsiloxane (a), the surface free energy at the surface of the release layer is 15 to 25 mJ / m². ２ It is within the range.

[0099] The release layer forming composition of the present invention may also contain a cationic curable resin (b) in addition to a cationic curable polydimethylsiloxane (a). In this case, (b) is a different resin from (a), and resin (b) does not have a polydimethylsiloxane structure. Specifically, it can be broadly classified into two types: a cationic curable compound (b-1) that does not have a silicone skeleton, and a siloxane compound (b-2) that has an alicyclic epoxy group.

[0100] In one embodiment, the release layer forming composition further contains a cationic curable compound (b-1) without a silicone skeleton in addition to a cationic curable polydimethylsiloxane (a). Examples of cationic curable compounds (b-1) without a silicone skeleton include polymers and monomers having two or more cationic curable functional groups in the molecule and without a silicone skeleton. Among these, resins having two or more epoxy groups or alicyclic epoxy groups are preferred, and having two or more alicyclic epoxy groups is more preferred. For example, the number of alicyclic epoxy groups may be six or less. Having two or more alicyclic epoxy groups allows a crosslinking reaction to proceed by the cationic curing reaction, resulting in a release layer with excellent solvent resistance. At the same time, a crosslinking reaction also proceeds with the polydimethylsiloxane (a) contained in the release layer, which is preferable because it has excellent release properties and suppresses the migration of polydimethylsiloxane (a) to the ceramic green sheet.

[0101] In one embodiment, the release layer forming composition contains both a cationic curable resin (b-1) without a silicone skeleton and polydimethylsiloxane (a), thereby achieving a release layer with high smoothness. By using a release layer containing compound (b-1), fine irregularities, minute foreign matter, and oligomer-derived protrusions present in the substrate film can be filled, resulting in an ultra-smooth release layer. Furthermore, since the curing reaction proceeds with ultraviolet light, a release layer with high smoothness is obtained. Although it should not be interpreted in a way that is limited to a specific theory, it can be inferred that during the drying process in the release layer forming composition during release layer processing, (b-1) and (a) level uniformly, and curing proceeds after the flatness is increased, thus obtaining a release layer with high smoothness. In addition, the polydimethylsiloxane (a) contained at the same time segregates on the surface of the release layer during the drying process in this invention, so a release layer with excellent peelability can be obtained.

[0102] The cation-curable compound (b-1) that does not have a silicone skeleton is preferably a low molecular weight monomer. Specifically, it is preferably a number-average molecular weight of 200 or more and less than 5000, more preferably 200 or more and less than 2500, and even more preferably 200 or more and less than 1000. A number-average molecular weight of 200 or more is preferable because the boiling point does not become low, and there is no risk of the cation-curable compound (b-1) volatilizing during the drying process of the release layer forming composition during release layer processing. A number-average molecular weight of less than 5000 is preferable because it increases the crosslinking density of the release layer and provides excellent solvent resistance. Furthermore, it is preferable because it can exist in a fluid liquid state during the drying process, resulting in excellent leveling properties and an ultra-smooth release layer.

[0103] A commercially available cation-curing compound (b-1) that does not have a silicone skeleton can be suitably used. Examples of compounds having alicyclic epoxy groups include Celoxide 2021P, Celoxide 2081, Epolid GT401, and EHPE3150 from Daicel Corporation, HiREM-1 from Shikoku Chemicals, and THI-DE, DE-102, and DE-103 from ENEOS Corporation. Examples of resins having epoxy groups include EPICLON® 830, 840, 850, 1051-75M, N-665, N-670, N-690, N-673-80M, and N-690-75M from DIC Corporation, and Denacol® EX-611, EX-313, and EX-321 from Nagase Chemtec Corporation.

[0104] In the release layer, the content of the cation-curable compound (b-1) without a silicone skeleton is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, per 100 parts by mass of the total of the cation-curable polydimethylsiloxane (a) and the cation-curable compound (b-1). A content of 80% by mass or more of the cation-curable compound (b-1) and making it the main component of the release layer is preferable because it results in a release layer with high crosslinking density and excellent release properties. Furthermore, it is preferable to reduce the content of the cation-curable polydimethylsiloxane (a) in the release layer, suppressing the aggregation of polydimethylsiloxane (a)-derived components on the surface of the release layer during the drying process, thus avoiding deterioration of flatness. While a higher content of the cation-curable compound (b-1) results in a release layer with superior smoothness, it is preferable that the content of the cation-curable compound (b-1) be 99.9% by mass or less in order to include cation-curable polydimethylsiloxane (a) and ensure release properties. In the present invention, the mold release layer formed by curing the mold release layer composition contains compounds (cured products) derived from a cationic curable compound (b-1) that does not have a silicone skeleton. In this specification, the compounds derived from (b-1) present in the mold release layer may also be simply referred to as a cationic curable compound (b-1) that does not have a silicone skeleton.

[0105] When the release layer forming composition contains a cationic curable polydimethylsiloxane (a) and a cationic curable compound (b-1), it is preferable because the release layer has a high crosslinking density, excellent solvent resistance, and excellent peeling power. Furthermore, the inclusion of a cationic curable compound (b-1) is preferable because it allows for a thicker release layer while keeping the content of cationic curable polydimethylsiloxane (a) within a predetermined range. A thicker release layer is preferable because it can fill in scratches and minute irregularities present in the substrate film, resulting in a smooth release layer as described above.

[0106] When the release layer forming composition contains a cationic curable polydimethylsiloxane (a) and a cationic curable compound (b-1), the thickness of the release layer is preferably 0.05 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. A thickness of 0.05 μm or more is preferable because it results in a smooth release layer. A thickness of 1.0 μm or less is preferable because it results in a release film with excellent flatness without curling.

[0107] In one embodiment, the release layer forming composition may further contain a siloxane compound (b-2) having an alicyclic epoxy group. Examples of siloxane compounds (b-2) having an alicyclic epoxy group include those shown in the following structural formulas (Chemical Formula 1) and (Chemical Formula 2). (In Chemical Formula 1, R2 is an alkyl group having 1 to 4 carbon atoms).

[0108]

[0109]

[0110] Using a siloxane compound (b-2) having an alicyclic epoxy group is preferable because it results in an ultra-smooth release layer for the same reasons as when using the cationic curable compound (b-1). That is, it can fill in fine irregularities, minute foreign matter, and protrusions derived from oligomers present in the substrate film. Furthermore, since the curing reaction proceeds with ultraviolet light, the compound (b-2) and polydimethylsiloxane (a) level uniformly during the drying process of the release layer forming composition during release layer processing, and curing proceeds after the flatness is improved, resulting in an ultra-smooth release layer. Moreover, in this invention, the polydimethylsiloxane (a) contained simultaneously segregates on the surface of the release layer during the drying process, so a release layer with excellent peelability can be obtained.

[0111] The siloxane compound (b-2) having an alicyclic epoxy group has good compatibility with the cationic curable polydimethylsiloxane (a), so it mixes appropriately in the release layer and crosslinking reactions proceed between them. Therefore, it is preferable because it forms a release layer with excellent solvent resistance and excellent release properties. Furthermore, since the siloxane compound (b-2) has a siloxane structure, it has a rigid molecular skeleton, which is preferable because it increases the hardness of the film when cured. With increased film hardness, the release layer is less likely to deform when peeling off a resin sheet, such as a ceramic green sheet, and good release properties can be achieved. Moreover, scratches are less likely to occur in the release layer, and there is no risk of scratches in the release layer being transferred to the resin sheet, such as a ceramic green sheet, causing defects, which is preferable.

[0112] It is preferable that the release layer forming composition contains a siloxane compound (b-2) because it improves the adhesion of the release layer to the base film. Improved adhesion of the release layer is preferable because it suppresses the occurrence of scratches during the transport process and eliminates the risk of the release layer transferring when the resin sheet is peeled off.

[0113] In one embodiment, the siloxane compound (b-2) has two or more alicyclic epoxy groups in its molecule. Having two or more alicyclic epoxy groups in its molecule allows for crosslinking by cationic curing, resulting in a release layer with excellent solvent resistance. Furthermore, since crosslinking also proceeds with polydimethylsiloxane (a) contained in the release layer, it is preferable because it has excellent release properties and suppresses the migration of polydimethylsiloxane (a) to the ceramic green sheet. For example, the siloxane compound (b-2) has six or fewer alicyclic epoxy groups in its molecule.

[0114] A commercially available siloxane compound (b-2) having an alicyclic epoxy group can be used. Examples include KR-470, X-40-2728, X-40-2678, and X-40-2669, all manufactured by Shin-Etsu Chemical Co., Ltd.

[0115] In the release layer, the content of siloxane compound (b-2) is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, based on 100 parts by mass of the total of cation-curable polydimethylsiloxane (a) and siloxane compound (b-2). A content of 80% by mass or more of siloxane compound (b-2) as the main component in the release layer is preferable because it results in a release layer with high crosslinking density and excellent release properties. Furthermore, the content of cation-curable polydimethylsiloxane (a) in the release layer can be reduced, which is preferable in this invention because it suppresses the aggregation of cation-curable polydimethylsiloxane (a) on the surface of the release layer during the drying process, thus avoiding deterioration of flatness. A higher content of siloxane compound (b-2) results in a release layer with superior smoothness. For example, to ensure release properties while containing cation-curable polydimethylsiloxane (a), the siloxane compound (b-2) is preferably 99.9% by mass or less. In the present invention, the mold release layer formed by the curing of the mold release layer-forming composition contains compounds (cured products) derived from siloxane compound (b-2). In this specification, compounds derived from siloxane compound (b-2) present in the mold release layer may also be simply referred to as siloxane compound (b-2).

[0116] When the release layer forming composition contains a cationic curable polydimethylsiloxane (a) and a siloxane compound (b-2), the thickness of the release layer is preferably 0.05 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. A thickness of 0.05 μm or more is preferable because it results in a smooth release layer. A thickness of 1.0 μm or less is preferable because it results in a release film with excellent flatness without curling.

[0117] In one embodiment, the release layer may contain both a cationic curable resin (b-1) and a siloxane compound (b-2), and the total amount of these cationic curable resins (b-1) and siloxane compounds (b-2) can be 80% by mass or more and 99.9% by mass or less, based on 100 parts by mass of the total of the cationic curable polydimethylsiloxane (a), cationic curable compound (b-1), and siloxane compound (b-2) in the release layer.

[0118] In the present invention, it is necessary to carry out a cationic curing reaction in order to form a release layer. Therefore, the release layer forming composition preferably contains an acid generator (c). Furthermore, compounds derived from the acid generator (c) may be present in the release layer. Here, compounds derived from the acid generator (c) present in the release layer may also be simply referred to as the acid generator (c). The acid generator is not particularly limited and general types can be used, but it is preferable to use a photoacid generator that generates acid under ultraviolet irradiation because it can reduce the amount of heat generated during processing and results in a release layer with excellent flatness.

[0119] From a reactivity standpoint, a salt consisting of an onium ion and a non-nucleophilic anion is preferred as the photoacid generator. 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.

[0120] 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. Triaryl, diaryl(monoalkyl), monoaryl(dialkyl), and trialkyl groups may be used as the organic group of the onium ion, 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. In addition, tetra(pentafluorophenyl)gallium ions or anions in which some of the fluorine anions are replaced with perfluoroalkyl groups or organic groups may be used, or other anionic components may be used.

[0121] The amount of photoacid generator added is 0.1 to 10% by mass, more preferably 0.5 to 8% by mass, based on 100 parts by mass of the total of the cationic curable polydimethylsiloxane (a) and cationic curable compound (b-1) and / or siloxane compound (b-2) having an alicyclic epoxy group in the release layer. Even more preferably, it is 1 to 5% by mass. An amount of 0.1% by mass or more is preferable because it prevents insufficient acid generation and the risk of inadequate curing. Furthermore, an amount of 10% 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.

[0122] In this specification, 100 parts by mass of the total of the cation-curable polydimethylsiloxane (a) and the cation-curable compound (b-1) and / or the siloxane compound (b-2) having an alicyclic epoxy group in the release layer means the sum of the solid content of the cation-curable polydimethylsiloxane (a) and the solid content of the cation-curable resin (b). In embodiments in which the release layer does not contain the cation-curable resin (b), the weight of the cation-curable polydimethylsiloxane (a) corresponds to 100 parts by mass of the resin solid content in the release layer.

[0123] In the present invention, additives such as adhesion enhancers and antistatic agents may be added to the release layer, 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, such as anchor coating, corona treatment, plasma treatment, or atmospheric pressure plasma treatment, before applying the release coating layer.

[0124] The release film obtained by the present invention preferably has a peeling force of 0.01 mN / mm or more and 2.0 mN / mm or less when peeling off the ceramic green sheet. More preferably, it has a peeling force of 0.05 mN / mm or more and 1.0 mN / mm or less. A peeling force of 0.01 mN / mm or more is preferable because there is no risk of the ceramic green sheet lifting up during transport. A peeling force of 2.0 mN / mm or less is preferable because there is no risk of the ceramic green sheet being damaged during peeling.

[0125] Because the release film obtained by the present invention uses a highly flattened base film, the surface of the release layer can be made smooth even if the thickness of the release layer is 1.0 μm or less, 0.5 μm or less, or even 0.3 μm or less. Therefore, the amount of solvent and resin used can be reduced, making it possible to create an environmentally friendly and inexpensive release film for molding ultrathin ceramic green sheets.

[0126] [Second aspect of the release layer] The release film of the present invention comprises a radical-curable substance having one or more radical-curable functional groups selected from (meth)acryloyl groups and alkenyl groups, the surface free energy of the surface of the release layer is 18 to 35 mJ / m2, the thickness of the release layer is 10 nm to 1500 nm, the average surface roughness (Sa) of the surface of the release layer is 7 nm or less, and the maximum protrusion height is in the range of 100 nm or less. By using this release film, smoothness in a small area and coarse protrusions such as antimony in a large area can be suppressed.

[0127] The release layer in the present invention is formed by curing a release layer forming composition, and the release layer forming composition contains a radical curable substance having one or more radical curable functional groups selected from (meth)acryloyl groups and alkenyl groups. Other components can be added in addition to the resin and additives, as long as they do not impair the effects of the present invention. For example, the release layer may contain a polyfunctional (meth)acrylate having two or more (meth)acryloyl groups in one molecule.

[0128] In the present invention, a radical-curable substance having one or more radical-curable functional groups selected from (meth)acryloyl groups and alkenyl groups can be used in the release layer, and any common one can be used. It may be a monomer, oligomer, or polymer, or a mixture thereof. More preferably, the radical-curable substance is a urethane acrylate, and more preferably has four or more functional groups. By using a urethane acrylate with four or more functional groups, the curing shrinkage of the release layer can be suppressed while improving the crosslinking density, thereby improving the elastic modulus of the release layer and reducing deformation during peeling. Furthermore, it is preferable because it can improve the solvent resistance of the release layer, thus preventing erosion of the release layer by solvents during slurry coating. The release layer is preferably laminated on the surface layer of the polyester film of the present invention. By including a certain amount of antimony compound, alkaline earth metal compound, and phosphorus compound, for example, protrusions containing antimony elements present on the surface layer of the substrate will appear, which helps to suppress deterioration of winding properties as a release film roll. It is also believed that an effect of improving adhesion with the release layer can be obtained. Furthermore, a release film having a release layer containing urethane acrylate and a polyester film substrate according to the present invention not only exhibits excellent adhesion between the release layer and the substrate, but also good release properties to the object to be released. For example, even if the ceramic green sheet, semiconductor product, optical component, or resin sheet to be peeled from the release layer is a thin film, it can be peeled off well. In addition, because the release layer exhibits high smoothness, it can suppress the occurrence of pinholes in green sheets and the like, and furthermore, it is possible to make the object to be released thinner compared to conventional methods.

[0129] (Urethane Acrylate) The urethane acrylate used in this invention refers to a material having a urethane bond and one or more reactive functional groups selected from acryloyl groups and methacryloyl groups in its molecular chain. In this invention, the term urethane acrylate is used to include urethane methacrylate. The urethane acrylate used in this invention preferably has four or more of the above-mentioned reactive functional groups in one molecule, more preferably six or more, and even more preferably nine or more. Having four or more reactive functional groups improves the crosslinking density of the release layer and increases the elastic modulus, which is preferable because it reduces deformation of the release layer when peeling off the ceramic green sheet. There is no particular upper limit for the number of reactive functional groups, but it is preferably 20 or less, and more preferably 15 or less. In this specification, when referring to a hexafunctional urethane acrylate, it means a urethane acrylate having six reactive functional groups in one molecule.

[0130] The urethane acrylate used in the present invention may be a monomer, an oligomer, or a mixture of monomer and oligomer. The weight-average molecular weight (Mw) of the urethane acrylate used in the present invention is not particularly limited, but is preferably 600 to 20,000, more preferably 800 to 10,000, and even more preferably 1,000 to 5,000. The above weight-average molecular weight Mw is a polystyrene equivalent value measured by GPC (gel permeation chromatography).

[0131] The method for synthesizing the urethane acrylate used in the present invention is not particularly limited, but it can be obtained, for example, by the reaction of a polyhydric alcohol and an organic polyisocyanate with a hydroxyacrylate.

[0132] Examples of the polyhydric alcohols mentioned above include neopentyl glycol, 3-methyl-1,5-pentanediol, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, tricyclodecanedimethylol, bis-[hydroxymethyl]-cyclohexane, etc.; polyester polyols obtained by the reaction of the polyhydric alcohols with polybasic acids (e.g., succinic acid, phthalic acid, hexahydrophthalic anhydride, terephthalic acid, adipic acid, azelaic acid, tetrahydrophthalic anhydride, etc.); polycaprolactone polyols obtained by the reaction of the polyhydric alcohols with ε-caprolactone; polycarbonate polyols (e.g., polycarbonate diols obtained by the reaction of 1,6-hexanediol and diphenyl carbonate, etc.); and polyether polyols. Examples of the polyether polyols mentioned above include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide-modified bisphenol A, etc.

[0133] Examples of the above-mentioned organic polyisocyanates include isocyanate compounds such as isophorone diisocyanate, hexamethylene diisocyanate, tolylene diisocyanate, xylene diisocyanate, diphenylmethane-4,4'-diisocyanate, and dicyclopentanyl isocyanate, as well as adducts of these isocyanate compounds, or polymers of these isocyanates.

[0134] Examples of the above-mentioned hydroxy(meth)acrylate compounds include pentaerythritol tri(meth)acrylate, pentaerythritol di(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol tetra(meth)acrylate, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxybutyl(meth)acrylate, dimethylolcyclohexylmono(meth)acrylate, and hydroxycaprolactone(meth)acrylate. Among these, pentaerythritol tri(meth)acrylate and dipentaerythritol penta(meth)acrylate are preferred from the viewpoint of hardness.

[0135] The urethane acrylate used in this invention can also be a commercially available product. Examples of commercially available products include: UV1700B (weight-average molecular weight 2000, 10-functional), UV7620EA (weight-average molecular weight 4100, 9-functional), UV7600B (weight-average molecular weight 1400, 6-functional), UV7610B (weight-average molecular weight 11000, 9-functional), UV7650B (weight-average molecular weight 2300, 5-functional); DPHA40H (weight-average molecular weight 7000, 10-functional), UX5003 (weight-average molecular weight 700, 6-functional); Beamset 577 (weight-average molecular weight 1000, 6-functional); Taisei Fine Chemical Co., Ltd.: 8UX-015A (weight-average molecular weight 1000, 15-functional); and Shin Nakamura Chemical Industry Co., Ltd.: U15HA (weight-average molecular weight 2300, 15-functional).

[0136] In the present invention, urethane acrylate can be used alone or in combination of two or more types. Furthermore, in addition to tetrafunctional or more functional urethane acrylate, acrylate-based compounds or urethane acrylate-based compounds may be included, as long as they do not hinder the effects of the present invention. The acrylate-based compounds may be acrylate monomers or acrylate oligomers, and the number of functional groups is not particularly limited, but it is preferable that they be polyfunctional with two or more types. When two or more types are included, it is preferable that they contain 30% by mass or more of tetrafunctional or more functional urethane acrylate in order to exhibit the effects of the present invention.

[0137] The (meth)acrylic acid ester is preferably at least one selected from polyfunctional (meth)acrylate monomers and (meth)acrylate oligomers, and more preferably at least one selected from trifunctional or higher (meth)acrylate monomers and (meth)acrylate oligomers, and even more preferably a trifunctional or higher (meth)acrylate monomer. Being trifunctional or higher results in excellent curability of the release agent composition C, and also better peelability of the surface of the resulting release agent layer 12.

[0138] Examples of polyfunctional (meth)acrylate monomers include trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris((meth)acryloxyethyl) isocyanurate, propionic acid-modified dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, and the like. These may be used individually or in combination of two or more.

[0139] Examples of polyfunctional (meth)acrylate oligomers include polyester acrylate oligomers, epoxy acrylate oligomers, urethane acrylate oligomers, polyether acrylate oligomers, polybutadiene acrylate oligomers, and silicone acrylate oligomers.

[0140] Polyester acrylate oligomers can be obtained, for example, by esterifying the hydroxyl groups of a polyester oligomer having hydroxyl groups at both ends, obtained by the condensation of a polycarboxylic acid and a polyhydric alcohol, with (meth)acrylic acid, or by esterifying the terminal hydroxyl groups of an oligomer obtained by adding an alkylene oxide to a polycarboxylic acid with (meth)acrylic acid.

[0141] Epoxyacrylate oligomers can be obtained, for example, by reacting (meth)acrylic acid with the oxirane ring of a relatively low molecular weight bisphenol-type epoxy resin or novolac-type epoxy resin to esterify it. Alternatively, carboxyl-modified epoxy acrylate oligomers, obtained by partially modifying epoxy acrylate oligomers with dibasic carboxylic acid anhydrides, can also be used.

[0142] Urethane acrylate oligomers can be obtained, for example, by esterifying polyurethane oligomers, which are obtained by the reaction of polyether polyols or polyester polyols with polyisocyanates, with (meth)acrylic acid.

[0143] Polyether acrylate oligomers can be obtained by esterifying the hydroxyl groups of polyether polyols with (meth)acrylic acid.

[0144] The above-mentioned polyfunctional (meth)acrylate monomers and polyfunctional (meth)acrylate oligomers can be used individually or in combination of two or more. Furthermore, polyfunctional (meth)acrylate monomers and polyfunctional (meth)acrylate oligomers can also be used in combination.

[0145] (Photoradical initiator) When a radical polymerization resin is used in the release layer of the present invention, it is preferable to add a photoradical polymerization initiator. Specific examples of photoradical polymerization initiators include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin methyl benzoate, benzoin dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexylphenyl ketone, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloranthraquinone, (2,4,6-trimethylbenzyldiphenyl)phosphine oxide, and 2-benzothiazole-N,N-diethyldithiocarbamate. In particular, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]-phenyl}-2-methylpropan-1-one, 1-hydroxycyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one are preferred, and among these, 2-hydroxy-2-methyl-1-phenyl-propan-1-one and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one are particularly preferred. These may be used individually or in combination of two or more.

[0146] The amount of photoradical polymerization initiator added is not particularly limited. For example, it is preferable to use about 0.1 to 20% by mass relative to the radical-curable resin used.

[0147] (Release Agent) In the present invention, the release agent used in the release layer (an additive that improves the release properties of the release layer) can be a silicone-based additive or a non-silicone-based additive such as an olefin-based, long-chain alkyl-based, or fluorine-based additive. However, from the viewpoint of release properties, it is preferable to use a silicone-based additive.

[0148] Silicone-based additives are compounds that have a silicone skeleton within their molecules, and polyorganosiloxanes are preferably used. Acrylic resins and alkyd resins that have polyorganosiloxanes in their side chains can also be used. Among polyorganosiloxanes, polydimethylsiloxane (abbreviated as PDMS) can be preferably used, and those with functional groups in part are also preferred.

[0149] The functional groups introduced into polydimethylsiloxane are not particularly limited and may be either reactive or non-reactive. Furthermore, the functional groups may be introduced at one end, both ends, or on the side chains of the polydimethylsiloxane. There may also be one or more positions where the functional groups are introduced. Additionally, a single molecule may contain two or more different functional groups.

[0150] Reactive functional groups that can be introduced into polydimethylsiloxane include amino groups, epoxy groups, hydroxyl groups, mercapto groups, carboxyl groups, methacrylic groups, and acrylic groups. Non-reactive functional groups that can be introduced include polyether groups, aralkyl groups, fluoroalkyl groups, long-chain alkyl groups, ester groups, amide groups, and phenyl groups. In this invention, in order to reduce the migration of the release agent to the ceramic green sheet, it is preferable to have methacrylic groups or acrylic groups that react with urethane acrylate.

[0151] Furthermore, it is also preferable to use polydimethylsiloxane-modified resins such as acrylic resins, polyester resins, and urethane resins that have polydimethylsiloxane in their side chains. Polydimethylsiloxane-modified resins are preferable because they have better compatibility with urethane acrylate than other general release agents and can form a uniform release layer, thus improving release properties. In addition, polydimethylsiloxane-modified resins that have methacrylic groups or acrylic groups that react with urethane acrylate are even more preferable in order to reduce the migration of the release agent to the ceramic green sheet. Examples of commercially available acrylic resins that have a PDMS skeleton in their side chains include Cymac® US350, Cymac® US352 (manufactured by Toagosei Co., Ltd.), 8BS-9000 (manufactured by Taisei Fine Chemical Co., Ltd.), GL-01, and GL-02R (manufactured by Kyoeisha Chemical Co., Ltd.). Examples of commercially available acrylic resins having a PDMS skeleton and acryloyl groups in the side chains include 8SS-723 (manufactured by Taisei Fine Chemical Co., Ltd.), GL-03, and GL-04R (manufactured by Kyoeisha Chemical Co., Ltd.).

[0152] 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) and Optool® (manufactured by Daikin Industries, Ltd.).

[0153] As long-chain alkyl additives, resins modified with long-chain alkyl can be used, and those having alkyl groups with approximately 8 to 20 carbon atoms in the side chains, such as polyvinyl alcohol or acrylic resin, are preferred. Polymers in which (meth)acrylic acid esters are the main repeating units, and copolymers containing long-chain alkyl groups with 8 to 20 carbon atoms in the transesterified portion, can also be suitably used. Octyl acrylate, lauryl acrylate, and stearyl acrylate, in which acrylate groups are attached to long-chain alkyl groups, can also be suitably used.

[0154] In the release layer of the present invention, it is preferable that the release agent is contained in an amount of 0.1% by mass or more and 15% 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. An amount of 0.1% by mass or more is preferable because it improves release properties and improves the peelability of the ceramic green sheet. On the other hand, an amount of 15% by mass or less is preferable because it prevents the elastic modulus of the entire release layer from decreasing too much, and deformation of the release layer is less likely to occur when peeling off the ceramic green sheet. In this case, the total solid content of the release layer is the sum of the solid content of the urethane acrylate component and the release agent.

[0155] The release layer of the present invention may contain particles with a particle diameter 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.

[0156] The release layer of the present invention may contain additives such as adhesion enhancers and antistatic agents, as long as they do not hinder the effects of the present invention. Furthermore, to improve adhesion to the substrate, it is preferable to pre-treat the polyester film surface with an anchor coat, corona treatment, plasma treatment, atmospheric pressure plasma treatment, etc., before applying the release coating layer.

[0157] In the present invention, the thickness of the release layer can be set according to its intended use and is not particularly limited, but preferably it is in the range of 0.2 to 2.0 μm after curing, more preferably 0.3 to 1.5 μm, even more preferably 0.4 to 1.2 μm, and even more preferably 0.6 to 1.0 μm. A release layer thickness of 0.2 μm or more is preferable because it allows for good curability of the urethane acrylate and improves the elastic modulus of the release layer, resulting in good peeling performance. Furthermore, a thickness of 2.0 μm or less is preferable because it is less likely to curl even if the thickness of the release film is thin, and does not cause poor runability during the molding and drying process of the ceramic green sheet.

[0158] The release film of the present invention preferably has a highly smooth surface on the release layer. Therefore, it is preferable that the average surface roughness (Sa) of the release layer surface is 7 nm or less. Furthermore, it is even more preferable that the above Sa is satisfied and the maximum protrusion height (P) of the release layer surface is 100 nm or less. Moreover, it is preferable that the average surface roughness (Sa) of the region is 5 nm or less, and at the same time, it is particularly preferable that the maximum protrusion height (P) is 80 nm or less. If the area surface roughness (Sa) is 7 nm or less, it is preferable that defects such as pinholes do not occur when forming the ceramic green sheet, resulting in a good yield. If the above Sa is satisfied and the maximum protrusion height (P) of the release layer surface is 100 nm or less, it is even more preferable as the risk of pinhole defects is reduced. It can be said that the smaller the above average surface roughness (Sa), the better, but it may be 0.1 nm or more, or 0.3 nm or more. It can also be said that the smaller the maximum protrusion height (P), the better, but it may be 1 nm or more, or 3 nm or more.

[0159] The surface free energy of the release layer surface of the release layer film of the present invention is preferably 18 mJ / m² or more and 40 mJ / m² or less. More preferably 21 mJ / m² or more and 35 mJ / m² or less, and even more preferably 23 mJ / m² or more and 30 mJ / m² or less. A surface free energy of 18 mJ / m² or more is preferable because it makes it less likely for repellency to occur when coating with ceramic slurry, and allows for uniform coating. A surface free energy of 40 mJ / m² or less is also preferable because there is no risk of a decrease in the release properties of the ceramic green sheet. By setting the surface free energy within the above range, it is possible to provide a release film that does not repellency during coating and has excellent release properties.

[0160] In the present invention, the method for forming the release layer is not particularly limited, and a method is used in which a coating solution containing a dissolved or dispersed release resin is applied to one side of a polyester film substrate, the solvent is removed by drying, and then the mixture is cured.

[0161] When the release layer of the present invention is applied to a base film by solution coating, the drying temperature for solvent drying is preferably 50°C or higher and 120°C or lower, and more preferably 60°C or higher and 100°C or lower. The drying time is preferably 30 seconds or less, and more preferably 20 seconds or less. Furthermore, after solvent drying, it is preferable to irradiate with active energy rays to promote the curing reaction. As the active energy rays used at this time, ultraviolet rays, electron beams, X-rays, etc., can be used, but ultraviolet rays are preferred because they are easy to use. The amount of ultraviolet light to irradiate is preferably 30 to 300 mJ / cm2 in terms of light intensity, and more preferably 30 to 200 mJ / cm2. By setting it to 30 mJ / cm2 or higher, the curing of the resin proceeds sufficiently, and by setting it to 300 mJ / cm2 or lower, the processing speed can be improved, so it is preferable that a release film can be produced economically.

[0162] The atmosphere in which the activated energy rays are irradiated can be either ordinary air or a nitrogen gas atmosphere. In a nitrogen gas atmosphere, the radical reaction can proceed more smoothly by reducing the oxygen concentration, thereby improving the elastic modulus of the release layer. However, if there are no practical problems with irradiation in air, it is preferable from an economic standpoint to irradiate in air.

[0163] 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.

[0164] 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.

[0165] The present invention will be described in more detail below using examples, but the present invention is not limited in any way by these examples. The characteristic values ​​used in the present invention were evaluated using the following methods. Hereinafter, the weight-average molecular weight may be simply referred to as Mw. Also, polydimethylsiloxane may be simply referred to as PDMS.

[0166] 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.

[0167] (Characteristics of the release layer) In the present invention, the thickness of the release layer is not particularly limited, but is preferably 50 nm to 1500 nm, and 100 nm to 1000 nm. When the thickness of the release layer is 50 nm or more, the average surface roughness (Sa) and the maximum protrusion height of the surface of the release layer can be suppressed within the range of the present invention. Furthermore, when the thickness is 1500 nm or less, the warping of the release layer can be eliminated and the curling of the film can be suppressed.

[0168] The release layer surface 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 preferably the average surface roughness (Sa) of the region is 7 nm or less and the maximum protrusion height (P) is 100 nm or less. Furthermore, it is more preferable that the average surface roughness of the region is 5 nm or less and the maximum protrusion height is 80 nm or less. If the region surface roughness is 7 nm or less and the maximum protrusion height is 100 nm or less, defects such as pinholes will not occur when forming the ceramic green sheet, resulting in a good yield, which is preferable. It can be said that a smaller average surface roughness (Sa) is preferable, but it may be 0.1 nm or more, or 0.3 nm or more. It can also be said that a smaller maximum protrusion height (P) is preferable, but it may be 1 nm or more, or 3 nm or more. 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 enables the release film to exhibit high longitudinal breaking strength, allowing for faster winding and unwinding of the film during manufacturing, for example, compared to conventional methods. In addition, because it achieves low thermal shrinkage stability of the release film, it can maintain dimensional stability of the release film even under high-temperature processing conditions during the manufacturing of ceramic green sheets and resin sheets.

[0169] Because the release film of the present invention uses a highly planarized base film, the surface of the release layer can be made smooth even when the thickness of the release layer is less than 0.5 μm, and even less than 0.2 μm. Therefore, even with a highly reactive radical-curable release layer, the occurrence of curl can be suppressed. In addition, the amount of solvent and resin used can be reduced, making it environmentally friendly and enabling the creation of a release film for ceramic green sheet molding at low cost.

[0170] 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.

[0171] 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 80°C for 5 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.

[0172] 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.

[0173] 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.

[0174] In the present invention, the release layer may contain additives such as adhesion enhancers and antistatic agents, as long as they do not hinder the effects of the present invention, but it is preferable that it does not contain particles. By not containing particles in the release layer, deterioration of the smoothness of the release layer surface and contamination of the resin sheet with particles due to particle detachment can be suppressed. In order to improve adhesion to the substrate, the polyester film surface may be pretreated with an anchor coat, corona treatment, plasma treatment, atmospheric pressure plasma treatment, etc., before applying the release coating layer.

[0175] The release film of the present invention preferably has a release layer that is less prone to static charge. More specifically regarding static charge, in the release film manufacturing process, when the film is wound up after the release layer is applied and stored in a roll, the static charge that increases over time can be a problem. For example, if the amount of static charge on the rolled film is large, minute environmental foreign matter during the slitting process and the ceramic green sheet molding process, as well as film scraps generated during slitting, are more likely to adhere to the film. Since these foreign matter adhering to the film may be mixed into the ceramic green sheet, potentially leading to defects, it is preferable that the release film has a release layer that is less prone to static charge.

[0176] One way to evaluate the resistance to static charge is to bring the release layer and surface layer B into contact, apply a load, and then evaluate the amount of charge on the release layer after holding it for a certain period of time. This evaluation method allows for a model-based evaluation of the amount of charge that increases over time when the film is stored in a roll. A detailed evaluation method will be described later.

[0177] The charge of the release layer, as measured by the evaluation method described later, is preferably ±5kV or less, for example, ±3.4kV or less, and more preferably ±3kV or less, with the smaller the absolute value, the better. Setting the charge of the release layer to ±5kV or less is preferable because it reduces the increase in charge over time when the film is stored in roll form, making it difficult for foreign matter to adhere to the film. While a smaller charge of the release layer is preferable, it may be 0.1kV or more, or 0.3kV or more.

[0178] The release film of the present invention may have a functional layer between the substrate and the release layer. Examples of functional layers include, but are not limited to, an antistatic layer and an easily soluble resin layer. Providing an antistatic layer is preferable because it prevents the adhesion of foreign matter due to static charge and suppresses static charge when peeling off ceramic green sheets, thereby achieving stable release properties. Providing an easily soluble resin layer is preferable because it allows for easy separation and removal of the release layer formed on the surface of the release film, and allows for the recovery of only the substrate film with little to no residue of the release layer.

[0179] For example, the release layer substantially does not contain particles with a particle size of 1.0 μm or larger. In this embodiment, particles with a particle size of less than 1.0 μm and 1 nm or larger may be present in the release layer. By substantially not containing inorganic particles with a particle size of 1.0 μm or larger in the release layer, the occurrence of pinholes in ultrathin resin sheets requiring high smoothness, such as ceramic green sheets, can be suppressed, and a resin sheet with a uniform film thickness can be formed. In one embodiment, since it is preferable for the release layer to have high smoothness, it is preferable to provide the release layer according to the present invention on a substrate film having a surface layer A that substantially does not contain inorganic particles, specifically, substantially does not contain particles with a particle size of less than 1.0 μm, preferably a surface layer A that substantially does not contain particles. For example, in a release layer that substantially does not contain particles with a particle size of less than 1.0 μm, it is preferable that it also substantially does not contain particles with a particle size of 1.0 μm or larger. When the release layer is provided on a surface layer A that substantially does not contain inorganic particles (surface layer A of the substrate film), the regional surface roughness (Sa) of the release layer is 3 nm or less, and the maximum protrusion height (P) is 200 nm or less. For example, (Sa) may be 0.1 nm to 3 nm and the maximum protrusion height (P) may be 1 nm to 200 nm, or (Sa) may be 0.2 nm to 3 nm and the maximum protrusion height (P) may be 1 nm to 100 nm. Preferably, the maximum protrusion height (P) may be 1 nm to 50 nm, or 1 nm to 40 nm, or the maximum protrusion height (P) may be 1 nm to 35 nm. By satisfying these conditions, the release layer can suppress the occurrence of pinholes in the thin resin sheet, such as the ceramic green sheet, and a resin sheet with a uniform film thickness can be formed.

[0180] Organic solvents include: (1) alcohols such as methyl alcohol, ethyl alcohol, N-propyl alcohol, isopropyl alcohol, N-butyl alcohol, tridecyl alcohol, cyclohexyl alcohol, and 2-methylcyclohexyl alcohol; (2) glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, and glycerin; (3) ethylene glycol monomethyl ether, ethylene glycol monoethylene ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol butyl ether. Examples include (4) glycol ethers such as ethers, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl acetate, ethylene glycol monobutyl acetate, diethylene glycol monomethyl acetate, diethylene glycol monoethyl acetate, and diethylene glycol monobutyl acetate; (5) esters such as ethyl acetate, isopropylene acetate, and N-butyl acetate; (6) ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, isophorone, and diacetone alcohol; and (7) aromatic compounds such as benzene, toluene, and xylene. These can be used individually or in combination of two or more.

[0181] If there is a risk of foreign matter or undissolved particles larger than 1 μm being present in the coating solution, it is preferable to remove them using a filter or the like before application, from the viewpoint of the appearance after application. Various types of filters can be suitably used, but it is preferable to use one that removes 99% or more of particles larger than 1 μm. When a coating solution from which foreign matter and undissolved particles larger than 1 μm have been removed is applied and dried, it is preferable because the occurrence of indentations on the surface of the release layer can be suppressed.

[0182] The solid content concentration of the release agent contained in the coating liquid is preferably 0.1% by mass or more and 10% by mass or less. When the solid content concentration is 0.1% by mass or more, the drying time after application can be shortened, which is preferable in terms of productivity, and the amount of solvent remaining in the coating film is small, which is also preferable in terms of long-term stability. On the other hand, when the solid content concentration is 10% by mass or less, the viscosity of the coating liquid does not become too high, the leveling properties are satisfied, and sufficient flatness is obtained, which is preferable. The viscosity of the coating liquid is preferably 10 cps or more and 300 cps or less in terms of the appearance of the coating, and it is preferable to adjust the solid content concentration, organic solvent, etc. so that it falls within this range.

[0183] As a method for laminating the release layer onto a transparent substrate on top of the surface layer by coating, commonly used methods such as gravure coating, kiss coating, dip coating, spray coating, curtain coating, air knife coating, blade coating, reverse roll coating, bar coating, and lip coating can be applied. Among these, the gravure coating method, particularly the reverse gravure method, is preferred because it allows for uniform coating. Furthermore, the diameter of the gravure is preferably 80 mm or less. A diameter of 80 nm or less is preferable because it suppresses the generation of ridges in the flow direction.

[0184] (Method for manufacturing release film) In another embodiment, the present invention provides a method for manufacturing a release film for resin sheet molding, comprising the following steps. Preferably, the following manufacturing method can be used in an embodiment in which the release layer forming composition comprises a cationic curable polydimethylsiloxane (a).

[0185] A coating step of applying a release layer forming composition onto the surface layer A of a polyester film having a surface layer A, wherein the surface layer A is a layer substantially free of inorganic particles, and the release layer forming composition comprises a cation-curable polydimethylsiloxane (a); a drying step of heating and drying the polyester film coated with the release layer forming composition, wherein the heating and drying step comprises a first drying step and a second drying step, wherein the drying temperature T1 in the first drying step is higher than the drying temperature T2 in the second drying step; a photocuring step of curing the release layer forming composition by irradiating it with active energy rays after the drying step.

[0186] With the manufacturing method of the present invention, by strengthening the first drying conditions (increasing the drying), aggregation of the resin constituting the release layer can be prevented, and a release layer with high smoothness can be obtained.

[0187] The present invention provides a method for producing a release film, comprising the following steps in order: a coating step of applying a release layer-forming composition containing an ultraviolet-curable compound, for example, a cationic-curable polydimethylsiloxane (a), onto a surface layer A of a polyester film that is substantially free of inorganic particles; a drying step of heating and drying the film after coating, for example, using a drying oven; and a photocuring step of curing the film using active energy rays after heating and drying. In particular, it is preferable to employ a method in which the steps are carried out in the order of coating, drying, and photocuring.

[0188] The amount of the release layer forming composition applied is preferably 10 g / m² or less, and more preferably 8 g / m² or less. An application amount of 10 g / m² or less is preferable because, for example, when applied by a gravure coating method, liquid disturbance is less likely to occur at the kiss area between the film and the gravure roll, resulting in a release layer with excellent smoothness.

[0189] In the present invention, the amount of coating solvent added to the release layer forming composition is preferably about 10 to 70% by mass relative to the total release layer forming composition. Examples of solvents with a boiling point of 100°C or higher include toluene, xylene, n-octane, cyclohexanone, methyl isobutyl ketone, propylene glycol monomethyl ether, propylene glycol monopropyl ether, isobutyl acetate, and n-butanol.

[0190] In the present invention, it is preferable to filter the coating liquid of the release layer forming composition before application. The filtration method is not particularly limited and known methods can be used, but it is preferable to use a surface type, depth type, or adsorption type cartridge filter. Using a cartridge type filter is preferable because it can be used when continuously supplying the coating liquid from the tank to the coating area, thus improving productivity and efficient filtration. The filtration accuracy of the filter is preferably such that it removes 99% or more of particles with a size of 1 μm, and more preferably it is such that it can filter 99% or more of particles with a size of 0.5 μm. Using a filter with the above filtration accuracy is preferable because it is possible to remove foreign matter mixed into the coating liquid that forms the release layer, reduce the amount of foreign matter adhering to the release film of the present invention, and obtain a release layer with excellent smoothness.

[0191] 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.

[0192] Methods for applying the release layer forming composition onto a base film and drying it include known methods such as hot air drying and infrared heaters, but hot air drying, which has a faster drying speed, is preferred. Drying in a drying oven is preferred, and there are no particular limitations; known drying ovens can be used. Regarding the type of drying oven, either a roll support type or a floating type is acceptable, but the roll support type is preferred because it allows for a wider range of adjustment of the airflow during drying, so the airflow can be adjusted according to the type of release layer.

[0193] The drying process can be divided into two stages: an initial constant-rate drying stage (hereinafter referred to as the first drying stage) and a decreasing-rate drying stage (hereinafter referred to as the second drying stage). Preferably, the two stages are consecutive, with the first drying stage followed by the second drying stage. These stages can be distinguished by dividing the drying oven into zones, and the first (initial) drying stage can be performed using the first drying oven, while the second (later) drying stage can be performed using the second drying oven.

[0194] The inventors have found that in order to improve the smoothness of the release layer, it is important that the drying temperature T1 in the first drying step is higher than the drying temperature T2 in the second drying step. It is preferable that the temperatures of the first and second drying ovens be within the ranges described below. By manufacturing under these conditions, the constant rate drying time in the first drying step can be shortened, and the decay rate drying time in the second drying step can be lengthened, which is preferable because it results in a release layer with excellent flatness.

[0195] Furthermore, the inventors have found that it is important to increase the temperature inside the first drying oven to shorten the constant-rate drying time. More specifically, the drying temperature T1 is preferably 90°C or higher and 180°C or lower, and preferably 100°C or higher and 150°C or lower. Increasing the temperature inside the first drying oven and shortening the constant-rate drying time is preferable because it prevents aggregation of the cation-curable polydimethylsiloxane (a) contained in the release layer forming composition. The higher the temperature inside the first drying oven, the shorter the constant-rate drying time, which is preferable, but if it is too high, the flatness of the film will deteriorate due to heat, so it is preferable to keep it at 180°C or lower. A temperature of 90°C or higher is preferable because it provides sufficient drying capacity.

[0196] The temperature inside the second drying oven is preferably 60°C to 140°C, and more preferably 80°C to 120°C. In the second drying step, slowing down the drying time allows drying without roughening the surface of the release layer before photocuring, and is preferable because it improves the smoothness of the release layer.

[0197] For example, it is preferable that the constant-rate drying time in the first drying step is shorter than the decay-rate drying time in the second drying step. This prevents deterioration of the film's flatness and allows drying without roughening the surface of the release layer before photocuring, thereby improving the smoothness of the release layer.

[0198] The time from application to entering the first drying oven is preferably 0.1 seconds or more and 2.5 seconds or less, preferably 0.1 seconds or more and 2.0 seconds or less, and the shorter the time, the better. By shortening the time to enter the first drying oven, the drying time in the first drying step can be shortened, the aggregation of cation-curable polydimethylsiloxane (a) is suppressed, and a release layer with excellent smoothness can be obtained, which is preferable. The time to enter the drying oven can be calculated from the processing speed and the structure of the processing machine stand.

[0199] The manufacturing method of the present invention includes a photocuring step in which the release layer forming composition is cured by irradiating it with an active energy ray after the drying step. In the photocuring step, the cationic curing reaction of the dried release layer forming composition proceeds by irradiating it with an active energy ray. Known technologies such as ultraviolet rays and electron beams can be used as the active energy ray, and ultraviolet rays are preferred. The cumulative light amount when using ultraviolet rays can be expressed as the product of illuminance and irradiation time. For example, it is preferable to have a value of 10 to 500 mJ / cm2. It is preferable to have a value above the lower limit so that the release layer can be sufficiently cured. It is preferable to have a value below the upper limit so that thermal damage to the film due to heat during irradiation can be suppressed and the smoothness of the release layer surface can be maintained.

[0200] When irradiating with active energy rays, it is preferable to hold the back surface of the film with a backup roll. Providing a backup roll allows the distance from the active energy ray source to be kept constant, which is preferable as it allows for uniform irradiation. Furthermore, it is preferable to cool the surface of the backup roll and irradiate the film with active energy rays while cooling it. Cooling is preferable because it reduces the film's susceptibility to thermal damage even when irradiated with active energy rays, and helps maintain the smoothness of the release layer surface.

[0201] In one embodiment, the manufacturing method of the present invention provides a method for producing a release film for manufacturing a resin sheet containing an inorganic compound.

[0202] (Resin Sheet) The resin sheet in the present invention is not particularly limited as long as it is a sheet containing resin. In one embodiment, the release film of the present invention is a release film for molding a resin sheet containing an inorganic compound. Examples of inorganic compounds include metal particles, metal oxides, minerals, etc. For example, calcium carbonate, silica particles, aluminum particles, barium titanate particles, etc. Because the present invention has a highly smooth release layer, even when these inorganic compounds are included in the resin sheet, it is possible to suppress defects that may be caused by the inorganic compounds, such as damage to the resin sheet and difficulty in peeling the resin sheet from the release layer. The resin component forming the resin sheet can be appropriately selected depending on the application. In one embodiment, the resin sheet containing the inorganic compound is a ceramic green sheet. For example, the ceramic green sheet may contain barium titanate as the inorganic compound. Also, for example, the resin component may contain polyvinyl butyral resin. In one embodiment, the resin sheet has a thickness of 0.2 μm or more and 1.0 μm or less. For example, the present invention can provide a method for producing a release film for producing such a resin sheet containing an inorganic compound. Furthermore, the method for manufacturing a release film for resin sheet molding according to the present invention may include a step of molding a resin sheet having a thickness of 0.2 μm or more and 1.0 μm or less.

[0203] (Ceramic Green Sheet and Ceramic Capacitor) Generally, a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. Inside the ceramic body, a first internal electrode and a second internal electrode are alternately arranged along the thickness direction. The first internal electrode is exposed on the first end face of the ceramic body. A first external electrode is provided on the first end face. The first internal electrode is electrically connected to the first external electrode at the first end face. The second internal electrode is exposed on the second end face of the ceramic body. A second external electrode is provided on the second end face. The second internal electrode is electrically connected to the second external electrode at the second end face.

[0204] In one embodiment, the release film of the present invention is a release film for manufacturing ceramic green sheets and is used to manufacture such multilayer ceramic capacitors. For example, a method for manufacturing a ceramic green sheet using the release film for manufacturing ceramic green sheets of the present invention can produce a ceramic green sheet having a thickness of 0.2 μm to 1.0 μm. More specifically, for example, the ceramic green sheet is manufactured as follows: First, the release film of the present invention is used as a carrier film, and a ceramic slurry for constituting a ceramic body is applied and dried. There is a growing demand for extremely thin ceramic green sheets with a thickness of 0.2 to 1.0 μm. A conductive layer for constituting a first or second internal electrode is printed on the applied and dried ceramic green sheet. A mother laminate is obtained by appropriately laminating the ceramic green sheet, the ceramic green sheet with the conductive layer for constituting the first internal electrode printed on it, and the ceramic green sheet with the conductive layer for constituting the second internal electrode printed on it, and pressing them. The mother laminate is divided into multiple parts to produce raw ceramic bodies. Ceramic bodies are obtained by firing the raw ceramic bodies. Subsequently, the multilayer ceramic capacitor can be completed by forming the first and second external electrodes.

[0205] In addition to the above-mentioned applications, the release film of the present invention can also be applied to release films for semiconductor product manufacturing and optical component manufacturing, for example. Therefore, even if the ceramic green sheet, semiconductor product, optical component, or resin sheet to be peeled from the release layer is a thin film, peeling can be performed smoothly. Furthermore, because the release layer exhibits high smoothness, the occurrence of pinholes in the green sheet and the like can be suppressed, and it is also possible to make the peeled material thinner compared to conventional methods.

[0206] The present invention will be described in more detail below using examples, but the present invention is not limited in any way by these examples. The characteristic values ​​used in the present invention were evaluated using the following method.

[0207] (Release Layer Thickness) The cut release film was embedded in resin and then ultra-thin sectioned using an ultramicrotome. Cross-sectional observation was then performed using a JEOL JEM2100 transmission electron microscope, and the thickness of the release layer was measured from the observed TEM images. If the thickness was too thin to be accurately evaluated by cross-sectional observation, it was measured using a reflectance spectrophotometer (Otsuka Electronics Co., Ltd., FE-3000).

[0208] (Weight of the release layer) In this specification, the weight per 1 μm of the release layer thickness is 1 g / m ２ The weight value calculated using this method was adopted. For example, if the release layer thickness measured by the method described above is 0.2 μm, the total weight of the release layer is 0.2 g / m². ２ Furthermore, the weight of the cation-curable polydimethylsiloxane (a), the cation-curable resin (b), and the acid generator (c) contained in the release layer were calculated from the blending ratio of each component contained in the release layer forming composition and the total weight of the release layer. For example, if the release layer thickness is 0.2 μm and the weight ratio of cation-curable polydimethylsiloxane (a) in the release layer is 5 parts by mass, the weight of (a) contained in the release layer is 0.01 g / m 2 The release layer weight ratio (mass%) was calculated assuming that the sum of component (a) and component (b) was 100 parts by mass.

[0209] (Amount of release layer forming composition applied) The value used was calculated from the liquid weight and processing area of ​​the release layer forming composition used in the application process.

[0210] (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).

[0211] (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 sample was taken from the sample, and 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 layer. (Image processing conditions) Image processing was performed in the following order: ・Interpolation: Full interpolation ・Filtering: Gaussian (cutoff 100) ・Surface correction: 4th order

[0212] 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. (Particle Analysis Conditions) Protrusion analysis processing was performed under the following conditions: Analysis type: protrusion analysis Image correction: none Processing height threshold: 0.025 μm Reference height: zero plane (average plane)

[0213] Of the protrusions (foreign objects) 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.

[0214] (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.

[0215] (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.

[0216] (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.

[0217] (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.

[0218] (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.

[0219] (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).

[0220] (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.

[0221] (Thermal shrinkage rate of the base film in the longitudinal direction) A sample of the base film was taken, measuring 10 mm in width and 220 mm in length. Marks were made at 200 mm intervals along the length of the sample, and the interval between the marks was measured (L0). The sample was then placed between sheets of paper and placed in a hot air oven controlled to 150°C for 30 minutes. After removal, the interval between the marks was measured (L), and the thermal shrinkage rate was calculated using the following formula: Thermal shrinkage rate (%) = {(L0 - L) / L0} × 100

[0222] (Breaking Strength of 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 force is then converted to a stress per unit area (unit: MPa) and expressed as such. Breaking strength was measured in accordance with JIS K 7127, specifically using the following method. 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 under conditions of 23°C and 65% RH. The breaking strength was calculated from the measured elongation at the time of breakage and the load required for breakage.

[0223] (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. ２Substrate 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.

[0224] (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 "○" in Table 3. On the other hand, those that do not meet these conditions are considered unacceptable and are indicated as "×" in Table 3. If the base film is unacceptable, breakage, cracking, etc. may occur during the manufacturing or use of the base film, or, for example, dimensional changes may become large when heating to form dielectric sheets and internal electrodes when the base film is used in the manufacture of multilayer ceramic chip capacitors (MLCCs).

[0225] (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.

[0226] (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). In embodiments containing a cation-curable polydimethylsiloxane as a release layer, a rating of [〇] was given when the surface free energy γs of the release layer was 15 mJ / m2 or more and 25 mJ / m2 or less.

[0227] (Surface Roughness and Surface Protrusions) 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 5 measurements was used, excluding the maximum and minimum values. (Measurement Conditions) ・Measurement mode: WAVE mode ・Objective lens: 10x ・0.5×Tube lens ・Measurement area: 936 μm × 702 μm (Analysis Conditions) ・Surface correction: 4th order correction ・Interpolation processing: Fully interpolated Surface roughness and surface protrusions were evaluated as [○] if the average surface roughness (Sa) of the region of the release layer surface was 7 nm or less, and the maximum protrusion height was 100 nm or less.

[0228] (Evaluation of release properties of ceramic green sheet) A composition consisting of the following materials was stirred and mixed, and dispersed for 60 minutes using a bead mill with zirconia beads with a diameter of 0.5 mm to obtain a ceramic slurry. 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 slurry was applied to the release surface of the obtained release film sample using 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 resulting ceramic green sheet-attached release film was statically removed using a static eliminator (Keyence Corporation, SJ-F020), and then peeled off using a peel tester (Kyowa Interface Science Co., Ltd., VPA-3) at a peel angle of 90 degrees, a peel temperature of 25°C, and a peel speed of 10 m / min. For peeling, double-sided adhesive tape (Nitto Denko Corporation, No. 535A) was attached to a SUS plate attached to the peel tester, and the release film was fixed on top of it with the ceramic green sheet side adhering to the double-sided tape. The release film was then peeled off by pulling it. From the obtained measurements, the average value of the peel force for peel distances of 20 mm to 70 mm was calculated and defined as the peel force. A total of five measurements were taken, and the average value of the peel force was adopted for evaluation. The obtained peel force values ​​were judged according to the following criteria. ○: 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

[0229] (film 1m ２ (Evaluation of the number of streaks per mark) 1m of film ２ The number of coating streaks per unit area was sampled by visual inspection and measured using a non-contact surface shape measurement system (VertScan R550H-M100) under the following conditions. Streaks were judged as follows: if the width of a single streak was 20 μm or more, and the difference in release layer thickness from the normal area was less than 10%, it was not counted; if it was 10% or more, it was counted as a streak defect. The pass / fail judgment was based on the number of streaks per meter of film. ２If there were 5 or more lines per area, it was marked with "×", if there were 1 to 4 lines it was marked with "△", and if there were 0 lines it was marked with "○". (Measurement conditions) ・Measurement mode: WAVE mode ・Objective lens: 10x ・0.5x Tube lens ・Measurement area: 936 μm × 702 μm (Analysis conditions) ・Surface correction: 4th order correction ・Interpolation processing: Full interpolation

[0230] (Method for measuring the weight-average degree of polymerization) Analytical conditions 16 mg of the sample was weighed and dissolved in 8 ml of chloroform. The solution was filtered through a 0.2 μm membrane filter, and GPC analysis of the obtained sample solution was performed under the following conditions. Apparatus: TOSOH HLC-8320GPC Column: K-G+ K-802 (exclusion limit molecular weight 5 × 10³) + K-801 (exclusion limit molecular weight 1.5 × 10³) (Shodex), Solvent: 100% chloroform Flow rate: 1.0 ml / min Concentration: 0.2% Injection volume: 50 μL Temperature: 40℃ Detector: RI The weight-average molecular weight was calculated in polystyrene equivalent, and the weight-average degree of polymerization was calculated based on that value. For polystyrene, PStQuick C (TOSOH) from the PStQuick series was used. Of the polystyrenes added to PStQuick C(TOSOH), polystyrenes Mw2110000, 427000, and 37900, which significantly exceed the column's exclusion limit molecular weight, were excluded from the calibration curve.

[0231] (Overall evaluation of release properties) The overall evaluation of release properties was conducted according to the following criteria: Overall evaluation ○: In the substrate film evaluation described in Table 4, there are no "×" ratings for surface evaluation, strength evaluation, and overall evaluation of the substrate, and further, in the evaluation of the release film described in Table 6, there are no "×" ratings for the number of Sb protrusions, surface roughness, surface free energy, peelability, and number of streaks. Overall evaluation ×: If there is a "×" rating in any of the above evaluations.

[0232] (Manufacturing Example 1) <Production of Polyester Resin (Melting Polymerization)> (Slurry Preparation) Terephthalic acid and ethylene glycol were continuously supplied to a slurry preparation tank in a ratio of 100 parts by mass of terephthalic acid to 46.4 parts by mass of ethylene glycol, while stirring under nitrogen flow to prepare the slurry.

[0233] (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. The reaction solution was removed from the first esterification reactor so that the liquid level remained constant, and then added to the second esterification reactor. Ethylene glycol was added from another inlet of the second esterification reactor at an average rate of 230 kg / hour, and the esterification reaction was carried out at atmospheric pressure, a temperature of 261°C, and an average residence time of 1.3 hours. The reaction solution was removed from the second esterification reactor so that the liquid level remained constant, 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.

[0234] (Polycondensation reaction) The reaction solution was removed from the third esterification reaction vessel so that the liquid level remained constant, and then added to the first polycondensation reaction vessel of the 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. The reaction solution was removed from the first polycondensation reaction vessel so that the liquid level remained constant, and then added to the second polycondensation reaction vessel. 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. The reaction solution was removed from the second polycondensation reaction vessel so that the liquid level remained constant, and then added to the third polycondensation 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 was in the range of 0.08 to 0.15 kPa. The polyester resin obtained through the above process was extruded into strands, cooled in water, and then cut into pellets.

[0235] <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.

[0236] <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.

[0237] <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.

[0238] <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.

[0239] <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.

[0240] 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.

[0241] 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.

[0242] <Manufacturing of Laminated Films X2-8> Except for changing the layer configuration, layer thickness ratio, and the types and ratios of constituent resins of layers A-C as shown in Table 1, laminated biaxially oriented PET films were manufactured in the same manner as in Example 1 and subjected to various evaluations. The evaluation results are shown in Tables 2-4.

[0243]

[0244]

[0245]

[0246]

[0247] The base films described in Manufacturing Examples 1 to 5 showed excellent results in both surface evaluation and strength evaluation, and were confirmed to be suitable as release sheets useful in, for example, the formation of dielectric sheets and printing of internal electrodes in the manufacture of MLCCs. On the other hand, the base films described in Comparative Manufacturing Examples 1 to 3 lacked performance in either surface evaluation or strength evaluation, failing to achieve a balance between surface performance and strength performance. For example, they were found to have significant room for improvement as release sheets used in the formation of dielectric sheets and printing of internal electrodes in the manufacture of MLCCs.

[0248] (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 8.1 g / m2, 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.

[0249] (Release layer forming composition) Methyl ethyl ketone 22.421 parts by mass Toluene 22.421 parts by mass n-heptane 54.829 parts by mass Cationic curable polydimethylsiloxane (a)-1 0.316 parts by mass (alicyclic epoxy group modified polydimethylsiloxane Poly215, solids content 100%, manufactured by Arakawa Chemical Industries, Ltd.) Photoinitiator (c)-1 0.013 parts by mass (UV cationic initiator CATA211, manufactured by Arakawa Chemical Industries, Ltd., trade name CATA211 (registered trademark), solids content 18%)

[0250] (Example 2) 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 X2. The composition and evaluation results of the release film are shown in Tables 5A and 6.

[0251] (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.

[0252] (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.

[0253] (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.

[0254] (Examples 6-8) 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.

[0255] (Example 9) A release layer was formed in the same manner as in Example 1, except that the release layer forming composition was changed to the following composition and the thickness of the release layer was changed. The composition and evaluation results for the release film are shown in Tables 5A and 6.

[0256] (Release layer forming composition) Methyl ethyl ketone 22.421 parts by mass Toluene 22.421 parts by mass n-heptane 53.145 parts by mass Cationic curable polydimethylsiloxane (a)-1 0.40 parts by mass (alicyclic epoxy group modified polydimethylsiloxane Poly215, solids content 100%, manufactured by Arakawa Chemical Industries, Ltd.) Cationic curable polydimethylsiloxane (b)-1 1.60 parts by mass (alicyclic epoxy monomer celloxide 2021P, solids content 100%, manufactured by Daicel Corporation) Photoinitiator (c)-1 0.013 parts by mass (UV cationic initiator CATA211, manufactured by Arakawa Chemical Industries, Ltd., trade name CATA211 (registered trademark), solids content 18%)

[0257] (Example 10) A release layer was formed in the same manner as in Example 1, except that the release layer forming composition was changed to the following composition and the thickness of the release layer was changed. The composition and evaluation results for the release film are shown in Tables 5A and 6.

[0258] (Release layer forming composition) Methyl ethyl ketone 22.421 parts by mass Toluene 22.421 parts by mass n-heptane 53.145 parts by mass Cationic curable polydimethylsiloxane (a)-1 0.20 parts by mass (Alicyclic epoxy group modified polydimethylsiloxane Poly215, 100% solids, manufactured by Arakawa Chemical Industries, Ltd.) Cationic curable polydimethylsiloxane (b)-1 1.80 parts by mass (Alicyclic epoxy monomer celloxide 2021P, 100% solids, manufactured by Daicel Corporation) Photoinitiator (c)-1 0.013 parts by mass (UV cationic initiator CATA211, manufactured by Arakawa Chemical Industries, Ltd., trade name CATA211 (registered trademark), 18% solids)

[0259] (Example 11) A release layer was formed in the same manner as in Example 1, except that the release layer forming composition was changed to the following composition and the thickness of the release layer was changed. The composition and evaluation results for the release film are shown in Tables 5A and 6.

[0260] (Release layer forming composition) Methyl ethyl ketone 22.421 parts by mass Toluene 22.421 parts by mass n-heptane 53.145 parts by mass Cationic curable polydimethylsiloxane (a)-1 0.40 parts by mass (alicyclic epoxy group modified polydimethylsiloxane Poly215, solids content 100%, manufactured by Arakawa Chemical Industries, Ltd.) Cationic curable polydimethylsiloxane (b)-2 1.60 parts by mass (alicyclic epoxy monomer KR470, solids content 100%, manufactured by Shin-Etsu Chemical Co., Ltd.) Photoinitiator (c)-1 0.013 parts by mass (UV cationic initiator CATA211, manufactured by Arakawa Chemical Industries, Ltd., trade name CATA211 (registered trademark), solids content 18%)

[0261] (Example 11) A release layer was formed in the same manner as in Example 1, except that the release layer forming composition was changed to the following composition and the thickness of the release layer was changed. The composition and evaluation results for the release film are shown in Tables 5A and 6.

[0262] (Release layer forming composition) Methyl ethyl ketone 22.421 parts by mass Toluene 22.421 parts by mass n-heptane 53.145 parts by mass Cationic curable polydimethylsiloxane (a)-1 0.20 parts by mass (alicyclic epoxy group modified polydimethylsiloxane Poly215, solids content 100%, manufactured by Arakawa Chemical Industries, Ltd.) Cationic curable polydimethylsiloxane (b)-2 1.80 parts by mass (alicyclic epoxy monomer KR470, solids content 100%, manufactured by Shin-Etsu Chemical Co., Ltd.) Photoinitiator (c)-1 0.013 parts by mass (UV cationic initiator CATA211, manufactured by Arakawa Chemical Industries, Ltd., trade name CATA211 (registered trademark), solids content 18%)

[0263] (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 X8. The longitudinal breaking strength was low, raising concerns that breakage may occur during release layer processing or, for example, when the release film is used in the manufacture of multilayer ceramic chip capacitors (MLCCs) to form dielectric sheets and internal electrodes. The composition and evaluation results for the release film are shown in Tables 5A and 6.

[0264] (Comparative Example 2) The 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 X6. Laminated film X6 had a large number of sb protrusions and could not be obtained with sufficient smoothness. The composition and evaluation results for the release film are shown in Tables 5A and 6. In addition, the same trend as in Comparative Example 2 was observed in laminated film X7, which also had a large number of sb protrusions and could not be obtained with sufficient smoothness (details of the evaluation results are omitted).

[0265] (Comparative Example 3) A release layer was formed in the same manner as in Example 1, except that the thickness of the release layer of the coating solution was adjusted to 200 mg / m2. The release layer showed a tendency to aggregate, and the maximum protrusion height on the surface was 100 nm or more. The composition and evaluation results for the release film are shown in Tables 5A and 6.

[0266]

[0267]

[0268] The release film of the present invention has high longitudinal breaking strength and allows for defect-free coating of resin sheet forming slurry without deteriorating thermal shrinkage. In particular, it can provide a release film that enables defect-free formation of ceramic green sheets. Furthermore, the release film of the present invention can prevent pinholes and localized thickness variations even when ceramic green sheets, semiconductor products, optical components, and resin sheets are thinned, for example. For example, when a ceramic green sheet is thinned, pinholes and localized thickness variations can be prevented, and the amount of antimony compound used in the production of the surface layer of the polyester film substrate can be reduced while suppressing the formation of protrusions and achieving high longitudinal breaking strength and low thermal shrinkage stability of the polyester film substrate.

[0269] On the other hand, in Comparative Example 1, the intrinsic viscosity of the surface layer was outside the range of the present invention, and it could not exhibit sufficient fracture strength. In Comparative Example 2, the antimony atom content of the surface layer was outside the range of the present invention, and it could not obtain sufficient smoothness. In Comparative Example 3, the amount of UV-curing compound significantly exceeded the range of the present invention, and the maximum protrusion height on the surface of the release layer was outside the range of the present invention.

[0270] (Example 21) 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 800 nm. After drying at 90°C for 15 seconds, ultraviolet light was irradiated using a high-pressure mercury lamp to a concentration of 150 mJ / cm2 to obtain a release film for manufacturing ultrathin ceramic green sheets. A ceramic slurry was applied to the obtained release film using the above method, and the coating properties and peelability were evaluated, yielding good evaluation results. Details are shown in Tables 7A and 7B.

[0271] (Coating Solution 1) Methyl ethyl ketone 39.5 parts by mass Isopropyl alcohol 38.5 parts by mass Urethane acrylate (15 functional groups, Mw 1000) 20.0 parts by mass (Product name: 8UX-015A, manufactured by Taisei Fine Chemical Co., Ltd., solids content 100% by mass) Release agent 1.0 part by mass (Acryloyl group-containing PDMS-modified acrylic resin, GL-04R, manufactured by Kyoeisha Chemical Co., Ltd., solids content 20% by mass) Photoradical initiator (Irgacure® 907, manufactured by BASF) 1.0 part by mass

[0272] (Example 22) The 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 X2.

[0273] (Example 23) The 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 X3.

[0274] (Example 24) The 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 X4.

[0275] (Example 25) The 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 X5.

[0276] (Examples 26-29) Release films were manufactured in the same manner as in Example 1, except that the various components and amounts listed in Table 7 were used, and their physical properties were evaluated. Specifically, in Example 26, the silicone content was changed. In Example 27, a release film for manufacturing ultrathin ceramic green sheets was obtained in the same manner as in Example 1, except that the release agent was changed to a PDMS-modified acrylic resin that does not contain acryloyl groups. PDMS-modified acrylic resin: GL-02R (manufactured by Kyoeisha Chemical Co., Ltd., solids content 20% by mass). In Example 28, a release film was manufactured in the same manner as in Example 1, except that a polyether-modified acryloyl group-containing polydimethylsiloxane (acryloyl group-containing PDMS, BYK®-3500, manufactured by Bic Chemie, solids content 100% by mass) was used as the release agent. In Example 29, a release film was prepared in the same manner as in Example 1, except that UV1700B (weight-average molecular weight 2000, 10-functional), manufactured by Nippon Synthetic Chemical Industry Co., Ltd., was used as the urethane acrylate.

[0277] (Comparative Example 21) 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 X8. Many antimony-induced protrusions were observed.

[0278]

[0279]

[0280] As is clear from the inventions of Examples 21 to 29, a second aspect of the present invention can suppress the formation of protrusions in the substrate and release layer, and furthermore, can achieve high longitudinal breaking strength and low thermal shrinkage stability of the polyester film that serves as the substrate. Furthermore, a release film with excellent smoothness and peelability is provided. In addition, deterioration of windability as a release film roll can be suppressed, and an effect of improving adhesion between the substrate and the release layer can be obtained.

[0281] On the other hand, Comparative Example 21 had an antimony content outside the range of the present invention, and many protrusions were observed compared to the present invention. In addition, the longitudinal fracture strength was lower. For example, it is highly likely to fracture during the manufacturing process of ceramic green sheets (MLCCs).

[0282] 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 biaxially oriented 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 at the surface of the release layer is 15 to 35 mJ / m ２ The aforementioned release layer has a regional average surface roughness (Sa) of 7 nm or less and a maximum protrusion height of 100 nm or less, and the release layer is a release film formed from a release layer forming composition.

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 layer forming composition contains cationic curable polydimethylsiloxane (a), and the release layer forming composition contains 1 mg / m² of cationic curable polydimethylsiloxane (a). ２ 50mg / m or more ２ The release film according to claim 1, comprising the following amounts.

4. The release film according to claim 3, wherein the cationic curable polydimethylsiloxane (a) contains a compound having an alicyclic epoxy group.

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

6. The release film according to claim 1, wherein the release layer comprises a radical-curable substance having one or more radical-curable functional groups selected from (meth)acryloyl groups and alkenyl groups.

7. The release film according to claim 1, wherein the release layer comprises a polyfunctional (meth)acrylate having two or more (meth)acryloyl groups in one molecule.

8. The release film according to claim 1, wherein the release layer contains a urethane acrylate having four or more functional groups in one molecule.

9. The release film according to claim 1, wherein the release film is a release film for manufacturing ceramic green sheets, semiconductor products, optical components, or resin sheets.

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