Release film for ceramic green sheet manufacturing process

Abstract

A release film for use in ceramic green sheet production process, the film comprising a base material and a release agent layer provided on one surface of the base material, wherein the release agent layer is formed from a release agent composition containing an amino resin (A), a hydroxyl group-containing acrylic resin (B), and a hydroxyl group-containing silicone-modified acrylic resin (C) which is a component different from the hydroxyl group-containing acrylic resin (B), and an acid catalyst (D). This release film for use in ceramic green sheet production process has excellent wettability with respect to a ceramic slurry and provides excellent easy-releasability to a ceramic green sheet.

Description

Technical Field

[0001] The present invention relates to a release film used in the process of manufacturing a ceramic green sheet.

Background Art

[0002] Conventionally, in order to manufacture laminated ceramic products such as multilayer ceramic capacitors (hereinafter sometimes referred to as "MLCC") and multilayer ceramic substrates, a ceramic green sheet is formed, and a plurality of the obtained ceramic green sheets are laminated and fired. The ceramic green sheet is formed by coating a ceramic slurry containing a ceramic material such as barium titanate or titanium oxide on a release film.

[0003] As the above-mentioned release film, those having a base material and a release agent layer provided on one side of the base material are widely used. Such a release film is required to have a light release property that can release a thin ceramic green sheet formed on the release film from the release film without breakage or the like. For this reason, those containing a polyorganosiloxane such as polydimethylsiloxane are widely used for the release agent layer. Further, as a release agent layer composition excellent in curability and stability over time in addition to release property, for example, Patent Document 1 proposes a thermosetting coating agent composition containing a methylated melamine resin, a hydroxyl group-containing modified silicone resin and / or a silicone-modified hydroxyl group-containing acrylic resin, and an acid catalyst.

[0004] On the other hand, with the miniaturization and increased performance of electronic devices in recent years, MLCCs and multilayer ceramic substrates have become smaller and more multilayered, leading to the thinning of ceramic green sheets. As ceramic green sheets become thinner, the coating thickness of the ceramic slurry, which is the material, decreases, causing a phenomenon called "repellency" where the ceramic slurry repels from the release film, which can prevent the formation of a uniform coating. In particular, if the thickness after drying is, for example, 2 μm or less, defects such as pinholes and uneven thickness are more likely to occur in the ceramic green sheet, which may lead to a decrease in the electrical properties and reliability of the multilayer ceramic product. For this reason, the release film used in the manufacture of ceramic green sheets is required to have good wettability with respect to the ceramic slurry. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-104661 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, in a release film formed from the thermosetting coating agent composition described in Patent Document 1, further improvements are needed to satisfy both the wettability that allows for the formation of a uniform coating film without repelling even when the coating thickness of the ceramic slurry is thin, and the easy peelability that allows for the removal of a thin ceramic green sheet without tearing or other damage.

[0007] This invention has been made in view of the above circumstances, and aims to provide a release film for the ceramic green sheet manufacturing process that has excellent wettability to ceramic slurry and easy release properties for ceramic green sheets. [Means for solving the problem]

[0008] To achieve the above objective, firstly, the present invention provides a release film for a ceramic green sheet manufacturing process, comprising a base material and a release agent layer provided on one side of the base material, wherein the release agent layer is formed from a release agent composition containing an amino resin (A), a hydroxyl group-containing acrylic resin (B), a hydroxyl group-containing silicone-modified acrylic resin (C) which is a different component from the hydroxyl group-containing acrylic resin (B), and an acid catalyst (D) (Invention 1).

[0009] According to the above invention (Invention 1), the release agent layer is formed from a release agent composition containing an amino resin (A), a hydroxyl group-containing acrylic resin (B), and a hydroxyl group-containing silicone-modified acrylic resin (C), which is a different component from the hydroxyl group-containing acrylic resin (B). As a result, the acrylic chains of the hydroxyl group-containing acrylic resin (B) and the hydroxyl group-containing silicone-modified acrylic resin (C) are incorporated into the crosslinked structure of the amino resin (A), resulting in good wettability to the ceramic slurry. Furthermore, because the hydroxyl group-containing silicone-modified acrylic resin (C) is included, the hydrophobic silicone side chains cause the hydroxyl group-containing silicone-modified acrylic resin (C) to easily segregate to the surface layer of the release agent layer, thus achieving excellent easy peelability to the ceramic green sheet. As a result, according to the above invention (Invention 1), the ceramic slurry can be uniformly coated with a thin film thickness of, for example, 2 μm or less, and a ceramic green sheet without defects such as pinholes can be obtained after curing. Moreover, such an extremely thin ceramic green sheet can be peeled off smoothly without damage.

[0010] In the above invention (Invention 1), it is preferable that the content of the amino resin (A) in the release agent composition is 15% by mass or more and 50% by mass or less, the content of the hydroxyl group-containing acrylic resin (B) is 20% by mass or more and 75% by mass or less, and the content of the hydroxyl group-containing silicone-modified acrylic resin (C) is 10% by mass or more and 40% by mass or less (Invention 2).

[0011] In the above inventions (Inventions 1 and 2), the amount of silicone modification in the hydroxyl group-containing silicone-modified acrylic resin (C) is preferably 0.1 mol / g or more and 30 mmol / g or less (Invention 3).

[0012] In the above inventions (Inventions 1 to 3), the hydroxyl value of the hydroxyl group-containing silicone-modified acrylic resin (C) is preferably 2 mg KOH / g or more and 200 mg KOH / g or less (Invention 4).

[0013] In the above inventions (Inventions 1 to 4), the hydroxyl value in the hydroxyl group-containing acrylic resin (B) is preferably 10 mg KOH / g or more and 200 mg KOH / g or less (Invention 5).

[0014] In the above inventions (Inventions 1 to 5), it is preferable that the maximum protrusion height (Rp) on the surface of the release agent layer opposite to the substrate is 100 nm or less (Invention 6). [Effects of the Invention]

[0015] The release film for the ceramic green sheet manufacturing process according to the present invention exhibits excellent wettability to ceramic slurry and easy release of the ceramic green sheet. [Modes for carrying out the invention]

[0016] Embodiments of the present invention will be described below. The release film for the ceramic green sheet manufacturing process according to this embodiment (hereinafter sometimes simply referred to as "release film") comprises a base material and a release agent layer provided on one side of the base material. In this specification, the surface of the release agent layer opposite to the base material may be referred to as the "release surface".

[0017] 1. Each element 1-1. Base material The substrate in this embodiment is not particularly limited as long as it can laminate a release agent layer. Examples of such substrates include films made of polyester such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene and polymethylpentene, polycarbonate, and polyvinyl acetate, and may be a single layer or a multilayer of two or more layers of the same or different materials. Among these, polyester films are preferred, polyethylene terephthalate films are particularly preferred, and biaxially oriented polyethylene terephthalate films are even more preferred in terms of smoothness, heat resistance, and cost. Polyethylene terephthalate films are less likely to generate dust during processing and use, so they can effectively prevent defects in ceramic slurry coating caused by dust, for example.

[0018] The substrate may contain fillers. Furthermore, if the substrate is multilayered, fillers may be included in at least one of the surface layers.

[0019] Furthermore, to improve adhesion with the release agent layer provided on its surface, the substrate may be subjected to surface treatment, such as oxidation or embossing, or primer treatment, on one or both sides as desired. Examples of oxidation methods include corona discharge treatment, plasma discharge treatment, chromium oxidation (wet), flame treatment, hot air treatment, ozone, and ultraviolet irradiation treatment. Examples of embossing methods include sandblasting and thermal spraying. These surface treatment methods are appropriately selected depending on the type of substrate film, but corona discharge treatment is generally preferred in terms of effectiveness and ease of operation.

[0020] The maximum protrusion height (Rp) of the surface on the release agent layer side of the base material is preferably 100 nm or less, particularly preferably 80 nm or less, and even more preferably 60 nm or less. Thereby, it becomes easier to keep the maximum protrusion height (Rp) on the release surface within the range described later, and thereby, the occurrence of defects in the formed ceramic green sheet can be effectively suppressed. The lower limit value of the maximum protrusion height (Rp) of the surface on the release agent layer side of the base material is not particularly limited, and for example, it may be 1 nm or more, particularly 5 nm or more, and even more preferably 10 nm or more. The maximum protrusion height (Rp) can be measured in the same manner as the measurement method of the maximum protrusion height (Rp) of the release surface in the test examples described later.

[0021] The thickness of the base material is not particularly limited. For example, it is preferably 10 μm or more, particularly preferably 15 μm or more, and even more preferably 20 μm or more. Also, the thickness of the base material is preferably 300 μm or less, particularly preferably 200 μm or less, and even more preferably 125 μm or less.

[0022] 1-2. Release Agent Layer The release agent layer in this embodiment is formed from a release agent composition containing an amino resin (A), a hydroxyl group-containing acrylic resin (B), a hydroxyl group-containing silicone-modified acrylic resin (C) which is a separate component from the hydroxyl group-containing acrylic resin (B), and an acid catalyst (D).

[0023] In the release agent layer of the present embodiment, the acrylic chains of the hydroxyl group-containing acrylic resin (B) and the hydroxyl group-containing silicone-modified acrylic resin (C) are incorporated into the crosslinked structure of the amino resin (A), thereby showing good wettability to the ceramic slurry. Further, the hydroxyl group-containing silicone-modified acrylic resin (C) is likely to segregate on the surface layer of the release agent layer due to the action of the hydrophobic silicone side chain, and excellent light release properties can be achieved with respect to the ceramic green sheet. As a result of these, according to the release film of the present embodiment, the ceramic slurry can be uniformly coated with a thin film thickness of, for example, from 2 μm or less, and a ceramic green sheet without defects such as pinholes can be obtained even after curing. Furthermore, such an extremely thin ceramic green sheet can be released well without being damaged or the like.

[0024] (1) Amino resin (A) In the release film according to the present embodiment, the release agent composition contains an amino resin (A). When forming the release agent layer from the release agent composition, the amino resin (A) undergoes a condensation reaction in the presence of an acid catalyst (D), and thus a three-dimensional structure formed by the amino resin (A) is formed in the obtained release agent layer. The condensation reaction of the amino resin (A) can be caused, for example, by heating. Since the release agent layer contains the three-dimensional structure described above, it exhibits sufficient elasticity, and thereby the release film according to the present embodiment can exhibit excellent release properties.

[0025] In the present specification, the term "amino resin" refers to a component capable of causing a condensation reaction, and does not necessarily have to be a high molecular compound. Here, the component may not have undergone any condensation reaction at all, or may have undergone a partial condensation reaction.

[0026] As the above amino resin (A), known resins can be used, for example, melamine resin, urea resin, guanamine resin, or aniline resin. Among these, it is preferable to use melamine resin, which has a very fast condensation reaction rate. In this specification, the term "melamine resin" means an aggregate of one type of melamine compound, or a mixture containing multiple types of melamine compounds and / or a polynuclear body formed by the condensation of said melamine compounds.

[0027] The melamine resin described above preferably contains a melamine compound represented by the following general formula (a), or a polynuclear body formed by the condensation of two or more such melamine compounds. [ka]

[0028] In formula (a), X is preferably -H, -CH2-OH, or -CH2-OR. These groups constitute the reactants in the condensation reaction between the melamine compounds. Specifically, the -NH group formed when X becomes H can undergo condensation reactions with the -N-CH2-OH group and the -N-CH2-OR group. Furthermore, the -N-CH2-OH group formed when X becomes -CH2-OH and the -N-CH2-OR group formed when X becomes -CH2-OR can both undergo condensation reactions with the -NH group, the -N-CH2-OH group, and the -N-CH2-OR group.

[0029] In the above -CH2-OR group, R preferably represents an alkyl group having 1 to 8 carbon atoms. The number of carbon atoms is preferably 1 to 6, and particularly preferably 1 to 3. Examples of alkyl groups having 1 to 8 carbon atoms include methyl, ethyl, propyl, butyl, pentyl, hexyl, and octyl groups, with methyl being particularly preferred.

[0030] The above X values ​​may be the same or different. Similarly, the above R values ​​may be the same or different.

[0031] Melamine compounds generally include types such as the full ether type where all X are -CH2-OR, the imino-methylol type where at least one X is -CH2-OH and at least one X is H, the methylol type where at least one X is -CH2-OH and no H X is present, and the imino type where at least one X is H and no -CH2-OH X is present. Any of these types of melamine compounds may be used in the release film according to this embodiment.

[0032] In a release agent composition for forming a release agent layer, the weight-average molecular weight of the melamine resin is preferably 150 or more, particularly preferably 300 or more, and even more preferably 500 or more. Furthermore, the weight-average molecular weight of the melamine resin is preferably 10,000 or less, particularly preferably 5,000 or less, and even more preferably 4,000 or less. A weight-average molecular weight of 150 or more stabilizes the crosslinking rate and allows for the formation of a smoother release surface. Additionally, a weight-average molecular weight of 10,000 or less results in a moderately low viscosity of the release agent composition, making it easier to apply the release agent composition coating solution to the substrate. Note that the weight-average molecular weight in this specification is a value equivalent to standard polystyrene measured by gel permeation chromatography (GPC).

[0033] In the release agent composition, the content of amino resin (A) is preferably 15% by mass or more, particularly preferably 17% by mass or more, and more preferably 20% by mass or more. Furthermore, the content of amino resin (A) is preferably 50% by mass or less, particularly preferably 40% by mass or less, and more preferably 30% by mass. By having the content of amino resin (A) within the above range, a good crosslinking structure can be formed with the hydroxyl group-containing acrylic resin (B) and hydroxyl group-containing silicone-modified acrylic resin (C) described later, and sufficient curing is achieved, effectively exhibiting the aforementioned easy release properties.

[0034] (2) Hydroxyl group-containing acrylic resin (B) In the release film of this embodiment, the release agent composition contains a hydroxyl group-containing acrylic resin (B). Since the hydroxyl group-containing acrylic resin (B) has a high affinity for ether-based solvents such as propylene glycol monomethyl ether (PGM), which is widely used as a solvent for ceramic slurries, the release agent layer obtained from the release agent composition containing the hydroxyl group-containing acrylic resin (B) exhibits good wettability with respect to ceramic slurries.

[0035] The hydroxyl group-containing acrylic resin (B) can preferably be produced by consisting only of acrylic monomers containing hydroxyl groups (hereinafter sometimes referred to as "hydroxyl group-containing monomers"), or by copolymerizing hydroxyl group-containing monomers with other copolymerizable monomers. Known methods for production include bulk polymerization, solution polymerization in organic solvents, and emulsion polymerization in water.

[0036] Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, neopentyl glycol mono(meth)acrylate, glycerin mono(meth)acrylate, polycaprolactone-modified hydroxylalkyl (meth)acrylate, and polycaprolactone-modified poly(oxyalkylene)(meth)acrylate. Hydroxyl group-containing monomers may be used individually or in combination of two or more. In this specification, (meth)acrylate means both acrylate and methacrylate. The same applies to other similar terms.

[0037] Other copolymerizable acrylic monomers include, for example, alkyl esters of (meth)acrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl acrylate, cyclohexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, and stearyl (meth)acrylate; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; and N,N-dimethylamino acid Examples include aminoalkyl (meth)acrylates such as ethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate; acrylamide, methacrylamide, or their derivatives; quaternary ammonium base-containing monomers such as 2-(methacryloyloxy)ethyltrimethylammonium chloride and 2-(methacryloyloxy)ethyltrimethylammonium bromide; sulfoalkyl (meth)acrylates such as (meth)acrylamide-alkanesulfonic acids such as 2-acrylamido-2-methylpropanesulfonic acid and 2-sulfoethyl (meth)acrylate; and acrylonitrile and methacrylonitrile. Other copolymerizable monomers other than acrylic monomers include vinyl acetate, styrene, vinyltoluene, and α-methylstyrene. These may be used individually or in combination of two or more.

[0038] The hydroxyl value of the hydroxyl group-containing acrylic resin (B) is preferably 10 mg KOH / g or more, particularly preferably 15 mg KOH / g or more, and even more preferably 20 mg KOH / g or more. This allows for good reaction with the amino resin (A) and subsequent curing. Furthermore, the hydroxyl value of the hydroxyl group-containing acrylic resin (B) is preferably 200 mg KOH / g or less, particularly preferably 150 mg KOH / g or less, and even more preferably 100 mg KOH / g or less. This allows for more effective achievement of easy peelability of the ceramic green sheet. In this specification, the hydroxyl value of the acrylic resin shall be the value measured in accordance with the neutralization titration method (JIS K0070).

[0039] The glass transition temperature Tg of the hydroxyl group-containing acrylic resin (B) is preferably 25°C or higher, particularly preferably 35°C or higher, and even more preferably 45°C or higher. This ensures that the cured film of the release agent composition exhibits sufficient strength. Furthermore, the glass transition temperature Tg is preferably 95°C or lower, particularly preferably 85°C or lower, and even more preferably 75°C or lower. This improves compatibility with other components in the release agent composition. The glass transition temperature shall be the value measured using a differential scanning calorimetry (DSC).

[0040] The hydroxyl group-containing acrylic resin (B) is preferably not silicone-modified, but may be silicone-modified in a considerably smaller amount than the hydroxyl group-containing silicone-modified acrylic resin (C). For example, the amount of silicone modification in the hydroxyl group-containing acrylic resin (B) is preferably 1 / 3 or less of the amount of silicone modification in the hydroxyl group-containing silicone-modified acrylic resin (C) in mmol / g terms, particularly preferably 1 / 4 or less, and even more preferably 1 / 5 or less.

[0041] The content of hydroxyl group-containing acrylic resin (B) in the release agent composition is preferably 20% by mass or more, particularly preferably 30% by mass or more, and even more preferably 40% by mass or more. This results in better wettability to ceramic slurry. Furthermore, the content of hydroxyl group-containing acrylic resin (B) is preferably 75% by mass or less, particularly preferably 70% by mass or less, and even more preferably 65% ​​by mass or less. This allows the effect of light release properties provided by the hydroxyl group-containing silicone-modified acrylic resin (C), described later, to be exhibited more effectively.

[0042] (3) Hydroxyl group-containing silicone-modified acrylic resin (C) In the release film of this embodiment, the release agent composition contains a hydroxyl group-containing silicone-modified acrylic resin (C). The hydroxyl group-containing silicone-modified acrylic resin (C) has an acrylic chain in its main chain and hydroxyl groups and silicone chains in its side chains. Because the silicone chains of the hydroxyl group-containing silicone-modified acrylic resin (C) are hydrophobic, when the release agent composition is applied, they segregate on the surface of the coating film, and the silicone chains of the side chains are oriented toward the coating film surface. This orientation of the silicone chains lowers the surface free energy of the release agent layer sufficiently, thus achieving excellent easy release properties. Furthermore, by using the hydroxyl group-containing silicone-modified acrylic resin (C) together with the hydroxyl group-containing acrylic resin (B), the amount of acrylic resin component on the surface of the release agent layer increases, and these acrylic skeletons result in excellent wettability of the resulting release agent layer to ceramic slurry.

[0043] Known hydroxyl group-containing silicone-modified acrylic resins (C) can be used. Hydroxyl group-containing silicone-modified acrylic resins (C) can be produced, for example, by (i) copolymerization of an acrylic monomer with a (meth)acryloyl group-containing polyorganosiloxane, or by (ii) direct chemical bonding between the functional groups of a functional group-containing acrylic polymer and a functional group-containing polyorganosiloxane, or by indirect chemical bonding via a compound having a functional group that reacts with both. Acrylic monomers, etc., can be those exemplified in hydroxyl group-containing acrylic resin (B), for example.

[0044] The amount of silicone modification in the hydroxyl group-containing silicone-modified acrylic resin (C) is preferably 0.1 mmol / g or more, particularly preferably 0.3 mmol / g or more, and even more preferably 0.5 mmol / g or more. This makes it possible to achieve better peelability. Furthermore, the amount of silicone modification in the hydroxyl group-containing silicone-modified acrylic resin (C) is preferably 30 mmol / g or less, particularly preferably 25 mmol / g or less, and even more preferably 20 mmol / g or less. This makes it possible to achieve good peelability without hindering good wettability to ceramic slurry.

[0045] The hydroxyl value of the hydroxyl-containing silicone-modified acrylic resin (C) is preferably 2 mg KOH / g or more, particularly preferably 5 mg KOH / g or more, and even more preferably 10 mg KOH / g or more. This allows for good reaction and curing with the amino resin (A). Furthermore, the hydroxyl value of the hydroxyl-containing silicone-modified acrylic resin (C) is preferably 200 mg KOH / g or less, particularly preferably 150 mg KOH / g or less, and even more preferably 100 mg KOH / g or less. This allows for more effective achievement of easy peelability of the ceramic green sheet.

[0046] In the release agent composition, the content of hydroxyl group-containing silicone-modified acrylic resin (C) is preferably 5% by mass or more, particularly preferably 7% by mass or more, and more preferably 10% by mass or more. This makes it possible to achieve better light release properties. Furthermore, the content of hydroxyl group-containing silicone-modified acrylic resin (C) is preferably 40% by mass or less, particularly preferably 35% by mass or less, and more preferably 30% by mass or less. This makes it possible to achieve light release properties without hindering good wettability to ceramic slurry.

[0047] (4) Acid catalyst (D) In the release film according to this embodiment, the release agent composition contains an acid catalyst (D). The inclusion of the acid catalyst (D) in the release agent composition allows for efficient reactions between amino resins (A), between hydroxyl group-containing acrylic resins (B), between hydroxyl group-containing silicone-modified acrylic resins (C), and between amino resins (A) and hydroxyl group-containing acrylic resins (B) and hydroxyl group-containing silicone-modified acrylic resins (C), resulting in the formation of a release agent layer exhibiting sufficient elasticity.

[0048] The acid catalyst (D) described above is not particularly limited as long as it has catalytic activity for the reaction described above, but it is especially preferable to use at least one of a sulfonic acid-based catalyst and a phosphoric acid-based catalyst. These catalysts have relatively high catalytic activity, which makes it easier to promote the hardening of the release agent layer at lower temperatures. Examples of sulfonic acid-based catalysts include p-toluenesulfonic acid, methanesulfonic acid, and dodecylbenzenesulfonic acid, and among these, p-toluenesulfonic acid is preferred. When a full-ether type melamine resin is mainly used as the amino resin (A), it is preferable to use a sulfonic acid-based catalyst from the viewpoint of efficiently promoting the condensation reaction of the melamine resin. Examples of phosphoric acid-based catalysts include phosphoric acid and phosphorous acid. When an iminomethylol-type melamine resin is mainly used as the amino resin (A), it is preferable to use a phosphoric acid-based catalyst from the viewpoint of efficiently promoting the condensation reaction of the melamine resin. Examples of acid catalysts (D) other than those described above include hydrochloric acid, sulfuric acid, nitric acid, etc.

[0049] The content of the acid catalyst (D) in the release agent composition is preferably 0.5 parts by mass or more, more preferably 0.7 parts by mass or more, and more preferably 1.0 part by mass or more, based on 100 parts by mass of the total of the amino resin (A), hydroxyl group-containing acrylic resin (B), and hydroxyl group-containing silicone-modified acrylic resin (C). This allows for efficient reaction between amino resins (A) themselves, between hydroxyl group-containing acrylic resins (B) themselves, between hydroxyl group-containing silicone-modified acrylic resins (C) themselves, and between amino resin (A) and hydroxyl group-containing acrylic resins (B) and hydroxyl group-containing silicone-modified acrylic resins (C). Furthermore, the above content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and more preferably 10 parts by mass or less. This makes it easier for low molecular weight components to be retained in the three-dimensional structure formed in the release agent layer, and effectively suppresses the precipitation of such components from the release agent layer.

[0050] (5) Other ingredients In addition to the above components, the release agent composition may optionally contain fillers, antistatic agents, dyes, pigments, and other additives.

[0051] 2. Physical properties of release film for ceramic green sheet manufacturing process (1) Thickness of the release agent layer In this embodiment, the thickness of the release agent layer is preferably 0.02 μm or more, particularly preferably 0.03 μm or more, and even more preferably 0.04 μm or more. This makes it easier to cure the release agent layer well, and consequently, easier to achieve the desired release properties. Alternatively, the thickness of the release agent layer is preferably 0.5 μm or less, particularly preferably 0.4 μm or less, and even more preferably 0.3 μm or less. This reduces the effect of curing shrinkage of the release agent composition, makes it easier to suppress curling of the release film, and makes it easier to maintain high accuracy in the thickness of the molded ceramic green sheet (especially in the width direction).

[0052] (2) Maximum projection height (Rp) of the peeling surface In the release film according to this embodiment, the maximum protrusion height (Rp) of the release surface is preferably 100 nm or less, particularly preferably 80 nm or less, and even more preferably 60 nm or less. This results in a release surface with excellent smoothness, effectively suppressing the occurrence of defects such as pinholes and thickness variations in the molded ceramic green sheet. The lower limit of the maximum protrusion height (Rp) is not particularly limited and may be, for example, 1 nm or more, particularly 5 nm or more, and even 10 nm or more. Details of the method for measuring the maximum protrusion height (Rp) of the release surface described above are as shown in the test examples below.

[0053] (3) Contact angle of the delamination surface The contact angle between the release surface of the release film according to this embodiment and propylene glycol monomethyl ether (PGM) (hereinafter sometimes referred to as the "PGM contact angle") is preferably 45° or less, particularly preferably 40° or less, and even more preferably 35° or less. This allows for excellent wettability to ceramic slurry, enabling uniform coating without repelling even thin coatings of ceramic slurry. Furthermore, the lower limit is not particularly limited, and the PGM contact angle may be 5° or more, particularly 10° or more, and even 15° or more. This results in better peelability to ceramic green sheets. The method for measuring the PGM contact angle is as described in the test examples below.

[0054] (4) Peeling force of the peeled surface In the release film according to this embodiment, the peeling force required to peel the ceramic green sheet formed on the release surface from the release film (peeling force on the ceramic green sheet) is preferably 50 mN / 40 mm or less, particularly preferably 40 mN / 40 mm or less, and even more preferably 30 mN / 40 mm or less. This allows for good peeling of the thin film ceramic green sheet without damage. Furthermore, the above peeling force is preferably 5 mN / 40 mm or more, more preferably 10 mN / 40 mm or more, and particularly preferably 15 mN / 40 mm or more. In the release film according to this embodiment, since the release agent layer is formed from a release agent composition containing an amino resin (A), a hydroxyl group-containing acrylic resin (B), and a hydroxyl group-containing silicone-modified acrylic resin (C), it is possible to achieve the above-mentioned relatively low peeling force while ensuring wettability. Details of the method for measuring the above peeling force are described in the test examples below.

[0055] 3. Method for manufacturing release film for ceramic green sheet manufacturing process The method for manufacturing the release film in this embodiment is not particularly limited, as long as it includes forming a release layer from the release agent composition described above. For example, it is preferable to apply a coating solution containing the release agent composition described above and optionally an organic solvent to one side of a substrate, and then dry and heat the resulting coating to cure the release agent composition and form a release layer, thereby obtaining a release film.

[0056] Specific coating methods mentioned above include, for example, gravure coating, bar coating, spray coating, spin coating, knife coating, roll coating, and die coating.

[0057] There are no particular restrictions on the organic solvents used, and a variety of them can be used. For example, hydrocarbon compounds such as toluene, hexane, and heptane, as well as isopropyl alcohol, isobutyl alcohol, acetone, ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and mixtures thereof can be used. In particular, it is preferable to use a mixture of methyl ethyl ketone and isopropyl alcohol.

[0058] The release agent composition coated as described above is preferably heat-cured. In this case, the heating temperature is preferably 100°C or higher, and particularly preferably 110°C or higher. Furthermore, the heating temperature is preferably 160°C or lower, and particularly preferably 140°C or lower. The heating time for heat curing is preferably 5 seconds or more, and particularly preferably 15 seconds or more. Furthermore, the heating time is preferably 120 seconds or less, and particularly preferably 90 seconds or less.

[0059] 4. Method of using release film in the ceramic green sheet manufacturing process The release film according to this embodiment is preferably used to manufacture a ceramic green sheet. In this case, first, a ceramic slurry containing a ceramic material such as barium titanate or titanium oxide is applied to the release surface of the release agent layer.

[0060] The above coating can be carried out using, for example, a slot die coating method or a doctor blade method. Examples of binder components contained in the ceramic slurry include butyral resins and acrylic resins. Examples of solvents contained in the ceramic slurry include organic solvents and aqueous solvents.

[0061] According to the release film of this embodiment, since it exhibits excellent wettability with respect to ceramic slurry, even if the coating thickness of the ceramic slurry is thin, it is possible to form a uniform coating film without repelling.

[0062] Following the application of the ceramic slurry to the release surface, the applied ceramic slurry is dried to form a ceramic green sheet. After forming the ceramic green sheet, the ceramic green sheet is separated from the release film. The release film according to this embodiment exhibits excellent light release properties to the ceramic green sheet, allowing it to be easily peeled off with a small peeling force without causing cracks, breaks, or other damage to the ceramic green sheet.

[0063] The thickness of the ceramic green sheet produced using the release film according to this embodiment is preferably 20 μm or less, more preferably 10 μm or less in the case of an aqueous system, and more preferably 4 μm or less in the case of a solvent system. Furthermore, using the release film according to this embodiment, extremely thin ceramic green sheets of 2 μm or less can also be successfully produced.

[0064] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Accordingly, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0065] For example, other layers may be provided on the surface of the substrate opposite to the release agent layer, or between the substrate and the release agent layer. [Examples]

[0066] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0067] [Example 1] 25 parts by mass (solid content equivalent, same applies hereafter) of methylated melamine resin (manufactured by Showa Denko Materials, product name "Tesfine 200") as amino resin (A), 60 parts by mass of acrylic resin (manufactured by DIC, product name "Acrydic WMU-504", hydroxyl value: 53.0-61.0 mg KOH / g, Tg: 60℃) as hydroxyl group-containing acrylic resin (B), 15 parts by mass of silicone-modified polyacrylate (OH functional) (C1; manufactured by Bic Chemie Japan, product name "BYK-SILCLEAN3700") as hydroxyl group-containing silicone-modified acrylic resin (C), and 3 parts by mass of p-toluenesulfonic acid as acid catalyst (D) component were mixed and diluted with an organic solvent (toluene:isopropanol = 60:40 (by mass)) to a solid content concentration of 2% to obtain a coating solution for the release agent composition.

[0068] The obtained coating solution was uniformly applied to a biaxially oriented polyethylene terephthalate (PET) film (thickness: 31 μm, maximum protrusion height Rp on the coated surface: 40 nm) as a substrate using the gravure coating method. Next, the coating film was cured by heating in a hot air circulating dryer at 130°C for 30 seconds, obtaining a release film in which a 100 nm thick release agent layer was laminated on one side of the substrate. Table 1 shows the details and formulation of each component.

[0069] [Example 2] A release film was manufactured in the same manner as in Example 1, except that the amount of hydroxyl group-containing acrylic resin (B) was changed to 45 parts by mass and the amount of hydroxyl group-containing silicone-modified acrylic resin (C) was changed to 30 parts by mass.

[0070] [Example 3] A release film was manufactured in the same manner as in Example 1, except that the hydroxyl group-containing silicone-modified acrylic resin (C) was replaced with a hydroxyl group-containing silicone-modified acrylic polymer (C2; manufactured by Taisei Fine Chemical Co., Ltd., product name "8BS-9000").

[0071] [Example 4] A release film was manufactured in the same manner as in Example 1, except that the base material was changed to a biaxially oriented polyethylene terephthalate (PET) film (thickness: 31 μm, maximum protrusion height Rp on the coated surface: 400 nm).

[0072] [Comparative Example 1] A coating solution containing a 2% by mass stripping agent composition was prepared by mixing 100 parts by mass of a solvent-type addition reaction silicone stripping agent (manufactured by Toray Dow Corning Silicone Co., Ltd., product name "SRX-211"), which mainly consists of polydimethylsiloxane having vinyl groups as functional groups and a crosslinking agent (polymethylhydrogensiloxane), with 1 part by mass of a platinum-based catalyst (manufactured by Toray Dow Corning Silicone Co., Ltd., product name "SRX-212") in an organic solvent mainly composed of toluene.

[0073] The obtained coating solution was uniformly applied to the same substrate as in Example 1 using the gravure coating method. Next, the coating film was cured by heating in a hot air circulating dryer at 120°C for 30 seconds, obtaining a release film in which a 100 nm thick release agent layer was laminated on one side of the substrate.

[0074] [Comparative Example 2] A release film was manufactured in the same manner as in Example 1, except that the amount of amino resin (A) was changed to 37 parts by mass, the amount of hydroxyl group-containing acrylic resin (B) to 63 parts by mass, and the amount of hydroxyl group-containing silicone-modified acrylic resin (C) to 0 parts by mass.

[0075] [Comparative Example 3] A release film was manufactured in the same manner as in Example 1, except that the amount of amino resin (A) was changed to 37 parts by mass, the amount of hydroxyl group-containing acrylic resin (B) was changed to 0 parts by mass, and the amount of hydroxyl group-containing silicone-modified acrylic resin (C) was changed to 63 parts by mass.

[0076] [Comparative Example 4] A release film was manufactured in the same manner as in Example 1, except that an alkyd resin (DIC Corporation, product name "Barnock D-145-55BA") was used instead of the hydroxyl group-containing acrylic resin (B).

[0077] [Comparative Example 5] A release film was manufactured in the same manner as in Example 1, except that a silicone-modified polyacrylate (C3; manufactured by BYK-3550, BYChemie Japan) that does not contain hydroxyl groups was used instead of a silicone-modified acrylic resin (C) containing hydroxyl groups.

[0078] [Comparative Example 6] A release film was manufactured in the same manner as in Example 1, except that the amount of amino resin (A) was changed to 0 parts by mass, the amount of hydroxyl group-containing acrylic resin (B) to 70 parts by mass, and the amount of hydroxyl group-containing silicone-modified acrylic resin (C) to 30 parts by mass.

[0079] [Test Example 1] (Evaluation of curing properties) The release films obtained in the examples and comparative examples were subjected to a load of 200 g / cm² on the surface of the release agent layer using a cloth containing methyl ethyl ketone (manufactured by Ozu Sangyo Co., Ltd., product name "BEMCOT AP-2"). 2 The surface was rubbed with [a specific tool / method]. The peeled surface was then visually inspected, and the hardening properties of the release agent layer were evaluated according to the following criteria. The evaluation results are shown in Table 2. A: The base material was not exposed even after rubbing it back and forth more than 20 times. B: The substrate was exposed after rubbing 11 to 20 times back and forth. C: The base material was exposed when rubbed back and forth 10 times or less.

[0080] [Test Example 2] (Evaluation of substrate adhesion) The surface of the release agent layer in the release films obtained in the examples and comparative examples was rubbed back and forth 50 times with a finger to check for any detachment of the release agent layer. The adhesion between the release agent layer and the substrate was then evaluated according to the following criteria. The evaluation results are shown in Table 2. A: The release agent layer did not detach. C: The release agent layer has come off.

[0081] [Test Example 3] (Evaluation of wettability) The contact angle of propylene glycol monomethyl ether (PGM) on the release surface of the release films obtained in the examples and comparative examples was measured using a fully automatic contact angle meter (Kyowa Interface Science Co., Ltd., product name "DM-701"). Specifically, under conditions of 23°C and 50% RH humidity, the release film was placed on a flat glass substrate tilted at 0 degrees, and a 2 μL droplet of propylene glycol monomethyl ether was dropped onto the release surface of the release film. Three seconds after the droplet had settled, the contact angle (PGM contact angle; °) was measured. The results are shown in Table 2.

[0082] Furthermore, the wettability of the release surface of the release film was evaluated based on the measured PGM contact angle according to the following criteria. The evaluation results are shown in Table 2. A: Contact angle is 40° or less C: Contact angle greater than 40°

[0083] [Test Example 4] (Evaluation of peelability of adhesive tape) Acrylic adhesive tape (manufactured by Nitto Denko Corporation, product name "31B Tape") was applied to the release surface of the release films obtained in the examples and comparative examples by using a 2 kg roller and making one pass back and forth motion. In this state, the samples were left to stand for 24 hours in an atmosphere of 23 degrees Celsius and 50% RH humidity. Next, the release film side of the prepared samples was fixed to a rigid plate with double-sided adhesive tape. Then, using a tensile testing machine, the acrylic adhesive tape was peeled off the release film at a peeling angle of 180° and a peeling speed of 300 mm / min, and the force required to peel (peeling force; mN / 20 mm) was measured. The results are shown in Table 2.

[0084] Furthermore, based on the measured peeling force, the peelability of the release surface of the release film was evaluated according to the following criteria. The evaluation results are shown in Table 2. A: Peeling force less than 1000mN / 20mm C: Peeling force of 1000mN / 20mm or more

[0085] [Test Example 5] (Evaluation of release properties for ceramic green sheets) A ceramic slurry was prepared by mixing 100 parts by mass of barium titanate powder (BaTiO3; manufactured by Sakai Chemical Industry Co., Ltd., product name "BT-03"), 8 parts by mass of polyvinyl butyral resin as a binder (manufactured by Sekisui Chemical Co., Ltd., product name "Eslec B·K BM-2"), and 4 parts by mass of dioctyl phthalate as a plasticizer (manufactured by Kanto Chemical Co., Ltd., dioctyl phthalate grade 1), with 135 parts by mass of a mixture of toluene and ethanol (mass ratio 6:4), in the presence of zirconia beads, using a ball mill to disperse the mixture, and then removing the beads.

[0086] The ceramic slurry was applied to the release surface of the release films obtained in the examples and comparative examples using a die coater, covering an area 250 mm wide and 10 m long. The film was then dried in a dryer at 80°C for 1 minute to obtain a ceramic green sheet with a release film, in which a ceramic green sheet with a thickness of 1 μm was formed on the release film.

[0087] The resulting ceramic green sheet with release film was left to stand for 24 hours in an atmosphere of 23°C and 50% RH. Next, the ceramic green sheet was cut into 40 mm wide strips, which were used as measurement samples.

[0088] The release film side of the measurement sample was fixed to a flat plate, and the ceramic green sheet was peeled from the release film using a tensile testing machine (Shimadzu Corporation, product name "AG-IS500N") at a peeling angle of 90° and a peeling speed of 0.3 m / min. The force required to peel the sheet (peeling force; mN / 40mm) was measured. The results are shown in Table 2.

[0089] Furthermore, based on the measured peeling force, the peelability of the release surface of the release film was evaluated according to the following criteria. The evaluation results are shown in Table 2. A: Peeling force less than 30mN / 40mm B: Peeling force of 30mN / 40mm or more C: Cannot be peeled off

[0090] [Test Example 6] (Evaluation of surface smoothness) The substrate-side surface of the release films obtained in the examples and comparative examples was fixed to a glass plate with double-sided adhesive tape. The maximum protrusion height (Rp; nm) on the release surface was then measured using an optical interference surface shape observation device (manufactured by Nippon Beeco Co., Ltd., product name "WYKO-1100") in PSI mode at 50x magnification. Ten measurements were taken, and the average value was taken as the maximum protrusion height (Rp) on the release surface. The results are shown in Table 2.

[0091] Furthermore, the surface smoothness of the release surface of the release film was evaluated based on the measured maximum protrusion height (Rp) according to the following criteria. The evaluation results are shown in Table 2. A: Maximum protrusion height (Rp) is less than 100 nm C: Maximum protrusion height (Rp) is 100 nm or more

[0092] [Table 1]

[0093] [Table 2]

[0094] As can be seen from Table 2, the release films obtained in the examples had low release strength and excellent wettability. Furthermore, the release films obtained in the examples also exhibited excellent curability of the release agent layer and adhesion to the substrate. [Industrial applicability]

[0095] The release film for the ceramic green sheet manufacturing process of the present invention is suitable for forming ceramic green sheets.

Claims

1. A release film for the ceramic green sheet manufacturing process, comprising a base material and a release agent layer provided on one side of the base material, The release agent layer is formed from a release agent composition containing an amino resin (A), a hydroxyl group-containing acrylic resin (B), a hydroxyl group-containing silicone-modified acrylic resin (C) which is a different component from the hydroxyl group-containing acrylic resin (B), and an acid catalyst (D). In the aforementioned release agent composition, the content of the amino resin (A) is 15% by mass or more and 50% by mass or less, the content of the hydroxyl group-containing acrylic resin (B) is 20% by mass or more and 75% by mass or less, and the content of the hydroxyl group-containing silicone-modified acrylic resin (C) is 10% by mass or more and 40% by mass or less. The content of the acid catalyst (D) is 0.5 parts by mass or more and 30 parts by mass or less, based on 100 parts by mass of the total of the amino resin (A), the hydroxyl group-containing acrylic resin (B), and the hydroxyl group-containing silicone-modified acrylic resin (C). The amino resin (A) is a melamine resin having a weight-average molecular weight of 150 or more and 10,000 or less, which is measured by gel permeation chromatography (GPC) on a standard polystyrene basis. The hydroxyl value of the hydroxyl group-containing acrylic resin (B) is 10 mg KOH / g or more and 200 mg KOH / g or less. The amount of silicone modification in the hydroxyl group-containing silicone-modified acrylic resin (C) is 0.1 mmol / g or more and 30 mmol / g or less. A release film for the ceramic green sheet manufacturing process, characterized by the following features.

2. The release film for the ceramic green sheet manufacturing process according to claim 1, characterized in that the hydroxyl value in the hydroxyl group-containing silicone-modified acrylic resin (C) is 2 mg KOH / g or more and 200 mg KOH / g or less.

3. The release film for the ceramic green sheet manufacturing process according to claim 1 or 2, characterized in that the maximum protrusion height (Rp) on the surface of the release agent layer opposite to the substrate is 100 nm or less.

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