JP7306395B2 - release film - Google Patents

Description

The present invention relates to a release film. More specifically, it is possible to reduce the manufacturing cost, and even when the sheet molded on the release layer is made thinner, the wettability of the slurry and the resin solution, and the appropriate sheet peeling force. It relates to a release film that can be equipped with all. For example, it is particularly preferably used for manufacturing ceramic green sheets, which are intermediate products in the manufacturing process of ceramic multilayer capacitors.

A release film is a member used for forming and releasing a sheet to be released uniformly without causing damage. Sheets include ceramic green sheets, sheets containing other particles and resin, resin sheets, and the like.

A release film is mainly produced by offline coating in which a solvent-based release formulation is applied in a separate process to a substrate film obtained in a film-forming process (see, for example, Patent Document 1). However, in such prior art, the process of forming the film base material and the process of forming the release layer are separate processes, which causes an increase in cost.

Therefore, techniques for producing a release film by applying an aqueous release formulation by in-line coating during the film-forming process have been disclosed (see, for example, Patent Documents 2 and 3). However, according to such prior art, since the main resin of the water-based release formulation is a silicone resin, the surface free energy becomes too low. There is a problem that pinholes are generated.

JP 2010-155459 A JP 2010-017932 A JP 2013-208810 A

The present invention has been made against the background of such problems of the prior art. That is, the object of the present invention is to reduce the manufacturing cost and produce a good sheet slurry and resin solution wettability even when the sheet molded on the release layer is further thinned. Another object of the present invention is to provide a release film capable of having all appropriate sheet peeling strength.

The present inventors have completed the present invention as a result of intensive studies to achieve the above object. That is, the present invention has the following configurations.
1. A release film comprising a polyester film and a release layer, the release layer having a release layer directly or via another layer on at least one side of the polyester film, and the release layer being an acrylic resin having a long-chain alkyl group. , and at least one cross-linking agent selected from oxazoline-based cross-linking agents and carbodiimide-based cross-linking agents.
2. The release film according to 1 above, wherein the acrylic resin contains a long-chain alkyl group-containing acrylate monomer, and the copolymerization ratio of the long-chain alkyl group-containing acrylate monomer in the acrylic resin is 5 mol % or more and 60 mol % or less.
3. 2. The release film according to 1 or 2 above, wherein the cross-linking agent is an oxazoline-based cross-linking agent, and the oxazoline-based cross-linking agent contains 3.0 to 9.0 mmol/g of oxazoline groups.
4. 3. The release film according to any one of 1st to 3rd above, wherein the acrylic resin having a long-chain alkyl group has an acid value of 40 mgKOH/g or more and 400 mgKOH/g or less.
5. 4. The release film as described in any one of the above 1 to 4, wherein the release layer has a thickness of 0.001 μm or more and 2 μm or less.
6. The release film according to any one of the above 1 to 5, which is a release film for producing a ceramic green sheet.
7. A method for producing a release film including a polyester film and a release layer,
The release film has a release layer on at least one side of the polyester film directly or via another layer,
The release layer is a release film obtained by curing a composition containing an acrylic resin having a long-chain alkyl group and at least one cross-linking agent selected from an oxazoline-based cross-linking agent and a carbodiimide-based cross-linking agent,
A method for producing a release film, comprising applying a release coating liquid to an unstretched film or a uniaxially stretched film, stretching the film in at least one unstretched direction, and heat-treating the film.
8. 7. The method for producing a release film as described in 7 above, wherein the method for producing a release film is a method for producing a release film for producing a ceramic green sheet.
9. The ceramic green sheet is molded using the release film for manufacturing the ceramic green sheet described in the sixth above or the method for manufacturing the release film for manufacturing the ceramic green sheet described in the eighth above. Production method.
10. 9. The method for producing a ceramic green sheet as described in 9 above, wherein the thickness of the ceramic green sheet to be produced is 0.2 μm or more and 2.0 μm or less.
11. A method for manufacturing a ceramic capacitor employing the method for manufacturing a ceramic green sheet according to the ninth or tenth aspect.

According to the present invention, it is possible to reduce the manufacturing cost, and even when the molded sheet is made thinner, it has good wettability of the sheet slurry and resin solution, and an appropriate sheet peeling force. It is possible to provide a release film that can be equipped with all.

The present invention will be described in detail below.
The release film of the present invention is preferably a release film having a release layer on at least one surface of a polyester film as a base film. Preferably, the polyester film is a biaxially oriented polyester film.

In the present invention, the release layer is formed by curing a composition containing a resin having a long-chain alkyl group and at least one cross-linking agent selected from oxazoline-based cross-linking agents and carbodiimide-based cross-linking agents.
With the release layer according to the present invention, the hardness of the release layer is moderately high and the surface free energy of the release layer is within a predetermined range, so a good peel force can be obtained.

(polyester film)
The polyester constituting the polyester film used as the base material in the present invention is not particularly limited, and is a polyester generally used as a release film base material, preferably from an aromatic dibasic acid component and a diol component. It is preferably a crystalline linear saturated polyester such as polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, and polytrimethylene terephthalate. It may be a copolymer that Polyethylene terephthalate is particularly preferred. In polyethylene terephthalate, the repeating unit of ethylene terephthalate is preferably 90 mol % or more, more preferably 95 mol % or more, and may be copolymerized with a small amount of other dicarboxylic acid component or diol component, but from the viewpoint of cost. , preferably made only from terephthalic acid and ethylene glycol. In addition, known additives such as antioxidants, light stabilizers, ultraviolet absorbers, crystallization agents, etc. may be added within limits that do not impair the effects of the film of the present invention. The polyester film is preferably a biaxially oriented polyester film because of its high bidirectional elastic modulus.

The intrinsic viscosity of the polyester film is preferably 0.50 to 0.70 dl/g, more preferably 0.52 to 0.62 dl/g. When the intrinsic viscosity is 0.50 dl/g or more, it is preferable because many breakages do not occur in the stretching process. Conversely, when it is 0.70 dl/g or less, the cutting performance is good when cutting into a predetermined product width, and dimensional defects do not occur, which is preferable. Moreover, it is preferable to sufficiently vacuum-dry the raw material pellets.

As a method for producing a polyester film in the present invention, for example, the polyester is melted with an extruder, extruded into a film shape, cooled with a rotating cooling drum to obtain an unstretched film, and the unstretched film is obtained. It can be obtained by uniaxially or biaxially stretching. The biaxially stretched film can be obtained by a method of sequentially biaxially stretching a longitudinally or laterally uniaxially stretched film in the lateral direction or longitudinal direction, or by a method of simultaneously biaxially stretching an unstretched film in the longitudinal direction and the lateral direction. I can. In the present invention, the release layer is applied during the production process of the polyester film. A so-called in-line coating method is preferably used.

In the present invention, the stretching temperature during stretching of the polyester film is preferably higher than the secondary transition point (Tg) of the polyester. It is preferable that the film is stretched 1 to 8 times, particularly 2 to 6 times, in each of the longitudinal and transverse directions.

The polyester film preferably has a thickness of 12 to 50 μm, more preferably 15 to 38 μm, more preferably 19 to 33 μm. If the thickness of the film is 12 μm or more, it is preferable because there is no risk of deformation due to heat during film production, the release layer processing step, the sheet molding step, and the like. On the other hand, if the thickness of the film is 50 μm or less, the amount of the film to be discarded after use is not excessively increased, which is preferable for reducing the environmental load.

The polyester film substrate may be a single layer or a multilayer of two or more layers. For example, the polyester film substrate preferably has a surface layer A substantially free of inorganic particles on at least one side. In the case of a laminated polyester film having a multilayer structure of two or more layers, it is preferable to have a surface layer B capable of containing particles and the like on the opposite side of the surface layer A which does not substantially contain inorganic particles. As for the laminated structure, the layer on the side where the release layer is applied (laminated side) is the surface layer A, the layer on the opposite side is the surface layer B, and the core layer other than these is the layer C, the layer structure in the thickness direction. may be a laminate structure such as release layer/A/B or release layer/A/C/B. As a matter of course, the layer C may be composed of a plurality of layers. Alternatively, the surface layer B may not contain particles. In that case, it is preferable to provide a coating layer containing particles and a binder on the surface layer B in order to impart lubricity for winding the film into a roll.

In the polyester film substrate of the present invention, the area surface average roughness (Sa) of the surface layer A is preferably 10 nm or less, more preferably 7 nm or less. When Sa is 10 nm or less, pinholes and the like are less likely to occur during molding of laminated ultra-thin sheets, which is preferable. When Sa is 7 nm or less, pinholes and the like are less likely to occur during molding of laminated ultra-thin sheets, which is preferable. It is preferable that the area surface average roughness (Sa) of the surface layer A is as small as possible. For example, the area surface average roughness (Sa) of the surface layer A is 0.1 nm or more.
In one embodiment, the area surface average roughness (Sa) of the surface layer A is 0.1 nm or more and 10 nm or less, for example, 0.1 nm or more and 7 nm or less, and may be 0.1 nm or more and 5 nm or less, It may be 0.5 nm or more and 3 nm or less.
Here, when the below-described anchor coat layer or the like is provided on the surface layer A, it is preferable that the coat layer does not substantially contain inorganic particles, and the region surface average roughness (Sa) after lamination of the coat layer is within the above range. It is preferable to enter In the present invention, "substantially free of inorganic particles" means a content of 50 ppm or less, preferably 10 ppm or less, most preferably a detection limit or less when the inorganic elements are quantified by fluorescence X-ray analysis. do. This is because even if inorganic particles are not positively added to the film, contaminants derived from foreign substances and dirt adhering to the lines and equipment in the raw material resin or film manufacturing process peel off and mix into the film. This is because there are cases.

In the polyester film substrate of the present invention, the surface layer B, which forms the surface opposite to the surface to which the release layer is applied, preferably contains particles from the viewpoint of the slipperiness of the film and the ease with which air can escape. Silica particles and/or calcium carbonate particles are preferably used. The content of the particles contained in the surface layer B is preferably 5000 to 15000 ppm in total. When the total amount of silica particles and/or calcium carbonate particles is 5000 ppm or more, when the film is wound into a roll, air can be released uniformly, and the roll shape and flatness are good, resulting in an ultra-thin sheet. It is suitable for the production of Further, when the total amount of silica particles and/or calcium carbonate particles is 15000 ppm or less, aggregation of the lubricant is less likely to occur and large protrusions are not formed, which is preferable because the quality is stable when producing an ultra-thin sheet.

In the polyester film substrate of the present invention, the surface layer B, which forms the surface opposite to the surface to which the release layer is applied, preferably contains particles from the viewpoint of the slipperiness of the film and the ease with which air can escape. Silica particles and/or calcium carbonate particles are preferably used. At this time, the area average surface roughness (Sa) of the film of the surface layer B is preferably in the range of 1 to 40 nm. More preferably, it is in the range of 5 to 35 nm. When Sa is 1 nm or more, when the film is wound into a roll, air can be released uniformly, and the rolled shape and flatness are good, making it suitable for the production of ultra-thin sheets. In addition, when Sa is 40 nm or less, aggregation of the lubricant is less likely to occur, and coarse projections are not formed.

As the particles contained in the surface layer B, inert inorganic particles and/or heat-resistant organic particles can be used in addition to silica and/or calcium carbonate. Silica particles and/or calcium carbonate particles are preferably used from the viewpoint of transparency and cost, but other usable inorganic particles include alumina-silica composite oxide particles and hydroxyapatite particles. Examples of heat-resistant organic particles include crosslinked polyacrylic particles, crosslinked polystyrene particles, and benzoguanamine particles. When silica particles are used, porous colloidal silica is preferable, and when calcium carbonate particles are used, light calcium carbonate surface-treated with a polyacrylic acid-based polymer compound is preferable from the viewpoint of preventing the lubricant from falling off. .

The average particle diameter of the particles added to the surface layer B is preferably 0.1 μm or more and 2.0 μm or less, and particularly preferably 0.5 μm or more and 1.0 μm or less. If the average particle size of the particles is 0.1 μm or more, the slipperiness of the release film is good, which is preferable. Further, if the average particle diameter is 2.0 μm or less, it is preferable because there is no risk of pinholes in the sheet due to coarse particles on the surface of the release layer.

The surface layer B may contain two or more kinds of particles made of different materials. Further, particles of the same type but different in average particle diameter may be contained.

When the surface layer B does not contain particles, it is preferable that a coating layer containing particles on the surface layer B provides lubricity. Although the present coat layer is not particularly limited, it is preferably provided as an in-line coat that is applied during film formation of the polyester film. When the surface layer B does not contain particles and the surface layer B has a coat layer containing particles, the surface of the coat layer has a region surface roughness (Sa) for the same reason as the region surface roughness (Sa) of the surface layer B The average surface roughness (Sa) is preferably in the range of 1-40 nm. More preferably, it is in the range of 5 to 35 nm.

From the viewpoint of reducing pinholes, it is preferable not to use recycled raw materials in the surface layer A, which is the layer on which the release layer is provided, in order to prevent particles such as lubricant from being mixed.

The thickness ratio of the surface layer A, which is the layer on which the release layer is provided, is preferably 20% or more and 50% or less of the total layer thickness of the base film. If it is 20% or more, the inside of the film is less likely to be affected by the particles contained in the surface layer B, etc., and it is easy for the region surface average roughness Sa to satisfy the above range, which is preferable. When the total thickness of the base film is 50% or less of the total thickness of the base film, the ratio of the recycled raw material used in the surface layer B can be increased, and the environmental load is reduced, which is preferable.

From the viewpoint of economy, the layers other than the surface layer A (the surface layer B or the intermediate layer C described above) may contain 50 to 90% by mass of recycled film scraps and PET bottle raw materials. Even in this case, the type and amount of lubricant contained in the surface layer B, the particle size, and the area surface average roughness (Sa) preferably satisfy the above ranges.

In addition, in order to improve the adhesion of the release layer to be applied and to prevent electrification, the surface of the surface layer A and / or surface layer B may be added to the film before stretching or after uniaxial stretching in the film forming process. A coat layer may be provided, and corona treatment or the like may be applied.

(release layer)
The release film of the present invention preferably has a release layer on one surface of the polyester base film as described above.
The release layer is a layer obtained by curing a composition containing an acrylic resin having a long-chain alkyl group and at least one cross-linking agent selected from oxazoline cross-linking agents and carbodiimide cross-linking agents.
The release film of the present invention having such a release layer can be produced at a reduced production cost. Furthermore, even when the sheet is further thinned, the release film of the present invention can have both good sheet slurry and resin solution wettability and appropriate sheet peeling force.
For example, the release layer preferably contains at least a binder resin, a cross-linking agent and an additive.
The release layer is a layer formed by applying a composition containing a resin and a cross-linking agent according to the present invention, and can also be referred to as a release coating layer.

(Binder resin in release layer)

The binder resin constituting the release layer in the present invention preferably contains an acrylic resin. The acrylic resin is preferably an acrylic resin having at least one selected from the group consisting of hydroxyl groups, carboxyl groups and long-chain alkyl groups in its molecule. In one embodiment, the acrylic resin is an acrylic resin having long chain alkyl groups.
In this specification, these acrylic resins may be simply referred to as acrylic resins.
It is more preferable that the structural unit having a hydroxyl group is contained in an amount of 5 to 90 mol % in 100 mol % of all structural units. It is preferable that the structural unit having a hydroxyl group is 5 mol % or more, since the water solubility of the acrylic resin can be appropriately maintained. On the other hand, when it is 90 mol % or less, the particles contained in the release layer do not cause excessive interaction with the hydroxyl groups of the acrylic resin, and the particles are uniformly dispersed, which is preferable.
In one embodiment, the constitutional unit having a hydroxyl group accounts for 5 to 50 mol%, for example 5 to 45 mol%, in 100 mol% of all constitutional units.

In order to introduce a hydroxyl group into an acrylic resin, a monomer having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, or 2-hydroxyethyl ( A ring-opening adduct of γ-butyrolactone or ε-caprolactone to meth)acrylate may be used as a copolymerization component. Among them, 2-hydroxyethyl (meth)acrylate is preferable because it does not inhibit water solubility. In addition, you may use together 2 or more types of these.

The hydroxyl value of the acrylic resin is preferably 2 mgKOH/g or more, more preferably 5 mgKOH/g or more, still more preferably 10 mgKOH/g or more. If the hydroxyl value of the acrylic resin is 2 mgKOH/g or more, the water solubility of the acrylic resin is improved, which is preferable.

The hydroxyl value of the acrylic resin is preferably 250 mgKOH/g or less, more preferably 230 mgKOH/g or less, still more preferably 200 mgKOH/g or less. If the hydroxyl value of the acrylic resin is 250 mgKOH/g or less, the particles contained in the release layer do not interact excessively with the hydroxyl groups of the acrylic resin, which is preferable because the particles are uniformly dispersed.

The acrylic resin used in the present invention may contain a resin having a hydroxyl group. Moreover, a resin having a carboxyl group may be included. In another aspect, the acrylic resin may contain both a resin having a hydroxyl group and a resin having a carboxyl group. By having a carboxyl group, it becomes possible to form a crosslinked structure with a crosslinking agent and to easily impart water solubility. Examples thereof include monomers containing a carboxy group such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid and fumaric acid, and monomers containing an acid anhydride group such as maleic anhydride and itaconic anhydride.

A monomer having a carboxyl group accounts for preferably 4 mol % or more, more preferably 10 mol % or more, in 100 mol % of all structural units of the acrylic resin. When it is 4 mol % or more, it becomes easy to form a crosslinked structure in the release layer and to impart water solubility, which is preferable. The monomer having a carboxyl group is preferably 65 mol % or less, more preferably 50 mol % or less. When it is 65 mol % or less, the Tg of the resulting coating film does not become too high relative to the preferable range described later, and the film-forming properties and the stretching suitability in in-line coating are favorable, which is preferable.

In order to develop good water solubility, it is preferable to neutralize the carboxyl groups introduced into the acrylic resin by copolymerization of acrylic acid or methacrylic acid. Basic neutralizers include amine compounds such as ammonia, trimethylamine, triethylamine and dimethylaminoethanol, and inorganic basic substances such as potassium hydroxide and sodium hydroxide. It is preferable to use an amine compound as a neutralizing agent for ease of application and ease of formation of a crosslinked structure. Among them, ammonia is most preferable because it does not cause aggregation of particles when particles are contained in the release layer. The neutralization rate is preferably 30 mol % to 95 mol %, more preferably 40 mol % to 90 mol %. When the neutralization rate is 30 mol% or more, the acrylic resin has sufficient water solubility, the acrylic resin can be easily dissolved during preparation of the coating solution, and there is no risk of whitening of the coated film surface after drying. preferable. On the other hand, when the neutralization rate is 95 mol % or less, the water solubility is not too high, and alcohol or the like can be easily mixed in preparation of the coating liquid, which is preferable.

The acid value of the acrylic resin is, for example, preferably 40 mgKOH/g or more, more preferably 50 mgKOH/g or more, still more preferably 60 mgKOH/g or more. If the acid value of the acrylic resin is, for example, 40 mgKOH/g or more, the number of cross-linking points with the oxazoline cross-linking agent or the carbodiimide cross-linking agent increases, so that a strong coating film with a higher cross-linking density can be obtained, which is preferable.

The acid value of the acrylic resin is, for example, preferably 400 mgKOH/g or less, more preferably 350 mgKOH/g or less, still more preferably 300 mgKOH/g or less.
In one embodiment, the acrylic resin has an acid value of 200 mgKOH/g or less, such as 150 mgKOH/g or less.
If the acid value of the acrylic resin is 400 mgKOH/g or less, the cross-linking density with the oxazoline cross-linking agent or carbodiimide cross-linking agent does not become too high, and cracks do not occur when stretched, which is preferable.
In addition, it is considered that such a tendency can be obtained even in an embodiment in which an oxazoline cross-linking agent and a carbodiimide cross-linking agent are used in combination.
Further, when the acid value of the acrylic resin is 400 mgKOH/g or less, the particles contained in the release layer do not interact extremely with the carboxyl groups of the acrylic resin, which is preferable because the particles are uniformly dispersed. Good dispersibility of the particles is preferable because coarse protrusions do not occur on the release coating surface and pinholes do not occur in the sheet.
In one embodiment, the oxidation of the acrylic resin having long-chain alkyl groups is 40 mgKOH/g or more and 400 mgKOH/g or less, such as 40 mgKOH/g or more and 300 mgKOH/g or less.

The acrylic resin used in the present invention preferably has at least one selected from the group consisting of hydroxyl groups, carboxyl groups and long-chain alkyl groups. Having a long-chain alkyl group is preferable because the sheet peeling force can be made easier. The acrylic resin having a long-chain alkyl group preferably has an alkyl group having 8 to 25 carbon atoms in the side chain of the acrylic resin, more preferably an alkyl group having 12 to 22 carbon atoms in the side chain of the acrylic resin. groups, more preferably those having an alkyl group of 16 to 20 carbon atoms in the side chain of the acrylic resin.
Further, a copolymer having a (meth)acrylic acid ester as a main repeating unit and containing a long-chain alkyl group having 8 to 20 carbon atoms in the transesterified portion can also be preferably used. Examples include lauryl (meth)acrylate, stearyl (meth)acrylate, and the like. Among them, stearyl methacrylate is preferably used in terms of availability, cost, and good peel strength.
For example, the acrylic resin used in the present invention further uses at least one selected from the group consisting of methyl methacrylate (MMA), hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA) in addition to stearyl methacrylate (SMA). It is a resin formed by
By containing such an acrylic resin, the release film of the present invention does not have an excessively high cross-linking density between the acrylic resin and the oxazoline cross-linking agent or carbodiimide cross-linking agent in the release layer. can be prevented from entering.
Furthermore, by containing such an acrylic resin, it is possible to reduce the manufacturing cost. Furthermore, even when the sheet is further thinned, the release film of the present invention can have both good sheet slurry and resin solution wettability and appropriate sheet peeling force.

The glass transition temperature (Tg) of the acrylic resin is preferably 50°C or higher, more preferably 55°C or higher, and still more preferably 60°C or higher. When the glass transition temperature of the acrylic resin is 50° C. or higher, the hardness of the release layer is appropriately increased, which is preferable.

The glass transition temperature (Tg) of the acrylic resin is preferably 110°C or lower, more preferably 105°C or lower, and still more preferably 100°C or lower. When the glass transition temperature of the acrylic resin is 110° C. or lower, the coating film is uniformly stretched without causing cracks in the stretching step after the release layer is applied, which is preferable.

A (meth)acrylic monomer or a non-acrylic vinyl monomer can be used as the Tg-adjusting monomer that is copolymerized to adjust the Tg to the above range. Specific examples of (meth) acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-amyl (meth) Acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, etc. (Meth)acrylic acid alkyl esters; Nitrogen-containing acrylic monomers such as (meth)acrylamide, diacetoneacrylamide, n-methylolacrylamide, (meth)acrylonitrile; Vinyl methacrylate and the like, which are one or two More than one species can be used.

Examples of non-acrylic vinyl monomers include styrene, α-methylstyrene, vinyltoluene (a mixture of m-methylstyrene and p-methylstyrene), styrene-based monomers such as chlorostyrene; vinyl acetate, vinyl propionate, and vinyl butyrate. , vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl pivalate, vinyl octylate, vinyl monochloroacetate, divinyl adipate, Vinyl esters such as vinyl crotonate, vinyl sorbate, vinyl benzoate and vinyl cinnamate; vinyl halide monomers such as vinyl chloride and vinylidene chloride;

The monomer having a long-chain alkyl group preferably accounts for 60 mol% or less, more preferably 50 mol% or less, in 100 mol% of all structural units of the acrylic resin. When it is 60 mol % or less, the Tg of the resulting coating film does not become too low relative to the preferred range, and the hardness of the coating film can be kept high, which is preferable. The monomer having a long-chain alkyl group preferably accounts for 5 mol% or more, more preferably 15 mol% or more, in 100 mol% of all structural units of the acrylic resin. If it is 5 mol % or more, the surface free energy is lowered, so that the peeling force is reduced, which is preferable.

The monomers for Tg adjustment are preferably used as the balance after determining appropriate amounts of the hydroxyl group-containing monomer, the carboxyl group-containing monomer and the long-chain alkyl group-containing monomer. The Tg of the copolymer is determined by the following Fox formula.

Ｗ_n：各モノマーの質量分率（質量％）
Ｔｇ_n：各モノマーのホモポリマーのＴｇ（Ｋ）

W _n : mass fraction of each monomer (% by mass)
Tg _n : Tg (K) of homopolymer of each monomer

The acrylic resin used in the present invention can be obtained by known radical polymerization. Emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization, and the like can all be adopted. From the point of handleability, solution polymerization is preferred. Water-soluble organic solvents that can be used for solution polymerization include ethylene glycol n-butyl ether, isopropanol, ethanol, n-methylpyrrolidone, tetrahydrofuran, 1,4-dioxane, 1,3-oxolane, methyl solosolve, and ethyl solosolve. , ethyl carbitol, butyl carbitol, propylene glycol monopropyl ether, propylene glycol monobutyl ether and the like. These may be used by mixing with water.

The polymerization initiator may be any known compound that generates radicals, but water-soluble azo polymerization initiators such as 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide are preferred. The temperature, time, etc. of the polymerization are appropriately selected.

The weight average molecular weight (Mw) of the acrylic resin is preferably about 10,000 to 200,000. A more preferred range is from 20,000 to 150,000. When Mw is 10,000 or more, there is no risk of thermal decomposition in the tenter, which is preferable. When the Mw is 200,000 or less, the viscosity of the coating liquid does not significantly increase and the coatability is good, which is preferable.

As the binder for the release layer in the present invention, other binder resin may be used in combination with the acrylic resin. Other binder resins include polyester resins, urethane resins, polyvinyl resins (polyvinyl alcohol, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches, and the like.

The content of the acrylic resin in the release layer is preferably 20% by mass or more and 95% by mass or less based on the total solid content. More preferably, it is 30% by mass or more and 90% by mass or less. If it is 20% by mass or more, the number of carboxyl groups, which are cross-linking components, does not decrease too much, and the cross-linking density does not decrease, which is preferable. If it is 95% by mass or less, the amount of the cross-linking agent to be cross-linked does not become too small and the cross-linking density does not decrease, which is preferable.

(crosslinking agent)
In the present invention, the release layer preferably contains at least one cross-linking agent selected from oxazoline cross-linking agents and carbodiimide cross-linking agents in order to form a crosslinked structure in the release layer. By incorporating an oxazoline-based cross-linking agent or a carbodiimide-based cross-linking agent, the coating strength of the release layer is improved by improving adhesion to the PET substrate and promoting cross-linking with the carboxyl group of the acrylic resin. As a result, the peel force can be reduced. Further, other cross-linking agents may be used in combination, and specific cross-linking agents that can be used in combination include urea-based, epoxy-based, melamine-based, isocyanate-based, silanol-based, and the like. In addition, a catalyst or the like can be appropriately used as necessary in order to accelerate the cross-linking reaction.

Examples of the cross-linking agent having an oxazoline group include, for example, a polymerizable unsaturated monomer having an oxazoline group, optionally together with other polymerizable unsaturated monomers, and a conventionally known method (e.g., solution polymerization, emulsion polymerization, etc.). and a polymer having an oxazoline group obtained by copolymerizing with.

Examples of polymerizable unsaturated monomers having an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2- Isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like can be mentioned. These may be used alone or in combination of two or more.

Other polymerizable unsaturated monomers include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) C1-C24 alkyl or cycloalkyl esters of (meth)acrylic acid such as acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, etc. hydroxyalkyl ester having 2 to 8 carbon atoms of (meth)acrylic acid; vinyl aromatic compounds such as styrene and vinyltoluene; (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, dimethylaminoethyl (meth)acrylate, adducts of glycidyl (meth)acrylate and amines; polyethylene glycol (meth)acrylate; N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, (meth)acrylonitrile and the like. These may be used alone or in combination of two or more.

Other polymerizable unsaturated monomers are hydrophilic monomers from the viewpoint of improving compatibility with other resins, wettability, cross-linking reaction efficiency, etc. by using the obtained cross-linking agent having an oxazoline group as a water-soluble cross-linking agent. A body is preferred. Hydrophilic monomers include monomers having a polyethylene glycol chain such as 2-hydroxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, monoester compounds of (meth)acrylic acid and polyethylene glycol; Aminoethyl (meth)acrylate and its salts, (meth)acrylamide, N-methylol (meth)acrylamide, N-(2-hydroxyethyl) (meth)acrylamide, (meth)acrylonitrile, sodium styrenesulfonate and the like. Among these, monomers having a polyethylene glycol chain such as methoxypolyethylene glycol (meth)acrylate and monoester compounds of (meth)acrylic acid and polyethylene glycol, which are highly soluble in water, are preferred.

The cross-linking agent having an oxazoline group preferably has an oxazoline group content of 3.0 to 9.0 mmol/g. More preferably, it is within the range of 4.0 to 8.0 mmol/g. If it is in the range of 3.0 to 9.0 mmol/g, it is preferable because an appropriate crosslinked structure can be formed and the peeling force becomes light. Moreover, when the content of the oxazoline cross-linking agent is within the above range, it is possible to form an appropriate cross-linked structure with the acrylic resin, and cracks do not occur when the film is stretched, which is preferable.

Examples of carbodiimide-based cross-linking agents include monocarbodiimide compounds and polycarbodiimide compounds. Examples of monocarbodiimide compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, and the like. . As the polycarbodiimide compound, those produced by a conventionally known method can be used. For example, it can be produced by synthesizing an isocyanate-terminated polycarbodiimide by condensation reaction accompanied by decarbonization of diisocyanate.

Examples of diisocyanates that are raw materials for synthesizing polycarbodiimide compounds include isomers of toluylene diisocyanate, aromatic diisocyanates such as 4,4-diphenylmethane diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate and 4 ,4-dicyclohexylmethane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane and other alicyclic diisocyanates, hexamethylene diisocyanate, and 2,2,4-trimethylhexamethylene diisocyanate and other aliphatic diisocyanates. Aromatic-aliphatic diisocyanates, alicyclic diisocyanates, and aliphatic diisocyanates are preferred because of the problem of yellowing.

In addition, the above diisocyanate may be used by controlling the degree of polymerization of the molecule to an appropriate degree by using a compound such as monoisocyanate that reacts with the terminal isocyanate. Examples of monoisocyanates for blocking the ends of polycarbodiimide to control the degree of polymerization include phenyl isocyanate, toluylene isocyanate, dimethylphenyl isocyanate, cyclohexyl isocyanate, butyl isocyanate, and naphthyl isocyanate. In addition, a compound having an OH group, —NH ₂ group, COOH group, or SO ₃ H group can be used as a terminal blocking agent.

The condensation reaction of diisocyanate with decarbonation proceeds in the presence of a carbodiimidation catalyst. Examples of catalysts include 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, 3-methyl-1-phenyl-2 -phospholene-1-oxide and phosphorene oxides such as 3-phospholene isomers thereof, and 3-methyl-1-phenyl-2-phospholene-1-oxide is preferred from the viewpoint of reactivity. The amount of the catalyst used can be the amount of catalyst.

The mono- or polycarbodiimide compound described above is desirably kept in a uniformly dispersed state when blended into a water-based paint. It is preferable to add a hydrophilic segment to the molecular structure of the compound and add it to the paint in the form of a self-emulsified product or a self-dissolved product.

The carbodiimide-based cross-linking agent used in the present invention includes water dispersibility and water solubility. Water-soluble is preferable because it has good compatibility with other water-soluble resins and improves the cross-linking reaction efficiency of the release layer. In order to make a carbodiimide compound water-soluble, after synthesizing an isocyanate-terminated polycarbodiimide by a condensation reaction accompanied by decarbonization of isocyanate, a hydrophilic moiety having a functional group reactive with an isocyanate group is further added. can be manufactured by

Hydrophilic moieties include (1) quaternary ammonium salts of dialkylaminoalcohols and quaternary ammonium salts of dialkylaminoalkylamines, (2) alkylsulfonates having at least one reactive hydroxyl group, and (3) Examples thereof include poly(ethylene oxide) terminally blocked with alkoxy groups, and a mixture of poly(ethylene oxide) and poly(propylene oxide). The carbodiimide compound becomes (1) cationic, (2) anionic, and (3) nonionic when the hydrophilic site is introduced. Among them, nonionic properties that are compatible with each other regardless of the ionic properties of other water-soluble resins are preferred.

The content of the cross-linking agent in the release layer is preferably 5% by mass or more and 80% by mass or less based on the total solid content. More preferably, it is 10% by mass or more and 70% by mass or less. If it is 5% by mass or more, it is preferable because the crosslink density of the resin in the coating layer does not decrease. If it is 80% by mass or less, the amount of carboxyl groups in the acrylic resin to be crosslinked does not become too small and the crosslink density does not decrease, which is preferable.

(Particles in release layer)
The release layer may contain lubricant particles in order to control the release force at the sheet release starting point and the release force during steady release, and to impart slipperiness to the surface. The particles may be inorganic particles or organic particles, and are not particularly limited, and include (1) silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, Barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, zirconium oxide, titanium dioxide, satin white, aluminum silicate, diatomaceous earth, calcium silicate, aluminum hydroxide, hydrated halloysite, calcium carbonate, magnesium carbonate, calcium phosphate, hydroxide inorganic particles such as magnesium and barium sulfate; Organic particles such as isoprene-based, methyl methacrylate/butyl methacrylate-based, melamine-based, polycarbonate-based, urea-based, epoxy-based, urethane-based, phenol-based, diallyl phthalate-based, polyester-based, and the like can be used.

The average particle size of the particles is preferably 10 nm or more, more preferably 20 nm or more, and still more preferably 30 nm or more. When the average particle size of the particles is 10 nm or more, it is preferable because the particles are less likely to aggregate and the lubricity can be ensured.

The average particle size of the particles is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. When the average particle diameter of the particles is 500 nm or less, pinholes are less likely to occur during sheet processing, and the particles do not fall off, which is preferable.

The method of measuring the average particle size of the particles is to observe the particles in the cross section of the film after processing with a transmission electron microscope or scanning electron microscope, observe 100 particles that are not agglomerated, and use the average value as the average particle size. It was performed by the method of using the diameter.

The shape of the particles is not particularly limited as long as it satisfies the object of the present invention, and spherical particles and non-spherical particles with irregular shapes can be used. The particle diameter of amorphous particles can be calculated as a circle equivalent diameter. The circle-equivalent diameter is a value obtained by dividing the observed particle area by π, calculating the square root, and doubling the result.

The ratio of the particles to the total solid content of the release layer is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 10% by mass or less. When the ratio of the particles to the total solid content of the release layer is 50% by mass or less, pinholes are less likely to occur during sheet processing, and the particles do not significantly drop off from the release layer, which is preferable. Moreover, it may be 0% by mass.

As a method for measuring the content of particles contained in the release layer, for example, when the release layer contains a resin as an organic component and inorganic particles, the following method can be used. First, the release layer provided on the processed film is extracted from the processed film using a solvent or the like and dried to obtain the release layer. Next, the obtained release layer is heated to burn and distill off the organic components contained in the release layer, thereby obtaining only the inorganic component. By measuring the weight of the obtained inorganic component and the release layer before combustion and distillation, the mass % of the particles contained in the release layer can be measured. At this time, a commercially available differential thermal/thermogravimetric simultaneous measurement device can be used for accurate measurement. In addition, the ratio of the above-mentioned particles in the total solid content of the release layer means the ratio of the total amount of the plural kinds of particles when plural kinds of particles are present.

(Additive)
In the present invention, releasability can be exhibited by using an acrylic resin having a long-chain alkyl group, and additives may be added to further improve releasability. Examples of additives used in the release layer include silicone-based additives and non-silicone additives such as olefin-based, long-chain alkyl-based, and fluorine-based additives. is preferably used. The silicone additive used in the present invention is effective not only for improving releasability but also for improving leveling property during coating and defoaming the coating solution.

(Silicone additive in release layer)
In the present invention, the silicone-based additive used in the release layer is a compound having a silicone structure in the molecule, and is not particularly limited as long as the effects of the present invention can be obtained. It can be used preferably. Among polyorganosiloxanes, polydimethylsiloxane (abbreviation: PDMS) can be preferably used, and polydimethylsiloxane having a functional group as a part thereof is also preferable. Having a functional group facilitates the expression of intermolecular interactions such as hydrogen bonding with the binder resin, making it difficult to migrate to the sheet, which is preferable.

The functional group to be introduced into polydimethylsiloxane is not particularly limited, and may be a reactive functional group or a non-reactive functional group. Moreover, the functional group may be introduced at one end of the polydimethylsiloxane, may be introduced at both ends, or may be a side chain. Also, the position to be introduced may be one or plural.

Amino groups, epoxy groups, hydroxyl groups, mercapto groups, carboxyl groups, methacryl groups, acryl groups and the like can be used as reactive functional groups to be introduced into polydimethylsiloxane. As non-reactive functional groups, polyether groups, aralkyl groups, fluoroalkyl groups, long-chain alkyl groups, ester groups, amide groups, phenyl groups and the like can be used. Although not bound by theory, among the above, those having an epoxy group, a carboxyl group, a polyether group, a methacrylic group, an acryl group, or an ester group are preferred.

As the functional group to be introduced into the polydimethylsiloxane, a polyether group and an ester group are preferable because they do not react with the binder resin, are easily oriented on the release layer surface, and are less likely to migrate to the green sheet.

The silicone additive used in the present invention preferably has a molecular weight of 40,000 or less. More preferably, it is 30,000 or less. When the molecular weight is 40,000 or less, the silicone additive tends to segregate on the surface of the release layer, which is preferable because the release property is good.

(Long-chain alkyl additive in release layer)
A long-chain alkyl-modified resin can be used as the long-chain alkyl-based additive, and those having an alkyl group having about 8 to 20 carbon atoms in the side chain, such as polyvinyl alcohol and acrylic resin, are preferable. Further, a copolymer having a (meth)acrylic acid ester as a main repeating unit and containing a long-chain alkyl group having 8 to 20 carbon atoms in the transesterified portion can also be preferably used. Releasability may be improved by using a long-chain alkyl-based additive different from the acrylic resin having a long-chain alkyl group, which is the main agent. Commercially available examples include Pyroyl® 406 (both Lion Specialty Chemicals, Inc.).

(Other Additives in Release Layer)
In order to impart other functionality to the release layer, various additives other than the silicone additive may be added as long as the coating appearance is not impaired. Examples of the additives include fluorescent dyes, fluorescent whitening agents, plasticizers, ultraviolet absorbers, pigment dispersants, foam inhibitors, antifoaming agents, preservatives, and the like.

The release layer may contain an additive other than the silicone additive for the purpose of improving leveling properties during coating and defoaming the coating solution. Additives may be cationic, anionic, or nonionic, but acetylene glycol-based or fluorine-based additives are preferred. These additives are preferably contained in the release layer within a range in which excessive addition does not cause an abnormality in coating appearance.

The additive used in the present invention is preferably 20% by mass or less. If it is 20% by mass or less, excessive transfer of the additive to the sheet does not occur, which is preferable. Moreover, the additive may be 0% by mass.

As the coating method, both the so-called in-line coating method in which the coating is applied at the same time as the formation of the polyester base film and the so-called off-line coating method in which the polyester base film is coated separately with a coater after the formation of the polyester base film can be applied. is efficient and preferred.

As a coating method, any known method can be used to apply the coating liquid to a polyethylene terephthalate (hereinafter sometimes abbreviated as PET) film. For example, reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method, etc. mentioned. These methods are applied singly or in combination.

In the present invention, the method of providing the release layer on the polyester film includes a method of applying a coating liquid containing a solvent, particles and a resin to the polyester film and drying the coating liquid. Examples of the solvent include an organic solvent such as toluene, water, or a mixed system of water and a water-soluble organic solvent. From the standpoint of environmental problems, water alone or a mixture of water and a water-soluble organic solvent is preferred. is preferred.

Although the solid content concentration of the release coating liquid depends on the type of binder resin and the type of solvent, it is preferably 0.5% by mass or more, more preferably 1% by mass or more. The solid content concentration of the coating liquid is preferably 35% by mass or less, more preferably 20% by mass or less. In addition, the release coating liquid may be described as a release coating liquid.

The drying temperature after coating also depends on the type of binder resin, the type of solvent, the presence or absence of a cross-linking agent, the solid content concentration, etc., but is preferably 70° C. or higher and preferably 250° C. or lower.

In the case of in-line coating, it may be applied to an unstretched film before stretching in the longitudinal direction, or may be applied to a uniaxially stretched film after stretching in the longitudinal direction and before stretching in the transverse direction. In the case of coating before stretching in the longitudinal direction, it is preferable to provide a drying step before roll stretching. When the uniaxially stretched film is coated before being stretched in the transverse direction, the film heating process in the tenter can also serve as the drying process, so a separate drying process is not necessarily required. The same applies to simultaneous biaxial stretching.

The film thickness of the release layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, still more preferably 0.02 μm or more, and particularly preferably 0.03 μm or more. It is preferable that the film thickness of the release layer is 0.001 μm or more because the film-forming property of the coating film is maintained and a uniform coating film is obtained.

The film thickness of the release layer is preferably 2 μm or less, more preferably 1 μm or less, still more preferably 0.8 μm or less, and particularly preferably 0.5 μm or less. When the film thickness of the coating layer is 2 μm or less, blocking is not likely to occur, which is preferable.

If the surface roughness of both sides of the base polyester film is different, the release layer may be laminated on either side. It is preferable to laminate a release layer on the smooth surface.

The outer surface of the film on which the release layer is formed (the release layer surface of the entire coated film that is not in contact with the polyester film) is desirably flat so as not to cause defects in the sheet coated and molded thereon. , the region surface average roughness (Sa) is preferably 5 nm or less and the maximum protrusion height (P) is preferably 50 nm or less. More preferably, the area surface average roughness is 5 nm or less and the maximum protrusion height is 40 nm or less. If the region surface roughness is 5 nm or less and the maximum protrusion height is 50 nm or less, defects such as pinholes do not occur during sheet formation, and the yield is favorable, which is preferable. It can be said that the smaller the region surface average roughness (Sa) is, the more preferable it is. It can be said that the smaller the maximum projection height (P) is, the more preferable it is, but the maximum projection height (P) may be 1 nm or more, or 3 nm or more.
In one embodiment, the area surface average roughness is less than 4.4 nm and the maximum protrusion height is 40 nm or less, for example, 4 nm or less and the maximum protrusion height is 40 nm or less.

The surface free energy of the release layer is preferably 45 mJ/m ² or less, more preferably 35 mJ/m ² or less. When the release layer has a surface free energy of 45 mJ/m ² or less, the release force of the sheet is reduced, which is preferable. The surface free energy of the release layer is preferably 20 mJ/m ² or more, more preferably 25 mJ/m ² or more. When the release layer has a surface free energy of 20 mJ/m ² or more, the release force of the sheet does not become too light, and repelling of the slurry or resin solution is less likely to occur, which is preferable.

(ceramic green sheet and ceramic capacitor)
Generally, a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. Inside the ceramic body, first internal electrodes and second internal electrodes are alternately provided along the thickness direction. The first internal electrode is exposed on the first end surface of the ceramic body. A first external electrode is provided on the first end surface. The first internal electrode is electrically connected to the first external electrode at the first end surface. 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 surface. The second internal electrode is electrically connected to the second external electrode at the second end surface.

The release film of the present invention is particularly suitable for producing such laminated ceramic capacitors. For example, it is manufactured as follows. First, using the release film of the present invention as a carrier film, a ceramic slurry for forming a ceramic body is applied and dried. A conductive layer for forming the first or second internal electrode is printed on the coated and dried ceramic green sheet. Ceramic green sheets, ceramic green sheets printed with conductive layers for forming first internal electrodes, and ceramic green sheets printed with conductive layers for forming second internal electrodes are appropriately laminated and pressed. Thus, a mother laminate is obtained. The mother laminate is divided into a plurality of pieces to produce raw ceramic bodies. A ceramic body is obtained by firing a raw ceramic body. After that, the multilayer ceramic capacitor can be completed by forming the first and second external electrodes.

EXAMPLES Next, the present invention will be described in detail using examples and comparative examples, but the present invention is of course not limited to the following examples. Moreover, the evaluation methods used in the present invention are as follows.

(NMR measurement)
The ratio of the copolymer components introduced into the acrylic resin (for example, acrylic polyol) was confirmed using nuclear magnetic resonance spectroscopy ( ¹ H-NMR, ¹³ C-NMR: Varian Unity 400, manufactured by Agilent). The measurement was carried out by removing the solvent in the synthesized acrylic resin (acrylic polyol) with a vacuum dryer, and then dissolving the dried product in heavy chloroform. From the obtained NMR spectrum, peaks with chemical shifts δ (ppm) assigned to the sites of each group were identified. The integrated intensity of each peak obtained was determined, and the composition ratio (mol%) of the copolymerization component introduced into the acrylic resin (acrylic polyol) was confirmed from the number of hydrogen atoms at the site of each group and the integrated intensity.

(Confirmation of Tg)
The Tg of each acrylic resin (acrylic polyol) was determined from the composition ratio of the copolymer components determined by the NMR measurement and the above-described Fox equation.

(stretchability)
In order to evaluate the stretchability of the acrylic resin (acrylic polyol) itself, the synthesized acrylic resins (acrylic polyol) (1) to (5) were mixed with 30% by mass of isopropanol and water so that the solid content concentration was 12% by mass. After preparing a solution of a single acrylic resin (acrylic polyol) by putting it in a 70% by mass mixed solvent (25 ° C.), the solution was applied to the surface of the polyester film that had been stretched only in the longitudinal direction with Mayer bar #5. coated with Then, the film sample with the coating layer (thickness 6.5 μm) was placed in a hot air circulation oven set at 60° C. for 30 seconds, then taken out from the oven and pre-dried. Next, the sample was set in a manual stretching device (manufactured by Toyobo Engineering Co., Ltd.), placed in a hot air circulating oven at 100° C., and slowly stretched. The stretching operation was performed until the length became four times the length before stretching, and the stretching device was removed from the hot air circulation oven. Thereafter, the stretched coating film was observed with an optical microscope (magnification: 200 times), and the presence or absence of cracking due to stretching was determined according to the following criteria.
◯: No cracks are observed.
Δ: Some cracks are observed (1 to 4 cracks).
x: 5 or more cracks or cracks are observed on the entire surface.

(Measurement of acid value)
About 0.2 g of a sample was precisely weighed (A (g)) in a side-armed Erlenmeyer flask, 10 ml of benzyl alcohol was added, and the resin was dissolved by heating with a heater at 230° C. for 15 minutes in a nitrogen atmosphere. After allowing to cool to room temperature, 10 ml of benzyl alcohol, 20 ml of chloroform and several drops of phenolphthalein solution were added and titrated with a 0.02 N KOH solution (titration = B (ml), titer of KOH solution = p). . A blank measurement was similarly performed (titration = C (ml)) and calculated according to the following formula.
Acid value (mgKOH/g) = (BC) x 0.02 x 56.11 x p/A

(Quantitative determination of oxazoline group in resin having oxazoline group)
A resin having an oxazoline group was freeze-dried, and 1H-NMR analysis using a nuclear magnetic resonance spectrometer (NMR) ("Gemini-200" manufactured by Varian) revealed the absorption peak intensity derived from the oxazoline group and other monomers. The absorption peak intensity derived from was determined, and the amount of oxazoline group (mmol/g) was calculated from the peak intensity.

(Surface properties of coated film and uncoated base film)
These are values measured under the following conditions using a non-contact surface profile measurement system (VertScan R550H-M100). The area surface average roughness (Sa) adopted the average value of 5 measurements, and the maximum projection height (P) adopted the maximum value of 5 measurements.
(Measurement condition)
・Measurement mode: WAVE mode ・Objective lens: 50x ・0.5×Tube lens ・Measurement area: 187×139 μm (Sa, P measurement)

(Surface free energy)
Water (drop volume 1.8 μL) on the release surface of the release film using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.: fully automatic contact angle meter DM-701) at 25 ° C. and 50% RH. , diiodomethane (appropriate amount of liquid: 0.9 μL), and ethylene glycol (appropriate amount of liquid: 0.9 μL) were prepared and their contact angles were measured. As the contact angle, the contact angle 10 seconds after dropping each liquid onto the release film was adopted. The contact angle data of water, diiodomethane, and ethylene glycol obtained by the above method are calculated from the "Kitazaki-Hata" theory to obtain the dispersion component γsd, the polar component γsp, and the hydrogen bond component γsh of the surface free energy of the release film, The sum of each component was taken as the surface free energy γs. This calculation was performed using the calculation software in this contact angle meter software (FAMAS).

(Pinhole evaluation of ceramic slurry)
A composition consisting of the following materials was stirred and mixed, and dispersed with zirconia beads having a diameter of 0.5 mm using a bead mill for 60 minutes 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 (S-lec BM-S manufactured by Sekisui Chemical Co., Ltd.) 6.5 parts by mass DOP (phthalic acid Dioctyl) 3.3 parts by mass Next, the release surface of the obtained release film sample was coated with an applicator so that the slurry after drying was 1 μm and dried at 90 ° C. for 1 minute to obtain a ceramic green sheet. was molded. Next, the release film was peeled off from the molded release film with the ceramic green sheet to obtain a ceramic green sheet. In the central region of the obtained ceramic green sheet in the film width direction, light was applied from the opposite side of the ceramic slurry-coated surface in a range of 25 cm ² , and the occurrence of pinholes that can be seen through light transmission was observed. judged visually.
○: No pinholes △: Almost no pinholes ×: Many pinholes

(Peelability evaluation of ceramic green sheet)
In the same manner as in the ceramic slurry coating property evaluation, the dried ceramic sheet was coated so as to have a thickness of 0.8 μm and dried at 60° C. for 1 minute to form a ceramic green sheet on a release film. The resulting release film with a ceramic green sheet was neutralized using a static eliminator (manufactured by Keyence Corporation, SJ-F020), and then a peel tester (manufactured by Kyowa Interface Science Co., Ltd., VPA-3) was used to obtain a peel angle of 90. temperature, a peeling temperature of 25° C., and a peeling speed of 10 m/min. As for the peeling direction, a double-sided adhesive tape (manufactured by Nitto Denko Co., Ltd., No. 535A) was attached to the SUS plate attached to the peel tester, and the ceramic green sheet side was adhered to the double-sided tape on the release film. was fixed and peeled off by pulling the release film side. Among the obtained measured values, the average value of the peel force at the peel distance of 20 mm to 70 mm was calculated, and the value was defined as the peel force. The measurement was carried out a total of 5 times, and the average value of the peel strength was used for evaluation. Judgment was made according to the following criteria from the numerical value of the obtained peel strength.
○: 3.5 mN / mm or less △: greater than 3.5 mN / mm, 6.0 mN / mm or less ×: greater than 6.0 mN / mm

(Pinhole evaluation of resin sheet)
Three types of resin solutions for resin sheet molding were prepared using the following method.
(resin sheet (1))
A resin solution (1) was prepared by dissolving 0.5 parts by mass of a cyclic olefin resin (ARTON® G7810/manufactured by JSR, solid content 100% by mass) in 80 parts by mass of toluene and 20 parts by mass of tetrahydrofuran.
The release surface of the release film sample was coated with an applicator so that the dried sheet had a thickness of 0.5 μm, and dried at 100° C. for 1 minute to form a cyclic olefin resin sheet. Next, the release film was peeled off from the molded release film with the cyclic olefin resin sheet to obtain a cyclic olefin resin sheet (1).
(resin sheet (2))
Mix 10 parts by mass of ion exchange resin (20% Nafion (registered trademark) 20Dispersion Solution DE2021 CS type, manufactured by Wako Pure Chemical Industries, Ltd., solid content 20% by mass), 10 parts by mass of water, and 20 parts by mass of isopropyl alcohol, A resin solution (2) was prepared. An ion-exchange resin sheet was formed by coating the release surface of the release film sample using an applicator so that the sheet after drying had a thickness of 0.5 μm and drying at 100° C. for 1 minute. Next, the release film was peeled off from the molded release film with the ion-exchange resin sheet to obtain an ion-exchange resin sheet (2).
(resin sheet (3))
UV curable resin (urethane acrylate, product name: 8UX-015A, manufactured by Taisei Fine Chemical Co., Ltd., solid content 100% by mass) 20 parts by mass, methyl ethyl ketone 40 parts by mass, isopropyl alcohol 39 parts by mass, photoradical initiator (Irgacure (registered trademark) ) 907, manufactured by BASF) was mixed to prepare a resin solution (3). The release surface of the release film sample was coated with an applicator so that the sheet after drying was 1.0 μm, dried at 90° C. for 15 seconds, and then was dried using a high-pressure mercury lamp so that the density was 300 mJ/cm ² . An ultraviolet curing resin sheet was molded by irradiating ultraviolet rays. Next, the release film was peeled off from the molded release film with the UV-curing resin sheet to obtain a UV-curing resin sheet (3).
All three types of resin sheets obtained were evaluated by the following methods.
In the central region of the obtained resin sheet in the film width direction, light was applied from the opposite side of the resin slurry-coated surface in a range of 25 cm ² , and the occurrence of pinholes that can be seen through light transmission was observed and visually observed according to the following criteria. Judged.
○: No pinholes △: Almost no pinholes ×: Many pinholes

(Preparation of polyethylene terephthalate pellets (PET (I)))
As the esterification reactor, a continuous esterification reactor comprising a three-stage complete mixing tank having a stirrer, a partial condenser, a raw material inlet and a product outlet was used. TPA (terephthalic acid) was adjusted to 2 tons/hour, EG (ethylene glycol) was adjusted to 2 mol per 1 mol of TPA, and antimony trioxide was adjusted to give an amount of Sb atoms of 160 ppm relative to the produced PET. It was continuously supplied to the first esterification reactor of the reaction apparatus and reacted at 255° C. for an average residence time of 4 hours under normal pressure. Next, the reaction product in the first esterification reaction can is continuously taken out of the system and supplied to the second esterification reaction can, and distilled off from the first esterification reaction can into the second esterification reaction can. 8 mass % of EG is supplied to the produced PET, and further, an EG solution containing magnesium acetate tetrahydrate in an amount such that the Mg atom is 65 ppm relative to the produced PET, and an EG solution containing 40 ppm of P atom relative to the produced PET. An EG solution containing TMPA (trimethyl phosphate) in an amount corresponding to the above was added and reacted at 260° C. under normal pressure for an average residence time of 1 hour. Next, the reaction product in the second esterification reactor was continuously taken out of the system and supplied to the third esterification reactor, and was subjected to 39 MPa (400 kg/cm ² ) using a high-pressure disperser (manufactured by Nippon Seiki Co., Ltd.). 0.2% by mass of porous colloidal silica having an average particle size of 0.9 μm, which has been subjected to dispersion treatment for an average number of 5 passes at a pressure of , and 1% by mass of ammonium salt of polyacrylic acid per calcium carbonate. While adding 0.4% by mass of synthetic calcium carbonate with a diameter of 0.6 μm as a 10% EG slurry, the mixture was reacted at normal pressure at 260° C. for an average residence time of 0.5 hours. The esterification reaction product produced in the third esterification reaction vessel was continuously supplied to a three-stage continuous polycondensation reactor for polycondensation to sinter stainless steel fibers having a 95% cut diameter of 20 μm. After filtration with a filter, ultrafiltration was performed, the product was extruded into water, and after cooling, it was cut into chips to obtain PET chips having an intrinsic viscosity of 0.60 dl/g (hereinafter abbreviated as PET (I)). . The lubricant content in the PET chip was 0.6% by mass.

(Preparation of polyethylene terephthalate pellets (PET (II)))
On the other hand, in the production of the PET(I) chip, a PET chip containing no particles of calcium carbonate, silica, etc. and having an intrinsic viscosity of 0.62 dl/g was obtained (hereinafter abbreviated as PET(II)).

(Preparation of polyethylene terephthalate pellets (PET (III)))
On the other hand, in the production of the above PET (I) chip, the particles of calcium carbonate, silica, etc. were changed to porous colloidal silica having an average particle size of 0.2 μm and synthetic calcium carbonate having an average particle size of 0.1 μm. to obtain a PET chip having an intrinsic viscosity of 0.62 dl/g (hereinafter abbreviated as PET (III)).

(Production of acrylic resin (acrylic polyol) A-1)
103 parts by mass of methyl methacrylate (MMA), 173 parts by mass of stearyl methacrylate (SMA), and 100 parts by mass of hydroxyethyl methacrylate (HEMA) were added to a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen blowing tube. , 22 parts by mass of methacrylic acid (MAA) and 929 parts by mass of isopropyl alcohol (IPA) were charged, and the temperature in the flask was raised to 80° C. while stirring. Stirring was performed for 3 hours while maintaining the inside of the flask at 80° C., and then 0.5 parts by mass of 2,2-azobis-2-methyl-N-2-hydroxyethylpropionamide was added to the flask. After purging with nitrogen while raising the temperature in the flask to 120° C., the mixture was stirred at 120° C. for 2 hours.
Subsequently, a pressure reduction operation of 1.5 kPa was performed at 120° C. to remove unreacted raw materials and solvent to obtain an acrylic resin (acrylic polyol). The inside of the flask was returned to atmospheric pressure and cooled to room temperature, and 1592 parts by mass of an IPA aqueous solution (water content: 50% by mass) was added and mixed. After that, using a dropping funnel while stirring, ammonia is added, and the acrylic resin (acrylic polyol) is neutralized until the pH of the solution is in the range of 5.5 to 7.5, and the solid content concentration is 20 mass. % acrylic resin (acrylic polyol) (A-1) was obtained. Table 1 also shows the composition ratio, Tg, stretching suitability, and acid value of the acrylic resin (acrylic polyol) (A-1) measured by NMR.

(Production of acrylic resin (acrylic polyol) (A-2) to (A-6))
As shown in Table 1, the solid content concentration was 20 in the same manner as in the production of acrylic resin (acrylic polyol) 1 except that the amounts of MMA, SMA, HEMA, MAA, IPA during preparation, and IPA aqueous solution during dilution were changed. % by mass of acrylic polyols ((A-2) to (A-6) were obtained.
Table 1 also shows the composition ratio, Tg, stretching suitability, and acid value of the acrylic resins (acrylic polyols) (A-2) to (A-6) measured by NMR. The composition ratios are expressed as n1 (unit) for MMA, n2 (unit) for SMA, n3 (unit) for HEMA, and n4 (unit) for MAA.

(Production of oxazoline-based cross-linking agent C-1)
A flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube and a thermometer was charged with 460.6 parts of isopropyl alcohol and heated to 80° C. while nitrogen gas was slowly passed through. A previously prepared monomer mixture consisting of 126 parts of methyl methacrylate, 210 parts of 2-isopropenyl-2-oxazoline and 84 parts of methoxypolyethylene glycol acrylate, and 2,2′-azobis as a polymerization initiator were added thereto. (2-Methylbutyronitrile) ("ABN-E" manufactured by Nippon Hydrazine Kogyo Co., Ltd.) 21 parts of an initiator solution and 189 parts of isopropyl alcohol are dropped from a dropping funnel over 2 hours to react, and dropwise. After completion, the reaction was continued for 5 hours. Nitrogen gas was continuously flowed during the reaction to keep the temperature in the flask at 80±1°C. Thereafter, the reaction solution was cooled to obtain an oxazoline group-containing resin (C-1) having a solid concentration of 10%. The resulting resin (C-1) having oxazoline groups had an oxazoline group content of 7.7 mmol/g and a number average molecular weight of 40,000 measured by GPC (gel permeation chromatography).

(Production of oxazoline-based cross-linking agent C-2)
Resin (C-2) having a solid content of 25% and having a different composition (oxazoline group weight and molecular weight) was obtained in the same manner as in the synthesis of resin (C-1) having oxazoline groups. The resulting oxazoline group-containing resin (C-2) had an oxazoline group weight of 4.3 mmol/g and a number average molecular weight of 20,000 measured by GPC.

(Production of carbodiimide cross-linking agent D-1)
A flask equipped with a stirrer, a thermometer and a reflux condenser was charged with 168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (M400, average molecular weight: 400), stirred at 120°C for 1 hour, and then stirred for 4 hours. 26 parts by mass of 4′-dicyclohexylmethane diisocyanate and 3.8 parts by mass of 3-methyl-1-phenyl-2-phosphorene-1-oxide as a carbodiimidation catalyst (2% by mass relative to the total isocyanate) were added, and the mixture was stirred under a nitrogen stream at 185°C. °C for an additional 5 hours. The infrared spectrum of the reaction solution was measured, and it was confirmed that absorption at wavelengths of 2200 to 2300 cm ^-1 had disappeared. After allowing to cool to 60° C., 567 parts by mass of ion-exchanged water was added to obtain a carbodiimide water-soluble resin (D-1) having a solid content of 40% by mass.

(Production of isocyanate cross-linking agent E-1)
100 parts by mass of a polyisocyanate compound having an isocyanurate structure (manufactured by Asahi Kasei Chemicals, Duranate TPA) made from hexamethylene diisocyanate in a flask equipped with a stirrer, a thermometer and a reflux condenser, 55 parts by mass of propylene glycol monomethyl ether acetate, 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight: 750) was charged, and the mixture was held at 70°C for 4 hours in a nitrogen atmosphere. After that, the temperature of the reaction solution was lowered to 50° C., and 47 parts by mass of methyl ethyl ketoxime was added dropwise. By measuring the infrared spectrum of the reaction solution, it was confirmed that the absorption of the isocyanate group had disappeared, and an aqueous blocked polyisocyanate dispersion (E-1) having a solid content of 75% by mass was obtained.

(Silica particles F-1)
Colloidal silica (manufactured by Nissan Chemical Industries, trade name Snowtex XL, average particle size 40 nm, solid content concentration 40% by mass)

(Example 1)
(Adjustment of release coating liquid 1)
A release coating liquid 1 having the following composition was prepared.
(Release coating liquid 1)
Water 48.01 parts by mass Isopropyl alcohol 25.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass)
14.00 parts by mass Oxazoline-based cross-linking agent C-1 (solid content concentration 10% by mass)
12.00 parts by mass Additive G-1
0.04 parts by mass (polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.)

(Manufacturing of polyester film)
After the PET chips are dried, they are melted at 285° C. and melted at 290° C. by a separate melt extruder extruder to form a filter made of sintered stainless steel fibers with a 95% cut diameter of 15 μm and a filter with a 95% cut diameter of 15 μm. Two-stage filtration of sintered stainless steel particles is performed, and they are combined in the feed block to form PET (I) as surface layer B (anti-separate surface side layer) and PET (II) as surface layer A. (Releasing surface side layer), extruded (casting) into a sheet at a speed of 45 m / min, electrostatically adhered on a casting drum at 30 ° C. by an electrostatic adhesion method, cooled, and unstretched A polyethylene terephthalate sheet was obtained. The layer ratio was adjusted so that PET (I)/(II)=60% by mass/40% by mass by calculating the discharge amount of each extruder.
Then, the unstretched sheet was heated with an infrared heater and then stretched 3.5 times in the machine direction at a roll temperature of 80° C. due to the speed difference between the rolls.

Then, the release coating solution was applied to the surface layer A of the PET film with a bar coater, and then dried at 80° C. for 15 seconds. The coating amount after the final stretching and drying was adjusted to 0.07 μm. Subsequently, the film was stretched 4.0 times in the width direction at 150°C with a tenter, heated at 230°C for 4 seconds while fixing the length of the film in the width direction, and further stretched at 170°C to 3% in the width direction. to obtain an in-line release coated polyester film having a thickness of 31 μm. The surface layer B (anti-release surface side) of the obtained film had Sa of 28 nm and P of 754 nm. Here, let Z be the PET substrate that does not include a release layer. The resulting PET base material had an intrinsic viscosity of 0.59 dl/g. The surface layer A of the PET base material without a release layer had an Sa value of 1 nm and a P value of 16 nm.

(Example 2)
A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 2.
(Release coating liquid 2)
Water 54.03 parts by mass Isopropyl alcohol 23.93 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass)
18.00 parts by mass Oxazoline-based cross-linking agent C-1 (solid content concentration 10% by mass)
4.00 parts by mass Additive G-1
0.04 parts by mass (polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.)

(Example 3)
A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 3.
(Release coating liquid 3)
water
51.01 parts by mass Isopropyl alcohol
24.95 parts by mass acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass)
16.00 parts by mass Oxazoline-based cross-linking agent C-1 (solid content concentration 10% by mass)
8.00 parts by mass Additive G-1
0.04 parts by mass (polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.)

(Example 4)
A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 4.
(Release coating liquid 4)
Water 41.99 parts by mass Isopropyl alcohol 27.97 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass)
10.00 parts by mass Oxazoline-based cross-linking agent C-1 (solid content concentration 10% by mass)
20.00 parts by mass Additive G-1
0.04 parts by mass (polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.)

(Example 5)
Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass) in release coating liquid 1 used in Example 1 was replaced with acrylic resin (acrylic polyol resin) A-2 (solid content concentration 20% by mass) ) was changed to obtain a release polyester film in the same manner as in Example 1.

(Example 6)
Example 1 except that the release coating liquid 6 in which the cross-linking agent in the release coating liquid 1 used in Example 1 was changed to oxazoline-based cross-linking agent C-2 (solid content concentration 25% by mass) was used. A release polyester film was obtained in the same manner as above.
(Release coating liquid 6)
Water 55.23 parts by mass Isopropyl alcohol 25.93 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass)
14.00 parts by mass Oxazoline-based cross-linking agent C-2 (solid content concentration 25% by mass)
4.80 parts by mass Additive G-1
0.04 parts by mass (polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.)

(Example 7)
Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass) in release coating liquid 1 used in Example 1 was replaced with acrylic resin (acrylic polyol resin) A-2 (solid content concentration 20% by mass) ) in the same manner as in Example 1 except that the release coating solution 7 was changed to oxazoline-based cross-linking agent C-2 (solid content concentration 25% by mass) was used. Release polyester film got
(Release coating liquid 7)
Water 55.23 parts by mass Isopropyl alcohol 25.93 parts by mass Acrylic resin (acrylic polyol resin) A-2 (solid content concentration 20% by mass)
14.00 parts by mass Oxazoline-based cross-linking agent C-2 (solid content concentration 25% by mass)
4.80 parts by mass Additive G-1
0.04 parts by mass (polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.)

(Example 8)
Example 1 except that the release coating solution 8 was changed from the release coating solution 1 used in Example 1 to a carbodiimide-based cross-linking agent D-1 (solid concentration: 40% by mass). A release polyester film was obtained in the same manner as above.
(Release coating liquid 8)
Water 56.63 parts by mass Isopropyl alcohol 26.97 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20 mass%) 12.00 parts by mass Carbodiimide-based cross-linking agent D-1 (solid content concentration 40 mass% )
4.00 parts by mass Additive G-1
0.04 parts by mass (polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.)

(Example 9)
A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 9.
(Release coating liquid 9)
Water 47.51 parts by mass Isopropyl alcohol 25.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass)
14.00 parts by mass Oxazoline-based cross-linking agent C-1 (solid content concentration 10% by mass)
12.00 parts by mass silica particles F-1
0.50 parts by mass (average particle size 40 nm, solid concentration 40% by mass)
Additive G-1
0.04 parts by mass (polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.)

(Example 10)
A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 10.
(Release coating liquid 10)
Water 47.01 parts by mass Isopropyl alcohol 25.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass)
14.00 parts by mass Oxazoline-based cross-linking agent C-1 (solid content concentration 10% by mass)
12.00 parts by mass silica particles F-1
1.00 parts by mass (average particle size 40 nm, solid concentration 40% by mass)
Additive G-1
0.04 parts by mass (polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.)

(Example 11)
Except for using a release coating liquid 11 in which the additive in the release coating liquid 1 used in Example 1 was changed to polyester-modified polydimethylsiloxane G-2 (solid content concentration 25% by mass) A release polyester film was obtained in the same manner as in 1.
(Release coating liquid 11)
Water 47.90 parts by mass Isopropyl alcohol 25.93 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass)
14.00 parts by mass Oxazoline-based cross-linking agent C-1 (solid content concentration 10% by mass)
12.00 parts by mass Additive G-2
0.17 parts by mass (polyester-modified polydimethylsiloxane, BYK-315N, solid concentration 25% by mass, manufactured by BYK-Chemie Japan)

(Example 12)
Except for using release coating liquid 12 in which the additive in release coating liquid 1 used in Example 1 was changed to long-chain alkyl additive G-1 (solid content concentration 15% by mass) A release polyester film was obtained in the same manner as in Example 1.
(Release coating liquid 12)
Water 47.80 parts by mass Isopropyl alcohol 25.93 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20 mass%) 14.00 parts by mass Oxazoline-based cross-linking agent C-1 (solid content concentration 10 mass% )
12.00 parts by mass Additive H-1
0.27 parts by mass (Peeloyl (registered trademark) 406, solid content concentration 15% by mass, manufactured by Lion Specialty Chemical Co., Ltd.)

(Example 13)
A release polyester film was obtained in the same manner as in Example 1, except that Release Coating Solution 13 below containing no additives in Release Coating Solution 1 used in Example 1 was used.
(Release coating liquid 13)
Water 48.05 parts by mass Isopropyl alcohol 25.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass)
14.00 parts by mass Oxazoline-based cross-linking agent C-1 (solid content concentration 10% by mass)
12.00 parts by mass

(Example 14)
A release polyester film was obtained in the same manner as in Example 1, except that the thickness of the release layer was changed to 0.035 μm.

(Example 15)
A release polyester film was obtained in the same manner as in Example 1, except that the thickness of the release layer was changed to 0.100 μm.

(Example 16)
A release polyester film was obtained in the same manner as in Example 1, except that the thickness of the release layer was changed to 0.140 μm.

(Example 17)
Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass) in release coating liquid 1 used in Example 1 was replaced with acrylic resin (acrylic polyol resin) A-4 (solid content concentration 20% by mass) ) was changed to obtain a release polyester film in the same manner as in Example 1.

(Example 18)
Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass) in release coating liquid 1 used in Example 1 was replaced with acrylic resin (acrylic polyol resin) A-5 (solid content concentration 20% by mass). ) was changed to obtain a release polyester film in the same manner as in Example 1.

(Example 19)
A release polyester film was obtained in the same manner as in Example 1, except that PET (II) in the surface layer A of the PET substrate was changed to PET (III).
Here, Y denotes a PET base material that does not include a release layer. The resulting PET base material had an intrinsic viscosity of 0.59 dl/g. The surface layer A of the PET base Y before the release layer was laminated had a Sa of 10 nm and a P of 130 nm.

(Example 20)
A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 16.
(Release coating liquid 16)
Water 47.85 parts by mass Isopropyl alcohol 25.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass)
14.00 parts by mass oxazoline cross-linking agent C-1 (solid content concentration 10% by mass)
12.00 parts by mass Additive G-1
0.20 parts by mass (polyether-modified polydimethylsiloxane, 67Additive, solid concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.)

(Example 21)
Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass) in release coating liquid 1 used in Example 1 was replaced with acrylic resin (acrylic polyol resin) A-6 (solid content concentration 20% by mass). ) to obtain a release polyester film in the same manner as in Example 1, except that (release coating solution 17) was used.

(Comparative example 1)
A release polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 18.
(Release coating liquid 18)
Water 76.76 parts by mass Isopropyl alcohol 19.19 parts by mass Curable silicone aqueous emulsion B-1
4.01 parts by mass (manufactured by Shin-Etsu Silicone Co., Ltd., solid content concentration 40%, KM3951)
Platinum-based catalyst B-2
0.04 parts by mass (CAT-PM-10A manufactured by Shin-Etsu Silicone Co., Ltd.)

(Comparative example 2)
Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass) in release coating liquid 1 used in Example 1 was replaced with acrylic resin (acrylic polyol resin) A-3 (solid content concentration 20% by mass) ) to obtain a release polyester film in the same manner as in Example 1, except that the release coating solution 19 was used.

(Comparative Example 3)
A polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 20.
(Release coating liquid 20)
Water 58.30 parts by mass Isopropyl alcohol 25.95 parts by mass Acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass)
14.00 parts by mass isocyanate cross-linking agent E-1 (solid content concentration 75% by mass)
1.72 parts by mass Surfactant G-1
0.04 parts by mass (polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.)

(Comparative Example 4)
A polyester film was obtained in the same manner as in Example 1, except that the release coating liquid 1 was changed to the following release coating liquid 21.
(Release coating liquid 21)
Water 57.04 parts by mass Isopropyl alcohol
22.93 parts by mass acrylic resin (acrylic polyol resin) A-1 (solid content concentration 20% by mass)
20.00 parts by mass Surfactant G-1
0.04 parts by mass (polyether-modified polydimethylsiloxane, 67Additive, solid content concentration 100% by mass, manufactured by Dow Corning Toray Co., Ltd.)

Table 2 shows the evaluation results of each example and comparative example.

In Table 2 above, the composition of each resin, cross-linking agent, particles, and additives in the release coating liquid is described as parts by mass of the solid content. The sum of the mass parts of the solid content of the agent, particles, and additives is the mass part of the total solid content of the release layer. By dividing by the mass part of the total solid content, the mass percentage of the resin, cross-linking agent, particles and additives in the total solid content in the release layer can be obtained.

In Examples 1 to 21, it is possible to reduce the manufacturing cost by in-line coating, and even when the molded sheet is further thinned, the wettability of the sheet slurry and the resin solution, and the moderate wettability showed excellent sheet peel strength. On the other hand, in Comparative Example 1, when the sheet was further thinned, the wettability of the sheet slurry and the resin solution was poor, and pinholes were generated. In Comparative Example 2, since the acrylic resin did not contain a long-chain alkyl component, the surface free energy increased and the sheet peeling force increased. Due to the heavy sheet peeling force, pinholes were generated in the sheet during peeling. In Comparative Examples 3 and 4, since no oxazoline-based cross-linking agent or carbodiimide-based cross-linking agent was used, the curing of the coating film was insufficient and the sheet peeling force increased. Due to the heavy sheet peeling force, pinholes were generated in the sheet during peeling.

According to the present invention, it is possible to manufacture the sheet at a low production cost, and even when the sheet is further thinned, it has good wettability of the sheet slurry and the resin solution, and an appropriate sheet peeling force. It is possible to manufacture a release film that can be used.

Claims (11)

A release film comprising a polyester film and a release layer,
It has a release layer on at least one side of the polyester film directly or via another layer, and the release layer is at least selected from an acrylic resin having a long-chain alkyl group, and an oxazoline-based cross-linking agent or a carbodiimide-based cross-linking agent. A cured composition containing a cross-linking agent,
The acrylic resin having a long-chain alkyl group has an acid value of 40 mgKOH/g or more and 400 mgKOH/g or less.
release film. The acrylic resin contains a long-chain alkyl group-containing acrylate monomer,
The release film according to claim 1, wherein the copolymerization ratio of the long-chain alkyl group-containing acrylate monomer in the acrylic resin is 5 mol% or more and 60 mol% or less. 3. The release film according to claim 1, wherein the cross-linking agent is an oxazoline-based cross-linking agent, and the oxazoline-based cross-linking agent contains 3.0 to 9.0 mmol/g of oxazoline groups. The release film according to any one of claims 1 to 3, wherein the acrylic resin contains stearyl (meth)acrylate . The release film according to any one of claims 1 to 4, wherein the release layer has a thickness of 0.001 µm or more and 2 µm or less. The release film according to any one of claims 1 to 5, which is a release film for producing a ceramic green sheet. A method for producing a release film including a polyester film and a release layer,
The release film has a release layer on at least one side of the polyester film directly or via another layer,
The release layer is a release film obtained by curing a composition containing an acrylic resin having a long-chain alkyl group and at least one cross-linking agent selected from an oxazoline-based cross-linking agent or a carbodiimide-based cross-linking agent. After coating the mold coating liquid on an unstretched film or a uniaxially stretched film, stretching in at least one direction in which it is not stretched, heat-treating ,
The acrylic resin having a long-chain alkyl group has an acid value of 40 mgKOH/g or more and 400 mgKOH/g or less.
A method for producing a release film. 8. The method for manufacturing a release film according to claim 7, wherein the method for manufacturing a release film is a method for manufacturing a release film for manufacturing a ceramic green sheet. A method for producing a ceramic green sheet, wherein a ceramic green sheet is molded using the release film for producing a ceramic green sheet according to claim 6 or the method for producing a release film for producing a ceramic green sheet according to claim 8. 10. The method for manufacturing a ceramic green sheet according to claim 9, wherein the thickness of the ceramic green sheet to be manufactured is 0.2 [mu]m or more and 2.0 [mu]m or less. A method for manufacturing a ceramic capacitor employing the method for manufacturing a ceramic green sheet according to claim 9 or 10.