JP2023147243A - release film - Google Patents

Abstract

To provide a release film that readily balances the peelability and wettability of a release layer and ensures uniform application of the release layer and excellent recyclability.SOLUTION: A release film according to the present invention has a base material film and a release layer obtained by reacting and solidifying an aqueous coating composition. The aqueous coating composition comprises an alkenyl group-containing silicone that has two or more intramolecular alkenyl groups, may have a Q unit represented by SiO4/2, and has a number-average molecular weight of 1000 or more and less than 10000, an Si-H group-containing silicone that has two or more intramolecular Si-H groups and has a number-average molecular weight of 1000 or more and 5000 or less, and a polyvinyl alcohol resin.SELECTED DRAWING: None

Description

The present invention relates to a release film having a base film and a release layer, and more particularly to a release film useful as a film for various processes.

Conventionally, release films based on polyester films have high heat resistance and mechanical properties, and are used as process films for forming adhesive sheets, cover films, resin sheets such as ceramic slurries and polymer electrolyte membranes. It is used. Further, as a release layer of a release film, many release layers formed from coating compositions containing silicone have been proposed because they have good heat resistance and peelability (for example, Patent Documents 1 to 7).

Patent Documents 1 and 2 disclose a release film in which a release layer is formed from a coating composition containing a polysiloxane having an unsaturated group, a polysiloxane having an Si-H group, a platinum group metal catalyst, etc., and an organic solvent. Proposed.

However, this technique has a problem in that it is not suitable for a method of coating during stretching of a base film (hereinafter referred to as "in-line coating") because it is an organic solvent-based coating composition. In other words, since an organic solvent is used alone as a solvent for the coating composition, large-scale explosion-proof equipment is required for film forming and stretching equipment, which increases manufacturing costs due to initial installation costs and complicated operation. There was a problem.

On the other hand, as a technique suitable for in-line coating, Patent Document 3 proposes a release film in which a release layer is formed using an aqueous coating composition containing an alkenyl group-containing silicone and a Si-H group-containing silicone. . Further, as an example, a release film is disclosed in which a release layer is formed using an alkenyl group-containing silicone having a number average molecular weight of 25,000 and a Si--H group-containing silicone having a number average molecular weight of 4,500.

In addition, Patent Document 4 describes an aqueous silicone containing an alkenyl group-containing silicone having a Q unit represented by SiO _4/2 and a Si--H group-containing silicone in order to achieve both easy releasability and good wettability. A release film in which a release layer is formed using a coating composition has been proposed. Further, as an example, a release film is disclosed in which a release layer is formed using an alkenyl group-containing silicone having a Q unit and a number average molecular weight of 25,000 and a Si-H group-containing silicone having a number average molecular weight of 4,500. There is.

Conventionally, when forming a release layer, relatively high molecular weight unsaturated group-containing polysiloxane was generally used so that the helical structure of polydimethylsiloxane could be easily formed on the coating surface. was. This point was also the same when using an organic solvent-based coating composition (eg, Patent Documents 1 and 2).

On the other hand, Patent Document 5 proposes a release film using polyvinyl alcohol as a primer layer of a silicone resin release layer. The primer layer is coated in a separate coating process from the release layer, and two coats are required to prepare the release film. Normally, after the primer layer is applied, the film is wound up into a film roll, and then the film roll is unwound at another processing location and a release layer is applied, which increases the number of control items and complicates the manufacturing process. , not efficient.

Additionally, Patent Document 6 proposes a technique in which a polyvinyl alcohol-based resin is added to an aqueous coating composition containing an addition-reactive silicone to form a release layer in order to adjust the releasability of the release layer. has been done. However, as in other patent documents, a relatively high molecular weight silicone was used as the addition reaction type silicone.

Japanese Patent Application Publication No. 2003-292894 Japanese Patent Application Publication No. 2003-292895 Patent No. 6077327 JP 2021-11081 Publication Japanese Patent Application Publication No. 2000-289168 Patent No. 5319329 International Publication WO2017/200056 Publication

However, in recent years, members such as ceramic green sheets formed on the release layer of a release film have tended to become thinner, and the surface of the release layer is required to have releasability as well as wettability to ceramic slurry, etc. In some cases, it becomes difficult to achieve both. In other words, when the chemical composition of the release layer is changed in order to improve wettability, there is a problem in that the releasability decreases.

In addition, Patent Document 7 discloses that mold release is performed using an organic solvent-based coating composition containing a polydimethylsiloxane having a vinyl group with a molecular weight of 500 to 30,000 and a polydimethylsiloxane having a Si-H group with a molecular weight of 150 to 10,000. Although a release film having layers has been proposed, it has not been suggested that both releasability and wettability can be achieved at the same time, and since it is based on an organic solvent, there is a problem that it is not suitable for in-line coating.

According to the studies of the present inventors, when a silicone-based release film is recycled and used as a raw material for a base film, depending on the composition of the release layer, foreign matter larger than a certain size may be generated. It was found that it was not suitable for recycling.

In addition, according to another study by the present inventors, when forming a release layer using a silicone-based aqueous coating composition, in order to respond to thinning of ceramic green sheets, etc., it is necessary to It has been found that the influence of the generated aggregates on the surface shape tends to be a problem.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a release film that can easily achieve both releasability and wettability of the release layer, and has good coating uniformity and recyclability of the release layer.

As a result of intensive studies to solve this problem, the present inventors have developed the above-mentioned method by adding polyvinyl alcohol-based resin to an aqueous coating composition that conventionally uses low-molecular-weight silicone to form a release layer. The inventors have discovered that the problem can be solved and have completed the present invention. That is, the present invention includes the following contents.

[1] A release film comprising a base film and a release layer formed by reacting and solidifying an aqueous coating composition,
The aqueous coating composition includes an alkenyl group-containing silicone having a number average molecular weight of 1,000 or more and less than 10,000, which has two or more alkenyl groups in the molecule and may have a Q unit represented by SiO _4/2 ; A release film comprising an Si-H group-containing silicone having a number average molecular weight of 1,000 to 5,000 and having two or more Si-H groups therein, and a polyvinyl alcohol resin.

[2] The polyvinyl alcohol resin has a viscosity of 5 mPa·s or more and 50 mPa·s or less when an aqueous solution with a concentration of 4% by mass is measured at a temperature of 20°C, and a saponification degree of 85 mol% or more and 99 mol% or less. The release film according to [1].

[3] The release film according to [1] or [2], wherein the alkenyl group-containing silicone has a Q unit represented by SiO _4/2 .

[4] The release film according to any one of [1] to [3], wherein the alkenyl group-containing silicone is represented by the following general formula (I).

(In general formula (I), R ¹ is an alkenyl group having 2 to 8 carbon atoms, or a monovalent hydrocarbon having 1 to 16 carbon atoms containing an alkyl group or an aryl group, which may be the same or different. One or more of R ¹ bonded to the silicon atom represented by [SiO] _b1 is an alkenyl group having 2 to 8 carbon atoms, and R ² is an alkyl group or It is a monovalent hydrocarbon group containing an aryl group and having 1 to 16 carbon atoms, and Y ¹ may be the same or different and is represented by the general formula (Ia).

(In general formula (Ia), R ¹ is the same as R ¹ in general formula (I), and may be the same or different.)
In the entire general formula (I) including ^Y1 , when all silicon atoms including terminals are 100 mol%, a1 is 50 mol% or more and 98 mol% or less, b1 is 0 mol% or more and 10 mol% or less, c1 is 0 mol% or more and 30 mol% or less, and d1 is 0 mol% or more and 50 mol% or less. In the entire general formula (I) including Y ¹ , two or more of R ¹ are alkenyl groups having 2 or more and 8 or less carbon atoms. )

[5] The release film according to any one of [1] to [4], wherein the Si--H group-containing silicone is represented by the following general formula (II).

(In general formula (II), R ³ is a monovalent hydrocarbon group having 1 to 16 carbon atoms and containing an alkyl group or an aryl group, which may be the same or different, and a2+b2 is 100 mol%. (In this case, a2 is 30 mol% or more and 90 mol% or less, and b2 is 10 mol% or more and 70 mol% or less.)

[6] Any one of [1] to [5], wherein the aqueous coating composition contains 1 part by mass or more and 50 parts by mass or less of the Si-H group-containing silicone based on 100 parts by mass of the alkenyl group-containing silicone. The release film according to item 1.

[7] The release layer is formed by applying the aqueous coating composition to the base film before crystal orientation is completed, stretching in at least one direction, and then heat-treating to complete crystal orientation. The release film according to any one of [1] to [6], which is

[8] The release film according to any one of [1] to [7], wherein the base film is a polyester film.

[9] The release film according to any one of [1] to [8], wherein the release film is a release film for a multilayer ceramic capacitor or a release film for a resin sheet.

According to the present invention, it is possible to provide a release film that is easy to achieve both releasability and wettability of the release layer, and has good coating uniformity and recyclability of the release layer.

Although the details of the reason for this effect are not clear, silicone crosslinked products in which relatively low-molecular-weight silicones react with each other tend to form dense three-dimensional structures, so they remain hard even when in contact with organic solvents. It is thought that the adhesive strength can be easily maintained and the adhesion force when peeling off the laminate coated and cast on the surface of the release layer can be reduced. In addition, silicone crosslinked materials with a dense three-dimensional structure are difficult to form a helical structure such as polydimethylsiloxane, and this affects the surface free energy of the release layer surface, so it is necessary to provide adequate wetting to the laminate. It is thought that this makes it easier to express sex. In particular, it is thought that when the aqueous coating composition contains a polyvinyl alcohol resin, the wettability can be improved while maintaining the releasability of the release layer.

Furthermore, by lowering the molecular weight of the silicone contained in the aqueous coating composition, it is believed that the stability and uniformity of the coating film will increase, and that aggregates will be less likely to form in the release layer, improving coating uniformity. It will be done. Furthermore, even when remelted during recycling, since the coated film is highly uniform, the coated films are likely to be easily dispersed within the remelted base film resin, making it difficult for foreign matter to be generated.

In particular, when the alkenyl group-containing silicone has a Q unit, it is thought that it becomes easier to form a dense three-dimensional structure and it becomes easier to achieve both releasability and wettability of the release layer.

The present invention will be explained in detail below.

[Release film]
The release film of the present invention includes a base film (hereinafter sometimes referred to as "substrate") and a release layer formed by reacting and solidifying an aqueous coating composition. As will be detailed later, since the aqueous coating composition contains two types of silicones that can react with each other, it is difficult to identify the structure of the resulting polymer and to identify claims based thereon, making it impractical. There are circumstances. Therefore, the release film of the present invention was specified in the form of a product-by-process claim.

[Release layer]
The release layer is obtained by reacting and solidifying an aqueous coating composition. The aqueous coating composition includes an alkenyl group-containing silicone having a number average molecular weight of 1,000 or more and less than 10,000, which has two or more alkenyl groups in the molecule and may have a Q unit represented by SiO _4/2 . The silicone contains an Si--H group-containing silicone having a number average molecular weight of 1,000 to 5,000 and has two or more Si--H groups, and a polyvinyl alcohol-based resin. Each component will be explained in detail below.

(Alkenyl group-containing silicone)
The alkenyl group-containing silicone includes an alkenyl group-containing silicone having two or more alkenyl groups in the molecule and a Q unit represented by SiO _4/2 , and/or an alkenyl group-containing silicone having two or more alkenyl groups in the molecule. Alkenyl group-containing silicones having a group and no Q unit represented by SiO _4/2 can be used.

The alkenyl group-containing silicone having a Q unit may be any compound having two or more alkenyl groups and a Q unit represented by SiO _4/2 in the molecule and having a siloxane bond in the main chain. However, polyorganosiloxanes having alkenyl groups at the terminals and/or side chains are preferred. Further, a copolymer containing a dialkylsiloxane unit or an alkylphenylsiloxane unit is preferable because the amount of alkenyl groups in one molecule can be easily adjusted while exhibiting releasability. The terminal silicon atom preferably has an alkenyl group, but may have a trialkylsilane structure such as trimethylsilane.

The alkenyl group-containing silicone that does not have a Q unit may be any compound as long as it has two or more alkenyl groups in the molecule and a siloxane bond in the main chain, but Polyorganosiloxanes having alkenyl groups are preferred. Further, a copolymer containing a dialkylsiloxane unit or an alkylphenylsiloxane unit is preferable because the amount of alkenyl groups in one molecule can be easily adjusted while exhibiting releasability. The terminal silicon atom preferably has an alkenyl group, but may have a trialkylsilane structure such as trimethylsilane.

In any alkenyl group-containing silicone, the alkenyl group may be introduced at one end, both ends, or a side chain, but it is preferably introduced at least at either end, and at both ends of the main chain. More preferably, it is introduced at the end. The alkenyl group has two or more in the molecule, preferably 2 or more and 20 or less, and more preferably 2 or more and 10 or less.

In the case of alkenyl group-containing silicone having Q units, the content of Q units expressed as SiO _4/2 is 0.5 mol% when all silicon atoms including terminals in the molecule are 100 mol%. The content is preferably 30 mol% or more, more preferably 0.5 mol% or more and 20 mol% or less. When the content of Q units is 0.5 mol % or more, it becomes easy to form a dense mold release layer with high cohesive force, and it becomes easy to achieve both releasability and wettability of the mold release layer. When the content of Q units is 30 mol % or less, it is easy to prevent the coating film from becoming too dense and brittle.

Examples of alkenyl group-containing silicones include organopolysiloxanes represented by the following general formula (I).

(In general formula (I), R ¹ is an alkenyl group having 2 to 8 carbon atoms, or a monovalent hydrocarbon having 1 to 16 carbon atoms containing an alkyl group or an aryl group, which may be the same or different. One or more of R ¹ bonded to the silicon atom represented by [SiO] _b1 is an alkenyl group having 2 to 8 carbon atoms, and R ² is an alkyl group or It is a monovalent hydrocarbon group containing an aryl group and having 1 to 16 carbon atoms, and Y ¹ may be the same or different and is represented by the general formula (Ia).

(In general formula (Ia), R ¹ is the same as R ¹ in general formula (I), and may be the same or different.)
In the entire general formula (I) including ^Y1 , when all silicon atoms including terminals are 100 mol%, a1 is 50 mol% or more and 98 mol% or less, b1 is 0 mol% or more and 10 mol% or less, c1 is 0 mol% or more and 30 mol% or less, and d1 is 0 mol% or more and 50 mol% or less. In the entire general formula (I) including Y ¹ , two or more of R ¹ are alkenyl groups having 2 or more and 8 or less carbon atoms. )
In addition, in the general formula (I), when c1 is 0 mol%, that is, in the case of an alkenyl group-containing silicone having no Q unit, the alkenyl group-containing silicone is, for example, a silicone represented by the following general formula (I'). Examples include organopolysiloxanes.

[SiO] R ² bonded to the silicon atom represented by _a1 may be a monovalent hydrocarbon group including an alkyl group or an aryl group, but may be a monovalent hydrocarbon group having 1 to 16 carbon atoms selected from an alkyl group or an aryl group. It is preferably a monovalent hydrocarbon group, more preferably a methyl group or a phenyl group, and even more preferably a methyl group.

[SiO] R ¹ bonded to the silicon atom represented by _b1 is an alkenyl group having 2 or more and 8 or less carbon atoms, or a monovalent hydrocarbon group containing an alkyl group or an aryl group, and one or more of them has 2 or more carbon atoms. Any alkenyl group having 8 or less carbon atoms may be used, but it is preferably an alkenyl group having 2 or more carbon atoms and 8 or less carbon atoms, or a monovalent hydrocarbon group having 1 or more carbon atoms and 16 or less carbon atoms selected from an alkyl group or an aryl group. When R ¹ is a hydrocarbon group other than an alkenyl group, a methyl group or a phenyl group is more preferable, and a methyl group is even more preferable.

[SiO] R ¹ bonded to the silicon atom represented by _d1 may be an alkenyl group having 2 to 8 carbon atoms, or a monovalent hydrocarbon group containing an alkyl group or an aryl group, but may be a monovalent hydrocarbon group containing 2 to 8 carbon atoms. It is preferably a monovalent hydrocarbon group having 1 to 16 carbon atoms selected from the following alkenyl groups, alkyl groups, and aryl groups; More preferably, it is a monovalent hydrocarbon group. When R ¹ is a hydrocarbon group other than an alkenyl group, a methyl group or a phenyl group is more preferable, and a methyl group is even more preferable.

R ¹ at both ends of the main chain is also the same as R ¹ bonded to the silicon atom shown in [SiO] _b1 , but the preferred structure is an alkenyl group having 2 to 8 carbon atoms, and the alkenyl group at the end is Si It is particularly preferred because when it reacts with the -H group, steric structural hindrance becomes relatively small and peelability is easily improved.

R ¹ bonded to the terminal silicon atom in general formula (Ia) is also the same as R ¹ bonded to the silicon atom represented by [SiO] _b1 , but the preferred structure is an alkenyl group having 2 or more and 8 or less carbon atoms. is preferable because it improves the cohesive force of the release layer and improves the release characteristics of process materials such as those using organic solvents.

Examples of the alkenyl group having 2 or more and 8 or less carbon atoms represented by R ¹ include a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group, and among these, a vinyl group is particularly preferred.

In the entire general formula (I) including ^Y1 , when all silicon atoms including terminals are 100 mol%, a1 is 50 mol% or more and 98 mol% or less, but 70 mol% or more and 98 mol% or less is preferred. Moreover, b1 is 0 mol% or more and 10 mol% or less, but preferably 0 mol% or more and 5 mol% or less. c1 is 0.5 mol% or more and 30 mol% or less, preferably 0.5 mol% or more and 20 mol% or less. d1 is 0 mol% or more and 50 mol% or less,
It is preferably 0 mol% or more and 30 mol% or less.

When the total structural units of [SiO] _a1 and [SiO] _b1 are 100 mol%, from the viewpoint of localizing hydrocarbon groups on the coating surface to improve releasability, [SiO] _a1 is The range of the constituent units is preferably 90 mol% or more and 100 mol% or less, and more preferably 95 mol% or more and 100 mol% or less.

The number average molecular weight of the alkenyl group-containing silicone is preferably 1,000 or more and less than 10,000, more preferably 3,000 or more and less than 10,000. If the number average molecular weight is smaller than 1000 or more, the hydrocarbon groups will be localized on the coating surface, making it easier to obtain sufficient removability. On the other hand, when the number average molecular weight is less than 10,000, the emulsifying property of the aqueous coating composition tends to be good and the uniform coating properties also tend to be good.

(Si-H group-containing silicone)
The Si-H group-containing silicone may be a compound that has two or more Si-H groups (that is, two or more hydrogen atoms directly bonded to a Si atom) in the molecule and has a siloxane bond in the main chain. Although any compound may be used, polyorganosiloxane having a Si--H group in the side chain is preferred. Further, a copolymer containing a dialkylsiloxane unit or an alkylphenylsiloxane unit is preferable because it is easy to adjust the amount of Si--H groups in one molecule while exhibiting releasability. The terminal silicon atom may have a Si--H group, but preferably has a trialkylsilane structure such as trimethylsilane.

An example of the Si--H group-containing silicone is an organohydrogenpolysiloxane represented by the following general formula (II).

(In general formula (II), R ³ is a monovalent hydrocarbon group having 1 to 16 carbon atoms and containing an alkyl group or an aryl group, which may be the same or different, and a2+b2 is 100 mol%. (In this case, a2 is 30 mol% or more and 90 mol% or less, and b2 is 10 mol% or more and 70 mol% or less.)
[SiO] A hydrogen atom (hydrogen group) is bonded to the silicon atom represented by _a2 , and ^R3 may be a monovalent hydrocarbon group including an alkyl group or an aryl group; It is preferable that it is a monovalent hydrocarbon group having 1 or more and 16 or less carbon atoms selected from the following.

[SiO] _b2 and ^R3 bonded to the terminal Si atom may be any monovalent hydrocarbon group containing an alkyl group or an aryl group, but are selected from alkyl groups and aryl groups having 1 to 16 carbon atoms. The following monovalent hydrocarbon groups are preferred.

For any R ³ , it is more preferable that the number of carbon atoms in the alkyl group or aryl group is smaller, so that steric structural hindrance becomes relatively small and the crosslinking reaction progresses easily. It is also preferable from the viewpoint of fluidity and uniformity of the reaction structure in the release layer. Therefore, the alkyl group is preferably a methyl group, ethyl group, propyl group, butyl group, etc., and the aryl group is preferably a phenyl group, tolyl group, etc.

When the sum of the structural units of [SiO] _a2 and [SiO] _b2 is 100 mol%, the range of the structural unit of [SiO] _a2 is preferably from 30 mol% to 90 mol%, and from 40 mol% to 80 mol%. The following are more preferred. [SiO] When _{the a2} structural unit is 30 mol% or more, there will be a sufficient amount of crosslinking reaction points, the cohesive force of the mold release layer will increase, and the scratch resistance and solvent resistance of the mold release layer will also be good. preferable. In addition, when the structural unit of [SiO] _a2 is 90 mol% or less, Si-H groups are less likely to remain in the release layer, and the surface activity of the release layer is less likely to increase, resulting in good releasability. Therefore, it is preferable.

The number average molecular weight of the Si--H group-containing silicone in the present invention is preferably 1,000 or more and 5,000 or less, more preferably 3,000 or more and 5,000 or less. When the number average molecular weight is 1000 or more, sufficient releasability can be easily obtained. On the other hand, when the number average molecular weight is 5,000 or less, the emulsification properties of the aqueous coating composition tend to be good, and the coating uniformity tends to be good as well. In addition, the crosslinking reaction is more likely to proceed efficiently, the amount of residual Si--H groups in the release layer is reduced, and releasability is improved.

In the aqueous coating composition, preferably 1 part by mass or more and 50 parts by mass or less of the Si--H group-containing silicone is contained, more preferably 2 parts by mass or more and 40 parts by mass or less, per 100 parts by mass of the alkenyl group-containing silicone. , more preferably 3 parts by mass or more and 30 parts by mass or less. When the content of the Si--H group-containing silicone is 1 part by mass or more, there will be a sufficient amount of crosslinking reaction points, making it easier to form a dense crosslinked structure and improving the release layer properties, which is preferable. When the content of the Si-H group-containing silicone is 50 parts by mass or less, the Si-H groups in the release layer are less likely to remain, and the surface activity of the release layer is less likely to increase, resulting in good releasability. Therefore, it is preferable.

(Polyvinyl alcohol resin)
As the polyvinyl alcohol resin, polyvinyl alcohol or a copolymer thereof is used. Examples of polyvinyl alcohol copolymers include vinyl alcohol-vinyl acetate copolymers, vinyl alcohol-vinyl butyral copolymers, ethylene-vinyl alcohol copolymers, and polyvinyl alcohol polymers having silyl groups in the molecule. Among these, vinyl alcohol-vinyl acetate copolymer and ethylene-vinyl alcohol copolymer are preferred. When the polyvinyl alcohol resin is a copolymer, the repeating unit derived from vinyl alcohol is preferably 70 mol% or more and 100 mol% or less, more preferably 85 mol% or more and 99 mol% or less.

The degree of polymerization of the polyvinyl alcohol resin in the present invention can be expressed by the viscosity of a 4% concentration aqueous solution at 20° C., and the viscosity is preferably 5 mPa·s or more and 50 mPa·s or less. When the viscosity is within the above numerical range, the aqueous coating composition has high miscibility and a more uniform release layer can be easily obtained. That is, it is preferable that the viscosity is 5 mPa·s or more, since it becomes difficult to flow within the coating film after the mold release layer is formed and the mold release properties are hard to deteriorate. It is preferable that the viscosity is 50 mPa·s or less because the viscosity of the entire aqueous coating composition is difficult to increase and uniform coating is facilitated.

Further, polyvinyl alcohol resin can be mixed with silicone before emulsification, and can also be used as an emulsifier.

Usually, polyvinyl alcohol is obtained by polymerizing vinyl acetate to obtain polyvinyl acetate and then saponifying the resulting polyvinyl acetate, and the amount of saponification is expressed as the degree of saponification. In the present invention, the degree of saponification of the polyvinyl alcohol resin is preferably 85 mol% or more and 99 mol% or less. When the degree of saponification is within the above-mentioned numerical range, the miscibility in the aqueous coating composition is high and a more uniform release layer can be easily obtained. In particular, when the degree of saponification is 85 mol% or more, adhesion to the base material is improved and miscibility with silicone is also improved. When the degree of saponification is 99% or less, the hydrophilicity of the release layer will not become too high, the cohesive force of the release layer coating will be easily maintained, and cases of deterioration of the adhesion of the release layer will be less likely to occur. .

As such polyvinyl alcohol resin, commercially available products can be used as they are. Specific examples of such commercial products include Poval manufactured by Kuraray Co., Ltd. and Gohsenol manufactured by Mitsubishi Chemical Corporation.

The release layer in the present invention preferably contains the polyvinyl alcohol resin in an amount of 1% by mass or more and 20% by mass or less based on the release layer. A more preferred range is 1% by mass or more and 15% by mass or less, and an even more preferred range is 1% by mass or more and 10% by mass or less. When the content of the polyvinyl alcohol resin is within the above-mentioned numerical range, the two properties of miscibility with silicone and adhesion between the base material and the release layer can be achieved more favorably. In other words, when the content of the polyvinyl alcohol resin in the release layer is 1% by mass or more, the stability of the silicone emulsion in the coating liquid tends to be good, and when the content is 20% by mass or less, the release layer tends to be good. Mold characteristics are less likely to deteriorate.

(Platinum-based catalyst)
The crosslinking reaction between the alkenyl group-containing silicone and the Si--H group-containing silicone is an addition reaction, and in one embodiment, it is preferable to use a platinum-based catalyst to accelerate the reaction.

Known platinum catalysts can be used, such as platinum chloride and chloroplatinic acid. The platinum-based catalyst may be a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum(0) complex (Karstedt catalyst) in consideration of its dispersibility in silicone, and emulsifies the silicone. By simultaneously dispersing them, uniform dispersibility can be ensured.

The content of the platinum-based catalyst is preferably such that the mass of the platinum element is in the range of 10 ppm or more and 400 ppm or less based on the combined mass of the alkenyl group-containing silicone and the Si-H group-containing silicone. By setting it within such a range, it is possible to sufficiently cure the silicone, suppress the generation of silicone aggregates, and obtain a release film with excellent surface properties. When the mass ratio of the platinum element is below the upper limit, the addition reaction between the alkenyl group and the Si--H group becomes appropriate, and the generation of silicone aggregates tends to be suppressed. From this viewpoint, the content of the platinum-based catalyst is more preferably 300 ppm or less, still more preferably 200 ppm or less. Furthermore, when the mass ratio of the platinum element is at least the lower limit, the addition reaction will proceed sufficiently, making it difficult to cause insufficient curing of silicone. From this viewpoint, the content of the platinum catalyst is more preferably 15 ppm or more, and still more preferably 20 ppm or more.

(aqueous solvent)
In addition to the alkenyl group-containing silicone and the Si--H group-containing silicone, the aqueous coating composition usually contains an aqueous solvent, and as the aqueous solvent, one containing water is preferably used. In one embodiment, an aqueous dispersion of a silicone containing alkenyl groups and an aqueous dispersion of a silicone containing Si-H groups are used for preparing an aqueous coating composition. As the aqueous dispersion of each silicone, preferably an aqueous emulsion is used.

The release layer is formed from such an aqueous emulsion, and the release layer is formed by applying an aqueous coating composition containing an aqueous emulsion (hereinafter sometimes referred to as "aqueous coating solution"). It is formed. By using an aqueous solvent in the aqueous coating liquid, a release layer can be formed during the film forming process without using explosion-proof equipment and recovery equipment that are required for organic solvents. It is also possible to contain some organic solvent, if necessary.

(Other ingredients)
In one embodiment, within the range that does not impair the effects of the invention, for example, surfactants, coupling agents, crosslinking reaction inhibitors, antistatic agents, ultraviolet absorbers, pigments, colorants, organic or inorganic particles, lubricants, blocking Other additives such as inhibitors can be mixed into the aqueous coating composition.

(surfactant)
In one embodiment, it is preferable to add a surfactant to the aqueous coating composition in order to promote wetting to the base film when providing the release layer. Such surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, etc., and it is also possible to use one or more of these. In order to prevent the aqueous emulsions of silicone from coagulating with each other and not to affect the curing reaction of silicone, it is preferable to use a nonionic surfactant as the emulsifier.

The nonionic surfactant preferably has an HLB value in the range of 6 or more and 18 or less, such as higher alcohols, alkylene oxide adducts of higher fatty acids, esters of alkylene oxide adducts of higher fatty acids and alcohols, and alkanolamides. At least one selected from alkylene oxide adducts such as alkylene oxide adducts of , alkylene oxide adducts of sorbitan esters, and alkylene oxide adducts of higher fatty acid glycerides. Here, the HLB value is a value calculated using the Griffin calculation formula.

Examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide, and one or more of these may be used. When using a plurality of them, the HLB value is preferably in the range of 8 or more and 18 or less, and more preferably in the range of 10 or more and 15 or less, although it does not matter whether the addition format is block or random. Among these nonionic surfactants, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, and the like are preferably mentioned. If necessary, two or more types of nonionic surfactants may be mixed. If a nonionic surfactant whose HLB value falls outside of this range is used as an emulsifier for a silicone aqueous dispersion, the emulsifying dispersion power and stability of the aqueous dispersion may decrease.

The surfactant is preferably used in a range of from 0.1% by mass to 20% by mass, more preferably from 0.2% by mass to 15% by mass, and even more preferably from 0.2% by mass to 15% by mass based on the total solid content. is in the range of 0.5% by mass or more and 10% by mass or less. If it is above the lower limit of this range, the emulsification state will be good, and if it is below the upper limit of this range, it will be difficult to cause heavy exfoliation.

(Crosslinking reaction inhibitor)
In one embodiment, a reaction inhibitor is preferably contained in order to suppress the activity of the platinum-based catalyst at room temperature in the form of an aqueous coating liquid. Such a reaction inhibitor is preferably a reaction inhibitor having an alkynyl group. The reaction inhibitor having an alkynyl group is not particularly limited as long as it has an alkynyl group, but specific examples include 1-ethynyl-1-cyclohexanol, 4-ethyl-1-octyn-3-ol, 3- Methyl-1-dodecyn-3-ol, 3,7,11-trimethyl-1-dodecyn-3-ol, 1,1-diphenyl-2-propyn-3-ol, 3-ethyl-6-ethyl-1- Examples include nonyn-3-ol, 3-methyl-1-pentadecyn-3-ol, 2,5-dimethyl-3-hexyne-2,5-diol, and 3-phenyl-1-butyn-3-ol. Since the present invention is an aqueous coating solution, it is preferable to use a reaction inhibitor having an alkynyl group and a hydroxyl group as exemplified in view of the balance between affinity and solubility in water, ability to coordinate with platinum, and boiling point. Alternatively, the platinum-based catalyst may be mixed with a general organopolysiloxane to be added to an aqueous coating solution and used as an aqueous emulsion.

The content of the crosslinking reaction inhibitor is preferably 5 ppm or more and 1000 ppm or less, more preferably 10 ppm or more and 700 ppm or less, and even more preferably 20 ppm or more and 500 ppm or less, based on the mass of the aqueous coating composition used to form the release layer. . When the content of the crosslinking reaction inhibitor is at least the lower limit, the pot life becomes long, the addition curing reaction of silicone is difficult to proceed at room temperature, and silicone aggregates tend to be difficult to generate. In addition, if the content of the crosslinking reaction inhibitor is below the upper limit, it will be difficult for silicone to transfer to the other material after the other material is peeled off, and the amount of reaction inhibitor that evaporates during heat treatment will be reduced, thereby preventing contamination inside the oven. Hard to occur.

(coupling agent)
In one embodiment, a coupling agent can be added to the aqueous coating composition in order to improve the adhesion between the silicone component and the base film. Examples of the coupling agent include a compound represented by the general formula YRSiX ₃ , such as a silane coupling agent. Here, Y is an organic functional group such as a vinyl group, an epoxy group, an amino group, a mercapto group, etc., and it is particularly preferable that Y is an epoxy group or a vinyl group.

R is an alkylene group such as methylene, ethylene, propylene group, or a single bond. X is a hydrolyzable group such as a methoxy group, an ethoxy group, an acetoxy group, or an alkyl group, and at least one of the three X's is a hydrolyzable group, preferably three X's are a hydrolyzable group. . As the hydrolyzable group, a methoxy group is preferred.

Preferred silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane, and vinyltris(2-methoxyethoxysilane). ) silane, vinylmethyldimethoxysilane, etc.

Other examples of coupling agents include organometallic compounds containing metals such as zirconium, titanium, aluminum, etc. The organometallic compounds are preferably classified into alkoxides, chelates, and acylates. Specific examples include zirconium tetraacetylacetonate, zirconium acetate, titanium acetylacetonate, triethanolamine titanate, titanium lactate, etc., but are not limited to these.

It is also possible to use two or more types of coupling agents, such as a silane coupling agent where Y is an epoxy group and a silane coupling agent where Y is a vinyl group. be.

In one embodiment, the addition of a coupling agent improves the durable adhesion between silicone, which is the main component of the release layer, and a polyester film or the like. For example, when casting a resin sheet using a solution casting method using an organic solvent, the organic solvent component may penetrate into the release layer and the release layer may be eroded, but the addition of a coupling agent can prevent this erosion. Can be suppressed. When casting a resin sheet using a melt casting method at high temperatures, the mold release layer is exposed to high temperatures and there is a possibility of thermal deterioration, but by adding a coupling agent, thermal deterioration can be suppressed and the mold release layer can be maintained.

From the above point of view, the content of the coupling agent is 0.1 parts by mass or more and 20 parts by mass based on the total of 100 parts by mass of the alkenyl group-containing silicone and the Si-H group-containing silicone contained in the release layer. Part or less is preferable, and more preferably 1 part or more and 10 parts or less by weight.

(Preparation of silicone water dispersion)
In one embodiment, the aqueous emulsion can be prepared by emulsifying the silicone using a predetermined alkenyl group-containing silicone or Si—H group-containing silicone, an aqueous solvent, and a surfactant. These components can be emulsified using a known method. For example, pre-prepared predetermined silicone, a surfactant, and other components as necessary are mixed using a stirring device such as a homogenizer, ajihomo mixer, or an ultra planetary mixer. Examples include a method of mechanically emulsifying in an aqueous medium using

Furthermore, the particle size of the aqueous dispersion can be adjusted by adjusting the size of the stirring blade, stirring speed, and stirring time. The average particle diameter of the dispersed particles of each silicone aqueous dispersion is preferably 200 nm or less, more preferably 100 nm or more and 200 nm or less.

[Base film]
The base film in the present invention is not particularly limited, but examples include sheets or films made of polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polycarbonate, polyethylene and polypropylene, polystyrene triacetylcellulose, acrylic, polyimide, etc. be able to. Among these, a film made of polyester is preferred from the viewpoint of excellent mechanical properties and heat resistance, and a good balance between these properties and price. Hereinafter, the case of a polyester film will be explained as an example, but even when using other resin films, the copolymerization components, blend components, additives, film manufacturing method, laminated structure, etc. are the same as described below.

(Polyester film)
The polyester constituting the polyester film used as the base film is not particularly limited, and a film formed from a polyester commonly used as a base material for a release film can be used. Preferably, it is a crystalline linear saturated polyester consisting of an aromatic dibasic acid component and a diol component, such as polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, or a combination of these resins. More preferred are copolymers containing the constituent components as main components. In particular, polyester films formed from polyethylene terephthalate are particularly suitable. In polyethylene terephthalate, the repeating units of ethylene terephthalate are preferably 90 mol% or more, more preferably 95 mol% or more, and a small amount of other dicarboxylic acid components and diol components may be copolymerized. For example, from the viewpoint of cost, it is preferable to use one made from only terephthalic acid and ethylene glycol. Further, known additives such as antioxidants, light stabilizers, ultraviolet absorbers, crystallizing agents, etc. may be added within a range that does not impede the effects of the release film of the present invention. The polyester film is preferably a biaxially oriented polyester film for reasons such as high elastic modulus in both directions.

The intrinsic viscosity of the polyester film is preferably 0.50 dl/g or more and 0.70 dl/g or less, more preferably 0.52 dl/g or more and 0.62 dl/g or less. When the intrinsic viscosity is 0.50 dl/g or more, it is preferable because many breaks do not occur during the stretching process. On the other hand, if it is 0.70 dl/g or less, it is preferable because the cutting properties are good when cutting into a predetermined product width and dimensional defects do not occur. Further, it is preferable that the raw material pellets be sufficiently vacuum dried.

In addition, in this specification, when it describes simply as a "polyester film," it means the polyester film which has surface layer A and surface layer B (laminate|stacked).

The method for producing the polyester film in the present invention is not particularly limited, and any conventionally commonly used method can be used. For example, it can be obtained by melting the polyester in an extruder, extruding it into a film, cooling it in a rotating cooling drum to obtain an unstretched film, and then biaxially stretching the unstretched film. A biaxially stretched film can be obtained by sequentially biaxially stretching a uniaxially stretched film in the longitudinal or transverse direction in the transverse or longitudinal direction, or by simultaneously biaxially stretching an unstretched film in the longitudinal and transverse directions. I can do it.

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 to stretch the film by a factor of 1 to 8 times, particularly 2 times to 6 times, in both the longitudinal and transverse directions.

The thickness of the polyester film is preferably 12 μm or more and 50 μm or less, more preferably 15 μm or more and 38 μm or less, and even more preferably 19 μm or more and 33 μm or less. If the thickness of the film is 12 μm or more, there is no risk of deformation due to heat during film production, processing, and molding, which is preferable. On the other hand, if the thickness of the film is 50 μm or less, the amount of film to be discarded after use will not be excessively large, which is preferable in terms of reducing environmental burden.

The polyester film base material may be a single layer or a multilayer of two or more layers. For example, the base film may be a polyester film having a surface layer A that does not substantially contain particles having a particle size of 1.0 μm or more and a surface layer B that contains particles. Preferably, surface layer A does not substantially contain inorganic particles having a particle size of 1.0 μm or more.

In this embodiment, particles having a particle size of less than 1.0 μm and 1 nm or more may be present in the surface layer A. Since the surface layer A does not substantially contain particles having a particle size of 1.0 μm or more, for example, inorganic particles, it is possible to reduce problems caused by transfer of the shape of particles in the base material to the resin sheet.

In one embodiment, the surface layer A does not contain particles with a particle size of less than 1.0 μm, so that problems caused by transfer of the particle shape in the base material to the resin sheet can be more effectively suppressed.
In one embodiment, the polyester film base material is preferably a laminated film having a surface layer A substantially free of inorganic particles on at least one side. Thereby, it is possible to more effectively suppress the transfer of the particle shape in the base material to the resin sheet and the occurrence of defects.
For example, it is preferable that the surface layer A that does not substantially contain particles with a particle size of less than 1.0 μm also substantially does not contain particles with a particle size of 1.0 μm or more.

Here, in the present invention, "contains substantially no particles" means, for example, in the case of inorganic particles of less than 1.0 μm, the amount of inorganic elements determined by fluorescent X-ray analysis is 50 ppm or less, preferably 10 ppm. Hereinafter, it most preferably means a content that is below the detection limit. Even if particles are not actively added to the film, contaminants derived from foreign substances or dirt attached to the raw resin or the line or equipment in the film manufacturing process are peeled off and mixed into the film. This is because there is. Further, "substantially not containing particles with a particle size of 1.0 μm or more" means that particles with a particle size of 1.0 μm or more are not included.

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, which can contain inorganic particles, on the opposite side of the surface layer A, which does not substantially contain inorganic particles.

Assuming that the layer on the side to which the release layer is applied is layer A, the layer on the opposite side is layer B, and the other core layer is layer C, the layer structure in the thickness direction is release layer/A/ B, or a laminated structure such as release layer/A/C/B. Naturally, the C layer may have a plurality of layers. Furthermore, the surface layer B may not contain inorganic particles. In that case, it is preferable to provide a coating layer containing at least inorganic particles and a binder on the surface layer B in order to provide slipperiness for winding up the film into a roll.

In the polyester film base material of the present invention, the surface layer B forming the opposite surface to the surface to which the release layer is applied preferably contains inorganic particles from the viewpoint of the slipperiness of the film and the ease with which air can escape. In particular, it is preferable to use silica particles and/or calcium carbonate particles. The total amount of inorganic particles contained in the surface layer B is preferably 5,000 ppm or more and 15,000 ppm or less.

At this time, the area surface average roughness (Sa) of the film of the surface layer B is preferably in the range of 1 nm or more and 40 nm or less. More preferably, the range is 5 nm or more and 35 nm or less. When the total amount of silica particles and/or calcium carbonate particles is 5000 ppm or more and Sa is 1 nm or more, air can be released uniformly when the film is rolled up, resulting in a good rolled shape and good flatness. , it is suitable for producing ultra-thin ceramic green sheets. In addition, when the total amount of silica particles and/or calcium carbonate particles is 15,000 ppm or less and Sa is 40 nm or less, the lubricant is less likely to aggregate and coarse protrusions are not formed, resulting in stable quality when producing ultra-thin ceramic green sheets. It is preferable.

In addition to silica and/or calcium carbonate, inert inorganic particles and/or heat-resistant organic particles can also be used as particles contained in layer B, but from the viewpoint of transparency and cost, silica particles and/or More preferably, calcium carbonate particles are used. In addition, other inorganic particles that can be used include alumina-silica composite oxide particles, hydroxyapatite particles, and the like. Examples of the heat-resistant organic particles include crosslinked polyacrylic particles, crosslinked polystyrene particles, and benzoguanamine particles. In addition, when using silica particles, porous colloidal silica is preferable, and when using calcium carbonate particles, light calcium carbonate whose surface is 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 inorganic particles added to the surface layer B is preferably 0.1 μm or more and 2.0 μm or less, particularly preferably 0.5 μm or more and 1.0 μm or less. It is preferable that the average particle diameter of the inorganic particles is 0.1 μm or more because the release film has good slip properties. Further, if the average particle diameter is 2.0 μm or less, there is no risk of adversely affecting the smoothness of the surface of the mold release layer, so there is no risk of pinholes occurring in the ceramic green sheet, which is preferable.

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

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, it is difficult to be influenced by particles contained in the surface layer B etc. from inside the film, and it is easy for the area surface average roughness Sa to satisfy the above range, which is preferable. When the thickness is 50% or less of the total thickness of the base film, the ratio of recycled raw materials used in the surface layer B can be increased, and the environmental burden is small, which is preferable.

In addition, from the economic point of view, it is possible to use film scraps or recycled raw materials from PET bottles in an amount of 50% by mass or more and 90% by mass or less for layers other than the above-mentioned surface layer A (surface layer B or the above-mentioned intermediate layer C). can. Even in this case, it is preferable that the type and amount of lubricant contained in the B layer, the particle size, and the area surface average roughness (Sa) satisfy the above ranges.

In addition, in order to improve the adhesion of a release layer to be applied later or to prevent static electricity, a film may be applied to the surface of surface layer A and/or surface layer B before or after uniaxial stretching during the film forming process. A coating layer may be provided on the surface, and a surface treatment or the like may be performed.

In one embodiment, the release layer forming surface to which the aqueous coating composition is applied may be subjected to surface treatment or provided with an easy-to-adhesion layer in order to improve adhesion to the release layer. Surface treatments include plasma treatment, corona discharge treatment, ultraviolet treatment, flame treatment, and electron beam/radiation treatment.The adhesive layer contains the same resin as the base film, and further contains antistatic agents and pigments. , a surfactant, a lubricant, an anti-blocking agent, and the like. If an adhesion improver such as a coupling agent is added to the aqueous coating composition, the release layer should have sufficient adhesion to the base film even without providing an easy-adhesion layer. I can do it.

[Formation of release layer]
In one embodiment, the release layer is formed by applying an aqueous coating composition containing an aqueous emulsion of alkenyl group-containing silicone and an aqueous emulsion of Si—H group-containing silicone. At that time, a release layer is formed on at least one surface of the base film. The release layer is formed by applying the aqueous coating liquid onto the base film and then heating and drying it to cause the components of the aqueous coating liquid to react and solidify. The release layer is preferably formed in a film forming process.

The thickness of the release layer after drying is preferably 5 nm or more and 100 nm or less. When the thickness of the release layer is at least the lower limit, it is easy to obtain sufficient peelability, and when it is below the upper limit, the peel strength tends to be difficult to increase, and the release layer components of the aqueous coating solution are not concentrated. It also eliminates the need to increase the amount of coating, making it easier to apply. Therefore, the thickness of the release layer is more preferably 5 nm or more and 70 nm or less, and even more preferably 5 nm or more and 50 nm or less.

When applying the water-based coating liquid onto the base film, the solid content concentration is preferably 20% by mass or less, more preferably 1% by mass or more and 10% by mass based on the release layer components in the water-based coating liquid. % or less. When the solid concentration of the release layer component in the aqueous coating liquid is at least the lower limit, film forming properties tend to improve. Moreover, when the solid content concentration is below the upper limit, the stability of the aqueous coating liquid and the appearance of the release layer tend to be good. Water is preferably used as the aqueous solvent to adjust the solid content concentration.

The aqueous coating liquid applied to the base film to form the release layer can be applied at any stage, but it is preferably applied during the polyester film manufacturing process, and furthermore, the oriented crystallization is completed. Preferably it is applied to the previous polyester film. Thereafter, after stretching in at least one direction, heat treatment can be performed to complete crystal orientation.

Here, the term "polyester film before crystal orientation is completed" refers to an unstretched film or an unstretched film in the longitudinal direction (hereinafter sometimes referred to as continuous film forming direction, longitudinal direction, MD direction) or transverse direction (hereinafter referred to as continuous film forming direction, longitudinal direction, MD direction). , a direction perpendicular to the machine direction, a width direction, or a TD direction), and a film oriented by low-magnification stretching in two directions, the machine direction and the width direction (sometimes referred to as the TD direction). This includes a biaxially stretched film (before finally being re-stretched in the longitudinal or transverse direction to complete oriented crystallization).

Among these, so-called in-line coating is preferred, in which a water-based coating liquid is applied to an unstretched film or a uniaxially stretched film oriented in one direction, and the film is directly subjected to longitudinal stretching and/or transverse stretching and heat setting. The release layer may be dried by a stretching process or a heat setting process after coating, and a drying process may be added if necessary. Further, in the case of curing the composition using a catalyst to obtain a cured coating, the curing can be performed by a stretching process or a heat setting process, but a curing process may be added as necessary.

When applying a water-based coating liquid to a polyester film, the film surface is subjected to physical treatment such as corona surface treatment, flame treatment, plasma treatment, etc. as a preliminary treatment to improve coating properties, or the above-mentioned emulsifier is added to the composition. It is preferable to use them together as a wetting agent or to additionally add a surfactant as a wetting agent.

Any known coating method can be used as the coating method. For example, a roll coating method, a gravure coating method, a roll brushing method, a spray coating method, an air knife coating method, an impregnation method, a curtain coating method, etc. can be used alone or in combination.

[Characteristics of release film]
In the present invention, the surface free energy of the release layer in the test method described below is preferably in the range of 10 mN/m or more and 40 mN/m or less, more preferably 12 mN/m or more and 38 mN/m or less, and even more preferably 14 mN/m. The range is 36 mN/m or more, particularly preferably 15 mN/m or more and 35 mN/m. When the surface free energy of the release layer is below the upper limit, the adhesive force is reduced and heavy peeling becomes difficult. Moreover, when it is more than the lower limit, defects due to repulsion of processed layers such as ceramic sheets and resin sheets coated on the surface of the mold release layer are less likely to occur, and pinhole defects are also less likely to occur.

[Application]
The release film of the present invention can be used as a process film used in manufacturing multilayer ceramic capacitors, casting resin sheets, and the like. In particular, even if a thin resin sheet with a thickness of 1 μm or less after drying is produced, the wettability is good, so pinholes in the processed layer are reduced, and, for example, when used as a release film for green sheet production. , it is possible to reduce the defective rate of thin-walled multilayer ceramic capacitors.

EXAMPLES Hereinafter, the present invention will be explained in more detail by showing examples and comparative examples, but the present invention is not limited by the following examples. In addition, the evaluation method of physical properties etc. in the following examples is as follows.

(1) Coating uniformity of the release layer When the release film was cut into an A4 size sheet and the surface of the release layer was visually observed using a fluorescent lamp or halogen light, the number of agglomerated coating defects (per A4 size sheet) was determined. number) and evaluated based on the following criteria.
◎: No coating defects ○: 1 to 2 coating defects △: 3 to 5 coating defects ×: 6 or more coating defects

(2) Surface free energy of release layer A sample that had been conditioned for 24 hours at 23°C and 50% RH was measured using a contact angle meter (DMo-501 manufactured by Kyowa Interface Science Co., Ltd.). was dropped and allowed to stand for 30 seconds, and the static contact angle was measured. The static contact angles of ethylene glycol and methylene iodide were measured in the same manner, and the following simultaneous equations regarding the surface tension components of the release layer were established using the surface tension components of each liquid below (water, ethylene The measurement solutions of glycol and methylene iodide are designated as 1, 2, and 3, respectively, where γLD is the dispersion force component of the liquid, γLP is the polar force component of the liquid, γLH is the hydrogen bond component of the liquid, and γL is each surface tension component of the liquid. In addition, γSD represents the dispersion force component of the mold release layer, γSP represents the polar force component of the mold release layer, γSH represents the hydrogen bond component of the mold release layer, and θ represents the contact angle).
(γSD・γLD1) ^1/2 + (γSP・γLP1) ^1/2 + (γSH・γLH1) ^1/2 = γL1 (1+cosθ1)/2
(γSD・γLD2) ^1/2 + (γSP・γLP2) ^1/2 + (γSH・γLH2) ^1/2 = γL2 (1+cosθ2)/2
(γSD・γLD3) ^1/2 + (γSP・γLP3) ^1/2 + (γSH・γLH3) ^1/2 = γL3 (1+cosθ3)/2
Note that γLD, γLP, γLH, and γL of water, ethylene glycol, and methylene iodide are as shown in Table 1.

Next, from the values of γSD, γSP, and γSH determined above, the surface free energy γS of the surface of the mold release layer was calculated using the following formula.
γS=γSD+γSP+γSH

(3) Smear test of release layer (friction resistance)
The release surface of the release film was rubbed once with an index finger under a load of about 500 gf, and the whitening state of the surface of the release layer was visually observed and evaluated according to the following criteria.
○: No change △: Slight whitening ×: Whitening

(4) Release layer rub-off test (adhesion)
Rub the release surface of the release film with your thumb 10 times under a load of approximately 500 gf, and in order to confirm that the silicone has not fallen off in that area, attach adhesive tape (manufactured by Nitto Denko Corporation, product name ``31B Tape'') to the adhesive. The peeling state of the tape was checked and evaluated according to the following criteria.
○: No change in peeling when peeling the adhesive tape △: Slight change in peeling when peeling the adhesive tape ×: Change in peeling when peeling the adhesive tape

(5) Ceramic sheet removability 100 parts by mass of barium titanate (BaTiO ₃ , manufactured by Kyoritsu Materials Co., Ltd.), 7 parts by mass of polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd.), 3 parts by mass of dioctyl phthalate, dispersant (DISPERBYK-103, manufactured by Byk Chemie Co., Ltd.) A slurry was prepared by adding 3 parts by mass of the product to a mixed solvent of toluene:ethanol=1:1 (volume ratio) and dispersing it in a ball mill. This slurry was uniformly coated onto the release layer of the release film to a thickness of 2 μm after drying, and then dried to form a ceramic sheet. The release film on which the ceramic sheet was formed was cut to 25 mm x 150 mm, and an adhesive tape (manufactured by Nitto Denko Corporation, trade name "31B tape") was attached to the ceramic sheet side to prepare a test piece. This test piece was conditioned for 24 hours at 23° C. and 50% humidity, and then the ceramic sheet was peeled off using a tensile tester at a peeling angle of 180° and a peeling speed of 300 mm/min, and the peel strength was measured. The peel strength of the ceramic sheet was determined based on the following index.
◎: Peel strength is less than 1 g/25 mm ○: Peel strength is 1 g/25 mm or more and less than 3 g/25 mm △: Peel strength is 3 g/25 mm or more and 12 g/25 mm or less ×: Peel strength is more than 12 g/25 mm, or ceramic This will cause the sheet to tear.

(6) Recyclability evaluation Recyclability was determined by magnifying the size and number of foreign particles contained in the film 20 times using a universal projector and counting the number of foreign particles with a maximum diameter of 50 μm or more. The measurement area was 0.05 ^m2 .
◎: Number of foreign objects: 10 pieces/less than 0.05 m ² , no problem in use.
○: Number of foreign objects: 10 pieces/0.05 m ² or more to 30 pieces/0.05 m ² or more, slightly affecting flatness, but not a problem in use.
Δ: Number of foreign objects: 30 pieces/0.05 m ² or more to less than 100 pieces/0.05 m ² , can be used for limited purposes.
×: Number of foreign objects: 100 pieces/0.05 m ² or more, the deformation of the cast surface is so noticeable that it cannot be used.

(7) Number average molecular weight Measured by gel permeation chromatography (GPC) and calculated as a polystyrene equivalent value.

(8) Thickness of release layer After cutting the release film into triangular pieces, a 2 nm thick Pt (platinum) layer was formed on the surface of the release layer by coating. The obtained sample was fixed in a multiaxial embedding capsule, embedded using epoxy resin, and sliced in a direction perpendicular to the surface direction of the film using a microtome ULTRACUT-S to obtain a 50 nm thick sample. An ultrathin sample was obtained. Next, the obtained ultra-thin sample was mounted on a grid and steam-stained with 2% osmic acid at 60° C. for 2 hours. Using an ultra-thin sample after steam staining, the cross section of the film was observed using a transmission electron microscope LEM-2000 at an accelerating voltage of 100 kV, and the thickness of the release layer was measured. Measurements were performed at arbitrary 10 points, and the average value was taken as the thickness of the release layer (unit: nm).

[Example 1]
Polyethylene terephthalate ([η] = 0.63 dl/g, Tg = 78°C) containing 0.25% by mass of calcium carbonate particles with an average particle diameter of 0.6 μm was melted in an extruder to create a filter with a filtration accuracy of 10 μm. The film was extruded through a die and cooled using a cooling drum in a conventional manner to obtain an unstretched film. Next, after stretching in the longitudinal direction to 3.2 times at 80°C, the aqueous coating solution (aqueous coating composition) obtained in Production Example 1 was rolled into a product so that the release layer thickness was as shown in Table 2. It was applied evenly with a coater. Note that the water-based coating liquid used was one that had been used within 24 hours after being prepared.

Next, the coated film was dried at 105°C, stretched 4.6 times in the transverse direction at 145°C, and further heat-set at 230°C for about 10 seconds to react and solidify the aqueous coating solution. A release film (thickness: 25 μm) having a mold layer was obtained and evaluated. The evaluation results are shown in Table 2.

In addition, when collecting the product roll, the part of the release film that did not become a product due to defects or the part of the release film that did not become a product due to defects etc. was crushed until the major axis of the film piece was approximately 5 mm or less for each example and comparative example. 40% by mass of the raw material that was recycled by melting was used.

<Manufacture example 1>
(Sample 1A)
Using an emulsifying device (manufactured by NP Lab Co., Ltd., device name "Ultra Planetary Mixer") that can stir the entire inside of the container, a1 of formula (1) is 100 mol%, b1 is 0 mol%, A raw material consisting of 97% by mass of silicone oil with a number average molecular weight of 8000 and 3% by mass of polyoxyethylene tridecyl ether (manufactured by Kao Corporation, trade name "Emulgen 1108") as a surfactant was mechanically processed in an aqueous medium. The mixture was emulsified to obtain an aqueous emulsion of Sample 1A having a solid content of 40% by mass. Furthermore, the emulsion particle size was adjusted to an average particle size of 200 nm by adjusting the stirring speed and stirring time during emulsification.

(Sample 2A)
Using an emulsifying device (manufactured by NP Lab Co., Ltd., device name "Ultra Planetary Mixer") that can stir the entire inside of the container, a2 of formula (2) is 50 mol%, b2 is 50 mol%, A raw material consisting of 96% by mass of silicone oil with a number average molecular weight of 3500 and 4% by mass of polyoxyethylene tridecyl ether (manufactured by Kao Corporation, trade name "Emulgen 1108") as a surfactant was mechanically processed in an aqueous medium. was emulsified to obtain an aqueous dispersion of Sample 2 with a solid content of 40% by mass. Furthermore, the emulsion particle size was adjusted to an average particle size of 180 nm by adjusting the stirring speed and stirring time during emulsification.

(Water-based coating liquid)
Water-based coating liquids were prepared so that the solid mass of silicone in Sample 1A and Sample 2A was as shown in Table 2, and the other components were as shown below. Based on the total mass of silicone, 5% by mass of the following polyvinyl alcohol, 3% by mass of the following coupling agent, 50 ppm of the following platinum catalyst based on the total solid mass of Sample 1 and Sample 2, and aqueous A water-based coating solution was prepared by mixing 100 ppm of the following crosslinking reaction inhibitor with respect to the mass of the coating solution, and diluting the solid content concentration of the water-based coating solution with water so as to obtain the target release layer thickness.
・Polyvinyl alcohol: Polyvinyl alcohol with a viscosity of 27 mPa・s (concentration: 4% by mass aqueous solution, temperature: 20°C), saponification degree of 96 mol% (manufactured by Kuraray Co., Ltd., product name: "Kuraray Poval 27-96")
・Coupling agent: 3-glycidoxypropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBE-403")
・Platinum-based catalyst: Platinum-based catalyst emulsion (manufactured by Wacker, product name "CATALYST EM440")
・Crosslinking reaction inhibitor: 1-ethynylcyclohexanol (manufactured by Alfa Lancaster)

[Example 2]
In Example 1, a release film was produced under exactly the same conditions as in Example 1, except that a water-based coating solution was prepared using Sample 1B produced in Production Example 2 instead of Sample 1A, and the above-mentioned evaluation was carried out. I did this. The results are shown in Table 2.
<Production Example 2> (Sample 1B)
Using an emulsifying device (manufactured by NP Lab Co., Ltd., device name "Ultra Planetary Mixer") that can stir the entire inside of the container, a1 of formula (1) is 100 mol%, b1 is 0 mol%, A raw material consisting of 97% by mass of silicone oil with a number average molecular weight of 4000 and 3% by mass of polyoxyethylene tridecyl ether (manufactured by Kao Corporation, trade name "Emulgen 1108") as a surfactant was machined in an aqueous medium. The mixture was emulsified to obtain an aqueous emulsion of Sample 1B having a solid content of 40% by mass. Furthermore, the emulsion particle size was adjusted to an average particle size of 180 nm by adjusting the stirring speed and stirring time during emulsification.

[Example 3]
In Example 1, a release film was produced under exactly the same conditions as in Example 1, except that a water-based coating solution was prepared using Sample 1C produced in Production Example 3 instead of Sample 1A, and the above-mentioned evaluation was carried out. I did this. The results are shown in Table 2.

<Production Example 3> (Sample 1C)
Using an emulsifying device (manufactured by NP Lab Co., Ltd., device name "Ultra Planetary Mixer") that can stir the entire inside of the container, a1 of formula (1) is 98 mol%, b1 is 2 mol%, A raw material consisting of 97% by mass of silicone oil with a number average molecular weight of 8000 and 3% by mass of polyoxyethylene tridecyl ether (manufactured by Kao Corporation, trade name "Emulgen 1108") as a surfactant was mechanically processed in an aqueous medium. The mixture was emulsified to obtain an aqueous emulsion of Sample 1C with a solid content of 40% by mass. Furthermore, the emulsion particle size was adjusted to an average particle size of 200 nm by adjusting the stirring speed and stirring time during emulsification.

[Example 4]
In Example 1, a release film was produced under exactly the same conditions as in Example 1, except that a water-based coating solution was prepared using Sample 1D produced in Production Example 4 instead of Sample 1A, and the above-mentioned evaluation was carried out. I did this. The results are shown in Table 2.

<Production Example 4> (Sample 1D)
Using an emulsifying device (manufactured by NP Lab Co., Ltd., device name "Ultra Planetary Mixer") that can stir the entire inside of the container, formula (A) is 1 mol%, formula (B) is 3 mol%, and formula (B) is 3 mol%. (C) is 93 mol%, formula (D) is 2 mol%, formula (E) is 1 mol%, 97% by mass of silicone oil having a number average molecular weight of 7000, and polyoxy as a surfactant. A raw material consisting of 3% by mass of ethylene tridecyl ether (manufactured by Kao Corporation, trade name "Emulgen 1108") was mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample 1D with a solid content of 40% by mass. . Furthermore, the emulsion particle size was adjusted to an average particle size of 180 nm by adjusting the stirring speed and stirring time during emulsification.

[Example 5]
In Example 4, when preparing the aqueous coating solution, a release film was produced under exactly the same conditions as in Example 4, except that the contents of Sample 1D and Sample 2A were changed as shown in Table 2. , the above-mentioned evaluation was performed. The results are shown in Table 2.

[Example 6]
In Example 1, a release film was produced under exactly the same conditions as in Example 1, except that a water-based coating solution was prepared using Sample 1E produced in Production Example 5 instead of Sample 1A, and the above-mentioned evaluation was carried out. I did this. The results are shown in Table 2.

<Production Example 5> (Sample 1E)
Using an emulsifying device (manufactured by NP Lab Co., Ltd., device name "Ultra Planetary Mixer") that can stir the entire inside of the container, formula (A) is 2 mol%, formula (B) is 4 mol%, formula (B) is 4 mol%, (C) is 91 mol%, formula (D) is 1 mol%, formula (E) is 2 mol%, 97% by mass of silicone oil having a number average molecular weight of 3000, and polyoxy as a surfactant. A raw material consisting of 3% by mass of ethylene tridecyl ether (manufactured by Kao Corporation, trade name "Emulgen 1108") was mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample 1E with a solid content of 40% by mass. . Furthermore, the emulsion particle size was adjusted to an average particle size of 170 nm by adjusting the stirring speed and stirring time during emulsification.

[Example 7]
Example 1 was exactly the same as Example 1, except that the water-based coating liquid was prepared using the following polyvinyl alcohol instead of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name "Kuraray Poval 27-96"). A release film was produced under the same conditions and evaluated as described above. The results are shown in Table 2.
・Polyvinyl alcohol: Polyvinyl alcohol with a viscosity of 23 mPa・s (concentration: 4% by mass aqueous solution, temperature: 20°C), saponification degree of 88 mol% (manufactured by Mitsubishi Chemical Corporation, product name: "Gohsenol GM-14R")

[Comparative Examples 1-2]
In Examples 4 and 5, mold release was performed under exactly the same conditions as in Examples 4 and 5, except that the aqueous coating liquid obtained in Production Example 6 was used instead of the water-based coating liquid obtained in Production Example 4. A film was produced and evaluated as described above. The results are shown in Table 2.

<Manufacture example 6>
(Sample 1F)
Using an emulsifying device that can stir the entire inside of the container (manufactured by NP Lab Co., Ltd., device name "Ultra Planetary Mixer"), formula (A) is 35 mol%, formula (B) is 5 mol%, formula (B) is 5 mol%, formula (C) is 25 mol%, formula (D) is 2 mol%, formula (E) is 33 mol%, 96% by mass of silicone oil having a number average molecular weight of 270,000, and polyoxy as a surfactant. A raw material consisting of 4% by mass of ethylene tridecyl ether (manufactured by Kao Corporation, trade name "Emulgen 1108") was mechanically emulsified in an aqueous medium to obtain an aqueous emulsion of sample 1F with a solid content of 40% by mass. . Furthermore, the emulsion particle size was adjusted to an average particle size of 260 nm by adjusting the stirring speed and stirring time during emulsification.

(Sample 2B)
Using an emulsifying device (manufactured by NP Lab Co., Ltd., device name "Ultra Planetary Mixer") that can stir the entire inside of the container, a2 of formula (2) is 50 mol%, b2 is 50 mol%, A raw material consisting of 96% by mass of silicone oil with a number average molecular weight of 9000 and 4% by mass of polyoxyethylene tridecyl ether (manufactured by Kao Corporation, trade name "Emulgen 1108") as a surfactant was mechanically processed in an aqueous medium. was emulsified to obtain an aqueous dispersion of Sample 2B with a solid content of 50% by mass. Furthermore, the emulsion particle size was adjusted to an average particle size of 230 nm by adjusting the stirring speed and stirring time during emulsification.

(Water-based coating liquid)
A water-based coating liquid was prepared under the same conditions as in Production Example 1, except that the solid mass of silicone in Sample 1F and Sample 2B was prepared in the amount shown in Table 2.

[Comparative example 3]
In Example 4, a release film was produced under exactly the same conditions as in Example 4, except that polyvinyl alcohol was not added as another component of the release layer, and the above-mentioned evaluation was performed. The results are shown in Table 2.

[Comparative example 4]
A base film was produced in the same manner as in Example 1 except that a release layer was not applied. Silicone: KS-774 (manufactured by Shin-Etsu Astec Co., Ltd., addition reaction type, number average molecular weight 750000) is 86.9% by mass, silicone: KS-3800 (manufactured by Shin-Etsu Astec Corporation, resin type) is 13% by mass. , Catalyst: CAT-PL-50T (manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed to contain 0.1% by mass, and the solid concentration of the coating solution was diluted with toluene to obtain the target release layer thickness. , a coating solution was prepared. A coating solution was applied to the base film using a coating machine to form a release layer, and the film was dried at a temperature of 150° C. for 30 seconds to produce a release film, and the above-mentioned evaluations were performed. The results are shown in Table 2. In addition, since the mold release layer was formed using an organic solvent, coating was required in special explosion-proof equipment, and exhaust treatment for the dried organic solvent was also required compared to the example. .

[Comparative example 5]
A base film was prepared in the same manner as in Example 1 by applying the coating liquid described below to form a primer layer instead of the release layer. As a coating liquid in place of the release layer, the solid content ratio of polyvinyl alcohol: Gohsenol GL-03 (manufactured by Mitsubishi Chemical Corporation) was 70% by mass, and polyester resin: Plus Coat Z-561 (manufactured by Gooo Kagaku Kogyo Co., Ltd.). and 5% by mass of Emulgen 420 (manufactured by Kao Corporation) as a surfactant, and the solid concentration of the coating solution was adjusted with water so that the coating thickness after film formation was 30 nm. and used it.

A release layer was coated in the same manner as in Comparative Example 4 on the surface of the primer layer of the base film on which the coating film was formed. The results are shown in Table 2. In addition, as in Comparative Example 4, since the mold release layer was formed using an organic solvent, coating was required in special explosion-proof equipment, and the exhaust treatment of the dried organic solvent was also compared with the example. It became extra necessary.

As shown in Table 2, in Examples 1 to 7, release films were obtained in which both the releasability and wettability of the release layer were easily achieved, and the release layer had good coating uniformity and recyclability. On the other hand, in Comparative Examples 1 and 2 in which the molecular weight of silicone was large, coating uniformity tended to deteriorate, ceramic sheet releasability tended to become difficult to peel, and recyclability also deteriorated. In Comparative Example 3, in which the release layer was formed using an aqueous coating solution that did not contain polyvinyl alcohol, the adhesion of the release layer was reduced.

Furthermore, in Comparative Examples 4 and 5, in which the release layer was formed off-line using a solvent-based coating liquid and silicone having a large molecular weight was used, wettability and recyclability were deteriorated. In particular, in Comparative Example 4, the adhesion of the release layer was also reduced.

The release film of the present invention has high coating uniformity and peelability of the release layer, has relatively good wettability, is easy to use as a film for various processes, is recyclable, and can reduce the burden on the environment. Its industrial value is extremely high.

Claims (9)

A release film comprising a base film and a release layer formed by reacting and solidifying an aqueous coating composition,
The aqueous coating composition includes an alkenyl group-containing silicone having a number average molecular weight of 1,000 or more and less than 10,000, which has two or more alkenyl groups in the molecule and may have a Q unit represented by SiO _4/2 ; A release film comprising an Si-H group-containing silicone having a number average molecular weight of 1,000 to 5,000 and having two or more Si-H groups therein, and a polyvinyl alcohol resin. The polyvinyl alcohol resin has a viscosity of 5 mPa·s or more and 50 mPa·s or less and a saponification degree of 85 mol% or more and 99 mol% or less when an aqueous solution with a concentration of 4% by mass is measured at a temperature of 20°C. Item 1. The release film according to item 1. The release film according to claim 1 or 2, wherein the alkenyl group-containing silicone has a Q unit represented by SiO _4/2 . The release film according to any one of claims 1 to 3, wherein the alkenyl group-containing silicone is represented by the following general formula (I).
(In general formula (I), R ¹ is an alkenyl group having 2 to 8 carbon atoms, or a monovalent hydrocarbon having 1 to 16 carbon atoms containing an alkyl group or an aryl group, which may be the same or different. One or more of R ¹ bonded to the silicon atom represented by [SiO] _b1 is an alkenyl group having 2 to 8 carbon atoms, and R ² is an alkyl group or It is a monovalent hydrocarbon group containing an aryl group and having 1 to 16 carbon atoms, and Y ¹ may be the same or different and is represented by the general formula (Ia).
(In general formula (Ia), R ¹ is the same as R ¹ in general formula (I), and may be the same or different.)
In the entire general formula (I) including ^Y1 , when all silicon atoms including terminals are 100 mol%, a1 is 50 mol% or more and 98 mol% or less, b1 is 0 mol% or more and 10 mol% or less, c1 is 0 mol% or more and 30 mol% or less, and d1 is 0 mol% or more and 50 mol% or less. In the entire general formula (I) including Y ¹ , two or more of R ¹ are alkenyl groups having 2 or more and 8 or less carbon atoms. ) The release film according to any one of claims 1 to 4, wherein the Si--H group-containing silicone is represented by the following general formula (II).
(In general formula (II), R ³ is a monovalent hydrocarbon group having 1 to 16 carbon atoms and containing an alkyl group or an aryl group, which may be the same or different, and a2+b2 is 100 mol%. (In this case, a2 is 30 mol% or more and 90 mol% or less, and b2 is 10 mol% or more and 70 mol% or less.) The aqueous coating composition according to any one of claims 1 to 5, wherein the aqueous coating composition contains 1 part by mass or more and 50 parts by mass or less of the Si-H group-containing silicone based on 100 parts by mass of the alkenyl group-containing silicone. Release film. The release layer is formed by applying the aqueous coating composition to the base film before the crystal orientation is completed, stretching it in at least one direction, and then heat-treating it to complete the crystal orientation. , the release film according to any one of claims 1 to 6. The release film according to any one of claims 1 to 7, wherein the base film is a polyester film. The release film according to any one of claims 1 to 8, wherein the release film is a release film for a multilayer ceramic capacitor or a release film for a resin sheet.