JP2023089432A - Peelable sheet - Google Patents

Abstract

To provide a peelable sheet which suppresses unintended peeling from an object before a change of a state, and exhibits excellent peelability after the change of the state, even in the case in which the state of the object is changed (for example, cured).SOLUTION: A peelable sheet has a base material, and a peeling agent layer provided on at least one surface side of the base material, wherein the peeling agent layer is formed of a peeling agent composition containing an acrylic resin, a melamine resin and an epoxy group-containing component having an epoxy group, the epoxy equivalent of the epoxy group-containing component is 600 or more, and the content of the epoxy group-containing component in the peeling agent composition is 10 mass% or more and 70 mass% or less.SELECTED DRAWING: None

Description

The present invention relates to release sheets.

In general, a release sheet (sometimes referred to as a "process film") has a substrate such as paper, plastic film, polyethylene-laminated paper, etc., and a release agent layer provided on the substrate. The release agent layer is formed by applying a release agent composition onto a substrate and drying or curing the resulting coating film.

The release sheet is widely used as, for example, a protective sheet for the adhesive layer of an adhesive sheet or the like, a process film for producing a resin sheet, a process film for forming a ceramic green sheet, a process film for producing synthetic leather, etc. (e.g. , Patent Documents 1 to 5).

WO2009/122984 JP 2018-104661 A JP 2019-171617 A JP 2020-146890 A JP 2020-153022 A

By the way, depending on the object to be laminated on the surface of the release sheet on the release agent layer side (hereinafter sometimes referred to as "release surface"), the release sheet may be removed from the object due to changes in the state of the object. It may become difficult to peel off.

For example, when a release sheet is used to protect an adhesive layer composed of a curable adhesive, the release sheet may be peeled off from the adhesive layer after the adhesive layer is cured. . Peeling in this case may be more difficult than peeling from an uncured adhesive layer.

In order to achieve good release from the adhesive layer after curing, it is conceivable to use a release sheet with very high releasability. becomes easy to occur. If such unintended peeling occurs, the original function of the release sheet, such as protection of the adhesive layer, cannot be sufficiently achieved.

The present invention has been made in view of such a situation, and even when the state of the object changes (for example, when it hardens), it suppresses unintended detachment from the object before the state change, and the state An object of the present invention is to provide a release sheet exhibiting excellent release properties after being changed.

In order to achieve the above object, the first aspect of the present invention is a release sheet comprising a substrate and a release agent layer provided on at least one side of the substrate, wherein the release agent layer is , an acrylic resin, a melamine resin, and a release agent composition containing an epoxy group-containing component having an epoxy group, wherein the epoxy equivalent of the epoxy group-containing component is 600 or more, and the release agent composition A release sheet is provided in which the content of the epoxy group-containing component in the product is 10% by mass or more and 70% by mass or less (Invention 1).

In the release sheet according to the above invention (Invention 1), since the release agent layer is formed from the above-described release agent composition, even when the target is a curable adhesive layer, for example, before curing, can exhibit excellent peelability after curing while suppressing unintended peeling from the object.

In the above invention (invention 1), the release agent composition preferably contains polyorganosiloxane (invention 2).

In the above inventions (inventions 1 and 2), the epoxy equivalent of the epoxy group-containing component is preferably 16000 or less (invention 3).

In the above inventions (Inventions 1 to 3), the melamine resin is preferably a full-ether type methylated melamine resin (Invention 4).

In the above inventions (Inventions 1 to 4), the stripping composition preferably contains an acid catalyst (Invention 5).

The release sheet according to the present invention suppresses unintended release from the object before the state change even when the state of the object changes (for example, when it is cured), and exhibits excellent peelability after the state change. Demonstrate.

Embodiments of the present invention will be described below.
A release sheet according to one embodiment of the present invention comprises a substrate and a release agent layer provided on one side of the substrate.

In the release sheet according to this embodiment, the release agent layer is formed from a release agent composition containing an acrylic resin, a melamine resin, and an epoxy group-containing component having an epoxy group. The epoxy equivalent of the epoxy group-containing component is 600 or more, and the content of the epoxy group-containing component in the release agent composition is 10% by mass or more and 70% by mass or less.

The release sheet according to the present embodiment exhibits excellent releasability due to the release agent layer formed from the release agent composition. In particular, when the release agent composition contains an epoxy group-containing component exhibiting the epoxy equivalent weight within the above range, it exhibits excessive release properties to the target before the state change (for example, before curing). is suppressed, and unintentional peeling of the release sheet from the object is suppressed satisfactorily. On the other hand, since the release agent composition contains the acrylic resin and the melamine resin, the releasability from the target after the state change is improved, and the release agent composition can be easily released from the target.

1. Substrate The substrate in the release sheet according to this embodiment is not particularly limited, and any substrate can be appropriately selected and used from conventionally known substrates. As such a substrate, for example, a plastic film, paper, or the like can be used. Examples of the plastic film include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene and polymethylpentene, and plastic films such as polycarbonate and polyvinyl acetate. These plastic films may be a single layer or a multilayer of two or more layers of the same or different types. Among these, a polyester film is preferable, and a polyethylene terephthalate film is particularly preferable. Polyethylene terephthalate film is less likely to generate dust during processing, use, etc., and thus can effectively prevent coating failures due to dust, etc., for example. Examples of the paper include fine paper, glassine paper, impregnated paper, coated paper, and the like.

In addition, for the purpose of improving adhesion to the release agent layer provided on the surface of the base material, one or both sides of the base material may optionally be subjected to a surface treatment such as an oxidation method or roughening method, or a primer treatment. can be done. Examples of the oxidation method include corona discharge treatment, plasma discharge treatment, chromium oxidation treatment (wet), flame treatment, hot air treatment, ozone, and ultraviolet irradiation treatment. A thermal spraying method and the like can be mentioned. These surface treatment methods are appropriately selected according to the type of substrate, but generally corona discharge treatment is preferably used from the viewpoint of effectiveness and operability.

The thickness of the substrate is preferably 10 μm or more, particularly preferably 15 μm or more, and more preferably 20 μm or more. Also, the thickness is preferably 300 μm or less, particularly preferably 200 μm or less, further preferably 125 μm or less.

2. Release agent layer 2-1. Components As described above, the release agent layer of the present embodiment is formed from a release agent composition containing an acrylic resin, a melamine resin, and an epoxy group-containing component having an epoxy group. The release agent composition may contain other components, and in particular, it is preferable to contain polyorganosiloxane from the viewpoint of adjustment of release properties (in particular, improvement of release properties for objects after state change). . Further, the release agent composition preferably contains an acid catalyst from the viewpoint of facilitating the formation of a well-cured release agent layer by promoting the reaction between the melamine resins and between the melamine resin and other components.

(1) Acrylic resin The acrylic resin in the present embodiment is not particularly limited, and for example, a (meth)acrylic acid ester polymer can be preferably used. The monomer constituting the (meth)acrylic acid ester polymer is not particularly limited, and examples thereof include (meth)acrylic acid alkyl esters and monomers having a hydroxy group in the molecule (hydroxy group-containing monomers).

As the (meth)acrylic acid alkyl ester, for example, a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms can be used. (meth) methyl acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, (meth) ) 2-ethylhexyl acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, (meth)acrylic and stearyl acid. Among these, it is preferable to use at least one of methyl (meth)acrylate and n-butyl (meth)acrylate from the viewpoint of easily exhibiting the desired releasability. In addition, these may be used independently and may be used in combination of 2 or more type.

The (meth)acrylic acid ester polymer preferably contains 10% by mass or more, more preferably 25% by mass or more, of the (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer. , It is particularly preferable to contain 30% by mass or more. In addition, the (meth)acrylic acid ester polymer preferably contains 95% by mass or less, particularly 90% by mass or less, of the (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer. Preferably, it is contained in an amount of 85% by mass or less. Within these ranges, the release sheet according to the present embodiment can easily exhibit desired release properties.

Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, (Meth)acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate. Among these, it is preferable to use 2-hydroxyethyl (meth)acrylate from the viewpoint of easily exhibiting the desired peelability. In addition, these may be used independently and may be used in combination of 2 or more type.

The (meth)acrylic acid ester polymer preferably contains 5% by mass or more, particularly preferably 10% by mass or more, more preferably 15% by mass or more of a hydroxy group-containing monomer as a monomer unit constituting the polymer. It is preferable to contain more than mass %. In addition, the (meth)acrylic acid ester polymer preferably contains 90% by mass or less, particularly preferably 75% by mass or less, of a hydroxy group-containing monomer as a monomer unit constituting the polymer. is preferably contained in an amount of 70% by mass or less. Within these ranges, the release sheet according to the present embodiment can easily exhibit desired release properties.

If desired, the (meth)acrylic acid ester polymer may contain other monomers as monomer units constituting the polymer. Examples of such monomers include monomers having a carboxy group in the molecule (carboxy group-containing monomer), monomers having an amino group in the molecule (amino group-containing monomer), and monomers having an alicyclic structure in the molecule (alicyclic Formula structure-containing monomers), non-reactive nitrogen atom-containing monomers such as N-acryloylmorpholine and N-vinyl-2-pyrrolidone, (meth) acrylics such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate acid alkoxyalkyl esters, vinyl acetate, styrene, and the like. These may be used alone or in combination of two or more.

The (meth)acrylate polymer is preferably a solution polymer obtained by a solution polymerization method. Moreover, the polymerization mode of the (meth)acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.

The weight average molecular weight of the (meth)acrylate polymer is preferably 10,000 or more, particularly preferably 20,000 or more, and further preferably 30,000 or more. The weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 1,000,000 or less, particularly preferably 500,000 or less, further preferably 250,000 or less. Within these ranges, the release sheet according to the present embodiment can easily exhibit desired release properties. In addition, the weight average molecular weight in this specification is the value of standard polystyrene conversion measured by the gel permeation chromatography (GPC) method.

The acrylic resin ((meth)acrylic acid ester polymer) in the present embodiment may be modified with desired components. Suitable examples in this case include polyorganosiloxane-modified acrylic resins. By using the polyorganosiloxane-modified acrylic resin, it becomes easy to adjust the releasability of the release sheet according to the present embodiment within a desired range.

The content of the acrylic resin in the release agent composition is preferably 7.5% by mass or more, particularly preferably 10% by mass or more, further preferably 15% by mass or more. Also, the content is preferably 65% by mass or less, particularly preferably 60% by mass or less, and further preferably 55% by mass or less. When the content of the acrylic resin is within these ranges, the release sheet according to the present embodiment can easily exhibit desired release properties.

(2) Melamine resin In general, "melamine resin" means a mixture containing multiple types of melamine compounds and/or polynuclear compounds formed by condensation of the melamine compounds. As used herein, the term "melamine resin" shall mean the above mixture or aggregate of one melamine compound.

Specifically, the melamine resin in the present embodiment preferably contains a melamine compound represented by the following general formula (a) or a polynuclear compound obtained by condensing two or more such melamine compounds.

In formula (a), X preferably represents —H, —CH ₂ —OH, or —CH ₂ —OR, and R preferably represents an alkyl group having 1 to 8 carbon atoms. The number of carbon atoms is preferably 1 to 6, particularly preferably 1 to 3. Examples of alkyl groups having 1 to 8 carbon atoms include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group and the like, with methyl group being particularly preferred.

Note that melamine compounds generally include full ether type compounds in which all Xs are —CH ₂ —OR, imino compounds in which at least one X is —CH ₂ —OH and at least one X is H. Methylol forms, absent methylol forms where at least one X is —CH ₂ —OH and H and where X is present, and where X is present where at least one X is H and —CH ₂ —OH There is a type such as an imino type that does not. Although the melamine resin according to the present embodiment may be based on any of these types of melamine compounds, it is a full-ether-type methylated melamine resin from the viewpoint that it is particularly easy to exhibit the desired peelability. is preferred.

The weight average molecular weight of the melamine resin in the present embodiment is preferably 150 or more, particularly preferably 300 or more, further preferably 500 or more. The weight average molecular weight is preferably 10,000 or less, particularly preferably 5,000 or less, and further preferably 4,000 or less. When the weight-average molecular weight is 150 or more, the reaction rate between melamine resins and between melamine resins and other components is stabilized, and a smoother release surface can be formed. Further, when the weight average molecular weight is 10,000 or less, the viscosity of the release agent composition is moderately low, and the coating liquid of the release agent composition can be easily applied onto the substrate.

The content of the melamine resin in the release agent composition is preferably 4% by mass or more, particularly preferably 6% by mass or more, and further preferably 8% by mass or more. Also, the content is preferably 30% by mass or less, particularly preferably 25% by mass or less, and further preferably 20% by mass or less. When the content of the melamine resin is within these ranges, the release sheet according to the present embodiment can easily exhibit desired release properties.

(3) Epoxy group-containing component The epoxy group-containing component in the present embodiment is not particularly limited as long as it has an epoxy group so as to satisfy the above-mentioned epoxy equivalent, and in particular at least one of epoxy resin and phenoxy resin is used. preferably. As used herein, the term "epoxy resin" refers to a curable epoxy resin, that is, an uncured epoxy resin.

Known epoxy resins can be used, for example, polyfunctional epoxy resins, biphenyl compounds, bisphenol A diglycidyl ether and hydrogenated products thereof, o-cresol novolak type epoxy resins, dicyclopentadiene type epoxy resins, and biphenyl type epoxy resins. Difunctional or higher epoxy compounds such as epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenylene skeleton type epoxy resins, and the like are included. These may be used alone or in combination of two or more.

Known phenoxy resins can be used. resins, phenoxy resins containing a fluorene skeleton, phenoxy resins containing a biphenyl skeleton, phenoxy resins containing an anthracene skeleton, phenoxy resins containing a pyrene skeleton, phenoxy resins containing a xanthene skeleton, phenoxy resins containing an adamantane skeleton, Examples include phenoxy resins containing a dicyclopentadiene skeleton. These may be used alone or in combination of two or more.

As described above, the epoxy equivalent of the epoxy group-containing component is 600 or more, but from the viewpoint of further improving the peelability from the target after the state change (especially curing), the epoxy equivalent is preferably 3000 or more. , particularly preferably 7000 or more. In addition, the epoxy equivalent of the epoxy group-containing component is preferably 17,500 or less, particularly preferably 16,000 or less, further preferably 15,000, from the viewpoint of preventing unintended peeling of the release sheet from the object before the state change. The following are preferable.

Moreover, as described above, the content of the epoxy group-containing component in the release agent composition is 10% by mass or more and 70% by mass or less. In particular, from the viewpoint of preventing unintentional peeling of the release sheet from the object before the state change, the content of the epoxy group-containing component in the release agent composition is preferably 15% by mass or more, particularly 20% by mass. It is preferable that it is above. Moreover, from the viewpoint of further improving the releasability from the object after the state change, the content is preferably 75% by mass or less, and particularly preferably 70% by mass or less.

(4) Polyorganosiloxane When the release agent composition in the present embodiment contains polyorganosiloxane, the polyorganosiloxane is not particularly limited as long as it can impart desired release properties to the release agent layer. . A polymer of a silicon-containing compound represented by the following general formula (b) can be preferably used as the polyorganosiloxane.

In formula (b), m is an integer of 1 or more. In formula (b), R ¹ to R ⁸ are preferably alkyl groups, aryl groups or alkenyl groups. R ¹ to R ⁸ may be the same or different. In addition, when multiple R ¹ and R ² are present, R ¹ and R ² may be the same or different between repeating units.

The alkyl group is preferably an alkyl group having 1 to 8 carbon atoms, and examples thereof include methyl, ethyl, propyl, butyl, pentyl, hexyl and octyl groups. Among these, the alkyl group is preferably a methyl group.

The aryl group is preferably an aryl group having 6 to 8 carbon atoms, such as a phenyl group and a methylphenyl group. In particular, the polyorganosiloxane in the present embodiment preferably has a phenyl group as the aryl group from the viewpoint of easily achieving the desired peelability.

Preferred examples of the alkenyl group include vinyl group, allyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group and octenyl group. Among these, the alkenyl group is preferably a vinyl group.

In the above formula (b), at least one of R ¹ to R ⁸ may be an organic group. The term "organic group" as used herein refers to a group that does not contain the aforementioned alkyl group, aryl group and alkenyl group. Examples of such organic groups include organic groups having repeating structures such as polyether, polyester and polyurethane. In such an organic group, one terminal atom of each polyether, polyester, polyurethane, etc. is bonded to the terminal of polyorganosiloxane or the silicon atom in the chain.

The weight average molecular weight of the polyorganosiloxane is preferably 100 or more, particularly preferably 500 or more, further preferably 1000 or more. When the weight-average molecular weight is 100 or more, the polyorganosiloxane easily lowers the surface free energy on the release surface of the release agent layer, and the desired release property can be easily achieved. Also, the weight average molecular weight is preferably 1,000,000 or less, particularly preferably 500,000 or less, further preferably 100,000 or less. When the weight-average molecular weight is 1,000,000 or less, the compatibility between the polyorganosiloxane and other components is improved, and a release agent layer having an excellent surface condition can be easily formed.

When the release agent composition contains polyorganosiloxane, the content of polyorganosiloxane in the release agent composition is preferably 0.1% by mass or more, particularly 0.3% by mass or more. is preferred, and more preferably 0.5% by mass or more. Also, the content is preferably 30% by mass or less, particularly preferably 20% by mass or less, and further preferably 10% by mass or less. When the content of the polyorganosiloxane is within these ranges, the release sheet according to the present embodiment can easily exhibit desired release properties.

(5) Acid catalyst When the release agent composition in the present embodiment contains an acid catalyst, as long as the acid catalyst can promote the condensation reaction between the melamine resins and the reaction between the melamine resin and other components. , is not particularly limited.

As examples of the acid catalyst, it is preferable to use at least one of a sulfonic acid-based catalyst and a phosphoric acid-based catalyst. Examples of sulfonic acid catalysts include p-toluenesulfonic acid, methanesulfonic acid, dodecylbenzenesulfonic acid, etc. Among these, p-toluenesulfonic acid is preferred. Examples of phosphoric acid-based catalysts include phosphoric acid and phosphorous acid. Examples of acid catalysts other than those mentioned above include hydrochloric acid, sulfuric acid, nitric acid, and the like. These may be used alone or in combination of two or more. Among these, it is preferable to use p-toluenesulfonic acid.

When the release agent composition contains an acid catalyst, the content of the acid catalyst in the release agent composition is preferably 0.1% by mass or more, particularly preferably 0.25% by mass or more. , and more preferably 0.5% by mass or more. Also, the content is preferably 10% by mass or less, particularly preferably 7.5% by mass or less, and further preferably 5% by mass or less. When the content of the acid catalyst is within these ranges, the condensation reaction between the melamine resins and the reaction between the melamine resin and other components are effectively promoted, and a well-cured release agent layer can be easily formed. becomes.

(6) Other Components In addition to the components described above, the release agent composition may contain fillers, dispersants, cross-linking agents, antistatic agents, reaction inhibitors, adhesion improvers, lubricants, and the like.

2-2. Production of release agent composition The release agent composition is produced by mixing the above acrylic resin, melamine resin, epoxy group-containing component, and optionally polyorganosiloxane, acid catalyst or other components. can be done. The resulting release agent composition may be diluted with a diluting solvent as necessary to prepare a coating liquid.

Examples of the diluent solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; , alcohols such as 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, cyclohexanone, propylene glycol monomethyl ether acetate, ethyl acetate, esters such as butyl acetate, cellosolve solvents such as ethyl cellosolve, Alternatively, a mixture thereof or the like is used.

The concentration/viscosity of the coating liquid thus prepared is not particularly limited as long as it is within a range that allows coating, and can be appropriately selected according to the situation. For example, the concentration of the release agent composition is diluted to 3% by mass or more and 60% by mass or less. When obtaining the coating liquid, the addition of a diluent solvent or the like is not a necessary condition, and the diluent solvent may not be added as long as the release agent composition has a viscosity that allows coating.

2-3. Thickness of Release Agent Layer In the release sheet according to the present embodiment, the thickness of the release agent layer is preferably 30 nm or more, particularly preferably 70 nm or more, further preferably 100 nm or more. Also, the thickness is preferably 5 μm or less, particularly preferably 3 μm or less, further preferably 1 μm or less. When the thickness of the release agent layer is within these ranges, the desired release property can be easily exhibited.

3. Physical properties of release sheet, etc. In the release sheet according to the present embodiment, the release force to the epoxy adhesive layer (before curing) is preferably 200 mN/50 mm or more, and particularly preferably 300 mN/50 mm or more. Furthermore, it is preferably 400 mN/50 mm or more. Within these ranges, it becomes easier to suppress unintended peeling of the release sheet from the object. On the other hand, the peel force is preferably 20,000 mN/50 mm or less, particularly preferably 18,000 mN/50 mm or less, further preferably 15,000 mN/50 mm or less. Within these ranges, even when the release sheet is peeled from the object before the state change, it can be easily peeled off. In addition, the method for measuring the peel force is as described in the test examples described later.

On the other hand, in the release sheet according to the present embodiment, the release force to the epoxy adhesive layer after curing is preferably 500 mN/50 mm or less, particularly preferably 400 mN/50 mm or less, and further preferably 300 mN/50 mm. The following are preferable. Within these ranges, the release sheet can be easily peeled off from the object after the state change. The lower limit of the peel force is not particularly limited, and may be, for example, 150 mN/50 mm or more, particularly 100 mN/50 mm or more, and further 50 mN/50 mm or more. In addition, the method for measuring the peel force is as described in the test examples described later.

The peel force reduction rate (%) calculated based on the following formula based on the peel force to the epoxy adhesive layer (before curing) and the peel force to the epoxy adhesive layer after curing is 50. % or more, particularly preferably 60% or more, more preferably 70% or more. According to the release sheet of the present embodiment, such a release force reduction rate can be realized by forming the release agent layer from the release agent composition described above. The upper limit of the peel force reduction rate is not particularly limited, and may be, for example, less than 100%, particularly 99% or less, or further 98% or less.
Peel force reduction rate (%) = (Peel force A - Peel force B) / Peel force A × 100
In the formula, the peel force A represents the peel force to the epoxy adhesive layer (before curing), and the peel force B represents the peel force to the epoxy adhesive layer after curing.

4. Method for Manufacturing Release Sheet The method for manufacturing the release sheet in the present embodiment is not particularly limited as long as it includes forming a release agent layer from the release agent composition described above. For example, after coating one side of the substrate with a coating liquid containing the aforementioned release agent composition and optionally an organic solvent, the resulting coating film is dried and heated to cure the release agent composition. to form a release agent layer, thereby obtaining a release sheet.

Specific coating methods include, for example, gravure coating, bar coating, spray coating, spin coating, knife coating, roll coating, and die coating.

The organic solvent is not particularly limited, and various solvents can be used. Examples include hydrocarbon compounds such as toluene, hexane and heptane, isopropyl alcohol, isobutyl alcohol, acetone, ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone and mixtures thereof. In particular, it is preferable to use a mixture of methyl ethyl ketone and isopropyl alcohol.

The release agent composition coated as described above is preferably heat-cured. The heating temperature in this case is preferably 70° C. or higher, particularly preferably 100° C. or higher. Moreover, the heating temperature is preferably 220° C. or lower, particularly preferably 200° C. or lower. The heating time for thermosetting is preferably 5 seconds or longer, and particularly preferably 15 seconds or longer. Also, the heating time is preferably 120 seconds or less, particularly preferably 90 seconds or less.

5. Usage of Release Sheet The release sheet according to the present embodiment can be used, for example, as a protective sheet for various adhesives such as adhesive sheets. It can also be used as a process film when producing various resin sheets, ceramic green sheets, synthetic leathers, various composite materials, and the like. Furthermore, it can also be used as a transfer sheet when producing an electromagnetic wave shielding film or the like.

When the release sheet according to the present embodiment is used as a process film or a transfer sheet, various sheet materials formed by applying an adhesive composition, resin, or the like to the release layer side surface of the release sheet are used as the release sheet. Used in the process of peeling from.

As described above, the release sheet according to the present embodiment enables good release even when the object changes state. Therefore, it is preferable to use the release sheet according to the present embodiment for an object that can cause such a change in state. For example, it is suitable for use in curable adhesives and pressure sensitive adhesives, and particularly suitable for use in thermosetting adhesives and pressure sensitive adhesives. Specific target examples include epoxy-based adhesives and urethane-based adhesives.

The embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiment is meant to include all design changes and equivalents that fall within the technical scope of the present invention.

For example, another layer such as an antistatic layer may be provided on the side of the base material of the release sheet opposite to the release agent layer or between the base material and the release agent layer.

EXAMPLES The present invention will be described in more detail with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

[Example 1]
(1) Preparation of acrylic resin 60 parts by mass of n-butyl methacrylate, 30 parts by mass of 2-hydroxyethyl methacrylate, and 10 parts by mass of methyl methacrylate are polymerized by a solution polymerization method to obtain an acrylic copolymer ( acrylic resin) was obtained. When the weight average molecular weight of the acrylic resin was measured by the following method, it was 50,000.

The weight average molecular weight (Mw) described above is a polystyrene-equivalent weight average molecular weight measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement).
<Measurement conditions>
・ GPC measurement device: HLC-8320 manufactured by Tosoh Corporation
・ GPC column (passed in the following order): TSK gel superH-H manufactured by Tosoh Corporation
TSK gel super HM-H
TSK gel super H2000
・Measurement solvent: tetrahydrofuran ・Measurement temperature: 40°C

(2) Preparation of release agent composition 28.0 parts by mass of the acrylic resin obtained in the above step (1) (in terms of solid content, the same applies hereinafter), and a full ether type methylated melamine resin (hexamethoxy methylated melamine) 12.0 parts by mass, 1.20 parts by mass of phenyl-modified polyorganosiloxane (polyorganosiloxane having a phenyl group introduced into the side chain) as a polyorganosiloxane, and an epoxy resin as an epoxy group-containing component (manufactured by Mitsubishi Chemical Corporation, "YX7200B35", phenoxy type, special type, epoxy equivalent: 9500) 60.0 parts by mass, and p-toluenesulfonic acid as an acid catalyst (manufactured by Shin-Etsu Chemical Co., Ltd., product name "CAT-PS- 80") was mixed in a mixed solvent of anone and methyl ethyl ketone (mass ratio 1:1) to obtain a coating liquid of a release agent composition having a solid content concentration of 4.0% by mass.

(3) Preparation of release sheet The obtained coating liquid of the release agent composition was applied to a polyethylene terephthalate (PET) film having a thickness of 50 μm (Mitsubishi Chemical Co., product name “PET50T-100”) using a Meyer bar #4. to form a coating film. The coating film was cured by drying at 150° C. for 1 minute to form a release agent layer with a thickness of 100 nm. As a result, a release sheet was obtained in which the substrate and the release agent layer were laminated.

[Examples 2 to 7 and Comparative Examples 1 to 4]
A release sheet was prepared in the same manner as in Example 1, except that the amount of the acrylic resin, the amount of the melamine resin, the amount of the polyorganosiloxane, and the type and amount of the epoxy group-containing component were changed as shown in Table 1. manufactured. In addition, in Comparative Example 4, no epoxy group-containing component was used.

[Test Example 1] (Measurement of peel strength)
The release sheets obtained in Examples and Comparative Examples were exposed to a high temperature environment of 40° C. for 7 days. Then, after cutting a sheet provided with an epoxy adhesive layer (manufactured by Lintec, product name “LE4777H”) to a width of 50 mm, the epoxy adhesive layer of the sheet is applied to the release surface of the release sheet after exposure. A thermal laminator (heating conditions: 60° C., 1 m/min) was used for transfer. Subsequently, a polyimide film (manufactured by Toray DuPont, product name “Kapton 100PI”) is attached to the surface of the transferred epoxy-based adhesive layer opposite to the release sheet, and the polyimide film and the epoxy-based adhesive are adhered. A laminate consisting of an agent layer and a release sheet was obtained.

Subsequently, the release sheet side of the laminate was fixed to a flat plate with a double-sided tape. Then, it was placed vertically on the ground in a peeling tester (manufactured by Shimadzu Corporation, product name: "Autograph AGS-20NX"). Then, according to JIS K6854: 1999, at a tensile speed of 0.3 m / min in the direction of 180 °, leaving the release sheet, only the polyimide film and the epoxy adhesive layer were peeled off, and the peel force at that time (mN/50mm) was measured. The results are shown in Table 1 as peel strength in the "normal state". Incidentally, when the peel force was 20000 mN/50 mm or more, it was described as "Peelable" in Table 1.

Also, the laminate prepared in the same manner as above was hot-pressed using a hot press (heating conditions: 150° C., 30 min). The peel force (mN/50 mm) was measured in the same manner as above for the laminate after the hot press. The results are shown in Table 1 as peel strength "after hot pressing".

Based on the peel force in the "normal state" and the peel force "after hot press" measured as described above, the peel force reduction rate (%) was calculated from the following formula. The results are also shown in Table 1.
Peel force reduction rate (%) = (Peel force in "normal state" - Peel force in "after hot press") / Peel force in "normal state" x 100

Details of abbreviations and the like in Table 1 are as follows.
[Epoxy group-containing component]
YX7200B35: Epoxy resin (manufactured by Mitsubishi Chemical Corporation, "YX7200B35", phenoxy type, special type, epoxy equivalent: 9500)
1256B40: epoxy resin (manufactured by Mitsubishi Chemical Corporation, "1256B40", phenoxy type, bis A type, epoxy equivalent: 7350)
YX7553BH30: Epoxy resin (manufactured by Mitsubishi Chemical Corporation, "YX7553BH30", phenoxy type, special type, epoxy equivalent: 12500)
872X75: Epoxy resin ("872X75" manufactured by Mitsubishi Chemical Corporation, flexible type, epoxy equivalent: 650)
YX8034: epoxy resin (manufactured by Mitsubishi Chemical Corporation, "YX8034", high-purity hydrogenated epoxy resin, epoxy equivalent: 270)
YX8000: Epoxy resin (manufactured by Mitsubishi Chemical Corporation, "YX8000", high-purity hydrogenated epoxy resin, epoxy equivalent: 205)

As is clear from Table 1, the release sheets obtained in Examples exhibit excellent releasability in that they can be easily releasable in the "after hot press" state while suppressing unintended release in the "normal state." found to perform.

The release sheet of the present invention is suitable for use as a release sheet for curable adhesives and adhesives.

Claims (5)

A release sheet comprising a substrate and a release agent layer provided on at least one side of the substrate,
The release agent layer is formed from a release agent composition containing an acrylic resin, a melamine resin, and an epoxy group-containing component having an epoxy group,
The epoxy equivalent of the epoxy group-containing component is 600 or more,
A release sheet, wherein the content of the epoxy group-containing component in the release agent composition is 10% by mass or more and 70% by mass or less. The release sheet according to claim 1, wherein the release agent composition contains polyorganosiloxane. 3. The release sheet according to claim 1, wherein the epoxy group-containing component has an epoxy equivalent of 16,000 or less. The release sheet according to any one of claims 1 to 3, wherein the melamine resin is a full-ether type methylated melamine resin. The release sheet according to any one of claims 1 to 4, wherein the release agent composition contains an acid catalyst.