JP6596789B2 - Release sheet - Google Patents

Description

  The present invention relates to a release sheet having an anchor coat layer and a release layer, and relates to a release sheet substantially free of a silicone compound and a fluorine-containing compound in both the anchor coat layer and the release layer.

  Electronic parts such as relays, various switches, connectors, motors, and hard disks are widely used in various products. An adhesive sheet is used for such a temporary fixing when assembling such electronic parts and displaying the contents of the parts. Before the adhesive sheet is attached to the electronic component, the release sheet is attached, the release sheet is peeled off, and the adhesive sheet is attached to the electronic component.

  In a semiconductor device that is desired to be small, thin, and lightweight, a release sheet provided with an adhesive layer is also used when forming an electronic circuit and a mounting pad. Electronic circuits and mounting pads are laminated with a heat-resistant film such as a polyimide film on the adhesive layer of the release sheet, then peeled off the release sheet, and then laminated with a copper foil on the surface of the adhesive layer. After curing, the copper foil is finally etched to manufacture an electronic circuit and a mounting pad.

  Release sheets used for manufacturing electronic components, electronic circuits, mounting pads, and the like may contain a silicone compound such as a silicone resin or a fluorine-containing compound in the release agent layer. Silicone compounds such as silicone resin, siloxane, and silicone oil migrate to the surface of the pressure-sensitive adhesive sheet or pressure-sensitive adhesive layer to which the release sheet is attached. The silicone compound transferred to the pressure-sensitive adhesive sheet or the pressure-sensitive adhesive layer is gradually vaporized, and the vaporized silicone compound is deposited on the surface of the electrical contact portion by, for example, an arc generated near the electrical contact portion of the electronic component, A fine silicon oxide compound layer is formed. As described above, when the silicon oxide compound layer is deposited on the surface of the electrical contact portion, it may cause a conduction failure or the like. Also, release sheets containing a fluorine-containing compound in the release agent layer are often heavy release compared to silicone release agents, and dehalogenation is desired to reduce the environmental burden in waste treatment. It does not fit even in the current situation.

  In view of the influence of the silicone compound and the like, the release sheet is a release film in which the release agent layer formed on at least one surface of the base sheet is a cured film obtained by curing a 1,4-polybutadiene polymer having functional groups at both ends. Is disclosed (Patent Document 1). This release agent layer is substantially free of a silicone compound.

Moreover, it is a release sheet having a release agent layer, wherein the release agent layer is formed by curing a material mainly composed of a diene polymer, and in accordance with JIS K6300 of a diene polymer before curing. A release sheet having a Mooney viscosity (ML _{1 + 4} (100 ° C.)) measured at 100 ° C. of 40 to 70 is disclosed (Patent Document 2). This release agent layer is substantially free of a silicone compound.

JP 2009-131977 A International Publication No. 2008/047532

However, the release sheet disclosed in Patent Document 1 has a relatively rigid structure in which 1,4-polybutadiene polymer having functional groups at both ends is crosslinked using a methylated melamine resin as a crosslinking agent. The melamine resin it has may be exposed on the outermost surface of the release agent layer. When the release agent layer with a relatively rigid cross-linking agent exposed on the surface has a large interaction with the adhesive layer attached to this release agent layer, it is difficult to achieve light release There is.
In addition, the release sheet described in Patent Document 2 is a diene series having rubber elasticity with a relatively high content of cis-1,4 bonds and a small polarity in order to set the Mooney viscosity before curing within a specific range. Since the release agent containing rubber is applied to the base material and cured by ultraviolet irradiation to form the release agent layer, the adhesion between the base material and the release agent layer is low. Further, even when a release agent layer is formed by curing a release agent containing a diene rubber having rubber elasticity and having a Mooney viscosity before curing, the thickness of the release agent layer is small. In some cases, it is difficult to achieve light peeling by reducing the surface elastic modulus of the release agent layer under the influence of physical properties of a substrate (for example, polyethylene terephthalate (PET) film). On the other hand, if the thickness of the release agent layer is increased so as not to be affected by the physical properties of the substrate, curing due to crosslinking between diene skeletons by ultraviolet irradiation may be insufficient.

  In view of the above problems, the present invention substantially does not contain a silicone compound and a fluorine-containing compound, has good adhesion to a substrate, is rich in flexibility, and has a desired curable property and a light detachability due to a low elastic modulus. It is an object of the present invention to provide a release sheet that can satisfy both requirements. The present invention also provides a release sheet in which the amount of migration of low molecular weight components to the surface of the material used in combination with the release agent layer (hereinafter also referred to as “back migration amount” in the present specification) is suppressed. can do.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a rubber having a functional group at the terminal between a release agent layer obtained by curing a material composed of a diene polymer and a substrate. By providing an anchor coat layer that is a cured film obtained by cross-linking a base elastomer with a cross-linking agent, it is possible to improve the adhesion to the base material, and it is rich in flexibility and light by desired curability and low elastic modulus. The present inventors have found that a release sheet having peelability can be provided and completed the present invention.
That is, the present invention provides the following (1) to (9).
(1) It has a base material, an anchor coat layer on the base material, and a release agent layer on the anchor coat layer, and the anchor coat layer is a rubber-based elastomer having a functional group at the terminal by a crosslinking agent. A release sheet, which is a crosslinked cured film, wherein the release agent layer is a cured film obtained by curing a material composed of a diene polymer.
(2) The release sheet according to (1), wherein the release agent layer has a surface elastic modulus of 0.5 to 15 MPa.
(3) The release sheet according to (1) or (2), wherein the total thickness of the anchor coat layer and the release agent layer is 70 to 550 nm.
(4) The diene polymer is composed of one or two or more diene polymers having no functional group at the terminal and having a cis-1,4 bond content of 90% or more. The release sheet according to any one of (1) to (3).
(5) The release sheet according to any one of (1) to (4), wherein the diene polymer is polybutadiene and / or polyisoprene.
(6) The release sheet according to any one of (1) to (5), wherein the release agent layer is a cured film cured by irradiation with ultraviolet rays.
(7) The rubber-based elastomer is at least one selected from the group consisting of polybutadiene, polyisoprene, styrene-butadiene rubber, styrene-isoprene rubber, acrylonitrile butadiene rubber, polychloroprene and hydrogenated products thereof, and polyisobutylene. The release sheet according to any one of (1) to (6).
(8) The functional group of the rubber elastomer is at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, an isocyanate group, an acryloyl group, and a methacryloyl group. The release sheet according to any one of (7).
(9) The functional group of the rubber elastomer is a hydroxyl group, and the crosslinking agent is a melamine compound, an isocyanate compound, an epoxy compound, an aziridine compound, a hydrazide compound, an oxazoline compound, a carbodiimide compound, urea. The release sheet according to any one of (1) to (8), which is at least one crosslinking agent selected from the group consisting of a system compound, a dialdehyde compound, and a metal chelate compound.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive sheet with a base material can be improved, and the release sheet which is rich in a softness | flexibility and has the light peelability by desired curability and low elastic modulus reduction can be provided. In addition, the release sheet of the present invention is capable of maintaining sufficient film strength while being rich in flexibility, and the amount of components transferred to the back surface of the release agent layer onto the surface of the material used in an overlapping manner with the release agent layer Therefore, it is possible to suppress contamination on the surface of the material used while being overlapped with the release agent layer.

It is explanatory drawing which shows schematic structure of the peeling sheet of this invention.

  The present invention has a base material, an anchor coat layer on the base material, and a release agent layer on the anchor coat layer, and the anchor coat layer is formed by crosslinking a rubber-based elastomer having a functional group at the terminal. The release agent layer is a release sheet that is a cured film obtained by curing a material composed of a diene polymer.

〔Base material〕
As the base material in the release sheet of the present invention, paper such as high-quality paper, clay coated paper, cast coated paper, kraft paper, laminated paper obtained by laminating a thermoplastic resin such as polyethylene resin on these paper, synthetic paper, etc. Paper sheet, polyolefin resin such as polyethylene resin and polypropylene resin; polyester resin such as polybutylene terephthalate resin, polyethylene terephthalate resin and polyethylene naphthalate resin; polyetherimide resin; acetate resin; polystyrene resin; Examples thereof include a resin sheet. The substrate may be a single layer or a multilayer of two or more layers of the same or different types.
Although the thickness of a base material does not have a restriction | limiting in particular, Usually, what is necessary is just 10-300 micrometers, Preferably it is 20-200 micrometers. When the thickness of the substrate is 10 to 300 μm, thermal contraction of the release sheet caused by drying or ultraviolet irradiation when applying the anchor coat layer or the release layer can be suppressed.

  Moreover, when using a synthetic resin as the base material, the surface on which the anchor coat layer of the base material is provided is a method such as an oxidation method or a concavo-convex method as required in order to improve the adhesion between the base material and the anchor coat layer. Thus, surface treatment can be performed. Examples of the oxidation method include corona discharge surface treatment, chromic acid surface treatment (wet), flame surface treatment, hot air surface treatment, ozone / ultraviolet irradiation surface treatment, and the like. Examples of the unevenness method include a sand blast method and a solvent treatment method. These surface treatment methods are appropriately selected according to the type of substrate, but generally, the corona discharge surface treatment method is preferably used from the viewpoints of effects and operability. Moreover, primer treatment can also be performed.

[Anchor coat layer]
The anchor coat layer in the release sheet of the present invention is a cured film obtained by crosslinking a rubber elastomer having a functional group at the terminal with a crosslinking agent.
The rubber-based elastomer used for the anchor coat layer is at least selected from the group consisting of polybutadiene, polyisoprene, styrene-butadiene rubber, styrene-isoprene rubber, acrylonitrile butadiene rubber, polychloroprene and hydrogenated products thereof, and polyisobutylene. One type can be used.
The rubber-based elastomer is preferably a polybutadiene and / or polyisoprene, more preferably a polybutadiene having functional groups at its ends, and even more preferably a functional group at both ends, since it can form a cured film with high flexibility. 1,4-polybutadiene having a group.

The 1,4-polybutadiene having functional groups at both ends is preferably a linear polymer, but may have a small amount of branching. This linear polymer is obtained by polymerizing butadiene by 1,4-addition, and the branched polymer is obtained by polymerizing butadiene by 1,2-addition. In 1,4-polybutadiene having functional groups at both ends, the proportion of units obtained by polymerizing butadiene by 1,4-addition is 50% or more, preferably 70% or more, and more preferably 80% or more.
The number average molecular weight of the 1,4-polybutadiene polymer having functional groups at both ends is preferably from 500 to 20,000, particularly preferably from 1,000 to 12,000. The number average molecular weight of the 1,4-polybutadiene polymer is a value in terms of polystyrene measured by a gel permeation chromatography method (GPC).

The functional group of the rubber-based elastomer is preferably at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, an isocyanate group, an acryloyl group, and a methacryloyl group.
The functional group possessed by the rubber-based elastomer is more preferably at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group and an isocyanate group, and more preferably a hydroxyl group, a carboxyl group and an amino group. At least one functional group selected from the group consisting of, particularly preferably at least one functional group selected from the group consisting of a hydroxyl group and a carboxyl group, and most preferably a hydroxyl group.

The rubber-based elastomer having a functional group at the end constituting the anchor coat layer is cross-linked by a cross-linking agent to form a cured film.
The crosslinking agent is selected according to the type of functional group of the rubber-based elastomer and is not particularly limited as long as a crosslinking reaction is possible.
When the functional group of the rubber-based elastomer is a hydroxyl group, the crosslinking agent may be a melamine compound, isocyanate compound, epoxy compound, aziridine compound, hydrazide compound, oxazoline compound, carbodiimide compound, urea compound. It is preferable that it is at least 1 type of crosslinking agent chosen from the group which consists of a dialdehyde type compound and a metal chelate compound.
When the functional group of the rubber elastomer is a hydroxyl group, the crosslinking agent is more preferably a melamine compound, an isocyanate compound, an epoxy compound, an aziridine compound, a hydrazide compound, an oxazoline compound, a urea compound, and It is at least one crosslinking agent selected from the group consisting of metal chelates, more preferably at least one crosslinking agent selected from the group consisting of melamine compounds, isocyanate compounds and epoxy compounds, particularly preferably melamine. It is at least one crosslinking agent selected from the group consisting of a series compound and an isocyanate series compound. Moreover, when the functional group of the rubber-based elastomer is an acryloyl group or a methacryloyl group, the crosslinking agent may be selected from photoinitiators. Photoinitiators used as these crosslinking agents include benzophenone photoinitiators, alkylphenone photoinitiators, acylphosphine oxide photoinitiators, titanocene photoinitiators, and oxime ester photoinitiators. And thioxanthone photopolymerization initiators.

When the rubber-based elastomer having a functional group at the terminal is 1,4-polybutadiene having a hydroxyl group at both terminals, the cross-linking agent is at least one selected from the group consisting of melamine-based compounds and isocyanate-based compounds. Is preferred. According to this combination, the peeling force can be adjusted by the blending amount of the melamine compound and / or the isocyanate compound, and the crosslinking reaction can be progressed substantially uniformly in the cured film. When the rubber-based elastomer having functional groups at the ends is 1,4-polybutadiene having hydroxyl groups at both ends, the cross-linking agent is more preferably a melamine-based compound, and solvent resistance is obtained by the melamine-based compound. be able to.
The content of the crosslinking agent is preferably 5 to 40 parts by mass, more preferably 8 to 20 parts by mass with respect to 100 parts by mass of 1,4-polybutadiene having hydroxyl groups at both ends as a solid content.

  Examples of melamine compounds include methylolated melamine resins, iminomethylolated melamine resins, methylated melamine resins, ethylated melamine resins, propylated melamine resins, butylated melamine resins, hexylated melamine resins, and octylated melamine resins. An alkylated melamine resin having an alkyl group with 3 or less carbon atoms is preferred, and a methylated melamine resin is particularly preferred.

In order to form the anchor coat layer, it is preferable to use a resin composition for the anchor coat layer containing a rubber-based elastomer having a functional group at the terminal and a crosslinking agent.
The resin composition for the anchor coat layer may contain an acidic catalyst. By using an acidic catalyst, the adhesion between the substrate and the anchor coat layer can be improved. The acid catalyst is not particularly limited, it can be appropriately selected from known acidic catalyst. As such an acidic catalyst, for example, an organic acidic catalyst such as p-toluenesulfonic acid, methanesulfonic acid, and alkyl phosphate is suitable.
This acidic catalyst may be used individually by 1 type, and may be used in combination of 2 or more type. Moreover, 0.1-15 mass parts is preferable with respect to 100 mass parts of rubber-type elastomer which has a functional group at the terminal, and the usage-amount is more preferable 0.1-10 mass parts.

The resin composition for the anchor coat layer is preferably used in the form of a solution containing an organic solvent in consideration of convenience in use. As an organic solvent, it can select suitably from the well-known solvent with the favorable solubility with respect to the rubber-type elastomer which has a functional group at the terminal. Examples of such a solvent include toluene, xylene, methanol, ethanol, isopropyl alcohol, isobutanol, n-butanol, acetone, methyl ethyl ketone, and tetrahydrofuran. These may be used individually by 1 type and may be used in combination of 2 or more type.
The amount of the organic solvent may be appropriately selected so that the resin composition for the anchor coat layer containing the rubber elastomer having a functional group at the terminal and the crosslinking agent has an appropriate viscosity at the time of coating.
The amount of solid content contained in the anchor coat layer resin composition is not particularly limited, but the solid content concentration is preferably 0.1 to 15% by mass, more preferably 0, relative to the total amount of the resin composition. It is preferable to prepare it in the range of 2 to 10% by mass, more preferably 0.5 to 5% by mass.

If necessary, the resin composition for the anchor coat layer may contain various additives such as an antioxidant, an ultraviolet absorber, an antistatic agent, a surfactant, a photoinitiator, and a light stabilizer. .
The antioxidant is not particularly limited, and any of known phosphite antioxidants, organic sulfur antioxidants, and hindered phenol antioxidants can be used. Specific examples of such antioxidants include pentaerythritol tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate), thiodiethylenebis [3- (3,5-di- t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N ′-(hexane-1,6-diyl) bis ( 3- (3,5-di-t-butyl-4-hydroxyphenyl) propanoic acid amide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4 Hydroxybenzyl) benzene, 2,4-bis (dodecylthiomethyl) -6-methylphenol, calcium bis (O-ethyl-3,5-di-t-butyl-4-hydroxyphosphonate), 2-methyl- 4,6-bis ((octylthio) methyl) phenol, triethylene glycol bis (3-tert-butyl-4-hydroxy-5-methylphenol) Nyl) propionate, 6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propanoyloxy] hexyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 2,4-bis (n-octylthio) -6- (4'-hydroxy-3,5-di-t-butylanilino) -1 , 3,5-triazine, tris (2,4-di-t-butylphenyl) phosphite, bis (2,4-di-t-butyl-6-methylphenyl) ethyl phosphite, N, N-di Examples include octadecylhydroxylamine.
These antioxidants may be used singly or may be used in combination of two or more kinds. Moreover, it is preferable to use 0.001 mass part or more and 1 mass part or less of the usage-amount with respect to 100 mass parts of rubber-type elastomers, and 0.003 mass part or more and 0.5 mass part or less are still more preferable.

As a method for producing an anchor coat layer in the release sheet of the present invention, a resin composition for an anchor coat layer containing a rubber-based elastomer having a functional group at a terminal and a crosslinking agent on at least one surface of the substrate is used. There is a method in which a cured film is formed by coating on at least one of the surfaces, heat-treating, and crosslinking a rubber elastomer having a functional group at a terminal with a crosslinking agent.
The heat treatment temperature is preferably from 100 to 170 ° C, more preferably from 130 to 160 ° C. The heat treatment time is not particularly limited, but is preferably 30 seconds to 5 minutes.
When the rubber-based elastomer is polybutadiene and / or polyisoprene, if desired, the heat-cured film is irradiated with active energy rays such as an electron beam or ultraviolet rays, and the unsaturation in the main chain of polybutadiene or polyisoprene. The crosslink density may be adjusted by reacting bonds. Ultraviolet rays are obtained with a high-pressure mercury lamp, a xenon lamp or the like, and the irradiation amount is usually 100 to 500 mJ / cm ² .

  Examples of the coating method for the resin composition for the anchor coat layer include a gravure coating method, a bar coating method, a spray coating method, a spin coating method, an air knife coating method, a roll coating method, a blade coating method, and a gate roll coating method. A die coating method or the like can be used.

  The thickness of the anchor coat layer obtained by coating the resin composition for the anchor coat layer is preferably 40 to 545 nm. More preferably, coating is performed so that the thickness is 50 to 500 nm. When the thickness of the anchor coat layer is 40 to 545 nm, when it is laminated (rolled) in the production process of the release sheet, blocking with the back surface can be suppressed, and the amount of back surface migration can be suppressed. it can. Further, when the thickness of the anchor coat layer is 40 to 545 nm, it is possible to suppress the feeding charge that is generated when the wound release sheet is fed.

The anchor coat layer of the present invention is made of a material that does not substantially contain a silicone compound and a fluorine-containing compound. In the present specification, the term “substantially free of silicone compound and fluorine-containing compound” means that the amount of each of the silicone compound or fluorine-containing compound is preferably 500 μg / m ² or less, more preferably 100 μg / m ² or less. Say. In the release sheet of the present invention, since the anchor coat layer is composed of a material that does not substantially contain a silicone compound and a fluorine-containing compound, the pressure-sensitive adhesive passes through the release agent layer and is attached to the release agent layer. The silicone compound does not migrate to the layer. As a result, the silicone compound is not released to the adherend from the adhesive from which the release sheet has been peeled off. In particular, when the adherend is an electronic component used in an electronic device, the silicone compound that is released does not have an adverse effect such as poor conductivity. Further, when waste is treated, fluorine is not released from the used release sheet, and the environmental load can be reduced.

[Release layer]
The release agent layer in the release sheet of the present invention is a cured film obtained by curing a material composed of a diene polymer.
Examples of the diene polymer that is a material constituting the release agent layer include diene homopolymers such as polybutadiene and polyisoprene, styrene-butadiene copolymers, styrene-isoprene copolymers, and ethylene-propylene-diene copolymers. Examples include diene copolymers such as (EPDM). As the diene polymer, polybutadiene and / or polyisoprene is particularly preferably used. The number average molecular weight of the diene polymer is preferably 100,000 to 1,200,000, more preferably 100,000 to 1,000,000. The number average molecular weight of the 1,4-polybutadiene polymer is a value in terms of polystyrene measured by a gel permeation chromatography method (GPC).

  The diene polymer used for the release agent layer is composed of one or two or more diene polymers having no functional group at the terminal and having a cis-1,4 bond content of 90% or more. From the viewpoint of obtaining a desired light peeling force, it is composed of one or more diene polymers having a cis-1,4 bond content of 90 to 99%. It is more preferable.

  The diene polymer used in the release agent layer is preferably polybutadiene and / or polyisoprene, more specifically 1,4-polybutadiene, from the viewpoint of reducing the peeling force. The 1,4-polybutadiene may have either a cis structure or a trans structure, but preferably has a cis-1,4 bond content of 90% or more, and a cis-1,4 bond content of 90-99. % Or more is more preferable. As a material having a slightly higher peeling force, 1,4-polybutadiene containing 1,2-polybutadiene may be used.

A photopolymerization initiator or a photosensitizer may be added to the material composed of the diene polymer in order to efficiently crosslink the diene polymer by ultraviolet irradiation.
Examples of the photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1 -One, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, oligo [2-hydroxy-2-methyl Examples thereof include -1- [4- (1-methylvinyl) phenyl] propanone.
As photosensitizers, aromatic ketones such as benzophenone, P, P′-dimethoxybenzophenone, P, P′-dichlorobenzophenone, P, P′-dimethylbenzophenone, acetophenone, and acetonaphthone give good results. Also, aromatic aldehydes such as terephthalaldehyde and quinone aromatic compounds such as methylanthraquinone can be used.

In addition to the diene polymer, components such as an antioxidant may be added to the material composed of the diene polymer in addition to the photopolymerization initiator and the photosensitizer.
There is no restriction | limiting in particular as antioxidant, It can select suitably from well-known phosphite type antioxidants, organic sulfur type antioxidants, hindered phenolic antioxidants, etc., and can use them. Specific examples of the antioxidant include the same as those described as the antioxidant used in the anchor coat layer. These antioxidants may be used singly or may be used in combination of two or more kinds. Further, the amount used is preferably 0.01 parts by mass or more with respect to 100 parts by mass of the diene polymer from the viewpoint of suppressing heavy peeling due to deterioration of the diene polymer, and the anchor coat layer. From the viewpoint of sufficiently maintaining the adhesion between the base material and the release agent layer by interposing the base, 10 parts by mass or less is preferable with respect to 100 parts by mass of the diene polymer. More preferably, it is the range of 0.003-5 mass parts with respect to 100 mass parts of diene polymer.
The release agent solution is a solution obtained by dissolving a diene polymer and other components (antistatic agent, photoinitiator, photosensitizer, plasticizer, stabilizer, etc.) blended as necessary in an organic solvent. .

The release agent layer is preferably formed by applying a release agent solution containing an organic solvent, a diene polymer, and other components as necessary onto the anchor coat layer. The organic solvent used as a solvent for the release agent solution is not particularly limited, and ketones such as dimethyl ketone, methyl ethyl ketone, diethyl ketone, and cyclohexanone, aromatic hydrocarbons such as benzene, toluene, and xylene, hexane, heptane, octane, and the like. Examples thereof include aliphatic hydrocarbons and mixed solvents thereof. The amount of the organic solvent is not particularly limited, and may be appropriately selected so that the release agent solution has an appropriate viscosity at the time of coating.
For the convenience of coating, the release agent solution uses these organic solvents, and the solid content concentration is preferably 0.1 to 15% by mass, more preferably 0.15 to 10% by mass, and still more preferably. It is preferable to prepare so that it may become the range of 0.2-5 mass%.

The release agent layer in the release sheet of the present invention is a cured film cured by irradiating an active energy ray to a material composed of a diene polymer in order to improve the release performance with the adhesive layer. It is preferable. Examples of the active energy ray include an electron beam and ultraviolet rays, and ultraviolet rays are preferred from the viewpoint of little damage (deterioration) to the substrate.
Conventionally known high-pressure mercury lamps, metal halide lamps, high-power metal halide lamps, electrodeless lamps, etc. can be used as ultraviolet lamps used for ultraviolet irradiation, but electrodeless lamps are most suitable in terms of curability of polybutadiene or polyisoprene. ing.

The amount of UV irradiation is preferably 20 mJ / cm ² or more from the viewpoint that the release agent layer is cured and the release performance with the pressure-sensitive adhesive layer is good, and the release agent layer is oxidized and deteriorated to avoid heavy release. From the viewpoint of being able to do so, 300 mJ / cm ² or less is preferable.
That is, the amount of ultraviolet irradiation is preferably in the range of 20~300mJ / cm ^2, in particular in the range of 20~255mJ / cm ² is preferred.

  Examples of the coating method of the release agent solution include a gravure coating method, a bar coating method, a spray coating method, a spin coating method, an air knife coating method, a roll coating method, a blade coating method, a gate roll coating method, and a die coating method. Can be used.

  The thickness of the release agent solution is such that the thickness of the release agent layer obtained by applying the resin composition, irradiating active energy rays, and then drying is preferably 5 to 300 nm. It is preferable to apply so that it may become 10-250 nm.

The release agent layer of the present invention is composed of a material that does not substantially contain a silicone compound and a fluorine-containing compound. The phrase “substantially free of silicone compound and fluorine-containing compound” means that the amount of each of the silicone compound or fluorine-containing compound is preferably 500 μg / m ² or less, more preferably 100 μg / m ² or less. In the release sheet of the present invention, both the anchor coat layer and the release agent layer are made of a material that does not contain a silicone compound and a fluorine-containing compound, and therefore, the silicone is applied to the adhesive layer adhered to the release agent layer of the release sheet. The compound does not migrate. As a result, the silicone compound is not released to the adherend from the pressure-sensitive adhesive layer from which the release sheet has been peeled off. In particular, when the adherend is an electronic component used in an electronic device, the silicone compound that is released does not have an adverse effect such as poor conductivity. Further, when waste is treated, fluorine is not released from the used release sheet, and the environmental load can be reduced.

[Peeling sheet]
FIG. 1 is a diagram showing a schematic configuration of a release sheet 1 of the present invention. As shown in FIG. 1, the release sheet 1 of the present invention comprises a base material 2, an anchor coat layer 3 which is a cured film obtained by crosslinking a rubber elastomer having a functional group at its terminal with a crosslinking agent, and a diene polymer. And a release agent layer 4 which is a cured film obtained by curing a material composed of
Release sheet, the release strength between the adhesive layer is adhered to the release agent layer is favorable. Examples of the pressure-sensitive adhesive layer adhered to the release agent layer include a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed on a pressure-sensitive adhesive base sheet. There is no restriction | limiting in particular as an adhesive used for an adhesive layer etc., For example, it can select suitably from conventionally well-known adhesives, such as an acrylic adhesive, a polyester adhesive, and a urethane type adhesive, for example. .

  In the release sheet of the present invention, the total thickness of the release agent layer and the anchor coat layer is not particularly limited, but the total thickness of the release agent layer and the anchor coat layer is preferably 70 to 550 nm, more preferably It is 80 to 500 nm, more preferably 90 to 480 nm, particularly preferably 100 to 450 nm. When the total thickness of the release agent layer and the anchor coat layer of the release sheet is 70 to 550 nm, the curability of the release agent layer is good while ensuring adhesion to the base material and being highly flexible. There can be obtained a release sheet having good light release properties due to the low elastic modulus. The total thickness of the release agent layer and the anchor coat layer of the release sheet is, for example, a spectroscopic ellipsometer manufactured by JA WOOLIAM Japan Co., Ltd. as will be described in detail in the examples described later. (Product name: SPECTROSCOPIC_Ellipsometers M-7000U).

In the release sheet of the present invention, the surface elastic modulus of the release agent layer is preferably 0.5 to 15 MPa, more preferably 1 to 14 MPa, further preferably 2 to 13 MPa, and particularly preferably 3 to 12 MPa. It is.
When the anchor coat layer is not provided between the base material and the release agent layer, and the thickness of the release agent layer is small, the surface elastic modulus of the release agent layer is affected by the base material and is sufficient. It is difficult to make the surface elastic modulus within an appropriate range so as to obtain peel properties. On the other hand, when the release agent layer is thick and the release agent layer is cured by irradiation with energy rays, the diene polymer is crosslinked and cured by ozone generated on the surface of the release agent layer irradiated with the energy rays. there to proceed, resulting poor curing, it may not be formed a cured film constituting the release agent layer.
The release sheet of the present invention is an anchor coat layer in which a rubber elastomer having a functional group at a terminal is crosslinked by a crosslinking agent between a base material and a release agent layer obtained by curing a material composed of a diene polymer. Therefore, the anchor coat layer has flexibility, and the surface elastic modulus of the release agent layer can be set to 0.5 to 15 MPa. When the surface elastic modulus of the release agent layer of the release sheet is 0.5 to 15 MPa, it is possible to obtain sufficient release physical properties while maintaining sufficient film strength while being rich in flexibility. Damage can be suppressed. In addition, when the release sheet of the release sheet is wound with the release sheet, the release sheet has a surface elastic modulus of 0.5 to 15 MPa. The amount of components transferred to the back surface of the release agent layer to the surface of the material used together is reduced, and contamination of the material surface can be prevented.

  The surface elastic modulus of the release agent layer of the release sheet of the present invention refers to a value obtained by measuring the surface of an object to be measured using an atomic force microscope. That is, with a cantilever installed in an atomic force microscope, the surface of the release agent layer of the release sheet is pushed in and pulled out, and the obtained curve curve is subjected to JKR theoretical formula and fitting to obtain the elastic modulus to obtain the surface of the present invention. Elastic modulus. An example of a specific measuring apparatus and measurement procedure used for measuring the surface elastic modulus of the present invention is as described in the examples described later.

The release sheet of the present invention preferably has a low back surface transfer amount to the surface of the material used by being overlapped with the release agent layer of the release sheet. As the measurement of the back migration amount, a polyester film is used as a material to be overlapped with the release agent layer of the release sheet, and evaluation is performed by displacement of the element amount on the surface of the polyester film. Since the surface element ratio of the C element of the polyester film before superimposing is approximately 70%, the surface element ratio of the C element of the polyester film used by overlapping with the release agent layer of the release sheet is close to 70%. A polyester film shows that there is little back migration amount.
Specifically, in the release sheet of the present invention, the surface element ratio of the C element on the surface of the polyester film superimposed on the release agent layer of the release sheet is preferably 70% or more and less than 90%, and the surface of the polyester film The surface element ratio of the C element is more preferably 85% or less, still more preferably 82% or less, and most preferably 80% or less. When the surface element ratio of the C element on the surface of the polyester film superimposed with the release agent layer of the release sheet is less than 90%, the back transfer of the components contained in the release agent layer to the polyester film surface superimposed with the release agent layer the amount is small, also it is possible to suppress the contamination of the material surface to be used in superposition with the release agent layer.

  The amount of transfer to the back side of the release sheet is the ratio of surface elements using the material (polyester film) that is overlapped with the release agent layer and using the X-ray photoelectric spectroscopic analyzer “PH1 Quantera II” (ULVAC-FOY Co., Ltd.). Can be measured. Specifically, it can be measured by the method of the examples described later. For example, a polyester film is stacked on the surface of the release agent layer of the release sheet, and a load is applied at a predetermined pressure and a predetermined time is set. After that, on the surface of the polyester film, measurement of 1 s of O, 1 s of N, and 1 s of C was performed, and the total of the elements of C, O, and N was set to 100% by using analysis software. The back surface migration amount can be evaluated by deriving the element ratio (%).

  The peeling force of the release agent layer of the release sheet of the present invention to the adhesive layer is preferably 250 mN / 20 mm or less, more preferably 80 to 250 mN / 20 mm, still more preferably 90 to 200 mN / 20 mm, and particularly preferably 100 to 180 mN / 20 mm. As an adhesive which comprises an adhesive layer, an acrylic adhesive is mentioned, for example. When the peeling force of the release sheet with respect to the release agent layer is 80 to 250 mN / 20 mm, desired light peelability can be obtained.

  The peeling force with respect to the adhesive of the release agent layer of a release sheet can be measured by the method of the Example mentioned later. Specifically, the pressure-sensitive adhesive sheet prepared by the method of the example was compliant with JIS Z0237 at a rate of 300 mm / min in the direction of 180 ° C. using a tensile tester in an atmosphere of 23 ° C. and 50% RH. Measure by peeling.

  The release sheet of the present invention is suitable as a release sheet for pressure-sensitive adhesive sheets such as temporary fixing during assembly of electronic components and component content display in the manufacturing process of electronic components such as relays, various switches, connectors, motors, and hard disks. Can be used. The release sheet of the present invention can also be suitably used as a release sheet that is attached to an adhesive layer for forming electronic circuits, mounting pads, and the like.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited by these examples.

Evaluation of the release sheets prepared in Examples and Comparative Examples was performed by the following method.
(A) Evaluation of the total thickness of the anchor coat layer and the release agent layer The total thickness of the anchor coat layer and the release agent layer of the obtained release sheet was measured using a spectroscopic ellipsometer (JAWOOLIAM )) Measured using a Japan trade name, SPECTROSCOPIC_Ellipsometers M-7000U).

(B) Evaluation of peeling force On the release agent layer of the obtained release sheet, an acrylic pressure-sensitive adhesive (manufactured by Toyochem Co., Ltd., trade name: Olivevine (registered trademark) BPS-5127) was applied with a 125 μm applicator, The film was dried at 100 ° C. for 2 minutes, and a polyethylene terephthalate (PET) film (manufactured by Toray Industries, Inc., trade name: Lumila (registered trademark) T-60, film thickness: 50 μm) was attached to prepare an adhesive sheet. The peel strength of the release sheet in the produced pressure-sensitive adhesive sheet is determined according to JIS Z0237 by using a tensile tester (Shimadzu Corporation, trade name: Autograph AG-IS 500N) in an atmosphere of 23 ° C. and 50% RH. Using, the peeling force (mN / 20 mm) of the release sheet was measured by peeling at a rate of 300 mm / min in the 180 ° direction.

(C) Evaluation of backside transfer property A polyethylene terephthalate (PET) film (manufactured by Mitsubishi Plastics Co., Ltd., trade name: Diafoil (registered trademark) T-100, film thickness: 50 μm) is superimposed on the release agent layer of the release sheet. As a laminated sample, a load of 10 kg / cm ² was applied for 24 hours. Thereafter, the PET film is peeled from the peeled laminate sample, and the surface of the PET film that is overlapped with the release agent layer is measured using an X-ray photoelectric spectroscopic analyzer (ULVAC-FOY Co., Ltd., trade name: PH1 Quantera II). The surface element ratio was derived. Specific X-ray excitation conditions were 100 μm-100 W-20 kV, and Al was used for the counter cathode. Irradiation range of X-ray to the sample, and 100 [mu] m × 100 [mu] m, detection angle of photoelectrons with 45 °. The measurement was performed in the order of 1 s of O, 1 s of N, and 1 s of C on the surface of the PET film, and the irradiation time of X-rays to the total sample in the total element measurement was within 30 minutes. For the data processing, analysis software “Multipack” (manufactured by ULVAC-FOY Co., Ltd.) was used. The sum of the detected values of C, O, N, and 3 elements was taken as 100%, and the ratio of the detected values of C element (surface element ratio;%) was calculated. When the surface element ratio of the measured C element is 90% or more, the back surface migration amount is large and the back surface migration property is evaluated as NG, and when the C element surface element ratio is 70% or more and less than 90%, the back surface migration amount. The backside transferability was evaluated as OK.

(D) Evaluation of surface elastic modulus Using an atomic force microscope (manufactured by Bruker Corporation, MultiMode8), this atomic force microscope was subjected to a silicon nitride material cantilever (manufactured by Bruker Corporation, trade name: MLCT, tip radius: 20 nm, (Resonance frequency: 125 kHz, spring constant: 0.6 N / m). With the cantilever installed in the atomic force microscope, the surface of the release agent layer of the release sheet was pushed in at a pushing amount of 2 nm and the scanning speed: 10 Hz, pulled away, and the obtained force curve curve was subjected to JKR theoretical formula and fitting, The surface elastic modulus is calculated. The surface elastic modulus was measured at 4096 points in the surface of the release agent layer of the release sheet at 1 μm × 1 μm, and these values were averaged to obtain the surface elastic modulus (MPa).

(E) Measurement of number average molecular weight The number average molecular weight used was a value in terms of porstyrene measured by gel permeation chromatography (GPC).

(F) Evaluation of adhesion The surface of the release agent layer of the release sheet prepared in the examples or comparative examples was rubbed with a finger to confirm whether the release agent layer was removed. The case where the release agent layer did not fall off was evaluated as OK, and the case where the release occurred was judged as NG.

Example 1
Terminal hydroxyl group-modified polybutadiene (Idemitsu Kosan Co., Ltd., trade name: Poly bd (registered trademark) R-45HT, solid content concentration 100% by mass, number average molecular weight 2,800, 1,4 addition unit polymerization ratio 80.8%) 100 parts by mass methylated melamine resin (Hitachi Chemical Polymer Co., Ltd.) as a crosslinking agent , Trade name: Tesfine (registered trademark) 200, solid content concentration: 80% by mass), 14.1 parts by mass, as acid catalyst, solution of p-toluenesulfonic acid (solid content concentration: 50% by mass, solvent: methanol / 3 parts by mass of a mixed solvent of isopropyl alcohol = 41.2 / 9.2 (mass ratio) was added to prepare a resin composition solution for the anchor coat layer. The solution of the resin composition for the anchor coat layer was diluted with a solvent (toluene / methyl ethyl ketone = 6/4 (mass ratio)) to prepare a coating liquid having a solid content concentration of 1.5 mass%. The prepared coating solution is a polyethylene terephthalate (PET) film having a thickness of 50 μm as a base material (manufactured by Mitsubishi Plastics, Inc., trade name: Diafoil (registered) so that the film thickness after drying with a Meyer bar is 200 nm. (Trademark) was applied onto one side of T-100) and dried at 150 ° C. for 1 minute to form an anchor coat layer on the PET film as the substrate.
Further, a polybutadiene resin (JSR Corporation, trade name: BR 01-A0 (cis-1,4 bond content: 98%, solid content: 100% by mass, number average molecular weight: 200,000)) with a solid content concentration of 0.25. It diluted with heptane so that it might become mass%, and the coating liquid for release agent layers was produced. The coating solution for the release agent layer was coated on the anchor coat layer so that the film thickness after drying with a Meyer bar was 15 nm, dried at 110 ° C. for 1 minute, and then irradiated with ultraviolet rays (22 mJ / cm ² ) Then, the coating liquid was cured to form a release agent layer, and a release sheet having a base material, an anchor coat layer on the base material, and a release agent layer on the anchor coat layer was obtained.

(Example 2)
The terminal hydroxyl group-modified polybutadiene of Example 1 was converted to a terminal hydroxyl group-modified polyisoprene (Idemitsu Kosan Co., Ltd., trade name: Poly ip (registered trademark)). A release sheet was obtained in the same manner as in Example 1, except that the solid content concentration was changed to 100% by mass and the number average molecular weight was 2,500).

(Example 3)
The terminal hydroxyl group-modified polybutadiene of Example 1 was used as a hydrogenated product of terminal hydroxyl group-modified polyisoprene (Idemitsu Kosan Co., Ltd., trade name: Epaul (registered trademark)). A release sheet was obtained in the same manner as in Example 1, except that the solid content concentration was changed to 100% by mass and the number average molecular weight was 2,500).

Example 4
A release sheet was prepared in the same manner as in Example 1 except that the methylated melamine resin of Example 1 was changed to 15 parts by mass of an isocyanate compound (Toyochem Co., Ltd., trade name: BHS8515, solid content concentration 35% by mass). Obtained.

(Example 5)
Terminal acrylate-modified polybutadiene (Osaka Organic Chemical Industry Co., Ltd., trade name: BAC-45, solid content concentration 100 mass%, number average molecular weight 10,000) is used as a crosslinking agent with bis (2, 4, 6-trimethylbenzoyl) -phenylphosphine oxide (BASF Corporation, trade name: IRGACURE 819, solid content concentration: 100% by mass) 3.1 parts by mass was added to prepare a resin composition solution for the anchor coat layer. Prepared. The resin composition solution for the anchor coat layer was diluted with a solvent (toluene / methyl ethyl ketone = 6/4 (mass ratio)) to prepare a coating liquid having a solid content concentration of 3.0 mass%. The prepared coating liquid is a PET film having a thickness of 50 μm as a base material (manufactured by Mitsubishi Plastics, Inc., trade name: Diafoil (registered trademark) T-) so that the film thickness after drying with a Meyer bar is 200 nm. 100) is coated on one surface, dried at 80 ° C. for 1 minute, dried and then irradiated with ultraviolet light (100 mJ / cm ² ), the coating solution is cured, and an anchor coat is applied onto the PET film as a substrate. A layer was formed.
Further, a polybutadiene resin (JSR Corporation, trade name: BR 01-A0 (cis-1,4 bond content: 98%, solid content: 100% by mass, number average molecular weight: 200,000)) with a solid content concentration of 0.25. It diluted with heptane so that it might become mass%, and the coating liquid for release agent layers was produced. The coating solution for the release agent layer was coated on the anchor coat layer so that the film thickness after drying with a Meyer bar was 15 nm, dried at 110 ° C. for 1 minute, and then irradiated with ultraviolet rays (22 mJ / cm ² ) Then, the coating liquid was cured to form a release agent layer, and a release sheet having a base material, an anchor coat layer on the base material, and a release agent layer on the anchor coat layer was obtained.

(Comparative Example 1)
A release sheet was obtained in the same manner as in Example 1 except that the release agent layer was directly formed on the substrate without providing the anchor coat layer.

(Comparative Example 2)
For 100 parts by mass of urethane resin (DIC Corporation, trade name: Crisbon (registered trademark) 5150S, solid content concentration 50 mass%), an isocyanate compound (Toyochem Co., Ltd., trade name: BHS8515, solid content concentration) as a crosslinking agent. : 35% by mass) 15 parts by mass was added and diluted with a solvent (cyclohexanone / methyl ethyl ketone = 6/4 (mass ratio)) so that the solid content concentration was 1.0% by mass to prepare a coating solution. The prepared coating liquid is a PET film having a thickness of 50 μm as a substrate (trade name: Diafoil (registered trademark) T-) manufactured by Mitsubishi Plastics Co., Ltd. so that the film thickness after drying with a Meyer bar is 140 nm. 100) and dried at 110 ° C. for 1 minute to form an anchor coat layer on the PET film as the substrate. Furthermore, in the same manner as in Example 1, a release agent layer was formed, and a release sheet having a base material, an anchor coat layer on the base material, and a release agent layer on the anchor coat layer was obtained.

(Comparative Example 3)
Mixture of 80 parts by mass of bisphenol A type epoxy resin ester and 20 parts by mass of melamine resin (Hitachi Chemical Polymer Co., Ltd., trade name: TA31-059D, solid content concentration 50% by mass, solvent: xylene / toluene / isobutanol = 18 / 16/16 (mass ratio) mixed solvent) of 100 mass parts of solid content, 2.5 parts by mass (solid content ratio) of p-toluenesulfonic acid solution (solid content concentration 50 mass%) as an acid catalyst. Then, it was further diluted with a mixed solvent of toluene / methyl ethyl ketone = 30/70 (mass ratio) to prepare a coating solution. The prepared coating liquid is a PET film having a thickness of 50 μm as a base material (manufactured by Mitsubishi Plastics, Inc., trade name: Diafoil (registered trademark) T-) so that the film thickness after drying with a Meyer bar is 200 nm. 100) and dried at 150 ° C. for 5 minutes to form an anchor coat layer on the PET film as the substrate. Furthermore, in the same manner as in Example 1, a release agent layer was formed, and a release sheet having a base material, an anchor coat layer on the base material, and a release agent layer on the anchor coat layer was obtained.

  The evaluation results of Examples and Comparative Examples are shown in Table 1.

As is clear from Table 1, the release sheets of Examples 1 to 5 are rubber-based having a functional group at the terminal between the release agent layer obtained by curing the material composed of the diene polymer and the base material. By providing an anchor coat layer that is a cured film obtained by crosslinking an elastomer with a crosslinking agent, the adhesion between the release agent layer and the substrate can be improved, and the desired curability and low elastic modulus are rich. It has light releasability due to crystallization. In addition, the release sheets of Examples 1 to 5 have a surface element ratio of C element to the material surface that is used by being superimposed on the release agent layer, which is 70% or more and less than 90%, and the back surface migration amount is small. Contamination on the surface of the material used in an overlapping manner is suppressed.
The release sheet of Comparative Example 1 is affected by the substrate and has a relatively large surface elastic modulus and a large peeling force as compared with Examples 1 to 5, and light peeling cannot be realized. In addition, the release sheet of Comparative Example 1 has a C element surface element ratio of 90% or more, a large amount of back surface migration, and contamination on the surface of the material used while being superimposed on the release sheet is not suppressed. The release sheet of Comparative Example 2 has a low surface elastic modulus and cannot measure the peel force. Moreover, the release sheet of Comparative Example 2 has a low surface elastic modulus, and a desired curability is not obtained. Furthermore, the release sheet of Comparative Example 2 has a C element surface element ratio of 90% or more, a large amount of back surface migration, and contamination on the surface of the material used while being superimposed on the release sheet is not suppressed. Further, the release sheet of Comparative Example 3 has a very large peeling force and surface elastic modulus compared to the release sheets of Examples 1 to 5, and cannot achieve a desired light release.

  The release sheet of the present invention is suitable as a release sheet for pressure-sensitive adhesive sheets such as temporary fixing during assembly of electronic components and component content display in the manufacturing process of electronic components such as relays, various switches, connectors, motors, and hard disks. Can be used. The release sheet of the present invention can also be suitably used as a release sheet that is attached to an adhesive layer for forming electronic circuits, mounting pads, and the like.

1: Release sheet 2: Base material 3: Anchor coat layer 4: Release agent layer

Claims (8)

A substrate, an anchor coat layer on the substrate, and a release agent layer on the anchor coat layer;
The anchor coat layer is a cured film obtained by crosslinking a rubber-based elastomer having a functional group at a terminal with a crosslinking agent,
The functional group of the rubber elastomer is a hydroxyl group, and the crosslinking agent is a melamine compound, an isocyanate compound, an epoxy compound, an aziridine compound, a hydrazide compound, an oxazoline compound, a carbodiimide compound, a urea compound, At least one cross-linking agent selected from the group consisting of dialdehyde compounds and metal chelate compounds,
The release agent layer is a release sheet which is a cured film obtained by curing a material composed of a diene polymer.   The release sheet according to claim 1, wherein the release agent layer has a surface elastic modulus of 0.5 to 15 MPa.   The release sheet according to claim 1 or 2, wherein the total thickness of the anchor coat layer and the release agent layer is 70 to 550 nm.   The diene polymer is composed of one or two or more diene polymers having no functional group at the terminal and having a cis-1,4 bond content of 90% or more. Item 4. The release sheet according to any one of Items 1 to 3.   The release sheet according to any one of claims 1 to 4, wherein the diene polymer is polybutadiene and / or polyisoprene.   The release sheet according to any one of claims 1 to 5, wherein the release agent layer is a cured film cured by irradiation with ultraviolet rays.   The rubber-based elastomer is at least one selected from the group consisting of polybutadiene, polyisoprene, styrene-butadiene rubber, styrene-isoprene rubber, acrylonitrile butadiene rubber, polychloroprene and hydrogenated products thereof, and polyisobutylene. Item 7. The release sheet according to any one of Items 1 to 6.   The functional group of the rubber-based elastomer is at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, an isocyanate group, an acryloyl group, and a methacryloyl group. A release sheet as described in