JP7466270B2 - Release sheet - Google Patents

Description

The present invention relates to a release sheet, preferably a release sheet onto which an adhesive layer of an adhesive sheet is laminated, a release sheet that can be used in the production of ceramic green sheets, etc.

Conventionally, in the manufacture of adhesive sheets, a release sheet having a release agent layer provided on the surface of a substrate has been used. For example, a coating solution of an adhesive composition for forming an adhesive layer of an adhesive sheet is applied to the surface of the release sheet of the release sheet opposite the substrate (sometimes referred to as the "release surface" in this specification), and the adhesive layer is formed by drying. Then, a substrate for the adhesive sheet is laminated on the surface of the adhesive layer opposite the release sheet, thereby obtaining an adhesive sheet consisting of a release agent layer and a substrate. At this time, the release sheet is laminated on the adhesive sheet, and by storing them in this state, the release sheet can also be used to protect the surface of the adhesive layer of the adhesive sheet that comes into contact with the adherend (sometimes referred to as the "adhesive surface" in this specification).

In addition, to manufacture multilayer ceramic products such as multilayer ceramic capacitors and multilayer ceramic substrates, ceramic green sheets are formed, and then multiple resulting ceramic green sheets are stacked and fired. Such ceramic green sheets can be formed by applying a ceramic slurry containing ceramic materials such as barium titanate and titanium oxide onto the release surface of the release sheet described above.

In such release sheets, the release agent layer is generally formed using a release agent composition containing a release component. Patent documents 1 to 5 disclose release sheets in which a release agent layer is formed using a cationically polymerizable silicone resin as the release component. This cationically polymerizable silicone resin cures in the presence of a cationic polymerization initiator when stimulated by ultraviolet light or the like. In the release sheets of Patent documents 1 to 5, a composition containing a cationically polymerizable silicone resin and a cationic polymerization initiator is applied to one side of a substrate, and the coating film is irradiated with ultraviolet light to cure the coating film, thereby forming a release agent layer.

Patent No. 4622079 Patent No. 5061405 Patent No. 4626055 JP 2012-206509 A Patent No. 5786798

Incidentally, there are a wide variety of possible objects onto which the release surface of a release sheet can be laminated. For each of these objects, it is necessary to use the most suitable release sheet. For this reason, the development of new release sheets is underway, with a view to increasing the options for release sheets.

The present invention has been made in consideration of these circumstances, and aims to provide a new release sheet with good releasability.

In order to achieve the above object, first, the present invention provides a release sheet comprising a substrate and a release agent layer provided on at least one side of the substrate, the release agent layer being formed from a release agent composition containing a cationic polymerizable compound not containing a polysiloxane skeleton, a release component, and a cationic polymerization initiator, the amount of the cationic polymerizable compound being greater than the amount of the release component and the amount of the cationic polymerization initiator being greater in the release agent composition (Invention 1).

In the release sheet according to the above invention (Invention 1), when the release agent layer is formed, the cationic polymerizable compound contained as the main agent in the release agent composition undergoes cationic polymerization due to the action of the cationic polymerization initiator. As a result, the release agent composition hardens and a release agent layer containing the release component is well formed. The release component contained in the release agent layer enables the release sheet to exhibit good releasability.

In the above invention (Invention 1), it is preferable that the cationically polymerizable compound is an epoxy compound (Invention 2).

In the above invention (Invention 2), it is preferable that the epoxy compound has three or more epoxy groups in one molecule (Invention 3).

In the above inventions (Inventions 1 and 2), it is preferable that the epoxy compound has a molecular weight of 200 or more and 2,000 or less (Invention 4).

In the above inventions (Inventions 1 to 4), it is preferable that the release component is at least one selected from the group consisting of silicone-based release components, fluorine-based release components, and long-chain alkyl-based release components (Invention 5).

In the above inventions (Inventions 1 to 5), it is preferable that the peeling component has a reactive group capable of reacting with the cationic polymerizable compound (Invention 6).

In the above invention (Invention 6), it is preferable that the release component is a reactive polyorganosiloxane (Invention 7).

In the above inventions (Inventions 1 to 7), the surface free energy measured on the surface of the release agent layer opposite to the substrate is preferably 25 mJ/ ^m2 or more and 35 mJ/ ^m2 or less (Invention 8).

In the above inventions (Inventions 1 to 8), it is preferable that the release sheet is for use in the ceramic green sheet manufacturing process (Invention 9).

According to the present invention, a novel release sheet having good releasability is provided.

Hereinafter, an embodiment of the present invention will be described.
A release sheet according to one embodiment of the present invention is configured to include a substrate and a release agent layer provided on one surface of the substrate.

In the release sheet according to this embodiment, the release agent layer is formed from a release agent composition containing a cationically polymerizable compound that does not contain a polysiloxane skeleton, a release component, and a cationic polymerization initiator.

In addition, in the release sheet according to this embodiment, the amount of the cationic polymerizable compound in the release agent composition is greater than the amount of the release component and the amount of the cationic polymerization initiator. That is, in the release agent composition according to this embodiment, the cationic polymerizable compound is blended as a main component.

The release agent layer of the release sheet according to this embodiment is formed by hardening the release agent composition described above. This hardening occurs when the cationic polymerizable compound contained as the main agent undergoes cationic polymerization due to the action of a cationic polymerization initiator. Therefore, the cationic polymerizable compound can be sufficiently polymerized, and a well-hardened release agent layer is formed. Furthermore, since the release agent layer contains a release component, the release sheet can exhibit good releasability.

Cationic polymerization generally refers to a reaction in which cations act as active species and the polymerization of a cationic polymerizable compound proceeds. This reaction is initiated by a cationic polymerization initiator.

1. Substrate The substrate in the release sheet according to the present embodiment is not particularly limited, and any one of the conventionally known substrates can be appropriately selected and used. Examples of such substrates include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene and polymethylpentene, polycarbonate, polyvinyl acetate, and other plastic films. These plastic films may be single-layered or may be multi-layered with two or more layers of the same or different kinds. Among these, polyester films are preferred, and polyethylene terephthalate films are particularly preferred. Polyethylene terephthalate films are less likely to generate dust during processing, use, etc., so that, for example, coating defects due to dust can be effectively prevented.

In addition, in order to improve adhesion to the release agent layer provided on the surface of this substrate, one or both sides may be subjected to a surface treatment such as an oxidation method or a roughening method, or a primer treatment, as desired. Examples of the oxidation method include corona discharge treatment, plasma discharge treatment, chromium oxidation treatment (wet), flame treatment, hot air treatment, ozone treatment, and ultraviolet irradiation treatment, and examples of the roughening method include sandblasting and thermal spraying treatment. These surface treatment methods are appropriately selected depending on the type of substrate, but generally, corona discharge treatment is preferably used in terms of effectiveness and operability.

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

2. Release Agent Layer In the release sheet according to this embodiment, the release agent layer is formed from a release agent composition containing a cationically polymerizable compound, a release component, and a cationic polymerization initiator.

(1) Cationic Polymerizable Compound As the cationic polymerizable compound, a compound capable of forming a polymer by cationic polymerization and not containing a polysiloxane skeleton can be used.

（式中、Ｒはそれぞれ、水素原子または有機基であり、ｎは、任意の正の整数である。） Here, the polysiloxane skeleton refers to a skeleton in which silicon atoms and oxygen atoms linked by covalent bonds are present alternately, and specifically refers to a structure represented by the following general formula (1).

(In the formula, each R is a hydrogen atom or an organic group, and n is any positive integer.)

Specific examples of cationic polymerizable compounds include compounds having cyclic ethers such as epoxy groups and oxetanyl groups. In particular, it is preferable to use epoxy compounds having epoxy groups, since there is a wide variety of polyfunctional compounds.

The epoxy compound preferably has three or more epoxy groups in one molecule. The epoxy compound preferably has 10 or less epoxy groups in one molecule, particularly preferably has 9 or less epoxy groups, and more preferably has 8 or less epoxy groups. When the number of epoxy groups in one molecule is 3 or more, the epoxy compound is more likely to undergo cationic polymerization, and the release agent composition is more likely to form a well-cured release agent layer. As a result, the release agent layer exhibits excellent solvent resistance, and blocking is less likely to occur when the release sheet according to this embodiment is wound up. When the number of epoxy groups in one molecule is 10 or less, good compatibility with the release component is obtained.

The above epoxy compound preferably has a molecular weight of 200 or more, particularly preferably 250 or more, and more preferably 300 or more. The above epoxy compound preferably has a molecular weight of 2000 or less, particularly preferably 1500 or less, and more preferably 1250 or less. When the molecular weight of the epoxy compound is 200 or more, repellency is unlikely to occur on the coated surface when the release agent composition is applied to a substrate. In addition, when the molecular weight of the epoxy compound is 2000 or less, the viscosity of the release agent composition or the coating liquid containing the release agent composition becomes relatively low. Therefore, by using the release agent composition or the coating liquid, the occurrence of streaks and the like on the surface is suppressed, and a release agent layer with excellent smoothness can be formed.

Examples of epoxy compounds that can be used in the release sheet according to this embodiment include glycidyl ethers of bisphenols such as bisphenol A and bisphenol F; glycidyl ethers of phenolic resins such as resorcinol, phenyl novolac, and cresol novolac; glycidyl ethers of other polyhydric alcohols; glycidyl esters of polycarboxylic acids such as phthalic acid, isophthalic acid, and tetrahydrophthalic acid; glycidylamine-type epoxy compounds consisting of epichlorohydrin adducts of amines and anilines; and so-called alicyclic epoxides in which epoxy is introduced by, for example, oxidizing the carbon-carbon double bonds in the molecule, such as vinylcyclohexane diepoxide, 3,4-epoxycyclohexylmethyl-3,4-dicyclohexanecarboxylate, and 2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)cyclohexane-m-dioxane.

Other polyhydric alcohols that constitute glycidyl ethers of polyhydric alcohols include glycerin, diglycerol, sugar alcohols, butanediol, polyethylene glycol, polypropylene glycol, and polyhydric alcohols having a biphenyl skeleton, a dicyclohexadiene skeleton, a naphthalene skeleton, etc.

Among these epoxy compounds, compounds having three or more epoxy groups in one molecule are preferred. As epoxy compounds having three or more epoxy groups in one molecule, glycidyl ethers of alcohols having three or more hydroxyl groups are preferred. Examples of such alcohols include glycerin (trivalent), diglycerol (tetravalent), trimethylolpropane (trivalent), ditrimethylolpropane (tetravalent), pentaerythritol (tetravalent), dipentaerythritol (tetravalent), sugar alcohols such as erythritol (tetravalent), xylitol (pentavalent), arabitol (pentavalent), sorbitol (hexavalent), mannitol (hexavalent), and galactitol (hexavalent), and ring-opening compounds of the above-mentioned epoxy compounds such as bisphenol A diglycerol ether (tetravalent), etc.

These epoxy compounds may be used alone or in combination of two or more. Among the above epoxy compounds, it is preferable to use diglycerol polyglycidyl ether and sorbitol polyglycidyl ether, which are glycidyl ethers of diglycerol, from the viewpoints of high reactivity and ease of availability.

As described above, in the release agent composition according to this embodiment, the cationic polymerizable compound is blended as a main agent. This allows the cationic polymerization of the cationic polymerizable compound to proceed effectively, and as a result, the release agent layer is well formed. Specifically, the amount of the cationic polymerizable compound blended in the release agent composition is preferably more than 50% by mass, particularly preferably 75% by mass or more, and more preferably 90% by mass or more. In addition, the blended amount is preferably 99.9% by mass or less, particularly preferably 99.75% by mass or less, and more preferably 99.5% by mass or less. When the blended amount is more than 50% by mass, a network (three-dimensional mesh structure) of the polymer of the cationic polymerizable compound is well formed with a sufficient amount of the cationic polymerizable compound, and a sufficiently hardened release agent layer is easily obtained. In addition, when the blended amount is 99.9% by mass or less, it is possible to relatively increase the blended amounts of the cationic polymerization initiator and the release component, which makes it easier to effectively proceed with the cationic polymerization and to achieve the desired release properties.

(2) Release Component The release component is not particularly limited as long as it can impart release properties to the release agent layer, and for example, at least one selected from the group consisting of silicone-based release components, fluorine-based release components, long-chain alkyl-based release components, alkyd-based release components, olefin-based release components, acrylic-based release components, and rubber-based release components can be used. Among these, from the viewpoint of easily imparting the desired release properties to the release agent layer, it is preferable to use at least one selected from the group consisting of silicone-based release components, fluorine-based release components, and long-chain alkyl-based release components, and it is particularly preferable to use a silicone-based release component.

It is preferable that the release component has a reactive group capable of reacting with a cationic polymerizable compound. This allows the release component to be fixed to the polymer formed by cationic polymerization of the cationic polymerizable compound in the release agent layer. As a result, a better network is formed in the release agent layer, the curing properties are further improved, and the release component can be prevented from migrating from the release agent layer to the object to which the release surface of the release sheet according to the present invention is laminated.

The reactive group is not particularly limited as long as it can react with the cationic polymerizable compound, and examples thereof include an epoxy group, an amino group, a mercapto group, a carboxyl group, and an anhydrous carboxyl group. When the cationic polymerizable compound has a reactive group, it is preferable that the release component has the same reactive group as the reactive group. This makes the release component highly reactive with the cationic polymerizable compound, and it is easy to firmly incorporate the release component into the above-mentioned network in the release agent layer by chemical bonding. In particular, when the cationic polymerizable compound has an epoxy group, it is preferable that the release component also has an epoxy group as a reactive group.

The position of the reactive group in the release component is not particularly limited. For example, when the release component has a linear structure or contains a main chain of a linear structure, the reactive group may be located at the end of the linear structure, or the reactive group may be located on the side chain of the linear structure. When located at the end, it may be located at one end of the linear structure, or it may be located at both ends. When located on the side chain, the side chain itself may be a reactive group, or a part of the side chain may be a reactive group. In addition, the reactive group may be located at both the end and the side chain. Among these, it is preferable that the release component has a reactive group at least as a side chain. This makes it easier to form a three-dimensional network structure containing the release component in the release agent layer, and the release component is less likely to migrate from the release agent layer to the object to which the release surface of the release sheet according to the present invention is laminated.

In the release sheet according to this embodiment, the release component is preferably a silicone-based release component as described above, and is particularly preferably a reactive polyorganosiloxane. Reactive polyorganosiloxanes have excellent reactivity with cationic polymerizable compounds, and by using reactive polyorganosiloxanes, better release properties can be achieved. As a result, a release sheet can be obtained that has a well-cured release agent layer and exhibits better release properties.

The weight average molecular weight of the reactive polyorganosiloxane is preferably 1000 or more, particularly preferably 1500 or more, and more preferably 2000 or more. The weight average molecular weight is preferably 100,000 or less, particularly preferably 50,000 or less, and more preferably 25,000 or less. When the weight average molecular weight is 1000 or more, it becomes easier to achieve the desired release properties. When the weight average molecular weight is 100,000 or less, the viscosity of the release agent composition or the coating liquid containing the release agent composition becomes relatively low, and the release agent composition or the coating liquid can be used to form a release agent layer with excellent smoothness and suppressed occurrence of streaks and the like on the surface.

A preferred example of the reactive polyorganosiloxane is epoxy-modified polydimethylsiloxane. In particular, it is preferable to use epoxy-modified polydimethylsiloxane having an epoxy group in the side chain, from the viewpoint of excellent surface condition of the coating film formed by the release agent composition or the coating liquid containing the release agent composition, and excellent curing properties of the coating film.

As the epoxy-modified polydimethylsiloxane, for example, commercially available compounds can be used. Examples of product names of such compounds include epoxy compounds having an epoxy group on the side chain, such as "X-22-343", "KF-101", "KF-1001", "X-22-2000", "KF-102", "X-22-4741", and "KF-1002", all of which are sold by Shin-Etsu Chemical Co., Ltd. Examples of epoxy compounds having epoxy groups on both ends, such as "X-22-163C" and "X-22-169B", all of which are sold by Shin-Etsu Chemical Co., Ltd. Examples of epoxy compounds having an epoxy group on one end, such as "X-22-173DX", all of which are sold by Shin-Etsu Chemical Co., Ltd. Furthermore, an example of an epoxy compound having epoxy groups at both ends and at a side chain is product name "X-22-9002" sold by Shin-Etsu Chemical Co., Ltd. These can be used alone or in combination of two or more.

As described above, in the release sheet according to this embodiment, the amount of the cationic polymerizable compound in the release agent composition is greater than the amount of the release component. This allows the cationic polymerization of the cationic polymerizable compound contained as the main agent to proceed effectively, and as a result, the release agent layer is well formed. In particular, the amount of the release component in the release agent composition is preferably 0.1 parts by mass or more, more preferably 0.25 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the cationic polymerizable compound. In addition, the amount of the release component in the release agent composition is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the cationic polymerizable compound. When the amount of the release component is 0.1 parts by mass or more, the release agent layer can exhibit better release properties. In addition, when the amount of the release component is 30 parts by mass or less, the amount of the cationic polymerizable compound is relatively large, and this makes it easier to obtain a well-cured release agent layer.

(3) Cationic Polymerization Initiator The cationic polymerization initiator is not particularly limited as long as it can initiate the cationic polymerization of the cationic polymerizable compound. In particular, the cationic polymerization initiator is preferably one that can initiate the cationic polymerization of the cationic polymerizable compound by at least one of irradiation with active energy rays and heating. By using such a cationic polymerization initiator, the initiation of cationic polymerization can be controlled, and as a result, it becomes possible to easily form a desired release agent layer. Among active energy rays and heat, it is preferable to use active energy rays from the viewpoint that it is easy to irradiate uniformly and it is possible to more easily control the initiation of cationic polymerization. In addition, as the active energy rays, ultraviolet rays, electron beams, etc. can be used, but among these, it is preferable to use ultraviolet rays from the viewpoint that it is easy to handle.

As the cationic polymerization initiator, a photoreaction initiator such as a sulfonium salt, an iodonium salt, a phosphonium salt, a diazonium salt, an ammonium salt, or a ferrocene is preferable, and known initiators can be used. Specific examples are given below, but the present invention is not limited to these compounds. Furthermore, these compounds may be used alone or in combination of two or more.

Examples of sulfonium salt photoinitiators include bis[4-(diphenylsulfonio)phenyl]sulfide bishexafluorophosphate, bis[4-(diphenylsulfonio)phenyl]sulfide bishexafluoroantimonate, bis[4-(diphenylsulfonio)phenyl]sulfide bistetrafluoroborate, bis[4-(diphenylsulfonio)phenyl]sulfide tetrakis(pentafluorophenyl)borate, diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate, diphenyl-4-(phenylthio)phenylsulfonium hexafluoroantimonate, diphenyl-4-(phenylthio)phenylsulfonium tetrafluoroborate, diphenyl-4-(phenylthio)phenylsulfonium tetrakis(pentafluorophenyl)borate, Examples of such compounds include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrafluoroborate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide bishexafluorophosphate, bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide bishexafluoroantimonate, bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide bistetrafluoroborate, and bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide tetrakis(pentafluorophenyl)borate.

Preferred examples of iodonium salt-based photoreaction initiators include diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis(pentafluorophenyl)borate, bis(dodecylphenyl)iodonium hexafluorophosphate, bis(dodecylphenyl)iodonium hexafluoroantimonate, bis(dodecylphenyl)iodonium tetrafluoroborate, bis(dodecylphenyl)iodonium tetrakis(pentafluorophenyl)borate, 4-methylphenyl-4-(1-methylethyl)phenyliodonium hexafluorophosphate, 4-methylphenyl-4-(1-methylethyl)phenyliodonium hexafluoroantimonate, 4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrafluoroborate, and 4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrakis(pentafluorophenyl)borate.

Preferred phosphonium salt photoinitiators include ethyltriphenylphosphonium tetrafluoroborate, ethyltriphenylphosphonium hexafluorophosphate, ethyltriphenylphosphonium hexafluoroantimonate, tetrabutylphosphonium tetrafluoroborate, tetrabutylphosphonium hexafluorophosphate, and tetrabutylphosphonium hexafluoroantimonate.

Preferred diazonium salt photoinitiators include phenyldiazonium hexafluorophosphate, phenyldiazonium hexafluoroantimonate, phenyldiazonium tetrafluoroborate, and phenyldiazonium tetrakis(pentafluorophenyl)borate.

Preferred ammonium salt-based photoreaction initiators include 1-benzyl-2-cyanopyridinium hexafluorophosphate, 1-benzyl-2-cyanopyridinium hexafluoroantimonate, 1-benzyl-2-cyanopyridinium tetrafluoroborate, 1-benzyl-2-cyanopyridinium tetrakis(pentafluorophenyl)borate, 1-(naphthylmethyl)-2-cyanopyridinium hexafluorophosphate, 1-(naphthylmethyl)-2-cyanopyridinium hexafluoroantimonate, 1-(naphthylmethyl)-2-cyanopyridinium tetrafluoroborate, and 1-(naphthylmethyl)-2-cyanopyridinium tetrakis(pentafluorophenyl)borate.

Preferred examples of ferrocene-based photoinitiators include (2,4-cyclopentadiene-1-yl)[(1-methylethyl)benzene]-Fe(II) hexafluorophosphate, (2,4-cyclopentadiene-1-yl)[(1-methylethyl)benzene]-Fe(II) hexafluoroantimonate, (2,4-cyclopentadiene-1-yl)[(1-methylethyl)benzene]-Fe(II) tetrafluoroborate, and (2,4-cyclopentadiene-1-yl)[(1-methylethyl)benzene]-Fe(II) tetrakis(pentafluorophenyl)borate.

Commercially available products of these photoreaction initiators include Asahi Denka Kogyo Co., Ltd., product names "SP-150", "SP-152", "SP-170", "SP-172", "CP-66", and "CP-77"; Union Carbide Corporation, product names "CYRACURE-UVI-6990", [CYRACURE-UVI-6974], and "CYRACURE-UVI-6992"; Nippon Soda Co., Ltd., product names "CI-2855", "CI-2639", and "CI-2758"; Sanshin Chemical Industry Co., Ltd., product names "San-Aid SI-60", "San-Aid SI-80", and "San-Aid SI-100"; and Chiba Specialty Examples of such products include those manufactured by Rhodia Chemicals, product names "Irgacure 261" and "Irgacure 250"; those manufactured by Rhodia Japan, product name "RHODORSIL 2074"; those manufactured by Midori Chemical, product name "bis(4-t-butylphenyl)iodonium hexafluorophosphate"; those manufactured by San-Apro, product names "CPI-100P", "CPI-101A", and "CPI-200K"; those manufactured by Lamberti, product names "ESACURE-1064" and "ESACURE-1187"; and those manufactured by Nippon Kayaku, product name "Kayacure PCI-220".

As the cationic polymerization initiator, a sulfonium salt or iodonium salt initiator is preferred in terms of curing speed, stability, and economy. Therefore, among the above-mentioned commercially available products, it is preferable to use as the cationic polymerization initiator the following: Ciba Specialty Chemicals, product name "Irgacure 250"; San-Apro, product names "CPI-100P", "CPI-101A", and "CPI-200K".

The cationic polymerization initiator may be used alone or in combination of two or more types.

In the release sheet according to this embodiment, the amount of the cationic polymerization initiator in the release agent composition is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, relative to 100 parts by mass of the cationic polymerizable compound. The amount of the cationic polymerization initiator in the release agent composition is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less, relative to 100 parts by mass of the cationic polymerizable compound. When the amount of the cationic polymerization initiator is within the above range, the cationic polymerization proceeds effectively, and thus it becomes easier to obtain a well-cured release agent layer.

(4) Other Components The release agent composition may contain, in addition to the components described above, an antistatic agent, a reaction inhibitor, an adhesion improver, and the like.

(5) Production of the release agent composition The release agent composition can be produced by mixing the above-mentioned cationic polymerizable compound, the release component, the cationic polymerization initiator, and other components as desired. The obtained release agent composition may be diluted with a dilution solvent as necessary to form a coating liquid.

Examples of the dilution 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 methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve-based solvents such as ethyl cellosolve.

The concentration and viscosity of the coating liquid prepared in this manner are not particularly limited as long as they are within the range in which coating is possible, and can be appropriately selected according to the situation. For example, the release agent composition is diluted so that its concentration is 10% by mass or more and 60% by mass or less. Note that the addition of a dilution solvent, etc. is not a necessary condition for obtaining the coating liquid, and if the release agent composition has a viscosity, etc. that allows coating, it is not necessary to add a dilution solvent.

(6) Thickness of the release agent layer In the release sheet according to the present embodiment, the thickness of the release agent layer is preferably 10 nm or more, particularly preferably 50 nm or more. In addition, the thickness is preferably 10,000 nm or less, particularly preferably 5,000 nm or less. When the thickness of the release agent layer is 10 nm or more, it is easy to achieve the desired release properties. In addition, when the thickness of the release agent layer is 10,000 nm or less, it is easy to form a well-cured release agent layer.

3. Physical properties of the release sheet In the release sheet according to this embodiment, the surface free energy (γtotal) measured on the surface of the release agent layer opposite to the substrate is preferably 25 mJ/m ² or more, particularly preferably 27 mJ/m ² or more. In addition, the surface free energy is preferably 35 mJ/m ² or less, particularly preferably 33 mJ/m ² or less. When the free energy is 25 mJ/m ² or more, the bonding between the release component and the network in the release agent layer is appropriately generated, and the transfer of the release component to the adhesive or green sheet in which the release sheet according to this embodiment is used is suppressed. In addition, when the surface free energy is 35 mJ/m ² or less, the release component is localized near the surface of the release agent layer, and the release force of the release sheet according to this embodiment to the adhesive or green sheet in which the release sheet is used can be effectively reduced.

In the release sheet according to this embodiment, the maximum projection height Rp of the surface of the release agent layer opposite the substrate is preferably less than 2000 nm, more preferably 500 nm or less, and even more preferably 50 nm or less. By having the maximum projection height Rp of less than 2000 nm, the release surface of the release sheet has excellent smoothness. As a result, the smoothness of the surface of the adhesive sheet or ceramic green sheet laminated on the release surface that comes into contact with the release surface is also excellent. As a result, it is possible to manufacture an adhesive sheet that exhibits excellent performance and a laminated ceramic product that exhibits excellent performance. Although the lower limit of the maximum projection height Rp is not particularly limited, it is preferably, for example, 10 nm or more, and more preferably 20 nm or more.

In the release sheet according to this embodiment, the peeling force required to peel the adhesive sheet from the release sheet after the release surface and the adhesive surface of the adhesive sheet are attached can be set as appropriate, but is preferably 100 mN/20 mm or more, and more preferably 150 mN/20 mm or more. The peeling force is preferably 2000 mN/20 mm or less, and more preferably 1500 mN/20 mm or less. According to the release sheet according to this embodiment, the release agent layer is formed using the above-mentioned release agent composition, so that the above-mentioned releasability can be exhibited well. The method for measuring the peeling force required to peel the release sheet from the adhesive sheet is as shown in the test example described later.

In the release sheet according to this embodiment, the peeling force required to peel the release sheet from the ceramic green sheet formed on the release surface can be set as appropriate, but is preferably 5 mN/20 mm or more, and more preferably 10 mN/20 mm or more. The peeling force is preferably 100 mN/20 mm or less, and more preferably 75 mN/20 mm or less. According to the release sheet according to this embodiment, the release agent layer is formed using the above-mentioned release agent composition, so that the above-mentioned releasability can be exhibited well. The method for measuring the peeling force required to peel the release sheet from the ceramic green sheet is as shown in the test example described later.

4. Method for Producing Release Sheet The release sheet according to the present embodiment can be produced by a general method. For example, a coating solution of the release agent composition described above can be applied to one side of a substrate, and then the resulting coating film can be cured to form a release agent layer, thereby obtaining a release sheet.

Coating methods that can be used include, for example, gravure coating, bar coating, spray coating, spin coating, knife coating, roll coating, and die coating.

When the coating is heated to dry the solvent in the coating liquid, the temperature is preferably 100°C or higher, and more preferably 120°C or higher. The temperature is preferably 180°C or lower, and more preferably 150°C or lower. The heating time is preferably 10 seconds or longer, and more preferably 15 seconds or longer. The heating time is preferably 60 seconds or shorter, and more preferably 30 seconds or shorter.

The coating film can be cured by promoting cationic polymerization of the cationic polymerizable compound. Here, the cationic polymerization can be initiated by at least one of irradiating the coating film with active energy rays and heating the coating film, depending on the type of cationic polymerization initiator.

Examples of active energy rays that can be used include ultraviolet rays, electron beams, etc., with ultraviolet rays being particularly preferred as they are easy to handle.

The irradiation of ultraviolet rays can be performed by a high pressure mercury lamp, a xenon lamp, or the like, and the amount of irradiation of ultraviolet rays is preferably 50 mW/cm ² or more in illuminance, particularly preferably 200 mW/cm ² or more. The illuminance is preferably 5000 mW/cm ² or less, particularly preferably 3000 mW/cm ² or less. The amount of ultraviolet light is preferably 10 mJ/cm ² or more, particularly preferably 30 mJ/cm ² or more. The amount of light is preferably 250 mJ/cm ² or less, particularly more preferably 150 mJ/cm ² or less. By performing the irradiation of ultraviolet rays under conditions related to the above range, it becomes possible to more satisfactorily cure the release agent composition, and it becomes possible to effectively form a good release agent layer.

Electron beam irradiation can be performed using an electron beam accelerator or the like, and the dose of electron beam irradiation is preferably 0.1 kGy or more, and more preferably 1 kGy or more. The dose is preferably 50 kGy or less, and more preferably 30 kGy or less.

According to the above-mentioned manufacturing method, it is possible to effectively proceed with the cationic polymerization of the cationic polymerizable compound, and a well-cured release agent layer can be formed. Furthermore, since the release agent layer thus obtained contains a release component, the release sheet can exhibit good releasability.

5. Method of Using the Release Sheet The release sheet according to this embodiment can be used for the same purposes as general release sheets.

For example, the release sheet according to this embodiment can be used in the manufacture of an adhesive sheet. In this case, a coating liquid of an adhesive composition for forming an adhesive layer of the adhesive sheet is applied onto the release surface of the release sheet according to this embodiment, and dried to form an adhesive layer. Thereafter, a substrate for the adhesive sheet is laminated on the surface of the adhesive layer opposite the release sheet, thereby manufacturing an adhesive sheet with a release sheet attached thereto. Alternatively, a double-sided adhesive sheet consisting of two release sheets and an adhesive layer laminated therebetween can be manufactured by laminating another release sheet, preferably the release surface of the release sheet according to this embodiment, on the surface of the adhesive layer formed as described above opposite the release sheet. In addition, the manufactured adhesive sheet can be stored with the release sheet attached, thereby protecting the adhesive surface of the adhesive sheet with the release sheet.

Furthermore, the release sheet according to this embodiment can also be used to produce a ceramic green sheet. For example, a ceramic slurry containing a ceramic material such as barium titanate or titanium oxide can be applied to the release surface of the release sheet, and then the ceramic slurry can be dried to produce a ceramic green sheet to which the release sheet is attached.

In the release sheet according to this embodiment, the release agent layer is formed using the release agent composition described above. In particular, when the release agent layer is formed, the cationic polymerizable compound contained as the main component in the release agent composition undergoes cationic polymerization due to the action of the cationic polymerization initiator, thereby hardening the release agent composition. This allows a good formation of a release agent layer containing a release component. Therefore, the release sheet according to this embodiment exhibits good releasability.

The above-described embodiments 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 embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

For example, other layers such as an antistatic layer may be provided on the side of the substrate in the release sheet opposite the release agent layer, or between the substrate and the release agent layer.

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

Example 1
A coating solution of a release agent composition having a solid content of 18% by mass was obtained by mixing 100 parts by mass (solid content equivalent; the same applies below) of diglycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, product name "Denacol EX-421", number of epoxy groups in one molecule: 3, molecular weight: 334) as a cationic polymerizable compound, 1.0 part by mass of polydimethylsiloxane having an epoxy-modified side chain (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KF-101", weight average molecular weight: 28,500) as a release component, and 8.0 parts by mass of diphenyl[4-(phenylthio)phenyl]sulfonium hexafluorophosphate (manufactured by San-Apro Co., Ltd., product name "CPI-100P") as a cationic polymerization initiator in methyl ethyl ketone.

The obtained coating solution of the release agent composition was applied to one side of a biaxially stretched polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name "Lumirror S10", thickness: 23 μm, maximum projection height on both sides Rp: 452 nm) as a substrate using a Mayer bar #5 to form a coating film. The coating film was heated at 120° C. for 15 seconds, and then irradiated with ultraviolet light from the side of the coating film opposite the substrate (illuminance: 1000 mW/cm ² , light quantity: 50 mJ/cm ² ) to form a release agent layer with a thickness of 1.0 μm. This resulted in a release sheet in which the substrate and the release agent layer were laminated together.

The thicknesses of the substrate and the obtained release agent layer were measured using a reflective film thickness meter (Filmetrics, product name "F20").

[Examples 2 to 6, Comparative Examples 1 and 2]
Release sheets were produced in the same manner as in Example 1, except that the amounts of the release component and the cationic polymerization initiator in the release agent composition were changed as shown in Table 1.

Test Example 1 (Evaluation of Curability of Release Agent Layer)
The release surface of the release sheets obtained in the Examples and Comparative Examples was rubbed with a finger 10 times, and the presence or absence of cloudiness (smear) and removal of the release agent layer (rub-off) was visually confirmed. Then, the hardening property of the release agent layer was evaluated according to the following criteria. The results are shown in Table 1.
○: Neither smear nor rub-off was observed.
×: At least one of smear and rub-off was observed.

[Test Example 2] (Evaluation of peelability from pressure-sensitive adhesive sheet)
For the release sheets according to Examples 1 to 6 and Comparative Example 2 which were rated as having a good hardening property for the release agent layer in Test Example 1, a 20 mm wide acrylic adhesive tape (manufactured by Nitto Denko Corporation, product name "31B Tape") was attached to the release surface using a 2 kg hand roller.

After storing for 30 minutes under conditions of 23°C and 50% RH, the release sheet side was fixed to a stainless steel plate and the acrylic adhesive tape side was peeled off at a peel angle of 180° and a peel rate of 300 mm/min using a tensile tester (manufactured by Shimadzu Corporation, product name "AG-IS500N"), and the force required to peel (peel force; mN/20 mm) was measured.

Based on the obtained peel strength (mN/20 mm), the peelability from the pressure-sensitive adhesive sheet was evaluated according to the following criteria. The results are shown in Table 1.
◯: Peel strength is less than 500 mN/20 mm.
×: The peeling force is 500 mN/20 mm or more.

[Test Example 3] (Evaluation of peelability from ceramic green sheet)
A ceramic slurry was prepared by adding 69 parts by mass of toluene and 46 parts by mass of ethanol to 100 parts by mass of barium titanate ( _BaTiO3 ; manufactured by Sakai Chemical Industry Co., Ltd., product name "BT-03"), 10 parts by mass of polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., product name "S-LEC B-KBM-2"), and 5 parts by mass of dioctyl phthalate (manufactured by Kanto Chemical Co., Ltd., product name "Dioctyl Phthalate Grade 1"), and mixing and dispersing the mixture in a ball mill.

The release sheets according to Examples 1 to 6 and Comparative Example 2, which were rated as good for the hardening of the release agent layer in Test Example 1, were stored at room temperature for 24 hours after production, and then the above ceramic slurry was uniformly applied to the release surface of the release agent layer using an applicator, and then dried at 80°C for 1 minute in a dryer. This resulted in a ceramic green sheet with a thickness of 3 μm on the release sheet. In this way, a release sheet with a ceramic green sheet was produced.

The ceramic green sheet with release sheet was left to stand for 24 hours in an atmosphere of 23°C and 50% RH. Next, an acrylic adhesive tape (manufactured by Nitto Denko Corporation, product name "31B tape") was attached to the surface of the ceramic green sheet opposite the release sheet, and in that state, it was cut to a width of 20 mm. This was used as the measurement sample.

The adhesive sheet side of the measurement sample was fixed to a flat plate, and a tensile testing machine (manufactured by Shimadzu Corporation, product name "AG-IS500N") was used to peel the release sheet from the ceramic green sheet at a peel angle of 180° and a peel rate of 100 mm/min, and the force required to peel (peel force; mN/20 mm) was measured.

Based on the obtained peel strength (mN/20 mm), the peelability from the ceramic green sheet was evaluated according to the following criteria. The results are shown in Table 1.
◯: Peel strength is less than 100 mN/20 mm.
×: The peeling force is 100 mN/20 mm or more.

[Test Example 4] (Measurement of surface free energy)
The surface free energy (γtotal) of the surface of the release agent layer side of the release sheet obtained in the examples and comparative examples was calculated. Specifically, the surface free energy (γtotal) and each component (dispersion component γd, polar component γp, hydrogen bond component γh) were calculated by using water, diiodomethane, and bromonaphthalene, which have known contact angles, as probe liquids, measuring the contact angle of each probe liquid with respect to the release agent layer using a contact angle meter, and calculating the surface free energy (γtotal) and the surface free energy (γtotal) from the contact angle obtained according to the Kitazaki-Hata method (see Kitazaki Yasuaki et al., Journal of the Japan Adhesion Association, Vol. 8, No. 3, 1972, pp. 131-141). As the contact angle meter, a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "Fully automatic contact angle meter DM-701") was used. The results are shown in Table 1.

As shown in Table 1, it was found that the release sheets of the examples had superior hardening properties of the release agent layer and good releasability compared to the release sheets of the comparative examples.

The release sheet of the present invention is suitably used as a release sheet onto which the adhesive layer of an adhesive sheet is laminated, a release sheet that can be used in the production of ceramic green sheets, etc.

Claims (7)

A release sheet comprising a substrate and a release agent layer provided on at least one surface of the substrate,
The substrate is a plastic film,
the release agent layer is formed from a release agent composition containing a cationically polymerizable compound not containing a polysiloxane skeleton, a release component, and a cationic polymerization initiator;
the cationic polymerizable compound is a glycidyl ether of a polyhydric alcohol,
the polyhydric alcohol is at least one selected from the group consisting of glycerin, diglycerol, sugar alcohols, butanediol, polyethylene glycol, polypropylene glycol, polyhydric alcohols having a biphenyl skeleton, polyhydric alcohols having a dicyclohexadiene skeleton, polyhydric alcohols having a naphthalene skeleton, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, and bisphenol A diglycerol ether;
In the release agent composition, the amount of the cationic polymerizable compound is greater than the amount of the release component and the amount of the cationic polymerization initiator,
the content of the cationically polymerizable compound in the stripping composition is 75% by mass or more and 99.9% by mass or less,
the amount of the release component in the release agent composition is 0.1 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the cationically polymerizable compound,
A release sheet, characterized in that the surface free energy of the release agent layer measured on the side opposite to the substrate is 25 mJ/ ^m2 or more and 35 mJ/ ^m2 or less. 2. The release sheet according to claim 1 , wherein the glycidyl ether has three or more epoxy groups in one molecule. 3. The release sheet according to claim 1 , wherein the glycidyl ether has a molecular weight of 200 or more and 2,000 or less . The release sheet according to any one of claims 1 to 3 , characterized in that the release component is at least one selected from the group consisting of silicone-based release components, fluorine-based release components, and long-chain alkyl-based release components. 5. The release sheet according to claim 1 , wherein the release component has a reactive group capable of reacting with the cationic polymerizable compound. 6. The release sheet of claim 5 , wherein the release component is a reactive polyorganosiloxane. The release sheet according to any one of claims 1 to 6 , which is used in a ceramic green sheet manufacturing process.