WO2022250125A1

WO2022250125A1 - Silicone composition for forming peelable cured film, and release sheet

Info

Publication number: WO2022250125A1
Application number: PCT/JP2022/021671
Authority: WO
Inventors: 修司遠藤; 賢一日野
Original assignee: ダウ・東レ株式会社
Priority date: 2021-05-28
Filing date: 2022-05-27
Publication date: 2022-12-01
Also published as: CN117255837A; KR20240013762A; JPWO2022250125A1; TW202311446A

Abstract

The present invention relates to a silicone composition for forming a peelable cured film, said silicone composition comprising: (A) a chain organopolysiloxane that has a viscosity greater than 100,000 mPa∙s at 25°C, and has at least two C2-12 alkenyl groups per molecule, but only in a side chain of the molecule; (B) a chain organopolysiloxane that has a viscosity of 1,000-100,000 mPa∙s at 25°C, has at least two C2-12 alkenyl groups within one molecule, but only in a side chain of the molecule, and has an alkenyl group content of 0.0018-0.0148 mol/100 g; (C) an organopolysiloxane that has at least two silicon-bonded hydrogen atoms within one molecule; and (D) a catalyst for a hydrosilylation reaction. This composition is capable of forming a peelable cured film that demonstrates a relatively light peeling resistance with regard to an adhesive substance, said peeling resistance changing little over time, and furthermore suppresses a reduction in the residual adhesion ratio of said adhesive substance.

Description

Silicone composition for forming release cured film and release sheet

The present invention relates to a cured release film-forming silicone composition and a release sheet having a cured release film obtained by curing the composition.

A release cured film-forming silicone composition is used to form a cured film that exhibits moderate release performance against sticky substances. As such a silicone composition for forming a cured release film, for example, Patent Document 1 discloses a silicone composition having a viscosity of 500,000 centistokes or more at 25° C., containing at least 0.1 mol % of a methylvinylsiloxane unit, and , an organopolysiloxane having a hydroxyl group or a vinyl group at the molecular chain end, an organopolysiloxane having a viscosity at 25° C. of 10 to 100,000 centistokes and having a vinyl group at the molecular chain end, at least 3 per molecule A composition consisting of an organopolysiloxane having silicon-bonded hydrogen atoms and a hydrosilylation reaction catalyst is disclosed in Patent Document 2, and has a viscosity of 50 to 10,000 cps at 25° C. and Organopolysiloxane having at least two vinyl groups, at least one of which is in a side chain of the molecular chain, the content of the vinyl group being 0.5 to 10 mol%, and having a viscosity at 25°C of 100, A composition comprising an organopolysiloxane having a vinyl group content of 000 cps or more and a vinyl group content lower than that of the above organopolysiloxane, an organopolysiloxane having at least two silicon-bonded hydrogen atoms in one molecule, and a catalyst for a hydrosilylation reaction. Patent Document 3 discloses an organopolysiloxane having two or more alkenyl groups having 2 to 8 carbon atoms in one molecule, and at least two silicon-bonded hydrogen atoms in one molecule. A composition comprising an organopolysiloxane, an organopolysiloxane containing no alkenyl groups and silicon-bonded hydrogen atoms in one molecule, a hydrosilylation inhibitor, and a hydrosilylation catalyst is disclosed.

However, the composition of Patent Document 1 has a viscosity of 10 to 100,000 centistokes at 25°C and uses an organopolysiloxane having a vinyl group at the end of the molecular chain. has a viscosity of 50 to 10,000 cps and uses an organopolysiloxane with a relatively large vinyl group content. However, there is a problem that the peeling resistance changes. On the other hand, the composition of Patent Document 3 uses an organopolysiloxane that does not have alkenyl groups and silicon-bonded hydrogen atoms in one molecule. , there is a problem that the residual adhesion rate of the sticky substance is remarkably reduced.

On the other hand, Patent Document 4 discloses that a 30% by weight toluene solution has a viscosity of 500 centistokes or more at 25° C., has an alkenyl group having 4 to 8 carbon atoms in the side chain of the molecular chain, and has a hydroxyl group and an alkenyl group at the end of the molecular chain. or alkyl group-blocked diorganopolysiloxane, a 30% by weight toluene solution having a viscosity of 500 centistokes or more at 25° C., a molecular chain end blocked with a hydroxyl group, an alkenyl group, or an alkyl group, and one molecule diorganopolysiloxanes having at least one alkenyl group therein, organopolysiloxanes having a viscosity of 1 to 1,000 centistokes at 25°C and having at least 3 silicon-bonded hydrogen atoms per molecule, hydrosilyl A composition comprising a reaction catalyst, a hydrosilylation inhibitor, and an organic solvent is disclosed. However, since the composition of Patent Document 4 contains two types of high-molecular-weight organopolysiloxanes, the viscosity of the composition is high, and there is a problem that the coating property and handling workability (handling property) are poor.

Further, in Patent Document 5, a 30% by weight toluene solution has a viscosity of 1.5 to 70 Pa·s at 25°C, and an organopolysiloxane whose molecular chain ends are blocked with alkenyl groups has a viscosity of 0.25°C at 25°C. One molecule of an organopolysiloxane having a viscosity of 1 to 500 Pa·s, having an alkenyl group in the side chain of the molecular chain, and having an alkenyl group content of 0.2 to 5 times the alkenyl group content of the organopolysiloxane. A composition is disclosed comprising an organopolysiloxane having at least three silicon-bonded hydrogen atoms therein, a catalyst for a hydrosilylation reaction, and an organic solvent. However, although the composition of Patent Document 5 has improved coatability and handling workability (handling property), it is said that it cannot sufficiently solve the problem of forming a cured film with light peeling resistance. I have a problem.

JP-A-50-025644 JP-A-61-159480 JP-A-02-145650 JP-A-09-125004 Japanese Patent Application Laid-Open No. 2004-190202

An object of the present invention is to provide a peelable cured film that exhibits relatively light peeling resistance to adhesive substances, undergoes little change over time, and further suppresses a decrease in the residual adhesion rate of the adhesive substances. An object of the present invention is to provide a silicone composition for forming a hardening film. Another object of the present invention is to provide a release sheet that exhibits relatively light peeling resistance to an adhesive substance, undergoes little change over time, and further suppresses a decrease in the residual adhesion rate of the adhesive substance. to do.

The silicone composition for forming a cured release film of the present invention is
(A) a linear organopolysiloxane having a viscosity at 25° C. exceeding 100,000 mPa·s and having at least two alkenyl groups having 2 to 12 carbon atoms in each molecule only on the side chains of the molecular chain;
(B) has a viscosity of 1,000 to 100,000 mPa·s at 25° C., has at least two alkenyl groups having 2 to 12 carbon atoms in one molecule only in the side chains of the molecular chain, and contains the alkenyl groups A linear organopolysiloxane in an amount of 0.0018 to 0.0148 mol/100 g [mass ratio of component (A) to component (B) {component (A)/component (B)} is 10/90 to 90 /10 amount],
(C) Organopolysiloxane having at least two silicon-bonded hydrogen atoms per molecule {Silicone atoms in component (C) per mole of alkenyl groups in components (A) and (B) and (D) a catalytic amount of catalyst for hydrosilylation reaction.

In the present composition, the alkenyl group in component (A) is preferably a hexenyl group.

In the present composition, the mass ratio of (A) component to (B) component {(A) component/(B) component} is preferably 40/60 to 80/20.

The composition preferably further contains (E) a hydrosilylation reaction inhibitor.

The composition preferably further contains (F) an organic solvent.

The release sheet of the present invention is characterized by having a cured release film obtained by curing the above silicone composition for forming a cured release film.

The silicone composition for forming a peelable cured film of the present invention exhibits relatively light peeling resistance to adhesive substances, exhibits little change over time, and suppresses a decrease in the residual adhesion rate of the adhesive substances. It is characterized by being able to form a peelable cured film. In addition, the release sheet of the present invention exhibits relatively low peel resistance to adhesive substances, exhibits little change over time, and is characterized in that it suppresses a reduction in the residual adhesion rate of the adhesive substances.

<Definition of terms>
The term "viscosity" used herein is defined in accordance with JIS K 7117-1: 1999 "Plastics - liquid, emulsion or dispersed resins - method for measuring apparent viscosity using a Brookfield rotational viscometer". means a value at 25°C (unit: mPa·s or Pa·s) measured with a B-type rotational viscometer.

The term "plasticity" used in this specification conforms to the method specified in JIS K 6249: 2003 "Testing methods for uncured and cured silicone rubber", and a load of 1 kgf is applied to a spherical sample of 4.2 g. Means the value (unit: mm) when applied for 3 minutes.

<Silicone Composition for Forming Releasable Cured Film>
The silicone composition for forming a cured release film of the present invention will be described in detail.

Component (A) is a chain organopolysiloxane having at least two alkenyl groups with 2 to 12 carbon atoms per molecule only on the side chains of the molecular chain. Examples of alkenyl groups in component (A) include vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl and octenyl groups, with hexenyl being preferred. Such alkenyl groups should be present only on the side chains of the molecular chain and should not be present on the ends of the molecular chain. Silicon-bonded groups other than alkenyl groups in component (A) include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and heptyl groups; aryl groups having 6 to 12 carbon atoms such as phenyl group, tolyl group and xylyl group; aralkyl groups having 7 to 12 carbon atoms such as benzyl group and phenethyl group; 3,3,3-trifluoropropyl group, 4,4, 4,3,3-pentafluorobutyl group, 5,5,5,4,4,3,3-heptafluoropentyl group, 6,6,6,5,5,4,4,3,3-nona fluoroalkyl groups having 3 to 12 carbon atoms such as fluorohexyl group and 7,7,7,6,6,5,5,4,4,3,3-undecafluoroheptyl group, preferably methyl is the base. In the component (A), a small amount of an alkoxy group having 1 to 3 carbon atoms such as a hydroxyl group, a methoxy group and an ethoxy group may be bonded to the silicon atom within a range that does not impair the purpose of the present invention.

Although the content of alkenyl groups in component (A) is not limited, it is preferably in the range of 0.0185 to 0.1110 mol/100 g, or in the range of 0.0185 to 0.0739 mol/100 g. This is because when the content of alkenyl groups in component (A) is at least the lower limit of the above range, the composition is sufficiently cured, and migration of the silicone component to the sticky substance of the resulting peelable cured film is suppressed. On the other hand, when the content is below the upper limit of the above range, the resulting peelable cured film has moderate light peeling resistance.

Component (A) is an organopolysiloxane having a high degree of polymerization with a viscosity at 25°C exceeding 100,000 mPa·s. shape. When the component (A) is in the form of crude rubber, it preferably has a plasticity of 3.0 mm or less, or 0.5 to 3.0 mm.

Although the molecular structure of component (A) is substantially linear, part of the molecular chain may be branched. Examples of such component (A) include a dimethylsiloxane/methylhexenylsiloxane copolymer having both molecular chain ends blocked with trimethylsiloxy groups, a molecular chain end substantially blocked with trimethylsiloxy groups, and some molecules having A dimethylsiloxane/methylhexenylsiloxane copolymer whose chain ends are blocked with dimethylhydroxysiloxy groups is exemplified.

Component (B) is a chain organopolysiloxane having at least two alkenyl groups with 2 to 12 carbon atoms per molecule only on the side chains of the molecular chain. The alkenyl group in component (B) is exemplified by the same alkenyl groups as in component (A), preferably vinyl group. Such alkenyl groups should be present only on the side chains of the molecular chain and should not be present on the ends of the molecular chain. Examples of silicon-bonded groups other than alkenyl groups in component (B) include the same groups as in component (A) above, preferably a methyl group. In the component (B), a small amount of an alkoxy group having 1 to 3 carbon atoms such as a hydroxyl group, a methoxy group and an ethoxy group may be bonded to the silicon atom within a range that does not impair the purpose of the present invention.

The viscosity of component (B) at 25°C is in the range of 1,000 to 100,000 mPa s, preferably in the range of 1,000 to 70,000 mPa s, preferably 2,000 to 50,000 mPa s. or within the range of 3,000 to 50,000 mPa·s. This is because when the viscosity of the component (B) is at least the lower limit of the above range, the curability of the present composition can be improved. This is because it is possible to form a peelable cured film that changes little over time.

The alkenyl group content of component (B) is in the range of 0.0018 to 0.0148 mol/100 g, preferably 0.000 mPa·s or more when the viscosity is 1,000 mPa·s or more and 10,000 mPa·s or less. 0026 to 0.0148 mol/100 g, and when the viscosity exceeds 10,000 mPa s and is 100,000 mPa s or less, the range is 0.0018 to 0.0111 mol/100 g, or the viscosity is 1,000 mPa s or less. Within the range of 0.0037 to 0.0148 mol/100 g when the viscosity is 000 mPa s or more and 10,000 mPa s or less, and 0.0018 when the viscosity exceeds 10,000 mPa s and 100,000 mPa s or less ~0.0074 mol/100g. This is because when the alkenyl group content of component (B) is at least the lower limit of the above range, the composition is sufficiently cured, and migration of the silicone component to the sticky substance of the resulting peelable cured film is suppressed. On the other hand, if it is at most the upper limit of the above range, the resulting peelable cured film has moderate light peel resistance and changes over time. can be made smaller.

The reason why the preferred alkenyl group content differs depending on the viscosity of the component (B) is as follows. When the viscosity of component (B) is low, the molecular weight is low, so even if the content of alkenyl groups is the same, the number of alkenyl groups in one molecule is reduced. Since the component (B) has low reactivity, the silicone component tends to migrate to the adhesive substance of the cured release film. This is because it is preferable to increase the alkenyl group content of component (B) in order to suppress this. On the other hand, when the viscosity of component (B) is high, the molecular weight is high, so even if the content of alkenyl groups is the same, the number of alkenyl groups in one molecule increases. Since such component (B) is highly reactive, it is less likely to be localized on the surface of the peelable cured film. In general, unreacted silicon-bonded hydrogen atoms may remain on the surface of the peelable cured film, and they may react with moisture to form silicon-bonded hydroxyl groups. are thought to be responsible for the increased interactions with toxic substances. In order to suppress the residual silicon-bonded hydrogen atoms on the surface of the peelable cured film, the localization of component (B) on the surface of the cured film is promoted, and the relative reactivity with component (A) is differentiated. This is because, when the viscosity of component (B) is high, it is preferable to reduce the content of alkenyl groups in component (B).

In the present composition, the content of component (B) is such that the mass ratio of component (A) to component (B) {(A) component/(B) component} is within the range of 10/90 to 90/10. preferably an amount within the range of 30/70 to 90/10, or an amount within the range of 40/60 to 80/20. This is because when the mass ratio {(A) component/(B) component} of component (A) and component (B) is equal to or higher than the lower limit of the above range, the curability of the present composition, particularly This is because it is possible to improve the curability of and increase the strength of the resulting cured film. In the present composition, since component (B) is blended in a specific ratio with respect to component (A), it has relatively light peeling resistance and a peeling property that suppresses a decrease in the residual adhesion rate of the sticky substance. A cured film can be formed.

Component (C) is an organopolysiloxane having at least two silicon-bonded hydrogen atoms in one molecule and is the cross-linking agent of the present composition. The bonding positions of the silicon-bonded hydrogen atoms in the component (C) are not limited, and are exemplified by molecular chain terminals and/or molecular chain side chains. Examples of groups bonded to silicon atoms other than hydrogen atoms in component (C) include alkyl groups having 1 to 12 carbon atoms such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group and heptyl group; aryl groups having 6 to 12 carbon atoms such as phenyl group, tolyl group and xylyl group; aralkyl groups having 7 to 12 carbon atoms such as benzyl group and phenethyl group; 3,3,3-trifluoropropyl group, 4,4, 4,3,3-pentafluorobutyl group, 5,5,5,4,4,3,3-heptafluoropentyl group, 6,6,6,5,5,4,4,3,3-nona fluoroalkyl groups having 3 to 12 carbon atoms such as fluorohexyl group and 7,7,7,6,6,5,5,4,4,3,3-undecafluoroheptyl group, preferably methyl is the base. Further, component (C) may have a small amount of alkoxy groups having 1 to 3 carbon atoms, such as hydroxyl, methoxy, and ethoxy groups, bonded to silicon atoms within the range not impairing the object of the present invention.

Although the viscosity of component (C) at 25°C is not limited, it is preferably in the range of 1 to 1,000 mPa·s, or in the range of 5 to 500 mPa·s. This is because when the viscosity of component (C) is at least the lower limit of the above range, volatilization of this component from the composition is suppressed and the composition is stabilized. , because the curability of the present composition is accelerated.

The molecular structure of component (C) is not limited, and may be, for example, linear, partially branched linear, branched, cyclic, or resinous. Examples of such component (C) include a dimethylsiloxane/methylhydrogensiloxane copolymer having both molecular chain terminals blocked with trimethylsiloxy groups, a dimethylsiloxane/methylhydrogensiloxane copolymer having both molecular chain terminals blocked with dimethylhydrogensiloxy groups, Dimethylhydrogensiloxy group-blocked dimethylpolysiloxane at both molecular chain ends, methylhydrogenpolysiloxane blocked at both molecular chain ends with trimethylsiloxy groups, cyclic methylhydrogenpolysiloxane, cyclic methylhydrogensiloxane/dimethylsiloxane copolymer, formula: H A copolymer consisting of a siloxane unit represented by (CH ₃ ) ₂ SiO _1/2 and a siloxane unit represented by the formula: SiO _4/2 , and a siloxane unit represented by the formula: (CH ₃ ) ₃ SiO _1/2 A copolymer consisting of a siloxane unit, a siloxane unit represented by the formula: H(CH ₃ ) ₂ SiO _1/2 and a siloxane unit represented by the formula: SiO _4/2 is exemplified.

In the present composition, the content of component (C) is 0.5 silicon-bonded hydrogen atoms in component (C) per 1 mol of alkenyl groups in components (A) and (B) in total. The amount is in the range of 5 mol, preferably in the range of 0.6 to 3.0, or in the range of 0.7 to 1.5. This is because when the content of component (C) is at least the lower limit of the above range, the composition is sufficiently cured. This is because it has an appropriate light peeling resistance and its change over time can be reduced.

The (D) component is a hydrosilylation reaction catalyst for promoting the hydrosilylation reaction of the present composition. Examples of such component (D) include platinum-based catalysts, palladium-based catalysts, and rhodium-based catalysts, with platinum-based catalysts being preferred. Examples of platinum-based catalysts include chloroplatinic acid, chloroplatinic acid hexahydrate, platinum dichloride, alcohol-modified chloroplatinic acid, platinum olefin complexes, platinum carbonyl complexes, platinum alkenylsiloxane complexes, and platinum diketone complexes. exemplified. In the alkenylsiloxane complex of platinum, examples of the alkenylsiloxane include 1,3-divinyltetramethyldisiloxane, 1,1,3,3-tetravinyldimethyldisiloxane, dimethylvinylsiloxy group-blocked methyl (3,3 ,3-trifluoropropyl)siloxane oligomers.

The content of component (D) is a catalytic amount for promoting the hydrosilylation reaction of the present composition. Specifically, the total amount of components (A) to (C) is The amount of the catalyst metal in the mass unit is in the range of 0.1 to 1,000 ppm, the amount in the range of 0.1 to 500 ppm, the amount in the range of 5 to 500 ppm, and the range of 0.1 to 300 ppm. or an amount within the range of 5 to 300 ppm. This is because when the content of component (D) is at least the lower limit of the above range, the curing of the present composition is accelerated. This is because problems such as coloring of the film are less likely to occur.

In addition, the composition may contain (E) a hydrosilylation reaction inhibitor for adjusting the curing speed. Examples of such component (E) include 2-methyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol, 3-methyl-1-pentyn-3-ol, 2- alkyne alcohols such as phenyl-3-butyn-2-ol, 1-ethynyl-1-cyclohexanol, 2-ethynylisopropanol, 2-ethynylbutan-2-ol; trimethyl(3,5-dimethyl-1-hexyne-3 -oxy)silane, dimethylbis(3-methyl-1-butynoxy)silane, methylvinylbis(3-methyl-1-butyn-3-oxy)silane, and [(1,1-dimethyl-2-propynyl)oxy ] silylated acetylenic alcohols such as trimethylsilane; methyl-3-hexene-1-yne, 1-ethynylcyclohexene, 3-ethyl-3-butene-1-yne, and 3-phenyl-3-buten-1-yne, etc. and enyne compounds; diallyl maleate, dimethyl maleate ate, diethyl fumarate, diallyl fumarate, bis-2-methoxy-1-methylethyl maleate, monooctyl maleate, monoisooctyl maleate, monoallyl maleate, monomethyl maleate, monoethyl fumarate, monoallyl Unsaturated carboxylic acid esters such as fumarate and 2-methoxy-1-methylethyl maleate; 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, 1,3 ,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane; other examples include benzotriazole.

Although the content of component (E) in the present composition is not limited, it is preferably 5 parts by mass or less, or 3 parts by mass or less with respect to a total of 100 parts by mass of components (A) and (B), On the other hand, the lower limit is 0.001 mass parts or more, 0.01 mass parts or more, or 0.1 mass parts or more.

In addition, the composition may contain (F) an organic solvent for improving coating properties and handling workability (handling properties). Examples of such component (F) include aromatic hydrocarbon solvents such as toluene and xylene; aliphatic hydrocarbon solvents such as hexane, octane and isoparaffin; ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; Ester solvents such as ethyl and isobutyl acetate; ether solvents such as diisopropyl ether and 1,4-dioxane; cyclic solvents with a degree of polymerization of 3 to 6 such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane siloxanes; exemplified by halogenated hydrocarbons such as trichlorethylene, perchlorethylene, trifluoromethylbenzene, 1,3-bis(trifluoromethyl)benzene, and methylpentafluorobenzene; The content of the component (F) is arbitrary, and can be determined as appropriate in order to adjust the film thickness when the present composition is applied onto a substrate.

Furthermore, it is preferable to cure the present composition by irradiating it with an energy beam, such as ultraviolet rays, electron beams, particularly ultraviolet rays, because the physical properties and peelability of the resulting peelable cured film are excellent. In this case, curing by ultraviolet rays can be performed by ultraviolet curing alone, or by combining ultraviolet curing and heat curing. The curing time of the composition can be appropriately adjusted according to the curing conditions used. In order to impart good ultraviolet curability to the present composition, it is preferable to further add a photopolymerization initiator to the present composition. This photopolymerization initiator is a component that imparts UV curability to the composition, and heat damage to plastic film substrates with low heat resistance is reduced by combining heat curing by hydrosilylation reaction and UV curing. There is an advantage that the adhesiveness of the resulting peelable cured film to the plastic film is improved. Furthermore, there is also the advantage that migration of silicone can be further reduced.

As the photopolymerization initiator, a known compound that generates radicals upon irradiation with ultraviolet rays can be used. can be used. Specifically, acetophenone, propiophenone, benzophenone, xanthol, fluoresin, benzaldehyde, anthraquinone, triphenylamine, 4-methylacetophenone, 3-pentylacetophenone, 4-methoxyacetophenone, 3-bromoacetophenone, 4-allyl Acetophenone, p-diacetylbenzene, 3-methoxybenzophenone, 4-methylbenzophenone, 4-chlorobenzophenone, 4,4-dimethoxybenzophenone, 4-chloro-4-benzylbenzophenone, 3-chloroxanthone, 3,9-dichloroxan Tone, 3-chloro-8-nonylxanthone, benzoin, benzoin methyl ether, benzoin butyl ether, bis(4-dimethylaminophenyl) ketone, benzyl methoxyketal, 2-chlorothioxanthone, diethylacetophenone, 1-hydroxycyclohexylphenyl Ketones, 2-methyl[4-(methylthio)phenyl]2-morpholino-1-propanone, 2,2-dimethoxy-2-phenylacetophenone, and diethoxyacetophenone are exemplified. Benzophenone, 4-methoxyacetophenone, 4-methylbenzophenone, diethoxyacetophenone, and 1-hydroxycyclohexyl phenyl ketone are preferred, especially diethoxyacetophenone and 1-hydroxycyclohexyl phenyl ketone, if the composition is to be cured with UV light. is preferred.

Such photopolymerization initiators may be used alone or in combination of two or more. Its content is not particularly limited, but it is preferably in the range of 0.01 to 10 parts by weight, or in the range of 0.01 to 2.5 parts by weight, per 100 parts by weight of component (A). This is because if the content of the photopolymerization initiator is within the above range, the peelable cured film obtained by curing the present composition has improved migration of silicone and excellent physical properties such as strength. This is because

Further, the present composition may contain, as other optional components, adhesion promoters such as 3-glycidoxypropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane; Phyto-based, sulfur-based, thioether-based antioxidants; triazole-based, benzophenone-based light stabilizers; phosphate-based, halogen-based, phosphorus-based, antimony-based flame retardants; cationic surfactants, anions Surfactants such as system surfactants and nonionic surfactants; and other known additives such as antistatic agents, heat-resistant agents, dyes and pigments.

The composition can be prepared by uniformly mixing components (A) to (D), components (E), (F), and other optional components. The order of addition of each component is not limited, but if the present composition is not used immediately after preparation, a mixture of components (A), (B), and (C) and (D) are mixed together. It is preferable to store them separately and mix them immediately before use. In addition, by adjusting the type and content of component (E) in a composition consisting of components (A) to (D), and optionally component (F) and other components, the composition does not crosslink at room temperature and can be heated. You may make it bridge|crosslink by this.

<Release sheet>
Next, the release sheet of the present invention will be described in detail.

The release sheet of the present invention is characterized by having a cured release film obtained by curing the above silicone composition for forming a cured release film. Specifically, the release sheet has a release cured film on the surface of a base material, an adhesive substance adheres to the release cured film, and then the adhesive substance is peeled off with light peeling resistance. is used.

The base material of the release sheet is not limited, but examples include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polypropylene and polymethylpentene; polycarbonate; polyimide; Paper such as Japanese paper, cardboard, cardboard, glassine paper, clay coated paper, polyolefin laminated paper, polyethylene laminated paper, synthetic paper; Cloth such as natural fiber cloth, synthetic fiber cloth, artificial leather cloth; Others, glass wool, metal foil. This film may be a single layer or may be composed of multiple layers of two or more layers of the same or different plastics. As this substrate, a plastic film, particularly a polyester film is preferable, a polyethylene terephthalate film is more preferable, and a biaxially stretched polyethylene terephthalate film is particularly preferable. Polyethylene terephthalate film is less likely to generate dust during processing and use. Therefore, it is possible to effectively prevent defective coating of the adhesive substance onto the release sheet caused by dust or the like. In addition, by applying an antistatic treatment to the polyethylene terephthalate film and using it as a base material, it is possible to prevent the occurrence of defective coating of the sticky substance.

Although the thickness of the base material of the release sheet is not limited, it is generally in the range of 10-300 μm, preferably in the range of 15-200 μm, or in the range of 20-125 μm.

The method for producing the present release sheet is not limited. and curing the composition after coating using a known coating method such as a method. Although the thickness of the peelable cured coating on the substrate is not limited, it is preferably in the range of 0.01 to 3 μm, or preferably in the range of 0.03 to 1 μm. This is because when the thickness of the release cured film is at least the lower limit of the above range, the adhesive substance is easily peeled off. This is because the occurrence of blocking is suppressed when the film is wound up to a high thickness.

The cured release film-forming silicone composition and release sheet of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In addition, the viscosity and plasticity in the examples are the values at 25°C, respectively, and the viscosity is measured according to JIS K 7117-1: 1999 "Plastics - liquid, emulsion or dispersed resins - Brookfield type rotational viscometer A value measured using a digital display B-type rotational viscometer (Vismetron VDA2 type manufactured by Shibaura Systems Co., Ltd.) in accordance with the provisions of "Method for measuring apparent viscosity by", and plasticity is JIS K 6249: 2003 "not Cure and Test Methods for Cured Silicone Rubber”, a value (unit: mm) when a load of 1 kgf is applied to a 4.2 g spherical sample for 3 minutes.

In addition, the production and evaluation of the release sheet were performed as follows.

<Method for preparing release sheet>
A silicone composition for forming a release cured film was applied to the surface of a polyester film (biaxially oriented polyester film manufactured by Mitsubishi Chemical Corporation) with a thickness of 38 μm using a Meyer bar. An amount of 0.6 g/m ² was applied. After coating, the composition on the polyester film was cured by heating for 30 seconds in a hot air circulating oven at 120°C. After that, it was allowed to stand in the air at 23° C. and 60% humidity for 72 hours to prepare a release sheet.

<Peeling resistance>
Adhesive tape manufactured by TESA (TESA7475 tape) was attached to the surface of the release sheet prepared as described above, and a load of 20 gf/cm ² was applied to the surface of the release sheet. placed. After that, using a tensile tester [Tensilon universal tester manufactured by A&D Co., Ltd.], the adhesive tape was pulled at an angle of 180 degrees and a peeling speed of 0.3 m / min, and the peeling resistance (mN / 25 mm) was measured. It was measured.

In addition, an adhesive tape (TESA7475 tape) manufactured by TESA Co., Ltd. was attached to the surface of the release sheet prepared as described above, and a load of 20 gf/cm ² was applied to the surface of the release sheet. left undisturbed. After that, it was cooled to 23 ° C., and the adhesive tape was pulled under the conditions of an angle of 180 degrees and a peel speed of 0.3 m / min using a tensile tester [Tensilon universal tester manufactured by A&D Co., Ltd.]. (mN/25mm) was measured. In Tables 1 and 2, the peel resistance value when left standing at 23 ° C. and humidity of 60% for 24 hours, the peel resistance value when left at 70 ° C. for 24 hours, and the difference between them are shown. Indicated.

<Residual adhesion rate>
Adhesive tape No. 1 manufactured by Nitto Denko Corporation was applied to the surface of the release sheet prepared as described above. 31B was laminated, a load of 20 gf/cm ² was applied, and the laminate was allowed to stand in a hot air circulating oven at 70° C. for 20 hours. Next, the adhesive tape is peeled off, the peeled adhesive tape is attached to a stainless plate, a load of 20 gf/cm ² is applied, and after standing for 30 minutes in air at 23° C. and humidity of 60%, a tensile tester is used. Using [Tensilon universal tester manufactured by A&D Co., Ltd.], the pressure-sensitive adhesive tape was pulled under conditions of an angle of 180 degrees and a peeling speed of 0.3 m/min, and the force (gf1) required for peeling was measured. In addition, as a blank test, the above tape was attached to a Teflon (registered trademark) sheet in the same manner as described above, and the force (gf2) required for peeling of this adhesive tape was measured in the same manner as described above. From these values, the residual adhesion rate (%) was calculated according to the following formula.
Residual adhesion rate (%) = (gf1/gf2) x 100

<Examples 1 to 4, Comparative Examples 1 to 5>
A silicone composition for forming a cured release film was prepared by uniformly mixing the following components so as to obtain the composition shown in Tables 1 and 2. In Tables 1 and 2, the content of component (D) is the amount of platinum in component (D) that is 200 ppm by mass with respect to the total amount of components (A) to (C). is. "SiH/Alkenyl" in Tables 1 and 2 indicates the number of moles of silicon-bonded hydrogen atoms in component (C) per 1 mole of alkenyl groups in components (A) and (B). there is The properties of the release sheets produced using the silicone composition for forming a cured release film thus prepared were measured, and the results are shown in Tables 1 and 2.

The following components were used as the (A) component.
(a-1): A dimethylsiloxane/methylhexenylsiloxane copolymer having a viscosity exceeding 100,000 mPa·s, a plasticity of 1.15, and having both ends of the molecular chain blocked with trimethylsiloxy groups (hexenyl group content = 0.0296 mol/100 g)
(a-2): A dimethylsiloxane/methylhexenylsiloxane copolymer having a viscosity exceeding 100,000 mPa·s, a plasticity of 1.15, and having both ends of the molecular chain blocked with trimethylsiloxy groups (hexenyl group content = 0.0185 mol/100 g)

The following components were used as the (B) component.
(b-1): A dimethylsiloxane/methylvinylsiloxane copolymer having a viscosity of 5,000 mPa·s and having both molecular chain ends blocked with trimethylsiloxy groups (vinyl group content = 0.0055 mol/100 g )
(b-2): A dimethylsiloxane/methylvinylsiloxane copolymer having a viscosity of 40,000 mPa·s and having both molecular chain ends blocked with trimethylsiloxy groups (vinyl group content = 0.0055 mol/100 g )

Also, the following components were used for comparison of the component (B).
(b-3): A dimethylsiloxane/methylvinylsiloxane copolymer having a viscosity of 35,000 mPa·s and having both molecular chain ends blocked with trimethylsiloxy groups (vinyl group content = 0.0185 mol/100 g )
(b-4): Dimethylpolysiloxane having a viscosity of 2,000 mPa·s and having both molecular chain ends blocked with dimethylvinylsiloxy groups (vinyl group content = 0.0085 mol/100 g)
(b-5): A dimethylsiloxane/methylvinylsiloxane copolymer having a viscosity of 350 mPa·s and having both molecular chain ends blocked with trimethylsiloxy groups (vinyl group content = 0.0462 mol/100 g).
(b-6): Dimethylpolysiloxane having a viscosity of 5,000 mPa·s and having both ends of the molecular chain blocked with trimethylsiloxy groups

The following components were used as the (C) component.
(c-1): Methylhydrogenpolysiloxane having a viscosity of 20 mPa·s and having both ends of the molecular chain blocked with trimethylsiloxy groups (content of silicon-bonded hydrogen atoms=1.56 mol/100 g)
(c-2): A dimethylsiloxane/methylhydrogensiloxane copolymer having a viscosity of 55 mPa·s and having both molecular chain ends blocked with trimethylsiloxy groups (content of silicon-bonded hydrogen atoms = 0.99 mol /100g)

The following components were used as the (D) component.
(d-1): 1,3-divinyltetramethyldisiloxane solution of 1,3-divinyltetramethyldisiloxane complex of platinum (content of platinum: 4,000 ppm)

The following components were used as the (E) component.
(e-1): 2-methyl-3-butyn-2-ol

The following components were used as the (F) component.
(f-1): toluene

From the results shown in Tables 1 and 2, when an organopolysiloxane having a content of alkenyl groups in terms of vinyl groups exceeding 0.0148 mol/100 g was used as the component (B) (Comparative Example 1), the molecular chain terminal When an organopolysiloxane having an alkenyl group is used for (Comparative Example 2), the peel resistance is heavy, and the difference between the peel resistance when left standing at 23 ° C. and the peel resistance when standing at 70 ° C. is large. , it was found that the peel resistance may change over time. In addition, when an organopolysiloxane having a viscosity of less than 1000 mPa·s was used as the component (B) (Comparative Example 3), the peel resistance at 23°C could be reduced, but when left standing at 23°C. It was found that the peel resistance may change over time, since the difference between the peel resistance of 1 and the peel resistance when left standing at 70° C. is large. Furthermore, when an organopolysiloxane having no alkenyl groups was used as the component (B) (Comparative Example 5), it was found that the peel resistance could be reduced, but the residual adhesion rate was significantly reduced. . In contrast, it was found that the present invention (Examples 1 to 4) had low peel resistance, little change in peel resistance over time, and did not lower the residual adhesion rate.

The silicone composition for forming a release cured film of the present invention is required to have a relatively low release resistance because it has a low release resistance, changes little in release resistance over time, and does not reduce the residual adhesion rate of sticky substances. Liquid crystal panels, plasma displays, polarizers, retardation plates, and other optical parts, printed circuit boards, ICs, transistors, capacitors, and other electrical and electronic parts. It is suitable as a forming material.

Claims

(A) a linear organopolysiloxane having a viscosity at 25° C. exceeding 100,000 mPa·s and having at least two alkenyl groups having 2 to 12 carbon atoms in each molecule only on the side chains of the molecular chain;
(B) has a viscosity of 1,000 to 100,000 mPa·s at 25° C., has at least two alkenyl groups having 2 to 12 carbon atoms in one molecule only in the side chains of the molecular chain, and contains the alkenyl groups A linear organopolysiloxane in an amount of 0.0018 to 0.0148 mol/100 g [mass ratio of component (A) to component (B) {component (A)/component (B)} is 10/90 to 90 /10 amount],
(C) Organopolysiloxane having at least two silicon-bonded hydrogen atoms per molecule {Silicone atoms in component (C) per mole of alkenyl groups in components (A) and (B) and (D) a catalytic amount of a hydrosilylation reaction catalyst.
2. The silicone composition for forming a cured release film according to claim 1, wherein the alkenyl group in component (A) is a hexenyl group.
2. The silicone composition for forming a cured release film according to claim 1, wherein the mass ratio of component (A) to component (B) {component (A)/component (B)} is from 40/60 to 80/20.
2. The silicone composition for forming a cured release film according to claim 1, further comprising (E) a hydrosilylation reaction inhibitor.
2. The silicone composition for forming a cured release film according to claim 1, further comprising (F) an organic solvent.
A release sheet having a cured release coating obtained by curing the silicone composition for forming a cured release coating according to any one of claims 1 to 5.