CN117255837A

CN117255837A - Silicone composition for forming release cured coating and release sheet

Info

Publication number: CN117255837A
Application number: CN202280030940.8A
Authority: CN
Inventors: 远藤修司; 日野贤一
Original assignee: Dow Corning Toray Co Ltd
Current assignee: DuPont Toray Specialty Materials KK
Priority date: 2021-05-28
Filing date: 2022-05-27
Publication date: 2023-12-19
Also published as: TW202311446A; WO2022250125A1; JPWO2022250125A1; KR20240013762A

Abstract

The present invention relates to a silicone composition for forming a release cured coating, comprising: (A) A chain polyorganosiloxane having a viscosity of more than 100000 mPas at 25 ℃ and having at least two alkenyl groups having 2 to 12 carbon atoms in a side chain of only a molecular chain in one molecule; (B) A chain polyorganosiloxane having a viscosity of 1000 to 100000 mPas at 25 ℃ and having at least two alkenyl groups having 2 to 12 carbon atoms in only a side chain of a molecular chain in one molecule, the alkenyl group content being 0.0018 to 0.0148 mol/100 g; (C) A polyorganosiloxane having at least two silicon-bonded hydrogen atoms in one molecule; and (D) a catalytic amount of a hydrosilylation catalyst. The composition can form a release cured film which exhibits a light release resistance to an adhesive substance, and which has a small change with time, and further suppresses a decrease in the residual adhesion rate of the adhesive substance.

Description

Silicone composition for forming release cured coating and release sheet

Technical Field

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

Background

The silicone composition for forming a releasable cured film is used for forming a cured film that exhibits moderate release properties for an adhesive substance. As such an organosilicon composition for forming a releasable cured film, for example, patent document 1 discloses a composition comprising an organosilicon having a viscosity of 500000 centistokes or more and containing at least 0.1 mol% of methylvinylsiloxane units and having hydroxyl groups or vinyl groups at the molecular chain ends, an organosilicon having a viscosity of 10 to 100000 centistokes or less and having vinyl groups at the molecular chain ends at 25 ℃, an organosilicon having at least three silicon atoms bonded to hydrogen atoms in one molecule, and a hydrosilylation catalyst, patent document 2 discloses a composition comprising an organosilicon having a viscosity of 50 to 10000cps in one molecule and having at least two vinyl groups in the molecular chain side chain and having a content of 0.5 to 10 mol% of at least one of them, an organosilicon having a viscosity of 100000 or more and having a content of vinyl groups less than that of the aforementioned organosilicon, an organosilicon having at least two silicon atoms bonded to hydrogen atoms in one molecule, a hydrosilylation catalyst having at least two silicon atoms bonded to hydrogen atoms in one molecule, and a hydrosilylation inhibitor having at least one silicon atom in one molecule and having a hydrosilylation catalyst having at least one silicon atom in the molecular chain of 8, and a hydrosilylation inhibitor having at least one silicon atom in the hydrosilylation catalyst.

However, the composition of patent document 1 uses a polyorganosiloxane having a viscosity of 10 to 100000 centistokes at 25 ℃ and a vinyl group at the terminal of the molecular chain, and the composition of patent document 2 uses a polyorganosiloxane having a viscosity of 50 to 10000cps at 25 ℃ and a large vinyl group content, but the following problems are all present: it is difficult to form a peel-off cured film having a light peel resistance, and the peel resistance changes with time. On the other hand, in the composition of patent document 3, since a polyorganosiloxane having no alkenyl group and no silicon atom-bonded hydrogen atom in one molecule is used, a release-curable film having a light release resistance can be formed, but there is a technical problem that the residual adhesion rate of an adhesive substance is significantly reduced.

On the other hand, patent document 4 discloses a composition comprising a 30 wt% toluene solution of a dimeric organosiloxane having a viscosity of 500 centistokes or more at 25 ℃ and having an alkenyl group having 4 to 8 carbon atoms in a side chain of a molecular chain and a terminal end of the molecular chain being blocked with a hydroxyl group, an alkenyl group, or an alkyl group, a 30 wt% toluene solution of a dimeric organosiloxane having a viscosity of 500 centistokes or more at 25 ℃ and a terminal end of the molecular chain being blocked with a hydroxyl group, an alkenyl group, or an alkyl group and having at least one alkenyl group in one molecule, a polyorganosiloxane having a viscosity of 1 to 1000 centistokes at 25 ℃ and having at least three silicon atoms in one molecule, a catalyst for hydrosilylation reaction, a hydrosilylation reaction inhibitor, and an organic solvent. However, the composition of patent document 4 has a problem in that the composition has a high viscosity, lacks coatability, and has handling workability (handleability) because two types of high molecular weight polyorganosiloxane are blended.

Further, patent document 5 discloses a composition comprising a polyorganosiloxane having a viscosity of 1.5 to 70pa·s at 25 ℃ and a molecular chain end capped with an alkenyl group in a 30 wt% toluene solution, a polyorganosiloxane having a viscosity of 0.1 to 500pa·s at 25 ℃ and an alkenyl group in a molecular chain side chain and a content of alkenyl groups 0.2 to 5 times that of the polyorganosiloxane, a polyorganosiloxane having at least three silicon-bonded hydrogen atoms in one molecule, a catalyst for hydrosilylation reaction, and an organic solvent. However, the composition of patent document 5 has a problem that although the coatability and handling workability (handleability) are improved, the problem of forming a cured film with a low peel resistance cannot be sufficiently solved.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 50-025644

Patent document 2: japanese patent laid-open No. 61-159480

Patent document 3: japanese patent laid-open No. 02-145650

Patent document 4: japanese patent laid-open No. 09-125004

Patent document 5: japanese patent application laid-open No. 2004-190202

Disclosure of Invention

Problems to be solved by the invention

The purpose of the present invention is to provide a silicone composition for forming a release cured film, which is capable of forming a release cured film that exhibits a low release resistance to an adhesive substance and that has little change over time, and further suppresses the decrease in the residual adhesion rate of the adhesive substance. Another object of the present invention is to provide a release sheet which exhibits a low release resistance to an adhesive substance and which is less susceptible to change with time, and further suppresses a decrease in the residual adhesion rate of the adhesive substance.

Solution for solving the problem

The silicone composition for forming a release cured coating of the present invention comprises:

(A) A chain polyorganosiloxane having a viscosity of more than 100000 mPas at 25 ℃ and having at least two alkenyl groups having 2 to 12 carbon atoms in a side chain of only a molecular chain in one molecule;

(B) A chain polyorganosiloxane [ (A) component/(B) component } having a viscosity of 1000 to 100000 mPas and having at least two alkenyl groups having 2 to 12 carbon atoms in only side chains of a molecular chain in one molecule, the alkenyl group content being 0.0018 to 0.0148 mol/100 g ] in a mass ratio of { (A) component/(B) component } of 10/90 to 90/10;

(C) A polyorganosiloxane having at least two silicon-bonded hydrogen atoms in one molecule { an amount of 0.5 to 5 moles of silicon-bonded hydrogen atoms in component (C) relative to 1 mole of the total of alkenyl groups in component (a) and component (B) }; and

(D) A catalytic amount of a hydrosilylation catalyst.

Preferably, in the present composition, the alkenyl group in component (a) is hexenyl.

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

Preferably, the present composition further comprises (E) a hydrosilylation reaction inhibitor.

Preferably, the present composition further comprises (F) an organic solvent.

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

Effects of the invention

The silicone composition for forming a release cured coating of the present invention has the following characteristics: a releasable cured film exhibiting a light peel resistance to an adhesive substance, which is less susceptible to change over time, and which further suppresses a decrease in the residual adhesion rate of the adhesive substance, can be formed. In addition, the release sheet of the present invention has the following features: exhibits a low peel resistance to an adhesive substance, and is less susceptible to change over time, thereby further suppressing a decrease in the residual adhesion rate of the adhesive substance.

Detailed Description

< definition of terms >

The term "viscosity" as used in the present specification means a viscosity obtained by using a viscosity-controlling agent according to JIS K7117-1: 1999 "Plastic-liquid, opaque or dispersible resin-value at 25℃measured by a B-type rotational viscometer specified in Brookfield (Brookfield) method of measuring apparent viscosity of a rotational viscometer" (unit: mPas or Pa.s).

The term "plasticity" as used in the present specification means a composition according to JIS K6249: 2003 "test method for uncured and cured Silicone rubber" values (unit: mm) when a load of 1kgf was applied to 4.2g of the spherical sample for 3 minutes.

< Silicone composition for Forming Release curable film >

The silicone composition for forming a release cured film of the present invention will be described in detail.

(A) The component (C) is a chain polyorganosiloxane having at least two alkenyl groups having 2 to 12 carbon atoms in one molecule only in the side chain of the molecular chain. Examples of the alkenyl group in the component (a) include: vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, preferably hexenyl. Such alkenyl groups need to be present only in the side chains of the molecular chain and not at the ends of the molecular chain. Examples of the group bonded to a silicon atom other than the alkenyl group in the component (a) include: alkyl groups having 1 to 12 carbon atoms such as methyl, ethyl, propyl, butyl, pentyl, hexyl and heptyl; aryl groups having 6 to 12 carbon atoms such as phenyl, tolyl, xylyl, and the like; aralkyl groups having 7 to 12 carbon atoms such as benzyl and phenethyl; fluoroalkyl groups having 3 to 12 carbon atoms such as 3, 3-trifluoropropyl group, 4,4,4,3,3-pentafluorobutyl group, 5,4, 3-heptafluoropentyl group, 6,6,6,5,5,4,4,3,3-nonafluorohexyl group, 7,7,7,6,6,5,5,4,4,3,3-undecylfluoroheptyl group, and the like are preferably methyl groups. In the component (A), an alkoxy group having 1 to 3 carbon atoms such as a hydroxyl group, a methoxy group, an ethoxy group or the like may be bonded to a silicon atom in a small amount within a range that does not impair the object of the present invention.

(A) The alkenyl group content of the component (a) is not limited, and 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, if the content of the alkenyl group of the component (a) is not less than the lower limit of the above range, the present composition is sufficiently cured, migration of the silicone component to the adhesive substance of the obtained release cured film is suppressed, and the decrease in the residual adhesive rate of the adhesive substance can be suppressed, whereas if the content of the alkenyl group of the component (a) is not more than the upper limit of the above range, the obtained release cured film has a moderately light release resistance.

(A) The component (C) was a polyorganosiloxane having a high polymerization degree and a viscosity of more than 100000 mPas at 25 ℃, and if the polymerization degree was increased, the resultant rubber-like product had a viscosity which could not be measured by a rotational viscometer. When the component (A) is rubbery, the plasticity is preferably 3.0mm or less, or 0.5 to 3.0mm.

(A) The molecular structure of the component is substantially linear, but a part of the molecular chain may be branched. Examples of such a component (a) include: dimethylsiloxane-methylhexenyl siloxane copolymers having both molecular chain ends terminated with trimethylsiloxy groups, dimethylsiloxane-methylhexenyl siloxane copolymers having molecular chain ends substantially terminated with trimethylsiloxy groups and a portion of molecular chain ends terminated with dimethylhydroxysiloxy groups.

(B) The component (C) is a chain polyorganosiloxane having at least two alkenyl groups having 2 to 12 carbon atoms in one molecule only in the side chain of the molecular chain. The alkenyl group in the component (B) is preferably a vinyl group, and the alkenyl group is the same as that in the component (a). Such alkenyl groups need to be present only in the side chains of the molecular chain and not at the ends of the molecular chain. Examples of the group bonded to a silicon atom other than the alkenyl group in the component (B) include the same groups as those in the component (a), and methyl groups are preferable. In the component (B), an alkoxy group having 1 to 3 carbon atoms such as a hydroxyl group, a methoxy group, an ethoxy group, etc. may be bonded to a silicon atom in a small amount within a range that does not impair the object of the present invention.

(B) The viscosity of the components at 25℃is in the range from 1000 to 100000 mPas, preferably in the range from 1000 to 70000 mPas, in the range from 2000 to 50000 mPas or in the range from 3000 to 50000 mPas. This is because, if the viscosity of the component (B) is equal to or higher than the lower limit of the above range, the curability of the present composition can be improved, and if the viscosity of the component (B) is equal to or lower than the upper limit of the above range, a peelable cured film having a low peeling resistance and a small change with time can be formed.

(B) The alkenyl group content of the component (B) is in the range of 0.0018 to 0.0148 mol/100 g, preferably in the range of 0.0026 to 0.0148 mol/100 g when the viscosity is 1000 mPas or more and 10000 mPas or less, in the range of 0.0018 to 0.0111 mol/100 g when the viscosity exceeds 10000 mPas and 100000 mPas or less, or in the range of 0.0037 to 0.0148 mol/100 g when the viscosity is 1000 mPas or more and 10000 mPas or less, and in the range of 0.0018 to 0.0074 mol/100 g when the viscosity exceeds 10000 mPas or less. This is because, if the content of the alkenyl group of the component (B) is not less than the lower limit of the above range, the present composition is sufficiently cured, migration of the silicone component to the adhesive substance of the resulting release cured film is suppressed, and the decrease in the residual adhesive rate of the adhesive substance can be suppressed, whereas if the content of the alkenyl group of the component (B) is not more than the upper limit of the above range, the resulting release cured film can have a moderately light release resistance and the change with time is small.

The reason why the content of the alkenyl group varies depending on the viscosity of the component (B) is as follows. When the viscosity of the component (B) is low, the molecular weight becomes low, and therefore the number of alkenyl groups in one molecule becomes small even if the content of alkenyl groups is the same. Since the reactivity of the component (B) is low, migration of the silicone component to the adhesive substance of the release cured film is likely to occur. This is because, in order to suppress this, it is preferable to increase the alkenyl group content of the component (B). On the other hand, when the viscosity of the component (B) is high, the molecular weight becomes high, and therefore the number of alkenyl groups in one molecule becomes large even if the content of alkenyl groups is the same. Since the component (B) has high reactivity, it is rarely locally present on the surface of the release cured film. In general, unreacted silicon-bonded hydrogen atoms may remain on the surface of the release cured film, or react with moisture to generate silicon-bonded hydroxyl groups, which is considered to be the cause of the increase in the interaction between the release cured film and the adhesive substance over time. This is because, in order to suppress the residual of silicon atom-bonded hydrogen atoms on the surface of the releasable cured film, it is necessary to promote the localized presence of the component (B) on the surface of the cured film and to make the relative reactivity with the component (a) different, and therefore, when the viscosity of the component (B) is high, it is preferable to reduce the alkenyl group content of the component (B).

In the present composition, the content of the component (B) is an amount in the range of 10/90 to 90/10, preferably 30/70 to 90/10, or 40/60 to 80/20 in terms of the mass ratio of the component (A) to the component (B) { (A/(B) component). This is because, if the mass ratio of the component (a) to the component (B) { (a)/(B) is equal to or more than the lower limit of the above range, the curability of the present composition, particularly the curability at a low temperature of about 100 ℃, can be improved, and the strength of the resulting cured film can be improved, whereas if the mass ratio of the component (a) to the component (B) { (a)/(B) is equal to or less than the upper limit of the above range, a release-type cured film having a low release resistance can be formed. In the present composition, the component (B) is blended in a specific ratio with respect to the component (a), and therefore, a release cured film in which the decrease in the residual adhesive rate of the adhesive substance is suppressed can be formed with a low release resistance.

(C) The component (c) is a polyorganosiloxane having at least two silicon-bonded hydrogen atoms in one molecule, and is a crosslinking agent of the present composition. (C) The bonding position of the silicon atom to the hydrogen atom in the component is not limited, and examples thereof include a molecular chain end and/or a molecular chain side chain. Examples of the group bonded to a silicon atom other than a hydrogen atom in the component (C) include: alkyl groups having 1 to 12 carbon atoms such as methyl, ethyl, propyl, butyl, pentyl, hexyl and heptyl; aryl groups having 6 to 12 carbon atoms such as phenyl, tolyl, xylyl, and the like; aralkyl groups having 7 to 12 carbon atoms such as benzyl and phenethyl; fluoroalkyl groups having 3 to 12 carbon atoms such as 3, 3-trifluoropropyl group, 4,4,4,3,3-pentafluorobutyl group, 5,4, 3-heptafluoropentyl group, 6,6,6,5,5,4,4,3,3-nonafluorohexyl group, 7,7,7,6,6,5,5,4,4,3,3-undecylfluoroheptyl group, and the like are preferably methyl groups. In the component (C), an alkoxy group having 1 to 3 carbon atoms such as a hydroxyl group, a methoxy group, an ethoxy group, etc. may be bonded to a silicon atom in a small amount within a range that does not impair the object of the present invention.

(C) The viscosity of the component at 25℃is not limited, but is preferably in the range of 1 to 1000 mPas, or in the range of 5 to 500 mPas. This is because, if the viscosity of the component (C) is not less than the lower limit of the above range, volatilization of the component from the composition is suppressed, and the composition is stable, while if the viscosity of the component (C) is not more than the upper limit of the above range, curability of the composition is promoted.

The molecular structure of the component (C) is not limited, and examples thereof include:linear, linear with partial branching, branched, cyclic, or resinous. Examples of such a component (C) include: trimethylsiloxy-terminated dimethylsiloxane-methylhydrosiloxane copolymer at both molecular chain ends, dimethylsiloxy-terminated dimethylsiloxane-methylhydrosiloxane copolymer at both molecular chain ends, dimethylhydrosiloxy-terminated dimethylpolysiloxane at both molecular chain ends, trimethylsiloxy-terminated methylhydrosiloxane at both molecular chain ends, cyclic methylhydrosiloxane-dimethylsiloxane copolymer, and a copolymer represented by the formula: h (CH) ₃ ) ₂ SiO _1/2 The siloxane units represented are of the formula: siO (SiO) _4/2 A copolymer of the indicated siloxane units and having the formula: (CH) ₃ ) ₃ SiO _1/2 The siloxane units represented are of the formula: h (CH) ₃ ) ₂ SiO _1/2 The siloxane units represented are of the formula: siO (SiO) _4/2 The indicated copolymers of siloxane units.

In the present composition, the content of the component (C) is 1 mol based on the total of the alkenyl groups in the component (A) and the component (B), and the amount of the silicon atom-bonded hydrogen atom in the component (C) is in the range of 0.5 to 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, if the content of the component (C) is not less than the lower limit of the above range, the present composition is sufficiently cured, and if the content of the component (C) is not more than the upper limit of the above range, the resulting release cured film can have a moderately light release resistance and also has little change with time.

(D) The component (c) is a hydrosilylation catalyst for promoting the hydrosilylation reaction of the present composition. Examples of such a component (D) include: platinum-based catalysts, palladium-based catalysts, and rhodium-based catalysts are preferable. The platinum-based catalyst may be exemplified by: chloroplatinic acid, chloroplatinic acid hexahydrate, platinum dichloride, alcohol-modified chloroplatinic acid, olefin complexes of platinum, carbonyl complexes of platinum, alkenylsiloxane complexes of platinum, diketone complexes of platinum. In addition, in the alkenylsiloxane complex of platinum, examples of alkenylsiloxane include: 1, 3-divinyl tetramethyl disiloxane, 1, 3-tetravinyl dimethyl disiloxane, dimethyl vinyl siloxy terminated methyl (3, 3-trifluoropropyl) siloxane oligomer.

(D) The content of the component (A) is a catalyst amount for promoting the hydrosilylation reaction of the present composition, specifically, an amount in the range of 0.1 to 1000ppm, an amount in the range of 0.1 to 500ppm, an amount in the range of 5 to 500ppm, an amount in the range of 0.1 to 300ppm, or an amount in the range of 5 to 300ppm in terms of mass unit with respect to the total amount of the components (A) to (C). This is because, if the content of the component (D) is not less than the lower limit of the above range, the curing of the present composition is promoted, whereas if the content of the component (D) is not more than the upper limit of the above range, the resulting release cured film is less likely to suffer from problems such as coloration.

In addition, the present composition may contain (E) a hydrosilylation reaction inhibitor for adjusting the curing rate. Examples of such a component (E) include: alkyne alcohols such as 2-methyl-3-butyn-2-ol, 3, 5-dimethyl-1-hexyn-3-ol, 3-methyl-1-pentyn-3-ol, 2-phenyl-3-butyn-2-ol, 1-ethynyl-1-cyclohexanol, 2-ethynyl isopropanol, and 2-ethynyl butane-2-ol; silylated alkynols such as trimethyl (3, 5-dimethyl-1-hexyne-3-yloxy) silane, dimethyl bis (3-methyl-1-butynyloxy) silane, methylvinylbis (3-methyl-1-butynyl-3-oxy) silane and [ (1, 1-dimethyl-2-propynyl) oxy ] trimethylsilane; eneyne compounds such as 2-isobutyl-1-butene-3-yne, 3, 5-dimethyl-3-hexene-1-yne, 3-methyl-3-pentene-1-yne, 3-methyl-3-hexene-1-yne, 1-ethynyl cyclohexene, 3-ethyl-3-butene-1-yne, and 3-phenyl-3-butene-1-yne; unsaturated carboxylic acid esters such as diallyl maleate, dimethyl maleate, diethyl fumarate, diallyl fumarate, bis-2-methoxy-1-methylethyl maleate, monooctyl maleate, monoisooctyl maleate, monoallyl maleate, monomethyl maleate, monoethyl fumarate, monoallyl fumarate, and 2-methoxy-1-methylethyl maleate; alkenyl siloxanes such as 1,3,5, 7-tetramethyl-1, 3,5, 7-tetravinyl cyclotetrasiloxane and 1,3,5, 7-tetramethyl-1, 3,5, 7-tetrahexenyl cyclotetrasiloxane; and benzotriazole.

The content of the component (E) in the present composition is not limited, but is preferably 5 parts by mass or less or 3 parts by mass or less based on 100 parts by mass of the total of the component (a) and the component (B), and on the other hand, the lower limit of the content of the component (E) is 0.001 parts by mass or more, 0.01 parts by mass or more or 0.1 parts by mass or more.

The present composition may contain (F) an organic solvent for improving the coatability and handling workability (handleability). Examples of such a component (F) include: aromatic hydrocarbon solvents such as toluene and xylene; aliphatic hydrocarbon solvents such as hexane, octane, isoparaffin, etc.; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester solvents such as ethyl acetate and isobutyl acetate; ether solvents such as diisopropyl ether and 1, 4-dioxane; cyclic siloxanes having a degree of polymerization of 3 to 6, such as hexamethylcyclotrisiloxane, octamethyltetrasiloxane, decamethylcyclopentasiloxane, etc.; halogenated hydrocarbons such as trichloroethylene, perchloroethylene, trifluoromethylbenzene, 1, 3-bis (trifluoromethyl) benzene, and methylpentafluorobenzene. (F) The content of the component (c) is arbitrary and may be appropriately determined in order to adjust the film thickness when the composition is applied to a substrate.

Further, since the obtained releasable cured film is excellent in physical properties and releasability, it is preferable to cure the present composition by irradiation with energy rays such as ultraviolet rays and electron beams, particularly ultraviolet rays. In this case, the curing with ultraviolet rays may be performed by ultraviolet ray curing alone or by a combination of ultraviolet ray curing and heat curing. The curing time of the present composition can be appropriately adjusted depending on 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. The photopolymerization initiator is a component imparting ultraviolet curability to the present composition, and has the following advantages: by using both heat curing and ultraviolet curing by hydrosilylation, damage to the plastic film base material having low heat resistance due to heat can be reduced, and the adhesion of the resulting release cured film to the plastic film can be improved. Furthermore, there is an advantage in that the migration of the silicone can be further reduced.

As the photopolymerization initiator, a known compound that generates a radical by irradiation with ultraviolet rays can be used, and for example, it can be appropriately selected from organic peroxides, carbonyl compounds, organic sulfur compounds, azo compounds, and the like. Specifically, examples are shown as follows: acetophenone, propiophenone, benzophenone, xanthol (xanthol), fluorene, benzaldehyde, anthraquinone, triphenylamine, 4-methylacetophenone, 3-pentylacetophenone, 4-methoxyacetophenone, 3-bromoacetophenone, 4-allylacetophenone, p-diacetylbenzene, 3-methoxybenzophenone, 4-methylbenzophenone, 4-chlorobenzophenone, 4-dimethoxybenzophenone, 4-chloro-4-benzylbenzophenone, 3-chloroxanthone, 3, 9-dichloroxanthone, 3-chloro-8-nonyloxyxanthone, benzoin methyl ether, benzoin butyl ether, bis (4-dimethylaminophenyl) ketone, benzylmethoxy ketal, 2-chlorothioxanthone, diethyl acetophenone, 1-hydroxycyclohexylphenyl ketone, 2-methyl [4- (methylthio) phenyl ] 2-morpholino-1-propanone, 2-dimethoxy-2-phenyl acetophenone. In the case of curing the present composition with ultraviolet rays, benzophenone, 4-methoxyacetophenone, 4-methylbenzophenone, diethoxyacetophenone and 1-hydroxycyclohexyl phenyl ketone are preferable, and diethoxyacetophenone and 1-hydroxycyclohexyl phenyl ketone are particularly preferable.

One kind of such photopolymerization initiator may be used alone, or two or more kinds may be used in combination. The content thereof is not particularly limited, but is preferably in the range of 0.01 to 10 parts by mass, or in the range of 0.01 to 2.5 parts by mass, relative to 100 parts by mass of the component (a). This is because, when the content of the photopolymerization initiator is within the above range, the migration of the silicone of the release cured film obtained by curing the present composition is improved, and the release cured film having excellent physical properties such as strength is obtained.

The composition may contain, as other optional components: adhesion promoters such as 3-glycidoxypropyl trimethoxysilane and 3-methacryloxypropyl trimethoxysilane; antioxidants such as phenols, quinones, amines, phosphorus, phosphoric acid esters, sulfur and sulfides; light stabilizers such as triazole-based and benzophenone-based; flame retardants such as phosphate, halogen, phosphorus, and antimony; surfactants such as cationic surfactants, anionic surfactants, and nonionic surfactants; known additives such as antistatic agents, heat-resistant agents, dyes, pigments, and the like.

The composition can be prepared by uniformly mixing the components (A) to (D), and further the component (E), the component (F), and any other components. The order of addition of the components is not limited, and in the case where the present composition is not used immediately after preparation, it is preferable to store the mixture of the component (a), the component (B) and the component (C) and the component (D) separately and mix them immediately before use. In addition, in the composition containing the component (A) to the component (D), any component (F) and other components, the crosslinking may be performed by heating without crosslinking at normal temperature by adjusting the type and content of the component (E).

< 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 comprising a release cured film obtained by curing the silicone composition for forming a release cured film. Specifically, the present release sheet is used for the following purposes: the surface of the base material has a releasable cured film, and the adhesive substance adheres to the releasable cured film, and then the adhesive substance is released with a light release resistance.

The base material of the present release sheet is not limited, and examples thereof include: polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polypropylene and polymethylpentene; a polycarbonate; polyimide; films formed of plastics such as polyvinyl acetate; papers such as paper, cardboard, corrugated paper, cellophane, clay coated paper, polyolefin laminated paper, polyethylene laminated paper, and synthetic paper; cloth such as natural fiber cloth, synthetic fiber cloth, and artificial leather cloth; glass wool and metal foil. The film may be a single layer or may be composed of two or more layers containing plastics of the same kind or different kinds. The substrate is preferably a plastic film, particularly preferably a polyester film, further preferably a polyethylene terephthalate film, and particularly preferably a biaxially stretched polyethylene terephthalate film. The polyethylene terephthalate film is less prone to dust generation during processing, use, and the like. Therefore, the coating failure of the adhesive substance due to dust or the like on the release sheet can be effectively prevented. Further, the antistatic treatment is performed on the polyethylene terephthalate film, and the antistatic treatment is used as a base material, whereby occurrence of coating failure or the like of an adhesive substance can be prevented.

The thickness of the base material of the release sheet is not limited, and is usually in the range of 10 to 300. Mu.m, preferably 15 to 200. Mu.m, or 20 to 125. Mu.m.

The method for producing the release sheet is not limited, and examples thereof include the following methods: the composition is applied to a substrate by a known coating method such as gravure coating, bar coating, spray coating, spin coating, doctor blade coating, roll coating, or die coating, and then cured. The thickness of the releasable cured film on the substrate is not limited, but is preferably in the range of 0.01 to 3 μm, or in the range of 0.03 to 1 μm. This is because, if the thickness of the releasable cured film is equal to or greater than the lower limit of the above range, the adhesive substance is likely to be released, while if the thickness of the releasable cured film is equal to or less than the upper limit of the above range, the occurrence of blocking can be suppressed when the obtained release sheet is wound into a roll.

Examples

The silicone composition for forming a release cured film and the release sheet according to the present invention will be described in further detail with reference to examples, but the present invention is not limited to these examples. Further, the viscosity and the plasticity in examples are values at 25℃respectively, and the viscosity is used in accordance with JIS K7117-1: 1999 "plastic-liquid, opaque or dispersed resin-method for measuring apparent viscosity by means of Brookfield rotary viscometer" specified in digital display type B rotary viscometer (model VISMETRON VDA2 manufactured by Zhima systems Co., ltd.) the plasticity is determined in accordance with JIS K6249: 2003 "test method for uncured and cured Silicone rubber" values (unit: mm) when a load of 1kgf was applied to 4.2g of the spherical sample for 3 minutes.

The release sheet was produced and evaluated as follows.

< method for producing Release sheet >

The silicone composition for forming a releasable cured film was prepared by using a Meyer bar (Mayer bar) to a concentration of 0.6g/m in terms of the solid content after removal of the solvent ² The coating was applied to the surface of a polyester film (biaxially oriented polyester film manufactured by Mitsubishi Chemical Co., ltd.) having a thickness of 38. Mu.m. After coating, the composition on the polyester film was cured by heating in a hot air circulating oven at 120 ℃ for 30 seconds. Thereafter, the mixture was allowed to stand in air at 23℃and 60% humidity for 72 hours to prepare a release sheet.

< resistance to peeling >

An adhesive tape (TESA 7475 tape) made by TESA was adhered to the surface of the release sheet produced as described above, and 20gf/cm was applied ² Is allowed to stand in air at 23℃and a humidity of 60% for 24 hours. Thereafter, a tensile tester [ Co., ltd. A ] was used&Universal tester for D-system TENSILON]The tape was stretched at an angle of 180℃and a peeling speed of 0.3 m/min, and peeling resistance (mN/25 mm) was measured.

Further, an adhesive tape (TESA 7475 tape) made by TESA was adhered to the surface of the release sheet manufactured as described above, and 20gf/cm was applied ² Is placed in a hot air circulation oven at 70 ℃ for 24 hours. Thereafter, the mixture was cooled to 23℃and a tensile tester [ Co., ltd., A ] was used&Universal tester for D-system TENSILON]The tape was stretched at an angle of 180℃and a peeling speed of 0.3 m/min, and peeling resistance (mN/25 mm) was measured. In tables 1 and 2, the peel resistance value when left to stand in air at 23 ℃ and 60% humidity for 24 hours, the peel resistance value when left to stand at 70 ℃ for 24 hours, and the difference between these values are shown.

< residual adhesion Rate >

The above-mentioned method is performedIs applied with 20gf/cm by adhering a tape No.31B made by Nito electric company ² Is placed in a hot air circulation oven at 70 ℃ for 20 hours. Then, the tape was peeled off, and the peeled tape was adhered to a stainless steel plate, and 20g/cm of the adhesive tape was applied ² Is allowed to stand in air at 23℃and a humidity of 60% for 30 minutes, and then a tensile tester [ Co., ltd., A ] is used&Universal tester for D-system TENSILON]The tape was stretched at an angle of 180 degrees at a peeling speed of 0.3 m/min, and the force (gf 1) required for peeling was measured. As a blank test, the adhesive tape was attached to a TEFLON (registered trademark) sheet in the same manner as described above, and the force (gf 2) required for peeling off the adhesive tape was measured in the same manner as described above. From these values, the residual adhesion (%) was calculated according to the following formula.

Residual adhesion (%) = (gf 1/gf 2) ×100

< examples 1 to 4, comparative examples 1 to 5>

The following components were uniformly mixed so as to have the compositions shown in tables 1 and 2, and silicone compositions for forming a release cured film were prepared. In tables 1 and 2, the content of the component (D) was such that the total amount of platinum in the component (D) relative to the components (a) to (C) was 200ppm in terms of mass unit. In tables 1 and 2, "SiH/alkenyl" represents the number of moles of silicon atom-bonded hydrogen atoms in the component (C) to 1 mole of the total of alkenyl groups in the components (a) and (B). The properties of a release sheet produced using the silicone composition for forming a release cured film thus prepared were measured, and the results are shown in tables 1 and 2.

As the component (a), the following components were used.

(a-1): a viscosity exceeding 100000 mpa.s, a plasticity of 1.15, and a dimethylsiloxane-methylhexenyl siloxane copolymer (hexenyl content=0.0296 mol/100 g) terminated at both molecular chain ends by trimethylsiloxy groups.

(a-2): a viscosity of more than 100000 mpa.s, a plasticity of 1.15, and a dimethylsiloxane-methylhexenyl siloxane copolymer (hexenyl content=0.0185 mol/100 g) terminated at both molecular chain ends by trimethylsiloxy groups.

As the component (B), the following components were used.

(b-1): dimethylsiloxane-methylvinylsiloxane copolymer having a viscosity of 5000 mpa.s and having both molecular chain ends terminated by trimethylsiloxy groups (vinyl content=0.0055 mol/100 g).

(b-2): dimethylsiloxane-methylvinylsiloxane copolymer having a viscosity of 40000 mpa.s and having both molecular chain ends terminated by trimethylsiloxy groups (content of vinyl groups=0.0055 mol/100 g).

In addition, for comparison of the component (B), the following components were used.

(b-3): dimethylsiloxane-methylvinylsiloxane copolymer having a viscosity of 35000 mpa.s and terminated at both molecular chain ends by trimethylsiloxy groups (content of vinyl groups=0.0185 mol/100 g).

(b-4): a dimethylpolysiloxane having a viscosity of 2000 mpa.s and a molecular chain terminated at both ends by dimethylvinylsiloxy groups (vinyl content=0.0085 mol/100 g).

(b-5): dimethylsiloxane-methylvinylsiloxane copolymer having a viscosity of 350 mpa.s and having both molecular chain ends terminated by trimethylsiloxy groups (vinyl content= 0.0462 mol/100 g).

(b-6): a dimethylpolysiloxane having a viscosity of 5000 mPas and having both molecular chain ends terminated by trimethylsiloxy groups.

As the component (C), the following components were used.

(c-1): methyl hydrogen polysiloxane having a viscosity of 20mpa·s and having both molecular chain ends terminated with trimethylsiloxy groups (content of silicon atom-bonded hydrogen atom=1.56 mol/100 g).

(c-2): dimethylsiloxane-methylhydrosiloxane copolymers having a viscosity of 55 mpa.s and having both molecular chain ends terminated by trimethylsiloxy groups (content of silicon atom-bonded hydrogen atoms=0.99 mol/100 g).

As the component (D), the following components were used.

(d-1): 1, 3-Divinyltetramethyldisiloxane solution of platinum 1, 3-Divinyltetramethyldisiloxane Complex (platinum content 4000 ppm).

As the component (E), the following components were used.

(e-1): 2-methyl-3-butyn-2-ol.

As the component (F), the following components were used.

(f-1): toluene.

TABLE 1

TABLE 2

/>

From the results shown in tables 1 and 2, it is found that when a polyorganosiloxane having an alkenyl group at the end of the molecular chain (comparative example 1) and a polyorganosiloxane having an alkenyl group at the end of the molecular chain (comparative example 2) are used as the component (B) and the content of alkenyl groups in terms of vinyl groups exceeds 0.0148 mol/100 g, the difference between the peeling resistance when left standing at 23 ℃ and the peeling resistance when left standing at 70 ℃ is large, and thus there is a possibility that the peeling resistance may vary with time. It is also found that when a polyorganosiloxane having a viscosity of less than 1000mpa·s is used as the component (B) (comparative example 3), the peeling resistance at 23 ℃ can be reduced, but the difference between the peeling resistance when left to stand at 23 ℃ and the peeling resistance when left to stand at 70 ℃ is large, and thus there is a possibility that the peeling resistance changes with time. It was also found that when a polyorganosiloxane having no alkenyl group was used as the component (B) (comparative example 5), the peeling resistance was reduced, but the residual adhesive ratio was significantly reduced. On the other hand, in the present invention (examples 1 to 4), the peeling resistance was small, the change in the peeling resistance with time was small, and the residual adhesive ratio was not lowered.

Industrial applicability

The silicone composition for forming a release cured film of the present invention is suitable as a release cured film-forming material for producing a release paper for use in a process of producing an optical member such as a liquid crystal panel, a plasma display, a polarizing plate, and a retardation plate, or a printed circuit board, an IC, a transistor, a capacitor, or other electrical/electronic parts, which requires a relatively light release resistance, because it has a light release resistance and little change in release resistance with time, and does not reduce the residual adhesion rate of an adhesive substance.

Claims

1. A silicone composition for forming a release cured coating, comprising:

a: a chain polyorganosiloxane having a viscosity of more than 100000 mPas at 25 ℃ and having at least two alkenyl groups having 2 to 12 carbon atoms in a side chain of only a molecular chain in one molecule;

b: a chain polyorganosiloxane having a viscosity of 1000 to 100000 mPas at 25 ℃ and having at least two alkenyl groups having 2 to 12 carbon atoms in only a side chain of a molecular chain in one molecule, the alkenyl group content being 0.0018 to 0.0148 mol/100 g, wherein the mass ratio of component A to component B is 10/90 to 90/10;

c: a polyorganosiloxane having at least two silicon-bonded hydrogen atoms in one molecule, wherein the amount of the silicon-bonded hydrogen atoms in the component C is 0.5 to 5 moles relative to 1 mole of the total of the alkenyl groups in the component A and the component B; and

d: a catalytic amount of a hydrosilylation catalyst.

2. The silicone composition for forming a release cured film according to claim 1, wherein,

alkenyl in component A is hexenyl.

3. The silicone composition for forming a release cured film according to claim 1, wherein,

the mass ratio of the component A to the component B, namely the component A/component B, is 40/60-80/20.

4. The silicone composition for forming a release cured film according to claim 1, wherein,

the silicone composition for forming a release cured film further contains an E hydrosilylation reaction inhibitor.

5. The silicone composition for forming a release cured film according to claim 1, wherein,

the silicone composition for forming a releasable cured coating further contains an F organic solvent.

6. A release sheet comprising a release cured film obtained by curing the silicone composition for forming a release cured film according to any one of claims 1 to 5.