Silicone gel-forming composition

Abstract

Provided is a novel silicone gel-forming composition. This silicone gel-forming composition contains: (A) a chain-like organopolysiloxane having two or more alkenyl groups in the molecule; (B) a chain-like organopolysiloxane having two or more mercaptoalkyl groups in the molecule; (C) a chain-like organopolysiloxane having one alkenyl group and a silicon-containing organic group in the molecule; and (D) a radical polymerization initiator.

Description

Silicone gel-forming composition

[0001] The present invention relates to a silicone gel-forming composition, a silicone gel obtained by curing the composition, an electronic component including the silicone gel, and a method for producing the electronic component.

[0002] As one type of curable organopolysiloxane composition, a composition capable of forming a silicone gel upon curing (silicone gel-forming composition) is known. Such silicone gel-forming compositions are widely used as encapsulants or sealants for electrical and electronic devices. In recent years, photocurable silicone gel-forming compositions that use high-energy rays such as UV and can be cured at room temperature have attracted attention as silicone gel-forming compositions from the perspective of sustainability, etc. Photocurable silicone gel-forming compositions are disclosed, for example, in Patent Documents 1 to 6.

[0003] Japanese Patent Application Publication No. 2020-172581 International Publication No. 2011 / 136170 Pamphlet International Publication No. 2012 / 086402 Pamphlet Japanese Patent Application Publication No. 2016-150958 Japanese Patent Application Publication No. 2018-058991 International Publication No. 2018 / 066379 Pamphlet

[0004] In light of these circumstances, the present invention provides a novel silicone gel-forming composition and the like.

[0005] The present invention provides the following silicone gel-forming compositions, etc.: [1] A silicone gel-forming composition comprising: (A) a linear organopolysiloxane having two or more alkenyl groups in the molecule; (B) a linear organopolysiloxane having two or more mercaptoalkyl groups in the molecule; (C) a linear organopolysiloxane having one alkenyl group and a silicon-containing organic group in the molecule; and (D) a radical polymerization initiator. [2] The composition according to [1], in which the linear organopolysiloxane of component (C) has a branched structure. [3] The composition according to [1] or [2], in which component (C) contains a branched compound having a structure represented by the following general formula (1): In the general formula (1), X is an organic group containing an alkenyl group, and R １are each independently selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxyl group, and an alkoxy group having 1 to 12 carbon atoms; m is an integer of 0 to 3; L ｉ the maximum number of generations c of the silicon-containing organic group is an integer of 1 to 10, i is an integer of 1 to c that indicates the generation of the silicon-containing organic group, and L ｉ is selected from the group consisting of alkyl groups having 1 to 12 carbon atoms and aryl groups having 6 to 12 carbon atoms when i=c, and is a silylalkyl group represented by the following general formula (2) when i is less than c: (In the general formula (2), Z is selected from the group consisting of a single bond, an oxygen atom, and an alkylene group having 2 to 12 carbon atoms; R ２ are each independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, and an aryl group having 6 to 12 carbon atoms; ３ are each independently selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxyl group, and an alkoxy group having 1 to 12 carbon atoms; ｉ＋１ is selected from the group consisting of alkyl groups having 1 to 12 carbon atoms and aryl groups having 6 to 12 carbon atoms when i=c, and is the above-mentioned silylalkyl group when i is less than c; ｉis a number from 0 to 3.)} [4] The composition according to any one of [1] to [3], wherein the content of mercapto groups in component (B) is 0.03 mmol / g or more, based on the total amount of the composition. [5] The composition according to any one of [1] to [4], wherein the molar ratio of mercapto groups in component (B) to alkenyl groups in components (A) and (C) is 0.20 or more. [6] The composition according to any one of [1] to [5], wherein the content ratio of component (C) to component (B) [component (C) / component (B)] is 0.05 or more, in mass ratio. [7] The composition according to any one of [1] to [6], wherein component (D) contains a photoradical polymerization initiator. [8] A silicone gel obtained by curing the silicone gel-forming composition according to any one of [1] to [7]. [9] The silicone gel according to [8], which has a loss factor (tan δ) of 0.20 or more at a frequency of 1.0 Hz.

[10] An electronic component comprising the silicone gel according to [8] or [9].

[11] A method for producing an electronic component, which comprises using the silicone gel-forming composition according to any one of [1] to [7].

[0006] According to one aspect of the present invention, there is provided a silicone gel-forming composition capable of forming a cured product (silicone gel) with reduced migration of uncured components. According to one aspect of the present invention, there is provided a silicone gel-forming composition capable of forming a cured product with appropriate viscoelasticity. According to a preferred aspect of the present invention, there is provided a silicone gel-forming composition capable of forming a cured product with reduced migration of uncured components and appropriate viscoelasticity.

[0007] The upper and lower limit values ​​of the numerical ranges described herein can be arbitrarily combined. For example, when a numerical range is described as "preferably 30 to 100, more preferably 40 to 80," the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described herein. Furthermore, when a numerical range is described as "preferably 30 or more, more preferably 40 or more, and preferably 100 or less, more preferably 80 or less," the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described herein. In addition, when a numerical range described herein as "60 to 100," for example, means a range of "60 or more and 100 or less."

[0008] 1. Silicone Gel-Forming Composition One aspect of the present invention provides a silicone gel-forming composition (hereinafter also referred to as the "composition of the present invention"). The composition of the present invention comprises (A) a linear organopolysiloxane having two or more alkenyl groups in the molecule, (B) a linear organopolysiloxane having two or more mercaptoalkyl groups in the molecule, (C) a linear organopolysiloxane having one alkenyl group and a silicon-containing organic group in the molecule, and (D) a radical polymerization initiator. Each of the components that make up the composition of the present invention is described in detail below.

[0009] 1.1 Component (A) Component (A) is an organopolysiloxane that serves as a base polymer. The composition of the present invention contains, as component (A), a linear organopolysiloxane having two or more alkenyl groups in the molecule. In one embodiment of the present invention, component (A) contains a linear organopolysiloxane having two or more alkenyl groups and no mercaptoalkyl groups. In one embodiment of the present invention, the alkenyl group may be an alkenyl group having 2 to 12 carbon atoms. Specific examples of alkenyl groups having 2 to 12 carbon atoms include vinyl, propenyl (including allyl), butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl groups. These groups also include structural isomers. In one embodiment of the present invention, the alkenyl group is preferably an alkenyl group having 2 to 10 carbon atoms, more preferably an alkenyl group having 2 to 8 carbon atoms, still more preferably a group selected from the group consisting of vinyl, allyl, and hexenyl, with vinyl or hexenyl being particularly preferred. The bonding position of the alkenyl group in component (A) may be, for example, at the molecular chain terminal and / or in a molecular chain side chain.

[0010] In one embodiment of the present invention, the vinyl (CH ２ The content of the (═CH—) moiety (hereinafter referred to as the “vinyl group content”) is preferably in the range of 0.01 to 5.0 mass%, more preferably 0.05 to 3.0 mass%, and even more preferably 0.09 to 1.5 mass%, relative to the mass of component (A).

[0011] In component (A), the silicon-bonded group other than an alkenyl group may be a monovalent hydrocarbon group having 1 to 12 carbon atoms and containing no aliphatic unsaturated bonds. Examples of monovalent hydrocarbon groups having 1 to 12 carbon atoms and containing no aliphatic unsaturated bonds include alkyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups. Examples of the alkyl groups include methyl, ethyl, propyl groups such as n-propyl and isopropyl, butyl groups such as n-butyl, isobutyl, s-butyl, and t-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl groups. These groups also include structural isomers. Examples of the aryl groups include phenyl, tolyl, xylyl, and naphthyl groups. Examples of the aralkyl groups include benzyl, phenethyl, 3-phenylpropyl, and 4-phenylbutyl groups. The halogenated alkyl group may be a group in which some or all of the hydrogen atoms bonded to carbon atoms in the alkyl group have been substituted with halogen atoms such as chlorine atoms or bromine atoms, and specific examples include a chloromethyl group, a 3-chloropropyl group, a 3,3,3-trifluoropropyl group, etc. Among these, the monovalent hydrocarbon group is preferably an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms, and even more preferably a methyl group or a phenyl group.

[0012] The molecular structure of component (A) may be linear, partially branched linear, branched, cyclic, network, dendritic, or the like. In one embodiment of the present invention, component (A) may be a mixture of two or more of these molecular structures. In another embodiment of the present invention, component (A) may be one or more selected from the group consisting of linear organopolysiloxanes, branched organopolysiloxanes, and mixtures thereof.

[0013] Specific examples of linear organopolysiloxanes include dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, dimethylpolysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups, methylphenylpolysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with dimethylvinylsiloxy groups, dimethylpolysiloxane-methylphenylpolysiloxane copolymers capped at both molecular chain terminals with dimethylvinylsiloxy groups, These include dimethylsiloxane-methylvinylsiloxane copolymers end-blocked with dimethylphenylsiloxy groups, dimethylpolysiloxanes end-blocked with methylvinylphenylsiloxy groups at both molecular chain terminals, dimethylsiloxane-diphenylsiloxane-methylvinylsiloxane copolymers end-blocked with trimethylsiloxy groups at both molecular chain terminals, dimethylsiloxane-diphenylsiloxane copolymers end-blocked with dimethylvinylsiloxy groups at both molecular chain terminals, dimethylsiloxane-diphenylsiloxane-methylvinylsiloxane copolymers end-blocked with dimethylvinylsiloxy groups at both molecular chain terminals, and dimethylsiloxane-diphenylsiloxane-methylvinylsiloxane copolymers end-blocked with dimethylphenylsiloxy groups at both molecular chain terminals.

[0014] Branched organopolysiloxanes include, for example, MDT resins, MQ resins, MDQ resins, MTQ resins, MDTQ resins, TD resins, TQ resins, and TDQ resins, which are composed of any combination of triorganosiloxy units (M units) (organo groups are methyl only, or methyl and vinyl or phenyl), diorganosiloxy units (D units) (organo groups are methyl only, or methyl and vinyl or phenyl), monoorganosiloxy units (T units) (organo groups are methyl, vinyl, or phenyl), and siloxy units (Q units). Depending on the combination of M units, D units, T units, and Q units, the branched organopolysiloxane can be liquid (e.g., oil-like) or solid (e.g., resin-like) at room temperature (e.g., 15 to 30°C, preferably 20 to 25°C; hereinafter, the same applies unless a specific temperature is specified).

[0015] The composition of one embodiment of the present invention may or may not contain the above-mentioned branched organopolysiloxane (MDT resin, MQ resin, MDQ resin, MTQ resin, MDTQ resin, TD resin, TQ resin, TDQ resin, etc.) that does not have an alkenyl group and / or a mercaptoalkyl group. The content of such branched organopolysiloxane may be less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, less than 0.0001 mass%, or less than 0.00001 mass%.

[0016] The composition of one embodiment of the present invention may or may not contain the above-mentioned branched organopolysiloxane (MQ resin, MDQ resin, MTQ resin, MDTQ resin, TD resin, TQ resin, TDQ resin, etc.) having at least three aliphatic unsaturated groups (e.g., alkenyl groups) per molecule. The content of such branched organopolysiloxane may be less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, less than 0.0001 mass%, or less than 0.00001 mass%.

[0017] In one embodiment of the present invention, the properties of component (A) at room temperature may be oily or rubbery, but are preferably oily. The viscosity of component (A) at 25°C is, for example, in the range of 1 to 100,000 mPa·s, preferably 100 to 80,000 mPa·s, more preferably 250 to 50,000 mPa·s, and may also be 500 to 10,000 mPa·s, 500 to 8,000 mPa·s, or 800 to 5,000 mPa·s. When the viscosity of component (A) is at or above the lower limit of the above range, the physical properties of the resulting silicone gel, particularly flexibility and elongation, can be significantly improved. Furthermore, when the viscosity of component (A) is at or below the upper limit of the above range, the handleability of the resulting silicone gel can be improved. Note that, in this specification, viscosity refers to the value measured at 25°C using a B-type viscometer.

[0018] In one embodiment of the present invention, the content of component (A) is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, relative to the total amount (100% by mass) of the composition, and is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less. In another embodiment of the present invention, the content of component (A) may be adjusted so that the molar ratio of mercapto groups to alkenyl groups described below falls within the range described below.

[0019] 1.2 Component (B) Component (B) functions as a crosslinking agent that reacts with the alkenyl groups in component (A) to crosslink component (A). The composition of the present invention contains, as component (B), a linear organopolysiloxane having two or more mercaptoalkyl groups in the molecule. In one embodiment of the present invention, the mercaptoalkyl groups include mercaptomethyl, 2-mercaptoethyl, 3-mercaptopropyl, 4-mercaptobutyl, and 6-mercaptohexyl groups. The mercaptoalkyl groups in component (B) may be bonded, for example, to the molecular chain terminals and / or molecular chain side chains. However, from the viewpoint of imparting more branched structures to the cured product, it is preferable that component (B) has a mercaptoalkyl group bonded to a silicon atom in a molecular chain side chain. The composition of one embodiment of the present invention does not contain a linear organopolysiloxane having a mercaptoalkyl group bonded to a silicon atom at the molecular chain terminal. The content of such chain organopolysiloxanes may be less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, less than 0.0001 mass%, or less than 0.00001 mass%.

[0020] The number of mercaptoalkyl groups in the molecule of component (B) may be 1 or more, 2 or more, or 5 or more, and may be 10 or less, 9 or less, or 8 or less.

[0021] In one embodiment of the present invention, the content of mercapto (—SH) moieties in the mercaptoalkyl groups in component (B) (hereinafter referred to as the “mercapto group content”) is preferably 0.030 mmol / g or more, more preferably 0.035 mmol / g or more, and even more preferably 0.040 mmol / g or more, based on the total amount of the composition. Furthermore, the mercapto group content is preferably 0.40 mmol / g or less, more preferably 0.25 mmol / g or less, and even more preferably 0.15 mmol / g or less, based on the total amount of the composition. By adjusting the mercapto group content to the above-mentioned lower limit or higher, a silicone gel-forming composition can be obtained that is capable of forming a cured product with reduced migration of uncured components. Furthermore, by adjusting the mercapto group content to the above-mentioned upper limit or lower, deterioration of the silicone gel-forming composition or the cured product thereof can be suppressed.

[0022] In component (B), the silicon-bonded group other than a mercaptoalkyl group may be a monovalent hydrocarbon group containing 1 to 12 carbon atoms and containing no aliphatic unsaturated bonds. Specific examples and preferred embodiments of the monovalent hydrocarbon group may be the same as those described above in "1.1 Component (A)."

[0023] The molecular structure of component (B) may be linear, partially branched linear, branched, cyclic, network, dendritic, or the like. In one embodiment of the present invention, component (B) may be a mixture of two or more of these molecular structures. In another embodiment of the present invention, component (B) may be one or more selected from the group consisting of linear organopolysiloxanes, branched organopolysiloxanes, and mixtures thereof. The linear organopolysiloxane of component (B) may be a linear organopolysiloxane in which two or more mercaptoalkyl groups are substituted on any side chain of the linear organopolysiloxanes and branched organopolysiloxanes listed above in "1.1 Component (A)."

[0024] In one embodiment of the present invention, the viscosity of component (B) at 25° C. is, for example, in the range of 1 to 2,000 mPa·s, preferably 10 to 1,000 mPa·s, and more preferably 50 to 500 mPa·s.

[0025] In one embodiment of the present invention, the content of component (B) is preferably 0.5% by mass or more, more preferably 2.0% by mass or more, and even more preferably 3.0% by mass or more, relative to the total amount (100% by mass) of the composition, and is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less.

[0026] In another embodiment of the present invention, the content of component (B) is such that the molar ratio of mercapto groups in component (B) to alkenyl groups (e.g., vinyl groups) in components (A) and (C) (mercapto groups / alkenyl groups) is 0.20 or more, 0.25 or more, or 0.30 or more. When the content of component (B) is equal to or greater than the above molar ratio, the curability of the composition can be improved. The upper limit of this molar ratio is not particularly limited, but may be, for example, 1.50 or less, 1.25 or less, or 1.00 or less.

[0027] 1.3 Component (C) Component (C) is a component for adjusting the crosslinking reaction. The composition of the present invention contains, as component (C), a linear organopolysiloxane having one alkenyl group and a silicon-containing organic group in the molecule. In one embodiment of the present invention, component (C) is a linear organopolysiloxane having a branched structure. The linear organopolysiloxane of component (C) may be used alone or in combination of two or more types.

[0028] Generally, in order to reduce the amount of migration of uncured components, a method of increasing the crosslink density of the silicone gel is adopted. However, increasing the crosslink density of the silicone gel tends to make the silicone gel excessively hard. As such, reducing the amount of migration of uncured components and realizing appropriate viscoelasticity are usually in a trade-off relationship, and it is not easy to achieve both of these simultaneously. The present inventors have discovered that by incorporating component (C) into the composition, both of the above-mentioned two effects can be achieved. Preferably, by containing component (C) and further adjusting the content of mercapto groups in component (B) to a specific numerical range, both of the above-mentioned two effects can be achieved.

[0029] In one embodiment of the present invention, the linear organopolysiloxane of component (C) more specifically comprises a branched compound having a structure represented by the following general formula (1):

[0030] In the general formula (1), X represents an organic group containing an alkenyl group. Specific examples of the organic group containing an alkenyl group include an alkenyl group and a (meth)acryloyl group-containing organic group represented by the following general formula (X-1). Note that "(meth)acryloyl" refers to acryloyl and / or methacryloyl.

[0031] Specific examples of the alkenyl group may be the same as those described above in "1.1 Component (A)." The alkenyl group is preferably an alkenyl group having 2 to 10 carbon atoms, more preferably an alkenyl group having 2 to 8 carbon atoms, still more preferably a group selected from the group consisting of a vinyl group, an allyl group, and a hexenyl group, and particularly preferably a vinyl group or a hexenyl group.

[0032] In the above general formula (X-1), R ４ is a hydrogen atom or a methyl group, and R ５ is preferably an alkylene group having 2 to 12 carbon atoms, more preferably an alkylene group having 2 to 6 carbon atoms, and even more preferably an alkylene group having 2 to 4 carbon atoms. Specific examples of the alkylene group include various propylene groups such as 1,1-ethylene group, 1,2-ethylene group, 1,3-propylene, 1,2-propylene, and 2,2-propylene, as well as butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, and dodecylene groups. These groups also include structural isomers.

[0033] More specifically, the (meth)acryloyl group-containing organic group represented by the general formula (X-1) above is an organic group containing, for example, an acryloyloxymethyl group, a 3-acryloyloxypropyl group, a methacryloyloxymethyl group, or a 3-methacryloyloxypropyl group.

[0034] In the above general formula (1), R １are each independently a group selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxyl group, and an alkoxy group having 1 to 12 carbon atoms. １ may be the same or different.

[0035] R １ Specific examples of the alkyl group that can be selected as include methyl, ethyl, propyl groups such as n-propyl and isopropyl, butyl groups such as n-butyl, isobutyl, s-butyl and t-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, etc. These groups also include structural isomers.

[0036] R １ Specific examples of the aryl group that can be selected as include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and the like.

[0037] R １ Specific examples of the alkoxy group that can be selected as include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, etc. These groups also include structural isomers.

[0038] Among these, R １ is preferably an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms, and further preferably a methyl group or a phenyl group.

[0039] In the above general formula (1), m is an integer of 0 to 3. m is preferably 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0040] In the above general formula (1), L ｉ The maximum number of layers c of L is an integer of 1 to 10. The number of layers is preferably 1 to 8, more preferably 1 to 5, and even more preferably 1 to 3. ｉIn the formula, "i" indicates the hierarchy of the silicon-containing organic group (in some cases, for example, a silyl group, a siloxy group, a silylalkyl group, etc.). The hierarchy i is an integer from 1 to c. The c in hierarchy i is as defined above.

[0041] In the above general formula (1), L ｉ When i=c, L is selected from the group consisting of alkyl groups having 1 to 12 carbon atoms and aryl groups. The alkyl groups and aryl groups are as described above. ｉ When i is less than c, it is a silylalkyl group represented by the following general formula (2):

[0042] In the above general formula (2), Z is selected from the group consisting of a single bond, an oxygen atom, and an alkylene group having 2 to 12 carbon atoms. The alkylene group is as described above.

[0043] In the above general formula (2), R ２ are each independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, and an aryl group having 6 to 12 carbon atoms. The alkyl group and the aryl group are as described above. ２ may be the same or different.

[0044] In the above general formula (2), R ３ are each independently selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxyl group, and an alkoxy group having 1 to 12 carbon atoms. The alkyl group, the aryl group, and the alkoxy group are as described above. R ３ may be the same or different.

[0045] In the above general formula (2), L ｉ＋１ When i=c, L is selected from the group consisting of alkyl groups having 1 to 12 carbon atoms and aryl groups having 6 to 12 carbon atoms. The alkyl groups and aryl groups are as described above. ｉ＋１ When i is less than c, it is a repetition of the silylalkyl group represented by the above general formula (2).

[0046] In the above general formula (2), a ｉ is a number from 0 to 3. ｉ is preferably 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0047] <Component (C1)> In one embodiment of the present invention, component (C) is L in the following general formula (1): ｉ The branched compound (C1) has a maximum generation number c of 1.

[0048] The branched compound (C1) is a compound represented by the general formula (1) in which X is an alkenyl group, preferably a vinyl group or a hexenyl group, and R １ is an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms, more preferably a methyl group or a phenyl group, m is 0 or 1, preferably 0, the hierarchy i of the silicon-containing organic group is 1, and L ｉ is an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and more preferably a methyl group or a phenyl group.

[0049] In one embodiment of the present invention, the branched compound (C1) is a branched compound represented by the following formula (wherein Me is a methyl group):

[0050] <Component (C2)> In one embodiment of the present invention, component (C) is L in the following general formula (1): ｉ The branched compound (C2) includes a branched compound (C3) having a maximum generation number c of 2 or 3. The branched compound (C2) is a dendrimer having a dendron structure.

[0051] The branched compound (C2) is a compound represented by the general formula (1) above, wherein X is a (meth)acryloyl group-containing organic group represented by the following general formula (X-1):

[0052] R in the above general formula (X-1) ４is a hydrogen atom or a methyl group, preferably R ４ is a methyl group, and R ５ is an alkylene group having 2 to 6 carbon atoms, preferably an alkylene group having 2 to 4 carbon atoms.

[0053] The branched compound (C2) is a compound represented by the general formula (1) above, wherein R １ is an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms, more preferably a methyl group or a phenyl group, m is 0 or 1, preferably 0, the generation i of the silicon-containing organic group is 1 to 3, and L ｉ When i=c (i.e., 2 or 3), it is an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, more preferably a methyl group or a phenyl group; when i is less than c (i.e., 2 or 3), it is a silylalkyl group represented by the following general formula (2):

[0054] The branched compound (C2) is a compound represented by the general formula (2) in which Z is an alkylene group having 2 to 12 carbon atoms, preferably an alkylene group having 2 to 6 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms; ２ is an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms, more preferably a methyl group or a phenyl group, and R ３ is an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms, more preferably a methyl group or a phenyl group, and L ｉ＋１when i=c (i.e., 2 or 3), it is an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, more preferably a methyl group or a phenyl group; when i is less than c (i.e., 2 or 3), it is a repetition of the silylalkyl group represented by the above general formula (2); ｉ is 0 or 1, preferably 0.

[0055] In one embodiment of the present invention, the branched compound (C2) is a branched compound represented by the following formula (wherein Me is a methyl group):

[0056] In one embodiment of the present invention, the content of component (C) is preferably 1.0 mass% or more, more preferably 1.5 mass% or more, and even more preferably 2.0 mass% or more, relative to the total amount (100 mass%) of the composition, and is preferably 10 mass% or less, more preferably 7.5 mass% or less, and even more preferably 5.0 mass% or less.

[0057] In one embodiment of the present invention, the ratio of the content of component (C) to the content of component (B) [component (C) / component (B)], expressed as a mass ratio, is preferably 0.05 or more, more preferably 0.07 or more, even more preferably 0.10 or more, and is preferably 0.80 or less, more preferably 0.75 or less, even more preferably 0.70 or less. By adjusting this ratio within the above range, a good blending balance is achieved between component (B), which is a crosslinking agent, and component (C), which regulates the crosslinking reaction, and appropriate viscoelasticity can be imparted to the cured product (silicone gel).

[0058] 1.4 Component (D) Component (D) is a component for initiating radical polymerization. Component (D) may be a photoradical polymerization initiator or a thermal radical polymerization initiator, but a photoradical polymerization initiator is preferred. The photoradical polymerization initiator is a component that promotes the photocuring reaction of the alkenyl group in component (A) and the mercaptoalkyl group in component (B) by irradiation with high-energy rays such as ultraviolet rays. The photoradical polymerization initiator may be one that can promote the curing reaction not only by irradiation with high-energy rays such as ultraviolet rays, but also by irradiation with light in the visible light range.

[0059] Examples of the photoradical polymerization initiator include α-ketol compounds, acetophenone compounds, benzoin ether compounds, ketal compounds, aromatic sulfonyl chloride compounds, photoactive oxime compounds, benzophenone compounds, thioxanthone compounds, bisacylphosphine oxides, monoacylphosphine oxides, anthraquinones, benzoic acid esters, and titanocenes.

[0060] Specific examples of the α-ketol compounds include 2-hydroxy-2-methyl-1-phenyl-1-propanone, 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and 1-hydroxycyclohexylphenyl ketone.

[0061] Specific examples of the acetophenone compounds include methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1.

[0062] Specific examples of the benzoin ether compounds include benzoin ethyl ether, benzoin isopropyl ether, anisoin methyl ether, and anisoin ethyl ether.

[0063] Specific examples of the ketal compounds include benzyl dimethyl ketal, etc. Specific examples of the aromatic sulfonyl chloride compounds include 2-naphthalenesulfonyl chloride, etc. Specific examples of the photoactive oxime compounds include 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime, etc. Specific examples of the benzophenone compounds include benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone, etc. Specific examples of the thioxanthone compounds include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone, etc.

[0064] Specific examples of the bisacylphosphine oxides include bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,6dichlorobenzoyl)-4-propylphenylphosphine oxide, bis(2,6dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, and bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

[0065] Specific examples of the monoacylphosphine oxides include 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphine acid methyl ester, 2-methylbenzoyldiphenylphosphine oxide, pivaloylphenylphosphinic acid isopropyl ester, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide.

[0066] Specific examples of the anthraquinones include anthraquinone, chloroanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, 2-amylanthraquinone, and 2-aminoanthraquinone. Specific examples of the benzoic acid esters include ethyl-4-dimethylaminobenzoate, 2-(dimethylamino)ethyl benzoate, and p-dimethylbenzoic acid ethyl ester. Specific examples of the titanocenes include bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium and bis(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1-pyr-1-yl)ethyl)phenyl]titanium.

[0067] In addition to the above, the photoradical polymerization initiator may also be camphorquinone, halogenated ketone, phenyl disulfide 2-nitrofluorene, butyroin, azobisisobutyronitrile, tetramethylthiuram disulfide, etc. The above-mentioned photoradical polymerization initiators may be used alone or in combination of two or more.

[0068] Commercially available photopolymerization initiators suitable as component (D) include Omnirad 184, 907, 369, 369E, 379, 651, and 1173 manufactured by IGM Resins.

[0069] In one embodiment of the present invention, the content of component (D) is preferably in the range of 0.01 to 10.0 mass%, more preferably 0.1 to 5.0 mass%, and even more preferably 0.3 to 3.0 mass%, based on the total amount (100 mass%) of the composition.

[0070] 1.5 Optional Components In addition to components (A) to (E), the composition of one embodiment of the present invention may contain, as necessary, other organopolysiloxanes; heat-resistant additives; adhesion promoters; cure inhibitors; antioxidants; inorganic fillers such as silica, glass, alumina, and zinc oxide; fine organic resin powders such as polymethacrylate; phosphors; dyes; pigments; flame retardants; solvents; and the like.

[0071] The composition of one embodiment of the present invention may or may not contain a hindered amine compound or a hindered phenol compound. The content of the hindered amine compound or the hindered phenol compound may be less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, less than 0.0001 mass%, or less than 0.00001 mass%.

[0072] The hindered amine compound includes, for example, compounds having groups represented by the following general formulas (3) and (4).

[0073] In the general formula (3), each R is independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. In the general formula (4), each R is independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and R' is independently a hydrogen atom or -CH ２ -R" (wherein R" is a hydrogen atom or a monovalent organic group).

[0074] Examples of the hindered phenol compound include 2,6-bis(hydroxymethyl)-p-cresol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-hydroxymethylphenol, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,4-dimethyl-6-(1-methylpentadecyl)phenol, diethyl[{ 3,5-bis(1,1-di-tert-butyl-4-hydroxyphenyl)methyl}phosphonate, 3,3',3",5,5',5"-hexane-tert-butyl-4-a,a',a"-(mesitylene-2,4,6-tolyl)tri-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], and hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0075] 1.6 Production Method and Form of the Composition of the Invention The composition of one embodiment of the invention can be produced by uniformly mixing components (A) to (D) and any optional components used as needed at room temperature using the mechanical force of a mixer or the like. The composition of one embodiment of the invention may be a one-component (single-liquid) composition or a multi-component composition of two or more components (two-liquid) or more.

[0076] 1.7 Uses of the Composition of the Present Invention The composition of one embodiment of the present invention can provide a cured product (silicone gel) with reduced migration of uncured components and appropriate viscoelasticity. Therefore, the composition of the present invention can be used for sealing electronic components. Specific examples of such electronic components include electrical and electronic devices. Such electrical and electronic devices may include electrical circuits or electrodes in which metal electrodes (silver, copper, aluminum, gold, etc.) and metal oxide film electrodes (ITO (indium tin oxide), etc.) are formed on a base material such as glass, epoxy resin, polyimide resin, phenolic resin, or ceramic. Furthermore, such electronic components include, for example, peripheral components of the above-mentioned electrical and electronic devices, automotive electronic components such as electronic control units (ECUs), automotive component cases, terminal boxes, lighting components, and solar cell modules, and other metal and / or resin structures that require durability and water resistance. Furthermore, such electronic components include, for example, power devices (power semiconductors) for engine control (in transportation equipment), power / train systems, and air conditioning control. The composition of one embodiment of the present invention can be suitably used as an adhesive, potting material, coating material, sealant, or the like for protecting or adhering such electronic components.

[0077] 2. Electronic Component Sealant One aspect of the present invention provides an electronic component sealant (hereinafter also referred to as "electronic component sealant of the present invention") containing the silicone gel-forming composition described above in "1. Silicone Gel-Forming Composition." The components and composition of the silicone gel-forming composition contained in the electronic component sealant of the present invention are the same as those described above in "1. Silicone Gel-Forming Composition." Furthermore, the electronic components to which the electronic component sealant of the present invention can be applied are the same as those described above in "1.7 Uses of the Composition of the Present Invention."

[0078] The content of the silicone gel-forming composition contained in the electronic component encapsulant of one embodiment of the present invention is not particularly limited, but may be 30 to 100% by mass, 40 to 99% by mass, or 50 to 98% by mass, based on the total amount (100% by mass) of the electronic component encapsulant. In some embodiments, the electronic component encapsulant of the present invention may consist essentially of the silicone gel-forming composition of one embodiment of the present invention. As used herein, "consisting essentially of the silicone gel-forming composition of one embodiment of the present invention" means that the composition may contain other components, such as impurities, that may be unavoidably contained during the manufacturing process of the silicone gel-forming composition. In these embodiments, the electronic component encapsulant of the present invention may contain, for example, 5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, 1.0% by mass or less, or 0.5% by mass or less of other components, based on the total amount (100% by mass) of the electronic component encapsulant.

[0079] The electronic component encapsulant according to one embodiment of the present invention is substantially transparent.

[0080] 3. Method for curing the composition of the present invention and silicone gel One aspect of the present invention provides a silicone gel (hereinafter also referred to as the "silicone gel of the present invention") obtained by curing the silicone gel-forming composition described above in "1. Silicone gel-forming composition" or the electronic component sealant described above in "2. Electronic component sealant." The silicone gel of the present invention can be prepared by subjecting the silicone gel-forming composition of one embodiment of the present invention to a photo-curing reaction by irradiating it with high-energy rays such as ultraviolet light under temperature conditions appropriate for the intended use. The temperature at which the silicone gel-forming composition is cured is not particularly limited, but may be room temperature, such as 15 to 30°C.

[0081] The silicone gel of one embodiment of the present invention preferably has a loss factor (tan δ) at a frequency of 1.0 Hz, as measured by the measurement method described in the Examples below, of 0.20 or more, more preferably 0.22 or more, even more preferably 0.24 or more, and particularly preferably 0.25 or more. A silicone gel having a loss factor (tan δ) in the above range can be said to be a gel that does not have excessive hardness and has appropriate viscoelasticity.

[0082] Furthermore, in one embodiment of the silicone gel of the present invention, the amount of migration of uncured components in the composition, measured using the mass loss measured by the measurement method described in the Examples below as an index, is preferably less than 2.0 mass%, more preferably less than 1.9 mass%, and even more preferably less than 1.8 mass%. Silicone gels in which the amount of migration of uncured components in the composition falls within the above range can be said to be gels suitable for sealing electronic components.

[0083] 4. Electronic Component and Method for Manufacturing Electronic Component As one aspect, the present invention provides an electronic component (hereinafter also referred to as the "electronic component of the present invention") comprising the silicone gel described above in "3. Method for Curing the Composition of the Present Invention and Silicone Gel." Specific examples of the electronic component include those described above in "1.9 Uses of the Composition of the Present Invention." An electronic component of one aspect of the present invention comprises a cured layer made of the silicone gel of one aspect of the present invention. The cured layer may have a thickness of 1 to 50 mm, 2 to 40 mm, 5 to 30 mm, 5 to 20 mm, or 5 to 10 mm, depending on the type of electronic component.

[0084] Furthermore, as one aspect, the present invention provides a method for producing an electronic component (hereinafter also referred to as the "method for producing an electronic component of the present invention"), which comprises using the silicone gel-forming composition described above in "1. Silicone Gel-Forming Composition" or the electronic component sealant described above in "2. Electronic Component Sealant" (hereinafter also referred to as the "method for producing an electronic component of the present invention"). Specific examples of such electronic components include those described above in "1.7 Uses of the Composition of the Present Invention." Furthermore, the use is not particularly limited, and may involve applying the silicone gel-forming composition of the present invention or the electronic component sealant of the present invention to the electronic component as an adhesive, potting material, coating material, sealant, or the like at any stage in the manufacturing process of the electronic component. The amount or range of application can be appropriately determined depending on the type of electronic component.

[0085] The present invention will be further described below based on examples, but the present invention is not limited to the following examples.

[0086] Examples 1-5 and Comparative Examples 1-2 The silicone gel-forming compositions of Examples 1-5 and Comparative Examples 1-2 were prepared by uniformly mixing the components listed below in the ratios shown in Table 1. These compositions were cured by the method described below, and the loss factor (tan δ) and migration amount of uncured components of the resulting cured products (silicone gels) were evaluated. The evaluation results are shown in Table 1. In Table 1, the "SH / Vi ratio" represents the ratio of the number of moles of mercapto groups (SH groups) in component (B) to the number of moles of vinyl groups in components (A) and (C). In Table 1, the "SH group content" represents the number of moles of mercapto groups in component (B) relative to the total amount of the composition.

[0087] <Components (A)> Component (A1): dimethylsiloxane-diphenylsiloxane copolymer endblocked at both ends with dimethylvinylsiloxy groups (viscosity = 4,500 mPa·s, vinyl group content = 0.18% by mass) Component (A2): dimethylsiloxane-diphenylsiloxane copolymer endblocked at both ends with dimethylvinylsiloxy groups (viscosity = 1,000 mPa·s, vinyl group content = 0.29% by mass) Component (A3): dimethylsiloxane polymer endblocked at both ends with dimethylvinylsiloxy groups (viscosity = 40,000 mPa·s, vinyl group content = 0.09% by mass) Component (A4): dimethylsiloxane-methylsiloxane copolymer endblocked at both ends with dimethylvinylsiloxy groups (viscosity = 500 mPa·s, vinyl group content = 0.21% by mass)

[0088] <Component (B)> Component (B1): dimethyl-methyl(3-mercaptopropyl)siloxane copolymer endblocked at both ends with trimethylsiloxy groups (viscosity = 130 mPa·s, mercapto group content = 4.0% by mass) Component (B2): dimethyl-methyl(3-mercaptopropyl)siloxane copolymer endblocked at both ends with trimethylsiloxy groups (viscosity = 70 mPa·s, mercapto group content = 2.0% by mass)

[0089] <Component (C)> Component (C1): Tris(trimethylsiloxy)vinylsilane represented by the following formula (wherein Me is a methyl group): Component (C2): A branched compound having a dendron structure represented by the following formula (wherein Me is a methyl group):

[0090] <Component (D)> Component (D1): 2-hydroxy-2-methyl-1-phenyl-1-propanone (product name: Omnirad 1173, manufactured by IGM Resins) Component (D2): 2,2-dimethoxy-2-phenylacetophenone (product name: Omnirad 651, manufactured by IGM Resins)

[0091] [Method of curing the composition] Each of the prepared compositions was cured using a UV-LED device with a wavelength of 365 nm, with an accumulated light dose of 1500 mJ / cm 2 2 The silicone gel was cured to a thickness of 1 mm under the above conditions to form a silicone gel.

[0092] [Method for measuring loss factor (tan δ) of silicone gel] A 1 mm thick silicone gel was placed in close contact between a rotating shear jig and a sample stage, and a shear stress (shear strain 1%, frequency 1 Hz) was applied to the sample at 25°C using an Anton Paar MCR302 to measure the loss factor. A loss factor of 0.15 or more was judged to be acceptable, and one less than 0.15 was judged to be unacceptable.

[0093] [Method for Measuring the Amount of Migration of Uncured Components] 0.5 g of each prepared composition was weighed onto a PET film and cured under air under the conditions described in the "Composition Curing Method" section above to prepare a test specimen. The cured surface of the test specimen was pressed against frosted glass, and a 1 kg weight was placed on the PET film side of the test specimen and allowed to stand for 1 minute to transfer the uncured components to the frosted glass. The test specimen was slowly peeled off the frosted glass, and the weight of the cured product was remeasured. A weight loss (i.e., migration amount) of less than 2.0% after pressing was judged to be acceptable, and a weight loss of 2.0% or more was judged to be unacceptable.

[0094]

[0095] As shown in Table 1, the silicone gels of Examples 1 to 5, which contained all of components (A) to (D), had a loss factor of 0.15 or greater and a migration amount of less than 2.0%, both of which met the criteria for acceptance. On the other hand, the silicone gels of Comparative Examples 1 and 2, which did not contain component (C), had a loss factor of less than 0.15 or a migration amount of 2.0% or greater, either of which did not meet the criteria for acceptance.

Claims

1. A silicone gel-forming composition comprising: (A) a linear organopolysiloxane having two or more alkenyl groups in the molecule; (B) a linear organopolysiloxane having two or more mercaptoalkyl groups in the molecule; (C) a linear organopolysiloxane having one alkenyl group and a silicon-containing organic group in the molecule; and (D) a radical polymerization initiator.

2. The composition according to claim 1, wherein the linear organopolysiloxane of component (C) has a branched structure.

3. The composition according to claim 1, wherein component (C) comprises a branched compound having a structure represented by the following general formula (1): In the general formula (1), X is an organic group containing an alkenyl group, R １ are each independently selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxyl group, and an alkoxy group having 1 to 12 carbon atoms; m is an integer of 0 to 3; L ｉ The maximum number of generations c of L is an integer from 1 to 10, i is an integer from 1 to c that indicates a generation of the silicon-containing organic group, ｉ is selected from the group consisting of alkyl groups having 1 to 12 carbon atoms and aryl groups having 6 to 12 carbon atoms when i=c, and is a silylalkyl group represented by the following general formula (2) when i is less than c: (In the general formula (2), Z is selected from the group consisting of a single bond, an oxygen atom, and an alkylene group having 2 to 12 carbon atoms; R ２ are each independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, and an aryl group having 6 to 12 carbon atoms; R ３ are each independently selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxyl group, and an alkoxy group having 1 to 12 carbon atoms; ｉ＋１ is selected from the group consisting of an alkyl group having 1 to 12 carbon atoms and an aryl group having 6 to 12 carbon atoms when i=c, and is the above-mentioned silylalkyl group when i is less than c; ｉ is a number from 0 to 3.

4. The composition according to claim 1, wherein the content of mercapto groups in component (B) is 0.03 mmol / g or more based on the total amount of the composition.

5. The composition of claim 1, wherein the molar ratio of mercapto groups of component (B) to alkenyl groups of components (A) and (C) is 0.20 or greater.

6. The composition according to claim 1, wherein the ratio of the content of component (C) to the content of component (B) [component (C) / component (B)] is 0.05 or more in terms of mass ratio.

7. The composition of claim 1, wherein component (D) comprises a photoradical polymerization initiator.

8. A silicone gel obtained by curing the silicone gel-forming composition according to any one of claims 1 to 7.

9. The silicone gel according to claim 8, which has a loss factor (tan δ) of 0.20 or more at a frequency of 1.0 Hz.

10. An electronic component comprising the silicone gel according to claim 8.

11. A method for producing an electronic component, comprising using the silicone gel-forming composition according to any one of claims 1 to 7.

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