UV curable silicone gel composition

Abstract

(A)A polyorganosiloxane containing an aliphatic unsaturated group; (B) A polyorganosiloxane containing a mercaptoalkyl group bonded to a silicon atom; (C) A photoreaction initiator that initiates the reaction between (A) and (B), (D) A hindered amine stabilizer; and (E) Fine particles containing a silicon-oxygen bond with an average particle size of 1 to 30 μm, which is an ultraviolet curable silicone gel composition. By this composition, a cured product having excellent damping properties and excellent long-term stability is provided.

Description

UV-curable silicone gel composition

[0001] The present invention relates to a silicone gel composition that cures upon exposure to ultraviolet light and has excellent long-term reliability.

[0002] A silicone gel composition contains at least a polyorganosiloxane and a crosslinking agent, and the polyorganosiloxane is crosslinked by the crosslinking agent to form a crosslinked silicone gel. Silicones have properties such as high chemical stability and heat resistance due to their silicon oxide skeleton, and a wide range of molecular design possibilities, similar to carbon compounds, can be achieved by changing the degree of polymerization and the design of the substituents. Therefore, they are used as resins in various forms that have flexibility and strength when cured (Patent Document 1). One example of the use of a silicone gel composition is the use of a composition containing a polyorganosiloxane, a crosslinking agent, a filler, and a light stabilizer as a vibration suppression material (damping material) applied to the vibration transmission parts of optical equipment such as cameras.

[0003] In applications to products such as optical devices, ultraviolet-curable resin compositions are used as silicone gels because they can be cured in a short time and have dimensional stability due to the suppression of cure shrinkage. As an example of an ultraviolet-curable silicone resin composition, a UV-curable silicone resin composition comprising a polyorganosiloxane containing a mercaptoalkyl group and a polyorganosiloxane containing an aliphatic unsaturated group has been proposed (Patent Documents 2 and 3).

[0004] For example, a silicone resin composition containing acetophenone and / or propiophenone as a compatibilizer has been proposed to homogenize the composition and prevent unstable areas (Patent Document 4). On the other hand, ene-thiol type UV-curable silicone resins such as those described in Patent Documents 2 to 4 can cause yellowing, cloudiness, and softening of the cured product when exposed to UV light, so the selection of various additives, such as antioxidants, to suppress this and improve storage stability has been investigated (Patent Documents 5 to 8).

[0005] International Publication No. 2022 / 019229 JP 2-245060 A JP 3-064389 A JP 2013-253179 A JP 2016-60782 A JP 2016-145297 A JP 2020-172581 A JP 2023-82381 A

[0006] Adding an inorganic filler is useful for ensuring damping properties. However, in the case of polyorganosiloxane compositions containing inorganic fillers, changes in properties are observed after curing depending on the type and amount of filler, making it difficult to achieve both damping properties and long-term reliability.

[0007] An object of the present invention is to provide an ultraviolet-curable silicone gel composition that can solve these problems and that can give a cured product that has excellent damping properties and long-term reliability.

[0008] The present inventors conducted extensive research to solve the above-mentioned problems and discovered that when a certain type of silicon microparticle and a specific hindered amine compound are used in an ultraviolet-curable silicone gel composition, it is possible to achieve both high damping properties and long-term reliability, leading to the present invention.

[0009] That is, the present invention relates to the following aspects: [1] An ultraviolet-curable silicone gel composition comprising: (A) a polyorganosiloxane containing an aliphatic unsaturated group; (B) a polyorganosiloxane containing a mercaptoalkyl group bonded to a silicon atom; (C) a photoinitiator that initiates the reaction of (A) and (B); (D) a hindered amine stabilizer; and (E) fine particles containing silicon-oxygen bonds and having an average particle size of 1 to 15 μm. [2] The ultraviolet-curable silicone gel composition of [1] above, wherein (A) is a polyorganosiloxane in which 1 to 10 mol % of groups other than aliphatic unsaturated groups that are directly bonded to silicon are C6 to C12 aryl groups. [3] The ultraviolet-curable silicone gel composition according to [1] or [2], wherein (A) comprises (a1) a linear polyorganosiloxane having at least two aliphatic unsaturated groups in the molecule and (a2) a linear polyorganosiloxane having, on average, one aliphatic unsaturated group in the molecule. [4] The ultraviolet-curable silicone gel composition according to [1] or [2], wherein (a1) is a compound represented by the following formula (I): (In the formula, each R １The ultraviolet-curable silicone gel composition of [3] above, comprising a linear polyorganosiloxane containing an aliphatic unsaturated group, represented by the formula: (R) is independently an aliphatic unsaturated group, each R is independently a C1 to C6 alkyl group or a C6 to C12 aryl group, and n is a number that provides a viscosity of 100 to 100,000 cP at 23°C. [5] The ultraviolet-curable silicone gel composition of any of [1] to [4] above, wherein the ratio of the number of mercaptoalkyl groups in (B) to the number of aliphatic unsaturated groups in (A) is 0.01 to 10. [6] The ultraviolet-curable silicone gel composition of any of [1] to [5] above, wherein (E) is a spherical or pulverized fine particle. [7] The ultraviolet-curable silicone gel composition of any of [1] to [6] above, wherein (E) is a fine particle derived from silicone or silicon dioxide. [8] The ultraviolet-curable silicone gel composition of any of [1] to [7] above, wherein the amount of (E) is 0.1 to 40 parts by weight, relative to a total of 100 parts by weight of the entire composition. [9] The ultraviolet-curable silicone gel composition of any of [1] to [8] above, further comprising (F) fumed silica.

[10] The ultraviolet-curable silicone gel composition of [9] above, wherein, relative to a total of 100 parts by weight of (A) to (F), the amount of (A) is 41 to 90 parts by weight, the amount of (B) is 0.1 to 3 parts by weight, the amount of (C) is 0.1 to 3 parts by weight, the amount of (D) is 0.1 to 3 parts by weight, the amount of (E) is 0.1 to 40 parts by weight, and the amount of (F) is 1 to 10 parts by weight.

[11] The ultraviolet-curable silicone gel composition of any of [1] to [7] above, wherein, relative to a total of 100 parts by weight of (A) to (F), the amount of (A) is 41 to 90 parts by weight, the amount of (B) is 0.1 to 3 parts by weight, the amount of (C) is 0.1 to 3 parts by weight, the amount of (D ...E) is 1 to 1 ２ The complex modulus of elasticity G when cured by irradiating for 30 seconds at an intensity of ＊ The ultraviolet-curable silicone gel composition according to any one of [1] to

[10] above, wherein the value of is 4000 Pa or more.

[12] A damping material comprising the ultraviolet-curable silicone gel composition according to any one of [1] to

[11] above.

[0010] According to the present invention, there is provided an ultraviolet-curable silicone gel composition that gives a cured product that has excellent damping properties and also has excellent long-term reliability.

[0011] In the present invention, the term "alkyl group" refers to a linear or branched, monovalent saturated hydrocarbon group. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, i-propyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, and nonyl groups. When indicating the range of the number of carbon atoms contained in a substituent, for example, "C １－６ The term "alkyl group" indicates that the number of carbon atoms ranges from 1 to 6.

[0012] As used herein, the term "alkenyl group" refers to a linear or branched monovalent hydrocarbon group having at least one C=C double bond. Examples of alkenyl groups include, but are not limited to, ethynyl (vinyl), propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl groups, and the like.

[0013] In the present invention, the term "aryl group" refers to a monovalent cyclic aromatic hydrocarbon group consisting of a monocyclic, bicyclic, or tricyclic aromatic ring. Examples of aryl groups include, but are not limited to, phenyl, tolyl, xylyl, naphthyl, phenanthryl, fluorenyl, indenyl, pentalenyl, azulenyl, oxydiphenyl, biphenyl, methylenediphenyl, aminodiphenyl, diphenylsulfidyl, diphenylsulfonyl, diphenylisopropylidenyl, benzodioxanyl, benzofuranyl, benzodioxylyl, benzopyranyl, benzoxazinyl, benzoxazinonyl, benzopiperazinyl, benzopyrrolidinyl, benzomorpholinyl, methylenedioxyphenyl, ethylenedioxyphenyl, and the like (including partially hydrogenated derivatives thereof that retain aromaticity).

[0014] [(A) Polyorganosiloxane Containing an Aliphatic Unsaturated Group] The UV-curable silicone gel composition of the present invention contains at least one polyorganosiloxane containing an aliphatic unsaturated group in the molecule as component (A). Component (A) is a component that functions as a base polymer for the UV-curable silicone gel composition.

[0015] The type of aliphatic unsaturated group contained in component (A) is not particularly limited as long as it is a functional group that undergoes a photocuring reaction, has a carbon-carbon double bond, and is capable of undergoing an addition reaction. Specific examples include aliphatic unsaturated groups such as (meth)acrylic groups or alkenyl groups. The alkenyl group preferably has 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms, and more preferably 2 to 6 carbon atoms. The alkenyl group may have a branched or cyclic structure. The carbon-carbon double bond in the hydrocarbon constituting the alkenyl group can be located at any position. From the standpoint of reactivity, the carbon-carbon double bond is preferably located at the terminal of the group. A preferred example of an alkenyl group is a vinyl group, as this facilitates the synthesis of polyorganosiloxanes. The aliphatic unsaturated group can be located at any position in the polyorganosiloxane molecule. For example, it may be located at the molecular terminal, or it may be located as a side chain at a position other than the terminal. In the case of a linear polyorganosiloxane, at least one aliphatic unsaturated group is preferably present at each end of the molecular main chain of component (A). Herein, the molecular main chain of component (A) refers to the relatively longest connecting chain in the molecule of component (A).

[0016] The molecular skeleton of component (A) is not particularly limited as long as the siloxane bond is the main skeleton. It can be any of a linear, branched, cyclic, and three-dimensional network skeleton. The siloxane skeleton may also be interrupted by a divalent organic group. Herein, in explaining the structure of the siloxane compound, the structural units of the siloxane compound may be abbreviated as follows. Hereinafter, these structural units may be referred to as "M unit," "D unit," etc., respectively. M: Si(CH ３ ) ３ O １／２ D: Si(CH ３ ) ２ O ２／２ T: Si(CH ３ ) O ３／２ Q: SiO ４／２Hereinafter, in this specification, the siloxane compound is constructed by combining the above structural units, but may at least partially contain those in which the methyl groups of the above structural units are replaced with other groups such as halogens such as fluorine, hydrocarbon groups such as phenyl groups, etc. In this case, to indicate a state of being replaced with a substituent, the D units replaced with phenyl groups will be referred to as D Ｐｈ It can also be written as, for example, D Ｐｈ ２０ D ２０ In the case of the notation, it is intended that a total of 20 phenyl groups are contained in the 40 D units, and D Ｐｈ It is not intended that 20 units are followed by 20 D units, and each unit may be arranged in any order. ２ O ２／２ (D Ｐｈ２ It is understood that the siloxane compound can have a variety of three-dimensional structures due to the T units or Q units, but component (A) can have a linear molecular skeleton formed by any combination of the above M and D units.

[0017] In order to cure the composition, the polyorganosiloxane (A) preferably contains a polyorganosiloxane (a1) having two or more aliphatic unsaturated groups. Such polyorganosiloxanes are not particularly limited as long as they have an average of two or more alkenyl groups bonded to silicon atoms per molecule and can form a crosslinked structure by addition reaction with component (B), which will be described later. Such polyorganosiloxanes include, for example, (R １ ) ｍ (R ２ ) ｎ SiO （４－ｍ－ｎ）／２ (In the formula, R １ is an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bonds; R ２ is an alkenyl group; m is an integer of 0 to 2; and n is an integer of 1 to 3, with the proviso that m+n is 1 to 3.

[0018] A specific example of (a1) is a compound represented by formula (I): (In the formula, each R １ are independently an aliphatic unsaturated group, each R is independently a C1 to C6 alkyl group or a C6 to C12 aryl group, and 0 to 40 mol % of the R are C6 to C12 aryl groups, and n is a number that provides a viscosity at 23°C of 100 to 300,000 cP.

[0019] In the above formula (I), R １ is an aliphatic unsaturated group. １ may be the same or different, but are preferably the same.

[0020] Examples of the aliphatic unsaturated group include alkenyl groups, such as C2 to C6 alkenyl groups (e.g., vinyl, propenyl, butenyl, hexenyl, etc.). Terminally unsaturated alkenyl groups are more preferred, and vinyl groups are preferred from the standpoint of ease of synthesis.

[0021] In formula (I), R is a C1-C6 alkyl group (e.g., methyl, ethyl, propyl, etc.) or a C6-C12 aryl group (e.g., phenyl, tolyl, xylyl, etc.). R may be the same or different.

[0022] When R contains a group other than a C1 to C6 alkyl group, from the viewpoint of adjusting the refractive index, it is preferable that 1 to 40 mol % of R be C6 to C12 aryl groups, and from the viewpoint of viscosity and thixotropy, it is more preferable that 1 to 20 mol % of R be C6 to C12 aryl groups, even more preferably 1 to 10 mol % be C6 to C12 aryl groups, and particularly preferably 3 to 7 mol % be C6 to C12 aryl groups.

[0023] From the standpoint of ease of synthesis, the C1 to C6 alkyl group is preferably methyl, and the C6 to C12 aryl group is preferably phenyl.

[0024] In formula (I), it is preferable that 1 to 40 mol% of R are phenyl groups, with the remainder being methyl groups; more preferably, 1 to 20 mol% of R are phenyl groups, with the remainder being methyl groups; and particularly preferably, 1 to 10 mol% of R are phenyl groups, with the remainder being methyl groups.

[0025] The polyorganosiloxane (A) may contain, as (a2), a polyorganosiloxane having, on average, one aliphatic unsaturated group. The type of polyorganosiloxane (a2) having, on average, one aliphatic unsaturated group per molecule is not particularly limited, and as long as it has, on average, one aliphatic unsaturated group, it can be used regardless of whether the position is at the end of the molecule or inside the molecule. One type of polyorganosiloxane may be used alone, or two or more different types of polyorganosiloxanes may be used in combination. Furthermore, a mixture of multiple types of polyorganosiloxanes that may be produced in the polyorganosiloxane production process and have different numbers of aliphatic unsaturated groups may be used as (a2). According to a method known to those skilled in the art, polyorganosiloxanes having an average of one alkenyl group can be obtained as a mixture of, for example, about 50 mol% of polyorganosiloxanes containing alkenyl groups at one end, about 25 mol% of polyorganosiloxanes containing alkenyl groups at both ends, and about 25 mol% of polyorganosiloxanes containing no alkenyl groups, and this can be used as (a2). The type of aliphatic unsaturated group is the same as that exemplified in (a1) above.

[0026] Such (a2) includes, for example, (R １ ) ｍ (R ２ ) SiO （３－ｍ）／２ (In the formula, R １ is an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bonds; R ２ is an alkenyl group; and m is an integer of 0 to 2) in each molecule.

[0027] The shape of the siloxane skeleton of the polyorganosiloxane (a2) is not particularly limited. Examples of linear polyorganosiloxanes include linear polyorganosiloxanes containing a phenyl-containing aliphatic unsaturated group, such as polydimethylsiloxanes containing a vinyl group at one end. From the viewpoint of workability of the composition, such linear polyorganosiloxanes can have a viscosity at 23°C of 100 to 100,000 cP, preferably 100 to 25,000 cP.

[0028] Examples of branched chains include M Ｖｉ Q Resin, MD Ｖｉ Q Resin, M Ｖｉ T resin, M Ｖｉ DT Resin, MD Ｖｉ T resin, etc. Here, the M unit is (CH ３ ) ３ SiO １／２ -unit, M Ｖｉ is (CH ２ =CH)(CH ３ ) ２ SiO １／２ - unit, and D is -(CH ３ ) ２ SiO ２／２ -units, and D Ｖｉ is -(CH ３ ) (CH ２ =CH)SiO ２／２ - units, and T is (CH ３ ) SiO ３／２ unit (trifunctional), and Q is SiO ４／２ unit (tetrafunctional).

[0029] Specifically, SiO ４／２ Units, R' ３ SiO １／２ Units and R' ２ SiO ２／２ units, and optionally further R'SiO ３／２ Examples of suitable branched polyorganosiloxanes include those consisting of units (wherein R' each independently represents a C1 to C6 alkyl group or an aliphatic unsaturated group), in which at least one R' per molecule is an aliphatic unsaturated group. ２ SiO２／２ For 1 mole of units, SiO ４／２ units, 6 to 10 moles, R' ３ SiO １／２ Examples include branched polyorganosiloxanes having 4 to 8 moles of the unit. The polyorganosiloxane containing aliphatic unsaturated groups other than component (A) is preferably a solid or viscous semi-solid resin or liquid at room temperature. Examples include those with a weight-average molecular weight of 1,000 to 400,000, preferably 2,000 to 200,000. The weight-average molecular weight is a value measured by gel permeation chromatography (GPC) using polystyrene as a calibration curve.

[0030] As the aliphatic unsaturated group for R', the groups and preferred groups exemplified as the aliphatic unsaturated group in (A) are applicable. The aliphatic unsaturated group R' may be present as R' in any unit, but is preferably R' ２ SiO unit or R' ３ SiO １／２ It exists as the unit R'.

[0031] R' other than the aliphatic unsaturated group is a C1 to C6 alkyl group (for example, methyl, ethyl, propyl, etc.), and in consideration of heat resistance, a methyl group is preferred.

[0032] Specific examples of the polyorganosiloxane (a2) having one curable functional group on average in the molecule include polyorganosiloxanes represented by the following general formula: (In the formula, R ａ is an aliphatic unsaturated group, and each R is independently C １－６ Alkyl group or C ６－１２ An example of such a resin is a linear polyorganosiloxane having an aliphatic unsaturated group at the molecular end, represented by the formula: (where n is an aryl group and n is a number that provides a viscosity of 10 to 50,000 cP at 23°C), but the resin is not limited to a resin with such a structure. ａ It is preferred to use linear siloxanes in which R is a vinyl group and each R is a methyl.

[0033] The number of aliphatic unsaturated groups in component (A) can be determined from the molecular weight obtained by determining the average structural formula by NMR and calculating the molecular weight.

[0034] There are no particular limitations on the method for preparing component (A). For example, component (A) can be obtained by polycondensing and re-equilibrating chlorosilanes required for the desired structure, such as dimethyldichlorosilane, diphenyldichlorosilane, methylphenyldichlorosilane, and dimethylvinylchlorosilane, or by co-hydrolyzing alkoxysilanes required for the desired structure, such as dimethyldimethoxysilane, diphenyldimethoxysilane, methylphenyldimethoxysilane, and dimethylvinylmethoxysilane, followed by polycondensation and re-equilibration. Alternatively, siloxanes required for the desired structure, such as 1,1,3,3,5,5,7,7-octamethylcyclotetrasiloxane, 1,1,3,3,5,5,7,7-octaphenylcyclotetrasiloxane, and 1,1,3,3-tetramethyl-1,3-divinyldisiloxane, can also be obtained by ring-opening polymerization and re-equilibration in the presence of an alkali catalyst (such as an alkali metal hydroxide, an alkali metal silanolate, or an ammonium hydroxide) or an acid catalyst (such as sulfuric acid, a silanolate sulfate, or trifluoromethanesulfonic acid).

[0035] From the viewpoint of workability of the composition, component (A) has a viscosity at 25°C of 100 to 500,000 cP, preferably 100 to 250,000 cP, more preferably 200 to 10,000 cP, and particularly preferably 300 to 300,000 cP. In this specification, viscosity is a value measured at 40 rpm and 25°C using a cone-plate type measuring jig CP25-2 with a rheometer (MCR302e) (manufactured by Anton Paar).

[0036] Component (A) may be used alone or in combination of two or more. When (A) is a mixture of two or more types, (A) can be a mixture of a polyorganosiloxane with a high viscosity (for example, a viscosity at 23°C of 10,000 to 25,000 cP) and a polyorganosiloxane with a low viscosity (for example, a viscosity at 23°C of 100 to 5,000 cP).

[0037] The amount of component (A) contained in the composition of the present invention is typically preferably 41 parts by weight or more, more preferably 50 parts by weight or more, per 100 parts by weight of the total composition. Furthermore, it is preferably 90 parts by weight or less, more preferably 70 parts by weight or less, per 100 parts by weight of the total composition. Here, the amount of component (A) refers to the total amount when two or more types of component (A) are used. When component (A) is a combination of the above-mentioned (a1) and (a2), the amount of (a1) is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, per 100 parts by weight of the total composition. Furthermore, it is preferably 30 parts by weight or less, more preferably 20 parts by weight or less, per 100 parts by weight of the total composition. The amount of (a2) is preferably 30 parts by weight or more, more preferably 40 parts by weight or more, per 100 parts by weight of the total composition. Furthermore, it is preferably 70 parts by weight or less, more preferably 60 parts by weight or less, per 100 parts by weight of the total composition.

[0038] When the above (a1) and (a2) are used in combination as component (A), the blending ratio (mass ratio) of (a1) and (a2) is also affected by the amount of mercaptoalkyl groups in component (B) described below, but (a1):(a2) can be in the range of 10:90 to 90:10, preferably in the range of 10:90 to 50:50, and more preferably in the range of 15:85 to 45:55. When producing the composition, it is preferable to blend (a1) and (a2) in a ratio within the above range, but if (a2) is a mixture of multiple types of polyorganosiloxanes and contains a polyorganosiloxane having two or more aliphatic unsaturated groups as one component, the ratio taking into account its content may be within the above range.

[0039] [(B) Polyorganosiloxane Containing a Mercaptoalkyl Group] The UV-curable silicone gel composition of the present invention contains (B) a polyorganosiloxane containing a mercaptoalkyl group bonded to a silicon atom.

[0040] In component (B), the number of mercaptoalkyl groups bonded to silicon atoms in one molecule can be set to an average of 2 to 20, in order to ensure a stable structure through the crosslinking reaction while suppressing excessive cure shrinkage. Of these, a number greater than 2 and no greater than 10 is preferred, and a number between 3 and 7 is more preferred.

[0041] In (B), the alkyl portion of the mercaptoalkyl group bonded to the silicon atom can be a C1 to C6 alkyl group. Examples of mercaptoalkyl groups include mercaptomethyl, 2-mercaptoethyl, 3-mercaptopropyl, 4-mercaptobutyl, and 6-mercaptohexyl. From the standpoint of ease of synthesis, mercaptomethyl and 3-mercaptopropyl are preferred, and 3-mercaptopropyl is more preferred.

[0042] In (B), the organic group other than the mercaptoalkyl group bonded to the silicon atom can be a substituted or unsubstituted monovalent hydrocarbon group (provided that it is not an aliphatic unsaturated group). Specific examples include alkyl groups such as C1 to C6 alkyl groups (e.g., methyl, ethyl, propyl, etc.); cycloalkyl groups such as C3 to C10 cycloalkyl groups (e.g., cyclohexyl, etc.); aryl groups such as C6 to C12 aryl groups (e.g., phenyl, tolyl, xylyl, etc.); aralkyl groups such as C7 to C13 aralkyl groups (e.g., 2-phenylethyl, 2-phenylpropyl, etc.); and substituted hydrocarbon groups such as halogen-substituted hydrocarbon groups (e.g., chloromethyl, chlorophenyl, 3,3,3-trifluoropropyl, etc.). From the standpoint of ease of synthesis, etc., alkyl groups are preferred, with methyl, ethyl, and propyl being preferred, and methyl being more preferred. To adjust the refractive index, aryl groups can be used in combination, with phenyl being preferred from the standpoint of ease of synthesis, etc.

[0043] The main chain structure of (B) may be linear, branched, or cyclic, and preferably branched. For example, R"SiO ３／２ Unit, R'' ３ SiO １／２ Units and R'' ２ SiO ２／２units, and optionally further SiO ４／２ Examples of suitable branched polyorganosiloxanes include those consisting of units (wherein R" each independently represents an unsubstituted or substituted monovalent hydrocarbon group (but is not an aliphatic unsaturated group)) in which 2 to 20 R"s per molecule are mercaptoalkyl groups. Examples of mercaptoalkyl groups and unsubstituted or substituted monovalent hydrocarbon groups include the groups listed above. The mercaptoalkyl group R" may be present as R" in any unit, but is preferably R"SiO ３／２ The mercaptoalkyl group exists as an R" unit. The above-mentioned groups can be used as the mercaptoalkyl group and the unsubstituted or substituted monovalent hydrocarbon group. From the viewpoints of workability and crosslinking reactivity, the ratio of the number of siloxane units containing a mercaptoalkyl group to the number of siloxane units not containing a mercaptoalkyl group is preferably 1:60 to 1:8, and more preferably 1:50 to 1:10.

[0044] (B) preferably has a viscosity of 20 to 10,000 cP at 23° C. From the standpoint of workability and refractive index, the viscosity can be set to, for example, 30 to 8,000 cP.

[0045] The number of mercapto groups in (B) can be measured by colorimetric titration with iodine, which can be determined by the following formula: 2RSH + I ２ This method utilizes the reaction RSSR + 2HI, where a small amount of excess iodine causes the titrant to turn slightly yellow during titration.

[0046] (B) preferably has high transparency. An index of the transparency of (B) is a transmittance of 80% or more. To measure the transmittance of (B), (B) is filled into a container at 23°C, and the transmittance of a 10 mm thick sample in the visible light region (360 to 780 nm) is measured using a spectrometer. A transmittance of 90% or more is preferred in order to stably maintain the transparency of the cured product of the composition.

[0047] The method for preparing (B) is not particularly limited, and it can be produced, for example, by hydrolyzing, polycondensing, and re-equilibrating a mercaptoalkylalkoxysilane such as mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, mercaptopropylmethyldiethoxysilane, mercaptopropyldimethylmethoxysilane, or mercaptopropyldimethylethoxysilane with a desired alkylchlorosilane, alkylalkoxysilane, or silanol-containing siloxane.

[0048] (B) may be used alone or in combination of two or more. The amount of component (B) contained in the composition of the present invention can be appropriately set depending on the amount of unsaturated groups contained in (A) and the amount of mercaptoalkyl groups contained in (B), and is not particularly limited. However, it is usually preferably 0.1 parts by weight or more, more preferably 0.4 parts by weight or more, per 100 parts by weight of the total composition. Furthermore, it is preferably 3 parts by weight or less, more preferably 2 parts by weight or less, per 100 parts by weight of the total composition. Here, the amount of component (B) means the total amount when two or more types of component (B) are used.

[0049] Since the amount of (B) is affected by the amount of unsaturated groups in (A), (B) is preferably used in the composition in an amount such that the ratio (HS / Vi) of the number of mercaptoalkyl groups (HS) in (B) to the number of aliphatic unsaturated groups (Vi) in (A) is 0.01 to 10. From the viewpoints of curability and hardness of the cured product, the ratio is more preferably 0.01 to 5, even more preferably 0.03 to 1, and particularly preferably 0.05 to 0.5.

[0050] [(C) Photoinitiator] The ultraviolet-curable silicone gel composition of the present invention contains (C) a photoinitiator that initiates the reaction between (A) and (B). (C) becomes excited by exposure to light and imparts excitation energy to unsaturated bonds, such as (meth)acrylic groups, in the polyorganosiloxane (A), thereby initiating a curing reaction upon ultraviolet irradiation.

[0051] From the viewpoint of reactivity, component (C) may be an aromatic hydrocarbon, acetophenone and its derivatives, benzophenone and its derivatives, o-benzoylbenzoic acid ester, benzoin and benzoin ether and its derivatives, xanthone and its derivatives, disulfide compounds, quinone compounds, halogenated hydrocarbons and amines, or organic peroxides. From the viewpoints of compatibility with silicone and chemical stability, compounds containing a substituted or unsubstituted benzoyl group or organic peroxides are more preferred.

[0052] Examples of component (C) include acetophenone, propiophenone, 2-hydroxy-2-methylpropiophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE 651, manufactured by BASF), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (DAROCUR 1173, manufactured by BASF), 1-hydroxy-cyclohexyl-phenyl-ketone (IRGACURE 184, manufactured by BASF), 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (IRGACURE 2959, manufactured by BASF), 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one (IRGACURE 127: manufactured by BASF), 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (IRGACURE 907: manufactured by BASF), 2-benzyl-2-dimethylamino-(4-morpholinophenyl)-butanone-1 (IRGACURE 369: manufactured by BASF), 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone (IRGACURE 379: manufactured by BASF); 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (LUCIRIN TPO: manufactured by BASF), bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (IRGACURE 819: manufactured by BASF); 1,2-octanedione, 1-[4-(phenylthio)phenyl-, 2-(O-benzoyloxime)] (IRGACURE OXE 01: manufactured by BASF); ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime) (IRGACURE OXE 02: manufactured by BASF);Examples of such an oxyphenylacetic acid include a mixture of 2-[2-oxo-2-phenylacetoxyethoxy]ethyl ester and 2-(2-hydroxyethoxy)ethyl ester of oxyphenylacetic acid (IRGACURE 754, manufactured by BASF), phenylglyoxylic acid methyl ester (DAROCUR MBF, manufactured by BASF), ethyl 4-dimethylaminobenzoate (DAROCUR EDB, manufactured by BASF), 2-ethylhexyl 4-dimethylaminobenzoate (DAROCUR EHA, manufactured by BASF), bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide (CGI 403, manufactured by BASF), benzoyl peroxide, and cumene peroxide.

[0053] In terms of compatibility and photoreactivity, acetophenone, propiophenone, 2-hydroxy-2-methylpropiophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE 651, manufactured by BASF), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (DAROCUR 1173, manufactured by BASF), 1-hydroxy-cyclohexyl-phenyl-ketone (IRGACURE 184, manufactured by BASF), 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (IRGACURE 907, manufactured by BASF), 2-benzyl-2-dimethylamino-(4-morpholinophenyl)butanone-1 (IRGACURE 369, manufactured by BASF), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (LUCIRIN TPO (manufactured by BASF), and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (IRGACURE 819 (manufactured by BASF)) are preferred.

[0054] Component (C) may be used alone or in combination of two or more. The amount of component (C) contained in the composition of the present invention is not particularly limited as long as it is an amount that can sufficiently promote the curing reaction, but from the perspective of curability and optical properties after curing, it is preferably 0.1 parts by weight or more, more preferably 0.4 parts by weight or more, per 100 parts by weight of the total composition. Furthermore, it is preferably 3 parts by weight or less, more preferably 2 parts by weight or less, per 100 parts by weight of the total composition. Here, the amount of component (C) means the total amount when two or more types of component (C) are used.

[0055] [(D) Hindered Amine Stabilizer] The UV-curable silicone gel composition of the present invention contains a hindered amine stabilizer as component (D). The use of a hindered amine stabilizer in the present invention makes it possible to achieve excellent long-term reliability of the UV-curable silicone gel composition, and by using the hindered amine stabilizer in combination with component (E), which will be described later, the effect of component (D) on the particle surfaces of component (E) is controlled to control the dispersion state of the particles, thereby improving the complex modulus G * This is based on the discovery that the effect of improving the damping characteristics is achieved.

[0056] Examples of the hindered amine antioxidant include N,N',N",N'"-tetrakis-(4,6-bis(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine, a polycondensate of dibutylamine / 1,3,5-triazine / N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine / N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine, poly[{6-(1,1,3,3-tetramethyl- tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}, polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, [decanedioic acid bis(2,2,6,6-tetramethyl-1(octyloxy)-4-piperidyl)ester, reaction products of 1,1-dimethylethyl hydroperoxide and octane (70%)]-polypropylene (30 %), bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, 1-[2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-tert- butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione, etc., but are not limited to these. In terms of obtaining a more transparent composition, it is particularly preferable to use bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate (Tinuvin 123).

[0057] Component (D) may be used alone or in combination of two or more. The amount of component (D) contained in the composition of the present invention is not particularly limited as long as it is an amount that can sufficiently proceed with the curing reaction, but it is preferably 0.1 parts by weight or more, more preferably 0.4 parts by weight or more, per 100 parts by weight of the total composition. Furthermore, it is preferably 3 parts by weight or less, more preferably 2 parts by weight or less, per 100 parts by weight of the total composition. Here, the amount of component (D) means the total amount when two or more types of component (D) are used.

[0058] [(E) Fine particles containing silicon-oxygen bonds] The composition of the present invention contains fine particles containing silicon-oxygen bonds (hereinafter, sometimes simply referred to as "silicon fine particles") as a filler for controlling the fluidity of the composition and improving the damping properties. Examples of the fine particles containing silicon-oxygen bonds include silica (silicon dioxide: SiO ２ ), silicone (a silicon compound composed of —O—Si—O— bonds), etc. can be used as component (E). The fine particles containing silicon-oxygen bonds may be prepared in the form of fine particles having the average particle size described below, and may be fine particles of various shapes such as spherical, blocky, plate-like, or pulverized, with spherical or pulverized shapes being preferred. Examples of fine particles containing silicon-oxygen bonds include spherical silicone resin, calcined silica, silica aerogel, precipitated silica, and pulverized silica. Of these, pulverized silica or spherical silicone resin fine particles are preferred from the viewpoint of the effect of improving the complex modulus of the cured product, and spherical silicone resin fine particles are more preferred from the viewpoint of placing greater importance on the damping properties upon curing.

[0059] The average particle size of the silicon microparticles ranges from 1 μm to 30 μm, with the lower limit being preferably 1.2 μm, more preferably 1.5 μm, even more preferably 2 μm, and particularly preferably 4 μm. The upper limit is preferably 25 μm, more preferably 15 μm, even more preferably 10 μm, and particularly preferably 6 μm. The average particle size here can be determined by measuring D50, particularly by laser dynamic light scattering using a Malvern Zetasizer, photon correlation spectroscopy in accordance with ISO 13320-1, or a method known as quasi-elastic light scattering. This method is particularly useful for measuring the uncured composition, but in some cases, determining the average particle size D50 using a transmission electron microscope (TEM) is also sufficient. By using silicon microparticles having a particle size within the above range, the viscosity of the composition can be appropriately controlled while improving the damping properties.

[0060] Silicon microparticles can be produced by methods known to those skilled in the art. Breakdown-type production methods for reducing particle size include solid-phase methods such as ball mills and bead mills, and build-up-type production methods for obtaining particles from the molecular level using chemical reactions, such as CVD and sol-gel methods, or liquid-phase production methods. These methods can be selected appropriately depending on the shape of the particles. Commercially available silicon microparticles may be used as is, or those treated with a known surface treatment agent may be used. In this specification, surface treatment refers to the use of a compound reactive with functional groups, such as silanol groups, present on the particle surface to covalently bond the functional groups to other groups. Surface treatment methods include silazane compounds (hexamethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, 1,3-bis(chloromethyl)tetramethyldisilazane, 1,3-bis(3,3,3-trifluoropropyl)-1,1,3,3-tetramethyldisilazane, 1,3-diphenyltetramethyldisilazane, heptamethyldisilazane, 2,2,4,4,6,6-hexamethylcyclotrisilazane, octamethylcyclotetrasilazane, 1,1,3,3-tetramethyldisilazane, 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane, etc.), alkoxysilane compounds (methyltrimethyi Examples of suitable hydrophobic treatments include those with silazane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, hexadecyltrimethoxysilane, etc.), chlorosilane compounds (methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, etc.), octamethylcyclotetrasiloxane, dimethylsiloxane oligomers, etc. Among these, chemical treatments with silazane compounds or chlorosilane compounds are preferred because they can hydrophobize the silica surface with a small amount of treatment. Hexamethyldisilazane and dimethyldichlorosilane are particularly preferred.Hexamethyldisilazane is preferred from the viewpoints of the degree of treatment and the stability (inactivation) of the surface state after treatment. These surface treatment agents may be blended with silica and kneaded together during preparation of the curable composition to perform the surface treatment of the particles.

[0061] Component (E) may be used alone or in combination of two or more. The amount of component (E) contained in the composition of the present invention is not particularly limited as long as it is an amount that can impart a certain level of viscoelasticity to the composition, but is preferably 0.1 parts by weight or more, more preferably 0.4 parts by weight or more, and even more preferably 10 parts by weight or more, relative to 100 parts by weight of the total composition. Furthermore, the amount is preferably 40 parts by weight or less, more preferably 35 parts by weight or less, relative to 100 parts by weight of the total composition. Within this range, a composition excellent in both strength and long-term reliability can be obtained. However, from the viewpoint of placing greater importance on the long-term reliability of the composition, the amount of component (E) is preferably suppressed, preferably 25 parts by weight or less. From the viewpoint of placing greater importance on the strength of the composition against deformation, a larger amount of component (E) is preferred, preferably 25 parts by weight or more. Here, when two or more types of component (E) are used, the amount of component (E) refers to the total amount thereof.

[0062] [UV-Curable Silicone Gel Composition] The UV-curable silicone gel composition of the present invention contains the above-mentioned components (A) to (E). The properties of the polyorganosiloxane composition of the present invention are not particularly limited, as long as the components are uniformly mixed and the composition has a fluidity sufficient to allow application to a substrate. The silicone gel composition of the present invention has high stability, and therefore can maintain high levels of hardness-related properties, including elastic modulus, for a long period of time after curing. The UV-curable silicone gel composition can be a one-component composition in which all components are mixed, or a two-component composition in which components (B) and (C) are separately blended. The choice of whether to use a one-component or two-component composition can be made appropriately taking into account workability, curing conditions, etc., and the method is well known to those skilled in the art.

[0063] The UV-curable silicone gel composition of the present invention can contain other known components as long as they do not impair its purpose and effects. Additives such as silane coupling agents, reaction inhibitors, and inorganic fillers may be included. Siloxane resins other than those falling under the category of components (A) and (B) can also be added. Examples of such resins include polyorganosiloxanes that do not have curable functional groups, such as dimethylsiloxane. These resins can be used as diluents.

[0064] Examples of the silane coupling agent include 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, trimethoxysilylpropyldiallyl isocyanurate, bis(trimethoxysilylpropyl)allyl isocyanurate, tris(trimethoxysilylpropyl)isocyanurate, triethoxysilylpropyldiallyl isocyanurate, bis(triethoxysilylpropyl)allyl isocyanurate, and tris(triethoxysilylpropyl)isocyanurate, and preferably 3-methacryloxypropyltriethoxysilane and 3-methacryloxypropyltrimethoxysilane.

[0065] Examples of the reaction inhibitor include hydroquinone, p-methoxyphenol, p-t-butylcatechol, and phenothiazine.

[0066] Examples of inorganic fillers include reinforcing fillers such as fumed titanium oxide; oxides such as fumed silica, diatomaceous earth, iron oxide, zinc oxide, titanium oxide, and aluminum oxide; carbonates such as calcium carbonate, magnesium carbonate, and zinc carbonate; silicates such as aluminosilicate, calcium silicate, and mica; talc; conductive fillers such as carbon black, copper powder, and nickel powder; and fillers whose surfaces have been treated with a hydrophobizing agent. Among these, the inorganic filler is preferably fumed silica, carbon black, or calcium carbonate, and more preferably fumed silica. A preferred embodiment of the present invention is an ultraviolet-curable silicone gel composition further comprising fumed silica as component (F). Fumed silica is silica with a particle diameter of approximately 10 nm and does not fall under the above-mentioned category (E). Fumed silica has the effect of increasing viscosity and can be used within a range that does not impair workability when preparing the composition of the present invention.

[0067] Component (F) is a cellulose ester having a BET specific surface area of ​​50 m ２ / g or more is preferred, and 50 to 300m ２ / g is more preferred.

[0068] When fumed silica is used as the inorganic filler, it is particularly preferable that the fumed silica is surface-treated. By using surface-treated silica, the fluidity of the composition can be suppressed and the cured product of the composition can be given mechanical strength. The surface treatment method can be the same as that for silicon fine particles.

[0069] The amount of inorganic filler is preferably 1 part by weight or more, more preferably 3 parts by weight or more, per 100 parts by weight of the total composition, and is preferably 10 parts by weight or less, more preferably 7 parts by weight or less, per 100 parts by weight of the total composition.

[0070] The curable polyorganosiloxane composition may further contain a siloxane resin that does not fall under the category of component (A) or (B). Such a resin can also be used as a diluent for adjusting viscosity. Such a siloxane resin includes a resin obtained by combining the M, D, T, and Q units and that does not have a curable functional group, particularly a resin represented by the following formula: ３ Si—O—(SiR ２ O) ｎ -SiR ３ (Wherein R is C １－６ Alkyl group or C ６－１２ (where n is an aryl group, and n is a number that provides a viscosity of 100 to 100,000 cP at 23° C.) siloxanes that do not have a curable functional group can be used. By using such siloxane resins, it is possible to control the hardness of the curable polyorganosiloxane composition when cured, and to control the viscosity of the composition, thereby enabling a wide range of handling and required physical properties to be achieved.

[0071] From the viewpoint of workability, the viscosity of the composition at 23° C. is preferably 100 to 50,000 cP, more preferably 100 to 20,000 cP, and even more preferably 500 to 13,000 cP.

[0072] The composition can be obtained by blending (A) to (E) and optional components. Because components (A) to (E) have excellent compatibility, simply mixing all of them together makes it easy to homogenize the composition and obtain a transparent cured product. While optional components can be added as needed, particularly when using an inorganic filler such as component (F) fumed silica, it is preferable to mix component (A) and the inorganic filler in a dispersed state before mixing with the other components.

[0073] The composition can be cured by irradiating it with ultraviolet light. The irradiation intensity of the ultraviolet light is 10 to 10,000 mW / cm. ２ is preferred, and more preferably 30 to 6,000 mW / cm ２ and more preferably 50 to 4,000 mW / cm ２The irradiation time of ultraviolet light depends on the intensity of the ultraviolet light, but is preferably 10 to 100 seconds, more preferably 15 to 80 seconds, and even more preferably 20 to 70 seconds. ２ It is preferable that the composition is prepared so that it will be completely cured by irradiation with ultraviolet light for 30 seconds at an intensity of 1000 nm. Note that the "cured" state here means a state in which the properties remain constant even when ultraviolet light is continued. The irradiation amount is a measured value of UVA, which refers to ultraviolet light in the range of 315 to 400 nm.

[0074] The composition exhibits good curability when irradiated with ultraviolet light having a wavelength of, for example, 250 to 450 nm. Examples of light sources that emit ultraviolet light of such wavelengths include a high-pressure mercury lamp (UV-7000) and a metal halide lamp (UVL-4001M3-N1) manufactured by Ushio Inc., a metal halide lamp (JM-MTL 2KW) manufactured by JM Tech Co., Ltd. in Korea, an ultraviolet irradiation lamp (OSBL360) manufactured by Mitsubishi Electric Corporation, an ultraviolet irradiator (UD-20-2) manufactured by Japan Storage Battery Co., Ltd., and a fluorescent lamp (FL-20BLB) manufactured by Toshiba Corporation, as well as H bulbs, H plus bulbs, V bulbs, D bulbs, Q bulbs, and M bulbs manufactured by Heraeus.

[0075] The composition of the present invention has a high complex modulus G ＊ Since the damping material has the above properties, it can be used as a damping material for devices such as image display devices. The damping material can be placed at a desired position, for example, between the image display unit and the protective unit, and cured by irradiating it with ultraviolet light to seal the image display unit and the protective unit. ＊ The larger the value of G, the better the properties as a damping material. In the composition of the present invention, it is preferable that the initial state and the state after the accelerated test under the conditions described below have a value of 3,000 Pa or more, and more preferably a value of 4,000 Pa or more. ＊ The value of G before the accelerated test ＊ It is preferable that the difference is within ±35% when G is taken as 100%. ＊ The measurement method is to use a rheometer and measure the G at a frequency of 10 Hz. ＊This is a method for recording data.

[0076] The composition of the present invention has high stability. The stability can be evaluated by measuring the complex modulus G ＊ In addition, this can be measured by the change in the loss tangent (tan δ). The loss tangent is a measure of the contribution of elasticity and viscosity in a viscoelastic substance such as the composition of the present invention; a smaller value indicates stronger elastic properties, and a larger value indicates stronger viscous properties. A large change in the loss tangent (Δtan δ) indicates a change in the viscoelastic properties of the composition. Therefore, a small Δtan δ value is preferred, and it is preferable that the change before and after an accelerated test under the conditions described below is 0.5 or less. The method for measuring tan δ is to use a rheometer and record data on tan δ at a frequency of 10 Hz.

[0077] The composition of the present invention has long-term stability as a damping material and can be suitably used for components that are susceptible to environmental damage such as moisture, temperature, and ultraviolet rays. Therefore, the composition of the present invention has a complex modulus of elasticity G, which is an evaluation standard for a damping material. ＊ It is preferable that the change in the complex modulus G and tan δ can be suppressed even when exposed to high temperature and high humidity for a long period of time. ＊ It is preferable that the tan δ and tan δ remain at the above values ​​or variations.

[0078] The composition of the present invention can be suitably used in the manufacture of image display devices that are expected to be used outdoors and require good UVA resistance, and is particularly suitable as a resin to be interposed between a protective part and an image display part as a damping material in a camera.

[0079] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0080] The materials used in the examples and comparative examples are as follows.<(A) Polyorganosiloxane Containing an Aliphatic Unsaturated Group> (a1) α,ω-divinylpolyphenylmethylsiloxane (phenyl 5 mol %) having a viscosity of 20,000 cP at 23°C (a2) Linear fragment vinylpolyphenylmethylsiloxane (phenyl 5 mol %) having a viscosity of 2,500 cP at 23°C <(B) Polyorganosiloxane Containing a Mercaptoalkyl Group> A mercaptoalkyl group-containing polyorganosiloxane having a viscosity of 200 cP at 23°C <(C) Photoinitiator> (1) 2-hydroxy-2-methyl-1-phenylpropan-1-one (DAROCUR 1173: manufactured by BASF) (2) 1-hydroxycyclohexylphenylketone (IRGACURE 184: manufactured by BASF) <(D) Hindered Amine Stabilizer> Bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate (Tinuvin 123) <(E) Microparticles containing silicon-oxygen bonds> (1) Spherical silicone resin microparticles (particle size 2 μm / Tospearl (registered trademark) 120 manufactured by Momentive Performance Materials) (2) Spherical silicone resin microparticles (particle size 2 μm / Tospearl (registered trademark) 120FL manufactured by Momentive Performance Materials) (3) Spherical silicone resin microparticles (particle size 4.5 μm / Tospearl (registered trademark) 145 manufactured by Momentive Performance Materials) (4) Spherical silicone resin microparticles (particle size 6 μm / Tospearl (registered trademark) 3000A manufactured by Momentive Performance Materials) (5) Spherical silicone resin microparticles (particle size 10 μm / Tospearl (registered trademark) 1100 manufactured by Momentive Performance Materials) (6) Spherical silica (particle size 0.3 μm / SO-C1 manufactured by Admatechs) (7) Spherical silica (particle size 1.2 μm / SO-C4 manufactured by Admatechs) (8) Spherical silica (particle size 1.9 μm / SO-C6 manufactured by Admatechs) (9) Crushed silica (particle size 1.4 μm / Crystalite (registered trademark) 5X) (10) Crushed silica (particle size 4 μm / Crystalite (registered trademark) VX-S) Furthermore, fumed silica (primary particle size 7 nm / Reolosil (registered trademark) HM-30S) was used as a further additive, and p-t-butylcatechol was used as a reaction inhibitor.

[0081] Examples 1 to 13, Comparative Examples 1 to 13 <Preparation of UV-Curable Silicone Gel Compositions> In order to prevent radical generation from the initiator due to UV rays, component (C) was handled in a yellow room. Components (A) to (E), fumed silica, and a reaction inhibitor were kneaded in a planetary mixer using a prescribed method in the blending amounts (parts by mass) shown in Tables 1 and 2 below, to obtain UV-curable silicone gel compositions. However, component (E) was not added in Comparative Examples 1 and 2, and component (D) was not added in Comparative Examples other than Comparative Examples 1 and 3. Each UV-curable silicone gel composition was prepared using an integrated light dose of 3,000 mJ / cm. ２ (100 mW / cm ２ Both surfaces of the gel sheet were irradiated with ultraviolet light at 1000 kJ / min for 30 seconds to cure the gel sheet, thereby obtaining a cured product.

[0082] <Complex viscoelasticity G ＊ Measurement of G of a 2 mm thick gel sheet at 25°C and 10 Hz * was measured using a rheometer. ＊ After measuring the value of the cured product of each UV-curable silicone gel composition, an accelerated test was carried out by leaving the cured product of each UV-curable silicone gel composition at 85°C and a relative humidity of 85% for 125 hours. ＊ After the accelerated test, G ＊ The test specimens were evaluated as "good" when they satisfied at least one of the following conditions: the value of the elastic modulus was 4,000 Pa or more; and the rate of change before and after the accelerated test was within ±35%. The test specimens were evaluated as "particularly excellent" when they satisfied both conditions. The results are shown in Tables 1 and 2.

[0083] <Measurement of tan δ> The tan δ of a 2 mm thick gel sheet was measured at 25°C and 10 Hz using a rheometer. After measuring tan δ in the initial state, an accelerated test was performed by leaving each cured product of UV-curable silicone gel composition at 85°C and 85% relative humidity for 125 hours. After leaving it at rest, tan δ was measured again. When the difference in tan δ before and after the accelerated test was within ±0.50, it was determined that there was no significant change in the viscoelastic properties of the UV-curable silicone gel composition. The results are shown in Tables 1 and 2.

[0084]

[0085]

[0086] From Tables 1 and 2, it can be seen that the complex modulus G of the composition can be increased by adding fine particles containing silicon-oxygen bonds having a predetermined particle size. ＊ The ultraviolet-curable silicone gel compositions of the examples have a high complex modulus of elasticity G ＊ It has excellent overall resistance to deformation. By adding a large amount of silicon fine particles, ＊ increases (Examples 1, 5, and 8). On the other hand, as the amount of silicon microparticles increases, the numerical decrease over time appears to increase, but in all Examples, the decrease rate is smaller than in Comparative Examples using the same silicon microparticles, and the numerical value remains high enough to fully demonstrate the performance of a material such as a damping material. On the other hand, if the particle size of the silicon microparticles is too small, the fluidity of the composition is impaired (Comparative Examples 3 and 4), resulting in problems with handling as a damping material. Furthermore, the addition of a hindered amine stabilizer is shown to reduce the amount of change in tan δ, particularly over time. Even under accelerated test conditions, the amount of change in tan δ is small, which means that the properties as a viscous or elastic body do not change significantly. Therefore, the UV-curable silicone gel compositions of the Examples can maintain long-term reliability against physical forces, vibrations, and the like.

[0087] The present invention provides an ultraviolet-curable silicone gel composition that produces a cured product with excellent long-term reliability. The composition maintains high levels of hardness properties, such as elastic modulus, for extended periods of time, making it suitable for use on components susceptible to environmental damage, such as moisture, temperature, and ultraviolet light. For example, the composition is suitable as a damping material for sealing between a protective section and an image display section in the manufacture of image display devices that are intended for outdoor use and require good UVA resistance.

Claims

1. An ultraviolet-curable silicone gel composition comprising: (A) a polyorganosiloxane containing an aliphatic unsaturated group; (B) a polyorganosiloxane containing a mercaptoalkyl group bonded to a silicon atom; (C) a photoinitiator that starts the reaction between (A) and (B); (D) a hindered amine stabilizer; and (E) fine particles containing silicon-oxygen bonds and having an average particle size of 1 to 30 μm.

2. The ultraviolet-curable silicone gel composition according to claim 1, wherein (A) is a polyorganosiloxane in which, of the groups other than aliphatic unsaturated groups that are directly bonded to silicon, 1 to 10 mol % are C6 to C12 aryl groups.

3. The ultraviolet-curable silicone gel composition according to claim 1, wherein (A) comprises (a1) a linear polyorganosiloxane having at least two aliphatic unsaturated groups in the molecule and (a2) a linear polyorganosiloxane having on average one aliphatic unsaturated group in the molecule.

4. The (a1) is represented by the following formula (I): (In the formula, each R １ are independently an aliphatic unsaturated group, each R is independently a C1 to C6 alkyl group or a C6 to C12 aryl group, and n is a number that provides a viscosity of 100 to 100,000 cP at 23° C. The ultraviolet-curable silicone gel composition according to claim 3, comprising a linear polyorganosiloxane containing an aliphatic unsaturated group, 5. The ultraviolet-curable silicone gel composition according to claim 1, wherein the ratio of the number of mercaptoalkyl groups in (B) to the number of aliphatic unsaturated groups in (A) is 0.01 to 10.

6. The ultraviolet-curable silicone gel composition according to claim 1, wherein (E) is spherical or pulverized fine particles.

7. The ultraviolet-curable silicone gel composition according to claim 1, wherein (E) is fine particles derived from silicone or silicon dioxide.

8. The ultraviolet-curable silicone gel composition according to claim 1, wherein the amount of (E) is 0.1 to 40 parts by weight per 100 parts by weight of the entire composition.

9. The ultraviolet-curable silicone gel composition according to claim 1, further comprising (F) fumed silica.

10. The ultraviolet-curable silicone gel composition according to claim 9, wherein, per 100 parts by weight of the total of (A) through (F), the amount of (A) is 41 to 90 parts by weight, the amount of (B) is 0.1 to 3 parts by weight, the amount of (C) is 0.1 to 3 parts by weight, the amount of (D) is 0.1 to 3 parts by weight, the amount of (E) is 0.1 to 40 parts by weight, and the amount of (F) is 1 to 10 parts by weight.

11. 100mW / cm of ultraviolet light with a wavelength of 315-400nm ２ The complex elastic modulus G when cured by irradiation for 30 seconds at an intensity of ＊ 2. The ultraviolet-curable silicone gel composition according to claim 1, wherein the value of is 4000 Pa or more.

12. A damping material comprising the ultraviolet-curable silicone gel composition according to any one of claims 1 to 11.