Ultraviolet-curable silicone gel composition

Abstract

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 photoreaction initiator that initiates a reaction between (A) and (B); (D) a hindered amine stabilizer; and (E) fine particles having an average particle diameter of 1-30 [mu] m and containing silicon-oxygen bonds. With this composition, a cured product having excellent damping characteristics and excellent long-term stability is provided.

Description

Technical Field

[0001] This invention relates to a silicone gel composition that exhibits excellent long-term reliability and is cured by ultraviolet irradiation. Background Technology

[0002] The silicone gel composition contains at least a polyorganosiloxane and a crosslinking agent. The polyorganosiloxane is crosslinked using the crosslinking agent, thereby forming a silicone gel as a crosslinked body. Due to the high chemical stability and heat resistance of the silica backbone, silicone, like carbon compounds, can be widely molecularly designed through changes in the degree of polymerization and substituent design. Therefore, it is used as a resin in various forms, possessing both flexibility and strength upon curing (Patent Document 1). One application of the silicone gel composition is as follows: compositions containing fillers and light stabilizers in addition to the polyorganosiloxane and crosslinking agent are used as vibration damping materials for vibration transmission parts in optical devices such as cameras.

[0003] When applied to products such as optical devices, from the viewpoint of being able to cure quickly and suppressing the dimensional stability caused by curing shrinkage, UV-curable resin compositions are used as silicone gels. As UV-curable silicone resin compositions, UV-curable silicone resin compositions containing polyorganosiloxanes with mercaptoalkyl groups and polyorganosiloxanes with aliphatic unsaturated groups have been proposed (Patent Documents 2 and 3).

[0004] For example, to homogenize the composition and prevent the formation of unstable sites, silicone resin compositions containing acetophenone and / or phenylacetone as compatibilizers have been proposed (Patent Document 4). On the other hand, olefin-thiol type UV-curable silicone resins such as those in Patent Documents 2-4 suffer from yellowing, fogging, and softening of the cured product due to UV exposure. Therefore, the selection of various additives, such as antioxidants, to suppress these problems and improve storage stability has been studied (Patent Documents 5-8).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2022 / 019229

[0008] Patent Document 2: Japanese Patent Application Publication No. 2-245060

[0009] Patent Document 3: Japanese Patent Application Publication No. 3-064389

[0010] Patent Document 4: Japanese Patent Application Publication No. 2013-253179

[0011] Patent Document 5: Japanese Patent Application Publication No. 2016-60782

[0012] Patent Document 6: Japanese Patent Application Publication No. 2016-145297

[0013] Patent Document 7: Japanese Patent Application Publication No. 2020-172581

[0014] Patent Document 8: Japanese Patent Application Publication No. 2023-82381 Summary of the Invention

[0015] The problem that the invention aims to solve

[0016] Adding inorganic fillers (fillers) is useful to ensure damping properties. However, in the case of polyorganosiloxane compositions containing inorganic fillers, changes in properties can be observed after curing due to the type and amount of filler, making it difficult to balance damping properties and long-term reliability.

[0017] The present invention addresses this problem by providing a UV-curable silicone gel composition that yields a cured product with excellent damping properties and excellent long-term reliability.

[0018] Methods for solving problems

[0019] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that, in the case of using certain silicon microparticles and specific hindered amine compounds in the UV-curable silicone gel composition, it is possible to achieve both high damping characteristics and long-term reliability, thus completing the present invention.

[0020] That is, the present invention relates to the following methods.

[0021] [1] A UV-curable silicone gel composition comprising:

[0022] (A) Polyorganosiloxanes containing aliphatic unsaturated groups;

[0023] (B) Polyorganosiloxanes containing mercaptoalkyl groups bonded to silicon atoms;

[0024] (C) A photoinitiator that triggers the reactions in (A) and (B) above;

[0025] (D) Hindered amine stabilizers; and

[0026] (E) Particles with an average particle size of 1–15 μm and containing silicon-oxygen bonds.

[0027] [2] According to the ultraviolet curable organosilicon gel composition of [1] above, wherein the above (A) is a polyorganosiloxane in which 1 to 10 mol% of the groups directly bonded to silicon, excluding aliphatic unsaturated groups, are C6 to C12 aryl groups.

[0028] [3] According to the ultraviolet curable organosilicon gel composition of [1] or [2] above, wherein (A) above comprises (a1) a linear polyorganosiloxane having at least two aliphatic unsaturated groups in the molecule and (a2) a linear polyorganosiloxane having an average of one aliphatic unsaturated group in the molecule.

[0029] [4] According to the ultraviolet-curable silicone gel composition of [3] above, wherein the above (a1) comprises a linear polyorganosiloxane containing aliphatic unsaturated groups as shown in formula (I) below.

[0030] [Chemical Formula 1]

[0031]

[0032] (In the formula,

[0033] Each R 1 It is an independent aliphatic unsaturated group.

[0034] Each R is independently a C1–C6 alkyl or C6–C12 aryl.

[0035] n is a number that makes the viscosity at 23°C between 100 and 100,000 cP.

[0036] [5] The UV-curable silicone gel composition according to any one 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) above is 0.01 to 10.

[0037] [6] The UV-curable silicone gel composition according to any one of [1] to [5] above, wherein (E) is spherical or pulverized microparticles.

[0038] [7] The UV-curable silicone gel composition according to any one of [1] to [6] above, wherein (E) is a microparticle derived from silicone or silica.

[0039] [8] The UV-curable silicone gel composition according to any one of [1] to [7] above, wherein the amount of (E) above is 0.1 to 40 parts by weight relative to a total of 100 parts by weight of the composition.

[0040] [9] The UV-curable silicone gel composition according to any one of [1] to [8] above further comprises (F) fumed silica.

[0041]

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

[0042]

[11] The UV-curable silicone gel composition according to any one of [1] to

[10] above, wherein, at 100 mW / cm 2 When cured by irradiating it with ultraviolet light with a wavelength of 315-400 nm for 30 seconds, the complex elastic modulus G* is above 4000 Pa.

[0043]

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

[11] above.

[0044] Invention Effects

[0045] According to the present invention, a UV-curable silicone gel composition is provided to obtain a cured product with excellent damping properties and excellent long-term reliability. Detailed Implementation

[0046] In this invention, the term "alkyl" refers to a straight-chain or branched monovalent saturated hydrocarbon group. Examples of alkyl groups, without limitation, include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, etc. Furthermore, when indicating the range of carbon atoms of a substituent, it is, for example, referred to as "C". 1-6 "alkyl", etc., in which case the range of carbon atoms is 1 to 6.

[0047] In this invention, the term "alkenyl" refers to a straight-chain or branched monovalent hydrocarbon group having at least one C=C double bond. Examples of alkenyl groups, without limitation, include ethynyl (vinyl), propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, etc.

[0048] In this invention, the term "aryl" refers to a monovalent cyclic aromatic hydrocarbon group comprising a monocyclic, bicyclic, or tricyclic aromatic ring. Examples of aryl groups include, but not limited to, phenyl, tolyl, xylyl, naphthyl, phenanthrene, fluorenyl, indyl, cyclopentadienyl, azulel, oxydiphenyl, biphenyl, methylenediphenyl, aminodiphenyl, diphenylthio, diphenylsulfonyl, diphenylisopropylidene, benzodioxane, benzofuranyl, benzodioxazinyl, benzoxazinoneyl, benzopiperazinyl, benzopyrroleyl, benzomorpholinyl, methylenedioxyphenyl, ethyldioxyphenyl, etc. (including derivatives of these moieties that are hydrogenated and have aromaticity).

[0049] [(A) Polyorganosiloxanes containing aliphatic unsaturated groups]

[0050] The UV-curable silicone gel composition of the present invention comprises at least one polyorganosiloxane containing aliphatic unsaturated groups as component (A). Component (A) is the component that functions as the base polymer of the UV-curable silicone gel composition.

[0051] The aliphatic unsaturated groups in component (A) are functional groups capable of photocuring; there are no particular restrictions as long as they have carbon-carbon double bonds and are capable of addition reactions. Specific examples include aliphatic unsaturated groups such as (meth)acryloyl or alkenyl groups. The alkenyl group preferably has 2 to 20 carbon atoms, more preferably 2 to 8, and even more preferably 2 to 6. The alkenyl group can have a branched structure or a ring structure. The position of the carbon-carbon double bond in the hydrocarbon constituting the alkenyl group can be arbitrary. From a reactivity perspective, it is preferable that the carbon-carbon double bond is located at the end of the group. As a preferred example of an alkenyl group, considering its ease of synthesis into polyorganosiloxanes, vinyl groups can be cited. The aliphatic unsaturated groups can exist at any position in the polyorganosiloxane molecule. For example, they can be present at the molecule's end or as side chains at other locations. In the case of linear polyorganosiloxanes, the aliphatic unsaturated groups are preferably present at least one at each end of the main molecular chain of component (A). Additionally, in this specification, the molecular backbone of component (A) refers to the longest bonded chain in the molecule of component (A).

[0052] As long as the siloxane bond is the main backbone, there are no particular restrictions on the molecular backbone of component (A). A linear, branched, cyclic, or three-dimensional mesh-like backbone can be used arbitrarily. Furthermore, the siloxane backbone can be interrupted by divalent organic groups. Herein, when describing the structure of siloxane compounds in this specification, the structural units of siloxane compounds are sometimes referred to by the following abbreviations. These structural units will sometimes be referred to as "M unit," "D unit," etc.

[0053] M: Si(CH3)3O 1 / 2

[0054] D: Si(CH3)2O 2 / 2

[0055] T: Si(CH3)O 3 / 2

[0056] Q: SiO 4 / 2

[0057] In this specification, siloxane compounds are compounds constructed by combining the above-described structural units, but may also be compounds in which at least partially the methyl group of the above structural units is replaced by other groups such as halogens like fluorine or hydrocarbon groups like phenyl. In this case, to indicate a state of substituent substitution, the phenyl-substituted D unit is sometimes described as D... Ph Additionally, for example, in the record as D Ph 20 D 20 In this context, the statement refers to the presence of a total of 20 phenyl groups within 40 D units, not to a continuous presence of 20 D groups. Ph Following the first unit are 20 consecutive D units, which can be understood as meaning that each unit can be arranged arbitrarily and can contain SiPh2O. 2 / 2 (represented as D) Ph2 The structural unit is as shown in the figure. Siloxane compounds can take on various three-dimensional structures based on T units or Q units, and component (A) can take on a linear molecular skeleton formed by arbitrarily combining the above M and D units.

[0058] To allow the composition to cure, the polyorganosiloxane of (A) preferably comprises a polyorganosiloxane having two or more aliphatic unsaturated groups as (a1). There are no particular limitations on such a polyorganosiloxane, as long as it has an average of two or more alkenyl groups bonded to silicon atoms in one molecule and can form a cross-linked structure through an addition reaction with the component (B) described later. For example, such a polyorganosiloxane has at least two (R) groups in its molecule. 1 ) m (R) 2 ) n SiO （4-m-n） / 2(where R) 1 R is an unsubstituted or substituted monovalent hydrocarbon group that does not have an aliphatic unsaturated bond; 2 The alkenyl group is represented by the following: m is an integer from 0 to 2; n is an integer from 1 to 3, where m + n is an integer from 1 to 3.

[0059] As one specific example of (a1) above, a linear polyorganosiloxane containing aliphatic unsaturated groups as shown in formula (I) is included.

[0060] [Chemical Formula 2]

[0061]

[0062] (In the formula,

[0063] Each R 1 It is an independent aliphatic unsaturated group.

[0064] Each R is independently a C1-C6 alkyl or C6-C12 aryl group, wherein 0-40 mol% of R is a C6-C12 aryl group.

[0065] n is a number that makes the viscosity at 23°C between 100 and 300,000 cP.

[0066] In the above formula (I), R 1 It is an aliphatic unsaturated group. The R at both ends... 1 They can be the same or different, but the same is preferred.

[0067] Examples of aliphatic unsaturated groups include alkenyl groups, such as C2-C6 alkenyl groups (e.g., vinyl, propenyl, butenyl, hexenyl, etc.). More preferably, terminally unsaturated alkenyl groups are preferred, and vinyl groups are preferred from the perspective of ease of synthesis.

[0068] 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 can be the same or different.

[0069] When R contains groups other than C1 to C6 alkyl groups, from the perspective of adjusting the refractive index, it is preferable that 1 to 40 mol% of R is C6 to C12 aryl. From the perspective of viscosity and thixotropy, it is more preferable that 1 to 20 mol% of R is C6 to C12 aryl, even more preferable that 1 to 10 mol% is C6 to C12 aryl, and particularly preferable that 3 to 7 mol% is C6 to C12 aryl.

[0070] From the perspective of ease of synthesis, methyl is preferred as a C1-C6 alkyl group, and phenyl is preferred as a C6-C12 aryl group.

[0071] In formula (I), preferably 1 to 40 mol% of R is phenyl and the remainder is methyl, more preferably 1 to 20 mol% of R is phenyl and the remainder is methyl, and particularly preferably 1 to 10 mol% of R is phenyl and the remainder is methyl.

[0072] (A) The polyorganosiloxane may comprise (a2) a polyorganosiloxane having an average of one aliphatic unsaturated group. The type of polyorganosiloxane (a2) having an average of one aliphatic unsaturated group within the molecule is not particularly limited; any polyorganosiloxane having an average of one aliphatic unsaturated group can be used, regardless of whether its position is at the end of the molecule or within the molecule. One type of polyorganosiloxane may be used alone, or two or more different types of polyorganosiloxanes may be used in combination. Alternatively, a mixture of multiple polyorganosiloxanes that can be produced in the manufacturing process of the polyorganosiloxane may be used as (a2), wherein the multiple polyorganosiloxanes have different numbers of aliphatic unsaturated groups. As a polyorganosiloxane having an average of one alkenyl group, according to methods known to those skilled in the art, it can be obtained, for example, in the form of a mixture of approximately 50 mol% of a mono-terminal alkenyl-containing polyorganosiloxane, approximately 25 mol% of a bi-terminal alkenyl-containing polyorganosiloxane, and approximately 25 mol% of a polyorganosiloxane without an alkenyl group, and can be used as (a2). The types of aliphatic unsaturated groups are as illustrated in (a1) above.

[0073] As such (a2), for example, having an average of 1 (R) in the molecule. 1 ) m (R) 2 SiO （3-m） / 2 (where R) 1 R is an unsubstituted or substituted monovalent hydrocarbon group that does not have an aliphatic unsaturated bond; 2 The alkenyl group (where m is an integer from 0 to 2) represents an alkenyl-containing siloxane unit.

[0074] The shape of the siloxane backbone of the polyorganosiloxane in (a2) is not particularly limited. Examples of linear polyorganosiloxanes include those containing aliphatic unsaturated groups with phenyl groups, such as polydimethylsiloxanes with a vinyl group at one end. From the viewpoint of workability, such linear polyorganosiloxanes have a viscosity of 100–100,000 cP at 23°C, preferably 100–25,000 cP.

[0075] As a branched polyorganosiloxane, M can be cited as an example. Vi Q Resin, MD Vi Q Resin, M Vi T Resin, M Vi DT Resin, MDVi T Resin et al. Here, the M unit is (CH3)3SiO 1 / 2 - Unit, M Vi CH2=CH)(CH3)2SiO 1 / 2 - Unit, D is -(CH3)2SiO 2 / 2 - Unit, D Vi -(CH3)(CH2=CH)SiO 2 / 2 - Unit, T is (CH3)SiO 3 / 2 Unit (3 functionalities), Q is SiO 4 / 2 Unit (4 functionalities).

[0076] Specifically, examples include SiO 4 / 2 Unit, R'3SiO 1 / 2 Unit and R'2SiO 2 / 2 Units, and further R'SiO as appropriate. 3 / 2 A branched polyorganosiloxane comprising units (where R' independently represents a C1-C6 alkyl or aliphatic unsaturated group) and at least one R' in each molecule being an aliphatic unsaturated group. Examples include R'2SiO 2 / 2 One mole of unit contains SiO at a ratio of 6 to 10 moles. 4 / 2 Units, containing R'3SiO at a ratio of 4 to 8 moles 1 / 2 Branched polyorganosiloxanes of the unit. (A) Polyorganosiloxanes containing aliphatic unsaturated groups, other than component (A), are preferably solid or viscous semi-solid resinous or liquid polyorganosiloxanes at room temperature. Examples include polyorganosiloxanes with a weight-average molecular weight of 1000 to 400000, preferably 2000 to 200000. The weight-average molecular weight is a value obtained by gel permeation chromatography (GPC) using polystyrene as a standard curve.

[0077] Regarding the aliphatic unsaturated group of R', the groups listed and preferred as aliphatic unsaturated groups in (A) are used. R' as an aliphatic unsaturated group can exist as any unit of R', but is preferably as an R'2SiO unit or R'3SiO unit. 1 / 2 The unit R' exists.

[0078] R' other than aliphatic unsaturated groups is a C1 to C6 alkyl group (e.g., methyl, ethyl, propyl, etc.), and methyl is preferred if heat resistance is taken into consideration.

[0079] As a specific example of a polyorganosiloxane (a2) having an average of one curable functional group within the molecule, the following general formula illustrates a linear polyorganosiloxane having an aliphatic unsaturated group at the molecule's end.

[0080] [Chemical Formula 3]

[0081]

[0082] (In the formula,

[0083] R a It is an aliphatic unsaturated group.

[0084] R is independently C 1-6 Alkyl or C 6-12 Aryl,

[0085] n is a number that makes the viscosity at 23°C between 10 and 50,000 cP.

[0086] There are no limitations on the type of resin with this structure. From the perspective of ease of acquisition or preparation, R is preferred. a A straight-chain siloxane in which each R is a vinyl group and each R is a methyl group.

[0087] The number of aliphatic unsaturated groups in component (A) can be determined by using NMR to obtain the average structural formula, calculating the molecular weight, and then determining the molecular weight based on the obtained molecular weight.

[0088] The preparation method of component (A) is not particularly limited. For example, it can be obtained by polycondensation and rebalancing of chlorosilanes such as dimethyldichlorosilane, diphenyldichlorosilane, methylphenyldichlorosilane, and dimethylvinylchlorosilane, which are required for the desired structure, or by co-hydrolysis of alkoxysilanes such as dimethyldimethoxysilane, diphenyldimethoxysilane, methylphenyldimethoxysilane, and dimethylvinylmethoxysilane, which are required for the desired structure, followed by polycondensation and rebalancing. Alternatively, siloxanes with desired structures, 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 be obtained by ring-opening polymerization and rebalancing in the presence of an alkaline catalyst (alkali metal hydroxide, alkali metal silanol, ammonium hydroxide, etc.) or an acid catalyst (sulfuric acid, silanol sulfate, trifluoromethanesulfonic acid).

[0089] From the viewpoint of workability of the composition, the viscosity of component (A) at 25°C is 100–500,000 cP, preferably 100–250,000 cP, more preferably 200–10,000 cP, and particularly preferably 300–300,000 cP. In this specification, viscosity is the value measured using a rheometer (MCR302e) (manufactured by Anton Paar) with a cone-plate measuring fixture CP25-2 at 40 rpm and 25°C.

[0090] Component (A) can be used alone or in combination with two or more. It should be noted that when (A) is a mixture of two or more, (A) can be a mixture of a high-viscosity (e.g., 10,000 to 25,000 cP at 23°C) polyorganosiloxane and a low-viscosity (e.g., 100 to 5,000 cP at 23°C) polyorganosiloxane.

[0091] Relative to 100 parts by weight of the total composition, the amount of component (A) contained in the composition of the present invention is generally preferably 41 parts by weight or more, more preferably 50 parts by weight or more. Furthermore, relative to 100 parts by weight of the total composition, it is preferably 90 parts by weight or less, more preferably 70 parts by weight or less. Regarding the amount of component (A) here, when using two or more components (A), it refers to their combined amount. When components (A) are used in combination with the above-described (a1) and (a2), relative to 100 parts by weight of the total composition, the amount of (a1) is preferably 5 parts by weight or more, more preferably 10 parts by weight or more. Furthermore, relative to 100 parts by weight of the total composition, the amount of (a1) is preferably 30 parts by weight or less, more preferably 20 parts by weight or less. Relative to 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. Furthermore, relative to 100 parts by weight of the total composition, it is preferably 70 parts by weight or less, more preferably 60 parts by weight or less.

[0092] When (a1) and (a2) are used together as component (A), the mixing ratio (mass ratio) of (a1) and (a2) is also affected by the amount of mercaptoalkyl group present in component (B) described later. The ratio of (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 manufacturing the composition, it is preferable to mix (a1) and (a2) in the ratio within the above range. However, when (a2) is a mixture of various polyorganosiloxanes and one component is a polyorganosiloxane having two or more aliphatic unsaturated groups, the ratio of their contents can be within the above range.

[0093] [(B) Polyorganosiloxanes containing mercaptoalkyl groups]

[0094] The UV-curable silicone gel composition of the present invention contains (B) a polyorganosiloxane containing a mercaptoalkyl group bonded to a silicon atom.

[0095] In component (B), from the perspective of ensuring a stable structure through cross-linking reaction while suppressing excessive curing shrinkage, the number of mercaptoalkyl groups bonded to silicon atoms in one molecule can be an average of 2 or more and 20 or less. Preferably, it is more than 2 and less than 10, and more preferably 3 to 7.

[0096] 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 perspective of ease of synthesis, mercaptomethyl and 3-mercaptopropyl are preferred, and 3-mercaptopropyl is more preferred.

[0097] In (B), the organic group other than the mercaptoalkyl group bonded to the silicon atom can be a substituted or unsubstituted monovalent hydrocarbon group (however, it is not an aliphatic unsaturated group). Specifically, examples include alkyl groups, such as C1-C6 alkyl groups (e.g., methyl, ethyl, propyl, etc.); cycloalkyl groups, such as C3-C10 cycloalkyl groups (e.g., cyclohexyl, etc.); aryl groups, such as C6-C12 aryl groups (e.g., phenyl, tolyl, xylyl, etc.); aralkyl groups, such as C7-C13 aralkyl groups (e.g., 2-phenylethyl, 2-phenylpropyl, etc.); and substituted hydrocarbon groups, such as halogenated hydrocarbon groups (e.g., chloromethyl, chlorophenyl, 3,3,3-trifluoropropyl, etc.). Alkyl groups are preferred from the perspective of ease of synthesis, among which methyl, ethyl, and propyl are preferred, and methyl is more preferred. Aryl groups can be used in combination to adjust the refractive index, among which phenyl is preferred from the perspective of ease of synthesis.

[0098] (B) The main chain structure can be linear, branched, or cyclic, with a branched structure being preferred. For example, an example containing R''SiO can be given. 3 / 2 Unit, R''3SiO 1 / 2 Unit and R''2SiO 2 / 2 Units, and, as appropriate, further SiO2. 4 / 2 A branched polyorganosiloxane containing a mercaptoalkyl group, wherein each unit (where R'' independently represents an unsubstituted or substituted monovalent hydrocarbon group (however, not an aliphatic unsaturated group)) and wherein two or more but less than 20 R'' in each molecule are mercaptoalkyl groups. Examples of mercaptoalkyl groups and unsubstituted or substituted monovalent hydrocarbon groups are as described above. The mercaptoalkyl R'' can exist as any unit of R'', but is preferably as R''SiO 3 / 2 The unit R' is present. The above-mentioned groups can be used as mercaptoalkyl and unsubstituted or substituted monovalent hydrocarbon groups. From the perspective of workability and crosslinking reactivity, the ratio of the number of siloxane units containing mercaptoalkyl to the number of siloxane units without mercaptoalkyl is preferably 1:60 to 1:8, more preferably 1:50 to 1:10.

[0099] (B) The viscosity at 23°C is preferably 20–10000 cP. From the perspective of workability and refractive index, for example, the viscosity can be set to 30–8000 cP.

[0100] The number of thiol groups in (B) can be determined by colorimetric titration using iodine. This method utilizes the reaction described in the following formula.

[0101] 2RSH+I2→RSSR+2HI

[0102] This method utilizes the fact that the titrant turns slightly yellow due to a trace amount of excess iodine during titration.

[0103] (B) preferably has high transparency. An example of transparency for (B) is a transmittance of 80% or higher. To measure the transmittance of (B), (B) is filled into a container at 23°C, and for a thickness of 10 mm, the transmittance in the visible light region (360–780 nm) is measured using a spectrophotometer. From the perspective of stably maintaining the transparency of the cured composition, a transmittance of 90% or higher is preferred.

[0104] (B) is not particularly limited in its preparation method. For example, it can be prepared by hydrolyzing, polycondensing, and rebalancing mercaptoalkylalkoxysilanes such as mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, mercaptopropylmethyldiethoxysilane, mercaptopropyldimethylmethoxysilane, and mercaptopropyldimethylethoxysilane with the desired alkylchlorosilane, alkylalkoxysilane, or silanol-containing siloxane.

[0105] (B) can be used alone or in combination with two or more ingredients. The amount of ingredient (B) contained in the composition of the present invention can be appropriately set according to the amount of unsaturated groups contained in (A) and the amount of mercaptoalkyl groups contained in (B), without particular limitation. Generally, it is preferably 0.1 parts by weight or more, more preferably 0.4 parts by weight or more, relative to 100 parts by weight of the whole composition. In addition, it is preferably 3 parts by weight or less, more preferably 2 parts by weight or less, relative to 100 parts by weight of the whole composition. Regarding the amount of ingredient (B) here, when using two or more ingredients (B), it refers to their total amount.

[0106] Since the amount of (B) is affected by the amount of unsaturated groups in (A), in the composition, (B) is preferably used in an amount where the ratio of the number of mercaptoalkyl groups (HS) in (B) to the number of aliphatic unsaturated groups (Vi) in (A) (HS / Vi) is 0.01 to 10. From the perspective of curability and hardness of the cured product, a ratio of 0.01 to 5 is more preferred, 0.03 to 1 is even more preferred, and a ratio of 0.05 to 0.5 is particularly preferred.

[0107] [(C) Photoreaction initiator]

[0108] The UV-curable silicone gel composition of the present invention contains a photoinitiator (C) that initiates the reactions (A) and (B) described above. (C) is excited by light, imparting excitation energy to the unsaturated bonds, such as (meth)acryloyl groups, present in the polysiloxane of (A), thereby initiating a UV-based curing reaction.

[0109] From a reactivity standpoint, component (C) can include aromatic hydrocarbons, acetophenone and its derivatives, benzophenone and its derivatives, o-benzoylbenzoate, benzoin and benzoin ethers and their derivatives, xanthones and their derivatives, disulfide compounds, quinone compounds, halogenated hydrocarbons and amines, and organic peroxides. From the viewpoint of compatibility with organosilicon and chemical stability, compounds or organic peroxides containing substituted or unsubstituted benzoyl groups are more preferred.

[0110] Examples of ingredients (C) include acetophenone, phenylacetone, 2-hydroxy-2-methylphenylacetone, 2,2-dimethoxy-1,2-diphenylethane-1-one (IRGACURE 651: manufactured by BASF), 2-hydroxy-2-methyl-1-phenyl-propane-1-one (DAROCUR 1173: manufactured by BASF), 1-hydroxy-cyclohexyl-phenyl-one (IRGACURE 184: manufactured by BASF), 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (IRGACURE 2959: manufactured by BASF), 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propanoyl)-benzyl]phenyl}-2-methyl-propane-1-one (IRGACURE 127: manufactured by BASF), 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-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-morpholino)phenyl]-1-butanone (IRGACURE 379: manufactured by BASF); 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (LUCIRIN TPO: manufactured by BASF), bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (IRGACURE 819: BASF manufactured); 1,2-octanedione, 1-[4-(phenylthio)phenyl-,2-(O-benzoyl oxime)] (IRGACURE OXE 01: BASF manufactured), acetone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-,1-(O-acetyl oxime) (IRGACURE OXE 02: BASF manufactured); a mixture of oxyphenylacetic acid, 2-[2-oxo-2-phenylacetoxyethoxy] ethyl ester and oxyphenylacetic acid, 2-(2-hydroxyethoxy) ethyl ester (IRGACURE 754: BASF manufactured), methyl phenylglyoxylate (DAROCUR MBF: BASF manufactured), ethyl-4-dimethylaminobenzoate (DAROCUR EDB: BASF manufactured), 2-ethylhexyl-4-dimethylaminobenzoate (DAROCUR EHA (manufactured by BASF), bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide (CGI403: manufactured by BASF), benzoyl peroxide, cumene peroxide, etc.

[0111] From the perspectives of compatibility and photoreactivity, the preferred formulations are acetophenone, phenylacetone, 2-hydroxy-2-methylphenylacetone, 2,2-dimethoxy-1,2-diphenylethane-1-one (IRGACURE 651: manufactured by BASF), 2-hydroxy-2-methyl-1-phenyl-propane-1-one (DAROCUR 1173: manufactured by BASF), 1-hydroxy-cyclohexyl-phenyl-one (IRGACURE 184: manufactured by BASF), 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one (IRGACURE 907: manufactured by BASF), 2-benzyl-2-dimethylamino-(4-morpholinophenyl)-butanone-1 (IRGACURE 369: manufactured by BASF), and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (LUCIRIN). TPO: manufactured by BASF, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (IRGACURE 819: manufactured by BASF).

[0112] Component (C) can 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 sufficient to allow the curing reaction to proceed sufficiently. From the perspective of curability and the optical properties after curing, it is preferably 0.1 parts by weight or more, more preferably 0.4 parts by weight or more, relative to 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, relative to 100 parts by weight of the total composition. Regarding the amount of component (C) here, when using two or more components (C), it refers to their combined amount.

[0113] [(D) Hindered amine stabilizers]

[0114] The UV-curable silicone gel composition of the present invention contains a hindered amine stabilizer as component (D). The present invention is based on the following discovery: by using a hindered amine stabilizer, particularly in terms of the long-term reliability of the UV-curable silicone gel composition, and by using it in conjunction with component (E) described later, along with the control of the particle dispersion state resulting from the effect of component (D) on the particle surface of component (E), the complex elastic modulus G*, i.e., the damping characteristics, are improved.

[0115] Examples of hindered amine antioxidants include N,N',N'',N'''-tetra-(4,6-bis(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine, dibutylamine•1,3,5-triazine•N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl-1,6-hexamethylenediamine•N-(2,2,6,6-tetramethyl-4-piperidinyl)butylamine condensates, and poly[{6-(1, 1,3,3-Tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidinyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidinyl)imino}, a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol, [bis(2,2,6,6-tetramethyl-1(octoxy)-4-piperidinyl) sebacate, the reaction product of 1,1-dimethylethyl hydroperoxide and octane (70%)] - polypropylene Alkene (30%), bis(1,2,2,6,6-pentamethyl-4-piperidinyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, methyl 1,2,2,6,6-pentamethyl-4-piperidinyl sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) 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 not limited to these. From the viewpoint of obtaining a more transparent composition, bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin 123) is particularly preferred.

[0116] Component (D) can 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 sufficient to allow the curing reaction to proceed sufficiently; preferably, it is 0.1 parts by weight or more, more preferably 0.4 parts by weight or more, relative to 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, relative to 100 parts by weight of the total composition. Regarding the amount of component (D) here, when using two or more components (D), it refers to their combined amount.

[0117] [(E) Particles containing silicon-oxygen bonds]

[0118] The composition of the present invention comprises silicon-oxygen bond-containing microparticles as fillers for controlling the flowability of the composition and improving its damping properties (hereinafter, sometimes simply referred to as "silicon microparticles"). Silicon-oxygen bond-containing microparticles can be silicon dioxide (SiO2), organosilicon (silicon compounds composed of -O-Si-O- bonds), etc., as component (E). The silicon-oxygen bond-containing microparticles can be prepared in a microparticle form having the following average particle size, and can be in various shapes such as spherical, blocky, plate-like, or pulverized, preferably spherical or pulverized. Examples of silicon-oxygen bond-containing microparticles include spherical organosilicon resin, calcined silica, silica aerogel, precipitated silica, pulverized silica, etc. From the viewpoint of improving the complex elastic modulus of the cured product, pulverized silica or spherical organosilicon resin microparticles are preferred; from the viewpoint of placing greater emphasis on the damping properties during curing, spherical organosilicon resin microparticles are more preferred.

[0119] The average particle size of the silicon microparticles ranges from 1 μm to 30 μm, with the lower limit preferably being 1.2 μm, more preferably 1.5 μm, further preferably 2 μm, and particularly preferably 4 μm. The upper limit of the average particle size is preferably 25 μm, more preferably 15 μm, further preferably 10 μm, and particularly preferably 6 μm. The average particle size can be determined by measuring D50, particularly by known methods such as dynamic light scattering using a Malvern Zetasizer-based laser, photon correlation spectrometry based on ISO 13320-1, or quasi-elastic light scattering. This method is used for determination in compositions that have not been specifically cured, but in some cases, determining the average particle size D50 by electron microscopy (TEM) is also sufficient. By using silicon microparticles with particle sizes within the aforementioned range, the viscosity of the composition can be moderately controlled while improving damping properties.

[0120] Silicon microparticles can be manufactured using methods known to those skilled in the art. As a decomposition method to reduce particle size, solid-phase methods such as ball mills or bead mills can be appropriately selected depending on the particle shape. As a packing method that utilizes chemical reactions to obtain particles at the molecular level, gas-phase methods such as CVD or sol-gel methods, or liquid-phase methods, can be appropriately selected depending on the particle shape. Furthermore, commercially available silicon microparticles can be used directly, or silicon microparticles treated with known surface-treatment agents can be used. In this specification, surface treatment refers to using a compound that reacts with functional groups such as silanol groups present on the particle surface to covalently bond these functional groups with other types of groups. Examples of surface treatment methods include the use of 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). Treatment can be performed using silazane compounds (such as methyltrimethoxysilane, 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 treatment with silazane or chlorosilane compounds allows for hydrophobic treatment of the silica surface with a smaller treatment amount, which is preferable from this perspective. Hexamethyldisilazane and dimethyldichlorosilane are particularly preferred. From the perspective of the degree of treatment and the stability (inactivation) of the treated surface state, hexamethyldisilazane is preferred. These surface treatment agents can be compounded and mixed with silica during the preparation of curable compositions, thereby performing particle surface treatment.

[0121] Component (E) can 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 imparts a certain degree of viscoelasticity to the composition. It 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, it 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 with excellent strength and long-term reliability can be obtained. However, from the viewpoint of prioritizing the long-term reliability of the composition, it is preferable to suppress the amount of component (E), preferably 25 parts by weight or less. From the viewpoint of prioritizing the strength of the composition against deformation, the amount of component (E) is preferably higher, preferably 25 parts by weight or more. Regarding the amount of component (E) here, when using two or more components (E), it refers to their combined amount.

[0122] [UV-curable silicone gel composition]

[0123] 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 have a degree of fluidity suitable for application to a substrate. Due to its high stability, the silicone gel composition of the present invention can maintain hardness-related properties, such as elastic modulus, at a high level for a long time after curing.

[0124] Furthermore, the UV-curable silicone gel composition can be a one-component composition in which all components are completely mixed, or a two-component composition in which components (B) and (C) are formulated separately. The choice between a one-component or two-component composition can be appropriately made considering factors such as workability and curing conditions, and such methods are well known to those skilled in the art.

[0125] The UV-curable silicone gel composition of the present invention can be combined with other known ingredients as long as it does not impair its purpose or effect. As additives, it may include silane coupling agents, reaction inhibitors, inorganic fillers, and other additives. Alternatively, it may be combined with silicone resins not belonging to components (A) and (B) above. Examples of such resins include polyorganosiloxanes that do not have curable functional groups, such as dimethylsiloxane. These resins can be used as diluents.

[0126] Examples of silane coupling agents include 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, and trimethoxypropyltriethoxysilane. Silylpropyl dielyl isocyanurate, bis(trimethoxysilylpropyl) allyl isocyanurate, tri(trimethoxysilylpropyl) isocyanurate, triethoxysilylpropyl dielyl isocyanurate, bis(triethoxysilylpropyl) allyl isocyanurate, tri(triethoxysilylpropyl) isocyanurate, preferably 3-methacryloyloxypropyltriethoxysilane or 3-methacryloyloxypropyltrimethoxysilane.

[0127] Examples of reaction inhibitors include hydroquinone, p-methoxyphenol, p-tert-butylcatechol, and phenothiazine.

[0128] Examples of inorganic fillers include reinforcing fillers such as fumed titanium dioxide; oxides such as fumed silica, diatomaceous earth, iron oxide, zinc oxide, titanium dioxide, 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 hydrophobic agents. Among these, fumed silica, carbon black, or calcium carbonate are preferred inorganic fillers, with fumed silica being more preferred. A preferred embodiment of the present invention is a UV-curable silicone gel composition further comprising fumed silica as component (F). Fumed silica is silica with a particle size of approximately 10 nm and does not belong to the particles described above (E). Fumed silica has the effect of increasing viscosity and can be used within a range that does not impair the workability of preparing the composition of the present invention.

[0129] As a component (F), the BET specific surface area is preferably 50 m². 2 / g or more, preferably 50-300mg 2 / g.

[0130] When using fumed silica as an inorganic filler, surface-treated fumed silica is particularly preferred. By using surface-treated silica, the flowability of the composition can be suppressed, and the cured composition can be given mechanical strength. The surface treatment method can be the same as that used for silicon microparticles.

[0131] The amount of inorganic filler is preferably 1 part by weight or more, more preferably 3 parts by weight or more, relative to 100 parts by weight of the total composition. Furthermore, it is preferably 10 parts by weight or less, more preferably 7 parts by weight or less, relative to 100 parts by weight of the total composition.

[0132] The curable polyorganosiloxane composition may further comprise a siloxane resin that is not one of the components (A) or (B) described above. Such a resin can also be used as a diluent for adjusting viscosity. As such a siloxane resin, a resin that does not have curable functional groups in the resin obtained from the combination of the above-described M, D, T, and Q units can be used, particularly a siloxane that does not have curable functional groups as shown in the following formula.

[0133] R3Si-O-(SiR2O) n -SiR3

[0134] (In the formula, R is C) 1-6 Alkyl or C 6-12 Aryl group, where n is the number that gives the viscosity at 23°C 100–100,000 cP.

[0135] By using such siloxane resins, it is possible to control the hardness of the curable polyorganosiloxane composition during curing, control the viscosity of the composition, and broadly address processability and required physical properties.

[0136] From an operational perspective, the viscosity of the composition at 23°C is preferably 100–50,000 cP, more preferably 100–20,000 cP, and even more preferably 500–13,000 cP.

[0137] The composition can be obtained by combining (A) to (E) and any other components. During preparation, considering the excellent compatibility of components (A) to (E), by mixing all of (A) to (E), the composition can be easily made homogeneous, resulting in a transparent cured product. Any other components can be added appropriately, especially when using inorganic fillers such as component (F) fumed silica; it is preferable to mix with other components while component (A) and the inorganic filler are mixed and dispersed.

[0138] The composition can be cured by irradiation with ultraviolet light. The preferred intensity of the ultraviolet light irradiation is 10–10000 mW / cm². 2 More preferably, it is 30–6000 mW / cm². 2 More preferably 50–4000 mW / cm 2 Furthermore, the duration of ultraviolet (UV) irradiation depends on the UV intensity, preferably 10–100 seconds, more preferably 15–80 seconds, and even more preferably 20–70 seconds. A UV intensity of 100 mW / cm² is preferred. 2The composition is prepared by irradiating it with ultraviolet light at an intensity of 30 seconds to allow it to fully cure. It should be noted that, here, "cured" means that the properties remain constant even with continued ultraviolet irradiation. Furthermore, the irradiation dose is a measured value of UVA, which refers to ultraviolet light in the range of 315–400 nm.

[0139] The composition exhibits good curing properties when irradiated with ultraviolet light of wavelengths, for example, in the range of 250–450 nm. Examples of light sources emitting such wavelengths of ultraviolet light include high-pressure mercury lamps (UV-7000) and metal halide lamps (UVL-4001M3-N1) manufactured by USHIO Electric Co., Ltd., metal halide lamps (JM-MTL2KW) manufactured by JM Tech Co., Ltd. (Korea), ultraviolet irradiation lamps (OSBL360) manufactured by Mitsubishi Electric Co., Ltd., ultraviolet irradiation machines (UD-20-2) manufactured by Nippon Battery Co., Ltd., fluorescent lamps (FL-20BLB) manufactured by Toshiba Co., Ltd., and H Bulb, H Plus Bulb, V Bulb, D Bulb, Q Bulb, and M Bulb manufactured by Heraeus Co., Ltd.

[0140] The composition of the present invention has a high complex modulus of elasticity G*, making it suitable as a damping material for devices such as image display devices. The damping material can be placed at a desired location, such as between the image display section and the protective section, and cured by ultraviolet light irradiation, thereby sealing the image display section and the protective section. A higher G* value indicates better properties as a damping material. In the composition of the present invention, a value of 3000 Pa or more is preferred after accelerated testing under the initial conditions and the conditions described later; more preferably, a value of 4000 Pa or more is preferred. Alternatively, the G* value after accelerated testing is preferably within ±35% of the value when the G* before accelerated testing is set to 100%. The G* is measured using a rheometer to record G* data at a frequency of 10 Hz.

[0141] The composition of the present invention exhibits high stability. In addition to the complex elastic modulus G*, stability can also be evaluated by the change in the value of the loss tangent (tanδ). The loss tangent is a measure of the contribution of elasticity and viscosity to a viscoelastic substance like the composition of the present invention; a smaller value indicates stronger elastomer properties, and a larger value indicates stronger viscous properties. A large change in the loss tangent (Δtanδ) indicates a change in the viscoelastic properties of the composition; therefore, a smaller Δtanδ value is preferred, and the change before and after accelerated testing under the conditions described later is preferably 0.5 or less. The tanδ is measured using a rheometer to record tanδ data at a frequency of 10 Hz.

[0142] The composition of the present invention exhibits long-term stability as a damping material, making it suitable for use in components susceptible to damage from environmental factors such as moisture, temperature, and ultraviolet radiation. Therefore, the composition of the present invention preferably suppresses changes in the complex elastic modulus G* and tanδ, which are evaluation criteria for damping materials, even under prolonged exposure to high temperature and humidity. As an evaluation of long-term stability, it is preferable that the complex elastic modulus G* and tanδ remain at the aforementioned values ​​or change after being placed in an environment of 85°C and 85% relative humidity for approximately 125 hours.

[0143] The compositions of the present invention are suitable for use in the manufacture of image display devices intended for use in the field and requiring good UVA resistance, and are particularly preferred as a damping material for cameras, used as a resin sandwiched between the protective part and the image display part.

[0144] [Example]

[0145] The present invention will now be described in more detail through examples and comparative examples. However, the present invention is not limited to these examples.

[0146] The materials used in the examples and comparative examples are as follows.

[0147] <(A) Polyorganosiloxanes containing aliphatic unsaturated groups>

[0148] (a1) α,ω-divinyl polyphenylmethylsiloxane (phenyl 5 mol%) with a viscosity of 20000 cP at 23°C.

[0149] (a2) Linear vinyl polyphenylmethylsiloxane (phenyl 5 mol%) with a viscosity of 2500 cP at 23°C.

[0150] <(B) Polyorganosiloxanes containing mercaptoalkyl groups>

[0151] A thiol-containing polyorganosiloxane with a viscosity of 200 cP at 23°C

[0152] <(C) Photoreaction initiator>

[0153] (1) 2-Hydroxy-2-methyl-1-phenyl-propane-1-one (DAROCUR 1173: manufactured by BASF)

[0154] (2) 1-Hydroxy-cyclohexyl-phenyl-one (IRGACURE 184: manufactured by BASF)

[0155] <(D) Hindered amine stabilizers>

[0156] Bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin123)

[0157] <(E) Particles containing silicon-oxygen bonds>

[0158] (1) Spherical silicone resin microparticles (particle size 2μm / Tospearl (registered trademark) 120 manufactured by Momentive Performance Materials)

[0159] (2) Spherical silicone resin microparticles (particle size 2μm / Tospearl (registered trademark) manufactured by Momentive Performance Materials, 120FL)

[0160] (3) Spherical silicone resin microparticles (particle size 4.5μm / Tospearl (registered trademark) 145 manufactured by Momentive Performance Materials)

[0161] (4) Spherical silicone resin microparticles (particle size 6μm / Tospearl 3000A manufactured by Momentive Performance Materials, a registered trademark)

[0162] (5) Spherical silicone resin microparticles (particle size 10 μm / Tospearl (registered trademark) 1100 manufactured by Momentive Performance Materials)

[0163] (6) Spherical silica (0.3 μm particle size / Admatechs SO-Cl)

[0164] (7) Spherical silica (particle size 1.2 μm / SO-C4 manufactured by Admatechs)

[0165] (8) Spherical silica (particle size 1.9 μm / Admatechs SO-C6)

[0166] (9) Grind silica (particle size 1.4μm / Crystalite (registered trademark) 5X)

[0167] (10) Crushed silica (particle size 4μm / Crystalite (registered trademark) VX-S)

[0168] In addition, fumed silica (7nm primary particle size / REOLOSIL (registered trademark) HM-30S) was used as a further additive, and p-tert-butylcatechol was used as a reaction inhibitor.

[0169] Examples 1-13, Comparative Examples 1-13

[0170] <Preparation of UV-curable silicone gel composition>

[0171] To prevent the generation of free radicals initiators caused by ultraviolet light, the treatment of component (C) was carried out in a yellow light chamber. Using the proportions (parts by mass) shown in Tables 1 and 2 below, components (A) to (E), fumed silica, and reaction inhibitors were mixed in a planetary mixer according to a prescribed method to obtain an ultraviolet-curable silicone gel composition. However, component (E) was not added in Comparative Examples 1 and 2, and component (D) was not added in the comparative examples other than Comparative Examples 1 and 3.

[0172] Regarding various UV-curable silicone gel compositions, with a cumulative light intensity of 3000 mJ / cm 2 (at 100mW / cm) 2 The gel sheet was irradiated with ultraviolet light for 30 seconds on both sides to cure it, resulting in a cured product.

[0173] <Determination of Complex Viscoelasticity G*>

[0174] The glycation depth (G*) of a 2 mm thick gel sheet at 25 °C and 10 Hz was measured using a rheometer. After measuring the G* in the initial state, the cured products of each UV-curable silicone gel composition were subjected to accelerated testing by standing at 85 °C and 85% relative humidity for 125 hours. After standing, the G* was measured again. A good rating was defined as a G* value of 4000 Pa or higher after accelerated testing and a change rate of ±35% before and after accelerated testing, with both being considered exceptionally good. The results are shown in Tables 1 and 2.

[0175] <Determination of tanδ>

[0176] Tanδ of a 2 mm thick gel sheet at 25 °C and 10 Hz was measured using a rheometer. After measuring the tanδ in the initial state, the cured products of each UV-curable silicone gel composition were subjected to accelerated testing by standing at 85 °C and 85% relative humidity for 125 hours. After standing, tanδ was measured again. When the difference in tanδ before and after the accelerated test was within ±0.50, the viscoelastic properties of the UV-curable silicone gel composition were considered to have not changed significantly. The results are shown in Tables 1 and 2.

[0177] [Table 1]

[0178]

[0179] [Table 2]

[0180]

[0181] Tables 1 and 2 show that the complex modulus G* of the composition was increased by adding silicon-oxygen bonds containing microparticles with a specified particle size. The UV-curable silicone gel compositions of the examples have a high complex modulus G* and excellent overall resistance to deformation. G* increases by adding a large amount of silicon microparticles (Examples 1, 5, 8). On the other hand, if the amount of silicon microparticles increases, the numerical decrease over time appears to increase as well, but in all examples, the decrease rate is small compared to the comparative examples using the same silicon microparticles, and the numerical value is maintained to fully utilize 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 flowability of the composition is impaired (Comparative Examples 3, 4), resulting in problems with the processability as a damping material. Furthermore, it is shown that by adding hindered amine stabilizers, the change in tanδ over time is particularly small. Even under accelerated testing conditions, the change in tanδ is small, which means that the properties as a viscous body or elastomer do not change significantly. Therefore, the UV-curable silicone gel compositions of the examples can maintain reliability against physical forces, vibrations, etc., for a long time.

[0182] Industrial availability

[0183] According to the present invention, a UV-curable silicone gel composition is provided, which yields a cured product with excellent long-term reliability. The composition can maintain hardness-related properties, such as elastic modulus, at a high level for a long time, making it suitable for components susceptible to damage from environments such as moisture, temperature, and ultraviolet radiation. For example, in the manufacture of image display devices intended for outdoor use and requiring good UVA resistance, it is suitable as a damping material for sealing between the protective part and the image display part.

Claims

1. A UV-curable silicone gel composition comprising: (A) Polyorganosiloxanes containing aliphatic unsaturated groups; (B) Polyorganosiloxanes containing mercaptoalkyl groups bonded to silicon atoms; (C) A photoinitiator that triggers the reaction between (A) and (B); (D) Hindered amine stabilizers; and (E) Particles with an average particle size of 1 μm to 30 μm and containing silicon-oxygen bonds.

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

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

4. The UV-curable silicone gel composition according to claim 3, wherein, The (a1) comprises a linear polyorganosiloxane containing aliphatic unsaturated groups as shown in formula (I). In the formula, Each R 1 It is an independent aliphatic unsaturated group. Each R is independently a C1–C6 alkyl or C6–C12 aryl. n is a number that makes the viscosity at 23°C between 100 cP and 100,000 cP.

5. The UV-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 UV-curable silicone gel composition according to claim 1, wherein, The (E) refers to spherical or pulverized particles.

7. The UV-curable silicone gel composition according to claim 1, wherein, The (E) refers to particles derived from organosilicon or silica.

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

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

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

11. The UV-curable silicone gel composition according to claim 1, wherein, At 100mW / cm 2 When cured by irradiating it with ultraviolet light with a wavelength of 315nm to 400nm for 30 seconds, the complex elastic modulus G* is above 4000Pa.

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

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