Curable silicone composition and cured product thereof

Abstract

A curable silicone composition is provided. The curable silicone composition comprises: (A) an organopolysiloxane comprising an average of two or more alkenyl groups; (B) a crosslinker with an average of three or more mercapto groups; (C) an epoxy-functional silicone resin having monovalent aromatic hydrocarbon groups; (D) an epoxy-functional silicone; (E) an iodonium salt type cationic photoinitiator; and (F) a cationic photoinitiator other than component (E). According to the present disclosure, a Silicone-Epoxy hybrid material having benefits of both silicones and organic epoxies, having excellent reliability performance and adhesiveness suitable for applications in the electronic display market may be provided.

Description

CURABLE SILICONE COMPOSITION AND CURED PRODUCT THEREOFCross-Reference to Related Applications

[0001] The application claims priority to and all advantages of U.S. Provisional Patent Application No. 63 / 524,263 filed on 30 June 2023, the content of which is incorporated herein by reference.Technical Field

[0002] The present invention relates to a curable silicone composition and a cured product thereof.Background Art

[0003] Silicone-based materials are known to display high flexibility, processability, and thermal reliability but have low surface hardness and adhesion. Organic epoxy materials are known to contain the opposite properties.

[0004] In efforts to combine the merits of both sides, preparation of Silicone-Epoxy hybrid material has been demonstrated. For example, WO 2022 / 072271 A1 describes preparation and formulation of a UV radiation curable Silicone-Epoxy hybrid resin that provides excellent adhesion and performance reliability favorable in display market. However, WO 2022 / 072271 A1 did not address the applicability of Silicone-Epoxy in B-stage applications, which requires initial UV cure to result in a B-stage that allows good processability followed by final heat cure. WO 2022 / 072271 A1 addresses this problem by combining an orthogonal cure chemistry, i.e., thiol-ene UV cure, with Silicone-Epoxy heat cure (by using HAG in place of PAG) to achieve stepwise B-stage and C-stage.Prior Art DocumentsPatent Documents

[0005] Patent Document 1 : International Publication No. WO 2022 / 072271 A1Summary of InventionTechnical Problem

[0006] Silicone-Epoxy hybrid material can be cured by both UV irradiation and heat by employing different types of acid generators, namely photo acid generator (PAG) and heat acid generator (HAG). An objective of the present invention is to provide a Silicone-Epoxy hybrid material having the benefits of both silicones and organic epoxies, having excellent reliability performance and adhesiveness suitable for applications in the electronic display market.Solution to Problem

[0007] The curable silicone composition of the present invention comprises:

[0008] (A) an organopolysiloxane comprising an average of two or more alkenyl groups represented by the following general formula:wherein R1and R8each independently represent a C2-30 alkenyl group; R2to R7each independently represent a C1 -30 monovalent aliphatic hydrocarbon group, or a C6-30 monovalent aromatic hydrocarbon group; and "n" is an integer of from 0 to 100;

[0009] (B) a crosslinker with an average of three or more mercapto groups represented by the following general formula:wherein R9each independently represents a C1 -30 monovalent aliphatic hydrocarbon group, or a C6-30 monovalent aromatic hydrocarbon group; R10each independently represents a C1 -30 divalent aliphatic hydrocarbon group, or a C6-30 divalent aromatic hydrocarbon group; and R11each independently represents a mercapto group or a C1 -6 alkyl group, provided that at least three of the R11's are mercapto groups;

[0010] (C) an epoxy-functional silicone resin represented by the following average unit formula:(R123SiOi / 2)a(R122SiO2 / 2)b (R12SiO3 / 2)c(SiO4 / 2)dwherein R12each independently represents a C1 -6 monovalent aliphatic hydrocarbon group, a C6-10 monovalent aromatic hydrocarbon group, or a monovalent epoxy-substituted organic group, provided that at least about 15 mol% of the total R12are C6-10 monovalent aromatic hydrocarbon groups; and "a", "b", "c" and "d" are numbers that satisfy the following conditions: 0<a<0.4, 0<b<0.5, 0<c<1 , 0<d<0.4, 0.1<b / c<0.6, and a+b+c+d=1 ; and about 2 to about 30 mol% of the total siloxane units have the monovalent epoxy-substituted organic groups;

[0011] (D) an epoxy-functional silicone represented by the following general formula: X1-R132SiO(SiR132O)mSiR132-X1wherein R13each independently represents a C1 -6 monovalent aliphatic hydrocarbon group, or a C6-10 monovalent aromatic hydrocarbon group; X1each independently represents a monovalent epoxy-substituted organic group, or an epoxy-functional siloxy group represented by the following general formula:X2-R142SiO(SiR142O)xSiR142-R15- wherein R14each independently represents a C1 -6 monovalent aliphatic hydrocarbon group; R15represents a C2-6 alkylene group; X2represents a monovalent epoxy-substituted organic group; "x" represents a number of from 0 to 5; and "m" represents a number of from 0 to 100;

[0012] (E) an iodonium salt type cationic photoinitiator; and

[0013] (F) a cationic photoinitiator other than component (E).

[0014] In various embodiments, in component (A), R1and R8each independently represent a vinyl group; R2, R3, R6, and R7each independently represent a C1 -6 alkyl group; R4and R5each independently represent a C6-12 aryl group; and "n" is an integer of from 0 to 40.

[0015] In various embodiments, in component (B), R9each independently represents a C1 - 6 alkyl group; R10each independently represents a C1 -6 alkylene group; and R11each independently represents a mercapto group.

[0016] In various embodiments, the monovalent epoxy-substituted organic groups in component (C) are groups selected from glycidoxyalkyl groups, 3,4-epoxycyclohexylalkyl groups, and epoxyalkyl groups.

[0017] In various embodiments, wherein the monovalent epoxy-substituted organic groups in component (D) are groups selected from glycidoxyalkyl groups, 3,4-epoxycyclohexylalkyl groups, and epoxyalkyl groups.

[0018] In various embodiments, component (E) is an iodonium salt type cationic photoinitiator having a structure represented by the following general formula:R162I+X- wherein, R16each independently represents a C1 -6 alkyl group, C6-24 aryl group, or a substituted C6-24 aryl group; and X- represents a non-nucleophilic non-basic anion.

[0019] In various embodiments, the curable silicone composition further comprises: (G) an adhesion promoter, in an amount of from about 0.01 to about 5 mass% of the total mass of components (A) to (F).

[0020] The cured product of the present invention is obtained by curing the curable silicone composition described above.Effects of Invention

[0021] UV curable Silicone-Epoxy hybrid material brings the benefits of silicones and organic epoxies that is suitable for the electronic display market. However, preliminary studies have revealed that Silicone-Epoxy alone is not suitable for applications that require UV and heat B- stage dual cure properties. B-stageable material with low viscosity can provide opportunities in applications that require multi-step processability such as spin-coating capable die attach processes in the semiconductor industry.Brief Description of the Drawings

[0022] Fig. 1 is a graph showing the storage modulus change over time after UV irradiation of the compositions of Example 1 and Comparative Example 1 .Detailed Description of the Invention

[0023] The terms “comprising” or “comprise” are used herein in their broadest sense to mean and encompass the notions of “including,” “include,” “consist(ing) essentially of,” and “consist(ing) of. The use of “for example,” “e.g.,” “such as,” and “including” to list illustrative examples does not limit to only the listed examples. Thus, “for example” or “such as” means “for example, but not limited to” or “such as, but not limited to” and encompasses other similar or equivalent examples. The term “about” as used herein serves to reasonably encompass or describe minor variations in numerical values measured by instrumental analysis or as a result of sample handling. Such minor variations may be in the order of ±0-25, ±0-10, ±0-5, or ±0- 2.5, % of the numerical values. Further, the term “about” applies to both numerical values when associated with a range of values. Moreover, the term “about” may apply to numerical values even when not explicitly stated. Generally, as used herein a “>” is “above” or “greater- than”; a “>” is “at least” or “greater-than or equal to”; a “<” is “below” or “less-than”; and a “<” is “at most” or “less-than or equal to.”

[0024] The terms “epoxy-functional” or “epoxy-substituted” as used herein refers to a functional group in which an oxygen atom, the epoxy substituent, is directly attached to two adjacent carbon atoms of a carbon chain or ring system. Examples of epoxy-substituted functional groups include, but are not limited to, glycidoxyalkyl groups such as 2-glycidoxyethyl groups, 3-glycidoxypropyl groups, 4-glycidoxybutyl groups or the like; (3,4- epoxycycloalkyljalkyl groups such as 2-(3,4-epoxycylohexyl)ethyl groups, 3-(3,4- epoxycylohexyljpropyl groups, 2-(3,4-epoxy-3-methylcylohexyl)-2-methylethyl groups, 2-(2,3- epoxycylopentyljethyl groups, 3-(2,3-epoxycylopentyl)propyl groups, and the like; and epoxyalkyl groups such as 2,3-epoxypropyl groups, 3,4-epoxybutyl groups, 4,5-epoxypentyl groups, and the like.<Curable silicone composition>

[0025] Component (A) is an organopolysiloxane comprising an average of two or more alkenyl groups represented by the following general formula:

[0026] In the formula, R1and R8each independently represent a C2-30 alkenyl group; R2to R7each independently represent a C1 -30 monovalent aliphatic hydrocarbon group, or a C6- 30 monovalent aromatic hydrocarbon group; and "n" is an integer of from 0 to 100.

[0027] Examples of the C1 -30 monovalent aliphatic hydrocarbon groups in component (A) include C1 -30 alkyl groups such as methyl groups, ethyl groups, propyl groups, butyl groups, and hexyl groups; C2-30 alkenyl groups such as vinyl groups, allyl groups, and hexenyl groups; and C1-30 halogenated alkyl groups such as 3-chloropropyl groups and 3,3,3- trifluoropropyl groups. Among these, methyl groups are generally preferred.

[0028] Examples of the C6-30 monovalent aromatic hydrocarbon groups in component (A) include phenyl groups, tolyl groups, xylyl groups, and naphthyl groups. Among these, phenyl groups are generally preferred.

[0029] In one embodiment of the present invention, R1and R8each independently represent a vinyl group; R2, R3, R6, and R7each independently represent a C1 -6 alkyl group; R4and R5each independently represent a C6-12 aryl group; and "n" is an integer of from 0 to 40.

[0030] Component (B) is a crosslinker with an average of three or more mercapto groups represented by the following general formula:

[0031] In the formula, R9each independently represents a C1 -30 monovalent aliphatic hydrocarbon group, or a C6-30 monovalent aromatic hydrocarbon group; R10each independently represents a C1 -30 divalent aliphatic hydrocarbon group, or a C6-30 divalent aromatic hydrocarbon group; and R11each independently represents a mercapto group or a C1 -6 alkyl group, provided that at least three of the R11's are mercapto groups.

[0032] Examples of the C1 -30 monovalent aliphatic hydrocarbon groups in component (B) include C1 -30 alkyl groups such as methyl groups, ethyl groups, propyl groups, butyl groups, and hexyl groups; C2-30 alkenyl groups such as vinyl groups, allyl groups, and hexenyl groups; and C1-30 halogenated alkyl groups such as 3-chloropropyl groups and 3,3,3- trifluoropropyl groups. Among these, methyl groups are generally preferred.

[0033] Examples of the C6-30 monovalent aromatic hydrocarbon groups in component (B) include phenyl groups, tolyl groups, xylyl groups, and naphthyl groups. Among these, phenyl groups are generally preferred.

[0034] Examples of the C1 -30 divalent aliphatic hydrocarbon groups in component (B) include C1 -30 alkylene groups such as methylene groups, ethylene groups, propylene groups, butylene groups, and hexylene groups; C2-30 alkenylene groups such as vinylene groups, propenylene groups, and hexenylene groups; and C1-30 halogenated alkyl groups such as 3- chloropropylene groups and 3,3,3-trifluoropropylene groups. Among these, methylene groups are generally preferred.

[0035] Examples of the C6-30 divalent aromatic hydrocarbon groups in component (B) include phenylene groups, tolylene groups, xylylene groups, and naphthylene groups. Among these, phenylene groups are generally preferred.

[0036] In one embodiment of the present invention, R9each independently represents a C1 - 6 alkyl group; R10each independently represents a C1 -6 alkylene group; and R11each independently represents a mercapto group.

[0037] Component (C) is an epoxy-functional silicone resin represented by the following average unit formula:(R123SiOi / 2)a(R122SiO2 / 2)b(R12SiO3 / 2)c(SiO4 / 2)d-

[0038] In the formula, R12each independently represents a C1 -6 monovalent aliphatic hydrocarbon group, a C6-10 monovalent aromatic hydrocarbon group, or a monovalent epoxysubstituted organic group, provided that at least about 15 mol% of the total R12are C6-10 monovalent aromatic hydrocarbon groups; and "a", "b", "c" and "d" are numbers that satisfy the following conditions: 0<a<0.4, 0<b<0.5, 0<c<1 , 0<d<0.4, 0.1<b / c<0.6, and a+b+c+d=1; and about 2 to about 30 mol% of the total siloxane units have the monovalent epoxysubstituted organic groups.

[0039] Examples of the C1 -6 monovalent aliphatic hydrocarbon groups in component (C) include C1 -6 alkyl groups such as methyl groups, ethyl groups, propyl groups, butyl groups, and hexyl groups; C2-6 alkenyl groups such as vinyl groups, allyl groups, and hexenyl groups; and C1 -6 halogenated alkyl groups such as 3-chloropropyl groups and 3,3,3-trifluoropropyl groups. Among these, methyl groups are generally preferred.

[0040] Examples of the C6-10 monovalent aromatic hydrocarbon groups in component (C) include phenyl groups, tolyl groups, xylyl groups, and naphthyl groups. Among these, phenyl groups are generally preferred.

[0041] Examples of the monovalent epoxy-substituted organic groups in component (C) include glycidoxyalkyl groups such as 3-glycidoxypropyl groups, 4-glycidoxybutyl groups and 5-glycidoxypentyl groups; 3,4-epoxycycloalkyl alkyl groups such as 2-(3,4- epoxycylohexyl)ethyl, 3-(3,4-epoxycylohexyl)propyl, 2-(3,4-epoxy-3-methylcylohexyl)-2- methylethyl, 2-(2,3-epoxycylopentyl)ethyl, and 3-(2,3-epoxycylopentyl)propyl; and epoxyalkyl groups such as 2,3-epoxypropyl groups, 3,4-epoxybutyl groups, and 4,5-epoxypentyl groups. Among these, 3,4-epoxycycloalkyl alkyl groups are generally preferred.

[0042] In component (C), at least about 15 mol%, optionally at least about 20 mol%, or optionally at least about 25 mol%, of the total R12are the C6-10 monovalent aromatic hydrocarbon groups. If the content of the monovalent aromatic hydrocarbon groups is greater than or equal to the lower limit described above, the optical transmittance of the cured product can increase as well as mechanical properties thereof increase.

[0043] In the formula, "a", "b", "c", and "d" are mole fractions and numbers that satisfy the following conditions: 0<a<0.4, 0<b<0.5, 0<c<1 , 0<d<0.4, 0.1 <b / c<0.6, and a+b+c+d=1 , optionally a=0, 0<b<0.5, 0<c<1 , 0<d<0.2, 0.1 <b / c<0.6, and b+c+d=1 , or optionally a=0, 0<b<0.5, 0<c<1 , d=0, 0.1 <b / c<0.6, and b+c=1 . "a" is 0<a<0.4, optionally 0<a<0.2, or optionally a=0, because the molecular weight of the epoxy-containing organopolysiloxane resin (C) drops when there are too many (R123SiOi / 2) siloxane units, and, when (SiO4 / s) siloxane units are introduced, the hardness of the cured product of the epoxy-functional silicone resin (C) is markedly increased and the product can be easily rendered brittle. For this reason, "d" is 0<d<0.4, optionally 0<d<0.2, or optionally d=0. In addition, the molar ratio "b / c" of the (R122SiO2 / 2) units and (R12SiO3 / 2) units can be not less than about 0.1 and not more than about 0.6. In some examples, deviation from this range in the manufacture of the epoxy-functional silicone resin (C) can result in generation of insoluble side products, in making the product more prone to cracking due to decreased toughness, or in a decrease in the strength and elasticity of the product and making it more prone to scratching. In some examples, the range molar ratio "b / c" is more than about 0.1 and not more than about 0.6. The epoxy-functional silicone resin (C) contains the (R122SiO2 / 2) siloxane units and the (R12SiO3 / 2) siloxane units, and its molecular structure is in most cases a network structure or a three-dimensional structure because the molar ratio of "b / c" is more than about 0.1 and not more than about 0.6. Thus, in the epoxy-functional silicone resin (C), the (R122SiO2 / 2) siloxane units and the (R12SiO3 / 2) siloxane units are present, whereas the (R123SiOi / 2) siloxane units and the (SiO4 / 2)siloxane units are optional constituent units. That is, there can be epoxy-functional silicone resins including the following average unit formulas:(R122SiO2 / 2)b(R12SiO3 / 2)c(R123SiOi / 2)a(R122SiO2 / 2)b (R12SiO3 / 2)c(R122SiO2 / 2)b(R12SiO3 / 2)c(SiO4 / 2)d(R123SiOi / 2)a(R122SiO2 / 2)b(R12SiO3 / 2)c(SiO4 / 2)d.

[0044] In component (C), about 2 to about 30 mol% of siloxane units, optionally about 10 mol% to about 30 mol%, or optionally about 15 mol% to about 30 mol%, of all the siloxane units in a molecule have epoxy-substituted organic groups. If there is greater than or equal to the lower limit of the range mentioned above of such siloxane units, the density of cross-linking during curing can increase. On the other hand, the amount is less than or equal to the upper limit of the range mentioned above can be suitable because it can bring about an increase in the optical transmittance and heat resistance of the cured product. In the epoxy-functional monovalent hydrocarbon groups, the epoxy groups can be bonded to silicon atoms through alkylene groups, such that these epoxy groups are not directly bonded to the silicon atoms. The epoxy-functional silicone resin (C) can be produced by well-known conventional manufacturing methods.

[0045] While there are no particular limitations concerning the weight-average molecular weight of the epoxy-functional silicone resin (C), if the toughness of the cured product and its solubility in organic solvents are taken into consideration, in some embodiments the molecular weight is not less than about 103and not more than about 106. In one embodiment, the epoxyfunctional silicone resin (C) includes a combination of two or more kinds of such epoxyfunctional silicone resins with different content and type of the epoxy-containing organic groups and monovalent hydrocarbon groups or with different molecular weights.

[0046] Component (D) is an epoxy-functional silicone represented by the following general formula:X1-R132SiO(SiR132O)mSiR132-X1.

[0047] In the formula, R13each independently represents a C1 -6 monovalent aliphatic hydrocarbon group, or a C6-10 monovalent aromatic hydrocarbon group; X1each independently represents a monovalent epoxy-substituted organic group, or an epoxyfunctional siloxy group represented by the following general formula:X2-R142SiO(SiR142O)xSiR142-R15-.

[0048] Examples of the C1 -6 monovalent aliphatic hydrocarbon groups in component (D) include C1 -6 alkyl groups such as methyl groups, ethyl groups, propyl groups, butyl groups, and hexyl groups; C2-6 alkenyl groups such as vinyl groups, allyl groups, and hexenyl groups;and C1 -6 halogenated alkyl groups such as 3-chloropropyl groups and 3,3,3-trifluoropropyl groups. Among these, methyl groups are generally preferred.

[0049] Examples of the C6-10 monovalent aromatic hydrocarbon groups in component (D) include phenyl groups, tolyl groups, xylyl groups, and naphthyl groups. Among these, phenyl groups are generally preferred.

[0050] Examples of the monovalent epoxy-substituted organic groups for X1include glycidoxyalkyl groups such as 3-glycidoxypropyl groups, 4-glycidoxybutyl groups and 5- glycidoxypentyl groups; 3,4-epoxycycloalkyl alkyl groups such as 2-(3,4-epoxycylohexyl)ethyl, 3-(3,4-epoxycylohexyl)propyl, 2-(3,4-epoxy-3-methylcylohexyl)-2-methylethyl, 2-(2,3- epoxycylopentyl)ethyl, and 3-(2,3-epoxycylopentyl)propyl; and epoxyalkyl groups such as 2,3- epoxypropyl groups, 3,4-epoxybutyl groups, and 4,5-epoxypentyl groups. Among these, 3,4- epoxycycloalkyl alkyl groups are generally preferred.

[0051] In the general formula above, each R14is the same or different C1 -6 monovalent aliphatic hydrocarbon group. Examples of the C1 -6 monovalent aliphatic hydrocarbon groups for R14include C1 -6 alkyl groups such as methyl groups, ethyl groups, propyl groups, butyl groups, and hexyl groups; C2-6 alkenyl groups such as vinyl groups, allyl groups, and hexenyl groups; and C1-6 halogenated alkyl groups such as 3-chloropropyl groups and 3,3,3- trifluoropropyl groups. Among these, methyl groups are generally preferred.

[0052] In the general formula above, R15is a C2-6 alkylene group. Examples of the C2-6 alkylene groups for R15include ethylene groups, methylethylene groups, propylene groups, butylene group, and hexylene groups. Among these, ethylene groups are generally preferred.

[0053] In the general formula above, X2is a monovalent epoxy-substituted organic group. Examples of the monovalent epoxy-substituted organic groups for X2include glycidoxyalkyl groups such as 3-glycidoxypropyl groups, 4-glycidoxybutyl groups and 5-glycidoxypentyl groups; 3,4-epoxycycloalkyl alkyl groups such as 2-(3,4-epoxycylohexyl)ethyl, 3-(3,4- epoxycylohexyl)propyl, 2-(3,4-epoxy-3-methylcylohexyl)-2-methylethyl, 2-(2,3- epoxycylopentyl)ethyl, and 3-(2,3-epoxycylopentyl)propyl; and epoxyalkyl groups such as 2,3- epoxypropyl groups, 3,4-epoxybutyl groups, and 4,5-epoxypentyl groups. Among these, 3,4- epoxycycloalkyl alkyl groups are generally preferred.

[0054] In the general formula above, "x" is a number of from about 0 to about 5, optionally from about 0 to about 2, or optionally about 0.

[0055] In the general formula above, "m" is a number of from about 0 to about 100, optionally from about 0 to about 20, or optionally from about 0 to about 10. If "m" is less than or equal to the upper limit of the range described above, mechanical strength of the cured product can increase.

[0056] The state of component (D) at 25qC is not limited, but it is generally a liquid. The viscosity at 25qC of component (D) is not limited; however, the viscosity is generally in a range of from about 5 to about 100 mPa s. Note that in the present specification, viscosity is the value measured using a type B viscometer according to ASTM D 1084 at 23 ± 2 °C.

[0057] Component (E) is a cationic photoinitiator used as a photoinitiator for epoxy-functional silicone, which is an iodonium salt type cationic photoinitiator.

[0058] The iodonium salt type cationic photoinitiator is not limited, and an example thereof may be a compound having a structure represented by the following general formula: R162I+X-.

[0059] In the formula, R16each independently represents a C1 -6 alkyl group, C6-24 aryl group, or a substituted C6-24 aryl group; and X- represents a non-nucleophilic non-basic anion.

[0060] In the formula, R16can stand for methyl, ethyl, propyl, butyl, and other C1 -6 alkyl groups; phenyl, naphthyl, biphenyl, tolyl, propylphenyl, decylphenyl, dodecylphenyl, and other C6-24 aryl groups; or alkyl group, aryl group, alkoxy group, mercapto atom, oxygen atom, or other heteroatom-substituted aryl groups, and X- in the formula can represent SbF6_, AsF6_, PF6_, BF4_, B(CeF5)4 , HSC -, CIC -, CF3SO3-, nonafluorobutanesulfonate, tris (pentafluoroethyl) trifluorophosphate, tris (heptafluoropropyl) trifluorophosphate, tris (nonafluoroisobutyl) trifluoro phosphate, bis (nonafluorobutyl isobutyl) tetrafluoro phosphate, and other non-nucleophilic non-basic anions.

[0061] In the formula, each R16is preferably C6-24 aryl group; or alkyl group or alkoxy groupsubstituted aryl groups. Specific examples of the cation moiety of the diaryliodonium salt include diphenyliodonium, 4-isopropyl-4'-methyldiphenyliodonium, 4-methyl-4'-methyl- propyldiphenyliodonium, bis(4-tert-butylphenyl)iodonium, 4-methoxyphenyphenyliodonium.

[0062] Specific examples of the iodonium salt type cationic photoinitiator include compounds represented by the following formulas:

[0063] In the formulae above, “Me”, “i-Pr,” and “t-Bu” respectively indicates methyl group, isopropyl group, and tert-butyl group; and X- is the same as mentioned above.

[0064] Specific trade names of the iodonium salt type cationic photoinitiator include TR-PAG- 30101 , 30201 , 30408, 30401 s, and 31102 (manufactured by TRONYL), and the like.

[0065] Component (F) is a cationic photoinitiator other than the aforementioned component (E), which is a photoinitiator for LIV thiol-ene cure. This component enables the composition of the present invention enter LIV B-stage by cure of thiol-ene in the composition, i.e., components (A) and (B).

[0066] In a formulation that includes both a photoacid generator (PAG) and a heat-activated generator (HAG) to achieve UV B-stage and heat dual cure, it was observed that UV irradiation does not result in B-stage where the modulus does not change over time until exposed to heat cure conditions. Varying the UV irradiation time also did not have an impact on stabilizing the storage modulus.

[0067] The composition of the present invention requires to be UV and heat curable, stable modulus over time after UV cure (B-stageable), and increased modulus at C-stage (heat cure) upon exposing B-staged material to heat. It was found that combining a cure system that is orthogonal to Silicone-Epoxy results in B-stage properties unavailable to Si-Ep alone.

[0068] Examples of component (F) include alpha-hydroxyketone and derivatives based on (1 -hydroxy-cyclohexyl-phenyl-ketone; 2-hydroxy-2-methyl-1 -phenyl-1 -propanone; 2-hydroxy-1 -[4-(2-hydroxyethoxy)phenyl]-2-methyl-1 -propanone); phenylglyoxylate and derivatives based on (methylbenzoylformate; oxy-phenyl-acetic acid 2-[2 oxo-2 oxy-phenyl-acetic acid 2- [2 oxo-2 phenyl-acetoxy-ethoxy]-ethyl ester and oxy-phenyl-acetic 2-[2-hydroxy-ethoxy]-ethyl ester); benzyldimethyl-ketal and derivatives based on (alpha, alpha-dimethoxy-alpha- phenylacetophenone). alpha-aminoketone and derivatives based on (2-benzyl-2- (dimethylamino)-l -[4-(4-morpholinyl)phenyl]-1 -butanone; 2-methyl-1 -[4-(methylthio)phenyl]-2-(4-morpholinyl)-1 -propanone / IRGACURE 369 (30 wt %)+IRGACURE 651 (70 wt %); mono acyl phosphine (MAPO) and derivatives based on (diphenyl(2,4,6-trimethylbenzoyl)- phosphine oxide. MAPO alpha-hydroxyketone and derivatives based on DAROCUR TPO (50 wt %)+DAROCUR 1173 (50 wt %); bis acyl phosphine (BAPO) and derivatives based on phosphine oxide, phenyl bis(2,4,6-trimethyl benzoyl); BAPO Dispersion based on (IRGACURE 819 (45% active) dispersed in water); BAPO / alpha-hydroxyketone (IRGACURE 819 (20 wt %)+DAROCUR 1173 (80 wt %); metallocene(Bis(eta 5-2,4-cyclopentadien-1 -yl), bis[2,6-difluoro-3-(1 H-pyrrol-1 -yl), phenyl]titanium), etc.

[0069] In one embodiment of the present invention, 2-hydroxy-2-methyl-1 -phenyl-1 - propanone may be used for component (F).

[0070] The present composition comprises components (A) to (F) described above; however, to impart better mechanical strength to a cured product of the present composition, (G) an adhesion promoter, and / or a photosensitizer, and / or an alcohol can be contained.

[0071] Component (G) is an adhesion promoter. Examples of adhesion promoters include epoxy-functional alkoxysilane such as 3-glycidoxypropyltrimethoxysilane, 3- glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyldimethoxysilane, 2-(3,4- epoxycyclohexyl)ethyldiethoxysilane and combinations thereof; unsaturated alkoxysilanes such as vinyltrimethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, hexenyltrimethoxysilane, undecylenyltrimethoxysilane, 3-methacryloyloxypropyl trimethoxysilane, 3-methacryloyloxypropyl triethoxysilane, 3-acryloyloxypropyl trimethoxysilane, 3-acryloyloxypropyl triethoxysilane, and combinations thereof; an epoxyfunctional siloxane with silicon atom-bonded alkoxy groups such as a reaction product of a hydroxy-terminated polyorganosiloxane with an epoxy-functional alkoxysilane (e.g. such as one of those described above), or a physical blend of the hydroxy-terminated polyorganosiloxane with the epoxy-functional alkoxysilane. The adhesion promoter may comprise a combination of an epoxy-functional alkoxysilane and an epoxy-functional siloxane. For example, the adhesion promoter is exemplified by a mixture of 3- glycidoxypropyltrimethoxysilane and a reaction product of hydroxy-terminated methylvinylsiloxane with 3-glycidoxypropyltrimethoxysilane, or a mixture of 3- glycidoxypropyltrimethoxysilane and a hydroxy-terminated methylvinylsiloxane, or a mixture of 3-glycidoxypropyltrimethoxysilane and a hydroxy-terminated methylvinyl / dimethylsiloxane copolymer.

[0072] The content of component (G) is not limited, but it is generally in an amount of from about 0.01 to about 5 mass%, or optionally in an amount of from about 0.1 to about 2 mass%, of the total mass of components (A) to (F). If the content of component (G) is greater than or equal to the lower limit of the range described above, adhesion properties of the cured product can increase. On the other hand, it is less than or equal to the upper limit of the range described above, mechanical properties of the cured product can increase.

[0073] Examples of the photosensitizers include isopropyl-9H-thioxanthen-9-one, anthrone, 1 -hydroxycyclohexyl-phenylketone, 2,4-diethyl-9H-thioxanthen-9-one, 2-isopropyl thioxanthene, 2-hydroxy-2-methyl-phenylpropan-1 -one, 2,6-bis( 1 ,1 -dimethylethyl)-4- methylphenol (BHT), pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert- butyl-4- hydroxyphenyl)propionate, 2,4-dimethyl-6-(1 -methylpentadecyl)phenol, diethyl[{3,5- bis(1 ,1 -di-tert-butyl-4-hydroxyphenyl)methyl}phosphonate, 33',3",5,5',5"-hexane-tert-butyl-4- a,a',a"-(mesitylene-2,4,6-tolyl)tri-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], and hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0074] Examples of the alcohol include monovalent alcohols such as ethyl alcohol, isopropyl alcohol, isobutyl alcohol, 1 -decanol, 1 -dodecanol, 1 -octanol, oleyl alcohol, 1 -hexadecanol, and stearyl alcohol; and multivalent alcohols such as ethylene glycol, diethylene glycol, propylene glycol, 1 ,10-decanediol, glycerol, and pentaerythritol.

[0075] The present composition can be cured by irradiation of UV ray (or ultraviolet (“UV”) light). For example, low pressure, high pressure or ultrahigh pressure mercury lamp, metal halide lamp, (pulse) xenon lamp, or an electrodeless lamp is useful as an UV lamp. Irradiation dose is generally in a range of from about 5 to about 6,000 mJ / cm2, or optionally in a range of from about 10 to about 4,000 mJ / cm2.<Cured product>

[0076] The present composition forms a cured product when cured by irradiation with UV ray. This cured product according to the present invention has a hardness, as measured using Shore D hardness specified in ASTM D2240, in the range from at least 20 to not more than 95, typically in the range from at least 30 to not more than 80, and more typically in the range from at least 30 to not more than 70. The reasons for this are as follows: the cured product may have insufficient strength when its hardness is less than the lower limit for the cited range; when, on the other hand, the upper limit for the cited range is exceeded, the flexibility of the cured product under consideration tends to be inadequate.

[0077] In order to exhibit a satisfactory flexibility, this cured product may have an elongation as specified in ASTM D412 of at least 10%. The reason for this is that the flexibility of the cured product becomes unsatisfactory at below the indicated range.

[0078] The cured product of the present invention, because it is demonstrates reliable B- stage properties and tunable adhesion, is useful as a member or component for semiconductor packaging. The uncured product of the present invention is useful as a member or component of a liquid type adhesive that can be spin coated to silicon wafers to achieve thin bondline thicknesses below 5 micrometers that must demonstrate B-stage property upon an initial light cure process, e.g., visible light, infrared, ultraviolet, far ultraviolet, x-ray, laser, and so forth, for ease of a die preparation process. The B-stage cured product of the present invention is useful as a member or component that must demonstrate adhesive properties that allows for a die stacking process.Examples

[0079] The curable silicone composition and cured product of the present invention will now be described in detail using Practical and Comparative Examples. Note that, in the formulas, "Me", "Pr", "Vi", "Ph", "Gly" and "Ep" respectively indicates methyl group, propyl group, vinyl group, phenyl group, 3-glycidoxypropyl group and 2-(3,4-epoxycyclohexyl)ethyl group. The structure of the silicone resins used in the examples was determined by conducting1H NMRand29Si NMR measurements. The weight-average molecular weight of the silicone resins was calculated using GPC based on comparison with polystyrene standards. The specifications of UV cure, high temperature cure, hardness, viscosity, modulus, and B-stage property are as follows.<UV cure>

[0080] All samples were cured by LED UV (Firejet FJ800) equipment with 365 nm and energy 5,000 mJ / cm2dosage of UVA.<High temperature cure>

[0081] After UV irradiation, all samples were immediately cured in the oven set at 150 °C for 60 mins.<Hardness>

[0082] Hardness is measured by durometer (Shore D) and cured samples were prepared by the thickness over 6 mm and surface of cured sample was made as flat as possible to reduce variances. Hardness was measured at least 3 points of the flat surface and used the average hardness value.<Viscosity>

[0083] Viscosities for all samples were measured using Brookfield cone and plate viscometer (HADV-III U) with the cone spindle CP-52. Measuring temperature was 25 ± 0.2 °C and sample were measured with a speed that torque had between 50 to 70%.<Modulus>

[0084] Modulus for all samples were measured using Anton Parr Modular Compact Rheometer (MCR 502) with torsion rectangular setting. Measurement oscillation was 0.01% 1 Hz with 0.5 N normal force. Temperature range was between -60 to 250 °C, with heating rate of 10°C / min. Modulus was measured in presence of UV irradiation and after UV irradiation was terminated.<B-stage property>

[0085] Measurement of B-stage property was achieved by applying a liquid sample on Anton Parr Modular Compact Rheometer (MCR 502) with 7 mm spindle equipped with UV irradiation accessory. Measurement oscillation was 0.1 % 1 Hz with 0.5 N normal force. UV irradiation accessory (OmniCure Series 2000) was used to irradiate the sample during modulus measurement to monitor modulus change during UV cure. Measurement of B-stage retention property was measured by preparing UV-cured torsion rectangular sample (5,000 mJ 365 nm UV LED, 2 mm thickness, 10x45 mm) and measuring change in modulus over time.<Practical Example 1 >

[0086] A UV & heat B-stageable organopolysiloxane composition was prepared by blending siloxane resin (C) 22.50 parts by mass, epoxy functional cross-linker (D) 50.00 parts by mass,siloxane polymer (A) 20.00 parts by mass, S-H Cross-linker (B) 1.50 parts by mass, photoinitiator (F) 1 .00 parts by mass, and HAG (E) 5.00 parts by mass. The mixture was mixed at 1 ,500 rpm for 2 minutes under vacuum. Well mixed sample was packaged in 30 mL syringes and vacuum sealed. Essential properties (viscosity, modulus, etc.) were measured and then samples were stored at negative temperature (-5°C).<Practical Examples 2 to 5>

[0087] Sample was prepared with the same methods as Practical Example 1 , except varying amounts as listed in Table 3 of formulations below. Practical Examples 2-5 exemplify the ability of this technology in controlling desired modulus at B-stage by varying the SH / Vi and thiolene / Si-Ep ratio.<Comparative Example 1 >

[0088] A UV & heat curable organopolysiloxane composition was prepared by blending siloxane resin (C) 20.00 parts by mass, epoxy functional cross-linker (D) 70.00 parts by mass, PAG 5.00 parts by mass, and HAG solution (HAG: epoxy functional cross-linker (C) = 1 :9) (E) 5.00 parts by mass. The mixture was mixed at 1 ,500 rpm for 2 minutes under vacuum. Well mixed sample was packaged in 30 mL syringes and vacuum sealed. Essential properties (viscosity, modulus, etc.) were measured and then samples were stored at negative temperature (-5 °C).

[0089] The components in Table 1 were used to prepare the curable silicone compositions of the Practical and Comparative Examples.[Table 1][Table 2][Table 3] - Part 1 of 2[Table 3] - Part 2 of 2[Table 4]

[0090] B-stageable silicone compositions of Examples 1 to 5 resulted in low viscosity material, ranging from 154 to 185 cP. After UV irradiation was terminated, modulus change over time of Example 1 was stable as shown in Figure 1 exemplifying B-stage property allowing for processability. Less than 10% increase in modulus after achieving saturated modulus as shown in Figure 1 demonstrated B-stage property. Hardness measurements showed the softness of B-stage material (Shore 0.0 of 62 to 91 ), which hardened greatly after heat cure (Shore D of 70 to 77). Modulus measurements also correlate to hardness, where B- stage modulus (1.16 to 17.3 MPa) increased after heat cure (189 to 443 MPa). Such large differences in B-stage and final cure hardness and modulus also match the success criteria for B-stageable material.

[0091] On the contrary, Comparative Example 1 aimed to obtain B-stageable Si-Ep material by adding PAG and HAG to initiate UV cure and then heat cure in a stepwise process. However, upon UV irradiation the modulus continuously increased over time as shown in Figure 1 . This demonstrates that Si-Ep alone cannot achieve B-stage property due to the uncontrollable epoxy cure. Hardness and modulus measurement after UV irradiation and heat cure resulted in insignificant differences, also exemplifying the unsuccessful B-stage capability.Industrial Applicability

[0092] The curable silicone composition of the present invention can be cured by irradiation with UV ray. Therefore, the present composition is useful as various adhesives, encapsulants, coating agents, and the like of electric / electronic parts.

Claims

CLAIMS1 . A curable silicone composition comprising:(A) an organopolysiloxane comprising an average of two or more alkenyl groups represented by the following general formula:wherein R1and R8each independently represent a C2-30 alkenyl group; R2to R7each independently represent a C1 -30 monovalent aliphatic hydrocarbon group, or a C6-30 monovalent aromatic hydrocarbon group; and "n" is an integer of from 0 to 100;(B) a crosslinker with an average of three or more mercapto groups represented by the following general formula:wherein R9each independently represents a C1-30 monovalent aliphatic hydrocarbon group, or a C6-30 monovalent aromatic hydrocarbon group; R10each independently represents a C1-30 divalent aliphatic hydrocarbon group, or a C6-30 divalent aromatic hydrocarbon group; and R11each independently represents a mercapto group or a C1-6 alkyl group, provided that at least three of the R11,s are mercapto groups;(C) an epoxy-functional silicone resin represented by the following average unit formula: (R123SiOi / 2)a(R122SiO2 / 2)b(R12SiO3 / 2)c(SiO4 / 2)dwherein R12each independently represents a C1 -6 monovalent aliphatic hydrocarbon group, a C6-10 monovalent aromatic hydrocarbon group, or a monovalent epoxy-substituted organic group, provided that at least about 15 mol% of the total R12are C6-10 monovalent aromatic hydrocarbon groups; and "a", "b", "c" and "d" are numbers that satisfy the following conditions: 0<a<0.4, 0<b<0.5, 0<c<1 , 0<d<0.4, 0.1 <b / c<0.6, and a+b+c+d=1; and about 2 to about 30 mol% of the total siloxane units have the monovalent epoxy-substituted organic groups;(D) an epoxy-functional silicone represented by the following general formula:X1-R132SiO(SiR132O)mSiR132-X1wherein R13each independently represents a C1 -6 monovalent aliphatic hydrocarbon group, or a C6-10 monovalent aromatic hydrocarbon group; X1each independently represents a monovalent epoxy-substituted organic group, or an epoxyfunctional siloxy group represented by the following general formula:X2-R142SiO(SiR142O)xSiR142-R15- wherein R14each independently represents a C1 -6 monovalent aliphatic hydrocarbon group; R15represents a C2-6 alkylene group; X2represents a monovalent epoxy-substituted organic group; "x" represents a number of from 0 to 5; and "m" represents a number of from 0 to 100;(E) an iodonium salt type cationic photoinitiator; and(F) a cationic photoinitiator other than component (E).

2. The curable silicone composition according to claim 1 , wherein in component (A), R1and R8each independently represent a vinyl group; R2, R3, R6, and R7each independently represent a C1 -6 alkyl group; R4and R5each independently represent a C6-12 aryl group; and "n" is an integer of from 0 to 40.

3. The curable silicone composition according to claim 1 , wherein in component (B), R9each independently represents a C1 -6 alkyl group; R10each independently represents a C1 - 6 alkylene group; and R11each independently represents a mercapto group.

4. The curable silicone composition according to claim 1 , wherein the monovalent epoxy-substituted organic groups in component (C) are groups selected from glycidoxyalkyl groups, 3,4-epoxycyclohexylalkyl groups, and epoxyalkyl groups.

5. The curable silicone composition according to claim 1 , wherein the monovalent epoxy-substituted organic groups in component (D) are groups selected from glycidoxyalkyl groups, 3,4-epoxycyclohexylalkyl groups, and epoxyalkyl groups.

6. The curable silicone composition according to claim 1 , wherein component (E) is an iodonium salt type cationic photoinitiator having a structure represented by the following general formula: R162l+X_wherein, R16each independently represents a C1 -6 alkyl group, C6-24 aryl group, or a substituted C6-24 aryl group; and X- represents a non-nucleophilic non-basic anion.

7. The curable silicone composition according to any one of claims 1 to 6, further comprising:(G) an adhesion promoter, in an amount of from about 0.01 to about 5 mass% of the total mass of components (A) to (F).

8. A cured product obtained by curing the curable silicone composition according to any one of claims 1 to 8.

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