UV curable silicone composition

Abstract

The present disclosure relates to a UV curable silicone composition comprising: (A) a branched organopolysiloxane having, per molecule, at least one alkenyl group bearing from 2 to 12 carbon atoms and at least one aryl group bearing from 6 to 12 carbon atoms; (B) a linear organopolysiloxane having, per molecule, at least two alkenyl groups having 2 to 12 carbon atoms and at least one aryl group having 6 to 12 carbon atoms; (C) an organosiloxane having, per molecule, at least two silicon-bonded hydrogen atoms and at least one aryl group bearing 6 to 12 carbon atoms; and (D) a photoactivated hydrosilylation reaction catalyst; wherein the content of total aryl groups in components (A) to (C) is at least 35 mass% of the total mass of components (A) to (C). The composition has a good useful life and cures by irradiation with ultraviolet rays to form a Grade B material, where the Grade B material exhibits slow gelation time, but can be fully cured at low temperatures (e.g., 75 DEG C or less).

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the priority and all the benefits of U.S. Provisional Patent Application No. 63 / 430,167, filed on December 05, 2022, the content of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to a UV - curable silicone composition. Background Art

[0004] When irradiated with ultraviolet light, the UV - curable silicone composition cures to form a cured product having excellent heat resistance, electrical insulation properties, and weather resistance. Therefore, the UV - curable silicone composition is widely used as a protective coating agent, an encapsulant, or a sealant for electrical / electronic devices.

[0005] For example, Patent Document 1 discloses a UV-curable silicone composition, which comprises: an organopolysiloxane having on average at least two silicon-bonded alkenyl groups per molecule, a silicone compound having on average at least two silicon-bonded hydrogen atoms per molecule, and a photoactivated hydrosilylation reaction catalyst; Patent Document 2 discloses a UV-curable silicone composition, which comprises: a branched organopolysiloxane having a vinyl group or an allyl group and having 5 to 300 continuously repeating D siloxane units, an organohydrogenpolysiloxane having a resin structure and having 5 to 300 continuously repeating D siloxane units, and a photoactive catalyst; Patent Document 3 discloses a UV-curable silicone composition, which comprises: a silicone compound having on average at least two silicon-bonded ethylenically unsaturated groups and at least one silicon-bonded phenyl group per molecule, a silicone compound having on average at least two silicon-bonded hydrogen atoms per molecule, a photoactivated hydrosilylation catalyst, and optionally a filler; Patent Document 4 discloses a UV-curable silicone composition, which comprises: a linear organopolysiloxane having two alkenyl groups and at least two aryl groups per molecule, an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule, a platinum metal catalyst activated by light having a wavelength between 200 nm and 500 nm, and a compound having one terminal alkenyl group per molecule; and Patent Document 5 discloses a UV-curable silicone composition, which comprises: a compound containing at least one aliphatic unsaturated monovalent hydrocarbon group in the molecule, a compound containing at least two hydrogen atoms bonded to silicon atoms in the molecule, a first hydrosilylation catalyst that exhibits activity in the composition without exposure to high-energy radiation, and a second hydrosilylation catalyst that does not exhibit activity unless exposed to high-energy radiation and exhibits activity in the composition by exposure to high-energy radiation.

[0006] Recently, UV-curable silicone compositions need to be initiated by UV light and remain in a non-flowable state for several hours at room temperature, waiting for the next process. Materials with a non-flowable state (i.e., "class B-like") need to remain in a gel state after UV irradiation during the working (or processing) time. In addition, UV-curable silicone compositions need to be easy to use, such as one-component compositions, and preferably cure within 30 minutes at a low temperature (e.g., 75 °C or lower) to achieve good processability and less module damage caused by high temperature. Finally, since soft materials cannot protect the circuits on plastics and maintain a bent shape, it is best to use fully cured silicone materials to obtain good hardness.

[0007] However, these UV-curable silicone compositions have several problems. For example, they have a short pot life and a significant increase in their viscosity at RT and cure too quickly after UV irradiation. In addition, they cannot be fully cured at 75 °C within 30 minutes.

[0008] Prior art documents

[0009] Patent documents

[0010] Patent Document 1: US Patent Application Publication No. 2003 / 0235383 A1

[0011] Patent Document 2: US Patent Application Publication No. 2013 / 0183776 A1

[0012] Patent Document 3: US Patent Application Publication No. 2017 / 0283655 A1

[0013] Patent Document 4: European Patent Application Publication No. 3-862-405 A1

[0014] Patent Document 5: US Patent Application Publication No. 2021 / 0179849 A1 Summary of the Invention

[0015] Technical problems

[0016] An object of the present invention is to provide a UV-curable silicone composition having a good pot life and cured by irradiation with ultraviolet light to form a Class B material, wherein the Class B material exhibits a slow gel time and can be fully cured at a low temperature (e.g., 75 °C or lower).

[0017] Solutions to the problems

[0018] The UV-curable silicone composition of the present invention comprises:

[0019] (A) a branched organopolysiloxane having at least one alkenyl group with 2 to 12 carbon atoms and at least one aryl group with 6 to 12 carbon atoms per molecule;

[0020] (B) a linear organopolysiloxane having at least two alkenyl groups with 2 to 12 carbon atoms and at least one aryl group with 6 to 12 carbon atoms per molecule;

[0021] (C) an organosiloxane having at least two silicon-bonded hydrogen atoms and at least one aryl group with 6 to 12 carbon atoms per molecule, the amount of the organosiloxane being such that the silicon-bonded hydrogen atoms in component (C) are 0.1 mole to 10 moles relative to 1 mole of alkenyl groups in components (A) and (B); and

[0022] (D) A catalytic amount of a photoactivated hydrosilylation reaction catalyst;

[0023] (E) The content of the total aryl groups in components (A) to (C) is at least 35% by mass of the total mass of components (A) to (C).

[0024] In various embodiments, component (B) is a branched organic polysiloxane represented by the following average unit formula:

[0025] (R 1 3 SiO 1 / 2 ) a (R 1 2 SiO 1 / 2 ) b (R 2 SiO 3 / 2 ) c (HO 1 / 2 ) d

[0026] where each R 1 is independently an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, provided that at least one R in the molecule 1 is an alkenyl group; R 2 is an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, provided that at least one R in the molecule 2 is an aryl group; and "a", "b", "c", and "d" are numbers satisfying the following conditions: 0 < a ≤ 0.3, 0 ≤ b ≤ 0.2, 0.5 ≤ c ≤ 0.9, 0 ≤ d ≤ 0.05 and a + b + c = 1.

[0027] In various embodiments, component (B) is a linear organic polysiloxane represented by the following general formula:

[0028] R 3 3 SiO(R 3 2 ) m SiR 3 3

[0029] where each R 3 is independently an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, provided that at least two Rs in the molecule 3is an alkenyl group and at least one R in the molecule 3 is an aryl group; and "m" is an integer from 10 to 1000.

[0030] In various embodiments, component (C) is an organosiloxane represented by the following general formula:

[0031] HR 4 2 SiO(R 4 2 SiO) n SiR 4 2 H

[0032] where each R 4 is independently an alkyl group or an aryl group, provided that at least one R 4 is an aryl group; and "n" is an integer from 0 to 10.

[0033] In various embodiments, the composition further comprises: (E) a hydrosilylation reaction inhibitor, and in this component, the amount of the hydrosilylation reaction inhibitor is 0.1 ppm to 10,000 ppm in terms of mass unit relative to the total mass of components (A) to (C).

[0034] In various embodiments, the composition further comprises: (F) an adhesion promoter, and the amount of the adhesion promoter is at most 10 parts by mass relative to 100 parts by mass of the total mass of components (A) to (C).

[0035] In various embodiments, the composition further comprises: (G) a silica filler, and the amount of the silica filler is 0.1 part by mass to 10 parts by mass relative to 100 parts by mass of the total mass of components (A) to (C).

[0036] Advantages of the invention

[0037] The UV-curable silicone composition of the present invention has a good pot life and is cured by irradiation with ultraviolet light to form a Class B material, where the Class B material exhibits a slow gel time, yet can be completely cured at a low temperature (e.g., 75 °C or lower).

[0038] Definition

[0039] The term "comprising" or "containing" is used herein in its broadest sense and means and encompasses the concepts of "including", "consisting essentially of", and "consisting of". The use of "for example", "for instance", "such as", and "including" to list exemplary examples does not mean limitation to the examples listed. 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. As used herein, the term "about" is used to reasonably cover or describe minor variations in values measured by instrumental analysis or as a result of sample handling. Such minor variations can be about ±0-25%, ±0-10%, ±0-5%, or ±0-2.5% of the value. Additionally, the term "about" applies to both values when associated with a range of values. Further, the term "about" applies to a value even when not explicitly stated.

[0040] It should be understood that the appended claims are not limited to the specific and particular compounds, compositions, or methods described in the specific embodiments, which may vary between specific embodiments falling within the scope of the appended claims. With respect to any Markush group relied upon herein to describe specific features or aspects of various embodiments, it should be understood that different, special, and / or unexpected results can be obtained from each member of the corresponding Markush group independent of all other Markush members. Each member of the Markush group can be relied upon individually and / or in combination and provides sufficient support for specific embodiments within the scope of the appended claims.

[0041] It should also be understood that any ranges and sub-ranges relied upon in describing various embodiments of the present invention independently and collectively fall within the scope of the appended claims, and it should be understood that all ranges, including integral values and / or fractional values therein, are described and contemplated, even if such values are not explicitly written herein. Those skilled in the art will readily recognize that the recited ranges and sub-ranges fully describe and enable the various embodiments of the present invention, and such ranges and sub-ranges can be further delineated into related one-half, one-third, one-fourth, one-fifth, etc. By way of example only, the range of "0.1 to 0.9" can be further delineated into the lower one-third (i.e., 0.1 to 0.3), the middle one-third (i.e., 0.4 to 0.6), and the upper one-third (i.e., 0.7 to 0.9), which independently and collectively fall within the scope of the appended claims and can be individually and / or collectively relied upon and provide sufficient support for specific embodiments within the scope of the appended claims. In addition, with respect to language that limits or modifies ranges, such as "at least," "greater than," "less than," and "not exceeding," it should be understood that such language includes sub-ranges and / or upper or lower limits. As another example, the range of "at least 10" inherently includes sub-ranges of at least 10 to 35, at least 10 to 25, 25 to 35, etc., and each sub-range can be individually and / or collectively relied upon and provide sufficient support for specific embodiments within the scope of the appended claims. Finally, the individual numbers within the disclosed ranges can be relied upon and provide sufficient support for specific embodiments within the scope of the appended claims. For example, the range of "1 to 9" includes each individual integer such as 3, as well as individual numbers including a decimal point (or fraction) such as 4.1, which can be relied upon and provide sufficient support for specific embodiments within the scope of the appended claims.

[0042] The term "Class B state" refers to the state of a curing intermediate of a UV-curable silicone composition, where when the UV-curable silicone composition is not fully cured, it swells due to the solvent but is not completely dissolved. And the "Class B product" goes into full cure to form the "Class C product." Detailed Description

[0043] The UV-curable silicone composition of the present invention will be explained in detail.

[0044] Component (A) is a branched organopolysiloxane having at least one alkenyl group with 2 to 12 carbon atoms and at least one aryl group with 6 to 12 carbon atoms per molecule. Examples of the alkenyl group include vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, and dodecenyl group, among which the vinyl group is preferred. Examples of the aryl group include phenyl group, tolyl group, xylyl group, and naphthyl group, among which the phenyl group is preferred. In addition, examples of the groups bonded to the silicon atom other than the alkenyl group and the aryl group in component (A) include alkyl groups with 1 to 12 carbon atoms, such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, and dodecyl group; aralkyl groups with 7 to 20 carbon atoms, such as benzyl group, phenethyl group, and phenylpropyl group; and groups in which some or all of the hydrogen atoms in these groups are substituted by halogen atoms (such as fluorine atom, chlorine atom, or bromine atom). In addition, the silicon atom in component (A) may also have a small amount of hydroxyl groups or alkoxy groups, such as methoxy group or ethoxy group, within the range not detrimental to the object of the present invention.

[0045] Component (A) is usually a branched organopolysiloxane represented by the following average unit formula:

[0046] (R 1 3 SiO 1 / 2 ) a (R 1 2 SiO 1 / 2 ) b (R 2 SiO 3 / 2 ) c (HO 1 / 2 ) d .

[0047] In the above formula, each R 1 is independently an alkyl group with 1 to 12 carbon atoms, an alkenyl group with 2 to 12 carbon atoms, or an aryl group with 6 to 12 carbon atoms, and its examples include the same groups as those described above. However, at least one R 1 in the molecule is an alkenyl group, preferably a vinyl group.

[0048] In the above formula, R 2is an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and examples thereof include the same groups as described above. However, at least one R in the molecule 2 is an aryl group, preferably a phenyl group.

[0049] In the above formula, "a", "b", "c", and "d" are numbers satisfying the following conditions: 0 < a ≤ 0.3, 0 ≤ b ≤ 0.2, 0.5 ≤ c ≤ 0.9, 0 ≤ d ≤ 0.05, and a + b + c = 1, optionally 0.1 ≤ a ≤ 0.5, b = 0, 0.5 ≤ c ≤ 0.9, 0 ≤ d ≤ 0.05, and a + b + c = 1, or optionally 0.1 ≤ a ≤ 0.3, b = 0, 0.7 ≤ c ≤ 0.9, 0 ≤ d ≤ 0.05, and a + b + c = 1. This is because, if "a", "b", "c", and "d" are numbers within the above ranges, the cured product obtained by curing the composition of the present invention will have appropriate hardness and mechanical strength.

[0050] Respectively based on the total mass of components (A) to (C), the amount of component (A) is not limited, but it is usually used in an amount of 60% by mass to 90% by mass, optionally 65% by mass to 90% by mass, optionally 60% by mass to 85% by mass, or optionally 65% by mass to 85% by mass. This is because, if the amount is equal to or higher than the lower limit of the above range, the cured product obtained by curing the composition of the present invention will have appropriate hardness and mechanical strength, and if the amount is equal to or lower than the upper limit of the above range, the composition will have a suitable viscosity at 25°C.

[0051] Component (B) is a linear organopolysiloxane having at least two alkenyl groups having 2 to 12 carbon atoms and at least one aryl group having 6 to 12 carbon atoms per molecule. Component (B) is used to impart good modulus to the cured product obtained by curing the composition. Examples of the alkenyl group include the same groups as described above. Examples of the aryl group include the same groups as described above. In addition, examples of the groups bonded to the silicon atom other than the alkenyl group and the aryl group in component (B) include the same groups as described above. In addition, the silicon atom in component (B) may also have a small amount of hydroxyl groups or alkoxy groups, such as methoxy groups or ethoxy groups, within the range that does not impair the object of the present invention.

[0052] The viscosity of component (B) at 25°C is not limited, but it is usually not more than 100,000 mPa·s, optionally not more than 50,000 mPa·s, or optionally not more than 20,000 mPa·s. It should be noted that in this specification, the viscosity is a value measured using a B-type viscometer according to ASTM D 1084 at 23°C ± 2°C.

[0053] Component (B) is usually a linear organopolysiloxane represented by the following general formula:

[0054] R 3 3 SiO(R 3 2 SiO) m SiR 3 3

[0055] In the above formula, each R 3 is independently an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and examples thereof include the same groups as the above R 1 . However, at least two Rs in the molecule 3 are alkenyl groups and at least one R in the molecule 3 is an aryl group. Usually, at least two Rs in the molecule 3 are vinyl groups and at least one R in the molecule 3 is a phenyl group.

[0056] In the above formula, "m" is an integer from 10 to 1000, optionally an integer from 10 to 500.

[0057] Component (B) is usually at least one selected from the organopolysiloxanes represented by the following formula:

[0058] (CH 2 =CH)(CH 3 ) 2 SiO[(C 6 H 5 ) 2 SiO] m Si(CH 3 ) 2 (CH=CH 2 )

[0059] (CH 2 =CH)(CH 3 ) 2 SiO[(C 6 H 5 ) 2 SiO] m1 [(CH 3 ) 2 SiO] m2 Si(CH 3 ) 2 (CH=CH 2 )

[0060] (CH2 =CH)(CH 3 ) 2 SiO[(C 6 H 5 )(CH 3 )SiO] m1 [(CH 3 ) 2 SiO] m2 Si(CH 3 ) 2 (CH=CH 2 )

[0061] (CH 2 =CH)(CH 3 ) 2 SiO[(C 6 H 5 )(CH 3 )SiO] m Si(CH 3 ) 2 (CH=CH 2 )

[0062] (CH 2 =CH)(CH 3 )(C 6 H 5 )SiO[(C 6 H 5 )(CH 3 )SiO] m1 [(CH 3 ) 2 SiO] m2 Si(CH 3 )(C 6 H 5 ) 2 (CH=CH 2 )

[0063] In the above formula, "m" is as described above, and "m2" is an integer, and "m1" and "m2" are each integers satisfying the following conditions: 10 ≤ (m1 + m2) ≤ 1,000, optionally 10 ≤ (m1 + m2) ≤ 500.

[0064] The amount of component (B) is not limited, but based on the total mass of components (A) to (C) respectively, this component is usually used in an amount of 1% to 20% by mass, optionally in an amount of 1% to 15% by mass, or optionally in an amount of 5% to 20% by mass. This is because if the amount is equal to or higher than the lower limit of the above range, the composition has good modulus, and if the amount is equal to or lower than the upper limit of the above range, the cured product obtained has good mechanical properties.

[0065] Component (C) is an organosiloxane having at least two silicon-bonded hydrogen atoms and at least one aryl group having 6 to 12 carbon atoms per molecule, and is used as a crosslinking agent for the composition. Examples of the group bonded to a silicon atom other than a hydrogen atom include alkyl groups having 1 to 12 carbon atoms, such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, and dodecyl group; aryl groups having 6 to 12 carbon atoms, such as phenyl group, tolyl group, xylyl group, and naphthyl group; aralkyl groups having 7 to 20 carbon atoms, such as benzyl group, phenethyl group, and phenylpropyl group; and groups in which some or all of the hydrogen atoms in these groups are substituted with halogen atoms (such as fluorine atom, chlorine atom, or bromine atom). However, at least one silicon-bonded organic group in the molecule is an aryl group, preferably a phenyl group. In addition, the silicon atoms in component (C) may also have a small amount of hydroxyl groups or alkoxy groups, such as methoxy group or ethoxy group, within the range not detrimental to the object of the present invention.

[0066] The viscosity of component (C) at 25 °C is not limited, but is generally not more than 1,000 mPa·s, optionally not more than 500 mPa·s, or optionally not more than 100 mPa·s. It should be noted that in this specification, the viscosity is a value measured at 23 °C ± 2 °C using a Brookfield viscometer according to ASTM D 1084.

[0067] The organosiloxane of component (C) is usually an organosiloxane oligomer represented by the following general formula:

[0068] HR 4 2 SiO(R 4 2 SiO) n SiR 4 2 H.

[0069] In the above formula, each R 4 is an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and examples thereof include the same groups as the above R 2 . However, at least one R 4 is an aryl group, usually a phenyl group.

[0070] In this formula, "n" is an integer from 0 to 10, optionally an integer from 0 to 5, optionally an integer from 0 to 3, or optionally 0 or 1.

[0071] Component (C) is usually at least one selected from the group consisting of organosiloxane oligomers represented by the following formulae:

[0072] H(CH 3 ) 2 SiO(C 6 H 5 ) 2 SiOSi(CH 3 ) 2 H

[0073] H(CH 3 ) 2 SiO(C 6 H 5 )(CH 3 )SiOSi(CH 3 ) 2 H

[0074] The amount of component (C) is such that the hydrogen atoms bonded to silicon in component (C) are each 0.1 to 10 moles, optionally in the range of 0.5 to 1.5, or optionally in the range of 0.8 to 1.5, relative to 1 mole of alkenyl groups in components (A) and (B). This is because, if the molar ratio is equal to or higher than the lower limit of the above range, the composition can be sufficiently cured, and the cured product obtained by curing the composition of the present invention will have appropriate hardness and mechanical strength, while if the molar ratio is equal to or lower than the upper limit of the above range, the cured product has good thermal stability.

[0075] The content of the total aryl groups in components (A) to (C) is at least 35% by mass of the total mass of components (A) to (C). In various embodiments, the content of the total aryl groups in components (A) to (C) is at least 40% by mass, optionally at least 45% by mass, or optionally at least 50% by mass of the total mass of components (A) to (C). In additional or other embodiments, the content of the total aryl groups in components (A) to (C) is at most 80% by mass, optionally at most 75% by mass, or optionally at most 70% by mass of the total mass of components (A) to (C).

[0076] Component (D) is a photoactivated hydrosilylation reaction catalyst activated by UV light. That is, this component is a catalyst that is inactive in the absence of UV light but becomes an active hydrosilylation reaction catalyst at room temperature when irradiated with UV light, thereby promoting the hydrosilylation reaction between the alkenyl groups in components (A) and (B) and the hydrogen atoms bonded to silicon in component (C).

[0077] Examples of the photoactivatable hydrosilylation reaction catalyst for component (D) include cyclopentadienyl platinum compounds and their derivatives, such as trimethyl(methylcyclopentadienyl)platinum(IV), trimethyl(cyclopentadienyl)platinum(IV), trimethyl(1,2,3,4,5-pentamethylcyclopentadienyl)platinum(IV), dimethylethyl(cyclopentadienyl)platinum(IV), dimethylacetyl(cyclopentadienyl)platinum(IV), trimethyl(trimethylsilylcyclopentadienyl)platinum(IV), trimethyl(methoxycarbonylcyclopentadienyl)platinum(IV), and trimethyl(dimethylphenylsilylcyclopentadienyl)cyclopentadienylplatinum(IV). Among them, trimethylcyclopentadienylplatinum, trimethyl(methylcyclopentadienyl)platinum, and their derivatives in which the cyclopentadienyl group has been modified are particularly preferred.

[0078] β-diketonato platinum compounds are also preferred examples of component (D). Examples of the β-diketonato platinum compounds for component (D) include trimethyl(acetylacetonato)platinum(IV), trimethyl(3,5-heptanedionato)platinum(IV), trimethyl(methyl acetoacetato)platinum(IV), bis(acetylacetonato)platinum(II), bis(2,4-pentanedionato)platinum(II), bis(2,4-hexanedionato)platinum(II), bis(2,4-heptanedionato)platinum(II), bis(3,5-heptanedionato)platinum(II), bis(1-phenyl-1,3-butanedionato)platinum(II), bis(1,3-diphenyl-1,3-propanedionato)platinum(II), and bis(hexafluoroacetylacetonato)platinum(II). Among them, bis(acetylacetonato)platinum compounds and their derivatives in which the acetylacetonato group has been modified are particularly preferred.

[0079] Component (D) is used in an effective amount for promoting the curing of the composition of the present invention. Specifically, in order to satisfactorily cure the composition of the present invention, the content of component (D) is usually an amount such that the content of the catalytic metal in component (D) is in the range of about 0.01 ppm to about 500 ppm, optionally in the range of about 0.01 ppm to about 250 ppm, optionally in the range of about 0.01 ppm to about 200 ppm, or optionally in the range of about 0.1 ppm to about 100 ppm, based on the mass of the composition of the present invention.

[0080] In various embodiments, the curable silicone composition comprises (E) a hydrosilylation reaction inhibitor to regulate the curing rate of the curable silicone composition. In certain embodiments, component (F) includes, but is not limited to, alkynols such as 2-methyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol or 2-phenyl-3-butyn-2-ol, 1-ethynylcyclohexan-1-ol; enyne compounds such as 3-methyl-3-penten-1-yne or 3,5-dimethyl-3-hexen-1-yne; or 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane, tris[(1,1-dimethyl-2-propynyl)oxy]methylsilane, diallyl maleate or benzotriazole are incorporated as optional components into the composition of the present invention.

[0081] The amount of component (E) in the composition of the present invention is not particularly limited, but if included, the amount of this component is generally about 1 ppm to about 10,000 ppm, optionally about 10 ppm to about 5,000 ppm, in mass units relative to the total mass of components (A) to (C). This is because when the amount of component (E) is greater than or equal to the lower limit of the above range, the storage stability of the composition is good, and when the amount of component (E) is less than or equal to the upper limit of the above range, the curability of the composition at low temperatures is good.

[0082] To improve the adhesion of the cured product to the substrate material contacted during curing, the composition of the present invention may contain (F) an adhesion promoter. In certain embodiments, the adhesion promoter for component (F) is generally a silicone compound having at least one alkoxy group bonded to a silicon atom in the molecule. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and a methoxyethoxy group; and the methoxy group is the most typical. In addition, examples of the non-alkoxy group bonded to the silicon atom of the silicone compound are: a substituted or unsubstituted monovalent hydrocarbon group, such as an alkyl group, an alkenyl group, an aryl group, an aralkyl group, and a haloalkyl group, etc.; a monovalent organic group containing an epoxy group, such as a 3-glycidoxypropyl group, a 4-glycidoxybutyl group, or a similar glycidoxyalkyl group; a 2-(3,4-epoxycyclohexyl)ethyl group, a 3-(3,4-epoxycyclohexyl)propyl group, or a similar epoxycyclohexyl group; and a 4-oxetanyl group, an 8-oxetanyloctyl group, or a similar oxetanyl group; a monovalent organic group containing an acrylic group, such as a 3-methacryloxypropyl group, etc.; and a hydrogen atom. The silicone compound generally has a silicon-bonded alkenyl group or a silicon-bonded hydrogen atom. In addition, due to the ability to impart good adhesion to various types of substrate materials, the silicone compound generally has at least one monovalent organic group containing an epoxy group in the molecule. Examples of this type of silicone compound are silane compounds, silicone oligomers, and alkyl silicates. Examples of the molecular structure of the silicone oligomer or alkyl silicate are a linear structure, a partially branched linear structure, a branched structure, a cyclic structure, and a network structure. The linear structure, the branched structure, and the network structure are typical. Examples of this type of silicone compound are silane compounds, such as 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, etc.; silicone compounds having at least one silicon-bonded alkenyl group or a silicon-bonded hydrogen atom and at least one silicon-bonded alkoxy group in the molecule; a mixture of a silane compound or a silicone compound having at least one silicon-bonded alkoxy group and a silicone compound having at least one silicon-bonded hydroxyl group and at least one silicon-bonded alkenyl group in the molecule; and methyl polysilicate, ethyl polysilicate, and ethyl polysilicate containing an epoxy group.

[0083] In the composition of the present invention, the amount of component (F) is not particularly limited, but in order to achieve good adhesion to the substrate material contacted during curing, this amount is generally at most 10 parts by mass relative to the total mass of 100 parts by mass of components (A) to (C).

[0084] To improve the mechanical properties of the cured product, the composition of the present invention may contain (G) silica filler. Component (G) is typically a silica filler having a BET surface area of at least 50 m 2 / g, optionally 80 m 2 / g to 400 m 2 / g or optionally 100 m 2 / g to 400 m 2 / g of fumed or precipitated silica filler. The surface of the silica filler may be untreated or treated with treating agents (such as organochlorosilanes, organoalkoxysilanes, organosilazanes, and organosiloxane oligomers).

[0085] The silica filler for component (G) is commercially available. Examples of the silica filler include fumed silica under the trade name AEROSIL TM such as AEROSIL TM R8200, R9200, R812, R812S, R972, R974, R805, R202 from Degussa Corporation; fumed silica under the trade name CAB-O-SIL TM ND-TS, TS610 or TS710 from Cabot Corporation; and fumed silica under the trade name REOLOSIL TM such as DM-10, DM-20S, DM-30, HM-30S, MT-10, PM-20L, QS-10, QS-20A and QS-25C from Tokuyama Corporation.

[0086] Relative to the total mass of 100 parts by mass of components (A) to (C), the amount of component (G) is in the range of 1 part by mass to 10 parts by mass, optionally in the range of 1 part by mass to 5 parts by mass. This is because if the amount of component (G) is equal to or higher than the lower limit of the above range, the cured product obtained by curing the composition of the present invention has appropriate hardness and mechanical strength, and if the amount is equal to or lower than the upper limit of the above range, the composition of the present invention has good transparency.

[0087] The refractive index of the composition of the present invention at 25°C is not limited, but it is typically in the range of 1.50 to 1.60. At the same time, the viscosity of the composition of the present invention at 25°C is not limited, and it is typically in the range of 1 Pa·s to 100 Pa·s, optionally in the range of 1 Pa·s to 50 Pa·s or optionally in the range of 1 Pa·s to 20 Pa·s, as measured at a shear rate of 1 / s.

[0088] Examples

[0089] The UV-curable silicone composition of the present invention will be described in detail below using working examples and comparative examples. However, the present invention is not limited by the descriptions of the examples listed below.

[0090] [Refractive index]

[0091] The refractive index of the UV-curable silicone composition at 25 °C was measured at a wavelength of 589 nm and an atmospheric pressure of 1013 mbar using an Abbe refractometer produced by ATAGO Co., Ltd. according to standard DIN 51423.

[0092] [Viscosity]

[0093] The viscosity (mPa·s or Pa·s) of all samples was measured using a Brookfield cone-plate viscometer (HADV-ⅢU) with a cone rotor CP-52. The measurement temperature was 25 °C ± 2 °C, and the samples were measured at a torque speed between 50% and 70%.

[0094] [Storage stability]

[0095] The UV-curable silicone composition was stored at room temperature of 25 °C ± 2 °C for 5 days and the viscosity was measured after 5 days. The increase in viscosity must not exceed 10% of the initial viscosity.

[0096] [Low-temperature curing]

[0097] After UV irradiation, all samples were cured in an oven set at 70 °C for 30 minutes.

[0098] [Shore D hardness]

[0099] The hardness was measured using a durometer (Shore D), and cured samples with a thickness of more than 6 mm were prepared, and the surface of the cured samples was as flat as possible to reduce variations. The hardness was measured at at least 3 points on the flat surface, and the average hardness value was used.

[0100] [Gel time after UV exposure]

[0101] The gel time was measured after UV exposure with UVA at 365 nm and an energy of 5,000 mJ / cm 2 dose. The UV-exposed samples were left at room temperature for more than 4 hours, and then the viscosity was measured in the same manner as the viscosity evaluation. In the case where the samples reached the gel time within the specified time, the results were recorded as "gelled" or "cured".

[0102] [Curing rate]

[0103] The curing rate was measured by using FT-IR (Nicolet Is50 FTIR) and Si-H intensity (2,100 cm -1 ). A silicone composition was coated on a glass slide using a perforated mask (10 mm × 30 mm × 0.5 mm T), and then the prepared sample was exposed to UV light (LED 365 nm, 5000 mJ / cm 2 UVA dose). The UV-exposed sample was placed in an oven set at 70 °C for 30 minutes. The curing rate was measured by a relative comparison method between the uncured sample and the fully cured sample, and the rate of decrease in Si-H intensity was calculated. The fully cured sample was prepared in the same manner as the other samples, except that it was held at a post-curing temperature of 120 °C for 30 minutes.

[0104] The cured sample was measured by FT-IR and the evaluation mode was single reflection ATR. The sample was placed on a diamond detector with a pressure clamp to press tightly, and then the intensity of Si-H was measured. The curing rate was calculated using the height of the peak, and the calculation formula is as follows. The height was corrected by the selected reference peak, which was the most constant peak among all samples.

[0105] Reaction rate (%) = [(H 0％ – H 样品 ) / (H 0％ – H 100％ )] × 100

[0106] H (X＝0％，样品,100％) = H @SiH / H @Ref

[0107] H 0％ : Peak height of the liquid before UV curing (reaction rate = 0%)

[0108] H 样品 : Peak height of the sample after UV curing

[0109] H 100％ : Standard peak height of the fully cured sample (reaction rate = 100%)

[0110] [Examples 1-4 and Comparative Examples 1-5]

[0111] The following components were mixed uniformly in the amount ratios shown in Table 1 to produce a UV-curable silicone composition. The composition was prepared as follows:

[0112] Components (A), (B), (C), (E), and (G) were mixed at 1,500 rpm for 2 minutes. Then, component (F) was added to the mixture prepared above and mixed twice at 2,000 rpm for 2 minutes each to disperse it thoroughly. Finally, component (D) was added to the mixture prepared above and mixed at 1,500 rpm for 2 minutes. The resulting ultraviolet-curable silicone composition was packaged in a 30 mL syringe and vacuum-sealed. These samples were stored in an aluminum bag at -5 °C to avoid light and had a long shelf life. The basic properties (viscosity, curing rate, etc.) were measured, and then the samples were stored at RT for shelf-life studies. These results are given in Table 1. The "SiH / Vi ratio" in Table 1 indicates the molar ratio of hydrogen atoms bonded to all silicon atoms in component (C) to vinyl groups bonded to all silicon atoms in components (A) and (B).

[0113] The following branched organopolysiloxane was used as component (A).

[0114] (a1): Branched organopolysiloxane represented by the following average unit formula:

[0115] [(CH 2 =CH)(CH 3 )(C 6 H 5 )SiO 1 / 2 0.23 (C 6 H 5 SiO 3 / 2 ) 0.77

[0116] It has a vinyl group content of 4.60 mass% and a phenyl group content of 57.03 mass%.

[0117] (a2): Branched organopolysiloxane represented by the following average unit formula:

[0118] [(CH 3 ) 3 SiO 1 / 2 0.14 [(CH 2 =CH)(CH 3 ) 2 SiO 1 / 2 0.11 (CH 3 SiO 3 / 2 ) 0.53 (C 6 H 5 SiO 3 / 2 ) 0.22

[0119] ​​​It has a vinyl group content of about 3.47% by mass and a phenyl group content of 19.81% by mass.

[0120] The following branched organopolysiloxane is used as a comparison for component (A).

[0121] (a3): An organopolysiloxane resin represented by the following average unit formula:

[0122] [(CH 2 =CH)(CH 3 ) 2 SiO 1 / 2 0.10 [(CH 3 ) 3 SiO 1 / 2 0.40 (SiO 4 / 2 ) 0.50

[0123] It has a vinyl group content of 3.76% by mass.

[0124] The following linear organopolysiloxane is used as component (B).

[0125] (b1): A methylphenyl polysiloxane represented by the following formula:

[0126] (CH 2 =CH)(CH 3 ) 2 SiO[(C 6 H 5 )(CH 3 )SiO] 23 Si(CH 3 ) 2 (CH=CH 2 )

[0127] It has a vinyl group content of about 1.63% by mass and a phenyl group content of 53.42% by mass, and has a viscosity of 2,700 mPa·s.

[0128] (b2): A copolymer of dimethylsiloxane and diphenylsiloxane represented by the following formula:

[0129] (CH 2 =CH)(CH 3 ) 2 SiO[(CH 3 ) 2 SiO] 210 [(C 6 H 5 ) 2 SiO] 51 Si(CH​​3 ) 2 (CH=CH 2 )

[0130] Having a vinyl group content of 0.21% by mass and a phenyl group content of 30.40% by mass, and having a viscosity of 14,500 mPa·s.

[0131] The following organopolysiloxane was used as a comparison for component (B).

[0132] (b3): Dimethylpolysiloxane represented by the following formula:

[0133] (CH 2 =CH)(CH 3 ) 2 SiO[(CH 3 ) 2 SiO] 493 Si(CH 3 ) 2 (CH=CH 2 )

[0134] Having a vinyl content of 0.15% by mass and having a viscosity of 10,000 mPa·s.

[0135] (b4): Dimethylpolysiloxane represented by the following formula:

[0136] (CH 2 =CH)(CH 3 ) 2 SiO[(CH 3 ) 2 SiO] 41 Si(CH 3 ) 2 (CH=CH 2 )

[0137] Having a vinyl group content of 1.68% by mass and having a viscosity of 60 mPa·s.

[0138] The following organopolysiloxane was used as component (C).

[0139] (c1): Organosiloxane represented by the following formula:

[0140] H(CH 3 ) 2 SiO[(C 6 H 5 ) 2 SiO]Si(CH 3 ) 2 H

[0141] It has a hydrogen atom content bonded to silicon atoms of about 0.61% by mass and has a viscosity of 4.4 mPa·s.

[0142] The following organopolysiloxane was used for comparison as component (C).

[0143] (c2): An organosiloxane represented by the following average unit formula:

[0144] [H(CH 3 ) 2 SiO 1 / 2 0.65 (SiO 4 / 2 ) 0.35

[0145] And it has a hydrogen atom content bonded to silicon atoms of about 0.99% by mass.

[0146] The following photoactivated hydrosilylation reaction catalyst was used as component (D).

[0147] (d1): Trimethyl(methylcyclopentadienyl)platinum(IV) in a 1% by mass solution of methyltrimethoxysilane

[0148] (d2): Bis(acetylacetonato)platinum(II) in a 0.5% by mass solution of methyltrimethoxysilane

[0149] The following hydrosilylation reaction catalyst was used for comparison as component (D).

[0150] (d3): Platinum 1,3 - divinyl - 1,1,3,3 - tetramethyldisiloxane complex in a 0.5% by mass solution of methyltrimethoxysilane

[0151] The following hydrosilylation reaction inhibitor was used as component (E).

[0152] (e1): Methyl - tris(1,1 - dimethyl - 2 - propynyloxy)silane

[0153] The following fumed silica was used as component (F).

[0154] (f1): Fumed silica with a BET specific surface area of 230 m 2 / g (REOLOSIL DM - 30S from Tokuyama Corporation)

[0155] The following adhesion promoter was used as component (G).

[0156] (g1): An organopolysiloxane represented by the following average unit formula:

[0157] [(CH 2 =CH)(CH 3 )SiO​2 / 2 0.23 [CH 2 (O)CHCH 2 OC 3 H 6 SiO 3 / 2 0.31 [(CH 3 ) 2 SiO 2 / 2 0.46 (CH 3 O 1 / 2 ) 0.2

[0158] [Table 1]

[0159]

[0160]

[0161] [Table 1 (continued)]

[0162]

[0163] According to Examples 1 to 4, the curable silicone composition containing a high phenyl group has a long gel time after UV irradiation because the Si-H reaction rate is less than 50% within 4 hours and remains in a gel state. The post-curing rate is also very fast at low temperatures because the curing rate exceeds 94% within 30 minutes. It is observed that a phenyl content of more than 26% has a significant effect on these properties. A higher phenyl content is used after the hardness increases.

[0164] According to Comparative Examples 1 to 3, reducing the phenyl content has the characteristics of a much faster gel time and reaching all the most complete curing within 4 hours after UV irradiation. In addition, the viscosity increases by more than 10%. For the methyl system (Comparative Example 3), it is observed that the curing curve has some limitations at lower temperatures, however, the methyl composition is completely cured at a high temperature of >100 °C.

[0165] According to Comparative Examples 4 and 5, hydrosilylation (thermal curing) has a poor pot life, and even the silicone composition with a high phenyl content is not completely cured at low temperatures (<75 °C). All samples were cured by UVA with a dose of 365 nm and an energy of 5,000 mJ / cm 2 using an LED UV (Firejet FJ800) device.

[0166] Industrial applicability

[0167] ​​​The UV-curable silicone composition of the present invention has a good pot life in the form of a one-component composition and is cured by irradiation with ultraviolet light to form a Class B material, where the Class B material exhibits a slow gel time yet can be fully cured at a low temperature (e.g., 75 °C or lower). Thus, the composition can be used as a sealant, adhesive, or coating for optical semiconductor elements in electrical / electronic devices.

Claims

1. A UV-curable silicone composition, the UV-curable silicone composition comprising: (A) A branched organopolysiloxane having at least one alkenyl group with 2 to 12 carbon atoms and at least one aryl group with 6 to 12 carbon atoms per molecule; (B) A linear organopolysiloxane having at least two alkenyl groups with 2 to 12 carbon atoms and at least one aryl group with 6 to 12 carbon atoms per molecule; (C) An organosiloxane having at least two silicon-bonded hydrogen atoms and at least one aryl group with 6 to 12 carbon atoms per molecule, the amount of the organosiloxane being such that, relative to 1 mole of alkenyl groups in components (A) and (B), the silicon-bonded hydrogen atoms in component (C) are 0.1 mole to 10 moles; and (D) A catalytic amount of a photoactivated hydrosilylation reaction catalyst; wherein the content of the total aryl groups in components (A) to (C) is at least 35% by mass of the total mass of components (A) to (C).

2. The UV-curable silicone composition according to claim 1, wherein component (A) is a branched organopolysiloxane represented by the following average unit formula: (R 1 3 SiO 1 / 2 ) a (R 1 2 SiO 1 / 2 ) b (R 2 SiO 3 / 2 ) c (HO 1 / 2 ) d Each R 1 is independently an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, provided that at least one R in the molecule 1 is an alkenyl group; R 2 is an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, provided that at least one R in the molecule 2 is an aryl group; and "a", "b", "c" and "d" are numbers satisfying the following conditions: 0 < a ≤ 0.3, 0 ≤ b ≤ 0.2, 0.5 ≤ c ≤ 0.9, 0 ≤ d ≤ 0.05 and a + b + c = 1.

3. The UV-curable silicone composition according to claim 1, wherein component (B) is a linear organopolysiloxane represented by the following general formula: R 3 3 SiO(R 3 2 SiO) m SiR 3 3 Each R 3 is independently an alkyl group having from 1 to 12 carbon atoms, an alkenyl group having from 2 to 12 carbon atoms or an aryl group having from 6 to 12 carbon atoms, provided that at least two Rs in the molecule 3 are alkenyl groups and at least one R in the molecule 3 is an aryl group; and "m" is an integer from 10 to 1000.

4. The UV-curable silicone composition according to claim 1, wherein component (C) is an organosiloxane represented by the following general formula: HR 4 2 SiO(R 4 2 SiO) n SiR 4 2 H Each R 4 is independently an alkyl group or an aryl group, provided that at least one R 4 is an aryl group; and "n" is an integer from 0 to 10.

5. The UV-curable silicone composition according to any one of claims 1 to 4, the UV-curable silicone composition further comprising: (E) A hydrosilylation reaction inhibitor, and in this component, the amount of the hydrosilylation reaction inhibitor is 0.1 ppm to 10,000 ppm in terms of mass unit relative to the total mass of components (A) to (C).

6. The UV-curable silicone composition according to any one of claims 1 to 4, the UV-curable silicone composition further comprising: (F) An adhesion promoter, and the amount of the adhesion promoter is at most 10 parts by mass relative to 100 parts by mass of the total mass of components (A) to (C).

7. The UV-curable silicone composition according to any one of claims 1 to 4, the UV-curable silicone composition further comprising: (G) A silica filler, and the amount of the silica filler is 0.1 part by mass to 10 parts by mass relative to 100 parts by mass of the total mass of components (A) to (C).

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