Addition-curing silicone composition, method for producing said composition, silicone cured product for light-reflecting material, light-reflecting material, and optical semiconductor device

Abstract

The present invention is an addition-curing silicone composition characterized by comprising: (A) a linear organopolysiloxane having at least two alkenyl groups bonded to silicon atoms in one molecule, having no trialkoxysilyl group and having a viscosity at 23°C of 500 to 100,000 mPa∙s, (B) an organopolysiloxane resin represented by average compositional formula (1): (1): (R1 3SiO1 / 2)a(R1 2R2SiO1 / 2)b(R1 2SiO)c(R1R2SiO)d(R1SiO3 / 2)e(R2SiO3 / 2)f(SiO4 / 2)g, (C) an organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule and not having an addition reactive carbon-carbon double bond, (D) a hydrosilylation catalyst containing a platinum group metal, (E) fumed silica, and (F) particles which are obtained by surface-treating (i) the surface of titanium oxide with an organosilicon compound having (ii) a trialkoxysilyl group and not having a hydrogen atom bonded to a silicon atom. As a result, an addition-curing silicone composition which has shape retention properties and little changes in viscosity over time and provides a cured product having excellent light reflection performance is provided.

Description

Addition-curable silicone composition, method for producing the composition, cured silicone product for light-reflecting material, light-reflecting material, and optical semiconductor device

[0001] The present invention relates to an addition-curable silicone composition, a method for producing the composition, a cured silicone product for use as a light reflector, a light reflector, and an optical semiconductor device.

[0002] A common method for manufacturing light-emitting diodes (hereinafter referred to as "LEDs") is a method called COB (Chip on Board), in which a light-reflective silicone rubber frame (dam material) and an LED chip are placed on a substrate, a sealing material is potted, and then the dam material and the sealing material are hardened by heating.

[0003] A widely used dam material is a one-component addition-curing liquid silicone rubber composition, which is made by mixing addition-curing silicone rubber with fumed silica or the like to increase viscosity and thixotropy, and then adding titanium oxide to impart light reflectivity (Patent Document 1).

[0004] Dam materials are required to have both adhesive properties to the substrate, shape retention properties to prevent flow and maintain their shape until curing, and ejectability when dispensed.

[0005] On the other hand, light-reflective addition-curable silicone compositions containing titanium dioxide have been plagued by a problem of increased viscosity due to reversion to plasticity caused by the addition of titanium dioxide. When the viscosity of the composition increases during storage, it loses its dispensing properties and its performance as a dam material for COB is impaired. Examples of problems include inability to dispense from a syringe, reduced productivity due to a decrease in dispensing speed, and poor dam shape.

[0006] Conventional dam materials inevitably thicken, even when sealed in syringes or cartridges and stored in a refrigerator. Furthermore, from the perspective of energy conservation, there is a movement to reduce energy consumption during transportation and storage, which has posed a major problem when stored in room temperature environments, where thickening becomes even more pronounced.

[0007] JP 2012-233035 A

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide an addition-curable silicone composition that has shape-retaining properties and exhibits little change in viscosity over time, and that gives a cured product with excellent light reflecting performance.

[0009] In order to solve the above problems, the present invention provides a composition comprising: (A) 40 to 90 parts by mass of a linear organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule, and no trialkoxysilyl groups, and having a viscosity of 500 to 100,000 mPa·s at 23°C; (B) 10 to 60 parts by mass of an organopolysiloxane resin represented by the following average composition formula (1) (provided that the total of components (A) and (B) is 100 parts by mass); (R １ ３ SiO １／２ ) ａ (R １ ２ R ２ SiO １／２ ) ｂ (R １ ２ SiO) ｃ (R １ R ２ SiO) ｄ (R １ SiO ３／２ ) ｅ (R ２ SiO ３／２ ) ｆ (SiO ４／２ ) ｇ (1) (wherein, R １ are independently unsubstituted or halogen-substituted monovalent hydrocarbon groups containing no addition-reactive carbon-carbon double bonds, and R ２are independently an alkenyl group. a, b, c, d, e, f, and g are numbers that satisfy b+d+f>0 and e+f+g>0, and a+b+c+d+e+f+g=1. (C) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule and having no addition-reactive carbon-carbon double bonds, in an amount such that 1.0 to 3.0 moles of silicon-bonded hydrogen atoms per mole of alkenyl groups in components (A) and (B); (D) a hydrosilylation catalyst containing a platinum group metal, in an amount of 0.0001 to 0.1 part by mass, calculated as the mass of the platinum group metal; (E) fumed silica, in an amount of 5 to 30 parts by mass; and (F) (i) particles of titanium oxide whose surfaces have been surface-treated with an organosilicon compound, in which (ii) trialkoxysilyl groups are present and which have no silicon-bonded hydrogen atoms, in an amount of 5 to 50 parts by mass of (i).

[0010] The addition-curable silicone composition of the present invention has shape-retaining properties, exhibits minimal change in viscosity over time, and provides a cured product with excellent light-reflecting properties.

[0011] Furthermore, the component (C) preferably contains an organohydrogenpolysiloxane represented by the following formula (3). (In the formula, R ３ are independently a hydrogen atom, a 2-(trimethoxysilyl)ethyl group, or a 3-(trimethoxysilyl)propyl group, provided that R ３ At least one of R is a 2-(trimethoxysilyl)ethyl group or a 3-(trimethoxysilyl)propyl group, and R ３ At least two of the groups are hydrogen atoms. p is an integer of 0 to 50, q is an integer of 1 to 50, and the arrangement of the siloxane units in parentheses is arbitrary.

[0012] Such an addition-curable silicone composition has excellent shape retention and adhesive properties.

[0013] Furthermore, the organosilicon compound in component (F) is preferably an organopolysiloxane represented by the following formula (4): (In the formula, R ４are independently a methyl group or a methoxy group, n is an integer of 0 to 10, m is an integer of 1 to 50, and the arrangement of the siloxane units in parentheses is arbitrary.

[0014] Such an addition-curable silicone composition can further suppress the volatilization of the organosilicon compound.

[0015] The present invention provides a method for producing the above addition-curable silicone composition, which comprises the step of heat-treating a composition containing (i) titanium oxide and (ii) an organosilicon compound that has a trialkoxysilyl group and no silicon-bonded hydrogen atoms at 100 to 180°C.

[0016] The composition obtained by such a production method has shape retention and little change in viscosity over time, and further gives a cured product with excellent light reflecting properties.

[0017] The present invention also provides a cured silicone product for use as a light reflector, which is a cured product of the addition-curable silicone composition described above.

[0018] The cured silicone product for light reflectors preferably has a reflectance of 95% or more at a wavelength of 450 nm at a thickness of 2 mm.

[0019] Such a cured silicone product for use as a light reflector has excellent light reflecting properties.

[0020] The present invention provides a light-reflecting material comprising the above-described cured silicone for light-reflecting materials.

[0021] Such a light reflecting material can be suitably used for optical semiconductor devices such as LEDs, particularly as a dam material.

[0022] Furthermore, the present invention provides an optical semiconductor device comprising the above light reflecting material.

[0023] Such an optical semiconductor device has a high light extraction efficiency.

[0024] The addition-curable silicone composition of the present invention is an addition-curable silicone composition that has shape retention and exhibits little change in viscosity over time, and gives a cured product with excellent light reflecting performance, making it particularly useful as a dam material for COB-type optical semiconductor devices.

[0025] As described above, there has been a need for the development of an addition-curable silicone composition that has shape-retaining properties, exhibits little change in viscosity over time, has excellent storage stability, and gives a cured product with excellent light reflecting performance.

[0026] As a result of extensive research into the above-mentioned problems, the present inventors have discovered that an addition-curable silicone composition containing the following components (A) to (F) can solve the above-mentioned problems and is suitable as a dam material for optical semiconductor devices, and have completed the present invention.

[0027] That is, the present invention provides a composition comprising: (A) 40 to 90 parts by mass of a linear organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule, and no trialkoxysilyl groups, and having a viscosity of 500 to 100,000 mPa·s at 23°C; (B) 10 to 60 parts by mass of an organopolysiloxane resin represented by the following average composition formula (1) (provided that the total of components (A) and (B) is 100 parts by mass); (R １ ３ SiO １／２ ) ａ (R １ ２ R ２ SiO １／２ ) ｂ (R １ ２ SiO) ｃ (R １ R ２ SiO) ｄ (R １ SiO ３／２ ) ｅ (R ２ SiO ３／２ ) ｆ (SiO ４／２ ) ｇ (1) (wherein, R １are independently unsubstituted or halogen-substituted monovalent hydrocarbon groups containing no addition-reactive carbon-carbon double bonds, and R ２ are independently an alkenyl group. a, b, c, d, e, f, and g are numbers that satisfy b+d+f>0 and e+f+g>0, and a+b+c+d+e+f+g=1. (C) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule and having no addition-reactive carbon-carbon double bonds, in an amount such that 1.0 to 3.0 moles of silicon-bonded hydrogen atoms per mole of alkenyl groups in components (A) and (B); (D) a hydrosilylation catalyst containing a platinum group metal, in an amount of 0.0001 to 0.1 part by mass, calculated as the mass of the platinum group metal; (E) fumed silica, in an amount of 5 to 30 parts by mass; and (F) (i) particles of titanium oxide, the surface of which has been surface-treated with an organosilicon compound, in which (ii) trialkoxysilyl groups are present and which have no silicon-bonded hydrogen atoms, in an amount of 5 to 50 parts by mass of (i).

[0028] The present invention will be described in detail below, but the present invention is not limited thereto. In this specification, viscosity is a value measured at 23°C using a BH type rotational viscometer at a rotation speed of 4 rpm.

[0029] [Addition-Curable Silicone Composition] Each component is described in detail below. [Component (A)] Component (A) is a linear organopolysiloxane that contains at least two silicon-bonded alkenyl groups per molecule, does not contain any trialkoxysilyl groups, and has a viscosity of 500 to 100,000 mPa·s at 23°C.

[0030] The number of alkenyl groups bonded to silicon atoms contained in one molecule is at least 2, preferably 2 to 20, and more preferably 2 to 5. If there are fewer than 2, the hardness of the cured product will be insufficient.

[0031] The bonding positions of the alkenyl groups in the linear organopolysiloxane of component (A) may be at the molecular chain terminals, non-terminal positions on the molecular chain, or both. However, it is preferable that the alkenyl groups be bonded to silicon atoms at both molecular chain terminals.

[0032] The viscosity of component (A) at 23°C is in the range of 500 to 100,000 mPa·s from the viewpoints of providing good physical properties to the resulting silicone rubber and also of the ejection stability of the composition. If it exceeds 100,000 mPa·s, the composition will have a high viscosity and ejection properties will be impaired, while if it is less than 500 mPa·s, the physical properties of the rubber after curing will be impaired, reducing reliability.

[0033] The component (A) is preferably represented by the following formula (2): (R １ ２ R ２ SiO １／２ ) ２ (R １ ２ SiO) ｈ (2)

[0034] In the above formula (2), R １ are independently unsubstituted or halogen-substituted monovalent hydrocarbon groups that do not contain an addition-reactive carbon-carbon double bond, and examples thereof include unsubstituted or halogen-substituted monovalent hydrocarbon groups typically having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, such as alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, and heptyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl and phenethyl; and halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl. Preferred are methyl and phenyl groups, and particularly preferred is methyl.

[0035] In the above formula (2), R ２ are independently an alkenyl group, and examples thereof include vinyl, allyl, butenyl, pentenyl, hexenyl, and heptenyl groups, each having a carbon number of typically 2 to 8, preferably 2 to 6. From the viewpoint of raw material supply, a vinyl group is particularly preferred.

[0036] In the above formula (2), h may be any integer that gives component (A) a viscosity of 500 to 100,000 mPa s, preferably 100 to 500, and more preferably 200 to 400. Component (A) may be used either alone or in combination of two or more types. When component (A) is used as a mixture of two or more types, the mixing ratio may be adjusted so that the viscosity after mixing is within the above range.

[0037] [Component (B)] Component (B) is an organopolysiloxane resin represented by the following average composition formula (1), which has a branched structure and functions as a reinforcing component for silicone rubber. (R １ ３ SiO １／２ ) ａ (R １ ２ R ２ SiO １／２ ) ｂ (R １ ２ SiO) ｃ (R １ R ２ SiO) ｄ (R １ SiO ３／２ ) ｅ (R ２ SiO ３／２ ) ｆ (SiO ４／２ ) ｇ (1) (wherein, R １ are independently unsubstituted or halogen-substituted monovalent hydrocarbon groups containing no addition-reactive carbon-carbon double bonds, and R ２ are independently an alkenyl group; a, b, c, d, e, f, and g are numbers such that b+d+f>0 and e+f+g>0, and a+b+c+d+e+f+g=1.

[0038] In the above formula (1), R １ Examples of the monovalent hydrocarbon group include the same groups as those exemplified in the above formula (2), and are preferably a methyl group or a phenyl group, and particularly preferably a methyl group.

[0039] In the above formula (1), R ２Examples of the alkenyl group include the same groups as those exemplified in the above formula (2), and a vinyl group is preferred.

[0040] In the above formula (1), it is preferable that a is a number from 0 to 0.65, b is a number from 0 to 0.65, c is a number from 0 to 0.5, d is a number from 0 to 0.5, e is a number from 0 to 0.8, f is a number from 0 to 0.8, and g is a number from 0 to 0.6. It is also preferable that b+d+f is a number from 0.01 to 0.30, particularly from 0.05 to 0.10, and it is preferable that e+f+g is a number from 0.1 to 0.8, particularly from 0.2 to 0.6.

[0041] Specific examples of the component (B) include, but are not limited to, the following: [(CH ３ ) ３ SiO １／２ ] ０．４０ [(CH ２ =CH)(CH ３ ) ２ SiO １／２ ] ０．０６ [SiO ４／２ ] ０．５４ , [(CH ３ ) ３ SiO １／２ ] ０．４８ [(CH ２ =CH)(CH ３ ) SiO ２／２ ] ０．０８ [SiO ４／２ ] ０．４４ [(CH ３ ) ３ SiO １／２ ] ０．４０ [(CH ２ =CH)(CH ３ ) SiO ２／２ ] ０．１０ [CH ３ SiO ３／２ ] ０．５０ [(CH ３ ) ３ SiO １／２ ] ０．２０ [(CH ２ =CH)(CH ３ ) ２ SiO １／２ ] ０．２０ [CH ３ SiO ３／２ ]０．３０ [SiO ４／２ ] ０．３０

[0042] The component (B) may be used alone or in combination of two or more types.

[0043] The blending amount of component (B) is 10 to 60 parts by mass, preferably 15 to 30 parts by mass, per 100 parts by mass of the combined total of components (A) and (B). If the blending amount of component (B) is less than 10 parts by mass per 100 parts by mass of the combined total of components (A) and (B), it becomes difficult to obtain a sufficient reinforcing effect. On the other hand, if the blending amount exceeds 60 parts by mass, the viscosity of the composition increases, resulting in a decrease in dischargeability.

[0044] [Component (C)] Component (C) is an organohydrogenpolysiloxane that contains at least two silicon-bonded hydrogen atoms (i.e., Si—H groups) per molecule and does not contain any addition-reactive carbon-carbon double bonds, and it acts as a crosslinking agent by undergoing a hydrosilylation reaction with the alkenyl groups in components (A) and (B).

[0045] The molecular structure of the organohydrogenpolysiloxane of component (C) is not particularly limited and may be, for example, linear, cyclic, branched, or a three-dimensional network structure (resinous), with linear or cyclic structures being preferred.

[0046] The bonding positions of the silicon-bonded hydrogen atoms in the organohydrogenpolysiloxane molecule of component (C) may be at the molecular chain terminals, non-terminal positions on the molecular chain, or both.

[0047] The organohydrogenpolysiloxane of component (C) has at least two, and preferably 3 to 40, Si-H groups in each molecule.

[0048] The amount of silicon-bonded hydrogen atoms in component (C) is preferably 0.001 to 1 mol, and particularly preferably 0.005 to 0.5 mol, per 100 g of component (C).

[0049] In the organohydrogenpolysiloxane molecule of component (C), there are no particular restrictions on the silicon-bonded hydrocarbon groups other than the silicon-bonded hydrogen atoms. Examples include unsubstituted or substituted monovalent hydrocarbon groups that do not contain an addition-reactive carbon-carbon double bond, such as alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, and heptyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl and phenethyl; halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl; and substituted alkyl groups such as 3-glycidoxypropyl and 2-(3,4-epoxycyclohexyl)ethyl. Methyl and phenyl groups are preferred, and methyl groups are particularly preferred.

[0050] Component (C) may have one or more alkoxy groups bonded to silicon atoms per molecule, which can improve the shape retention and adhesiveness of the addition-curable silicone composition of the present invention. Examples of alkoxy groups include methoxy, ethoxy, propoxy, and butoxy groups, with methoxy groups being preferred. Furthermore, an alkoxysilyl group may be bonded to the silicon atom via an alkylene group, and specific examples of such groups include 2-(trimethoxysilyl)ethyl and 3-(trimethoxysilyl)propyl groups.

[0051] Component (C) preferably contains an organohydrogenpolysiloxane represented by the following formula (3): (In the formula, R ３ are independently a hydrogen atom, a 2-(trimethoxysilyl)ethyl group, or a 3-(trimethoxysilyl)propyl group, provided that R ３ At least one of R is a 2-(trimethoxysilyl)ethyl group or a 3-(trimethoxysilyl)propyl group, and R ３ At least two of the groups are hydrogen atoms. p is an integer of 0 to 50, q is an integer of 1 to 50, and the arrangement of the siloxane units in parentheses is arbitrary.

[0052] In the above formula (3), p is preferably from 0 to 50 in order to improve the curability of the composition and the rubber properties of the cured product, and q is preferably from 1 to 50 in order to improve the shape retention and adhesiveness of the composition.

[0053] In the organohydrogenpolysiloxane represented by formula (3) above, the 2-(trimethoxysilyl)ethyl group or 3-(trimethoxysilyl)propyl group bonded to the silicon atom may be bonded either to the terminal or to a side chain of the molecular chain, but it is preferred that the alkoxy group be bonded only to the terminal of the molecular chain.

[0054] In the above formula (3), p is preferably 0 to 20, more preferably 1 to 10, and q is preferably 1 to 30, more preferably 2 to 10.

[0055] The organohydrogenpolysiloxane represented by the above formula (3) can be obtained, for example, by subjecting a dimethylsiloxane-hydrogenmethylsiloxane copolymer, both molecular chain terminals of which are blocked with dimethylsiloxy groups, to a hydrosilylation reaction with vinyltrimethoxysilane or allyltrimethoxysilane in the presence of a platinum group metal catalyst.

[0056] Specific examples of component (C) include, but are not limited to, organohydrogenpolysiloxanes represented by the following formula: (In the formula, the siloxane units enclosed in siloxane brackets may be arranged in any order.)

[0057] The organohydrogenpolysiloxane of component (C) may use either a single compound, or a combination of two or more different compounds.

[0058] The viscosity of component (C) at 25°C is preferably in the range of 0.1 to 5,000 mPa·s, more preferably 0.5 to 1,000 mPa·s, and particularly preferably 2 to 200 mPa·s, so that the composition is easy to work with and the cured product has excellent optical and mechanical properties, and is in a liquid state at 23°C. When such a viscosity is satisfied, the number of silicon atoms (or degree of polymerization) per molecule of the organohydrogenpolysiloxane is typically 2 to 1,000, preferably 3 to 200, and more preferably 4 to 50.

[0059] The amount of component (C) to be added is an amount that results in 1.0 to 3.0 moles, and preferably 1.5 to 2.5 moles, of silicon-bonded hydrogen atoms per mole of alkenyl groups in components (A) and (B). If the amount is less than 1.0 mole, the adhesive strength of the cured product may decrease, while if it exceeds 3.0 moles, the hardness of the cured product may decrease, resulting in inferior rubber strength.

[0060] [Component (D)] The platinum group metal hydrosilylation catalyst for component (D) is not particularly limited, so long as it promotes the hydrosilylation reaction between the alkenyl groups in components (A) and (B) and the Si—H groups in component (C). Specific examples include platinum group metals such as platinum, palladium, and rhodium; platinum compounds such as chloroplatinic acid, alcohol-modified chloroplatinic acid, and coordination compounds of chloroplatinic acid with olefins, vinylsiloxanes, or acetylene compounds; and platinum group metal compounds such as tetrakis(triphenylphosphine)palladium and chlorotris(triphenylphosphine)rhodium. Of these, platinum compounds are preferred, and coordination compounds of chloroplatinic acid with vinylsiloxanes are particularly preferred.

[0061] Furthermore, the component (D) may be a platinum catalyst that is inactive under light-shielded conditions and that changes into an active platinum catalyst when irradiated with light or when exposed to radicals generated by decomposition of an organic peroxide, as described below. Specific examples of such component (D) include, but are not limited to, cyclopentadienyltrimethylplatinum and derivatives thereof in which the cyclopentadienyl group has been modified, and bis(acetylacetonato)platinum and derivatives thereof in which the acetylacetonato group has been modified.

[0062] The component (D) may use either a single compound or a combination of two or more compounds.

[0063] The amount of component (D) to be blended need only be an effective amount as a hydrosilylation catalyst, but is generally 0.0001 to 0.1 parts by mass, and preferably 0.0003 to 0.01 parts by mass, calculated as the mass of platinum group metal, per 100 parts by mass of components (A) and (B) combined. When this range is met, the reaction rate of the addition reaction becomes appropriate, and a cured product with high strength can be obtained.

[0064] [Component (E)] Component (E) is fumed silica, which provides the addition-curable silicone composition of the present invention with suitable ejection properties and shape retention, and improves the strength of the cured product. From the standpoint of shape retention, the fumed silica of the present invention has a specific surface area measured by the BET method of 150 to 350 m ２ It is preferable that the molecular weight is 1 / g.

[0065] Furthermore, since this improves dispersibility in the addition-curable silicone composition of the present invention, it is preferable that component (E) has been surface-treated. For example, it is preferable to treat the surface hydroxyl groups with a silicon compound such as dimethyldichlorosilane or hexamethyldisilazane, and particularly preferable is fumed silica that has been surface-treated with hexamethyldisilazane.

[0066] The fumed silica was Musil 120A (manufactured by Shin-Etsu Chemical Co., Ltd., hexamethyldisilazane treatment, BET 200m ２ / g) and Musil 130A (Shin-Etsu Chemical Co., Ltd., hexamethyldisilazane treatment, BET 300m ２ / g), NSX-200 (manufactured by Nippon Aerosil Co., Ltd., hexamethyldisilazane treatment, BET200m ２ / g) and Reolosil DM30S (manufactured by Tokuyama Corporation, treated with dimethyldichlorosilane).

[0067] The content of component (E) is 5 to 30 parts by mass, and preferably 10 to 20 parts by mass, per 100 parts by mass of the total of components (A) and (B). If the content is less than 5 parts by mass, the addition-curable silicone composition of the present invention will be poor in shape retention after being discharged, and the height of the dam material may be insufficient. If the content exceeds 30 parts by mass, the dischargeability of the composition may be impaired.

[0068] [Component (F)] Component (F) is a particle of (i) titanium oxide whose surface has been surface-treated with (ii) an organosilicon compound that has trialkoxysilyl groups and no hydrogen atoms bonded to silicon atoms, and is a component that imparts light reflecting properties to the addition-curable silicone composition of the present invention.

[0069] If the surface of titanium oxide is not treated with the organosilicon compound, the viscosity of the addition-curable silicone composition of the present invention will change significantly over time, which may result in problems such as reduced productivity due to a decrease in the dischargeability of the composition and poor formation of dam materials.

[0070] The particle size of the titanium oxide (i) is not particularly limited, but from the viewpoint of dispersibility and reflectance, it is preferable that the average particle size be 0.1 to 0.5 μm as determined by particle size distribution measurement using a laser diffraction method.

[0071] The crystalline form of titanium oxide is classified into anatase, rutile, and brookite, but it is preferable to use the rutile type, which has the most stable thermal transition. In addition, the surface may be treated with a surface treatment agent other than an organosilicon compound, or with a metal such as silicon, aluminum, or zirconium, or an oxide thereof.

[0072] As such titanium oxide, commercially available products may be used, and specific examples include R-820 (rutile type, average particle size 0.26 μm, Al / Si / Zn surface treatment), CR-60 (rutile type, average particle size 0.21 μm, Al surface treatment), and PF-691 (rutile type, average particle size 0.21 μm, polyol surface treatment), all manufactured by Ishihara Sangyo Kaisha, Ltd.

[0073] The amount of (i) titanium oxide is 5 to 50 parts by mass, and preferably 10 to 30 parts by mass, per 100 parts by mass of the total of components (A) and (B). If the amount is less than 5 parts by mass, the light reflectivity of the cured product may be insufficient, and if the amount is more than 50 parts by mass, the dischargeability and storage stability of the composition may be reduced.

[0074] The (ii) organosilicon compound having a trialkoxysilyl group and no hydrogen atoms bonded to silicon atoms is distinguished from the components (A) and (B) in that it has a trialkoxysilyl group, and from the component (C) in that it has no hydrogen atoms bonded to silicon atoms.

[0075] Examples of the trialkoxysilyl group include a trimethoxysilyl group, a triethoxysilyl group, and a tripropoxysilyl group, with a trimethoxysilyl group being particularly preferred.

[0076] The group bonded to the silicon atom other than the alkoxy group is not particularly limited, and examples thereof include unsubstituted or substituted monovalent hydrocarbon groups, such as alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, and heptyl; alkenyl groups such as vinyl, allyl, and 3-butenyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl and phenethyl; halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl; and substituted alkyl groups such as 3-glycidoxypropyl and 2-(3,4-epoxycyclohexyl)ethyl, with methyl, vinyl, and 3-glycidoxypropyl being preferred.

[0077] In the addition-curable silicone composition of the present invention, the organosilicon compound in component (F) is preferably an organopolysiloxane represented by the following formula (4). (In the formula, R ４ are independently a methyl group or a methoxy group, n is an integer of 0 to 10, m is an integer of 1 to 50, and the arrangement of the siloxane units in parentheses is arbitrary.

[0078] In the addition-curable silicone composition of the present invention, when the organosilicon compound component in component (F) is an organopolysiloxane represented by the above formula (4), volatilization of the organosilicon compound can be further suppressed.

[0079] Specific examples of such (ii) organosilicon compounds having trialkoxysilyl groups and no hydrogen atoms bonded to silicon atoms include, but are not limited to, those represented by the following formulas: (In the formula, the order of the parenthesized siloxane units is not specified.)

[0080] The amount of (ii) organosilicon compound having a trialkoxysilyl group and no hydrogen atom bonded to a silicon atom is preferably 10 to 60% by mass, and more preferably 20 to 50% by mass, based on the mass of (i) titanium oxide, from the viewpoints of dispersibility of component (F) and suppressing an increase in viscosity of the composition over time.

[0081] Component (F) can be obtained, for example, by heat treating a composition containing (i) titanium oxide and (ii) an organosilicon compound having trialkoxysilyl groups and no hydrogen atoms bonded to silicon atoms at 100 to 180° C. A heat treatment temperature in the range of 100 to 180° C. is preferred because it allows the hydrolysis and condensation reaction of the trialkoxysilyl groups on the titanium oxide surface to proceed efficiently.

[0082] The temperature during the heat treatment is preferably 120 to 160°C, and the heat treatment time is preferably 30 minutes to 5 hours, more preferably 1 to 3 hours. In order to efficiently remove alcohol and water that are by-produced by the hydrolysis and condensation reaction of the alkoxy groups on the titanium oxide surface and to promote the reaction, it is preferable to carry out the heat treatment under reduced pressure.

[0083] The component (F) may be used alone or in combination of two or more types.

[0084] <Other Components> Depending on the purpose, components such as a reaction inhibitor, an organic peroxide, or an adhesion improver may be added to the addition-curable silicone composition of the present invention.

[0085] Examples of reaction inhibitors include phosphorus-containing compounds such as triphenylphosphine; nitrogen-containing compounds such as tributylamine, tetramethylethylenediamine, and benzotriazole; sulfur-containing compounds; acetylene compounds; hydroperoxy compounds; maleic acid derivatives; and acetylene alcohol-based reaction inhibitors such as 1-ethynyl-1-cyclohexanol, 3-methyl-1-tridecyn-3-ol, and 3,5-dimethyl-1-hexyn-3-ol, with acetylene alcohol-based reaction inhibitors being preferred.

[0086] Because the degree of curing inhibition effect of a reaction inhibitor varies greatly depending on the chemical structure of the reaction inhibitor, it is preferable to adjust the amount of reaction inhibitor to an optimal amount for each reaction inhibitor used. Typically, 0.001 to 5 parts by mass per 100 parts by mass of the total of components (A) and (B) is preferred. When the amount is 0.001 part by mass or more, the composition can be sufficiently stored for a long time at room temperature. When the amount is 5 parts by mass or less, there is no risk of inhibiting curing of the composition.

[0087] Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, o-methylbenzoyl peroxide, p-methylbenzoyl peroxide, dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,3-trimethylcyclohexane, 1,6-bis(t-butylperoxycarbonyloxy)hexane, and di(4-methylbenzoylperoxy)hexamethylene biscarbonate.

[0088] The amount of organic peroxide added is preferably 0.01 to 5 parts by mass, and particularly preferably 0.05 to 3 parts by mass, per 100 parts by mass of the total of components (A) and (B). Within this range, further improvements in resin strength can be achieved. These can be used alone or in combination of two or more types.

[0089] As the adhesion improver, from the viewpoint of imparting self-adhesiveness to the composition of the present invention, which is an addition reaction curing type, an organosilicon compound such as silane or siloxane, or a non-silicone organic compound containing a functional group that imparts adhesiveness, is used.

[0090] Specific examples of functional groups that impart adhesiveness include alkenyl groups such as vinyl groups and allyl groups, or hydrogen atoms; epoxy groups (e.g., 3-glycidoxypropyl group, 2-(3,4-epoxycyclohexyl)ethyl group, etc.), acryloxy groups (e.g., 3-acryloxypropyl group, etc.), or methacryloxy groups (e.g., 3-methacryloxypropyl group, etc.) bonded via a carbon atom.

[0091] Examples of non-silicone organic compounds include organic acid allyl esters, epoxy group ring-opening catalysts, organic titanium compounds, organic zirconium compounds, and organic aluminum compounds.

[0092] [Method for Producing Addition-Curable Silicone Composition] The addition-curable silicone composition of the present invention may be produced by mixing components (A) to (E), (i) titanium oxide and (ii) an organosilicon compound having a trialkoxysilyl group and no silicon-bonded hydrogen atoms that constitute component (F), and other components as needed, followed by heat treatment at 100 to 180°C, or by preparing component (F) first and then mixing this with components (A) to (E) and other components as needed. In the latter case, component (F) is first prepared by heat treating (i) titanium oxide and (ii) an organosilicon compound having a trialkoxysilyl group and no silicon-bonded hydrogen atoms at 100 to 180°C, and the resulting component (F) is then mixed with components (A) to (E) and other components as needed to produce the addition-curable silicone composition of the present invention.

[0093] [Cured silicone product for light reflectors] By curing the addition-curable silicone composition of the present invention, a white cured silicone product for light reflectors can be obtained. Because the addition-curable silicone composition of the present invention has good dischargeability, it can be discharged using a dispensing device and then cured to form a light reflector. The curing conditions for the addition-curable silicone composition of the present invention are not particularly limited, but are typically 80 to 200°C, preferably 100 to 150°C, for 30 minutes to 4 hours, and more preferably 30 minutes to 1 hour.

[0094] The hardness (Durometer Type A hardness) of a sheet obtained by curing the addition-curable silicone composition of the present invention at 150°C for 1 hour is preferably in the range of 50 to 70. A Type A hardness of 50 or higher provides sufficient rubber strength for use as a dam material, while a Type A hardness of 70 or lower provides flexibility that can prevent defects such as cracks under actual use conditions.

[0095] The light reflectivity of the cured silicone product for light reflectors of the present invention is evaluated by measuring the relative light reflectance (light reflectance) at a wavelength of 450 nm when an aluminum oxide plate is used as a blank (100%). Specifically, the silicone composition for light reflectors of the present invention is cured at 150°C for 1 hour to produce a 2 mm thick cured silicone product for light reflectors of the present invention, and the relative light reflectance (light reflectance) of this 2 mm thick cured product at a wavelength of 450 nm is measured. A cured product with a light reflectance of 95% or more is evaluated as being preferable.

[0096] [Light Reflecting Material] A light reflecting material made of the cured silicone product for light reflecting material of the present invention can be suitably used, for example, in optical semiconductor devices such as LEDs, particularly as a dam material.

[0097] [Optical Semiconductor Device] Furthermore, the present invention provides an optical semiconductor device having the above-mentioned light-reflecting material.

[0098] As described above, the addition-curable silicone composition of the present invention provides a cured silicone product for use as a light reflector that has excellent light reflecting performance. Therefore, optical semiconductor devices such as white LEDs that use the light reflector of the present invention can maintain high light extraction efficiency for a long period of time.

[0099] There are no particular limitations on the method of using the addition-curable silicone composition of the present invention, but for example, the addition-curable silicone composition of the present invention is dispensed using a dispenser around an LED element placed on a substrate such as an FRP (fiber reinforced plastic) resin using an epoxy resin, to form a frame in a shape such as a square as a dam material. The dispensed composition is cured in a heating furnace, and a resin (epoxy resin, silicone resin, etc.) that seals the LED element is potted inside the dam material and cured to seal it.

[0100] If the viscosity of the dam material increases during this process, defects such as stringiness will occur during extrusion, reducing productivity, and the dam material will not be formed properly, adversely affecting optical properties such as light reflectivity. The addition-curable silicone composition of the present invention can suppress increases in viscosity during storage, thereby improving productivity.

[0101] EXAMPLES The present invention will be specifically explained below using examples and comparative examples, but the present invention is not limited to these.

[0102] In the following, the viscosity at 23°C is measured using a BH type rotational viscometer at 4 rpm. The abbreviations for each siloxane unit are as follows: M: (CH ３ ) ３ SiO １／２ M Ｖｉ :(CH ２ =CH)(CH ３ ) ２ SiO １／２ M Ｈ : H(CH ３ ) ２ SiO １／２ M Ｓｉ : D: (CH ３ ) ２ SiO ２／２ D Ｖｉ :(CH ２ =CH)(CH ３ ) SiO ２／２ D Ｈ : H(CH ３ ) SiO ２／２ Q: SiO ４／２

[0103] Examples 1 to 6, Comparative Examples 1 to 4 Addition-curable silicone compositions were prepared by mixing the following components in the amounts shown in Tables 1 and 2. The numerical values ​​for each component in Table 1 represent parts by mass.

[0104] That is, first, using a 5-liter gate mixer (manufactured by Inoue Seisakusho Co., Ltd., product name: 5-liter planetary mixer), component (A), component (B), component (Fi), and component (F-ii) were mixed for 1 hour at 25°C, followed by a heat treatment for 2 hours at 150°C and a reduced pressure of 0.1 MPa. Next, component (E) was added at 25°C and mixed for 30 minutes, followed by component (D) and component (G) (and component (H) in Examples 5 and 6 and Comparative Example 4) and mixed for 30 minutes at 25°C, and finally component (C) was added and mixed for 30 minutes at 25°C under reduced pressure (30 mmHg), yielding an addition-curable silicone composition.

[0105] (A) Component: (A-1)M Ｖｉ ２ D ２１６ (A-2)M is a linear organopolysiloxane having a vinyl group content of 0.012 mol / 100 g and a viscosity of 1,000 mPa·s at 23°C. Ｖｉ ２ D ３８８ and a linear organopolysiloxane having a vinyl group content of 0.007 mol / 100 g and a viscosity of 5,000 mPa·s at 23°C.

[0106] Component (B): (B-1) Average structural unit ratio is M ０．４ M Ｖｉ ０．０６ Q ０．５４ and the organopolysiloxane resin (B-2) is solid at 23°C and has a vinyl group content of 0.085 mol / 100 g, and has an average structural unit ratio of M ０．４８ D Ｖｉ ０．０８ Q ０．４４ and an organopolysiloxane resin that is solid at 23°C and has a vinyl group content of 0.11 mol / 100 g.

[0107] (C) Component: (C-1)M ２ D Ｈ ８ and an organohydrogenpolysiloxane (C-2)M having a SiH content of 0.012 mol / g. Ｈ M Ｓｉ D ２ D Ｈ ７Organohydrogenpolysiloxane (C-3)M ２ D Ｈ ３８ (C-4) Organohydrogenpolysiloxanes represented by the following structural formula:

[0108] Component (D): (D-1) a hydrosilylation catalyst prepared by diluting a reaction product of hexachloroplatinic acid and 1,3-divinyltetramethyldisiloxane with dimethylpolysiloxane having a viscosity of 600 mPa·s to give a platinum content of 1% by mass; and (D-2) a hydrosilylation catalyst prepared by diluting trimethyl(methylcyclopentadienyl)platinum complex with dimethylpolysiloxane having a viscosity of 600 mPa·s to give a platinum content of 0.5% by mass.

[0109] (E) Component: (E-1) BET specific surface area 200m ２ / g of surface-hydrophobized fumed silica (Musil 120A, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0110] (Fi) Components: (Fi-1) Rutile-type titanium dioxide having an average particle size of 0.21 μm and an Al-treated surface (CR-60 manufactured by Ishihara Sangyo Kaisha, Ltd.) (Fi-2) Rutile-type titanium dioxide having an average particle size of 0.21 μm and an Al-treated surface (PF-691 manufactured by Ishihara Sangyo Kaisha, Ltd.)

[0111] Component (F-ii): (F-ii-1) Organopolysiloxane represented by the following formula (viscosity: 31 mPa·s) (F-ii-2) Organopolysiloxane represented by the following formula (viscosity 18 mPa s) (In the formula, the order of the parenthesized siloxane units is not specified.) (F-ii-3) 3-glycidoxypropyltrimethoxysilane

[0112] Component (G): Reaction inhibitor (G-1) 1-ethynyl-1-cyclohexanol

[0113] Component (H): Peroxide (H-1) 1,6-bis(t-butylperoxycarbonyloxy)hexane (containing 30% aliphatic plasticizer) (Kayalene 6-70, manufactured by Nouryon Chemical Co., Ltd.)

[0114]

[0115]

[0116] The addition-curable silicone compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were evaluated as follows, and the results are shown in Table 3.

[0117] [Viscosity and Viscosity Increase Rate] Immediately after production, the viscosity of each addition-curable silicone composition was measured using a BH-type viscometer (manufactured by Toki Sangyo Co., Ltd.) with a rotor No. 7 at a rotation speed of 4 rpm. Each composition was then allowed to stand at 40°C for 7 days, after which the viscosity was measured again, and the viscosity increase rate was calculated according to the following formula: Viscosity increase rate (%) = (viscosity after 7 days - viscosity immediately after production) / viscosity immediately after production × 100 A smaller viscosity increase rate indicates better storage stability. A viscosity increase rate of less than 25% can be evaluated as having sufficient storage stability for a one-component addition-curable silicone composition.

[0118] [Slump] In accordance with JIS A 1439:2022, each addition-curable silicone composition was filled into the groove of a stainless steel grooved container (20 mm wide x 10 mm deep x 200 mm long) to prepare a test specimen. Immediately after preparation, the test specimen was suspended vertically and allowed to stand at 23°C for 30 minutes. The distance from the bottom end of the groove of the grooved container to the hanging tip of each test specimen sample was measured. The shape retention of the addition-curable silicone composition of the present invention was evaluated by marking it as ◯ if it was less than 5 mm and x if it was 5 mm or more.

[0119] [Hardness] Each addition-curable silicone composition was cured at 150°C for 1 hour and measured in accordance with JIS K 6249: 2003. A hardness (Durometer Type A hardness) of 50 to 70 was evaluated as having good rubber properties.

[0120] [Light Reflectance] Each composition was cured at 150°C for 1 hour to produce a 2 mm thick cured product of the addition-curable silicone composition of the present invention. The relative light reflectance of the resulting cured product at a wavelength of 450 nm, using an aluminum oxide plate as a blank (100%), was measured using a spectrophotometer U-3310 with a Φ60 integrating sphere accessory manufactured by Hitachi, Ltd.

[0121]

[0122] As shown in Table 3, the addition-curable silicone compositions of Examples 1 to 6 had low slump values ​​and excellent shape retention as dam materials, and after storage at 40°C for 7 days, their viscosity increase rate was less than 25%, demonstrating excellent storage stability. The hardness and light reflectance of the resulting cured products were also good.

[0123] On the other hand, in Comparative Example 3, which did not contain the components (Fi) and (F-ii) constituting the component (F) of the present invention, the light reflectivity was insufficient due to the absence of titanium oxide. Furthermore, in Comparative Examples 1, 2, and 4, which did not contain the component (F-ii), which is an organosilicon compound having a trialkoxysilyl group and no hydrogen atoms bonded to silicon atoms, the surface of the titanium oxide was not surface-treated with component (F-ii), resulting in a significant increase in viscosity after storage at 40°C for 7 days.

[0124] As described above, it has been found that the present invention can provide an addition-curable silicone composition that has shape-retaining properties, exhibits little change in viscosity over time, has excellent storage stability, and gives a cured product with excellent light reflecting performance.Furthermore, it has been found that the cured product of the addition-curable silicone composition of the present invention exhibits little change in viscosity over time, exhibits excellent storage stability, and has excellent light reflecting performance, and therefore provides a light reflecting material that can be suitably used for optical semiconductor devices such as LEDs, particularly as a dam material.

[0125] This specification encompasses the following embodiments: [1]: (A) 40 to 90 parts by mass of a linear organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule and no trialkoxysilyl groups, and having a viscosity of 500 to 100,000 mPa·s at 23°C, (B) 10 to 60 parts by mass of an organopolysiloxane resin represented by the following average composition formula (1) (provided that the total of components (A) and (B) is 100 parts by mass), (R １ ３ SiO １／２ ) ａ (R １ ２ R ２ SiO １／２ ) ｂ (R １ ２ SiO) ｃ (R １ R ２ SiO) ｄ (R １ SiO ３／２ ) ｅ (R ２ SiO ３／２ ) ｆ (SiO ４／２ ) ｇ (1) (wherein, R １ are independently unsubstituted or halogen-substituted monovalent hydrocarbon groups containing no addition-reactive carbon-carbon double bonds, and R ２are independently an alkenyl group. a, b, c, d, e, f, and g are numbers that satisfy b+d+f>0 and e+f+g>0, and a+b+c+d+e+f+g=1. (C) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule and no addition-reactive carbon-carbon double bonds: in an amount such that 1.0 to 3.0 moles of silicon-bonded hydrogen atoms per mole of alkenyl groups in components (A) and (B), (D) a hydrosilylation catalyst containing a platinum group metal: 0.0001 to 0.1 parts by mass, calculated as the mass of the platinum group metal, (E) fumed silica: 5 to 30 parts by mass, and (F) (i) particles of titanium oxide whose surfaces have been surface-treated with an organosilicon compound, the particles having (ii) trialkoxysilyl groups and no silicon-bonded hydrogen atoms: 5 to 50 parts by mass of (i). [2]: The addition-curable silicone composition according to item [1] above, wherein component (C) comprises an organohydrogenpolysiloxane represented by the following formula (3): (In the formula, R ３ are independently a hydrogen atom, a 2-(trimethoxysilyl)ethyl group, or a 3-(trimethoxysilyl)propyl group, provided that R ３ At least one of R is a 2-(trimethoxysilyl)ethyl group or a 3-(trimethoxysilyl)propyl group, and R ３ where two or more of the groups are hydrogen atoms. p is an integer from 0 to 50, q is an integer from 1 to 50, and the arrangement of the parenthesized siloxane units is arbitrary.) [3]: The addition-curable silicone composition according to [1] or [2] above, wherein the organosilicon compound in component (F) is an organopolysiloxane represented by the following formula (4): (In the formula, R ４are independently a methyl group or a methoxy group, n is an integer of 0 to 10, m is an integer of 1 to 50, and the arrangement of the parenthesized siloxane units is arbitrary.) [4]: ​​A method for producing the addition-curable silicone composition described in any one of [1] to [3] above, comprising a step of heat-treating a composition containing (i) titanium oxide and (ii) an organosilicon compound having a trialkoxysilyl group and no hydrogen atoms bonded to silicon atoms at 100 to 180°C. [5]: A cured silicone product for light reflectors, characterized by being a cured product of the addition-curable silicone composition described in any one of [1] to [3] above. [6]: A cured silicone product for light reflectors described in [5] above, characterized by having a reflectance of 95% or more at a thickness of 2 mm for light with a wavelength of 450 nm. [7]: A light-reflecting material characterized by comprising the cured silicone product for light reflectors described in [5] or [6] above. [8]: An optical semiconductor device characterized by comprising the light-reflecting material described in [7] above.

[0126] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. (A) A linear organopolysiloxane having at least 2 alkenyl groups bonded to silicon atoms in one molecule and no trialkoxysilyl group, with a viscosity at 23°C of 500 to 100,000 mPa·s: 40 to 90 parts by mass, (B) An organopolysiloxane resin represented by the following average composition formula (1): 10 to 60 parts by mass (provided that the total of component (A) and component (B) is 100 parts by mass).), (R １ ３ SiO １／２ ) ａ (R １ ２ R ２ SiO １／２ ) ｂ (R １ ２ SiO) ｃ (R １ R ２ SiO) ｄ (R １ SiO ３／２ ) ｅ (R ２ SiO ３／２ ) ｆ (SiO ４／２ ) ｇ (1) (In the formula, R １ is independently an unsubstituted or halogen-substituted monovalent hydrocarbon group that does not contain an addition-reactive carbon-carbon double bond, R ２ is an alkenyl group independently. a, b, c, d, e, f, and g are numbers that satisfy b + d + f > 0 and e + f + g > 0, and a + b + c + d + e + f + g = 1. ) (C) An organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule and no addition-reactive carbon-carbon double bond: an amount such that the hydrogen atoms bonded to silicon atoms are 1.0 to 3.0 moles per mole of the alkenyl group in components (A) and (B), (D) A hydrosilylation catalyst containing a platinum group metal: 0.0001 to 0.1 part by mass in terms of the mass of the platinum group metal, (E) Fumed silica: 5 to 30 parts by mass, and (F) (i) Particles whose surface of titanium oxide is surface-treated with (ii) an organosilicon compound having a trialkoxysilyl group and no hydrogen atom bonded to a silicon atom: 5 to 50 parts by mass as the mass of (i), An addition-curing type silicone composition characterized by containing.

2. The addition-curing silicone composition according to claim 1, wherein the component (C) contains an organohydrogenpolysiloxane represented by the following formula (3). (In the formula, R ３ is independently a hydrogen atom, a 2-(trimethoxysilyl)ethyl group or a 3-(trimethoxysilyl)propyl group, provided that one or more of R ３ are a 2-(trimethoxysilyl)ethyl group or a 3-(trimethoxysilyl)propyl group, and two or more of R ３ are hydrogen atoms. p is an integer from 0 to 50, q is an integer from 1 to 50, and the arrangement of the siloxane units in parentheses is arbitrary.) 3. The addition-curing silicone composition according to claim 1, wherein the organosilicon compound in the component (F) is an organopolysiloxane represented by the following formula (4). (In the formula, R ４ is independently a methyl group or a methoxy group, n is an integer of 0 to 10, m is an integer of 1 to 50, and the arrangement of the siloxane units with parentheses is arbitrary.) 4. A method for producing an addition-curable silicone composition according to any one of claims 1 to 3, comprising the step of heat-treating a composition containing (i) titanium oxide and (ii) an organosilicon compound having a trialkoxysilyl group and no hydrogen atom bonded to a silicon atom at 100 to 180 °C.

5. A silicone cured product for a light reflecting material, which is a cured product of the addition-curable silicone composition according to any one of claims 1 to 3.

6. The silicone cured product for a light reflecting material according to claim 5, wherein the reflectance of light having a wavelength of 450 nm at a thickness of 2 mm is 95% or more.

7. A light reflecting material comprising the silicone cured product for a light reflecting material according to claim 5.

8. An optical semiconductor device comprising the light reflecting material according to claim 7.

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