KR20080103898A - Liquid silicone rubber compositions for optical waveguide plate - Google Patents

Abstract

A liquid silicone rubber composition for optical waveguide plate is provided to form a hardened material having the hardness and flexibility and to be suitable as a backlighting device. A curable liquid silicone rubber composition for optical waveguide plate comprises a unit selected from (A) 100 pats by mass of silicon resin which consists of R3SiO1/2 unit(M unit), SiO4/2 unit(Q unit), R2SiO2/2 unit(D unit) and RSiO3/2 unit(T-unit), wherein the total amount of Q unit and M unit is 80mol% or greater in the whole components and the molar ratio of M unit to Q unit is 0.5~1.5 (wherein R is a C1-6 hydrocarbon group and at least two in one molecule are an alkenyl group); (B) 50~200 pats by mass of organopolysiloxane containing an alkenyl group and having the average polymerization degree of 2,000 or less, which is the liquid at a room temperature; (C) 1~50 pats by mass of organopolysiloxane containing an alkenyl group capable of bonding silicon atom and having the average polymerization degree of 2,000 or more, which is the raw rubber at a room temperature; and (D) organo hydrogen polysiloxane containing a hydrogen atom bonded with a silicon atom.

Description

Liquid silicone rubber composition for light wave plate {LIQUID SILICONE RUBBER COMPOSITIONS FOR OPTICAL WAVEGUIDE PLATE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid silicone rubber composition for an optical waveguide, which is mainly composed of organopolysiloxane and is cured by a hydrosilylation reaction. In particular, since a molded article having high transparency and hardness is obtained, a backlight device for keypad dimming of a cellular phone is obtained. It is suitably used for an optical waveguide.

Many keypads are equipped with a dimming backlight device for night use of a mobile phone, and conventionally, a plurality of light emitting diodes (LEDs) are arranged at the back of the keypad. However, with the recent increase in the high functionality of mobile phones, the demand for thinner, lighter weight, higher luminance, and cost down has also increased in dimming backlight devices, and a dimming backlight device using an optical waveguide that is also employed in liquid crystal monitors (LCDs) has been proposed. It is composed of an LED light source and an optical waveguide that introduces and diffuses light from inside of a cross section facing the light source, and reflects light from a reflecting surface provided at a key portion to be illuminated to project reflected light to the outside (patent) Document 1: See Japanese Patent Laid-Open No. 2003-59321. The feature of this device is that it can be made thinner by installing the LED in the lateral direction, and the front surface of the keypad can be uniformly dimmed with high brightness even if the number of LEDs is reduced compared to the type of LEDs installed in the rear. In addition, since the power consumption was also reduced, the size and weight of the battery were also advanced, contributing to the reduction in cost.

The optical waveguide of the LCD backlight unit requires only optical characteristics. The optical waveguide of the keypad dimming backlight unit also transmits the displacement (click) of the key input to the switching element, so that in addition to being highly transparent, elasticity or temperature dependency A small thing, the thing which can shape | mold a surface smooth film with thin, uniform thickness, etc. are also needed. In general, acrylic resins and polycarbonate resins are highly transparent and have good film formability. However, cracks may occur during key input due to elastic temperature dependence, particularly at low temperature, due to embrittlement. Therefore, highly transparent silicone resin applied to optical materials, such as LED sealing material (patent document 2: Unexamined-Japanese-Patent No. 2002-265787, patent document 3: Unexamined-Japanese-Patent No. 2006-202952, patent document 4: Japanese patent) Japanese Patent Application Laid-Open Publication No. 2006-342200) has been noted for its excellent low temperature characteristics. Among them, a cured product of a hydrosilylation-curable liquid silicone rubber composition, which is highly transparent because it does not contain any silica and does not impair elasticity even at low temperatures and is relatively easy to form a film by thermal curing, is used as an optical waveguide of a backlight device for a keypad. It became.

However, silicone rubber which does not contain any silica as a reinforcing material is generally not suitable for film molding because it has no strength and is soft and has surface adhesiveness. When the crosslinking density is increased, the film formability is improved because the strength and hardness are improved and the adhesiveness is also reduced, but it becomes a soft film without flexibility.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2003-59321

[Patent Document 2] Japanese Unexamined Patent Publication No. 2002-265787

[Patent Document 3] Japanese Unexamined Patent Publication No. 2006-202952

[Patent Document 4] Japanese Unexamined Patent Publication No. 2006-342200

 This invention is made | formed in view of the said situation, As a highly transparent hydrosilylation-curable liquid silicone rubber composition which does not contain the silica as a reinforcement material at all, it can form the hardened | cured material which made both hardness and flexibility, especially for a backlight device. It is an object to provide a hydrosilylation-curable liquid silicone rubber composition suitable for an optical waveguide.

MEANS TO SOLVE THE PROBLEM The present inventors earnestly examined in order to achieve the said objective, and made it the hydrosilylation-curable liquid silicone rubber composition which used together the silicone resin for expressing the hardness of hardened | cured material, and the raw rubber type organopolysiloxane for giving flexibility. It was found out that both the hardness and the flexibility of the molded film after curing were possible, and the present invention was reached.

That is, the present _{invention, (A) R 3 SiO 1} /2 units (M units), SiO _4/2 units (Q units), R ₂ SiO _2/2 units (D units) and RSiO _3/2 units (T units 100 parts by mass of a silicone resin, wherein the total amount of the M unit and the Q unit is 80 mol% or more, and the molar ratio of the M unit to the Q unit is in the range of 0.5 to 1.5.

(Wherein R is a monovalent hydrocarbon group having 1 to 6 carbon atoms and at least two of the molecules are alkenyl groups.)

(B) 50 to 200 parts by mass of an organopolysiloxane which is a liquid at room temperature having an average degree of polymerization of 2,000 or less and containing an alkenyl group bonded to at least two silicon atoms in one molecule,

(C) 1 to 50 parts by mass of an organopolysiloxane in the form of a raw rubber at room temperature containing an alkenyl group bonded to at least two silicon atoms in one molecule with an average degree of polymerization of more than 2,000,

(D) a silicon atom per one alkenyl group in which an organohydrogenpolysiloxane containing a hydrogen atom bonded to at least two silicon atoms in one molecule is bonded to a silicon atom in the components (A), (B) and (C) In an amount such that the number of hydrogen atoms bonded to is 1.0 to 10.0, and

(E) catalytic amount of hydrosilylation reaction catalyst

It provides a hydrosilylation-curable liquid silicone rubber composition for an optical waveguide comprising as an essential component.

Since the hardened | cured material film of the hydrosilylation hardening type liquid silicone rubber composition of this invention is highly transparent, high hardness, and flexible, it is optimal as an optical waveguide of the backlight device for keypad dimming of a mobile telephone.

Hereinafter, the present invention will be described in more detail.

Silicone resin (A) in the hydrosilylation-curable liquid silicone rubber composition of the present invention component, R ₃ SiO _1/2 units (M units), SiO _4/2 units (Q units), R ₂ SiO _2/2 Unit (D unit) and RSiO _3/2 unit (T unit), and the total amount of M unit and Q unit among these constituent units is 80 mol% or more, and the molar ratio of M unit to Q unit is It is of a branched or three-dimensional mesh structure ranging from 0.5 to 1.5. Here, R is a C1-C6 monovalent hydrocarbon group and at least 2 of 1 molecule is an alkenyl group.

As a specific example of the C1-C6 monovalent hydrocarbon group R of the said silicone resin, Alkyl groups, such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a vinyl group, an allyl group, butenyl group, a pentenyl group, Said monovalent hydrocarbon groups, such as unsubstituted monovalent hydrocarbon groups, 3,3,3- trifluoropropyl group, cyanomethyl group, such as alkenyl groups, such as hexenyl group, a cyclohexyl group, a cyclohexenyl group, and a phenyl group Substituted monovalent hydrocarbon groups, such as a substituted alkyl group in which at least a part of the hydrogen atoms of the hydrogen atom is substituted by a halogen atom and a cyano group, and a plurality of R contained in the silicone resin of (A) component may be same or different, From the viewpoint of compatibility with other components of the hydrosilylation-curable liquid silicone rubber composition, it is preferable that at least 80 mol% of R is a methyl group. It is because transparency of the hardened | cured material of a hydrosilylation-curable liquid silicone rubber composition will fall when the compatibility of each component deteriorates. Moreover, a vinyl group is preferable as an alkenyl group, and this is also the reason for maintaining compatibility with other components.

In the silicone resin of the above component (A), the structural unit of the R ₃ SiO _1/2 units (M units) and SiO _1/2 units (Q units) of the above mentioned four are required, hydrosilylation-curable liquid silicone In order to improve the hardness of the hardened | cured material of a rubber composition, it is necessary for the ratio of these two structural units to all structural units to be 80 mol% or more, Preferably it is 90 mol% or more, More preferably, it is 100 mol%. R ₂ SiO _2/2 units (D units) and RSiO _3/2 unit (T unit) may or may not be included.

In addition, SiO _4/2 units if R is less than 0.5 molar ratio of ₃ SiO _1/2 units (M units) to (Q units), the compatibility with the hydrosilylation-curable liquid silicone other components of the rubber composition is deteriorated, When it is larger than 1.5, the hardness of the cured product of the hydrosilylation-curable liquid silicone rubber composition is lowered. Therefore, the molar ratio of M units to Q units needs to be in the range of 0.5 to 1.5, preferably in the range of 0.7 to 1.2.

Specifically as a silicone resin of said (A) component, the copolymer of a vinyl dimethyl siloxy group and a Q unit, the copolymer of a vinyl dimethyl siloxy group, a trimethyl siloxy group, a Q unit, a vinyl dimethyl siloxy group, a dimethylsiloxane unit, and Q Copolymer of unit, copolymer of vinyl dimethyl siloxy group, phenyl silsesquioxane unit and Q unit, copolymer of vinyl dimethyl siloxy group, dimethyl siloxane unit, phenyl silsesquioxane unit and Q unit, trimethylsiloxy group vinyl The copolymer of a methyl siloxane unit and a Q unit, etc. are mentioned.

The organopolysiloxane liquid at room temperature of the component (B) of the hydrosilylation-curable liquid silicone rubber composition of the present invention has an average degree of polymerization of 2,000 or less and contains an alkenyl group bonded to at least two silicon atoms in one molecule. It is a well-known thing used as a base polymer of a silylated curable liquid silicone rubber composition, and the viscosity in 25 degreeC is 1-100 Pa.s, Preferably it has a viscosity of 5-100 Pa.s.

In addition, the organopolysiloxane in the form of a raw rubber at room temperature of component (C) of the hydrosilylation-curable liquid silicone rubber composition of the present invention has an average degree of polymerization of more than 2,000 and contains an alkenyl group bonded to at least two silicon atoms in one molecule. It is a well-known thing currently used as a base polymer of a millable type | mold silicone rubber compound. The average degree of polymerization is preferably 2,100 to 100,000, more preferably 3,000 to 10,000.

As the average degree of polymerization of the component (B) and the component (C), for example, an average value (weight average degree of polymerization) calculated from the weight average molecular weight by polystyrene conversion in gel permeation chromatography (GPC) analysis can be applied.

The above-mentioned (B) component and (C) component are all alkenyl-group containing organopolysiloxane, The difference is only molecular weight (degree of polymerization). These are usually the average composition formula (I)

R ¹ _a SiO _{(4-a) / 2} (I)

Here, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms, and specific examples include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group and hexyl group, vinyl group, allyl group, Unsubstituted monovalent hydrocarbon groups such as alkenyl groups such as butenyl groups, pentenyl groups and hexenyl groups, cyclohexyl groups, cyclohexenyl groups and phenyl groups, 3,3,3-trifluoropropyl groups and cyanomethyl groups At least a portion of the hydrogen atom of the monovalent hydrocarbon group is a substituted monovalent hydrocarbon group such as a substituted alkyl group substituted with a halogen atom or a cyano group, etc. A plurality of substituents may be different or the same, And a is a number in the range of 1.9 to 2.4, preferably 1.95 to 2.05.)

It may be represented by a straight chain or may be branched. Preferably, the main chain is made of repetition of diorgano polysiloxane units (D units), and both ends of the molecular chains are linear organo polysiloxanes sealed with triorgano siloxy groups (M units), and substituents bonded to silicon atoms Is preferably a methyl group or a phenyl group. In addition, the alkenyl group bonded to the silicon atom which is essential to contain two or more in one molecule is preferably a vinyl group, which may be at the end of the molecular chain or at the side chain, but is preferably contained at both ends.

(B) component is 50-200 mass parts and (C) component with respect to 100 mass parts of (A) component, in order to make the hydrosilylation hardening-type liquid silicone rubber composition of this invention compatible with the hardness and flexibility of the molded film after hardening. The range of 1-50 mass parts is suitable. Both the component (B) and the component (C) are soft films without flexibility in the composition below this range, and on the contrary, in the composition exceeding this range, the film is flexible and the surface adhesiveness is not suitable. Preferably, (B) component is 80-150 mass parts and (C) component is 5-20 mass parts with respect to 100 mass parts of (A) component.

The organohydrogenpolysiloxane of the component (D) of the hydrosilylation-curable liquid silicone rubber composition of the present invention contains a hydrogen atom (SiH group) bonded with at least two silicon atoms in one molecule, and has the following average composition formula (II)

R ² _b H _c SiO _{(4-bc) / 2} (II)

(Wherein R ² is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms and preferably does not have an aliphatic unsaturated bond. Specific examples thereof include methyl group, ethyl group, propyl group, butyl group, pentyl group, and hex). Hydrogen atom of the said monovalent hydrocarbon groups, such as unsubstituted monovalent hydrocarbon groups, 3,3,3- trifluoropropyl group, cyanomethyl group, such as alkyl groups, such as a real group, a cyclohexyl group, a cyclohexenyl group, and a phenyl group At least part of is a substituted monovalent hydrocarbon group such as a substituted alkyl group substituted with a halogen atom or a cyano group, b is 0.7 to 2.1, c is 0.18 to 1.0, b + c is 0.8 to 3.0, preferably b is 0.8 -2.0, c is expressed as a positive integer satisfying 0.2-1.0, b + c is 1.0-2.5.)

Conventionally known organo hydrogenpolysiloxanes represented by are applicable. In addition, the molecular structure of the organohydrogenpolysiloxane may be any one of a linear, cyclic, branched, and three-dimensional mesh. In this case, the number (or degree of polymerization) of silicon atoms in one molecule is suitably used at room temperature of about 2 to 300, particularly about 4 to 200. In addition, the hydrogen atom (SiH group) couple | bonded with a silicon atom may exist in the terminal of a molecular chain, may be in a side chain, or may be in both of them, and at least 2 (usually 2 to 300) among 1 molecule, Preferably it is 3 Or more (eg, 3 to 200), more preferably about 4 to 150, are used.

Specific examples of organohydrogenpolysiloxanes of the above-mentioned component (D) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrocyclocyclopolysiloxane, methyl Hydrogensiloxane, dimethylsiloxane cyclic copolymer, tris (dimethylhydrogensiloxy) methylsilane, tris (dimethylhydrogensiloxy) phenylsilane, both terminal trimethylsiloxy group blocking methylhydrogenpolysiloxane, both terminal trimethylsiloxy group blocking dimethyl Siloxane-methylhydrogensiloxane copolymer, both terminal dimethylhydrogensiloxane group blocking dimethylpolysiloxane, both terminal dimethylhydrogensiloxy group blocking dimethylsiloxane, methylhydrogensiloxane copolymer, both terminal trimethylsiloxy group blocking methylhydrogensiloxane di Phenylsiloxane copolymer, both terminal trimethylsiloxy group blocking methylhydrogensiloxane diphenyl Siloxane-dimethyl siloxane copolymer, cyclic methylhydrogen polysiloxane, cyclic methylhydrogen siloxane, dimethyl siloxane copolymers, cyclic methylhydrogen siloxane, diphenylsiloxane-dimethylsiloxane copolymer, (CH ₃₎ and ₂ HSiO _1/2 units SiO _{4 /} copolymer consisting of _two units, in the _{(CH 3) 2 HSiO 1/} 2 units and SiO _4/2 units and _{(C 6 H 5) SiO 3} / formed of _two units copolymer and each of the exemplified compound One part or all part of methyl group substituted with other alkyl groups, such as an ethyl group and a propyl group, and aryl groups, such as a phenyl group, etc. are mentioned.

About the compounding quantity of (D) component, in order to make the hardness and flexibility of the molded film after hardening of the hydrosilylation-cure liquid silicone rubber composition of this invention compatible, the silicon atom in (A) component, (B) component, and (C) component It is necessary to adjust the amount of (D) component so that the number of hydrogen atoms couple | bonded with the silicon atom per alkenyl group couple | bonded with and may be in the range of 1.0-10.0, Preferably it is 1.5-5.0. If it is less than this range, it will be flexible and will be a film with surface adhesiveness, and if it exceeds this range, it will become a film without flexibility.

As the hydrosilylation reaction catalyst of the component (E) of the hydrosilylation-curable liquid silicone rubber composition of the present invention, a known one is applicable, and for example, a reactant of platinum black, platinum chloride, chloroplatinic acid, chloroplatinic acid and monohydric alcohol And complexes of chloroplatinic acid with olefins, platinum-based catalysts such as platinum bisacetoacetate, palladium-based catalysts, and rhodium-based catalysts. In addition, the compounding quantity of this hydrosilylation reaction catalyst can be made into the amount of catalysts, Usually, it is 0.5-1,000 ppm with respect to (A) component as a platinum group metal, Preferably it is about 1-200 ppm.

In the hydrosilylation-curable liquid silicone rubber composition of the present invention, an alkoxysilane compound containing an alkoxysilyl group, a silane coupling agent, a condensation catalyst such as titanium-based or zirconium-based compound, etc., may be blended as a crosslinking aid within a range that does not impair the effects of the present invention. It may be.

Also, for example, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane or 1,3,5-triallyl-1,3,5-triazine-2,4,6 Polyfunctional alkenyl compounds such as-(1H, 3H, 5H) -trione (triallyl isocyanurate), 1-ethynylcyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, and the like Hydrosilylation reaction inhibitors, such as acetylene alcohol derivatives, may be added to secure pot life. For example, inorganic fillers such as trimethylchlorosilane or treated silica, surface-treated with octamethyltetracyclosiloxane, may be used as the hardness of the cured product. Or in order to improve strength. Furthermore, compounding of a dye, a pigment, a flame retardant, a mold release agent, etc. can also be carried out if it is a range which does not impair the effect of this invention.

Each of these optional components may be used individually by 1 type, or may use 2 or more types together.

The hydrosilylation-curable liquid silicone rubber composition of the present invention can be prepared by uniformly mixing each of the above components using a normal mixing stirrer, a kneader, and the like.

The optical waveguide for backlight device which consists of hardened | cured material of the hydrosilylation-hardening type | mold liquid silicone rubber composition of this invention makes the said hydrosilylation-curable liquid silicone rubber composition which mixed each component uniformly 80-350 degreeC, Preferably it is 100- It can obtain by heat-hardening at 200 degreeC, More preferably, 120-150 degreeC. As the molding method, a film molding method using a known thermosetting resin can be used. For example, in the case of a press molding method, the hydrosilylation-curable liquid silicone rubber composition of the present invention is introduced between two resin films (liners), and a predetermined mold and conditions are used. What is necessary is just to vulcanize by pressure. Moreover, as an example of the extending | stretching shaping | molding, it extends to a predetermined thickness with a roll, supplying the hydrosilylation-hardening type | mold liquid silicone rubber composition of this invention between two continuous resin films, is continuously supplied to a heating furnace, and it is atmospheric pressure hot-air vulcanization. After curing, after cooling, the liner is peeled off to obtain an optical waveguide.

In this case, the cured product of the hydrosilylation-curable liquid silicone rubber composition of the present invention preferably has a rubber hardness of 70 degrees or more (usually 70 to 85 degrees), particularly 75 to 85 degrees, in the durometer A. In addition, it is preferable that the total light transmittance of the hardened | cured material sheet of thickness 2mm is 90% or more, especially 92% or more by the measured value by the Suga Shikenki Co., Ltd. direct reading base computer HGM-2. Moreover, it is preferable that a crack does not arise even if the cured | curing material film of thickness 0.2mm is bend | folded by two-fold folding (namely, 180 degrees).

<Example>

Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to a following example. In addition, the unit of a compounding quantity is a mass part. In addition, a weight average molecular weight and a weight average degree of polymerization are polystyrene conversion values in a gel permeation chromatography (GPC) analysis. Viscosity is a value with a rotary viscometer.

[Examples 1-7, Comparative Examples 1-6]

(A) Silicone resin, (B) Liquid alkenyl group containing organo polysiloxane, (C) Raw-rubber alkenyl group containing organo polysiloxane, (D) organo hydrogen polysiloxane about each example of a hydrosilylation-hardening type | mold liquid silicone rubber composition , (E) hydrosilylation reaction catalyst, (F) hydrosilylation reaction control agent, and each compounding quantity are shown in Table 1. Each composition was uniformly mixed, stirred and degassed under reduced pressure.

A polyethylene terephthalate (PET) liner and a mold having a thickness of 2.2 mm were stacked on the press plate, and the hydrosilylation-curable liquid silicone rubber composition described above was introduced into the mold, and the PET liner and the press plate were further laminated thereon to obtain 120 ° C. Press molding for 10 minutes at. After removing to two PET liners and cooling, the PET liners were peeled off to obtain a silicone rubber transparent film having a thickness of about 2 mm.

Similarly, a silicon rubber transparent sheet having a thickness of about 0.2 mm was obtained by press molding at 150 ° C. for 2 minutes using a spacer (frame) having a thickness of 0.2 mm.

The following physical properties were evaluated about these.

Rubber hardness: JIS-K6249 (2mm sheet), durometer A

Transparency: The total light transmittance of the 2 mm sheet was measured.

Flexibility: A piece of 60 mm long x 20 mm wide was cut out of a 0.2 mm sheet, and folded in two layers at approximately the center in the longitudinal direction, and no crack was generated in the bent portion.

Overall evaluation: When rubber hardness was 70 or more in durometer A, transparency was 90% or more in total light transmittance, and all three items of the passability were satisfied, (circle) and others were made into x.

Material used

(A) silicone resin

_{A-1 (CH 3) 3} SiO 1/2 _{units, (CH 2 = CH) (} CH 3) a copolymer of ₂ SiO _1/2 unit, SiO _4/2 units

Molar _{ratio: (CH 3) 3 SiO 1} /2 / (CH 2 = CH) (CH 3) 2 SiO 1/2 / SiO 4/2 = 40/10/50

  Number of alkenyl groups per molecule: 4.2 (weight average molecular weight = 3,000)

_{A-2 (CH 3) 3} SiO 1/2 _{units, (CH 2 = CH) (} CH 3) a copolymer of ₂ SiO _1/2 unit, SiO _4/2 units

Molar _{ratio: (CH 3) 3 SiO 1} /2 / (CH 2 = CH) (CH 3) 2 SiO 1/2 / SiO 4/2 = 40/5/55

  Number of alkenyl groups per molecule: 3.5 (weight average molecular weight = 5,000)

_{A-3 (CH 3) 3} SiO 1/2 _{units, (CH 2 = CH) (} CH 3) SiO 2/2 unit, SiO _{4/2 units,} copolymers of

Molar _{ratio: (CH 3) 3 SiO 1} /2 / (CH 2 = CH) (CH 3) SiO 2/2 / SiO 4/2 = 45/10/45

  Number of alkenyl groups per molecule: 4.2 (weight average molecular weight = 3,000)

_{A-4 (CH 3) 3} SiO 1/2 unit, SiO _{4/2 units,} copolymers of

Molar _{ratio: (CH 3) 3 SiO 1} /2 / SiO 4/2 = 50/50

  Number of alkenyl groups per molecule: 0 (weight average molecular weight = 3,000)

(B) liquid alkenyl group-containing organo polysiloxane

B-1 Both Terminals Dimethylvinylsiloxy Group Blocking Dimethylpolysiloxane

  Weight average degree of polymerization: about 1,100 (weight average molecular weight = about 80,000)

  Viscosity: about 100 Pa

B-2 Both Terminals Dimethylvinylsiloxy Group Blocking Dimethylpolysiloxane

  Weight average degree of polymerization: about 450 (weight average molecular weight = about 33,000)

  Viscosity: about 5 Pa

B-3 Both Terminals Trimethylsiloxy Group Blocking Dimethyl Polysiloxane / Dimethyl Polysiloxane Copolymer

  Weight average degree of polymerization: about 750 (weight average molecular weight = about 56,000)

  Viscosity: about 30 Pa

  Alkenyl groups per molecule: 3.8

(C) Raw rubber alkenyl group-containing organo polysiloxane

C-1 Both Terminals Dimethylvinylsiloxy Group Blocking Dimethyl Polysiloxane

  Weight average degree of polymerization: about 8,000 (weight average molecular weight = about 600,000)

C-2 both terminal trimethylsiloxy group blockade vinylmethylsiloxane dimethylpolysiloxane copolymer

  Weight average degree of polymerization: about 8,000 (weight average molecular weight = about 600,000)

  Alkenyl groups per molecule: 10

C-3 Both Terminals Trimethylsiloxy Group Blocking Dimethylpolysiloxane

  Weight average degree of polymerization = about 8,000 (weight average molecular weight = about 600,000)

  Alkenyl groups per molecule: 0

(D) organo hydrogenpolysiloxane

D-1 both terminal trimethylsiloxy group blockade methylhydrogenpolysiloxane

  Viscosity: 20 mPas

  Number of SiH groups per molecule: 40 (SiH group content of 0.016 mol / g)

D-2 Both Terminals Dimethylhydrogen Siloxy Group Blocking Dimethyl Polysiloxane, Methyl Hydrogen Polysiloxane Copolymer

  Viscosity: 40 mPas

  Number of SiH groups per molecule: 45 (SiH group content 0.011 mol / g)

(E) hydrosilylation reaction catalyst

E-1 1-ethynylcyclohexanol

 (F) hydrosilylation reaction catalyst

F-1 platinum catalyst

Pt concentration: 1 wt%

Claims (5)

_{(A) R 3 SiO 1/} 2 units (M units), SiO _4/2 units (Q units), R ₂ SiO _2/2 units selected from the units (D units) and units of RSiO _3/2 (T unit) 100 parts by mass of a silicone resin having a total amount of M units and Q units of at least 80 mol% and a molar ratio of M units to Q units of 0.5 to 1.5, (Wherein R is a monovalent hydrocarbon group having 1 to 6 carbon atoms and at least two of the molecules are alkenyl groups.) (B) 50 to 200 parts by mass of an organopolysiloxane which is a liquid at room temperature having an average degree of polymerization of 2,000 or less and containing an alkenyl group bonded to at least two silicon atoms in one molecule, (C) 1 to 50 parts by mass of an organopolysiloxane in the form of a raw rubber at room temperature containing an alkenyl group bonded to at least two silicon atoms in one molecule with an average degree of polymerization of more than 2,000, (D) a silicon atom per one alkenyl group in which an organohydrogenpolysiloxane containing a hydrogen atom bonded to at least two silicon atoms in one molecule is bonded to a silicon atom in the components (A), (B) and (C) In an amount such that the number of hydrogen atoms bonded to is 1.0 to 10.0, and (E) catalytic amount of hydrosilylation reaction catalyst A hydrosilylation-curable liquid silicone rubber composition for an optical waveguide, comprising as an essential component. The hydrosilylation-curable liquid silicone rubber composition for an optical waveguide according to claim 1, wherein component (B) and component (C) are linear diorgano polysiloxanes. The hydrosilylated curable liquid silicone rubber composition for optical waveguide according to claim 1 or 2, wherein the rubber hardness of the cured product of the hydrosilylation curable liquid silicone rubber composition is 70 degrees or more in durometer A. 3. The hydrosilylation curable liquid silicone rubber composition for optical waveguide according to claim 1 or 2, wherein the total light transmittance of the cured product sheet having a thickness of 2 mm of the hydrosilylation curable liquid silicone rubber composition is 90% or more. The hydrosilylation-curable liquid silicone rubber for optical waveguides according to claim 1 or 2, wherein cracking does not occur even when the cured product film having a thickness of 0.2 mm of the hydrosilylation-curable liquid silicone rubber composition is bent. Composition.