Ultraviolet-curable silicone resin composition, and image display device using the same

1. An ultraviolet-curable silicone resin composition comprising

(A) a polyorganosiloxane having a mercaptoalkyl group bonded to a silicon atom and a viscosity at 25° C. of 20 to 25000 cP;

(B) an organopolysiloxane having aliphatic unsaturated groups which comprises

(B1) a linear polyorganosiloxane having aliphatic unsaturated groups represented by the formula (I):

wherein

each R 1 independently represents an aliphatic unsaturated group,

each R independently represents a C 1 -C 6 alkyl group or a C 6 -C 12 group, and among Rs, 1 to 60 mol % is a C 6 -C 12 aryl group,

n is a number which results in a viscosity at 23° C. of 100 to 25000 cP, and

(B2) a branched organopolysiloxane which comprises an SiO 4/2 unit, an R′ 3 SiO 1/2 unit and an R′ 2 SiO 2/2 unit, and optionally further comprises an R′SiO 3/2 unit, wherein each R′ independently represents a C 1 -C 6 alkyl group or an aliphatic unsaturated group, and at least three of R′ per one molecule are aliphatic unsaturated groups, provided that an amount of (B2) is an amount where a number of the aliphatic unsaturated group in (B2) based on a total number of the aliphatic unsaturated groups in (B) is 50% or less;

(C) a photoinitiator; and

(D) one or more silane compounds containing an aliphatic unsaturated group selected from the group of 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane and vinyltriethoxysilane,

wherein

a ratio of a number of the mercaptoalkyl groups present in (A) based on a total number of the aliphatic unsaturated groups in (B) and (D) is 0.5 to 1.05,

a ratio of a number of the mercaptoalkyl groups present in (A) based on a number of the aliphatic unsaturated groups in (B) is 0.95 to 3, and

a ratio of a number of the mercaptoalkyl groups present in (A) based on a number of the aliphatic unsaturated groups in (D) is 1.5 to 3.

2. The ultraviolet-curable silicone resin composition according to claim 1 , wherein an amount of (C) is 0.05 to 50 parts by weight based on 100 parts by weight of (B).

3. The ultraviolet-curable silicone resin composition according to claim 1 , wherein the composition further comprises (E) one or more silicone resin series adhesion improvers selected from the group consisting of a MQ resin, a MDQ resin, a MT resin, a MDT resin, a MDTQ resin, a DQ resin, a DTQ resin and a TQ resin.

4. The ultraviolet-curable silicone resin composition according to claim 1 , wherein visible light transmittance after curing is 95% or more.

5. The ultraviolet-curable silicone resin composition according to claim 1 , wherein a cure shrinkage of the composition is 1.0% or less.

6. The ultraviolet-curable silicone resin composition according to claim 1 , wherein an E hardness after curing of the composition is 5 to 40.

7. The ultraviolet-curable silicone resin composition according to claim 1 , wherein a ratio (G′(T)/G′(23)) of a storage modulus G′(T) in the temperature range of −50° C. to 100° C. to a storage modulus G′(23) at 23° C. after curing of the composition is 0.1 to 30.

8. The ultraviolet-curable silicone resin composition according to claim 1 , wherein a ratio (G″(T)/G″(23)) of a loss modulus G″(T) in the temperature range of −50° C. to 100° C. to a loss modulus G″(23) at 23° C. after curing of the composition is 0.1 to 300.

9. A sealing agent for an image display device comprising the ultraviolet-curable silicone resin composition according to claim 1 .

10. An image display device comprising an image display portion and a protective portion being encapsulated by using the sealing agent for an image display device according to claim 9 .

11. The ultraviolet-curable silicone resin composition according to claim 2 , wherein the composition further comprises (E) one or more silicone resin series adhesion improvers selected from the group consisting of a MQ resin, a MDQ resin, a MT resin, a MDT resin, a MDTQ resin, a DQ resin, a DTQ resin and a TQ resin.