Organo polysiloxane, hard coating composition, and resin substrate having hard coating layer

1. A hard coating composition comprising an organo polysiloxane component consisting of an organo polysiloxane (a) having silicon-containing bond units represented by the following formulae T1 to T3 and an organo polysiloxane (b) having silicon-containing bond units represented by formulae T1 to T3, wherein the organo polysiloxane (a) contains silicon-containing bond units represented by formulae T1 to T3 in a ratio of T1:T2:T3=0-5:15-40:55-85 and in a ratio of T3/T2=1.5-4.0, in a number of such units, wherein a ratio of the number (B) of hydroxy groups bonded to silicon atoms to the number (A) of alkoxy groups bonded to silicon atoms in the organo polysiloxane (a), (B)/(A), is from 12 to 58.7, and which has a weight average molecular weight of from 800 to 8,000, and wherein the organo polysiloxane (b) is an organo polysiloxane having a weight average molecular weight between 1/10 and 1/1.5 of the weight average molecular weight of the organo polysiloxane (a):

R—Si(—OX) 2 (—O*—)  T1:

R—Si(—OX)(—O*—) 2   T2:

R—Si(—O*—) 3   T3:

wherein R is a hydrogen atom or a C 1-10 substituted or unsubstituted monovalent organic group, X is a hydrogen atom or a C 1-6 alkyl group, and O* is an oxygen atom linking two silicon atoms, and

the ratio of the content of the organo polysiloxane (b) to the organo polysiloxane (a) is from 1.5 to 30 by mass ratio;

wherein a proportion of the number of T units in said organo polysiloxane (a) is 95 to 100% based on the total number of units T, M, D and Q, wherein M is of formula R 3 —Si(—O*—), Q is of formula Si(—O*—) 4 and D is of formula R 2 —Si(—O*—) 2 ; and

wherein the total number of units D in the organo polysiloxane (b) is 0.

2. The hard coating composition according to claim 1 , whereby a cured film having a tensile stress (σ) as represented by the following formula (1), of at most 31 MPa, is obtainable,

σ

=

E

·

h

2

(

1

-

v

)

·

6

·

R

·

t

(

1

)

wherein R is a difference [m] between the radius of curvature of a silicon wafer itself as measured at an ambient temperature of 25° C. by a thin film stress measuring apparatus and the radius of curvature of a silicon wafer sample prepared by using the silicon wafer and having on its surface a cured coating film formed by curing the hard coating composition as a test specimen under conditions of 120° C. for 1 hour, E/(1−v) is a biaxial elastic coefficient (crystal face (100): 1.805×10 11 Pa) as calculated from the elastic modulus E of the silicon wafer and the Poisson's ratio ν, h is the thickness [m] of the silicon wafer, and t is the thickness [m] of the cured coating film.

3. The hard coating composition according to claim 1 , wherein the organo polysiloxane (b) is obtained by subjecting an alkoxysilane to hydrolytic condensation in a solvent in the presence of acetic acid as an acid catalyst.

4. The hard coating composition according to claim 1 , wherein the organo polysiloxane (b) also contains T0 units, which are non-reacted T monomers, not silicon-containing bond units and which are represented by the formula T0: R—Si(—OX) 3 , wherein T0 units and the silicon-containing bond units represented by formulae T0 to T3 are in a ratio of T0:T1:T2:T3=0-5:0-50:5-70:10-90.

5. The hard coating composition according to claim 1 , wherein a proportion of T units in said organo polysiloxane (b) is 90 to 100% based on the total number of units T, M, and Q, wherein M is of formula R 3 —Si(—O*—), and Q is of formula Si(—O*—) 4 .

6. The hard coating composition according to claim 1 , wherein the total number of units M in the organo polysiloxane (b) is 0.

7. The hard coating composition according to claim 1 , wherein the total number of units Q in the organo polysiloxane (b) is 0.

8. The hard coating composition according to claim 1 , wherein the total number of units T in the organo polysiloxane (b) based on the total number of units T, M, and Q is at least 99.9.

9. The hard coating composition according to claim 1 , wherein X is a methyl group.

10. The hard coating composition according to claim 1 , wherein the organo polysiloxane (a) has a weight average molecular weight of from 1,000 to 6,000.

11. The hard coating composition according to claim 1 , which contains a solvent to dissolve the organo polysiloxane (a) and the organo polysiloxane (b), in an amount of at least 20 mass % based on the entire amount of the composition.

12. The hard coating composition according to claim 11 , wherein based on the entire amount of the composition excluding the solvent, the content of the organo polysiloxane (a) is from 1 to 35 mass %, and the content of the organo polysiloxane (b) is from 40 to 65 mass %.

13. The hard coating composition according to claim 1 , which further contains silica particles (c) having an average particle size of from 1 to 100 nm.

14. The hard coating composition according to claim 13 , which further contains a solvent, and wherein based on the entire amount of the composition excluding the solvent, the content of the organo polysiloxane (a) is from 1 to 35 mass %, the content of the organo polysiloxane (b) is from 40 to 65 mass %, and the content of the silica particles (c) is from 1 to 50 mass %.

15. The hard coating composition according to claim 1 , wherein the organo polysiloxane (a) is produced by subjecting an organo polysiloxane having a ratio (B)/(A) lower than that of organo polysiloxane (a) to hydrolysis of alkoxy groups in the presence of an acid catalyst.

16. The hard coating composition according to claim 15 , wherein the organo polysiloxane (a) has a weight average molecular weight of from 1,000 to 6,000.

17. The hard coating composition according to claim 15 , wherein R and X are both CH 3 .

18. The hard coating composition according to claim 15 , which contains a solvent to dissolve the organo polysiloxane (a) and the organo polysiloxane (b), in an amount of at least 20 mass % based on the entire amount of the composition.

19. The hard coating composition according to claim 18 , wherein based on the entire amount of the composition excluding the solvent, the content of the organo polysiloxane (a) is from 1 to 35 mass %, and the content of the organo polysiloxane (b) is from 40 to 65 mass %.

20. The hard coating composition according to claim 15 , which further contains silica particles (c) having an average particle size of from 1 to 100 nm.

21. The hard coating composition according to claim 20 , which further contains a solvent, and wherein based on the entire amount of the composition excluding the solvent, the content of the organo polysiloxane (a) is from 1 to 35 mass %, the content of the organo polysiloxane (b) is from 40 to 65 mass %, and the content of the silica particles (c) is from 1 to 50 mass %.

22. A resin substrate having, on at least one side thereof, a hard coating layer made of a cured product of the hard coating composition as defined in claim 1 .

23. The resin substrate having a hard coating layer according to claim 22 , wherein the hard coating layer has a thickness of from 0.1 to 20 μm.

24. The resin substrate having a hard coating layer according to claim 22 , which has a primer layer between the resin substrate and the hard coating layer.

25. The resin substrate having a hard coating layer according to claim 22 , wherein the material for the resin substrate is a polycarbonate resin.

26. The resin substrate having a hard coating layer according to claim 22 , which is a flat plate form, is forcibly bendable and is operable in a bent state at ordinary temperature.

27. The resin substrate having a hard coating layer according to claim 26 , wherein the operability in a bent state is carried out under a condition of at least an allowable radius of curvature.

28. The resin substrate having a hard coating layer according to claim 26 , wherein the hard coating layer has a thickness of from 0.1 to 6 μm.