Process for producing optical element

Details Process for producing optical element Process for producing optical element

2003-07-01

2004-06-01

Moore, Margaret G. (Department: 1712)

Stock material or miscellaneous articles

Composite

Of silicon containing

C156S329000, C156S099000, C528S039000, C528S043000

Reexamination Certificate

active

06743517

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for producing an optical device, more specifically, a process for producing an optical device by bonding an optical part to another part by means of an adhesive, an optical device produced by bonding parts, and an adhesive composition.
DESCRIPTION OF THE PRIOR ART
The following adhesive compositions for optical parts which comprise a metal alkoxide are known: (i) JP-A 62-297369 discloses that an optical device is bonded by means of an adhesive comprising a hydrolyzate of a silicon alkoxide, (ii) U.S. Pat. No. 4,374,696 teaches that glass is bonded by means of a sol-gel organic-inorganic adhesive which contains dichloromethylvinylsilane, dichlorodiphenylsilane, aminopropyltriethoxysilane and tetraalkoxysilane, and (iii) U.S. Pat. No. 5,991,493 discloses that an optical part is bonded by means of an organic-inorganic composite adhesive obtained by hydrolyzing a sol which comprises polydimethylsiloxane, methyltriethoxysilane and phenyltrifluorosilane.
However, the above prior art technologies involve the following problems. The above method (i) has a problem that when the thickness of an adhesive layer becomes 1 &mgr;m or more, the adhesive layer cracks and sufficient adhesive force cannot be obtained as the metal alkoxide used is tetraethoxysilane. In the methods (ii) and (iii), an adhesive layer having a thickness of 1 &mgr;m or more is obtained but the separation of the layer of a solution composition readily occurs and the work of preparing an adhesive composition is troublesome.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical device assembled by means of an adhesive composition which is free from the cracking of an adhesive layer thereof, is easily prepared and has excellent adhesive strength, and a process for producing the optical device.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by a process for producing an optical device, comprising the steps of:
placing an adhesive composition prepared by hydrolyzing, dehydrating and condensing a starting solution containing:
(A) 10 to 50 mol % of a silane compound represented by the following formula (1):
SiX
1
4
  (1)
 wherein X
1
is a hydrolyzable group, or a combination of this silane compound and a metal alkoxide represented by the following formula (7):
M(OR
4
)
n
  (7)
 wherein M is Ti, Al or Zr, R
4
is an alkyl group or trialkoxysilyl group, and n is 4 when M is Ti or Zr and n is 3 when M is Al, with the proviso that only one of the three R
4
's can be a trialkoxysilyl group when M is Al, the amount of the metal alkoxide being 50 mol % or less based on 100 mol % of the total of the metal alkoxide and the silane compound represented by the above formula (1),
(B) 25 to 65 mol % of a silane compound represented by the following formula (2):
PhSiX
2
3
  (2)
 wherein Ph is a phenyl group or substituted phenyl group, and X
2
is a hydrolyzable group, and
(C) 25 to 65 mol % of a silane compound represented by the following formula (3):
(CH
3
)
2
SiX
3
2
  (3)
 wherein X
3
is a hydrolyzable group, between an optical part and another part; and
heating it to bond the optical part to the another part.
According to the present invention, secondly, the above objects and advantages of the present invention are attained by an optical device assembled by bonding an optical part to another part by means of an adhesive layer containing:
(1) 10 to 50 mol % of silica represented by the following formula (4):
SiO
2
  (4)
 or a combination of the silica and at least one metal oxide selected from the group consisting of TiO
2
, Al
2
O
3
, ZrO
2
and composite oxide thereof,
(2) 25 to 65 mol % of phenylsiloxane or substituted phenylsiloxane represented by the following formula (5):
PhSiO
3/2
  (5)
 wherein Ph is a phenyl group or substituted phenyl group, and
(3) 25 to 65 mol % of dimethylsiloxane represented by the following formula (6):
(CH
3
)
2
SiO
2/2
  (6).
The adhesive composition of the present invention contains unreacted (unhydrolyzed) and hydrolyzed/condensed forms of the silane compound represented by the formula (1) or a combination of the above forms of the silane compound represented by the formula (1) and a metal alkoxide represented by the formula (7) (to be referred to as “component (A)” hereinafter), unreacted and hydrolyzed/condensed forms of the silane compound represented by the formula (2) (to be referred to as “component (B)” hereinafter) and unreacted and hydrolyzed/condensed forms of the silane compound represented by the formula (3) (to be referred to as “component (C)” hereinafter). The silane compound as the component (A) is a raw material component which provides a silica component through hydrolytic and polycondensation reactions and contributes to the improvement of the heat resistance, chemical resistance and mechanical strength of the adhesive layer and the control of the linear expansion coefficient of the adhesive layer. Preferred examples of the hydrolyzable group X
1
in the formula (1) include alkoxyl group, acetoxyl group and halogen atom. As the component (A) is preferably used a tetraalkoxysilane or tetrahalogenated silane for example. The tetraalkoxysilane is preferably tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane or oligomer thereof for example. Out of these, tetramethoxysilane and tetraethoxysilane are preferably used because they are easily acquired.
The metal alkoxide represented by the above formula (7) of the component (A) forms a composite metal oxide with silica to contribute to the improvement of the chemical durability and mechanical durability of a bonded portion. It also provides a cutoff effect (a passivation effect) for ions and an alkali component which elute from an optical part as an adherend to the outside and contributes to the improvement of the humidity resistance of the bonded optical part. By controlling the amount of the metal alkoxide, the refractive index of the adhesive layer is increased to a value close to the refractive index values of two optical devices to be bonded together and a light transmission loss between the two optical devices can be made small. Further, the metal alkoxide functions as a catalyst for hydrolytic and dehydration/condensation reactions among the silane compound of the component (A), the component (B) and the component (C) and provides the effect of promoting these reactions at a low temperature. Therefore, when the metal alkoxide is used, an acid catalyst or basic catalyst which will be described hereinafter is not necessary. Examples of the alkyl group R
4
in the formula (7) include methyl group, ethyl group, propyl group and butyl group. Examples of the metal alkoxide (titanium alkoxide) when M in the formula (7) is Ti (titanium) include titanium tetraisopropoxide, titanium tetranormalbutoxide and chelate compounds thereof. Examples of the metal alkoxide (aluminum alkoxide) when M in the formula (7) is Al (aluminum) include aluminum-tri-sec-butoxide. Examples of the metal alkoxide (zirconium alkoxide) when M in the formula (7) is Zr (zirconium) include zirconium tetraisopropoxide and zirconium tetrabutoxide. They may be used directly or in the form of a chelate compound or hydrolyzate. Examples of the aluminum compound in which R
4
in the formula (7) is a trialkoxysilyl group include di-sec-butoxyaluminoxytriethoxysilane. It may be an oligomer. When the content of the metal alkoxide component in the adhesive composition is too low, the above effect is not obtained and when the content is too high, it is difficult to increase the thickness of the obtained film, and the film becomes brittle. Therefore, the amount of the metal alkoxide is preferably 5 to 50 mol % based on 100 mol % of the component (A).
When the amount of the componen

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