Optical waveguides – Accessories – External retainer/clamp
Reexamination Certificate
1999-03-26
2001-11-20
Lee, John D. (Department: 2874)
Optical waveguides
Accessories
External retainer/clamp
C065S102000, C065S275000, C385S083000
Reexamination Certificate
active
06321020
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a glass substrate, which is formed with a concave portion, such as a V-groove portion and a countersunk portion, with a high surface accuracy on the surface of the glass substrate, and a two-stage forming method for the same.
As a fiber arraying part, there have been known a fiber array for the connection of a fiber to other optical parts and an MT connector for connecting fibers to each other. These optical parts for connection are manufactured by using a glass substrate having a fiber fixing groove. As one example,
FIG. 5
shows the shape of the glass substrate having a groove in the surface thereof, what we call a V-grooved substrate.
As a method for molding a V-grooved glass substrate
3
having a V-groove
1
and a countersunk portion
2
, which is a coated fiber storage portion, shown in
FIG. 5
, a reheat press is thought to be effective. The reheat press is a method in which molten glass is inserted into a mold, and a molded body roughly press molded into a desired shape or a body worked into a desired shape by grinding a glass material is press molded precisely by using a die while being reheated. Although a molded product having a V-groove only can be formed by even grinding, the countersunk shape as shown in
FIG. 5
cannot be obtained by grinding. Therefore, the reheat press, which can precisely transfer the molding surface of die, is effective. Also, other than the reheat press, ultrasonic machining may be considered. However, this method has a problem in that chipping occurs on the machined surface when the roughness of machined surface has a P.V value not lower than 10 &mgr;m.
For the reheat press, since the accuracy of a die is reflected in the shape of molded surface, how the accuracy of a die surface is improved is an important problem. A die
4
for molding a V-grooved glass substrate shown in
FIG. 5
is as shown in FIG.
6
.
The shape of a convex portion
5
for the V-groove of this die
4
requires an accuracy within 1 &mgr;m on the surface thereof, so that it is difficult to achieve this accuracy unless grinding is performed. However, since in grinding, a grinding stone hits on the convex portion
5
for V-groove and a convex portion
6
for countersunk portion, it is actually difficult to manufacture this die by grinding.
A method in which a die is divided into several parts and these parts are assembled into one die, for example, a method in which a die part including the V-groove portion and a die part including a countersunk portion are manufactured separately and these two die parts are fixed with screws, has a high machining accuracy because each die part can be ground. However, as shown in
FIG. 6
, a gap of several micrometers is produced at a connecting portion
7
. Therefore, if reheat press is performed by using this die
4
, convex wall shaped burrs are produced on the molded product. If this burr is present between the V-groove and the countersunk portion, when a fiber core is placed, the fiber core is undesirably damaged.
Further, since misalignment easily occurs between the top surface of the V-groove portion and the top surface of the countersunk portion, the positional relationship between the fiber and the countersunk portion is shifted. Even if the gap is filled by welding of the connecting portion, the gap is reproduced by wear at the time of reheat press.
If the whole shape is manufactured by electrical discharge machining, the surface roughness of die becomes 10 &mgr;m and larger. Even if this surface is subjected to mirror polishing, the undulation of surface of about 5 &mgr;m is produced.
For the conventional optical fiber array, the boundary between the V-groove portion and the countersunk portion of the V-grooved glass substrate is as shown in FIG.
7
. That is, since the countersunk portion
2
is formed by grinding, an edge is formed at a V-groove end portion
14
, which is the boundary between the V-groove portion
1
and the countersunk portion
2
. If the fiber core
15
hits on this edge, there is a possibility of the fiber core
15
being damaged and broken. Also, because of grinding, the surface roughness is also about 1 &mgr;m in Rmax, or about 0.2 &mgr;m or more in Ra.
On the other hand, formation of a concave portion in which the diameter of the bottom surface is larger than other diameters, for example, the diameter of the surface opening portion (hereinafter referred to as a dovetail-shaped concave portion for convenience) in the surface of the glass substrate is impossible to do by grinding, and even in press molding, mold release cannot be performed, so that molding is very difficult to do. As shown in
FIG. 4
, the dovetail-shaped concave portion
8
has an advantage in that if a resin
11
is poured into the dovetail-shaped concave portion
8
and is cured when two substrates
9
and
10
having such a concave portion are joined to each other, the resin
11
entering the bottom part of the concave portion is caught by a taper
12
(due a to so-called anchoring effect), so that separation is less liable to occur. For this reason, there is a demand for manufacturing a glass substrate having such a dovetail-shaped concave portion.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems, and an object thereof is to provide a glass substrate which has a high surface accuracy of a concave portion such as a V-groove portion and a countersunk portion and is provided with a dovetail-shaped concave portion, which is difficult to manufacture by conventional molding methods, and a two-stage molding method for the glass substrate.
To achieve the above object, the present invention provides a glass substrate comprising a V-groove portion for arranging an optical fiber core and a countersunk portion for containing an optical fiber coated portion, formed on the extension of the V-groove portion, on the surface thereof, wherein the surface roughness of an inside side face of the countersunk portion is 1 &mgr;m or less in Rmax at least at the connecting portion of the V-groove portion and the countersunk portion.
Also, the present invention provides a glass substrate comprising a V-groove portion for arranging an optical fiber core and a countersunk portion for containing an optical fiber coated portion, formed on the extension of the V-groove portion, on the surface thereof, wherein the surface roughness of an inside side face of the countersunk portion is 0.2 &mgr;m or less in Ra at least at the connecting portion of the V-groove portion and the countersunk portion.
Further, the present invention provides a two-stage molding method for a glass substrate, comprising:
a first molding step for forming a concave portion in the surface of a glass substrate molded body by grinding or pressing, and
a second molding step for pressing the glass substrate molded body obtained by said first molding step from the top and bottom surfaces while reheating said molded body,
whereby a glass substrate having a concave portion with a high surface accuracy is manufactured.
In the present invention, the concave portion such as the countersunk portion preferably has a shape having a portion where an opening portion diameter is smaller than the opening diameter at the bottom.
REFERENCES:
patent: 5540746 (1996-07-01), Sasaki et al.
patent: 5608827 (1997-03-01), Boscher et al.
patent: 5812726 (1998-09-01), Jinnai et al.
patent: 5835659 (1998-11-01), Ota et al.
patent: 6079228 (2000-06-01), Tomisaka
Fukuyama Masashi
Tohyama Kazutoshi
Burr & Brown
Lee John D.
NGK Insulators Ltd.
LandOfFree
Glass substrate and two-stage molding method therefor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Glass substrate and two-stage molding method therefor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Glass substrate and two-stage molding method therefor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2569030