Abrading – Machine – Rotary tool
Reexamination Certificate
2002-01-31
2003-04-29
Morgan, Eileen P. (Department: 3723)
Abrading
Machine
Rotary tool
C451S041000, C451S054000, C451S398000
Reexamination Certificate
active
06554689
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an abrading method and abrading machine suitable for abrading liquid crystal cells for liquid crystal displays.
BACKGROUND OF THE INVENTION
In recent years, rectangular thin glass substrates 0.5 mm to 1.5 mm thick have been used for flat displays such as liquid crystal displays. Precise flatness is required of these substrates. Glass substrates molded by standard industrial processes contain minute surface imperfections, waviness and irregularities. Such substrates are not flat enough to be used in flat displays without further processing. Generally, therefore, the surfaces of molded glass substrates are abraded to a desired flatness on an abrading machine.
In a liquid crystal display, a liquid crystal material is encapsulated between a pair of glass substrates forming a liquid crystal cell. One of the glass substrates is a color filter substrate while the other is a TFT (Thin Film Transistor) array substrate. Liquid crystal cells tend to become increasingly thin as the weight of liquid crystal displays is reduced. In order to obtain a thin liquid crystal cell, the liquid crystal cell is typically abraded by using a double-sided abrading machine until the color filter substrate and the TFT array substrate are laminated, that is, abraded to a desired thickness after forming the liquid crystal cell.
A conventional double-sided abrading machine will be described below with reference to
FIGS. 4
,
5
A and
5
B.
FIG. 4
is a side view of a conventional double-sided abrading machine.
FIGS. 5A and 5B
show a work carrier used in a conventional double-sided abrading machine,
FIG. 5A
is a plan view of the work carrier, and
FIG. 5B
is a sectional view taken along line A—A in FIG.
5
A.
FIG. 4
also shows an abrasion process in which a liquid crystal cell
6
as a workpiece is being abraded by using two work carriers of the type shown in FIG.
5
.
The double-sided abrading machine
100
shown in
FIG. 4
includes an upper plate
4
and a vertically opposed lower plate
5
, as well as a carrier
101
serving as a holding member placed between the upper plate
4
and the lower plate
5
.
A shaft
16
is secured to the upper plate
4
and a shaft
17
is secured similarly to the lower plate
5
. The shaft
16
and the shaft
17
are rotated by a drive means (not shown) to rotate the upper plate
4
and the lower plate
5
.
As shown in
FIGS. 5A and 5B
, a holding hole
101
a
is formed in the carrier
101
to fit the outer shape of the liquid crystal cell
6
, which is inserted and held in holding hole
101
a
. The hole is slightly larger the liquid crystal cell
6
to make it easy to insert liquid crystal cell
6
. The liquid crystal cell has a TFT array substrate
61
and a color filter substrate
62
stacked together, above and below a thin liquid crystal layer (not shown). The color filter substrate
62
has a surface area slightly smaller than that of the TFT array.
The double-sided abrading machine
100
has a small-diameter sun gear
7
inside the perimeter of the upper plate
4
and lower plate
5
, and a large-diameter internal gear
8
around the perimeter. The sun gear
7
is secured to a drive shaft (not shown) which passes through the lower plate
5
. Gear
7
rotates coaxially with the shaft
17
as the drive shaft rotates. The internal gear
8
is mounted outside the upper plate
4
and lower plate
5
and driven coaxially with the shaft
17
by a drive source (not shown).
The carrier
101
has a gear formed along its circumference, as shown in FIG.
5
A. This gear is positioned so as to mesh with the sun gear
7
and internal gear
8
. Therefore, since it is held between the rotating upper plate
4
and lower plate
5
and meshed with the sun gear
7
and internal gear
8
, the carrier
101
revolves around the sun gear
7
while rotating on its axis. The front and rear faces of the liquid crystal cell
6
, held by the carrier
101
and pressed by the upper plate
4
and lower plate
5
, are abraded while an abrasive is supplied automatically between the upper plate
4
and lower plate
5
.
In a conventional arrangement, a workpiece is held by a single carrier throughout the entire process of mechanical abrasion. Consequently, when a large volume of stock is removed, the clearance between the upper plate and carrier (that is, the range of the carrier's vertical displacement) increases, making the workpiece prone to breakage and the like, as detailed below.
The thickness of the carrier
101
must be smaller than the target thickness of the workpiece (that is, the liquid crystal cell
6
) after mechanical abrasion. Otherwise, the upper plate
4
and lower plate
5
, between which the carrier
101
is placed to receive and hold the liquid crystal cell
6
, cannot come into contact with the liquid crystal cell
6
, which in turn makes it impossible to grind the liquid crystal cell
6
. Consequently, a problem arises if a large volume of stock is to be removed, as is the case with a liquid crystal cell including laminated substrates; for example, the TFT array substrate
61
and the color filter substrate
62
with a smaller surface area than the TFT array (see FIG.
4
). Specifically, with such a workpiece, there is a large clearance L between the upper plate
4
and carrier
101
in an early stage of mechanical abrasion. This may cause carrier
101
to contact an exposed portion of the top surface of TFT array substrate
61
, resulting in chips, cracks, or other damage to the liquid crystal cell
6
. Damage is noticeable especially when the liquid crystal cell
6
is abraded on the conventional double-sided abrading machine
100
compared to other types of workpieces.
FIG. 6
shows how the liquid crystal cell
6
is abraded on the conventional double-sided abrading machine
100
. As shown in
FIG. 6
, the liquid crystal cell
6
consists of the TFT array substrate
61
and color filter substrate
62
. Normally, the TFT array substrate
61
and color filter substrate
62
have the same thickness, but the TFT array substrate
61
generally has a larger surface area than the color filter substrate
62
to secure space for electrode wires. Therefore, a step is formed around the liquid crystal cell
6
. If the liquid crystal cell
6
with such a step is abraded on the conventional double-sided abrading machine
100
, it is often the case not only that the carrier
101
is displaced vertically during mechanical abrasion as shown in
FIG. 6A
, but also that the carrier
101
contacts the step around the liquid crystal cell
6
as shown in
FIG. 6B
, resulting in breakage of the carrier
101
. If the thickness of the carrier
101
is increased these problems will not arise, but the desired stock removal then cannot be performed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an abrading method and abrading machine which will allow a workpiece to be abraded without damage even in the case of heavy stock removal. This is done by stacking a plurality of carriers for holding the workpiece, so that the carrier height may be varied according to the stage of mechanical abrasion. In this way, the vertical displacement of the carriers can be restricted and breakage of workpieces caused by carriers can be avoided, even in the case of heavy stock removal, as long as the clearance between the upper plate and carriers is kept within a designated range.
In accordance with a first aspect of the present invention, a work holding member for mechanical abrasion is provided, comprising a first holding member which has a socket for receiving a workpiece and transmits external drive force to the workpiece, and a second holding member which is placed on the first holding member and has a socket for receiving the workpiece.
Since the work holding member for mechanical abrasion according to the present invention includes a first holding member and second holding member, the workpiece can be held by the first holding member alone (by taking away the second holding member), depending on the abraded quantity. Spec
Fujikawa Makoto
Johnai Tomohito
Kunii Yutaka
Maruyama Satoshi
Ohkuma Hideo
Anderson Jay H.
Morgan Eileen P.
Shakeri Hadi
LandOfFree
Work holding member for mechanical abrasion, abrading... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Work holding member for mechanical abrasion, abrading..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Work holding member for mechanical abrasion, abrading... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3068566