U.S. patent application number 12/117317 was filed with the patent office on 2008-10-09 for flexible mold and method of manufacturing microstructure using the same.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Hiroshi Kikuchi, Akira Yoda, Chikafumi Yokoyama.
Application Number | 20080246190 12/117317 |
Document ID | / |
Family ID | 30112572 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080246190 |
Kind Code |
A1 |
Yokoyama; Chikafumi ; et
al. |
October 9, 2008 |
FLEXIBLE MOLD AND METHOD OF MANUFACTURING MICROSTRUCTURE USING THE
SAME
Abstract
To provide a flexible mold useful for manufacturing a PDP rib
having a lattice pattern and other microstructures, and capable of
highly precisely manufacturing the microstructures without
involving defects such as occurrence of bubbles and pattern
deformation. A flexible mold comprises a base layer made of a first
curable material having a viscosity of 3,000 to 100,000 cps at 10
to 80.degree. C. and a coating layer coating a surface of the base
layer and made of a second curable material having a viscosity of
200 cps or below at 10 to 80.degree. C.
Inventors: |
Yokoyama; Chikafumi;
(Zama-shi, JP) ; Yoda; Akira; (Machida-city,
JP) ; Kikuchi; Hiroshi; (Yamato-shi, JP) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
30112572 |
Appl. No.: |
12/117317 |
Filed: |
May 8, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10517644 |
Dec 9, 2004 |
7404919 |
|
|
PCT/US03/18232 |
Jun 10, 2003 |
|
|
|
12117317 |
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Current U.S.
Class: |
264/446 ;
425/174.4 |
Current CPC
Class: |
H01J 9/242 20130101;
B29D 11/0074 20130101; B29C 33/3857 20130101; B29L 2031/3475
20130101; B29C 33/424 20130101; B29C 35/0888 20130101; B29C 37/0053
20130101; H01J 2217/49264 20130101; B29C 33/40 20130101; B29C
2035/0827 20130101 |
Class at
Publication: |
264/446 ;
425/174.4 |
International
Class: |
B29C 33/50 20060101
B29C033/50 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 10, 2002 |
JP |
JP 2002-201539 |
Claims
1. A flexible mold having a groove pattern having a predetermined
shape and a predetermined size on a surface thereof, comprising: a
flexible support film; a base layer disposed on the flexible
support film the base layer made of a first curable material having
a viscosity of 3,000 to 100,000 cps at 10 to 80.degree. C.; a
coating layer disposed on the base layer, the coating layer made of
a second curable material having a viscosity of not greater than
200 cps at 10 to 80.degree. C.
2. The flexible mold as defined in claim 1, wherein said base layer
and said coating layer are transparent.
3. The flexible mold as defined in claim 1, wherein said first
curable material and said second curable material are a
photo-curable material.
4. The flexible mold of claim 3 wherein the first curable material
contains a urethane acrylate oligomer, an epoxy acrylate oligomer,
or a combination thereof.
5. The flexible mold of claim 3 wherein the second curable material
contains an acrylic monomer selected from the group consisting of
acrylamide, acrylonitrile, acrylic acid, and acrylic acid
ester.
6. The flexible mold of claim 1 wherein the support film is
optically transparent such that rays of light irradiated for curing
can transmit through the support film.
7. The flexible mold of claim 1 wherein the support film is
selected from the group consisting of polyethylene terephthalate,
polyethylene naphthalate, and polycarbonate.
8. The flexible mold of claim 1 wherein the support film has a
thickness ranging from 50 to 500 .mu.m.
9. The flexible mold of claim 1, wherein said groove pattern has a
lattice-like pattern constituted by a plurality of groove portions
so arranged as to be substantially parallel with one another while
crossing one another with predetermined gaps.
10. The flexible mold of claim 1, wherein said flexible mold is
suitable for making microstructures of a back plate for a plasma
display panel.
11. A method of manufacturing a microstructure having a projection
pattern having a predetermined shape and a predetermined size on a
surface of a substrate, comprising the steps of: providing a
flexible mold according to claim 1; arranging a curable molding
material between said substrate and said coating layer of said mold
and filling said molding material into said groove pattern of said
mold; curing said molding material and forming a microstructure
having said substrate and said projection pattern integrally bonded
to said substrate; and releasing said microstructure from said
mold.
12. The manufacturing method of claim 11, wherein said molding
material is a photo-curable material.
13. The manufacturing method of claim 11 wherein the molding
material contains a ceramic component, a glass component, and a
binder component.
14. The manufacturing method of claim 11, wherein said
microstructure is a back plate for a plasma display panel.
15. The manufacturing method of claim 9, which further comprises a
step of independently arranging a set of address electrodes
substantially in parallel with each other while keeping a
predetermined gap between them.
Description
RELATED APPLICATION DATA
[0001] This application is a divisional of application Ser. No.
10/517,644, now allowed, which is a '371 national stage application
of International Application Publication No. WO2004/007166,
published Jan. 22, 2004, which claims priority to JP2002-201539,
filed Jul. 10, 2002.
FIELD OF THE INVENTION
[0002] This invention relates to a molding technology. More
particularly, this invention relates to a flexible mold and to a
manufacturing method of a micro-structure using the flexible mold.
The manufacturing method of a microstructure according to the
invention is advantageous for manufacturing a rib of a back plate
of a plasma display panel, for example.
BACKGROUND
[0003] Display devices of a cathode ray tube (CRT) have
economically been mass-produced owing to the progress and
development of television technologies achieved up to this date, as
is well known in the art. In recent years, however, a thin and
lightweight flat panel display has drawn an increasing attention as
a display device of a next generation that will replace the display
devices of the CRT.
[0004] One of the typical examples of such flat panel displays is a
liquid crystal display (LCD), and the LCD has already been used as
a compact display device of notebook type personal computers,
cellular telephone sets, personal digital assistants (PDA) and
other mobile electronic information devices. On the other hand, a
plasma display panel (PDP) is a typical example of thin and
large-scale flat panel displays. This plasma display panel has
practically been used as wall-hung television receivers for
business or home use.
[0005] A typical PDP includes a large number of small discharge
display cells. In general, each discharge display cell is
encompassed and defined with a pair of glass substrates opposing
each other in a spaced-apart relation and a rib of a microstructure
having a predetermined shape and interposed between these glass
substrates. Electrodes are arranged in a spaced-apart relation on
the inner surfaces of the glass substrate and are patterned. A rare
gas is filled into each discharge display cell so that desired
self-light emission can be effected by plasma discharge between the
electrodes. Therefore, the PDP is substantially free from
field-of-view angle dependence.
[0006] The rib described above is generally formed of a ceramic
microstructure, is arranged in advance on the back of the glass
substrate and constitutes a part of the PDP back plate. In this
instance, the PDP back plate mostly has the ribs having the shapes
broadly classified into the following two types. One of them is a
shape called "straight pattern", and is described in International
Publication Gazette No. 00/39829, for example. This straight
pattern is simple and can relatively easily manufacture PDP having
a large scale.
[0007] As described in International Publication Gazette No.
00/39829, a flexible resin mold can be used to mold the rib having
the straight pattern. The resin mold is manufactured in the
following way. First, a photosensitive resin is filled into a metal
master mold having a pattern and a shape corresponding to those of
the resin mold, that is, into the metal master mold having the same
pattern and the same shape as those of the rib to be manufactured.
Next, this photosensitive resin is covered with a plastic film and
is cured to integrate the photosensitive resin after curing with
the film. The film is then released with the photosensitive resin
from the metal master mold.
[0008] Here, the photosensitive resin has a high viscosity of 500
to 5,000 cps. This is for suppressing shrinkage of the
photosensitive resin upon curing. When the photosensitive resin
having such a viscosity is used, the photosensitive resin can be
filled without entrapping air bubbles between the metal master mold
and the film.
[0009] Another rib has a shape called "lattice pattern". The
lattice pattern can suppress much more the drop of vertical
resolution of PDP than the straight pattern. For, ultraviolet rays
from the discharge display cell are more difficult to leak outside.
When compared with the straight pattern, the lattice pattern can
keep light emission efficiency from the display discharge cell at a
higher level. Another reason is that a phosphor necessary for color
display of the PDP can be applied with a relatively greater area to
the discharge display cell.
[0010] A mold can be used to manufacture the rib having the lattice
pattern, too. For example, Japanese Unexamined Patent Publication
(Kokai) No. 11-96903 describes a method that pushes a rib material
into a metal master mold by use of a vacuum press molding machine,
cools the rib material and then withdraws it from the metal master
mold. However, since the size of the vacuum press molding machine
is limited, it can manufacture a back plate for PDP having a size
of only a few cm, and is not suitable for manufacturing PDP to
serve as a large display. Japanese Unexamined Patent Publication
(Kokai) No. 9-283017 discloses the use of a cylindrical metal
master mold having an opposite pattern to that of a lattice. This
metal master mold moves and turns on a substrate through a barrier
member and pushes the barrier member to the substrate. In this way,
the metal master mold can manufacture the rib having the lattice
pattern. Generally, however, the barrier member is by far softer
than the metal master mold. In consequence, when the rib is
released with the substrate from the metal master mold, the rib is
likely to be broken. Breakage of the rib is particularly remarkable
in a substrate having the ribs in a direction vertical to the
rotating/moving direction of the metal master mold.
[0011] If the flexible mold described above can be applied to
molding of the rib, breakage of the rib may be avoided. According
to the existing molding technology, however, it is difficult to
manufacture such a mold. For, as typically shown in FIG. 10(A),
when a photosensitive resin 2 having a high viscosity of 500 to
5,000 cps is filled between the mold 5 and the plastic film 1, it
is difficult to fill the photosensitive resin 2 without entrapping
bubbles 12. When the photosensitive resin 2 is photo-cured while
containing the bubbles 12, the bubbles 12 remain as such inside and
on the outer surface of the photosensitive resin 2 after curing as
shown in FIG. 10(B). Such bubbles 12 result in rib defects when the
ribs are manufactured by using the mold. Therefore, it is preferred
not to entrap the bubbles as much as possible into the mold.
[0012] A photosensitive resin having a high viscosity such as
described above can be filled into the metal master mold without
entrapping the bubbles if vacuum equipment such as a vacuum press
molding machine is employed. As described in Japanese Unexamined
Patent Publication (Kokai) No. 11-96903, however, the size of
vacuum equipment is generally limited. Therefore, a mold having a
side of only a few cm can be manufactured, and this means is not
suitable for manufacturing PDP as a large display.
[0013] A photosensitive resin having a low viscosity of not higher
than 500 cps may be filled into a metal master mold without
entrapping the bubbles even when vacuum equipment is not used. On
the other hand, it may be difficult to manufacture a mold into a
desired shape because of curing shrinkage that cannot be neglected.
When the photosensitive resin 3 having a low viscosity is filled
between the metal master mold 5 and the plastic film 1 as typically
shown in FIG. 11(A), it is easy to fill the resin 3 without
entrapping the bubbles. However, when this photosensitive resin 3
is photo-cured, voids 13 develop between the photosensitive resin 2
after curing and the metal master mold 5 due to a large curing
shrinkage ratio of the resin, inviting thereby deformation of the
pattern. This pattern deformation is remarkable particularly when a
metal master mold generally having a high aspect ratio of
projections corresponding to the ribs is used to manufacture a mold
such as a rib mold for PDP. Therefore, the mold manufactured by
using a photosensitive resin having a low viscosity is not expected
to form relatively easily high-quality ribs of the lattice pattern
over a broad range on the PDP back plate.
SUMMARY OF THE INVENTION
[0014] To solve the problems of the technologies described above,
it is an object of the invention to provide a flexible mold that is
useful for manufacturing a high-quality PDP rib of a lattice
pattern or other microstructures and can highly precisely
manufacture the desired product without occurrence of bubbles,
pattern deformation, and so forth.
[0015] It is another object of the invention to provide a
manufacturing method of a microstructure such as a ceramic
microstructure by using such a flexible mold.
[0016] These and other objects of the invention will be more easily
understood from the following detailed description.
[0017] According to one aspect of the invention, there is provided
a flexible mold having a groove pattern having a predetermined
shape and a predetermined size on a surface thereof, comprising a
base layer made of a first curable material having a viscosity of
3,000 to 100,000 cps at 10 to 80.degree. C., and a coating layer
made of a second curable material having a viscosity of not greater
than 200 cps at 10 to 80.degree. C., and coating a surface of the
base layer.
[0018] According to another aspect of the invention, there is
provided a method of manufacturing a microstructure having a
projection pattern having a predetermined shape and a predetermined
size on a surface of a substrate, comprising the steps of preparing
a flexible mold having a groove pattern having a shape and a size
corresponding to those of the projection pattern on a surface
thereof, and including a base layer made of a first curable
material having a viscosity of 3,000 to 100,000 cps at 10 to
80.degree. C., and a coating layer made of a second curable
material having a viscosity of not greater than 200 cps at 10 to
80.degree. C., and coating a surface of the base layer; arranging a
curable molding material between the substrate and the coating
layer of the mold and filling the molding material into the groove
pattern of the mold; curing the molding material and forming a
microstructure having the substrate and the projection pattern
integrally bonded to the substrate; and releasing the
microstructure from the mold.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a perspective view showing a flexible mold
according to an embodiment of the invention.
[0020] FIG. 2 is a sectional view taken along a line II-II of FIG.
1.
[0021] FIG. 3 is a sectional view serially showing a manufacturing
method (former half steps) of a flexible mold according to the
invention.
[0022] FIG. 4 is a sectional view serially showing a manufacturing
method (latter half steps) of a flexible mold according to the
invention.
[0023] FIG. 5 is a sectional view showing distribution of first and
second curable materials during a manufacturing process of a
flexible mold according to the invention.
[0024] FIG. 6 is a sectional view showing distribution of the first
and second curable materials during a manufacturing process of the
flexible mold according to the invention.
[0025] FIG. 7 is a sectional view serially showing a manufacturing
method (former half steps) of a PDP back plate according to the
invention.
[0026] FIG. 8 is a sectional view serially showing a manufacturing
method (latter half steps) of the PDP back plate according to the
invention.
[0027] FIG. 9 is a perspective view showing appearance of the PDP
back plate manufactured in the embodiment.
[0028] FIG. 10 is a sectional view showing one problem of a
conventional manufacturing method of a flexible mold.
[0029] FIG. 11 is a sectional view showing another problem of a
conventional manufacturing method of the flexible mold.
DETAILED DESCRIPTION
[0030] This invention relates to a flexible mold and to a
manufacturing method of a microstructure using the flexible mold.
Preferred embodiments of these inventions will be explained with
reference to the accompanying drawings. As will be appreciated by
those skilled in the art, however, the invention is not
particularly limited to the following embodiments. Incidentally,
the same reference numeral will be used in the drawings to identify
the same or corresponding portion.
[0031] FIG. 1 is a partial perspective view that shows a flexible
mold according to an embodiment of the invention, and FIG. 2 is a
sectional view taken along a line II-II of FIG. 1.
[0032] As shown in these drawings, a flexible mold 10 has a groove
pattern having a predetermined shape and a predetermined size on
its surface. The groove pattern is a lattice pattern defined by a
plurality of groove portions 4 that are arranged substantially
parallel to one another while crossing one another and keeping
predetermined gaps. Since the flexible mold 10 has the groove
portions of the lattice pattern opening on the surface, it can be
advantageously used for forming a PDP rib having a lattice
projection pattern, for example, though it can be suitably applied
to the manufacture of other microstructures. The flexible mold 10
may include an additional layer, whenever necessary, or an
arbitrary treatment may be applied to each layer that constitutes
the mold. However, the flexible mold 10 fundamentally includes a
base layer 2 and a coating layer 3 as shown in FIG. 2.
[0033] The base layer 2 of the flexible mold 10 is substantially
uniformly made of a first curable material having a relatively high
viscosity of 3,000 to 100,000 cps when measured at a temperature of
10 to 80.degree. C., but remains substantially free of bubbles.
Generally, such a first curable material does not undergo
substantial shrinkage when cured. Therefore, the mold having the
grooves made of such a first curable material does not easily
undergo deformation but has excellent dimensional stability.
[0034] The first curable material is a heat-curable material or a
photo-curable material. Particularly when the first curable
material is the photo-curable material, the flexible mold can be
manufactured within a relatively short time without calling for an
elongated heating furnace. A photo-curable material useful for the
first curable material mainly contains an oligomer (curable
oligomer) due to easy availability. Particularly when the oligomer
is an acrylic oligomer such as a urethane acrylate oligomer and/or
an epoxy acrylate oligomer, the base layer is optically
transparent. Therefore, when this base layer is combined with a
transparent coating layer as will be described later, the flexible
mold can use a photo-curable molding material. The molding material
can be irradiated through the flexible mold.
[0035] The coating layer 3 is disposed on the surface of the base
layer 2 in close adhesion with the base layer 2. In this instance,
bubbles are excluded between the base layer 2 and the coating layer
3 on the former. The coating layer 3 is substantially uniformly
formed of a second curable material having a relatively low
viscosity of not higher than 200 cps when measured at 10 to
80.degree. C., and is substantially free of air bubbles. This
second curable material preferably has low tackiness. Because the
coating layer 3 has low tackiness, tackiness on the surface of the
flexible mold becomes low. Therefore, handling property can be
improved, and adhesion of the forming mold to the substrate and the
production apparatus can be prevented.
[0036] The second curable material may be either a heat-curable
material or a photo-curable material in the same way as the first
curable material. Unlike the first curable material, however, the
photo-curable material useful for the second curable material
includes a monomer (curable monomer). Particularly when the monomer
is an acrylic monomer such as acrylamide, acrylonitrile, acrylic
acid, acrylic acid ester, and so forth, the coating layer becomes
optically transparent. Therefore, the flexible mold can use the
photo-curable molding material in combination with the transparent
base layer as described above.
[0037] Turning back again to FIG. 2, in the flexible mold 10
according to the invention, the distance (d) from the bottom of
each groove portion 4 to the back of the base layer 2 is preferably
at least 1/10 of the depth (L) of the groove portion 4. When such a
dimensional structure is employed, the formation of the groove
portion solely depends on the base layer, so that deformation of
the mold 10 and the groove portions 4 becomes difficult to occur.
When the distance (d) is smaller than 1/10 of the depth (L) of the
groove portion 4, on the contrary, the groove portion 4 is likely
to be formed substantially by the coating layer 3 alone as will be
explained later with reference to FIG. 6. In this case, curing
shrinkage becomes great and deformation is likely to occur.
[0038] Preferably, the base layer 2 further includes a support
layer on its back. The support layer can be formed of various
materials that can support the mold without its deformation. A
support film is one of its examples, though it is in no way
restrictive. The support film can be advantageously used for
forming the base layer as will be described later.
[0039] The support film can be used at a variety of thickness. In
view of mechanical strength and handling property, however, the
film thickness is generally from 50 to 500 .mu.m and preferably 100
to 400 .mu.m. Preferably, the support film is optically
transparent. When the support film is optically transparent, the
rays of light irradiated for curing can transmit through this film.
Therefore, it is possible to form the base layer and the coating
layer by respectively using the photo-curable first and second
curing materials. Particularly when the support film is uniformly
formed of a transparent material, a uniform base layer and a
uniform coating layer can be formed more effectively. Typical
examples of the transparent support film are polyethylene
terephthalate (PET), polyethylene naphthalate (PEN) and
polycarbonate from the aspect of easy availability. A preferred PET
support film contains moisture to almost maximum it can absorb
under the environment where the flexible mold is used, and has a
predetermined size. Therefore, this support film can keep the shape
of the groove portion during the use of the flexible mold, and can
restrict variance of the size and shape of the moldings.
[0040] The flexible mold according to the invention can be
manufactured by various means. When the photo-curable first and
second curable materials are used, for example, the flexible mold
can be advantageously manufactured in the sequence shown in FIGS. 3
and 4.
[0041] First, a metal master mold 5 having a shape and a size
corresponding to those of a flexible mold as the object of
manufacture, a transparent support film 1 and a laminate roll 23
are prepared as shown in FIG. 3(A). Here, since the flexible mold
is used for manufacturing the PDP back plate, in particular, the
metal master mold 5 has partitions having the same pattern and the
same shape as those of the ribs of the PDP back plate on its
surface. Therefore, the space (recess) 15 defined by the adjacent
partitions 14 is the portion that is to become a discharge display
cell of PDP. The laminate roll 23 is means for pressing the support
film 1 to the metal master mold 5, and known and customary laminate
means may be used in place of the laminate roll 23, whenever
necessary.
[0042] Next, known and customary coating means (not shown) such as
a knife coater or a bar coater is used to apply the photo-curable
first curable material 2 to one of the surfaces of the support film
1 to a predetermined thickness as shown in FIG. 3(B). The
photo-curable second curable material 3 is applied to the
partition-holding surface of the metal master mold 5 to a
predetermined thickness by the same method, and is filled into the
recess 15 defined in the gap between the partitions 14. In this
invention, the second curable material 3 is easy to fluidize due to
its low viscosity. Therefore, even when the metal master mold 5 has
the partitions 14 having a high aspect ratio, the second curable
material 3 can be uniformly filled without entrapping bubbles.
[0043] Next, the laminate roll 23 is caused to slide on the metal
master mold 5 in a direction indicated by arrow A in FIG. 3(C),
while the first curable material 2 and the second curable material
3 keep adhesion with each other. As a result of this laminate
treatment, the second curable material 3 can be substantially
removed from the recess 15.
[0044] It is preferred during this laminate treatment to bring both
curable materials into adhesion while the distance from the top
(free end) of the partitions 14 to the support film 1 is kept
sufficiently greater than the height of the partitions (for
example, at least 1/10 of the height of the partitions). For, it is
possible to effectively exclude most of the second curable material
3 from the space of the partitions 14 and to replace it by the
first curable material 2 as shown in FIG. 5. As a result, the base
layer 2 can be used for forming the groove pattern of the mold
besides the coating layer 3.
[0045] When the distance from the top (free end) of the partition
14 to the support film 1 is sufficiently smaller than the height of
the partition (such as smaller than 1/10 of the height of the
partition) as shown in FIG. 6, on the contrary, the second curable
material 3 can hardly be excluded from the space of the partitions
14 and cannot be replaced by the first curable material 2.
Therefore, the groove pattern of the mold consists almost fully of
the coating layer 3.
[0046] After the laminate treatment is completed, the first and
second curable materials 2 and 3 are irradiated by light (hv)
through the support film 1 while the support film 1 is laminated on
the metal master mold 5 as shown in FIG. 4(D). If the support film
1 does not contain light scattering elements such as the bubbles
but is uniformly formed of the transparent material, the rays of
light irradiated hardly attenuate and can uniformly reach the first
and second curable materials 2 and 3. As a result, the first
curable material is efficiently cured to give the uniform base
layer 2 that is bonded to the support film 1. The second curing
material, too, is similarly cured to give the uniform coating layer
3 bonded to the base layer 2.
[0047] After a series of manufacturing steps described above, there
is obtained a flexible mold including the support film 1, the base
layer 2 and the coating layer 3 that are integrally bonded to one
another. Thereafter, the flexible mold 10 is released from the
metal master mold 5 while keeping its integrity as shown in FIG.
4(E).
[0048] This flexible mold can be manufactured relatively easily
irrespective of its size in accordance with known and customary
laminate means and coating means. Therefore, unlike the
conventional manufacturing method using vacuum equipment such as a
vacuum press machine, this invention can easily manufacture a large
flexible mold without any limitation.
[0049] Furthermore, the flexible mold according to the invention is
useful for manufacturing various microstructures. As disclosed in
Japanese Unexamined Patent Publication (Kokai) No. 2001-191345, for
example, the mold according to the invention is particularly and
extremely useful for molding a rib (microstructure) of PDP having a
lattice pattern. When this flexible mold is employed, it becomes
possible to easily manufacture a large screen PDP having lattice
ribs, in which ultraviolet rays do not easily leak from discharge
display cells, by merely using a laminate roll in place of vacuum
equipment and/or a complicated process.
[0050] Next, a method of manufacturing a PDP substrate having ribs
on a flat glass sheet by using the manufacturing equipment shown in
FIGS. 1 to 3 will be explained with reference to FIGS. 7 and 8.
[0051] First, as shown in FIG. 7(A), a flat glass sheet 31 is
prepared in advance having parallel electrodes 32 with
predetermined gaps, and is then arranged on a support table 21. If
a stage, not shown, capable of displacement is used, the support
table 21 supporting the flat glass sheet 31 thereon is put at a
predetermined position of the stage.
[0052] Next, the flexible mold 10 having the groove pattern on its
surface according to the invention is set to a predetermined
position of the flat glass sheet 31.
[0053] The flat glass sheet 31 and the mold 10 are positioned
relative to each other. In detail, this positioning is made with
eye or, as shown in FIG. 7(B), by use of a sensor 29 such as a CCD
camera in such a fashion that the groove portion of the mold 10 and
the electrodes of the flat glass sheet 31 are parallel. At this
time, the groove portion of the mold 10 and the space between the
adjacent electrodes on the flat glass sheet 31 may be brought into
conformity by adjusting the temperature and humidity, whenever
necessary. Generally, the mold 10 and the flat glass sheet 31
undergo extension and contraction in accordance with the change of
the temperature and humidity, and control is so made as to keep
constant the temperature and humidity when positioning between the
flat glass sheet 31 and the mold 10 is completed. Such a control
method is particularly effective for the manufacture of a
large-area PDP substrate.
[0054] Subsequently, the laminate roll 23 is set to one of the end
portions of the mold 10 as shown in FIG. 7(C). One of the end
portions of the mold 10 is preferably fixed at this time onto the
flat glass sheet 31. In this way, deviation of positioning between
the flat glass sheet 31 and the mold 10 previously positioned can
be prevented.
[0055] Next, as shown in FIG. 7(D), the other free end portion of
the mold 10 is lifted up and moved with a holder 28 above the
laminate roll 23 to expose the flat glass sheet 31. Caution is to
be paid at this time not to impart any tension to the mold 10 so as
to prevent crease of the mold 10 and to keep positioning between
the mold 10 and the flat glass sheet 31. Other means may also be
employed so long as positioning can be kept. A predetermined amount
of a rib precursor 33 necessary for forming the rib is supplied
onto the flat glass sheet 31. The example shown in the drawing uses
a paste hopper 27 having a nozzle as a rib precursor feeder.
[0056] Here, the term "rib precursor" means an arbitrary molding
material capable of forming the rib molding as the final object,
and does not particularly limit the materials so long as they can
form the rib molding. The rib precursor may be of a heat-curing
type or a photo-curing type. As will be explained below with
reference to FIG. 8(F), the photo-curing rib precursor, in
particular, can be used extremely effectively in combination with
the transparent flexible mold described above. The flexible mold
hardly has defects such as bubbles and deformation and can suppress
non-uniform scattering of light. In consequence, the molding
material is uniformly cured and provides a rib having constant and
excellent quality.
[0057] An example of compositions suitable for the rib precursor
basically contains (1) a ceramic component giving the rib shape,
such as aluminum oxide, (2) a glass component filling gaps between
the ceramic components and imparting compactness to the rib, such
as lead glass or phosphate glass and (3) a binder component for
storing, holding and bonding the ceramic component and the glass
component, and a curing agent or a polymerization initiator for the
binder component. Preferably, curing of the binder component does
not rely on heating but uses irradiation of light. In such a case,
heat deformation of the flat glass sheet need not be taken into
consideration. An oxidation catalyst consisting of oxides, salts or
complexes of chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co),
nickel (Ni), copper (Cu), zinc (Zn), indium (In) or tin (Sn),
ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), iridium
(Ir), platinum (Pt), gold (Au) or cerium (Ce) is added to this
composition, whenever necessary, so as to lower a removal
temperature of the binder component.
[0058] In the practice of the manufacturing method shown in the
drawings, the rib precursor 33 is not uniformly supplied to the
entire part of the flat glass sheet 31. In other words, the rib
precursor 33 may be supplied to only the flat glass sheet 31 in the
proximity of the laminate roll 23 as shown in FIG. 7(D). This is
because the rib precursor 33 can be uniformly spread when the
laminate roll 23 moves on the mold 10 in the subsequent step.
However, the rib precursor 33 preferably has a viscosity of about
100,000 cps or below, more preferably about 20,000 cps or below, in
this case. When the viscosity of the rib precursor is higher than
about 100,000 cps, the laminate roll does not sufficiently spread
the rib precursor, so that air is entrapped into the groove
portions of the mold and results in the rib defects. As a matter of
fact, when the viscosity of the rib precursor is about 100,000 cps
or below, the rib precursor uniformly spreads between the flat
glass sheet and the mold only when the laminate roll is moved once
from one of the end portions of the flat glass sheet to the other
end, and the rib precursor can be uniformly filled into all the
groove portions without entrapping bubbles. However, the supplying
method of the rib precursor is not limited to the method described
above. For example, the rib precursor may be coated to the entire
surface of the flat glass sheet, though this method is not shown in
the drawings. At this time, the rib precursor for coating has the
same viscosity as the viscosity described above. Particularly when
the rib of the lattice pattern is formed, the viscosity is 20,000
cps or below, preferably about 5,000 cps or below.
[0059] Next, a rotating motor (not shown) is driven to move the
laminate roll 23 on the mold 10 at a predetermined speed as
indicated by arrow in FIG. 8(E). While the laminate roll 23 moves
on the mold 10 in this way, the pressure is serially applied to the
mold 10 from one of its ends to the other due to the self-weight of
the laminate roll 23. Consequently, the rib precursor 33 spreads
between the flat glass sheet 31 and the mold 10, and the molding
material is filled into the groove portions of the mold 10. In
other words, the rib precursor 33 of the groove portions serially
replaces air and is filled. The thickness of the precursor at this
time can be adjusted to a range of several microns to dozens of
microns when the viscosity of the rib precursor or the diameter,
weight or moving speed of the laminate roll is controlled
appropriately.
[0060] According to the manufacturing method of the invention, even
when the groove portions of the mold serve as channels of air and
collect air, they can efficiently discharge air outside or to the
periphery of the mold when they receive the pressure described
above. As a result, the manufacturing method of the invention can
prevent residual bubbles even when filling of the rib precursor is
carried out at the atmospheric pressure. In other words, vacuum
need not be applied to fill the rib precursor. Needless to say, the
bubbles may be removed more easily in vacuum.
[0061] Subsequently, the rib precursor is cured. When the rib
precursor 33 spread on the flat glass sheet 31 is of the
photo-curing type, the rib precursor (not shown) is placed with the
flat glass sheet 31 and the mold 10 into a light irradiation
apparatus 26 as shown particularly in FIG. 8(F), and the rays of
light such as ultraviolet rays (UV) are irradiated to the rib
precursor through the flat glass sheet 31 and/or the mold 10 to
cure the rib precursor. In this way, the molding of the rib
precursor, that is, the rib itself, can be acquired.
[0062] Finally, the resulting rib as bonded to the flat glass sheet
31, the flat glass sheet 31 and the mold 10 are withdrawn from the
light irradiation apparatus, and the mold 10 is then peeled and
removed. Since the mold according to the invention has high
handling property, the mold can be easily peeled and removed
without breaking the rib bonded to the flat glass sheet.
[0063] Though the invention has thus been explained with reference
to one preferred embodiment thereof, the invention is not
particularly limited thereto.
[0064] The flexible mold is not particularly limited to the form
described above so long as it can accomplish the objects and the
operation and effect of the invention. For example, the flexible
mold may have a so-called "straight groove pattern" formed by
arranging a plurality of groove portions substantially in parallel
with one another with gaps among them without crossing one another.
Such a flexible mold can be used for forming a rib of PDP of a
straight pattern.
[0065] The flexible mold according to the invention is not solely
used for forming the PDP rib but can be advantageously used for
forming a variety of microstructures having similar shapes or
patterns.
EXAMPLES
[0066] The invention will be more concretely explained with several
examples thereof. However, the invention is not limited to the
following examples as will be appreciated by those skilled in the
art.
Example 1
[0067] To manufacture a PDP back plate, this example prepares a
rectangular metal master mold 5 having partitions 14 of a lattice
pattern as typically shown in FIG. 9. The explanation will be given
in further detail. This metal master mold 5 is constituted by
arranging longitudinal partitions (longitudinal ribs) having an
isosceles trapezoidal section in a predetermined pitch in a
longitudinal direction and transverse partitions (transverse ribs)
having an isosceles trapezoidal section in a predetermined pitch in
a direction perpendicular to the longitudinal ribs as tabulated in
the following Table 1. The spaces (recess) 15 defined by the
partitions 14 in the longitudinal and transverse directions are
discharge display cells of PDP.
TABLE-US-00001 TABLE 1 top bottom taper pitch height width width
angle longi. rib 300 .mu.m 208 .mu.m 55 .mu.m 115 .mu.m 82.degree.
trans. rib 500 .mu.m 208 .mu.m 37 .mu.m 160 .mu.m 75.degree.
[0068] A first curable material is prepared by mixing 80 wt % of
aliphatic urethane acrylate oligomer (a product of Henkel Co.,
trade name "Photomer 6010"), 20 wt % of 1,6-hexanediol diacrylate
(a product of Shin-Nakamura Kagaku K. K.) and 1 wt % of
2-hydroxy-2-methyl-1-phenyl-propane-1-on (a product of Ciba
Specialties Co., trade name "Darocure 1173"). When the viscosity of
this first curable material is measured, it is 8,500 cps at
22.degree. C. A Brookfield viscometer (B type viscometer) is used
to measure the viscosity of the first curable material. The
measurement mode uses a spindle #5 at a number of revolution of 20
rpm.
[0069] Further, 40 wt % of Photomer 6010 described above, 60 wt %
of 1,6-hexanediol diacrylate and 1 wt % of Darocure 1173 are mixed
to prepare a second curable material. When the viscosity of this
second curable material is measured in the same way as described
above, it is 110 cps at 22.degree. C.
[0070] Next, the first curable material prepared in the manner
described above is coated to a thickness of 200 .mu.m to a PET
support film having a thickness of 188 .mu.m. On the other hand,
the second curable material is coated to a surface of a metal mold
separately prepared in such a fashion as to fill recesses of the
metal mold.
[0071] The first curable material on the support film is laminated
with the second curable material on the metal master mold by use of
a laminate roll in such a fashion that the distance from the upper
surface of the top of partitions of the metal master mold to the
support film becomes 25 .mu.m.
[0072] Rays of light having a wavelength of 300 to 400 nm are
irradiated for 30 seconds to the first and second curable materials
under this state through the support film from a florescent lamp, a
product of Mitsubishi Denki-Oslam K. K. The first and second
curable materials are respectively cured, giving a base layer and a
coating layer covering the former. Subsequently, the support film
is peeled with the base layer and the coating layer from the metal
master mold to give a flexible mold.
[0073] When the resulting flexible mold is inspected through an
optical microscope, existence of bubbles and deformation of the
pattern are not confirmed on the mold.
Example 2
[0074] A flexible mold is manufactured and inspected in the same
way as in Example 1 with the exception that the first curable
material on the support film is laminated with the second curable
material on the metal mast mold in such a fashion that the distance
from the upper surface of the top of the partitions of the metal
master mold to the support film is 55 .mu.m.
[0075] In the flexible mold of this example, existence of bubbles
and deformation of the pattern cannot be confirmed, either.
Example 3
[0076] A flexible mold is manufactured and inspected in the same
way as in Example 1 with the exception that the second curable
material having a viscosity of 200 cps at 22.degree. C. is prepared
by mixing 50 wt % of Photomer 6010, 50 wt % of 1,6-hexanediol
diacrylate and 1 wt % of Darocure 1173.
[0077] In the flexible mold of this example, existence of bubbles
and deformation of the pattern cannot be confirmed, either.
Example 4
[0078] A flexible mold is manufactured and inspected in the same
way as in Example 1 with the exception that the second curable
material having a viscosity of 18 cps at 22.degree. C. is prepared
by mixing 100 wt % of 1,6-hexanediol diacrylate and 1 wt % of
Darocure 1173.
[0079] In the flexible mold of this example, existence of bubbles
and deformation of the pattern cannot be confirmed, either.
Comparative Example 1
[0080] A flexible mold is manufactured and inspected in the same
way as in Example 1 with the exception that the second curable
material is not used, the first curable material is laminated with
the metal master mold after it is coated to a thickness of 200
.mu.m to the support film, and the distance from the upper surface
of the top of the partitions of the metal master mold to the
support film is 25 .mu.m for comparison.
[0081] Existence of a large number of bubbles is confirmed in the
flexible mold of this comparative example. However, deformation of
the pattern cannot be confirmed.
Comparative Example 2
[0082] A flexible mold is manufactured and inspected in the same
way as in Example 1 with the exception that the first curable
material is disposed linearly on one of the end portions of the
second curable material coated to the metal master mold, a
lamination roll is moved to the other end portion of the metal
master mold applied with the second curable material after the
lamination roll is arranged at the outer edge portion of the first
curable material, and the distance from the upper surface of the
top of the partitions of the metal master mold to the support film
is 25 .mu.m for comparison.
[0083] Existence of bubbles is not confirmed in the flexible mold
of this comparative example, but deformation of the pattern is
locally confirmed.
[0084] As explained above, this invention can provide a flexible
mold that is useful for manufacturing a PDP rib having a high
quality lattice pattern or other microstructures and can highly
precisely manufacture the microstructures without involving defects
such as occurrence of bubbles and pattern deformation.
[0085] The invention can also provide a flexible mold that is
effective for relatively easily manufacturing a PDP rib having a
high quality lattice pattern or a variety of other
microstructures
[0086] The invention can further provide a manufacturing method of
a PDP rib having a high quality lattice pattern or other
microstructures such as a ceramic microstructure.
* * * * *