U.S. patent application number 12/743348 was filed with the patent office on 2010-11-18 for articles and methods of making articles having a concavity or convexity.
Invention is credited to Shoichi Masuda, Atsushi Toyota.
Application Number | 20100290250 12/743348 |
Document ID | / |
Family ID | 40667816 |
Filed Date | 2010-11-18 |
United States Patent
Application |
20100290250 |
Kind Code |
A1 |
Toyota; Atsushi ; et
al. |
November 18, 2010 |
ARTICLES AND METHODS OF MAKING ARTICLES HAVING A CONCAVITY OR
CONVEXITY
Abstract
Articles and methods of making an articles having at least one
convexity or at least one concavity are described. A first article
having at least one concavity is prepared using a molding surface
that includes at least one gas bubble. A second article having at
least one convexity is prepared using the first article as a
mold.
Inventors: |
Toyota; Atsushi; (Tokyo,
JP) ; Masuda; Shoichi; (Tokyo, JP) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Family ID: |
40667816 |
Appl. No.: |
12/743348 |
Filed: |
November 18, 2008 |
PCT Filed: |
November 18, 2008 |
PCT NO: |
PCT/US08/83898 |
371 Date: |
July 29, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60988994 |
Nov 19, 2007 |
|
|
|
Current U.S.
Class: |
362/608 ;
249/60 |
Current CPC
Class: |
G02B 3/0031 20130101;
G02B 5/0215 20130101; G02B 5/0278 20130101; G02B 3/0056 20130101;
Y10T 428/249971 20150401 |
Class at
Publication: |
362/608 ;
249/60 |
International
Class: |
F21V 7/22 20060101
F21V007/22; B29C 33/42 20060101 B29C033/42 |
Claims
1. A molding surface comprising a plurality of gas bubbles forming
a lattice pattern.
2. The molding surface of claim 1, wherein the gas bubbles comprise
concavities or convexities.
3. The molding surface of claim 1, wherein the gas bubbles comprise
linear side walls.
4. The molding surface of claim 1, wherein the lattice pattern
comprises a row pattern.
5. The molding surface of claim 1, wherein the lattice pattern
comprises a zigzag pattern.
6. The molding surface of claim 1, wherein the lattice pattern
comprises a radial pattern.
7. A surface comprising a lattice pattern of concavities or
convexities and a lattice pattern of prisms.
8. The surface of claim 7, wherein the concavities or convexities
comprise substantially spherical surfaces.
9. The surface of claim 7, wherein the concavities or convexities
have the same shape.
10. The surface of claim 7, wherein the concavities or convexities
have the same size.
11. The surface of claim 7, wherein the concavities or convexities
are in direct contact with gas bubbles.
12. The surface of claim 7, wherein the concavities or convexities
are in direct contact with a hardenable fluid.
13. The surface of claim 7, wherein the concavities or convexities
are in direct contact with a hardened fluid.
14. An article comprising a plurality of concavities, each
concavity being surrounded by grooves.
15. The article of claim 14, wherein the concavities are arranged
at predetermined positions.
16. The article of claim 14, wherein the concavities form a lattice
pattern.
17. The article of claim 14, wherein the grooves comprise prism
portions.
18. The article of claim 14 further comprising a hardened
fluid.
19. An article comprising a plurality of convexities, each
convexity being surrounded by walls.
20. The article of claim 19, wherein the convexities are arranged
at predetermined positions.
21. The article of claim 19, wherein the convexities form a lattice
pattern.
22. The article of claim 19, wherein the walls comprise prism
portions.
23. The article of claim 19 further comprising a hardened
fluid.
24. An article comprising: a mold comprising a first structured
surface comprising a plurality of walls separating a plurality of
depressions; and a hardenable fluid covering the first structured
surface of the mold and contacting at least the plurality of the
walls, such that if the fluid is hardened and removed from the
mold, then the removed hardened fluid comprises a second structured
surface that is substantially different than the inverse of the
first structured surface.
25. The article of claim 24 wherein the second, but not the first,
structured surface has a plurality of concavities or
convexities.
26. An article comprising: a mold comprising a plurality of
depressions; a fluid covering the mold; and one or more gas bubbles
in each depression, the one or more bubbles forming a concavity in
the fluid.
27. The article of claim 26, wherein the plurality of depressions
form a lattice pattern.
28. The article of claim 26, wherein each of the plurality of
depressions has a pointed bottom.
29. The article of claim 26, wherein each of the plurality of
depressions has an edge line at the bottom.
30. The article of claim 26, wherein each of the plurality of
depressions comprises a pyramid portion.
31. The article of claim 26, wherein each of the plurality of
depressions comprises one or more planar sides.
32. The article of claim 26, wherein each of the plurality of
depressions has a shape that tapers.
33. The article of claim 26, wherein the one or more gas bubbles in
each depression comprise a sidewall.
34. The article of claim 26, wherein the concavity in the fluid
comprises an over-hang portion.
35. A display device comprising: a backlight emitting light; a
display panel displaying an image; and an optical film disposed
between the backlight and the display panel and having an optical
gain of at least 1.2, the optical film comprising a structured
major surface comprising a plurality of discrete structures, each
structure comprising: a concavity or a convexity; and a side
wall.
36. The display device of claim 35, wherein the sidewall comprises
a prism portion.
37. The display device of claim 35, wherein the structured major
surface of the optical film faces the backlight.
38. The display device of claim 35, wherein the structured major
surface of the optical film faces the display panel.
39. The display device of claim 35, wherein the concavity or the
convexity comprises a substantially spherical concavity or
convexity.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to articles and methods of
manufacturing articles that have at least one concavity or
convexity.
BACKGROUND OF THE INVENTION
[0002] An article having a component with a concave surface or a
convex surface or an article having a number of concave surfaces or
convex surfaces arranged thereon can be used in various industrial
fields. In some applications, the concave or convex surface can
function as a lens. For example, a sheet-like article having a
number of concave surfaces or convex surfaces arranged thereon can
function as an array of lenses such as an array of microlenses
(i.e., microlens array). Such a sheet-like article that can be used
as a microlens array has recently received a great amount of
attention. Microlens array may be suitable for various optical
applications including, for example, a display, a semiconductor
laser, and an optical fiber.
[0003] Japanese Patent Application Laid-Open No. H11-142609
describes a manufacturing method for a microlens array using an
indentation method. According to this manufacturing method, many
indentations are formed on the surface of a mold using a pressing
tool. The pressing tool, which has a spherical shaped head of
different sizes, is repeatedly pressed on the surface of the mold
at regular intervals. A microlens array can then be manufactured by
compression molding an optical-grade plastic, such as an acrylic
polymer, using the mold having the indentations formed thereon.
However, the manufacturing method of a microlens array using this
indentation method requires considerable time and cost because of
the amount of work needed to form the mold with many
indentations.
[0004] Japanese Patent Application Laid-Open No. H05-134103
describes a manufacturing method for a microlens array using an
electron-beam lithographic method. In this manufacturing method,
many microlenses can be formed on a base sheet using an electron
beam. Like the indentation method for manufacturing a microlens
array, this method requires considerable time and cost. It could
take greater than ten days to several hundred days to manufacture
more than ten thousand to several hundred thousand microlenses with
each microlens having a diameter of about 100 micrometers (.mu.m),
for example.
[0005] Japanese Patent Application Laid-Open No. S62-260104
describes a manufacturing method for a microlens using a laser
chemical vapor deposition (CVD) method. In this manufacturing
method, a substrate is set in a container filled with a mixed gas
composition, a laser beam is irradiated on the substrate to
decompose the gas composition, and a lens material is deposited on
the substrate to form the microlens. The desired shape can be
obtained by changing the energy distribution of the laser beam to
vary the amount of material deposited on the substrate. However,
because each microlens is formed individually by finely changing
the energy distribution of the laser beam, this manufacturing
method is slow and costly.
[0006] Japanese Patent Application Laid-Open No. H05-134103
describes a manufacturing method for a microlens array that
includes preparing a lattice frame, placing a resin within the
lattice frame, and melting the resin to form curved surfaces
suitable for microlenses by means of the surface tension of the
melted resin. Although an article having a convex surface can be
manufactured relatively easily with this manufacturing method in
comparison with the aforementioned electron-beam lithographic
method and laser chemical vapor deposition method, it is necessary
to prepare the lattice frame using a photoresist prior to forming
microlenses. The method of preparing the lattice frame can be
complicated. Therefore, the overall steps of manufacturing a
microlens array using this method can be time consuming and costly.
Further, because this manufacturing method includes the step of
melting the photo-resist or resin material, the range of suitable
materials that can be used is limited. It can be difficult to find
materials that have suitable melting properties as well as suitable
optical properties.
[0007] C. Y. Chang et al. reported a manufacturing method for a
microlens array made of a resin material in Infrared Physics &
Technology, 48, pp. 163-173 (2006). In this manufacturing method, a
resin film is set on a mold disposed in a closed chamber and then
heated. High gas pressures are used to extrude the resin film into
dimples of the mold, thereby forming convex surfaces. The size and
shape of the convex surfaces that can be formed are limited,
however, because the hardened resin film must be reheated to form
the microlenses. Additionally, since this method involves
high-temperatures and high gas pressures, the manufacturing cost
can be high.
[0008] Easier methods are desired for manufacturing an article
having at least one concavity or at least one convexity on its
surface. More particularly, easier methods are desired for
manufacturing an article having at least one micro-concavity or at
least one micro-convexity on its surface.
SUMMARY OF THE INVENTION
[0009] The present invention relates to articles and to methods of
manufacturing the articles that have at least one concavity or
convexity. More particularly, an article having at least one
concavity is manufactured using a molding surface that includes at
least one gas bubble. This article having at least one concavity
can then be used as a second mold to form a second article having
at least one convexity.
[0010] One aspect of the present invention is a method of making an
article that has a surface comprising at least one concavity. The
method comprises using at least one gas bubble deliberately
introduced to impart the at least one concavity to the surface of
the article.
[0011] In some embodiments of this method, multiple gas bubbles
arranged in a pattern are used to impart an arranged pattern of
concavities to the surface of the article.
[0012] Another aspect of the present invention is a method of
making a second article that has a surface comprising at least one
convexity. The method comprises using the article having at least
one concavity as a second mold to impart the at least one convexity
to the surface of the second article. In some embodiments of this
method, the first article that is used as the second mold has an
arranged pattern of concavities and the second article has an
arranged pattern of convexities.
[0013] Yet another aspect of the present invention is an article
that has a surface comprising an arranged pattern of concavities,
wherein gas bubbles imparted the arranged pattern of concavities to
the surface of the article during its manufacture.
[0014] Still another aspect of the invention is a second article
having a surface comprising an arranged pattern of convexities. The
arranged pattern of the convexities is an inversion of an arranged
pattern of concavities of a second mold, wherein gas bubbles
imparted the arranged pattern of concavities to a surface of the
second mold during its manufacture.
[0015] In another embodiment, a molding surface includes a
plurality of gas bubbles, where the bubbles form a lattice pattern.
In some cases, the gas bubbles include concavities or convexities.
In some cases, the gas bubbles have linear side walls. In some
cases, the lattice pattern includes a row pattern, or a zigzag
pattern, or a radial pattern.
[0016] In another embodiment, a surface includes a first lattice
pattern of concavities or convexities and a second lattice pattern
of prisms. In some cases, the concavities or convexities of the
first lattice pattern and the prisms of the second lattice pattern
alternate. In some cases, the concavities or convexities have
spherical or substantially spherical surfaces. In some cases, the
concavities or convexities have the same shape. In some cases, the
concavities or convexities have the same size. In some cases, the
concavities or convexities are in direct contact with gas bubbles.
In some cases, the concavities or convexities are in direct contact
with a hardenable fluid. In some cases, the concavities or
convexities are in direct contact with a hardened fluid.
[0017] In another embodiment, an article includes a plurality of
concavities, where each concavity is surrounded by walls. In some
cases, the concavities are arranged at predetermined positions. In
some cases, the concavities form a lattice pattern. In some cases,
the walls have prism portions. In some cases, the article also
includes a hardened fluid.
[0018] In another embodiment, an article includes a plurality of
convexities, where each convexity is surrounded by grooves. In some
cases, the convexities are arranged at predetermined positions. In
some cases, the convexities form a lattice pattern. In some cases,
the grooves have prism portions. In some cases, the article also
includes a hardened fluid.
[0019] In another embodiment, an article includes a hardened fluid
that includes a structured surface. The structured surface includes
a lattice pattern of convexities or concavities. The article
further includes a hardenable fluid that is adjacent to the
hardened fluid. In some cases, the hardenable fluid includes a
structured surface.
[0020] In another embodiment, an article includes a mold that
includes a plurality of depressions and a fluid that covers the
mold. The article further includes one or more gas bubbles in each
depression. The one or more bubbles form a concavity in the fluid.
In some cases, the plurality of depressions form a lattice pattern.
In some cases, each of the plurality of depressions has a pointed
bottom. In some cases, each of the plurality of depressions has an
edge line at the bottom. In some cases, each of the plurality of
depressions comprises a pyramid portion. In some cases, each of the
plurality of depressions includes one or more planar sides. In some
cases, each of the plurality of depressions has a shape that
tapers. In some cases, the one or more gas bubbles in each
depression include a sidewall. In some cases, the concavity in the
fluid includes an over-hang portion.
[0021] In another embodiment, a display device includes a backlight
that emits light and a display panel that displays an image. The
display device further includes an optical film that is disposed
between the backlight and the display panel. In some cases, the
optical film has an optical gain of at least 1.2. The optical film
has a structured major surface that includes a plurality of
discrete structures. Each discrete structure includes a concavity
or a convexity and a side wall. In some cases, the side wall
includes a prism portion. In some cases, the optical gain of the
optical film is at least 1.3. In some cases, the optical gain of
the optical film is at least 1.4. In some cases, the optical gain
of the optical film is at least 1.5. In some cases, the structured
major surface of the optical film faces the backlight. In some
cases, the structured major surface of the optical film faces the
display panel. In some cases, the concavity or the convexity
includes a substantially spherical concavity or convexity.
[0022] In another embodiment, an article includes a mold that has a
first structured surface that includes a plurality of walls that
separate a plurality of depressions. The article further includes a
hardenable fluid that covers the first structured surface of the
mold and contacts at least the plurality of the walls. If the fluid
is hardened and removed from the mold, then the removed hardened
fluid has a second structured surface that is substantially
different than the inverse of the first structured surface. In some
cases, the second, but not the first, structured surface has a
plurality of concavities or convexities.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIGS. 1A to 1D are schematic sectional views exemplifying
one embodiment of a method of manufacturing a first article having
at least one concavity.
[0024] FIGS. 1E to 1G are schematic sectional view exemplifying one
embodiment of a method of manufacturing a second article having at
least one convexity.
[0025] FIG. 2A is a schematic view exemplifying one embodiment of a
mold having multiple depressions.
[0026] FIG. 2B is a schematic view exemplifying another embodiment
of a mold having multiple depressions.
[0027] FIG. 3A is a schematic sectional view exemplifying another
embodiment of a method of manufacturing a first article having at
least one concavity.
[0028] FIG. 3B is a schematic sectional view exemplifying another
embodiment of a method of manufacturing a second article having at
least one convexity.
[0029] FIG. 4 is a schematic sectional view showing conditions for
a bubble of gas existing at the surface of the mold in a depression
(i.e., the gas bubble is positioned between the mold surface and
the hardenable fluid).
[0030] FIG. 5 is an exemplary diagram showing the position of gas
bubbles within a depression of a mold.
[0031] FIGS. 6A to 6D are schematic sectional views exemplifying
other embodiments of a method of manufacturing a second article
having at least one convexity.
[0032] FIGS. 7A to 7D are schematic sectional views exemplifying
another embodiment of a method of manufacturing a first article
having at least one concavity.
[0033] FIGS. 7E to 7G are schematic sectional views exemplifying
another embodiment of a method of manufacturing a second article
having at least one convexity.
[0034] FIG. 8 is a schematic perspective view showing one example
of an article having concavities arranged in a lattice pattern.
[0035] FIG. 9 is a scanning electron micrograph showing one example
of a second article having convexities arranged in a lattice
pattern.
[0036] FIGS. 10A and 10B are schematic top views showing examples
of a mold having multiple depressions arranged in a lattice
pattern.
[0037] FIG. 11 is a schematic perspective view showing another
example of an article having multiple concavities arranged in a
lattice pattern.
[0038] FIG. 12 is a scanning electron micrograph showing another
example of a second article having multiple convexities arranged in
a lattice pattern.
[0039] FIG. 13 is a schematic perspective view showing yet another
example of an article having concavities arranged in a lattice
pattern.
[0040] FIG. 14 is a schematic perspective view showing yet another
example of a second article having convexities arranged in a
lattice pattern.
[0041] FIGS. 15A and B are scanning electron micrographs of
articles made using treated and untreated molding surfaces,
respectively.
[0042] FIG. 16 is a display device that includes a direct-lit
backlight.
[0043] FIG. 17 is a side-lit backlight.
[0044] FIGS. 18A and 18B are schematic cross-sectional views of
articles having prisms separating convexities or concavities.
DETAILED DESCRIPTION OF THE INVENTION
[0045] Articles are provided that have at least one concavity or at
least one convexity. Methods of making these articles are also
provided. The at least one convexity or concavity of the articles
can be used, for example, as a lens or as an array of lenses. In
some embodiments, the at least one convexity or concavity of the
article can be used as a microlens or an array of microlenses
(i.e., a micrlens array). As used herein, the term "microlens"
refers to a lens having a dimension such as a diameter in the range
of about 0.1 micrometer to about 1000 micrometers. The microlens
corresponds to a micro-convexity or micro-concavity on the surface
of the article. As used herein, the terms "micro-concavity" and
"micro-convexity" refer respectively to a concavity or convexity
having a diameter in the range of about 0.1 micrometer to about
1000 micrometers. As used herein, the term "diameter" when
referring to a concavity or convexity corresponds to the largest
cross-sectional dimension.
[0046] According to one aspect of the present invention, an article
that has a surface comprising at least one concavity can be
manufactured. During manufacture, at least one gas bubble is
deliberately introduced to impart the at least one concavity to the
surface of the article. More particularly, the article is
manufactured using a molding surface that includes at least one gas
bubble. That is, an article can be manufactured by a method the
comprises: (a) providing a hardenable fluid; and (b) molding the
article from the hardenable fluid using a molding surface
comprising at least a portion of an outer surface of a gas
bubble.
[0047] Multiple concavities such an arranged pattern of concavities
can be formed on the surface of the article using a molding surface
that includes a plurality of gas bubbles located at different
positions on the molding surface. That is, an article with an with
an arranged pattern of concavities can be manufactured using a
method that comprises: (a) providing a hardenable fluid; and (b)
molding the article from the hardenable fluid using a molding
surface comprising at least a portion of an outer surface of
multiple gas bubbles, wherein the multiple gas bubbles are arranged
in the pattern on the molding surface.
[0048] A smooth concave surface, which is the inversion of a
portion of the smooth convex surface of the gas bubble, can be
imparted to the article. In contrast to this relatively easy
manufacturing method, similar surfaces have conventionally been
formed using complicated manufacturing processes.
[0049] The terms "a", "an", and "the" are used interchangeably with
"at least one" to mean one or more of the elements being
described.
[0050] The term "at least one concavity" refers to a single concave
surface or to multiple concave surfaces. The single or multiple
concave surface can be imparted to the article using a single gas
bubble introduced at a single position on the molding surface or
using multiple gas bubbles introduced at a plurality of positions
on the molding surface. Multiple concavities can be located or
arranged in random or arbitrary positions or arranged in a pattern
on the surface of the article.
[0051] As used herein, the term "deliberately introducing" means
introducing gas bubbles for the purpose of using them as a
substantial tool in the process of making the articles. That is,
the gas bubbles are part of the molding surface that is used to
impart the at least one concavity to the surface of the article. In
some embodiments, the term deliberately introducing means not
removing or entrapping any gas bubbles that may already be present.
For example, deliberately introducing can mean not removing any gas
bubbles that may be positioned in one or more depressions of a mold
during application of the hardenable fluid to a portion of the
mold. That is, deliberately introducing can mean entrapping a gas
bubble in a depression of a mold prior during application of the
hardenable fluid to a portion of the mold. An entrapped gas bubble
is part of the molding surface that contacts the hardenable
fluid.
[0052] In some embodiments, an article that has a surface
comprising an arranged pattern of concavities can be manufactured.
During manufacture, gas bubbles are supplied at a plurality of
positions to impart the arranged pattern of concavities to the
surface of the article. More specifically, the articles are
manufactured using a molding surface that includes a plurality of
gas bubbles arranged in a pattern that corresponds to the pattern
of concavities imparted to the article. The article having the
arranged pattern of concavities can be easily manufactured.
[0053] The "arranged pattern of concavities" is a pattern of a
plurality of concavities arranged at predetermined positions,
arranged with some degree of regularity, or arranged in any desired
manner. For example, the arranged pattern of concavities can
include an arranged row pattern, an arranged lattice pattern such
as an arranged square lattice pattern, an arranged zigzag pattern,
or an arranged radial pattern. The arranged pattern of concavities
need not be formed evenly on the entire article, but may be formed
in only a portion of the article. The pattern of concavities may
vary or remain the same over any portion of the article. For
example, similar or different patterns can be used within the same
plane. The concavities within the pattern can be of the same size
and shape or can have different sizes and shapes.
[0054] Any suitable gas can be used to form the gas bubble that
imparts a concavity to the surface of an article. For example, the
gas can be air or an inert gas including nitrogen and argon. The
molding surface that is used to form the article includes a portion
of the outer surface of at least one gas bubble. The outer shape of
the gas bubble included in the molding surface, which is in contact
with the hardenable fluid, can be inversely transferred to the
article. Since gas bubbles with various shapes and sizes having
diameters ranging from a few nanometers to several centimeters or
more can be included in the molding surface, it is possible to form
concavities with a wide range of shapes and sizes. Further, when
multiple concavities are formed in the article, the multiple
concavities can have the same size and shape or can have different
sizes and shapes. That is, the molding surface can include multiple
gas bubbles having different sizes and shapes or the same size and
shape.
[0055] One embodiment of the article that has a surface comprising
at least one concavity can be manufactured according to the
following processes: (a) providing a mold having a mold surface;
(b) applying hardenable fluid onto at least a portion of the mold
surface; (c) deliberately introducing at least one gas bubble
between the mold surface and the hardenable fluid; and (d)
hardening the hardenable fluid to form an article having the at
least one concavity on the surface thereof and imparted thereto by
the gas bubble. The article is typically removed from the mold.
[0056] This method can be used to form a single concavity on the
surface of the article or a plurality of concavities on the surface
of the article. If multiple concavities are formed, these multiple
concavities can be positioned in any manner on the surface of the
article. In some examples where multiple concavities are formed,
the multiple concavities are arranged in a pattern.
[0057] An article that has a surface comprising an arranged pattern
of concavities can be manufactured according to the following
processes: (a) providing a mold having a mold surface; (b) applying
hardenable fluid onto at least a portion of the mold surface; (c)
providing gas bubbles at multiple, separate positions between the
mold surface and the hardenable fluid, wherein the separate
positions are selected based on the arranged pattern; and (d)
hardening the hardenable fluid to form an article having the
arranged pattern of concavities on the surface thereof and imparted
thereto by the gas bubbles. The article is typically removed from
the mold.
[0058] The "mold surface" is the actual surface of the mold. When a
gas bubble is introduced between the mold surface and the
hardenable fluid, the hardenable fluid is in direct contact with
the actual surface of the mold in at least one location and with a
gas bubble in at least one other location. The combination of the
actual mold surface and the surface of at least gas bubble provide
a molding surface. That is, as used herein, the term "molding
surface" refers to the surface that is in direct contact with the
hardenable fluid. The shape of the molding surface (specifically,
the inverted shape of the molding surface) can be imparted to a
surface of an article formed when the hardenable fluid is hardened.
A concavity on the surface of the article corresponds to a position
where the hardenable fluid is in contact with a gas bubble during
the hardening process. Thus, the shape and size of the portion of
the gas bubble in contact with the hardenable fluid can be imparted
to the hardened article to provide one or more concavities.
[0059] Any suitable organic material, inorganic material, or
organic-inorganic composite material can be used as a material for
the mold. Some exemplary materials for the mold include a resin
(e.g., a polymeric resin), a metal, a glass, a ceramic, or a clay.
The mold can be composed of one or more pieces. For example, a mold
having multiple pieces can be composed of a first layer having at
least one opening and a second layer that is laminated to the first
layer.
[0060] The mold typically has depressions. These depressions can
correspond to the opening or the pattern of openings of the first
layer of a mold having multiple pieces or can be part of a mold
that is a single piece. The depressions are often used to provide
the at least one gas bubble that is part of the molding surface.
For example, the at least one gas bubble can be entrapped within
the depression when the hardenable fluid is applied to a portion of
the mold surface.
[0061] When depressions of a mold are used to entrap the at least
one gas bubble, the article that has a surface comprising at least
one concavity can be manufactured according to the following
processes: (a) providing a mold having a mold surface with a
depression; (b) applying a hardenable fluid onto at least a potion
of the mold surface; (c) entrapping a gas bubble between the mold
surface and the hardenable fluid in the depression; (d) hardening
the hardenable fluid to form an article having a concavity on the
surface thereof and imparted thereto by the gas bubble in the
depression. The article is typically removed from the mold.
[0062] When the mold has a plurality of depressions that can be
used to entrap the gas bubbles, the depressions can be arranged in
a pattern. An article having an arranged pattern of concavities can
be manufactures according to the following processes: (a) providing
a mold having a mold surface with multiple depressions arranged in
a pattern; (b) applying a hardenable fluid onto at least a portion
of the mold surface; (c) entrapping multiple gas bubbles between
the mold surface and the hardenable fluid in the multiple
depressions; and (d) hardening the hardenable fluid to form an
article having an arranged pattern of concavities on the surface
thereof and imparted thereto by the multiple gas bubbles in the
multiple depressions. The article is typically removed from the
mold.
[0063] The "hardenable fluid" is a fluid that has enough fluidity
to be applied to a mold, and that can be hardened without regard to
the hardening method. Suitable hardenable fluids include, for
example, an organic material, an inorganic material, or an
organic-inorganic composite material that is in the form of a gel,
paste, or liquid. Other suitable hardenable fluids include a
solution, dispersion, suspension, or the like obtained by diluting
an organic material, an inorganic material, or an organic-inorganic
composite material with a suitable solvent (i.e., an organic
solvent or an aqueous-based solvent). Herein, "hardening" refers to
the process of making the hardenable fluid hard enough to retain
the shape imparted by the molding surface. More specifically, the
hardenable fluid becomes hard enough to retain the shape imparted
by the at least one gas bubble that is part of the molding surface;
the resulting "hardened layer" has at least one concavity. The
hardened layer is the product formed upon hardening of the
hardenable fluid.
[0064] When an organic material is included in the hardenable
fluid, a resin material or the precursor of a resin material can be
used. The hardenable fluid can, for example, include monomers or
polymers that are polymerized, cured, or crosslinked when hardened.
As the "hardening method", any suitable method can be used
including, but not limited to, polymerization of a polymerizable
resin, cooling a thermoplastic resin to at least a softening
temperature, or drying a solvent. Exemplary resin materials
include, but are not limited to, a reactive resin such as
photo-curable resin that can be hardened by polymerization when
irradiated with radiation (e.g., ultraviolet rays, visible light,
or electron beam), a thermoset resin that is hardened by
heat-oriented polymerization, a reactive resin that can be hardened
by oxidization-oriented polymerization, a reactive resin that can
be hardened by reduction-oriented polymerization, or a
thermoplastic resin that can be hardened when cooled to at least a
softening temperature, or the like.
[0065] In some applications, a soluble resin can be used as the
hardenable fluid. Suitable soluble resins include a water-soluble
resin dissolved in water, an organic solvent-soluble resin
dissolved in an organic solvent, or the like. If these soluble
resins are used as a mold to form a second article, they can often
be removed from the second article by dissolution.
[0066] When an inorganic material is used as a hardenable fluid,
various inorganic materials can be used such as a glass, concrete,
plaster, cement, mortar, ceramics, clay, and metal. These materials
can often be hardened by heating or removing water. It is also
possible to use an organic-inorganic composite material, which can
be a composite of any of the above mentioned organic materials and
inorganic materials, as the hardenable fluid.
[0067] The step of applying a hardenable fluid onto at least a
portion of the mold surface can be achieved by any known method. In
some methods of applying the hardenable fluid, a mold having
depressions is used and the hardenable fluid is applied so that the
depressions are not filled or are only partially filled. Some
suitable application methods include coating, spraying, injecting,
brushing, or pouring the hardenable fluid onto at least a portion
of the mold surface. Coating can include, for example, adding the
hardenable fluid to a surface and spreading the hardenable fluid
over at least a portion of that surface. In many examples, the
application method includes coating and any suitable coating method
can be used. In some coating methods, the hardenable fluid is
applied using a knife coating method. An optimal application method
can be selected based on the type of hardenable fluid, the desired
shape of an article, the desired size of the article, and so
forth.
[0068] The hardenable fluid can be applied onto the mold surface
before the gas bubble is provided or at the same time the gas
bubble is provided. In many embodiments, the at least one gas
bubble is present while applying the hardenable fluid to the mold
surface. For example, the gas bubble can be present in a depression
on the mold. The gas bubble can be entrapped within the depression
during the application of the hardenable fluid to the mold surface.
The size, shape, and position of the gas bubble provided often can
be selected and varied. For example, if the gas bubbles are
provided using depressions in a mold, the size, shape, and
locations of these depressions can be varied.
[0069] The hardenable fluid is in contact with the molding surface.
That is, the hardenable fluid is in contact with at least one gas
bubble in at least one position and in contact with the mold
surface in at least one other position. When the hardenable fluid
is hardened, the at least one concavity is formed in the portion of
the hardened layer that was in contact with the at least one gas
bubble that is part of the molding surface. When a hardenable fluid
is hardened, the position of the at least one gas bubble can be
controlled to be located at a predetermined position between the
mold surface and the hardenable fluid. For example, the gas bubble
can be confined within a depression of the mold. The size and the
shape of the depression can influence the size and shape of the gas
bubble as well as the size and shape of the resulting concavity in
the hardened layer. The size and shape of the depression can be
varied to provide concavities of different sizes and shapes.
Multiple gas bubbles can be provided, for example, by using a mold
that contains multiple depressions. If multiple gas bubbles are
provided, the size and shape of each gas bubble can be the same or
different.
[0070] The above mentioned processes to manufacture an article can
be carried out in the air. In this embodiment, an article having at
least one concavity or an arranged pattern of concavities can be
manufactured with a simple device configuration that does not
require special devices such as an environmental chamber. The at
least one gas bubble can be provided, for example, by entrapment
within at least one depression of a mold.
[0071] A gas bubble often tends to form a spherical surface based
on the balance of all the forces that can affect its shape. These
forces include a summation of the interface energy between the gas
bubble and the hardenable fluid, the interface energy between the
mold surface and the hardenable fluid, and the interface energy
between the mold surface and the gas bubble. In addition to these
forces, other process variables in the vicinity of the region where
the gas bubble contacts the hardenable fluid such as, for example,
buoyancy, gravity, and viscosity of the hardenable fluid can
influence the shape of the gas bubble. When an approximately
uniform force is applied to the surface of the gas bubble or when
approximately symmetrical forces are applied to the top of the gas
bubble, the gas bubble does not deform and has a relatively uniform
and smooth convex surface. This shape is often a substantially
spherical convex surface adaptable to a lens or the like. The outer
shape of the gas bubble having a substantially spherical surface
can be inversely transferred from the molding surface to the
article prepared by hardening the hardenable fluid. Therefore, the
concavity imparted by the portion of the gas bubble that contacts
the hardenable fluid can comprise a concavity at least partially
having a substantially spherical surface.
[0072] As used herein, the term "spherical surface" means that the
surface can be considered to be a portion of a sphere or the
surface has a spherical curvature. Some spherical surfaces can be
considered to be dome-shaped or hemispherical. Other spherical
surfaces can cover a smaller or larger portion of a sphere than a
hemisphere. As used herein, the term "substantially spherical
surface" means that the surface can generally be considered to be a
portion of a sphere but may differ slightly from being a perfectly
spherical surface. All the substantially spherical surfaces can
have the same or different curvature and can include a mixture of
spherical surfaces whose curvatures continuously change depending
on the position.
[0073] Some concave surfaces are an asymmetrical surface rather
than a symmetrical spherical surface. A concave surface with an
asymmetrical shape can be imparted to an article using the outer
surface of a gas bubble having an asymmetrical shape. The
asymmetrically shaped gas bubble can be formed by applying
non-uniform forces to the convex surface of the gas bubble or by
applying a force that has an asymmetrical distribution to the top
of the convex surface of the gas bubble.
[0074] The articles having at least one concavity can be
manufactured using a relatively simple process. A single concavity
can be formed on the surface of the article or a plurality of
concavities can be formed that can be arranged randomly or in a
pattern. The at least one concavity can be spherical or
substantially spherical and can be used as a lens. An article
having an arranged pattern of concavities such as micro-concavities
can be manufactured in a simple process that is less time consuming
and less costly than other known process for making similar
articles. Further, it is possible to modify the manufacturing
process so that it can be performed in continuous manner and so
that any desired size article can be prepared.
[0075] According to one embodiment of the present invention, the
mold can comprise at least one depression, and the at least one gas
bubble is deliberately introduced at the molding surface by
entrapping it in the at least one depression of the mold while
applying the hardenable fluid to the mold surface. That is, the gas
bubble is entrapped in the depression of the mold and is positioned
between the mold surface and the hardenable fluid. The molding
surface in contact with the hardenable fluid includes a combination
of the mold surface (i.e., the actual mold surface) and at least
one gas bubble.
[0076] For example, the mold can comprise an arranged pattern of
multiple depressions and a plurality of gas bubbles can be
deliberately introduced at the molding surface by entrapping them
in the arranged pattern of multiple depressions of the mold while
applying the hardenable fluid to the molding surface. That is,
multiple gas bubbles can be entrapped in the plurality of
depressions of the mold that are arranged in a pattern. Each of the
multiple gas bubbles can be entrapped within a depression of the
mold between the mold surface and the hardenable fluid. The molding
surface in contact with the hardenable fluid includes a combination
of the mold surface (i.e., the actual mold surface) and multiple
gas bubbles arranged in a pattern.
[0077] In these embodiments, since at least one depression or an
arranged pattern of depressions are provided in the mold
beforehand, gas bubbles can be entrapped in the at least one
depression of the mold while applying the hardenable fluid to the
molding surface. The location of the at least one depression
corresponds to the position of the at least one gas bubble that is
part of the molding surface. The position of the at least one gas
bubble corresponds to the location of the concavities imparted to
the articles prepared by hardening the hardenable fluid in contact
with the molding surface. Therefore, the at least one concavity can
be located at a predetermined position on the article certainly and
easily. In addition, because the locations of the depressions
correspond to the positions where the concavities are formed in the
article, multiple concavities having a high positional accuracy can
be formed on the article.
[0078] The volume of a depression in the mold influences the amount
of gas than can be entrapped within the depression between the
hardenable fluid and the mold surface. If there are multiple
depressions, the volumes of multiple depressions can be similar or
any portion of the multiple depressions can be similar. The size of
any concavity can be varied by varying the volume of the depression
that entraps that gas bubble that results in that particular
concavity. For example, a first group of concavities can have a
first size that is different from a second group of concavities
that have a second size.
[0079] Any desired pattern of depressions can be included in the
mold. For example, the arranged pattern of depressions can include
an arranged row pattern, an arranged lattice pattern such as a
square lattice pattern (i.e., a lattice pattern is a pattern with
multiple rows, multiple columns, or both), an arranged zigzag
pattern, or an arranged radial pattern. The depressions within the
pattern can be the same size and shape or can be different.
[0080] According to the above mentioned embodiments, a gas bubble
can be provided between the mold surface and the hardenable fluid
by entrapping it in the depression of the mold while applying the
hardenable fluid to at least a portion of the mold surface. For
example, a portion of the total gas (e.g., air) existing around the
mold can be entrapped within a space between the hardenable fluid
and the mold surface while the hardenable fluid is applied to the
mold by coating or injection. An entrapped gas bubble can become
part of the molding surface and can impart a concavity to the
hardened layer. In this case, if a coating is applied, various
coating devices, such as, for example, a knife coater, a bar
coater, a blade coater, and a roll coater, can be used.
[0081] Entrapping the at least one gas bubble can be controlled by
adjusting factors such as, for example, the viscosity of hardenable
fluid, the coating speed, various interfacial tension relationships
among the hardenable fluid, the gas and the mold, or the like.
Conditions of the entrapped bubble of the gas such as size, shape
and position can also be controlled by the similar factors for
entrapping the bubble of the gas mentioned above such as, for
example, the size, shape, and position of the depressions in the
mold. The entire process can be conducted under atmospheric
pressure and no evacuation is needed.
[0082] Another aspect of the present invention is an article having
a surface comprising at least one concavity such as an arranged
pattern of concavities manufactured according the above mentioned
manufacturing method. During manufacture, one or more gas bubbles
impart the at least one concavity such as the arranged pattern of
concavities to the surface of the article.
[0083] In one embodiment of the article, at least one smooth
concave surface can be formed using a molding surface that includes
at least one gas bubble. If multiple concavities are formed, these
multiple concavities can be arranged randomly or in a pattern. An
arranged pattern of concavities can be formed using a molding
surface that includes an arranged pattern of gas bubbles. This
arranged pattern of gas bubbles often corresponds to an arranged
pattern of depressions in the mold. Each smooth concave surface
produced is the inverse of a portion of the outer surface of a gas
bubble that is part of the molding surface. In many examples, the
gas bubble has a substantially spherical surface and the resulting
concavity imparted to the article has a substantially spherical
surface.
[0084] If multiple concavities are arranged in a pattern on the
surface of the article, the pattern can be of any design. For
example, the arranged pattern can be an arranged row pattern, an
arranged lattice pattern, an arranged zigzag pattern or an arranged
radial pattern. The concavities can all be of a similar size and
shape or any portion of the concavities can be of a similar size
and shape. In some articles having an arranged pattern of
concavities, some or all of the concavities has a substantially
spherical surface.
[0085] Additionally, a concavity having an overhang shape (e.g.,
see 32a in FIG. 3A), which is difficult to form using conventional
mechanical machining, can be formed on the surface of the
article.
[0086] The articles described herein can be used in various fields
and applications. Especially, if the at least one concavity on the
surface of the article is substantially transparent or translucent
to visible light and has a substantially spherical surface, the
article can be used in various optical applications. For example,
the concavity can function as a lens such as a microlens. An
arrangement of multiple concavities that are transparent or
translucent to visible light and that have substantially spherical
surfaces can be used as an array of lenses such as a microlens
array.
[0087] A first article having a surface comprising at least one
concavity such as an arranged pattern of concavities can be used as
a mold (i.e., a second mold) to produce a second article having at
least one convexity such as an arranged pattern of convexities on
its surface. The at least one convexity on the second articles is
the inverse of the at least one concavity present on the first
article that is used as the second mold. That is, any concavity
present in the first article can be imparted to the second article
as a convexity.
[0088] The term "at least one convexity" refers to a single convex
surface or to multiple convex surfaces. The at least one convex
surface can be imparted to the article using a mold with at least
one concave surface. An "arranged pattern of convexities" is a
pattern of a plurality of convexities arranged at predetermined
positions, arranged with some degree of regularity, or arranged in
any desired manner. For example, the arranged pattern of
convexities can include an arranged row pattern, an arranged
lattice pattern such as an arranged square lattice pattern, an
arranged zigzag pattern, or an arranged radial pattern. The
arranged pattern of convexities need not be formed evenly on the
entire article, but may be formed in only a portion of the article.
The pattern of convexities may vary or remain the same over any
portion of the article. For example, similar or different patterns
can be used within the same plane. The convexities within the
pattern can be of the same size and shape or can have different
sizes and shapes.
[0089] By virtue of using the first article as a second mold to
form the second article, the second article that has at least one
convexity such as arranged pattern of convexities can be formed
using relatively simple processes and relatively short
manufacturing times compared to other conventional methods of
forming similar articles. More specifically, a second article
having at least one substantially spherical convex surface such as
an arranged pattern of convex surfaces can be formed using a first
article that has at least one substantially spherical concave
surface. The at least one convex surface formed in the second
article can be, for example, a micro-convexity.
[0090] Thus, another aspect of the present invention is a second
article that has a surface comprising at least one convexity such
as an arranged pattern of convexities. The method comprises using
the first article made by the above mentioned manufacturing method
as a second mold to impart the at least one convexity such as an
arranged pattern of convexities to the surface of the second
article.
[0091] The second article can be manufactured by applying a second
hardenable fluid to the first article using an application method
such as coating or injection. The second hardenable fluid is
applied to the surface of the first article that contains at least
one concavity. Suitable second hardenable fluids are often the same
types of hardenable fluids described above that can be used to
prepare the first article with at least one concavity. The second
hardenable fluid is typically selected to be compatible with the
first article that is used as the second mold. More specifically,
the second hardenable fluid it often selected so that it does not
dissolve or alter the shape and dimensions of the second mold. The
second hardenable fluid can include an organic material, inorganic
material, or organic-inorganic composite material that is in the
form of a gel, paste, liquid, dispersion, suspension, or the like.
After the hardenable fluid has been applied to the second mold but
prior to hardening, a deaeration process can be added to remove
entrapped gas bubbles such as entrapped gas bubbles between the
surface of the second mold and the second hardenable fluid. In some
instances, the presence of entrapped gas bubbles can cause defects
in the second article.
[0092] In some examples, the at least one convexity has a
substantially spherical surface and the process involves the use of
a second mold that has at least one concavity with a substantially
spherical surface. The at least one concavity in the second mold
often has a diameter less than 1000 micrometers, less than 100
micrometers, or less than 10 micrometers. The at least one
convexity formed in the second article has a diameter comparable to
the diameter of the at least one concavity present in the second
mold. The second mold is prepared using at least one gas bubble
such as an arranged pattern of gas bubbles in a molding surface
that imparts at least one concavity such as an arranged pattern of
concavities to the surface of the second mold.
[0093] In some exemplary second articles, the at least one
convexity has a substantially spherical surface. If this at least
one convexity is substantially transparent or translucent in the
visible region, the second article can be used in various optical
fields. More specifically, the at least one convexity can be used
as a lens such as a microlens and an arranged pattern of
convexities can be used as an array of lenses such as a microlens
array.
[0094] If there are more than one convexity on the surface of the
second article, all or any portion of the convexities can be
similar. For example, there can be a first group of convexities
having substantial similarity and a second group of convexities
having substantial similarity but that are different from the first
group of convexities.
[0095] A surface of the second article can be covered with the
first article that serves as the second mold. In this case, the
second article is not removed from the first article during the
manufacturing processes. Such a combined article composed of both
the first article and the second article can be used in various
fields. For example, when materials with different refractive
indexes are used to prepare the first article and the second
article, the combined article can function as a lens even if the
combined article has a flat surface.
[0096] One exemplary process for preparing a first article having
at least one concavity and a second article having at least one
convexity is schematically illustrated in FIGS. 1A to 1G. More
specifically, FIGS. 1A to 1D schematically illustrate one
embodiment of a manufacturing method for making an article having a
surface comprising multiple concavities such as an arranged pattern
of concavities. FIGS. 1E to 1G schematically illustrate one
embodiment of a manufacturing method for making a second article
having a surface comprising multiple convexities such as an
arranged pattern of convexities.
[0097] FIGS. 1A to 1D schematically illustrate one exemplary
manufacturing process that can be used to manufacture the article
31 having a plurality of concave surfaces 32. FIG. 1A illustrates
the step of providing a mold 10 that has a plurality of depressions
11. FIG. 1B illustrates the step of applying a hardenable fluid to
the mold 10 and providing gas bubbles 50. The gas bubbles 50 are
entrapped in the depressions 11 and are positioned between the mold
surface 12, 13 and the hardenable fluid 30. FIG. 1C illustrates
hardening the hardenable fluid 30 to form the article 31 having the
arranged pattern of concavities 32 on a surface thereof and
imparted thereto by the gas bubbles 50. FIG. 1D illustrates
removing the article 31 from the mold 10. The article 31 is shown
with three concavities 32 but any desired number of concavities can
be formed. The concave surfaces 32 are formed at locations
corresponding to the depressions 11 in the mold and to the
locations of the entrapped gas bubbles 50. The outer shape of the
gas bubbles 50 are imparted to the article 31 resulting in the
concavities 32. Each of the manufacturing processes in FIG. 1A to
1D can be carried out while the mold 10 is under ambient
conditions. The molding process used to manufacture article 31 does
not need to be placed in a special environmental chamber.
[0098] The gas bubbles 50 are entrapped while applying the
hardenable fluid 30 to the mold surface with a coating device 40.
In many embodiments, the hardenable fluid 30 comprises a hardenable
resin. The hardenable fluid 30 preferably is applied over the
depressions in the mold in such a manner that the multiple
depressions are not filled with the hardenable fluid 30. That is,
the hardenable fluid 30 preferably does not contact mold surface
13. The gas bubbles 50, however, contact mold surfaces 12 and 13 as
well as a portion of the hardenable fluid 30 positioned over
depression 11. The molding surface is the surface in contact with
the hardenable fluid 30 and includes both the outer surface of the
gas bubbles 50 in direct contact with the of the hardenable fluid
30 and any portion of the mold surface in direct contact with the
hardenable fluid 30. For example, the portion of the mold between
the depressions 11 is in direct contact with the hardenable fluid
30. After applying the hardenable fluid 30 and entrapping the gas
bubbles 50, the hardenable fluid 30 is hardened and removed from
the mold 10. The resulting article 31 has a plurality of concave
surfaces 32 to which a portion of the outer shapes of the gas
bubbles 50 are imparted.
[0099] The construction or article that is shown in FIG. 1B
includes a mold 10 that includes a plurality of depressions 11 and
a fluid 30, such as a hardenable fluid 30, covering mold 10. The
construction or article also includes one or more gas bubbles 50 in
each depression 11. The one or more bubbles 50 in each depression
forms a concavity 32 in fluid 30. The plurality of depressions 11
can be arranged in any form that may be desirable in an
application. For example, depressions 11 can be arranged randomly.
As another example, depressions 11 can be arranged in
pre-determined positions and can, for example, form a lattice
pattern.
[0100] In some cases, such as when depressions 11 are pyramids, the
depsressions can have pointed bottoms. In some cases, such as in
the case of mold 10 shown in FIG. 2B, the depressions can have edge
lines at the bottom. In some cases, depression 11 can have a
pyramid portion and can, for example, be a frustum. In some cases,
depression 11 can have one or more planar sides. In some cases,
depression 11 can have a tapering shape. In general, depression 11
can have any shape that may be desirable in an application.
Exemplary shapes includes a cube, a pyramid, an obelisk, a wedge, a
portion of a sphere such as a hemisphere, a portion of an
ellipsoid, a catenoid, a cylinder such as a right cylinder, or a
cone.
[0101] In some cases, such as in the case shown in FIG. 1C, gas
bubbles 50 in each depression include a sidewall and a convex or
concave top. In some cases, such as in the case shown in FIG. 3A,
the concavity in the fluid can include an over-hang portion, such
as over-hang portion 32A.
[0102] The construction or the article shown in FIG. 1C includes a
mold 10 that has a top first structured surface shown in FIG. 1A
that includes a plurality of walls 220 separating a plurality of
depressions 11, where walls 220 and depressions 11 alternate. The
construction or the article in FIG. 1C further includes a
hardenable fluid 31 that covers the first structured surface of the
mold. Fluid 31 also contacts at least the plurality of walls 220.
In some cases, such as in the case shown in FIG. 1C, the fluid also
contacts a portion of each depression. Gas bubbles 50 prevent fluid
31 from contacting the entire surface of each depression, resulting
in fluid 31 having a bottom structured surface 210. If fluid 31 is
hardened and removed from the mold, then the removed hardened fluid
has a second structured surface 210 (also shown as the bottom
structured surface of layer 31 in FIG. 1D) that is substantially
different than the inverse of the first structured surface (the top
structured surface in mold 10). In the exemplary construction shown
in FIG. 1D, the second, but not the first, structured surface has a
plurality of convexities or concavities 32.
[0103] If the mold contains multiple depressions 11, these multiple
depressions can be arranged randomly or arranged in any desired
pattern. In some embodiments, a plurality of depressions 11 can be
arranged in a single row or in a lattice pattern. As used herein, a
mold having a lattice pattern of depressions means that there are
at least two rows, at least two columns, or at least two rows and
at least two columns of depressions 11 in the mold. For example,
some lattice patterns are square lattice patterns where the number
of rows is equal to the number of columns. In other embodiments,
the depressions can be arranged in a pattern such as a zigzag
pattern or a radial pattern.
[0104] In the process shown in FIG. 1A, the mold 10 having a
plurality of depressions 11 is provided. The plurality of
depressions 11 can be arranged randomly or arranged in any desired
pattern based on the use of the resulting articles. The location of
the depressions 11 determines the positions of the entrapped gas
bubbles 50 that impart the at least one concavity to the surface of
the articles. The location of the concavities 32 on the surface of
the article 31 can be selected by the arrangement of the
depressions 11 on the mold 10.
[0105] Any suitable material can be used to prepare the mold 10. In
some exemplary methods, an organic resin material such as
polypropyrene, polyethylene, polystyrene, or poly-cyclo-olefin can
be used for the mold 10. In other exemplary methods, other suitable
organic materials, inorganic materials such as metals (e.g.,
nickel, copper, or brass), glasses or ceramic materials, or
organic-inorganic composite materials can be used. The mold 10 can
be flexible or hard. A flexible mold 10 often can be more easily
handled. However, a mold 10 made of hard material such as a metal
or a crystallized polymer often can provide improved dimensional
accuracy. The mold 10 can be any suitable size but the size is
often selected based on the dimensions of the coating device 40.
Some exemplary molds 10 have a vertical dimension in the range of 1
to several thousand millimeters, a horizontal dimension in the
range of 1 to several thousand millimeters, and a thickness
dimension in the range of 10 micrometers to greater than 10
millimeters.
[0106] The depression 11 can have any suitable shape. The planar
shape observed from above the depression 11 can be, for example, a
circle, triangle, square, rectangle, ellipsoid, trapezoid,
pentagon, hexagon or cross. For example, the depression 11 can have
a square or rectangular cross section as shown in FIG. 1A. In this
case, a side surface 12 and a bottom surface 13 of the depressions
may be configured with linear shapes or with curved shapes. The
relationship between the shape of the depression 11 and the shape
of the gas bubble 50 will be described in detail later.
[0107] FIG. 2A is a schematic view observed from above showing
another exemplary mold 10 having multiple quadrangular pyramid
depressions 11 with rectangular planar shaped sides. Each of the
pyramids in FIG. 2A has a pointed bottom. FIG. 2B is a schematic
view observed from above showing yet another exemplary mold 10
having multiple quadrangular pyramid depressions 11 with triangular
planar shaped sides. Each of the pyramids in FIG. 2B has an edge
line at the bottom.
[0108] In other examples, depression 11 can have a triangular cross
section and this cross-sectional shape becomes narrower from the
top side toward the bottom side. A side surface may be configured
with a linear shape or with a curved shape. A bottom portion of the
depression 11, which is a part of the mold surface, may be
configured, for example, with a flat shape as shown in FIG. 1A, a
pointed shape, a linear shape, or a rounded shape. In still other
examples, depressions 11 can have a trapezoidal cross sectional
shape and the cross-sectional width may become narrower from the
top towards the bottom or may become wider from the top towards the
bottom. The side surfaces and the bottom surface may be configured
with linear shapes or with curved shapes. Any other suitable shapes
for the depressions 11 can be used.
[0109] The depressions 11 can have any suitable dimensions. As
examples of the size of the depression 11, the depth can be 0.1
.mu.m or more, 1 .mu.m or more, or 10 .mu.m or more. The depth can
often be 100 mm or less, 10 mm or less, or 1 mm or less. The
cross-sectional area of the depression opening can be 0.01
.mu.m.sup.2 or more, 0.1 .mu.m.sup.2 or more, or 1 .mu.m.sup.2 or
more. The cross-sectional area can often be 1000 mm.sup.2 or less,
100 mm.sup.2 or less, or 10 mm.sup.2 or less. The dimensions are
not limited, however, to these values.
[0110] In the process shown in FIG. 1B, the coating device 40 is
set adjacent to the mold 10. The coating composition is coated on
at least a portion of the mold 10 with the coating device 40 to
form the hardenable fluid layer 30. The hardenable fluid layer 30
does not fill the depressions 11. That is, the hardenable fluid 30
does not contact the mold surface 13. At the same time, gas bubbles
50 are provided in the depression 11 of the mold 10. The coating
process can be performed in the air under normal atmospheric
conditions.
[0111] In some embodiments of the coating process shown in FIG. 1B,
the hardenable fluid includes a hardenable polymeric resin. Any
suitable polymeric resin can be used alone or in combination with
other polymeric resins. For example, the hardenable fluid can be a
solution of a polymer resin such as a photo-curable resin (e.g., a
UV curable resin) or a soluble resin (e.g., a water or organic
solvent soluble resin). If the mold 10 has a sufficient heat
resistance, the polymer resin can be a thermoplastic resin or a
thermoset resin. Any of the polymeric resins can contain various
additives, such as a thickener, a curing agent, a crosslinking
agent, an initiator, an oxidant inhibitor, an antistatic agent, a
diluent, a detergent, a pigment, or a dye.
[0112] Exemplary photo-curable resins include, but are not limited
to, a photopolymerizable monomer, oligomer, or mixture thereof.
Photopolymerizable monomers include acrylate based monomers,
methacrylate based monomers, and epoxy based monomers.
Photopolymerizable oligomers include acrylate based oligomers,
methacrylate based oligomers, urethane acrylate based oligomers,
epoxy based oligomers, epoxy acrylate based oligomers, and ester
acrylate based oligomers. A photoinitiator is usually added to the
photo-curable resins. When a UV curable resin is used, the resin
can usually be hardened quickly using ultraviolet radiation without
exposing the mold or the like to a high temperature.
[0113] Exemplary thermoset resins that can be included in the
hardenable fluid include, but are not limited to, acrylate based
resins, methacrylate based resins, epoxy based resins, phenol based
resins, melamine based resins, urea based resins, unsaturated ester
based resins, alkyd based resins, urethane based resins, or ebonite
based resins. A polymerization initiator is typically added to the
thermoset resin. The resulting cured polymeric material can have
good heat and solvent resistance. Additionally, if fillers are
added, the resulting cured polymeric material can be quite
strong.
[0114] Exemplary thermoplastic resins that can be included in the
hardenable fluid include, but are not limited to, polyolefin
resins, polystyrene resins, polyvinyl chloride resins, polyamide
resins, or polyester resins.
[0115] Exemplary soluble resins that can be included in the
hardenable fluid include, but are not limited to, water-soluble
resins and organic solvent-soluble resins. Suitable water-soluble
resins include, for example, polyvinyl alcohols, polyacrylic acids,
polyacrylic amides, and polyethylene oxides.
[0116] Any suitable hardening method can be used. The hardening
method is typically selected based on the composition of the
hardenable fluid. Some hardening methods include a drying process
to remove water or an organic solvent. Other hardening methods
include exposing the hardenable fluid to actinic radiation such as
UV radiation. Still other hardening methods include exposing the
hardenable fluid to heat or cooling the hardenable fluid.
[0117] Any suitable coating device 40 can be used to apply the
hardenable fluid layer 30 to at least a portion of the mold 10. In
some embodiments, the coating device 40 is a knife coater. For
example, when a thermoplastic resin is used as the hardenable fluid
resin, a heated knife coater that is heated to a temperature at
which the resin has a sufficient fluidity can be used. In other
embodiments, the coating device 40 can be a bar coater, a blade
coater, or a roll coater.
[0118] To apply the hardenable fluid layer 30 to at least a portion
of the mold 10, either the coating device 40 or the mold can be
moved. In some examples, the mold is stationary and the coating
device is moved adjacent to the mold 10. In other examples, the
coating device 40 can be stationary and the mold 10 can be provided
from a roll that is passed by the coating device 40. In these
examples, a continuous manufacturing line can be designed to form
articles having at least one concavity.
[0119] Referring to FIG. 1B, as the coating device 40 moves in the
direction of an arrow A (from left to right), the hardenable fluid
layer 30 is coated on the mold 10. Although FIG. 1B illustrates the
application of the hardenable fluid layer 30 to the mold 10 by
coating, other application methods such as, for example, injection
can be used as long as the other application methods can entrap gas
bubbles 50.
[0120] The average thickness of the hardenable fluid layer 30 can
be any desired thickness and can be varied according to the article
desired. In some examples, the average thickness of the hardenable
fluid layer 30 is about 10 .mu.m to 100 mm or 10 .mu.m to 10 mm. As
the hardenable fluid layer 30 is applied to the mold 10, a part of
the air existing around the mold 10 can be pushed out from the
space around the mold 10 as indicated by an arrow B and another
part of the air can be entrapped in the depressions 11. Air that is
entrapped in the depression 11 can contact mold surface 12 and 13
of the depression 11 as a gas bubble 50.
[0121] The entrapment of gas bubbles 50 within the depressions 11
can be controlled, for example, by adjusting factors such as the
viscosity of hardenable fluid 30, the coating speed, and the
interfacial tension relationships among the hardenable fluid 30,
the gas bubble 50, and the mold 10. For example, if the coating
speed is faster than the natural flow rate of the hardenable fluid
on a surface of the depression of the mold, a bubble of the gas can
be entrapped within each depression of the mold. The natural flow
rate means the flow rate of the hardenable fluid when it is placed
on the mold and may be affected, for example, by the viscosity of
hardenable fluid and the interfacial tension relationships among
the hardenable fluid, the gas, and the mold. If the viscosity of
hardenable fluid is low, gas bubbles 50 can be entrapped by
increasing the coating speed or by changing materials of the
mold.
[0122] The process is a controlled displacement of gas (air)
entrapped in the mold 10 and advantageously results in gas bubbles
50 being entrapped in the mold depressions 11 so that they can be
used as part of the molding surface. The sizes and positions of the
gas bubbles 50 can be controlled by adjusting the process variables
including the moving speed of the coating device 40.
[0123] Although the gas bubbles 50 are positioned inside the
depressions 11 in FIGS. 1B and 1C, they are not limited thereto.
That is, the outer surface of the gas bubbles 50 can be outside the
depressions 11. For example, the upper portions (i.e., the upper
surface) of the gas bubbles 50 may extend beyond from the top
surface of the mold 10 as shown in the sectional view of FIG. 4.
Although a single gas bubble 50 can exist in a single depression 11
as shown in FIGS. 1B and 1C, more than one gas bubble may exist
within a single depression 11.
[0124] Referring to FIG. 1C, the top surface of mold 10 and gas
bubbles 50 define or form a molding surface 210 that imparts
structure to the bottom surface of layer 31. Molding surface 210
includes a plurality of gas bubbles 50 that form a lattice pattern
that may include a row pattern, a column pattern, a zigzag pattern,
or a radial pattern, or a combination of such patterns, or any
other pattern that may be desirable in an application. In the
exemplary molding surface 210, the gas bubbles include convexities
that impart concavities to layer 31. In general, gas bubbles 50 can
include portions that have any shape that may be desirable in an
application, such as concavities, convexities, or planar portions,
such as the planar portions of gas bubbles 50 shown in FIG. 1B or
1C.
[0125] In the exemplary construction shown in FIGS. 1B and 1C,
bubbles 50 have linear or planar side walls. In some cases, such as
when depressions 11 have curved side walls, gas bubbles 50 can have
curved side walls.
[0126] In the process shown in FIG. 1C, the hardenable fluid layer
30 is hardened to form the hardened layer 31. Any suitable
hardening method can be used that is compatible with the hardening
fluid 30. For example, when the hardenable fluid is a UV curable
resin, the hardened layer 31 can be formed by irradiating the
hardenable fluid layer 30 with a UV light source to polymerize the
resin. When the hardenable fluid layer contains a soluble resin,
the hardened layer 31 can be formed by drying to remove the
solvent. When the hardenable fluid is a thermoplastic resin, the
hardened layer 31 can be formed by cooling the thermoplastic resin
to at least the softening temperature. When the hardenable fluid is
a thermoset resin, the hardened coating 31 can be formed by heating
the thermoset resin to at least the curing temperature.
[0127] The hardened layer 31 as shown in FIG. 1C has a plurality of
concave surfaces 32 that result from contacting the outer surface
of the gas bubbles 50 during hardening. That is, the outer shapes
of the gas bubbles 50, which can have a substantially spherical
surface, are inversely transferred to the hardened layer 31. That
is, the outer shapes of the gas bubbles 50 are part of the molding
surface in contact with the hardenable fluid 30. The hardened layer
31 has the inverse shape of the molding surface.
[0128] The gas bubbles 50 are part of the molding surface, which is
the operational surface in contact with the hardenable fluid 30.
Because the gas bubbles 50 are part of the molding surface and the
gas bubbles 50 often have substantially spherical convex outer
surfaces, the hardened layer 31 often has substantially spherical
concave surfaces. The concavities formed in the hardened layer 31
can be micro-concavities.
[0129] In the process shown in FIG. 1D, an article (i.e., hardened
layer) 31 having a plurality of concave surfaces 32 such as a
plurality of micro-concavities can be obtained by removing or
separating the hardened layer 31 from the mold 10. In some
embodiments, the mold 10 can be used to form other hardened layers
31. The article 31 having at least one concavity can be used as an
optical article such as a lens or array of lenses or can be used to
prepare a second article that has at least one convexity.
[0130] In some embodiments of the article 31, a first surface of
the article has multiple concavities and a second surface opposite
the first surface is flat. The flat surface can have a matte or
glossy finish. The surface roughness of either surface can be, for
example, less than 100 nanometers, less than 50 nanometers, less
than 10 nanometers, or less than 5 nanometers. The surface
roughness can be measured using a profilometer such as a Surface
Profiler System P-16 from KLA-Tencor Corporation.
[0131] The process shown in FIGS. 1A to 1D can be performed in a
continuous manner to provide articles 31 having at least one
concavity such as an arranged pattern of concavities. Any pattern
of concavities can be imparted to the article from a molding
surface in contact with the hardenable fluid 30. The molding
surface includes at least a portion of at least one gas bubble 50.
A concavity in the resulting hardened layer is formed where the
outer surface of the at least one gas bubble 50 contacts the
hardenable fluid 30.
[0132] The article 31, manufactured through the processes of the
steps of FIG. 1A to FIG. 1D, has a surface that is the inverse of
the molding surface used to form the article. More particularly,
the article 31 has concavities that were imparted by portions of
the outer surface of gas bubbles 50. Often, the shape of concavity
32 is the inversion of a substantially spherical surface having a
curvature determined by the size of the gas bubbles 50. The
concavities can have any suitable size depending on the use of the
article 31. Some exemplary concavities have a cross-sectional area
in the bottom portion that is about 0.01 .mu.m.sup.2 or more, 0.1
.mu.m.sup.2 or more, or 1 .mu.m.sup.2 or more. This cross-sectional
area is often 100 mm.sup.2 or less, 10 mm.sup.2 or less, or 1
mm.sup.2 or less. The height of the concavity 32 is often 0.1 .mu.m
or more, 10 .mu.m or more, or 10 .mu.m or more. This height can be,
for example, 100 mm or less, 10 mm or less, or 1 mm or less.
[0133] FIG. 3A illustrates another manufacturing process
corresponding to the process shown in FIG. 1D. FIG. 3A shows a
process that can be used to obtain an article 31 having a concave
surface 32 with an over-hang portion 32A. Over-hang portions can
often be formed using a mold that has depressions with a subulate
shape (i.e., depressions having a shape that tapers to a point)
such as triangle pyramid, square pyramid, circular cone, or the
like. Additionally, the over-hang portion can have a sharp or
pointed edge. Articles with concave surfaces that include an
over-hang portion can be easily manufactured; these types of
structures can be very difficult to form using methods such as
mechanical machining or the like.
[0134] FIGS. 3A and 1D illustrate how the shape of the depression
can be selected to alter the shape of the at least one concavity
formed on the surface of the article. In addition to the shape of
the depression 11, other variables can be used to alter the shape
of the concavities formed when the hardenable fluid 30 is hardened
to article 31. That is, the molding surface in contact with the
hardenable fluid 30 can be varied by altering the size and shape of
the depressions and other process variables.
[0135] Since the concave surfaces 32 are formed by entrapping gas
bubbles 50 in the respective depressions 11 arranged in the mold
10, a plurality of concave surfaces 32 can have substantially the
same shape if the depressions have substantially the same shape.
That is, the repeatability of the process of making concave
surfaces can be controlled by controlling the entrapped gas
bubbles. More particularly, by controlling the size, shape, and
position of the entrapped gas bubbles 50, the size, curvature, and
position of the concave surfaces 32 can be controlled.
[0136] The size (e.g., volume, diameter, or cross-sectional area)
of the gas bubbles 50 may be controlled by, for example, (a)
adjusting the size and shape of the depressions 11 of the mold 10,
(b) adjusting the viscosity of the hardenable fluid 30 that is
applied to the mold 10, (c) adjusting the speed of applying the
hardenable fluid 30 to the mold 10, (d) adjusting the interfacial
tensions among the hardenable fluid 30, the mold 10, and the gas
bubbles 50, (e) adjusting the time from coating of the hardenable
fluid 30 to the hardening thereof, (f) adjusting the temperature of
the gas bubbles 50, and (h) adjusting the pressure to be applied to
the gas bubbles 50. The specific size of the gas bubbles 50
adjustable in the above mentioned manner may have, for example, a
diameter in the range of 0.1 .mu.m to 100 mm. Each adjustment is
further described below.
[0137] The size and shape of the depressions 11 can be used to
adjust the size of the gas bubbles 50. The gas bubbles 50 within
the depressions 11 are significantly influenced by the interfacial
tension between the gas bubbles 50 and the hardenable fluid 30 in
the region where the gas bubbles 50 contact the hardenable fluid
30. In the vicinity of the region where the gas bubbles 50 contact
the hardenable fluid, the gas bubbles 50 are also influenced by the
interfacial tension between the gas bubbles 50 and the mold
surfaces of the depressions 11 and the interfacial tension between
the hardenable fluid and the mold surfaces of the depressions 11.
The gas bubbles 50 often form smooth substantially spherical convex
surfaces in the region where the gas bubbles 50 contact the
hardenable fluid, while the curvature and shape of the convex
surfaces are influenced by the size and shape of the depressions
11.
[0138] The size and configuration of the depressions 11 affect the
curvature and shape of the gas bubbles 50 whose curvature and shape
are subsequently imparted to the molded articles. While the
depressions 11 can take various planar shapes, if the resulting
concavities will be used as a lens, it is often preferable that the
planar shape of the depressions 11 be a symmetrical shape (point
symmetrical or line symmetrical) or a shape similar to symmetrical
shape. That is, when the depression 11 is arranged in such a way
that the vertex of the convex surface of the gas bubble 50 comes to
the center of the approximately symmetrical planar shape, the gas
bubble 50 can have a smooth convex surface that has few
deformations. As the mold 10 is placed horizontally, buoyancy and
gravity can be uniformly applied to the convex surfaces so that the
gas bubbles 50 can have substantially spherical convex
surfaces.
[0139] The viscosity of the hardenable fluid can be adjusted to
control the size of the gas bubbles 50. For example, in the process
schematically illustrated in FIG. 1B, the size of the entrapped gas
bubbles 50 can be controlled by adjusting the viscosity of the
hardenable fluid 30 that is applied to the mold 10. Specifically,
the size of the gas bubbles 50 can be increased by increasing the
viscosity of the hardenable fluid, while the size of the gas
bubbles 50 can be decreased by decreasing the viscosity of the
hardenable fluid. The viscosity of the hardenable fluid is not
limited, but is often 1 mPa-sec or more, 10 mPa-sec or more, or 100
mPa-sec or more. The viscosity of the hardenable fluid can be
100000 mPa-sec or less, 10000 mPa-sec or less, or 1000 mPas or
less. The adjustment of the viscosity can be carried out by
adjusting the concentration of the hardenable fluid (solvent can be
added or removed) or by adding a thickener.
[0140] The coating speed can be adjusted to control the size of the
gas bubbles 50. In the process schematically illustrated in FIG.
1B, the size of the trapped gas bubbles 50 can be controlled by
adjusting the speed of coating the hardenable fluid 30 to the mold
10. If the mold is stationary, the speed of moving the coating
device 40 can be adjusted. Alternatively, if the coating device 40
is stationary, the speed of moving the mold can be adjusted. As
exemplified in FIG. 1B, the movement of the coating device 40 is
indicated by the arrow A. If a knife coater is used as the coating
device 40, the coating speed can be defined by the speed of the
moving the knife edge. Specifically, the size of the gas bubbles 50
can be increased by increasing the coating speed, while the size of
the gas bubbles 50 can be decreased by decreasing the coating
speed. Although any suitable coating speed can be used, some
exemplary coating speeds are in the range of 0.01 to 1000
centimeters/second, in the range of 0.5 to 100 centimeters/second,
in the range of 1 to 50 centimeters/second, or in the range of 1 to
25 centimeters/second.
[0141] In the process shown in FIG. 1B, the size of the entrapped
gas bubbles 50 can also be controlled by adjusting the interfacial
tension between the hardenable fluid 30 and the molding surface of
the mold 10, the interfacial tension between the hardenable fluid
30 and the gas bubbles 50, and the interfacial tension between the
gas bubbles 50 and the surface of the mold 10. Specifically, for
example, the size of the gas bubbles 50 can be increased by
increasing the contact angle between the hardenable fluid 30 and
the surface of the mold 10 (decreasing the wettability), while the
size of the gas bubbles 50 can be decreased by decreasing the
contact angle between the hardenable fluid 30 and the surface of
the mold 10 (increasing the wettability).
[0142] In some cases, the contact angle can be changed by treating
the molding surface of mold 10. For example, in some cases, the
molding surface can be treated using, for example, a plasma
treatment, a vapor treatment, a liquid treatment, or in any other
treatment that can change the contact angle. For example, the
molding surface can be treated in a plasma that includes fluorine
or a fluorine-based material. As another example, the molding
surface can be treated with a solution of Novec (registered
trademark) EGC-1720 electronic coating solution available from 3M
(St. Paul, Minn.). EGC-1720 is a clear, low viscosity solution of a
fluorosilane polymer and can, in some cases, increase the contact
angle.
[0143] In the processes shown in FIGS. 1B and 1C, the size of the
entrapped gas bubbles 50 can be controlled by adjusting the time
from coating of the hardenable fluid 30 to hardening thereof.
Specifically, the size of the gas bubbles 50 can be increased by
shortening the time from coating of the hardenable fluid 30 to
hardening thereof, while the size of the gas bubbles 50 can be
decreased by lengthening the time from coating of the hardenable
fluid 30 to hardening thereof.
[0144] In the processes shown in FIGS. 1B and 1C, the size of the
entrapped gas bubbles 50 also can be controlled by adjusting the
temperature of the gas bubbles after coating the hardenable fluid
30 but before or during hardening of the hardenable fluid 30.
Specifically, the size of the gas bubbles 50 can be increased by
raising the temperature of the gas bubbles 50, while the size of
the bubbles 50 can be decreased by lowering the temperature of the
gas bubbles 50. The adjustment of the temperature of the gas
bubbles 50 is one of control methods that can change the size of
the bubbles 50 after the gas bubbles 50 are entrapped.
[0145] The size of the trapped gas bubbles 50 can be controlled by
adjusting the pressure applied to the gas bubbles 50 after coating
the hardenable fluid 30 but before or during hardening of the
hardenable fluid 30. Specifically, the size of the gas bubbles 50
can be increased by increasing the pressure applied to the gas
bubbles 50, while the size of the gas bubbles 50 can be decreased
by decreasing the pressure applied to the gas bubbles 50. The
adjustment of the pressure of the gas bubbles 50 another control
methods that can change the size of the bubbles 50 after the
bubbles 50 are trapped.
[0146] The positions of the gas bubbles 50 may be controlled, for
example, by adjusting the interfacial tension between the liquid
resin and the molding surface of the mold 10. The positions can
also be controlled by adjusting the viscosity of the liquid resin
and the length of time from coating of the hardenable fluid to
hardening thereof.
[0147] In the process shown in FIG. 1B, the gas bubbles 50 should
remain at the positions where the gas bubbles 50 contact the
surfaces 12 and 13 of the depressions 11 until the liquid resin is
hardened after the entrapment of the gas bubbles 50. As shown in
FIG. 4, whether the gas bubbles 50 remain or not in contact with
the mold surface in a depression can be influenced by the
interfacial tension f1 between the hardenable fluid 30 and the mold
surface 12 of the mold 10, the interfacial tension f2 between the
hardenable fluid 30 and the gas bubbles 50, and the interfacial
tension f3 between the gas bubbles 50 and the mold surface 12 of
the mold 10. The position of the gas bubbles within the depression
can also be influenced by gravity and buoyancy.
[0148] Among those process variables, the positions and shapes of
gas bubbles 50 can be controlled especially by adjusting the
interfacial tension f1 between the hardenable fluid and the mold
surface 12 of the mold 10. Even if the contact angle between the
hardenable fluid 30 and the mold is relatively high, the gas
bubbles 50 can remain in the depression 11 if the viscosity of the
hardenable fluid 30 is sufficiently high. Likewise, even if the
contact angle between the hardenable fluid 30 and the mold is
relatively high, when the hardenable fluid 30 is hardened rapidly
(e.g., a UV curable resin can be irradiated with high intensity UV
radiation very soon after coating), the gas bubbles 50 can remain
in position long enough to function as part of the molding surface
and can impart their shape to the resulting hardened layer.
[0149] Any other means known in the art for controlling the shape
of the gas bubbles can be used. For example, means such as gravity,
electromagnetism, or vibration (including ultrasonic vibration) can
be used to control the shape of the gas bubbles.
[0150] In another aspect, a method is provided for preparing a
second article having at least one convexity from the article
having at least one concavity. The article having at least one
concavity is used as a mold (second mold) to form the second
article. FIGS. 1E to 1G illustrate one embodiment of a
manufacturing method for the second article. In this embodiment, an
article 31 manufactured as shown in FIG. 1A to 1D can be used as
the second mold. A second hardenable fluid 60 is applied to the
second mold 31 and hardened to form a second article 61 having a
plurality of convex surfaces 62. FIGS. 1E to 1G are schematic
sectional views illustrating the individual manufacturing processes
to manufacture the second article 61 having a plurality of convex
surfaces 62.
[0151] Like the manufacturing process shown schematically in FIGS.
1A to 1D, the manufacturing processes shown in FIG. 1E to 1G can
also carried out in air. In FIG. 1E, a second mold 31 having a
plurality of concave surfaces 32 is provided. In FIG. 1F, a second
hardenable fluid 60 is applied to the second mold 31. The second
hardenable fluid 60 is hardened to a second hardened layer 61. In
FIG. 1G, the second hardened layer 61 is removed from the second
mold 31 to obtain a second article having a plurality of convex
surfaces 62. The shape of the convexities 62 correspond to the
shape of the gas bubbles 50 used to impart the concavities to the
second mold 31.
[0152] In FIG. 1E, the second mold (first article) 31 is provided
that can be manufactured using the processes schematically
illustrated in FIGS. 1A to 1D. In some embodiments, second mold 31
is prepared from a hardenable fluid 30 that is selected, for
example, from a UV curable resin, soluble resin, thermoplastic
resin, thermoset resin, or the like. Any of the hardenable fluids
described above can be hardened to from the second mold 31.
[0153] In FIG. 1F, a second hardenable fluid 60 is applied to the
second mold 31. Although any suitable application method can be
used, the hardenable fluid 60 is often applied to the second mold
31 using a coating process. In contrast to the process
schematically illustrated in FIG. 1B, however, gas bubbles are
typically not deliberately entrapped during the process shown in
FIG. 1F. Methods that may be difficult to use in the process of
FIG. 1B can be used in the process of FIG. 1F. For example,
processes such as injection, heat pressing, or electroforming can
be used for applying the second hardenable fluid 60 to the second
mold 31.
[0154] The second hardenable fluid 60 can be any material that is
described above for use as the hardenable fluid 30. In some
examples, the second hardenable fluid 60 can be selected to be a UV
curable resin or a soluble resin. When the second mold 31 has
sufficient heat resistance, a thermoplastic resin or a thermoset
resin can also be used for the second hardenable fluid 60. The
second hardenable fluid 60 can contain an additive such as, for
example, a thickener, a curing agent, a crosslinking agent, an
initiator, an oxidant inhibitor, an antistatic agent, a diluent, a
detergent, a pigment, or a dye.
[0155] In some applications such as those where the at least one
convexity will be used as a lens, the second hardenable fluid 60 is
a polymeric resin that will result in the formation of a hardened
layer that has good optical properties. For example, the polymeric
resin can be a polymeric resin that includes polycarbonate, acrylic
resin, polyester, epoxy resin, polyurethane, polyamide, polyolefin,
or silicone (including modified silicone such as silicone polyurea,
or similar material.
[0156] The hardenable fluid 60 is often applied to the second mold
31 using a coating method although other suitable application
methods can be used. Suitable coating devices include, but are not
limited to, a knife coater, a bar coater, a blade coater, and a
roll coater. If the coating method is used, a deaeration process
can be added before or after coating the second hardenable fluid 60
to remove any bubbles or air that might cause defects in the second
article. Suitable deaeration processes often include an evacuation
step. The deaeration process can often remove bubbles or air in the
second hardenable fluid 60 or positioned between the second
hardenable fluid 60 and the second mold 31.
[0157] The second hardenable fluid 60 is hardened to form the
second hardened layer 61. When the second hardenable fluid is a UV
curable resin, the second hardened layer 61 can be formed by
irradiating with ultraviolet rays. When the second hardenable fluid
60 is a solution of a soluble resin, the second hardened layer 61
can be formed by removing the solvent such as by drying. When the
second hardenable fluid 60 is a thermoplastic resin, the second
hardened layer 61 can be formed by cooling the resin down to at
least a softening temperature. When the second hardenable fluid 60
is a thermoset resin, the second hardened layer 61 can be formed by
heating the resin to at least a hardening temperature.
[0158] Through the process shown in FIG. 1F, the second hardened
layer 61 having a plurality of convex surfaces 62 can be formed.
The convex surfaces 62 are the inversion of the outer shapes of the
concave surfaces 32 of the second mold 31. Specifically, the convex
surfaces 62 formed on the second hardened layer 61 can be
substantially spherical convex surfaces that are similar to the
outer shapes of the gas bubbles 50 used to impart the concavities
to the second mold 31. Thus, a second article having at least one
substantially spherical convex surfaces such as an arranged pattern
of substantially spherical convex surfaces can be prepared.
[0159] In some embodiments of the article 61, a first surface of
the article has multiple convexities and a second surface opposite
the first surface is flat. The flat surface can have a matte or
glossy finish. The surface roughness of either surface can be, for
example, less than 100 nanometers, less than 50 nanometers, less
than 10 nanometers, or less than 5 nanometers.
[0160] In the process shown in FIG. 1G, a second article 61 having
a plurality of convex surfaces 62 can be obtained by removing the
hardened layer 61 formed in the process shown in FIG. 1F from the
second mold 31. It is also possible to coat another resin material
or the like on the convex surfaces 62 of the manufactured second
article 61.
[0161] The second article can be prepared using a continuous
manufacturing process. By repeatedly providing additional second
molds 31 to a coating device, the second hardenable fluid 60 can be
repeatedly applied to each additional second mold 31. Each
additional hardenable fluid 60 can be hardened to form second
articles 61 having at least one convexity. By repeating the
processes shown in FIG. 1A to 1D and the processes shown in FIG. 1E
to 1G, articles 31 each having a plurality of concave surfaces 32
and second articles 61 each having a plurality of convex surfaces
62 can be manufactured continuously.
[0162] Similar processes to those shown in FIGS. 1A to 1G can be
used to provide articles having at least one convexity on a first
surface as well as on a second surface opposite the first surface.
In one such process, the second article can be prepared that has at
least one convexity. A third article can then be prepared by
contacting the second article with a hardenable fluid layer. For
example, the finished second article can be laminated to the
hardenable fluid layer 60 shown in FIG. 1F. That is, a hardenable
fluid layer 60 can be positioned between a finished second article
and the second mold. When the hardenable fluid layer 60 is
hardened, the second article would adhere and the resulting third
article can have convexities on two opposite surfaces. The second
mold could then be removed to provide the third article. In another
process, two finished second articles can be laminated using a
hardened fluid layer 60 positioned between the two second articles.
The hardened fluid layer would face a flat surface of the two
second articles.
[0163] Alternatively, a hardenable fluid layer can be positioned
between two second molds 31. The hardenable fluid layer would face
a flat surface of the two second molds. Upon hardening of the
hardenable fluid layer, the resulting third article would have
concavities on two opposite surfaces.
[0164] An adhesive layer can be positioned between a first article
and a second article, between a first article and another first
article, or between a second article and another second article to
provide articles having concavities or convexities on multiple
surfaces. In these embodiments, the adhesive layer would face a
flat surface of the first article and a flat surface of the second
article.
[0165] Regarding the process shown in FIG. 1F and FIG. 1G, other
conventional molding process can be used. For example, molding
process described in U.S. Pat. No. 6,761,607 or U.S. Pat. No.
6,758,992 can be used.
[0166] FIG. 3B shows a process similar to the process shown in FIG.
1G. FIG. 3B illustrates an exemplary process that can be used to
obtain a second article 61 having convex surfaces 62 by removing a
second hardened layer 61 from the second mold 31 that has
concavities 32 with a sharper edged overhang portion 32a in
comparison to the corresponding concavities shown in FIG. 1G. If
both the second mold 31 and the second hardened layer 61 are both
hard in the process exemplified in FIG. 3B, it can be difficult to
separate the second mold 31 without damaging the hardened layer
61.
[0167] A removal process that damages the hardened layer 61 is
depicted as case 1 in the sectional views of FIGS. 6A and 6B. The
second mold in FIG. 6A is made of a material that is not readily
soluble in water or an organic solvent. When the hardened layer 61
is removed from the second mold 31, the hardened layer 61
interferes with the overhang portion 32a of the second mold 31. If
the hardened layer 61 and the second mold 31 are both are hard and
not flexible, damage is likely. FIG. 6B illustrates that the
hardened layer 61 and the second mold 31 can both be damaged. The
overhang portion 32b is broken off of the second mold 31.
[0168] One method of removing the hardened layer 61 from the second
mold 31 without damaging the hardened layer 61 is depicted as case
2 in the sectional views of FIGS. 6C and 6D for case 2. In FIG. 6C,
the second mold is formed of a soluble material such as
water-soluble resin. In FIG. 6D, the second mold is removed by
dissolution. Since the second mold 31 is dissolved by water, the
hardened coating layer 61 is removed undamaged from the second mold
31. Although the second mold 31 in FIG. 6C is a water-soluble
resin, a similar process can be used with any other mold materials
that can be dissolved with another type of solvent such as an
organic solvent or a solution containing an acid or base.
[0169] In other examples, the second mold 31 can be readily
separated from the hardened layer 61 when a thermoset resin is used
for the hardened layer 61 and a thermoplastic resin is used for the
second mold 31. The second mold can be heated to at least the
softening temperature to remove it readily from the hardened layer
61 without damaging the hardened layer 61.
[0170] The manufactured second article 61 is an article having at
least one convex surface 62. Some second articles have an arranged
pattern of convexities such as a lattice pattern. The convex
surfaces 62 are often substantially spherical convex surfaces that
correspond to the outer surfaces of the gas bubbles 50 used to form
the concavities in the second mold 31. The size of the convex
surface 62, as measured by the cross-sectional area of the base, is
often in the range of 0.01 .mu.m.sup.2 to 1000 mm.sup.2. The height
of the convex surface 62 often ranges from 0.1 .mu.m to 100 mm.
Convexities outside this range can also be prepared and the size is
dependent on the particular use chosen for the articles.
[0171] In some second articles 61, there is a plurality of
convexities arranged in a pattern. Some arranged patterns are
arranged in lattice patterns such as an arranged square lattice
pattern. Additionally some of the articles have substantially
identical convex surfaces 62. When the convex surfaces 62 are
spherical and substantially transparent or translucent, they can be
used as lenses or an array of lenses. Some of the convexities 62
can be used as microlenses or microlens arrays.
[0172] Additionally, the second article 61 can have another layer
of material coated on the convex surfaces 62. In this case, if the
convex surfaces 62 are used as lenses, the coating layer can be
used as a protecting layer or can be used to adjust the refractive
index. A lens having a wide range of refractive indexes can be
obtained by coating materials having various refractive indexes as
the outermost layer of the lens.
[0173] When forming a second article 61 using a first article 31 as
a mold, the first article 31 need not be removed from the second
article 61. That is, the first article 31 can remain adjacent to
the second article 61; for example, the second article 61 can be
laminated to the first article 31. Another single coating layer or
multiple coating layers can be formed on the second article 61. In
this case, the first article 31 remaining on the second article 61
or any additional coating layer can be used as a protecting layer
for the second article 61, or as a layer for adjusting the optical
characteristics of the second article 61.
[0174] As shown in the FIG. 1G, the manufactured second article 61
can have a shape in which each convex surface 62 is surrounded by a
horizontal wall 63 because the second mold 31 has a shape in which
each concave surface 32 is surrounded by a groove-like portion 33.
Because the shape of the second article 61 is the inversion of the
article 31, the second article 61 has horizontal walls 63
corresponding to the groove-like portions 33 of the second mold 31.
See FIG. 8 schematically showing an exemplary three-dimensional
article 131 and FIG. 9 showing an exemplary three-dimensional
article 161. One way to handle the second article 61 having a shape
in which each convex surface 62 is surrounded by the horizontal
wall 63 is to positively utilize the horizontal walls 63 as optical
components such as prisms. Two exemplary such articles are shown in
FIGS. 18A and 18B. FIG. 18A is a schematic cross-section of an
article 1850 that includes a structured top surface and a planar or
flat bottom surface. The top structured surface includes a
plurality of convexities 1810 and a plurality of prisms 1820
pointing outward, meaning that the apex of each prism points away
from the bottom surface. In the exemplary article 1850, convexities
1810 and prisms 1820 alternate. In general, the prisms and the
convexities may or may form an alternate arrangement.
[0175] FIG. 18B is a schematic cross-section of an article 1860
that includes a structured top surface and a planar or flat bottom
surface. The top structured surface includes a plurality of
concavities 1830 and a plurality of prisms 1840 pointing inward,
meaning that the apex of each prism points toward the bottom
surface. In the exemplary article 1860, concavities 1810 and prisms
1820 alternate. In general, the prisms and the concavities may or
may form an alternate arrangement.
[0176] In FIGS. 18A and 18B, the top structured surface of articles
1850 and 1860 includes a lattice pattern of concavities 1830 or
convexities 1810 and a lattice pattern of prisms 1820 or prisms
1840. In some cases, concavities 1830 or convexities 1810 are or
include spherical or substantially spherical surfaces. In some
cases, concavities 1830 have the same shape and convexities 1810
have the same shape. In some cases, concavities 1830 have the same
size and convexities 1810 have the same size.
[0177] In some cases, such as when articles 1850 and 1860 are being
formed using, for example, process steps shown in FIGS. 1A through
1G, concavities 1830 or convexities 1810 are in direct contact with
gas bubbles, such as with gas bubbles 50.
[0178] In some cases, such as when the top structured surfaces of
articles 1850 and 1860 are molding surfaces, concavities 1830 or
convexities 1810 are in direct contact with a hardenable fluid
before the fluid is cured, such as layer 30 in FIG. 1B, or in
direct contact with a hardened fluid, such as layer 31 in FIG.
1C.
[0179] In some cases, articles 1850 and 1860 can be optical films
and can be used in a display system such as a liquid crystal based
display system. In such cases, optical films 1850 and 1860 can be
substantially optically transparent. For example, in such cases,
the total (specular and diffuse) optical transmission of optical
films 1850 and 1860 is at least 70%, or at least 80%, or at least
90%. In some cases, optical films 1850 and 1860 can be optical gain
diffusers in a liquid crystal based display system. In such cases,
concavities 1830, convexities 1810, prisms 1820, and prisms 1840
can diffuse and/or redirect the light resulting in increased
brightness along a preferred, such as axial, direction and/or
increased diffusion that can result in increased viewing angle
and/or improved light intensity uniformity.
[0180] In other embodiments, the second article 61 does not have
horizontal walls 63 between the convexities 62. The horizontal
walls 63 can be removed from the manufactured second article 61 by
a post-processing. If the horizontal walls 63 are formed but not
desired, they can be removed using any suitable mechanical,
physical, or chemical means. When the second article 61 having the
convex surfaces 62 is adapted to a lens member, for example, it is
possible to provide microlenses in which lens portions having
spherical surfaces are arranged on a sheet by removing the
horizontal wall 63 formed between the adjacent convex surfaces 62
of the second article 61. Additionally, the curvature can also be
altered by further processing the curved surface portions of the
convex surfaces 62. An article could be manufactured in which
partly-cutaway convex surfaces are formed by cutting off a given
portion of each of a plurality of convex surfaces 62.
[0181] Alternatively, the second article can be prepared using a
mold that does not result in the formation of the horizontal walls
63. More particularly, the groove-like portion can be eliminated
between adjacent concave surfaces of the second mold. One such
second mold 31 can be manufactured, for example, as illustrated
schematically in FIGS. 7A to 7D. The second article 161 having a
shape in which each convex surface 162 is not surrounded by a wall
is manufactured as shown in FIG. 7E to 7G. FIG. 11 shows a
three-dimensional example corresponding to the article 131'A and
FIG. 12 showing a three-dimensional corresponding to the second
mold 161.
[0182] The manufacturing processes shown in FIGS. 7A to 7D are
similar to the processes shown in FIGS. 1A to 1D; however, a two
piece mold is used rather than a one piece mold. The first piece of
the mold is a first layer having at least one opening such as a
pattern of openings. The second piece of the mold is laminate to
the first layer. The resulting two piece mold can have depressions
consisting of the opening of the first layer and a surface of the
second layer.
[0183] The two piece mold 110 of FIG. 7A has a side wall portion
110a corresponding to the first layer mentioned above and a bottom
portion 110b corresponding to the second layer mentioned above. The
first layer and the second layer are separable each other, and as a
result, as shown in FIG. 7D, the side wall portion 110a can be
removed from the bottom portion 110b along with hardened layer
131.
[0184] The two piece mold 110 can be prepared from any materials
described above for the mold 10. For example, an organic resin
material such as polyimide, polypropyrene, polyethylene,
polystyrene or poly-cyclo-olefin can be used. Alternatively, other
organic materials, inorganic materials including a metal such as
nickel, copper, or brass, glass or ceramics, or organic-inorganic
composite material can be used. Preferably, a material chosen for
the side wall portion 110a (first layer) is different from a
material chosen for the bottom portion 110b (second layer). For
example, an organic resin material can be used for the side wall
portion 110a, and an inorganic material such as metal, glass or
ceramic can be used for the bottom portion 110b.
[0185] The two piece mold can be made by the following process.
First, a layered sheet having a first layer and a second layer
laminated on the first layer can be prepared. Then openings can be
formed in the first layer using any suitable method. In some
methods of forming the opening, a dry etching method such as laser
ablation or a wet etching method using a mask can be used. If the
first layer material is different from the second layer material,
the opening patterns can be formed only in the first layer.
[0186] Suitable layered sheets are commercially available but can
also be manufactured by the following process. The first layer can
be prepared and then the second layer can be provided to contact
the first layer. The second layer can be formed on the first layer
using any method including, for example, coating, deposition,
electroforming or the like. For example, a polymeric resin sheet
can prepared as the first layer. Then second layer can be formed on
the first layer by chemical deposition, physical deposition, or
electroforming a metal.
[0187] In the process shown in FIG. 7D, the hardened layer 131,
which is formed by the process shown in FIG. 7C, and the side wall
portion 110a are removed from the bottom portion 110b of the mold
110. Upon removal from the bottom portion 110b of the mold, the
hardened layer 131 and the side wall portion 110a are connected
together to obtain an article 131'. The article 131' is configured
so that each concave surface 132 is surrounded by the side wall
portion 110a. In other words, any grove-like portion does not exist
between adjacent concave surfaces 132.
[0188] The removing process shown in FIG. 7D can be performed by
selective etching of the bottom portion 110b of the mold 110. For
example, if the bottom portion 110b is made of metal such as copper
or nickel and the side wall portions 110a are made of polymeric
resin such as polyimide, the bottom portion 110b can be removed by
such a selective etching. For example, the metal can be dissolved
with an acidic solution.
[0189] Manufacturing processes shown in FIGS. 7E to 7G are similar
to the processes shown in FIGS. 1E to 1G. However, a second article
161 is manufactured using the second mold 131' having a shape in
which any grove-like portion does not exist between adjacent
concave surfaces 132. As a result, as shown in FIG. 7G, a second
article 161 having a shape in which each convex surface 162 is not
surrounded by a horizontal wall is manufactured. In the other
points, the processes shown in FIG. 7E to 7G are similar to the
processes shown in FIG. 1E to 1G.
[0190] The second article 161 in which each convex surface 162 is
not surrounded by a horizontal wall can be obtained by using the
second mold 131' in which a groove like portion does not exist
between adjacent concave surfaces 132. When the second article 161
having the convex surfaces 162 not surrounded by horizontal walls
is adapted to a lens member, for example, the second article has a
construction without a prism or rib portion. Such an article is
well suited for a lens such as a microlens because there is no
horizontal wall between adjacent convex surfaces 162 (equivalent to
lens portion) of the second article 161. See FIG. 13 for a
three-dimensional representation of the second mold 131'B and FIG.
14 for a three-dimensional representation of the second article
161B.
[0191] In addition to the use of the first article or the second
article as a lens or as an array of lenses, the first article or
the second article can be used as a mold. For example, the first
article or the second article can be used to prepare a metal
stamper. In one exemplary process, the first metal layer such as
chromium or copper can be deposited on a surface of the first
article or on a surface of the second article. Then, a second metal
layer such as a nickel metal layer can be deposited on the first
metal layer. The second metal layer can then be removed resulting
in a second metal stamper such as a nickel metal stamper that has
the same shape as the first article or the second article.
[0192] The embodiments of the method of making a first article that
has a surface comprising at least one concavity or an arranged
pattern of concavities, the method of making a second article using
the first article as a second mold, the first article, and the
second article are not limited to those described above, and
various other embodiments are within the scope of the
invention.
EXAMPLES
[0193] These examples are for illustrative purposes and are not
meant to be limiting on the scope of the appended claims. Examples
of the first and second articles were manufactured and tested.
These examples are described referring to the accompanying
drawings.
Examples 1-1 to 1-9
[0194] The influence of the interfacial tension between the
hardenable fluid and a mold surface were investigated. Nine kinds
of test plates with flat surfaces were prepared and the contact
angles of the hardenable fluid (e.g., liquid resin) on the flat
surfaces of the test plates were measured. Further, test articles
were manufactured using nine kinds of test molds that were made of
the same materials of the test molds respectively according to the
manufacturing process shown in FIG. 1A to FIG. 1D.
Liquid Resin: A UV curable resin was used as the hardenable fluid.
The composition of the UV curable resin contained 90 parts by
weight (pbw) of a UV hardenable acrylate, which was a polyester
base urethane acrylate (commercially available under the trade
designation EBECRYL 8402 from DAICEL-CYTEC Co., Ltd.), 10 pbw of an
unsaturated aliphatic acid hydroxylalkylester modifier
.epsilon.-carprolactone (commercially available under the trade
designation PLACEL FA2D from Daicel Chemical Industries, Ltd.), and
1 pbw of a photopolymerization initiator (commercially available
under the trade designation IRGACURE 2959 from Ciba Specialty
Chemicals Inc.). Test Plates: Each of the nine test plates had a
flat surface. Materials used for the test plates are described
below.
[0195] Test Molds: All test molds had depressions in the shape of a
quadrangular pyramid having a depth of 50 .mu.m, an apex angle of
90 degree, and a square bottom shape. Each side of the square
bottom was 100 .mu.m. The depressions were arranged in a square
lattice pattern with pitches of 100 .mu.m. Materials used for the
test molds are described below.
Materials for the Test Plates and the Test Molds:
[0196] Test Plate 1 and Test Mold 1 were prepared from a two
component room temperature vulcanizable (RTV) silicon rubber, which
is commercially available under the trade designation ELASTOSIL RT
601 from Wacker Asahikasei Silicone Co., Ltd.
[0197] Test Plate 2 and Test Mold 2 were prepared from a two
component RTV silicon rubber, which is commercially available under
the trade designation ELASTOSIL M4470 from Wacker Asahikasei
Silicone Co., Ltd.
[0198] Test Plate 3 and Test Mold 3 were prepared from
polypropylene, which is commercially available under the trade
designation NOVATEC MA-3 from Japan Polypropylene Co., Ltd.
[0199] Test Plate 4 and Test Mold 4 were prepared from polystyrene,
which is commercially available under the trade designation GPPS
G9401 from Japan Polystyrene Inc.
[0200] Test Plate 5 and Test Mold 5 were prepared from
polyethylene, which is commercially available under the trade
designation HY-430 from Japan Polyethylene Co., Ltd.
[0201] Test Plate 6 and Test Mold 6 were prepared from
polycarbonate, which is commercially available under the trade
designation IUPILON H-3000R from Mitsubishi Engineering-Plastics
Co., Ltd.
[0202] Test Plate 7 and Test Mold 7 were prepared from
polypropylene, which is commercially available under the trade
designation POLYPRO3445 from Exxon Mobil Co.
[0203] Test Plate 8 and Test Mold 8 were prepared from
polymethylmethacrylate, which is commercially available under the
trade designation LG35 from Sumitomo Chemical Co., Ltd.
[0204] Test Plate 9 and Test Mold 9 were prepared from nickel plate
that was manufactured using electroforming.
[0205] The hardenable fluid, which was the UV curable resin, was
coated on a surface of each test mold using a knife coater to form
a coated layer. The coating device was a knife coater with a 150 mm
width. A PET film was positioned over the UV curable resin such
that the UV curable resin was between the test plate and the PET
film. The coating thickness of the UV curable resin was 150 .mu.m.
The coated layer was cured after coating using ultraviolet
radiation of 3450 mJ/cm.sup.2 from a UV lamp obtained from Ushio,
Inc. The hardened resin was then removed from the test mold.
TABLE-US-00001 TABLE 1 Contact Angle [degree] of Liquid Article
made Resin on Test Plate using Test Test Plate No. and (Average of
10 Mold shown Example Test Mold No. samples) in FIG. 5 1-1 1 63.4 A
1-2 2 60.9 A 1-3 3 59.5 B 1-4 4 41 C 1-5 5 57.3 C 1-6 6 34.5 C 1-7
7 64 B 1-8 8 33.4 C 1-9 9 38.2 C
[0206] Under the above test conditions, the contact angle between
the UV resin and the mold was changed by changing the material of
the test plate. The relationship between the contact angle (between
the UV resin and the test plate) and the position and shape of the
gas bubble 50 entrapped in the test mold depressions were studied.
Table 1 shows the average values of the measured values of the
contact angle between the liquid resin (UV curable resin) and the
test plates. The average values of ten measurements are given in
Table 1.
[0207] The static contact angles were measured using an instrument
commercially available under the trade designation DROPMASTER 700
from Kyowa Interface Co., Ltd., and the static contact angle was
measured by the sessile drop method at room temperature.
[0208] FIG. 5 is a diagram exemplifying the relationship between
the contact angle and the position and the shape of the gas bubbles
within the mold depressions. More particularly, FIG. 5 shows three
representative types A to C of the concavities made by the
manufacturing process using the test molds. In FIG. 5, a
perspective view (left), a side sectional view (center), and a
plane view (right) of the articles manufactured.
[0209] Articles made using Test Molds 1 and 2, corresponding to a
contact angle greater than 60 degree, were Type A where the gas
bubbles do not stay in the depressions. That is, no gas bubbles
remained in the depressions. Articles made using Test Molds 3 and 7
were Type B. The gas bubbles remained at the top portions of the
quadrangular pyramid depressions and the curvature of the convex
surfaces of the gas bubbles were relatively small (the diameters
were relatively large). The outer shape of the gas bubbles was
approximately spherical as seen from the top or bottom side of the
quadrangular pyramid. Articles made using Test molds 4-6, 8 and 9,
were Type C. The gas bubbles remained at the top portions of the
quadrangular pyramid depressions and the curvature of the convex
surfaces of the gas bubbles were larger than for Type B (the
diameter is smaller than for Type B). The outer shape of the gas
bubbles became nearly a four-leaved shape as seen from the top or
bottom side of the quadrangular pyramid.
[0210] According the test result, the positions and shapes of the
gas bubbles could be at least partially controlled by adjusting the
interfacial tension (contact angle) between the UV resin and the
mold surface. Various other variables such as the viscosity of the
UV resin and the time from coating to hardening of the UV resin can
also affect the position and shape of the gas bubbles. For example,
even if the contact angle between the UV resin and the mold exceeds
60 degrees, gas bubbles can remain in the depressions if the
viscosity of the UV resin is sufficiently high. Likewise, even if
the contact angle between the liquid resin and the mold exceeds 60
degrees, when the UV resin is hardened by high-intensity
ultraviolet irradiation in a short period of time after coating,
the gas bubbles can remain for a time sufficient for the UV resin
to harden.
Example 1-10
[0211] In this example, the mold material was cyclic olefin
copolymer (COC) 8007F-04 obtained from Polyplastics Co. (Frankfurt,
Germany). The mold (COC-1) was treated with EGC-1720 and dried in
an oven at 60 degrees for 30 minutes. The dried mold COC-1 was kept
at room temperature overnight for being used. For comparison
purposes, a similarly prepared but untreated mold (COC-2) was also
used. The COC-1 and COC-2 molds had the same shape similar to the
shape of the molds used in examples 1-1 through 1-9. In particular,
each mold had depressions in the shape of a quadrangular pyramid
having a depth of 50 .mu.m, an apex angle of 90 degree, and a
square shaped bottom. Each side of the square bottom was 100 .mu.m.
The depressions were arranged in a two-dimensional lattice pattern
with a pitch of 100 .mu.m along the rows and the columns.
[0212] Using the DROPMASTER 700 instrument, the measured static
contact angle of deionized water on COC-1 and COC-2 were 105 and
87.2 degrees, respectively. Next, each mold was coated with the UV
resin using a coating knife with a coating gap of 150 microns at a
coating speed of 16 cm/sec. The UV resin coatings were subsequently
cured using UV radiation at 3450 mJ/cm2. After curing, the cured
samples were removed from the molds resulting in samples COC-A and
COC-B corresponding to molds COC-1 and COC-2, respectively. FIGS.
15A and 15B are scanning electron micrographs of samples COC-A and
COC-B, respectively. The convexities in sample COC-A have a larger
radius of curvature than those in sample COC-B.
Example 2-1
[0213] In Example 2-1, a polypropylene mold was prepared.
Initially, depressions were made on a surface of the copper plate
using a cutting machine. Then a surface of the copper plate was
oxidized by dipping the copper plate in an oxidizing agent. A
nickel layer was formed on the oxidized surface of the copper plate
by electroplating. After electroplating, the nickel layer was
removed from the copper plate. Polypropylene, which is commercially
available under the trade designation POLYPRO3445 from Exxon Mobil
Co., was melted into the nickel mold at 200 to 250.degree. C. and
then was cooled down to room temperature (20 to 25.degree. C.). The
hardened polypropylene mold was removed from the nickel mold. The
resulting mold (sheet) had a square lattice pattern of depressions.
The depressions were quadrangular pyramid concavities that had a
depth of 50 .mu.m, an apex angle of 90 degrees, and a square bottom
shape. Each side of the square bottom was 100 .mu.m and the
pyramids were arranged at pitches of 100 .mu.m. The shape of the
quadrangular pyramid depressions is exemplified in a planar view in
FIG. 2A.
[0214] The polypropylene mold (sheet) was cut to make a piece (8 cm
in width and 10 cm in length) that was adhered onto a polyethylene
terephthalate (PET) film having a thickness of 50 .mu.m (15 cm in
width and 30 cm in length) to make a sheet mold. The PET film is
commercially available under the trade designation "TEIJIN TETRON
FILM A31 from Teijin Dupon Films Japan Limited. The polypropylene
mold (sheet) was adhered to the PET film using double-faced
adhesive tape that is commercially available from 3M under the
trade designation 3M SCOTCH TAPE.
[0215] Another PET film having a thickness of several ten .mu.m (15
cm in width and 30 cm in length) was prepared as a transparent
cover sheet. The PET film was the same as described above.
[0216] Around 10 cc of the UV curable resin was dropped on a
surface of the sheet mold, wherein the UV curable resin was
provided along one side of the area having the depressions. The UV
curable resin used in this example is the same as the UV Resin used
in Example 1 and the viscosity thereof was about 10,000 mPas
(measured by B-type viscometer).
[0217] One side of the cover sheet was laid on the sheet mold,
however, the rest of the cover sheet was kept apart from the sheet
mold. Next, the one side of the set of the sheet mold and the cover
sheet ("set of the sheets") was placed on a knife coater having a
knife edge that is 150 mm wide. The set of sheets was then moved
under the knife edge at the speed of 16 cm/sec ("coating speed")
and the UV curable resin was spread between the sheets at the
thickness of 200 .mu.m and coated over the depressions of the sheet
mold while air around the mold was entrapped at each depressions.
The coating process was carried out in the air at room temperature
(about 20-25 degree C.).
[0218] Then, a ultraviolet light (Ushio Inc.) was used to irradiate
the UV curable resin on the mold sheet through the transparent PET
cover sheet with ultraviolet rays of 3450 mJ/cm.sup.2. The radiant
intensity was measured at the surface of the UV resin layer using
an ultraviolet light meter (UV-350 from ORC Manufacturing Co.,
Ltd.). The UV curable resin polymerized and formed a hardened
layer. After polymerization, the transparent PET cover sheet was
taken off the mold sheet. The hardened layer was removed from the
polypropylene mold by hand. In this manner, an article having
concave surfaces (an article having an arranged lattice pattern of
concavities) was obtained from the UV curable resin.
Example 2-2
[0219] The hardenable fluid contained 20 weight percent polyvinyl
alcohol as a water-soluble resin (commercially available under the
trade designation KURARY POVAL PVA-217 from Kurary Co., Ltd.) and
80 weight percent distilled water. That is, the hardenable fluid
contained 20 weight percent PVA-217 in an aqueous mixture. Using
the article having concave surfaces manufactured in Example 2-1 as
the second mold, the hardenable fluid was dropped onto the second
mold to cover the concavities and then a deaeration process was
used to prevent the formation of bubble defects. The atmospheric
pressure was reduced to less than 1000 Pa for 15 minutes. After
deaeration, the hardenable fluid was spread and set at a thickness
of 200 micrometer using the knife coater. Then, the hardened layer
was obtained by drying the coating layer for two hours in an oven
at 60 degree C. and was then overnight at room temperature. After
drying, the hardened layer was removed from the second mold. The
resulting article made of a polyvinyl alcohol resin had convex
surfaces (the article had an arranged lattice pattern of
convexities).
Example 2-3
[0220] Using a manufacturing method similar to that used in Example
2-1, articles having concave surfaces were obtained by varying the
time from coating of the UV curable resin to hardening thereof. The
start time of hardening, which is the length of time between
coating and hardening, was 0 minute, 30 minutes, or 60 minutes.
During any time between coating and hardening, the samples were
stored under ambient light.
[0221] The resulting articles having concave surfaces were imaged
using a scanning electron microscope (SEM) (VE-7800, Keyence Co.,
Ltd); the image obtained is hereinafter called a "SEM image". In
the SEM image of the concave surface portions observed
substantially vertically above, the maximum diameters of the
concave surface portions were measured at five positions. The
average value of the measurements was determined to be the average
diameter of the concave surfaces.
[0222] The following Table 2 shows the relationship between the
time from coating to hardening and the average diameter of the
concave surfaces for this example.
TABLE-US-00002 TABLE 2 Time from UV Drying coating to curable
temperature, Concentration, Viscosity, hardening, Ave. diameter,
resin .degree. C. weight percent mPa-sec min. micrometers PVA-217
60 20 60000 0 78.7 30 78.4 60 78.0
Example 2-4
[0223] An article was prepared as described in Example 2-1 except
that the mold was varied. More particularly, a nickel mold was used
and the shape of the depressions provided in the mold was changed
to a square cylinder from a quadrangular pyramid. The square
cylinders each had a square bottom shape with each side of the
square being 115 .mu.m. The depressions were arranged in a square
lattice pattern at pitches of 140 .mu.m. This nickel mold was
prepared from a copper plate. Depressions were made on a surface of
the copper plate using a cutting machine. Then a surface of the
copper plate was oxidized by dipping the copper plate in an
oxidizing agent. Then, a nickel layer was formed on the oxidized
surface of the copper plate by electroplating. After
electroplating, the nickel layer was removed from the copper
plate.
[0224] FIG. 8 shows a perspective view of the article 31A obtained
that had concave surfaces 32A. The article 31A had an arranged
pattern of concavities. Each concave surface has a substantially
the same shape, and was surrounded by a groove-like portion.
[0225] An article having convex surfaces was obtained using the
obtained article 31A having concave surfaces as the second mold
under the same conditions as those of Example 2-2. FIG. 9 shows a
perspective view of the obtained article 61A having convex surfaces
62A (article having an arranged pattern of convexities). Each
convex surface has a substantially the same shape, and is
surrounded by a wall 63A.
[0226] Article 61A in FIG. 9 includes a plurality of convexities
62A. Each convexity 62A is surrounded by walls 63A. Convexities 62A
are arranged at predetermined positions and form a lattice pattern.
In some cases, walls 63A can have prism portions positioned, for
example, on top of the walls, resulting in an article similar to
article 1850 shown in FIG. 18A. In some cases, such as when article
61A is made using the process steps shown in FIG. 1C, article 61A
can be or include a hardened fluid.
[0227] In the exemplary article 61A, the curved portions are
convexities surrounded by walls. In some cases, an article, such as
article 31 in FIG. 1D or article 1860 in FIG. 18B, can include a
plurality of concavities where each concavity is surrounded by
grooves, such as grooves 33 in FIG. 1D or grooves 1840 in FIG. 18B.
In some cases, such as in the case of article 1860, the concavities
are arranged at predetermined positions and form a lattice pattern.
In some cases, such as in the case of article 1860, the concavities
are surrounded by grooves that are or include prism portions. In
some cases, such as when article 1860 is made using the process
steps outlined in FIG. 1A-1G, the article 1860 can be or include a
hardened fluid.
Example 2-5
[0228] An article having concave surfaces was prepared using a
process similar to that used to prepare Example 2-1 except with a
different mold. The depressions in the mold were changed to a
quadrangular prismoid from a quadrangular pyramid. The material of
mold was a silicone resin sheet made of ELASTSIL M4470 from Wacker
Asahikasei Silicone Co., Ltd. The quadrangular prismoid depressions
each had a square bottom shape with each side of the square bottom
being 25 .mu.m and a square top shape with each side of the square
top being 50 .mu.m. The depressions were arranged in a square
lattice pattern with pitches of 50 .mu.m. An article having concave
surfaces (an article having an arranged lattice pattern of
concavities) was manufactured.
[0229] This article was then used as a secondary mold under
conditions similar to those used in Example 2-2 except that the
second hardenable resin was different. For this example, a 15
weight percent polyvinyl alcohol as a water-soluble resin (KURARY
POVAL.TM. PVA-205, Kurary Co., Ltd.) and 85 weight percent
distilled water were mixed. This 15 weight percent PVA-205 aqueous
mixture was coated on the second mold. An article made of a
polyvinyl alcohol resin having convex surfaces (an article having
an arranged pattern of convexities) was prepared.
Comparative Example 1
[0230] An article was obtained by performing processes similar to
those of Example 2-1 except that after coating of the UV curable
resin, the UV curable resin was left under vacuum for 15 minutes to
remove gas bubbles entrapped at the time of coating. The outer
shapes of gas bubbles were not imparted to the resulting article.
Rather, the shape of the mold surface (including the depressions)
was imparted to the article.
Example 3-1
[0231] The hardenable fluid contained 20 weight percent polyvinyl
alcohol, which is commercially available under the trade
designation KURARY POVAL PVA-205 from Kurary Co., Ltd., and 80
weight percent distilled water. This hardenable fluid was a
water-soluble resin. A polypropylene sheet, identical to the sheet
used in Example 2-1, was used as the mold.
[0232] The coating process was performed as described in Example
2-1 except for the liquid resin. More specifically, the
water-soluble resin was coated on the mold using a knife coater,
thereby forming a coating layer with a thickness of 200 .mu.m. The
coating speed was 16 cm/sec and air was entrapped around the
mold.
[0233] The coating layer was subsequently dried for two hours in
the oven at 60 degree C. The coating layer was further dried at
room temperature overnight to form a hardened layer. The hardened
layer was removed from the polypropylene mold, thus obtaining an
article having concave surfaces made of a water-soluble resin (the
article had an arranged pattern of concavities). The curvature of
the concave surfaces was smaller than those of Example 2-1.
Example 3-2
[0234] Using the article having concave surfaces manufacture in
Example 3-1 as the second mold, a UV curable resin identical to
that used in Example 2-1 was coated on the second mold with a
thickness of 200 .mu.m. The UV curable resin layer was placed in
contact with a 50 .mu.m PET film. A deaeration process was
performed by reducing the atmosphere pressure in the same manner as
Example 2-2. Then, a hardened layer was formed by irradiating the
UV curable resin from the PET film side with ultraviolet rays of
3450 mJ/cm.sup.2 using the same ultraviolet lamp used in Example
2-1. After polymerization, the hardened layer was removed from the
second mold to obtain an article made of a UV curable resin having
convex surfaces (the article had an arranged pattern of
convexities).
Example 3-3
[0235] Articles were prepared using a process similar to that
described in Example 3-1 but with different concentrations of
polyvinyl alcohol in the hardenable fluid. The polyvinyl alcohol is
commercially available under the trade designation KURARAY POVAL
PVA-205 from Kurary Co., Ltd. Distilled water was mixed with the
polyvinyl alcohol to prepare aqueous mixtures respectively having 5
wt % of PVA-205, 10 wt % of PVA-205, 15 wt % of PVA-205, 25 wt % of
PVA-205, and 30 wt % of PVA-205. After the preparation of the
hardenable fluid compositions, each sample was coated on the
polypropylene mold shown in FIG. 2A at a thickness of 200 .mu.m
using a coating speed of 16 cm/sec.
[0236] Each coating layer was dried for two hours in the oven at 60
degree C. and further dried at room temperature (about 25 degree
C.) overnight to form a hardened layer. Thereafter, each hardened
layer was removed from the polypropylene mold, thus obtaining
articles with concave surfaces made of polyvinyl alcohol.
[0237] In the SEM images observed substantially vertically above
the concave surfaces, the maximum diameters of the concave surface
portions were measured at five positions. The average value of the
measurements was determined to be the average diameter of the
concave surfaces.
[0238] Table 3 shows the relationship between the viscosity
(concentration) of the water-soluble resin and the average diameter
of the concave surfaces for this embodiment.
TABLE-US-00003 TABLE 3 Drying Coating Curable temperature,
Concentration, Viscosity, speed, Ave. diameter, resin .degree. C.
weight percent mPa-sec cm/sec micrometers PVA-205 60 to 25 5 9 16
72.05 10 40 77.20 15 180 83.33 20 500 89.09 25 3000 90.48 30 7000
87.94
Example 3-4
[0239] A manufacturing process similar to that described for
Example 3-1 was used. A 20 weight percent aqueous mixture of
polyvinyl alcohol water-soluble resin (KURARY POVAL PVA-205 from
Kurary Co., Ltd.) was prepared. Using the polypropylene mold as
described in Example 2-1, six samples were prepared by coating the
water-soluble resin on the mold at a thickness of 200 .mu.m and
with a coating speed of 16 cm/sec.
[0240] The first sample was dried for two hours in the oven at 25
degree C., the second sample was dried for two hours in the oven at
60 degree C., the third sample was dried for two hours in the oven
at 80 degree C., the fourth sample was dried for two hours in the
oven at 100 degree C., the fifth sample was dried for two hours in
the oven at 120 degree C., and the sixth sample was dried for two
hours in the oven at 140 degree C. Then, the six samples were dried
at room temperature overnight, thus forming hardened layers.
Thereafter, the hardened layers were removed from the polypropylene
molds, thus obtaining six articles having concave surfaces made of
a water-soluble resin.
[0241] In the SEM image of the concave surface portions observed
substantially vertically above, the maximum diameters (diagonal
distances in case of the samples dried at a temperature of 120
degree C. or more) of the concave surface portions whose shapes
were measured at five positions. The average value of the
measurements was determined to be the average diameter of the
concave surfaces.
[0242] Table 4 shows the relationship between the drying
temperature and the average diameter of the concave surfaces in one
embodiment of the invention.
TABLE-US-00004 TABLE 4 Drying Coating Curable temperature,
Concentration, speed, Ave. diameter, Resin .degree. C. weight
percent cm/sec micrometers PVA-205 25 20 16 63.84 60 91.80 80 97.12
100 95.84 120 105.18 140 105.70
Example 3-5
[0243] As in Example 3-1, a 20 weight percent aqueous mixture of
polyvinyl alcohol as a water-soluble resin (KURARY POVAL PVA-205
from Kurary Co., Ltd.) was prepared. Then, the solution was coated
on the mold while entrapping air around the mold at the coating
speeds of 1.44 cm/sec, 4.03 cm/sec, and 23.36 cm/sec.
[0244] Then, the three coating layers were dried for two hours in
the oven at 60 degree C., and dried further at room temperature
overnight, thus forming hardened layers. Thereafter, all of the
hardened layers were removed from the polypropylene mold, thus
obtaining articles having concave surfaces made of a water-soluble
resin (article having an arranged pattern of concavities).
[0245] In the SEM images of the concave surface portions observed
substantially vertically above, the maximum diameters of the
concave surface portions were measured at five positions. The
average value of the measurements was determined to be the average
diameter of the concave surfaces.
[0246] Table 5 shows the relationship between the coating speed for
the water-soluble resin mixture and the average diameter of the
concave surfaces in one embodiment of the invention.
TABLE-US-00005 TABLE 5 Drying Coating Curable temperature,
Concentration, speed, Ave. diameter, Resin .degree. C. weight
percent cm/sec micrometers PVA-205 60 to 25 20 23.36 95.13 4.03
94.44 1.44 90.55
Example 4-1
[0247] As the hardenable fluid in this example, a thermoplastic
resin was used. More specifically, the thermoplastic resin was
polyethylene, commercially available under the trade designation
LDPEC13 from Eastman Chemical Japan Co., Ltd. A nickel sheet having
a square lattice pattern of quadrangular pyramid depressions was
used as the mold. These quadrangular pyramid depressions were 25
.mu.m in depth, had an apex angle of 90 degree C., and a square
bottom shape. Each side of the square bottom was 50 .mu.m and the
convexities were arranged at pitches of 50 .mu.m. The nickel sheet
was prepared as described in Example 2-4.
[0248] The thermoplastic resin was coated on the mold using a
heated knife coater, thus forming a coating layer. More
specifically, the thermoplastic resin was heated to a temperature
(140 degree C.) at which the resin would have a sufficient
fluidity, and was coated on the mold at a coating speed of 16
cm/sec to the thickness of 200 .mu.m while trapping the air around
the mold.
[0249] Then, the coating layer was cooled down to room temperature,
thus forming a hardened layer. Thereafter, the hardened layer was
removed from the nickel mold, thus obtaining an article having
concave surfaces made of a thermoplastic resin (the article had an
arranged pattern of concavities).
Example 4-2
[0250] Using the article having concave surfaces manufactured in
Example 4-1 as the second mold, the UV curable resin which is the
same as one used in Example 2-1 was coated on the second mold to
the thickness of 200 .mu.m. A 50 .mu.m PET film was placed in
contact with the UV curable resin and then pressed with a roller. A
deaeration process was performed by reducing the atmosphere
pressure in the same manner of Example 2-2. Then, the same
ultraviolet lamp as used in Example 2-1 was used to irradiate the
UV resin from the PET film side with ultraviolet rays of 3450
mJ/cm.sup.2. The UV curable resin was polymerized to form a
hardened layer. After polymerization, the hardened layer was
removed from the second mold, thus obtaining an article made of a
UV curable resin having convex surfaces (article having an arranged
pattern of convexities).
Example 5-1
[0251] A multilayer film was provided that had a copper layer with
a thickness of 5 .mu.m on a polyimide sheet with a thickness of 75
.mu.m. The film is commercially available under the trade
designation TWO LAYER COPPER CLAD SUBSTRATE from Japan
Interconnection Systems Limited. A laser beam was irradiated onto
the polyimide side of the resulting multilayer film to form a
depression, thus manufacturing a mold. The polyimide layer
corresponds to the side wall portion (first layer 110a) and the
copper layer corresponds to the bottom portion (second layer 110b)
in FIG. 7A.
[0252] More specifically, Beam, Inc. (Tokyo, Japan) prepared the
openings in the polyimide layer. An excimer laser beam was
irradiated on the polyimide layer side using a mask to form an
opening array pattern only in the polyimide layer and a surface of
the copper layer was exposed at the bottom of each opening, thereby
manufacturing a mold having depressions arranged in a square
lattice pattern. Each depression had cylindrical concavities. In
this case, a mold #1 and a mold #2 which have different arranged
patterns as shown in Table 6 were prepared by two kinds of
masks.
TABLE-US-00006 TABLE 6 Diameter of opening, micrometers Thickness
of Thickness of Pitch, Top - Bottom - Polyimide layer, Cu layer,
Mold micrometers Polyimide side Cu side micrometers micrometers #1
250 151.63 137.01 75 5 #2 80 50.54 36.34 75 5
[0253] The mold #1 had 100 depressions (10.times.10 lattice) in the
form of cylindrical concavities formed at pitches of 250 .mu.m, and
each cylindrical concavity has a sectional shape with a diameter of
151.63 .mu.m at a top surface side and a diameter of 137.01 .mu.m
at a bottom surface side (cupper layer side). The mold #2 has 100
depressions (10.times.10 lattice) in the form of cylindrical
concavities formed at pitches of 80 .mu.m, and each cylindrical
concavity has a sectional shape with a diameter of 50.54 .mu.m at a
top surface side and a diameter of 36.34 .mu.m at a bottom surface
side (cupper layer side).
[0254] FIG. 10A is a plane view from the top showing the mold #1
(110A) having openings 115A and FIG. 10B is a plane view from the
top showing the mold #2 (110B) having openings 115B.
Example 5-2
[0255] An article having concave surfaces was manufactured using
the above mentioned mold #1. As a hardenable fluid for this
example, a UV curable resin was prepared by mixing 90 parts by
weight of a UV hardenable oligomer, polyester based urethane
acrylate (commercially available under the trade designation
EBECRYL 8402 from DAICEL-CYTEC Co., Ltd.), 10 parts by weight of an
unsaturated aliphatic acid hydroxylalkylester modifier
.epsilon.-carprolactone (commercially available under the trade
designation PLACEL FA2D from Daicel Chemical Industries, Ltd.), and
1 parts by weight of a photo polymerization initiator (commercially
available under the trade designation IRGACURE 2959 from CIBA
Specialty Chemicals Inc.
[0256] An etchant for removing the cupper layer after forming a
hardened coating layer was prepared by mixing 6.4 parts by weight
hydrogen peroxide, 18 parts by weight concentrated sulfuric acid,
33 parts by weight copper sulfate, and 42.6 parts by weight
distilled water.
[0257] The UV curable resin was coated on the mold using a knife
coater, thereby forming a coating layer. More specifically, the UV
curable resin was coated on the mold at a thickness of 200 .mu.m
while entrapping air around the mold at the coating speed of 16
cm/sec in the same manner of Example 2-1. Then, the UV curable
resin was irradiated with ultraviolet rays of 3450 mJ/cm.sup.2
using the ultraviolet lamp of Example 2-1. The UV curable resin was
hardened (e.g., polymerized and cured).
[0258] After hardening, the copper layer (bottom portion) was
removed using the etchant heated to 45 degree C. The resulting
article was rinsed with distilled water. The article had concave
surfaces (the article had an arranged pattern of concavities). FIG.
11 shows a perspective view of the obtained article 131'A having
concave surfaces 132A. As the polyimide portion does not exist
between adjacent concave surfaces arranged in a square lattice
pattern in the article, the article having concave surfaces in
which any groove-like portion did not exist between adjacent
concave surfaces could be obtained.
[0259] An article having convex surfaces was manufactured using the
article manufactured with concave surfaces. The curable resin was a
mixture containing 20 weight percent polyvinyl alcohol as a
water-soluble resin (commercially available under the trade
designation KURARY POVAL PVA-217 from Kurary Co., Ltd.) and 80
weight percent distilled water. Using the article having concave
surfaces manufactured in Example 5-1 as the second mold, the 20
weight percent PVA-217 aqueous mixture was coated on the second
mold to the thickness of 200 .mu.m using a knife coater. A
deaeration process was performed by reducing the atmosphere
pressure in the same manner of Example 2-2.
[0260] The hardened layer was obtained by drying the coating layer
for two hours in the oven at 60 degree C. and at room temperature
(about 25 degree C.) overnight. After drying, the hardened layer
was removed from the second mold, thus obtaining an article made of
a polyvinyl alcohol resin having convex surfaces (the article had
an arranged pattern of convexities). FIG. 12 shows a perspective
view of the obtained article 161A having convex surfaces 162A.
[0261] Each convex surface of the article was not surrounded by a
groove-like portion. That is, second article was obtained that had
convex surfaces not surrounded by a horizontal wall.
Example 5-3
[0262] An article having concave surfaces was manufactured using
the mold #2 instead of the mold #1. In this case, the article was
manufactured using the same conditions Example 5-2 except for the
mold.
[0263] FIG. 13 shows a perspective view of the obtained article
131'B having concave surfaces 132B. As with the article prepared in
Example 5-2, an article was obtained that had concave surfaces
without groove-like portions between adjacent concave surfaces. An
article having convex surfaces was manufactured using the article
manufactured as mentioned above as a second mold. In this case, the
second article was manufactured on the same conditions as the above
mentioned Example 5-2 except for the second mold.
[0264] FIG. 14 shows a perspective view of the obtained article
161B having convex surfaces 162B. As each concave surface of the
second mold is not surrounded by a groove-like portion, the second
article has convex surfaces that are not surrounded by a horizontal
wall.
[0265] FIG. 16 is a schematic side-view of a display device 1600
that includes a pixilated liquid crystal panel 1610, an optical
film 1620 that includes a structured major surface 1630 and a
backlight 1640. Backlight 1640 is a direct-lit backlight and
includes a light diffuser plate 1670, multiple light sources 1650,
and a back reflector 1660.
[0266] Structured major surface 1620 of optical film 1620 can be or
include any structured surface disclosed herein. For example,
structured surface 1620 can be the structured surface shown in FIG.
14 where each structure includes a convexity and a sidewall. As
another example, structured surface 1620 can be the structured
surface shown in FIG. 13 where each structure includes a concavity
and a sidewall, where in some cases, the sidewall can have a prism
portion that can, for example, provide gain and/or redirect light
to a desired direction. As another example, structured surface 1620
can be similar to the structured surface shown in FIG. 11 where
each structure includes a concavity or a convexity but not a
sidewall. As yet another example, structured surface 1620 can be
the structured surface shown in FIG. 9 and include a plurality of
concavities, where each concavity is surrounded by walls.
[0267] Optical film 1620 has an optical gain of at least 1.0, or at
least 1.1, or at least 1.1, or at least 1.2, or at least 1.3, or at
least 1.4, or at least 1.5, or at least 1.6. As used herein,
"optical gain" of optical film 1620 is defined as the ratio of the
axial output luminance of an optical system, such as display device
1600, with the optical film to the axial output luminance of the
same optical system without the optical film.
[0268] In the exemplary display device 1600, structured major
surface 1630 faces pixilated liquid crystal panel 1610. In some
cases, structured major surface 1630 can face backlight 1640.
[0269] In the exemplary display device 1600, backlight 1640 is a
direct-lit backlight. In some cases, backlight 1640 can be a
side-lit backlight. For example, in some cases, backlight 1640 can
be replaced with side-lit backlight 1740 a schematic side-view of
which is shown in FIG. 17. Backlight 1740 includes a lightguide
1750, a back reflector 1780, a light source 1720 placed along a
side 1745 of lightguide 1750, and a side reflector 1730.
* * * * *