U.S. patent application number 09/950159 was filed with the patent office on 2003-11-20 for display panel filter for connection to a display panel.
Invention is credited to Kokoschke, Jeffrey L., Woodruff, Daniel P..
Application Number | 20030214461 09/950159 |
Document ID | / |
Family ID | 22367954 |
Filed Date | 2003-11-20 |
United States Patent
Application |
20030214461 |
Kind Code |
A9 |
Woodruff, Daniel P. ; et
al. |
November 20, 2003 |
Display panel filter for connection to a display panel
Abstract
The present invention provides a device in the form of a filter
which is useable in conjunction with a plasma display panel, which
is applied to the front face of a display, and which functions to
reduce reflection after assembly to acceptable levels, to increase
contrast enhancement ratios, to reduce EMI emissions to levels
which comply with consumer safety regulations and with military and
aircraft standards and to reduce infrared transmission in the 800
nm-1000 nm range to a level which does not interfere with IR remote
control operation. The present invention also relates to a method
of making such a plasma display panel filter and device.
Inventors: |
Woodruff, Daniel P.;
(Lakeville, MN) ; Kokoschke, Jeffrey L.;
(Faribault, MN) |
Correspondence
Address: |
DORSEY & WHITNEY LLP
INTELLECTUAL PROPERTY DEPARTMENT
50 SOUTH SIXTH STREET
MINNEAPOLIS
MN
55402-1498
US
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 0075203 A1 |
June 20, 2002 |
|
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Family ID: |
22367954 |
Appl. No.: |
09/950159 |
Filed: |
September 10, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09950159 |
Sep 10, 2001 |
|
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09487124 |
Jan 19, 2000 |
|
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60116562 |
Jan 21, 1999 |
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Current U.S.
Class: |
345/41 |
Current CPC
Class: |
B32B 17/10073 20130101;
C03C 17/3642 20130101; B32B 17/10174 20130101; H01J 2211/446
20130101; B32B 17/10834 20130101; B32B 2457/204 20130101; C03C
17/3639 20130101; C03C 17/3676 20130101; B32B 17/10761 20130101;
B32B 2307/204 20130101; C03C 17/3652 20130101; G02B 1/116 20130101;
C03C 2218/365 20130101; B32B 2307/202 20130101; H01J 29/896
20130101; C03C 17/3644 20130101; C03C 2217/78 20130101; B32B
2311/08 20130101; C03C 17/36 20130101; C03C 17/3618 20130101; Y10T
428/24975 20150115 |
Class at
Publication: |
345/41 |
International
Class: |
G09G 003/10 |
Claims
What is claimed is:
1. An optical display comprising: a transparent first substrate
having first and second sides; and a multi-layer optical film
applied to one of said first and second sides, said film comprising
at least one electrically conductive layer, at least one dielectric
layer and a protective layer positioned between said dielectric
layer and said electrically conductive layer; and a second
substrate comprised of a thin plastic film with a thickness less
than about 0.06 inches laminated to said first substrate with said
optical film positioned therebetween.
2. The display of claim 1 wherein said plastic film is PET.
3. The display of claim 2 wherein said protective layer is
comprised of first and second layers of protective material.
4. The display of claim 3 wherein said dielectric is comprised of
niobium pentoxide.
5. The display of claim 4 wherein said first protective layer is
oxidized titanium and said second layer comprises a material having
a plasma energy level less than niobium pentoxide.
6. The optical filter of claim 5 wherein said second layer is tin
oxide.
7. The optical filter of claim 6 wherein said oxidized titanium is
adjacent to said electrically conductive layer and said tin oxide
is adjacent to said dielectric layer.
8. The optical filter of claim 7 wherein said electrically
conductive layer is silver.
9. The optical filter of claim 1 wherein said second substrate has
a thickness of less than about 0.025 inches.
10. The optical film of claim 5 wherein said second protective
material layer is one or more of tin oxide (SnO.sub.2), zinc oxide
(ZnO.sub.2) and a silicon dioxide (SiO.sub.2).
11. The optical film of claim 10 wherein said oxidized titanium is
adjacent to said electrically conductive layer and said second
protective material is adjacent to said dielectric layer.
12. The optical film of claim 11 wherein said conductive material
layer is silver.
13. The optical film of claim 12 including a plurality of
electrically conductive layers and a plurality of dielectric layers
alternating with said electrically conductive layers.
14. A method of making an optical filter comprising: providing a
transparent substrate having a first side and a second side;
applying a multi-layer optical film to one of said first and second
sides of said transparent substrate, said film comprising at least
one electrically conductive layer, at least one dielectric layer,
and at least one protective layer between said electrically
conductive layer and said dielectric layer; and laminating a second
substrate to said first substrate with said optical film positioned
therebetween, said second substrate comprised of a thin plastic
film with a thickness less than about 0.06 inches.
15. The method of claim 14 wherein said plastic film is PET.
16. The method of claim 15 wherein said protective layer comprises
first and second layers.
17. The method of claim 16 wherein the application step includes
applying an electrically conductive layer to said one side of said
first transparent substrate or to a dielectric layer applied to
said first substrate, applying said first layer to said
electrically conductive layer, applying said second layer to said
first layer and applying said dielectric layer to said second
layer.
18. The method of claim 17 wherein said dielectric layer is niobium
pentoxide, said first layer is titanium and said second layer is a
material having a plasma energy level less than niobium
pentoxide.
19. The method of claim 18 wherein said electrically conductive
layer is silver and wherein said second layer is one or more of tin
oxide (SnO.sub.2), zinc oxide (ZnO.sub.2) and silicon dioxide
(SiO.sub.2).
20. The method of claim 14 including applying the optical filter to
the front face of a display.
Description
[0001] This application claims the benefit of Provisional
Application Serial No. 60/116,562 filed Jan. 21, 1999.
FIELD OF THE INVENTION
[0002] The present invention relates generally to a display panel
filter, and more particularly to a filter having particular
application for use with a plasma display panel or flat panel
display. The present invention also relates to an IR/EMI filter
film applied to a substrate for use in a display panel filter or
otherwise and a method of making such a film and a display panel
filter. The invention also relates to applying the display panel
filter directly to a display panel and laminating the optical film
between a pair of substrates in which one is a thin plastic film
such as PET or other optical film.
DESCRIPTION OF THE PRIOR ART
[0003] Visual display panels commonly known as plasma display
panels or flat panel displays have been recently introduced for the
purpose of displaying visual images or information on relatively
large, flat screens. Plasma display panel technology utilizes
selectively energized gas ions to bombard phosphors on a display
screen, similar to an electron beam bombarding phosphors on a
cathode ray tube (CRT) screen. Plasma display panels are similar to
CRT displays in that both provide a means for visually displaying
information or images from an input signal; however, important
differences exist. First, a CRT display requires a significant
depth dimension relative to the size of its display screen to
accommodate a generally funnel shaped rearward portion for
generation and deflection of the electron beam. Second, most CRT
screens are curved. In contrast, the energization of the ions in a
display panel using plasma display technology occurs in a
relatively thin vacuum chamber adjacent to the display screen,
resulting in a relatively thin display panel with a flat view face.
Thus, plasma display panels are currently used primarily for
relatively large display panels where CRTs are impractical or where
a display panel with a significantly reduced depth dimension is
necessary or desirable.
[0004] Although plasma display panels provide significant
advantages and improvements by facilitating relatively large visual
displays with a reduced panel depth and by otherwise facilitating
the use of displays in environments with space restrictions which
preclude the use of conventional CRT displays, new problems have
arisen. These problems relate to the quality of the visual display,
increased infrared (IR) and electromagnetic interference (EMI)
emissions, low contrast ratio and consumer safety issues. For
example, photopic reflection from many plasma display panels is in
excess of 15%. This adversely affects the quality of the display.
Further, operation of the plasma display panel produces or has the
potential of producing infrared (IR) emissions which are capable in
some cases of interfering with a remote control of the panel or
other devices utilizing infrared signaling. Still further,
operation of the plasma display panel results in the generation and
emission of electromagnetic interference (EMI). Accordingly, many
plasma panel displays fail to meet governmental TCO and FCC
requirements for EMI emissions and the stricter standards for
various military, aircraft and other uses. The above problems
necessary limit the applicability and desirability of using plasma
display panels.
[0005] Accordingly, there is a critical need in the art for a
device or a filter, and in particular a multi-layer filter film,
useable in conjunction with plasma display panels for addressing
and solving the above problems and limitations. A need also exists
for a method of making such a device, filter or film.
SUMMARY OF THE INVENTION
[0006] To satisfy the need in the art, the present invention
provides a device in the form of a single filter which is useable
in conjunction with plasma display panels or other applications and
which functions to reduce reflection after assembly to acceptable
levels, to increase contrast enhancement, to maintain transmission
integrity, to assist in reducing EMI emissions to levels which
comply not only with consumer safety regulations, but preferably
with various stricter standards, and to reduce infrared emissions
in the 800 nm-1000 nm range to a level which does not interfere
with remote control operation.
[0007] Generally, the present invention comprises a substrate with
a filter film (preferably an optical IR/EMI shielding film) applied
thereto for use in a display panel filter. One embodiment of a
filter device in accordance with the invention includes a filter
film comprised of one or more conductive layers and one or more
dielectric layers applied to a substrate which is then laminated to
a second substrate. This second substrate may comprise a piece of
transparent glass, plastic or other material, a thin flexible film
such as PET or other optically clear film or the front face of the
display device itself. The combination of the conductive and
dielectric layers functions to provide the desired EMI and IR
shielding and assists in reducing reflection and increasing
contrast enhancement. This combination of layers may be provided as
a single film containing both conductive and dielectric layers.
Because lamination of the substrates necessarily requires use of an
adhesive or other bonding agent and exposure of the same to at
least one surface of the shielding film or filter, a layer of
silicon dioxide (SiO.sub.2) or other material may be applied to the
filter or film, if desired, to improve compatibility with and/or
limit possible reactions between the outer layer of the filter or
film and the adhesive. The outer surfaces of one or both substrates
is also preferably an anti-reflective (AR) coating. The filter
further includes an electrical connection member electrically
connected to conductive layers within the EMI/IR shielding film.
Grounding means is also provided in the form of an electrical wire
or the like for electrically connecting the electrical connection
member to a grounded terminal. Other means, however, may also be
utilized.
[0008] The preferred embodiment of the shielding film comprises one
or more layers of a conductive material and one or more alternating
layers of a dielectric. The conductive material may include various
conductive metals or other materials such as silver, copper, gold
and indium tin oxide, among others, although silver metal is
preferred. The dielectric may include various materials such as
niobium pentoxide, titanium dioxide and tin oxide, among others,
although niobium pentoxide is preferred. Additionally, a thin
protective layer is provided between adjacent conductive/dielectric
layers to eliminate or limit undesirable oxidation or other
deterioration of the conductive layer during formation of the film
or otherwise. Such a protective layer is desirable when the
conductive layer is subject to oxidation or other deterioration
and/or the manufacturing conditions result in the film being
exposed to high temperatures. Such conditions exist when the film
is manufactured using sputtering or various other thin film
deposition techniques, particularly for multiple layer films of two
or more conductive material layers. In some cases, the protective
layer is comprised of two or more layers of different
materials.
[0009] In the preferred embodiment, the transparent substrates
comprise view side and panel side substrates with the panel side
substrate being the substrate closest to, or adjacent to, the
display screen. Similarly, each of the substrates includes a view
side facing away from the display screen and a panel side facing
the display screen. In one embodiment, the EMI/IR shielding film or
filter is applied directly to one side of one of the substrates and
is then laminated to a second substrate by a urethane or other
adhesive with the optical shielding film positioned therebetween.
The laminated substrates are then mounted in front of a display
with the first substrate preferably adjacent to the display. This
embodiment further includes an environmental degradation barrier
for the conductive layers within the EMI/IR shielding layer. This
barrier extends around the edge of the laminated filter and is
constructed of a conductive material. This barrier is electrically
connected both with the electrical connection member or busbar and
with a grounding terminal.
[0010] In a further embodiment, the EMI/IR shielding film or filter
is applied to the panel side of the view side substrate (the
substrate furthest from the display). Subsequently, such substrate,
with the film applied thereto, is laminated onto, or otherwise
applied directly to, the front face of the display with the optical
film positioned therebetween.
[0011] In a still further embodiment, the optical film is applied
to a first substrate, with a second substrate in the form of a thin
transparent plastic film such as, but not limited to,
polyethyleneterephthalate (PET) laminated to the first substrate
with a thickness preferably less than about 0.06 inches (60 mils).
Subsequently, the laminated structure is applied directly to, or
mounted in front of, the front face of a display unit.
[0012] One aspect of the method of the present invention relates to
a method of making a film or filter of the type described above for
use in conjunction with a plasma display panel. Such method
generally includes providing a transparent substrate, applying an
EMI/IR shielding film or filter to such substrate and then
laminating such substrate to a second substrate. A further aspect
of the method is to apply such substrate, with the film thereon,
directly to the front face of the flat panel or other display. A
still further aspect of the method is to laminate a coated
substrate to a second substrate comprised of a plastic film such as
PET and then applying it to, or mounting it in front of, a display
unit.
[0013] Accordingly, an object of present invention is to provide a
film or filter for use in conjunction with a plasma display
panel.
[0014] Another object of the present invention is to provide a
plasma display panel filter which provides anti-reflective, EMI
shielding, contrast enhancement and infrared shielding capabilities
and which also complies with consumer safety requirements.
[0015] A further object of the present invention is to provide a
plasma display panel filter having one or more conductive layers
and one or more dielectric layers formed on a transparent substrate
for subsequent lamination to a second substrate.
[0016] A still further object of the present invention is to
provide a plasma display panel filter with an improved film
providing both EMI and IR shielding capabilities.
[0017] A further object of the present invention is to provide a
plasma display panel filter with an improved means for electrically
connecting the EMI shielding layer to a grounding terminal.
[0018] A still further object of the present invention is to
provide a plasma display panel fiter with an electrically
conductive material around the edge of the filter to prevent
environmental degradation of the EMI shielding layer and to
maximize the EMI shielding efficiency of such layer.
[0019] A still further object of the present invention is to
provide a plasma display panel as described above which includes a
layer to prevent or minimize possible reactions between the
lamination adhesive and the shielding film and/or to improve
compatibility with the adhesive and promote the adhesive
strength.
[0020] Another object of the present invention is to provide a
substrate with an optical EMI/IR shielding film thereon which is
applied directly to the front face of a display or display
panel.
[0021] A still further object of the present invention is to
provide an optical filter comprised of an optical film laminated
between a first substrate and a second substrate comprised of a
plastic film such as PET.
[0022] Another object of the present invention is to provide a
method of making a film and plasma display panel filter of the type
described above.
[0023] A still further object of the present invention is a method
of making a substrate with an EMI/IR shielding film as described
above and applying the same directly to the front face of a
display.
[0024] These and other objects of the present invention will become
apparent with reference to the drawings, the description of the
preferred embodiment and method and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is an isometric, exploded view of a plasma display
panel and associated filter in accordance with the present
invention.
[0026] FIG. 2 is an enlarged view, partially in section, of one
embodiment of a plasma display panel filter as viewed along the
section line 2-2 of FIG. 1.
[0027] FIG. 3 is a schematic sectional view of the EMI/IR shielding
film in accordance with the present invention.
[0028] FIG. 4 is a view similar to that of FIG. 2 of a further
plasma display panel filter.
[0029] FIG. 5 is an enlarged view, partially in section, and
similar to that of FIG. 2, of a further embodiment of a plasma
display panel filter.
[0030] FIG. 6 is a schematic sectional view of a further embodiment
of the shielding film in accordance with the present invention.
[0031] FIG. 7 is a view showing application of a coated substrate
directly to the front face of a display.
[0032] FIG. 8 is a view showing lamination of a coated substrate to
a second substrate comprised of a plastic film.
DESCRIPTION OF THE PREFERRED EMBODIMENT AND METHOD
[0033] The present invention relates to a plasma display panel
filter, or shielding film for use therein, which functions to
provide EMI and IR shielding capabilities. Preferably the filter
also provides anti-reflective (AR) capability. Various features of
the present invention have possible application other than for
display panel filters. However, the description of the preferred
embodiment will be for use in a plasma display panel filter.
[0034] Reference is first made to FIG. 1 illustrating an exploded,
isometric view of a plasma display panel 10 and associated filter
14 in accordance with the present invention. The display panel 10
as illustrated in FIG. 1 in accordance with the preferred
embodiment is a generally rectangular configured device having a
front viewing or display screen 11 and a recessed area 12 for
receiving a display panel filter 14. It should be understood,
however, that the possible relationships between a plasma display
panel and a filter in accordance with the present invention is not
limited to the embodiment disclosed in FIG. 1. If desired, the
display panel 10 can be assembled with the filter 14 being an
integral part of the panel 10. Alternatively, the panel 10 and
filter 14 can be separate, stand alone items which are purchased
separately. In such case, means may be provided for suspending the
filter 14 from a portion of the panel 10 or connecting the filter
14 to the panel 10 so that the filter 14 is directly in front of
and substantially adjacent to the display screen 11. It is also
contemplated that the filter can be bonded or laminated directly to
the display screen 11, if desired.
[0035] With continuing reference to FIG. 1, the filter 14 of the
preferred embodiment includes a generally flat, planer filter
lamination 15 having a view side 16 facing away from the display
screen 11 and an opposite panel side 17 facing the display screen
11. The filter 14 further includes an electrically conductive
element 18 in the form of a strip of conductive material applied to
the peripheral edge of the filter lamination 15. As illustrated in
FIG. 1, the electrically conductive material 18 of the preferred
embodiment extends around the periphery of the lamination 15 and
for a limited distance inwardly on both the view side 16 and the
panel side 17. As will be described in greater detail below, the
conductive element 18 functions in conjunction with electrically
conductive layers within the lamination 15 to provide EMI and other
shielding capability to the filter. Grounding means comprised of
one or more grounding clips 19 with an electrical lead 20, or some
other means, is commonly electrically connected with the conductor
18 for electrically connecting the conductor 18 to a ground
terminal 21.
[0036] Reference is next made to FIG. 2 which is a partial
sectional view of the filter lamination 15 as viewed along the
section line 2-2 of FIG. 1. In general, the filter lamination 15
includes a pair of transparent substrates 22 and 24. In the
preferred embodiment, the substrate 22 is the view side substrate
and the substrate 24 is the panel side substrate. Each of the
substrates 22 and 24 is provided with an anti-reflective coating 25
and 26, respectfully, which is applied to the outer surfaces of the
substrates, namely, to the view side of the view side panel and the
panel side of the panel side panel. An EMI/IR shielding film 27
comprised of a combination of dielectric and conductive layers is
applied to the view side of the panel side substrate 24 and between
the substrate 22 and 24 to reduce and limit EMI emissions and to
provide infrared shielding and contrast enhancement. The film 27 is
thus laminated between the substrates 22 and 24 via the adhesive or
lamination layer 30 after being applied to the substrate 24 by
sputtering.
[0037] In the preferred embodiment, the transparent substrates 22
and 24 are comprised of generally flat, planer sheets of glass. It
is contemplated, however, that the transparent substrates 22 and 24
could, if desired, be constructed of a transparent plastic or other
synthetic material or a composite glass/synthetic material. The
thicknesses of the substrates 22 and 24 should be selected to be as
thin as possible while still being thick enough to provide the
necessary and desirable safety and strength characteristics. In the
preferred embodiment, the thickness of the substrates is preferably
in the range of about 1.0 mm to about 6.0 mm or less for a filter
having a viewing surface of about 2-10 square feet. However, it is
contemplated that at least one of the substrates 22, 24 could also
be a thin film synthetic material such as polyethylene terapthalate
(PET) on the order of 0.010 inches thick, however, other film
thickness would work as well. One of the substrates could also be
the front face of a display device if the one substrate with film
thereon is laminated directly to the display device.
[0038] The anti-reflective coating 25 applied to the view side of
the substrate 22, is similar to the anti-reflective coating 26
applied to the panel side of the substrate 24, and can be any
anti-reflective coating known in the art. Preferably, the
anti-reflective coatings 25 and 26 in accordance with the present
invention are comprised of a plurality of individual layers which
are applied to the respective surfaces of the substrates 22 and 24
via sputtering or reactive sputtering in accordance with processes
known in the art. The particular makeup of these anti-reflective
coatings should be effective to reduce the photopic reflection from
the view side 16 and panel side 17 of the filter 15 to an
acceptable level. In a structure incorporating the filter of the
present invention, the photopic reflection normally exhibited by
the display screen 11 (FIG. 1) is significantly reduced in some
embodiments by as much as a factor of 10 or more, from a reflection
of over 15% to a reflection of about 4 or 5% to 1.0% or less.
[0039] The specific structure of the anti-reflective coatings 25
and 26 is described in U.S. Pat. No. 5,372,874, the substance of
which is incorporated herein by reference, and is currently sold by
Viratec Thin Films, Inc. of Faribault, Minn. under the trademark
CDAR. Other anti-reflective coatings, however, can also be
used.
[0040] The film 27 is comprised of a combination of dielectric and
conductive layers and is primarily designed to reduce the EMI and
IR emissions to acceptable levels, while at the same time
minimizing any adverse affect on the transmission of visible light
through the filter. The film 27 is transparent and each of its
dielectric and conductive layers is transparent. In the preferred
embodiment, the film 27 is applied to the view side of the panel
substrate 24 by sputtering or reactive sputtering and comprises a
series of dielectric layers separated by layers of an electrically
conductive material. Specifically, the film 27 includes four
dielectric layers 50, 54, 58 and 61 and three interleaved
electrically conductive layers 51, 55 and 59.
[0041] With reference to FIG. 3, the layers 50, 54, 58 and 61 are
layers of relatively high refractive index dielectrics having a
refractive index of at least 1.7 and preferably about 2.2 to 2.8.
The layers 51, 55 and 59 are layers of electrically conductive
materials such as conductive metals. In some film 27 structures,
layers 52, 56 and 60 of a further metal or other material are added
adjacent to the conductive layers 51, 55 and 59 to prevent
oxidation of the conductive layers during deposition of the
dielectric layers 54, 58 and 61.
[0042] The electrically conductive layers 51, 55 and 59 function
primarily to reduce IR and EMI emissions generated in the plasma
display panel. Preferably, EMI emissions are reduced to levels
which comply with various governmental or other regulations or
standards. In general, the thicker the conductive layers 51, 55 and
59, the more effective they are in reducing IR and EMI emissions.
However, increasing the thickness of the conductive layers 51, 55
and 59 also lowers the transmission of visible light. Thus, to
obtain the desired shielding capability, two or more, and
preferably three, conductive layers of limited thickness are
preferred. In the preferred embodiment, the conductive material
layers 51, 55 and 59 are silver; however, various other conductive
materials can be used as well including materials such as copper,
gold and indium tin oxide, among others. Preferably, each of the
layers 51, 55 and 59 has a thickness of about 5 mn to 20 nm and
more preferably a thickness of about 10 nm to 15 nm. Most
preferably, the thicknesses of the layers 51, 55 and 59 are 12 nm,
13 nm and 12 nm, respectively. The conductive layers are preferably
applied by sputtering, reactive sputtering, or other thin film
deposition techniques.
[0043] The dielectric layers 50, 54, 58 and 61 are high refractive
index materials and function primarily to reduce reflectivity, and
thus improve transmission of visible light in the regions of about
380 nm to 800 nm. In the preferred embodiment, the dielectric
material of the layers 50, 54, 58 and 61 may include materials such
as niobium pentoxide (Nb.sub.2O.sub.5), titanium dioxide
(TiO.sub.2) and tin oxide (SnO.sub.2), among others. Preferably,
however, the dielectric material is niobium pentoxide
(Nb.sub.2O.sub.5).
[0044] The outer dielectric layers 50 and 61 have a preferred
optical thickness of between about 0.4 to 0.8 at a wavelength of
about 450 nm to 650 nm, while the inner dielectric layers 54 and 58
have an optical thickness between about 0.7 to 1.5 at a wavelength
of about 450 nm to 650 nm. As used above and throughout this
application, the term "optical thickness" shall mean the "quarter
wave optical thickness" or QWOT as it is known in the art.
Preferably, the physical thickness of the outer layers 50 and 61 is
about 20 nm to 50 nm and most preferably is about 30 nm to 40 nm.
The physical thickness of the inner dielectric layers 54 and 58 is
preferably about 50 nm to 90 nm and is most preferably about 60 nm
to 70 nm.
[0045] In some structures where the film 27 is formed by sputtering
or reactive sputtering, the various film layers and the conductive
material is reactive to one or more of the materials making up the
adjacent layer. In such cases, it is necessary to first provide a
thin protective or sacrificial material layer next to the
conductive material layer to prevent its oxidation or other
reaction to the reactive materials of the dielectric layers. In the
embodiment of FIG. 3, the layers 52, 56 and 60 perform such a
function. In the preferred structure of FIG. 3, a thin layer of
titanium or some other sacrificial material is applied adjacent to
the conductive material layer so that when the Nb.sub.2O.sub.5 or
other dielectric material is applied by sputtering or reactive
sputtering, the oxygen oxidizes the titanium layer 52, 56 and 60 to
TiO.sub.2 rather than the conductive layer 51, 55 and 59. The
oxidized titanium layer then forms part of the adjacent dielectric
layer. In the preferred embodiment, the thickness of the protective
layers 52, 56 and 60 are about 0.5 nm to 5 nm and most preferably
about 3 nm to 5 nm.
[0046] The preferred embodiment of the film 27 is a seven layer
film comprising three conductive material layers and four
dielectric material layers. It is contemplated, however, that films
with different total layers can also be utilized. Preferably,
however, the number of dielectric layers should exceed the number
of conductive layers by one. Thus, where n equals the number of
conductive layers, the number of dielectric layers is preferably
n+1.
[0047] Accordingly, the film 27 of FIG. 2 comprises a plurality of
conductive and dielectric layers including a pair of end dielectric
layers and alternating conductive and inner dielectric layers
disposed therebetween. The end dielectric layers have an optical
thickness of between about 0.4 to 0.8 and preferably 0.6 at a
wavelength of about 450 nm to 650 nm, the inner dielectric layers
have an optical thickness of about 0.7 to 1.5 at a wavelength of
about 450 nm to 650 nm and the conductive layers have a physical
thickness of about 5 nm to 15 nm.
[0048] In the embodiment of FIG. 2, the film 27 is applied by
sputtering the various film layers to the view side of the panel
side or film carrying substrate 24, with the layer 50 sputtered
first and then followed by the layer 51, the layer 52 and
sequentially by the layers 54, 55, 56, 58, 59, 60 and 61. The film
carrying substrate 24 is then laminated to the substrate 22 via the
adhesive or lamination layer 30, with the film 27 facing the
substrate 22. The lamination material 30 in the preferred
embodiment comprises a sheet of polyurethane adhesive. As shown,
the adhesive sheet 30 is positioned between the film 27 and the
panel side of the substrate 22. Many adhesives or laminations such
as PVB, acrylic and/or others can, of course, be used to laminate
the substrates 22 and 24 together; however, the particular adhesive
or lamination materials selected should be capable of exhibiting
substantially transparent properties upon completion of the
lamination. The adhesives may also be tinted or otherwise be
provided with IR shielding capabilities, if desired. In accordance
with the present invention, the layer 30 is positioned between the
substrates 22 and 24 as shown and then placed in an autoclave under
appropriate heat and pressure conditions for approximately three to
four hours to laminate the layers together.
[0049] A further embodiment of the filter in accordance with the
present invention is shown in FIG. 6. FIG. 6 is similar to the
embodiment of FIG. 3 except that it illustrates a modified film
27'. The film 27' of FIG. 6 differs from the film 27 of FIG. 3 in
two respects: First, the film 27' includes additional protective or
sacrificial layers 53a, 53b and 53c adjacent to the layers 52, 56
and 60, respectively, and second, an additional layer 57 is applied
over the outer dielectric layer 61 so that when the substrates are
laminated together, the layer 57 is positioned between the
dielectric layer 61 and the adhesive 30.
[0050] As discussed above with respect to the embodiment of FIG. 3,
the protective or sacrificial layers 52, 56 and 60 are preferably
titanium. The reasons, among possible others, are that titanium is
easily oxidized and when oxidized, the resulting titanium oxide is
clear. As also disclosed above with respect to the embodiment of
FIG. 3, the dielectric layers 50, 54 and 58 and 61 are preferably
niobium pentoxide (Nb.sub.2O.sub.5). The reasons, among possible
others, are that niobium pentoxide has a high sputter rate and
lower optical dispersion. Despite the distinct advantages of using
titanium and niobium pentoxide as the sacrificial layer and the
dielectric layers, respectively, certain disadvantages or
limitations exist when they are used adjacent to one another or
when the conductive material is highly reactive and multiple layers
are necessary. These disadvantages are believed to arise from two
primary factors. First, the relatively high plasma energy and
deposition temperature of niobium pentoxide adversely affects the
protective ability of the titanium. Thus, when both niobium
pentoxide and titanium are used as in the preferred embodiment, it
is necessary to increase the thickness of the sacrificial titanium
layers in order to fully protect the underlying conductive layers
(51, 55 or 59) from being oxidized or otherwise damaged during
application of the niobium pentoxide. Second, the oxidation of
titanium metal is an exothermic reaction. Because more protective
titanium is needed when it is oxidized in the presence of niobium
pentoxide, the level of heat caused by the exothermic reaction
increases significantly. Because excess heat causes silver to
agglomerate, excessive oxidation of titanium can result in damage
to the underlying silver conductive layer.
[0051] To prevent, or at least minimize, the disadvantages
associated with adjacent layers of titanium and niobium pentoxide
as described above, and to thereby facilitate the use of both
titanium and niobium in the filter of the present invention, a thin
layer of a further protective material 53a, 53b and 53c is applied
to the titanium layers 52, 56 and 60 as shown in the embodiment of
FIG. 6. Preferably these layers 53a, 53b, 53c are tin oxide which
is more durable than titanium and the underlying silver and which
exhibits a significantly reduced difference in plasma energy level
and deposition temperature relative to niobium pentoxide. Other
materials such as ZnO.sub.2 and SiO.sub.2, among others, may also
be used provided they are more durable than titanium and exhibit a
reduced plasma energy level and deposition temperature, compared to
niobium pentoxide. In the embodiment of FIG. 6, the layers 52, 56
and 60 are preferably about 0.5 nm to 15 nm thick and most
preferably about 3 nm to 5 nm thick, while the layers 53a, 53b and
53c are preferably about 5 nm to 40 nm thick and most preferably
about 10 nm to 30 nm thick.
[0052] For the same reasons as discussed above, niobium pentoxide
is the preferred dielectric for the layers 50, 54, 58 and 61,
including the outer dielectric layer 61. Despite being preferred,
however, strength of adhesion between the niobium pentoxide outer
layer 61 and many of the adhesives is less than desired. To
overcome these limitations, the embodiment of FIG. 6 provides a
thin layer 57 of silicon dioxide (SiO.sub.2) or other adhesive
compatible layer on the outer surface of the outer dielectric layer
61 so that when the substrates 22 and 24 are laminated together
with an adhesive 30, the layer 57 is positioned between the layer
61 and the adhesive 30.
[0053] This additional layer 57 improves the adhesive bond between
the coated substrate 24 and the substrate 22 and thus acts as an
adhesion promoter and also limits any possible reaction between the
dielectric and the adhesive. Preferably this layer is silicon
dioxide or some other silicon based composition. However, other
materials or compositions will work as well. The layer 57 is
preferably about 2 nm to 50 nm thick and more preferably about 10
nm to 30 nm thick.
[0054] Both the film 27 of FIGS. 2 and 4 and the film 27' of FIG. 6
provide sufficient sheet resistance to reduce EMI emissions to
acceptable levels. Preferably, the films 27 and 27' function to
exhibit sheet resistance of less than 5 ohms per square and more
preferably less than 1.5 ohms, per square. The films 27 and 27'
also are designed to block IR emissions and thus reduce the same to
acceptable levels, to optically match the adhesive used to laminate
the second substrate and to generally provide desired optical
performance by reducing reflection and improving contrast
enhancement.
[0055] During assembly of the filter lamination 15, a busbar 32 is
applied to the outer peripheral edge portion of the substrate 24.
Preferably this busbar includes a first leg 34 electrically
contacting the film 27 and extending inwardly from the outer
peripheral edge of the substrate 24, a second leg 36 applied over
the anti-reflective coating 26 and also extending inwardly from the
outer peripheral edge of the substrate 24 and a third leg 35
electrically connected with the legs 34 and 36 and essentially
extending over the entire peripheral edge of the substrate 24. If
desired, the legs 35 and 36 can be eliminated as shown in FIG.
4.
[0056] In the preferred embodiment, the legs 34 and 36 extend
inwardly from the peripheral edge of the substrate 24 for a
distance of at least 1.0 mm and preferably a distance greater than
or about 2.0 mm. Further, the busbar 32 in accordance with the
present invention preferably extends around the entire periphery of
the substrate 24 and thus the film 27. It is contemplated that the
busbar 32 can be applied in a variety of ways. In the preferred
embodiment, however, the busbar 32 is a solder based, electrically
conductive material applied via ultrasonic soldering.
[0057] Following application of the busbar 32 to the peripheral
edge portion of the substrate 24, a conductive environmental
degradation barrier member 38 in the form of electromagnetic
shielding tape is applied over the leg portion 35 of the busbar 32.
The member 38 is applied to the outer or panel side of the
anti-reflective coating 26 along the outer peripheral edge of such
coating 26. The member 38 extends inwardly a limited distance from
the outermost peripheral edge of the coating 26. This limited
distance is greater than 5 nm and preferably equal to or greater
than about 9 nm. If desired, the barrier member 38 can be applied
to all three legs 34, 35 and 36 of the buss bar 32. The member 38
is preferably applied to and connected with leg 35 of the busbar 32
by an electrically conductive adhesive. Accordingly, the member 38
serves the primary function of making an electrical connection with
the busbar 32 via the electrically conductive adhesive.
[0058] Grounding means is also provided for electrically connecting
the member 38, and thus the busbar 32 and the conductive layers 51,
55 and 59, to a grounding terminal 21. In one embodiment as shown
in FIGS. 1, 2, 4 and 5, this means is in the form of a grounding
clip 19 having a first leg 42 engaging the member 38, a second leg
45 with a spring contact member 46 for making electrical contact
with the coating 25 of the substrate 22, and a third leg 44 joining
the legs 42 and 45. An electrical lead 20 has one end connected to
the connector clip 19 and a second end connected with the grounding
terminal 21. Other means can of course also be provided for making
this electrical grounding connection.
[0059] FIG. 4 shows an alternate embodiment for connecting the
busbar 32 to the film 27 and connecting the member or tape 38 to
the busbar 32. As shown in FIG. 4, the busbar is comprised only of
the leg 34, with the legs 35 and 36 having been eliminated. In this
embodiment a leg 41 of the tape 38 is provided directly over the
busbar leg 34, with the legs 40 and 39 of the tape 38 covering the
end and a portion of the face, respectively, of the substrate 24.
In his embodiment, both the busbar and the tape would be applied to
the substrate 24 before lamination to the substrate 22.
[0060] FIG. 7 illustrates a further embodiment in accordance with
the present invention. In the embodiment of FIG. 7, the substrate
to which the EMI/IR film has been applied is bonded or otherwise
applied directly to the front face of a flat panel or other
display. This has several advantages. First, it eliminates an
additional substrate layer and thus surface reflection from such
layer. This accordingly improves the optical performance of the
display. Secondly, direct bonding of the coated substrate to the
front face of the display eliminates the need for any mounting
mechanism for a separate filter such as that illustrated in FIG. 1.
Thirdly, applying the coated substrate directly to the front face
of the display results in a lighter and less complex display
unit.
[0061] With reference to FIG. 7, the display is illustrated
generally by the reference character 65 and includes an outer frame
66 and a front face substrate 68. The coated substrate to be
applied to the front face substrate 68 includes a substrate 69
preferably constructed of glass or transparent plastic. This
substrate 69, in the embodiment of FIG. 7, is considered to be the
view side substrate with the substrate 68 of the display 65 being
considered the panel side substrate. In the embodiment of FIG. 7,
the optical shielding film 70 is applied to the panel side of the
view side substrate 69. This film 70, in the preferred embodiment,
comprises the film 27 of FIG. 3 or the film 27' of FIG. 6 as
described above. If desired, an AR coating 71 can also be applied
to the view side of the view side substrate 69. The substrate 69,
with the film 70 and the coating 71 (if desired) applied thereon is
laminated or otherwise bonded to the front surface of the display
substrate 68. To facilitate this, an adhesive sheet 72 is
positioned between the coated substrate 69 and the front face
substrate 68 to bond the substrates together. The adhesive sheet 72
can comprise a polyurethane adhesive, PVB, acrylic or any other
materials commonly used as adhesives in such an application.
[0062] FIG. 8 illustrates a further embodiment in accordance with
the present invention. In the embodiment of FIG. 8, the substrate
69 to which the optical EMI/IR shielding film 70 has been applied
is laminated to a second substrate 73 comprised of a thin plastic
film such as PET with a thickness less than 0.06 inches (60 mils),
more preferably less than about 0.025 inches (25 mils) and most
preferably less than about 0.015 inches (15 mils). While the
preferred film substrate 73 is PET, other films such as
polycarbonates, acrylics and others may also be used. Materials
suitable for use as the film substrate 73 should preferably be
optically clear so as to not adversely affect light transmission.
This entire filter structure is then mounted in front of a display
unit as shown in FIG. 1, or bonded or otherwise applied directly to
the front face of a flat panel or other display.
[0063] With specific reference to FIG. 8, the display is
illustrated generally by the reference character 65 and includes an
outer frame 66 and a front face substrate 68. The coated substrate
69 is preferably constructed of glass or transparent plastic and,
in the embodiment of FIG. 8, is considered to be the view side
substrate. In the embodiment of FIG. 8, the optical shielding film
70 is applied to the panel side of the view side substrate 69 via
sputtering or the like. The second substrate 73 in the form of a
thin plastic film such as PET as described above is then laminated
or otherwise applied to the substrate 69 with the optical film 70
positioned therebetween.
[0064] In one embodiment, this filter structure comprised of the
substrates 69 and 73 with the film 70 positioned therebetween is
then mounted in front of the display 65 and display substrate 68
such as is shown in FIG. 1. In this embodiment, an anti-reflective
(AR) coating 71 can be applied to the view side of the substrate 69
and an AR coating 74 can be applied to the panel side of the
substrate 73 as shown in FIG. 8. If an AR coating is to be applied
to the film substrate 73 by a technique such as sputtering, it is
preferable to first apply an abrasion resistant coating or hard
coat to the substrate 73 to facilitate adherence of the sputtered
AR coating. Such abrasion resistant coatings are known in the art
and can include thermally cured siloxane based coatings and UV
cured acrylic based coatings, among others.
[0065] In a further embodiment, the filter comprised of the
substrates 69 and 73 with the film 70 therebetween may be bonded or
otherwise applied directly to the front face of the display
substrate 68. This bonding can be accomplished, if desired, with
the use of an adhesive sheet 72 positioned between the PET
substrate 73 and the front face substrate 68 as shown. In this
further embodiment, the AR coating 74 may be eliminated.
[0066] The method aspect of the present invention, including the
method of forming the filter film on a first substrate and
subsequently laminating the same to a second substrate can be
understood as follows. First, a transparent substrate preferably of
glass or plastic is provided. If desired, the non-coated side
surface of such substrate can be provided with an anti-reflective
coating by sputtering or other deposition technologies. In some
cases this ultimately may be the view side, while in other cases it
may ultimately be the panel side.
[0067] Following this, the film 27 (FIG. 3) or the film 27' (FIG.
6) comprised of the plurality of dielectric and conductive layers
is applied to the side of the substrate opposite to the
anti-reflective coating. If no anti-reflective coating is applied,
the film 27 or 27' can be applied to either surface. Preferably,
the film 27 or 27' and its individual layers are applied by
sputtering as previously described. Although the preferred
embodiment shows the film 27 or 27' being applied directly to the
substrate surface, one or more intermediate layers of a further
material may also be applied to the substrate prior to application
of the film. Next, for the embodiment of FIG. 2, the busbar 32 is
applied to the entire peripheral edge portion of the film coated
substrate 24. Preferably the legs of the busbar are applied in
stages with the leg 34 first applied to the outer edges of the film
27 or 27' and the leg 35 applied to the outer peripheral edge of
the substrate 24. In the embodiment of FIG. 4, the busbar is
applied only in the form of the leg 34 and the tape or member 38 is
then applied to the substrate.
[0068] The film coated substrate is then preferably laminated to a
second substrate 22 which may also be provided with an AR coating,
either before or after lamination. The lamination is preferably
accomplished by positioning the adhesive sheet 30 between the side
of the substrate 22 opposite the AR coating 25 and the side of the
substrate 24 carrying the film 27 or 27'. The entire lamination
lay-up is then placed in an autoclave under appropriately elevated
heat and pressure conditions to laminate the lay-up together. In
the preferred procedure, the lamination lay-up is exposed to a
temperature of approximately 220.degree. F. and a pressure of
approximately 40 p.s.i. for about three hours. Alternatively, the
film coated substrate 24 can be applied to a plastic film such as
PET film or directly to the front face of a display device.
[0069] When the lamination is complete, the conductive member or
tape 38 is applied to the outer peripheral edge portions of the
filter 15 as illustrated in FIG. 2. The grounding clip or other
grounding means 19 is then applied to the member 38 as shown.
[0070] In the embodiment of FIG. 5, the EMI/IR filter is provided
by the layers 28 and 29. Specifically, a conductive EMI shielding
material layer 28 is applied to the panel or inner side of the
substrate 22 to reduce and limit EMI emissions and an infrared
absorbing layer 29 is laminated between the substrates 22 and 24
via the adhesive or lamination layers 33 and 31.
[0071] In the embodiment of FIG. 5, the electrically conductive
material layer 28 is applied to the panel side of the substrate 22
as shown. Although this layer 28 can be constructed of a variety of
materials, it must preferably include an electrically conductive
component or layer which provides sufficient electrical
conductivity, and thus sufficiently low electrical resistance,
while still maintaining acceptable visible light transmission.
Preferably, the conductive layer 28 exhibits sheet resistance of
less than 5 ohms per square and more preferably less than 1.5 ohms
per square. The layer 28 provides electromagnetic interference (EMD
shielding and assists in reducing EMI emissions to levels which
comply with consumer safety and other regulations and standards.
The layer 28 also provides an IR shielding function as well to
assist in reducing infrared emissions to acceptable levels.
Preferably the conductive layer 28 extends over the entire panel
side of the substrate 22. This layer 28 can, if desired, comprise a
single layer of an electrically conductive material such as silver
or indium tin oxide (ITO) and can also comprise additional layers
and materials such as other metals and materials which may be
conductive as well as dielectrics and materials which may not be
conductive. Such additional layers and materials can be provided to
assist in infrared shielding and reduction of reflection as well as
to provide contrast enhancement to the filter. This may be
accomplished by introducing color or tint into the coating.
[0072] The layer 28 in the present invention can be applied to the
substrate 22 by any known means. Preferably, however, the layer or
layers which form the electrically conductive material layer 28 is
applied by sputtering or reactive sputtering one or more metals
such as silver, gold or copper. The thickness of the layer 28
should preferably be in the range of less than 2500 .ANG. and most
preferably in the range of 2000-2500 .ANG..
[0073] The layer 29 comprises an infrared absorbing film which is a
separate, free-standing film and is sandwiched between, and
laminated to, the substrates 22 an 24 by the lamination material 33
and 31. The infrared shielding film 29 can comprise any film which
functions to provide near infrared absorbing capability such as
dyed polyethylene terapthalate (PET) or dyed polyurethane. In the
preferred embodiment, the film thickness ranges from 5-10 mils and
further includes contrast enhancement capability. The film 29 is
effective to reduce the infrared transmission in the 800 nm-1000 nm
range to a level preferably less than 20%. At these reduced levels,
interference with infrared remote control transmitters either for
the panel display in question or other remote control devices is
eliminated.
[0074] The lamination materials 33 and 31 in the preferred
embodiment comprise sheets of polyurethane adhesive. As shown, one
adhesive sheet 33 is positioned between the film 29 and the coating
28, while the other polyurethane adhesive sheet 31 is positioned
between the film 29 and the view side of the substrate 24. Many
adhesives or laminations such as PVB, acrylic and/or others can, of
course, be used to laminate the film 29 between the coated
substrates 22 and 24; however, the particular adhesive or
lamination materials selected should be capable of exhibiting
transparent properties upon completion of the lamination. The
adhesives may also be tinted or otherwise be provided with IR
absorbing or shielding capabilities. Preferably, the layers 29, 33
and 31 are positioned between the substrates 22 and 24 as shown and
then are placed in an autoclave under appropriate heat and pressure
conditions for approximately four hours to laminate the layers
together.
[0075] Alternative methods of applying the layer 29 may also be
utilized. For example, a recently introduced technique involves
positioning the coated substrates 22 and 24 in spaced relationship
and sealing the edges so as to form a cavity for accommodating an
infrared shielding or absorbing material between the spaced
substrates. A liquid or flowable material such as an acrylic into
which infrared absorbing material is incorporated is then
introduced into the space between the substrates so that it flows
over the entire substrate surfaces. This material is then allowed
to cure via ultraviolet exposure or otherwise to produce the
infrared absorbing layer.
[0076] The method aspect of the present invention relating to the
embodiment of FIG. 5, including the method of making the plasma
display panel filter, can be understood as follows. First, a pair
of transparent substrates such as glass or plastic are provided.
One of these substrates will ultimately form the view side
substrate 22 positioned on the view side of the filter, while the
other substrate will ultimately form the panel side substrate 24.
Both of these substrates 22 and 24 are provided with
anti-reflective coatings 25 and 26, respectively by sputtering.
[0077] Following this, the EMI shielding layer in the form of the
electrically conductive coating 28 is also applied to the panel
side of the substrate 22. Preferably, this coating is also applied
by sputtering. Next, the busbar 32 is applied to the entire
peripheral edge portion of the substrate 22. Preferably the legs of
the busbar are applied in stages with the leg 34 first applied to
the outer edges of the coating 28 and the leg 35 applied to the
outer peripheral edge of the substrate 22.
[0078] The infrared film 29 is then laminated between the coated
substrates 22 and 24 by positioning one adhesive sheet 33 between
the film 29 and the conductive coating 28 of the substrate 22 and a
second adhesive lamination sheet 31 between the other side of the
film 29 and the view side of the substrate 24. The entire
lamination lay-up is then placed in an autoclave under
appropriately elevated heat and pressure conditions to laminate the
lay-up together. In one procedure, the lamination lay-up is exposed
to a temperature of approximately 220.degree. F. and a pressure of
approximately 150 p.s.i. for about four hours.
[0079] When the lamination is complete, the conductive member 38,
comprised of the legs 39, 40 and 41, is applied to the outer
peripheral edge portions of the filter 15 as illustrated in FIG. 5.
The grounding clip 19 is then applied to the member 38 as
shown.
[0080] With respect to the embodiment of FIG. 7, the optical
shielding film 70 is first applied to one side of substrate 69. If
desired, an AR coating 71 can also be applied to the other side of
the substrate 69. If applied, the coating 71 is preferably
comprised of a plurality of individual layers which together
provide the substrate 69 with anti-reflective properties. Next, the
substrate 69 is bonded to the front face of the display substrate
68 by an adhesive sheet 72 or some other bonding technique.
Finally, electrical and/or grounding connections are made in a
manner similar to that described above with respect to the other
embodiments.
[0081] With respect to the embodiment of FIG. 8, the method
involves applying an optical shielding film 70 to one side of a
first substrate 69. If desired, an AR coating 71 can be applied to
the other side of the substrate 69. Next, a second substrate 73 in
the form of a thin plastic film such as PET or other optically
clear film is laminated to the first substrate 69 with the optical
film 70 positioned therebetween. Next, the entire filter structure
is mounted in front of a display 65 as shown in FIG. 1, or
otherwise directly bonded to the front surface of the display
substrate 68 by an adhesive sheet 72 or some other bonding
technique. If an AR coating 74 is to be applied to the film
substrate 73, it is preferable to first apply an abrasion resistant
coating.
[0082] Although the description of the preferred embodiment and
method have been quite specific, it is contemplated that various
modifications may be made without deviating from the--spirit of the
present invention. For example, although the preferred embodiment
has been described with respect to a plasma display device, certain
features have broader applications. For example, the additional
protective layer for the silver or other conductive material may
have applications for other than display devices. In general, any
application where oxidation or other deterioration of the
conductive layer is a concern, can use this feature of the
invention. Accordingly, it is intended that the scope of the
present invention be dictated by the appended claims rather than by
the description of the preferred embodiment and method.
* * * * *