U.S. patent application number 11/276442 was filed with the patent office on 2007-08-30 for optical display with fluted optical plate.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Susan E. Anderson, Mark D. Gehlsen, James T. Richard.
Application Number | 20070203267 11/276442 |
Document ID | / |
Family ID | 38444883 |
Filed Date | 2007-08-30 |
United States Patent
Application |
20070203267 |
Kind Code |
A1 |
Richard; James T. ; et
al. |
August 30, 2007 |
OPTICAL DISPLAY WITH FLUTED OPTICAL PLATE
Abstract
A display system has a light source, a display panel and an
arrangement of light management layers disposed between the light
source and the display panel. The light source illuminates the
display panel through the arrangement of light management layers.
The arrangement of light management layers includes a fluted plate
that has a front layer facing the display panel, a back layer
facing the light source, and a plurality of connecting members
connecting the front and back layers. In some embodiments the
fluted plate includes a first light management layer, a cross
member substantially parallel to, and spaced apart from, the first
light management layer, and an arrangement of first connecting
members connecting the cross member and the first light management
layer.
Inventors: |
Richard; James T.; (Lake
Elmo, MN) ; Gehlsen; Mark D.; (Eagan, MN) ;
Anderson; Susan E.; (Woodbury, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
38444883 |
Appl. No.: |
11/276442 |
Filed: |
February 28, 2006 |
Current U.S.
Class: |
524/47 |
Current CPC
Class: |
G02F 1/133606
20130101 |
Class at
Publication: |
524/047 |
International
Class: |
D21H 19/54 20060101
D21H019/54 |
Claims
1. A display system, comprising: a light source; a display panel;
and an arrangement of light management layers disposed between the
light source and the display panel so that the light source
illuminates the display panel through the arrangement of light
management layers, the arrangement of light management layers
comprising a fluted plate, the fluted plate comprising a front
layer facing the display panel, a back layer facing the light
source and a plurality of connecting members connecting the front
and back layers.
2. A system as recited in claim 1, wherein the arrangement of light
management layers comprises at least one of a reflective polarizer
layer, a diffuser layer, and a prismatic brightness enhancement
layer.
3. A system as recited in claim 1, wherein at least a portion of
the fluted plate is formed of a diffusing material.
4. A system as recited in claim 1, further comprising at least one
light management layer attached to the fluted plate.
5. A system as recited in claim 4, wherein the at least one light
management layer comprises at least one of a diffuser layer, a
reflecting polarizer layer, and a prismatic brightness enhancing
layer.
6. A system as recited in claim 1, wherein at least one of the
front and back layers comprises a first light management layer.
7. A system as recited in claim 6, wherein the first light
management layer comprises at least one of a prismatic brightness
enhancing layer, a diffuser layer, and a reflective polarizer
layer.
8. A system as recited in claim 6, wherein the connecting members
comprise first and second connecting members, the first connecting
members being attached to a cross member and connecting to the
front layer, the second connecting members being attached to the
cross member and connecting to the back layer, the first light
management layer being attached to one of the first connecting
members and the second connecting members, and further comprising a
second light management layer connected to the other of the first
connecting members and the second connecting members.
9. A system as recited in claim 1, further comprising a controller
coupled to control an image displayed by the display panel.
10. A system as recited in claim 1, wherein the display panel
comprises a liquid crystal display (LCD).
11. A system as recited in claim 1, further comprising a coolant
circulator for forcing a cooling medium through flutes of the
fluted plate.
12. A system as recited in claim 11, wherein the coolant circulator
is a fan and the coolant is air.
13. A system as recited in claim 1, wherein flutes of the fluted
plate are arranged vertically to permit natural convective passage
of air therethrough.
14. A system as recited in claim 1, wherein the connecting members
comprise first connecting members attached to the front layer and
second connecting members attached to the back layer, the first
connecting members interlocking with the second connecting
members.
15. A light management unit for use between a display panel and a
backlight, the light management unit having a display panel side
for orienting towards the display panel and a backlight side for
orienting towards the backlight, the unit comprising: a fluted
layer comprising a first light management layer, a cross member
substantially parallel to, and spaced apart from, the first light
management layer and an arrangement of first connecting members
integral with the cross member, the first connecting members
attached to the first light management layer.
16. A unit as recited in claim 15, wherein the first light
management layer comprises one of a diffuser layer, a brightness
enhancing layer, and a reflective polarizer layer.
17. A unit as recited in claim 15, further comprising a second
light management layer attached to the fluted layer.
18. A unit as recited in claim 17, wherein an arrangement of second
connecting members connects the second light management layer and
the cross member.
19. A unit as recited in claim 17, wherein the second light
management layer is connected to the first light management layer
so that the first light management layer lies between the cross
member and the second light management layer.
20. A unit as recited in claim 15, wherein the first connecting
members are disposed on a display panel side of the cross member
and extending from the cross member, the unit further comprising
second connecting members disposed on a backlight side of the cross
member, the second connecting members extending from the cross
member, and further comprising a second light management layer
attached to the second connecting members.
Description
FIELD OF THE INVENTION
[0001] The invention relates to optical displays, and more
particularly to display systems that are illuminated from behind,
such as may be used in LCD monitors and LCD televisions.
BACKGROUND
[0002] Liquid crystal displays (LCDs) are optical displays used in
devices such as laptop computers, hand-held calculators, digital
watches and televisions. Some LCDs include a light source that is
located to the side of the display, with a light guide positioned
to guide the light from the light source to the back of the LCD
panel. Other LCDs, for example some LCD monitors and LCD
televisions (LCD-TVs), are directly illuminated using a number of
light sources positioned behind the LCD panel. This arrangement is
increasingly common with larger displays, because the light power
requirements, to achieve a certain level of display brightness,
increase with the square of the display size, whereas the space
available for locating light sources along the side of the display
only increases linearly with display size. In addition, some LCD
applications, such as LCD-TVs, require that the display be bright
enough to be viewed from a greater distance than other
applications, and the viewing angle requirements for LCD-TVs are
generally different from those for LCD monitors and hand-held
devices.
[0003] Some LCD monitors and most LCD-TVs are commonly illuminated
from behind by a number of cold cathode fluorescent lamps (CCFLs).
These light sources are linear and stretch across the full width of
the display, with the result that the back of the display is
illuminated by a series of bright stripes separated by darker
regions. Such an illumination profile is not desirable, and so a
diffuser plate is used to smooth the illumination profile at the
back of the LCD device.
[0004] Currently, LCD-TV diffuser plates employ a polymeric matrix
of polymethyl methacrylate (PMMA), poly(carbonate), cycloolefins,
random copolymers of polymethylmethacrylate or polystyrene,
combined with a variety of dispersed phases that include glass,
polystyrene beads, and CaCO.sub.3 particles. These plates often
deform or warp after exposure to the elevated temperatures of the
lamps. In addition, some diffusion plates are provided with a
diffusion characteristic that varies spatially across its width, in
an attempt to make the illumination profile at the back of the LCD
panel more uniform. Such non-uniform diffusers are sometimes
referred to as printed pattern diffusers. They are expensive to
manufacture, and increase manufacturing costs, since the diffusing
pattern must be registered to the illumination source at the time
of assembly. In addition, the diffusion plates require customized
extrusion compounding to distribute the diffusing particles
uniformly throughout the polymer matrix, which further increases
costs.
[0005] Furthermore, to prevent warping or other types of physical
distortions, the diffuser plate has to be of a minimum thickness
relative to its height and width. As the size of the display
increases, this means that the diffuser plate also becomes
increasingly thick, thus increasing the weight of the display.
SUMMARY OF THE INVENTION
[0006] One embodiment of the invention is directed to a display
system that has a light source, a display panel, and an arrangement
of light management layers disposed between the light source and
the display panel. The light source illuminates the display panel
through the arrangement of light management layers. The arrangement
of light management layers includes a fluted plate that has a front
layer facing the display panel, a back layer facing the light
source, and a plurality of connecting members connecting the front
and back layers.
[0007] Another embodiment of the invention is directed to a light
management unit that includes a fluted layer. The fluted layer has
a first light management layer, a cross member substantially
parallel to, and spaced apart from, the first light management
layer and an arrangement of first connecting members connecting the
cross member to the first light management layer.
[0008] These and other aspects of the present application will be
apparent from the detailed description below. In no event, however,
should the above summaries be construed as limitations on the
claimed subject matter, which subject matter is defined solely by
the attached claims, as may be amended during prosecution.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention may be more completely understood in
consideration of the following detailed description of various
embodiments of the invention in connection with the accompanying
drawings, in which like reference numerals designate like elements,
and wherein:
[0010] FIG. 1 schematically illustrates a display device that uses
a fluted plate;
[0011] FIG. 2A schematically illustrates a fluted plate;
[0012] FIGS. 2B and 2C schematically illustrate fluted plates with
attached optical films;
[0013] FIG. 3 schematically illustrates a fluted plate having a
spatially variable single pass transmission;
[0014] FIG. 4 schematically illustrates a fluted plate having a
spatially variable refractive index;
[0015] FIGS. 5A and 5B schematically illustrate fluted plates whose
upper and lower layers have respectively spatially varying
thicknesses;
[0016] FIGS. 6A and 6B schematically illustrate fluted plates whose
upper and lower layers have respectively spatially varying
thicknesses;
[0017] FIGS. 7A and 7B schematically illustrate fluted plates
having flutes of different cross-sectional shape;
[0018] FIG. 8A schematically illustrates a top view of a fluted
plate showing flutes arranged parallel;
[0019] FIG. 8B schematically illustrates a top view of a fluted
plate showing sets of parallel flutes arranged perpendicularly;
[0020] FIGS. 9 and 10 schematically illustrate fluted plates with
optically useful surface structure;
[0021] FIGS. 11A, 11B, 12A and 12B schematically illustrate various
optical film arrangements that include a fluted plate;
[0022] FIGS. 13A and 13B schematically illustrate the construction
of a fluted plate using a spine attached to an optical film;
[0023] FIGS. 14A and 14B schematically illustrate the construction
of a fluted plate using a double-sided spine attached to optical
films;
[0024] FIGS. 15 and 16 schematically illustrate different film
arrangements built around a double-sided spine;
[0025] FIG. 17 schematically illustrates the construction of a
fluted plate using first and second layers having interconnecting
members; and
[0026] FIG. 18 schematically illustrates a display system having a
heat transfer medium flow through flutes of the fluted plate.
[0027] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to the particular embodiments described. On the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims.
DETAILED DESCRIPTION
[0028] The present invention is applicable to liquid crystal
displays (LCDs, or LC displays), and is applicable to LCDs that are
directly illuminated from behind and to LCDs that are edge lit, for
example, LCDs used in LCD monitors and LCD televisions
(LCD-TVs).
[0029] The diffuser plates currently used in LCD-TVs are based on a
polymeric matrix, for example polymethyl methacrylate (PMMA),
polycarbonate (PC), or cyclo-olefins, formed as a rigid sheet. The
sheet contains diffusing particles, for example, organic particles,
inorganic particles or voids (bubbles). These plates often deform
or warp after exposure to the elevated temperatures of the light
sources used to illuminate the display. These plates also are more
expensive to manufacture and to assemble in the final display
device.
[0030] The present application discloses directly illuminated LCD
devices that have an arrangement of light management layers
positioned between the LCD panel itself and the light source. The
arrangement of light management layers can include a diffuser layer
whose transmission and haze levels are designed to provide a
direct-lit LC display whose brightness is relatively uniform across
the display.
[0031] A schematic exploded view of an exemplary direct-lit LC
display device 100 is presented in FIG. 1. Such a display device
100 may be used, for example, in an LCD monitor or LCD-TV. The
display device 100 is based on the use of an LC panel 102, which
typically comprises a layer of LC 104 disposed between panel plates
106. The plates 106 are often formed of glass, and may include
electrode structures and alignment layers on their inner surfaces
for controlling the orientation of the liquid crystals in the LC
layer 104. The electrode structures are commonly arranged so as to
define LC panel pixels, areas of the LC layer where the orientation
of the liquid crystals can be controlled independently of adjacent
areas. A color filter may also be included with one or more of the
plates 106 for imposing color on the image displayed.
[0032] An upper absorbing polarizer 108 is positioned above the LC
layer 104 and a lower absorbing polarizer 110 is positioned below
the LC layer 104. In the illustrated embodiment, the upper and
lower absorbing polarizers are located outside the LC panel 102.
The absorbing polarizers 108, 110 and the LC panel 102 in
combination control the transmission of light from the backlight
112 through the display 100 to the viewer. In some LC displays, the
absorbing polarizers 108, 110 may be arranged with their
transmission axes perpendicular. When a pixel of the LC layer 104
is not activated, it may not change the polarization of light
passing therethrough. Accordingly, light that passes through the
lower absorbing polarizer 110 is absorbed by the upper absorbing
polarizer 108, when the absorbing polarizers 108, 110 are aligned
perpendicularly. When the pixel is activated, on the other, hand,
the polarization of the light passing therethrough is rotated, so
that at least some of the light that is transmitted through the
lower absorbing polarizer 110 is also transmitted through the upper
absorbing polarizer 108. Selective activation of the different
pixels of the LC layer 104, for example by a controller 114,
results in the light passing out of the display at certain desired
locations, thus forming an image seen by the viewer. The controller
may include, for example, a computer or a television controller
that receives and displays television images. One or more optional
layers 109 may be provided over the upper absorbing polarizer 108,
for example to provide mechanical and/or environmental protection
to the display surface. In one exemplary embodiment, the layer 109
may include a hardcoat over the absorbing polarizer 108.
[0033] It will be appreciated that some type of LC displays may
operate in a manner different from that described above. For
example, the absorbing polarizers may be aligned parallel and the
LC panel may rotate the polarization of the light when in an
unactivated state. Regardless, the basic structure of such displays
remains similar to that described above.
[0034] The backlight 112 includes a number of light sources 116
that generate the light that illuminates the LC panel 102. Linear,
cold cathode, fluorescent tubes, that extend across the display
device 100, are commonly used as the light sources 116 in the
display device 100. Other types of light sources may be used,
however, such as filament or arc lamps, light emitting diodes
(LEDs), lasers, flat fluorescent panels or external fluorescent
lamps. This list of light sources is not intended to be limiting or
exhaustive, but only exemplary.
[0035] The backlight 112 may also include a reflector 118 for
reflecting light propagating downwards from the light sources 116,
in a direction away from the LC panel 102. The reflector 118 may
also be useful for recycling light within the display device 100,
as is explained below. The reflector 118 may be a specular
reflector or may be a diffuse reflector. One example of a specular
reflector that may be used as the reflector 118 is Vikuiti.TM.
Enhanced Specular Reflection (ESR) film available from 3M Company,
St. Paul, Minn. Examples of suitable diffuse reflectors include
polymers, such as polyethylene terephthalate (PET), polycarbonate
(PC), polypropylene, polystyrene and the like, loaded with
diffusely reflective particles, such as titanium dioxide, barium
sulphate, calcium carbonate and the like. Other examples of diffuse
reflectors, including microporous materials and fibril-containing
materials, are discussed in U.S. Pat. No. 6,780,355 (Kretman et
al.), incorporated herein by reference.
[0036] An arrangement 120 of light management layers is positioned
between the backlight 112 and the LC panel 102. The light
management layers affect the light propagating from backlight 112
so as to improve the operation of the display device 100. For
example, an arrangement 120 of light management layers may include
a diffuser layer 122. The diffuser layer 122 is used to diffuse the
light received from the light sources, which results in an increase
in the uniformity of the illumination light incident on the LC
panel 102. Consequently, this results in an image perceived by the
viewer that is more uniformly bright. The diffuser layer 122 may
include bulk diffusing particles distributed throughout the layer,
or may include one or more surface diffusing structures, or a
combination thereof.
[0037] The arrangement of light management layers 120 may also
include a gain diffuser, a layer that diffuses light generally in
the viewing direction. In some embodiments a gain diffuser contains
transparent particles that protrude from the surface of the film,
thus providing optical power to light that passes through the
particles. This reduces the divergence of the light, resulting in
an increase in on-axis brightness, sometimes refered to as gain.
Some types of gain diffusers are described in greater detail in
U.S. Pat. No. 6,572,961 (Koyama et al.), incorporated herein by
reference.
[0038] The arrangement 120 of light management layers may also
include a reflective polarizer 124. The light sources 116 typically
produce unpolarized light but the lower absorbing polarizer 110
only transmits a single polarization state, and so about half of
the light generated by the light sources 116 is not transmitted
through to the LC layer 104. The reflective polarizer 124, however,
may be used to reflect the light that would otherwise be absorbed
in the lower absorbing polarizer, and so this light may be recycled
by reflection between the reflective polarizer 124 and the
reflector 118. At least some of the light reflected by the
reflective polarizer 124 may be depolarized, and subsequently
returned to the reflective polarizer 124 in a polarization state
that is transmitted through the reflective polarizer 124 and the
lower absorbing polarizer 110 to the LC layer 104. In this manner,
the reflective polarizer 124 may be used to increase the fraction
of light emitted by the light sources 116 that reaches the LC layer
104, and so the image produced by the display device 100 is
brighter.
[0039] Any suitable type of reflective polarizer may be used, for
example, multilayer optical film (MOF) reflective polarizers;
diffusely reflective polarizing film (DRPF), such as
continuous/disperse phase polarizers, wire grid reflective
polarizers or cholesteric reflective polarizers.
[0040] Both the MOF and continuous/disperse phase reflective
polarizers rely on the difference in refractive index between at
least two materials, usually polymeric materials, to selectively
reflect light of one polarization state while transmitting light in
an orthogonal polarization state. Some examples of MOF reflective
polarizers are described in co-owned U.S. Pat. No. 5,882,774 (Jonza
et al.), incorporated herein by reference. Commercially available
examples of MOF reflective polarizers include Vikuiti.TM. DBEF-D200
and DBEF-D440 multilayer reflective polarizers that include
diffusive surfaces, available from 3M Company, St. Paul, Minn.
[0041] Examples of suitable DRPF include continuous/disperse phase
reflective polarizers as described in co-owned U.S. Pat. No.
5,825,543 (Ouderkirk et al.), incorporated herein by reference, and
diffusely reflecting multilayer polarizers as described in e.g.
co-owned U.S. Pat. No. 5,867,316 (Carlson et al.), also
incorporated herein by reference. Other suitable types of DRPF are
described in U.S. Pat. No. 5,751,388 (Larson).
[0042] Some examples of suitable wire grid polarizers include those
described in U.S. Pat. No. 6,122,103 (Perkins et al.). Wire grid
polarizers are commercially available from, inter alia, Moxtek
Inc., Orem, Utah.
[0043] Some examples of suitable cholesteric polarizers include
those described in, for example, U.S. Pat. No. 5,793,456 (Broer et
al.), and U.S. Pat. No. 6,917,399 (Pekorny et al.). Cholesteric
polarizers are often provided along with a quarter wave retarding
layer on the output side, so that the light transmitted through the
cholesteric polarizer is converted to linear polarization.
[0044] The arrangement 120 of light management layers may also
include a brightness enhancing layer 128. A brightness enhancing
layer is one that includes a surface structure that redirects
off-axis light in a direction closer to the axis of the display.
This increases the amount of light propagating on-axis through the
LC layer 104, thus increasing the brightness of the image seen by
the viewer. One example is a prismatic brightness enhancing layer,
which has a number of prismatic ridges that redirect the
illumination light, through refraction and reflection. Examples of
prismatic brightness enhancing layers that may be used in the
display device include the Vikuiti.TM. BEFII and BEFIII family of
prismatic films available from 3M Company, St. Paul, Minn.,
including BEFII 90/24, BEFII 90/50, BEFIIIM 90/50, and BEFIIIT.
[0045] The arrangement 120 of light management layers may also
include a support layer 130, which may be used for providing
support to the other light management layers. In some arrangements,
one of the other light management layers may be integrated with the
support layer 130. For example, some existing televisions include
diffusing particles in a relatively thick (2-3 mm), rigid polymer
sheet, thus combining the functions of providing support and
optical diffusion into a single layer.
[0046] Support layer 130 advantageously includes a fluted plate,
which is a plate that includes flutes, or spaces, between the two
surfaces of the plate. A cross-sectional view of an exemplary
fluted plate 200 is schematically illustrated in FIG. 2A. The
fluted plate 200 includes a first layer 202 and a second layer 204,
with connecting members 206 connecting the first and second layers
202, 204. The open spaces 208 surrounded by the connecting members
206 and the first and second layers 202, 204 may be considered to
be flutes.
[0047] The fluted plate 200 is self-supporting and may, in some
exemplary embodiments, be used to provide support to other light
management layers. The fluted plate 200 may be made of any suitable
material, for example organic materials such as polymers. For
example, the fluted plate 200 may be formed using any suitable
method, for example extrusion, molding, and the like.
[0048] The thickness of the fluted plate 200 and the size of the
flutes 208 may be selected depending on the particular application.
For example, the fluted plate may be a few mm thick, for example in
the range of approximately 1 mm-4 mm, or may be thicker. The fluted
plate 200 may also be thinner, for example having a thickness of
approximately 50 .mu.m or more. Also, the center-to-center spacing
of the flutes 208 may be selected to be any suitable value. For
example, the spacing may be in the range of about 1-4 mm, or
greater. In other embodiments, the flute spacing may be less, for
example down to around 50 .mu.m or less.
[0049] The use of a fluted plate may reduce the weight of a display
system such as a television. For example, in a 40 inch LCD-TV, a
conventional solid diffuser plate typically weighs about 2.3 lbs (1
kg), and accounts for about 5% of the overall weight of the
television. A fluted plate weighs only a fraction of a comparable
solid plate, commonly about 25%, and so a fluted plate would
provide only about 1% of the overall weight of the television.
[0050] In addition, the fluted plate has the mechanical advantages
of an "I-beam" with upper and lower plates separated by an air
space and a connecting member. Accordingly, the fluted plate
provides high resistance to warping and curling under the high
illumination conditions typical in many display systems.
[0051] The directions of the flutes may be oriented in a desired
direction with respect to the light sources. For example, if the
light sources are elongated, as with most fluorescent lamps, the
flutes may be oriented to be parallel to the light sources, or may
be oriented to be not parallel. A specific orientation between the
light sources and the flutes, for a given design of light source
and fluted plate, may provide improved illumination uniformity and
also improved thermal response, e.g. warp, curl, etc.
[0052] Suitable polymer materials for the fluted plate may be
amorphous or semi-crystalline, and may include homopolymer,
copolymer or blends thereof. Polymer foams may also be used.
Example polymer materials include, but are not limited to:
amorphous polymers such as poly(carbonate) (PC); poly(styrene)
(PS); acrylates, for example acrylic sheets as supplied under the
ACRYLITE.RTM. brand by Cyro Industries, Rockaway, N.J.; acrylic
copolymers such as isooctyl acrylate/acrylic acid;
poly(methylmethacrylate) (PMMA); PMMA copolymers; cycloolefins;
cylcoolefin copolymers; acrylonitrile butadiene styrene (ABS);
styrene acrylonitrile copolymers (SAN); epoxies;
poly(vinylcyclohexane); PMMA/poly(vinylfluoride) blends; atactic
poly(propylene); poly(phenylene oxide) alloys; styrenic block
copolymers; polyimide; polysulfone; poly(vinyl chloride);
poly(dimethyl siloxane) (PDMS); polyurethanes;
poly(carbonate)/aliphatic PET blends; and semicrystalline polymers
such as poly(ethylene) (PE); poly(propylene) (PP); olefin
copolymers, such as PP/PE copolymers; poly(ethylene terephthalate)
(PET); poly(ethylene naphthalate)(PEN); polyamide; ionomers; vinyl
acetate/polyethylene copolymers; cellulose acetate; cellulose
acetate butyrate; fluoropolymers; poly(styrene)-poly(ethylene)
copolymers; PET and PEN copolymers; and blends that include one or
more of the polymers listed.
[0053] Some exemplary embodiments of the fluted plate 200 include
polymer materials that are substantially transparent to light. Some
other exemplary embodiments may include diffusive material in the
fluted plate 200 using, for example, a polymer matrix containing
diffusing particles. The polymer matrix may be any suitable type of
polymer that is substantially transparent to visible light, for
example any of the polymer materials listed above.
[0054] The diffusing particles may be any type of particle useful
for diffusing light, for example transparent particles whose
refractive index is different from the surrounding polymer matrix,
diffusely reflective particles, or voids or bubbles in the matrix.
Examples of suitable transparent particles include solid or hollow
inorganic particles, for example glass beads or glass shells, solid
or hollow polymeric particles, for example solid polymeric spheres
or polymeric hollow shells. Examples of suitable diffusely
reflecting particles include particles or beads of PS, PMMA,
polysiloxane, titanium dioxide (TiO.sub.2), calcium carbonate
(CaCO.sub.3), barium sulphate (BaSO.sub.4), magnesium sulphate
(MgSO.sub.4) and the like. In addition, voids in the polymer matrix
may be used for diffusing the light. Such voids may be filled with
a gas, for example air or carbon dioxide.
[0055] Other additives may be provided to the fluted plate. For
example, the fluted plate may include antioxidants, such as Irganox
1010 available from Ciba Specialty Chemicals, Tarrytown, N.Y. Other
examples of additives may include one or more of the following: an
anti-weathering agent, UV absorbers, a hindered amine light
stabilizer, a dispersant, a lubricant, an anti-static agent, a
pigment or dye, a nucleating agent, a flame retardant, a blowing
agent, or nanoparticles.
[0056] The entire fluted plate 200 may be formed from diffusing
material or selected portions of the fluted plate 200 may be made
of diffusing material. For example, the first layer 202, or the
second layer 204, may be formed of diffusing material while the
remainder of the plate 200 is formed of some other material. In
other embodiments, both the first and second layers 202, 204 may be
formed of diffusing material. When a fluted plate 200 formed of a
diffusive material is used in a display system, such as is
exemplified in FIG. 1, the fluted plate provides mechanical support
as well as providing a diffusing function, so that a separate
diffuser layer may be omitted.
[0057] In other exemplary embodiments, the fluted plate 200 may be
provided with a diffuser layer 210, for example as schematically
illustrated in FIG. 2B. The diffuser layer 210 may be attached to
either the first layer 202 or the second layer 204. In addition, in
some embodiments, there may be diffuser layers attached to each of
the first and second layers 202, 204. The diffuser layer 210 may be
attached to the fluted plate 200 using an adhesive layer (not
shown) or, in other embodiments, the diffuser layer 210 may itself
be an adhesive layer attached to the fluted plate 200.
[0058] Commercially available materials suitable for use in a
diffusing layer include 3M.TM. Scotchcal.TM. Diffuser Film, type
3635-70 and 3635-30, and 3MT.TM. Scotchcal.TM. ElectroCut.TM.
Graphic Film, type 7725-314, available from 3M Company, St. Paul,
Minn. Other commercially available diffusers include acrylic foam
tapes, such as 3M.TM. VHB.TM. Acrylic Foam Tape No. 4920.
[0059] In some exemplary embodiments, the diffuser layer 210 has a
diffusion characteristic that is uniform across its width, in other
words the amount of diffusion experienced by light is the same for
points across the width of the diffuser layer 210.
[0060] The diffuser layer 210 may optionally be patterned, or
supplemented with or replaced by an optional patterned diffuser
210a. The optional patterned diffuser 210a may include, for
example, a patterned diffusing surface or a printed layer of
diffuser, such as particles of titanium dioxide (TiO.sub.2). The
patterned diffuser 210a may lie on the diffuser layer 210, between
the diffuser layer 210 and the fluted plate 200. In addition, a
patterned diffuser may be applied to a fluted plate 200 that is
formed, at least partially, of diffusing material.
[0061] The fluted plate 200 may be provided with protection from
ultraviolet (UV) light, for example by including UV absorbing
material or material that is resistant to the effects of UV light.
Suitable UV absorbing compounds are available commercially,
including, e.g., Cyasorb.TM. UV-1164, available from Cytec
Technology Corporation of Wilmington, Del., and Tinuvin.TM. 1577,
available from Ciba Specialty Chemicals of Tarrytown, N.Y. The
fluted plate 200 may also include brightness enhancing phosphors
that convert UV light into visible light.
[0062] Other materials may be included into the layers of the
fluted plate 200 to reduce the adverse effects of UV light. One
example of such a material is a hindered amine light stabilizing
composition (HALS). Generally, the most useful HALS are those
derived from a tetramethyl piperidine, and those that can be
considered polymeric tertiary amines. Suitable HALS compositions
are available commercially, for example, under the "Tinuvin"
tradename from Ciba Specialty Chemicals Corporation of Tarrytown,
N.Y. One such useful HALS composition is Tinuvin 622. UV absorbing
materials and HALS are further described in U.S. Pat. No. 6,613,819
(Johnson et al.), incorporated herein by reference.
[0063] In other embodiments, the fluted plate 200 may have two
diffuser layers 210, 212 attached respectively to the first and
second layers 202, 204 of the fluted plate 200. The diffuser layers
210, 212 may each be applied directly to the respective layer 202,
204 of the fluted plate 200, as is illustrated in FIG. 2C, or may
be attached using a layer of adhesive (not shown).
[0064] The two diffuser layers 210, 212 may have the same diffusion
properties, or may have different diffusing properties. For
example, the diffuser layer 210 may possess a different
transmission or haze level from the second diffuser layer 212, or
may be of a different thickness.
[0065] The optical properties of the fluted plate may be uniform
across its width, but this is not necessary. In some exemplary
embodiments, for example the fluted plate 300 shown in FIG. 3, the
amount of diffusion imparted by the fluted plate 300 itself may
spatially vary across the width of the plate 300. This may be
achieved, for example, by introducing bulk diffusing particles
nonuniformly across an extruded fluted plate. The graph above the
fluted plate shows a spatial variation in the single pass
transmission, T. The single pass transmission is the fraction of
incident light that is transmitted through the fluted plate 300:
higher levels of transmission indicate less diffusion and lower
levels of transmission indicate more diffusion. In the illustrated
example, the periodicity in the spatial variation of the
transmission is equal to the separation distance between the
connecting members 306. Such a spatial variation in the diffusion
may be useful for reducing nonuniformities in the brightness of the
transmitted light due to the connecting members 306. There is no
requirement, however, that the variation in T have this
periodicity, and the variation in T may have some other
periodicity, or need not be periodic.
[0066] Another optical characteristic of the fluted plate that may
vary across the fluted plate 400 is the refractive index of one or
both of the first and second layers 402, 404, as is schematically
illustrated in FIG. 4. Such a variation may be achieved, for
example, by introducing a material of a different refractive index
nonuniformly across an extruded fluted plate. The graph above the
fluted plate 400 shows a spatial variation in the refractive index.
In the illustrated example, the periodicity in the spatial
variation of the refractive index is equal to the separation
distance between the connecting members 406. Such a spatial
variation in the diffusion may be useful for reducing
nonuniformities in the brightness of the transmitted light due to
the connecting members 406. There is no requirement, however, that
the variation in the refractive index have this periodicity, and
the variation in the refractive index may have some other
periodicity, or need not be periodic.
[0067] In some exemplary embodiments, one or more of the layers of
the fluted plate may have a thickness that varies across the plate.
For example, in the fluted plate 500 schematically illustrated in
FIG. 5A, the thickness of the first layer 502 varies from being
relatively thin at the edges of the plate 500 to relatively thick
at the center of the plate 500, while the second layer 504
maintains a constant thickness across its width. A variation in the
thickness of the first layer 502 may be used, inter alia, to
provide additional strength to the plate or to provide a variation
in the optical characteristics of the plate. In an illustrative
example, where the first layer 502 contains a uniform concentration
of bulk diffusive particles, a variation in the thickness of the
first layer 502 may be used to provide a spatially varying
diffusive characteristic. In the illustrated example, there is
greater diffusion of the light passing through the center portion
of the plate 500 than at the edge.
[0068] In other embodiments, the second layer 504, or both the
first and second layers 502, 504 may have a variable thickness. For
example, as illustrated in FIG. 5B, a fluted plate 520 has a first
layer 522 of uniform thickness and a second layer 524 of variable
thickness. It will be appreciated that variations in the thickness
of the first and/or the second layer 502, 504, 522, 524 may be
periodic or non-periodic.
[0069] In some embodiments, the surfaces of the material
surrounding the spaces or flutes may be parallel or perpendicular
to the outer surfaces of the fluted plate, but this is not a
necessary condition. In some exemplary embodiments, the surfaces of
the first or second layer defining the flutes may be non-parallel
to the upper surface of the fluted plate. This is schematically
illustrated in FIG. 6A for one particular fluted plate 600, in
which the lower surface 602a of the first layer 602 is non-parallel
to the upper surface 604b of the second layer 604, at least for
some of the flutes 608. Consequently, the cross-sectional shapes of
some of the flutes 608a are not square or rectangular.
[0070] The lower surface of the flute may also be non-parallel to
the lower surface of the second layer. For example, in the
embodiment of FIG. 6B, the thicknesses of both the first and second
layers 622, 624 are not uniform over the width of the plate 620. In
other exemplary embodiments, the first layer may be uniformly thick
while only the second plate has a non-uniform thickness.
[0071] The flutes need not be quadrilateral in shape, and may take
on other shapes. For example, in one exemplary embodiment
schematically illustrated in FIG. 7A, the fluted plate 700 has
triangle-shaped connecting members 706 connecting between the first
and second layers 702, 704. Consequently, the flutes 708 have a
triangle cross-section also. In another exemplary embodiment,
schematically illustrated in FIG. 7B, the fluted plate 720 has
upper and lower layers 722, 724 that have sinusoidal inner surfaces
722a, 724a defining the flutes 728. The connecting members 726 are
formed where the sinusoidal surfaces coincide.
[0072] In another exemplary embodiment, schematically illustrated
in FIG. 7C, the fluted plate 730 has upper and lower layers 732,
734 that are connected together via curved connecting members 736.
In the illustrated embodiment, the curved connecting members 736
alternate between curving in one direction and the opposite
direction, to produce a corrugated effect.
[0073] Many different cross-sections may be used for the connecting
members and the flutes, in addition to those illustrated herein.
Further, the illustrated embodiments are presented for purposes of
illustration only, and there is no intention to limit the scope of
the invention only to those cross-sections illustrated herein.
[0074] In some exemplary embodiments, for example the fluted plate
800 schematically illustrated in FIG. 8A which shows a top view of
the plate 800, the flutes 808 are linear and arranged parallel to
each other. In other exemplary embodiments, for example the fluted
plate 820 schematically illustrated in FIG. 8B, the flutes 828 are
linear but are arranged with a first group of flutes parallel to
each other and a second group of flutes 828 parallel to each other
but perpendicular to the first group. In other embodiments,
different flutes may lie at different angles to each other.
[0075] In some embodiments, the surface of the first or second
layers may be flat, and provided with an anti-reflection coating.
In other embodiments, the first and/or the second layer may provide
some optical function. For example, the outer or inner surface of
the first and/or second layers may be provided with a matte finish.
In another exemplary embodiment, the first and second layers may be
provided with some surface structure. For example, the fluted plate
900 schematically illustrated in FIG. 9 has first and second layers
902, 904 attached together via connecting members 906. In this
particular embodiment, the upper surface 910 of the first layer 902
is provided with a series of prismatic ribs 912. The ribs 912 may
lie parallel to each other, in which case the surface 910 operates
like a prismatic brightness enhancing layer, redirecting some
off-axis light, exemplified by light ray 914, to propagate in a
direction more parallel to the axis 916.
[0076] The fluted plate may have other types of surfaces. In
another example, schematically illustrated in FIG. 10, the first
layer 1002 of the fluted plate 1000 has an upper surface 1010 that
comprises a series of lenses 1012 that provide optical power to the
light 1014 passing through the plate. The lenses 1012 may, but are
not required to, have a width equal to the spacing between the
connecting members 1006. The lenses 1012 may be lenticular lenses,
stretching across the width of the plate 1000. This type of lens is
particularly well suited to a plate manufactured using an extrusion
process. Other methods may be used to form the lenses 1012, such as
molding.
[0077] The fluted plate may be used for supporting other optical
layers in a display. For example, one or more other layers may be
attached to the fluted plate. The following examples are presented
to illustrate some possible combinations of other layers with a
fluted plate. FIG. 11A shows an arrangement 1100 of optical layers,
having a fluted plate 1101 with a reflective polarizer layer 1110
attached to the upper surface of an upper layer 1102 of the fluted
plate. The reflective polarizer layer 1110 may be attached using an
adhesive, for example a clear adhesive or an optically diffusing
adhesive. A prismatic brightness enhancing layer 1112 may be
attached above the reflecting polarizer layer 1110. In some
exemplary embodiments, it may be desirable for at least some of the
light to enter the brightness enhancing layer 1112 through an air
interface or an interface going from a low to a high refractive
index. Therefore, a layer of low index material, for example a
fluorinated polymer, may be placed between the brightness enhancing
layer 1112 and the next layer below the brightness enhancing layer
1112.
[0078] In other exemplary embodiments, an air gap may be provided
between the brightness enhancing layer 1112 and the layer below the
brightness enhancing layer 1112. One approach to providing the air
gap is to include a structure on one or both of the opposing faces
of the brightness enhancing layer 1112 and the layer below the
brightness enhancing layer 1112. In the illustrated embodiment, the
lower surface 1114 of the brightness enhancing layer 1112 is
structured with protrusions 1116 that contact the adjacent layer
layer. Voids 1118 are thus formed between the protrusions 1116,
with the result that light entering into the brightness enhancing
layer 1112 at a position between the protrusions 1116 does so
through an air interface. In other embodiments, the reflecting
polarizer layer 1110 may be omitted and the prismatic brightness
enhancing layer 1112 attached directly to the fluted plate 1101. In
some embodiments, the fluted layer 1101 may provide optical
diffusion, or a separate diffusing layer may be provided, for
example attached to a lower layer 1104 of the fluted layer 1101 or
attached to the first layer 1102 of the fluted layer 1101, between
(i) the fluted layer and (ii) the reflective polarizer layer 1110
and/or the prismatic brightness enhancing layer 1112.
[0079] Other approaches to forming voids, and thus providing an air
interface to light entering the brightness enhancing layer, may be
used. For example, the brightness enhancing layer may have a flat
lower surface, with the adjacent layer being structured with
protrusions. These, and additional approaches, are discussed in
U.S. Patent Publication No. 2003/0223216 A1 (Emmons et al.),
incorporated herein by reference. Any of the embodiments of a
fluted plate discussed herein may be adapted to provide an air
interface for light entering the brightness enhancing layer.
[0080] The order of the films attached to the fluted plate 1101 may
be different. For example, a reflective polarizer layer 1110 may be
attached to the prismatic surface of the brightness enhancing layer
1112, and the brightness enhancing layer 1112 is attached to the
fluted plate 1101. This arrangement 1120 is schematically
illustrated in FIG. 11B. Attachment of optical films to the
prismatic surface of a brightness enhancing layer is further
described in U.S. Pat. No. 6,846,089 (Stevenson et al.),
incorporated herein by reference.
[0081] An exemplary embodiment illustrating an arrangement 1200 in
which one or more films are attached to the lower layer of the
fluted plate is schematically illustrated in FIG. 12A. In this
embodiment, a reflective polarizer 1210 is attached to the second
layer 1204 of the fluted plate 1201, and a prismatic brightness
enhancing layer 1212 is attached to the first layer of the fluted
plate 1201. An optional diffuser layer 1214 may be attached to the
lower surface of the reflective polarizer 1210. In other
embodiments, the fluted plate itself may provide some diffusion. In
such a case, it may be desired that the fluted plate 1201 does not
significantly depolarize the light that has passed through the
reflective polarizer 1210.
[0082] Another exemplary embodiment 1220 of a fluted plate 1201
attached to an arrangement of light management films is
schematically illustrated in FIG. 12B. In this embodiment 1220, a
diffuser layer 1222 is attached to the fluted plate 1201. An
intermediate layer 1224 is disposed on the diffuser layer 1222 and
a prismatic brightness enhancing layer 1226 is disposed over the
intermediate layer 1224. The diffuser layer 1222 may be, for
example, an acrylic foam tape: the foam tape deforms when the
intermediate layer 1224 is pushed into the foam tape, creating a
recessed region that the intermediate layer sits in. The
intermediate layer 1224 may have an optical function: for example,
the intermediate layer 1224 may be a reflective polarizer film.
Examples of other suitable arrangements of light management films
that may be used with a fluted plate are described in further
detail in U.S. application Ser. No. 11/244,666, "LIQUID CRYSTAL
DISPLAYS WITH LAMINATED DIFFUSER PLATES", Docket No. 60107US003,
filed on Oct. 6, 2005 and incorporated herein by reference.
[0083] In addition to molding, there exist other methods of
manufacturing a fluted plate. One method is to attach a spine, that
has connecting members already applied, to another optical film.
This approach is schematically illustrated in FIGS. 13A and 13B.
The spine 1302 has a cross member 1304 and an array of connecting
members 1306. The connecting members 1306 may be integrated with
the cross member 1304. For example, the spine 1302 may be formed by
molding or extrusion. The spine 1302 may be formed from the same
types of materials as discussed earlier for a fluted plate. Thus,
the spine 1302 may be formed of optically transparent or optically
scattering material.
[0084] An optical film 1310 is attached to the connecting members
1306. The optical film may be any suitable type of film. For
example, the film 1310 may be a prismatic brightness enhancing
film, a diffuser film, a reflective polarizer film, a gain diffuser
film, a lens film, an absorbing polarizer, a matte film or the
like. In addition, the optical film 1310 may simply be a
transparent film. Furthermore, optical films may also be attached
to the spine 1302 below the cross member 1304.
[0085] FIG. 13B shows the optical film 1310 attached to the
connecting members 1306. The film 1310 may be attached to the
connecting members using any suitable method. For example, the
lower surface 1312 of the film 1310 and/or the tips 1314 of the
connecting members 1306 may be applied with an adhesive which is
cured after the lower surface 1312 and the connecting member tips
1314 are placed in contact. In another approach, in which the film
1310 and connecting members 1306 are both formed of polymeric
materials, the film 1310 and connecting members 1306 may be placed
in contact before the respective polymeric materials have been
fully cross-linked, and the film 1310 and connecting members 1306
are subsequently cross-linked together. Some other approaches may
be used, for example contacting the optical film to the molten
polymer immediately following extrusion to create a bond between
the optical film and the flutes. In another approach, the flutes
may be heated (post extrusion) and laminated at a later time. Also,
a coextruded flute may also be employed whereby the flute is formed
of one material as the matrix (non adhesive, structural member)
with another material coextruded on the tip (adhesive type
material).
[0086] After the film 1310 has been attached, the film 1310 and
spine 1302 together form a plate having flutes 1316.
[0087] In another embodiment, schematically illustrated in FIG. 14A
(elements separated) and 14B (elements attached together), a spine
1402 has sets of connecting members 1406a, 1406b on respective
sides of a cross member 1404. Two optical films 1410a, 1410b may be
attached to the respective sets of the connecting members 1406a,
1406b. The optical films 1406a, 1406b may be any desired type of
optical film, such as a transparent film, a diffuser film, a
prismatic brightness enhancing film, a reflective polarizing film
or the like.
[0088] After at least one of the films 1410a, 1410b has been
attached to the spine 1402, the films 1410a and 1410b and spine
1402 together form a plate having flutes 1416.
[0089] One particular embodiment of an arrangement 1500 of optical
films that includes a spine 1502 of the type illustrated in FIG.
14B, is schematically illustrated in FIG. 15. In this embodiment, a
diffuser layer 1510 is attached to the lower connecting members
1506b and a prismatic brightness enhancing layer 1512 is attached
to the upper connecting members. A reflective polarizer layer 1514
may optionally be attached to the structured side of the prismatic
brightness enhancing layer 1512.
[0090] Another illustrative arrangement 1600 is schematically
illustrated in FIG. 16, in which the reflective polarizer 1514 is
positioned between the diffuser layer 1510 and the spine 1502.
[0091] Another approach for attaching two layers together is to use
layers that are interconnectable. For example, the two layers may
be mechanically attachable to each other using an attaching
mechanism like that used to seal food storage bags. An exemplary
embodiment of such a mechanism is illustrated in FIG. 17, which
shows parts of the upper and lower layers 1702, 1704. Each layer
1702, 1704 has respective interconnecting members 1706, 1708 that
are directed to the other layer. When the two layers 1702, 1704 are
pressed together, the interconnecting members 1706, 1708 lock
together to form the connecting members. The layers 1702, 1704 with
respective interconnecting members 1706, 1708 may be formed, for
example, using an extrusion process. The interconnecting members
1706 may be, but are not required to be, of the same shape as the
interconnecting members 1708.
[0092] Whether or not spines are used to connect the upper and
lower layers, the fluted plate may be formed in a partially
continuous process. The films forming the upper and lower layers,
and the optional spine, may be taken off respective rolls and
attached together. Once the layers are attached to one another, the
resulting fluted product is relatively stiff. Individual plates can
be cut from the continuous fluted product.
[0093] A fluted plate may be used to improve thermal management in
a display system, such as a television display or monitor. An
exemplary embodiment of display system 1800, schematically
illustrated in FIG. 18, includes one or more light sources 1802, a
fluted plate 1804, an arrangement of light management layers 1806,
and a display panel 1808. A coolant may flow through the flutes of
the fluted plate 1804, which results in a lower operating
temperature of the display system. The coolant may be air and, in
some embodiments, the air may flow through vertically oriented
flutes due simply to natural convection. In other embodiments, the
coolant may be forced through the flutes by a coolant circulator.
For example, a fan 1810 may be used to force air through the flutes
of the fluted plate 1804. In other embodiments, a transparent
fluid, such as water, may be forced through the flutes by a
pump.
[0094] It will be appreciated that there are many different
possible arrangement within the scope of the invention, in which
different layers appear in different orders from bottom to top of
the arrangement, or in different positions relative to the
spine.
[0095] The present invention should not be considered limited to
the particular examples described above, but rather should be
understood to cover all aspects of the invention as fairly set out
in the attached claims. Various modifications, equivalent
processes, as well as numerous structures to which the present
invention may be applicable will be readily apparent to those of
skill in the art to which the present invention is directed upon
review of the present specification. For example, free standing
optical films may also be used within a display device alongside a
fluted plate that is attached with other optical layers. Also, a
display may use more than one fluted plate. The flutes of the
multiple fluted plates may be arranged parallel to each other, or
the flutes of one plate may be oriented non-parallel to the flutes
of another fluted plate. The claims are intended to cover such
modifications and devices.
* * * * *