United States Patent [t9J
`Plesinger
`
`111111111111111111111111111111111111111111111111111111111111111111111111111
`US005146354A
`[II] Patent Number:
`[45] Date of Patent:
`
`5,146,354
`Sep.8, 1992
`
`[54] LCD SYSTEM WITH A BACKLIGHT
`HAVING A LIGHT SOURCE AT A LIGHT
`PIPE'S EDGE AND WITH THE LCD
`ENFRAMED
`[75~ Inventor: Boris Plesinger, Tomball, Tex.
`[73] Assignee: Compaq Computer Corporation,
`Houston, Tex.
`
`[21] Appl. No.: 696,779
`[22] Filed:
`May 7, 1991
`[51]
`Int. Cl.s .................. GOlF 1/1335; G02F 1!1333;
`F21V 7/04
`[52] U.S. CI •........................................ 359/49; 359/83;
`362/31
`[58] Field of Search ............... 359/48, 49, 83; 362/31,
`362/222, 296, 341
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`4,042,294 8/1977 Billings, Jr. et al. ................. 359/49
`4,118,111 10/1978 Laesser ................................. 359/49
`4,929,062 5/1990 Guzik et al. ........................ 362/297
`4,958,911 9/1990 Beiswenger et al. ................. 359/83
`5,046,826 9/1991
`Iwamoto et al. ..................... 359/49
`5,050,946 9/1991 Hathaway et al. ................... 359/48
`5,064,276 11/1991 Endo et al. ........................... 359/49
`Primary Examiner-Stanley D. Miller
`Assistant Examiner-Anita Pellman Gross
`
`Attorney, Agent, or Firm-Pravel, Gambrell, Hewitt,
`Kimball & Krieger
`ABSTRACT
`[57]
`A backlighted liquid crystal display (LCD) system with
`a light source and a light pipe which is separated from
`the LCD panel by an air gap to facilitate uniform
`brightness of the viewing area. The air gap effectively
`blocks conductive heat transfer from the light source to
`the LCD panel. The LCD panel is enframed within a
`metal frame that serves as a heat sink which prevents a
`temperature gradient across the LDC panel. The light
`source is fastened to the light pipe and remaining ex(cid:173)
`posed areas of the light source are covered with an
`insulating material to trap heat and prevent heat radia(cid:173)
`tion to the LCD panel. A sheet of heat conductive
`material, which lines the inner back surface of a plastic
`enclosure surrounding the LCD display assembly,
`serves to equally distribute heat throughout the inner
`area of the enclosure. The exposed surface of the heat
`conductive lining is preferably blackened. Optionally,
`the heat conductive shield may be included to capture
`heat radiating from the light source and convey this
`heat to the heat conductive lining. Insulating material is
`placed between the· heat conductive shield and the
`metal frame of the LCD panel to prevent heat transfer
`to the LCD panel.
`
`10 Claims, 2 Drawing Sheets
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`122 ___,........,. .. -
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`, ..... ~-
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`116
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`132
`136
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`138
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`140
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`104
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`102
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`100
`I'MI:::.I.I--110
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`~-.~-..-120
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`112
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`116
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`TOYOTA EXHIBIT 1003
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`Page 1 of 8
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`U.S. Patent
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`Sep. 8, 1992
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`Sheet 1 of 2
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`5,146,354
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`FIG.1
`(PRIOR ARTJ
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`38
`20
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`32
`36
`42
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`126"
`128
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`122
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`·116
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`/ 118
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`120
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`F7G.2
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`132
`136
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`138
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`140
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`104
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`102
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`100
`110
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`120
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`104
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`136
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`112
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`128
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`116
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`100
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`144
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`FIG.3
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`..-11--".N--142
`l.l:::z:::;z::Z:::.:;11.
`141-..31~ 145
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`~~----140
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`FIG.5
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`Page 2 of 8
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`U.S. Patent
`U.S. Patent
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`Sep. 8, 1992
`Sep. 8, 1992
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`Sheet 2 of 2
`Sheet 2 of 2
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`5,146,354
`5,146,354
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`«mmwé
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`Page 3 of8
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`Page 3 of 8
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`1
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`5,146,354
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`LCD SYSTEM WITH A BACKLIGHT HAVING A
`LIGHT SOURCE AT A LIGHT PIPE'S EDGE AND
`WITH THE LCD ENFRAMED
`
`5
`
`10
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The invention relates to a backlighted liquid crystal
`di~,..Jay system with uniform brightness of the viewing
`area.
`2. Description of the Related Art
`Liquid crystal displays (LCD's) are commonly used
`in portable computer systems, televisions and other
`electronic devices. An LCD requires a source of light
`for operation because the LCD is effectively a light 15
`valve, allowing transmission of light in one state and
`blocking transmission of light in a second state. Portable
`and laptop computers typically use an LCD panel that
`comprises a liquid crystal polymer encapsulated be(cid:173)
`tween at least two planar glass plates in parallel with 20
`each other. A polarization layer is bonded to the outer
`surface of each glass plate such that the glass plates are
`sandwiched between two polarization layers. An alter(cid:173)
`nate type of LCD panel may include a thin polymer
`film, or retardation layer, located between each glass 25
`plate and its respective polarization layer.
`The inner surface, or the surface facing the liquid
`crystal polymer, of each glass plate includes mutually
`perpendicularly oriented conductive transparent lines.
`The volume between any two orthogonal lines forms a 30
`cube whose face area constitutes a pixel. The lines are
`connected on the periphery of the glass plates via input(cid:173)
`/output (10) strips to accompanying electronic cir(cid:173)
`cuitry. The functions of the LCD panel elements intro(cid:173)
`duced above will not be described as they are well 35
`known by those skilled in the art.
`Backlighting the LCD panel bas become the most
`popular source of light in portable computer systems
`because of the improved contrast ratios and bright(cid:173)
`nesses possible. A backlight including, a light source 40
`and a light pipe located next to and aligned parallel with
`the back surface of the LCD panel provides light to the
`LCD panel. The light pipe is capable of reflecting are
`distributing the light perpendicularly over its entire
`front surface, wherein the front surface was either opti- 45
`cally bonded or placed adjacent to the back surface of
`the LCD panel. The light source is conventionally a
`florescent tube attached to at least one edge surface of
`the light pipe. A reflective material may be wrapped
`around the light source to redirect light from the light 50
`source into the light pipe.
`The brightness of the LCD panel is related to the
`transmission characteristic of the liquid crystal polymer
`and the retardation layer polymer. The LCD panel is
`temperature sensitive in that the transmission character- 55
`istic of the liquid crystal polymer and retardation layer
`polymer changes significantly with variations in tem(cid:173)
`perature. A uniform transmission characteristic over
`the LCD panel requires as uniform a temperature distri(cid:173)
`bution as possible. The main drawback of the assembly 60
`described above is that the beat dissipated by the light
`source(s) is either radiated directly or conducted via the
`light pipe to the LCD panel. The undesirable result is a
`temperature gradient between the back and front sur(cid:173)
`faces as well as a temperature gradient between the 65
`edges and the center of the LCD panel. These tempera(cid:173)
`ture gradients cause the LCD display to have different
`brightnesses around its edges as compared to its center
`
`2
`so that the viewing area does not have a uniform bright(cid:173)
`ness.
`
`SUMMARY OF THE PRESENT INVENTION
`The object of the present invention is to provide
`uniformity of brightness of the LCD panel by reducing
`beat transfer from the light source to the LCD panel.
`The exposed portions of each light source are wrapped
`with reflective insulating material, such as white felt, to
`maintain the optimally efficient operating temperature
`of the backlight and to reduce thermal radiation to the
`LCD panel. The backlight is separated from the LCD
`panel by a relatively wide air gap which effectively
`blocks conductive heat transfer from each light source
`to the LCD panel. The LCD panel is also enframed
`with metal so that the resulting metal frame shields
`against electromagnetic interference (EMI), adds rigid(cid:173)
`ity to the LCD panel, and serves as a heat sink which
`prevents a temperature gradient across the LCD panel.
`The present invention also includes a sheet of beat ·
`conductive material which lines the inner back surface
`of a plastic enclosure surrounding the LCD display
`assembly. The heat conductive lining is preferably
`blackened to function as a black body which absorbs
`and equally distributes the heat generated by each light
`source throughout the inner area of the enclosure. The
`heat conductive lining also increases heat transfer
`through the enclosure wall to the surrounding ambient
`air.
`Optionally, a heat conductive shield may be included
`to capture heat radiating from each light source and
`convey this beat to the heat conductive lining. The heat
`conductive shield is located between the light source(s)
`and the metal frame, and is fastened in good thermal
`contact with the heat conductive lining. A layer of
`insulating material is placed between the heat conduc(cid:173)
`tive shield and the metal frame of the LCD panel to
`prevent heat transfer to the LCD panel.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`A better understanding of the present invention can
`be obtained when the following detailed description of
`the preferred embodiment is considered in conjunction
`with the following drawings, in which:
`FIG. 1 is a cross-sectional side view of a liquid crystal
`display system of prior art;
`FIG. 2 is a cross-sectional side view of a liquid crystal
`display system according to the present invention;
`FIG. 3 is a partial cross-sectional side view of the
`liquid crystal display system of FIG. 2 showing further
`details of the invention;
`FIG. 4 is an exploded partial isometric view of the
`liquid crystal display system of FIG. 2; and
`FIG. 5 is a partial cross-sectional side view of the
`backlight looking along lines 5-5 of FIG. 4.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`FIG. 1 illustrates a backlighted LCD. display system
`of the prior art. Two light sources 20 and 22, which are
`typic!llly florescent tubes, are attached to the respective
`edge surfaces 21 and 23 of a light pipe 24. The light pipe
`24 is capable of reflecting and distributing the light from
`the light sources 20 and 22 perpendicularly out of its
`entire front surface 26. The light sources 20 and 22 and
`the light pipe 24 together form a backlight. An LCD
`panel 28 typically includes a liquid crystal polymer (not
`
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`5,146,354
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`3
`4
`insulating material 110 preferably redirects light from
`shown) encapsulated between at least two pl;mar glass
`the light source 100 into the light pipe and also traps
`plates (not shown) in parallel with each other. The glass
`plates of the LCD panel28 may be sandwiched between
`heat in order to maintain the temperature of the light
`pipe 104 to its optimally efficient operating tempera-
`two thin polymer film retardation layers (not shown)
`The LCD panel 28 includes a back surface 30 for re- 5 ture. The heat insulating function of the reflective insu-
`lating material 110 is taught and more fully described in
`ceiving light from the light pipe 24, and a front surface
`31 for viewing light allowed to pass through the LCD
`Hathaway et al. The light source 100 and light pipe 104
`panel 28. The brightness of the front surface 31 of the
`are separated from an LCD panel112 by an air gap 114.
`LCD panel 28 is related to the transmission characteris-
`The air gap 114 .effectively prevents substantial conduc-
`tic vi the liquid crystal polymer and the polymer of the 10 tive heat transfer from the light source 100 to the LCD
`retardation layers. The LCD panel 28 is temperature
`panel 112.
`sensitive in that the transmission characteristic of the
`Electronic circuitry 116 is attached to the periphery
`liquid crystal polymer and retardation polymer changes
`of the LCD panel 112. The LCD panel 112 and the
`significantly with variations in temperature. The corn-
`electronic circuitry 116 are "enfrarned" in a metal frame
`plete function of the LCD panel28 is not described as it 15 118 comprised of a back frame member 120 attached to
`is well known to those skilled in the art.
`a front frame member 122, which will be described in
`The front surface 26 of the light pipe 24 is either
`more detail below. The inner border of the metal frame
`optically bonded or placed adjacent to the back surface
`118 thus forms the viewing, visible or exposed area of
`30 of the LCD panel 24. Electronic driving circuitry 32
`the LCD panel 112. The metal frame 118 shields against
`is connected at the periphery of the LCD panel 28 to 20 electromagnetic interference (EMI) which emanates
`allow control of the LCD panel 28. All of the elements
`from additional LCD driving circuitry 124 (FIG. 4) and
`described above are encased in a metal enclosure corn-
`the high voltage supply used with the light source 100,
`prising a metal back piece 34 fastened to a metal front
`adds rigidity to the LCD panel 112, and serves as a heat
`piece 36. The metal front piece 36 covers only the pe-
`sink that prevents temperature gradients across the
`ripheral edge areas of the LCD panel 28 so that the 25 LCD panel 112. Note that the metal enclosure of the
`majority of the front surface can be viewed. Two pieces
`prior art LCD display system comprising the metal
`of reflective rnaterial38 and 40 may be wrapped around
`back piece 34 fastened to the metal front piece 36 (FIG.
`the light sources 20 and 22, respectively, and adhesively
`1) does not "enfrarne" the LCD panel 28 but instead
`bonded to the light pipe 24. The pieces of reflective
`encases the entire assembly. The metal frame 118 of the
`material 38 and 40 redirect light from the light sources 30 LCD display system of the present invention enfrarnes
`20 and 22 into the light pipe.
`the LCD panel 112 and the electronic circuitry 116,
`Much of the heat dissipated by the light sources 20
`whereas the entire assembly described above is enclosed
`and 22 is either radiated to the LCD panel 28 or con-
`in a separate plastic enclosure 126. The plastic enclosure
`ducted through the edge surfaces 21 and 23 to end areas
`126 preferably comprises a front panel 128 having plas-
`42 of the LCD panel 28. The dissipated heat creates a 35 tic tabs 130 (FIG. 4), and a pan-shaped back member
`132 having lip members 134 (FIG. 4), wherein the tabs
`temperature gradient between the end areas 42 of the
`LCD panel28 and a center area 46 of the LCD panel28.
`130 align and snap together with the lip members 134
`The heat may also create a temperature gradient be-
`such that the front panel 128 attaches to the back rnern-
`tween the back surface 30 and the front surface 31 at the
`ber 132 to form the enclosure 126 which encompasses
`end areas 42 of the LCD panel 28. These temperature 40 the entire LCD display system.
`gradients create a nonuniform transmission characteris-
`A heat conductive lining 136 is bonded in good ther-
`tic of the liquid crystal polymer and retardation poly-
`mal contact to the inner back surface 138 of the back
`mer which creates nonuniform brightness of the front
`member 132 of the enclosure 126. The heat conductive
`surface 31 of the LCD display 28. The brightness of the
`lining 136 is preferably made from a sheet of high ther-
`LCD display 28 is, therefore, different at the end areas 45 rnally conductive material, such as aluminum, copper,
`42 as compared to the center area 46.
`or the like. The exposed surface 140 of the heat conduc-
`FIG. 2 is a cross-sectional side view illustrating the
`tive lining 136 is preferably black anodized or otherwise
`LCD display system of the present invention. A single
`blackened. The heat conductive lininq 136 absorbs and
`light source 100, preferably a florescent light tube, is
`equally distributes the heat generated from the light
`attached to one edge surface 102 of a light pipe 104. The 50 source 100 throughout the inner area enclosed by the
`light pipe 104 functions similarly as the light pipe 24 in
`enclosure 126. The heat conductive lining 136 also in-
`that light from the light source 100 is directed by a back
`creases heat transfer through the walls of the enclosure
`surface 106 which is capable of reflecting and distribut-
`126 to the surrounding ambient air.
`ing the light from the light source 100 perpendicularly
`FIG. 3 is· a partial cross-sectional side view of the
`over an entire opposite, or front surface 108 of the light 55 liquid crystal display system of FIG. 2. A heat conduc-
`pipe 104. Together the light source 100 and the light
`tive shield 142 is optionally included which is prefera-
`pipe 104 form a backlight. This particular backlight
`bly made of a high thermally conductive material, such
`structure is more completely described in U.S. patent
`as aluminum, copper, or the like. The heat conductive
`application Ser. No. 589,325, flled Sep. 27, 1990, entitled
`shield 142 includes a heat-fin member 144 which is
`"Faceted Light Pipe" by Hathaway et al., which is 60 located between the light source 100 and the back frame
`assigned to a common assignee and which is hereby
`member 120, and a fastening member 145. When pres-
`incorporated by reference. A layer of light reflective,
`ent, the fastening member 145 of the heat conductive
`heat insulating material 110 is included which wraps
`shield 142 is preferably fastened in good thermal
`around the exposed portions of the light source 100 and
`contact to the exposed surface 140 of the heat conduc-
`is adhesively bonded to the backlight 104. The layer of 65 tive lining 136. The fastening means could be one of
`reflective insulating material 110 is preferably made
`several methods known in the art, but is preferably done
`from a piece of reflective and heat insulating material,
`with 2-sided tape (not shown). In this manner when the
`such as white felt or the like. The layer of reflective
`heat conductive shield 142 is provided, any heat that
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`5,146,354
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`6
`of reflective insulating material 110 is wrapped around
`the light source 100 and runs partially up the backside of
`the light pipe 104, along the length of the light pipe 104.
`Since the light source 100 extends beyond the sides of
`5 the light pipe 104 (FIG. 4), the layer of reflective insu(cid:173)
`lating material 110 wraps around the exposed portions
`of the light source 100, as clearly shown in FIGS. 4 and
`5.
`
`5
`radiates or conducts from the light source 100 away
`from the light pipe 104 or the heat conductive lining 136
`is captured by the heat conductive shield 142 and trans(cid:173)
`ferred to the heat conductive lining 136.
`Additionally, a heat insulation layer 146 is sand(cid:173)
`wiched between the back frame member 120 of the
`metal frame 118, and the heat-fin member 144 of the
`heat conductive shield 142. The heat insulation layer
`146 is preferably made of a heat insulating material with
`low i.hermal conductivity, such as felt or the like. The 10
`heat insulation layer 146 prevents heat from radiating
`from the heat-fm member 144 to the back frame mem(cid:173)
`ber 120.
`FIG. 4 is an exploded partial isometric view of the
`LCD display system of the present invention. The LCD 15
`panel 112 is enframed between the back frame member
`120 and the front frame member 122 of the metal frame
`118. The front frame member includes punched tabs 148
`which position and hold the LCD panel 112 in place in
`the metal frame 118. The front frame member includes 20
`lip extensions 152 which encompass the back frame
`member when the front and back frame members 122
`and 120 are placed together. The lip extensions 152
`include metal tabs 156 which are bent inward against
`the backside of the back frame member 120 to hold the 25
`back frame member 120 securely to the front frame
`member 122.
`The light source 100 is shown attached to the lower
`edge surface 102 of the light pipe 104. Note that the
`light source 100 is longer than the light pipe 104 such 30
`that the light source 100 extends beyond the sides of the
`light pipe 104 as shown in FIG. 4. The top edge 166 of
`the light pipe 104 abuts against several metal tabs (not
`shown) punched out of the back frame member 120, and
`the light pipe 104 is set flush with the backside of the 35
`back frame member 120. The back frame member 120
`holds the light pipe away from the LCD panel 112 to
`allow for the resulting air gap 114 of at least the thick(cid:173)
`ness of the back frame member 120, and more if the
`back frame member 120 includes appropriate raised and 40
`lowered portions, particularly a recessed or lowered
`portion providing clearance between the light source
`100 and the back frame member 120 to limit heat trans-
`fer directly from the light source 100 to the back frame
`member 120. The light pipe 104 is then securely fas- 45
`tened to the back frame member 120 using at two brack-
`ets 160 and 162, and preferably two screws 164 for each
`of the brackets 160. Only one of the brackets 160 and
`screws 164 are shown for clarity. The light pipe 104
`extends beyond the inner boarder of the metal frame 50
`118, so that the entire viewing area of the LCD panel
`112 is illuminated and to provide the air gap 114. The
`front frame member includes four metal tabs 170, each
`including a hole 172, which aligns with four screw
`sockets 174. Only two of the screw sockets 174 are 55
`shown for clarity. Four screws 176, only two shown for
`clarity, are then inserted into the holes 172 and screwed
`into the screw sockets 174 to securely fasten the metal
`frame 118 and the light pipe 104 to the back member 132
`of the plastic enclosure 126. The heat conductive lining 60
`136 is, as described previously, bonded to the plastic
`pan-shaped back member 132. The front panel 128 and
`the back member 132 are then snapped together, using
`the lip members 134 and the tabs 130 as previously
`described, thus sandwiching all of the elements of the 65
`LCD display system together.
`FIG. 5 is a partial cross-sectional side view of the
`backlight looking along lines 5-5 of FIG. 4. The layer
`
`The foregoing disclosure and description of the in(cid:173)
`vention are illustrative and explanatory thereof, and
`various changes in the size, shape, materials, compo(cid:173)
`nents, elements, connections and contacts, as well as in
`the details of the illustrated system and construction
`may be made without departing from the spirit of the
`invention.
`I claim:
`1. A backlighted liquid crystal display system, com(cid:173)
`prising:
`a liquid crystal display panel having a back surface
`for receiving light;
`a metal frame having an inner border, wherein said
`metal frame enframes said liquid crystal display
`panel, said inner border defining the exposed area
`of said back surface of said liquid crystal display
`panel;
`a light pipe having a planar front surface for provid(cid:173)
`ing light to said liquid crystal display panel back
`surface, having at least one end surface for receiv(cid:173)
`ing light to be transmitted through said front sur-
`face, and having a back surface, said front surface
`being aligned generally parallel with and separated
`from said liquid crystal display panel back surface,
`and wherein said light pipe planar front surface
`extends in a plane beyond said metal frame inner
`border; and
`light source means for providing light to said light
`pipe, a light source located adjacent each said end
`surface for receiving light of said light pipe.
`2. The system of claim 1, wherein each of said light
`source means is partially encompassed by insulation.
`3. The system of claim 1, further comprising:
`an enclosure having an inner cavity with a resulting
`inner surface for generally receiving said light
`source, light pipe, metal frame and liquid crystal
`display panel, wherein a portion of said inner sur-
`face generally faces towards said light pipe back
`surface and said light source means;
`a sheet of heat conductive material with a first side
`and a second side; and
`means to bond said first side of said heat conductive
`sheet to said inner cavity inner surface portion so as
`to be in good thermal contact with said enclosure.
`4. The system of claim 3, wherein said second side of
`said heat conductive-sheet is blackened.
`5. The system of claim 3, wherein said heat conduc(cid:173)
`tive sheet is formed of copper.
`6. The system of claim 3, wherein said heat conduc(cid:173)
`tive sheet is formed of aluminum.
`7. The system of claim 3, further comprising:
`at least one heat conductive shield, each heat conduc(cid:173)
`tive shield including a member for fastening to said
`heat conductive sheet and a heat-fin member inte(cid:173)
`grally formed with said fastening member, said
`heat-fin member being placed between said metal
`frame and said light source means; and
`means to fasten said heat conductive shield fastening
`member to said heat conductive sheet for provid-
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`7
`ing good thermal contact between said heat con(cid:173)
`ductive sheet and said heat conductive shield.
`8. The system of claim 7, wherein said heat conduc-
`tive shield is formed of aluminum.
`
`8
`9. The system of claim 7, wherein said heat conduc(cid:173)
`tive shield is formed or copper.
`10. The system of claim 7, further comprising a layer
`of heat insulation material between said heat conductive
`shield and said metal frame.
`* * * * *
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`5,146,354
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`5
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`10
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`IS
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`20
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`25
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`so
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`UNITED STATES PATENT AND TRADEMARK OFFICE
`CERTIFICATE OF CORRECTION
`
`PATENT NO.
`DATED
`INVENTOR(S)
`
`:5,146,354
`:September 8, 1992
`:Boris Plesinger
`
`Page 1 of 1
`
`It is certified that error appears in the above-identified patent and that said Letters Patent is
`hereby corrected as shown below:
`
`Column 6,
`Line 55, delete "conductive-sheet" and insert -- conductive sheet --.
`
`Column 8,
`Line 2, after "formed" delete "or" and insert-- of--.
`
`Signed and Sealed this
`
`Seventh Day of March, 2006
`
`JONW.DUDAS
`Director of the United States Patent and Trademark Office
`
`Page 8 of 8
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