(12) United States Patent
`Matsushita et al.
`
`(10) Patent NO.: US 6,864,930 B2
`Mar. 8,2005
`(45) Date of Patent:
`
`(54) LIQUID CRYSTAL DISPLAY DEVICE
`
`(75)
`
`Inventors: Junichi Matsushita, Shizuoka (JP);
`Kunimitsu Aoki, Shizuoka (JP)
`
`(73) Assignee: Yazaki Corporation, Tokyo (JP)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 281 days.
`
`(21) Appl. No.: 091901,913
`
`(22) Filed:
`
`Jul. 11, 2001
`
`(65)
`
`Prior Publication Data
`US 200310206255 A1 Nov. 6, 2003
`
`Related U.S. Application Data
`
`(62) Division of application No. 091282,161, filed on Mar. 31,
`1999.
`Foreign Application Priority Data
`(JP) ........................................ P. 10-89069
`
`Apr. 1, 1998
`
`(30)
`
`Int. CL7 ........................................ GOlF 111335
`(51)
`(52) U.S. C1. ............................. 349165; 349161; 349162;
`349164; 349170; 3491110
`(58) Field of Search .............................. 349165, 61, 62,
`349164-110
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`411997 Funamoto et al. ............ 349161
`911997 Ohta et al. .................... 349162
`811998 Kanda et al. ................. 349164
`911998 Oyama et al. ................ 349165
`311999 Okamoto et al. ............. 349174
`611999 Dakiu ......................... 349165
`612000 Sasako ........................ 362134
`712000 Ushiyama et al. .......... 3591627
`712000 Gardiner et al. ............ 3591625
`
`6,504,589 B1 * 112003 Kashima et al. .............. 349196
`200110038425 A1 * 1112001 Lee ............................. 349161
`200210057562 A1 * 512002 Sasako et al. ................ 362131
`200210172039 A1 * 1112002 Inditsky ...................... 3621231
`
`FOREIGN PATENT DOCUMENTS
`
`* cited by examiner
`
`Primary Examinerqathan J. Plynn
`Assistant Examiner-dmed N. Sefer
`(74) Attorney, Agent, or F i r m a o r g a n , Lewis & Bockius
`LLP
`
`ABSTRACT
`(57)
`An LCD provided with an edge light type back light unit
`which is arranged in a manner that the light emitted from a
`CCT in the form of a linear light source is condensed at the
`end portion of a light conduction plate, then the light
`reflected by a reflecting sheet and then ejected from the light
`conduction plate transmits through a light diffusion plate
`thereby to indirectly irradiate on a liquid crystal panel from
`the rear direction thereof in the form of alanar linht with
`uniform luminance. A light reflecting plate having a curved
`surface is disposed in the vicinity of the CCT. A light
`shielding plate is disposed in a manner that a part of the light
`emitted from the CCT and reflected by the light reflecting
`plate is condensed at the end portion of the light conduction
`plate. Another part of the light emitted from the CCT and
`reflected by the light reflecting plate is directed upward and
`directly irradiates a part of the display area of the liquid
`crystal panel thereby to form a high luminance irradiation
`portion. Accordingly, thus configured LCD is improved in
`its visibility and so can be formed as a vehicle-mounted
`alarm display device for displaying various alarms.
`
`a
`
`1 Claim, 3 Drawing Sheets
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`Valeo Ex. 1010_001
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`

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`U.S. Patent
`
`Mar. 8,2005
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`Sheet 1 of 3
`
`FIG.
`
`FIG. 2
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`Valeo Ex. 1010_002
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`U.S. Patent
`
`Mar. 8,2005
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`Sheet 2 of 3
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`FIG. 3
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`Valeo Ex. 1010_003
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`U.S. Patent
`
`Mar. 8,2005
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`Sheet 3 of 3
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`FIG. 4 PRIOR ART
`
`FIG. 5 PRIOR ART
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`Valeo Ex. 1010_004
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`

`

`1
`LIQUID CRYSTAL DISPLAY DEVICE
`
`US 6,864,930 B2
`
`This is a divisional of copending application Ser. No.
`091282,161 filed on Mar. 31, 1999.
`
`2
`light emitted from the CCT 4 as the linear light source passes
`through the light conduction plate 3 and the light diffusion
`plate 7 or the light modulation film 9, SO that the luminance
`of the light is attenuated. Thus, the luminance of the light
`s illuminated on the liquid crystal panel 8 from the planar light
`BACKGROUND OF THE INVENTION
`source is reduced. Further, the luminance of the displayed
`image is reduced to about 150 cd/m2 due to the transmitta&e
`1. Field of the Invention
`of the liquid crystal panel 8.
`The present invention relates to a liquid crystal display
`device (LCD) intended to increase the luminance of a
`In the case of displaying various kinds of alarms within a
`display screen thereof so as to be suitable for an alarm 10 vehicle such as an automobile, the luminance of the dis-
`display device to be mounted on a vehicle such as an
`played image is desirably 200 cd/m2 or more at the maxi-
`automobile or the like.
`mum. However, the luminance of the displayed image of the
`LCD is generally about 150 cd/m2 at the maximum. In the
`2. Description of the Related Art
`aforesaid conventional examples, since the luminance of the
`FIG, 4 is a sectional side view of a lighting unit and a
`displayed image of the LCD is reduced to about 150 cd/m2
`liquid crystal display device using it described in Japanese
`due to the attenuation, the shortage of the luminance of the
`
`patent unexamined hblication N ~ , ~
`
`
`i~9-281492, ,
`
`
`this
`displayed image arises. Therefore, the aforesaid COnven-
`case, a back light unit called an edge light type or a side light
`tional LCDs are disadvantageous in that the visibility and
`3 is employed as a
`type using a light conduction
`the attention calling function thereof are deteriorated when
`lighting unit for irradiating a liquid crystal panel 8 of an
`20 used for a particular object such as a vehicle-mounted alarm
`LCD 1.
`A housing 2 having an upper surface portion and a lower
`surface portion respectively shown in the upper and lower
`directions in the figure is provided with the light conduction
`plate 3 made of light transmission material at the center
`Accordingly, an object of the present invention is to
`portion thereof. Afluorescent tube (hereinafter referred to as 25 provide an LCD which is intended to increase the luminance
`a CCT) 4 of a hot cathode tube or a cold cathode tube in the
`of a display screen thereof to thereby improve the visibility
`form of a linear light source is disposed at one end side of
`thereof so as to be effective for a vehicle-mounted alarm
`the light conduction plate 3. The linear light emitted from the
`display device, in particular.
`CCT 4 is condensed at the end face of the light conduction 30
`In Order to achieve the aforesaid object, the present
`plate 3 by means of a reflecting plate 5 having a curved
`invention provides a liquid crystal display device including
`surface and then conducted within the light conduction plate
`an edge light type back light unit in which light emitted from
`3. The light from the CCT 4 thus conducted within the light
`a linear light source is condensed at an end portion of a light
`conduction plate 3 is reflected upward by a reflecting sheet
`conduction plate, then conducted and reflected, and a
`6 disposed at the lower back side of the light conduction 35 reflected light ejected from the light conduction plate is
`plate 3. In this manner, the light from the CCT 4 is formed
`transmitted through a light diffusion plate to form a planar
`as a planar light source, and the light from the planar light
`light source with a uniform luminance thereby to indirectly
`source transmits a light diffusion plate 7 disposed at the
`irradiate a liquid crystal panel from a rear side thereof,
`upward portion of the light conduction plate 3 thereby to
`wherein a reflecting plate having a curved surface is dis-
`illuminate the liquid crystal panel 8 provided at the upper- 40 posed in a vicinity of the linear light source, and a light
`most portion of the housing 2 from the lower direction
`shielding plate is disposed so that a part of the light emitted
`thereof. The light diffusion plate 7 is formed by an optical
`from the linear light source and reflected by the reflecting
`Part such as a prism sheet or an element formed by trans-
`plate is condensed at the end portion of the light conduction
`lucent material effective for light diffusion.
`plate, whereby another part of the light emitted from the
`Since the light from the CCT 4 transmits the light diffu- 45 linear light source and reflected by the reflecting plate is
`directly irradiated with a higher luminance on a part of a
`sion plate 7, the light is formed as a planar light source with
`a uniform luminance and then illuminated on the entire
`display area of the liquid crystal panel than that of another
`surface of the liquid crystal panel 8. As a result, the LCD 1
`part of the display area.
`is formed as a dot matrix type LCD which displays charac-
`Further, the present invention provides a liquid crystal
`ters or images on the display screen of the liquid crystal so display device including an under light type back light unit
`panel 8 in the form of the aggregation of dots, for example.
`in which light emitted from a plurality of linear light sources
`FIG. 5 shows another conventional example of the LCD
`is reflected by a reflecting sheet disposed at a rear side of the
`having such an edge light type back light unit.
`plurality of linear light sources, then transmitted through a
`In this case, a plurality of CCTs 4 are disposed at the
`light modulation film and a light diffusion plate to form a
`lower portion of the housing 2. A part of the light emitted 55 planar light source with a uniform luminance thereby to
`from the respective CCTs 4 is reflected upward by a reflect-
`indirectly irradiate a liquid crystal panel from a rear side
`ing sheet 5 which is formed in a wave shape and disposed
`thereof, wherein one end portion of the light modulation film
`beneath the CCTs. The reflected light passes through a light
`is shielded by a light shielding plate, and light emitted from
`modulation film 9 and transmits the light diffusion plate 7,
`one of the plurality of linear light sources is shielded by the
`whereby the light is formed as planar light with uniform 60 light shielding plate and transmitted through only the light
`luminance and then illuminated on the entire surface of the
`diffusion plate thereby to directly irradiate with a higher
`liquid crystal panel 8 from the lower direction thereof.
`luminance on a part of a display area of the liquid crystal
`-
`In each of the conventional LCDs shown in FIGS. 4 and
`vane1 than that of another vart of the disvlav area.
`5, the back light unit serving as a planar light source still has
`BRIEF DESCRIPTION OF THE DRAWINGS
`the following problem to be improved.
`- .
`FIG. 1 is a sectional side view showing an LCD with an
`The luminance of the light emitted from the surface of the
`side light type CCT 4 is usually about 30,000 cd/m2. The
`edge light type back light unit according to a first embodi-
`
`SUMMARY OF THE INVENTION
`
`65
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`A
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`Valeo Ex. 1010_005
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`US 6,864,930 B2
`
`10
`
`3
`ment of the present invention and further showing the main
`portion thereof in an enlarged scale.
`FIG, 2 is a plan view showing a high-luminance display
`area of a liquid crystal panel in the first embodiment.
`FIG. 3 is a sectional side view showing an LCD with an
`under light type back light
`a
`embodiment of the present invention and further showing
`the main portion thereof in an enlarged scale.
`FIG. 4 is a sectional side view showing a conventional
`LCD with an edge light type back light unit.
`FIG, 5 is a sectional side view showing another conven-
`tional LCD with an under light type back light unit.
`
`4
`slanted surface of the lower surface thereof. The light
`emitted from the CCT 4 and condensed at the one end
`surface of the light conduction plate 3 is reflected upward by
`means of the reflecting sheet 6. A light diffusion plate 7 is
`disposed in the upper direction of the light conduction plate
`3, whereby the light reflected by the reflecting sheet
`and
`then ejected from the light conduction plate 3 transmits the
`light diffusion plate 7 disposed above the light conduction
`plate thereby to be formed in uniform planar light. The light
`thus transmitted through the light diffusion plate 7 is indi-
`rectly irradiated on the liquid crystal panel 8 from the lower
`direction thereof as a back light of a planar light source with
`uniform luminance. The light diffusion plate 7 may be
`formed by an optical part such as a prism sheet or an element
`DETAILED DESCRIPTION OF THE
`formed by translucent material effective for light diffusion.
`PREFERRED EMBODIMENTS
`According to the aforesaid configuration, the LCD of the
`me L C D ~ according to the embodiments of the present
`first embodiment operates in the following manner. The
`operation of the LCD will be described also with reference
`invention will be described in detail with reference to the
`to FIG. 2 showing the entire main surface of the liquid
`accompanying drawings,
`the following embodiments,
`crysta1 pane'
`elements same as or common to those of the conventional
`LCDs shown in FIGS, 4 and 5 are designated by the same 20 A part of the light emitted from the CCT 4 as the linear
`light source is reflected
`the light reflecting plate ''2
`then
`reference characters and the explanation thereof is omitted,
`passes beneath the light shielding plate 10 and is condensed
`FIG. 1 is a sectional side view of an LCD 1 according to
`at the one end surface of the light conduction plate
`(as
`the first embodiment and further shows the main portion
`shown by a dotted arrow a in FIG, A part of the light
`thereof (circled portion) in an enlarged scale. In this case, the 2~ incident into the light conduction plate 3 is reflected
`upper surface portion and the lower surface portion of the
`by means of the reflecting sheet 6 disposed at the rear
`surface of the light conduction plate 3 and transmits through
`LCD
`in the
`are
`and lower
`the light diffusion plate 7. The light transmitted through the
`directions in the figure, like the conventional examples
`shown in FIGS. 4 and 5 . The LCD 1 according to the
`plate 7 is irradiated as uniform planar indirect light with a
`embodiment is arranged to have an edge light type back light 30 normal luminance on a display area (B) which occupies the
`unit.
`most part of an entire display area (A) of the liquid crystal
`A light conduction plate 3 disposed at the center portion
`panel 8, from the lower direction thereof.
`of a housing 2 is formed by transparent resin material or the
`On the other hand, another part of the light emitted from
`like so that each of the upper and lower surfaces thereof is
`the CCT 4 is shielded by the light shielding plate 10, and still
`formed to be flat and smooth. The light conduction plate 3 35 another part of the light emitted from the CCT 4 is reflected
`by the light reflecting plate 11 and directed upward, then
`is slanted from one side toward the other side thereof such
`transmits the light diffusion plate 12 and irradiates a part of
`that the thickness thereof becomes smaller so as to have a
`the liquid crystal panel 8 (as shown by a dotted arrow b in
`substantially rectangular shape in its sectional side view. A
`cold cathode fluorescent tube CCT 4 in the form of a linear
`FIG. 1). Since this irradiated light only transmits the light
`light source is disposed to face on the one end side with the 40 diffusion plate 12 with a thin thickness on the way thereof,
`larger thickness of the light conduction plate 3.
`the irradiated light is riot attenuated and so can be irradiated
`Alight shielding plate 10 is disposed between the one end
`on the part of the liquid crystal panel 8 with a required high
`side of the light conduction plate 3 and the CCT 4 so as to
`luminance from the lower direction thereof.
`have such a size and a shape that almost half of the light
`That is, as shown in FIG. 2, a part of the linear light
`emitted from the CCT 4 toward the one end side of the light 45 emitted from the CCT 4 and ejected from the light conduc-
`conduction plate 3 is shielded by the light shielding plate. A
`tion plate 3 transmits the light diffusion plate 7 and then
`light reflecting plate 11 having a curved surface opened
`indirectly irradiates the display area (B) which occupies the
`upward is disposed at the position opposite to the light
`most part of the entire display area (A) of the liquid crystal
`shielding plate 10. Further, a light diffusion plate 12 having
`panel 8, from the lower direction thereof. According to this
`a thin thickness is disposed in the upper direction of the CCT 50 indirect irradiation, the irradiated display area occupying the
`4. These constituent elements configure the gist of the LCD
`most part of the entire display area serves as a normal
`of the present invention.
`luminance irradiation portion (B) of the display portion of
`According to such a configuration, a part of the planar
`the liquid crystal panel. In contrast, the light emitted upward
`light emitted from the CCT 4 is reflected by the light
`from the CCT 4 transmits only the light diffusion plate 12
`reflecting plate 11, then the reflected light passes below the 5s and then directly irradiates a part of the display area of the
`light shielding plate 10 and is condensed at the end face of
`liquid crystal panel 8 from the lower direction thereof.
`the one end side of the light conduction plate 3. Further,
`According to this direct irradiation, this irradiated part of the
`another part of the planar light emitted from the CCT 4 is
`display area of the liquid crystal panel serves as a high
`reflected by the light reflecting plate 11 and the reflected
`luminance irradiation portion (C) of the display portion of
`light directed upward is transmittable through the light 60 the liquid crystal panel.
`diffusion plate 12. That is, the part of the light emitted from
`Since the high luminance irradiation portion (C) is formed
`the CCT 4 is directed upward and capable of directly
`at the part of the entire display area (A) of the liquid crystal
`irradiating the part of a liquid crystal panel 8 from the lower
`panel 8, the shortage of the luminance in the liquid crystal
`panel 8 is eliminated. Accordingly, a display screen with a
`direction thereof by merely transmitting through the light
`diffusion plate 12.
`65 high luminance and good visibility can be obtained when
`On the other hand, a reflecting sheet 6 is disposed at the
`this LCD 1 is employed as a vehicle-mounted alarm display
`rear surface side of the light conduction plate 3 along the
`device.
`
`Valeo Ex. 1010_006
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`

`US 6,864,930 B2
`
`6
`5
`form a high luminance area in the liquid crystal panel 8 with
`FIG. 3 shows an LCD 1 according to the second embodi-
`a lower cost without using particular parts as compared with
`ment of the present invention. In this figure, elements same
`the conventional LCDs.
`as or common to those of the first embodiment are desig-
`nated by the same reference characters. In this embodiment,
`Each of the LCDs according to the aforesaid embodi-
`a plurality of CCTs 4 are disposed at the lower portion of a s ments may be applied to the segment type as the display
`housing 2. The light emitted from these CCTS 4 is reflected
`method of characters and images, and is effective in par-
`upward by a reflecting sheet 5 which is formed in a wave
`ticular for the dot matrix type which displays characters or
`shape and disposed at the rear portion thereof. A light
`images in the form of the aggregation of dots.
`modulation film 9 is disposed above the CCTs 4, and a light
`As described above, in the conventional LCD, when a
`diffusion plate 7 is disposed above the light modulation film 10 back light unit called an edge light type or a side light type
`9. That is, the LCD 1 of the second embodiment is a kind of
`using a light conduction plate is employed as a lighting unit
`the under light type back light unit.
`for lighting a liquid crystal panel of the LCD, there arises a
`Thus, this embodiment is arranged in a manner that the
`problem that the luminance becomes insufficient when the
`light modulation film 9 is not disposed in the upper direction
`LCD is used for a particular object such as a vehicle-
`of one of the CCTs 4 (that is, CCT 4a) and the light emitted
`mounted alarm device. In contrast, the LCD according to the
`from the CCT 4a is shielded by a light shielding plate 13,
`present invention is advantageous in that the display can be
`whereby the light emitted from the CCT 4a transmits the
`~erformed with a high luminance through the constructional
`light diffusion plate 7 and can be directly irradiated on a part
`improvement without using particular parts thereby to elimi-
`of a liquid crystal panel 8.
`nate the aforesaid conventional problem.
`Accordingly, in this embodiment, since the light emitted 20 What is claimed is:
`1. A liquid crystal display device including an under light
`from the plurality of CCTs 4 transmits the light modulation
`film 9 and the light diffusion plate 7, a display area (B)
`type back light unit in which light emitted from a plurality
`of linear light sources is reflected by a reflecting sheet
`which occupies the most part of an entire display area (A) of
`the liquid crystal panel 8 is indirectly irradiated, from the
`disposed at a rear side of the plurality of linear light sources,
`lower direction thereof. According to this indirect 2s then transmitted through a light modulation film and a light
`irradiation, the irradiated display area occupying the most
`diffusion plate to form a planar light source with a first
`part of the entire display area serves as a normal luminance
`uniform luminance indirectly irradiating a first portion of a
`irradiation portion (B) of the display portion of the liquid
`liquid crystal panel from a rear side thereof,
`crystal panel. In contrast, the light emitted upward from the
`wherein one end portion of the light modulation film is
`CCT 4a transmits only the light diffusion plate 7 and then 30
`shielded by a light shielding plate, and light emitted
`directly irradiates a part (C) of the display area of the liquid
`from one of the plurality of linear light sources is
`crystal panel 8 from the lower direction thereof. According
`shielded by the light shielding plate and transmitted
`to this direct irradiation, this irradiated part of the display
`through only the light diffusion plate to irradiate a
`area of the liquid crystal panel serves as a high luminance
`second portion of the liquid crystal panel from the rear
`side thereof with a second luminance higher than the
`irradiation portion (C) of the display portion of the liquid 3s
`crystal panel.
`first luminance.
`As will be understood from the LCDs according to the
`first and second embodiments, the present invention can
`
`Valeo Ex. 1010_007
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