United States Patent [19J
`Funamoto et al.
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006108060A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,108,060
`Aug. 22, 2000
`
`[54] SURFACE-TYPE ILLUMINATION DEVICE
`AND LIQUID CRYSTAL DISPLAY
`
`[75]
`
`Inventors: Tatsuaki Funamoto; Toru Yagasaki;
`Fumiaki Akahane, all of Suwa, Japan
`
`[73] Assignee: Seiko Epson Corporation, Tokyo,
`Japan
`
`5,057,974
`5,124,890
`5,130,898
`5,134,549
`5,283,673
`5,363,294
`5,764,493
`5,949,505
`
`10/1991 Mizobe ..................................... 362/26
`6/1992 Choi et a!. ................................ 362/27
`7/1992 Akahane ................................... 362/31
`7/1992 Yokoyama ................................ 362/31
`2/1994 Murase et a!. ............................ 362/31
`...................... 362/26
`11/1994 Yamamoto et a!.
`6/1998 Liao .......................................... 362/31
`9/1999 Funamoto et a!. ........................ 349/65
`
`[21] Appl. No.: 09/321,687
`
`[22] Filed:
`
`May 28, 1999
`
`Related U.S. Application Data
`
`[62] Division of application No. 08/689,424, Aug. 9, 1996, Pat.
`No. 5,949,505, which is a division of application No.
`08/204,374, May 10, 1994, Pat. No. 5,619,351.
`Foreign Application Priority Data
`
`[30]
`
`May 13, 1993
`
`[JP]
`
`Japan .................................... 5-111852
`
`[51]
`
`Int. Cl? ......................... G02F l/1335; GOlD 11!28;
`F21V 7/04
`[52] U.S. Cl. ................................. 349/65; 362/26; 362/27;
`362/31
`[58] Field of Search .......................... 349/65, 70; 362/26,
`362/27, 31
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3,892,959
`3,968,584
`4,568,179
`4,630,895
`4,648,690
`4,729,067
`4,729,068
`4,811,507
`4,842,378
`4,860,171
`4,933,814
`4,974,122
`4,985,809
`
`7/1975 Pulles ........................................ 362/31
`7/1976 Kingston ................................... 362/31
`.......................... 362/343
`2/1986 Durbin et a!.
`12/1986 Abdala, Jr. et a!. ...................... 362/31
`3/1987 Ohe ........................................... 362/31
`3/1988 Ohe ........................................... 362/26
`3/1988 Ohe ........................................... 362/31
`3/1989 Blanchet ................................... 362/31
`6/1989 Flasck et a!.
`............................. 362/31
`8/1989 Kojima ...................................... 362/31
`6/1990 Sanai ......................................... 362/26
`11/1990 Shaw ......................................... 362/31
`............................. 362/31
`1!1991 Mitsui et a!.
`
`FOREIGN PATENT DOCUMENTS
`
`0317250
`0 442 529
`0 561 329
`
`5/1989 European Pat. Off ..
`8/1991 European Pat. Off ..
`9/1993 European Pat. Off ..
`
`(List continued on next page.)
`
`OTHER PUBLICATIONS
`
`"Advancements In Backlighting Technologies For LCDs",
`K. Hathaway, SPIE Proceedings, High-Resolution Displays
`and Projection Systems, vol. 1664, Feb. 1992, pp. 108-116.
`Electronic Design, Aug. 2, 1961, p. 47.
`Voltarc Technical Bulletin "Fluorescent Lamp", 1987.
`
`Primary Examiner-William L. Sikes
`Assistant Examiner-Walter Malinowski
`Attorney, Agent, or Firm-Mark P. Watson
`
`[57]
`
`ABSTRACT
`
`A surface-type illumination device suitable for providing
`backlight in a liquid crystal display is disclosed. For
`example, an L-shaped fluorescent light can be used as an
`illuminant and mounted next to two edges of a substantially
`rectangular light guide plate. The corner of an edge portion
`between the two edges is removed. The fluorescent light, the
`length of whose illuminating portion is long, is positioned
`with an appropriate gap from the light guide plate allowing
`for illumination with high brightness and low power con(cid:173)
`sumption. Consequently, when the illumination device is
`used in a color liquid crystal display, appropriate backlight
`with high brightness can be obtained. Moreover, because the
`influence of the temperature from the illumination device is
`small, a stable color display can be achieved.
`
`12 Claims, 12 Drawing Sheets
`
`~41c
`
`21
`
`'
`
`[ ]
`'
`0
`
`-41d
`
`LG Display Ex. 1013
`
`LGD_001323
`
`

`

`6,108,060
`Page 2
`
`FOREIGN PATENT DOCUMENTS
`
`0 587 766
`0 145 934
`0 327 493
`2 620 795
`2 632 432
`54-40086
`60-205576
`61-166585
`61-248079
`62-102226
`63-062105
`
`4/1925
`10/1957
`5/1958
`3/1989
`12/1989
`3/1979
`10/1985
`7/1986
`11/1986
`5/1987
`3/1988
`
`France .
`France .
`France .
`France .
`France .
`Japan .
`Japan .
`Japan .
`Japan .
`Japan .
`Japan .
`
`63-45537
`63-175301
`63-124217
`64-45002
`64-45003
`1-183626
`3-15476
`3-201304
`4-102888
`0 664 193
`W088/08149
`
`Japan .
`3/1988
`Japan .
`7/1988
`Japan .
`8/1988
`Japan .
`2/1989
`Japan .
`2/1989
`Japan .
`7/1989
`Japan .
`5/1991
`Japan .
`9/1991
`Japan .
`4/1992
`1!1952 United Kingdom .
`10/1988 WIPO.
`
`LGD_001324
`
`

`

`U.S. Patent
`
`Aug. 22, 2000
`
`Sheet 1 of 12
`
`6,108,060
`
`II
`
`__,/
`
`3
`FIG._1
`
`4
`
`FIG._2
`
`LGD_001325
`
`

`

`U.S. Patent
`
`Aug. 22, 2000
`
`Sheet 2 of 12
`
`6,108,060
`
`1
`
`a
`
`FIG._3
`
`LGD_001326
`
`

`

`U.S. Patent
`
`Aug. 22, 2000
`
`Sheet 3 of 12
`
`6,108,060
`
`7
`
`I
`
`/i
`
`26
`
`41b
`
`~
`21b __/
`
`41d
`
`23bj'
`I
`- c::tc::tc::t
`-
`-
`-
`-
`- • • -
`•
`-
`-
`-
`-
`-
`-
`•
`-
`-
`-
`•
`. • • • . • • • - . . • • • . • • . . • -Oc::tc::t
`I
`- c::tc::tc::r
`-
`-
`-
`-
`-
`-
`-
`-
`-
`-
`•
`-
`-
`-
`-
`-
`-
`-
`-
`- - - - - - -
`- - - - - - .. - - - - . - - .. - -
`-----------------------.-- -~- 24
`-
`' I
`_- _- _- _- _- _- _- _- _- _- _- _- _- _- _- _- _- _- _- _- _- _- _- _- _- _- _-
`I
`- . - - - - - - - - - - - - -
`- - - . - - . - - -
`-
`-
`§§§- -~- -~--~--~--~--~--~- -~--~- -~--~--~--~ _-~--~--~ --~- -~--~--:t§§?
`
`-
`
`I
`
`6
`
`' I
`I
`
`'
`
`f=k(========='l-25
`
`FIG._4
`
`LGD_001327
`
`

`

`U.S. Patent
`
`Aug. 22, 2000
`
`Sheet 4 of 12
`
`6,108,060
`
`14
`
`10b
`
`~ .. :-:
`
`'
`'
`'
`'
`'
`'
`'
`'
`'
`'
`'
`'
`'
`'
`~ --'
`
`--22
`
`f VII
`
`1 VII
`
`--------------------------------------- -------------------------------
`--------------------------------------- ---------------------------------
`
`'
`_,'
`
`'
`/
`~
`
`20d
`
`21
`
`23b
`
`22b
`
`42
`
`FIG._5
`
`FIG._6
`
`22c
`
`42
`
`22
`
`43 ---'
`22a
`
`LGD_001328
`
`

`

`U.S. Patent
`
`Aug. 22, 2000
`
`Sheet 5 of 12
`
`6,108,060
`
`22b
`
`23a
`
`41c-- _ ,
`--
`'
`-1
`' '
`' ' ' ' '
`
`40
`
`FIG._7
`
`21
`
`FIG._BA
`
`41d
`
`22
`
`22c
`
`FIG._BB
`
`'
`'
`: :
`..
`I
`'"'.,.J
`'
`'
`'
`'
`_; : :
`
`I
`I
`
`I
`I
`
`I
`:
`
`.;'
`, '
`
`--
`
`'
`,'/
`
`'
`...... '
`'
`,,
`.,.' \
`
`·-22a
`
`41c--
`
`'" ..
`
`41d-,
`'
`' '
`'
`__________ ! _________ , --~
`------------------------
`
`40
`
`-..
`\
`
`23b
`
`LGD_001329
`
`

`

`U.S. Patent
`
`Aug. 22, 2000
`
`Sheet 6 of 12
`
`6,108,060
`
`21
`
`FIG._9
`
`41d
`
`21
`
`41c
`
`FIG._10A
`
`FIG._10B
`
`21
`
`41c
`
`41c
`
`41d
`
`FIG._10C
`
`FIG._10D
`
`LGD_001330
`
`

`

`U.S. Patent
`
`Aug. 22, 2000
`
`Sheet 7 of 12
`
`6,108,060
`
`41b
`
`41d
`
`41b
`
`DOD·
`DOD·
`ODD·
`
`ODD·
`DOD·
`ODD·
`FIG._11
`
`DOD·
`DOD·
`DOD·
`
`41a
`
`41a
`
`r 128
`
`ODD·
`DOD·
`DOD·
`FIG._12A
`
`r--------------------
`
`41d
`
`29a
`
`FIG._12B
`
`29b
`
`·DOD
`·ODD
`·ODD
`
`41c
`
`0 0 0 0
`
`40
`
`29
`
`·ODD
`·ODD
`·DOD
`
`51
`
`41c
`
`1 128
`
`43
`
`·DODO
`·DODO
`·DOD
`
`40
`
`29
`
`LGD_001331
`
`

`

`U.S. Patent
`
`Aug. 22, 2000
`
`Sheet 8 of 12
`
`6,108,060
`
`10b
`
`61
`
`'
`: ,' -·62
`X
`
`'
`
`: ! ,' -·41c
`,,
`'
`~ ~ ..
`
`' ' ' 1
`
`r XIV
`
`XIV
`I '"===============~---l.-4--1
`L
`,
`-'
`.... _ --------------------------------------------:--------------------------------- .... '
`,..,'
`.-"'
`----------------------------------------------~---------------------------------·-·
`'
`
`I
`
`5
`
`41a ---
`
`'
`
`:
`
`'
`
`I
`
`.,"~
`
`... ~ .... ~-
`'-
`.,
`\,.
`
`'
`
`26
`
`61
`
`FIG._13
`
`41d)
`
`38
`
`---------
`
`________________________________________ j
`-------------------------+-----
`52
`'
`3·/
`
`FIG._14
`
`LGD_001332
`
`

`

`U.S. Patent
`
`Aug. 22, 2000
`
`Sheet 9 of 12
`
`6,108,060
`
`t::==L ======';;27
`f;;;;;;;::=:::/ =======:::lil ::
`
`61
`
`60
`
`FIG._15
`
`LGD_001333
`
`

`

`U.S. Patent
`
`Aug. 22, 2000
`
`Sheet 10 of 12
`
`6,108,060
`
`61
`
`41b
`
`41a
`
`41c
`
`40a
`
`41d
`
`40b
`
`FIG._16
`
`52
`
`61b
`
`ODD·
`DOD
`DOD·
`
`·DOD
`·DOD
`·ODD
`
`41c
`
`41a
`
`0 0 0
`0
`0
`
`•
`•
`•
`
`40b
`
`0 0 0.
`DOD·
`ODD·
`
`41d
`
`FIG._17
`
`0 0 0
`0 0
`0 0
`
`40a
`
`LGD_001334
`
`

`

`U.S. Patent
`
`Aug. 22, 2000
`
`Sheet 11 of 12
`
`6,108,060
`
`SURFACE TEMPERATURE
`
`65
`
`45
`
`35
`
`FIG._18
`
`~ - - - - - - - - - - - - - - - - - - - - - -
`ROOM TEMPERATURE
`
`POSITION DIRECTLY J
`OVER THE
`LIGHT SOURCE
`
`CENTRALJ
`PORTION OF
`THE IMAGE
`
`t
`POSITION DIRECTLY
`OVER THE
`LIGHT SOURCE
`
`72a
`
`71
`
`40
`
`FIG._19
`
`40
`
`SURFACE TEMPERATURE
`
`FIG._22
`
`ROOM TEMPERATURE
`
`END PORTION _j CENTRALJ
`
`OF THE IMAGE
`
`PORTION OF
`THE IMAGE
`
`t
`
`POSITION DIRECTLY
`OVER THE LAMP
`LIGHT SOURCE
`
`LGD_001335
`
`

`

`U.S. Patent
`
`Aug. 22, 2000
`
`Sheet 12 of 12
`
`6,108,060
`
`82a
`
`82b
`
`FIG._20
`
`,;--90
`
`FIG._21
`
`r-92
`
`I
`
`LGD_001336
`
`

`

`6,108,060
`
`1
`SURFACE-TYPE ILLUMINATION DEVICE
`AND LIQUID CRYSTAL DISPLAY
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`5
`
`This is a Divisional of prior application Ser. No. 08/689,
`424 filed Aug. 9, 1996, now U.S. Pat. No. 5,949,505, which
`is a Division of application Ser. No. 08/204,374 filed May
`10, 1994, now U.S. Pat. No. 5,619,351. Application Ser.
`Nos. 08/689,424 and 08/204,374 are incorporated herein by 10
`reference in their entirety.
`
`2
`Consequently, in the case when several fluorescent tubes are
`used in one illumination device, extra time is required during
`the manufacturing process to obtain a balanced and fixed
`illumination intensity.
`Another problem is the increased number of driver cir(cid:173)
`cuits required to turn on the fluorescent tubes. The number
`of these driver circuits can not be easily increased in devices
`such as microcomputers where thinness and small size are
`important.
`
`BACKGROUND OF THE INVENTION
`
`15
`
`This invention relates in general to a thin, surface-type
`illumination device for providing backlight for liquid crystal
`displays (LCD) and, in particular, to a suitable illumination
`device for use in a notebook computer display that provides
`high brightness with low power consumption as well as to a
`liquid crystal display that uses this illumination device.
`Surface-type illumination devices with a cylindrical light
`source and a fiat light guide plate such as the devices
`described in Japanese Laid-Open Patent Application No.
`60-205576 and Japanese Laid-Open Patent Application No.
`61-248079 are well-known. One such example is shown in
`FIG. 21. In the illumination device 90, cylindrical fluores(cid:173)
`cent light 92 is positioned on one side of the substantially
`rectangular and fiat light guide plate 91. The light introduced
`to light guide plate 91 from fluorescent light 92 is reflected
`by the diffusion pattern printed on light guide plate 91 and
`emitted from the surface of the light guide plate at a fixed
`density of light.
`This type of surface illumination device, in recent years,
`has been used extensively to provide backlight for liquid
`crystal display panels. Liquid crystal display panels are
`increasingly used as displays in such devices as laptop
`computers, televisions and cameras. The use of liquid crystal
`display panels for color displays is also increasing. As the
`size of personal computers and televisions become smaller,
`it is imperative that liquid crystal display panels become
`thinner and lighter.
`Accordingly, it is necessary that the surface-type illumi(cid:173)
`nation device used for liquid crystal display panels to
`provide backlight, along with the color displays, becomes
`thinner and lighter with less power consumption. Also, to
`use in color displays, a sufficient brightness is necessary to
`clearly show the colors displayed in the liquid crystal. This
`requires the use of a high output fluorescent light in the
`illumination device. However, along with the light, heat is
`also radiated from the high-output fluorescent light. The
`effect of this heat, as shown in FIG. 22, is significant. The
`temperature may rise 30-40° C. above a normal temperature
`of 25° C. Consequently, when this type of illumination
`device is used for providing backlight in an MIM active
`color display panel or in an STN passive color display panel,
`a special method to reduce the heat is necessary to control,
`to a certain extent, the color and brightness irregularities.
`Instead of using one high output fluorescent tube, one may
`also increase the number of fluorescent tubes. In this way, it
`is possible to control to some extent the temperature increase 60
`due to the light source. However, as the number of fluores(cid:173)
`cent tubes is increased, many other problems appear. One of
`these problems is the variations in the illumination of the
`fluorescent tubes. Because the illumination intensity of
`florescent tubes varies according to each tube, it is necessary 65
`to adjust such things as the resistance within the fluorescent
`tube driver circuit to obtain a fixed illumination intensity.
`
`SUMMARY OF THE INVENTION
`In accordance with the instant invention, a suitable illu(cid:173)
`mination device for color liquid crystal displays can be
`obtained that is small in size, lightweight, and has high and
`uniform brightness. Further, it is an object of the invention
`to provide a surface-type illumination device that can pre(cid:173)
`vent heat generation and its resulting bad effects to the liquid
`crystal display panel.
`Another object of the invention is to provide a surface-
`20 type illumination device that, without increasing the number
`of driver circuits for driving the fluorescent lights, displays
`a brightness higher than that in conventional illumination
`devices and restricts heat radiation.
`A further object of the invention is to generate a suitable
`25 diffusion pattern to realize a surface-type illumination
`device, this diffusion pattern being used in the illumination
`device.
`Still another object of the invention is to provide a stable
`liquid crystal display where the driver IC for driving the
`30 liquid crystal display panel is positioned so that it will not be
`affected by heat.
`In accordance with the instant invention, by employing an
`illuminant longer than conventional illuminants, illumina(cid:173)
`tion with high illumination intensity is obtained without
`35 increasing the number of driver circuits for driving the
`illuminants and without concentrating the heat diffusion.
`Further, by bending the illuminant, light can be introduced
`along the polygon-shaped light guide plate. Also, to main(cid:173)
`tain proper space between the light guide plate and the
`40 illuminant and to increase the efficiency of the light intro(cid:173)
`duced to the light guide plate, a corner is removed from an
`edge of the light guide plate. According to the invention, the
`surface-type illumination device comprises a light guide
`plate which is polygon-shaped and substantially transparent;
`45 a diffusion pattern arranged on one surface of the light guide
`plate for substantially evenly emitting light, the light being
`introduced from the illuminant to the other surface of the
`light guide plate; and a cylindrically-shaped illuminant bent
`so that the illuminant faces at least two sides of the light
`50 guide plate; wherein the edge between the two sides is
`processed so that the corner does not protrude.
`By using an illuminant bent along the light guide plate,
`the length of the cylindrically-shaped illuminant is long, and
`an illuminant with large illuminating area can be used.
`55 Consequently, the rise in temperature of the illuminant can
`be kept down and high brightness can be obtained.
`Furthermore, the number of driver circuits for driving the
`illuminant can be decreased. When an illuminant such as a
`fluorescent light is bent to adjust for interference between
`the bent portion and the corner of the light guide plate, the
`width or length of the entire illumination device becomes
`longer, preventing miniaturization. In the instant invention,
`by removing a corner of the light guide plate, the distance
`between the light guide plate and the illuminant can be kept
`within a fixed range for high incident efficiency, and thus, a
`highly efficient illumination device that is small in size can
`be realized.
`
`LGD_001337
`
`

`

`6,108,060
`
`10
`
`4
`the light incident to the light guide plate from the first side
`and the density distribution of the presupposed diffusion
`pattern; and then compensating the density distribution of
`the presupposed diffusion pattern so that the sum of the
`predicted emitted light intensity distribution for the
`x-direction and the predicted emitted light intensity distri-
`bution for the y-direction on arbitrary rectangular xy coor(cid:173)
`dinates of the light guide plate fit within a fixed range.
`When an edge reflector is installed at at least one of the
`two sides opposite to the first side and the second side,
`respectively, for reflecting the light from the inner part of the
`light guide plate to the light guide plate, it is desirable to
`compensate the density distribution by computing the
`reflected light intensity incident from the edge reflector to
`15 the light guide plate with a fixed attenuation factor; finding
`a predicted emitted light intensity distribution for at least
`one of the x and y directions of the reflected light intensity;
`and adding this to the predicted emitted light intensity
`distribution found above.
`By printing the diffusion pattern described above on the
`light guide plate or by putting on the light guide plate a sheet
`with the pattern formed on it, light introduced from the bent
`illuminant can be evenly radiated from the light guide plate.
`Similarly, light can be evenly emitted by making the thick-
`25 ness of a light guide plate with an even diffusion pattern
`inversely proportion to the compensated density distribution
`of the diffusion pattern.
`Effects of the heat from the illuminant can be minimized
`by using as a bent illuminant an L-shaped illuminant and by
`placing in a position opposite to the illuminant a driver
`device such as a driver IC for driving the liquid crystal
`display. Consequently, as the threshold value of the driver
`does not become unstable due to the heat, a color display
`with stable contrast is obtained. Further, a high quality
`display with high brightness and a small illumination device
`are also obtained.
`Further, a stable, high quality display can be obtained that
`reduces heat using an even longer U-shaped illuminant. The
`40 brightness of the display is easy to adjust when illuminants
`such as L-shaped and U-shaped illuminants are used because
`nearly the same intensity of light is incident from the
`periphery of the light guide plate. Of course, an 0-shaped
`illuminant can also be arranged around the periphery of a
`45 rectangular light guide plate as well as an illuminant bent to
`fit the shape of any other polygon.
`Other objects and attainments together with a fuller
`understanding of the invention will become apparent and
`appreciated by referring to the following description and
`claims taken in conjunction with the accompanying draw(cid:173)
`ings.
`
`3
`Further, by using a long illuminant as mentioned above,
`an improvement in the conversion efficiency from power to
`light is also attained. For example, in illuminants such as a
`fluorescent light, the power to the illuminant is consumed by
`the cathode drop, which is due to the glow discharge, and by 5
`positive column gradient voltage, which is due to light
`emission. When a plurality of illuminants are used and the
`input voltage increased, the portion consumed by the cath(cid:173)
`ode drop voltage significantly increases and an increase in
`the positive column gradient tendency for light emission is
`small. However, in the illumination device of the instant
`invention, which uses a long illuminant, power is efficiently
`converted into light as the increase in the positive column
`gradient voltage is smaller than in the case when the number
`of illuminants is increased.
`The edge of the light guide plate can be processed into
`many different shapes, for example, the corner in the shape
`of an isosceles triangle can be removed. In the case of the
`isosceles triangle, a high incident efficiency of light from the
`illuminant to the light guide plate can be maintained. It is 20
`desirable to make the length of one of the sides of the
`isosceles triangle in the approximate range of 0.6 times to
`1.0 times the smallest radius of curvature of the bent portion
`of the illuminant so as to realize a small-sized illumination
`device. Also, in order to prevent light incident from the edge,
`and to increase the uniformity of the light radiated from the
`light guide plate, it is effective to include a shield at the edge
`portion to prevent introduction of light from the illuminant.
`Also, the corner of the edge in a diamond-shape may be
`removed. In order to make the incident efficiency high and 30
`keep the size of the device small, it is desirable to make the
`length of one of the sides of the removed corner in a
`diamond-shape within a range of 0.6 times to 1.0 times the
`smallest radius of curvature of the bent portion of the
`illuminant. Also, if all the corners are removed from the 35
`edges of the light guide plate so that they do no protrude, the
`directionality of the light guide plate disappears and the
`manufacturing process time for positioning the light guide
`plate is saved.
`It is common to cover the illuminant with a reflector to
`increase the incident efficiency of the light from the illumi(cid:173)
`nant to the light guide plate. When a bent illuminant such as
`the one described above is used, it is desirable for the
`reflector to include a straight first reflector and a second
`reflector positioned along two sides of the light guide plate
`such that at the edge the first reflector is covered by the
`second reflector. It is also possible for the reflector to include
`a first reflector that covers the lower half portion of the
`illuminant on one side of the light guide plate and a second
`reflector that covers the upper half of the illuminant from the 50
`other side of the light guide plate.
`The diffusion pattern that diffuses light incident to the
`light guide plate from the bent illuminant can be generated
`by the following method. To generate a diffusion pattern that
`evenly radiates, from the other side of the light guide plate,
`light introduced from the illuminant to the light guide plate
`in an illumination device where a cylindrically-shaped illu(cid:173)
`minant is positioned near at least a first side and a second
`side of a substantially rectangular light guide plate, the
`density distribution per unit area of the diffusion pattern can 60
`be found by the following method: finding a predicted
`emitted light intensity distribution for the y-direction along
`the first side based on the intensity of the light incident to the
`light guide plate from the second side and the density
`distribution of a presupposed diffusion pattern; then finding 65
`a predicted emitted light intensity distribution for the
`x-direction along the second side based on the intensity of
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a sketch of a liquid crystal display using the
`55 surface-type illumination device in accordance with the first
`embodiment of the invention.
`FIG. 2 is a cross-sectional view of FIG. 1 showing the
`structure of the liquid crystal display.
`FIG. 3 is a break-down view showing the structure of the
`liquid crystal display shown in FIG. 1.
`FIG. 4 is a break-down view showing the construction of
`the surface-type illumination device used in the liquid
`crystal display shown in FIG. 1.
`FIG. 5 is a top plan view illustrating the combination of
`the surface-type illumination device shown in FIG. 4 and the
`liquid crystal display panel.
`
`LGD_001338
`
`

`

`6,108,060
`
`30
`
`5
`6
`FIG. 6 is an explanatory drawing showing the positioning
`The basic structure of one embodiment of liquid crystal
`display 1 will be explained using the cross-sectional view of
`of the light guide plate and fluorescent light of the surface(cid:173)
`liquid crystal display 1 shown in FIG. 2 and the break-down
`type illumination device of FIG. 4.
`view of liquid crystal display 1 shown in FIG. 3. In liquid
`FIG. 7 is a cross-sectional view taken along the line
`5 crystal display 1, illumination device 20 is installed in lower
`VII-VII in FIG. 5 showing the relationship of the light
`case 3. Above device 20, liquid crystal display panel 10 is
`guide plate, fluorescent light, and reflector of the surface(cid:173)
`installed using frames 30 and 31. Liquid crystal display
`type illumination device of FIG. 4.
`panellO is formed by enclosing the liquid crystal, transpar(cid:173)
`FIGS. SA and 8B illustrate the assembly of the reflector
`ent electrodes, etc. between two layers of transparent glass
`of FIG. 7.
`substrates 11 and 12. At side lOa of liquid crystal display
`FIG. 9 is an enlarged view of the edge of the light guide 10
`panel 10, a plurality of driver ICs 13 are installed for
`plate.
`latching pixel data for the rows and sending it to the liquid
`crystal display panel. Also, at side lOb, which is adjacent to
`FIGS. lOA-lOD show enlarged views of several possible
`side lOa, a plurality of driver ICs 14 are installed for latching
`edge formations of the light guide plate.
`pixel data for the columns and sending it to the liquid crystal
`FIG. 11 is an explanatory drawing showing the diffusion
`15 display panel.
`pattern formed on the diffusion sheet which sticks to the
`Frames 30 and 31 are used to protect illumination device
`light guide plate.
`20 and to position it within the case. At the same time, it also
`FIG. 12Ais a plan view showing a light guide plate whose
`fills the role of maintaining a fixed distance for gap 33
`thickness has been changed.
`between illumination device 20 and liquid crystal display
`FIG. 12B is a cross-sectional view showing a light guide
`20 panellO, for example, 0.2-1 mm. For this reason, frames 30
`and 31 are prepared so that their lower halves 34 and 35
`plate whose thickness has been changed.
`support illumination device 20 and their upper halves 36 and
`FIG.l3 is a top plan view showing the combination of the
`37 act as spacers between illumination device 20 and liquid
`liquid crystal display panel and illumination device in accor(cid:173)
`crystal display panellO. In this example the frame is divided
`dance with the second embodiment of this invention.
`into two pieces, however, the number of pieces is not limited
`FIG. 14 is a cross-sectional view showing the relationship 25
`to two. For example, three pieces, four pieces, or even more
`of the liquid crystal display panel, illumination device, and
`is possible, and even just one piece is also possible.
`illuminant as shown in FIG. 13.
`Furthermore, the frame need not cover the entire periphery
`FIG. 15 is a break-down view showing the construction of
`of illumination device 20 or liquid crystal display panellO.
`the structure of the surface-type illumination device used in
`A plurality of pieces may be arranged in appropriate places.
`the liquid crystal display shown in FIG. 14.
`Illumination device 20 is a surface-type illumination
`FIG. 16 is an explanatory drawing showing the relation(cid:173)
`device set up with a cylindrically-shaped fluorescent light 22
`ship of the light guide plate and the fluorescent light which
`at the edge of substantially rectangular light guide plate 21.
`is in the surface-type illumination device of FIG. 15.
`Fluorescent light 22 is roughly L-shaped and is covered by
`FIG. 17 is an explanatory drawing showing the diffusion
`35 reflectors 23a and 23b. Wires for supplying power to drive
`pattern that is printed on the light guide plate of FIG. 15.
`fluorescent light 22 extend from both ends of fluorescent
`light 22 and are connected to the driver circuit on the host
`FIG. 18 is a graph showing the surface temperature of the
`side through connector 7 which is for turning on the light.
`liquid crystal display panel shown in FIG. 13.
`FIG. 4 is a break-down view of illumination device 20 and
`FIG. 19 is an explanatory drawing showing another
`relationship of the light guide plate and the fluorescent light. 40 will be used to explain the structure of the illumination
`device of this embodiment. Illumination device 20 is com(cid:173)
`FIG. 20 is an explanatory drawing showing still another
`prised of light guide plate 21, which is substantially rectan(cid:173)
`relationship of the light guide plate and the fluorescent light.
`gular in shape and has the corner of at edge 40 missing,
`FIG. 21 is an explanatory drawing showing a conven(cid:173)
`fluorescent light 22, which encompasses edge 40 in an
`tional light guide plate and fluorescent light.
`45 L-shape, and reflectors 23a and 23b, which cover fluorescent
`FIG. 22 is a graph showing the surface temperature of a
`light 22 in the direction of light guide plate 21 and efficiently
`liquid crystal display panel using a surface-type illumination
`reflect light from fluorescent light 22 to light guide plate 21.
`device similar to the one shown in FIG. 21.
`On lower surface 2lb of light guide plate 21, i.e., the side
`opposite to the side where liquid crystal display panellO is
`50 arranged, pattern sheet 24, which is printed with diffusion
`pattern 50, and reflecting sheet 25 are arranged in that order.
`On upper surface 2la of light guide plate 21, i.e., the side
`where liquid crystal display panellO is arranged, diffusion
`sheet 26 and prism sheet 27 are arranged. Edge reflective
`55 tape 28 is put on edge 4la and 4lb, opposite to fluorescent
`light 22 of light guide plate 21.
`Light guide plate 21 is a transparent material whose index
`of refraction is greater than that of air. An index of refraction
`equal to or greater than 1.41 is desirable using such materials
`60 as acrylic resin, polycarbonate resin, amorphous
`polyolefine-type resin, and polystyrene resin. Use of these
`types of materials for light guide plate 21 results in a critical
`angle of 45° or less. If upper surface 2la and lower surface
`2lb are smooth and mirror-like, the light incident from
`65 edges 4la, 4lb, 4lc, and 4ld, which are formed at right
`angles to surface 2la and 2lb, is completely reflected from
`surfaces 2la and 2lb.
`
`EMBODIMENT 1
`FIG. 1 is a sketch of liquid crystal display 1 in accordance
`with one embodiment of this invention. Liquid crystal
`display 1 is constructed with liquid crystal display panellO
`and an illumination device to be described later sandwiched
`between upper case 2 and lower case 3. Upper case 2 and
`lower case 3 are fixed in place by tooth 4. The scanning data
`that comprises the image is supplied from the host side to
`each row or column through tape electrode 5 and tape
`electrode 6. This data is latched by a driver IC which will be
`described below, is synchronized, and is supplied to liquid
`crystal display panellO where the image is formed. Power
`is supplied from the driver circuit of the host side to the
`fluorescent light comprising the illumination device through
`connector 7, connector 7 extending past liquid crystal dis(cid:173)
`play 1 and used for initiating lighting.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`LGD_001339
`
`

`

`6,108,060
`
`20
`
`7
`Pattern sheet 24 is a transparent sheet with a fixed number
`of diffusion patterns 50 printed on it, the printed diffusion
`patterns being adhered to lower surface 2lb of light guide
`plate 21. Light incident from sides 41, to some extent,
`reaches diffusion pattern 50 and, without being completely
`reflected, will be diffused in the direction of upper surface
`2la. Consequently, light incident from the fluorescent light
`by way of the edges is emitted to liquid crystal display panel
`10 from upper surface 2la.
`Reflecting sheet 25 is a thin PET sheet with a thickness of 10
`approximately 0.05--0.5 mm. Light coming from upper
`surface 2la of light guide plate 21 through diffusion pattern
`50 travels through diffusion sheet 26 and prism sheet 27,
`which are arranged on the upper portion of upper surface
`2la and light up liquid crystal display panellO. However, a 15
`portion of the light is reflected from sheets 26 and 27 in the
`lower direction. The light reflected from the upper direction
`is returned to light guide plate 21, among others, through
`reflecting sheet 25 among others. Reflecting sheet 25 may be
`aluminum or other non-PET material. Also, lower case 3
`may be used as a reflector in place of a reflecting sheet.
`Further, the frame of a computer or similar part carrying the
`illumination device or liquid crystal display can also be used
`as a reflector in place of the reflecting sheet.
`Diffusion sheet 26 is an approximately 0.05-0.5 mm thi