[19]
`United States Patent
`6,108,060
`[11] Patent Number:
`[45] Date of Patent: Aug. 22, 2000
`Funamoto et al.
`
`
`
`U8006108060A
`
`[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
`
`[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.
`
`[30]
`
`Foreign Application Priority Data
`
`May 13, 1993
`
`[JP]
`Japan .................................... 5—111852
`
`
`[51]
`
`Int. Cl?
`
`.......... GozF 1/1335; G01D 11/28;
`F21V 7/04
`349/65; 362/26; 362/27;
`362/31
`[58] Field of Search .......................... 349/65, 70; 362/26,
`362/27, 31
`
`[52] US. Cl.
`
`[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
`2/1986 Durbin et al.
`.
`362/343
`
`12/1986 Abdala, Jr. et a].
`. 362/31
`3/1987 Ohe
`.. 362/31
`3/1988 Ohe .
`.. 362/26
`
`3/1988 Ohe
`.. 362/31
`.. 362/31
`3/1989 Blanehet
`
`6/1989 Flasck et a1.
`.. 362/31
`.. 362/31
`8/1989 Kojima
`
`.. 362/26
`6/1990 Sanai ..
`11/1990 Shaw
`.. 362/31
`1/1991 Mitsui et al.
`..... 362/31
`
`5,057,974 10/1991 Mizobe
`.362/26
`5,124,890
`6/1992 Choi et al.
`362/27
`
`5,130,898
`7/1992 Akahanc .....
`. 362/31
`. 362/31
`5,134,549
`7/1992 Yokoyauia ..
`
`5,283,673
`2/1994 Murase et a1.
`362/31
`.. 362/26
`5,363,294 11/1994 Yamamoto et a1.
`. 362/31
`6/1998 Lian ...............
`5,764,493
`
`
`.. 349/65
`9/1999 Funamoto et a1
`5,949,505
`FOREIGN PATENT DOCUMENTS
`
`0 317 250
`0 442 529
`0 561 329
`
`5/1989
`8/1991
`9/1993
`
`European Pat. Off. .
`European Pat. Oif. .
`European Pat, Off. .
`
`(List continued on next page.)
`OTHER PUBLICATIONS
`
`“Advancements ln Backlighting Technologies For LCDs”,
`K. Hathaway, SPIE Proceedings, HighiResolution 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%ark 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-
`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
`
`
`
`so
`
`
`
`LGE_000836
`
`LG Electronics Ex. 1013
`
`LGE_000836
`
`LG Electronics Ex. 1013
`
`

`

`6,108,060
`Page 2
`
`3/1988
`
`Japan.
`
`63-45537
`,
`,
`,
`Japan.
`7/1988
`63-175301
`Japan.
`8/1988
`637124217
`Japan-
`2/1989
`64-45002
`Japan.
`2/1989
`64-45003
`Japan.
`7/1989
`1—183626
`Japan.
`5/1991
`3—15476
`Japan.
`9/1991
`3-201304
`(C,
`7,
`Japan.
`4/1))2
`4-102888
`1/1952 United Kingdom.
`0664193
`W088/08149 10/1988 WIPO.
`
`FOREIGN PATENT DOCUMENTS
`rance.
`F
`4/1925
`0587 766
`0145 934 10/1957 France.
`0327 493
`5/1958 France.
`2620795
`3/1989 France.
`2632 432 12/1989 France.
`54-4008?
`3/1979
`Japan~
`6020557"
`19/1985
`Jap‘m'
`61-166585
`//1986
`Japan.
`61-248079
`11/1986
`Japan.
`62-102226
`5/1987
`Japan.
`63-062105
`3/1988
`Japan.
`
`LGE_000837
`
`LGE_000837
`
`

`

`US. Patent
`
`Aug. 22, 2000
`
`Sheet 1 0f 12
`
`6,108,060
`
`
`
`36
`10X
`33
`37
`2
`
`
`'lm'lnnnn'lmnn-
`I
`
`V—_ L
`J—‘F—F‘
`
`
`
`
`11
`
` —-m‘.sl
`
`
`LGE_000838
`
`LGE_000838
`
`

`

`US. Patent
`
`Aug. 22, 2000
`
`Sheet 2 0f 12
`
`6,108,060
`
`
`
`
`
`
`FIG._3
`
`LGE_000839
`
`LGE_000839
`
`

`

`US. Patent
`
`Aug. 22, 2000
`
`Sheet 3 0f 12
`
`6,108,060
`
`\
`
`
`
`FIG._4
`
`LGE_000840
`
`LGE_000840
`
`

`

`US. Patent
`
`Aug. 22, 2000
`
`Sheet 4 0f 12
`
`6,108,060
`
`
`
`LGE_000841
`
`LGE_000841
`
`

`

`US. Patent
`
`Aug. 22, 2000
`
`Sheet 5 0f 12
`
`6,108,060
`
` W1/17/7 {3}
`
`!
`5
`
`!
`!
`I
`
`26
`
`!
`5
`
`!
`!
`0 L!
`
`FIG._7
`
`25
`
`FIG._8A
`
`FIG._BB
`
`22
`
`LGE_000842
`
`LGE_000842
`
`

`

`US. Patent
`
`Aug. 22, 2000
`
`Sheet 6 0f 12
`
`6,108,060
`
`FIG._9
`
`
`22
`
`21
`
`41c
`
`40
`
`45b
`
`41d
`
`FIG._ 10A
`
`41d
`
`HQ. 103
`
`41c
`
`47C 41d
`
`HQ. 100
`
`'
`
`FIG._10D
`
`LGE_000843
`
`LGE_000843
`
`

`

`US. Patent
`
`Aug. 22, 2000
`
`Sheet 7 0f 12
`
`6,108,060
`
`[24
`
`410
`
`41C
`
` 41a
`
`41a
`
`123
`
`
` HQ. 125
`29b
`
`LGE_000844
`
`LGE_000844
`
`

`

`US. Patent
`
`Aug. 22, 2000
`
`Sheet 8 0f 12
`
`6,108,060
`
`
`
`
`27
`26.
`
`61
`
`25
`
`LGE_000845
`
`
`
`L_‘_L“/_:\\\\\\\\\\\‘
`'
`
`
`__________________________________ J
`
`.
`
`LGE_000845
`
`

`

`US. Patent
`
`Aug. 22, 2000
`
`Sheet 9 0f 12
`
`6,108,060
`
`
`
`
`
`
`
`LGE_000846
`
`LGE_000846
`
`

`

`US. Patent
`
`Aug. 22, 2000
`
`Sheet 10 0f 12
`
`6,108,060
`
`
`
`FIG._ 16
`
`41C
`
`40b
`
`4“
`
`FIG._17
`
`LGE_000847
`
`LGE_000847
`
`

`

`US. Patent
`
`Aug. 22, 2000
`
`Sheet 11 0f 12
`
`6,108,060
`
`SURFACE TEMPERATURE
`
`65
`
`55
`
`45
`
`35
`
`(°C)
`
`FIG 18
`'_
`
`25 ——————————————————————
`ROOM TEMPERATURE
`
`POSITION DIRECTLYj
`
`OVER THE
`LIGHT SOURCE
`
`CENTRAL!T
`
`PORTION OF
`THE IMAGE
`
`POSITION DIRECTLY
`
`OVER THE
`LIGHT SOURCE
`
`
`72b
`ROOM TEMPERATURE
`
`65
`
`55
`
`( C) 45
`
`35
`
`25
`
`FIG. -22
`
`SURFACE TEMPERATURE
`
`
`
`END PORTION —T CENTRAL!T
`
`OF THE IMAGE
`
`PORTION OF
`THE IMAGE
`
`POSITION DIRECTLY
`
`OVER THE LAMP
`LIGHT SOURCE
`
`LGE_000848
`
`LGE_000848
`
`

`

`US. Patent
`
`Aug. 22, 2000
`
`Sheet 12 0f 12
`
`6,108,060
`
`828
`
`82b
`
`FIG._20
`
`[90
`
`91
`
`92
`
`FIG._21
`
`LGE_000849
`
`LGE_000849
`
`

`

`6,108,060
`
`1
`SURFACE-TYPE ILLUMINATION DEVICE
`AND LIQUID CRYSTAL DISPLAY
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This is a Divisional of prior application Ser. No. 08/689,
`424 filed Aug. 9, 1996, now US. 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
`reference in their entirety.
`BACKGROUND OF THE INVENTION
`
`10
`
`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 flat
`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—
`cent light 92 is positioned on one side of the substantially
`rectangular and flat 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-
`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
`due to the light source. However, as the number of fluores-
`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
`floresecnt tubes varies according to each tube, it is necessary
`to adjust such things as the resistance within the fluorescent
`tube driver circuit to obtain a fixed illumination intensity.
`
`tom
`
`30
`
`L» .n
`_
`
`40
`
`50
`
`60
`
`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-
`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.
`
`SUMMARY OF THE INVENTION
`
`In accordance with the instant invention, a suitable illu-
`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—
`vent heat generation and its resulting bad effects to the liquid
`crystal display panel.
`Another object of the invention is to provide a surface-
`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
`diffusion pattern to realize a surface-type illumination
`device, this dilfusion 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
`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-
`tion with high illumination intensity is obtained without
`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—
`tain proper space between the light guide plate and the
`illuminant and to increase the efliciency of the light intro-
`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;
`a dilfusion 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
`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.
`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.
`
`LGE_000850
`
`LGE_000850
`
`

`

`6,108,060
`
`3
`Further, by using a long illuminant as mentioned above,
`an improvement in the conversion efliciency 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
`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-
`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
`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
`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
`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—
`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
`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 dilfusion 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—
`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
`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
`a predicted emitted light
`intensity distribution for the
`x-direction along the second side based on the intensity of
`
`10
`
`tom
`
`30
`
`L»LA
`
`40
`
`50
`
`60
`
`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—
`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
`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-
`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
`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 O—shaped
`illuminant can also be arranged around the periphery of a
`rectangular light guide plate as well as an illuminant bent to
`fit the shape of any other polygon.
`fuller
`Other objects and attainments together with a
`understanding of the invention will become apparent and
`appreciated by referring to the following description and
`claims taken in conjunction with the accompanying draw-
`ings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG 1 is a sketch of a liquid crystal display using the
`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 vier illustrating the combination of
`the surface—type illumination device shown in FIG. 4 and the
`liquid crystal display panel.
`
`LGE_000851
`
`LGE_000851
`
`

`

`6,108,060
`
`5
`FIG. 6 is an explanatory drawing showing the positioning
`of the light guide plate and fluorescent light of the surface-
`type illumination device of FIG. 4,
`FIG. 7 is a cross-sectional View taken along the line
`VII—VII in FIG. 5 showing the relationship of the light
`guide plate, fluorescent light, and reflector of the surface—
`type illumination device of FIG. 4,
`FIGS. 8A and 8B illustrate the assembly of the reflector
`of FIG. 7.
`
`FIG. 9 is an enlarged view of the edge of the light guide
`plate.
`FIGS. 10A—10D show enlarged views of several possible
`edge formations of the light guide plate.
`FIG. 11 is an explanatory drawing showing the diffusion
`pattern formed on the diffusion sheet which sticks to the
`light guide plate.
`FIG. 12A is a plan view showing a light guide plate whose
`thickness has been changed.
`FIG. 12B is a cross-sectional view showing a light guide
`plate whose thickness has been changed.
`FIG. 13 is a top plan view showing the combination of the
`liquid crystal display panel and illumination device in accor-
`dance with the second embodiment of this invention.
`
`FIG. 14 is a cross—sectional view showing the relationship
`of the liquid crystal display panel, illumination device, and
`illuminant as shown in FIG. 13,
`
`FIG. 15 is a break-down view showing the construction of
`the structure of the surface-type illumination device used in
`the liquid crystal display shown in FIG. 14.
`FIG. 16 is an explanatory drawing showing the relation-
`ship of the light guide plate and the fluorescent light which
`is in the surface-type illumination device of FIG. 15.
`FIG. 17 is an explanatory drawing showing the diffusion
`pattern that is printed on the light guide plate of FIG. 15.
`FIG. 18 is a graph showing the surface temperature of the
`liquid crystal display panel shown in FIG. 13.
`FIG. 19 is an explanatory drawing showing another
`relationship of the light guide plate and the fluorescent light.
`FIG. 20 is an explanatory drawing showing still another
`relationship of the light guide plate and the fluorescent light.
`FIG. 21 is an explanatory drawing showing a conven-
`tional light guide plate and fluorescent light.
`FIG. 22 is a graph showing the surface temperature of a
`liquid crystal display panel using a surface-type illumination
`device similar to the one shown in FIG. 21.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`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 panel 10
`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 panel 10 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—
`play 1 and used for initiating lighting.
`
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`The basic structure of one embodiment of liquid crystal
`display 1 will be explained using the cross-sectional view of
`liquid crystal display 1 shown in FIG. 2 and the break—down
`View of liquid crystal display 1 shown in FIG. 3. In liquid
`crystal display 1, illumination device 20 is installed in lower
`case 3. Above device 20, liquid crystal display panel 10 is
`installed using frames 30 and 31. Liquid crystal display
`panel 10 is formed by enclosing the liquid crystal, transpar-
`ent electrodes, etc. between two layers of transparent glass
`substrates 11 and 12. At side 10a of liquid crystal display
`panel 10, a plurality of driver ICs 13 are installed for
`latching pixel data for the rows and sending it to the liquid
`crystal display panel. Also, at side 10b, which is adjacent to
`side 10a, a plurality of driver ICs 14 are installed for latching
`pixel data for the columns and sending it to the liquid crystal
`display panel.
`Frames 30 and 31 are used to protect illumination device
`20 and to position it within the case. At the same time, it also
`fills the role of maintaining a fixed distance for gap 33
`between illumination device 20 and liquid crystal display
`panel 10, for example, 0.2—1 mm. For this reason, frames 30
`and 31 are prepared so that their lower halves 34 and 35
`support illumination device 20 and their upper halves 36 and
`37 act as spacers between illumination device 20 and liquid
`crystal display panel 10. In this example the frame is divided
`into two pieces, however, the number of pieces is not limited
`to two. For example, three pieces, four pieces, or even more
`is possible, and even just one piece is also possible.
`Furthermore, the frame need not cover the entire periphery
`of illumination device 20 or liquid crystal display panel 10.
`Aplurality of pieces may be arranged in appropriate places.
`Illumination device 20 is a surface-type illumination
`device set up with a cylindrically—shaped fluorescent light 22
`at the edge of substantially rectangular light guide plate 21.
`Fluorescent light 22 is roughly L-shaped and is covered by
`reflectors 23a and 23b. Wires for supplying power to drive
`fluorescent light 22 extend from both ends of fluorescent
`light 22 and are connected to the driver circuit on the host
`side through connector 7 which is for turning on the light.
`FIG. 4 is a break-down view of illumination device 20 and
`will be used to explain the structure of the illumination
`device of this embodiment. Illumination device 20 is com—
`prised of light guide plate 21, which is substantially rectan-
`gular in shape and has the corner of at edge 40 missing,
`fluorescent
`light 22, which encompasses edge 40 in an
`L-shape, and reflectors 23a and 23b, which cover uorescent
`light 22 in the direction of light guide plate 21 and efficiently
`reflect light from fluorescent light 22 to light guice plate 21.
`On lower surface 21b of light guide plate 21, i.e., the side
`opposite to the side where liquid crystal display aanel 10 is
`arranged, pattern sheet 24, which is printed wit] diffusion
`pattern 50, and reflecting sheet 25 are arranged in that order.
`On upper surface 21a of light guide plate 21, i.e., the side
`where liquid crystal display panel 10 is arrangec, diffusion
`sheet 26 and prism sheet 27 are arranged. Edge reflective
`tape 28 is put on edge 41a and 41b, opposite to ’uorescent
`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 0 refraction
`equal to or greater than 1.41 is desirable using suca materials
`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 21a and lower surface
`21b are smooth and mirror-like,
`the light incident from
`edges 41a, 41b, 410, and 41d, which are formed at right
`angles to surface 21a and 21b, is completely reflected from
`surfaces 21a and 21b.
`
`
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`LGE_000852
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`LGE_000852
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`6,108,060
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`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 21b of light guide
`plate 21. Light
`incident from sides 41,
`to some extent,
`
`
`reaches diffusion pattern 50 and, without being completely
`
`
`reflected, will be di ‘used in the direction of upper surface
`21a. Consequently, light incident from the fluorescent light
`by way of the edges is emitted to liquid crystal display panel
`10 from upper surface 21a.
`Reflecting sheet 25 is a thin PET sheet with a thickness of
`approximately 005—05 mm. Light coming from upper
`surface 21a 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
`21a and light up liquid crystal display panel 10. However, a
`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.
`Ilurther, 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.
`DiIfusion sheet 26 is an approximately 0.05—0.5 mm thin
`PET sheet or PC sheet. Diffusion sheet 26 diffuses the light
`that is reflected by dilfusion pattern 50 and radiated from
`upper surface 21a. DiIIusion pattern 50 is often formed in a
`narrow line configuration or net configuration. The light that
`is reflected by these types of patterns is diffused by diffusion
`
`sheet 26. The diffusion pattern cannot be recognized from
`liquid crystal display panel 10. Di usion sheet 26 is
`arranged with a very small layer of air 3etween it and upper
`surface 21;; of light guide plate 21. Tie angle mentioned
`above is maintained in regards to the angle of upper surface
`21a. Reflection sheet 26 is not limitec to a PET sheet and
`such sheets as acrylic-type sheets, among others, may be
`used.
`
`
`
`Prism sheet 27, which is arranged on diffusion sheet 26,
`is made up of very small linear prisms lined in a cross—
`sectional array. The angle of the light radiating from diffu-
`sion sheet 26 is arranged to improve the illuminating inten-
`sity of liquid crystal display panel 10. Although the
`brightness can be improved through prism sheet 27, when
`sufficient brightness is achieved through diffusion sheet 26,
`prism sheet 27 can be omitted, thus reducing manufacturing
`cost.
`
`Fluorescent light 22, which is used as the light source of
`illumination device 20, is in an I.—shape, and is positioned
`adjacent to edges 41c and 41d of light guide plate 21. It is
`desirable, as will be explained later,
`to maintain a gap
`between edges 410 and 41d and fluorescent
`light 22 of
`around 0.84.5 mm. The corner of edge 40 of light guide
`plate 21 is removed and fluorescent light 22 is able to be
`positioned with the above noted gap. Also, by removing this
`corner, fluorescent light 22 and the corner of light guide
`plate 21 are prevented from touching and damage to the
`fluorescent light can no prevented.
`Fluorescent light 22 is covered by reflectors 23a and 23b
`to make the light discharged from fluorescent
`light 22
`incident with good e iciency from edge 40 of light guide
`plate 2|. Reflectors 23a and 23b are PET sheets deposited
`with silver and of a hickness of approximately 0.01—0.1
`mm. In order to provide low cost reflectors that cover the
`I.-shaped fluorescent light and that are easy to install, two
`straight reflectors are used. This will be explained in greater
`detail below.
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`Edge reflective tape 28 is arranged at two edges 41a and
`41b, which are opposite to edges 41c and 41d, respectively,
`where fluorescent light 22 and reflector 23 are installed.
`Edge reflective tape 28 is a PET sheet deposited with silver
`with thickness of approximately 0.01—0.1 mm. The light
`introduced to light guide plate 21 from fluorescent light 22
`is completely reflected away. The light
`that reaches the
`edges of the opposite side is returned to light guide plate 21.
`Materials such as white PET sheets and aluminum can be
`used for the edge reflective tape as well as the reflectors
`mentioned above. It is also possible to integrate these into a
`case or frame.
`FIG. 5 shows liquid crystal display panel 10 installed on
`illumination device 20. Driver ICs 13 and 14 are arranged on
`sides 10a and 10b, respectively, adjacent to liquid crystal
`display panel 10. Opposite to sides 10a and 10b, L-shaped
`fluorescent light 22 extends along two sides 20C and 20d of
`illumination device 20. Because of this arrangement, driver
`ICs 13 and 14 are not directly influenced by the