(11) Japanese Unexamined Patent Application Publication No.
`H6-214230
`(43) Publication Date: August 5, 1994
`(21) Application No. H5-020854
`(22) Application Date: January 14, 1993
`(71) Applicant: Koito Manufacturing Co., Ltd.
`(72) Inventor: Furuya et al.
`(74) Agent: Patent Attorney, Masaki YAMAKAWA
`(54) [Title of the Invention] LIQUID CRYSTAL DISPLAY DEVICE
`(57) [Abstract]
`[Object] An object is to illuminate the entire display
`portion with uniform luminance and with high brightness.
`[Construction] Plural insertion holes 32 are formed
`through longer sidewalls 24D and 24E of a reflector plate 24,
`which has the shape of a front-open rectangular shallow box.
`LEDs 2 are arranged and inserted through the insertion holes
`32. A liquid crystal display board 10 and a wiring circuit
`board 22 are electrically connected to each other via a pair
`of electrically conductive members 21 provided along the
`respective two longer side edges of the reflector plate 24.
` [Claim]
`[Claim 1] A liquid crystal display device in which a reflector plate or a light-guiding
`plate is arranged on a rear face side of a liquid crystal display board, configured such that
`light emitted from light sources is guided to the liquid crystal display board via the
`reflector plate or light-guiding plate to backlight the liquid crystal display board, wherein
`the reflector plate or light-guiding plate is formed in a rectangular shape and disposed
`on a wiring circuit board, the liquid crystal display board and the wiring circuit board are
`electrically connected by electrically conductive members arranged along both longer
`side edges of the reflector plate or light-guiding plate, and a plurality of light sources are
`arranged next to one another along one or both of the longer sides of the reflector plate or
`light-guiding plate.
`[Detailed Description of the Invention]
`[0001]
` [Field of Industrial Application] The present invention
`relates to a liquid crystal display device in which a liquid crystal display board is backlit
`using a reflector plate or a light-guiding plate.
`
`[0002]
`[Description of the Related Art] In general, in a liquid
`crystal display device used as a display unit in various
`kinds of devices/equipment, including but not limited to
`office automation (OA) equipment, a watch/clock, a blood
`pressure meter, and a hot water supply device, a display portion is backlit from the inside,
`thereby enhancing the visibility of displayed
`characters. In a typical battery-powered compact liquid
`crystal display device, reflective-type illumination is used
`
`K.J. Pretech Ex. 1009
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`Pretech_000429
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`

`
`for the purpose of achieving low power consumption, and a
`light bulb (incandescent bulb) is turned on for illumination
`only when required by a user. This is
`because it is not possible to provide always-ON illumination
`by means of a light bulb due to the low power of 60 to 100 mW that can be
`used for such always-ON illumination, though it depends on
`the capacity of a battery built in an apparatus. In view of the above,
`recently, a backlight illumination method with the use of,
`as a light source, an LED (light emitting diode), which is
`one low-power-consumption light emission medium, has been
`employed. The power consumption of an LED (20 mW per piece)
`is far lower than that of a light bulb. In addition, an LED
`offers comparatively high brightness and comparatively long
`service life. Moreover, besides red LEDs, LEDs for various
`emission colors, such as green LEDs and yellow LEDs, are
`easily available on the market. For these reasons, an LED
`is suitable for use as an illuminating light source of a
`liquid crystal display device. However, light emitted from
`an LED has high directivity. Therefore, with the mere use
`of an LED, it is difficult to provide uniform illumination
`throughout an entire wide area. In order to overcome this
`difficulty, in prior art, as illustrated in Fig. 9, a flatpanel-
`type light emitter that is a combination of a lightguiding
`plate 1 and an LED 2 is used. In this flat-paneltype
`light emitter, the light-guiding plate 1, which is made
`of transparent resin that has excellent transparency to
`light, for example, acrylic resin, has the shape of a wedge
`in a side view. The back 3 of the light-guiding plate 1 is
`formed as a sloped surface. Light 4 emitted from the LED 2
`enters the inside of the light-guiding plate 1 through a
`thicker side edge face 5, which is the incident light
`receiving portion of the light-guiding plate 1. The light
`that has gone into the light-guiding plate 1 is reflected by
`the light-guiding plate back 3. The reflected light goes out through a
`surface 6. By this means, uniform plane illumination
`throughout a light output area is obtained. As compared
`with other kinds of flat-panel light emitters using
`electroluminescence, optical fiber, etc. the illustrated
`flat-panel light emitter has advantages of a simpler
`structure and lower cost. In the LED 2, in order to
`overcome a small source emission area size, a diode chip 8
`is molded by means of transparent resin 7 such as acrylic
`resin, and a convex lens 7a is provided on the tip of the
`transparent resin 7. The convex lens 7a magnifies the light
`emitted from the diode chip 8 for easier view. The inclined
`surface at the back 3 of the light-guiding plate 1 is formed
`
`Pretech_000430
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`

`
`as the plane of reflection by aluminum vapor deposition, bonding
`of a reflective sheet 9 thereto, or the like. The reference
`numeral 10 denotes a liquid crystal display board.
`[0003]
`[Problems to be Solved by the Invention] In the liquid
`crystal display device described above, when the liquid crystal
`display board 10 has a rectangular shape, the following structure is
`typically adopted: electrodes for liquid-crystal-driving use are
`arranged next to one another along each of two longer side
`edges of said rectangular board; these electrodes are
`connected via lead wires, etc. to a liquid crystal driving circuit provided on a
`wiring circuit board. Therefore, the
`LEDs 2 are arranged along and next to a shorter thicker side
`edge of the light-guiding plate 1. In such a structure,
`because of optical attenuation, luminance decreases with
`distance from the light source in inverse proportion to the
`square of the distance. This makes it difficult to
`illuminate the entire display portion with uniform luminance.
`In this respect, there is a problem in the structure of
`prior art.
`[0004]
`The present invention has been made in view of the
`problem of prior art described above. An object of the
`invention is to provide a liquid crystal display device that
`can realize illumination with uniform luminance for the
`entire display portion and with high brightness.
`[0005]
`[Means for Solving Problem] In order to achieve the above object, the present invention
`is a liquid crystal display device in which a reflector plate or a light-guiding plate is
`arranged on a rear face side of a liquid crystal display board, configured such that light
`emitted from light sources is guided to the liquid crystal display board via the reflector
`plate or light-guiding plate to backlight the liquid crystal display board, where
`the reflector plate or light-guiding plate is formed in a rectangular shape and disposed
`on a wiring circuit board, the liquid crystal display board and the wiring circuit board are
`electrically connected by electrically conductive members arranged along both longer
`side edges of the reflector plate or light-guiding plate, and a plurality of light sources are
`arranged next to one another along one or both of the longer sides of the reflector plate or
`light-guiding plate.
`[0006]
`[Operation] In the present invention, since the plurality
`of light source elements are arranged next to one another
`along one or both of the two longer side edges of the
`reflector plate or the light-guiding plate, as compared with
`a case where they are arranged next to one another along one
`or both of the two shorter side edges thereof, light is less
`susceptible to attenuation, and therefore, it is possible to
`
`Pretech_000431
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`

`
`illuminate the liquid crystal display board with uniform
`greater luminance. Each of the electrically conductive members
`electrically connects the liquid crystal display board and
`the wiring circuit board to each other, and forms a gap
`space for accommodating the light source elements between
`itself and the reflector plate or between itself and the
`light-guiding plate.
`[0007]
`[Embodiments] On the basis of exemplary embodiments
`illustrated in the drawings, the present invention will now
`be explained in detail. Fig. 1 is a sectional view that
`illustrates a liquid crystal display device according to an
`exemplary embodiment of the present invention. Fig. 2 is a
`side sectional view of a flat-panel-type light emitter. Fig.
`3 is an exploded perspective view of the flat-panel-type
`light emitter. In these drawings, the same reference
`numerals are assigned to components/portions that are the
`same as those of Fig. 9. In these drawings, a liquid
`crystal display device 11 includes a case 12, which has the
`shape of a shallow rectangular box with an opening 13 at
`the center of its top, a liquid crystal display board 10,
`which is housed inside the case 12 and can be seen from the
`outside through the opening 13, a transparent protection
`plate 14, which is fitted inside the opening 13 to protect
`the surface of the liquid crystal display board 10, a flatpanel-
`type light emitter 16, which is housed inside the case
`12 and backlights the liquid crystal
`display board 10, a power supply 17
`for the liquid crystal display board 10 and LEDs 2, plural
`operation switches 18, which are provided on the top face of
`the case 12, and the like.
` [0008]
`The liquid crystal display board 10 has a well-known
`panel structure, in which nematic liquid crystal, etc. is
`sealed between an upper glass plate 10a and a lower glass
`plate 10b. The width of the upper glass plate 10a is
`greater than that of the lower glass plate 10b. Plural electrodes
`19 for liquid-crystal-driving use are arranged next to one
`another on the back of the upper glass plate 10a
`along each of two longer side edges. These electrodes 19 are connected to a liquid
`crystal driving circuit (not shown) provided on a wiring
`circuit board 22 via left and right electrically conductive
`members 21, which make up a pair.
`[0009]
`The flat-panel-type light emitter 16 includes a
`reflector plate 24, which is provided behind the rear of and
`
`Pretech_000432
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`

`
`in parallel with the liquid crystal display board 10, the
`above-mentioned plural LEDs 2, which are arranged next to
`one another along each of two longer side edges of the
`reflector plate 24, the above-mentioned wiring circuit board
`22, to which the reflector plate 24 is fixed, a light
`diffusing plate 25, which is provided between the liquid
`crystal display board 10 and reflector plate 24, the abovementioned
`pair of electrically conductive members 21, which
`supports the liquid crystal display board 10 and
`electrically connects the liquid crystal display board 10 to
`the wiring circuit board 22, and a cover 26, which encloses
`the liquid crystal display board 10 and the wiring circuit
`board 22, with the liquid crystal display board 10
`therebetween, etc.
`[0010]
`The reflector plate 24 is made of resin and has the
`shape of a front-open rectangular shallow box. The
`reflector plate 24 is made up of a bottom plate 24A, a pair
`of shorter sidewalls 24B and 24C, and a pair of longer
`sidewalls 24D and 24E. The shorter sidewalls 24B and 24C
`are formed facing each other in the length direction of
`the reflector plate 24, and the longer sidewalls 24D and 24E
`are formed facing each other in the direction perpendicular to the length direction
`of the reflector plate 24. Due
`to reflection treatment applied to the inner surface of the
`reflector plate 24, said surface is formed as a reflection
`surface 27. To form the reflection surface 27, for example,
`a white paint is applied thereto, an aluminum foil is bonded
`thereto, or aluminum is vapor-deposited thereon. If necessary,
`ultra-small irregularities are formed therein for diffused
`reflection. A ridge 28, which extends through the center of
`the inner bottom surface of the reflector plate 24
`throughout the entire length of the reflector plate 24 in
`its length direction, is formed as a part of said inner
`bottom surface. The ridge 28 has the shape of an inverted V in
`cross section. For supporting the edges of the light
`diffusing plate 25, a continuous fitting groove 29 is
`formed in such a way as to surround the opening 13. Each of
`the longer sidewalls 24D and 24E is formed at a relatively
`inner position as compared with the position of the
`corresponding one of two width-directional side edges 31 of
`the bottom plate 24A, with a predetermined distance
`therebetween. Each of the longer sidewalls 24D and 24E
`faces the corresponding one of the electrically conductive
`members 21, with a predetermined clearance therebetween.
`Plural insertion holes 32, through which the LEDs 2 are
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`Pretech_000433
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`inserted, are formed in each of the longer sidewalls 24D and
`24E. For the purpose of preventing glare, the interval
`between the sidewalls 24D and 24E is greater than the width
`of the display portion 10A of the liquid crystal display
`board 10. The insertion holes 32 are formed in a line at
`predetermined regular intervals in the length direction of
`each of the longer sidewalls 24D and 24E.
`[0011]
`In the present embodiment, for the purpose of
`increasing the amount of direct light which is emitted from
`the LED 2 and propagates directly toward the liquid crystal
`display board 10 the insertion
`hole 32 is inclined with a predetermined angle of
`inclination (
`) in such a way that its outer open end is
`located behind its inner open end, as illustrated in Fig. 2. The angle of inclination
`of the insertion hole 32 is approximately 4.5 . For this
`reason, the LED 2 is also inserted through and supported
`inside the insertion hole 32 at the angle of inclination
`.
`Its optical axis L intersects with a virtual line extending
`in parallel with the liquid crystal display board 10 to form
`the angle
`. To increase the amount of reflected light
`reflected at the reflection surface 27 of the
`reflector plate 24, inverted inclination, which is the
`opposite of the inclination of Fig. 3, can be employed.
`More specifically, this can be done by, as illustrated in
`Fig. 4, forming the insertion hole 32 with a predetermined
`angle of inclination
`in such a way that its outer open end
`is located in front of its inner open end. Needless to say,
`the insertion hole 32 may be formed to be parallel to the
`liquid crystal display board 10 without any inclination.
`[0012]
`The optical emission of the LEDs 2 is not in one and
`the same color. For example, the emission color of the 1st,
`4th, 7th, 10th, 13th, and 16th LEDs 2A counted from the left
`in Fig. 5, which are indicated by hatched lines, is red.
`The emission color of the other LEDs 2B is green. The
`circuit for driving these LEDs 2 is configured to usually
`switch on the green LEDs 2B only for back illumination of
`the liquid crystal display board 10 in response to the
`operation of the operation switch 18 (Fig. 1), and to switch
`on the red LEDs 2A in the case of an alarm display. Such
`illumination color differentiation increases the variety of
`illumination. Lead wires 35 of the LEDs 2 are routed
`through slits 36 (Fig. 3), which are arranged along two
`edges of the bottom plate 24A of the reflector plate 24, and
`through lead-wire holes (not shown) of the wiring circuit
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`Pretech_000434
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`
`board 22. The lead wires 35 are connected therethrough to
`an electric circuit.
`[0013]
`Each of the pair of electrically conductive members 21 is
`made of an electrically conductive rubber, and is provided on the wiring
`circuit board 22 along the corresponding one of the two
`longer side edges 31 of the reflector plate 24. The back regions along
`the respective two longer side edges of the upper glass
`plate 10a of the liquid crystal display board 10 are in tight contact with the front faces of
`the electrically
`conductive members 21, and are fixed by
`means of the cover 26. On the wiring circuit board 22,
`plural electrodes 38 (Fig. 3) are arranged next to one
`another along each of two longer side edges of said wiring
`board. The electrodes 38 are arranged in such a way as to
`correspond to the electrodes 19 of the liquid crystal
`display board 10. The electrodes 38 are electrically
`connected to the electrodes 19 via the electrically conductive
`members 21. When the liquid crystal display board 10 and
`the wiring circuit board 22 are sandwiched by means of the
`cover 26, there is a risk that the elastic deformation
`of electrically conductive member 21 might occur inward due to
`compression. For the purpose of preventing such elastic
`deformation in the inward direction, plural ribs 40 are
`formed on, and each as a protruding part of, the outer wall
`surface of each of the longer sidewalls 24D and 24E of the
`reflector plate 24 at predetermined regular intervals. To
`avoid damage caused by vibration, external forces, etc., the
`liquid crystal display board 10 is mounted at a distance
`from the reflector plate 24. That is, there is a proper
`clearance d (Fig. 2) between the liquid crystal display
`board 10 and the reflector plate 24. Though a structure in
`which an electrically conductive rubber is used as the material of the
`electrically conductive members 21 is explained in the present
`embodiment, the scope of the invention is not limited
`thereto. Needless to say, a
`lead frame 46 or a lead wire may be used for connection
`instead, as illustrated in Fig. 6.
`[0014]
`The light diffusing plate 25 can be formed by coating
`the surface of acrylic resin with an opacifier, embossing
`the surface of transparent resin, or coating said surface
`with a transparent paint containing microscopic glass beads
`or metal particles. However, the structure of the light
`diffusing plate 25 is not limited thereto, and can be
`modified or adapted in various ways. For example, as
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`Pretech_000435
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`

`
`illustrated in Fig. 4, the light diffusing plate 25 may be
`made up of two diffusing films 25A and 25B, one of which is
`formed in front of the other, with an air layer 47 formed
`therebetween for enhancing the diffusion effect.
`[0015]
`The wiring circuit board 22 includes the aforementioned
`liquid crystal driving circuit, which includes various
`electronic parts 48 such as liquid crystal driving ICs,
`transistors, resistors, etc. In addition, the wiring
`circuit board 22 includes LED constant current circuits.
`The wiring circuit board 22 is electrically connected to the
`power supply 17 (Fig. 1) via a lead wire 49. The constant
`current circuit compensates for the temperature of the LED 2.
`When a diode voltage changes due to temperature, the electric current changes in order to
`make the constant power voltage constant, and the brightness of the LED 2 also changes.
`To avoid this, the FET transistor and the LED 2 are built in
`series to make up the constant current circuit. This is
`especially effective when the diode voltage is low, for
`example, 3 V, 4.5 V, or 6 V.
`[0016]
`In the liquid crystal display device 11 having the
`structure described above, the green LEDs 2B are ON during
`normal non-alarm use. Due to directly striking the inner
`surface of the reflector plate 24, that is, the reflection
`surface 27, a part of light emitted from these LEDs 2 turns
`into direct reflected light as a result of frontward total
`reflection. Another part turns into direct light
`propagating toward the front of the reflector plate 24. The
`reflected light and the direct light are diffused when
`passing through the light diffusing plate 25. The diffused
`light is used for backlighting of the display portion
`10A of the liquid crystal display board 10. Therefore, the
`illumination apparatus 16 behaves as a planar
`light source. In the present invention, because the LEDs 2 are
`arranged next to one another along the two longer
`side edges of the reflector plate 24, as compared with a
`case where they are arranged next to one another along each
`of the two shorter side edges thereof, the distance for
`illumination of the liquid crystal display board 10 is
`shorter, which results in less optical loss. Therefore, it
`is possible to illuminate the entire display portion 10A
`with uniform greater luminance. Moreover, with the
`frontward tilt of the LED 2 as illustrated in Fig. 2, it is
`possible to increase the amount of direct light with a
`decrease in the amount of reflected light. With the
`backward tilt of the LED 2 as illustrated in Fig. 4, it is
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`Pretech_000436
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`possible to increase the amount of reflected light with a
`decrease in the amount of direct light.
`[0017]
`Fig. 7 is a perspective view that illustrates
`essential parts of another embodiment of the present
`invention. In the present embodiment, the LEDs 2 are
`mounted on printed circuit boards 51. The printed
`circuit boards 51 are attached to the outer wall
`surface of each of the longer sidewalls 24D and 24E of the
`reflector plate 24, with the LEDs 2 inserted through the
`insertion holes 32. The lead wires 35 of each of the LEDs 2
`protrude slightly and are bent at the back of the printed
`circuit board 51, and are joined by soldering to the
`electric circuit of the printed circuit board 51.
`The reference numeral 52 denotes a resistor for switching on
`the LED 2. The reference numeral 53 denotes a ground
`terminal inserted through the slit 36. The other structural
`features are the same as those of the foregoing embodiment.
`The structure of the present embodiment is advantageous in
`the operation of attaching the LEDs 2 to the reflector plate 24 may be performed all at
`once for each printed circuit board 51.
`[0018]
`Fig. 8 is a perspective view that illustrates
`essential parts of still another embodiment of the present
`invention. In the present embodiment, a light-guiding plate
`55 is used instead of a reflector plate to guide
`light emitted from the LEDs 2 toward the liquid crystal
`display board 10. Many concave portions 56 for housing the
`LEDs 2 are formed next to one another as recesses in the
`edge face of each of two longer side edges of the lightguiding
`plate 55. Small dot-pattern recesses 57, each of
`which has the shape of a conical cavity, are formed in the
`back of the light-guiding plate 55. The surface of the back
`of the light-guiding plate 55 is bent in a V-shape. Therefore, the lightguiding
`plate 55 is the thickest at each of its two ends in
`the width direction, and is the thinnest at its center in
`the width direction. The LEDs 2 are arranged in parallel
`with the front face of the light-guiding plate 55. In other
`words, the LEDs 2 are arranged in parallel with the liquid
`crystal display board 10. The other structural features are
`the same as those of the foregoing embodiments. With this
`structure, as in the foregoing embodiments, it is possible
`to obtain uniform planar illumination
`with high brightness.
`[0019]
`The scope of the present invention is not limited to
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`Pretech_000437
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`

`
`the embodiments described above. It can be modified/adapted
`in various ways. For example, the LEDs 2 may be arranged
`next to one another along either one of the two longer side
`edges of the reflector plate 24 or the light-guiding plate
`55, instead of both. In the embodiments described above,
`the green LEDs 2B are switched on for green emission at the
`time of normal non-alarm use, and the red LEDs 2A are
`switched on for red emission at the time of alarm use,
`thereby increasing the variety of illumination. However, plural LEDs
`2 of one and the same color, without such illumination color
`differentiation, may be used, or a multi-color
`LED that is provided with plural diode chips with emission
`colors different from one another may be used as each of the
`LEDs 2, and emission-color switching may be performed by
`means of a switch.
`[0020]
`[Advantages] As explained above, in a liquid crystal
`display device according to the present invention, an
`electrically conductive member is provided along each of two
`longer side edges of a reflector plate or a light-guiding
`plate, and plural light source elements are arranged next to
`one another along one or both of the two longer side edges
`of the reflector plate or the light-guiding plate each at a
`relatively inner position as compared with a position of the
`electrically conductive member. With less optical attenuation,
`it is possible to illuminate the entire area of the display
`portion of a liquid crystal display board with uniform
`greater luminance, and therefore improve illumination
`effects. The liquid crystal display device
`disclosed herein is particularly advantageous for use as a compact liquid
`crystal display device.
`[Brief Description of the Drawings]
`[Fig. 1] Fig. 1 is a sectional view that illustrates a
`liquid crystal display device according to an exemplary
`embodiment of the present invention;
`[Fig. 2] Fig. 2 is a sectional view of a flat-panel-type
`light emitter;
`[Fig. 3] Fig. 3 is an exploded perspective view of the
`flat-panel-type light emitter;
`[Fig. 4] Fig. 4 is a sectional view that illustrates an
`essential part of another embodiment;
`[Fig. 5] Fig. 5 is a plan view that illustrates the layout
`of LEDs;
`[Fig. 6] Fig. 6 is a perspective view that illustrates an
`electrically conductive member according to another embodiment;
`[Fig. 7] Fig. 7 is a perspective view that illustrates an
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`Pretech_000438
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`essential part of another embodiment of the present
`invention;
`[Fig. 8] Fig. 8 is a sectional view of another embodiment
`of the present invention; and
`[Fig. 9] Fig. 9 is a diagram that illustrates a flat-paneltype
`light emitter according to prior art, using a
`combination of a light-guiding plate and an LED.
`[Reference Numerals]
`1 light-guiding plate
`2 LED
`10 liquid crystal display board
`11 liquid crystal display device
`12 case
`16 flat-panel-type light emitter
`22 wiring circuit board
`24 reflector plate
`25 light diffusing plate
`27 reflection surface
`55 light-guiding plate
`
`Pretech_000439
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`

`
`I hereby certify that the attached English translation of Japanese Patent
`Application Publication No. H6—214230 titled “LIQUID CRYSTAL DISPLAY
`DEVICE” is, to the best of my knowledge and ability, an accurate translation.
`
`And I declare under penalty of perjury under the laws of the United States of
`America that the foregoing is true and correct.
`
`Executed on September 11, 2015
`
`Pretech_000440
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`

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`(57)【要約】
`【目的】 表示部全体を均一な明るさで高輝度照明す
`る。
`【構成】 矩形浅底箱型に形成した反射板２４の長辺側
`側板２４Ｄ，２４Ｅに複数個の挿通孔３２を形成し、こ
`れら挿通孔３２にＬＥＤ２を挿入配置する。反射板２４
`の長辺側側端縁に沿って配設した一対の導電部材２１に
`よって液晶表示板１０と配線基板２２を電気的に接続す
`る。
`
`Pretech_000441
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`

`
`(2)
`
`特開平６−２１４２３０
`
`【特許請求の範囲】
`【請求項１】 液晶表示板の裏面側に反射板または導光
`板を配設し、光源から出た光を前記反射板または導光板
`を介して液晶表示板に導きバック照明するようにした液
`晶表示装置において、
`前記反射板または導光板は矩形に形成されて配線基板上
`に設置され、前記反射板または導光板の長辺側両側縁に
`沿って配設した導電部材によって前記液晶表示板と配線
`基板を電気的に接続し、かつ前記導電部材の内側で前記
`反射板もしくは導光板の少なくともいずれか一方の長辺
`に沿って複数個の光源を並設したことを特徴とする液晶
`表示装置。
`【発明の詳細な説明】
`【０００１】
`【産業上の利用分野】本発明は、反射板または導光板を
`用いて液晶表示板をバック照明する液晶表示装置に関す
`る。
`【０００２】
`【従来の技術】一般に、ＯＡ機器、時計、血圧計、給湯
`器、その他各種装置、機器の表示装置に用いられる液晶
`表示装置は、表示部を内部からバック照明し、表示文字
`の視認性の向上を図っている。この場合、一般に電池駆
`動の小型液晶表示装置においては、低電力消費のため反
`射型照明を行ない、使用者が必要とする時のみバルブ
`（白熱電球）を点灯して照明していた。これは装置に内
`蔵される電池容量にもよるが、常時点灯する場合、使用
`できる電力は６０ｍＷ〜１００ｍＷと小さく、バルブで
`は常時点灯が不可能なためである。そこで、最近では低
`消費電力発光体の１つであるＬＥＤ（発光ダイオード）
`を光源として用い、バックライト方式にて照明すること
`が行なわれている。ＬＥＤは消費電力がバルブと比較し
`て著しく少なく（２０ｍＷ／１個）、また高輝度、長寿
`命で、赤色以外に緑色、黄色等各種の発光色のものが手
`軽に入手できることから液晶表示装置の照明用光源とし
`て好適である。しかし、単にＬＥＤを用いるだけでは発
`光出力の指向性が高いことから広い面積を全面にわたっ
`て均一に照明することが難しく、そのため図９に示すよ
`うに導光板１とＬＥＤ２とを組合せたフラットパネル型
`発光体を照明装置として用いている。このフラットパネ
`ル型発光体は、導光板１をアクリル樹脂等の光透過性に
`優れた透明樹脂によって側面視楔形に形成して裏面３を
`斜面とし、ＬＥＤ２から出射した光４を導光板１の入光
`部を形成する厚肉部側端面５からその内部に導き、導光
`板裏面３で反射して表面６から出光させることにより均
`一な面照明を得るもので、エレクトロルミネッセンス、
`光ファイバ等を用いた他のフラットパネル型発光体に比
`べて構造が簡単で安価であるという利点を有する。ＬＥ
`Ｄ２としては発光面積が小さいためダイオードチップ８
`をアクリル樹脂等の透明樹脂７でモールドし、この透明
`樹脂７の先端に設けた凸状のレンズ部７ａでダイオード
`
`チップ８から出た光を拡大し、見易くしている。なお、
`導光板１の傾斜した裏面３は、アルミニウムの蒸着、反
`射シート９の接着等によって反射面を形成している。１
`０は液晶表示板である。
`【０００３】
`【発明が解決しようとする課題】ところで、上記した従
`来の液晶表示装置にあっては、液晶表示板１０を矩形に
`形成した場合、通常その長辺側両端部に液晶駆動用電極
`を並設し、この電極を配線基板の液晶駆動回路にリード
`線等によって接続する構成を採っていた。そのため、Ｌ
`ＥＤ２を導光板１の短辺側厚肉端部に並設しているが、
`このような構成においては光の減衰により光源から遠の
`くにしたがって明るさが距離の二乗に逆比例して低下す
`るため、表示部全体を均一な明るさで照明することが難
`しいという問題があった。
`【０００４】したがって、本発明は上記したような従来
`の問題点に鑑みてなされたもので、その目的とするとこ
`ろは、表示部全体を均一な明るさで高輝度照明すること
`ができるようにした液晶表示装置を提供することにあ
`る。
`【０００５】
`【課題を解決するための手段】上記目的を達成するため
`本発明は、液晶表示板の裏面側に反射板または導光板を
`配設し、光源から出た光を前記反射板または導光板を介
`して液晶表示板に導きバック照明するようにした液晶表
`示装置において、前記反射板または導光板は矩形に形成
`されて配線基板上に設置され、前記反射板または導光板
`の長辺側両側縁に沿って配設した導電部材によって前記
`液晶表示板と配線基板を電気的に接続し、かつ前記導電
`部材の内側で前記反射板もしくは導光板の少なくともい
`ずれか一方の長辺に沿って複数個の光源を並設したもの
`である。
`【０００６】
`【作用】本発明において、光源は反射板または導光板の
`長辺側側縁に沿って並設されているので、短辺側側縁に
`沿って配設した場合に比べて光の減衰が少なく、液晶表
`示板をより明るくかつ均一な明るさで照明する。導電部
`材は液晶表示板と配線基板とを電気的に接続すると共
`に、反射板または導光板との間に光源の収納空間を形成
`する。
`【０００７】
`【実施例】以下、本発明を図面に示す実施例に基づいて
`詳細に説明する。図１は本発明に係る液晶表示装置の一
`実施例を示す断面図、図２はフラットパネル型発光体の
`側断面図、図３は同発光体の分解斜視図である。なお、
`図中図９と同一構成部材のものに対しては同一符号をも
`って示す。これらの図において、液晶表示装置１１は、
`矩形薄箱型に形成され上面中央に開口部１３を有するケ
`ース１２と、開口部１３に臨んでケース１２内に収納配
`置された液晶表示板１０と、開口部１３にはめ込み固定
`
`Pretech_000442
`
`

`
`(3)
`
`特開平６−２１４２３０
`
`されて液晶表示板１０の表面を保護する透明な保護板１
`４と、ケース１２内に配設され液晶表示板１０をバック
`照明するフラットパネル型発光体１６と、液晶表示板１
`０およびＬＥＤ２の電源部１７と、ケース１２の上面に
`配設された複数個の操作スイッチ１８等を備えている。
`【０００８】前記液晶表示板１０は上下のガラス板１０
`ａ，１０ｂ間にネマティック液晶等を封止した従来周知
`のもので、上ガラス板１０ａが下ガラス板１０ｂより幅
`広にに形成されて長辺側両側縁部裏面に複数個の液晶駆
`動用電極１９が並設されており、これらの電極１９は左
`右一対の導電部材２１によって配線基板２２に形成され
`ている液晶駆動用回路（図示せず）に接続されている。
`【０００９】前記フラットパネル型発光体１６は、前記
`液晶表示板１０の背面側にこれと平行に配設された反射
`板２４と、この反射板２４の長辺側両端部に沿ってそれ
`ぞれ並設された複数個のＬＥＤ２と、反射板２４が固定
`される前記配線基板２２と、液晶表示板１０と反射板２
`４との間に配設された光拡散板２５と、液晶表示板１０
`を支持すると共に液晶表示板１０と配線基板２２を電気
`的に接続する前記一対の導電部材２１と、液晶表示板１
`０および配線基板２２を挾持するカバー２６等で構成さ
`れている。
`【００１０】反射板２４は樹脂によって前面が開放する
`矩形の浅底箱型に形成されることにより底面板２４Ａ
`と、反射板２４の長手方向に対向する一対の短辺側側板
`２４Ｂ，２４Ｃと、長手方向と直交する方向に対向する
`一対の長辺側側板２４Ｄ，２４Ｅとで構成されている。
`反射板２４の内面は反射処理、例えば白色塗料の塗布、
`アルミ箔の貼着、アルミニウムの蒸着等によって反射面
`２７を形成しており、必要に応じて微小な凹凸が形成さ
`れることにより拡散反射面とされる。また反射板２４の
`内底面中央には反射板２４の長手方向全長にわたって延
`在する断面山形の突状体２８が一体に突設されており、
`開口部内側面には前記光拡散板２５の周縁部を保持する
`嵌合溝２９が全周にわたって形成されている。長辺側両
`側板２４Ｄ，２４Ｅは、底面板２４Ａの幅方向両側端３
`１より所要寸法内側に位置して設けられることにより、
`導電部材２１と所要間隔を保って対向し、前記ＬＥＤ２
`が嵌挿される複数個の挿通孔３２を有している。両側板
`２４Ｄ，２４Ｅの間隔は、グレア防止のため液晶表示板
`１０の表示部１０Ａの幅より大きく設定されている。挿
`通孔３２は各長辺側側板２４Ｄ，２４Ｅの長手方向に所
`定の間隔をおいて一列に形成されている。
`【００１１】この場合、本実施例においてはＬＥＤ２か
`ら出射し液晶表示板１０に向かう直射光を多くするため
`図２に示すように挿通孔３２を、その外側開口端が内側
`開口端よりも後方側に位置するように所要角度（θ）傾
`斜させて形成した場合を示す。挿通孔３２の傾斜角度θ
`は４．５°程度である。このため、ＬＥＤ２も角度θだ
`け傾斜して挿通孔３２に挿入保持され、光軸Ｌが液晶表
`
`示板１０と角度θで交差している。反対に反射板２４の
`反射面２７に当たって反射する反射光を多くしたい場合
`には図４に示すように、挿通孔３２を図３とは反対に、
`その外側開口端が内側開口端よりも前方側に位置するよ
`うに角度θ傾斜させればよい。勿論、挿通孔３２を傾斜
`させず、液晶表示板１０と平行な挿通孔であってもよい
`ことは言うまでもない。
`【００１２】ＬＥＤ２の発光色は異なり、例えば図５に
`斜線で示す左端から１，４，７，１０，１３および１６
`番目のＬＥＤ２Ａの発光色が赤色で、それ以外のＬＥＤ
`２Ｂの発光色が緑色とされる。そして、これらのＬＥＤ
`２は、操作スイッチ１８（図１）の操作によって通常は
`緑色のＬＥＤ２Ｂのみが点灯して液晶表示板１０をバッ
`ク照明し、警告表示時に赤色のＬＥＤ２Ａが点灯するよ
`うに回路構成されている。このように照明色を変える
`と、照明の多様化を図ることができる。なお、ＬＥＤ２
`のリード線３５は、前記反射板２４の底面板２４Ａの両
`端部に形成されたスリット３６（図３）を経て配線基板
`２２のリード線用孔（図示せず）に挿通され、電気回路
`に接続されている。
`【００１３】前記一対の導電部材２１は導電ゴムからな
`り、前記反射板２４の長辺側両端縁３１に沿って配線基
`板２２上に配設されており、前端面に前記液晶表示板１
`０の上ガラス板１０ａの長辺側両端部裏面が密接され前
`記カバー２６によって固定されている。配線基板２２の
`長辺側両端部上面には複数個の電極３８（図３）が液晶
`表示板１０の電極１９に対応して並設されており、これ
`らの電極１９，３８を前記導電部材２１によって電気的
`に接続している。カバー２６によって液晶表示板１０と
`配線基板２２を挾持した際、導電部材２１は圧縮されて
`内側に弾性変形する虞れがある。この内側方向の弾性変
`形を防止するため前記反射板２４の長辺側両側板２４
`Ｄ，２４Ｅの外側面には複数個のリブ４０が所要の間隔
`をおいて一体に突設されている。液晶表示板１０は、振
`動、外力等による破損を防止するため反射板２４から離
`間しており、反射板２４との間に適宜な隙間ｄ（図２）
`が設定されている。なお、本実施例においては導電部材
`２１として導電ゴムを用いた場合について示したが、本
`発明はこれに特定されるものではなく、図６に示すよう
`にリードフレーム４６あるいはリード線を用いて接続し
`てもよいことは勿論である。
`【００１４】前記光拡散板２５は、アクリル樹脂に乳白
`剤を塗布したり、透明樹脂の表面にエンボス加工、微小
`なガラスビーズまたは金属粒子入り透明塗料の塗布等に
`よって形成されるが、これに限らず図４に示すように適
`宜間隔をおいて前後に配設された２枚の拡散フィルム２
`５Ａ，２５Ｂで構成し、これら両フィルム２５Ａ，２５
`Ｂ間に拡散効果を高めるため空気層４７を設けるなど種
`々の変形、変更が可能である。
`【００１５】前記配線基板２２は、液晶駆動用ＩＣ、ト
`
`Pretech_000443
`
`

`
`(4)
`
`特開平６−２１４２３０
`
`ランジスタ、抵抗等の各種電子部品４８を含む液晶駆動
`用回路と、ＬＥＤ２の定電流回路を有し、前記電源部１
`７（図１）にリード線４９によって電気的に接続されて
`いる。定電流回路はＬＥＤ２の温度に対する補償を行な
`うものである。すなわち、温度によってダイオード電圧
`が変化すると、電源電圧一定のため電流が変化し、ＬＥ
`Ｄ２の輝度も変化する。これを防止するためＦＥＴトラ
`ンジスタをＬＥＤ２と直列に組み込んで定電流回路を形
`成している。特に、ダイオード電圧が３Ｖ、４．５Ｖ、
`６Ｖと低い場合に有効とされる。
`【００１６】このような構成からなる液晶表示装置１１
`において、通常使用時に発光色が緑色のＬＥＤ２Ｂが点
`灯される。これらのＬＥＤ２から出射した光は、一部が
`反射板２４の内面、すなわち反射面２７に直接当たって
`前方に全反射することにより直反射光となり、一部が反
`射板２４の前方に向かう直射光となり、これらの光が光
`拡散板２５を通過する際拡散されて液晶表示板１０の表
`示部１０Ａをバック照明する。したがって、照明装置１
`６は面光源を構成する。ここで、本発明においてはＬＥ
`Ｄ２を反射板２４の長辺に沿って並設しているので、液
`晶表示板１０の照射距離が短く、そのため短辺側に並設
`した場合に比べて光の損失が少なく、表示部１０Ａ全体
`をより明るくかつ均一な明るさで照明することができ
`る。また、図２に示すようにＬＥＤ２を前方側に傾斜さ
`せると反射光より直射光を増大させることができ、反対
`に図４に示すように後方側に傾斜させると反射光を直射
`光より増大させることができる。
`【００１７】図７は本発明の他の実施例を示す要部斜視
`図である。この実施例はＬＥＤ２をプリント基板５１に
`実装し、このプリント基板５１を反射板２４の両側板２
`４Ｄ，２４Ｅの外側面に密接し、ＬＥＤ２を挿通孔３２
`に嵌挿するよ