Ulllted States Patent [19]
`Yoshikawa et al.
`
`USOO5775791A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,775,791
`Jul. 7, 1998
`
`[54] SURFACE EMISSION APPARATUS
`
`2-126501
`
`5/ 1990 Japan ~
`
`[75] Inventors: Yukio Yoshikawa: Shigekazu
`Nakamura~ both of Tokyo- Japan
`
`[73] Assignee: Copal Company Limited. Tokyo.
`Japan
`
`_
`[21] APPL N°--
`[22] PCI‘ Filed:
`
`338580
`Sep. 1, 1993
`
`mums/01238
`Apr. 27, 1995
`
`[86] PCP NO':
`§ 371 Date:
`_
`v
`§ 102(6) Date‘ Apr‘ 27’ 1995
`[87] PCT Pub. No; W095/o6889
`
`PCT Pllb- Date: M311 9, 1995
`.
`.
`.
`.
`.
`Forelgn Apphcatmn Pnomy Data
`[30]
`Aug. 31, 1992
`[JP]
`Japan . . . . . .
`. . . . . . . . .. 4-061246
`
`[51] rm. c16 [52] US. Cl. ............................ .. 362/31, 362/26, 362/327, .................... .2 ......... ._ rzlv 8/011
`
`
`_
`362/330
`[53] Fleld of Search .............................. .. 36%31. 26. 330.
`362/327; 359/49; 349/62‘ 65
`_
`References cued
`U_S_ PATENT DOCUMENTS
`
`[56]
`
`4,890,201 12/1939 TOfl ..- ....................................... .. 362/31
`4985309 1/1991 Mam“ a‘ a1
`"" " 362/31
`$070,431 [2/1991 Kitazawa et a1.
`.... .. 361/31
`5,377,084 12/1994 Kojima et a]. .......................... .. 362/31
`FOREIGN PATENT DOCUMENTS
`
`'
`
`61-145902
`63-208670
`
`9/1986 Japan .
`8/1988 Japan .
`
`OTHER PUBLICATIONS
`International Search Report for International Application
`N . PCI‘/JP93/0l238.
`0
`Primary Examiner-Alan Cariaso
`Attorney, Agent, or Firm—Merchant. Gould. Smith. Edell.
`Welter & Schmidt
`[57]
`
`ABSTRACT
`
`The present invention relates to a surface emission apparatus
`for causing light. emitting from a light source arranged to a
`side of a light-emitting surface thereof. to emerge from the
`light-emitting surface. The surface emission apparatus
`includes a transparent light-guide plate in which re?ecting
`shape portions formed with small projecting or concaving
`portions are arranged on its bottom surface portion opposing
`the light-emitting surface such that a density of the project
`ing or concaving portions is gradually increased in accor
`dance with a distance from the light source. Light incident
`
`?ght emerging from the light Source is m?ccted toward the
`light-emitting surface in accordance with the density of the
`re?ecting Shap? Portions_ uniform light emission can be
`obtained throughout the entire light-emitting surface. Since
`the re?ecting shape portions are formed in a staggered
`manner in a direction away from the light source. light
`emitted from the light source can be easily incident on many
`projecting or concaving portions directly. The re?ecting
`Shapc portions are preferably $111311 pl‘OjCCtillg OI‘ concaving
`portions whose contiguous side portions extending from
`.
`.
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`iz‘irio‘fgixfg?gn‘ii?‘luigggi?l: tgcsrfitltf?oiwgg
`or concaving portions whose contiguous side portions
`extending from their vertex portions and contiguous to the
`bottom surface portion form circular cones.
`
`6 Claims, 6 Drawing Sheets
`
`10
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`LGE_000570
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`LG Electronics Ex. 1011
`
`

`
`US. Patent
`
`Jul. 7, 1998
`
`Sheet 1 of 6
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`5,775,791
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`LGE_000571
`
`

`
`US. Patent
`
`Jul. 7, 1998
`
`Sheet 2 0f 6
`
`5,775,791
`
`2
`
`FIG.
`
`1f I Z
`
`O O O O O O O O
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`*
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`
`\
`
`LGE_000572
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`

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`US. Patent
`
`Jul. 7, 1998
`
`Sheet 3 of 6
`
`5,775,791
`
`LGE_000573
`
`

`
`US. Patent
`
`Jul. 7, 1998
`
`Sheet 4 of 6
`
`5,775,791
`
`LGE_000574
`
`

`
`US. Patent
`
`Jul. 7, 1998
`
`Sheet 5 0f 6
`
`5,775,791
`
`LGE_000575
`
`

`
`US. Patent
`
`Jul. 7, 1998
`
`Sheet 6 of 6
`
`5,775,791
`
`FIG. 6A
`
`LGE_000576
`
`

`
`5.775.791
`
`1
`SURFACE EMISSION APPARATUS
`
`TECHNICAL FIELD
`
`The present invention relates to a surface emission appa
`ratus used for illuminating. from the back. a liquid crystal
`display panel or the like serving as a body to be illuminated
`in. e.g.. a liquid crystal television. a potable personal
`computer. or a wordprocessor.
`
`10
`
`20
`
`25
`
`30
`
`35
`
`45
`
`BACKGROUND ARI"
`
`Conventionally. in a surface emission apparatus. in order
`to guide light emitted from a light source to a light-emitting
`surface. light from the light source is made to be incident on
`a light-guide plate and emerges toward the light-emitting
`surface. As the technique to form such a light-guide plate by
`subjecting a surface of the light-guide plate opposing the
`light-emitting surface to hairline formation so as to ran
`domly re?ect light incident on this surface. thereby e?i
`ciently guiding light from the light source to the light
`emitting surface. one disclosed in. e.g.. Japanese Patent
`Publication No. 58- 17957 is known.
`In recent years. however. the size of. e.g.. the liquid
`crystal panel. is increasing. and the area of the light-emitting
`surface of a surface emission apparatus which serves as the
`back light of the liquid crystal panel is also increasing. On
`the other hand. a low-pro?le surface emission apparatus is
`demanded to obtain a compact. lightweight system in which
`a liquid crystal panel or the like is incorporated. When the
`surface emission apparatus is increased in size at a low
`pro?le. in a surface emission apparatus using a conventional
`light-guide plate. a portion of the light-emitting surface
`closer to the light source is bright while a portion thereof
`farther from the light source is dark since light does not
`easily reach there. leading to a non-uniformity in brightness
`of the light-emitting surface. Thus. it is di?icult to obtain
`light emission with entirely uniform brightness.
`As an improvement over this drawback in the surface
`emission apparatus. a technique disclosed in. e.g.. Japanese
`Patent Laid-Open No. 2-126501 is known. which uniforms
`the brightness of the light-emitting surface by printing an ink
`dot pattern on a surface of the light-guide plate opposing the
`light-emitting surface such that the farther from the light
`source. the higher the dot density.
`When an ink or the like is printed in this manner. however.
`it is di?icult to completely eliminate absorption of light by
`the ink itself. leading to a decrease in emission e?iciency.
`Also. since a step of printing the ink is needed. the manu
`facturing process is complicated. leading to an increase in
`cost.
`The present invention has been made in view of the above
`conventional techniques. and has as its object to provide a
`surface emission apparatus capable of uniformly emitting
`light of the light source by uniformly emitting light toward
`the entire light-emitting surface.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a sectional view of a surface emission apparatus
`according to an embodiment of the present invention;
`FIG. 2 is a plan view of the surface emission apparatus;
`FIG. 3 is an enlarged view of the bottom surface of a
`light-guide plate;
`FIG. 4 is a sectional view showing a projecting portion
`formed on the bottom surface of the light-guide plate shown
`in FIG. 3;
`
`65
`
`2
`FIG. 5 is a sectional view showing a light-guide plate
`according to another embodiment of the present invention;
`and
`FIGS. 6(A) and 6(B) are sectional views showing pro
`jecting portions formed on the bottom surfaces of light
`guide plates according to other embodiments.
`DISCLOSURE OF INVENTION
`In order to achieve the above object. according to the
`present invention. there is provided a surface emission
`apparatus for causing light. emitted from a light source
`arranged on a side of a light-emitting surface thereof. to
`emerge from the light-emitting surface. comprising a trans
`parent light-guide plate in which re?ecting shape portions
`formed with small projecting portions are arranged on a
`bottom surface portion thereof opposing the light-emitting
`surface such that a density of the projecting portions is
`gradually increased in accordance with a distance from the
`light source. Light incident from the light source is re?ected
`by the re?ecting shape portions and emerges from the
`light-emitting surface. With this arrangement. light emitted
`from the light source is re?ected toward the light-emitting
`surface in accordance with the density of the re?ecting shape
`portions. so that uniform light emission can be obtained
`throughout the light-emitting surface.
`Preferably. the re?ecting shape portions are disposed in a
`staggered manner in a direction to be remote from the light
`source. With this arrangement. light emitted from the light
`source can be easily incident on many projecting portions
`directly.
`Preferably. the re?ecting shape portions are small pro
`jecting portions whose contiguous parts extending from
`vertex portions thereof and contiguous to the bottom surface
`portion are formed with curved surfaces. Alternatively. the
`re?ecting shape portions are small projecting portions whose
`contiguous parts extending from vertex portions thereof and
`contiguous to the bottom surface portion form circular
`cones. and preferably are circular cones whose vertex angle
`satis?es a range of 90° to 140°. In ether case. the projecting
`portions of the re?ecting shape portions can be integrally
`formed in the process. so that any post-process is not needed.
`BEST MODE OF CARRYING OUT THE
`INVENTION
`Preferable embodiments of the present invention will be
`described in detail with reference to the accompanying
`drawings.
`FIG. 1 is a sectional view of a surface emission apparatus
`according to an embodiment of the present invention. Refer
`ring to FIG. 1. a light source 4 is mounted on a board 5. and
`a light-guide plate 1 made of a transparent member. e.g.. an
`acrylic member. is disposed close to the board 5 such that
`light from the light source is incident on it through its end
`face If. The surfaces of the light-guide plate 1 excluding its
`upper surface 1a on the light-emitting surface side are
`covered with a re?ection frame 3. The surfaces of the
`light-guide plate 1 excluding its bottom surface 1b opposite
`the upper surface 1a are smoothed Small projecting por
`tions 31 whose sections parallel to the bottom surface are
`circular are formed on the bottom surface 1b of the light
`guide plate 1 to be integral with the light-guide plate 1. The
`vertex surface of each projecting portion 31 is ?at. As shown
`in FIG. 3. the leading and trailing portions extending from
`the vertex of each projecting portion 31 and contiguous to
`the bottom surface portion form a curved surface having a
`radius R. The projecting portions 31 are formed as shown in
`FIG. 2.
`
`LGE_000577
`
`

`
`5.775.791
`
`3
`A diffusion plate 2 is mounted above the upper surface 10
`of the light-guide plate 1. The dilfusion plate 2 is made of
`ground glass or the like. and di?uses light emerging from the
`upper surface 1a of the light-guide plate 1 to illuminate a
`body to be illuminated (not shown) by its light-emitting
`surface 2a.
`FIG. 3 is a partial enlarged perspective view of the bottom
`surface 1b of the light-guide plate 1. Each small projecting
`portion 31 is a re?ecting shape portion that re?ects light
`from the light source. The cross-section of each projecting
`portion 31 is circular. and the outer circumferential portion
`of each projecting portion 31 contiguous to the light-guide
`plate 1 forms a funnel having a curved surface with the
`radius R (this curved portion will be referred to as an edge
`portion hereinafter).
`FIG. 4 shows an enlarged sectional view of the projecting
`portion 31. Regarding the size of the projecting portion 31.
`a height h of each projecting portion is about 0.03 to 0.07
`mmwhereas a thickness H of the light-guide plate 1 is about
`1 mm. and a diameter d of each projecting portion is about
`0.05 to 0.2 mm. All the projecting portions have the same
`shape.
`FIG. 2 is a plan view of the surface emission apparatus of
`this embodiment. from which the diffusion plate 2 is
`removed. Referring to FIG. 2. each small circle is a small
`projecting portion 31. The projecting portions 31 are
`arranged in a staggered manner in a direction to be remote
`from the light source 4. Regarding the density of the
`projecting portions 31 formed on the light-guide plate 1. it
`is gradually increased in accordance with an increase in
`distance from the light source.
`Light emitted from the light source is incident on the
`light-guide plate 1 through its end face If opposing the light
`source 4. When the light-guide plate is made of an acrylic
`resin. a refractive index n of the acrylic resin is n: 1.49. or
`the critical angle with which the incident light is totally
`re?ected by the interface of the light-guide-plate is 42.16".
`light incident through the end face If and refracted is totally
`re?ected when it impinges on the upper surface 1a, surfaces
`1d and 1e, or the ?at portion of the bottom surface 1b, of the
`light-guide plate 1 at an angle equal to or more than the
`critical angle. and will not leak to the outside. When light
`impinges on an end face 10, it is re?ected by the re?ection
`frame 3.
`In this manner. light incident on the light-guide plate 1
`impinges on the edge portions of the projecting portions 31
`of the bottom surface 1b directly or after repeating total
`re?ection described above. The edge portions form curved
`surfaces. as described above. Light impinging on the edge
`portions is re?ected and emerges from the upper surface In,
`is diffused by the di?iusion plate 2. and emerges from the
`light-emitting surface 20.
`Since light emerging from the light-guide plate 1 is
`re?ected by the edge portions of the projecting portions 31.
`as described above. the higher the density of the projecting
`portions 31. the larger the quantity of light emerging from
`the upper surface In near the projecting portions 31.
`Therefore. when the density of the projecting portions 31 is
`gradually increased in accordance with the increase in
`distance from the light source 4. so that the quantity of light
`decreasing in accordance with the increase in distance from
`the light source 4 is corrected. the quantity of emerging light
`is decreased near the light source where the quantity of
`incident light is large. and the quantity of emerging light is
`increased at portions where the quantity of incident light is
`small. thereby uniforming the quantity of light emerging
`from the upper surface 1a of the light-guide plate 1.
`
`30
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`35
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`50
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`55
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`65
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`4
`When the small funnel-type projecting portions whose
`leading and trailing portions form curved surfaces are
`arranged on the bottom surface of the light-guide plate 1 in
`this manner such that the density is decreased in accordance
`with the increase in distance from the light source. the
`following effects can be obtained:
`@ Since the circular projecting portions are arranged.
`light from any directions can be re?ected with the same
`re?ectance without any directivity regardless of the
`shapes of the projecting portions. thereby obtaining
`optical uniformity.
`(2) Since the projecting portions have the same shape. the
`re?ectance can be controlled by the density of the
`projecting portions. thereby uniforming the quantity of
`light of the surface-emission light source.
`6) Since the projecting portions are arranged in the
`staggered manner. light emitted from the light source
`can be easily incident on many projecting portions
`directly. thereby obtaining optical uniformity without
`increasing the brightness at a particular portion.
`@ This light-guide plate can be manufactured at a low
`cost by integrally forming the projecting portions in the
`process without requiring any post-process such as
`hairline formation.
`FIG. 5 shows another embodiment of the present inven
`tion. FIG. 5 is a sectional view showing a light-guide plate
`of a surface emission apparatus according to this another
`embodiment. This embodiment is different from the above
`embodiment in the shape of the projecting portions. and
`other portions have the same structure as that of the above
`embodiment. Thus. the same reference numerals are used to
`denote the same portions. and a detailed description thereof
`will be omitted.
`As shown in FIG. 5. each projecting portion 33 forms a
`circular cone such that its section parallel to the bottom
`surface is circular. As is apparent from FIG. 5. the leading
`and trailing portions extending from the vertex of each
`projecting portion 32 and contiguous to the bottom surface
`portion. i.e.. the edge portion of each projecting portion. has
`a linear section having a predetermined vertex angle 0.
`The optical path of light emitted from a light source 4 and
`incident on a light-guide plate 1 when the projecting por
`tions 33 are circular cones in this manner will be described.
`As described above. when the light-guide plate 1 is made
`of an acrylic resin. the critical angle is 42.16°. Light emitted
`from the light source 4 and incident on the light-guide plate
`1 through an end face 1]" has an angle a of incidence of 0°
`to 42.16° in the light-guide plate. Thus. light emitted from
`the light source and directly reaching the projecting portion
`33 through the end face If without being re?ected by other
`surfaces of the light-guide plate has an angle b of 47.84°
`(=90—42.l6) to 90°.
`When the vertex angle 6 of the projecting portion 33 is set
`such that the projecting portion 33 re?ects light with its edge
`portion in a direction perpendicular to a light-emitting
`surface 1a of the light-guide plate 1. it falls within a range
`of 90° to 132.16’ (=90—47.84/2)l2).
`As the critical angle of the light-guide plate 1 is 42.16".
`light emitted from the light source 4. passing through the end
`face If, re?ected by another surface (e.g.. a surface within
`the light-emitting surface 1a) of the light-guide plate 1. and
`reaching the edge portion of the projecting portion 33 has an
`angle b of 42.16’ to 90°. Therefore. when the vertex angle
`6 of the projecting portion 33 is set such that the projecting
`portion 33 re?ects light with its edge portion to be perpen
`dicular to the light-emitting surface In of the light-guide
`plate 1. it falls within the range of 90° to 137.85° (=90
`42.16/2)/2).
`
`LGE_000578
`
`

`
`5.775.791
`
`15
`
`20
`
`25
`
`5
`From the foregoing. it is preferable that the vertex angle
`6 of the projecting portion 33 be set within the range of 90°
`to 140°. More preferably. when calculation is performed
`under an assumption that the average angle of light reaching
`the projecting portion 33 is 68.92° (=(90+48.74)/2). the
`vertex angle 6 will be 111.08". Thus. the vertex angle of the
`projecting portion 33 is preferably about 110°.
`Circular conical projecting portions 34 having ?at vertex
`portions may be employed. as shown in FIG. 6(A). or
`circular conical projecting portions 35 having vertex por- 10
`tions with curved surfaces may be employed. as shown in
`FIG. 6(B).
`In this manner. when the small funnel-like circular conical
`projecting portions. whose leading and trailing portions have
`a linear section. are arranged on the bottom surface of the
`light-guide plate 1 such that the density of the projecting
`portions is decreased in accordance with the increase in
`distance from the light source. effects @ to @ similar to
`those of the ?rst embodiment described above can be
`obtained. and the rate of light re?ected by the projecting
`portions to be perpendicularly directed toward the light
`emitting surface can be increased. so that the brightness
`before the light-emitting surface can be increased.
`In the ?rst and other embodiments described above. the
`light source 4 is arranged such that light is incident on one
`end face of the light-guide plate 1. However. when a large
`light-guide plate 1 is used. light sources can be arranged at
`the two ends of the light-guide plate 1. In this case. the
`projecting portions are arranged on the bottom surface of the
`light‘guide plate 1 with a density gradient such that the
`density is the highest at the central portion of the bottom
`surface which is farthest from the two light sources and is
`low near the light sources. With this arrangement. a uniform
`surface emission apparatus can be realized.
`Furthermore. in any of the above embodiments. in for
`mation of the projecting portions. recesses are formed in the
`light-guide plate 1 so that the vertices of the projecting
`portions are directed to the light-emitting surface In.
`However. the projecting portions may be formed such that
`their vertexes are directed to the re?ection frame 3 opposite
`the light-emitting surface. In this case as well. effects
`substantially similar to those of the above embodiments can
`be obtained.
`
`35
`
`Industrial Applicability
`
`As has been described above. with the surface emission
`apparatus according to the present invention. light from the
`light source can be uniformly emitted toward the entire
`light-emitting surface to obtain uniform light emission at a
`low cost without requiring a complicated structure.
`We claim:
`1. A surface emission apparatus characterized in that light
`emitted from a light source arranged near a side portion of
`a ?at light-emitting member thereof emerges from a ?at
`light-emitting surface of said ?at light-emitting member.
`comprising:
`
`45
`
`50
`
`55
`
`6
`a transparent light-guided plate in which re?ecting shape
`portions formed with small projecting portions each
`with a circular cone having predetermined vertex angle
`are arranged on a bottom surface portion thereof oppos
`ing said ?at light-emitting surface such that a density of
`said projecting portions is gradually increased in accor
`dance with a distance from said light source and also
`being formed in a staggered manner along parallel lines
`with respect to said side portion;
`said small projecting portions being formed to have small
`curved surfaces at top end corners of the vertex angles
`thereof and also being formed to have small curved
`surfaces at bottom portions thereof so as to continue
`with said bottom surface portion;
`wherein light incident from said light source is re?ected
`by said re?ecting shape portions and emerges from said
`?at light-emitting surface.
`2. A surface emission apparatus according to claim 1.
`wherein said small projecting portions are formed with
`circular cones whose vertex angles are between a range of 90
`to 140 degrees.
`3. A surface emission apparatus according claim 1.
`wherein said transparent light-guide plate including said
`small projecting portions is made of acrylic resin.
`4. A surface emission apparatus characterized in that light
`emitted from a light source arranged near a side portion of
`a ?at light-emitting member thereof emerges from a ?at
`light-emitting surface of said ?at light-emitting member.
`comprising:
`a transparent light-guide plate in which re?ecting shape
`portions formed with small concaving portions are
`arranged on a bottom surface portion thereof opposing
`said ?at light-emitting surface such that a density of
`said concaving portions is gradually increased in accor
`dance with a distance from said light source and also
`being formed in a staggered manner along the parallel
`lines with respect to said side portion;
`said small concaving portions being formed to have small
`curved surfaces at top end corners thereof and also
`being formed to have small curved surfaces at bottom
`portions thereof so as to continue with said bottom
`surface portion;
`wherein light incident from said light source is re?ected
`by said re?ecting shape portions and emerges from said
`?at light-emitting surface.
`5. A surface emission apparatus according to claim 4.
`wherein said small concaving portions are formed with
`circular cones whose vertex angle is between a range of 90
`to 140 degrees.
`6. A surface emission apparatus according to claim 4.
`wherein said transparent light-guide plate together with said
`small concaving portions is made of acrylic resin.
`
`*****
`
`LGE_000579