`6-230378
`(43) Publication Date: August 19, 1994
`(21) Application No. 5-014823
`(22) Application Date: February 1, 1993
`(71) Applicant: Fine Plus Co., Ltd.
`(72) Inventor: Kisoo et al.
`(74) Agent: Patent Attorney, Shigenobu NAKAMURA
`
`(54) [Title of the Invention] BACKLIGHT APPARATUS FOR
`LIQUID CRYSTAL DISPLAY ELEMENT
`
`
`(57) [Abstract]
` [Object] An object is to provide a thin LCD backlight
`apparatus whose luminance does not vary from one area to
`another, thereby realizing uniform illumination.
` [Construction] The apparatus includes a molded resin LED
`lamp 10, in which plural LEDs are connected in series, a
`light conductor 11, which is provided at a light emitting
`side of the LED lamp 10, and a reflector 12, which surrounds
`the light conductor 11 with the lamp 10. The front surface
`of the light conductor 11 is a crimp-textured surface 11a
`formed by surface texturing. Recessed optical paths 11b,
`each of which extends in a light propagation direction and
`has a triangular shape in cross section, are formed in the
`
`- 1 -
`
`Sony Corp. Exhibit 1026
`
`SONY_001014
`
`
`
`reverse surface of the light conductor 11.
`[Operation] Light emitted from the LED lamp 10 is guided
`partly through the recessed optical paths 11b to every nook
`and corner of the light conductor 11, and is diffused into
`multiple directions by the reflector 12 and the crimp-
`textured surface 11a.
`
`- 2 -
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`SONY_001015
`
`
`
`[Claim]
`[Claim 1] A backlight apparatus for a liquid crystal
`display element, comprising:
`
`a light source that includes plural light emitting
`elements connected in a line;
`
`a flat light conductor for directing light emitted from
`the light source, said light conductor being provided at a
`light emitting side of the light source and having a light
`emission surface as a front surface; and
`
`a reflector that is provided behind a reverse surface
`of the conductor;
`
`wherein the front surface of the light conductor is a
`crimp-textured surface, and
`
`wherein many recessed optical paths extending in a
`light propagation direction are formed in the reverse
`surface.
`[Detailed Description of the Invention]
`[0001]
`[Field of Industrial Application] The present invention
`relates to a backlight apparatus for a liquid crystal
`display element that requires an illuminating light source.
`More particularly, the invention relates to a sidelight-type
`backlight apparatus that directs light of a light source to
`a light emission surface in a lateral direction (parallel
`direction).
`
`- 3 -
`
`SONY_001016
`
`
`
`[0002]
`[Description of the Related Art] A liquid crystal display
`(LCD) backlight apparatus is widely used as an illuminating
`light source for an LCD built in various kinds of equipment
`such as an electronic calculator, a digital watch/clock, a
`personal computer, a personal word processor, and the like.
`A sidelight backlight apparatus, which includes a light
`source made up of plural light emitting elements [e.g.,
`light emitting diodes (LED)] connected at regular intervals,
`and a light conductor (light guiding plate) provided at a
`light emitting side of the light source, is known as a type
`of such a backlight apparatus. In a sidelight backlight
`apparatus, typically, the front/top of a light conductor
`functions as a light emission surface, and other surfaces
`(back and sides) function as reflection surfaces. In such a
`backlight apparatus, light emitted from a light source is
`diffused in and by a light conductor and is finally
`outputted in multiple directions from a light emission
`surface. To increase efficiency in light diffusion, in some
`apparatuses, the inside of a light emission surface is crimp
`(pear's skin) textured, or a light-transmissive diffusion
`sheet is on the outside of the light emission surface.
`[0003]
`[Problems to be Solved by the Invention] In a backlight
`apparatus according to prior art described above, since the
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`- 4 -
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`SONY_001017
`
`
`
`intensity of LED light decreases with distance from a light
`source, though it is bright at an area near the light source,
`luminance decreases in proportion to the distance. To
`overcome this relationship, a known apparatus offers
`illumination with greater uniformity by diffusing light by
`means of a reflector (reflection plate). However, the
`problem of differences in the level of lightness/darkness
`between the center area of a light emission surface and the
`peripheral area thereof (darker at the peripheral area) has
`not been solved yet.
`[0004]
`
`One known approach for obtaining uniform illumination
`is to increase the intensity of illumination by increasing
`the number of LEDs or raising a voltage applied to LEDs.
`However, if this approach is taken, it will not only
`increase the amount of heat generated by the light source
`but also accelerate the deterioration of the light source.
`Another known solution is to provide partitions, etc., in a
`light conductor or a reflector for obtaining uniform and
`sharp illumination. However, such a structure is more
`complex, and significantly decreases light transmittance.
`[0005]
`
`The thickness of prior-art backlight apparatuses is
`within a range from 2.5 to 6.0 mm. In the art, it is
`difficult to reduce a thickness to 2.0 mm or less. The
`
`- 5 -
`
`SONY_001018
`
`
`
`present invention has been made in view of the above
`problems. An object of the invention is to provide a thin
`LCD backlight apparatus whose luminance does not vary from
`one area to another, thereby realizing uniform illumination.
`[0006]
`[Means for Solving the Problems] In order to achieve the
`above object, a liquid crystal display backlight apparatus
`according to the present invention comprises: a light source
`that includes plural light emitting elements connected in a
`line; a flat light conductor for directing light emitted
`from the light source, said light conductor being provided
`at a light emitting side of the light source and having a
`light emission surface as a front surface; and a reflector
`that is provided behind a reverse surface of the conductor;
`wherein the front surface of the light conductor is a crimp-
`textured surface, and wherein many recessed optical paths
`extending in a light propagation direction are formed in the
`reverse surface.
`[0007]
`[Operation] The most part of light emitted from the light
`source go into the light conductor and propagates inside the
`light conductor while being diffused in multiple directions.
`A part of the emitted light goes through the recessed
`optical paths, which are formed in the reverse surface. In
`this process, the light is diffused by the optical paths,
`
`- 6 -
`
`SONY_001019
`
`
`
`and is irregularly reflected by the reflector for reflected
`diffusion. Direct light, which propagates straight toward
`the light emission surface of the light conductor, and
`diffused reflected light, are finally diffused and outputted
`in multiple directions by the crimp-textured surface when
`passing therethrough.
`[0008]
`
`That is, in the backlight apparatus of the invention,
`light is guided partly through the recessed optical paths to
`every nook and corner of the light conductor. In addition,
`reflection by the reflector and diffusion by the crimp-
`textured surface produce synergistic effects. For these
`reasons, an illuminating light source that achieves uniform
`light emission with high brightness is provided.
`[0009]
`[Embodiment] On the basis of an exemplary embodiment, a
`backlight apparatus according to the present invention will
`now be explained. Fig. 1 is an exploded perspective view
`that illustrates, for example, a liquid crystal display
`(LCD) in which a backlight apparatus according to an
`exemplary embodiment is built as a light source for
`illuminating a liquid crystal display element with backlight.
`Fig. 2 is an essential-part sectional view thereof. In the
`illustrated example, a backlight apparatus 1 is mounted on a
`circuit board 2 that has a suitable size. A liquid crystal
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`- 7 -
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`SONY_001020
`
`
`
`device 3, which is bridged over the backlight apparatus 1,
`is mounted on the circuit board 2. The liquid crystal
`device 3 is enclosed by a cover 4, which is also on the
`circuit board 2.
`[0010]
`
`The backlight apparatus 1, which will be described
`later in detail, includes a molded resin LED lamp (light
`source) 10, in which plural LEDs are aligned and connected
`in series as light emitting elements, a light conductor
`(light guiding plate) 11, which is provided at a light
`emitting side of the LED lamp 10 and has a shape of a plate
`extending in a direction in which light propagates, and a
`reflector (reflection plate) 12, which surrounds the
`surfaces (sides and back) of the light conductor 11
`excluding the light emission surface thereof. The LED lamp
`10 is connected to the wiring pattern (not shown) of the
`circuit board 2.
`[0011]
`
`The liquid crystal device 3 has a structure in which an
`LCD 30 is sandwiched between two polarization plates 31 and
`32. A connector 33 for connection to the wiring pattern of
`the circuit board 2 is fixed to the LCD 30. The liquid
`crystal device 3 is a prior-art device and is not a part of
`the gist of the invention. Therefore, a detailed
`explanation is not given here. Fig. 3(a) is a plan view of
`
`- 8 -
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`SONY_001021
`
`
`
`the backlight apparatus 1. Fig. 3(b) is a sectional view
`taken along the line A-A of Fig. 3(a). Fig. 4 is an
`exploded perspective view. As described above, the LED lamp
`10 is manufactured by connecting plural LEDs in series and
`resin-molding them. Though not illustrated in the drawing,
`for example, the LED lamp 10 can be manufactured by using
`lead frames on each of which an LED chip is mounted,
`connecting the lead frame to the LED chip by means of an Au
`wire, connecting lead frames that are adjacent to each other
`by means of an Au wire, and resin-molding the entire
`structure.
`[0012]
`
`In the present embodiment, the LED lamp 10 described
`above is inserted at one edge portion of the light conductor
`11 (refer to Fig. 4). As partially illustrated in Fig. 4,
`the light emission surface 11a of the light conductor 11 is
`a crimp-textured surface formed by (pear's skin) surface
`texturing. The crimp-textured surface 11a has a diffusing
`function when light guided by the light conductor 11 finally
`passes through the light emission surface 11a.
`[0013]
`
`The back (reverse surface, which is the opposite of the
`light emission surface) of the light conductor 11 has many
`recessed optical paths 11b extending in the light
`propagation direction from an edge that is closest to the
`
`- 9 -
`
`SONY_001022
`
`
`
`LED lamp 10 to the opposite edge. In the present embodiment,
`each of the recessed optical paths 11b has a triangular
`shape in cross section (refer to Fig. 6). Because of the
`presence of the recessed optical paths 11b, the back of the
`light conductor 11 is serrated. Therefore, there are gap
`spaces between the serrated surface 11b and the reflector 12.
`The gap spaces function as said optical paths. Since there
`are the optical paths 11b, light emitted from the LED lamp
`10 propagates farther stably.
`[0014]
`
`The reflector 12 has a housing space 12a for
`accommodating the light conductor 11 with the LED lamp 10.
`The light conductor 11 is fitted into the housing space 12a.
`The inner surfaces of the housing space 12a are formed as
`reflection surfaces for reflecting light going out through
`the sides and back of the light conductor 11. Next, the
`operation of the backlight apparatus 1 having the structure
`described above will now be explained with reference to Fig.
`5 (longitudinal sectional view along the recessed optical
`paths 11b) and Fig. 6 (cross sectional view across the
`recessed optical paths 11b). The most part of light emitted
`from the LED lamp 10 propagates inside the light conductor
`11 and is diffused in multiple directions. The remaining
`part of the light goes into the optical paths 11b at the
`back of the light conductor 11 to be diffused by the
`
`- 10 -
`
`SONY_001023
`
`
`
`serrated surface 11b, and is irregularly reflected by the
`reflector 12 for reflected diffusion. Needless to say,
`light that arrives at the reflector 12 after having passed
`through the light conductor 11 is reflected by the reflector
`12. Direct light, which propagates straight toward the
`light emission surface 11a of the light conductor 11, and
`diffused reflected light, are finally diffused and outputted
`in multiple directions by the crimp-textured surface 11a
`when passing therethrough.
`[0015]
`
`As described above, since a part of light emitted from
`the LED lamp 10 propagates through the recessed optical
`paths 11b, the light reaches throughout the entire effective
`light emission surface area. In addition, reflection by the
`reflector 12 and diffusion by the crimp-textured surface 11a
`produce synergistic effects. For these reasons, a high-
`quality illuminating light source that achieves uniform
`light emission with high brightness is provided. Therefore,
`the entire surface of the LCD 30 of the liquid crystal
`device 3 is illuminated with the light uniformly.
`Consequently, the prior-art problem of differences in the
`level of lightness/darkness from one spot to another on the
`LCD 30 does not occur.
`[0016]
`
`In the embodiment described above, each of the recessed
`
`- 11 -
`
`SONY_001024
`
`
`
`optical paths 11b formed in the back of the light conductor
`11 has a triangular shape in cross section as illustrated in
`Fig. 7(a). However, the cross-sectional shape of the path
`11b is not limited to a triangle as long as it functions as
`an optical path. For example, the path 11b may have a
`circular (Fig. 7(b)), hexagonal (Fig. 7(c)), or quadrangular
`(Fig. 7(d)) shape. To increase an effective light emission
`area size by increasing the depth of the light conductor 11,
`that is, by increasing the length of the recessed optical
`path 11b in the extending direction, preferably, for example,
`in addition to one LED lamp provided along one edge of the
`light conductor 11, another LED lamp should be provided
`along the opposite edge thereof. With such dual sidelight,
`it is possible to increase the depth up to approximately 65
`mm without impairing uniform light emission.
`[0017]
`
`In the embodiment described above, an LED lamp is used
`as the light source. However, needless to say, the scope of
`the invention is not limited thereto. Other light emitting
`element such as an EL lamp, a white-light lamp, etc., may be
`used.
`[0018]
`[Advantages] Since an LCD backlight apparatus according to
`the present invention has the structure explained above, it
`produces the following effects:
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`- 12 -
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`SONY_001025
`
`
`
`(1) Since a light conductor has a crimp-textured front
`surface and a recessed reverse surface, a part of light
`emitted from a light source propagates through the recessed
`optical paths, and the light reaches throughout the entire
`effective light emission surface area; in addition, because
`of synergistic effects produced by reflection by a reflector
`and diffusion by the crimp-textured surface, the light is
`diffused and outputted in multiple directions efficiently;
`the differences in the level of lightness between the center
`area of the light emission surface and the peripheral area
`thereof are eliminated. Consequently, an illuminating light
`source that achieves uniform light emission with high
`brightness is provided.
`(2) It is not necessary to increase the number of light
`emitting elements or raise a voltage applied thereto. Nor
`is it necessary to provide partitions, etc., in a light
`conductor or a reflector. Therefore, the amount of heat
`generated by a light source does not increase, and
`accelerated deterioration of the light source does not occur.
`In addition, the structure is simple, and there is no
`significant decrease in light transmittance.
`(3) The structure of the invention diffuses light into
`multiple directions by means of the recessed optical paths
`of the light conductor, the crimp-textured surface of the
`light conductor, and the reflector. Therefore, it is
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`- 13 -
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`SONY_001026
`
`
`
`possible to provide a thin low-profile apparatus, for
`example, one having a thickness of 2.5 mm or less (in
`particular, 2.0 mm).
`[Brief Description of the Drawings]
`[Fig. 1] Fig. 1 is an exploded perspective view of a liquid
`crystal display in which a backlight apparatus according to
`an exemplary embodiment of the invention is built as an
`illuminating light source;
`[Fig. 2] Fig. 2 is an essential-part sectional view of the
`liquid crystal display illustrated in Fig. 1;
`[Fig. 3] Fig. 3(a) is a plan view of the backlight
`apparatus of the embodiment, and Fig. 3(b) is a sectional
`view taken along the line A-A of Fig. 3(a);
`[Fig. 4] Fig. 4 is an exploded perspective view of the
`backlight apparatus illustrated in Fig. 3;
`[Fig. 5] Fig. 5 is a diagram for explaining the operation
`of the backlight apparatus illustrated in Fig. 3;
`[Fig. 6] Fig. 6 is a diagram for explaining the operation
`of the backlight apparatus illustrated in Fig. 3; and
`[Fig. 7] Fig. 7(a) is a sectional view that illustrates the
`shape of recessed optical paths of a light conductor of the
`backlight apparatus illustrated in Fig. 3; and each of Figs.
`7(b), 7(c), and 7(d) is a sectional view of a variation
`example thereof.
`[Reference Numerals]
`
`- 14 -
`
`SONY_001027
`
`
`
`1 backlight apparatus for liquid crystal display element
`10 LED lamp (light source)
`11 light conductor
`11a crimp-textured surface (light emission surface)
`11b recessed optical path
`12 reflector
`
`- 15 -
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`SONY_001028