`6-003526
`(43) Publication Date: January 14, 1994
`(21) Application No. 4-159403
`(22) Application Date: June 18, 1992
`(71) Applicant: Fujitsu Limited
`(72) Inventor: Nagatani et al.
`(74) Agent: Patent Attorney, Aoki et al.
`
`(54) [Title of the Invention] ILLUMINATION APPARATUS
`
`(57) [Abstract]
` [Object] An object of the invention, which relates to an
`illumination apparatus, is to provide a plane illumination
`apparatus that realizes high brightness and high
`productivity.
` [Construction] An illumination apparatus at least
`includes a light-guiding plate 11 and a light source 12
`provided along and next to a side edge of the light-guiding
`plate. The apparatus is characterized in that, a light-
`diffusing plate 21 is provided on an outgoing-light emission
`surface of the light-guiding plate 11; a concave portion 14
`having a substantially triangular cross-sectional shape is
`formed in an opposite surface of the light-guiding plate 11
`as a line pattern or a dot pattern; a transparent layer 16
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`Sony Corp. Exhibit 1020
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`SONY_000750
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`is formed on the opposite surface of the light-guiding plate
`11, in which the concave portion 14 is formed, by using a
`material that has an index of refraction that is greater
`than that of the light-guiding plate 11, said transparent
`layer being formed in such a way that the concave portion 14
`is filled in by said material; and a reflection sheet 18 is
`either provided on or formed integrally on an outer surface
`of the transparent layer 16.
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`- 2 -
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`SONY_000751
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`
`
`[Claims]
`[Claim 1] An illumination apparatus that at least includes
`a light-guiding plate (11) and a light source (12) that is
`provided along and next to a side edge of the light-guiding
`plate,
`
`characterized in that,
`
`a light-diffusing plate (21) is provided on an
`outgoing-light emission surface of the light-guiding plate
`(11);
`
`a concave portion (14) that has a substantially
`triangular cross-sectional shape is formed in an opposite
`surface of the light-guiding plate (11) as a line pattern or
`a dot pattern;
`
`a transparent layer (16) is formed on the opposite
`surface of the light-guiding plate (11), in which the
`concave portion (14) is formed, by using a material that has
`an index of refraction that is greater than an index of
`refraction of the light-guiding plate (11), said transparent
`layer being formed in such a way that the concave portion
`(14) is filled in by said material; and
`
`a reflection sheet (18) is either provided on or formed
`integrally on an outer surface of the transparent layer (16).
`[Claim 2] An illumination apparatus that at least includes
`a light-guiding plate (11) and a light source (12) that is
`provided along and next to a side edge of the light-guiding
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`- 3 -
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`SONY_000752
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`plate,
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`characterized in that,
`
`a concave portion (34) that has a substantially
`triangular cross-sectional shape is formed in an outgoing-
`light emission surface of the light-guiding plate (11) as a
`line pattern or a dot pattern;
`
`a transparent layer (36) is formed on the outgoing-
`light emission surface of the light-guiding plate (11) by
`using a material that has an index of refraction that is
`greater than an index of refraction of the light-guiding
`plate (11), said transparent layer being formed in such a
`way that the concave portion (34) is filled in by said
`material;
`
`a light-diffusing plate (38) is provided on an outer
`surface of the transparent layer (36); and
`
`a reflection sheet (32) is provided on an opposite
`surface of the light-guiding plate (11).
`[Claim 3] An illumination apparatus that at least includes
`a light-guiding plate (11) and a light source (12) that is
`provided along and next to a side edge of the light-guiding
`plate,
`
`characterized in that,
`
`a concave portion (34) that has a substantially
`triangular cross-sectional shape is formed in an outgoing-
`light emission surface of the light-guiding plate (11) as a
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`SONY_000753
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`line pattern or a dot pattern;
`
`a transparent layer (36) is formed on the outgoing-
`light emission surface of the light-guiding plate (11) by
`using a material that has an index of refraction that is
`greater than an index of refraction of the light-guiding
`plate (11), said transparent layer being formed in such a
`way that the concave portion (34) is filled in by said
`material;
`
`a light-diffusing plate (38) is provided on an outer
`surface of the transparent layer (36);
`
`a concave portion (14) that has a substantially
`triangular cross-sectional shape is formed in an opposite
`surface of the light-guiding plate (11) as a line pattern or
`a dot pattern;
`
`a transparent layer (16) is formed on the opposite
`surface of the light-guiding plate (11), in which the
`concave portion (14) is formed, by using a material that has
`an index of refraction that is greater than an index of
`refraction of the light-guiding plate (11), said transparent
`layer being formed in such a way that the concave portion
`(14) is filled in by said material; and
`
`a reflection sheet (18) is either provided on or formed
`integrally on an outer surface of the transparent layer (16).
`[Claim 4] The illumination apparatus according to any of
`Claims 1, 2, and 3, further characterized in that either one
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`SONY_000754
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`of two surfaces each having the largest area size among
`surfaces of the light-guiding plate (11) is, or both of said
`two surfaces are, sloped.
`[Claim 5] A liquid crystal display device, characterized by
`being assembled as a combination of the illumination
`apparatus (40) according to any of Claims 1, 2, 3, and 4 and
`a liquid crystal panel (41).
`[Detailed Description of the Invention]
`[0001]
`[Field of Industrial Application] The present invention
`relates to a plane illumination apparatus used for enhancing
`the display viewability of a display device such as a liquid
`crystal display device.
`[0002]
`
`Two popular types of plane illumination apparatuses are
`a direct lighting type, which is for illumination from below,
`and an edge-light type (light-guiding type). In an edge-
`light-type plane illumination apparatus, a diffusing
`reflection layer is formed on its back to cause light to go
`out. For the purpose of obtaining uniform brightness
`distribution throughout the area of a plane for light
`emission, in such a plane illumination apparatus, a light-
`diffusing reflection portion is formed in a dot pattern, a
`mesh pattern, etc. that has area-size percentage
`corresponding to a distance from a light source. The ratio
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`SONY_000755
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`of the diffusing reflection portion to a non-diffusing
`reflection portion, that is, the percentage of a diffusing
`reflection amount, is pre-designed for realizing uniform
`brightness distribution irrespective of a position on the
`light emission plane.
`[0003]
`
`In prior art, a paint containing white pigments or a
`paint containing glass beads is used to form such a
`diffusing reflection layer by printing. Optical diffusion
`occurs due to the light-diffusing effects of the diffusing
`reflection layer, and light that propagates while meeting
`the conditions of total reflection, that is, perfect
`internal reflection, fails to meet said conditions due to
`the diffusion and, as a result, is taken out as outgoing
`light. To meet an increasing demand for an apparatus having
`a low-profile body, a light-guiding plate has recently been
`becoming thinner and thinner, as a component of the entire
`body structure. In the art, the lack of uniformity in
`brightness appears conspicuously on the light emission plane
`of a plane illumination apparatus due to an error in the
`percentage of area size, which is caused by the lack of
`precision in printing. In order to obtain a plane
`illumination apparatus that has excellent plane illumination
`characteristics, high-precision print technology is required.
`In the art, this is an obstacle to improved productivity and
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`SONY_000756
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`low cost.
`[0004]
`
`Moreover, for the purpose of increasing brightness, it
`is necessary to improve the optical characteristics of each
`portion. For example, for this purpose, it is necessary to
`improve a reflection factor and a transmission factor.
`Improved optical characteristics are required for the
`diffusing reflection layer mentioned above, too. That is,
`the development of a novel means for increasing brightness
`is awaited.
`[0005]
`[Description of the Related Art] The structure of an edge-
`light-type illumination apparatus according to prior art is
`illustrated in Fig. 9. In this drawing, the reference
`numeral 1 denotes a light-guiding plate. The light-guiding
`plate 1 is mainly made of transparent acrylic resin. A
`diffusing reflection layer 2, which has dots 2a as
`illustrated in Fig. 9(b), is formed on the reverse surface
`of the light-guiding plate 1. Each of the dots 2a is
`printed with the use of a paint having light-diffusing
`property such as a light-diffusing white paint. The method
`of screen printing, etc. is used for dot printing. As
`illustrated in Fig. 9(a), a reflector plate is provided on
`the diffusing reflection layer 2. On the opposite surface
`of the light-guiding plate 1, a diffusing plate 4 is
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`SONY_000757
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`provided.
`[0006]
`
`The reference numeral 5 denotes a light source (light
`sources) using a fluorescent tube. For the purpose of
`causing light emitted from the light source 5 to go into the
`light-guiding plate 1 efficiently, a reflection cover 6,
`which is made of Al, Ag, or the like, is provided around the
`light source 5. The reflection cover 6 reflects light
`emitted from the light source 5 in such a way as to condense
`the emitted light onto an end face of the light-guiding
`plate 1. The condensed light goes into the light-guiding
`plate 1 as incident light. By the law of total reflection,
`the light having gone into the light-guiding plate 1
`propagates inside the light-guiding plate 1 within a
`critical angle. The propagation light does not turn into
`outgoing light, which goes out of the light-guiding plate 1,
`until a failure to meet the conditions of total reflection
`occurs. Due to the diffused reflection of the propagation
`light by the diffusing reflection layer 2 explained above,
`this failure occurs, and the propagation light turns into
`outgoing light.
`[0007]
`
`When going out, the outgoing light is further diffused
`at the diffusing plate 4, which enhances uniformity in
`brightness for use as plane illumination light. At the
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`SONY_000758
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`reverse-surface side of the light-guiding plate 1, the
`reflector plate 3 reflects, toward a light emission surface
`1a, light coming from the diffusing plate 4 and leaking
`through the diffusing reflection layer 2 at the back,
`thereby increasing brightness. As a general tendency, the
`closer to the light source 5 on the light emission surface
`1a, the higher the brightness. For the purpose of avoiding
`this tendency, as well known in the art, the diffusing
`reflection layer 2 described above is formed in such a way
`as to have a pattern determined depending on various
`conditions.
`[0008]
`[Problems to be Solved by the Invention] In an edge-light-
`type illumination apparatus according to prior art such as
`one described above, a diffusing reflection layer that
`diffuses light originating from a light source is formed
`with the use of a printing method. Therefore, the area size
`of the diffusing reflection layer, which has an influence on
`the degree of uniformity in brightness, is susceptible to an
`error. In the art, this area-size error is a cause of low
`productivity (yield). In addition, optical absorption by
`the paint used for the printing increases due to multiple
`reflections inside a light-guiding plate. This makes it
`difficult to realize high brightness.
`[0009]
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`SONY_000759
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`Ideally, 100% of light originating from a light source
`
`should turn into outgoing light after going into a light-
`guiding plate. This is advantageous from the viewpoint of
`efficiency in the use of light. In this respect, in
`diffusion by a diffusing reflection layer according to prior
`art, it is not possible to control the amount of light
`propagating inside a light-guiding plate because it is not
`possible to control the direction of reflected light. For
`this reason, either the returning of light to the light-
`source side or, if plural light sources are provided, the
`reaching of light to the opposite light-source side occurs,
`which makes it difficult to realize high brightness.
`[0010]
`
`An object of the present invention is to provide a
`plane illumination apparatus that realizes high brightness
`and high productivity.
`[0011]
`[Means for Solving the Problems] An illumination apparatus
`according to an aspect of the present invention at least
`includes a light-guiding plate 11 and a light source 12 that
`is provided along and next to a side edge of the light-
`guiding plate, characterized in that, a light-diffusing
`plate 21 is provided on an outgoing-light emission surface
`of the light-guiding plate 11; a concave portion 14 that has
`a substantially triangular cross-sectional shape is formed
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`SONY_000760
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`in an opposite surface of the light-guiding plate 11 as a
`line pattern or a dot pattern; a transparent layer 16 is
`formed on the opposite surface of the light-guiding plate 11,
`in which the concave portion 14 is formed, by using a
`material that has an index of refraction that is greater
`than an index of refraction of the light-guiding plate 11,
`said transparent layer being formed in such a way that the
`concave portion 14 is filled in by said material; and a
`reflection sheet 18 is either provided on or formed
`integrally on an outer surface of the transparent layer 16.
`[0012]
`
`An illumination apparatus according to another aspect
`of the present invention at least includes a light-guiding
`plate 11 and a light source 12 that is provided along and
`next to a side edge of the light-guiding plate,
`characterized in that, a concave portion 34 that has a
`substantially triangular cross-sectional shape is formed in
`an outgoing-light emission surface of the light-guiding
`plate 11 as a line pattern or a dot pattern; a transparent
`layer 36 is formed on the outgoing-light emission surface of
`the light-guiding plate 11 by using a material that has an
`index of refraction that is greater than an index of
`refraction of the light-guiding plate 11, said transparent
`layer being formed in such a way that the concave portion 34
`is filled in by said material; a light-diffusing plate 38 is
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`SONY_000761
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`provided on an outer surface of the transparent layer 36;
`and a reflection sheet 32 is provided on an opposite surface
`of the light-guiding plate 11.
`[0013]
`
`An illumination apparatus according to still another
`aspect of the present invention at least includes a light-
`guiding plate 11 and a light source 12 that is provided
`along and next to a side edge of the light-guiding plate,
`characterized in that, a concave portion 34 that has a
`substantially triangular cross-sectional shape is formed in
`an outgoing-light emission surface of the light-guiding
`plate 11 as a line pattern or a dot pattern; a transparent
`layer 36 is formed on the outgoing-light emission surface of
`the light-guiding plate 11 by using a material that has an
`index of refraction that is greater than an index of
`refraction of the light-guiding plate 11, said transparent
`layer being formed in such a way that the concave portion 34
`is filled in by said material; a light-diffusing plate 38 is
`provided on an outer surface of the transparent layer 36; a
`concave portion 14 that has a substantially triangular
`cross-sectional shape is formed in an opposite surface of
`the light-guiding plate 11 as a line pattern or a dot
`pattern; a transparent layer 16 is formed on the opposite
`surface of the light-guiding plate 11, in which the concave
`portion 14 is formed, by using a material that has an index
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`SONY_000762
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`of refraction that is greater than an index of refraction of
`the light-guiding plate 11, said transparent layer being
`formed in such a way that the concave portion 14 is filled
`in by said material; and a reflection sheet 18 is either
`provided on or formed integrally on an outer surface of the
`transparent layer 16. In addition, said apparatus is
`further characterized in that either one of two surfaces
`each having the largest area size among surfaces of the
`light-guiding plate 11 is, or both of said two surfaces are,
`sloped.
`[0014]
`
`A liquid crystal display device according to an aspect
`of the present invention is characterized by being assembled
`as a combination of the illumination apparatus 40 mentioned
`above and a liquid crystal panel 41. With the structure
`described above, an illumination apparatus that realizes
`high brightness and high productivity, and a liquid crystal
`display device that includes said illumination apparatus,
`can be obtained.
`[0015]
`[Operation] In the present invention, a concave portion(s)
`that has a substantially triangular cross-sectional shape is
`formed in a surface(s) of a light-guiding plate 11 as a line
`pattern or a dot pattern, and a layer that has a relatively
`high index of refraction is formed on a concave-formed
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`SONY_000763
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`surface. Light having gone into the light-guiding plate 11
`from a light source 12 causes refraction and reflection, and
`goes out within a substantially constant angular range due
`to prismatic effects irrespective of an angle of incidence.
`In addition, since reflection effects arise from reflection
`caused due to a refractive index difference and reflection
`by a reflector/reflection plate, it is possible to suppress
`optical absorption and therefore increase brightness.
`[0016]
`[Embodiments] Fig. 1 is a set of diagrams of a first
`embodiment of the present invention, wherein (a) is a
`sectional view; (b) is an enlarged view of a part B
`illustrated in (a); (c) is an enlarged view of a part C
`illustrated in (a); and (d) is an enlarged view of a part D
`illustrated in (a). In Fig. 1, the reference numeral 11
`denotes a light-guiding plate, and the reference numeral 12
`denotes a light source provided along and next to each of
`two side edges of the light-guiding plate 11. For example,
`a cold-cathode tube that has a tube diameter of 4 mm is used
`as the light source 12. A reflection cover 13 is provided
`around the light source 12. The reflection cover 13 is made
`of an Al plate that has a thickness of 0.5 mm. As
`illustrated in Fig. 1(b), a thin reflection layer 13a, which
`is an Ag film that has a thickness of 1,000 angstrom, is
`formed on the inner surface of the reflection cover 13, and
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`SONY_000764
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`a protection layer 13b, which is a PET resin coat that has a
`thickness of 100 m, is formed on the thin reflection layer
`13a. The thin reflection layer 13a gives high reflection
`property to the reflection cover 13. The protection layer
`13b increases its durability. The reflection cover 13
`reflects light emitted from the light source 12 in such a
`way as to condense the emitted light onto an end face of the
`light-guiding plate 11, and the condensed light goes into
`the light-guiding plate 11 efficiently.
`[0017]
`
`A plate that is made of transparent acrylic resin and
`has a thickness of 4 mm is used as the light-guiding plate
`11. As illustrated in Fig. 1(c), grooves 14, each of which
`extends as a line pattern (or a pattern of aligned dots) in
`a direction parallel to the linear cold-cathode-tube
`direction of the light source 12, are formed as concave
`portions in one surface (reverse face) of the light-guiding
`plate 11. As illustrated therein, each of the concave
`portions 14 has a substantially triangular cross-sectional
`shape with a vertex angle of 90. The concave portions 14
`are arranged in such a way that the ratio of the area size
`of a concave-present region, which is recessed, to the area
`size of a concave-absent region, which is not recessed,
`satisfies the following formula. Note that the formula
`shown below is an empirical equation that has conventionally
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`SONY_000765
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`been used in the art.
`Area-size percentage = [(-2.42 10-5 L2 + 4.42 10-3 L +
`0.4)2]-1
`, where L: Distance from the light source
`The formula shown above is adapted to a range from the end
`of the light-guiding plate 11 to the center thereof. A
`range from the center to the respective two ends is set
`symmetrically.
`[0018]
`
`A transparent plate 16, on one surface of which convex
`portions 15 are formed, is bonded to the light-guiding plate
`11 at its concave-formed surface, that is, a surface in
`which the concave portions 14 are formed, with the use of a
`transparent acrylate ultraviolet ray curing adhesive 17.
`Each of the convex portions 15 has a shape for mating with
`the corresponding one of the concave portions 14. The index
`of refraction of the ultraviolet ray curing adhesive 17 is
`substantially equal to that of the light-guiding plate 11.
`A thin reflection layer 18, which is an Ag film that has a
`thickness of approximately 1,000 angstrom, is formed on the
`outer surface of the transparent plate 16. A protection
`layer 19, which is a PET resin coat that has a thickness of
`approximately 100 m, is formed on the thin reflection layer
`18.
`[0019]
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`SONY_000766
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`A light-diffusing plate 21, which is made up of two
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`polycarbonate resin films (manufactured by GE, LEXAN 8B36)
`21a and 21b formed in layers, each with a crimp-treated
`irregular surface and with a thickness of 0.25 mm, is
`provided on the opposite surface (light emission plane 20)
`of the light-guiding plate 11. The purpose of providing the
`light-diffusing plate 21 thereon is to conceal the concave
`portions 14, which are arranged in the reverse surface, in
`such a way that these recesses cannot be seen from the
`outside through the surface 20, and, in addition, to enhance
`uniformity in brightness.
`[0020]
`
`Next, the operation of the present embodiment with the
`structure described above will now be explained. First,
`light originating from the light source 12 goes into the
`light-guiding plate 11. By the law of total reflection, the
`light having gone into the light-guiding plate 11 propagates
`inside the light-guiding plate 11 while repeating internal
`reflection as done in the prior-art structure. Since the
`concave portion 14 has the same structure as that of a prism
`held in the air, when propagation light goes into the
`concave portion 14, refraction/reflection occurs inside the
`concave portion 14. The light condensed within an angular
`range of approximately 45 as viewed from a direction
`perpendicular to the light emission plane 20 is outputted as
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`SONY_000767
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`outgoing light that has characteristics illustrated in Fig.
`2. The angular range of the outgoing light does not exceed
`45 in relation to the surface 11a of the light-guiding
`plate 11, too. Therefore, as can be derived from the
`following conditions of total reflection of the present
`embodiment, most of the outgoing light is direct outgoing
`light, which goes to the light emission plane 20.
`c = sin-1 (N1 / N2) 42
`, where the index of refraction N1 of air = 1
`the index of refraction N2 of the light-guiding plate =
`1.491
`[0021]
`
`A part of incoming light does not turn into light
`outgoing to the light emission plane 20 because its angle
`falls within a critical angle. However, such a part has a
`function of enhancing uniformity in brightness by behaving
`as propagation light. Since the concave portions 14
`described above are arranged in such a way as to satisfy the
`area-size percentage formula expressed above, when viewed in
`a macro level, outgoing light obtained on the light emission
`plane 20 is almost constant, and does not vary from one
`position to another.
`[0022]
`
`Because of the prismatic effects of the concave portion
`14, most of light originating from the light source 12 goes
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`out from the light emission plane 20. Therefore, with the
`present embodiment described above, greater brightness as
`compared with that of prior art can be obtained. In
`addition, since an ordinary resin molding technique can be
`used mainly for the manufacturing of a light-guiding plate
`due to its structure, said manufacturing is easy, resulting
`in improved productivity.
`[0023]
`
`Fig. 3 is a sectional view of a second embodiment of
`the present invention. The present embodiment is basically
`the same as the foregoing embodiment. There are the
`following points of difference between the two: in the
`present embodiment, a single light source 12 is provided;
`and an aluminum-evaporated tape 22 is bonded or attached to
`the opposite end face of a light-guiding plate 11, that is,
`an end at which the light source 12 is not provided. The
`aluminum-evaporated tape 22 serves as a reflection plate,
`and light reflected by this reflection plate can be assumed
`as light originating from a pseudo light source. With the
`present embodiment, the same effects as those of the
`foregoing embodiment can be obtained.
`[0024]
`
`Fig. 4 is a set of diagrams of a third embodiment of
`the present invention, wherein (a) is a sectional view; (b)
`is an enlarged view of a part B illustrated in (a); and (c)
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`is an enlarged view of a part C illustrated in (a). The
`structure of the present embodiment is directed to obtaining
`illumination light having high directivity. The basic
`feature of the structure of the present embodiment lies in
`the turning of the light-guiding plate of the first
`embodiment upside down. More specifically, in the present
`embodiment, the reverse surface of a light-guiding plate 11
`is formed as a flat surface. A thin reflection layer 32,
`which is an Ag film that has a thickness of approximately
`1,000 angstrom, is formed on this flat surface. A
`protection layer 33, which is a PET resin coat that has a
`thickness of approximately 100 m, is formed on the thin
`reflection layer 32.
`[0025]
`
`As in the first embodiment, in the present embodiment,
`grooves 34, each of which extends linearly, are formed as
`concave portions in the light emission plane 11a of the
`light-guiding plate 11. Each of the concave portions 34 has
`a substantially triangular cross-sectional shape. A
`transparent plate 36, on one surface of which convex
`portions 35 are formed, is bonded to the light-guiding plate
`11 at its concave-formed surface, that is, a surface in
`which the concave portions 34 are formed, with the use of a
`transparent acrylate ultraviolet ray curing adhesive 37.
`Each of the convex portions 35 has a shape for mating with
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`SONY_000770
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`the corresponding one of the concave portions 34. The index
`of refraction of the ultraviolet ray curing adhesive 37 is
`substantially equal to that of the light-guiding plate 11.
`To slightly conceal the pattern of lines formed by the
`concave portions 34 and enhance uniformity in brightness, a
`light-diffusing plate 38, which is made of a polycarbonate
`resin film (manufactured by GE, LEXAN 8A13) with a crimp-
`treated irregular surface and with a thickness of 0.25 mm,
`is provided on the transparent plate 36. In the present
`embodiment, the vertex angle b of each of the concave
`portions 34 having a substantially triangular shape in cross
`section as illustrated in Fig. 4(b) is 70.
`[0026]
`
`The structure of the present embodiment described above
`produces prismatic effects, as in the first embodiment. In
`addition, with the present embodiment, it is possible to
`obtain high-directivity light, most of outgoing light of
`which is within an angular range of approximately 12 as
`viewed from a direction perpendicular to the light emission
`plane 11a of the light-guiding plate 11. It is easy to
`apply optical technology such as lens technology to the
`high-directivity light mentioned above. Especially when
`said high-directivity light is applied to a liquid crystal
`display device, it is possible to cause light condensed by
`means of a lens to go into the opening portion of each dot
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`SONY_000771
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`on a display surface efficiently. By this means, it is
`possible to increase efficiency in the use of light inside a
`liquid crystal display device, realize high brightness, make
`the body of the device thinner, and achieve power savings.
`If a method of optical diffusion after the passing of high-
`directivity light through a liquid crystal panel, it is
`possible to obtain excellent display characteristics
`irrespective of visual sensation.
`[0027]
`
`Fig. 5 is a set of diagrams of a fourth embodiment of
`the present invention, wherein (a) is a sectional view; (b)
`is an enlarged view of a part B illustrated in (a); and (c)
`is an enlarged view of a part C illustrated in (a). In this
`drawing, the same reference numerals are assigned to
`components/portions that are the same as those illustrated
`in Fig. 1 or 4. The present embodiment is a combination of
`the first embodiment illustrated in Fig. 1 and the third
`embodiment illustrated in Fig. 4. That is, the same
`structure as that of the first embodiment is adopted at the
`reverse surface of the light-guiding plate 11, and the same
`structure as that of the third embodiment is adopted at the
`light-emission-side surface. Therefore, the present
`embodiment produces a combination of the effects of the
`first embodiment and the effects of the third embodiment.
`[0028]
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`SONY_000772
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`Fig. 6 is a sectional view of a fifth embodiment of the
`
`present invention. In this drawing, the same reference
`numerals are assigned to components/portions that are the
`same as those illustrated in Fig. 1. The present embodiment
`is basically the same as the first embodiment. As the point
`of difference therebetween, in the present embodiment, the
`upper surface of the light-guiding plate 11 is formed as a
`sloped surface, thereby increasing efficiency in the use of
`light.
`[0029]
`
`Fig. 7 is a sectional view of a sixth embodiment of the
`present invention. In this drawing, the same reference
`numerals are assigned to components/portions that are the
`same as those illustrated in Fig. 4. The present embodiment
`is basically the same as the third embodiment. As the point
`of difference therebetween, in the present embodiment, the
`lower surface of the light-guiding plate 11 is formed as a
`sloped surface, thereby increasing efficiency in the use of
`light. In the present embodiment and the preceding
`embodiment, a surface in which no concave portion is formed
`is formed as a sloped surface. The opposite surface, in
`which concave portions are formed, may be formed as a sloped
`surface. Even with such a modification, it is possible to
`efficiently use light arriving at the opposite end face
`directly from the incident-side end face of a light-guiding
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`SONY_000773
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`plate.
`[0030]
`
`Fig. 8 is a diagram that illustrates an example of the
`use of an illumination apparatus according to an exemplary
`embodiment of the present invention as the plane
`illumination unit of a liquid crystal display device. In
`the illustrated application example, an illumination
`apparatus 40, which is an illumination apparatus according
`to an exemplary embodiment of the present invention, and a
`liquid crystal panel unit 41 are assembled into one
`integrated component by means of exterior cover plates 42,
`which are made of steel plates. The illustrated application
`example realizes high brightness, a thin and lightweight
`body, and power savings. Note that circuitry, etc. for
`driving the panel of the liquid crystal panel unit 41 is not
`shown separately, and a detailed explanation of the
`circuitry, etc. is not given here. In the illustrated
`application example, an illumination apparatus according to
`the first embodiment is used as the illumination apparatus
`40. However, needless to say, an illumination apparatus
`according to any other embodiment may be used.
`[0031]
`
`Though specific materials of components/portions are
`mentioned in the foregoing embodiments, the scope of the
`invention is not limited thereto. For example, other
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`SONY_000774
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`transparent member such as polystyrene, polycarbonate, etc.
`may be used as the material of a light-guiding plate. A
`white paint or a metal layer such as an Al, Au, Cr layer or
`the like may