(11) Japanese Unexamined Utility Model Registration
`Application Publication No. 6-025802
`(43) Publication Date: April 8, 1994
`(21) Application No. 4-061246
`(22) Application Date: August 31, 1992
`(71) Applicant: Copal Co., Ltd.
`(72) Creator of Device: Yoshikawa et al.
`(74) Agent: Patent Attorney, Ohtsuka et al.
`(54) [Title of the Device] SURFACE EMISSION APPARATUS
`(57) [Abstract]
`[Object] An object is to provide a surface emission
`apparatus that realizes uniform brightness on its light-
`emitting surface.
`[Construction] Light emitted from an LED 4 enters a light-
`guide plate 1 as incident light. Having entered the light-
`guide plate 1, the light is totally reflected at the upper
`surface 1a and the bottom surface 1b of the light-guide
`plate 1, or is reflected by a reflection frame 3, and
`impinges on projecting portions 31. The projecting portions
`31 are formed integrally with said bottom surface. Each of
`the projecting portions 31 has a shape of a funnel. The
`light impinging on the projecting portions 31 is reflected,
`emerges from the upper surface 1a, and is diffused by the
`diffusion plate 2. An illumination target object is
`illuminated with the diffused output light.
`
`- 1 -
`
`TOYOTA EXHIBIT 1008
`
`Page 1 of 12
`
`
`Application Publication No. 6-025802
`(43) Publication Date: April 8, 1994
`(21) Application No. 4-061246
`(22) Application Date: August 31, 1992
`(71) Applicant: Copal Co., Ltd.
`(72) Creator of Device: Yoshikawa et al.
`(74) Agent: Patent Attorney, Ohtsuka et al.
`(54) [Title of the Device] SURFACE EMISSION APPARATUS
`(57) [Abstract]
`[Object] An object is to provide a surface emission
`apparatus that realizes uniform brightness on its light-
`emitting surface.
`[Construction] Light emitted from an LED 4 enters a light-
`guide plate 1 as incident light. Having entered the light-
`guide plate 1, the light is totally reflected at the upper
`surface 1a and the bottom surface 1b of the light-guide
`plate 1, or is reflected by a reflection frame 3, and
`impinges on projecting portions 31. The projecting portions
`31 are formed integrally with said bottom surface. Each of
`the projecting portions 31 has a shape of a funnel. The
`light impinging on the projecting portions 31 is reflected,
`emerges from the upper surface 1a, and is diffused by the
`diffusion plate 2. An illumination target object is
`illuminated with the diffused output light.
`
`- 1 -
`
`TOYOTA EXHIBIT 1008
`
`Page 1 of 12
`
`
`
`[Claims]
`[Claim 1] A surface emission apparatus for outputting light
`from its light-emitting surface, incident light coming from
`a light source arranged near a side of the light-emitting
`surface,
`
`characterized by,
`
`said surface emission apparatus comprising a
`transparent light-guide plate, reflecting shape portions
`being arranged on a bottom surface portion of the light-
`guide plate, said bottom surface being a surface that is the
`opposite of the light-emitting surface, the reflecting shape
`portions being formed as small projecting portions, the
`reflecting shape portions being arranged in such a way that
`array density of the small projecting portions increases
`gradually in accordance with a distance from the light
`source;
`
`the incident light having entered the light-guide plate
`from the light source being reflected by the reflecting
`shape portions; and
`
`the light reflected by the reflecting shape portions
`emerging from the light-emitting surface.
`[Claim 2] The surface emission apparatus according to Claim
`1,
`
`
`
`further characterized in that,
`the reflecting shape portions are arranged in a
`
`- 2 -
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`Page 2 of 12
`
`
`
`staggered array with respect to a direction of going away
`from the light source to increase the distance therefrom.
`[Claim 3] The surface emission apparatus according to Claim
`1,
`further characterized in that,
`
`each of the reflecting shape portions is formed as the
`
`small projecting portion that has a contiguous portion,
`which is a portion that is contiguous from its vertex
`portion to its bottom surface portion; and
`
`the contiguous portion has a curved surface.
`[Brief Description of the Drawings]
`[Fig. 1] Fig. 1 is a sectional view of a surface emission
`apparatus according to an exemplary embodiment of the
`present device;
`[Fig. 2] Fig. 2 is a top view of the surface emission
`apparatus; and
`[Fig. 3] Fig. 3 is an enlarged view of the bottom surface
`of a light-guide plate.
`[Reference Numerals]
`1 light-guide plate
`2 diffusion plate
`3 reflection frame
`4 light source
`31 projecting portion
`
`- 3 -
`
`Page 3 of 12
`
`
`
`[Detailed Description of the Device]
`[0001]
` [Technical Field of the Device]
`
`The present device relates to a surface emission
`apparatus used for illuminating, from the back, a liquid
`crystal display panel or the like serving as a body to be
`illuminated.
`[0002]
` [Description of the Related Art]
`
`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 randomly reflect light incident on this
`surface, thereby efficiently guiding light from the light
`source to the light-emitting surface, one disclosed in, e.g.,
`Japanese Examined Patent Application Publication No. 58-
`17957 is known.
`[0003]
` [Problems to be Solved by the Device]
`
`In recent years, however, the size of, e.g., the liquid
`crystal panel, is increasing, and the size of a surface
`
`- 4 -
`
`Page 4 of 12
`
`
`
`emission apparatus that serves as the backlight of the
`liquid crystal panel is also increasing. As the size of the
`surface emission apparatus increases, 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 difficult to obtain light emission with entirely
`uniform brightness.
`[0004]
`
`The present device has been made in view of the state
`of the prior art described above. An object of the device
`is to provide a surface emission apparatus that receives
`light coming from a light source and can output surface-
`emission light throughout the entire emission area of its
`light-emitting surface uniformly, thereby realizing uniform
`illumination.
`[0005]
` [Means for Solving the Problems]
`
`In order to achieve the object described above, a
`surface emission apparatus according to the present device
`has the following structure. The surface emission apparatus
`receives incident light coming from a light source arranged
`near a side of its light-emitting surface and outputs light
`
`- 5 -
`
`Page 5 of 12
`
`
`
`from the light-emitting surface. Said surface emission
`apparatus includes a transparent light-guide plate.
`Reflecting shape portions are arranged on a bottom surface
`portion of the light-guide plate. Said bottom surface is a
`surface that is the opposite of the light-emitting surface.
`The reflecting shape portions are formed as small projecting
`portions, and the reflecting shape portions are arranged in
`such a way that array density of the small projecting
`portions increases gradually in accordance with a distance
`from the light source. The incident light having entered
`the light-guide plate from the light source is reflected by
`the reflecting shape portions. The light reflected by the
`reflecting shape portions emerges from the light-emitting
`surface.
`[0006]
` [Operation]
`
`With the structure described above, light emitted from
`the light source goes into the light-guide plate; the
`reflecting shape portions reflect the light inside the
`light-guide plate; the light reflected by the reflecting
`shape portions goes out from the light-emitting surface.
`[0007]
` [Embodiment]
`
`Preferred embodiments of the present device will now be
`described in detail with reference to the accompanying
`
`- 6 -
`
`Page 6 of 12
`
`
`
`drawings.
`<Structure>
`
`Fig. 1 is a sectional view of a surface emission
`apparatus according to an embodiment of the present device.
`Referring 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 light
`source 5 such that light from the light source is incident
`on it through its end face 1f. The surfaces of the light-
`guide plate 1 excluding its upper surface 1a on the light-
`emitting surface side are covered with a reflection frame 3.
`The surfaces of the light-guide plate 1 excluding its bottom
`surface 1b opposite the upper surface 1a are smoothed.
`Small projecting portions 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 flat. 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.
`[0008]
`
`A diffusion plate 2 is mounted above the upper surface
`1a of the light-guide plate 1. The diffusion plate 2 is
`
`- 7 -
`
`Page 7 of 12
`
`
`
`made of ground glass or the like, and diffuses 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.
`[0009]
`
`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 reflecting shape portion that
`reflects 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). Regarding
`the size of the projecting portion 31, a height h of each
`projecting portion is about 0.03 to 0.07 mm whereas 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.
`[0010]
`
`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
`
`- 8 -
`
`Page 8 of 12
`
`
`
`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.
`<Process of Light Emission>
`
`Light emitted from the light source 4 is incident on
`the light-guide plate 1 through its end face 1f 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 reflected by the interface of the light-
`guide-plate is 42.10°. Light incident through the end face
`1f and refracted is totally reflected when it impinges on
`the upper surface 1a, surfaces 1d and 1e, or the flat
`portion of the bottom surface 1b, of the light-guide plate 1,
`and will not leak to the outside. When light impinges on an
`end face 1c, it is reflected by the reflection frame 3.
`[0011]
`
`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 reflection described above. The edge portions form
`curved surfaces, as described above. Light impinging on the
`edge portions is reflected and emerges from the upper
`surface 1a, is diffused by the diffusion plate 2, and
`
`- 9 -
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`Page 9 of 12
`
`
`
`emerges from the light-emitting surface 2a.
`[0012]
`
`Since light emerging from the light-guide plate 1 is
`reflected 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 1a 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.
`[0013]
`
`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:
`
`- 10 -
`
`Page 10 of 12
`
`
`
` Since the circular projecting portions are arranged, light
`from any directions can be reflected with the same
`reflectance without any directivity, which would otherwise
`depend on the shapes of the projecting portions. Therefore,
`optical uniformity can be obtained.
` Since the projecting portions have the same shape, the
`reflectance can be controlled by the density of the
`projecting portions, thereby making the quantity of light of
`the surface-emission light source uniform.
` 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 any unbalanced
`greater 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.
`[0014]
`[Another Embodiment]
`
`In the embodiment 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 is used, light sources can be arranged at the two ends
`of the light-guide plate. In this case, the projecting
`
`- 11 -
`
`Page 11 of 12
`
`
`
`portions 31 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.
`[0015]
` [Advantages]
`
`As has been described above, with the surface emission
`apparatus according to the present device, light from the
`light source can be uniformly emitted toward the entire
`light-emitting surface to obtain uniform light emission.
`
`- 12 -
`
`Page 12 of 12
`
`
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