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`5,808,784
`Sep. 15, 1998
`
`ー
`
`United States Patent [19]
`Ando et al.
`
`[11] Patent Number:
`[45] Date of Patent:
`
`[54] LENS ARRAY SHEET SURFACE LIGHT
`SOURCE, AND TRANSMISSION TYPE
`DISPLAY DEVICE
`
`Primary Examiner---Daniel P. Malley
`Attorney, Agent, or Firmー-Parkhurst& Wendel, L.L.P.
`
`[75] Inventors: Rika Ando; Haruo Ono; Hisanori
`Ishida; Michiko Takeuchi; Toshikazu
`Nishio; Nobu Masubuchi, all of
`Tokyo-To, Japan
`
`[73] Assignee: Dai Nippon Printing Co., Ltd., Japan
`
`[21] Appl. No.: 523,609
`Sep. 5, 1995
`
`[22] Filed:
`
`[30]
`
`Foreign Application Priority Data
`
`Sep.6タ 1994 [JP] Japan .................................... 6-236017
`May 18タ 1995 [JP] Japan .................................... 7-142386
`Jun. 12タ 1995 [JP] Japan ........・ H ・......・ H ・.....・ H ・.....7-167861
`
`[51] Int. CI.6
`..................................................... G02B 27/10
`[52] U.S. CI. .....…………. 359/443; 359/452; 359/400
`[58] Field of Search ...........………... 359/443, 452,
`359/453, 454, 459, 460, 591, 592, 594,
`596
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`[57]
`
`ABSTRACT
`
`A lens array sheet according to the present invention,
`comprising a transparent substrate, a lens array having lens
`elements that are one-dimensionally or two-dimensionally
`formed on the front surface of the transparent substrate, and
`a cluster having a large number of cluster members ran-
`domly formed in a prism shape on the rear surface of the
`transparent substrate, each of the length, the width, and the
`height of each of the cluster members being in the range
`from the wave length of source light to 500μm. Thus, a lens
`array sheet that effectively uses light energy of the light
`source, maintains the light condensing effect, prevents the
`luminan∞ from deteriorating, homogeneously distributes
`the luminan∞on the light emitting surface, prevents equal-
`thickness interferen∞fringes and wasteful light dispersion
`to out of the angular range of visual angle can be provided.
`In addition, a surface light source having the lens array sheet
`is provided. Moreover, a bright transmission type display
`device having the surface light source is provided
`
`5タ592タ332 1/1997 Nishio et al. ...・ H ・.....・ H ・...........359/619
`
`14 Claims, 18 Drawing Sheets
`
`ζ2
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`
`Sony Corp. Exhibit 1024
`
`SONY_000973
`
`
`
`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 1 of 18
`
`5,808,784
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`
`SONY_000974
`
`
`
`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 2 of 18
`
`5,808,784
`
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`SONY_000975
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`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 3 of 18
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`5,808,784
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`SONY_000976
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`Sep. 15, 1998
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`Sheet 5 of 18
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`5,808,784
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`SONY_000978
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`u.s. Patent
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`Sep. 15, 1998
`
`Sheet 6 of 18
`
`5,808,784
`
`FIG. 8
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`SONY_000979
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`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 7 of 18
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`5,808,784
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`SONY_000980
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`u.s. Patent
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`Sep. 15, 1998
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`Sheet 8 of 18
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`5,808,784
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`SONY_000981
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`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 9 of 18
`
`5,808,784
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`SONY_000982
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`
`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 10 of 18
`
`5,808,784
`
`FIG. 14A
`
`FIG. 148
`
`FIG. 15
`
`SONY_000983
`
`
`
`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 11 of 18
`
`5,808,784
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`F I G. 18
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`SONY_000984
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`
`
`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 12 of 18
`
`5,808,784
`
`FIG. 19
`
`F I G. 20
`
`SONY_000985
`
`
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`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 13 of 18
`
`5,808,784
`
`41
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`SONY_000986
`
`
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`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 14 of 18
`
`5,808,784
`
`41
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`SONY_000987
`
`
`
`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 15 of 18
`
`5,808,784
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`F I G. 27
`
`41
`
`F I G. 28
`
`F I G. 29
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`SONY_000988
`
`
`
`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 16 of 18
`
`5,808,784
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`
`SONY_000989
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`
`
`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 17 of 18
`
`5,808,784
`
`/'01
`
`53
`
`F I G. 32
`
`F I G. 33
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`
`SONY_000990
`
`
`
`u.s. Patent
`
`Sep. 15, 1998
`
`Sheet 18 of 18
`
`5,808,784
`
`51
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`SONY_000991
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`
`
`5ラ808ラ784
`
`SUMMARY OF THE INVENTION
`
`BACKGROUND OF THE INVENTION
`
`1
`LENS ARRAY SHEET SURFACE LIGHT
`SOURCE, AND TRANSMISSION TYPE
`DISPLAY DEVICE
`
`2
`Due to small di旺eren∞sof the distances of lens elements
`of the two lens array sheets, Newton rings that are equal-
`thickness interference fringes as a concentric circle pattern
`or a concentric ellipse pattern may occur on the entire
`5 surfac芯 ofthe surface light source.
`To prevent such a problem, the rear surface of the lens
`1. Field of the Invention
`The present invention relates to a lens array sheet that has array sheet is matted so as to form small concave and convex
`a homogeneous lighting characteristic as a lighting means portions (hereinafter referred to as a cluster). Thus, the lens
`for use with a transmission type liquid crystal display array sheets are prevented from contacting. This method has
`device, a back light source for a transmission type display 10 been disclosed in Japanese Patent Laid-Open Publication
`device for an advertisement board. In addition, the present NO.7-151909
`However, when the rear surface of the lens array sheet is
`invention relates to a surface light source and a transmission
`matted, light is di旺use-refiectedon the matted surface. Thus,
`type display device with the lens array sheet.
`2. Description of the Related Art
`. _ the matted surface operates as a light diffusion sheet.
`15
`In recent years, requirements for low weight and low V Consequently, the function of the lens array sheet, which
`power consumption have been made for transmission type condenses light in a desired di旺usionangle within a desired
`liquid crystal devices. Various surface light sour∞s that diffusion angle is remarkably deteriorated. Thus, the lumi-
`effectively use light emitted from light sources and guide the nance is remarkably decreased. In addition, since the height
`resultant light only to a necessary and satisfactory direction ,n of each portion of the cluster of the matted surface is not
`20
`L.U completely homogeneous, there are small di旺'erencesin the
`have been proposed.
`In these related art references, a light source is disposed distances of the lens elements of the two lens array sheets
`on a side surface of an opt悶 1condl叫 orcomposed of ~ plate (hereina自己r,each portion of the cluster is民 ferredto as a
`of, for example, a transparent acrylic resin. The light entered cluster member). Thus, the equal-thickness interference
`from the side surfa∞into thcoptical conductor is rcncctcd25fringcs tGIld to tab placc.
`on a refiection layer on the rear surface of the optical -- On the other hand, in the structure of which only one lens
`conductor. The light is emitted from the light emitting array sheet is used, in the case that the rear surface of the lens
`surface that is the upper surface of the optical conductor array sheet is smooth, when the lens array sheet is disposed
`(1ight guide). At this point, to homogenize the light, a on the light emitting surface of an optical conductor of an
`diffusion sheet is disposed on the upper surface of the optical 30 edge light type surf~c芯 light sourc芯, since the lens array
`conductor. Alternatively, to condense the light as emitted sheet contacts the light emitting surface of the optical
`light only within predetermined angular range, a lens array conductor, they are optically unified. Thus, the emitted light
`sheet that operates as a lens is disposed as a surface light of the light source cannot be homogeneously total-refiected
`source. The surface light sour∞of which the light source is on the front surface of the optical conductor. Even if spacers
`disposed on the side surface of the optical conductor is 35 are disposed at four corners of the optical conductor or the
`referred to as an edge light type surface light source.
`lens array sheet so as to have a space between the optical
`Although a box-type planar light source of which a light conductor and the lens array sheet, since the lens array sheet
`source is disposed immediately below a di旺usionsheet or a is bent and deformed, small di旺'erencesin distances of the
`lens array sheet is known, since the thickness thereof lens elements of the lens array sheet and the optical con-
`increases, the application thereof is limited.
`40 ductor cause the equal-thickness interferenc~ fringes to take
`As described above, various methods for e庄ectivelyusing place. To prevent this problem, a structure of which a cluster
`light emitted from light sour∞s without loss have been with a height of the wave length of a source light or larger
`proposed. As an example, a lens array sheet for condensing is formed has been disclosed in for example Japanese Patent
`light as emitted light ~ithin a predet~rmined angular rang~ Laid-Open Publication Nos. 5-323319 and 6-324205.
`is known. As shown in FIG. 24, the linear lens array sheet 45 However, the cluster is formed as an optically-
`is composed of a large number of triangular prisms as lens homogeneous diffusion pattern such as a sand-face pattern
`elements that are one-dimensionally arranged so that their or a pear-face pattern. Thus, part of light emitted from the
`edge lines are arranged in parallel. In addition, a two-layer optical conductor diffuses out of the angular range of visual
`type linear lens array sheet has been proposed so as to field. Consequently, the light condensing effect of the lens
`condensed more light and improve the luminance.
`50 array sheet deteriorates and thereby wasting the energy of
`For example, two-layer type linear lens array sheets of the light of the light source and deteriorating the luminance
`which linear triangular prisms are arrayed as lens elements
`have been disclosed in Japanese Patent Laid-Open Publica-
`tion Nos. 5-203950, 5-313156, and 5-313164.
`An object of the present invention is to provide a lens
`However, although the two-layer lens array sheet has an 55 array sheet that can solve the above-described problems,
`advantage of an improvement of luminance due to the light e庄ectivelyuse light energy of the light sour∞, maintain the
`condensing effect, it also has the following disadvantage. In light condensing effect, prevent the luminance from
`the lens array sheet of which the lens elements are arrayed deteriorating, homogeneously distribute the luminance on
`on the front surface and of which the rear surface is fiat, the the light emitting surface, prevent equal-thickness interfer-
`rear surface of the upper lens array sheet microscopically 60 ence fringes and wastefullight dispersion to out of the angle
`cont山 thevertex portions of the lens elements of the lower of visual angle from t出 ngpla∞. Another 0吋ectof the
`lens array sheet. Thus, the optically transparent contact present invention is to provide a surface light source having
`portion accords with the vertex portions of the lower lens the lens array sheet. A further other object of the present
`elements. Consequently, the lens vertex portions become invention is to provide a light transmission type display
`visible. When the lens elements are triangular prisms, the 65 device having the surface light source.
`To ac∞mplish the objects, a lens array sheet according to
`vertex portions are shaped as edge lines. As a result, many
`lines are visible.
`the first aspect of the present invention comprises a trans-
`
`SONY_000992
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`5ラ808ラ784
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`4
`3
`parent substrate, a lens array having lens elements that are of visual field is redu∞d and thereby the decrease of the
`one-dimensionally or two-dimensionally formed on the luminan∞ within angular ranges of visible field can be
`front surfa∞ of the transparent sulヲstrate,and a cluster minimized in comparison with the conventional contact
`having a large number of cluster members randomly formed preventing method using the mat process.
`in a prism shape on the rear surface of the transparent 5 In addition, since the cluster members that compose the
`substrate, each of the length, the width, and the height of cluster are randomly formed, the moire fringes due to the
`each of the cluster members being in the range from the interference of lens array or pixel array of the liquid crystal
`wave length of source light to 500μm.
`display device and the cluster members can be prevented.
`In the lens array sheet, each of the cluster members may
`When the cluster members are formed in a rectangular
`10 parallelepiped shape, the transmission type display device
`be formed in a rectangular parallelepiped shape.
`In the lens array sheet, the line of intersection of a can be easily fabricated. In addition, when the relation
`horizontal surface of the lens array sheet and a surfa∞that between the side surface of the rectangular parallelepiped
`composes the lens elements may be not in parallel with the cluster and the surface of the lens elements of the lens array
`line of intersection of the horizontal surface and a side is designated in a predetermined manner, the moire fringes
`surface of each of the rectangular parallelepiped shape of the 15 due to the lens array can be prevented.
`cluster members.
`According to the edge light type surface light source of
`A surface light source according to the first aspect of the the first aspect of the present invention, since the lens array
`present invention comprises an optical conductor composed sheet does not contact the light emitting surface of the
`of at least a transparent fiat plate, a light source unit disposed ~O optical conductor, the light emitted from the light source can
`20
`adjacent to at least one of side edge surfaces of the optical L.U be widely and homogeneously distributed in the optical
`conductor, a light refiection layer formed on the rear surface conductor. Thus, the luminance distribution of the light
`of the optical conductor, and one or two lens array sheets of emitted from the optical conductor can be homogenized on
`the first aspect of the present invention and disposed on a the light emitting surface. In addition, the light energy can
`light emitting surface of the front surface of the optical ~ _ be effectively used and thereby be bright. Moreover, the
`25
`conductor so that the lens array sheets face the front surface L.J light diffusion dot pattern which is formed in the rear surface
`of the optical conductor can become invisible. The amount
`of the optical conductor.
`In the edge light type surface light source, the lens array of light that is emitted in the vicinity of the normal direction
`sheet may b~ coriIposed of two lens-array sheet members th~t of the light emitting surface is large. In addition, the amount
`arclaycrcd,thcclustcr of thGlowcr lcns array shcct mcmbcr300f light that iscmittcd in othcr than thcnormal dirCCHon can
`facing the front surface of the optical conductor.
`J U be reduced in comparison with the homogeneous di庄USlOn
`sheet
`The edge light type surface light source may comprise a
`light diffu~ion ~heeí formed on th~ light emitting surfa-ce that
`According _to the transmission type. display device of the
`is~ the front surface of the optica( conductor~ and having first .asp~ct of ~he present invention, the light emitted from
`concaVGand convcx portions on thcfront and rcar SUrfaccs,35thcdisplay SUrfaccis bright on thcGIltircSUrfaccrcgardlcss
`the height of the con~ave and convex portions being homo- ~~ of th: angular range of visual field within the predetermined
`geneous to or greater than the wave l~ngth of sour-;;e light, angular range.
`To accomplish the objects, a lens array sheet according to
`a rear-surface fiat lens array sheet having a lens array with
`lens elements that are one-dimensionally or two- the second aspect of the present invention comprises a
`dimensionally formed on the front surface of the transparent 40 transparent substrate, a lens array having lens_elements that
`substrate, the rear surface of the rear-surface fiat lens array are one-dimensionally or two-dimensionally formed on the
`sheet facing the front surface of the optical conductor, and front surface of the transparent substrate, and a cluster
`a lens array sheet of the first aspect of the present invention, having a large number of cluster members randomly formed
`wherein the light diffusion sheet, the rear-surface fiat lens in a prism shape on the rear surface of the transparent
`array sheet, and the lens array sheet of the present invention 45 substra!e, each of the length, the width, and the ~eight of
`are layered in the order.
`each of the cluster members being in the range from the
`百letransparent type display device of the first aspect of wave length of source light to 500μm.
`the present i~vention comp~is~s a surface light sourc~ of the
`The random two-dimensional distribution is a distribution
`first-aspect of the present invention, the surface light source of which the position of each lattice point of the two-
`being lised as a b;ck light source for the transmi~sion type 50 dimensional periodic array is randomly moved and reallo-
`display device.
`cated
`Thus, according to the transmission type display device of
`In lens array sheet, each of the cluster members may be
`the first aspect of the present invention, since-th~ cluster is formed in a rectangular parallelepiped shape.
`formed on the rear surface, when two lens array sheets are
`In the lens array sheet, the line of intersection of a
`layered or a lens array sheet is disposed as a surface light 55 horizontal surface of the lens array sheet and a surface that
`source on the light emitting surface of the optical conductor, composes the lens elements may be not in parallel with the
`the rear surface of the lens array sheet can be prevented from line of intersection of the horizontal surface and a side
`being contacted, thereby suppressing the equal-thickness surfa∞of each of the rectangular parallelepiped shape of the
`interference fringes from taking place. When the lens array cluster members.
`sheet is disposed on the optical conductor in such a manner 60 A surface light source according to the second aspect of
`that the rear surface of the lens array sheet (on which the the present i町 はIt聞 1∞mprisesan optical conductor com-
`cluster is formed) faces the optical conductor, si即 ethe light posed of at least a transparent fiat plate, a light source unit
`distribution is not affected by the total refiection on the front disposed adjac則 ltto at least one of side edge surfac芯sof the
`surface of the optical conductor, light is homogeneously optical conductor, a light refiection layer formed on the rear
`emitted with a homogeneous luminan∞distribution on the 65 surfa∞of the optical conductor, and one or two lens array
`entire surface of the light emitting surface. In other words, sheets of the second aspect of the present invention and
`the amount of light that is emitted out of the angular range disposed on a light emitting surfa∞of the front surface of
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`SONY_000993
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`5ラ808ラ784
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`5
`6
`the optical conductor so that the lens array sheets face the conductor. Thus, the luminance distribution of the light
`emitted from the optical conductor can be homogenized on
`front surface of the optical conductor.
`In the edge light type surface light source, the lens array the light emitting surface. In addition, the light energy can
`sheet may be composed of two lens array sheet members that be effectively used and thereby be bright. Moreover, the
`are layered, the cluster of the lower lens array sheet member 5 light diffusion dot pattern can become invisible. The amount
`of light that is emitted in the vicinity of the normal direction
`facing the front surface of the optical conductor.
`百166dplight typcSUrfacc11dlt sourccmay comprisca of thclight cmitting SUrfaccis larp.In addition,thcamount
`light diE11Sion shcct formcd on thclight GIIliumg SUrfaccthat of light that iscmittcd in othcr than thcnormal dirCCHon can
`is~ the front surface of the optica( conductor~ and having b,e reduced in comparison with the homogeneous di庄USlOn
`concave and convex portions ~n the front and rear surface;' 10 sheet
`the height of the concave and convex portions being homo-
`According to the transmission type display device of the
`geneous to or greater than the wave length of source light, second aspect of the present invention, the light emitted
`a rear-surface fiat lens array sheet having a lens array with from the display surface is bright on the entire surface
`lens elements that are one-dimensionally or two- regardless of the angular range of visual field.
`dimensionally formed on the front surface of the transparent 15 To ac∞mplish the objects, a lens array sheet according to
`substrate, the rear surface of the rear-surface fiat lens array the third aspect of the present invention comprises a trans-
`sheet facing the front surface of the optical conductor, and parent substrate, a lens array having lens elements that are
`a lens array sheet of the second aspect of the present one-dimensionally or two-dimensionally formed on the
`invention, wherein the light diffusion sheet, the rear-surface front surface of the transparent substrate, and a cluster
`fiat lens array sheet, and the lens array sheet are layered in 20 having a large number of cluster members randomly formed
`that order.
`in a prism shape on the rear surface of the transparent
`A transparent type display device according to the second sulヲstrate,wherein each of the cluster members is composed
`aspect of the present invention comprises a surface light of cluster member elements formed in a prism shape or a
`~ _ truncated prismoid shape, each of the length of the minimum
`source of the second aspect of the present invention.
`IT111s,according to thctransmission typcdisplay dcviccof 25diagonal 11I16and thchcidlt of thctop and bottom of cach
`thcsCCOIld aspcct of thcprcscntIIIVGIltiOII,S1nccthcclustcr of thcclustcr mcmbcrclcmcnts bcing homogGI16011s to or
`is formcd on thcrcar SUrfacc,whGIltwo lGIIs array shccts arcgrcatcr than thcwavclcngth of thcsourcclight,ιach 0ぱft白hι
`lay ι r ι d or a leι引叩nsar町ra勾ys油hι∞ι t iおsdiおsposιd as a surfac ι light leι引叩ngt白hoぱft白hι maximum diagonallinι and t白hι h ι i氾gh加ltt白hιrι∞of
`
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`
`being contacted, thereby suppressing the ~qual-thickness percolation cluster in a two-d~mensiona~, lattice with a criti-
`interference fringes fro~ takidg plac;' When the lens array cal p~rcol~tion co~ce?tra~ion ~c or smaller, adjacent cluster
`sheet is disposed on the opticalc'anductor in such a manne"r member elements being fused.
`that the rear su巾ccofthclcmamy st166t (on which thG35In thclcmamy shcct,latticcPOInts of thctwo-
`cluster is formed) faces the optical conductor, si即 ethe light J~ dimensionallattice may be allocated to the cluster member
`distribution is not a庄'ectedby the total refiection on the front elements with an occupying probability P that may be
`surface of the optical conductor, light is homogeneously smaller than the critical percolation con∞ntration Pc, the
`emitted with a homogeneous luminan∞distribution on the cluster members being composed by fusing the adjacent
`entire surface of the light emitting surface. In other words, 40 cluster member elements.
`In the lens array sheet, the two-dimensionallattice may be
`the amount of light that is emitted out of the angular range
`of visual field is rαluced and thereby the decrease of the a square lattice, the latti∞member elements allocated to the
`luminance can be minimized in comparison with the con- lattice points being formed in a rectangular parallelepiped
`ventional contact preventing method using the mat process. shape.
`In particular, since the cluster m~mbers are ra_ndomly dis- 45 In the lens array sheet, the line of intersection of the
`tributed with a homogeneous surface density of the number horizontal surface of the lens array sheet and the surface
`of cluster members, uneven luminance does not take pla∞ composing each of the lens elements may be not in parallel
`In addition, since the cluster members that compose the with the line of intersection of the horizontal surface and a
`cluster are randomly formed by the predetermined random- side surface of each of the cluster members.
`izing method, the homogeneous luminance distribution 50 A surface light source according to the third aspect of the
`without an uneven distribution of the density of the cluster present invention comprises an optical conductor composed
`member regardless of the number of the cluster members of at least a transparent fiat plate, a light source unit disposed
`can be accomplished and thereby the moire fringes due to adjacent to at least one of side edge surfaces of the optical
`the interference of lens array and pixel array of the liquid conductor, a light refiection layer formed on the rear surface
`55 of the optical conductor, and one or two lens array sheets of
`crystal display device can be prevented.
`When the cluster members are formed in a rectangular the third aspect of the present invention and disposed on a
`parallelepiped shape, the transmission type display device light emitting surface of the front surfa∞ of the optical
`can be easily fabricated. In addition, when the relation conductor so that the lens array sheets face the front surface
`between the side surface of the rectangular parallelepiped of the optical conductor.
`cluster and the surface of the lens elements of the lens array 60 In the edge light type surface light source, the lens array
`is designated in a predetermined manner, the moire fringes sheet may be composed of two lens array sheet members that
`are layered, the cluster of the lower lens array sheet member
`due to the lens array can be prevented.
`According to the edge light type surface light source of facing the front surface of the optical conductor.
`the second aspect of the present invention, since the lens
`The edge light type surface light source may comprise a
`array sheet does not contact the light emitting surface of the 65 light diffusion sheet formed on the light emitting surface that
`optical conductor, the light emitted from the light source can is the front surface of the optical conductor and having
`be widely and homogeneously distributed in the optical concave and convex portions on the front and rear surfaces,
`
`SONY_000994
`
`
`
`5ラ808ラ784
`
`15
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`8
`7
`the height of the concave and convex portions being homo- of light that is emitted in the vicinity of the normal direction
`geneous to or greater than the wave length of source light, of the light emitting surface is large. In addition, the amount
`a rear-surface fiat lens array sheet having a lens array with of light that is emitted in other than the normal direction can
`lens elements that are one-dimensionally or two- be reduced in comparison with the homogeneous diffusion
`dimensionally formed on the front surface of the transparent 5 sheet
`substrate, the rear surface of the rear-surface fiat lens array
`According to the transmission type display device of the
`sheet facing the front surface of the optical conductor, and third aspect -of the present invention, the Iight emitted from
`a lens array sheet oft~e third aspect ofthe prese.nt in"ention, the display surface-is bright on the entire siirface regardless
`wherein the light diffusion sheet, the rear-surface fiat lens of the ~ngular range of visual field.
`array st166t,and tt1616IIs array shcct arclaycrcd in thcordcr.10Thcscand othGr objccts,fcat11rcs and advantagcs of thc
`A transparent type display device according to _ the third present invention will become more apparent in light of the
`aspect of the present invention comprises a surface light following detailed description of best mode emb-odiments
`source of the third aspect of the present invention, the thereof, ~s illustrated in tI1e accompanying drawings.
`surface light source being used as a back light sour∞for the
`transmission type display devi∞
`IT111s,accordIIlg to thctransmiss10IItypcdisplay dcviccof
`FIG.1is a pcrspcctivcvicw showing a lcns array shcct
`thctturd aspcct of thcprcscnt iIIVGIltion,siI1ccthcclustcrIS accordmg to ancmbodimGIlt of a arst aspcct and a sCCOIld
`formed on the rear surface, when two le.ns array s"heet~. a~e aspect of the present invention;
`layered or a lens array sheet is disposed as a surface light
`20 FIG.2 is a perspective view showing the shape of a cluster
`source on the light emitting surface of the optical conductor,
`member of the lens array sheet according to the embodiment
`the rear surface of the lens array sheet can be prevented from
`of the first aspect and the second aspect of the present
`being contacted, thereby suppressing the equal-thickness ::,,::::・mvennon:
`interference fringes from taking place. When the lens array U"::::
`sheet is disposed on the opticalc'anductor in such a mann~r __ FIG. 3 is an enlarged perspective view for explaining
`that the re~r surface of the lens array sheet (on which the 25 cluster 即 mbersformed on the lens array sheet;
`cluster is formed) faces the optical conductor, si即 ethe light
`FIGS. 4A and 4B are sch叩 laticd時 間nsfor explaining
`distribution is not affected by the total refiection on the front that the side surfaces of the cluster members are not in
`surface of the optical conductor, light is homogeneously parallel with the structural surface of the lens array;
`emitted with a homogeneous luminan∞distribution on the on FIGS. 5A, 5B, and 5C are schematic diagrams for
`30
`entire surface of the light emitting surface. In other words, J U explaining a process for randomly forming the cluster mem-
`the amount of light that is absorbed or emitted out of the bers;
`~ngular ra~g_e of visual field is re?~ce? and thereby the
`FIGS. 6A and 6B are schematic diagrams for explaining
`decrease of the luminance can be minimized i.n c.om~aris?n a process for forming cluster member; that overlap;
`WIth thCCOIlVGIltIonaI contact prcvcntmg II16thod USIng thG35FIGS.7A,7B,7c,7D,and 7E arcschGIIlatic diagrams for
`~~ explaining ~ two-dimensional lattice and a ra;domized
`mat process.
`_ .
`In particular,. tI:e shape of the cluster is fractal and chister c;rresponding to the second aspect of the present
`randomly formed. Thus, although the average rotating radius invention:
`is larp,non-clustcr portions arcrandomly formcd in thcFIG.81s a pcrspcctIVGV16w shOWIng a lGIIs array shcct
`radius.COIlscq11GIltly,thcclustGr is invisiblGand uncvcn40according to a third aspcct of thcprcscnt inVGIltion,
`luminance hardly takes place.
`FIG. 9 is a perspective view showing an example of a
`In addition,S1nccthcclustcr II16IIIbcrs that composcthcprism shapcclustcr mcmbcr of thclGIIs array st166t accord-
`clustcr arcrandomly shapcd and forII16d by t