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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
`tQ
`
`Sony Corp. Exhibit 1024
`
`SONY_000973
`
`

`
`u.s. Patent
`
`Sep. 15， 1998
`
`Sheet 1 of 18
`
`5，808，784
`
`Q ζ 2
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`FIG. 3
`
`SONY_000974
`
`

`
`u.s. Patent
`
`Sep. 15， 1998
`
`Sheet 2 of 18
`
`5，808，784
`
`X
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`42
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`FIG. 4A
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`FIG.48
`
`SONY_000975
`
`

`
`u.s. Patent
`
`Sep. 15， 1998
`
`Sheet 3 of 18
`
`5，808，784
`
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`
`SONY_000976
`
`

`
`Sheet 4 of 18
`
`5，808，784
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`SONY_000977
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`

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`u.s. Patent
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`Sep. 15， 1998
`
`Sheet 5 of 18
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`5，808，784
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`SONY_000978
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`

`
`u.s. Patent
`
`Sep. 15， 1998
`
`Sheet 6 of 18
`
`5，808，784
`
`FIG. 8
`d2
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`FIG. 10
`
`SONY_000979
`
`

`
`u.s. Patent
`
`Sep. 15， 1998
`
`Sheet 7 of 18
`
`5，808，784
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`\
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`FIG.IIA
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`FIG.118
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`SONY_000980
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`

`
`u.s. Patent
`
`Sep. 15， 1998
`
`Sheet 8 of 18
`
`5，808，784
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`FIG. 128
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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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`FIG. 17
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`F I G. 18
`
`SONY_000984
`
`

`
`u.s. Patent
`
`Sep. 15， 1998
`
`Sheet 12 of 18
`
`5，808，784
`
`FIG. 19
`
`F I G. 20
`
`SONY_000985
`
`

`
`u.s. Patent
`
`Sep. 15， 1998
`
`Sheet 13 of 18
`
`5，808，784
`
`41
`
`41
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`FIG. 238
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`
`SONY_000986
`
`

`
`u.s. Patent
`
`Sep. 15， 1998
`
`Sheet 14 of 18
`
`5，808，784
`
`41
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`41
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`F I G. 26
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`SONY_000987
`
`

`
`u.s. Patent
`
`Sep. 15， 1998
`
`Sheet 15 of 18
`
`5，808，784
`
`F I G. 27
`
`41
`
`F I G. 28
`
`F I G. 29
`
`SONY_000988
`
`

`
`u.s. Patent
`
`Sep. 15， 1998
`
`Sheet 16 of 18
`
`5，808，784
`
`〆----100
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`FIG.31
`
`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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`" d
`
`SONY_000990
`
`

`
`u.s. Patent
`
`Sep. 15， 1998
`
`Sheet 18 of 18
`
`5，808，784
`
`51
`
`F I G. 34
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`SONY_000991
`
`

`
`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
`
`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
`
`SONY_000993
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`

`
`5ラ808ラ784
`
`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
`
`:立;z::::fユニ:2ir:cJ:t号i?t官口:己i立2幻f:主:Z::fJ;zJz;;:;:;J211口30EEtzzrti22口lzhLihU6222;
`
`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