CN100354720C - Back light for liquid crystal display device - Google Patents

Back light for liquid crystal display device Download PDF

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Publication number
CN100354720C
CN100354720C CNB200410012057XA CN200410012057A CN100354720C CN 100354720 C CN100354720 C CN 100354720C CN B200410012057X A CNB200410012057X A CN B200410012057XA CN 200410012057 A CN200410012057 A CN 200410012057A CN 100354720 C CN100354720 C CN 100354720C
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China
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light
wedge
guide plate
light guide
groove
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CN1617028A (en
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笹川智广
结城昭正
岩崎直子
松本贞行
井上满夫
小田恭一郎
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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Abstract

The present invention provides back light. Appropriate light distribution and uniform emitted light can be obtained according to the back light of the present invention. The present invention is provided with a rod-shaped light source (1) of light used for the irradiation for the display of a liquid crystal plate, and a flat light guide plate (3), wherein the light guide plate is provided with an incident end surface (20) which is arranged on the side surface and is in parallel with the rod-shaped light source, a light exit surface (21) which is in parallel with the liquid crystal plate, and a bottom surface (22) which faces the light exit surface in parallel. The present invention is characterized in that the bottom surface (22) of the light guide plate is provided with a reflecting prism, the reflecting prism is provided with a wedge-shaped reflecting groove (4) which upwards extends along the direction of the incident end surface (20), and a zonal breaking flat part (5) which breaks the wedge-shaped reflecting groove in the direction crossing the extension direction of the wedge-shaped reflecting groove (4) to avoid the formation of the wedge-shaped reflecting groove, wherein the depth of the wedge-shaped reflecting groove (4) increases following the increase of the distance between the wedge-shaped reflecting groove and the incident end surface (20), and the width of the zonal breaking flat part (5) decreases following the increase of the distance between the zonal breaking flat part and the incident end surface (20).

Description

Back light for liquid crystal display device
This division is that application number is 00137377.3, the applying date is on October 20th, 2000, denomination of invention is divided an application for the application of " back light for liquid crystal display device ".
Technical field
The present invention relates to a kind of back light for liquid crystal display device.
Background technology
Figure 27 is the available liquid crystal display device with sectional drawing backlight (for example, pine this positive one compile [lcd technology] (industry books) P.255).With reference to Figure 27, the above-mentioned cold cathode fluorescent lamp (CCFL:Cold Cathode FloorescentLamp) 101 that possesses as light source backlight, catoptron 102, light guide plate 103, point-like body at random disposes regularly, make light be the radial reflection of dispersing white point figure 110, reflecting plate 107, prism plate 111 and diffusing panel 112 with wide-angle.
The following describes above-mentioned action backlight.The light that sends from cold cathode fluorescent lamp 101 directly or with the reflection of catoptron 102 incides light guide plate 103 from incident end face 120, carries out total reflection and propagation repeatedly by bottom surface 122 and exiting surface 121 in light guide plate, penetrates from exiting surface 121 at last.At this moment, when light touched point 110 white at random on the bottom surface of light guide plate 122, light was by at random, and 122 to light guide plate 103 outside ejaculations from the bottom surface.The light that penetrates from bottom surface of light guide plate 122 by reflecting plate 7 reflections after, incide on the bottom surface 122 of light guide plate further above-mentioned repeatedly total reflection, and penetrate from exiting surface 121.The light that penetrates from light guide plate is by one or two distributions that prism plate 111 is adjusted light, the diffusing panel 112 through removing thin luminous intensity distribution, the liquid crystal board (not shown) of shining the place ahead backlight.
Therefore like this backlight, after just penetrating from light guide plate, distribute because of wide-angle has big luminous intensity distribution because used point 110 at random in order to take out light, inevitable only at visual direction.Yet,, distribute so that become the luminous intensity distribution of deflection visual direction because the light harvesting effect of prism 111 just is necessary to adjust luminous intensity distribution and distributes.Therefore, as mentioned above, just must 1 or 2 high price prisms 111 of configuration.Owing to disposed this prism, thereby increased the quantity of parts, caused assembling process complicated.
For fear of the increase of this number of components, as shown in figure 28, the one-piece type light guide plate of prism optical element (spy opens flat 10-282342 communique) has been proposed.With reference to shown in Figure 28, light guide plate 103 in the above-mentioned parts possesses the direction extension of extending along incident end face, what wedge-like ran through the light guide plate depth direction is the wedge-like light reflection groove 104 and the prism-like jog 106 in a space, and wherein many of jog 106 parallel crest lines and incident end face 120 are vertical and extend.
Incide light total reflection and propagation repeatedly in light guide plate of light guide plate 103 from incident end face 120.At this moment, the light that is positioned on the inclined-plane of incident end face side of wedge-like reflection groove is reflected by this ramp effect upward.The light of reflection is owing to not satisfying total reflection condition rather than penetrating from exiting surface in the total reflection mode.Effect at exiting surface 121 places because of the prism-like jog, the luminous intensity distribution distribution narrow.Because this formation, under the condition of not adding prism plate, the luminous intensity distribution that can control emergent light distributes.Under situation about constituting like this, for the ejaculation light intensity that can control the position that is positioned at light guide plate equably distributes, must the interior position control wedge-like reflection groove shape of corresponding light guide plate.
Because having now backlight is as above to constitute, therefore,, must adopt a plurality of individual components for the suitable luminous intensity distribution that obtains emergent light distributes, therefore, can raise the cost like this.The backlight of the one-piece type light guide plate of existing use prism optical element disposed owing to the wedge-like reflection groove is regularly, therefore, is difficult to guarantee that the light intensity that penetrates in the space is even.
Summary of the invention
The objective of the invention is to have suitable luminous intensity distribution to distribute, can control again and penetrate the intensity uniformity of light in the space, realize the backlight of low-cost high-efficiency.
Back light for liquid crystal display device of the present invention has provides bar-shaped light source and the flat light guide plate that is used to the light that shines for the demonstration of liquid crystal board, this light guide plate has the incident end face that is positioned at the side that is parallel to bar-shaped light source, be parallel to the exiting surface of liquid crystal board ground configuration and the bottom surface of facing exiting surface abreast, it is characterized in that on the bottom surface of light guide plate, being provided with reflecting prism, this reflecting prism has at the upwardly extending wedge-like reflection groove and in order not form the wedge-like reflection groove along the side of incident end face, the banded disjunction par of this wedge-like reflection groove of direction disjunction that intersects along the direction of extending with this wedge-like reflection groove, wherein, the degree of depth of above-mentioned wedge-like reflection groove increases along with the distance of distance incident end face and deepens, and the width of above-mentioned banded disjunction par increases along with the distance of distance incident end face and decrescence.
Have above-mentioned formation backlight because the reflection of the wedge-like reflecting surface of being had no progeny by the disjunction flat, only just can make light with suitable light distribution characteristic ejaculation by light guide plate without prism plate etc.In addition, when being configured in the light harvesting prism on the exiting surface,, can realize high briliancy owing to have the light harvesting effect that exiting surface produced of prism-like jog.In addition, owing to just can adjust from the space distribution of the light intensity of light guide plate ejaculation by both sides apart from the width of the degree of depth of Change Example such as wedge-like reflection groove and wedge-like reflection groove and par corresponding to the distance incident end face, therefore, can reduce parts backlight, and reduce cost, realize having backlight that homogeneous space distributes and suitable luminous intensity distribution distributes.Above-mentioned effect is specifically under the occasion of wedge-like reflection groove, this degree of depth is along with the distance of distance incident end face increases and increases, in addition, situation for the width of cutting apart the par, this width diminishes along with the increase of distance incident end face distance, just can obtain above-mentioned effect in mode so simply and easily.
For the back light for liquid crystal display device of the invention described above, be preferably in configuration light harvesting prism on the exiting surface of light guide plate, this light harvesting prism with the direction of incident end face quadrature on have the prism-like jog that many parallel crest lines extend.
As mentioned above, by configuration light harvesting prism on exiting surface, producing the high briliancy of realization on the suitable luminous intensity distribution basis by reflecting prism.
For above-mentioned back light for liquid crystal display device, the width of banded disjunction par can change with for example distance apart from incident end face.
Only just obtain near the incident end face of light guide plate, being necessary to form imperceptible groove under the situation that the homogeneous space of emergent light distributes up to number μ m by the degree of depth of wedge-like reflection groove.But, if combined, then near incident end face, the degree of depth of the wedge-like reflection groove of handling ease is deepened with the wide variety of banded disjunction par, it is easier then to make, in addition, on the direction parallel, because the wedge-like reflection groove is with identical size with incident end face, form uniform shape, so it almost is impossible that the light on this direction penetrates the The Uniform Control of intensity, but, just might on this direction, realize homogenising by adjusting the width of disjunction par.
In the above-mentioned back light for liquid crystal display device, preferably the degree of depth of wedge-like reflection groove is along with the distance of distance incident end face increases and increases.
For the strongest, apart from the distance increase of incident end face, light intensity can slowly die down light in the light guide plate near incident end face.Its degree of depth of wedge-like reflection groove is dark more, will increase catoptrical intensity, just can increase the light intensity that penetrates from exiting surface.Thereby, by increasing the degree of depth of wedge-like reflection groove, can not be subjected to that ejaculation light is evenly distributed as mentioned above.
For above-mentioned back light for liquid crystal display device, the width of best banded disjunction par along with the distance of distance incident end face decrescence.
In zone, do not form the wedge-like reflection groove corresponding to banded disjunction par.The width of banded disjunction par increases along with the distance of distance incident end face and decrescence the time, the wedge-like reflection groove is cumulative thereupon.The result can not be subjected to that ejaculation light is evenly distributed.
For above-mentioned back light for liquid crystal display device, preferably the wedge-like reflection groove is 40-50 ° from the inclined-plane of incident end face side and the angle α of bottom surface.
By adopting above-mentioned angular range, can reduce reflection by the part of the prism-like jog at exiting surface place, make to have the light that suitable luminous intensity distribution distributes and penetrate more expeditiously.The result can realize the backlight of high-level efficiency and the distribution of suitable luminous intensity distribution with low cost.
For above-mentioned back light for liquid crystal display device, for the part of the prism-like jog on the exiting surface that is arranged on light guide plate, the protuberance apex angle ss is more than 100 °.
As a result, can reduce reflection, make to have the light that suitable luminous intensity distribution distributes and penetrate more expeditiously by the part of the prism-like jog at exiting surface place.Therefore, can reduce reflection, make to have the light that suitable luminous intensity distribution distributes and penetrate more expeditiously by the part of the prism-like jog at exiting surface place.The result can realize the backlight of high-level efficiency and the distribution of suitable luminous intensity distribution with low cost.
The invention provides another kind of back light for liquid crystal display device, having provides bar-shaped light source and the flat light guide plate that is used to the light that shines for the demonstration of liquid crystal board, this light guide plate has the incident end face that is positioned at the side that is parallel to bar-shaped light source, be parallel to the exiting surface of liquid crystal board ground configuration and the bottom surface of facing exiting surface abreast, it is characterized in that on the bottom surface of light guide plate, being provided with reflecting prism, this reflecting prism has at the upwardly extending wedge-like reflection groove and in order not form the wedge-like reflection groove along the side of incident end face, the banded disjunction par of this wedge-like reflection groove of direction disjunction that intersects along the direction of extending with this wedge-like reflection groove, wherein, between the groove between the adjacent above-mentioned wedge-like reflection groove flat part on darker position, the depth ratio disjunction par from the bottom surface to the light guide plate internal direction.
Because the par is formed on than extending on the darker position, staggered disjunction par with the wedge-like reflection groove between groove, therefore, needn't carry out high-precision groove processing, can make making more easy.Thereby, just can realize having light and penetrate the backlight of uniform space distribution and the distribution of suitable luminous intensity distribution with low cost.
The present invention also provides a kind of back light for liquid crystal display device, having provides bar-shaped light source and the flat light guide plate that is used to the light that shines for the demonstration of liquid crystal board, this light guide plate has the incident end face that is positioned at the side that is parallel to bar-shaped light source, be parallel to the exiting surface of liquid crystal board ground configuration and the bottom surface of facing exiting surface abreast, it is characterized in that on the bottom surface of light guide plate, being provided with reflecting prism, this reflecting prism has at the upwardly extending wedge-like reflection groove and in order not form the wedge-like reflection groove along the side of incident end face, the banded disjunction par of this wedge-like reflection groove of direction disjunction that intersects along the direction of extending with this wedge-like reflection groove, wherein, the width of above-mentioned disjunction par corresponding to the distance incident end face apart from random variation.
Because the width of disjunction par is made random variation, therefore, Ah interferes line just can to prevent to take place not between wedge-like reflection groove and the liquid crystal board pixel.Therefore, can realize good visual effect with low cost, it is backlight that suitable luminous intensity distribution distributes.
The present invention also provides a kind of back light for liquid crystal display device, having provides bar-shaped light source and the flat light guide plate that is used to the light that shines for the demonstration of liquid crystal board, this light guide plate has the incident end face that is positioned at the side that is parallel to bar-shaped light source, be parallel to the exiting surface of liquid crystal board ground configuration and the bottom surface of facing exiting surface abreast, it is characterized in that on the bottom surface of light guide plate, being provided with reflecting prism, this reflecting prism has at the upwardly extending wedge-like reflection groove and in order not form the wedge-like reflection groove along the side of incident end face, the banded disjunction par of this wedge-like reflection groove of direction disjunction that intersects along the direction of extending with this wedge-like reflection groove, wherein, above-mentioned banded disjunction par is configured to curve-like.
Because curvilinear banded disjunction par, Ah interferes line to have prevented to take place not between wedge-like reflection groove and the liquid crystal board pixel, therefore, can realize good visual effect with low cost, and it is backlight that suitable luminous intensity distribution distributes.
The present invention also provides a kind of back light for liquid crystal display device, having provides bar-shaped light source and the flat light guide plate that is used to the light that shines for the demonstration of liquid crystal board, this light guide plate has the incident end face that is positioned at the side that is parallel to bar-shaped light source, be parallel to the exiting surface of liquid crystal board ground configuration and the bottom surface of facing exiting surface abreast, it is characterized in that on the bottom surface of light guide plate, being provided with reflecting prism, this reflecting prism has at the upwardly extending wedge-like reflection groove and in order not form the wedge-like reflection groove along the side of incident end face, the banded disjunction par of this wedge-like reflection groove of direction disjunction that intersects along the direction of extending with this wedge-like reflection groove, wherein, make the angle [alpha] on inclined-plane of the incident end face side of above-mentioned wedge-like reflection groove be cyclical variation.
Because above-mentioned bevel angle is cyclical variation, emergent light increases at the shooting angle of the direction vertical with incident end face, and therefore the luminous intensity distribution distribution equalization of emergent light, can realize good visual effect with low cost, and it is backlight that suitable luminous intensity distribution distributes.
The present invention also provides a kind of back light for liquid crystal display device, having provides bar-shaped light source and the flat light guide plate that is used to the light that shines for the demonstration of liquid crystal board, this light guide plate has the incident end face that is positioned at the side that is parallel to bar-shaped light source, be parallel to the exiting surface of liquid crystal board ground configuration and the bottom surface of facing exiting surface abreast, it is characterized in that in light guide plate the bottom surface (on be provided with reflecting prism, this reflecting prism has at the upwardly extending wedge-like reflection groove and in order not form the wedge-like reflection groove along the side of incident end face, the banded disjunction par of this wedge-like reflection groove of direction disjunction that intersects along the direction of extending with this wedge-like reflection groove, wherein, make the inclined-plane of the incident end face side of above-mentioned wedge-like reflection groove become to the incident end face side recessed, towards cylindric that extends along the direction of incident end face.
By above-mentioned inclined-plane is become to recessed cylindric of incident end face side, thereby, increased emergent light with incident end vertical direction on shooting angle, make being evenly distributed of luminous intensity distribution of emergent light, therefore, can realize good visual effect with low cost, it is backlight that suitable luminous intensity distribution distributes.
For above-mentioned back light for liquid crystal display device, the width of best banded disjunction par is greater than 10 μ m.
Width by making the disjunction par is greater than 10 μ m, just do not need not use high precision to be used as the planing tool of groove processing usefulness with planing tool, and making can be easier.Therefore, just can realize having light and penetrate the backlight of uniform space distribution and the distribution of suitable luminous intensity distribution with low cost.
For above-mentioned back light for liquid crystal display device, par between the groove of the above width of 10 μ m is set between preferably adjacent wedge-like reflection groove.
By par between the groove that the width more than the 10 μ m is set, just do not need to use high precision to be used as the planing tool that groove is processed usefulness with planing tool, making can be easier.Therefore, just can realize having light and penetrate the backlight of uniform space distribution and the distribution of suitable luminous intensity distribution with low cost.
For above-mentioned back light for liquid crystal display device, on the prism-like jog, preferably the range difference towards the exiting surface direction is at random from the bottom surface of this concavo-convex adjacent crest line and valley line.
Ah interferes line to the result owing to prevented to take place not between prism-like jog and liquid crystal board pixel, therefore, can realize good visual effect with low cost, and it is backlight that suitable luminous intensity distribution distributes.
For above-mentioned back light for liquid crystal display device, the bottom surface that is preferably near light guide plate disposes reflecting plate again, and this reflecting plate makes the light diffusion of advancing along incident end face.
By the configuration said reflection plate, construct the angle ground reflection of the light maintenance of reflection by the prism on the exiting surface perpendicular to the direction of incident end face, therefore, the light with suitable luminous intensity distribution distribution is penetrated expeditiously.The result can realize good visual effect with low cost, and it is backlight that suitable luminous intensity distribution distributes.
For above-mentioned back light for liquid crystal display device, the exiting surface that is preferably near light guide plate disposes diffusing panel again, this diffusing panel make with the light diffusion of advancing along the direction in the direction plane orthogonal of incident end face.
Owing to disposed above-mentioned diffusing panel, make luminous intensity distribution distribution planarization perpendicular to the emergent light of the direction of incident end face, therefore, can realize good visual effect with low cost, it is backlight that suitable luminous intensity distribution distributes.
For above-mentioned back light for liquid crystal display device, between the end face of light source and light guide plate, dispose the optical element of concavo-convex structure again, the protuberance of this element is towards the incident end face side.
Owing to disposed above-mentioned optical element, penetrate the more suitably light of luminous intensity distribution distribution from the wedge-like reflecting surface, therefore, can realize good visual effect with low cost, it is backlight that suitable luminous intensity distribution distributes.
For above-mentioned back light for liquid crystal display device, the direction that best light guide plate is propagated in this light guide plate along light after promptly being cut apart perpendicular to the direction of incident end face, combines these partitioning portions again.
Because above-mentioned cutting apart, when making light guide plate, unnecessary processing large tracts of land makes making more easy, thereby, can have backlight that uniform space distribution/suitable luminous intensity distribution distributes with the low cost realization.
Of the present invention aforesaid, and the purpose beyond above-mentioned, feature, curved surface and effect will be clearer according to detailed description of the invention described later with reference to accompanying drawing.
Description of drawings
Fig. 1 is the skeleton view backlight of the embodiment of the invention 1 of part perspective.
Fig. 2 A and Fig. 2 B show the structure of light guide plate.Fig. 2 A is the ground plan that the distribution of wedge-like reflection groove on the light guide plate and disjunction par is shown, and Fig. 2 B is the front view (FV) of seeing from the incident end face direction.
Fig. 3 A and Fig. 3 B illustrate near the analog result of the angular distribution of the incident light incident end face in the light guide plate.Fig. 3 A illustrates in the CCFL vertical plane and the angular distribution of the incident light in the CCFL parallel surface, and Fig. 3 B illustrates the angular orientation in the CCF vertical plane.
Fig. 4 illustrates the effect of the wedge-like reflection groove of embodiment 1.
Fig. 5 illustrates the effect of the prism-like jog of embodiment 1.
Fig. 6 A and Fig. 6 B illustrate the light distribution characteristic of the emergent light backlight of embodiment 1.Fig. 6 A illustrates 0 ° of common direction on the direction of CCFL parallel surface and CCFL vertical plane and the two sides.Fig. 6 B illustrates the angular distribution that light penetrates from the exiting surface on CCFL parallel surface and the CCFL vertical plane.
Fig. 7 is the angular distribution presentation graphs of light percent of pass of the prism-like jog backlight (90 ° of drift angles) of embodiment 1.
Fig. 8 illustrates the angular distribution of the percent of pass of groove parallel direction among Fig. 7 (groove vertical angle=0 °) and groove vertical direction (the parallel angle of groove=0 °).
Fig. 9 is the angular distribution presentation graphs of light percent of pass of the prism-like jog backlight (100 ° of drift angles) of embodiment 1.
Figure 10 illustrates the angular distribution of the percent of pass of groove parallel direction among Fig. 9 (groove vertical angle=0 °) and groove vertical direction (the parallel angle of groove=0 °).
Figure 11 is the mode chart that the formation backlight of the embodiment of the invention 2 is shown.
Figure 12 A illustrates near the wedge-like reflection groove the bottom surface, par between disjunction par and groove.Figure 12 B is the details drawing that the depth relationship of par between the banded par of Figure 12 A and groove is shown.
Figure 13 A illustrates the job operation of par between groove on the mould of light guide plate, and Figure 13 B is the front elevation of the planing tool that uses in the processing of wedge-like reflection groove.
Figure 14 A illustrates the job operation of the disjunction par on the mould of light guide plate, and Figure 14 B is the front elevation that the branch par of processing disjunction par adds used planing tool in man-hour.
Figure 15 is the structure of the depth direction of the bottom surface of light guide plate the when par is more shallow than banded par between groove.
Figure 16 is the structure of the depth direction of the bottom surface of light guide plate the when par is darker than banded par between groove.
Figure 17 is the sectional drawing of prism-like jog of the degree of depth at random backlight of embodiments of the invention 3.
Figure 18 is the ground plan of the wedge-like reflection groove of embodiment 3.
Figure 19 is the ground plan of the other wedge-like reflection groove of embodiment 3.
Figure 20 is other the ground plan of wedge-like reflection groove of embodiment 3.
Figure 21 A is the sectional drawing of pattern that the formation backlight of the embodiment of the invention 4 is shown.Figure 21 B is the amplification profile diagram that continuous 3 the wedge-like reflection grooves among Figure 21 A are shown.
Figure 22 is the sectional drawing that the pattern of the other formation backlight of the embodiment of the invention 4 is shown.
Figure 23 is the skeleton view that the formation backlight of the embodiment of the invention 5 is shown.
Figure 24 is the skeleton view that the formation backlight of the embodiment of the invention 6 is shown.
Figure 25 is the skeleton view backlight of the embodiment of the invention 7 of part perspective.
Figure 26 is the skeleton view backlight of the embodiment of the invention 8 of part perspective.
Figure 27 is the sectional drawing that existing formation backlight is shown.
Figure 28 is the oblique view that the formation of the one-piece type light guide plate of existing prism is shown.
Embodiment
Below, with reference to the description of drawings embodiments of the invention.
Embodiment 1
With reference to Fig. 1, Fig. 2 A and Fig. 2 B, the above-mentioned cold cathode lamp 1 that possesses as light source, catoptron 2 and light guide plate 3 backlight.Be located at the wedge-like reflection groove 4 of the reflecting prism the inside on the bottom surface, inclined angle alpha on the inclined-plane of light incident side is that the angle on the inclined-plane of 45 ° of emitting sides is 85 °, the spacing of wedge-like reflection groove 4 is 200 μ m, the degree of depth of wedge-like reflection groove is minimum 50 μ m, be 160 μ m to the maximum, dark more from the light source degree of depth far away more.Herein, [degree of depth] is 22 distances towards the light guide plate internal direction to wedge-like reflection groove front end from the bottom surface.Above-mentioned light guide plate 3 22 has along wedge-like reflection groove bearing of trend vertically in the bottom surface, and in addition, there is being bottom reflection plate 7 par 15 between the banded disjunction par 5 of disjunction wedge-like reflection groove and the groove between the wedge-like reflection groove near 22 places, bottom surface.In addition, above-mentioned light guide plate has prism-like jog 6 on the exiting surface 21 of upper surface.This prism-like jog 6, the prism vertex angle β of its protuberance is 100 °, separation is 180 μ m.
The light that penetrates from cold cathode fluorescent lamp 1 is directly incident on the incident end face 20 or in catoptron 2 reflections and reenters on the incident end face 20 that is mapped to light guide plate 3, carries out total reflection repeatedly and propagate on the bottom surface 22 of light guide plate and exiting surface 21.At this moment, be mapped to light on the inclined-plane 24 of light incident side of wedge-like reflection groove 4 because of the effect on this inclined-plane 24 reflection that makes progress.Because wedge-like reflection groove 4 parts by 5 disjunctions of banded disjunction par, so intactly propagate by the light of disjunction par 5, can be controlled the space distribution of light ejaculation amount in light guide plate.Light by the reflecting surface reflection is penetrated by exiting surface 21 because of total reflection condition is damaged.On exiting surface, make the luminous intensity distribution distribution narrow by prism-like jog 6.
Fig. 3 A and Fig. 3 B illustrate from cold cathode fluorescent lamp 1 (CCFL:Cold CathodeFluorescent Lamp) and just incided the angular distribution analog result example of propagating on the light guide plate in light guide plate.On the both direction for all directions in all directions in the axle that contains cold cathode lamp 1 and the CCFL parallel surface of light guide plate face and the CCFL vertical plane vertical with this, formation with in light guide plate along the light guide plate rectilinear direction, i.e. 0 ° of symmetrical distribution that direction is the center.Angle in the CCFL parallel surface and angle and the initial point in the CCFL vertical plane all are along the light guide plate rectilinear direction in light guide plate.Such light is subjected to wedge-like reflection groove reflex time, because the wedge-like reflection groove is configured on the bottom surface 22 of light guide plate, so such shown in Fig. 3 B by the light of wedge-like reflection groove reflection, angle accounts for major part at the light below 0 ° in the CCFL vertical plane.Light in addition becomes 0 ° to arrive wedge-like reflection groove 4 behind the lower angle by upper surface 1 reflection of light guide plate.
In addition, as shown in Figure 4, just incide light on the wedge-like reflection groove with the incident angle that satisfies total reflection condition by the light of wedge-like reflection groove 4 reflection, major part in addition continues to propagate in light guide plate by the wedge-like reflection groove.When the bevel angle of the light incident side of wedge-like reflection groove is 45 °, be about 1.5, therefore, stand upright on the vertical line on the above-mentioned inclined-plane relatively owing to constitute the refractive index of the general material of light guide plate, can total reflection with the light of about incident angle incident below 40 °.As shown in Figure 4, just incide bevel angle α and be being reflected on 45 ° the inclined-plane, and substantially vertically penetrate from light guide plate 3 with 0 ° of light that enters in the light in the light guide plate with lower angle from 0 ° of-5 ° of scope angle.Therefore, the angular distribution of light in the CCFL vertical plane that penetrates from light guide plate because of wedge-like reflection groove 4 only becomes and has high-intensity light distribution characteristic at visual direction.
Penetrate light, because of the prism-like jog 6 that is arranged on the light harvesting prism on the exiting surface 21 as shown in Figure 5, from cold cathode fluorescent lamp parallel direction light within the specific limits with the direction refraction that is substantially perpendicular to exiting surface afterwards by light harvesting.On the other hand, with respect to the light of the subvertical angle of exiting surface because of total reflection once more to light guide plate internal reflection recycle.Because this effect, the angular distribution in the plane parallel with cold cathode fluorescent lamp also on perpendicular to the direction of exiting surface by light harvesting, also have light distribution characteristic.Like this, owing to be configured on the light guide plate, the effect of prism-like jog 6 and wedge-like reflection groove 4 does not need the optical element of additional prism plate in addition etc. just to be partial to the direction of vertical exiting surface, can be for vision distributes with suitable luminous intensity distribution to penetrate light.
Fig. 6 A and Fig. 6 B illustrate from the analog result of the angular distribution of this light guide plate ejaculation.Fig. 6 A is the mode chart of light intensity angular distribution, and Fig. 6 B is the mode chart of angular orientation.Perpendicular to the direction in the CCFL parallel surface of light guide plate and perpendicular to the both direction of the direction in the CCF face of CCFL axle, perpendicular to 0 ° of the exiting surface direction, promptly visual direction illustrates peak strength for the axle that comprises cold cathode lamp 1.Especially, as the effect of prism-like jog, the light in the cold-cathode tube vertical plane illustrates kurtosis at 0 °.The both direction of the direction in direction in the CCFL parallel surface and the CCFL vertical plane, initial point, i.e. 0 ° of direction that is perpendicular to exiting surface 21.
In order from the whole surface of light guide plate, to draw light equably,, the probability on the reflecting surface 24 that incides wedge-like reflection groove 4 is changed along with the change in location in the light guide plate.Backlight for based on present embodiment, should change two aspects of width of the banded disjunction par 5 of the degree of depth of the wedge-like reflection groove 4 shown in Fig. 2 B and disjunction wedge-like reflection groove 4, the homogenising of coming the implementation space by the probability that in light guide plate, changes on the reflecting surface 24 that light incides wedge-like reflection groove 4.If only change wherein either party, the deep processing that will occur making wedge-like reflection groove 4 is to the extremely shallow degree of having only several μ m, and perhaps, the depth-width ratio that makes wedge-like reflection groove 4 is high shape.The result requires the machining precision height of wedge-like groove, causes manufacturing cost to rise.
Below, the incident angle that Fig. 7-Figure 10 illustrates the light percent of pass of light when the inboard of light guide plate 3 is incided above the light guide plate on 21 the prism-like jog 6 distributes.Fig. 7 when being 90 ° according to prism vertex angle β-8, about parallel with the direction of extending with prism-like jog 6, perpendicular to the incident angle in the plane of exiting surface, 20% of the highest percent of pass during just with basic vertical incidence passes through.On the contrary, Fig. 9 when prism vertex angle β is 100 °-10, the highest percent of pass in above-mentioned surpasses 60%, thus as can be known, apex angle ss is big more, and percent of pass is high more.
Because stop the light pass through to be subjected to the reflection on this prism-like jog surface, further change direction, again towards top 21 direction, so finally almost all penetrate by bottom reflecting plate 7 grades by the prism-like jog.But, also lost the good luminous intensity distribution that obtains because of wedge-like reflection groove 4 this moment and distributed.Here, in order to obtain the light that the high only luminous intensity distribution of efficient distributes, must reduce light by 6 reflections of prism-like jog as far as possible.If the apex angle ss of prism-like jog 6 is narrowed down, as described above, the scope of passing through for the incident angle that is parallel to prism-like jog direction narrows down, if less than 100 °, the incident angle zone of passing through is almost constant.Surpass under 100 ° the situation at above-mentioned drift angle, the light that must make the basic vertical direction consistent with the scope of the incident angle that can pass through is towards top.Therefore, the only scope of angle [alpha] on the inclined-plane 24 of wedge-like reflection groove is 40-50 °.
(embodiment 2)
Figure 11-Figure 12 illustrates the back light for liquid crystal display device of embodiments of the invention 2.Figure 11 is above-mentioned skeleton view backlight, and Figure 12 A is the skeleton view of wedge-like reflection groove, and Figure 12 B is the enlarged drawing of A part.In this form of implementation, for the banded disjunction par 5 of disjunction wedge-like reflection groove 4, the light source 1 of distance light guide plate 3 be maximum distance/the narrowest position of the width of disjunction par 5 on, its width is 10 μ m.The width of par 15 between the groove that the wedge-like reflection groove is 4 also is 10 μ m in the narrowest place.In addition, the par is the top that benchmark is positioned at the disjunction par of disjunction wedge-like reflection groove with bottom surface 22 between the groove between the wedge-like reflection groove, that is to say, approaches top 21 position.Relevant its reason will be utilized Figure 13 A, Figure 13 B, and Figure 14 A, Figure 14 B elaborates.
Other basic comprising is identical with form of implementation 1, the above-mentioned cold cathode lamp 1 that possesses as light source, catoptron 2, light guide plate 3 and backside reflection plate 7 backlight.Light guide plate 3 possesses wedge-like reflection groove 4, the banded par 5 of disjunction wedge-like reflection groove and prism-like jog 6.With form of implementation 1 in the same manner because wedge-like reflection groove and prism-like jog can obtain penetrating from light guide plate with suitable light distribution characteristic the effect of light.
When producing the light guide plate that has as the wedge-like reflection groove of light guide plate 3 of the present invention, in most cases, use mould to produce a large amount of by the plastic-blasting moulding.When making mold for forming, as Figure 13 A, Figure 13 B, Figure 14 A shown in Figure 14 B, can utilize the material of adamas planing tool 31/32 cutting NiP etc., the method for the mould of processing wedge-like reflection groove 4 and prism-like jog 6.At this moment, for example,, be suitable shape, just can make correct processing more easy by making adamas planing tool 31/32 for the inclined-plane of wedge-like reflection groove.The par is such formation between the groove between the wedge-like reflection groove: make adamas planing tool 31/32 front end have to a certain degree flat, cut repeatedly with the spacing below the planing tool flat width.For example, the width of par 15 can be done by a relatively large margin variation corresponding to the position in the light guide plate in order evenly to be penetrated light intensity distributions aspect the space between the groove between the wedge-like reflection groove.Because the processing of the following width of flat of adamas planing tool is impossible, so the par of adamas planing tool must be littler than the width of the par of narrow part.But when the width of par was too small, the flat of planing tool can not correctly be made, it is very difficult that the making of adamas planing tool becomes, and the result adds man-hour in the par to mould, can leave thinner concavo-convexly, this is to cause light diffusing reason, is inappropriate.Because the width minimum of par 15 and banded par 5 is 10 μ m between groove, so the making meeting of adamas planing tool is easier, the result can reduce the correct cost of processing of mould.
With reference to Figure 13 A, 13B, 14A and 14B, during the banded par 35 of (omitting on the mould later on) wedge-like reflection groove 34 on processing mold and this wedge-like reflection groove 34 of disjunction, for example, shown in Figure 13 B, the planing tool 31 of the par that 10 μ m is arranged with inclined-plane with 45 ° and 85 ° and top sweeps away par 45 between cutting wedge-like reflection groove 34 and groove with being parallel to incident end face.Afterwards, change the planing tool 32 of the banded disjunction of processing par 35, and change machine direction or change to and the vertical direction of wedge-like reflection groove 34 bearing of trends, shown in Figure 14 A and Figure 14 B, process disjunction par 35.At this moment, for the processing of wedge-like reflection groove 34 and the processing of disjunction par 35, because the adamas planing tool also changes, and machine direction is conversion also, therefore, the location can be more difficult, and par 45 and banded disjunction par 35 be not on one side between the groove between the wedge-like reflection groove, and the possibility that produces step is very big., if produce step, then the light ejaculation characteristic generation of reflecting light guide plate because of light leak and light from stage portion has a strong impact on.
When Mould Machining, when deeper processing disjunction par 5, thereby under the more shallow situation in disjunction par on the actual light guide plate, as shown in figure 15, step is configured on the vertical direction of incident end 20 of relative light guide plate.On the other hand, deeper process under the situation of par 15 between the groove between the wedge-like reflection groove, thereby on the light guide plate of reality between groove under the more shallow situation in par, as shown in figure 16, step is configured to the direction parallel with respect to the incident end face 20 of light guide plate.In light guide plate, when propagating as if the relative incident end face of consideration light, in Mould Machining, disjunction par 5 should process deeplyer, makes step up dispose along the side perpendicular to incident end face 20, reduces the influence of step.Therefore, as the shape of light guide plate, owing to adopt par 15 between groove is positioned on the darker position, score par 5, therefore, the influence that step produces is less, and is more easy with low precision processing, can process the mould of the good light guide plate of characteristic.
(embodiment 3)
Back light for liquid crystal display device for form of implementation 3, shown in Figure 17-18,6 one-tenth following modes of prism-like jog, being adjacent crest line and valley line becomes random value apart from the range difference ([note is made the degree of depth of prism jog]) of the thickness direction of bottom surface and the spacing ((note is made the spacing of prism-like jog]) of overlooking adjacent crest line and valley line, in addition, make the interval of the configuration of disjunction par 5 become random value.Other basic comprising is identical with embodiment's 1 (Fig. 1), has the cold cathode lamp 1 as light source, catoptron 2, light guide plate 3, backside reflection plate 7.The effect that light penetrates with suitable light distribution characteristic from light guide plate because of the wedge-like reflection groove 4 on the light guide plate and prism-like jog 6 also can get the effect identical with embodiment 1 in the present embodiment.
In liquid crystal board, the pixel of about 100 μ m sizes is periodic arrangement. and therefore, if backlight holding aspect prism-like jog 6 and wedge-like reflection groove 4 when periodically constructing, the light of ejaculation is also held periodic distribution, take place not between the two that Ah interferes line, the sense of vision effect descends.Here, as Figure 17 and shown in Figure 180, make the degree of depth and the interval randomness of prism-like jog 6, and make the spacing randomness of the configuration of disjunction par 5, or curved shape, just can prevent that Ah does not interfere the generation of line and the decline of visual effect.
Ah interferes line in order to prevent to take place not between wedge-like reflection groove and liquid crystal board, as shown in figure 19, banded disjunction par 5 is made random arrangement and made its curved shape, and aperiodicity just can prevent that Ah does not interfere the generation of line.In addition, as shown in figure 20, the width randomization of par 15 between the configuration space randomization of wedge-like reflection groove 4 and groove and banded disjunction par 5 curveizations can be separated also disappear not that Ah interferes line.The width randomization of disjunction par can be separated also disappear not that Ah interferes line.
(embodiment 4)
Figure 21 A and Figure 21 B illustrate the back light for liquid crystal display device of embodiments of the invention 4.In the present embodiment, shown in Figure 21 A and Figure 21 B, make the inclination alpha on inclined-plane 24 of the light incident side of 3 continuous wedge-like reflection grooves be respectively 43 °, 45 °, 48 °, 3 continuous wedge-like reflection grooves as one-period, are periodically and change.Other basic comprising backlight is identical with embodiment's 1, thereby, similarly to Example 1, also can obtain the effect that light penetrates from light guide plate with suitable light distribution characteristic by wedge-like reflection groove and prism-like jog with the form of embodiment.
Under near the situation of the light angle of reflecting surface is 45 ° by the reflection of wedge-like reflection groove, shown in Fig. 6 A of embodiment 1, hold narrow angular distribution about the direction in the CCFL vertical plane.Can obtain extremely bright demonstration like this under the situation consistent with visual direction, deviation is arranged slightly, then briliancy descends significantly.Therefore, because this liquid crystal indicator, even in order to change slightly at visual direction, the still demonstration that can obtain becoming clear is hopeful to hold the situation that wider angle distributes.If the bevel angle of the light incident side of wedge-like reflection groove is respectively 43 °, 45 °, 48 ° shown in Figure 21 B, with 3 continuous wedge-like reflection grooves is the cyclical variation of one-period ground, the light that penetrates overlaps separately, in a big angular range, can access briliancy and be higher than the above light ejaculation distribution of certain value.
As shown in figure 22, even the inclined-plane of the light incident side of wedge-like reflection groove is become to recessed cylindric of incident end face 20 sides, also can access same effect.
(embodiment 5)
Figure 23 illustrates the skeleton view of the back light for liquid crystal display device of embodiment 5.Present embodiment is characterised in that backside reflection plate 7 becomes the reflecting surface that has along the sag and swell of the prism-like of extending perpendicular to incident end face 20 directions of light guide plate.Above-mentioned backlight aspect other basic comprising identical with embodiment 1, possess light guide plate 3, the banded disjunction par 5 and the prism-like jog 6 of wedge-like light reflection groove 4 disjunction wedge-like light reflection grooves.Thereby, the same with embodiment 1, also can access the effect that light penetrates from light guide plate with suitable light distribution characteristic by wedge-like reflection groove and prism-like jog for present embodiment.
A part of light in the light that utilizes the wedge-like reflection groove to penetrate from light guide plate in the certain angle scope parallel with the CCFL axle has been arranged under the optical element effect of the prism-like jog on the exiting surface 21 of light guide plate to the light guide plate internal reflection in formation.The light of this reflection changes to towards the direction by the prism-like jog from the direction that is parallel to CCFL when 7 reflections of 22 backside reflection plate below light guide plate, arrives exiting surface once more and penetrates.Usually, for backside reflection plate 7, use square diffusing panel, because of diffusion, the angle of the direct of travel of light changes.But, if use square diffusing panel, not only parallel direction with CCFL, and also when being reflected by the wedge-like reflection groove, the light of the direction in the plane vertical with CCFL also changes its direction.Therefore, reduced the light distribution characteristic of final ejaculation light.For present embodiment, owing to used the reflecting plate that has along the sag and swell of the prism-like of extending as backside reflection plate 7 perpendicular to incident end face 20 directions of light guide plate, just reflect, so light distribution characteristic can not descend to being parallel to the axial light of CCFL with changing direction.Utilize other means of non-square reflecting plate, refraction grating, holograph etc. to replace above-mentioned prism-like jog also can realize preventing such light distribution characteristic variation.
(embodiment 6)
Figure 24 shows the back light for liquid crystal display device of embodiment 6.For present embodiment, disposing non-square diffusing panel 8 near 21 ground above the light guide plate, 8 of this plates allow and pass through perpendicular to the light diffusion of incident end face 20 directions.Above-mentioned backlight in, other basic comprising is identical with embodiment's 1, has and possesses light guide plate 3, the banded disjunction par 5 and the prism-like jog 6 of wedge-like light reflection groove 4 disjunction wedge-like light reflection grooves.Thereby, the same with embodiment 1, also can access the effect that light penetrates from light guide plate with suitable light distribution characteristic by wedge-like reflection groove and prism-like jog for present embodiment.
When the light of wedge-like reflection groove reflection is near the angle [alpha] on inclined-plane 24 is 45 °, shown in embodiment 1, hold narrow angular distribution on the direction in the CCFL vertical plane.Can obtain extremely bright demonstration like this under the situation consistent with visual direction, deviation is arranged slightly, then briliancy descends significantly.Therefore, because this liquid crystal indicator, even in order to change slightly at visual direction, the still demonstration that can obtain becoming clear is hopeful to hold the situation that wider angle distributes.Here, the non-square diffusing panel that only allows the light diffusion of CCFL vertical plane all directions pass through is configured in above the light guide plate near 21, the luminous intensity distribution of the direction that is parallel to incident end face 20 distributed can not exert an influence, and expansion is penetrated distribution along the luminous intensity distribution distribution of the vertical direction of incident end 20 directions at this light that can access on a large scale more than certain briliancy.
Above-mentioned non-square diffusing panel 8 can reflect displacements such as grating, holograph, lenticular lens plate in week.
(embodiment 7)
Figure 25 illustrates the back light for liquid crystal display device of embodiment 7.In the present embodiment, be characterised in that 90 ° of drift angles, the optical element 9 of the prism-like sag and swell of spacing 180 μ m is configured between light source and the incident end face.The bevel angle of the light incident side of wedge-like reflection groove 4 is 45 °, and the bevel angle of emitting side is 85 °, spacing 200 μ m, and the minimum 50 μ m of groove depth, maximum 160 μ m are along with dark more from the light source degree of depth far away more.With reference to Figure 25, the above-mentioned cold cathode lamp 1 that possesses as light source, catoptron 2, light guide plate 3 and backside reflection plate 7 backlight.
The light that penetrates from light source directly or through mirror reflects incides on the optical element 9 with prism-like groove.On the direction of light harvesting effect in the CCFL parallel surface that comprises CCFL axle and light guide plate face of this incident light because of prism structure (with Fig. 3 B be equidirectional orientation.With Fig. 6 A, 8,10 different) combine in the certain limit, be that central transformation becomes narrow luminous intensity distribution to distribute with direction perpendicular to incident end face.Incide light on the light guide plate and in light guide plate, propagate through total reflection, at this moment, be positioned at wedge-like reflection groove 4 light incident side inclined-plane 24 (Fig. 3 B) light because of the effect on this inclined-plane to the exiting surface lateral reflection.Wedge-like reflection groove 4 parts are propagated in light guide plate by the light of this band shape disjunction par 5 unceasingly by 5 disjunctions of banded disjunction par, therefore, and the homogeneity in the space in the time of can controlling bright dipping.Light by 24 reflections of above-mentioned inclined-plane disappears the back from exiting surface 2 ejaculations at total reflection condition.
Light guide plate 3 in the back light for liquid crystal display device of the present invention is being taken out light time use wedge-like reflection groove 4, and the direct reflection of utilization generation total reflection makes the light reflection with the direction of correct control.And for existing light guide plate, owing to use diffusion to take out light, therefore, the adjustment that the luminous intensity distribution of light distributes must be carried out after light guide plate is taken out through diffusion at light.But, take out the light time by direct reflection, particularly on the direction parallel with cold cathode lamp 1, if before light guide plate incident, adjust the angular distribution of light, taking out the light time, owing to just changed direction through reflection, therefore, can keep original angular distribution state ground to take out light.Here, before light guide plate incident, utilize prism-like optical element 9 to adjust luminous intensity distribution and distribute, therefore, can utilize little optical element, just can easily penetrate the light of suitable light distribution characteristic.
(embodiment 8)
The back light for liquid crystal display device of the embodiment of the invention 8 as shown in figure 26.In the present embodiment, light guide plate is not integrally formed, along perpendicular to the direction of incident end face 20,2 parts of 3a of cutting apart and 3b in conjunction with and constitute.Other basic comprising is identical with embodiment 1, possesses light guide plate 3a and 3b, wedge-like reflection groove 4, the banded disjunction par 5 and the prism-like jog 6 of disjunction wedge-like reflection groove.
When plastic-blasting formed the light guide plate 3 with the optical element that constitutes the prism-like jog, when area was big, material was from the material introducing port very big scope of must flowing through.Thereby, can not there be enough materials to flow in as the position, summit of prism-like jog tiny, thereby, the bad phenomenon of moulding takes place easily.Thereby light guide plate is cut apart, and its one-time formed size is cut apart diminish, and just can easily form light guide plate completely.When cutting apart light guide plate, in order not occur on the cut-point 2 part prism jogs are connected mistake, therefore, in the above on 21 the prism-like jog, in paddy portion, and on the prism-like jog on the bottom surface 22 on the disjunction planar section, preferably form cut-point respectively.
As mentioned above, though be illustrated according to embodiments of the invention, the embodiments of the invention of above-mentioned announcement are some examples, and are not limited to the foregoing description within the scope of the invention.Scope of the present invention is by the record of the scope of claims, and scope of the present invention also is included in the scope of claim record and whole improvement of making under the identical with it implication.

Claims (2)

1. back light for liquid crystal display device, having provides bar-shaped light source (1) and the flat light guide plate (3) that is used to the light that shines for the demonstration of liquid crystal board, this light guide plate has the incident end face that is positioned at the side (20) that is parallel to bar-shaped light source, parallel and in the face of the exiting surface (21) of liquid crystal board ground configuration and the bottom surface (22) of facing exiting surface abreast, it is characterized in that:
On the bottom surface (22) of light guide plate, be provided with reflecting prism, this reflecting prism has along upwardly extending wedge-like reflection groove in the side of incident end face (20) (4) and the feasible banded disjunction par (5) that does not form the wedge-like reflection groove of this wedge-like reflection groove of direction disjunction that intersects along the direction of extending with this wedge-like reflection groove (4), wherein
Par (15) is positioned on the darker position, depth ratio disjunction par (5) from bottom surface (22) to the light guide plate internal direction between the groove between the adjacent above-mentioned wedge-like reflection groove (4).
2. back light for liquid crystal display device according to claim 1 is characterized in that: the direction that above-mentioned light guide plate (3) is propagated in this light guide plate along light after promptly being cut apart perpendicular to the direction of incident end face (20), combines these partitioning portions again.
CNB200410012057XA 2000-10-20 2000-10-20 Back light for liquid crystal display device Expired - Fee Related CN100354720C (en)

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EP2848858B1 (en) * 2012-05-10 2019-07-03 Panasonic Intellectual Property Management Co., Ltd. Light guide
WO2019137831A1 (en) * 2018-01-10 2019-07-18 Koninklijke Philips N.V. A light guiding unit
CN110026745A (en) * 2019-05-24 2019-07-19 长春理工大学 A kind of V-groove double plane iron-quarter combined machining method

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JPH07168026A (en) * 1993-12-15 1995-07-04 Shimura Kaken Kogyo Kk Light guiding plate and luminaire using it
JPH09269489A (en) * 1996-02-02 1997-10-14 Hitachi Ltd Manufacture of liquid crystal display device and light transmission plate for rear illuminating part
US5838403A (en) * 1996-02-14 1998-11-17 Physical Optics Corporation Liquid crystal display system with internally reflecting waveguide for backlighting and non-Lambertian diffusing
JPH1152370A (en) * 1997-07-31 1999-02-26 Hitachi Ltd Liquid crystal display device

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JPH06194653A (en) * 1992-10-01 1994-07-15 Internatl Business Mach Corp <Ibm> Transflective nonradiant display device
JPH07168026A (en) * 1993-12-15 1995-07-04 Shimura Kaken Kogyo Kk Light guiding plate and luminaire using it
JPH09269489A (en) * 1996-02-02 1997-10-14 Hitachi Ltd Manufacture of liquid crystal display device and light transmission plate for rear illuminating part
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JPH1152370A (en) * 1997-07-31 1999-02-26 Hitachi Ltd Liquid crystal display device

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