USRE35704E - Plane light source unit - Google Patents

Plane light source unit Download PDF

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Publication number
USRE35704E
USRE35704E US08/267,380 US26738094A USRE35704E US RE35704 E USRE35704 E US RE35704E US 26738094 A US26738094 A US 26738094A US RE35704 E USRE35704 E US RE35704E
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United States
Prior art keywords
light
light emitting
light source
source unit
plane
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US08/267,380
Inventor
Ithussei Chiba
Makoto Oe
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Mitsubishi Rayon Co Ltd
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Mitsubishi Rayon Co Ltd
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Priority to US08/267,380 priority Critical patent/USRE35704E/en
Priority to US08/887,112 priority patent/USRE38243E1/en
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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/0035—Means for improving the coupling-out of light from the light guide provided on the surface of the light guide or in the bulk of it
    • G02B6/0038—Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G02B6/0053—Prismatic sheet or layer; Brightness enhancement element, sheet or layer
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G02B6/0055—Reflecting element, sheet or layer
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0066—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form characterised by the light source being coupled to the light guide
    • G02B6/0068—Arrangements of plural sources, e.g. multi-colour light sources
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F13/00—Illuminated signs; Luminous advertising
    • G09F13/18—Edge-illuminated signs
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0066—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form characterised by the light source being coupled to the light guide
    • G02B6/007—Incandescent lamp or gas discharge lamp
    • G02B6/0071—Incandescent lamp or gas discharge lamp with elongated shape, e.g. tube
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/04—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres

Definitions

  • FIG. 1 shows general construction of a liquid crystal color TV set.
  • reference numeral 1 denotes a liquid crystal display
  • 2 a body of the liquid crystal color TV set
  • 3 a normal line to the liquid crystal display 1
  • 4 an eye of an observer.
  • the liquid crystal display 1 is tilted upwardly at an angle of about 45 degrees with respect to the body 2 and is normally observed by an observer in a direction at an angle of about 15 degrees with respect to the normal line 3.
  • a backlighting means which presents a higher luminance within a particular angular range indicated by X than at any other angular position would be advantageous in that the amount of emitted light can be concentrated to the particular angular range.
  • the luminance of such a plane light source will exhibit a maximum value in a desired direction, which may be several times greater than a luminance value of an alternative plane light source of the type which emits light uniformly in all directions. Accordingly, if the backlighting means is used in a display device which has a narrow viewing angle in a particular direction, the display device can present a high luminance with a small power consumption.
  • a plane light source device of the type wherein a reflector having a parabolic section is disposed below a lamp as described hereinabove has a thickness substantially equal to twice to four times the diameter of the lamp. Accordingly, the light source device just mentioned cannot meet the requirement of small size.
  • FIGS. 2(a) and 2(b) are schematic sectional views of a conventional plane light source device
  • FIGS. 6(a) and 6(b) are diagrammatic representations illustrating paths of rays of light passing through a prism
  • FIGS. 10 and 11 are schematic sectional views showing different plane light source units according to the present invention together with lamp;
  • FIGS. 13 and 14 are schematic sectional views but showing still further different plane light source unit according to the present invention.
  • FIG. 15 is a schematic view illustrating an example of lens unit of a first element
  • FIGS. 16(a), 16(b) and 16(c) are diagrams showing angular distributions of light in the case of the example 1-1;
  • FIGS. 17(a), 17(b) and 17(c) are diagrams showing angular distributions of light in the case of another example 1-2;
  • FIGS. 18(a), 18(b) and 18(c) are diagrams showing angular distributions of light in the case of a further example 1-3;
  • FIGS. 19(a) and 19(b) are diagrams showing angular distributions of light in the case of a plane light source device of a comparative example
  • FIG. 20 is a schematic sectional view showing a first element wherein lens units are triangular pole-shaped lenticular lenses;
  • FIG. 21 is a schematic sectional view showing another first element wherein lens units are concave cylindrical lenticular lenses
  • FIG. 22 is a schematic sectional view showing a further first element wherein lens units are convex polygonal pole-shaped lenticular lenses;
  • FIGS. 23(a) and 23(b) are schematic sectional views showing still further first elements wherein lens units are different anisotropic lenticular lenses;
  • FIG. 24 is a diagrammatic sectional view illustrating a manner of measuring angular distributions of light from a first element of reverse type
  • FIGS. 25(a) and 25(b) are diagrams showing angular distributions of light emitted by first elements in the case of the front and reverse types, respectively, wherein convex cylindrical lenticular lenses are employed;
  • FIGS. 28(a) and 28(b) are diagrams showing angular distributions of light emitted by first elements in the case of the front and reverse types, respectively, wherein polygonal pole-shaped lenticular lenses are employed;
  • FIGS. 31(a) and 31(b) are diagrams showing angular distributions of light emitted by plane light source units of the front and reverse types which employ convex cylindrical lenticular lenses, respectively;
  • FIGS. 32(a) and 32(b) are diagrams showing angular distributions of light emitted by plane light source units of the front and reverse types which employ triangular pole-shaped lenticular lenses, respectively;
  • FIGS. 33(a) and 33(b) are diagrams showing angular distributions of light emitted by plane light source units of the front and reverse types which employ concave cylindrical lenticular lenses, respectively;
  • FIGS. 34(a) and 34(b) are diagrams showing angular distributions of light emitted by plane light source units of the front and reverse types which employ polygonal pole-shaped lenticular lenses, respectively;
  • FIGS. 36(a) to 36(f) are diagrams showing angular distributions of light emitted by different surface light source units of the present invention.
  • FIG. 3(a) is a schematic perspective view showing such a construction described just above
  • FIG. 3(b) is a schematic sectional view taken along line A--A' of FIG. 3(a).
  • the direction of emitted light falls within an angular range of 40 to 60 degrees with respect to the normal line to the imaginary plane of the light emitting surface having convex lenses 16, and little light is emitted in the normal line direction (refer to FIG. 3(b)).
  • FIGS. 4(a) and 4(b) are diagrams illustrating angular distributions of light illustrated in FIG. 3(b) within a plane perpendicular to the direction of the convex lenses 16.
  • the diagrams show rates of luminance at various angles where the maximum luminance value is represented by 100 percent.
  • a plane light source unit of the present invention is constructed in its principle such that a number of lenses such as the lenses 16 are employed wherein light emitted through the lenses is concentrated in a particular direction so that the distribution of light falls within a narrow range and besides the amount of emitted light is large, and the light emitted toward the opposite sides of the normal line such as the lights 20, 21 illustrated in FIG. 3(b) are refracted by a set of prisms serving as a second element so as to concentrate the light in a desired direction.
  • FIGS. 6(a) and 6(b) are diagrammatic representations showing one of such prisms of the second element as described just above.
  • reference numerals 20 and 21 represent emergent rays of light in the rightward and leftward directions, respectively, from the lens set 16 of the first element
  • ⁇ 1 and ⁇ 2 represent angles made by the normal lines and surfaces 31 and 30 of the prism, respectively
  • reference numeral 32 represents an emergent surface (a second light emitting surface) of the prism.
  • reference symbols ⁇ 1 to ⁇ 6 and ⁇ 1 to ⁇ 6 denote angles of rays with respect to the individual surfaces of the prism or reference lines. The angles are taken as shown in FIGS. 6(a) and 6(b).
  • the configuration of the lenses 16 of the first element is not particularly limited and may by any one if emergent rays of light are concentrated in a particular direction so that the distribution of emitted light falls within a narrow range and besides the amount of emitted light is large.
  • the lights 20, 21 may not always be emitted symmetrical to each other with respect to the normal line depending upon a configuration of the lens set 16 of the first element, in such a case the light can be emitted by the second element in a desired direction by varying the prism angles ( ⁇ 1 and ⁇ 2 of FIG. 6) of each prism which is a component unit of a prism set of the second element.
  • FIGS. 8(a) to 8(f) are diagrams illustrating angular distributions of light shown in FIG. 7(b).
  • FIGS. 8(a) to 8(f) illustrate rates of luminance at various angles where the maximum luminance value is represented by 100 percent (samples for measurement and measuring methods will be described below).
  • the present invention is made on a principle that, making use of a light guide (first element) which has a mat finished emitting surface wherein emitted light is concentrated in a particular direction so that the distribution of light falls within a narrow range and the amount of emitted light is large, light 20 and 21 (refer to FIG. 7(b)) emitted toward the opposite sides of the normal line i are all refracted by a prism set serving as a second element to concentrate the light in a desired direction.
  • reference numeral 14 represents a light source such as a fluorescent lamp, 15 a reflector, 13 a reflecting layer formed on the opposite side to a first light emitting surface 12 of a first element 50, 16 a lens unit like the lens described hereinabove, 40 a prism unit, and a second light emitting surface 32.
  • the lens units 16 and the prism units 40 have convex linear configurations extending in a direction parallel to the light source (lamp).
  • the plane light source unit of the present embodiment thus comprises a first element 50 having a light incident face at least at one side end 11 of a light guide and a first light emitting surface which extends in a perpendicular direction to the incident face and on which the lens unit 16 are formed, the first element 50 further having a reflecting layer 13 on the opposite surface of the light guide to the first light emitting surface, and a second element 51 having an incident surface on which the prism units 40 into which light from the first element 50 is introduced in predetermined directions are formed and a second light emitting surface 32.
  • Light rays emerging from the individual lens units 16 are caused to emerge from the second element as represented by light rays 54 and 55, and the object of the invention can be attained by setting the lens units and the prism units such that the angles ⁇ 6 and ⁇ 6 may be substantially equal to each other.
  • light emitted through the second light emitting surface 32 of the second element can be concentrated in the normal line direction as represented by light rays 56 and 57.
  • a linear light source having continuous configuration for example, a filament lamp may be employed instead.
  • n represents a refraction index of a material which constitutes the element.
  • the emergent angles of emergent light rays from the prisms calculated in accordance with the expressions given above are concentrated on the one side with respect to the normal line (only examples of calculations are given wherein the difference in emergent angle between two light rays from the left and right sides falls within 2 degrees).
  • ⁇ 55 degrees (only examples of calculations are given wherein the difference in emergent angle between two light rays from the left and right sides falls within 2 degrees).
  • the lens units 16 are formed on the first light emitting surface of the light guide of the first element 50, similar effects can be attained otherwise by forming lens units on a surface opposite to the first light emitting surface of the light guide of the first element or else by forming lens units on both of the light emitting surface and the opposite surface of the light guide if characteristics of the lens units are suitably selected.
  • FIG. 12 is a partial sectional view of a plane light source unit together with a lamp showing a further embodiment of the present invention.
  • reference numeral 14 represents a light source such as a fluorescent lamp, 15 a reflector, 13 a reflecting layer formed on the opposite side to a first light emitting surface 12 of a first element 50, and 60 a mat finished first light emitting surface, which is substantially parallel to the reflecting layer 13.
  • Reference numeral 40 represents a prism unit of a second element, and 32 a second light emitting surface of the prism units 40.
  • the prism units 40 have a convex linear configuration extending in a direction parallel to the light source (lamp).
  • the plane light source unit of the present embodiment thus comprises a first element 50 having a light incident face at least at one side end 11 thereof and a mat finished first light emitting surface 12 which extends a perpendicular direction to the incident face, the first element 50 further having a reflecting layer 13 on the opposite surface thereof to the first light emitting surface, and a second element 51 having an incident surface on which the prism units 40 into which light from the first element 50 is introduced and from which light rays emerge in predetermined directions are formed and a second light emitting surface 32.
  • Light rays emerging from the first element are caused to emerge from the second element as represented by light rays 54 and 55, and the object of the invention can be attained by setting the prism units such that the angles ⁇ 6 and ⁇ 6 may be substantially equal to each other.
  • FIGS. 13 and 14 are partial sectional views of plane light source unit together with a lamp, showing still further embodiments of the present invention.
  • a first element (light guide) 50-1 has such a configuration that the opposite side to a first light emitting surface 12 is formed as mat finished surface 60 and is disposed opposing to a reflecting layer 13, and the first light emitting surface 12 of the first element 50-1 is formed as a smooth surface.
  • FIG. 14 shows an example of construction wherein a first element 50-2 is used in which upper and lower surfaces are formed as mat finished surfaces 60.
  • an imaginary plane of mat finished first light emitting surface of a light guide extends substantially in a parallel relationship to the reflecting layer 13 in the present invention means that the first element is a member in the form of a plate having a uniform thickness, and therefore the present invention has an advantage that it employs a transparent member which can be readily produced and assembled.
  • the lens pattern of the metal mold was transferred to an acrylic resin plate having a thickness of 5 mm by thermal press work to make a first element.
  • the two opposite sides of the first element having the length of 61 mm were polished by a conventional polishing method while aluminum vacuum deposited polyester films with an adhesive layer were applied to the other opposite sides having the width of 56 mm, and another silver vacuum deposited polyester film was secured on the surface opposing to the transferred lens surface.
  • a fluorescent lamp having a diameter of 8 mm and a length of 90 mm (FLE-8.90 ADIPS 3 by Elevam Corp.) was arranged on each of the two sides of 61 mm length of the first element, and a reflector made of aluminum foil was applied to each of the lamps. Each lamp was then lit by means of DC 5 V power supply with an invertor.
  • Luminance was then measured at the points near the lamps and the central point on a center line of the first element (refer to FIG. 5(a)) at various angles with respect to the normal line by means of a luminance meter (luminance meter nt-1 by Minolta Camera Co., Ltd.), and angular distributions of light were determined (refer to FIG. 5(b)).
  • luminance meter nt-1 by Minolta Camera Co., Ltd.
  • the second element was arranged on the first element with the prism side of the former opposed to the lens side of the latter and was secured to the sides of the image by means of double-sided adhesive tapes having a width of about 5 mm. Then, similar measurements to those of the first element were carried out by a quite same method, and angular distributions of light were determined. The data thus obtained are illustrated in FIGS. 16(a), 16(b) and 16(c). Maximum luminance values and angles at which the maximum luminance value was observed are listed in Table 2 below.
  • angles at which the maximum luminance value was observed fall within a narrow range from 12 to 20 degrees, and the half-width of angular distribution is about 40 degrees.
  • Acrylic resin pellet (HIPET HBS trade mark! by Mitsubishi Rayon Co., Ltd.) was dry-blended with 1.5 percent by weight of rutile type titanium oxide and molded into a film of 50 microns thickness by a conventional extruder. The film was extended on an inorganic flat glass plate so as not to include air bubbles, and after being provisionally secured with methylmethacrylate, a cell was formed with glass plates by means of a spacer in a conventional manner. Methylmethacrylate syrup was poured in the clearance of the cell and polymerized to cure by a conventional manner to obtain an acrylic resin plate of 5 mm thickness.
  • the plate produced in this manner was cut into a size of 61 mm length ⁇ 56 mm width, and the two sides of 61 mm length were polished in a conventional manner while aluminum vacuum deposited films with an adhesive layer were adhered to the other opposite sides of 56 mm width, whereafter a silver vacuum deposited polyester film (similar to that of the example 1-1) was arrange on the surface opposite to a white thin layer formed on the surface of the plate. Subsequently, evaluation was made by a quite same method as the measuring method of the first element of the example 1-1. The resultant data are illustrated in FIGS. 19(a) and 19(b). Meanwhile, luminance values at the specific points are listed in Table 5 below.
  • the plane light source unit produced in comparative example has a characteristic that light is emitted uniformly in all directions
  • the plane light source unit produced in accordance with the present invention has advantages that light is emitted in particular direction and that the maximum luminance value at the central point is higher, about 3.5 times, than that obtained in comparative example.
  • the lenses 16 of the first element may have any configuration only if light is concentrated in particular directions so that the angular distribution of light falls within narrow ranges and the amount of emitted light is large, and the configuration of the lenses 16 is not particularly limited.
  • first elements having lenses of the following configurations were produced including the first element of the convex cylindrical lenticular lenses in the examples 1-1 to 1-3 described hereinabove.
  • Thickness of the first element t 6 mm.
  • Triangular pole-shaped lenticular lens which has such a configuration as shown in FIG. 20 and wherein
  • Thickness of the first element t 6 mm.
  • Thickness of the first element t 6 mm.
  • Thickness of the first element t 6 mm.
  • Thickness of the first element t 6 mm.
  • Anisotropic lenticular lens B which has such a configuration as shown in FIG. 23(b) and wherein
  • the first elements were produced by transferring lens patterns to acrylic resin plates of 6 mm thickness by thermal press work using metal molds which have individually such predetermined configurations as described above.
  • FIG. 26(a) illustrates the angular distribution of light from the first element of the front type in which the triangular pole-shaped lenticular lenses were employed. Meanwhile, the angular distribution of light from the first element of the reverse surface type is illustrated in FIG. 26(b). The maximum luminance value appeared in the direction of 70 to 80 degrees from the normal line in the case of the first element of the front type but in the direction of 30 to 35 degrees from the normal line in the case of the first element of the reverse type.
  • FIG. 28(a) illustrates the angular distribution of light from the first element of the front type in which the convex polygonal pole-shaped lenticular lenses were employed. Meanwhile, the angular distribution of light from the first element of the reverse type is illustrated in FIG. 28(b). The maximum luminance value appeared in the direction of 75 to 80 degrees from the normal line in the case of the first elements of both of the front and reverse types.
  • FIG. 29(a) The angular distribution of light from the front element in which the anisotropic lenticular lenses A were employed is illustrated in FIG. 29(a). Meanwhile, the angular distribution of light from the first element in which the anisotropic lenticular lenses B were employed is illustrated in FIG. 29(b).
  • the maximum luminance value appeared in the direction of about 60 degrees from the normal line in the case of the first element in which the anisotropic lenticular lenses A were employed and in the direction of about 50 degrees from the normal line in the case of the first element in which the anisotropic lenticular lenses B were employed.
  • a silver vacuum deposited polyester film was secured on the lens surface of each of the first elements, and the second element described hereinabove (substantially same as that used in the examples 1-1 to 1-3) was placed on the surface opposing to the lens surface of each of the first elements to produce plane light source units of a construction in which the lens surface 16 is located on the opposite side to the emitting surface 12 of the first element (i.e., the reverse type).
  • plane light source units of the front and reverse types wherein the concave lenticular lenses were employed are shown in FIGS. 30(a) and 30(b), respectively.
  • the luminance is a little lower in the case of the reverse type than in the case of the front type, but the difference is very little. Accordingly, they can be satisfactory for practical use whether the first elements are either of the front type or of the reverse type.
  • Angular distributions of light from the individual plane light source units at the central point (point of 1 of FIG. 5(a)) were measured in accordance with the measurements of angular distributions of light from the first elements described hereinabove.
  • FIG. 31(b) shows the angular distribution of light from the plane light source unit of the reverse type in which the first element having the convex cylindrical lenticular lenses of the configuration shown in FIG. 15 was employed. Meanwhile, the angular distribution of light from the plane light source unit of the front type is shown in FIG. 31(a).
  • the maximum luminance value appeared in the direction of 15 to 20 degrees and the half-width was about 57 degrees.
  • the maximum luminance value appeared in the direction of 15 to 20 degrees and the half-width was about 77 degrees.
  • FIG. 32(a) shows the angular distribution of light from the plane light source unit of the front type in which the first element having the triangular pole-shaped lenticular lenses was employed. Meanwhile, the angular distribution of light from the plane light source unit of the reverse type is shown in FIG. 32(b).
  • the maximum luminance value appeared in the direction of 13 to 15 degrees and the half-width was about 75 degrees.
  • the maximum luminance value appeared in the direction of 15 to 17 degrees and the half-width was about 90 degrees.
  • FIG. 34(a) shows the angular distribution of light from the plane light source unit of the front type in which the first element having the convex polygonal pole-shaped lenticular lenses was employed. Meanwhile, the angular distribution of light from the plane light source unit of the reverse type is shown in FIG. 34(b).
  • the maximum luminance value appeared in the direction of 15 to 17 degrees and the half-width was about 85 degrees.
  • the maximum luminance value appeared in the direction of 13 to 15 degrees and the half-width was about 65 degrees.
  • the first element emits the light symmetrically or asymmetrically with respect to the normal line as seen in FIGS. 25(a) to 29(b)
  • the light is emitted by the second element in particular direction as seen in FIGS. 31(a) to 35(b) and Table 6 above and the maximum luminance value is sufficient for practical use, about 2 to 3.5 times that of the cases of non-directional light emission, provided that the second element has an appropriate configuration.
  • a surface of a metal plate was treated by a conventional honing technique wherein glass beads of 60 mesh were blown to one face of a polished brass plate (about 3 mm ⁇ 250 mm ⁇ 250 mm) to produce a metal mold having a mat finished surface.
  • a polished brass plate about 3 mm ⁇ 250 mm ⁇ 250 mm
  • the mat pattern w s transferred to one surface of each of acrylic resin plates having a thickness of 5 mm by thermal press work to make a first element.
  • Specimens of a 50 ⁇ 50 mm size were cut off from the acrylic resin plate of 5 mm thickness having a mat finished surface produced in the preceding step (1) to obtain samples for measurement of haze values.
  • a transparent acrylic resin plate was cut similarly into pieces of a 50 ⁇ 50 mm size.
  • the acrylic resin plates were cut into pieces of 61 mm long ⁇ 56 mm wide, and the two sides of 61 mm length of each of the pieces were polished by a conventional method while aluminum vacuum deposited polyester films with an adhesive layer were adhered to the other two sides of 56 mm width. Then, a silver vacuum deposited polyester film was secured on a surface opposing to the mat finished surface, and then a fluorescent lamp having a diameter of 7 mm and a length of 245 mm (CB7-245W cold cathode tube by Stanley Electric Co., Ltd.) was arranged on each of the two sides of 61 mm length with aluminum foil applied as a reflector, whereafter the lamp was lit by means of DC 12 V power supply with an invertor.
  • a fluorescent lamp having a diameter of 7 mm and a length of 245 mm (CB7-245W cold cathode tube by Stanley Electric Co., Ltd.) was arranged on each of the two sides of 61 mm length with aluminum foil applied as a reflector, whereafter
  • Luminance was measured at the central point (point 1 shown in FIG. 9(a)) of the thus obtained first elements at various angles with respect to the normal line by means of a luminance meter (luminance meter nt-1 by Minolta Camera Co., Ltd.) to obtain angular distributions of light (refer to FIG. 9(b)).
  • FIGS. 8(a) to 8(d) The data obtained in this manner are listed in Table 8 below and illustrated in FIGS. 8(a) to 8(d).
  • a luminance value is represented in a radial direction and a light emergent angle is represented in a circumferential direction,.
  • Data of the sample-5 and the comparative sample are omitted from Table 8 below because the amount of emitted light is too small in any direction to attain accurate measurement.
  • luminance values of lamp surface at the central portion were 5,000 and 5,200 cd/cm 2 .
  • the aforementioned second element was cut into pieces of 61 mm length and 56 mm width such that the multi-prisms thereof might extend in parallel to the longitudinal edges of the pieces, and the second element pieces were arranged on the first elements such that the prism surfaces thereof might face the first light emitting surfaces of the first elements whereafter they were secured along the sides of the lamps (the sides of 61 mm length) with double-sided adhesive tapes of about 5 mm width to produce plane light source units according to the present invention.
  • Angular distributions of light from the plane light source units were measured by a quite similar method as the method of evaluation of angular distributions of light from the first elements described hereinabove. Results of the measurements are listed in Table 9 below and illustrated in FIGS. 36(a) to 36(d).
  • the mat pattern was transferred to both surfaces of an acrylic resin plate of 5 mm thickness to make a sample-6. This sample corresponds to the first element 50-2 shown in FIG. 14.
  • a haze value of the sample-6 was measured by a quite same method as in the example 3 described above.
  • sample-7 corresponds to the light guide 50-1 shown in FIG. 13. Results of measurements of angular distributions of light are listed in Table 10 below and illustrated in FIGS. 8(e) and 8(f).
  • Luminance values of lamp surface at the central portion were 5,000 and 5,200 cd/m 2 .
  • Plane light source units were produced, and angular distributions of light from the plane light source units were measured in a quite similar manner as in the example 3 described above.
  • Acrylic resin pellet (HIPET HBS trade mark! by Mitsubishi Rayon Co., Ltd.) was dry-blended with 1.5 percent by weight of rutile type titanium oxide and molded into a film of 50 microns thickness by a conventional extruder.
  • the film was extended on an inorganic flat glass plate so as not to include air bubbles, and after being provisionally secured with methylmethacrylate, a cell was formed with glass plates by means of a spacer in a conventional manner.
  • Methylmethacrylate syrup was poured in the clearance of the cell and polymerized to cure to a conventional manner to polymerize and solidify the film to obtain an acrylic resin plate of 5 mm thickness.
  • the plate produced in this manner was cut into a size of 61 mm length ⁇ 56 mm width, and the two sides of 61 mm length were polished in a conventional manner while aluminum vacuum deposited films with an adhesive layer were applied to the other opposite sides of 56 mm width, whereafter a silver vacuum deposited polyester film was arranged on the surface opposite to a white thin layer formed on the surface of the plate. Subsequently, measurements similar to those of the first elements described hereinabove were made by a quite same method to determine angular distribution of light. The resultant data are listed in Table 12 below and illustrated in FIG. 37.
  • the plane light source unit of the present invention is advantageous in that light is emitted in particular direction and that the maximum luminance value at the central point is higher, about 3.5 to 4 times, than that obtained in comparative example.
  • a plane light source unit was produced and an angular distribution of light was measured in a quite similar manner as in the example 3 described hereinabove.
  • Results of measurement of maximum luminance value of the first element are listed in Table 13 below while results of measurement of maximum luminance value of the plane light source unit are listed in Table 14 below, and an angular distribution of light from the plane light source unit is illustrated in FIG. 38.
  • the plane light source unit was produced wherein light could be emitted in the normal line direction to the picture plane.
  • a plane light source unit can be provided wherein light can be emitted readily at a desired direction without increasing the power consumption of a light source and which has a decreased thickness (substantially equal to a diameter of a lamp) and is advantageous for backlighting means for a display device which has a directivity of viewing angle such as a liquid crystal display device;
  • Directive light can be obtained readily using a fluorescent lamp which primarily is a source of diffused light, and a desired direction of emitted light can be determined readily similar to focusing of a convex lens.

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Abstract

A plane light source unit is provided which comprises a first element having a light incident face at least at one side end thereof and a first light emitting surface extending perpendicularly to the light incident face, the first element further having a reflecting layer provided on a surface thereof opposite to the first light emitting surface, and a second element having a light incident surface which receives the light emitting by the first element and a second light emitting surface through which light is emitted in a predetermined direction, the first light emitting surface and/or the opposite surface of the first element having a directive function to cause incident light through the light incident face to emit through the first light emitting surface in a direction oblique to the direction of the light, the second element having a large number of prism units formed on the light incident surface thereof. The plane light source unit is advantageously used as a backlighting means for a liquid crystal display device or the like.

Description

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a plane light source unit, and more particularly to a plane light source unit which is applied advantageously as a backlighting means for a liquid crystal display device or the like.
2. Description of the Prior Art
Conventionally, a backlighting means for a liquid crystal display or the like generally has such a construction that a lamp is located at a focus of a reflector having a parabolic section while a milk-white diffusing plate is located above the lamp. Various inventions have been made to optimize the configuration of a reflector, to adjust the diffusion coefficient of a diffusing plate, and so on.
Special constructions have also been provided which employ such a combination of a linear lamp and a light guide, one side end of which is adjacent to the lamp, and the configuration of the light guide is simulated by approximation to a point source and worked into a curved surface so as to emit the light in a particular direction, or the thickness of the light guide is varied along the direction of light, or else a lenticular is used wherein the prism angle is varied in accordance with the distance from the lamp, or otherwise such configurations as described above are combined suitably. With approximation to a point source, a light path can be simulated in almost every case, and it is possible to change the configuration of a light guide in accordance with the distance in the light direction depending upon such simulation. Such proposals have been made in a large number of patents and utility model registrations. Such plane light sources are disclosed, for example, in U.S. Pat. Nos. 4,126,383, 4,043,636, 4,059,916, 4,373,282, 4,285,889, 4,252,416, 3,546,438, 4,642,736 and 4,648,690 and Japanese Patent Laid-Open No. 62-278505.
While almost all of plane light sources are designed to emit light as uniformly as possible in all directions, it may be sometimes desired to concentrate emitted light in a particular direction depending upon application of a plane light source.
For example, in the case of application to a liquid crystal color TV set for personal use having a comparatively small viewing angle, it is required to emit the light only in a particular direction and make the amount of emitted light as uniform as possible over an entire emitting surface. FIG. 1 shows general construction of a liquid crystal color TV set. Referring to FIG. 1, reference numeral 1 denotes a liquid crystal display, 2 a body of the liquid crystal color TV set, 3 a normal line to the liquid crystal display 1, and 4 an eye of an observer. With the arrangement of the type mentioned, the liquid crystal display 1 is tilted upwardly at an angle of about 45 degrees with respect to the body 2 and is normally observed by an observer in a direction at an angle of about 15 degrees with respect to the normal line 3. Accordingly, a backlighting means which presents a higher luminance within a particular angular range indicated by X than at any other angular position would be advantageous in that the amount of emitted light can be concentrated to the particular angular range. In particular, the luminance of such a plane light source will exhibit a maximum value in a desired direction, which may be several times greater than a luminance value of an alternative plane light source of the type which emits light uniformly in all directions. Accordingly, if the backlighting means is used in a display device which has a narrow viewing angle in a particular direction, the display device can present a high luminance with a small power consumption.
However, a point source is not used as the light source for a backlighting means of the liquid crystal color TV set shown in FIG. 1 or the like except very rare special cases where the display has a small area. A light source actually used is generally such a volume light source as a fluorescent lamp which cannot be regarded as a point source and is very low in coincidence of approximation to a point source. Accordingly, while such plane light sources as have been proposed in the prior art have accurate and complicated configurations and require a high production cost, it is difficult for them to achieve such desired characteristics as described above.
Besides, light emitted by such a volume light source as a fluorescent lamp is diffused light and non-directive. In a strict sense, it is very difficult to assure a desired directivity using a diffused light emitting source.
Further, i order to obtain a plane light source of small size, it is preferable to make its greatest thickness substantially equal to the diameter of a light source lamp. However, a plane light source device of the type wherein a reflector having a parabolic section is disposed below a lamp as described hereinabove has a thickness substantially equal to twice to four times the diameter of the lamp. Accordingly, the light source device just mentioned cannot meet the requirement of small size.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a plane light source unit which has a reduced thickness substantially equal to the diameter of a lamp so that it is suitable for backlighting for a display device such as a liquid crystal color TV set which is small in size with a small viewing angle.
It is another object of the present invention to provide a plane light source unit which can readily produce light concentrated in a direction to be observed by a user without increasing power consumption.
In order to attain the objects, according to the present invention, there is provided a plane light source unit which comprises a first element having a light incident face at least at one side end thereof and a first light emitting surface extending perpendicularly to the light incident face, the first element further having a reflecting layer provided on a surface thereof opposite to the first light emitting surface, and a second element having a light incident surface which receives the light emitted by the first element and a second light emitting surface through which light is emitted in a predetermined direction, the first light emitting surface and/or the opposite surface of the first element having a directive function to cause incident light through the light incident face to emit through the first light emitting surface in a direction oblique to the direction of the light, the second element having a large number of prism units formed on the light incident surface thereof.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic representation illustrating relative angles of a liquid crystal color TV set in an observed condition;
FIGS. 2(a) and 2(b) are schematic sectional views of a conventional plane light source device;
FIGS. 3(a) and 3(b) are a schematic perspective view and a schematic sectional view, respectively, showing a first element of a plane light source unit of the present invention together with lamp units;
FIGS. 4(a) and 4(b) are diagrams showing angular distributions of light emitted by a first element of an example 1-1 of the present invention;
FIG. 5(a) is a schematic front elevational view illustrating a method of measuring angular distributions of light emitted by a plane light source unit of the present invention, and FIG. 5(b) is a diagrammatic representation as viewed in a direction indicated by arrow marks A--A' of FIG. 5(a);
FIGS. 6(a) and 6(b) are diagrammatic representations illustrating paths of rays of light passing through a prism;
FIGS. 7(a) and 7(b) are a schematic perspective view and a schematic sectional view, respectively, showing a first element of a plane light source unit of the present invention together with lamp units;
FIGS. 8(a) and 8(b) are diagrams showing angular distributions of light from different first elements of the present invention;
FIGS. 9(a) and 9(b) are diagrammatic representations illustrating a method of measuring an angular distribution of light;
FIGS. 10 and 11 are schematic sectional views showing different plane light source units according to the present invention together with lamp;
FIG. 12 is a schematic sectional view but showing a further different plane light source unit according to the present invention;
FIGS. 13 and 14 are schematic sectional views but showing still further different plane light source unit according to the present invention;
FIG. 15 is a schematic view illustrating an example of lens unit of a first element;
FIGS. 16(a), 16(b) and 16(c) are diagrams showing angular distributions of light in the case of the example 1-1;
FIGS. 17(a), 17(b) and 17(c) are diagrams showing angular distributions of light in the case of another example 1-2;
FIGS. 18(a), 18(b) and 18(c) are diagrams showing angular distributions of light in the case of a further example 1-3;
FIGS. 19(a) and 19(b) are diagrams showing angular distributions of light in the case of a plane light source device of a comparative example;
FIG. 20 is a schematic sectional view showing a first element wherein lens units are triangular pole-shaped lenticular lenses;
FIG. 21 is a schematic sectional view showing another first element wherein lens units are concave cylindrical lenticular lenses;
FIG. 22 is a schematic sectional view showing a further first element wherein lens units are convex polygonal pole-shaped lenticular lenses;
FIGS. 23(a) and 23(b) are schematic sectional views showing still further first elements wherein lens units are different anisotropic lenticular lenses;
FIG. 24 is a diagrammatic sectional view illustrating a manner of measuring angular distributions of light from a first element of reverse type;
FIGS. 25(a) and 25(b) are diagrams showing angular distributions of light emitted by first elements in the case of the front and reverse types, respectively, wherein convex cylindrical lenticular lenses are employed;
FIGS. 26(a) and 26(b) are diagrams showing angular distributions of light emitted by first elements in the case of the front and reverse types, respectively, wherein triangular pole-shaped lenticular lenses are employed;
FIGS. 27(a) and 27(b) are diagrams showing angular distributions of light emitted by first elements in the case of the front and reverse types, respectively, wherein concave cylindrical lenticular lenses are employed;
FIGS. 28(a) and 28(b) are diagrams showing angular distributions of light emitted by first elements in the case of the front and reverse types, respectively, wherein polygonal pole-shaped lenticular lenses are employed;
FIGS. 29(a) and 29(b) are diagrams showing angular distributions of light emitted by first elements in the case of the front and reverse types, respectively, wherein different anisotropic lenticular lenses are employed;
FIGS. 30(a) and 30(b) are schematic sectional views showing different plane light source units of the front and reverse types which employ different concave cylindrical lenticular lenses, respectively, together with lamp;
FIGS. 31(a) and 31(b) are diagrams showing angular distributions of light emitted by plane light source units of the front and reverse types which employ convex cylindrical lenticular lenses, respectively;
FIGS. 32(a) and 32(b) are diagrams showing angular distributions of light emitted by plane light source units of the front and reverse types which employ triangular pole-shaped lenticular lenses, respectively;
FIGS. 33(a) and 33(b) are diagrams showing angular distributions of light emitted by plane light source units of the front and reverse types which employ concave cylindrical lenticular lenses, respectively;
FIGS. 34(a) and 34(b) are diagrams showing angular distributions of light emitted by plane light source units of the front and reverse types which employ polygonal pole-shaped lenticular lenses, respectively;
FIGS. 35(a) and 35(b) are diagrams showing angular distributions of light emitted by plane light source units of the front and reverse types which employ different anisotropic lenticular lenses;
FIGS. 36(a) to 36(f) are diagrams showing angular distributions of light emitted by different surface light source units of the present invention;
FIG. 37 is a diagram showing an angular distribution of light emitted by a surface light source device of comparative example; and
FIG. 38 is a diagram showing an angular distribution of light emitted by a plane light source unit of the θ1 =θ2 type according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Prior to description of the preferred embodiments of the present invention, a basic concept of a plane light source unit according to the present invention will be described.
The refractive index of a light guide with respect to air is generally n=1.5 to 1.6 or so, and in the case of such a configuration as shown in FIG. 2(a) wherein a light incident face 11 and a light emitting surface 12 of a light guide 10 extend in perpendicular directions to each other (i.e., edge lighting configuration), the critical angle is about 45 degrees at which no light is emitted through the surface 12 in principle. It is to be noted that, in FIG. 2(a), reference numeral 14 represents a light source such as a fluorescent lamp, 15 a reflector for the fluorescent lamp 15, and 13 a reflecting layer formed on the opposite side of the light guide 10 to the surface 12.
Generally, either the surface 12 is formed into a light diffusing surface 12a or the reflecting layer 13 is formed into a light diffusing reflecting layer 13a as shown in FIG. 2(b). However, for the present object of directivity of emitted light, such means cannot be employed by itself because light emitted by the light guide 10 becomes diffused light.
Thus, construction of a device is considered wherein a number of linear convex lenses 16 of a same profile are formed, on an emitting surface such that they extend in the same direction while a reflecting layer 13 is formed on a surface opposite to the emitting surface, and linear light sources 14 such as fluorescent lamps are arranged in parallel to the linear convex lenses 16 at opposite ends, of the first element. FIG. 3(a) is a schematic perspective view showing such a construction described just above, and FIG. 3(b) is a schematic sectional view taken along line A--A' of FIG. 3(a).
With such a geometrical positional relationship, the direction of emitted light falls within an angular range of 40 to 60 degrees with respect to the normal line to the imaginary plane of the light emitting surface having convex lenses 16, and little light is emitted in the normal line direction (refer to FIG. 3(b)).
FIGS. 4(a) and 4(b) are diagrams illustrating angular distributions of light illustrated in FIG. 3(b) within a plane perpendicular to the direction of the convex lenses 16. In particular, the diagrams show rates of luminance at various angles where the maximum luminance value is represented by 100 percent.
FIGS. 5(a) and 5(b) are diagrammatic representations illustrating a luminance measuring method, and FIG. 5(a) is a front elevational view of a plane light source unit together with lamps showing positions at which luminance is measured, and FIG. 5(b) is a diagrammatic representation as viewed in a direction indicated by arrow marks A--A' of FIG. 5(a). In FIG. 5(b), reference numeral represents a luminance meter.
FIG. 4(a) shows an angular distribution of light at the central point 1 shown in FIG. 5(a) while FIG. 4(b) shows another angular distribution of light at another position 2 spaced by a distance of 10 mm from the lamp. It can be seen also from the graphs that there is little light emitted in the normal line direction.
Thus, a plane light source unit of the present invention is constructed in its principle such that a number of lenses such as the lenses 16 are employed wherein light emitted through the lenses is concentrated in a particular direction so that the distribution of light falls within a narrow range and besides the amount of emitted light is large, and the light emitted toward the opposite sides of the normal line such as the lights 20, 21 illustrated in FIG. 3(b) are refracted by a set of prisms serving as a second element so as to concentrate the light in a desired direction.
FIGS. 6(a) and 6(b) are diagrammatic representations showing one of such prisms of the second element as described just above. In FIGS. 6(a) and 6(b), reference numerals 20 and 21 represent emergent rays of light in the rightward and leftward directions, respectively, from the lens set 16 of the first element, θ1 and θ2 represent angles made by the normal lines and surfaces 31 and 30 of the prism, respectively, and reference numeral 32 represents an emergent surface (a second light emitting surface) of the prism. Further, reference symbols ψ1 to ψ6 and ψ1 to φ6 denote angles of rays with respect to the individual surfaces of the prism or reference lines. The angles are taken as shown in FIGS. 6(a) and 6(b).
Referring to FIG. 6(b), if a ray of light enters the prism from the right-hand side like a ray 21, it enters through the prism surface 30, then is totally reflected by the prism surface 31, and then emerges from the prism through the emergent surface 32 at a predetermined angle ψ6. To the contrary, referring to FIG. 6(a), if a ray of light enters the prism from the left-hand side like a ray 20, it enters through the prism surface 31 and then is totally reflected by the prism surface 30 whereafter it emerges at the predetermined angle φ6 from the prism through the emergent surface 32. The predetermined angles ψ6 and φ6 can be adjusted by the configuration of the lens units of the first element and the emergent angle from the lens set, the angles θ1 and θ2 and the refraction index n of the lens set.
It is to be noted that the configuration of the lenses 16 of the first element is not particularly limited and may by any one if emergent rays of light are concentrated in a particular direction so that the distribution of emitted light falls within a narrow range and besides the amount of emitted light is large. Further, while the lights 20, 21 may not always be emitted symmetrical to each other with respect to the normal line depending upon a configuration of the lens set 16 of the first element, in such a case the light can be emitted by the second element in a desired direction by varying the prism angles (θ1 and θ2 of FIG. 6) of each prism which is a component unit of a prism set of the second element.
It is to be noted that, as a special example of the present invention, where the first element emits the light at an angle of 60 degrees with respect to the normal line, the prism angles of the second element (θ1 and θ2 of FIG. 6) may be set to θ1 =θ2 =30 degrees in order to direct the light from the first element to the direction of the normal line.
Meanwhile, also as will be hereinafter described with reference to several embodiments of the present invention, the amount of light emitted by the light guide in the normal line direction i is very small (refer to FIG. 7(b)). Thus, the inventors examined a directivity of emitted light with a finely roughened surface formed by roughening a surface of a light guide serving as a first element as uniformly as possible. Such an examination revealed that almost all of light is emitted in directions of 70 to 80 degrees with respect to the normal line to the emitting surface. The present invention has been completed by an idea to combine the above light guide and a second element in order to change the direction of the light to the normal line direction. Here, the term "finely roughened surface" signifies a so-called "mat finished surface" and contains what a so-called "orange peel".
Construction of the first element is shown in a perspective view of FIG. 7(a). Referring to FIG. 7(a), a light emitting surface of the first element is mat finished uniformly while a reflecting layer 13 is formed on the opposite surface of the first element, and linear light sources 14 such as fluorescent laps are arranged at opposite ends of the first element. FIG. 7(b) is a sectional view taken along line A--A' of FIG. 7(a).
FIGS. 8(a) to 8(f) are diagrams illustrating angular distributions of light shown in FIG. 7(b). In particular, FIGS. 8(a) to 8(f) illustrate rates of luminance at various angles where the maximum luminance value is represented by 100 percent (samples for measurement and measuring methods will be described below).
FIGS. 9(a) and 9(b) are diagrammatic representations illustrating measuring methods, and FIG. 9(a) is a front elevational view showing a measuring point and FIG. 9(b) is a view in the direction indicated by arrow marks A--A' of FIG. 9(a). In FIG. 9(b), reference numeral 48 represents a luminance meter. The results of the measurements are shown in FIGS. 8(a) to 8(f) from which it can be seen that little light is emitted in a direction normal to the emitting surface but emitted light is concreted in particular directions of 75 to 80 degrees (as also seen in FIG. 7(b)). Thus, the present invention is made on a principle that, making use of a light guide (first element) which has a mat finished emitting surface wherein emitted light is concentrated in a particular direction so that the distribution of light falls within a narrow range and the amount of emitted light is large, light 20 and 21 (refer to FIG. 7(b)) emitted toward the opposite sides of the normal line i are all refracted by a prism set serving as a second element to concentrate the light in a desired direction.
The prisms of the second element which makes another component for the function described above are similar to that shown in FIGS. 6(a) and 6(b).
It is to be noted that since the light emitted through the mat finished surface 60 of the first element is symmetrical with respect to the normal line, desired angles (ψ6 and φ6) can be obtained by varying the prism angles (θ1 and θ2 of FIG. 6) and the refraction index of the second element.
In the following, particular construction of several plane light source units according to the present invention will be described in detail with reference to the drawings.
FIG. 10 is a partial sectional view showing an embodiment of plane light source unit according to the present invention together with a lamp and is a view corresponding to FIG. 3(b).
Referring to FIG. 10, reference numeral 14 represents a light source such as a fluorescent lamp, 15 a reflector, 13 a reflecting layer formed on the opposite side to a first light emitting surface 12 of a first element 50, 16 a lens unit like the lens described hereinabove, 40 a prism unit, and a second light emitting surface 32. It is to be noted that the lens units 16 and the prism units 40 have convex linear configurations extending in a direction parallel to the light source (lamp).
The plane light source unit of the present embodiment thus comprises a first element 50 having a light incident face at least at one side end 11 of a light guide and a first light emitting surface which extends in a perpendicular direction to the incident face and on which the lens unit 16 are formed, the first element 50 further having a reflecting layer 13 on the opposite surface of the light guide to the first light emitting surface, and a second element 51 having an incident surface on which the prism units 40 into which light from the first element 50 is introduced in predetermined directions are formed and a second light emitting surface 32. Light rays emerging from the individual lens units 16 are caused to emerge from the second element as represented by light rays 54 and 55, and the object of the invention can be attained by setting the lens units and the prism units such that the angles ψ6 and φ6 may be substantially equal to each other.
FIG. 11 is a diagrammatic representation showing an embodiment of plane light source unit wherein the lens units of the first element are set such that emergent light rays may emerge at angles of 60 degrees with respect to the normal line and the angles (θ1 and θ2 of FIG. 6) of the prism units of the second element 51 are set to θ1 θ2 =30 degrees. According to the embodiment, light emitted through the second light emitting surface 32 of the second element can be concentrated in the normal line direction as represented by light rays 56 and 57.
The elements of the plane light source unit of the present invention may be preferably made of such a material as an acrylic resin or a polycarbonate resin which has a higher transmittance to visible light to attain the object of small size and light weight, but the material of the elements need not be limited to such a specific material.
Further, while a small size fluorescent lamp is used as the light source 14, a linear light source having continuous configuration (for example, a filament lamp may be employed instead.
Subsequently, an example of determination of prism angles where the primary emergent rays from the first element emerge symmetrically to each other with respect to the normal line will be described. Also where the primary emergent rays do not emerge symmetrically to each other with respect to the normal line, prism angles can be determined in a similar manner. It is to be noted that a character n represents a refraction index of a material which constitutes the element.
(1) Where a light ray enters from the left-hand side of a prisms: (all symbols are based on FIG. 6(a))
Where 90°-ψ<θ.sub.1 :                     (i)
φ.sub.1 =(θ.sub.1 +ψ)-90.
sinφ.sub.2 =sin(θ.sub.1 +ψ-90)/n.
φ.sub.5 =90-(2θ.sub.2 +θ.sub.1 -φ.sub.2),
sinφ.sub.6 =n×sinφ.sub.5,
φ.sub.6 =sin.sup.-1 (n×sinφ.sub.5)
Where 90°-ψ>θ.sub.1 :                     (ii)
φ.sub.1 =90-(θ.sub.1 +ψ),
sinφ.sub.2 =sin(90-θ.sub.1 -ψ)/n.
φ.sub.5 =90-(2θ.sub.2 +θ.sub.1 +φ.sub.2),
sinφ.sub.6 =n×sinφ.sub.5
Where 90°=ψ=θ.sub.1 :                     (iii)
φ.sub.1 =0,
φ.sub.5 =90-(2θ.sub.2 +θ.sub.1),
sinφ.sub.6 =n×sinφ.sub.5
(2) Where a light ray enters from the right-hand side of a prism: (all symbols are based on FIG. 6(b)).
Where 90°-ψ<θ.sub.2 :                     (iv)
ψ.sub.1 =(θ.sub.2 +ψ)-90,
sinψ.sub.2 =sin(θ.sub.2 +ψ-90)/n,
ψ.sub.5 =(2θ.sub.1 +θ.sub.2 -ψ.sub.2)-90,
sinψ.sub.6 =n×sinψ.sub.5,
Where 90°-ψ>θ.sub.2 :                     (v)
ψ.sub.1 =90-(θ.sub.2 +ψ),
sinψ.sub.2 =sin(90-θ.sub.2 -ψ)/n,
ψ.sub.5 =(2θ.sub.1 +θ.sub.2 +ψ.sub.2)-90,
sinψ.sub.6 =n×sinψ.sub.5
Where 90°-ψ=θ.sub.2 :                     (vi)
ψ.sub.1 =0,
ψ.sub.5 =(2θ.sub.2 +θ.sub.1)-90,
sinψ.sub.6 =n×sinψ.sub.5
Meanwhile, where the prisms are made of an acrylic resin material, the refraction index is n=1.49, and if it is assumed that the incident angles to the prism 40 are symmetrical and ψ=55 degrees with respect to the normal line, the emergent angles of emergent light rays from the prisms calculated in accordance with the expressions given above are concentrated on the one side with respect to the normal line (only examples of calculations are given wherein the difference in emergent angle between two light rays from the left and right sides falls within 2 degrees).
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                 Light from the                                           
                            Light from the                                
                 Left-Hand Side                                           
                            Right-Hand Side                               
θ.sub.1                                                             
      θ.sub.2                                                       
                 (φ.sub.6)                                            
                            (φ.sub.6)                                 
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32°                                                                
      25° 8.9°                                              
                            8.5°                                   
33°                                                                
      24° 11.5°                                             
                            11.0°                                  
34°                                                                
      23° 14.0°                                             
                            13.5°                                  
35°                                                                
      22° 16.5°                                             
                            16.0°                                  
36°                                                                
      21° 19.1°                                             
                            18.6°                                  
37°                                                                
      20° 21.7°                                             
                            21.1°                                  
38°                                                                
      19° 24.3°                                             
                            23.7°                                  
39°                                                                
      18° 26.9°                                             
                            26.3°                                  
40°                                                                
      17° 29.6°                                             
                            29.0°                                  
41°                                                                
      16° 32.3°                                             
                            31.7°                                  
42°                                                                
      15° 35.1°                                             
                            34.4°                                  
______________________________________
Meanwhile, where the prisms are made of a polycarbonate resin material, the refraction index is n=1.59, and calculations depending upon similar conditions to the acrylic resin material lead to the following results. Here, ψ=55 degrees (only examples of calculations are given wherein the difference in emergent angle between two light rays from the left and right sides falls within 2 degrees).
______________________________________                                    
                 Light from the                                           
                            Light from the                                
                 Left-Hand Side                                           
                            Right-Hand Side                               
θ.sub.1                                                             
      θ.sub.2                                                       
                 (φ.sub.6)                                            
                            (φ.sub.6)                                 
______________________________________                                    
32°                                                                
      25° 9.7°                                              
                            8.4°                                   
33°                                                                
      24° 12.4°                                             
                            11.0°                                  
34°                                                                
      23° 15.0°                                             
                            13.6°                                  
35°                                                                
      22° 17.7°                                             
                            16.2°                                  
36°                                                                
      21° 20.3°                                             
                            18.9°                                  
37°                                                                
      20° 23.1°                                             
                            21.6°                                  
38°                                                                
      19° 25.8°                                             
                            24.3°                                  
39°                                                                
      18° 28.6°                                             
                            27.0°                                  
40°                                                                
      17° 31.4°                                             
                            29.8°                                  
41°                                                                
      16° 34.3°                                             
                            32.6°                                  
______________________________________
While in the case of the embodiments of FIGS. 10 and 11 the lens units 16 are formed on the first light emitting surface of the light guide of the first element 50, similar effects can be attained otherwise by forming lens units on a surface opposite to the first light emitting surface of the light guide of the first element or else by forming lens units on both of the light emitting surface and the opposite surface of the light guide if characteristics of the lens units are suitably selected.
FIG. 12 is a partial sectional view of a plane light source unit together with a lamp showing a further embodiment of the present invention.
Referring to FIG. 12, reference numeral 14 represents a light source such as a fluorescent lamp, 15 a reflector, 13 a reflecting layer formed on the opposite side to a first light emitting surface 12 of a first element 50, and 60 a mat finished first light emitting surface, which is substantially parallel to the reflecting layer 13. Reference numeral 40 represents a prism unit of a second element, and 32 a second light emitting surface of the prism units 40. The prism units 40 have a convex linear configuration extending in a direction parallel to the light source (lamp).
The plane light source unit of the present embodiment thus comprises a first element 50 having a light incident face at least at one side end 11 thereof and a mat finished first light emitting surface 12 which extends a perpendicular direction to the incident face, the first element 50 further having a reflecting layer 13 on the opposite surface thereof to the first light emitting surface, and a second element 51 having an incident surface on which the prism units 40 into which light from the first element 50 is introduced and from which light rays emerge in predetermined directions are formed and a second light emitting surface 32.
Light rays emerging from the first element are caused to emerge from the second element as represented by light rays 54 and 55, and the object of the invention can be attained by setting the prism units such that the angles ψ6 and φ6 may be substantially equal to each other.
Subsequently, determination of prism angles where the primary emergent rays from the first element emerge symmetrically to each other with respect to the normal line is carried out in a similar manner to those of FIGS. 10 and 11.
Thus, where the prisms are made of an acrylic resin material, the refraction index is n=1.49, and if it is assumed that the incident angles to the prisms 40 are symmetrical and ψ=65 degrees with respect to the normal line, the emergent angles of emergent rays of light from the prisms calculated in accordance with the expressions given hereinabove are concentrated on the one side with respect to the normal line (only examples of calculations are given wherein the difference in emergent angle between two light rays from the left and right sides falls within 2 degrees).
______________________________________                                    
                 Light from the                                           
                            Light from the                                
                 Left-Hand Side                                           
                            Right-Hand Side                               
θ.sub.1                                                             
      θ.sub.2                                                       
                 (φ.sub.6)                                            
                            (φ.sub.6)                                 
______________________________________                                    
35°                                                                
      28° 8.5°                                              
                            8.9°                                   
36°                                                                
      27° 11.0°                                             
                            11.5°                                  
37°                                                                
      26° 13.5°                                             
                            14.0°                                  
38°                                                                
      25° 16.0°                                             
                            16.5°                                  
39°                                                                
      24° 18.6°                                             
                            19.1°                                  
40°                                                                
      23° 21.1°                                             
                            21.7°                                  
41°                                                                
      22° 23.7°                                             
                            24.3°                                  
42°                                                                
      21° 26.3°                                             
                            26.9°                                  
43°                                                                
      20° 29.0°                                             
                            29.6°                                  
______________________________________
FIGS. 13 and 14 are partial sectional views of plane light source unit together with a lamp, showing still further embodiments of the present invention.
Referring to FIG. 13, a first element (light guide) 50-1 has such a configuration that the opposite side to a first light emitting surface 12 is formed as mat finished surface 60 and is disposed opposing to a reflecting layer 13, and the first light emitting surface 12 of the first element 50-1 is formed as a smooth surface. FIG. 14 shows an example of construction wherein a first element 50-2 is used in which upper and lower surfaces are formed as mat finished surfaces 60. It is to be noted that the description that an imaginary plane of mat finished first light emitting surface of a light guide extends substantially in a parallel relationship to the reflecting layer 13 in the present invention means that the first element is a member in the form of a plate having a uniform thickness, and therefore the present invention has an advantage that it employs a transparent member which can be readily produced and assembled.
In the following, there are described various examples of construction of the present invention which are designated for backlighting for a 3-inch liquid crystal TV set and wherein the size of a panel is 61 mm long×56 mm wide.
While the examples of construction of the present invention described below were produced using a plate of a transparent acrylic resin material having a thickness of 5 mm for the first element and another plate of an acrylic resin material or a polycarbonate resin material having a thickness of 1 mm for the second element, it is apparent that the sizes and the materials are not limited to such specific ones.
EXAMPLES Example 1-1
Using a metal mold for convex cylindrical lenticular lenses of smooth curved surfaces wherein the pitch is 0.38 mm and the height of the curved lens surfaces is 0.051 mm (refer to FIG. 15), the lens pattern of the metal mold was transferred to an acrylic resin plate having a thickness of 5 mm by thermal press work to make a first element. Meanwhile, a viewing angle and an inclination angle from the normal line to the picture plane of a portable liquid crystal TV set were measured and the emergent angle was determined so that it might be 15 degrees (ψ6 =φ6) with respect to the normal line to the picture plane while the prism angles were set to 35 degrees (=θ1) on the left-hand side and 22 degrees on the right-hand side (=θ2) (refer to FIGS. 6(a) and 6(b)). Then, a metal mold having a multi-prism pattern wherein the pitch was 0.38 mm and each of the thus set prisms had an apex angle (=θ1 +θ2) of 57 degrees was produced, and using the metal mold, the multi-prism pattern was transferred to an acrylic resin plate having a thickness of 1 mm by thermal press work to make a second element. The first and second elements were cut in predetermined sizes.
Subsequently, the two opposite sides of the first element having the length of 61 mm were polished by a conventional polishing method while aluminum vacuum deposited polyester films with an adhesive layer were applied to the other opposite sides having the width of 56 mm, and another silver vacuum deposited polyester film was secured on the surface opposing to the transferred lens surface. A fluorescent lamp having a diameter of 8 mm and a length of 90 mm (FLE-8.90 ADIPS 3 by Elevam Corp.) was arranged on each of the two sides of 61 mm length of the first element, and a reflector made of aluminum foil was applied to each of the lamps. Each lamp was then lit by means of DC 5 V power supply with an invertor. Luminance was then measured at the points near the lamps and the central point on a center line of the first element (refer to FIG. 5(a)) at various angles with respect to the normal line by means of a luminance meter (luminance meter nt-1 by Minolta Camera Co., Ltd.), and angular distributions of light were determined (refer to FIG. 5(b)). The data obtained in this manner are illustrated in FIGS. 4(a) and 4(b) mentioned hereinabove. Maximum luminance values of those points are listed in Table 1 below.
              TABLE 1                                                     
______________________________________                                    
Luminance Values observed                                                 
                 3,500 cd/m.sup.2, 3,200 cd/m.sup.2                       
at 55 degrees on the left                                                 
and right side, respectively;                                             
at the central points                                                     
Luminance values observed                                                 
                 4,000 cd/m.sup.2, 3,800 cd/m.sup.2                       
at 55 degrees on the left                                                 
and right side, respectively;                                             
at point spaced by 10 mm                                                  
from the lamp                                                             
______________________________________
Further, the second element was arranged on the first element with the prism side of the former opposed to the lens side of the latter and was secured to the sides of the image by means of double-sided adhesive tapes having a width of about 5 mm. Then, similar measurements to those of the first element were carried out by a quite same method, and angular distributions of light were determined. The data thus obtained are illustrated in FIGS. 16(a), 16(b) and 16(c). Maximum luminance values and angles at which the maximum luminance value was observed are listed in Table 2 below.
              TABLE 2                                                     
______________________________________                                    
             Maximum Luminance                                            
             Value       Angle                                            
______________________________________                                    
Central Point 1                                                           
               3,100 cd/m.sup.2                                           
                             15°                                   
10 mm Point from                                                          
               3,500 cd/m.sup.2                                           
                             20°                                   
Lamp 2                                                                    
10 mm Point from                                                          
               3,700 cd/m.sup.2                                           
                             12°                                   
Lamp 3                                                                    
______________________________________
The angles at which the maximum luminance value was observed fall within a narrow range from 12 to 20 degrees, and the half-width of angular distribution is about 40 degrees.
It is to be noted that the luminance value of lamp surface in the present example was 10,000 cd/m2.
Example 1-2
The same first element as in the example 1-1 described above was used, and while the same metal mold for preparing the second element as in the example 1-1 was used, the second element was produced from a polycarbonate resin plate having a thickness of 1 mm. Then, angular distributions of light were measured in luminance value by the similar setting to that of the example 1-1. The resultant data are illustrated in FIGS. 17(a) and 17(b). Meanwhile, maximum luminance values and angles at which the maximum luminance value was observed are listed in Table 3 below.
              TABLE 3                                                     
______________________________________                                    
             Maximum Luminance                                            
             Value       Angle                                            
______________________________________                                    
Central Point 1                                                           
               3,200 cd/m.sup.2                                           
                             17°                                   
10 mm Point from                                                          
               3,700 cd/m.sup.2                                           
                             23°                                   
Lamp 2                                                                    
10 mm Point from                                                          
               3,400 cd/m.sup.2                                           
                             12°                                   
Lamp 3                                                                    
______________________________________
Example 1-3
The same first element as in the example 1-1 was used. While is a requirement that the emergent angle of emergent light rays from a first element be 60 degrees in order to emit light from a plane light source unit in the direction of the normal line, because more than 90 percent of the maximum luminance value is exhibited at the angle of 60 degrees as can be seen from FIGS. 4(a) and 4(b), a metal mold for a multi-prism pattern wherein the prism angles were set to θ1 =θ2 =30 degrees and the prism pitch was set to 0.38 mm was produced, and the multi-prism pattern was thermally transferred to an acrylic resin plate of a thickness of 1 mm to make a second element.
Angular distributions of light were measured in luminance value with quite similar settings to those of the example 1-1 described hereinabove. The resultant data are illustrated in FIGS. 18(a), 18(b) and 18(c). Meanwhile, maximum luminance values and angles at which the maximum luminance value was observed are listed in Table 4 below.
              TABLE 4                                                     
______________________________________                                    
             Maximum Luminance                                            
             Value       Angle                                            
______________________________________                                    
Central Point 1                                                           
               2,900 cd/m.sup.2                                           
                             0°                                    
10 mm Point from                                                          
               3,100 cd/m.sup.2                                           
                             -5°                                   
Lamp 2                                                                    
10 mm Point from                                                          
               3,200 cd/m.sup.2                                           
                             7°                                    
Lamp 3                                                                    
______________________________________
Comparative Example
Acrylic resin pellet (HIPET HBS trade mark! by Mitsubishi Rayon Co., Ltd.) was dry-blended with 1.5 percent by weight of rutile type titanium oxide and molded into a film of 50 microns thickness by a conventional extruder. The film was extended on an inorganic flat glass plate so as not to include air bubbles, and after being provisionally secured with methylmethacrylate, a cell was formed with glass plates by means of a spacer in a conventional manner. Methylmethacrylate syrup was poured in the clearance of the cell and polymerized to cure by a conventional manner to obtain an acrylic resin plate of 5 mm thickness.
The plate produced in this manner was cut into a size of 61 mm length×56 mm width, and the two sides of 61 mm length were polished in a conventional manner while aluminum vacuum deposited films with an adhesive layer were adhered to the other opposite sides of 56 mm width, whereafter a silver vacuum deposited polyester film (similar to that of the example 1-1) was arrange on the surface opposite to a white thin layer formed on the surface of the plate. Subsequently, evaluation was made by a quite same method as the measuring method of the first element of the example 1-1. The resultant data are illustrated in FIGS. 19(a) and 19(b). Meanwhile, luminance values at the specific points are listed in Table 5 below.
              TABLE 5                                                     
______________________________________                                    
              Maximum Luminance Value                                     
______________________________________                                    
Central Point 1   900 cd/m.sup.2                                          
10 mm Points from Lamp                                                    
                1,200 cd/m.sup.2                                          
2 & 3                                                                     
______________________________________
As can be seen from comparison between, for example, FIGS. 16(a), 16(b) and 16(c) and FIGS. 19(a) and 19(b), while the plane light source unit produced in comparative example has a characteristic that light is emitted uniformly in all directions, the plane light source unit produced in accordance with the present invention has advantages that light is emitted in particular direction and that the maximum luminance value at the central point is higher, about 3.5 times, than that obtained in comparative example.
Example 2 Production of Various First Elements
As described hereinabove, the lenses 16 of the first element may have any configuration only if light is concentrated in particular directions so that the angular distribution of light falls within narrow ranges and the amount of emitted light is large, and the configuration of the lenses 16 is not particularly limited. As examples of such lens configurations, first elements having lenses of the following configurations were produced including the first element of the convex cylindrical lenticular lenses in the examples 1-1 to 1-3 described hereinabove.
(1) Lens which has a substantially similar configuration to that of the convex cylindrical lenticular lens shown in FIG. 15 and wherein
Pitch P=0.38 mm,
Height H=0.05 mm, and
Thickness of the first element t=6 mm.
(2) Triangular pole-shaped lenticular lens which has such a configuration as shown in FIG. 20 and wherein
Pitch P=0.5 mm,
Apex Angle θ=25 degrees, and
Thickness of the first element t=6 mm.
(3) Concave cylindrical lenticular lens which has such a configuration as shown in FIG. 21 and wherein
Pitch P=0.5 mm,
Depth D=0.06 mm, and
Thickness of the first element t=6 mm.
(4) Polygonal pole-shaped lenticular lens which has such a configuration as shown in FIG. 22 and wherein
Pitch P1 =0.10 mm, θ1 =30 degrees,
Pitch P2 =0.15 mm, θ2 =10 degrees,
Pitch P3 =0.15 mm, θ3 =5 degrees,
Pitch P=0.8 mm,
Heigh: H=0.097 mm, and
Thickness of the first element t=6 mm.
(5) Anisotropic lenticular lenses
1 Anisotropic lenticular lens A which has such a configuration as shown in FIG. 23(a) and wherein
Pitch P=0.41 mm,
Height H1 =0.051 mm, and
Thickness of the first element t=6 mm.
2 Anisotropic lenticular lens B which has such a configuration as shown in FIG. 23(b) and wherein
Pitch P=0.41 mm,
Height H2 =0.102 mm, and
Thickness of the first element t=6 mm.
The first elements were produced by transferring lens patterns to acrylic resin plates of 6 mm thickness by thermal press work using metal molds which have individually such predetermined configurations as described above.
Light Emitting Characteristics of Individual First Elements
Angular distributions of light of the individual first elements were determined by a similar method to that described hereinabove with reference to FIG. 5(b). In particular, the two sides of 61 mm length of each of the first element were polished by a conventional method while aluminum vacuum deposited polyester films with an adhesive layer were applied to the other two sides of 56 mm width. Then, a silver vacuum deposited polyester film was secured on a surface of each first element opposing to the thus transferred lens surface, and then a fluorescent lamp having a diameter of 8 mm and a length of 90 mm (FLE-8.90 ADIP 3 by Elevam Corp.) was arranged on each of the two sides of 61 mm length of each first element with aluminum foil applied as a reflector, whereafter the lamp was lit by means of DC 5 V power supply with an invertor. The construction in this case will be hereinafter referred to as front type. It is to be noted that, before angular distributions of light were examined, in order to make sure that such a construction can be adopted that a reflecting layer is positioned on the surface of lenses 16 such that light remitted from the lenses 16 may be reflected by the reflecting layer and then, after being transmitted through the first element 50, is emitted through the emitting surface on the opposite side to the lenses 16 (hereinafter referred to as reverse type), the lens surfaces of the first elements (1) to (5) specified as above were faced a mirror and angular distributions of such emitted light were measured. The manner of such measurement is illustrated in FIG. 24 by way of example of the concave cylindrical lenticular lens. In FIG. 24, reference numeral 13 represents a mirror.
RESULTS OF MEASUREMENTS OF ANGULAR DISTRIBUTIONS OF LIGHT
(1) FIG. 25(b) illustrates the angular distribution of light from the first element of the reverse type in which the convex cylindrical lenticular lenses of the configuration shown in FIG. 15 were employed. Meanwhile, the angular distribution of light from the first element of the front type is illustrated in FIG. 25(a). The maximum luminance value appeared in the direction of about 70 degrees from the normal line in the case of the first element of the reverse type but in the direction of about 70 to 80 degrees from the normal line in the case of the first element of the front type.
(2) FIG. 26(a) illustrates the angular distribution of light from the first element of the front type in which the triangular pole-shaped lenticular lenses were employed. Meanwhile, the angular distribution of light from the first element of the reverse surface type is illustrated in FIG. 26(b). The maximum luminance value appeared in the direction of 70 to 80 degrees from the normal line in the case of the first element of the front type but in the direction of 30 to 35 degrees from the normal line in the case of the first element of the reverse type.
(3) FIG. 27(a) illustrates the angular distribution of light from the first element of the front type in which the concave cylindrical lenticular lenses were employed. Meanwhile, the angular distribution of light from the first element of the reverse type is illustrated in FIG. 27(b). The maximum luminance value appeared in the direction of 75 to 80 degrees from the normal line in the case of the first elements of both of the front and reverse types.
(4) FIG. 28(a) illustrates the angular distribution of light from the first element of the front type in which the convex polygonal pole-shaped lenticular lenses were employed. Meanwhile, the angular distribution of light from the first element of the reverse type is illustrated in FIG. 28(b). The maximum luminance value appeared in the direction of 75 to 80 degrees from the normal line in the case of the first elements of both of the front and reverse types.
(5) The angular distribution of light from the front element in which the anisotropic lenticular lenses A were employed is illustrated in FIG. 29(a). Meanwhile, the angular distribution of light from the first element in which the anisotropic lenticular lenses B were employed is illustrated in FIG. 29(b). The maximum luminance value appeared in the direction of about 60 degrees from the normal line in the case of the first element in which the anisotropic lenticular lenses A were employed and in the direction of about 50 degrees from the normal line in the case of the first element in which the anisotropic lenticular lenses B were employed.
Production of Plane Light Source Units
The second element described hereinabove (substantially same as that used in the examples 1-1 to 1-3) was placed on a surface of each of the first elements produced in such a manner as described above in accordance with the configuration of the latter to produce plane light source units in each of which the lens surface 16 was located on the side of the emitting surface 12 of the first element (i.e., the front type).
On the other hand, a silver vacuum deposited polyester film was secured on the lens surface of each of the first elements, and the second element described hereinabove (substantially same as that used in the examples 1-1 to 1-3) was placed on the surface opposing to the lens surface of each of the first elements to produce plane light source units of a construction in which the lens surface 16 is located on the opposite side to the emitting surface 12 of the first element (i.e., the reverse type). As examples of such plane light source units, plane light source units of the front and reverse types wherein the concave lenticular lenses were employed are shown in FIGS. 30(a) and 30(b), respectively.
Measurements of Luminance and So on of Individual Plane Light Source Units
Maximum luminance values and angles at which the maximum luminance value was observed as well as half-width of angular distribution were examined for such individual plane light source units described above. The results are listed in Table 6 below. Here, the half-width shows an angular range within which the luminance value is equal to or greater than 50 percent of the maximum luminance value.
              TABLE 6                                                     
______________________________________                                    
Luminances of Plane Light Source Units                                    
in Which Vayious Light Guides Are Employed                                
Lenticular Shape                                                          
            Apex Angle Maximum                                            
of First Element                                                          
            of Second  Luminance       Half-                              
Type        Element Prism                                                 
                       Value     Angle Width                              
______________________________________                                    
Convex  Front   63° 3,200 Cd/m.sup.2                               
                                   16°                             
                                         57°                       
Cylindrical                                                               
(FIG. 15)                                                                 
        Reverse 63° 3,000 Cd/m.sup.2                               
                                   17°                             
                                         77°                       
Triangular                                                                
        Front   66° 2,350 Cd/m.sup.2                               
                                   15°                             
                                         75°                       
Pole                                                                      
(FIG. 20)                                                                 
        Reverse 30° 2,300 Cd/m.sup.2                               
                                   16°                             
                                         90°                       
Concave Front   63° 3,100 Cd/m.sup.2                               
                                   14°                             
                                         60°                       
Cylindrical                                                               
(FIG. 21)                                                                 
        Reverse 63° 2,950 Cd/m.sup.2                               
                                   14°                             
                                         60°                       
Convex  Front   63° 3,140 Cd/m.sup.2                               
                                   16°                             
                                         85°                       
Polygonal                                                                 
Pole    Reverse 63° 3,080 Cd/m.sup.2                               
                                   14°                             
                                         65°                       
(FIG. 22)                                                                 
Aniso-  A       52° 3,450 Cd/m.sup.2                               
                                   16°                             
                                         95°                       
trops                                                                     
(FIG. 23)                                                                 
        B       52° 3,800 Cd/m.sup.2                               
                                   16°                             
                                         55°                       
______________________________________
As can be seen from Table 6 above, as for the plane light source units which include the first elements of the convex cylindrical lenticular, triangular pole-shaped lenticular, concave cylindrical lenticular and convex polygonal pole-shaped lenticular lens units, the luminance is a little lower in the case of the reverse type than in the case of the front type, but the difference is very little. Accordingly, they can be satisfactory for practical use whether the first elements are either of the front type or of the reverse type.
Angular Distribution of Light from the Individual Plane Light Source Units
Angular distributions of light from the individual plane light source units at the central point (point of 1 of FIG. 5(a)) were measured in accordance with the measurements of angular distributions of light from the first elements described hereinabove.
(1) FIG. 31(b) shows the angular distribution of light from the plane light source unit of the reverse type in which the first element having the convex cylindrical lenticular lenses of the configuration shown in FIG. 15 was employed. Meanwhile, the angular distribution of light from the plane light source unit of the front type is shown in FIG. 31(a). In the case of the plane light source unit of the front type, the maximum luminance value appeared in the direction of 15 to 20 degrees and the half-width was about 57 degrees. To the contrary, in the case of the plane light source unit of the reverse type, the maximum luminance value appeared in the direction of 15 to 20 degrees and the half-width was about 77 degrees.
(2) FIG. 32(a) shows the angular distribution of light from the plane light source unit of the front type in which the first element having the triangular pole-shaped lenticular lenses was employed. Meanwhile, the angular distribution of light from the plane light source unit of the reverse type is shown in FIG. 32(b). In the case of the plane light source unit of the front type, the maximum luminance value appeared in the direction of 13 to 15 degrees and the half-width was about 75 degrees. To the contrary, in the case of the plane light source unit of the reverse type, the maximum luminance value appeared in the direction of 15 to 17 degrees and the half-width was about 90 degrees.
(3) FIG. 3(a) shows the angular distribution of light from the plane light source unit of the front type in which the first element having the concave cylindrical lenticular lenses was employed. Meanwhile, the angular distribution of light from the plane light source unit of the reverse type is shown in FIG. 33(b). In the case of the plane light source unit of the front type, the maximum luminance value appeared in the direction of 13 to 15 degrees and the half-width was about 60 degrees. To the contrary, in the case of the plane light source unit of the reverse type, the maximum luminance value appeared in the direction of 13 to 15 degrees and the half-width was about 60 degrees.
(4) FIG. 34(a) shows the angular distribution of light from the plane light source unit of the front type in which the first element having the convex polygonal pole-shaped lenticular lenses was employed. Meanwhile, the angular distribution of light from the plane light source unit of the reverse type is shown in FIG. 34(b). In the case of the plane light source unit of the front type, the maximum luminance value appeared in the direction of 15 to 17 degrees and the half-width was about 85 degrees. To the contrary, in the case of the plane light source unit of the reverse type, the maximum luminance value appeared in the direction of 13 to 15 degrees and the half-width was about 65 degrees.
(5) FIG. 35(a) shows the angular distribution of light from the plane light source unit in which the first element having the anisotropic lenticular lenses A was employed. Meanwhile, FIG. 35(b) shows the angular distribution of light from the plane light source unit in which the first element having the anisotropic lenticular lenses B was employed. In the case of the plane light source unit employing the first element having the anisotropic lenticular lenses A, the maximum luminance value appeared in the direction of 15 to 17 degrees and the half-width was about 95 degrees. To the contrary, in the case of the plane light source unit employing the first element having the anisotropic lenticular lenses B, the maximum luminance value appeared in the direction of 13 to 17 degrees and the half-width was about 55 degrees.
Summary
Whether the first element emits the light symmetrically or asymmetrically with respect to the normal line as seen in FIGS. 25(a) to 29(b), the light is emitted by the second element in particular direction as seen in FIGS. 31(a) to 35(b) and Table 6 above and the maximum luminance value is sufficient for practical use, about 2 to 3.5 times that of the cases of non-directional light emission, provided that the second element has an appropriate configuration.
Example 3 Production and Evaluation of Example of Construction Shown in FIG. 12 Production of First Element
At first, a surface of a metal plate was treated by a conventional honing technique wherein glass beads of 60 mesh were blown to one face of a polished brass plate (about 3 mm×250 mm×250 mm) to produce a metal mold having a mat finished surface. Actually, five different kinds of metal molds were produced by varying the treating condition.
Subsequently, using the metal molds, the mat pattern w s transferred to one surface of each of acrylic resin plates having a thickness of 5 mm by thermal press work to make a first element.
Production of Second Element
A viewing angle and an inclination angle from the normal line to the picture plane of a portable liquid crystal TV set (refer to FIG. 1) were measured, and the emergent angle was determined so that it might be 15 degrees (ψ6 =φ6) with respect to the normal line to the picture plane while the prism angles were set to 38 degrees (=θ1) on the left-hand side and 25 degrees on the right-hand side (=.sub.θ2) (refer to FIGS. 6(a) and 6(b)). Then, a metal mold having a multi-prism pattern wherein the pitch was 0.38 mm and each of the thus set prisms had an apex angle (=θ1 +θ2) of 63 degrees was produced, and using the metal mold, the multi-prism pattern was transferred to an acrylic resin plate having a thickness of 1 mm by thermal press work to make a second element.
Measurements of Haze Values of Light Guide for First Elements
(1) Specimens of a 50×50 mm size were cut off from the acrylic resin plate of 5 mm thickness having a mat finished surface produced in the preceding step (1) to obtain samples for measurement of haze values. As comparative samples, a transparent acrylic resin plate was cut similarly into pieces of a 50×50 mm size.
In order to measure haze values of the samples, they were put on a measuring instrument with the mat finished surfaces thereof directed toward the light incidence side in accordance with ASTM-D 1003-61, and the haze values were calculated in accordance with the following expression:
              TABLE 7                                                     
______________________________________                                    
       Sample  Haze                                                       
______________________________________                                    
       Sample-1                                                           
               70.8%                                                      
       Sample-2                                                           
               64.8                                                       
       Sample-3                                                           
               40.8                                                       
       Sample-4                                                           
               28.8                                                       
       Sample-5                                                           
               4.1                                                        
       Comparative                                                        
               0.3                                                        
       Sample                                                             
______________________________________
(2) Results of the measurements were such as listed in Table 7 below.
              TABLE 7                                                     
______________________________________                                    
       Sample  Haze                                                       
______________________________________                                    
       Sample-1                                                           
               70.8%                                                      
       Sample-2                                                           
               64.8                                                       
       Sample-3                                                           
               40.8                                                       
       Sample-4                                                           
               28.8                                                       
       Sample-5                                                           
               4.1                                                        
       Comparative                                                        
               0.3                                                        
       Sample                                                             
______________________________________
Production of and Evaluation of Angular Distributions of Light from First Elements
Subsequently, the acrylic resin plates were cut into pieces of 61 mm long×56 mm wide, and the two sides of 61 mm length of each of the pieces were polished by a conventional method while aluminum vacuum deposited polyester films with an adhesive layer were adhered to the other two sides of 56 mm width. Then, a silver vacuum deposited polyester film was secured on a surface opposing to the mat finished surface, and then a fluorescent lamp having a diameter of 7 mm and a length of 245 mm (CB7-245W cold cathode tube by Stanley Electric Co., Ltd.) was arranged on each of the two sides of 61 mm length with aluminum foil applied as a reflector, whereafter the lamp was lit by means of DC 12 V power supply with an invertor. Luminance was measured at the central point (point 1 shown in FIG. 9(a)) of the thus obtained first elements at various angles with respect to the normal line by means of a luminance meter (luminance meter nt-1 by Minolta Camera Co., Ltd.) to obtain angular distributions of light (refer to FIG. 9(b)).
The data obtained in this manner are listed in Table 8 below and illustrated in FIGS. 8(a) to 8(d). In FIGS. 8(a) to 8(f), a luminance value is represented in a radial direction and a light emergent angle is represented in a circumferential direction,. Data of the sample-5 and the comparative sample are omitted from Table 8 below because the amount of emitted light is too small in any direction to attain accurate measurement.
              TABLE 8                                                     
______________________________________                                    
            Maximum Luminance Values in                                   
            Leftward & Rightward Directions                               
Sample No. Left           Right                                           
______________________________________                                    
Sample-1   2,790          2,770 cd/m.sup.2                                
Sample-2   1,960          1,800                                           
Sample-3   2,100          2,500                                           
Sample-4   2,400          2,400                                           
______________________________________
It is to be noted that the luminance values of lamp surface at the central portion were 5,000 and 5,200 cd/cm2.
Production and Evaluation of Plane Light Source Units According to the Present Invention
The aforementioned second element was cut into pieces of 61 mm length and 56 mm width such that the multi-prisms thereof might extend in parallel to the longitudinal edges of the pieces, and the second element pieces were arranged on the first elements such that the prism surfaces thereof might face the first light emitting surfaces of the first elements whereafter they were secured along the sides of the lamps (the sides of 61 mm length) with double-sided adhesive tapes of about 5 mm width to produce plane light source units according to the present invention.
Angular distributions of light from the plane light source units were measured by a quite similar method as the method of evaluation of angular distributions of light from the first elements described hereinabove. Results of the measurements are listed in Table 9 below and illustrated in FIGS. 36(a) to 36(d).
              TABLE 9                                                     
______________________________________                                    
        Maximum                      Haze of                              
Sample No.                                                                
        Luminance Value                                                   
                    Angle   Half-Width                                    
                                     1st Element                          
______________________________________                                    
Sample-1                                                                  
        1,660 cd/m.sup.2                                                  
                    15°                                            
                            45° (-12°, 33°)          
                                     70.8%                                
Sample-2                                                                  
        1,450       15°                                            
                            48° (-15°, 33°)          
                                     64.8                                 
Sample-3                                                                  
        1,300       15°                                            
                            49° (-12°, 37°)          
                                     40.8                                 
Sample-4                                                                  
        1,340       15°                                            
                            42° (-10°, 32°)          
                                     28.8                                 
______________________________________
From the results, it can be seen that a sufficient luminance and a sufficient half-width for a plane light source unit can be obtained where the haze value is higher than about 30 percent, preferably higher than 50 percent.
Example 4 Production and Evaluation of Examples of Constructions Shown in FIGS. 13 and 14
Using the metal mold with which the sample-2 of the example 3 described above was produced, the mat pattern was transferred to both surfaces of an acrylic resin plate of 5 mm thickness to make a sample-6. This sample corresponds to the first element 50-2 shown in FIG. 14.
Measurement of Haze Value of Light Guide
A haze value of the sample-6 was measured by a quite same method as in the example 3 described above.
______________________________________                                    
              Haze                                                        
______________________________________                                    
       Sample-6                                                           
              81.5%                                                       
______________________________________
Production of and Evaluation of Angular Distribution of Light from First Element
Using the sample-2 and the sample-6 as light guide, first elements were produced in a quite same manner as in the example 3 described hereinabove, where the sample-2 was used after the silver vacuum deposited polyester film was arranged on the mat finished surface of the same light guide (refer to FIG. 13). The sample of such arrangement will be hereinafter referred to as sample-7. The sample-7 corresponds to the light guide 50-1 shown in FIG. 13. Results of measurements of angular distributions of light are listed in Table 10 below and illustrated in FIGS. 8(e) and 8(f).
              TABLE 10                                                    
______________________________________                                    
             Maximum Luminance Values in                                  
             Leftward & Rightward Directions                              
Sample No.     Left         Right                                         
______________________________________                                    
Sample-6       1,600 cd/m.sup.2                                           
                            1,700 cd/m.sup.2                              
Sample-7       1,800        1,750                                         
______________________________________
Luminance values of lamp surface at the central portion were 5,000 and 5,200 cd/m2.
Production and Evaluation of Plane Light Source Units According to the Present Invention
Plane light source units were produced, and angular distributions of light from the plane light source units were measured in a quite similar manner as in the example 3 described above.
Resultant data are listed in Table 11 below and illustrated in FIGS. 36(e) and 36(f).
              TABLE 11                                                    
______________________________________                                    
        Maximum                      Haze of                              
Sample No.                                                                
        Luminance Value                                                   
                    Angle   Half-Width                                    
                                     Light Guide                          
______________________________________                                    
Sample-6                                                                  
        1,250 cd/m.sup.2                                                  
                    15°                                            
                            61° (-23°, 38°)          
                                     81.5%                                
Sample-7                                                                  
        1,270       15°                                            
                            52° (-12°, 40°)          
                                     64.8                                 
______________________________________
From the results, it can be seen that the angular distribution of light can become broad where both surfaces of a light guide were mat finished (sample-6) or a surface in contact with a reflecting layer was mat finished (sample-7) (the maximum luminance value is decreased as much).
Comparative Example
Acrylic resin pellet (HIPET HBS trade mark! by Mitsubishi Rayon Co., Ltd.) was dry-blended with 1.5 percent by weight of rutile type titanium oxide and molded into a film of 50 microns thickness by a conventional extruder. The film was extended on an inorganic flat glass plate so as not to include air bubbles, and after being provisionally secured with methylmethacrylate, a cell was formed with glass plates by means of a spacer in a conventional manner. Methylmethacrylate syrup was poured in the clearance of the cell and polymerized to cure to a conventional manner to polymerize and solidify the film to obtain an acrylic resin plate of 5 mm thickness.
The plate produced in this manner was cut into a size of 61 mm length×56 mm width, and the two sides of 61 mm length were polished in a conventional manner while aluminum vacuum deposited films with an adhesive layer were applied to the other opposite sides of 56 mm width, whereafter a silver vacuum deposited polyester film was arranged on the surface opposite to a white thin layer formed on the surface of the plate. Subsequently, measurements similar to those of the first elements described hereinabove were made by a quite same method to determine angular distribution of light. The resultant data are listed in Table 12 below and illustrated in FIG. 37.
              TABLE 12                                                    
______________________________________                                    
        Maximum                                                           
        Luminance Value                                                   
                  Angle/Half-Width                                        
______________________________________                                    
Evaluation                                                                
          420 cd/m.sup.2                                                  
                      0° (normal line direction)/                  
                      About 160° (-80°, 80°)         
______________________________________
Summary
As can be seen from comparison between, for example, FIGS. 36(a) to 36(f) and FIG. 37, while the plane light source unit produced in comparative example has a characteristic that light is emitted uniformly in all directions, the plane light source unit of the present invention is advantageous in that light is emitted in particular direction and that the maximum luminance value at the central point is higher, about 3.5 to 4 times, than that obtained in comparative example.
Example 5
As an example wherein the light is emitted to the direction of the normal line to a picture plane, a second element was produced by thermal transfer to an acrylic resin plate of 1 mm thickness by thermal press work using a metal mold of a multi-prism pattern wherein the prism angles were set symmetrically to θ1 =θ2 =3.15 degrees on the left and right sides and the pitch was set to 0.5 mm.
Using the element of the sample-1 of Table 8 above as a first element, a plane light source unit was produced and an angular distribution of light was measured in a quite similar manner as in the example 3 described hereinabove. Results of measurement of maximum luminance value of the first element are listed in Table 13 below while results of measurement of maximum luminance value of the plane light source unit are listed in Table 14 below, and an angular distribution of light from the plane light source unit is illustrated in FIG. 38.
              TABLE 13                                                    
______________________________________                                    
Maximum Luminance Values in Leftward                                      
and Rightward Directions (±80°)                                 
Sample No. Left        Right     Haze                                     
______________________________________                                    
Sample-1   2,790       2.770 cd/m.sup.2                                   
                                 70.8%                                    
______________________________________                                    

              TABLE 14                                                    
______________________________________                                    
Maximum                                                                   
Luminance Value                                                           
           Angle    Half-Width  Haze of Light Guide                       
______________________________________                                    
1,780 cd/m.sup.2                                                          
           0°                                                      
                    40° (-18°, 22°)                  
                                70.8%                                     
______________________________________
As can be seen from Table 14 above and FIG. 38, by setting the prism angles θ1 and θ2 in such a manner as described hereinabove, the plane light source unit was produced wherein light could be emitted in the normal line direction to the picture plane.
As apparent from the foregoing description, according to the present invention, the following effects are exhibited:
(1) A plane light source unit can be provided wherein light can be emitted readily at a desired direction without increasing the power consumption of a light source and which has a decreased thickness (substantially equal to a diameter of a lamp) and is advantageous for backlighting means for a display device which has a directivity of viewing angle such as a liquid crystal display device; and
(2) Directive light can be obtained readily using a fluorescent lamp which primarily is a source of diffused light, and a desired direction of emitted light can be determined readily similar to focusing of a convex lens.
Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit and scope of the invention as set forth herein.

Claims (16)

We claim:
1. A plane light source unit, comprising a first element having a light incident face at . .lest.!. .Iadd.least .Iaddend.at one side end thereof and a first light emitting surface extending perpendicularly to said light incident face, said first element further having a reflecting layer provided on a surface thereof opposite to said first light emitting surface, and a second element having a light incident surface which receives the light emitted by said first element and a second light emitting surface through which light is emitted in a predetermined direction, at least one of said first light emitting surface and the opposite surface of said first element comprising means having a directive function to cause incident light through said light incident face to emit through said first light emitting surface in two preferential directions oblique to, and on opposite sides of, a normal line thereof, said second element having a large number of prism units formed on said light incident surface thereof, each prism unit having at least one surface positioned for effecting total reflection of the light received by said second element,
wherein the direction of substantially all of the light emitting from said second element makes an angle ranging from 0 degrees to 20 degrees with respect to a normal line of said first light emitting surface of said first element.
2. A plane light source unit according to claim 1, wherein either said first light emitting surface or the opposite surface of said first element has a large number of lens units formed thereon which contribute to the directive function.
3. A plane light source unit according to claim 2, wherein said large number of lens units are convex cylindrical lenticular lenses.
4. A plane light source unit according to claim 2, wherein said large number of lens units are concave cylindrical lenticular lenses.
5. A plane light source unit according to claim 2, wherein said large number of lens units are triangular pole-shaped lenticular lenses.
6. A plane light source unit according to claim 2, wherein said large number of lens units are polygonal pole-shaped lenticular lenses.
7. A plane light source unit according to claim 2, wherein said large number of lens units are anisotropic lenticular lenses.
8. A plane light source unit according to claim 1, wherein said first light emitting surface and/or the opposite surface of said first element has a mat finished surface which extends substantially in parallel to a plane of said reflecting layer and contribute to the directive function.
9. A plane light source unit according to claim 8, wherein a haze of said first element on which said mat finished surface is formed is equal to or greater than 30 percent.
10. A plane light source unit according to claim 1, wherein said first element has a pair of light incident surfaces at two opposing side ends thereof.
11. A plane light source unit according to claim 1, wherein said first element is made of an acrylic resin material.
12. A plane light source unit according to claim 1, wherein said first element is made of a polycarbonate resin material.
13. A plane light source unit according to claim 1, wherein said second element is made of an acrylic resin material.
14. A plane light source unit according to claim 1, wherein said second element is made of a polycarbonate resin material.
15. A plane light source unit according to claim 1, wherein the direction of light emitting from said first element makes an angle equal to or greater than 45 degrees and smaller than 90 degrees with respect to a normal line of said first light emitting surface of said first element. .Iadd.
16. A plane light source unit, comprising a first element having a light incident face at least at one side end thereof and a first light emitting surface extending perpendicularly to said light incident face, said first element further having a reflecting layer provided on a surface thereof opposite to said first light emitting surface, and a second element having a light incident surface which receives the light emitted by said first element and a second light emitting surface through which light is emitted in a predetermined direction, at least one of said first light emitting surface and the opposite surface of said first element comprising means having a directive function to cause incident light through said light incident face to emit through said first light emitting surface in a preferential direction oblique to a normal line thereof, said second element having a large number of prism units formed on said light incident surface thereof, each prism unit having at least one surface positioned for effecting total reflection of the light received by said second element,
wherein the direction of substantially all of the light emitting from said second element makes an angle ranging from 0 degrees to 20 degrees with respect to a normal line of said first light emitting surface of said first element. .Iaddend..Iadd.17. A plane light source unit, comprising a first element having a light incident face at least at one side end thereof and a first light emitting surface extending perpendicularly to said light incident face, said first element further having a reflecting layer provided on a surface thereof opposite to said first light emitting surface, and a second element having a light incident surface which receives the light emitted by said first element and a second light emitting surface through which light is emitted in a predetermined direction, at least one of said first light emitting surface and the opposite surface of said first element comprising a roughened surface having a directive function to cause incident light through said light incident face to emit through said first light emitting surface in a preferential direction oblique to a normal line thereof, said second element having a large number of prism units formed on said light incident surface thereof, each prism unit having at least one surface positioned for effecting total reflection of the light received by said second element,
wherein the direction of substantially all of the light emitting from said second element makes an angle ranging from 0 degrees to 20 degrees with respect to a normal line of said first light emitting surface of said first element. .Iaddend.
US08/267,380 1987-11-12 1994-06-29 Plane light source unit Expired - Lifetime USRE35704E (en)

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US08/267,380 USRE35704E (en) 1987-11-12 1994-06-29 Plane light source unit
US08/887,112 USRE38243E1 (en) 1987-11-12 1997-07-02 Plane light source unit

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JP28428987 1987-11-12
JP62-284289 1987-11-12
JP63-134393 1988-06-02
JP13439388 1988-06-02
US07/269,723 US5126882A (en) 1987-11-12 1988-11-10 Plane light source unit
US08/267,380 USRE35704E (en) 1987-11-12 1994-06-29 Plane light source unit
US08/887,112 USRE38243E1 (en) 1987-11-12 1997-07-02 Plane light source unit

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US07/269,723 Continuation US5126882A (en) 1987-11-12 1988-11-10 Plane light source unit

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US08/267,380 Expired - Lifetime USRE35704E (en) 1987-11-12 1994-06-29 Plane light source unit
US08/887,112 Expired - Lifetime USRE38243E1 (en) 1987-11-12 1997-07-02 Plane light source unit

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6151169A (en) 1998-05-20 2000-11-21 Lg Electronics, Inc. Sheet type optical device and backlighting unit using the same
US6559909B1 (en) * 1998-09-16 2003-05-06 Teijin Limited Application of light source including light guide for emanating linearly polarized light to liquid crystal display with haze anisotropy
US6648485B1 (en) 2000-11-13 2003-11-18 International Business Machines Corporation Highly collimating tapered light guide for uniform illumination of flat panel displays
US6791639B2 (en) 2002-05-14 2004-09-14 International Business Machines Corporation Direct view display with lenticular lens for improved brightness and wide viewing angle
US6880946B2 (en) 2002-01-15 2005-04-19 Reflexite Corporation Grooved optical microstructure light collimating films
US20070008456A1 (en) * 2005-07-08 2007-01-11 Etienne Lesage Illumination system and a display incorporating the same
US20070086208A1 (en) * 2005-10-14 2007-04-19 Lg Electronics Inc. Back light unit
US20070091642A1 (en) * 2005-10-14 2007-04-26 Lg Electronics, Inc. Light guide plate and backlight unit having the same

Families Citing this family (121)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5667289A (en) * 1989-05-18 1997-09-16 Seiko Epson Corporation Background lighting apparatus for liquid crystal display
CA2068422A1 (en) * 1990-09-12 1992-03-13 Makoto Ohe Surface light source element
DE69201168T2 (en) * 1991-06-21 1995-09-14 Mitsubishi Rayon Co Process for the production of graft polymers.
US5349503A (en) * 1991-12-31 1994-09-20 At&T Bell Laboratories Illuminated transparent display with microtextured back reflector
US5394255A (en) * 1992-01-27 1995-02-28 Sekisui Kagaku Kogyo Kabushiki Kaisha Liquid crystal display using a plurality of light adjusting sheets angled at 5 degrees or more
US5528720A (en) 1992-03-23 1996-06-18 Minnesota Mining And Manufacturing Co. Tapered multilayer luminaire devices
US6002829A (en) * 1992-03-23 1999-12-14 Minnesota Mining And Manufacturing Company Luminaire device
CA2097109C (en) * 1992-06-01 2000-01-11 Shozo Kokawa Liquid crystal display
EP0607453B1 (en) * 1992-07-13 2002-05-08 Seiko Epson Corporation Surface illumination device and liquid crystal display
JP3136200B2 (en) * 1992-07-22 2001-02-19 株式会社日立製作所 Liquid crystal display
US5359691A (en) * 1992-10-08 1994-10-25 Briteview Technologies Backlighting system with a multi-reflection light injection system and using microprisms
USRE37377E1 (en) 1992-10-09 2001-09-18 Asahi Glass Company, Ltd. LCD device including an illumination device having a polarized light separating sheet between a light guide and the display
JPH071428U (en) * 1993-06-04 1995-01-10 株式会社エンプラス Surface light source
US5863113A (en) * 1993-06-22 1999-01-26 Mitsubishi Rayon Co., Ltd. Plane light source unit
CA2099067C (en) * 1993-06-23 2001-02-13 Makoto Oe Plane light source unit
US6129439A (en) * 1993-11-05 2000-10-10 Alliedsignal Inc. Illumination system employing an array of multi-faceted microprisms
US5555329A (en) * 1993-11-05 1996-09-10 Alliesignal Inc. Light directing optical structure
US5428468A (en) * 1993-11-05 1995-06-27 Alliedsignal Inc. Illumination system employing an array of microprisms
US5396350A (en) * 1993-11-05 1995-03-07 Alliedsignal Inc. Backlighting apparatus employing an array of microprisms
US5521725A (en) * 1993-11-05 1996-05-28 Alliedsignal Inc. Illumination system employing an array of microprisms
US5598281A (en) * 1993-11-19 1997-01-28 Alliedsignal Inc. Backlight assembly for improved illumination employing tapered optical elements
US5485291A (en) * 1994-02-22 1996-01-16 Precision Lamp, Inc. Uniformly thin, high efficiency large area lighting panel with two facet grooves that are spaced apart and have light source facing facets with smaller slopes than the facets facing away from the light source
US5732148A (en) * 1994-09-16 1998-03-24 Keagy; John Martin Apparatus and method for electronically acquiring fingerprint images with low cost removable platen and separate imaging device
EP0942227B1 (en) * 1994-09-27 2004-03-24 Minnesota Mining And Manufacturing Company Luminance control film
AU4409496A (en) * 1994-11-29 1996-06-19 Precision Lamp, Inc. Edge light for panel display
JP3920364B2 (en) * 1994-12-28 2007-05-30 株式会社エンプラス Two-beam generation method and two-beam generation type surface light source device
WO1997000168A1 (en) 1995-06-14 1997-01-03 Mitsubishi Rayon Co., Ltd. Resin sheet, method and apparatus for producing the same, surface light source, and laminated body
EP0876632B1 (en) * 1995-10-18 2002-07-03 Minnesota Mining And Manufacturing Company Totally internally reflecting light conduit
US5926601A (en) * 1996-05-02 1999-07-20 Briteview Technologies, Inc. Stacked backlighting system using microprisms
US5897184A (en) * 1996-07-02 1999-04-27 Dimension Technologies, Inc. Reduced-thickness backlighter for autostereoscopic display and display using the backlighter
JP3324678B2 (en) * 1996-08-05 2002-09-17 株式会社エンプラス Light guide plate, side light type surface light source device, and component mold for side light type surface light source device
US5854872A (en) * 1996-10-08 1998-12-29 Clio Technologies, Inc. Divergent angle rotator system and method for collimating light beams
US6577358B1 (en) * 1997-06-25 2003-06-10 Dai Nippon Printing Co., Ltd. Lens film with conductive lens layer or conductive layer
US6104455A (en) * 1997-08-27 2000-08-15 Dai Nippon Printing Co., Ltd. Back light device and liquid crystal display apparatus
US6224223B1 (en) 1997-12-22 2001-05-01 Casio Computer Co., Ltd. Illumination panel and display device using the same
US6166787A (en) * 1998-03-17 2000-12-26 Motorola, Inc. Optical display device having prismatic film for enhanced viewing
US6106128A (en) * 1998-09-11 2000-08-22 Honeywell International Inc. Illumination system having edge-illuminated waveguide and separate components for extracting and directing light
JP2000164016A (en) 1998-09-24 2000-06-16 Sharp Corp Surface light source device
KR100623953B1 (en) * 1999-04-09 2006-09-13 삼성전자주식회사 Back light unit for liquid crystal display device
US6425673B1 (en) 1999-09-20 2002-07-30 Mitsubisshi Chemical Corporation Light guide pipe having elongate roughened protrusions and/or roughened concaves, planar light source unit having a broad viewing angle characteristic, and liquid crystal display device
US7046905B1 (en) 1999-10-08 2006-05-16 3M Innovative Properties Company Blacklight with structured surfaces
US6356391B1 (en) 1999-10-08 2002-03-12 3M Innovative Properties Company Optical film with variable angle prisms
US6447135B1 (en) 1999-10-08 2002-09-10 3M Innovative Properties Company Lightguide having a directly secured reflector and method of making the same
US6845212B2 (en) 1999-10-08 2005-01-18 3M Innovative Properties Company Optical element having programmed optical structures
US6570710B1 (en) 1999-11-12 2003-05-27 Reflexite Corporation Subwavelength optical microstructure light collimating films
US6356389B1 (en) 1999-11-12 2002-03-12 Reflexite Corporation Subwavelength optical microstructure light collimating films
KR100383033B1 (en) * 1999-11-13 2003-05-09 전자부품연구원 Backlight device for display
CA2392947A1 (en) 1999-11-30 2001-06-21 Reflexite Corporation Luminaire system
US6767106B2 (en) * 2000-05-08 2004-07-27 Lexalite International Corporation Edge-lit luminaire having prismatic optical control
US6956608B1 (en) 2000-08-11 2005-10-18 Identix Incorporated Fingerprint imaging device including an optical plate having microreflectors
US20020131624A1 (en) * 2000-08-11 2002-09-19 Yury Shapiro Fingerprint imaging device with fake finger detection
US8054416B2 (en) 2000-08-15 2011-11-08 Reflexite Corporation Light polarizer
WO2002014909A2 (en) * 2000-08-15 2002-02-21 Reflexite Corporation A light polarizer
US7230764B2 (en) * 2000-08-18 2007-06-12 Reflexite Corporation Differentially-cured materials and process for forming same
AU2001284844A1 (en) * 2000-08-18 2002-03-04 Reflexite Corporation Differentially cured materials and process for forming same
US20040190102A1 (en) * 2000-08-18 2004-09-30 Mullen Patrick W. Differentially-cured materials and process for forming same
EP1852737A1 (en) * 2000-12-13 2007-11-07 Mitsubishi Rayon Co. Ltd. Light source device
KR100432438B1 (en) * 2001-01-18 2004-05-22 주식회사 송산 Prism Diffuser
US6827460B2 (en) 2001-08-03 2004-12-07 Casio Computer Co., Ltd. Lighting panel having light-collecting function and display device using same
CN1328610C (en) * 2001-08-06 2007-07-25 Mei公司 Document validator subassembly
KR100989695B1 (en) * 2001-12-05 2010-10-26 솔리드 스테이트 옵토 리미티드 Transreflectors, transreflector systems and displays and methods of making transreflectors
US6863414B2 (en) * 2002-12-27 2005-03-08 Quanta Display Incorporation Front light module
US7236217B2 (en) * 2003-01-16 2007-06-26 3M Innovative Properties Company Package of optical films with zero-gap bond outside viewing area
US7518663B2 (en) * 2003-03-31 2009-04-14 Koninklike Philips Electronics N.V. Display device with multi-grooved light direction element and first and second alternating illuminated light sources simultaneously switched for 2D display and synchronously switched for 3D display
WO2004099823A2 (en) * 2003-05-02 2004-11-18 Reflexite Corporation Light-redirecting optical structures
CN1802534A (en) * 2003-06-12 2006-07-12 欧姆龙株式会社 Planar light source and image display
US7413336B2 (en) * 2003-08-29 2008-08-19 3M Innovative Properties Company Adhesive stacking for multiple optical films
US7147358B2 (en) * 2003-12-31 2006-12-12 3M Innovative Properties Company Cover removal tab for optical products
US20050238852A1 (en) * 2004-04-23 2005-10-27 Naoki Nakayama Optical products for displays
US7339635B2 (en) * 2005-01-14 2008-03-04 3M Innovative Properties Company Pre-stacked optical films with adhesive layer
KR100682875B1 (en) * 2005-06-08 2007-02-15 삼성전기주식회사 Light guide plate having multi-period patterns and illumination apparatus using the diffuser sheet
JP2007121675A (en) * 2005-10-28 2007-05-17 Hitachi Displays Ltd Liquid crystal display apparatus
US7777832B2 (en) * 2005-11-18 2010-08-17 3M Innovative Properties Company Multi-function enhancement film
KR20070079204A (en) * 2006-02-01 2007-08-06 삼성전자주식회사 Manufacturing method of optical plate, optical plate therefrom and liquid crystal display device having optical plate
WO2007138908A1 (en) * 2006-05-31 2007-12-06 Konica Minolta Holdings, Inc. Surface illuminant, and display device
JP2008034240A (en) * 2006-07-28 2008-02-14 Citizen Electronics Co Ltd Backlight
US8328371B2 (en) * 2006-08-09 2012-12-11 Tokyo University Of Science Educational Foundation Administrative Organization Anti-reflection structure body, method of producing the same and method of producing optical member
KR20090088438A (en) * 2006-12-08 2009-08-19 미츠비시 레이온 가부시키가이샤 Lens sheet, surface light source device and liquid crystal display device
TW200837452A (en) * 2007-03-12 2008-09-16 Wintek Corp Back light module
US7530721B2 (en) * 2007-04-18 2009-05-12 Skc Haas Display Films Co., Ltd. Double-sided turning film
US7991257B1 (en) 2007-05-16 2011-08-02 Fusion Optix, Inc. Method of manufacturing an optical composite
TW201007233A (en) * 2008-08-08 2010-02-16 Coretronic Corp Light guide plate and edge-lighting type backlight module
CN101382254B (en) * 2008-10-29 2011-11-09 友达光电股份有限公司 Light plate and backlight module based on the light plate
TWM353379U (en) * 2008-11-03 2009-03-21 Nano Prec Corp Backlight module
US8317352B2 (en) 2008-12-11 2012-11-27 Robert Saccomanno Non-invasive injection of light into a transparent substrate, such as a window pane through its face
US8248554B2 (en) * 2009-06-19 2012-08-21 Apple Inc. Edge-lit backlight unit with thin profile
TWI451046B (en) * 2009-10-26 2014-09-01 Young Lighting Technology Corp Light source apparatus
BR112012026329A2 (en) 2010-04-16 2019-09-24 Flex Lighting Ii Llc signal comprising a film-based light guide
CA2796519A1 (en) 2010-04-16 2011-10-20 Flex Lighting Ii, Llc Illumination device comprising a film-based lightguide
US9028123B2 (en) 2010-04-16 2015-05-12 Flex Lighting Ii, Llc Display illumination device with a film-based lightguide having stacked incident surfaces
US9261638B2 (en) * 2010-06-07 2016-02-16 Ubright Optronics Corporation Light guide film
US8735791B2 (en) 2010-07-13 2014-05-27 Svv Technology Innovations, Inc. Light harvesting system employing microstructures for efficient light trapping
CA2829388C (en) 2011-03-09 2018-09-25 Flex Lighting Ii, Llc Light emitting device with adjustable light output profile
US9188733B2 (en) 2013-06-07 2015-11-17 Steelcase Inc. Panel light assembly
KR102394030B1 (en) 2015-03-31 2022-05-06 삼성디스플레이 주식회사 Prism plate, display device having the same, and method of manufacturing prism plate
US10012783B2 (en) * 2015-04-02 2018-07-03 Philips Lighting Holding B.V. Lighting system using a light guide and a lighting method
KR20170099457A (en) 2016-02-23 2017-09-01 삼성디스플레이 주식회사 Display device
CN110785694B (en) 2017-05-08 2023-06-23 瑞尔D斯帕克有限责任公司 Optical stack for directional display
TW201921060A (en) 2017-09-15 2019-06-01 美商瑞爾Ｄ斯帕克有限責任公司 Optical stack for switchable directional display
US11256023B2 (en) * 2017-10-29 2022-02-22 Himax Technologies Limited Light wave-guide optical element and method for forming the same
US11109014B2 (en) 2017-11-06 2021-08-31 Reald Spark, Llc Privacy display apparatus
JP7291444B2 (en) 2018-01-25 2023-06-15 リアルディー スパーク エルエルシー Display device and viewing angle control optical element
JP7353007B2 (en) 2018-01-25 2023-09-29 リアルディー スパーク エルエルシー Touch screen for privacy display
JP7495027B2 (en) 2018-03-22 2024-06-04 リアルディー スパーク エルエルシー Optical waveguide, backlight device and display device
WO2020005748A1 (en) 2018-06-29 2020-01-02 Reald Spark, Llc Optical stack for privacy display
WO2020018552A1 (en) 2018-07-18 2020-01-23 Reald Spark, Llc Optical stack for switchable directional display
JP2022504376A (en) 2018-11-07 2022-01-13 リアルディー スパーク エルエルシー Directional display device
US11287677B2 (en) 2019-01-07 2022-03-29 Reald Spark, Llc Optical stack for privacy display
CN113646695B (en) 2019-02-12 2024-05-24 瑞尔D斯帕克有限责任公司 Diffuser for privacy displays
TW202102883A (en) 2019-07-02 2021-01-16 美商瑞爾Ｄ斯帕克有限責任公司 Directional display apparatus
EP4038605B1 (en) 2019-10-02 2024-09-25 RealD Spark, LLC Privacy display apparatus
JP2023501988A (en) 2019-11-13 2023-01-20 リアルディー スパーク エルエルシー off-axis display device
US11796828B2 (en) 2019-12-10 2023-10-24 Reald Spark, Llc Control of reflections of a display device
EP4143043A4 (en) 2020-04-30 2024-06-05 RealD Spark, LLC Directional display apparatus
EP4143631A4 (en) 2020-04-30 2024-05-29 RealD Spark, LLC Directional display apparatus
WO2021222606A1 (en) 2020-04-30 2021-11-04 Reald Spark, Llc Directional display apparatus
US11624944B2 (en) 2020-07-29 2023-04-11 Reald Spark, Llc Backlight for switchable directional display
TW202204818A (en) 2020-07-29 2022-02-01 美商瑞爾Ｄ斯帕克有限責任公司 Pupillated illumination apparatus
US11892717B2 (en) 2021-09-30 2024-02-06 Reald Spark, Llc Marks for privacy display
US11977286B2 (en) 2022-02-09 2024-05-07 Reald Spark, Llc Observer-tracked privacy display
WO2023196440A1 (en) 2022-04-07 2023-10-12 Reald Spark, Llc Directional display apparatus

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1535985A (en) * 1920-08-27 1925-04-28 Paul L Clark Projection screen
US2855523A (en) * 1954-01-21 1958-10-07 Gen Electric Light responsive system
US3740119A (en) * 1970-03-17 1973-06-19 Sansui Electric Co Optical lenticular grid for display apparatus
US3840695A (en) * 1972-10-10 1974-10-08 Westinghouse Electric Corp Liquid crystal image display panel with integrated addressing circuitry
US4043636A (en) * 1974-12-23 1977-08-23 Intel Corporation Illumination-panel for liquid crystal display of similar device
US4126383A (en) * 1976-06-03 1978-11-21 Bbc Brown, Boveri & Company Limited Electrooptic display device
JPS58159517A (en) * 1982-03-18 1983-09-21 Seiko Epson Corp Liquid crystal display panel
EP0167721A1 (en) * 1984-07-02 1986-01-15 Mitsubishi Rayon Co., Ltd. Light diffuser
US4714983A (en) * 1985-06-10 1987-12-22 Motorola, Inc. Uniform emission backlight
US4798448A (en) * 1988-02-16 1989-01-17 General Electric Company High efficiency illumination system for display devices
US4958911A (en) * 1988-10-19 1990-09-25 Jonand, Inc. Liquid crystal display module having housing of C-shaped cross section

Family Cites Families (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2351034A (en) 1944-06-13 Optical system composed of
GB1133367A (en) 1900-01-01
US2248638A (en) 1937-02-22 1941-07-08 Merton Thomas Ralph Sheet material with prismatic surfaces
US2175067A (en) 1938-04-23 1939-10-03 Holophane Co Inc Prismatic reflector
US3222515A (en) 1963-01-03 1965-12-07 Sheffield Plastics Inc Room light control
US3972593A (en) 1974-07-01 1976-08-03 Minnesota Mining And Manufacturing Company Louvered echelon lens
US4064433A (en) 1976-06-30 1977-12-20 K-S-H, Inc. Prismatic lighting panel
JPS5823631B2 (en) 1976-11-02 1983-05-16 株式会社エコ− Light guide diffuser plate in LCD clocks
US4154219A (en) 1977-03-11 1979-05-15 E-Systems, Inc. Prismatic solar reflector apparatus and method of solar tracking
US4242723A (en) 1979-05-14 1980-12-30 Keene Corporation Low level work area lighting system
JPS56111804A (en) 1980-02-09 1981-09-03 Dainippon Printing Co Ltd Manufacture of body differing in optical property according to direction
JPS56139101A (en) 1980-04-02 1981-10-30 Hitachi Ltd Vapor-liquid contacting apparatus
JPS58159317A (en) * 1982-03-17 1983-09-21 Matsushita Electric Ind Co Ltd Thin type transformer
JPS60146590A (en) 1984-01-10 1985-08-02 Citizen Watch Co Ltd Polychromatic image display device
CA1279783C (en) 1985-11-21 1991-02-05 Minnesota Mining And Manufacturing Company Totally internally reflecting thin, flexible film
US5056892A (en) 1985-11-21 1991-10-15 Minnesota Mining And Manufacturing Company Totally internally reflecting thin, flexible film
GB8600021D0 (en) 1986-01-02 1986-02-12 Rca Corp Light box
GB8600022D0 (en) 1986-01-02 1986-02-12 Rca Corp Arrangement to minimize reflected ambient light
US4791540A (en) 1987-05-26 1988-12-13 Minnesota Mining And Manufacturing Company Light fixture providing normalized output
DE3872084T2 (en) 1987-06-29 1992-12-03 Asahi Keiki Seisakusho Ageo Kk DRAWING APPARATUS.

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1535985A (en) * 1920-08-27 1925-04-28 Paul L Clark Projection screen
US2855523A (en) * 1954-01-21 1958-10-07 Gen Electric Light responsive system
US3740119A (en) * 1970-03-17 1973-06-19 Sansui Electric Co Optical lenticular grid for display apparatus
US3840695A (en) * 1972-10-10 1974-10-08 Westinghouse Electric Corp Liquid crystal image display panel with integrated addressing circuitry
US4043636A (en) * 1974-12-23 1977-08-23 Intel Corporation Illumination-panel for liquid crystal display of similar device
US4126383A (en) * 1976-06-03 1978-11-21 Bbc Brown, Boveri & Company Limited Electrooptic display device
JPS58159517A (en) * 1982-03-18 1983-09-21 Seiko Epson Corp Liquid crystal display panel
EP0167721A1 (en) * 1984-07-02 1986-01-15 Mitsubishi Rayon Co., Ltd. Light diffuser
US4714983A (en) * 1985-06-10 1987-12-22 Motorola, Inc. Uniform emission backlight
US4798448A (en) * 1988-02-16 1989-01-17 General Electric Company High efficiency illumination system for display devices
US4958911A (en) * 1988-10-19 1990-09-25 Jonand, Inc. Liquid crystal display module having housing of C-shaped cross section

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
IBM Technical Disclosure Bulletin, vol. 29, No. 11, Apr. 1987, pp. 4838 4839, New York, N.Y., Backlighting for liquid crystal display . *
IBM Technical Disclosure Bulletin, vol. 29, No. 11, Apr. 1987, pp. 4838-4839, New York, N.Y., "Backlighting for liquid crystal display".

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6151169A (en) 1998-05-20 2000-11-21 Lg Electronics, Inc. Sheet type optical device and backlighting unit using the same
US6559909B1 (en) * 1998-09-16 2003-05-06 Teijin Limited Application of light source including light guide for emanating linearly polarized light to liquid crystal display with haze anisotropy
US6648485B1 (en) 2000-11-13 2003-11-18 International Business Machines Corporation Highly collimating tapered light guide for uniform illumination of flat panel displays
US6880946B2 (en) 2002-01-15 2005-04-19 Reflexite Corporation Grooved optical microstructure light collimating films
US6791639B2 (en) 2002-05-14 2004-09-14 International Business Machines Corporation Direct view display with lenticular lens for improved brightness and wide viewing angle
US20070008456A1 (en) * 2005-07-08 2007-01-11 Etienne Lesage Illumination system and a display incorporating the same
US20070086208A1 (en) * 2005-10-14 2007-04-19 Lg Electronics Inc. Back light unit
US20070091642A1 (en) * 2005-10-14 2007-04-26 Lg Electronics, Inc. Light guide plate and backlight unit having the same

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KR100319327B1 (en) 2002-04-22
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KR890008587A (en) 1989-07-12
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US5126882A (en) 1992-06-30
DE3889297T2 (en) 1994-08-04
CA1312320C (en) 1993-01-05

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