EP1303725A2 - Illuminateur a surface creuse - Google Patents

Illuminateur a surface creuse

Info

Publication number
EP1303725A2
EP1303725A2 EP01961683A EP01961683A EP1303725A2 EP 1303725 A2 EP1303725 A2 EP 1303725A2 EP 01961683 A EP01961683 A EP 01961683A EP 01961683 A EP01961683 A EP 01961683A EP 1303725 A2 EP1303725 A2 EP 1303725A2
Authority
EP
European Patent Office
Prior art keywords
light
prismatic
film
conducting
opening
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01961683A
Other languages
German (de)
English (en)
Inventor
Kazuhiko Toyooka
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
3M Innovative Properties Co
Original Assignee
3M Innovative Properties Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 3M Innovative Properties Co filed Critical 3M Innovative Properties Co
Publication of EP1303725A2 publication Critical patent/EP1303725A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • 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
    • G02B6/005—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
    • G02B6/0096—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the lights guides being of the hollow type

Definitions

  • the present invention relates to a light-conducting unit, which is used as a surface light source of a back-light for a liquid crystal display or an outdoor signboard, or as an interior or exterior lighting device.
  • the light-conducting unit of the present invention can be used as a substitute for a conventional light-conducting plate, and can reduce the weight of a light-conducting unit and in turn a surface light source, since it has a hollow light- conducting space therein.
  • a conventional surface light source uses a solid light- conducting plate 10 to emit light, which is received from a spot light source or a linear light source, that is, a lamp 4 in Fig. 1.
  • the light-conducting plate is usually made of a polymer material such as an acrylic resin.
  • the light from the light source enters in the light-conducting plate through the light-incident edge (light-incident side face), and is allowed to emit from one of the major surfaces of the light-conducting plate while the light propagates through the plate from the light-incident edge towards the remote edge of the plate opposing the light-incident edge.
  • the surface light emission is achieved.
  • the propagation of the light through the light-conducting plate utilizes total internal reflection of light at the interface between air and the light-conducting plate due to the difference of the refractive index between the air and the light-conducting plate (polymer material).
  • a light-conducting plate is an essential part of a back-lighting surface light source for a liquid crystal display.
  • Such a light-conducting plate and a backlight comprising the same are disclosed, for example, in Japanese Laid Open Patent Application A- 11 - 142845.
  • the weight increase of the light-conducting plate makes it very difficult to reduce the weight of the surface light source and, in turn, the weight of the liquid crystal display. Even in the case of small- sized liquid crystal displays, it is highly desired to reduce the weight of the surface light sources in the case of portable terminals such as mobile PCs, cellular phones, PHS, etc Accordingly, it has been proposed to use a hollow light-conducting unit instead of the solid light-conducting plate.
  • a hollow light-conducting unit which comprises a light-emitting plate and a back plate which are arranged in parallel with each other to form a hollow light-conducting space, and two prismatic films which are placed on the respective surfaces of the light-emitting plate and the back plate facing inside of the light-conducting space.
  • the prismatic film is a well known optical element and means a light-transmitting film one major surface of which is flat, while the other major surface of which carries a plurality of prisms arranged in parallel with each other in the lengthwise direction (so- called parallel prisms).
  • a light-transmitting film is usually placed between the light- conducting plate and an object to be illuminated (e.g. a liquid crystal display panel, etc.).
  • a linear light source e.g. a fluorescent tube, etc.
  • a linear light source is placed along the opening which is formed at one end of the above light-conducting space, and the light is irradiated in the light-conducting space through the opening.
  • Such an opening is formed by arranging the above pair of the prismatic films substantially in parallel with each other with leaving a gap between them.
  • the pair of the prismatic films are usually arranged with allowing their flat surfaces to be in parallel with each other.
  • Such a light-conducting unit has a first opening formed at one end of the unit, and a second opening formed at the other end of the unit opposing the one end (the farthest end from the one end), and two light sources are placed at the respective openings to irradiate light into the light-conducting space. Since the pair of the prismatic films are arranged in parallel with each other, the height of the light-conducting space (in the thickness direction), that is, the size perpendicular to the light-emitting surface, does not substantially change from the first opening at the one end to the second opening at the farthest end from the one end.
  • JP-A-6-180552 One embodiment of such a hollow light-conducting unit, and a surface light source comprising the light-conducting unit and a light source is proposed by the present inventor in JP-A-6-180552. Prior to the invention of JP-A-6-180552, another embodiment of the light-conducting unit was known.
  • the arranging direction of the prisms of the prismatic film on the light-emitting plate is in parallel to the direction of light from the light source, and the prismatic surface carrying the parallel prisms is arranged to face the outside of the light-conducting space. Furthermore, (ii) the direction of the prisms of the prismatic film on the back plate is also in parallel with the direction of light from the light source, and the prismatic surface is arranged to face the outside of the light-conducting space.
  • the illumination of light emitted from the light-emitting surface tends to decrease as the distance from the light source increases.
  • an additional optical element is necessary to rectify such the decrease of the illumination.
  • Such an additional optical is a so-called extractor, which has sawtooth-form reflective projections the distances of which increase as the distance from the light source increases.
  • Such an extractor is usually arranged on the flat surface of the prismatic film on the back plate side.
  • the present inventor proposed, in JP-A-6-180552, an improved light-conducting unit to provide an inexpensive light-conducting unit and a surface light source which does not require any extractor and thus can be very easily designed and produced, and a surface light source.
  • the proposed hollow light-conducting unit comprises a pair of prismatic films which are fixed in respective positions so that they are arranged in the specific three- dimensional configuration, wherein (I) the prismatic surface of one prismatic film, which functions as a light-emitting plane, is arranged, so that the direction of the prisms of this prismatic film is perpendicular to the direction of light from the light source, and the prismatic surface faces the inside of the light-conducting space.
  • the other prismatic film is arranged so that the direction of the prisms of the other prismatic film is in parallel with the direction of light from the light source, and the prismatic surface faces the inside of the light-conducting space.
  • the illumination on the light-emitting surface is made uniform without the use of an extractor.
  • the light which is reflected by the prismatic film, is emitted from the light-emitting surface or propagated from one end near the light source to the farthest end from the light source by being repeatedly reflected and transmitted by the prismatic films in the light-conducting space. That is, the balance between the leakage of light and the propagation of light is important. If the light-leaking effect is too high, the amount of light to be propagated decreases so that the uniformity of light emission tends to deteriorate. The increase of the light-leaking effect leads to the increase of the illumination brightness.
  • the optimization of the construction of the light-conducting unit for example, the optimization of the three-dimensional configuration of the two prismatic films and the combination of the shapes of the prisms, or the selection and use of optical elements such as extractors, is necessary to balance the leakage of light and the propagation of light and to attain the desired brightness and also the uniformity of emitted light, in accordance with the application, size and the like of the light-conducting unit, that is, the surface light source.
  • the hollow light-conducting comprising a pair of the prismatic films which are arranged in parallel with each other and fixed in the specific configuration can reduce the weight of the unit itself, the surface light source and an apparatus comprising the surface light source (e.g. a liquid crystal display, etc.).
  • the surface light source e.g. a liquid crystal display, etc.
  • the thickness of the light- conducting unit that is, the thickness (height) of the light-conducting space
  • the reduction of the thickness of the light-conducting unit means the decrease of the height of the light-conducting space, that is, the size of the space which is in perpendicular to the propagation direction of the light.
  • the area of the light-emitting surface that is, the propagation distance of light, does not decrease significantly in connection with the decrease of the thickness of the unit.
  • the present invention provides a light-weight light-conducting unit which can effectively balance the light-leaking effect and the light-propagation effect of the prismatic films forming the light-conducting space, and satisfy the requirements to reduce the weight of the unit.
  • a light- conducting unit comprising the first prismatic film and the second prismatic film, each having two major surfaces, one of which is a prismatic surface, and the other of which is a flat surface carrying no prism, said prismatic surface carrying a plurality of prisms which are arranged substantially in parallel with each other along the lengthwise direction of the prisms, wherein said two prismatic films are arranged so that the first edges of said prismatic films are positioned substantially in parallel with each other leaving a gap between them to form an opening, a light-conducting space, which is in continuous from said opening, between said prismatic films, and the height (the size in the thickness direction) of said light-conducting space does not substantially increase from said opening to the remote edges opposing said opening, and the major surface of said first prismatic film, which faces outside said light-conducting space, is a light-emitting surface to emit light which is propagated from said opening into said light-conducting space, characterized in that said prismatic surface of
  • a light- conducting unit comprising the first prismatic film and the second prismatic film, each having two major surfaces, one of which is a prismatic surface, and the other of which is a flat surface carrying no prism, said prismatic surface carrying a plurality of prisms which are arranged substantially in parallel with each other along the lengthwise direction of the prisms, wherein said two prismatic films are arranged so that the first edges of said prismatic films are positioned substantially in parallel with each other with a gap between them to form an opening, a light-conducting space, which is in continuous from said opening, between said prismatic films, and the height (the size in the thickness direction) of said light-conducting space does not substantially increase from said opening to the remote edges opposing said opening, and the major surface of said first prismatic film, which faces outside said light-conducting space, is a light-emitting surface to emit light which is propagated from said opening into said light-conducting space, characterized in that said prismatic surface of
  • a light- conducting unit comprising a first prismatic film and a second prismatic film, each having two major surfaces, one of which is a prismatic surface, and the other of which is a flat surface carrying no prism, said prismatic surface carrying a plurality of prisms which are arranged substantially parallel with each other along the lengthwise direction of the prisms, wherein said two prismatic films are arranged so that the first edges of said prismatic films are arranged substantially parallel with each other leaving a gap between them to form an opening and a light-conducting space, which is in continuous from said opening, formed between said prismatic films, and the major surface of said first prismatic film, which faces outside said light-conducting space, is a light-emitting surface to emit light which is propagated from said opening into said light-conducting space, characterized in that said prismatic surface of said first prismatic film is placed facing outside of said light-conducting space, the direction of said prisms of said first prismatic film is parallel with
  • a light- conducting unit comprising a first prismatic film and a second prismatic film, each having two major surfaces, one of which is a prismatic surface, and the other of which is a flat surface carrying no prism, said prismatic surface carrying a plurality of prisms which are arranged substantially in parallel with each other along the lengthwise direction of the prisms, wherein said two prismatic films are arranged so that the first edges of said prismatic films are positioned substantially parallel with each other leaving a gap between them to form an opening, a light-conducting space, which is continuous from said opening, between said prismatic films, and the height (the size in the thickness direction) of said light-conducting space does not substantially increase from said opening to the remote edges opposing said opening, and the major surface of said first prismatic film, which faces outside said light-conducting space, is a light-emitting surface to emit light which is propagated from said opening into said light-conducting space, characterized in that said prismatic surface of
  • a light- conducting unit comprising a first prismatic film and a second prismatic film, each having two major surfaces, one of which is a prismatic surface, and the other of which is a flat surface carrying no prism, said prismatic surface carrying a plurality of prisms which are arranged substantially parallel with each other along the lengthwise direction of the prisms, wherein said two prismatic films are arranged so that the first edges of said prismatic films are positioned substantially parallel with each other leaving a gap between them to form an opening, a light-conducting space, which is continuous from said opening, between said prismatic films, and the height (the size in the thickness direction) of said light-conducting space does not substantially increase from said opening to the remote edges opposing said opening, and the major surface of said first prismatic film, which faces outside said light-conducting space, is a light-emitting surface to emit light which is propagated from said opening into said light-conducting space, characterized in that said prismatic surface of said
  • a light- conducting unit comprising a first prismatic film and a second prismatic film, each having two major surfaces, one of which is a prismatic surface, and the other of which is a flat surface carrying no prism, said prismatic surface carrying a plurality of prisms which are arranged substantially parallel with each other along the lengthwise direction of the prisms, wherein said two prismatic films are arranged so that the first edges of said prismatic films are positioned substantially parallel with each other leaving a gap between them to form an opening, a light-conducting space, which is continuous from said opening, between said prismatic films, and the height (the size in the thickness direction) of said light-conducting space does not substantially increase from said opening to the remote edges opposing said opening, and the major surface of said first prismatic film, which faces outside said light-conducting space, is a light-emitting surface to emit light which is propagated from said opening into said light-conducting space, characterized in that said prismatic surface of said
  • Fig. 1 is a cross section of a conventional surface light source
  • Fig. 2 illustrates the optical functions which depend on the structures of the prismatic films
  • Fig. 3 is a cross section of a surface light source comprising one preferred example of the light-conducting unit according to the present invention.
  • the prismatic film functions to totally internally reflect light, or to allow light to refract and pass therethrough depending on the apex angles of the prisms, the surface at which light enters, the incident angle of light, etc.
  • Such optical functions of the prismatic film is explained by making reference to Fig. 2.
  • the shown prismatic film has, on its prismatic surface, a plurality of parallel prisms having the same shape and the same size, which are arranged in the lengthwise direction of the prisms.
  • the example of Fig. 2 qualitatively illustrates the optical function of a prismatic film comprising prisms, which have an apex angle of 90 degrees, and a base angle of 45 degrees.
  • the light which reaches the film through the zone indicated with "A" is totally reflected, while the light which reaches the film through other zones propagates in the film and is refracted.
  • the refracted light may return to the inside of the hemisphere or pass through the film and then it is emitted (leak out) from the surface opposite to the incident surface depending on the refractive angle or the number of refractions. That is, depending on the incident angle of light, the light is totally internally reflected and propagated to the farthest end, or is refracted and allowed to pass through the film and then emitted selectively.
  • the shape and size of the zone A vary with the nature of the incident surface which faces the inside of the light-conducting space, that is, whether the incident surface being the prismatic surface or the flat surface, or the shape and size of the prisms. Accordingly, the effective combination of a pair of the prismatic films having such optical functions can adjust the balance between the light-leaking effect and the light- propagation effect. According to the present invention, the thickness of the unit can be easily reduced by the suitable selection of the three-dimensional configuration of the prismatic films and the combination of the shapes of the prisms and balancing the light-leaking effect and the light-propagation effect.
  • the three-dimensional configuration of the prismatic films and the combination of the shapes of the prisms, which should be optimally designed, are summarized as follows:
  • Fig. 3 is a vertical cross section of the surface light source (60) comprising the light-conducting unit (6) of the present invention, and the light source (4).
  • This figure is a cross section of the surface light source in the plane perpendicular to the light-emitting surface along the incident direction of the light (40) from the light source (4) into the light- conducting space (3).
  • the two prismatic films (1, 2) are arranged to form the light-conducting unit (6) comprising the prismatic films (1, 2) leaving a distance to provide the hollow light-conducting space (3) between them. Furthermore, the one edges (11, 21) of the prismatic films (1, 2) are positioned in parallel with each other with leaving a gap between them to form the opening (30), and the opening (30) and the light- conducting space (3) are continued.
  • the light source (4) is provided near the opening (30) so that it can effectively illuminate the inside of the light-conducting space (3), and form the surface light source (60) together with the light-conducting unit (6).
  • the reflection plate (41) is placed so that it partially covers the illumination surface of the light source (4).
  • the reflection plate (41) is effective to prevent the light from illuminating other directions than the light-conducting space (3).
  • the reflection film (5) is provided on the back surface of the second prismatic film (2), that is, the outside surface opposite to the surface facing the inside of the light-conducting space, to increase the luminance of the light-emitting surface of the first prismatic film (1), that is, the upper surface in Fig. 3.
  • the cross section of the light-conducting space (3) preferably has a wedge shape. That is, the flat surfaces of the prismatic films (1, 2) are not parallel to each other, and the two prismatic films are arranged so that the height of the light-conducting space (3) decreases from the opening (30) at the first edges (11, 21), where the light source (4) is provided, towards the farthest edges (12, 22).
  • the first prismatic film which is placed on the light-emitting surface side, is placed so that its prismatic surface faces outside of the light-conducting space.
  • the direction of the prisms of the first prismatic film should not be parallel with the direction of the light. Thereby, the light-leaking effect and the light-propagation effect are well balanced, and thus the thickness of the light-conducting unit can be easily reduced.
  • the three-dimensional arrangement and the shape of the prisms of the second prismatic film are not limited.
  • the direction of the prisms of the second prismatic film is preferably not parallel with the direction of the prisms of the first prismatic film, in particular, the angle between the two directions of the prisms is preferably in the range between 40 and 90 degrees.
  • the light-leaking effect and the light-propagation effect are very easily balanced, even when the light-conducting space has a height of 30 mm or less, in particular, 20 mm or less.
  • the apex angle of the prisms of the first prismatic film is preferably in the range between 80 and 95 degrees, while that of the second prismatic film is preferably in the range between 65 to 80 degrees.
  • the angle between the direction of the prisms of the first prismatic film and the direction of the light is not 0 (zero), that is, these two directions are not in parallel with each other. In general, such an angle is in the range between 40 and 90 degrees.
  • the prismatic surface of the first prismatic film is placed with facing outside of the light-conducting space and the direction of the prisms of the first prismatic film is in parallel with the direction of the light.
  • the three-dimensional configuration of the second prismatic film is defined as follows. That is, the direction of the prism of the second prismatic film is not parallel with the direction of said light. Thereby, the light-leaking effect and the light-propagation effect are well balanced, and thus the thickness of the light-conducting unit can be easily reduced.
  • the angle between the direction of the prisms of the second prismatic film and the direction of the light is not 0 (zero), that is, these two directions are not parallel with each other. In general, such an angle is in the range between 40 and 90 degrees.
  • the prismatic surface of the first prismatic film is placed with facing outside of the light-conducting space, the direction of the prisms of the first prismatic film is parallel with the direction of the light, and also the direction of the prism of the second prismatic film is parallel with the direction of the light.
  • the relative configuration of the two prismatic films is defined as follows. That is, as shown in Fig. 3, the two prismatic films are arranged so that the height (the size in the thickness direction) of the light-conducting space decreases from the opening at the first edges of the films towards the farthest edges from the opening.
  • the prismatic surface of the second prismatic film is placed facing outside the light-conducting space.
  • the structure in which the prismatic surface of the first prismatic film is placed facing outside of the light-conducting space, and the directions of the prisms of the two prismatic films are both parallel with the direction of the light, is relatively disadvantageous to increase the light-leaking effect.
  • the prismatic surface of the first prismatic film may be placed facing inside of the light-conducting space.
  • the three- dimensional configuration and the shape of the prisms of the second prismatic film may be defined as follows.
  • the prismatic surface of the first prismatic film is placed with facing inside of the light-conducting space, while the prismatic surface of the second prismatic film is placed facing outside of the light- conducting space.
  • the direction of the prisms of the second prismatic film is substantially in parallel with the direction of the light.
  • the angle between the direction of the prisms of the first prismatic film and the direction of the light is in the range between 40 and 90 degrees.
  • the prismatic surface of the first prismatic film is placed facing inside of the light-conducting space, and also the prismatic surface of the second prismatic film is placed facing inside of the light-conducting space.
  • the direction of the prism of the first prismatic film is not perpendicular to the direction of the light.
  • the angle between the direction of the prisms of the first prismatic film and the direction of the light is preferably in the range between 30 and 60 degrees.
  • the angle between the direction of the prisms of the first prismatic film and the direction of the light is more preferably in the range between 40 and 50 degrees.
  • the direction of the prisms of the second prismatic film is substantially parallel with the incident direction of the light. More preferably, the angle between the direction of the prisms of the first prismatic film and the direction of the light is in the range between 30 and 60 degrees, and the direction of the prisms of the second prismatic film is substantially parallel with the direction of the light.
  • the light-leaking effect and the light-propagation effect are very easily balanced, even when the light-conducting space has a height of 20 mm or less.
  • the prismatic surface of the first prismatic film is placed facing inside of the light-conducting space, and also the prismatic surface of the second prismatic film is placed facing inside of the light-conducting space, and the direction of the prisms of the first prismatic film is perpendicular to the direction of the light.
  • the apex angle of the prism of the first prismatic film is smaller than that of the prism of said second prismatic film.
  • the direction of the prisms of the second prismatic film is substantially in parallel with the direction of the light.
  • the apex angle of the prisms of the first prismatic film is preferably in the range between 65 and 80 degrees, while that of the prisms of the second prismatic film is preferably in the range between 80 and 95 degrees.
  • a plurality of the prisms extend along the lengthwise direction of the prisms, and are parallel with each other.
  • the shape of the apex of each prism may be a polygon, or a rounded form.
  • the apex of the prism is preferably a polygon having a specific apex angle.
  • its apex angle is usually from 60 to 100 degrees, preferably from 65 to 95 degrees, more preferably from 70 to 90 degrees.
  • the prismatic films to be used in the present invention are produced from polymers having a light transmittance of at least 80 %, preferably at least 85 %, more preferably at least 90 %.
  • the light transmittance is a total light transmittance measured according to JIS K 7105.
  • the prismatic films may be produced by shaping the polymer using a mold having the specific shape and arrangement corresponding to those of the prisms.
  • the polymers to be used to shape the prismatic films are preferably highly transparent ones having a refractive index of 1.4 to 1.9, such as acrylic polymers, epoxy-modified acrylic polymers, polycarbonate, etc.
  • the size of the prismatic film is not limited insofar as the effects of the present invention are not impaired.
  • the thickness of the prismatic film (a distance from the flat surface to the apexes of the prisms) is from 50 ⁇ m to 2 mm.
  • the pitch of the prisms (a distance between the adjacent apexes) is usually from
  • the height of the prism (a height from the bottom between the adjacent prisms and the apex) is usually from 0.01 to 1 mm, preferably from 0.011 to 0.6 mm.
  • the surface light source may be assembled like the above-described conventional surface light sources. That is, the component of the surface light source may be the same as those of the conventional ones except the light-conducting unit.
  • a light source having a conventional shape such as a linear (rod-like) light source, a sphere light source, etc. can be used.
  • fluorescent tubes, cold cathode-ray tubes, light-emitting diodes, etc. may be used.
  • An additional light source may be provided near the second opening which is formed at the farthest edges of the prismatic films in addition to the light source provided near the first opening formed at the one edges of the prismatic films.
  • the height of the light-conducting space does not substantially change from the first opening to the second opening at the edges farthest from the first opening. That is, the flat surfaces of the two prismatic films are substantially parallel to each other.
  • a frame or a case is provided, which surrounds the light-conducting space so that the light does not leak from any part other than the light-emitting surface of the prismatic film.
  • an opaque film such as a reflective film may be provided on the outer surface of the second prismatic film (in relation to the light-conducting space).
  • one of the major surface of the first prismatic films that is, the outer surface in relation to the light-conducting space, is the light-emitting surface.
  • the light-conducting unit of the present invention can be used for a LC display having a small screen of about 2 cm 2 on one hand and for a LC display having a large screen of about 1 m 2 on the other hand.
  • the height of the light- conducting space can be decreased, and the thickness of the light-conducting unit and also the surface light source can be reduced.
  • the height of the light-conducting space is usually from 1 to 30 mm, preferably from 2 to 20 mm.
  • the height of the light-conducting space is a distance between the facing major surfaces of the two prismatic films measured at the opening formed on the first edges of the films at which the light source is provided.
  • the height of the light- conducting space is a distance between the apex of the prism of the one prismatic film to the major surface of the other prismatic film.
  • the height of the light-conducting space is the distance from the apex of the prism of one prismatic film to that of the other prismatic film.
  • the light-conducting units of Examples and Comparative Examples were produced as described below.
  • the structure and sizes of the prismatic film used in each Example were as follows.
  • the plane size of the prismatic film used in each Example was 40 mm x 40 mm.
  • BEF II Prismatic film (brightness-enhancing film) "BEF® II, 90/50" available from
  • This film carried a plurality of parallel prisms on its prismatic surface, and the widthwise cross section of each prism was an isosceles triangle having an apex angle of 90 degrees.
  • the distance between the apexes of the adjacent prisms (prism pitch) was 50 ⁇ m, and the thickness of the prismatic film (a distance from the flat surface of the film to the apex of the prism) was 155 ⁇ m.
  • TRAP Prismatic film "TRAF® II" available from 3M, USA.
  • This film carried a plurality of parallel prisms on its prismatic surface, and the widthwise cross section of each prism was an isosceles triangle having an apex angle of 70 degrees.
  • the prism pitch was 31 ⁇ m, and the thickness of the prismatic film was 145 ⁇ m.
  • IDF 20 Prismatic film "IDF® 20" available from 3M, USA. This film carried a plurality of parallel prisms on its prismatic surface, and the widthwise cross section of each prism was a triangle having an apex angle of 70.7 degrees, one base angle of 77.6 degrees, and the other base angle of 31.7 degrees.
  • the prism pitch was 50 ⁇ m, and the thickness of the prismatic film was 150 ⁇ m.
  • either side plane of the prism may face the light source.
  • the side plane to face the light source may be selected so that the light-leaking effect and the light-propagation effect are well balanced.
  • Examples 4, 7, 12, 20 and 24 the prismatic film was arranged so that the side planes of the prisms corresponding to the larger base angle (the base angle of 77.6 degrees in the case of IDF 20) faced the light source, while in Examples 3 and 6, the prismatic film was arranged so that the side planes of the prisms corresponding to the smaller base angle (the base angle of 31.7 degrees in the case of IDF 20) faced the light source.
  • the surface light sources of Examples 3 and 16 had the same structure except that only the side plane of the prism of the first prismatic film facing the light source was different.
  • Examples 1 to 24 A light-conducting unit having the structure of Fig. 3 was assembled as described below. The combination of the types and three-dimensional configurations of the prismatic films in each Example is shown in Table 1. Hereinafter, the production steps of the light-guiding unit is explained by making reference to Example 1.
  • BEF® II (available from 3M) as the first prismatic film was placed on the light-emitting side so that the prismatic surface faced the outside of the light-guiding space (which is indicated by “O" (outside) in Table 1), while BEF® II as the second prismatic film was placed on the back surface side so that the prismatic surface faced the inside of the light-conducting space (which is indicated by "I" (inside) in Table 1).
  • An opening was formed at one edges of the two prismatic films.
  • the height of the light-conducting space measured at this opening was 4 mm.
  • the farthest edges from the opening of the two prismatic films were set as close as possible so that they were almost in contact with each other.
  • the arranging direction of the prisms of the first prismatic film was vertical to the plane of the paper sheet, while that of the prisms of the second prismatic film was parallel with the plane of the paper sheet. That is, the direction of the prisms of the first prismatic film was perpendicular to the incident direction of light from the light source (which is indicated by "H” in Table 1), while that of the prisms of the second prismatic film was parallel with the incident direction of light from the light source (which is indicated by "V” in Table 1).
  • a light-conducting unit of each of other Examples was assembled in the same way as that in Example 1 except that the combination of the types and three-dimensional configurations of the prismatic films shown in Table 1 was used. With each light-conducting unit assembled in the Examples, the conditions of the light propagation and leakage were observed as follows:
  • the light-conducting unit was set in a dark room, and four point light sources (LED) were lined up in parallel with the opening, and lighted. Then, the conditions of the irradiation and propagation of light were observed from the light-emitting surface. In all the Examples, the four bright streams of light emitted from the LEDs continuously run on the light-emitting surface (the major surface of the prismatic film) from the first edges having the light source to the farthest edges from the light source.
  • LED point light sources
  • the light-lealcing effect and the light-propagation effect can be balanced in the thin light-conducting space, and the desired brightness and the uniformity of light-emission can be achieved in accordance with the brightness of the light source (illumination) and so on. Comparative Example 1
  • a light-conducting unit of this comparative example was assembled in the same manner as that in Example 1 except that two transparent acrylic resin films (having no prism on either surface) were used in place of the two prismatic films.
  • Comparative Example 2 A light-conducting unit of this Comparative Example was assembled in the same manner as that in Example 1 except that the three-dimensional configuration of the first prismatic film was such that the prismatic surface faced outside, and the direction of the prisms was parallel with the incident direction of the light (which is indicated by "VO"), while the three-dimensional configuration of the second prismatic film was such that the prismatic surface faced inside, and the direction of the prisms was parallel to the direction of the light (which is indicated by "VI").
  • H The direction of the prisms being perpendicular to the direction of light from the light source.
  • V The direction of the prisms being parallel to the incident direction of light from the light source.
  • 45 The direction of the prisms inclining at 45 degrees to the incident direction of light from the light source.
  • O The prismatic surface facing the outside of the light- conducting space.

Abstract

La présente invention concerne une unité conductrice de lumière qui peut efficacement équilibrer l'effet de perte de lumière et l'effet de la propagation de la lumière des films prismatiques formant l'espace conducteur de lumière et satisfaire les besoins liés à la réduction du poids de l'unité. Une unité conductrice de lumière comprend le premier film prismatique et le deuxième film prismatique qui comportent chacun deux surfaces principales dont une est une surface prismatique alors que l'autre est une surface plate, ladite surface prismatique portant des prismes disposés sensiblement parallèles les uns par rapport aux autres, lesdits deux films prismatiques étant prévus de sorte que les premiers bords des films prismatiques soient positionnés pour former une ouverture, un espace conducteur de lumière étant formé entre lesdits films prismatiques et la hauteur dudit espace conducteur de lumière n'augmentant pas sensiblement depuis ladite ouverture en direction des bords éloignés des films prismatiques opposés à ladite ouverture et la surface principale dudit premier film prismatique qui est orientée vers l'extérieur dudit espace conducteur de lumière est une surface émettant de la lumière. La disposition des deux films prismatiques et le sens des prismes des deux films prismatiques par rapport au sens incident de la lumière sont définis dans des conditions spécifiques.
EP01961683A 2000-07-26 2001-07-20 Illuminateur a surface creuse Withdrawn EP1303725A2 (fr)

Applications Claiming Priority (3)

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JP2000225276 2000-07-26
JP2000225276A JP4485026B2 (ja) 2000-07-26 2000-07-26 導光ユニット
PCT/US2001/023022 WO2002008663A2 (fr) 2000-07-26 2001-07-20 Illuminateur a surface creuse

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EP1303725A2 true EP1303725A2 (fr) 2003-04-23

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JP (1) JP4485026B2 (fr)
KR (1) KR20030026325A (fr)
CN (1) CN1211675C (fr)
AU (1) AU2001282930A1 (fr)
TW (1) TW512292B (fr)
WO (1) WO2002008663A2 (fr)

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CN100465729C (zh) * 2001-11-02 2009-03-04 霍尼韦尔国际公司 用于背式照明的中空楔形光导
CN1306295C (zh) * 2002-03-28 2007-03-21 皇家飞利浦电子股份有限公司 紧凑型照明系统及显示器件
US7303322B2 (en) 2003-12-23 2007-12-04 3M Innovative Properties Company Multiple lightguide backlight
US7223005B2 (en) 2003-12-23 2007-05-29 Lamb David J Hybrid lightguide backlight
US20060221610A1 (en) * 2005-04-01 2006-10-05 Chew Tong F Light-emitting apparatus having a plurality of overlapping panels forming recesses from which light is emitted
KR100781350B1 (ko) 2005-12-26 2007-11-30 주식회사 바다테크 고휘도 백라이트장치
KR20070096457A (ko) * 2006-03-24 2007-10-02 엘지전자 주식회사 광 파이프를 이용한 면 광원 장치, 이를 구비한 백라이트유닛 및 액정 표시 장치
KR101488042B1 (ko) * 2007-05-20 2015-01-29 쓰리엠 이노베이티브 프로퍼티즈 컴파니 광-재순환 유형의 얇은 중공 공동 백라이트의 설계 파라미터
KR20100126389A (ko) * 2008-02-22 2010-12-01 쓰리엠 이노베이티브 프로퍼티즈 컴파니 선택된 출력 광속 분포를 갖는 백라이트 및 이를 사용한 디스플레이 시스템
JP2011134481A (ja) * 2009-12-22 2011-07-07 Lecip Holdings Corp 照明装置
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WO2002008663A2 (fr) 2002-01-31
AU2001282930A1 (en) 2002-02-05
JP2002050220A (ja) 2002-02-15
JP4485026B2 (ja) 2010-06-16
KR20030026325A (ko) 2003-03-31
WO2002008663A3 (fr) 2002-05-30
TW512292B (en) 2002-12-01
CN1444711A (zh) 2003-09-24
CN1211675C (zh) 2005-07-20

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