JP2008512834A - Lighting device - Google Patents

Abstract

The present invention relates to a lighting device that illuminates a flat panel monitor, such as a display for mobile applications, from behind. The illumination device includes a light source (14) and a light guide member (10). The light emitted from the light source enters the light guide member (10) and is emitted from the light exit surface (28). On the light exit surface (28) of the light guide member (10), there is formed a diffractive surface element (30) having a surface structure with a constant amplitude for diffracting light when emitted.

Description

  The present invention relates to a lighting device for backlighting a flat display, in particular a display used for mobile applications.

  A display illumination device used for a known mobile application includes a light source such as a tubular light source (CCFL). The light emitted from the light source is guided into a light guide member having a wedge-shaped cross section at the end face. In particular, since the light guide member is wedge-shaped, total reflection of the light beam occurs at the boundary surface, and the light beam is emitted from the surface of the wedge-shaped light guide member through the corresponding scattering center. The surface of the wedge-shaped light guide member is provided to face the display illuminated by the transmitted light, and the surface is structured to emit from the light guide member by light refraction. The refracted light is focused and guided to a plurality of films provided between the light guide member and the display, and substantially white light reaches the display. The structure of such an illuminating device is complicated, and for example, a plurality of films are provided in a frame or the like, and it is necessary to ensure that there is no slippage of the film, so that it is further complicated. Due to this complex structure, the manufacturing costs are high and there is a risk of malfunction.

  From European Patent No. 1194915, a light guide member for a mobile phone is known. In this case, light from a light source such as an LED (light emitting diode) enters the light guide member. In order to derive light, a diffraction grating is provided on the surface of the light guide member. The light guide member is provided with different diffraction gratings on the entire surface so that the diffraction gratings are adjacent to each other. In order to obtain light derivation uniformity, the diffraction grating is configured to have different diffraction effects. By changing the amplitude of each diffraction grating or the height of the grating structure, diffraction gratings having different diffraction effects can be obtained. However, it is extremely difficult to produce a surface structure with different amplitudes of diffraction gratings, and since the individual diffraction gratings are in direct contact with each other, accuracy that is difficult to achieve technically is required. If the required accuracy is not obtained, for example, diffraction tends to cause difficult to predict situations such as unwanted interference.

  An object of the present invention is to provide a lighting device for the back surface of a flat display, which has high efficiency and low cost, and guarantees superior operational reliability.

  The object is achieved by the invention having the features of claim 1.

  The illumination device is particularly suitable for flat displays such as mobile phones, PDA displays, and cameras. Furthermore, this lighting device is also suitable for back lighting such as advertising billboards and display panels. The illuminator comprises a light source that may include one or more LEDs or CCFLs.

  Light emitted from the light source enters the light guide member. Preferably, the light guide member is made of transparent plastic and inorganic glass such as PPMA, PC, PET, PT, or transparent plastic or inorganic glass. The light incident on the light guide member is emitted from the light exit surface of the light guide member. When the illumination device is used in a mobile phone, a light exit surface is provided facing the display so that light is emitted from the light guide member toward the display. According to the present invention, the light exit surface has a surface structure provided with a diffractive surface element. Preferably, by providing a plurality of such diffractive surface elements, the present invention can achieve sufficiently good illumination with the diffractive surface element. The formed film can be omitted.

  One or more side surfaces of the light guide member can be provided with a reflecting mirror to increase the amount of light emitted from the light exit surface. Similarly, the light source can be partially surrounded by a reflecting mirror in order to increase the amount of light incident on the light guide member.

  With this illumination device, it is possible to omit further light guide components such as a film provided between the light exit surface of the light guide member and the display. In addition to the reflective elements described above, the present invention provides transflective or transmissive backlighting without using any light guide components. By providing the diffractive surface element on the light exit surface of the light guide member, the structure of the lighting device can be simplified, thereby enhancing the quality of the lighting device, particularly the service life.

  Preferably, each diffractive surface element has a shape that acts as a diffractive element for obtaining a suitable light beam focused by spectral dispersion. In this sense, each diffractive surface element preferably has a surface structure with a corrugated cross section, and the corrugated pitch is selected according to the wavelength of the diffracted light. The individual diffractive surface elements are preferably provided with different diffraction gratings.

  Particularly preferred is that the diffractive surface element is configured to be made by superimposing at least two monochromatic light and white light or adjacent light beams of monochromatic light or white light. In this case, the wavelength range of monochromatic light is ± 100 nm, particularly ± 50 nm. According to the present invention, by providing such a diffractive surface element, it is possible to generate focused light having a particularly high luminance, most of which is monochromatic light.

  The surface structure of the diffractive surface element can further adjust the direction of light irradiation from the light exit surface. For this purpose, the diffraction grating provided on the diffractive surface element must be modified in accordance with Fraunhofer's diffraction law. The adjustable range is preferably in the range of 0 to 90 ° with respect to the light exit surface.

  Similarly, the color temperature of the irradiation light can be adjusted by selecting the diffractive surface element or its structure. The color temperature can be adjusted preferably in the range of 3,000 ° K to 10,000 ° K.

  The form of the light exit surface with this diffractive surface element in particular avoids or significantly reduces spectral dispersion. In addition, sufficient light amplification and at the same time low energy consumption are achieved. Further, by providing a diffractive surface element, in particular, the structure of the diffractive surface element, good light focusing can be achieved. It is particularly advantageous that these advantages can be obtained in terms of light amplification or light focusing without the need for further light guiding systems such as films that perform diffraction or reflection.

Area of the diffractive surface element of the present invention is preferably 0.04μm ² ~10,000μm ^2, in particular 0.04μm ² ~500μm ^2. Since such a minute surface is provided, even a very small flat display such as a mobile phone can be provided with a plurality of diffractive surface elements.

  In this case, the mutual spacing between the individual diffractive surface elements is preferably in the range from 0 to 100 μm, in particular from 0 to 50 μm, particularly preferably from 0 to 15 μm. It is particularly preferred that the diffractive surface elements have a finite spacing. Preferably, this distance is at least 1 μm, in particular at least 3 μm. This reduces the distance between the diffractive surface elements in the region of the light guide member from which more light is to be derived, and on the other hand, increases the distance in the region of the light guide member from which less light is to be derived. It is advantageous in that it can. Thereby, the illuminance distribution can be made sufficiently uniform. Furthermore, it becomes easier to always arrange the individual diffractive surface elements at the same interval in terms of manufacturing. For example, if the diffractive surface element is manufactured by combining a curable paint and an element forming element or a mold, if a space is provided between the elements, for example, destruction at the boundary of the diffractive surface element due to the formation of a paint web Avoided. Furthermore, the provision of spaces between the individual surface surface elements ensures that adverse effects of refraction and diffraction caused by adjacent surface structures are avoided.

  Preferably, a plurality of diffractive surface elements having different surface structures are included in one diffractive surface element group. By doing so, different surface structures are selected, so that one diffractive surface element group emits substantially monochromatic light and white light, or monochromatic light or white light. The type of surface structure, in particular the wavelength change of light caused by the surface structure, is determined according to the wavelength range emitted by the light source.

  Preferably, one diffractive surface element group preferably includes at least two diffractive surface elements having different surface structures, and the diffractive surface element group includes at least four, especially six diffractive surface elements each having a different surface structure. Is preferred.

  According to an embodiment of the present invention, the individual diffractive surface elements have the same surface structure with respect to height or amplitude, so that the diffractive effects of the individual diffractive surface elements are the same. Although a fluctuation range due to a small error occurs during manufacturing, it has only a minor effect on the diffraction effect.

  It is particularly preferable to form the individual diffractive surface elements as different surface structures so that the amplitude is constant and varies by wavelength. Although not necessarily a sinusoidal surface structure, depending on the type of surface structure, generally the raised portions are all the same height and are different from each other.

  For this reason, the light emitted from the light source has different diffraction depending on the individual diffractive surface elements. In this regard, there is a special advantage that changing the interval is easier than changing the height.

  Preferably, the diffractive surface elements are provided, for example, as a group consisting of six diffractive surface elements having different surface structures, and preferably have the same amplitude of, for example, 550 nm. The respective amplitudes of one diffractive surface element group are, for example, 490 nm, 503 nm, 517 nm, 530 nm, 575 nm and 620 nm. In particular, these diffractive surface elements have a sinusoidal surface structure. The spacing between the individual diffractive surface elements is preferably in the range 1-100 μm, in particular 1-50 μm, most preferably 1-15 μm.

  The manufacture of such a diffractive surface element with a minute surface structure is described in, for example, EP05003358, and is incorporated into this product by referring to the disclosure. A suitable material for producing a diffractive surface element preferably has the following composition:

11g of acrylic acid-1H, IH, 2H, 2H-perfluoro Chi le acrylate, dipropylene glycol diacrylate 8 g, Irgacure of 0.1 g ^(R) 819 and 0.2g of Irgacure ^(R) 184 (IRGACURE ^{(Registered Trademark} : Distributor: Ciba Specialty Chemicals Rampersheim GmbH) 60 μl of this mixture was applied onto a 2 cm × 2 cm nickel plate that had been surface patterned using a mold with a scattering center .

  Next, on the surface of the mixture on the nickel plate, a small plate of polymethyl methacrylate having dimensions of 1 mm thickness and 1 cm × 1 cm was placed. Thereafter, the sandwich sandwiching the mixture thus obtained on the nickel plate was irradiated with ultraviolet rays from a conventional mercury lamp for 2 seconds. Thereafter, the substrate having the cured molding compound bonded thereto was removed from the molding die.

  The light guide member may be wedge-shaped in cross section, but it is preferable to provide a light guide member having a parallel array tubular shape, and the light introduction surface is on the side surface of the parallel array tube. Preferably, the parallel-aligned tubular light guide members are cubes.

  Due to the good luminous efficiency obtained by the diffractive surface element provided by the present invention, it is possible to provide tubular light guide members arranged in parallel. This achieves a substantial simplification of manufacturing. The thickness of the tubular light guide members arranged in parallel is preferably in the range of 0.1 to 3 mm.

  Preferably, the one or more LEDs or CCFL light sources are arranged inside and outside the light guide member, or inside or outside. The diffractive surface elements are arranged according to the position of the light source or the light source. By arranging the diffractive surface elements so as to correspond to each other, different light intensities, etc. existing at different positions on the light exit surface are compensated uniformly, that is, particularly focused, monochromatic light and white light, or monochromatic light or white Light is emitted from the light exit surface by the diffractive surface element.

  In order to increase the amount of light directed to the light exit surface, a reflecting mirror may be provided. These reflecting mirrors partially surround the light source, for example. As an example, the tubular light source is preferably provided at the focal point of a parabolic reflector. Similarly, a plurality of plane reflecting mirrors may be provided additionally or instead of the parabolic reflecting mirror. Furthermore, a reflecting mirror may be provided on the outer surface of the light guide member that is not the light exit surface of the light guide member in order to prevent light loss. The diffractive surface element according to the present invention may be provided, for example, on the side surface of the light guide member to guide the corresponding light. This diffractive surface element may be provided on the surface of the light source to intentionally achieve light guiding, focusing and / or spectral dispersion.

  A diffractive surface element may be provided on the light exit surface of the light guide member, or alternatively, such a diffractive surface element may be provided on the opposite side, that is, on the bottom of the light guide member. The light diffracted by the diffractive surface element is thereby directed to the display through the light guide member.

  In a particularly preferred embodiment of the invention, the spacing between adjacent diffractive surface elements provided specifically on the light exit surface or on the opposite surface decreases as the distance to the light source increases. As a result, the light intensity is high in the vicinity of the light source, and may decrease as the distance from the light source increases. For example, the light source provided inside the light guide member is surrounded by concentric circles of the diffractive surface element, and the distance between these concentric circles decreases as the distance to the light source increases. Depending on the type of light source, especially the illumination characteristics of the light source, it would be advantageous to have a different arrangement of diffractive surface elements suitable for it.

  In this way, periodic and aperiodic arrangements of diffractive surface elements are possible. Preferably, the diffractive surface element is arranged according to the type and position of the light source or the light source.

  One preferred embodiment of the present invention is a flat display having a liquid crystal element such as an LCD element. According to the present invention, the liquid crystal element is illuminated from the back using an illumination device formed in accordance with the above specifications.

  A known display or liquid crystal element according to the prior art comprises an optical element such as a light source box. The optical element is provided with a plurality of fluorescent tubes, particularly CCFLs, as light sources. A foil (foil) is provided between the fluorescent tube and the liquid crystal element in order to make the light emitted by the fluorescent tube more uniform and thereby make the illumination of the liquid crystal element more uniform. These foils are respectively called so-called BEF and DBEF foils. A BEF foil increases luminous intensity. In order to achieve this, a plurality of prisms are arranged on the foil. The DBEF foil is used to change the polarization of light reflected from the back side of the liquid crystal element and return the light toward the liquid crystal element. In addition, the PRF foil is used to change the polarization. However, the provision of such foils has the disadvantage that these foils absorb part of the light.

  In the flat display of the present invention, the BEF foil, and preferably the DBEF foil and the PDF foil are also replaced by the light guide member formed according to the present invention. It is preferable to provide a plurality of tubular light sources such as CCFL. The light guide member of the present invention is disposed in front of a tubular light source and includes a plurality of diffractive surface elements or diffractive surface element groups as described above. It is particularly preferred that the light guide member has one section for each tubular light source, which section is arranged parallel to the tubular light source and comprises a plurality of diffractive surface elements or diffractive surface element groups. The individual sections may have the same configuration. In this way, the manufacturing cost can be reduced.

  Each diffractive surface element or group of diffractive surface elements within an individual area is preferably arranged in columns and rows. It is particularly preferred here that the spacing between the rows decreases as the distance from the tubular light source increases. In this way, the light emitted from the light exit surface of the light guide member can be made uniform. That is, in particular, the luminous intensity distribution and the wavelength distribution, or the luminous intensity distribution or the wavelength distribution can be made more uniform. As a result, the BEF foil, DBEF foil, and PRF file may also be omitted.

  This area can be divided into individual sub-areas (sub-zones). Preferably, the sub-area is a rectangular area, and the number of diffractive surface elements or diffractive surface element groups in the sub-area located at the side edge of the light guide member is equal to the number of diffraction surfaces in the sub-area located further inside. More than the number of surface elements or diffractive surface element groups. Further, instead of providing areas and sub-areas, it is also possible to arrange the diffractive surface elements or diffractive surface element groups aperiodically. In this case, the individual diffractive surface elements or diffractive surface element groups are arranged according to the luminous intensity characteristics of the tubular light source. Preferably the density of the diffractive surface element or group of diffractive surface elements is higher at the corners and at the edges.

  DETAILED DESCRIPTION OF THE INVENTION The best mode of the present invention which will be described below will be described in more detail for those having ordinary skill in the art with reference to the accompanying drawings.

The illumination device includes a light guide member 10. The light guide member 10 is cubic in this embodiment, and can be manufactured from a plastic material such as transparent resin or PPMA, for example. In the present embodiment, a tubular light source 14 is disposed along one side surface 12 of the light guide member 10. The longitudinal axis of the light source 14 is arranged parallel to the side surface 12. The light source 14 is surrounded by a parabolic reflector 16 whose open surface is directed to the side surface 12. For this reason, the amount of light incident on the side surface 12 increases. The light source 14 may be a plurality of LEDs instead of the tubular light source 14 as shown, and preferably has a luminance in the range of 20,000 to 50,000 cd / m ² . When the tubular light source 14 is provided, the light source 14 is preferably provided on the focal axis of the parabolic reflector 16.

  A reflective mirror 20 is provided on the bottom surface 18 of the light guide member 10, which may be a reflective film or the like. Further, if a reflecting mirror is used, it may be provided on the side surfaces 22, 24 and 26 or any one of them. Instead of providing a reflecting mirror, the corresponding surface may be polished. Alternatively, a reflective layer may be deposited.

  A plurality of diffractive surface elements 30 are arranged on the light exit surface 28 of the light guide member 10 to form the surface structure of the present invention.

  Each diffractive surface element 30 acts as a diffraction grating. In this case, each diffractive surface element 30 may be designed as a linear diffraction grating having different lattice constants.

  The surface 32 (see FIG. 2) of each diffractive surface element 30 is designed as a sinusoidal grating, for example. In this case, each diffractive surface element 30 preferably comprises two sinusoidal half-wave surfaces.

  The manufacture of the individual diffractive surface elements 30, in particular the surface 32 structure of the diffractive surface element 30, is performed according to the invention using an optical lithography process. In a further particularly preferred embodiment, the diffractive surface element 30 may be manufactured as disclosed in EP05003358.

  In a particularly preferred embodiment of the invention, the individual diffractive surface elements 30 are included in a diffractive surface element group 33 (see FIG. 3). As in the illustrated embodiment, the diffractive surface element group 33 preferably comprises six diffractive surface elements 30 arranged at regular intervals. Each diffractive surface element 30 has a different surface structure such that the diffractive surface element group 33 emits substantially monochromatic or white light.

  In order to emit light having different wavelengths, it is preferable to include diffractive surface elements 30 having different surface structures, that is, diffractive surface elements 30 having different surface structures. For example, as in the embodiment shown in FIG. 3, it is preferable that the six diffractive surface elements 30 labeled 1 to 6 in FIG. 3 are different from each other. As is apparent from FIG. 3, in this embodiment, different diffractive surface elements 1 to 6 are arranged as a repeating structure in order to derive light of a predetermined wavelength.

  In the present embodiment, the diffractive surface element 30 has a square shape and an end length of about 15 μm. In a particularly preferred embodiment (see FIG. 4), the individual diffractive surface elements 30 are arranged in each zone, and each zone (Zone) is denoted by 1-10 and 1_1-1_4. The length (Width) and width (Width) of each area and the distance (distance surface el.) Between the diffractive surface elements in each area are shown in FIG.

  In the embodiment shown in FIGS. 4 and 5, the light source is on the left side, ie next to the area labeled 1 in FIG. Starting from this light source, the spacing between the individual diffractive surface elements 30 gradually decreases as the distance from the light source increases.

  Within the individual areas or regions, the diffractive surface elements 30 are at regular intervals. However, the spacing of the diffractive surface elements 30 can be different within one area. In particular, the longitudinal interval, that is, the interval from left to right in FIG. 4, may be different from the interval perpendicular to the longitudinal direction.

  Using the simulation software “Light Tools” from ORA, a lighting device as described with reference to FIGS. 1 to 5 was constructed with the areas defined in FIGS. Uniformity, hue, brightness, illuminance and focusing direction were then measured. Corresponding measurement was performed at a total of nine locations, the corner, the center of the end approximately 2 mm from the end, and the center of the light guide member.

  A simulation was performed on the arrangement of the diffractive surface elements 30 defined in FIGS. 4 and 5 and the results were as follows.

Uniformity: 91%
Hue: white,
Average illumination: 1,600 lux,
Average brightness: 2,950 nits,
Optical axis direction: 17 °

  In another simulation, the spacing of the diffractive surface elements 30 in the individual areas (see FIG. 4) was determined as shown in FIG. The results were as follows:

Uniformity: 86%
Hue: neutral (slightly blue),
Average illuminance: 1,000 lux,
Average brightness: 1,900 nits,
Optical axis direction: 17 °

  In another simulation, the spacing of the diffractive surface elements 30 in the individual areas (see FIG. 6) was determined as shown in FIG. The results were as follows:

Uniformity: about 78%
Hue: white,
Average illumination: 1,050 lux
Average luminance: 1,850 nits,
Optical axis direction: 17 °

  In another test, areas 8, 9 and 10 were omitted. Thereby, the shortened light guide member 10 was tested, and light was similarly guided into the light guide member 10 from the left side corresponding to the light guide member 10 shown in FIG. The dimensions of the light guide member 10 thus tested are about 36 mm in length and about 44 mm in width, and the length is measured in the direction of increasing area numbers, that is, from the left to the right in FIG. The spacing of the individual diffractive surface elements 30 is the same as that defined in FIG. 5 for the areas 1-6, 1_1, 1_2, 1_3 and 1_4. The measurement results are as follows:

Uniformity: about 88%,
Hue: white,
Average illumination: 1,100 lux,
Average brightness: 2,150 nits,
Optical axis direction: 17 °

  In the subsequent test, the surface of the light guide member 10 was not divided into areas, and a predetermined constant value was selected as the distance between the individual diffractive surface elements. The results obtained are as follows:

Interval: 4 μm
Uniformity: about 75%,
Hue: white,
Average illumination: 1,850 lux
Average luminance: 3,350 nits,
Optical axis direction: 17 °

Interval: 6 μm,
Uniformity: about 78%
Hue: white,
Average illumination: 1,600 lux,
Average brightness: 2,400 nits,
Optical axis direction: 17 °

Interval: 8 μm,
Uniformity: about 82%
Hue: white,
Average illumination: 1,400 lux
Average brightness: 2,500 nits,
Optical axis direction: 17 °

Interval: 10 μm,
Uniformity: about 84%
Hue: white,
Average illumination: 1,200 lux,
Average brightness: 2,200 nits,
Optical axis direction: 17 °

Interval: 11 μm
Uniformity: about 87%
Hue: white,
Average illumination: 1,200 lux,
Average brightness: 2,150 nits,
Optical axis direction: 17 °

  From the above test results, the following conclusions can be drawn:

  1. Depending on the arrangement and distribution of the diffractive surface element 30, the uniformity regarding the light distribution can be set large.

  2. Even if the diffractive surface element 30 has a relatively inconvenient arrangement with low uniformity, white light can always be obtained by mixing the hue.

  3. The light focusing direction may be set regardless of the distribution of the diffractive surface element 30.

  4). The brightness is a function of the spacing of the diffractive surface element 30.

  In particular, when the present lighting device is used as a backlight for a mobile phone that needs to have a uniformity of 75% or more, a high-quality display illumination that is acceptable to the user is achieved. Specifically, desired light focusing can be achieved by a combination with a predetermined color temperature without the help of a light guide foil. For this reason, the entire apparatus can be further reduced in size, and the number of parts is reduced at the same time, thereby increasing the degree of freedom in layout.

  FIG. 8 and FIG. 9 illustrate two other embodiments of a lighting device that is particularly suitable as a backlight for a mobile phone.

  The light guide member 10 is basically configured as described with reference to the aforementioned drawings. The light source is an LED. In the embodiment shown in FIG. 8, a single LED 34 is arranged at the corner portion 36 of the light guide member 10. The corner portion 36 is preferably chamfered so that the light source of the LED 34 is disposed in the corner portion or inside the rectangular light guide member 18. In this case, light is introduced into the light guide member 10 from the inclined surface 38 of the chamfered portion. Since the light guide member 10 is not square but usually rectangular, the angle α formed between the short side 40 and the inclined surface 38 is not 45 °, and the angle α is less than 45 °.

  In this embodiment, the individual diffractive surface elements or the individual diffractive surface element groups are arranged so that light is derived as uniformly as possible. In this case, the distance between individual diffractive surface elements or individual diffractive surface element groups in the direction of broken line 42 is such that the distance between individual diffractive surface elements or individual diffractive surface element groups increases as the distance from the LED increases. Change to decrease.

  9 also includes an LED 44 as a light source, and in this embodiment, three LEDs 44 are arranged on the short side 40 of the light guide member 10. In this case, the light guide member 10 is preferably provided with a recess 46 on the short side 40. Preferably, the recess 46 is semicircular. In this embodiment, the recess 46 is larger than the entire thickness of the light guide member 10. However, it is also possible to provide a hemispherical recess 46 smaller than the thickness of the light guide member 10.

  Also in the present embodiment, the diffractive surface elements or the diffractive surface element groups are arranged so that the illuminance distribution is uniform on the light exit surface.

  Needless to say, different embodiments as described above may be combined. For example, LEDs may be provided on several sides. Specifically, a plurality of LEDs are arranged around the entire circumference of the light guide member 10. Similarly, combinations of the embodiments shown in FIGS. 8 and 9 are possible. In particular, it is also possible to combine the LED with one or several CCFL tubes. For example, the lighting device shown in FIG. 1 can be modified so that each LED is provided at two corners facing the CCFL tube 14 as shown in FIG. This ensures that these two corners at a distance from the CCFL tube 14 are sufficiently illuminated by simple means.

  In an embodiment of the lighting device, this lighting device is provided for a flat display. An essential element of the flat display is a liquid crystal 50 (see FIG. 10). The liquid crystal is usually an LCD element, and a light source box including a plurality of tubular light sources 54 parallel to each other is provided as the light source 52. Preferably, the tubular light source 54 is a CCFL.

  According to the prior art, several foils are provided between the light source box 52 and the liquid crystal element 50. These are so-called BEF, DBEF and PRF foils.

  According to the present invention, at least the BEF foil is replaced with the light guide member 56. The light guide member 56 is basically configured as described above with reference to FIGS.

  The light guide member 56 preferably comprises a plurality of areas 58 arranged horizontally or parallel to the tubular light source 54. Preferably, each zone 58 is combined with a tubular light source 54, which is located centrally behind zone 58. The areas 58 are preferably of the same structure, i.e. the arrangement of diffractive surface elements or diffractive surface element groups in each area 58 is the same.

  FIG. 12 shows a preferred arrangement of the diffractive surface element group 33. In this case, the individual groups 33 of diffractive surface elements are arranged symmetrically with respect to the center line 60. Starting from the center line 60, the spacing between the individual diffractive surface element groups 33 decreases as they proceed in the direction of the arrow 62, ie outward.

  In this embodiment, the diffractive surface element groups 33 are arranged in rows and columns, and the distance between the columns is constant. In a variant of the invention, the area 58 may be divided into preferably rectangular sub-areas. In FIG. 12, the sub-areas will be arranged adjacent to each other. In this case, it is possible to provide different intervals between the individual sub-regions, and it is preferable to have a smaller interval in the end sub-regions, ie the left or right sub-regions in FIG.

  Instead of or in addition to the light source box 52 (see FIG. 10), four or more tubular light sources 54 are provided, for example, disposed around the periphery of the light guide member 56 so that the light is guided by the light guide member 56. You may make it inject from the side. As described above, the diffractive surface elements or the diffractive surface element groups are arranged so that the luminous intensity is distributed as uniformly as possible from the light guide member toward the LCD element. Preferably, the distance between individual diffractive surface elements or diffractive surface element groups decreases toward the center of the light guide member. It is also possible to divide the surface of the light guide member into four areas or portions, preferably four identical rectangular portions, each of which is formed point-symmetrically at the center of the light guide member.

  Although the invention has been described and illustrated with reference to specific illustrated embodiments, it is not intended that the invention be limited to these embodiments. Those skilled in the art will recognize that changes and modifications can be made without departing from the scope of the invention as defined by the following claims. Accordingly, all such changes and modifications are intended to be included within the scope of this invention as falling within the scope of the claims and their equivalents.

It is a perspective view which shows the structure of the illuminating device of this invention. It is a figure which shows the surface structure of the diffraction surface element with which the said illuminating device is provided. It is a figure which shows the arrangement | sequence of the said diffraction surface element. It is a figure which shows the example which divided | segmented the light emission surface of the light guide member of the said illuminating device into a different area. FIG. 5 is a table describing the areas shown in FIG. FIG. 5 is a table describing the areas shown in FIG. FIG. 5 is a table describing the areas shown in FIG. It is a schematic plan view of the other Example of the illuminating device of this invention. It is a schematic plan view of the other Example of the illuminating device of this invention. It is a schematic exploded view of a flat display. It is an upper model top view of the light guide member of the present invention used for a flat display. It is a one part enlarged view of the light guide member of this invention.

Claims (23)

An illumination device for illuminating a flat display, in particular, a display of a portable device from the back, comprising a light source and a light guide member into which light emitted from the light source is introduced and from which the light is led out, The light emitting surface has a surface structure including a diffractive surface element that diffracts light, and all the diffractive surface elements have a surface structure having a constant amplitude. 2. The illumination device according to claim 1, wherein each diffractive surface element acts as a diffractive element that generates a light beam focused by spectral dispersion. 3. Illumination according to claim 1 or 2, characterized in that the diffractive surface element is arranged to generate monochromatic light and white light or monochromatic light or white light by superimposing at least two adjacent light beams. apparatus. ^2. The illumination device according to claim 1, wherein the area of the diffractive surface element is 0.04 to 10,000 [mu] m < ² >, particularly 0.04 to 500 [mu] m < ² >. 2. A lighting device according to claim 1, characterized in that the distance between the diffractive surface elements is 0 to 100 [mu] m, in particular 0 to 50 [mu] m, and particularly preferably 0 to 15 [mu] m. 2. A lighting device according to claim 1, wherein the spacing between adjacent diffractive surface elements decreases with increasing distance from the light source. The illumination device according to claim 6, wherein a distance between adjacent diffractive surface elements decreases stepwise. The illuminating device according to claim 1, wherein the diffractive surface elements are aperiodically arranged. The illumination device according to claim 1, wherein the light exit surface includes a region where the distance between the diffractive surface elements is the same. The lighting device according to claim 1, wherein the light source is disposed inside and outside the light guide member, or inside or outside. The lighting device according to claim 1, wherein the light source is partially surrounded by a reflecting mirror in order to enhance the introduction of light. The illumination device according to claim 11, further comprising a parabolic mirror, wherein a light source that is a fluorescent tube is disposed at a focal point thereof. The illuminating device according to claim 1, wherein the light guide member includes a reflecting mirror and a reflecting surface, or a reflecting mirror or a reflecting surface, on at least one side surface that is not the light exit surface. The lighting device according to claim 1, wherein the light source includes one or a plurality of LEDs. The illumination device according to claim 1, wherein the light guide members have a tube shape in which the light guide members are arranged in parallel. The lighting device according to claim 1, wherein the light guide member has a wedge shape, and the light source is disposed on a small corner side of the wedge. A plurality of, preferably at least 2, in particular at least 4, and most preferably 6 diffractive surface elements are included in a diffractive surface element group, the diffractive surface element group comprising monochromatic light and white light, or monochromatic light or The illuminating device according to claim 1, which emits white light. A flat display comprising the illuminating device according to claim 1, wherein the liquid crystal element and the liquid crystal element are illuminated from the back. A plurality of, in particular, mutually parallel tubular light sources are provided as light sources, the light guide member comprises one area for each tubular light source, said areas being preferably arranged parallel to the tubular light sources, diffractive surface elements and diffractive surface element groups The flat display according to claim 18, further comprising a diffractive surface element or a diffractive surface element group. Diffractive surface elements and diffractive surface element groups, or diffractive surface elements or diffractive surface element groups are arranged in rows and columns within an area, and the spacing between the columns preferably decreases as the distance from the tubular light source increases. 20. The flat display according to claim 19, wherein 21. Flat according to claim 19 or 20, characterized in that the arrangement of diffractive surface elements and diffractive surface element groups in each zone is symmetrical with respect to the center line, the center line being preferably provided at the shortest distance from the tubular light source. display. 20. A flat display according to claim 19, wherein the area is divided into sub-areas, preferably the sub-areas are rectangular. 23. The flat display as claimed in claim 22, wherein the sub-area provided at the lateral end comprises more diffractive surface elements or groups of diffractive surface elements than the other sub-areas.

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