Patent Application
20130169905
This application relates to and claims priority from Japanese Patent Application No. 2011-145123 filed on Jun. 30, 2011, the entire disclosure of which is incorporated herein by reference.
The present invention relates to a backlight device applying a light emitting diode (LED) therein, for example, and a liquid crystal display apparatus using the same therein, and it relates, in particular, the backlight device for enabling to increase an efficiency of using the lights from a light source, thereby obtaining a picture of high-quality, and also the liquid crystal display apparatus using the same therein.
The liquid crystal display apparatus is widely used in various kinds of fields, because it can be made thin and light-weight. But, since the liquid crystal display apparatus does not emit the lights by itself, a backlight is disposed on a rear surface of a liquid crystal display panel. On the liquid crystal display apparatus having a relatively large picture plane or frame, such as, a television display apparatus, etc., for example, a fluorescence tube has been applied as such backlight. However, since it encloses vapor of mercury therein, the fluorescence tube has a load being large to the global environment, and in particular, in and area, Europe or the like, for example, it is in a tendency of being inhibited from using thereof.
Also, in order to deal with a regulation or request for energy saving in recent years, reduction of electric power is requested for the liquid crystal backlight device.
Then, in the place of the fluorescence tube, it is started to apply the light emitting diode (LED) as a light source of the backlight. The number of the liquid crystal display apparatuses applying an LED light source is increasing, every year, even in the field of a large display device, such as the TV, etc. The backlight for the liquid crystal display apparatus must be a surface or plane-like light source, but the LED is a point or dot-like light source. Accordingly, in the backlight for the liquid crystal display apparatus applying the LED light source therein, an optical system is necessary for forming the plane-like light source from the dot-like light source, such as, the LED light source or the like (thus, a one for converting the dot-like light source into the plane-like light source). The followings are already known, as the conventional arts relating to the optical system for obtaining such plane-like light source.
For example, in the following Patent Document 3 is disclosed the configuration of disposing a light guiding plate just below a liquid crystal display panel, with forming line-like recessed portions on this light guiding plate, wherein side-emission type LED light sources are disposed in this recessed portion in a line-like manner. Further, in the Patent Document 3 is also disclosed the configuration, wherein the side-emission type LED light sources are constructed with applying optical parts, for emitting the lights from the LED light sources from side surfaces thereof, and on a reflection sheet portion are formed a diffusion reflection region having a function of reflecting/diffusing the light and a regular reflection region having a function of regular reflection, so as to reflect/diffuse the lights at a predetermined ratio, intentionally, and thereby to increase an efficiency of using the lights and also reduce unevenness of the brightness thereof.
Also, for achieving the energy saving, but through other approach to that, an area lighting control for controlling each of blocks while dividing a backlight device into plural numbers of blocks (or being called “a local dimming”) is put into an actual practice. Such conventional technology is already known, as described in the following Patent Document 1, for example, disposing light guiding blocks divided in a tandem manner as a plane light source device having a large light emitting area. In this is disclosed in that, a pileup portion between the light guiding blocks neighboring with each other forms a tang-like pileup portion being cut off, for protecting from shortage of the brightness generating, due to electrode portions at both ends of a primary light source, by taking the difference of brightness into the consideration, between both ends and a central portion as the primary light source, which is disposed for each of the light guiding blocks, and further that electrode portions at both ends of the primary light source are wound round and those electrode portions wound round are disposed in an outside of the region of the light guiding blocks.
Also, the following Patent Document 2 discloses therein, backlight units, which are divided, are combined with in the vertical and horizontal directions, for a backlight in a large-size liquid crystal display, and further, a transparent acryl plate is put into or a desired space is held, between the backlight including the light guiding plate and the liquid crystal panel and the diffusion plate, for preventing the unevenness of brightness from generating in each of connection portions between the respective backlight units.
The backlight relating to the conventional technologies mentioned above has the configuration of guiding the lights propagating in the horizontal direction, with using the light guiding plates, by a unit of the block or the backlight unit, to the side of the liquid crystal, to be emitted therefrom. For that reason, an optical member is necessary, newly, such as, the light guiding plate, etc., therefore it brings about a cost-up due to an increase of the optical members and also an increase of a number of parts for positioning/fixing thereof, and further needs a structural measure for fixing the light guiding plate, etc.
Also, when aligning the optical members, such as, the blocks or the light guiding plates of the backlight units, etc., there is a possibility of generating positional shift or the like, therein. If the positional shift is generated, it brings about leakage of the light from a boundary defined between the blocks or the backlight units with each other, thereby generating a bright line, and/or brings about shortage of the light, thereby generating a dark line; i.e., bringing the spatial distribution of the lights emitting from the backlight to be un-uniform, and therefore bringing about a drawback of generating the so-called unevenness of the brightness. For avoiding such drawback, with the conventional technologies described in the Patent Documents 1 and 2 motioned above, there is necessity of applying special structures therein, such as, treating machining on the light guiding blocks neighboring with each other, changing the configuration of the light emitting source, and further providing an acryl plate for use of diffusion in an upper portion of the light guiding plate, etc. Moreover, with those conventional technologies, since each block is so arranged that the brightness comes to be uniform in an inside thereof, there is brought about a drawback that the bright line on the boundary comes to be remarkable, on the contrary to that.
Also, with the conventional technology described in the Patent Document 3, it is necessary to form a diffusing reflection region having a diffusing reflection function and a regular reflection region having a regular reflection function on the reflection sheet portion, and therefore there is a drawback of restricting on thin-sizing of the backlight, as well as, needing a complex optical design; however the Patent Document 3 never describes about such problem therein.
The present invention is to provide a technology for enabling to obtain an appropriate optical output while increasing an efficiency of using the lights from the light source (for example, uniformity of brightness), with a simple structure, in a backlight device and a video display apparatus applying the same therein.
The present invention is characterized by the constituent elements described in the claims, which will be mentioned below. In more details thereof, the present invention comprises the followings.
(1) The backlight for irradiating lights onto the liquid crystal panel is constructed with plural numbers of backlight blocks, dividing the backlight in 2-dimensional manner, wherein each backlight block comprises a sheet-like reflection member, which is disposed on a bottom surface (i.e., on the side opposite to the liquid crystal panel) of that backlight block, a plate-like optical element, which is provided opposing to that reflection member and is disposed in the direction perpendicular to a light emitting surface of the backlight (i.e., on the side of the liquid crystal panel), separating from that reflection member by a predetermined distance, and a light source (for example, a side-view LED (s)) for radiating the lights into the horizontal direction (in the direction in parallel with the light emitting surface of the backlight), so that the lights from that light source transmit through the optical element in the direction of the surface thereof while reflecting within a space defined between the optical element and the reflection member, repetitively, to be guided to the liquid crystal panel.
(2) In an inside of the each backlight block, such as, on the optical member and/or the reflection sheet mentioned above is/are provided a predetermined pattern(s).
(3) In a backlight device for irradiating lights onto a liquid crystal panel, plural numbers of backlight blocks, each having plural numbers of light sources, each having a light emitting axis (i.e., an optical axis) in the direction in parallel with a light is irradiating surface of the backlight, and being disposed in the direction perpendicular to that emitting axis, a sheet-like reflection member for reflecting the lights from said light sources, and a plate-like optical element, being disposed separating from that reflection member by a predetermined distance and for guiding the lights from the light sources, are disposed in parallel with in the direction of a surface of the backlight, wherein an optical control member for controlling or adjusting an amount of emission of the lights is provided on a rear surface (on the side facing to the reflection member) or a front surface (on the side facing to the liquid crystal panel) or both surfaces of the optical element mentioned above, or in the vicinity thereof.
(4) The light control member mentioned above has at least two (2) or more numbers of functions, among reflection, transmission, diffusion, shielding, absorption, re-emission, coloring, wavelength conversion and polarization of the lights.
(5) On the light control member or the optical element is provided patterns, each having a predetermined configuration, wherein a pitch or a density or a shape of those patterns in the horizontal direction is changed depending on the position of the light control member of the optical element, while keeping the pitch or the density or the shape of those patterns to be nearly equal to, in the direction perpendicular to the optical axes of the light sources, in the direction in parallel with the light emitting surface of the optical element or the rear surface thereof (i.e., the direction, in which the light sources are aligned).
(6) A condition, p≦a≦c is satisfied, where assuming that largeness (size) of the pattern is “a”, in the direction perpendicular to the optical axes of the light sources, and in direction in parallel with the light emitting surface or the rear surface of the optical element, largeness of each light emitting surface is “c” of said light sources, and the pitch of the light sources is “p”.
(7) In (6) mentioned above, further is satisfied a condition, n p≦a≦0.5×e, where assuming that a pitch of said patterns is “e”.
(8) In (6) mentioned above, further is satisfied a condition h≦a, where assuming that the distance is “h” between the optical member and the reflection member (i.e., the diffusion distance).
(9) Other pattern is provided at a position corresponding to that between two (2) light sources neighboring with each other, and a transmission factor “T” of the other pattern satisfies a condition, 0.1% T<50%.
(10) The patter of the predetermined shape has a deformed surface, having a concave/convex surface, a prism, a convex lens or a concave lens, and the deformed surface is formed through a mold injection, a laser machining or a printing.
(11) The optical element has a selective transmission factor control layer for enabling to control the transmission factor, selectively, at least upon basis of a relative and positional relationship with respect to the light sources, and a diffusion layer. Further preferably, the optical element builds up a laminated structure of piling up a brilliant layer, the transmission factor control layer, a transparent layer, and a diffusion layer, in an order starting from the light source.
(12) In (11) mentioned above, the selective transmission factor control layer is made up with a light shield layer having plural numbers of light takeout portions, an area or size of each light takeout portion per a standard area differs from, depending on an amount of lights irradiating on the light shield layer, per the standard area, which is determined from the relative and positional relationship with respect to the light sources.
(13) In (12) mentioned above, the light shield layer includes a reflection member of diffusion/reflection property.
(14) In (12) or (11) mentioned above, on the light shield layer is provided no light takeout portion, in the vicinity of an area or region where the amount of lights irradiating on the light shield layer, per the standard area, comes to the maximum.
(15) In any one of (11) to (14) mentioned above, the light takeout portion of the light shield layer is an opening of either one of a circular shape, an oval shape, or a slit shape, or a combination thereof. When applying a prism sheet as the optical sheet to be disposed between the liquid crystal panel and the optical element, it is preferable that a longitudinal direction of a slit of the light takeout portion is coincident with the direction, in which ridges of prisms of the prism sheet extend.
(16) In (1) to (15) mentioned above, there is a light source substrate for mounting the light sources thereon, and the light sources are mounted on the light source substrate in such a manner that the light emitting surfaces of the light sources are nearly coincident with an end portion of the light source substrate. Further, on the reflection member is provided an incline portion being inclined directing from an upper portion of the light source substrate to a bottom surface of the backlight.
According to the present invention, it is possible to obtain an appropriate optical output while increasing an efficiency of using the lights from the light source (for example, uniformity of brightness), even with a simple structure. Thus, with such simple structure of not using the light guiding plate, conventionally being necessary in the optical system for obtaining a plane-like light source, it is possible to obtain a uniformity of lights within a surface of the backlight unit, or a uniform distribution of brightness on the whole light emission surface of the backlight. Also, with such a predetermined pattern as was motioned above, it is possible to mitigate the difference of the brightness on the boundaries among the backlight units to be unremarkable, and also to reduce the unevenness of brightness within an each surface of the backlight blocks.
Also, by controlling plural numbers of light sources corresponding to the backlight blocks as a one (1) group of the light source, it is possible to control the brightness for each of the backlight blocks.
Those and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings wherein:
Hereinafter, explanation will be given on a backlight device according to an embodiment of the present invention, in details thereof, by referring to drawings attached herewith. However, same reference numerals are given to elements having the same functions or structures among the different drawings, and therefore the duplicated explanations thereof will be omitted.
First of all, explanation will be made on an outlook of the entire structures of applying the backlight device according to the present embodiment into a video display apparatus, by referring to
As is shown in
The backlight device 3 according to the present embodiment, as is shown in
The backlight device 3 mentioned above, as is shown in
As the optical element 2 is applied, for example, a diffusion plate, a transparent acryl plate, a mirror-surface plate, a diffusion plate with fine patterns, an optical sheet, an optical characteristic control plate, a polarization select plate, etc. On the rear surface of this optical element 2 is provided a light control member 9 for controlling or adjusting a supply amount of lights onto the optical element 2 depending on the position of the optical element 2. In the example shown in
With this, apart of lights incident thereon passes through the light control member 9 and on the spot it is emitted from the optical element 2 as the diffusion light. Also, other part of the lights incident thereon is reflected upon the light control member 9, and it propagates in the direction of the optical axis of the light source 7 within the space mentioned above in cooperation with the reflection function by the reflection sheet 19 mentioned above; i.e., the lights are guided or transmitted far from the light source 7. Namely, the light control member 9 reflects a part of the lights from the light source 7 and the light reflected on the reflection sheet 19 thereon, while passing through other part thereof, and conducts this, along the direction of the optical axis, repetitively, and thereby supplying the lights up to a tip portion of the backlight block 4 (i.e., a portion opposite to the position of the light source 7), fully. With this, it is possible to obtain a uniform distribution of brightness, as well as, an increase or improvement of an efficiency of using the lights, irrespective of sizes of the backlight block 4. On the light control member 9 is provided slits or patterns for achieving the transmission and the reflection of the light mentioned above.
The optical element 2 and the light control member 9, in particular, the light control element 9 changes optical functions thereof, such as, the size or the configuration of the slits or the pattern, or a transmission factor of lights, a reflection factor, diffusivity, a degree of capture, a propagation rate, a polarization transmission factor, a color transmission factor and spectral characteristics, etc., as it is far from the vicinity of the light source 7 in the direction of the optical axis of the light source 7. With doing this, it is possible to achieve the uniformity within the backlight block 4, easily.
Herein, when assuming that the distance between the optical element 2 and the reflection sheet 19 (i.e., the height of the space mentioned above) is “h”, the height of the LED 7 “Lh”, respectively, then it is preferable to bring the relationship between the distance “h” and the height “Lh” into 5Lh>h>1.2Lh. With doing so, it is possible to enlarge or diffuse the lights leaking from an upper surface of the LED 7, and also a hotspot (s) generating in the vicinity of the light emitting portion of the LED 7 (i.e., a portion where the light comes to be bright locally), within the space having the distance “h”, according to so-called a COS4 angle (i.e., a low of 4th power), and thereby bringing it/them to be uneven, i.e., being difficult to be recognized. The condition mentioned above can be also called, the distance necessary for reducing the light passing through the light control member 9 directly entering from the LED 7, because the side-view type LED 7 and the light control member 9 come close too much.
Also, on the optical element 2 is arranged a group of optical sheets 8, such as, prism sheets or brightness increasing sheets, etc., thereby reducing the unevenness of brightness on the whole irradiation surface of the backlight. In
Further in
As shown in the figures, patterns 101 to 103, being formed in the direction of the optical axis of the light source 7 (i.e., in the left/right direction on the paper surface) are changed, in pitches, densities or shapes thereof, depending on the distance from the light source 7. On the other hand, patterns 91, being formed in the direction of the vertical direction to the optical axis of the light source 7 (i.e., in the up/down direction on the paper surface) are same in the pitch, the density or the shape thereof. In more details, the patterns 101 to 103 are formed, being extended or expanded in the optical direction much more than in the direction opposite to the light emitting direction (the optical direction) of the light source 7. Also, the patterns 101 to 103 are formed, being changed depending on the distance from the light source 7 in the optical direction thereof; for example, it may be formed in a shape of being tapered or thinner much more, as the distance from the light source 7 becomes larger in the optical direction thereof, like the pattern 101, in a shape of combining an oval having the major or long axis in the optical direction of the light source 7, with an oval perpendicular to the direction of the optical axis, like the pattern 102, or in a shape of expanding much more as the distance from the light source 7 becomes larger in the direction of the optical axis, like the pattern 103.
Basically, the patterns 101 to 103 mentioned above are formed on the rear surface of the optical element 2, however they may be provided on the front surface of the optical element 2. Also, the patterns 101 to 103 may be formed, by attaching a print sheet, a thermal transfer sheet, a reflection/transmission sheet having holes, a reflection with patterns, or an optical sheet, on which the patterns are printed, on the rear surface or the front surface or both of them of the optical element 2, in the vicinity of the light source 7.
As the patterns 101 to 103 may be applied any kind of shapes or made from any kind of materials, as far as they can control or adjust the light shielding function, the transmission, the reflection and/or the propagation rate, etc., depending on the position (i.e., the distance from the light source 7). For example, density of the patterns is reduced as they are separated from the light source 7, gradually, in the direction of the optical axis of the light source 7, to increase the light shielding and the reflection to be large in the vicinity of the light source 7, so that an amount of transmitting lights therethrough comes to be less than 10%, while bringing the transmitting lights to be large at the positions far from the light source 7. With this, not only the lights from the light source 7 advancing into the axial direction, but also the lights propagating 2-dimensionally (e.g., radially) are increased in the amount of transmission thereof, and therefore it is possible to rise up the amount of lights emitting to the liquid crystal panel depending on the distance from the light source 7. And, with such structure, it is possible to reduce the unevenness of brightness in the direction of the optical axis of the light source 7, and also to increase a uniformity of brightness within the backlight unit and on the front surface of the backlight irradiation surface.
The patterns 101 to 103 mentioned above can be formed with such an aggregate of fine dots, as is shown in
Also, when forming through printing, the patterns can be adjusted, easily, on a film-thickness of ink, a color of ink (applying the gradations by mixing the colors, such as, blue and black, thereby to control the transmission factor), a dot size, a dot shape, a pattern configuration just upon the LED, thickness of orienting, and therefore it is possible to form the outer configuration of the dots and/or the aggregation of dots, more preferably. Accordingly, when forming the patterns through the printing, the uniformity of brightness can be increased, much more.
Herein, as is shown in
As shown in the figure, a signal control substrate 15, an LED drive circuit 16 and a power source 14 are disposed between a back cover 17, being the rear surface housing of the liquid crystal display apparatus, and the chassis 11. The signal control substrate 15, the LED drive circuit 16 and the power source 14 are attached on the chassis 11. The chassis 11 may be one pasted the reflection sheet 19 mentioned above thereon. Also, it is possible to form a contraction on the chassis 11 pasted with the reflection sheet 19 through the pressing work, so as to form a curved surface or an inclined surface along the optical axis of the light source 7, and thereby changing the reflection angles of the lights upon the surface of the reflection sheet 19. With this, there can be obtained an effect of propagating the lights, easily, from the light source 7 in the direction of the optical axis thereof, and increasing the amount of lights to be supplied to the tip portion of the backlight block 4 (e.g., the portion opposite to the position of the light source 7) much more.
The space between the reflection sheet 19 and the light control member 9 is held by pin molds 38 having a corn shape, maintain a predetermined distance therefrom. With this, the lights can emit, gradually, from the light control member 9 and the optical element 2, while propagating within the backlight block 4, and thereby enabling to control a uniform light as a whole by a unit of each the backlight block.
By referring to
Herein, in the example of the structures shown in
Next, explanation will be given about the technology for mitigating the difference of brightness between the brightness on the boundary of the backlight block and the brightness within the backlight block in the backlight device according to the present embodiment, thereby bringing the brightness on the boundary to be unremarkable, by referring to
As was mentioned above, when the plural numbers of the backlight blocks 4 are aligned in horizontal/vertical, the leakage of the lights from the boundary of the backlight blocks and/or just above the LED 7 brings about the bright line or the hot spot, and the light/dark portion of brightness is generated due to this. Or, on the contrary, there may be a chance that shortage of the lights is generated on the rear surface on the boundary of the backlight block and the rear surface of the LED 7, and thereby resulting into the dark line.
Then, in this example, such optical patterns 40, 41 and 42 as shown in the figure are disposed on the rear surface and/or the front surface of the optical element 2, so that the lights emitting from the light source can emit uniformly (i.e., in the direction of this side in the vertical direction on the figure), i.e., to be uniform in the brightness.
Within the backlight device according to the present embodiment, the intentional light/dark difference of brightness is formed within the backlight block, so that the unevenness of brightness reaches all over the entire thereof, and thereby mitigating line-like or grid-like light (or dark) portions of brightness on the boundary between the backlight blocks; thus, it is characterized of being difficult to be recognized, visually. In the example shown in
However, when the dark line is generated on the boundary, for making this dark line unremarkable, it is enough to provide a pattern, being darker than a surface of uniform brightness of the backlight block and brighter than the dark line mentioned above, so as to form the light/dark difference of brightness in the backlight block 4.
Also, this light/dark pattern has a rectangular shape, as is shown in
With such the structure as shown in
However, the light/dark difference of brightness mentioned above can be achieved, not limiting to form the pattern (s) on the optical element 2 or the light control member 9, but also on the reflection sheet 19, or the optical sheet or the like 18.
Also, not shown in the figure, an oval-shaped intermediate light/dark portion of brightness may be formed within the backlight block 4. This intermediate light/dark portion of brightness can be formed with so-called a roughen surface, such as, a fine or dense concave/convex surface formed on the surface of the optical element 2. This oval-shaped roughen surface is aligned by plural numbers of thereof, on the optical element in the direction in parallel with the direction of alignment of LEDs 7 (e.g., in the direction of short side of the optical element 2 in the present embodiment), and thereby forming a one (1) area or region of the intermediate light/dark portion of brightness, and this area is provided by two (2) or more numbers thereof, in the direction perpendicular to the direction of alignment of the LEDs 7 (e.g., in the direction of short/long sides of the optical element, in the present embodiment). With this, those roughen surfaces achieve the function of enlarging an amount of lights advancing to the front than surrounding surfaces thereof, and thereby generating the light brightness.
When seeing the entire of the backlight device 3 including the boundaries of the backlight blocks 4, the unevenness or the non-uniformity is produced in the light/dark distribution of the brightness emitting ahead from this backlight device 3, due to existence of the intermediate light/dark portion of brightness, and it is difficult to recognize a degree of the light/dark of brightness, visually (i.e., the brightness on the boundary becomes unremarkable). The intermediate light/dark portion of brightness should not limited to the oval shape, but may be the circular shape or an oblong shape, or may be provided by a different number of pieces thereof, neighboring with each other (for example, a number of pieces in the direction of the vertical direction on the paper surface), such as, two (2) or three (3) pieces, for example. The point is that the intermediate light/dark portion of brightness can be formed, so that the non-uniformity of the difference of brightness can be generated between the dark portion of brightness.
In the embodiment mentioned above, an element for giving a light portion (hereinafter, being called “a light portion grant element”) is formed on the surface of the optical element 2 (e.g., the diffusion plate), such as, the roughen surface, the concave/convex surface, the prism surface, the concave lens or the convex lens, etc., mentioned above, elongating in the direction in parallel with the direction of aligning the LEDs 7 (e.g., in the direction of the short side of the optical element 2, in the present embodiment), and at least two (2) or more numbers of this light portion grant element are aligned in the direction perpendicular to the direction of aligning the LEDs 7 (e.g., in the direction of the short side of the optical element 2, and in particular, in the direction, into which the lights from the LED advance within the optical element, in the present embodiment). With applying such structure, since on the surface of the optical element 2 can be produced the difference of brightness (i.e., the unevenness of brightness), being shorter than a cycle of the light portion of brightness (or the dark portion of brightness) on the boundary portion of the backlight block 4, then that light portion of brightness (or the dark portion of brightness) on the boundary portion of the backlight block 4 is hardly recognized, visually.
The distance between the maximum points of brightness themselves among at least two (2) or more numbers of light portion grant elements is, preferably, approximately from 0.5 to 3 cm, and further, it is preferable to determine the distance between those maximum points themselves, being longer, at least two (2) times or more, than the distance from the surface of the diffusion plate up to a plane of incidence of the optical sheet or the like (the plane of incidence of the diffusion plate, which is disposed at the position closest to the diffusion plate). Also, the difference of brightness between the lights transmitting the light portion grant elements and the lights emitting from portions other than the light portion grant elements on the surface of the diffusion plate is preferably 500 or more than that, of the difference of brightness between the lights emitting from the light portion of brightness (or the dark portion of brightness) on the boundary portions of the backlight block 4 and the portion(s) other than the light portion grant elements on the surface of the diffusion plate. Forming the light portion grant elements in such a manner as to satisfy those conditions enables to bring the light portion of brightness (or the dark portion of brightness) on the boundary portions of the backlight block 4 to be unremarkable.
Also, with provision of the element for diffusing the lights mentioned above on the surface of the diffusion plate in the direction perpendicular to that of aligning the LEDs 7, the light portion of brightness (or the dark portion of brightness) on the boundary of the backlight block 4 generating in the direction perpendicular to that of aligning the LEDs 7 (in the left/right direction on the paper surface of
With such the structure of the embodiment as was mentioned above, it is possible to bring the light portion of brightness or the dark portion of brightness on the boundary of the backlight block 4 to be unremarkable; but it is also possible to bring the light portion of brightness or the dark portion of brightness, generating within the backlight block 4 other than that on the boundary, to be unremarkable.
In
The diffusion plate 2 has a roll of directing an array of light sources, which is constructed by arranging a large number of LEDs 7, being the dot-like light sources, on plural numbers of stages, in an array-like manner, towards the liquid crystal panel 1 as a uniform plane-like light source. The diffusion plate in the present embodiment is characterized that it has a multi-layer structure of piling up a diffusion layer 22, a transparent layer 23, a light shield layer 24 including a light takeout portion 25, and a polish layer not shown herein, in an order from that closest to the liquid crystal panel 1 (i.e., one by one, from the liquid crystal panel 1 to the chassis 11). The light takeout portion 25 is an opening (e.g., a penetrating hole), such as, a bore or a slit, etc., for example, which is provided on the light shield layer 24, as will be mentioned later.
The diffusion layer 22 is thin and plate-like in the shape thereof, and although, in the present embodiment, as the diffusion layer 22 is applied a diffusion plate, DRIIIC series, made by Nitto Jushi Kogyo Co., Ltd., having 1 mm thickness; however, it is also apply a diffusion plate, in the similar manner, if being lower than 80% in the transmission factor, and the thickness should not be limited to 1 mm, or it may be formed in one body by painting a resin, including particles having diffusibility therein, on a side of an acryl transparent resin substrate, being the transparent layer, facing to the liquid crystal panel, or mixing them into the transparent resin plate.
On a lower surface of the diffusion plate 22 is applied an acryl substrate, ACRYLITE® made by Mitsubishi Rayon Co., Ltd., having 1 mm thickness, as the transparent layer 23. This acryl substrate is mirror finished on both surfaces thereof, so that the haze value indicating the diffusibility thereof is suppressed down to around 0.5%. Almost of parts of the lights entering from the LEDs 7 into the transparent layer 23 are refracted or reflected on the mirror depending on an incident angle, without being diffused. Because the transparent layer 23 is a flat plate having both surfaces in parallel with, all of the lights entering into the transparent layer 23 due to refraction enter into the diffusion layer 22, in accordance with the Snell's law in relation to the refraction. On the other hand, in case where no transparent layer 23 is provided, since a part of the lights is diffused/reflected depending on the diffusibility or the transmission factor of the diffusion layer 22, it is difficult to take out a sufficient amount of lights therefrom, and then for the light takeout portion 25 it is necessary to be a large opening. In this case, separation of the functions becomes insufficient, between taking out of lights and propagation/guiding of lights, and in particular, when the size of the light source block is large, it is difficult to obtain the uniformity of brightness. According to the present embodiment, addition of the transparent layer 23 enables the lights to propagate to far, with uniformity.
Under the transparent layer 23 is formed the light shield layer 24 having the light takeout portion 25, for adjusting an amount of lights to be taken out depending on the intensity of the lights propagating/radiating from the LEDs 7 upon the lower surface of the diffusion plate.
In the present embodiment, a diffusion/reflection sheet E6SP, made by TORAY INDUSTRIES, INC., having high brilliance on both surfaces thereof, is pasted on the acryl plate of the transparent layer 23, as the light shield layer 24, in one (1) body. As the structure according to the present embodiment, the polish or brilliant layer is not necessary between the transparent layer 23 and the light shield layer 24; however, since there cannot be found almost no difference in an index of refraction between the brilliant layer of the diffusion/reflection sheet and the transparent layer 23, there is no difference in the optical characteristics.
On the light shield layer 24, as is shown in
Increasing the brilliance on the surface of the light shield layer 24 enables to guide the lights from the LEDs 7 to a faraway. The diffusion/reflection sheet E6SP, made by TORAY INDUSTRIES, INC., is high, 120%, in the brilliance, with respect to the incident light by 60 degrees, and therefore, comparing to the case of applying a normal diffusion/reflection sheet having the brilliance around 30%, there can be obtained a light guiding distance, as two (2) times longer as that of the normal one.
In the present embodiment, although as the light shield layer 24 is applied the diffusion/reflection sheet E6SP, made by TORAY INDUSTRIES, INC., but it should not be restricted to this. For example, in case where the size of the backlight block is large and it is required that a ratio of reducing or dimming the lights is large in periphery of the light source, it is possible to obtain the uniformity by applying the diffusion/reflection sheet, being low in the transmission factor of light beam, as the light shield layer 24. In case where the brilliance is not enough, a resin having the brilliance may be painted or a resin film having the brilliance may be pasted on the surface thereof.
In normal, when trying to propagate the lights to a faraway, it is common to apply an optical system, only using mirror reflection therein; however, for the purpose of achieving the uniformity of brightness within the backlight block, it is a problem to be dissolved to satisfy both, maintaining the distance of light guiding, and at the same time, propagating the lights in between the LEDs 7, being disposed in a line-like manner and neighboring with each other, and also behind the LED light source, too. According to the present embodiment, by taking such problem(s) into the consideration thereof, among the lights incident upon the diffusion plate, being the optical element 2, from the LEDs 7, the lights incident upon by a shallow angle are guided based on the mirror reflection, while the lights incident upon by a deep angle are guided in combination of the direct transmission and the diffusion/reflection by the light shield sheet, and also the transmission through the opening portions of the light takeout portion 25; thereby maintaining the uniformity of the lights emitting from the backlight.
In more details thereof, within the light shield layer 24, upon which the lights are irradiated from the LEDs 7, and also the transparent layer 22, at least a side surface, upon which the lights transmitting through the hole portions of the light takeout portion 25 are irradiated (i.e., the surface facing to the LEDs 7) is made by a mirror surface, so as to reflect the lights thereupon, and thereby improving the characteristic of propagating the lights reflecting on the surface to a faraway, while for a component of light being diffused/reflected by the light shield layer 24, other than the surface reflection, a reflection sheet is applied, having high performance or capacity, not only of the front diffusion, but also the back diffusion.
As shown in
From the flat portion 34 up to an LED 7 of a next stage, because the reflection angle upon the surface of the reflection sheet 32 comes upwards, with provision of an inclining portion 35 directing from the surface of the chassis 11 towards the LED substrate 6, on the reflection sheet 32, a high efficiency of taking out the lights can be obtained, with compensating shortage of the amount of lights, which is generated due to separation far from the LED light source 30.
With controlling the transmission factor of the light shield layer 24, appropriately, there can be obtained a desired brightness only due to the lights reaching to the diffusion plate directly transmitting through the light shield layer 24, without forming the light takeout portion 25 on the light shield layer 24 in an area where the light intensity is most strong on the light shield layer 24. With this, it is possible to achieve the backlight having a uniform distribution of brightness, without generating the unevenness of brightness, being called the “hot spot(s)” caused due to the light source.
Also, the LEDs 7, in particular, light emitting portions thereof, are arranged to be close to an end portion of the LED substrate 6, and also, as shown in
As is shown in
In the present embodiment, it is also possible to form the diffusion plate by a resin plate made of transparent acryl resin, or polycarbonate resin, with changing the density of arrangement of the pinholes having a fine diameter depending on the intensity of the lights irradiating thereon. In this instance, the thickness of the plate must be sufficient for mixing up the lights passing through the neighboring pinholes, fully, and if assuming that the maximum distance between the pinholes is about 1 mm, then the uniformity can be obtained with the thickness of about 3 mm of the transparent resin plate.
According to the present method, as the group of optical sheets 18 to be piled up on the transparent resin plate, one (1) or two (2) piece (s) of the diffusion sheet (s) D121U, made by TSUJIDEN Co., Ltd., are disposed, and thereby the backlight without unevenness of brightness can be achieved. With this, a thin-type backlight being superior in the uniformity can be achieved, without using the diffusion plate or the prism sheet, being expensive, and also piling up of the diffusion plate on the transparent resin enables to achieve thin-sizing, without miniaturizing the pinholes and/or the slits so much.
The configuration of the light takeout portion 2032 (e.g., the opening) mentioned above can be selected into an appropriate shape, depending on combination with the group of optical sheets 18 or an accuracy when machining the light takeout portion 25.
Also, the light shield layer 24 may be painted with the high brilliant resin or pasted with the high brilliant resin film on the surface thereof, after being formed on the lower surface of the diffusion plate.
Since application of the resin film of high brilliance enables to obtain high propagating characteristics, without using the diffusion/reflection sheet of high brilliance, it is possible to achieve a backlight capable with the size of a large-size light source block. Further, as a secondary effect thereof, since it is laminated or pasted, after forming the pinholes and/or the slits, the resin film also functions, of an improvement of an anti-sticking, an index against rubbing or abrasion, and as a protection layer for preventing the characteristics from being deteriorated due to accumulation or adhesion of dusts in the hole portions.
Also, with forming the light takeout portion 25 by holes, being large a little bit, a print pattern of high accuracy may be treated on any surface of the transparent layer 23 or the side of the diffusion layer 22 facing to the LED 7, and thereby obtaining a duplicated light shield structure, jointly applying the forming of the detail patterns of the light takeout portion 25.
In the structure of the present embodiment, since the LEDs 7, being the dot-like light source, are aligned in a line-like manner below the diffusion plate 2, it is possible to control the brightness for each area or region of a screen, i.e., an area control. Herein, the area control means control, such as, while lighting up the LEDs 7 of the backlight block corresponding to a bright portion of the screen, the LEDs 7 of the backlight blocks corresponding to a dark portion are not lighten up or turned to be dark, for example.
Such area control can be achieved by lighting up only the LEDs 7 of the backlight blocks corresponding to the bright portion, while memorizing video information in a frame memory and by discriminating or identifying the bright portion and the dark portion on the screen. With conduction of such area control, it is possible to obtain reduction of the power consumption and also an improvement of the contrast.
In this manner, according to the present embodiment, controlling the LEDs 7 for each backlight block 4, separately, enables the area control (i.e., the local dimming) depending on the video.
In
Although the fundamental configurations are similar to that shown in
Although the fundamental configurations are similar to those shown in
As was mentioned above, according to the present embodiment, in spite of the simple structure thereof, it is possible to obtain an appropriate uniformity of brightness by increasing an efficiency of utilizing the lights from the light source. Thus, with the simple structure, not applying the light guiding plate, which is necessary in the conventional optical system for obtaining the plane-like light source, it is possible to obtain the uniformity of lights within the surface of the backlight block, or the uniform distribution of brightness covering over the entire light emitting surface of the backlight. Also, with the patterns having the predetermined shapes mentioned above, the difference of brightness from the boundary of the backlight block can be mitigated or made unremarkable, and therefore it is also possible to reduce the unevenness of brightness within the surface of the backlight block.
Also, with controlling the plural numbers of the light sources corresponding to each backlight block to be one (1) group of the light sources, it is possible to control the brightness for each backlight block.
The present invention may be embodied in other specific forms without departing from the spirit or essential feature or characteristics thereof. The present embodiment(s) is/are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the forgoing description and range of equivalency of the claims are therefore to be embraces therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-145123 | Jun 2011 | JP | national |
