Patent Application
20090066878
The present invention relates to a liquid crystal display apparatus, and in particular, it relates to a liquid crystal display apparatus, in which elaboration is made for irradiating a light of a backlight upon a liquid crystal display, suitably, by means of light emitting diodes.
For the purpose of further increasing the picture quality or thin-sizing of the liquid crystal display, there is a case where the light emitting diodes (LED) are applied as the backlight. Also, accompanying with the large-sizing of the liquid crystal panel, the backlight method of applying the LED therein is shifted from a sidelight method (i.e., the method of disposing the LED on a side surface of the liquid crystal panel) into a directly underlying light method (i.e., the method of disposing the LED on the rear surface of the liquid crystal panel).
In general, since the LED is a point light source having a predetermined directivity, then it is necessary to irradiate the light, which is radiated from the LED directly underlying the liquid crystal display, uniformly as a surface light source upon the liquid crystal display.
As the conventional technology for equalizing or obtaining uniformity of the light from the LED, the followings are already known, which are described in the Patent Documents 1 through 3, for example.
The Patent Document 1 discloses therein a technology of providing a light control plate forming a purism structure for controlling the light emission direction from the light source, i.e., each LED, for each of a plural number of LED light sources, which are aligned on a circuit board.
The Patent Document 2 discloses therein a backlight device for guiding a light of a light source, which is disposed in a concave portion provided around a center on one surface of a transparent light guiding plate, by means of a light guiding plate, thereby emitting the light from an emission surface of that light guiding plate, and in particular, a technology of providing a concentric circle-like prism for reflecting the light from the light source, on the one surface of the light guiding plate.
Also, the Patent Document 3 discloses therein a technology of building up a translucent means for diffusing and polarizing the light from the light generating source (i.e., LED), from a polarizing material, having a characteristic of reflecting the light incident at a predetermined angle from the light generating source, and further providing a re-reflection member for reflecting the reflection light from that polarizing member, again thereon, so as to emit it to the translucent means.
[Patent Document 1] Japanese Patent Laying-Open No. 2006-344409 (2006);
[Patent Document 2] Japanese Patent Laying-Open No. 2007-48489 (2007); and
[Patent Document 3] Japanese Patent Laying-Open No. 2007-59146 (2007).
The technology described in the Patent Document 1 mentioned above takes the high-angle radiant light from the LED light source into no consideration thereof. Herein, the high-angle radiant light is a light emitted from the LED light source, having a large angle from the optical axis of the LED light source (i.e., the direction perpendicular to a light emitting plane), and it is the light emitted at an angle in the direction near to a main plane of the circuit board. Since the structures shown in the Patent Document 1 has the light control plate, which is provided at the opposite position on the light emission side of the LED light source, it is impossible to make such control that the high-angle radiant light directs to the side of the liquid crystal display.
The technology described in the Patent Document 2 shows the backlight device, wherein this light source is made up with the light emitting diodes, the entire side surfaces of which are made of the light emitting surfaces thereof. However, the structure of letting the lights propagate from a center of the light guiding plate to all of the directions is basically an application of the principle of a sidelight-type backlight, and therefore it has a drawback that brightness of the light is lowered down when separating from the light source; however, it never take such the drawback into the consideration thereof.
The technology described in the Patent Document 3 uses a lot of reflection members therein, so as to control the lights of a light source to propagate into a desired direction, and also the light emission source and the reflection members are made up in one body; therefore, the light source is complex in the structures thereof. Also, since the light emitted by the reflection members of the light emission source is determined by a positional relationship among the light emission source, the reflection members, and a prism sheet, therefore it is impossible to determine the performances as the backlight device, by itself, and also there is a necessity of determining the position where the light emission source should be provided, for each of the liquid crystal display apparatuses, and there is also possibility that the performances on brightness may be changed depending upon accuracy, in particular, in positioning the members mentioned above.
The present invention is accomplished by taking the drawbacks mentioned above into the consideration thereof, and an object thereof is to provided a technology of illuminating the liquid crystal panel having a large area, with uniformity and high brightness, within the liquid crystal display apparatuses applying the LED therein, as the backlight thereof.
For accomplishing the object mentioned above, according to the present invention, there is provided the liquid crystal display apparatus, which is described in the present pending claims attached herewith.
Thus, according to the present invention, there is provided a liquid crystal display apparatus, comprising: a liquid crystal display; and a directly underlying type backlight, which is disposed on a rear surface of said liquid crystal display, so as to irradiate lights upon said liquid crystal display, wherein said backlight is made of a group of plural numbers of light emitting diodes, and has a translucent light guidance member, which is provided at least corresponding to each one or more of said plural numbers of light emitting diodes, wherein said translucent light guidance member is in such cylindrical configuration, that it provides a light guiding portion in a direction perpendicular to a display surface of said liquid crystal display, and that a reflection surface is defined on each of outer wall surfaces and inner wall surfaces of said cylindrical light guidance member, whereby reflecting a light from said light emitting diode upon those reflection surfaces, and guiding it onto a side of said liquid crystal display by the light guidance member.
In the liquid crystal display apparatus, as described in the above, said cylindrical light guidance member may have a polygonal or circular cross-section, in parallel with the display surface of said liquid crystal display.
In the liquid crystal display apparatus, as described in the above, the inner wall surface and the outer wall surface of said light guidance member on the side of the liquid crystal display may be built up with parallel wall surfaces having a predetermined length thereof, and an end portion of the inner wall surface of said light guidance member on the side of said light emitting diode may be located at a position near to the side of said liquid crystal display than an end portion of the outer wall surface of said light guidance member, on the side of said light emitting diode, and an inclination surface may be defined or connected with, between an end portion of the parallel wall surface of said inner wall surface on the side of said light emitting diode and an end portion side of the parallel wall surface of the outer wall surface on the side of said light emitting diode.
In the liquid crystal display apparatus, as described in the above, on a surface opposite the side of said light guidance member on the side of said liquid crystal display may be formed a fine concave/convex light diffusion pattern for diffusing the light of said light emitting diode to emit it therefrom.
In the liquid crystal display apparatus, as described in the above, upon a surface opposite the side of said light guidance member on the side of said liquid crystal display is formed a fine concave/convex light diffusion pattern for diffusing the light of said light emitting diode to emit it therefrom. And further, upon the inclination surface of said light guidance member may be formed a prism pattern.
With such the structures of the present invention, as is described above, it is possible to irradiate the liquid crystal display having a large area thereof, equally or uniformly, with high brightness, in particular, within the liquid crystal display apparatus applying LED therein, as the backlight thereof.
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:
a) and 1(b) are views for showing a liquid crystal display apparatus, according to an embodiment of the present invention;
a) to 5(c) are views for showing the manner of a high-angle radiant light to be incident upon a light guidance member 5.
Hereinafter, embodiments according to the present invention will be fully explained by referring to the attached drawings.
a) and 1(b) are views for showing a liquid crystal display apparatus, according to an embodiment of the present invention. In a front view shown in
Next, explanation will be made on a first embodiment of the backlight device, according to the present invention, by referring to
Therefore, in the present embodiment, each one of the surface area of the circuit board 4, on which the plural number of LEDs 7 are mounted, a total of all the cross-section areas of the light guidance members 5, which are provided corresponding to each LED 7, and the surface area of the light diffusion member 6, comes to be nearly equal to the surface area of the liquid crystal display 3, respectively.
Herein, the backlight device, according to the present embodiment, comprises the light sources (i.e., LED) 7, which are mounted on the circuit board 4, as is shown in
Following to the above, explanation will be given in more details thereof, in particular, on the structures of the backlight structures, according to the present embodiment. The LEDs 7 are mounted on planes 41 of the circuit board 4, in particular, on the side of the liquid crystal display 3, and are electrically connected with wirings (not shown in the figure), which are provided on a plane 41 or an opposite plane 42 of the circuit board 4, through wire bonding or the like, i.e., being conductive with.
The light guidance member 5 is made up with a material having a transparency, such as, a translucent resin, for example. Also, the light guidance member 5 is mounted on the plane 41 of the circuit board 4, and defines a cylinder surrounding the peripheries of the LED 7 around a central axis in the direction perpendicular to the plane 41 of the circuit board 4. In other words, the light guidance member 5 defines a square pole, an inside of which is hollow, and it is disposed on the plane 41 of the circuit board 4, so that the LED 7 is located within that hollow portion 57. Further, the light guidance member 5, according to the present embodiment, is built up with a thick portion (i.e., a translucent resin portion), being defined by a inner wall surface 52 and an outer wall surface 53 thereof, as a light guidance portion, and further upon the inner wall surface 52 and the outer wall surface 53 are formed reflection surfaces, respectively. Therefore, the light guidance member 5, according to the present embodiment, builds up a combined light guidance portion comprising two (2) light guidance portions, i.e., the hollow portion 57 for disposing the LED 7 therein and the thick portion located around the LED 7. Herein, the inner wall surface 52 and the outer wall surface 53 are in parallel with each other, on each of the four (4) surfaces thereof.
However, although the light guidance member 5 is mentioned to be cylindrical in the configuration thereof, such as, the square pole, within the embodiment shown in
The light guidance member 5 is so disposed, for the purpose that the lights of LEDs can be irradiated, effectively, upon the liquid crystal display 3, that a lower end portion 51 thereof is in contact with or in vicinity of the plane 41 of the circuit board 4, on which the LEDs are disposed, and also it is so provided that it includes the LED 7 on the circuit board 4 within a hollow portion of the light guidance member 5. The size in the central axis direction (i.e., a height) of the light guidance member 5 is “h”, as is shown in
Further, the lower end portion 51 of the outer wall surface 53 and the lower end portion 58 of the inner wall surface 52 are connected with each other, at an inclination portion 521. Thus, between the lower end portion 51 of the outer wall surface 53 and the lower end portion 58 of the inner wall surface 52 is defined the inclination portion 521, and this inclination portion 521 has such configuration of expanding, gradually, towards the lower end portion of the outer wall surface 53.
Herein, the outer wall surface 53 of the light guidance member 5 is treated with such a process, that it functions as a reflection surface for reflecting the light incident upon the light guidance member 5, and thereby guiding it onto the liquid crystal display 3. Thus, it is so arranged that, basically, the light irradiated from the LED 7 and incident upon the light guidance member 5 will not go beyond, into an area outside the outer wall surface 53 of the light guidance member 5. Therefore, width (D) of the outer wall surface 53 of the light guidance member 5 is determined corresponding to a desired region (L) where the liquid crystal display 3 should be irradiated with a desired brightness. On the other hand, the width (d) of the inner wall surface 52 of the light guidance member 5 is determined upon basis of directivity of the LED 7, e.g., a directivity angle of the emission light from the LED (the details of which will be mentioned, later).
Further, upon the inclination surface (or portion) 521, which is provided in the lower portion of the light guidance member 5 (on the side of LED 7), there is made up with a prism pattern 55 (
With the light guidance member 5, according to the first embodiment shown in
In the first embodiment mentioned above, the light diffusion member 6 and the light guidance member 5 are built up, separately, but the light diffusion member 6 and the light guidance member 5 may be built up within one body or as a unit. This will be explained as a second embodiment of the present invention, by referring to
The light guidance members, according to the present embodiment, builds up a box-like configuration, with the cylindrical light guidance member 5 having the hollow portion therein and the light diffusion surface 542, which is attached on the upper surface of the light guidance member 5, so as to cover the upper side thereof. Thus, the present embodiment, i.e., combining the light guidance member 5 and the light diffusion member 6, substantially, as a unit, has both the light guiding function within the first embodiment and the light diffusing function of the light diffusion member 6, together. Therefore, according to the present embodiment, it is possible to build up the backlight device for guiding and diffusing the light of LED 7 onto the liquid crystal display 3, in the structures being simple much more.
Next, explanation will be made on the condition where the light from the LED 7 is guided onto the liquid crystal display 3 by means of the light guidance member 5, by referring to
The light of the LED 7 has a predetermined directivity, and it is assumed that the directivity angle is “α”, which is determined by that directivity. The light “a” emitted from the LED 7 within this directivity angle “α”, i.e., the low-angle radiant light is incident upon the light diffusion surface 542, directly, but without incident (or entering) upon the inner wall surface 52 of the light guidance member 5. Herein, it is assumed that, the low-angle radiant light is the light, which is emitted from the LED 7 at a small angle to the optical axis of the LED 7 (herein, within the directivity angle “α”). Also, it is assumed that a boundary of the angle “α” is indicated by a straight line “A”. This low-angle radiant light is diffused by the concave/convex light diffusion pattern 56, which is formed on the light emission surface of the light diffusion surface 542, and is irradiated upon the liquid crystal display 3. With this, the light from the LED 7 can be irradiated, uniformly or evenly with high brightness, upon the liquid crystal display 3.
Herein, a region or area on the liquid crystal display 3, where the low-angle radiant light from the LED 7 can irradiate, directly, is an area within an inside than the position where the straight line “A” intersects with the liquid crystal display 3, in particular, the surface on the LED side. If assuming that the liquid crystal display 3 is irradiated only by the low-angle radiant light shown by the light “a” in
For the purpose of obtaining a uniform picture or image of high brightness with the simple structures thereof, while obtaining the thin-sizing of the liquid crystal display apparatus 1 and also reduction of the number of the light sources, i.e., the LEDs 7, it is necessary to utilize, not only the low-angle irradiant light mentioned above, but also the lights “b” and “c”, i.e., the high-angle radiant lights having an emitting angle larger than the directivity angle “α” of the LED 7. According to the present embodiment, with utilizing such the high-angle irradiant lights, effectively, by means of the light guidance member 5 mentioned above, it is achieved to obtain an image of high picture quality, while thinning the size of the liquid crystal display apparatus 1 and also reducing the number of parts thereof.
Thus, as is shown in
The light (c), i.e., the high-angle radiant light further higher than that critical angle “β” is refracted and incident upon the inclination surface 521 of the light guidance member 5.
As shown in
As is shown in
Also, as is shown in
The light guidance member 5, according to the present embodiment, is able to irradiate each of the low-angle radiant light and the high-angle radiant lights of the LED 7, respectively, through the most suitable method, corresponding to the directivity of the LED 7, with reducing the loss thereof. Thus, with the light guidance member 5, according to the present embodiment, it is possible to guide the reflection lights into the irradiation direction while reducing the loss or down to zero. With this, according to the present embodiment, it is possible to utilize the point-like light source of the LED 7 as the surface-like light source for the liquid crystal display 3, and thereby obtaining the liquid crystal display apparatus of picture quality, being much more equal and high in the brightness, while achieving the thin-sizing of the apparatus.
However, both the inner wall surface 52 and the outer wall surface 53 have the plane-like configuration, and the process treated upon the reflection surfaces thereof can be conducted by sticking a sheet member or the like, having a high-reflective characteristic, on the light guidance member 5. Alternatively, they may be built up, by pasting a paint of the high reflectivity on the inner wall surface 52 and the outer wall surface 53 of the light guidance member 5, or evaporating a metal of high reflectivity thereon, such as, aluminum or silver, etc.
With the one (1) set of the backlight device is built up with, using the light guidance member 5 having the size (D) nearly equal to the irradiation area (L), according to the present embodiment, for the purpose of irradiating the predetermined area (L) on the liquid crystal display 3 with the desired brightness, then it is possible to determine the light irradiation capacity of the one (1) set of the backlight device, appropriately, and also to maintain the same performances or conditions thereof. Therefore, with making up the liquid crystal display 3 while combining a plural number of that one (1) set of the backlight devices corresponding to the display area thereof, it is possible to provide a backlight device corresponding to a desired screen size, and also to obtain a predetermined brightness, easily, irrespective of the screen size thereof.
Also, even the backlight device can be made up, by combining the small-sized small backlight devices, corresponding to the large screen, then it is possible to deal with a small-scaled manufacturing facility, in particular, in the production of the light guidance member, etc., and also to achieve an efficiency of production, with omitting a new development corresponding to the screen size. Further, since it is enough to produce the same thing (i.e., small-sized small backlight device), in a large number thereof, and then there can be achieved an effect of reducing the price thereof, etc.
However, the plural pieces of the backlight devices may be combined by holding them by means of a frame member, or the backlight devices themselves are combined with each other through adhesion therebetween.
While we have shown and described several embodiments in accordance with our invention, it should be understood that disclosed embodiments are susceptible of changes and modifications without departing from the scope of the invention. Therefore, we do not intend to be bound by the details shown and described herein but intend to cover all such changes and modifications that fall within the ambit of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-234855 | Sep 2007 | JP | national |
