Patent Application
20110128450
The present invention relates to an illumination device that is used as a backlight of a liquid crystal display device or the like, and to a liquid crystal display device that includes the illumination device.
Liquid crystal display devices have increasingly replaced cathode-ray tube (CRT) based display devices. Such liquid crystal display devices have advantages in features such as energy saving, reduced thicknesses, and lightweights. For their advantages, the liquid crystal display devices have been widely used in liquid crystal display televisions, monitors, mobile phones, and the like. One way to utilize the advantages of the liquid crystal display devices is to improve an illumination device (so called a backlight) provided behind a light crystal display device.
Backlights are illumination devices, and are broadly classified into a side light type (also kwon as edge light type) and a direct backlight type. The side light type is configured such that light guides are provided behind a liquid crystal display panel and light sources are provided to edges of the respective light guides. In the configuration, light emitted from a light source is reflected in a corresponding light guide such that the liquid crystal display panel is irradiated with the light indirectly and uniformly. With the configuration, it is possible to realize an illumination device having a reduced thickness and good luminance uniformity although its luminance is low. Thus, a side light type illumination device is mainly employed in a small to medium size liquid crystal display for use in a mobile phone or a laptop personal computer.
One example of the side light type illumination devices is disclosed in Patent Literature 1. Patent Literature 1 discloses a surface-emitting device which includes a light guide having its reflecting surface provided with a plurality of dots so as to allow for uniform light emission from a light-emitting surface. In the surface-emitting device, no light is transmitted to a corner portion of the reflecting surface due to a directivity of a light source, and as such, the corner portion of the reflecting surface is darkened. Patent Literature 1 deals with this by employing an arrangement in which the corner portion of the reflecting surface has a higher dot-density than the remaining part of the reflecting surface.
A direct backlight type illumination device is, on the other hand, configured such that a plurality of light sources are arranged behind a liquid crystal display panel so as to directly illuminate the liquid crystal display panel. As such, it is easier even for a large screen to have high luminance. Therefore, the direct backlight type illumination device is mainly employed in a large size liquid crystal display of 20 inches or larger. However, a currently-available direct backlight type illumination device has a thickness of approximately 20 to 40 mm, and this constitutes a barrier to a further reduction of a thickness of a display.
The large size liquid crystal display can have a further reduced thickness, in a case where light sources and a liquid crystal display panel are provided closer to each other. In the case, however, it is impossible for an illumination device to have luminance uniformity unless a plurality of light sources are provided. Yet, providing of the plurality of light sources increases a cost. In such circumstances, there is a demand for a development of a thin illumination device which can have good luminance uniformity can without the need for the increased number of light sources.
Conventionally, the following attempt has been made in order to solve the problem. Specifically, a plurality of side light type illumination devices are arranged so as so that a the large size liquid crystal display has a reduced thickness.
For example, Patent Literature 2 discloses a surface-emitting device that includes (i) tabular light guide blocks, which partially overlap with one another and thereby have a tandem structure, and (ii) primary light sources, which are provided to the respective corresponding light guide blocks and supply primary light to them. In the surface-emitting device configured as such, it is possible to secure a wide light-emitting area by a compact structure. Thus, the surface-emitting device disclosed in Patent Literature 2 is suitably applicable in a large size liquid crystal display. An illumination device configured as described above, i.e., including an array of a plurality of light emitting units each including a combination of a light source and a light guide, is called as a tandem illumination device.
Patent literatures 3 and 4 disclose respective illumination devices both including a single large size reflecting sheet which is shared by two or more light optical guides.
Generally, in each configuration discussed above, light guides are configured to have a minus tolerance, so that it is possible to (i) prevent adjacent light guides from damaging one another, (ii) to realize an illumination device having a reduced thickness, (iii) to tolerate a production error, and the like. However, this causes a gap to be formed in a joint part between adjacent light guides in accordance with a size of the minus tolerance.
The gap thus formed in the joint part due to a drawback of the configuration of the light guides is detected, as a region emitting no light, on a light emitting surface formed by an array of outputting surfaces of the respective light guides. Therefore, there is a problem that in a case where a backlight of a display device is the illumination device including an array of the light guides, generation of luminance unevenness of the light emitting surface causes a deterioration in quality of a display image.
Patent Literature 2 discloses a surface light emitting device of a tandem type. However, Patent Literature 2 pays absolutely no attention to an issue that a gap formed in a joint part between light guides causes a deterioration in quality of a display image. Therefore, Patent Literature 2 does not deal with the gap. Thus, there is a problem that the gap does not emit light at all and thereby causes a dark line to be formed.
Patent Literatures 3 and 4 disclose illumination devices in which a single reflecting sheet is provided in a gap so as to extend across corresponding adjacent light blocks. The illumination devices, however, have a drawback described as follows. In a case where the reflecting sheet is lifted due to thermal expansion or the like, the light guides is deformed accordingly. This increases a risk that luminance unevenness of a light emitting surface is generated.
The present invention is made in view of the problem, and an object of the present invention is to provide an illumination device which includes a plurality of light guides and still realizes improved uniformity in luminance of a light emitting surface.
Another object of the present invention is to provide a liquid crystal display device including the illumination device and thereby having good display quality and a reduced thickness.
In order to attain the object, an illumination device of the present invention includes: a plurality of combinations of a light source and a light guide for causing surface emission of light that comes from the light source; and reflecting members, each of which faces and covers that surface of corresponding one of the light guides which is an opposing surface of a light emitting surface, the reflecting members being configured to partially overlap with their adjacent ones, in a normal direction of the light emitting surface, over a gap between corresponding two of the light guides that are arranged adjacently to one another so as not to overlap with one another. Furthermore, it is preferable that the illumination device of the present invention be configured so that: each of the light guides includes (i) a light emitting section having the light emitting surface and (ii) a light guiding section for directing, to the light emitting section, the light that comes from a corresponding light source; and the light guides are configured so that a light emitting section of one of adjacent two of the light guides is placed on a light guiding section of the other one of the adjacent two of the light guides.
In the invention above, any adjacent two of the reflecting members overlap with each other in the normal direction of the light emitting surface so as to cover the space between the corresponding two of the light guides which are adjacent to each other and arranged so as not to overlap with each other. Thus, any adjacent two of the light guides cover the space, and reflect back light that has left the corresponding two of the light guides, so as to reenter the light into the corresponding two of the light guides. This brings about an effect that causes light use efficiency in the corresponding two of the light guides to be improved. Also, with the invention, it is further possible to cause light use efficiency of a liquid crystal panel to be increased, by reflecting the light back to a liquid crystal panel direction.
In the invention, furthermore, each of the reflecting members faces and covers that surface of corresponding one of the light guides which is an opposing surface of a light emitting surface. That is, each of the light reflecting members is provided to corresponding one of the light guides. This brings about an effect that realizes a reduction in cost, as compared to a backlight in which two reflecting members are used in combination to cover a space between such corresponding two light guides.
It is preferable that the illumination device of the present invention be configured so that each of the reflecting members faces corresponding two or more of the light guides which are adjacent to one another.
In the illumination device of the present invention configured as such, it is possible to (i) reflect back light that has passed through the gap (gap between two light guides which are arranged adjacent to each other and do not overlap with each other), so as to reenter the light into the two light guides, and also to (ii) direct light that has left the two light guides to the liquid crystal panel direction. This brings about an effect that realizes improved light use efficiency. Therefore, the illumination device of the present invention can obtain further improved luminance uniformity of the light emitting surfaces.
Furthermore, it is preferable that the illumination device of the present invention be configured so that each of the reflecting members extends out over a gap between corresponding two of the light guides which are arranged adjacently to one another so as to overlap with one another.
This can prevent a problem that the space (space between corresponding two light guides which are arranged adjacent to each other so as to overlap with each other) becomes a part darker than the light emitting section in a case where no reflecting member extends over the space. Therefore, the illumination device of the present invention configured as such can obtain further improved luminance uniformity of the light emitting surfaces.
Furthermore, it is preferable that the illumination device of the present invention be configured so that each of the reflecting members performs two-side reflection.
This realizes an improved reflectance. Therefore, the illumination device of the present invention configured as such can obtain further improved luminance uniformity of the light emitting sections. This is described specifically as follows. Each of the reflecting members reflects, back into a corresponding light guide 7, light that has passed through an upper surface (which is a surface on a same side as the light emitting surface). As such, each of the reflecting members has a role to cause light use efficiency in a corresponding light guide to be improved.
Furthermore, it is preferable that the illumination device of the present invention be configured so that each of the reflecting members is a reflecting member for performing two-side diffusion reflection, a reflecting member for performing diffusion reflection by one surface and performing mirror reflection by an opposing surface, or a reflecting member for performing two-side mirror reflection.
This makes it possible, in a case where reflecting members are provided for realizing diffusion reflection, to cause a reduction in cost of the illumination device of the present invention. The same makes it possible, in a case where the reflecting members are provided for realizing mirror reflection, to obtain a higher reflectance and improved light reuse efficiency. Therefore, employing of the configuration is advantageous in terms of improvement of luminance uniformity of the light emitting surfaces.
In order to attain the object of the object, an illumination device of the present invention includes: a plurality of combinations of a light source and a light guide for causing surface emission of light that comes from the light source; and reflecting members, each of which faces and covers that surface of corresponding one of the light guides which is an opposing surface of a light emitting surface, the each of the reflecting members being configured to extend out into a gap between corresponding two of the light guides which are arranged adjacently to one another so as not to overlap with one another, and the reflecting members being configured not to overlap with their adjacent ones, in a normal direction of a light emitting surface, in a gap between corresponding two of the light guides that are arranged adjacently to one another so as not to overlap with one another. It is preferable that the illumination device of the present invention be configured so that: each of the light guides includes (i) a light emitting section having the light emitting surface and (ii) a light guiding section for directing, to the light emitting section, the light that comes from a corresponding light source; and the light guides are arranged so that a light emitting section of one of adjacent two of the light guides is placed on a light guiding section of the other one of the adjacent two of the light guides.
In the invention, each of the reflecting members extends over a space between corresponding two of the light guides which are arranged adjacent to each other so as not to overlap with each other. Thus, each of the reflecting members covers the space between corresponding two light guides. Since each of the reflecting members reflects, back into the corresponding two light guides, light that has existed the corresponding two light guides, it is possible to cause light use efficiency in the corresponding two light guides to be improved. In the invention, furthermore, light that has existed the light guides is reflected back to a liquid crystal panel direction. This makes it possible to obtain improved light use efficiency of the liquid crystal panel.
In the invention, furthermore, no adjacent two of the reflecting members overlap with each other, in the normal direction of the light emitting surface, over a space between corresponding two of the light guides which are adjacent to each other so as not to overlap with each other. Thus, the invention is advantageous in terms of assembly ease and workability, since it is easy to perform rework, e.g., exchange of a light guide, a reflecting member, and/or the like.
Furthermore, it is preferable that the illumination device of the present invention be configured so that: each of the reflecting members (i) extends out, by a first width, from one end of corresponding one of the light guides in a direction in which the light guides are arranged adjacently to one another so as not to overlap with one another, and (ii) extends out, by a second width smaller than the first width, from an opposing end of the corresponding one of the light guides in the direction.
In the illumination device of the present invention configured as such, it is thus further easier to (i) assemble (and remove) the light guides in such a manner that any two adjacent light guides are arranged so as not overlap with each other, and (ii) assemble (and remove) the light guides in such a manner that any two adjacent light guides are arranged so as to partially overlap with each other.
Furthermore, it is preferable that the illumination device of the present invention be configured so that each of the reflecting members extends out over a gap between corresponding two of the light guides which are arranged adjacently to one another so as to overlap with one another.
This makes it possible to prevent a problem that the gap (gap between corresponding two of the light guides which are arranged adjacent to each other so as to overlap with each other) becomes a part darker than the light emitting sections in a case where no reflecting member extends over the gap. Therefore, the illumination device of the present invention configured as such can obtain further improved luminance uniformity of the light emitting surfaces.
Furthermore, it is preferable that the illumination device of the present invention be configured so that each of the reflecting members performs two-side reflection.
This realizes an improved reflectance. Therefore, the illumination device of the present invention configured as such can obtain improved luminance uniformity of the light emitting sections. This is described in detail as follows. Each of the reflecting members reflects light that has passed through an upper surface (which is a surface on a same side as a light emitting surface) of a light guiding section of the corresponding light guide, so as to reenter the light into the corresponding light guide. Thus, each of the reflecting members has a role to cause light use efficiency in the corresponding light guide to be improved.
Furthermore, it is preferable that the illumination device of the present invention be configured so that each of the reflecting members is a member for performing two-side diffusion reflection, a member for performing diffusion reflection by one surface and performing mirror reflection by an opposing surface, or a member for performing two-side mirror reflection.
This makes it possible, in a case where the reflecting members are provided for realizing diffusion reflection, to realize a reduction in cost of the illumination device of the present invention. The same makes it possible, in a case where the reflecting members are provided for realizing mirror reflection, to obtain a higher reflectance and improved light reuse efficiency. Therefore, the configuration is advantageous in terms of improvement of luminance uniformity of the light emitting surfaces.
It is preferable that a liquid crystal display device of the present invention include any of the illumination devices as a backlight.
The liquid crystal display device of the present invention configured as such obtains excellent luminance uniformity.
It is preferable that a television receiver device of the present invention includes: a built-in tuner; and a backlight, which is any of the illumination devices.
This causes the television receiver device of the present invention including the built-in tuner to obtain excellent luminance uniformity.
As described earlier, an illumination device of the present invention includes: a plurality of combinations of a light source and a light guide for causing surface emission of light that comes from the light source; and reflecting members, each of which faces and covers that surface of corresponding one of the light guides which is an opposing surface of a light emitting surface, the reflecting members being configured to partially overlap with their adjacent ones, in a normal direction of the light emitting surface, over a gap between corresponding two of the light guides that are arranged adjacently to one another so as not to overlap with one another. It is preferable that the illumination device of the present invention be configured so that: each of the light guides includes (i) a light emitting section having the light emitting surface and (ii) a light guiding section for directing, to the light emitting section, the light that comes from a corresponding light source; and the light guides are arranged so that a light emitting section of one of adjacent two of the light guides is placed on a light guiding section of the other one of the adjacent two of the light guides.
As describe earlier, an illumination device of the present invention includes: a plurality of combinations of a light source and a light guide for causing surface emission of light that comes from the light source; and reflecting members, each of which faces and covers that surface of corresponding one of the light guides which is an opposing surface of a light emitting surface, the each of the reflecting members being configured to extend out into a gap between corresponding two of the light guides which are arranged adjacently to one another so as not to overlap with one another, and the reflecting members being configured not to overlap with their adjacent ones, in a normal direction of a light emitting surface, in a gap between corresponding two of the light guides that are arranged adjacently to one another so as not to overlap with one another. It is preferable that the illumination device of the present invention be configured so that: each of the light guides includes (i) a light emitting section having the light emitting surface and (ii) a light guiding section for directing, to the light emitting section, light that comes from a corresponding light source; and the light guides are arranged so that a light emitting section of one of adjacent two of the light guides is placed on a light guiding section of the other one of adjacent two of the light guides.
Therefore, in the illumination device of the present invention, it is possible to obtain improved use efficiency of light passing through light guides. This brings about an effect that obtains an improved uniformity of luminance in a light emitting surface.
One embodiment of the present invention is described below with reference to
<Liquid Crystal Display Device>
The liquid crystal display panel 3 is not particularly limited, and is a same liquid crystal display panel as a normal liquid crystal display panel for use in a conventional liquid crystal display device. Though it is not illustrated in
A configuration of the backlight 20 of the liquid crystal display device 30 is described in detail below.
<Backlight (Illumination Device)>
The backlight 20 is placed behind the liquid crystal display panel 3 (i.e., the backlight 20 is provided closer to a rear surface of the liquid crystal display panel 3 which is an opposing surface to a display surface). As shown in
The light source 5 is provided so as to face one surface of the light guide 7. The light source 5 is, for example, a light emitting diode (LED) of side emitting type, a cold cathode fluorescent tube (CCFL), or the like. In the present embodiment, there is raised an example in which the light source 5 is an LED. The light source 5 is an LED of side emitting type that has three color chips (i.e., red (R), green (G), and blue (b) color chips) molded in a single package. Use of such LED as the light source 5 makes it possible to realize a backlight having a wide color reproducibility range. The light source 5 is placed on a substrate 11 (which is not shown). The light source 5 is not limited to a dot-like light source.
A combination of the colors of light emitting diodes can be determined as appropriate, based on color properties of color LEDs, a desirable color property of a surface light source device which varies accordingly to a purpose of use of the liquid crystal display device 30, or the like.
The light guide 7 is provided for receiving light coming from the light source 5, and for causing surface emission of the light via a light emitting surface (which is also referred to as a light outputting surface or an outputting surface) 7a. The light emitting surface 7a is a surface for irradiating an irradiation target with light. In the light emitting guide 7, (i) the light emitting surface 7a or (ii) a rear surface or a light emitting section 7c is subjected to treatment and a process so that light directed thereto is outputted in a front direction. Thus, the light directed to the light emitting surface 7a or the rear surface or the light emitting section 7c is emitted from the light emitting surface 7a of the light guide 7 in a direction toward the liquid crystal display device 3. The light guide 7 further includes a light guiding section 7d, which is subjected to treatment and a process. Concrete examples of the treatment and the processes performed for the light guiding section 7d encompass prisming, texturing, printing, and the like. However, the present embodiment is limited to any of them. As such, the treatment and the process can be any known methods as needed.
The light guide 7 is mainly made from a transparent resin such as polycarbonate (PC), polymethyl methacrylate (PMMA), or the like. However, the present embodiment is not limited to this. The light guide 7 is preferably made from a material having a high optical transmittance. The light guide 7 can be prepared by, for example, injection molding, extrusion molding, hot-press molding, cutting, or the like. However, the present embodiment is not limited to any of them. The light guide 7 can be prepared by a processing method exercising a similar effect to the above.
The reflecting sheet 6 is provided so as to face the rear surface (opposing surface to the light emitting surface 7a) of the light guide 7. The reflecting sheet 6 reflects light coming from the light guide 7, so as to cause a greater amount of light to be emitted from the light emitting surface 7a. The reflecting sheet 6 is made from a resin such as foamed PET (polyethylene terephthalate), a mixture of PET and barium sulfate, a mixture of PET and polyolefin, or the like. The reflecting sheet 6 has a thin metal film having a high reflectance, such as silver, aluminum, or the like, which is sputtered on its surface. Among all materials of the reflecting sheet 6, it is preferable to use a PET-based white colored reflecting sheet having an excellent heat stability. The PET-based white colored reflecting sheet is classified, based on its composition, roughly into any of the following types (i) through (iii): (i) a PET-based white colored reflecting sheet prepared by adding a white colored inorganic particle to PET; (ii) a PET-based white colored reflecting sheet prepared by adding, to PET, a resin (olefin-based resin) insoluble to PET; (iii) a PET-based white colored reflecting sheet prepared by impregnating a PET sheet with carbon dioxide or the like and then causing foaming, and the like. In the present embodiment, the reflecting sheet 6 can be any of those types of the PET-based white colored reflecting sheets. However, the present embodiment is not limited to any of the materials described above. The reflecting sheet 6 can be made from any material, provided that a shape of the reflecting sheet 6 can be kept after the reflecting sheet 6 is prepared.
The reflecting sheet 6 has a configuration for realizing two-side diffusion reflection (two-side reflection), one-side diffusion reflection (in this case, the reflecting sheet 6 has one surface for realizing the one-side diffusion reflection and an opposing surfaces for realizing mirror reflection), or two-side mirror reflection. It is preferable that, in a case where the reflecting sheet 6 has the configuration for realizing two-side mirror reflection (two-side reflection), for example, both surfaces of the reflecting sheet 6 be coated by evaporated silver, evaporated aluminum, or the like.
The reflecting sheet 6 can be prepared by, for example, injection molding, press molding, heat-press molding, cutting, or the like. Specifically, in a case where the reflecting sheet 6 is a positive reflecting sheet, (i) at least one surface of the positive reflecting sheet is processed so as to have asperities, or (ii) at least one surface of the positive reflecting sheet has a white pigment applied thereto. This makes it possible to easily provide a diffusing reflecting layer in a desired region of the at least one surface of the positive reflecting sheet. An example of a method for providing asperities in the positive reflecting sheet encompasses a method for providing asperities by injection molding, metal molding, embossing, or the like at same as producing a sheet. Another example of the method encompasses a method for performing prisming, dotting, roughening by a laser, or the like for a surface of the positive reflecting sheet.
In the present embodiment, as shown in
“The reflecting sheet 6 partially overlaps with an adjacent reflecting sheet 6 in a normal direction of a light emitting surface 7a” indicates that it is satisfactory, irrespective of an overlapping degree, as long as adjacent reflecting sheets 6 overlap with each other.
It is preferable that the reflecting sheet 6 extend from one of the two light guides 7 and 17 to the other one of them.
The reflecting sheet 6 extends out over a gap 1 between corresponding two of light guides 7 which are arranged adjacently to one another so as not to overlap with one another. It is preferable that the reflecting sheet 6 (i) extend out, by a first width, from one end of a corresponding light guide 7 in a direction in which any adjacent two of light guides 7 are arranged so as not to overlap with each other, and (ii) extend out, by a second width smaller than the first width, from an opposing end of the corresponding light guide 7 in the direction.
The diffusing plate 8 faces light emitting surfaces 7a of light guides 7, so as to entirely cover a flat light emitting surface made up of the light emitting surfaces 7a. The diffusing plate 8 is provided so as to (i) diffuse light that has been emitted from the light emitting surfaces 7a and (ii) irradiate the optical sheet 9 with the light thus diffused.
The optical sheet 9 is made up of a plurality of optical sheets that are stacked on one another. The optical sheet 9 is provided so as to (i) uniform and converge the light having been emitted from the light emitting surfaces 7a of the light guides 7, and (ii) irradiate the liquid crystal panel 3 with the light thus uniformed and converged. Therefore, the optical sheet 9 can be made up of sheets such as: a diffusing sheet for converging and diffusing light; a lens sheet for converging light so as to improve luminance of a front direction (liquid crystal display panel direction); and/or a polarized light reflecting sheet for reflecting one polarized light component and passing through the other polarized light component so as to improve luminance of the liquid crystal display device 30, or the like. The sheets are preferably used in combination appropriate in accordance with a price and performance of the liquid crystal display device 30.
The transparent plate 10 is provided in a case where the light guides 7 and the diffusing plate 8 are provided away from each other in a fixed distance. The transparent plate 10 causes a light diffusing region to be formed. The transparent plate 10 is made from a transparent material such as a polyethylene film or the like. The transparent plate 10 is not necessarily provided. As such, no transparent plate 10 may be provided so that the light guides 7 and the diffusing plate 8 face each other.
The substrate 11 shown in
By the members configured as such, light coming from the light source 5 (i) passes through within the light guide 7 while being subjected to diffusion and reflection, (ii) leaves the light guide 7 via the light emitting surface 7a, and (iii) passes through the diffusing plate 8, the optical sheet 9, and the like, to be incident on the liquid crystal display panel 3.
The configuration of the backlight 20 is described in more detail below with reference to
As shown in
<Light Guide>
As described earlier, light guides are normally produced to have a minus tolerance, so that it is possible to (i) prevent light guides from damaging one another, (ii) realize a reduction in thickness of a backlight, (iii) tolerate a production error, or the like. This, however, causes gaps to be formed in joint parts between any adjacent two of the light guides, based on the minus tolerance. The gaps are seen, on a light emitting surface made up of light emitting surfaces of an array of the light guides, as a region emitting no light. A backlight including an array of such light guides may be used as a backlight of a display device. This, however, causes luminance unevenness of the light emitting surface, and thereby causes a deterioration in quality of a display image.
In the backlight 20 included in the liquid crystal display device 30 of one embodiment of the present invention, there are two variations of gaps due to differences in mechanisms how they are formed. As described below, the two variations of gaps are (i) a gap formed between any adjacent two of light guides 7 which are arranged so as not overlap with one another, and (ii) a gap formed between any adjacent two of light guides 7 which are arranged so as to partially overlap with one another. As shown in
(Gap Between Light Guides which are Arranged so as Not to Overlap with Each Other)
“A gap between any adjacent two of light guides which are arranged so as not to overlap with one another” is a gap between any adjacent two of a plurality of light guides which are arranged in a same plane so as not to overlap with one another. Specifically, as shown in
In the backlight 20 included in the liquid crystal display device 30 of the one embodiment of the present invention, the reflecting sheet 6 overlaps with an adjacent reflecting sheet, in a normal direction of a light emitting surface 7a, over the gap 1. This brings about an effect that (i) reenters light, which has leaked from a side surface 7b of a light guide 7, into the light guide 7 (or a light guide 17) with higher certainty by using the two reflecting sheets 6, and (ii) reflects the light to the liquid crystal display panel 3. It is therefore possible to obtain improved light use efficiency and cause a dark line to be less detectable.
(Gap Between Light Guides Arranged so as to Partially Overlap with Each Other)
“A gap between any adjacent two of light guides which are arranged so as to partially overlap with one another” is described below. For example, each of the light guides includes (i) a light emitting section having a light emitting surface (outputting surface) and (ii) a light guiding section for directing light coming from a light source to the light emitting section. The light guides are arranged so that a light emitting section of one of any adjacent two of the light guides is placed on a light guiding section of the other one of any adjacent two of the light guides. This causes a gap to be formed in a joint part between light emitting surfaces of the respective adjacent two of the light guides. The gap is “the gap between any adjacent two of light guides which are arranged so as to partially overlap with one another”.
In the present embodiment, it is preferable that a reflecting member be provided so as to extend over a gap between corresponding two of the light guides which are arranged adjacent to one another so as to partially overlap with one another.
Similarly to “the gap between any adjacent two of light guides which are arranged so as not to overlap one other”, “the gap between any adjacent two of light guides which are arranged so as to partially overlap with one another” causes a part darker than the light emitting sections to be formed, since no reflecting sheet extends over the gap.
This is described in detail as follows. In a case where a light emitting section 7c of one of any adjacent light guides 7 is placed on a light guiding section 7d of the other one of any adjacent light guides 7, as shown in
Even in a case of lengthening the reflecting sheet 6 in the direction D2 so that the reflecting sheet 6 covers a part of the gap 2, it is still possible to bring about an effect that prevents, to some extent, the region from causing a dark line. However, in a case of maximizing the length of the reflecting sheet 6 in the direction D2, i.e., extending the reflecting sheet 6 from a corresponding light guide 7 to a boundary between a light guiding section 7c and a light emitting section 7c of an adjacent light guide 7, so that the reflecting sheet 6 covers an enter part of the gap 2, it is possible to maximize the effect that reduces the dark line.
In the light guides 7, light that enters a light guide 7 from an incidence surface 7e facing a light source 5 should be emitted from a light emitting surface 7a with good efficiency. For this, it is necessary that light loss to be caused in a light guiding section 7d of the light guide 7 be minimized.
Thus, the light guiding section 7d should be so that its upper and lower surfaces are substantially parallel with each other. This allows incoming light to be directed within the light guiding section 7d while satisfying a total reflection condition. Therefore, the light guiding section 7d can prevent an amount of light directed therein from being reduced.
Any adjacent light guides 7 incline with respect to the optical sheet 9, which is a surface to be irradiated with light, and overlap with each another. Thus, in each of the light guides 7, a light emitting surface 7a is not parallel with an opposing surface thereto. Therefore, the light guide 7 has a shape tapered toward a direction extending away from a corresponding light source 5.
By the configuration, light being directed within the light guide 7 (i) gradually fails to satisfy the total reflection condition as it travels away from the light source 5, and therefore, (ii) exits the light guide 7 via the light emitting surface 7a.
<Reflecting Sheet (Reflecting Member)>
As shown in
Specifically, in
Specifically, in
The reflecting sheet 6 reflects back light that has left a corresponding light guide 7 via an opposing surface to a light emitting surface 7a, so as to reenter the light in the light guide 7. As such, the reflecting sheet 6 has a role to cause light use efficiency in the light guide 7 to be improved. This is described in more detail as follows. As shown in
Furthermore, as shown in
In the present embodiment, as shown in
In the present embodiment, furthermore, the reflecting sheet 6 extends so as to cover a gap 2 between corresponding two of light guides 7 which are arranged adjacently to one another so as to partially overlap with one another. Therefore, as shown in
It is preferable that, in the backlight 20 included in the liquid crystal display device 30 of one embodiment of the present invention, (i) the reflecting sheet 6 extend so as to cover at least a plane where a light emitting section 7c of one of adjacent light guides 7 is in contact with a light guiding section 7d of the other one of the adjacent light guides 7, and (ii) the reflecting sheet 6 be made up of a two-side reflecting sheet.
As shown in
That part of the reflecting sheet 6, which faces that surface of the light guide 7 which is an opposing surface to the light emitting surface 7a, has a reflectance that may or may not be same with a reflectance of another part of the reflecting sheet 6 which extends over the gap 1 or 2. That is, the reflectances of the respective parts of the reflecting sheet 6 are not particularly limited, provided that the reflecting sheet 6 can reflect light back into the light guides 7.
<Uniformity in Luminance>
With reference to
(a) and (b) of
In the conventional backlight 102, a light guide 107 receives light coming from a light source 105. In the light guide 107, most of the light thus received is directed to a direction (which is shown by a solid arrow line in (a) of
This is described in detail as follows. As shown in (b) of
In order to solve the problem, it can be thought to provide separate pieces (i.e., not combined to each other) of reflecting sheets 6 in a backlight, so that the separate pieces of the reflecting sheets 6 extend over the opposing region to the region S100, in addition of facing the respective light guide 107 and 117. In this case, as shown in (c) of
Thus, the backlight as shown in (c) of
Regarding the gap 1 between two adjacent light guides 107 and 117 which are arranged so as not to overlap with each other, it is preferable that:
d≧D;
where d is a size of the gap 1, and D is a size of that part of the reflecting sheet 6 which extends out from one end of the light guide 107 or 117. Note that d≧D is satisfied by only that part of the reflecting sheet 6 which extends out from the one end of the light guide 107 or 117. This is because the configuration makes it possible to, in a case where a part of the backlight emits no light due to assembly error, a failure of a member, or the like, easily remove only the part of the backlight.
The illumination device (backlight) of the present invention is advantageous in terms of luminance uniformity of a large light emitting area realized by an array of plural light guides. As such, it is preferable that the illumination device of the present invention be used particularly as a backlight of a liquid crystal display device having a large-size screen. However, the present invention is not limited to this. Instead, the illumination device of the present invention can be used as a backlight of a various type of liquid crystal display devices, or the like.
With reference to
The liquid crystal display panel 54 includes a first liquid crystal display panel and a second liquid crystal display panel, and can have any of the configurations described earlier.
In the liquid crystal display device 61 configured as such, at first, the Y/C separation circuit 50 receives a television signal as an input video signal, and separates a luminance signal and a color signal from it. The luminance signal and the color signal are sent to the video chroma circuit 51, and converted to an analogue RGB signal indicative of three primary colors in light. Then, the analogue RGB signal is sent to the A/D converter 52, and converted to a digital RGB signal. Then, the digital RGB signal is inputted to the liquid crystal controller 53.
The liquid crystal display panel 54 receives (i) the digital RGB signal inputted from the liquid crystal controller at given timings, and (ii) corresponding gradation voltages to R, G, and B values from the gradation circuit 58. In response to the digital RGB signal and the gradation voltage thus received, the liquid crystal display panel 54 displays an image. Control of an entire system, inclusive of control of the processes above, is carried out by the microcomputer 57.
The video signal can a video signal of an image on television broadcasting, a video signal of an image captured by a camera, and a video signal of an image supplied via the Internet network, a video signal of an image recorded on DVD, or the like. The liquid crystal display panel 54 can display an image in response to such wide variety of video signals.
The tuner section 60 shown in
The liquid crystal display device 61 may constitute a television receiver device. In this case, for example, the liquid crystal display device 61 is sandwiched by a first chassis 31 and a second chassis 36 so as to be housed in between them.
The first chassis 31 has an aperture 31a via which an image displayed on the liquid crystal display device 61 is transmitted.
The second chassis 36 is provided for covering a rear surface of the liquid crystal display device 61. The second chassis 36 is provided with (i) an operation circuit 35 for operating the liquid crystal display device 61, and (ii) a supporting member 38 attached to a bottom of the second chassis 36.
The present invention is not limited to any of the aforementioned embodiments, but can be altered within the scope of the following claims. That is, an embodiment realized by combining technical means modified as appropriate within the scope of the claims is included within the technical scope of the present invention.
The invention being thus described, it will be obvious that the same way may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
The present invention is applicable to (i) an illumination device for use in a backlight of a liquid crystal display device or the like, (ii) a liquid crystal display device including the illumination device, and (iii) a television receiver device with a built-in a tuner, or the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-254403 | Sep 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/067094 | 9/30/2009 | WO | 00 | 1/28/2011 |
