Backlight apparatus and display apparatus using same

A backlight apparatus has a housing composed of a first frame and a second frame, each having a side wall, put together, an optical guide plate housed in the housing, and a reflector inserted between the side surface of the light guide plate and the side wall of the housing. A reflector guide is formed on the side wall of the housing, and has a tilted surface tilted toward an insertion direction of the reflector.

This application is based on Japanese Patent Application No. 2007-140486 filed on May 28, 2007, the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a backlight apparatus, more particularly to a technology which improves ease of insertion and replacement of a reflector including a light source in a backlight apparatus.

2. Description of the Prior Art

In recent years, flat panel displays are becoming the mainstream and expanding their market instead of cathode ray tubes which have been conventionally used as display apparatuses. Among others, liquid crystal displays (LCDs) are characterized by their thinness, light weight, low power consumption, and high definition, and have been widely used in the fields of televisions, personal computers and the like.

An LCD display usually comprises: an LCD module composed of an LCD panel—having a pair of mutually facing electrode boards and liquid crystal sealed therebetween—and a polarizing plate; a backlight apparatus which illuminates the LCD module from the rear surface; and various circuit boards which are used to drive the LCD module.

FIG. 5is an exploded perspective view of a backlight apparatus1of the edge type (hereinafter called as a backlight apparatus1) before a line light source7(not shown inFIG. 5) is built in. The backlight apparatus1is so constituted that a reflecting sheet5, an optical sheet3and an light guide plate4are housed in a housing2which is formed by putting a first frame2aand a second frame2btogether. Here, the optical sheet3is a laminate of a diffusing sheet and a light condensing sheet and is disposed on the upper surface of the light guide plate4, and the reflecting sheet5is disposed on the lower surface of the light guide plate4.

FIG. 6is a perspective view of the backlight apparatus1before a reflector6is built in. As shown inFIG. 6, the backlight apparatus1houses the light guide plate4and various optical sheets3(not shown inFIG. 6). The reflector6, which retains therein the line light source7, can be inserted from an inserting opening8formed through a side wall of the housing2. The reflector6is disposed in a space between a side surface of the optical guide plate4and a side wall of the housing2, and the line light source7is disposed in a position to facing the side surface of the light guide plate4. Besides, the light guide plate4and the reflector6are sandwiched vertically between a first frame2aand a second frame2bto be retained in position (seeFIG. 5).

When the backlight apparatus1structured as described above is used in an LCD display apparatus, the light emitted from the line light source7enters the light guide plate4through a side surface thereof, travels throughout the light guide plate4by repeating irregular reflection, reflects off the reflecting sheet5disposed on the lower surface of the light guide plate4in the upward direction and exits from the light guide plate4through the upper surface thereof, passes through the optical sheet3and illuminates evenly the LCD panel (not shown inFIG. 6).

On the other hand, when the line light source7retained inside the reflector6is replaced, the line light source7is pulled out via the inserting opening8together with the reflector6, and the line light source7is replaced. Thus, the reflector6only can be removed without disassembling the backlight apparatus1. After the line light source7is replaced, the reflector6is inserted via the inserting opening8again, and can be built in the housing2by being slid into the space between the side surface of the light guide plate4and the side wall of the housing2.

To curb unevenness in the optical properties of the backlight apparatus1and make the entire apparatus small and thin, only the space for housing the reflector6needs to be formed between the side surface of the light guide plate4and the side wall of the housing2to reduce an unnecessary clearance.

FIG. 7is a perspective view of the reflector retaining the line light source7therein. As shown inFIG. 7, an upper plate6a, a side plate6band a lower plate6cof the reflector are put together to have substantially a C-shaped section, house the line light source7therein and retain both ends of the line light source7with retaining members9. Besides, an anode and a cathode are connected to leads10aand10brespectively at both ends of the line light source7. The one lead10apasses along the rear side of the side plate6bof the reflector6and is bundled with the other lead10b, and electrically connected to their respective inverters.

FIG. 8is a perspective view of the backlight apparatus1after the reflector6is built in. As shown inFIG. 8, when the reflector6is inserted into the housing2, the one lead10bis pulled through the space between the rear surface of the side plate6bof the reflector6and the side wall of the housing2, and is drawn out via the inserting opening8.

However, in this structure, although the reflector6housed in the housing2is vertically sandwiched and retained between the first frame2aand the second frame2b, it is not supported tightly thereby in the direction perpendicular to the inserting direction of the reflector6, because the space through which the lead10bpasses is formed between the side plate6band the side wall of the housing2. Therefore, there has been a problem that the reflector6is not securely fixed in the housing2and unevenness in the optical properties is caused. Also there has been a disadvantage that if the space between the side plate6bof the reflector6and the side wall of the housing2is made small to make the lead10bsupport tightly the side plate6bof the reflector6, the lead10bcan be damaged and the efficiency of insertion and replacement of the reflector can be lowered.

Accordingly, conventionally, to solve the problems, in JP-A-H11-134921, for example, a predetermined clearance is formed between the side wall of the housing and the reflector, and a lamp cover is disposed over the rear surface of the side plate of the reflector to protect the lead.

However, according to the invention described in JP-A-H11-134921, because the lamp cover needs to be disposed between the side wall of the housing and the reflector, the backlight apparatus cannot be made compact and the insertion of the reflector cannot be carried out efficiently.

SUMMARY OF THE INVENTION

To cope with the conventional problems mentioned above, it is an object of the present invention to provide a backlight apparatus which allows easy and efficient insertion and replacement of a reflector and which suppresses unevenness in the optical properties of the reflector.

To achieve the above object, according to one aspect of the invention, a backlight apparatus comprises: a housing that is composed of a first frame and a second frame, each having a side wall, combined together and that has a light guide plate housed therein; and a reflector that has a line light source housed therein and that is inserted between the side surface of the light guide plate and the side walls of the housing via an opening formed in the housing. Here, a reflector guide is formed on the side wall of the housing to protrude therefrom, and has a tilted surface tilted toward the insertion direction of the reflector.

In the backlight apparatus described above, a plurality of said reflector guides may be formed on the side wall of said housing.

According to another aspect of the invention, a display apparatus comprises: the backlight apparatus described above; and a light control member fro controlling the light emitted from the line light source.

In the display apparatus described above, the light control member may be a liquid crystal panel.

With the first structure according to the present invention, because the reflector guide having a tilted surface tilted toward the inserting direction of the reflector is formed on the side wall of the housing, an end portion of the reflector slides along the tilted surface and is guided into the housing. Thus the reflector is easily inserted into the housing and the reflector replacing efficiency is improved.

Further, after the reflector is inserted, because the reflector is supported tightly by the reflector guide in the direction perpendicular to the inserting direction, the reflector is securely retained in the housing, and unevenness in the optical properties can be suppressed.

In addition, when the reflector guide is formed lower than the side wall of the housing, a space through which the lead can pass is ensured between the upper surface of the reflector and the upper surface of the housing. Thus when the reflector is built in, the lead is not sandwiched nor damaged between the side wall of the housing and the side surface of the reflector. Moreover, the reflector guide is designed as small as possible taking into account the thickness of the lead, which allows the backlight apparatus to be compact.

With the second structure according to the present invention, a plurality of reflector guides formed on the side wall of the housing securely retain the reflector in the housing, and unevenness of the optical properties can be curbed.

With the third structure according to the present invention, a display apparatus equipped with the backlight apparatus having the above-mentioned features can be provided.

With the fourth structure according to the invention, a liquid crystal display apparatus equipped with the backlight apparatus having the above-mentioned features can be provided.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be explained referring to the drawings. The portions which are the same as or similar to those inFIGS. 5-8showing the conventional apparatus are numbered with the same numerals and the description of them is omitted. In these drawings, for easy understanding, the dimensional ratios of the members are different from the actual ones and the structure is schematically shown with details omitted.

FIG. 1is an exploded perspective view showing a state before the reflector6is built in a backlight apparatus according to an embodiment of the present invention. Like the conventional apparatus shown inFIG. 5, the backlight apparatus according to the embodiment of the present invention has the structure in which the optical sheet3is laminated on the upper surface of the light guide plate4and the reflecting sheet5is laminated on the lower surface of the light guide plate4. The reflector6(not shown inFIG. 1) retaining the line light source7is disposed at the side surface of the light guide plate4. These components are housed in the housing2which is formed by putting together the first frame2aand the second frame2b.As two inserting openings8, openings are formed in a side wall of the first frame2aand the second frame2b. The reflectors6(not shown inFIG. 1) are inserted in or pulled out via the inserting openings8to replace the line light sources7. A reflector guide11which guides the insertion of the reflector6is disposed on the inner surface of a side wall of the first frame2a.

The light guide plate4changes the optical path of the light which is emitted from the line light source7and which enters the light guide plate4from the side surface of the light guide plate4and converts the light into light which has an optical distribution of light emitted from a surface light source. The light guide plate4is a wedge-type plate or a parallel-plate type plate molded of polycarbonate or acryl resin.

In the line light source7according to the embodiment, cold-cathode tubes are used. However, instead of them, hot-cathode tubes, or xenon tubes as discharge tubes, may be used.

The reflecting sheet5is a flexible sheet of white resin, either alone or having silver, aluminum, or the like vapor-deposited thereon as a reflective layer having high reflectance. The reflecting sheet5efficiently reflects the light from the light guide plate4toward an LCD panel.

The optical sheet3is a laminate of a diffusing sheet and a plurality of light condensing sheets. Fine concaves and convexes are formed on one side of the diffusing sheet and irregularly reflect the light from the light guide plate4. The upper surface of the light condensing sheet is a prism surface which improves the brightness toward the LCD panel.

FIG. 2is a perspective view of the first frame2aaccording to the embodiment. The first frame2ahas side walls2L which form a housing space and are partially cut out to form the inserting openings8through which the reflectors6are inserted. The first frame2ais made of resin, and a plurality of reflector guides11made of resin are formed on the inner surface of the side wall2L. The reflector guides11have a parallel surface11aparallel to the side wall2L of the first frame2aand a tilted surface11bwhich is tilted toward the inserting direction, and are formed lower than the side walls2L. The reflector guides11and the first frame2aare unitarily made of resin.

FIG. 3Ais a perspective view of the backlight apparatus1showing how the reflector6is inserted into the backlight apparatus1according to the embodiment.FIG. 3bis a sectional view taken along A-A′ inFIG. 3A. As shown inFIG. 3A, in the backlight apparatus1according to the embodiment, the reflector6can be slidably inserted and incorporated in the space between the side wall of the light guide plate4and the side wall of the housing2via the inserting opening8formed through the side wall of the housing2. Inversely, the reflector6can be drawn out and removed via the inserting opening8. When the reflector6is inserted, the tip end of the side plate6bof the reflector6is guided by the tilted surface11bof the reflector guide11and inserted. After the insertion, the side plate6bcontacts the parallel surface11aof the reflector guide11(seeFIG. 2). Thus the tip end of the side plate6bis not obstructed by the reflector guide11and the reflector6can be smoothly inserted. The parallel surface11asupports tightly the reflector6, and the reflector6is securely retained in the housing2even if the reflector6is vibrated in the direction perpendicular to the inserting direction.

As shown inFIG. 3B, the reflector guide11is made lower than the side wall2L of the housing2, which ensures the space for the lead10abetween the side plate6bof the reflector6and the side wall2L of the housing2. Accordingly, when inserting the reflector6, the lead10apassing along the rear surface of the side plate6bis prevented from rubbing against the side plate6bor the side wall2L and being damaged. And the lead10ainserted in the housing2is pulled through the space between the side plate6bof the reflector6and the side wall2L of the housing2and drawn out via the inserting opening8.

FIG. 4is a plan view of the backlight apparatus1according to the embodiment of the invention. As shown inFIG. 4, the backlight apparatus1according to the embodiment is a type of apparatus in which the reflectors6are disposed at both opposite side surfaces of the light guide plate4. Accordingly, the reflector guides11are also respectively formed at opposite side walls2L of the housing2and allow the easy insertion and remove of each reflector6. In the embodiment, three reflector guides11are substantially equally spaced on the side walls2L of the housing2. However, this is not meant to limit the scope of the present invention; that is, only one reflector guide11also can bring the same effect of the present invention. Besides, it is possible to form a plurality of reflector guides11and securely retain them. The reflector guides11may be unitarily formed with the first frame2aor separate members may be fixed to the side walls2L. When separate members are fixed to the side walls2L, the reflector guides11may be made of an elastically deformable material to enhance the pushing function.

Further, the present invention is not limited to the structure in which the reflectors6are disposed at both side surfaces of the light guide plate4. In other words, the reflector6may be disposed at one side surface of the light guide plate4and used for the type of backlight apparatus in which light is shone from one direction.