TECHNICAL FIELD

The present invention relates to a light guide plate, a planar light source apparatus, a display apparatus, and an electronic device.

BACKGROUND ART

In recent years, advances have been made in reducing sizes and thicknesses of electronic devices. There are demands for a reduction in a thickness of a light guide plate of a liquid crystal display apparatus (a liquid crystal display) to be mounted to such electronic devices. Backlight systems for liquid crystal display apparatuses include a system referred to as an edge light-type backlight and a system referred to as a direct-type backlight. Direct-type backlights which feature high light utilization efficiency and which enable higher brightness to be readily achieved are used as backlights for large-size liquid crystal display apparatuses. For example, an LED (Light Emitting Diode) which emits white light is used as a light source of a backlight. In the case of a direct-type backlight, while a plurality of LEDs are arranged directly underneath a light guide plate, brightness non-uniformity easily occurs on the light guide plate between portions directly above the LEDs and other portions. Regarding the technique described above, a planar light source apparatus has been proposed in which, for the purpose of reducing variations in brightness of a light source, the light source is installed in a conical depression for light source insertion provided on a rear surface of a light guide plate and light-scattering dots for scattering light inside the light guide plate are provided on the rear surface of the light guide plate (refer to Patent document 1).

CITATION LIST

[Patent Document]

[Patent document 1] Japanese Patent No. 3427636

SUMMARY OF INVENTION

Technical Problem

There are demands for a reduction in sizes of light guide plates and suppression of brightness non-uniformity in light guide plates. In consideration of such circumstances, an object of the present invention is to promote a reduction in thickness of a light guide plate and to provide a technique for suppressing brightness non-uniformity in the light guide plate.

Means for Solving the Problems

In the present invention, the following means is adopted in order to solve the problem described above. Specifically, the present invention is alight guide plate including: a light exit surface from which light is emitted; an opposite surface on an opposite side of the light exit surface; a depressed portion provided on the opposite surface; and a plurality of scattering portions which are provided on the light exit surface, the opposite surface, and a bottom surface of the depressed portion and which refract and scatter light, wherein the depressed portion has a tapered surface which spreads from the bottom surface of the depressed portion toward an opening of the depressed portion.

According to the present invention, due to light striking the tapered surface and being refracted and made incident into the light guide plate, the light incident into the light guide plate widely spreads. According to the present invention, light strikes the scattering portion provided on the bottom surface of the depressed portion, and the light is refracted, scattered, and made incident into the light guide plate. According to the present invention, the light inside the light guide plate strikes the scattering portion provided on the opposite surface, and the light inside the light guide plate is refracted and scattered. According to the present invention, the light inside the light guide plate strikes the scattering portion provided on the light exit surface, the light inside the light guide plate is refracted, scattered, and emitted from the light exit surface of the light guide plate to the outside. According to these configurations, a brightness distribution of the light exit surface of the light guide plate can be made uniform and brightness non-uniformity of the light guide plate can be suppressed without increasing a thickness of the light guide plate.

In the light guide plate according to the present invention, a plurality of scattering portions provided on the light exit surface, the opposite surface, and the bottom surface of the depressed portion are respectively densely arranged. According to this configuration, since the likelihood that the light inside the light guide plate and light emitted from the light exit surface of the light guide plate are refracted and scattered increases, the brightness distribution of the light exit surface of the light guide plate can be made more uniform and brightness non-uniformity of the light guide plate can be further suppressed without increasing the thickness of the light guide plate.

In the light guide plate according to the present invention, the depressed portion has a truncated cone shape. According to this configuration, since a light source with a small size can be housed inside the depressed portion, the brightness distribution of the light exit surface of the light guide plate can be made uniform and the brightness non-uniformity of the light guide plate can be suppressed without increasing the thickness of the light guide plate.

In the light guide plate according to the present invention, an angle of the tapered surface is set in accordance with an angle of a major axis of the light source housed inside the depressed portion. According to this configuration, even when the major axis of the light source is changed by changing a type of the light source, an angle of incidence of light incident into the light exit surface of the light guide plate can be maintained at a constant angle. In addition, a peak direction of emitted light of the light source can be controlled. Therefore, a brightness distribution of the light exit surface of the light guide plate can be controlled for each light source.

In the light guide plate according to the present invention, the depressed portion is provided in plurality on the opposite surface. According to this configuration, a light source can be housed in each of the depressed portions. A planar light source apparatus according to the present invention includes: the light guide plate according to the present invention; and a light source housed inside a depressed portion, wherein an angle of the tapered surface is set in accordance with an angle of a major axis of the light source. Since such a planar light source apparatus includes the light guide plate according to the present invention, the planar light source apparatus can be provided in which a brightness distribution of the light exit surface of the light guide plate is made uniform and the brightness non-uniformity of the light guide plate is suppressed without increasing the thickness of the light guide plate.

The planar light source apparatus according to the present invention includes: the light guide plate according to the present invention; a light source arranged on a side of the opposite surface of the light guide plate; and a transparent resin layer arranged between the light guide plate and the light source, wherein the light source is embedded in the transparent resin layer. In addition, the planar light source apparatus according to the present invention includes: the light guide plate according to the present invention; a plurality of light sources arranged on a side of the opposite surface of the light guide plate; and a transparent resin layer arranged between the light guide plate and the plurality of light sources, wherein the plurality of light sources are embedded in the transparent resin layer. According to these configurations, a distance between the light guide plate and the light source can be kept constant without increasing the thickness of the light guide plate. By separating the light guide plate and the light source from each other without housing the light source inside the depressed portion of the light guide plate, spread of light incident into the light guide plate can be increased. In addition, by housing the light source and the transparent resin layer inside the depressed portion of the light guide plate and increasing a distance between the light guide plate and the light source, spread of light incident into the light guide plate can be increased.

A display apparatus according to the present invention includes: the planar light source apparatus according to the present invention; and a display panel which receives light emitted from the planar light source apparatus. Since such a display apparatus includes the light guide plate and the planar light source apparatus according to the present invention, the display apparatus can be provided in which a brightness distribution of the light exit surface of the light guide plate is made uniform and the brightness non-uniformity of the light guide plate is suppressed without increasing the thickness of the light guide plate.

An electronic device according to the present invention includes the display apparatus according to the present invention. Since such an electronic device includes the light guide plate, the planar light source apparatus, and the display apparatus according to the present invention, the electronic device can be provided in which a brightness distribution of the light exit surface of the light guide plate is made uniform and the brightness non-uniformity of the light guide plate is suppressed without increasing the thickness of the light guide plate.

Advantageous Effects of Invention

According to the present invention, a reduction in thickness of a light guide plate can be promoted and brightness non-uniformity of the light guide plate can be suppressed.

