JP2003132723A - Light guide plate and surface light-source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a surface light-source device always have a superior appearance wherein bright and dark lines optically generated at a light-emitting face of a light guide plate can be concealed in the device using the light guide plate. SOLUTION: This device is provided with the plate-formed light guide plate 1 to make the incident light into the inside from the side face outgo from the surface, and at the upper part prism face of this light guide plate 1, a scattering treatment part 2 with a prescribed width to make outgoing beam be scattered is installed in parallel with the light guide plate side face. Further, the width of the scattering treatment part 2 of the light guide plate 1 is made to have the width proportionate to the thickness of the incident light part of the side face of the light guide plate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate and a surface light source device used for a backlight of an LCD display unit.

[0002]

2. Description of the Related Art A surface light source device having a light guide plate is used for a backlight of an LCD display unit. The light guide plate of the surface light source device allows light from a light source such as a fluorescent tube to enter the inside from the side surface and uniformly emits the light from the surface. 7 to 9 show the main parts of a surface light source device having such a conventional light guide plate.

In FIG. 7, the prism sheet 12 is arranged on the upper surface of the light guide plate 11, and the bottom surface of the light guide plate 11 is subjected to a dot-like scattering process. Prism sheet 12
Is a downward prism, and its shape is symmetric or asymmetric. Then, the light from the straight tube-shaped light source 13 is made incident from the side surface of the light guide plate 11 and emitted from the surface.
FIG. 8 shows the brightness level of the emitted light from the light incident surface of the light guide plate 11 to the opposite surface.

In the structure shown in FIG. 9, the entire surface of the light guide plate 11 is formed into a prism shape, the lower surface is subjected to a dot-like scattering treatment, the diffusion sheet 14 is arranged on the upper part of the light guide plate 11, and the reflection sheet 15 is arranged on the lower part. It is arranged. And the light source 1
The light that is incident from 3 directly or through the reflector 6 is made uniform and surface-emitted. In this case, the bottom surface of the light guide plate 11 may be processed with a prism and the top surface may be subjected to a scattering process.

[0005]

By the way, in the surface light source device using the light guide plate as described above, the thickness of the light exit part on the surface of the light guide plate is substantially the same as the thickness of the light entrance part on the side surface of the light guide plate. A dark line having a width is generated, and the dark line is repeatedly generated toward the light incident portion side of the plate, which may cause deterioration of appearance.

The present invention has been made in view of the above problems, and it is possible to hide bright and dark lines that are optically generated on the light emitting surface of the light guide plate, so that the light guide plate and the surface light source always look good. The purpose is to provide a device.

[0007]

The light guide plate according to the present invention comprises:
It is a plate-shaped light guide plate that emits light from a light source that has entered inside from a side surface and that has a scattering processing section of a predetermined width for scattering the emitted light provided in parallel with the side surface.

Further, the width of the scattering processing portion is the width corresponding to the thickness of the light incident portion on the side surface.

A surface light source device according to the present invention is a surface light source device having a plate-shaped light guide plate that emits light from a light source that enters inside from a side surface, and scatters the emitted light on the light guide plate. A scattering processing part having a predetermined width is provided in parallel with the side surface.

Further, the width of the scattering-processed portion of the light guide plate is the width corresponding to the thickness of the light incident portion on the side surface of the light guide plate.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing a light guide plate of a surface light source device according to the present invention, in which (a) shows a structure of the embodiment (plan view and side view), and (b) shows a general structure for reference. The structure (plan view and side view) is shown.

The light guide plate 1 of the present embodiment is a plate-shaped light guide plate that emits light from a straight tube-shaped light source that enters the inside from the side surface, and has a predetermined width for scattering the emitted light on the surface. The scattering processing unit 2 is provided in parallel with the side surface.
Here, the width of the scattering processing portion 2 is the width corresponding to the thickness of the light incident portion on the side surface of the light guide plate 1.

The above-mentioned scattering processing unit 2 is one in which the upper prism surface on one side of the light entrance side of the light guide plate 1 is subjected to a scattering process, and the above-mentioned dark line generated near the light entering part cannot be recognized as a dark line in the scattering process. It is performed so that the contrast ratio of the brightness of the bright and dark lines thereafter cannot be visually judged.

At this time, depending on the combination with other elements other than the light guide plate 1, the scattering process needs to be performed uniformly within the region where it is performed or to blur the boundary, or to change the shape of the region.

2 (a) and 2 (b) show the brightness level of the emitted light from the light incident surface of the light guide plate 1 to the opposite surface.

FIG. 3 is a diagram showing a specific example (type) of the scattering processing unit 2. (A), (b), (c), (d)
In addition to the scattering processing units 2a, 2b, 2c, and 2d shown in FIG.

As described above, in this embodiment, since the scattering processing portion 2 is provided on the light-incident side of the light guide plate 1 in parallel with the light source, the bright and dark lines optically generated on the light emitting surface of the light guide plate 1 are hidden. Therefore, it is possible to realize a surface light source device that always looks good.

Here, the cause of the occurrence of the bright and dark lines will be described. In the light emitting surface of the conventional light guide plate shown in FIG. 4, A1 is a portion where a problem of a critical angle occurs (dark portion), B1 is a portion due to direct light from the light source 3 and reflected light on the bottom surface (bright portion), and C1 is a light source. Light and dark continue while being attenuated by reflection, and a portion by direct light from 3 and reflected light on the upper surface. The bright and dark lines are caused by the imbalance of light emitted to the light emitting surface due to the difference in optical characteristics between the light emitting surface side and the reflecting surface side of the light guide plate. It is conspicuous when it is arranged or when it is combined with a downward prism or a silver reflection sheet.

The first dark line is as shown in FIG.
Refractive index (n1) of material of light guide plate and refractive index (n2) of air
Difference (n1 <n2).

Therefore, in the present embodiment, the light-incident portion side of the light guide plate is subjected to the scattering process in parallel with the light source 3 to conceal the bright and dark lines. That is, in the light exit surface of the light guide plate of the present embodiment shown in FIG. 6, A2 is a part where light is emitted by a scattering process having a width corresponding to the thickness of the light entrance part of the light guide plate, and B2 is direct light from the light source 3 and the bottom surface. The portion C2 due to the reflected light is followed by the direct light from the light source 3, the reflected light from the bottom surface, and the portion emitted by the scattering process. Then, the above scattering process can disperse the deviation of the optical characteristics, destroy the contrast of the bright and dark lines, and improve the appearance. L in the figure indicates reflected light that does not go outside.

Incidentally, the scattering process is a blast process,
It can be applied directly to the mold or the light guide by etching or the like. Further, the range varies depending on the refractive index or the cross-sectional shape of the light guide, but in the case of acrylic, the width corresponding to the thickness of the light entrance part of the light guide plate is good.

[0023]

As described above, according to the present invention,
Bright and dark lines that are optically generated can be concealed on the light emitting surface of the light guide plate, and surface light emission that always looks good can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a light guide plate of a surface light source device according to the present invention.

FIG. 2 is a diagram showing the brightness level of light emitted from the light guide plate of the embodiment.

FIG. 3 is a diagram showing a specific example of a scattering processing unit according to the embodiment.

FIG. 4 is an explanatory diagram showing the cause of the bright and dark lines.

FIG. 5 is an explanatory diagram showing the cause of occurrence of dark lines.

FIG. 6 is an explanatory diagram showing a concealment process for bright and dark lines.

FIG. 7 is a side view showing a main part of a conventional example.

FIG. 8 is a diagram showing the brightness level of light emitted from a light guide plate of a conventional example.

FIG. 9 is a perspective view showing a main part of another conventional example.

[Explanation of symbols]

1 Light guide plate 2 Scattering processing section 3 light sources 2a Scattering processing unit 2b Scattering processing unit 2c Scattering processing unit 2d scattering processing unit

Claims (4)

[Claims] 1. A plate-shaped light guide plate that emits light from a light source that enters inside from a side surface, wherein a scattering processing portion having a predetermined width for scattering the emitted light is provided in parallel with the side surface. A light guide plate characterized in that. 2. The light guide plate according to claim 1, wherein the width of the scattering processing portion is a width corresponding to the thickness of the light incident portion on the side surface. 3. A surface light source device having a plate-shaped light guide plate that emits light from a light source that enters inside from a side surface, wherein the light guide plate has a predetermined width for scattering the emitted light. A surface light source device, wherein a processing unit is provided in parallel with the side surface. 4. The surface light source device according to claim 3, wherein the width of the scattering treatment portion of the light guide plate is set to a width corresponding to the thickness of the light incident portion on the side surface of the light guide plate.