JP2000221330A - Light guide plate and backlight unit - Google Patents

Abstract

(57) [Problem] To prevent poor dot appearance without increasing manufacturing cost. A plate-like member (11) of a light guide plate (10) is formed in a plate shape by a transparent member such as acrylic, and one of four circumferences constituting the plate shape is a light incident surface (12) on which illumination light enters. The light-emitting surface 13 is a front surface of the plate, and a reflection sheet 15 serving as a light reflection layer is disposed on the rear surface 14 of the plate.
The reflection sheet 15 is obtained by processing the surface of a metal sheet into a satin finish, and diffuses and reflects light. The rear surface 14 is provided with a plurality of recesses 16 having concavities and convexities concentric with the bottom as viewed from the vertical direction, and the other portions are flat portions 17.

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 for diffusing illuminating light incident from a side surface by a diffusion means and emitting the light from the front surface, and a backlight unit using such a light guide plate.

[0002]

2. Description of the Related Art Conventionally, some liquid crystal display devices such as personal computers and personal digital assistants using a liquid crystal screen use a backlight device and some do not use a backlight device. Devices using a backlight device have become mainstream.

A backlight device used for a liquid crystal display device has been required to be thinner and lighter, and an illumination light from a primary light source described in Japanese Patent Laid-Open No. 10-104431 or the like is used to transmit illumination light from a light guide plate (transparent substrate). ), The illumination light is diffused by the diffusion means and emitted from the front surface of the light guide plate. The light guide plate is becoming thinner and wedge-shaped. In addition, due to demand for cost reduction, a light guide plate formed by die molding is mainly used.

As a diffusion means of a light guide plate formed by molding, V
There are a groove, a conical groove, a half-moon-shaped groove, and the like. However, as the thickness of the light guide plate becomes thinner, poor dot appearance that can be visually confirmed on the light emitting surface of the backlight device occurs. Poor dot appearance
These are dot-like bright spots appearing on the light-emitting surface, and those seen through the liquid crystal screen are defective.

In response to this, a light guide plate has been developed in which diffusion means are formed by dot printing using white ink.

FIG. 11 is a sectional view showing a light guide plate using such conventional dot printing.

In FIG. 11, a plate-like member 101 is formed in a plate shape by a transparent member such as acrylic, and one of four circumferences constituting the plate shape is a light incident surface 102 on which illumination light enters. The front surface constituting the plate shape is the light emitting surface 103, and the light emitting surface 1
03, a reflection sheet 105 of a light reflection layer is disposed on the rear surface 104 side.

On the rear surface 104, a dot pattern 106 of a diffusion means is formed by dot printing using white ink.

Illumination light incident on the light incident surface 102 is directly radiated to the dot pattern 106 and diffused, or is reflected on the light emitting surface 103, the rear surface 104, the reflection sheet 105, etc., and then irradiates the dot pattern 106. The illumination light diffused and diffused in the dot pattern 106
Emitted from

Dot pattern 10 using white ink
6 has good performance of diffusing the irradiated illumination light,
Poor dot appearance can be prevented.

However, dot printing using white ink has a problem in that the manufacturing cost is increased as compared with the case where diffusion means are formed by die molding.

[0012]

In the light guide plate formed by the above-mentioned conventional mold, many dot appearance defects which can be visually confirmed on the light emitting surface of the backlight device have been generated. Further, in the conventional light guide plate using dot printing, since dot printing using white ink is performed, there is a problem in that the manufacturing cost is increased as compared with the case where diffusion means is formed by die molding.

Accordingly, an object of the present invention is to provide a light guide plate capable of preventing dot appearance defects without increasing the manufacturing cost.

[0014]

According to a first aspect of the present invention, there is provided a light guide plate formed of a transparent member in the shape of a plate, and light incident on at least one peripheral side of four rounds constituting the plate shape. A plate-shaped member having a light-emitting layer disposed on a rear surface of the plate-shaped member; and a light-emitting layer formed on at least one of the light-emitting surface and the rear surface of the plate-shaped member. , A plurality of concave portions or convex portions having concentric concave and convex portions on the bottom portion.

According to a second aspect of the present invention, there is provided a light guide plate.
The light guide plate according to claim 1, wherein an interval between the plurality of concave portions or the convex portions is changed according to a position of the light emitting surface or the rear surface.

According to a third aspect of the present invention, there is provided a light guide plate.
The light guide plate according to claim 1, wherein a diameter of the plurality of concave portions or the convex portions is changed according to a position of the light emitting surface or the rear surface.

According to a fourth aspect of the present invention, there is provided a light guide plate.
The light guide plate according to any one of claims 1 to 3, wherein a depth of forming the concentric unevenness of the concave portion or the convex portion is changed according to a distance from a center of the concave portion or the convex portion.

According to a fifth aspect of the present invention, there is provided a backlight unit as set forth in any one of the first to fourth aspects; a light source disposed on a light incident surface of the light guide plate; And optical means opposed to each other.

According to the first to fifth aspects of the present invention, the concentric concavities and convexities of the concave portion or the convex portion can be formed by forming a mold, and the illumination light can be transmitted and reflected on average. It is possible to prevent poor dot appearance without increasing the cost.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 5 show a first embodiment of a light guide plate according to the present invention.
1 is a cross-sectional view of a main part, FIG. 2 is a rear view showing a plate-shaped member in an enlarged manner, FIG. 3 is a cross-sectional view showing a diffusion means, and FIG. 4 is a rear view showing the entire light guide plate. FIG. 5 and FIG. 5 are side views showing the entire light guide plate.

In FIG. 1, a plate-like member 11 of a light guide plate 10 is shown.
Is formed in a plate shape with a transparent member such as acrylic, and one of four circumferences forming the plate shape is a light incident surface 12 on which illumination light is incident, and a front surface forming the plate shape is a light emitting surface 13. A reflection sheet 15 serving as a light reflection layer on the rear surface 14 side forming a plate shape
Is arranged. The reflection sheet 15 is obtained by processing the surface of a metal sheet into a satin finish, and diffuses and reflects light.

On the rear surface 14, a plurality of concave portions or convex portions 16 having concentric unevenness as viewed from the vertical direction are formed on the bottom portion, and the other portions are flat portions 17.

In FIG. 2, concavities and convexities 18 which are concentric when viewed from the vertical direction are formed at the bottom of the plurality of concaves or convexes 16 on the rear surface 14 of the plate-like member 11.

In FIG. 3, the unevenness 18 is formed in a mountain shape when viewed from the side. The diameter of the concave portion or the convex portion 16 is 0.
The depth is set to 1 mm to 1.5 mm, and the depth of the concave portion or the convex portion 16 is set to 0.5 mm or less. In this case, the depth of the concave or convex portion 16 is a distance between the flat portion 17 and the deepest portion of the concave and convex 18.

In FIG. 4, the plate-like member 11 of the light guide plate 10 is shown.
Is formed in a long-sided plate shape corresponding to the liquid crystal screen, and a plurality of concave portions or convex portions 16 are formed on the rear surface 14 of the plate-shaped member 11 at equal intervals and vertically and horizontally.

In FIG. 5, the plate member 11 of the light guide plate 10 is shown.
Is wedge-shaped when viewed from the side.

Hereinafter, the operation of the light guide plate 10 will be described.

In FIG. 1, a light incident surface 12 of a light guide plate 10 is shown.
Illumination light incident on the concave portion or the convex portion 16 is directly radiated to the concave portion or the convex portion 16, or is reflected by the light emitting surface 13, the rear surface 14, the reflection sheet 15, and the like, and then radiated to the concave portion or the convex portion 16. As shown in FIG. 3, the unevenness 18 at the bottom of the concave portion or the convex portion 16 is formed in a mountain shape when viewed from the side, so that the surface is divided into a surface that totally reflects the illumination light and a surface that transmits the illumination light. The light is diffusely reflected by the reflection sheet 15 as shown in FIG. The diffused light diffusely reflected by the reflection sheet 15 passes through the concave or convex portion 16 and passes through the light emitting surface 13.
At this time, the brightness is improved by the lens effect of the unevenness 18 shown in FIG. In addition, since the concave or convex portions 16 can transmit and reflect the illumination light on average, there is no local light reflection like a light guide plate using a conventional forming mold, and the dot is not formed. Poor appearance can be prevented.

According to the embodiment of the present invention shown in FIGS. 1 to 5, concentric concave and convex portions of the concave portion or the convex portion can be formed by forming a mold, and can transmit and reflect illumination light on average. Therefore, it is possible to prevent poor dot appearance without increasing the manufacturing cost, and it is possible to make the backlight device thin and uniform in light emission without increasing the manufacturing cost of the backlight device.

In the light guide plate 10 shown in FIGS. 1 to 5, one of the four circumferences constituting the plate shape of the plate member 11 is a light incident surface on which illumination light is incident. The edge side may also be a light incident surface. Further, although a plurality of concave portions or convex portions 16 are formed on the rear surface 14 of the plate-shaped member 11, the concave portions or convex portions 16 may be formed on both the light emitting surface 13 and the rear surface 14, and may be formed only on the light emitting surface 13. You may.

FIG. 6 is a perspective view showing a case where the light guide plate 10 shown in FIG. 1 is applied to a backlight device (backlight unit).

Referring to FIG. 6, the backlight device 1 includes the light guide plate 10 of FIG. 1, the reflection sheet 15 of FIG. 1, the primary light source 2, and the reflector 3.

The primary light source 2 is a cold-cathode tube that emits light by a high-frequency AC voltage, and the illumination light can be directly incident on the light guide plate 10 in the longitudinal direction adjacent to one peripheral side of the light guide plate 10. The reflector 3 transmits light from the primary light source 2 to the light guide plate 1.
In order to make the light incident on the primary light source 2, it is arranged to be wound around the primary light source 2.

The light guide plate 10 can be applied by such a backlight device 1.

FIG. 7 is a rear view of a light guide plate according to a second embodiment of the present invention.

In FIG. 7, the plate-like member 21 of the light guide plate 20 is shown.
Is formed in a long-sided plate shape corresponding to the liquid crystal screen, and a plurality of concave portions or convex portions 26 are formed on the rear surface 24 of the plate-shaped member 21 so as to change the distance between each other according to the position of the rear surface 24. .
In this case, the distance between the concave portions or the convex portions 26 decreases as the distance from the light incident surface 22 increases.

According to the embodiment of the present invention, the distance between the concave portions or the convex portions 26 becomes shorter as the distance from the primary light source becomes relatively far, thereby making the light emission amount per unit area on the light emitting surface uniform. Can be.

FIG. 8 is a rear view of a light guide plate according to a third embodiment of the present invention. In FIG. 8, the plate member 31 of the light guide plate 30 is formed in a long-sided plate shape corresponding to the liquid crystal screen, and a plurality of concave portions or convex portions 36 are formed on the rear surface 34 of the plate member 31 at the above-mentioned intervals. The diameter is changed according to the position of the rear surface 34, and the diameter of the plurality of concave portions or convex portions 36 is changed according to the position of the rear surface 34. In this case, as the distance from the light incident surface 32 increases, the concave or convex portion 36 increases.
And the diameter of the concave or convex portion 36 is increased.

According to such an embodiment of the present invention, the distance between the concave portions or the convex portions 36 is made smaller and the diameter of the concave portions or the convex portions 36 is made larger as the distance from the primary light source becomes relatively far, so that the light emitting surface in the light emitting surface can be obtained. The amount of light emission per unit area can be made uniform.

FIG. 9 is a sectional view of a concave portion or a convex portion showing a light guide plate according to a fourth embodiment of the present invention.

In FIG. 9, the plate member 41 of the light guide plate 40
Are concentric concave-convex portions 48 of the concave portions or convex portions 46 of the rear surface 44.
Is changed in accordance with the distance from the center of the concave portion or the convex portion 46. In this case, the shorter the distance from the center, the greater the depth at which the irregularities 48 are formed.

FIG. 10 is an explanatory diagram for explaining the shape of the recess shown in FIG.

In FIG. 10, reference numerals 51, 52, 53,
Reference numeral 54 designates the concave portion 46 of FIG. 1 at the positions A1, A2, A3 and A4.
This shows that the depth of the concentric unevenness 48 increases as the distance from the center of the concave portion 46 decreases.

According to such an embodiment of the present invention, the same effects as those of the embodiment shown in FIGS. 1 to 5 can be obtained, and the concentric unevenness becomes smaller as the distance from the center of the concave portion 46 becomes shorter. Since the depth at which the recess 48 is formed is increased, the lens effect of the recess 46 can be enhanced.

[0046]

According to the present invention, it is possible to prevent poor dot appearance without increasing the manufacturing cost, and it is possible to make the backlight device thin and uniform in light emission without increasing the manufacturing cost of the backlight device.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a light guide plate according to a first embodiment of the present invention.

FIG. 1 is an enlarged rear view showing a plate-like member.

FIG. 3 is a cross-sectional view showing the diffusion means of FIG.

FIG. 4 is a rear view showing the entire light guide plate of FIG. 1;

FIG. 1 is a side view showing the entire light guide plate.

FIG. 6 is a perspective view showing a case where the light guide plate shown in FIG. 1 is applied to a backlight device.

FIG. 7 is a rear view showing a second embodiment of the light guide plate according to the present invention.

FIG. 8 is a rear view showing a third embodiment of the light guide plate according to the present invention.

FIG. 9 is a sectional view of a concave portion showing a fourth embodiment of the light guide plate according to the present invention.

FIG. 10 is an explanatory view illustrating the shape of the concave portion in FIG. 9;

FIG. 11 is a sectional view showing a light guide plate using conventional dot printing.

[Explanation of symbols]

 Reference Signs List 10 light guide plate 11 plate member 12 light incident surface 13 light emitting surface 14 rear surface 15 reflection sheet 16 concave portion

Claims (5)

[Claims] 1. A plate formed of a transparent member, wherein at least one of four circumferences forming the plate shape is a light incident surface on which illumination light is incident, a front surface forming the plate shape is a light emitting surface, A plate-shaped member having a light reflecting layer disposed on a rear surface constituting a shape; and a plurality of concave portions or convex portions formed on at least one of a light-emitting surface and a rear surface of the plate-shaped member and having concentric concave-convex portions on a bottom portion. And a light guide plate comprising: 2. The light guide plate according to claim 1, wherein an interval between the plurality of concave portions or convex portions is changed according to a position of the light emitting surface or the rear surface. 3. The light guide plate according to claim 1, wherein the diameter of the plurality of concave portions or the convex portions is changed according to the position of the light emitting surface or the rear surface. 4. The light guide plate according to claim 1, wherein a depth of forming the concentric unevenness of the concave portion or the convex portion is changed according to a distance from a center of the concave portion or the convex portion. 5. A light guide plate according to claim 1, a light source disposed on a light incident surface of the light guide plate, and an optical means optically opposed to the light source and the light guide plate; A backlight unit comprising: