JP2002139731A - Backlight of liquid crystal display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain light irradiation characteristics of a sidelight type light source, although the light source is a type directly disposed under a liquid crystal display panel. SOLUTION: The liquid crystal display panel includes a case main body 10 having a box shape whose upper surface is opened, a light guide plate 20 covering an upper surface opening part and the light source 30 provided in the case main body 10. A first light guide inclined surface 111 for directing the light from the light source 30 to the side of the upper surface opening part is formed on the sidewall 11 of the case main body 10 and a light reflection layer 21 is provided on the lower surface on the case main body 10 side of the light guide plate 20 except a light incident surface 201 opposed to the first light guide inclined surface 111. A second light guide inclined surface 202 for directing the light incident from the light incident surface 201 to the inside of the light guide plate 20 is formed on the end surface of the light guide plate 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight for a liquid crystal display panel, and more particularly, to a structure of a backlight in which a sidelight type light irradiating characteristic can be obtained while being a direct type. It is about.

[0002]

2. Description of the Related Art A transmissive or transflective liquid crystal display panel is provided with a lighting device called a backlight so that a bright display can be obtained even in a dark place. The backlight is roughly classified into a direct type and a sidelight type.

[0003] The direct type refers to a type in which a light bulb as a light source or a straight tube or a U-tube / W-tube fluorescent lamp is disposed directly below a liquid crystal display panel. As the optical system,
A reflector is provided on the back side of the light source, and a light diffusion plate is provided on the front side of the light source, so that light from the light source is reflected and diffused to form a surface light source.

In the side light type (edge light type),
A material having good light transmittance such as acrylic resin is used as the light guide plate, a light source is arranged on one side or two opposite sides of the light guide plate, and a light diffusion sheet is arranged on the upper surface on the liquid crystal display panel side, A reflective sheet is placed on the back side.

[0005]

According to the direct type, high efficiency of light utilization and high luminance can be obtained. On the other hand, thermal effects on the liquid crystal display panel are concerned, and uniform luminance can be obtained. There is a problem that it is difficult to obtain. In addition, if the brightness of the light source is too high, the shape of the light source can be seen through the liquid crystal display panel.

For this reason, the shape of the light reflecting plate and the thickness of the light diffusing plate are devised, and a lighting curtain (light screen) for changing the light blocking density according to the luminance distribution of the light source is provided between the light source and the light diffusing plate. In order to optimize the brightness, this is not a preferable solution because of the cost.

According to the sidelight type, since the light guide plate is used, the uniformity of luminance is better than that of the direct type, and
Further, heat from the light source is not easily transmitted to the liquid crystal display panel.
However, since the light source is arranged on the side of the light guide plate, the light source tends to spread laterally, and there is a case where the arrangement space is restricted.

The present invention has been made in order to solve such a problem, and an object of the present invention is to obtain a side-light-type light irradiation characteristic while being a direct type in which a light source is disposed directly below a liquid crystal display panel. It is an object of the present invention to provide a backlight for a liquid crystal display panel.

[0009]

In order to achieve the above object, the present invention provides a box-shaped case body having an open top,
The case body includes a light guide plate disposed so as to cover an upper surface opening thereof, and a light source provided in the case body.At least one side wall of the case body includes a light source from the light source. First for directing light to the upper opening side
A light guide inclined surface is formed, and a light reflection layer is provided on a lower surface of the light guide plate on the case body side except for a light incident surface facing the first light guide inclined surface. The end surface of the light guide plate is characterized in that a second light guide inclined surface for directing light incident from the light incident surface into the light guide plate is formed.

According to the above configuration, the light emitted from the light source is directed to the light incident surface provided around the light guide plate at the first light guide inclined surface formed on the inner surface of the side wall of the case body. The light is guided into the light guide plate by the second light guide inclined surface. Therefore, it exhibits a side-light type light irradiation characteristic with uniform luminance.

According to a preferred aspect of the present invention, a light source storage section having an upper surface closed by a ceiling wall and a light exit window on a side surface is provided at a central portion of the case main body. Further, a light reflection sheet such as a silver vapor-deposited film is provided from the first light guide inclined surface to the second light guide inclined surface.

In the present invention, a preferable inclination angle of the first light guide inclined surface with respect to the bottom surface of the case body is 11.
0-150 °. Further, it is preferable that the light reflecting layer has white reflection on the surface on the light guide plate side and specular reflection on the opposite surface.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a backlight according to the present invention will be described with reference to FIG. Although FIG. 1 shows only the configuration of the left portion of the backlight, the configuration of the right portion (not shown) is symmetric with the left portion.

This backlight has a basic structure including a case body 10, a light guide plate 20, and a light source 30. The case main body 10 is formed in a box shape with a shallow bottom with an open upper surface, and is made of a synthetic resin in this embodiment.

The case body 10 has two pairs of two sides (walls) opposed to each other. The two sides forming one pair, that is, in FIG. A first light guide inclined surface 11 is provided on the inner surface side of each case.
1 is formed. A preferred range of the angle formed by the first light guide inclined surface 111 and the case bottom surface is 110 to 150 °, and in this embodiment, 135 ° is selected. Note that a similar light guide inclined surface may be provided on the other pair of two sides.

The light source housing 1 is located at the center of the case body 10.
2 are provided. The light source housing 12 extends in parallel with the left side wall 11 (in the direction perpendicular to the paper surface in FIG. 1), and its upper surface is closed by a ceiling wall 121. Also,
Light exit windows 122 are formed on both side surfaces of the light source housing 12.

The light exit window 122 may be formed as one continuous opening, or may be a plurality of vertical slits or horizontal slits formed at predetermined intervals. In this embodiment, a straight tubular cold cathode fluorescent tube (CFL) is housed in the light source housing 12 as the light source 30. A light bulb may be used instead of the cold cathode fluorescent tube.

The light guide plate 20 is made of a plate material having good light transmittance such as an acrylic resin, and has a size to cover the opening on the upper surface of the case body 10. A light reflecting layer (sheet) is provided on the lower surface of the light guide plate 20 (the surface facing the case body 10).
21 are provided.

The light reflecting layer 21 is formed so that the light guide plate 20 located above the first light guide inclined surface 111 is not the entire lower surface of the light guide plate 20 but the periphery of the light guide plate 20 is a light incident surface 201 having a predetermined width. It is provided on the remaining part except the incident surface 201. The surface of the light reflection layer 21 on the light guide plate 20 side is white reflection,
The surface on the case body 10 side is specular reflection.

On the end face of the light guide plate 20, there is formed a second light guide inclined surface 202 for guiding the light incident from the light incident surface 201 toward the inside of the light guide plate 20. In this embodiment, the angle of the second light guide inclined surface 202 is set to 45 ° with respect to the bottom surface of the light guide plate 20.

From the first light guide inclined surface 111 to the second light guide inclined surface 202, a light reflection sheet 22 such as a silver vapor-deposited film is provided. For convenience of explanation, the first
221 is a light reflection sheet on the light guide inclined surface 111;
The light reflection sheet on the second light guide inclined surface 202 is designated as 222. A light diffusion sheet 23 is provided on the upper surface of the light guide plate 20.

Next, the operation of the backlight will be described. Since the surface of the light reflection layer 21 on the case body 10 side is specular reflection, most of the light emitted from the light source 30 goes to the first light guide inclined surface 111, and the light reflection sheet of the first light guide inclined surface 111 The light 221 reflects the light toward the light incident surface 201.

Light incident from the light incident surface 201 is guided into the light guide plate 20 by the light reflecting sheet 222 of the second light guide inclined surface 202. That is, the second light guide inclined surface 20
2 is an apparent light source of the light guide plate 20. Light reflection layer 21
Since the surface on the light guide plate 20 side is white reflection, the light in the light guide plate 20 is reflected upward, passes through the light diffusion sheet 23, and illuminates a liquid crystal display panel (not shown).

The scope of the present invention is not limited to the above embodiment. For example, in the above embodiment, the upper surface of the light source housing 12 is covered by the ceiling wall 121, but the ceiling wall 121 can be omitted on condition that the light reflection layer 21 does not leak light. This means that the light source housing 12 itself has an optional configuration. In addition, the arrangement of the light source is not limited to one central portion of the case body 10, and the light source can be arranged on, for example, the left side wall or the right side wall.

[0025]

As described above, according to the backlight of the present invention, the light emitted from the light source in the case body is formed on the end surface of the light guide plate by the first light guide inclined surface on the inner surface of the side wall. To the second light guide inclined surface side,
Since the second light guide inclined surface enters the light guide plate from the second light guide inclined surface, the second light guide inclined surface becomes an apparent light source of the light guide plate, so that the light source is disposed immediately below the liquid crystal display panel. Although it is a mold, it is possible to obtain side-light-type light irradiation characteristics.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a part of a backlight according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Case main body 11 Side wall 111 First light guide inclined surface 12 Light source accommodating part 121 Ceiling wall 122 Light emission window 20 Light guide plate 201 Light incident surface 202 First light guide inclined surface 21 Light reflection layer 22 Light reflection sheet 23 Light diffusion sheet 30 light source

Claims (5)

[Claims] 1. A box-shaped case body having an open upper surface,
The case body includes a light guide plate disposed so as to cover an upper surface opening thereof, and a light source provided in the case body.At least one side wall of the case body includes a light source from the light source. A first light guide inclined surface for directing light toward the upper surface opening is formed, and a lower surface of the light guide plate on the case body side except for a light incident surface opposed to the first light guide inclined surface. A liquid crystal, comprising: a light reflection layer; and a second light guide inclined surface formed on an end surface of the light guide plate to direct light incident from the light incident surface into the light guide plate. Display panel backlight. 2. The back of the liquid crystal display panel according to claim 1, wherein a light source storage portion having an upper surface closed by a ceiling wall and a light exit window on a side surface is provided at a central portion of the case body. Light. 3. The backlight of a liquid crystal display panel according to claim 1, wherein a light reflecting sheet is provided from the first light guide inclined surface to the second light guide inclined surface. 4. The backlight for a liquid crystal display panel according to claim 1, wherein an inclination angle of the first light guide inclined surface with respect to a bottom surface of the case body is 110 ° to 150 °. 5. The backlight for a liquid crystal display panel according to claim 1, wherein the light reflection layer has white reflection on the surface on the light guide plate side and mirror reflection on the opposite surface.