JP3451297B2 - Liquid crystal display device and backlight device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device (LC
D) and a backlight device equipped with the same.

[0002]

2. Description of the Related Art Conventionally, as an LCD in which a display screen of a liquid crystal panel is irradiated with light from a backlight device, for example, one schematically shown in FIG. 5 is known.
That is, a backlight device is arranged behind the liquid crystal panel 1, and in this backlight device, light from the tubular light source 3 is passed through the diffusion plate 2 to illuminate the liquid crystal panel 1, and the reflection device arranged behind the light source 3 is reflected. The plate 4 prevents the backscattering of light and reflects it forward. In the case of this structure, since the light source 3 is a tubular surface light source, uneven brightness is likely to occur on the display screen of the liquid crystal panel 1. In order to prevent such a problem of occurrence of uneven brightness, the light source 3 is devised such that the light source 3 is separated from the position of the virtual line in the figure relatively close to the diffusion plate 2 to the position of the solid line as far as possible. In addition, FIG.
Shows a conventional example of a structure relating to a backlight device.
In this case, since the portion where the light source 5 is closest to the diffuser plate 6 has the highest brightness on the display screen of the liquid crystal panel, the reflective band 7 is printed on the diffuser plate 6 in a band-shaped range corresponding to the tubular projection area of the light source 5. In this case, the uneven brightness is suppressed and the brightness is made uniform.

[0003]

However, in the backlight device equipped in the LCD shown in FIG. 5, the light source 3 is used in order to suppress uneven brightness on the display screen of the liquid crystal panel.
If the distance from the diffuser plate 2 is increased, the depth of the entire LCD device is increased and the LCD device is enlarged, resulting in an increase in size. Further, in the backlight device as shown in FIG. 6, since the print reflection surface 7 is separately provided on the diffusion plate 6 for uniforming the brightness, there is a disadvantage that the cost becomes high. Therefore, an object of the present invention is to improve a backlight device provided with a cylindrical light source that serves as a surface light source, and make it possible to uniformize the light from the backlight device and suppress uneven brightness generated on the liquid crystal display screen. An object of the present invention is to provide a liquid crystal display device and a backlight device that can be manufactured at low cost.

[0004]

In order to achieve the above object, a liquid crystal display device according to the present invention irradiates a display screen of a liquid crystal panel with light from a tubular light source through a diffusion plate. However, the first diffusing section is composed of a first diffusing section and a second diffusing section having a light diffusivity smaller than that of the first diffusing section and provided adjacent to each other.
It is provided in a strip shape in the longitudinal direction at the center, and is provided with the first diffusion part and the first diffusion part.
2 The boundary surface of the diffusion part is a flat surface or a curved surface that is inclined.
ing. Further, the backlight device according to the present invention includes a tube.
A reflector that reflects light forward is placed behind the light source
The light from the light source is passed through the diffuser plate.
And the diffuser plate is more than the first diffuser and the first diffuser.
The second diffuser, which has a small light diffusivity and is adjacent to each other,
The first diffusing portion in the width direction of the second diffusing portion.
The first diffusion part and the second
The boundary surface of the diffusion part becomes an inclined flat surface or curved surface
There is. Further, the liquid crystal display device and the buckler according to the present invention.
The first device and the second diffuser are two-color molded
can do.

[0005]

The light from the cylindrical light source is blunted by lowering the illuminance at the first diffusing portion having a large diffusivity in the diffusing plate. The diffusivity is an amount representing the degree of diffusion of light in a unit thickness, and has a relationship in which the luminous flux (amount) is reduced as the diffusivity increases. Therefore, the illuminance of the portion where the light source closely faces is increased, but by arranging the first diffusing portion at the portion where the illuminance is high, the illuminance of the second diffusing portion is made uniform, and as a result, the liquid crystal The uneven brightness of the screen display of the panel is suppressed and
By making the boundary surface between the first diffusion portion and the second diffusion portion an inclined surface,
Extreme illumination at the interface, such as with a vertical interface.
It has the meaning of avoiding changes in degree. Further, by configuring the diffuser plate of the backlight device by the first diffuser and the second diffuser as described above, the light from the cylindrical light source, which is easy to become a surface light source, is made uniform by the diffuser, and the liquid crystal display When used in the device, it suppresses the uneven brightness of the display screen,
By making the boundary surface between the diffusion part and the second diffusion part an inclined surface,
Extreme illuminance at the interface, such as when using a direct interface
It makes sense to avoid changes. Also, the first diffusion unit
And two-color molding of the second diffusing section are generally different in material and color.
It has the same meaning as two-color molding that simultaneously molds several materials
Then, integral molding becomes possible.

[0006]

Embodiments of the liquid crystal display device and the backlight device according to the present invention will be described below with reference to the drawings.
As shown in the exploded perspective view of FIG. 1, the liquid crystal display device 10 is
A liquid crystal panel 12 is held on a substrate 11 such as an LSI substrate, and the backlight device of the embodiment is arranged behind the liquid crystal panel 12. In this backlight device, the light from the tubular light source 13 is passed through the diffusion plate 20 to irradiate the liquid crystal panel 12, and the reflection plate 15 disposed behind the light source 13 is illuminated.
This prevents the backscattering of light and reflects it forward. The tubular light source 13 is attached to a support plate 14, and a diffuser plate 20 having a rectangular shape or the like, which is the essential member of the present invention, is arranged between the liquid crystal panel 12 and the light source 13, and the light source 13 is passed through the diffuser plate 20. Light is emitted to the display screen of the liquid crystal panel 12. Further, on the back side of the light source 13, a reflection plate 15 having a shape that expands toward the liquid crystal panel 12 is arranged, which prevents backscattering of the light of the light source 13 and reflects the light forward so that the entire liquid crystal panel 12 can be irradiated. Is configured.

The diffusion plate 20 is the support plate 14 described above.
Attached to. For example, the locking pieces 26, 26 are bent at both ends of the rectangular shape of the diffusion plate 20, and the locking pieces 21 are formed.
Can be dropped and fixed to the locking slits 14a provided at both ends of the support plate 14 with one touch. Further, the light source 13 can be attached to the support plate 14 by elastic holding while being protected by a spring-shaped holding member 16.

As for the rectangular diffuser plate 20, the diffuser plate 20 is composed of a first diffuser portion 21 and a second diffuser portion 22 which are two-color molded by, for example, a multi-color dedicated molding machine as shown in the drawing. It is made of resin. First diffusion part 21
The diffusivity of the light is larger than that of the second diffusing portion 22, and the light is diffused in the longitudinal direction at the center of the second diffusing portion 22 in the width direction. As described above, when the acrylic resin is used, the dense portion in which the acrylic resin is used as the base material and the diffusing material is mixed in a large mixing ratio is the first diffusing portion 21, and the rough portion having a small mixing ratio is the second diffusing portion 22. Can be
Therefore, the light source 13 has its cylindrical entire length direction in the diffusion plate 2
The light from the light source 13 is arranged so as to be aligned in the extending direction of the first diffusing portion 22 of 0, and the light from the light source 13 has a large diffusing rate.
Thus, the illuminance is reduced and slowed down, and is made uniform with the illuminance of the light diffused by the second diffusing section 21.

FIG. 2 shows a diffusion plate 2 according to the arrow AA in FIG.
FIG. The boundary surface between the second diffusion portion 21 and the second diffusion portion 22 is formed as an inclined flat surface 23. Also,
The inclined surface may be an inclined curved surface 24 as shown in FIG. Further, as shown in FIG. 4, an inclined flat surface 25 having an inclination opposite to that of the inclined flat surface 23 of FIG. 2 can be used. In this way, the reason why the boundary surface is inclined is to avoid a rapid change in illuminance due to a difference in the diffusivity between the first diffusing section 21 and the second diffusing section 22, as in the case of a vertical boundary surface.
The illuminance change is alleviated by gradually changing the plate thicknesses of the first diffusing section 21 and the second diffusing section 22 by the inclined surface.

Next, with the backlight device of the embodiment using the diffusion plate 20 as described above, the following effects can be obtained in the liquid crystal display device. That is, in FIGS. 2 to 4, the light source 1
The light from 3 is reflected by the reflecting plate 15 on the back side without being scattered back, and the light is irradiated to the entire liquid crystal panel 12 on the front side. Further, the light of the light source 13 is diffused through the diffusion plate 20 and travels toward the liquid crystal panel 12. At this time, in the first diffusing portion 21 of the diffusing plate 20 which is close to the cylindrical light source 13 and extends in the longitudinal direction and faces the cylindrical light source 13, the illuminance of the light from the light source 13 is reduced here because the diffusion rate is large. The illuminance of the light diffused by the second diffusing unit 21 is made uniform, and the illuminance is made uniform. That is,
The light from the cylindrical light source 13 is likely to become a surface light source, but since it is made uniform by the diffusion plate 20 and applied to the display screen of the liquid crystal panel 12, it is possible to suppress the occurrence of uneven brightness on the entire display screen. You can

[0011]

As described above, in the liquid crystal display device and the backlight device according to the present invention, when the light source is cylindrical, it becomes a surface light source, which easily causes uneven brightness on the display screen. The diffusing plate of the device is composed of a first diffusing section and a second diffusing section having different diffusivities, and the first diffusing section having a large diffusing rate reduces the illuminance of the light of the cylindrical light source facing the second diffusing section to make the second diffusing section. was illuminance and uniformity of light at the parts, first a first diffusion portion
2 By making the boundary surface of the diffusion part an inclined surface, it becomes a vertical boundary surface.
As in the case of
Therefore, when used in a liquid crystal display device, it is possible to suppress the occurrence of uneven brightness due to the irradiation light on the display screen of the liquid crystal panel, and to manufacture such a backlight device at low cost.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a liquid crystal display device including a backlight device according to the present invention.

FIG. 2 is a cross-sectional view showing the relationship between the diffuser plate and the light source of the embodiment along the line AA in FIG.

FIG. 3 is a cross-sectional view showing the relationship between the light source and the diffuser plate of another embodiment along the line AA of FIG.

FIG. 4 is a transverse cross-sectional view showing the relationship between the light source and the diffuser plate of another embodiment taken along the line AA of FIG.

FIG. 5 is a plan view of a liquid crystal display device including a conventional backlight device.

FIG. 6 is a perspective view showing an arrangement of a cylindrical light source and a diffusion plate in a conventional backlight device.

[Explanation of symbols]

12 LCD panel 13 Cylindrical light source 14 Support plate 15 Reflector 20 Diffuser 21 First diffusion unit 22 Second diffuser 23, 25 inclined flat surface 24 inclined curved surface

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/13357 F21V 5/02 G02B 5/02 G02B 6/00 331

Claims (3)

(57) [Claims] 1. A liquid crystal display device in which light from a tubular light source is applied to a display screen of a liquid crystal panel through a diffusing plate, wherein the diffusing plate has a first diffusing section and a light diffusing rate of light from the first diffusing section. And a second diffusing portion provided adjacent to each other in a small size, and the first diffusing portion is elongated in the widthwise center of the second diffusing portion.
It is provided in the shape of a strip in the direction, and the boundary surface between the first diffusion portion and the second diffusion portion is inclined flat.
Liquid crystal table characterized by being a flat or curved surface
Indicating device. 2. The light is reflected forward from behind the tubular light source.
Arrange a reflector to let the light from the light source pass through the diffuser
In the backlight device that is The diffusing plate has a first diffusing portion and a light
It has a small diffusivity and consists of a second diffusing part that is placed next to it.
I mean The first diffusing portion is elongated in the widthwise center of the second diffusing portion.
It is provided in a strip shape toward The boundary surface between the first diffusion portion and the second diffusion portion has a flat surface.
A back characterized by a flat or curved surface
Light device. 3. The liquid crystal according to claim 1, wherein the first diffusing portion and the second diffusing portion are molded in two colors.
The display device and the backlight device according to claim 2.