JPH095737A - Backlight device and liquid crystal display device provided with the back light device - Google Patents

Abstract

PURPOSE: To provide a liquid crystal display device provided with a hollow type backlight device in which a light guide plate is not used and temperature hardly rises because of its structure. CONSTITUTION: A back surface reflecting plate 3 and a front surface transmission plate 4 are arranged in parallel so that the surfaces face each other at a specified distance. A bar-like light source 1 is provided on the peripheral part of a space 6 formed between the surfaces, and a reflecting layer 5 having a specified numeral aperture distribution is formed on the plate 4 so as to make the space 6 a light guide space. Furthermore, at least one more prism sheet 7 is arranged on the plate 4 so as to illuminate a body 9 to be illuminated. A translucent on-plate member 8 is arranged to spatially cut between the light source 1 and the space 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device for a liquid crystal panel and a liquid crystal display device including the same, and more particularly to a hollow backlight device which does not use a light guide plate.

[0002]

2. Description of the Related Art A conventional backlight device of this type is constructed, for example, as shown in the sectional view of FIG. The front transmission plate 4 and the rear reflection plate 3 are arranged in parallel at a predetermined interval, and a space 6 is formed between them.
A rod-shaped light source 1 made of a fluorescent tube or the like is arranged around the space 6, and a reflector 2 is provided outside the light source 1.

A reflective layer 5 having a predetermined aperture ratio distribution is formed on the front transmissive plate 4, and the light from the light source 1 is located on both sides of the light guide space 6 and the rear reflective plate 3 and the reflective layer 5 are provided. The light is reflected by the front transmission plate 4 and is emitted through the opened portion of the front transmission plate 4, but it is possible to make the in-plane distribution of the illumination light uniform by appropriately setting the aperture ratio distribution. The uniform planar illumination light from 10 is obtained.

Reference numeral 7 is a lens sheet, which is a front transmission plate 4.
It plays the role of making the light emitted from the light as perpendicular to the surface as possible. Reference numeral 9 is a transmissive liquid crystal panel.

Since this type of backlight device is constructed in this manner, a large-sized backlight device can be easily made without using a light guide such as acrylic, and the light guide is not necessary. It has the feature that it can be made lighter.

[0006]

However, in the backlight device, the heat emitted from the light source 1 reaches the entire front transmission plate 4 and the lens sheet 7 forming the illumination surface 10 by the air convection in the light guide space 6. The temperature of the illuminating surface 10 is raised, and by extension, the liquid crystal panel 9 which is an illuminated object.
Had the drawback of raising the temperature.

It is an object of the present invention to provide a hollow backlight device that does not use a light guide plate and has a structure in which the temperature does not rise easily, and a liquid crystal display device provided with the backlight device. .

[0008]

In a backlight device according to the present invention, a rear reflection plate and a front transmission plate are arranged in parallel so that their surfaces face each other at a constant distance, and are formed between them. A rod-shaped light source is provided in the peripheral portion of the space, and a reflective layer having a predetermined aperture ratio distribution is formed on the front transmission plate to form the space as a light guide space, and at least one prism sheet is provided on the front transmission plate. The arranged backlight device is characterized in that a translucent plate member is arranged between the light source and the light guide space to spatially block the space between them.

In this case, it is desirable that the aperture ratio distribution of the reflective layer formed on the front transmission plate be increased from the end of the light guide space on the light source side toward the center of the light guide space. The front transmission plate may be made of a transparent sheet.

Further, it is preferable that the prism ridge direction of the prism sheet is aligned with the longitudinal direction of the rod-shaped light source, and that the apex angle side of the prism faces the front transmission plate side.

Further, the translucent plate member may be made of a material having a heat absorbing property or a heat reflecting property.

A liquid crystal display device according to the present invention is characterized by using the backlight device.

[0013]

Since the present invention is constructed as described above,
The light emitted from the light source enters the light guide space and is reflected by the rear reflector and then passes through the portion of the front transmissive plate where the reflective layer is not formed and is emitted through the prism sheet, or the rear reflector and the front face. The reflection is repeated by the reflection layer formed on the transmission plate, and the light is emitted to the illumination surface via the prism sheet through the portion of the front transmission plate where the reflection layer is not formed, and functions as a backlight.

On the other hand, the heat generated by the light source is shielded by the translucent plate member from convection and radiation to the light guide space, so that the temperature rise of the illumination surface is reduced.

Therefore, the temperature rise of the liquid crystal panel is reduced,
The liquid crystal display device becomes lighter and more stable in temperature.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. Note that the same or corresponding parts as those described in the section of the related art are designated by the same reference numerals.

FIG. 1 is a diagram showing a cross section of an embodiment of a backlight device for a liquid crystal panel according to the present invention.

In the figure, 1 is a rod-shaped light source such as a fluorescent lamp, 2 is a reflector, 3 is a rear reflector, and 4 is a front transparent plate made of a thin transparent acrylic plate. The reflector 2 and the rear reflector 3 are made of an aluminum plate that is mirror-finished by Ag vapor deposition and are integrated.

The space 6 formed between the rear reflection plate 3 and the front transmission plate 4 functions as a light guide space for guiding light in the surface direction. A prism sheet 7 is installed above the front transmission plate 4. In this prism sheet 7, the ridge direction of each prism matches the longitudinal direction of the light source 1,
Furthermore, the apex angle side of the prism is arranged so as to face the front transmission plate 4.

On the upper side of the prism sheet 7, the liquid crystal panel 9 which is an illuminated object is located. A reflective layer 5 made of Al vapor deposition is formed on the lower surface of the front transmission plate 4 in a mesh shape or a dot pattern shape so as to have a predetermined aperture ratio. The aperture ratio of the reflective layer 5 is set to increase as the distance from the light source 1 increases. A transparent plate member 8 that divides the light guide space 6 is provided between the light guide space 6 and the light source 1.

Although only one side of the cross section of the backlight device is shown in FIG. 1, it is actually developed symmetrically in both the left and right directions. The light source 1 and the translucent plate member 8 are arranged on the sides. Therefore, the aperture ratio of the reflective layer 5 is set to increase from the end portion to the central portion of the light guide space 6.

With this structure, the light emitted from the light source 1 is reflected by the rear reflection plate 3 and the reflection layer 5 after passing through the translucent plate member 8 as shown in FIG. While repeating the above, the light guide space 6 is transmitted.

During this light guiding process, light leaks from the opening of the reflection layer 5 to the upper side of the front transmission plate. This leaked light becomes illumination light, and the amount of leaked light at each position is adjusted by the aperture ratio distribution of the reflective layer 5. In order to obtain illumination light having a uniform in-plane luminance distribution, it is preferable that the distribution of the aperture ratio of the reflective layer 5 be increased from the end of the light guide space on the light source side toward the center.

Most of the light emitted from the front transmission plate 4 has a large emission angle (angle with respect to the vertical line of the front transmission plate) (about 60 degrees), but is totally reflected by the prism surface of the prism sheet 7. , Emitted in the front direction to become illumination light.

The apex angle of the prism at this time is preferably an acute angle of about 60 degrees. Furthermore, in order to blur the pattern of the reflection layer 5 which is emitted by the illumination light emitted from the front transmission plate 4, a diffusion plate or a diffusion sheet is separately provided.
Alternatively, it may be arranged outside the prism sheet 7.

Here, the light source 1 generates heat when it emits light, and the temperature of the air around the light source 1 rises due to this heat generation. However, since the translucent plate member 8 separates the light guiding space below the illumination surface and the light source periphery from the light transmitting plate member 8 between the air around the light source and the air in the light guiding space below the illumination surface, the light transmission plate upper member 8 separates the light guiding space below the illumination surface. Convection is blocked. Therefore, heat transfer due to convection of air is blocked, and the temperature rise of the illumination surface 10 with respect to the liquid crystal panel 9 is greatly reduced.

In this embodiment, as described above, the light source and the translucent plate-like member are provided on the two opposite sides of the light guide space by deploying the configuration of FIG. 1 symmetrically in both the left and right directions. Although the light source and the translucent plate-shaped member are provided only on one side of the light guide space by providing a reflecting means at the right end portion of FIG. 1 so as to oppose the reflector 2, it may be arranged. It can be said that such a configuration is more suitable for a small backlight.

Further, such a structure may be developed in the back, the front and the left and right, and the light source and the translucent plate member may be arranged on the four sides around the light guiding space. In this case, the prism ridge lines of one prism sheet are directed toward the front side, and the prism ridge lines of the other prism sheet are directed in the left-right direction. It is preferable to use them so as to cross each other.

At this time, the aperture ratio distribution of the reflective layer 5 is also 2
A dimensional distribution is preferred. Even in the case of such a configuration, heat transfer by air convection from the light source is blocked by the same mechanism, and the temperature rise of the illumination surface with respect to the liquid crystal panel is greatly reduced.

By the way, instead of the front transmission plate 4 having the reflection layer 5 formed on the surface used in this example, A is formed on the PET sheet.
A so-called lighting curtain having a reflective layer of 1 may be used, and the same optical function can be obtained.

When heat-absorbing glass, heat-reflecting glass having an infrared reflection coating, or the like is used as the translucent plate member 8, the translucent plate member also blocks radiant heat from the light source. Therefore, there is an effect of further reducing the temperature rise of the illumination surface.

FIG. 2 shows an embodiment of the liquid crystal display device according to the present invention, in which the backlight 17 is the backlight device of the above-mentioned embodiment and illuminates the liquid crystal panel 9. The liquid crystal panel 9 is driven by an X driver 12, a Y driver 13, and a liquid crystal panel drive controller 14, and the liquid crystal panel drive controller 14 also sends an on / off signal, a dimming signal, etc. to the backlight lighting circuit 11.

The power supply unit 16 supplies power to the backlight lighting circuit 11 and the liquid crystal panel drive controller 14.

In the liquid crystal display device of this embodiment having such a structure, as described above, the temperature rise of the illumination surface of the backlight 17 is small, and therefore the thermal influence on the liquid crystal panel 9 located in front of the backlight 17 is large. It will be reduced. Therefore, more stable display performance is obtained even in various temperature environments. Also, the weight is reduced because the backlight device does not use a light guide plate.

[0035]

As described above, according to the present invention,
Since the transparent light-transmissive plate member that spatially separates the light guide space and the light source in the hollow backlight device is provided, it is possible to reduce the temperature rise of the illumination surface of the backlight device.

When the translucent plate member is made of a heat-absorbing or heat-reflecting member, the radiant heat is also blocked and the temperature rise of the illumination surface can be further reduced.

Further, the liquid crystal display device according to the present invention has an effect that the temperature rise is small and the weight is light.

[Brief description of drawings]

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

FIG. 2 is a system configuration diagram of a liquid crystal display device according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional hollow backlight device.

[Explanation of symbols]

 1 Light Source 2 Reflector 3 Rear Reflector 4 Front Transmitter 5 Reflective Layer 6 Light Guide Space 7 Prism Sheet 8 Translucent Plate Upper Member 9 Liquid Crystal Panel 10 Illumination Surface 11 Backlight Lighting Circuit 17 Backlight

Claims (7)

[Claims] 1. A rear reflection plate and a front transmission plate are arranged in parallel so that their surfaces face each other at a constant distance, and a rod-shaped light source is provided in the peripheral portion of the space formed between them, and A backlight device in which a reflective layer having a predetermined aperture ratio distribution is formed on a transmission plate, the space is used as a light guide space, and at least one prism sheet is arranged on the front transmission plate. A backlight device characterized in that a translucent plate member is arranged between the optical space and the space between them to be spatially blocked. 2. The aperture ratio distribution of the reflective layer formed on the front transparent plate is increased from the end of the light guide space on the light source side toward the center of the light guide space. The backlight device according to 1. 3. The backlight device according to claim 1, wherein the front transmission plate is formed of a sheet-shaped transparent body. 4. The prism sheet is arranged such that the prism ridge direction of the prism sheet coincides with the longitudinal direction of the rod-shaped light source and the apex angle side of the prism faces the front transmission plate side. Backlight device. 5. The backlight device according to claim 1, wherein the translucent plate member is made of a material having a heat absorbing property. 6. The backlight device according to claim 1, wherein the translucent plate member has a heat reflection characteristic. 7. A liquid crystal display device provided with a backlight device, wherein the backlight device is constituted by the backlight device according to any one of claims 1 to 6.