JPH10154411A - Piezoelectric inverter unit and back-light device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the size of a plane to the minimum without making a backlight device large in thickness by considering the layout of the elements of a piezoelectric inverter unit, and effectively utilizing the back face space of a wedge-like lightguide plate. SOLUTION: A cold cathode fluorescent tube 27 is arranged at an end section, the light is guided to the whole fluorescent screen by a lightguide plate 28, and the back face of a liquid crystal panel is illuminated via a diffusion plate 29. The lightguide plate 28 of this backlight device is formed into a wedge shape made large in thickness on the side of the cold cathode fluorescent tube 27 and made thinner toward the far side from it. A piezoelectric inverter unit 20 is arranged on the back face side of the lightguide plate 28, only the portion mounted with low-height parts, such as a piezoelectric transformer and chip parts are located on the back face of the lightguide plate 28, and the portion mounted with the other low-height parts is located apart from the lightguide plate 28. About a half of the piezoelectric inverter unit 20 is stored in the back face space of the lightguide plate 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight used for a liquid crystal display device and the like and a piezoelectric inverter unit used therefor, and more particularly to an arrangement of elements of a piezoelectric inverter unit and an arrangement of a light guide plate and a piezoelectric inverter unit. .

[0002]

2. Description of the Related Art A small liquid crystal display device is used in various fields as a portable display or the like. In order to obtain the brightness of the liquid crystal display device, a transmissive type that irradiates light from the back is often used, and a backlight device that emits a cold cathode fluorescent tube for irradiating the light is used. I have.

[0003] As a fluorescent tube for a backlight, there is also a planar light-emitting fluorescent tube. In general, a cylindrical fluorescent tube is arranged at one end, and a light guide plate guides the light to the entire back surface of the liquid crystal panel. Many have adopted. In many cases, a wedge-shaped light guide plate is used in which the cold-cathode tube side is thicker and becomes thinner as it goes away.

[0004] A high voltage is required to light a cold cathode tube, and an inverter unit for boosting the voltage is used for the lighting. Although this inverter unit mainly uses a winding transformer, it is considered that a piezoelectric transformer is adopted in terms of thinning and the like.

[0005]

When a piezoelectric transformer is used, the piezoelectric transformer and a connector, a coil, an IC, an electrolytic capacitor, a chip capacitor, a chip resistor and the like are arranged and connected on a circuit board. It is desirable that the area of the circuit board be as small as possible, and that the height of the mounted elements be reduced to reduce the overall height. However, there is a limit in reducing the height of connectors, coils, electrolytic capacitors, and the like.

A conventional inverter unit using a piezoelectric transformer generally has a structure in which components are sequentially arranged in a length direction on an elongated circuit board in accordance with a circuit configuration. In this structure, since the relatively tall parts are mounted as described above, it cannot be arranged on the back of the light guide plate,
It is often placed beside it. Therefore, the area of the entire device becomes large, which is an obstacle to miniaturization. In addition, there is a disadvantage that the thickness of the device is increased when the device is disposed on the back surface of the light guide plate.

The present invention makes it possible to reduce the size and thickness by efficiently using the back surface of the thin portion of the light guide plate as a storage space for the piezoelectric inverter unit.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by improving the arrangement of elements on a circuit board.

That is, in a piezoelectric inverter unit having a circuit element including a piezoelectric transformer on a rectangular circuit board, a piezoelectric transformer or a piezoelectric transformer and a low-profile component are arranged on one end face side in the width direction of the circuit board. Is characterized in that a relatively tall circuit element is disposed on the other end face side in the width direction of the circuit board.

In a backlight device including a cold cathode tube, a wedge-shaped light guide plate, and a piezoelectric inverter unit for lighting the cold cathode tube, the piezoelectric inverter unit includes a rectangular circuit board and a circuit element including a piezoelectric transformer. A piezoelectric transformer or a piezoelectric transformer and a low-profile component are placed on one end face in the width direction of the circuit board, and other circuit elements that are relatively tall are placed on the other end face in the width direction of the circuit board. In this case, the portion where the piezoelectric transformer is disposed is located behind the thin portion of the light guide plate.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Since a piezoelectric transformer and low-profile components can be accommodated on the back of a thin portion of a light guide plate, the only portion protruding from the light guide plate is a portion where relatively tall components are arranged. As a result, the space can be effectively used, and the entire device can be reduced in size and thickness.

[0012]

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

1A is a plan view, FIG. 1B is a front view, and FIG. 1C is a side view of a piezoelectric inverter unit according to the present invention. A piezoelectric transformer is mounted on a rectangular printed circuit board 10.
11 and chip components such as chip capacitors and chip resistors
Along with 12, a connector 13, a coil 14, an IC 15, an electrolytic capacitor 16 and the like are arranged.

In the piezoelectric inverter unit according to the present invention, low-profile components such as the piezoelectric transformer 11 and the chip components 12 are collectively arranged on one end face side of the printed circuit board 10 in the width direction. Therefore, this portion has a small overall thickness. In contrast, connector 13, electrolytic capacitor 16
Tall components such as are located on the opposite end face side.

FIG. 2 is a front view of a backlight device using the piezoelectric inverter unit according to the present invention. A cold-cathode fluorescent tube 27 is arranged at the end, and the light is guided to the entire light emitting surface by the light guide plate 28, and irradiates the back surface of the liquid crystal panel via the diffusion plate 29. The light guide plate 27 has a wedge shape that is thicker on the cold cathode tube 27 side and becomes thinner as it goes away.

The piezoelectric inverter unit is disposed on the back side of the thin portion of the light guide plate, but only the portion on which low-profile components such as a piezoelectric transformer and chip components are mounted is located on the back surface of the light guide plate. The other parts where relatively tall parts are mounted are located off the light guide plate 27. As a result, about half of the piezoelectric inverter unit is stored in the space behind the light guide plate.

As described above, since about half of the piezoelectric inverter unit is housed on the back surface of the light guide plate, the entire size may be increased by an area for housing only the part on which the other parts are mounted. In addition, since only the thickness of the light guide plate and the mounting portion of the low-profile component can be used, a thin backlight device can be obtained.

The arrangement of the components is not limited to the above example, and any arrangement may be adopted as long as the components located on the back surface of the light guide plate are of low height. If there are many low-profile parts, a part may be arranged on the side opposite to the end face where the piezoelectric transformer is arranged. In the description, the low-profile components are described as chip components. However, the components need not always be chip-type components, but may be low-profile components.

[0019]

According to the present invention, the piezoelectric inverter unit can be efficiently stored by effectively utilizing the space on the back surface of the wedge-shaped light guide plate.

Therefore, it is possible to minimize the size of the backlight device without increasing the thickness thereof.

[Brief description of the drawings]

FIG. 1A is a plan view, FIG. 1B is a front view, and FIG. 1C is a side view showing an example of a piezoelectric inverter unit according to the present invention.

FIG. 2 is a front view showing an example of a backlight device according to the present invention.

[Explanation of symbols]

 11: Piezoelectric transformer 20: Piezoelectric inverter unit 27: Cold cathode tube 28: Light guide plate

Claims (4)

[Claims] 1. A piezoelectric inverter unit comprising a circuit element including a piezoelectric transformer on a rectangular circuit board,
A piezoelectric inverter unit, wherein a piezoelectric transformer is arranged on one end face side in a width direction of a circuit board, and another circuit element is arranged on another end face side in a width direction of the circuit board. 2. A piezoelectric inverter unit comprising a circuit element including a piezoelectric transformer on a rectangular circuit board,
A piezoelectric inverter unit, wherein a piezoelectric transformer and a chip component are arranged on one end face side in a width direction of a circuit board, and another circuit element is arranged on another end face side in a width direction of the circuit board. 3. A backlight device comprising a cold cathode fluorescent lamp, a wedge-shaped light guide plate, and a piezoelectric inverter unit for lighting the cold cathode fluorescent lamp, wherein the piezoelectric inverter unit comprises a circuit element including a piezoelectric transformer on a rectangular circuit board. The piezoelectric transformer is disposed on one end face side in the width direction of the circuit board, another circuit element is disposed on the other end face side in the width direction of the circuit board, and the portion where the piezoelectric transformer is disposed is the thickness of the light guide plate. A backlight device, which is located on the back of a thin portion of the backlight. 4. A backlight device comprising a cold cathode tube, a wedge-shaped light guide plate, and a piezoelectric inverter unit for lighting the cold cathode tube, wherein the piezoelectric inverter unit comprises a circuit element including a piezoelectric transformer on a rectangular circuit board. The piezoelectric transformer and the chip component are arranged on one end face side in the width direction of the circuit board, the other circuit elements are arranged on the other end face side in the width direction of the circuit board, and the portion on which the piezoelectric transformer is arranged is a conductor. A backlight device, which is located behind a thin portion of a light plate.