JPH07272513A - Backlight unit - Google Patents

Abstract

PURPOSE:To prevent the luminance reduction of plural straight tube type fluorescent lamps for high frequency lighting by preventing the fluorescent lamps attached to the end face of a light conductor and reflecting covers covering them from making contact with each other. CONSTITUTION:A pair of two straight tube type fluorescent lamps 5, 6 are attached in parallel to the end face (m) of a rectangular light conductor 1 and encircled with approximately cylindrical reflecting covers 8 so that the fluorescent lamps 5, 6 may be lit with high frequency of 15KHz or more. On the outer peripheries nearly at the centers of a pair of two fluorescent lamps 5, 6, insulating spacers 11, 11 are mounted to prevent the contact of the fluorescent lamps 5, 6 with the reflecting covers 8 due to the warping of the fluorescent lamps 5, 6. The insulating spacers 11, 11 are formed with short transparent or elastic rings such as silicon pipes which are also capable of keeping a distance between the fluorescent lamps 5, 6 constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit such as a liquid crystal display panel, and more particularly to an edge light type backlight unit in which a straight tube type fluorescent lamp is attached to an end face of a rectangular flat plate-shaped light guide. .

[0002]

2. Description of the Related Art A conventional example of an edge light type backlight unit is shown in FIG. 7 and FIG.
A plurality of, for example, two straight tube fluorescent lamps 5 and 6 are additionally provided on each of the two opposite end faces m of the above, and each fluorescent lamp 5 and 6 is surrounded by a substantially semi-cylindrical reflection cover 8.

In the light guide 1, a white reflective plate 3 is attached to the back surface of a light guide plate 2 which is, for example, a rectangular transparent acrylic plate, and a diffusion plate 4 is attached to the front surface. As shown in FIG. 9, the two pairs of fluorescent lamps 5 and 6 are fitted in rubber caps 7 at both ends and supported in parallel. It is installed in parallel to the end face m of the light guide 1 via 7. The reflection cover 8 is configured by attaching a metal reflection sheet 10 such as a silver vapor deposition sheet to the inner surface of a main body 9 of an aluminum plate having substantially the same length as the fluorescent lamps 5 and 6, for example.
Both ends of the opening of the reflection cover 8 are attached to the front and back surfaces of the end portion of the light guide body 1, and surround the two pairs of fluorescent lamps 5 and 6.

Each of the fluorescent lamps 5 and 6 has a tube diameter of 3 to 5 mm.
The slender cold-cathode type or hot-cathode type fluorescent lamp is connected to an inverter circuit (not shown) and is lit at high frequency. As a result of the limitation of the brightness of one fluorescent lamp, two fluorescent lamps 5 and 6 are arranged on one end face m of the light guide 1 to obtain an effective brightness as a backlight of a liquid crystal display panel. Further, a set of two fluorescent lamps 5 and 6 is arranged in an oblique arrangement with respect to the end face m of the light guide 1 in accordance with the thickness of the light guide 1.

The set of two fluorescent lamps 5 and 6 is an inverter circuit, and the inverter is lit at a high frequency of, for example, 45 KHz. The lights of the lit fluorescent lamps 5 and 6 directly and
The light is reflected by the metal reflection sheet 10 of the reflection cover 8 and enters the end surface m of the light guide plate 2 of the light guide 1. Light incident on the light guide plate 2 is reflected by the reflector plate 3, diffused by the diffuser plate 4, transmitted through the diffuser plate 4 with a uniform brightness distribution, and is disposed on the light guide body 1 (see FIG. Illuminate (not shown).

[0006]

A pair of two fluorescent lamps 5 and 6 attached to the end face m of the light guide 1 are supported by rubber caps 7 at both ends thereof to maintain the parallelism of the two. However, the total length of each fluorescent lamp 5, 6 with a tube diameter of 3 to 5 mm is 20
As the length increases from 0 to 300 mm, the fluorescent lamps 5 and 6 are warped or bent due to variations in manufacturing and heat generated during operation, and the central portions of the fluorescent lamps 5 and 6 and their vicinity are closer to the reflection cover 8. It may come into contact with the metal reflection sheet 10. Further, the metal reflection sheet 10 such as a silver vapor deposition sheet attached to the body 9 of the reflection cover 8 may be peeled off from the body 9 and come into contact with the central portions of the fluorescent lamps 5 and 6 or the vicinity thereof.

As described above, when the central portions of the fluorescent lamps 5 and 6 which are turned on at a high frequency or the vicinity thereof come into contact with the metal reflection sheet 10, a leakage current is generated at the contact portions of the both, and the brightness of the fluorescent lamps 5 and 6 is increased. May decrease. Actually, for example, 1200V, 45KH is applied to the electrodes on both ends of the fluorescent lamps 5 and 6.
Although a high frequency voltage of z is applied, this fluorescent lamp 5,
When the central portion of 6 comes into contact with the metal reflection sheet 10, the luminance on the low voltage side (earth side) of the fluorescent lamps 5 and 6 on the side where the electrode is present decreases from the contact point to the extent that it can be visually recognized. The overall brightness was reduced to about 10%. Such a decrease in the brightness of the fluorescent lamps 5 and 6 causes a lack of brightness as a backlight of a liquid crystal display panel and a decrease in uniformity, thus lowering the product value of the backlight unit.

If the fluorescent lamps 5 and 6 are lit at a frequency lower than 15 KHz, the fluorescent lamps 5 and 6
It has been found that even if 6 contacts the metal reflection sheet 10, no leakage current is generated and the luminance is hardly reduced. However, the fluorescent lamps 5 and 6 have a tube diameter of 2.5 to 5 m.
If the length is 200 m to 300 mm and the length is 200 to 300 mm, it is difficult to put the LED into practical use when it is lit at a high frequency lower than 15 KHz, because of problems such as insufficient brightness as a backlight of a liquid crystal display panel and an increase in size of an inverter. There's a problem.

An object of the present invention is to reliably prevent a decrease in brightness due to contact between a plurality of straight tube fluorescent lamps provided on the end surface of a light guide and a reflective cover surrounding the fluorescent lamp, which is highly reliable. To provide a backlight unit.

[0010]

In order to achieve the above object, the present invention provides a plurality of straight tube fluorescent lamps which are installed parallel to the end face of a rectangular flat plate-like light guide and which are lit at a high frequency at 20 KC or more, A plurality of straight tube fluorescent lamps are provided on the end surface of the light guide, surrounding the outside of each straight tube fluorescent lamp, and provided with a reflection cover that reflects the light of the fluorescent lamp that is lit at high frequency and condenses it on the end surface of the light guide. Partly, an insulating spacer for preventing contact with the reflection cover is attached. The above-mentioned insulating spacer is attached to one fluorescent lamp as a single unit,
Alternatively, it is practically desirable to apply a single unit that is mounted over a plurality of fluorescent lamps.

[0011]

[Function] The insulating spacers partially attached to the outer circumference of the plurality of straight tube fluorescent lamps attached to the end surface of the light guide prevent contact between each fluorescent lamp and the reflection cover surrounding each fluorescent lamp. Then, the leakage current is prevented from occurring when the fluorescent lamp is turned on at a high frequency of 15 KHz or more, and the brightness of the fluorescent lamp is prevented from lowering. In addition, the insulating spacer has a holder-like function of keeping a constant interval between the fluorescent lamps mounted with the insulating spacer, a function of preventing the fluorescent lamps from colliding with each other, and a fluorescent lamp which receives an impact force from the outside. It also has the function of protecting.

[0012]

Embodiments Embodiments will be described below with reference to FIGS. 1 to 6. It should be noted that, in all the figures including FIG. 7 to FIG.
Alternatively, the corresponding parts are denoted by the same reference numerals and the description thereof is omitted.

The difference between the backlight unit of the first embodiment shown in FIGS. 1 to 3 and the conventional one is that a set of two straight tube fluorescent lamps attached to the end face m of the light guide 1 is provided. That is, the separate insulating spacers 11 and 11 are attached to each of the substantially central portions 5 and 6, respectively. The insulating spacers 11 and 11 of the two fluorescent lamps 5 and 6 are, for example, transparent cylinders of the same size such as silicon pipes, and are inserted from the ends to the center of the fluorescent lamps 5 and 6.

As shown in FIG. 3, the insulating spacers 11 and 11 are fitted in the substantially central portions of the pair of two fluorescent lamps 5 and 6 so as not to interfere with each other by slightly shifting their positions. Both ends of the pair of two fluorescent lamps 5 and 6 are supported by the rubber caps 7, the fluorescent lamps 5 and 6 are attached to the end face m of the light guide plate 2, and the fluorescent lamps 5 and 6 are reflected by the reflection cover 8. Surround. At this time, as shown in FIG. 2, insulation is performed so that, for example, the outer peripheries of the insulating spacers 11 of the fluorescent lamps 5 and 6 come into light contact with the end face m of the light guide 1 and the metal reflection sheet 10 of the reflection cover 8. The outer diameter of the spacers 11, 11 is set.

In the backlight unit of FIG. 1, 2
Even if the pair of fluorescent lamps 5 and 6 is warped or bent, the insulating spacer 11 at the central portion of the fluorescent lamps 5 and 6,
11 directly contacts the metal reflection sheet 10 of the reflection cover 8 to prevent direct contact between the fluorescent lamps 5 and 6 and the metal reflection sheet 10. Therefore, the fluorescent lamps 5 and 6 are 15KH
When the inverter is turned on at a high frequency equal to or higher than z, there is no concern that a leakage current will be generated due to the contact between the fluorescent lamps 5 and 6 and the metal reflection sheet 10, and the brightness of the fluorescent lamps 5 and 6 will not decrease.

Further, the insulating spacers 11 and 11 maintain a constant interval between the central portions of the two fluorescent lamps 5 and 6,
It also has the function of preventing damage due to collisions between fluorescent lamps. Further, the insulating spacers 11 and 11 also have a function of directly receiving an impact force applied from the outside of the reflection cover 8 toward the central portions of the fluorescent lamps 5 and 6 and protecting the fluorescent lamps 5 and 6 from an external impact force. . Such a function is effectively exhibited by using an elastic silicon pipe or the like for the insulating spacers 11, 11.

It is desirable that the insulating spacers 11, 11 are transparent in order to increase the effective light utilization rate of the fluorescent lamps 5, 6, but the insulating spacers 11, 11 have a length of 2 mm in the axial direction.
If a small one is used, the light of the fluorescent lamps 5 and 6 is hardly blocked even if it is opaque, and there is no problem in practical use. In addition, in the above-mentioned embodiment, the insulating spacers 11 and 1 are used.
One of the fluorescent lamps 5 and 6 is attached to one of the fluorescent lamps 5, but a plurality of fluorescent lamps may be attached to one of the fluorescent lamps 5 and 6 depending on the total length of the fluorescent lamps 5 and 6.

The insulating spacers 12, 12 shown in the second embodiment of FIG. 4 are elastic bodies having a C-shaped cross section in which a part of the cylindrical portion is cut out in the axial direction. This insulating spacer 12, 12
Pushes the notched openings 13, 13 to the outer circumferences of the corresponding fluorescent lamps 5, 6 to expand the fluorescent lamps 5, 6,
It is attached to 6 with one touch. Therefore, the insulating spacers 12 and 12 in FIG. 4 can be attached to the fluorescent lamps 5 and 6 after both ends of the pair of fluorescent lamps 5 and 6 are supported by the rubber caps 7. Mounting work on the lamps 5 and 6 becomes convenient.

The insulating spacer 14 shown in the third embodiment of FIGS. 5 and 6 is commonly used for a pair of two fluorescent lamps 5 and 6. That is, the insulating spacer 14 has a structure in which two of the insulating spacers 12 and 12 of FIG. 4 are integrated in parallel, and a pair of C-shaped cross-sections that are fitted to the outer circumferences of the two fluorescent lamps 5 and 6 with one touch. It has the lamp holders 15 and 15. The openings 16 and 16 of each lamp holder 15 and 15 are
By pressing the outer circumferences of the two fluorescent lamps 5 and 6, one insulating spacer 14 is attached to the two fluorescent lamps 5 and 6 at the same time, and the work of attaching the insulating spacers to the fluorescent lamps 5 and 6 is further improved. In addition, the number of insulating spacers can be reduced, which facilitates maintenance and management.

The present invention is not limited to the above embodiments, but can be applied to a backlight unit in which three or more straight tube fluorescent lamps are attached in parallel to the end surface of the light guide. In the case where three or more straight tube fluorescent lamps are attached to the end surface of the light guide, the insulating spacers may be attached only to the outer circumference of the fluorescent lamp that may come into contact with the reflection cover. In addition to the above-mentioned embodiment, the reflection cover itself may be constituted by a reflection member such as a silver vapor deposition sheet.

[0021]

According to the present invention, an insulating spacer partially attached to the outer circumference of a plurality of straight tube type fluorescent lamps attached to the end face of the light guide body is provided for each fluorescent lamp and each fluorescent lamp. Prevent the fluorescent lamp from contacting the surrounding reflective cover.
Since leakage current is prevented from occurring when the lamp is turned on at a high frequency of KHz or higher and the luminance of the fluorescent lamp is prevented from decreasing, a backlight unit such as a liquid crystal display panel with stable luminance and high reliability can be provided.

In addition, the insulating spacers mounted on the plurality of fluorescent lamps keep the intervals between the fluorescent lamps constant to prevent damage due to collision of the fluorescent lamps, and also receive an impact force from the outside to cause the fluorescent lamps to fluoresce. Since the lamp is protected, a backlight unit having excellent impact resistance can be provided.

[Brief description of drawings]

FIG. 1 is a plan view of a main part including a partially omitted part of a backlight unit according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view taken along the line AA of FIG.

3 is a partially enlarged perspective view of a fluorescent lamp and an insulating spacer in the backlight unit of FIG.

FIG. 4 is a partially enlarged perspective view of a fluorescent lamp and an insulating spacer of a backlight unit according to a second embodiment of the present invention.

FIG. 5 is a sectional view of an insulating spacer mounting portion of a fluorescent lamp in a backlight unit according to a third embodiment of the present invention.

6 is a perspective view of an insulating spacer in the backlight unit of FIG.

FIG. 7 is a plan view including a partially omitted portion of a conventional backlight unit.

FIG. 8 is an enlarged sectional view taken along the line BB of FIG.

9 is a perspective view of a fluorescent lamp in the backlight unit of FIG.

[Explanation of symbols]

 1 Light Guide 5 Fluorescent Lamp 6 Fluorescent Lamp 8 Reflective Cover 11 Insulating Spacer 12 Insulating Spacer 14 Insulating Spacer 15 Lamp Holder

Claims (3)

[Claims] 1. A plurality of straight tube fluorescent lamps, which are provided in parallel with the end surface of a rectangular flat plate-like light guide and which are turned on at a high frequency of 15 KHz or more, and surround the outside of each of the straight tube fluorescent lamps, and are turned on at a high frequency. A reflection cover that reflects the light of the fluorescent lamp to collect the light on the end surface of the light guide, and a part of the plurality of straight tube fluorescent lamps attached to the end surface of the light guide, the reflection cover and A backlight unit that is equipped with an insulating spacer that prevents contact between the two. 2. The single unit of the insulating spacer corresponds to
The fluorescent lamp of the present invention is mounted on a fluorescent lamp.
Backlight unit described. 3. The backlight unit according to claim 1, wherein the single unit of the insulating spacer has a plurality of lamp holders mounted on a plurality of straight tube fluorescent lamps.