JP2003195306A - Back light device for liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make adaptable to rearrangement of a light emitting diode and change in the number of chips without redesigning a circuit board. <P>SOLUTION: A back light device for a liquid crystal display element includes the circuit board 30A on which the light emitting diode 20 is mounted and irradiates the liquid crystal display element with light from the light emitting diode 20. On the circuit board 30A, N (≥3) lands 31a to 31j are linearly arranged at substantially the same intervals with the inter-terminal distance L of the anode terminal 20a and cathode terminal 20b of the light emitting diode 20; and odd-numbered or even-numbered lands among the N lands are connected to the plus electrode (+E) of an illumination power source for the light emitting diode and the other lands are connected to the minus electrode (-E) side of the illumination power source. <P>COPYRIGHT: (C)2003,JPO

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 illuminating a liquid crystal display element from the back side thereof, and more particularly to a backlight device for a liquid crystal display element using a light emitting diode as a light source. is there.

[0002]

2. Description of the Related Art A transmissive or semi-transmissive liquid crystal display element is equipped with a backlight device on its back side (opposite viewing side). The backlight device includes a sidelight type and a direct type, and FIG. 2 shows an example of the sidelight type.

In the side light type, the light from the light source is incident on the light guide plate 10 from the side thereof. The light guide plate 10 is arranged on the back side of a liquid crystal display element (not shown), a light diffusion plate 11 is provided on the upper surface side thereof, and a light reflection plate 12 is provided on the bottom surface side thereof.

In the side light type, a chip type light emitting diode 20 is often used as a light source. The chip type light emitting diode 20 is classified into a side view type in which a light emitting portion is provided on a side surface of the chip and a top view type in which a light emitting portion is provided on an upper surface of the chip.

In this conventional example, a top-view type light emitting diode 20 is used because there is no space for arranging the light source on the side of the light guide plate 10. That is,
The side surface of the light guide plate 10 is a tilted surface 10a for total reflection, and a top-view type light emitting diode 20 is arranged below the tilted surface 10a.

In any case, the light emitting diode 20 is used in a state of being mounted on the circuit board 30, and its plan view is shown in FIG. A land La for mounting the light emitting diode on the surface is formed on the circuit board 30.
0 is soldered to the land La by the reflow soldering method.

A plurality of pairs of lands La are prepared in advance, with the anode side and the cathode side of the light emitting diode 20 as a pair and the number of chips to be used. Therefore, for example, the light emitting diode 20
When changing the number of chips of the circuit board 30
Must be redesigned.

[0008]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to make it possible to deal with the arrangement of light emitting diodes and the change in the number of chips without changing the design of the circuit board.

[0009]

In order to solve the above problems, the present invention includes a circuit board on which a light emitting diode is mounted, and a backlight for a liquid crystal display device for irradiating the liquid crystal display device with light from the light emitting diode. In the device, N lands (3 or more) are linearly arranged on the circuit board at a distance substantially the same as the distance between the anode terminal and the cathode terminal of the light emitting diode,
The land belonging to either the odd-numbered or even-numbered one of the N lands is connected to the positive side of the lighting power source of the light-emitting diode, and the land belonging to the other side is connected to the negative side of the lighting power source. It is characterized by being connected.

According to this structure, the arrangement of the light emitting diodes and the number of chips can be changed by selecting an arbitrary pair of adjacent lands.

In the present invention, the land is "+,-, +".
... "or"-, +, -... "
Depending on the location, it may be necessary to switch the anode side and the cathode side of the light emitting diode and connect them to the land. Therefore, it is preferable that the light emitting diode is a top view type in which the position of the light emitting portion does not change even if the anode side and the cathode side are exchanged.

In the side-hue type, when the anode side and the cathode side are replaced with each other, the light emitting portion is in the opposite direction, so even if the land selection width on the layout may be narrowed, the layout and the number of chips are reduced. Can still be changed and is therefore within the scope of the invention.

The present invention is not limited to the chip type light emitting diode, but can be applied to a discrete type (lead terminal same direction type) light emitting diode. In that case, the land may be a through hole into which the lead terminal can be inserted.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a plan view showing a light emitting diode mounting region of a circuit board 30A included in the backlight device of the present invention.

The circuit board 30A according to this embodiment is also arranged below the light guide plate 10 similarly to the circuit board 30 shown in FIG. 2, and the mounted light emitting diode is a top view type chip type light emission. The diode 20.

In order to change the arrangement of the light emitting diodes 20 and the number of chips thereof, a land row 31 including a plurality of lands arranged in a line is provided in the light emitting diode mounting area of the circuit board 30A. .

In the present invention, it is essential that the number of lands is three or more, and in this embodiment, there are ten lands 31a to 31j. Here, the distance between the anode terminal 20a and the cathode terminal 20b of the light emitting diode 20 is D
Then, the lands are arranged at substantially the same distance as the distance D.

That is, the distance between the respective lands is set so that the anode terminal 20a and the cathode terminal 20b of the light emitting diode 20 straddle between the pair of adjacent lands, regardless of which of the pair of adjacent lands the light emitting diode 20 is arranged. ing.

The lighting power source of the light emitting diode 20 is bipolar and the circuit board 30A is provided with its + E terminal and -E terminal. Each land is alternately + E terminal, -E
Connected to either one of the terminals.

In this embodiment, odd-numbered lands 31 are used.
a, 31c, 31e, 31g and 31i are connected to the + E terminal, and even-numbered lands 31b, 31d, 31f,
31h and 31j are connected to the -E terminal. Of course, the connection to the lighting power source may be the reverse.

According to the land row 31, the position of the light emitting diode 20 can be changed with the distance D as a minimum unit. Also, the number of chips can be mounted up to 5. When mounting the light emitting diode 20, the anode terminal 20a is on the + E terminal side and the cathode terminal 20a
b must be on the −E terminal side.

Therefore, for example, the land 31c and the land 3
When mounted between 1d and land 31d and land 3
When mounted between 1e and the anode terminal 20a
The direction of the cathode terminal 20b is reversed. Thus, even if the positions of the terminals 20a and 20b are exchanged,
In the case of the top view type, there is no problem because the light emitting part is always on the upper surface side of the chip.

When a side-view type light emitting diode is used, if the positions of the anode terminal and the cathode terminal are switched, the position of the light emitting portion is changed by 180 °. Therefore, the minimum unit for changing the position is the above distance. 2 of D
It becomes double interval.

That is, regarding the case of this embodiment, the arrangement of the side-view type light emitting diodes is as follows.
31a-31b, 31c-31d, 31e-31f
It will be limited to 31g-31h and 31i-31j.

In the present invention, if the number of lands is three or more, the total number may be an odd number or an even number. Further, the land row 31 is not limited to one row. It is also applicable to the direct type, and in that case, it is expected that a plurality of columns will be provided. Furthermore, by changing each of the lands 31a to 31j into a through hole, it can be applied to a discrete type (lead terminal same direction type) light emitting diode.

[0026]

As described above, according to the present invention,
In a backlight device for a liquid crystal display element, which includes a circuit board on which a light emitting diode is mounted, and irradiates the liquid crystal display element with light from the light emitting diode, the circuit board has a distance between the anode terminal and the cathode terminal of the light emitting diode. N (three or more) lands are arranged linearly at substantially the same intervals, and the land belonging to either the odd-numbered or even-numbered one of the N-lands is the positive electrode of the lighting power source of the light-emitting diode. Side and the land belonging to the other side is connected to the negative side of the lighting power source, it is possible to cope with the arrangement of the light emitting diodes and the change in the number of chips without changing the design of the circuit board. .

[Brief description of drawings]

FIG. 1 is a plan view of essential parts showing an embodiment of a circuit board included in a backlight device of the present invention.

FIG. 2 is a sectional view showing a part of a backlight device as a conventional example.

FIG. 3 is a plan view showing a circuit board used in the conventional example.

[Explanation of symbols]

10 Light guide plate 20 light emitting diode 20a Anode terminal 20b cathode terminal 30A circuit board 31 land line 31a-31j land

Claims (2)

[Claims] 1. A backlight device for a liquid crystal display device, comprising a circuit board on which a light emitting diode is mounted, and irradiating light from the light emitting diode to a liquid crystal display device, wherein the circuit board has an anode terminal of the light emitting diode. And N (3 or more) lands are arranged linearly with a distance substantially the same as the distance between the terminals of the cathode terminal, and either the odd-numbered or even-numbered one of the N lands is arranged. 2. The backlight device for a liquid crystal display element according to claim 1, wherein the land belonging to the above is connected to a positive electrode side of a lighting power source of the light emitting diode, and the land belonging to the other one is connected to a negative electrode side of the lighting power source. 2. The backlight device for a liquid crystal display device according to claim 1, wherein the light emitting diode is a top-view type.