JPH0829749A - Illumination device and liquid crystal display device using it - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display device which is constituted so that power consumption is reduced or brightness is improved by the identical power consumption, whose power consumption is low and whose brightness is high by making a wiring part between a light source and an inverter substrate short and preventing the impedance of the wiring part from becoming high. CONSTITUTION:A side-lighting system back light 1 is provided with a light transmission plate 2, the light source 3 arranged along the end part of the plate 2 and the inverter substrate 7 loading an inverter transformer 8 driving the light source 3. Then, the output lead wires 9 and 9 of the light source 3 are directly electrically connected to the output terminal of the substrate 7 at the almost shortest distance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sidelight type illuminating device mounted on a liquid crystal display device and used as a backlight for illuminating a liquid crystal panel from the back side.

[0002]

2. Description of the Related Art In recent years, a backlight for illuminating a liquid crystal panel from the back side, which is mounted on a liquid crystal display device, can easily be made thin. Therefore, a tubular light source such as a cold cathode fluorescent lamp (CCFT) can be used to transmit light. PMMA (polym that is a light guide with excellent properties)
It is attached along the side edge of a flat light guide plate made of acrylic resin such as ethyl methacrylate), guides the light from the light source into the light guide plate, and emits the light from the light emitting surface on the upper surface of the light guide plate. The light type is the mainstream.

Further, in the liquid crystal display device, it is strongly demanded in the market that the liquid crystal display device is thin, low in power consumption and high in brightness, and accordingly, the above-mentioned backlight mounted in the liquid crystal display device is also thin. Therefore, low power consumption and high brightness are essential factors.

An example of a liquid crystal display device having a sidelight type backlight is shown in FIGS. 3 (a) and 3 (b). As shown in the figure, the liquid crystal display device includes a liquid crystal panel (L
CD) 31, a backlight 32, and a bezel 33.

The liquid crystal panel 31 is provided with a pair of substrates on which transparent electrodes and the like are formed, and a liquid crystal layer is sandwiched between the substrates.
It is supported by the D unit plastic chassis 34.

The bezel 33 is a frame body made of metal, and the portion of the liquid crystal panel 31 located in the frame is used for display.

The backlight 32 has a light guide plate 35 in the form of a parallel plate, which has a diffuser plate 42 having a light diffusing function on the upper surface and a reflector plate 43 on the lower surface. A linear light source 36 is arranged at one end of the. This light source 36 is used for the backlight holder 3
Supported by 7. Further, the light source 36 is driven by an inverter transformer 38, and the inverter substrate 3 having the inverter transformer 38 mounted therein.
9 is attached to the LCD unit plastic chassis 34 with screws 40.

The reason why the inverter is used to drive the light source 36 is to allow the user to freely adjust the brightness of the display portion.

Conventionally, the inverter board 39 and the light source 36 are electrically connected to an output lead wire (not shown) extending from both ends of the light source 36 by electrically connecting wires 41, 41 in which a copper wire is covered with a resin such as vinyl chloride. Then, this is electrically connected to the output terminals formed at both ends of the inverter board 39.

In such a liquid crystal display device, the light emitted from the light source 36 of the backlight 31 enters the inside of the light guide plate 35, propagates inside the light guide plate 35, and is reflected by the reflection plate 4.
It is reflected at 3 and is emitted from the upper surface. The emitted light is effectively diffused by the diffusion plate 42, reaches the liquid crystal panel 31 arranged above, and illuminates the liquid crystal panel 31 from the back side.

[0011]

By the way, when an inverter is used in the drive circuit and the wiring portion connecting the drive circuit and the driven portion is long, the impedance of the wiring portion becomes large, and the influence of the increase in the impedance is not affected. It cannot be ignored. Therefore, when an inverter is used, the wiring section that connects the drive circuit and the driven section should be as short as possible,
And it is desirable to make it thick.

However, in the above-described conventional liquid crystal display device, since the inverter substrate 39, which is a driving circuit, and the light source 36, which is a driven portion, are connected via the wire 41, the wiring portion becomes long. There is. Therefore, wire 4
The driving voltage is increased due to an increase in the impedance of the copper wire portion in No. 1 and the power consumption is high. This also means that the brightness is low at the same power consumption. In particular, since the starting voltage becomes high during low temperature operation, it is strongly affected by an increase in impedance of the copper wire portion, etc., resulting in remarkable increase in power consumption and decrease in brightness.

Moreover, if the connection is made via a wire or the like, current leakage occurs through the medium in contact with the wire or the like, which also increases power consumption.

The present invention has been made in view of the above problems. A first object of the present invention is to provide an illumination device which is thin and has low power consumption and high brightness, and a second object is to provide the same. A thin liquid crystal display device with low power consumption and high brightness is provided by mounting the lighting device as a backlight.

[0015]

In order to solve the above-mentioned problems, an illuminating device according to claim 1 of the present invention comprises a light guide plate,
In a lighting device including a light source arranged along an end of the light guide plate and a circuit board on which a drive circuit for driving the light source is mounted, an output lead wire of the light source is almost at an output end of the circuit board. It is characterized by being directly and electrically connected at the shortest distance.

In order to solve the above-mentioned problems, an illumination device according to a second aspect of the present invention is the illumination device according to the first aspect, wherein the circuit board is a back member provided on the back side of the light source. It is characterized in that it is arranged along the direction of the thickness of the light guide plate and the direction of the normal line of the circuit board.

A liquid crystal display device according to claim 3 of the present invention comprises:
In order to solve the above problems, the lighting device according to claim 1 or 2 is provided as a backlight of a liquid crystal panel.

[0018]

According to the structure of the first aspect of the present invention, the output lead wire of the light source is directly and electrically connected to the output end of the circuit board at a substantially shortest distance. Therefore, the light source and the circuit board are connected to each other. The wiring portion to be connected becomes shorter, and the impedance of the wiring portion becomes smaller. For example, in the case where an inverter is used for the circuit board, the conventional configuration in which the circuit board is connected via a wire or the like has a problem that the driving voltage becomes high due to the impedance of the wiring part and the power consumption increases. But this
It is possible to prevent an increase in drive voltage due to an increase in the impedance of the wiring portion and reduce power consumption.

Further, as compared with the conventional structure, the wiring portion becomes very short, so that the amount of current leaking through the medium in contact with the wiring portion becomes very small, which can also reduce the power consumption. As a result, the lighting device has low power consumption and high brightness.

According to the second aspect of the present invention, when the output lead wire of the light source is directly connected to the output end of the circuit board at the shortest distance, the circuit board is provided on the back side of the light source. Since it is arranged along the back member and so that the thickness direction of the light guide plate and the normal direction of the circuit board are orthogonal to each other, for example, the circuit board is formed on the upper surface or the lower surface of the back member (the light guide plate Compared with the configuration in which the thickness direction and the normal direction of the circuit board are parallel to each other, even if they are connected at the same shortest distance, the thickness of the lighting device does not increase, and the lighting device can be kept thin.

According to the third aspect of the present invention, the liquid crystal display device includes the illumination device according to the first or second aspect as a backlight. This lighting device is thin, has low power consumption, and has high brightness. Therefore, by using such a lighting device as a backlight, it is possible to obtain a liquid crystal display device that is thin, has low power consumption, and has high brightness. You can

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

In the liquid crystal display device according to this embodiment, as shown in FIG. 2, a liquid crystal panel (LCD) 11 is illuminated from the back by a backlight 1 which is an illuminating device.

The liquid crystal panel 11 and the backlight 1 are housed in a plastic casing 17 in a state of being assembled in the bezel 12.

The liquid crystal panel 11 has a structure in which a liquid crystal layer is enclosed between a pair of transparent substrates having transparent electrodes and alignment films formed on opposite surfaces thereof. The end side is supported.
The thickness of the liquid crystal panel 11 is 2 mm here.

A common side TCP (Tape Carrier Package) 16 is connected to the end of the liquid crystal panel 11, and the common side TCP 16 is used for the LCD driving circuit 13.
PWB (Printed Wiring Board) for common connected to
It is connected to 15.

On the other hand, the backlight 1 is arranged on the back side of the liquid crystal panel 11 with the plastic chassis 14 maintaining a fixed mounting distance from the liquid crystal panel 11.

The structure of the backlight 1 is shown in FIG.
This will be described in detail with reference to (a) and (b). FIG. 3A is a plan view of the backlight, and FIG. 3B is a sectional view taken along the line AA ′ in the plan view of FIG.

As shown in the figure, the backlight 1 is a side-light type illuminating device which is mainly composed of a light guide plate 2 and a light source unit 18.

The light guide plate 2 is made of an acrylic resin such as PMMA (polymethyl methacrylate), which is a light guide having excellent light transmittance, and propagates the light guided inside to the inside of the light guide plate 2. At the same time, the light is reflected by a reflection pattern (not shown) formed on the lower surface.
Its thickness is 2 mm here. The notch 2 for mounting the light source unit 18 is provided on both end surfaces of the light guide plate 2 on the end side where the light source 3 is mounted.
a are formed respectively.

A diffuser plate 5 is provided on the upper surface of the light guide plate 2 for efficiently diffusing the light emitted from the light guide plate 2 and irradiating it to the liquid crystal panel 11 arranged thereabove, while the lower surface thereof is provided. Is provided with a reflection plate 6 for reflecting light leaking from the light guide plate 2 and preventing light leakage. The diffusion plate 5 is made of, for example, PET (polyethylene terephthalate) or the like, and has a thickness of about 0.1 mm to 0.2 mm. The reflector plate 6 is made of, for example, an aluminum alloy coated with a highly reflective white coating, and, like the diffuser plate 5, has a thickness of 0.1 mm to
It has a thickness of about 0.2 mm.

The light source unit 18 includes the light source 3 and the reflecting member 1.
0, and three members of the inverter board 7 on which the inverter transformer 8 is mounted are unitized.

The reflection member (back surface member) 10 is a U-shaped resin molded product provided on the back surface of the light source 3.
It has a function of reflecting the light emitted from the light source 3 to the light guide plate 2. Therefore, it is formed of a resin having high reflectivity such as polycarbonate (trade name: Lexan LX2801). Further, cutout portions 2a, 2a provided in the light guide plate 2 are provided at both ends of the reflecting member 10.
The mounting claws 10a, 10a having elasticity that enable mounting to the light guide plate 2 by being engaged with are integrally formed. Mounting claw 1 provided on the reflecting member 10
The light source unit 18 is attachable to and detachable from the light guide plate 2 by 0a and 10a. The light source 3 is, for example, a CCFT (cold cathode tube) or the like. Rubber caps 4 are fitted into both ends of the rubber cap 4, and the rubber caps 4 are fixed inside the reflecting member 10.

The inverter board (circuit board) 7 is mounted with an inverter transformer 8 which is a drive circuit for a light source, and is made of a printed board such as epoxy resin. The inverter board 7 and the light source 3 are electrically connected to each other by an output lead wire 9 which is an output terminal for connection extending from both ends of the light source 3.
9 through the hole 10b formed in the reflecting member 10,
Directly to the output terminals provided on both ends of the inverter board 7,
It is made by connecting electrically. Soldering is the simplest method for electrically connecting the inverter board 7 and the output lead wires 9 to each other. However, considering the time and effort required when the light source 3 is replaced, it is possible to use one pin instead of soldering. It is preferable to use a connector.

The length of the inverter board 7 is set longer than that of the light source 3. this is,
The length of the output lead wires 9 extending from both ends of the light source 3 is
This is because the length is made the shortest and the inverter board 7 is connected at the shortest distance. However, if the length of the light source 3 is 200 mm or more, if the size of the inverter board 7 is set accordingly, the cost may increase, so
The inverter board 7 may be made smaller than the light source 3 although it is slightly longer than the shortest distance.

In addition, the inverter board 7 includes the reflecting member 10
Along the back surface of the inverter board 7 so that the normal direction of the inverter board 7 is orthogonal to the thickness direction of the light guide plate 2 and the board surface is made of the reflection member 10.
It is attached to the back of each other. The inverter board 7 and the reflection member 10 are attached to each other by using a double-sided tape or an adhesive, or by providing an attachment claw on the reflection member 10 and utilizing the elasticity of the attachment claw or simply fixing with a screw. You may.

As described above, in the backlight 1 mounted on the liquid crystal display device of this embodiment, the output lead wires 9 of the light source 3 are directly electrically connected to the output end of the inverter board 7 at the shortest distance. It is connected to the. Thereby, the light source 3
The wiring portion connecting the wiring board and the inverter board 7 becomes short, and the impedance of the wiring portion becomes small. Therefore, for example, in the case where an inverter is used for the drive unit of the light source, there is a problem that the power consumption is increased due to the impedance of the wiring unit in the configuration in which the connection is made through the conventional wire. The drive voltage can be prevented from increasing due to the increase in the impedance of the wiring portion, and the power consumption can be reduced. With the same power consumption, the brightness can be improved.

In addition, since the wiring portion is much shorter than that of the conventional structure, the amount of current leaking through the medium in contact with the wiring portion becomes very small, which also reduces the power consumption of the backlight 1 and the same. In terms of power consumption,
The brightness can be improved.

Moreover, since the output lead wires 9 of the light source 3 and the output end of the inverter board 7 are directly connected, the connection processing between the output lead wire and the wire is more difficult than the conventional wire construction. Will be needed.

In the backlight 1, the inverter board 7 is provided on the back side of the light source 3 and the reflecting member 10 is provided.
Along with the thickness direction of the light guide plate 2 and the inverter board 7
Of the reflecting member 10 such that the substrate surface is perpendicular to the normal direction of
Since they are attached so as to face each other, the inverter board 7 is provided, for example, on the upper surface or the lower surface of the reflection member 10 (the thickness direction of the light guide plate 2 and the normal direction of the inverter board 7 are parallel). In comparison, even if they are connected at the same shortest distance, the thickness of the backlight 1 does not increase and the backlight 1 can be kept thin.

As a result, it is possible to obtain a thin liquid crystal display device with low power consumption, high brightness.

In the backlight 1, the light source 3, the reflecting member 10, and the inverter board 7 are unitized as the light source unit 18, so that they are treated as one member. Therefore, the workability at the time of attachment to the light guide plate 2 is significantly superior to the configuration in which they are separately provided.

Furthermore, in this case, the light source unit 18 is attached to and detached from the light guide plate 2 by engaging the notches 2a and 2a formed on the side end surface of the light guide plate 2 and the mounting claws 10a and 10a of the reflecting member 10. It's very easy because it can be done just by letting it work.

It should be noted that the above-mentioned embodiments are merely to clarify the technical contents of the present invention, and should not be construed in a narrow sense by limiting only to such specific examples.
Various modifications can be made without departing from the spirit of the invention and the scope of the claims.

[0045]

As described above, the illumination device according to the first aspect of the present invention is provided with the light guide plate, the light source arranged along the end of the light guide plate, and the drive circuit for driving the light source. In the lighting device including the circuit board, the output lead wire of the light source is directly and electrically connected to the output end of the circuit board at a substantially shortest distance.

As a result, the wiring portion connecting the light source and the circuit board becomes short, and the impedance of the wiring portion becomes small.
Therefore, for example, when an inverter is used for the circuit board, the conventional structure in which the wiring is connected through the wire has a problem that the driving voltage increases due to the impedance of the wiring portion and the power consumption increases. , This allows
It is possible to prevent an increase in drive voltage due to an increase in the impedance of the wiring part and reduce the power consumption,
The brightness can be improved with the same power consumption.

Further, as compared with the conventional structure, since the wiring portion is very short, the amount of current leaking through the medium in contact with the wiring portion becomes very small, which also reduces the power consumption, and the brightness is the same at the same power consumption. Can be improved.

As a result, it is possible to obtain an illuminating device with low power consumption and high brightness.

As described above, the illumination device according to the second aspect of the present invention is the illumination device according to the first aspect, wherein the circuit board is provided along the back member provided on the back side of the light source, and It is arranged such that the thickness direction of the light guide plate and the normal direction of the circuit board are orthogonal to each other.

As a result, for example, even if the circuit boards are connected at the same shortest distance as compared with the structure in which they are provided on the upper surface and the lower surface of the back member (the thickness direction of the light guide plate is parallel to the normal direction of the circuit board). As a result, the thickness of the lighting device does not increase, and the thin shape can be maintained.

As a result, it is possible to obtain a thin lighting device with low power consumption, high brightness.

The liquid crystal display device according to claim 3 of the present invention is
As described above, the lighting device according to claim 1 or 2,
This is a configuration provided as a backlight of a liquid crystal panel.

As a result, it is possible to obtain a liquid crystal display device which is thin and has low power consumption and high brightness.

[Brief description of drawings]

1A and 1B show an embodiment of the present invention, in which FIG. 1A is a plan view of a backlight provided in a liquid crystal display device, and FIG. 1B is a plan view of FIG. FIG.

FIG. 2 is a cross-sectional view of a liquid crystal display device including the backlight.

FIG. 3A is a plan view of a conventional backlight provided in a liquid crystal display device, and FIG. 3B is a cross-sectional view of relevant parts.

[Explanation of symbols]

 1 Backlight (illumination device) 2 Light guide plate 3 Light source 7 Inverter board (circuit board) 8 Inverter transformer (drive circuit) 9 Output lead wire 10 Reflecting member (backside member) 11 Liquid crystal panel

Claims (3)

[Claims] 1. An illumination device comprising a light guide plate, a light source arranged along an end of the light guide plate, and a circuit board on which a drive circuit for driving the light source is mounted. However, the lighting device is characterized in that it is electrically connected directly to the output end of the circuit board at almost the shortest distance. 2. The circuit board is arranged along a back member provided on the back side of the light source, and the thickness direction of the light guide plate and the normal direction of the circuit board are orthogonal to each other. The lighting device according to claim 1, wherein: 3. A liquid crystal display device comprising the illumination device according to claim 1 or 2 as a backlight of a liquid crystal panel.