JPH11231144A - Lighting device, and liquid crystal display device including lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device hardly causing capacitive coupling without leaking light and high in the availability of light. SOLUTION: This device has a cold cathode tube having at both its ends electrodes where an electric wire 6 is connected, a light guide plate 7 which guides emitted light, a reflecting plate 8 which reflects the light propagated in the light guide plate 7, an unillustrated diffusion pattern which is mounted on the surface of the light guide plate 7 and diffuses the light propagated through the light guide plate 7 upward, and a diffusion plate 3 which diffuses light to irradiate a liquid crystal panel; and white PETs 5 as nonconductive reflecting materials are mounted on both the end parts of the cold cathode tube and AgPET4 as a conductive reflecting material is mounted on the center part of the cold cathode tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for irradiating a liquid crystal display surface with light and a liquid crystal display device including the lighting device.

[0002]

2. Description of the Related Art An illumination system is an optical system for irradiating a liquid crystal panel with uniform light, and an edge light type illumination system, a direct illumination system, and the like have been proposed.

FIG. 3 is an explanatory sectional view showing the structure of an edge light type illumination device. This illuminating device includes a cold-cathode tube 1 as a linear light source, a light guide plate 7 for guiding light emitted from the cold cathode tube 1, and a light guide mounted on the back surface of the light guide plate 7 for reflecting light propagating through the light guide plate 7. And a diffusion pattern (not shown) mounted on the surface of the light guide plate 7 for diffusing light propagating through the light guide plate 7 upward, and the diffusion plate 3 for diffusing light for irradiating the liquid crystal panel. Further, on the outer surface of the cold-cathode tube 1, Ag (silver) having a high reflectivity for reflecting emitted light to enter the light guide plate 7 over the entire length in the longitudinal direction is provided. ) Reflector 1
0 is attached.

[0006] The lighting device is fixed at a predetermined position in the housing 20 and is combined with a liquid crystal panel (not shown) to constitute a liquid crystal display device.

[0005] For example, in the case of a cold cathode tube 1 having a length of 50 (mm), a voltage of about 250 (V) and a frequency of about 30 to 100 (kHz) are usually required to drive the lighting device. Is applied to an electric wire (not shown) connected to the cold cathode tube 1. Further, the cold-cathode tube 1 to which the voltage is applied via the electric wire performs a light emitting operation, and the emitted light is a direct light,
Alternatively, the light is reflected by the Ag reflector 10 and becomes indirect light, propagates through the light guide plate 7, and reflects the reflection effect of the reflection plate 8 and the diffusion plate 3.
Acted so as to irradiate light to the liquid crystal panel by the diffusion effect of.

[0006]

However, when a high-frequency high voltage is applied to the cold-cathode tube 1, the conventional lighting device has a problem such as a voltage drop. This is because, since Ag is a conductive material, capacitive coupling occurs between the cold cathode tube 1 and the Ag reflector 10 and between the Ag reflector 10 and the housing 20, and the high frequency of the applied high frequency This is because voltage leaks through this capacitor.

Therefore, even if a voltage of 250 (V) is applied, actually, for example, the voltage drops by 10 (%) to 225 (V).
Since only about a voltage is applied, the luminance of the lighting device is reduced. In order to solve this, instead of mounting the Ag reflector 10 over the entire length of the cold cathode tube 1 in the longitudinal direction, the Ag reflector 10 is provided only at the center portion of the cold cathode tube 1 except for the high-voltage electrode end. According to this, it is not possible to take a sufficient distance with little leakage, and light leaks from the end, so that the amount of light irradiated on the liquid crystal panel is reduced and the liquid crystal is mounted. This causes a reduction in the brightness of the display device.

On the other hand, when a non-conductive material such as white PET which is a PET (polyethylene terephthalate) mixed with a white pigment is mounted over the entire length of the cold cathode tube 1 in the longitudinal direction, the occurrence of capacitive coupling is suppressed. However, the light use efficiency is reduced by about 15 (%) as compared with the Ag reflector 10, so that the amount of light applied to the liquid crystal panel is also reduced, and the brightness of the liquid crystal display device is reduced.

The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide an illuminating device which does not generate capacitive coupling and has no light leakage.

[0010]

To achieve the above object, according to the first aspect of the present invention, there is provided at least a line light source, and a light guide plate for guiding light emitted from the line light source,
A lighting device is provided, wherein the reflector disposed around the linear light source is configured by combining a non-conductive material and a conductive material.

For example, if a non-conductive material and a conductive material are combined so that a conductive material is disposed only at the center portion of the line light source and a non-conductive material is disposed at the end portion, In addition, the occurrence of capacitive coupling can be suppressed, and light leakage at the end can also be prevented.

According to the second aspect of the present invention, there is provided at least a line light source, and a light guide plate for guiding light emitted from the line light source, wherein the line light source has at least one of both ends. A non-conductive reflective material is attached to the end,
A lighting device is provided, wherein a conductive reflecting material is mounted in a central portion.

According to this, since the conductive reflecting material is mounted only on the central portion of the line light source, it is possible to suppress the occurrence of capacitive coupling, and to mount the non-conductive reflecting material on the end portion. Light leakage can be prevented.

According to a third aspect of the present invention, in the first aspect, an electrode of the line light source and an end of the conductive reflecting member are provided with a distance in a longitudinal direction of the line light source. It is characterized by having.

According to this, in the longitudinal direction of the line light source, the electrode of the line light source and the end of the conductive reflector do not overlap, and the conductive reflector covers the electrode having the highest voltage. Is not mounted, the occurrence of capacitive coupling is further suppressed.

According to a fourth aspect of the present invention, in any one of the second and third aspects, the non-conductive reflecting material comprises:
It is a white resin, and the conductive reflection material is a metal reflection surface.

According to this, since the reflecting material can be manufactured on the reflecting surface of the white resin or metal, the reflecting material can be manufactured at low cost.

According to a fifth aspect of the present invention, in the fourth aspect, the white resin is PET (polyethylene terephthalate) mixed with a white pigment, and the reflection surface of the metal is made of PET (polyethylene terephthalate). ) Is formed by evaporating silver.

According to this, since a reflecting material can be manufactured by mixing a white pigment into PET or depositing silver on PET,
It is possible to realize an illumination device that is more inexpensive and has good mounting workability.

According to a sixth aspect of the present invention, there is provided the lighting device according to any one of the first to third aspects, and a liquid crystal panel to which light emitted from the lighting device is incident. And a liquid crystal display device including:

According to this, since the conductive reflecting material is mounted only on the central portion of the line light source, it is possible to suppress the occurrence of capacitive coupling, and to mount the non-conductive reflecting material on the end portion. In addition, a liquid crystal display device that can prevent light leakage can be realized, and the luminance characteristics of the liquid crystal display device can be improved.

In addition, mixing of white pigment into PET or PE
If a reflective material is manufactured by silver vapor deposition on T, an inexpensive lighting device with good mounting workability can be provided.

[0023]

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

FIG. 1 is a plan view of a lighting device according to an embodiment of the present invention, and FIG. 2 is an external view of the lighting device according to the embodiment of the present invention.

This illuminating device comprises a cold cathode tube 1 having electrodes 2 connected to electric wires 6 at both ends, a light guide plate 7 for guiding light emitted from the cold cathode tube 1, and a light guide plate 7 mounted on the back of the light guide plate 7. Reflector 8 for reflecting light propagating through the
And a diffusion pattern (not shown) mounted on the surface of the light guide plate 7 for diffusing light propagating through the light guide plate 7 upward, and a diffusion plate 3 for diffusing light for irradiating the liquid crystal panel.
Further, white PET5 (PET (polyethylene terephthalate) mixed with a white pigment), which is a non-conductive reflective material, is attached to both ends of the cold cathode fluorescent lamp 1. AgPET4 (PET (polyethylene terephthalate) on which silver is vapor-deposited), which is a conductive reflective material, is mounted at the center of the device 1. In addition, AgPE
Both reflectors are mounted on the cold cathode tube 1 so that the boundary between T4 and white PET5 is continuous.

The driving of this lighting device is performed at a voltage value of 250.
This is performed by applying a voltage of about (V) and a frequency of about 30 to 100 (kHz) to the electric wire 6. The cold cathode tube 1 to which the voltage is applied via the electric wire 6 performs a light emitting operation,
The emitted light is reflected by the AgPET 4 and the white PET 5 as indirect light after being reflected by the AgPET 4 and the white PET 5, and propagates through the light guide plate 7. It operates to irradiate the light.

Then, an electric wire 6 is used to drive the lighting device.
Even when a high-frequency high voltage is applied, since only the central portion of the cold-cathode tube 1 is provided with the conductive reflective material AgPET4, the capacitive coupling unlike the conventional case is unlikely to occur, and the electric leakage is prevented. Is prevented, and a desired voltage can be applied without causing a voltage drop.

Further, when the reflector is attached only to the central portion of the cold cathode tube 1, light leakage has conventionally occurred, but according to this embodiment, light leakage has conventionally occurred. Since the light can be reflected by the white PET 5, a decrease in the light amount of the lighting device is prevented.

As described above, since only the central portion of the cold-cathode tube 1 is provided with the conductive reflective material AgPET4, the occurrence of capacitive coupling can be suppressed. It is possible to prevent light leakage by attaching white PET5 which is a reflective material.

In this embodiment, the cold cathode fluorescent lamp 1 has a structure in which white PETs 5 are mounted at both ends, but this corresponds to a structure in which a high voltage is applied to both electrodes to drive the cold cathode fluorescent lamp 1. When the cold cathode tube 1 is driven by applying a high voltage to only one of the electrodes, a configuration in which the white PET 5 is attached only to the end where the electrode on the high voltage side exists is used. Is also good.

If a distance is provided between the end of the electrode 2 and the end of the AgPET 4 in the longitudinal direction of the cold cathode tube 1, the electrode 2 and the AgPET 4 may overlap in the longitudinal direction of the cold cathode tube 1. Is eliminated, so that the occurrence of capacitive coupling can be further suppressed, which is preferable.

Next, a liquid crystal display device including a lighting device according to an embodiment of the present invention will be described.

FIG. 4 is a sectional view of the liquid crystal display device. The liquid crystal display device includes a lighting device and a liquid crystal panel 25 that irradiates the lighting device and performs liquid crystal display. The lighting device and the liquid crystal panel 25 are mounted on a housing 20. The circuit system for driving the liquid crystal panel 25 and the cold cathode tube 1 is not shown.

As described with reference to FIGS. 1 and 2, the illuminating device has a cold-cathode tube 1 having an electrode (not shown) to which an electric wire (not shown) is connected at the end, and emits light. A light guide plate 7 for guiding light, a reflection plate 8 for reflecting light propagating through the light guide plate 7, and light propagating through the light guide plate 7 is diffused upward to irradiate the liquid crystal panel 25. Further, a white PET 5 is attached to both ends of the cold cathode tube 1, and an Ag PET 4 (not shown) is attached to a central portion of the cold cathode tube 1. I have.

As described above, in order to drive the lighting device, a voltage value of about 250 (V) and a frequency of 30 to 100 are used.
When a voltage of about (kHz) is applied to the electric wire, the cold-cathode tube 1 to which the voltage is applied performs a light emitting operation, and the emitted light is direct light or AgPET4 and white PET5.
Then, the light is reflected as an indirect light and propagates through the light guide plate 7, and the light is irradiated on the upper liquid crystal panel 25 by the reflection effect of the reflection plate 8 and the diffusion effect of the diffusion plate 3. Further, the liquid crystal panel 25 is driven by a driving unit (not shown) to perform display.

Therefore, only the central portion of the cold cathode tube 1 has A
Since gPET4 is mounted, capacitive coupling hardly occurs, electrical leakage is prevented, and a desired voltage can be applied without causing a voltage drop.
Since the light that has been leaked in the past can be reflected by the white PET 5, the display luminance of the liquid crystal is prevented from lowering.

According to the embodiment described above, each of the non-conductive and conductive reflectors is made of white P
The reason why ET and AgPET are described as examples is that they are inexpensive and have good mounting workability. Of course, non-conductive and conductive reflecting materials are not limited to these.

According to the embodiment described above, since the AgPET which is a conductive reflecting material is mounted only on the central portion of the cold cathode tube as the line light source, it is possible to suppress the occurrence of capacitive coupling, At the end of the cold-cathode tube, white PET, which is a non-conductive reflecting material, is attached to prevent light leakage.

[0039]

As described above, according to the present invention,
For example, conductive material only in the center of the line light source,
By combining a non-conductive material and a conductive material such that a non-conductive material is disposed at the end, it is possible to suppress the occurrence of capacitive coupling and also to prevent light leakage. .

[Brief description of the drawings]

FIG. 1 is a plan view of a lighting device according to an embodiment of the present invention.

FIG. 2 is an external view of a lighting device according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of a conventional technique.

FIG. 4 is a cross-sectional view of a liquid crystal display device including the lighting device according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cold-cathode tube 2 Electrode 3 Diffusion plate 4 AgPET 5 White PET 6 Electric wire 7 Light guide plate 8 Reflection plate 20 Housing 25 Liquid crystal panel

Claims (6)

[Claims] 1. A light source comprising: a line light source; and a light guide plate for guiding light emitted from the line light source, wherein a reflection material disposed around the line light source comprises a non-conductive material and a conductive material. A lighting device characterized by being configured in combination with 2. A linear light source, and at least a light guide plate for guiding light emitted from the linear light source, wherein the linear light source has a non-conductive reflective material at at least one end of both ends. A lighting device, wherein the lighting device is mounted and has a conductive reflective material mounted in a central portion. 3. The illumination according to claim 2, wherein an electrode of the line light source and an end of the conductive reflecting material are configured to have a distance in a longitudinal direction of the line light source. apparatus. 4. The lighting device according to claim 2, wherein the non-conductive reflecting member is a white resin, and the conductive reflecting member is a metal reflecting surface. apparatus. 5. The method according to claim 4, wherein the white resin is PET (polyethylene terephthalate) mixed with a white pigment, and the reflection surface of the metal is formed by depositing silver on PET (polyethylene terephthalate). A lighting device characterized by the above-mentioned. 6. A liquid crystal display device comprising: the lighting device according to claim 1; and a liquid crystal panel to which light emitted from the lighting device is incident. .