JPH05251043A - Lighting system - Google Patents

Abstract

PURPOSE:To suppress the attachment of a pattering to a tube wall in the direction of a transmission plate even though a spattering is generated from the end edge, and to reduce a reduction of luminous energy owing to a blackening, by sealing the continuous surface of a cold cathode on the end of a discharge lamp and facing the surface to a light diffusion transmission plate. CONSTITUTION:In a cold cathode 10, a spattering of the electrode subatance is generated by a high cathode drop voltage. This spattering generates at the end edges 102a and 102b more than at the plain surface of a plate 102. As a result, the plain surface of the plate 102 is faced to a light-diffusion transmission plate 15, and the end edges 102a and 102b are provided in the direction to cross square to the transmission plate 15. As a result, the spattering is scattered to the left side and the right side to be attached to a bulb wall, and the amount attaching to the bulb wall in the direction from the cold cathode to the transmission plate 15 is reduced. Consequently, even though a blackening is generated, a brightness reduction of the light diffusion transmission plate is reduced, and the brightness distribution is prevented from dispersing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device used as a backlight of a liquid crystal display device or the like and using a cold cathode discharge lamp such as a cold cathode fluorescent lamp as a light source.

[0002]

2. Description of the Related Art A backlight of a liquid crystal display device or the like contains a low-pressure discharge lamp such as a fluorescent lamp in a casing, and the light emitted from this lamp is reflected by a reflection surface on the inner surface of the casing. Is diffused through a light diffusion / transmission plate provided in the opening on the upper surface of the casing, and this diffused light is applied to the back surface of the liquid crystal display panel.

A cold cathode fluorescent lamp is widely used as the low-pressure discharge lamp. The cold cathode fluorescent lamp is superior in light emission efficiency to the incandescent lamp, generates less heat, has a long lamp life, and has a long light emitting portion, and is therefore advantageous in illuminating a wide light emitting area with uniform brightness.

By the way, the cold cathode of the cold cathode fluorescent lamp has a cylindrical shape, a flat plate shape, a roof (mountain) shape or the like made of a metal such as nickel Ni in order to increase the electron emission surface. However, in this type of cold cathode, the electrode material tends to scatter (sputter) during lighting. The scattered electrode material adheres to the tube wall of the arc tube bulb, and this blackens and blocks the light, which causes a problem that the luminous flux is reduced.

For this reason, in the conventional case, the cold cathode sealed at the end of the arc tube bulb has the bulb end of the cold cathode portion projected outside the casing so as not to face the light diffusion and transmission plate. Even if blackening occurs on the tube wall around the cold cathode, this blackening does not occur in a portion facing the light diffusion and transmission plate, that is, in an area effective for irradiation. However, in the case of such a configuration, since the end of the bulb does not face the light diffusion / transmission plate, the light at the end of the bulb that is originally emitting light due to the coating of the phosphor is not effectively used, For this reason, the effective light emitting region with respect to the entire length of the bulb becomes short.

In order to utilize the light emitted from the lamp as effectively as possible, it is desirable that the light emitted from the end of the bulb that surrounds the cold cathode is also transmitted through the light diffusion / transmission plate and applied to the liquid crystal display plate. ..

Therefore, if the cold cathode extended from the light diffusion / transmission plate is opposed to the bulb end, that is, the cold cathode portion is covered by the end of the light diffusion / transmission plate, the light is emitted from the bulb end. It is considered that effective use of light will be possible and the amount of light will increase. On the contrary, if the emission length is the same, the lamp length can be shortened and the casing can be downsized.

[0008]

However, when the bulb end portion in which the cold cathode is arranged is housed in the casing so as to face the light diffusion and transmission plate, if the above-mentioned blackening occurs at the bulb end portion. Since the brightness at the end of the bulb is reduced, the brightness of the light diffusion / transmission plate in the region facing the end of the bulb is reduced, causing unevenness in the overall luminance distribution.

The present invention has been made in view of the above circumstances. An object of the present invention is to effectively utilize the light emitting portion at the end of the bulb to increase the amount of light and to blacken the end. It is an object of the present invention to provide a lighting device in which the decrease of the luminous flux due to the above is reduced and the luminance does not vary over a long period of time.

[0010]

In order to achieve the above-mentioned object, the present invention has a structure in which the cold cathode sealed at the end of the discharge lamp has a continuous surface. It is characterized by being face-to-face with the diffuse transmission plate.

[0011]

The present inventor has stopped the fact that the sputtering that occurs at the cold cathode often occurs at the left and right edge portions of the surface that is continuous with the electrode. Therefore, if the continuous surface of the cold cathode is made to face the light diffusing / transmitting plate, the left and right side edges face the direction perpendicular to the direction facing the light diffusing / transmitting plate. Even if sputtering occurs, since it does not face the light diffusing and transmitting plate in a face-to-face manner, it is less likely to adhere to the tube wall in the direction toward the light diffusing and transmitting plate. Less. Therefore, it is possible to effectively use the light emission at the bulb end portion, increase the amount of light, and reduce the decrease in brightness due to blackening.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in FIGS. The drawing shows a liquid crystal display device, FIG. 6 is an overall exploded perspective view, FIG. 4 is a plan view with a light diffusing and transmitting plate removed, and FIG. 5 is a sectional view. In the figure, reference numeral 1 denotes a shallow dish-shaped casing having an opened upper surface, which is made of a metal such as aluminum or a synthetic resin such as polycarbonate and has an opened upper surface. A partition plate 2 is fixed to one end of the casing 1 and divides the interior of the casing 1 into a lighting effective area 3 and a lighting circuit component accommodating chamber 4. The entire inner surface of the effective illumination area 3 is a reflecting surface 5, and the light reflected by the reflecting surface 5 is directed to the opening. The partition plate 2
The lamp supporting notches 6, 6 are formed in the.

A bent cold cathode fluorescent lamp 7 is housed in the casing 1. The lamp 7 of this embodiment is a W-shaped cold cathode fluorescent lamp, and has a bulb 8 bent and formed into a W-shape. The bulb 8 has bent portions 9a and 9b whose U-shaped straight portions are substantially parallel to each other. , 9c are formed so as to communicate with each other.

Both ends of the bulb 7 are sealed, and cold cathode electrodes 10, 10 described later are mounted on these sealed portions. The sealing portion may be sealed using a flare stem, a button stem, or a pinch seal.

On the inner surface of the bulb 8 is a phosphor coating 8a.
Is formed, and a predetermined amount of mercury is enclosed in the bulb 7, and a starting rare gas such as argon or xenon is enclosed.

The fluorescent lamp 7 having such a structure is housed in the casing 1. In this case, the lamp holders 11, 12, 12 are attached to the casing 1, and the lamp 7 is supported by the lamp holders 11, 12, 12. The lamp holders 11, 12, 12 are made of an elastic material such as rubber and are fixed to the casing 1 by an appropriate means such as an adhesive. One lamp holder 11 is disposed inside the other end of the casing 1 and has two U-shaped bent portions 9a of the bulb 8 bent in a W shape.
It has recesses 11a and 11b into which 9b is fitted. Further, the other lamp holders 12, 12 are fitted into the lamp supporting notches 6, 6 formed in the partition plate 2,
Insertion holes 12a, 12 through which both ends of the lamp 7 are penetrated
a. Therefore, the fluorescent lamp 7 is supported by the lamp holders 11, 12 and 12 at two U-shaped bent portions 9a and 9b of the bulb 8 and the lamp holders 11, 12 and 12, so that the casing is provided via the lamp holders 11, 12 and 12. It is attached to 1.

In this case, the cold cathodes 10 and 10 sealed at both ends of the lamp 7 have the lamp holder 1 as shown in FIG.
It is desired and arranged closer to the illumination effective area 3 than the second and the second. In other words, the cold cathodes 10 and 10 are the lamp holders 1.
It is arranged so as to be located inside the casing 1 so as not to be hidden by the numerals 2 and 12.

A light diffusion / transmission plate 15 is attached to the upper opening of the casing 1. The light diffusion / transmission plate 15 has a milky white color such as acrylic resin and performs a light diffusion / transmission function. The outer surface (or the inner surface) of the light diffusion / transmission plate 15 is provided with the linear portions of the bulb 8. The thick portions 16 ... Are formed in the facing portions. These thick portions 16 ... Are gradually thinned as they move away from the valve 8.

The light diffusion / transmission plate 15 covers the illumination effective area 3. In this case, the light diffusion transmission plate 1
Reference numeral 5 also covers the cold cathodes 10 and 10 of the lamp 7 housed in the casing 1, that is, the end of the light diffusion / transmission plate 15 faces the cold cathodes 10 and 10.

A liquid crystal display panel 18 is arranged above the light diffusion / transmission plate 15. This liquid crystal display panel 1
Reference numeral 8 has a liquid crystal display surface 19 facing the effective irradiation area 3 of the light diffusion / transmission plate 15.

A circuit board 20 is attached to the lighting circuit component accommodating chamber 4 formed at one end of the casing 1.
The circuit board 20 is mounted with circuit components necessary for lighting the lamp at a high frequency. As the high frequency lighting circuit components, for example, an inverter transformer 21, a capacitor 22,
A choke 23, a noise filter 24, etc. The upper surface of the lighting circuit component housing chamber 4 housing the circuit board 20 is covered with a cover 25.

By the way, one of the cold cathodes 10 and 10 is constructed by joining a pair of flat plates 102 and 102 to the tip of a lead wire 101 by butting them in a roof shape as shown in FIG. The lead wire 101 is made of nickel, copper or alloys thereof, or dumet wire, and is used for the valve 8
Is hermetically penetrated. The flat plates 102, 102 are made of nickel plates, and a getter 103 such as zircon is attached to the front surface thereof, and a mercury alloy 104 is attached to the rear surface thereof.

A roof-shaped cold cathode 10 having such a structure
Is sealed to the valve 8 so that one flat plate 102 faces the upper direction of the casing 1. Therefore, the one flat plate 102 of the cold cathode 10 faces the light diffusion / transmission plate 15 attached to the upper opening of the casing 1. That is, the left and right edges 102a, 10 of the flat plate 102
2b is arranged in a direction orthogonal to the direction toward the light diffusion transmission plate 15. The operation of the embodiment having such a configuration will be described.

When the fluorescent lamp 7 is energized, the lamp 7 emits light in a shape along the W-shaped bulb 8. A part of the light emitted from the fluorescent lamp 7 is reflected by the reflecting surface 5 formed on the inner surface of the casing 1 and the light diffusing and transmitting plate 1 in the opening is formed.
5 and the rest of the light is directly diffused and transmitted by light 15
Head to. Therefore, all the light emitted from the lamp 7 is guided to the light diffusion / transmission plate 15. Most of this light is diffused by the light diffusion / transmission plate 15 and illuminates the liquid crystal display plate 18.

In this case, the thick portion 16 is formed on the outer surface of the light diffusing and transmitting plate 15 so as to face the substantially parallel straight portions of the W-shaped bulb 8.
.. is formed, the thick portion 16 exists just above the bulb 8. The thick portion 16 reduces the amount of light transmission and
The light transmission amount increases because the thickness decreases as the distance from the thick portion 16 increases. Therefore, the light diffusion / transmission plate 15 has uniform brightness over the entire surface.

In this embodiment, since the cold cathodes 10 and 10 at the ends of the bulb 8 are arranged in the effective irradiation region 3, the cold cathodes 10 and 10 are surrounded by the bulb wall. It is possible to effectively utilize the emitted light by directing it to the light diffusion / transmission plate 15. That is, the phosphor coating 8a normally formed on the inner surface of the bulb 8 is the cold cathode 1
Not only around 0 and 10, but also around the cold cathodes 10 and 10 to the region closer to the sealed portion are adhered and formed, and therefore, upon arrival of ultraviolet rays, these parts originally emit light. In the present embodiment, since the light emitting portions around the cold cathodes 10 and 10 are exposed in the effective irradiation region 3, the light emitted from these end portions in addition to the light emitted from the straight portions and the bent portions. Can also be used for the backlight of the liquid crystal display plate 18, and therefore, the amount of light is increased and the light can be effectively used. Also, if the emission length is equivalent to the conventional one,
The substantial length of the lamp can be shortened, so that the casing 1 can be downsized.

By the way, in the cold cathodes 10 and 10,
The high cathode drop voltage causes scattering of the electrode material (nickel). This sputtering occurs more frequently on the left and right edges 102a and 102b than on the flat surface of the flat plate 102. Therefore, in the present invention, the flat plate 102
The flat surface at is opposed to the light diffusion / transmission plate 15, and the left and right edges 102a and 102b are arranged in a direction orthogonal to the direction toward the light diffusion / transmission plate 15 as shown in FIG. Therefore, as shown by imaginary lines 108 and 108 in FIG. 2, the sputtering generated at the left and right edges 102a and 102b mainly scatters mainly in the left and right directions, and the sputtering in the left and right directions approaching these edges 102a and 102b. The rate of adhesion to the valve wall increases. That is, the scattered electrode material is less attached to the bulb wall in the direction from the cold cathode 10 toward the light diffusion / transmission plate 15.

Therefore, even if blackening occurs on the end wall of the bulb 8 as the lighting time elapses, this blackening often occurs in the direction orthogonal to the direction toward the light diffusion and transmission plate 15. The ratio of blocking the light traveling to the diffuse transmission plate 15 is reduced.

As described above, the luminance distribution on the light diffusion / transmission plate 15 is kept in a uniform state for a long period of time, and the occurrence of uneven luminance on the liquid crystal display surface 19 of the liquid crystal display panel 18 is reduced. The present invention is not limited to the above embodiment.

That is, the cold cathode 10 of the present invention is not limited to the roof type shown in the first embodiment, but as shown in FIG. 7 and FIG. Alternatively, it may have a structure such as a parallel plate cold cathode 300 in which the plates 301, 301 are arranged in parallel. In short, the cold cathode can be implemented as long as it has a shape having a continuous surface such as a flat surface or a curved surface. Further, the cold cathode fluorescent lamp is not limited to the bent shape such as the W shape and the U shape, and may be a straight tube shape or the like, and one lamp or a plurality of lamps may be used. Further, the lamp is not limited to the fluorescent lamp, but may be a cold cathode rare gas discharge lamp.

[0031]

As described above, according to the present invention, since the continuous surface of the cold cathode is face-to-face with the light diffusion / transmission plate, the left and right side edges of the continuous surface are opposite to the light diffusion / transmission plate. It faces in a right angle direction, and even if sputtering occurs from this edge, it does not face the light diffusing and transmitting plate in a face-to-face manner, so it is less likely to adhere to the tube wall in the direction toward the light diffusing and transmitting plate, and thus toward the light diffusing and transmitting plate. The rate of blocking light is reduced. Therefore, the light emitted from the end portion of the bulb can be used for irradiation of the light diffusion / transmission plate, the amount of light is increased, and the lamp and the casing can be downsized. Even if blackening occurs, it is possible to reduce the decrease in the brightness of the light diffusion / transmission plate, and it is possible to prevent variations in the brightness distribution in the light diffusion / transmission plate.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view of the same embodiment.

FIG. 3 is a perspective view of a cold cathode of the same embodiment.

FIG. 4 is a plan view showing a state in which a light diffusion / transmission plate of the embodiment is removed.

FIG. 5 is a sectional view of the embodiment.

FIG. 6 is an exploded perspective view of the entire lighting device of the embodiment.

FIG. 7 is a sectional view of a main part of another embodiment of the present invention.

FIG. 8 is a cross-sectional view of a main part of still another embodiment of the present invention.

[Explanation of symbols]

1 ... Casing, 2 ... Partition plate, 3 ... Effective illumination area, 4
... Lighting circuit component accommodating chamber, 5 ... Reflecting surface, 7 ... Fluorescent lamp, 8 ... Bulb, 8a ... Fluorescent film, 10 ... Cold cathode,
15 ... Light diffusion / transmission plate, 20 ... Circuit board, 101 ... Lead wire, 102 ... Flat plate, 102a, 102b ... Edge.

Claims (2)

[Claims] 1. A cold cathode discharge lamp is housed in a casing, and a light diffusion / transmission plate is provided in an opening of the casing, and light emitted from the discharge lamp is irradiated through the light diffusion / transmission plate. The light diffusion / transmission plate is arranged up to a position facing the cold cathode sealed at the end of the discharge lamp so as to transmit the light emitted from the bulb wall surrounding the cold cathode, and An illuminating device in which a cathode has a continuous surface, wherein a continuous surface of the cold cathode faces the light diffusion and transmission plate. 2. The lighting device according to claim 1, wherein the cold cathode has a roof shape, and a flat surface of the cold cathode faces the light diffusion / transmission plate.