JPH07240179A - Flat fluorescent tube - Google Patents

Abstract

PURPOSE:To provide a flat fluorescent tube suitable for making compact by decreasing the width and area of a dead space on a luminescent surface to increase the area ratio of an effective luminescent surface. CONSTITUTION:Both ends 1a, which change the color black by long time lighting, of a discharge path 1 formed by meandering in a W-shape between two glass plates 4, 5 are bent perpendicularly to the discharge direction, and electrodes 2 are arranged in the innermost parts of the bent ends 1a. The meandered discharge part 1b in the central part of the W-shaped discharge path 1 is arranged on a straight line as the ends la, and an electrode 3 is arranged in the center of the meandered discharge part 1b to divide the discharge path 1 into two. Both ends 1a, where change color black, of the discharge path 1 and a region in the central meandering discharge part 1b become a dead space D, and other part of the discharge path 1a becomes an effective luminescent path S. The width of the dead space D is narrowed to the degree near the width W1 of the ends 1a independent of the length of color change to black at the ends 1a, and the dimension of a flat fluorescent tube is decreased and the area of the effective luminescent part S is enlarged by the dimension equivalent to decreased width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat fluorescent tube used as a backlight of a liquid crystal display panel.

[0002]

2. Description of the Related Art As a backlight of a liquid crystal display panel, a flat fluorescent tube, which has a strip-shaped discharge path meandering to emit surface light, has been favored. This flat fluorescent tube has a discharge width of 1 between two abutted glass plates.
There are a long strip-shaped discharge path of about 0 mm or less formed, and a strip-shaped discharge path formed of a thin tube fluorescent lamp with a tube diameter of 10 mm or less. Typical general examples thereof are shown in FIGS. 7 to 9. And explain.

In the flat fluorescent tube shown in the figure, a front glass plate 15 in the form of a rectangular flat plate and a back glass plate 16 in a rectangular corrugation are airtightly overlapped with each other to form a front glass plate 1 of the back glass plate 16.
A concave portion 1 formed in a meandering shape by drawing on the abutting surface with 5
7 and the surface glass plate 15 form a meandering discharge path 18. The recess 17 meanders in a W shape, for example, and a phosphor coating (not shown) is formed on the inner surface thereof. W-shaped discharge path 1
Electrodes 19 and 20 are arranged on both end portions 18a of 8 and the meandering discharge portion 18b at the center, respectively. The electrodes 19 are cold cathode or hot cathode type electrodes, and the leads 21 are connected to the glass plate 15,
16 is derived outside. The discharge path 18 is filled with an inert gas such as argon and mercury after being heated and degassed in a vacuum state.

When the electrodes 19 at both ends of the discharge path 18 have the same polarity and the central electrode 20 has a different polarity and a predetermined voltage is applied between the electrodes 19 at both ends and the central electrode 20, the discharge path 18 is divided into two parts.
Glow discharge is generated in each of the letter-shaped first discharge path 18m and second discharge path 18n, and the phosphor coating of each discharge path 18m, 18n emits light. The light from each of the discharge paths 18m and 18n is surface-emitted on the surface glass plate 15 and illuminates a liquid crystal display panel (not shown) arranged above the surface glass plate 15.

In such a flat fluorescent tube, an electrode 20 is arranged in the meandering discharge part 18b at the center of the W-shaped discharge path 18 so that the discharge path 18 is formed into a first discharge path 18m and a second discharge path 18n. The discharge start voltage is further lowered and the power consumption is reduced by shortening the arc length between the electrodes of the discharge paths 18m and 18n. Further, by making the discharge path 18 a rectangular cross section, the upper and lower glass plates 15,
The thickness of 16 as a whole is reduced to a thickness of 10 mm or less.

[0006]

By the way, in the flat fluorescent tube as described above, when the lighting time becomes long as in a normal fluorescent lamp, the inner wall surface near the electrodes of the discharge path 18, that is, both end portions 18a. The inner wall surface of the meandering discharge part 18b in the center is blackened by electrode sputtering, and the brightness is extremely lowered [the blackened part is shown by diagonal lines]. Therefore, both ends 18a where the blackening phenomenon of the discharge path 18 occurs and the meandering discharge part 18b in the center are formed.
A dead space that cannot be used as the backlight area of the liquid crystal display panel is provided on the area where the area exists. In fact, from the end of the surface glass plate 15 on the electrode arrangement side, the discharge path 18
The end portions up to a predetermined length where the blackening phenomenon of the both end portions 18a is set as the dead space portion D ', and the portion excluding the dead space portion D'on the front glass plate 15 is effective as the backlight of the liquid crystal display panel. It is used as an effective light emitting portion S '.

The blackening phenomenon at the end portion 18a of the discharge path 18 in such a flat type fluorescent tube depends on the lighting conditions. For example, when the input power is several watts and the lighting time is about 10,000 hours, 5 to 5 in the discharge direction. Since it occurs with a length of about 8 mm, the width of the dead space portion D ′ at the end of the front surface glass plate 15 needs to be substantially 20 mm or more. The width of such a dead space portion D ′ is determined regardless of the size of the effective light emitting portion S ′ on the surface glass plate 15, and the smaller the flat fluorescent tube becomes, the more the dead space portion D on the surface glass 15 becomes. The area ratio of the 'has become high, and it has been difficult to downsize the flat fluorescent tube substantially.

In order to reduce the dead space on the surface glass 15 and increase the effective light emitting area, the length of the electrode 19 in the discharge direction is shortened, and the width of the dead space portion D'is reduced by the shortened length. Some things are being made smaller. However, there is almost no practical effect of reducing the width of the dead space due to the miniaturization of the electrode 19, and there is a problem that the life of the electrode is shortened and the life of the fluorescent tube is shortened.

Further, the discharge path 18 in the effective light emitting portion S '
Is a U-shaped first discharge path 18m and a second discharge path 18n,
The meandering discharge part 18d meandering in a U-shape of each of the discharge paths 18m and 18n has a substantially semicircular shape.
The four parallel linear discharge parts 18c, ... Of n have the same interval, and the discharge paths 18m and 18n are caused to emit light with the same brightness. Therefore, the central point Q ₁ of the effective light emitting portion S ′ corresponding to the intermediate position between the discharge paths 18m and 18n becomes the brightest, and the semi-circular meandering discharge portion 18c of the discharge paths 18m and 18n becomes brighter.
A rectangular effective light-emitting portion S ', which is distant from the corner, has three points, that is, a corner neighboring point Q ₂ at both ends of one side and a center neighboring point Q _{3 on} one side, which is noticeably darkened, and is the entire luminance distribution of the effective light-emitting portion S'. There was also a problem that the uniformity was poor.

The object of the present invention is to minimize the dead space on the surface emitting light, increase the area ratio of the effective light emitting surface on the entire surface, and improve the uniformity of the luminance distribution. An object is to provide a flat fluorescent tube that has a long life and is easy to miniaturize.

[0011]

According to the present invention, an end portion of a strip-shaped discharge path having electrodes at both ends is bent in a direction substantially orthogonal to a discharge direction in the discharge path, and a predetermined distance is provided from a bending point of the end portion. By arranging the electrodes in the inner part of the, the above-mentioned object is achieved.

As the discharge path, a discharge tube formed between two glass plates closely adhered to each other or a thin tube fluorescent lamp is used.

When the discharge path is formed in a meandering shape, both ends of the meandering discharge path and about 180 between the both ends are formed.
It is practically desirable to divide the meandering discharge path into a plurality of discharge paths between the electrodes by arranging the meandering discharge parts that are meandering in a straight line and arranging electrodes on both ends and the meandering discharge part.

When the discharge path is formed to meander in a W shape on a rectangular flat surface, the width of the four substantially linear linear discharge portions of the W-shaped discharge path is set to the width of each adjacent linear discharge portion. The width is larger than the width of the meandering discharge part that communicates with each other, and the central portions of the four linear discharge parts are adjacent to each other at two different intervals, small, large, and small.
Except for the meandering discharge part at the center of the W-shaped discharge path, two adjacent meandering discharge parts are parallel to one side of the rectangular plane, and the inner end of each of the meandering discharge parts overhangs near the center of one side of the rectangular plane.
It is desirable that the outer ends of the meandering discharge parts project to near the corners of both ends of one side of the rectangular plane in order to improve the uniformity of the rectangular effective light emitting surface.

[0015]

[Function] When both ends of a strip-shaped discharge path having electrodes at both ends are bent in a direction orthogonal to the discharge direction and the electrodes are arranged at the bent ends, the inner wall surface of the discharge path near the electrodes is blackened by electrode sputtering. However, this blackened portion occurs only at the bent end of the discharge path. Therefore, a portion of the discharge path excluding the bent end can be set as the effective light emitting portion. In this case, the width of the dead space protruding from the effective light emitting portion is
The width and area of the dead space are reduced corresponding to the width of the L-shaped end of the discharge path.

If the discharge path is meandered in a W shape in a rectangular plane and the width of the linear discharge part of this discharge path is made larger than the width of the meandering discharge part, the brightness of the central part of the rectangular plane is lowered and the meandering discharge part is formed. Is formed so as to project in the vicinity of the corner of the rectangular plane, the brightness in the vicinity of the corner of the rectangular plane is increased, and the brightness distribution of the effective light emitting surface of the rectangular plane becomes more uniform as a whole and the uniformity is improved.

[0017]

EXAMPLES Examples will be described below with reference to FIGS. 1 to 6.

The flat type fluorescent tube of the embodiment shown in FIGS. 1 to 3 is of the same type as the flat type fluorescent tube of FIG. 7, and is a rectangular flat plate-shaped surface glass plate which is airtightly superposed and joined integrally. A strip-shaped discharge path 1 meandering in a substantially W-shape is formed between the rear surface glass plate 4 and the rectangular corrugated back glass plate 5. A recess 6 formed in a substantially W shape on the abutting surface of the back glass plate 5 by drawing.
And the surface glass plate 4 form the discharge path 1, and the phosphor coating is formed on the recess 6 or the inner surface of the discharge path 1.

The above embodiment is characterized in that both ends 1a of the discharge path 1 are bent inward in the direction orthogonal to the discharge direction, and the electrodes 2 are arranged at the inner portions of the both ends 1a.
Further, the above embodiment is characterized in that the meandering discharge part 1b at the center of the discharge path 1 is formed in line with both end parts 1a, and the electrode 3 is arranged at the center of the meandering discharge part 1b. Each of the electrodes 2 and 3 is a cold cathode or hot cathode type electrode, the lead 7 is led out from each of them to the outside of the glass plates 4 and 5, and the inside of the discharge path 1 is inert such as argon after the heat degassing process. Gas and mercury are enclosed.

When a predetermined voltage is applied between the end electrodes 2 and the central electrode 3 with the electrodes 2 at both ends 1a of the discharge path 1 having the same polarity and the central electrode 3 having different polarities, the discharge path 1 is divided into two U-shapes. A glow discharge or an arc discharge is generated in each of the first discharge path 1m and the second discharge path 1n, and the phosphor coating of each discharge path 1m, 1n emits light. It emits light.

When the W-shaped discharge path 1 is turned on, the inner wall surfaces of both end portions 1a and the central meandering discharge portion 1b are blackened by electrode sputtering [blackened portions are shown by diagonal lines]. This blackening phenomenon occurs in a length of about 5 to 8 mm in the discharge direction. Therefore, the length from the bending point of both ends 1a of the discharge path 1 to the electrode 2 and the length from the center electrode 3 to the bending point of both ends of the meandering discharge portion 1b are made linear. The length is set to about the length at which the blackening phenomenon occurs. In this case, the W-shaped discharge path 1 is blackened and the dead space is the only end portions 1a and the central meandering discharge portion 1b aligned in a straight line. The width is about the width W ₁ of both ends 1a of the discharge path 1.

For example, when the average width of the strip-shaped discharge path 1 in a small flat fluorescent tube is set to about 5 mm, the width of the dead space portion D on the surface glass plate 4 is reduced to about 8 mm. Therefore, assuming that the effective light emitting portion S of the flat fluorescent tube of FIG. 1 and the effective light emitting portion S ′ of the flat fluorescent tube of FIG. 7 have the same size and area, the dead space of the flat fluorescent tube of FIG. The size of the flat fluorescent tube of FIG. 7 is reduced by the width reduction of the portion D. Further, if the flat fluorescent tube of FIG. 1 and the flat fluorescent tube of FIG. 7 have the same outer diameter size, the area of the effective light emitting portion S of the flat fluorescent tube of FIG. 1 is equal to the width reduction of the dead space portion D. This is larger than the effective light emitting area of the flat fluorescent tube of FIG.

Next, a specific structural example of the above embodiment and other embodiments will be described.

The discharge path 1 formed by stacking two glass plates 4 and 5 has a substantially rectangular cross section, and the electrodes 2 and 3 arranged in the discharge path 1 having such a cross section are shown in FIG. (B) and FIG.
Flat hollow cathode electrodes as shown in (a) and (b) are desirable because they have a long life and excellent starting characteristics.

4A and 4B show both ends 1 of the discharge path 1.
There is shown an electrode 2 arranged at a, which contains a cerium-tungsten filament 9 in a flat cap nickel hollow cathode 8 with one end open and the other end closed. By arranging the opening of the hollow cathode 8 toward the discharge direction of the discharge path 1 at the back of the end 1a of the discharge path 1, electrons are less sneak around the electrode at the time of discharge, and good discharge characteristics are obtained. can get. In addition, the hollow cathode 8 keeps the internal filament 9 warm, and discharge with low power consumption becomes possible.

5 (a) and 5 (b) show a flat cap-shaped nickel hollow cathode 10 (with both ends open and closed at the center) of the electrode 3 (disposed at the meandering discharge portion 1b at the center of the discharge path 1).
A cerium-tungsten filament 11 is housed in each of the openings at both ends. At the center of the meandering discharge end 1b of the discharge path 1, openings at both ends of the hollow cathode 10 are arranged in the discharge direction of the discharge path 1. The hollow cathode 10 of the electrode 3 is shared by both the discharges of the first discharge path 1m and the second discharge path 1n and receives twice the voltage of the other electrodes 2, so that the size in the width direction is increased. Keep it. Corresponding to the widened electrode 3, as shown in FIG. 1, the width of the central portion of the meandering discharge portion 1b is slightly enlarged, and the electrode 3 is arranged in the wide central portion. The expansion of the width of the central portion of the meandering discharge part 1b can be executed without any problem by reducing the width of the dead space described above.

The luminance distribution of the effective light emitting portion S of the flat fluorescent tube of FIG. 1 becomes more uniform and the uniformity is improved by setting the width and spacing of the W-shaped discharge path 1 as follows.

That is, the effective light emitting portion S of the rectangular surface glass 4
The downwardly meandering discharge path 1 is composed of four linear straight line discharge portions 1c arranged substantially in parallel and a pair of left and right meandering discharge portions 1d. Here, the four linear discharge portions 1c in the effective light emitting portion S
The width W _{2 of the} central portion excluding both end portions is set larger than the width W ₃ of the left and right meandering discharge portions 1b, and the interval P ₁ between the two inner linear discharge portions 1c is set to the inner two linear discharge portions 1c.
It is set to be larger than the interval P ₂ between the two adjacent linear discharge parts 1c on the outside. With such a width and interval setting, the brightness of the central portion of the rectangular effective light emitting portion S (the portion that has been too bright in the past) is slightly reduced, and the luminance distribution in the width direction of the central portion of the rectangular effective light emitting portion S is reduced. Homogenize.

Further, the narrow meandering discharge portion 1d on the left and right in the discharge path 1 of the effective light emitting portion S is made linear in the discharge direction,
Along the one side of the rectangular surface glass 4, the one side of the meandering discharge part 1d is meandered so as to extend to a corner 4 '' of one side of the surface glass 4, and the other end side of the meandering discharge part 1d. Is made to meander so as to project to the central portion 4'of one side of the surface glass 4. By doing so, the meandering discharge portion 1d having a narrower width and increased brightness has three points of the corner portion 4 ″ and the central portion 4 ′ of one end portion of the rectangular effective light emitting portion S (the portion which is conventionally dark). ) Brightness increases. By increasing the brightness of the end portion and decreasing the brightness of the central portion of the effective light emitting portion S, the effective light emitting portion S
It is possible to make the brightness of the entire display uniform.

It should be noted that both ends of the meandering discharge part 1d of the discharge path 1 may be projected to the vicinity of the corner of one side of the rectangular effective light emitting part S and the vicinity of the center thereof at an acute angle, but as shown in FIG.
It is desirable to slightly bend both ends of the meandering discharge portion 1d so that the meandering discharge portion 1d is meandered in order to shorten the arc length at this portion, lower the discharge start voltage, and reduce the load on the discharge drive circuit.

Further, the meandering shape of the discharge path 1 of the flat fluorescent tube shown in FIG. 1 is not limited to the W shape, but may be other than the meandering shape. Further, the discharge path 1 is not limited to the one formed between the two glass plates 4 and 5, and may be a straight tube or a curved tube fluorescent lamp. To be shown.

FIG. 6 shows a single U-shaped fluorescent lamp 12 which is U-shaped.
It is a flat fluorescent tube having a V-shaped discharge path. Both ends 12a of the U-shaped fluorescent lamp are bent inwardly at right angles, and the electrodes 13 are arranged at the inner portions of the both ends 12a. In this case, the fluorescent lamp 12 is sandwiched between a reflection plate and a diffusion plate (not shown) to form a flat fluorescent tube. In the flat fluorescent tube of FIG. 6, the dead space portion D is the area where the bent ends 12a of the fluorescent lamp 12 are present.
The U-shaped discharge portion other than the both end portions 12a is used as the effective light emitting portion S. In this case as well, the width of the dead space portion D is
The size is reduced to about the tube diameter of the fluorescent lamp 12.

[0033]

According to the present invention, since the end portion of the strip-shaped discharge path having the electrodes at both ends is bent in the direction orthogonal to the discharge direction, the discharge path is lit for a long time and the discharge in the vicinity of the electrode is performed by electrode sputtering. Even if the inner wall surface is blackened, this blackened part is only the bent end of the discharge path.Therefore, from the effective light emitting part when the part excluding the bent end of the discharge path is set as the effective light emitting part. The width of the protruding dead space is reduced to about the width of the bent end of the discharge path. As a result, the proportion of the dead space area occupying the entire light emitting surface of the flat fluorescent tube becomes small, and the proportion of the effective light emitting surface becomes large on the contrary, resulting in a small flat fluorescent tube having an effective light emitting surface of a predetermined area. It is possible to make the device compact and increase the area of the effective light emitting surface of the flat fluorescent tube of a predetermined size.

Further, the discharge path is meandered in a W shape in a rectangular plane, the width of the linear discharge part of this discharge path is made larger than the width of the meandering discharge part, and the narrow meandering discharge part is made into a corner of the rectangular effective light emitting surface. If it is projected in the vicinity, the brightness of the central part of the rectangular effective light emitting surface decreases, and on the contrary, the brightness near the corners of the rectangular effective light emitting surface increases, making the brightness distribution of the entire effective light emitting surface more uniform and uniform. It is possible to provide a flat fluorescent tube of high practical value with a high degree of practicality.

[Brief description of drawings]

FIG. 1 is a plan view including an omitted part showing an embodiment of the present invention.

FIG. 2 is a front view of the flat fluorescent tube of FIG.

3 is a sectional view taken along the line AA of FIG.

4 (a) and (b) are a plan view and a cross-sectional view of electrodes arranged at both ends of the discharge path of the flat fluorescent tube of FIG.

5 (a) and 5 (b) are a plan view and a cross-sectional view of an electrode arranged at the center of the discharge path of the flat fluorescent tube of FIG.

FIG. 6 is a plan view of a main part showing another embodiment of the present invention.

FIG. 7 is a plan view including a partially omitted portion of a conventional flat fluorescent tube.

FIG. 8 is a front view of the flat fluorescent tube of FIG.

9 is a sectional view taken along line BB of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge path 1a Bent end 1b Meandering discharge part 1d Meandering discharge part 2 Electrode 3 Electrode 4 Glass plate 5 Glass plate 12 Fluorescent lamp 12a Bend end 13 electrode

Claims (5)

[Claims] 1. An end portion of a strip-shaped discharge path having electrodes at both ends is bent in a direction substantially orthogonal to a discharge direction in the discharge path, and an electrode is arranged in a deep portion at a predetermined distance from a bending point of the end portion. A flat fluorescent tube characterized by the above. 2. The flat fluorescent tube according to claim 1, wherein a discharge path is formed between two glass plates which are closely adhered and overlapped. 3. The flat fluorescent tube according to claim 1, wherein the discharge path is formed by a thin tubular fluorescent lamp. 4. A discharge path is formed in a meandering shape on a rectangular plane, and both ends of the discharge path, which are bent, and a meandering discharge part that meanders 180 ° between the ends are formed in a straight line. 2. The flat fluorescent tube according to claim 1, wherein electrodes are arranged in the inner portions of both ends arranged in a line and in the center of the meandering discharge portion to divide the meandering discharge path into a plurality of discharge paths between the electrodes. 5. A discharge path is formed to meander in a W shape on a rectangular flat surface, and the width of the four substantially linear linear discharge portions of the discharge path is defined by the meandering width that connects adjacent linear discharge portions. The width is larger than the width of the discharge portion, and the central portions of the four linear discharge portions are adjacent to each other at two different intervals of small, large, and small, and adjacent to each other except the meandering discharge portion at the center of the discharge path. The meandering discharge part is parallel to one side of the rectangular plane, the inner end of each meandering discharge part projects near the center of one side of the rectangular plane, and the outer end of each meandering discharge part is near the corners of one side of the rectangular plane. The flat fluorescent tube according to claim 4, which extends to the extent.