JPS6147058A - Flat surface type fluorescent lamp - Google Patents

Abstract

PURPOSE:To prevent the noise resulting from an AC electric field and plasma discharge from being leaked externally without deteriorating luminous intensity by forming a conductive coating almost on all surfaces and using a transparent conductive coating as the conductive coating formed on a surface in which at least a liquid crystal display panel is opposed. CONSTITUTION:A transparent conductive coating 10 made of ITO is formed on an upper sealing glass 1 top surface (luminous surface) and a carbon coating 11 is formed on the surfaces other than the upper sealing glass 1 top surface and lower sealing glass 2. However, the insulation between an electrode lead and a shielded coating is maintained without applying any shielding coating to the preset sections in the vicinity of the electrode leads 4 and 4. An aluminum coating may be formed instead of the carbon coating 11. As a result, the noise resulting from the AC electric field applied between electrodes 3 and 3 and the noise resulting from the plasma at discharge can be prevented from being mixed in another circuit that is arranged in the vicinity, for example, a liquid crystal TV circuit, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a flat fluorescent lamp suitable for backlighting of liquid crystal display devices such as liquid crystal TVs.

(b) Prior Art In recent years, development of flat display devices such as liquid crystal TVs has been progressing.

Since the liquid crystal panel used in the above-mentioned liquid crystal TV does not emit light by itself, it is necessary to use some kind of light source as a backlight to transmit light through the liquid crystal to obtain a predetermined brightness.

The above-mentioned backlight has conventionally been used, for example,
A flat fluorescent lamp as shown in Japanese Patent No. 111985 is used.

A flat fluorescent lamp as described above is usually driven by an AC power source, and an AC electric field is applied between the electrodes.

Therefore, noise due to alternating current is generated. Furthermore, noise is also generated due to plasma discharge.

Therefore, in a liquid crystal TV in which liquid crystal panels are arranged close to each other, for example, this noise may enter the TV circuit and disturb the image.

(c) Problems to be Solved by the Invention The present invention has been made to eliminate the above-mentioned drawbacks, and even if it is used as a backlight for a liquid crystal TV in which liquid crystal display panels are arranged close to each other, it will not work in a television circuit, etc. To provide a flat fluorescent lamp that does not introduce noise.

(d) Means for Solving the Problems The present invention forms a conductive film on substantially the entire surface of a flat fluorescent lamp, and at least the conductive film formed on the surface facing the liquid crystal display panel is a transparent conductive film. It is the composition.

(E) Function The above-described configuration allows shielding without degrading the luminous intensity at the light emitting surface of the flat fluorescent lamp, and prevents noise generated by the alternating current electric field and plasma discharge from leaking to the outside.

(f) Examples An embodiment of the present invention will be described below with reference to the drawings.

Figure 2 is an exploded perspective view of the flat fluorescent lamp in this embodiment;
Figure 3 (a), (b), and () 1) are respectively the same plan view, front view, and side view, and Figure 4 (a) and (mouth) are respectively, Figure 3 (a).
FIG. 2 is an AA' cross-sectional view and a BB' cross-sectional view.

In the figure, (1 bar 2) denotes an upper sealing glass in the form of a dish and a lower sealing glass in the form of a flat plate, each of which is formed into a rectangular shape with an aspect ratio of 3:4. An exhaust pipe (1a) is formed on one side of the upper sealing glass in the longitudinal direction.

(3) (3) is a pair of electrodes made of stainless steel or iron-nickel alloy and facing each other. These pair of electrodes are respectively connected to a rear wall (3a), a pair of side walls (3b) (3c) having elasticity with respect to the rear wall, a soil wall (3d), and a bottom wall (3a).
36), and its cross section and longitudinal section are each U-shaped. Also, the amount of protrusion (j22) of the side walls (3b) (3c) is greater than the amount of protrusion (21) of the upper and lower walls (3d bar 3e).
) is larger than 11-511 in this example.
11% j! 2-"7ml toshii:Ir%le1 furthermore,
The electrode type in this embodiment is a cold cathode type in which the cathode is a cold cathode.

Further, among the side walls of the pair of electrodes, the exhaust pipe (1a)
Flat electrode leads (4) (4) made of the same material as the electrodes are electrically and mechanically connected to the sides M (3b) (3b) on which the electrodes are located, respectively, by spot welding. This electrode lead is curved approximately 90 inches in the middle to form the upper and lower walls (3d
)(3e) and extends laterally of the electrode (3), and the curved portion is elastic.

On the other hand, the other side walls (3c) (3c) are also provided with flat electrode support plates (5) (5) made of the same material as the electrodes.
are mechanically connected by spot welding. This electrode support plate is also curved approximately 90 degrees in the middle, and the above-mentioned upper and lower! ! ! (
3d) The curved portion extends to the side of the electrode (3) in parallel with (3e) and has elasticity similar to the electrode lead.

Here, the difference between the electrode lead and the electrode support plate is that the electrode lead mechanically supports the electrode (3) and is electrically connected to the electrode (3), thereby serving as an electrical lead to the outside. On the other hand, the electrode support plate merely provides mechanical support for the electrode (3).

The upper and lower sealing glasses (1 bar 2) are hermetically sealed at their edges by heat welding with a sealing material (6) such as glass frit. At this time, the electrode lead and the electrode support plate are also thermally welded between the upper and lower sealing glasses and fixed to the sealing glass at the same time. Although the electrode support plate (5 bar 5) does not protrude from the ends of the upper and lower sealing glasses, the electrode leads (4) (4>) further protrude from the ends to the outside.

That is, the electrode is elastically supported by the electrode lead and the electrode support plate.

Therefore, when the upper and lower sealing glasses and the electrodes cool down to room temperature after thermal welding, due to the difference in thermal expansion coefficient between the two, the supporting parts of the electrodes, that is, the upper and lower sealing glasses, and the electrode leads and electrode support plates Since the mechanical stress generated at the joint is absorbed by the elastic support of the electrodes, no cracks occur in the upper and lower sealing glasses.

Furthermore, after air is exhausted from the exhaust pipe (1a), mercury and argon gas are introduced into the upper and lower sealing glasses.

Then, the tip of the exhaust pipe is sealed by heat welding.

Further, on the inner surface of the lower sealing glass (2), there are traces of formation of a reflective film (7), as shown in FIGS. 4(a) and 4(b).

This reflective film (7) is made of vacuum-deposited aluminum and is formed into a thin film.

Furthermore, fluorescent films (8) and (9) are formed on the inner surfaces of the upper and lower sealing glasses (1) and (2), respectively, to a predetermined thickness to be described later.

The fluorescent film (8) is formed by coating directly on the inner surface of the upper sealing glass, but the fluorescent film (9) is formed by coating on the reflective film formed on the lower sealing glass.

Therefore, all the light that is about to be emitted after passing through the lower sealing glass (2) is reflected upward by the reflective film (7), and is efficiently emitted outside by passing only through the upper sealing glass (1). Ru.

Next, the thickness setting of the fluorescent films (8) and (9) will be explained.

FIG. 5 is a diagram showing the relationship between the transmittance of the fluorescent film on the lower sealing glass and the emission intensity. The experiment was carried out by forming a fluorescent film on a glass substrate i on which a reflective film was formed, and measuring the intensity of the reflected light when the fluorescent film was irradiated with ultraviolet rays of a predetermined intensity, and the horizontal axis represents the intensity of the fluorescent film. Transmittance (transmittance and film thickness are in an inversely proportional relationship), and the vertical axis indicates relative luminous intensity with the maximum luminous intensity being 1.

As is clear from the figure, when the transmittance is 50% or more, the film thickness and the emission intensity are approximately proportional, but when the transmittance is 50% or less, the emission intensity is almost saturated even if the film thickness is increased. It can be seen that it remains approximately constant.

Therefore, it is desirable to set the thickness of the fluorescent film (9) on the lower sealing glass (2) so that the transmittance is 50% or less.

Next, FIG. 6 is a diagram showing the relationship between the transmittance of the fluorescent film on the upper sealing glass and the emission intensity. The experiment was conducted by measuring the transmitted light when a fluorescent film formed on a glass substrate was irradiated with ultraviolet rays of a predetermined intensity, with the horizontal axis representing the transmittance of the fluorescent film and the vertical axis representing the transmittance of 100%. In other words, the relative luminescence intensity is shown, with the luminescence intensity in a state where no fluorescent film is coated as 1.

As is clear from the figure, when the film thickness is increased too much, the emission intensity decreases rapidly. In other words, when the transmittance is 15% or less, the relative emission intensity becomes 1 or less. This is because when the transmittance is relatively high, the decrease in transmittance due to increasing the film thickness is more than the decrease in the transmittance due to the phosphor film itself. Since the rate of increase in luminescence is higher, the luminescence intensity of transmitted light increases as the film thickness increases.However, when the transmittance is relatively low, increasing the film thickness beyond a predetermined value will increase the luminescence intensity of the phosphor film itself. This is thought to be because the intensity of the transmitted light is greatly influenced by the decrease in transmittance because it becomes saturated.

Therefore, the thickness of the fluorescent film (8) on the upper sealing glass (1) is preferably such that the transmittance is 15% or more.

For the above reasons, in this example, the transmittance of the fluorescent films (8 and 9) on the upper and lower sealing glasses (1) and (2') is 39.8% and 18.2%, respectively. Good emission intensity was obtained by setting various film thicknesses.

Furthermore, as shown in FIGS. 4(a) and 4(b), the flat fluorescent lamp of this embodiment is provided with a shield film over substantially the entire outside of the upper and lower sealing glasses (1) and (2). That is, a transparent conductive film (10 mm) made of ITO is formed on the top surface (light emitting surface) of the upper sealing glass (1), and a transparent conductive film (10 mm) made of ITO is formed on the top surface of the upper sealing glass (1) and on the lower sealing glass (2). is carbon film (11
) is formed. Note that it is necessary to maintain insulation between the electrode lead and the shield film without applying any shield film to a predetermined portion near the electrode lead (4) (4).

Note that an aluminum film may be formed instead of the carbon film.

Further, by using this aluminum film, it is possible to double the function of the aluminum reflective film (7), so this reflective film (7) can be omitted.

With the shield film formed as described above, the electrode (-j) (
a) It is possible to prevent noise generated by an alternating current electric field applied therebetween and noise caused by plasma during discharge from entering other circuits disposed in close proximity, such as a liquid crystal TV circuit.

Next, an embodiment in which the above-described flat type fluorescent lamp is used in a 3-inch liquid crystal TV will be described with reference to FIGS. 1(A) and 1(B).

<100> This is a liquid crystal panel for a liquid crystal TV using Hajul's amorphous silicon TPT active matrix, (101) and (102) are a pair of upper and lower glass substrates, (
103) (103) is a pair of deflection plates arranged on the outside of the pair of glass substrates, (104> is a color filter formed on the lower glass substrate, and (105) and (106) are the upper glass substrates, respectively. (101) and color filter (
104) Display electrode and counter electrode formed on (10
7) (107) is an alignment film formed on the display electrode and the counter electrode, (108) (10g> is a spacer that connects the upper and lower glass substrates at a predetermined interval, and (109) is sealed in the upper and lower glass substrates. It is a twisted nematic liquid crystal.

The liquid crystal panel (100) is bonded to the top surface of the upper sealing glass (1) of the flat lamp using an adhesive or the like.

Next, the relationship between the display section of the liquid crystal panel and the light emitting section of the flat lamp will be explained.

In FIG. 1(a), the horizontal length of the effective display area of the liquid crystal panel (100) (indicated by the two-dot chain line in FIG. )Dotted chain line shown)
Assuming that the horizontal length tb of The conditional expression is b≧@+2 dtan (θ/2).
...(1).

That is, since there is a predetermined height difference d between the effective display section and the effective light emitting section, when viewed at a predetermined viewing angle θ, (1
) If the flat lamp does not satisfy the formula, the liquid crystal panel (100
) ends become dark.

Therefore, in order to satisfy the formula (1) in the liquid crystal TV in this embodiment, the effective light emitting part of the flat type overhead light is larger than the effective display part of the liquid crystal panel (100).

Therefore, in this embodiment, θ■90°, d-5-, and b-a+10tan45°-a+lQmm. That is, the horizontal length of the effective light-emitting part of the flat lamp is made longer than the horizontal length of the effective display part of the liquid crystal panel (100) by iom+. Further, for the same reason, the vertical length of the effective light emitting section is also made longer than the vertical length of the effective display section by a predetermined amount.

Therefore, the liquid crystal TV in this embodiment does not have the disadvantage that the edges of the screen become dark.

(G) Effects of the Invention As described above, according to the present invention, the noise generated by the alternating current electric field and plasma discharge can be prevented from leaking to the outside without deteriorating the luminous intensity on the light emitting surface of the flat lamp. Therefore, even when used as a backlight for a liquid crystal TV in which a liquid crystal panel is arranged close to each other, it is possible to obtain a good image without introducing noise into the TV circuit or the like.

[Brief explanation of the drawing]

The drawings all relate to one embodiment of the present invention, and FIG.
1 is a schematic cross-sectional view of the LCD TV, FIG. 1 (B) is a plan view thereof, FIG. (c) is a plan view, a front view and a side view of the same, FIG. FIG. 3 is a diagram showing the relationship between transmittance and emission intensity. (1)(2)...Top and bottom sealing glass, (3)(3)...
・Electrode, (4) (4)... Electrode lead, (5) (5)
... Electrode support plate, (7) ... Reflection film, (8) (9)
... Fluorescent film, (10) ... Transparent conductive film, (11)
...Carbon film, (100)...Liquid crystal panel.

Claims (1)

[Claims] (1) In a flat fluorescent lamp composed of a pair of substantially flat plates of sealing glass disposed opposite to a liquid crystal display panel, a conductive film is formed on substantially the entire surface, and at least on the surface facing the liquid crystal display panel. A flat fluorescent lamp characterized in that the conductive film to be formed is a transparent conductive film.