JPH05225957A - Flat type fluorescent lamp device - Google Patents

Abstract

PURPOSE:To eliminate a discharge lag under darkness via the supply of electric energy to an auxiliary electrode, even when no additional space is available for a resistor or the like, by providing a conductor in such a way as sandwiching a printed circuit board. CONSTITUTION:The same copper foil as a copper foil (conductor) 41 pasted to the upper surface of a printed circuit board 3 is applied to the reverse side as well, in such a way as opposite to each other like a sandwich form. This copper foil is connected to a pair of anode lead fixing sections 31 via printed wiring connected to a positive high voltage section at the secondary side of a high-frequency transformer 5. Then, when secondary high voltage is generated and a flat type fluorescent lamp 1 is turned on, main discharge between an anode 21 and a cathode 22 is not disturbed after discharge between an electrode 23 and the cathode 22, because a line branched from the positive high voltage section and connected to an auxiliary electrode 23 is fitted with a capacitor comprising the foil 41 or the like via the board 3. Consequently, even when there is no space available for fitting a resistor, a discharge lag under darkness can be eliminated, and a viewfinder can be made compact, because the electrode 23 is fitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact flat fluorescent lamp device suitably used as a backlight of a liquid crystal display incorporated in a viewfinder of a video camera or the like, and more specifically, left for a long time in the dark. The present invention relates to a flat-type fluorescent lamp device that can be reliably turned on even when lighted.

[0002]

2. Description of the Related Art In recent years, with the increasing density of LSIs, all products tend to be miniaturized, and personal computers, word processors, video cameras, etc. are no exception. A liquid crystal is often used as a display for such products, but since the liquid crystal has a bright screen and can be colored, a transmissive type is becoming mainstream, and a fluorescent lamp is mainly used as a backlight. ing.

In the case of a small liquid crystal display for a viewfinder of a video camera, one having a size of 1 inch or less is becoming mainstream due to the miniaturization. Therefore, a straight tube fluorescent lamp is used as a backlight. With the increasing pressure, flat fluorescent lamps have been demanded. In addition, in order to cope with the miniaturization, not only the backlight but also the lighting device is required to be miniaturized.

[0004]

On the other hand, it is well known that a lamp left in the dark for a long time causes a discharge delay. This discharge delay is caused by, for example, a backlight of a viewfinder of a video camera. In that case, even if the switch is turned on, a problem such as the screen not appearing will occur. And as an effective means for solving this discharge delay, it has been proposed to provide an auxiliary electrode in the vicinity of the cathode, but in this case, the auxiliary electrode is sufficiently provided so as not to interfere with the discharge at the time of shifting to the main discharge. It is necessary to place a resistor or capacitor with a large impedance in between, and in the viewfinder designed for a small video camera, there is actually no space to place such a resistor or capacitor. there were.

The present invention has been made to solve the above problems, and an object thereof is to provide an auxiliary electrode with electric energy even if there is no extra space for providing a resistor or a capacitor. It is an object of the present invention to provide a flat type fluorescent lamp device capable of supplying the electric field and eliminating a discharge delay in the dark.

[0006]

SUMMARY OF THE INVENTION A flat fluorescent lamp device of the present invention is a flat fluorescent lamp having an anode and a cathode opposed to each other and an auxiliary electrode arranged in the vicinity of the cathode, and the flat fluorescent lamp. In a flat fluorescent lamp device comprising a printed circuit board arranged on the back side of the lamp and a high frequency lighting circuit including a high frequency transformer, the printed circuit board has metal coatings on both sides of the rear surface on which the flat fluorescent lamp is located. Alternatively, a conductor made of a metal foil is provided in a sandwich shape, one of the conductors is connected to a positive high voltage on the secondary side of the high frequency transformer, and the other of the conductors is connected to the auxiliary electrode. Characterized by

[0007]

[Function] Since a conductor composed of a metal film or a metal foil is provided on the back surface where the flat fluorescent lamp is located so as to sandwich the printed circuit board in a sandwich shape, a capacitor having the printed circuit board as a dielectric is formed. It Therefore,
If the auxiliary electrode is connected through this conductor, it is not necessary to provide a resistor or a capacitor separately. In addition, the conductor contacting the back surface of the flat fluorescent lamp also serves as a proximity conductor, which is useful for preventing lighting delay in darker conditions.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a view showing the assembled flat fluorescent lamp device of the present invention, showing a state before the flat fluorescent lamp 1 is attached to a printed circuit board 3. The flat fluorescent lamp 1 is composed of an upper surface glass plate 11 and a box-shaped member 12. The inner surface of the upper surface glass 11 and the bottom surface of the box-shaped member 12 are coated with a fluorescent paint, and a central portion 13 of the upper surface glass 13 is provided.
Is the light emitting surface. And this flat fluorescent lamp 1
An anode 21 and a cathode 22 are arranged opposite to each other on both sides, and an auxiliary electrode 23 is arranged close to the cathode 22. still,
14 is the remaining portion of the exhaust pipe.

The printed circuit board 3 is made of glass epoxy resin and has a thickness of about 1 mm. Then, the high frequency transformer 5 is fixed by cutting one side, and a pair of anode lead fixing portions 31 into which the lead portions of the anode 21 are inserted and fixed by soldering, and a pair of cathode lead fixing portions 32 are also fixed.
And an auxiliary electrode lead fixing portion 33 to which the lead of the auxiliary electrode 23 is fixed is provided. The auxiliary electrode lead fixing portion 33 is connected to the copper foil 41 attached to the printed circuit board on the rear surface on which the flat fluorescent lamp 1 is arranged by the printed wiring 34. This copper foil has a thickness of about ten and several μm.

FIG. 2 shows a rear surface state of the printed circuit board 3 of FIG. 1 seen through from the front side, and the same copper foil 42 is attached so as to face the copper foil 41 attached to the front surface. The copper foil 42 is connected to the printed wiring 37 connected to the positive and high voltage on the secondary side of the high frequency transformer 5, and the printed wiring 37 is also connected to the pair of anode lead fixing portions 31. Reference numerals 35 and 36 are print wirings for inputting to the high frequency transformer 5 on the primary side, and 38 is a print wiring connected to the low voltage side on the secondary side, which is connected to the pair of cathode lead fixing portions 32 and will be described later. It is also connected to the drain of the current switching FET of the lighting circuit.

FIG. 3 shows an example of a lighting circuit which can be used in the present invention, which is a pulse lighting circuit of a flyback system. That is, a pulse signal generated from the timing and drive circuit 6 is applied to the gate of the FET 7 in synchronization with the synchronization signal. Then, the FET 7 switches the current on the primary side of the high frequency transformer 4 to generate a secondary high voltage, and the flat fluorescent lamp 1 is turned on. At this time, the capacitor 9 formed by the pair of copper foils 41 and 42 is inserted via the printed circuit board 3 into the line branched from the positive voltage on the secondary side and connected to the auxiliary electrode 23. Therefore, after the discharge between the auxiliary electrode 23 and the cathode 22, the main discharge between the anode 21 and the cathode 22 does not hinder the discharge. Reference numeral 8 is a capacitor for preventing voltage fluctuation.

Here, the capacitor formed by the pair of copper foils 41 and 42 with the printed circuit board 3 interposed is the anode 21.
It is necessary to make the impedance sufficiently large so as not to interfere with the normal main discharge between the cathode 22 and the cathode 22, and the required capacitor capacity and the area of the copper foil required at that time were investigated. Generally, the relative permittivity of the material used for the printed board is about 3 to 6, and the approximate area S of the capacitor to be formed on the board is calculated by the following equation (1). S = (C · d) / ε ─────────────────── (1) where C is the capacitance of the capacitor (F), d is the thickness of the substrate (m), ε is the dielectric constant (F / m) of the substrate material.

The capacitor capacity C is given by the following equation (2). C = 1 / (2πf · Z) ───────────────── (2) where π is the pi, f is the lighting frequency, and Z is the impedance (Ω). .. First, in order to calculate the required capacitor capacity from the equation (2), the value of the resistance inserted in the auxiliary electrode was variously changed to examine how the lamp brightness changes. The results are shown in Table 1.

[0014]

[Table 1]

As shown in Table 1, it can be seen that the impedance of 2 MΩ or more has almost no effect on the main discharge. The flat fluorescent lamp is turned on with a high-frequency high-voltage pulse in order to prevent uneven discharge, but in order not to be affected by noise due to this pulse, the flat fluorescent lamp is turned on during a pause period of the horizontal synchronizing signal on the screen. A pulse is generated at the same time. Normally, the NTSC horizontal sync signal that is standardly adopted in Japan is approximately 15.7K.
Since it is Hz, in equation (2), π = 3.14, f = 15.
Substituting 7 × 10 ³ and Z = 2 × 10 ⁶ , C≈5 × 1
It becomes 0 ^-12 F (5 pF).

A glass epoxy board used for a small printed board usually has a thickness of about 1 mm.
Its permittivity is 4.43 × 10 ^-11 F / m (relative permittivity is 5
Then, by substituting the values of C calculated by the equation (2) and these values into the equation (1), S = 113 mm
It becomes ² . This is a size of 10.6 mm × 10.6 mm, which is a size that can be sufficiently manufactured even for a 0.7-inch type viewfinder display that is becoming mainstream at present. And actually 10.0 x 10.0
When the lamp brightness was examined by using a copper foil having a size of mm, it was 4195 nt, and it was confirmed that there was almost no effect compared with the brightness 4210 nt when not used.

The influence of discharge delay in the dark was investigated by a comparative experiment. As a lamp device, there is an aluminum tape (20 x
19 mm) and 10 types of B type with auxiliary electrodes as shown in FIG. 1 (copper foil size is 10 × 10 mm) were manufactured and left in the dark at −10 ° C. for 48 hours. It was used to measure the number of seconds for lighting at room temperature. The results are shown in Table 2.

[0018]

[Table 2]

As shown in Table 2, in the B type according to the present invention, all 10 lamps were turned on within 2 seconds, whereas in the A type without the auxiliary electrode, it was 2 seconds. Only two lights lit within, and two took up to 3 minutes. As described above, the luminance is not affected even during the main discharge.

In the present invention, a copper foil having a size of about 100 to 120 mm ² is used. If the size is about this, the copper foil also plays a role as a proximity conductor, so that a proximity conductor is separately provided. Need not be provided. Further, the present invention is not limited to this embodiment, and for example, a metal foil such as aluminum can be used instead of the copper foil.

[0021]

As described above in detail, in the flat fluorescent lamp device of the present invention, the auxiliary electrode can be provided even when there is no space for providing the resistor and the capacitor, so that the discharge delay in the dark can be eliminated. Both the requirements for downsizing the viewfinder and the viewfinder can be solved at once.

[Brief description of drawings]

FIG. 1 is a view showing the assembled flat fluorescent lamp device of the present invention.

FIG. 2 is a diagram showing a back surface state of the printed circuit board seen through from the front surface.

FIG. 3 is a diagram showing an example of a lighting circuit.

[Explanation of symbols]

 1 Flat Fluorescent Lamp 21 Anode 22 Cathode 23 Auxiliary Electrode 3 Printed Circuit Board 31 Anode Lead Fixing Part 32 Cathode Lead Fixing Part 33 Auxiliary Electrode Lead Fixing Part 34, 35, 36, 37, 38 Printed Wiring 41, 42 Conductor 5 High Frequency Transformer 6 Timing and drive circuit 7 FET 8 capacitor 9 capacitor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Oshima 1194 Sado, Bessho-cho, Himeji-shi, Hyogo Ushio Electric Co., Ltd.

Claims (1)

[Claims] 1. A flat fluorescent lamp having an anode and a cathode opposed to each other and an auxiliary electrode arranged in the vicinity of the cathode, a printed circuit board arranged on the back side of the flat fluorescent lamp, and a high frequency wave. In a flat fluorescent lamp device comprising a high-frequency lighting circuit including a transformer, the printed circuit board is provided with a conductor made of a metal coating or a metal foil in a sandwich shape on both sides of the back surface on which the flat fluorescent lamp is located, One of the conductors is connected to a positive high voltage on the secondary side of the high frequency transformer,
The flat fluorescent lamp device, wherein the other of the conductors is connected to the auxiliary electrode.