JP2002208379A - Rare-gas fluorescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare-gas fluorescent lamp of high efficiency and high illumination intensity which does not need an insulation tube. SOLUTION: With the rare-gas fluorescent lamp arranging one electrode along a tube axis direction of a tubular glass bulb as an inner electrode, and the other electrode outside the glass bulb as an outer electrode, the former covered with a dielectric layer, and in which rare gas is sealed in the glass bulb and a phosphor film is formed in the glass bulb except for an aperture part, area of the inner electrode per unit length of the glass bulb toward the tube axis direction is characteristically smaller than that of the outer electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light source for general lighting,
The present invention relates to a rare gas fluorescent lamp used as a light source for illuminating a document such as a facsimile or a copying machine, a light source for a liquid crystal panel backlight, or the like.

[0002]

2. Description of the Related Art Conventionally, in a rare gas fluorescent lamp used for illuminating a document in information equipment such as a facsimile, a copying machine, and an image reader, or for a backlight of a liquid crystal panel display, a glass bulb forming a discharge vessel An external electrode type rare gas fluorescent lamp is known, in which a pair of strip-shaped electrodes extending in the length direction are disposed on the outer wall of the lamp facing each other, and is widely used because it does not use mercury and provides high illuminance. It has been used. Recently, as the speed of a copying machine increases and the reading resolution increases, a lamp with low power consumption, that is, high efficiency and high illuminance is demanded.

For example, Japanese Unexamined Patent Publication No. 3-225745 discloses a technique relating to the rare gas fluorescent lamp described above. In general, a rare gas fluorescent lamp of an external electrode type needs to apply a high voltage to both electrodes in order to apply a voltage via a discharge vessel. Is subjected to insulation treatment. As this insulation treatment, measures such as covering the electrode with a transparent tube and covering the electrode with a glass bulb have been taken.

On the other hand, JP-A-11-25923 proposes an internal electrode type rare gas fluorescent lamp in which electrodes are provided on the inner surface of a discharge vessel. According to the technology disclosed in this publication, in a conventional internal electrode type rare gas fluorescent lamp in which an internal electrode made of a metal wire is provided substantially at the center of the tubular glass bulb in the axial direction, the thermal expansion coefficient of the metal wire and the tubular glass bulb is large. The conductive member is tightly fixed to the inner surface of the glass bulb together with the low-melting glass in order to prevent the occurrence of excessive pulling and loosening due to the difference in the temperature.

However, in the technology disclosed in Japanese Patent Application Laid-Open No. 3-225745, it is inevitable to increase the input to some extent in order to increase the illuminance. However, when the input is increased, the surface temperature of the lamp increases. In addition, the cumulative lighting time of the lamp is increased, and the transparent tube is deteriorated and colored by the heat generated by the lamp and the high voltage, and the amount of lamp light is attenuated.

In the technique disclosed in Japanese Patent Application Laid-Open No. H11-25923, a high voltage is applied to the internal electrodes, so that a transparent tube for insulation is not required unlike the above example.

Further, it is considered that the phosphor film on the internal electrode also functions as a dielectric, but its thickness is smaller than that of a glass bulb. That is, since the thickness of the dielectric layer is thin, the internal electrode type becomes a lamp with higher efficiency than the external electrode type. However, in the lamp described in this publication, the lead wire to the internal electrode is exposed in the discharge space. However, there is a problem that discharge is likely to be concentrated at the location, and this is not a technique sufficient for realizing a lamp with low power consumption and high illuminance.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rare gas fluorescent lamp with high efficiency and high illuminance which does not require an insulating tube.

[0009]

In order to solve this problem, according to the first aspect of the present invention, one electrode is disposed inside the glass bulb along the tube axis direction of the tubular glass bulb. An electrode, the internal electrode is covered with a dielectric layer, the other electrode is disposed outside the glass bulb and used as an external electrode, a rare gas is sealed in the glass bulb, and an aperture is formed inside the glass bulb. In the rare gas fluorescent lamp on which the phosphor film is formed, the area of the internal electrode per unit length in the tube axis direction of the glass bulb is smaller than the area of the external electrode per unit length in the tube axis direction. It is a rare gas fluorescent lamp characterized by the above.

According to a second aspect of the present invention, the electrostatic capacitance formed between the internal electrode and the dielectric layer and between the phosphor film and the discharge space is such that the external electrode, the glass bulb and the fluorescent light 2. The rare gas fluorescent lamp according to claim 1, wherein the capacitance is smaller than a capacitance formed between the body film and the discharge space.

[0011] As for the capacitance here,
This will be described with reference to the equivalent circuit shown in FIG. In FIG. 3, the phosphor film is omitted. For example, regarding the capacitance (Ci) on the internal electrode side, the area (S
i), the thickness of the dielectric layer (Di), and the dielectric constant of the dielectric layer (ε
From i), Ci = εi · Si / Di is obtained. Further, the capacitance (Co) on the external electrode side is calculated from the area (Sg) of the external electrode, the thickness (Dg) of the glass bulb, and the dielectric constant (εg) of the glass bulb.
= Εg · Sg / Dg.

The capacitors having these capacitances are:
For example, it can be explained by a series connection with a resistance component R expressed as a function of time called discharge plasma. Here, the effects of the present invention can be explained by the above definition without considering the spatial bending or twisting of the external electrode or the internal electrode. The method for measuring the dielectric constant will be described later.

The invention according to claim 3 is characterized in that the internal electrode and the external electrode are arranged closer to each other on the side opposite to the aperture than on the side of the aperture. Of the rare gas fluorescent lamp.

According to a fourth aspect of the present invention, the internal electrode disposed on the inner surface of the glass bulb in the longitudinal direction of the glass bulb and the external electrode disposed on the outer surface of the glass bulb are connected in the shortest way. When the line segment is IE, the line segment I
The length of 0 <IG, where G is a boundary point between the glass bulb and the discharge space in E, wherein 0 <IG.
And a rare gas fluorescent lamp described in (1).

[0015]

When the area of the internal electrode per unit length in the tube axis direction of the glass bulb is smaller than the area of the external electrode, the dielectric constant of the dielectric layer and the phosphor film covering the internal electrode is reduced by the glass. Irrespective of the magnitude of the dielectric constant of the bulb, the electric energy supplied to the internal electrode having a relatively small area is efficiently converted into a discharge plasma, and after the emission process from the plasma, the area is relatively reduced via a glass tube. Is sufficiently transmitted to the large external electrode.

Further, a capacitance formed between the internal electrode and the dielectric layer and between the phosphor film and the discharge space is a capacitance formed between the external electrode and the glass bulb and the discharge space. By being smaller, the electric energy supplied to the internal electrode is more efficiently converted into a discharge plasma, and after the radiation process from the discharge plasma, is sufficiently transmitted to the external electrode via the glass bulb.

Further, at least one of the internal electrode and the external electrode is arranged closer to each other on the anti-aperture side than on the aperture side.
The shortest distance between the external electrode and the internal electrode is shortened, the discharge starting voltage is reduced, and even if the gas pressure is increased, uniform discharge can be easily obtained over the entire length of the lamp.

Further, in the technical idea of the present invention, the gas to be filled also includes an excimer-producing gas. For example, when an excimer-producing gas is used, the pressure in the discharge plasma is increased by increasing the pressure of the filling gas. Excimer generation efficiency is increased, and the generation of ultraviolet light from the excimer is increased. That is, the generation efficiency of ultraviolet light can be improved with the same electric energy, and a brighter lamp can be provided that is converted into visible light by the phosphor. Here, the internal electrode and the external electrode are
On the aperture side, it is possible to limit the approach to each other in order to secure the aperture portion, but on the anti-aperture side, it is not limited to this, and it is easy to set an optimal position.

The shortest line connecting the internal electrode disposed on the inner surface of the glass bulb in the longitudinal direction of the glass bulb and the external electrode disposed on the outer surface of the glass bulb is defined as IE. If 0 <IG when the boundary point between the glass bulb and the discharge space is G, the loss in the glass bulb can be minimized, and the electric energy can be efficiently converted into the discharge plasma.

[0020]

Embodiments of the present invention will be described. 1 and 2 are schematic sectional views of the rare gas fluorescent lamp according to the present invention, FIG. 1 is a sectional view perpendicular to the tube axis, and FIG. 2 is a sectional view along the tube axis. A pair of external electrodes 4 and internal electrodes 5 are disposed on the glass bulb 2,
The frit 9 is used to seal one end of the glass bulb. A dielectric layer 8 is coated on the inner surface of the internal electrode 5, and a phosphor film 6 is provided thereon. The inner surface of the internal electrode 5 may be covered with the phosphor film 6 and the dielectric layer 8 may be omitted. In this case, the insulating film in the glass bulb is inferior, but the phosphor film also functions as a dielectric layer. The capacitance of each electrode part was calculated in order to investigate that the relationship between the electrode area of the internal electrode and the external electrode affected the lamp efficiency. The electrode portion is a region including a member with which the electrode is in contact.

The capacitance of each electrode is obtained as follows. C = εS / d (1) S: electrode area d: thickness of the discharge space side dielectric layer (and / or phosphor) in the case of the internal electrode (the thickness of the glass bulb in the case of the external electrode) ε ... In the case of the internal electrode part, the dielectric constant of the discharge space side dielectric layer (measured separately) In the case of the external electrode part, ε is determined from the relative dielectric constant (catalog value) of the glass bulb.

FIG. 6 shows the external electrode and the internal electrode in the rare gas fluorescent lamp in which the electrode length is 0.36 m for both the internal and external electrodes and the electrode area is changed by changing the electrode width. It is the result of having measured. The dielectric constant of glass ε _g = 7 × 10 ⁻¹² F / m, and the dielectric constant of the dielectric layer ε _Z = 3 × 10 ⁻¹² F / m.

As can be seen from the above equation (1), a predetermined capacitance can be obtained by changing the dielectric constant ε and the thickness d even when the electrode area is constant.

From the measurement of the electrode capacity and the illuminance, it is found that the smaller the area of the internal electrode (per unit length) is, the smaller the area of the external electrode is, the larger the illuminance of the lamp is.
Furthermore, the area of the internal electrode (per unit length) is smaller than the area of the external electrode, and the capacitance formed between the internal electrode and the discharge space is the capacitance formed between the external electrode and the discharge space. It can be seen that the lamp illuminance is further increased when it is smaller.

In the present invention, if the area of the internal electrode per unit length is made smaller than the area of the external electrode per unit length partially along the tube axis direction, not along the entire length of the glass bulb, the brightness of the rare gas fluorescent lamp is reduced. It is also possible to change the illuminance (illuminance of the irradiation surface) in the tube axis direction.

Here, a phosphor for evaluating the capacitance formed between the internal electrode, the dielectric layer and the discharge space, and the capacitance formed between the external electrode, the glass bulb and the discharge space. A method for evaluating the dielectric constant of the film and the dielectric layer will be described with reference to FIG.

<Evaluation Method of Dielectric Constant> FIG. 4 is a diagram for explaining a dielectric constant measurement method. Two electrodes 10 are printed on a plate glass 9 to form two sheets, a phosphor film 11 is formed on one of the sheets, and the other is sandwiched and fixed so that the electrode 10 contacts the phosphor film 11. Then, an LCR meter (HIOKI 3531) is connected between the electrodes 10 and 10, and the capacitance C
Is measured. Pre phosphor film thickness d, measured beforehand the electrode area S, which than the dielectric constant, exactly the vacuum of the dielectric constant .epsilon.s for dielectric constant epsilon ₀ is εs = C · d / (ε 0 · S) relationship Obtained from the formula. The phosphor film 11 shown here may be a multilayer film including, for example, a reflection film and a dielectric film for insulating the internal electrodes. The thickness of the phosphor film or the dielectric layer disposed on the inner surface of the glass tube or the like may be measured by optically enlarging with a microscope or the like.

Since the inner electrode and the outer electrode are arranged closer to each other on the anti-aperture side than the aperture side, the shortest distance between the outer electrode and the inner electrode is shortened, the discharge starting voltage is reduced, and the charged gas is reduced. Even if the pressure is increased, a bright and uniform discharge can be easily obtained over the entire length of the lamp.

FIGS. 7A to 7C show that the valve outer diameter is 8
A rare gas fluorescent lamp using a glass tube having a φ of 0.55 mm in thickness and having a constant width of 4 mm for the internal electrode 5 is shown in a cross section perpendicular to the tube axis direction. The aperture 7 has an opening angle (α) from the center of the lamp downward of 65.4 ° in the figure, and is formed by removing the phosphor film 6 on the inner surface of the glass bulb 2 in the tube axis direction. . Note that the dielectric layer covering the internal electrodes 5 is omitted from the drawing for convenience. The angle (β) between the phosphor film end 6A and the aperture-side end 5A of the internal electrode is 2
With the position of the internal electrode 5 fixed at 4.9 °, the width of the external electrode 4 is fixed at 6 mm, and the position of the external electrode 4 is gradually reversed in the order of FIGS. 7 (a) to 7 (c). It is shifted to the aperture side. FIG. 7A shows an example in which the internal electrode and the external electrode are closer on the aperture side than on the anti-aperture side. FIG. 7B and FIG.
In this case, the position of the external electrode 4 is gradually shifted toward the anti-aperture side, so that the internal electrode and the external electrode are closer to each other than the aperture side.

The illuminance on a plane 8 mm away from the rare gas fluorescent lamp shown in FIGS. 7A to 7C is 26000 lux for the lamp of FIG. 7A and the illuminance of FIG. In the lamp of FIG. 7C, the internal electrode and the external electrode increased to 27,600 lux as the inner electrode and the outer electrode approached on the anti-aperture side rather than on the aperture side.

Similarly, the rare gas fluorescent lamps shown in FIGS. 7D to 7F have a bulb outer diameter of 8φ and a wall thickness of 0.55.
A rare gas fluorescent lamp using a mm glass tube,
A rare gas fluorescent lamp in which the width of the internal electrode 5 is fixed to 4 mm is shown in a cross section perpendicular to the tube axis direction. Aperture 7
In the figure, the opening angle (α) from the lamp center is 6
It has a width of 5.4 ° and is formed by removing the phosphor film 6 on the inner surface of the glass bulb in the tube axis direction. The dielectric layer covering the internal electrodes 5 is omitted from the drawing for convenience. The angle (β) between the phosphor film edge 6A and the aperture-side edge 5A of the internal electrode is kept constant at 24.9 °, and the width of the external electrode 4 is kept constant at 8 mm with the position of the internal electrode 5 fixed. The positions of the external electrodes 4 are gradually shifted in the order from FIG. 7D to FIG. 7F toward the anti-aperture side. In FIG. 7 (d), a glass tube having a bulb outer diameter of 8φ and a wall thickness of 0.55 mm is used, and the width of the internal electrode 5 is set to 4 mm.
mm and the width of the external electrode 4 are constant at 8 mm, the aperture angle (α) is 65.4 °, and the phosphor film end 6A.
This is an example in which the distance between the internal electrode and the external electrode on the most anti-aperture side is widened when the angle (β) formed between the internal electrode and the aperture end 5A of the internal electrode is kept constant at 24.9 °.

The illuminance on a plane 8 mm away from the rare gas fluorescent lamp shown in FIGS.
Compared to the illuminance of 27700 lux in (d), FIG.
In the case of the lamp of FIG.
In the lamp of (c), the internal electrode and the external electrode increased to 28800 lux as the distance between the inner electrode and the outer electrode became closer on the anti-aperture side than on the aperture side.

Here, the illuminance data is data in which the arrangement of the internal electrode 5 and the aperture 7 is fixed and only the external electrode 4 is moved. This is a relative positional relationship, and the illuminance data is fixed. The internal electrode 5 and the external electrode 4
Both may be brought closer to the anti-aperture side, or even if the external electrode 4 is fixed and only the internal electrode 5 is brought closer to the anti-aperture side, the effect of increasing the illuminance by bringing the internal electrode and the external electrode closer on the anti-aperture side is the same. Becomes

As shown in FIG. 5, a line segment connecting the inner electrode provided on the inner surface of the glass bulb in the longitudinal direction of the glass bulb and the outer electrode provided on the outer surface of the glass bulb in the shortest distance. Is defined as IE, and if the boundary point between the glass bulb and the discharge space is G in the line segment IE, 0 <
If a rare gas fluorescent lamp having an IG length is used, the loss in the glass bulb can be minimized, and electric energy can be efficiently converted to discharge plasma.

In relation to the shortest connected line segment IE, for example, when a high voltage is applied to the internal electrode and the external electrode is grounded, a part of the line of electric force passes from point I through point G to point E. Reach. Here, the lines of electric force between point I and point G contribute to the discharge, but between point G and point E are simply glass bulbs (dielectric).
Not only does not contribute to discharge but also causes loss such as heat generation due to dielectric loss.

Therefore, it is desirable to keep the distance between the points G and E as small as possible to the thickness of the glass bulb. By setting 0 <IG, loss in the glass bulb can be minimized, electric energy can be efficiently converted to discharge plasma, and a rare gas fluorescent lamp with high efficiency and high illuminance can be obtained.

FIGS. 7 (g) to 7 (i) show specific examples. FIGS. 7 (g) to 7 (i) show a rare gas fluorescent lamp using a glass tube having a bulb outer diameter of 8φ and a wall thickness of 0.55 mm, wherein the width of both the inner electrode 5 and the outer electrode 4 is constant at 6 mm. The noble gas fluorescent lamp is shown in a cross section perpendicular to the tube axis direction.

The aperture has an opening angle (α) from the center of the lamp downward of 65.4 ° in the figure, and is formed by removing the phosphor film on the inner surface of the glass bulb in the tube axis direction. . Note that the dielectric layer covering the internal electrodes 5 is omitted from the drawing for convenience. The angle (β) between the end of the aperture and the end of the internal electrode is kept constant at 24.9 °, and the position of the internal electrode is fixed, and gradually from FIG. 7D to FIG. 7F. The position of the external electrode is shifted toward the non-aperture side. FIG. 7D shows the relationship of 0 <IG, and the illuminance was 28100 lux. However, in FIG. 7 (h) and FIG. 7 (i) in which IG = 0, the values decreased to 24600 lux and 19700 lux, respectively.

In the case where the external electrode and the internal electrode have a deformed portion, there may be scattered places where 0 <IG is satisfied or not, but the effect of the present invention is recognized even in such a case. Can be The reason is that, due to the efficient conversion of electric energy into discharge plasma at the location where 0 <IG is satisfied, a higher illuminance can be obtained with a fluorescent substance than at the location where 0 <IG is not satisfied. This is because the illuminance at the location where is not satisfied is compensated for.

[0040]

According to the first aspect of the present invention, when the area of the internal electrode per unit length in the tube axis direction of the glass bulb is smaller than the area of the external electrode, the internal electrode is covered. Regardless of the magnitude of the dielectric layer with respect to the dielectric constant of the glass bulb, the electric energy supplied to the relatively small-area internal electrode is efficiently converted into a discharge plasma, and after the plasma is radiated, the electric energy is converted through the glass tube. As a result, a sufficient efficiency and a high illuminance of a rare gas fluorescent lamp can be obtained by sufficiently transmitting to the external electrode having a relatively large area.

Further, according to the second aspect of the present invention, since the dielectric constant of the internal electrode portion is smaller than the dielectric constant of the external electrode portion, the electric energy supplied to the internal electrode is more efficiently converted into a discharge plasma. After the emission process from the discharge plasma, the light is sufficiently transmitted to the external electrode via the glass bulb, thereby providing a rare gas fluorescent lamp with high efficiency and high illuminance.

According to the third aspect of the present invention, the luminous efficiency of the lamp is improved, and uniform discharge can be obtained over the entire lamp. Also, on the aperture side, it is possible to limit the approach to each other, but on the anti-aperture side,
However, the present invention is not limited to this, and it is easy to set an optimal position for the arrangement of the aperture and the electrode, assuming that the lamp is mounted on an irradiation device or the like.

According to the fourth aspect of the present invention, the internal electrode disposed on the inner surface of the glass bulb in the longitudinal direction of the glass bulb and the external electrode disposed on the outer surface of the glass bulb are shortest. When the line segment is IE and the boundary point between the glass bulb and the discharge space is G in the line segment IE, 0 <I
When the length is G, the loss in the glass bulb can be minimized, electric energy can be efficiently converted to discharge plasma, and a rare gas fluorescent lamp with high efficiency and high illuminance can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a rare gas fluorescent lamp of the present invention in a direction perpendicular to a tube axis.

FIG. 2 is a schematic cross-sectional view of a rare gas fluorescent lamp of the present invention in a direction along a tube axis.

FIG. 3 shows an equivalent circuit diagram of the rare gas fluorescent lamp device.

FIG. 4 is a diagram illustrating a dielectric constant measurement method.

FIG. 5 is a view for explaining the relationship of line segments in the invention of claim 3;

FIG. 6 is a table showing the effects of the present invention.

FIG. 7 is a diagram for explaining the arrangement of each electrode for explaining the effect of the present invention.

[Description of Signs] 1 Noble gas fluorescent lamp 2 Glass bulb 3 Closure 4 External electrode 5 Internal electrode 5A Aperture side end of internal electrode 6 Phosphor film 6A Phosphor film end 7 Aperture 8 Dielectric layer 9 Plate glass 10 Electrode 11 phosphor film

Claims (4)

[Claims] 1. An electrode is disposed inside a glass bulb along a tube axis direction of the tubular glass bulb to serve as an internal electrode. The internal electrode is covered with a dielectric layer, and the other electrode is disposed on the glass bulb. In a rare gas fluorescent lamp in which a rare gas is sealed inside the glass bulb and a phosphor film is formed inside the glass bulb except for an aperture portion, the external electrode is provided outside the bulb as an external electrode. A rare gas fluorescent lamp, wherein the area of the internal electrode per unit length is smaller than the area of the external electrode per unit length in the tube axis direction. 2. The electrostatic capacity formed between the internal electrode and the dielectric layer and between the phosphor film and the discharge space is determined by the capacitance between the external electrode, the glass bulb, the phosphor film and the discharge space. 2. The rare gas fluorescent lamp according to claim 1, wherein the capacitance is smaller than a capacitance formed between the fluorescent lamps. 3. The rare gas fluorescent lamp according to claim 1, wherein the internal electrode and the external electrode are arranged closer to each other on the anti-aperture side than on the aperture side. 4. A line segment connecting the internal electrode disposed on the inner surface of the glass bulb in the longitudinal direction of the glass bulb and the external electrode disposed on the outer surface of the glass bulb in the shortest direction is defined as IE. 4. The rare gas fluorescent lamp according to claim 3, wherein, when a boundary point between the glass bulb and the discharge space is G in the line segment IE, 0 <IG length.