JP2003187740A - Cold-cathode type electrode, discharge lamp and lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold-cathode type electrode which improves luminosity efficiency, a discharge lamp and a lighting unit provided with this cold-cathode type electrode. <P>SOLUTION: The cold-cathode type electrode 4 is provided with an exterior conductive tube 4a and an interior conductive tube 4b which has a conductive connection with the exterior conductive tube 4a and is coaxially arranged inside the exterior conductive tube 4a having a small space from the exterior conductive tube 4a. As the other structure, the cold-cathode type electrode 4 is also provided with a conductive tube formed of a sintered compact mainly composed of one kind or a plurality of kinds selected from among a group of Mo, W and Ta. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold cathode electrode, a discharge lamp having the same, and a lighting device.

[0002]

2. Description of the Related Art A discharge lamp having a cold cathode type electrode can be miniaturized, has low power consumption, and has a relatively long life. Therefore, a backlight for illuminating a liquid crystal display panel from its back side is provided. It is also widely used as a light source for small lighting devices. In this type of discharge lamp, a phosphor layer is formed on the inner surface of a glass bulb, and mercury as a discharge medium and a rare gas, for example, a mixed gas of neon and argon are enclosed,
A pair of cylindrical cold cathode electrodes are sealed inside both ends of the glass bulb.

[0003]

In this type of discharge lamp, further improvement in efficiency, longer life, and constant lamp characteristics during the life are expected to be improved.

Electrode loss is a factor that affects the luminous efficiency of the discharge lamp. The electrode loss is proportional to the cathode drop voltage.
When an electron emissive material is applied to the cold cathode electrode, electron emission is improved and the cathode drop voltage can be lowered.
As the electron emitting substance, a material mainly composed of a barium compound, a yttrium compound and a lanthanum compound is used.

However, since the electron emissive material is scattered by sputtering from the cold cathode electrode due to ion bombardment due to the discharge during lighting, it is gradually consumed. As a result, the cathode drop voltage gradually increases, and the lamp voltage accordingly increases. That is, the luminous efficiency is reduced during the life, the lamp characteristics are changed, and the life is shortened.

Further, in the case of a discharge lamp provided with a cold cathode type electrode, since the cold cathode type electrode is small, abnormal glow discharge and sputtering are likely to occur. That is, when a negative glow discharge is generated, mercury is sputtered on the inner surface of the translucent airtight container in the vicinity of the electrode in addition to the electron emissive material, and mercury is rapidly consumed, resulting in a decrease in luminous efficiency and a shortened life.

[0007] However, conventionally, there has not been found an appropriate remedy for solving these problems.

An object of the present invention is to provide a cold cathode electrode having improved luminous efficiency, a discharge lamp provided with the same, and a lighting device.

Further, according to the present invention, the luminance maintenance factor is improved,
Another object is to provide a cold cathode electrode having a long life, a discharge lamp including the same, and a lighting device.

[0010]

A cold cathode electrode according to the invention of claim 1 is an outer conductive cylindrical body; conductively connected to the outer conductive cylindrical body and coaxial with the inner side thereof; , And an inner conductive cylindrical body that is arranged with a small gap therebetween.

In the present invention and the following inventions, the definitions and technical meanings of terms are as follows unless otherwise specified.

The outer conductive cylinder and the inner conductive cylinder are made of a suitable conductive material such as nickel, molybdenum,
It consists of a fusible metal or sintered body containing one or more of tantalum and tungsten as its main components. In addition,
The "melting metal" means a metal formed by a melting method. It suffices that the outer conductive cylinder has an outer diameter that can be disposed inside the transparent airtight container of the discharge lamp, and thus allows the maximum outer diameter to be equal to or smaller than the inner diameter of the transparent airtight container. In order to prevent the occurrence of negative glow discharge in the outer peripheral portion of the cold cathode electrode, it is preferable that the discharge space formed around the cold cathode electrode is as narrow as possible. A discharge lamp equipped with a cold cathode type electrode has a transparent airtight container with an inner diameter of 1.0 to
The outer conductive cylindrical body of the cold cathode type electrode suitable for such a discharge lamp has an outer diameter of about 0.4 to about 2.0 mm and a length of about 40 to 800 mm.
The thickness is about 2.0 mm, the wall thickness is about 0.1 to 0.3 mm, and the length is about 1.5 to 4 mm.

The inner conductive cylinder is conductively connected to the outer conductive cylinder and is coaxially arranged inside the outer conductive cylinder. In addition, a small space is formed between the outer conductive tubular body and the inner conductive tubular body. In addition, the "small interval" means that the gap formed thereby exhibits a hollow cathode effect.
When the inner diameter of the outer conductive cylindrical body is d1 and the outer diameter of the inner conductive cylindrical body is d2, a suitable numerical range (d1-d2) / 2 (mm) of the small interval is expressed by the following formula. The thickness is in a satisfactory range and the wall thickness is about 0.05 to 0.3 mm. However, the small distance d1-d2 is optimally 0.1 to
It is 0.7 mm.

0 <(d1-d2) / 2 <1 Thus, in the present invention, between the outer conductive cylindrical body and the inner conductive cylindrical body arranged coaxially inside thereof. Since the hollow electrode structure is formed in the small gaps that are formed, negative glow occurs in that part, and high-energy, high-density ions and photons hit the electrode, resulting in good electron emission. . As a result, the cathode drop voltage decreases. Along with this, the electrode loss is reduced and the luminous efficiency is improved. In addition, since sufficient electron emissivity can be obtained without using an electron emissive substance, the lamp voltage rises due to the gradual consumption of the electron emissive substance found in the conventional cold cathode electrode, and the lamp characteristics Does not occur, that is, the change in temperature and the shortening of life.

However, in the present invention, one or more kinds of materials mainly composed of one or more kinds selected from barium compounds, yttrium compounds, lanthanum compounds and the like are used as the electron emissive material, if desired. It can be applied to the inner surface and / or the outer surface of the tubular body and / or the inner conductive tubular body.
Even in such a configuration, since the action of the hollow electrode structure formed between the outer conductive tubular body and the inner conductive tubular body is unchanged, the above-described effects of the present invention can be obtained.

The cold cathode type electrode of the invention of claim 2 is Mo,
It is characterized in that it is provided with a conductive cylindrical body made of a sintered body containing one or more kinds selected from the group of W and Ta as a main component.

In the present invention, the conductive cylindrical body may have a single structure, or a plurality of cylindrical bodies arranged in a coaxial relationship with a small interval therebetween. Good.
Also, if desired, the electron emissive material can be applied to the outer and / or inner surface of the conductive tubular body. As the electron emissive substance, for example, a material containing, as a main component, one or more kinds of compounds selected from alkaline earth elements such as barium and rare earth elements such as yttrium and lanthanum can be used.

Thus, in the present invention, since the conductive tubular body is made of a sintered body of the above-mentioned metal, the electrode drop voltage and hence the lamp voltage are remarkably lowered, so that the electrode loss is reduced and the luminous efficiency is reduced. Is improved.

Further, sputtering by the electrode during lighting is suppressed, and consumption of mercury is reduced. As a result, the brightness retention rate is improved and the life is extended. Therefore, even when it is used as a backlight light source that requires a long life for large monitors and large televisions, it can sufficiently meet the expectation.

A discharge lamp according to a third aspect of the present invention is an elongated translucent airtight container; a pair of cold cathode electrodes according to claim 1 or 2 enclosed in the translucent airtight container; And a discharge medium containing mercury and a rare gas enclosed in an airtight container.

The translucent airtight container is generally formed of glass, but may be translucent material other than glass, such as ceramics, if necessary. Further, the glass may be hard glass, semi-hard glass or soft glass, quartz glass or microcrystallized glass. It should be noted that the term "translucent" means that the other part may be light-shielding as long as it is substantially translucent to the wavelength of the light used by the required part of the translucent airtight container. means.

The cross-section of the transparent airtight container, that is, the cross-section perpendicular to the discharge path, has an arbitrary inner surface shape, for example, a substantially circular shape, and its inner diameter is generally 5 mm or less, preferably It can be configured as a small-diameter tube of about 1.0 to 2.6 mm. However, if necessary, the cross section may be flat. The axial length of the translucent airtight container can be set according to the requirements of the lighting device to be used, but in the case of a tubular translucent airtight container, if it is 800 mm or less,
In practice, it can be set to any desired value. further,
The translucent airtight container is not limited to a straight tube and may have a curved or bent shape. For example, circular, semicircular,
L-shape, M-shape, U-shape, U-shape, V-shape, etc. are allowed. Further, the translucent airtight container is not limited to a tubular shape, and may be a flat plate shape if necessary.

Further, the translucent airtight container, when utilizing the ultraviolet rays generated from the phosphor layer, has a transmittance characteristic of transmitting the ultraviolet rays and utilizes the visible light generated by the phosphor layer. In this case, it has a transmittance characteristic of transmitting the visible light.

The pair of cold cathode electrodes may be formed according to claim 1 or 2.
Having the configuration described, in the translucent airtight container,
It is sealed via the discharge path, that is, generally at both ends inside the translucent airtight container so as to be spaced apart and opposed to each other.

The discharge medium contains mercury and a rare gas and is enclosed in a translucent airtight container. Mercury has a suitable amount of liquid mercury or mercury whose vapor pressure characteristics are relatively close to those of liquid mercury.
It can be encapsulated in the form of amalgam such as nHg or Gemedis. The rare gas acts as a starting gas and a buffer gas, and its type and filling pressure are not particularly limited, but it is preferable to use a mixture of neon and argon in an appropriate ratio. In addition, one or more other noble gases such as krypton, xenon and helium can be added if desired.

Although not an essential component of the present invention, by selectively adding the following components as necessary, the performance of the discharge lamp can be improved, the function can be increased, and the manufacturing can be facilitated. .

1 Phosphor Layer The phosphor layer wavelength-converts ultraviolet rays centered at a wavelength of 254 nm radiated by the low-pressure mercury vapor discharge of the discharge medium to generate visible light and longer-wave ultraviolet rays, and transmits them. It is used when leading out to the outside of the light tight container. Then, it is formed on the inner surface side of the translucent airtight container. Note that the phosphor layer is formed on the “inner surface side” of the translucent airtight container means that the phosphor layer is directly formed on the inner surface of the translucent airtight container and indirectly through a protective film or the like. It means that any structure formed on the inner surface of the transparent airtight container may be used.

As the phosphor used in the phosphor layer, any desired phosphor can be used depending on the application. For example, in the case of a fluorescent lamp for backlight devices, in-vehicle instrument lighting, color reading, and the like, a white phosphor such as a three-wavelength light-emitting phosphor or a halophosphate phosphor can be used. Further, in the case of a fluorescent lamp for monochrome reading, a rare earth phosphate phosphor (LaPO ₄ :
A green-based monochromatic phosphor such as Ce ³⁺ , Tb ³⁺ ) or a phosphor mainly containing this can be used.

Further, the phosphor layer may be formed over the entire circumference on the inner surface side of the translucent discharge vessel, or the phosphor layer may not be formed in a part along the axial direction of the translucent discharge vessel. May form an aperture.

2 Protective film The protective film is protected by mercury or discharge.
To block the ultraviolet rays emitted by the inside of the translucent airtight container
Al is a means to prevent it from reaching_TwoO_Three, T
iO _Two, SiO_Two, CeO_TwoAnd Y_TwoO_ThreeEtc.
Or composed mainly of fine particles of multiple types,
It is formed on the inner surface of the airtight container. Forming a protective film
This reduces mercury consumption and irradiates ultraviolet rays.
This makes it possible to prevent the glass from being colored.

3 Getter Member The getter member is a means for adsorbing and cleaning up the impure gas remaining inside the translucent airtight container, and a known one can be used. For example, when using a Zr-Al alloy, Fe
-A getter member obtained by sintering a Zr-Al alloy layer on the surface of a support base material made of a Ni alloy is used. Further, the getter member can be supported on the inside or the outside of the cold cathode type electrode and enclosed in a translucent airtight container.

4 Reflective Film A reflective film can be provided on a desired portion of the inner surface of the translucent airtight container. As the constituent material of the reflective film, for example, fine particles such as TiO ₂ or Al ₂ O ₃ can be used. A reflective film can be formed by adjusting a dispersion liquid of these materials, applying the dispersion liquid to the inner surface of the translucent airtight container except for the aperture portion, and baking. Then, by forming a reflective film,
The light emission of the discharge lamp can be directed in a desired direction.

Next, the operation of the present invention will be described. When the discharge lamp is lit, the low-pressure mercury vapor discharge mainly causes ultraviolet rays having a wavelength of 254 nm and a partial wavelength of 185 nm.
Ultraviolet radiation, including, is generated inside the translucent airtight container.
This ultraviolet radiation irradiates the phosphor layer formed on the inner surface side of the transparent airtight container according to the configuration of the discharge lamp, and is converted into visible light or long-wavelength ultraviolet light, and the transparent airtight container. It can be used for illumination because it can be emitted to the outside after passing through or can be directly transmitted through the translucent airtight container as ultraviolet rays.

Further, since the cold cathode electrode has the structure according to the first or second aspect, the luminous efficiency is improved, the consumption of mercury is significantly suppressed, and the life is extended.

The discharge lamp according to the invention of claim 4 has an inner diameter Bd.
And a pair of cold-cathode electrodes having an outer diameter Ed (mm) satisfying the following formula, which is enclosed in the light-transmitting airtight container; And a discharge medium containing mercury and a noble gas sealed in.

Bd-0.4 <Ed <Bd In the present invention, the inner diameter Bd of the transparent airtight container is 1 to 2
mm. As described above, in the small diameter tube, the lamp voltage and hence the electrode drop voltage are effectively reduced by satisfying the above conditions. In addition, a discharge lamp having a small-diameter tube of this degree is widely used as a light source for a backlight. The length of the translucent airtight container is 40 to 800 mm.
The degree is a suitable range.

The phosphor layer may or may not be provided on the inner surface side of the translucent airtight container. In the former case, the phosphor layer may or may not be formed on the portion facing the cold cathode electrode. In any case, visible light or ultraviolet light having a relatively long wavelength can be generated by wavelength conversion by the phosphor layer.

The structure of the pair of cold cathode electrodes is not limited as long as the outer diameter is within the above range, but since they have a tubular shape, a hollow cathode effect is produced inside the tube. This is preferable because it can be configured as follows. Further, as the pair of cold cathode electrodes, if desired, it is permissible to adopt the structure according to claim 1 or 2 and the structure incidental thereto. Furthermore, the cold cathode electrode is
In addition to the above conditions, the outer diameter is preferably 0.4 mm to 2 mm. Furthermore, the cold cathode electrode preferably has a wall thickness of 0.1 to 0.3 mm and a length of 1.5 to 4 mm. Furthermore, it is preferable that an electron emissive substance is applied. As an electron radioactive substance,
One or more selected from the group of barium compounds, yttrium compounds and lanthanum compounds can be used.

Thus, in the present invention, the cold cathode type electrode and the translucent airtightness are set by setting the outer diameter of the cold cathode type electrode within the above predetermined range in relation to the inner diameter of the translucent airtight container. 0.2 mm gap formed between the inner surface of the container
The following is true, and during glowing of the discharge lamp, negative glow discharge is unlikely to occur where there is an abnormal discharge on the outer peripheral portion of the cold cathode electrode. Therefore, the sputtering of mercury on the inner surface of the transparent airtight container in the vicinity of the cold cathode electrode is suppressed, and the consumption of mercury is reduced. Therefore, it is possible to avoid a decrease in luminous efficiency and a shortening of the life due to consumption of mercury.

The present invention also has the advantage of shortening the discharge delay time.

An illumination device according to a fifth aspect of the present invention comprises: an illumination device main body; a discharge lamp according to the third or fourth aspect, which is supported by the illumination device main body; and a lighting circuit for lighting the discharge lamp. It is characterized by that.

In the present invention, the "illuminating device" is a broad concept including all devices that utilize the light emission of a fluorescent lamp, such as a lighting fixture, a reading device, a backlight device and a liquid crystal display device including the same. , And various devices incorporating one or more of these. Examples of devices incorporating the reading device include OA devices such as copiers, facsimiles, and scanners. Examples of equipment incorporating a liquid crystal display device include a personal computer, a portable information terminal, a liquid crystal television image receiving device, a liquid crystal display device incorporating equipment such as a car navigation device, and an instrument panel lighting device for a mobile body such as an automobile, and a decorative device. Lighting fixtures are applicable. The light generated by the fluorescent lamp is not limited to visible light, and may be ultraviolet light if necessary.

The "illuminator main body" refers to the remaining portion of the illumination device excluding the fluorescent lamp and the lighting circuit. Further, the lighting circuit may have any structure as long as it can light the fluorescent lamp, but from the viewpoints of downsizing, weight saving and high efficiency, it is preferable to mainly use a high frequency inverter.

[0044]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show a first embodiment of a cold cathode electrode of the present invention and a discharge lamp provided with the same, and FIG. 1 is a conceptual front view of a principal part for perspectively explaining the main part. ,
FIG. 2 is a perspective view of an essential part for explaining the dimensional relationship of the cold cathode electrode. The present invention is the invention described in claim 1. In each figure, the discharge lamp DL is configured to include a light-transmitting airtight container 1, a phosphor layer 2, a pair of lead-in wires 3, 3, a pair of cold cathode electrodes 4, 4 and a discharge medium.

The translucent airtight container 1 has an outer diameter of 2.6 mm, an inner diameter of 2.0 mm, a cross-sectional shape of substantially a circle, and an overall length of 300 m.
m. This translucent airtight container 1 is formed by bead-sealing both ends of an elongated glass bulb 1a. That is, the translucent airtight container 1 is formed by sealing both ends of the elongated glass bulb 1a by glass welding of the pair of bead glasses 1b, 1b.

The phosphor layer 2 is mainly composed of a three-wavelength light-emitting phosphor, and is arranged on the inner surface side of the translucent airtight container 1.

The pair of introduction lines 3 and 3 are transparent airtight container 1
Is hermetically pierced, and is supported by welding a discharge-generating means 4 described later to its inner tip. In addition, the pair of lead-in wires 4 and 4 are glass-welded in advance to the bead glass 1b, and after forming a bead mount in which the discharge-generating means 4 is supported at the tip, the bead glass 1b is formed.
By glass-welding both ends of the glass bulb 1a, the light-permeable airtight container 1 is airtightly penetrated, and a cold cathode electrode 4 described later is sealed at a predetermined position inside the light-permeable airtight container 1. There is.

Each of the pair of cold cathode electrodes 4 and 4 is composed of an outer conductive cylindrical body 4a and an inner conductive cylindrical body 4b made of metal containing nickel as a main component. The outer conductive tubular body 4a and the inner conductive tubular body 4b are conductively connected to each other and are fitted in a coaxial relationship. Then, a small space is formed between the outer conductive cylindrical body 4a and the inner conductive cylindrical body 4b. In the present embodiment, as shown in FIG. 3, the inner diameter d1 of the outer conductive cylindrical body 4a is 1.7 mm, and the outer diameter d2 of the inner conductive cylindrical body 4b is 1.5 mm. Therefore, the outer conductive cylindrical body 4a
And the small gap formed between the inner conductive cylindrical body 4b and
It is 0.1 mm. In addition, a pair of cold cathode type electrodes 4, 4
In each of the above, the center of the base end is welded to the tip of the lead-in wire 3. The electron emissive material was not applied to the cold cathode electrode.

The discharge medium is a rare gas composed of mercury and a mixed gas of neon and argon.

FIG. 3 is a graph showing the change of the lamp voltage with respect to the elapsed time of lighting in the first embodiment of the cold cathode electrode and the discharge lamp of the present invention together with that of the comparative example. In the figure, the horizontal axis represents the elapsed time (Hrs) and the vertical axis represents the lamp voltage (Vrms). Further, the curve A is the present invention, the curve B is the comparative example 1, the curve C is the comparative example 2,
Are shown respectively. Comparative Example 1 is a discharge lamp having the same specifications as the present embodiment except that the cold cathode electrode is composed only of the outer conductive cylindrical body. In addition, in Comparative Example 2, in addition to the configuration of Comparative Example 1, an electron emitting substance is applied to the outer conductive cylindrical body. The measurement conditions of the data are that the ambient temperature is 25 ° C. and the lamp current Il is 8 mA.

As is apparent from the figure, according to the present invention,
The lamp voltage is kept approximately constant at about 390V from the initial lighting up to 10,000 hours, and the lamp characteristics are stable for a long period of time. On the other hand, Comparative Example 1
In the above example, the lamp voltage remains almost constant from the initial lighting up to 10,000 hours, but the value is 420V, which is 30V higher than that of the present invention. This is because the electrode drop voltage is high, and therefore, in comparison with this, the low electrode drop voltage in the present invention means that high luminous efficiency can be obtained. Further, according to Comparative Example 2, by applying the electron emissive material, the lamp voltage becomes lower than that of the present invention from the initial lighting up to 5000 hours, but it is 500
After 0 hours, it becomes higher than that of the present invention, and at about 7,000 hours, the lamp voltage becomes almost the same as that of Comparative Example 1. Therefore, in Comparative Example 2, it means that the change in the lamp characteristics during the life is large because the change in the lamp voltage is large. In Comparative Example 2, the electron-emissive substance was significantly consumed due to sputtering, and almost disappeared after 7,000 hours.

FIG. 4 is a graph showing the relationship between the lamp current and the lamp voltage in the first embodiment of the cold cathode electrode and the discharge lamp of the present invention together with that of Comparative Example 1. In the figure, the horizontal axis represents the lamp current (mA) and the vertical axis represents the lamp voltage (Vrms). Also, curve A
Shows the present invention, and curve B shows a comparative example. The comparative example has the same configuration as the comparative example 1 in FIG. The ambient temperature at the time of data measurement is 25 ° C.

As is apparent from the figure, according to the present invention,
It will be appreciated that a low lamp voltage is always obtained regardless of the lamp current. Further, the lamp current and the lamp voltage change linearly.

FIG. 5 is a graph showing the relationship between the small space between the cold cathode electrodes and the lamp voltage in the first embodiment of the cold cathode electrodes and discharge lamp of the present invention. In the figure, the horizontal axis represents the small interval (d1-d2) / 2 (mm), and the vertical axis represents the lamp voltage (Vrms).

As can be seen from the figure, the small interval (d1-
If d2) / 2 is 1 mm or less, the lamp voltage decreases. Especially when the small interval is 0.7 mm or less, a sufficiently low lamp voltage can be obtained.

Hereinafter, another embodiment of the cold cathode electrode and the discharge lamp of the present invention will be described with reference to FIGS. 6 to 11. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

6 to 8 show a second embodiment, FIG. 6 is a longitudinal sectional view of a main part of a discharge lamp, and FIG. 7 is a graph showing the relationship between a lamp current and a lamp voltage together with those of a comparative example. 8 is a graph showing the relationship between the lighting time and the luminance maintenance rate together with that of the comparative example. The present invention provides claim 2
It is the invention described in.

In the cold cathode type electrode 4, the conductive cylindrical body 4c is M
It is formed of a sintered body of o. Conductive tubular body 4c
Has a cylindrical shape as a whole, and the base end portion 4c1 has a reduced diameter. Then, the base end portion 4c1 is inserted into the inner end of the introduction wire 3, and is welded and supported. Also,
The cold-cathode type electrode 4 includes an electron emissive substance 5 and a conductive cylindrical body 4
It is carried on both the inner and outer surfaces of c. The electron radioactive substance 5 is
It is mainly composed of a barium compound, and about 0.5 g thereof is applied. The barium compound is
It has an EXO electron emission function.

The translucent airtight container 1 has an outer diameter of 1.8 mm, an inner diameter of 1.4 mm and a total length of 200 mm, and its cross section is substantially circular. A pair of cold cathode electrodes 4 are sealed at both ends inside the translucent airtight container 1 with an inter-electrode distance of 188 mm, so that a discharge space is formed between the pair of cold cathode electrodes 4, 4. .

The lead-in line 3 is made of W.

Thus, in the present embodiment, as indicated by the curve D in FIG. 7, the lamp voltage for various values of the lamp current in the discharge lamp DL becomes lower than the curve E indicating that in the comparative example. In the figure, the horizontal axis represents the lamp current (mA) and the vertical axis represents the lamp voltage (V). In addition, the comparative example is a discharge lamp having the same specifications as the present embodiment except that the conductive tubular body of the cold cathode type electrode is formed by pressing a molten metal plate of Ni.

Next, as shown by the curve D in FIG. 8, the luminance retention ratio characteristic of this embodiment is clearly superior to the curve E showing that of the comparative example. In addition, in the comparative example, mercury disappeared at 17,000 hours of lighting, a rare gas discharge was generated, and the life was reached. On the other hand, in the present embodiment, even if the lighting is performed for 20000 hours, 6
The brightness of 0% is maintained, which is about 1400 of the comparative example.
This corresponds to the brightness retention rate at 0 hours. In FIG. 8, the horizontal axis represents the lighting time (Hr) up to 25,000 hours.
Is the luminance maintenance rate (%) with the vertical axis as 100%
Are shown respectively.

9 to 11 show the third embodiment, FIG. 9 is a partially cutaway vertical sectional view of the discharge lamp, FIG. 10 is a graph showing the relationship between the outer diameter of the electrode and the discharge delay time, and FIG. 6 is a graph showing the relationship between the outer diameter playing card voltage of the electrode. The present invention is the invention described in claim 4.

The transparent airtight container 1 has an outer diameter of 1.8 mm, an inner diameter of 1.4 mm and a total length of 290 mm. The phosphor layer 2 is
It is mainly composed of a three-wavelength emission type phosphor. The lead-in wire 3 is a W wire having an outer diameter of 0.6 mm.

The cold cathode electrode 4 is made of Mo, and the electron emissive material 5 mainly containing barium oxide is applied to both the inner and outer surfaces of the conductive cylindrical body 4c having an outer diameter of 1.1 mm and a length of 3 mm. . A gap of 0.15 mm is formed between the cold cathode electrode 4 and the inner surface of the translucent airtight container 1.

The discharge medium is composed of mercury and a rare gas mixed with neon and argon.

FIG. 10 shows changes in the lamp voltage when the outer diameter of the cold cathode electrode of the discharge lamp is variously changed with respect to the inner diameter of the transparent airtight container in this embodiment. In the figure, the horizontal axis represents the outer diameter Ed (mm) of the electrode, and the vertical axis represents the lamp voltage (V).

As can be seen from the figure, the cold cathode electrode 4
If the outer diameter Ed is 1/2 or more of the inner diameter Bd of the translucent airtight container 1, the lamp voltage is significantly reduced, and the outer diameter Ed is the lowest in the vicinity of 3/4 of the inner diameter Bd.

Next, FIG. 11 shows the discharge delay time when the outer diameter of the cold cathode type electrode of the discharge lamp is variously changed with respect to the inner diameter of the transparent airtight container. In the figure, the horizontal axis represents the outer diameter Ed (mm) of the electrode, and the vertical axis represents the discharge delay time (second). Further, the straight line extending in the vertical direction shows the maximum and minimum distribution of the discharge delay time in each electrode outer diameter, the curve shows the distribution of the average value in each electrode outer diameter,
The dotted line extending in the horizontal direction indicates the standard value.

As can be understood from the figure, the discharge delay time may be equal to or shorter than the standard value, so that the outer diameter Ed of the cold cathode electrode 4 is 1/2 or more of the inner diameter Bd of the transparent airtight container 1. For example, even if the variation is taken into consideration, the discharge delay time is remarkably shortened, and the discharge delay time is shortened as the outer diameter Ed approaches the inner diameter Bd.

FIG. 12 is a conceptual partially sectional front view showing a liquid crystal backlight device as an embodiment of the illuminating device of the present invention and a sectional view taken along the line AA '.

The liquid crystal backlight device is of a direct type, and includes a backlight device main body 11 and a plurality of fluorescent lamps 12.
And a lighting circuit (not shown).

The backlight device main body 11 includes a diffusion plate 11
a, the back reflector 11b and the case 11c. The diffusion plate 11a constitutes a light emitting surface of the backlight device. The back reflector 11b includes a plurality of recesses 11b.
1 and each recess 11b1 is arranged so as to surround the back of the fluorescent lamp 12, and the diffusion plate 1
The light emitted from the fluorescent lamp 12 is reflected in a direction that does not directly enter the light la 1a and enters the light guide 11a. Case 1
1 c houses the back reflector 11 b, the fluorescent lamp 12 and the diffuser 11 a in a predetermined positional relationship.

The plurality of fluorescent lamps 12 have the structure shown in FIG. 1 and are arranged in the recess 11b1 of the back reflector 11b.

Then, a liquid crystal display unit (not shown) is arranged on the front surface of the diffusion plate 11a. Then, the liquid crystal display unit is illuminated by the backlight device main body 11 from its back surface, and a transmissive liquid crystal display is performed.

[0077]

According to the first aspect of the present invention, the outer conductive cylindrical body is electrically connected to the outer conductive cylindrical body and is coaxially arranged inside the outer conductive cylindrical body with a small space therebetween. By including the inner conductive cylindrical body which is, the electron emission becomes good, the cathode drop voltage is lowered, and along with this, the electrode loss is reduced and the luminous efficiency is improved.
Since a sufficient electron emission property can be obtained without using an electron emission substance, it is possible to provide a cold cathode electrode in which the lamp characteristics are hard to change and the life is not shortened.

According to the second aspect of the present invention, since the conductive tubular body is provided, which is made of a sintered body containing one or more kinds selected from the group of Mo, W and Ta as a main component, It is possible to provide a cold cathode electrode in which the electrode loss is reduced and the luminous efficiency is improved, and the consumption of mercury is reduced to improve the luminance maintenance rate and the life is long.

According to the third aspect of the present invention, the slender translucent airtight container and the translucent airtight container are sealed inside.
Or a pair of cold cathode electrodes according to claim 2; and a discharge medium containing mercury and a rare gas enclosed in a translucent airtight container, whereby a discharge lamp having a drop according to claim 1 or 2 is provided. Can be provided.

According to the invention of claim 4, the inner diameter Bd is 1 to
2 mm elongated translucent airtight container; a pair of cold cathode electrodes whose outer diameter Ed (mm) sealed inside the translucent airtight container satisfies the following formula, and enclosed in the translucent airtight container And a discharge medium containing mercury and a rare gas, the sputtering of mercury on the inner surface of the transparent airtight container in the vicinity of the cold cathode electrode is suppressed during operation of the discharge lamp. It is possible to provide a discharge lamp capable of avoiding a decrease in luminous efficiency and a shortening of the life due to the exhaustion of the lamp, and shortening the discharge delay time.

Bd-0.4 <Ed <Bd According to the invention of claim 5, the invention is supported by the lighting device body.
By including the fluorescent lamp and the lighting circuit according to any one of the above, it is possible to provide an illumination device having the effects of claims 1 to 4.

[Brief description of drawings]

FIG. 1 shows a cold cathode type electrode of the present invention and a first embodiment of a discharge lamp including the same, and is a conceptual main part front view for explaining a main part in perspective.

FIG. 2 is a perspective view of an essential part for explaining the dimensional relationship of the cold cathode electrode.

FIG. 3 shows a first cold cathode electrode and discharge lamp of the present invention.
In the embodiment of the present invention, a graph showing the change in the lamp voltage with respect to the elapsed time of lighting together with that of the comparative example.

FIG. 4 is a first cold cathode electrode and discharge lamp of the present invention.
3 is a graph showing the relationship between the lamp current and the lamp voltage in the embodiment of FIG.

FIG. 5 is a first cold cathode electrode and discharge lamp of the present invention.
Of the embodiment, the graph showing the relationship between the small voltage of the cold cathode electrode and the lamp voltage.

FIG. 6 is a second view of the cold cathode electrode and the discharge lamp of the present invention.
FIG. 3 is a vertical cross-sectional view of a main part of a discharge lamp showing an embodiment of

FIG. 7 is a graph showing the relationship between the lamp current and the lamp voltage, together with that of the comparative example.

FIG. 8 is a graph showing the relationship between the lighting time and the luminance maintenance rate, together with that of the comparative example.

FIG. 9 is a partially cutaway vertical sectional view showing a third embodiment of the discharge lamp of the present invention.

FIG. 10 is a graph showing the relationship between the outer diameter of the electrode and the discharge delay time.

FIG. 11 is a graph showing the relationship of the outer diameter playing card voltage of the electrode.

FIG. 12 is a conceptual partial cross-sectional front view showing a liquid crystal backlight device as an embodiment of a lighting device of the present invention and a cross-sectional view taken along the line AA ′.

[Explanation of symbols]

1 ... Translucent airtight container, 2 ... Phosphor layer, 3 ... Introduction line, 4 ...
Cold cathode type electrode, 4a ... Outer conductive tubular body, 4b ... Inner conductive tubular body, 5 ... Electron emissive material

Claims (5)

[Claims] 1. An outer conductive tubular body; an inner conductive tubular body which is electrically conductively connected to the outer conductive tubular body and is coaxially arranged inside the outer conductive tubular body with a small gap therebetween. And a cold cathode electrode. 2. A cold cathode electrode comprising a conductive cylindrical body made of a sintered body containing one or more selected from the group of Mo, W and Ta as a main component. 3. An elongated translucent airtight container; a pair of cold cathode electrodes according to claim 1 or 2 which is sealed inside the translucent airtight container; mercury enclosed in the translucent airtight container And a discharge medium containing a rare gas; 4. An elongated translucent airtight container having an inner diameter Bd of 1 to 2 mm; an outer diameter Ed sealed inside the translucent airtight container.
A discharge lamp comprising a pair of cold cathode electrodes (mm) satisfying the following formula; and a discharge medium containing mercury and a rare gas enclosed in a light-transmitting airtight container. Bd-0.4 <Ed <Bd 5. A lighting device, comprising: a lighting device main body; a discharge lamp according to claim 3 supported by the lighting device main body; and a lighting circuit for lighting the discharge lamp.