JP2004327458A - Cold-cathode fluorescent lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold-cathode fluorescent lamp capable of reducing wear of mercury and realizing a longer life through restraint of sputtering by discharge, in spite of a small-diameter light-emitting tube with large lamp current. <P>SOLUTION: An inner diameter (D1) of the light-emitting tube 1 is to be within the range of 1 to 6 mm, and an interval (d) between an inner face of the light-emitting tube 1 and an outer face of a cylindrical electrode 4 is regulated within the range of 0<d≤0.2 mm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cold cathode fluorescent lamp used for a backlight of a liquid crystal display device or the like.

  A cold cathode fluorescent lamp used as a backlight light source for a liquid crystal display device is provided with a cylindrical or plate-shaped metal as an electrode in an arc tube in which a phosphor is coated on the inner surface of a glass tube, and mercury is sealed therein. The fluorescent material is excited by ultraviolet rays generated inside the arc tube by the discharge to obtain visible light.

  With the diversification of liquid crystal display devices, various studies have been made on such cold cathode fluorescent lamps, such as miniaturization, diameter reduction, high brightness, and long life. For example, in order to suppress the consumption of mercury in the lamp when performing high-power discharge and to optimize the discharge area of the electrode, a metal cylindrical electrode is provided at the end of the arc tube to extend the life. A cold-cathode fluorescent lamp has been proposed (see, for example, Patent Document 1).

However, the conventional cold cathode fluorescent lamp configured as described above has a cylindrical shape when the lamp current is a relatively large current of 5 mA or more and the inner diameter of the arc tube is as small as 1 to 6 mm. Both the inner and outer surfaces of the electrode are exposed to the discharge. Therefore, a so-called mercury trap phenomenon is promoted, in which mercury in the lamp is consumed due to an increase in electrode sputtered substances generated by the discharge, which hinders a long life of the cold cathode fluorescent lamp.
JP-A-1-151148

  In view of the above problems, the present invention provides a cold cathode fluorescent lamp that suppresses sputtering due to discharge, reduces mercury consumption, and achieves a longer life, even when the lamp current is large and the arc tube has a small diameter. The purpose is to do.

  The cold cathode fluorescent lamp according to claim 1 of the present invention is provided with a cylindrical electrode at the end of an arc tube which is hermetically sealed and coated with a phosphor on its inner surface, and is provided with ultraviolet rays generated inside the arc tube by discharge. A cold cathode fluorescent lamp that excites a phosphor provided in the arc tube to obtain visible light, wherein an inner diameter (D1) of the arc tube is in a range of 1 to 6 mm, and an inner surface of the arc tube and the cylindrical electrode. Is characterized in that the distance (d) to the outer surface is restricted within the range of 0 <d ≦ 0.2 mm.

  Further, the cold cathode fluorescent lamp according to claim 2 of the present invention is provided with a cylindrical electrode at the end of the arc tube, which is sealed and coated with a phosphor on the inner surface, and is generated inside the arc tube by discharge. A cold cathode fluorescent lamp for exciting visible light by exciting a phosphor provided on the arc tube with ultraviolet light, wherein the inner diameter (D1) of the arc tube is in the range of 1 to 6 mm, and the outer diameter of the cylindrical electrode ( D2) is regulated in a range of D1-0.4 ≦ D2 <D1 mm.

  A cold cathode fluorescent lamp according to a third aspect of the present invention is the cold cathode fluorescent lamp according to any one of the first and second aspects, wherein the maximum lamp current is 5 mA or more.

  A cold cathode fluorescent lamp according to claim 4 of the present invention is the cold cathode fluorescent lamp according to any one of claims 1 to 3, wherein the inner surface and the outer surface of the cylindrical electrode are formed of different materials. The work function of the material forming the outer surface is made larger than the work function of the material forming the inner surface.

  A cold cathode fluorescent lamp according to a fifth aspect of the present invention is the cold cathode fluorescent lamp according to any one of the first to fourth aspects, wherein an inner surface of the cylindrical electrode is provided inside the cylindrical electrode. An electron-emitting substance including a material having a work function smaller than the work function of the material to be formed is provided.

  A cold cathode fluorescent lamp according to a sixth aspect of the present invention is the cold cathode fluorescent lamp according to any one of the first to fifth aspects, wherein an outer surface of the cylindrical electrode contacts an inner surface of the arc tube. It is characterized in that a projection is provided.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a large-current and small-diameter arc tube, excessive sputtering of an electrode can be suppressed, the consumption rate of mercury can be suppressed, and the life of a cold cathode fluorescent lamp can be extended. In particular, even when the inner diameter (D1) of the arc tube is as small as 1 to 6 mm and the maximum lamp current is as large as 5 mA or more, the outer diameter (D2) of the cylindrical electrode is in the range of D1−0.4 ≦ D2 <D1 mm. By doing so, it is possible to suppress the consumption of mercury due to the increase in discharge sputtering, to reduce the consumption of the electrodes, to extend the life, and to obtain a further practical improvement effect.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
(Embodiment 1)
FIG. 1 shows a cold cathode fluorescent lamp according to the first embodiment.

  In FIG. 1, a conductive tubular electrode 4 is provided via an electrode support lead 5 at an end of a light emitting tube 1 in which a phosphor 3 is attached to an inner surface of a glass tube 2. Is sealed with an appropriate amount of mercury and a rare gas. When a current is supplied to the cylindrical electrode 4 via the electrode support lead 5, a discharge is generated inside the arc tube 1, and the ultraviolet light generated by the discharge excites the phosphor 3 to obtain visible light. In FIG. 1, reference numeral 6 denotes a connection point between the cylindrical electrode 4 and the electrode support lead 5.

  In the cold cathode fluorescent lamp configured as described above, in the first embodiment, the inner surface of the arc tube 1 and the outer surface of the cylindrical electrode 4 so that the mercury in the lamp is not depleted by the mercury trapping phenomenon due to the electrode sputtered substance at the time of lighting. Is restricted. Specifically, even when the inner diameter D1 of the arc tube 1 is as small as 1 to 6 mm and the lamp current during lighting is a relatively large current of 5 mA or more, excessive sputtering is suppressed and stable lighting can be performed. Thus, the outer diameter D2 of the cylindrical electrode 4 is regulated as in the following equation (1). The inner diameter D1 of the arc tube 1 here corresponds to the inner diameter of the glass tube 2.

このような構成とすると、点灯中の放電が筒状電極４の外側に移行しにくくなり、過剰のスパッタリングを抑制して水銀の消耗速度を抑えることができ、冷陰極蛍光ランプの長寿命化が図れる。

With such a configuration, it is difficult for the discharge during lighting to move to the outside of the cylindrical electrode 4, it is possible to suppress excessive sputtering and suppress the consumption rate of mercury, and to extend the life of the cold cathode fluorescent lamp. I can do it.

  Further, when the gap distance d between the inner surface of the arc tube 1 and the outer surface of the cylindrical electrode 4 satisfies the following formula (2), appropriate discharge maintenance during lighting can be performed, and in particular, the amount of spatter is lower than that at room temperature. Even in a low-temperature use environment (0 ° C. or less), the discharge to the gap formed between the inner surface of the arc tube 1 and the outer surface of the cylindrical electrode 4 can be suppressed. It is possible to suppress a large amount of consumption in a short period of time, and it is possible to suppress a short life due to early electrode consumption and the like, and to achieve a long life.

（実施の形態２）
図２は、本実施の形態２における冷陰極蛍光ランプを示す。なお、実施の形態１で説明した部材に対応する部材には同一の符号を付して、説明を省略する。

(Embodiment 2)
FIG. 2 shows a cold cathode fluorescent lamp according to the second embodiment. The members corresponding to those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The cold cathode fluorescent lamp according to the second embodiment is different from the first embodiment in that the outer surface and the inner surface of the cylindrical electrode 4 are formed of different materials.
Specifically, the cylindrical electrode 4 has a two-layer structure in which the outside and the inside are formed of different materials, and the work function of the material forming the outer layer 4a (the outer surface) forms the inner layer 4b (the inner surface). It is formed to be larger than the work function of the material to be formed. Examples of such a combination of materials include a material in which the outer layer 4a of the cylindrical electrode 4 is formed of nickel and the inner layer 4b is formed of a material such as titanium, niobium, or tantalum.

  By using the cylindrical electrode 4 configured as described above, discharge outside the cylindrical electrode 4 can be suppressed, and mercury consumption due to extra discharge spatter outside the cylindrical electrode 4 and early consumption of the electrode can be reduced. Since it can be suppressed, the life of the cold cathode fluorescent lamp can be extended.

  Here, the outer layer 4 a is provided on the entire outer surface of the cylindrical electrode 4. However, the present invention is not limited to this, and the outer layer 4 a formed of a material having a large work function The same effect can be obtained if it is formed so as to be about 1/4 or more of the outer peripheral surface on the part side.

  The thickness of each of the outer layer 4a and the inner layer 4b is not particularly limited. For example, the inner layer 4b may be a base metal of the electrode, and the outer layer 4a may be such that the outer layer 4a coats the base metal.

  In the above description, the cylindrical electrode 4 has a two-layer structure including the outer layer 4a and the inner layer 4b. However, the present invention is not limited to this, and a material having a higher work function on the outside of the cylindrical electrode 4 than on the inside. , It may have a configuration of two or more layers.

(Embodiment 3)
FIG. 3 shows a cold cathode fluorescent lamp according to the third embodiment. The members corresponding to those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the second embodiment, the outer surface and the inner surface of the cylindrical electrode 4 are formed of different materials. However, in the third embodiment, the work function is larger inside the conventional cylindrical electrode 4 than the inner surface of the cylindrical electrode 4. Low material. With such a configuration, similarly to the above, discharge outside the cylindrical electrode 4 can be suppressed, and mercury consumption due to extra discharge sputtering outside the cylindrical electrode 4 and early consumption of the electrode can be suppressed. The life of the cold cathode fluorescent lamp can be extended.

  Specifically, an electron-emitting substance including a material having a work function smaller than the work function of the material forming the inner surface of the cylindrical electrode 4 is provided inside the cylindrical electrode 4. For example, an electron emitting material 7 made of an oxide containing barium having a work function smaller than that of nickel is applied to the inside of the cylindrical electrode 4 made of nickel. Examples of the electron emitting material 7 include oxides and alloys of alkali metals or alkaline earth metals such as Cs, Li, and Mg.

(Embodiment 4)
FIG. 4 shows a cold cathode fluorescent lamp according to the fourth embodiment. The members corresponding to the members described in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. The cold cathode fluorescent lamp according to the fourth embodiment is different from the above-described first embodiment in that a convex portion 8 that contacts the inner surface of the arc tube 1 is provided on the outer surface of the cylindrical electrode 4.

  Specifically, as shown in FIGS. 4A and 4B, in the cold cathode fluorescent lamp configured as in FIG. 1, the outer surface of the cylindrical electrode 4 is brought into contact with the inner surface of the arc tube 1. A plurality of protrusions 8 for positioning the mounting position of the cylindrical electrode 4 on the arc tube 1 are provided at equal intervals in the circumferential direction.

  By providing such a convex portion 8, it is possible to prevent the cylindrical electrode 4 from being biased or inclined with respect to the inner wall at the end of the arc tube 1 and coming into contact with the inner wall of the arc tube 1. The gap between the outer surface of the electrode 4 and the inner surface of the arc tube 1 can be kept at a constant distance. Even in the case of an ultra-small cold-cathode fluorescent lamp having an inner diameter of 1 to 6 mm, the cylindrical electrode 4 and the inner wall of the arc tube 1 are not sealed when the cylindrical electrode 4 is sealed to the end of the arc tube 1. Can be prevented, and a local rise in temperature of the outer wall of the arc tube 1 can be suppressed.

  In the above description, the cold cathode fluorescent lamp in the first embodiment has been described as an example. However, the present invention is not limited to this, and can be applied to the cold cathode fluorescent lamps shown in FIGS. 2 and 3. In FIG. 4, an example in which four convex portions 8 are provided has been described. However, the number of the convex portions 8 is not particularly limited, and the same effect can be obtained by using an annular convex portion. Further, as a material for forming the convex portion 8, a material that does not affect the discharge can be suitably used, and for example, an insulating ceramic or the like can be used.

Hereinafter, specific examples in the above embodiments will be described.
(Example 1)
The cold cathode fluorescent lamp shown in FIG. 1 was produced according to the following procedure.

  An inner surface of a glass tube 2 made of borosilicate glass and having an inner diameter D1 of 1.6 mm is coated with a required amount of a three-wavelength region light-emitting phosphor 3 having a color temperature of 5000 K to form an arc tube 1. The bottom was provided with a bottomed cylindrical electrode 4 having an outer diameter D2 of 1.2 mm, an inner diameter of 0.8 mm, and a length of 5 mm formed of a nickel material.

  200 μg of mercury and 8 kPa of a mixed gas of argon and neon were filled in the arc tube 1, and a cold cathode lamp having a rated lamp current of 8 mA and a total length of 300 mm was prepared. A prototype lamp B was prepared in the same manner as the prototype lamp A except that the outer diameter D2 of the cylindrical electrode 4 was 1.0 mm.

A lighting experiment was performed using the prototype lamp A and the prototype lamp B, using a high-frequency inverter lighting circuit having a lighting frequency of 60 kHz, and a lamp current of 6 mA under a normal ambient temperature environment.
The cylindrical electrode 4 used for the prototype lamps A and B cannot secure the electrode area required for discharge only by the inner surface of the cylindrical electrode 4, but the prototype lamp A has the inner surface of the arc tube 1 and the cylindrical electrode. Since the distance from the outer surface of the cylindrical electrode 4 to the outer surface of the cylindrical electrode 4 is within the range of the present invention, the discharge on the outer surface of the cylindrical electrode 4 can be suppressed, and the discharge is mainly performed on the inner surface of the cylindrical electrode 4. Obtained. When the discharge is performed on the inner surface of the cylindrical electrode 4 as described above, the generated sputtered substance adheres to the inner surface of the electrode again and is reused to suppress the generation of electrode spatter. Was reduced to about 1/10 of the prototype lamp B, and the target life time of 30,000 hours was satisfied without any trouble.

  The hollow effect means that when the electrode is made cylindrical, the electrons emitted from the electrode hit the opposite surface, heat it, reflect it back near the original surface and improve the electron emission rate The electrode structure that provides such an effect is called a hollow structure.

  On the other hand, in the prototype lamp B, since the distance between the inner surface of the arc tube 1 and the outer surface of the cylindrical electrode 4 is wider than the range of the present invention, discharge on the outer surface of the cylindrical electrode 4 cannot be suppressed. And the mercury in the lamp was completely depleted by 15,000 hours before reaching the target life time of 30,000 hours due to the mercury trap phenomenon by the electrode sputtered substance, and the lamp luminance was reduced to 50 times the initial luminance. %.

  Based on the results of this experiment, experiments were conducted with various changes in the inner diameter D1 of the arc tube 1 and the outer diameter D2 of the cylindrical electrode 4. When the inner diameter D1 of the arc tube 1 was in the range of 1 to 6 mm, the cylindrical shape was changed. It has been confirmed that when the outer diameter D2 of the electrode 4 satisfies the following formula (1), discharge does not leak to the outer peripheral surface of the cylindrical electrode 4 and a sufficient effect as a hollow electrode is obtained. Further, since the cylindrical electrode 4 does not contact the inner surface of the glass tube 2, it has been clarified that the temperature of the outer surface of the glass tube 2 corresponding to the electrode portion does not increase and can be used in actual use.

また、筒状電極４の外径Ｄ２がＤ１−０．４ｍｍ以下であると、放電が筒状電極４の外周面に漏れて電極スパッタ物質が増加し、水銀の消耗量が増加するため、目標寿命を達成できなかった。また、ガラス管２の内径Ｄ１と筒状電極４の外径Ｄ２とが等しいものは、筒状電極３がガラス管２の内面に接触するため、電極部に対応するガラス管２の外面温度が高くなり、実使用に耐え得るものではなかった。

If the outer diameter D2 of the cylindrical electrode 4 is less than D1-0.4 mm, the discharge leaks to the outer peripheral surface of the cylindrical electrode 4 to increase the amount of electrode sputtered material and increase the consumption of mercury. Life could not be achieved. In the case where the inner diameter D1 of the glass tube 2 is equal to the outer diameter D2 of the cylindrical electrode 4, since the cylindrical electrode 3 contacts the inner surface of the glass tube 2, the outer surface temperature of the glass tube 2 corresponding to the electrode portion is lower. It was not high enough for practical use.

(Example 2)
Next, in order to determine the optimal design conditions of the cylindrical electrode 4 for a cold cathode fluorescent lamp in which the inner diameter D1 of the arc tube 1 is as small as 1 to 6 mm and the lamp current is 5 mA or more using a sine wave output waveform inverter. Was conducted.

  First, in a cold cathode fluorescent lamp in which the inner diameter D1 of the glass tube 2 forming the arc tube 1 is 1.4 mm, the outer diameter D2 of the cylindrical electrode 4 is 1.0 mm, the inner diameter is 0.8 mm, and the length is 3 mm. A trial lamp C was prepared with a constant gap distance d between the inner surface of the tube 1 and the outer surface of the cylindrical electrode 4 of 0.2 mm.

In addition, a trial lamp D was prepared in which the cylindrical electrode 4 was inclined so that the gap distance d between the inner surface of the arc tube 1 and the outer surface of the cylindrical electrode 4 was 0.35 to 0.05 mm.
Using the obtained prototype lamp C and prototype lamp D, a lighting experiment was performed in a use environment at an ambient temperature of 0 ° C.

  The prototype lamp C had no practical problem in mercury consumption. On the other hand, in the prototype lamp D, the target life was able to be achieved although the consumption of mercury increased. However, discharge leakage was concentrated on the side where the gap between the inner surface of the arc tube 1 and the outer surface of the cylindrical electrode 4 was wide, and the temperature of the outer surface of the arc tube 1 was increased.

  From this result, when the gap distance d between the inner surface of the arc tube 1 and the outer surface of the cylindrical electrode 4 satisfies the following expression (2), the amount of mercury consumed can be sufficiently suppressed and the gap toward the wide side of the gap can be reduced. It has been clarified that a practical improvement effect of suppressing the concentration of discharge leakage and suppressing the temperature rise on the outer surface of the arc tube 1 can be obtained.

（実施例３）
図２に示すように、筒状電極４の外層４ａが内層４ｂに比べて仕事関数が大きくなるよう、外層４ａがニッケルにて形成され、内層４ｂがニッケルよりも仕事関数の小さいチタン、タンタル、ニオブもしくはそれらの合金等の材料にて形成された筒状電極４を作成した。そしてそれ以外は試作ランプＡと同様にして、試作ランプＥを作成した。また、試作ランプＥの筒状電極４の外層４ａと内層４ｂの材料を逆にした筒状電極４を有する試作ランプＦを作成した。

(Example 3)
As shown in FIG. 2, the outer layer 4a of the cylindrical electrode 4 is formed of nickel so that the outer layer 4a has a higher work function than the inner layer 4b, and the inner layer 4b is formed of titanium, tantalum, and titanium having a smaller work function than nickel. A cylindrical electrode 4 made of a material such as niobium or an alloy thereof was prepared. Otherwise, a prototype lamp E was prepared in the same manner as the prototype lamp A. Further, a trial lamp F having a tubular electrode 4 in which the material of the outer layer 4a and the inner layer 4b of the tubular electrode 4 of the trial lamp E was reversed was prepared.

Using the prototype lamp E and the prototype lamp F, a lighting experiment was performed using a high-frequency inverter lighting circuit having a lighting frequency of 60 kHz and an ambient temperature of 0 ° C. and a lamp current of 6 mA.
In the prototype lamp E, discharge mainly occurred on the inner surface of the cylindrical electrode 4 having a low work function, and discharge leakage to the outer surface could be reduced, so that the amount of electrode spatter was suppressed and the consumption of mercury was reduced. On the other hand, in the prototype lamp F, discharge was generated only on the outer surface of the cylindrical electrode having a low work function, and the amount of discharge from the inner surface due to the hollow effect was reduced, the amount of electrode spatter increased, and the amount of mercury consumed increased.

  Thus, when the outer layer 4a of the cylindrical electrode 4 is formed of a material having a larger work function than the inner layer 4b, it is clear that the practical advantage is larger than that of the prototype lamp A manufactured in the first embodiment. .

  In the third embodiment, an example in which the entire outer surface of the cylindrical electrode is formed of the outer material is described. However, about １ ／ or more of the outer peripheral surface of the cylindrical electrode on the opening side is formed of the outer material. It was confirmed that a similar effect could be obtained if it was performed.

(Example 4)
As shown in FIG. 3, an electron containing barium oxide as an electron emitting material containing a material having a lower work function than nickel is provided inside a cylindrical electrode 4 made of nickel of the prototype lamp A made in Example 1. Prototype lamp G was prepared by providing a radiation material.

  When a lighting experiment similar to the above was conducted using this prototype lamp G, discharge entered only the inner surface of the cylindrical electrode 4 and there was no discharge leakage to the outer surface, the amount of electrode spatter was suppressed, and the consumption of mercury was reduced. A practical improvement effect of being able to reduce was confirmed.

(Example 5)
When sealing the cylindrical electrode 4 to the end of the arc tube 1 using the glass tube 2 having an inner diameter D1 of 1 to 6 mm, a means for preventing the cylindrical electrode 4 from being inclined and fixed is studied. did.

  As shown in FIG. 4, a ceramic projection 8 which is arranged at equal intervals in the circumferential direction and is in contact with the inner surface of the arc tube 1 on the outer surface near the tip of the cylindrical electrode 4 of the prototype lamp A prepared in Example 1. Were provided in two places.

  This cylindrical electrode 4 was mounted on the same arc tube 1 as in Example 1 to obtain a prototype lamp H. In the prototype lamp H, the cylindrical electrode 4 is arranged at an appropriate position and sealed at the end of the glass tube 2. Since ceramic has a low thermal conductivity, the portion where the electrode and the glass in contact with the electrode being lit come into contact with each other. There was no local temperature rise on the outer surface of the glass, and no reduction in life due to consumption of mercury occurred. In addition, it was confirmed that stable attachment of the cylindrical electrode 4 to the arc tube 1 can be realized if the protrusions 8 are provided at two or more places.

  In each of the above-described embodiments and examples, an example is described in which a cylindrical bottomed electrode is used as the cylindrical electrode 4. However, the present invention is not limited to this. Also, the present invention can be applied to a case where the outside of the cylindrical electrode 4 is made of an insulating material, a case where an oxidized film is formed on the outside of the cylindrical electrode 4, and the like.

  Further, the size, design, material, shape, rating and the like of the cold cathode fluorescent lamp are not limited to those described above.

  The cold-cathode fluorescent lamp according to the present invention suppresses sputtering by electric discharge, reduces consumption of mercury, can achieve a long life, and is used for a liquid crystal panel or the like using a cold-cathode fluorescent lamp having a small arc tube and a large lamp current. Useful.

FIG. 2 is a side cross-sectional view illustrating a main part of the cold cathode fluorescent lamp according to the first embodiment of the present invention. Side sectional view showing a main part of a cold cathode fluorescent lamp according to Embodiment 2 of the present invention. Side sectional view showing a main part of a cold cathode fluorescent lamp according to Embodiment 3 of the present invention. 4 is a side sectional view showing an essential part of a cold cathode fluorescent lamp according to a fourth embodiment of the present invention, and an enlarged longitudinal sectional view taken along line AA ′.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Arc tube 2 Glass tube 3 Phosphor 4 Cylindrical electrode 4a Outer layer 4b Inner layer 5 Electrode support lead 6 Connection point between cylindrical electrode and electrode support lead 7 Electron emitting material 8 Convex part

Claims (6)

  A tubular electrode is provided at the end of the arc tube, which is sealed and coated with a phosphor on the inner surface, and excites the phosphor provided on the arc tube with ultraviolet light generated inside the arc tube by discharge to generate visible light. The inner diameter (D1) of the arc tube is in the range of 1 to 6 mm, and the distance (d) between the inner surface of the arc tube and the outer surface of the cylindrical electrode is 0 <d ≦ 0. A cold-cathode fluorescent lamp characterized by being regulated within a range of 2 mm.   A tubular electrode is provided at the end of the arc tube, which is sealed and coated with a phosphor on the inner surface, and excites the phosphor provided on the arc tube with ultraviolet light generated inside the arc tube by discharge to generate visible light. A cold cathode fluorescent lamp to be obtained, wherein the inner diameter (D1) of the arc tube is in the range of 1 to 6 mm, and the outer diameter (D2) of the cylindrical electrode is regulated in the range of D1-0.4 ≦ D2 <D1 mm. A cold cathode fluorescent lamp characterized in that:   3. The cold cathode fluorescent lamp according to claim 1, wherein a maximum lamp current is 5 mA or more.   4. The cylindrical electrode according to claim 1, wherein the inner surface and the outer surface are formed of different materials, and the work function of the material forming the outer surface is larger than the work function of the material forming the inner surface. Cold cathode fluorescent lamp.   The cold-cathode fluorescent light according to any one of claims 1 to 4, wherein an electron-emitting substance containing a material having a work function smaller than the work function of a material forming the inner surface of the cylindrical electrode is provided inside the cylindrical electrode. lamp. The cold cathode fluorescent lamp according to any one of claims 1 to 5, wherein a convex portion that contacts an inner surface of the arc tube is provided on an outer surface of the cylindrical electrode.

Images