JP2008084594A - Discharge lamp and light-emitting device equipped with the discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp and a light-emitting device using it of high darkness startability, in one with electrodes arranged at the outer periphery of a bulb. <P>SOLUTION: The discharge lamp 1 is provided with a bulb 2, a pair of electrodes arranged at either end of the bulb 2, a phosphor layer 5 and a protective film 4 arranged on an inner face of the bulb 2, and a discharging medium 7 sealed in the bulb 2. At least one of the pair of the electrodes is an outer electrode 3 in contact with an outer periphery face of the bulb 2, and the protective film 4 is at least arranged at the inner periphery face part, in correspondence with a part of the bulb 2 where the outer electrode 3 is in contact, containing rare-earth metal with an electronegativity of 1.2 or smaller. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a discharge lamp and a light emitting device including the discharge lamp.

  In a discharge lamp, generally, as a discharge medium, for example, an ionizable gas containing mercury and a rare gas is sealed in a bulb, and a phosphor layer is applied to the inside of the bulb. A pair of electrodes is disposed at both ends of the bulb. When a high voltage is applied between the electrodes, electrons in the bulb are attracted by the anode and collide with a rare gas while moving at a high speed to form cations, and electrons are released by the γ action. Mercury is excited by the electrons to emit ultraviolet rays, and the phosphor is subsequently excited, so that visible light is emitted from the phosphor layer.

  As such a discharge lamp, a cold cathode fluorescent lamp (CCFL) used as a backlight light source for a straight tube fluorescent lamp, an annular fluorescent lamp, a liquid crystal display or the like, an external electrode type fluorescent lamp (EEFL) is used. There are types such as Electrodes Fluorescent Lamp (HCFL) and Hot Cathode Fluorescent Lamp (HCFL). The CCFL has a plate-like, rod-like or cylindrical internal electrode disposed in the bulb, and the EEFL has an external electrode made of silver or the like formed on the outer peripheral surface of the bulb. In addition, when a plurality of CCFLs and HCFLs are used, they must be connected to an inverter to apply a voltage, whereas EEFL also has a difference that a plurality of lamps can be connected in parallel using a lamp holder or the like.

  By the way, as one of the general problems related to the discharge lamp, there is a dark start delay. This is because a phenomenon in which a considerable amount of time is required until the start of discharge because the initial electrons that trigger the discharge are extremely reduced in a state where no external light can be expected when the discharge tube is lit (under dark conditions). This is a phenomenon in which there is a delay between starting the power switch and starting.

  In the case of having an internal electrode such as CCFL, a discharge lamp is known in which an auxiliary agent containing an electron-emitting substance serving as an emitter is applied to the electrode surface. Since electrons are emitted from the emitter when a voltage is applied to the electrodes, the dark startability can be improved.

  On the other hand, when an external electrode is provided like EEFL, the emitter cannot be used on the electrode surface. Therefore, at least one conductive material selected from aluminum, silver, zinc, tin oxide, indium oxide, barium, and nickel, a valve inner surface portion corresponding to the installation portion of the external electrode, and a portion where no electrode is installed There is known a discharge lamp arranged linearly across the bulb inner surface portion corresponding to (for example, see Patent Document 1). Electric field concentration occurs in the vicinity of the electrode by charging the conductive substance, so that initial electrons are easily collected and dark startability can be improved. There is also known a discharge lamp in which a cesium-based substance is applied in a bulb and is released by applying an applied voltage (see, for example, Patent Document 2).

JP-A-10-188910 JP 2006-019100 A

  However, since the conductive material is not an electron emitting material, the discharge lamp described in Patent Document 1 has a problem that it cannot sufficiently solve the dark start delay when left in a dark place for a long time. In addition, since a cesium-based material can be dissolved only in a small amount in a solvent, a discharge lamp in which a cesium-based material is applied in a bulb has a problem that the start delay in a dark place cannot be sufficiently solved when the number of uses increases. Under such circumstances, discharge lamps having external electrodes are required to have improved dark startability.

  The present invention provides a discharge lamp having a high dark startability and a light emitting device using the discharge lamp with respect to a discharge lamp in which electrodes are arranged on the outer peripheral surface of the bulb.

  The discharge lamp of the present invention includes a bulb, a pair of electrodes disposed at the end of the bulb, a phosphor layer and a protective film disposed on the inner surface of the bulb, and a discharge sealed in the bulb. A discharge lamp including a medium, wherein at least one selected from the pair of electrodes is an external electrode in contact with an outer peripheral surface of the bulb, and the protective film is in contact with the external electrode of the bulb It includes a rare earth metal that is disposed at least on an inner peripheral surface portion corresponding to the portion and has an electronegativity of 1.2 or less.

  In addition, a light emitting device of the present invention includes a plurality of discharge lamps, and a light emitting device that includes a window portion that is capable of transmitting light emitted from the plurality of discharge lamps and stores the plurality of discharge lamps. It is an apparatus, Comprising: The said discharge lamp is the discharge lamp of this invention mentioned above, It is characterized by the above-mentioned.

  According to the discharge lamp of the present invention, the dark startability can be improved.

  Further, according to the light emitting device of the present invention, the discharge lamp of the present invention having good dark startability can be used as the light emission source.

  The discharge lamp of the present invention includes a bulb, a pair of electrodes arranged at the end of the bulb, a phosphor layer and a protective film arranged on the inner surface of the bulb, and a discharge medium sealed in the bulb. And at least one selected from the pair of electrodes is an external electrode in contact with the outer peripheral surface of the bulb. The protective film includes a rare earth metal that is disposed at least on an inner peripheral surface portion corresponding to a portion of the bulb that is in contact with the external electrode and has an electronegativity of 1.2 or less. In the present specification, the electronegativity is Pauling's electronegativity.

  According to the discharge lamp of the present invention, when a voltage is applied to the electrodes, the initial electrons that trigger the discharge are provided from the protective film to the discharge space, thus ensuring good startability even under dark conditions. it can. Therefore, the discharge lamp of the present invention can improve the dark startability. This is because the rare earth metal having an electronegativity of 1.2 or less has a low work function, that is, it requires a small amount of energy to extract one electron from the Fermi level to the vacuum level, and thus is easily liberated.

  Further, according to the discharge lamp of the present invention, the protective film is disposed at least on the inner peripheral surface portion of the bulb, which is opposite to the portion where the external electrode of the bulb is in contact, so that the bulb can be protected. Since a protective film has not been disposed on the inner peripheral surface portion in the past, for example, there was a possibility that a hole is opened in the valve by electrons moving between the electrodes. This is because it can be reduced.

  It is preferable that at least a part of the protective film is exposed to the discharge space side of the bulb and is in contact with the discharge medium, since electrons serving as initial electrons are easily released from the protective film into the discharge space. For example, the protective film may be disposed in contact with the inner peripheral surface portion of the bulb corresponding to the portion in contact with the external electrode of the bulb, or the phosphor layer is disposed on the inner peripheral surface portion, A protective film may be disposed thereon, the protective film may be disposed in contact with the inner peripheral surface portion, and the phosphor layer may be disposed in a spot shape. Further, a protective film including a phosphor having a function as a phosphor layer may be disposed on the inner peripheral surface portion. Note that the protective film disposed on the electrically neutral inner peripheral surface portion other than the inner peripheral surface portion of the bulb does not emit electrons to the discharge space and reduces the area exposed to the discharge space of the phosphor layer. If it does so, the light emission area of a discharge lamp will also be made small. The protective film is preferably disposed on the inner peripheral surface portion that becomes an electric field, and the larger the area exposed to the discharge space, the easier it is to emit electrons to the discharge space.

  Further, if the protective film is disposed on at least a part of the inner peripheral surface portion corresponding to the portion where the external electrode of the bulb is in contact, the dark startability can be improved. More preferably, it is arranged so as to cover the whole. This is because not only higher dark startability can be obtained, but also the valve surface can be sufficiently protected. At this time, the protective film may be disposed not only on the inner peripheral surface portion but also on the other valve inner peripheral surface, but only on the inner peripheral surface portion so as not to overlap the phosphor layer. More preferably. Further, from the viewpoint of protecting the bulb, it is more preferable to dispose the protective film and the phosphor layer so that the inner peripheral surface of the bulb is not exposed.

  The protective film is not particularly limited as long as it includes a rare earth metal having an electronegativity of 1.2 or less. For example, the protective film may contain the rare earth metal compound and an additive such as a binder. The rare earth metals are cerium (electronegativity 1.12, work function 2.9), samarium (electronegativity 1.17, work function 3.0), europium (electronegativity 1.2, work function 3. It is preferable to include at least one selected from the group consisting of 1) and terbium (electronegativity 1.1, work function 2.8), and more preferably cerium or europium. This is because the work function is lower and the dark startability can be further improved. The rare earth metal may be contained in the protective film as a rare earth compound such as a rare earth oxide. Substances having an electronegativity of 1.2 or less include alkali metals and alkaline earth metals, but these substances are highly basic. Therefore, a protective film containing these substances as a main component is not suitable for a discharge lamp because it has a high possibility of gradually dissolving the bulb when it is disposed on the inner peripheral surface of the bulb.

  The protective film preferably further contains cesium (electronegativity 0.79, work function 2.1), and more preferably contains cesium sulfate. Since cesium, which is an alkali metal, has a lower work function than the rare earth metal, dark startability can be further improved. In particular, cesium sulfate has a relatively high melting point and is difficult to evaporate during production. In addition, by appropriately selecting materials such as a binder and an adhesive, both the rare earth metal and the cesium compound can be easily dispersed and can be easily manufactured.

  Although the said bulb | bulb will not be specifically limited if it is the sealed container which has the translucency generally used for a discharge lamp, It is preferable to consist of glass containing sodium. If glass containing sodium is used, sodium ions are knocked out of the glass by the activation step, and the dark startability can be further improved. For example, a valve made of soda glass, borosilicate glass, lead glass, lead-free glass, or the like containing an alkali metal oxide, particularly sodium oxide, may be used, and hard borosilicate glass is particularly preferable in consideration of optical characteristics. Further, the shape of the valve may be, for example, a straight tube shape, a U shape, a U shape, an L shape, a W shape, or the like. In this specification, lead-free glass is defined not only as glass containing no lead but also as glass containing lead at an impurity level of 0.1% by weight or less as lead-free glass. This is because lead may be contained as an impurity in the glass manufacturing process.

  The pair of electrodes is an electrode generally used in a discharge lamp, and is not particularly limited as long as at least one of the electrodes is the external electrode. However, if both electrodes are the external electrodes, the light emitting device It is preferable because the discharge lamp is easy to install and the productivity is improved. The external electrode is not particularly limited as long as it is an electrode formed on the outer peripheral surface of the end portion of the bulb. For example, an electrode obtained by covering a silver paste disposed on the outer peripheral surface of the bulb with a solder paste and using it is used. That's fine.

  The light-emitting device of the present invention includes a plurality of discharge lamps, and a case that includes a window portion that can transmit light emitted from the plurality of discharge lamps, and in which the plurality of discharge lamps are housed. The discharge lamp is the discharge lamp of the present invention described above.

  According to the light-emitting device of the present invention, a discharge lamp with good dark startability, in which initial electrons are provided from the protective film to the discharge space when a voltage is applied to the electrodes, can be used as the light-emitting source.

  It is preferable that the discharge lamp includes a bulb including a light transmitting part in the vicinity of the protective film, and the case is arranged such that a light emitting diode faces the light transmitting part. Since the light emitted from the light emitting diode passes through the light transmitting portion and enters the protective film, the dark startability of the discharge lamp can be further improved.

  The position of the light transmitting portion is not particularly limited as long as it is in the vicinity of the protective film, but may be, for example, a valve peripheral surface portion or a bottom surface portion close to the external electrode. If the bottom part of the bulb is a light-transmitting part, it is more preferable because it is easy to manufacture and the light emitted from the light-emitting diode easily reaches the protective film.

  The light emitting diodes may be arranged for a plurality of discharge lamps respectively, but if arranged for one discharge lamp, the effect of sufficiently improving the dark startability can be obtained. is there. This is because when the protective film of one discharge lamp is irradiated with light of a light emitting diode and the discharge lamp is turned on, adjacent discharge lamps are also turned on instantaneously one after another. The light emitting diode may be lit for a period of time until the discharge lamp is turned on, and may be turned off after the discharge lamp is turned on.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a sectional view showing a straight tubular EEFL which is an example of a discharge lamp according to the present invention.

  As shown in FIG. 1, the EEFL 1 of this embodiment includes a light-emitting tube in which a protective film 4, a phosphor layer 5, and a metal oxide film 6 are disposed on the inner surface of a glass tube 2, a pair of external electrodes 3, A discharge medium 7 enclosed in a glass tube 2 is provided. The external electrode 3 is disposed in contact with the end portions 2b of both glass tubes 2 so as to surround the entire outer peripheral surface of the end portion 2b of the glass tubes 2. The protective film 4 is disposed in contact with the inner peripheral surface portion of the end 2b corresponding to the outer peripheral surface portion with which the external electrode 3 of the glass tube 2 is in contact, and the rare earth metal having an electronegativity of 1.2 or less Is included.

  By configuring the EEFL 1 of the present embodiment as described above, for example, even if the EEFL 1 is stored under dark conditions for a long time, if a voltage is applied to the external electrode 3, electrons that become initial electrons from the protective film 4 are generated. It becomes a discharge lamp with good dark startability that is easily released.

  The protective film 4 is not particularly limited as long as it includes a rare earth metal having an electronegativity of 1.2 or less, and preferably includes the rare earth metal and cesium. Moreover, you may further contain additives, such as a binder. The rare earth metal is not particularly limited as long as the electronegativity is 1.2 or less, but is preferably at least one selected from the group consisting of cerium, samarium, europium and terbium, and more preferably selected from the above group. It is a metal oxide. The cesium is more preferably cesium oxide. This is because these oxides have a low work function, a decomposition temperature that is not too high, are easily compatible with a dispersant and the like, and can be applied to the glass tube 2. The protective film 4 contains, for example, 5 to 10% by weight of europium oxide and 0.3 to 0.5% by weight of cesium sulfate.

  The thickness of the protective film 4 may be 0.5 μm or more in order to suppress erosion of the inner peripheral surface of the glass tube 2 due to ion bombardment. Further, the surface roughness Ry (JIS B 0601) of the protective film 4 may be 0.12 μm or less, preferably 0.05 μm or less. By reducing the surface roughness, the surface of the protective film 4 can be made dense so that ion bombardment between the particles contained in the protective film 4 and the inner peripheral surface of the glass tube 2 and discharge concentration can be suppressed. is there.

The phosphor layer 5 is not particularly limited as long as it includes a phosphor, and may further include an additive such as a binder. In particular, it is preferable to use a mixture of three or more kinds of phosphors that emit light corresponding to each wavelength region of red, blue, and green, because it becomes a highly demanding RGB color system lamp, particularly a white lamp. For example, Y ₂ O ₃ : Eu ³⁺ (YOX) as a red phosphor, LaPO ₄ : Ce ³⁺ , Tb ³⁺ (LAP) as a blue phosphor, and BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ as a green phosphor. Include it. The composition of the phosphor contained in the phosphor layer 5 preferably includes a phosphor that absorbs ultraviolet light having a wavelength of 313 nm (so-called high color reproduction phosphor), and 2 phosphors that absorb ultraviolet light having a wavelength of 313 nm. It is more preferable to include more than one type. This is because a wider range of wavelengths can be reproduced by using a high color reproduction phosphor. As an example of the composition of the above phosphor, BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ (BAM) as a blue phosphor and BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ , Mn ²⁺ (BAM: Mn as a green phosphor) ²⁺ ), YVO ₄ : Eu ³⁺ (YVO ₄ ) may be included as a red phosphor.

  Here, “absorbing ultraviolet light having a wavelength of 313 nm” means an excitation wavelength spectrum near 254 nm (excitation wavelength spectrum is a plot of excitation wavelength and emission intensity by causing the phosphor to emit light while changing the wavelength. )) Is defined as having an intensity of the excitation wavelength spectrum of 313 nm of 80% or more. That is, a phosphor that absorbs ultraviolet light having a wavelength of 313 nm is a phosphor that can absorb ultraviolet light having a wavelength of 313 nm and convert it into visible light. When the phosphor that absorbs ultraviolet rays having a wavelength of 313 nm contains 50% by weight or more of the total weight of the phosphors, the ultraviolet rays having a wavelength of 313 nm can be almost prevented from leaking outside the glass tube 2.

Examples of the phosphor that absorbs ultraviolet light having a wavelength of 313 nm include BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ , Sr ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu ²⁺ , (Sr, Ca, Ba) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu ²⁺ , Ba _1-xy Sr _X Eu _y Mg _1-z Mn _z Al ₁₀ O ₁₇ (where x, y and z are 0 ≦ x ≦ 0.4 and 0.07 ≦, respectively) a blue phosphor such as BaMg ₂ , where y ≦ 0.25, 0.1 ≦ z ≦ 0.6, and z is particularly preferably 0.4 ≦ z ≦ 0.5. Green phosphor such as Al ₁₆ O ₂₇ : Eu ²⁺ , Mn ²⁺ , MgGa ₂ O ₄ : Mn ²⁺ , CeMgAl ₁₁ O ₁₉ : Tb ³⁺ , YVO ₄ : Eu ³⁺ , YVO ₄ : Dy ³⁺ ( Red phosphors such as green and red light emission) can be used.

Note that phosphors of different compounds may be mixed and used for one kind of emission color. For example, only BAM as a blue phosphor, LAP (does not absorb 313 nm wavelength) and BAM: Mn ²⁺ as a green phosphor, and YOX (does not absorb 313 nm wavelength) and YVO ₄ : Eu ³⁺ as a red phosphor. May be used. In such a case, it is possible to prevent the ultraviolet rays from leaking out of the glass tube 2 almost certainly by adjusting the phosphor that absorbs the wavelength of 313 nm so that the total weight composition ratio is 50% by weight or more. .

The phosphor preferably has an average particle diameter of 1 to 10 μm, and more preferably has a surface coated with a film. This is because if the coating is coated, the phosphor is easily dispersed uniformly when forming the phosphor layer 5, and unevenness in the thickness of the phosphor layer 5 is difficult. As the coating, for example, oxides such as Y ₂ O ₃ , La ₂ O ₃ , MgO and SiO, preferably Y ₂ O ₃ and La ₂ O ₃ can be used. This is because mercury or the like hardly adheres to the phosphor, and the luminous flux of the lamp can be improved.

  The thickness of the phosphor layer 5 is not particularly limited, but may be 20 to 30 μm in order to maintain the luminous flux of the lamp. In addition, it is preferable that the phosphor layer 5 has substantially the same thickness because the light emission of the EEFL 1 can be made uniform.

The metal oxide film 6 is not particularly limited as long as it includes a metal oxide. For example, a metal oxide such as Y ₂ O ₃ , La ₂ O ₃ , MgO, and SiO may be included. The metal oxide film 6 prevents the metal deposited from the glass tube 2 from adsorbing to the phosphor layer 5 and deteriorating the glass tube 2, and protects the glass tube 2 to improve the lamp life. be able to.

  The thickness of the metal oxide film 6 may be 0.5 to 1.5 μm. This is because if the thickness of the metal oxide film 6 is larger than 1.5 μm, the translucency cannot be maintained, and if it is smaller than 0.5 μm, the effect of protecting the glass tube 2 of the metal oxide film 6 cannot be obtained.

The glass tube 2 is made of glass such as lead glass, lead-free glass, soda glass or borosilicate glass, preferably hard borosilicate glass. If it consists of these glass, the dark startability of EEFL1 can be improved more. More specifically, the glass material described above contains a large amount of alkali metal oxides typified by sodium oxide (Na ₂ O). For example, in the case of sodium oxide, the sodium (Na) component is contained in the glass tube 2 over time. Elutes on the inner surface. This is because sodium has low electronegativity, so that sodium eluted on the inner peripheral surface of the bottom surface portion 2a of the glass tube 2 contributes to the improvement of the dark startability. As for EEFL1 formed so that the external electrode 3 may cover the outer peripheral surface of the edge part 2b, the content rate of the alkali metal oxide in the said glass material has preferable 3 mol% or more and 20 mol% or less. For example, when the alkali metal oxide is sodium oxide, the content of sodium oxide is preferably 5 mol% or more and 20 mol% or less. If it is less than 5 mol%, the probability that the dark start time will exceed 1 second increases (in other words, if it is 5 mol% or more, the probability that the dark start time will be within 1 second increases), and if it exceeds 20 mol%, the probability increases. This is because the glass tube 2 is blackened (browned brown) and whitened due to use of time, leading to a decrease in luminance and a decrease in strength of the glass tube 2. Moreover, when natural environment protection is considered, it is preferable that the glass tube 2 consists of lead-free glass.

  The glass tube 2 is not particularly limited, but has an inner diameter of 1.2 to 7.0 mm, preferably 1.4 to 5.0 mm, a thickness of 0.2 to 0.6 mm, and a tube length of 200 to 2400 mm. Preferably it is 200-1500 mm. This is because with such a glass tube 2, the phosphor layer 5 can be formed evenly.

  The external electrode 3 is made of a metal such as silver, solder, aluminum, or copper, preferably silver and solder. An electrode in which silver coated on the bulb is covered with solder is preferable because silver has high conductivity, and solder can suppress sulfur from being exposed to the atmosphere and being sulfided. The external electrode 3 is disposed in contact with a portion of 1.0 to 5.0 mm, preferably 2.5 to 3.5 mm from the end of the glass tube 2. At this time, the external electrode 3 is not disposed on the bottom surface portion 2a corresponding to the end of the glass tube 2, and the bottom surface portion 2a is exposed.

  The discharge medium 7 is not particularly limited as long as it is generally used for the EEFL 1, but a light emitting material such as mercury, rare gas such as argon, neon, etc. may be used.

  The EEFL 1 of the present embodiment has a configuration in which a metal oxide film 6 is disposed between the glass tube 2 and the phosphor layer 5, but the phosphor layer 5 and the metal are disposed between the glass tube 2 and the protective film 4. A configuration in which the oxide film 6 is further arranged may be employed, or a configuration in which the phosphor layer 5 is further arranged in a spot shape on the protective film 4 may be employed. Further, the metal oxide film 6 may have a larger area than the phosphor layer 5.

  Although the manufacturing method of EEFL1 of this embodiment is not specifically limited, For example, what is necessary is just to manufacture as follows.

  First, the glass tube 2 in which both ends are coated with the metal oxide film 6 applied to the inner peripheral surface and the phosphor solution are prepared. Next, the phosphor layer 5 is formed by applying this phosphor solution to the inner peripheral surface of the glass tube 2 and drying it. Next, the metal oxide film 6 and the phosphor layer 5 applied to the inner peripheral surface of the end 2b are removed.

The phosphor solution may be prepared by, for example, stirring and dispersing a phosphor and additives such as a thickener, a binder, and a dispersant using a planetary mixer. At this time, it is preferable to uniformly disperse the phosphor in the form of primary particles. This is because the thickness of the phosphor layer 5 becomes uniform and emission spots can be prevented. Although this fluorescent substance solution is not specifically limited by a viscosity etc., what is necessary is just to prepare so that the application quantity of the fluorescent substance solution with respect to the glass tube 2 may be 20-50 g / m < ² >. As the thickener, nitrocellulose, ethylcellulose or the like having high viscosity and low combustion temperature may be used. As the binder, barium oxide, calcium oxide, boron oxide, calcium phosphate, a double oxide containing calcium, a double oxide containing boron, or the like may be used. As the dispersant, a liquid selected from butyl acetate, propyl acetate, and ethyl acetate may be used, and it is particularly preferable to use butyl acetate that has a low vapor pressure, ensures work safety, and improves the work environment.

  Examples of a method of applying the phosphor solution to the inner peripheral surface of the glass tube 2 include a method of pouring the phosphor solution with a nozzle from the upper end of the glass tube 2 in a hanging posture, or a glass in a hanging posture. A method of sucking up the phosphor solution from the lower end of the tube 2 by vacuum suction, opening it into the atmosphere, and discharging the excess phosphor solution may be used. In the case of a thin glass tube 2 having an inner diameter of 8 mm or less, a method of sucking up the phosphor solution is preferable. This is because, in the method of pouring the phosphor solution, the phosphor is solidified on the outer peripheral surface of the nozzle and it is difficult to insert the nozzle into the glass tube 2, and the productivity may be lowered. As a method of removing only the metal oxide film 6 and the phosphor solution at the end 2b of the glass tube 2, for example, a method of removing by putting a brush or the like from the end 2b, a method of ultrasonic cleaning, or the like may be used.

  Next, a protective film solution is prepared, and this protective film solution is applied to the inner peripheral surface (the part from which the phosphor solution is removed) of the end 2b of the glass tube 2. The protective film solution includes, for example, a compound containing a rare earth metal having an electronegativity of 1.2 or less, a compound containing cesium, and additives such as a thickener, a binder, and a dispersant, a planetary mixer, etc. The mixture may be stirred and dispersed using At this time, it is preferable to disperse the rare earth compound and the cesium compound up to the limit melting amount. For example, it is only necessary to disperse 5 to 10% by weight of europium oxide and 0.3 to 0.5% by weight of cesium sulfate in isopropyl alcohol as a dispersant. This is because the dark startability can be further improved. The thickener and the binder may be the same as the phosphor solution described above. As the dispersant, isopropyl alcohol or the like may be used.

  Next, the phosphor layer 5 and the protective film 4 are formed through the steps of drying and baking, the discharge medium 7 is introduced, and the glass tube 2 is sealed. Finally, the external electrode 3 is formed on the outer peripheral surface of the end 2b to obtain the EEFL 1 of this embodiment.

  As the method for drying, it is only necessary to blow dry air into the glass tube 2 or adjust the temperature and pressure. For example, dry air at a temperature of 20 to 30 ° C. may be supplied at a supply rate of 50 to 200 ml / min until the phosphor solution and the protective film solution are dried. As the firing method, firing may be performed at a temperature of 600 to 700 ° C. for 5 to 10 minutes, the solvent contained in the phosphor solution and the protective film solution may be vaporized and sintered. In order to improve unevenness of the phosphor layer 5 and the protective film 4, it is preferable to adjust the drying temperature and the flow rate of the dry air.

(Embodiment 2)
FIG. 2 is a partially cutaway view showing a backlight unit which is an example of a light emitting device according to the present invention.

  As shown in FIG. 2, the backlight unit 10 of the present embodiment is disposed on the case 11 covered with the light-transmitting plate 11 a, the plurality of EEFLs 1 accommodated in the case 11, and the inner surface of the case 11. A light emitting diode 14 and an inverter 15 are provided. The EEFL 1 uses the EEFL of Embodiment 1 as it is, and includes a glass tube 2 in which a protective film and a phosphor layer are applied to the inner peripheral surface and a discharge medium is disposed inside, and an external electrode 3. Further, the bottom surface portion 2a of the glass tube 2 is a translucent portion having translucency where the external electrode 3 is not disposed. The light emitting diode 14 is disposed so as to face the bottom surface portion 2a of one EEFL1, and the light emitted from the light emitting diode 14 is disposed so as to pass through the bottom surface portion 2a and be irradiated to the protective film. The case 11 includes a power feeding plate 13 disposed on the bottom surface thereof and a lamp holder 12 disposed on the power feeding plate 13, and the external electrode 3 is fitted into the lamp holder 12. Further, the power feeding plate 13 and the light emitting diode 14 are respectively connected to the inverter 15 by lead wires.

  The backlight unit 10 of the present embodiment is configured as described above. For example, even if the backlight unit 10 is stored under dark conditions for a long time, if the voltage is applied to the external electrode 3 while the light emitting diode 14 is turned on, A light-emitting device using EEFL1 with good dark startability, in which electrons as initial electrons are easily emitted from the protective film, is obtained.

  Although case 11 is not specifically limited, What is necessary is just to include the bottom face used as a reflecting plate, the side surface including the one surface where the light emitting diode 14 is arrange | positioned, and the translucent board 11a. The translucent plate 11a functions as a window that can transmit light emitted by the EEFL1, and may be a diffuser plate including optical sheets, for example. In order to prevent the resin or the like used for the optical sheets from being deteriorated by ultraviolet rays, the phosphor contained in the phosphor layer of EEFL1 uses a phosphor that absorbs ultraviolet rays having a wavelength of 313 nm as described above. It is preferable to contain 50% by weight or more of the total weight of the body. In this case, since it is possible to prevent the ultraviolet rays having a wavelength of 313 nm from leaking outside the glass tube 2, the characteristics of the backlight unit 10 can be maintained for a long time. In particular, when a polycarbonate (PC) resin is used as the optical sheet, it is more susceptible to deterioration and discoloration due to ultraviolet rays having a wavelength of 313 nm than when an acrylic resin is used. The effect of including a phosphor that absorbs ultraviolet rays of 313 nm is great.

  The power supply plate 13 is not particularly limited, but a power supply member made of phosphor bronze, stainless steel, or the like may be provided on the surface of an elongated insulating plate made of polycarbonate.

  The lamp holder 12 is electrically connected to the power supply plate 13 and is not particularly limited as long as it can hold the EEFL1 and supply power to the external electrode. However, the lamp holder 12 is made of an elongated plate made of a conductive material such as phosphor bronze or stainless steel, and has a EEFL1 tip. What is necessary is just to be formed in the shape along an outer periphery, and when an external electrode is inserted, this front-end | tip part bends outside, and an external electrode is hold | maintained with the restoring force. Further, the number of lamp holders 12 corresponds to the number of EEFL1.

  The light emitting diode 14, the inverter 15, and the lead wire are not particularly limited as long as they are generally used in a light emitting device.

  According to the discharge lamp of the present invention, the dark startability can be improved. In particular, the ability to connect in parallel can improve the dark startability of EEFL, which is attracting attention as a light source of a backlight unit, and is thus useful.

  Further, according to the light emitting device of the present invention, a discharge lamp having good dark startability, for example, EEFL having good dark startability can be used as a light emission source.

It is sectional drawing which shows an example of the discharge lamp of this invention. It is a partially broken figure which shows an example of the light-emitting device of this invention.

Explanation of symbols

1 EEFL
DESCRIPTION OF SYMBOLS 2 Glass tube 2a Bottom part 2b End part 3 External electrode 4 Protective film 5 Phosphor layer 6 Metal oxide film 7 Discharge medium 10 Light-emitting device 11 Case 11a Light-transmitting plate 12 Lamp holder 13 Power supply plate 14 Light-emitting diode 15 Inverter

Claims (7)

A discharge lamp comprising a bulb, a pair of electrodes respectively disposed at an end of the bulb, a phosphor layer and a protective film arranged on an inner surface of the bulb, and a discharge medium sealed in the bulb There,
At least one selected from the pair of electrodes is an external electrode in contact with the outer peripheral surface of the bulb;
The protective film includes a rare earth metal that is disposed at least on an inner peripheral surface portion corresponding to a portion of the bulb that is in contact with the external electrode and has an electronegativity of 1.2 or less. Discharge lamp.   The discharge lamp according to claim 1, wherein the protective film is exposed to a discharge space side of the bulb and is in contact with the discharge medium.   The discharge lamp according to claim 1, wherein the rare earth metal includes at least one selected from the group consisting of cerium, samarium, europium, and terbium.   The discharge lamp according to claim 1, wherein the protective film further contains cesium.   The discharge lamp according to claim 1, wherein the bulb is made of glass containing sodium. A plurality of discharge lamps;
A light emitting device including a window capable of transmitting light emitted by the plurality of discharge lamps, and a case storing the plurality of discharge lamps;
The said discharge lamp is a discharge lamp of any one of Claims 1-5, The light-emitting device characterized by the above-mentioned.   The light-emitting device according to claim 6, wherein the discharge lamp includes a bulb including a light-transmitting part in the vicinity of the protective film, and a light-emitting diode is disposed in the case so as to face the light-transmitting part.

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