WO2007004464A1

WO2007004464A1 - Discharge lamp, backlight unit, and liquid crystal display

Info

Publication number: WO2007004464A1
Application number: PCT/JP2006/312769
Authority: WO
Inventors: Toshihiro Terada; Shingo Tsutsumi; Hideki Wada; Tomokazu Matsuura
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2005-07-06
Filing date: 2006-06-27
Publication date: 2007-01-11
Also published as: KR20080025683A; TW200707502A; WO2007004464A8; JPWO2007004464A1

Abstract

Disclosed is an external electrode fluorescent lamp. Specifically disclosed is an external electrode fluorescent lamp (10) comprising a glass container (12), external electrodes (14, 16) arranged on the outer surface of the glass container, a protective film (18) arranged on the inner surface of the glass container, and a phosphor film (20). The protective film is formed at least in regions corresponding to the external electrodes, and composed of an aggregate of metal oxide (yttrium oxide) particles. The protective film has an average film thickness of not more than 2 μm, and a surface roughness of not more than 1.7 μm. By having such a protective film, the glass container can be prevented from formation of pin holes.

Description

Specification

Discharge lamp, backlight unit, and liquid crystal display device

Technical field

The present invention relates to a discharge lamp, a knock light unit, and a liquid crystal display device, and more particularly, to a discharge lamp having an external electrode disposed on the outer surface of a glass container.

Background art

One of discharge lamps having external electrodes is an external electrode fluorescent lamp (EEFL). The external electrode type fluorescent lamp is suitable for small diameter lamps as compared with the hot cathode fluorescent lamp, like the cold cathode fluorescent lamp. For this reason, it is preferably used as a light source of a backlight unit that is required to be thin (downsized).

The backlight unit can be roughly divided into an edge light system in which a light guide plate is placed on the back surface of the LCD panel, and a fluorescent lamp is disposed on the end surface of the light guide plate, and a plurality of fluorescent lamps on the back surface of the LCD panel. There are two types, directly below, arranged in parallel on the back. When comparing the two, in general, the edge light method is excellent in thinning and luminance uniformity of the light emitting surface, but it is disadvantageous in terms of high luminance, while the direct method is superior in terms of high luminance, but thin. It can be said that it is disadvantageous in terms of conversion.

[0003] For this reason, the LCD system used in a liquid crystal television set with an emphasis on high brightness often employs a direct method.

If a cold cathode fluorescent lamp is used as the light source for the direct-type backlight unit, one high-frequency lighting circuit (inverter) is required for each cold negative fluorescent lamp, leading to increased costs. Recently, an external electrode fluorescent lamp that emits light by dielectric barrier discharge by providing external electrodes on the outer circumferences of both ends of a tubular glass container and using the glass tube wall as a capacitance has been actively developed. Since the external electrode fluorescent lamp itself has a capacitance, it can be used to light a large number of lamps with one inverter.

[0004] However, in the external electrode fluorescent lamp, when the lamp is turned on, the inner wall of the glass container corresponding to the external electrode is exposed to the impact of argon ions or mercury ions, which causes the gas The lath container part is eroded, and in some cases, a hole (pinhole) is created. Therefore, in the external electrode type fluorescent lamp described in Patent Document 1, a large number of metal oxide particles are gathered on the inner wall portion of the glass container corresponding to the outer electrode so as to protect the inner wall from the impact of argon ions and mercury ions. Provide a protective film.

Patent Document 1: Japanese Unexamined Patent Publication No. 2003-17005

Patent Document 2: Japanese Patent Laid-Open No. 11-354079

Disclosure of the invention

Problems to be solved by the invention

[0005] By the way, with the increase in luminance of liquid crystal televisions, there is a demand for higher luminance of external electrode fluorescent lamps used in backlight units for the liquid crystal televisions. In order to achieve this, for example, it is conceivable to increase the driving current, which is conventionally about 4 to 4.5 mA, to improve the luminance. However, even when the external electrode fluorescent lamp is provided with the protective film, the present inventor has found that when the driving current is increased, the glass container is suddenly perforated. It was.

[0006] To cope with this, it is conceivable to increase the thickness of the protective film, but the luminance decreases in proportion to the thickness of the protective film.

The above problem is common to external electrode type discharge lamps that do not have a phosphor layer.

In view of the above-described problems, the present invention provides a discharge lamp capable of suppressing the occurrence of defects such as perforation as much as possible even when the luminance is improved by increasing the drive current, and the like. And a liquid crystal display device having the backlight unit.

Means for solving the problem

[0007] In order to achieve the above object, a discharge lamp according to the present invention includes a glass container, an external electrode disposed on a part of the outer surface of the glass container, and at least a portion facing the external electrode. A protective film made of an aggregate of metal oxide particles formed on the inner surface of the glass container, the protective film has an average film thickness of 2 m or less, and the protective film has a surface roughness of 1.7. It is characterized by being less than μm. [0008] In order to achieve the above object, a discharge lamp according to the present invention includes a glass container, an external electrode disposed on a part of the outer surface of the glass container, and at least a portion facing the external electrode. A protective film made of an aggregate of metal oxide particles formed on the inner surface of the glass container, wherein the protective film has an average film thickness of 2 m or less, and is an internal void in the protective film. The average cross-sectional area per hole is 0.1 μm ² or less

[0009] Further, an alkali metal compound is dispersed in the protective film. In this case, the alkali metal compound is a cesium compound, and the surface roughness of the protective film is 0.6 μm or more.

In addition, an alkaline earth metal compound is dispersed in the protective film, and the metal oxide particles have yttrium oxide force.

[0010] Further, the glass container is made of glass containing sodium oxalate in a range of 5% to 20%, and the inner surface of the glass container has a region where the protective film is not formed. A part of the external electrode is formed on the outer surface of the glass container facing the region.

The external electrode is characterized in that the thickness in the vicinity of the end portion is gradually reduced gradually toward the end portion.

[0011] Further, the external electrode is characterized by comprising a solder layer formed in a region subjected to a roughening treatment on the outer surface of the glass container.

The external electrode is made of a metal sleeve extrapolated to the glass container and solder filled between the metal sleeve and the outer peripheral surface of the glass container. In order to achieve the above object, a backlight unit according to the present invention includes the above-described discharge lamp as a light source.

[0012] In order to achieve the above object, in the liquid crystal display device according to the present invention, the backlight unit includes an envelope that houses a plurality of the discharge lamps, and a liquid crystal display panel; The above-mentioned backlight unit is provided on the back surface of the liquid crystal display panel. The invention's effect

[0013] According to the discharge lamp of the present invention, the average film thickness of the protective film made of an aggregate of metal oxide particles is set to 2 m or less, so that the luminance decreases when the protective film thickness is increased. It can be suppressed as much as possible, and the surface roughness of the protective film is 1. or less, and the denseness of the protective film has been improved, so even if the brightness is improved by increasing the drive current, etc. The occurrence of problems such as these can be suppressed as much as possible.

[0014] Further, according to the discharge lamp of the present invention, the average thickness of the protective film made of an aggregate of metal oxide particles is as follows, and per closed hole that is an internal void in the protective film: Since the average cross-sectional area is set to 0 .: L m ² or less, the same effect as described above can be obtained.

Furthermore, since the alkali metal oxide is dispersed in the protective film, good dark startability can be obtained. In this case, if a cesium compound is used as the alkali metal oxide and the surface roughness of the protective film is 0.6 m or more, good dark startability can be obtained more reliably.

[0015] Further, since the alkaline earth metal compound is dispersed in the protective film, good dark startability can be obtained.

Further, since the metal oxide particles forming the protective film are made of yttrium oxide, adsorption of mercury by the protective film is reduced, and unnecessary consumption of mercury can be suppressed.

Further, the glass container is made of glass containing sodium oxalate in a range of 5% or more and 20% or less, and an outer surface portion of the glass container facing a region where the protective film is not formed on the inner surface of the glass container. Thus, a part of the external electrode is formed, so that the dark startability is improved.

[0016] Further, since the thickness of the external electrode is gradually reduced gradually toward the end, the corona discharge generated at the end of the external electrode is prevented, and the generation of ozone is prevented. It can be suppressed.

Further, since the external electrode is composed of a solder layer formed in the roughened surface of the outer surface of the glass container, a discharge lamp having an external electrode with high adhesion strength to the outer surface of the glass container is used. It is out. [0017] Further, since the external electrode includes a metal sleeve extrapolated to the glass container and solder filled between the metal sleeve and the outer peripheral surface of the glass container, the external electrode is connected to the apparatus. It is possible to reduce damage to the external electrode that tends to occur when the socket is attached to or detached from the socket. Further, according to the backlight unit and the liquid crystal display device according to the present invention, since the discharge lamp is provided, the temperature of the external electrode The rise can be suppressed, and discoloration due to thermal degradation of the other member constituting the knocklight unit, which is in the vicinity of the external electrode, can be suppressed.

Brief Description of Drawings

FIG. 1 is a half sectional view showing a schematic configuration of an external electrode fluorescent lamp according to an embodiment.

FIG. 2 is an electron micrograph showing a cross section of a protective film in a comparative fluorescent lamp.

FIG. 3 is a graph showing experimental results of examining the relationship between drive current and electrode temperature for a comparative fluorescent lamp and an example fluorescent lamp.

FIG. 4 is a diagram schematically showing a cross section of a protective film.

FIG. 5 is an electron micrograph showing a cross section of a protective film in an example fluorescent lamp.

FIG. 6 is a diagram for explaining a method of forming a protective film in relation to the method of manufacturing the external electrode fluorescent lamp according to the embodiment.

FIG. 7 is a diagram showing the results of a test relating to the dark start rate.

FIG. 8 is an electron micrograph of a cross section of a protective film in one of the external electrode fluorescent lamps used in an experiment relating to dark startability.

FIG. 9 is an electron micrograph of a cross-section of a protective film in one of the external electrode fluorescent lamps used in an experiment relating to dark startability.

FIG. 10 is a perspective view showing a schematic configuration of a backlight unit according to the embodiment.

FIG. 11 is a block diagram of the backlight unit.

FIG. 12 is a diagram showing a schematic configuration of a liquid crystal television using the backlight unit according to the embodiment.

FIG. 13 is a view showing a modification of the external electrode.

FIG. 14 is a view showing a modification of the external electrode. FIG. 15 is a diagram showing a schematic configuration of an external electrode fluorescent lamp according to a modification.

FIG. 16 is a diagram showing a schematic configuration of an external electrode fluorescent lamp according to another modification.

Explanation of symbols

[0019] 10, 76, 90 External electrode fluorescent lamp

12, 92 Glass container

14, 94 1st external electrode

16, 96 Second external electrode

18, 98 Protective film

40 knock light unit

48 Envelope

60 LCD TV

62 LCD panel

BEST MODE FOR CARRYING OUT THE INVENTION

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

FIG. 1 is a half sectional view showing a schematic configuration of an external electrode fluorescent lamp 10 (hereinafter simply referred to as “fluorescent lamp 10”) according to an embodiment. In FIGS. 1, 6, and 10 to 16, the scales between the constituent members are not unified.

The fluorescent lamp 10 has a glass container 12 in which both ends of a glass tube made of borosilicate are hermetically sealed. The total length L1 of the glass container 12 is 740 mm, the outer diameter is 4. Omm, and the inner diameter is 3. Omm.

A first external electrode 14 and a second external electrode 16 are formed on the outer periphery of both end portions of the glass container 12. The first and second external electrodes 14 and 16 are cylindrical electrodes having a width Wl = 20 mm and formed over the entire circumference of the glass container 12. The first external electrode 14 has a two-layer structure. Of the two layers, the one closer to the glass container 12 is a silver (Ag) paste film 14A, and the farther one is a lead (Pb) -free solder film 14B. Similarly, the second external electrode 16 also has a two-layer structure in which a silver (Ag) paste film 16A and a lead (Pb) free solder film 16B are laminated in this order from the glass container 12 side.

[0022] A portion of the inner peripheral surface of the glass container 12 facing the first and second external electrodes 14, 16 A protective film 18 is formed on substantially the entire surface including the entire length. The protective film 18 is made of an aggregate of metal oxide particles. In this example, yttrium oxide (YO

twenty three

) Is used. In addition, as the metal oxide, for example, alumina (Al 2 O 3)

2 3 can also be used. However, when yttrium oxide and alumina are compared, yttrium oxide is less likely to adsorb mercury, so it suppresses unnecessary consumption of mercury that contributes to light emission. Yttrium oxide is preferred. The protective film does not necessarily have to be formed over almost the entire length as in the illustrated example, and is formed at least on the inner peripheral surface portion of the glass container 12 facing the first and second external electrodes 14, 16. I don't mind. Details of the protective film 18 will be described later.

A phosphor film 20 is formed by being laminated inside the protective film 18. The formation range of the phosphor film 20 in the longitudinal direction of the glass container 12 is between the first external electrode 14 and the second external electrode 16. A part of the phosphor film 20 may be applied to the inner peripheral surface portion of the glass container 12 facing the first external electrode 14 and the second external electrode 16. The phosphor film 20 includes three kinds of rare earth phosphors of red (R), green (G), and blue (B), and emits white light as a whole. In this example, red phosphor (Y 2 O: Eu), green phosphor (LaPO: Ce, Tb), blue phosphor (BaMg Al

2 3 4 2

O: Eu, Mn) is used.

16 27

In addition, a predetermined amount of mercury and a mixed rare gas having a predetermined pressure are enclosed in the glass container 12. In this example, a neon argon mixed gas (Ne90% + ArlO%) of about 7 kPa (20 ° C) is enclosed as a rare gas mixture with a mercury power of about 2000 g!

In the fluorescent lamp 10 having the above-described constituent power, when a high frequency voltage is applied to the first and second outer electrodes 14 and 16 by the inverter, a discharge phenomenon occurs in the hermetic sealed space (discharge space) in the glass 12. Then, ultraviolet rays are emitted, and the ultraviolet rays are converted into visible light by the phosphor film 20 and emitted outside the glass container 12. As the inverter, for example, an inverter having a maximum applied voltage of 2.5 kV and an operating frequency of 60 kHz can be used. The above discharge is an dielectric barrier discharge. That is, when a high-frequency, high-voltage AC voltage is applied to the first and second external electrodes 14 and 16, dielectric polarization occurs in the glass immediately below the first and second external electrodes in the dielectric glass container 12, The inner wall of that part acts as an electrode. As a result, a high voltage is introduced into the glass container 12, and a dielectric barrier is introduced into the glass container 12. A discharge occurs. As described above, the dielectric barrier discharge is a discharge in which the discharge space is surrounded by the dielectric (glass container 12) and the electrode is not directly exposed to the plasma.

[0025] Although the electrode (external electrode) is not directly exposed to the plasma, the inner peripheral portion of the glass container mainly corresponding to the region where the external electrode is disposed is composed of mercury ions, neon ions, and argon ions (hereinafter referred to as these). When collectively said, it is simply called “ion”). Therefore, the protective film 18 is provided for the purpose of protecting the impact container and the glass container.

Conventionally, an external electrode fluorescent lamp used in a knocklight unit is generally lit with a drive current of about 4 to 4.5 mA. In response to the demand for higher brightness of the knocklight unit in recent years, in order to improve the brightness of the external electrode fluorescent lamp, if the current value of the drive current is increased or the glass container is made thinner, The temperature of the external electrode rose and reached around 140 ° C, causing a thermal runaway, which will be described later, and pinholes were observed to appear sharply in the glass container.

[0026] The inventor of the present application conducted various experiments to find out the cause. Although the details of the experiment are omitted, it was finally found that the cause of the above phenomenon was that the protective film did not fully function.

Figure 2 shows a photomicrograph of the cross section of the protective film of the external electrode fluorescent lamp (hereinafter referred to as “comparative fluorescent lamp”) where this phenomenon occurs. Both (a) and (b) are cross sections of the portion corresponding to the external electrode, (a) corresponds to one external electrode, and (b) corresponds to the other external electrode. The reason why the thickness of the protective film is different between (a) and (b) will be described later.

[0027] Although the protective film is formed by agglomeration of metal oxide particles, the protective film is not completely packed with metal oxide particles, and the protective film communicates with the outer surface. It has an open hole and a closed hole that is an internal space. As shown in Fig. 2, it is considered that the higher the number of open holes and the smaller the number of open holes, the higher the probability of receiving an impact on the inner wall force of the glass container.

Increasing the drive current value increases the temperature of the external electrode. When the temperature of the external electrode rises, the temperature of the glass container part in contact with it rises, the dielectric loss of the glass increases, and the temperature rises further. In addition, the temperature of glass containers rises due to ion bombardment. To do. Due to the electronegativity, ions collide with the glass rather than collide with the protective film, resulting in greater energy loss and greater heat generation.

[0028] Then, when the temperature at the electrode (hereinafter referred to as "electrode temperature") reached about 140 ° C, thermal runaway occurred and pinholes suddenly appeared in the glass container.

Fig. 3 shows the relationship between the drive current value and the electrode temperature in the comparative fluorescent lamp. The electrode temperature was measured with a radiation thermometer. A broken line shows a comparative fluorescent lamp. Conventionally, as described above, since it is used at a drive current value of about 4 to 4.5 mA, the electrode temperature is less than 80 ° C, and there is no problem of pinholes due to thermal runaway. However, at present, it may be lit at a drive current of about 8 mA, and in the future it is planned to illuminate at 10 mA. In this case, the pinhole due to the thermal runaway becomes a problem.

[0029] To suppress the collision of ions with the glass container, it is conceivable to further increase the thickness of the protective film. However, the thicker the protective film, the lower the brightness of the fluorescent lamp. The inventors of the present invention have confirmed that when the average thickness of the protective film exceeds 2 m, the luminance is reduced by about 20 to 25% compared to the state without the protective film, and the required luminance cannot be obtained. Therefore, the inventor of the present application solves the problem of pinholes by further improving the denseness of the protective film, thereby suppressing the collision of ions with the inner wall of the glass container and thereby suppressing the amount of heat generated in the part. It was decided. The denseness of the protective film was evaluated using the following indices.

FIG. 4 is a diagram schematically showing a cross section of the protective film. In FIG. 4, the reference numeral 22 indicates metal oxide particles, and the reference numeral 24 indicates closed pores serving as internal voids.

The surface roughness appearing in the cross section of the protective film was measured, and the measured value was used as one of the indicators showing the denseness of the protective film. It can be said that the smaller the surface roughness is, the smaller the pores communicating with the outer surface in the protective film are. The surface roughness is the “maximum height Ry” measured according to JIS B 0601: '94.

[0031] In addition, in the cross section of the protective film, the area of each cross section of the closed holes 24 serving as internal voids is measured and averaged, and the average value (hereinafter simply referred to as "closed hole area"). ) Was taken as another indicator of compactness. Naturally, the smaller the closed hole, the higher the density of the protective film. Here, the closed hole is in the cross section of the protective film. Thus, it is assumed that the voids are enough to contain at least 1.0 metal oxide particles having an average particle diameter. In addition, the closed hole is not completely closed by the wall formed by the metal oxide particle group, but the wall is converted to the size of the metal oxide particle having an average particle diameter. There may be 4.0 or less discontinuous portions.

[0032] Further, in addition to the above-mentioned average area of closed holes, the number of closed holes per unit cross-sectional area of the protective film (hereinafter simply referred to as "the number of closed holes") was also used as an indicator of denseness.

Although detailed experimental results are omitted, it was found that if the surface roughness does not exceed 1 m (1 μm or less), the electrode temperature is about 120 ° C (when 10 mA is lit). This is a temperature value in which the 140 ° C force in question is sufficiently suppressed.

[0033] Further, if exceeded closed porosity area 0. 1 μ m ² (if 0. 1 μ m ² or less), the electrode temperature can be suppressed to 120 ° C about (at 10mA lit) However, it was divided. Further, in this case, (if four Z mu m ² or less) number closed pores four Z mu m ² and unless exceeded, the electrode temperature can be suppressed to about 120 ° C (at 10mA lit) However, it was divided.

FIG. 5 shows one of the external electrode fluorescent lamps used in the experiment, and is a cross-sectional microscope of the protective film in the external electrode fluorescent lamp according to the example (hereinafter referred to as “Example fluorescent lamp”). It is a photograph. (A) is a partial cross-section of the protective film corresponding to the first external electrode (hereinafter referred to as “first part”), and (b) is a part of the protective film corresponding to the second external electrode. It is a cross section (hereinafter referred to as “second part”). Example fluorescent lamp, the surface roughness of the first portion 0. 05 ^ m, closed pore area 0. 008 ^ m ^2, closed pore number 1. is two Z m ^2, put the second portion The surface roughness was 0.12 / ζ πι, the closed hole area was 0.007 μm ² , and the number of closed holes was 3.4 Z / m ² . In addition, the average particle diameter of the metal oxide particles in the example fluorescent lamp was 0.113111 in the first part and 0.12 / zm in the second part.

In addition, when the relationship between the drive current value and the electrode temperature was examined for the example fluorescent lamp, the result shown by the solid line in FIG. 3 was obtained. As can be seen from FIG. 3, in the fluorescent lamp of the embodiment, even when the driving current is 10 mA, the electrode temperature is about 104 ° C, and the problem of pinholes due to thermal runaway can be suppressed.

Further, dividing from FIG. 3 is that the example fluorescent lamp can suppress the electrode temperature more than the comparative fluorescent lamp if the magnitude of the drive current is the same. Example According to the fluorescent lamp, the electrode loss is reduced as the calorific value of the electrode portion decreases, and as a result, the power consumption can be reduced.

Next, a method for forming a protective film in the manufacturing process of the fluorescent lamp 10 will be described with reference to FIG. Except for the method of forming the protective film, the method is the same as a general known manufacturing method of the external electrode type fluorescent lamp, and the description thereof is omitted.

First, a suspension 32 containing metal oxide particles is adhered to the inner surface of a glass tube 30 that is a material of the glass container 12 (FIG. 1).

[0036] Specifically, a tank 34 containing a suspension 32 is prepared. The suspension 32 is obtained by adding a predetermined amount of metal oxide particles and -trocellulose (NC) as a thickener in butyl acetate as an organic solvent.

Then, the glass tube 30 is held vertically and held at a lower end portion immersed in the suspension 32. By the suction force of a vacuum pump (not shown), the upper end force of the glass tube 30 is also evacuated from the glass tube 30, and the suspension 32 is sucked up by making the inside of the glass tube 30 a negative pressure [step A]. While the liquid level in the glass tube 30 reaches the upper end (predetermined height), the suction is stopped and the glass tube 30 is pulled up from the suspension 32. As a result, the suspension 32 adheres in a film form to a predetermined region on the inner periphery of the glass tube 30. In this case, since the suspension 32 flows downward on the inner wall of the glass tube 30 due to gravity, the thickness of the suspension 32 becomes thicker toward the lower part than the upper part. This is why the thickness of the protective film was different between (a) and (b) in the photographs in Figs.

[0037] Next, while the glass tube 30 held vertically is rotated around the tube axis, the suspension 32 adhering to the film is dried [step B]. At this time, centrifugal force acts on each metal oxide particle in the direction toward the inner wall of the glass tube. As a result, the metal oxide particles clog toward the inner wall of the glass tube, and the final protective film is denser than when no centrifugal force is applied (when the glass tube is not rotated). Will be improved. In this case, the denseness of the protective film finally obtained can be changed (adjusted) depending on the rotation speed and the viscosity of the suspension (fluidity of the metal oxide particles in the suspension). Optimum values for the number of rotations and the viscosity of the suspension can be obtained by trial and error through experiments.

[0038] Further, the inventor of the present application has developed a fluorescent lamp with improved dark startability which is particularly required when used as a light source of a backlight unit, as will be described later. Such fluorescent lamp In order to realize the above, a cesium (Cs) compound was mixed with the suspension to form a protective film. In other words, the dark startability is improved by dispersing a cesium (Cs) compound having a low electronegativity in the protective film.

[0039] The mixing ratio of the cesium compound in the suspension was 0.60% by weight or less in this example.

It is also confirmed that the jelly formation of the suspension started from around 0. 60% by weight, and the degree of jelly formation became severe when it exceeded 0. 65% by weight, making it useless. Therefore, the mixing ratio of the cesium compound in the suspension for forming the protective film is preferably 0.65% by weight or less, more preferably 0.60% by weight or less.

[0040] Note that, even when the cesium compound is dispersed in the protective film, the relationship between the respective indicators (surface roughness, closed area, number of closed holes) indicating the denseness of the protective film and the electrode temperature. It has been confirmed that there is little effect on the above-mentioned correlation. This seems to be because the volume of the protective film, which is very low such that the mixing ratio of the cesium compound is 0.6% by weight or less, is extremely small.

[0041] The inventor of the present application creates a lamp (lamp A, B, C, D) in which a cesium compound is dispersed in a protective film based on the fluorescent lamp 10, and confirms the effect of dark startability. I went. For comparison, a lamp X that does not disperse the cesium compound in the protective film was made and a similar experiment was conducted.

Lamps A, B, C, D, and X have basically the same configuration except that the cesium compound is present in the protective film and the type and mixing ratio are different. W1 (Fig. 1) is 40mm longer than other lamps.

[0042] In lamps A, B, C, and D, the types of cesium compounds mixed in the protective film and the mixing ratio (wt% in the suspension) are as follows.

Lamp A ... cesium sulfate (Cs SO), mixing ratio: 0. 60 weight ^_0/0

twenty four

Lamp B ... Shioi匕cesium (CsCl), the mixing ratio: 0. 37 wt ^_0/0 Lamp C ... Shioi匕cesium (CsCl), the mixing ratio: 0. 60 weight ^_0/0 lamp D ... cesium sulfate (Cs SO ), mixing ratio: 0. 37 wt ^_0/0

twenty four

Twenty lamps A, B, C, D, and X were prepared, and the dark start rate after leaving for 22 hours in the dark and the dark start rate after leaving for 94 hours were investigated. Where "dark start rate" Is the percentage obtained by dividing the number of passing lights by the number of specimens (20 in this example), with those that turned on within 1 second from the start of power supply to both external electrodes passed and those that were not passed passed.

[0043] The test results are shown in FIG. In the bar graph shown in Fig. 7, the dark start rate when the white one is left in the dark for 22 hours and the dark start rate when the black one is left in the dark for 94 hours are shown. The

As is clear from FIG. 7, it can be seen that the lamps A, B, C, and D have an improved dark start rate compared to the comparative lamp X. Above all, since the dark start rate of lamps A and D is 100% in any standing time, cesium sulfate is considered to be excellent in improving the dark startability among cesium compounds.

[0044] The difference in the dark starting rate between lamp B and lamp C seems to be due to the difference in the mixing ratio. That is, as a matter of course, the dark start-up rate is considered to be improved as the mixing ratio increases for the same kind of cesium compound. In addition, even when the mixing ratio is small, it is possible to improve the dark start rate by increasing the electrode width, and the test result strength of lamp B and lamp D is also inferred.

[0045] Furthermore, the present inventor has defined a range of the surface roughness of the protective film suitable for improving the dark startability. As described above, it is better to make the protective film as dense as possible in order to solve the pinhole problem. However, the inventors of the present invention have found through experiments that satisfactory dark startability cannot be obtained if the protective film is made dense beyond a certain limit. This is presumed to be due to the following reason.

[0046] The cesium compound is considered to be substantially uniformly dispersed on the surface of the protective film and in the inside thereof. The cesium compound that is in direct contact with the discharge space is considered to contribute to the improvement of the dark start. That is, it is considered that the cesium compound mainly present on the surface of the protective film contributes to the improvement of the dark start. However, as is clear from the above-described manufacturing method, the denser the protective film, the flatter the surface of the protective film (that is, the smaller the surface roughness) and the smaller the surface area of the protective film. Less cesium compounds are present on the surface (ie, directly in contact with the discharge space). As a result, the dark startability is degraded.

[0047] Therefore, in order to improve the dark startability, it is only necessary to reduce the denseness of the protective film, but in this case, the problem of pinholes will rise again. Therefore, the inventors of the present application obtained an experiment to determine the surface roughness (the “maximum height Ry”) that can solve the problem of pinholes while satisfying the dark startability.

In this experiment, yttrium oxide (Y 2 O 3) as the metal oxide and sulfuric acid as the cesium compound

twenty three

Using cesium (Cs SO), these are dispersed in IPA (isopropyl alcohol).

twenty four

A suspension was made. In suspension, the mixing ratio of yttrium oxide is 10 wt%, the mixing ratio of the cesium sulfate is 0.5 wt ^_0/0.

[0048] The method of applying the suspension to the inner peripheral surface of the glass tube, drying, and firing are the same as described with reference to FIG. As described above, the jelly formation of the suspension becomes noticeable when the mixing ratio of the cesium compound exceeds 0.60% by weight, but there is a sign even if it is less than 0.60% by weight. It is recognized that the suspension applied to the surface agglomerates and the surface of the coating film has a wave shape with a pitch of several meters to several tens of meters. It was also observed that this pitch varied depending on the mixing ratio of the cesium compound. Depending on the number of rotations of the glass tube in the drying process, the pitch does not change much, but the wave height, that is, the maximum height Ry (surface roughness) changes.

[0049] Twenty different external electrode fluorescent lamps having different surface roughnesses were produced for each surface roughness, and the dark starting rate after being left in the dark for 22 hours was investigated.

Although detailed experimental results are omitted, it was found that if the surface roughness was at least 0.6 111 (if it was above 0), the dark start-up rate would be 100%. Moreover, even if cesium compounds are dispersed in the protective film, the range of “surface roughness” and “closed hole area” for solving the pinhole problem does not disperse the cesium compound in the protective film. It is confirmed that it is the same as described above!

FIG. 8 is a photomicrograph of the cross section of the protective film in one of the external electrode fluorescent lamps used in the experiment. The lamp shown in Fig. 8 has a dark start rate of 70%, but has failed in terms of the dark start rate, although the pinhole problem has been solved. Incidentally, the surface roughness (maximum height Ry) of the protective film in the lamp shown in FIG. 8 was 0.43 μm. Figure 9 is a photomicrograph of the cross section of the protective film in another external electrode fluorescent lamp used in the experiment. The lamp shown in Fig. 9 eliminates the pinhole problem and starts dark. The rate was also 100%. Incidentally, the surface roughness (maximum height Ry) of the protective film in the lamp shown in FIG.

[0051] Next, an example in which the fluorescent lamp 10 according to the above embodiment is used as a light source of a knocklight unit will be described. Needless to say, any one of the lamps A, B, C, and D may be used as the light source.

FIG. 10 is a perspective view showing a schematic configuration of a direct-type backlight unit 40. FIG. FIG. 10 is a view in which a translucent plate 46 described later is broken. The knock light unit 40 is arranged and used on the back of an LCD (liquid crystal display) panel (not shown in FIG. 10), and constitutes an LCD device.

The knock light unit 40 includes an envelope 48 including a rectangular reflecting plate 42, a side plate 44 surrounding the reflecting plate 42, and a translucent plate 46 provided in parallel with the reflecting plate 42. Both the reflector 42 and the side plate 44 are reflective films (not shown) in which silver or the like is vapor-deposited on one main surface of the plate made of PET (polyethylene terephthalate) resin (the inner surface when assembled as the envelope 48). ) Is formed.

The light transmissive plate 46 is formed by laminating a light diffusing plate 50, a light diffusing sheet 52, and a lens sheet 54 in this order from the reflecting plate 42 side.

Inside the envelope 48, a plurality of (in this example, 16) fluorescent lamps 10-power reflecting plates 42 are housed at equal intervals in the short side direction in parallel with the long sides. These fluorescent lamps 10 are electrically connected in parallel by a wiring member (not shown).

[0054] As described above, the fluorescent lamp 10 can suppress the amount of heat generated in the electrode portion more than before. As a result, it is possible to suppress discoloration (yellowing) or the like due to thermal deterioration in the vicinity of the electrode portion of the translucent plate 46 and other members constituting the envelope 48.

FIG. 11 is a block diagram showing the backlight unit 40 including an inverter 56 that is a power supply circuit unit for lighting the 16 fluorescent lamps 10.

The inverter 56 converts AC power of 50 Z 60 Hz from the commercial power source 58 into high frequency power (for example, 60 kHz as described above), and supplies the fluorescent lamp 10 with power.

Next, an example in which the knocklight unit 40 is used in a liquid crystal television shown as an example of a liquid crystal display device will be described. FIG. 12 is a diagram showing the liquid crystal television 60 with a part of the front surface thereof cut away. A liquid crystal television 60 shown in FIG. 12 includes a liquid crystal display panel 62, a backlight unit 40, and the like.

The liquid crystal display panel 62 is a color filter substrate, a liquid crystal, a TFT substrate, or the like, and is driven by a drive module (not shown) based on an external image signal to form a color image.

The envelope 48 of the backlight unit 40 is provided on the back surface of the liquid crystal display panel 62, and the back surface force also irradiates the liquid crystal display panel 62.

The inverter 56 is disposed inside the casing 64 of the liquid crystal television 60 and outside the envelope 56.

As described above, the present invention has been described based on the embodiments. Of course, the present invention is not limited to the above-described embodiments. For example, the following embodiments may be employed.

(1) In the above embodiment, the present invention has been described using an example in which the present invention is applied to an external electrode type silver fluorescent lamp. However, the present invention is not limited to a fluorescent lamp and can also be applied to an external electrode type ultraviolet lamp. It is. That is, the phosphor film may be removed from the configuration of the external electrode fluorescent lamp according to the above-described embodiment (the phosphor film is not formed) and configured as an external electrode ultraviolet lamp. The ultraviolet lamp irradiates the irradiated object with ultraviolet rays and is used for sterilization of the irradiated object.

(2) The external electrodes provided on the outer periphery of both ends of the glass container are not limited to those in the above-described embodiment, and may be, for example, in the following forms.

(0 FIG. 13 shows an example in which the external electrode 114 is formed on the outer surface of the end portion of the glass container 112 by known ultrasonic solder dipping. In this case, prior to ultrasonic solder dipping. The area where the external electrode 112 is to be formed on the outer surface of the glass container 112 is roughened to a surface roughness of about 1 to 3 m by sandblasting, which is due to the adhesion of the solder to the glass container surface. The external electrode 112 is formed by immersing the glass container 112 in the ultrasonic solder layer and pulling it up while holding the glass container 112 vertically.

[0059] As the solder material, any of tin, an alloy of tin and indium, and an alloy of tin and bismuth can be used. Can be used. Further, from the viewpoint of adhesion to the glass container 112, it is preferable to contain at least one of antimony, zinc, and aluminum as an additive. Further, from the viewpoint of wettability with the surface of the glass container 112, it is preferable to contain antimony or zinc as an additive.

Further, as shown in FIG. 13, the external electrode 114 has a thickness in the vicinity of the end thereof that gradually decreases gradually toward the end. If the end of the external electrode is angular, corona discharge occurs between the end of the external electrode and the outer peripheral surface of the glass container, and ozone is generated. By adopting the shape shown in FIG. It is possible to effectively suppress the generation of corona discharge and prevent the generation of ozone.

In FIG. 13, reference numeral 116 indicates a phosphor film, and reference numeral 118 indicates a protective film. In this example, the protective film is formed only on the portion of the inner peripheral surface of the glass container facing the external electrode.

(ii) FIG. 14 (a) shows that a metal sleeve 124 as shown in FIG. 14 (b) is extrapolated to the outer periphery of the end of the glass container 122, and the metal sleeve 124 and the outer peripheral surface of the glass container 122 are Solder in between 12

In this example, the external electrode 128 is configured by filling 6. By using a metal sleeve for the external electrode, it is possible to reduce damage to the external electrode that tends to occur when the socket is attached to or detached from the socket of the knocklight unit (device).

[0062] The metal sleeve 124 is made of a material having substantially the same linear expansion coefficient as the glass container 122, for example,

Made of Fe-Ni-Co alloy. The solder 126 may be, for example, 311- eight ₈ - 01 alloy (in weight percent 311 95. 2, Ag is 3. 8, Cu is 1. The ratio of 0) composed of.

In FIG. 14A, reference numeral 130 indicates a phosphor film, and reference numeral 132 indicates a protective film.

(3) In the external electrode type fluorescent lamp 10 of the above embodiment, the external electrodes are provided on the outer periphery of both ends of the glass container 12. , "Third external electrode") may be provided. In this case, the third external electrode is connected to the ground line (ie, grounded). Needless to say, a protective film is formed on the inner surface of the glass container facing the third external electrode.

(4) In the above embodiment, the present invention relates to a fluorescent lamp provided with external electrodes at both ends of a glass container. The force described based on the example applied to the lamp In the present invention, as shown in FIG. 15, the electrode on one end side of the glass container 70 is an external electrode 72, and the electrode on the other end side is in the glass container 70. The present invention can also be applied to a fluorescent lamp 76 configured as an internal electrode 74 to be installed. The end of the glass container 70 on the side where the internal electrode 74 is disposed is sealed with a lead wire 78 and hermetically sealed. The internal electrode 74 is bonded to the inner end of the glass container 70 of the lead wire 78. The lead wire 78 is made of tungsten wire. The internal electrode 74 is a so-called hollow-type electrode having a bottomed cylindrical shape and is a cover of a niobium rod. In the figure, reference numeral 80 indicates a phosphor film, and reference numeral 82 indicates a protective film.

(5) The present invention can also be applied to an external electrode type fluorescent lamp 90 (hereinafter simply referred to as “fluorescent lamp 90”) as shown in FIG. 16 (a) is an external view showing a schematic configuration of the fluorescent lamp 90, and FIG. 16 (b) is a cross-sectional view of the fluorescent lamp 90. FIG. Note that FIG. 16 (b) is a cross-sectional view, but in order to avoid complications, knitting and pinching are omitted.

[0063] The fluorescent lamp 90 has a glass container 92 similar to the fluorescent lamp 10 (FIG. 1). On the outer periphery of the glass container 92, a first external electrode 94 having a “C” cross section extends in the longitudinal direction of the glass container 92. A second external electrode 96 having the same shape is formed on the outer periphery of the glass container 92 so as to face the first external electrode 94. A protective film 98 is formed on the inner peripheral surface portion of the glass container 92 facing the first outer electrode 94 and the second outer electrode 96, and the phosphor film 100 is formed on the remaining portion of the inner peripheral surface of the glass container 92. Is formed.

[0064] An outline of a method for forming the phosphor film 100 and the protective film 98 of the fluorescent lamp 90 having the above-described constitutional power will be described below.

First, a phosphor film is formed on substantially the entire inner peripheral surface of the glass tube, which is the material of the glass container 92. Next, the phosphor film on the inner surface of the glass tube facing the first and second external electrodes 94, 96 is spread. (In this stage, the external electrodes 94 and 96 are not formed yet. However, in order to show the removal range of the phosphor film, the external electrodes are removed for convenience of explanation. ) O

Then, a protective film 98 is formed in the same manner as in the above embodiment described with reference to FIG. As mentioned above, the phosphor film 98 also has a suspension 32 ( Fig. 6) is applied. As a result, the suspension 32 penetrates into the phosphor film 98 as well. Therefore, strictly speaking, the film indicated by reference numeral 100 in FIG. 16B includes not only phosphor particles but also metal oxide particles.

(6) In the above embodiment, cesium sulfate and sodium chloride cesium are exemplified as the cesium compounds dispersed in the protective film in order to improve the dark startability. Cesium (Cs CO) may be used.

twenty three

[0066] The compound dispersed in the protective film is not limited to the cesium compound, and may be a compound of another alkali metal [for example, lithium (Li), sodium (Na), potassium (K)].

Further, not limited to alkali metal compounds, compounds of alkaline earth metals [for example, magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba)] may be used.

[0067] Since the alkali metal and alkaline earth metal described above have low electronegativity, the ability to improve dark startability is improved by dispersing them in the protective film.

(7) In the above embodiment, 1S using borosilicate glass as a material for forming the glass container is not limited to this, and lead glass, lead-free glass, soda lime glass, or the like may be used. In this case, the dark startability can be improved by forming the external electrode so as to cover the end face (outer end face) of the glass container. That is, the glass as described above contains a large amount of sodium oxide (Na 2 O), and the sodium (Na) component is the inner surface of the glass container over time.

2

To elute. Since sodium has a low electronegativity, it is likely that the sodium eluted at the inner edge of the glass container (without a protective film) will contribute to the improvement of dark startability. In consideration of natural environment protection, it is preferable to use lead-free glass. However, glass that does not contain lead at all is difficult for manufacturing reasons, and may actually contain lead as an impurity. Therefore, glass containing lead at an impurity level of 0.1% or less is also defined as lead-free glass.

[0068] Further, the content of sodium oxalate in the glass material forming the glass container is preferably 5% or more and 20% or less. If it is less than 5%, the probability that the dark start time will exceed 1 second increases (in other words, if it is 5% or more, the probability that the dark start time will be within 1 second increases), and if it exceeds 20%, This is because problems such as whitening of the glass container resulting in a decrease in luminance due to long-term use, and a decrease in strength of the glass container occur. [0069] Further, the following may be considered as the external electrodes in this case. For example, a metal cap shape is extrapolated to the end portion of the glass container, or as shown in FIG. 13 and described above, the glass container end is placed in a solder tank in which molten solder is stored. The portion is dated, and consists of a solder layer formed on the end portion. Further, it may be an external electrode as shown in FIG. 14 and described above. In short, a protective film is formed on the inner surface of the glass container, and a part of the external electrode is formed on the outer surface of the glass container opposite to the large area!

Industrial applicability

[0070] The discharge lamp according to the present invention can be suitably used, for example, as a light source of a backlight unit requiring high brightness.

Claims

The scope of the claims

[1] a glass container;

An external electrode disposed on a part of the outer surface of the glass container;

A protective film formed on the inner surface of the glass container at least in a portion facing the external electrode and having an aggregate strength of metal oxide particles,

The protective film has an average film thickness of 2 μm or less,

A discharge lamp characterized in that the surface roughness of the protective film is 1.7 m or less.

[2] a glass container;

The protective film has an average film thickness of 2 μm or less,

The discharge lamp according to claim 1, wherein the average cross-sectional area per closed hole which is an internal space in the protective film is 0.1 μm ² or less.

[3] The discharge lamp according to claim 1, wherein an alkali metal compound is dispersed in the protective film.

4. The discharge lamp according to claim 3, wherein the alkali metal compound is a cesium compound, and the surface roughness of the protective film is 0.6 m or more.

5. The discharge lamp according to claim 1, wherein an alkaline earth metal compound is dispersed in the protective film.

6. The discharge lamp according to claim 1, wherein the metal oxide particles have yttrium oxide force.

[7] The glass container is made of glass containing sodium oxide in a range of 5% to 20%,

2. The glass container inner surface includes a region where the protective film is not formed, and a part of the external electrode is formed on a glass container outer surface portion facing the region. Discharge lamp.

[8] The external electrode has a thickness in the vicinity of its end that gradually decreases gradually as it is directed toward the end. The discharge lamp according to claim 1, wherein V is V.

9. The discharge lamp according to claim 1, wherein the external electrode comprises a solder layer formed in a region subjected to a roughening treatment on the outer surface of the glass container.

10. The electric discharge according to claim 1, wherein the external electrode comprises a metal sleeve extrapolated to the glass container and solder filled between the metal sleeve and the outer peripheral surface of the glass container. lamp.

11. The discharge lamp according to claim 2, wherein an alkali metal compound is dispersed in the protective film.

12. The discharge lamp according to claim 11, wherein the alkali metal compound is a cesium compound, and the surface roughness of the protective film is 0.6 μm or more.

13. The discharge lamp according to claim 2, wherein an alkaline earth metal compound is dispersed in the protective film.

14. The discharge lamp according to claim 2, wherein the metal oxide particles have yttrium oxide force.

[15] The glass container is made of glass containing sodium oxide in a range of 5% to 20%,

3. The glass container inner surface includes a region where the protective film is not formed, and a part of the external electrode is formed on the outer surface of the glass container facing the region. Discharge lamp.

[16] The external electrode has a thickness in the vicinity of the end portion that gradually decreases smoothly as it is directed toward the end portion.

3. The discharge lamp according to claim 2, wherein V is V.

17. The discharge lamp according to claim 2, wherein the external electrode comprises a solder layer formed in a region where the outer surface of the glass container has been roughened.

18. The electric discharge according to claim 2, wherein the external electrode comprises a metal sleeve extrapolated to the glass container and solder filled between the metal sleeve and the outer peripheral surface of the glass container. lamp.

[19] A backlight unit comprising the discharge lamp according to any one of claims 1 to 18 as a light source. The backlight unit includes an envelope that houses a plurality of the discharge lamps, a liquid crystal display panel,

The knock light unit according to claim 19, wherein the envelope is disposed on a back surface of the liquid crystal display panel.

A liquid crystal display device comprising: