WO2007032320A1

WO2007032320A1 - Hot cathode discharge lamp, lamp unit and display

Info

Publication number: WO2007032320A1
Application number: PCT/JP2006/318003
Authority: WO
Inventors: Shiro Iida
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2005-09-13
Filing date: 2006-09-11
Publication date: 2007-03-22
Also published as: EP1936660A1; TW200729275A; KR20080044264A; CN101263576A; JPWO2007032320A1

Abstract

Disclosed is a hot cathode discharge lamp (20) comprising a glass bulb (22) whose cross section perpendicular to the tube axis has a flattened shape, and electrode coils (31a, 31b) arranged within the glass bulb (22) so that the axes thereof are aligned along the major diameter of the flattened shape. The length L of the electrode coils (31a, 31b) in the axis direction satisfies the following relation: L2 < L < L1, with L1 being the major inner diameter of the flattened shape of the glass bulb (22)and L2 being the minor inner diameter thereof. Also disclosed is a backlight unit (5) comprising the hot cathode discharge lamp (20) as a light source.

Description

Specification

Hot-cathode discharge lamp, lamp unit, and display device

Technical field

The present invention relates to a hot cathode discharge lamp, a lamp unit including the same as a light source, and a display device. Background art

At present, a cold cathode discharge lamp is mainly adopted as a light source of a backlight unit of a liquid crystal display. The cold cathode discharge lamp is suitable as a light source for a backlight unit that is required to be thin because it is suitable for reducing the diameter.

By the way, with the upsizing of the liquid crystal display, there is a demand for higher efficiency of a lamp used as a light source of a backlight unit of the liquid crystal display. At present, cold cathode discharge lamps are mainly adopted as light sources for backlight units, but hot cathode discharge lamps, which have higher efficiency than these lamps, are noted as new light sources for backlight units. I'm starting.

[0003] Patent Document 1 discloses a hot cathode discharge lamp in which the cross section of the annular glass bulb is flat. By doing so, it is stated that the illuminance directly below the illumination device using the hot cathode discharge lamp as a light source can be increased, and thus the lamp efficiency can be improved.

Further, in Patent Document 2, in a fluorescent lamp used for a light source of a backlight unit, a technology for improving the uniformity of the brightness without lowering the brightness of the knock unit by making the cross section of the glass bulb elliptical. Is disclosed.

Patent Document 1: Japanese Patent Application Laid-Open No. 63-81753

Patent Document 2: Japanese Patent Application Laid-Open No. 2000-10094

Disclosure of the invention

Problem that invention tries to solve

However, the hot cathode discharge lamp has a problem in adopting it as a light source of the backlight unit in view of the short life of the lamp. The present invention has been made in view of the above-described points, and an object thereof is to provide a long-life hot cathode discharge lamp, a lamp unit, and a display device.

Means to solve the problem

The inventor of the present invention has conducted intensive studies in order to prolong the life of a hot cathode discharge lamp used as a light source of a backlight unit which is required to be thin. The inventor noted that the lifetime of the hot cathode discharge lamp depends on the amount of emitter applied to the electrode coil. That is, the inventor noted that if the amount of emitter applied per unit length of electrode coil is the same, the life is extended in proportion to the length of the electrode coil. However, when the length of the electrode coil of the hot cathode discharge lamp is increased, the diameter of the glass bulb, which is an envelope of the hot cathode discharge lamp, must be increased accordingly. However, as back light units are required to be thinner, it is not desirable to increase the diameter of the glass bulb.

Therefore, in a hot cathode discharge lamp according to the present invention, a glass bulb whose cross section perpendicular to the tube axis is a flat shape, and an electrode disposed in the glass bulb with the axis directed in the long diameter direction of the flat shape. And the axial length L of the electrode coil is L2 <L <L1 where L1 is the length of the long inner diameter of the flat shape of the glass bulb and L2 is the length of the short inner diameter. It is characterized by the fact that the relationship is fulfilled and it is a feature.

Effect of the invention

In the above configuration, since the glass bulb has a flat shape, the hot cathode discharge lamp is disposed in the thickness direction of the backlight unit by arranging the short inner diameter of the glass bulb. It is possible to reduce the thickness. In the hot cathode discharge lamp according to the present invention, the axis of the electrode coil is disposed in the major axis direction of the glass bulb, and the length L of the electrode coil is longer than the length L2 of the short inner diameter of the glass bulb. Therefore, the life can be extended as compared with the cross-sectional circular (diameter L2) hot cathode discharge lamp having the same thickness.

In the present specification, “flat shape” means that a glass tube having a circular cross section is squeezed in the vertical direction, and the inner diameter in the vertical direction is short and the inner diameter in the horizontal direction is long. In addition to the shape including the two flat portions facing the contour and the curved portion connecting them, it also includes an elliptical shape in which all the contours are represented by a curve. In addition, the inventor of the present invention conducted intensive studies to extend the life of a hot cathode discharge lamp for a backlight unit. The inventor noted that increasing the partial pressure ratio of krypton as a buffer noble gas lengthens the life. However, it has been known that the lamp output (total luminous flux) decreases when the krypton partial pressure ratio is increased, so the krypton partial pressure ratio is limited to about 15%. However, the inventor found that the problem that the lamp output decreases as the krypton partial pressure ratio is increased occurs when the hot cathode discharge lamp is turned on in a normal temperature atmosphere, and the case of the backlight unit is It has been found that when the lamp is placed in the body and turned on in an atmosphere of about 50 ° C. to 70 ° C., there is no problem that the lamp output decreases.

Therefore, a hot cathode fluorescent lamp disposed in a housing, and a rare gas is enclosed in the glass bulb, and the rare gas contains 20% or more of krypton as a partial pressure ratio. It is preferable to be included.

In the above-described configuration, since krypton is enclosed by 20% or more in the partial pressure ratio, the effect that the lamp life is longer than the conventional one can be obtained. Further, the hot cathode discharge lamp according to the present invention is disposed in the housing of the lamp unit, and since the atmosphere in which the lamp is disposed is higher than room temperature, krypton is enclosed as a buffer noble gas. Also the lamp output is good. In addition, when the voltage division ratio of krypton is increased, the lamp voltage is decreased, so that the starting characteristic is improved and the discharge maintenance can be facilitated.

Here, the partial pressure ratio of krypton is preferably 60% or less. The partial pressure ratio of krypton in the noble gas is 60. This is because it becomes difficult to dim the lamp if / ₀ is exceeded. In addition, since Talypton has a larger atomic weight compared to argon, the mercury enclosed in the envelope diffuses as the krypton partial pressure ratio increases, so the luminous flux at lamp starting is also increased. The partial pressure ratio of krypton in the rare gas is preferably 60% or less because the rising characteristics of Furthermore, since krypton is very expensive compared to argon, enclosing krypton more than necessary leads to meaningless cost increase, so the partial pressure ratio of krypton in the noble gas is 60% or less. Is preferred. This is because when the partial pressure ratio of krypton in the rare gas exceeds 60%, so-called moving stripes are generated at the time of lamp lighting. Further, the partial pressure ratio of krypton is more preferably 45% or more. As a result, the lamp voltage can be decreased to increase the lamp current, which is a power that can obtain a very high efficiency lamp.

Here, the partial pressure ratio of krypton is more preferably 55% or less. It is because experiments have shown that the lamp efficiency decreases when the krypton partial pressure ratio exceeds 55%.

A lamp unit according to the present invention is characterized by including a housing and any one of the above-mentioned hot cathode discharge lamps disposed in the housing. This makes it possible to obtain a lamp unit with high efficiency and long life S.

A display device according to the present invention includes the lamp unit as a light source. This makes it possible to obtain a display device with long life and high efficiency with low power consumption.

Another display device according to the present invention is characterized by comprising a housing and any one of the above-mentioned hot cathode discharge lamps disposed in the housing. As a result, it is possible to obtain a display device with a long life and high efficiency with low power consumption.

Brief description of the drawings

FIG. 1 is a schematic perspective view showing a configuration of a liquid crystal display device with an aspect ratio of 16: 9 according to the present embodiment.

[FIG. 2] FIG. 2 is a schematic perspective view showing the configuration of the backlight unit according to the present embodiment.

[FIG. 3] FIG. 3 is a diagram showing the configuration of the hot cathode discharge lamp according to the present embodiment, and FIG. 3 (a) is a plan sectional view, and FIG. 3 (b) is a cross section taken along the A-A section. It is a cross-sectional view at the time of

[FIG. 4] FIG. 4 is a view for explaining the process of deforming a glass tube whose cross section perpendicular to the tube axis is circular in cross section into an elliptical shape.

[FIG. 5] FIG. 5 is a table showing the relationship between the partial pressure ratio of krypton in the buffer noble gas and the lamp life.

[FIG. 6] FIG. 6 is a schematic view showing movement stripes generated at the time of lamp light control lighting.

[FIG. 7] FIG. 7 is a cross-sectional view of a glass bulb according to a modification. Explanation of sign

[0015] 1 knotter unit

20 hot cathode discharge lamp

21 Mercury

22 glass bulb

24 protective film

26 Phosphor layer

31a, 31b electrode coil

Length of L electrode coil

Length of long inner diameter of LI glass bulb

Length of short inner diameter of L2 glass bulb

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a hot cathode discharge lamp, a backlight unit, and a liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings.

First, the configuration of the liquid crystal display device according to the present embodiment will be described with reference to FIG. FIG. 1 is a view showing a liquid crystal display device according to the present invention, in which a part is cut away so that the internal state can be seen.

The liquid crystal display device 1 is, for example, a liquid crystal color television, and a liquid crystal display unit 3 and a backlight unit 5 are incorporated in a housing 4. The liquid crystal screen unit 3 includes, for example, a color filter substrate, a liquid crystal, a TFT substrate, a drive module, etc. (not shown), and a color image is displayed on the liquid crystal screen unit based on the image signal of the external force of the liquid crystal screen 3 Displayed on screen 6 of 3.

First, the configuration of the backlight unit according to the present embodiment will be described with reference to FIG. FIG. 2 is a schematic perspective view showing the configuration of the liquid crystal display knock light unit 5 with an aspect ratio of 16: 9 according to the present embodiment. In order to show the internal structure in the same figure, a part of the front panel 16 is cut away, and is shown. As shown in FIG. 2, the backlight unit 5 includes a plurality of hot cathode discharge lamps 20, a case 10 having an opening and containing the lamps 20, and an opening of the case 10 And a front panel 16 covering the

The housing 10 is made of, for example, polyethylene terephthalate (PET) resin, and a metal such as silver is vapor-deposited on its inner surface 11 to form a reflective surface.

The lamps 20 have a straight tubular shape, and in the present embodiment, the fourteen lamps 20 are disposed in a direct system in the housing 10 and electrically connected in parallel. The lamp 20 is constant current controlled by a lighting circuit not shown. The configuration of the lamp 20 will be described later. The opening of the case 10 is covered with a translucent front panel 16 in which the diffusion plate 13, the diffusion sheet 14 and the lens sheet 15 are laminated, and foreign matters such as dust and dirt do not get inside. , As sealed.

The diffuser plate 13 and the diffuser sheet 14 in the front panel 16 diffuse and diffuse the light emitted from the lamp 20, and the lens sheet 15 aligns the light in the normal direction of the sheet 15. They are configured such that the light emitted by the lamp 20 forces the light forwardly uniformly over the entire surface (light emitting surface) of the front panel 16.

First Embodiment

[Configuration of hot cathode discharge lamp]

Next, a hot cathode discharge lamp according to a first embodiment of the present invention will be described. FIG. 3 is a view showing the configuration of a hot cathode discharge lamp (hereinafter, may be simply referred to as “lamp”) 20 according to the present embodiment, and FIG. 3 (a) is a plan sectional view Fig. 3 (b) is a cross-sectional view taken along the line A-A.

The lamp 20 has a straight tubular glass bulb 22 and a pair of electrodes 30 a and 30 b disposed at both ends in the glass bulb 22.

The glass bulb 22 is made of barium.strontium silicate glass (soft glass having a softening point of 675. C). As shown in FIG. 2 (b), the glass bulb 22 has an elliptical cross section perpendicular to the tube axis, having a long inner diameter L1 and a short inner diameter L2. As described above, since the glass bulb 22 has an oval shape, the short inner diameter of the glass bulb 22 is disposed in the thickness direction of the backlight unit 5, that is, the short inner diameter of the glass bulb 22 is the front panel 16 Against By arranging them vertically, it is possible to make the backlight unit 5 thinner. Incidentally, even in the case where the short diameter of the force glass bulb 22 whose thickness is to be increased may be disposed in parallel to the front panel 16, the long life can be realized also in this case.

Further, an exhaust pipe 28 is sealed at one end (left end in the drawing) of the glass bulb 22. The exhaust pipe 28 is used for evacuating the inside of the glass valve 22 and for sealing a rare gas, and is sealed after the exhaust and sealing. By providing the exhaust pipe 28 at one end of the glass bulb 22 instead of both ends, the cold spot control can be facilitated. In other words, it is because it does not know which cold spot part can be made if it is provided at both ends.

The length Li of the portion of the exhaust pipe 28 that protrudes to the outside is 10 mm. Here, this length Li is preferably 5 mm or more and 30 mm or less, more preferably 15 mm or more and 30 mm or less. If it is less than 5 mm, sealing and cutting becomes difficult. If it is 15 mm or more and 30 mm or less, the efficiency can be improved by controlling the coldest spot. If it exceeds 30 mm, the longer it becomes, it becomes easier to break, more parts do not shine, and the commercial value decreases. Moreover, even if it exceeds 30 mm, no further improvement in efficiency can be expected.

The electrodes 30a, 30b are of the so-called glass bead mounting type, and are pinch sealed (crush sealed) on the glass bulb 22. Electrodes 30a and 30b are triplenoidal coils, each having a 6.5-turn electrode coil 31a and 31b, and a pair of lead wires 32a, 32b, 33a and 33b for supporting the electrode coils 31a and 31b, and the leads. It becomes a force with the bead glass 34a, 34b holding the lines 32a, 32b, 33a, 33b. The electrode coils 31a and 31b are made of, for example, tungsten, and oxides of strontium, calcium, and nickel are applied as an emitter.

As shown in FIG. 3 (b), the axes of the electrode coils 31a and 31b are disposed in the long inner diameter direction, and the length L of the electrode coils 31a and 31b is longer than the short inner diameter L2. It is shorter than L1.

A protective film 24 made of alumina is formed on the inner surface of the glass bulb 22. A phosphor layer 26 is stacked on the protective film 24. As the phosphor in the phosphor layer 26, red (Y

2

:: Eu), green (LaP〇: Ce, Tb) and blue (BaMg Al 2 O: Eu, Mn) are emitted

3 4 3 2 16 27

A mixture of rare earth phosphors is used.

In the glass bulb 22, about 5 mg of mercury 21 and argon (Ar) having a pressure of 500 Pa at normal temperature as a buffer noble gas are sealed. The mercury 21 sealed in the glass bulb 22 may be sealed in the form of an amalgam such as zinc mercury, tin mercury, bismuth, indium mercury, etc. in addition to mercury alone. Here, the specifications of the dimensions and the like of the lamp 20 in the case of use in a 45-inch liquid crystal display backlight unit will be described.

[0028] The long inside diameter L1 of the glass bulb 22 is 17 mm, the short inside diameter L2 is 10 mm, and the total length L is 1010 mm

o

The inter-electrode distance Le is 950 mm, and the tube wall load We is 0. 05 (W / cm ² ). The tube wall load is a value obtained by dividing the lamp power by the inner surface area of the portion of the glass bulb 22 corresponding to the inter-electrode distance Le.

In order to obtain a long-life lamp, it is preferable that the tube wall load We of the lamp 20 be defined in the range of 0.205-0. 07 (W / cm ² ).

When the tube wall load is greater than 0.70 (W / cm ² ), the luminous flux deterioration becomes severe in a short time, and a long strain life can not be obtained. Also, if it becomes smaller than 0.025 (W / cm ² ), the tube diameter of the lamp becomes too thick if the lamp power is fixed to obtain the necessary luminous flux, and it is not suitable for use as a backlight unit. . Also, if the power is reduced by fixing the shape, it will be difficult to maintain the discharge.

The above-described lamp 20 has characteristics of a lamp voltage of 125 V, a lamp efficiency of 811 m / W, and an average life of 39,000 hours.

[Method of manufacturing lamp]

Next, a method of manufacturing the lamp 20 will be described. First, prepare a straight tube glass tube whose cross section perpendicular to the tube axis is circular. After the glass tube is washed and dried, alumina is applied to the inner surface of the glass bulb by a known method and dried to form a protective film. Furthermore, the phosphor suspension is applied and dried on the protective film by a known method.

Then, the glass tube is heated at about 600 ° C. in an electric furnace to bake the phosphor. After firing, the cross-sectional shape is deformed while keeping the temperature of the glass tube not falling. FIG. 4 is a view for explaining the process of deforming a glass tube whose cross section perpendicular to the tube axis is circular in cross section into an elliptical shape.

Prepare oval hollow molds 25a and 25b made of stainless steel as shown in Fig. 4 (a). As shown in Fig. 4 (b), with the temperature of the glass tube kept warm, the glass tube is used as a mold 25a, 25b. Place it between the two. Then, as shown in FIG. 4 (c), the cross section of the glass tube 23 is deformed into an elliptical shape by the weight of the mold 25a. Thereby, a glass bulb 22 having an elliptical cross section as shown in FIG. 4 (d) can be obtained.

In the above method, the cross section of the glass tube is deformed from circular to elliptical at the time of firing of the phosphor, so in order to deform the glass tube, the step of separately heating the glass tube is carried out. The manufacturing process can be simplified.

In the above, when the inner diameter of the glass tube is 15 mm, it is possible to obtain a glass bulb having a cross-sectional oval shape with a long inner diameter Ll = 17 mm and a short inner diameter L2 = 10 mm. In addition, when the glass tube having an inner diameter of 20 mm is used, it is possible to obtain a cross-sectional oval glass bulb having a long inner diameter Ll = 24 mm and a short inner diameter L2 = 16 mm. The dimensions of the inner diameter of the glass bulb can be adjusted to various values by changing the material of the glass bulb.

Thereafter, the phosphor in the extra portion in the glass bulb 22 is peeled off to form the phosphor layer 26 shown in FIG.

Then, the electrodes 30a and 30b are sealed to the glass bulb 22 by a known pinch seal, mercury 21 and buffer rare gas are added and exhausted from the exhaust pipe 28 to seal the exhaust pipe 28. You can get a lamp 20.

[Effect of this embodiment]

As described above, with the axes of the electrode cones 31a and 31b directed in the major axis direction of the glass bulb 22, the length L of the coil of the electrode cones 31a and 31b is longer than the length L2 of the short inner diameter of the glass bulb. Here, if the amount of emitter applied to the electrode coil per unit length is the same, the lamp life will be approximately proportional to the length (number of turns) of the electrode coil. Therefore, with the configuration of the lamp 20 according to the present embodiment, it is possible to achieve longer life than the cross section circular hot cathode discharge lamp having the same thickness.

In addition, since the glass bulb has a flat shape, the backlight unit 5 can be made thinner by arranging the hot cathode type discharge lamp in the thickness direction of the backlight unit 5 by arranging the short inner diameter of the glass bulb. You can make money.

In addition, the conventional backlight unit uses a cold cathode discharge lamp as a light source, and the lamp efficiency of the cold cathode discharge lamp is usually about 501 m / W. The efficiency as a tot was low. On the other hand, the backlight unit according to the present embodiment

5 uses the hot cathode discharge lamp 20 as a light source, and the lamp efficiency of the hot cathode discharge lamp 20 is about 801 mZW, so the backlight unit 5 is said to be very efficient.

Furthermore, if the distance between the lamps 20 in the housing 10 of the backlight unit 5 and the distance to the liquid crystal panel is equal to the distance between the lamps 20 disposed in the housing 10 of the knock light unit 5. It is known that the brightness unevenness of the liquid crystal display can be suppressed. In the present embodiment, since the shape of the glass bulb 22 is elliptical, the distance from the lamp 20 to the liquid crystal panel (not shown) can be increased with respect to the length of the electrode coils 31a and 31b. . Along with this, even if the distance between the lamps 20 arranged in the housing 10 of the backlight unit 5 is increased to a size equal to the distance from the lamp 20 to the liquid crystal panel, uneven brightness is suppressed. Therefore, the distance between lamps of the lamps 20 disposed in the housing 10 can be increased, and the number of lamps 20 required as light sources can be reduced. As a result, the number of parts required for the backlight unit 5 can be reduced, which contributes to the low cost of the backlight unit 5.

In FIG. 2, the number of the lamps 20 disposed in the housing 10 of the backlight unit 5 is the same as that of the force lamp 20 described in the configuration in which 14 lamps 20 are disposed. It may be suitably changed according to the screen size etc. of the liquid crystal display.

Second Embodiment

Next, a hot cathode discharge lamp according to a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment in the components of the buffer noble gas and the other components are the same as the first embodiment, and therefore, the description of the parts other than the components of the buffer noble gas is omitted.

The inventors of the present invention conducted intensive studies to extend the life of a hot cathode discharge lamp used as a light source of a backlight unit. The inventor noted that mixing the krypton in addition to argon as a buffer noble gas to increase the partial pressure ratio of krypton prolongs the lamp life. The lamp life is prolonged when the partial pressure ratio of krypton is increased. The emitter is less likely to scatter from the electrode coil by increasing the partial pressure ratio of krypton, which has a larger atomic weight than argon, mainly when argon is mainly used. It is because Force Tari It has been conventionally known that the lamp output (total luminous flux) decreases as the amount of packed pton is increased, so the krypton partial pressure ratio is limited to about 15%.

However, according to the intensive studies of the inventors of the present invention, the problem that the lamp output decreases as the krypton partial pressure ratio is increased occurs when the hot cathode discharge lamp is lit in a normal temperature atmosphere. It has been found that when the lamp is disposed in the casing of the backlight unit and turned on in an atmosphere of about 50 ° C. to 70 ° C., there is no problem that the lamp output decreases.

Therefore, the inventor examined how to set the partial pressure ratio of krypton in the buffer noble gas. FIG. 5 is a table showing the relationship between the partial pressure ratio of krypton in the buffer noble gas and the lamp life. In the column of “moving stripes at 30% of light control” in FIG. 5, “o” indicates a state in which no moving stripes are generated, and “X” indicates a state in which no moving stripes are generated. In the column of “Luminous flux rise characteristics”, “o” indicates a good state, “Δ” indicates a good state, and “X” indicates a bad state.

From FIG. 5, it can be seen that the lamp life force exceeds 50000 hours when the partial pressure ratio of krypton as a buffer noble gas is 20% or more, so it is preferable that the partial pressure ratio of krypton is 20% or more. It is. In addition, when the voltage division ratio of krypton is increased, the lamp voltage is decreased, so that the starting characteristics are improved and the discharge maintenance becomes easy.

In addition, with the lamp 20 having a constant rated power (eg, 20 W), the lamp voltage decreases and the lamp current increases as the krypton voltage division ratio is increased. When the lamp is lit, the electrode coil 31a, 31b needs to be heated in order to release the emitter force electron applied to the electrode coil 31a, 31b. The lamp current alone can sufficiently heat the electrode coil 31a, 31b I can do it. Therefore, conventionally, the filament current is separately supplied to the electrode coils 31a and 31b, and the electrode coils 3la and 31b are heated by heat generation due to the application of the filament current. That is, as the lamp current is lower, more filament current must be applied to raise the temperature of the electrode coils 31a and 31b. Since the filament current is separately supplied in addition to the lamp power, it is desirable to increase the lamp current as much as possible and reduce the necessary filament current from the viewpoint of reducing the power consumption. After intensive research, the present inventors have found that by increasing the partial pressure ratio of krypton, By reducing the lamp voltage and increasing the lamp current, it was found that the required filament current can be reduced and energy loss can be suppressed.

By the way, it turned out that when the partial pressure ratio of krypton exceeds 60%, it becomes difficult to dim the lamp a little, so it can be said that the partial pressure ratio of krypton is preferably 60% or less. . It should be noted that although dimming becomes more difficult when the partial pressure ratio of krypton exceeds 60%, the life becomes longer as the partial pressure ratio of krypton becomes higher, so longer life and good dimming characteristics It is desirable to determine the partial pressure ratio of krypton by weighing the requirements.

In addition, since krypton has a larger atomic weight than argon, the mercury enclosed in the glass bulb 22 becomes more diffused as the krypton partial pressure ratio increases, so the lamp has been exposed since lamp startup. From this point of view also, the partial pressure ratio of Talyton in the rare gas is preferably 60% or less because the luminous flux start-up characteristic is lowered. The luminous flux rise characteristics of FIG. 5 were visually confirmed.

[0044] Furthermore, since krypton is very expensive compared to argon, it is unnecessary to enclose cryptone, which leads to a meaningless cost increase, so the partial pressure ratio of krypton in the noble gas is 60 It is preferable that the ratio is not more than%.

If the partial pressure ratio of krypton in the rare gas exceeds 60%, so-called movement stripes will occur when the lamp is lit. FIG. 6 is a schematic view showing moving stripes generated at the time of lamp dimming, and is a diagram for describing the moving stripes described above.

With moving stripes, when the lamp 20 is turned on, bright parts and dark parts appear alternately in a part or the whole of the lamp 20 to form a stripe pattern, which is directed toward one of the tube ends of the lamp 20. It refers to the phenomenon of movement. In the example shown in FIG. 6, the stripe pattern moves from the right side to the left side of the paper and shows how to move.

The cause of the generation of moving stripes has not been clarified at this stage, but it has been confirmed that moving stripes are generated when dimming is performed or the partial pressure ratio of talipton is increased. The inventors of the present invention have intensively studied that when the krypton partial pressure ratio exceeds 60%, the generation of moving stripes becomes remarkable.

Particularly in the above, it is more preferable that the mixing ratio of krypton is 45% or more for the rare gas sealed in the glass bulb 22. This causes the lamp voltage to drop sufficiently. Because the lamp current can be increased, a very high efficiency lamp can be obtained.

In addition, as shown in Fig. 5, when the partial pressure ratio of krypton exceeds 55%, the lamp efficiency slightly decreases by experiments, so the partial pressure ratio of krypton is 55% or less. Is desirable. This is because the krypton partial pressure ratio can suppress energy loss due to a decrease in filament current as the lamp current increases up to 45%. When the krypton partial pressure ratio exceeds 55%, the lamp current itself Is too large and is consumed as heat when the electrode coils 31a and 31b are energized, which is considered to increase energy loss.

In addition, when a backlight unit using as a light source a hot cathode type discharge lamp in which 50% of argon and 50% of krypton are enclosed as a buffer noble gas is prepared and tested, there is a problem of decrease in lamp output. Was not confirmed. In addition, since a hot cathode discharge lamp is used as a light source, a highly efficient backlight unit can be obtained.

As described above, the present invention can provide a long-life, high-efficiency hot cathode fluorescent lamp, a lamp unit, and a liquid crystal display device.

Although the present invention has been described above based on the embodiment, it goes without saying that the content of the present invention is not limited to the specific example shown in the above embodiment, and, for example, the following modifications Can be considered.

(1) In the above, as shown in FIG. 3 (b), the glass bulb has been described to have an elliptical cross section perpendicular to the tube axis, but it is not limited to this and has a long inner diameter and a short inner diameter. Any shape may be used. For example, as shown in Fig. 7 (a), it may be flat, or as shown in Fig. 7 (b), it may be rectangular. Also in these cases, since the long inner diameter L1 is larger than the size of the short inner diameter L2, the axial length of the electrode coil can be increased. Thus, the length of the electrode coil can be increased relative to the length of the short inner diameter L2, so that a long-life hot cathode discharge lamp can be provided. In addition, by arranging the glass bulb 22 so that the short inner diameter L2 is perpendicular to the liquid crystal panel surface, it is possible to make the device thinner. (2) In the above, the glass bulb 22 has been described as having a linear appearance. The force S is not limited to this. For example, the glass bulb 22 has a U-shaped appearance, a U-shaped appearance, etc. It may be in the form of

(3) In the above, although argon and krypton were enclosed as the buffer noble gas, neon and xenon may be enclosed in addition to these. Since xenon has a large amount of atoms, it suppresses the scattering of the emitter coated on the electrode coil, and by enclosing xenon, the life can be further extended.

(4) In the above, the case where the protective film 26 is formed on the inner surface of the glass bulb 22 has been described, but the protective film 26 may not be formed.

(5) In the above, the backlight unit has been described as an example of the lamp unit, but the invention is not limited thereto. For example, a casing and the heat according to the present embodiment disposed in the casing It may be a general lighting unit provided with a cathode discharge lamp.

(6) In the above, the liquid crystal display device has been described as an example of the display device. However, the present invention is not limited to this. For example, the display device is provided in a housing and the housing The sign apparatus may be provided with the hot cathode discharge lamp of the present embodiment.

Industrial applicability

The present invention can be widely applied to a hot cathode discharge lamp. In addition, since the present invention can provide a high efficiency and long life hot cathode discharge lamp, a lamp unit, and a display device, its industrial utility value is extremely high.

Claims

The scope of the claims

[1] A glass bulb having a flat cross section perpendicular to the tube axis,

And an electrode coil disposed in the glass bulb so that the axis is directed in the direction of the long inner diameter of the flat shape,

The axial length L of the electrode coil satisfies the relationship of L2 <L <L1 when the length of the long inner diameter of the flat shape of the glass bulb is L1 and the length of the short inner diameter is L2. The hot cathode discharge lamp according to claim 1, characterized in that

[2] A hot cathode fluorescent lamp disposed in a housing, comprising:

A noble gas is enclosed in the glass bulb,

The rare gas contains 20% or more of krypton at a partial pressure ratio.

The hot cathode discharge lamp according to claim 1, characterized in that

3. The heat negative discharge lamp according to claim 2, wherein the partial pressure ratio of the krypton is 60% or less.

[4] The hot cathode discharge lamp according to claim 2 or claim 3, wherein a partial pressure ratio of the diluted krypton is 45% or more.

[5] The hot cathode discharge lamp according to any one of claims 2 to 4, wherein a partial pressure ratio of the diluted krypton is 55% or less.

[6] case,

The hot cathode type discharge lamp according to any one of claims 1 to 5, which is disposed in the case and any one of the following.

A lamp unit comprising:

[7] A display device comprising the lamp unit according to claim 6 as a light source.

[8] case,

The hot cathode type discharge lamp according to any one of claims 1 to 5, which is disposed in the housing.

A display device comprising: