KR20100014238A - Backlight comprising hot cathode fluorescent lamp and liquid crystal display device - Google Patents

Abstract

The hot cathode fluorescent lamp 10 and the lamp holder 75 for supporting the hot cathode fluorescent lamp 10, the hot cathode fluorescent lamp 10 is composed of a bulb 12 and the filament 14, the lamp holder 75 ) Is disposed on the outer surface of the bulb 12 of the filament existence region 14c in which the filament 14 is present, and the lamp holder 14 is a backlight 100 made of a metallic material, thereby providing a hot cathode fluorescent lamp. The thermal problem of the backlight 100 provided was solved with a simple configuration.

Description

BACKLIGHT COMPRISING HOT CATHODE FLUORESCENT LAMP AND LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a backlight having a hot cathode fluorescent lamp, and more particularly, to a backlight for a large screen television or a signboard.

Currently, cold cathode fluorescent lamps are mainly employed as light sources of backlight units of liquid crystal displays. Since a cold cathode fluorescent lamp is suitable for thinning, it is used as a light source of the backlight unit which requires thinning (for example, refer patent document 1).

Patent Document 1: Japanese Patent Application Laid-Open No. 56-73855

In recent years, the enlargement of the liquid crystal display is progressing, and the backlight unit is also enlarged with this. As the size of the backlight unit increases, there is a concern that when the cold cathode fluorescent lamp is used as the light source, the lighting circuit becomes complicated and power consumption increases.

Specifically, the cold cathode fluorescent lamp needs to use a high voltage power source because the voltage (driving voltage) required for driving is larger than other lamps. In particular, large liquid crystal displays with screen sizes greater than or equal to 32 inches (e.g., 32 inch, 42 inch, 46 inch, 65 inch or more liquid crystal displays) have recently emerged, resulting in longer lamp lengths and more drive. The voltage tends to become more high.

In addition, since the cold cathode fluorescent lamp has a small power input per unit, it is necessary to increase the number in order to secure the screen brightness. Therefore, there is a possibility of a problem that the assembly cost is increased and the time is required for assembly. This is big.

In the meantime, a method of employing a hot cathode fluorescent lamp as a light source of a backlight unit, which is higher in efficiency than the cold cathode fluorescent lamp and can simplify a lighting circuit, is being considered. However, as a result of the development and research of cold cathode fluorescent lamps to the present day, the defects of hot cathode fluorescent lamps are not overcome.

The inventors of the present invention attempt to solve the problem of the backlight unit, which is becoming more and more prominent with the increase in the size of the liquid crystal display, by using a hot cathode fluorescent lamp rather than by improving the current cold cathode fluorescent lamp.

In the backlight unit using the hot cathode fluorescent lamp, the heat generation is much higher than that using the cold cathode fluorescent lamp. This is because, unlike a cold cathode fluorescent lamp, an electrode including a filament for emitting hot electrons is used in a hot cathode fluorescent lamp. This is because electric power for maintaining discharge current or hot electrons must be input to the filament, and in addition, the power (power) input to the hot cathode fluorescent lamp is larger than that of the cold cathode fluorescent lamp. In addition, the liquid crystal display backlight is preferably required to have a long lifetime of about five times as compared to a hot cathode fluorescent lamp for general illumination. This is because a cold cathode fluorescent lamp that is used as a backlight has a lifespan of 60,000 hours, and a hot cathode fluorescent lamp also needs about five times as long as general lighting to secure an equivalent lifetime. Therefore, the filament coil was lengthened to mount a large number of emitters, and the preheating power increased so much that the amount of heat generated was significantly higher than that of a hot cathode fluorescent lamp for general lighting. As a result, it became clear in our studies that a problem that the large amount of heat generation deteriorates the optical member of the liquid crystal display portion, which is weak at high temperatures, adversely affects the image quality. This problem is expected to become more prominent as the volume of the backlight unit becomes smaller and the distance between the backlight and the optical member decreases in accordance with the recent trend of thinning of liquid crystal displays.

In the actual backlight unit, it is necessary to introduce a heat dissipation member such as a fan in order to counter the heat of the hot cathode fluorescent lamp, but this leads to an increase in cost. However, if the power input is reduced to such an extent that heat from the hot cathode fluorescent lamp does not affect the optical member, the advantage of the hot cathode fluorescent lamp is lost.

This invention is made | formed in view of this point, The main objective is to provide the structure which can solve the thermal problem by the simple structure in the backlight provided with a hot cathode fluorescent lamp.

The backlight of the present invention includes a hot cathode fluorescent lamp, a lamp holder for supporting the hot cathode fluorescent lamp, the hot cathode fluorescent lamp comprises a bulb having a phosphor formed on an inner surface thereof, and a filament installed in the bulb and emitting hot electrons. The lamp holder is disposed on an outer surface of the bulb in the filament presence region in which the filament is present, and the lamp holder is made of a metallic material.

In a preferred embodiment, the filament present region is in the range of ± 30mm from the center position of the filament.

The filament presence area is preferably in the range of ± 10 mm from the center position of the filament.

Another backlight of the present invention includes a hot cathode fluorescent lamp, a lamp holder for supporting the hot cathode tube, wherein the hot cathode fluorescent lamp is composed of a bulb having a phosphor formed on an inner surface thereof, and a filament installed in the bulb to emit hot electrons. The lamp holder supports the outer surface of the bulb in the range of the end side of the bulb from the location where the filament is present, and the lamp holder is made of a metallic material.

In a preferred embodiment, all of the lamp holders are made of a metallic material.

In a preferred embodiment, a resin material containing a filler is formed in the gap between the lamp holder and the bulb.

In a preferred embodiment, the backlight is a backlight for a direct type image display device.

In a preferred embodiment, the backlight is a light source for a liquid crystal display having a screen size of 32 inches to 46 inches, and four to six hot cathode fluorescent lamps are disposed in the backlight.

In an embodiment the filament is a quadruple coil.

In the embodiment, the hot cathode fluorescent lamp is a lamp having a rated life of 20,000 hours or more.

In an embodiment, an emitter of 5.0 mg or more is applied to the filament of one of the pair of electrodes in one of the hot cathode fluorescent lamps.

In an embodiment, the gas pressure in the bulb of the hot cathode fluorescent lamp is 500 Pa or more.

In an embodiment, the cross section of the bulb of the hot cathode fluorescent lamp is circular.

In an embodiment, the cross section of the bulb of the hot cathode fluorescent lamp is substantially elliptical.

According to the backlight of the present invention, since the outer surface of the bulb of the filament existence region where the filament exists is supported by the lamp holder, and the lamp holder is made of a metallic material, it is made of resin without using a heat radiating member such as a fan. The effect of remarkably lowering the temperature of the lamp holder can be obtained.

1 is an exploded perspective view for explaining a configuration of an image display apparatus 1000 including a backlight 100 according to an exemplary embodiment of the present invention.

2 is a cross-sectional view schematically showing the hot cathode fluorescent lamp 10 of the embodiment of the present invention.

3 is a cross-sectional view showing the configuration of the backlight 100 of the embodiment of the present invention.

4 is a plan view showing the configuration of a backlight 100 according to an embodiment of the present invention.

5 is a perspective view for explaining the configuration of the lamp holder 75 of the embodiment of the present invention.

6 (a) and 6 (b) are plan views showing the configuration of the backlight of the embodiment of the present invention.

7 is a perspective view for explaining the configuration of the lamp holder 75 of the embodiment of the present invention.

8 is a graph showing the temperature lowering effect based on the temperature [° C.] of the reflecting plate.

9 is a graph showing the relationship between the position in the tube axis direction and the tube surface temperature.

10 is a graph showing the relationship between the position in the tube axis direction and the tube surface temperature.

11 is a graph showing the relationship between the position in the tube axis direction and the tube surface temperature.

12 is a graph showing the relationship between the position in the tube axis direction and the temperature in the lamp.

(Explanation of the sign)

10 hot cathode fluorescent lamp 11 electrodes

12 Glass Bulb 13 Lead Wire

14 Filament 14c Filament Center Position

15 Bead glass 16 Seal

17 Exhaust Pipe 18 Extension

21 Reflector 22 Auxiliary Reflector

23 Reflective Sheet 24 Shore

30 Optical Sheet 31 Deflection Sheet

32 Lens Sheet 33 Diffusion Sheet

34 diffuser 50 base

55 Filament Existing Area 60 Liquid Crystal Panel

62 Top cover 65 Image display area

70 Lighting circuit 72 Lower cover

75 Lamp Holder 77 Resin Material

90 Screen Orientation 92 Bulb Longitudinal

100 backlight

1000 Image Display (Liquid Crystal Display)

The inventors of the present invention do not use a cold cathode fluorescent lamp (CCFL), which is currently mainstream, suitable for a backlight for a liquid crystal display in which a large screen is gradually accelerating, and a hot cathode fluorescent lamp capable of inputting a large output power per unit compared to a cold cathode fluorescent lamp. I was doing research and development thinking that I would move to using a lamp (HCFL). The reason for this transition is that by utilizing the feature of the "large output" of the hot cathode fluorescent lamp, the contrast ratio in the liquid crystal television can be increased, enabling high-definition image quality including a moving image, and at the same time as the backlight compared to the cold cathode fluorescent lamp. This is because the number of lamps to be used can be significantly reduced, thereby reducing the cost.

However, a backlight using a hot cathode fluorescent lamp has an inherent problem of high temperature compared to a backlight using a cold cathode fluorescent lamp. When the backlight becomes high temperature, the optical members (e.g., optical sheets and reflecting plates) used in the backlight are often weak at high temperatures, and the deterioration thereof causes deterioration of optical characteristics and image characteristics of the image display apparatus (liquid crystal display apparatus). Will result.

In order to alleviate the influence of the high temperature from the hot cathode fluorescent lamp, the present inventors usually use a heat dissipation member when the lamp holder is made of metal, when the lamp holder placed away from the filament of the hot cathode fluorescent lamp is forcibly arranged. The invention has been found by chance that the temperature of the backlight can be lowered without having to.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, for the sake of brevity of description, components having substantially the same functions are denoted by the same reference numerals. In addition, this invention is not limited to a following example.

A backlight 100 according to an exemplary embodiment of the present invention will be described with reference to FIGS. 1 to 4.

1 is an exploded perspective view schematically showing the configuration of an image display device (liquid crystal display device) 1000 including a backlight 100 of the present embodiment, and FIG. 2 is a hot cathode fluorescent lamp constituting the backlight 100 of this embodiment. The cross-sectional structure of the lamp 10 is shown typically. 3 and 4 are cross-sectional views and top views showing the configuration of the backlight 100 and the image display apparatus 1000 according to the present embodiment, respectively.

As shown in FIG. 1, the backlight 100 of the present exemplary embodiment includes a hot cathode fluorescent lamp 10 and a lamp holder 75 supporting the hot cathode fluorescent lamp 10. The hot cathode fluorescent lamp 10 is composed of a bulb 12 having a phosphor (not shown) formed on the inner surface 12a as shown in FIG. 2, and the filament 14 emitting hot electrons in the bulb 12. Is installed.

The lamp holder 75 supports the outer surface 12b of the bulb 12 of the filament existence region 55 (see FIG. 2) in which the filament 14 exists, and the lamp holder 75 is made of a metal material. Consists of. The filament presence area 55 can be, for example, in the range of ± 30 mm, preferably in the range of ± 10 mm at the filament center position 14c.

The lamp holder 75 in the example shown in FIG. 1 is all made of a metal material, and the metal material is, for example, aluminum, brass, stainless steel, iron (or plated iron), or the like. In the present embodiment, although the lamp holder 75 made of aluminum is used, it is also possible to selectively construct a part of the filament existence region 55 with metal even if all the lamp holders 75 are not made of metal. In addition, the thickness of the lamp holder 75 is not particularly limited, but is, for example, 1 mm or more, and in the example of the present embodiment, a lamp holder 75 having a thickness of 1 to 10 mm is used. In addition, the effect etc. of the lamp holder 75 are mentioned later.

A base 50 is provided at the end of the hot cathode fluorescent lamp 10 of the present embodiment. The base 50 is made of, for example, a resin material (PET (polyethylene terephthalate), PBT (polybutylene terephthalate), or the like), or a metal material (aluminum, etc.). A socket (not shown) is disposed around the base 50 so as to be connected to an external terminal (for example, a pin-shaped terminal) of the 50. The external terminal of the base 50 is, for example, a bulb 12. ) Extends in a direction substantially perpendicular to the longitudinal direction 92 (for example, the direction opposite to the screen direction 90), and the outer terminal of the base 50 extends in the longitudinal direction 92 of the bulb 12. ) May be formed to extend from the end face of the base 50.

In addition, the hot cathode fluorescent lamp 10 used for the backlight 100 of the present embodiment will be described. Since the hot cathode fluorescent lamp 10 of the present embodiment is used for the backlight, one having a long life is used. Preferably, the hot cathode fluorescent lamp 10 is a lamp having a rated life of 120,000 hours or more, and more preferably a lamp having a rated life of 20,000 hours or more, or 30,000 hours or more. In addition, since the lifetime of the CRT (cathode ray tube), which has been widely used in the past for display, is about 20000 hours, it is required to be a lamp having a longer lifetime.

The illustrated hot cathode fluorescent lamp 10 is composed of a straight tube-shaped glass bulb 12 and a pair of electrodes 11 arranged at both ends of the glass bulb 12.

The glass bulb 12 is made of soda lime glass or barium strontium silicate (soft glass having a softening point of 675 ° C). If the dimension of the bulb 12 is illustrated, it is the outer diameter 12mm, thickness 0.8mm, and length 730mm of the bulb 12 for 32 inches. For 45 inches, the bulb 12 has an outer diameter of 12 mm, a thickness of 0.8 mm, and a length of 1010 mm. For 65 inches, the bulb 12 has an outer diameter of 25.5 mm, a thickness of 0.8 mm, and a length of 1499 mm. Moreover, for 105 inches, the bulb 12 has an outer diameter of 38 mm, a thickness of 0.9 mm, and a length of 2367 mm. Moreover, the thickness of a bulb can also be 1.0 mm.

Phosphors (not shown) are coated on the inner surface of the glass bulb 12. More specifically, a protective film made of alumina is formed on the inner surface 12a of the glass bulb 12, and a phosphor layer is laminated on the protective film. The phosphors constituting the phosphor layer emit light of each color of red (Y ₂ O ₃ : Eu), green (LaPO ₄ : Ce, Tb), and blue (BaMg ₂ Al ₁₆ O ₂₇ : Eu, Mn). A mixture of rare earth phosphors can be used. As the phosphor, other rare earth phosphors can be used. For example, enemy by _{(Y, La) 2 O 3} : Eu, 3.5MgO · 0.5MgF 2 · GeO 2: Mn, CeMgAl as rust _{11 O 19: Tb, GdMgB 2} O 10: a Ce, Tb, and blue ( Sr, Ca) ₁₀ (PO ₄ ) ₆ C ₁₂ : Eu.

Mercury and a rare gas are enclosed in the glass bulb 12. In this embodiment, about 5 mg of mercury (not shown) and argon (Ar) at a pressure of 500 Pa at normal temperature are enclosed in the glass bulb 12. The mercury encapsulated in the bulb 12 may be encapsulated in the form of amalgam such as zinc mercury, tin mercury, bismuth, indium mercury, etc., in addition to the mercury alone.

In addition, as the rare gas, the mixing ratio of argon (Ar) is 100%, and a mixture of krypton (Kr) with argon (Ar) may be used. The mixing ratio (partial pressure ratio) of krypton (Kr) is 20%-60%, for example, Argon: Krypton = 50%: 50% of mixed gas (gas pressure 600 Pa) is mentioned, for example.

In this embodiment, the electrode 11 includes a filament 14, a pair of lead wires 13 supporting the filament 14, and a bead glass 15 supporting the pair of lead wires 13. Consists of Bead glass 15 is also referred to as bead mount. The illustrated electrode 11 is of a so-called glass bead mount system.

The filament 14 is made of tungsten, and in one example of the configuration of the present embodiment, in order to form a lamp with a long lifetime, the filament 14 has a complicated coil shape so as to increase the amount of emitter applied. In other words, a long basket-like structure is formed by winding a thin tungsten wire so as to cover the thick tungsten wire loosely, and the spiral wound is called a double coil. The filament 14 is wound into the spiral coil once more to form a triple coil or wound into the spiral coil once more to form a quadruple coil. In the case where the filament 14 is a triple coil, the third coil is an electrode coil of 5 to 7 rotations. Moreover, when the filament 14 is a quadruple coil, it is an electrode coil of 2-4 revolutions.

Emitters applied to the filaments 14 are, for example, oxides of strontium, calcium and barium. In this embodiment, in order to realize a lamp having a long lifetime, the amount of emitters applied to the filament 14 is increased. In this embodiment, one filament 14 of one pair of electrodes per one of the hot cathode fluorescent lamps 10 is provided. 5.0 mg or more of the emitter is applied. In addition, when the composition of the rare gas is not 100% of argon but krypton having a larger atomic weight than argon is mixed at a predetermined mixing ratio, the emitter is less likely to be scattered from the filament 14, so that the lamp life can be extended in the technical sense. .

The illustrated electrode 11 is pinched by the sealing portion 16 of the glass bulb 12. In addition, an exhaust pipe 17 is sealed to at least one end of the glass bulb 12. The exhaust pipe 17 is used to exhaust the bulb 12 or to seal the rare gas, and is sealed after the exhaust and the sealing. In addition, if the exhaust pipe 17 is provided at both ends of the bulb 12 instead of at one end, there is an advantage that the exhaust and the sealing of the gas can be made efficient. Moreover, the ratio of the impurity in the bulb 12 can also be reduced by this.

The base 50 is provided in the edge part of the glass bulb 12 so that the sealing part 16 and the exhaust pipe 17 may be covered. Moreover, what is necessary is just to determine suitably the connection method of the extension part 18 and the base 50 of the lead wire 13 extended outward from the sealing part 16 according to the specification of the lamp 10. As shown in FIG. Specifically, the external terminal (for example, pin) formed in the base 50 and the extension part 18 of the lead wire 13 are electrically connected. The external terminal (not shown) of the base 50 is connected to the socket (not shown).

1, 3 and 4, the backlight 100 including the hot cathode fluorescent lamp 10 is included in the liquid crystal display 1000, and the backlight 100 in the present embodiment is directly below. Type backlight for an image display device. In addition, the backlight 100 is used as a planar light source for a liquid crystal display of 26 inches or more (preferably 32 inches or more, for example, 32 inches, 40 inches, 42 inches, 46 inches, 65 inches, etc.). do. In addition, although the liquid crystal panel 60 is not shown in FIG. 1, the liquid crystal panel is shown in FIG.

In the illustrated example, six hot cathode fluorescent lamps 10 are shown. However, the number of hot cathode fluorescent lamps 10 is not limited to this number. In addition, in one preferred embodiment of the present embodiment, four to six hot cathode fluorescent lamps 10 may be disposed and turned on and operated on a panel of a liquid crystal display having a screen size of 32 inches to 46 inches. In addition, the lamp holder 75 may be of the structure which supports all the lamps 10 (6 in this example), and the structure which can support the lamp 10 one by one, or multiple (for example, Two or three) may be provided.

The reflecting plate 21 serving as a part of the housing housing the backlight 100 of the present embodiment is made of a metal plate (eg, made of plated iron or aluminum), and the thickness thereof is 1.5 mm. In the illustrated example, part of the reflecting plate 21 is bent in a convex shape (triangular shape) to form the auxiliary reflecting plate 22. The reflective sheet 23 is formed on the upper surface (the main surface 20b of the housing) of the reflecting plate 21 including the auxiliary reflecting plate 22. The reflective sheet 23 is composed of a resin layer of polyethylene terephthalate (PET) formed by dispersing white titanium oxide (or calcium carbonate), and the thickness thereof is 2.0 mm. A part of the apex (or ridge) of the auxiliary reflecting plate 22 is formed with a support 24 for supporting the lower surface of the optical sheet 30. The strut 24 is made of white resin. In addition, the height H (the height from the upper surface of the reflecting plate 21 to the surface where the optical sheet 30 is located) of the backlight 100 shown in FIG. 3 is 27 mm, for example.

Further, a lighting circuit (ballast circuit or ballast) 70 can be disposed below the reflecting plate 21 of the backlight 100 as shown in FIG. 3. In this example, one lighting circuit 70 is provided in each lamp 10, and thus six lighting circuits 70 are used for the six lamps 10. As shown in FIG. However, the number of the lighting circuits 70 and the lamps 10 may be different.

The lighting circuit 70 is electrically connected to the lamp 10 via the base 50, and also has a dimming function. The lower cover 72 is provided under the reflecting plate 21 to accommodate the lighting circuit 70. The lower cover 72 is comprised by the metal plate of thickness 1.5mm. In the space between the lower cover 72 and the reflecting plate 21, for example, a wiring is arranged. In addition, the lower cover 72 may not be provided in the backlight 100. In this case, the lighting circuit 70 may be arranged in a housing of a liquid crystal display (for example, a liquid crystal television).

4, the lamp holder 75 mentioned above is provided in the edge part of the reflecting plate 21. As shown in FIG. The optical sheet 30 is disposed in the opening 20a of the housing of the backlight 100. In this example, the optical sheet 30 is a deflection sheet 31 (Dual Brightness Enhancement Film (DBEF), 0.440 mm thick, manufactured by Tsutomo 3M), lens sheet 32 (thickness 0.155 mm), and diffusion in order from the top. The sheet 33 (thickness 0.113 mm) and the diffusion plate 34 (thickness 2.0 mm) are included. The lens sheet may be further provided on the lower surface of the diffusion plate 34.

In addition, a liquid crystal panel (for example, thickness of about 2 mm) 60 is disposed on the optical sheet 30, and an upper cover 62 is disposed to cover the liquid crystal panel 60 and the optical sheet 30. It is. The upper cover 62 is made of, for example, a metal plate having a thickness of 1.5 mm. Incidentally, the image display area 65 (see Fig. 4) in this example is 1018 mm x 573 mm, but of course, it is not limited to the dimension, and other dimensions may be sufficient. Moreover, the periphery of the sealing part 16 of the lamp 10 is covered with the side frame area in order to hide the non-lighting part of the lamp 10, and the non-lighting part is not visible from the outside. In addition, the direction in which the liquid crystal panel 60 is positioned as viewed from the backlight 100 becomes the screen direction 90.

Next, the hot cathode fluorescent lamp 10 and the lamp holder 75 of this embodiment will be further described with reference to FIG. 5. 5 is a perspective view for explaining the hot cathode fluorescent lamp 10 and the lamp holder 75.

As described above, the lamp holder 75 of the present embodiment supports the lamp 10 by supporting the outer surface of the bulb 12 of the filament existence region 55 in which the filament 14 exists, and this lamp holder 75 is not comprised with an insulating member (especially resin) but with a metal material.

Herein, the present invention will be described in comparison with the cold cathode fluorescent lamp (CCFL), which is the mainstream. Therefore, the electrical impedance of the lamp increases, and leakage of current occurs when there is metal around it. The occurrence of this leakage current is undesirable because it leads to luminance unevenness in the axial direction of the lamp or a decrease in brightness. Therefore, even if a lamp holder is used to support a cold cathode fluorescent lamp, it is inevitable to use a resin (insulating material).

The reason why the lamp voltage of the cold cathode fluorescent lamp is high is as follows. In the cold cathode fluorescent lamp, a phosphor is coated on the inner wall of the glass bulb, and a rare gas (Ne or Ar) and an appropriate amount of mercury are sealed as a buffer gas. The electrode is mounted with a metal such as nickel in a cylindrical shape, and discharge occurs when a high voltage is applied between the electrodes. Unlike a hot cathode fluorescent lamp, a cold cathode fluorescent lamp does not emit hot electrons from an electrode, and a very high cathode effect voltage (about 100 to 200 V) is required to supply electrons from the electrode (about 10 V in a hot cathode fluorescent lamp). In addition, since the diameter of the lamp tube of the cold cathode fluorescent lamp is very thin and the electrical impedance as the lamp is high, the tube voltage (lamp voltage) becomes high along with the height of the cathode drop voltage. Therefore, in a lamp requiring such a high voltage, it is very difficult to use a conductive material (metal material) for the lamp holder.

On the other hand, hot cathode fluorescent lamps have a feature of generating much more heat than cold cathode fluorescent lamps. This is because, unlike a cold cathode fluorescent lamp, an electrode including a filament for emitting hot electrons is used in a hot cathode fluorescent lamp, and a power (power) input to the hot cathode fluorescent lamp is larger than that of the cold cathode fluorescent lamp.

In the case of using a hot cathode fluorescent lamp having such a high heat generation, the lamp holder is preferably disposed far from the filament of the hot cathode fluorescent lamp in order to avoid the influence of heat. This is because arranging the lamp holder in the high temperature region near the filament increases the possibility of the lamp holder deforming.

The inventors of the present invention replaced lamp holders with those of typical resins and with metals, and placed them in the vicinity of filaments that were not normally arranged. As a result of the experiment, the inventors found an effect of lowering the temperature of the backlight. The temperature drop was remarkable, comparable to using a cooling means such as a fan.

The effect of the temperature decrease will be described with reference to FIGS. 6 to 8. The inventors of the present invention prepared a set of metal lampholders 75 and hot cathode fluorescent lamps 10 and carried out experiments of measuring the temperature thereof. The bulb 12 of the used hot cathode fluorescent lamp 10 was a substantially elliptical cross-section, and the filament 14 was observed in the longitudinal direction and in the transverse direction. FIG. 6A illustrates a hot cathode fluorescent lamp 10 in which the filament 14 is disposed in the longitudinal direction, and FIG. 6B illustrates a hot cathode fluorescent lamp 10 in which the filament 14 is disposed in the transverse direction.

In addition, the base 50 in FIG. 6 (a) denotes a pin (external terminal) 51 extending perpendicular to the longitudinal direction of the bulb 12. Extending the pin 51 in the lateral direction of the base 50 has the effect of easy design of a narrow side frame (that is, an edge portion outside the screen display area).

If the structure of the lamp 10 shown to FIG. 6 (a) is shown with the perspective view like FIG. 5, it will become like FIG. 6 (a) and 6 (b), the lamp holder 75 is shifted by the distance L2 (8 mm) from the filament center position 14c, and the thickness of the lamp holder 75 is A thin (1 mm in this example) aluminum lampholder was used. Moreover, length L1 (side frame length: what is called a non-display surface) located in the outer side from the outer edge (reference line) of the lamp holder 75 was 30 mm. In addition, a lamp holder made of a resin was prepared in the same configuration as that in FIG.

The result is shown in FIG. FIG. 8 is a graph showing the results of measuring the temperature of the configuration shown in FIGS. 6A and 6B, that is, the lamp 10 of the elliptic bulb 12 is installed in the backlight. In addition, the vertical axis | shaft in FIG. 8 is the temperature of the reflecting plate [degreeC], and the horizontal axis | shaft is the system input power [W] at the time of dimming. The system input power [W] shows a dimming condition of approximately 100% duty ratio in the backlight used in the experiment, and a dimming condition of 40% or less of duty ratio near 80W. In addition, control of this dimming is performed by changing electric power by PWM control.

As shown in Fig. 8, when the duty ratio is 40% or more, the line (C) of the comparative example (of the resin lampholder) and the lines (A) and (B) of the metal lampholder are about 20 ° C. The effect of lowering the temperature was observed, and the lowering effect was observed at about 25 ° C to 30 ° C in the duty ratio of less than 40%. In addition, the lines (A) and (B) in FIG. 8 correspond to the form of FIG. 6 (a) and (b), respectively. Since lines (A) and (B) corresponding to Figs. 6A and 6B have almost the same result, even when the hot cathode fluorescent lamp 10 of the bulb 12 having a circular cross section is used, It is speculated to be the result.

It is not usually conceivable to obtain such a temperature lowering effect without introducing a member such as a cooling fan. In other words, in order to obtain the effect of a certain temperature reduction (for example, 10 ° C. or higher), a means for introducing a dedicated member such as a cooling fan or giving up a large input of lamp power must be adopted. none. That is, the problem of the heat resistance of the reflecting plate 21 and the optical sheet 30 cannot be avoided, and even if the lamp brightness is to be increased, for example, a temperature rise of 10 ° C becomes a limit (i.e., a design constraint) and the cooling part ( For example, it is necessary to add a cooling fan), to make a significant change in the thermal design of the backlight, or to give up the improvement of the lamp output (brightness).

However, according to the structure of this embodiment, the effect of the remarkable fall of the lamp ambient temperature (especially the temperature of the reflecting plate 21 and the optical sheet 30) can be implement | achieved by the method of making the lamp holder 75 metal. Thus, the effect of lowering the temperature can be achieved without incurring new component costs or development costs for the thermal design, resulting in a very large technical contribution.

In addition, if the configuration of the present embodiment is used, the cooling effect of the present embodiment can be used even when the domestic cooling and heat dissipation means are introduced, so that a simple or inexpensive means can be introduced or the thermal design is changed. Even small changes can increase the likelihood that they can respond. Therefore, there is a technical value in that.

In addition to the stability of the assembly with the lamp holder 75, in order to improve heat dissipation of the lamp 10, a resin material 77 containing a filler in the gap between the bulb 12 and the lamp holder 75 (see Fig. 7). It is also preferable to interpose. Such a resin material 77 may be composed of a silicon sheet containing a filler, and according to the type of the filler, the heat conductivity of the resin material 77 may be increased to improve heat dissipation. For example, when Al ₂ O ₃ , BN, AlN, and SiO ₂ are added to the resin (or an elastic body made of a resin) 77 as the inorganic filler, the thermal conductivity can be improved. In addition, the coefficient of thermal expansion can be adjusted by selecting an appropriate inorganic filler.

The inventors of the present application considered the reason why the temperature can be lowered by the method of using the lamp holder 75 made of metal. It is considered that this is due to the difference in thermal conductivity between the lamp holder made of resin and the lamp holder made of metal. That is, since the metal has a good thermal conductivity, for example, 1000 times or more, as compared with the resin, the heat of the hot cathode fluorescent lamp 10, in particular the heat of the filament present region 55, is transferred through the metal lamp holder 75. It can be transmitted to the housing and the air, and as a result, it is assumed that the efficiency of heat dissipation can be remarkably increased. In fact, in the experimental example shown in FIG. 8, the thickness of the metal lamp holder 75 is only 1 mm, but it was confirmed that the presence of such a small member brought a temperature drop comparable to the introduction of the cooling fan. .

This remarkable effect of temperature reduction is due to the fact that the inventors of the present invention have considered using a material having high heat resistance as a material for a lamp holder that supports a hot cathode fluorescent lamp that generates a lot of heat compared to a cold cathode fluorescent lamp. Although a metal, a ceramic, etc. can be considered as a material with high heat resistance, this inventor manufactured the metal lamp holder in consideration of workability and the cost of a material. In addition, the inventor of the present invention accidentally found a remarkable effect of the temperature drop when the lamp holder, which is usually located away from the filament and avoids the filament present region which becomes hot, is sometimes placed in the filament present region, and reached the effect of the marked temperature decrease. . In addition, it will be described below that the effect of the temperature reduction has little effect on the lamp efficiency due to the cold spot temperature.

Fig. 12 is a plot of temperature distribution in a lamp in a 45-inch backlight (length 1010 mm) taking a distance in the tube axis direction from the center position F of one side of the filament coil on the horizontal axis as the origin. Fig. 12 (a) shows a lamp without a base, and Fig. 12 (b) shows a lamp with a base and is lit with lamp currents of 140 mA, 400 mA and 540 mA, respectively.

As can be seen from Figs. 12 (a) and 12 (b), the point where the temperature in the lamp is the lowest (cold point) is near the center P of the lamp in the tube axis direction, and the distance is far from the metal lamp holders at both ends. There is little direct impact. Therefore, the metal lamp holder of the present invention can solve the thermal problem of the optical member of the liquid crystal display part with little effect on the efficiency of the lamp.

As can be seen from FIGS. 12A and 12B, the filament region D is hotter than other regions due to the influence of the filament. Therefore, the temperature of the filament existence area D does not fall below the temperature of the center part P of a lamp by the cooling effect of a metal lamp holder. That is, the part cooled by the metal lamp holder does not become a cold spot.

Next, the temperature distribution of the periphery (filament presence area) of the filament 14 is demonstrated, referring FIG. 9 to FIG. (A) of each figure is a graph which shows the relationship of tube surface temperature [degreeC] and tube axial direction position [mm], and (b) has shown sectional drawing of the lamp corresponding to the tube axial direction position.

Lines (A) and (B) in FIG. 9A show the results of measuring the top and side surfaces when the long diameter of the elliptic lamp is arranged in the transverse direction, respectively. Lines (A) and (B) in Fig. 10A are also the same as those in Fig. 9. 9 shows the result when the inverter (lighting circuit) input 40W and the lamp input 30W, while FIG. 10 shows the result when the inverter (lighting circuit) input 26W and the lamp input 9W.

In addition, the line (A) and (B) in FIG. 11 (a) are the result of measuring the side surface at the time of arrange | positioning the long diameter of an elliptical lamp in the horizontal direction with respect to the case of lamp input 9W and 30W, respectively. As shown in Fig. 11 (b), the base 50 is not provided in the bulb 12 in the measurement in Fig. 11 (a).

As can be seen from the results of FIG. 9 to FIG. 11, there is a region that becomes hot at a range within 30 mm from the central position 14c of the filament 14. In other words, in the range of ± 30 mm from the center position 14c of the filament 14, there exists a high temperature region where it can be known that the acid is formed on the basis of the base line located farther than that. In the graphs shown in FIGS. 9A and 10A, the lines on the lamp cross-section side are shifted from each other in a symmetrical manner due to the influence of the base 50. However, in FIG. 11 without the base 50, the lines of the symmetry are symmetrical. It can be seen that the acid is formed. In addition, since the acid occupies a region of high acid (ie, a region of higher temperature) within a range of ± 10 mm from the center position 14c of the filament 14, placing the lamp holder 75 made of metal at this position has a greater effect. Can be obtained.

In addition, since the relation of the 30 mm or 10 mm area described above is basically the same in any of the hot cathode fluorescent lamps 10, the remarkable temperature reduction effect of the metal lamp holder 75 can be achieved using the technique of this embodiment. have. Even if the shape of the hot cathode fluorescent lamp 10 changes, the reason why the filament presence region 55 can be applied within the range of 30 mm or 10 mm at the filament center position 14c is as follows.

First, even if the length of the hot cathode fluorescent lamp (that is, the length of the bulb 12) changes, the basic structure around the electrode structure 11, especially the filament 14, of the hot cathode fluorescent lamp 10 is not changed. That is, in the hot cathode fluorescent lamp 10, a predetermined filament 14 is used, and it is fixed by a predetermined structure (lead wire 13, etc.), and the basic structure is 65 inches even for a 32-inch lamp, for example. This is because the lamp does not change. In addition, under the conditions in which the type and gas pressure of the gas encapsulated in the bulb 12 operate well as the hot cathode fluorescent lamp 10, there is no great change, and the temperature around the filament 14 is not changed significantly.

Moreover, even if the diameter of the glass of the bulb 12 changes, the range of the high temperature area | region (filament presence area | region 55) does not change in the position of the bulb in the longitudinal direction (pipe axis direction). That is, when the diameter of the glass of the bulb 12 changes, the distance between the filament 14 and the tube wall of the bulb 12 changes, and at that point, the temperature increases or decreases, but the longitudinal direction of the bulb (tube axis direction) This is because the same tendency is maintained with respect to the position of). This measures the temperature of the different points (A) and (B) of the elliptical bulb 12 in cross-section in FIGS. 9 and 10, ie, the tube wall of the filament 14 and the bulb 12. Even if the distance from the filament is measured, it is understood from the fact that the high temperature region (filament presence region 55) around the filament 14 does not change in accordance with the position of the bulb in the longitudinal direction (pipe axis direction). Can be.

In addition, since the area from the filament center position 14c to the lamp end side overlaps within the range of ± 30 mm from the filament center position 14c, which can be defined as the filament existence area 55, for this reason, a lamp holder made of metal You may arrange | position 75 to the end part of a lamp from the filament center position 14c, and exhibit a remarkable temperature fall effect.

As mentioned above, although this invention was demonstrated by the preferred embodiment, such description is not limited and of course various changes are possible for it.

For example, the cross section of the bulb 12 of the hot cathode fluorescent lamp 10 is not limited to a circular (or approximately circular) shape, and as described above, an elliptical (elliptical, long circle, or other flat shape) may be used. There is a number. The structure and arrangement of the filament (coil) 14 of the hot cathode fluorescent lamp 10 can also be suitably adopted. Moreover, although the pin-shaped thing was illustrated as the external terminal of the base 50, it is not limited to this, A thing of other shape (for example, a rectangular thing) can also be used.

In addition, as described above, the backlight of the embodiment of the present invention may be suitably used for, for example, a 32-inch or larger large-area liquid crystal TV, but is not limited thereto. Applicable Moreover, it is not limited to a liquid crystal TV, It may be used for the backlight of another liquid crystal display device (especially for a big screen), or it may be used for the backlight of an advertisement signboard.

According to the present invention, a thermal problem can be solved with a simple configuration in a backlight having a hot cathode fluorescent lamp.

Claims (11)

Hot cathode fluorescent lamps, A lamp holder for supporting the hot cathode fluorescent lamp, The hot cathode fluorescent lamp is composed of a bulb having a phosphor formed on the inner surface, and a filament installed in the bulb to emit hot electrons, The lamp holder is disposed on the outer surface of the bulb of the filament existence region where the filament is present, The lamp holder may be made of a metallic material. The method of claim 1, And the filament presence area is in a range of ± 30 mm from the center position of the filament in the tube axis direction of the bulb. The method of claim 2, And the filament presence area is in a range of ± 10 mm from the center position of the filament in the tube axis direction of the bulb. Hot cathode fluorescent lamps, A lamp holder for supporting the hot cathode fluorescent lamp, The hot cathode fluorescent lamp is composed of a bulb having a phosphor formed on the inner surface, and a filament installed in the bulb to emit hot electrons, The lamp holder supports the outer surface of the bulb in the range of the end side of the bulb from the location where the filament is present, The lamp holder may be made of a metallic material. The method according to any one of claims 1 to 4, The lamp holder is all made of a metallic material backlight. The method according to any one of claims 1 to 5, And a resin material containing a filler is formed in the gap between the lamp holder and the bulb. The method according to any one of claims 1 to 6, And said backlight is a backlight for a direct type image display device. The method of claim 7, wherein The backlight is a light source for a liquid crystal display having a screen size of 32 inches to 46 inches, And four to six hot cathode fluorescent lamps arranged on the backlight. The method according to any one of claims 1 to 8, The backlight unit is a backlight unit that is equipped with an amount of emitter equivalent to a rated life of 20,000 hours or more. The method according to any one of claims 1 to 9, The backlight is a backlight having a quadruple coil. The liquid crystal display device which mounted the backlight of any one of Claims 1-10.

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