JP2007272042A - Backlight device for liquid crystal display, and liquid crystal display device using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device for a liquid crystal display that suppresses moving stripes generated on a flash tube when lighting is started in low temperature atmosphere. <P>SOLUTION: In the backlight device 101 for the liquid crystal display equipped with a fluorescent tube 103 constituted by arranging a first electrode and a second electrode, each comprising two lead-in wires and a filament coil provided between the lead-in wires, at both ends of a container in which mercury and noble gas are charged and which has a phosphor and a protection film formed on its inner peripheral surface, and equiped with a case 104 housing it, the mercury is condensed nearby at least one of the first electrode and second electrode during an extinction period of the flash tube 103. More electric power is supplied to filament coils when the fluorescent tube 103 is turned on than during normal illumination. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backlight device for a liquid crystal display provided with a thermal electrode and a liquid crystal display device using the same, and more particularly to stabilization of discharge of an arc tube at a low temperature start.

Conventional display devices such as personal computer monitors and televisions have various methods such as CRT and PDP. In recent years, demands for thinner display devices and larger screens in conjunction with power saving have increased, and liquid crystal displays have become one of the mainstream display devices.
The liquid crystal display device includes a liquid crystal panel and a backlight. As the intensity of light supplied from the backlight increases, the brightness of image display can be ensured, and high uniformity without local shading can be obtained when a uniform image is displayed. Conventionally, a cold cathode fluorescent lamp has been mainly used as a backlight of a liquid crystal display of a small television having a size up to about 26 inches. For example, Patent Document 1 describes an invention in which a direct-type backlight is arranged in a liquid crystal display device.

  However, the cold cathode fluorescent lamp requires a large voltage for driving, and requires a high-voltage power supply compared to other light sources. For this reason, it is necessary to sufficiently insulate the backlight structure. This insulation problem becomes a prominent problem as an ultra-large liquid crystal display device exceeding the 26-inch size is put into practical use, and leads to an increase in cost. Furthermore, since the cold cathode fluorescent lamp requires a small amount of electric power to be supplied per lamp, a large number of lamps are required to secure screen luminance as a liquid crystal display device, and there is a problem that it takes assembling steps.

Therefore, it is conceivable to apply a light source other than the cold cathode fluorescent lamp, for example, a hot cathode fluorescent lamp to the backlight device for liquid crystal display.
Japanese Patent Application Laid-Open No. 07-064083 Japanese Patent Laid-Open No. 61-074298 Toshiro Sakakibara, Masatoshi Sano, Analysis of unstable discharge phenomenon in low-pressure Hg-rare gas system, Journal of Illumination, Vol.83, No.2, p.101-108, 1999 Hiroshi Yoshimoto, phenomenon of moving stripes, Journal of the Physical Society of Japan, Vol. 17, No. 11, 790-798, 1962

  By the way, the hot cathode fluorescent lamp has an electrode made of a coiled structure for thermionic emission, and the tube diameter is larger to accommodate the electrode than the cold cathode fluorescent lamp. In a hot cathode fluorescent lamp, there is a case where a phenomenon in which light emission differs in brightness along the axial direction of the lamp, that is, a so-called moving stripe. Since these moving stripes appear at intervals close to the tube diameter, this is not a problem for a cold cathode fluorescent lamp, but is a problem for a hot cathode fluorescent lamp having a tube diameter larger than that of a cold cathode fluorescent lamp.

That is, when dimming in a low-temperature atmosphere where the discharge state is unstable or when moving stripes are generated at start-up, the difference in brightness and darkness that appears on the screen of the liquid crystal display is large due to the large tube diameter, which degrades the quality of the displayed image I will let you. In particular, moving stripes are a problem because the discharge state is not stable at the start in a low temperature atmosphere.
An object of the present invention is to provide a backlight device for a liquid crystal display and a liquid crystal display device using the same, which suppresses moving stripes at the start of a hot cathode fluorescent lamp as much as possible and prevents deterioration of display image quality.

  In order to solve the above-mentioned problems, the present invention provides a backlight device for a liquid crystal display, in which mercury and a rare gas are enclosed, and a first electrode and An arc tube sealed with the second electrode; and a housing for housing the arc tube; and other locations near at least one of the first electrode and the second electrode during the extinction period of the arc tube In other words, the arc tube is provided with a low temperature promoting structure that is lower in temperature.

With the above-described configuration, during the extinguishing period, the vicinity of at least one of the first electrode and the second electrode has a lower temperature than the other portions and mercury is condensed. Due to the heat generated by the electrodes, mercury vapor is rapidly generated, the mercury vapor pressure inside the arc tube reaches a predetermined value, and generation of moving stripes can be suppressed.
Moreover, the said low temperature promotion structure shall be the structure which has arrange | positioned at least one end of the arc_tube | light_emitting_element below the gravitational direction.

  With such a configuration, the temperature inside the casing is lower in the lower part than in the upper part due to natural convection when the backlight is turned on, so that the temperature in the vicinity of at least one electrode at one end of the lower part becomes lower when the light is turned off. . This condenses mercury vapor in the vicinity of this electrode. At the start of lighting, the condensed mercury rapidly becomes mercury vapor, the mercury vapor pressure inside the arc tube reaches a predetermined value, and generation of moving stripes can be suppressed.

Further, the low temperature promotion structure is a contact member provided in contact with the outer surface of the arc tube in the vicinity of at least one of the first electrode and the second electrode, and the contact member is in contact with the casing. Yes.
With such a configuration, when the backlight is extinguished, the contact member abruptly lowers the temperature of the arc tube that is in contact, so that mercury vapor is condensed inside the arc tube that is in contact with the contact member. When the backlight is turned on, mercury condensed by heat generation of the filament is rapidly evaporated, the mercury vapor pressure reaches a predetermined value, and the generated moving stripes can be eliminated.

Further, the first electrode and the second electrode are composed of two lead wires and a filament connected between them, and the low temperature promoting structure is a metal body disposed on at least one lead wire.
With such a configuration, when the backlight is turned off, the heat of the metal body is dissipated to the outside of the arc tube via the lead-in line, so that the temperature of the metal body is drastically decreased as compared with other portions. For this reason, mercury vapor condenses on the surface of the metal body. The mercury condensed on the surface of the metal body is heated by the filament when the backlight is turned on, and suddenly becomes mercury vapor. This suppresses the generation of moving stripes.

  The present invention also relates to a backlight device for a liquid crystal display, in which a voltage is applied between the first electrode and the second electrode, and the filaments provided on the first electrode and the second electrode are respectively heated. And a temperature raising means for supplying more electric power to the filament at the time of starting than at the time of normal lighting and raising the temperature in the vicinity of the electrode.

With such a configuration, when the backlight is turned on, the temperature riser rapidly raises the temperature of the condensed mercury existing region, thereby evaporating mercury and raising the mercury vapor pressure rapidly to a predetermined value. Therefore, the moving stripe can be eliminated in a short time.
The temperature raising means increases the current supplied to at least one of the first electrode and the second electrode for a predetermined period from the start.

With such a configuration, the filament for a predetermined period in which the mercury vapor pressure inside the arc tube reaches a predetermined value shows a large amount of heat generation, and the mercury condensed in the vicinity of the filament is evaporated in a short time. As a result, the moving fringes generated in the arc tube can be eliminated.
The temperature raising means substantially matches the phases of the current supplied to at least one filament of the first electrode and the second electrode and the discharge current flowing between the first electrode and the second electrode. I am going to do that.

With such a configuration, the amount of current supplied to the filament increases and the amount of heat generated is also large, so the condensed mercury is evaporated in a short time and the mercury vapor pressure is rapidly increased, resulting in moving fringes generated in the arc tube. Can be eliminated in a short time.
The temperature raising means is configured by superposing a peak waveform on a current flowing in at least one filament of the first electrode and the second electrode.

With such a configuration, the filament can generate heat, the mercury vapor pressure can be rapidly increased, and the moving stripes generated in the arc tube can be eliminated in a short time.
Further, the present invention is a liquid crystal display device characterized in that a liquid crystal display is installed in front of the backlight device for liquid crystal display.
With such a configuration, moving stripes generated in the backlight device can be suppressed, so that a high-quality image can be displayed on the display screen of the liquid crystal display.

Hereinafter, a backlight device for a liquid crystal display according to the present invention and a liquid crystal display device using the same will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is an exploded perspective view schematically showing a liquid crystal display device according to the present invention.
The liquid crystal display device includes a liquid crystal display backlight device 101 and a liquid crystal panel 102. The basic configuration of the backlight device 101 includes a plurality of arc tubes 103, a housing 104 that holds the arc tubes 103 substantially in parallel, and a reflection that reflects the light from the arc tube 103 forward behind the arc tube 103. A member 106, a condensing member 107 that condenses the light from the arc tube 103 and the light from the reflection member 106 in front of the arc tube 103, and a lighting circuit 105 that is a power supply circuit that supplies power to the arc tube 103; Consists of.

The backlight device 101 is a backlight device in which the diagonal screen size of the liquid crystal panel 102 is 45 inches.
The condensing member 107 includes a diffusing plate, a diffusing sheet, a prism sheet 108, and a polarizing plate 109, and irradiates the liquid crystal panel 102 from the back surface with light emitted from the arc tube 103.
FIG. 2 is an example of a sectional view of the arc tube 103 in the tube axis direction.

The arc tube 103 includes a glass tube 200, and a first electrode 201 and a second electrode 202 provided at both ends of the glass tube 200. The glass tube 200 has an outer diameter of φ8 to φ30 and has a length of 1,010 mm. The glass tube 200 is filled with Ar 50% and Kr 50% filled gas at a gas pressure of 600 Pa, and 3 to 8 mg of Hg.
The first electrode 201 includes two lead wires 203 and a filament coil 204 provided between the lead wires 203. The second electrode 202 has the same configuration. A protective film 206 is formed on the inner peripheral surface of the container 200, and a phosphor 207 is formed on the surface of the protective film 206. A base 206 is attached to both ends of the glass tube 200.

In the present embodiment, during the extinguishing period, at least one electrode of the first electrode 201 or the second electrode 202 or the vicinity of both the first electrode 201 and the second electrode 202 is located more than the other part of the arc tube 103. The temperature is lowered and mercury evaporated during the lighting period is condensed in the vicinity of the electrode. Thus, the mercury condensed when the arc tube 103 is turned on is rapidly evaporated. Examples that are specific examples of the present embodiment will be described below.
Example 1
FIG. 3 is a cross-sectional view taken along the tube axis of the arc tube 103 of the backlight device 101.

  The arc tube 103 was a hot cathode fluorescent lamp having a glass tube with an outer diameter of φ18 or φ15 and electrodes at both ends of 570 mm in length. The sealing gas is Ar 50%, Kr 50%, the sealing gas pressure is 600 Pa, and 5 mg of mercury is sealed. The arc tube 103 is arranged in a substantially vertical (vertical) direction with respect to the screen of the liquid crystal panel 102, and is a backlight device having a diagonal screen size of 45 inches. The arc tube 103 is substantially sealed by a casing 104, a rear reflecting member 106, and a front light collecting member 107.

Hereinafter, the operation of this embodiment will be described.
When the arc tube 103 is turned on, convection causes warm air to move to the upper layer portion of the housing 104 and cold air to move to the lower layer portion. As a result, the upper part of the arc tube 103 is warmed and the temperature of the lower part is relatively lowered. When the arc tube 103 is turned off in this state, the mercury vapor is condensed on the inner peripheral surface of the arc tube 103 in the vicinity of the first electrode 201 having a low temperature. At the next lighting start, the condensed mercury is heated by the heat of the filament coil 204 of the first electrode 201 and is evaporated in a short time, and the mercury vapor is diffused to the central portion of the arc tube 103. As a result, the moving stripe disappears when the mercury vapor pressure reaches a certain value.

In this embodiment, although the arc tube 103 is a straight tube, both the first electrode and the second electrode may be arranged in the lower portion of the housing 104 as a U-order tube. In this way, when the next lighting is started, the filament coil 204 of the first electrode and the second electrode warms up more rapidly, so that the diffusion of mercury vapor is promoted.
(Example 2)
FIG. 4 is a cross-sectional view along the tube axis direction of the arc tube 103 when the backlight device 101 is viewed from above. In the present embodiment, unlike the first embodiment, the arc tube 103 is arranged in a substantially horizontal (horizontal) direction on the screen of the liquid crystal panel 102. Further, the outer diameter of the arc tube 103 and the conditions of the sealed gas are the same as in Example 1, but the backlight device has a length of the arc tube 103 of 1100 mm and a diagonal screen size of 45 inches.

  A contact member 401 interposed between the housing 104 and a part of the outer peripheral surface of the arc tube 103 in the vicinity of the filament coil 204 is provided. The contact member 401 is made of a material that is larger than the thermal conductivity around the arc tube 103. For example, a normal substance has a higher thermal conductivity than air, but is preferably formed of a metal having a higher thermal conductivity such as aluminum or copper than resin or wood. In this figure, only the first electrode portion is shown, but the second electrode portion has the same configuration.

The operation of this embodiment will be described below.
Since the temperature of the filament coil 204 is high when the arc tube 103 is turned on, even if heat is radiated from the contact member 401 to the outside through the housing 104, the vicinity of the filament coil 204 becomes higher than the other parts of the arc tube 103, Mercury vapor diffuses into the central portion of the arc tube 103. When the arc tube 103 is turned off, the filament coil 204 no longer generates heat, and the outer peripheral portion of the arc tube 103 in contact with the contact member 401 is dissipated through the contact member 401 and the housing 104, and is rapidly cooled. The As a result, the evaporated mercury is condensed on the inner peripheral surface of the arc tube 103 facing the contact member 401.

FIG. 5 is a diagram schematically showing a state when the arc tube 103 is turned on again. Mercury 501 is condensed on the inner peripheral surface of the arc tube 103. The mercury 501 is heated by the heat generated by the filament coil 204 and diffused as mercury vapor 502.
In this embodiment, the contact member 401 is interposed between the arc tube 103 and the casing 104. However, instead of the contact member 401, a protrusion that directly contacts the casing 104 with the arc tube 103 is provided. May be.

Further, although the contact member 401 helped the heat radiation of the arc tube 103, a cooling member that cools the arc tube 103 when the light is turned off may be provided instead of the contact member 401.
(Example 3)
FIG. 6 is a cross-sectional view taken along the tube axis of the arc tube 103 of the backlight device 101.
In this embodiment, a metal body 601 is provided in the vicinity of the filament coil 204 of the lead-in wire 203. The metal body 601 is made of, for example, stainless steel having a thickness of 0.5 mm, a length of 8 mm, and a width of 4 mm and 100 mesh. The shape of the arc tube 103 and the conditions of the sealed gas are the same as in the second embodiment.

The operation of this embodiment will be described below.
When the arc tube 103 is turned off, the metal body 601 dissipates heat through the lead-in wire 203 and is cooled earlier than the other parts of the arc tube 103. The evaporated mercury is condensed on the surface of the metal body 601 having a lower temperature than the surroundings. Next, when the arc tube 103 is turned on, mercury condensed on the front surface of the metal body 601 is rapidly evaporated by the heat generated by the filament coil 204 and diffuses to the central portion of the arc tube 103. Accordingly, when the mercury vapor pressure reaches a predetermined value, the moving stripe disappears.

In addition, although the mesh-shaped thing was used for the metal body 601, since the condensing effect of mercury is exhibited, so that the surface area of the metal body 601 is large, you may make it use the metal body made porous.
In this embodiment, only the first electrode is shown in FIG. 6, but the second electrode has the same configuration.
(Embodiment 2)
Next, a second embodiment for promoting the heat generation of the filament coil 204 at the start of lighting will be described. The greater the heat generated by the filament coil 204, the faster the evaporation of mercury condensed in the vicinity of the electrode.

Specific embodiments will be described below with reference to the drawings.
Example 4
FIG. 7 is a diagram showing how the current flowing through the filament coil 204 from the start of lighting in Example 4 changes with the elapsed time from the start of lighting. The lighting circuit 105 is designed so that the current flowing through the filament coil for a predetermined time t1 from the start of lighting flows 1.5 times the rated current. As a result, the filament coil 204 is rapidly heated, and mercury condensed in the vicinity of the electrode can be rapidly evaporated.

FIG. 8 is a diagram illustrating an example of the lighting circuit 105 used in the present embodiment.
The lighting circuit 105 includes a control circuit 1 801, a main circuit 802 connected to the control circuit 1 801, a control circuit 2 803, and a preheating circuit 804 connected to the control circuit 2 803. Electric power is supplied to the first electrode 201 and the second electrode 202.
FIG. 9A is a diagram showing the frequency f1 of the power supplied between the first electrode 201 and the second electrode 202 of La103 from the main circuit 802 and the time from the start of lighting. The relationship between the frequency f1, the lamp voltage, and the lamp current is shown in FIG.

  In this embodiment, a rectangular wave signal having a different cycle is sent from the control circuit 803 to the preheating circuit 804 to control the ON / OFF cycle of the transistors Q3 and Q4, and the frequency of the current supplied to the filament coil 204 of La103. Is a predetermined time t1 from the start of lighting, and as shown in FIG. 9C, b2 (<a2), and after a predetermined time t1, the frequency a2. The relationship between the preheating current and the frequency f2 is shown in FIG.

The predetermined time t1 is a time required for disappearance of the moving stripes generated in the direction perpendicular to the direction along the tube axis of the arc tube 103.
The backlight device 101 used was the one shown in Example 2 above.
The operation of this embodiment will be described below.
Mercury condensed in the vicinity of the first electrode 201 and the second electrode 202 during the extinguishing period of the arc tube 103 is the heat of the filament coil 204 heated to a high temperature with a filament current 1.5 times the rated at the start of lighting. And rapidly becomes mercury vapor and diffuses to the central portion of the arc tube 103. When the mercury vapor pressure reaches a predetermined value, the moving stripe disappears. Thus, by flowing a large filament current at the start of lighting, the time until the moving stripe disappears can be greatly shortened.

In this embodiment, although 1.5 times the rated current is passed through the filament coil 204, it is effective if the current is larger than the rated current, and the rated current is within a range where the filament coil 204 is hardly consumed. A larger current can be passed.
(Example 5)
In this embodiment, as shown in FIG. 10, the phase of the filament current and the lamp current is made to coincide with each other for a predetermined period at the start of lighting, and the phase difference between the filament current and the lamp current is provided after the lapse of the predetermined period. It is said.

Note that the backlight device 101 used in the second embodiment is used.
FIG. 11 is a diagram showing an example of a specific example of the lighting circuit 105 used in this embodiment. The lighting circuit 105 includes an oscillation circuit 1101, a control circuit 1 1102, a main circuit 1103, a phase shift circuit 1104, a control circuit 2 1105, and a preheating circuit 1106.
The oscillation circuit 1101 outputs a switching signal shown in the upper part of FIG. The control circuit 1 1102 outputs the same switching signal as the switching signal input to the main circuit 1103. The phase shift circuit 1104 outputs the same switching signal as the input switching signal shown in the middle stage of FIG. 12 to the preheating circuit 1106 for a predetermined period at the start of lighting. The phase shift circuit 1104 outputs, to the preheating circuit 1106, a switching signal in which the phase shown in the lower part of FIG. As a result, during the predetermined period at the start of lighting, a large total current shown in FIG. After the elapse of the predetermined period, a current having a small total current is supplied to the filament coil 204 as shown during stable lighting in FIG.

Here, the filament current is a current that flows from one introduction line of the introduction line 203 in the same electrode to the other introduction line, and the lamp current is one electrode, for example, the first electrode 201 to the other electrode, for example, the first electrode. This is the current flowing through the two electrodes 202. The filament coil 204 generates heat by a combined current (total current) of the filament current and the lamp current.
The operation of this embodiment will be described below.

At the start of lighting of the arc tube 103, a large current having a total current in which the phases of the filament current and the lamp current coincide with each other flows through the filament coil 204. As a result, the filament coil 204 rapidly generates heat, evaporates the condensed mercury, and mercury vapor diffuses into the central portion of the arc tube 103. Accordingly, when the mercury vapor pressure reaches a predetermined value, the moving stripe disappears. If the phase of the filament current and the lamp current is shifted after the predetermined period, a reactive current is generated, and the total current flowing through the filament coil 204 can be returned to the rated value. In this way, by setting the filament current and lamp current to the same phase only at the start of lighting, it is possible to significantly reduce the time until the moving stripe disappears without greatly changing the waveform of the filament current. It becomes.
(Example 6)
In this example, the backlight device 101 of Example 2 is used, and the lighting circuit 105 shown in FIG. 8 used in Example 4 is used.

  In the present embodiment, similarly to the second embodiment, rectangular wave signals having different cycles are sent from the control circuit 2 803 to the preheating circuit 804 to control the ON / OFF cycle of the transistors Q3 805 and Q4 806, and the filament of La103 As shown in FIG. 13A, the frequency of the current supplied to the coil 204 is periodically superimposed on the current of the frequency f1 for a predetermined time from the start of lighting, as shown in FIG. As a result, the filament current supplied to the filament coil 204 has a peak current peak value 1301 that is 2 to 5 times the filament current peak value, as shown in FIG. It will be several hundred nanoseconds. Note that if the current greatly exceeds this peak value, the glass tube forming the arc tube 103 may be overheated, possibly damaging the glass tube.

Next, the operation of this embodiment will be described.
By superimposing the peak current on the filament current at the start of lighting, a large potential difference is instantaneously generated between the filament coil 204 and the contact member 401 as shown in FIG. By this discharge, the mercury 501 condensed in the vicinity of the filament coil 204 is heated in a short time, the mercury vapor pressure rises, and diffuses to the central portion of the arc tube 103. When the mercury vapor pressure reaches a predetermined value, the moving stripe disappears.

Next, the time until the disappearance of the moving stripe in each of the above embodiments will be described based on the experimental results.
FIG. 14 is a diagram showing the relationship between the mercury vapor pressure [Pa] at the center of the arc tube and the elapsed time [S] from the start of lighting.
Here, in each of the comparative examples and the first to third embodiments, only the lamp current supplied from the main circuit 802 described in the fourth embodiment is supplied to the filament coil 204. In addition, as the backlight device of the comparative example, a backlight device without the contact member 401 of the arc tube 103 shown in Example 2 was used.

As is clear from FIG. 14, in Comparative Example a in which means for condensing mercury vapor in the vicinity of the electrode during the extinguishing period is not provided, it takes about 115 seconds until the moving stripe disappears. However, in Example 4e, the moving stripe disappears in about 50 seconds, which is half or less. It is proved that other examples are also effective as compared with the comparative example a from the graphs b to f.
Example 1 to Example 3 and Example 4 to Example 6 can be implemented in combination with each other. For example, the metal body 601 is provided on the lead-in wire 203 of Example 3, and the example of Example 4 is used. In this manner, if a current that is 1.5 times the rated current is supplied to the filament coil 204 at the start of lighting, the time until the moving stripe disappears can be further shortened.

  The moving stripe disappears when the mercury vapor pressure in the central portion of the arc tube 103 becomes 0.16 Pa. In each of the above embodiments, the predetermined time at the start of lighting refers to the time until the mercury vapor pressure at the center of the arc tube 103 reaches 0.16 Pa.

  The liquid crystal display device according to the present invention is used in the home appliance industry as a display device of a large size TV exceeding 26 type, and the backlight device for a liquid crystal display according to the present invention is a backlight for a large size liquid crystal display. Used in the home appliance industry as a device.

1 is an exploded perspective view schematically showing Embodiment 1 of a liquid crystal display device according to the present invention. It is an example of sectional drawing of the arc tube of the said embodiment. It is sectional drawing which shows the structure of Example 1 of the backlight apparatus for liquid crystal displays of the said embodiment. It is sectional drawing which shows the structure of Example 2 of the said embodiment. It is sectional drawing which showed typically the state at the time of the arc tube lighting start of Example 2 of the said embodiment. It is sectional drawing which shows the structure of Example 3 of the said embodiment. It is a figure which shows the filament current at the time of the arc tube lighting start of Example 4 of Embodiment 2 of the backlight apparatus for liquid crystal displays which concerns on this invention. It is a figure which shows an example of a structure of the lighting circuit of the said Example. It is a figure for demonstrating the filament current and lamp current of the said Example. It is a figure which shows the electric current value at the time of lighting start of Example 5 of the said embodiment, and the time of stable lighting. It is a figure which shows an example of the lighting circuit of the said Example 5. FIG. It is a figure which shows an example of the switching signal output from the phase shift circuit of the said Example 5. FIG. It is a figure for demonstrating the filament current given in Example 6 of the said Embodiment 2. FIG. It is a graph which shows the relationship from the arc tube lighting start time of the mercury vapor pressure in the arc tube center part of each said Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Backlight apparatus for liquid crystal display 102 Liquid crystal panel 103 Light emission tube 104 Case 105 Lighting circuit 106 Reflective member 107 Condensing member 108 Diffusing plate, diffusion sheet, prism sheet 109 Polarizing plate 200 Glass tube 201 First electrode 202 Second electrode 203 Lead wire 204 Filament coil 205 Base 206 Protective film 207 Phosphor 401 Contact member 501 Mercury 502 Mercury vapor 601 Metal body

Claims (9)

A backlight device for a liquid crystal display,
An arc tube in which mercury and a rare gas are enclosed, and a first electrode and a second electrode are sealed at both ends of a glass tube in which a phosphor is formed on an inner peripheral surface;
A housing for housing the arc tube,
A back-up for a liquid crystal display, characterized in that, during the extinguishing period of the arc tube, the arc tube is provided with a low-temperature promoting structure that is lower in temperature than the other portions in the vicinity of at least one of the first electrode and the second electrode. Light equipment.   2. The backlight device for a liquid crystal display according to claim 1, wherein the low-temperature promoting structure is a structure in which at least one end of the arc tube is disposed below the gravity direction.   The low temperature promoting structure is a contact member provided in contact with the outer surface of the arc tube in the vicinity of at least one of the first electrode and the second electrode, and the contact member is in contact with the housing. The backlight device for a liquid crystal display according to claim 1.   2. The first electrode and the second electrode are each composed of two lead wires and a filament connected between them, and the low temperature promoting structure is a metal body disposed on at least one lead wire. LCD backlight device. A backlight device for a liquid crystal display,
A lighting circuit that applies a voltage between the first electrode and the second electrode and flows currents for heating the filaments provided on the first electrode and the second electrode, respectively;
A backlight device for a liquid crystal display, characterized in that the filament is provided with a temperature raising means for raising the temperature in the vicinity of the electrode by supplying more electric power at the time of startup than during normal lighting. The temperature raising means is
6. The backlight device for a liquid crystal display according to claim 5, wherein a current supplied to at least one of the first electrode and the second electrode is increased for a predetermined period from the start. The temperature raising means is
6. The phase of each of a current supplied to at least one of the first electrode and the second electrode and a discharge current flowing between the first electrode and the second electrode are substantially matched. The backlight apparatus for liquid crystal displays as described. The temperature raising means is
6. The backlight device for a liquid crystal display according to claim 5, wherein a peak waveform is superimposed on a current flowing in at least one filament of the first electrode and the second electrode.   A liquid crystal display device comprising a liquid crystal display installed in front of the backlight device for a liquid crystal display according to claim 1.

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