JP2007109588A - Fluorescent discharge tube and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorescent discharge tube capable of retaining a non-defective level by improving dark starting characteristics, and of improving quality and yield. <P>SOLUTION: This is provided with an ultraviolet ray transmitting glass tube in which a phosphor film is formed on the inner face, and in which a noble gas and mercury, or the noble gas are sealed inside, a pair of cup electrodes CE which are sealed and arranged opposite to both end parts of this glass tube, and a pair of lead wires for power feeding in which one end is connected to these cup electrodes CE and the other end is airtightly sealed and drawn outside the glass tube. By integrally forming a recess groove DEN which is recessed in the electrode axial direction along the electrode axial direction on the outer face of the pair of cup electrodes CE, an electric charge becomes easy to be collected at starting, and lighting delay is efficiently eliminated, since sputtering from the recessed groove DEN of the cup electrodes CE becomes easier to be film-formed as a sputtering thin film on the inner wall faces of the opposite glass tube in an aging process during the manufacturing process. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fluorescent discharge tube having improved dark start characteristics and a liquid crystal display device using the fluorescent discharge tube, and more particularly to an electrode structure of an internal electrode type fluorescent discharge tube suitable for use in a light source device of a liquid crystal display device. It is about.

  Among various light source devices, a discharge tube is often used as a light source with low power consumption, high luminance, or small dimensions. Among these discharge tubes, a low voltage discharge tube in which an inert gas and mercury are enclosed in a glass tube made of a translucent insulating material with a phosphor coated on the inner wall surface is widely known as a fluorescent lamp. It has been. This type of low voltage discharge tube includes a hot cathode type using thermoelectrons and a cold cathode type using cold electrons.

  For example, a cold cathode fluorescent tube (CCFL) that emits cold electrons to excite phosphors to emit light is employed as a light source in a light source device of a liquid crystal display device. Generally, a metal material such as nickel is used for an electrode that emits cold electrons. Such electrodes dissipate and wear out during operation due to their sputtering properties. Accordingly, the cold cathode fluorescent tube requires a certain size of electrode. On the other hand, as the electrode dimensions increase, the surface area also increases, the current density per unit area decreases, and the amount of sputtering of the electrode material onto the inner wall of the outer tube during discharge (especially during aging before product shipment) decreases.

  This type of cold cathode fluorescent tube is required to shorten the discharge start time (discharge start time), and there is a problem that the time required for the discharge start in the dark is delayed. In general, when a part of an electrode made of a nickel material or the like is sputtered on the inner wall of the outer tube, an effect that electrons induced from the sputtered film shorten the discharge start time is known. When a cup-shaped electrode is used as a cold cathode, if the outer diameter of the electrode (especially the outer diameter of the open end) is made smaller than the inner diameter of the outer tube, sputtering of the electrode material onto the inner wall of the outer tube is promoted. However, sputtering of the electrode material shortens the life of the electrode due to wear of the electrode itself. Moreover, even if the sputtered film is formed by the aging process, it cannot be said that the discharge start time is sufficiently shortened.

  In order to improve the delay in the discharge start time, it is effective to dispose a substance that induces discharge on the inner wall surface of the outer tube (particularly in the vicinity of the electrode). For this purpose, the following method is currently employed. A metal compound having a high electron emission property, for example, a cesium compound such as cesium tungstate is attached to the surface of the electrode. A metal compound having a high electron emission property such as the cesium compound mixed with a mercury-emitting substance is used, and a metal compound having a high electron emission property such as the cesium compound is diffused into the tube during the mercury emission heating in the manufacturing process. A high current (for example, about 8 to 15 mA when the outer diameter of the electrode is about 1.7 mm) is applied to the electrode to heat the electrode, and a part of the electrode material is dissipated to form a sputtered film on the inner wall near the electrode of the outer tube. Form. Then, alumina is added into the phosphor film.

  As a concrete means to improve the delay of the discharge start time, a sputtered film mainly composed of a metal or a metal compound thereof is formed on the inner wall near the cup-shaped electrode in the outer tube, and generated by a voltage applied to the electrode. This induces a discharge caused by cold electrons and shortens the discharge start time. Also, in order to increase the electrode area, the electrode shape is cup-shaped, a thin film containing the above metal material is formed on the inner wall surface, and the thin film containing the metal material is heated and evaporated on the inner wall near the electrode in the outer tube in the aging process. A sputtered film is formed. This type of technology is disclosed in, for example, Patent Document 1 and Patent Document 2 below.

JP 2001-76617 A JP 2002-231133 A

  However, when the sputtered film resulting from the inside of the cup-shaped electrode is formed on the inner wall of the glass tube in the vicinity of the opening of the cup-shaped electrode in the aging process, the sputtering resulting from the inside of the cup-shaped electrode lacks process stability. For this reason, from the viewpoint of quality assurance, after leaving it in a dark atmosphere of about 0.1 lux or less for about 24 hours or more, 100% lighting inspection is performed one by one in the dark atmosphere of about 0.1 lux or less. Therefore, a great deal of labor is spent, yield decreases, and productivity decreases.

  In addition, as a result of 100% lighting inspection, about half of the defective products are judged to be defective by re-inspection, and conversely, about half of the defective products are judged to be good by re-inspection. In addition to being low, the occurrence of a few percent of defective products also has the problem of worsening profits. Furthermore, in order to obtain a sufficient amount of sputtering, aging for a long time (about 2 hours) is required, which reduces productivity, and is one of the biggest obstacles to business expansion. there were.

  Therefore, the present invention has been made to solve the above-described conventional problems, and the object thereof is to maintain a non-defective product level by improving the dark starting characteristics and to improve the yield. Is to provide.

  Another object of the present invention is to provide a high-quality, high-quality liquid crystal display device in which the delay in lighting is reduced while suppressing an increase in the peripheral portion of the image display area of the liquid crystal display panel (location where no image is displayed: frame). Is to provide.

  In order to achieve such an object, a fluorescent discharge tube according to the present invention includes an ultraviolet ray transmissive glass tube in which a phosphor film is formed on an inner surface, and a rare gas and mercury or a rare gas are enclosed therein, A pair of cup electrodes encapsulated and arranged opposite to both ends of the glass tube, and a pair of power supply lead wires that are connected to the cup electrode at one end and hermetically sealed outside the glass tube And forming a concave groove recessed in the electrode axial direction on the outer surface of the pair of cup electrodes along the electrode length direction so that sputtering from the concave groove of the cup electrode can be performed in the aging process during the manufacturing process. It is stably formed as a sputtered film on the inner wall surface of the opposing glass tube, and charges are easily collected when the fluorescent discharge tube is started, so that the problem of background art is solved by effectively eliminating the lighting delay. Can Kill.

  A liquid crystal display device according to the present invention includes a liquid crystal display panel configured by sandwiching a liquid crystal layer between a pair of translucent substrates having electrodes for forming pixels on the inner surface, and illumination light on the back of the liquid crystal display panel. A backlight device having at least one fluorescent discharge tube to be irradiated; an optical compensation sheet laminate interposed between the liquid crystal display panel and the backlight device; and a frame for housing the liquid crystal display panel and the backlight device. In the liquid crystal display device having the above, the fluorescent discharge tube is provided with a concave groove recessed in the electrode axial direction on the outer surface of a pair of cup electrodes encapsulated and arranged at both ends of the ultraviolet ray transparent glass tube facing the electrode opening end. By integrally forming along the long direction, a liquid crystal display device can be realized in which the lighting delay of the fluorescent discharge tube is efficiently eliminated.

  In addition, this invention is not limited to the said structure, A various change is possible without deviating from the technical idea of this invention.

  According to the fluorescent discharge tube of the present invention, the dark start characteristic can be maintained at a high level and the lighting delay can be reduced, so that an extremely excellent effect that the quality and the yield can be greatly improved is obtained. .

  In addition, the fluorescent discharge tube according to the present invention eliminates the need for a dark starting characteristic inspection, which can greatly reduce the manufacturing process, reduce investment in the aging device, and facilitate maintenance of existing aging equipment. An extremely excellent effect such as is obtained.

  According to the liquid crystal display device of the present invention, a high-quality and high-quality image display in which the delay in lighting of the fluorescent discharge tube is reduced while suppressing an increase in the peripheral portion where the image in the image display area of the liquid crystal display panel is not displayed. It has extremely excellent effects such as being obtained.

  As is well known, a cold cathode fluorescent discharge tube is likely to have a time delay from when the switch is turned on to when it is actually turned on in a dark environment such as a dark room. Lights up instantly when switched on in a bright environment. When the environment is bright, some of the gas sealed inside the fluorescent discharge tube is ionized by light and becomes ionized. When switched on, the ions move by the electric field and ionize the gas to the surroundings. This phenomenon occurs in a chain, and gas ionization rapidly proceeds throughout the fluorescent discharge tube.

  However, in a dark environment such as mounting a fluorescent discharge tube on a backlight device such as a liquid crystal display device, it is necessary to rely on something other than light for the first gas ionization that triggers discharge. When relying on something other than light as the starting point of the discharge, it is important to know at which part of the cold cathode fluorescent discharge tube the first gas ionization can be efficiently eliminated. The elucidation of the mechanism requires a high level of technical ability, but the inventors have clarified this mechanism through the following experiment.

Hereinafter, an outline of a fluorescent discharge tube according to the present invention will be described with reference to FIGS.
FIG. 6 is a cross-sectional view of the main part showing the schematic structure of the fluorescent discharge tube. The fluorescent discharge tube CCFL shown in FIG. 6 is configured by arranging a pair of cup electrodes CE with the tip opening portions facing each other inside both ends of a translucent glass tube VAL and enclosing rare gas and mercury. . A phosphor film FLU is deposited on the inner wall surface of the glass tube VAL. Further, the pair of cup electrodes CE have both front end openings facing the main discharge region, and the rear end portions thereof are joined by abutting inner leads ILE to be electrically connected.

  The inner leads ILE are supported by the glass beads GBE and sealed inside and outside of the glass tube VAL in an airtight state, and the pair of inner leads ILE protruding outside are joined and electrically connected to the outer leads OLE. ing. The pair of outer leads OLE is connected to a power supply circuit to supply lighting power to the cup electrode CE.

  FIG. 7 is a schematic cross-sectional view of an experimental apparatus for explaining an experimental method for obtaining the data for improving the dark starting characteristics by ascertaining the discharge starting point that grows into a discharge in the entire fluorescent discharge tube CCFL described above. Reference numeral 8 denotes a power supply circuit of the fluorescent discharge tube CCFL. In FIG. 7, in this experiment, the fluorescent discharge tube CCFL is a glass tube VAL having a diameter of about 2.4 mm and the inner wall surface is not coated with a phosphor film, and the cup electrode CE has an electrode length of about 3.00 mm. A cup-shaped electrode having an opening diameter of about 1.8 mm was used.

  Here, in the fluorescent discharge tube CCLF in which the phosphor film is not applied to the inner wall surface, even if a rated voltage is applied by a power supply circuit (inverter) in a dark atmosphere, the discharge in the tube hardly occurs. Further, since there is no scattering by the phosphor film, light can be introduced into a narrow range in the tube, so that the gas in the tube can be ionized in a spot manner. Even if the fluorescent discharge tube CCFL is turned on once, the dark start-up characteristic is restored to the original state by being left in the dark atmosphere for several minutes after the power is turned off. Therefore, by using the glass tube VAL that is not applied to the phosphor film, the accuracy and efficiency can be dramatically improved in the experiment.

  First, the fluorescent discharge tube CCFL as a sample is first left in a dark atmosphere. Next, the hot side of the inverter IV of the power supply circuit of FIG. 8 installed in the dark room is connected to the outer lead OLE of this sample, and this sample is placed horizontally and away from the experimental table. Here, attention is paid to the arrangement of the sample in order to avoid the influence of reflection of light from an object arranged around.

  Next, while the power source of the inverter IV is turned on and off in pulses, the light collected from the projector LG is condensed on a part of the sample through a narrow slit SL and a lens LEN and is about 0.5 mm long and narrow. While irradiating the vicinity of the electrode with the light beam LF, the ion beam moved in the XX ′ direction indicated by an arrow, and the irradiation position where discharge was triggered by ionized ions generated in a spot manner by the light beam LF in the in-tube gas was searched. That is, the first ion generation site when growing into a discharge in the entire tube was identified.

  In the fluorescent discharge tube CCFL not coated with the phosphor film, the discharge in the tube hardly occurs when a rated voltage is applied in a dark atmosphere. Furthermore, since there is no reflection by the phosphor film, the light beam LF can be easily inserted into the tube. In addition, even if it is once lit, if the power is turned off and left in a dark atmosphere for several minutes, the starting characteristics are restored to the original state, so that the efficiency of the experiment can be greatly improved. In practice, it was confirmed that there was reproducibility by repeatedly turning on and off the power source of the inverter IV several times repeatedly at the irradiation site.

  If ionization of the gas in the tube by electron emission is performed at the ion generation site in the actual tube, discharge of the entire tube is caused. Therefore, in order to improve the dark start-up characteristics, it is only necessary that the ion generation site is easily subjected to electron emission by an electric field.

  That is, the irradiation with the light beam LF that has passed through the narrow slit SL is to cause minute gas ionization at an arbitrary position. If there is a slight amount of ionized gas, the phenomenon of ionizing surrounding gas will occur in a chain, and light will be irradiated to the part that will be turned on instantly by rapidly advancing gas ionization throughout the fluorescent discharge tube CCFL. Then, since the fluorescent discharge tube CCFL is turned on instantaneously by gas ionization by the energy of the light beam LF, the distribution of the ion generation site can be known in detail.

  Here, as shown in FIG. 7, the portion that irradiates the light beam LF to the glass tube VAL is A near the center of the cup electrode CE, B is near the opening, and the distance d1 is about 3 mm away from the opening B. Fluorescent discharge when the light beam LF is irradiated while moving the projector LG in the direction of the arrow XX ′ to each of the above portions in the vicinity of the cup electrode CE connected to the hot side of the inverter IV. Experiments were conducted on 15 samples of the fluorescent discharge tube CCFL with respect to the frequency at which the tube CCFL is lighted instantaneously. The results are shown in Table 1 below.

  As shown in Table 1, in the vicinity A of the central portion of the side surface of the cup electrode CE, 11 of the 15 samples were turned on instantaneously by irradiation with the light beam LF. The remaining four lights were turned on within 1 second after irradiation with the light beam LF. In addition, lighting within 1 second has no problem in practice. In the vicinity of the opening B, 14 out of 15 lights up instantaneously by irradiation with the light beam LF. The remaining one lighted up within 1 second. In the part C at a distance d = about 3 mm from the vicinity B of the cup opening, 12 of the 15 lights were instantly turned on by irradiation with the light beam LF. The remaining three lights turned on within 1 second. However, as the distance from the cup electrode CE increases, the probability of instantaneous lighting decreases rapidly.

  Further, regarding the limit distance from the cup electrode ELE that the fluorescent discharge tube CCFL is instantaneously turned on when the light beam LF is irradiated to the portion D that is a distance d2 away from the vicinity B of the opening of the cup electrode ELE connected to the hot side of the inverter IV. Table 2 below shows the results of experiments performed on 10 samples of the fluorescent discharge tube CCFL.

  As shown in Table 2, among the 10 samples, the shortest distance d2 is about 5 mm, and the longest distance d2 is about 45 mm. Note that the phenomenon shown in Tables 1 and 2 does not occur in the case of the cup electrode to which the ground side of the inverter IV is connected.

  The actual length of the fluorescent discharge tube CCFL, except for special ones, may be several hundred mm to over about 1000 mm, but it is directly related to the hot side of the inverter IV when the fluorescent discharge tube CCFL is turned on. It was revealed that it was only in the vicinity of the cup electrode CE connected to the.

In the present invention, as a means for causing gas ionization in a portion having a high probability of instantaneous lighting described above, electrons due to field emission are generated in the portion. The generation of electrons by field emission follows the Fowler-Nordheim equation as is well known. The current density J in electron emission is expressed as shown in Equation 1 below. Here, E: electric field, φ: work function, A, B: constant.

  In the above formula 1, there are the electric field E and the work function φ of the electron emission source as the effect factors of the field emission. First, consider the strength of the electric field E. FIG. 9 is a photographic diagram showing an example of computer simulation of the electric field strength and equipotential distribution in the vicinity of the cup-shaped electrode at the time before the start of the discharge of the fluorescent discharge tube CCFL in the mounted state in the backlight device. VAL is a glass tube, INL is an inner lead, CE is a cup electrode, and OCE is an opening of the cup electrode. As shown in FIG. 9, the portion where the electric field strength is large is only in the vicinity of the cup electrode CE. Since the part C away from the cup opening vicinity B shown in FIG. 7 is away from the cup electrode ELE, it is difficult to increase the electric field. The portions where the electric field can be further strengthened are only the vicinity A of the side surface of the cup electrode CE and the vicinity B of the opening thereof in FIG.

  There are a plurality of means for increasing the electric field E, one of which is a thin film formed by sputtering the cup electrode onto the inner wall surface of the glass tube while the cup electrode is ground with ions. Since a phosphor film made of phosphor particles is formed on the inner wall surface of the glass tube, the surface is an aggregate of roughened projections. Since a sputtering film from the cup electrode, which is a conductive material, is formed thereon, a strong electric field can be formed. In this case, the more the amount of electrons emitted by the strong electric field, the easier the gas ionization is promoted. In particular, in the aging process of the fluorescent discharge tube manufacturing process, it is possible to form a conductive film with a large area on the inner wall surface of the glass tube and to collect the charges induced around the cup electrode by sputtering intentionally. The delay in lighting of the fluorescent discharge tube can be reduced.

  FIG. 10 is a developed perspective view when the fluorescent discharge tube CCFL is mounted on a backlight device and assembled as a liquid crystal display device. In the drawing, the DFL accommodates a plurality of fluorescent discharge tubes CCFL arranged in parallel at predetermined intervals. The lower frame, RFP is a reflecting plate laid on the bottom surface of the lower frame DFL, HOL is a holding member that holds a plurality of fluorescent discharge tubes CCFL, SCB is a light diffusion plate, and LCD is a liquid crystal display panel that displays an image.

  There are many necessary items as a liquid crystal display device, and one of them is a demand for making an area where no image is displayed other than the image display area AR of the liquid crystal display panel LCD as small as possible. This is a portion called a frame of the peripheral surface portion of the image display area AR. The length in the left-right direction at this location is mainly determined by the region length L of the fluorescent discharge tube CCFL that does not emit light. The factors determining the region length L are the electrode length in the tube axis direction of the cup electrode CE in FIG. 7, and the inner wall surface of the cup electrode of the fluorescent discharge tube CCFL is ground by ions during energization and sputtered onto the inner wall surface of the glass tube. And the thin film formed.

  The length of the fluorescent discharge tube CCFL is difficult to change in design. However, in the aging process of the manufacturing process of the fluorescent discharge tube CCFL, a sputtering thin film is used as a means for forming a conductive film on the inner wall surface of the glass tube by concentrating sputtering and concentrating charges induced around the cup electrode CE. When the surface area increases, the ultraviolet rays in the cold cathode fluorescent discharge tube CCFL do not hit the phosphor film of the part, and thus the area where the phosphor film does not emit light is expanded. Therefore, a contradiction arises from this condition that the area of the sputtering thin film should be small.

  In the present invention, by forming a groove on the side surface of the cup electrode CE and forming a sputtering thin film on the inner wall surface of the glass tube facing the side surface of the cup electrode CE, cold cathode fluorescent discharge is performed while suppressing an increase in the frame. The lighting delay of the tube CCFL can be reduced.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings of the examples.

  FIG. 1 is an enlarged cross-sectional view of a main part of a cold cathode fluorescent discharge tube for explaining the configuration of Embodiment 1 of the fluorescent discharge tube according to the present invention. The same parts as those shown in FIG. In the fluorescent discharge tube CCFL shown in FIG. 1, a pair of cup electrodes CE having openings on the discharge region side are arranged opposite to each other inside both ends of the ultraviolet ray transmissive glass tube VAL. In FIG. 1, only one end is shown. The glass tube VAL is filled with a rare gas and mercury or a rare gas, and a rare earth phosphor film FLU is deposited on the inner wall surface of the glass tube VAL.

  In addition, the pair of cup electrodes CE has an opening diameter of electrodes as shown in FIG. 2 (a), a plan view of the main part viewed from the electrode opening end side, and a plan view of the main part viewed from the side in FIG. 2 (b). The opening diameter is different between one direction passing through the center of the shaft and the other direction intersecting with the one direction. That is, it is formed in a substantially elliptical shape. A concave groove DEN that is recessed in the tube axis direction of the cup electrode CE is integrally formed on the outer surface of the cup electrode CE along the tube axis direction. The concave groove DEN is formed at a location that is symmetrical with respect to the electrode axis of the cup electrode CE and is close to the inner wall surface of the glass tube VAL (a location where the radius of curvature of the elliptical cup electrode CE is small).

  As shown in FIG. 2, the pair of cup electrodes CE has an electrode length D1 of about 3.0 mm, an open end major axis D2 of about 2.0 mm, a minor axis D3 of about 1.8 mm, and a groove depth. The thickness D4 is about 0.1 mm, and the thickness is about 0.5 mm.

  Further, as shown in FIG. 1, the pair of cup electrodes CE is formed, for example, by pressing a nickel material into a cup shape by a press molding method and sintering, for example, aluminum oxide as a white metal oxide on the inner wall surface thereof. Sputtering source ASP is formed, and both opposing opening portions of the front end face the main discharge region, and the rear end portion thereof is an inner lead made of, for example, nickel-cobalt-iron alloy that approximates the thermal expansion coefficient of glass. The ILEs are butted together and joined by a resistance welding method such as welding to be electrically connected.

  The inner lead ILE is supported by the glass beads GBE and sealed inside and outside of the glass tube VAL in an airtight state. The glass beads GBE are welded to both ends of the glass tube VAL to seal off the glass tube VAL, and a pair of inner leads ILE projecting to the outside, for example, an outer lead OLE made of a nickel material or the like by a laser welding method or the like. They are joined and electrically connected. The pair of outer leads OLE is connected to a power supply circuit (not shown), and lighting power is supplied to the cup electrode CLE.

  The fluorescent discharge tube CCFL configured in this way has a groove DEN which is recessed along the electrode axis direction of the cup electrode CE on the outer surface of the pair of cup electrodes CE and is symmetrical with respect to the electrode axis of the cup electrode CE. Since the elliptical cup electrode CE adjacent to the inner wall surface of the tube VAL has a small radius of curvature, the sputter from the concave groove DEN of the cup electrode CE as shown in FIG. Is easily formed as a sputtering thin film SPM on the inner wall surface of the opposing glass tube VAL, so that charges are easily collected when the fluorescent discharge tube CCFL is started up, and the lighting delay is effectively eliminated.

  In addition, since the clearance between the concave groove DEN of the pair of cup electrodes CE and the inner wall surface of the glass tube VAL is large, a large amount of ion flow is selectively generated in this portion, and the concave groove DEN is formed. Since the amount of spatter increases from the non-existing location, the thickness of the sputtered thin film SPM is increased, and the conductivity is improved, it is easy to collect charges when starting the fluorescent discharge tube CCFL.

  Furthermore, since the sputtered thin film SPM formed by sputtering during the aging process is formed on the phosphor film FLU whose surface is not smooth, the surface inevitably becomes a thin film with a rough surface. Acicular growth takes place. This phenomenon is caused by the fact that the material evaporate of the cup electrode CE that has come in by sputtering loses energy before forming a smooth film by two-dimensional movement because the base is not a smooth surface. .

  Such a needle-like shape of the thin film SPM by sputtering increases the strength of the electric field E of the above-described formula 1, and therefore, electron emission is easily performed. In addition, the amount of sputtering can be increased by reducing the overall outer shape of the cup electrode ELE, but in this case, sputtering occurs from the entire circumference of the cup electrode ELE and becomes excessive.

  In such a configuration, by forming the concave groove DEN on the outer surface of the cup electrode CE, the ion flow reaches the outer surface of the cup electrode CE through the concave groove DEN during aging, and the spatter caused by the concave groove DEN. The film SPM is stably formed on the inner wall surface of the glass tube VAL facing the outer surface of the cup electrode CE in a short time (about 30 minutes). As a result, the dark start characteristic can be maintained at a high level. In addition, since the part where the sputtering thin film SPM is formed mainly includes the part where the phosphor film FLU does not emit light, the expansion of the part where the luminance is reduced by the sputtering thin film SPM can be suppressed.

  According to such a configuration, the sputtering thin film SPM formed by the concave groove DEN formed on the outer surface of the cup electrode CE is optimal because the starting characteristics of the fluorescent discharge tube CCFL and the sputtering amount are well balanced.

  FIG. 3 is a diagram for explaining the configuration of a cup electrode according to Example 2 of a fluorescent discharge tube according to the present invention. FIG. 3 (a) is a plan view seen from the opening end side of the cup electrode, and FIG. It is a top view seen from the side surface side of a cup electrode, The same code | symbol is attached | subjected to the same part as FIG. 2 mentioned above, and the description is abbreviate | omitted. The cup electrode CE shown in FIG. 3 is integrally formed in an oblique direction in which a recessed groove DEN formed on the outer surface of the cup electrode CE differs from FIG. Even in such a configuration, the same effects as those of the first embodiment can be obtained.

  4A and 4B are diagrams for explaining the configuration of a cup electrode according to Embodiment 3 of the fluorescent discharge tube of the present invention. FIG. 4A is a plan view seen from the opening end side of the cup electrode, and FIG. It is a top view seen from the side surface side of a cup electrode, The same code | symbol is attached | subjected to the same part as FIG. 2 mentioned above, and the description is abbreviate | omitted. The cup electrode CE shown in FIG. 4 is formed integrally with a concave groove DEN formed at the outer surface of the cup electrode CE at 90 ° intervals symmetrically with respect to the electrode axis. In such a configuration, since the sputtering thin film is stably formed on almost the entire inner wall surface of the glass tube VAL opposite to the outer surface of the cup electrode CE, the dark starting characteristics can be maintained at a higher level. .

Comparative Example 1

  FIG. 5 is a diagram showing a cup electrode for explaining a configuration example of a current fluorescent discharge tube, FIG. 5 (a) is a plan view seen from the opening end side of the cup electrode, and FIG. 5 (b) is a view of the cup electrode. It is the top view seen from the side surface side. Since the outer shape of the cup electrode CE shown in FIG. 5 is formed in a substantially circular shape, the same effects as those of the above embodiments cannot be obtained.

  Further, in each of the embodiments described above, the ultraviolet transmissive glass tube VAL constituting the fluorescent discharge tube EEFL may be replaced with an ultraviolet transmissive resin tube that is less devitrified by ultraviolet rays. The effect is obtained.

  Further, in each of the embodiments described above, a case has been described in which a pair or two of the concave grooves DEN are provided symmetrically with respect to the electrode axis on the outer surface of the pair of cup electrodes CE, but the present invention is limited to this. Instead, three or more pairs may be provided, and it is needless to say that substantially the same effect as described above can be obtained even if at least one (plural) is provided at random without being specified as paired symmetrically with respect to the electrode axis. .

  FIG. 11 is an exploded perspective view schematically illustrating a configuration example of a liquid crystal display device in which a fluorescent discharge tube according to the present invention is mounted on a backlight device. In FIG. 11, the upper frame is above the liquid crystal display panel LCD, but is omitted in FIG. FIG. 12 is a cross-sectional view schematically illustrating the configuration of a liquid crystal display device in which constituent members are integrated. Further, FIG. 13 is a plan view schematically illustrating a configuration example of the lower frame as viewed from the optical compensation sheet laminate side. 12 corresponds to a cross section cut along the line AA in FIG.

  11 to 13, a liquid crystal display panel LCD has a liquid crystal layer sealed between glass substrates having electrodes for forming pixels, and is one of two glass substrates (usually referred to as an active matrix substrate). The side protrudes from the other substrate (usually also referred to as a color filter substrate), and the flexible printed circuit board FPC1 in which the scanning signal line driving circuit chip GCH is mounted on the protruding portion, and the data signal line driving circuit chip A flexible printed circuit board FPC2 mounted with DCH is mounted.

  In such a liquid crystal display device, a reflection sheet RFS is laid in a lower frame DFL, and a plurality of cold cathode fluorescent discharge tubes CCFL according to the present invention are installed in parallel above the reflection sheet RFS to constitute a backlight BL. . The lower frame DFL is formed of a metal plate, and has a function of stacking and integrating the liquid crystal display panel LCD together with the optical compensation sheet laminate PHS between the upper frame UFL formed of the same metal plate. As the size of the liquid crystal display panel LCD increases, the length of the cold cathode fluorescent discharge tube CCFL increases. The cold cathode fluorescent discharge tube CCFL is a fluorescent lamp composed of a glass tube having a small diameter, and is usually installed by supporting both ends by a rubber bush GBS.

  Further, in the liquid crystal display device, a light guide plate GLB made of a translucent resin material is installed on the upper part of the backlight BL, and a plurality of kinds of light guide plates GLB are provided above the light guide plate GLB (between the liquid crystal display panel LCD). An optical compensation sheet group is installed. The optical compensation sheet laminate PHS is configured by stacking a diffusion plate SCB, a first diffusion sheet SCS1, two prism sheets PRZ arranged in an intersecting manner, and a second diffusion sheet SCS2. The direct type backlight BKL has a resin side holding frame SMLD called a side mold provided on the side edge of the bottom frame DFL having a bottom and a side edge. The light guide plate GLB and the side holding frame SMLD are provided on the side holding frame SMLD. The peripheral edge of the optical compensation sheet laminate PHS is bridged and held.

  Also, as shown in FIG. 12, the backlight BL holding the light guide plate GLB and the optical compensation sheet laminate PHS is combined with the liquid crystal display panel LCD by the mold frame MLD, and then covered with the upper frame UFL. The UFL and the lower frame DFL are coupled by a locking member (not shown) and integrated to form a liquid crystal display device. In the configuration in which the liquid crystal display panel LCD is enlarged, a light diffusion plate or a light diffusion sheet is used instead of the light guide plate GLB.

  In the liquid crystal display device configured as described above, the concave portion DEN is provided on the outer surface of the cup electrode CE of the fluorescent discharge tube CCFL, thereby increasing the peripheral portion where the image of the image display area AR of the liquid crystal display panel LCD is not displayed. High-quality and high-quality image display with reduced lighting delay of the fluorescent discharge tube can be obtained.

It is a principal part expanded sectional view which shows the structure of Example 1 of the fluorescent discharge tube by this invention. 2A and 2B are diagrams illustrating a configuration of a cup electrode in FIG. 1, in which FIG. 2A is a plan view of a main part viewed from an electrode opening end, and FIG. 2B is a plan view of a main part viewed from a side surface. It is a figure which shows the structure of Example 2 of the fluorescent discharge tube by this invention, Fig.3 (a) is the principal part top view seen from the electrode opening end, FIG.3 (b) is the principal part top view seen from the side. is there. It is a figure which shows the structure of Example 3 of the fluorescent discharge tube by this invention, Fig.4 (a) is the principal part top view seen from the electrode opening end, FIG.4 (b) is the principal part top view seen from the side. is there. It is a figure which shows the structure of the fluorescent discharge tube now, Fig.5 (a) is the principal part top view seen from the electrode opening end, FIG.5 (b) is the principal part top view seen from the side surface. It is sectional drawing which shows schematic structure of the fluorescent discharge tube by this invention. It is typical sectional drawing which shows the structure of the confirmation experiment apparatus of the micro ionization place used as the trigger of the whole discharge in a fluorescent discharge tube. It is a figure which shows the power supply circuit which makes a fluorescent discharge tube light. It is a photograph figure which shows the simulation result of the electric field strength of the cup electrode vicinity, and equipotential distribution when a fluorescent discharge tube is mounted in a backlight apparatus. FIG. 3 is an exploded perspective view when the fluorescent discharge tube according to the present invention is mounted on a backlight device and assembled as a liquid crystal display device. It is an expansion | deployment perspective view which illustrates typically the structural example of the liquid crystal display device with which the fluorescent discharge tube was mounted | worn with the backlight apparatus. It is sectional drawing which illustrates typically the structure of the liquid crystal display device which integrated the structural member. It is a top view explaining typically the example of composition of the lower frame seen from the optical compensation sheet layered product side.

Explanation of symbols

CCFL ... fluorescent discharge tube, VAL ... glass tube, CE ... cup electrode, OCE ... cup electrode opening, FLU ... phosphor film, ILE ... inner lead, OLE ... Outer leads, GBE ... glass beads, SPM ... sputtering thin film, DEN ... concave groove, ASP ... sputter source, IV ... inverter, LG ... light projector, SL ... slit, LEN ... Lens, LF ... Luminous flux, LCD ... Liquid crystal display panel, AR ... Image display area, SCB ... Diffusion plate, SCS ... Diffusion sheet, SCS1 ... First diffusion sheet, SCS2 ... second diffuser sheet, PRZ ... prism sheet, DFP ... diffuser plate, PHS ... optical compensation sheet laminate, GLB ... light guide plate, RFP ... reflector plate, UFL ... ·Up Frame, DFL · · · lower frame, BL · · · backlight device, HOL · · · holding member.

Claims (6)

An ultraviolet light transmissive glass tube in which a phosphor film is formed on the inner surface and a rare gas and mercury or a rare gas are sealed inside;
A pair of cup electrodes encapsulated and disposed at opposite ends of the glass tube with the electrode opening ends facing each other;
One end of the cup electrode is connected to the other end, and the other end is hermetically sealed outside the glass tube.
A fluorescent discharge tube comprising:
A fluorescent discharge tube characterized in that a concave groove recessed in the electrode axial direction is integrally formed along the electrode length direction on the outer surface of the pair of cup electrodes.   The fluorescent discharge tube according to claim 1, wherein the concave groove is formed along an oblique direction intersecting with the electrode axis direction.   3. The fluorescent discharge according to claim 1, wherein the pair of cup electrodes have different aperture diameters in one direction passing through the electrode axis and in another direction intersecting the one direction. 4. tube.   4. The fluorescent discharge tube according to claim 1, wherein at least a pair of the concave grooves are formed axially symmetrical with respect to the electrode axis. 5.   The fluorescent discharge tube according to any one of claims 1 to 4, wherein the concave groove is formed at a position closest to an inner wall surface of the glass tube. A liquid crystal display panel configured by sandwiching a liquid crystal layer between a pair of translucent substrates each having an electrode for pixel formation on the inner surface;
A backlight device having at least one fluorescent discharge tube for irradiating illumination light on the back surface of the liquid crystal display panel;
An optical compensation sheet laminate interposed between the liquid crystal display panel and the backlight device;
A frame for housing the liquid crystal display panel and the backlight device;
A liquid crystal display device comprising:
The fluorescent discharge tube is integrally formed along the electrode length direction with a concave groove recessed in the electrode axial direction on the outer surface of a pair of cup electrodes encapsulated and arranged at both ends of an ultraviolet ray transmissive glass tube toward the electrode opening end. A liquid crystal display device characterized in that the liquid crystal display device is formed.