JP2008177012A - Low pressure discharge lamp, backlight unit and liquid crystal display device - Google Patents

Abstract

The present invention provides a low-pressure discharge lamp, a backlight unit and a liquid crystal display device capable of preventing cracks from occurring at the end of a glass bulb.
A glass bulb (2) and an external electrode (101) provided on at least one of both ends of the glass bulb (2) are provided, and the external electrode (101) has at least an electrode body layer (101a) formed on the outer surface of the glass bulb (2). And a transparent conductive layer 101b laminated on the electrode body layer 101a.
[Selection] Figure 1

Description

  The present invention relates to a low-pressure discharge lamp, a backlight unit, and a liquid crystal display device.

A cross-sectional view including the tube axis of the conventional low-pressure discharge lamp 1 is shown in FIG. The low-pressure discharge lamp 1 is an external electrode fluorescent lamp having an external electrode 3 on the outer periphery of the end of the glass bulb 2. The external electrode 3 is made of solder, and is formed by performing a solder dipping process on the outer periphery of the end of the glass bulb 2 (see, for example, Patent Document 1).
JP 2004-146351 A

  However, when the solder dipping process is performed on the outer periphery of the end portion of the glass bulb 2, there is a possibility that the end portion of the glass bulb 2 is distorted due to the heat of the melted solder, and a crack is generated in that portion. In particular, when a glass material having a thermal expansion coefficient larger than that of borosilicate glass, such as lead-free glass or soda glass, is used for the glass bulb 2, distortion due to heat is increased, and the risk is further increased.

  Therefore, an object of the present invention is to provide a low-pressure discharge lamp, a backlight unit, and a liquid crystal display device that can prevent cracks from occurring at the end of a glass bulb.

  In order to solve the above problems, a low-pressure discharge lamp according to the present invention includes a glass bulb and external electrodes provided at at least one of both ends of the glass bulb, and the external electrode is an outer surface of the glass bulb. It is comprised by the electrode main body layer formed in this, and the transparent conductive layer laminated | stacked on the said electrode main body layer at least.

  In the low-pressure discharge lamp according to the present invention, the transparent conductive layer is preferably made of at least one of tin oxide and indium tin oxide.

  In the low-pressure discharge lamp according to the present invention, it is preferable that the electrode body layer includes at least one of gold, silver, copper, and aluminum.

  In the low-pressure discharge lamp according to the present invention, it is preferable that characters are marked on the outer surface of the electrode body layer.

  In the low-pressure discharge lamp according to the present invention, it is preferable that the thickness of the electrode main body layer is 70 [μm] or less, and the thickness of the edge portion of the electrode main body layer becomes thinner as approaching the edge.

  The backlight unit according to the present invention includes the low-pressure discharge lamp.

  The liquid crystal display device according to the present invention includes the backlight unit.

  The low-pressure discharge lamp, illumination device, and liquid crystal display device according to the present invention can prevent cracks from occurring at the end of the glass bulb.

(First embodiment)
Low-pressure discharge lamps 100 according to the first embodiment of the present invention (hereinafter, simply. As "lamp 100") shows a cross-sectional view including the tube axis X ₁₀₀ of Figure 1. The lamp 100 is an external electrode type fluorescent lamp having external electrodes 101 on the outer surfaces of both ends of the glass bulb 2.

  The glass bulb 2 is produced by sealing both ends of a glass tube made of, for example, borosilicate glass, and its total length is 730 [mm]. Further, the glass bulb 2 has, for example, an annular cross section cut perpendicular to its tube axis, an outer diameter of 4.0 [mm], an inner diameter of 3.0 [mm], and a thickness of 0.0. 5 [mm].

  In addition, the dimension of the glass bulb | bulb 2 is not limited to the said dimension. However, when used as a backlight for notebook PCs, monitors, televisions, etc., the glass bulb 2 has an outer diameter of 1.8 [mm] to 6.0 [mm] and an inner diameter of 1.4 [mm] to 5 It is preferable to be within the range of 0.0 [mm].

The material of the glass bulb 2 is not limited to borosilicate glass, and lead glass, lead-free glass, soda glass, or the like may be used. In this case, the dark startability can be improved. That is, the glass as described above contains a large amount of alkali metal oxide typified by sodium oxide (Na ₂ O). For example, in the case of sodium oxide, the sodium (Na) component elutes on the inner surface of the glass bulb over time. To do. This is because sodium is low in electronegativity, so that sodium eluted at the inner end of the glass bulb 2 (without a protective film) is considered to contribute to the improvement of the dark startability.

  In particular, in the external electrode type fluorescent lamp, the content of the alkali metal oxide in the material of the glass bulb 2 is preferably 3 [mol%] or more and 20 [mol%] or less.

  For example, when the alkali metal oxide is sodium oxide, the content is preferably 5 [mol%] or more and 20 [mol%] or less. If it is less than 5 [mol%], the probability that the dark start time will exceed 1 [second] increases (in other words, if it is 5 [mol%] or more, the probability that the dark start time will be within 1 [second] is high. If it exceeds 20 [mol%], the glass bulb 2 will be blackened (brown brown) or whitened due to long-term use, resulting in a decrease in brightness, or the strength of the glass bulb 2 may be reduced. This is because a problem such as a problem occurs.

  In consideration of protection of the natural environment, it is preferable to use lead-free glass. However, even lead-free glass may contain lead as an impurity during the manufacturing process. Therefore, in the present invention, glass containing lead at an impurity level of 0.1 [wt%] or less is also defined as lead-free glass.

A phosphor layer 4 is formed on the inner surface (excluding both ends) of the glass bulb 2. The phosphor layer 4 includes, for example, a red phosphor (Y ₂ O ₃ : Eu ³⁺ ), a green phosphor (LaPO ₄ : Ce ³⁺ , Tb ³⁺ ), and a blue phosphor (BaMg ₂ Al ₁₆ O ₂₇ : Eu). ²⁺ ). In addition, it is preferable that the fluorescent substance layer 4 is not formed in the part corresponding to the electrode main body layer 101a mentioned later in the inner surface of the glass bulb | bulb 2. FIG. This is because the portion corresponding to the electrode main body layer 101a on the inner surface of the glass bulb 2 is directly exposed to the discharge, so that the phosphor of the portion is easily deteriorated.

Further, a protective film (not shown) may be provided at a portion corresponding to the electrode main body layer 101a on at least the inner surface of the glass bulb 2. The protective film is made of, for example, yttrium oxide (Y ₂ O ₃ ). The protective film has a role of preventing a hole from being opened in the inner surface of the glass bulb 2 due to ion bombardment. The constituent material of the protective film is not limited to the above, and may be formed of, for example, silica (SiO ₂ ) or alumina (Al ₂ O ₃ ). When the protective film is made of yttrium oxide or silica, mercury hardly adheres to the protective film, and mercury consumption is low. Further, the protective film is not limited to the above portion, and may be a portion where the phosphor layer 4 is formed, for example, and may be formed between the glass bulb 2 and the phosphor layer 4. In this case, the protective film can prevent mercury that has passed through the phosphor layer 4 from reacting with sodium (Na) of the glass bulb 2 while the lamp 100 is turned on. In addition, it is preferable that the thickness of a protective film is 0.1 [micrometer] or more, for example.

  In the glass bulb 2, for example, about 2.0 [mg] mercury and a neon / argon mixed gas (Ne: 90 [%] + Ar) of about 7 [kPa] (20 [° C.]) as a rare gas. : 10 [%]) is enclosed. Note that the composition of the rare gas is not limited to the above composition, and for example, a neon-krypton mixed gas (Ne: 95 [%] + Kr: 5 [%]) may be enclosed as the rare gas.

The external electrode 101 includes an electrode main body layer 101a and a transparent conductive layer 101b. The electrode body layer 101a is, for example, silver paste, and is formed by printing on the outer surface of the end portion of the glass bulb 2 by screen printing. The thickness D ₁ of the electrode body layer 101a is, for example, about 3.0 [μm]. Here, the thickness of the electrode main body layer 101a in the present invention means an average thickness of the entire electrode main body layer 101a. In addition, this average thickness is an average thickness of the thicknesses d _{1 to} d _{6 in} the cross section including the tube axis of the lamp 100 as shown in FIG. Specifically, d ₂ and d ₅ are the thicknesses of the midpoints separated from both edges by m [mm] in the longitudinal direction of the electrode body layer 101a, respectively, and d ₁ , d ₃ , d ₄ and d ₆ are It is the thickness at a position that is n [mm] away from both edges in the longitudinal direction of the electrode body layer 101a. In the present invention, n is 5 [mm].

Average thickness, using a JEOL Ltd. of SEM (scanning electron microscope) taken cross-sectional photograph of including the tube axis X ₁₀₀ of the lamp 100 (magnification 2000 [times]), the thickness of d ₁ to d ₆ It measured and calculated | required by calculating the average value. In the case where the electrode body layer 101a is formed in a cap shape so as to cover the entire outer surface of the end portion of the glass bulb 2, the edge of the electrode body layer 101a on the end side in the longitudinal direction of the glass bulb 2 is The edge of the portion of the electrode body layer 101a where the glass bulb 2 is substantially parallel to the tube axis.

  The material of the electrode body layer 101a is not limited to the above. For example, it may contain at least one of gold, copper, and aluminum, or may be a compound or mixture containing silver or copper as a main component. Here, the meaning of “having silver or copper as the main component” includes the case where an alloy of silver and copper is the main component. The “main component” is a component that is contained most in the composition and means a component that greatly affects the physical properties of the composition. Therefore, substances other than silver or copper may be included as additives. Since silver has a small electric resistance, the electrode main body layer 101a having high conductivity can be obtained when the main component of the electrode main body layer 101a is used. Further, when silver is used as the main component of the electrode main body layer 101a, the baking operation in the electrode main body layer 101a forming step can be performed in the air. That is, since silver is difficult to oxidize, it is not necessary to perform a baking operation in an atmosphere such as nitrogen or argon, and the productivity of the lamp 100 is high. Further, since copper has the second lowest electrical resistance after silver, the external electrode 101 having high conductivity can be obtained even when copper is used as the main component of the electrode body layer 101a.

  In order to improve the adhesion of the electrode body layer 101a to the glass bulb 2, for example, it is conceivable to add glass frit to the electrode body layer 101a. For example, when a glass frit containing 1.0 [wt%] to 5.0 [wt%] of bismuth (Bi) is added, the adhesion of the electrode body layer 101a to the glass bulb 2 is improved by the anchor effect of the glass frit. To do. Other additives include ethyl cellulose and the like.

  In addition, although the electrode main body layer 101a shown in FIG. 1 is formed in the headband shape without covering the front-end | tip of a glass bulb on the end part outer surface of the glass bulb 2, it is not restricted to this, The edge part of the glass bulb 2 It may be formed in a cap shape so as to cover the entire outer surface.

The transparent conductive layer 101b is made of, for example, tin oxide (SnO or SnO ₂ ), and is formed by being laminated on at least the electrode body layer 101a. The thickness D ₂ of the transparent conductive layer 101b is, for example, about 0.3 [μm]. In the present invention, “the thickness of the transparent conductive layer 101b” means the average thickness of the transparent conductive layer 101b formed on the electrode body layer 101a.

  The method for measuring the average thickness of the transparent conductive layer 101b is the same as the method for measuring the average thickness of the electrode main body layer 101a in the longitudinal direction of the lamp 100 in the same measurement method as the average thickness of the electrode main body layer 101a described above. The thickness of the transparent conductive layer 101b at the position is measured and averaged.

  Note that the material of the transparent conductive layer 101b is not limited to the above. For example, indium tin oxide (ITO) or a mixture of tin oxide and indium tin oxide may be used.

  In addition, when antimony (Sb) is contained in the material of the transparent conductive layer 101b, since the adhesive force with the glass bulb | ball 2 can be improved, it can prevent that the transparent conductive layer 101b peels.

A conceptual diagram of the process of forming the transparent conductive layer 101b is shown in FIG. As shown in FIG. 2, in the step of forming the transparent conductive layer 101b, a cylindrical container 102 made of soda glass, quartz or the like is arranged substantially horizontally, and the nozzle 104 for spraying the solvent 103 of the transparent conductive layer is cylindrical. The container 102 is disposed near the opening at one end. The solvent 103 is, for example, a mixed solution of tin monoxide (SnO), water, alcohol (such as methanol or ethanol) and hydrochloric acid (HCl), a mixed solution of tin dioxide (SnO ₂ ), alcohol and hydrofluoric acid (HF), or the like. .

The glass bulb 2 in which the electrode body layer 101a is formed on the outer surface of the end portion of the glass bulb 2 is disposed inside the cylindrical vessel 102, and the nozzle is rotated while rotating the cylindrical vessel 102 about the tube axis _X102 as a rotation axis. The solvent 103 is sprayed from 104 to the end of the glass bulb 2. Thereafter, the transparent conductive layer 101b can be formed by baking at about 600 [° C.].

  In addition, although the transparent conductive layer 101b shown to Fig.1 (a) covers the whole edge part of the glass bulb | bulb 2 containing the electrode main body layer 101a, it may cover only the electrode main body layer 101a. . Further, the transparent conductive layer 101b is formed beyond the end of the electrode main body layer 101a on the center side in the longitudinal direction of the glass bulb 2. In the glass bulb 2, the region sandwiched between the electrode main body layers 101a is substantially the light emitting portion, but the transparent conductive layer 101b is transparent, so that a part of the light emitting portion exceeds the electrode main body layer 101a as described above. The luminous flux of the lamp 100 formed in this way is not impaired. Moreover, since the electrical resistance value (about 2 [kΩ]) of the material used for the transparent conductive layer 101b is larger than the electrical resistance value (about 0.2 [kΩ]) of the material forming the electrode body layer 101a, the transparent conductive layer 101b is transparent. The portion of the conductive layer 101b that does not cover the electrode main body layer 101a does not contribute to the discharge. Even if the electrical resistance value of the transparent conductive layer 101b is ∞, if the thickness is up to several hundreds [nm], the conductivity to the electrode body layer 101a is maintained by the so-called tunnel effect. Can do.

  The electrical resistance value was measured by using a tester (FLUKE87 manufactured by Fluke Co., Ltd.) and pressing both ends of the tester 10 mm apart in the direction of the tube axis X100 and vertically against the surface of the electrode part.

  When the electrode body layer 101a is covered with an opaque conductive layer, the portion of the conductive layer that protrudes from the electrode body layer 101a is a loss of the luminous flux of the lamp 100. In addition, when using a conductive layer that does not have a large electrical resistance compared to the electrode body layer 101a, the portion of the conductive layer that protrudes from the electrode body layer 101a contributes to the discharge, and between the electrodes at both ends, Differences and variations in capacitance may occur. Therefore, when using the conductive layer as described above, it is necessary to perform a masking process.

Further, the entire glass bulb 2 may be covered with the transparent conductive layer 101b. In this case, for example, when soft glass having a thermal expansion coefficient of 60 [K ⁻¹ ] or more and 110 [K ⁻¹ ] or less is used as the material of the glass bulb 2, the surface of the glass bulb 2 is prevented from being damaged. The glass bulb 2 can be prevented from being damaged.

  The low-pressure discharge lamp 100 according to the first embodiment of the present invention can form the external electrode 101 without passing through a process of applying a thermal shock to the end portion of the glass bulb 2 such as a solder dip by the above-described configuration. It is possible to prevent cracks from occurring at the end of the glass bulb 2. Moreover, even when glass having a higher thermal expansion coefficient than borosilicate glass, such as lead-free glass or soda glass, is used for the glass bulb 2, it is possible to prevent cracks from occurring at the ends thereof.

The thickness D ₁ of the electrode main body layer 101a is 70 [μm] or less, and it is preferable that the thickness of the edge of the electrode main body layer 101a becomes thinner as it approaches the edge. This is because generation of ozone can be suppressed while the lamp 100 is turned on. Here, the "edge of the electrode body layer", the thickness of the electrode body layer 101a means a portion of the edge from the position of the change point becomes thinner than the thickness D _1.

The inventors used experimental samples having different electrode body layer structures and thicknesses, and turned on by changing the tube voltage, and confirmed the relationship between the thickness of the electrode body layer and the amount of ozone generated. The sample used for the experiment is an external electrode fluorescent lamp having the same specifications as the low-pressure discharge lamp according to the first embodiment of the present invention except for the structure of the electrode body layer. The thickness of the electrode body layer 101a is the same. 70 μm, and the thickness of the edge of the electrode main body layer 101a becomes thinner as it approaches the edge, and is the same as that of the first embodiment except for the thickness of the electrode main body layer 101a. An electrode body layer 101a having a thickness of 45 [μm] was taken as Example 2. Further, except for the structure of the electrode main body layer 101a, the specification is the same as that of the first and second embodiments, the electrode main body layer 101a has a thickness of 70 [μm], and the thickness of the edge of the electrode main body layer 101a has an edge. not become thinner as it approaches, FIG. 3 (a), the edge of which has stepped in the glass bulb 2 and the electrode body layer 101a in a cross-sectional view including a tube axis X ₁₀₅ as shown in (b) The example in which a step is generated between the outer surface of the glass bulb 2 is referred to as Comparative Example 1 and has the same configuration as that of Comparative Example 1 except for the thickness of the electrode main body layer 101a, and the electrode main body layer 101a has a thickness of 30 [ μm] was designated as Comparative Example 2. As described above, by using four types of experimental samples and changing the tube voltage to light, the amount of generated ozone was confirmed.

  The amount of ozone generated was measured at ambient temperature of 25 ± 1 [° C] by turning on each of the experimental lamps one by one, and using the Okahara business product's ozone meter (EG2001F). The measurement was performed by placing the detection unit at a position of 5 mm directly above the part.

  FIG. 4 shows a relationship between the thickness of the electrode main body layer and the tube voltage, which is the result of the experiment. The tube voltage of a general external electrode type fluorescent lamp is designed to be about 2000 [Vrms] to 2200 [Vrms]. Therefore, even if the tube voltage is 2200 [Vrms], ozone is hardly generated unless ozone is generated. Can be evaluated.

  As shown in FIG. 4, in the case of Comparative Example 1, ozone was generated when the tube voltage exceeded 1800 [Vrms]. Also in Comparative Example 2, ozone was generated when the tube voltage exceeded 2100 [Vrms].

  On the other hand, in the case of Example 1, ozone was not generated until the tube voltage reached 2300 [Vrms]. In the case of Example 2, ozone was not generated even when the tube voltage exceeded 2500 [Vrms].

  The reason for this result was considered as follows. As shown in FIG. 3B, in the case of Comparative Example 1 and Comparative Example 2, the edge portion of the electrode main body layer 101a is not configured to become thinner as it approaches the edge, but the edge portion is stepped. For this reason, corona discharge that causes generation of ozone is likely to occur.

  On the other hand, as shown in FIG. 1B, in the case of Example 1 and Example 2, the edge of the electrode main body layer 101a becomes thinner as it approaches the edge, and corona discharge hardly occurs.

  However, although the detailed mechanism is unknown, when the thickness of the electrode body layer 101a exceeds 70 [μm], the tube voltage is 2200 [Vrms] even though the thickness of the edge portion becomes thinner as it approaches the edge. It was found that ozone is easily generated below.

  As described above, since the electrode main body layer 101a has a thickness of 70 [μm] or less and the thickness of the edge portion becomes thinner as it approaches the edge, generation of ozone can be suppressed. Furthermore, since it is preferable that ozone is not generated even when the tube voltage exceeds 2500 [Vrms] in order to give a margin to the lamp design, the thickness of the electrode body layer 101a may be 30 [μm] or less. More preferred. However, it is difficult to manufacture the electrode body layer 101a having a thickness of less than 5 [μm].

FIG. 5 shows an enlarged view obtained by further enlarging FIG. In the cross-sectional view of the electrode main body layer 101a as shown in FIG. 5, the ridge line trajectory 107 representing the outer surface of the electrode main body layer 101a is the trajectory X indicated by the alternate long and short dash line (the position P that is the edge of the electrode main body layer 101a). ₁ and a trajectory Y indicated by a two-dot chain line in the figure (position connecting the position P ₂ on the trajectory 107 of the ridge line returned from the position P _{1 in} the longitudinal direction of the glass bulb 2 by a distance L ₁ ). It is preferable that it is in the space between the P ₂ and the orbit parallel to the outer surface of the glass bulb 2 and swells in an R shape on the orbit Y side like a beak. In this case, generation of ozone can be further suppressed. The thickness L ₂ of the position P ₂ is preferably less than one-tenth or more of the maximum thickness D _1. When the thickness L _{2 at the} position P ₂ is 1/10 or more of the maximum thickness D ₁ , the electrode body layer 101a is difficult to peel from the glass bulb 2. Further, when the thickness L ₂ of the position P ₂ is less than the first maximum thickness D _1, it is possible to further suppress the corona discharge, it is possible to suppress the generation of ozone.

Further, as shown in FIG. 1B, the trajectory N (the position P ₁ and the position P ₃ where the thickness of the electrode body layer 101a becomes thinner than the thickness D ₁ ) indicated by the alternate long and short dash line and the glass bulb 2 The angle Q formed with the outer surface is preferably in the range of 5 [°] to 45 [°]. In this case, ozone is hardly generated by corona discharge, and the electrode main body layer 101a is difficult to peel from the glass bulb 2.

  By the way, as shown in FIG. 6, it is preferable that a character 101c such as a lot number is marked on the surface of the electrode body layer 101a of the external electrode 101, and a transparent conductive layer 101b is formed thereon. In general, in an external electrode type fluorescent lamp, when a letter such as a lot number is marked on a portion other than where the external electrode is formed, that is, a light emitting portion sandwiched between the external electrodes 101, loss of light flux occurs. Not suitable for. However, if a character is simply marked on the external electrode 101, the character may not be recognized due to contact with the socket, friction, or sulfidation or oxidation of the external electrode. Therefore, a letter is marked on the electrode body layer 101a of the external electrode 101, and the transparent conductive layer 101b is laminated thereon, so that the letter is scraped or the electrode body layer 101a is sulfided or oxidized. It is possible to prevent the recognition from becoming impossible.

  In addition, the method of marking a character on the outer surface of the electrode main body layer 101a can use various well-known methods, such as an inkjet system and a laser marking.

(Second Embodiment)
FIG. 7 shows a cross-sectional view including the tube axis X ₂₀₀ of the low-pressure discharge lamp according to the second embodiment of the present invention. The low-pressure discharge lamp (hereinafter simply referred to as “lamp 200”) according to the second embodiment of the present invention is an external internal electrode type having an external electrode 101 at one end of the glass bulb 2 and an internal electrode 201 at the other end. It is a fluorescent lamp. The lamp 200 has an internal electrode 201 inside the other end portion, and has substantially the same configuration as the low-pressure discharge lamp 100 according to the first embodiment of the present invention except for the configuration associated therewith. Therefore, the internal electrode 201 and the configuration associated therewith will be described in detail, and the other points will be omitted.

The internal electrode 201 is a bottomed cylindrical hollow electrode made of, for example, nickel (Ni), and has a total length of 5.2 [mm], an outer diameter of 2.7 [mm], and an inner diameter of 2.3 [mm]. The wall thickness is 0.2 [mm]. The material of the internal electrode 201 is not limited to nickel, and may be niobium (Nb), tantalum (Ta), molybdenum (Mo), or the like. The internal electrode 201 is arranged so that its tube axis substantially coincides with the tube axis X ₂₀₀ of the glass bulb 2, and the distance between its outer peripheral surface and the inner surface of the glass bulb 2 is substantially uniform over the entire area. ing. The distance between the outer peripheral surface of the electrode 201 and the inner surface of the glass bulb 2 is preferably 0.2 [mm] or less, for example, set to 0.15 [mm]. In this way, by defining the interval to be 0.2 [mm] or less, during lighting, discharge does not enter the space formed between the outer peripheral surface of the internal electrode 201 and the inner surface of the glass bulb 2, and the internal electrode Discharge occurs only inside 201. Therefore, it becomes difficult for the discharge during lighting to shift to the outside of the internal electrode 201, the excessive sputtering on the inner surface of the glass bulb 2 can be suppressed, the mercury consumption rate can be suppressed, and the life of the lamp 200 can be extended. be able to. Further, by preventing the discharge from wrapping around the lead wire 202 described later, the consumption of the lead wire 202 can be suppressed.

  The lead wire 202 is, for example, a connection between an internal lead wire 202a made of tungsten (W) and an external lead wire 202b made of nickel (Ni) that easily adheres to solder or the like, and the internal lead wire 202a and the external lead wire. The joint surface with 202b is substantially flush with the end surface of the glass bulb 2. That is, one end of the internal lead 202a is electrically and mechanically connected to the bottom of the hollow electrode 201, and most of the other end connected to the external lead 202b is connected to the glass bulb 2. Sealed. The external lead wire 202b is substantially entirely located outside the glass bulb 2. The internal lead wire 202a has a total length of 3 [mm] and a wire diameter of 1 [mm]. The external lead wire 202b has a total length of 5 [mm] and a linear shape of 0.8 [mm].

  The configuration of the lead wire 202 is not limited to the above configuration. For example, the internal lead wire 202a and the external lead wire 202b are not separated, and may be configured by a single wire, or the internal lead wire 202a or The external lead wire 202b may further connect a plurality of wires.

  The low-pressure discharge lamp 200 according to the second embodiment of the present invention is cracked at the end portion of the glass bulb 2 by the above-described configuration, similarly to the low-pressure discharge lamp 100 according to the first embodiment of the present invention. Can be prevented.

(Third embodiment)
FIG. 8 shows an exploded perspective view of the backlight unit according to the third embodiment of the present invention. As shown in FIG. 8, the backlight unit 300 is a direct type, and includes a rectangular parallelepiped housing 301 having one surface opened, a plurality of lamps 100 housed in the housing 301, and a housing. And an optical sheet 302 covering the opening of 301. The backlight unit 300 is disposed on the back surface of a liquid crystal panel (not shown), and is used as a light source device in the liquid crystal display device 400 (see FIG. 9).

The housing 301 is made of, for example, polyethylene terephthalate (PET) resin, and a reflective surface 303 is formed on the inner surface thereof by vapor deposition of a metal such as silver. In addition, as a material of the housing | casing 301, you may comprise by metal materials, such as materials other than resin, for example, aluminum, a cold rolled material (for example, SPCC). In addition to the metal vapor-deposited film, for example, a reflective sheet having a higher reflectance by adding calcium carbonate, titanium dioxide (TiO ₂ ) or the like to polyethylene terephthalate (PET) resin is attached to the casing 301 as the inner reflective surface 303. You may comprise.

  In addition, a lamp 100, a socket 304, and a cover 305 are disposed inside the housing 301.

  The socket 304 is paired with two terminals that are spaced apart from each other in the longitudinal direction of the housing 301, and the lamp 100 is incorporated between the pair of two terminals.

  As shown in FIG. 8, the socket 304 is formed by bending a plate made of a copper alloy such as phosphor bronze, and is adjacent to a pair of sandwiching pieces 304 a into which the external electrode 101 of the lamp 100 is fitted. It comprises a connecting piece 304b that electrically connects the holding pieces 304a at the lower edge. When the external electrode 101 of the lamp 100 is fitted into the holding piece 304a, the lamp 100 is held in the socket 304 by the holding piece 304a, and the socket 304 and the external electrode 101 portion are electrically connected. Then, power is supplied to the lamp 100 attached to the backlight unit 300 from a lighting circuit (not shown) of the backlight unit 300 via the socket 304.

  The cover 305 is for ensuring insulation of terminals arranged in the short direction of the housing 301.

  As shown in FIG. 8, the lamp 100 is the low-pressure discharge lamp 100 (cold cathode fluorescent lamp) according to the first embodiment of the present invention, but is not limited to this, and the second embodiment of the present invention. The low-pressure discharge lamp 200 (external internal electrode fluorescent lamp) according to the above can also be applied.

  For example, as shown in FIG. 8, the optical sheet 302 includes a diffusion plate 306, a diffusion sheet 307, and a lens sheet 308. The diffusion plate 306 is a plate-like body made of, for example, polymethyl methacrylate (PMMA) resin, and is disposed so as to close the opening of the housing 301. The diffusion sheet 307 is made of, for example, a polyester resin. The lens sheet 308 is, for example, a laminate of an acrylic resin and a polyester resin. These optical sheets 302 are arranged so as to be sequentially superimposed on the diffusion plate 306.

  The backlight unit 300 according to the third embodiment of the present invention can prevent cracks from occurring at the end of the glass bulb 2 with the above configuration.

(Fourth embodiment)
FIG. 9 shows an outline of a liquid crystal display device according to the fourth embodiment of the present invention. As shown in FIG. 9, the liquid crystal display device 400 is, for example, a 32 [inch] liquid crystal television, a liquid crystal screen unit 401 including a liquid crystal panel and the like, a backlight unit 300 according to the third embodiment of the present invention, and a lighting circuit. 402.

  The liquid crystal screen unit 401 is a known one and includes a liquid crystal panel (color filter substrate, liquid crystal, TFT substrate, etc.) (not shown), a drive module, etc. (not shown), and is based on an image signal from the outside. To form a color image.

  The lighting circuit 402 lights the lamp 100 inside the backlight unit 300. The lamp 100 is operated at, for example, a lighting frequency of 40 [kHz] to 100 [kHz] and a lamp current of 3 [mA] to 25 [mA].

  In FIG. 9, the case where the low-pressure discharge lamp 100 according to the first embodiment is inserted into the backlight unit 300 according to the third embodiment of the present invention as the light source device of the liquid crystal display device 400 has been described. The low-pressure discharge lamp 200 according to the second embodiment of the present invention is not limited thereto.

  The liquid crystal display device 400 according to the fourth embodiment of the present invention can prevent the occurrence of cracks at the end of the glass bulb 2 with the above configuration.

<Modification>
As described above, the present invention has been described based on the specific examples shown in the above embodiments. However, the content of the present invention is not limited to the specific examples shown in the respective embodiments. Variations can be used.

1. Glass bulb material (1) UV absorption Absorption of 254 [nm] and 313 [nm] ultraviolet rays by doping glass, which is a glass bulb material, with a predetermined amount of transition metal oxide depending on the type. Can do. Specifically, for example, in the case of titanium oxide (TiO ₂ ), the composition ratio of 0.05 [mol%] or more is doped to absorb ultraviolet rays of 254 [nm], and the composition ratio is 2 [mol%] or more. Thus, it is possible to absorb ultraviolet rays of 313 [nm]. However, when titanium oxide is doped more than the composition ratio of 5.0 [mol%], the glass is devitrified, so the composition ratio is 0.05 [mol%] or more and 5.0 [mol%] or less. It is preferable to dope in the range.

In the case of cerium oxide (CeO ₂ ), 254 [nm] ultraviolet rays can be absorbed by doping at a composition ratio of 0.05 [mol%] or more. However, when cerium oxide is doped more than 0.5 [mol%], the glass is colored, so cerium oxide has a composition ratio of 0.05 [mol%] to 0.5 [mol%]. It is preferable to dope in the following range. In addition, since coloring of glass by cerium oxide can be suppressed by doping tin oxide (SnO) in addition to cerium oxide, cerium oxide can be doped to a composition ratio of 5.0 [mol%] or less. . In this case, if cerium oxide is doped with a composition ratio of 0.5 [mol%] or more, ultraviolet rays of 313 [nm] can be absorbed. However, even in this case, when the composition ratio of cerium oxide is more than 5.0 [mol%], the glass is devitrified.

  In the case of zinc oxide (ZnO), ultraviolet rays of 254 [nm] can be absorbed by doping at a composition ratio of 2.0 [mol%] or more. However, when zinc oxide is doped more than 20 [mol%], the glass may be devitrified, so zinc oxide is in the range of 2.0 [mol%] to 20 [mol%]. It is preferable to dope.

Further, in the case of iron oxide (Fe ₂ O ₃ ), 254 [nm] ultraviolet rays can be absorbed by doping at a composition ratio of 0.01 [mol%] or more. However, when iron oxide is doped more than the composition ratio of 2.0 [mol%], the glass is colored, so the iron oxide is contained in the composition ratio of 0.01 [mol%] to 2.0 [mol%]. It is preferable to dope in the following range.

(2) Infrared transmission coefficient The infrared transmission coefficient indicating the water content in the glass is adjusted to be in the range of 0.3 to 1.2, particularly 0.4 to 0.8. Is preferred. When the infrared transmittance coefficient is 1.2 or less, it becomes easy to obtain a low dielectric loss tangent applicable to a high voltage application lamp such as an external electrode fluorescent lamp (EEFL) or a long cold cathode fluorescent lamp, and 0.8 or less. If so, the dielectric loss tangent becomes sufficiently small and can be applied to a high voltage application lamp.

  The infrared transmittance coefficient (X) can be expressed by the following formula.

(3) About the shape of the glass bulb (a) About the overall shape The shape of the glass bulb is not limited to a straight tube shape, but may be, for example, an L shape, a U shape, a U shape, a spiral shape, etc. Good. Moreover, the cross section cut perpendicularly to the tube axis of the glass bulb is not limited to a substantially circular shape, and may be a flat shape such as a track shape or a rounded round shape, an elliptical shape, or the like.

(B) End Shape As shown in FIG. 10, the shape of the end portion of the glass bulb 2 is one end portion, and the outer shape of the first sealing portion is a hemispherical 2 a, and the other end portion is the second end portion. 2 The hemispherical thing of the outer diameter whose sealing part 2b is smaller than the outer diameter of a glass bulb | bulb may protrude. In this case, the outer diameter of the second sealing portion 2 b is 3 [mm], which is smaller than the outer diameter 4 [mm] of the straight portion S of the glass bulb 2. Here, the “straight portion S” is a portion sandwiched between the first sealing portion and the second sealing portion in the glass bulb 2, and the outer surface thereof is _relative to the tube axis X _{108 of the} glass bulb 2. This refers to the substantially parallel part. The range indicated by W in the tube axis direction of the glass bulb 2 on the second sealing portion side (that is, the range from the inner end to the straight portion S in the glass bulb 2) is the central portion in the tube axis direction from the inner end of the glass bulb 2. The taper has a substantially tapered shape that expands toward the bottom (hereinafter simply referred to as “taper portion”).

Electrode body layer 110a of the second outer electrode, avoiding the tapered portion W as described above, it is preferably formed in the tube axis direction X ₁₀₈ closer to the center than the tapered portion W. That is, when a part of the electrode main body layer 110a overlaps the tapered portion W, a gap may be generated between the electrode main body layer 110a and the outer surface of the glass bulb 2 as described later. This is because when the gap is generated, discharge occurs between the electrode main body layer 110a and the glass bulb 2 in the gap portion, and ozone having a strong oxidizing power is generated.

  The reason for the occurrence of the gap is when the metal paste is applied by screen printing, in the tapered portion W where the coated surface shape is not stable, the metal paste is blurred or the end portion is serrated in a jagged manner. This is because.

(C) About shape of outer surface Moreover, as shown in FIG. 11, it is on the outer surface of the glass bulb 2, Comprising: The rough surface process part 2c in which the rough surface process was given to the formation part of the electrode main body layer 101a is formed. May be. In this case, since the surface area of the electrode main body layer 101a can be increased as compared with the case where the rough surface treatment portion 2c is not formed, the corresponding capacitance can be increased and the efficiency of the lamp 100 can be increased. be able to. Furthermore, since the rough surface treatment portion 2c is formed, the electrode main body layer 101a is well adapted to the glass bulb 2, and the adhesive force between the glass bulb 2 and the electrode main body layer 101a can be increased.

  Moreover, the rough surface treatment part 2c may be formed on the outer surface of the glass bulb 2 and in the formation part of the transparent conductive layer 101b. In this case, the adhesive force between the glass bulb 2 and the transparent conductive layer 101b can be increased as compared with the case where the rough surface treatment portion 2c is not formed.

2. Regarding phosphors in the phosphor layer (1) About ultraviolet absorption For example, in recent years, with the increase in size of liquid crystal color televisions, polycarbonate with good dimensional stability has been used for the diffusion plate that closes the opening of the backlight unit. ing. This polycarbonate is easily deteriorated by ultraviolet rays having a wavelength of 313 [nm] emitted from mercury. In such a case, a phosphor that absorbs ultraviolet light having a wavelength of 313 [nm] may be used. The following phosphors absorb 313 [nm] ultraviolet rays.

(A) Blue Europium / manganese co-activated barium aluminate / strontium / magnesium [Ba _1-xy Sr _x Eu _y Mg _1-z Mn _z Al ₁₀ O ₁₇ ] or [Ba _1-xy Sr _x Eu _y Mg _{2− z} Mn _z Al ₁₆ O ₂₇ ]
Here, x, y, and z are preferably numbers satisfying the conditions of 0 ≦ x ≦ 0.4, 0.07 ≦ y ≦ 0.25, and 0 ≦ z <0.1, respectively.

Examples of such phosphors include europium activated barium magnesium aluminate [BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ ], [BaMgAl ₁₀ O ₁₇ : Eu ²⁺ ] (abbreviation: BAM-B), Europium activated barium aluminate / strontium / magnesium [(Ba, Sr) Mg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ ], [(Ba, Sr) MgAl ₁₀ O ₁₇ : Eu ²⁺ ] (abbreviation: SBAM-B) Etc.

(B) Green • Manganese inactive magnesium gallate [MgGa ₂ O ₄ : Mn ²⁺ ] (abbreviation: MGM)
Manganese activated cerium aluminate, magnesium, zinc [Ce (Mg, Zn) Al ₁₁ O ₁₉ : Mn ²⁺ ] (abbreviation: CMZ)
· Active aluminate, cerium-magnesium with terbium ^{_{[CeMgAl 11 O 19: Tb 3+}} ] ( abbreviation: CAT)
• Europium • Manganese co-activated barium aluminate • Strontium • Magnesium [Ba _{1 -xy} Sr _x Eu _y Mg _{1 -z} Mn _z Al ₁₀ O ₁₇ ] or [Ba _{1 -xy} Sr _x Eu _y Mg _{2 -z} Mn _z Al ₁₆ O ₂₇ ]
Here, x, y and z are numbers satisfying the conditions of 0 ≦ x ≦ 0.4, 0.07 ≦ y ≦ 0.25, and 0.1 ≦ z ≦ 0.6, respectively, and z is 0.4 It is preferable that ≦ x ≦ 0.5.

Examples of such phosphors include europium / manganese co-activated barium aluminate / magnesium [BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ , Mn ²⁺ ], [BaMgAl ₁₀ O ₁₇ : Eu ²⁺ , Mn ^{2]. +} ] (Abbreviation: BAM-G), europium / manganese co-activated barium aluminate / strontium / magnesium [(Ba, Sr) Mg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ , Mn ²⁺ ], [(Ba, Sr) MgAl ₁₀ O ₁₇ : Eu ²⁺ , Mn ²⁺ ] (abbreviation: SBAM-G).

(C) Red • Europium activated phosphorus • Yttrium vanadate [Y (P, V) O ₄ : Eu ³⁺ ] (abbreviation: YPV)
Europium activated yttrium vanadate [YVO ₄ : Eu ³⁺ ] (abbreviation: YVO)
・ Europium-activated yttrium oxysulfide [Y ₂ O ₂ S: Eu ³⁺ ] (abbreviation: YOS)
Manganese-activated magnesium fluoride germanate [3.5MgO.0.5MgF ₂ .GeO ₂ : Mn ⁴⁺ ] (abbreviation: MFG)
Dysprosium-activated yttrium vanadate [YVO ₄ : Dy ³⁺ ] (red and green two-component phosphor, abbreviation: YDS)
In addition, you may mix and use the fluorescent substance of a different compound with respect to one type of luminescent color. For example, only BAM-B (absorbs 313 [nm]) in blue, LAP (does not absorb 313 [nm]) in green, BAM-G (absorbs 313 [nm]) in green, and YOX in red Alternatively, a phosphor of YVO (absorbs 313 [nm]) may be used. In such a case, as described above, the phosphor that absorbs the wavelength 313 [nm] is adjusted so that the total weight composition ratio is larger than 50%, so that the ultraviolet rays almost leak out of the glass bulb. Can be prevented. Therefore, when the phosphor layer 105 includes a phosphor that absorbs ultraviolet rays of 313 [nm], deterioration due to ultraviolet rays such as a diffusion plate made of polycarbonate (PC) that closes the opening of the backlight unit is suppressed, The characteristics as a backlight unit can be maintained for a long time.

  Here, “absorbing ultraviolet rays of 313 [nm]” means an excitation wavelength spectrum near 254 [nm] (excitation wavelength spectrum means that excitation light is emitted while changing the wavelength of the phosphor, and the excitation wavelength and emission intensity are changed. The intensity of the excitation wavelength spectrum at 313 [nm] is defined as 80 [%] or more. That is, the phosphor that absorbs ultraviolet rays of 313 [nm] is a phosphor that can absorb ultraviolet rays of 313 [nm] and convert it into visible light.

(2) High color reproduction Liquid crystal display devices typified by liquid crystal color televisions have been used as a light source for a backlight unit of the liquid crystal display device in accordance with the recent high color reproduction that is performed as part of the improvement in image quality. There is a need to expand the reproducible chromaticity range in cathode fluorescent lamps and external electrode fluorescent lamps.

  In response to such a request, for example, by using the following phosphor, the chromaticity range can be expanded as compared with the case of using the phosphor in the embodiment. Specifically, in the CIE 1931 chromaticity diagram, the chromaticity coordinate value of the phosphor for high color reproduction includes a triangle formed by connecting the chromaticity coordinate values of the three phosphors used in the embodiment. Located at the coordinates that expand the reproduction range.

(A) Blue • Europium-activated strontium chloroapatite [Sr ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu ²⁺ ] (abbreviation: SCA), chromaticity coordinates: x = 0.151, y = 0.065
In addition to the above, europium activated strontium, calcium, barium, chloroapatite [(Sr, Ca, Ba) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu ²⁺ ] (abbreviation: SBCA) can also be used, and the wavelength 313 (nm) SBAM-B, which can absorb ultraviolet rays), can also be used for high color reproduction.

(B) Green BAM-G, chromaticity coordinates: x = 0.139, y = 0.574
CMZ, chromaticity coordinates: x = 0.164, y = 0.722
CAT, chromaticity coordinates: x = 0.267, y = 0.663
As described above, these can also absorb ultraviolet rays having a wavelength of 313 [nm], and in addition to the three phosphor particles described here, MGM can also be used for high color reproduction.

(C) Red • YOS, chromaticity coordinates: x = 0.651, y = 0.344
YPV, chromaticity coordinates: x = 0.658, y = 0.333
MFG, chromaticity coordinates: x = 0.711, y = 0.287
As described above, these can also absorb ultraviolet rays having a wavelength of 313 [nm], and besides the three phosphor particles described here, YVO and YDS can also be used for high color reproduction.

  In addition, the chromaticity coordinate values shown above are representative values measured only with each phosphor powder, and due to the measurement method (measurement principle), etc., the chromaticity coordinates indicated by each phosphor powder The value may be slightly different from the value listed above. For reference, the chromaticity coordinate values of the phosphor powders of the first embodiment are YOX (x = 0.644, y = 0.353), LAP (x = 0.351, y = 0.585). , BAM-B (x = 0.148, y = 0,056).

  Furthermore, the phosphor used for emitting each color of red, green, and blue is not limited to one type for each wavelength, and a plurality of types may be used in combination.

  Here, the case where a phosphor layer is formed using the above-described phosphor particles for high color reproduction will be described. In this evaluation, there are three evaluations in the case of using a phosphor for high color reproduction based on the area of the NTSC triangle (NTSC triangle) connecting the chromaticity coordinate values of the three primary colors of the NTSC standard in the CIE1931 chromaticity diagram. A triangular area ratio formed by connecting chromaticity coordinate values (hereinafter referred to as NTSC ratio) is used.

  For example, when BAM-B is used as blue, BAM-G as green, and YVO as red (Example 1), the NTSC ratio is 92%, and SCA is used as blue, BAM-G as green, and YVO as red. (Example 2) When NTSC ratio is 100%, SCA is used as blue, BAM-G is used as green, and YOX is used as red (Example 3), NTSC ratio is 95%. The luminance can be improved by 10 [%] as compared with the above.

  Note that the chromaticity coordinate values used for the evaluation here are measured in the state of a liquid crystal display device in which a lamp or the like is incorporated, so that the color reproduction range is around the above value depending on the combination with the color filter. there is a possibility.

3. Regarding the types of lamps In the above-described low-pressure discharge lamps according to the first and second embodiments of the present invention, the one having the phosphor layer 4 on the inner surface of the glass bulb 2 has been described. An ultraviolet lamp without the phosphor layer 4 may be used.

  The present invention can be widely applied to low-pressure discharge lamps, backlight units, and liquid crystal display devices.

(A) Sectional drawing including the tube axis | shaft of the low pressure discharge lamp which concerns on the 1st Embodiment of this invention, (b) The enlarged view of the A section of Fig.1 (a). Conceptual diagram of the transparent conductive layer formation process (A) Sectional view including the tube shaft showing the structure of Comparative Example 1 and Comparative Example 2, (b) Enlarged view of FIG. Diagram showing the relationship between electrode body layer and ozone generation Enlarged view of Fig. 1 (b) The principal part enlarged front view which shows the modification of the external electrode in the low pressure discharge lamp which concerns on the 1st Embodiment of this invention Sectional drawing containing the tube axis | shaft of the low voltage | pressure discharge lamp which concerns on the 2nd Embodiment of this invention. The disassembled perspective view of the backlight unit which concerns on the 3rd Embodiment of this invention. Schematic perspective view of a liquid crystal display device according to a fourth embodiment of the present invention. Sectional drawing containing the tube axis | shaft of the modification 1 of the low voltage | pressure discharge lamp which concerns on the 1st Embodiment of this invention. Sectional drawing including the tube axis | shaft of the modification 2 of a low-pressure discharge lamp similarly Sectional view including the tube axis of a conventional low-pressure discharge lamp

Explanation of symbols

2 Glass bulb 100, 108, 111, 200 Low pressure discharge lamp 101, 109, 110 External electrode 101a, 109a, 110a Electrode body layer 101b, 109b, 110b Transparent conductive layer 300 Backlight unit 400 Liquid crystal display device

Claims (7)

A glass bulb and an external electrode provided on at least one of both ends of the glass bulb, the external electrode being laminated on an electrode body layer formed on an outer surface of the glass bulb, and at least on the electrode body layer A low-pressure discharge lamp comprising: a transparent conductive layer formed on the substrate. The low-pressure discharge lamp according to claim 1, wherein the transparent conductive layer is made of at least one of tin oxide and indium tin oxide. The low-pressure discharge lamp according to claim 1, wherein the electrode main body layer includes at least one of gold, silver, copper, and aluminum. The low-pressure discharge lamp according to any one of claims 1 to 3, wherein characters are marked on an outer surface of the electrode body layer. The thickness of the said electrode main body layer is 70 [micrometers] or less, Comprising: The thickness of the edge part of the said electrode main body layer becomes thin as the edge is approached, The any one of Claims 1-4 characterized by the above-mentioned. The low-pressure discharge lamp described. A backlight unit comprising the low-pressure discharge lamp according to claim 1. A liquid crystal display device comprising the backlight unit according to claim 6.

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