JP2006294516A - Flat plate-shaped light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a flat plate-shaped light source capable of maintaining stable light emission state for long time. <P>SOLUTION: The flat plate-shaped light source is composed of a front panel 10 having a dielectric layer 14 covering a pair of discharge electrodes 12, 12 formed on one face, a back panel 20 having phosphor layer 22 on one face, and a barrier rib 30 arranged between the front panel 10 and the back panel 20 forming a discharging space 70 in which discharge gas is enclosed, wherein, the dielectric layer 14 on the front panel 10 and the phosphor layer 22 on the back panel are made to face each other. A stable glow discharge can be maintained and a phenomenon of discharge contraction is eliminated by forming a compact dielectric layer 14 on which leak current density between the discharge electrodes 12, 12 becomes not higher than 1×10-<SP>7</SP>A/cm<SP>2</SP>at electric field strength of 1MV/cm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flat light source that can be used as a backlight of a liquid crystal display device and the like and can perform stable light emission.

2. Description of the Related Art As an image display device that can replace a mainstream cathode ray tube (CRT), a flat type display device such as a liquid crystal display device (LCD), a plasma display device (PDP) is commercially available. .
In particular, liquid crystal display devices are widely used as various information video displays such as personal computers and televisions because they have advantages such as thin and light weight, low power consumption, and long life. In this liquid crystal display device, since the liquid crystal itself is not a light emitting element, a backlight for supplying light from the back surface of the liquid crystal panel is necessary for display. The backlight that is usually used is mainly a combination of a small fluorescent lamp and an acrylic light guide, but a light source using a flat discharge lamp is also used.

  FIG. 5 is a cross-sectional view of a conventional flat light source disclosed in Patent Document 1, for example. As shown in the figure, a translucent front plate 10 made of soda glass or the like, and an insulating substrate 20 and side plates 30 made of soda glass or ceramic are integrally hermetically sealed with, for example, low-melting glass (not shown). A flat airtight container 1 is constructed. A pair of discharge electrodes 40 and 41 parallel to each other are provided on the inner surface of the front plate 10 serving as a light emitting surface, and the surfaces of the discharge electrodes 40 and 41 are covered with a dielectric layer 50. A phosphor 60 is applied to the inner surface of the insulating substrate 20, and mercury and a mixed gas such as argon or neon-argon as a starting gas or xenon, krypton, argon in the discharge space 70 in the sealed container 1. A rare gas discharge gas such as helium or neon is enclosed.

In the flat light source according to this configuration, a high frequency voltage (for example, 20 kHz) is applied between the discharge electrodes 40 and 41 to cause glow discharge in the discharge gas in the discharge space 70, and ultraviolet rays generated by the glow discharge are generated. The phosphor 60 is excited to emit light, and light is emitted to the outside through the front plate 10.
In the flat light source, ultraviolet light having a wavelength corresponding to the type of the enclosed discharge gas is generated, and the ultraviolet light exhibits a specific emission color corresponding to the type of the phosphor material.

In the flat light source shown in FIG. 5, only a pair of discharge electrodes are arranged in the discharge space. Therefore, the phosphor layer is required to emit light uniformly by glow discharge generated between the discharge electrodes.
In general, in a discharge at a low pressure, as the electrode voltage increases, the current shifts from a very small dark current (townsend discharge) to a glow discharge. In this glow discharge, there is a light emitting region called a positive column near the anode and a negative glow in the vicinity of the cathode, and shows a unique color depending on the type of gas. A space charge layer of ions is generated between the negative glow and the cathode, and there is a large potential difference. The accelerated positive ions bombard the cathode and replenish secondary electrons. When the current is further increased, the cathode temperature rises and thermionic emission becomes active, resulting in an arc discharge state in which the voltage between the electrodes decreases to about 10 V (Iwanami Shoten RIKEN Dictionary 5th edition).

The discharge with the flat light source needs to be made so as to maintain the state of stable discharge shown in FIG. 6A in which glow discharge is stably performed and light is emitted in all regions in the discharge space. In addition, the area | region L which has light-emitted in FIG. 6 is shown with the oblique line.
Japanese Patent Laid-Open No. 9-115483

  However, the discharge state of a flat light source needs to maintain a stable discharge state in which light is emitted in the entire region in the discharge space shown in FIG. 6A. 6A and 6B, and a transition state from a glow discharge to an arc discharge or a transition to an arc discharge. As shown in FIGS. 6B and 6C, the discharge is performed in a local region in the discharge space. There was a problem that.

The dielectric layer 50 of the flat light source disclosed in Patent Document 1 shown in FIG. 5 is made of, for example, lead oxide (PbO) by screen printing on the upper surface of the front plate 10 on which the discharge electrodes 40 and 41 are formed. The low melting point glass (frit glass) paste contained is formed substantially uniformly and then fired.
The lead oxide contained in the dielectric layer 50 used here has a relatively large particle size, so that the density when viewed as the film quality of the dielectric layer 50 is insufficient. The dielectric layer 50 is damaged due to the continuation, and as a result, the leak current increases, the glow discharge cannot be maintained, the arc shifts to the state of discharge contraction, and the applicant of the present application has earnestly As a result of examination, it found out.

  That is, the dielectric layer 50 obtained by printing and baking a low melting point glass paste containing lead oxide by a screen printing method cannot be a dense dielectric layer, and as a result, the dielectric layer 50 is predetermined in a relatively short time. Since a leak current larger than the value is generated, a stable light emission state cannot be maintained.

  In view of the above, an object of the present invention is to enable stable light emission over a long period of time.

The flat plate-type light source of the present invention includes at least a pair of discharge electrodes provided on one surface, a first substrate provided with a dielectric layer covering the discharge electrodes, a second substrate provided with a phosphor layer on one surface, A flat plate disposed between the two substrates and the first substrate and having a partition wall forming a discharge space for sealing the discharge gas, wherein the dielectric layer of the first substrate and the phosphor layer of the second substrate are arranged to face each other In the type light source, a dielectric layer having a leakage current density between the discharge electrodes of 1 × 10 ⁻⁷ A / cm ² or less at an electric field intensity of 1 MV / cm is formed.

  According to the present invention, in the flat light source described above, the dielectric layer has a silicon compound layer.

  According to the present invention, in the flat light source described above, the thickness of the dielectric layer is 50 μm or less.

  According to the present invention, in the flat light source described above, the silicon compound layer of the dielectric layer is made of SiOx.

  Further, the present invention is the flat light source described above, wherein the silicon compound layer of the dielectric layer is made of SiNy.

  Further, according to the present invention, in the flat light source described above, the silicon compound layer of the dielectric layer is made of SiOxNy.

  According to the flat light source of the present invention configured as described above, the dielectric layer is formed by providing a silicon compound layer alone or in addition to another dielectric, and the silicon compound has a small particle size. Since the dielectric layer can be densely formed, the current density of leakage can be kept small.

  According to the flat light source of the present invention, since the film quality of the dielectric layer is dense, the discharge shrinkage hardly occurs and stable light emission can be performed over a long period of time.

  Hereinafter, an example of the best mode for carrying out the flat light source of the present invention will be described with reference to FIGS.

In FIG. 1, reference numeral 1 denotes a flat light source of this example. The flat light source 1 is a front plate 10 having a substantially rectangular shape corresponding to a front panel on the illumination surface side, and one side corresponding to a rear panel is short of the front plate 10. A back plate 20 having a substantially square shape that is approximately the same size as the side is bonded via a partition wall 30, and a predetermined discharge gas is sealed in a discharge space 70 that forms a substantially rectangular parallelepiped. Then, lead terminals 13 and 13 are provided on the short side of the back surface of the front plate 10 in which two discharge electrodes 12 and 12 covered with a dielectric layer 15 described later are extended outside the discharge space 70.
Here, as the flat light source 1, for example, the discharge space 70 has a light emitting surface whose width is 158 mm × depth 130 mm × thickness 1.8 mm and whose diagonal length is approximately 8 inches.

FIG. 2 is an exploded view of the flat light source 1 shown in FIG.
The front plate 10 is formed by forming a pair of discharge electrodes 12 and 12 on one surface 11-2 of the transparent plate 11 and a dielectric layer 14 in a predetermined region so as to cover the discharge electrodes 12 and 12.

  The transparent plate 11 is an insulating transparent and flat plate made of refractory glass or soda glass. The strip-shaped discharge electrodes 12 and 12 formed on one surface 11-2 of the transparent plate 11 are, for example, A chromium film is formed on the entire surface 11-2 by vapor deposition or the like, and then the pattern of the discharge electrodes 12 and 12 is transferred to the photoresist by photolithography, and then the chromium film is patterned by etching. . Here, the gap G between the discharge electrodes 12 and 12 is a discharge gap. In this example, the discharge gap G is about 50 mm, for example.

  Then, after forming the dielectric layer 14 made of a silicon compound and the protective film layer 15 on the entire surface 11-2 on which the discharge electrodes 12 and 12 are formed, the periphery on the surface 11-2 side of the transparent plate 11 is substantially omitted. The rectangular frame shape is removed by a well-known photolithography technique and etching technique, and as shown in FIG. 2, the lead terminals 13 and 13 are exposed, and the surface 11-2 that becomes a bonding region with the partition wall 30 described later is exposed. .

The dielectric layer 14 may be formed of any one of silicon compounds such as silicon oxide (SiOx), silicon nitride (SiNy), and silicon oxynitride (SiOxNy) alone, for example, by screen printing. These silicon compound films may be formed on a dielectric layer mainly composed of lead oxide (PbO).
As a method for forming a silicon compound film, a PVD method such as a sputtering method or a CVD (chemical vapor deposition) method is preferable in terms of uniformity, homogeneity, and denseness of the film quality. When a single dielectric layer made of a compound is used, the thickness is about 7 μm. When a silicon compound film is formed on a separately formed dielectric layer, the total thickness does not exceed 50 μm.

Even if the dielectric layer 14 is formed by PVD or CVD, the dielectric breakdown voltage is insufficient with respect to the driving voltage if it is less than 1 μm, and it is necessary to set the driving voltage high if the film thickness exceeds 50 μm. Since it occurs and is not realistic, the range of 1 to 50 μm is preferable.
In addition, the subscripts (signs) x and y in silicon oxide (SiOx), silicon nitride (SiNy), and silicon oxynitride (SiOxNy) can be real values. Thus, for example, SiOx contains from Si (silicon) rich oxide film to O (oxygen) rich film compositions for general SiO _2.

  Further, as the protective film layer 15 formed on the dielectric layer 14, for example, magnesium oxide (MgO) is formed with a thickness of approximately 0.6 μm by vapor deposition or sputtering.

  The partition wall 30 is formed in a frame shape from an insulating material having heat resistance, and as shown in FIG. 2, in this example, a plurality of rectangular parallelepiped glass pieces 30-1 to 30-4 are formed into a substantially square shape with a glass paste. Glass spacers joined in a frame shape. In addition, although the thickness of the partition 30 is substantially the height of the discharge space 70, this thickness is about 1 to 3 mm. In this example, the thickness is 1.8 mm which is relatively thin as described above. Further, an exhaust pipe (not shown) for exhausting the inside of a discharge space 70 described later is provided on one side of the substantially square frame.

The back plate 20 is formed by forming a phosphor layer 22 in a substantially square shape in a predetermined region of the one surface 21-2 of the insulating plate 21. The phosphor layer 22 used here is a mixture of phosphors that emit red, green, and blue light, which are the three primary colors of light, since the flat light source 1 requires white light.
Examples of phosphor materials that emit red light when irradiated with ultraviolet rays include yttrium and gadolinium borate and europium-activated (Y ₂ O ₃ : Eu) and [(Y, Gd) BO ₃ : Eu], green As the phosphor material that emits light, for example, zinc silicate activated with manganese (ZnSiO ₂ : Mn), and as the phosphor material that emits blue light, for example, barium magnesium aluminate (BaMgA1 ₁₄ O ₂₃ : Eu) or the like is used. To do.

The front plate 10, the partition wall 30, and the back plate 20 shown in FIG. 2 configured in this way are actually assembled into the planar light source 1 as follows.
First, after applying a glass paste in a substantially square frame shape to the periphery of the surface 21-2 of the insulating plate 21 on which the phosphor layer 22 is not formed, a partition wall 30 made of a glass spacer is placed thereon and baked. And fix. The firing (partition firing process) at this time is performed in air, the firing temperature is about 560 ° C., and the firing is about 2 hours.

  Next, a liquid in which at least three kinds of phosphors are mixed is applied on the surface 21-2 exposed on the inner side of the partition wall 30 fixed to the insulating plate 21, and then fired in a firing furnace to obtain a phosphor layer. 22 is formed. The firing temperature at that time is about 510 ° C., and the firing time is about 10 minutes.

  Next, a glass paste is supplied in a frame shape on the substantially square frame of the partition wall 30 of the insulating plate 21 by, for example, screen printing.

Next, the front plate 10 is pressed and bonded to the frame-shaped glass paste on the partition wall 30, the glass paste is cured by baking and bonded, and the front plate 10, the partition wall 30 and the back plate 20 are integrated. .
At this time, the edge of the dielectric layer 14 formed in a substantially square shape and the protective film layer 15 are joined to the front plate 10 so that the edges of the dielectric layer 14 and the transparent plate 11 are slightly inserted. The metal surfaces of the lead terminals 13 and 13 are prevented from being exposed to the internal space formed by integrating the 30 and the back plate 20.

Finally, for example, air in the space formed between the front plate 10 and the back plate 20 is exhausted from an exhaust pipe (not shown) provided in the partition wall 30 and then replaced with a predetermined discharge gas. The space is sealed to form a discharge space 70 having a predetermined gas pressure.
Here, the discharge gas is sealed at a total pressure of 1 × 10 ³ Pa to 4 × 10 ⁵ Pa, for example, a He—Xe (2%) mixed gas having a large Penning effect that can be expected to decrease the discharge start voltage.

  An example of the operation of the flat light source 1 having such a configuration will be described. First, an alternating voltage whose phase is shifted by 180 ° is applied to each of the pair of discharge electrodes 12 and 12 shown in FIGS. That is, as shown in FIG. 4, for example, at time t, the voltage Vsus is applied to one discharge electrode 12 (FIG. 4A), and −Vsus having a voltage opposite to the voltage Vsus is applied to the other discharge electrode 12 (FIG. 4A). 4B), a discharge is generated between the discharge electrodes 12 and 12. By irradiating the phosphor layer 22 with ultraviolet light generated by this discharge, white light is obtained through the transparent plate 10 by causing each of the red, green, and blue phosphors to emit light.

  A description will be given of the discharge state of the planar light source 1 configured as described above with reference to FIG. 3 and FIG.

The examination procedure was as follows.
First, as shown in FIG. 3, the dielectric layer film 120 (thickness δ) is formed on the Si wafer 100, and the electrode 110 whose area is known is formed on the film 120. A voltage is applied between the Si wafer 100 and the upper electrode 110 with the LCR meter connected, and the amount of current flowing through the dielectric layer film 120 is measured.

At this time, the voltage is applied so that the electric field strength in the film is 1 MV / cm, and at this time, a current flowing per unit area (1 cm ² ) is obtained.
Here, for example, when the area of the upper electrode 110 is 10 cm ² and the dielectric film thickness δ is 10 μm and a voltage of 100 V is applied between the Si wafer 100 and the electrode, the current intensity is 100 ⁻⁶ A. / Δ = 100 / (10 × 10 ⁻⁵ ) = 1 MV / cm, and the current density of the leak is 10 ⁻⁶ / 10 = 10 ⁻⁷ A / cm ² .

  Next, the AC voltage is set so that the electric field strength between the discharge electrodes 12 and 12 in the film of the dielectric layer 14 formed by the CVD method with the planar light source 1 shown in the example of FIG. 1 is about 1 MV / cm or more at the peak. Was applied to discharge, and the light emission state was visually observed to observe the discharge state.

As shown in FIG. 3, a silicon oxide (SiOx) film 120 is formed on the Si wafer 100 as a film quality of silicon oxide (SiOx), and a voltage is applied so that the electric field strength in the film is 1 MV / cm. As a current density of leakage at this time, 2.5 × 10 ⁻⁸ A / cm ² was obtained. Then, the planar light source 1 using this silicon oxide (SiOx) for the dielectric layer 14 was produced and discharged to observe the light emission state.
As a result, in the dielectric layer 14 of silicon oxide (SiOx), the discharge did not shift to the contracted state shown in FIG. 6B or FIG. 6C in a predetermined light emission time.

As shown in FIG. 3, a silicon nitride (SiNy) film 120 is formed on the Si wafer 100 as a film quality of silicon nitride (SiNy), and a voltage is applied so that the electric field strength in the film is 1 MV / cm. As the current density of the leak at this time, 1.0 × 10 ⁻⁷ A was obtained. Then, a planar light source using this silicon nitride (SiNy) for the dielectric layer 14 was produced, and discharged to observe the light emission state.
As a result, in the dielectric layer 14 of silicon nitride (SiNy), the discharge did not shift to the contracted state shown in FIG.

As a film quality of silicon oxynitride (SiOxNy), as shown in FIG. 3, a silicon oxynitride (SiOxNy) film 120 is formed on the Si wafer 100, and a voltage is applied so that the electric field strength in the film is 1 MV / cm. In addition, 9.0 × 10 ⁻⁸ A / cm ² A was obtained as the current density of leakage at this time. Then, a planar light source using this silicon oxynitride (SiOxNy) for the dielectric layer 14 was produced and discharged to observe the light emission state.
As a result, in the dielectric layer 14 of silicon oxynitride (SiOxNy), the discharge did not shift to the contracted state shown in FIG.

That is, when the electric field density is 1 MV / cm, if the current density due to leakage is 1.0 × 10 ⁻⁷ A / cm ² or less, the dielectric layer 14 can maintain a stable state in which the discharge does not shrink. I understood.

Here, silicon oxide (SiOx) is formed by reacting SiH ₄ (monosilane) gas and N ₂ O (nitrous oxide, laughing gas) gas in a plasma atmosphere, and silicon nitride (SiNy) is The film is formed by reacting SiH ₄ gas and NH ₃ (ammonia) gas in a plasma atmosphere, and silicon oxynitride (SiOxNy) has a gas flow rate ratio different from that of silicon oxide (SiOx). The film was formed by

  According to the flat light source 1 of this example, the dielectric layer 14 on the discharge electrodes 12 and 12 is made of a silicon compound, for example, a silicon oxide layer, a silicon nitride layer, a silicon oxynitride layer, etc., so that the dielectric layer 14 is dense. Thus, the dielectric layer 14 itself is less likely to be damaged, an increase in leakage current density is suppressed, and discharge contraction is less likely to occur, so that stable light emission can be maintained.

As the substrate 1 and the substrate 2, not only the high melting point glass and soda glass (Na ₂ O · CaO · SiO ₂ ) described above but also borosilicate glass (Na ₂ O · B ₂ O ₃ · SiO ₂ ), Stellite (2MgO · SiO ₂ ) and lead glass (Na ₂ O · PbO · SiO ₂ ) can be used.

Further, although a chrome film is formed on the substrate 1 by vapor deposition as the flat light source of this example, the present invention is not limited to this, and a plurality of pairs of discharge electrodes 12 and 12 made of a conductor material having low electric resistance are substantially parallel. The discharge electrode material may be Ni, Al, Au, Ag, Pd / Ag, Ta, Cu, and the transparent electrode may be ITO (indium tin oxide) or SnO ₂ singly or in appropriate combination. Can be used. The film formation method of the discharge electrodes 12 and 12 is not limited to the vapor deposition method, and a conductor is formed on the surface 11-2 of the transparent plate 11 by a sputtering method, a screen printing method, a plating method, etc., and then a photolithography method or a sandblasting method. It may be processed into a predetermined electrode pattern by the method, the lift-off method or the like.
Moreover, the dimension of the discharge gap 13, which is the gap between each pair of discharge electrodes 12, 12, is not particularly limited, but is preferably 10 to 200 mm.

In this example, the dielectric layer 14 formed on the surface of the discharge electrode 12 is formed of a single film made of silicon oxide (SiOx), silicon nitride (SiNy), silicon oxynitride (SiOxNy), or the like. Although described above, the present invention is not limited to this, and it is only necessary to have a film of these silicon compounds on the entire surface of a film such as lead oxide (PbO) as a conventional dielectric layer.
In addition, as a forming method, a PVD method such as a sputtering method or a CVD method is preferable in terms of film quality uniformity, homogeneity, and denseness. In addition, an ion plating method, a printing method, and a dry film method are used. Also, application methods (including spray coating methods), transfer methods, and the like can be employed depending on the required uniformity of light emission. In the film forming method other than the PVD method and the CVD method, the film thickness is generally large. Therefore, in order to make the electric field density predetermined, the voltage amplitude of the AC voltage to be applied is increased.

As a material constituting the protective film layer 15, magnesium oxide (MgO) has been described as an example. However, the material is not limited to this, and magnesium fluoride (MgF ₂ ), calcium fluoride (CaF ₂ ), and the like can also be used. . In addition, as the protective film layer 15, it is good also as not only the film | membrane by a single material but the laminated film structure comprised from the material of at least 2 types selected from these. Although the description has been given assuming that magnesium oxide is 0.6 μm as the film thickness, the present invention is not limited to this.

Further, as the composition of the phosphor layer 22, the description for red is [(Y, Gd) BO ₃ : Eu], (Y ₂ O ₃ : Eu), but is not limited to this, for example, (YBO ₃ Eu) , (YVO ₄ : Eu), (Y _0.96 P _0.60 V _0.40 O ₄ : Eu _0.04 ), (GdBO ₃ : Eu), (ScBO ₃ : Eu), (3.5MgO · 0 .5MgF ₂ · GeO ₂ : Mn). In addition, the green color has been described with (ZnSiO ₂ : Mn), but not limited thereto, for example, (BaAl ₁₂ O ₁₉ : Mn), (BaMg _{2 A} 1 ₁₆ O ₂₇ : Mn), (MgGa ₂ O ₄ : Mn) ), (YBO ₃ : Tb), (LuBO ₃ : Tb), (Sr ₄ Si ₃ O ₈ Cl ₄ : Eu) may be used, and the blue color has been described in (BaMgA1 ₁₄ O ₂₃ : Eu). For example, (Y ₂ SiO ₅ : Ce), (CaWO ₄ : Pb), CaWO ₄ , YP _0.85 V _0.15 O ₄ , (Sr ₂ P ₂ O ₇ : Eu), (Sr ₂ P ₂ O ₇ : Sn) can be used.
In the above example, the example of emitting white light as a backlight of a liquid crystal display device such as a liquid crystal television has been described. However, the present invention is not limited to this, and a flat plate light source of monochromatic light of red, green, and blue, or other than the three primary colors of light It is possible to obtain a flat plate light source of the above-mentioned emission color by using a phosphor layer in which the above-mentioned phosphors are used alone or in combination.

  In addition to the thick film printing method, the method for forming the phosphor layer 22 is, for example, a method in which phosphors mixed at a predetermined ratio are applied by spraying, and a sticky substance is attached in advance to the site where the phosphor layer 22 is formed. Alternatively, a method of attaching phosphor particles can be employed.

As the structure of the partition wall 30, in this example, an example using a glass spacer obtained by joining a substantially rectangular glass piece into a substantially square frame shape is used, but not limited thereto, a rectangular frame formed of glass, In addition to the substrate 2 provided with recesses and integrally formed partitions, a well-known insulating material in which a metal oxide such as alumina is mixed with a conventionally used low-melting glass can be used.
In addition to using a glass spacer, it can also be formed by, for example, a screen printing method, a sand blast method, a dry film method, a photosensitive method, or the like.

Here, the screen printing method means that an opening is formed in the screen plate, a partition wall forming material is extruded from the opening to the lower side of the plate with a squeegee, a partition wall forming material layer is formed on the substrate, and then fired and cured. This is a method of forming the partition wall 30.
The sand blasting method is, for example, forming a partition wall forming material layer on the entire surface of the substrate using screen printing, roll coater, doctor blade, nozzle discharge type coater, etc., and then curing the partition wall forming material layer. A part is covered with a mask layer, and then an exposed part is removed by sandblasting.

  The dry film method is a method of laminating a photosensitive film on a substrate, removing the photosensitive film at the part where the partition is to be formed by exposure and development, embedding a material for forming the partition into the recess (groove) formed by the removal, and baking. It is a method to do. The remaining photosensitive film other than the partition wall forming portion is burned and removed by baking, and the partition wall forming material embedded in the recesses (grooves) remains to form partition walls.

  The photosensitive method is a method in which a barrier rib forming material layer having photosensitivity is formed on a substrate, the material layer is patterned by exposure and development, and then fired.

  The discharge gas sealed in the discharge space 70 can be variously used in addition to the He—Xe mixed gas. For example, He gas (resonance line wavelength = 58.4 nm), Ne gas (74.4 nm), Ar gas (107 nm), Kr gas (124 nm), and Xe gas (147 nm) can be used alone or in combination. In particular, when used alone, Xe gas having the longest resonance line wavelength among noble gases is a preferable noble gas because it emits strong ultraviolet rays even at a molecular beam wavelength of 172 nm.

Also, two kinds of rare gases such as Ne—Ar mixed gas, Ne—Xe mixed gas, He—Kr mixed gas, Ne—Kr mixed gas, and Xe—Kr mixed gas, which can be expected to lower the discharge start voltage and have a large Penning effect. It is good also as 3 types of discharge gas, such as Ne-Xe-Ar mixed gas, for example.
In addition, there exist the following (1)-(4) as a characteristic requested | required of discharge gas. (1) From the viewpoint of extending the lifetime of a flat light source, it must be chemically stable and the gas pressure can be set high. (2) From the viewpoint of high brightness of the flat light source, the radiation intensity of ultraviolet rays is large. (3) The wavelength of the emitted ultraviolet light is long from the viewpoint of increasing the energy conversion efficiency from ultraviolet light to visible light. (4) From the viewpoint of reducing power consumption, the discharge start voltage is low.

The total pressure of the enclosed discharge gas is preferably 1 × 10 ³ Pa to 4 × 10 ⁵ Pa, but may be 1 × 10 ² Pa to ⁵ × 10 ⁵ Pa. In such a pressure range, the phosphor layer 22 irradiated with the ultraviolet rays generated in the rare gas emits light well, and as the pressure increases, the sputtering rate of various members constituting the flat light source decreases. The life of the light source can be extended.

In the above-described example, the reflective flat plate light source using the transparent plate 11 as the front plate 10 has been described. However, the reflective flat plate light source is not limited to the reflective plate, and a transparent flat plate light source using a transparent insulating material for the back plate 20. For example, silicon oxide (SiOx), silicon nitride (SiNy), oxynitride, which is an example of a silicon compound, has a leakage current density of 1 × 10 ⁻⁷ A / cm ² or less at an electric field strength of 1 MV / cm. A dielectric layer of silicon (SiOxNy) can be applied. In the transmission type flat light source, the light emission of the phosphor layer 22 is observed through the back plate 20.

  Of course, the planar light source of the present invention is not limited to the above-described examples, and can take various other configurations without departing from the gist of the present invention.

FIG. 1 is a side sectional view and B is a perspective view of an embodiment of a flat light source according to the present invention. It is a disassembled perspective view of the flat type light source of the example of FIG. It is sectional drawing with which it uses for description of the evaluation method of the film quality of a dielectric material. It is a drive voltage waveform supplied to the lead terminal of the flat type light source of the example of FIG. A is a plan view, B is a side sectional view, and C is a perspective view for explaining a conventional flat light source. A for explaining the light emission state in the flat light source is A for the entire light emission state, B for one discharge contraction state, and C for another discharge contraction state.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Front plate, 12 ... Discharge electrode, 14 ... Dielectric layer, 20 ... Back plate, 22 ... Phosphor layer, 30 ... Partition, 70 ... Discharge space

Claims (6)

A first substrate provided with at least a pair of discharge electrodes on one surface and provided with a dielectric layer covering the discharge electrodes;
A second substrate provided with a phosphor layer on one surface;
A barrier rib disposed between the second substrate and the first substrate and forming a discharge space for sealing a discharge gas; and the dielectric layer of the first substrate and the phosphor layer of the second substrate In a flat light source arranged opposite to each other,
A flat-type light source, wherein the dielectric layer having a current density of leakage between the discharge electrodes of 1 × 10 ⁻⁷ A / cm ² or less at an electric field strength of 1 MV / cm is formed. The flat light source according to claim 1,
A flat light source comprising a silicon compound layer in the dielectric layer. The flat light source according to claim 1,
A flat light source characterized in that the dielectric layer has a thickness of 50 μm or less. The flat light source according to claim 2,
A flat light source characterized in that the silicon compound layer of the dielectric layer is made of SiOx. The flat light source according to claim 2,
A flat light source characterized in that the silicon compound layer of the dielectric layer is SiNy. The flat light source according to claim 2,
A flat light source, wherein the silicon compound layer of the dielectric layer is made of SiOxNy.

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