JP2007265652A - Backlight unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a backlight unit, with a flat-face fluorescent lamp as a light source, to securely discharge in a whole discharge area partitioned by spacers and obtain illumination of uniform luminance for a whole light-emitting face. <P>SOLUTION: The backlight unit 10 is provided with a flat-face fluorescent lamp 11 in which a front substrate 13 and a rear-face substrate 16 opposed to each other at a given interval are sealed, a phosphor layer 21 is formed on (an)inner side face(s) facing either or both discharge space(s)of the front and rear-face substrates, and at least a pair of outer-face electrodes 19a, 19b are installed outside the discharge space, and an optical plate 12 placed at an interval at a light-emitting face of either a front substrate side or a rear-face substrate side of the flat-face fluorescent lamp, with a conductive matter layer 33 formed on the surface of the optical plate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backlight unit.

  In general, a flat fluorescent lamp constituting a light source of a backlight unit forms a planar discharge vessel by bonding and bonding two glass plates of a front substrate and a rear substrate facing each other, and the planar discharge vessel The space between the glass plates is kept airtight, gas as a discharge medium is sealed, and a phosphor layer is formed on the inner side surfaces of the front substrate and the rear substrate.

  As such a flat fluorescent lamp, one having a configuration as described in Japanese Patent Application Laid-Open No. 11-31490 (Patent Document 1) has been known. In this conventional flat fluorescent lamp, no reinforcing spacer is provided inside the planar discharge vessel. However, in the case of a flat fluorescent lamp equipped with a planar discharge vessel having such a structure, since the discharge space is wide, discharge occurs only between some electrodes, and concentrated discharge where the discharge concentrates is generated. There was a problem that occurred.

  As a flat fluorescent lamp capable of avoiding such concentrated discharge, the one shown in FIG. 10 can be considered. This improved flat fluorescent lamp has a structure in which a large number of spacers 5 are provided inside a planar discharge vessel 1 to divide a discharge space and a pair of outer surface electrodes 6a and 6b are arranged. , 6b, a discharge is generated in each of the divided discharge spaces by applying an AC voltage between the two and 6b.

However, in the proposed flat fluorescent lamp having a spacer, as shown in FIG. 10, when an AC voltage is applied between the electrodes 6a and 6b, a discharge path is formed in all of the divided discharge spaces. However, the problem of partial discharge in which light is partially emitted may occur. (In FIG. 10, the discharge space A indicated by hatching indicates that a discharge path is formed, and the discharge space B not indicated by hatching indicates that no discharge path is formed.)
As a method for avoiding such a problem, a configuration can be adopted in which a conductive film is provided on the light emitting surface, as in a flat fluorescent lamp described in JP-A-10-074482 (Patent Document 2).

However, in a flat fluorescent lamp in which electrodes are provided on the outer surface of the discharge vessel, the provision of a conductive film on the light emitting surface between the outer electrodes as in Patent Document 2 is a cause of dielectric breakdown outside the lamp. Therefore, it is structurally difficult. In addition, when a conductive film is formed on the light emitting surface, the distance between the outer surface electrode and the lamp body and the conductive film is close, and a large amount of current leaks to the conductive film. Since a larger amount of current must be passed between the electrodes for discharging, it may cause an increase in applied voltage and a decrease in efficiency.
Japanese Patent Laid-Open No. 11-31490 Japanese Patent Application Laid-Open No. 10-074482

  The present invention has been made in view of such a conventional technical problem, and by providing conductivity to an optical plate, which is an essential component of a backlight unit, a spacer is provided inside the planar discharge vessel. In a backlight unit having a flat fluorescent lamp provided with an outer surface electrode as a light source, it discharges reliably in all discharge spaces partitioned by spacers without partial discharge, and is uniform over the entire light emitting surface. An object of the present invention is to provide a backlight unit capable of illumination with luminance.

  The backlight unit according to the first aspect of the present invention has a light-transmitting front substrate and a rear substrate disposed opposite to each other, encloses a discharge medium therein, and is disposed inside at least one of the front substrate and the rear substrate. Forming a phosphor layer to form a planar discharge container, and on the surface of the planar discharge container, at least a pair of electrodes are installed so as not to contact the discharge medium, the interior of the planar discharge container, and A flat fluorescent lamp provided with a plurality of spacers in a direction substantially perpendicular to the electrode; and an optical plate disposed at an interval with respect to the surface of the flat fluorescent lamp that uses light. A conductive material layer is formed on the surface of the optical plate.

  According to a second aspect of the present invention, in the backlight unit of the first aspect, the conductive material layer on the surface of the optical plate is mainly composed of at least one oxide of indium tin oxide, zinc oxide, and tin oxide. It is characterized by being.

  According to a third aspect of the present invention, in the backlight unit of the first or second aspect, the optical plate is made of a transparent glass plate or a light diffusion plate.

  According to the present invention, since there is a gap between the flat fluorescent lamp that is discharged by applying alternating current to the electrode and the optical plate, leakage current to the conductive optical plate, that is, reduction in luminous efficiency is suppressed. And generation | occurrence | production of partial discharge can be prevented and discharge light emission can be made uniformly in the whole planar discharge vessel. In addition, since the optical plate installed at a distance on the light emitting surface side of the flat fluorescent lamp is made conductive, even if the lamp has a large area, the conductive optical plate can provide a starting assist effect and is good. Startability can be obtained, noise generated from the lamp can be removed by the optical plate on which the conductive material layer is formed, and adverse effects of noise on the liquid crystal display and other devices in which the backlight unit is incorporated can be prevented.

  In addition, according to the present invention, the conductive material layer is formed on the optical plate independent from the flat fluorescent lamp to make it conductive. It is difficult to receive, and the lifetime of the film is prolonged without causing deterioration of the conductive properties, etc., and at the same time, a conductive material layer can be formed on the optical plate separately from the production of the flat fluorescent lamp in the production process. Finishing the conductive material layer into a uniform film is easy in manufacturing, and in addition, it is necessary for forming a conductive film that is necessary when forming a conductive film directly on the light emitting surface of a flat fluorescent lamp. There is also an advantage that no heat load is applied to the flat fluorescent lamp.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a backlight unit according to one embodiment of the present invention. The backlight unit 10 according to the present embodiment includes a flat fluorescent lamp 11 and an optical plate 12 that is disposed on the light emitting surface side with an interval.

  As shown in detail in FIGS. 2 to 4, the flat fluorescent lamp 11 includes a front substrate 13 made of a translucent glass plate, and a rear substrate 16 integrally formed with a side wall 14 and a spacer 15. A planar discharge vessel 18 having a structure in which the peripheral portions are arranged so as to face each other and sealed at the periphery with a bullet glass 17 is a main component. Inside the planar discharge vessel 18, one of mercury vapor, xenon, krypton, argon, neon, and helium is used as a discharge medium, or a mixture of two or more kinds, and several kPa to several hundred kPa is enclosed. It is sealed with pressure. An example of the enclosed gas is a mixed gas of mercury vapor, argon, and neon, and the ratio of neon to argon gas is 50:50 to 99: 1 when priority is given to luminous efficiency and low voltage starting of the lamp. When the composition ratio is increased and priority is given to the rising speed of light emission, the composition is increased from 1:99 to 50:50 and the argon composition ratio is increased. The gas pressure is in the range of 1 Torr to 700 Torr, and is preferably set in the range of 20 to 100 Torr from the viewpoint of low voltage startability, luminous efficiency, and life.

  On the outer surface of the front substrate 13, along the end of the discharge vessel 18, an outer electrode 19 a that applies a high voltage and an outer electrode 19 b that applies a low voltage are arranged so as not to contact the discharge medium. In the present embodiment, the outer electrodes 19a and 19b and the discharge medium inside the discharge vessel 18 are blocked by the front substrate 13 itself. However, the outer surface electrodes 19a and 19b and the discharge medium inside the discharge vessel 18 may be blocked by interposing a dielectric layer. In the present embodiment, both electrodes 19a and 19b are configured to be cut off from the discharge medium inside the discharge vessel 18, but one electrode is used as the internal electrode and only the other electrode is cut off from the discharge medium. Any configuration may be used. In the present embodiment, the outer electrodes 19a and 19b are provided only on the front substrate 13, but the configuration in which the outer electrodes are formed only on the outer surface of the rear substrate 16 and both the front substrate 13 and the rear substrate 16 are provided. It is also possible to adopt a configuration that is formed on the outer surface, a front substrate 13, a rear substrate 16, and a side surface that joins the front substrate 13 and the rear substrate 16 together.

  As a method for forming the outer electrodes 19a and 19b, a method of forming a conductive tape such as an aluminum material on the discharge vessel 18 through a conductive adhesive, a metal powder such as silver and a solvent are mixed in a binder. A method in which the conductive paste is applied to the surface of the discharge vessel 18 by screen printing, dispenser application or dipping, followed by drying and baking, at least one of tin, indium, bismuth, lead, zinc, antimony or silver For example, a method in which the solder containing the above is melted by heating is applied to the surface of the discharge vessel 18 by a dispenser or dipping while applying ultrasonic vibration. In order to improve the adhesion between the electrode layer and the discharge vessel 18, a method can be employed in which the surface of the discharge vessel 18 at the position where the outer electrodes 19a and 19b are formed is made uneven by, for example, sandblasting.

  The elongated spacers 15 formed integrally with the rear substrate 16 are arranged at a predetermined interval, and the distance between the front substrate 13 and the rear substrate 16 is kept constant, and the difference between the internal and external atmospheric pressure of the discharge vessel 18 is maintained. Prevent damage from lamp implosion. The spacer 15 is disposed in a direction perpendicular to the electrodes 19a and 19b, and divides the electrodes 19a and 19b into a plurality of discharge regions. The spacer 15 has an arbitrary shape such as a corrugated shape as shown in FIG. 5A and a semi-elliptical shape as shown in FIG. 5B in addition to the trapezoidal shape shown in FIGS. be able to. Further, as shown in FIG. 5C, the front substrate 13 and the back substrate 16a may both be flat and the spacers 15a may be provided separately. In the present embodiment, the back substrate 16 is thermally processed and integrally formed with the spacer 15, but the front substrate 13a is thermally processed as shown in FIGS. 5 (d) and 5 (e). Further, it is possible to adopt a configuration in which the front substrate 13b and the back substrate 16b are bonded together by thermal processing as shown in FIG. 5 (f).

  The size of each discharge space 20 divided by the spacer 15 in the planar discharge vessel 18 is set in accordance with the required lamp starting voltage, tube voltage, and light quantity. For example, the width W of the discharge space is 0.1. The height H of the discharge space 20 is set in the range of 0.5 mm to 6 mm in the range of 5 mm to 30 mm. The ratio of the width W to the height H of the discharge space is set in the range of 1.5: 1 to 10: 1, preferably in the range of 2: 1 to 5: 1. Further, in the present embodiment, the case where the cross-sectional areas of the discharge spaces 20 are all the same is illustrated, but the cross-sectional area of the discharge spaces 20 may be different depending on the location.

  A phosphor layer 21 is formed inside the front substrate 13, the rear substrate 16, and the spacer 15 in the planar discharge vessel 18. The phosphor layer 21 converts ultraviolet rays emitted from the discharge medium by discharge into visible light. The phosphor layer 21 uses phosphors used in general illumination, cold cathode fluorescent lamps, and PDPs, and is coated with several kinds of phosphors having different emission colors. In addition, the fluorescent substance layer 21 can also be comprised by apply | coating the fluorescent substance of a different luminescent color separately in stripe form or dot shape.

  In order to transmit light from the phosphor layer 21 on the back substrate 16 side without loss, the phosphor layer 21 of the front substrate 13 on the light extraction side, that is, the light emitting surface side, for example, has an average particle diameter (primary particle diameter). ) Is formed as thin as 5 μm to 15 μm. On the other hand, the phosphor layer 21 on the back substrate 16 side that does not extract light guides phosphor particles having an average particle diameter of about 2.5 μm or less to a thickness of 30 μm to 100 μm, for example, in order to guide much light to the front substrate 13 side. The thickness is increased to increase the reflection luminance. Although not shown, in the front substrate 13 on which the outer electrodes 19a and 19b are formed, when the phosphor layer 21 is inside the substrate at the position where the outer electrodes 19a and 19b are formed, the phosphor layer 21 is In general, the phosphor layer 21 is not provided on the inner side of the substrate where the outer electrodes 19a and 19b are provided, because the gas is sputtered by the discharge to increase the gas consumption rate. A reflective layer of fine metal oxide can also be formed between the back substrate 16 and the phosphor layer 21. Further, a metal oxide layer such as titanium oxide, aluminum oxide or yttrium oxide is formed between the front substrate 13 and the rear substrate 16 and the phosphor layer 21 to prevent mercury from moving to the glass surface. It is also possible to absorb ultraviolet rays generated by discharge. In the flat fluorescent lamp 11 according to the present embodiment, the phosphor layer 21 is provided on the inner surfaces of both the glass substrates 13 and 16, but either one of the phosphor layers may be omitted. .

  The backlight unit 10 of the present embodiment shown in FIG. 1 accommodates the flat fluorescent lamp 11 having the above configuration as a light source. The casing of the backlight unit 10 includes a front frame 31a and a back frame 31b. The flat fluorescent lamp 11 is disposed 0.1 mm to 5 mm away from the bottom surface of the back case 31b of the backlight unit 10, and is fixed by fixing members 32a and 32b. In order to further improve the light emission uniformity of the flat fluorescent lamp 11, a space of about 0.1 mm to 30 mm, preferably 0.5 mm to 15 mm is provided on the front substrate 13 side which is the light emitting surface of the flat fluorescent lamp 11. An optical plate 12 having a light diffusion function with a transmittance of 40% or more is disposed. In addition, when it is necessary to further improve the light emission uniformity and the luminance, a diffusion sheet, a light collecting sheet, and a polarization reflection sheet are disposed on the upper surface side of the optical plate 12.

  FIG. 6 shows an enlarged view of a cross section of the optical plate 12. A conductive material layer 33 is formed on the lamp-side surface of the optical plate 12. 7A, the conductive material layer 33 is formed only on the light emitting surface side of the optical plate 12, and the conductive material is formed on both the front and back surfaces of the optical plate 12 as shown in FIG. What formed the layer 33 can be used. Further, the conductive material layer 33 is formed on a film 34 having a thickness of 1 μm to 1000 μm, preferably 3 μm to 70 μm, and the film 34 is mounted on the optical plate 12 as shown in FIGS. 8A and 8B. It is also possible to adopt a configuration in which it is applied or pasted.

  The conductive material layer 33 is mainly composed of at least one oxide of indium tin oxide (ITO), zinc oxide, and tin oxide. For example, a material obtained by adding tin to indium oxide, oxidized to zinc oxide. A material in which aluminum or gallium oxide is added, or a material in which tin oxide is doped with antimony oxide or fluorine, these materials are deposited on the optical plate 12 by, for example, a spray method, a sputtering method, a vacuum deposition method, a sol-gel method, or a cluster beam. And PLD method. That is, since the conductive material layer 33 is formed in a process separate from the lamp, the conductive material layer 33 is easy to form and easily forms the conductive material layer 33, and also during the process of forming the conductive material layer 33, This is advantageous because an extra thermal load is not required.

  As the optical plate 12, a conventionally used resin or glass can be selected according to the molding temperature of the material of the conductive material layer 33. The light transmittance of the optical plate 12 is preferably about 40% or more. The conductive material layer 33 may be formed transparent with a transmittance of 60% or more in order to reduce light loss in the conductive film. Alternatively, it may be formed in a particle shape so as to have a light diffusing function in order to reduce light emission unevenness of the lamp 11. The conductive material layer 33 is preferably electrically grounded, but may be configured not to be grounded.

  The backlight unit 10 having the above configuration is used so as to illuminate the liquid crystal panel from the back side. As described above, the light emitting surface of the lamp 11 is used for the purpose of transmitting or diffusing light from the flat fluorescent lamp 11. By forming the conductive material layer 33 on the optical plate 12 disposed at a distance on the side, the conductive material layer 33 functions as a proximity conductor of the lamp 11 and reduces the starting voltage in the discharge space. In addition, by improving the startability of the lamp 11, the discharge wraparound phenomenon at the outer surface electrodes 19a and 19b is improved, and the discharge is performed in all the many discharge spaces 20 divided by the spacers 15 as shown in FIG. A path 20A can be formed. In addition, the conductive material layer 33 provided on the optical plate 12 can block noise generated from the lamp 11, and as a result, emission of noise from the light emitting surface of the backlight unit 10 can be suppressed.

The top view and sectional drawing of the backlight unit of one embodiment of this invention. The perspective view of the planar fluorescent lamp mounted in the backlight unit of the said embodiment. The partially broken perspective view seen from the front substrate side of the flat type fluorescent lamp mounted in the backlight unit of the said embodiment. The partially broken perspective view seen from the back substrate side of the flat type fluorescent lamp mounted in the backlight unit of the said embodiment. Sectional drawing of the modification of the flat fluorescent lamp mounted in the backlight unit of the said embodiment. Sectional drawing of the optical plate in the backlight unit of the said embodiment. Sectional drawing of the other example of the optical plate in the backlight unit of the said embodiment. Sectional drawing of the further another example of the optical plate in the backlight unit of the said embodiment. The top view which shows the lighting state of the flat fluorescent lamp mounted in the backlight unit of the said embodiment. The top view which shows the lighting state of the flat fluorescent lamp mounted in the backlight unit of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Backlight unit 11 Planar type fluorescent lamp 12 Optical plate 13 Front substrate 15 Spacer 16 Back substrate 18 Planar discharge container 19a, 19b External electrode 20 Discharge space 21 Phosphor layer 33 Conductive material layer

Claims (3)

A translucent front substrate and a rear substrate are arranged to face each other, a discharge medium is sealed inside, and a phosphor layer is formed inside at least one of the front substrate and the rear substrate to form a planar discharge vessel And at least a pair of electrodes are installed on the surface of the planar discharge vessel so as not to contact the discharge medium, and a plurality of electrodes are disposed inside the planar discharge vessel and substantially perpendicular to the electrodes. A flat fluorescent lamp provided with a spacer;
An optical plate disposed at an interval with respect to the surface on the side of utilizing the light of the flat fluorescent lamp,
A backlight unit comprising a conductive material layer formed on a surface of the optical plate.   The conductive material layer on the surface of the optical plate is mainly composed of at least one oxide of indium tin oxide (ITO), zinc oxide, and tin oxide. Backlight unit. The backlight unit according to claim 1, wherein the optical plate is made of a transparent glass plate or a light diffusion plate.

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