JP2008140695A - Backlight unit and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight unit in which a pin hole hardly occurs, and a liquid crystal display device. <P>SOLUTION: The backlight unit includes a back frame 1b of an open bottom, a flat surface fluorescent lamp 2 which is housed in the back frame 1b and has external electrodes 25a, 25b on the outer surface, and power supply clips 3a, 3b connected to the flat surface fluorescent lamp 2 so as to be electrically connected to the external electrodes 25a, 25b, and is lighted with the light-emitting face of the flat surface fluorescent lamp 2 in the nearly vertical state to the ground surface. Then, the power supply clips 3a, 3b are positioned at the upper part of the flat surface fluorescent lamp 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backlight unit and a liquid crystal display device that are used in a liquid crystal display or the like and include a planar light source that is turned on with a light emitting surface substantially perpendicular to the ground.

  In recent years, backlight units using planar light sources have been developed. Examples of such a backlight include the inventions described in Japanese Unexamined Patent Application Publication No. 2005-203164 (hereinafter referred to as Patent Document 1) and Japanese Unexamined Patent Application Publication No. 2006-156323 (hereinafter referred to as Patent Document 2). This backlight unit is configured by disposing a planar light source inside a housing and a diffuser plate or the like in an opening of the housing. In addition, as the electrode of the planar light source, an external electrode structure in which an electrode is formed on the outer surface of the discharge vessel is generally employed.

JP-A-2005-203164 JP 2006-156323 A JP 2006-196460 A JP 2006-164968 A JP 2003-157803 A

  However, when the light emitting surface of the planar light source is arranged so as to be substantially perpendicular to the ground and lit (hereinafter referred to as vertical lighting), it is understood that a so-called pinhole phenomenon is likely to occur in which a hole is formed in the glass. It was. Pinholes were most likely to occur in the glass portion of the discharge vessel above the planar light source placed vertically. This is considered to be related to the fact that the upper part of the lamp is likely to become hot due to heat burn or the like due to vertical lighting.

  Therefore, the inventors considered that it is necessary to lower the temperature of the glass portion in order to solve this problem, and came up with the idea of using a power feeding clip connected to the external electrode as a power feeding means. In other words, because the power supply means is disposed on the top of the planar light source where pinholes are likely to occur, and the temperature of the electrode portion on the planar light source and the glass portion thereof is reduced, it has been found that the generation of pinholes can be suppressed, I came to propose.

  In addition, as a well-known example using a power feeding means for electrical connection with an external electrode, JP 2006-196460 A (hereinafter referred to as Patent Document 3), JP 2006-164968 A (hereinafter referred to as Patent Document 4). ), Japanese Patent Application Laid-Open No. 2003-157803 (hereinafter referred to as Patent Document 5), but since the usage state of the backlight unit and the positional relationship of the power supply means at that time are not clear, the invention intended to solve the problem Absent.

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a backlight unit and a liquid crystal display device in which pinholes are unlikely to occur.

  In order to achieve the above object, a backlight unit of the present invention includes a case having a bottomed opening, a planar light source having an external electrode on the outer surface, which is accommodated in the case, and an electrical connection to the external electrode. Power supply means connected to the planar light source so as to be connected, the light emitting surface of the planar light source is lit in a state substantially perpendicular to the ground, and the power supply means is an upper part of the planar light source It is located in.

  According to the present invention, the generation of pinholes can be suppressed.

  The backlight unit according to the first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view for explaining a state before components are assembled in the backlight unit according to the first embodiment of the present invention. 2 is a cross-sectional view for explaining the backlight unit when XX ′ in FIG. 1 is viewed from the arrow direction, and FIG. 3 is for explaining the backlight unit when YY ′ in FIG. 1 is viewed from the arrow direction. It is sectional drawing for doing.

  The envelope of the backlight unit is made of, for example, white plastic resin, and is composed of two parts, a front case 1a and a back case 1b that are fitted to each other.

  The front case 1a is a case located on the light emitting surface side of the backlight unit, and has a wide opening surface 1a1.

  The back case 1b is a case with a bottomed opening constituted by a bottom portion 1b1 and a side portion 1b2. A lamp spacer 1b11 is formed at the center of the bottom 1b1 with a distance from the lamp. The lamp spacer 1b11 is intended to reduce the amount of heat of the lamp conducted to the outside through the bottom 1b1 by reducing the contact between the lamp and the bottom 1b1. That is, the back case 1b itself has a structure for keeping the lamp warm. A metal conductor for assisting the start of the lamp may be disposed on the bottom 1b1. Two through holes 1b21 for guiding lead wires 3a4 and 3b4 of a power feeding clip 3a (3b) described later are formed in the upper portion of the side portion 1b2. Further, a stepped portion 1b3 is formed at a connection portion between the bottom portion 1b1 and the side portion 1b2. Similar to the lamp spacer 1b11, the step portion 1b3 is formed to reduce the contact area with the lamp, and holds the frame portion of the lamp.

  A flat fluorescent lamp 2 is arranged as a planar light source inside the back case 1b.

  The flat fluorescent lamp 2 has a flat rectangular discharge vessel 21. The discharge vessel 21 is a vessel in which frit glass 22 is formed as a bonding member at the edges of the flat glass 21a and the corrugated processed glass 21b, and a discharge cell 23 is formed in which the discharge space is divided into a plurality of portions. ing. The processed glass 21b is not limited to a wave shape, and may be a rectangular shape, a triangular shape, or the like. Moreover, you may comprise the light emission surface side as processed glass, or may comprise both surfaces with flat glass or processed glass. The discharge cell 23 is filled with a rare gas of neon and argon and mercury at a pressure of several kPa to several hundred kPa. In addition, helium, xenon, and krypton can be used as the rare gas, and the sealing form may be a single substance or a mixture of two or more. Further, phosphor layers 24a and 24b are formed on the inner surfaces of the flat glass 21a and the processed glass 21b, respectively. At this time, in consideration of light extraction efficiency, it is desirable that the phosphor layer 24a has a thickness of 5 to 30 μm and the phosphor layer 24b has a thickness of 60 to 200 μm.

  A pair of external electrodes 25 a and 25 b are formed in the direction crossing the discharge cell 23 at the end of the outer surface of the flat glass 21 a. The external electrodes 25a and 25b are formed by heating and melting a solder containing at least one kind of tin, indium, bismuth, lead, zinc, antimony, silver or the like, or attaching a conductive tape such as aluminum with a conductive adhesive. It can be formed by applying or applying a conductive paste made by mixing a metal powder such as silver, a solvent and a binder, followed by drying and baking. The external electrodes 25a and 25b may be formed only on the processed glass 21b, or may be formed on both the flat glass 21a and the processed glass 21b.

  The flat fluorescent lamp 2 is connected with feeding clips 3a and 3b formed by bending a conductive and elastic material such as stainless steel or a copper plate as feeding means from the upper side of the lamp. At this time, mechanical connection to the flat fluorescent lamp 2 and electrical connection to the external electrodes 25a and 25b are performed. The connection positions of the power feeding clips 3a and 3b are the external electrodes 25a and 25b located above the flat fluorescent lamp 2 during vertical lighting. Here, “the external electrodes 25a and 25b are located at the upper part of the flat fluorescent lamp” means that there is at least a contact point with the external electrodes 25a and 25b in a range of 1/5 from the top in the vertical state. Means state.

  FIG. 4 is a perspective view for explaining the power feeding clip. The power feeding clip 3a (3b) includes a first clamping part 3a1 (3b1), a second clamping part 3a2 (3b2), a side part 3a3 (3b3), and a lead wire 3a4 (3b4). The 1st clamping part 3a1 (3b1) is corrugated shape, and is arrange | positioned at the flat glass 21a side. The 2nd clamping part 3a2 (3b2) is flat plate shape, and is arrange | positioned at the processed glass 21b. The side part 3a3 (3b3) is a part connecting the first clamping part 3a1 (3b1) and the second clamping part 3a2, 3b2, and is disposed on the side surface of the discharge vessel 1. The lead wire 3a4 (3b4) extends from the side 3a3 (3b3), and a terminal (not shown) for connecting to the lighting circuit is connected to the end of the lead wire 3a4 (3b4). The feeding clip 3a (3b) has a first clamping part 3a1 (3b1) and a second clamping part 3a2 (3b2) rather than the thickness of the lamp so as to be clamped by elasticity when connected to the flat fluorescent lamp 2. ) And the tip distance is slightly narrower.

  For example, a frame-shaped holding member 4 made of the same white plastic resin as the case is arranged on the flat fluorescent lamp 2 arranged in the back frame 1b. The holding member 4 is paired with the stepped portion 1b3, that is, the frame portion of the flat fluorescent lamp 2 is sandwiched from the front and rear. Further, since the holding member 4 is fixed by the front frame 1a via a diffusion plate 5 described later, even if the backlight unit is used in a vertical position, it is possible to prevent the flat fluorescent lamp 2 from being displaced in the front-rear direction. it can.

  An optical surface material 5 is disposed on the light emitting surface side of the back frame 1b. The optical surface material may be a material such as a flat plate that hardly changes in shape, and a diffusion plate or a transparent plate having a higher transmittance than the diffusion plate can be used. Further, if necessary, an optical sheet such as a diffusion sheet, a prism sheet, or a polarizing sheet may be further disposed on the optical surface material.

  Here, FIG. 5 which is an enlarged view for explaining the structure of the two-dot chain line Z portion of FIG. 1 with respect to the connection state of the flat fluorescent lamp 2, the external electrode 25a (25b) and the feeding clip 3a (3b). This will be described in detail.

The power supply clip 3 a holds the flat fluorescent lamp 2. The 1st clamping part 3a1 is contacting the external electrode 25a formed in the surface of the flat glass 21a. At this time, since the first sandwiching portion 3a1 has a wave shape, a contact portion and a non-contact portion are formed with respect to the external electrode 25a. A hollow layer 3c is interposed in the non-contact portion. In the hollow layer 3c, since the external electrode 25a is in contact with the atmosphere, the temperature of the electrode portion can be reduced by the flow of the atmosphere. Incidentally, since pinholes are likely to occur in the flat glass 21a near the center of the discharge cell 23, it is desirable that the hollow layer 3c be located in the glass portion. Therefore, when the width of the discharge cell 23 is W1 and the width of each wave of the first sandwiching portion 3a1 is W2, it is most preferable that W1 = W2 so that the hollow layer 3c is located in the entire discharge cell 23. Is preferred. Note that the area of the hollow layer 3c formed by the first sandwiching portion 3a1 and the external electrode 25a is preferably 10 mm ² or more in view of the effect of reducing the electrode temperature.

  Moreover, the 2nd clamping part 3a2 is contacting the processed glass 21b and the bottom part 1b1. Therefore, the heat of the external electrode 25a can be exhausted through the contact portion with the first sandwiching portion 3a1, the side portion 3a2, and the second sandwiching portion 3a3.

  In the case where the power supply clip 3a is sandwiched between the upper portion of the discharge vessel 21 and the lead wire 3a4 is taken out from the upper portion of the back frame 1b as in the present embodiment, the lead wire 3a4 is pulled upward. Thus, the downward force applied to the discharge vessel 21 in the vertically placed state can be reduced, and even if the lower edge surface of the flat fluorescent lamp 2 collides with the back frame 1b due to vibration or the like, the loss due to the impact is prevented. Can do.

Hereinafter, an embodiment of the backlight unit of the present invention will be shown.
Front case 1a, back case 1b: made of white plastic resin,
Discharge vessel 2: made of soda glass, 736 mm × 412 mm, discharge cell 23 width W1 = 6.5 mm, height H = 3.0 mm, average particle size of phosphor layer 24a = 6.0 μm, layer thickness = 15 μm The average particle size of the phosphor layer 24b = 2.0 μm, the layer thickness = 150 μm,
Feeding clips 3a and 3b: nickel plated copper,
Holding member 4: white plastic resin,
Optical surface material 5: diffusion plate + diffusion sheet,
The width W2 of the hollow layer 3c = 4.0 mm, the area = 20 mm ²
When a vertical lighting test was performed in the above example and the comparative example in which the power feeding clips 3a and 3b were connected to the middle part or the lower part, a pinhole was generated in the glass portion on the upper part of the discharge vessel of the comparative example, leading to no lighting. This is presumably because, in the lamp of the comparative example, the upper side became hot and the glass temperature reached the pinhole generation temperature. That is, in the present invention, it can be concluded that the glass can be made lower than the pinhole generation temperature by arranging the power supply clips 3a and 3b on the upper part of the lamp.

  Therefore, the backlight unit of the present embodiment is the upper part of the discharge vessel 21 and the portions where the external electrodes 25a and 25b are formed when the light emission surface of the flat fluorescent lamp 2 is turned on in a substantially vertical state with respect to the ground. Is sandwiched and connected by the power supply clips 3a and 3b, whereby mechanical and electrical connection can be easily performed, and the heat of the glass portion on the top of the discharge vessel 21 in which the external electrodes 25a and 25b are formed is supplied to the power supply clip 3a. Since the heat can be exhausted through 3b, pinholes can be suppressed. At this time, if at least a part of the power feeding clips 3a and 3b is in contact with the back frame 1b, the heat exhaust effect can be further enhanced.

  Further, by interposing the hollow layer 3c between the external electrodes 25a, 25b and the first sandwiching portions 3a1, 3b1 of the power supply clips 3a, 3b, a temperature reduction effect due to atmospheric flow can be obtained, and pinholes Can be further suppressed. Since pinholes are most likely to occur in the flat glass 21a in the vicinity of the center of the discharge cell 23, it is more effective if the hollow layer 3c is positioned at that portion.

(Second Embodiment)
FIG. 6 is a cross-sectional view of the backlight unit according to the second embodiment of the present invention. About each part of this 2nd Embodiment, the same part as each part of the planar fluorescent lamp of 1st Embodiment is shown with the same code | symbol, and the description is abbreviate | omitted.

  In the second embodiment, the heat dissipating member 6 having high thermal conductivity is interposed between the second sandwiching portion 3a2 and the side portion 3a3 of the power supply clip 3a and the back frame 1b. Thereby, the heat generated in the external electrode 25a can be efficiently exhausted to the outside of the backlight via the power supply clip 3a, the heat radiating member 6, and the back frame 1b. Here, examples of the “heat dissipating member having high thermal conductivity” include PPS (polyphenylene sulfide) and silicon rubber. Of course, it is desirable to have heat resistance that does not cause deformation or the like due to heat during lighting. Further, if a highly insulating material is used for the heat radiating members 3a4 and 3b4, the back frame 1b can be formed of a metal such as iron, which is advantageous in terms of ease of molding and cost.

  Therefore, in the present embodiment, the effect of exhaust heat is superior to that of the first embodiment, so that the generation of pinholes can be further suppressed.

(Third embodiment)
FIG. 7 is a cross-sectional view of the backlight unit according to the third embodiment of the present invention. About each part of this 3rd Embodiment, the same part as each part of the planar fluorescent lamp of 1st Embodiment is shown with the same code | symbol, and the description is abbreviate | omitted.

  In the third embodiment, the power feeding clip 3a (3b) having the comb-shaped first sandwiching portion 3a1 (3b1) formed with a plurality of protruding tip portions 3a11 (3b11) as shown in FIG. In use, the flat fluorescent lamp 2 is clamped from the side surface, and the tip 3a11 (3b11) is brought into contact with the external electrode 25a (25b) at a plurality of locations. Since the hollow layer 3c is formed between the protruding tip portions 3a11 (3b11) and between the edge of the lamp and the side portions 3a3, 3b3, the air is easily convected and the temperature reduction effect is high. In addition, strong clamping is possible, and even if the energization of any of the tip portions 3a11 is deteriorated, the entire power supply is not deteriorated.

  Therefore, in this embodiment, the same effect as that of the first embodiment can be obtained, and the reliability of connection of the power feeding clips 3a and 3b can be improved.

(Fourth embodiment)
FIG. 9 is an overall view for explaining a liquid crystal display device using the flat fluorescent lamp of the present invention.

  The envelope of the liquid crystal display device is made of, for example, PPE (polyphenylene ether) or PC (polycarbonate), and includes two parts of a front frame FF and a back frame BF that are fitted to each other.

  The front frame FF has an opening surface, and a liquid crystal panel LCP is connected to the opening surface.

  The back frame BF has a bottomed opening and a pedestal at the bottom. A backlight BL is arranged in the back frame BF. Further, the lead wires 3a4 and 3b4 of the derived feeding clips 3a and 3b and the lighting circuit INV are connected to the backlight BL. Since a known lighting circuit can be used as the lighting circuit INV, details are omitted. At the time of lighting, the lamp is lit by applying a sine wave voltage having a frequency of 10 to 200 kHz continuously or intermittently from the lighting circuit INV.

  The liquid crystal display device configured as described above is used in a vertically placed state. That is, the flat fluorescent lamp FFL is lit with the light emitting surface vertical.

  Therefore, in the present embodiment, it is possible to provide a long-life liquid crystal display device that can suppress pinholes in the flat fluorescent lamp 2 even when the light emitting surface is used in a vertical state.

  In the present invention, the embodiment described above is not limited to the above, and may be modified as follows, for example.

  In the first to third embodiments, as shown in FIG. 10, the frit glass 22 for welding the flat glass 21a and the processed glass 21b is sufficiently separated from the power supply clips 3a and 3b, and the frit glass 22 is subjected to voltage. It is desirable not to be applied. This is because when a voltage is applied to the frit glass 22, pinholes are generated, cracks are generated, and the joining member is melted (for details, see Japanese Patent Application No. 2006-193998, which is our previous application. Described in). Note that an insulator may be interposed between the frit glass 22 and the power supply clips 3a and 3b to insulate them.

  In the first embodiment, the first clamping portions 3a1 and 3b1 of the power feeding clips 3a and 3b are wave-shaped in the width direction of the external electrodes 25a and 25b, and the hollow layer 3c is formed of the external electrodes 25a and 25b as shown in FIG. You may form along a longitudinal direction.

  In the third embodiment, the power feeding clip 3a (3b) sandwiched from the side surface of the flat fluorescent lamp 2 may have a shape as shown in FIGS.

  In FIG. 12A, a tip portion 3a11 (3b11) having the same pitch as the wave-like portion of the processed glass 21b is formed in the second sandwiching portion 3a2 (3b2). In this case, since the front end portion 3a11 (3b11) is fitted to the corrugated portion of the processed glass 21b, the longitudinal displacement of the external electrodes 25a and 25b can be prevented, and the feeding clip 3a (3b) can be prevented from falling off.

  In FIG. 12B, the tip portion 3a11 (3b11) of the first clamping portion 3a1 (3b1) is a comb shape as in (a), but the shape is squeezed. With this shape, it is possible to easily attach the power supply clip 3a (3b) to the flat fluorescent lamp 2. Note that the hooked tip 3a11 (3b11) can be obtained by bending.

  In FIG. 12C, the first clamping part 3a1 (3b1) has a bowl-shaped tip part 3a11 (3b11), and the second clamping part 3a2 (3b2) has a bowl-shaped tip part 3a21 (3b21). Yes. This shape of the power supply clip 3a (3b) is particularly effective when mounted on the flat fluorescent lamp 2 in which the discharge vessel 21 is configured by bonding two processed glasses (for example, corrugated glass).

  In FIG. 12D, the tip portions 3a11 (3b11) and 3a21 (3b21) are projecting from the power supply clip 3a (3b) of FIG. The power supply clip 3a (3b) having this shape is particularly effective when the flat plate fluorescent lamp 2 in which the discharge vessel 21 is configured by attaching two flat glass plates to each other.

The perspective view before incorporating each component which comprises the backlight unit of the 1st Embodiment of this invention. Sectional drawing for demonstrating the backlight unit which looked at X-X 'of FIG. 1 from the arrow direction. Sectional drawing for demonstrating the backlight unit which looked at Y-Y 'of FIG. 1 from the arrow direction. The perspective view for demonstrating an electric power feeding clip. The enlarged view for demonstrating the structure of the dashed-two dotted line Z part of FIG. Sectional drawing of the backlight unit of the 2nd Embodiment of this invention. Sectional drawing of the backlight unit of the 3rd Embodiment of this invention. The perspective view for demonstrating the structure of the electric power feeding clip of 3rd Embodiment. BRIEF DESCRIPTION OF THE DRAWINGS The whole figure for demonstrating the liquid crystal display device using the flat type fluorescent lamp of this invention. Sectional drawing for demonstrating the structure of the suitable electric power feeding clip in the 1st-3rd embodiment. The modification of the electric power feeding clip of 1st Embodiment. The modification of the electric power feeding clip of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Front case 1b Back case 2 Flat fluorescent lamp 21a Flat glass 21b Processed glass Bottom part 22 Frit glass 23 Discharge cell 24a, 24b Phosphor layer 25a, 25b External electrode 3a, 3b Feed clip 3a1, 3b1 1st clamping part 3a2, 3b2 2nd clamping part 3a3, 3b3 Side part 3a4, 3b4 Lead wire 4 Holding member 5 Optical surface material 6 Heat radiation member

Claims (6)

  A housing having a bottomed opening, a planar light source having an external electrode on an outer surface, housed in the housing, and a power supply means connected to the planar light source so as to be electrically connected to the external electrode The light emitting surface of the planar light source is lit in a state substantially perpendicular to the ground, and the power supply means is located above the planar light source.   The backlight unit according to claim 1, wherein an outer surface of the power feeding unit and the housing are in contact with each other.   The backlight unit according to claim 2, wherein a portion where a hollow layer is interposed exists between the external electrode and the power feeding unit.   The said planar light source has a some discharge cell inside, and the said hollow layer is located in the said external electrode of the said discharge cell part, The Claim 1 thru | or 3 characterized by the above-mentioned. Backlight unit.   The backlight unit according to claim 4, wherein a heat dissipating member made of PPS or silicon rubber is interposed between the power supply means and the housing. The backlight unit according to any one of claims 1 to 5, wherein the light emitting surface is disposed in a state substantially perpendicular to the ground;
A liquid crystal panel disposed on the light emitting surface side of the backlight unit;
A liquid crystal display device comprising: a lighting circuit connected to the backlight unit.

Images