JP2008152001A - Light source unit and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source unit hardly causing afterimage and having high luminance and to provide a liquid crystal display device. <P>SOLUTION: In the light source unit, a plurality of discharge cells 13 formed inside a discharge chamber 1 are grouped into three light emitting groups by external electrodes 15a1 to 15c2, and external electrodes 15a1 to 15c2 of the respective light emitting groups are connected to inverters 3a to 3c. Each light emitting group is sequentially turned on and off ford period of 1/3 of a cycle at different timings by shifting the cycle by 1/3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light source unit and a liquid crystal display device using a planar light source used for a backlight of a liquid crystal display or general illumination.

  In recent years, attention has been focused on liquid crystal display devices such as liquid crystal televisions. This is because the liquid crystal display device is excellent in that images are clean and power consumption is low. However, liquid crystal display devices are conventionally said to be weak against moving images, and when moving images are projected on a liquid crystal screen, the movement is blurred and it tends to look like an afterimage. Such a problem is pointed out in the pamphlet of International Publication No. 04/053826 (hereinafter referred to as Patent Document 1) and JP-A-2002-6815 (hereinafter referred to as Patent Document 2).

  An attempt has been made to improve the above problem by changing the lighting method of the backlight. Typical examples are a full-flash lighting system in which the entire backlight is repeatedly turned on and off, and a sequential flashing lighting system in which the light source is turned on at different timings for each light emitting area. JP-A 2000-321551 (hereinafter referred to as Patent Document 3) is a known example that describes the sequential blinking lighting method. As described above, the conventional sequential blinking lighting system employs a configuration in which a plurality of linear light sources such as cold cathode fluorescent lamps are used and the light emission timings of these lamps are shifted and lighted.

International Publication No. 04/053826 Pamphlet Japanese Patent Laid-Open No. 2002-6815 JP 2000-321551 A

  However, it was found that when a blinking lighting system was sequentially performed using a cold cathode fluorescent lamp, a sufficient luminance could not be obtained although an afterimage suppressing effect was obtained. This is because in a cold cathode fluorescent lamp, there is a limit to the current passed through each lamp, and luminance cannot be obtained. This problem can be solved by increasing the number of lamps used, but this is not preferable because it leads to an increase in the number of parts and cost.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a light source unit and a liquid crystal display device that are less likely to cause an afterimage and have high luminance.

  In order to achieve the above object, a light source unit of the present invention includes a planar light source in which electrodes are arranged so that a plurality of discharge spaces formed inside a discharge vessel can discharge, and the electrode of the planar light source. And a lighting circuit electrically connected to the discharge vessel, wherein the discharge vessel is divided into a plurality of light emitting groups including a plurality of discharge spaces, and the light emitting groups are lit to blink sequentially. And

  According to the present invention, it is possible to provide a light source unit and a liquid crystal display device that are less likely to cause an afterimage and have high luminance.

  The light source unit according to the first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining an overall view of a light source unit according to a first embodiment of the present invention.

  The light source unit of the present embodiment includes a flat fluorescent lamp 1, inverters 2a to 2c, and a controller 3.

  The structure of the flat fluorescent lamp will be described with reference to FIG. FIG. 2 is a view of the X-X ′ cross section of FIG. 1 as viewed from the direction of the arrow.

  The discharge vessel 11 constituting the vessel of the flat fluorescent lamp 1 is configured by applying frit glass 121, for example, as a bonding material to the edges of the flat glass substrate 11a and the corrugated glass substrate 11b and bonding them together.

  The flat glass substrate 11a is made of translucent glass, such as soda glass, and serves as a light emitting surface in the present embodiment. An exhaust hole 11 a 1 is provided at the end of the flat glass substrate 11 a, and an exhaust chip 11 a 2 is attached to the exhaust hole 11 a 1 by a frit glass 122.

  The corrugated glass substrate 11b is made of, for example, soda glass, like the flat glass substrate 11a, and serves as a reflecting surface in the present embodiment. Since most of the corrugated glass substrate 11b has a corrugated shape, when the flat glass substrate 11a and the corrugated glass substrate 11b are combined, the discharge space is divided by the corrugated portion, and a plurality of discharge cells 13 are formed. Is formed.

  A discharge medium containing mercury and a rare gas is sealed in the discharge cell 13. The rare gas can be sealed as at least one gas selected from xenon, krypton, argon, neon, and helium, or a mixed gas of two or more. In addition, when two or more kinds of rare gases are mixed and sealed, it is desirable to seal in consideration of characteristics peculiar to the rare gas. For example, in the case of a mixed gas composed of neon and argon, if neon: argon = 50: 50 to 99: 1, the luminous efficiency and the low voltage startability characteristics of the lamp can be improved, and neon: argon = 1. If it is set to 99:50:50, the rising characteristic of light emission can be improved. The gas pressure should be 1 to 700 torr, preferably 20 to 100 torr, taking into consideration the characteristics of luminous efficiency, low voltage startability, and life.

Phosphor layers 14a and 14b are formed on the inner surface of the discharge vessel 1, that is, the surfaces on the discharge space side of the flat glass substrate 11a and the corrugated glass substrate 11b, respectively. The phosphor layers 14a and 14b only need to convert ultraviolet rays radiated from mercury by discharge into visible light. For example, the phosphor layers 14a and 14b may be a single-color phosphor or a plurality of RGB used in general illumination or cold cathode fluorescent lamps. Species phosphors can be used. In the present invention, it is more desirable that the phosphor has a high response rate. For example, in an RGB three-wavelength phosphor, Y ₂ O ₃ : Eu ³⁺ (R), Y ₂ Si ₅ : Tb ³⁺ (G), BaMg ₂ Al ₁₀ O ₁₇ : Eu ²⁺ (B), etc. each emit 90%. It is preferable to use a combination of phosphors having a rise time of 5 msec or less and a 1/10 afterglow time of 5 msec or less.

  Here, in the present embodiment, the flat glass substrate 11a side is a light emitting surface, and the corrugated glass substrate 11b side is a reflecting surface. Therefore, the flat glass substrate 11a side increases light transmission efficiency, and the corrugated glass substrate 11b side transmits light. It is desirable to increase the reflection efficiency. For example, the phosphor layer 14a has an average particle diameter of about 2.5 μm or more and a thickness of 5 to 15 μm, and the phosphor layer 14b has an average particle diameter of about 2.5 μm or less and a thickness of 30 to 200 μm. Good. In order to further improve the reflection efficiency on the corrugated glass substrate 11b side, a fine metal oxide layer made of titanium oxide, aluminum oxide, yttrium oxide or the like is formed between the corrugated glass substrate 11b and the phosphor layer 14b. Is good. In order to prevent mercury from diffusing, a protective layer of aluminum oxide or yttrium oxide may be formed between the phosphor layers 14a and 14b.

  At both ends of the outer surface of the flat glass substrate 11a, strip-shaped external electrodes 15a1, 15a2, 15b1, 15b2, 15c1, 15c2 to which a high voltage and a low voltage are applied are formed in a direction crossing the discharge cell 13. Yes. The external electrodes 15a1 to 15c2 are formed by dispensing a solder containing at least one kind of tin, indium, bismuth, lead, zinc, antimony and silver by a dispenser or dipping while applying ultrasonic vibration. The formation of the external electrodes 15a1 to 15c2 is not limited, and a conductive paste formed by adhering a conductive tape such as aluminum with a conductive adhesive or mixing a metal powder such as silver, a solvent and a binder is screened. The electrode may be formed by printing.

  FIG. 3 is an enlarged view of a portion Y in FIG. As can be seen from the figure, a gap d is provided between the adjacent external electrodes 15a1 and 15b1. This is to maintain electrical insulation, and the distance d is preferably 2 mm to 20 mm.

  Note that the electrode structure that can be implemented in carrying out the present invention is not limited to this embodiment. For example, in the present embodiment, the external electrode is formed on the flat glass substrate 11a, but the external electrode may be formed on the corrugated glass substrate 11b or both the flat glass substrate 11a and the corrugated glass substrate 11b. Moreover, the internal electrode type by which a pair of electrode is arrange | positioned at each discharge cell 13 may be sufficient, and it is not limited to an external electrode type. Further, it may be an internal / external electrode type in which an internal electrode and an external electrode are combined.

  Below, one specification of the flat fluorescent lamp of this Embodiment is shown.

Discharge vessel 1 Size = 750 mm × 450 mm × 4 mm, width W of each discharge cell 13: 6.5 mm, height H: 2.4 mm,
Discharge medium Mercury = 100 mg, neon: argon = 9: 1, 8 kPa,
Phosphor layer 14a particle size = 5.0 μm, layer thickness = 10 μm,
Phosphor layer 14b particle size = 2.4 μm, layer thickness = 150 μm,
External electrodes 15a1 to 15c2 20 mm × 143 mm, distance d between adjacent electrodes d = 5.5 mm,
Inverters 3a, 3b, and 3c are connected to the external electrodes 15a1 and 15a2, 15b1 and 15b2, and 15c1 and 15c2, respectively, of the planar fluorescent lamp configured as described above by lead wires. That is, in the flat fluorescent lamp, three electrically independent light emitting groups are formed. As shown in FIG. 4, between the external electrodes 15a1 and 15a2, the light emitting group A and between the external electrodes 15b1 and 15b2 are formed. The light emitting group B and the external electrodes 15c1 and 15c2 can be individually turned on as the light emitting group C. The light emission timings of the light emission groups A to C can be controlled by the controller 3 connected to the inverters 2a, 2b, and 2c.

  FIG. 5 is a diagram for explaining the light emission timing of each light emission group of the present embodiment. The lighting frequency of the flat fluorescent lamp is 65 kHz.

  As can be seen from the figure, the light emission groups A to C have a 1/3 ON period with respect to one cycle, and are turned on with the light emission timings of the ON periods of each light emission group being shifted. Specifically, the light emission groups A to C have an ON period of 2.78 msec for one cycle of 8.3 msec (120 Hz), and the light emission group A → light emission group B → light emission group C →. It is lit while changing the light emitting groups that are sequentially lit (hereinafter flashing steadily). In FIG. 5, when the light emitting group is turned off, the other light emitting groups are turned on so that the light emission is not interrupted as a whole and does not overlap with the light emission of the other groups. Alternatively, there may be some period in which the light emission overlaps. By turning on the light source unit at such a light emission timing, it was confirmed that the moving image on the liquid crystal screen became clear and no afterimage was generated.

  Note that it has been confirmed by the present inventor that, in the lighting method as described above, when one cycle is short (= frequency is high), or when a large number of light emitting groups are divided, an afterimage is particularly easily suppressed. The former is a problem of control, and one cycle can be shortened depending on improvement of the IC and the like, and can be shortened to about 1 msec (= 1 kHz) at present. On the other hand, the latter may divide a large number of light emitting groups, and in the present invention, it can be divided up to about 10. However, as the light emitting group is divided, the amount of light obtained from one light emitting group decreases, and the luminance decreases. This problem of luminance reduction can be solved by increasing the current value supplied to each light emitting group in the flat fluorescent lamp of the present embodiment. This is a method that can be realized because each light emitting group is a flat fluorescent lamp including a plurality of discharge cells. That is, the luminance of one light emitting group is determined by the current passed through the external electrode, but in a flat fluorescent lamp, the current is shunted in proportion to the number of discharge cells included in the light emitting group, so that it can be passed through each discharge cell The luminance desired by the light emitting group can be obtained within the current limit. By the way, when using a linear light source such as a cold-cathode fluorescent lamp for sequential blinking lighting, the linear light source has a low limit on the current value that can be passed to one lamp, so the problem of brightness will be solved if the number of lamps is not increased. This is not possible, and the number of parts and the cost increase. From the above points, the flat fluorescent lamp is optimal in this lighting system.

  Accordingly, in the present embodiment, the discharge vessel 11 of the flat fluorescent lamp 1 is divided into a plurality of light emitting groups including a plurality of discharge cells 13, and the light emitting groups are sequentially flashed and lit, thereby moving a moving image on the liquid crystal screen. It is possible to prevent an afterimage that is likely to occur when the image is projected. In addition, since each light emitting group includes a plurality of discharge cells 13, a large current can flow between the electrodes, so that high luminance can be achieved.

  In addition, since the afterimage can be sufficiently prevented only by the light source unit, it is not necessary to take measures against the afterimage on the liquid crystal panel side, and the configuration of the liquid crystal panel can be simplified.

(Second Embodiment)
FIG. 6 is a diagram for explaining an overall view of the light source 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 light source unit of 1st Embodiment is shown with the same code | symbol, and the description is abbreviate | omitted.

  In the second embodiment, three horizontally long planar fluorescent lamps 1a to 1c are used, and they are connected vertically, and each lamp is configured as a light emitting group A to C that independently emits light. Therefore, also in this embodiment, lighting control with shifted timing can be performed as in the first embodiment. Further, this embodiment is advantageous in that one lamp is smaller than the first embodiment, so that the manufacture is easy and the electrode insulation between adjacent lamps can be easily obtained.

  Therefore, in the present embodiment, as in the first embodiment, it is possible to prevent an afterimage that is likely to occur when a moving image is projected on a liquid crystal screen.

  In addition, since one light emitting group is formed by one lamp, each lamp can be easily manufactured. Further, the insulation between the light emitting groups can be easily and reliably taken.

(Third embodiment)
FIG. 7 is a diagram for explaining an overall view of the light source 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 light source unit of 1st Embodiment is shown with the same code | symbol, and the description is abbreviate | omitted.

  In the third embodiment, six external electrodes are formed on each side, and apparently divided into six light emitting groups. However, since the external electrodes 15a11 and 15a12 and the external electrodes 15a21 and 15a22 are connected to the inverter 3a, they emit light at the same timing. The external electrodes 15b11 and 15b12 and the external electrodes 15b21 and 15b22 are connected to the inverter 3b, and the external electrodes 15c11 and 15c12 and the external electrodes 15c21 and 15c22 are connected to the inverter 3c. That is, there are three light emitting groups with different light emission timings in lighting, and the light emitting groups are substantially divided into three light emitting groups as in the first and second embodiments. In this embodiment, since the light emitting groups A, B, C, A, B, and C are divided from the top, the upper half surface and the lower half surface of the liquid crystal screen can be turned on and off sequentially. It becomes easy to suppress.

  Therefore, in the present embodiment, as in the first embodiment, it is possible to prevent an afterimage that is likely to occur when a moving image is projected on a liquid crystal screen.

(Fourth embodiment)
FIG. 8 is a diagram for explaining an overall view of a liquid crystal display device according to a fourth embodiment of the present invention. About each part of this 4th Embodiment, the same part as each part of the light source unit of 1st Embodiment is shown with the same code | symbol, and the description is abbreviate | omitted.

  The liquid crystal display device according to the present embodiment includes a backlight BL, a front frame FF, and a back frame BF.

  The backlight BL is provided with a diffusion plate or the like on the light emitting surface side of the light source unit introduced in the above embodiment and held by a case. Inverters 3a to 3b are arranged on the back of the case.

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

  The back frame BF has a housing with a bottomed opening, and the backlight BL is disposed therein. A pedestal is attached to the bottom of the bottomed casing. That is, this liquid crystal display device is used in a state where the light emitting surface is substantially perpendicular to the ground.

  The liquid crystal display device configured as described above can prevent afterimages on the liquid crystal screen even if the liquid crystal panel LCP is not operated specially by the lighting method of the light source unit of the back frame BF as described above. it can.

  Therefore, in this embodiment, it is possible to prevent an afterimage that is likely to occur when a moving image is projected on a liquid crystal screen with a simple structure.

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

  In the present embodiment, the light emitting groups are lit in the vertical direction, but the light emitting groups may be lit in the horizontal or vertical and horizontal directions.

  In FIG. 5, in order to simplify the structure of the light source unit, the light emission groups A to C are lit with the same light emission periods, but they are not necessarily the same. Also, a lighting method may be performed in which the liquid crystal panel is also turned on and off, and the light emitting groups A to C are turned on and off in accordance with the timing of the liquid crystal panel.

1 is an overall front view of a light source unit according to a first embodiment of the present invention. The figure which looked at the X-X 'cross section of FIG. 1 from the arrow direction. The enlarged view of the Y part of FIG. The figure for demonstrating the light emission timing of each light emission group of this Embodiment. The figure for demonstrating the whole figure of the light source unit of the 2nd Embodiment of this invention. The figure for demonstrating the whole figure of the light source unit of the 3rd Embodiment of this invention. The figure for demonstrating the whole figure of the liquid crystal display device of the 4th Embodiment of this invention. FIG. 8 is a graph of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flat fluorescent lamp 11 Discharge vessel 11a Front glass substrate 11b Rear glass substrate 121, 122 Frit glass 13 Discharge cell 14a, 14b Phosphor layer 15a1-15c2 External electrode 2a-2c Inverter 3 Controller

Claims (5)

A planar light source in which electrodes are arranged so that a plurality of discharge spaces formed inside the discharge vessel can be discharged, and a lighting circuit electrically connected to the electrodes of the planar light source,
The light source unit, wherein the discharge vessel is divided into a plurality of light emission groups including a plurality of discharge spaces, and the light emission groups are lit to blink sequentially.   The discharge space is divided into n light emitting groups, and each of the light emitting groups is lit so as to blink sequentially with a light emission timing of approximately 1 / n period and with a light emission timing of approximately 1 / n period. The light source unit according to claim 1.   The electrode is an external electrode formed on the outer surface of the discharge vessel so as to cross the plurality of discharge spaces, and the light emitting group is divided by forming a plurality of the external electrodes. Item 3. The light source unit according to item 1 or 2.   The light source unit according to claim 1, wherein the light emitting group is formed by using a plurality of planar light sources each having one or a plurality of light emitting groups. The light source unit according to any one of claims 1 to 4,
A liquid crystal display device comprising: a liquid crystal panel disposed on a light emitting surface side of the light source unit.

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