JP2007227060A - Backlight unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight unit structured so that color characteristics of the hue and tone of light reflected from each portion forming a reflecting surface of light from a luminescent lamp becomes uniform on the light emitting surface of a diffusion plate. <P>SOLUTION: In the inside of the casing 2 of this backlight unit 1, 1A, the surface of the portion other than the main reflecting surface 3d of a reflecting plate 3, 3A, which reflects light emitted from the fluorescent lamp 4 toward the diffusion plate 7, are formed by using the same material as that of the main reflecting surface 3d. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a backlight unit used in an illumination device such as a liquid crystal display device.

  In a liquid crystal display device (LCD device), the performance of the backlight unit is regarded as extremely important in order to obtain a clear image display. This is because a clear and high-quality image display can be performed by maintaining the image display area surface of the liquid crystal display device as a whole with substantially uniform hue and color tone.

  FIG. 4 is an exploded perspective view showing an example of a conventional direct type backlight unit. That is, the backlight unit 40 that is an illuminating device for the liquid crystal panel 30 includes a large number of parallel dielectric barrier discharge type discharge lamps (hereinafter simply referred to as fluorescent lamps) 41 in the socket 42. It is held and fixed to the socket holder 43. A harness 45 that feeds a high-frequency voltage from an inverter 44 that forms a high-frequency power source is connected to the socket 42.

The socket holders (lamp holders) 43 on both sides are fixed to the lower frame 46 at predetermined positions. Below the multiple fluorescent lamps 41, a reflector 47 that reflects the light emitted from the back surface of the fluorescent lamps 41 is disposed. On the other hand, above the multiple fluorescent lamps 41, the light from the fluorescent lamps 41 is reflected. A diffusion plate 48 and a diffusion sheet 49 for uniformly diffusing and an upper frame 50 are arranged, and the respective parts are assembled together. (For example, see Patent Document 1)
In the case of this configuration, the light emitted from the fluorescent lamp 41 is reflected by the reflection plate 47 and enters the diffusion plate 48 from the back surface. Further, the light emitted from the end surface of the fluorescent lamp 41 in the tube axis direction is reflected by the socket holder, and the reflected light enters the diffusion plate 48. The reflector 47 and the socket holder (lamp holder) 43 that reflect the respective emitted light are different in material hue and color characteristics of the surface tone.

  That is, for example, when white reflection is used, the surface of the reflection plate 47 is formed of a white PET film as a white reflection material. Alternatively, it is formed of a metal film made of a sputtered silver layer having excellent regular reflection characteristics.

  On the other hand, the socket holder (lamp holder) 43 is formed of a flame-retardant / insulating resin molding such as PC (polycarbonate).

  FIG. 5 is an exploded perspective view showing another example of a conventional direct type backlight unit. FIG. 6 is a partially cutaway enlarged view of the side cross section.

  The basic configuration of the backlight unit 40A is the same as that shown in FIG. 4 except that the electrode cover 51 is provided so as to cover the socket holder socket holder (lamp holder) 43. Therefore, in FIG.5 and FIG.6, the same code | symbol is attached | subjected to the same function location as FIG. 4, and each description is abbreviate | omitted.

  In the case of the backlight unit 40A, the electrode cover 51 disposed so as to cover the socket holder (lamp holder) 43 is molded using, for example, PMMA (polymethyl methacrylate), It is provided for the purpose of ensuring the brightness uniformity and holding the fluorescent lamp 41.

  Moreover, the surface of the reflecting plate 47 is formed of a white PET film as a white reflecting material, for example, when white reflection is used, as in the case described above. Alternatively, it is formed of a metal film made of a sputtered silver layer having excellent regular reflection characteristics.

  Therefore, the electrode cover 51 and the surface of the reflection plate 47 are different in material.

  In the case of the backlight units 40 and 40A having the above-described configurations, the paths through which the emitted light from the fluorescent lamp 41 enters the diffusion plate 48 can be broadly classified into direct light and reflected light paths. The direct light path is a path that is emitted from a surface facing the diffusion plate 48 that is an upper portion of the fluorescent lamp 41 and directly enters the diffusion plate 48. On the other hand, there are a plurality of paths of reflected light. That is, a path through which light emitted from the side surface and the back surface of the fluorescent lamp 41 is reflected by the surface of the reflection plate 47 and the socket holder (lamp holder) 43 and enters the diffusion plate 48. Further, the light directed toward the diffuser plate 47 is reflected by the diffuser plate 47 in a relationship of incident angles (when the incident angle is equal to or greater than a predetermined incident angle), and the reflected light is reflected by each part inside the backlight units 40 and 40A. This is a path for entering the diffuser plate 48 again as Nth order reflected light.

In those cases, the reflected light has a different wavelength range and intensity depending on the material of the reflector. That is, the hue and color tone, which are color characteristics, differ depending on the location where the direct light and the reflected light or the reflected light is reflected.
JP-A-2004-164907 [0014]

  The backlight units 40 and 40A shown in FIGS. 4 to 6 described above have a reflector 47 for reflecting the light emitted from the fluorescent lamp 41 in the back direction to the diffuser plate 48 arranged in the front direction. The surface material differs from the material of the socket holder (lamp holder) 43 and the electrode cover 51 that reflect the emitted light in the tube axis direction of the fluorescent lamp 41 in the direction of the diffusion plate 48.

  When the surface member of the reflector 47 and the material of the socket holder (lamp holder) 43 and the electrode cover 51 are different, the hue and color tone, which are the color characteristics of the reflected light of the respective materials, are also different. Therefore, a boundary due to a difference in reflected light characteristics from different materials may appear on the surface of the diffusion plate 48.

  Further, depending on the surface member of the reflector 47, the material of the socket holder (lamp holder) 43, and the electrode cover 51, the discoloration characteristics (yellowing degree; fading change with time) of deterioration due to ultraviolet rays irradiated from the fluorescent lamp 41 are different. Along with this, with the passage of time, there arises a problem that the difference in hue and color characteristics on the surface of the diffusion plate 48 becomes clearer.

  FIG. 7 is a graph showing the change in yellowing degree (degree of separation from colorless or white toward yellow) with respect to the irradiation time of the fluorescent lamp (discharge lamp) for PC and PMMA. After 100 hours, the value of PC is larger than that of PMMA. In any case, it is shown that there is a difference in the degree of yellowing due to the difference in material.

  The present invention has been made based on these circumstances, and the color characteristics of hue and color tone of the reflected light from each part forming the reflective surface from the fluorescent lamp are made uniform on the light emitting surface of the diffusion plate. The purpose is to provide a backlight unit.

The first feature of the backlight unit of the present invention is that the diffusion plate having a light emitting surface for irradiating diffused light to the outside, the rear surface of the diffusion plate, and arranged in parallel facing the back surface of the diffusion plate, and the diffusion plate A plurality of fluorescent lamps that irradiate the back surface of the fluorescent lamp, a socket that holds both ends of the fluorescent lamp, a lamp holder that fixes the socket, and a main reflection surface that faces the back surface of the plurality of fluorescent lamps. A backlight unit including a reflector and a housing,
Inside the housing, the surface of the part that reflects the emitted light from the fluorescent lamp to the diffuser plate other than the main reflecting surface of the reflecting plate is formed of the same material as the main reflecting surface. is there.

  The second feature of the backlight unit of the present invention is that the surface of the portion of the casing that reflects the emitted light from the fluorescent lamp to the diffuser plate other than the main reflection surface of the reflection plate, It is made of the same material as the main reflecting surface and has the same color characteristics.

  Further, a third feature of the backlight unit of the present invention is that the reflecting plate is a return portion including the socket and the lamp holder at both ends of the main reflecting surface of the reflecting plate in the tube axis direction of the fluorescent lamp. Is formed.

  Moreover, the 4th characteristic of the backlight unit of this invention is that the said reflecting plate is formed with PET material.

  It is possible to realize a backlight unit that is light in weight so that the color characteristics of hue and color tone of the reflected light from each part forming the reflective surface from the fluorescent lamp are uniform on the light emitting surface of the diffusion plate.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a partially cutaway cross-sectional view of a backlight unit showing an example of an actual aspect of the present invention. FIG. 2 is a perspective view thereof.

  The direct-type backlight unit 1 has a dish-shaped housing 2 including a bottom plate 2a and a side wall portion 2b erected from the bottom plate 2a. Dielectric barrier discharge type so that the reflective plate 3 is formed with a reflective surface on the surface and bent portions are formed at both ends, and the light source is disposed above the reflective plate 3 as the light source. A plurality of fluorescent lamps 4 such as discharge lamps are arranged at regular pitches or regularly in a plane. Terminal portions 4 b at both lamp ends of each fluorescent lamp 4 are held by a socket 6 fixed to the lamp holder 5. Above the fluorescent lamps 4 arranged in a plane, a diffusing plate 7 formed of a translucent milky white resin plate for uniform luminance on the entire light emitting surface is sequentially mounted. It is incorporated in the housing 2 and formed integrally. The socket 6 is connected to a power source side such as a high-frequency inverter through a harness (not shown).

  The fluorescent lamp 4 has a glass tube 4a filled with a filler made of a mixed gas of mercury and a rare gas, and a phosphor layer is formed on the inner wall surface as required, and external electrodes are formed on the outer surfaces of both lamp ends. (Not shown) is provided. The external electrode is formed of a conductive film-like, coil-like, or tape-like conductor. In particular, aluminum tape is wound or the end of the lamp is formed by ultrasonic solder dipping as having good conductivity and easy formation.

  The socket 6 is made of, for example, a rod-shaped conductive material having a flexible rubber elasticity obtained by mixing and molding carbon particles in an appropriate ratio in silicon rubber. The socket 6 is provided with a large number of lamp insertion holes 6a at regular intervals in the longitudinal direction. The diameter of the lamp insertion hole 6a is set to be smaller than the outer diameter of the external electrode of the fluorescent lamp 4, and the end of the fluorescent lamp 4 is press-fitted into the lamp insertion hole 6a and attached, whereby the external electrode is attached to the socket 6. It is in close electrical contact with. At the same time, the socket 6 mechanically holds the lamp end of the fluorescent lamp 4.

  In addition, a harness connecting portion (not shown) is formed at one end of the socket 6, and the harness from the high frequency inverter is fixedly connected by a metal fitting or the like.

  The lamp holder 5 is formed of, for example, a flame-retardant, electrically insulating resin molded body such as polycarbonate, and a socket 6 is fixed to a predetermined position by fixing.

  The reflection plate 3 is formed of a molded body of white PET (polyethylene terephthalate) material. As a cross-sectional shape, bent portions 3a are formed on both sides of the main reflecting surface 3d (both sides of the fluorescent lamp 4 in the tube axis direction). The return portion 3a has both end portions of the main reflecting surface 3d of the reflecting plate 3 along the bottom plate 2a of the housing 2 rising up to the height of the upper surface of the lamp holder 5 along the side wall portion 2b of the housing 2. Then, after bending along the upper surface of the lamp holder 5 by a predetermined dimension in the horizontal direction, a slope portion 3b is formed toward the main reflecting surface 3d at a position including the socket 6 and grounded. That is, the lamp holder 5 and the socket 6 are included in the return portion 3a. In the slope portion 3 b, escape holes 3 c for the fluorescent lamps 4 are formed corresponding to the arrangement of the fluorescent lamps 4.

  The main reflecting surface 3d is not particularly limited in shape as long as it is a plane, a curved surface, or a wavy surface that can reflect light efficiently and efficiently.

  FIG. 3 is a partially cutaway perspective view of the backlight unit 1A showing an example of a modification of the above-described actual state. In this modified example, the reflecting plate 3A is not formed as a single unit but is formed of a plurality of members. That is, the return portion 3a and the main reflecting surface 3d of the reflecting plate 3A are configured separately and combined. The main reflection surface 3d is provided with a long hole 3e, and the inside of the long hole 3e is formed by a bottom plate 3f. However, all the members constituting the reflector 3A are made of the same material. For example, a PET material is used.

  In addition, when the reflecting plate 3A is constituted by a plurality of members, the meaning that all the members are the same material means that the surface of the reflecting plate 3A is the same material literally when all the members are the same material. Including cases. That is, the case where the surface of the member which comprises is formed by sticking etc. the member similar to another member is also included.

  In the backlight units 1 and 1A including the reflectors 3 and 3A having the shapes as described above, the diffuser plate in which the emitted light emitted from the fluorescent lamp 4 in the back direction is arranged in the front direction of the fluorescent lamp 4 7 and the return part 3a, which is a part for reflecting the emitted light in the tube axis direction of the fluorescent lamp 4 in the direction of the diffusion plate 7, is formed of the same material. Has been.

  Therefore, the hue and color tone, which are the color characteristics of the reflected light that is reflected from the interior of the backlight units 1 and 1A, are uniform. Therefore, a boundary due to a difference in color characteristics of reflected light from different materials does not appear on the surface of the diffusion plate 7. As a result, a balanced outgoing light can be obtained on the surface of the diffusion plate 7.

  In addition, there arises a problem that occurs when there is a difference in material between the reflector 3 and other reflection parts, that is, a difference in discoloration characteristics (yellowing degree; fading change with time) due to ultraviolet rays irradiated from the fluorescent lamp 4. Can also be prevented. Thereby, it is possible to realize the backlight units 1 and 1A having long-term stable characteristics.

  Conventionally, the resin cover was used as the electrode cover (reference numeral in the figure described in the background art section), but it was made into a sheet shape, so the backlight unit can be made lighter and 1A. became.

  Further, when a PET material is used as the material of the reflector 3, the PET material is excellent in processability and impact resistance, and since it uses a polyester resin as a raw material, it decomposes into water and carbon dioxide when completely burned. Since it is an environmentally friendly plastic, it is possible to prevent environmental problems from occurring during disposal.

  Further, in each of the above-described embodiments, the external electrode type (dielectric barrier discharge lamp) fluorescent lamp in which electrodes are formed on the outer surfaces of both end portions of the glass tube is exemplified as the fluorescent lamp. However, the fluorescent lamp is not limited to the external electrode type. In addition, a fluorescent lamp of an internal electrode type in which a pair of discharge electrodes are sealed at both ends of a glass tube, or a fluorescent lamp of a dielectric barrier discharge lamp in which a pair of discharge electrodes is configured by a combination of an internal electrode and an external electrode is used. be able to. In that case, a socket adapted for each electrode type is used.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The partially cutaway sectional view of the backlight unit showing an example of the actual state of the present invention. The perspective view of the backlight unit which shows an example of the actual condition aspect of this invention. The partially cutaway sectional view of the backlight unit showing an example of the modification of the actual state of the present invention. The disassembled perspective view which shows an example of the conventional direct type backlight unit. The disassembled perspective view which shows another example of the conventional direct type backlight unit. The partially notched enlarged view of the side cross section of another example of the conventional direct type backlight unit. The graph which showed the change of the yellowing degree by the irradiation time of a fluorescent lamp about PC and PMMA.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 1A ... Backlight unit, 2 ... Housing | casing 3, 3A ... Reflector plate, 3a ... Return part, 3b ... Slope part, 3c ... Escape hole, 3d ... Main reflection surface, 4 ... Fluorescent lamp, 5 ... Lamp holder 6 ... Socket 7 ... Diffusion plate

Claims (4)

A diffusing plate having a light emitting surface for irradiating diffused light to the outside, a plurality of fluorescent lamps arranged in parallel facing the back surface of the diffusing plate and irradiating the back surface of the diffusing plate with emitted light; A backlight unit including a socket for holding both ends of the fluorescent lamp, a lamp holder to which the socket is fixed, and a reflector having at least a main reflection surface facing the back of the plurality of fluorescent lamps. There,
Inside the casing, the surface of a portion that reflects the light emitted from the fluorescent lamp to the diffuser plate other than the main reflection surface of the reflection plate is formed of the same material as the main reflection surface. Characteristic backlight unit.   Inside the casing, the surface of the part that reflects the light emitted from the fluorescent lamp to the diffuser plate other than the main reflection surface of the reflection plate is made of the same material as the main reflection surface and has the same color characteristics. The backlight unit according to claim 1, wherein the backlight unit is formed of.   2. The reflecting plate is characterized in that return portions including the socket and the lamp holder are formed at both ends of the main reflecting surface of the reflecting plate in the tube axis direction of the fluorescent lamp. Backlight unit.   The backlight unit according to claim 1, wherein the reflector is made of a PET material.

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