JP4543701B2 - Backlight and liquid crystal display device using the same - Google Patents

Description

  The present invention relates to a backlight in a liquid crystal display device, and more particularly to assembling and fixing a linear lamp of a backlight in an edge light type backlight unit using a linear lamp as a backlight light source.

As a display device such as a large television, a power-saving, thin, and light-weight liquid crystal display device has been awarded, and a highly reliable backlight with stable luminance used for the display device is required.

In this type of liquid crystal display device, there is a method of irradiating light from a backlight arranged on the back of the liquid crystal panel to the liquid crystal panel to view the image formed on the liquid crystal panel, a direct light method and a side light method However, the direct light system is often used for backlights that require high brightness, such as large liquid crystal modules and medium-sized televisions. However, the direct light system is thick and unsuitable for a thin module, and requires a large number of light sources, which is expensive. Therefore, a sidelight system is generally used for a medium-sized notebook personal computer or monitor that is thin and does not require so high luminance.

A sidelight type backlight uses a light guide plate that changes a linear light source disposed on a side surface to a planar light source. A reflection plate is disposed on the back surface of the light guide plate, and a diffusion plate is disposed on the front surface. Conventionally, a linear cold cathode tube is often used as the light source, and this light source is provided at the edge of the light guide plate, so it is also referred to as an edge light type backlight.

In the backlight unit of the edge light type backlight, a side edge (side end surface) which is a light incident surface of a light guide plate made of acrylic resin or the like is arranged in parallel with the light exit surface of the linear lamp. However, with the increase in size of liquid crystal display devices such as liquid crystal televisions, the number of long linear lamps used tends to increase due to the lack of luminance and the requirement for homogeneity of light quantity.

This type of conventional backlight has a substantially U-shaped or semi-cylindrical lamp reflector with the side facing the light guide plate of the linear lamp arranged along the side end surface of the light guide plate extending over the entire length of the linear lamp. The reflection efficiency is increased, and the light emitted from the linear lamp is introduced into the light guide plate to illuminate the liquid crystal panel.

The light guide plate is, for example, a transparent acrylic plate, and a white reflecting plate is disposed on the back surface and a diffusion plate is disposed on the front surface. The backlight is provided on two opposing side end surfaces of the light guide plate, and one or two linear lamps are arranged.

Among these, the backlight currently disclosed by patent document 1 is demonstrated using FIG. The backlight 60 accommodates a linear lamp 61 disposed along a side end surface that is a light incident surface of a light guide plate (not shown) made of a transparent plate disposed on the back surface of the liquid crystal panel, and the linear lamp 61. The lamp reflector 62 having an opening on the side end surface of the light guide plate, and the linear lamp 61 with respect to the inner wall of the lamp reflector 62 is interposed between the inner wall of the lamp reflector 62 and the outer wall of the linear lamp 61. The lamp spacer 63 is held at a predetermined interval. The lamp reflecting plate 62 has a plurality of spacer locking holes 64 that face each other at a plurality of positions excluding the side end face of the light guide plate of the linear lamp 61. The lamp spacer 63 is provided with an interval restricting projection 631 that contacts the outer wall of the linear lamp 61 and a fitting portion 632 that fits into a spacer locking hole 64 formed in the lamp reflecting plate 62 so that the linear lamp is replaced with the lamp reflecting plate. It is held at a predetermined interval with respect to the inner wall. According to such a structure, the linear lamp is held by the lamp spacer attached to the lamp reflector instead of the O-ring, thereby simplifying the work of storing the linear lamp in the lamp reflector and the lamp reflector. In contrast, the linear lamp can be accurately installed.

In addition, when a set of two lamps provided along the side end surface of the light guide plate is used, both ends of the lamp are supported by rubber caps to maintain parallelism, but the lamp tube diameter is small and long. In large liquid crystal display devices, the lamp may warp or bend due to manufacturing variations or heat generated during operation, and the center of the lamp may come into contact with the reflective cover. Leakage current may occur and the brightness may decrease.

The backlight unit shown in Patent Document 2 below, as shown in the plan view of the main part of FIG. 7 (a), is attached in parallel to the side end surface of the rectangular flat light guide 71, and is lit at a high frequency at 15 KHz or higher. The two straight tube fluorescent lamps 75 and 76 arranged obliquely to each other, and the light of the fluorescent lamp which surrounds the outside of each of the straight tube fluorescent lamps and operates at high frequency is reflected on the side end surface of the light guide. A reflective cover 78 for condensing light is provided, and the fluorescent lamps 75 and 76 are partially bent around the outer periphery of the two straight tube fluorescent lamps 75 and 76 attached to the end face of the light guide. An insulating spacer 79 for preventing the lamp and the reflection cover 78 from coming into contact is mounted. As the insulating spacer 79, a short transparent ring such as a silicon pipe, an elastic ring or the like as shown in 791 and 792 of FIGS. 7B and 7C is used, and the distance between the fluorescent lamps 75 and 76 is kept constant. Combine functions. By preventing the reflection cover and the fluorescent lamp from coming into contact with each other, the luminance of the fluorescent lamp that operates at a high frequency is prevented from decreasing.

The structure of the backlight 60 disclosed in Patent Document 1 described above is that the OLED is not inserted into the linear lamp, but the lamp is reflected by holding the linear lamp with a spacer previously attached to the lamp reflector. It is intended to simplify the work of storing the linear lamp on the plate and to accurately install the linear lamp on the lamp reflector. For this reason, a spacer locking hole 64 must be formed in the lamp reflector 62, and a spacer 63 formed on the lamp reflector 62 and an interval restricting projection 631 that contacts the outer wall of the linear lamp 61. Since a fitting portion 632 that fits into the locking hole 64 must be provided and attached to the lamp reflector, there is a problem that the member becomes expensive.

In addition, the backlight unit disclosed in Patent Document 2 is a part of the fluorescent lamp partially around the outer periphery of the central portion of the two straight tube fluorescent lamps 75 and 76 attached to the end face of the light guide 71. An insulating spacer 79 for preventing the fluorescent lamps 75 and 76 and the reflection cover 78 from coming into contact with each other due to warpage is mounted. However, how to use the fluorescent tube when using three or more fluorescent lamps in a large liquid crystal display device. Nothing is disclosed about what to keep.

Furthermore, when using three or more fluorescent lamps on one side in a large liquid crystal display device, the distance between the lamps cannot be obtained with the oblique arrangement of the fluorescent lamps as shown in FIG. Other lamps get in the way and the reflection efficiency is poor, and it is difficult to obtain brightness. Therefore, when using three or more fluorescent lamps on one side, how to increase the light utilization efficiency, and because the back of the lamp reflector is flat or curved, it was routed to both ends through the back It is an unresolved problem to provide a backlight that solves how to disperse a large number of wirings for a fluorescent lamp, and to provide a spacer that can be efficiently attached to a large number of fluorescent lamps. Met.

JP 2002-203419 A Japanese Patent Laid-Open No. 7-272513

As a result of various studies to solve the above problems, the inventor of the present application pays attention to the fixing state and fixing means of the linear lamp, and three or more linear lamps and one end face of the light guide plate are close to each other. The above-mentioned problems can be solved by devising the arrangement of the linear lamps, the structure of the lamp reflector that fixes the linear lamps, and the shape of the insulating spacers that maintain the interval between the linear lamps. It has been found that the problem can be solved, and the present invention has been completed.

That is, the present invention relates to a lamp arrangement of a backlight. In particular, in a backlight of a large-sized liquid crystal display device using a linear cold cathode tube as a light source, the light guide plate efficiently utilizes the light emitted from the linear lamp. The purpose of this is to increase the brightness.

Also, the present invention provides a means for facilitating the fixing and wiring of the linear lamp in the assembly of the members, because it is easy to accurately place the linear lamp on the side end surface of the light guide plate of the backlight unit. Objective.

Furthermore, the present invention maintains an appropriate distance between the plurality of linear lamps in the insulating spacer, and prevents a decrease in luminance due to high frequency interference caused by the proximity of or contact between each linear lamp and the reflector. It is another object of the present invention to provide an insulating spacer for a linear lamp in a backlight unit, which does not require any special processing for producing a complicated mold or attaching a member to a reflector.

In order to solve the above problems, the invention according to claim 1 of the present application is directed to a light guide plate disposed on the back surface of the liquid crystal panel, and three or more linear lamps disposed along an end surface of the light guide plate. And a lamp reflector that is disposed so as to surround the linear lamp and reflects the light of the linear lamp toward the light guide plate, the center of the linear lamp with respect to the thickness direction of the end face of the light guide plate It is characterized in that the part of the linear lamp is arranged so as to be closer to the light guide plate side than the other linear lamps.

The invention according to claim 2 of the present application is characterized in that, in the backlight according to claim 1, the plurality of linear lamps is an odd number.

The invention according to claim 3 of the present application is the backlight according to any one of claims 1 to 2, wherein when the plurality of linear lamps are viewed from the end face side of the light guide plate, all the linear lamps are other. It is arranged so that it can be seen directly without being blocked by the lamp.

The invention according to claim 4 of the present application is the backlight according to any one of claims 1 to 3, wherein the lamp reflecting plate supports a back surface facing a plurality of linear lamps, and the back surface supports the light guide plate. And a back surface of the reflecting plate having a convex surface at the inner center along the longitudinal direction of the reflecting plate.

The invention according to claim 5 of the present application is the backlight according to any one of claims 1 to 4, wherein a longitudinal groove is formed on the back surface of the lamp reflector, and the linear lamp is formed in the groove. The connected cable is accommodated.

The invention according to claim 6 of the present application is the backlight according to any one of claims 1 to 4, further supporting the plurality of linear lamps and being fitted to both ends of the lamp reflector. A cap is disposed in the cap so that the support hole of the central linear lamp is closer to the light guide plate side than the support holes of the other linear lamps, and a recess is provided on the back of the cap. It is characterized by that.

Further, the invention according to claim 7 of the present application is the backlight according to any one of claims 1 to 4, further supported by an insulating spacer having elasticity in the middle in the length direction of the linear lamp, The spacer has a plurality of holes, and is arranged such that a central hole of the plurality of holes is closer to the light guide plate side than the other holes, and at least one of the plurality of holes is a through hole, The remainder is a hole having a split groove reaching the hole from the outer periphery.

The invention according to claim 8 of the present application is the backlight according to claim 7, wherein the insulating spacer is made of transparent silicon rubber having three or more holes corresponding to the number of linear lamps. It is characterized by that.

  According to the first aspect of the invention, the distribution of incident light from the linear lamp to the light guide plate of the backlight unit is uniform and can be used efficiently, and a high-quality backlight with high brightness can be obtained. When used in a large liquid crystal display device using a plurality of linear lamps as a backlight, a bright and high-quality liquid crystal display device can be obtained.

According to the invention according to claim 2 of the present application, since the plurality of linear lamps is an odd number, the arrangement of the linear lamps in the backlight is balanced.

According to the invention of claim 3 of the present application, the plurality of linear lamps are arranged so that all the linear lamps can be directly viewed without being blocked by other lamps when viewed from the end face side of the light guide plate. Therefore, other lamps do not interfere with the reduction of the reflection efficiency and it is difficult to obtain the brightness.

According to the invention according to claim 4 of the present application, the light reflecting surface of the linear lamp is widened because the back surface of the lamp reflecting plate has a reflecting surface that is convex in the center along the inner longitudinal direction of the reflecting plate. Self-absorbed light is reduced and reflected light can be used efficiently, and a higher-quality backlight with higher brightness can be obtained.

According to the fifth aspect of the present invention, since the cable to be wired to the linear lamp can be stored uniformly and compactly, the linear lamp and the lamp reflector can be easily assembled.

According to the sixth aspect of the present invention, the caps fitted to both ends of the lamp reflector can easily hold the distance between the linear lamps and the distance between the linear lamp and the lamp reflector at a predetermined value. Therefore, it is easy to accurately place the linear lamp on the side end surface of the light guide plate, the desired incident efficiency is obtained, and the luminance distribution of the surface light source emitted from the surface of the light guide plate is not uneven.

According to the invention of claim 7, since the insulating spacer having a specific shape is used, the interval between the linear lamps can be easily and accurately positioned and fixed, and the work efficiency of assembling the backlight is improved. At the same time, a high-quality backlight can be obtained. In addition, the arrangement of the linear lamps is maintained by insulating spacers, and the lamp reflectors surrounding each linear lamp and the lamp reflector surrounding each linear lamp are prevented from being too close or in contact with each other, thereby reducing the luminance due to leakage current when lit at a high frequency. Can be prevented. Further, it is possible to prevent the linear lamps from being damaged due to the collision between the linear lamps, and to protect the linear lamps against an external impact.

Furthermore, according to the eighth aspect of the present invention, it is possible to easily provide a backlight unit that fixes a distance between three or more linear lamps constant without adversely affecting the quality of the backlight light. it can.

As described above, according to the present invention, it is possible to appropriately arrange the linear lamp in the backlight with respect to the light guide plate, to effectively introduce and diffuse the emitted light into the light guide plate, and to position the linear lamp. As a result, the assembly of the members is facilitated, the production efficiency can be improved, and when used as a backlight of a liquid crystal display device, an excellent effect can be obtained.

  Embodiments of fixing a linear lamp to a lamp reflector in a backlight according to the present invention will be described below in detail with reference to the accompanying drawings.

That is, the backlight unit of the liquid crystal display device is not illustrated, but includes a prism sheet disposed on the back surface of the liquid crystal panel, a diffusion plate disposed on the front surface of the light guide plate, a rectangular flat acrylic light guide plate, and a light guide plate. Reflecting plates arranged on the back surface are combined, and linear lamps attached to the lamp reflecting plate are attached to two opposite side end surfaces of the light guiding plate so as to be parallel to the light guiding plate.

FIG. 1 is an exploded perspective view of a backlight 10 of the present invention attached to a side end surface of a light guide plate of a liquid crystal display device such as a large television, and FIG. 2 is a structural sectional view of the backlight 10 of FIG. . When the size of the liquid crystal display device becomes large, the luminance of one linear lamp is limited. Therefore, it is necessary to increase the number of linear lamps in the backlight. In FIGS. 1 and 2, three linear lamps are used. An example of using will be described.

The three linear lamps 11a to 11c, which are cold cathode tubes, are elongated straight tubes having a diameter of 1.8 to 3.0 mm and a length of 300 to 460 mm. After connecting the cable to the terminals at both ends of the linear lamp, the caps 12a and 12b made of silicon rubber are fitted, and the caps 12a and 12b are fixed to both ends of the lamp reflector 13 to fix the linear lamps 11a to 11c to the lamp reflector 13. Install to. An insulating spacer 14 is previously inserted in the hole in the center of the linear lamp 11a arranged in the center in the longitudinal direction, and the other two linear lamps 11b and 11c are also caps. When attaching to 12a, 12b, it is inserted into the hole of the insulating spacer 14, and the parallelism of the lamp is maintained by maintaining the interval.

The lamp reflecting plate 13 is formed by forming a metal plate having substantially the same length as that of the linear lamp, such as an aluminum plate, into a substantially U-shaped cross section, and attaching a reflecting sheet such as a silver vapor deposition sheet on the inner surface thereof. The lamp reflector 13 fixed so as to surround the linear lamp is attached with the U-shaped opening facing the side end face of the light guide plate. The lamp reflecting plate 13 has a back surface 130 that faces a plurality of linear lamps, and side surfaces 132 and 133 that support the back surface with respect to the light guide plate. The back surface 130 of the lamp reflecting plate has a length of the reflecting plate. It has a reflective surface that is convex at the center inside along the direction. That is, the back surface of the lamp reflecting plate 13 is provided with a continuous recess toward the inside of the U shape along the longitudinal direction, and a groove 131 is formed on the back surface.

Light emitted from the linear lamp 11 to the back side is reflected by the lamp reflecting plate 13 and guided to the light guide plate 17. When three linear lamps 11 a to 11 c are accommodated in the lamp reflecting plate 13, The reflected light from the lamp may be blocked by other linear lamps. Therefore, the lamp reflector 13 of the present invention has a groove 131, and the shape of the groove 131 is designed to efficiently reflect light from the linear lamps 11a to 11c toward the light guide plate 17 side. In this embodiment, the three surfaces constituting the groove 131 are substantially flat, the surface facing the central linear lamp 11a is disposed substantially parallel to the end surface of the light guide plate 17, and the other two surfaces are guided. It arrange | positions so that it may incline with respect to the end surface of the optical plate 17. FIG. The inclination direction of this surface is set so that the width of the groove 131 becomes narrower toward the light guide plate 17 side. Since the surface facing the central linear lamp 11a is formed substantially parallel to the end surface of the light guide plate 17, the light from the linear lamp 11a is reflected by this surface and is reflected on the other linear lamps 11b and 11c. It is guided to the light guide plate 17 without being obstructed. Moreover, since the surface located adjacent to the linear lamps 11b and 11c in the groove 131 is inclined toward the light guide plate 17, the light from the linear lamps 11b and 11c is efficiently transmitted to the light guide plate 17 side by this surface. Reflected. In this groove 131, a plurality of cables 15a, 15b, 15c attached to one end of each linear lamp are accommodated, drawn to the other end through the outside of the lamp reflector 13, and a cap at the other end of the linear lamp. The cable 15d, 15e, 15f connected to the other end of the linear lamp through the hole 121 of 12b and pulled out from the other end is pulled out from the front face of the cap and distributed, and connected to the connectors 16a, 16b. . The plurality of cables 15a, 15b, and 15c may be not only passed through the groove 131 but also fixed to the groove with an adhesive or the like.

The backlight unit 10 will be described. The caps 12a, 12b made of silicon resin fitted in the lamp reflector 13 are arranged with holes to which the linear lamps 11a, 11b, 11c are attached, and the support hole 122a in the center is formed. Close to the light guide plate 17 side, the support holes 122b and 122c on both sides are arranged to recede. For this reason, as shown in FIG. 2, among the three linear lamps provided on the lamp reflector 13, the central linear lamp 11a is closer to the light guide plate 17 side than the other linear lamps 11b and 11c. 3 and the back surface of the lamp reflector 13 is formed with a groove 131, and the groove wall is convexly inclined inward, and the back surface has the same flat width shown in FIG. Compared to the comparative sectional view arranged on the same surface of the lamp reflector, the distance between the linear lamps becomes longer and the reflecting surfaces of the lamps on both sides become wider. As a result, the emitted light of each lamp is efficiently incident on the light guide plate 17 without being absorbed by the lamp itself. In addition, in the back surface of the caps 12 a and 12 b fitted to both ends of the lamp reflecting plate 13, recesses that match the grooves of the lamp reflecting plate 13 are provided. In FIG. 2, reference numeral 18 denotes a diffusion plate, and reference numeral 19 denotes a reflection plate. In FIG. 3, the same parts as those in FIG.

FIG. 4 shows a plan view of the insulating spacer 14 used in the present invention.
An intermediate center portion in the length direction of each linear lamp 11a, 11b, 11c is supported by an insulating spacer 14 having elasticity having a plurality of holes 141a, 141b, 141c. At least one of the holes in the insulating spacer, in this case, the central hole 141a is a through hole, and the other holes 141b and 141c are holes having split grooves 142a and 142b reaching the holes from the outer periphery. The insulating spacer 14 is arranged such that the central hole 141a is closer to the light guide plate than the other holes 141b and 141c. The insulating spacer 14 is preferably made of transparent silicon rubber so as not to hinder the emission of light from the linear lamp. If only one linear lamp is inserted by providing the dividing groove, the other lamp can be easily mounted by fitting an insulating spacer after being assembled to the cap. A recess 143 is formed on the back surface of the insulating spacer 14 so as to fit in the groove on the back surface of the lamp reflector 13.

Even if the insulating spacer 14 is warped or bent in a set of three linear lamps 11a, 11b, and 11c due to heat generation or the like, the insulating spacer in the center of each linear lamp is a metal reflecting sheet ( It is possible to prevent direct contact between the linear lamp and the metal reflection sheet. For this reason, it does not cause the occurrence of high-frequency leakage current due to excessive proximity or direct contact between the linear lamp and the metal reflection sheet, and there is no possibility of a decrease in luminance of the linear lamp.

In addition, since the insulating spacer 14 keeps the distance between the lamps constant at the center in the longitudinal direction of the three linear lamps, it is possible to prevent damage due to the collision between the linear lamps. It is possible to protect the linear lamp against the impact force of and prevent the breakage. A plurality of insulating spacers may be used at intervals depending on the length of the linear lamp.

The insulating spacer 14 is preferably transparent in order to improve the light utilization efficiency of the linear lamp. However, if an insulating spacer having an axial thickness of 2 mm or less is used, the luminance of the light guide plate 17 is hardly affected. do not do.

FIG. 5 shows a plan view of another embodiment of the insulating spacer. This insulating spacer 14 'is used for a linear lamp of a backlight having a set of five, and the support hole is centered on a hole 141a' having a central kerf disposed closest to the light guide plate. Further, the holes 141d 'and 141e' at both ends having the kerfs are arranged in an arc shape gradually away from the light guide plate with the through holes 141b 'and 141c' having no kerfs therebetween. The holes at the center and both ends have slits that reach the holes. In this structure, two linear lamps can be inserted and the other linear lamps can be inserted later. is there. In this case, it goes without saying that the holes of the caps fitted to both ends of the linear lamp are similarly arranged in an arc.

In the above-described embodiments, the lamp reflector is described as having a U-shaped cross section. However, the lamp reflector is not limited to a U-shaped lamp, and the lamp reflector is not limited to a semicircular, semi-elliptical or parabolic shape. The invention is equally applicable.

The embodiments of the present invention have been described above with reference to the drawings. However, the embodiment described above is an example of a fixing device in a liquid crystal display device for embodying the technical idea of the present invention, and is not intended to specify the present invention in this embodiment. The present invention can be equally applied to various modifications without departing from the technical idea shown in the claims.

FIG. 1 is an exploded perspective view showing the structure of the backlight of the backlight unit of the present invention. FIG. 2 is a structural cross-sectional view of the backlight of FIG. FIG. 3 is a structural sectional view of a backlight which is a comparative example of FIG. FIG. 4 is a plan view of an insulating spacer used in the present invention. FIG. 5 is a plan view of another embodiment of the insulating spacer. FIG. 6 is an exploded perspective view showing a structure of a backlight in a conventional liquid crystal display device. FIG. 7A is a partially cutaway plan view of a conventional backlight unit, and FIGS. 7B and 7C are perspective views for explaining a conventional insulating spacer. FIG. 8 is an enlarged sectional view taken along line AA in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Backlight 11a, 11b, 11c Linear lamp 12a, 12b Cap 13 Lamp reflecting plate 14, 14 'Insulating spacer 15a, 15b, 15c Cable 16a, 16b Connector 17 Light guide plate 18 Diffusing plate 19 Reflecting plate 131 Groove

Claims (6)

A light guide plate, three or more linear lamps arranged along the end face of the light guide plate, and a lamp reflector that is arranged so as to surround the linear lamp and reflects light of the linear lamp to the light guide plate side In the backlight having, the linear lamp in the central portion with respect to the thickness direction of the end face of the light guide plate among the linear lamps is arranged closer to the light guide plate side than the other linear lamps ,
The lamp reflector has a back surface facing a plurality of linear lamps, and a side surface that supports the back surface with respect to the light guide plate, and the back surface is a reflection that protrudes toward the inner center along the longitudinal direction of the reflector plate. A backlight characterized by having a surface . The backlight according to claim 1 , wherein a longitudinal groove is formed on a back surface of the lamp reflector, and a cable connected to the linear lamp is accommodated in the groove. The cap includes a cap that supports the plurality of linear lamps and is fitted to both ends of the lamp reflecting plate, and the cap has a support hole for the linear lamp in the central portion, and a support hole for another linear lamp. The backlight according to claim 1 , wherein the backlight is disposed so as to be closer to the light guide plate side, and a recess is provided on the back surface of the cap. The middle in the longitudinal direction of the linear lamp is supported by an insulating spacer having elasticity, and the spacer has a plurality of holes, and the central hole of the plurality of holes is closer to the light guide plate than the other holes. are arranged so as to approach to, in at least one through-hole of the encapsulating number of holes, the remaining is claimed in claim 1 or 2, characterized in that a hole having a split groove reaching the hole from the outer periphery Back light. 5. The backlight according to claim 4, wherein the insulating spacer is made of transparent silicon rubber having three or more holes corresponding to the number of linear lamps. A liquid crystal display device in which the backlight according to claim 1 is disposed on a back surface.

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