JP4188450B2 - Light source and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light source for projecting linear illumination light using a plurality of light emitting elements and a method for manufacturing the same, and is particularly suitable as a backlight illumination light source for a transmissive liquid crystal display device.
[0002]
[Prior art]
A light source using a light emitting element such as a light emitting diode is extremely effective as a low power consumption light source replacing a cold cathode tube, particularly as a backlight illumination light source of a small transmissive liquid crystal display device.
[0003]
As an example of such a light source, one disclosed in Japanese Utility Model Publication No. 4-14943 is known. In this case, a light emitting diode is accommodated in a rectangular cup-shaped reflection case, and a plurality of the light-emitting diodes are embedded in opposite ends at both ends in the longitudinal direction of an elongated diffusion plate. According to this, the light projected from the light emitting diode spreads over the entire area of the diffusion plate while reflecting the inside along the longitudinal direction of the diffusion plate, and finally is emitted almost uniformly from the surface.
[0004]
Further, as an improvement of this, a rectangular cup-shaped reflection case having a long length and a plurality of light emitting diodes arranged at predetermined intervals is also considered.
[0005]
[Problems to be solved by the invention]
Since the conventional light source disclosed in Japanese Utility Model Publication No. 4-14943 contains one light emitting diode in one reflecting case, when forming a linear light emitting diode array corresponding to a cold cathode tube, It was necessary to connect the individual reflective cases in series. For this reason, the side walls of the reflection case are interposed between the adjacent light emitting diodes, which restricts the shortening of the arrangement pitch of the light emitting diodes, and also the arrangement direction of the light emitting diodes due to the presence of the side walls between the adjacent light emitting diodes. There is a drawback that unevenness of the light amount distribution occurs along the line.
[0006]
Moreover, as disclosed in Japanese Utility Model Publication No. 4-14943, in the type of light source in which the light source is embedded in the side end portion of the diffusion plate, the light projected from the light emitting diode is blocked by the side wall of the reflection case, Since the amount of light reaching the diffusion plate located on the side of the light source is insufficient, it cannot be used as a display part of the display device, and there is a possibility that the compactness of the display device may be hindered.
[0007]
On the other hand, a rectangular cup-shaped reflective case with a plurality of light emitting diodes arranged at a predetermined interval can avoid the above-mentioned problems, but a transparent mold is provided in the cup-shaped reflective case. When the agent is filled and solidified, there is a problem that the influence of shrinkage stress along the longitudinal direction appears greatly, and the cup-type reflection case is warped and curved.
[0008]
In addition, the light projected from each light emitting diode is basically omnidirectional, and the light amount tends to attenuate in inverse proportion to the square of the distance from the light emitting diode. When this is used as an illumination light source, a plurality of light sources must be arranged opposite to each other at both ends in the longitudinal direction of the display device, and the advantage as a low power consumption light source is impaired and the display device is made compact. Will be inhibited.
[0009]
OBJECT OF THE INVENTION
An object of the present invention is to provide a light source capable of shortening the arrangement pitch of the light emitting elements and effectively controlling the directivity of light projected from the light emitting elements, and a method for manufacturing the same.
[0010]
Another object of the present invention is to provide a light source that is particularly effective as a backlight illumination light source for a small and long transmissive liquid crystal display device and a method for manufacturing the same.
[0011]
[Means for Solving the Problems]
First embodiment according to the present invention, have a pair of side walls a rectangular bottom plate portion and rising from both side edges of the bottom plate portion, and an opaque insulating casing groove-shaped longitudinal ends are open, the A pair of leads provided at both longitudinal ends of the bottom plate portion of the insulating casing, and both ends of the pair of leads are coupled to the pair of leads extending along the longitudinal direction of the bottom plate portion of the insulating casing. A lead frame, a plurality of light emitting elements joined on the lead frame at a predetermined interval along the longitudinal direction of the lead frame, and the pair of side wall portions of the insulating casing so as to fill the light emitting elements a light source equipped with a transparent mold material filled in the gap, the upper end of the pair of sidewall portions, alternately to shape forming a circular arc-shaped convex portion opposed to each other and the recesses in a continuous curved surface Waveform No, the convex portion is equal to or number of the light emitting element, or is formed more, the light emitting element is characterized by being located respectively between said protrusions opposed to each other.
[0012]
According to the present invention, the light emitting element emits light by connecting the pair of leads to the power source, and the light projected from the light emitting element is caused in the longitudinal direction of the insulating casing by the collimating action of the molding agent interposed in the convex portion. The light beam substantially corresponds to the width of the projecting portion along the light and is emitted in a direction substantially perpendicular to the bottom plate portion. Moreover, the light from the light emitting elements located on both sides in the longitudinal direction of the insulating casing is emitted from between the pair of side wall portions along the bottom plate portion of the insulating casing. The light emitted from the concave portion is emitted in a diffused state along the pair of side wall portions by the light diffusion action of the molding agent interposed in the concave portion.
[0013]
On the other hand, the second embodiment according to the present invention, have a pair of side walls a rectangular bottom plate portion and rising from both side edges of the bottom plate portion, and an opaque insulating casing groove-shaped longitudinal ends are open A pair of leads provided at both ends in the longitudinal direction of the bottom plate portion of the insulating casing, and both ends coupled to the pair of leads extending along the longitudinal direction of the bottom plate portion of the insulating casing A plurality of light emitting elements joined to the lead frame at predetermined intervals along the longitudinal direction of the lead frame, and the pair of side wall portions of the insulating casing so as to fill the light emitting elements. A method of manufacturing a light source comprising a transparent mold agent filled in a sandwiched gap, the viscosity between the pair of side walls of the insulating casing to which the light emitting element is bonded Is characterized in that comprises a step of solidifying is filled with a transparent mold material in the range of 550~800cp at 25 ° C..
According to the present invention, when the viscosity of the molding agent is lower than 550 cp at 25 ° C., it flows down from both longitudinal ends of the insulating casing, making it difficult to hold the molding agent between the pair of side wall portions. On the other hand, if the viscosity of the molding agent is higher than 800 cp, it becomes difficult to cause the molding agent to flow between the pair of side wall portions over the entire longitudinal direction of the insulating casing, and workability is significantly reduced.
[0014]
According to the present invention, when the viscosity of the molding agent is lower than 550 cp at 25 ° C., it flows down from both longitudinal ends of the insulating casing, making it difficult to hold the molding agent between the pair of side wall portions. On the other hand, if the viscosity of the molding agent is higher than 800 cp, it becomes difficult to cause the molding agent to flow between the pair of side wall portions over the entire longitudinal direction of the insulating casing, and workability is significantly reduced.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the light source according to a first embodiment of the present invention, there radius of curvature of the convex portion is in the range of 0.8～3Mm, range height extending from the lower end of the recess to the upper end of the convex portion of the 0.3~1.5mm It is preferable to be within. It is also effective to color the molding agent in order to adjust the hue of light projected from the light emitting element. The casing may be formed of a white resin having good reflectivity with respect to the light projected from the light emitting element, and generally a light emitting diode can be adopted as the light emitting element.
[0016]
【Example】
An embodiment in which the light source according to the present invention is applied to a backlight illumination light source of a transmissive liquid crystal display device will be described in detail with reference to FIGS. 1 to 3, but the present invention is not limited to such an embodiment. It can also be applied to technologies in other fields that contain similar problems.
[0017]
As shown in FIG. 1 representing the front shape of the present embodiment, FIG. 2 representing the planar shape thereof, and FIG. 3 representing the right side shape thereof, the insulating casing 11 having a groove shape includes a rectangular bottom plate portion 12, The lead frame 15 has a pair of side wall portions 13 rising from both side edge portions of the bottom plate portion 12, and the lead frame 15 is against the insulating casing 11 by the holding portions 14 formed at the corners of the bottom plate portion 12 and the side wall portions 13. It is molded integrally. Both ends in the longitudinal direction of the lead frame 15 are exposed on the back side of the bottom plate portion 12 to form a pair of leads 16 and 17. On the lead frame 15, a plurality of (four in this embodiment) light emitting elements 18 such as LEDs are bonded at a constant interval, for example, an interval of about 9 mm, and these light emitting elements 18 are in the longitudinal direction of the lead frame 15. Is located in the middle of the pressing portions 14 adjacent to each other. A space formed between the pair of side wall portions 13 of the insulating casing 11 is filled with a transparent molding agent 19, and the light emitting element 18 is embedded with the molding agent 19.
[0018]
The pair of side wall portions 13 in the present embodiment has an inner method set to about 1 mm, and alternately has convex portions 20 and concave portions 21 whose upper ends are corrugated by a continuous curve. The radius of curvature r of the convex portion 20 is in the range of 0.8 to 3 mm, and the height h from the lower end of the concave portion 21 to the upper end of the convex portion 20 is in the range of 0.3 to 1.5 mm. In addition, the light emitting element 18 in the present example is disposed in an offset state at a position that is approximately ½ of the curvature radius r of the convex portion 20 toward the bottom plate portion 12 from the upper end of the convex portion 20. You may make it make the optical axis of the light emitting element 18 correspond on the surface which connects the upper end of the convex part 20, and its curvature center O. FIG.
[0019]
In order to improve the reflectivity of the light projected from the light emitting element 18 to the insulating material such as the liquid crystal polymer made of modified polyamide, polybutylene terephthalate, aromatic polyester, or the like as the insulating casing 11 described above, and at the same time obtain light shielding properties. A mixture of white powder such as barium titanate can be used.
[0020]
Further, the molding agent 19 is formed of an ultraviolet curable epoxy resin or the like, and dispenser from the vicinity of the upper end of the convex portion 20 is slightly larger than the volume of the gap sandwiched between the pair of side wall portions 13 in consideration of shrinkage at the time of curing. It injects | pours using a syringe etc., It matches with the waveform of the side wall part 13 using the viscosity and surface tension. For this reason, the viscosity of the molding agent 19 at the time of injection is preferably in the range of 550 to 800 cp at 25 ° C., and in this embodiment, an ultraviolet curable epoxy resin having a viscosity of 680 cp at 25 ° C. is used. That is, when the viscosity of the molding agent 19 is lower than 550 cp at 25 ° C., the molding agent 19 flows down from both longitudinal ends of the insulating casing 11 and it becomes difficult to hold the molding agent 19 between the pair of side wall portions 13. . On the other hand, if the viscosity of the molding agent 19 is higher than 800 cp, it becomes difficult to cause the molding agent 19 to flow between the pair of side wall portions 13 over the entire length of the insulating casing 11, and workability is improved. It drops significantly.
[0021]
In this embodiment, since the insulating casing 11 has a groove shape with both ends in the longitudinal direction opened, it is possible to relieve the shrinkage stress of the molding agent 19 warped in the longitudinal direction when the molding agent 19 is cured. Therefore, it is possible to reduce product shape errors such as warpage as compared with the conventional one.
[0022]
Accordingly, the light L projected from the light emitting element 18 is emitted as a light beam parallel to the straight line connecting the center of curvature O of the convex portion 20 and the light emitting element 18 due to the collimating lens effect of the convex portion 20, and is emitted. Since the attenuation of the light amount due to the distance from the element 18 can be reduced, it is possible to function effectively even if only one side is provided as a backlight light source of an elongated transmissive liquid crystal display device, and low power consumption is intended. obtain. Further, the light reaching the concave portion 21 from the light emitting element 18 is totally reflected here and returns to the bottom plate portion 12 side of the insulating casing 11, but is finally emitted from the surface of the molding agent 19. In this case, since the light is emitted from both sides in the longitudinal direction of the insulating casing 11, it can be used as a display portion of the transmissive liquid crystal display device, and the transmissive liquid crystal display device can be made compact.
[0023]
In the embodiment described above, four pairs of the convex portions 20 are formed corresponding to the number of the light emitting elements 18, but the number of the convex portions 20 is not necessarily the same as the number of the light emitting elements 18, and is more than the number of the light emitting elements 18. It is good also as a light source which forms many and has the location which does not interpose the light emitting element 18 between the convex parts 20 which oppose. This is effective when a light source having a different number of light emitting elements 18 is also used as a single insulating casing.
[0024]
【The invention's effect】
According to the light source of the present invention, since the plurality of light emitting elements are arranged in one insulating casing, the arrangement pitch of the light emitting elements can be reduced to the minimum, and a high-luminance linear light source can be obtained. Is possible.
[0025]
In addition, since the corrugated convex portions and concave portions corresponding to the arrangement pitch of the light emitting elements are formed in the pair of side wall portions, the collimating action of the molding agent in which the light projected from the light emitting elements is interposed in the convex portions causes the insulating casing to A light beam substantially corresponding to the width of the convex portion along the longitudinal direction can be emitted in a direction substantially perpendicular to the bottom plate portion. For this reason, the amount of attenuation of light along the emission direction can be greatly reduced as compared with the conventional one. When this is used as a backlight light source of an elongated transmission type liquid crystal display device, it is used on both sides of the elongated diffusion plate. Therefore, it is possible to reduce the power consumption of the backlight light source.
[0026]
Furthermore, since the insulating casing is formed in a groove shape, light from the light emitting element can be emitted from three directions other than the bottom plate portion and the pair of side wall portions, that is, both front and left and right sides, and a light shielding sheet or the like becomes unnecessary. Cost and productivity can be improved. In addition, since the shrinkage stress of the molding agent warped in the longitudinal direction of the insulating casing can be relieved, it is possible to reduce product shape errors such as warpage as compared with the conventional one.
[Brief description of the drawings]
FIG. 1 is a front view illustrating an appearance of an embodiment of a light source according to the present invention.
FIG. 2 is a plan view of the embodiment shown in FIG.
FIG. 3 is a side view of the embodiment shown in FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Insulating casing 12 Bottom plate part 13 Side wall part 14 Holding part 15 Lead frame 16, 17 Lead 18 Light emitting element 19 Molding agent 20 Convex part 21 Concavity r The curvature radius h of a convex part The height from the lower end of a concave part to the upper end of a convex part O Center of curvature of convex part

Claims (4)

Have a pair of side wall portions rising from a rectangular bottom plate portion and both side edge portions of the bottom plate portion, and an opaque insulating casing groove-shaped longitudinal ends are open, longitudinal of the bottom plate portion of the insulating casing A pair of leads provided at both ends in the direction, a lead frame extending along the longitudinal direction of the bottom plate portion of the insulating casing and having both ends coupled to the pair of leads, and a length of the lead frame A plurality of light emitting elements joined at predetermined intervals on the lead frame along the direction, and a transparent mold filled in a gap sandwiched between the pair of side wall portions of the insulating casing so as to fill the light emitting elements A light source comprising an agent,
The upper end of the pair of side wall portions, forms a waveform that forms form alternately an arcuate convex portion opposed to each other and the recesses in a continuous curved surface, the convex portion is equal to or number of the light emitting element, Alternatively, the light source is formed more than that, and the light emitting elements are respectively positioned between the convex portions facing each other.   The light source according to claim 1, wherein the light emitting element is disposed at a substantially intermediate position between an upper end of the convex portion and a center of curvature thereof. The radius of curvature of the convex portion is in the range of 0.8 to 3 mm, and the height from the lower end of the concave portion to the upper end of the convex portion is in the range of 0.3 to 1.5 mm. The light source according to claim 1 or 2 . Have a pair of side wall portions rising from a rectangular bottom plate portion and both side edge portions of the bottom plate portion, and an opaque insulating casing groove-shaped longitudinal ends are open, longitudinal of the bottom plate portion of the insulating casing A pair of leads provided at both ends in the direction, a lead frame extending along the longitudinal direction of the bottom plate portion of the insulating casing and having both ends coupled to the pair of leads, and a length of the lead frame A plurality of light emitting elements joined at predetermined intervals on the lead frame along the direction, and a transparent mold filled in a gap sandwiched between the pair of side wall portions of the insulating casing so as to fill the light emitting elements A method of manufacturing a light source comprising an agent,
A step of filling and solidifying a transparent molding agent having a viscosity in the range of 550 to 800 cp at 25 ° C. between the pair of side walls of the insulating casing to which the light emitting element is bonded is provided. A method for manufacturing a light source.

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