JPH09138402A - Led back light device for illuminating liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the reduction of the light quantity of an emitting surface, to enhance luminance, to include an emphasis display and the like, to prevent luminance irregularity from occurring and to prevent dust and the like from entering from a gap. SOLUTION: Light emitted from an LED chip 26 mounted on a printed circuit board 20 is guided by light guides 60 and 50 and used as the back light of a liquid crystal display device. The guides 40 and 50 are partitioned by a partition plate 19 in order to guide the different-color back light. The plate 19 is integrally formed as one part of a reflection case 10 provided with a bottom 11 and a side wall 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an L for a liquid crystal display device.
The present invention relates to an ED backlight device, and more particularly, to an LED backlight device installed on the back surface of a liquid crystal display device and capable of multi-color split display of the liquid crystal display device.

[0002]

2. Description of the Related Art FIG. 10 shows an L for illuminating a conventional liquid crystal display device.
1 illustrates an ED backlight device. A conventional LED backlight device for illuminating a liquid crystal display device includes an LED light emitter unit 120 that emits a backlight and a transparent or semitransparent plate 130 that guides the backlight.
The LED luminous body unit 120 has a substantially rectangular reflection case 80 having a recess, an electrode plate 100 disposed in the recess of the reflection case 80, an external lead 90 integrally formed with the electrode plate 100, and an electrode. It comprises a light emitting diode chip 110 mounted on a plate 100.

The plate 130 is made of rectangular plastic and has a fitting groove 140 along which two opposite sides are fitted with the LED light emitting unit 120. In the LED light emitter unit 120, the emission surface for emitting backlight light is directed to the inner side surface of the plate body 130, and the fitting groove 14 of the plate body 130 is provided.
It is fitted with 0. In the above LED backlight device, when a predetermined voltage is applied to the external lead 90, the light emitting diode chip 110 emits light, and together with the reflection of the reflection case 80, the backlight light is emitted from the emission surface of the backlight light. The backlight light emitted from the emission surface enters the plate body 130 and is guided inside the plate body 130. As a result, the entire surface of the plate body 130 becomes an illumination plate.
A liquid crystal display device (not shown) is provided on the emission surface of the plate body 130. Therefore, the display content of the liquid crystal display device is displayed by the backlight light emitted from the plate body 130.

[0004]

However, the conventional LED
According to the backlight device, the LED light emitter unit 12
The LED light emitted from 0 is partially reflected from the contact surface between the plate 130 and the LED light emitter unit 120, and
Since the LED light transmitted through this contact surface is emitted to the outside from the side surface of the plate 130, the amount of light is reduced and the brightness is reduced.
In addition, since the backlight of the plate 130 is inevitably a single color or a mixed color, it is impossible to incorporate highlighting or the like into the display content of the liquid crystal display device. Further, since the light emitting diode chip 110 functions as a point light source, the plate 130 has uneven brightness. In addition, since the LED light emitter unit 120 is configured to fit in the fitting groove 140, dust, dust, etc. may enter the gap.
Therefore, the object of the present invention is to suppress the decrease in the amount of light, improve the brightness, incorporate highlighting, etc. to achieve a variety of displays, and use a light-emitting diode to approximate a surface light source to reduce uneven brightness. An object of the present invention is to provide an LED backlight device for illuminating a liquid crystal display device, which is capable of preventing invasion of dust, dust and the like and improving dust resistance.

[0005]

SUMMARY OF THE INVENTION The present invention suppresses a decrease in light amount, improves brightness, incorporates highlighting, etc.,
A backlight is provided on the back of the liquid crystal display device in order to improve the display diversity and prevent uneven brightness by approximating a surface light source while using light emitting diodes and suppressing dust and dust to improve dust resistance. In an LED backlight device for illuminating a liquid crystal display device that emits light, the light emitting plate is formed of a light-transmissive plate-shaped member, and has an emission surface that emits the backlight to the back surface of the liquid crystal display device. A light guide, a light-reflecting reflective case that surrounds the light guide except for the emission surface of the light guide, and a plurality of LEs that are arranged on the inner side surface of the reflective case and supply emission light to the light guide.
Provided is an LED backlight device for illuminating a liquid crystal display device, which includes a printed circuit board on which a D chip is mounted. The reflect case has at least two of the light guides.
It is desirable to have a partition that divides into one exit surface.
It is preferable that the light guide has a gradation pattern composed of regular fine irregular patterns on the surface opposite to the emission surface. The plurality of LED chips are covered with a molding resin molded into a lens shape,
It is preferable that the light guide is formed into a lens shape complementary to the mold resin on the surface facing the mold resin. The plurality of LED chips supply emission light of a first color to at least one emission surface of the at least two emission surfaces of the light guide,
It is desirable to supply the emission light of the second color to the remaining emission surface. The light guide may be covered with a tape member that reflects the emitted light inward at an end portion to which the emitted light is supplied from the plurality of LED chips and prevents the emitted light from leaking to a non-illuminated portion. desirable.

[0006]

1 to 9 show a first embodiment of an LED backlight device for illuminating a liquid crystal display device. FIG. 1 shows an LED backlight device for illuminating a liquid crystal display device. An LED backlight device for illuminating a liquid crystal display device includes light guides (transparent or translucent acrylic resin) 40 and 50 formed of a light-transmissive plate-shaped member having an emission surface for emitting the backlight, and the emission. Light guides 40 and 50, except for the surface, with a light-reflective bottom 1
It has a box-shaped reflect case (white) 10 having a partition plate 19 for partitioning 1, the side wall 12, and the light guides 40 and 50. External leads 2 for supplying power to a printed circuit board 20 on which LED chips to be described later are mounted
2, 23, and 24 are the bottom 11 of the reflective case 10.
External leads (not shown) for supplying power also project to the substrate 30 on the opposite side. Concave lens cuts 45, 46, and 54 are formed in the light guides 40 and 50, and a light-shielding tape (white) 60 extends from the printed circuit board 20 to the light guides 40 and 50 and a light guide from the printed circuit board 30. A light-shielding tape (white) 70 is provided over 40. The side wall 12 of the reflect case 10 has a key groove 13 and is provided at the boundary between the bottom 11 and the side wall 12.
5 and 16.

In FIG. 2, an emitting portion for emitting LED light from the LED chip 26 to the light guide 40 is shown. The LED chip 26 is mounted on the printed circuit board 20 covered with a white resist, is connected to the external lead 22 for supplying power, and is covered with the lens 28 molded in a convex shape by the surface tension according to the viscosity of the molding resin. Has been done. In the light guide 40 that receives the supply of the emitted light,
A gradation 47 having a regular fine uneven pattern is provided. The printed circuit board 20 is fitted into the lead hole 18 of the reflect case 10 composed of the bottom 11 and the side wall 12, and is held by the stopper 41 of the light guide 40. The light shielding tape 60 is attached from the printed circuit board 20 to the light guide 40.

FIG. 3 shows a printed circuit board 20 on which three LED chips 26 having an emission color of yellow green and two LED chips 27 having an emission color of standard red are mounted. The printed circuit board 20 includes stoppers 41 and 51 of the light guides 40 and 50.
An insulating substrate 29 having a notch key 29a for engaging with LE,
It has copper foil wiring 21 for connecting the D chip and external leads 22, 23, and 24 for power supply. Further, a recognition mark 25 for mounting an LED chip is provided. As shown in FIG. 2, the LED chips 26 and 27 are covered with a lens 28 formed into a lens shape.

FIG. 4 is a printed circuit board 30 on which four LED chips 36 having a yellow-green color are mounted.
Is shown. The printed circuit board 30 includes a cutout key 3 that engages with a stopper 41 of a light guide 40 on an insulating substrate 38.
It has an insulating substrate 29 having 8a, a copper foil wiring 31 for connecting the LED chip, and external leads 32, 33, and 34 for power supply. Further, a recognition mark 35 for mounting the LED chip is provided. Like the LED chips 26 and 27, the LED chip 36 is covered with a lens 37 formed in a lens shape. The external lead 33 for power supply is a dummy terminal.

FIG. 5 shows a light guide 40 having a flat plate-shaped main body 48, and stoppers 41, 41
Claws (engagement) 42, keys 43, protrusions 44 (engagement), and lens cuts 45 and 46 having a shape that receives the supply of emitted light.
And a gradation 4 consisting of regular fine irregular patterns
7 are formed. The protrusions 44 are rectangular fitting members having a size of several millimeters, which are arranged in two places on the left and right with the long side surface of the light guide 40 as the center. The key 43 is a protrusion formed by the mold resin injection hole of the molding die when the light guide 40 is molded.

FIG. 6 shows a light guide 50 having a flat plate-shaped main body 56, and stoppers 51,
The tabs 52, the keys 53, the lens cuts 54 having a shape to receive the emitted light, and the gradations 55 having a regular fine uneven pattern are formed. The key 53 is the same as the key 43.

FIG. 7 shows the reflect case 10, which is composed of a bottom 11, a side wall 12, and a partition plate 19 surrounded by the bottom 11 and the side wall 12 to divide the light guide accommodation space into two parts. ing. Further, the reflect case 10 has key grooves 13 and 14 for receiving the keys 43 and 53 of the light guides 40 and 50,
The recesses 15 and 16 and the lead holes 17 and 18 for fitting the printed circuit board on which the LED chip is mounted are prepared. KUBOMI 15 and 16 have side walls 12
2 on the long side of the and the boundary of the bottom 11, 2 on the opposite side,
Also, provided on the long side of the partition plate 19, the dents at five places are long holes of several millimeters. There are one key groove 13 and 14 on each long side of the side wall 12, one on the short side of the partition plate 19,
Symmetrically cut out from the center of each side into a rectangle with a size of a few millimeters.

FIG. 8 is a circuit diagram showing the connection of the LED chip 26 having the emission color of yellow green and the LED chip 27 having the emission color of standard red. The circuit includes three LED chips 26 in series, two LED chips 27 in series, an anode side of the three LED chips 26 in series, and an outside commonly connected to the anode side of the two LED chips 27 in series. It is composed of a lead 23, an external lead 22 connected to the cathode side of three LED chips 26 in series, an external lead 24 connected to the cathode side of two LED chips 27 in series, and a copper foil wiring 21. ing.

FIG. 9 is a circuit diagram showing the connection of the LED chips 36 having the emission color of yellow green. The circuit is composed of four LED chips 36 in series, external leads 32 connected to the anode side of both ends thereof, external leads 34 connected to the cathode side, and copper foil wiring 31. As described above, the external lead 33 is a dummy terminal that is not connected to the copper foil wiring 31.

Hereinafter, the LED for illuminating the liquid crystal display device of the present invention
A method for manufacturing the backlight device will be described. The reflect case 10 having the key grooves 13 and 14, the recesses 15 and 16, the lead holes 17 and 18 is manufactured by a molding die using a white heat-resistant ABS resin. Reflect case 1 removed from the mold
In the case of 0, the bottom 11, the side wall 12, and the reflecting surface of the partition plate 19 are mirror-finished by the transfer of the polished surface of the molding die. The printed circuit board 20 is manufactured by printing a copper foil wiring 21 for connection, external leads 22, 23 and 24 for power supply, and an identification mark 25 for mounting an LED chip on an insulating substrate 29 made of glass epoxy. To be done. In this printed board 20, a copper foil is attached to an insulating substrate 29, exposed and developed with a mask pattern, and unnecessary portions are etched to form a copper pattern. Further, except for the gold-plated portion for bonding, a white resist is coated in a thin film shape, and the portion without the resist is gold-plated. Next, while reading the identification mark 25 for mounting the LED chip, the LED chips 26 and 27 are positioned on the mounting portion of the copper foil wiring 21 and connected to the gold-plated portion by wire bonding.
A molding resin whose surface tension is adjusted by viscosity is dropped on the LED chips 26 and 27 to form a lens 28. The printed circuit board 30 is manufactured similarly to the printed circuit board 20. The light guide 40 is manufactured by a molding die using a transparent or translucent acrylic resin, and the key 43 or the like is generated at that time. The light guide 40 taken out from the molding die is the exit surface of the light guide 40,
The lens cuts 45 and 46 are mirror-finished by transferring the polished surface of the molding die. The light guide 50 is manufactured similarly to the light guide 40.

The assembly of the LED backlight device for illuminating the liquid crystal display device of the present invention will be described. As shown in FIGS. 1, 2 and 7, the printed circuit board 20 includes a side wall 12 and a bottom 11 on one short side of the reflect case 10.
The printed circuit board 30 is fitted in the lead hole 18 provided at the boundary between the lead wire 17 and the lead hole 17 provided at the other short side. Next, the light guide 40 is fitted to the key groove 13 and the recess 15 provided on the side wall 12, and the light guide 50 is fitted to the key groove 14 and the recess 16 provided on the side wall 12 and the partition plate 19. To be done. Due to such a mating type assembly, the printed circuit boards 20 and 30 are
Reflect case 10, light guide 40, and 5
It is held by 0 stoppers 41 and 51. Next, as shown in FIG. 2, the printed circuit board 20 is covered with the light shielding tape 60 so as to cover the emitting portion of the LED chip 26.
To the light guides 40 and 50. On the opposite side, the shading tape 70 and the shading tape 60
It is affixed in the same manner as.

The operation of the LED backlight device for illuminating the liquid crystal display device of the present invention will be described. LED described above
The backlight device is fixed to the back surface of a negative type liquid crystal display device, for example. The negative type liquid crystal display device has a structure in which the base is black and the character portion for display transmits light.
As the characters for display, for example, “time”, “temperature”, “during hot water”, “bath”, corresponding to the light guide 40,
There is a display such as "washroom" and a display such as "high temperature" corresponding to the light guide 50. External leads 22 and 2
A voltage of 6 V (= 2 V × 3 pieces) is applied between 3 and 8 V (= 2 V) between the external leads 32 and 34.
Voltage of 4 volt) is applied. Therefore, the LED chips 26 and 36 emit light, and the emitted light of yellow green enters the light guide 40 through the lenses 28 and 37, the lens cuts 45 and 46. In addition, a voltage of 4 V (= 2 V × 2) is applied between the external leads 23 and 24. Therefore, the LED chip 27
Is emitted, and the standard red emission light is emitted from the lens 28,
Then, the light enters the light guide 50 through the lens cut 54. In this way, the LED backlight device always maintains the lighting state. When the liquid crystal display device is used to display the hot water temperature of the water heater, the passage of the backlight light is controlled depending on whether the applied voltage is on or off. In the "hot water supply" in the normal state, the portion of the liquid crystal display device corresponding to the light guide 40 is controlled to the light transmitting state and displayed in yellow green. On the other hand, when the hot water supply temperature becomes high, the portion of the liquid crystal display device corresponding to the light guide 50 is controlled to the light transmitting state, "high temperature" is displayed in standard red, and the warning is highlighted. In the above embodiment, the printed boards 20 and 30 shown in FIGS. 3 and 4 can use the insulating boards 29 and 38 having the same shape, and only the etching pattern needs to be changed, so that the cost can be reduced. Further, although the negative type is used as the liquid crystal display device, it may be a positive type. However, in consideration of the visibility of highlighted display, the negative type is preferable.

[0018]

As described above, according to the LED backlight device for illuminating the liquid crystal display device of the present invention, the LED emitting portion and the light guide are housed in the reflect case, so that the outside light enters behind. Is prevented, the decrease in the amount of light is suppressed, and the reflection of LED light is improved. Further, since the light guide is divided into two as the partition of the reflect case, it is effective for ensuring the highlighted display by the red display and for achieving the variety of the display. Further, since the light-shielding tape is attached from the printed board to the light guide so as to cover the LED emitting part, invasion of dust, dust, etc. is prevented, and the point light source serves as a surface light source to prevent uneven brightness. Since the concave lens of the light guide is opposed to the convex lens on the LED chip, reduction of the amount of light incident on the light guide is suppressed. The LED light incident on the light guide is reflected by the reflect case and is uniformly reflected and scattered by the gradation applied to the light guide, so that the brightness is improved. Further, since the printed circuit board and the light guide are integrated by the reflect case, all the assembly can be completed simply by attaching the reflect case to the back surface of the liquid crystal display device.

[Brief description of the drawings]

FIG. 1 is a perspective view of an LED backlight device.

FIG. 2 is a partial perspective view of an AA cross section of the LED backlight device.

FIG. 3 is a perspective view of a printed circuit board 20.

FIG. 4 is a perspective view of a printed circuit board 30.

5 is a perspective view of a light guide 40. FIG.

6 is a perspective view of a light guide 50. FIG.

7 is a perspective view of the reflect case 10. FIG.

FIG. 8 is a circuit diagram of the printed circuit board 20.

9 is a circuit diagram of the printed circuit board 30. FIG.

FIG. 10 is an assembled perspective view of the prior art.

[Explanation of symbols]

 10. Reflect case 11. Bottom 12. Side wall 13. Keyway 14. Keyway 15. Kubomi 16. Kubomi 17. Lead hole 18. Lead hole 19. Partition plate 20. Printed circuit board 21. Copper foil wiring 22. External lead 23. External lead 24. External lead 25. Recognition mark 26. LED chip (yellow green) 27. LED chip (standard red) 28. Lens 29. Insulating substrate 29a. Notch key 30. Printed circuit board 31. Copper foil wiring 32. External lead 33. External lead 34. External lead 35. Recognition mark 36. LED chip (yellow green) 37. Lens 38. Insulating substrate 38a. Notch key 40. Light guide 41. Stopper 42. Claw 43. Key 44. Protrusion 45. Lens cut 46. Lens cut 47. Gradation 48. Main body 50. Light guide 51. Stopper 52. Claw 53. Key 54. Lens cut 55. Gradation 56. Main body 60. Shading tape 70. Shading tape 80. Reflective case 90. External lead 100. Electrode plate 110. Light emitting diode chip 120. LED light emitter unit 130. Plate 140. Mating groove

Claims (6)

[Claims] 1. An LED backlight device for illuminating a liquid crystal display device, wherein a backlight is emitted to the rear surface of the liquid crystal display device to display the display contents of the liquid crystal display device, the LED backlight device being formed of a light-transmissive plate-shaped member, A light guide having an emission surface that emits a backlight to the back surface of the liquid crystal display device; a light-reflecting reflective case that surrounds the light guide except for the emission surface of the light guide; An LED backlight device for illuminating a liquid crystal display device, comprising a printed circuit board, which is disposed on an inner surface and has a plurality of LED chips for supplying emitted light to the light guide. 2. The LED backlight device for illuminating a liquid crystal display device according to claim 1, wherein the reflect case has a partition plate which divides the light guide into at least two emission surfaces. 3. The LED backlight device for illuminating a liquid crystal display device according to claim 1, wherein the light guide has a gradation pattern composed of regular fine irregular patterns on the surface opposite to the emission surface. 4. The plurality of LED chips are covered with a molding resin molded into a lens shape, and the light guide is molded into a lens shape complementary to the molding resin on a surface facing the molding resin. The LED backlight device for illuminating the liquid crystal display device according to claim 1, which has the above structure. 5. The plurality of LED chips supply emission light of a first color to at least one emission surface of the at least two emission surfaces of the light guide, and emit light of a second color to the remaining emission surfaces. The LED backlight device for illuminating a liquid crystal display device according to claim 2, wherein the emitted light is supplied. 6. The light guide is a tape member that reflects the emitted light to the inside at an end portion to which the emitted light is supplied from the plurality of LED chips and prevents the emitted light from leaking to a non-illuminated portion. The LED backlight device for illuminating a liquid crystal display device according to claim 1, wherein the LED backlight device is covered.