JP2011238448A - Backlight, its manufacturing method, and liquid crystal display - Google Patents

Abstract

A sidelight type backlight unit using an LED as a light source, which is thin, has an efficient use of light from a light source, and has small luminance unevenness.
An LED 1 is disposed on a substrate 2 with an emission surface 1b inclined upward. An optical sheet 6 is disposed on the light guide plate 3, and a reflective sheet 5 is disposed on the lower side. The light incident surface 3 a formed on the side surface of the light guide plate 3 is inclined downward and faces the light exit surface 1 b of the LED 1. The use efficiency of the light from LED1 increases when the opposing area of LED1 and the light-guide plate 3 increases. Further, since the emission surface 1b of the LED 1 is inclined upward, stray light is prevented from entering between the reflection sheet 5 and the lower surface 3c of the light guide plate 3 to cause uneven brightness. As a result, a backlight unit having high luminance and low luminance unevenness can be realized.
[Selection] Figure 1

Description

The present invention relates to a backlight unit for illuminating a liquid crystal panel from the back and an LED light source module used for an illumination device.

2. Description of the Related Art Conventionally, a sidelight type backlight unit that is used to illuminate a liquid crystal panel from the back side uses a light guide plate to provide a cold cathode fluorescent lamp or a plurality of LEDs as a linear light source on the end face of the light guide plate. The light from the light source is introduced from the end surface of the light guide plate, and the light is reflected and diffused by one of the reflection surfaces on the front surface or the back surface of the light guide plate, and emitted from the other light output surface on the front surface or the back surface. It is.

  FIG. 7 shows a configuration of a conventional sidelight type backlight unit. In FIG. 7, 1 is a side view type LED, 1a is the light emission part of LED1, and 1b is the emitting surface of LED. Reference numeral 2 denotes a substrate on which a plurality of LEDs are arranged.

  In FIG. 7, the surface side of the light guide plate 3 is a light exit surface 3b. The light guide plate 3 introduces light from the light emitting portion 1a of the LED 1 into the plate from the light incident surface 3a at the end surface and reflects it by the reflection surface 3c. It diffuses and functions to emit light uniformly from the light exit surface 3b over the entire surface. The reflective sheet 5 is installed on the reflective surface 3 c side of the light guide plate 3, and the optical sheet 6 for making the luminance uniform is installed on the light output surface 3 b side of the light guide plate 3.

In the conventional sidelight type backlight unit, a plurality of LEDs are arranged in a line and used as a linear light source. Therefore, the light output direction can be controlled by packaging the LED element, and the light guide plate can receive light. Light can be emitted only in the direction facing the end face. Therefore, the thickness of the light guide plate can be made substantially equal to the thickness of the LED. On the other hand, if the light source is thinned and the light guide plate is correspondingly thinned, light radiated from the light emitting surface 1b of the LED 1 escapes from the incident surface 3a of the light guide plate 3 as shown in FIG. 15 occurs, and the incident efficiency is deteriorated.
As a technique for solving this, for example, “Patent Document 1” discloses a technique in which an incident surface of a light guide plate is inclined and an LED is arranged so that a light emitting surface thereof is parallel to the light guide plate incident surface. Yes.

  In this technique, as shown in FIG. 9, the incident surface 3 a of the light guide plate 3 is formed on a slope inclined with respect to the back surface 3 c of the light guide plate 3. The LED 1 is arranged so that the light emitting surface 1b of the LED 1 is parallel to the incident surface 3a when the LED 1 is incorporated in the substrate 2 in the vicinity of the incident surface 3a. Thus, the light guide plate 3 formed with the incident surface 3a inclined can make the effective diameter of the incident surface 3a larger than its thickness.

  In FIG. 9, the substrate 2 is formed such that the bottom wall portion of the recess in which the LED 1 is disposed has a top surface as an inclined surface facing the light guide plate 3 in the recess. The LED 1 disposed at the predetermined position is disposed in a state where the light emitting surface 1 a is inclined so as to be parallel to the incident surface 3 a of the light guide plate 3.

  However, as the backlight is made thinner and larger, the thickness of the light guide plate 3 is reduced and the area is increased. As a result, warpage and distortion of the light guide plate increase, and the light guide plate back surface 3c and the reflection sheet 5 are increased. There will be a space in between. In that case, the light which went to the board | substrate 2 direction among the emitted light from LED1b enters between the light-guide plate back surface 3c and the reflective sheet 5, and the subject that the light leak which cannot enter into the light-guide plate 3a surface becomes large Cannot be solved by the structure of FIG.

JP 2005-242249 A

The present invention has been made in view of such a conventional technical problem, and in an LED module such as a sidelight type backlight unit or an LED lighting device, the incident efficiency to the light guide plate can be further improved. And it aims at providing the LED module which can also achieve power-saving of the module of LED.

  In order to achieve the above-described object, the backlight unit of the present invention allows light emitted from the light emitting surface of the LED to enter the light guide plate from an incident surface provided on a side surface of the light guide plate having a front surface and a back surface. The backlight unit is configured to be incident and multiple-reflected inside the light guide plate to emit as planar light from the surface of the light guide plate facing the liquid crystal display panel. The LED mounting surface is inclined and arranged such that the LED emission surface is obliquely upward with respect to the bottom surface of the substrate.

  The incident surface of the light guide plate may be parallel to the emission surface of the LED. In the LED mounting surface, a metal core ball or a resin core ball is placed on the side close to the light guide plate, so that the light emitting surface of the LED is inclined with respect to the substrate. In addition, a liquid crystal display device of the present invention includes the backlight unit having the above-described configuration.

  According to the present invention, it is possible to realize a backlight with high light use efficiency from a power source and less luminance unevenness. Moreover, such a backlight can be efficiently manufactured by the manufacturing method of the present invention. In addition, by using the backlight of the present invention, a bright liquid crystal display device with small luminance unevenness can be realized.

1 is a cross-sectional view of a backlight of Example 1. FIG. 6 is a cross-sectional view of a backlight of Example 2. FIG. 6 is a cross-sectional view of a backlight of Example 3. FIG. It is process drawing which shows the manufacturing method of the backlight of this invention. It is a disassembled perspective view of the liquid crystal display device of this invention. It is AA sectional drawing of FIG. It is explanatory drawing of the conventional backlight unit. It is explanatory drawing which shows the problem which the conventional backlight unit should solve. It is explanatory drawing which shows the problem which the conventional backlight unit should solve.

  Hereinafter, the present invention will be described in detail by way of examples.

  FIG. 1 shows a sidelight type backlight unit as the best mode of the LED module of the present invention. In FIG. 1, the same components as those of the backlight unit of the conventional example shown in FIG. 7 are denoted by the same reference numerals. That is, 1 is a side-view type white light emitting LED having a size of 2 mm × 3 mm including the emission surface 1b and a depth of about 1 mm, and 1a is a light emitting portion of the LED 1 and indicates an LED chip. Reference numeral 2 denotes a substrate on which a plurality of LEDs are arranged. The LED 1 is coupled and fixed via a bonding member 7 between the bonding surface 1 c of the LED 1 and the wiring 8 provided on the substrate 2.

  In FIG. 1, the joining surface 1c and the emitting surface 1b of the LED 1 are perpendicular to each other. This type of LED 1 is referred to as a side view type LED. In addition, in the top view type LED described later, the joint surface 1c and the emission surface 1b are parallel to each other. In FIG. 1, the bonding member 7 is bonded to the substrate 2 so that the bonding surface 1 c and the emission surface 1 b of the LED 1 maintain a bonding angle 10 of 5 to 30 °. The reason for setting the joining angle in such a range is as follows.

  That is, in order to prevent the light from the LED from entering between the light guide plate and the reflection sheet, or to improve the utilization efficiency of the light from the LED, 5 ° or more is necessary. On the other hand, if the bonding angle is larger than 30 °, the processing accuracy of the light guide plate 3 becomes a problem, and the protrusion of the LED 1 below the light guide plate increases, so that the thickness of the entire backlight increases. Because there is a problem.

  The light guide plate 3 has a light incident surface 3 a that faces the light emitting surface 1 b of the LED 1 in parallel through the air layer 9. The air layer is a space of 0.03 to 1 mm. The surface side of the light guide plate 3 is a light exit surface 3b, and the surface of 3b is provided with a white ink printing pattern or a microlens unevenness formation pattern that is optically designed to achieve uniform brightness in the surface. ing. The light guide plate 3 introduces light from the light emitting portion 1a of the LED 1 into the plate from the light incident surface 3a at the end surface, reflects and diffuses the light at the reflecting surface 3c, and uniformly emits light from the light emitting surface 3b over the entire surface. To do. The reflective sheet 5 is installed on the reflective surface 3 c side of the light guide plate 3, and the optical sheet 6 for making the luminance uniform is installed on the light output surface 3 b side of the light guide plate 3.

  Here, the LED 1 is a white light emitting LED, but it may be a red, blue and green colored light emitting LED, or a combination thereof. Although a glass epoxy substrate is preferably used for the LED substrate 2, a flexible substrate or a metal-based substrate can also be used. The number of LEDs used depends on the size of the target backlight unit. The light guide plate 3 is generally manufactured by injection molding a resin such as acrylic or polycarbonate. The joining member 7 is a member capable of electrical connection such as conductive resin and solder and LED holding.

  The light generated in the LED light emitting unit 1a spreads from the emission surface 1b and is emitted to the air layer 9 with directivity. Since the bonding surface of the LED 1 is coupled to the substrate 2 so as to maintain the bonding angle 10, light emitted toward the substrate 2 reaches the light guide plate back surface 3c and the reflection sheet 5 in the conventional structure. Since the direct light 13 shown in FIG. 1 that should have been directly introduced into the light guide plate 3b, light leakage does not occur even if there is a gap between the back surface 3c of the light guide plate and the reflection sheet 5.

  Furthermore, by making the emission center 1d of the LED 1 coincide with the central axis 3d of the light incident surface 3a of the light guide plate 3, light leakage does not occur and the thickness of the light guide plate can be minimized. Moreover, since the direct light 13 emitted from the emission surface 1b can be introduced into the incident surface 3a of the light guide plate without being reflected on the surface of the substrate 2, the incident efficiency can be improved.

  Furthermore, since the light incident surface 3a of the light guide plate is installed in parallel with the light emitting surface 1b of the LED, the light from the LED 1a can be efficiently taken into the light guide plate. Due to these effects, the total amount of light captured from the LED 1 is increased, so that the light emission efficiency as the backlight unit is improved. Therefore, the power consumption for obtaining the standard luminance can be reduced. In addition, even if the entrance surface 3a of the light guide plate and the exit surface 1b of the LED 1 are not completely parallel, stray light enters between the light guide plate 3 and the reflection sheet 5 by the upward exit surface of the LED 1. Therefore, the effect of preventing luminance unevenness can be obtained.

  A feature of the present invention is that stray light from the LED 1 can be prevented from entering between the light guide plate 3 and the reflection sheet 5, and thus uneven brightness due to stray light can be prevented. Further, since stray light from the LED 1 can be prevented from entering between the reflection sheet 5 and the circuit board 2, it is possible to prevent a decrease in luminance. Furthermore, since the area of the opposing surface of the light emission surface 1b of LED1 and the light-incidence surface 3a of the light-guide plate 3 can be enlarged, the utilization efficiency of the light from LED1 can be raised. This is an effect common to the embodiments.

  FIG. 2 shows a sidelight type backlight unit as a second embodiment of the LED module of the present invention. The feature of the present embodiment is a method for stably maintaining the bonding angle 10 between the bonding surface 1c and the emission surface 1b of the LED 1 with respect to the first embodiment shown in FIG. is there.

  The joining member 7 is solder or a conductive paste. A resin core ball or a metal core ball 11 is disposed at a position near the LED emission surface 1 b of the wiring 4 installed on the substrate 2. The resin core ball is one in which solder is coated around a ball-shaped resin core, and the metal core ball 11 is one in which solder is coated around a ball-shaped metal core.

Since the height of the core of the metal core ball 11 is constant, the emission surface 1b of the LED 1 can stably maintain the bonding angle 10 between the bonding surface 1c and the emission surface 1b of the LED 1 and the substrate 2. Furthermore, the joining angle can be freely changed by changing the core ball diameter of the metal core ball 11. The same applies when a resin core ball is used.
In the embodiment, the resin core ball 11 or the metal core ball 11 has been described as an example, but the shape is not limited, and a triangular or square member may be substituted.

  FIG. 3 shows a sidelight type backlight unit as a third embodiment of the LED module of the present invention. The feature of this embodiment is that the LED 1 is a top view type and the substrate 2 is installed in a direction perpendicular to the back surface 3c of the light guide plate 3 with respect to the first embodiment shown in FIG. It is characterized by that. LED 1 in FIG. 3 is a top-side view type white light emitting LED having a size of 2 mm × 3 mm including the emission surface 1 b and a depth of about 1 mm.

  Since the emission surface 1 b and the bonding surface 1 c of the LED 1 are parallel, the wiring land 8 of the substrate 2 is attached perpendicularly to the back surface 3 c of the light guide plate 3. The substrate 2 and the light guide plate 3 are positioned and fixed to the chassis 12 so that the emission surface 1b of the LED and the light incident surface 3a of the light guide plate are parallel to each other. As a method of forming the tilt angle 10 with respect to the LED 1, a resin core ball or a metal core ball can be used as in the second embodiment.

  FIG. 4 shows a mounting process of the LED 1 for the LED light source module shown in FIG. 2 or FIG. First, the side view LED will be described. As a first step, the cream solder 7 is applied on the solder lands 8 provided on the substrate 2 by a normal printing step. In the second step, the metal core ball 11 is supplied onto the cream solder 7 placed on the solder land 8. Here, the supply of the metal core ball is unevenly distributed on the emission surface side of the LED 1.

  In the third step, the LED 1 is placed on the solder land. In the fourth step, the LED 1 is solder-fixed by a normal solder reflow step. In this step, the LED 1 and the metal core ball 11 are accurately fixed at predetermined positions by the self-alignment effect of the solder. Further, when the solder is melted, the LED 1 comes into close contact with the solder land 8 from its own weight.

  The portion where the metal core ball 11 is installed sinks into the solder 7 due to the weight of the LED 1 and the metal core ball 11. Accordingly, the LED 1 is fixed in a state where it is increased by the height of the diameter of the metal core ball 11. Thereby, the LED light source in which the emission surface 1b of the LED 1 has an upward inclination with respect to the substrate 2 can be produced. In the above description, the case where the metal core ball is used has been described. However, the resin core ball can be manufactured in the same manner.

  The case where the side view type LED is used has been described above, but the process when the top view type LED is used is basically the same. However, in the case of the top view type, since the LEDs are arranged on the upright substrate 2, first, in a state where the substrate 2 is horizontally oriented, the top view type LED is in a state where the emission surface 3 b is up, The board | substrate 2 and LED1 are joined according to the 4th process from the 1st process in FIG. 4 demonstrated above. Then, the board | substrate 2 is arrange | positioned in the chassis 12 in the state which stood up. As a result, the emission surface 1b of the top view type LED 1 is set slightly upward with a predetermined inclination angle 10 from the horizontal. The formation of the predetermined inclination 10 using a resin core ball or a metal core ball is the same as when a side view type LED is used.

  According to the manufacturing process described above, the conventional solder reflow apparatus can be used for manufacturing, and the conventional solder reflow process only includes the second step, so that the conventional manufacturing process is greatly changed. It is possible to produce an LED light source.

  FIG. 5 is an exploded perspective view of the liquid crystal display device when the backlight unit described in the first to third embodiments is used in the liquid crystal display device. In FIG. 5, a display region in which TFTs and pixel electrodes are arranged in a matrix, a TFT substrate 21 on which scanning lines, video signal lines and the like are formed and an opposite substrate 22 on which color filters and the like are formed are not shown in FIG. Are bonded through. A liquid crystal (not shown) is sandwiched between the TFT substrate 21 and the counter substrate 22. Since terminals and the like are formed on the TFT substrate 21, the TFT substrate 21 is made larger than the counter electrode 22. A lower polarizing plate 24 is attached to the lower side of the TFT substrate 21, and an upper polarizing plate 23 is attached to the upper side of the counter substrate 22.

  A state in which the TFT substrate 21, the counter substrate 22, the lower polarizing plate 24, and the upper polarizing plate 23 are bonded together is referred to as a liquid crystal display panel. A backlight unit as described in the first to third embodiments is disposed on the back surface of the liquid crystal display panel. The backlight unit is formed of an LED 1, a light guide plate 3, and an optical sheet 6 disposed on the substrate. In FIG. 5, the reflection sheet is not shown.

  In FIG. 5, the light guide plate 3 has a wedge shape, but the light guide plate 3 need not be limited to the wedge type. When the light guide plate 3 and the circuit board 2 are combined, a plurality of LEDs 1 are arranged to face the side surface of the light guide plate 3. Three diffusion sheets are arranged as the optical sheet 6. The diffusion sheet 6 has a role of making the luminance of light emitted from the light guide plate 3 uniform.

  6 is a cross-sectional view taken along the line AA in FIG. In FIG. 6, the optical sheet 6, the light guide plate 3, the reflection sheet 5, the LED 1, and the substrate 2 on which the optical sheet 6 is mounted are disposed on the back surface of the liquid crystal display panel 30. In FIG. 6, the light guide plate 3 and the reflection sheet 5 are drawn in close contact with each other, but in reality, a slight gap is often generated. LED1 is arrange | positioned with an inclination angle so that the output surface 1b may face upward. The side surface of the light guide plate 3 is an inclined surface and faces the emission surface 1 b of the LED 1.

  With the arrangement as shown in FIG. 6, the light from the LED 1 does not enter the stray light between the light guide plate 3 and the reflection sheet 5, so that uneven brightness of the liquid crystal display screen can be prevented. Furthermore, since the area where the light emitted from the LED 1 is incident on the side surface of the light guide plate 3 can be increased, the utilization efficiency of the light from the LED 1 can be increased, and a bright screen liquid crystal display device can be realized. I can do it.

1 Side view LED
DESCRIPTION OF SYMBOLS 1a Light emission part 1b LED output surface 1c LED joint surface 1d LED output center 2 Substrate 3 Light guide plate 3a
3b Light-exiting surface 3c of the light guide plate Back surface 5 of the light guide plate Reflective sheet 6 Optical sheet 7 Joining member 8 Solder land 9 Air layer 10 Inclination angle 11 Metal core ball 12 Chassis 13 Light that can be taken in 15 Light leakage 21 TFT substrate 22 Counter substrate 23 Upper polarizing plate 24 Lower polarizing plate 30 Liquid crystal display panel.

Claims (9)

An LED having a light emitting portion, a bonding surface with a substrate, and an emission surface;
A backlight unit having a light exit surface that is a main surface, a back surface, and a light guide plate having a light incident surface formed on a side surface,
The emission surface of the LED is disposed to be inclined toward the light output surface side of the light guide plate,
The light incident surface of the light guide plate is inclined in a direction opposite to the light output surface of the light guide plate,
The backlight unit, wherein the light emission surface of the LED and the light incident surface of the light guide plate are opposed to each other.   The backlight unit according to claim 1, wherein the emission surface of the LED and the light incident surface of the light guide plate are parallel to each other. The inclination angle of the LED with respect to the main surface of the light exit surface of the light guide plate is 5 degrees to 30 degrees,
The backlight unit according to claim 1, wherein an inclination angle of the light incident surface of the light guide plate with respect to a main surface of the light output surface of the light guide plate is 5 degrees to 30 degrees.   The backlight unit according to claim 1, wherein an emission surface of the LED is perpendicular to the bonding surface of the LED.   The backlight unit according to claim 1, wherein an emission surface of the LED is parallel to the bonding surface of the LED.   In the joint portion of the LED with the substrate, a metal core ball or a resin core ball is disposed on the side close to the light guide plate, thereby forming an inclination angle of the emission surface of the LED. The backlight unit according to any one of claims 1 to 6. An LED that is disposed on a substrate and has a joining surface and an emitting surface, and the joining surface and the emitting surface are perpendicular to each other, a light emitting surface that is a main surface, a back surface, and a light incident surface formed on a side surface A method of manufacturing a backlight in which the light exit surface of the LED and the light incident surface of the light guide plate are opposed to each other,
A step of forming solder on the substrate; and a step of arranging a metal edge ball or a resin core ball on the solder near the backlight among the solders;
Disposing the joining surface of the LED on the solder of the substrate;
A step of reflowing the solder and bonding the LED to the substrate to incline the emitting surface of the LED toward the light emitting surface of the light guide plate. Manufacturing method of light unit. An LED that is disposed on a substrate and has a bonding surface and an emission surface, and the bonding surface and the emission surface are parallel to each other, a light emission surface that is a main surface, a back surface, and a light incident surface formed on a side surface. A method of manufacturing a backlight having a light guide plate having a chassis on which the substrate is mounted, wherein the light emission surface of the LED and the light incident surface of the light guide plate are opposed to each other,
A step of forming solder on the bonding surface of the substrate; and a step of placing a metal edge ball or a resin core ball on the solder close to the backlight among the solders;
Disposing the joining surface of the LED on the solder of the substrate;
Reflowing the solder to join the LED to the substrate;
A step of arranging the joining surface of the substrate at a right angle with respect to the chassis to incline the emitting surface of the LED toward the light emitting surface of the light guide plate. Manufacturing method of light unit. A liquid crystal display device having a liquid crystal display panel and a backlight unit,
The liquid crystal display device according to any one of claims 1 to 6, wherein the backlight is the backlight unit according to any one of claims 1 to 6.

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