JP2010161029A - Back light unit and liquid crystal display device equipped with this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight unit capable of satisfying certainly an existing design condition regarding the distance from a light emitting element to a light guide member and an incident angle of light, and a liquid crystal display device. <P>SOLUTION: In the backlight unit X, a light guide plate 2 has a light incident part 2a to which light irradiated from an LED 1 enters, a light diffusion part 2b which is inclined from the light incident part 2a toward a direction separating from a substrate 3 and diffuses the light entered into the light incident part 2a, and a light emitting part 2c which irradiates the light diffused by the light diffusion part 2b. Then, the LED 1 and the light guide plate 2 are fixed in a state of contacting the both faces of the fringe portion (rear side fringe portion 31b and front side fringe portion 31a) of an aperture 31 of the substrate 3 so that the light irradiated from the LED 1 may enter the light incident part 2a of the light guide plate 2 through the aperture 31 formed in the substrate 3 (Fig.1(c)). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a backlight unit used in a liquid crystal display device such as a liquid crystal television or a liquid crystal monitor, and more particularly to an arrangement structure of a plurality of sets of light emitting elements and light guide plates mounted on the backlight unit.

In general, a liquid crystal display device such as a liquid crystal television or a liquid crystal monitor is provided with a backlight unit for illuminating the liquid crystal panel from behind. In addition, the backlight unit is provided with a light emitting element such as an LED that emits light, a light guide plate that diffuses and emits light emitted from the light emitting element (see, for example, Patent Document 1).
FIG. 3 is a schematic diagram for explaining a schematic configuration of a conventional backlight unit Z configured in the same manner as the backlight unit disclosed in Patent Document 1, and FIG. FIG. 3B is a cross-sectional view taken along the line CC in FIG.
As shown in FIG. 3A, the backlight unit Z has a plurality of sets of LEDs 101 and a light guide plate 102, and after the light emitted from each of the LEDs 101 is diffused inside each of the light guide plates 102. , Are emitted from the light emitting portions 102a of the respective light guide plates 102. Here, the LED 101 and the light guide plate 102 are mounted on the same surface of the substrate 103 as shown in FIG.
In the backlight unit Z, as shown in FIG. 3 (b), since the distance from irradiation with the LED 101 to irradiation from the light emitting portion 102a of the light guide plate 102 is short, the light is guided to the light guide plate. It cannot diffuse sufficiently at 102. For this reason, for example, the RGB three-color LED light emitted from the LED 101 may not be sufficiently mixed, or there may be uneven brightness in the light emitted from the light emitting portion 102a of the light guide plate 102. Therefore, a configuration for solving such problems is being studied.

FIG. 4 is a schematic diagram for explaining a schematic configuration of the backlight unit Y improved to solve the above problems. 4A is a plan view, FIG. 4B is a cross-sectional view taken along the line BB in FIG. 4A, and FIGS. 4C to 4E are diagrams for explaining problems of the backlight unit Y. FIG. 5 is a schematic diagram of a main part showing an encircled region E indicated by an alternate long and short dash line in FIG.
As shown in FIG. 4A, the backlight unit Y has a plurality of sets of LEDs 201 and a light guide plate 202 in the same manner as the backlight unit Z. The LED 201 and the light guide plate 202 are mounted on the same surface of the substrate 203.
Here, in the backlight unit Y, as shown in FIG. 4B, each of the light guide plates 202 includes a light incident part 202a on which the light emitted from the LED 201 is incident and a light incident on the light incident part 202a. And a light radiating portion 202c that radiates light diffused by the light diffusing portion 202b. The light diffusion portion 202b is inclined in a direction (upward oblique direction) away from the substrate 203 from the light incident portion 202a.
Thereby, in the backlight unit Y, the light irradiated from the LED 201 can be sufficiently diffused in the light diffusion part 202b from the light incident part 202a of the light guide plate 202 to the light emitting part 202c. Therefore, the RGB three-color LED light emitted from the LED 201 can be sufficiently mixed, and the light without uneven brightness can be emitted from the light emitting portion 202 c of the light guide plate 202.

JP 2007-293339 A

However, in the backlight unit Y, since the LED 201 and the light guide plate 202 are not positioned on the same reference, an error in the mounting position or an error in the mounting angle may occur between the LED 201 and the light guide plate 202.
Specifically, as shown in FIG. 4C, in a configuration without a reference that can keep the distance between the LED 201 and the light guide plate 202 constant, any of the fixed positions is shifted. The distance d from the light incident portion 202a of the light guide plate 202 changes. In addition, as shown in FIG. 4C, in the configuration where there is no reference that can maintain a constant angle between the light irradiation surface of the LED 201 and the light incident portion 202a of the light guide plate 202, the LED 201 is soldered. As the fixed angle θ shifts, the angle of light emitted from the LED 201 to the light incident portion 202a of the light guide plate 202 changes.
As described above, when the distance from the LED 201 to the light guide plate 202 and the incident angle of light change and the predetermined design conditions are not satisfied, for example, luminance unevenness occurs in the light emitted from the backlight unit Y. The problem arises.
Therefore, the present invention has been made in view of the above circumstances, and the object of the present invention is to make it possible to reliably satisfy predetermined design conditions for the distance from the light emitting element to the light guide member and the incident angle of light. The object is to provide a light unit and a liquid crystal display device including the same.

In order to achieve the above object, the present invention includes a plurality of sets of light emitting elements and a light guide member mounted on a substrate, and the light guide member includes a light incident portion on which light emitted from the light emitting elements is incident. , A light diffusing part that is inclined in a direction away from the substrate from the light incident part, and diffuses the light incident on the light incident part, and a light emitting part that emits light diffused by the light diffusing part The present invention is applied to a backlight unit having
In the backlight unit according to the present invention, the light emitting element and the light guide member allow light emitted from the light emitting element to enter the light incident portion of the light guide member through an opening formed in the substrate. As described above, the substrate is fixed in contact with both edge portions of the opening of the substrate.
In the backlight unit according to the present invention, since the light emitting element and the light guide member are fixed in contact with the substrate, the distance from the light emitting element to the light guide member and the light incident angle are It can be kept constant with respect to the substrate, and a predetermined design condition can always be satisfied. Specifically, the distance from the light emitting element to the light incident portion of the light guide member depends on the thickness of the substrate. In addition, since the light emitting element and the light guide member are in contact with each other with the substrate interposed therebetween, the angle of light emitted from the light emitting element to the light incident portion of the light guide member is always perpendicular to the surface of the substrate. Direction. Therefore, the backlight unit according to the present invention can irradiate uniform light with no luminance unevenness as a whole.

In the backlight unit, it is preferable that the opening of the substrate is closed by the light emitting element and the light guide member. Accordingly, dust or the like does not enter the opening of the substrate used as a light path from the light emitting element to the light incident portion of the light guide member. Therefore, luminance unevenness caused by light attenuation in the light path. Can be prevented. In addition, all of the light emitted from the light emitting element can be incident on the light incident portion of the light guide member.
Incidentally, in the conventional configuration, since the light emitting element and the light guide member are arranged on the same surface of the substrate, it is difficult to provide a heat radiating member in the vicinity of the light emitting element.
However, in the backlight unit, since the light emitting element and the light guide member are disposed with the substrate interposed therebetween, it is possible to provide a heat radiating member at a position sandwiching the light emitting element between the substrate and the substrate. It is. Thereby, the heat of the light emitting element can be effectively radiated by the heat radiating member.

Further, in order to facilitate positioning of the light incident portion of the light guide member and the opening of the substrate, it is considered that the light incident portion of the light guide member has a protrusion shape that is fitted into the opening. It is done. Accordingly, the light guide member can be easily positioned with respect to the substrate by fitting the light incident portion into the opening. At this time, the distance between the light emitting element and the light incident portion of the light guide member is determined by the thickness of the substrate and the amount of protrusion of the light incident portion into the opening.
Furthermore, it is desirable that the light incident surface from the light emitting element in the light incident portion of the light guide member has a shape that diffuses the light. Thereby, the light irradiated from the light emitting element can be sufficiently diffused on the incident surface of the light incident part and the light diffusion part. Note that the shape of the incident surface may be, for example, unevenness with a sawtooth cross section.
The present invention can also be understood as an invention of a liquid crystal display device comprising a liquid crystal display panel that displays an image and the above-described backlight unit that illuminates the liquid crystal display panel from the back.

According to the present invention, since the light emitting element and the light guide member are fixed in contact with each other with the substrate interposed therebetween, the distance of the light guide member from the light emitting element and the incident angle of light are set to the substrate. It can be kept constant as a reference, and the predetermined design conditions can always be satisfied. Specifically, the distance from the light emitting element to the light incident portion of the light guide member depends on the thickness of the substrate. In addition, since the light emitting element and the light guide member are in contact with each other with the substrate interposed therebetween, the angle of light emitted from the light emitting element to the light incident portion of the light guide member is always perpendicular to the surface of the substrate. Direction. Therefore, the backlight unit according to the present invention can irradiate uniform light with no luminance unevenness as a whole.
In addition, by closing the opening of the substrate with the light emitting element and the light guide member, intrusion of dust and the like from the light emitting element to the light incident portion of the light guide member to the light path is prevented, and uneven brightness is prevented. Generation | occurrence | production can be prevented and it becomes possible to make all the light irradiated from the said light emitting element inject into the light-incidence part of the said light guide member.
Furthermore, by disposing the heat dissipating member on the opposite side of the substrate from the light guide member so as to sandwich the light emitting element between the substrate, the light emitting element can be dissipated.

The schematic diagram for demonstrating schematic structure of the backlight unit X which concerns on embodiment of this invention. The figure for demonstrating an example of the fixation structure of the light-guide plate 2 in the backlight unit X which concerns on embodiment of this invention. The schematic diagram for demonstrating schematic structure of the conventional backlight unit Z. FIG. The schematic diagram for demonstrating schematic structure of the conventional backlight unit Y. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a schematic diagram for explaining a schematic configuration of the backlight unit X according to the embodiment of the present invention. FIG. 1 (a) is a plan view, and FIG. 1 (b) is FIG. FIG. 1A is a cross-sectional view taken along the line AA in FIG. 1A, and FIG. 1C is a schematic diagram of a main part showing an encircled region D indicated by an alternate long and short dash line in FIG. It is a principal part schematic diagram for doing.
As shown in FIG. 1, a backlight unit X according to an embodiment of the present invention includes a plurality of sets of LEDs 1 (an example of a light emitting element) and a light guide plate 2 (an example of a light guide member), the LED 1 and the light guide plate. 2, a heat dissipation sheet 10 and a backlight (BL) shield 11. The backlight unit X is mounted on a liquid crystal display device such as a liquid crystal television or a liquid crystal monitor having a liquid crystal panel for displaying an image, and illuminates the liquid crystal panel from behind. The present invention may be understood as an invention of the liquid crystal display device including the backlight unit X.
FIG. 1 shows an arrangement structure of the LED 1 and the light guide plate 2 when the backlight unit X is viewed macroscopically. In the backlight unit X, the liquid crystal television, Depending on the size of the liquid crystal panel such as a liquid crystal monitor, a large number of sets of the LEDs 1 and the light guide plates 2 are arranged, for example, 30-40 vertically and 50-60 horizontally.

Each of the LEDs 1 is mounted on the back surface opposite to the surface of the substrate 3 on which the light guide plate 2 is mounted, and emits light of R (red), G (green), and B (blue) 3 It is a light emitting element containing two LEDs. The LED 1 may be one or a plurality of white LEDs. Further, an LED driver circuit (not shown) for controlling the presence or absence of light emission of each LED 1 is mounted on the back surface of the substrate 3.
Each LED 1 is controlled by the LED driver circuit to irradiate light toward the surface side of the substrate 3 through the opening 31 formed in the substrate 3. Here, the opening 31 of the substrate 3 is a circular or rectangular opening formed in a size that allows all the light emitted from the LED 1 to pass therethrough.
In addition, the heat radiation sheet 10 and the BL shield 11 are arranged at a position opposite to the substrate 3 of each LED 1, that is, a position where the LED 1 is sandwiched between the LED 1 and the substrate 3. Thereby, the heat of each LED 1 is efficiently radiated through the heat radiating sheet 10 and the BL shield 11. Here, the heat dissipation sheet 10 and the BL shield 11 are examples of heat dissipation members.

As shown in FIG. 1B, the light guide plate 2 includes a light incident part 2a through which light emitted from the LED 1 is incident through an opening 31 of the substrate 3, and a light incident part 2a through the substrate 3; A light diffusing portion 2b that is inclined in the direction of separation and diffuses light incident on the light incident portion 2a, and a light radiating portion 2c that radiates light diffused by the light diffusing portion 2b. Yes. The light incident on the light incident portion 2a from the LED 1 is guided to the light emitting portion 2c while being diffused by the light diffusing portion 2b of the light guide plate 2. In addition, a reflecting plate 4 is attached to the lower surface of the light guide plate 2, and in the backlight unit X, the light traveling direction (from the light incident portion 2 a to the light emitting portion) in the light diffusion portion 2 b of the light guide plate 2. The upper surface of the light diffusing portion 2b of the light guide plate 2 in front of the light guide plate 2 is covered by the reflector 4 of the rear light guide plate 2 as viewed in the direction 2c.
In the light guide plate 2 configured as described above, after the light emitted from the LED 1 is sufficiently diffused in the light diffusion part 2b from the light incident part 2a to the light emitting part 2c, It can be made to radiate | emit from the light emission part 2c. Accordingly, it is possible to sufficiently mix the light of the RGB three-color LEDs emitted from the LED 1 and to irradiate light without unevenness of brightness from the light emitting portion 2 c of the light guide plate 2.
In the backlight unit X, as shown in FIG. 1B, the light is traveling in the light diffusing portion 2b of the light guide plate 2 (in the direction from the light incident portion 2a toward the light emitting portion 2c). Two light guide plates 2 that are arranged in the same direction and that are adjacent to each other in the front and rear are such that a part of the front light guide plate 2 is in a gap formed between the light diffusion portion 2 b of the rear light guide plate 2 and the substrate 3. It is arranged to be located. Thereby, the clearance gap between the light emission parts 2c of the said light-guide plate 2 adjacent to front and back can be eliminated.

In the backlight unit X according to the present invention, the fixing structure of the LED 1 and the light guide plate 2 is devised, and the distance from the LED 1 to the light guide plate 2 and the incident angle of light are always kept constant. It has the feature that can be done.
Hereinafter, the details of the fixing structure of the LED 1 and the light guide plate 2 in the backlight unit X will be described with reference to FIG.
As shown in FIG. 1 (c), in the backlight unit X, the LED 1 contacts the entire periphery of the back surface side edge portion 31b of the opening 31 so as to close the back surface side of the opening 31 of the substrate 3. In this state, the substrate 3 is soldered and fixed by the solder 1a. At this time, the LED 1 is arranged so that all the light emitted from the LED 1 enters the opening 31. Further, the soldering of the LED 1 is performed, for example, at two locations on the back surface side edge portion 31b facing the opening 31 as a center. Thereby, the LED 1 is fixed in a stable state. In FIG. 1C, one module including RGB three-color LEDs is shown as one LED 1, but when each of the LEDs is individually fixed to the substrate 3, the opening 31 is the LED. A plurality may be formed for each.
Thus, the LED 1 fixed to the substrate 3 is fixed on the basis of the angle of the back surface side edge portion 31b of the substrate 3, that is, the substrate 1 is always at an angle parallel to the back surface of the substrate 3. Will be fixed to 3. The LED 1 only needs to be fixed so that light can be irradiated to the front surface side of the substrate 3 through the opening 31, and is in contact with the entire periphery of the back surface side edge portion 31 b of the opening 31. The back surface side of the opening 31 may not be closed.

On the other hand, the rear end of the light guide plate 2 is provided with an opening 2e through which a screw 5 for screwing the light guide plate 2 to the substrate 3 is inserted. The board 3 is provided with screw holes 3a for arranging the light guide plate 2 at a predetermined interval.
The light guide plate 2 penetrates into the opening 2e of the light guide plate 2 in a state where the light guide plate 2 is in contact with the entire circumference of the surface side edge portion 31a of the opening 31 so as to close the surface side of the opening 31 of the substrate 3. The board 5 is screwed and fixed by the inserted screw 5. At this time, the light guide plate 2 is disposed so that the light incident portion 2 a covers at least the opening 31, and all light emitted from the LED 1 is incident on the light guide plate 2 through the opening 31. It is incident on the portion 2a.
Thus, the light incident portion 2a of the light guide plate 2 fixed to the substrate 3 is fixed with reference to the angle of the surface side edge portion 31a of the substrate 3, that is, always the surface of the substrate 3 Is fixed to the substrate 3 at an angle parallel to the substrate 3.

As described above, in the backlight unit X, the LED 1 and the light guide plate 2 allow the light emitted from the LED 1 to enter the light incident portion 2 a of the light guide plate 2 through the opening 31 formed in the substrate 3. The distance from the LED 1 to the light guide plate 2 is fixed so as to be in contact with both sides of the opening 31 of the substrate 3 (back side edge 31b, front side edge 31a) so as to be incident. And the incident angle of light can be kept constant with reference to the substrate 3 sandwiched between the LED and the light guide plate 2. As a result, the backlight unit X can always satisfy predetermined design conditions for the distance from the LED 1 to the light guide plate 2 and the incident angle of light. can do.
More specifically, the light emitted from the LED 1 toward the light guide plate 2 is always in a direction perpendicular to the substrate 3, and from the light irradiation surface of the LED 1 to the light incident portion 2 a of the light guide plate 2. The distance always depends on the thickness of the substrate 3.
In the backlight unit X, since the opening 31 of the substrate 3 is sandwiched and closed by the LED 1 and the light guide plate 2, entry of dust and the like into the opening 31 can be prevented. Attenuation of light in the opening can be prevented.

Hereinafter, in this embodiment, another example of the fixing structure of the LED 1 and the light guide plate 2 in the backlight unit X will be described with reference to FIGS. The description of the same points as those of the fixing structure described in the above embodiment (see FIG. 1C) is omitted here.
First, in the example shown in FIG. 2A, the light incident portion 2 a of the light guide plate 2 has a protrusion shape that is inserted into the opening 31 of the substrate 3. Here, the opening size of the opening 31 and the projection size of the light incident part 2a are substantially the same.
The light guide plate 2 has the light incident portion 2 a inserted into the opening 31 of the substrate 3 so that the light guide plate 2 is in contact with the surface side edge portion 31 a of the substrate 3. Fixed to.
According to such a configuration, the light guide plate 2 can be easily positioned and fixed to the substrate 3 so that the light incident portion 2 a is located in the opening 31. In this case, the distance between the LED 1 and the light incident portion 2a of the light guide plate 2 can be maintained at a constant value depending on the thickness of the substrate 3 and the amount of protrusion of the light incident portion 2a. .

Next, in the example shown in FIG. 2B, the light incident surface from the LED 1 in the light incident portion 2a of the light guide plate 2 has a shape for diffusing the light. Specifically, the incident surface of the light incident portion 2a has an uneven shape with a saw-shaped cross section. Note that the present invention is not limited to this shape, and other shapes may be used as long as the light from the LED 1 can be diffused.
Thereby, after the light irradiated from the LED 1 is diffused and incident on the incident surface of the light incident portion 2a, it can be further diffused by the light diffusing portion 2b in the light guide plate 2. It is possible to sufficiently mix the emitted light and prevent luminance unevenness.

Further, in the example shown in FIG. 2C, the light guide plate 2 emits light incident from the LED 1 in a direction perpendicular to the substrate 3 and incident on the light incident portion 2a in a direction substantially parallel to the substrate 3. It further has a light deflection part 2f that is deflected to enter the light diffusion part 2b.
Specifically, the light deflecting unit 2f is formed at a position in the vertically upward direction of the light incident part 2a of the light guide plate 2, and directs light irradiated in the vertically upward direction from the opening 31 toward the light diffusing unit 2b. It is an inclined surface to be reflected. The light deflecting portion 2f can more reliably guide the light incident on the light incident portion 2a to the light diffusing portion 2b.

1 ... LED (an example of a light emitting element)
1a ... solder 2 ... light guide plate (an example of a light guide member)
2a ... light incident part 2b ... light diffusing part 2c ... light emitting part 2e ... opening 2f ... light deflecting part 3 ... substrate 31 ... opening 31a ... front surface side edge part 31b ... back surface side edge part 3a ... screw hole 4 ... reflecting plate 5 ... Screw 10 ... Heat dissipation sheet 11 ... BL shield

Claims (6)

A plurality of sets of light emitting elements and light guide members are mounted on a substrate,
The light guide member is inclined in a direction in which the light emitted from the light emitting element is incident, and in a direction away from the substrate from the light incident portion, and the light incident on the light incident portion is A backlight unit comprising a light diffusing unit for diffusing and a light emitting unit for radiating light diffused by the light diffusing unit,
The light emitting element and the light guide member have both edges of the opening of the substrate such that light emitted from the light emitting element enters the light incident portion of the light guide member through the opening formed in the substrate. The backlight unit is fixed in a state of being in contact with the backlight unit.   The backlight unit according to claim 1, wherein an opening of the substrate is closed by the light emitting element and the light guide member.   The backlight unit according to claim 1, wherein a heat dissipation member is provided at a position sandwiching the light emitting element between the substrate and the substrate.   The backlight unit according to any one of claims 1 to 3, wherein the light incident portion of the light guide member has a projection shape that is fitted into the opening.   The backlight unit according to claim 1, wherein an incident surface of light from the light emitting element in the light incident portion of the light guide member has a shape that diffuses the light.   A liquid crystal display device comprising: a liquid crystal display panel that displays an image; and the backlight unit according to claim 1 that illuminates the liquid crystal display panel from the back.

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