JP2001332116A - Surface light source device and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device preventing unevenness of brightness and mal-display and a liquid crystal display device provided with the same. SOLUTION: A light guide body 26 has a wedge shaped section provided with a thicker part 26a and thinner part 26b and has an emission face 26c emitting light entered from an entry face 26d provided on the thicker part 26a. A reflector 48 surrounding a light source 33 arranged at a position facing the entry face 26d of the light guide body 26 has a cover part 48A covering at least one long side 26X of the entry face 26d on the light guide body 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device and a liquid crystal display device provided with the surface light source device, and more particularly to a structure for preventing luminance unevenness of light emitted from the surface light source device.

[0002]

2. Description of the Related Art A liquid crystal display device includes a surface light source device for illuminating a transmission type liquid crystal display panel from the back. The surface light source device includes a light guide having a wedge-shaped cross section, a reflection sheet disposed on a back surface of the light guide, a tubular light source disposed along an end surface of a thick portion of the light guide, and a reflector surrounding the light source. It is constituted by such as. The reflector is assembled by sandwiching the thick portion of the light guide and the reflection sheet. The uniformity of the light emitted from the vicinity of the light source of the surface light source device is determined by the shapes and positional relationships of the light guide, the reflection sheet, and the reflector.

[0003]

In the conventional surface light source device as described above, when the reflector is sandwiched between the light guides,
A part of the reflector may not be arranged at a predetermined position with respect to the light guide. In other words, due to errors in component accuracy,
A gap may be formed between the reflector and the light guide. In this case, irregular light enters from the ridge line of the thick portion of the light guide, that is, from the long side that forms the incident surface of the light guide facing the light source. As a result, in the effective area of the surface light source device, a bright line is generated near the light source, and light leaks from a gap between the reflector and the light guide.

As described above, when luminance unevenness occurs in a part of the surface light source device, there is a possibility that a display defect may occur on a liquid crystal display panel illuminated by the surface light source device.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to provide a surface light source device and a surface light source device capable of suppressing uneven brightness and preventing occurrence of display defects. An object of the present invention is to provide a liquid crystal display device provided with:

[0006]

In order to solve the above problems and achieve the object, a surface light source device according to a first aspect of the present invention is to apply light incident from an incident surface provided on one side surface to the incident surface. A light guide that emits from an emission surface provided on one intersecting main surface, and a light source that is arranged to face the incident surface of the light guide,
A reflector surrounding the light source, wherein the reflector has a cover portion that covers at least one long side of an incident surface of the light guide.

According to a seventh aspect of the present invention, there is provided a liquid crystal display device comprising a transmission type liquid crystal display panel having a liquid crystal layer sandwiched between a pair of substrates;
A surface light source device for illuminating the liquid crystal display panel, wherein the surface light source device transmits light incident from an incident surface provided on one side surface to one principal surface crossing the incident surface. In a surface light source device including: a light guide that emits light from an output surface provided; a light source disposed to face an incident surface of the light guide; and a reflector that surrounds the light source.
The reflector may include a cover that covers at least one long side of an incident surface of the light guide.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a surface light source device of the present invention and a liquid crystal display device provided with the surface light source device will be described below with reference to the drawings.

As shown in FIG. 1, the liquid crystal display device includes a transmissive liquid crystal display panel 10, an edge light type surface light source device that illuminates the liquid crystal display panel 10 from the back side, that is, a backlight unit 12, and a rectangular frame. Are laminated.

The liquid crystal display panel 10 controls a rectangular array substrate 100 and a counter substrate 200, a twisted nematic liquid crystal layer 300 sealed between these substrates via an alignment film, and the liquid crystal display panel 10, respectively. The control circuit boards 510 and 520, the drive integrated circuit 600 for electrically connecting the liquid crystal display panel 10 to the control circuit boards 510 and 520, and supplying drive signals to the liquid crystal display panel 10 are provided. The array substrate 100 includes a sealing material 331.
Is bonded to the opposing substrate 200 via the. The outer surface of each of the substrates 100 and 200 is covered by a deflecting plate arranged so that its polarization axis is orthogonal to each other.

The array substrate 100 is, for example, 1024 × 3
The signal line 115 includes 768 scanning lines 113 arranged to be orthogonal to each other. In the vicinity of the intersection between each signal line 115 and each scanning line 113, a thin film transistor or TFT using an amorphous silicon film or polysilicon in a channel region is provided.
117 are arranged. The gate electrode of the TFT 117 is electrically connected to the scanning line 113. TFT
The drain electrode 117 is electrically connected to the signal line 115. The source electrode of the TFT 117 is electrically connected to a pixel electrode 119 formed of a transparent conductive member, for example, ITO (indium-tin-oxide).

The drive integrated circuit 600 for electrically connecting the array substrate 100 and the control circuit substrate 510 includes the signal line 11
And a signal line driving integrated circuit 610 electrically connected to the signal line driving integrated circuit 610. The array substrate 100 and the control circuit substrate 52
0 is electrically connected to the scanning line driving integrated circuit 620 which is electrically connected to the scanning line 113.
It has.

The signal line driving integrated circuit 610 converts a digital image signal input from the outside into a desired analog signal voltage based on a control signal and outputs the analog signal voltage. It is composed of a buffer circuit and the like. Further, the scanning line driving integrated circuit 620 includes a shift register, a buffer circuit, and the like so as to sequentially transfer and output scanning pulses based on a control signal input from the outside.

The opposing substrate 200 includes a color filter layer arranged for each pixel area, and an opposing electrode 217 formed of a transparent conductive member, for example, ITO. The color filter layer is formed of, for example, a colored resin colored red, green, and blue, respectively.

Next, the structure of a surface light source device applied to the liquid crystal display device, that is, a backlight unit will be described.

As shown in FIGS. 1 and 2, the backlight unit 12 includes a rectangular plate-like holding frame 24, a light guide 26, and a plurality of sheet members, for example, three optical sheets 2.
8, 30, 32, an elongated tubular cold cathode ray tube 33 as a light source, a protective cover 34, and the like.

The holding frame 24 is formed of, for example, a synthetic resin and has a rectangular storage recess 36.

The optical sheet 28 is a reflection sheet made of, for example, milky white polyimide resin, and is formed in a rectangular shape having substantially the same size as the storage recess 36 of the holding frame 24.

The light guide 26 is formed of, for example, an acrylic resin, and is formed in a rectangular shape having substantially the same size as the storage recess 36 of the holding frame 24. This light guide 26
Has a thick portion 26a on one side thereof, a thin portion 26b on a side facing the thick portion 26a, and has a wedge-shaped cross section. One side surface 26d of the thick portion 26a of the light guide 26 is disposed to face the cold cathode ray tube 33, and serves as an incident surface on which light emitted from the cold cathode ray tube 33 enters.
On the back surface 26e side of the light guide 26, the reflection sheet 2 described above is provided.
8 are provided. One main surface of the light guide 26, that is, a main plane 26c opposed to the back surface 26e provided with the reflection sheet 28 is an emission surface from which light incident from the incident surface 26d is emitted.

The optical sheet 30 is, for example, a diffusion sheet and is formed in a rectangular shape having substantially the same size as the storage recess 36. The optical sheet 30 is laminated on the light exit surface 26c of the light guide 26. The optical sheet 32 is a prism sheet and is formed in a rectangular shape having substantially the same size as the storage recess 36. The optical sheet 32 is laminated on the diffusion sheet 30.

In the vicinity of the side wall 24a of the holding frame 24, an elongated lamp accommodating groove 40 extending over the entire length in the width direction is formed. A rib 41 having substantially the same height as the side wall 24a is provided upright at a central portion in the longitudinal direction of the lamp accommodating groove 40, and extends along the longitudinal direction of the lamp accommodating groove 40 and a predetermined distance from the inner surface of the side wall 24a. It extends at intervals.

The cold cathode ray tube 33 is accommodated in the region of the lamp accommodating groove 40 on the side of the accommodating recess 36 of the rib 41. That is, the cold cathode ray tube 33 is assembled integrally with the reflector 48 in a state where both ends are supported by the holder 42 in a predetermined positional relationship. The reflector 48 has a substantially U-shaped cross section, and the cold cathode ray tube 3
It is arranged so as to surround a peripheral surface other than the peripheral surface facing the light guide 26 in the periphery of the light guide 2. This cold cathode ray tube 33 is
6 is disposed at a predetermined position facing the thick portion 26a.

From the pair of holders 42, the cold cathode ray tubes 33
The connection cables 44a and 44b for supplying a voltage to are connected to each other. The connection cable 44a is routed to the other holder 42 side through the region between the rib 41 and the side wall 24a in the lamp housing groove 40, and is drawn out together with the other connection cable 44b. The two connection cables 44a and 44b pulled out are as shown in FIG.
Are connected to the lamp drive circuit 46 as shown in FIG.

The upper surface of the lamp accommodating groove 40 is covered by a protective cover 34 fitted to the holding frame 24. The protective cover 34 is formed by bending a thin metal plate into an L shape, and has an elongated upper surface wall 50 that covers the lamp accommodating groove 40.
a and a side wall 50b fitted to the outer surface of the side wall 24a of the holding frame 24.

As shown in FIG. 1, the liquid crystal display panel 10
Is the backlight unit 12 configured as described above.
And is adjacently opposed to the optical sheet 32. The bezel 14 is formed in a rectangular shape having an opening exposing an effective area of the liquid crystal display device, and the backlight unit 1 is overlapped with the periphery of the liquid crystal display panel 10.
2 with the holding frame 24. Then, by fixing the bezel 14 to the holding frame 24 by screwing or the like, the liquid crystal display panel 10 is fixed to the holding frame 24 while being sandwiched by the bezel 14.

During operation of the liquid crystal display device, part of the light emitted from the cold cathode ray tube 33 directly enters the light guide 26 from the incident surface 26 d of the light guide 26, and the remaining light is reflected by the reflector 48. After being reflected by the light guide 26, the light enters the light guide 26 through the incident surface 26d. The incident light propagates through the entire inside of the light guide 26, and the light exit surface 26 of the light guide 26
The light exits from c toward the diffusion sheet 30.

The light leaked from the light guide 26 to the reflection sheet 28 is reflected by the reflection sheet 28 and reenters the light guide 26. Light emitted from the emission surface 26c of the light guide 26 is diffused by the diffusion sheet 30 and guided to the entire surface of the liquid crystal display panel 10 by the prism sheet 32.

In the liquid crystal display panel 10, transmission and non-transmission of light guided for each pixel is selectively controlled, and an image is displayed.

Next, the structure of the reflector 48 applied to the backlight unit 12 will be described in more detail.

The reflector 48 is formed of a metal plate having a thickness of about 0.1 to 0.2 mm. The reflector 48 includes a cover 48A as shown in FIG. The cover portion 48A corresponds to a concave portion obtained by bending a metal plate forming the reflector 48 toward the cold cathode ray tube 33. This recess extends in the longitudinal direction of the light guide 26. The height of the cover portion 48A, that is, the depth of the concave portion is set so as to be able to absorb an error in the component accuracy of the light guide 26 and the reflector 48, and is, for example, 0.2 mm.

The reflector 48 is assembled integrally with the cold cathode ray tube 33, and then the thick portion 26a of the light guide 26 is assembled.
And the reflection sheet 28 is interposed. At this time, the reflector 48 is assembled such that the cover 48 </ b> A contacts the incident surface 26 d of the light guide 26. Thus, at least one long side of the incident surface 26d of the light guide 26 is covered by the cover 48A.

In the example shown in FIG. 3, the cover 48A
The reflector 48 is formed so as to cover only one side 26X where the light exit surface 26c and the light entrance surface 26d of the light guide 26 intersect.

If there is a gap between the light guide 26 and the reflector 48 due to an error in the precision of the components, when these are assembled, the incident surface 26d of the light guide 26
Irregular light incident from the long sides 26X and 26Y generates bright lines in the effective area A of the surface light source device. For example, as shown in FIG.
The light incident from 6X is reflected by the reflection sheet 28 on the back surface side of the light guide 26, is emitted from the emission surface 26c in the effective area A, and generates a bright line. On the other hand, the incident surface 26
Light incident from the long side 26Y of d is often emitted from the emission surface 26c outside the effective area A.

Therefore, the incident surface 2 of the light guide 26
Since at least the long side 26X of 6d is covered by the cover portion 48A of the reflector 48, it is possible to suppress the generation of the bright line in the effective area A of the surface light source device.

Further, even when a gap is formed between the light guide 26 and the reflector 48, light can be prevented from leaking because the cover 48A closes the gap.

Further, the cover portion 48A functions as a positioning portion for positioning the reflector 48 with respect to the light guide 26. That is, the reflector 48 is
A is attached so as to abut the incident surface 26 d of the light guide 26, so that the reflector 48 integrated with the cold cathode ray tube 33 is provided.
And the positional relationship with the light guide 26 can be uniquely determined.

In the example shown in FIG.
A and 48B are one side 26X where the exit surface 26c and the entrance surface 26d of the light guide 26 intersect, respectively, and the light guide 2
The side 26Y where the back surface 26e of the No. 6 intersects with the incident surface 26d
The reflector 48 is formed so as to cover

In this case, the incident surface 26 of the light guide 26
Since the long side 26X and the long side 26Y of d are covered by the cover 48A and the cover 48B of the reflector 48, respectively, it is possible to suppress the generation of the bright line in the effective area A of the surface light source device.

Further, even when a gap is formed between the light guide 26 and the reflector 48, light leakage can be prevented because the covers 48A and 48B close the gap.

Further, the covers 48A and 48B function as positioning portions for positioning the reflector 48 with respect to the light guide 26. That is, since the reflector 48 is attached so that the cover portions 48A and 48B abut on the incident surface 26d of the light guide 26, the positional relationship between the reflector 48 integrated with the cold cathode ray tube 33 and the light guide 26 is unified. It is possible to decide.

Thus, the incident surface 26d of the light guide 26 and the cold cathode ray tube 33, and the incident surface 26d of the light guide 26
And the reflector 48 can be positioned in a predetermined positional relationship that allows light to be efficiently incident on the incident surface 26d.

Accordingly, it is possible to prevent a decrease in luminance due to a decrease in the efficiency of light incident on the incident surface 26d of the light guide 26, and to prevent irregular light incident from the long side of the incident surface 26d. The generation of bright lines can be prevented. Therefore, in the liquid crystal display panel illuminated by such a surface light source device, it is possible to prevent a display defect from occurring.

[0043]

As described above, according to the present invention, there is provided a surface light source device capable of suppressing luminance unevenness and preventing occurrence of display defects, and a liquid crystal display device provided with the surface light source device. Can be provided.

[Brief description of the drawings]

FIG. 1 is an exploded view schematically showing a structure of a liquid crystal display device provided with a surface light source device of the present invention.

FIG. 2 is an exploded view schematically showing the structure of the surface light source device of the present invention.

FIG. 3 is a diagram showing a part of the surface light source device shown in FIG.
It is sectional drawing at the time of cutting along the A line.

FIG. 4 is a cross-sectional view schematically showing a part of another surface light source device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display panel 12 ... Surface light source device 100 ... Array substrate 200 ... Counter substrate 300 ... Liquid crystal layer 26 ... Light guide 26a ... Thick part 26b ... Thin part 26c ... Emission surface 26d ... Incident surface 26e ... Back part 33 ... Cold cathode ray tube 48 ... Reflector 48A, 48B ... Cover

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G09F 9/00 336 F21Y 103: 00 // F21Y 103: 00 G02F 1/1335 530

Claims (7)

[Claims] A light guide for emitting light incident from an incident surface provided on one side surface from an output surface provided on one principal surface intersecting the incident surface; A surface light source device comprising: a light source disposed to face the light source; and a reflector surrounding the light source, wherein the reflector has a cover portion that covers at least one long side of an incident surface of the light guide. Surface light source device. 2. The light guide according to claim 1, wherein the cover covers one side where an incident surface and an exit surface of the light guide intersect.
A surface light source device according to claim 1. 3. The cover portion covers one side where the incident surface and the exit surface of the light guide intersect, and one side where the incident surface and the back surface of the exit surface of the light guide intersect. The surface light source device according to claim 1. 4. The light source device according to claim 1, further comprising: a reflection sheet provided on a back surface side of an emission surface of the light guide, for reflecting light propagating inside the light guide toward the emission surface. The surface light source device according to claim 1, further comprising: an optical sheet provided on an emission surface of the light body and providing predetermined optical characteristics to light emitted from the emission surface. 5. The apparatus according to claim 1, wherein the cover is a recess formed by bending the reflector toward the light source.
A surface light source device according to claim 1. 6. The surface light source device according to claim 5, wherein said cover portion functions as a positioning portion for positioning said reflector with respect to said light guide. 7. A liquid crystal display device comprising: a transmissive liquid crystal display panel that sandwiches a liquid crystal layer between a pair of substrates; and a surface light source device that illuminates the liquid crystal display panel. A light guide that emits light incident from an incident surface provided on a side surface from an exit surface provided on one principal surface crossing the incident surface, and is disposed to face the incident surface of the light guide. A liquid crystal display device, comprising: a light source; and a reflector surrounding the light source, wherein the reflector has a cover that covers at least one long side of an incident surface of the light guide.