JP2010205614A - Illumination unit, and liquid crystal display device equipped with this illumination unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illumination unit capable of preventing generation of an emission line, and a liquid crystal display device equipped with this illumination unit, and superior in display quality. <P>SOLUTION: This device is equipped with a liquid crystal display panel 2 and the illumination unit 15 to illuminate the liquid crystal display panel 2. The illumination unit 15 is equipped with a light-emitting diode 41, a light guide plate 22 having an incident face 22c to which radiation light radiated from the light-emitting diode 41 is made incident, and a circuit board 42 on which a plurality of light-emitting diodes 41 are mounted. The light guide plate 22 has a plurality of convex parts 22P protruding from the incident face 22c, and a flat and thick-walled part 22W having the thickness W2 larger than the thickness W1 of the convex parts 22P at one end on the incident face 22c side. The circuit board 42 is arranged on the convex parts 22P via an adhesive 44 so that it is contacted with a thick-walled part 22W of the light guide plate 22 and that the light-emitting diodes 41 are arranged between the convex parts 22P. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an illumination unit and a liquid crystal display device including the illumination unit, and more particularly to an illumination unit including a light emitting diode (LED) as a light source and a liquid crystal display device including the illumination unit.

  Liquid crystal display devices are utilized in various fields as display devices for OA equipment such as personal computers and televisions, taking advantage of features such as light weight, thinness, and low power consumption. In recent years, liquid crystal display devices are also used as display devices for portable devices such as mobile phones, portable music players, and portable navigation.

  As such a liquid crystal display device, a reflection type that selectively reflects external light to display an image, a transmission type that selectively transmits backlight light to display an image, and a reflection type and transmission type A module such as a transflective module that has both functions of a mold has been developed.

  Among these, a transmissive or transflective liquid crystal display device includes a transmissive liquid crystal display panel and an illumination unit (that is, a backlight) disposed on the back side of the liquid crystal display panel.

In portable devices, there are high demands for miniaturization, thinning, and power saving, and thinning and power saving of liquid crystal display devices are desired. For this reason, in recent years, an illumination unit mounted on a liquid crystal display device in which a side-view type light emitting diode is used as a light source has been put into practical use. For example, Patent Document 1 discloses a backlight unit in which a light output surface (side surface) of a point light source device (LED chip) installed on a flexible substrate is disposed to face an end surface of a light guide plate.
JP 2008-140849 A

  In the liquid crystal display device having the above-described configuration, the circuit board on which the side-view type light emitting diode is mounted is generally sandwiched and fixed between a plurality of members, but may be displaced due to an external impact or the like. Therefore, it may be fixed through an adhesive member such as a double-sided tape. For example, when the circuit board is bonded to the light exit surface of the light guide plate via a double-sided tape, a gap corresponding to the thickness of the double-sided tape is formed between the light guide plate and the circuit board. For this reason, a part of the light emitted from the light emitting diode may not be taken into the light guide plate and may leak from the gap between the light guide plate and the circuit board.

  The height of the light emitting surface of the light emitting diode from the circuit board varies depending on the amount of solder between the light emitting diode and the circuit board when the light emitting diode is mounted on the circuit board by solder. That is, the height of the light emitting surface of the light emitting diode from the circuit board varies depending on the mounting condition of the light emitting diode. For example, when the amount of solder is relatively large, the height of the light emitting surface of the light emitting diode from the circuit board becomes high, and when the amount of solder is relatively small, the height of the light emitting surface of the light emitting diode from the circuit board. Becomes lower. If the height of the light emitting surface of the light emitting diode from the circuit board is low, part of the light emitted from the light emitting diode may not be taken into the light guide plate and may leak from the gap between the light guide plate and the circuit board. .

  In the lighting unit, when the light emitted from the light emitting diode leaks from the gap between the light guide plate and the circuit board, a part of the light emitted from the light emitting diode is directly incident on various optical sheets arranged on the light emitting surface of the light guide plate. There is. In particular, when the light emitted from the light emitting diode is directly incident on the optical sheet having a condensing function, it may appear as a bright line. Moreover, in a liquid crystal display device equipped with such an illumination unit, display quality may be deteriorated.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an illumination unit capable of preventing generation of bright lines and a liquid crystal display device having a good display quality provided with the illumination unit. There is to do.

A lighting unit according to an aspect of the present invention comprises:
A light emitting diode having a light emitting surface substantially perpendicular to the mounting surface;
A circuit board on which a plurality of the light emitting diodes are mounted side by side at a predetermined interval;
An incident surface facing the light emitting surface of the light emitting diode; a main plane that the circuit board contacts; and a plurality of protrusions that protrude substantially perpendicularly from the incident surface so as to be positioned between the light emitting diodes. A light guide plate,
The convex portion has a thickness smaller than the thickness of the incident surface, and forms a step with the main plane;
The circuit board is bonded onto the convex portion through an adhesive member.

A liquid crystal display device according to an aspect of the present invention includes:
A liquid crystal display panel having a display area composed of a plurality of pixels;
An illumination unit for illuminating the liquid crystal display panel,
The lighting unit is:
A light emitting diode having a light emitting surface substantially perpendicular to the mounting surface;
A circuit board on which a plurality of the light emitting diodes are mounted side by side at a predetermined interval;
The light incident surface of the light emitting diode faces the light emitting surface, the main plane that contacts the circuit board and faces the liquid crystal display panel, and protrudes substantially perpendicularly from the light incident surface so as to be positioned between the light emitting diodes. A light guide plate having a plurality of convex portions,
The convex portion has a thickness smaller than the thickness of the incident surface, and forms a step with the main plane;
The circuit board is bonded onto the convex portion through an adhesive member.

  According to the present invention, it is possible to provide an illumination unit capable of preventing the generation of bright lines and a liquid crystal display device having a good display quality provided with the illumination unit.

  That is, in the illumination unit, the convex portion of the light guide plate has a thickness smaller than the thickness of the incident surface, and further, a step is formed between the light emitting diode and the main surface. Can be placed between the extended surface of the main plane and the upper surface of the convex section when the circuit board is placed in contact with the main plane of the light guide plate. It becomes.

  For this reason, the light leakage from the clearance gap between a circuit board and a light-guide plate can be suppressed. As a result, in the lighting unit, regardless of the mounting conditions of the light emitting diode, the light emitted from the light emitting diode is taken into the incident surface of the light guide plate, and it is possible to prevent the generation of bright lines and the light utilization efficiency. As a result, the luminance can be increased while the power consumption is low.

  Further, in a liquid crystal display device equipped with such an illumination unit, it is possible to prevent display quality deterioration such as display unevenness.

  Hereinafter, an illumination unit according to an embodiment of the present invention and a liquid crystal display device including the illumination unit will be described with reference to the drawings. Here, a transmissive liquid crystal display device that selectively transmits backlight light from a backlight unit that is an illumination unit and displays an image will be described.

  That is, as shown in FIG. 1, the liquid crystal display device 1 includes a transmissive liquid crystal display panel 2 having a substantially rectangular flat plate shape, and an illumination unit 15 that illuminates the liquid crystal display panel 2. The liquid crystal display panel 2 is configured by holding a liquid crystal layer between a pair of substrates. That is, the liquid crystal display panel 2 includes a substantially rectangular array substrate 3 and a counter substrate 4, and a liquid crystal layer 5 sealed between the array substrate 3 and the counter substrate 4. The array substrate 3 and the counter substrate 4 are bonded to each other through a sealing material (not shown).

  The liquid crystal display panel 2 includes a substantially rectangular display area 6 for displaying an image on the inner side surrounded by a sealing material. The display area 6 is composed of a plurality of pixels PX arranged in a matrix.

  In the display area 6, the array substrate 3 includes a plurality of scanning lines Y (1, 2,...), A plurality of signal lines X (1, 2,...), A switching element 7 disposed in each pixel PX, and each pixel PX. The pixel electrode 8 connected to the switching element 7 is provided. The pixel electrode 8 is formed of a light-transmitting conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO).

  Each scanning line Y extends along the row direction of the pixel PX. Each signal line X extends along the column direction of the pixels PX so as to intersect with each scanning line Y via an insulating layer. Each switching element 7 is disposed in a region including an intersection of the scanning line Y and the signal line X.

  The switching element 7 is composed of, for example, a thin film transistor (TFT) having a semiconductor layer formed of amorphous silicon, polysilicon, or the like. The gate electrode 7G of the switching element 7 is electrically connected to the corresponding scanning line Y (or formed integrally with the scanning line). The source electrode 7S of the switching element 7 is electrically connected to the corresponding signal line X (or formed integrally with the signal line). The drain electrode 7D of the switching element 7 is electrically connected to the pixel electrode 8 of the corresponding pixel PX.

  The common electrode 9 for applying a voltage to the liquid crystal layer 5 due to a potential difference with the pixel electrode 8 may be provided on the array substrate 3 or on the counter substrate 4. That is, in the horizontal electric field mode mainly using the horizontal electric field (electric field substantially parallel to the main surface of the substrate), the array substrate 3 has the common electrode 9 that is electrically insulated from the pixel electrode 8 and opposed to the pixel electrode 8. I have. In the vertical electric field mode mainly using the vertical electric field (electric field substantially perpendicular to the main surface of the substrate), the counter substrate 4 includes a common electrode 9 that faces the pixel electrode 8 with the liquid crystal layer 5 interposed therebetween. Similar to the pixel electrode 8, the common electrode 9 is formed of a light-transmitting conductive material.

  The surfaces of the array substrate 3 and the counter substrate 4 that are in contact with the liquid crystal layer 5 are each covered with an alignment film (not shown). The array substrate 3 and the counter substrate 4 are bonded to each other with the alignment films facing each other via a spacer (not shown) (for example, a columnar spacer formed integrally with one substrate). At this time, a predetermined gap is formed between the array substrate 3 and the counter substrate 4 by a spacer. The liquid crystal layer 5 is formed of a liquid crystal composition sealed in the gap between the array substrate 3 and the counter substrate 4.

  In the liquid crystal display panel 2, optical elements OD1 and OD2 are provided on the outer surface of the array substrate 3 and the outer surface of the counter substrate 4, respectively. These optical elements OD1 and OD2 include a polarizing plate whose polarization direction is set in accordance with the characteristics of the liquid crystal layer 5. Further, the optical elements OD1 and OD2 may include a retardation plate as necessary.

  In the color display type liquid crystal display device, the liquid crystal display panel 2 has a plurality of types of pixels in the display area 6, for example, a red pixel that displays red (R), a green pixel that displays green (G), and a blue (B ) Is displayed. That is, the red pixel includes a red color filter that transmits light having a red main wavelength. The green pixel includes a green color filter that transmits light having a green dominant wavelength. The blue pixel includes a blue color filter that transmits light having a blue main wavelength. These color filters are arranged on the main surface of the array substrate 3 or the counter substrate 4.

  The liquid crystal display device 1 includes a bezel cover 11 having a rectangular frame shape. The bezel cover 11 includes a rectangular window portion 11A that exposes the display area 6 of the liquid crystal display panel 2, and a rectangular frame-shaped main body portion 11B that defines the window portion 11A. The liquid crystal display panel 2 configured as described above is sandwiched between the illumination unit 15 and the bezel cover 11. At this time, the illumination unit 15 is arranged with the surface thereof facing the back side of the liquid crystal display panel 2 (that is, the array substrate side), and illuminates the liquid crystal display panel 2 from the back side.

  As shown in FIGS. 2 to 5, the illumination unit 15 includes a light source unit 21, a light guide plate 22, frames 23a and 23b, a back cover 25, an optical sheet 26, and the like.

  The light source unit 21 includes a light emitting diode (LED) 41 that is a point light source, a circuit board 42, and the like.

  The light-emitting diode 41 is a side-view type semiconductor light-emitting element having a light-emitting surface 41E that is substantially orthogonal to the mounting surface 41D mounted on the circuit board 42. In particular, as shown in FIG. 5, the circuit board 42 is formed in a substantially rectangular shape (a rectangular shape having a long side 42a having a length substantially equal to the long side 21c1 of the incident surface 22c). The plurality of light emitting diodes 41 are mounted on the circuit board 42 at a predetermined interval in a direction parallel to the long side 42a. The plurality of light emitting diodes 41 are arranged in a line.

  The light guide plate 22 has a function of guiding emitted light from the light source unit 21 toward the liquid crystal display panel 2. The light guide plate 22 is made of a light-transmissive resin material such as acrylic resin or polycarbonate resin.

  As shown in FIG. 4, the light guide plate 22 includes a first main plane 22a facing the liquid crystal display panel 2, a second main plane 22b facing the first main plane 22a, and the first main planes. 22a and an end face connecting the second main plane 22b. The one end surface 22c functions as an incident surface facing the light source. Further, the first main plane 22 a functions as an exit slope that emits light toward the liquid crystal display panel 2.

  The light guide plate 22 has a plurality of convex portions 22P protruding from the incident surface 22c. The plurality of convex portions 22P protrude substantially perpendicular to the incident surface 22c. In the example shown in FIG. 4, the incident surface 22c is formed in a rectangular shape. The plurality of convex portions 22P are arranged at a predetermined interval along a direction parallel to the long side 22c1 of the incident surface 22c. The plurality of convex portions 22P are arranged in a line.

  In particular, the thickness W1 of the convex portion 22P is smaller than the thickness W2 of the incident surface 22c (W2> W1). Here, the thickness corresponds to the height along the normal direction of the first main plane 22a facing the liquid crystal display panel 2 side. Moreover, this convex part 22P forms a level | step difference between the 1st main planes 22a.

  That is, the thickness W2 of the incident surface 22c and the thickness W1 of the convex portion 22P are the extension surface of the first main plane 22a (surface on the liquid crystal display panel 2 side) orthogonal to the incident surface 22c and the upper surface (liquid crystal) of the convex portion 22P. And the display panel 2 side surface).

  In the example shown in FIG. 6, the bottom surface (surface opposite to the top surface) of the convex portion 22P and the second main plane 22b are formed on the same plane. Thereby, a step corresponding to the difference (W2−W1) between the thickness W2 of the incident surface and the thickness W1 of the convex portion 22P is formed between the upper surface of the convex portion 22P and the first main plane 22a.

  The frames 23a and 23b are mainly configured to hold the light guide plate 22. Such frames 23a and 23b are formed of a resin material.

  The back cover 25 is generally formed in a box shape and can store the light guide plate 22 and the like together with the frames 23a and 23b.

  The optical sheet 26 is disposed between the liquid crystal display panel 2 and the first main plane 22 a of the light guide plate 22 and between the back cover 25 and the second main plane 22 b of the light guide plate 22. An optical sheet 26B is provided.

  The optical sheet 26 </ b> A is, for example, a light collecting sheet 26 </ b> A <b> 1, a diffusion sheet 26 </ b> A <b> 2, and the like. In the example shown in FIG. 3, the diffusion sheet 26A2 is disposed on the first main plane 22a of the light guide plate 22, and the two light collecting sheets 26A1 are stacked on the diffusion sheet 26A2. The optical sheet 26 </ b> B is a reflection sheet, and reflects the light leaking from the second main plane 22 b of the light guide plate 22 toward the light guide plate 22 again.

  In the illumination unit 15 having such a configuration, the circuit board 42 is disposed such that the mounting surface 41D is in contact with the first main plane 22a and is located between the light emitting diode 41 convex portions 22P. At this time, the light emitting surface 41E of the light emitting diode 41 faces the incident surface 22c.

  Such a circuit board 42 is bonded onto the convex portion 22 </ b> P via an adhesive member 44. The adhesive member 44 is, for example, a double-sided tape.

  According to such a structure, the area | region D which can arrange | position the adhesive member 44 is formed between the extended surface of the 1st main plane 22a, and the upper surface of the convex part 22P. When the circuit board 42 arranged so as to be in contact with the main plane of the light guide plate is bonded to the convex portion 22P of the light guide plate 22 via the adhesive member 44, the adhesive material 44 is arranged in the region D. For this reason, light leakage from the gap between the circuit board 42 and the light guide plate 22 can be suppressed. As a matter of course, part of the LED light does not directly enter the condensing sheet 26A1.

  Thereby, in the illumination unit 15, regardless of the mounting conditions of the light emitting diode 41, the emitted light from the light emitting diode 41 is taken into the incident surface 22 c of the light guide plate 22, and it is possible to prevent the generation of bright lines. The use efficiency of light is improved, and high luminance can be achieved with low power consumption. Further, in the liquid crystal display device 1 equipped with such an illumination unit 15, it is possible to prevent display quality from being deteriorated.

  In the example shown in FIG. 3, the light guide plate 22 includes a thick portion 22W including the incident surface 22c, a thin portion 22T having a uniform thickness smaller than the thickness of the thick portion 22W, and a thick portion 22W. And an inclined portion 22S that connects the thin portion 22T. While the second main plane 22b is a flat surface, the first main plane 22a has a flat portion corresponding to the thick portion 22W and the thin portion 22T and an inclined surface corresponding to the inclined portion 22S. In the first main plane 22a, it is desirable that the inclination angle between the flat surface and the inclined surface is 5 ° to 10 °. The thick portion 22W desirably has a width in the direction perpendicular to the incident surface 21c of 0.1 μm to 0.2 μm.

  At this time, the diffusion sheet 26A2 disposed on the first main plane 22a is disposed so as to cover at least the inclined surface 22SL corresponding to the inclined portion 22S. In the example shown in FIG. 3, the diffusion sheet 26A2 covers the inclined portion 22S and the thin portion 22T.

  Even if a part of the LED light incident on the thick portion 22W leaks from the inclined surface 22SL by arranging the diffusion sheet 26A2 on the inclined surface 22SL between the thick portion 22W and the thin portion 22T, the diffusion sheet 26A2 Therefore, the generation of bright lines can be suppressed.

  According to such a configuration, it is possible to prevent light leakage from the light guide plate 22 in the illumination unit 15. Further, in the liquid crystal display device 1 equipped with such an illumination unit 15, it is possible to prevent display quality from being deteriorated.

  In addition, this invention is not limited to the said embodiment itself, In the stage of implementation, it can change and implement a component within the range which does not deviate from the summary. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

FIG. 1 is an exploded perspective view schematically showing the structure of a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is an exploded perspective view schematically showing the structure of the illumination unit in the liquid crystal display device shown in FIG. 3 is a cross-sectional view schematically showing the structure of the illumination unit shown in FIG. FIG. 4 is a perspective view schematically showing the structure of the light guide plate in the illumination unit shown in FIGS. 2 and 3. FIG. 5 is a perspective view schematically showing the structure of the light guide plate and the light source unit in the illumination unit shown in FIGS. 2 and 3. FIG. 6 is a cross-sectional view schematically showing a structure when the light guide plate and the light source unit shown in FIG. 5 are cut along the line A-A ′.

2 ... Liquid crystal display panel 2
DESCRIPTION OF SYMBOLS 15 ... Illumination unit 22 ... Light guide plate 22c ... Incident surface 22P ... Convex part 22W ... Thick part 41 ... Light emitting diode 42 ... Circuit board 44 ... Adhesive material

Claims (7)

A light emitting diode having a light emitting surface substantially perpendicular to the mounting surface;
A circuit board on which a plurality of the light emitting diodes are mounted side by side at a predetermined interval;
An incident surface facing the light emitting surface of the light emitting diode; a main plane that the circuit board contacts; and a plurality of protrusions that protrude substantially perpendicularly from the incident surface so as to be positioned between the light emitting diodes. A light guide plate,
The convex portion has a thickness smaller than the thickness of the incident surface, and forms a step with the main plane;
The said circuit board is adhere | attached on the said convex part via an adhesive member, The illumination unit characterized by the above-mentioned. The light guide plate includes a thick part including the incident surface, the thin part having a uniform thickness smaller than the thickness of the thick part, and an inclined part connecting the thick part and the thin part, Have
The lighting unit according to claim 1, wherein the main plane includes a flat surface corresponding to the thick portion and the thin portion, and an inclined surface corresponding to the inclined portion. Furthermore, a diffusion sheet disposed on the main plane of the light guide plate,
The lighting unit according to claim 2, wherein the diffusion sheet covers at least the inclined surface on the main plane.   The lighting unit according to claim 2, wherein an inclination angle between the flat surface and the inclined surface in the main plane is 5 ° to 10 °.   The lighting unit according to claim 2, wherein the thick portion has a width in a direction perpendicular to the incident surface of 0.1 μm to 0.2 μm.   The lighting unit according to claim 1, wherein a level difference between the main plane and the convex portion is equal to or greater than a thickness of the adhesive member. A liquid crystal display panel having a display area composed of a plurality of pixels;
An illumination unit for illuminating the liquid crystal display panel,
The lighting unit is:
A light emitting diode having a light emitting surface substantially perpendicular to the mounting surface;
A circuit board on which a plurality of the light emitting diodes are mounted side by side at a predetermined interval;
The light incident surface of the light emitting diode faces the light emitting surface, the main plane that contacts the circuit board and faces the liquid crystal display panel, and protrudes substantially perpendicularly from the light incident surface so as to be positioned between the light emitting diodes. A light guide plate having a plurality of convex portions,
The convex portion has a thickness smaller than the thickness of the incident surface, and forms a step with the main plane;
The liquid crystal display device, wherein the circuit board is bonded onto the convex portion through an adhesive member.

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