JP5227856B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device including a wiring board connected to a liquid crystal display panel.

  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 mobile terminal devices such as mobile phones, display devices such as car navigation devices and game machines.

  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.

  Further, such a liquid crystal display device includes a wiring board disposed on one side edge of the liquid crystal display panel, for example, a flexible printed circuit (FPC). The wiring board is connected to a signal source such as an external circuit, and supplies a driving signal output from the signal source to the liquid crystal display panel.

As such a liquid crystal display device, for example, according to Patent Document 1, a liquid crystal display device in which a liquid crystal display panel, a flexible circuit board, and an illumination unit are housed in a case is disclosed. This flexible circuit board is fixed to the back surface of the lighting unit. Further, the flexible circuit board is attached to the back of the case with a double-sided adhesive tape attached to the case portion.
JP 2006-163100 A

  In recent years, mobile phones have a function of receiving terrestrial digital broadcasting, and it is desired to increase the display screen. On the other hand, the size of the mobile phone itself does not change so much, but rather is becoming smaller. For this reason, there is an increasing demand for narrowing the frame of a liquid crystal display device mounted on a mobile phone.

  In a liquid crystal display device having a structure in which the wiring substrate is bent to the back side of the liquid crystal display panel and fixed via an adhesive member, the adhesive region of the adhesive member is also reduced in accordance with the narrowing of the frame of the liquid crystal display device. For this reason, the adhesive force of the adhesive member may be defeated by the repulsive force of the wiring substrate, and the wiring substrate may be peeled off from the adhesive member.

  As a result, a liquid crystal display device having an outer shape different from the specification is manufactured, and the liquid crystal display device may not be incorporated into a mobile phone or the like. Further, when the light emitting diode is mounted on the wiring board, the light emitting diode may be displaced from a predetermined position. As a result, luminance unevenness may occur and 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 a liquid crystal capable of realizing a narrow frame, securely fixing a wiring board, and preventing a decrease in manufacturing yield. It is to provide a display device.

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;
A wiring board connected to one side edge of the liquid crystal display panel and bent to the back of the lighting unit;
The lighting unit is:
A plurality of light emitting diodes arranged at predetermined intervals;
A light guide plate having an incident surface facing each light emitting surface of the light emitting diode and having a recess recessed from the incident surface facing the light emitting surfaces of two adjacent light emitting diodes;
Having a convex part fitted in the concave part, and holding the light guide plate,
The back surface of the convex portion is on the same plane as the back surface of the light guide plate,
The wiring board is bonded to the back surface of the convex portion via an adhesive member.

  According to the present invention, it is possible to provide a liquid crystal display device that can realize a narrow frame, can securely fix a wiring board, and can prevent a decrease in manufacturing yield.

  That is, in the illumination unit, the light guide plate has a recess that is recessed from the incident surface facing the light emitting surfaces of the two light emitting diodes arranged at a predetermined interval, and the frame that holds the light guide plate has a recess. It has a convex part fitted in. The wiring board connected to one side edge of the liquid crystal display panel and bent to the back surface of the illumination unit can be bonded to the back surface of the convex portion on the same plane as the back surface of the light guide plate via an adhesive member. . That is, in the lighting unit, the frame has a convex portion, so that an adhesion area for bonding the wiring board is increased, and an adhesive force between the wiring board and the lighting unit is increased.

  As a result, it is possible to prevent the wiring board from being peeled off from the lighting unit due to the repulsive force of the wiring board. Therefore, it is possible to prevent a decrease in manufacturing yield.

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

  That is, as shown in FIGS. 1 and 2, the liquid crystal display device 1 includes a transmissive liquid crystal display panel 2 having a substantially rectangular flat plate shape, an illumination unit 15 that illuminates the liquid crystal display panel 2, and the illumination unit 15. A back cover 25 for housing is provided. 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 through 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) including 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 spacers (not shown) (for example, columnar spacers integrally formed on 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.

  Further, the liquid crystal display device 1 includes a wiring substrate 13 that is electrically connected to the liquid crystal display panel 2. The wiring board 13 is connected to a signal source such as an external circuit, and supplies a driving signal output from the signal source (that is, various signals necessary for driving the pixel PX such as a video signal and a power source) to the liquid crystal display panel 2. To do. The wiring board 13 includes a terminal portion connected to the liquid crystal display panel 2.

  Such a wiring board 13 is bent and arranged on the back surface of the illumination unit 15 (that is, the surface opposite to the surface facing the liquid crystal display panel 2). That is, the wiring board 13 is disposed between the illumination unit 15 and the back cover 25.

  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.

  The illumination unit 15 includes a light source 21, a light guide plate 22, a frame 23, an optical sheet 26, and the like as shown in FIG.

  The light source 21 is composed of light emitting diodes (LEDs) that are a plurality of point light sources. The light emitting diode 21 is a semiconductor light emitting element having a light emitting surface 21E. The plurality of light emitting diodes 21 are arranged side by side at a predetermined interval.

  The light guide plate 22 has a function of guiding the emitted light from the light emitting diode 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. The light guide plate 22 includes a wedge-type plate having a thin portion at one end and a thick portion at the other end facing the thin portion, and a flat plate type having a substantially uniform thickness over the whole. However, in this embodiment, a rectangular flat plate type is adopted.

  The light guide plate 22 includes a rectangular first main plane 22a facing the liquid crystal display panel 2, a rectangular second main plane 22b facing the first main plane 22a, and the first main plane 22a. And four rectangular end faces connecting the second main plane 22b. The one end surface 22c functions as an incident surface facing the light emitting surface 21E of the light emitting diode. Further, the first main plane 22 a functions as an emission surface that emits light toward the liquid crystal display panel 2.

  The frame 23 is mainly configured to hold the light guide plate 22. The frame 23 is made of a resin material. The wiring board 13 is bonded to the back surface of the frame 23 (that is, the surface opposite to the surface facing the liquid crystal display panel 2) via an adhesive member GL such as a double-sided tape.

  The optical sheet 26 is disposed between the liquid crystal display panel 2 and the optical sheet 26 </ b> A disposed between the first main plane 22 a of the light guide plate 22 and 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 condensing sheet or a diffusion sheet, and imparts predetermined optical characteristics to the light emitted from the light guide plate 22 and guides it to the liquid crystal display panel 2. 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.

  The back cover 25 is disposed so as to face the back surface of the lighting unit 15. 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 frame 23 and the like.

  By the way, as shown in FIG. 3, the light guide plate 22 has a concave portion 28 having a rear end surface 28 </ b> A that is retracted from the incident surface 22 c facing the light emitting surfaces 21 </ b> E of the plurality of light emitting diodes 21. In the example shown in FIG. 3, four light emitting diodes, that is, a first light emitting diode 21a, a second light emitting diode 21b, a third light emitting diode 21c, and a fourth light emitting diode 21d are arranged side by side at a predetermined interval. Yes. The light guide plate 22 has a recess 28 having a receding surface 28A that recedes from the incident surface 22c facing the light emitting surface 21E of the second light emitting diode 21b and the third light emitting diode 21c.

  More specifically, as shown in FIG. 3, the recess 28 has a shape that is recessed from the incident surface 22c. The recess 28 has a height equivalent to the thickness of the light guide plate 22, and has a rear end surface 28A, and two side end surfaces 28B and 28C that connect the incident surface 22c and the rear end surface 28A. Such a recess 28 is formed so as not to overlap the display area 6 when the illumination unit 15 and the liquid crystal display panel 2 overlap.

  The frame 23 has a convex portion 29 having a shape corresponding to the concave portion 28. The convex portion 29 has a protruding surface 29A protruding from the facing surface 23c facing the incident surface 22c, and two side end surfaces 29B and 29C connecting the facing surface 23c and the protruding surface 29A. The convex portion 29 is fitted into the concave portion 28. That is, the projecting surface 29A, the rear end surface 28A, the side end surface 28C, the side end surface 29C, the side end surface 28B, and the side end surface 29B are arranged to face each other. Further, the back surface of the convex portion 29 (that is, the surface opposite to the surface facing the liquid crystal display panel 2) and the back surface of the light guide plate 22 (that is, the second main plane 22b) are formed on the same plane. .

  Further, the reflection sheet 26 </ b> B is formed so that the convex portion 29 is exposed when it is superimposed on the light guide plate 22. For example, the reflection sheet 26 </ b> B has a notch corresponding to the recess 28.

  In such a configuration, as shown in FIGS. 4 and 5, the wiring substrate 13 connected to one side edge of the liquid crystal display panel 2 and bent to the back surface of the illumination unit 15 includes the back surface of the convex portion 29 and the light guide plate. Since the back surface of 22 is on the same plane, the back surface of the convex portion 29 can be bonded via the adhesive member GL. That is, in the illumination unit 15, since the frame 23 has the convex portion 29, an adhesion region for adhering the wiring board 13 by the adhesive member GL is increased without increasing the entire frame size. The adhesive force with the lighting unit 15 is increased. Thereby, it is possible to prevent the wiring board 13 from being peeled off from the illumination unit 15 due to the repulsive force of the wiring board 13.

  That is, it is possible to manufacture a liquid crystal display device that satisfies the external specifications, and it is possible to easily incorporate the liquid crystal display device into a mobile phone or the like. Therefore, in such a liquid crystal display device, it is possible to realize a narrow frame and to securely fix the wiring board and to prevent a decrease in manufacturing yield.

  Further, when the light emitting diode 21 is mounted on the wiring board 13, the light emitting diode 21 can be kept at a predetermined position, and the occurrence of uneven brightness in the liquid crystal display device can be prevented. Therefore, it is possible to suppress deterioration of display quality.

  Incidentally, it is desirable that the angle θ1 formed by the end surfaces 28B and 28C and the reference surface REF orthogonal to the incident surface 22c be smaller than 90 °. In other words, it is desirable that the angle formed between the side end surfaces 28B and 28C and the incident surface 22c is an obtuse angle.

  The light emitting diode 21 has light directivity that travels in the direction of the optical axis parallel to the normal line of the light emitting surface 21E, and has a specific divergence angle. The outgoing light emitted from the light emitting surface 21E of the light emitting diode 21 travels in a radial manner, that is, in a fan shape while diverging at an angle θ with respect to the optical axis. The angle θ at this time is the divergence angle.

  As shown in FIG. 6, the recess 28 is formed such that an angle θ1 formed by the side end surfaces 28B and 28C and the reference surface REF orthogonal to the incident surface 22c is larger than the divergence angle θ2 with respect to the optical axis 21D of the light emitting diode 21. It is desirable that

  That is, the width W1 of the rear end surface 28A of the recess 28 in the direction parallel to the incident surface 22c is formed smaller than the width W2 of the opening surface 28D on the same plane as the incident surface 22c. That is, the recess 28 is formed in a trapezoidal shape on the first main plane 22 a and the second main plane 22 b of the light guide plate 22.

  According to such a configuration, in the illumination unit 15, the recess 28 is formed so as not to prevent light emitted from the light emitting diode 21 from entering the light guide plate 22. That is, the emitted light from the light emitting diode 21 does not leak from the recess 28 after being taken into the incident surface 22 c of the light guide plate 22. For this reason, the optical characteristic equivalent to the light-guide plate 22 in which the recessed part is not formed is acquired, and the fall of the brightness | luminance of an illumination unit is suppressed.

  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.

  In the example shown in FIG. 3, the concave portion 28 of the light guide plate 22 is disposed at the center of the incident surface 22c, but the present invention is not limited to this example. For example, the concave portion 28 of the light guide plate 22 may be formed between one end and the other end of the incident surface 22c. Even in such a configuration, the same effect as the present embodiment can be obtained.

  In the example illustrated in FIG. 3, the light guide plate 22 includes one concave portion 28 on the incident surface 22 c, but is not limited to this example, and may include a plurality of concave portions 28 on the incident surface 22 c. For example, two recesses 28 may be disposed between the light emitting diodes 21.

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 a cross-sectional view schematically showing the structure of the liquid crystal display device shown in FIG. FIG. 3 is an exploded perspective view schematically showing the structure of the light guide plate and the frame in the illumination unit shown in FIGS. 1 and 2. FIG. 4 is a perspective view schematically showing the structure of the liquid crystal display panel and the illumination unit. FIG. 5 is a perspective view schematically showing the structure of the back surface of the liquid crystal display panel and the illumination unit shown in FIG. FIG. 6 is a diagram showing an angle formed by the light emitting region of the light emitting diode, and the end surface of the recess and the surface orthogonal to the incident surface.

1 ... Liquid crystal display device 2 ... Liquid crystal display panel
15 ... Lighting unit 13 ... Wiring board
PX ... Pixel 6 ... Display region 21 ... Light source (light emitting diode) 21E ... Light emitting surface 22 ... Light guide plate 22c ... Incident surface 28 ... Concave portion 23 ... Frame 29 ... Convex portion GL ... Adhesive member

Claims (5)

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;
A wiring board connected to one side edge of the liquid crystal display panel and bent to the back of the lighting unit;
The lighting unit is:
A plurality of light emitting diodes arranged at predetermined intervals;
A light guide plate having an incident surface facing each light emitting surface of the light emitting diode and having a recess recessed from the incident surface facing the light emitting surfaces of two adjacent light emitting diodes;
Having a convex part fitted in the concave part, and holding the light guide plate,
The back surface of the convex portion is on the same plane as the back surface of the light guide plate,
The liquid crystal display device, wherein the wiring substrate is bonded to a back surface of the convex portion through an adhesive member. The recess further has a side end surface connected to the incident surface,
The liquid crystal display device according to claim 1, wherein an angle formed between the side end surface and a surface orthogonal to the incident surface is smaller than 90 °.   The liquid crystal display device according to claim 2, wherein an angle formed between the side end surface and a surface orthogonal to the incident surface is larger than a divergence angle with respect to an optical axis of the light emitting diode.   The liquid crystal display device according to claim 2, wherein a width of a rear end surface of the concave portion in a direction parallel to the incident surface is smaller than a width of an opening surface on the same plane as the incident surface.   The liquid crystal display device according to claim 1, wherein the concave portion is formed so as not to overlap the display region.

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