JP2006313331A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent contact between a reflecting sheet and an electrically continuing part of a flexible print wiring board (FPC). <P>SOLUTION: A liquid crystal display device is provided with a light guiding plate 1 making the light from a light source h emit to a prescribed direction, a reflecting sheet 2 disposed to lie in parallel to the back of the light guiding plate 1, a second frame part 4a disposed to fix the light guiding plate 1, and a flexible print wiring board (FPC) 5 intended to effect electric connection, wherein the top end 2a of the reflecting sheet 2 is disposed to be positioned on the inner side of the second frame part 4a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a device for preventing contact between a reflective sheet of a lighting unit and a flexible printed wiring board.

  In recent years, display devices for information devices such as notebook personal computers and word processors, or display devices for video devices such as portable televisions, video movies, and car navigation systems have been used for liquid crystal displays, taking advantage of their light weight, thinness, and low power consumption. Many devices are used. Many of these liquid crystal display devices have a configuration in which illumination light is applied from behind a display element by an illumination unit in order to realize a bright display screen.

  In this lighting unit, an edge light system in which a light guide plate is placed on the back surface of a display element and a linear light source such as a fluorescent discharge tube is disposed on the end face of the light guide plate is characterized by being thin and excellent in luminance uniformity of the light emitting surface. Therefore, as a backlight method of a liquid crystal display device used for a notebook personal computer or the like, this edge light method is often adopted in consideration of thinness. In liquid crystal display devices used for mobile phones, PDAs (Personal Digital Assistance), etc., in order to achieve both thinness and brightness, an edge-light method or a single-sided light source such as a fluorescent discharge tube is arranged on the left and right sides of the light guide plate There are many cases where the edge light method is used.

FIG. 4 is an example of a liquid crystal display device LCD used in a conventional mobile phone, such as a liquid crystal display panel P, an edge light type illumination unit UT, a flexible printed circuit board (FPC) 5 for electrical connection, and the like. Is provided. The illumination unit UT includes a flat transparent light guide plate 1 that transmits light from the light source h to the entire irradiation surface, a reflection sheet 2 that reflects light from the light guide plate 1, the light guide plate 1, and the liquid crystal display panel P. A frame portion 4 to be fixed is provided. Here, together with the light guide plate 1, one end of the reflection sheet 2 is also fixed from above by the second frame 4 a of the frame 4, but is not necessarily fixed. The liquid crystal display panel P is configured by sandwiching a liquid crystal layer between a pair of substrates on the irradiation surface side (upper side in FIG. 4) of the illumination unit UT. An external control circuit for controlling the liquid crystal display device LCD is arranged on a circuit board independent of the liquid crystal display panel P, and is connected to an internal circuit of the liquid crystal display panel P by, for example, a flexible printed wiring board (FPC) 5. On the flexible printed circuit board (FPC) 5, pattern wiring, lands, and electronic components 5b for electrical connection are mounted. Patent Document 2 discloses a technique in which a sheet material such as a reflection sheet included in a backlight for a liquid crystal display element is fixed in a housing recess of the frame without using an adhesive means such as a double-sided adhesive. .
JP 2001-350004 A JP 2004-264400 A

  By the way, as shown in Patent Document 1, a reflective sheet having a metal layer on which a metal such as silver is deposited tends to be excellent in corrosion resistance and light resistance and used as a highly reflective film. For this reason, when a reflective sheet having a metal layer and conducting at the tip (end face) is used, depending on the positional relationship between the flexible printed circuit board (FPC) and the reflective sheet, the flexible printed circuit board (FPC) for driving the light source is used. There is a case where a land, a wiring pattern, or an electrically conductive portion such as an electronic component mounted on a flexible printed wiring board comes into contact with the tip (end surface) of the reflection sheet, causing a short circuit. That is, in the example of FIG. 4, since the front end (end surface) 2z of the reflection sheet 2 is exposed from the outer wall 4z of the second frame portion 4a of the frame 4, the present liquid crystal display device LCD is mounted on an electronic unit (for example, a mobile phone). When incorporated in a telephone, PDA, small terminal, etc., the tip (end face) 2z may come into contact with the electrically conductive portion of the flexible printed circuit board (FPC), which may cause a short circuit.

  Therefore, an object of the present invention is to provide a liquid crystal display device that prevents contact between a reflective sheet and a flexible printed circuit board (FPC).

  The liquid crystal display device of the present invention includes a liquid crystal display panel having a liquid crystal layer between two substrates, a backlight unit, and a flexible wiring board on which electronic components are mounted and electrically connected to the liquid crystal display panel. In the liquid crystal display device, the backlight unit fixes a light guide plate that emits light from a light source in a predetermined direction, a reflection sheet that is disposed along the back surface of the light guide plate, and the light guide plate and the liquid crystal display panel. A first frame part extending in a direction substantially parallel to the light guide plate, and the light guide plate substantially from the back surface of the first frame part toward the reflection sheet side. A second frame portion extending in a vertical direction, and the reflective sheet is disposed inside the second frame portion, and the flexible printed wiring is disposed outside the second frame portion. Plate is disposed, the flexible printed circuit board side front end of the reflecting sheet is characterized by being arranged to be positioned on the light guide plate side than the inner wall of the second frame portion. According to the present invention, the flexible printed wiring board (FPC) is arranged such that the tip of the reflective sheet on the side of the flexible printed wiring board is positioned closer to the light guide plate than the inner wall of the second frame portion. ) Can be prevented and a short circuit can be prevented.

  According to the present invention, the front end of the reflective sheet on the side of the flexible printed circuit board is guided more than the inner side wall of the second frame part by bending the reflective sheet along the inner side wall of the second frame part. It is good also as a structure arrange | positioned so that it may be located in the optical plate side. If comprised in this way, in addition to the front-end | tip of a reflection sheet not contacting a flexible printed wiring board (FPC), it can prevent the leakage of the light from a light source, and can prevent the penetration | invasion of dust. .

  Further, the liquid crystal display device of the present invention includes a liquid crystal display panel having a liquid crystal layer between two substrates, a backlight unit, a flexible wiring board on which an electronic component is mounted and which is electrically connected to the liquid crystal display panel. The backlight unit includes a light guide plate that emits light from a light source in a predetermined direction, a reflection sheet that is disposed along the back surface of the light guide plate, a light guide plate, and a liquid crystal display panel. A first frame portion that is extended in a direction substantially parallel to the light guide plate, and the light guide plate from the back surface of the first frame portion toward the reflective sheet. And a second frame portion extending in a substantially vertical direction, the reflective sheet is disposed inside the second frame portion, and the flexible print is disposed outside the second frame portion. Wiring board is disposed, a flexible printed circuit board side front end of the reflecting sheet is characterized by being fitted in the notches formed on the inner wall of the second frame portion.

  According to the present invention, the front end of the reflective sheet is fitted to the notch formed on the inner wall of the second frame portion so that the front end of the reflective sheet is exposed to the outside. It is not exposed and does not come into contact with the flexible printed circuit board (FPC). In addition, when the reflection sheet is fixed to the frame, the cutout portion can be used as a guide for alignment.

  According to the present invention, since the tip of the reflection sheet is disposed inside the second frame portion, the reflection sheet and the flexible printed circuit board (FPC) do not come into contact with each other, and a short circuit occurs. Can be prevented. In addition, when the reflection sheet is configured to be along the inner wall of the second frame portion, light leakage from the light source can be prevented and dust can be prevented from entering, so the luminous intensity is good. And it can be set as the liquid crystal display device which is hard to be influenced by dust etc. In addition, according to the present invention, the front end of the reflection sheet is fitted into the cutout portion provided in the second frame portion, so that it does not come into contact with the flexible printed circuit board (FPC) and a short circuit occurs. It is possible to prevent this, and when fixing the reflective sheet to the frame, it is possible to assemble using the above-mentioned notched portions as a guide for alignment, facilitating assembly work, and further, fixing the reflective sheet at an accurate position.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the present embodiment is a liquid crystal display device LCD used in a mobile phone, and includes a liquid crystal display panel P, an edge light type illumination unit UT, the liquid crystal display device LCD, and the liquid crystal display. A flexible printed circuit board 5 is provided for electrical connection with an electronic unit (for example, a mobile phone, a PDA, a small terminal, etc.) in which the device LCD is incorporated. The flexible printed wiring board 5 is fixed to a predetermined position of the electronic unit, and electrical connection is achieved between the liquid crystal display device LCD and the electronic unit. The fixing method between the flexible printed circuit board 5 and the electronic unit is not shown in the present invention because it is unquestioned.

  The illumination unit (backlight unit) UT includes a flat transparent light guide plate 1 that transmits light from the light source (LED) h to the entire irradiation surface, and a reflection sheet 2 that reflects light traveling to the back side of the light guide plate 1. And a frame 4 for fixing the light guide plate 1 and the reflection sheet 2. The light guide plate 1 is made of a material such as acrylic having optimal optical characteristics represented by transmittance and refractive index necessary for light transmission. The light guide plate 1 is provided with a dot pattern or a groove pattern (not shown) whose shape is changed according to the distance from the light source on the back surface.

  The reflection sheet 2 has a role of increasing the illumination light by returning the light that is about to go out from the back surface of the light guide plate 1 back into the light guide plate 1, so that the illumination light extends along the back surface of the light guide plate 1. Has been placed. The reflective sheet 2 is made of a white resin film having a high reflectance, and has a metal layer on which a metal such as silver is deposited. With such a metal layer, a highly reflective film excellent in corrosion resistance and light resistance is obtained. Although the reflection sheet 2 of the present embodiment uses a metal layer as a reflection layer, there is also one that includes a means having a desired reflection function without having a metal layer (for example, a reflection material (non-metal reflection)). When such a non-metallic reflective material is used, the probability of a short circuit with an electronic component is significantly reduced. However, by using the configuration of the present invention, the liquid crystal display device LCD Since effects such as improvement in light shielding performance and improvement in work efficiency due to easy positioning of the reflection sheet are expected, such a configuration is also included in the present invention. However, what has as a metal layer is especially meaningful from the high probability of short-circuiting by contact with the flexible printed wiring board (FPC) 5.

  The frame 4 has a role of fixing the liquid crystal display panel P and the light guide plate 1 and also has a role of fixing the reflection sheet 2, and a protruding portion (hereinafter referred to as a second frame portion) that fixes one end of the reflection sheet 2. ) 4a. The light guide plate 1 is not necessarily fixed from above, but is fixed from above in the present embodiment. The frame 4 according to the present embodiment includes a first frame portion 4b extending in a direction substantially parallel to the light guide plate 1, and the light guide plate 1 from the back surface 4x of the first frame portion 4b toward the reflection sheet 2 side. And a second frame portion 4a extending in a direction substantially perpendicular to the second frame portion 4a. When the liquid crystal display device LCD is seen through from the side, the direction in which the light guide plate 1 is disposed is the second frame portion. The reflection sheet 2 is disposed inside the portion 4a, and the flexible printed circuit board (FPC) 5 is disposed outside the second frame portion 4a.

  The flexible printed wiring board 5 side tip 2a of the reflection sheet 2 is arranged so as to be positioned closer to the light guide plate 1 than the inner wall 4y of the second frame portion 4a. As a result, contact with the land, wiring pattern, electronic component 5b, etc. of the flexible printed circuit board (FPC) 5 is eliminated, thereby preventing a short circuit with these electrically conductive portions (FIG. 1). . Further, as the present embodiment, for example, as shown in FIG. 3, the reflection sheet 2 is bent in a substantially L shape along the inner wall 4y of the second frame portion 4a, and the tip 2a thereof is The liquid crystal display panel P may be directed toward the liquid crystal display panel P side. Even in such a configuration, the distal end 2a is arranged so as to be positioned closer to the light guide plate 1 than the inner wall 4y of the second frame portion 4a. Therefore, the flexible printed circuit board (FPC) 5 The contact with the land, the wiring pattern, the electronic component 5a, etc. is eliminated, and a situation where a short circuit with these electrically conductive parts is prevented is prevented. In addition, light from the light source h can be prevented from leaking outside the second frame portion 4a, and dust can be prevented from entering from the gap S between the second frame portion 4a of the frame 4 and the light guide plate 1. In addition, the liquid crystal display device LCD having good light intensity and being hardly affected by dust or the like can be obtained.

  As another embodiment of the present invention, as shown in FIG. 2, it has substantially the same configuration as the liquid crystal display device LCD (FIGS. 1 and 3) described above, but the inner wall 4y of the second frame portion 4a. The liquid crystal display device LCD may be formed by forming a notch 4k in the notch 4k and fitting the tip 2a of the reflective sheet 2 on the flexible printed wiring board 5 side into the notch 4k. Thus, when it fits into the notch part 4k, the said front-end | tip 2a of the reflection sheet 2 will not be exposed outside, but it will not contact the flexible printed wiring board (FPC) 5, especially an electrical conduction part. In addition to this, when fixing the reflective sheet 2 to the frame 4, it is possible to assemble using the notch 4k as a guide for alignment, making the assembly work easy, and fixing the reflective sheet 2 at an accurate position. It becomes possible.

  As shown in FIG. 1 and the like, a liquid crystal display panel P is mounted on the irradiation surface side (upward in the drawing) of the illumination unit UT, and a flexible printed circuit board (FPC) 5 is electrically connected to provide a liquid crystal display. The apparatus LCD is assembled (the flexible printed wiring board (FPC) 5 is connected only to the liquid crystal display panel P at this stage, and the flexible printed wiring board 5 is fixed to a predetermined position of the electronic unit later, and the liquid crystal An electrical connection is established between the display device LCD and the electronic unit (not shown).

  According to the present embodiment, since the reflection sheet 2 is structured to prevent contact with the electrically conductive portion of the flexible printed circuit board (FPC) 5, it is possible to prevent short-circuiting due to these contacts. .

It is sectional drawing of the liquid crystal display device in one embodiment of this invention. It is sectional drawing of the liquid crystal display device in other embodiment of this invention. It is sectional drawing of the liquid crystal display device in other embodiment of this invention. It is sectional drawing of the conventional liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light guide plate 2 Reflection sheet 4 Frame 4a Projection part of a frame (2nd frame part)
4b First frame portion 4k Notch portion 4x formed on the inner wall of the second frame portion Back surface 4y of the first frame portion Inner wall surface 5 of the second frame portion Flexible printed circuit board (FPC)
h Light source LCD Liquid crystal display device P Liquid crystal display panel

Claims (4)

A liquid crystal display device having a liquid crystal display panel having a liquid crystal layer between two substrates, a backlight unit, and a flexible wiring board on which electronic components are mounted and electrically connected to the liquid crystal display panel,
The backlight unit includes a light guide plate that emits light from a light source in a predetermined direction, a reflection sheet that is disposed along the back surface of the light guide plate, and a frame that fixes the light guide plate and the liquid crystal display panel. ,
The frame is extended in a direction substantially perpendicular to the light guide plate from the back surface of the first frame portion toward the reflection sheet side, with a first frame portion extended in a direction substantially parallel to the light guide plate. A second frame portion, the reflective sheet is disposed inside the second frame portion, the flexible printed wiring board is disposed outside the second frame portion,
The liquid crystal display device, wherein the tip of the reflective sheet on the side of the flexible printed wiring board is positioned so as to be positioned closer to the light guide plate than the inner wall of the second frame portion.   The front end of the reflective sheet on the side of the flexible printed wiring board is positioned closer to the light guide plate than the inner side wall of the second frame part by bending the reflective sheet along the inner side wall of the second frame part. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is arranged as described above. A liquid crystal display device having a liquid crystal display panel having a liquid crystal layer between two substrates, a backlight unit, and a flexible wiring board on which electronic components are mounted and electrically connected to the liquid crystal display panel,
The backlight unit includes a light guide plate that emits light from a light source in a predetermined direction, a reflection sheet that is disposed along the back surface of the light guide plate, and a frame that fixes the light guide plate and the liquid crystal display panel. ,
The frame is extended in a direction substantially perpendicular to the light guide plate from the back surface of the first frame portion toward the reflection sheet side, with a first frame portion extended in a direction substantially parallel to the light guide plate. A second frame portion, the reflective sheet is disposed inside the second frame portion, the flexible printed wiring board is disposed outside the second frame portion,
The flexible printed wiring board side front end of the reflection sheet is fitted into a notch formed on the inner wall of the second frame portion. The liquid crystal display device according to claim 1, wherein the reflection sheet is formed by covering a resin sheet with a metal layer.

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