JP2003324255A - Flexible substrate and liquid crystal display element provided with flexible substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent the disconnection of inner wiring on a folded part without requiring additional members such as a reinforcing tape on a flexible substrate used for connection between prescribed electronic components in a state that a specified part of the flexible substrate is folded. <P>SOLUTION: The flexible substrate 30 is constituted by forming a plurality of lead electrodes 34 on a base film and coating a prescribed part on the lead electrode forming surface with a resist resin film, and allowed to be used for connection between prescribed electronic components in the folded state of the specific part 3a. An aperture 51 has a length longer than a lead electrode forming width W on the folded part 3a by removing a part of the base film like a slit along a virtual folding line X-X, and dummy electrodes 52L, 52R extended along the aperture 51 are formed outsides the lead electrodes 34L, 34R arranged on outermost sides of the lead electrodes 34. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible substrate and a liquid crystal display device having the flexible substrate, and more particularly to a technique for preventing breakage of a bent portion of the flexible substrate.

[0002]

2. Description of the Related Art In many cases, a flexible board is used as a relay board for connecting electric parts, and is flexible and freely bendable. It is convenient for connecting movable electric parts that are separated. In the field of liquid crystal display devices, for example, it is used as a means for connecting a liquid crystal panel and its drive circuit board.

An example thereof will be described with reference to FIG. The liquid crystal panel 1 is provided with a terminal portion 1a formed with a lead electrode connected to the transparent electrode. The terminal portion 1a and the drive circuit board 2 are provided.
And are connected via the flexible substrate 3.

The terminal portion 1a and the flexible substrate 3 are fixedly connected by an anisotropic conductive film (ACF) or soldering, but the flexible substrate 3 and the drive circuit substrate 2 are
It is detachably connected in consideration of maintainability.

In this example, the connector 2a is provided on the drive circuit board 2 side, and the terminal portion formed at the end of the flexible board 3 is inserted into the connector 2a. Since the flexible substrate 3 is flexible,
The reinforcing plate 4 is attached to the terminal portion.

[0006]

Flexible substrate 3
Are almost always used in the folded state. In the example of FIG. 3, since the liquid crystal panel 1 and the drive circuit board 2 are arranged at different height positions, the flexible board 3 is bent in two steps 3a and 3b in a stepwise manner.

In this case, the bending portions 3a and 3b are almost fixed positions and the bending angle is gentle. However, when the application is repeated vibration such as an in-vehicle device or a mobile phone, the flexible substrate 3 is caused by metal fatigue. The internal wiring (lead electrode) may be broken.

[0008] As one of the methods for preventing this, it is known to attach a reinforcing tape. However, in addition to the cost of the reinforcing tape itself, an attaching operation cost is newly generated, which is preferable. Absent.

Therefore, an object of the present invention is to provide a flexible substrate, which is used for connection between predetermined electric parts in a state where a specified portion is bent, without requiring a separate member such as a reinforcing tape. The purpose is to reliably prevent disconnection of the internal wiring in the.

[0010]

In order to solve the above problems, the present invention comprises forming a plurality of lead electrodes on a base film and coating a predetermined portion of the lead electrode formation surface with a resist resin film. , A flexible substrate provided for connection between predetermined electric components in a state in which a specified portion is bent, wherein the specified bending portion has a slit-shaped portion of the base film along the virtual bending line. The opening formed by removing the lead electrode is formed with a length equal to or larger than the lead electrode formation width, and a dummy electrode extending along the opening is formed further outside the lead electrode located on the outermost side. It is characterized by that.

According to this structure, the dummy electrode plays a role of reinforcing the bent portion. That is, since the bending stress applied to the lead electrode which is the internal wiring is dispersed by the dummy electrode, the breakage of the lead electrode is effectively prevented.

The dummy electrode may be formed in a state of non-conduction with the lead electrode, but in order to disperse the bending stress as uniformly as possible, the dummy electrode should be formed integrally with the lead electrode located on the outermost side. Is preferred. Further, it is more preferable that the dummy electrodes are formed with blank portions having the same width as the line width of the lead electrodes at the same pitch as the lead electrodes.

Further, the present invention also includes a liquid crystal display element in which a liquid crystal panel and a drive circuit board existing in different planes are connected by a flexible board having the above-mentioned characteristics.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described with reference to FIGS. 1 is an enlarged plan view of an essential part of the flexible substrate 30 according to the present invention, and FIG. 2 is an enlarged cross-sectional view taken along the line AA of FIG. 2. The use here is for the liquid crystal display device of FIG. 3 described above. Therefore, it is assumed that the flexible substrate 3 is used instead of the conventional flexible substrate 3.

That is, the flexible substrate 30 described as this embodiment includes the liquid crystal panel 1 and the drive circuit substrate 2.
It is used as a relay board for connecting to and, and its bent portions are specified at two positions 3a and 3b, but only one bent portion 3a is shown in FIG. 1 for the sake of drawing.

The flexible substrate 30 has a base film 31 made of, for example, a polyimide resin as a base material.
A copper foil 33 is attached to one surface (lower surface in FIG. 2) of the base film 31 via an adhesive material 32. The plurality of lead electrodes 34 shown in FIG. It is formed by applying a resist (photosensitive resin), exposing and developing.

A resist resin film 35 is formed on the portion of the base film 31 where the lead electrode is formed that needs electrical insulation. Although not the gist of the present invention, the lead electrode 34 is exposed at the terminal portion T inserted into the connector 2a of the drive circuit board 2 described with reference to FIG. A terminal reinforcing plate 4 is attached.

As shown in FIG. 1, in this example, the flexible substrate 30 has a pair of holding holes 36 for mounting the terminal reinforcing plate 4 on both left and right sides. Wiring is provided so as to extend from the liquid crystal panel 1 side and converge so as to avoid the holding holes 36, 36, that is, to reach the terminal portion T in a state in which both the line width and the line width of each lead electrode 34 are narrowed. ing.

Further, in this example, the two bent portions 3a and 3b are set at the portions where the lead electrodes 34 are converged. Since the bent portions 3a and 3b have the same configuration, only one bent portion 3a will be described here.

First, it is assumed that the virtual bending line of the bent portion 3a is XX and the lead forming width including all the lead electrodes 34 in the converged portion is W. The virtual bending line XX is substantially orthogonal to the extending direction of the flexible substrate 30.

The bent portion 3a has a virtual bending line X-.
Along the X, an opening 51 is formed by removing a part of the base film 31 in a slit shape. Opening 51
May have any width, but the length of the opening 51 needs to be equal to or larger than the lead forming width W, and as shown in FIG.
It is preferable that the left and right lead electrodes 34L and 34R located on the outermost sides are formed so as to extend further outward and have the same length on the left and right sides, and extend over substantially the entire width of the flexible substrate 30.

Further, in the bent portion 3a, the lead electrodes 34L and 34R located on the outermost side are directed further outward,
Dummy electrodes 52L and 52R are formed along the opening 51 and preferably extend in equal lengths on the left and right sides. The dummy electrodes 52L and 52R are also preferably formed so as to extend over substantially the entire width of the flexible substrate 30 as long as the design permits.

The dummy electrodes 52L and 52R are formed of the copper foil 33 on the base film 31 like the lead electrodes 34. The dummy electrodes 52L and 52R may be non-conductive with respect to the lead electrodes 34, but in order to disperse the bending stress as evenly as possible, they should be formed integrally with the lead electrodes 34L and 34R located on the outermost sides. Is preferred.

The width of the dummy electrodes 52L and 52R is
It is preferable that the width of the opening 51 is larger than that of the opening 51 and only the central portion thereof is exposed in the opening 51. Further, as shown in FIG. 1, the dummy electrodes 52L and 52R are
More preferably, the blank portions 53 having the same width as the line width of the lead electrodes 34 are formed at the same pitch as the lead electrodes 34.

When the lead electrode 34 includes a lead electrode 34V for power supply whose line width is almost twice that of the other lead electrodes as in this example, the bent portion 3a is formed. Further, it is preferable to form the blank portion 53 in order to uniformly disperse the bending stress.

Although the lead electrodes 34 and the dummy electrodes 52L and 52R are exposed in the opening 51, in order to prevent the electrodes from being oxidized and to prevent accidental contact with surrounding metal parts, It is preferable to provide a coating film 55 made of a protective resin having flexibility on this portion.

[0027]

As described above, according to the present invention,
A plurality of lead electrodes are formed on the base film, and a predetermined portion of the lead electrode formation surface is covered with a resist resin film, which is used for connection between predetermined electric parts in a state where a specified portion is bent. In the flexible substrate to be formed, an opening formed by removing a part of the base film in a slit shape along the virtual bending line is formed in the specified bending portion with a length equal to or larger than the lead electrode formation width, and at the outermost side. By forming a dummy electrode extending along the opening further outside the lead electrode located at, it is possible to reliably prevent disconnection of the internal wiring at the bent portion without requiring a separate member such as a reinforcing tape. it can.

[Brief description of drawings]

FIG. 1 is an enlarged plan view of an essential part of a flexible substrate according to the present invention.

FIG. 2 is an enlarged sectional view taken along line AA of FIG.

FIG. 3 is a schematic side view showing a state in which a liquid crystal panel and a drive circuit board are connected by a conventional flexible board.

[Explanation of symbols] 1 LCD panel 1a terminal part 2 drive circuit board 3a, 3b Bent section 30 flexible substrate 31 Base film 33 Copper foil 34 Lead electrode 35 Resist resin film 51 opening 52L, 52R dummy electrode 53 Blank part

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H092 GA50 GA51 HA11 NA11 NA15                       NA16 NA17 RA10                 5E338 AA05 AA12 BB16 BB17 BB56                       EE27                 5E344 AA02 AA12 AA22 AA23 BB02                       BB04 CC05 CD04 DD02 DD10                       DD14 EE17

Claims (4)

[Claims] 1. A plurality of lead electrodes are formed on a base film, a predetermined portion of the lead electrode formation surface is covered with a resist resin film, and a predetermined electric part is bent in a specified portion. In the flexible substrate used for connection between the above-mentioned specified bent portions, an opening formed by removing a part of the base film in a slit shape along the virtual bending line has a width equal to or larger than the lead electrode formation width. A flexible substrate having a length and a dummy electrode extending along the opening further outside the lead electrode located on the outermost side. 2. The flexible substrate according to claim 1, wherein the dummy electrode is formed integrally with the lead electrode located on the outermost side. 3. The flexible substrate according to claim 1, wherein the dummy electrodes are formed with blank portions having the same width as the line width of the lead electrodes at the same pitch as the lead electrodes. 4. A liquid crystal panel having a flexible substrate in which a plurality of lead electrodes are formed on a base film and a predetermined portion of the lead electrode formation surface is covered with a resist resin film, and which are present in different planes In a liquid crystal display device in which a specified portion of the flexible substrate is bent and connected to a drive circuit substrate, the flexible substrate according to any one of claims 1 to 3 is used as the flexible substrate. Characteristic liquid crystal display element.