JPH0521059Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a liquid crystal display device, and more particularly to a mounting structure of a liquid crystal display cell on a circuit board using a plastic film substrate.

Prior Art A liquid crystal display panel that uses a flexible plastic film as a substrate for forming transparent electrodes has excellent advantages such as being able to be made lighter and thinner and easier to display in a variety of display formats such as curved displays. It is desirable to have a structure that takes advantage of these characteristics during implementation.

Therefore, even if the mounting structure of a glass substrate liquid crystal display panel, which has been mainly used in the past, is adopted as it is, satisfactory results cannot be obtained. For example, in the conventional mounting method using an anisotropic conductive connector such as a zebra connector that does not have the function of bonding a liquid crystal display cell and a printed circuit board, the electrode part is held down through the connector with a metal fastener, etc. connection and fixation. However, this method not only requires laborious work, but also requires heavy and large metal fittings, making it impossible to achieve thin and lightweight mounting.

Therefore, the present inventors first connected the electrode extraction part of a liquid crystal display cell with a plastic film substrate to the external electrode part of a circuit board using a heat-sealable film having anisotropic conductivity. proposed a liquid crystal display device in which liquid crystal display cells were electrically connected and fixed to a circuit board (Utility Model Application No. 69385/1983).

According to this mounting structure, the characteristics of a liquid crystal display cell using a plastic film substrate can be fully utilized to achieve thin and lightweight mounting, and the mounting operation is simple and can be manufactured at low cost.

However, it has been found that this mounting structure causes difficulties as the size of the liquid crystal display cell increases.

FIG. 8 is an exploded perspective view for explaining the mounting structure of this conventional example, in which reflective polarizing plate 31, liquid crystal display cell 39,
A viewing side polarizing plate 71 is provided. A signal line electrode 51 is provided on the back surface of the upper substrate 35 of the liquid crystal display cell 39.
A signal line electrode extraction portion 43 is formed on a protruding portion 41' of the upper substrate 35 from the lower substrate 37. FIG. 9 is a partially enlarged view showing the signal line electrode extraction portion 43, in which the signal line electrodes 51 are formed at a predetermined pitch p and interval d. To connect and fix the printed circuit board 11 to the external electrode section 15, a heat-sealable anisotropic conductive film 27 is placed on the external electrode section 15, and then the signal line electrode of the liquid crystal display cell 39 is placed on top of the heat-sealable anisotropic conductive film 27. The lead-out portions 43 are overlapped, and then, as shown in FIG. 10, a heating head 75 is pressed onto the signal line electrode lead-out portions 43 of the liquid crystal display cell 39 for heat sealing. However, heating head 75
The length l has a limit due to restrictions in terms of head temperature distribution and uniformity of pressing force. On the other hand, there is a strong demand for larger screens for liquid crystal display cells. Therefore, using the heating head 75 shorter than the length of the electrode extraction part 43,
It is necessary to do the work in several parts as shown in Figure 10. At this time, if the first and second heat sealing positions are slightly overlapped, poor connection of the electrodes is likely to occur at the overlapped position where the two heat seals are performed. On the other hand, if you try to prevent the heat seal positions from overlapping, the pitch of recent dot-type liquid crystal display devices is narrow (for example, around 0.4 mm).
In order to align the heating head at this interval, an alignment jig or device for the heating head and the circuit board is required, which is complicated. Furthermore, since the temperature at the edge of the heating head tends to be different from that at the center, the temperature conditions during heat sealing are different, which tends to cause poor connection.

Purpose of the invention This invention enables thin mounting of liquid crystal display cells using plastic film substrates with simple operations.
Moreover, it provides a mounting structure that allows for highly reliable connections and provides good image quality.

Structure of the invention The liquid crystal display device of the invention has a liquid crystal display cell using a plastic film as a substrate and a circuit board for driving the liquid crystal display cell, and includes an electrode extraction part of the liquid crystal display cell and an external electrode of the circuit board. A liquid crystal display device in which a heat-sealable anisotropic conductive film is used to electrically connect and fix an electrode-forming part to a plurality of parts with a predetermined length. , the adjacent divided portions are formed on the end face side of different liquid crystal display cells so that they are not adjacent to each other, and an adhesive layer is formed on the end face side where the anisotropic conductive film is not provided. It is characterized by

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view to explain the mounting structure of the present invention, and FIG. It is a cross-sectional view of a part,
Figure 3 is a sectional view taken along the line - in Figure 2;
The figure is a sectional view taken along that line.

On the printed circuit board 11, a reflective polarizing plate 31, a liquid crystal display cell 39, and an observation side polarizing plate 7 are sequentially arranged.
1. A protection plate 73 is provided. The back surfaces of the first upper substrate protrusion 41 and the second upper substrate protrusion 47 of the liquid crystal display cell 39 are provided with a first signal line electrode extraction part 43a and a third signal line electrode extraction part 43c, respectively. 2 signal line electrode extraction portions 43b are formed. In this way, the signal line electrode extraction portion 43
are divided into three parts, which are formed in a staggered manner (staggered) on opposite end surfaces of the upper substrate 35. On the other hand, the signal line external electrode portions 15a, 15b, 15c of the printed circuit board 11 are also formed in sections corresponding to the signal line electrode extraction portions 43a, 43b, 43c. In this way, the signal line electrode extraction parts 43a, 43b, 43c are divided into a plurality of parts, and the divided parts are formed on different extraction surfaces so as not to be adjacent to each other, and accordingly, the printed circuit board 1
No. 1 signal line external electrode portions 15a, 15b, 15
The structure of the liquid crystal display device shown in FIG. 1 is almost the same as that shown in FIG. 7 except for the formation of the liquid crystal display device c.

Furthermore, a scanning line electrode extraction portion 55 is formed on the surface of the protruding portion 53 from the display surface of the lower substrate 37 of the liquid crystal display cell 39 .

First, second, and third signal line external electrode portions 15a, 15b, and 15c of the printed circuit board 11 and first, second, and third signal line electrode extraction portions 43a, 43b, and 43c of the liquid crystal display cell. and are connected and fixed via heat-sealable anisotropic conductive films, respectively. In addition, the first and second upper substrate protrusions 4
The portion 19 where the signal line electrode extraction portions 1 and 47 are not formed is adhered and fixed to the printed circuit board 11 with an electrically insulating adhesive layer 17. The adhesive layer 17 is made of a pressure-sensitive adhesive (for example, Nitto Denko #9469), a heat-fusion adhesive (for example, Toray Chemit R-99), silicone-based, urethane-based,
It can be formed using a reaction curing adhesive such as a polyester adhesive or a solvent removable adhesive. On the other hand, the scanning line external electrode section 21 of the printed circuit board 11 and the scanning line electrode extraction section 55 of the liquid crystal display cell 39 are arranged at the same pitch as the scanning line electrodes by heat-sealing anisotropic conductive films 29 and 61. They are connected via a flexible substrate 63 having a conductive electrode 65 of a width.

First, on the signal line external electrode parts 15a, 15b, 15c of the printed circuit board circuit 11, a heat-sealable anisotropic conductive film 25 having a separator on the upper surface is placed.
a, 25b, and 25c are placed and preheated at a low temperature with a heating head to temporarily fix them. Next, printed circuit board 1
An adhesive 17 is applied to the portion 19 where the external signal line electrode 1 is not formed, and the separator is peeled off from the heat-sealable anisotropically conductive films 25a, 25b, and 25c. The adhesive layer 17 can be formed using, for example, a pressure-sensitive adhesive with a base and separator.
First, after pasting, the separator is peeled off. Also,
If you use a heat-fusion adhesive, heat it to temporarily fix it.
Alternatively, if it is a reaction curing type, apply it, and if it contains a solvent, remove it. Next, the electrodes are aligned, the liquid crystal display cell 39 is placed on the adhesive layer 17, and the adhesive layer 17 is pressed (in the case of a pressure-sensitive adhesive), heated and pressed (in the case of a heat-sealing type), or heat treated (in the case of a heat-curing type). case), and the printed circuit board 11 and the liquid crystal display cell 39 are fixed by the adhesive layer 17.
Next, the heat-sealing type anisotropic conductive films 25a, 25b, 25 are placed on the upper substrate 35 by the heating head 75.
By heating and pressing c, the liquid crystal display cell 39
The signal line electrode extraction parts 43a, 43b, and 43c are fixed to the printed circuit board 11, and the signal line electrodes 51 and the corresponding external signal line electrodes 13 are electrically connected. Heat-sealable anisotropic conductive film is a film that can be heat-sealed at relatively low temperatures using a heating head, etc., and has conductivity in the thickness direction and insulation in the plane direction.For example, Anisolum (trade name, Hitachi Chemical) Co., Ltd.).

As shown in FIG. 7, first, the first signal line electrode extraction portion 43a is heat-sealed with the heating head 75, and then the second and third signal line electrode extraction portions 43b and 43c are similarly heat-sealed. I can do it. Therefore, by setting the length of one signal line electrode extraction part according to the length of the heating head, it is possible to avoid heat-sealing the same place twice.
Moreover, it is possible to reliably heat seal the necessary parts. Furthermore, if the length of the signal line electrode lead-out portion is shortened with respect to the heating head 75, the heating head 75 can be
Since the edge portions do not need to be used, adverse effects caused by uneven temperature at the edge portions are prevented and reliability is further increased. Heat-fused anisotropic conductive film 25
Since the film can be made thinner than the lower substrate 37 and the reflective polarizing plate 31, the liquid crystal display cell can be mounted thinly. Moreover, this film allows the liquid crystal display cell 39 to be fixed to the printed circuit board 11 at the same time as the electrodes are made conductive, thereby simplifying the mounting work. Since a liquid crystal display cell using a flexible plastic film as a substrate is light, it can be sufficiently fixed with such a heat-sealable film.

The adhesive layer 17 adheres and fixes the printed circuit board 11 and the liquid crystal display cell 39, as well as the heat-sealable anisotropic conductive films 25a, 25b, 25c.
The liquid crystal display cell 39 is connected to the printed circuit board 11 by
To prevent distortion or poor connection from occurring when fixing on the top. Since the lower substrate 37 and the reflective polarizing plate 31 are located between the upper substrate 35 and the printed circuit board 11, the heat-sealable anisotropic conductive film 2
The parts fixed by 5a, 25b, 25c are:
It is bonded to the printed circuit board 11 so that it can be bent by utilizing the flexibility of the upper substrate. if,
Without the adhesive layer 17, the parts that are not fixed by the heat-sealable anisotropically conductive films 25a, 25b, and 25c tend to become horizontal, so as shown in FIG. Sex film 25a, 25
Distortion 77 occurs around the boundary between b and 25c and the fixed part. Although the cell gap of the liquid crystal display cell 39 is kept uniform by a gap material (not shown), distortion such as waviness of the cell occurs as shown in FIG. 11, and the image quality deteriorates. On the other hand, when the adhesive layer 17 is present, the protruding portions of the upper substrate 35 are evenly bonded, thereby preventing the above-mentioned distortion from occurring. In addition, adhesive layer 1
7 is not present, the force that causes the upper substrate 35 to return to its original height will cause the heat-sealed anisotropic conductive films 25a, 25b, and 25c to cool and close the liquid crystal display cell 39 after being heat-sealed. This occurs even before the signal line electrode 51 and the signal line external electrode 13 are completely fixed on the printed circuit board 11, and a connection failure is likely to occur between the signal line electrode 51 and the signal line external electrode 13. In contrast, in the mounting structure of the present invention, the presence of the adhesive layer 17 effectively prevents distortion and poor connection. It is desirable that the thickness of the adhesive layer and the thickness of the heat-sealable anisotropic conductive film be approximately the same.

FIG. 5 is a partial cross-sectional view of the vicinity of the scanning line external electrode section for schematically showing the connection state between the scanning line electrode extraction section 55 and the scanning line external electrode section 23;
FIG. 6 is a sectional view taken along that line. Since both the scanning line electrode 57 and the scanning line external electrode section 21 face upward, it is not possible to connect them directly. Therefore, they are connected via a flexible printed circuit board 63 having conductive electrodes 65 having the same pitch width as the scanning line electrodes 57. The coupling between the flexible printed circuit board 63 and the scanning line electrode extraction section 55 and the coupling between the flexible printed circuit board 63 and the scanning line external electrode section 23 are as follows.
This can be done using heat-sealable anisotropic conductive films 29 and 61 in the same way as explained in FIGS. 2 and 3. Here, the heat-sealable anisotropic conductive films 29 and 61 are used both for electrically connecting the liquid crystal display cell 39 and the printed circuit board 11 and for fixing the liquid crystal display cell 39 to the printed circuit board 11. It is fulfilling its role. Due to the thickness of the substrate, polarizing plate, etc., there is a difference in height between the scanning line external electrode section 23 surface of the printed circuit board 11 and the scanning line electrode extraction section 55 surface of the liquid crystal display cell 39, but it is flexible. By using the printed circuit board 63, the two can be reliably connected despite the difference in height.

In the embodiments described above, the case where the scanning line electrode lead-out portion is connected without being divided is shown, but it can also be divided in the same way as the signal line electrode lead-out portion. Further, fixation using a heat-sealable anisotropic conductive film may be adopted for only one of the signal line electrode extraction portion and the scanning line electrode extraction portion. Of course, by fixing with both electrode extraction parts, it can be firmly fixed at any time.

As the protection plate 73, a rigid plate such as an acrylic plate is suitable. The protection plate is fixed to the printed circuit board by screws, adhesive, or the like. Further, if a protective plate having a polarizing function is used, the polarizing plate can be omitted. Liquid crystal display cells that use plastic film are easily damaged by external pressure or cutting force, but by integrating the protective plate and mounting it, the module is easier to handle, and the surface of the liquid crystal display cell can be easily damaged. do not have.

The polarizing plate and the reflective polarizing plate may or may not be fixed to the liquid crystal display cell or the protective plate. Instead of the reflective polarizing plate, a reflecting plate and a polarizing plate may be used, respectively.

Effects of the invention According to the invention, a heat-sealable anisotropic conductive film is used as a connector to connect the electrode extraction part of the liquid crystal cell and the external electrode part of the circuit board, and electrically connect the two electrodes. At the same time, by fixing and mounting the liquid crystal display cell on a printed circuit board, thin mounting becomes possible, making it possible to take full advantage of the characteristics of the liquid crystal display cell using a flexible film substrate, and making mounting operations easier. is simple and can be manufactured at low cost.

Furthermore, the electrode lead-out portion is divided into a plurality of parts, and the divided parts are formed on the lead-out surfaces on different end faces of the liquid crystal display cell so as not to be adjacent to each other, and correspondingly, external electrode parts of the circuit board are formed. According to
Electrical connection between the electrodes can be reliably established without heat-sealing the same location twice using a heating head, resulting in high reliability.

Furthermore, by fixing the portion of the extraction surface where no electrode is provided to the circuit board with an adhesive layer, it is possible to effectively prevent the occurrence of distortion and poor connection.

[Brief explanation of drawings]

1 is an exploded perspective view showing an embodiment of the present invention, FIG. 2 is a cross-sectional view of the vicinity of the first upper substrate protrusion 41 in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line - in FIG. 2. Figure 4 is a sectional view taken along the line - in Figure 2;
FIG. 5 is a partial sectional view of the vicinity of the external scanning line electrode section, and FIG. 6 is a sectional view taken along the line - in FIG. FIG. 7 is an explanatory diagram showing heat sealing by a heating head in an embodiment of the present invention. FIG. 8 is an exploded perspective view showing a conventional liquid crystal display device. FIG. 9 is a partially enlarged view showing the vicinity of the signal line electrode extraction portion. FIG. 10 is an explanatory diagram showing heat sealing by a heating head in a conventional liquid crystal display device. FIG. 11 is an external view of a liquid crystal display device without an adhesive layer. 11...Printed circuit board, 13...External electrode for signal line, 15...External electrode part for signal line, 1
5a...First signal line external electrode part, 15b...
...Second signal line external electrode part, 15c...Third
external electrode part for signal line, 17...adhesive layer, 2
1... External electrode for scanning line, 23... External electrode part for scanning line, 25, 25a, 25b, 25c, 2
9,61...Heat-sealable anisotropic conductive film, 31
... Reflective polarizing plate, 35 ... Upper substrate, 37 ... Lower substrate, 39 ... Liquid crystal display cell, 41 ... First upper substrate protrusion, 43 ... Signal line electrode extraction part, 43a ...
...First signal line electrode take-out part, 43b...Second signal line electrode take-out part, 43c...Third signal line electrode take-out part, 47...Second upper substrate protrusion, 51...Signal line Electrode, 53... Lower board protrusion, 55... Scanning line electrode extraction part, 57... Scanning line electrode, 63... Flexible printed circuit board, 65... Conductive electrode, 7
1... Observation side polarizing plate, 73... Protective plate, 77...
distorted.

Claims (1)

[Scope of utility model registration request] It has a liquid crystal display cell using a plastic film as a substrate and a circuit board for driving the liquid crystal display cell, and the electrode lead-out part of the liquid crystal display cell and the external electrode part of the circuit board are heat-fused anisotropically conductive. A liquid crystal display device in which an electrode connection portion is formed by being electrically connected and fixed with a magnetic film, and the electrode forming portion is divided into a plurality of parts with a predetermined length, and the adjacent divided parts are not adjacent to each other. A liquid crystal display characterized in that an adhesive layer is formed on an end face side of a different liquid crystal display cell, and an adhesive layer is formed on a portion of the end face side where a heat-sealable anisotropic conductive film is not provided. Device.