JPH06160881A - Liquid crystal display panel - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display panel which is stable in the electrical and mechanical connection to the IC-driven liquid crystal display panel and decreases picture element defects. CONSTITUTION:This liquid crystal display panel is constituted, for example, by face down bonding a driving IC 106 having, projecting electrodes 107 to the wiring electrodes on the substrate of the liquid crystal display panel by using conductive adhesives 108 via the projecting electrodes. The above mentioned liquid crystal display panel is made into a two-layered structure formed by further providing a second transparent electrode layer 112 consisting of an ITO film by a vacuum vapor deposition method on a first transparent electrode layer 111 consisting of an ITO film provided with pixel electrodes 104, 105, and wiring electrodes 103 by a sputtering method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a transparent electrode provided on a substrate which constitutes a liquid crystal display panel, and more specifically to improvement of connectivity between the transparent electrode and other members.

[0002]

2. Description of the Related Art In a liquid crystal display panel, basically, two transparent substrates having transparent electrodes are sealed with a sealing material,
The transparent electrode is formed by injecting a liquid crystal material into this, and the transparent electrode forms a pixel electrode inside the sealing material and is drawn out of the sealing material to form a wiring electrode.

The wiring electrode of this transparent electrode is directly connected to the FPC.
(Flexible printed circuit) or connected to an external circuit via an anisotropic conductive rubber or the like, and also when a semiconductor integrated circuit device (hereinafter referred to as a drive IC) for driving a liquid crystal display panel is connected. is there.

The following description will be made on a liquid crystal display panel in which a driving IC is face-down bonded to a substrate constituting a liquid crystal display panel. However, the present invention, as described above, includes the transparent electrode and other members such as the driving IC and FPC. The present invention relates to the improvement of the connectivity with and is not limited to the mode of the description.

FIG. 3 is a schematic plan view showing a liquid crystal display panel in which a drive IC is face-down bonded to a substrate constituting the liquid crystal display panel. As shown in FIG. 3, the first substrate 101 and the second substrate 102 are sealed with a sealing material 110.
And the liquid crystal is filled in the sealed region. The drive IC 1 is attached to the wiring electrode 103 drawn on the first substrate 101.
06 is connected. Further, the FPC 11 is provided on the wiring electrode 103.
3 is connected and a signal or the like is supplied from the outside.

FIG. 4 is a schematic sectional view showing an example of a conventional structure and shows a section taken along the line AA of FIG. In FIG. 4, structural details such as the alignment film are omitted. A conventional liquid crystal display panel will be described below with reference to FIG.

In the conventional liquid crystal display panel shown in FIG. 4, the pixel electrode 104 and the wiring electrode 103 corresponding to the electrode of the driving IC 106 are formed on the first substrate 101 by the steps described below.

First, an indium tin oxide (hereinafter referred to as ITO) film which is a transparent electrode film is formed on the entire surface of the first substrate 101 by a sputtering method, a vacuum evaporation method, a pyrosol method or the like.

After that, a photoresist is applied to the entire surface on which the ITO film is formed, and exposure, development and etching are performed through a photomask having a desired pattern shape. The so-called photo-etching technique is used to form the pixel electrode 104 and the wiring electrode 103. To form.

Pixel electrodes 105 and wiring electrodes (not shown) are formed on the second substrate 102 by the same process, and the first substrate 101 and the second substrate 102 are separated by a predetermined distance. It is sealed with the sealing material 110.

Further, the first substrate 101 and the second substrate 10
Liquid crystal (not shown) is sealed in a region overlapping with 2 and inside the sealing material 110.

Then, the wiring electrode 103 formed on the first substrate 101 and the projection electrode 107 formed in advance on the electrode portion of the driving IC 106 are connected with a conductive adhesive 108.
Face down bonding is performed to make electrical and mechanical connections.

The first substrate 1 further including a driving IC 106
The surface of 01 is resin-sealed with resin 109, and solder plating 1
The FPC 113 provided with 14 is connected to the wiring electrode 103 by a thermocompression bonding method.

[0014]

The above-mentioned structure is simple, is capable of high-density multi-terminal connection, and is effective in providing a small-sized and inexpensive liquid crystal display panel.

By the way, when the present vacuum vapor deposition method is adopted as a method for forming ITO, there are the following drawbacks. That is, the ITO film formed by the vacuum evaporation method is relatively rough, and pinholes are easily generated.

When pinholes are formed on the pixel electrodes 104 and 105, a pixel defect is caused, and the wiring electrode 103 is formed.
When a pinhole is generated above, the wiring electrode 103 is broken, and the yield is significantly reduced.

Wiring electrode 103, pixel electrodes 104, 105
It is also considered to increase the film thickness of ITO in order to prevent the occurrence of the above pinholes, but since the light transmittance of the ITO film is lowered or the stepped portion of the ITO film becomes large,
The liquid crystal orientation becomes non-uniform, and new problems such as deterioration of display quality occur, which is not a practical solution.

On the other hand, the ITO film formed by the sputtering method or the pyrosol method is relatively dense and has few pinholes.

Therefore, the wiring electrode 103 and the pixel electrode 10
If the ITO films 4 and 105 are formed by a sputtering method or a pyrosol method, a decrease in yield due to pixel defects, disconnection, etc. can be suppressed.

However, when the ITO film actually formed by the sputtering method or the pyrosol method is used as the transparent electrode layer, the wiring electrode 103 via the conductive adhesive 108 is formed.
Connection between the bump and the protruding electrode 107, or solder plating 11
In the connection portion between the wiring electrode 103 and the FPC 113 via the wiring 4, some electrical and mechanical connections are unstable.

In such a case, the wiring electrode 103 has been conventionally used.
The method of applying the gold plating to was used. In fact, this conventional method eliminates the instability of the connection. However, in this conventional technique, the process is significantly extended and the cost is also significantly increased.

The present invention has been made to solve the above problems, and an object thereof is to obtain a transparent electrode with few pinholes and at the same time improve the connectivity between the wiring electrode and other members, An object of the present invention is to provide a liquid crystal display panel having stable physical and mechanical connection and high display quality.

[0023]

To achieve the above object, the basic means used by the present invention is to provide at least a part of a transparent electrode of a liquid crystal display panel with a first transparent electrode layer and a first transparent electrode layer thereof. A multilayer structure having a second transparent electrode layer formed above the electrode layer.

[Action]

The above-mentioned phenomenon of unstable connection is not seen when the wiring electrode is formed of the ITO film formed by the vacuum evaporation method, and the IT formed by the vacuum evaporation method is not observed.
When the wiring electrode is formed of an O film, the connecting portion between the wiring electrode and the protruding electrode via the conductive adhesive or the connecting portion between the wiring electrode and the FPC via the solder plating is electrically and mechanically. stable.

When the cause of the instability of electrical and mechanical connection in the case of forming the wiring electrode by the ITO film formed by the sputtering method or the pyrosol method was investigated, the following situation was found.

That is, the ITO film formed by the sputtering method or the pyrosol method is relatively dense, and the surface thereof has very good smoothness. As a result, the adhesiveness with a conductive adhesive, solder, etc. is inferior, and the connectivity is reduced. On the other hand, the ITO film formed by the vacuum evaporation method is relatively rough, and its surface has poor smoothness. As a result, the adhesiveness with a conductive adhesive or solder is good, and the connectivity is improved.

Therefore, the wiring electrode is an IT with few pinholes.
The above problem can be solved by using a multi-layer structure including a first transparent electrode layer made of an O film and a second transparent electrode layer made of an ITO film having a rough surface and having good connectivity with other members.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. The embodiment is carried out on a liquid crystal display panel in which a drive IC is face-down bonded to a substrate constituting the liquid crystal display panel in accordance with a conventional example.

FIG. 1 is a schematic sectional view of a liquid crystal display panel showing a first embodiment of the present invention, and the corresponding plan view also serves as FIG. FIG. 1 shows a cross section taken along the line AA in FIG.
The liquid crystal display panel of the present invention will be described below with reference to FIG. 1. However, the drawing shows only the structure, and does not show the dimensions or the like.

As shown in FIG. 1, a first ITO film is formed on the entire surface of the first substrate 101 by a sputtering method.
The transparent electrode layer 111 is provided. Next, a portion other than the portion where the wiring electrode 103 is formed is masked, and only the portion where the wiring electrode 103 is formed is formed into a second ITO film using a vacuum deposition method.
The transparent electrode layer 112 is selectively provided.

After that, a photoresist is applied on the entire surface of the ITO film, and a pixel electrode 104 and a wiring electrode 103 are formed by a so-called photoetching method in which exposure, development and etching are performed through a photomask having a predetermined pattern shape.

As a result, the pixel electrode 104 has a one-layer structure including only the first transparent electrode layer 111 made of an ITO film provided by the sputtering method. On the other hand, the wiring electrode 1
03 has a two-layer structure of a first transparent electrode layer 111 made of an ITO film provided by a sputtering method and a second transparent electrode layer 112 made of an ITO film provided by a vacuum deposition method. Become.

When the means of the present invention is applied to the second substrate 102 as well, the pixel electrode 1 is formed by the same process as the first substrate 101.
05, a wiring electrode (not shown) is formed.

After that, the first substrate 101 and the second substrate 1
02 is separated from the pixel electrode 104 by a predetermined distance.
The surfaces on which 05 are formed face each other, and the periphery is surrounded by the sealing material 110.
Seal with.

Further, the first substrate 101 and the second substrate 10
Liquid crystal (not shown) is sealed in the region where the two overlap with the inside of the sealing material 110.

Then, the wiring electrode 103 formed on the first substrate 101 and the protruding electrode 107 formed in advance on the electrode portion of the driving IC 106 are face-down bonded with a conductive adhesive 108 to electrically and mechanically connect. I take the.

First substrate 1 further including drive IC 106
The surface of 01 is resin-sealed with resin 109, and the FPC 113 which is further plated with solder is connected to the wiring electrode 103 by a thermocompression bonding method.

FIG. 2 is a schematic sectional view showing a liquid crystal display panel which is a second embodiment of the present invention, and shows a section taken along the line AA of FIG. A second embodiment of the present invention will be described below with reference to FIG.

As shown in FIG. 2, a first transparent electrode layer 111 made of an ITO film is first formed on the entire surface of the first substrate 101 by a sputtering method. Next, a second transparent electrode layer 112 made of ITO using a vacuum deposition method is provided on the entire surface of the first transparent electrode layer 111 to form a two-layer structure.

After that, a photoresist is applied on the entire surface of the ITO film, and the pixel electrode 104 and the wiring electrode 103 are formed by a so-called photoetching method in which exposure, development and etching are performed through a photomask having a predetermined pattern shape.

As a result, the pixel electrode 104 and the wiring electrode 10
Reference numeral 3 has a two-layer structure of a first transparent electrode layer 111 made of an ITO film, which is provided by a sputtering method, and a second transparent electrode layer 112 made of an ITO film, which is provided by a vacuum deposition method. It will be.

When the means of the present invention is applied to the second substrate 102 as well, the pixel electrode 1 is formed in the same process as the first substrate 101.
05, a wiring electrode (not shown) is formed.

After that, the first substrate 101 and the second substrate 1
02 is separated from the pixel electrode 104 by a predetermined distance.
The surfaces on which 05 are formed face each other, and the periphery is surrounded by the sealing material 110.
Seal with.

Further, the first substrate 101 and the second substrate 10
Liquid crystal (not shown) is sealed in the region where the two overlap with the inside of the sealing material 110.

Then, the wiring electrode 103 formed on the first substrate 101 and the protruding electrode 107 formed in advance on the electrode portion of the driving IC 106 are face-down bonded with a conductive adhesive 108 to establish an electromechanical connection. take.

First substrate 1 further including drive IC 106
The surface of 01 is resin-sealed with resin 109, and the FPC 113 which is further plated with solder is connected to the wiring electrode 103 by a thermocompression bonding method.

In the second embodiment, the second transparent electrode layer 11 is used.
2 is provided on the entire upper surface of the first transparent electrode layer 111. Therefore, as in the first embodiment, the second transparent electrode layer 112 is formed.
The masking means necessary for selectively providing the is not necessary, and there is an advantage that the process is simplified.

In the above two examples, the conductive adhesive 108
As the Ag / Pd paste, a fine powder of Ag / Pd, which is a conductive particle, was mixed in an epoxy resin.

The conductive adhesive 108 made of this Ag / Pd paste is spread on a substrate with a squeegee, and then the protruding electrode 107 of the driving IC 106 is brought into contact with the Ag / Pd paste to attach the conductive adhesive 108 to the protruding electrode 107. Transcribe.

In this stamp method, a uniform amount of conductive adhesive 108 is applied to the protruding electrode 107 formed on the driving IC 106.
Can be transferred.

Projection electrode 10 to which conductive adhesive 108 is transferred
The drive IC 106 having No. 7 is face-down bonded to a predetermined position of the wiring electrode 103 formed on the first substrate 101, and lightly pressed from the opposite side of the projecting electrode 107 of the drive IC 106.

After heat-curing the conductive adhesive 108,
The surface of the substrate including the drive IC 106 is resin-sealed with resin 109.

When the liquid crystal display panel having the structure shown in this embodiment is manufactured, the driving IC 106 or the FPC 11 is manufactured.
The liquid crystal display panel was stable in electrical and mechanical connection with No. 3, and was free from pixel defects due to pinholes and disconnection of wiring electrodes.

This means that the surface of the wiring electrode 103 of the present invention has a relatively rough surface I formed by the vacuum deposition method.
The validity of the configuration is shown in which the TO film is used and the other parts are the ITO film formed by the sputtering method with few pinholes.

In the above embodiment, the first transparent electrode layer 1
Although the case where both 11 and the second transparent electrode layer 112 are ITO films is shown, they may be formed of a transparent conductive layer having a composition different from that of the ITO film such as tin oxide.

However, it is preferable that the first transparent conductive layer 111 and the second transparent electrode layer 112 have the same or similar composition from the viewpoint of the process, and the ITO film is generally used as a transparent electrode. Since it is a material that does not require new equipment, it is desirable that both the first transparent electrode layer 111 and the second transparent electrode layer 112 are ITO films.

In the above embodiment, the first transparent electrode layer 11
In the example, 1 is formed by the sputter method and the second transparent electrode layer 112 is formed by the vacuum evaporation method.

However, the gist of the present invention is to combine the first transparent electrode layer 111 with few pinholes and the second transparent electrode layer 112 with a moderately large surface roughness to obtain different characteristics required for the transparent electrode. Therefore, any method may be used to form each transparent electrode layer as long as this purpose is achieved.

For example, the first transparent electrode layer 111 is formed by the sputtering method under the forming condition for obtaining a dense layer, and the second transparent electrode layer 112 is formed by the sputtering method under the forming condition for obtaining the rough layer. Is also good.

In this case, the first transparent electrode layer 111 and the second transparent electrode layer 112 can be continuously formed by changing the forming conditions on the way. As the formation conditions, the substrate temperature, oxygen partial pressure, film formation rate, etc. are controlled.

However, in order to easily obtain a transparent electrode layer having a rough surface as the second transparent electrode layer 112, it is easiest to use the vacuum vapor deposition method.

When at least the first transparent electrode layer 111 is formed of an ITO film, it is desirable that the sputtering method be used.

ITO formed by, for example, a pyrosol method
Although the film has few pinholes, it has a relatively high specific resistance, and the electric resistance values of the wiring electrode 103 and the pixel electrodes 104 and 105 cannot be made sufficiently small. As is well known, these increases in electrical resistance cause so-called crosstalk,
The display quality of the liquid crystal display panel may be degraded.

Of course, if the film thickness of the transparent electrode layer is increased, the electric resistance value is lowered, but the light transmittance is lowered, and the display quality is lowered due to the non-uniform alignment of the liquid crystal in the step portion of the ITO film.

IT formed by this point sputtering method
Since the specific resistance value of the O film can be reduced, when the same film thickness is obtained, the wiring electrode 103,
This is convenient because the electric resistance of the pixel electrodes 104 and 105 can be reduced.

By the way, as is clear from the description of the above embodiment, the practice of the present invention may be limited to only the first substrate 101. In this example, a so-called active panel is provided on the second substrate. There may be a case where the connection condition between the wiring electrode and the other member is different from that of the first substrate 101.

Further, it has been described above that the present invention is effective when the method of using the conductive adhesive and the method of thermocompression bonding with the solder interposed are used for connecting the wiring electrode 103 and other members. For example, it is also effective in other connection methods such as a method of press-contacting anisotropic conductive rubber.

Further, although the present invention is intended mainly for the stability of electrical and mechanical connection, in the second embodiment, the second transparent electrode layer 112 is replaced by the first transparent electrode layer 111.
Since it is provided on the entire upper surface, the adhesion between the sealing material 110 or the alignment film (not shown) and the second transparent electrode layer 112 is also improved. Therefore, in order to obtain such an effect, it may be used only for the purpose of improving mechanical connectivity.

It should be noted that another layer may be provided between the first transparent electrode layer 111 and the second transparent electrode layer 112 for the purpose of enhancing the adhesiveness of these two layers, or the first transparent electrode layer may be formed. When the formation of the electrode layer 111 and the second transparent electrode layer 112 is continuously performed, the formation conditions are gradually changed, and even when the boundary between the two layers is not clear, it is partially seen. In this case, the case where there is a part having a different characteristic which is consistent with the gist of the present invention is included in the present invention.

When the contents of the present invention are summarized here, the first means is that "at least a part of the transparent electrode is a relatively dense first electrode".
Of the transparent electrode layer and the second transparent electrode layer having a relatively rough surface formed above the first transparent electrode layer. " It is possible to obtain a transparent wiring electrode having good connectivity with the member.

Further, the second means is "a wiring electrode and a pixel electrode both have a multi-layer structure having a first transparent electrode layer and a second transparent electrode layer formed above the first transparent electrode layer".
This makes it possible to simplify the implementation process of the first means.

The third means is to make the first transparent electrode layer and the second transparent electrode layer both transparent electrode layers formed of indium tin oxide together with the first or second means.
This makes it possible to effectively use conventional processes and equipment.

The fourth means is to "use the first transparent electrode layer as a transparent electrode layer formed by a sputtering method" together with the first, second or third means, which has a small number of pinholes and is electrically conductive. The first transparent electrode layer having low resistance can be easily obtained.

The fifth means is to "make the second transparent electrode layer a transparent electrode layer formed by a vacuum vapor deposition method" together with the first, second, third or fourth means. The second transparent electrode layer having a rough surface can be easily obtained.

The sixth means is that, together with the first, second, third, fourth or fifth means, "the drive IC is on the wiring electrode,
Face down bonding with a conductive adhesive through the protruding electrodes. "
The effect of implementing the means can be enhanced.

[0076]

As is apparent from the above description, according to the present invention, in the liquid crystal display panel, at least the wiring electrode,
By forming a multilayer structure having a relatively dense first transparent electrode layer and a relatively rough and rough surface second transparent electrode layer formed thereabove, pixel defects with stable electromechanical connection can be achieved. It is possible to manufacture a liquid crystal display panel with a low yield at a high yield and at a low cost.

Particularly in the case of the second embodiment, a wiring electrode and
Since the pixel electrode and the pixel electrode have exactly the same structure, only the step of simply providing one extra transparent electrode layer having a rough surface is added. Such a simple solution is the conventional gold plating layer,
In other words, it was impossible with the means of providing an opaque layer, and the present invention could be achieved only by using a new means of adding a transparent electrode layer.

In recent years, with the demand for higher-definition liquid crystal display panels, the electrode widths of the pixel electrodes and wiring electrodes have become thinner, the electrical resistance has increased, and the connection area between the wiring electrodes and other members has decreased. However, although the connection conditions tend to deteriorate, the present invention can meet the demand even in such a situation.

The method of providing the driving IC on the substrate as in the first and second embodiments enables high-density mounting and is most suitable for a high-definition liquid crystal display panel. Since the connection is made in a very small area, the stability of the connection part is very important, and the effect of implementing the present invention is particularly great.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a liquid crystal display panel in a first embodiment of the present invention.

FIG. 2 is a sectional view showing a liquid crystal display panel in a second embodiment of the present invention.

FIG. 3 is a plan view showing a liquid crystal display panel in which a drive IC is face-down bonded on a substrate of the liquid crystal panel.

FIG. 4 is a cross-sectional view showing a conventional liquid crystal display panel.

[Explanation of symbols]

 101 First Substrate 102 Second Substrate 103 Wiring Electrode 104 Pixel Electrode 105 Pixel Electrode 106 Driving IC 111 First Transparent Electrode Layer 112 Second Transparent Electrode Layer 113 FPC

Claims (6)

[Claims] 1. A liquid crystal characterized in that at least a part of the transparent electrode has a multi-layer structure having a first transparent electrode layer and a second transparent electrode layer formed above the first transparent electrode layer. Display panel. 2. Both the wiring electrode and the pixel electrode of the transparent electrode have a multi-layer structure having a first transparent electrode layer and a second transparent electrode layer formed above the first transparent electrode layer. The liquid crystal display panel according to claim 1, wherein the liquid crystal display panel is a liquid crystal display panel. 3. The liquid crystal display panel according to claim 1, wherein both the first transparent electrode layer and the second transparent electrode layer are made of indium tin oxide. 4. The liquid crystal display panel according to claim 1, 2, or 3, wherein the first transparent electrode layer is a transparent electrode layer formed by a sputtering method. 5. The liquid crystal display panel according to claim 1, 2, or 3, wherein the second transparent electrode layer is a transparent electrode layer formed by a vacuum vapor deposition method. 6. The liquid crystal display panel according to claim 1, claim 2, claim 3, claim 4, or claim 5, wherein the wiring electrode and the other member are connected by a conductive adhesive. .