JPS62276581A - Liquid crystal display panel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a display device used in an automobile instrument panel, office automation equipment, etc. The present invention relates to display panels such as liquid crystal and EL that are mounted on the display panel.

[Conventional technology]

In recent years, graphic ink displays have become widely used as man-machine interfaces, and along with this, liquid crystal display devices have also come to be used in automobile instrument panels.
This trend tends to accelerate as color liquid crystal display elements become more practical.

By the way, in such a liquid crystal display device (hereinafter referred to as a display panel), by taking advantage of its panel-like form, one of its electrode substrates is expanded, and a driving electronic circuit element (LSI) is installed in this expanded portion. ) is directly installed, and a module is known in which both are modularized. Incidentally, such examples are disclosed in, for example, Japanese Patent Application Laid-Open No. 53-60199 and Japanese Patent Application Laid-Open No. 53-104198.

Therefore, a conventional example of such a display panel will be explained with reference to FIG. 2.

FIG. 2 shows a liquid crystal display element (display panel) composed of a glass substrate 1 and a glass substrate 2 which is an electrode substrate. On the glass substrate 2 is an LSI chip 4 for driving the liquid crystal display element. is mounted by directly connecting it to the wiring circuit using solder 5. The metal 2'! between this liquid crystal display section and the terminals of the LSI chip 4! IIA6
, and the metal wiring 7 between the terminals of the LSI chip 4 and the terminals for connection with an external circuit are made of the same conductive material, for example, Cr-Cu.
A conductor layer made of a -CrS layer film is used.

Further, in FIG. 2, reference numeral 3 denotes a sealant for sealing the liquid crystal sandwiched between the glass substrates 1.degree. Although it is omitted because it is difficult to show in FIG. 2, a protective resin is actually provided to cover the LSI chip 4, as will be described later.

Next, FIG. 3 shows a cross section taken along line A-A' in FIG. 2, and in this FIG. 3, 1.2 is a glass substrate;
3 is a sealant, 4 is an LSI chip, 9 is a terminal portion of the LSI chip 4, 5 is a solder, 6 is a metal wiring consisting of three layers of 12°, 13 and 14, and 12 is Cr.

13 is Cu, 14 is Cr, 7 is a metal wiring consisting of 15, 16 and 1703 layers, 15 is Cr, 1
6 is Cu.

17 is Cr, 10 is a liquid crystal layer, 18 and 19 are In
This is a transparent electrode made of a transparent conductive film made of z○3°Snug or a mixture thereof.

The liquid crystal display element portion 11 includes a glass substrate 1 and a glass substrate 2.
It has a structure in which a liquid crystal layer 10 is sandwiched between them.

A transparent electrode 19 is formed on the glass substrate 1, and a transparent electrode 18 is formed on the glass substrate 2. This transparent electrode 18 is
It is extended to the outside from the liquid crystal display part 11, and there,
Electrical connection is ensured by laminating metal wirings 6 and 7 in one layer. For the metal wirings 6 and 7, the first layer 12 and the third layer 14 are made of Cr, and the second layer 13 is made of Cu. That is, the metal film 12 and the metal film 14 contain Cr,
Cu is used for the metal film 13.

Furthermore, Cr is used for the metal film 15 and the metal film 17, and Cu is used for the metal film 16. The metal films 14 and 17 include L
A through hole is opened in the connection area corresponding to the position of the terminal part 9 of the SI chip, and the connection area 20 of the metal wirings 6 and 7 is formed.
．． 21, the third layer of Cr14.17 is not present and the second layer of Cu13.16 is directly exposed, and the LSI chip 4
The structure is such that the LSI chip 4 is connected onto the glass substrate 2 by the solder 5 of the terminal portion 9 . Furthermore, L
The SI chip 4 is coated and protected with a coating resin 8 (not shown).

Incidentally, a liquid crystal display element mounted with an LSI chip having such a structure is required to have various types of reliability. This reliability evaluation is divided into two types: a non-energized reliability test and an energized reliability test. Note that the current conduction reliability test refers to an operation test of a liquid crystal display element under various conditions.

First, in the non-current reliability test, high temperature storage (90℃-
500h), high temperature and high humidity (70℃/95%-1)
000h), temperature/humidity cycle (-30°C→70°
C/95%RH.

40 cycles), temperature cycle (-30℃-80℃
, 500 cycles or more), vibration test (LOG, 10~
500 Hz - 100 hours each).

The conventional liquid crystal display elements having the structures shown in FIGS. 2 and 3 were subjected to various non-current reliability tests as described above, and as a result, it was confirmed that the specifications were satisfied.

Therefore, we conducted a current reliability test. This communication reliability test is an operation test that is performed while actually displaying the liquid crystal, and this energization reliability test includes a high temperature operation test (85'C-250h) and a low temperature operation test (- 3
5'c -250h), high temperature high temperature operation test (70
"C/95%12H-250h).

As a result of conducting these current reliability tests, it was found that the above-mentioned conventional example also satisfies the target specifications for high temperature and low temperature operation tests. However, a problem arose in that a display failure occurred after about 100 hours of operation in a high-temperature high-temperature operation test.

As a result of investigating the cause of this problem, as shown in FIG. It was confirmed that a short circuit had occurred.
Furthermore, it was found that the whisker-like precipitates were deposited from the metal constituting the metal wirings 6 and 7, that is, Cu13.16.

However, in high-temperature high-temperature operation tests, short circuits between metal wiring or connection terminals that cause display defects can significantly reduce the reliability of liquid crystal display elements and make them unsuitable for use as products. It is complete.

[Problem that the invention seeks to solve]

As described above, conventional display panels have a problem in that it is difficult to maintain sufficient reliability when applied to automobiles and the like.

The purpose of the present invention is to solve the above-mentioned problems of the prior art, eliminate the risk of short circuits between metal wiring or connection terminals even when operated in high temperature and high humidity conditions, and allow use in display elements such as automobiles. An object of the present invention is to provide a liquid crystal display panel that can maintain sufficient reliability.

Means for Solving Problem C] To achieve this object, the present invention provides an organic resin that is heat-treated in vacuum on the metal wiring and connection terminals of a liquid crystal display panel equipped with electronic circuit elements. It is characterized in that the coating is formed to a predetermined thickness. Note that the present invention is based on the following findings. In other words, as a result of various investigations into short circuits between the metal wiring and connection terminals of display panels, the inventors of the present invention found that the electrode on the positive electrode potential side melts due to the presence of moisture, and the electrode on the negative electrode potential side melts. It was revealed that an electrochemical reaction was occurring in which a type of precipitate was formed, and it was also confirmed that the electrochemical reaction was concentrated at the connection terminal where the electric field strength was the highest.

As a result, as mentioned above, a film made of organic resin heat-treated in vacuum is formed on the metal wiring and connection terminals to a thickness greater than that of the metal wiring to prevent moisture from entering. I discovered what I should do.

By using organic resin heat-treated in vacuum,
It has fewer pinholes, improves adhesion to the substrate, forms a film with excellent step covering properties, and can prevent short circuits between metal wiring and connection terminals even under high temperature and high humidity conditions.

To form a film, in the case of polyimide resin, for example, a resin with a viscosity of about 60 to 100 cps is applied, and 1O-5
30 to 12 at a temperature of about 350℃ in a vacuum below Torr
Cook for 0 minutes, usually 60 minutes. In addition, epoxy resin is also used as the resin for forming the film, and 1fl'T
.

It may be heated at 150° C. for about 60 minutes or more in a vacuum below rr.

〔Example〕

Hereinafter, the display panel according to the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, in which 1
．． 2 is a glass substrate, 3 is a sealant, 4 is an LSI chip, 9
is the terminal part of LSI chip 4, 5 is solder, 6 is Cr (1
2), metal wiring made of Cu(13), Cr(14), 7 is Cr(15), Cu(16), C
metal wiring consisting of r (17), 10 is a liquid crystal, 18 and 1
9 is Ir+zOi.

This is a transparent electrode made of a transparent conductor film made of 5nOz or a mixture thereof.

A polyimide resin layer 22 is formed to protect the metal wiring 6.7 and the connection terminal portion 20.21. 8
is a coating resin to protect the LSI chip.

The liquid crystal display element portion 11 includes a glass substrate 1 and a glass substrate 2.
It has a structure in which the liquid crystal layer 10 is sandwiched between the two layers.

A transparent electrode 19 is formed on the glass substrate 1, and a transparent electrode 18 is formed on the glass substrate 2. This transparent electrode 18 is
It comes out from the liquid crystal display element part 11, and a part of the metal wiring "!1IA6.7" is laminated there to ensure electrical connection.

According to this embodiment, the metal wirings 6 and 7 and the connection terminal portion 20
．． 21 is provided with a polyimide resin layer 22 that has been subjected to vacuum heat treatment, which prevents water from entering and prevents the conductor material from dissolving or precipitating during high-temperature operation tests.
We were able to eliminate short circuits between connection terminals and metal wiring, improving reliability.

Table 1 shows the high-temperature high-temperature operation test results of the display panel according to this example.

(Margins below this page) Table 1 shows the results obtained by keeping the thickness of the metal wiring 6.7 constant at 2.0 μm in the embodiment shown in FIG. 1, and varying the thickness of the polyimide resin 22 formed thereon. This is the result of conducting a high-temperature high-temperature operation test and investigating the occurrence of whisker-like precipitates 22 between the connecting terminals.

As is clear from this, it satisfies the high temperature operation test (7
0°C/95%RH, 250 hours), the polyimide resin must be heat treated in a vacuum, and the required film thickness must be 2.
．． It was confirmed that it is sufficient if the thickness is 0 μm or more.

The effects of heat-treating the polyimide resin in vacuum are thought to be due to improved adhesion to the substrate and the complete removal of volatile substances in the polyimide resin to form a high-quality polyimide resin.

According to this embodiment, it is possible to prevent a short circuit from occurring due to water intrusion into the connection terminal portion, and at the same time, it is possible to protect the entire surface of the metal wirings 6 and 7 with the polyimide resin layer 22.
It has the advantage of preventing damage to conductors (scratches, disconnections) during assembly of liquid crystal elements.

In another embodiment of the invention, instead of polyimide resin,
It has been confirmed that the same effect can be expected using photosensitive polyimide resin. A further characteristic of this case is that
Since the photolithography process is simplified compared to Example 1, further cost reduction is possible.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to eliminate the risk of short circuits between metal wirings and at connection terminals in a liquid crystal display panel equipped with electronic circuit elements, thereby solving the problems of the prior art. In addition, an improvement in yield can be expected, and a display panel that can maintain sufficient reliability for use in automobiles and the like can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a display panel according to the present invention;
FIG. 2 is a perspective view showing an example of a conventional display panel, FIG. 3 is a sectional view taken along line AA' in FIG. 2, and FIGS. 4a and 4b are photographs showing problems of the conventional display panel. 1.2...Glass substrate, 3...Sealing agent, 4...L
SI chip, 5...Solder, 6,7...Metal wiring,
8... Coating resin, 9... Terminal part of LSr chip, 10... Liquid crystal layer, 11... Liquid crystal display part, 1
2.15... Lower layer Cr, 16=Cu, 14.17-.
・Upper layer Cr, 18.19...Transparent electrode, 20, 2/L
... Connection terminal part, 22... Polyimide resin. Agent Patent Attorney Yusuke Hiraki Figure 1 1: Metal wiring Figure 2 4: LSI depth 7: Metal wiring Figure 3

Claims (1)

[Scope of Claims] 1. In a display panel in which one of the electrode substrates of a display element is expanded to form a wiring board, and electronic circuit elements for driving the display element are mounted on this wiring board, the electrode wiring and electronic circuit elements of the wiring board are mounted. The connection terminals for the circuit elements are made of organic resin and heat treated in vacuum to form a coating with few pinholes, good adhesion to the substrate, and excellent step coverage. LCD display panel. 2. The liquid crystal display panel according to claim 1, wherein the organic resin is a polyimide resin. 3. The liquid crystal display panel according to claim 1, wherein the organic resin is a photosensitive polyimide resin. 4. The liquid crystal display panel according to claim 2, wherein the polyimide resin has a thickness that is at least equal to or greater than the thickness of the electrode wiring.