JPS61183152A - Glass substrate - Google Patents

Abstract

PURPOSE:To obtain a glass substrate having a conductor pattern adhered to a surface with high bonding strength by interposing a dielectric layer contg. Al2O3 dispersed in glass frit between the surface of a glass substrate and a thick filmlike conductor pattern. CONSTITUTION:When a liq. crystal display device is produced by using the glass substrate, an electrode 1 is formed on the surface of the liq. crystal display cell forming part of a glass substrate 2. A dielectric layer 12 is formed on the whole surface of the remaining part of the substrate 2, and a thick filmlike conductor pattern 5 is formed on the layer 12. Powder of one or more kinds of oxides selected among aluminum oxide, beryllium oxide, nickel oxide and silicon oxide, and resulting dielectric paste is applied to the pattern forming part of the substrate 2 and baked to form the dielectric layer 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a glass substrate, and particularly to a glass substrate having a thick film-like conductor pattern formed on its surface.

[Prior Art] In recent years, surface A glass substrate on which a film-like conductor pattern is formed is used.

For example, in a liquid crystal display device, two glass substrates 2 on which electrodes 1 are formed are placed facing each other and the periphery is sealed with a sealing material 3 to form a cell, as shown in a cross-sectional view of an example in FIG. Then, a liquid crystal substance 4 is injected into the cell, and if necessary, two polarizing plates (not shown) are installed on the outside of the cell so as to sandwich the cell, and a display device is configured. I am using it. At this time, at least one of the two glass substrates 2 is extended to the outside of the cell, a conductor pattern 5 is formed on the extended portion, and a circuit pattern 7 is formed from copper foil or the like on a substrate 6 such as polyimide. IC in flat package form
A method is used in which an external circuit board on which chips 8 and the like are mounted is soldered onto the conductor pattern 5 with solder 9 to supply power from the external circuit to the liquid crystal display device. Note that the soldered portion between the glass substrate 2 and the polyimide substrate 6 is sealed with a sealing resin 10, and on the circuit pattern 7 on the polyimide substrate 6,
Protective coating 1 made of polyimide, etc., except for the soldered part
1 is applied to prevent oxidation, etc.

On the other hand, in recent years, there has been a demand for high-density display images.
In order to meet this demand, a large number of uniform patterns 5 must be formed on the glass substrate 2, and in response to this, the circuit patterns 7 on the polyimide substrate 6 have also become finer. In this case, as the pattern width of the circuit pattern 7 becomes finer, for example, to about 0.15 mm to 0.2+em, the cumulative error in the width direction of the polyimide circuit board 6 becomes large. The pitch error is about 2004 tx, and the conductor pattern 5 and the circuit pattern 7 may be misaligned, resulting in poor electrical connection between the glass substrate 2 and the polyimide substrate 6. Further miniaturization is impossible.

In addition, as the pitch of the conductor pattern 5 and the circuit pattern 7 becomes finer, it becomes difficult to align the glass substrate 2 and the polyimide substrate 6 when connecting them, resulting in lower yields and higher costs in the production process. There are also drawbacks.

Furthermore, while high-density screens are required, on the other hand, the display screens themselves are also required to be larger, and as liquid crystal panels become larger, the cost of polyimide substrates becomes a larger proportion of the overall cost of liquid crystal display devices. This also makes it difficult to reduce the cost of liquid crystal display devices.

This is the same situation when connecting the two boards with various connectors such as zebra connectors and bin connectors instead of directly soldering the polyimide board 6 to the glass board 2 as shown in Figure 2. As the density increases, the number of connection terminals increases, which poses problems in terms of reliability and cost.

For this purpose, as shown in the cross-sectional view in FIG. 3, a conductor pattern 5 is formed on the glass substrate 2 extending outside the cell, and a driving IC chip 8 such as a flat package IC or a flip chip is attached to the conductor pattern 5. and other circuit elements are directly soldered using solder 9, and a part of the external electronic circuit is transferred onto the glass substrate 2, thereby reducing the number of connection terminals with the external circuit. )
type of liquid crystal display device is being considered.

[Problems to be Solved by the Invention] A method for forming a conductor pattern on a glass substrate of a COG type liquid crystal display device is a method of forming a conductor pattern 5 on an electrode 1 as shown in FIG. A method is being considered in which the conductor pattern 5 is formed directly on the glass substrate 2 with the electrode l limited to the inside of the cell and connected to the electrode l inside the cell.

In the method of forming the conductor pattern 5 on the first electrode 1, it is difficult to align the electrode 1 and the conductor pattern 5. Especially as both patterns become finer, this difficulty increases rapidly, and production The capacitance decreases rapidly, resulting in a cost increase.Also, in liquid crystal display devices, electrodes are usually made of indium Φ tin oxide.
However, the adhesive strength between ITO and the conductor pattern 5 is weaker than the adhesive strength between the glass substrate 2 and the conductor pattern 5, which also poses a problem.

There are two methods for forming the conductive pattern 5 directly on the second glass substrate 2. The first method is to form the conductor pattern 5 as a thin film using a plating method, sputtering method, vapor deposition method, etc., and the second method is to form the conductor pattern 5 as a thick film using a method such as screen printing with the conductor in the form of a paste. This is the way to do it.

If the conductor pattern 5 is formed of a thin film, the metal forming the conductor pattern will melt and diffuse into the solder due to the heat of the soldering iron when installing or replacing circuit components such as ICs, resulting in electrical contact. This has the drawback that a so-called solder-eating phenomenon, which results in a defective state, occurs, and sufficient reliability cannot be obtained.

Therefore, it is desirable to form the conductor pattern 5 with a thick film, but if the substrate is glass, the conductor paste should be heated to a high temperature (550°C or higher) to prevent the glass from melting.
This was not realized due to reasons such as the fact that it is impossible to bake at low temperatures, a conductor paste for low-temperature firing has not been developed, and that the adhesive strength between the glass substrate 2 and the conductor paste is not necessarily sufficient. Not yet.

Although the above explanation has been made using a liquid crystal display device as an example, there are circumstances in which it is desirable to form a thick conductive pattern on the glass substrate, but it cannot be realized for the reasons mentioned above. The same applies to devices using electrochromic substances other than liquid crystal display devices, as well as glass substrates used in fluorescent display tubes, plasma displays, etc. In the following description, we will mainly explain COG type liquid crystal display devices as an example. The same applies to other devices.

The present invention was made in order to solve the above-mentioned drawbacks of conventional glass substrates, and it avoids the difficulties of manufacturing processes and provides a thick film-like film formed with strong adhesive strength on the substrate surface. An object of the present invention is to provide a glass substrate having a conductor pattern.

[Means for Solving the Problems] The glass substrate of the present invention has a thick film-like conductor pattern formed on at least one surface, and there is no oxidation between the surface of the glass substrate and the conductor pattern. It is characterized by interposing a dielectric layer in which at least one of aluminum, beryllium oxide, nickel oxide, or silicon oxide is dispersed in a glass lift.

Hereinafter, the present invention will be described in detail by taking a COG type liquid crystal display device as an example.

FIG. 1 is a sectional view showing an example of a liquid crystal device constructed using a glass substrate according to the present invention.

In the figure, an electrode 1 such as TTO is formed on at least one surface of a portion of a glass substrate 2 where a liquid crystal display cell is formed. Note that an alignment film (not shown) made of polyimide or the like is formed on the electrode l if necessary. A dielectric N12 is formed over almost the entire surface of the glass substrate 2 extending outside the cell forming portion of the surface on which the electrode 1 is formed, and a thick film conductor is formed on the dielectric layer 12. Pattern 5 is formed. One end of the conductor pattern 5 is overlapped and electrically connected to one end of the electrode 1 formed within the cell forming portion. Further, a protective coating 11 is formed on the upper surface of the conductor pattern 5 except for the soldering portion and the portion penetrating into the cell forming portion.

The glass substrate 2 on which the electrodes 1 and the conductor pattern 5 have been formed in this way is placed so that the electrode 1-forming surface faces another glass substrate 2 on which the electrodes 1 and, if necessary, the conductor patterns 5 are formed, and the peripheral portion is covered with a sealing material. 3 to form a liquid crystal display cell, and a liquid crystal substance 4 is injected into the cell to form a liquid crystal display device.

Thereafter, external components such as the IC chip 8 are soldered onto the conductive pattern 5, and the liquid crystal display device is completed. In the illustrated example, a flip chip is used as the IC chip 8, and the solder 9 is a solder bump of the flip chip. Furthermore, if the external parts are sealed with a sealing resin 10 as shown, the external parts can be protected from external effects such as oxidation from the outside air and impact.

As described above, the electrode 1 is usually made of ITO, but it may also be made of indium oxide or tin oxide, or if transparency is not required, a commonly used electrode such as a metal foil made of copper or the like may be used.

The electrode 1 can be formed on the glass substrate 2 by a commonly used method such as vapor deposition, sputtering, or plating when using ITO or simple tin oxide, or when using metal foil or the like. may be formed by bonding with an adhesive or the like.

As the glass substrate 2, ordinary soda lime glass may be used. In addition, when soda lime glass is used,
In order to prevent gaseous sodium from being generated during firing of the conductor pattern 5, a thin film of silica or the like is sometimes applied on the surface of the glass (so-called undercoat film). Since the dielectric layer 12 is interposed between the substrate 2 and the conductive pattern 5, the dielectric layer 12 prevents the generation of sodium gas, making an undercoat unnecessary. Note that the glass substrate 2 is of course not limited to soda lime glass, and may be other types of glass such as borosilicate glass.

The sealing material 3 is made of epoxy resin or the like.

The liquid crystal material 4 may be any type of liquid crystal, such as a normal twisted nematic type liquid crystal or a guest-host type liquid crystal.

The dielectric layer 12 is made of glass frit, which is glass powder, made into a paste with an organic binder, and powder of one or more oxides selected from oxides of aluminum oxide, beryllium oxide, nickel oxide, and silicon oxide. This dielectric paste is applied to at least a portion of the surface of the glass substrate 2 where the conductive pattern 5 is to be formed and is baked. At this time, the glass substrate 2 is used as a glass frit.
If a material with a lower melting point is used, it can be fired at a temperature lower than the melting point of the glass substrate 2. As such a low melting point glass frit, lead-containing glass frit (e.g. EVA Pb0-Bz03-S
iOz) (7) Glass frit may be used, and the composition of a typical example thereof is shown below.

(The values are weight percentages) The softening point of the glass frit with composition (■) in the table above is 450℃, and the softening point of the glass frit with composition (2) is 530℃. Similarly, increasing the content of lead oxide (pbo) lowers the softening point.

As the organic binder, a mixture of biolein or terpineol oil, a thickener such as ethyl cellulose, and a dispersant such as rosin or linseed oil is used.

The dielectric layer 12 fired in this manner at a low temperature of, for example, about 500° C. is such that the organic binder vaporizes and evaporates during firing, the glass frit melts, and the oxide particles are dispersed and solidified in the glass frit. state.

The thickness of the dielectric layer 12 at this time is, for example, about 3 to 10 p.

Note that the linear expansion coefficient of the dielectric paste is the same as that of the glass substrate 2.
If an additive such as zircon or cordierite is added that has a linear expansion coefficient equal to Since the shrinkage is performed, the adhesive state between the glass substrate 2 and the dielectric layer 12 is maintained more reliably.

The conductor pattern 5 is made by dispersing conductive fine particles such as silver fine particles or silver and palladium fine particles and the above-mentioned low melting point glass frit in an organic binder, and adding a thickener 1 and a dispersing agent to form a paste. It is formed by coating the dielectric layer 12 on the dielectric layer 12 by a method such as screen printing, and firing it at a temperature below the melting point of the glass substrate 2. The thickness of this conductor pattern 5 is also formed to be, for example, about 3 to 10 Bm. Note that zircon is also included in the conductive paste.

If an additive such as cordierite is added to an extent that does not significantly reduce the conductivity, the adhesion between the conductive pattern 5 and the dielectric layer 12 can be maintained more reliably.

As shown in FIG. 1, the end of the conductor pattern 5 thus formed is overlapped with the end of the electrode 1 at the position of the sealant 3 of the liquid crystal cell and pressed with the sealant 3. In this case, the connection between the conductor pattern 5 and the electrode 1 can be made more reliably.

The protective film 11 is formed by applying and heating an organic material such as polyimide to a portion of the conductor pattern 5 that is outside the soldering part. This protective coating 11 also functions as a solder dam to prevent the solder 9 from flowing out.

Thereafter, external components such as the IC chip 8 are soldered with solder 9 as in the conventional COG, sealed with a sealing resin IO, and mounted on the glass substrate 2.

Note that if a flat package IC such as a flip chip is used as the IC chip 8, as shown in FIG.
The area occupied by the C chip 8 on the glass substrate 2 is reduced, which is advantageous for COG, which requires a fine circuit pattern.

[Function] In the glass substrate of the present invention, in the example of FIG.
The adhesion between the glass substrate 2 and the dielectric layer 12 is performed using the dielectric layer 12.
The adhesion is strengthened by the double bond of the glass bond between the glass lift inside and the glass substrate 2 and the oxide bond between the oxide in the dielectric layer 12 and the glass substrate 2. Further, the bond between the dielectric layer 12 and the conductor pattern 5 is the glass bond between the glass frit in the dielectric layer 12 and the glass frit in the conductor pattern 5, and the bond between the oxide in the dielectric layer 12 and the conductor pattern 5. The bond is strengthened by the double oxide bond with. Therefore, the bonding between the glass substrate 2 and the dielectric layer 12 and the dielectric layer 12 and the conductor pattern 5 of the present invention is achieved by double bonding of glass bonding and oxide bonding. The pattern 5 is firmly adhered onto the glass substrate 2.

This can also be experimentally verified by observing that the adhesive strength of the conductor pattern 5 varies depending on the amount of oxide (alumina in this example) in the dielectric layer I2, as shown in FIG. That is, when the alumina component is gradually increased in the dielectric layer 12, oxide bonds are added to the glass bonds, increasing the adhesive strength. Note that when the alumina component is increased beyond a certain amount, the adhesive strength decreases, but this is because the alumina component begins to concentrate on the surface of the dielectric layer 12 and the strength due to glass bonding decreases. Therefore, dielectric layer 12
The oxide component contained therein is desirably in a predetermined amount, and in the case of the two experimental examples, it is desirable to contain alumina in an amount of 3% to 20%, more preferably 6% to 14%.

Note that the surface roughness of the dielectric layer 12 also contributes to an increase in the adhesive strength between the glass substrate 2 and the conductor pattern 5. 6 to 8 show data showing examples of measuring the surface roughness of the dielectric layer 12, and the surface roughness increases as the content of oxide (alumina in this example) increases. That is, Figures 6 and 7
Figure, No. 8rXJ each contains 7% alumina.

These are measurement diagrams showing the surface roughness of the dielectric layer 12 containing 17% and 34% alumina, and as is clear from each diagram, the surface roughness of the dielectric M12 increases as the alumina content increases.

However, if the alumina content increases significantly,
As can be seen from the measurement diagram of a ceramic substrate with an alumina content of 96% in the figure, the degree of surface roughness actually decreases.

When the surface of the dielectric layer 12 has appropriate roughness, L
±、Glass substrate 2 so as to fill the concave portion of the 柁驱体层12
The conductive pattern 5 is bonded to the dielectric layer 12, and the mutual adhesion is strengthened by the so-called anchor effect. Therefore, a dielectric layer 12 in which a metal oxide such as alumina is dispersed in a glass frit is connected to a glass substrate 2 and a conductor pattern 5.
The interposition between the conductive pattern 5 and the glass substrate 2 has the effect of strengthening the adhesion of the conductive pattern 5 to the glass substrate 2 from this aspect as well.

[Example] A dielectric paste was applied to a thickness of 8 μl on the surface of a glass substrate other than the cell forming portion, on which TO was vapor-deposited on the surface of the cell forming portion of soda lime glass. The dielectric paste contains 70% by weight of a mixture of glass frit and zircon with a volume ratio of 2:1 of the composition (1) in the table above, and 20% by weight of a mixture containing 10% by weight of alumina powder added to this mixed powder. It is kneaded into a paste with a vehicle. The vehicle was 85% by weight pine olein in a solvent with 5% by weight ethylcellulose as a thickener and 10% by weight rosin as a dispersant.

In this way, the glass substrate with ITO2 applied to the surface of the cell part and dielectric paste applied to the other parts was heated to 480°C.
The dielectric paste was solidified by firing.

Next, 80% by weight of silver is mixed with 10% by weight of glass frit having the same composition as that used for the dielectric paste, and this mixed powder is mixed with 10% by weight of a vehicle having the same composition as that used for the dielectric paste. A conductive paste was made into a paste.

This conductive paste was applied to a thickness of 8 layers on the dielectric layer and the ends of the ITO using a screen printing method, and was fired at 480° C. to form a conductive pattern.

When the adhesive strength of this conductive pattern was measured, an adhesive strength of 2.6 kg was obtained, which was about 2.5 times that of a case where the conductive pattern was directly formed on a glass substrate.

Next, after forming a polyimide protective film on areas other than the soldered parts of the conductor pattern, another glass substrate on which ITO was vapor-deposited was placed to face the ITO surface of the above-mentioned glass substrate, and the peripheral area was covered with a sealant. A cell was sealed, a TN type liquid crystal was injected inside, external parts such as an IC chip were soldered to the conductive pattern, and deflection plates were provided on both outsides of the cell to produce a liquid crystal display device.

[Effects of the Invention] The glass substrate of the present invention has a dielectric layer interposed between the substrate surface and the conductor pattern to form the conductor pattern, so that the conductor pattern has strong adhesive strength on the surface of the glass substrate. A bonded glass substrate is obtained. Furthermore, even if the conductor pattern becomes a fine pattern, since the conductor pattern is a thick film, there will be no phenomena such as solder eating, resulting in excellent reliability.
Since there is no need to align the circuit pattern, the production yield is good, and since the conductor pattern can be formed by screen printing, the manufacturing cost can be reduced. Furthermore, when forming a liquid crystal display cell, etc., by forming the display electrode and the conductor pattern to overlap in the sealing material part of the cell, it is possible to form a liquid crystal display cell with high reliability in the connection part. .

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a liquid crystal display device formed using the glass substrate of the present invention, FIG. 2 is a sectional view showing an example of a connection state between a conventional liquid crystal display device and a flexible substrate, and FIG. 3 4 is a sectional view showing an example of COG, FIG. 4 is a graph showing an example of the adhesive strength of the conductor pattern of the glass substrate of the present invention, and FIGS. 5 to 8 are diagrams showing the surface condition of the dielectric layer. 1--one electrode, 2--11 glass substrate, 3-m-sealing material, 4-m=liquid crystal material, 5-m=conductor pattern, 8--
IC chip, 9--1 solder, 11-m-protective coating,
12-m-dielectric layer.

Claims (2)

[Claims] (1) In a glass substrate on which a thick conductor pattern is formed on at least one surface, an oxide of aluminum oxide, beryllium oxide, nickel oxide, or silicon oxide is formed between the surface of the glass substrate and the conductor pattern. 1. A glass substrate comprising a dielectric layer in which at least one kind of material is dispersed in a glass frit. (2) The glass substrate according to claim 1, wherein the conductor pattern is formed by dispersing at least silver in a glass frit.