JPH10255669A - Glass substrate for flat panel display and plasma display device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass substrate suppressing coloring by silver even when a silver electrode is formed on the surface by polishing the face molded into a plate shape by the float method and formed with a metal electrode, and removing a reducing heterogeneous layer formed on the surface. SOLUTION: A surface layer having an average thickness of 1-1000μm is preferably machined and removed by polishing. The composition is preferably set to SiO2 : 50-65wt.%, Al2 O3 : 1-15wt.%, RO: 10-27wt.%, ZrO2 : 1-9wt.%, Na2 O: 2-12wt.%, K2 O: 2-13wt.%, and TiO2 : 0-5wt.%. When a metal electrode is formed on the surface and a metal component is diffused on the glass surface by heat treatment in the post-process, no reduction occurs, and coloring can be prevented. Silver which is easily reduced and made colloidal can be used for the constituting material of the metal electrode, and the electrode can be formed by inexpensive screen printing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass substrate for a flat panel display formed by a float method and a plasma display device using the glass substrate as a front glass substrate.

[0002]

2. Description of the Related Art Conventionally, a method for forming a glass substrate includes:
Float method, roll-out method, fusion method and the like are known.

[0003] The float method is a method in which molten glass is floated on molten metal tin and formed into a plate shape. Large-area glass substrates can be stably produced at low cost and can be mass-produced. Used.

A glass substrate used for a plasma display device has a large area, for example, 40 inches, and is considered to be most suitable for production by a float method.

[0005]

In manufacturing a plasma display device, a front glass substrate and a rear glass substrate are first prepared, and a metal paste or an insulating paste is applied and baked on these glass substrates to form a chromium (glass) substrate. Cr), aluminum (Al), nickel (Ni),
An electrode such as an ITO film or a Nesa film, a dielectric layer, a partition, and a phosphor are formed. Then, the front glass substrate and the rear glass substrate are sealed with a low-melting sealing glass, and a gas mixture of xenon and neon of a main discharge gas is sealed therein to hermetically seal.

Generally, chromium,
Aluminum and nickel are used, but expensive metallization methods such as vapor deposition and sputtering are required to form these metal films, so it has been attempted to use silver electrodes that can be formed by inexpensive screen printing. Have been.

However, when a silver (Ag) electrode is formed on a glass substrate formed by the float method, there is a problem that silver reacts on the surface of the glass substrate to cause color development. In addition, this color is likely to appear not only in the electrode part but also in the peripheral part thereof. When the color of such a silver electrode and its peripheral substrate appears on the front glass substrate, the display performance (transparency, color balance) is impaired. .

The present invention has been made in view of the above circumstances, and a glass substrate for a flat panel display, which is formed by a float method and suppresses color development by silver even when a silver electrode is formed on the surface thereof, It is an object of the present invention to provide a plasma display device using as a front glass substrate.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted various experiments to achieve the above object, and as a result, when a silver electrode is formed on the surface of a glass substrate formed by a float method, a color develops. It has been found that this is caused by a reducing foreign layer formed on the surface of the glass substrate.

That is, when the glass substrate is formed by the float method, the upper surface of the glass is exposed to a reducing atmosphere in the forming step, and the lower surface of the glass comes into contact with the metal tin bath. A foreign layer is formed. The thickness of the heterogeneous layer varies in the range of about 0.1 to 1000 μm depending on the glass composition and molding conditions.

When a silver paste is applied to the glass substrate on which such a surface heterogeneous layer is formed and subjected to heat treatment, the silver component diffuses into the glass surface layer and is reduced to form a metal colloid, thereby causing color formation. Based on this finding, the present inventors have proposed the present invention.

That is, the glass substrate for a flat panel display of the present invention is formed into a plate shape by a float method, and the surface on which the metal electrodes are formed is polished, so that the reducing foreign layer formed on the surface is reduced. It is characterized by being removed.

[0013] The glass substrate for a flat panel display of the present invention is characterized in that the surface opposite to the surface on which the metal electrode is formed is unpolished, and the metal electrode is a silver electrode. 1 in average thickness by polishing
It is characterized in that a surface layer of up to 1000 μm is processed and removed.

Furthermore a flat panel glass substrate for a display of the present invention is characterized by use in a plasma display, also in weight percent, SiO ₂ 50 to
_{65%, Al 2 O 3 1~15} %, RO 10~27
_{%, ZrO 2 1~9%, Na} 2 O 2~12%, K 2
It is characterized by having a composition of _{2 to} 13% of O and 0 to 5% of TiO2.

Next, the plasma display device of the present invention has a structure in which a metal electrode, a dielectric layer, a partition, and a phosphor are formed between a front glass substrate and a rear glass substrate which are opposed to each other with a predetermined space therebetween. In the plasma display device, the front glass substrate is formed by a float method,
The method is characterized in that the reductive foreign layer formed on the inner surface is removed by polishing the inner surface.

The plasma display device according to the present invention is characterized in that the outer surface of the front glass substrate is unpolished, and the metal electrode is a silver electrode.
The front glass substrate has an average thickness of 1 to 10 by polishing.
It is characterized in that a surface layer of 00 μm is processed and removed.

Further, in the plasma display device according to the present invention, the front glass has a SiO ₂ content of 50 to ₆ % by weight.
5%, Al ₂ O ₃ 1-15%, RO 10-27%,
ZrO ₂ 1-9%, Na ₂ O 2-12%, K ₂ O
It is characterized by having a composition of _{2 to} 13% and TiO2 of 0 to 5%.

[0018]

The glass substrate for a flat panel display of the present invention is formed by the float method, but the surface on which the metal electrode is formed is polished to remove the reducible foreign layer formed on the surface. ing. Therefore, a metal electrode is formed on the surface in a later step, and even if the metal component is diffused to the glass surface by the heat treatment, the metal component is not reduced, and color formation can be prevented. Therefore, silver that is reduced and easily converted to colloid can be used as a constituent material of the metal electrode, and the electrode can be formed by inexpensive screen printing.

In the present invention, when the polishing loss is too small, the reducing foreign layer formed on the surface of the glass substrate cannot be sufficiently removed. Conversely, when the polishing loss is too large, the polishing cost becomes extremely high. It is not preferable because it rises. Further, it is technically difficult to polish the film with an extremely small thickness, and the cost is rather increased. Therefore, the polishing loss is 1 to 1 in average thickness.
The thickness is adjusted in the range of 000 μm, preferably 10 to 100 μm, according to the thickness of the reducing foreign layer.

Conventionally, surface polishing has been widely performed for the purpose of improving the flatness of the surface of a glass substrate after forming. However, in the case of a glass substrate formed by a float forming method, a relatively good flatness is obtained. Are not usually polished. Even if it is polished, it is several μm to several tens of μ.
m, and when the thickness of the reducing foreign layer as described above is large, the foreign layer may remain.

Further, in the present invention, the surface opposite to the surface on which the metal electrode is formed is preferably kept unpolished in consideration of the polishing cost.

The reasons for limiting the composition range of the glass substrate of the present invention as described above are as follows.

SiO ₂ is a glass network former, and its content is preferably 50 to 65%. 5
If it is less than 0%, the strain point of the glass decreases, the heat shrinkage during the heat treatment of the glass substrate increases, and the displacement of the pattern occurs, which is not preferable. On the other hand, if it is more than 65%, the coefficient of thermal expansion becomes small, and it becomes inconsistent with that of the insulating paste or the sealing frit, so that warpage is likely to occur.

Al ₂ O ₃ is a component for increasing the strain point of glass, and its content is preferably 1 to 15%. If it is less than 1%, the above effect cannot be obtained, while if it is more than 15%, the coefficient of thermal expansion becomes too small.

RO (MgO, CaO, SrO, BaO)
Has an effect of facilitating melting of glass and adjusting a thermal expansion coefficient, and its content is 10 to 27%. 1
If it is less than 0%, the strain point becomes too low, while 27%
If the amount is larger, the glass tends to be devitrified, and the molding becomes difficult.

ZrO ₂ is a component for improving the chemical durability of glass, and its content is 1 to 9%. 1%
If the amount is less than the above, the above effects cannot be obtained. On the other hand, if the amount is more than 9%, the coefficient of thermal expansion becomes too small, and a devitrified substance is easily generated at the time of melting of the glass, so that molding becomes difficult.

Na ₂ O is a component for adjusting the thermal expansion coefficient, and its content is 2 to 12%. If it is less than 2%, the coefficient of thermal expansion becomes too small, while 12%
If it is larger, the strain point becomes too low, which is not preferable.

K ₂ O is also a component for adjusting the coefficient of thermal expansion, and its content is 2 to 13%. If it is less than 2%, the coefficient of thermal expansion becomes too small, while if it is more than 13%, the strain point becomes too low.

TiO ₂ is a component for preventing glass from being colored by ultraviolet rays, and its content is 0 to 5%. In the case of a plasma display, ultraviolet rays are generated at the time of discharge. However, if the glass substrate is colored with the ultraviolet rays, the display screen gradually becomes difficult to see during use for a long period of time. Therefore, it is desirable to add TiO ₂ . However, if TiO ₂ is more than 5%, the glass is apt to devitrify,
Molding becomes difficult.

In the present invention, in addition to the above components, Li ₂ O for adjusting the coefficient of thermal expansion, and components such as Cl and SO ₃ as defoaming agents are used within a range not to impair the glass properties. It can also be contained.

In the plasma display device of the present invention, although not as much as the front glass substrate, there is a possibility that color may appear on the rear glass substrate. It is desirable to use a glass substrate which is polished.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments.

Table 1 shows the composition and characteristics of the glass substrate for a flat panel display of the present invention.

[0034]

[Table 1]

The glass substrates shown in Table 1 were prepared by mixing raw materials so as to have the glass compositions shown in the table, and then formed into a plate having a thickness of 3 mm by a float method.
It was produced by cutting into a size of mm.

These glass substrates have a low heat shrinkage due to a strain point of 571 ° C. or higher, are difficult to devitrify because a liquidus temperature is 1050 ° C. or lower, and have a coefficient of thermal expansion of 83 to 89 × 1.
Since it was 0 ^-7 / ° C, it matched that of the insulating paste and sealing frit, and was suitable as a glass substrate for a plasma display. Also, when the volume resistivity of this type of glass substrate is low, the alkali component in the glass reacts with the thin film electrode, and the electric resistance of the electrode material tends to change, which is not preferable. Rate is 10
^It was as high as ^11.4 or more, and the degree of coloring by ultraviolet rays was also small.

The strain points in the table are based on ASTM C336-
The liquidus temperature was measured based on the method of No. 71, and the liquidus temperature was determined by putting glass powder having a particle size of 297 to 500 μm in a platinum boat and observing devitrification after holding the glass powder in a temperature gradient furnace for 48 hours.

The coefficient of thermal expansion is obtained by measuring the average coefficient of thermal expansion at 30 to 380 ° C. with a dilatometer, and the volume resistivity is determined by ASTM C657-78.
The value at 150 ° C. was measured based on.

Further, the degree of coloring by ultraviolet rays was measured by irradiating the glass substrate with a 400 W mercury lamp for 48 hours, and measuring the ultraviolet transmittance at a wavelength of 400 nm before and after the irradiation.
The difference in transmittance is shown. The larger this value is, the more easily it is colored by ultraviolet rays.

Next, with respect to each of the glass substrates in Table 1, only one surface thereof was polished so that the polishing loss was as shown in the table.

Thereafter, a silver paste was printed on the polished surface of the glass substrate by screen printing and heat-treated at 600 ° C. for 1 hour to form an electrode film.

No color development was observed in any of the samples in which the surface of each glass substrate had been processed and removed by polishing at an average thickness of 10 μm or more.
In each case, the color developed very slightly. In addition, color development was clearly observed in all of the samples that had been processed and removed by 0.1 μm, and in all of the unpolished samples, the color developed strongly.

From these data, it is estimated that the thickness of the reducing heterogeneous layer formed on the surface of these glass substrates is 1 μm or more and less than 10 μm in average thickness.

The sample No. in the table was used. Two samples prepared by polishing 10 μm on one side of the glass substrate of No. 2 were prepared, and a silver electrode, a dielectric layer, a partition, a phosphor, etc. were formed by applying and baking a silver paste or an insulating paste on these glass substrates. did. Next, these glass substrates were sealed with a low-melting-point sealing glass, and a mixed gas of xenon and neon as a main discharge gas was sealed therein and hermetically sealed to produce a plasma display device.

When the plasma display device thus manufactured was operated, an image having excellent transparency and color balance was obtained.

The above polishing was carried out using an Oscar type polishing machine using cerium oxide as a polishing agent. The degree of color development is determined by the reflectance curve (700 to
400 nm), the degree of color development using the C light source is represented by chromaticity coordinates. In the case where no color was formed on the sample having one side polished to 1000 μm, the color difference between the sample and each comparative sample was less than 0.1 and no color formation was observed, and the coordinate difference was 0.1 to 0.2.極 indicates that the color slightly developed. Further, those which clearly developed a color with a coordinate difference of 0.2 to 0.5 were indicated by Δ, and those which strongly developed a color with a coordinate difference larger than 0.5 were indicated by X.

[0047]

As described above, the glass substrate for a flat panel display of the present invention is formed by a float method, and even if a silver electrode is formed on the surface, there is no reducing foreign layer on the electrode forming surface. No color development due to the silver component occurs.

Further, the plasma display device of the present invention using this glass substrate as a front glass substrate has an image excellent in transparency and color balance.

Claims (11)

[Claims] 1. A flat plate, which is formed into a plate shape by a float method and a surface on which a metal electrode is formed is polished to remove a reducing foreign layer formed on the surface. Glass substrate for panel display. 2. The glass substrate for a flat panel display according to claim 1, wherein the surface opposite to the surface on which the metal electrodes are formed is unpolished. 3. The glass substrate for a flat panel display according to claim 1, wherein the metal electrode is a silver electrode. 4. An average thickness of 1 to 1000 by polishing.
4. The glass substrate for a flat panel display according to claim 1, wherein a surface layer of μm is processed and removed. 5. The glass substrate for a flat panel display according to claim 1, which is used for a plasma display. 6. SiO ₂ 50-65 by weight percentage.
_{%, Al 2 O 3 1~15%} , RO 10~27%, Z
rO ₂ 1-9%, Na ₂ O 2-12%, K ₂ O 2
To 13%, claims a composition of TiO ₂ 0 to 5% 5
The glass substrate for a flat panel display according to the above. 7. A plasma display apparatus comprising a metal electrode, a dielectric layer, a partition, and a phosphor formed between a front glass substrate and a rear glass substrate facing each other with a predetermined distance therebetween. Is formed by a float method, and an inner surface thereof is polished to remove a reducing foreign layer formed on the inner surface. 8. The plasma display device according to claim 6, wherein the outer surface of the front glass substrate is not polished. 9. The plasma display device according to claim 6, wherein the metal electrode is a silver electrode. 10. The plasma display device according to claim 6, wherein the front glass substrate has a surface layer having an average thickness of 1 to 1000 μm processed and removed by polishing. 11. The method according to claim 11, wherein the front glass substrate has a weight percentage of S.
_{iO 2 50~65%, Al 2 O} 3 1~15%, RO
10-27%, ZrO ₂ 1-9%, Na ₂ O 2
_{12%, K 2 O 2~13%} , plasma display device according to claim 6, 7, 8 and 9, wherein the having the composition TiO ₂ 0 to 5%.