JP2001039734A - Low melting point glass for formation of transparent insulating coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a low melting point glass such that not only a glass having high strain point but a soda lime silica glass having about 510 to 530 strain point can be used for a display panel substrate, that the low melting point glass does not cause devitirification or residual fine bubbles when the glass is baked or formed into a film near the strain point, and that the glass can be formed into a film without causing peeling of the film from the substrate or deformation of the substrate. SOLUTION: The low melting point glass is used to form a transparent insulating coating film on the pattern of transparent electrode lines and bus electrode lines arranged on the transparent substrate for a display panel. The components of the composition are, by wt.%, 1 to 10 of SiO2, 0 to 4 of Al2O3, 8 to 23 of B2O3, 3 to 10 of ZnO, 65 to 76 PbO, and 0 to 1 of oxides of the metals which form the bus electrodes. The glass has 400 to 450 deg.C softening point and 75-95×10-7/ deg.C coefficient of thermal expansion from normal temperature to 300 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a so-called low-melting glass having a low softening temperature, such as an indium-tin oxide (ITO) or an indium-tin oxide (ITO) disposed on a transparent substrate of various display panels, particularly a plasma display panel (PDP). For forming a transparent insulating film suitable for coating a transparent electrode wire pattern such as tin oxide (SnO ₂ ) and a bus electrode wire pattern such as metallic copper or metallic silver with a transparent and transparent glass coating. Related to low melting point glass.

[0002]

2. Description of the Related Art JP-A-49-110709 and JP-A-8-1196
No. 65 discloses a glass composition comprising a SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —ZnO—PbO-based component and suitable for forming a thick film in a display panel.

[0003] The former does not disclose in detail the thermophysical properties such as the softening point of glass. The latter has a different component composition range from the present invention, and aims at a glass having a lower coefficient of thermal expansion than soda-lime-silica glass as a PDP substrate.
It is a low-melting glass composition for coating a back substrate.

[0004]

Conventionally, an insulating film on a PDP substrate has been formed by applying a paste made of glass powder having a low melting point to the substrate and then baking it around 600 ° C. In the baking at around 600 ° C., the strain point (temperature corresponding to a viscosity of 10 ^14.5 poise) of the substrate needs to be around 600 ° C., and the strain point is lower by 40 to 50 ° C. or more than that. If there is, there is a problem that the deformation (expansion and shrinkage) of the substrate becomes large and a pattern shift occurs at the time of panel bonding.

In order to eliminate the above-mentioned adverse effects, a glass substrate having a strain point of about 600 ° C. or higher is usually used. However, it is a soda-lime-silica glass (strain point) which is mass-produced at low cost. (Approximately 510 to 530 ° C.) has a problem that the component composition is different and the production cost of the product itself rises.

According to the present invention, not only glass having a high strain point but also soda-lime-silica glass having a strain point of about 510 to 530 ° C. can be used as a substrate.
This enables film formation. During baking and film formation, it is necessary that there be no fine bubbles remaining, the coefficient of thermal expansion is close to that of the substrate, and no peeling of the film from the substrate, warping of the substrate, and undulation occurring. Needless to say.

[0007] Further, an electrode wire patterned on a substrate, particularly a bus electrode wire (especially copper) of copper, silver or the like, is formed of thermally softened glass when a transparent insulating film is formed thereon. Erosion of formed metal (diffusion of metal into glass),
Although a remarkable increase in the bus electrode wire resistance based on this is observed, according to the present invention, it can be suppressed as much as possible.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a low-melting glass for forming a transparent insulating film on an electrode line pattern disposed on a transparent substrate for a display panel, wherein the composition of the glass is wt%. And SiO ₂ 1-10, Al ₂ O ₃ 0-4, B ₂ O ₃ 8
~ 23, ZnO 3 ~ 10, PbO 65 ~ 76, oxide of metal forming bus electrode 0 ~ 1, containing glass softening point 400 ~ 450
℃, the coefficient of thermal expansion from room temperature to 300 ℃ is 75-95 × 10 ^-7 / ℃
Is a low melting glass for forming a transparent insulating film.

In the above, a strain point of 510 to 5
A soda-lime-silica glass of about 30 ° C. or a glass having a higher strain point than the soda-lime-silica glass is used.

Further, the glass temperature for baking on a transparent substrate is set at 500 to 550 ° C.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Cases in which each electrode line pattern is formed on a substrate and covered with a low-melting glass for forming an insulating film include liquid crystal display panels, electroluminescent panels, fluorescent display panels, electrochromic display panels, and light emitting diodes. Although there are a display panel and a PDP, any of the display panels is included in the present invention. PD below
The present invention will be described by showing an example of a front substrate at P.

[Front Substrate in PDP] As the transparent front substrate in the present invention, not only the above-mentioned glass having a high strain point but also a soda-lime-silica glass having a strain point of about 510 to 530 ° C. can be used.

A transparent electrode wire, usually indium-tin oxide (ITO), is provided on one side (inside of the panel) of the front substrate glass.
Alternatively, a tin oxide (SnO ₂ ) -based electrode wire is patterned. Further, since the transparent electrode wire alone has a high resistance value and the discharge performance is not good, a bus electrode wire made of a metal material is arranged on the transparent electrode wire. Although the bus electrode lines are opaque, the line width is thinner than the transparent electrode lines and is hardly visible from the outside.

The bus electrode wire is excellent in conductivity but has a low melting point, and when baking an insulating coating covering the same, copper and silver, particularly copper, whose components are easy to leach out, and copper and silver having a higher melting point than the insulating coating. For example, chromium which is difficult to react, for example, is arranged on the upper and lower sides, and it is appropriate to form a laminate like chromium / copper (silver) / chromium. Other conductive metals include gold and gold-
Silver alloy or the like can be adopted. The transparent electrode wire and the bus electrode wire may be formed into a film by an appropriate means such as a physical vapor deposition means (for example, a sputtering method) or a chemical vapor deposition means (for example, a normal pressure CVD method), and may be patterned by etching. it can.

A transparent insulating film made of low-melting glass is formed on the entire surface of one side of the substrate glass so as to cover the transparent electrode lines and the bus electrode lines. In this method, a paste containing glass powder having a low melting point is applied over the front substrate, the transparent electrode wires, and the bus electrode wires, and baked to form a film. The details will be described later.

On the front substrate of the PDP, a magnesia layer is provided on the transparent insulating film, which is a well-known technique for protecting the transparent insulating film during discharge by the magnesia layer. .

An address electrode, a back side insulating film (a low-melting glass film) covering the address electrode, and a fluorescent material are disposed on a rear substrate (glass) opposed to the front substrate glass. A partition wall of a ceramic material for partitioning is formed, the peripheral portions of the front substrate glass and the rear substrate glass are sealed with a sealing layer, and a rare gas is sealed in a space between the two substrate glasses, thereby completing the manufacture of the PDP.

In the manufacturing process of the front substrate, a transparent electrode line pattern (for example, ITO) and a bus electrode line pattern (for example, chromium / copper / chrome) are formed on the substrate glass by sputtering or the like, and then a transparent insulating film is formed. Forming and baking by screen printing etc., and further dissolving and removing the covering insulating film just above the drive circuit wiring portion of the transparent electrode wire and bus electrode wire with acid (for example, dilute nitric acid), exposing the drive circuit wiring portion and wiring. Complete by being able to.

[0019] In the film formation of [transparent insulating film-forming low-melting glass] low-melting glass, the viscosity of suitable glass for burning the substrate is 10 ^2.5 poise of about to 10 ³ poise order less than the above range, The fluidity of the low-melting glass increases, and the leaching of components from the transparent electrode wire and the bus electrode wire becomes remarkable, and their conductive performance is easily impaired. Occurs. On the other hand, if the ratio exceeds the above range, the bubbles of the glass are apt to be insufficient, resulting in turbidity.

The strain point, that is, the temperature at which the glass viscosity is equal to 10 ^14.5 poise (in the case of a substrate glass, it is difficult to be deformed even if held at this viscosity / temperature for several tens of minutes. When a coating with a low melting point glass is formed on a soda-lime-silica glass substrate having a low tendency (causing a tendency), it is necessary to bake around the above-mentioned strain point (more preferably below the strain point), The temperature corresponding to the glass viscosity in the above range is preferably from 500 to 550 ° C. 550
If the temperature exceeds ℃, the strain point of the substrate glass is remarkably exceeded, so that the substrate glass is deformed and a pattern shift easily occurs. 500 ℃
If it is less than 10, it is necessary to make the low-melting glass excessive in PbO, in which case the durability and stability of the coating, for example, the long-term stability to electric discharge, are likely to be impaired. Of course, even when using a glass having a higher strain point than the soda-lime-silica-based glass as the substrate, the baking may be performed at the temperature, 500 to 550 ° C., that is, baking to soda-lime-silica-based glass is possible. If so, there is no problem in baking to a glass having a higher strain point.

Further, in order to enable baking in the above viscosity and temperature range, the softening point of the low melting point glass (viscosity of 10 ^7.6
Temperature at which poise) intended to be 400 to 450 ° C., if the range of the softening point, the temperature corresponding to 10 ^2.5 poise to 10 ³ poise order can be 500-550 ° C.. The softening point is called a specific point together with the strain point and the like, and is a point (temperature) that is easy to measure and serves as an index in defining the temperature-viscosity at the time of baking.

Soda-lime-silica based glass on front substrate
And other glasses have thermal expansion coefficients (room temperature to 300 ° C)
Is approximately 70 to 90 orders (× 10^-7/ ° C)
Therefore, the same thermal expansion is obtained in the low melting point glass of the present invention.
Tension coefficient, i.e. 75-95 × 10 ^-7/ ° C.
If it is less than or beyond the range, baking to cooling
Warping or cracking the substrate glass,
The coating itself cracks.

The component composition of the low-melting glass is in the following range. SiO ₂ is intended to be contained within a range in 110 wt.% Glass, glass-forming becomes unstable in less than 1 wt%, prone to devitrification. If it exceeds 10% by weight, the fluidity deteriorates, and it becomes difficult to remove bubbles during baking after coating the film. Preferably 2
The range is 5% by weight.

B ₂ O ₃ is a glass-forming component similar to SiO ₂ and suppresses an increase in the coefficient of thermal expansion and imparts a suitable fluidity to the glass, and is contained in the glass in the range of 8 to 23 wt%. Let it. If less than 8 wt%, glass formation is unstable, and 23
If the amount exceeds wt%, the fluidity deteriorates and it becomes difficult to remove bubbles during baking after coating the film. Preferably, it is in the range of 9 to 21% by weight.

Al ₂ O ₃ is appropriately contained for stabilizing the glass and adjusting the thermal expansion coefficient. However, if it exceeds 4% by weight, the viscosity of the glass increases, making it difficult to remove bubbles and increasing the acid resistance, making it difficult to dissolve and remove with dilute nitric acid.

ZnO is used for imparting fluidity to the glass and for controlling the coefficient of thermal expansion.
To 10 wt%. If the content is less than 3 wt%, the effect cannot be exerted. If the content exceeds 10 wt%, the glass becomes unstable and tends to crystallize.

PbO is a component necessary for lowering the melting point of glass, that is, lowering the softening temperature and imparting fluidity.
It is contained in the range of 76 wt%. If the content is less than 65 wt%, the effect cannot be sufficiently exhibited, and the bubble removal at the time of firing becomes insufficient. If it exceeds 76 wt%, the thermal expansion coefficient becomes excessive and the durability stability of the glass is impaired.

One or more oxides of other divalent metal components such as MgO, CaO, SrO, and BaO can be contained in an amount of 3 wt% or less for the purpose of adjusting viscosity and adjusting thermal expansion coefficient. . However, if it exceeds 3 wt%, the stability of glass formation is impaired, and devitrification tends to occur.

Oxides of alkali metal components such as Na ₂ O and K ₂ O can be mixed up to 1 wt% as impurities,
If the amount exceeds wt%, the above-mentioned components may be volatilized into a rare gas space during discharge during operation of the PDP, thereby shortening the panel life.

It is desirable to further include the following metal oxide for forming a bus electrode. That is, when baking low-melting glass, the components (especially Cu) of the bus electrode wire composed of highly conductive components such as Cu and Ag are leached and diffused into the low-melting glass, thereby lowering the conductivity of the electrode wire. May come. Of course, as described above, a high melting point, non-reactive metal (eg,
A technique for protecting electrode wires is known, in which Cr) is arranged vertically and laminated as Cr / Cu (Ag) / Cr, but is exposed to heat of 500 ° C or more and comes into contact with fluidized glass. Therefore, it is impossible to prevent erosion and deterioration of the conductive performance. In this case, a metal oxide for forming a bus electrode line (eg, CuO, Ag ₂ O)
Is contained in the glass in advance, so that the leaching and diffusion of the above-mentioned components into the glass, and thereby a decrease in the conductive performance of the electrode wire can be suppressed as much as possible. Content is 1
wt% or less, preferably in the range of 0.1 to 1 wt%.
If it exceeds t%, coloring of the glass becomes remarkable.

In the case of Cu0, for example, even if the content is within the above range, the glass is slightly colored blue by Cu ⁺⁺ ions, but it is convenient because it becomes easy to see through blue light emission with low luminous efficiency in PDP. .

In order to suppress the leaching and diffusion of the components (ITO or SnO _2, etc.) of the transparent electrode wire into the low melting glass at the time of baking the low melting glass, a reduction in the conductive performance of the electrode wire is required in advance. It is known that a transparent electrode wire component oxide (for example, In ₂ O ₃ , SnO ₂ ) is contained in the low-melting glass. However, in baking at 550 ° C. or lower, the decrease in the conductive performance is not significant, Even if it is intentionally contained, a content of about 2 wt% or less is sufficient.

The transparent insulating film made of the low-melting-point glass is prepared by applying a mixture of a low-melting-point glass powder and paste oil, which have been manufactured and sized in advance, onto the front substrate, the transparent electrode lines, and the bus electrode lines by screen printing or the like. It is applied and baked at about 500 to 550 ° C to form a thick film with a thickness of about 30 µm. The thickness of about 30 μm is necessary and sufficient for exhibiting display performance by gas discharge and long-term stability of withstand voltage.

Conventionally, a transparent insulating film is formed in two layers, and has a relatively high softening point on the side in contact with the substrate. When the low-melting glass is baked, the viscosity of the glass is slightly high. The low melting point glass which is difficult to leach into, has a lower softening point thereon, and when baked, a low melting point glass which is easy to remove bubbles due to low viscosity of the glass and easily forms a film is arranged. It is not necessary to particularly form two layers, and the labor of the film-forming treatment can be saved by that much.

[0035]

The present invention will be described below by way of specific examples.

[Preparation of low melting glass mixed paste] SiO ₂
Fine silica sand as a source, boric acid as a B ₂ O ₃ source, aluminum hydroxide as an Al ₂ O ₃ source, zinc white as a ZnO source,
Lead oxide is used as a PbO source, cupric oxide is used as a CuO source for the bus electrode wire Cu, and these are mixed as much as possible to have a desired low melting glass composition, and then put into a platinum crucible,
The glass was heated and melted at 1,000 to 1,100 ° C. for 1 to 2 hours in an electric heating furnace to obtain Examples and Comparative Examples shown in Table 1. A part of the glass was poured into a mold, made into a block, and used for measuring thermophysical properties (thermal expansion coefficient, softening point). The remaining glass is flaked by a quenching twin roll forming machine, and has an average particle size of 2 by a crusher.
４4 μm, and the maximum particle size was less than 15 μm.

Next, ethyl cellulose as a binder and the above-mentioned glass powder were mixed with a paste oil consisting of α-terpineol and butyl carbitol acetate, and the viscosity was adjusted.
A paste suitable for screen printing of about 300 ± 50 poise was prepared.

[Formation of transparent insulating film]
Soda-lime based substrate glass of size 150mm □ (strain point 520
℃, thermal expansion coefficient 90 × 10 ^-7 / ℃)
The paste was applied by screen printing using a # 250 aperture screen with consideration given to a thickness of 30 μm.
Then, after drying at 140 ° C. for 15 minutes, baking was performed at 530 ° C. for 40 minutes to form a clear thick film. The obtained sample was subjected to the following tests.

[Measurement of Coefficient of Thermal Expansion] The glass block for measuring thermophysical properties was cut and polished to a predetermined size to prepare a sample for measuring the coefficient of thermal expansion, which was set in a thermodilatometer and set at a rate of 5 ° C./min. Measure the elongation by raising the temperature at, record the temperature, and normal temperature (room temperature)
The average coefficient of thermal expansion at 300300 ° C. was calculated.

[Measurement of Softening Point] A glass from a glass block is heated by a conventional method to produce a glass beam having a predetermined thickness and dimensions, set in a Littleton viscometer, and heated.
The temperature at which the viscosity coefficient η reached ^107.6 , that is, the softening point, was measured.

[Presence or absence of devitrification, presence or absence of residual bubbles] The transparent insulating film was observed under a magnifying glass for the presence or absence of devitrification and the presence or absence of residual bubbles (good or bad bubble removal). If there is devitrification, and if there are no fine bubbles,
Those with fine bubbles were evaluated as having.

[Reference: Measurement of Degree of Erosion of Transparent Electrode Wire] An ITO thin film was formed on a glass substrate by a sputtering method, and a transparent insulating film was formed by the above-described method and procedure. Next, after dissolving and removing the transparent insulating film in a 7% nitric acid solution, the electric resistance value of the ITO thin film was measured by the four probe method. In addition, the case where the increase in the electric resistance value was 3 times or less the value before the formation of the transparent insulating film was evaluated as acceptable, and the case where the increase exceeded 3 times was evaluated as unacceptable.

[Reference: Measurement of Degree of Erosion of Bus Electrode Wire] A metal copper film having a thickness of 1 μm was formed in a stripe shape on a glass substrate by a sputtering method.
After forming the transparent insulating film by the procedure, the electric resistance value of the metal film was measured with a tester. In addition, the case where the increase in the electric resistance value was twice or less the value before the formation of the copper film was evaluated as acceptable.

[Results] Table 1 shows the composition of the low-melting glass for forming a transparent insulating film and the results of various tests. As is clear from the table, in Examples 1 to 5, the composition and various characteristics are within the scope of the present invention. In Example 5, erosion of the bus electrode wire was observed because the CuO component involved in the bus electrode wire was not included, but the soda lime silica having a low strain point of about 510 to 530 ° C., which is the purpose of the present invention, was used. It is possible to adopt a system glass as a substrate, which is within the scope of the present invention. In any of the embodiments, it is particularly suitable as a low-melting glass for an insulating film of a PDP panel substrate.

On the other hand, in Comparative Examples 2 and 4, the PbO component was excessive, the coefficient of thermal expansion was high, and the durability stability of the glass was considered to be insufficient. In Comparative Examples 1 and 3,
The PbO component is too small, the coefficient of thermal expansion is low, and the softening temperature is too high, and the bubble removal is insufficient. Although not shown, in Comparative Examples 2 and 3, there is a remarkable difference in the thermal expansion coefficient between the low-melting glass and the substrate glass. In Comparative Example 2, deformation of the substrate was visually observed, and Comparative Example 3 was sintered (fused). ) Due to insufficiency, partial cracking of the coating and peeling from the substrate were observed, and the coloring was remarkable due to excessive CuO component.

[0046]

[Table 1]

[0047]

According to the present invention, not only glass having a high strain point but also soda-lime-silica glass having a strain point of about 510 to 530 ° C. can be used as a substrate. During film formation, there is no devitrification or residual fine bubbles,
Further, the film can be formed without peeling the film from the substrate or causing deformation of the substrate.

Continued on the front page F-term (reference) 4G062 AA08 AA09 AA15 BB04 DA03 DB01 DB02 DB03 DC03 DC04 DD01 DE03 DF06 DF07 EA01 EA10 EB01 EC01 ED01 EE01 EF01 EG01 FA01 FA10 FB01 FC01 FD01 FE01 FF01 GC01 F0101 HH01 HH03 HH04 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM07 NN26 NN30 NN32 PP13 PP14 PP16 5C040 FA01 GA09 GD07 KB10 KB04 KB04 KB04

Claims (3)

[Claims] 1. A low-melting glass for forming a transparent insulating film on a pattern of a transparent electrode line and a bus electrode line arranged on a transparent substrate for a display panel, wherein the composition of the glass is wt.
% _{In, SiO 2 1~10, Al 2 O} 3 0~4, B 2 O 3 8~23, Z
nO 3 to 10, PbO 65 to 76, includes a range of oxide 0-1 of bus electrodes formed of metal, glass softening point of 400 to 450 ° C., the thermal expansion coefficient of up to normal temperature to 300 ° C. is 75 to 95 × 10 ^{- A} low-melting glass for forming a transparent insulating film having a temperature of ⁷ / ° C. 2. The transparent insulation according to claim 1, wherein soda-lime-silica glass having a strain point of about 510 to 530 ° C. or glass having a higher strain point than said soda-lime-silica glass is used as the transparent substrate. Low-melting glass for forming a functional film. 3. The glass temperature for baking on a transparent substrate is
The low melting glass for forming a transparent insulating film according to claim 1, wherein the temperature is 500 to 550 ° C. 4.