JPH11246233A - Low melting point glass for formation of transparent insulating coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low melting point glass suitable to cover a transparent electrode line pattern such as an indium oxide-tin or tin oxide film arranged on a transparent substrate and to suppress corrosion of the electrode lines. SOLUTION: The low melting point glass is used to form a transparent insulating coating film on a transparent electrode line pattern formed on a display panel substrate. The glass has the compsn. of, by wt.%, 2 to 6 SiO2 , 20 to 40 B2 O3 , 0 to 5 Al2 O3 , 20 to 25 ZnO, 10 to 40 PbO, and 5 to 35 of one or more kinds selected from CaO, MgO, SiO and BaO. The glass has <=590 deg.C softening point and 70×10<-7> to 90×10<-7> coefft. of thermal expansion in the range from normal temp. to 300 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called low-melting glass having a low softening temperature, comprising a liquid crystal display panel, an electroluminescence panel, a fluorescent display panel, an electrochromic display panel, a light emitting diode display panel, and the like.
Transparent electrode wire pattern arranged on the transparent substrate of the gas discharge type display panel or the like, for example, indium oxide - tin (indium oxide, a conductive material mainly composed of tin oxide: IT0) or tin oxide (SnO ₂₎ based film The present invention relates to a low-melting glass for forming a transparent insulating film, which is suitable for coating with a glass film rich in transparency and transparency.

[0002]

The BACKGROUND OF problem to be solved that] JP 49-110709 _{discloses, SiO 2 1~20wt%, B 2} O 3 5~25wt%, Al 2 O
_{31 to} 8 wt%, ZnO _{3 to} 15 wt%, PbO 60 to 80 wt%, insulating glass for covering electrode wires in a display panel using gas discharge, insulation for display panel that can emit light effectively at low voltage Glass is disclosed.

[0003] JP-A-8-119665 discloses that SiO _{2
17wt%, B 2 O 3 8~15wt} %, Al 2 O 3 0.1 ~5wt%, ZnO
Suitable for forming a thick film on a PDP substrate composed of 5 to 12 wt% and PbO of 60 to 70 wt% and having a coefficient of thermal expansion (room temperature to 300 ° C) of 62 to 76 × 10 ^-7 / ° C. Disclosed is a glass composition for a PDP in which a substrate is hardly warped or cracked when a thick film is formed by firing.

In these prior arts, when the low-melting glass mixed paste is applied to a substrate on which an electrode wire pattern is provided and baked, the electric resistance of the electrode wire increases due to mutual leaching of components at the interface between the electrode wire and the glass. There is a problem that it is easy to do. In addition, the dielectric constant is generally high. For example, in a gas discharge type display panel, there is a disadvantage that power consumption is increased during driving. The prior art discloses an insulating low-melting glass suitable for light emission and a low-melting glass matched to the thermal expansion of a substrate, and does not show any of these problems.

The present invention solves the above-mentioned disadvantages such as erosion of an electrode wire and an increase in electric resistance in a conventionally known example, and forms a transparent insulating film having characteristics suitable for application to a display panel substrate. A low melting glass is provided.

[0006]

SUMMARY OF THE INVENTION The present invention provides a low-melting glass for forming a transparent insulating film on a transparent electrode line pattern disposed on a display panel substrate, wherein the glass has a composition of wt. % _{in, SiO 2 2~6, B 2 O} 3 20~40, Al 2 O 3 0
-5, ZnO 20-25, PbO 10-40, one or more selected from CaO, MgO, SrO, BaO in the range of 5-35, and the softening point is 590 ° C or less, room temperature-300. thermal expansion coefficient of up to ° C. is a transparent insulating low-melting glass for the film formed in the range of 70 to 90 × 10 ^{over 7} / ° C..

Further, in the above, it is preferable that the dielectric constant is 9 or less. In particular, the low-melting glass is a low-melting glass for forming a transparent insulating glass film covering a transparent electrode wire pattern, and further has a softening point of 480 ° C. stacked thereon.
It may be formed as a base layer of a second transparent insulating glass coating made of the following low-melting glass.

[0008]

DETAILED DESCRIPTION OF THE INVENTION In the low-melting glass for insulating film formation, a known example of mainly SiO ₂ -B ₂ O ₃ -PbO -ZnO system is not a little, but they comprises large amounts of PbO component, The
The PbO component is an important component in forming the low-melting glass, but if it is contained in a large amount, the transparent electrode wire during baking of the low-melting glass, that is, tin oxide-indium oxide, tin oxide, etc. Of the transparent electrode wire component, and also the transparent electrode wire component also leaks to the glass side to increase the resistance of the electrode wire (decrease in conductivity). Leaching of electrode wire components,
Diffusion can be suppressed, and an increase in resistance of the electrode wire can be suppressed as much as possible.

The case in which the transparent electrode line pattern is formed on the substrate and covered with the low-melting glass for forming an insulating film is a liquid crystal display panel, an electroluminescence panel, a fluorescent display panel, an electrochromic display panel, a light emitting diode display. Although there are a panel, a gas discharge type display panel, and the like, any article is included in the present invention.

Further, for example, in the case of a gas discharge type display panel, it is desired to lower the dielectric constant of the low melting point glass in order to suppress power consumption during driving. It can be:

An example of a gas discharge type display panel will be described below.
The present invention will be described in detail, but the present invention is not limited thereto.

[Structure of Gas Discharge Display Panel] FIG. 1 is a schematic side sectional view showing a part of the display panel. The transparent front substrate glass 1 is made of soda-lime glass or glass having similar composition and thermophysical properties. On one surface of the front substrate glass 1, a patterned transparent electrode wire 2 is provided. The transparent electrode wire 2 is usually made of indium tin oxide (ITO).
Or tin oxide (SnO ₂ ) type. Further, a transparent insulating film (hereinafter, also referred to as “dielectric layer”) 3α made of the low-melting glass according to the present invention as one embodiment is applied to cover the front substrate glass 1 and the transparent electrode wires 2. The dielectric layer 3α is formed by applying a mixture of a low-melting glass powder and paste oil, which have been manufactured and sized in advance, onto the front substrate 1 and the transparent electrode wires 2 by screen printing or the like.
It is baked at about ℃ to form a thick film about 30μm thick. The thickness of about 30 μm is necessary and sufficient for exhibiting display performance by gas discharge and long-term stability.

The dielectric layer is a dielectric layer according to the present invention.
(I) 3. The film thickness is around 10 μm, and its softening point is lower than that (4
More preferably, the dielectric layer (II) 4 and the film thickness of about 20 μm are laminated and formed, which will be described later.

Further, a magnesia layer 5 is applied over the dielectric layer 3α or the dielectric layer 4 by a sputtering method or the like. The magnesia layer 5 protects the dielectric layer from being sputtered during discharge, and thus covering the protective magnesia layer is a common means in forming a gas discharge type display panel.

On the other hand, on a rear substrate (glass) 6, an address electrode 7 facing the transparent electrode and a phosphor 8 emitting light of a desired color are arranged. 9 is formed. The periphery of the front substrate glass 1 and the rear substrate (glass) 6 are sealed with a low melting point glass 10. Low melting point glass 10 sealing transparency in the main purpose, perspective, etc. is not in question, completely by calcining a mixture of PbO -SiO ₂ based low melting point glass powder and paste oil at approximately 450 ° C. Can be sealed. A rare gas 11, for example, a Ne gas is filled in a space (discharge space) between the front substrate glass 1 and the rear substrate (glass) 6.

The front substrate is manufactured by forming a transparent electrode line pattern on the substrate glass by a sputtering method, a CVD method, or the like, or by further forming a metal electrode (for example, a chromium electrode).
(Copper-chromium) is formed as a bus electrode, and then a dielectric layer 3α is formed by screen printing or the like and is baked to complete.

In this case, if the dielectric layer 3α has a low softening point, the fluidity at the time of baking increases, and even though the PbO component is reduced, the erosion of the components of the transparent electrode wire becomes remarkable. It is desirable that the temperature be 550 ° C or higher. On the other hand, if the softening point is as described above, bubbles cannot be easily removed at the time of baking, and a sufficiently clear coating film is not easily obtained. Therefore, the dielectric layer is preferably a dielectric layer according to the present invention.
(I) 3. The film thickness is around 10 μm, and its softening point is lower (4
80 ° C or less) Dielectric layer (II) 4 with easy bubble removal, thickness 20 μm
It is preferable to adopt a laminated form of front and rear.

That is, a step of forming a transparent electrode line pattern and a metal electrode as a bus electrode on a substrate glass by a sputtering method or the like, and then forming and baking the dielectric layer (I) 3 by screen printing or the like, is performed. desirable.

Thus, the front substrate and the rear substrate are integrated and a rare gas is sealed to form a gas discharge type display panel. By applying a voltage, a potential difference is generated between the transparent electrode 2 and the address electrode 7, and the rare gas 11 Is excited to emit ultraviolet light, which stimulates the phosphor 8 to emit light and display a color, which is visually recognized from the front substrate side.

[Low-melting glass for forming transparent insulating film] As described above, the low-melting glass for forming a transparent insulating film in the present invention is made of SiO ₂ —PbO—B ₂ O ₃ —ZnO—RO (CaO, MgO,
(SrO, BaO) -based components, but the low-melting glass for forming a transparent insulating film applied to a soda-lime-based or similar glass-based display panel such as a gas discharge type display panel further includes the following: Thus, it is preferable to limit the thermophysical properties and the component composition range.

That is, the softening point (viscosity of the low melting point glass)
10 ^7.6 poise) is 590 ° C or less.
As a result, the baking at 570 to 600 ° C. and the dielectric layer 3
When α is formed, it is fluid to some extent and allows bubbles to escape. If the softening point exceeds 590 ° C, bubble removal tends to be insufficient.On the other hand, if the baking temperature is increased to ensure sufficient bubble removal, the temperature exceeds the heat resistance temperature of the substrate glass, causing problems such as contraction and deformation of the substrate glass. Occurs.

It is preferable that the softening point is lower. However, if the softening point is too low, the fluidity during baking increases, the erosion from the transparent electrode wire pattern becomes remarkable, and the resistance of the transparent electrode wire increases. As described above, it is desirable to form a thin layer at 550 ° C. or higher and easily bleed (the formation of the dielectric layer (I) 3), and a dielectric layer made of low melting point glass having a softening point of 480 ° C. or lower (the dielectric layer (II) ) 4) is preferred.

If the softening point of the low-melting-point glass dielectric layer (dielectric layer (II) 4) is lower than 450 ° C., about 450 ° C. is required for sealing with the aforementioned low-melting glass 9 for sealing. When baking with low melting point glass (dielectric layer (II)
The fluidity of 4) is increased, and problems such as cracks are generated in the magnesia layer formed thereon, which is not preferable.
Therefore, the softening point should be 450 ° C or higher.

As the low melting point glass for the dielectric layer (II) 4, for example, SiO ₂ 4 wt%, B ₂ O ₃ 17 wt%, Al ₂ O ₃ 2 wt
%, ZnO 10% by weight, PbO 67% by weight, glass having a softening point of 460 ° C., or SiO ₂ 4% by weight, B ₂ O ₃ 22% by weight, ZnO 6
Glass having a softening point of 470 ° C. or the like can be suitably used.

The transparent glass such as soda-lime glass in the front substrate glass 1 has a coefficient of thermal expansion (from room temperature to 300 ° C.) of about 80 to 90 × 10 ⁻⁷ / ° C., and therefore comprises the low melting glass of the present invention. Dielectric layer 3α or dielectric layer (I)
3 also adopts a thermal expansion coefficient close to it. Specifically, the temperature is set to 70 to 90 × 10 ⁻⁷ / ° C., and if it is less than or exceeds the range, the substrate glass may be warped or cracked, or the dielectric layer itself may be cracked.

In the low-melting glass for forming a transparent insulating film, SiO ₂ , B ₂ O ₃ , PbO and ZnO components are indispensable, and it is necessary that these are contained in the glass in a total of 70% by weight or more.

Of the SiO ₂ and B ₂ O ₃ ,
By containing 25 to 40 wt%, glass formation is facilitated and a stable glass phase can be obtained. ZnO and PbO
By containing 30 to 70% by weight in the glass in total, the softening point of the glass can be appropriately lowered, bubbles can be easily removed during the above-described firing, and the coefficient of thermal expansion can be adjusted to an appropriate range.

The individual components are as follows. That is, SiO ₂ is a glass-forming component, which can expand and stabilize the vitrification range. Si
The O ₂ introduction amount is in the range of _{2 to 6} wt%. If the content is less than 2 wt%, the effect cannot be exerted. If the content exceeds 6 wt%, the glass viscosity increases, and it becomes difficult to remove bubbles during baking. More preferably, it is in the range of 3 to 6% by weight.

ZnO is used to impart fluidity to the glass and to adjust the coefficient of thermal expansion.
25 wt%. If it is less than 20 wt%, the effect cannot be exhibited,
If it exceeds 25% by weight, the glass becomes unstable and tends to crystallize. More preferably, it is in the range of 22 to 37% by weight.

B ₂ O ₃ is introduced as a main component of glass formation like SiO ₂ , and the amount of B ₂ O ₃ introduced is in the range of 20 to 40 wt%. If it is less than 20% by weight, glass formation is unstable and devitrification tends to occur, and crystals are easily formed. On the other hand, if it exceeds 40% by weight, the viscosity of the glass increases, making it difficult to remove bubbles during baking. More preferably, it is in the range of 20 to 30 wt% and the ratio to ZnO is 1.
1 or more. When the ratio is 1.1 or more, the stability of the glass is increased, and a decrease in the light scattering rate due to precipitation of crystals can be suppressed.

PbO is a component necessary for lowering the melting point of glass, that is, lowering the softening temperature and imparting fluidity.
Introduce in the range of 40wt%. If the content is less than 10 wt%, the effect cannot be sufficiently exhibited, and the bubble removal during firing becomes insufficient. If it exceeds 40 wt%, erosion of the transparent electrode wire becomes remarkable.

Al ₂ O ₃ is introduced as appropriate for stabilizing the glass and adjusting the coefficient of thermal expansion. However, introduction exceeding 5% by weight increases the viscosity of the glass, making it difficult to remove bubbles.

Further, one or more selected from MgO, CaO, SrO and BaO are introduced in the range of 5 to 35% by weight. These divalent component oxides can maintain a thermal expansion coefficient suitable for the substrate glass in place of the PbO component, and can suppress erosion of the transparent electrode wires. If the content is less than 5 wt%, the effect is not sufficient, and if it exceeds 35 wt%, the glass becomes unstable and devitrification tends to occur. Also, introduction of an excessive amount rather increases the glass viscosity and increases the thermal expansion coefficient.

R ₂ O (Na ₂ O, K ₂ O, etc.) as an impurity
The mixing amount of R ₂ 0 component in the rare gas space may shorten the panel life, so it is preferable to set the mixing amount to 1 wt% or less.

[0035]

The present invention will be described below by way of specific examples. The [low Preparation of melting glass mixed paste] fine silica sand as a SiO ₂ source, a boric acid as a B ₂ O ₃ source, the aluminum hydroxide Al ₂ O ₃ source, a zinc oxide as a ZnO source, a lead oxide as a PbO source Using calcium carbonate as a CaO source, strontium carbonate as a SrO source, and barium carbonate as a BaO source, these were blended so as to have a desired low melting glass composition, and then charged into a platinum crucible. Ten
Example 1 of Table 1 by heating and melting at 00 to 1100 ° C for 1 to 2 hours
4 were obtained. For comparison, glasses having conventionally known compositions (Comparative Examples 1 and 2) were prepared. 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 was flaked by a quenching twin roll forming machine, and sized by a pulverizer into a powder having an average particle size of 2 to 4 μm and a maximum particle size of less than 15 μm.

Next, ethyl cellulose as a binder and the above 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 Dielectric Layer] Thickness 2-3 mm, size
The paste was applied to a 150 mm square soda-lime glass substrate glass by screen printing using a # 250 open screen, taking into account that the film thickness after baking was 8 to 10 μm.

Then, after drying at 140 ° C. for 15 minutes,
For 10 minutes to form a clear thick film made of the first dielectric glass. Further, SiO ₂ 4 wt%, B ₂ O ₃ 22
wt%, ZnO 6wt%, PbO 68wt%, softening point 470 ℃
The second dielectric made of low-melting glass is printed and coated using a # 250 aperture screen, taking into account that the total thickness of the second dielectric after baking is about 30 μm in total of I and II, 140
After drying at 15 ° C. for 15 minutes, baking was performed at 590 ° C. for 10 minutes to form a clear thick film of dielectric glass. 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 elevating the temperature at
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.

[Measurement of Transmittance] The transmittance of a substrate glass (thickness: 3 mm) on which the first and second dielectric layers were formed was measured by a conventional method using a spectrophotometer, and the average transmittance in the visible region was calculated. did. A visible light transmittance of 80% or more was considered good, and was evaluated as good, and those with less than 80% were classified as bad.

[Measurement of Dielectric Constant] The molded glass body was subjected to 1.
A disk having a thickness of 0 mm and a diameter of 50 mm was polished, electrodes were formed on both surfaces of the glass, and the dielectric constant at room temperature was measured by a known guard ring method.

[Measurement of Degree of Erosion of Transparent Electrode Wire] A dielectric layer was formed on a glass substrate provided with an ITO thin film, and the dielectric layer was dissolved and removed in a 7% nitric acid solution. The electrical resistance of the ITO thin film was measured. In addition, those having an increase in electric resistance of twice or less of the value before the formation of the dielectric layer were evaluated as good, and those with more than twice the increase were evaluated as bad.

[Presence or absence of devitrification] The dielectric layer was observed under a mirror for the presence or absence of devitrification.

[Warp of glass plate] Thickness 2 mm, size 300
Similarly, a clear thick film made of dielectric glass is formed on a soda-lime-based substrate glass of mm □, and the warpage of the dielectric film-formed substrate glass is measured with a non-contact straightness / thickness measuring device, and the deflection is measured. Those with a depth of 50 μm / 300 mmL or less were evaluated as good, and those with a deflection depth exceeding 50 μm / 300 mmL were evaluated as bad.

The reason why the thickness of the substrate glass is set to 2 mm is that by making the substrate thin, the warpage is more likely to occur, and strict classification evaluation can be performed.

[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 evident from Table 1, in the examples according to the present invention, in addition to the non-erosion property and low dielectric constant of the transparent electrode wires, good thermal properties, optical properties, devitrification resistance, suppression of substrate warpage, etc. It is suitable as a low-melting glass for forming a transparent insulating film, particularly as the low-melting glass for a gas discharge type display panel. In Comparative Example 1, the dielectric constant was too high and the electrode wire was significantly eroded.
Comparative Example 2 has disadvantages such as a low thermal expansion coefficient, warpage of the substrate glass, and a low visible light transmittance.

[0048]

[Table 1]

[0049]

According to the present invention, there is a remarkable effect that erosion of the transparent electrode wire is suppressed. In addition, it has a low dielectric constant, is excellent in thermophysical properties, optical properties and the like, and is suitable as a low-melting glass for forming a transparent insulating film on a display panel substrate, particularly a low-melting glass for forming a transparent insulating film in a gas discharge display panel. is there.

[Brief description of the drawings]

FIG. 1 is a schematic sectional side view of a gas discharge panel.

[Explanation of symbols]

 1 -------- Front substrate glass 2 -------- Transparent electrode 3α ------ Dielectric layer 3 -------- Dielectric layer (I) 4- ------- Dielectric layer (II) 5 -------- Magnesia layer 6 -------- Back substrate glass 7 -------- Address electrode 8 --- ------ Phosphor 9 -------- Partition wall 10 -------- Low melting point glass for sealing 11 -------- Rare gas

Claims (3)

[Claims] To 1. A display panel substrate in arranged transparent electrode line pattern, a low-melting point glass to form a transparent insulating film, in wt% is component composition of the glass, SiO _2. 2 to
_{6, B 2 O 3 20~40,} Al 2 O 3 0~5, ZnO 20~25, PbO 10~
40, containing one or more selected from MgO, CaO, SrO, and BaO in the range of 5 to 35, and has a softening point of 590 ° C or less, and a coefficient of thermal expansion from room temperature to 300 ° C of 70 to 90 ×. A low-melting glass for forming a transparent insulating film having a temperature of ^10-7 / ° C. 2. The low melting glass for forming a transparent insulating film according to claim 1, which has a dielectric constant of 9 or less. 3. A second low-melting glass for forming a transparent insulating glass film for covering a transparent electrode line pattern, further comprising a low-melting glass having a softening point of 480 ° C. or lower which is laminated thereon. 3. The low-melting glass for forming a transparent insulating film according to claim 1, wherein the glass is formed as an underlayer of the transparent insulating glass film.