JP2007161524A - Bismuth-based glass composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bismuth-based glass composition which is excellent in weatherability and in which a crystal is not easily deposited although the bismuth-based glass composition can be used even when heat-treated at 600°C or lower. <P>SOLUTION: The bismuth-based glass composition contains by mol% 20-50% Bi<SB>2</SB>O<SB>3</SB>, 10-40% B<SB>2</SB>O<SB>3</SB>and 0.5-10% Ta<SB>2</SB>O<SB>5</SB>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bismuth-based glass composition suitable for adhesion, sealing, coating of electronic parts, adhesion of a magnetic core type magnetic head, a fixing material, and the like.

  Conventionally, glass has been used as a bonding and sealing material for electronic components, as a coating material for protecting and insulating electrodes and resistors formed on electronic components, or as a material for bonding and fixing ferrite core type magnetic heads. It is used.

  These glasses are required to have various properties such as chemical durability, mechanical strength, fluidity, and electrical insulation depending on the application, but can be fired at a low temperature as a property common to all applications. Can be mentioned. Therefore, in any application, low-melting glass containing a large amount of PbO that has an extremely large effect of lowering the melting point of glass is widely used.

  The reason why lead-based low-melting glass has been widely used as a sealing glass for magnetic heads is that low temperature (600 ° C.) is used to prevent deterioration due to heating of ferrite materials, especially metal magnetic films of magnetic heads called MIG type. This is because sealing in the following is required.

Recently, however, environmental problems have been pointed out with respect to PbO-containing glasses, and it is desired to replace them with glass containing no PbO. Accordingly, bismuth-based glass compositions have been proposed as lead-free glass (see, for example, Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 08-110220 JP-A-10-299712

  However, the bismuth-based glasses disclosed in Patent Documents 1 and 2 have a problem in weather resistance, and there are problems in that crystals are precipitated by heat treatment and fluidity is impaired.

  An object of the present invention is to provide a bismuth-based glass composition that has excellent weather resistance and can be used even when heat treatment is performed at a temperature of 600 ° C. or lower, but crystals do not easily precipitate.

The present invention has been made in view of the above circumstances, and as a result of intensive studies, the inventors of the present invention have a weather resistance when an appropriate amount of Ta ₂ O ₅ is added to Bi ₂ O ₃ —B ₂ O ₃ glass. Thus, it is not necessary to change the heat treatment temperature almost at all, and it is found that it is difficult to precipitate crystals even after the heat treatment, and is proposed as the present invention.

That is, the bismuth-based glass composition of the present invention contains, in mol%, Bi ₂ O ₃ 20 to 50%, B ₂ O ₃ 10 to 40%, Ta ₂ O ₅ 0.5 to 10%. And

The bismuth-based glass composition of the present invention is excellent in weather resistance and has a heat treatment temperature because 0.5 to 10 mol% of Ta ₂ O ₅ is added to Bi ₂ O ₃ -B ₂ O ₃ glass. Even if it is hardly changed, it can be used, and even if it is heat-treated, crystals are hardly precipitated and the fluidity is not impaired.

  The reason for limiting the composition of the bismuth-based glass composition of the present invention as described above is as follows.

Bi ₂ O ₃ is a main component for lowering the softening point of the glass, and its content is 20 to 50%, preferably 25 to 45%. If the Bi ₂ O ₃ content is less than 20%, the softening point tends to be too high and firing tends to be impossible at 600 ° C. or less, and if it exceeds 50%, stable glass tends not to be obtained.

B ₂ O ₃ is an essential component as a glass forming component, and its content is 10 to 40%, preferably 18 to 40%. If the content of B ₂ O ₃ is less than 10%, the glass becomes unstable and tends to devitrify. Even when devitrification does not occur, the deposition rate of crystals during firing is extremely high, and there is a tendency that the fluidity necessary for operations such as adhesion, sealing, and coating cannot be obtained. On the other hand, if B ₂ O ₃ exceeds 40%, the viscosity of the glass becomes too high and firing at a temperature of 600 ° C. or less tends to be difficult.

Ta ₂ O ₅ is an essential component of the present invention. Ta ₂ O ₅ has the effect of improving weather resistance and reducing crystals generated on the glass surface during heat treatment. Its content is 0.5 to 10%, preferably 1 to 5%. When the content of Ta ₂ O ₅ is less than 0.5%, there is a tendency that the effect of improving weather resistance and thermal stability cannot be obtained. On the other hand, if it exceeds 10%, the glass composition system becomes unstable and devitrification tends to occur during melting. Moreover, since it is expensive compared with other elements in terms of cost, it is not realistic to increase the content above 10%.

  Optional components are shown below.

  ZnO has a great effect on glass stabilization, and its content is 0 to 30%, preferably 15 to 25%. If the content exceeds 30%, the glass tends to crystallize and the fluidity tends to deteriorate.

  CuO is a component for stabilizing the glass, and its content is 0 to 20%, preferably 0 to 15%. When CuO exceeds 20%, it tends to be crystallized and the fluidity tends to deteriorate.

Fe ₂ O ₃ is a component for stabilizing the glass, and its content is 0 to 5%, preferably 0 to 2%. If Fe ₂ O ₃ exceeds 5%, the glass tends to be unstable.

SiO ₂ and Al ₂ O ₃ are components added to further stabilize the glass. The content of SiO ₂ is 10% or less, preferably 7% or less, and the content of Al ₂ O ₃ is 10% or less. , Preferably 5% or less. If each content is more than 10%, the viscosity of the glass becomes too high, and heat treatment at a temperature of 600 ° C. or lower may not be possible.

SiO ₂ and Al ₂ O ₃ can be added up to 15% in total. If the content is more than 15%, the viscosity of the glass becomes too high, and heat treatment may not be performed at a temperature of 600 ° C. or lower, which is not preferable. The preferable content of the total amount of SiO ₂ and Al ₂ O ₃ is 10% or less.

Cs ₂ O and F ₂ are components that lower the viscosity of the glass. The content of Cs ₂ O is 0 to 5%, preferably 0 to 3%, and the content of F ₂ is 0 to 20%, preferably 0 to 10%. If these components exceed the above range, the chemical durability of the glass tends to decrease.

In addition, WO ₃ , Sb ₂ O _3, Sb ₂ O ₅ , In ₂ O ₅ or the like can be added up to 10% for stabilizing the glass in the glass composition.

In addition to the above components, MgO, La ₂ O ₃ , TiO ₂ , ZrO ₂ , V ₂ O ₅ , Nb ₂ O ₅ , MoO ₃ , TeO ₂ , Ag are used for adjusting the viscosity and thermal expansion coefficient of the glass. ₂ O, Na ₂ O, K ₂ O, Li ₂ O and the like can be added up to 5% each. However, intentional addition of environmentally problematic components such as PbO should be avoided, and the PbO content should be suppressed to 0.5%.

  The bismuth-based glass composition of the present invention having the above composition is an amorphous glass exhibiting good fluidity at a temperature of 600 ° C. or lower, preferably 500 ° C. or lower.

Further, the coefficient of thermal expansion at 30 to 300 ° C. is about 90 × 10 ⁻⁷ / ° C. or higher, and a high expansion material compatible therewith can be bonded, sealed or coated at a temperature of 600 ° C. or lower.

  On the other hand, when adhering, sealing, or coating a material that does not match the thermal expansion coefficient, it is possible to mix and use a refractory filler in order to correct the difference in thermal expansion coefficient with the object. Also, when the mechanical strength is insufficient, a refractory filler can be mixed and used.

  When mixing a refractory filler, the mixing ratio is preferably 45 to 95% by volume of glass and 55 to 5% by volume of refractory filler. The reason why the ratio of the two is defined in this way is that if the amount of the refractory filler is less than 5% by volume, the added effect is difficult to obtain, and if the amount is more than 55% by volume, the fluidity tends to deteriorate.

  As the refractory filler, powders such as willemite ceramic, β-eucryptite, cordierite, zircon ceramic, tin oxide ceramic, mullite, quartz glass, and alumina can be used alone or in combination. .

  Specific uses of the bismuth-based glass composition of the present invention include (1) hermetic sealing of fluorescent display tubes and formation of insulating layers, and (2) hermetic sealing of plasma display panels, insulating layers and dielectrics. Examples include formation of a body layer, formation of a barrier rib, and (3) sealing of a magnetic head-core or between a core and a slider. Moreover, the form at the time of use does not have a restriction | limiting in particular, According to a use, it can shape | mold and use it in various forms, such as a powder form, paste shape, plate shape, rod shape.

    Hereinafter, the bismuth-based glass composition of the present invention will be described in detail based on examples.

  Tables 1 and 2 show examples (sample Nos. 1 to 8), and Table 3 shows comparative examples (samples No. 9 to 11). Table 1 is a glass suitable for sealing a display tube, and Table 2 is a glass suitable for sealing a magnetic head.

  Each sample was produced as follows.

  First, a glass batch prepared by preparing glass materials such as various oxides and carbonates so as to have the glass composition shown in the table was prepared, and this was put in a platinum crucible and melted at 950 ° C. for 2 hours. Subsequently, the molten glass was poured into a stainless steel mold and molded to prepare a sample. About each obtained sample, the glass transition point, the thermal expansion coefficient in 30-300 degreeC, the calcination temperature, the surface crystal | crystallization after baking, and the weather resistance were evaluated. The results are shown in the table.

As is apparent from the table, No. 1 in Table 1 which is an example of the present invention. Each of the samples 1 to 5 had a glass transition point of 353 to 382 ° C., a thermal expansion coefficient of 102 to 111 × 10 ⁻⁷ / ° C. in a temperature range of 30 to 300 ° C., and a firing temperature of 480 ° C. or less. . All samples were non-crystalline after firing.

In addition, No. 2 in Table 2 which is an example of the present invention. Each of the samples 6 to 8 had a glass transition point of 419 to 425 ° C. and a thermal expansion coefficient of 93.5 to 96.5 × 10 ⁻⁷ / ° C. in a temperature range of 30 to 300 ° C. The firing temperature was 540 ° C. or lower, and all the samples were amorphous after firing.

On the other hand, No. of Table 3 which is a comparative example. Each of the samples 9 to 11 had a glass transition point of 350 to 423 ° C. and a thermal expansion coefficient in the temperature range of 30 to 300 ° C. of 97.5 to 112 × 10 ⁻⁷ / ° C. In addition, the weather resistance was poor.

  In addition, the transition point was calculated | required with the differential thermal analyzer (DTA).

  The thermal expansion coefficient was measured using a push rod type thermal expansion coefficient measuring device after polishing the molded glass body into a cylindrical shape having a diameter of 4 mm and a length of 40 mm.

  The firing temperature was determined as follows.

  First, a glass body was pulverized to obtain a glass powder, and a glass powder having a mass corresponding to the true specific gravity of the glass was press-molded into a button shape having an outer diameter of 20 mm and a height of about 5 mm.

  Next, this button was placed on a plate glass, put into an electric furnace, heated at a rate of 10 ° C./min, and held at the temperature shown in the table for 10 minutes. The temperature at which the outer diameter of the button thus obtained was in the range of 20 to 22 mm was defined as the firing temperature.

  For the evaluation of the surface crystal, the appearance of the sample fired at the firing temperature was observed with a microscope, and the presence or absence of crystal precipitation was evaluated.

  In addition, the evaluation of the weather resistance test was conducted by immersing a glass bulk having a surface of 2 cm × 2 cm in warm water at 80 ° C. for 24 hours, and then observing the surface state at 50 times with an optical microscope to confirm alteration and discoloration. Those in which no alteration or discoloration was observed were evaluated as “good”, and those in which alteration or discoloration was observed were determined as “bad”.

  As described above, the bismuth-based glass composition of the present invention has excellent weather resistance, and crystals do not easily precipitate even when fired. Therefore, as an alternative material for low-melting glass containing conventional PbO, bonding of electronic components It can be suitably used for applications such as sealing and coating.

Claims (3)

A bismuth-based glass composition containing Bi ₂ O ₃ 20 to 50%, B ₂ O ₃ 10 to 40%, and Ta ₂ O ₅ 0.5 to 10% in terms of mol%. Furthermore, according 0~30% ZnO, 0~20% CuO, Fe 2 O 3 0~5%, SiO 2 0~10%, in claim 1, characterized in that it contains Al ₂ O ₃ 0~10% Bismuth glass composition.   The bismuth-based glass composition according to claim 1 or 2, which does not substantially contain PbO.