JP4972954B2 - Bismuth-based glass composition and bismuth-based sealing material - Google Patents

Description

  The present invention relates to a bismuth-based glass composition and a bismuth-based sealing material that are suitable for sealing and covering electronic parts and displays. In particular, the present invention relates to a bismuth-based glass composition and a bismuth-based sealing material suitable for sealing a plasma display panel.

  Conventionally, glass has been used as a sealing material for electronic parts and displays. Glass is excellent in chemical durability and heat resistance as compared with a resin-based adhesive, and is suitable for ensuring airtightness of a display or the like.

  These glasses require various properties such as mechanical strength, fluidity, and electrical insulation depending on the application, but must be usable at least at temperatures that do not degrade the fluorescence properties of the phosphors used in displays. Is required. Therefore, as a glass that satisfies the above characteristics, lead borate glass (see, for example, Patent Document 1) containing a large amount of PbO that has an extremely large effect of lowering the melting point of the glass has been widely used.

Recently, however, environmental problems have been pointed out with respect to PbO contained in lead borate glass, and it is desired to replace lead borate glass with glass containing no PbO. Therefore, various low melting glass has been developed as a substitute for lead borate glass. Among them, the bismuth glass (also referred to as Bi ₂ O ₃ —B ₂ O ₃ glass) described in Patent Document 2 is a lead borate glass in various properties such as chemical durability and mechanical strength. Therefore, it is expected as an alternative candidate, but in reality, it does not reach the characteristics of lead borate glass in terms of fluidity and thermal stability.

  By the way, the sealing material used for a plasma display panel (hereinafter referred to as PDP) undergoes the following heat treatment process.

  First, a paste-like sealing material dispersed in a vehicle is applied to the outer peripheral portion of the back substrate of the PDP, and the vehicle components are pyrolyzed or incinerated at a high temperature to perform primary firing (also called a glaze process or a pre-firing process). Do). Here, the sealing material is generally a composite powder containing a glass powder, also called a sealing glass, and a refractory filler powder, and the vehicle for uniformly dispersing the sealing material contains an organic solvent or a resin. Contains. Further, as the resin used for the vehicle, nitrocellulose or an acrylic resin that is thermally decomposed well at a temperature below the softening point of glass is generally used. The sealing material and the vehicle are uniformly dispersed using a kneading apparatus such as a three-roll mill. The primary firing is performed under a temperature condition in which the resin used for the sealing material is completely thermally decomposed. If the resin is incompletely thermally decomposed, the secondary firing (both sealing and sealing steps) to be provided thereafter is performed. As a result, a resin residue may remain in the sealing material, and as a result, a fatal defect may be caused in the sealing material to ensure the airtightness of the PDP such as devitrification or bubbles. .

Next, secondary baking of the sealing material is performed, and the front substrate and the back substrate of the PDP are sealed. Finally, the inside of the PDP is evacuated through the exhaust pipe, and then a necessary amount of rare gas is injected to seal the exhaust pipe. In this way, the PDP is manufactured.
Japanese Unexamined Patent Publication No. Sho 63-315536 JP 2003-095597 A

  Patent Document 2 exemplifies a bismuth-based glass composition that can be used for applications such as sealing and coating electronic components. However, this bismuth-based glass composition has a higher softening point and poor glass fluidity than glass containing PbO. Furthermore, the thermal stability of the glass is extremely poor and cannot be applied to applications that undergo multiple heat treatment steps.

In order to lower the softening point, it is necessary to increase the content of Bi ₂ O ₃ which is a main component. However, if the content of Bi ₂ O ₃ is increased, crystals containing Bi ₂ O ₃ as constituent components can be obtained. It tends to precipitate during firing and fluidity is likely to be impaired. Therefore, the fluidity is not easily increased only by increasing the content of Bi ₂ O ₃ .

  The first object of the present invention is to provide a bismuth-based glass composition and a bismuth-based sealing material which are substantially free of PbO and can be fired at a temperature equal to or lower than 480 ° C. equivalent to lead borate-based glass. That is.

  Further, in the PDP manufacturing process, the primary firing of the phosphor material and the primary firing of the sealing material may be performed at the same time in order to improve work efficiency. In general, when the primary firing temperatures of both materials are compared, the firing temperature of the phosphor material is higher and is 480 ° C. or higher (about 500 ° C.). For this reason, when the thermal stability of the sealing material is low, devitrification occurs at this point, and the fluidity in the subsequent secondary firing (450 to 480 ° C.) is impaired, and air-tight sealing may not be achieved.

  The second object of the present invention is substantially free of PbO, and does not devitrify or precipitate crystals even after primary firing at about 500 ° C. in the production process of PDP. It is to provide a bismuth-based glass composition and a bismuth-based sealing material that can be hermetically sealed by secondary firing at ° C.

Even if the content of Bi ₂ O ₃ , which is a component that lowers the softening point, is increased by adding 0.01 to 5 mol% of Sb ₂ O ₃ to the bismuth-based glass composition, The inventors have found that the precipitation of crystals in the inside is suppressed and that it can be used at a firing temperature equivalent to that of lead borate glass, and is proposed as the present invention.

That is, the bismuth-based glass composition of the present invention represents Bi ₂ O ₃ 30 to 60%, B ₂ O ₃ 10 to 35%, and Sb ₂ O ₃ 0.01 to 5% in terms of the following oxide reference mol%. It is characterized by containing.

Further, the bismuth-based sealing material of the present invention is a sealing material containing glass powder and refractory filler powder, in terms of mol%, Bi ₂ O ₃ 30 to 60%, B ₂ O ₃ 10 to 35%, It contains 40 to 95% by volume of glass powder made of a bismuth-based glass composition containing 0.01 to 5% of Sb ₂ O _{3 and} 5 to 60% by volume of refractory filler powder.

Even if the content of Bi ₂ O ₃ , which is a component that lowers the softening point of glass, is increased by adding 0.01 to 5 mol% of Sb ₂ O ₃ in the bismuth-based glass composition of the present invention, Crystal precipitation during firing can be suppressed. Therefore, it is excellent in fluidity and can be fired at a temperature equal to or lower than 480 ° C., which is equivalent to that of lead borate glass, although it does not substantially contain PbO. Furthermore, the bismuth-based glass composition of the present invention can be added to 0.01 to 5 mol% of Sb ₂ O ₃ , so that devitrification and crystal precipitation occur even in the first firing at 480 ° C. or higher in the PDP manufacturing process. Can be suppressed and can be hermetically sealed at 450 to 480 ° C.

  The bismuth-based sealing material of the present invention is excellent in fluidity and can be fired at a temperature equal to or lower than 480 ° C., equivalent to that of a lead boric acid-based sealing material, although it does not substantially contain PbO. Further, the bismuth-based sealing material of the present invention is effective in a situation where crystals are not devitrified even when subjected to primary firing at a temperature of 480 ° C. or higher in the PDP manufacturing process, and crystals are grown by secondary firing provided thereafter. And the fluidity required in the secondary firing can be ensured. Furthermore, the bismuth-based sealing material of the present invention does not precipitate crystals on the glass even after secondary firing at a temperature of 450 to 480 ° C. after primary firing at a temperature of 480 ° C. or higher. Even if it exists, fluidity | liquidity is favorable. Therefore, the bismuth-based sealing material of the present invention can be said to be a non-crystalline (also referred to as amorphous) sealing material having extremely high thermal stability and a very wide usable temperature range.

  In addition, since the bismuth-based sealing material of the present invention has extremely excellent fluidity, the reaction at the interface between the substrate glass and the sealing material is sufficiently advanced, and the sealing strength between the front substrate and the rear substrate can be significantly increased. it can. As a result, it can greatly contribute to maintaining the long-term reliability of the PDP. That is, since the bismuth-based sealing material of the present invention has excellent thermal stability, it does not cause a decrease in fluidity due to devitrification, and has a low softening point of glass, which is inherently good for the sealing material. Can be maximized without sacrificing fluidity. In particular, in sealing the exhaust pipe and the back substrate, the bismuth-based sealing material flows well in the secondary firing, so that an accurate sealing shape can be formed for sealing the exhaust pipe. It is possible to suppress as much as possible the occurrence of cracks at the interface between the sealing material and the exhaust pipe and between the sealing material and the substrate. Therefore, for the purpose of sealing the exhaust pipe, a method of using a sintered body (also referred to as a tablet) of a bismuth-based sealing material is adopted as a sealing material that replaces the lead boric acid-based sealing material. This is unnecessary, and can greatly contribute to the improvement of manufacturing cost, manufacturing efficiency, and the like.

  However, the bismuth-based sealing material of the present invention does not exclude an embodiment used as a sintered body. In the production of the sintered body, it is necessary to go through a plurality of thermal processes independently, and the thermal stability is required for the sealing material constituting the sintered body, as described above, Needless to say, the bismuth-based sealing material of the present invention is also excellent in this application because of its excellent thermal stability. Furthermore, since the bismuth-based sealing material of the present invention is extremely excellent in thermal stability and fluidity, even if the sintering temperature of the sealing material is increased for the purpose of increasing production efficiency in the production of a sintered body, The fluidity of the sintered body is not impaired by the secondary firing.

  Furthermore, since the bismuth-based sealing material of the present invention can obtain good fluidity in a wide temperature range, the bismuth-based sealing material can be used for applications other than PDP sealing applications, that is, electronic components and displays that undergo multiple heat treatment steps. Not only can the sealing be properly handled, but also the sealing of electronic components and displays that have undergone a high-temperature heat treatment process can be accurately handled.

  The reason why the glass composition of the bismuth-based glass composition of the present invention is limited as described above is as follows. In addition, the following% display points out mol% unless there is no limitation in particular.

Bi ₂ O ₃ is a main component for lowering the softening point of glass, and its content is 30 to 60%, preferably 33 to 60%, more preferably 35 to 60%, still more preferably 35 to 55. %, Most preferably 35-52%. If the content of Bi ₂ O ₃ is less than 30%, the softening point of the glass becomes too high and it becomes difficult to fire at a temperature of 480 ° C. or less, and if it exceeds 60%, devitrification tends to occur.

B ₂ O ₃ is an essential component as a glass forming component, and its content is 10 to 35%, preferably 15 to 30%, and more preferably 18 to 28%. If the content of B ₂ O ₃ is less than 10%, it is difficult to form a glass network, so that devitrification is likely to occur. For this reason, the fluidity necessary for sufficient sealing and coating may not be obtained. On the other hand, if it exceeds 35%, the viscosity of the glass tends to be high, and firing may be difficult at a temperature of 480 ° C. or lower.

Sb ₂ O ₃ is a component added to prevent crystals from precipitating and fluidity from being impaired during firing, and is an essential component. Further, when Sb ₂ O ₃ is contained in the glass composition, the glass does not devitrify even if the sealing material portion is repeatedly fired. As a result, in the manufacturing process of the PDP, primary firing is performed at about 500 ° C. However, it does not devitrify or crystal precipitates, and can be hermetically sealed by secondary firing at 450 to 480 ° C. The content of Sb ₂ O ₃ is 0.01 to 5%, preferably 0.05 to 5%, more preferably 0.1 to 5%, still more preferably 0.1 to 2.5%, most preferably 0.3 to 1.5%. In order to lower the softening point, it is necessary to increase the content of Bi ₂ O ₃ as a main component. However, if the content of Bi ₂ O ₃ is increased, Bi ₂ O ₃ is used as a crystalline constituent during firing. Crystals that are likely to precipitate, and fluidity is likely to be impaired. In particular, when Bi ₂ O ₃ is 40% or more, the tendency becomes remarkable. As the cause, and Bi ₂ O ₃ during sintering a crystalline product formed by bismuth oxide alone (Bisumaito), Bi ₂ O ₃ and composed of B ₂ O ₃ Metropolitan _{2Bi 2 O 3 · B 2 O} 3 or 12Bi ₂ O ₃ · B ₂ O ₃ is believed to be due to precipitation as a crystal. When this crystal is precipitated, the fluidity is impaired, but Sb ₂ O ₃ has a function of stabilizing the Bi ₂ O ₃ —B ₂ O ₃ glass network and suppressing the above-described crystal precipitation. However, it is not preferable to add more than 5% of Sb ₂ O ₃ because crystals are likely to precipitate during firing.

In addition, when Sb ₂ O ₃ is added, antimony trioxide (Sb ₂ O ₃ ), antimony pentoxide (Sb ₂ O ₅ ), or the like can be used as a raw material, but Sb ₂ O ₅ that contains a large amount of oxygen. It is preferable to use bismuth because bismuth is less likely to be reduced during melting, and thus tends to suppress precipitation of bismuth-based crystals.

  The bismuth-based glass composition of the present invention may contain the following components in addition to the components described above.

  BaO, SrO, MgO and CaO have an effect of suppressing devitrification when the glass is melted or fired, and the total content thereof is 1 to 15%, preferably 3 to 10%. If the total amount of these components is less than 1%, it is difficult to obtain the above effect, and if it exceeds 15%, the softening point tends to increase. The BaO content is 0 to 15%, preferably 1 to 15%, more preferably 1 to 13%, and still more preferably 2 to 10%. Further, the contents of SrO, MgO, and CaO are each preferably 0 to 5%, particularly preferably 0.5 to 3%.

  ZnO has an effect of suppressing devitrification when the glass is melted or fired, and its content is 5 to 30%, preferably 10 to 25%, more preferably 13 to 25%. If the content is less than 5% or more than 30%, crystals are likely to precipitate on the glass during firing, resulting in poor fluidity.

  CuO is a component that suppresses devitrification when the glass is melted or fired, and its content is 0 to 10%, preferably 0.1 to 10%, more preferably 2 to 10%. If the CuO content is more than 15%, crystals tend to precipitate very easily during firing and the fluidity tends to deteriorate.

Fe ₂ O ₃ is a component that suppresses devitrification when the glass is melted or fired, and its content is 0 to 5%, preferably 0.1 to 5%, more preferably 0.1 to 2%. It is. When Fe ₂ O ₃ is greater than 5%, there is a tendency not to vitrified Bunsho during melting.

The total amount of CuO and Fe ₂ O ₃ is preferably 1 to 11%. When the total amount of CuO and Fe ₂ O ₃ is more than 11%, devitrification tends to occur when fired at about 500 ° C. For this reason, it may not be possible to seal hermetically. On the other hand, when the total amount of CuO and Fe ₂ O ₃ is less than 1%, there is a tendency that devitrification at the time of glass melting or firing cannot be suppressed. The total amount of CuO and Fe ₂ O ₃ is more preferably 3 to 8%.

Moreover, it is preferable to add Al ₂ O ₃ , which is a component that suppresses devitrification at the time of melting of the glass, since precipitation of crystals can be further suppressed even during firing. The content is 0 to 5%, preferably 0 to 3%, more preferably 0.1 to 3%. When the addition amount is more than 5%, the softening point of the glass becomes high and it becomes difficult to fire at a temperature of 480 ° C. or lower.

SiO ₂ can be added up to 1% for the purpose of enhancing the weather resistance. If it exceeds 1%, the softening point of the glass becomes high and it becomes difficult to fire at a temperature of 480 ° C. or lower.

  The oxides of Li, Na, K, and Cs are components that lower the softening point of the glass. However, since they have an action of promoting devitrification of the glass when melted, the total amount is preferably 2% or less.

P ₂ O ₅ is a component that suppresses devitrification at the time of melting. However, if the addition amount is more than 1%, it is not preferable because the glass tends to phase-separate at the time of melting.

MoO ₃ , La ₂ O ₃ , Y ₂ O ₅ and CeO ₂ are components that suppress the phase separation of the glass at the time of melting, but if the total amount of these is more than 3%, the softening point of the glass becomes high, It becomes difficult to fire at a temperature of 480 ° C. or lower.

  Moreover, even if it is another component, it is possible to add to 5% in the range which does not impair the characteristic of glass.

Furthermore, in sealing applications of PDP, Bi ₂ O ₃ 35-50%, B ₂ O ₃ 20-35%, ZnO 10-25%, BaO + SrO + MgO + CaO 3-15%, BaO 1-15%, CuO + Fe ₂ O ₃ 1 More preferably, a bismuth-based glass composition containing ˜11% and Sb ₂ O ₃ 0.1˜5% is used.

The bismuth-based glass composition of the present invention does not exclude the embodiment containing PbO, but as described above, it is preferable that PbO is not substantially contained for environmental reasons. Further, when PbO is contained in the glass, Pb ²⁺ present in the glass may diffuse to lower the electrical insulation. In the present invention, “substantially does not contain PbO” refers to a case where the content of PbO in the glass composition is 1000 ppm or less.

The bismuth-based glass composition having the above glass composition is an amorphous glass exhibiting good fluidity at a temperature of 480 ° C. or less, and has a thermal expansion coefficient of about 100 to 120 × 10 ^{−7 at} 30 to 300 ° C. / ° C. Therefore, if the material has substantially the same thermal expansion coefficient as this bismuth-based glass composition, the powder composed of the bismuth-based glass composition can be used alone as a sealing material without adding a refractory filler powder. At the same time, it can be satisfactorily sealed at a temperature of 450 to 480 ° C.

Further, when sealing a material that does not match the thermal expansion coefficient with the bismuth-based glass composition, such as high strain point glass (85 × 10 ⁻⁷ / ° C.), soda plate glass (90 × 10 ⁻⁷ / ° C.), Bismuth glass powder and refractory filler powder may be mixed to form a composite material, which may be used as a sealing material. It is important that the thermal expansion coefficient of the sealing material is designed to be lower by about 10 to 30 × 10 ⁻⁷ / ° C. than the object to be sealed. This is for preventing distortion of the sealing material by setting the strain applied to the sealing material after compression to the compression (compression) side. In addition to adjusting the thermal expansion coefficient, for example, a refractory filler powder can be added to improve mechanical strength.

  When mixing the refractory filler powder, the mixing ratio is preferably 40 to 95% by volume for the bismuth glass powder and 5 to 60% by volume for the refractory filler powder. Moreover, when mixing a refractory filler powder, as for the mixing ratio, it is still more preferable that a bismuth-type glass powder is 40-90 volume% and a refractory filler powder 10-60 volume%. The reason why the ratio of the two is defined in this way is that when the amount of the refractory filler powder is less than 5% by volume, the above-mentioned effect tends to be hardly obtained. This is because there is a risk that it will not be possible.

Refractory filler powder is required to have low reactivity to the extent that thermal stability does not decrease even when added to bismuth-based glass powder, and depending on the application, low thermal expansion coefficient and high mechanical strength are required. Is done. Further, as the refractory filler powder, it is preferable to use a refractory filler powder substantially not containing PbO. Various materials can be used as the refractory filler powder. Specifically, cordierite, zircon, zirconia, tin oxide, aluminum titanate, quartz, β-spodumene, mullite, titania, quartz glass, β -Eucryptite, β-quartz solid solution, willemite, a compound having a basic structure of [AB ₂ (MO ₄ ) ₃ ],
A: Li, Na, K, Mg, Ca, Sr, Ba, Zn, Cu, Ni, Mn etc. B: Zr, Ti, Sn, Nb, Al, Sc, Y etc. M: P, Si, W, Mo etc. Alternatively, a mixture of these may be selected and used depending on the application. In particular, cordierite is preferable because it has the least tendency to lower the thermal stability of bismuth-based glass. For example, even when the temperature is 500 ° C. or higher, devitrification hardly occurs in the glass. In addition, Willemite has the smallest tendency to lower the fluidity of bismuth-based glass, and in the PDP manufacturing process, it becomes possible to obtain good fluidity by secondary firing. It is accurately crushed and can sufficiently secure the airtightness of the PDP, promote the reaction at the interface between the substrate and the sealing material, and remarkably improve the sealing strength between the front substrate and the back substrate. In particular, in sealing the exhaust pipe and the back substrate, the bismuth-based sealing material flows well in the secondary firing, so that an accurate sealing shape can be formed for sealing the exhaust pipe. It is possible to suppress as much as possible the occurrence of cracks at the interface between the sealing material and the exhaust pipe and between the sealing material and the substrate. Furthermore, cordierite and willemite have features of low expansion and excellent mechanical strength. Note that tin oxide is preferably added in an appropriate amount for the purpose of improving the mechanical strength of the sealing material.

  The refractory filler powder is preferably coated with a fine powder such as alumina, zinc oxide, zircon, titania, zirconia because the reaction between the bismuth glass powder and the refractory filler powder can be suppressed. In particular, alumina is preferable because it has a high melting point and hardly reacts with bismuth glass.

  As described above, the bismuth-based sealing material of the present invention has a very wide usable temperature range, in other words, a large temperature difference (ΔT) between the softening point of glass and the crystallization precipitation temperature. Therefore, it cannot be overemphasized that it can be used conveniently for the display and electronic component which pass through several heat processing processes. Specific applications include (I) PDP insulating layer and dielectric layer forming material, barrier rib forming material, (II) fluorescent display tube (hereinafter referred to as VFD) sealing material, insulating layer forming material (III) Magnetic head-sealing material between cores or core and slider, (IV) Sealing material such as crystal resonator package and semiconductor package.

  A sealing material in which bismuth-based glass powder and refractory filler powder are mixed may be used as a sealing material as it is, but it is easy to handle if the sealing material and vehicle are uniformly kneaded and used as a paste. . The vehicle is mainly composed of an organic solvent and a resin, and the resin is added for the purpose of adjusting the viscosity of the paste. Moreover, surfactant, a thickener, etc. can also be added as needed. The produced paste is applied using an applicator such as a dispenser or a screen printer.

  As organic solvents, N, N′-dimethylformamide (DMF), α-terpineol, higher alcohol, γ-butyllactone (γ-BL), tetralin, butyl carbitol acetate, ethyl acetate, isoamyl acetate, diethylene glycol monoethyl ether , Diethylene glycol monoethyl ether acetate, benzyl alcohol, toluene, 3-methoxy-3-methylbutanol, water, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl Ether, tripropylene glycol monobutyl ether, propylene carbonate, dimethyl sulfoxide (DMSO) N- methyl-2-pyrrolidone and the like can be used. In particular, α-terpineol is preferable because it is highly viscous and has good solubility in resins and the like.

  As the resin, acrylic resin, ethyl cellulose, polyethylene glycol derivative, nitrocellulose, polymethylstyrene, polyethylene carbonate, methacrylic acid ester and the like can be used. In particular, acrylic resin and nitrocellulose are preferable because they have good thermal decomposability.

  Hereinafter, the present invention will be described in detail based on examples.

  Tables 1 to 3 show examples (samples a to y) of the bismuth glass composition, and Table 4 shows comparative examples (samples a1 to h1).

  Samples a to y described in Tables 1 to 3 and a1 to h1 described in Table 4 were prepared as follows.

  First, a glass batch prepared by preparing raw materials such as various oxides and carbonates so as to have the glass compositions shown in Tables 1 to 4 was prepared, and this was put in a platinum crucible and melted at 900 to 1000 ° C. for 1 to 2 hours. did. Next, a part of the molten glass was poured into a stainless steel mold as a sample for measuring the coefficient of thermal expansion, and the other molten glass was formed into a thin piece with a water-cooled roller. The sample for measuring the thermal expansion coefficient was subjected to a predetermined slow cooling treatment (annealing) after molding. Finally, the flaky glass was pulverized with a ball mill and then passed through a sieve having an opening of 75 μm to obtain each sample having an average particle size of about 10 μm.

  Using the above samples, the thermal expansion coefficient, glass transition point, softening point, and devitrification state were evaluated. The results are shown in Tables 1-4.

  The softening point was determined by a differential thermal analysis (DTA) apparatus using a powder sample.

  The glass transition point and the thermal expansion coefficient were determined by a push rod type thermal expansion measuring device.

  Samples a to h in Table 1 were evaluated for devitrification by observing crystals in the sample with an optical microscope (magnification 100 times) after holding at the firing temperature in the table for 30 minutes. Samples i to y in Tables 2 and 3 and a1 to h1 in Table 4 were lost by observing crystals in the sample visually using an optical microscope (100 times magnification) after holding at 500 ° C. for 30 minutes. The transparent state was evaluated. The case where no devitrification was observed was indicated as “◯”, the case where slight devitrification was observed was indicated as “Δ”, and the case where clear devitrification was observed was indicated as “X”. In addition, each sample used what dry-pressed the powder of the weight corresponded to the density of each sample to the button shape of outer diameter 20mm with a metal mold | die. The temperature raising / lowering rate was 10 ° C./min.

As apparent from Tables 1 to 3, samples a to y as examples of the present invention have a coefficient of thermal expansion of 105 to 120 × 10 ⁻⁷ / ° C. at 30 to 300 ° C., and a glass transition point of 332 to 320 ° C. The temperature was 373 ° C, and the softening point was 395 to 449 ° C. Furthermore, samples a to w, which are examples of the present invention, had good thermal stability of glass, and evaluation of devitrification was also good.

  As is clear from Table 4, the samples a1 to h1 were inferior in evaluation of the devitrification state.

Next, the sealing material was produced using the glass composition of Tables 1-4. Tables 5 to 7 show examples of bismuth-based sealing materials (sample Nos. 1 to 25), and Table 8 shows comparative examples (samples Nos. 26 to 3 2 ).

  Each sample was prepared by mixing glass powder and refractory filler powder in the proportions shown in Tables 5-8. Willemite or cordierite was used as the refractory filler powder. In the fillers in the table, A represents willemite and B represents cordierite.

Willemite is prepared by blending zinc oxide, optical stone powder and aluminum oxide in a composition of 70% ZnO, 25% SiO _{2 and} 5% Al ₂ O ₃ by weight, and after mixing, firing at 1440 ° C. for 15 hours. Next, the fired product was pulverized and passed through a 250 mesh stainless steel sieve to obtain a powder having an average particle size of 10 μm. Cordierite is prepared by mixing magnesium oxide, aluminum oxide and optical stone powder in a ratio of 2MgO · 2Al ₂ O ₃ · 5SiO ₂ , mixing and firing at 1400 ° C. for 10 hours, and then pulverizing the fired product. A 250 mesh stainless steel sieve was used to obtain an average particle size of 10 μm.

The flow diameter was dry-pressed into a button shape with an outer diameter of 20 mm using a mold and the weight corresponding to the synthesis density of each sample, and this was placed on a 40 mm × 40 mm × 2.8 mm thick high strain point glass substrate. Then, after raising the temperature in air at a rate of 10 ° C./min, after firing under the firing conditions shown in Tables 5 to 8, the temperature is lowered to room temperature at 10 ° C./min, and the diameter of the obtained button is measured. It was evaluated. The synthetic density is a theoretical density calculated by mixing the density of the glass powder and the density of the refractory filler powder at a predetermined volume ratio. Also means that the flow diameter When it is more than 21 mm, excellent fluidity of the sealing material definitive in tested firing conditions.

  The devitrification state was evaluated using an optical microscope (100 times) after holding each sample for 30 minutes at the firing temperature described in Tables 5-8. The temperature raising / lowering rate was 10 ° C./min. As a result, it can be judged that the sample which obtained the evaluation of “◯” in this test is not devitrified by the primary firing.

  Resealability was evaluated as follows. First, each sample and acrylate resin-containing α-terpineol were uniformly kneaded to form a paste, and then linear (80 × 3 × 3 mm) at the end of a high strain point glass substrate (100 × 100 × 3 mm). And dried at 120 ° C. for 15 minutes. Next, the high strain point glass substrate was subjected to the firing temperature described in the table (sample Nos. 1 to 8 are temperatures 10 ° C. higher than the firing temperature in the table), and the time described in the table for the purpose of debinding. After holding, the substrate was allowed to cool in the room. Subsequently, a glass plate having a thickness of 150 μm was placed in the middle of the substrate, and the same size substrate was covered from above, and then both substrates were fixed with clips and baked at 480 ° C. for 30 minutes. The temperature raising / lowering rate was 10 ° C./min.

  Evaluation was made as “◯” when the distance between the substrates was 150 μm after reflowing by firing, and “X” when the distance between the substrates was larger than 150 μm without sufficiently softening and flowing again. In addition, what was "(circle)" by this evaluation had favorable resealability, since the thermal stability of glass was favorable.

As is clear from Tables 5 to 7, sample No. 1 to 25 had a thermal expansion coefficient of 70 to 80 × 10 ⁻⁷ / ° C. at 30 to 300 ° C. Moreover, the flow diameter of 21.0-26.2 mm was shown on the baking conditions shown in the table | surface, and it had favorable fluidity | liquidity. Furthermore, sample no. In Nos. 1 to 25, crystals did not precipitate under the conditions shown in the table, and the resealability was excellent.

  Sample No. Since 1-4 can be sealed at a low temperature of 450-460 ° C., it can be suitably used for applications such as VFD. Sample No. Since 5-25 has favorable thermal stability, it can be used conveniently for uses, such as PDP.

As is apparent from Table 8, sample No. 26-3 2, condition crystals precipitated in shown in the table, was also inferior re sealable. Specifically, Sample No. 26-3 2, the thermal stability of the glass is impaired, crystals are precipitated in the conditions in the table, as a result, re-sealable has been compromised. Sample No. 3 2, contrary to the crystals will deposit at the time of firing, it has also impaired re sealable. Therefore, sample no. 26-3 2, since the thermal stability is poor, is considered to be unsuitable for applications such as PDP.

  The glass composition having the above configuration does not substantially contain PbO and can be fired at a temperature equal to or lower than 480 ° C. equivalent to that of lead borate glass. It has thermal stability and has a very wide temperature range that can be used stably. As a result, it is suitable for sealing VFD or the like that requires low-temperature sealing. Furthermore, the bismuth-based glass composition of the present invention does not precipitate crystals on the glass after the primary firing at a high temperature of 480 ° C. or higher in the PDP manufacturing process, and the secondary firing at 450 to 480 ° C. Crystals do not precipitate on the glass. In particular, even when the primary firing is performed at 500 ° C. or higher, crystals are not precipitated on the glass, and further, the precipitation of crystals does not progress in the subsequent secondary firing. Furthermore, the bismuth-based glass composition of the present invention also has a feature that the softening point is low, and can flow well by secondary firing at 450 to 480 ° C.

  Further, the bismuth-based sealing material having the above-described structure does not substantially contain PbO, and can be fired at a temperature of 480 ° C. or less equivalent to that of the lead boric acid-based sealing material. It has a thermal stability equivalent to or better than that of the sealing material, and the temperature range in which it can be used stably is extremely wide. As a result, it is suitable for sealing VFD or the like that requires low-temperature sealing. Further, in the PDP manufacturing process, crystals are not deposited on the glass after primary firing at a high temperature of 480 ° C. or higher, and crystals are not deposited on the glass even when subjected to secondary firing at 450 to 480 ° C. In particular, even when the primary firing of the bismuth-based sealing material is performed at 500 ° C. or higher, there is a situation in which crystals are precipitated on the glass and further the precipitation of crystals proceeds in the subsequent secondary firing. Absent. Therefore, good fluidity can be ensured by the secondary firing, and the sealing material can be accurately crushed by the secondary firing, so that the airtightness of the PDP can be sufficiently secured. Further, since the bismuth-based sealing material of the present invention has extremely excellent fluidity, the reaction at the interface between the substrate glass and the sealing material also proceeds sufficiently, and the sealing strength between the front substrate and the rear substrate can be extremely increased. it can. As a result, it can greatly contribute to maintaining the long-term reliability of the PDP. That is, since the bismuth-based sealing material of the present invention has excellent thermal stability, it does not cause a decrease in fluidity due to devitrification, and in addition to the low softening point of glass, the sealing material It can be maximized without impairing the original fluidity. In addition, since good fluidity can be obtained in a wide temperature range, it can not only properly deal with other applications, that is, sealing and coating of electronic parts and displays that have undergone multiple heat treatment steps, It is possible to accurately cope with the sealing and covering of electronic parts and displays that have undergone a heat treatment process. Specifically, the bismuth-based sealing material of the present invention is used for sealing a display such as a field emission display (FED) or a cathode ray tube (CRT), for forming an insulating dielectric layer such as a VFD or PDP, or for a barrier rib of a PDP. Suitable for use, sealing of magnetic head-core or core and slider, and sealing of electronic parts such as crystal resonator and IC package.

Claims (10)

Bismuth-based glass composition containing Bi ₂ O ₃ 30 to 60%, B ₂ O ₃ 10 to 35%, Sb ₂ O ₃ 0.01 to 5% in terms of mol% based on the following oxides object. It contains Bi ₂ O ₃ 35-60%, B ₂ O ₃ 10-35%, and Sb ₂ O ₃ 0.1-5% in terms of mol% based on the following oxides. The bismuth-based glass composition described. By mol%, BaO + SrO + MgO + CaO 1~15%, 5~30% ZnO, 0~15% CuO, bismuth glass as claimed in claim 1 or 2, characterized in that it contains Fe ₂ O ₃ 0 to 5% Composition. By mol%, 0.1 to 10% CuO, bismuth glass composition according to any one of claims 1 to 3, characterized in that it contains Fe ₂ O ₃ 0.1~5%.   The bismuth-based glass composition according to any one of claims 1 to 4, which is substantially free of PbO.   In the sealing material containing glass powder and a refractory filler powder, 40-95 volume% of glass powder which consists of a bismuth-type glass composition in any one of Claims 1-5, and refractory filler powder 5-60 volume %. A bismuth-based sealing material characterized by comprising:   In the sealing material containing glass powder and a refractory filler powder, 40-90 volume% of glass powder which consists of a bismuth-type glass composition in any one of Claims 1-5, and refractory filler powder 10-60 volume %. A bismuth-based sealing material characterized by comprising:   The refractory filler powder is one or more refractory filler powders selected from the group consisting of willemite, cordierite, β-eucryptite, zircon, tin oxide, mullite, quartz glass and alumina. The bismuth-based sealing material according to claim 6 or 7.   The bismuth-based sealing material according to any one of claims 6 to 8, which is used for sealing or coating applications.   The bismuth sealing material according to any one of claims 6 to 9, which is used for sealing a fluorescent display tube or a plasma display panel.