KR20080025020A - Sealing material - Google Patents

Abstract

A sealing material is provided to show improved thermal stability and flowability, and to improve grain size and coefficient of heat expansion of a refractory filler powder, thereby preventing generation of slow leak. A sealing material comprises bismuth-based glass powder and refractory filler powder, wherein the refractory filler powder has an average particle diameter(D50) of 9-24 micrometers, a 90% particle diameter(D90) of 32-90 micrometers and a relative thermal expansion coefficient of -35 x 10^-7/deg.C to 15 x 10^-7/deg.C. In the sealing material, the bismuth-based glass powder comprises 67-90% of Bi2O3, 2-12% of B2O3, 0-5% of Al2O3, 1-20% of ZnO, 0-10% of BaO, 0-5% of CuO, 0-2% of Fe2O3, 0-5% of CeO2 and 0-5% of Sb2O3 based on the calculated mass of oxide, and the refractory filler powder comprises cordierite powder.

Description

Sealing Material {SEALING MATERIAL}

The present invention relates to a sealing material suitable for electronic parts, flat panel display devices, and the like. In particular, the present invention relates to a sealing material which is preferable for a plasma display panel (PDP).

Conventionally, glass is used as sealing material, such as a flat panel display. Glass is excellent in chemical durability and heat resistance as compared with resin-based adhesives, and is suitable for securing airtightness such as flat panel displays.

These glasses require various properties such as mechanical strength, fluidity, electrical insulation, etc., depending on the application, but they are required to be usable at a temperature that does not deteriorate the fluorescent property of the phosphor used for at least a flat panel display or the like. For this reason, lead boric acid-based glass having a large effect of lowering the melting point of glass has been widely used as glass that satisfies the above characteristics. (See Patent Document 1).

By the way, the environmental problem is pointed out about PbO contained in lead-boric-acid glass in recent years, and it is anticipated that it will replace with PbO-containing glass from lead-boric-acid glass. Therefore, as a substitute for lead boric acid-based glass, various low melting glass have been developed. Among them, bismuth-based glass (Bi ₂ O ₃ -B ₂ O ₃ -based glass) described in Patent Document 2 and the like has substantially the same properties as lead boric acid-based glass in various properties such as coefficient of thermal expansion, and as an alternative candidate thereof. Although it is expected, it is a fact that it still falls short of lead boric acid type glass in the characteristics, such as fluidity | liquidity and thermal stability.

Incidentally, the sealing material is generally a composite material containing glass powder and refractory filler powder, and conventionally low expansion lead titanate or the like has been used as the refractory filler powder. However, similarly to the case of glass, lead titanate etc. are also expected to be replaced by the refractory filler which does not contain PbO. For example, Patent Document 3 discloses a sealing material containing 50 to 95% by volume of lead-free low melting point glass powder and 5 to 50% by volume of zirconium tungsten phosphate powder, and using zirconium tungstate phosphate as the refractory filler powder. Is disclosed.

By the way, the sealing material used for the PDP which is a flat panel display device goes through the following heat processing processes. First, the sealing material dispersed in a vehicle is apply | coated to the outer peripheral edge part of the back glass substrate of PDP, and primary baking (also called a glazing process and a temporary baking process) is performed by pyrolyzing or incineration of a vehicle component at high temperature. The vehicle for uniformly dispersing the sealing material contains an organic solvent, a resin and the like. Generally, nitrocellulose, an acrylic resin, etc. which thermally decompose well at the temperature below the softening point of glass are used. The sealing material and the vehicle are processed into a paste by kneading uniformly using a kneading apparatus such as three roll mills. Primary baking is performed on the temperature conditions which resin decomposes completely. In primary firing, for example, when the thermal decomposition of the resin is incomplete, residues of the resin remain in the glass in the secondary firing (also referred to as the sealing step and the sealing step) provided thereafter, and as a result, PDP such as devitrification or air bubbles in the glass. Fatal defects are likely to occur in order to ensure the confidentiality of the device. Next, after aligning the front glass substrate and the back glass substrate, secondary firing of the sealing material is performed to seal the front glass substrate and the back glass substrate. In the same manner, after fixing the exhaust pipe on the rear glass substrate, secondary firing of the sealing material (usually press frit rather than the paste material) is performed to seal the rear glass substrate and the exhaust pipe. Finally, after evacuating the inside of the PDP through the exhaust pipe, the required amount of rare gas is injected to seal the exhaust pipe. In this way, a PDP is produced.

[Patent Document 1] Japanese Patent Application Laid-Open No. 63-315536

[Patent Document 2] Japanese Patent Application Laid-Open No. 2003-095697

[Patent Document 3] Japanese Patent Application Laid-Open No. 2005-35840

As a sealing material used for flat display devices, such as a PDP, the composite material of glass powder and a refractory filler powder is used for the purpose of matching a thermal expansion coefficient and improving a mechanical strength. In order to improve the thermal stability of the sealing material, it is of course effective to improve the thermal stability of the glass itself. However, since the sealing material is a composite material of the glass powder and the refractory powder, it is also important to suppress the devitrification of the glass due to the refractory filler. .

However, many attempts have been made to improve the glass composition as a means of improving the thermal stability of the sealing material. However, attempts to improve the refractory filler, in particular, restrict the particle size of the refractory filler powder to an appropriate range to improve the thermal stability of the sealing material. Attempts are rarely made. As described above, since bismuth-based glass has a problem in thermal stability, there is a great advantage in improving the thermal stability of the sealing material at the point of time regarding the particle size of the refractory filler powder. In addition, in the bismuth-based glass, when the content of Bi ₂ O _{3 in} the glass composition is large, for example, when the content of Bi ₂ O ₃ is 76% by mass or more, the content of components other than Bi ₂ O ₃ is relatively decreased, thereby improving the glass composition. Since there is insufficient space, it is thought that improving the particle size of the refractory filler powder is meaningful.

When the particle size of the refractory filler powder is specifically explained, if the particle size of the refractory filler powder is fine, the refractory filler powder is easily dissolved in the glass during firing, and since the melting point of the refractory filler is usually higher than the melting point of the glass, The softening point of the sealing material rises, resulting in difficulty in low temperature sealing. In addition, when the refractory filler powder is dissolved in the glass, there is a fear that the thermal stability of the sealing material deteriorates when the compatibility of the refractory filler powder and the glass is poor. On the other hand, when the particle size of the refractory filler powder is increased, the amount of dissolution of the refractory filler powder during firing can be reduced. However, microcracks tend to occur in the sealing layer, making it difficult to secure the airtightness in the flat panel display device.

Accordingly, the present invention improves the particle size and coefficient of thermal expansion of the refractory filler powder, improves the thermal stability of the sealing material and improves the fluidity of the sealing material in the sealing material containing the bismuth-based glass powder and the refractory filler powder. Therefore, it is a technical problem to obtain a flat display device in which a slow leak or the like is unlikely to occur.

The present inventors have sought results example, bismuth in the sealing material containing a glass powder and the refractory filler powder, the mean particle size D ₅₀ of the refractory filler powder 9~24㎛, 32~90㎛ the 90% particle diameter D ₉₀ The present invention seeks to solve the above technical problem by regulating to and propose as the present invention. That is, the sealing material of the present invention is a bismuth-based according to the sealing material containing a glass powder and the refractory filler powder, the mean particle size D ₅₀ of the refractory filler powder 9~24㎛, 90% particle size D ₉₀ 32~90㎛ It is characterized by that. In addition, "Bismuth-based glass" according to the present invention, the content of Bi ₂ O ₃ in the glass composition indicates the glass not less than 20% by weight. In addition, "average particle diameter D _50", "90% particle diameter D _90" refers to a value measured by a laser diffraction method. In addition, the mean particle size D ₅₀ is the particle size of the amount of the accumulated grains is 50%, and 90% particle diameter D ₉₀ is the particle size of the amount of the accumulated grains is 90%.

When the average particle diameter D ₅₀ of the refractory filler powder is regulated to 9 to 24 µm, the proportion of the fine powder component of the refractory filler powder can be reduced. Part of the refractory filler powder (surface layer portion of the refractory filler powder) is known to dissolve in the glass when the sealing material is fired. However, when the proportion of the fine powder component of the refractory filler powder is small, the amount of the refractory filler powder to be dissolved decreases. The devitrification of the glass resulting from the fusion of the filler powder can be suppressed, and as a result, the thermal stability of the sealing material can be maintained. In addition, if the average particle diameter D ₅₀ of the refractory filler powder is regulated, the amount of dissolution of the refractory filler powder at the time of baking becomes small, so that the rise of the softening point of the sealing material can be suppressed, and the fluidity of the sealing material is maintained. That is, by regulating the average particle diameter D ₅₀ of the refractory filler powder, the low temperature sealing property of the sealing material can be maintained.

By regulating the 90% particle diameter D ₉₀ of the refractory filler powder to 32 to ₉₀ µm, the coefficient of thermal expansion and fluidity of the sealing material can be adjusted, and the probability of occurrence of microcracks in the sealing layer after firing can be reduced. That is, since the sealing material of this invention contains a predetermined amount or more of coarse particle | grains in a refractory filler powder, the situation which microcracks generate | occur | produce in the sealing layer after baking can be avoided, while aggravating the effect of the thermal expansion coefficient of a refractory filler powder. . When the 90% particle size D ₉₀ of the refractory filler powder is regulated to 32 to ₉₀ µm, the proportion of the fine component of the refractory filler powder can be reduced. When the ratio of the fine powder component of the refractory filler powder is small, the amount of dissolution of the refractory filler powder is reduced, so that the glass can be devitrified due to the fusion of the refractory filler powder, and as a result, the thermal stability of the sealing material can be maintained. have. The conventional sealing material is not considered about 90% particle diameter D ₉₀ of a refractory filler powder, and it is thought that the effect of restricting the average particle diameter D ₉₀ of a refractory filler powder to 32-90 micrometers is large.

When the average particle diameter D ₅₀ of the refractory filler powder is ₉ to 24 µm, in order to regulate the 90% particle diameter D ₉₀ of the refractory filler powder to 32 to ₉₀ µm, for example, the refractory filler powder is classified by a sieve such as 350 mesh. Then, a method of adding a certain amount of coarse particles (for example, about 50 µm) or a method of collecting a refractory filler powder that passes through a 150 mesh sieve and does not pass through a 500 mesh sieve may be employed.

In addition, the sealing material of this invention uses bismuth type glass powder as glass powder. When bismuth-based glass is used, the softening point of the glass can be lowered even if PbO is not contained in the glass composition, thereby satisfying the recent environmental requirements.

Secondly, the sealing material of the present invention is characterized in that the relative thermal expansion coefficient of the refractory filler powder is from -35 x 10 ^-7 / 캜 to 15 x 10 ^-7 / 캜. The calculation method of the "relative thermal expansion coefficient of a refractory filler powder" said by this invention is as showing below. The relative coefficient of thermal expansion (αf) of the refractory filler powder is αg as the thermal expansion coefficient of bismuth glass, Vg as the volume ratio of the bismuth glass powder, Vf as the volume ratio of the refractory filler powder, and α as the thermal expansion coefficient of the sealing material. It points out the value computed from the relationship of (alpha) xVg + (alpha) x * Vf = (alpha). That is, the relative thermal expansion coefficient (alpha) f of a refractory filler powder points out the value computed by the relational formula of (alpha) f = ((alpha)-(alpha) -gxVg) / Vf. In addition, (alpha), (alpha) g shows the thermal expansion coefficient in the temperature range of 30-250 degreeC, and points out the value measured by the well-known pressure-type thermal expansion coefficient measurement (TMA) apparatus. Vg and Vf can be easily calculated if the mixing ratio and density of the bismuth-based glass powder and the refractory filler powder are clear. Vg and Vf can be easily calculated by separating the refractory filler powder from the sealing material even if the mixing ratio of the bismuth-based glass powder and the refractory filler powder is unclear. For example, if the refractory filler powder is separated by dissolving the bismuth-based glass powder in a hydrochloric acid solution or the like, and then the mass and density of the refractory filler powder are measured, the volume ratio of the bismuth-based glass powder and the refractory filler powder can be easily calculated. have.

Here, the relative coefficient of thermal expansion of the refractory filler powder serves as an index of the effect of lowering the coefficient of thermal expansion of the refractory filler powder in the sealing material, and the smaller the value, the greater the effect of lowering the coefficient of thermal expansion of the refractory filler powder. In addition, the coefficient of thermal expansion inherent to the refractory filler is an index different from the relative coefficient of thermal expansion of the refractory filler powder because no factor such as particle size distribution of the refractory filler powder is added.

In the sealing material of the present invention, when the relative coefficient of thermal expansion of the refractory filler powder is regulated to -35 × 10 ⁻⁷ / ° C. to 15 × 10 ⁻⁷ / ° C., the microcracks are formed in the sealing layer after firing while improving the fluidity of the sealing material. This occurrence can be avoided. If the relative thermal expansion coefficient of a refractory filler powder is the said range, even if content of a refractory filler powder is reduced, the thermal expansion coefficient of a sealing material can be reduced to a predetermined range. In other words, if the relative coefficient of thermal expansion of the refractory filler powder is within the above range, the coefficient of thermal expansion of the sealing material does not unduly rise even if the content of the glass powder, which is flux, is increased, and as a result, the fluidity of the sealing material can be improved. In addition, if the content of the refractory filler powder can be reduced, the amount of dissolution of the refractory filler powder during firing also decreases, so that the thermal stability of the sealing material can be improved.

Third, the sealing material of the present invention is characterized in that the relative thermal expansion coefficient of the refractory filler powder is from -35 x 10 ^-7 / 캜 to 10 x 10 ^-7 / 캜.

Fourthly, the sealing material of the present invention is characterized in that the refractory filler powder contains cordierite powder.

Fifthly, in the sealing material of the present invention, the bismuth-based glass powder is represented by the glass composition in terms of mass% of the following oxides in terms of Bi ₂ O ₃ 67 to 90%, B ₂ O _{3 2 to} 12%, and Al ₂ O ₃ 0 to 5 %, ZnO 1-20%, BaO 0-10%, CuO 0-5%, Fe ₂ O ₃ 0-2%, CeO ₂ 0-5%, Sb ₂ O ₃ 0-5% Lose.

Sixth, the sealing material of this invention is characterized by containing 40 to 95% of glass powder and 5 to 60% of fire-resistant filler powder by volume% display.

Seventh, the sealing material of the present invention is characterized by being substantially free of PbO. Here, "substantially free of PbO" as used in the present invention refers to the case where the PbO content contained in the sealing material is 1000 ppm or less.

Eighth, the sealing material of this invention is characterized by using for sealing a PDP.

In the ninth, the sealing material of the present invention is a sealing material containing a bismuth-based glass powder and the refractory filler powder, the mean particle size D ₅₀ of the refractory filler powder 9~24㎛, also the relative coefficient of thermal expansion of the refractory filler powder to be ^{-35 × 10 -7 / ℃ ~15 ×} 10 -7 / ℃ characterized.

Th column, the sealing material of the present invention is bismuth in the sealing material containing a glass powder and the refractory filler powder, the relative coefficient of thermal expansion α _1, the refractory filler in the case where the mean particle size D ₅₀ of the refractory filler powder to 8㎛ When the relative coefficient of thermal expansion when the average particle diameter D ₅₀ of the powder is 18 μm is α ₂ , the refractory filler powder is 10 × 10 ⁻⁷ / ° C. ≦ (α ₁ −α ₂ ) ≦ 30 × 10 ⁻⁷ / It is characterized by having a relationship of degrees Celsius. In addition, although surprisingly, according to the calculation of the α ₁ and α ₂ other than the condition relating to the average particle diameter D ₅₀ of the refractory filler is the same.

Eleventh, the press pleat of the present invention is characterized in that in the press pleat obtained by sintering the sealing material into a predetermined shape, the sealing material is the above sealing material.

Twelfth, the PDP of the present invention is characterized by being sealed with the sealing material.

In the sealing material of the present invention, the average particle diameter D ₅₀ of the refractory filler powder is 9 to 24 µm, preferably 9.8 to 20 µm, more preferably 10 to 17 µm, still more preferably 11 to 16 µm. If the average particle diameter D ₅₀ of the refractory filler powder is smaller than 9 µm, the thermal stability of the sealing material is lowered when the bismuth-based glass powder and the refractory filler powder have poor phase properties due to excessive dissolution of the refractory filler powder during firing. It becomes easy to be. If the average particle diameter D ₅₀ of the refractory filler powder is smaller than 9 µm, the amount of dissolution of the refractory filler powder at the time of firing is excessive, the softening point of the sealing material is unreasonably raised, and it is difficult to seal at low temperatures. On the other hand, when the average particle diameter D ₅₀ of the refractory filler powder is larger than 24 µm, the proportion of coarse components of the refractory filler powder is relatively excessively large, and microcracks and the like are likely to occur in the sealing layer after firing, which is slow to a flat display device or the like. Leaks tend to occur. In addition, when the average particle diameter D ₅₀ of the refractory filler powder is larger than 24 μm, when the average particle diameter D ₅₀ of the bismuth-based glass powder is smaller, it becomes difficult to uniformly mix the bismuth-based glass powder and the refractory filler powder. When the bismuth-based glass powder and the refractory filler powder are easily separated, the life of the paste material (so-called pot life) is shortened.

In the sealing material of the present invention, the 90% particle diameter D ₉₀ of the refractory filler powder is 32 to ₉₀ µm, preferably 40 to 85 µm, more preferably 42 to 78 µm. When the 90% particle diameter D ₉₀ of the refractory filler powder is smaller than 32 µm, the proportion of coarse components of the refractory filler powder is too small, and the effect of lowering the coefficient of thermal expansion of the refractory filler powder is insufficient. When the 90% particle diameter D ₉₀ of the refractory filler powder is larger than ₉₀ µm, the probability of microcracks occurring in the sealing layer after firing increases, making it difficult to secure the airtight reliability of a flat panel display or the like.

In the sealing material of the present invention, the relative coefficient of thermal expansion of the refractory filler powder is ^{-35 × 10 -7 / ℃ ~15 ×} 10 -7 / ℃ is ^{preferably, -35 × 10 -7 / ℃ ~10} × 10 -7 / ℃ it is more preferred, and even more preferably ^{-30 × 10 -7 / ℃ ~4 ×} 10 -7 / ℃. If the relative thermal expansion coefficient of the refractory filler powder is smaller than -35 x 10 ^-7 / deg. C, the probability that microcracks will occur in the sealing layer after firing increases, and there is a possibility that the airtight reliability of a flat panel display or the like cannot be ensured. If the relative thermal expansion coefficient of the refractory filler powder is larger than 15 × 10 ⁻⁷ / ° C., the effect of lowering the thermal expansion coefficient of the refractory filler powder is insufficient. If the relative coefficient of thermal expansion of the refractory filler powder is within the above range, the coefficient of thermal expansion of the sealing material can be maintained within a predetermined range even if the content of the refractory filler powder is reduced. In other words, the content of the bismuth type glass powder which is a flux can be increased as much as content of a refractory filler powder can be reduced, and as a result, the fluidity | liquidity of a sealing material can be improved. In addition, when the content of the refractory filler powder is reduced, the amount of dissolution of the refractory filler powder during firing also decreases, so that the thermal stability of the sealing material can be improved.

Since high waejeom glass ^{(85 × 10 -7 / ℃)} , soda glass plate (90 × 10 ^-7 / ℃) When the sealing or the like, bismuth-based glass powder alone does not match the coefficient of thermal expansion thereof, the bismuth-based glass It is necessary to mix powder and fire-resistant filler powder to make a composite material, and to make it a sealing material. It is important to design the thermal expansion coefficient of the encapsulation material as low as 10-30 × 10 ^-7 / ℃ for the encapsulated material. This is to prevent the breakage of the sealing layer by placing the stress acting on the sealing layer on the compression (compression) side. In addition to adjusting the coefficient of thermal expansion, for example, a refractory filler powder may be added for the purpose of improving the mechanical strength.

1 is data showing the characteristics of the refractory filler powder (the relationship between the coefficient of thermal expansion of the sealing material and the average particle diameter D ₅₀ of the refractory filler powder). Here, FIG. 1 uses the sealing material which mixed bismuth type glass powder and cordierite powder in the ratio of 67.5 volume%: 32.5 volume%, and the thermal expansion coefficient ((alpha)) of glass is 103x10 <^-7> / degreeC to be. As is apparent from FIG. 1, as the average particle diameter D ₅₀ of the refractory filler powder increases, the coefficient of thermal expansion of the sealing material decreases. Further, it can be seen from FIG. 1 that when the grain size of the refractory filler powder is coarsened, the relative coefficient of thermal expansion of the refractory filler powder decreases. The cordierite powder of FIG. 1 was produced by solid-state reaction. Here, the method of producing a refractory filler powder by solid-state reaction is a method of manufacturing a fire resistant filler powder by combining solid raw materials, such as an oxide, so that it may become a predetermined composition, after baking this, pulverizing and classifying the obtained fired body. . In addition, when the grain boundary of the cordierite powder is observed, it can be easily determined that the cordierite powder is produced by the solid phase reaction.

When mixing refractory filler powder, it is preferable that the mixing ratio is 40 to 95 volume% of bismuth type glass powder, 5 to 60 volume% of fire resistant filler powder, 40 to 90 volume% of bismuth type glass powder, and a fire resistant filler powder It is more preferable that it is 10 to 60 volume%, and it is still more preferable that the bismuth type glass powder is 60 to 80 volume% and the fire resistant filler powder 20 to 40 volume%. The reason for defining both ratios in this way is that when the refractory filler powder is less than 5% by volume, the effect of adding the refractory filler powder is difficult to obtain, and when more than 60% by volume, the fluidity of the encapsulating material is deteriorated and the flat display device is used. Because it becomes difficult to seal.

In the sealing material of the present invention, both the glass and the crystal can be used for the refractory filler powder. Crystals are preferable because they have a great effect of lowering the coefficient of thermal expansion of the sealing material and can improve the mechanical strength of the sealing material.

In the sealing material of the present invention, the refractory filler powder is cordierite, willemite, tin oxide, alumina, zircon, zirconia, zirconium phosphate, β-quartz solid solution, zinc petalite, β-eucryptite Powder, such as gahnite, is preferable. These refractory filler powders are preferred because they not only have a large effect of lowering the coefficient of thermal expansion, but also have good compatibility with bismuth-based glass and are unlikely to impair the thermal stability of the sealing material. In addition, refractory filler powders other than the refractory filler powder having the composition (for example, tin oxide, zirconia, zircon, alumina, etc.) may be suitably added within the range of not impairing the properties in order to increase the mechanical strength and the like of the sealing material. Can be.

Since cordierite powder has good compatibility with bismuth-based glass, even if cordierite is dissolved in the glass during firing, crystals having Bi ₂ O ₃ as a constituent are less likely to precipitate. In addition, cordierite powder has a property of being easily fused to bismuth-based glass at the time of firing, compared to other refractory filler powders, but since the present invention strictly regulates the particle size of the refractory filler powder, the refractory filler powder is cordierite. Even in this case, the effect of the present invention (in particular, the effect of reducing the amount of dissolution of the refractory filler powder during firing) can be obtained.

In addition, when the refractory filler powder is coated with fine powder such as alumina, zinc oxide, zircon, titania, zirconia, the reaction between the bismuth-based glass powder and the refractory filler powder can be adjusted. Therefore, when the refractory filler powder is coated with fine powder such as alumina, zinc oxide, zircon, titania, zirconia, thermal stability, fluidity and the like of the sealing material can be controlled.

Bismuth-based glass has properties equivalent to lead boric acid-based glass in various properties, and can also meet recent environmental requirements. Particularly, as a glass composition, in terms of mass% in terms of the following oxides, Bi ₂ O ₃ 67 to 90%, B ₂ O _{3 2 to} 12%, Al ₂ O ₃ 0 to 5%, ZnO 1 to 20%, BaO 0 to 10 The bismuth-based glass containing%, CuO 0-5%, Fe ₂ O ₃ 0-2%, CeO ₂ 0-5%, and Sb ₂ O ₃ 0-5% has good thermal stability and low temperature sealing. It is suitable for sealing PDP etc. as much as possible.

Patent Document 2 discloses a bismuth-based glass that can be used for applications such as sealing of electronic components and coating. However, this bismuth type glass has a high softening point compared with the glass containing PbO, and lacks the fluidity | liquidity of glass. Moreover, this bismuth type glass is insufficient in the thermal stability of glass, and cannot be applied to the use through several heat processing processes. In order to lower the softening point of glass, it is necessary to increase the content of Bi ₂ O ₃ , which is a main component, but when the content of Bi ₂ O ₃ is increased, crystals containing Bi ₂ O ₃ as constituents are easily precipitated during firing. The fluidity of the glass is likely to be impaired. Therefore, only by simply to increase the content of Bi ₂ O _3, it is difficult to improve the fluidity of the glass. On the other hand, when the content of Bi ₂ O ₃ is reduced, the thermal stability of the glass is improved, but the softening point is increased, thereby impairing the fluidity of the glass. In view of the above, it seems to be difficult to achieve both the thermal stability and fluidity of the glass in bismuth-based glass. By the way, when the glass composition range of bismuth type glass is regulated as mentioned above, the thermal stability and fluidity of glass can be made compatible at a high level.

In the sealing material of this invention, the reason which limited the glass composition range of bismuth type glass powder as mentioned above is shown below.

Bi ₂ O ₃ is the main component to lower the softening point. The content is 67 to 90%, preferably 70 to 89%, more preferably 72 to 88%, still more preferably 76 to 86%. When the content of Bi ₂ O ₃ is less than 67%, the softening point of the glass becomes too high, making it difficult to seal at low temperature below 500 ° C. On the other hand, when the content of Bi ₂ O ₃ is more than 90%, the glass becomes thermally unstable, and the glass is easily devitrified at the time of melting or baking.

Bi ₂ O ₃ is a component for forming a glass network, the bismuth-based glass and is an essential component. The content is 2 to 12%, preferably 3 to 10%, more preferably 4 to 10%, still more preferably 5 to 9%. When the content of Bi ₂ O ₃ is less than 2%, the glass becomes thermally unstable, and the glass is easily devitrified at the time of melting or firing. On the other hand, when the content of Bi ₂ O ₃ is more than 12%, the viscosity of the glass becomes too high, and it becomes difficult to seal at a low temperature of 500 ° C or lower.

Al ₂ O ₃ is a component that improves the weather resistance of the glass. The content is 0 to 5%, Preferably it is 0 to 2%. When the content of Al ₂ O ₃ is more than 5%, the softening point of the glass becomes too high, making it difficult to seal at a low temperature of 500 ° C or lower.

SiO ₂ is a component that improves weather resistance of glass. The content is 0 to 10%, preferably 0 to 3%. If the content of SiO ₂ is more than 10% high and the softening point of glass becomes too difficult to sealing at a low temperature of less than 500 ℃.

ZnO has the effect of suppressing the devitrification of glass at the time of melting or baking. The content is 1 to 20%, preferably 3 to 18%, more preferably 4 to 17%, still more preferably 5 to 15%. When the content of ZnO is less than 1%, the effect of suppressing the devitrification of the glass at the time of melting or baking becomes difficult. When the content of ZnO is more than 20%, the balance in the glass composition is broken, conversely, the thermal stability of the glass is impaired, and as a result, the glass is likely to devitrify.

BaO, SrO, MgO, and CaO are components that have an effect of suppressing devitrification of glass at the time of melting or firing. These components can be contained in a glass composition up to 15% in total amount. When the total amount of these components is more than 15%, the softening point of glass becomes too high and it becomes difficult to seal at low temperature below 500 degreeC.

0-10% is preferable and, as for content of BaO, 0-8% is more preferable. When the content of BaO is more than 10%, the balance in the glass composition is broken, conversely, the thermal stability of the glass is impaired, and as a result, the glass is likely to devitrify. Moreover, it is preferable to make content of BaO into 1% or more from a viewpoint of improving the thermal stability of glass.

0-5% is preferable and, as for each content of SrO, MgO, CaO, 0-2% is more preferable. When content of each component is more than 5%, glass will become devitrification or powdering.

CuO has the effect of suppressing the devitrification of glass at the time of melting or baking, and can be added up to 5%. When content of CuO is more than 5%, glass will deviate easily and the fluidity | liquidity of glass will fall easily. Moreover, it is preferable to add a trace amount of CuO from a viewpoint of improving the thermal stability of glass, and it is preferable to make content of CuO specifically 0.01% or more.

Fe ₂ O ₃ has the effect of suppressing devitrification of the glass at the time of melting or firing, and the content thereof is preferably 0 to 2%, more preferably 0 to 1.5%. When the content of Fe ₂ O ₃ is more than 2%, the balance in the glass composition is broken, conversely, the thermal stability of the glass is impaired, and as a result, the glass is easily devitrified. Also preferable to add a trace amount of Fe ₂ O ₃ from the viewpoint of improving the thermal stability of the glass, and specifically, it is preferable that the content of Fe ₂ O ₃ 0.01% or more.

CeO ₂ has an effect of suppressing devitrification of glass at the time of melting or firing, and the content thereof is 0 to 5%, preferably 0 to 2%, and more preferably 0 to 1%. When the content of CeO ₂ is more than 5%, the glass is easily devitrified and the fluidity of the glass is easily damaged. Also preferable to add a small amount of CeO ₂ in terms of improving the thermal stability of the glass, and specifically, it is preferable that the content of CeO ₂ 0.01% or more.

Sb ₂ O ₃ is a component for inhibiting the devitrification of the glass, the content thereof is 0 to 5%, preferably 0 to 2%, more preferably 0-1%. Sb ₂ O ₃ has an effect of stabilizing the network structure of bismuth-based glass, and when Sb ₂ O ₃ is appropriately added in bismuth-based glass, when the content of Bi ₂ O ₃ is large, for example, Bi ₂ O ₃ Even if content is 76% or more, the thermal stability of glass will become difficult to fall. However, when the content of Sb ₂ O ₃ is more than 5%, the balance in the glass composition is broken, conversely, the thermal stability of the glass is impaired, and as a result, the glass is likely to devitrify. Also preferable to add a trace amount of Sb ₂ O ₃ from the viewpoint of improving the thermal stability of the glass, and specifically, it is preferable that the content of Sb ₂ O ₃ less than 0.05%.

WO ₃ is a component for suppressing devitrification of glass, the content of which is preferably from 0 to 10%, more preferably from 0 to 2%. In the bismuth-based glass tends to lower the softening point of the glass is determined to precipitate from the glass at the time when the need to increase the content of Bi ₂ O _3, more when the content of Bi ₂ O _3, but the firing, the flowability of the sealing material Tend to be inhibited. In particular, when the content of Bi ₂ O ₃ is large, for example, when the content of Bi ₂ O ₃ is 76% or more, the tendency becomes remarkable. However, in the bismuth-based glass, when WO ₃ is appropriately added, even if the content of Bi ₂ O ₃ is 76% or more, the thermal stability of the glass is less likely to be lowered. However, when the content of WO ₃ is more than 10%, the balance in the glass composition is broken, conversely, the thermal stability of the glass is impaired, and as a result, the glass is easily devitrified.

_{In 2 O 3, Ga 2 O} 3 is an essential component, but, a component for inhibiting the devitrification of the glass, the content of 0 to 5% is preferred, and the total amount, more preferably 0-3%. In ₂ O ₃ and Ga ₂ O ₃ have an effect of stabilizing the network structure of bismuth-based glass, and the content of Bi ₂ O ₃ is increased by appropriately adding In ₂ O ₃ and Ga ₂ O ₃ in bismuth-based glass. a high volume, e.g., O when the content of Bi ₂ O ₃ more than 76% also makes it difficult to decrease the thermal stability of the glass. However, when the content of In ₂ O ₃ and Ga ₂ O ₃ is more than 5% in total, the balance in the glass composition is broken, and consequently, the thermal stability of the glass is impaired. As a result, the glass is easily devitrified. The content of In ₂ O ₃ is more preferably 0 to 1%, and more preferably 0 to 0.5% of the content of Ga ₂ O ₃ .

Oxides of Li, Na, K and Cs are components which lower the softening point of the glass, but are preferably 2% or less in total amount because they have a function of promoting the devitrification of the glass during melting.

P ₂ O ₅ is a component, but to inhibit the devitrification of the glass during the melting, it is not preferable since the amount added is liable to phase separation when the glass melt much less than 1%.

MoO ₃ , La ₂ O ₃ , Y ₂ O ₃ and Gd ₂ O ₃ are components which suppress the powder phase of the glass at the time of melting, but when the total amount of these is more than 3%, the softening point of the glass becomes too high and the temperature is below 500 ° C. It becomes difficult to fire.

Moreover, even another component can be added in glass composition to 15% (preferably 5%) in the range which does not impair the characteristic of glass.

Bismuth type glass which has the above glass composition is amorphous glass which shows favorable fluidity at the temperature of 500 degrees C or less, and the thermal expansion coefficient in 30-250 degreeC is about 100-120x10 <^-7> / degreeC.

Although the sealing material of this invention does not exclude the form containing PbO, As mentioned above, it is preferable that it does not contain PbO substantially for environmental reasons. Moreover, when PbO is contained in a glass composition, Pb2 ⁺ which exists in glass may diffuse and may reduce the electrical insulation of a sealing material.

The sealing material of the present invention contains bismuth-based glass powder and refractory filler powder, and the relative coefficient of thermal expansion when the average particle diameter D ₅₀ of the refractory filler powder is 8 μm is α ₁ and the average particle diameter D ₅₀ of the refractory filler powder. When the relative coefficient of thermal expansion in the case of 18 μm is α ₂ , 10 × 10 ⁻⁷ / ° C. ≦ (α ₁ -α ₂ ) ≦ 30 × 10 ⁻⁷ / ° C., preferably 15 × 10 ⁻⁷ / It is preferable to select a fire resistant filler having a relationship of 占? (? _1- ? ₂ )? 25 × 10 ⁻⁷ / ° C. The refractory filler having a value of (α ₁ -α ₂ ) of less than 10 × 10 ⁻⁷ / ° C., even if the particle size of the refractory filler powder is increased, makes it difficult to lower the coefficient of thermal expansion of the encapsulating material and thus the coefficient of thermal expansion of the encapsulating material in a predetermined range. It is difficult to improve the fluidity of the sealing material while maintaining the temperature. When the refractory filler having a value of (α ₁ -α ₂ ) is larger than 30 × 10 ⁻⁷ / ° C., microcracks are likely to occur in the sealing layer after firing, which makes it difficult to secure airtight reliability such as a flat panel display. .

It is preferable to use the sealing material of this invention for sealing an electronic component. Electronic components may use members (for example, IC elements and conductive adhesives) whose properties deteriorate at high temperatures. In that sense, the sealing material of the present invention can be sealed at a low temperature, so that the sealing material can be sealed without deteriorating the characteristics of the member having insufficient heat resistance. In addition, the sealing material of the present invention is preferably used for sealing flat display devices. If the flat display device can be sealed at a low temperature as much as possible, the manufacturing efficiency can be improved by that amount, and the deterioration of characteristics of other members such as phosphors can be prevented. In view of the above, the sealing material of the present invention can be sealed at a low temperature, so that the sealing material can be suitably used for flat panel display devices. In addition, in order to simplify the manufacturing process, even if the flat display device is sealed at a high temperature (for example, 500 to 530 ° C), since the sealing material of the present invention has excellent thermal stability, glass cannot be devitrified and a desired sealing strength can be secured. Can be.

It is preferable to use the sealing material of this invention for sealing PDP. In the manufacturing process of a PDP, in order to improve manufacturing efficiency, primary baking of a fluorescent material and a sealing material may be performed simultaneously. When the primary firing temperatures of both materials are compared, the primary firing temperature of the phosphor material is generally higher, and is about 480 to 500 ° C. Therefore, when the thermal stability of the sealing material is low, when the primary firing of the phosphor material and the sealing material is performed at the same time, the glass will deviate, and the fluidity of the sealing material is impaired in the subsequent secondary firing (450 to 500 ° C.), thereby PDP. There is a fear that confidentiality of the product cannot be secured. In this regard, the sealing material of the present invention is difficult to precipitate crystals even when the first firing is performed at about 500 ° C. in the manufacturing process of the PDP, and flows satisfactorily at the secondary firing at 450 to 500 ° C., without impairing the reliability of the PDP. In addition, the manufacturing efficiency of the PDP can be improved.

It is preferable to seal the PDP of this invention with said sealing material. In the manufacturing process of the PDP, the sealing material hardly precipitates even when the first firing is performed at about 500 ° C, and flows well in the secondary firing at 450 to 500 ° C. Therefore, the use of the sealing material can easily improve the manufacturing efficiency and reliability of the PDP.

Although the sealing material containing bismuth type glass powder and fire-resistant filler powder may be used as a sealing material as a powder, when sealing material and vehicle are knead | mixed uniformly and used as a paste material, it is easy to handle. The vehicle mainly consists 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 prepared paste is applied onto the object to be sealed using an applicator such as a dispenser or a screen printer.

As an organic solvent, N, N'- dimethylformamide (DMF), (alpha)-terpineol, a higher alcohol, (gamma)-butyl lactone ((gamma) -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 mono Methyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, propylene carbonate, dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone, etc. can be used. In particular, α-terpineol is preferred because of its high viscosity and good solubility such as resin.

As the resin, acrylic resin, ethyl cellulose, polyethylene glycol derivatives, nitrocellulose, polymethylstyrene, polyethylene carbonate, methacrylic acid ester and the like can be used. In particular, acrylic resins and nitrocelluloses are preferred because of their good thermal decomposition.

The sealing material of the present invention is preferably sintered into a predetermined shape to form a press pleat. Since the press pleat of the present invention is produced by sintering the above sealing material, it has good fluidity and thermal stability, and is suitable for fixing the exhaust pipe of a PDP and the like. Specifically, since the press pleats are sintered in a predetermined shape, it is easy to connect the exhaust pipe to the exhaust facility when the exhaust pipe is attached, and the inclination of the exhaust pipe can be reduced with respect to the back glass substrate, that is, the exhaust pipe with respect to the panel surface. Can be attached vertically, and can be attached so as to maintain airtightness while maintaining the light emitting capability of the PDP.

It is preferable that the press pleat of this invention is ring-shaped. In this way, the exhaust pipe can be easily inserted into the opening of the press pleat, the front end of the exhaust pipe can be easily fitted to the exhaust hole of the rear glass substrate, and it is easy to fix with a pressing member such as a clip. In addition, when the press pleat is fired at a predetermined sealing temperature, the press pleat softens and flows so that the exhaust pipe can be attached to the panel.

The press pleats of the present invention are produced separately through a plurality of heat treatment steps as follows. First, a binder and a solvent are added to a sealing material, and a slurry is formed. Then, this slurry is thrown into granulation apparatuses, such as a spray dryer, and granules are produced. At that time, the granules are heat treated at a temperature (about 100 to 200 ° C) at which the solvent is volatilized. In addition, the produced granules are put into a mold designed to predetermined dimensions, and are dry press-molded in a ring shape to produce a press body. Next, a press pleat is produced by decomposing and volatilizing the binder remaining in the press body in a firing furnace such as a belt furnace and firing at a temperature of about the softening point of glass. In addition, baking in a kiln may be performed in multiple times. When firing is performed a plurality of times, the strength of the press pleats is improved, and it is possible to effectively prevent defects or breakage of the press pleats. Moreover, since the press flit of this invention has favorable thermal stability, even if baking is performed multiple times in the vicinity of the softening point of glass, it is hard to see devitrification on glass.

EXAMPLE

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail based on an Example.

First, bismuth type glass is demonstrated. Each sample a-n of Tables 1-3 was prepared as follows.

First, the glass batch which combined raw materials, such as various oxides and carbonates, was prepared so that it might become the glass composition shown in Tables 1-3, it put into a platinum crucible and melted at 900-1000 degreeC for 1-2 hours. Next, a part of molten glass was flowed to the metal mold | die made as a sample for TMA, and the other molten glass was shape | molded in flake shape by the water cooling roller. In addition, the TMA sample was subjected to predetermined slow cooling treatment (annealing) after molding. Finally, after crushing the flake-shaped glass by a ball mill, each sample having an average particle diameter of about 10 µm was obtained by passing through a sieve having a mesh size of 75 µm.

The thermal expansion coefficient, glass transition point, and devitrification state were evaluated using the above sample. The results are shown in Tables 1-3.

The glass transition point and the coefficient of thermal expansion were obtained by TMA apparatus. The thermal expansion coefficient was measured in the temperature range of 30-250 degreeC.

The samples a to n of Tables 1 to 3 were subjected to an evaluation of the devitrification state by visually observing the surface crystals of the samples using an optical microscope (100x magnification) after maintaining the powder compact in a firing furnace at 500 ° C for 30 minutes. "(Circle)" that the devitrification was not confirmed at all was made into "x" that the devitrification was confirmed. In addition, the temperature increase / speed rate was 10 degreeC / min.

Each sample a-1 of Tables 1-3, and the predetermined | prescribed refractory filler powder in the table were mixed, and the sealing material shown in Tables 4-7 was obtained. Sample Nos. 1 to 12 of Tables 4 to 6 show examples of the present invention, and Sample Nos. 13 to 17 of Table 7 show comparative examples of the present invention. The coefficients of thermal expansion, the flow diameter and the devitrification state were evaluated for Sample Nos. In addition, the coefficient of thermal expansion and the devitrification state were measured in the same manner as in the case of the glass sample, and the average particle diameter D ₅₀ and the 90% particle diameter D ₉₀ of the refractory filler powder were SALD-2000J (manufactured by Shimadzu Corporation). Was measured.

Table 4-7 (Example 3, 9, excluding 12) in coordination with the light, and a combination such that the magnesium oxide, aluminum oxide, silicon oxide in a molar ratio of _{2MgO · 2Al 2 O 3 · 5SiO} 2, mix After that, the product was baked at 1400 ° C. for 10 hours, and then the fired product was ground to obtain a powder having a predetermined particle size. Examples 3, 9, 12 in coordination with the light as the molar ratio 2MgO · 2Al ₂ O ₃ · 10 hours to fire the composition of the glass powder having a mean particle size D ₅₀ of the 20㎛ 5SiO ₂ at 1400 ℃ and crystallized glass Subsequently, this fired product was pulverized to obtain a powder having a predetermined particle size. Moreover, the alumina fine powder was coated on the surface of the glass powder so that glass powders might not sinter at the time of baking. Willemite is combined with zinc oxide, silicon oxide, and aluminum oxide in a mass% of 70% ZnO, 25% SiO ₂ , and 5% Al ₂ O ₃ , and after mixing, calcining at 1440 ° C. for 15 hours, and then calcining Water was pulverized to obtain a powder having a predetermined particle size. The zircon powder is soda-decomposed natural zircon sand, dissolved in hydrochloric acid, and concentrated crystallization is repeated to make zirconium oxychloride having very little α-emitting substance U or Th, and after alkali neutralization, heating to purify the purified ZrO ₂ . To this, high purity silica powder and ferric oxide were combined in a mass ratio of 66% ZrO ₂ , 32% SiO ₂ , and ₂ % Fe ₂ O ₃ , mixed, and then fired at 1400 ° C. for 16 hours. Grinding in an alumina ball mill yielded a powder having a predetermined particle size. β- quartz solid solution is SiO ₂ 46.5% by weight, Al ₂ O ₃ 23.3% by mass, mixing the batch (batch) component such that 23.3% by weight ZnO, ZrO ₂ 6.9% by mass, followed by melting at 1550 ℃ 3 hours. Subsequently, after crushing molten glass, predetermined crystal nuclei were added, and the baked material obtained after baking at 900 degreeC for 2 hours was grind | pulverized, and the powder which has a predetermined particle size was obtained. Zirconium phosphate is ZrOC ₁₂ · 8H ₂ O were mixed in a predetermined molar ratio of the aqueous solution of phosphoric acid, followed by shattering of the fired product obtained after baking the resulting precipitate at 1400 ℃ to obtain a powder having a desired particle size of the. Moreover, in order to obtain the fire-resistant filler powder which has a predetermined particle size, the mesh size of the sieve was changed suitably and classification of several times was performed.

As for the flow diameter, the powder of the mass corresponding to the synthesis density of each sample is dry-pressed by the metal mold | die in the button shape of 20 mm outside diameter, and this is a high distortion glass substrate (Nippon Denki Glass Co., Ltd.) of 40 mm x 40 mm x 2.8 mm thickness. The diameter of the button obtained by loading on Kakae PP-8C), heating up in air at a speed | rate of 5 degree-C / min, baking at the baking conditions of Tables 4-6, and then lowering to 5 degree-C / min to room temperature It evaluated by measuring. In addition, a synthetic density is a theoretical density computed by mixing the density of glass and the density of a refractory filler in a predetermined volume ratio. In addition, when the flow diameter is 19 mm or more, it means that it can be sealed in the baking conditions tested.

Micro crack was evaluated using the sample of the button shape provided for the measurement of a flow diameter. The surface of the button-shaped sample was observed with a stereo microscope (200 times), and it evaluated that "(circle)" and the thing which generate | occur | produced "x" that the microcracks did not generate | occur | produce on the button surface.

Substrate cracks were evaluated using a button-shaped sample provided for the measurement of the flow diameter. The high-distortion glass substrate located below the button-shaped sample was observed with a microscope or strain indicator, and it was observed that cracks did not appear on the high-distortion glass substrate, and that cracks occurred. Evaluated.

Sample Nos. 1 to 12 of Tables 4 to 6 had a coefficient of thermal expansion of 60.0 to 72.5 × 10 ⁻⁷ / ° C., and had a coefficient of thermal expansion suitable for high strain glass or the like. Further, Sample Nos. 1 to 12 had a flow diameter of 20.0 to 21.5 mm under the firing conditions in the table, were sealed at a temperature of 500 ° C. or lower, and had low melting point characteristics suitable for sealing such as PDP. In addition, the samples Nos. 1 to 12 have good evaluation of the devitrification state, good thermal stability, no micro cracks or cracks in the glass substrate, and it is considered that airtightness such as a flat panel display device can be ensured.

Samples Nos. 13 to 17 in Table 7 have a coefficient of thermal expansion of 60.0 to 73.0 × 10 ⁻⁷ / ° C., and a flow diameter of 19.0 (ex. No. 15 is devitrified) to 21.5 mm under predetermined firing conditions in the table. It was. However, samples No. 13 and 14 did not regulate the 90% particle size D ₉₀ to a predetermined range, so microcracks occurred on the button surface. Since Sample No. 15 did not regulate the average particle diameter D ₅₀ and 90% particle diameter D ₉₀ in a predetermined range, evaluation of the devitrification state was poor. Since Sample No. 16 did not regulate the average particle diameter D ₅₀ and 90% particle diameter D ₉₀ to a predetermined range, a crack occurred in the glass substrate. Since Sample No. 17 did not regulate the average particle diameter D ₅₀ and 90% particle diameter D ₉₀ to a predetermined range, evaluation of the devitrification state was poor, micro cracks occurred on the button surface, and cracks also occurred on the glass substrate. .

The sealing material of the present invention is suitable for sealing electronic components such as quartz crystal oscillators and IC packages, sealing applications for flat panel displays such as PDPs and field emission displays (FEDs), and sealing applications for displays such as cathode ray tubes (CRTs). Do.

1 is data showing the characteristics of the refractory filler powder (the relationship between the coefficient of thermal expansion of the sealing material and the average particle diameter D ₅₀ of the refractory filler powder).

Claims (12)

In the sealing material containing bismuth type glass powder and fire-resistant filler powder, The sealing material characterized in that the average particle diameter D ₅₀ of the refractory filler powder is 9 to 24 µm, and the 90% particle diameter D ₉₀ is 32 to ₉₀ µm. The sealing material according to claim 1, wherein the relative thermal expansion coefficient of the refractory filler powder is from -35x10 ^-7 / ° C to 15x10 ^-7 / ° C. The sealing material according to claim 1, wherein the relative thermal expansion coefficient of the refractory filler powder is from -35x10 ^-7 / ° C to 10x10 ^-7 / ° C. The sealing material according to any one of claims 1 to 3, wherein the refractory filler powder contains cordierite powder. Claim 1 to claim 4 according to any one of claims, wherein said bismuth-based glass powder is a glass composition, to 67~90% Bi ₂ O ₃ as shown in terms of oxides by _{mass%, B 2 O 3 2~12%} , Al ₂ O ₃ 0-5%, ZnO 1-20%, BaO 0-10%, CuO 0-5%, Fe ₂ O ₃ 0-2%, CeO ₂ 0-5%, Sb ₂ O ₃ 0-5 Sealing material, characterized in that it contains%. The sealing material according to any one of claims 1 to 5, wherein the sealing material contains 40 to 95% of bismuth-based glass powder and 5 to 60% of a refractory filler powder in a volume% display.  The sealing material according to any one of claims 1 to 6, which is substantially free of PbO. The sealing material according to any one of claims 1 to 7, which is used for sealing a plasma display panel. In the sealing material containing bismuth type glass powder and fire-resistant filler powder, The sealing material characterized in that the average particle diameter D ₅₀ of the refractory filler powder is 9 to 24 µm, and the relative thermal expansion coefficient of the refractory filler powder is -35 × 10 ⁻⁷ / ° C. to 15 × 10 ⁻⁷ / ° C. In the sealing material containing bismuth type glass powder and fire-resistant filler powder, If the relative thermal expansion coefficients in the case where the relative thermal expansion coefficients in the case where the mean particle size D ₅₀ of the refractory filler powder to 8㎛ the α _1, the mean particle size D ₅₀ of the refractory filler powder to 18㎛ by α _2, the refractory Sealing material characterized in that the filler powder has a relationship of 10 × 10 ⁻⁷ / ° C. ≦ (α ₁ −α ₂ ) ≦ 30 × 10 ⁻⁷ / ° C. In a press pleat in which a sealing material is sintered to a predetermined shape, The said sealing material is a sealing material of any one of Claims 1-10, The press pleat characterized by the above-mentioned. It sealed with the sealing material in any one of Claims 1-10, The plasma display panel characterized by the above-mentioned.