GLASS COMPOSITION AND SEALING MATERIAL

Abstract

A glass composition according to an embodiment of the present invention includes, in mol %, from 1 to 20% of B.sub.2O.sub.3, from 30 to 80% of TeO.sub.2, and from 5 to 30% of MoO.sub.3 as glass composition.

Claims

1: A glass composition comprising, in mol %, from 1 to 20% of B.sub.2O.sub.3, from 30 to 80% of TeO.sub.2, and from 5 to 30% of MoO.sub.3 as glass composition.

2: The glass composition according to claim 1, further comprising from 0 to 30 mol % of Li.sub.2O+Na.sub.2O+K.sub.2O.

3: The glass composition according to claim 1, further comprising from 0 to 30 mol % of MgO+CaO+SrO+BaO+ZnO.

4: The glass composition according to claim 1, further comprising from 0 to 10 mol % of TiO.sub.2+Al.sub.2O.sub.3.

5: The glass composition according to claim 1, further comprising, in mol %, from 0 to 30% of CuO, from 0 to 20% of WO.sub.3, from 0 to 10% of P.sub.2O.sub.5, and from 0 to 10 mol % of Fe.sub.2O.sub.3 as glass composition.

6: A sealing material comprising from 40 to 100 volume % of a glass powder including the glass composition according to claim 1, and from 0 to 60 volume % of a refractory filler powder.

7: The sealing material according to claim 6, wherein the refractory filler powder is substantially spherical.

8: The sealing material according to claim 6, wherein the refractory filler powder comprises entirely or partially Zr.sub.2WO.sub.4(PO.sub.4).sub.2.

9: The sealing material according to claim 6 for use in a crystal oscillator package.

10: A sealing material paste comprising the sealing material according to claim 6 and a vehicle.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0019] The FIGURE is a schematic view illustrating a measurement curve to be obtained with a macro-differential thermal analyzer.

DESCRIPTION OF EMBODIMENTS

[0020] A glass composition according to an embodiment of the present invention contains in mol % from 1 to 20% of B.sub.2O.sub.3, from 30 to 80% of TeO.sub.2, and from 5 to 30% of MoO.sub.3 as glass composition. The reason for limiting the glass composition range as described above will be described below. In the description regarding the content of each component, “%” means “mol %” unless otherwise indicated.

[0021] B.sub.2O.sub.3 is a component for forming a glass network. The B.sub.2O.sub.3 content is from 1 to 20%, preferably from 2 to 15%, and more preferably from 4 to 10%. If the B.sub.2O.sub.3 content is too small, weather resistance may likely deteriorate. On the other hand, if the B.sub.2O.sub.3 content is too large, the viscosity (i.e., the softening point) of the glass may increase, low-temperature sealing may become difficult as well as the glass may be prone to phase separation, and vitrification may become difficult.

[0022] TeO.sub.2 is a component for forming a glass network and enhancing weather resistance. The TeO.sub.2 content is from 30 to 80%, preferably from 40 to 70%, and more preferably from 50 to 65%. If the TeO.sub.2 content is too small, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. On the other hand, if the TeO.sub.2 content is too large, the viscosity (i.e., the softening point) of the glass may increase, low-temperature sealing may become difficult as well as the thermal expansion coefficient may tend to be too large.

[0023] MoO.sub.3 is a component for forming a glass network. The MoO.sub.3 content is from 5 to 30%, preferably from 7 to 27%, more preferably from 10 to 25%, even more preferably from 12 to 22%, and particularly preferably from 15 to 20%. If the MoO.sub.3 content is too small, vitrification may become difficult as well as the viscosity (i.e., the softening point) of the glass may increase, and low-temperature sealing may become difficult. On the other hand, if the MoO.sub.3 content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing as well as the thermal expansion coefficient may tend to be too large.

[0024] In addition to the above components, a component below may be introduced.

[0025] Li.sub.2O, Na.sub.2O, and K.sub.2O are components that reduce the viscosity (i.e., the softening point) of the glass. The Li.sub.2O+Na.sub.2O+K.sub.2O content is preferably from 0 to 30%, more preferably from 5 to 25%, and more preferably from 10 to 20%. If the Li.sub.2O+Na.sub.2O+K.sub.2O content is too small, the viscosity (i.e., the softening point) of the glass may increase, and sealing at low temperatures may become difficult. In addition, vitrification may become difficult. On the other hand, if the Li.sub.2O+Na.sub.2O+K.sub.2O content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. In addition, weather resistance may likely deteriorate as well as the thermal expansion coefficient may tend to be too large.

[0026] Li.sub.2O is a component for significantly reducing the viscosity (i.e., the softening point) of the glass compared with Na.sub.2O and K.sub.2O. The Li.sub.2O content is preferably from 0 to 30%, more preferably from 1 to 20%, even more preferably from 3 to 15%, and particularly preferably from 5 to 13%. If the Li.sub.2O content is too small, the viscosity (i.e., the softening point) of the glass may increase, and sealing at low temperatures may become difficult. In addition, vitrification may become difficult. On the other hand, if the Li.sub.2O content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. In addition, weather resistance may likely deteriorate as well as the thermal expansion coefficient may tend to be too large.

[0027] Na.sub.2O is a component for reducing the viscosity (i.e., the softening point) of the glass compared with K.sub.2O. The Na.sub.2O content is preferably from 0 to 20%, more preferably from 0 to 15%, even more preferably from 0 to 10%, and particularly preferably from 1 to 7%. If the Na.sub.2O content is too small, the viscosity (i.e., the softening point) of the glass may increase, and sealing at low temperatures may become difficult. In addition, vitrification may become difficult. On the other hand, if the Na.sub.2O content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. In addition, weather resistance may likely deteriorate as well as the thermal expansion coefficient may tend to be too large.

[0028] K.sub.2O is a component for reducing the viscosity (i.e., the softening point) of the glass. The K.sub.2O content is preferably from 0 to 30%, more preferably from 1 to 20%, even more preferably from 3 to 15%, and particularly preferably from 5 to 13%. If the K.sub.2O content is too small, the viscosity (i.e., the softening point) of the glass may increase, and sealing at low temperatures may become difficult. In addition, vitrification may become difficult. On the other hand, if the K.sub.2O content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. In addition, weather resistance may likely deteriorate as well as the thermal expansion coefficient may tend to be too large.

[0029] To reduce the softening point by the alkali mixing effect, the molar ratio Li.sub.2O/K.sub.2O is preferably from 0.3 to 5, more preferably from 0.4 to 4, from 0.5 to 3, even more preferably from 0.6 to 2, and particularly preferably from 0.7 to 1.5. If the molar ratio Li.sub.2O/K.sub.2O is outside the above range, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. “Li.sub.2O/K.sub.2O” refers to a value obtained by dividing the content of Li.sub.2O by the content of K.sub.2O.

[0030] MgO, CaO, SrO, BaO, and ZnO are components that extend the vitrification range and improve weather resistance. MgO+CaO+SrO+BaO+ZnO is preferably from 1 to 30%, more preferably from 3 to 20%, and even more preferably from 5 to 15%. If the MgO+CaO+SrO+BaO+ZnO content is too small, the viscosity (i.e., the softening point) of the glass may increase, and sealing at low temperatures may become difficult. In addition, vitrification may become difficult. On the other hand, if the MgO+CaO+SrO+BaO+ZnO content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. In addition, weather resistance may likely deteriorate as well as the thermal expansion coefficient may tend to be too large.

[0031] MgO is a component for extending the vitrification range and improving weather resistance. The MgO content is preferably from 0 to 25%, more preferably from 0 to 20%, even more preferably from 0 to 10%, and particularly preferably from 1 to 7%. If the MgO content is small, vitrification may become difficult. In addition, the viscosity (i.e., the softening point) of the glass may increase, and sealing at low temperatures may become difficult. On the other hand, if the MgO content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. In addition, weather resistance may likely deteriorate as well as the thermal expansion coefficient may tend to be too large.

[0032] CaO is a component for extending the vitrification range and improving weather resistance. The CaO content is preferably from 0 to 25%, more preferably from 0 to 20%, even more preferably from 0 to 10%, and particularly preferably from 1 to 7%. If the CaO content is small, vitrification may become difficult. In addition, the viscosity (i.e., the softening point) of the glass may increase, and sealing at low temperatures may become difficult. On the other hand, if the CaO content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. In addition, weather resistance may likely deteriorate as well as the thermal expansion coefficient may tend to be too large.

[0033] SrO is a component for extending the vitrification range and improving weather resistance. The SrO content is preferably from 0 to 25%, more preferably from 0 to 20%, even more preferably from 0 to 10%, and particularly preferably from 1 to 7%. If the SrO content is small, vitrification may become difficult. In addition, the viscosity (i.e., the softening point) of the glass may increase, and sealing at low temperatures may become difficult. On the other hand, if the SrO content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. In addition, weather resistance may likely deteriorate as well as the thermal expansion coefficient may tend to be too large.

[0034] BaO is a component for extending the vitrification range and improving weather resistance. The BaO content is preferably from 0 to 25%, more preferably from 0 to 20%, even more preferably from 0 to 10%, and particularly preferably from 1 to 7%. If the BaO content is small, vitrification may become difficult. In addition, the viscosity (i.e., the softening point) of the glass may increase, and sealing at low temperatures may become difficult. On the other hand, if the BaO content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. In addition, weather resistance may likely deteriorate as well as the thermal expansion coefficient may tend to be too large.

[0035] ZnO is a component for extending the vitrification range and improving weather resistance. The ZnO content is preferably from 0 to 25%, more preferably from 0 to 20%, even more preferably from 0 to 10%, and particularly preferably from 1 to 7%. If the ZnO content is too small, vitrification may become difficult. In addition, the viscosity (i.e., the softening point) of the glass may increase, and low-temperature sealing may become difficult. On the other hand, if the ZnO content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. In addition, weather resistance may likely deteriorate as well as the thermal expansion coefficient may tend to be too large.

[0036] TiO.sub.2 and Al.sub.2O.sub.3 are components for improving weather resistance. The TiO.sub.2+Al.sub.2O.sub.3 content is preferably from 0 to 10%, more preferably from 0.1 to 8%, even more preferably from 1 to 6%, and particularly preferably from 2 to 5%. If the TiO.sub.2+Al.sub.2O.sub.3 content is too large, the viscosity (i.e., the softening point) of the glass may increase, and low-temperature sealing may become difficult.

[0037] Al.sub.2O.sub.3 is a component for improving weather resistance. The Al.sub.2O.sub.3 content is preferably from 0 to 10%, more preferably from 0.1 to 8%, even more preferably from 1 to 6%, and particularly preferably from 2 to 5%. If the Al.sub.2O.sub.3 content is too large, the viscosity (i.e., the softening point) of the glass may increase, and low-temperature sealing may become difficult.

[0038] TiO.sub.2 is a component for improving weather resistance. The TiO.sub.2 content is preferably from 0 to 8%, more preferably from 0.1 to 6%, even more preferably from 1 to 5%, and particularly preferably from 2 to 4%. If the TiO.sub.2 content is too large, the viscosity (i.e., the softening point) of the glass may increase, and low-temperature sealing may become difficult.

[0039] CuO is a component for reducing the viscosity (i.e., the softening point) of the glass and reducing the thermal expansion coefficient. In addition, CuO is a component for increasing adhesion strength of glass and metal in sealing metal. Although the mechanism of increasing the adhesion strength is unknown at present, Cu atoms have high diffusivity and thus diffuse from the surface toward the inside of the metal, and this presumably facilitates the integration of glass and metal. The type of metal to be sealed is not particularly limited, but examples include iron, iron alloys, nickel, nickel alloys, copper, copper alloys, aluminum, and aluminum alloys. The CuO content is preferably from 0 to 30%, more preferably from 0 to 10%, even more preferably from 0.1 to 5%, and particularly preferably from 0.5 to 3%. In addition, the CuO content in sealing metal is preferably from 1 to 30%, more preferably from 1 to 20%, more preferably from 3 to 15%, and particularly preferably from 5 to 10%. If the CuO content is too large, the glass may become thermally unstable, and the metal Cu precipitates from the glass surface in the sealing process. This may adversely affect the sealing strength and electrical properties, and the glass may be prone to devitrification during melting or firing.

[0040] WO.sub.3 is a component for reducing the thermal expansion coefficient. The WO.sub.3 content is preferably from 0 to 20%, from 0.1 to 10%, and particularly from 1 to 5%. If the WO.sub.3 content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing as well as the viscosity (i.e., the softening point) of the glass may increase, and low-temperature sealing may become difficult.

[0041] P.sub.2O.sub.5 is a component for forming a glass network and thermally stabilizing the glass. The P.sub.2O.sub.5 content is preferably from 0 to 10%, more preferably from 0.1 to 5%, even more preferably from 0.2 to 2%, and particularly preferably from 0.5 to 1%. If the P.sub.2O.sub.5 content is too large, the viscosity (i.e., the softening point) of the glass may increase, and low-temperature sealing may become difficult as well as weather resistance may likely deteriorate.

[0042] Fe.sub.2O.sub.3 is a component for increasing reactivity with an object to be sealed. The Fe.sub.2O.sub.3 content is preferably from 0 to 25%, more preferably from 0 to 20%, even more preferably from 0 to 10%, and particularly preferably from 1 to 7%. If the Fe.sub.2O.sub.3 content is too large, vitrification may become difficult as well as the viscosity (i.e., the softening point) of the glass may increase, and low-temperature sealing may become difficult.

[0043] Ag.sub.2O is a component for reducing the viscosity (i.e., the softening point) of the glass. The Ag.sub.2O content is preferably from 0 to 10%, more preferably from 0 to 5%, even more preferably from 0 to 3%, and particularly preferably from 0 to 2%. If the Ag.sub.2O content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing. In addition, metal Ag may precipitate from the glass depending on the firing atmosphere.

[0044] AgI is a component for reducing the viscosity (i.e., the softening point) of the glass. The AgI content is preferably from 0 to 10%, more preferably from 0 to 5%, even more preferably from 0 to 2%, and particularly preferably from 0 to 1%. If the AgI content is too large, the thermal expansion coefficient may tend to be too large.

[0045] Nb.sub.2O.sub.5 is a component for thermally stabilizing the glass and increasing weather resistance. The Nb.sub.2O.sub.5 content is preferably from 0 to 10%, more preferably from 0 to 5%, even more preferably from 0 to 2%, and particularly preferably from 0 to 1%. If the Nb.sub.2O.sub.5 content is too large, the viscosity (i.e., the softening point) of the glass may increase, and low-temperature sealing may likely be difficult.

[0046] V.sub.2O.sub.5 is a component for forming a glass network and reducing the viscosity (i.e., the softening point) of the glass. The V.sub.2O.sub.5 content is preferably from 0 to 10%, more preferably from 0 to 5%, even more preferably from 0 to 3%, and even more preferably from 0 to 2%. If the V.sub.2O.sub.5 content is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing as well as weather resistance may likely deteriorate.

[0047] Ga.sub.2O.sub.3 is a component for thermally stabilizing the glass and increasing weather resistance but is very expensive. Thus, the content is preferably less than 0.01%.

[0048] GeO.sub.2, Nb.sub.2O.sub.5, CeO.sub.2, Sb.sub.2O.sub.3, and La.sub.2O.sub.3 are components that thermally stabilize the glass and prevent devitrification, each of which can be added up to less than 5%. If the content of these is too large, the glass may become thermally unstable, and the glass may be prone to devitrification during melting or firing.

[0049] The glass composition according to an embodiment of the present invention preferably contains substantially no PbO for environmental reasons. Here, “contains substantially no PbO” refers to a case where the PbO content in the glass composition is less than 0.1%.

[0050] A sealing material according to an embodiment of the present invention contains a glass powder including the glass composition described above. The sealing material according to an embodiment of the present invention may contain a refractory filler powder to improve mechanical strength or adjust the thermal expansion coefficient. The mixing ratio is preferably from 40 to 100 volume % of the glass powder and from 0 to 60 volume % of the refractory filler powder, more preferably from 50% to 99 volume % of the glass powder and from 1 to 50 volume % of the refractory filler powder, even more preferably from 60 to 95 volume % of the glass powder and from 5 to 40 volume % of the refractory filler powder, and particularly preferably from 70 to 90 volume % of the glass powder and from 10 to 30 volume % of the refractory filler powder. If the content of the refractory filler powder is too large, the proportion of the glass powder may become relatively small, and thus a desired fluidity may become difficult to ensure.

[0051] The refractory filler powder preferably contains Zr.sub.2WO.sub.4(PO.sub.4).sub.2. Zr.sub.2WO.sub.4(PO.sub.4).sub.2 has properties of hardly reacting with the glass powder according to an embodiment of the present invention and further significantly reducing the thermal expansion coefficient of the sealing material.

[0052] In addition, for the sealing material according to an embodiment of the present invention, a refractory filler powder other than Zr.sub.2WO.sub.4(PO.sub.4).sub.2 can also be used as the refractory filler powder. Examples of such another refractory filler powder include powders made of NbZr(PO.sub.4).sub.3, Zr.sub.2MoO.sub.4(PO.sub.4).sub.2, Hf.sub.2WO.sub.4(PO.sub.4).sub.2, Hf.sub.2MoO.sub.4(PO.sub.4).sub.2, zirconium phosphate, zircon, zirconia, tin oxide, aluminum titanate, quartz, β-spodumene, mullite, titania, quartz glass, β-eucryptite, β-quartz, willemite, cordierite, or Sr.sub.0.5Zr.sub.2(PO.sub.4).sub.3. Such a powder can be used individually, or two or more of such powders can be mixed and used.

[0053] The refractory filler powder is preferably substantially spherical. Such a refractory filler powder is less likely to inhibit the fluidity of the glass powder when the glass powder is softened, resulting in the improvement of the fluidity of the sealing material. In addition, this makes it easier to obtain a smooth glaze layer. Furthermore, even if a portion of the refractory filler powder is exposed to the surface of the glaze layer, the stress of this portion may be dispersed because of the substantially spherical shape of the refractory filler powder. This is less likely to apply improper stress to an object to be sealed and easily ensures airtightness even when the object to be sealed is brought into contact with the glaze layer upon sealing.

[0054] The average particle size D.sub.50 of the refractory filler powder is preferably from 0.2 to 20 μm and particularly preferably from 2 to 15 μm. If the average particle size D.sub.50 is too large, the sealing layer may be likely to become thicker. On the other hand, if the average particle size D.sub.50 is too small, the refractory filler powder may be eluted into the glass during sealing, and the glass may be prone to devitrification.

[0055] In the sealing material according to an embodiment of the present invention, the softening point is preferably 350° C. or lower and particularly preferably 340° C. or lower. If the softening point is too high, the viscosity of the glass may increase, thus the sealing temperature may increase, and the heat during sealing may degrade the element. The lower limit of the softening point is not particularly limited but is realistically 180° C. or higher. Here, the “softening point” refers to a value determined by measuring a sealing material with an average particle size D.sub.50 of 0.5 to 20 μm as a measurement sample with a macro-differential thermal analyzer. The measurement conditions include starting the measurement from room temperature and a rate of temperature increase of 10° C./minute. The softening point measured with a macro-differential thermal analyzer refers to the temperature (Ts) of the fourth inflection point on the measurement curve illustrated in the FIGURE.

[0056] In the sealing material according to an embodiment of the present invention, the thermal expansion coefficient in a temperature range of 30 to 150° C. is preferably from 20×10.sup.−7/° C. to 200×10.sup.−7/° C., more preferably from 30×10.sup.−7/° C. to 160×10.sup.−7/° C., even more preferably from 40×10.sup.−7/° C. to 140×10.sup.−7/° C., and particularly preferably from 50×10.sup.−7/° C. to 120×10.sup.−7/° C. If the thermal expansion coefficient is outside the above range, the thermal expansion difference between the sealing material and a material to be sealed may make the sealing portion easy to break during or after sealing.

[0057] Next, an example of a manufacturing method and a use method of the glass powder and the sealing material according to an embodiment of the present invention will be described.

[0058] First, a raw material powder mixed to give glass composition as desired is melted at 800 to 1000° C. for 1 to 2 hours until homogeneous glass is obtained. Next, the resulting molten glass is formed into a film shape or the like, and then this is ground and classified to produce the glass powder. The average particle size D.sub.50 of the glass powder is preferably approximately from 1 to 20 μm. As necessary, a refractory filler powder of various types is added to and mixed with the glass powder to form the sealing material.

[0059] Next, a vehicle is added to and kneaded with the sealing material to prepare a sealing material paste. The vehicle is mainly made of an organic solvent and a resin, and the resin is added to adjust the viscosity of the paste. In addition, a surfactant, a thickener, or the like can also be added as necessary.

[0060] The organic solvent preferably has a low boiling point (i.e., a boiling point of 300° C. or lower), leaves little residue after firing, and does not deteriorate the glass. The content is preferably from 10 to 40 mass %. Examples of the organic solvent that is preferably used include propylene carbonate, toluene, N,N′-dimethylformamide (DMF), 1,3-dimethyl-2-imidazolidinone (DMI), dimethyl carbonate, butyl carbitol acetate (BCA), isoamyl acetate, dimethyl sulfoxide, acetone, and methyl ethyl ketone. In addition, a higher alcohol is more preferably used as the organic solvent. The higher alcohol itself has viscosity and thus can be formed into a paste without adding any resin to the vehicle. Furthermore, pentanediol and its derivatives, specifically diethylpentanediol (C.sub.9H.sub.20O.sub.2), have excellent viscosity and thus can be used as the solvent.

[0061] The resin preferably has a low decomposition temperature, leaves little residue after firing, and hardly deteriorate the glass. The content is preferably from 0.1 to 20 mass %. Examples of the resin that is preferably used include nitrocellulose, polyethylene glycol derivatives, polyethylene carbonate, and acrylic esters (acrylic resins).

[0062] The sealing material paste is then applied to the sealing portion of an object to be sealed, the object made of metal, ceramic, or glass, using a coating machine, such as a dispenser or a screen printer, dried, and glazed at 300 to 350° C. Another object to be sealed is then brought into contact with and heat-treated at 350 to 400° C. to allow the glass powder to soften and flow, and both are sealed.

[0063] The glass powder according to an embodiment of the present invention can be used for purposes, such as coating or filling, in addition to sealing applications. In addition, the glass powder can also be used in a form other than the paste, specifically such as a powder, a green sheet, or a tablet (a form prepared by sintering the powder material into a given form).

EXAMPLES

[0064] The present invention will be described in detail based on examples. Table 1 illustrates examples of the present invention (Sample Nos. 1 to 10) and comparative examples (Sample Nos. 11 and 12).

TABLE-US-00001 TABLE 1 No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8 No. 9 No. 10 No. 11 No. 12 Glass B.sub.2O.sub.3 4 4 4 4 4 4 10 5 6 3 35 composition TeO.sub.2 62 62 62 62 62 56 59 47 58 67 38 62 (mol %) MoO.sub.3 10 10 10 10 10 10 5 30 9 9 9 13 Li.sub.2O 9 9 9 9 9 10 9 6 10 8 9 8 Na.sub.2O 6 9 9 K.sub.2O 9 9 9 9 9 10 9 6 8 10 MgO 6 CaO 6 4 6 SrO 6 4 BaO 6 ZnO 6 TiO.sub.2 2 2 Al.sub.2O.sub.3 4 CuO 4 WO.sub.3 4 P.sub.2O.sub.5 3 Fe.sub.2O.sub.3 5 Li.sub.2O + Na.sub.2O + K.sub.2O 18 18 18 18 18 20 18 18 18 18 18 17 MgO + CaO + SrO + 6 6 6 6 6 4 4 0 0 0 0 6 BaO + ZnO TiO.sub.2 + Al.sub.2O.sub.3 0 0 0 0 0 6 0 0 0 0 0 2 Refractory filler powder ZWP ZWP NZP ZWP ZWP ZWP ZWP ZWP ZWP NZP Not ZWP (volume %) 20 20 45 20 20 20 20 20 20 40 vitrified 20 Glass transition point (° C.) 277 276 276 273 278 282 297 291 292 287 292 Thermal expansion coefficient 73 73 74 76 76 70 69 72 71 73 71 (×10.sup.−7/° C.) Softening point (° C.) 335 331 330 328 333 347 350 343 344 341 344 Fluidity Good Good Good Good Good Good Good Good Good Good Good Weather resistance Good Good Good Good Good Good Good Good Good Good Poor

[0065] First, a raw material powder mixed to give the glass composition as listed in the table, was placed in a platinum crucible and melted at 800 to 1000° C. in the air for 1 to 2 hours. The molten glass was then formed into a film shape with a water-cooled roller. The film-shaped glass was ground with a ball mill and then passed through a sieve with an opening of 75 μm, and a glass powder with an average particle size D.sub.50 of about 10 μm was obtained.

[0066] The resulting glass powder was then mixed with a refractory filler powder as listed in the table, and a mixed powder was obtained.

[0067] The refractory filler powders used were substantially spherical Zr.sub.2WO.sub.4(PO.sub.4).sub.2, which is denoted as ZWP in the table, and NbZr(PO.sub.4).sub.3, which is denoted as NZP in the table. The average particle size D.sub.50 of the refractory filler powder was about 10 μm.

[0068] Samples Nos. 1 to 12 were evaluated for the glass transition point, thermal expansion coefficient, softening point, fluidity, and weather resistance.

[0069] The thermal expansion coefficient at the glass transition point and a temperature range of 30 to 150° C. was evaluated as follows. First, the mixed powder was placed in a bar-shaped mold, press-molded, and then fired at 380° C. for 10 minutes on an alumina substrate coated with a release agent. Thereafter, the fired body was processed into a predetermined shape and measured with a TMA apparatus.

[0070] The softening point was measured with a macro-differential thermal analyzer, and the fourth inflection point was taken as the softening point. The measurement atmosphere was in the air, the rate of temperature increase was 10° C./min, and the measurement was started from room temperature.

[0071] The fluidity was evaluated as follows. The mixed powder of the mass of the combined density of the mixed powder was placed in a mold with a size of 20 mm, press-molded, and then fired at 380° C. for 10 minutes on a glass substrate. A fired body with a flow diameter of 19 mm or greater was rated as “good”, and a fired body with a flow diameter of less than 19 mm was rated as “poor”.

[0072] The weather resistance was evaluated by an accelerated degradation test according to a pressure cooker test (PCT). Specifically, the fired body produced above was held in an environment at 121° C., 2 atm, and a relative humidity of 100% for 24 hours and then visually observed. A fired body with no precipitate from the surface was rated as “good” and otherwise as “poor”.

[0073] As is clear from the table, sample Nos. 1 to 10 were well evaluated for fluidity and weather resistance. On the other hand, sample No. 11 contained a large amount of B.sub.2O.sub.3 in the glass composition and thus did not vitrify. Sample No. 12 contained no B.sub.2O.sub.3 in the glass composition and thus had poor weather resistance.

INDUSTRIAL APPLICABILITY

[0074] The glass composition according to an embodiment of the present invention is suitable for sealing a crystal oscillator package and in addition, suitable for sealing an airtight package, such as those of a semiconductor integrated circuit, a flat display device, a glass terminal for an LED, and an aluminum nitride substrate. In addition, the glass composition can also be used as a sealing material for metal.