JP2007204328A - Lead-free low melting glass material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead-free low melting glass composition which is free of lead, can be subjected to working such as sealing or sintering/shaping at a low temperature, and has practical performance sufficient to substitute for lead-based glass. <P>SOLUTION: The lead-free low melting glass material contains, as main components, oxides comprising Li<SB>2</SB>B<SB>4</SB>O<SB>7</SB>and at least one of ZnO and BaO. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electronic tube, a fluorescent display tube, a fluorescent display panel, a plasma display panel, a backlight panel for a liquid crystal display, a sealing process for openings and joints of various electronic parts and electrical products such as semiconductor packages, and a high vacuum portion. The present invention relates to a lead-free glass material used for sintering molding such as partition walls and electrode surrounding parts.

  Generally, a low-melting glass material is used for sealing and sintering molding of various electronic parts and electrical products that are used with a high vacuum inside. This low-melting glass material is made of low-melting glass powder, and this powder is pasted with an organic binder solution, applied to the portion to be sealed of the article to be sealed, and fired in an electric furnace or the like, thereby producing a vehicle. The component is volatilized to form a continuous glass layer in which the glass powder is fused.

Conventionally, PbO—B ₂ O ₃ -based lead glass powder has been widely used as such a low-melting glass material. That is, lead glass can be processed at a low temperature and in a wide temperature range due to the low melting point and high meltability of PbO, and also has low thermal expansion, and is excellent in adhesion, adhesion, chemical stability, and the like. There is an advantage that high sealing performance, fusion strength, and durability can be obtained. However, since lead is a toxic substance, there are problems with occupational safety and health in the manufacturing process of lead-based glass, and when electronic parts and electrical products using lead-based glass reach the end of their life, they are discarded as they are. As a result, there are concerns about soil contamination and groundwater contamination due to elution of lead, but there are significant restrictions on usage because it contains lead even if it is recycled. .

Therefore, in recent years, the development of lead-free low-melting glass materials that are free from toxic problems has been widely promoted. Then, it has already been reported many compositions of lead-free glass material, the patent art, for example, P ₂ O ₅ -ZnO- alkali metal oxide (Patent Document _{1), P 2 O 5 -WO} 3 - alkali metal oxide Physical system (Patent Document 2), SnO—P ₂ O ₅ —ZnO system (Patent Document 3), CuO—P ₂ O ₅ system (Patent Document 4), SnO—P ₂ O ₅ —B ₂ O ₃ system (Patent Document 3) Document 5), Bi ₂ O ₃ —B ₂ O ₃ —SiO ₂ —Al ₂ O ₃ —CeO system (Patent Document 6), Bi ₂ O ₃ —B ₂ O ₃ —ZnO system (Patent Document 7), SnO— P ₂ O ₅ —Cl system (Patent Document 8), B ₂ O ₃ —ZnO—BaO—SnO system (Patent Document 9), B ₂ O ₃ —ZnO—BaO—Na ₂ O system (Patent Document 10), SiO 2 ₂ -B ₂ O ₃ -ZnO-BaO- alkali metal oxide (Patent Document _{11), B 2 O 3 -Bi} 2 O 3 -BaO -based (JP Permissible documents 12) have been proposed.
JP-A-5-132339 Japanese Patent Laid-Open No. 9-208259 JP 2001-302279 A JP 2001-199740 A JP 2003-183050 A JP 2003-54987 A JP 2003-128430 A JP 2004-59366 A JP 2005-15280 A Japanese Patent Laid-Open No. 2005-47778 JP-A-2005-147572 JP-A-2005-231923

  However, these proposed lead-free glass materials do not have low melting, low thermal expansion, adhesiveness, sealing properties, and chemical durability comparable to lead-based glass materials. Can not be completely replaced.

  In view of the above-mentioned circumstances, the present invention has a practical performance that can be processed at a very low temperature as a low-melting lead-free glass material and can be sufficiently substituted for lead-based glass, and has already been described above. It aims at providing the thing without a problem like a system low-melting glass material.

  In order to achieve the above object, the inventors of the present invention have proposed that the glass constituent component is a network-forming oxide that forms a three-dimensional network structure, which is the basic skeleton of glass, and has no glass-forming ability alone, but a three-dimensional network. A network-modified oxide that penetrates into the structure and affects the glass properties, and has no glass-forming ability by itself, but replaces part of the network-forming oxide to participate in network formation, and also plays a role as a network-modified oxide Attention was paid to the classification into three types of intermediate oxides that can be achieved. In order to investigate the suitability as a glass material for processing with a composition that does not substantially contain lead, various combinations of the above-mentioned three kinds of oxides belonging to each of these functional components have been set. Various physicochemical properties were evaluated, and studies were made from various angles.

As a result, Li ₂ B ₄ O ₇ as a network-forming oxide, ZnO as a component replacing PbO of a lead-based glass material as an intermediate oxide or network-modifying oxide, and BaO as a network-modifying oxide, respectively. By selecting and using a glass material containing these oxides as a basic component, that is, a Li ₂ B ₄ O ₇ —ZnO—BaO-based glass material, it has been found that particularly suitable performance can be obtained as a low-melting lead-free glass material, It came to make this invention.

That is, the low-melting lead-free glass material according to claim 1 of the present invention is mainly composed of an oxide composed of Li ₂ B ₄ O ₇ and at least one of ZnO and BaO.

The invention of claim 2 is the low fusible lead-free glass material of the first aspect, and Li ₂ B ₄ O ₇ 20 to 85 mol%, and 0 to 50 mol% of ZnO, 0 to 65 mol% It is set as the structure containing this BaO.

The invention of claim 3 is the low-melting lead-free glass material of claim 1, wherein 20 to 40 mol% Li ₂ B ₄ O ₇ , 10 to 40 mol% ZnO, and 40 to 60 mol% BaO. It is set as the structure containing these.

According to the first aspect of the present invention, the low-melting lead-free glass material is Li ₂ B ₄ O ₇ —ZnO—BaO-based, and has no toxicity problem as in the lead-based glass material, and is sealed at a low temperature. In addition to being able to process and sinter-mold, it has low thermal expansion, excellent adhesion and sealing properties, good chemical durability, and sufficient practical performance that can replace lead-based glass materials. In addition, since the color tone is white, it can be preferably applied to the white barrier ribs (ribs) and the white dielectric layer in the plasma display panel, and the color can be easily adjusted by blending the pigment.

According to the second aspect of the present invention, Li ₂ B ₄ O ₇ , ZnO and BaO are present in a specific molar ratio range as the low-melting lead-free glass material. Provided is a material having a point of 475 ° C. or lower, a softening point of 490 ° C. or lower, and capable of reliably processing at a low temperature of 550 ° C. or lower.

According to the invention of claim 3, as the low-melting lead-free glass material, Li ₂ B ₄ O ₇ , ZnO and BaO are in a more preferable molar ratio range, so that the glass transition point is 380 ° C. or less, softening A material having a point of around 400 ° C. and capable of reliably processing at a very low temperature of 450 ° C. or less is provided.

The low-melting lead-free glass material according to the present invention basically has a Li ₂ B ₄ O ₇ —ZnO—BaO-based glass composition, but is an intermediate oxide or network-modified oxide ZnO and a network-modified oxide. This includes a composition in which one of BaO is omitted, that is, a binary system of Li ₂ B ₄ O ₇ —ZnO and a binary system of Li ₂ B ₄ O ₇ —BaO. In any composition, there is no problem of toxicity as in lead-based glass, and a glass transition point [Tg] is 500 ° C. or lower, and further 400 ° C. or lower is possible. Processing such as sinter molding can be performed at a low temperature, the thermal influence on the workpiece can be reduced, and the consumption of thermal energy can be reduced.

  In addition, this lead-free glass material has a small coefficient of thermal expansion, and it is easy to adapt the thermal expansion characteristics with the part to be processed. In addition, the surface of the workpiece made of glass, ceramic, metal, etc. Because it provides excellent adhesion and adhesion, it is difficult for peeling and cracks to occur in the processed part, and the chemical stability and strength of the glass layer after processing are excellent. It becomes good. Furthermore, since the color tone of the glass layer after processing exhibits white, it can be preferably applied to the white partition walls (ribs) and the white dielectric layer in the plasma display panel, and toning by blending of pigments is facilitated.

Thus, in this Li ₂ B ₄ O ₇ —ZnO—BaO-based lead-free glass material, 20 to 85 mol% Li ₂ B ₄ O ₇ , 0 to 50 mol% ZnO, and 0 to 60 mol% A glass composition containing BaO and containing at least one of ZnO and BaO as an essential component is preferable. In such a glass composition, as shown in the sealing test of Examples described later, a good glass state is obtained by melting, the softening point [Tf] is 490 ° C. or less, and the glass transition point [Tg] is 475 ° C. Therefore, processing at a low temperature of 550 ° C. or less can be performed reliably, and the glass recovery rate, that is, the yield of glass by melting from the oxide powder as a raw material can be as good as about 80% or more.

Furthermore, more suitable lead-free glass material, include a Li ₂ B ₄ O ₇ 20 to 40 mol%, 10 to 40 mol% of ZnO, those glass composition consisting of 40 to 60 mol% of BaO It is done. That is, in such a glass composition, the softening point is around 400 ° C., the glass transition point is 380 ° C. or lower, and processing at a very low temperature such as 450 ° C. or lower can be reliably performed.

The network-forming oxide Li ₂ B ₄ O ₇ is a composite oxide of lithium and boron. As Li ₂ O · 2B ₂ O ₃ , 1 mol of Li ₂ O and ₂ mol of B ₂ O ₃ It corresponds to the compound of However, Li ₂ B ₄ O ₇ molar ratio between Li ₂ O and B ₂ O ₃ in place of the 1: If used in a proportion of 2, the lead-free glass material of the present invention using Li ₂ B ₄ O ₇ In comparison, it has been found that the thermal stability (ΔT = crystallization start temperature Tx−glass transition point Tg) is lowered and that the glass layer after processing becomes brown.

  In order to produce the low-melting lead-free glass material of the present invention, a powder mixture of raw materials is put into a container such as a platinum crucible, and this is baked and melted for a predetermined time in a heating furnace such as an electric furnace to be vitrified. The melt may be poured into an appropriate formwork such as an alumina boat and cooled, and the obtained glass block may be pulverized to an appropriate particle size by a pulverizer. The particle size of the glass powder is preferably in the range of 0.05 to 100 μm, and the coarse particles by the pulverization may be classified and removed.

  In addition, such a low-melting lead-free glass material may be used alone when subjected to processing such as sealing and sintering modeling, but in particular, when three-dimensionally placing and sintering modeling, glass powder is used. It is preferable to use in the form of a mixture in which fillers such as fillers and aggregates are mixed as a sintering base material. In such a mixture form, the low-melting glass material functions as a binder for binding the filler particles to each other, so that three-dimensional shaping can be easily performed, and a high-strength and dense ceramic sintered body can be obtained. . In addition, since this glass material melts to become colorless and transparent glass, the sintered body can be set to a highly light-reflective white by blending filler and aggregate, and the light extraction effect when used in the light emitting part There is also an advantage that it can be enlarged.

  The filler is not particularly limited as long as it has a higher melting point than the low-melting lead-free glass material and does not melt at the firing temperature during processing. For example, zirconium silicate, cordierite, zirconyl phosphate, β -Powders such as eucryptate, β-spodumene, zircon, alumina, mullite, silica, β-quartz solid solution, zinc silicate, and aluminum titanate are suitable. Therefore, the blending amount of these fillers should be in the range of about 95/5 to 55/45 in terms of the weight ratio of low-melting lead-free glass material / filler, and if it is too much, the binding force due to the glass composition is insufficient. Thus, a strong sintered body cannot be formed.

  Furthermore, various pigments can be blended in the low-melting lead-free glass material of the present invention and the mixture obtained by mixing the glass material with the filler as necessary. Since this lead-free glass material melts and exhibits a white color as described above, it is easy to adjust the color by blending the pigment.

  The powder of the low-melting lead-free glass material of the present invention, and the mixed powder obtained by mixing the filler and the pigment with the powder are filled in a molding die in the form of powder in the sintering molding and pressure-molded, and the molded product obtained May be placed and fired at the required part of the work piece, but in general, the paste is made by dispersing the powder in an organic binder solution at a high concentration, and this is applied or placed on the required part of the work piece. Since it is used for baking, it may be commercialized as a paste form in advance.

  The organic binder solution used for the paste is not particularly limited, but for example, cellulose binders such as nitrocellulose and ethyl cellulose, pine oil, butyl diglycol acetate, aromatic hydrocarbon solvents, mixed solvents such as thinner, etc. And those obtained by dissolving an acrylic resin binder in solvents such as ketones, esters and low-boiling aromatics. Therefore, the viscosity of the paste is preferably in the range of 100 to 2000 dPa · s from the viewpoint of coating workability.

  In the sealing process, the above paste is applied to the sealed portion of the article to be sealed, and the article is baked in a heating furnace such as an electric furnace to melt and integrate the glass powder to form a sealed glass layer. May be formed. Thus, this firing can be performed once, but in order to improve the sealing quality, it is preferable to perform the firing in two stages of temporary firing and main firing. That is, in the two-stage baking, first, a paste of a lead-free glass material for sealing is applied to the sealed portion of the article to be sealed, and this coated article is softened by the softening point [Tf of the lead-free glass contained in the paste. ] Preliminary firing in the vicinity causes the vehicle components (binder and solvent) of the paste to be volatilized and thermally decomposed to leave only the glass component, and then the firing is performed near the crystallization start temperature [Tx] of the lead-free glass. A sealing glass layer in which the glass components are completely melted and integrated is formed.

  According to such two-stage firing, the vehicle components are volatilized and removed at the preliminary firing stage, and the glass components are fused to each other in the main firing. Therefore, there is a pinhole due to bubbles or deaeration in the sealing glass layer. Can be prevented, and thus the reliability of sealing and the strength of the sealing portion can be increased. Also, if the article to be sealed is one that joins multiple members by sealing, such as a vacuum package, or is sealed and fixed with electrodes, lead wires, exhaust pipes, etc. in the sealed part, before assembly After performing the preliminary firing for each member, the member taken out from the heating furnace is assembled into a product form, and the main firing is performed in this assembled state.

  A particularly preferable temperature range for the pre-baking is the softening point [Tf] -10 ° C. to + 40 ° C., and a particularly preferable temperature range for the main baking is a crystallization start temperature [Tx] -20 ° C. to + 50 ° C. Further, in the pre-baking, it is preferable to set a moderate temperature increase rate in order to surely remove bubbles generated in the layer from the room temperature. It is preferably about 0.1 to 10 ° C./minute from about the glass transition point [Tg] to the softening point [Tf]. On the other hand, in the main firing, it is preferable that the temperature is raised from room temperature to around the crystallization start temperature [Tx] at about 0.1 to 50 ° C./min and kept constant near the crystallization start temperature [Tx].

There are no particular restrictions on the object to be processed with the low-melting lead-free glass material of the present invention. Openings and joints of parts and electrical products, and high-vacuum partition walls and electrode enclosures are used for sintered molding. The present invention is particularly like a vacuum package that has a high vacuum of 10 ⁻⁶ Torr or more inside. It is excellent in applicability to sealed articles that require a high degree of sealing performance.

  Hereinafter, the present invention will be specifically described by way of examples. In addition, all the raw material oxides used in the following are special grade reagents manufactured by Wako Pure Chemical Industries, and the special grade reagents were similarly used for the other analysis reagents and the like.

[Manufacture of lead-free glass]
A mixture of Li ₂ B ₄ O ₇ powder, ZnO powder, and BaO powder as raw material oxides in the proportions (mol%) described in Table 1 and Table 2 (total amount 15 g) is placed in a platinum crucible and placed in an electric furnace. After baking at about 1000 ° C. for 60 minutes, the melt is poured into an alumina port to prepare a glass bar. After cooling in the air, the glass bar is pulverized in an automatic mortar, and the pulverized product is classified. Samples having a particle size of 100 μm or less were collected to produce lead-free glass materials G1 to G41.

  For the lead-free glass materials G1 to G41 produced in the above examples, the glass recovery rate, glass transition point [Tg], softening point [Tf], crystallization start temperature [Tx], thermal stability [ΔT], crystallization state The thermal expansion coefficient [a] was examined. The results are shown in Tables 1 and 2 below. The measurement method for each item is as follows.

[Glass recovery rate]
In the above production process, the recovery rate was calculated from the yield when the melt was poured into the alumina boat from the platinum crucible. The recovery rate is the weight percentage of the inflow amount of the alumina boat with respect to the total weight after firing, and the remainder corresponds to the amount remaining in the platinum crucible.

(Glass transition point, softening point, crystallization start temperature, thermal stability)
Using a differential thermal analyzer (DT-40 manufactured by Shimadzu Corporation), α-alumina was used as a reference (standard sample), the heating rate was 10 ° C / min, and the sample was measured under the measurement conditions of a temperature range of 25 ° C (room temperature) to 600 ° C. The glass transition point [Tg], softening point [Tf], and crystallization start temperature [Tx] were measured, and thermal stability [ΔT = Tx−Tg] was calculated from the results. In addition, although the thing with the said glass recovery rate of 0 cannot be measured naturally, the measurement was abbreviate | omitted also about the one with this low recovery rate.

[Vitrification state]
Using a powder X-ray analyzer (Geiger Flex 2013 model manufactured by Rigaku Denki Co., Ltd.), the glass powder was subjected to structural analysis under the conditions of scanning speed: 2 ° / min, measurement angle: 2θ = 60 ° → 20 °, and amorphous ( A state of complete amorphous glass) was classified as ◯, a part of crystallization (a state of phase separation into a glassy part and a crystal part) was represented by Δ, and a part of crystallization (a state of almost no vitrification) was classified as x. In addition, it is desirable that it is amorphous for processing such as sealing and sintering modeling.

[Coefficient of thermal expansion]
The thermal expansion coefficient was measured by a thermomechanical analyzer (TMA8310 manufactured by Rigaku Corporation) for a part of the lead-free glass material that was amorphous in the structural analysis by the powder X-ray analyzer. In this measurement, the lead-free glass material powder is melted again, and this is formed into a square column of 5 × 5 × 20 mm (length × width × height), and the upper bottom surface is formed in parallel and used as a measurement sample. The temperature was increased from 25 to 200 ° C. at 5 ° C./min, and the average thermal expansion coefficient α was determined. Furthermore, the standard sample was used α-Al ₂ O _3.

In the triangular diagram of FIG. 1, the Li ₂ B ₄ O ₇ —ZnO—BaO-based lead-free glass materials Nos. 1 to 36 manufactured in the above-described examples have a glass composition and a vitrification state. A region Z that is in an amorphous vitrified state is surrounded by an imaginary line, and a most preferable region G having a glass transition point [Tg] of 380 ° C. or lower is surrounded by a broken line. . In addition, (circle) is an amorphous, (triangle | delta) is a partially crystallized glass, and x is a glass composition of crystallization.

From the results of Tables 1 and 2 and FIG. 1, the Li ₂ B ₄ O ₇ has a Li ₂ B ₄ O ₇ of 20 in which a completely amorphous glass state can be obtained in a Li ₂ B ₄ O ₇ —ZnO—BaO-based lead-free glass material. It can be seen that the glass composition is in the range of ˜85 mol%, ZnO of 0 to 50 mol%, and BaO of 0 to 60 mol%. The lead-free glass material having such a glass composition has a glass transition point of 475 ° C. or lower, a softening point of 490 ° C. or lower, a small coefficient of thermal expansion, and can be reliably processed at a low temperature of 550 ° C. or lower. It will be a thing. Furthermore, the most preferable lead-free glass material in the region G shown by the broken line in FIG. 1 is composed of 20 to 40 mol% Li ₂ B ₄ O ₇ , 10 to 40 mol% ZnO, and 40 to 60 mol% BaO. Since the glass composition has a glass transition point of 380 ° C. or lower, a softening point is around 400 ° C., and processing at a very low temperature of 450 ° C. or lower can be performed reliably, it is comparable to conventional lead glass materials. It can be said that it has performance.

Regarding the Li ₂ B ₄ O ₇ —ZnO—BaO-based lead-free glass material produced in the above example, the relationship between the content of each oxide component (mol%) and the glass transition point [Tg] is shown in FIG. FIGS. 3A to 3C show the relationship between the content (mol%) of each oxide component and the thermal expansion coefficient α (× 10 ⁻⁶ K ⁻¹ ) in FIGS. From FIG. 2, the glass transition point [Tg] tends to decrease as the Li ₂ B ₄ O ₇ content decreases and the BaO content increases. However, the glass transition point [Tg] has a great influence on the ZnO content. It turns out not to be. On the other hand, from FIG. 3, there is no clear correlation between the thermal expansion coefficient α and the content of each component.

Since glass is a fragile material, it is necessary to control the stress (stress) of the sealing part by adapting the thermal expansion coefficient between the glass and the object to be sealed, and to make a strong sealing body. It is desirable that the thermal expansion coefficient α of the sealing material is low. In this respect, the thermal expansion coefficient of 7 to 11 × 10 ⁻⁶ K ⁻¹ in the lead-free glass material of the present invention is a very low value, and it can be seen that it is excellent as a sealing material.

[Sealing test]
The lead-free glass material No. in the said Example. A glass paste is prepared by adding a thinner solution of ethyl cellulose to 27 powder and sufficiently kneaded. The glass paste is uniformly applied to one side of soda lime plate glass, and this is heated at a heating rate of 10 ° C./min in an electric furnace. The temperature was raised to 230 ° C., held at this temperature for 5 minutes, and further heated to 390 ° C. near the softening point [Tf] (375.5 ° C.) at a heating rate of 4 ° C./minute, and at this temperature for 10 minutes. Pre-baking was performed. Thereafter, the plate glass not coated with the glass paste is overlapped on the plate glass taken out from the electric furnace, fixed with clips, put again into the electric furnace, and the crystallization start temperature [Tx] (439.4) at a heating rate of 40 ° C./min C.) The main calcination was performed by raising the temperature to 450 ° C., which is close to the temperature, and maintaining the temperature for 20 minutes. As a result, it has been found that peeling and cracking due to stress do not occur in the sealing portion, and sufficient confidentiality can be secured as a glass material for sealing processing.

The glass composition of _{Li 2 B 4 O 7 -ZnO-} BaO -based lead-free glass material manufactured in Example is a triangular diagram showing with vitrified state. The correlation between the content of each oxide component of the lead-free glass material and the glass transition point is shown, (A) is a correlation diagram of Li ₂ B ₄ O ₇ , (B) is a correlation diagram of ZnO, (C) is BaO. FIG. The correlation between the content of each oxide component of the lead-free glass material and the thermal expansion coefficient is shown, (A) is a correlation diagram of Li ₂ B ₄ O ₇ , (B) is a correlation diagram of ZnO, (C) is BaO. FIG.

Claims (3)

A low-melting lead-free glass material mainly composed of an oxide composed of Li ₂ B ₄ O ₇ and at least one of ZnO and BaO. And 20-85 mol% of Li ₂ B ₄ O _7, and 0 to 50 mol% of ZnO, low fusible lead-free glass material according to claim 1, further comprising a 0-60 molar amount% of BaO. 20 to 40 mol% of Li ₂ B ₄ O _7, and 10 to 40 mol% of ZnO, low fusible lead-free glass material according to claim 1, further comprising a 40 to 60 mole% BaO.

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