JPS6256095B2 - - Google Patents

Description

[Detailed description of the invention]

PbO-containing sealing glasses, especially PbO-
_{B2O3 -} ZnO sealing glasses are most commonly used commercially to seal glass faceplates to the glass funnels of color television vacuum tubes. These sealing glass types are low temperature,
That is, the temperature is usually below 500°C, preferably 475°C, which promotes a moist state on the glass surface to be sealed.
It has the following melting point and pour point. moreover,
The opacified or crystallized seal formed also has a higher fiber softening point than that of the original sealing glass. However, PbO in the sealing glass is easily reduced to metallic lead when the sealing process is carried out in a reducing atmosphere or in a harmful organic gas. Television tube manufacturers must take special measures to prevent dielectric breakdown of the seals. Before the glass face plate of a color television tube is sealed to its glass funnel, both parts must first be subjected to a number of different processing steps. The face plate and the metal grid and perforated mask forming an important part of the inner surface of this face plate are first joined together and then introduced into a fixing process in which the joint is heated at a heating rate of about 10°C per minute. It is heated to a temperature of 450-460°C and maintained at this temperature for about 2 hours. This fixation process normalizes the various changes that occur between the two parts during subsequent heating and cooling stages during the formation of the finished television tube. After these parts have cooled, the grid or perforation mask is removed and marked for subsequent bonding with a similar glass face plate. This faceplate is then separately provided with green, blue and red phosphors in a known manner, and optionally a carbon or graphite backing gland is provided around the phosphors, whereby Provides sharp contrast.
Each phosphor is present on the inner surface of the faceplate as a collection of individual dots arranged in a uniform manner. A resinous or plastic film is applied to the surface of the phosphor, and the inner surface of the faceplate is subsequently aluminized, ie, a thin aluminum film is applied under vacuum to form a conductive surface. The aluminum adhesion surface is bonded to a metal stud on the inside surface of the faceplate, which in turn is bonded by a spring clip connecting the sealing surface of the faceplate to the conductive inside surface of the funnel. Such inner surface, in turn, is connected to a cathode terminal on the outer surface of the funnel, and thus to the high voltage supply of the television set. Once this aluminum deposition step is complete, a grid or perforated mask is inserted into the faceplate and secured therein. At this stage, at least about nine organic compounds are provided to the inner surface of the faceplate, and these compounds must subsequently be baked onto the faceplate or facepanel. Usually 400°~450
During this baking process, which is carried out at temperatures of .degree., various organic gases are evolved. Because these organic gases have a detrimental effect on the PbO contained in the sealing glass used to seal the faceplate to the funnel, the baking process is not performed before such sealing is applied. There must be. When such gases come into contact with the sealing glass during the sealing process, the PbO is reduced to metallic lead, causing dielectric breakdown of the resulting seal. Such tubes are unusable and are returned without passing voltage tests such as those applied in actual equipment. To recover the faceplate and funnel for reuse from returned tubes, the sealing glass is partially corroded, the tube is then opened by thermal cycling, and the faceplate and funnel are removed. It must be removed, the glass solder removed from each part, any phosphor or other deposits removed from the faceplate, and used again. This process is both time consuming and costly to the television manufacturer. The high voltages applied to the television tube while it is working in a television set are 20K volts to 35K volts or more, and induced breakdown of the seal between the funnel and faceplate may result in malfunction of the tube. Not only that, but it can also result in electric shock when a person touches the vacuum tube. As mentioned above, between the time the metal grid or perforated mask is bonded to the face plate and the time the plate is subsequently sealed to the funnel with sealing or glass solder, the face plate will have approximately 8 to 12 Separate processing operations such as inspection, firing, etching of the edges of the faceplate that is sealed to the funnel after various treatments, and removal of various components after re-inspection must be carried out. Eliminating some or all of the steps between inserting the mask into the faceplate and sealing the faceplate to the funnel saves labor and time, and thus improves the production of complete color television tubes. It also reduces costs. However, due to the formation of organic gases during the firing process that the faceplate must undergo, the television tube manufacturing industry requires firing of the faceplate and sealing of the faceplate to the funnel.
Simultaneously using a PbO-containing sealing glass was not possible without undergoing reduction of the PbO in the sealing glass to Pb-metal. Moreover, the only binder whose use has been commercially successful for PbO-containing sealing glasses, such as PbO-B ₂ O ₃ -ZnO sealing glasses, is with amyl acetate as the preferred solvent for it. It is only a solution containing 1 to 1.4% nitrocellulose. The use of other binders in place of nitrocellulose does not prevent the reduction of PbO to Pb metal during the sealing process. In this case, instead of the yellow seal formed by the opaque glass solder, the presence of metallic lead results in the formation of a gray or grey-black seal. However, nitrocellulose also has a number of drawbacks when used as a sealing glass binder. First of all, pastes containing such binders are unstable and have a lifespan of only about 4 hours. This means that the color television tube manufacturer must prepare the paste immediately before applying it from the distributor to the outer sealing edge of the funnel.
It is not possible to dispense more than approximately 20 lb (9.08 Kg) at one time and send it to the distributor. Additionally, great care must be taken in dispensing the ribbon or bead of sealing glass paste from the distributor orifice to the outer periphery of the funnel edge. The dispenser operator must constantly adjust the pressure while the paste is being extruded to maintain substantially uniform ribbon width and weight. The width of this ribbon must be narrower than the width of the funnel edge; if this width is too wide, a large amount of paste will spill out from between the interface of the funnel and face plate during the sealing process. On the other hand, if this width becomes too narrow, the supplied paste will not be able to form an effective and acceptable seal. with nitrocellulose as binder
When using PbO-containing glass solder paste in practice, it may be necessary to quickly extrude into different funnels by changing the width of the extruded ribbon or the weight of the extruded ribbon to a certain length. It is also true that there are many. This means that the person operating the dispenser must constantly monitor the dispenser and make adjustments to it. A 20lb (9.08Kg) sealing glass will fit approximately 100 23″ (58cm) television tubes measured diagonally.
In the case of 18" (46 cm) vacuum tubes, 175 pieces can be made in about 2 hours.The distributor used will be stopped after this, and the glass paste tank for sealing will be taken out, and about 120 to 300 g will be made. Remove and discard any remaining residue paste from the tank, clean the tank, and add 20lb (9.08Kg) of freshly prepared
of paste formulation shall be filled into this tank. Load this tank into the distributor again,
The air hose is connected to prevent loss of amyl acetate that evaporates at room temperature, the air pressure is adjusted, and extrusion of the paste begins again to the outer edge of the television funnel. Most manufacturers of color television tubes still use nitrocellulose as a binder for sealing glass frits, which is still used today due to the inability to dispense, using a 20 lb (9.08 kg) charge. ,
The operator constantly monitors the operation, and also periodically stops the equipment, prepares and prepares a new sealing glass mixture, and restarts the equipment.
And operations such as adjustment are expensive. These manufacturers believe that nitrocellulose is
Efforts continue to be made to eliminate the limitations and drawbacks of nitrocellulose, as it avoids the dielectric breakdown of sealing glass due to the reduction of PbO in the glass due to the reducing atmosphere that occurs when other binders are used. It is coming. These manufacturers are
Furthermore, by separately firing the phosphor-containing faceplate before sealing the glass faceplate to the glass funnel, organic evaporation formed during the firing step no longer removes PbO from the sealing glass. Efforts have been made to prevent this from being reduced to metal, causing dielectric breakdown, and causing vacuum tubes to be returned. PbO-containing glass frit for sealing and glass sealing paste obtained from it are normally present in the sealing glass in the form of lower metal oxides such as PbO and BaO. , and the higher oxide form has a sufficient amount of metal higher oxide powder to resist decomposition at the temperatures at which the sealing glass is heated, softened, and melted for sealing to the face plate and funnel. When the sealing glass is melted and sealed, even if the sealing glass comes into contact with the ring agent, the higher oxide of the metal is only reduced to its lower oxide state, and the sealing glass is It has been found that PbO in glass is not reduced to Pb metal. further added to the PbO-containing sealing glass in an amount of at least 0.1% to about 1.5% by weight of the sealing glass in powder form;
It has also been found that the addition of preferably about 0.25-0.7% by weight of Pb ₃ O ₄ avoids the reduction of PbO to Pb metal in the sealing glass. This _{Pb3O4 is}
The small amount of PbO that is reduced to PbO and formed does not adversely affect the properties of the sealing glass. The use of Pb ₃ O ₄ powder in PbO-containing sealing glass means that the sealing glass comes into contact with vapors liberated from the interior of television vacuum tubes or various organic components used in television vacuum tube parts. It would be possible for color television tube manufacturers to avoid the consequent aging of the sealing glass. Furthermore, when adding such small amounts of Pb ₃ O ₄ powder into sealing glasses and pastes prepared therefrom, small amounts of hydroxypropylcellulose binder can be used in conjunction with nitrocellulose binder, as will be clear from the reference examples below. It's clear. The presence of 5 to 30% by weight of a 4% hydroxypropylcellulose solution mixed with a 1.2% nitrocellulose solution provides a very stable seal that can be formulated into doses up to several thousand pounds (0.5 x thousands of kilograms). A glass paste is obtained which has a shelf life of at least 3 months or more. Additionally, the paste can be used continuously in a dispensing device from start to finish without requiring constant adjustments to the dispensing device that are required when using nitrocellulose alone as a binder for glass frits. This results in reduced labor for the manufacturer, reduced dispenser operating time, reduced paste preparation time, etc. Reference Example 1 24 parts by weight of hydroxypropylcellulose having an average molecular weight of 60,000 was slowly poured into 150 parts by weight of amyl acetate which had been preheated to 60°C while stirring. An additional 150 parts by weight of amyl acetate was added to this solution and stirred well.
To this solution, 300 parts by weight of ethylene glycol methyl ether preheated to 60° C. was slowly added, while stirring was continued continuously. A 4% by weight clear solution of hydroxypropyl cellulose was formed. Five parts by weight of the 4% hydroxypropylcellulose solution thus prepared were thoroughly mixed with 95 parts by weight of a solution of nitrocellulose in amyl acetate (nitrocellulose content in the solvent 1.2% by weight). The resulting binder solution was well mixed with 1170 parts by weight of a commercially available glass solder containing 0.25% by weight of Pb ₃ O ₄ . The above glass solder had the following composition:
PbO75.5%, _{B2O3 8.5} %, ZnO12%, SiO2 ₂ %,
BaO2%. The glass solder paste thus prepared remained stable for 50 hours in the formulation at room temperature. When dispersed in beads on a TV funnel and baked at a temperature of about 430°C, this glass solder softened and then became fluid and translucent.
The color of the seal was orange-yellow, indicating that some Pb ₃ O ₄ remained in the seal and was not completely reduced to PbO.
No significant change was observed in the width of the extruded ribbon even after it was extruded into a ribbon and pasted on a television funnel for several hours. Hydroxypropylcellulose comprising 0.195% by weight vehicle was used in this example. Reference Example 2 100 parts by weight of a solution of nitrocellulose in amyl acetate solvent (1.2% by weight nitrocellulose) was mixed with 1170 parts by weight of the glass solder used in Reference Example 1 to make a glass solder paste. This paste is stable for only about 4 hours, and when the paste is dispensed into the funnel of a vacuum tube, continuous pressure is applied to the dispenser to keep the bead sizes within a substantially uniform range. had to be added. Additionally, the weight of the extruded beads can vary by as much as 30% or more of the desired ribbon weight, requiring continuous adjustments in the distributor to maintain a constant ribbon weight. It was hot. Reference Example 3 A paste was prepared in the same manner as Reference Example 2 except that 1230 parts by weight of glass solder was used. The formulation is placed at the extrusion start in the distributor, and a pressure of 5.2 psi (0.37 Kg/cm ² ) is applied to the formulation.
The ribbon thus extruded is 0.213″ (0.541cm)
It had a bead width of , and a weight of 80.1 g per unit length. After 1 hour at the same pressure, the width of this extruded bead is 0.227″ (0.577cm), and its weight per unit length is 101.3g, an increase rate of 26%.
It was hot. After applying similar pressure to this formulation for 2 hours, the bead width increased to 0.239″ (0.607 cm), while the weight per unit length increased to 117.0 g, which is a 46% increase rate. After 3 hours, the bead width was 0.252'' (0.640 cm) and the weight per unit length was 123.6 g, an increase rate of 54%. A deviation of 30% of the weight per unit length is the permissible limit,
If it exceeds this amount, it may be forced out between the sealed surfaces of the vacuum tube, resulting in waste, or in extreme cases, creating undesirable stress points that can interfere with the handling and operation of the tube. Become. Therefore, in order to maintain the width of the extruded vacuum tube at approximately 0.213" (0.541 cm) and its weight per unit length at approximately 80 g, the person operating the dispenser must During,
Care must be taken to reduce the extrusion pressure at regular intervals. Reference Example 4 100 parts by weight of the glass solder used in Reference Example 1 was mixed with 1.5% by weight of Pb ₃ O ₄ powder, and the resulting glass solder had an average molecular weight of about 60.000 at 5% by weight.
of hydroxypropylcellulose dissolved in an equal mixture of 95% by weight ethylene glycol methyl ether and amyl acetate. The resulting glass solder paste was stable; it was well distributed from a distributor similar to that used in Reference Example 3 without adjustment of the extrusion pressure. The variation in dispensed beads or ribbons was approximately ±0.008 inches (0.02 cm). Fired Seal Glass Bolt/0.001 inch (Bolt/0.00254
The dielectric strength, expressed in cm) or V/mil, was 135% that of conventional sealing glass frits. When a nitrocellulose binder alone is used in the sealing glass, the dielectric strength of the fired sealing glass is 100 to 150 V/mil (V/0.00254
cm), which is known to be lower than the dielectric strength of ordinary glass frit itself for sealing. Hydroxypropylcellulose comprising 5% by weight vehicle was used in this example. Reference Example 5 Reference Example 1 is a 1.33% solution of hydroxypropyl cellulose (average molecular weight approximately 300,000) in equal weight parts of ethylene glycol methyl ether and amyl acetate.
1% by weight of glass sealing solder similar to
It was mixed _with one containing _Pb3O4 . The ratio of glass solder + Pb ₃ O ₄ solid to binder solution is
It was 11.3:1. The resulting paste had not only good distribution properties but also good uniform bead manufacturing properties. The dielectric strength of the seals made with this glass solder paste is 25% higher than that of the sealing powder alone and 80% higher than that of the glass powder and standard binder solution of Reference Example 2, except that _it does not contain _Pb3O4 . was 150% higher than the strength of the glass solder paste prepared in the same manner as Reference Example 5. Hydroxypropylcellulose comprising 1.33% by weight vehicle was used in this example. Reference Example 6 1 part by weight of a binder solution consisting of equal parts of amyl acetate and 10% of a 4% solution of hydroxypropylcellulose in ethylene glycol methyl ether and 90% of nitrocellulose (1.2% nitrocellulose solution) in amyl acetate. and 11.7 parts by weight of solid material (glass solder of Reference Example 1 + 0.3 parts by weight)
A glass solder paste was prepared using Pb ₃ O ₄ ). This paste remained stable after 6 days.
When subsequently dispensed into ribbons, a −0.008″ (0.02 cm) change in bead width was observed from ribbons extruded using the same extrusion pressure at the beginning of the 6-day period. The weight change was only +3%. Hydroxypropyl cellulose comprising 0.4% by weight of vehicle was used in this example. Reference Example 7 Glass solder of Reference Example 1 containing 0.5% by weight of Pb ₃ O ₄ 9 parts by weight were mixed with 1 part by weight of a binder solution consisting of 70% by weight of a nitrocellulose solution, similar to Reference Example 6, and 30% by weight of a hydroxypropylcellulose solution, also similar to Reference Example 6.24
The paste was stable over time and suitable for extrusion into ribbons. Hydroxypropylcellulose comprising 1.2% by weight vehicle was used in this example. Reference Example 8 1170 parts by weight of sealing glass containing 0.25% Pb ₃ O ₄ as in Reference Example 1 was mixed with 90% of the nitrocellulose binder solution in Reference Example 6 and also in the same manner as in Reference Example 6. A sealing glass paste was prepared by mixing with 100 parts by weight of a mixture with a 10% hydroxypropyl cellulose binder solution. This paste was placed in a distributor similar to that used in Reference Example 3. 2.2psi
(0.155 Kg/cm ² ) the ribbons or beads are extruded and the beads thus obtained are 0.255″ (0.648
cm), and the weight per unit length was 78.4 g. When operated at the same extrusion pressure, after one hour the bead width was 0.267'' (0.678 cm) and the weight per unit length was 80.4 g, representing a 3% increase rate.
After 2 hours, the bead width was increased at the same extrusion pressure.
The weight per unit length of 0.283″ (0.719cm) was 83.4g, showing an increase rate of 6%. After 3 hours, the bead width was 0.283″ (0.719cm) and the weight was 84.5g, indicating an increase of 8g per unit length. % increase rate. After 4 hours,
The bead width is 0.287″ (0.729cm) and the weight is 85
g, the increase rate per unit length was 9%. The extrusion pressure was 2.2 psi (0.155 psi) throughout all extrusion operations.
kg/cm ² ). From these facts, the changes in bead width and weight per unit length were within the tolerance range required in the television vacuum tube manufacturing industry. For this reason, when using this sealing glass paste, compared to using a conventional glass solder paste as shown in Reference Example 3, which requires regular monitoring, spot checks are required from time to time as necessary. This has the advantage that the distributor can be left alone for a long time without being monitored. Further, the dispensing device for making beads or ribbons of glass solder paste includes a central glass solder paste supply that continuously charges the device with glass solder.
glass paste supply) can also be adopted.
Such dispensing equipment is suitable for dispensing glass solder paste.
Since it is mixed and used in 20lb (9.08Kg) portions,
Continuous operation throughout the day is possible, unlike the 20lb (9.08Kg) batch system used by most of today's color television vacuum tube manufacturers, which requires frequent equipment shutdowns. The term "weight per unit length" as used so far refers to the length of the ribbon that will completely mold the outer sealing edge of the funnel of a television tube without overlapping it. . Reference Example 9 1230 parts by weight of a glass sealing solder frit containing 0.5% Pb ₃ O ₄ was dissolved in a 95% nitrocellulose solution (1.2% nitrocellulose in amyl acetate)
and a binder solution comprising 5% of a solution of 4% hydroxypropylcellulose in equal parts ethylene glycol methyl ether and amyl acetate to prepare a sealing glass paste. This sealing glass had the following composition: PbO 75%, ZnO 12.6%, BaO ₃ 8.3%, SiO ₂ 2.1
%, and BaO2% (all weight %). This paste was extruded into the funnel of an 18" (46 cm) television tube (18" (46 cm) is measured diagonally across the tube surface). Faceplates with masks, phosphor coatings, aluminized coatings, etc. are joined at each funnel such that their sealing edges are joined with glass solder ribbons. The bonded television parts were then placed in an airless oven and heated at a rate of about 10°C per minute to a temperature of 450°C and held there for 1 hour. The tube was then cooled to room temperature at a rate of 7°C per minute. Not only the faceplates that seal to the vacuum tube funnel, but also the seals between the faceplate and the funnel, are capable of absorbing vapors liberated from volatile organic components in the interior confine of the faceplate and funnel. I was brought into contact. Each vacuum tube underwent a frit breakdown test (frit breakdown test).
test). A metal ring is placed in contact with the seal near the outer periphery of the connection between the face plate and the funnel, and is attached to the funnel's cathode terminal.
A voltage of 50KV was applied. No dielectric breakdown was immediately observed;
Similarly, no signs of damage were observed. All of the vacuum tubes produced did not suffer from any dielectric failure, nor did any current flow through their seals. However, in the case of television tubes sealed with conventional glass solder and then sealed and treated as shown in this example, the PbO in the glass solder conducts electricity through the seal. Dielectric breakdown was observed due to the reduction to . Hydroxypropylcellulose comprising 0.2% vehicle by weight was used in this example. PbO-containing glasses for sealing the faceplate of TV tubes to the funnel are commercially available. Most of them are of the PbO-B ₂ O ₃ -ZnO type and fall within the following general composition ratio range: Component Weight % PbO 75-82 ZnO 7-14 B ₂ O ₃ 6.5-12 SiO ₂ 1.5-3 BaO 0-2 Other metal oxides may also be used, as long as the oxides are compatible with the glass and do not materially change the basic properties of the glass or the opaque seal formed from the glass.
Usually it can be present in amounts less than 5% by weight. On the other hand, nitrocellulose dissolved in amyl acetate is a well-known binder solution for glass sealing, and the amount of nitrocellulose in this solution is usually about 1 to 1.4%. Nitrocellulose binders can be used with sealing glass frits containing Pb ₃ P ₄ . However, unless about 5% to 30% of the 4% hydroxypropyl cellulose solution in the solvent is present as a binder solution, either with the nitrocellulose or, preferably, as the sole binder solution of the sealing glass, the shelf life of the resulting paste (Shelf life) will be shortened. Although a 4% hydroxypropyl cellulose solution is described as a suitable binder solution, other concentrations of this binder solution can also be used. The molecular weight of hydroxypropyl cellulose is approximately
It can vary from 40,000 to 300,000 or more. Higher molecular weights make them more difficult to use. Other binders may also be used in sealing glass pastes, as long as they have the ability to maintain the glass solder frit in ribbon form long enough to bond and seal the parts being joined, i.e., faceplates and funnels. You can. The binder needed for the paste is added to the glass solder frit in a wet state.
The binder is then decomposed at a heating temperature below the temperature at which the sealing glass frit is fired; Only a small amount remains in the frit and evaporates. thermal gravitation analysis
According to analysis), approximately 0.3 to 1.2% nitrocellulose remains in the fired frit. The solvent used is preferably amyl acetate because it quickly volatilizes from the extruded ribbon and allows the ribbon to be fired more quickly to seal the glass surfaces to be joined. Also suitable is ethylene glycol methyl ether, which can be used alone or in a mixture with amyl acetate. Other binder solvents that can be used include ethylene glycol ethyl ether, methyl amyl acetate, ethyl hexyl acetate, n-butyl acetate, isobutyl acetate, secondary butyl acetate, and diethylene glycol monobutyl ether acetate. On the other hand, the amount of binder used is such that it is capable of fixing the sealing glass frit parts together as an extrudable paste, and the amount of sealing glass solids to binder solution, including Pb ₃ O ₄ , is usually about It is in the range of 10:1 to 12.8:1. _Pb3O4 is present in the range of approximately 0.1% _to 1.5%,
The preferred range is about 0.25-0.7%, and for 0.5%,
Consistently good results. If amounts of 1.5% or more are used, the glass solder composition must be adjusted to account for the PbO formed by reduction of Pb ₃ O ₄ . Although Pb ₃ O ₄ is shown in each of the above reference examples, BaO 2 can also be used instead of Pb 3 O 4 as a reference example, and it is also possible to use BaO ₂ instead of Pb 3 O 4 as well. Also use other metal oxides that have a high oxygen content or that can form part of the opaque sealing glass without materially impairing the basic properties of the opaque sealing glass. I can do it. _BaO2 is reduced to BaO while the glass solder is in the firing temperature range and forms an opaque seal. Reduction of BaO ₂ in a reducing atmosphere or in the oxygen-containing gas formed during the firing step of the face plate suppresses the simultaneous reduction of PbO to metallic lead, thereby preventing dielectric breakdown caused by the formation of metallic lead. It also prevents Metal oxides with high oxygen content, e.g. Pb ₃ O ₄
It is necessary that the sealing glass is stable in the temperature range in which the sealing glass is fired and that it does not decompose at this temperature. This is important because Pb ₃ O ₄ must be in a form that is slowly reduced to PbO by a reducing atmosphere or organic gas. If it is decomposed, it will not be able to perform its intended function. PbO
- Although the firing temperature of glass solder-containing materials ranges from approximately 400 to 460°C, in many cases such glasses are
Fired at 425-455℃. Pb ₃ O ₄ is stable at temperatures up to 500°C. US Patent No. 27, 1968
No. 3370966 discloses the use of an oxidizing agent in glass solder to form a joint between two glass components; must be rapidly decomposed to release free oxygen to burn off contaminants during normal manufacturing processes.
These additives also combine with any metallic lead formed by the decomposition of the lead-containing components of the frit. In cases where metal powder such as aluminum is mixed in cement, it is
It will be oxidized to Al ₂ O ₃ . The above reference example is essentially different from U.S. Patent No. 3,370,966 because Pb ₃ O ₄ must remain even when the sealing glass paste is introduced and placed at the firing temperature. It is something. The dielectric strength improving effect due to the presence of Pb ₃ O ₄ itself in combination with a small amount of hydroxypropylcellulose is evident from the following data. Average volt/mil (Average volt/0.00254cm) 1 Glass solder of reference example 1 720 2 Glass solder binder A of reference example 1 580 3 Glass solder of reference example 1 + 0.25%Pb ₃ O ₄ + binder A 740 4 Reference Glass solder of Example 1 + 0.25% Pb ₃ O ₄ + Binder B 780 Binder A is a 1.2% solution of nitrocellulose in amyl acetate. Binder B contains 95% Binder A, equal parts amyl acetate and 5% of a 4% solution of hydroxypropyl cellulose having an average molecular weight of 60,000 in ethylene glycol methyl ether. Hydroxypropylcellulose 0.2% by weight
Contains a vehicle. The glass solder paste of the above-mentioned reference example has a dielectric strength up to about twice that of the glass solder itself. In the above examples, hydroxypropylcellulose comprises 0.195-1.2% by weight vehicle when used with nitrocellulose, and 1.3-5% by weight vehicle when used only as a binder in the vehicle. Become. In particular, the vehicle in the above example comprises the following components (% by weight): hydroxypropyl cellulose 0.195-1.2 nitrocellulose 0.84-5.9 amyl acetate 83.5-96.45 ethylene glycol methyl ether 2.4-14.4 and hydroxypropyl cellulose 1.3-5 Amyl acetate 47.5-49.3 Ethylene glycol methyl ether 47.4-49.3 _Pb3O4 and _BaO2 are the two most useful reference metal oxides, while the chemistry _of PbO in Pb-containing sealing glasses A second group of reference examples of inorganic oxides that have been shown to substantially inhibit reduction includes metal oxides having thermal decomposition temperatures of about 400°C or higher. Representatives of this second group of compounds are
_CrO3 , _MnO2 , _MnO3 , _Fe2O3 , _{Fe3O4 , CuO} ,
_{Cu2O and Tl2O3} . Another group of oxides as a reference example was found to have the effect of suppressing the chemical reduction of PbO, although it was less effective than the first and second groups. This third group of oxides is a compound with a relatively high oxygen content (i.e., a higher number of oxygen atoms than the oxides of the first and second groups) or a relatively high melting point (i.e., when used or a combination of these factors. Examples of the third group of oxides are Sb ₂ O ₅ , TeO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , V ₂ O ₅ and
It is _CeO2 . Another compound of the third group is
_It is _Bi2O3 . This compound is the least effective of the third group, but some efficacy is seen. A fourth group of effective oxides is characterized by compounds with thermal decomposition temperatures below 400°C. Within this fourth group is AS ₂ O ₅ .
These compounds work by a different mechanism than the compounds described above. The fourth group of compounds decomposes producing free oxygen within the range of temperatures during which the sealing glass frit is fired. In addition to oxides, inorganic nitrates are also present in PbO−
It has been found that the chemical reduction of PbO in sealing glass is substantially suppressed. This nitrate can be divided into three groups. The first group produces the most pronounced effect and has a decomposition temperature of about 30°~
600°C, a melting point of about 36° to 264°C, and a compound with water of hydration. Examples of this group of compounds are Ca(NO ₃ ) _{2.4H 2} O:Zn(NO ₃ ) ₂ .
6H ₂ O; La(NO ₃ ) ₃・6H ₂ O; Bi(NO ₃ ) ₂・5H ₂ O;
Ce(NO ₃ ) ₃・6H ₂ O; Ni(NO ₃ ) ₂・6H ₂ O; and
Cd(NO ₃ ) ₂ ·4H ₂ O. A second group of nitrates produces comparable results to compounds of the first group of nitrates, but this second group has a melting point lower than the firing temperature of the PbO-containing sealing glass, and the PbO
- Characterized by being a compound having a thermal decomposition temperature higher than the firing temperature of the sealing glass it contains. Examples of compounds that fall into this second group are:
_LiNO3 and _AgNO3 . A third group of nitrates, although less effective than the first and second groups, is observed and is characterized by compounds with melting points of about 414° to 592°C. Examples of this group of compounds are _CsNO3 , Pb( _NO3 ) ₂ and Ba( _NO3 ) ₂ . Another group of inorganic nitrates has been found to be particularly effective in sealing glass pastes containing cellulose binders. This group has a fiber softening point of about 150°, which is the fiber softening point of sealing glass.
softening point)
Characterized by being a nitrate producing _HNO3 . Examples of such compounds are Cu
(NO ₃ ) ₂ ·3H ₂ O and BiO(NO ₃ )·H ₂ O.
Although the mechanism of action is not completely understood, it is theorized that these compounds release _HNO3 , which reacts with the cellulose binder to produce a nitrocellulose-type binder (i.e., the cellulose binder has nitro groups). . Nitrocellulose binder is suitable for PbO-containing sealing glasses.
It is known that chemical reduction of PbO is not as problematic as for example with hydroxypropylcellulose binders. Another method that can substantially suppress the chemical reduction of PbO in PbO-containing sealing glasses.
One group of inorganic compounds are hydroxides of metals that act like oxides. The compounds contained therein are hydroxides that are thermally stable at the temperature at which the sealing glass is fired and do not decompose thermally within the firing temperature range, but react when placed in the reducing state that exists during the firing of the sealing glass. be. Examples include LiOH;
LiOH・H ₂ O; Zr(OH) ₄ ; ZrO ₂・XH ₂ O; Ba
(OH) ₂ ; Ba(OH) _{2.8H 2} O. In the case of hydroxides, water of hydration is considered to have no significant effect. For example, substantially anhydrous lithium hydroxide and hydrated lithium hydroxide exhibit substantially the same apparent effects. A less effective group of inorganic hydroxides are hydroxides that thermally decompose at temperatures below the temperature at which the sealing glass seals the glass surfaces together. An example of these compounds is Mg(OH) ₂ . Another group of inorganic compounds that have been shown to substantially inhibit the chemical reduction of PbO in PbO-containing sealing glasses comprises metal carbonates.
These carbonates are characterized by compounds that produce carbon dioxide at temperatures above the firing temperature of the sealing glass. Examples of such compounds include:
There are _MgCO3 and these give a very noticeable and obvious effect. Another group of carbonates that are less effective than magnesium carbonate are _CdCO3 and _ZnCO3 . Compounds falling into this second group lose carbon dioxide within a temperature range of about 300-500°C, and e.g.
Has a relatively low firing temperature of °C or lower
It shows a very obvious effect when used on PbO-containing sealing glasses. Inorganic oxygen-containing chlorine compounds have also been shown to be suitable additives to PbO-containing sealing glass frits. Inorganic oxygen-containing halogen compounds may also be used, but preferably the compounds have a thermal decomposition temperature equal to or higher than the firing temperature of the sealing glass. Particular preference is given to perchlorates, especially KClO ₄ . Another group of inorganic additives that have proven useful are dichromates. In particular, an effective amount of K ₂ Cr ₂ O ₇ can be used. Typically, dichromates with decomposition temperatures of no more than about -100°C or no more than about +100°C can be used with respect to the firing temperature of the PbO-containing sealing glass. Another group of inorganic additives are pyrosulfates and peroxosulfates with a high oxygen content (e.g. about 7 to 8 oxygen atoms) and preferably compounds with a thermal decomposition temperature higher than about 300°C. It is. It was found that K ₂ S ₂ O ₇ and K ₂ S ₂ O ₈ showed a clear effect. Unexpectedly, it has been found that _P2O5 does not work well with PbO- _containing solder glasses having firing temperatures above about 400<0>C. This suggests that the use of materials that sublimate below the firing temperature of the solder glass must be avoided, since P ₂ O ₅ sublimates at about 300°C. When sealing glass frit is mixed with a vehicle to make a paste and then fired.
A series of tests were conducted on PbO-containing sealing glass frits to determine the ability of several additives to inhibit chemical reduction of the PbO component. Additives are shown in column 1 of the table. Each of the additives was mixed with the sealing glass frit to create test sample mixtures containing 0.2%, 0.8%, 1.5%, or 3%, respectively, by weight of the additive mixed into individual portions of the sealing glass frit. . Each of the resulting samples was mixed with sufficient vehicle to make a paste. One sample of each additive-sealing glass frit paste at the indicated additive concentration was incubated at separate temperatures: 400°C, 450°C or 525°C.
It was fired in These temperature ranges were chosen because they fall within the typical operating range in the manufacture of color television picture tubes. Below is a summary of the operations performed in conducting the test. Microscope slides were prepared by depositing typical cathode ray tube sealing glass in paste form with and without the additives. The sealing glass (also referred to herein as "base glass") was a PbO-containing sealing glass having one of the following compositions with oxide content in weight percent: Glass A Glass B PbO 75 84 ZnO 12.6 2.7 B ₂ O ₃ 8.3 12.3 SiO ₂ 2.1 0.4 BaO 2 0.6 These base glasses were sealing glass frits with coarse particles removed by sieving;
All particles are substantially smaller than 200 mesh. A sample of the base glass was applied to each slide using deionized water as the vehicle to establish the base line color after firing. Another sample of the base glass containing 0.8% by weight of additive was applied to each slide to determine the effect of the additive on the base glass. A sealing glass paste was made by mixing 92 parts by weight of base glass and 8 parts by weight of vehicle.
Vehicle was 96% nitrocellulose solution (1.2% nitrocellulose by weight in amyl acetate);
and 4% by weight of a solution containing 1.32% by weight of hydroxypropyl cellulose having a molecular weight of about 60,000 and amyl acetate in Dowanol EM. Each of these pastes is prepared by mixing a small amount of base glass, an appropriate amount of vehicle, on a glass plate,
made by stirring. Other pastes were made containing additives, a base glass and a hydroxypropylcellulose-nitrocellulose vehicle. The additive is
It was intended to suppress the chemical reduction of PbO. Each of these pastes was made by mixing the base glass and additives in small batches in a paint shaker. The resulting mixture was formulated with a hydroxypropylcellulose-nitrocellulose vehicle to give weight concentrations of 0.2%, 0.8%, and 1.5%.
A sealing glass paste containing % or 3% additive was prepared. Each paste was transferred to a previously cleaned glass slide by wiping with acetone. Samples of each paste were applied by depositing randomly sized drops onto a glass slide using a spatula. The paste will take about 3 hours, approx.
Dry by heating in air at a temperature of 120°C (49°C). Each glass slide was fired to seal the sealing glass to the glass slide. Three different firing cycles were performed by varying the peak temperature. The firing cycle consists of heating the glass slide in air at a temperature increase of 11 °C/min to peak temperature, holding at peak temperature for 35 minutes, and cooling to room temperature at a rate of 6 °C/min. Contained. Peak temperature is 400
℃, 450℃ or 525℃. The results of these tests are shown in the table. Recognizing that the purpose of these tests is to know the effect of various vehicles and additives on the chemical reduction of PbO, these tests are based on observing the color of each sample of the fired paste. It will be understood. The formation of free lead or lead in a low oxidation state during firing is characterized by a gray or black color in the fired sample if the additive is not black or gray. Good results are obtained when samples Nos. 4, 5 and 6 in the table are lighter or different in color than sample No. 3. The results in the table are based on visual observation.
Dots or tabs mainly indicate incomplete mixing. A more uniform shade will result from a more uniform mixing of the frit and powder additive.

【table】

【table】

【table】

【table】

Table: In addition to the compounds shown in the table, the following additional results were observed. Cupric oxide gave very good results at concentrations of 0.2%, 0.8% and 1.5%. Cuprous oxide shows a clear effect, but it is not as effective as cupric oxide. Ferric oxide gives excellent results in glass binder A even at concentrations as low as 0.2%. Triiron tetroxide (Fe ₃ O ₄ ) is not as effective as ferric oxide, but
Shows obvious effects. Zr(OH) ₄ and _ZrO2・
Both H ₂ O are effective at high concentrations, eg, 3% addition level. At a concentration of 1.5% the latter compound exhibits some orange tinge. Mg(OH) ₂ shows a fairly pronounced effect but is not as effective as the other hydroxides tested. Among other nitrates tested, BiO(NO ₃ )
_H2O gave excellent results at concentrations of 0.2%, 0.8% and 1.5%. Fired samples containing this additive exhibited a white color. Cu(NO ₃ ) ₂・3H ₂ O is
Very good results were obtained with sealing glass B at concentrations of 0.2%, 0.8% and 1.5%. Potassium pyrosulfate gave very good results with additive concentrations of 0.8% and 1.5% when fired at 400°C and 450°C in either sealing glass A or sealing glass B. Potassium peroxodisulfate was somewhat less effective than potassium pyrosulfate. The sample containing potassium peroxodisulfate exhibited some white dots on a gray matrix. Another compound tested was boric acid (H ₃ BO ₃ ), which produced a fairly good color effect. However, this compound is not among the best compounds for suppressing the chemical reduction of PbO in PbO-containing sealing glasses. It is noted that the effectiveness of hydrated compounds is surprising to those skilled in the art. It is expected that compounds containing water of hydration will cause bubbles in fired samples of sealing glass. On the contrary, some hydrated additives have been shown to be very effective in suppressing the chemical reduction of PbO without resulting in the formation of bubbles in the fired sealing glass. It was done. The tests in the table show that Base Glass A, applied to glass slides using only deionized water as the vehicle, has a yellow color after firing. In Glass B, on the contrary, a gray or black tint is obtained in the absence of cellulose binder. This is more for glass B than for glass A.
The presence of PbO results in the reduction of this PbO to free lead. Therefore, this is not the case for glass B since there is not much PbO reduction in base glass A in the absence of an organic cellulose-containing vehicle. PbO in a frit containing glass B
The issue of restitution is more important. It will be clear from the table that some additives are more effective in frits containing Glass B. The use of glass B in the TV industry would be advantageous since it can be fired at low temperatures due to its high PbO content. It can be seen from the table that when the glass contains a cellulose binder, some PbO reduction occurs as seen by the black or gray color of sample No. 3. In some cases, the gray or black tint is more apparent when the glass slide is viewed from its back side. As mentioned above, these samples were divided into sample No. 4 and
When compared with 5 and 6, it is clear that the additive has a clear effect on suppressing the chemical reduction of PbO. The present invention provides a PbO-containing sealing glass frit mixed with a powder additive for sealing two glass surfaces together, wherein the sealing glass is heated to a temperature sufficient to seal the glass surfaces together. The prevention of PbO in the sealing glass from being reduced when fired under reducing conditions is sufficient to prevent reduction of PbO in the sealing glass upon sealing under reducing conditions. adding into the sealing glass frit an amount of a powdered additive of the group: (A) a cationic hydroxide, the hydroxide being thermally stable at temperatures that seal two glass surfaces together; the hydroxide is capable of being chemically reduced when subjected to reducing conditions; the hydroxide is LiOH, LiOH・H ₂ O, Zr(OH) ₄ , Ba
(OH) selected from the group consisting of _{2.8H 2} O and ZrO _{2.xH 2} O; (B) thermal decomposition temperature of about 30-600°C and melting point of about 36-264
℃ and contains water of hydration, the nitrates are Ca(NO ₃ ) ₂ ·4H ₂ O, Zn(NO ₃ ) ₂ ·
6H ₂ O, La(NO ₃ ) ₃・6H ₂ O, Bi(NO ₃ ) ₂・
5H ₂ O, Ce (NO ₃ ) ₃・6H ₂ O, Ni (NO ₃ ) ₂・6H ₂ O
and Cd(NO ₃ ) _{2.4H 2} O; (C) an inorganic nitrate which is pyrolyzable to yield HNO ₃ between about 150° C. and the fiber softening point of the sealing glass;
The nitrates are _Cu (NO ₃ ) 2.3H ₂ O and BiO
selected from the group consisting of (NO ₃ ).H ₂ O; (D) an inorganic material which is pyrolyzable to produce carbon dioxide at a temperature above that at which the sealing glass frit seals two glass surfaces together; carbonate,
(E) an inorganic oxygen- _{containing chlorine compound having a thermal decomposition temperature above the temperature at which the sealing glass seals two glass surfaces together, the oxygen-containing chlorine compound being KClO 4 ;} wherein the powder additive is miscible with the fired sealing glass.
Concerning glass frit for PbO-containing seals. The powder and its product after firing are miscible with the fired sealing glass. The powder is present in the frit in an amount sufficient to prevent chemical reduction of the PbO during sealing of the PbO sealing glass under reducing conditions. Typically the powder is approximately
Present in the frit in an amount of 0.1-3% by weight,
Preferably it is present at about 0.2-1.5% by weight. If a smaller proportion were used, it would be necessary to adjust the solder glass composition to account for the powder and the product obtained after firing. The sealing glass paste may contain an amount of organic or inorganic acid sufficient to prevent gelling of the paste upon aging. This can be accomplished by adding enough acid to maintain an acidic PH in the paste. Usually only small additions are required. A particularly preferred acid is citric acid. Glass frit for sealing 440lbs
The addition of about 10-15 g of citric acid per (200 kg) was found to be effective in preventing gel formation.
The use of such acids is advantageous in that it allows precise control of the bead width and allows the use of more consistent dispensing pressure when the sealing glass is applied to the surfaces to be sealed together. It is. Other acids such as tartaric acid, phosphoric acid and sulfuric acid also
can be used. Optimal amounts can be determined with a minimum of experimentation.

Claims (1)

[Claims] 1. For sealing two glass surfaces together,
In a sealing glass frit containing PbO mixed with a powder additive, when the sealing glass is fired under reducing conditions at a temperature sufficient to seal the glass surfaces together, the
PbO is prevented from being reduced by adding a powder additive into the sealing glass frit in an amount sufficient to prevent reduction of PbO in the sealing glass upon sealing under reducing conditions. (A) a cationic hydroxide, the hydroxide being thermally stable at the temperature at which the sealing glass frit seals two glass surfaces together; Yes; the hydroxide can be chemically reduced when placed under reducing conditions; the hydroxide is LiOH, LiOH・H ₂ O, Zr(OH) ₄ , Ba
(OH) selected from the group consisting of _{2.8H 2} O and ZrO _{2.xH 2} O; (B) thermal decomposition temperature of about 30-600°C and melting point of about 36-264
℃ and contains water of hydration, the nitrates are Ca(NO ₃ ) ₂ ·4H ₂ O, Zn(NO ₃ ) ₂ ·
6H ₂ O, La(NO ₃ ) ₃・6H ₂ O, Bi(NO ₃ ) ₂・
5H ₂ O, Ce (NO ₃ ) ₃・6H ₂ O, Ni (NO ₃ ) ₂・6H ₂ O
and Cd(NO ₃ ) _{2.4H 2} O; (C) an inorganic nitrate which is pyrolyzable to yield HNO ₃ between about 150° C. and the fiber softening point of the sealing glass;
The nitrates are _Cu (NO ₃ ) 2.3H ₂ O and BiO
selected from the group consisting of (NO ₃ ).H ₂ O; (D) an inorganic material which is pyrolyzable to produce carbon dioxide at a temperature above that at which the sealing glass frit seals two glass surfaces together; carbonate,
(E) an inorganic oxygen- _{containing chlorine compound having a thermal decomposition temperature above the temperature at which the sealing glass seals two glass surfaces together, the oxygen-containing chlorine compound being KClO 4 ;} wherein the powder additive is miscible with the fired sealing glass.
Glass frit for PbO-containing seals.