WO1999015471A1 - Thermal dimensional stability treatment of vitreous sheet material by contacting with a molten alkali metal salt - Google Patents
Thermal dimensional stability treatment of vitreous sheet material by contacting with a molten alkali metal salt Download PDFInfo
- Publication number
- WO1999015471A1 WO1999015471A1 PCT/BE1998/000137 BE9800137W WO9915471A1 WO 1999015471 A1 WO1999015471 A1 WO 1999015471A1 BE 9800137 W BE9800137 W BE 9800137W WO 9915471 A1 WO9915471 A1 WO 9915471A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- sheet
- molten salt
- vitreous material
- temperature
- alkali metal
- Prior art date
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C21/00—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
- C03C21/001—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions
- C03C21/002—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions to perform ion-exchange between alkali ions
Definitions
- the present invention relates to treatment of a sheet of a vitreous material such as glass and to the sheet so-formed It is especially concerned with the production of sheets of vitreous material having improved dimensional stability Because glass and like vitreous materials are non-crystalline treating them by means involving heating and cooling tends to result in dimensional changes such as reduction in area The reduction in the dimensions also known as compaction or shrinkage is for many purposes insignificant There are however increasing demands for glass with improved dimensioned stability for example for glass sheets to be used as substrates m electronic applications In these applications even very small shrinkages may be unacceptable because of the need for precise alignment of the glass sheet with other components
- Annealing is a known densification process but it involves prolonged treatment at elevated temperatures requiring substantial heat energy input, and the results tend to be of inconsistent quality
- the extent of the densification varies with the annealing temperature time and cooling rate
- Another difficulty is that the glass viscosity is reduced at the elevated temperature such that a glass sheet may become warped or acquire surface defects during the annealing process
- An alternative solution consists of selecting a special composition glass with a very high strain point which when processed undergoes negligible shrinkage
- Chemical tempering treatment of a vitreous material is well known. Its purpose is to impart an increased mechanical and thermomechanical resistance to vitreous materials such as glass and vitrocrystalline materials.
- the chemical tempering can be of two types. According to one type of process ion exchange is performed at a temperature which is sufficiently high to cause stress relaxation to occur in the glass, while the ions entering the glass are such as to impart a lower co-efficient of thermal expansion to the glass surface layers. According to the other type of process, ions already in the glass surface layers are replaced by larger ions and the ion exchange is effected at a temperature below the glass annealing point so that stress relaxation does not occur to any substantial degree.
- GB patent 1276186 teaches chemical tempering treatment of a vitreous body by the entry of ions of at least one substance into the superficial layers of the body, followed by the application of a coating layer such as an oxide of titanium, silicon, aluminium, chromium or other metals, titanium nitride, or a carbide of silicon, titanium, tantalum or other metals.
- a coating layer such as an oxide of titanium, silicon, aluminium, chromium or other metals, titanium nitride, or a carbide of silicon, titanium, tantalum or other metals.
- the chemical tempering increases the adherence of the coating layer.
- Examples of chemicals in the said patent for effecting the tempering include potassium nitrate, sodium nitrate, lithium carbonate and lithium chloride.
- a method for producing a sheet of vitreous material for use as a substrate characterised in that prior to any firing step or other heat treatment associated with the application of coating layers to the said sheet it is contacted with a molten alkali metal salt to improve its thermal dimensional stability.
- the method is conducted such that alkali metal ions from the molten salt diffuse into superficial layers of the said sheet and ions from the said superficial layers diffuse into the molten salt, the resulting ion exchange producing or increasing compressive stresses in the superficial layers.
- the chemical tempering improves its dimensional stability, such that wide ranges of heating and cooling applied by heat treatment do not create an unacceptable amount of shrinkage.
- a heat treatment such as firing at a higher temperature than the annealing point of the vitreous material, for example 580°C. all the stresses induced by the ion exchange in the superficial layers of the sheet will have disappeared and the vitreous material will have lost its strengthening from chemical tempering.
- the resulting sheet also has a better uniformity of dimensional stability than sheets treated solely by annealing.
- the invention thus provides a sheet of vitreous material which is suitable for use in applications which demand precision in the sheet ' s sizing.
- the invention is typically applicable to a conventional soda lime glass and the present description relates primarily to this type, the method of the invention can be applied if required to other types of glass, for example borosilicate, aluminosilicate and vitrocrystalline material.
- molten salt of a metal or metals selected from lithium and potassium is suitable.
- Molten potassium nitrate is particularly suitable for soda-lime glass.
- Contact between the sheet and the molten salt is conveniently achieved by immersing the sheet in the salt in a suitable vessel.
- the temperature profile of the vitreous material should be carefully regulated through the stages of the method of the invention.
- the salt is necessarily at a high temperature to maintain it in a molten state.
- the temperature of the vitreous material is preferably raised slowly towards the temperature of the molten salt, most preferably at a rate of less than 15°C/minute. Soaking in the molten salt for an extended period to achieve the required tempering ensures that the temperature of the vitreous material rises to, and is held at, the molten salt temperature.
- the molten salt should be at a temperature below the annealing point of the vitreous material, which temperature is typically in the range 400 to 500°C. Uniformity of temperature of the molten salt is important, both throughout the tank in which it is held and throughout the soaking period.
- the molten salt temperature should preferably have a maximum deviation of 2°C. Mixing of the molten salt to maintain the uniform conditions can conveniently be achieved by blowing carbon dioxide through the salt, for example as taught in our earlier patent GB-A- 1274733.
- the vitreous material Upon removal from the molten salt, the vitreous material should be cooled slowly from the salt temperature, preferably at a rate of less than 15°C/minute. Slow rates of cooling appear to be desirable to avoid structural damage to the vitreous material and to encourage a low level of shrinkage. In some instances it is advantageous to conduct the cooling in two stages, each stage having a different rate of cooling.
- the invention is further described with reference to the following non-limiting examples. These employed sample sheets of glass, cut to nominal dimensions of 350 x 270 mm. The sheets for examples 1 to 5 had a thickness of 1.1 mm and the sheets for examples 6 and 7 had a thickness of 3 mm. The samples for examples 1 to 5 were held in a warmed chamber at 200°C until they were withdrawn for treatment as described below.
- the 350 mm length dimension was accurately measured for each sample before treatment and at various stages of the process, all the length measurements being made at an ambient temperature of 20°C.
- Example 1 Twelve sample sheets of ordinary soda lime float glass at 200°C were placed in a carrier and introduced into a pre-heating chamber in which they were steadily heated to 460°C over a period of 1 hour 30 minutes, representing a heating rate of about 3°C/minute.
- the glass and carrier were then placed in a tank of molten potassium nitrate at a temperature of 460°C and held therein for a period of four hours for the ion exchange to proceed.
- the glass and carrier were then placed in a drainage chamber at 460°C for 30 minutes, during which period most of the molten potassium nitrate removed from the tank with the glass and carrier drained off and was collected for reuse.
- the glass samples were then placed in a cooling chamber in which they were slowly cooled, first for a period of 2 hours at a rate of about l°C/minute and next for a period of 1 hour 15 minutes at a rate of about 2°C/minute.
- a batch of ten sample sheets of ordinary soda lime float glass at 200°C was placed in a carrier and treated generally as described in Example 1, but with the difference that the carrier was placed directly into the tank of molten potassium nitrate, omitting the step of pre-heating to the 460°C tank temperature.
- the glass was thereby heated more quickly to the tank temperature, it being estimated that the rate of temperature increase was about 50°C/minute.
- the nominal 350 mm dimension of each of the sample sheets was again accurately measured at 20°C and compared with the figure obtained before the treatment to show the extent of shrinkage. The average result is shown in the accompanying table.
- Example 3 Seven of the sample sheets treated according to Example 1 were subjected to a Treatment (A) which comprised heating from the ambient temperature of 20°C at a rate of 5 min to 460°C. holding at that temperature for 30 minutes and then slowly cooling to the ambient temperature. The nominal 350 mm dimensions were again accurately measured and compared with the figure obtained before Treatment (A) . The average shrinkage is shown in the table.
- A Treatment
- Treatment (A) comprised heating from the ambient temperature of 20°C at a rate of 5 min to 460°C. holding at that temperature for 30 minutes and then slowly cooling to the ambient temperature.
- the nominal 350 mm dimensions were again accurately measured and compared with the figure obtained before Treatment (A) .
- the average shrinkage is shown in the table.
- Example 5 Five of the sample sheets treated according to Example 1 were subjected to a Treatment (B) which comprised heating from the ambient temperature of 20°C at 3 min to 460°C, i.e. a slower rate than in Treatment (A), holding at that temperature for 30 minutes and then slowly cooling to the ambient temperature. The nominal 350 mm dimension was again accurately measured at 20°C and compared with the figure obtained before Treatment (B). The average shrinkage is shown in the table.
- Treatment (B) comprised heating from the ambient temperature of 20°C at 3 min to 460°C, i.e. a slower rate than in Treatment (A), holding at that temperature for 30 minutes and then slowly cooling to the ambient temperature.
- the nominal 350 mm dimension was again accurately measured at 20°C and compared with the figure obtained before Treatment (B). The average shrinkage is shown in the table.
- Example 5 Example 5
- sample sheets of ordinary soda lime float glass were subjected to a simple thermal treatment, excluding any contact with potassium nitrate or other chemical tempering agent.
- the treatment comprised heating the samples from 200°C to 460°C at a rate of 37minute, holding the temperature at that level for 30 minutes and slowly cooling to 20°C.
- the shrinkage was again measured and the average figure, shown in the table, was more than double that measured for the samples which had been subjected to a chemical tempering and heat treatment.
- the sample sheets prepared according to Example 3 were especially advantageous in that the amount of shrinkage caused by high temperature treatment was less than 100 ⁇ m/m.
- Examples 6 & 7 were conducted in a typical industrial unit for chemical tempering of glass in molten potassium nitrate.
- the unit included a pre-heating chamber, a tank containing the molten potassium nitrate, a drainage chamber and a cooling chamber and then a washing station.
- the samples employed for example 6 were of ordinary soda lime float glass whereas those for example 7 were of extra-clear glass (having a very low iron content).
- the samples (20 for example 6. 10 for example 7) were placed in carriers and put into a pre-heating chamber where their temperature was raised at a rate of about 10°C/minute to 400°C. i.e. approaching the working temperature of the molten potassium nitrate.
- the carrier was then placed in the tank of molten potassium nitrate and left to soak for a period of eight hours.
- a push-rod gradually advanced the carrier through the molten salt tank to the drainage chamber over the said period.
- the temperature of the molten potassium nitrate was maintained at within 2° of 465°C throughout the period.
- Treatment of a sheet of a vitreous material according to the present invention is especially useful in the production of display panels as described in the copending patent application n Q 97 11815 filed in France by Thomson Tubes Electroniques under the title "Procede de realisation d'unarriage de visualisation comportant une dalle a stabilite dimensionelle amelioree" [Process for production of a display panel comprising a sheet of improved dimensional stability] on September 23, 1997.
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020007003004A KR100347832B1 (en) | 1997-09-23 | 1998-09-18 | Treatment of vitreous material |
JP2000512785A JP2001517599A (en) | 1997-09-23 | 1998-09-18 | Thermal dimensional stabilization of vitreous sheet materials by contact with molten alkali metal salts |
EP98944903A EP1021382A1 (en) | 1997-09-23 | 1998-09-18 | Thermal dimensional stability treatment of vitreous sheet material by contacting with a molten alkali metal salt |
AU92463/98A AU9246398A (en) | 1997-09-23 | 1998-09-18 | Thermal dimensional stability treatment of vitreous sheet material by contactingwith a molten alkali metal salt |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9720230.3 | 1997-09-23 | ||
GB9720230A GB2329382A (en) | 1997-09-23 | 1997-09-23 | Chemical treatment of vitreous material |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1999015471A1 true WO1999015471A1 (en) | 1999-04-01 |
Family
ID=10819520
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/BE1998/000137 WO1999015471A1 (en) | 1997-09-23 | 1998-09-18 | Thermal dimensional stability treatment of vitreous sheet material by contacting with a molten alkali metal salt |
Country Status (8)
Country | Link |
---|---|
EP (1) | EP1021382A1 (en) |
JP (1) | JP2001517599A (en) |
KR (1) | KR100347832B1 (en) |
CN (1) | CN1121991C (en) |
AU (1) | AU9246398A (en) |
GB (1) | GB2329382A (en) |
TW (1) | TW546263B (en) |
WO (1) | WO1999015471A1 (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100833371B1 (en) * | 2001-04-27 | 2008-05-28 | 젠야쿠코교가부시키가이샤 | Heterocyclic compound and antitumor agent containing the same as active ingredient |
DE10319708A1 (en) * | 2003-05-02 | 2004-11-25 | Tu Bergakademie Freiberg | Alkali-containing glasses with modified glass surfaces and process for their preparation |
WO2014007222A1 (en) * | 2012-07-03 | 2014-01-09 | 旭硝子株式会社 | Glass production method and chemically strengthened glass |
KR102145229B1 (en) * | 2013-05-24 | 2020-08-18 | 니폰 덴키 가라스 가부시키가이샤 | Method for manufacturing tempered glass sheet |
Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3628934A (en) * | 1967-04-28 | 1971-12-21 | Glaverbel | Temperature control of chemical tempering of solid glass or vitrocrystalline bodies |
GB1274733A (en) * | 1969-08-15 | 1972-05-17 | Glaverbel | Process for modifying glass and other articles |
GB1276186A (en) * | 1968-09-12 | 1972-06-01 | Glaverbel | Surface coated glass bodies |
US4290793A (en) * | 1978-12-08 | 1981-09-22 | Liberty Glass Company | Fluid bed chemical strengthening of glass objects |
JPS58156554A (en) * | 1982-03-11 | 1983-09-17 | Nippon Electric Glass Co Ltd | Treatment of glass surface |
US5277946A (en) * | 1989-08-24 | 1994-01-11 | Nippon Electric Glass Co., Ltd. | Alumina package for hermetically containing an electronic device therein |
DE19616679C1 (en) * | 1996-04-26 | 1997-05-07 | Schott Glaswerke | Chemically toughened alumino-silicate glass production |
US5654057A (en) * | 1994-12-28 | 1997-08-05 | Hoya Corporation | Sheet glass flattening method, method of manufacturing glass substrate for an information recording disk using flattened glass, method of manufacturing a magnetic recording disk using glass substrate, and magnetic recording medium |
US5676722A (en) * | 1994-07-08 | 1997-10-14 | Vetrotech Ag | Method for producing flat or arcuate glass plates |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
BE754450Q (en) * | 1960-11-15 | 1971-01-18 | Research Corp | GLASS TREATMENT PROCESS |
US3506423A (en) * | 1969-05-28 | 1970-04-14 | Ppg Industries Inc | Glass strengthening by ion exchange |
GB1307595A (en) * | 1970-04-28 | 1973-02-21 | Owens Illinois Inc | Glass articles having high modulus of rupture |
DD88841A1 (en) * | 1970-12-14 | 1972-03-20 | ||
FR2128031B1 (en) * | 1971-03-01 | 1976-03-19 | Saint Gobain Pont A Mousson | |
US4483700A (en) * | 1983-08-15 | 1984-11-20 | Corning Glass Works | Chemical strengthening method |
US4897371A (en) * | 1987-02-03 | 1990-01-30 | Nippon Sheet Glass Co., Ltd. | Glass article protected from coloring by electron rays and method of using |
-
1997
- 1997-09-23 GB GB9720230A patent/GB2329382A/en not_active Withdrawn
-
1998
- 1998-09-17 TW TW087115502A patent/TW546263B/en not_active IP Right Cessation
- 1998-09-18 KR KR1020007003004A patent/KR100347832B1/en not_active IP Right Cessation
- 1998-09-18 CN CN98809436A patent/CN1121991C/en not_active Expired - Fee Related
- 1998-09-18 JP JP2000512785A patent/JP2001517599A/en not_active Withdrawn
- 1998-09-18 EP EP98944903A patent/EP1021382A1/en not_active Ceased
- 1998-09-18 AU AU92463/98A patent/AU9246398A/en not_active Abandoned
- 1998-09-18 WO PCT/BE1998/000137 patent/WO1999015471A1/en active IP Right Grant
Patent Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3628934A (en) * | 1967-04-28 | 1971-12-21 | Glaverbel | Temperature control of chemical tempering of solid glass or vitrocrystalline bodies |
GB1276186A (en) * | 1968-09-12 | 1972-06-01 | Glaverbel | Surface coated glass bodies |
US3785792A (en) * | 1968-09-12 | 1974-01-15 | Glaverbel | Surface coating of chemically tempered vitreous bodies |
GB1274733A (en) * | 1969-08-15 | 1972-05-17 | Glaverbel | Process for modifying glass and other articles |
US4290793A (en) * | 1978-12-08 | 1981-09-22 | Liberty Glass Company | Fluid bed chemical strengthening of glass objects |
JPS58156554A (en) * | 1982-03-11 | 1983-09-17 | Nippon Electric Glass Co Ltd | Treatment of glass surface |
US5277946A (en) * | 1989-08-24 | 1994-01-11 | Nippon Electric Glass Co., Ltd. | Alumina package for hermetically containing an electronic device therein |
US5676722A (en) * | 1994-07-08 | 1997-10-14 | Vetrotech Ag | Method for producing flat or arcuate glass plates |
US5654057A (en) * | 1994-12-28 | 1997-08-05 | Hoya Corporation | Sheet glass flattening method, method of manufacturing glass substrate for an information recording disk using flattened glass, method of manufacturing a magnetic recording disk using glass substrate, and magnetic recording medium |
DE19616679C1 (en) * | 1996-04-26 | 1997-05-07 | Schott Glaswerke | Chemically toughened alumino-silicate glass production |
Non-Patent Citations (1)
Title |
---|
PATENT ABSTRACTS OF JAPAN vol. 007, no. 277 (C - 199) 9 December 1983 (1983-12-09) * |
Also Published As
Publication number | Publication date |
---|---|
CN1121991C (en) | 2003-09-24 |
CN1271335A (en) | 2000-10-25 |
JP2001517599A (en) | 2001-10-09 |
KR100347832B1 (en) | 2002-08-07 |
TW546263B (en) | 2003-08-11 |
GB9720230D0 (en) | 1997-11-26 |
GB2329382A (en) | 1999-03-24 |
KR20010030654A (en) | 2001-04-16 |
AU9246398A (en) | 1999-04-12 |
EP1021382A1 (en) | 2000-07-26 |
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