Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
1999-03-02
2001-08-28
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S426000, C065S060500, C065S060510
Reexamination Certificate
active
06280849
ABSTRACT:
TECHNICAL FIELD
This invention relates to a glass article having a surface-protection coating and a method for producing the glass article with the surface-protection coating, and, in particular, to material of the surface-protection coating.
BACKGROUND ART
During storage and handling operation of glass articles such as glass plates, glass bottle, glass tubes, glass bulbs and other glass products, glass surfaces are often contaminated by dust, dirt, moisture or others, cracked and/or streaked by touch or collision with any other objects, or weathered in long time. As a result, the glass articles have defects before use and cannot actually be used. For example, it is impossible to supply cracked or streaked glass plates in commerce for window glass plates. Contaminated glass bottles cannot be used for containers of drinks, foods and pharmaceuticals. Glass parts having those defects cannot be used at all in electric and electronic products such as cathode ray tubes (CRTs), liquid crystal displays (LCDs) or others.
Therefore, it is well known in the prior art to coat a glass surface of a glass article with a surface-protection coating. The coating is a layer or film of any substance for protecting the glass surface from streak and/or crack, weathering, and contamination by dirt, moisture and others during storage and handling operation. It is desired that the surface-protection coating can readily removed in practical use of the glass article.
Japanese patent publication No. 45-1193 (that is, No. 1193/1970, which will be referred to as Reference I) discloses a glass plate having a surface-protection coating which is soluble in water and, therefore, readily removed by water washing. The surface-protection coating is of ethylene-maleic acid copolymer with a bridged structure and is formed by applying a water solution of the copolymer onto a glass surface of the glass plate.
JP-A-46 48061 (Reference II) discloses to form a water-soluble thin coating of a nonionic surfactant on a glass surface of a glass bottle by spraying a water solution of polyoxyethylene alkyl phenol ether to the glass bottle.
JP-A-56 25970 (Reference III) discloses to form a water-soluble thin coating of silicate on a glass surface of a glass substrate by spraying a water solution of silicate to the glass substrate.
JP-A-4 11981 (Reference IV) discloses to form a thin coating of water-soluble plastic resin on a glass surface of a glass substrate by applying a water solution of plastic resin to the glass substrate. The water-soluble plastic resin is at least one selected from polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polyethylene oxide, polyvinylpyrrolidone, pyrrolidone vinyl acetate copolymer, methyl vinyl maleic acid copolymer, and acrylic acid-methacrylic acid ester copolyer.
JP-A-6 340865 (Reference V) discloses a glass substrate coated with a water-soluble salt such as sodium tripolyphosphate, sodium sesquicabonate, sodium hydrogencarbonate, sodium carbonate, sodium tetracarbonate, or potassium tetracarbonate.
JP-A-7 10600 (Reference VI) discloses a glass article such as glass bottle with a water-soluble coating such as phosphate, borate, silicate, sulfate, inorganic salt including sulfur, halide, carbonate, bicarbonate, nitrate, organic acid salt, double salt of those slats, organic acid, monosaccharides, and polysaccharides. Some of sodium salts are disclosed as the salts actually used.
As described above, it is known in the prior art that organic substances are used for water-soluble surface-protection coating of glass article. However, it is desired that organic substances are avoided from use for such coatings, because the organic substances may often cause the environmental pollution after being washed away by water.
The use of inorganic salts is also known in the prior art as disclosed in References III, V and VI. Among various inorganic salts, sodium salt is known superior in water solubility, and, therefore, useful for the water-soluble surface-protection coating. However, sodium ions in the coating unfortunately degrade the glass surface on which the coating is applied. The use of salts of other alkali metals has the similar problem.
On the other hand, JP-A-3 44857 (Reference VII) discloses a protective film or sheet attached by use of adhesive agent onto an outer face of a CRT tube for protecting a screen face. However, the adhesive agent used often contaminates the face and/or other area of the CRT. Further, there is a problem for wasting the protective sheet after being removed from the CRT.
It is also well known in the prior art to bring a glass article into contact with sulfuric acid gas or hydrochloric acid gas to form a protective layer. This is disclosed in, for example, JP-A-2 120256 (Reference VIII). The protective layer is a chemical compound of sodium in the glass with the gas. The protective layer can be washed out by water. However, since sulfuric acid gas or hydrochloric acid gas is used, there are problems in apparatus and safety.
DISCLOSURE OF INVENTION
Accordingly, it is an object of this invention to provide a glass with a water-soluble surface-protection coating which is neither of organic substance nor inorganic salt.
According to this invention, there is obtained a glass article having a water-soluble surface-protection coating, which is characterized in that the surface-protection coating is of boric acid.
The surface-protection coating is preferably a thin layer of 0.001-1000 &mgr;m, more preferably, 0.01-500 &mgr;m in thickness. When the surface-protection coating has a decreased thickness, it is difficult to protect the glass surface from streak or crack due to collision or friction with other objects. On the contrary, when it has an increased thickness, it takes excessive time for washing out the coating.
This invention further provides a method for producing a glass article having a water-soluble surface-protection coating on a glass surface thereof, characterized by steps of:
preparing the glass article having a glass surface while preparing a boric acid water solution;
applying the boric acid water solution onto the glass article to form a thin layer of the boric acid water solution on the glass surface; and
drying the thin layer of the boric acid water solution to form the water-soluble surface-protection coating of the boric acid on the glass surface.
Brushing or spraying can be used for applying the boric acid water solution onto the glass surface of the glass article. Alternatively, the glass article can be immersed into a bath contained with the boric acid water solution.
The boric acid is preferably orthoboric acid (H
3
BO
3
) in the view point of cost. However, metaboric acid (HBO
2
) or tetraboric acid (H
2
B
4
O
7
) can be used.
In applying the surface-protection coating, the water solution of orthoboric acid used may preferably consist of 0.01-3 wt % orthoboric acid and the balance of water. When a water solution containing orthoboric acid less than 0.01 wt % is used, it is difficult to obtain a coating having a desired surface protection. When a water solution containing orthoboric acid more than 3 wt % is used, the resultant coating is difficult to be washed out by water.
According to a preferable embodiment, the glass article is a glass funnel part for a cathode ray tube. The glass funnel part has an inner surface coated with the surface-protection coating of boric acid.
In another embodiment, the glass article is a glass panel part for a cathode ray tube. The glass panel part has an inner surface coated with the surface-protection coating of boric acid.
REFERENCES:
patent: 2324601 (1943-07-01), Spanagel et al.
patent: 4304812 (1981-12-01), Perkins
patent: 5962565 (1999-10-01), Pagano
patent: 5972517 (1999-10-01), Kondo
patent: 661 817 (1935-11-01), None
patent: 32 45 584 (1984-06-01), None
patent: 441 603 (1936-01-01), None
patent: 56 25970 (1956-03-01), None
patent: 45 1193 (1970-01-01), None
patent: 46 48061 (1973-02-01), None
patent: 57 172 631 (1982-10-01), None
patent: 2 120256 (1990-05-01), None
patent
Collard & Roe P.C.
Jones Deborah
Nippon Electric Glass Co. Ltd.
Savage Jason
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