Coating processes – Removable protective coating applied
Reexamination Certificate
2000-02-15
2002-12-10
Nakarani, D. S. (Department: 1773)
Coating processes
Removable protective coating applied
C427S421100, C427S428010, C427S443200, C428S332000, C428S442000
Reexamination Certificate
active
06491972
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of applying an at least one-layer removable polymer coating on glass substrates, in particular display glasses or solid plate substrates, as a protective layer. The present invention also relates to a display glass,:and an electronic device, which includes the display glass. Moreover, the present invention also relates to hard disk substrates of glass or glass ceramic.
Glass substrates are substrates of conventional glass as well as substrates or glass ceramic. During the production of glass substrates, in particular for display glasses or solid plate substrate of glass or glass ceramic, there are massive yield problems, since the glass substrate due to treatment and transportation have defects in form of scratches and particles. These scratches moreover can induce glass breakage which acts destructively when occurred during a process step, since-the process must be interrupted for cleaning the machines from such chips which can cause further scratches.
During splitting and cross cutting, particles are released, and they lie on the glass surface and act as abrasive particles during the further transportation and treatment so as to lead to scratching of the surface. Also, the edge treatment which follows the separation of the substrate leads to loading of the glass surface with glass particles, which again act as abrasive bodies. Moreover, during the edge treatment for cooling and for removal of the grinding solution, a high pressure water jet is oriented to the edges.
Methods are known, in which at both sides polymer foil is laminated. Such methods have several disadvantages. The protective foil can be applied after the cutting of the glass and can therefore protect only during the transport and during the edge treatment. During the edge treatment the foil is partially lifted at the edges and under it a grinding dust is collected and the glass is damaged. Moreover, especially in thin glass, due to the required pulling force for removing the foil glass breakage again occurs in many instance.
For the lamination of the polymer protective foil, adhesives materials are required, which not always can be removed without resides. The glass surface must be polished thereafter in certain circumstances, to obtain the required quality. The post-polishing is performed mainly mechanically and removes the adhesive residuals, but on a microscopic plane does not lead to an optimal surface quality, as desired for example for display glass or optical special glass or also solid plate substrate, since by polishing minute scratches are produced. A great disadvantage is also the high refuse by glass breakage during polishing.
The German patent document DE 36 15 277 A1 discloses a method, in which the flat glass is provided with a scratch-resistant splinter protecting coating. Immediately after the manufacture, within the cooling region a synthetic plastic powder is applied, which is melted on the glass band. For increasing the mechanical stability, a base layer and a scratch-resistant cover layer are applied. The sprinter protective layer produced in this manner can not be again removed. In addition, no surface quality which is suitable for display is obtained. Utilization as a solid plate substrate is not possible due to the synthetic plastic layer.
The Japanese patent document JP-H 102 26537 discloses a method, in which a water-soluble protective film is applied, which does not affect the glass (it does not contain alkali salt) and is resistant against moisture. For the protective film, polyvinyl alcohol solutions in water are utilized, wherein the polyvinyl alcohol has an average molecular mass of at most 51,600 g/mol, preferably under 25,800 g/mol, and is partially hydrolyzed, preferably between 55% and 85%. The upper limits are based on that, with high average molecular masses as well as with hydrolysis degrees below substantially 95%, the water solubility dramatic drastically reduces. With low hydrolysis degrees, to the contrary, the water solubility increases with the hydrolysis degree. This protective film of polyvinyl alcohol with an average molecular mass of less than approximately 50,000 g/mol and a hydrolysis degree between 55% and 85% is sufficiently water soluble even below 30° C. Such a polyvinyl alcohol protective film is removed during the edge treatment in the shortest time.
The patent document BE 714347 discloses a further process on the basis of a water soluble polymer protective film. In this process a mixture of hydroxylethycellulose and dialdehyde in water or of polyvinylalcohol and dialdehyde in water is used. The dialdehyde has the action of a crosslinking agent which makes the protective film swellable and reduces the adherence of the protective film to the glass. By the admixing of a dialdehyde, the water solubility of the polymer protective layer is adjusted. There is no disclosure as to the polymerization degree of the preferable polyvinylalcohol. The hydrolysis degree must be at 85% or higher. It has been however shown that the protective films of such polymers are removed during the edge treatment.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method for protection of surfaces of glass substrates, in accordance with which the surfaces of glass substrates from the production to the end stages of the treatment, in particular the wet edge treatment, and during all intermediate transports are protected from scratching and abrasive bodies, which also can be performed with a lowest possible number of process steps, with which the refuse is minimized, and which guarantees the highest possible surface quality of the end product.
It is also an object of present invention to provide a display glass which at low manufacturing cost has an excellent surface quality, or an electronic device which is provided with such a display glass.
Moreover, it is also an object of present invention to provide a hard disk substrate, which has low manufacturing costs and an excellent surface quality.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a method of applying a detachable protective coating comprising at least one layer of polyvinyl alcohol on a glass substrate, in particular a display glass or a hard disk substrate in which the applied polyvinyl alcohol has an average molecular weight ≧55,000 g/mol and a hydrolysis degree ≧95%.
In accordance with another feature of present invention a method is provided, in accordance with which a polymer is utilized, which is soluble in polar organic solvent.
Still another feature of present invention resides in a display glass which before, during or after transport and/or complete treatment is not polished.
In accordance with a further feature of present invention a display glass is provided which has at least one removable polymer layer, and the at least one polymer layer is soluble in water at a temperature ≧50° C., or in a polar organic solvent, or in a mixture of water and a polar organic solvent.
In accordance with still a further feature of present invention, an electronic device is proposed which has a display glass, and the display glass before, during or after the transport and/or complete treatment is not polished.
Also, a hard disk of glass or ceramic is disclosed, which before, during after transportation and/complete treatment is not polished.
In accordance with another feature of the invention, also a hard disk is disclosed, which is composed of glass or glass ceramic and has at least one releasable polymer layer, and the at least one polymer layer is soluble in water at a temperature greater than or equal to 50° C. or in a polar organic solvent or in a mixture of water and a polar organic solvent.
Finally, it is proposed to use a glass or ceramic substrate as an initial blank for a hard disk used in electronic devices.
In accordance with a further method, at least one layer of polyvinyl alcohol is applied on the gl
Berndt Andreas
Buerkle Roland
Mauch Reiner
Schlatterbeck Dirk
Walther Marten
Nakarani D. S.
Schott Glas
Striker Michael J.
LandOfFree
Method of protecting surfaces of glass substrates does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of protecting surfaces of glass substrates, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of protecting surfaces of glass substrates will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2972228