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Two-layer protective coating system for LCD glass

a coating system and glass technology, applied in coatings, transportation and packaging, chemical instruments and processes, etc., can solve the problems of glass surface quickly becoming contaminated, contamination being observed, rendering glass useless for many applications, etc., to improve the scratch resistance of the coating system, evaluate the cleanness of the glass surface, and the effect of the same chemistry and smoothness

Inactive Publication Date: 2005-07-21
ALLAIRE ROGER A +6
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

"The present invention provides a method for protecting a clean surface of glass from being contaminated by ambient contaminants and scratches during processing and handling. The method involves applying a first protective coating to the surface using a polysaccharide coating composition, optionally removing a portion of the coating to leave a thin layer of coating, and then applying a second protective coating over the first coating. The second coating is less soluble in water than the first coating, and both coatings can be removed using an aqueous cleaning composition to leave a substantially clean surface. The method can be used for protecting any glass surface that needs temporary protection. The first coating can be applied during the glass manufacturing process or afterwards. The second coating can be applied by spraying or other coating methods. The method can also include steps of cutting and grinding the glass, and applying water or a water-containing composition to the coated glass surface."

Problems solved by technology

When exposed to the environment, glass surface can quickly become contaminated with dust and other inorganic and / or organic ambient contaminants, with contamination being observed within a few hours.
Some of these particles irreversibly adhere to the clean glass surface, rendering the glass useless for many applications.
This is particularly a serious problem for LCD glass surfaces.
Although the adhesive-backed film protects the surface from scratching by the handling equipment, it causes other problems.
Another problem with this film is that it may leave an adhesive residue on the glass surface.
A further problem with the film approach is glass breakage during peeling of the film from the glass surface, especially for large and / or thin glass sheets.
However, few of them can be completely removed in a cleaning solution at a temperature as low as 40° C. in a typical manufacturing process.
However, the high water solubility of polysaccharides, especially starches, constitutes a potential drawback of this method.
Due to their high solubility in water, the polysaccharide coatings may be diminished during such stages, leading to reduced particle protection and scratch resistance.

Method used

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  • Two-layer protective coating system for LCD glass
  • Two-layer protective coating system for LCD glass

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0141] Two coating systems were tested in this example, both using polymers that are more hydrophobic than starch as the second protective coating over a starch first protective coating.

[0142] In this example, the first coating composition had a concentration of starch of 10%. The two second coating compositions used in this example were (i) a styrene / acrylic co-polymer based emulsion (20% solids) available from Johnson Wax Professional, Sturtevant, Wiss., and (ii) Chempeel WB high solids (55-60%) strippable coating product available from PPG Industries, One PPG Place, Pittsburgh, Pa., respectively.

[0143] The first protective coating was formed as discussed above. After the first coating dried up, the second coating composition was applied to the surface of the first protective coating layer and dried with an IR heater to form a second protective coating layer. Water contact angle was then measured on the surface of the second protective coating layer thus obtained and recorded as...

example 2

[0145] One coating system was tested in this example, using petrolatum as the second protective coating over a starch first protective coating.

[0146] In this example, the first coating composition has a concentration of starch of 5%. The second coating composition used in this example was petrolatum gel available from Fisher Scientific, Pittsburgh, Pa.

[0147] The first protective coating was formed as discussed above. The thickness of the dried first protective coating was about 1 μm. After the first coating dried up, the second coating composition (petrolatum gel) was applied to the surface of the first protective coating layer by smearing to form a second protective coating layer. Water contact angle was then measured on the surface of the second protective coating layer thus obtained and recorded as the first water contact angle θ1 in TABLE I.

[0148] Half of the glass sheet was then subjected to water treatment by dipping and immersion in deionized water for 1 minute. Coating th...

example 3

[0152] Two coating systems were tested in this example, both using polymer beads as the second protective coating over a starch first protective coating.

[0153] In this example, the first coating composition has a concentration of starch of 10%. The second coating composition used in this example was (iii) poly(styrene-divinylbenzene) (PSDB, 20% divinyl benzene, average molecular weight 250,000 g / mol) beads and (iv) poly(methyl methacrylate) (PMMA, average molecular weight 25,000 g / mol) beads, respectively, both available from Polysciences, Inc., Warrington, Pa.

[0154] The first protective coating was formed as discussed above. Once the first coating composition was applied to the hot glass surface and before it dried up, the glass sheet was placed horizontally and the second coating composition (iii) or (iv) was applied to the surface of the first protective coating layer by sprinkling. After the coating dried up, excessive loose polymer beads were removed by flipping the glass she...

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Abstract

Two-layer protective coating system for glass surfaces is disclosed. The base coating comprises at least one polysaccharide, and the top coating has a lower solubility in water than the base coating. The coating system provides good protection against contaminants and glass chips, good removability in mild cleaning condition, and extra water resistance during process steps where water is used as a cooling agent.

Description

FIELD OF THE INVENTION [0001] The present invention relates to the protection of glass surfaces, and in particular, to the temporary protection of the surfaces of glass sheets used in producing liquid crystal displays (LCDs). The invention is useful, for example, in protecting the glass sheets from being contaminated by ambient dirt or glass chips produced during the processing of the sheets, such as cutting, grinding, packing and transportation. In addition, the invention is useful in protecting the glass sheets from scratching. BACKGROUND OF THE INVENTION [0002] Many uses of glass, including glass for producing LCDs, require a very clean glass surface that is substantially free of dust and other organic and / or inorganic contaminants. When exposed to the environment, glass surface can quickly become contaminated with dust and other inorganic and / or organic ambient contaminants, with contamination being observed within a few hours. [0003] Current procedures used to cut and grind gla...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B05D5/00B05D7/00C03C17/34
CPCC03C17/3405C03C2217/42C03C2217/47Y10T428/25C09D5/008Y10T428/265C03C2218/355Y10T428/31641B05D1/36B05D5/00B32B17/06
Inventor ALLAIRE, ROGER A.BACA, ADRA S.CHIEN, CHING-KEEPOWELL-JOHNSON, ANDRIENNE M.SCHISSEL, DAVID N.SEVER, EDWARD J.SHI, YOUCHUN
Owner ALLAIRE ROGER A
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