Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
1999-06-29
2001-10-23
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S046000, C428S048000, C428S428000, C428S432000, C428S433000, C428S410000
Reexamination Certificate
active
06306510
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a laminate comprising a glass layer and a second layer.
More specifically the invention is related to a laminate comprising a glass layer and a polymer layer.
BACKGROUND OF THE INVENTION
Patent application WO 99/21707 discloses a laminate having at least one glass layer as a constituting layer, the glass layer having a thickness of less than 4 mm. Such a laminate presents several advantages over e.g. transparent polymer layers, such as a high thermal stability, a high physical density, high hardness, very good resistance to chemicals, good barrier properties against moisture, solvents and oxygen. Moreover, glass has a high transparency and good optical characteristics.
However, a problem of such a laminate is its limited flexibility. Due to the brittleness of glass, the laminate cannot be deformed to a considerable extent, especially if the glass has a rather large thickness, e.g. larger than 1 mm, or if the deformed glass has a small radius of curvature. Even very thin, and hence flexible glass layers may break.
It would be advantageous to use such a glass laminate for the production of security cards. Because of the high physical density of glass, an original security card comprising a glass laminate can be distinguished from a counterfeited plastic card, by measuring the density of the card. However, a security card comprising such a glass laminate may break easily, e.g. when put away in a wallet in a trouser pocket.
It would also be advantageous to use such a glass laminate for making photomasks, that can e.g. be used to manufacture printed circuit boards, semiconductor devices, integrated circuits. Prior art masks having a polymer support suffer from insufficient dimensional stability, due to environmental changes in temperature and/or humidity. A glass layer support provides the important advantage of a high dimensional stability. However, a photomask comprising such a glass laminate may break e.g. during manipulation, due to its low flexibility.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a laminate that comprises a glass layer and that has an improved flexibility.
It is another object of the invention to provide a laminate that preserves advantages of prior art laminates comprising a glass layer.
These objects are realised by a laminate having the specific features as claimed. Specific features for preferred embodiments of the invention are also claimed. The above mentioned objects are also realised by a method, comprising the steps as claimed.
It is yet another object of the present invention to provide a security card having a high physical density and good flexibility. This object is realised by a security card, having the specific features as claimed.
It is still another object of the present invention to provide a material for making a photomask having a high dimensional stability and good flexibility. This object is realised by a laminate, having the specific features as claimed.
It is yet another object of the present invention to provide a method for making a deformed laminate, the method allowing very large deformations in three dimensions. This object is realised by a method, comprising the steps as claimed.
Some terms used in the claims are defined below.
A “crack line” in a glass layer stands for a long, narrow opening in the glass layer surface (see e.g.
FIG. 1
, crack lines
11
in glass layer
10
), the opening being made in a controlled way, i.e. so that the properties of the crack lines, e.g. their number, their width, their depth, etc. are known before the crack lines are made. An occasional break is not a crack line. A crack line can start and end at an edge of the glass layer, at another crack line, or at an arbitrary position on the glass layer surface. The depth of a crack line is smaller than or equal to the glass layer thickness; a crack line has a nonzero minimum depth, as is discussed hereinafter. A crack line can have zero width, as a special case (a crack line having zero width can e.g. be created by cutting the glass layer, thus splitting it into two glass layer portions with a narrow opening in-between, and by subsequently closing the opening by moving the first portion until it contacts the second portion). The edges of the cross section of a crack line may be sharp or rounded; the cross section may have rounded edges at the “bottom” side of the crack line, e.g. a cross section may have a U-shape, or the cross section may have rounded edges at the “top” side opposite to the bottom side, or some edges of the cross section may be sharp and other edges may be rounded.
A “pattern” is formed by a set of crack lines on a surface. A “pattern element” is an entity that is completely enclosed by these crack lines and possibly by the edges of the surface. As an example, the pattern elements in
FIG. 3
a
are hexagons. A pattern element may comprise one or more crack lines starting and ending within the enclosure of the pattern element, or starting on the edge of the pattern element and ending within the enclosure of the pattern element; both cases are illustrated in
FIG. 3
f.
A pattern element has a “pattern element size”, defined as being calculated from the area of the pattern element as follows: size={square root over (area/&pgr;)} (in fact, the pattern element size equals the radius of a circle having the same area as the pattern element. As an example, for a pattern of squares with side c, the pattern element size is c/{square root over (&pgr;)}).
In a preferred embodiment, one or more glass layers in the laminate comprise a number of portions that have crack lines, and a number of portions that have no crack lines. Thus, some portions of the laminate may have an improved flexibility (as explained below), while other portions may have the flexibility of prior art laminates. In this case, the maximum pattern element size of the laminate is defined as the maximum pattern element size of the portions of the glass layers having crack lines.
When deforming a laminate comprising a glass layer having crack lines, the glass layer does not act as a uniform layer having a high stiffness, determined by its material properties and its thickness. Instead, the individual pattern elements can move about the crack lines. In this way, a laminate comprising a glass layer and having a high flexibility is obtained. This is discussed more in detail hereinafter.
A laminate according to the present invention preserves advantages of prior art laminates comprising a glass layer, and offers an improved flexibility.
Further advantages and embodiments of the present invention will become apparent from the following description and drawings.
REFERENCES:
patent: 1219853 (1917-03-01), Okada
patent: 2887806 (1959-05-01), Hassett
patent: 4774143 (1988-09-01), Gondela et al.
patent: 5558827 (1996-09-01), Howes
Tahon Jean-Pierre
Verlinden Bartholomeus
Vermeulen Leo
AGFA-GEVAERT
Bahta Abraham
Breiner & Breiner L.L.C.
Jones Deborah
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