Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
1999-08-12
2001-02-27
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S281100, C430S286100, C430S905000, C430S913000, C549S228000
Reexamination Certificate
active
06194124
ABSTRACT:
FIELD OF THE INVENTION
The invention is directed to a new polycarbonate polymer and its use in a photosensitive composition and tape.
BACKGROUND OF THE INVENTION
Photosensitive pastes are widely used in electronic circuit fabrications to build conductors, resistors, dielectrics, or substrates. There is a need in the industry to replace the use of pastes with ceramic green tapes. Ceramic tapes are used primarily as a dielectric or insulating material for building multilayer ceramic substrates and other current tape products.
Both pastes and tapes contain components such as polymers, surfactants, plasticizers, photoreactive components, etc., which give certain pastes and tapes green properties that are necessary in their use. The organics are removed completely from the system during the process to achieve end use properties. Such organic removal is normally done by a thermal heating of the system above the highest decomposition temperature of the organic components (“burn-out” process).
As the application of the ceramic tape/paste products gets increasingly sophisticated and expands into new technology areas, there is a growing need to lower the ceiling temperature for the organic burn-out. One such need, for example, exists in the product development for the plasma display panel, one of emerging flat panel display technologies, where the window glass is used for the panel substrate and therefore the firing temperature has to be kept below the low softening temperature of the substrate glass (~600C).
The decomposition temperature of organics currently used in the industry for ceramic products (cellulose or acrylate polymers and monomers after polymerization) is close to the high end limit allowed for the burn-out step in a number of applications. Therefore, the polycarbonates and use of such polycarbonates, as disclosed herein, meet the need of a lower decomposition temperature which may be used in pastes and tapes.
SUMMARY OF THE INVENTION
The invention is directed to polymer comprising the repeat unit
wherein each of R
1
through R
7
are independently hydrogen or alkyl, and R
8
is hydrogen or methyl.
The invention is further directed to a photosensitive composition comprising an admixture of: (a) finely divided particles if inorganic solids selected from the group consisting of ceramic, metal, metal oxide or metal alloy; (b) finely divided particles of an inorganic binder having a glass transition temperature in the range of form 550 to 825° C. a surface area to weight ratio of no greater than 10 m
2
/g and at least 95 wt. % of the particles having a size of 1-10 &mgr;m, dispersed in an organic vehicle comprising; (c) polymer as recited herein above; (d) photoinitiation system; (e) organic medium. With removal of the organic medium the above composition can be utilized for a tape. Also, in the given composition the polymer as recited above may be replaced by the polycarbonate resulting from the polymerization of 5-carbomethoxy-5-methyl-1,3-dioxin-2-one.
DETAILED DESCRIPTION
The invention includes the use of polymers carbonated in the back bone with acrylate pendant groups known as polycarbonates which are used in photosensitive thick film compositions for pastes and tapes. Polycarbonate polymers can replace the standard acrylic monomers and/or polymers in conventional photosensitive compositions. The tapes or pastes that include the use of polycarbonates are intended for applications where the firing temperature for organic burn-out is limited by the substrate material. The invention utilizes the low thermal decomposition temperature of the carbonate group in the backbone of the polymer. The invention is also directed to a new polycarbonate polymer and its use in compositions for pastes and tapes. In order to produce pastes and tapes with lower decomposition temperatures a class of polycarbonate polymer binders are admixed with inorganic solids and inorganic binders accompanied by a photoinitiation system to form photosensitive pastes and tapes. Components of the invention are discussed hereinbelow along with a new polycarbonate polymer.
A. Ceramic Solids and Metal Powders
The invention is applicable to virtually any high melting inorganic solid material which include ceramic, metal, metal alloy, metal oxide or mixtures thereof. However, it is particularly suitable for making dispersions of dielectric pastes or tapes using solids such as alumina, titanates, zirconates and stannates. It is also applicable to precursors of such materials, i.e., solid materials which upon firing are converted to dielectric solids, and to mixtures of any of these. Among the many dielectric solids which are likely to be used in the invention are BaTiO
3
, CaTiO
3
, SrTiO
3
, PbTiO
3
, CaZrO
3
, BaZrO
3
, CaSnO
3
, BaSnO
3
, and Al
2
O
3
. As will be apparent to those skilled in the ceramic arts, the exact chemical composition of the ceramic solids to be used in the composition of the invention is not ordinarily critical in the rheological sense. It is also preferred that the ceramic solids not have swelling characteristics in the organic dispersion since the rheological properties of the dispersion may be substantially changed thereby. Examples of suitable conductive inorganic solids may include for example silver, gold, copper, platinum and alloys, oxides and mixtures thereof and lead ruthenate pyrochlore.
It has been found that the dispersion of the invention must contain no significant amount of solids having a particle size of less than 0.3 &mgr;m in order to obtain adequately complete burnout of the organic medium when the films or layers thereof are fired to remove the organic medium and to effect sintering of the inorganic binder and the ceramic solids. However, it is preferred that none of the ceramic solids exceed 20 &mgr;m and, furthermore, at least 75 wt. % of the inorganic solids should have a size of 1-10 &mgr;m. In other words, when the dispersions are used to make thick film pastes, which are usually applied by screen printing, the maximum particle size must not exceed the thickness of the screen, and when the dispersion is used to make dry photosensitive film, the maximum particle size must not exceed the thickness of the film. It is preferred that at least 90 wt. % of the inorganic solids fall within the 1-10 &mgr;m range.
In addition, it is preferred that surface area/weight ratio of the ceramic particles not exceed 10 m
2
/g for the reason that such particles tend to affect adversely the sintering characteristics of the accompanying inorganic binder. It is still further preferred that the surface area/weight ratio not exceed 5 m
2
/g. Ceramic particles having a surface area/weight ratio of 1-5 have been found to be quite satisfactory.
B. Inorganic Binder
The glass frit used in the present invention aids in sintering the inorganic crystalline particulates and may be of any well known composition which has a melting temperature below that of the inorganic solids. Nevertheless, in order to get adequate hermeticity of the devices, it is preferred that the glass transition temperature (Tg) of the inorganic binder be 550-825° C. and still more preferably 575-750° C. If melting takes place below 550° C., organic material will likely be encapsulated and blisters will tend to form in the dielectric layer as the organics decompose. On the other hand, a glass transition temperature above 825° C. will tend to produce a porous dielectric when sintering temperatures compatible with copper metallizations, e.g., 900° C., are used.
The glass frits most preferably used are the borosilicate frits, such as lead borosilicate frit, bismuth, cadmium, barium, calcium, or other alkaline earth borosilicate frits. The preparation of such glass frits is well known and consists, for example, in melting together the constituents of the glass in the form of the oxides of the constituents and pouring such molten composition into water to form the frit. The batch ingredients may, of course, be any compound that will yield the desired oxides under the usual conditions of frit production. For example, boric o
Choi John Haetak
Drysdale Neville Everton
Baxter Janet
Clarke Yvette M
E. I. Du Pont de Nemours and Company
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