Radiation imagery chemistry: process – composition – or product th – Diazo reproduction – process – composition – or product – Composition or product which contains radiation sensitive...
Reexamination Certificate
1999-12-07
2001-06-19
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Diazo reproduction, process, composition, or product
Composition or product which contains radiation sensitive...
C430S281100, C430S288100, C430S909000, C525S059000
Reexamination Certificate
active
06248498
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to photoresist compositions comprising a polymeric backbone and a quaternary heterocyclic pendant group and other components, particularly useful in the preparation of screen printing and sandblast etching photoresists. The invention also relates to methods of preparing photocross-linkable polymeric systems which do not require purification steps.
BACKGROUND OF THE INVENTION
Photosensitive or photoreactive polymers are commonly used in coatings which have properties that can change when exposed to suitable radiation. Such a change in properties is usually a change in solubility and results in a sharp distinction between exposed and unexposed areas. Photocross-linking and photoinitiated polymerization are commonly used to exploit the photosensitivity of materials. This invention relates to photocross-linking between ethylenically unsaturated sites. Exposure to light of the photosensitive or photoreactive material results in a solubility change and creation of the image in the exposed material. Most commonly, resist images are produced by solvent development of photoinduced cross-linking (negative processing). Photoresist polymer compositions must satisfy a number of physical property dependent requirements under practical working conditions. The most important, and most difficult, requirements to fulfill are image discrimination, thermal stability, ink resistance and etch resistance when exposed. For image discrimination, the developing solvent must remove the soluble portion of the exposed material without distorting or swelling the insoluble areas to give a sharp true image.
Exposure of the photopolymer to light generally provides energy necessary to cross-link adjacent polymeric molecules. In many instances, this provides for a three dimensional cross-linked polymer. For example, with sufficient exposure to light, a polymer having diazo units becomes hydrophobic. A variety of photo-chemical systems have been used in photoresist applications including cinnamates, chalcones, p-azidophenyls, azidophthalates, p-phenylene, bis(acrylates), and many others.
There are a number of examples in the art of photosensitive compounds which have pendant pyridinium groups. Mino et al., Japanese Laid Open Patent Application No. Showa 61-186955 (1986) and Toyofuku et al., Japanese Laid Open Patent Application No. Showa 59-154442 (1984) both disclose the use of a polyvinyl alcohol backbone with side groups of the formula:
wherein R
1
, R
2
, n and Y are as defined in the reference.
Yanagi et al., Japanese Laid Open Patent Application No. Showa 55-135834 (1984) also teaches the use of side groups containing terminal substituted pyridinium groups, as shown in the formulae:
wherein n, m and X are as defined in the reference.
Yanagi also discloses the use of side chains with terminal styryl and substituted styryl groups, as shown in the formulae:
wherein n, m and X are as defined in the reference.
Yanagi continues by displaying a side chain with a terminal furanyl group, as shown here in the formula:
wherein n, m and X are as previously defined.
Ichimura et al., U.S. Pat. No. 4,925,770, also discloses the use of furanyl containing molecules. However, Ichimura teaches the inclusion of such a molecule freely in solution, rather than grafted to a backbone. Ichimura teaches a free molecule of the formula:
wherein R
1
and R
2
are as defined in the reference.
Engraving images on materials such as glass, metal and plastic traditionally involve the steps of first forming a resist layer containing an image and then sandblasting the entire surface. Any areas not covered by the resist are etched away to form an image while the protected areas remain intact. When imaging glass, a hydrofluoric acid treatment can substitute for sandblasting. In contrast, an aqueous solution of ferric chloride can be used if processing copper plate.
An example of this process is given by Suzuki et al., U.S. Pat. No. 5,427,890, who teach the use of a photosensitive laminate film to form the resist layer. The laminate film includes a water-soluble resin composition which exhibits photocrosslinkability. The areas exposed to light become insoluble in water while the protected portions remain water soluble. A water rinse is sufficient to remove the soluble portions to form the resist layer. While a number of possible photosensitive materials are known in the art, Suzuki is limited to the use of stilbazolium groups as the photosensitive moiety.
SUMMARY OF THE INVENTION
The present invention relates to photoresists based on a photocross-linkable polymer. The photocross-linkable polymer of the invention has a polymeric backbone and at least 0.1 mol-% of a quaternary heterocyclic pendant group grafted thereon and can be illustrated by the formula I:
where n ranges from 0 to 4 and Z denotes the atoms necessary to complete a substituted or unsubstituted nitrogen containing heterocyclic ring.
A preferred aspect of the invention involves a photosensitive polymer having a polymeric backbone derived from polyvinyl alcohol with at least 0.1 mol-% of a furanyl substituted quaternary heterocyclic grafted thereon that can be illustrated by the formula II:
Another embodiment of the invention is found in a liquid photoresist composition that contains a liquid carrier and about 1 to 50 wt-% of a photosensitive polymer of formula (I), where n and Z are as previously defined. The invention is also found in a liquid photoresist composition utilizing a photosensitive polymer of formula (II).
Another aspect of the invention can be found in an aqueous screen printing composition having an aqueous carrier and about 1 to 50 wt-% of a photosensitive polymer of formula (I), where n and Z are as previously defined. The invention is also found in an aqueous screen printing composition utilizing a photosensitive polymer of formula (II).
Another aspect of the invention involves a sandblast photoresist composition having an aqueous carrier and about 1 to 50 wt-% of a photosensitive polymer of formula (I), where n and Z are as previously defined. The invention is also found in a sandblast photoresist composition utilizing a photosensitive polymer of formula (II).
Another aspect of the invention involves in a photosensitive resin composition that has an aqueous dispersion of solutions and emulsions including at least about 1 to 50 wt-% of a photosensitive polymer of formula (I), where n and Z are as previously defined; a water dispersible or hydrophobic polymer; and a photopolymerizable compound that has an ethylenically unsaturated group; and optionally includes a photopolymerization initiator; and a water soluble diazo compound.
Still another aspect of the invention involves in a photosensitive resin composition that has an aqueous dispersion of solutions and emulsions including at least about 1 to 50 wt-% of a photosensitive polymer of formula (II), where n and Z are as previously defined; a water dispersible or hydrophobic polymer; and a photopolymerizable compound that has an ethylenically unsaturated group; and optionally includes a photopolymerization initiator; and a water soluble diazo compound.
Creating the photosensitive polymers generally involves forming the photosensitive molecule and then grafting it onto the polyvinyl backbone. The molecule is created by starting with a commercially available diether alcohol, which is reacted with a leaving group containing compound (R
3
X) in the presence of pyridine, resulting in a compound in which the R
3
group has been substituted onto the alcohol oxygen. In the next step, this molecule is reacted with methyl-substituted nitrogen heterocyclic to form an intermediate in which the methyl-substituted nitrogen heterocyclic replaces the R
3
O group. The reactions are illustrated in the Detailed Description section. Finally, the intermediate is reacted with furfural in the presence of piperidine to form the light sensitive pendant group.
The linkage of the pendant group to the polymeric backbone can be discussed with reference to R
1
and R
2
in the above structu
Chu John S.
Merchant & Gould P.C.
The Chromaline Corporation
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