Optical: systems and elements – Deflection using a moving element
Reexamination Certificate
1999-08-24
2001-07-17
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
C359S211200, C359S212100, C359S223100, C359S226200, C347S260000, C358S493000
Reexamination Certificate
active
06262825
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to apparatus and methods for the treatment of photosensitive materials (i.e., printing plates) to impart an image thereon. In a particular aspect, the invention relates to apparatus for the enhanced imagewise exposure of photosensitive materials. In other aspects, the invention relates to methods for pre-treating photosensitive materials for imagewise exposure and for enhancing the imagewise exposure of photosensitive materials.
BACKGROUND OF THE INVENTION
Images can be imparted to photosensitive polymeric materials (e.g., materials employed for the production of printing plates) in a variety of ways. For example, a mask (typically a negative mask, although a positive mask can also be utilized) can be placed over the matrix, which is then exposed to energy sufficient to promote photoreaction of the matrix where exposed. Photoreaction occurs only where energy is allowed to impact the matrix. For negative acting materials, the unexposed photosensitive polymeric material is then removed (e.g., by washing), leaving the desired image material on the matrix. For positive acting materials, the exposed material is removed, leaving the desired image as a substantial absence of material on the matrix.
With the advent of laser technology, it is now possible to directly impart an image to a photosensitive matrix without the need for a mask. Instead, coherent energy can be directed onto the surface of the photosensitive matrix in the desired pattern. Because certain actinic wavelengths are produced relatively inefficiently and because laser imaging exposures are very brief (on the order of 30×10
−9
seconds per pixel), the use of highly sensitive resins is required in order to avoid the problems associated with an insufficient exposure of the imaged matrix. Problems encountered with negative acting materials include lack of resin strength, poor resilience, solvent swell (due to the generation of inadequate molecular weights during the curing process), and the need for extended exposure times. Problems encountered with positive acting materials include insufficient transformation of the positive exposing material for complete removal from the matrix in order to create the desired image, and the need for extended exposure times.
To address these problems, efforts have been made to develop more highly reactive photosensitive resins. Such materials would be expected to give more complete photoreaction (e.g., crosslinking, dissolution of crosslink bonds, rearrangement, and the like), even with brief laser exposures, as the desired image is scanned onto the photosensitive resin.
Alternatively, conventional photosensitive photoimageable materials (i.e., known resins which are not so highly photosensitive or reactive) may find wider use in the field of laser imaging if methods and apparatus can be developed to further enhance the exposure sensitivity of such materials. Since there is a large variety of conventional photosensitive photoimageable materials, such methodology would likely find widespread applicability.
Thus, there is a clear need in the art for methods and apparatus to enhance the “imagewise” exposure sensitivity of photosensitive materials, thereby permitting photoimaging to proceed as rapidly as possible, allowing for the rapid conversion of these photosensitive materials into finished articles, and providing for the widespread use of conventional resins in photosensitive imaging applications.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with one aspect of the present invention, there are provided apparatus which use otherwise wasted laser energy to subject photosensitive materials to a relatively low energy pre-exposure (i.e., via a backscan beam exposure) prior to subjecting such materials to an imagewise exposure (i.e., an imaging beam exposure). Invention apparatus provide an increase of the effective exposure sensitivity of a wide variety of photosensitive materials, allowing shorter exposure times and increased exposure speeds, and providing improved image quality (i.e., resolution of fine detail) in the exposed photosensitive material.
In accordance with an additional aspect of the present invention, there are provided methods for enhancing the imagewise exposure of photosensitive materials, imagewise exposed photosensitive materials made according to these methods, methods for enhancing sensitivity of a photosensitive material for imagewise exposure, and photosensitive materials having enhanced sensitivity for imagewise exposure made according to these methods. Invention methods, and exposed and enhanced sensitivity photosensitive materials, provide for increased exposure sensitivity of a wide variety of photosensitive materials.
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Mueller Gregory E.
Whittle Daniel John
Foley & Lardner
Napp Systems Inc.
Phan James
Reiter Stephen E.
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