WO1997043696A1 - Methods to increase the exposure sensitivity of photopolymerizable matrices and apparatus useful therefor - Google Patents

Methods to increase the exposure sensitivity of photopolymerizable matrices and apparatus useful therefor Download PDF

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Publication number
WO1997043696A1
WO1997043696A1 PCT/US1997/007789 US9707789W WO9743696A1 WO 1997043696 A1 WO1997043696 A1 WO 1997043696A1 US 9707789 W US9707789 W US 9707789W WO 9743696 A1 WO9743696 A1 WO 9743696A1
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Prior art keywords
exposure
matrix
photopolymerizable
radiation
imaging
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PCT/US1997/007789
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French (fr)
Inventor
Gregory E. Mueller
Mitch G. Male
David H. Roberts
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Napp Systems, Inc.
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Application filed by Napp Systems, Inc. filed Critical Napp Systems, Inc.
Priority to AU31193/97A priority Critical patent/AU3119397A/en
Publication of WO1997043696A1 publication Critical patent/WO1997043696A1/en

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    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/20Exposure; Apparatus therefor
    • G03F7/2022Multi-step exposure, e.g. hybrid; backside exposure; blanket exposure, e.g. for image reversal; edge exposure, e.g. for edge bead removal; corrective exposure

Definitions

  • the present invention relates to methods for the treatment of photopolymerizable matrices (e.g., printing plates) and related materials to impart an image thereon.
  • the present invention relates to apparatus useful for imparting an image onto photopolymerizable matrices and related materials.
  • Images can be imparted to photosensitive polymeric materials (e.g., materials employed for the production of printing plates) in a variety of ways.
  • a mask typically a negative
  • a mask can be placed over the matrix, which is then exposed to light of sufficient energy to promote the crosslinking of the matrix. This crosslinking occurs only where light is allowed to impact the matrix. Uncured photosensitive polymeric material is then removed (e.g., by washing), leaving the desired image.
  • imaging apparatus useful for carrying out the above-described process.
  • Invention imaging apparatus enable one to increase the effective exposure sensitivity of photopolymerizable materials.
  • the invention method comprises pre-exposing the above-described matrix (i.e., subjecting the matrix to a low fluence of actinic radiation) prior to digitally imaging the matrix.
  • the effective exposure sensitivity of a photopolymerizable material is substantially increased.
  • the energy input required to cause photopolymerization thereof is reduced.
  • actinic radiation refers to electromagnetic radiation capable of initiating photochemical reactions.
  • Ultraviolet and visible wavelength radiation (with wavelengths typically falling in the range of 300-700 nm) is commonly employed for this purpose.
  • Preferred wavelengths are those which correspond to the spectral sensitivity of the photopolymerizable material being imaged.
  • pre-exposure i.e., “exposure to a low fluence of actinic radiation” refers to radiation which imparts less energy to the photopolymerizable matrix than the threshold level required to initiate a substantial level of curing thereof.
  • the "threshold level” required to initiate a substantial level of curing of the photopolymerizable matrix can vary widely, depending on such factors as the particular material being imaged, the processing methodology employed for developing the imaged material, and the like. Radiation levels are said to exceed threshold levels when the pre-exposed photopolymer cannot be completely removed from the support therefor under normal processing conditions.
  • the level of curing of the photopolymerizable matrix imparted by this treatment is generally controlled so as to be insufficient to produce any significant change in the physical properties of the photopolymerizable matrix.
  • Pre-exposure contemplated by the present invention can be imparted either by coherent or non-coherent radiation, and will typically have a wavelength comparable to the wavelength employed for the actual imaging exposure.
  • a variety of methods can be used to achieve the desired pre-exposure employed herein. For example, a lower intensity of radiation than used for the imaging exposure can be employed, or a longer wavelength than used for the imaging exposure can be employed, etc.
  • pre-exposure employed in the practice of the present invention is accomplished employing radiation which imparts energy equal to about 10-99 % of the threshold level required to initiate substantial curing of the photopolymerizable matrix.
  • pre-exposure employed in the practice of the present invention is accomplished employing radiation which imparts energy equal to about 75-96 % of the threshold level required to initiate substantial curing of the photopolymerizable matrix, with radiation which imparts energy equal to about
  • the area of photopolymerizable matrix subjected to pre-exposure is at least as great as the area of the same portion of the matrix as is subjected to digital imaging substantially immediately following the pre-exposure. It is presently preferred that over the entire surface of the photopolymerizable matrix, there is a substantially constant delay between initial pre-exposure of photopolymerizable matrix and the imaging exposure which follows.
  • photopolymerizable matrix is subjected to pre-exposure at least about 0.05 seconds before, but no greater than about 5 minutes before being subjected to digital imaging.
  • the photopolymerizable matrix is subjected to pre-exposure at least about 0.1 seconds, but no greater than about 30 seconds before being subjected to digital imaging.
  • Photopolymerizable matrices contemplated for use in the practice of the present invention include flexographic printing plates, letterpress printing plates, offset printing plates, circuit board resists, stereolithography resins, and the like. Such materials can be prepared from a variety of photopolymerizable resins, such as, for example, (meth)acrylate-based resins (see, for example, U.S. Patent No. 5,348,844, incorporated herein by reference), thiol/ene-based resins (see, for example, U.S. Patent No. 3,783,152, incorporated herein by reference), vinyl ether-based resins (see, for example, U.S. Patent No.
  • Digital imaging contemplated by the present invention is typically accomplished by exposure of the photopolymerizable matrix to coherent (e.g., laser) irradiation.
  • coherent e.g., laser
  • the angle of incidence at which the photopolymerizable matrix is contacted with either the pre-exposure radiation and/or the digital imaging radiation can vary substantially.
  • the angle of incidence is relatively unimportant (and consequently can vary widely, e.g., from 0° up to about 45" or more) .
  • photopolymerizable matrices used for the preparation of circuit boards are relatively insensitive to the angle of incidence.
  • thicker photopolymer matrices i.e., thicknesses of greater than about 5 mils
  • the angle of incidence be substantially perpendicular to the photopolymerizable matrix (i.e., an angle of incidence of about 0°), in order to maximize penetration of the incident radiation into the photopolymerizable matrix, thereby maximizing the effectiveness of the pre-exposure and/or digital imaging.
  • invention apparatus for digitally imaging photopolymerizable surfaces.
  • invention apparatus comprises conventional imaging equipment (having a first exposure means for digitally imaging the photopolymerizable surface) , modified so as to include a second exposure means capable of delivering pre-exposure radiation to the photopolymerizable surface substantially immediately prior to digital imaging thereof.
  • exposure means refers to both a source of radiation, as well as the resulting beam produced by said source.
  • exposure means refers to both a source of radiation, as well as the resulting beam produced by said source.
  • Imaging apparatus contemplated for use in accordance with the present invention include any configuration typically used for exposure of a photopolymerizable matrix to impart an image thereto.
  • Such apparatus include exterior-drum devices (see, for example, European Patent Application No. 491,368, U.S. Patent No. 5,247,883 and U.S. Patent No. 5,385,092, each of which are hereby incorporated by reference herein) ; flatbed devices (see, for example, U.S. Patent No. 5,385,092 and U.S. Patent No. 4,312,590, each of which are hereby incorporated by reference herein) ; interior-arc devices (also known as internal drum devices; see, for example, U.S. Patent No. 5,385,092 and U.S. Patent No. 4,054,928, each of which are hereby incorporated by reference herein) ; and the like.
  • Pre-exposure contemplated by the present invention can be accomplished employing either coherent or non-coherent radiation, and can be provided by a variety of sources, e.g., an ion gas laser (e.g., an argon ion laser, a krypton laser, a helium:cadmium laser, and the like), a solid state laser (e.g., a frequency-doubled Nd:YAG laser), a semiconductor diode laser, an arc lamp (e.g., a medium pressure mercury lamp, a Xenon lamp, a carbon arc lamp, and the like) , and the like.
  • Exposure sources capable of providing ultraviolet and visible wavelength radiation
  • the first exposure means and the second exposure means can be provided by a single source, or by two separate elements. When a single source is employed (in conjunction with a beam splitter) , a portion of the beam is employed for pre- exposure of the photopolymerizable matrix, and the remainder of the beam is employed as the main exposure beam.
  • apparatus comprising: support means for a photopolymerizable matrix, a first exposure means capable of delivering pre-exposure radiation to the surface of said photopolymerizable matrix, wherein said first exposure means is movably positioned with respect to said support means, and a second exposure means capable of digitally imaging said matrix, wherein said second exposure means is movably positioned with respect to said support means, and wherein the positioning of said first exposure means and said second exposure means are interrelated so as to effect a substantially constant delay between pre-exposure of a photopolymerizable matrix mounted on said support means and said digital imaging.
  • Support means contemplated for use in the practice of the present invention include any means suitable to aid in presenting the photopolymerizable matrix to the pre-exposure and the imaging exposure contemplated herein. Examples include the support carriage of an exterior-drum device, the support element of a flatbed device, the support element of an interior-arc device, and the like.
  • the means capable of delivering pre-exposure radiation can deliver either coherent or non-coherent radiation. Such radiation will impart less energy to the photopolymerizable matrix than the threshold level required to initiate substantial curing of the photopolymerizable matrix.
  • pre-exposure contemplated by the present invention can be provided by a separate source, or by the same source as used to generate the main exposure beam.
  • Apparatus according to the invention is designed so that the area of photopolymerizable matrix subjected at any particular point in time to pre-exposure by said first exposure means is at least as great as the area of the same portion of the matrix as is later subjected to exposure by the second exposure means (typically substantially immediately following pre-exposure) .
  • the support means is movably adjustable with respect to the output beam of said first and second exposure means.
  • the output beam of said first and second exposure means are movably adjustable with respect to a relatively stationary support means.
  • both the support means and the output beam of said first and second exposure means are movably adjustable with respect to one another.
  • NAPPflex NF-1 NAPP Systems Inc., San Marcos
  • Plates were exposed employing an external drum device and an ultraviolet argon ion laser delivering wavelengths in the range of 333-364 nm (although wavelengths falling in the range of about 320-550 nm, with wavelengths in the range of about 330-365 nm are also suitable) .
  • the power for pre-exposure was split from the main beam using a beamsplitter, and injected into a fiber optic which guided the beam to the appropriate point.
  • the time delay between the pre-exposure and main beams typically falls in the range of about 30 sec.
  • the pre-exposure threshold fluence was determined by subjecting the material under test to a series of pre-exposures of varying intensities; the material under test was then processed according to the manufacturer's instructions.
  • the threshold fluence is defined as the fluence required to produce a slight scum on the plate after processing (the pre-exposure threshold fluence was thus determined to within a few percent) .
  • the material under test was exposed to the desired pre-exposure, and then a brief (e.g., 5 millisecond) exposure to irradiation by the main laser.
  • the plate was then processed according to the manufacturer's instructions and evaluated.
  • the evaluation comprised measuring the radius, r, of the polymerized area left by the main - exposure with a measuring microscope and finding the main imaging threshold fluence, I(r), using the following equation:
  • I 0 is the peak fluence
  • w is 1/e 2 beam radius
  • the total power requirement i.e., the total of the power requirement for the pre-exposure and imaging exposures
  • the invention process employing a low fluence pre-exposure, followed by an imaging exposure.

Abstract

In accordance with the present invention, there are provided methods to substantially increase the effective exposure sensitivity of photopolymerizable materials without chemical modification thereof. This is accomplished by subjecting such materials to a relatively low energy pre-exposure prior to subjecting such materials to the main imaging exposure. Increase in the effective exposure sensitivity of photopolymerizable materials provides improved image quality in the exposed matrix and allows increased exposure speeds to be employed. In accordance with another aspect of the present invention, there are provided imaging apparatus useful for carrying out the above-described process. Invention apparatus enable one to increase the effective exposure sensitivity of photopolymerizable materials.

Description

Methods to Increase the Exposure Sensitivity of Photopolymerizable Matrices and
Apparatus Useful Therefor
FIELD OF THE INVENTION
The present invention relates to methods for the treatment of photopolymerizable matrices (e.g., printing plates) and related materials to impart an image thereon. In a particular aspect, the present invention relates to apparatus useful for imparting an image onto photopolymerizable matrices and related 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) can be placed over the matrix, which is then exposed to light of sufficient energy to promote the crosslinking of the matrix. This crosslinking occurs only where light is allowed to impact the matrix. Uncured photosensitive polymeric material is then removed (e.g., by washing), leaving the desired image.
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. However, when employing coherent energy to expose a photosensitive matrix, the available power is relatively low and expensive, and exposure times are typically quite short. To address these problems, the use of highly sensitive and reactive resins is required, so that the imaged matrix avoids the problems associated with insufficient curing (e.g., 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) .
To address these problems, efforts have been made to develop more highly reactive photosensitive resins. Such materials would be expected to give more complete crosslinking, even with brief laser exposure, as the desired image is scanned onto the resin. Alternatively, conventional photosensitive resins may find wider use in the field of laser imaging if methods can be developed to enhance the exposure sensitivity of such materials. Furthermore, there is a clear need in the art for photopolymerization reactions to proceed as rapidly as possible, thereby allowing for the rapid conversion of photopolymerizable materials into finished articles.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with the present invention, we have discovered that a substantial increase in the effective exposure sensitivity of photopolymerizable materials can be achieved by subjecting such materials to a relatively low energy pre-exposure prior to subjecting such materials to the main imaging exposure. Increase in the effective exposure sensitivity of photopolymerizable materials provides improved image quality (e.g., resolution of fine detail) in the exposed matrix and allows increased exposure speeds to be employed.
In accordance with another aspect of the present invention, there are provided imaging apparatus useful for carrying out the above-described process. Invention imaging apparatus enable one to increase the effective exposure sensitivity of photopolymerizable materials. DETAILED DESCRIPTION OF THE INVENTION
In accordance with the present invention, there are provided methods to increase the effective exposure sensitivity of a photopolymerizable matrix when digitally imaged. The invention method comprises pre-exposing the above-described matrix (i.e., subjecting the matrix to a low fluence of actinic radiation) prior to digitally imaging the matrix.
Thus, according to the present invention, the effective exposure sensitivity of a photopolymerizable material is substantially increased. In other words, without any chemical modification of the photopolymerizable material, the energy input required to cause photopolymerization thereof is reduced.
As is commonly used in the art, the term "actinic radiation" refers to electromagnetic radiation capable of initiating photochemical reactions. Ultraviolet and visible wavelength radiation (with wavelengths typically falling in the range of 300-700 nm) is commonly employed for this purpose. Preferred wavelengths are those which correspond to the spectral sensitivity of the photopolymerizable material being imaged.
As employed herein, "pre-exposure" (i.e., "exposure to a low fluence of actinic radiation") refers to radiation which imparts less energy to the photopolymerizable matrix than the threshold level required to initiate a substantial level of curing thereof. The "threshold level" required to initiate a substantial level of curing of the photopolymerizable matrix can vary widely, depending on such factors as the particular material being imaged, the processing methodology employed for developing the imaged material, and the like. Radiation levels are said to exceed threshold levels when the pre-exposed photopolymer cannot be completely removed from the support therefor under normal processing conditions.
Thus, while some level of curing of the photopolymerizable matrix may be induced by pre-exposure (i.e., by exposure to a low fluence of actinic radiation), the level of curing of the photopolymerizable matrix imparted by this treatment is generally controlled so as to be insufficient to produce any significant change in the physical properties of the photopolymerizable matrix.
Pre-exposure contemplated by the present invention can be imparted either by coherent or non-coherent radiation, and will typically have a wavelength comparable to the wavelength employed for the actual imaging exposure. A variety of methods can be used to achieve the desired pre-exposure employed herein. For example, a lower intensity of radiation than used for the imaging exposure can be employed, or a longer wavelength than used for the imaging exposure can be employed, etc.
Typically, pre-exposure employed in the practice of the present invention is accomplished employing radiation which imparts energy equal to about 10-99 % of the threshold level required to initiate substantial curing of the photopolymerizable matrix. Preferably, pre-exposure employed in the practice of the present invention is accomplished employing radiation which imparts energy equal to about 75-96 % of the threshold level required to initiate substantial curing of the photopolymerizable matrix, with radiation which imparts energy equal to about
80-90 % of the threshold level required to initiate substantial curing of the photopolymerizable matrix being presently preferred.
In accordance with the present invention, the area of photopolymerizable matrix subjected to pre-exposure (at any particular point in time) is at least as great as the area of the same portion of the matrix as is subjected to digital imaging substantially immediately following the pre-exposure. It is presently preferred that over the entire surface of the photopolymerizable matrix, there is a substantially constant delay between initial pre-exposure of photopolymerizable matrix and the imaging exposure which follows. Typically, photopolymerizable matrix is subjected to pre-exposure at least about 0.05 seconds before, but no greater than about 5 minutes before being subjected to digital imaging. Preferably, the photopolymerizable matrix is subjected to pre-exposure at least about 0.1 seconds, but no greater than about 30 seconds before being subjected to digital imaging.
Photopolymerizable matrices contemplated for use in the practice of the present invention include flexographic printing plates, letterpress printing plates, offset printing plates, circuit board resists, stereolithography resins, and the like. Such materials can be prepared from a variety of photopolymerizable resins, such as, for example, (meth)acrylate-based resins (see, for example, U.S. Patent No. 5,348,844, incorporated herein by reference), thiol/ene-based resins (see, for example, U.S. Patent No. 3,783,152, incorporated herein by reference), vinyl ether-based resins (see, for example, U.S. Patent No. 5,446,073, incorporated herein by reference), cationic- based resins (see, for example, U.S. Patent No. 5,437,964, incorporated herein by reference) , diazonium-based resins (see, for example, U.S. Patent No. 4,263,392, incorporated herein by reference) , and the like, as well as combinations of any two or more thereof.
Digital imaging contemplated by the present invention is typically accomplished by exposure of the photopolymerizable matrix to coherent (e.g., laser) irradiation. As readily recognized by those of skill in the art, the angle of incidence at which the photopolymerizable matrix is contacted with either the pre-exposure radiation and/or the digital imaging radiation can vary substantially. For example, with relatively thin photopolymer matrices (i.e., thicknesses of about 2 microns or less) , the angle of incidence is relatively unimportant (and consequently can vary widely, e.g., from 0° up to about 45" or more) . Similarly, photopolymerizable matrices used for the preparation of circuit boards (i.e., having thicknesses in the range of about 1-2.5 mils), are relatively insensitive to the angle of incidence. In contrast, thicker photopolymer matrices (i.e., thicknesses of greater than about 5 mils) are typically less tolerant of the angle of incidence, and consequently will vary within a narrower range than set forth above, e.g., from 0° up to about 15°. Indeed, it is presently preferred that the angle of incidence be substantially perpendicular to the photopolymerizable matrix (i.e., an angle of incidence of about 0°), in order to maximize penetration of the incident radiation into the photopolymerizable matrix, thereby maximizing the effectiveness of the pre-exposure and/or digital imaging.
In accordance with another embodiment of the present invention, there are provided improved imaging apparatus for digitally imaging photopolymerizable surfaces. Invention apparatus comprises conventional imaging equipment (having a first exposure means for digitally imaging the photopolymerizable surface) , modified so as to include a second exposure means capable of delivering pre-exposure radiation to the photopolymerizable surface substantially immediately prior to digital imaging thereof.
As employed herein, "exposure means" refers to both a source of radiation, as well as the resulting beam produced by said source. When reference is made herein to specifically directing the output of an exposure means, it is understood that it is the beam produced by the exposure means which is actually being directed.
Imaging apparatus contemplated for use in accordance with the present invention include any configuration typically used for exposure of a photopolymerizable matrix to impart an image thereto. Such apparatus include exterior-drum devices (see, for example, European Patent Application No. 491,368, U.S. Patent No. 5,247,883 and U.S. Patent No. 5,385,092, each of which are hereby incorporated by reference herein) ; flatbed devices (see, for example, U.S. Patent No. 5,385,092 and U.S. Patent No. 4,312,590, each of which are hereby incorporated by reference herein) ; interior-arc devices (also known as internal drum devices; see, for example, U.S. Patent No. 5,385,092 and U.S. Patent No. 4,054,928, each of which are hereby incorporated by reference herein) ; and the like.
Pre-exposure contemplated by the present invention can be accomplished employing either coherent or non-coherent radiation, and can be provided by a variety of sources, e.g., an ion gas laser (e.g., an argon ion laser, a krypton laser, a helium:cadmium laser, and the like), a solid state laser (e.g., a frequency-doubled Nd:YAG laser), a semiconductor diode laser, an arc lamp (e.g., a medium pressure mercury lamp, a Xenon lamp, a carbon arc lamp, and the like) , and the like. Exposure sources capable of providing ultraviolet and visible wavelength radiation
(with wavelengths typically falling in the range of 300-700 nm) are commonly employed for the practice of the present invention. Preferred wavelengths are those which correspond to the spectral sensitivity of the photopolymerizable material being imaged. Those of skill in the art recognize that the first exposure means and the second exposure means can be provided by a single source, or by two separate elements. When a single source is employed (in conjunction with a beam splitter) , a portion of the beam is employed for pre- exposure of the photopolymerizable matrix, and the remainder of the beam is employed as the main exposure beam.
In accordance with yet another embodiment of the present invention, there are provided apparatus comprising: support means for a photopolymerizable matrix, a first exposure means capable of delivering pre-exposure radiation to the surface of said photopolymerizable matrix, wherein said first exposure means is movably positioned with respect to said support means, and a second exposure means capable of digitally imaging said matrix, wherein said second exposure means is movably positioned with respect to said support means, and wherein the positioning of said first exposure means and said second exposure means are interrelated so as to effect a substantially constant delay between pre-exposure of a photopolymerizable matrix mounted on said support means and said digital imaging.
Support means contemplated for use in the practice of the present invention include any means suitable to aid in presenting the photopolymerizable matrix to the pre-exposure and the imaging exposure contemplated herein. Examples include the support carriage of an exterior-drum device, the support element of a flatbed device, the support element of an interior-arc device, and the like.
In accordance with the present invention, the means capable of delivering pre-exposure radiation can deliver either coherent or non-coherent radiation. Such radiation will impart less energy to the photopolymerizable matrix than the threshold level required to initiate substantial curing of the photopolymerizable matrix. As noted above, pre-exposure contemplated by the present invention can be provided by a separate source, or by the same source as used to generate the main exposure beam.
Apparatus according to the invention is designed so that the area of photopolymerizable matrix subjected at any particular point in time to pre-exposure by said first exposure means is at least as great as the area of the same portion of the matrix as is later subjected to exposure by the second exposure means (typically substantially immediately following pre-exposure) .
In order to scan extensive portions of the photopolymerizable matrix, it must be possible for the image to be imparted to the photopolymerizable matrix (i.e., the support means) to be movably positionable with respect to the output beam of said first and second exposure means. Thus, in one aspect of the invention, the support means is movably adjustable with respect to the output beam of said first and second exposure means. In another aspect of the invention, the output beam of said first and second exposure means are movably adjustable with respect to a relatively stationary support means. In yet another aspect of the invention, both the support means and the output beam of said first and second exposure means are movably adjustable with respect to one another.
The invention will now be described in greater detail by reference to the following non-limiting examples. Example
The effect of pre-exposure according to the invention on exposure sensitivity of a variety of photopolymerizable resins was tested as follows. Three different commercially available resins were tested:
NAPPflex NF-1 (NAPP Systems Inc., San Marcos,
CA), Printight EM76 (Toyobo Co., Ltd. Osaka, Japan), Anocoil 372 (Anocoil, Rockville, CT 06066).
Plates were exposed employing an external drum device and an ultraviolet argon ion laser delivering wavelengths in the range of 333-364 nm (although wavelengths falling in the range of about 320-550 nm, with wavelengths in the range of about 330-365 nm are also suitable) . The power for pre-exposure was split from the main beam using a beamsplitter, and injected into a fiber optic which guided the beam to the appropriate point. The time delay between the pre-exposure and main beams typically falls in the range of about 30 sec.
Each of the test materials was subjected to the following procedure: First, the pre-exposure threshold fluence was determined by subjecting the material under test to a series of pre-exposures of varying intensities; the material under test was then processed according to the manufacturer's instructions. The threshold fluence is defined as the fluence required to produce a slight scum on the plate after processing (the pre-exposure threshold fluence was thus determined to within a few percent) . Second, the material under test was exposed to the desired pre-exposure, and then a brief (e.g., 5 millisecond) exposure to irradiation by the main laser. The plate was then processed according to the manufacturer's instructions and evaluated. The evaluation comprised measuring the radius, r, of the polymerized area left by the main - exposure with a measuring microscope and finding the main imaging threshold fluence, I(r), using the following equation:
I(r) = I0exp(-2(r/w)2)
wherein I0 is the peak fluence, and w is 1/e2 beam radius.
Each of the photopolymerizable resins was subjected to pre-exposure fluences of 0%, 25%, 50% and 90% of the pre-exposure threshold fluence, followed by the appropriate imaging fluence, then processed as per manufacturer's specifications. Results are summarized in the following table.
Table
Figure imgf000013_0001
Inspection of the results presented in the table indicates that, for each material tested, an increase in pre-exposure fluence results in a decrease of the imaging fluence. This reflects an increase in the effective sensitivity of the test material to actinic radiation.
In addition, in most instances, the total power requirement (i.e., the total of the power requirement for the pre-exposure and imaging exposures) is reduced by the invention process employing a low fluence pre-exposure, followed by an imaging exposure.
While the invention has been described in detail with reference to certain preferred embodiments thereof, it will be understood that modifications and variations are within the spirit and scope of that which is described and claimed.

Claims

That which is claimed is:
1. A method to increase the effective exposure sensitivity of a photopolymerizable matrix when digitally imaged, said method comprising pre-exposing said matrix to a low fluence of actinic radiation prior to digitally imaging said matrix.
2. A method according to claim 1 wherein said digital imaging is accomplished by exposure of said photopolymerizable matrix to laser irradiation.
3. A method according to claim 1 wherein said photopolymerizable matrix is selected from a flexographic printing plate, a letterpress printing plate, an offset printing plate, a circuit board resist, or a stereolithography resin.
4. A method according to claim 1 wherein said photopolymerizable matrix is selected from (meth)acrylate- based resins, thiol/ene-based resins, vinyl ether-based resins, maleate/fumarate-based resins, cationic-based resins, naphthalene diazoquinone-based resins, or mixtures of any two or more thereof.
5. A method according to claim 1 wherein said pre-exposure is accomplished employing radiation which imparts less energy to said matrix than the threshold level required to initiate a substantial level of curing of the photopolymerizable matrix.
6. A method according to claim 5 wherein the level of curing of the photopolymerizable matrix is not sufficient to produce any significant change on the physical properties of the photopolymerizable matrix.
7. A method according to claim l wherein said pre-exposure is accomplished employing radiation which imparts energy equal to about 10-99 % of the threshold level required to initiate substantial curing of the photopolymerizable matrix.
8. A method according to claim 1 wherein said pre-exposure is accomplished employing radiation which imparts energy equal to about 75-96 % of the threshold level required to initiate substantial curing of the photopolymerizable matrix.
9. A method according to claim 1 wherein said pre-exposure is accomplished employing radiation which imparts energy equal to about 80-90 % of the threshold level required to initiate substantial curing of the photopolymerizable matrix.
10. A method according to claim 5 wherein said radiation is coherent.
11. A method according to claim 5 wherein said radiation is non-coherent.
12. A method according to claim 1 wherein the area of said matrix subjected to pre-exposure at any particular point in time is at least as great as the area of the same portion of said matrix as is subjected to digital imaging immediately following said pre-exposure.
13. A method according to claim 12 wherein said matrix is pre-exposed at least 0.05 seconds before being subjected to digital imaging, but no greater than about 5 minutes before being subjected to digital imaging.
14. A method according to claim 12 wherein said matrix is pre-exposed at least 0.1 seconds before being subjected to digital imaging, but no greater than about 30 seconds before being subjected to digital imaging.
15. A method according to claim 12 wherein, over the entire surface of said photopolymerizable matrix, there is a substantially constant delay between pre-exposure of said photopolymerizable matrix and said digital imaging.
16. A method according to claim 2 wherein said photopolymerizable matrix is contacted with said pre-exposure radiation and said laser radiation at an angle of incidence of up to about 45°.
17. A method according to claim 16 wherein said angle of incidence is about 0°C, i.e., the angle of incidence is substantially perpendicular to said photopolymerizable matrix.
18. In an imaging apparatus for digitally imaging a photopolymerizable surface, the improvement comprising including in said apparatus a second exposure means capable of pre-exposing the photopolymerizable surface substantially immediately prior to digital imaging thereof.
19. An apparatus according to claim 18 wherein said photopolymerizable surface is selected from a flexographic printing plate, a letterpress printing plate, an offset printing plate, a circuit board resist, or a stereolithography resin.
20. An apparatus according to claim 18 wherein said imaging apparatus is selected from an exterior-drum device, a flatbed device or an interior-arc device.
21. Apparatus comprising: support means for a photopolymerizable matrix, a first exposure means capable of pre-exposing the surface of said photopolymerizable matrix, wherein said first exposure means is movably positioned with respect to said support means, and a second exposure means capable of digitally imaging said matrix, wherein said second exposure means is movably positioned with respect to said support means, and wherein the positioning of said first exposure means and said second exposure means are interrelated so as to effect a substantially constant delay between pre-exposure of a photopolymerizable matrix mounted on said support means and said digital imaging.
22. Apparatus according to claim 21 wherein said support means is selected from an exterior-drum device, a flatbed device or an interior-arc device.
23. Apparatus according to claim 21 wherein said means capable of delivering pre-exposure radiation imparts less energy to said matrix than the threshold level required to initiate substantial curing of the photopolymerizable matrix.
24. Apparatus according to claim 21 wherein the area of said matrix subjected at any particular point in time to exposure by said first exposure means is at least as great as the area of the same portion of said matrix as is subjected to exposure by said second exposure means substantially immediately following said pre-exposure.
25. Apparatus according to claim 21 wherein said support means is movably adjustable with respect to said first and second exposure means.
26. Apparatus according to claim 21 wherein said first and second exposure means are movably adjustable with respect to said support means.
PCT/US1997/007789 1996-05-16 1997-05-06 Methods to increase the exposure sensitivity of photopolymerizable matrices and apparatus useful therefor WO1997043696A1 (en)

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EP2176073A1 (en) * 2007-08-08 2010-04-21 MacDermid Printing Solutions, LLC Method of pre-exposing relief image printing plate
EP3944021A1 (en) * 2020-07-22 2022-01-26 Esko-Graphics Imaging GmbH Method and apparatus for curing a printing plate

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004021080A1 (en) * 2002-08-29 2004-03-11 Eudes Dantas Stereoflexography
WO2006019450A2 (en) 2004-07-20 2006-02-23 Macdermid Printing Solutions, Llc Improved method for bump exposing relief image printing plates
EP1769285A2 (en) * 2004-07-20 2007-04-04 MacDermid Printing Solutions, LLC Improved method for bump exposing relief image printing plates
EP1769285A4 (en) * 2004-07-20 2011-10-19 Macdermid Printing Solutions Improved method for bump exposing relief image printing plates
WO2008145316A2 (en) 2007-05-25 2008-12-04 Eos Gmbh Electro Optical Systems Method for the layered production of a three-dimensional object
WO2008145316A3 (en) * 2007-05-25 2009-01-22 Eos Electro Optical Syst Method for the layered production of a three-dimensional object
RU2469851C2 (en) * 2007-05-25 2012-12-20 Эос Гмбх Электро Оптикал Системз Method of producing 3d structure layer-by-layer
US9011982B2 (en) 2007-05-25 2015-04-21 Eos Gmbh Electro Optical Systems Method for a layer-wise manufacturing of a three-dimensional object
EP2176073A1 (en) * 2007-08-08 2010-04-21 MacDermid Printing Solutions, LLC Method of pre-exposing relief image printing plate
EP2176073A4 (en) * 2007-08-08 2013-07-10 Macdermid Printing Solutions Method of pre-exposing relief image printing plate
EP3944021A1 (en) * 2020-07-22 2022-01-26 Esko-Graphics Imaging GmbH Method and apparatus for curing a printing plate
WO2022017632A1 (en) * 2020-07-22 2022-01-27 Esko-Graphics Imaging Gmbh Method and apparatus for curing a printing plate

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