Photopolymerization Printing Plate Edge Sharpness via Roughened Support

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Solution Overview

Problem

Current photopolymerization type photosensitive lithographic printing plate precursors face issues with edge sharpness and halftone dot uniformity, particularly when used for high definition AM screen printing or FM screen printing, due to inadequate polymerization and surface roughness, leading to impaired image quality and reproducibility.

Innovation Solution

A negative-working photopolymerization type photosensitive lithographic printing plate precursor is developed, featuring a hydrophilic support with a photopolymerizable layer and a protective layer, incorporating a sensitizing dye with absorption in the 350-450 nm range, a hexaarylbisimidazole photopolymerization initiator, and a yellow dye or pigment with absorption within the laser emission wavelength range, along with a sulfur-containing compound, to enhance uniformity and edge sharpness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a photopolymerization type photosensitive lithographic printing plate precursor is used for laser beam exposure, then sensitivity is improved, but edge sharpness deteriorates due to insufficient polymerization in the edge region

Engineering Contradiction:

ImprovesensitivityVSAvoidedge sharpness

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The patent applies local quality by using a roughened support surface that selectively scatters laser light to increase exposure energy density at image edges and halftone dot peripheries, where polymerization is insufficient, while maintaining normal exposure in central regions. This localized energy enhancement resolves the edge sharpness problem without compromising overall sensitivity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the physical parameter of the support surface from smooth to roughened, which alters the laser beam propagation characteristics. The roughened surface causes light scattering that increases energy penetration and polymerization at previously insufficient edge regions, thereby improving both sensitivity utilization and edge sharpness.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a support with roughened surface is used to ensure hydrophilicity, then hydrophilicity is improved, but image quality deteriorates due to scattering of reflection light at laser exposure

Engineering Contradiction:

ImprovehydrophilicityVSAvoidimage quality

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent converts the harmful effect of light scattering (which degrades image quality) into a beneficial effect by intentionally roughening the support surface to scatter laser light in a way that enhances polymerization at image edges. The same scattering that was previously harmful is now used to improve edge sharpness and halftone dot uniformity.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of manufacture

If conventional photosensitive layer is used, then ease of manufacture is maintained, but halftone dot uniformity deteriorates in FM screen printing

Engineering Contradiction:

Improveease of manufactureVSAvoidhalftone dot uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent segments the photosensitive layer into distinct functional components: a polymerizable compound for image formation, a binder polymer for structural integrity, and a yellow dye for optical absorption. This segmentation allows each component to be optimized independently, achieving both ease of manufacture and superior halftone dot uniformity in FM screen printing.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution achieves improved uniformity of halftone dots and reduced edge spreading, particularly in shadow areas, enabling high definition AM screen printing and FM screen printing with enhanced image quality and reproducibility.

Implementation Method 1

a photopolymerization type photosensitive lithographic printing plate precursor... a photopolymerizable photosensitive layer... a sensitizing dye having an absorption maximum in the wavelength range 350 to 450 nm, a photopolymerization initiator

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

a yellow dye or pigment having an absorption maximum falling within the range of λ-50 to λ+50 wherein λ is the wavelength of the laser emission in nm

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentEP1906245B1Photopolymerization type photosensitive lithographic printing plate precursor

Publication Date: 2013.02.27 FUJIFILM CORP

AI summary

A negative-working photopolymerization type photosensitive lithographic printing plate precursor for exposing with laser, includes: a hydrophilic support; at least one photopolymerizable photosensitive layer; and a protective layer, provided in this order, wherein the photopolymerizable photosensitive layer contains a sensitizing dye, a dye or pigment capable of absorbing light having a wavelength of a laser emission wavelength ± 50 nm, which is different from the sensitizing dye; and a photopolymerization initiator.