Aluminum Sheet Material for Lithographic Plates
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Solution Overview
Problem
Lithographic printing plates experience image defects due to swelling of the protective layer caused by aluminum carbide reacting with water, leading to exposure failures and image loss, even when the aluminum carbide content is limited to less than 10 ppm.
Innovation Solution
The aluminum sheet material is processed to ensure that the number of aluminum carbide particles with a circle equivalent diameter of 3 μm or more is four or less, using the PoDFA method to measure and control the particles, thereby preventing swelling and image defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the aluminum carbide content is limited to less than 10 ppm, then the overall aluminum carbide quantity is reduced, but swelling with diameter of 50 μm or more still occurs causing image loss
Solution Approach 1:
The invention changes the parameter from total aluminum carbide content (concentration) to the size distribution and number of aluminum carbide particles. By specifying that particles with circle equivalent diameter of 3 μm or more must be 4 or less per 3000g of molten metal, the patent addresses the fact that even low total content can cause swelling if large particles are present. This parameter shift from concentration to particle size distribution resolves the contradiction by providing a more precise control criterion.
Solution Approach 2:
The invention replaces the conventional chemical analysis method for measuring aluminum carbide content with the PoDFA (Porous Disc Filtration Apparatus) method. This mechanical filtration approach physically separates and counts particles based on size, allowing direct observation and measurement of particle dimensions. The substitution enables precise control of particle size rather than relying on indirect chemical content measurement, thereby preventing swelling caused by large particles.
2Reliability
If the number of large aluminum carbide particles is reduced, then swelling and image defects are prevented, but the measurement and control complexity increases
Solution Approach 1:
The invention extracts only the harmful large aluminum carbide particles (circle equivalent diameter of 3 μm or more) from consideration by setting a specific threshold size. Rather than measuring all aluminum carbide particles regardless of size, the PoDFA method specifically targets and counts only those particles large enough to cause swelling. This extraction approach simplifies the measurement by focusing on the critical subset of particles that actually cause problems.
Solution Approach 2:
The invention introduces the porous disc filter as an intermediary device in the measurement process. The filter with specific pore size (160 μm) acts as a mediator that physically separates and retains particles of interest while allowing smaller particles and molten metal to pass through. This intermediary enables direct visual counting of large particles under a microscope, providing a simple and effective measurement approach despite the complexity of measuring impurities in molten metal.
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
This approach effectively prevents exposure failures by reducing the size of aluminum carbide particles, ensuring that the protective layer does not swell, thus eliminating image defects and maintaining image quality.
Implementation Method 1
aluminum carbide present in the surface area of the aluminum sheet material reacts with water to produce aluminum hydroxide (i.e., increase in volume)
Implementation Method 2
filtering 2000 g of the molten metal through a dedicated filter
Data Source
AI summary
An aluminum sheet material for lithographic printing plates wherein the number of aluminum carbide particles having a circle equivalent diameter, measured by the PoDFA method, of 3 μm or more is four or less, the number of aluminum carbide particles having a circle equivalent diameter, measured by the PoDFA method, of 3 μm or more.