Absorbent Article Indicator Back Sheet Pore Size Control
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Solution Overview
Problem
Conventional absorbent articles with indicators struggle to accurately indicate when to replace the diaper due to bleeding and diffusion of the colored indicator, making it difficult to distinguish the wet region and leading to inaccurate timing for replacement.
Innovation Solution
Adjusting the light transmittance and average hole diameter of the back sheet to 20-45% and 0.3-3 μm respectively, and using a covering material with hydrophilic properties to suppress bleeding and enhance visibility of the indicator's color change, ensuring accurate timing for replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a moisture absorbing paper is used as the ink covering layer, then the indicator can show clearly when wetting occurs, but the absorbed urine diffuses into the paper causing the colored indicator to blur and fade
Solution Approach 1:
The patent changes the material parameter of the ink covering layer from moisture absorbing paper to a non-woven fabric with specific properties (hydrophobic treatment, controlled porosity). This parameter change prevents urine diffusion while maintaining indicator visibility, resolving the contradiction between measurement precision and color stability.
Solution Approach 2:
The patent uses a composite structure combining a non-woven fabric base material with hydrophobic treatment and specific pore structure. This composite material approach allows the ink covering layer to simultaneously provide mechanical support, prevent urine penetration, and maintain optical properties for indicator visibility.
2Measurement precision
If the back sheet has high light transmittance, then the indicator color change is visible, but the bled portion of the colored indicator becomes noticeable
Solution Approach 1:
The patent optimizes the light transmittance parameter of the back sheet to a specific range (30-70%) and controls the pore size (0.3-3 μm). This parameter optimization allows sufficient light transmission for indicator visibility while restricting urine diffusion that causes bleeding, thus resolving the contradiction between color visibility and bled portion visibility.
Solution Approach 2:
The patent applies different properties to different parts of the back sheet structure - the pore size and hydrophobic treatment are specifically optimized in the region where the indicator is located. This local quality approach prevents bleeding at the indicator area while maintaining overall light transmittance for visibility.
3Reliability
If the back sheet pore size is reduced to prevent indicator bleeding, then color stability improves, but moisture-vapor permeability decreases
Solution Approach 1:
The patent optimizes the pore size parameter to a specific range (0.3-3 μm) that balances two opposing requirements: small enough to prevent indicator bleeding and color diffusion, but large enough to allow moisture-vapor permeability. This precise parameter control resolves the contradiction between color stability and moisture management.
Solution Approach 2:
The patent utilizes a porous non-woven fabric structure with controlled pore size distribution. The porous structure allows selective permeability - blocking liquid urine while permitting water vapor transmission. This porous material approach simultaneously achieves color stability and prevents moisture accumulation.
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 effectively reduces the visibility of the bled indicator, allowing for precise determination of when to replace the absorbent article, while maintaining comfort and moisture-vapor permeability, ensuring accurate and comfortable use.
Implementation Method 1
a back sheet (20) made of a porous resin or a nonwoven fabric having a pore size of 0.3 μm to 3 μm
Implementation Method 2
a covering material (31) made of a nonwoven fabric or a tissue paper
Data Source
AI summary
An absorbent article is provided which has such a structure that a bled portion of the colored indicator is unnoticeable. The absorbent article includes a liquid permeable top sheet, a liquid impermeable back sheet, an absorbing core interposed between the two sheets, and an indicator making it possible to visually ascertain that the absorbing core is in the wet state. The back sheet has an average hole diameter of 0.3 μm to 3 μm, and has a light transmittance of not less than 20% and not more than 45% in a state in which the absorbing core is dry.