Thermosensitive Recording Material Undercoat Layer Bimodal Particle Distribution

Solution Overview

Problem

Current undercoating compositions for thermosensitive recording materials fail to balance the strength of the paper coating with the optical density of printed paper effectively.

Innovation Solution

A bimodal distribution of core-shell polymer particles with specific diameter and dry bulk density ranges, applied as an undercoat layer on paper, enhances the strength and optical density of thermosensitive recording materials by optimizing the ratio and size of first and second hollow sphere polymer particles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a single-size hollow polymer particle undercoat is used, then the manufacturing process is simple, but the balance between coating strength and optical density is insufficient

Engineering Contradiction:

Improvesimplicity of undercoat applicationVSAvoidbalance between coating strength and optical density

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The undercoat comprises a bimodal distribution of hollow polymer particles with two distinct size ranges: first particles (0.5-2.0 μm) and second particles (0.1-0.5 μm). This segmentation of particle sizes allows the larger particles to provide structural strength while the smaller particles fill interstices to enhance optical density, resolving the contradiction between manufacturing simplicity and performance balance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The undercoat forms a composite structure by combining hollow polymer particles of two different size ranges with a binder. This composite approach leverages the complementary properties of different particle sizes: the larger particles contribute to mechanical strength and the smaller particles improve optical density by filling void spaces, achieving a balanced performance that neither single-size system could provide alone.

Inventive Principle:

Principle #40Composite materials

2Strength

If only large hollow polymer particles are used, then the coating strength is improved, but the optical density is insufficient

Engineering Contradiction:

Improvecoating strengthVSAvoidoptical density of printed paper

Core Design Contradiction:

StrengthVSIllumination intensity

Solution Approach 1:

The bimodal particle distribution creates local quality variations within the undercoat structure. Larger particles (0.5-2.0 μm) are distributed to provide structural strength, while smaller particles (0.1-0.5 μm) occupy the interstitial spaces between larger particles to enhance optical density. This spatial differentiation of particle functions resolves the contradiction between strength and optical density.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The hollow polymer particles create a porous structure that, when combined in a bimodal distribution, optimizes both mechanical properties and optical characteristics. The hollow cores provide lightweight structural support while the interstitial filling by smaller particles reduces light transmission, achieving both strength improvement and enhanced optical density.

Inventive Principle:

Principle #31Porous materials

3Illumination intensity

If only small hollow polymer particles are used, then the optical density is improved, but the coating strength is insufficient

Engineering Contradiction:

Improveoptical density of printed paperVSAvoidcoating strength

Core Design Contradiction:

Illumination intensityVSStrength

Solution Approach 1:

The bimodal particle distribution creates local quality variations within the undercoat structure. Larger particles (0.5-2.0 μm) are distributed to provide structural strength, while smaller particles (0.1-0.5 μm) occupy the interstitial spaces between larger particles to enhance optical density. This spatial differentiation of particle functions resolves the contradiction between strength and optical density.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The undercoat forms a composite structure by combining hollow polymer particles of two different size ranges with a binder. This composite approach leverages the complementary properties of different particle sizes: the larger particles contribute to mechanical strength and the smaller particles improve optical density by filling void spaces, achieving a balanced performance that neither single-size system could provide alone.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentEP3175994B1Thermosensitive recording material

Publication Date: 2022.06.22 DOW GLOBAL TECHNOLOGIES LLC

AI summary

The present invention relates to a thermosensitive recording material comprising paper, an undercoat layer disposed on the paper, and a thermosensitive recording layer disposed on the undercoat layer, wherein the undercoat layer comprises a binder and first and second hollow sphere polymer particles, wherein the first hollow sphere polymer particles have a diameter in the range of from 1.2 µm to 1.8 µm; the second hollow sphere polymer particles have a diameter in the range of from 0.25 µm to 1.0 µm; the number ratio of the second to the first hollow sphere polymer particles is in the range of from 1:1 to 20:1; the diameter of the second hollow sphere polymer particles is in the range of from 15 to 65% of the diameter of the first hollow sphere polymer particles; the dry bulk density of the first hollow sphere polymer particles is in the range of 0.25 to 0.5 g/mL; and the dry bulk density of the second hollow sphere polymer particles is in the range of 0.30 to 0.90 g/mL.