Piezoelectric films with low haze and methods of making and using

Inventors

Tonar, William L. • Neuman, George A. • Saenger Nayver, Mario F. • Geerlings, Kurtis L. • Franz, Sue F.

Assignees

Gentex Corp Carbondale

Abstract

A touch-sensitive assembly and method of making includes a first electrically conductive layer disposed on a first substrate and a second electrically conductive layer disposed on a second substrate. A piezoelectric film is disposed between the first electrically conductive layer and the second electrically conductive layer. The piezoelectric film includes a plurality of aligned piezoelectric particles disposed in a polymeric matrix and is characterized by a haze value of about 5% or less.

Core Innovation

A touch-sensitive assembly includes a first electrically conductive layer disposed on a first substrate and a second electrically conductive layer disposed on a second substrate. A piezoelectric film is disposed between the first electrically conductive layer and the second electrically conductive layer, and the piezoelectric film comprises a plurality of aligned piezoelectric particles disposed in a polymeric matrix. The piezoelectric film is characterized by a haze value of about 5% or less.

The polymeric matrix comprises a filler selected to change an index of refraction of the polymeric matrix so that a difference in an index of refraction of the piezoelectric particles and the index of refraction of the polymeric matrix is less than about ±1, as measured for at least one wavelength in a range of about 400 nm to about 700 nm. The polymeric matrix comprises a silicone-based polymer resin, and atoms of a metal take the place of a portion of silicon atoms in the polymeric matrix to change a refractive index of the polymeric matrix to be closer to an index of refraction of the piezoelectric particles.

A method of making the touch-sensitive assembly includes providing the first electrically conductive layer on the first substrate and the second electrically conductive layer on the second substrate. A first material selected from a polymer solution, polymer melt, reactive monomers, reactive prepolymers, and combinations thereof is provided, with piezoelectric particles dispersed within the first material. An electric field is applied to align the piezoelectric particles along a first axis to form a second material, and the second material is solidified to form a piezoelectric film comprising aligned piezoelectric articles disposed within a polymeric matrix, followed by disposing the piezoelectric film between the first and second electrically conductive layers with the haze value characterized as about 5% or less.

Claims Coverage

The document provides two independent claims: one directed to a touch-sensitive assembly and one directed to a method of making the touch-sensitive assembly. Across these independent claims, the core inventive features are concentrated in a low-haze piezoelectric film with aligned piezoelectric particles in a polymeric matrix, refractive-index matching between the piezoelectric particles and the polymeric matrix across 400–700 nm, and fabrication using electric-field alignment followed by solidification and placement between conductive layers.

Overall, the independent claims cover a touch-sensitive assembly where a low-haze piezoelectric film contains aligned piezoelectric particles in a polymeric matrix with refractive-index difference less than about ±1 over at least one wavelength in 400–700 nm. They also cover a making method that forms the aligned piezoelectric film by electric-field alignment and solidification, with a silicone-based polymer matrix modified by metal atoms taking the place of silicon atoms to achieve refractive-index closeness.

Stated Advantages

Documented Applications