US 7,858,953 B2 · Use of fluorescent nanoparticles to measure individual layer thicknesses or composition in multi-layer films and to calibrate secondary measurement devices

Abstract

Fluorescent nanoparticles such as quantum dots are incorporated into plastic, paper and other web layered products to achieve cross-direction and machine direction on-line analysis of the individual layers therein. Fluorescent nanoparticles markers are added in known proportions into product formulations. By detecting the fluorescence from the nanoparticles, the thickness and other physical characteristics of the web can be traced at various stages of production. In addition, by using different populations of fluorescent nanoparticles that emit radiation at different wavelengths, data from individual layers in a composite structure can be ascertained simultaneously with a single sensor. The technique is particularly suited for monitoring difficult-to-measure polymers in complex multilayer structures.

Claims21

Dependent claims

A method or non-contact determination of a physical property of a layer of composition that comprises the steps of:

(a) introducing a homogeneous distribution of a single population of fluorescent nanoparticles into the layer wherein the quantity of fluorescent nanoparticles per unit mass or volume of the layer can be determined;
(b) irradiating the layer with a light source of sufficient irradiance to create a population of excited fluorescent nanoparticles that emit fluorescent light;
(c) measuring the radiance of fluorescent light that is emitted from an area on a surface of the layer;
and
(d) calculating the physical property based on the measured radiance of the fluorescent light.

2 more elements

A method of measuring a physical property of at least two individual layers in a multilayer structure that comprises the steps of:

(a) forming a multilayer structure that has at least two layers including a first layer and a second layer wherein the first layer has a homogeneous distribution of a single population of first fluorescent nanoparticles in the first layer wherein the quantity of first fluorescent nanoparticles per unit mass or unit volume of the first layer can be determined and the second layer has a homogeneous distribution of single population of second fluorescent nanoparticles in the second layer wherein the quantity of second fluorescent nanoparticles per unit mass or unit volume of the second layer can be determined;
(b) irradiating the first layer to a light source of sufficient irradiance to create a population of excited first fluorescent nanoparticles that emit fluorescent light;
(c) measuring the radiance of fluorescent light that is emitted from an area on a surface of the first layer;
(d) irradiating the second layer to a light source of sufficient irradiance to create a population of excited second fluorescent nanoparticles that emit fluorescent light;
(e) measuring the radiance of fluorescent light that is emitted from an area on a surface of the second layer;
(f) calculating a physical property of the first layer based on the measured radiance of fluorescent light that is emitted from the first layer;
and
(g) calculating a physical property of the second layer based on the measured radiance of fluorescent light that is emitted from the second layer.

5 more elements

A method of monitoring the continuous production of a multilayer plastic film, that moves in a machine direction and that is formed by laminating at least two polymeric layers, which method comprises the steps of:

(a) forming a first polymer layer comprising a first polymer and a single population of first fluorescent nanoparticles, wherein the quantity of the first fluorescent nanoparticles per unit mass or volume of the first polymeric layer can be determined;
(b) forming a second polymer layer;
(c) forming the multilayer plastic film at a first location wherein the film contains the first polymeric layer and the second polymeric layer;
(d) exposing the population of first fluorescent nanoparticles to a light source that causes them to emit fluorescent light;
(e) measuring the fluorescent light that is emitted by the population of first fluorescent nanoparticles at a second location that is downstream from the first location;
and
(f) calculating the thickness or weight of the first polymeric layer in the multilayer film based on the measured fluorescent light.

4 more elements

A method of measuring a physical property of at least two individual layers in a multilayer structure that comprises the steps of:

(a) forming a multilayer structure that has at least two layers including a first layer and a second layer wherein the first layer has a homogeneous distribution of a first population of first fluorescent nanoparticles in the first layer wherein the quantity of first fluorescent nanoparticles per unit mass or unit volume of the first layer can be determined and the second layer has a homogeneous distribution of second population of second fluorescent nanoparticles in the second layer wherein the quantity of second fluorescent nanoparticles per unit mass or unit volume of the second layer can be determined;
(b) irradiating the first layer to a light source of sufficient irradiance to create a population of excited first fluorescent nanoparticles that emit fluorescent light by exposing the first layer to radiation including wavelengths in at least a first wavelength region;
(c) measuring the radiance of fluorescent light that is emitted from an area on a surface of the first layer by measuring radiation that is emitted by the fluorescent nanoparticles having wavelengths at a second wavelength region;
(d) irradiating the second layer to a light source of sufficient irradiance to create a population of excited second fluorescent nanoparticles that emit fluorescent light by exposing the second layer to radiation including wavelengths in at least the first wavelength region;
(e) measuring the radiance of fluorescent light that is emitted from an area on a surface of the second layer by measuring radiation that is emitted by the fluorescent nanoparticles having wavelengths at a third wavelength region;
(f) calculating a physical property of the first layer based on the measured radiance of fluorescent light that is emitted from the first layer;
and
(g) calculating a physical property of the second layer based on the measured radiance of fluorescent light that is emitted from the second layer.

5 more elements

Dependencies are inferred from the claim text.

Use of fluorescent nanoparticles to measure individual layer thicknesses or composition in multi-layer films and to calibrate secondary measurement devices

Life of this patent

Use of fluorescent nanoparticles to measure individual layer thicknesses or composition in multi-layer films and to calibrate secondary measurement devices

Life of this patent

Abstract

Claims21