WO2001016223A1

WO2001016223A1 - Retroreflective inks and fabrics

Info

Publication number: WO2001016223A1
Application number: PCT/US2000/024291
Authority: WO
Inventors: Gary D. Shaffer
Original assignee: Visibility Enhancement Technologies
Priority date: 1999-09-02
Filing date: 2000-08-31
Publication date: 2001-03-08
Also published as: AU7347600A

Abstract

Described is a retroreflective ink adapted for use on fabrics and other substrates. A retroreflective ink includes a non-volatile matrix material, a volatile component, and a plurality of uncoated beads. Also described are methods of printing fabrics with retroreflective inks.

Description

RETROREFLECTIVE INKS AND FABRICS

Field Of The Invention

The invention relates the field of inks suitable for printing onto textiles.

More particularly, the invention relates to inks suitable for printing retroreflective patterns onto fabrics.

Background Of The Invention

Retroreflective surfaces redirect light from environmental sources such as

automobile headlights and overhead streetlights into the eyes of others.

Retroreflectorized objects are therefore more visible under low light conditions

than nonreflectorized objects. In order to promote public safety, objects

commonly encountered in motor vehicle traffic that are often made

retroreflective. For example, traffic signs, emergency response vehicles, vehicle

license plates, bicycles, and the like are made retroreflective to make them more

conspicuous, especially at nighttime and during inclement weather. In a similar

fashion, various articles of clothing are sometimes made retroreflective to make

the wearer more visible to others.

Retroreflective compositions for use on fabrics and other objects are

known in the art. For example, retroreflective coating compositions are

disclosed in Palmquist et al. U.S. Pat. No. 2,963,378; Nellessen, U.S. Pat. Nos.

3,099,637; 3,228,897; and 3,420,597; Longlet et al. U.S. Pat. No. 3,535,01 9; Bingham U.S. Pat. Nos. 4, 1 03,060; Re. 30,892; and 4,263,345; Fouche Jr.

U.S. Pat. No. 4, 1 87,332; and Rizika et al. U.S. Patent No. 5,650,21 3.

Commercially available retroreflective compositions include SCOTCHLITE textile

ink (Minnesota Mining and Manufacturing Co., St. Paul, MN) and ILLUMITE

textile ink (Reflective Technologies, Inc., Cambridge, MA).

Conventional retroreflective compositions are useful for rendering various

objects more visible. They are, however, expensive and difficult to work with.

For example, conventional retroreflective compositions generally comprise

translucent beads hemispherically coated with a reflectorizing substance such as

metallic aluminum. E.g., Rizika et al. U.S. Patent No. 5,650,21 3. Such beads

are not only relatively costly to manufacture but also result in the retroreflective

compositions being unstable. That is, when such beads are dispersed in

commonly used liquid carriers, the resulting mixture becomes unusable within a

period of a few days. Because this mixture has a relatively short shelf life,

conventional retroreflective compositions are sold as two or three separated

precursor components. Prior to use, these precursor components must be mixed

together to form a retroreflective ink.

Conventional retroreflective compositions are also not optimized for

printing onto textiles because they often clog printing screens, require a

relatively high curing temperature, and are compatible only for printing onto

darker fabrics as the retroreflective compositions themselves typically have a

dark gray color. Moreover, many of the available retroreflective compositions

are not suitable for use on garments because coating of such compositions onto

a fabric often renders the fabric inflexible or rough to the touch. Summary Of The Invention

A easy to use retroreflective ink has been developed. The components of

this ink are stable relative to one another, allowing the ink to be stored for

relatively long periods in premixed form. This ink is also adapted for use on

garments and is particularly suited for use in automated printing processes.

Accordingly, the invention features a retroreflective ink composed of a

multitude of components including a non-volatile matrix material, a volatile

component, and a plurality of beads exhibiting retroreflective qualities but not

having a reflective coating. In some variations of the foregoing, the beads

comprising this ink can have a mean diameter of about 1 0-40 microns (e.g.,

about 25 to 35 microns, less than 30 microns, and about 25 microns), can be

clear (i.e., transparent or colorless) or tinted to a predetermined color, solid,

spherical or nonspherical in shape, and/or comprised of a glass such as silica.

In one aspect of the invention, the beads comprise about 55-60% the ink

volume when all of the volatile carrier (e.g., water) has been removed from the

ink. In another aspect of the invention, the non-volatile matrix material (e.g., an

acrylic copolymer) comprises about 40-45 % of the ink volume when all of the

volatile carrier has been removed from the ink. In some embodiments, the

volatile component comprises about 45-50% by volume of the ink.

Also within the invention is a retroreflective ink containing numerous

components including a non-volatile matrix material, a volatile component, and a

plurality of beads, but not containing any pigment particles.

The invention additionally features a fabric having an ink of the invention thereon. Also within the invention are methods of making a retroreflective

fabric, the methods including the step of printing a fabric with a retroreflective

ink of the invention.

In another aspect, the invention features a retroreflective ink including a

mixture having both 409 AG Reflective Clear LF Base and Grancill PWX Binding

and Finishing Agent.

As used herein, the word "retroreflective" is an adjective that indicates

that an object or substrate reflects rays of light in directions close to opposite

the direction of the incident rays (e.g., along their originating path) with this

property being maintained over wide variations of incident ray directions.

As used herein, the word "ink" means a fluid useful for depositing a

substance onto a substrate, e.g., a retroreflective composition onto a fabric.

As used herein, an object has a "reflective coating" when it has applied

thereon one or more layers of a reflective material such as a metallic material

(e.g., aluminum) or a non-metallic material (e.g., an organic compound) . For

example, spherical beads having with metallic aluminum hemispherically

covering their surfaces have a reflective coating.

As used herein, the word "colorless" is an adjective that describes an

object having no readily observable tint or hue. For example, common glass

having no exogenously added tinting agent or dye is colorless. By "tinted" is

meant having an added color or hue. For example, retroreflective beads are

tinted when a coloring agent or dye is added to impart a color to the beads. As used herein, the phrase "pigment particle" means is particulate solid

(although not a "spherical bead") which is insoluble in, and essentially physically

and chemically unaffected by, the vehicle in which it is incorporated. Typically,

pigment particles are used to impart a color in the substance in which they are

incorporated.

As used herein, the word "fabric" means a woven material such as a

textile. Fabrics can be composed of natural or synthetic materials such as

cotton, nylon, polyester and the like, and are often fashioned into garments such

as article of clothing.

Unless otherwise defined, all technical terms used herein have the same

meaning as commonly understood by one of ordinary skill in the art to which

this invention belongs. Although methods and materials similar or equivalent to

those described herein can be used in the practice or testing of the present

invention, suitable methods and materials are described below. All publications,

patent applications, patents, and other references mentioned herein are

incorporated by reference in their entirety. In the case of conflict, the present

specification, including definitions will control. In addition, the particular

embodiments discussed below are illustrative only and not intended to be

limiting.

Detailed Description

The invention encompasses retroreflective inks comprising a non-volatile

matrix material, a volatile component, and a plurality of beads.

Components of the Retroreflective Ink

Beads suitable for use in the compositions of the invention are

commercially available. For example, spherical beads are available from Potter's

Industries (Valley Forge, PA) and Light Bead (Arlington, MA) . In preferred

embodiments of the invention, the beads are roughly spherical in shape,

composed of glass (e.g., silica), and have a diameter of approximately 1 0 to 200

microns (e.g., 1 0, 1 2, 14, 1 6, 1 8, 20, 22, 24, 25, 26, 28, 30, 32, 34, 35, 40,

50, 60, 70, 80, 90, 1 00, 1 10, 1 20, 1 30, 140, 1 50, 1 60, 1 70, 1 80, 1 90, or

200 microns) . Although the beads can be a heterogenous mixture of beads of

varying diameter, in preferred embodiments, the beads are a fairly homogenous

mixture of beads having a mean diameter of approximately 25 to 35 microns.

For screen printing, preferred embodiments feature smaller beads because

smaller beads flow more easily through the pores of the screen mesh and are

less apt to cause clogging. The particular mean diameter of the bead can be

selected by one of ordinary skill in the art according to the mesh count of the

screen. For example, beads having a mean diameter of approximately 25

microns are suitable for use with screens having a mesh count in the range of

1 10 threads per inch (tpi). Likewise, smaller diameter beads (e.g., 1 5 to 20

microns) would be suitable for use with finer mesh counts. By varying the composition of the glass used to make the beads, the beads can have an index

of refraction ranging from 1 .7 to 2.5. In preferred embodiments, in order to

ensure sufficient retroreflectivity, the beads have a mean index of refraction of

at least about 1 .9 (e.g., 1 .9, 2.O., 2.1 , 2.2., 2.3, 2.4, 2.5) . In preferred

embodiments, the beads are translucent and not colored.

In some applications, however, the glass comprising the beads is tinted a

particular color so that the beads have a tint (e.g., a red, orange, yellow, green,

blue, or violet hue). In preferred embodiments the beads are solid. In other

embodiments, however, they can also be hollow, or perforated (e.g., with pores

of varying diameter such as 1 , 2, 5, 1 0, 20 microns in diameter).

The beads within the subject invention may have a roughly spherical

shape. In alternate embodiments, the beads may have other shapes. For

example, the beads may be polygonal, cone-shaped, star-shaped, of an irregular

shape, etc. The beads may even comprise a mixture of two or more differently-

shaped beads. Preferred shapes of the beads are those that enhance

retroreflectivity.

The non-volatile matrix material featured in the invention is any suitable

material that facilitates coating of the beads onto a substrate (i.e., the object to

which the ink of the invention is applied such as textiles, fabric, paper, leather,

plastic, glass, metals, wood, rubber, synthetic rubber, composites, etc.).

Suitable compositions for use as the non-volatile matrix material are known in

the art. For example, matrix materials typically used in conventional (non-

retroreflective) textile inks may be used. In preferred embodiments, the non-volatile matrix material takes the form

of a transparent or translucent non-volatile film-forming emulsion. Exemplary

non-volatile matrix materials suitable for use on fabric such as those used to

make clothing include, but are not limited to acrylic, vinylidene chloride,

butadiene, acrylonitrile or urethane polymers, or any of suitable mixture of the

foregoing. Materials suitable for use as or preparation of the non-volatile matrix

are commercially available from chemical suppliers such as Sigma-Aldrich (St.

Louis, MO) . In a particularly preferred embodiment, the non-volatile matrix

material is an acrylic copolymer. Still other materials suitable for use as the non-

volatile matrix material can be selected by one skilled in the art based on the

properties desired for a particular application. For example, various oils, resins,

solvents can be used as the non-volatile matrix material in certain applications.

The volatile component of the invention is a liquid component conducive

to evaporation. The volatile component can be any suitable liquid or

combination of two or more liquids such as volatile organic solvents. Materials

suitable for use as or preparation of the volatile component are commercially

available from chemical suppliers (e.g., Sigma-Aldrich). In a particularly preferred

embodiment, the volatile component is water. Water that has been distilled,

deionized, and/or filtered to remove contaminants is preferred. Still other

materials suitable for use as the volatile component can be selected by one

skilled in the art based on the properties desired for a particular application.

While the foregoing comprise the minimal elements typically needed to

fabricate the inks of the invention, other components can be added to the ink depending on the particular qualities desired. For example, although the

preferred inks of the invention are colorless and do not contain insoluble coloring

agents such as pigment particles, such particles or, alternatively, soluble coloring

dyes can be added to the ink so that a substrate treated with the ink takes on a

pre-selected color or hue. Additionally, in certain embodiments, texturizing

agents may be added to the inks where it is desired to impart a particular

surface quality to the substrate to which the ink is applied. For example, sand

particles may be added to the ink so that the substrate to which the ink is

applied exhibits a high friction surface. Still other ink additives may be included.

These can be selected by one skilled in the art depending on what particulars

qualities are desired. For example, to further adapt the inks for use in a screen

printing process, materials such as lubricants, surfactants, dispersants,

thickeners, defoamers, stretch additives (i.e., agents that impart elasticity),

binding agents (i.e., agents that help adhere solid particulates to substrates),

finishing agents, low crocking agents, cross link agents (e.g., CX100, Zeneca

Industries, Wilmington, MA), low cure additives (i.e., agents that reduce the

time and/or temperature of curing), fixers and/or ammonium hydroxide can be

added.

Preparation of the Retroreflective Ink

In various preferred embodiments of the invention, the retroreflective ink

is prepared for use by mixing the beads, non-volatile matrix material, volatile

component, and, optionally, the aforementioned additives together to form an ink. Appropriate amounts of each of the foregoing components are added

together in a predetermined ratio then mixed to form the ink. Mixing can be

accomplished by any means known in the art, e.g., using a high speed mixer or

blender.

The precise ratio selected will depend on the particular application for

which the ink will be used and can be selected by one of skill in the art based on

the characteristics of each component. For example, in a particularly preferred

embodiment suitable for use in screen printing fabrics, a bead-matrix mixture is

prepared where the mixture comprises by volume about 55-60% beads and

about 40-45 % non-volatile matrix material. The volatile component is added to

the bead-matrix material in an amount so that the volatile component is present

at about 45-50% the volume of the ink (i.e., the total volume of the beads,

matrix material, and volatile component). That is, the volatile component is

added to the bead-matrix material mixture in a ratio of about 1 :2 by volume.

After mixing the foregoing components together to form the ink, the ink is

stored in an airtight container so that the volatile component does not

appreciably evaporate prior to use.

Applying Retroreflective Inks to Substrates

The inks of the invention can be applied to substrates by any suitable

method known in the art. For example, the inks can by manually applied to a

piece of fabric by simply dispensing (e.g., using a pipet) a quantity of the ink

onto the fabric. Other suitable methods for applying the inks to a substrate include coating (e.g., Floating Knife or Knife Over Roll method), stenciling, ink jet

printing, and web or rotary screen printing. In commercial processes where a

large number of fabric articles to be treated with the inks of the invention, the

preferred method of application is screen printing.

In one exemplary embodiment, a rotary screen printing process is used to

apply the ink to a substrate. In this method, the ink is pumped into the inner

portion of a perforated cylindrical screen and forced out onto a substrate through

the tiny screen perforations. The screen perforations can be made in the form of

a predetermined image, so that the ink becomes deposited onto the substrate in

a repeating pattern of the predetermined image. Thus, for example, where it is

desired to render a pre-existing image printed on a fabric retroreflective, a

transparent version of the retroreflective ink of the invention is printed directly

over the pre-existing image using a screen duplicating the image. To add a

retroreflective tint to the image, a dye or coloring agent is added to the

retroreflective ink before it is printed onto the image.

Substrates printed with a retroreflective ink of the invention are cured by

applying heat for a predetermined period of time to the substrate. The exact

amount of heat added and time needed to effect a cure will depend upon the

particular retroreflective ink and substrate used. This can be determined without

undue experimentation. In a typical application, the temperature of the ink is

raised to 325 degrees F. With the addition of low cure additive this curing

temperature can be reduced to 225 degrees F. Low temperature curing is preferred when fabrics with low melting points are used as the substrate (e.g.,

synthetic materials such as polyester or nylon).

Example

A retroreflective ink of the invention was prepared by mixing 3 parts of

409 AG REFLECTIVE CLEAR LF base (International Coatings Corporation,

Cerritos, CA) with 1 part Grancill PWX binding and finishing agent (Grant

Industries, Elmwood Park, NJ 07407) . 409 AG REFLECTIVE CLEAR LF base

includes water as a volatile component, uncoated roughly spherical glass beads

having a mean diameter of about 25 microns, and a matrix material. 409 AG

Reflective Clear LF base is made by mixing approximately 2 pounds of uncoated

roughly spherical glass beads into each gallon of a textile ink base sold by

International Coatings Corporation (400 series Waterbase #402LF) and then

adjusting the viscosity using a volatile component to approximately 0.090 to

0.1 1 0 centistokes (i.e., a specific gravity compatible with screen printing and for

maintaining bead suspension) . Grancill PWX includes water as a volatile

component, binding agents that help adhere solid particle to a substrate, and

finishing agents that facilitate the use of the ink in screen printing applications.

CX100 cross link (Zeneca Industries) was then added in a quantity of 2% of the

total volume. This ink was screen printed onto a fabric in a predetermined

pattern. The printed fabric exhibited low daytime noticeability, while

manifesting readily detectible retroreflectivity under low light conditions (e.g.,

under typical nightime lighting) . From the foregoing, it can be appreciated that the retroreflective inks and

related methods of the invention provide compositions and processes for

enhancing the visibility various objects under low visibility conditions.

Other Embodiments

While the above specification contains many specifics, these should not

be construed as limitations on the scope of the invention, but rather as examples

of preferred embodiments thereof. Many other variations are possible.

Accordingly, the scope of the invention should be determined not by the

embodiments illustrated, but by the appended claims and their legal equivalents.

Claims

ClaimsWhat is claimed is:

1 . A retroreflective ink comprising:

a non-volatile matrix material;

a volatile component; and

a plurality of beads;

wherein said beads lack a reflective coating.

2. The retroreflective ink of claim 1 , wherein said beads have a mean

diameter of about 1 0 to 40 microns.

3. The retroreflective ink of claim 2, wherein said beads have a mean

diameter of about 25 to 35 microns.

4. The retroreflective ink of claim 2, wherein said beads have a mean

diameter of less than 30 microns.

5. The retroreflective ink of claim 4, wherein said beads have a mean

diameter of about 25 microns.

6. The retroreflective ink of claim 1 , wherein said beads are colorless.

7. The retroreflective ink of claim 1 , wherein said beads are tinted.

8. The retroreflective ink of claim 1 , wherein said beads are solid.

9. The retroreflective ink of claim 1 , wherein said beads comprise

silica.

10. The retroreflective ink of claim 1 , wherein said beads are roughly

spherical in shape.

1 1 . The retroreflective ink of claim 1 , wherein said beads are not

spherical.

12. The retroreflective ink of claim 1 , wherein said volatile component

consists essentially of water.

1 3. The retroreflective ink of claim 1 , wherein said beads comprise

about 55-60% the ink volume when all of the volatile carrier has been removed

from the ink.

14. The retroreflective ink of claim 1 , wherein the non-volatile matrix

material comprises about 40-45% of the ink volume when all of the volatile

carrier has been removed from the ink.

1 5. The retroreflective ink of claim 1 , wherein the non-volatile matrix

material comprises an acrylic copolymer.

1 6. The retroreflective ink of claim 1 , wherein the volatile component,

comprises about 45-50% by volume of said retroreflective ink.

1 7. A retroreflective ink comprising:

a non-volatile matrix material;

a volatile component; and

a plurality of beads;

wherein the retroreflective ink does not comprise pigment particles.

1 8. A fabric comprising the retroreflective ink of claim 1 .

1 9. A fabric comprising the retroreflective ink of claim 1 5.

20. A method of making a retroreflective fabric, said method

comprising the step of printing a fabric with the retroreflective ink of claim 1 .

21 . A method of making a retroreflective fabric, said method

comprising the step of printing a fabric with the retroreflective ink of claim 1 7.

22. A retroreflective ink comprising a mixture comprising 409 AG

REFLECTIVE CLEAR LF base and Grancill PWX binding and finishing agent.