WO2003061351A1

WO2003061351A1 - Electroluminescent coating system

Info

Publication number: WO2003061351A1
Application number: PCT/US2002/039466
Authority: WO
Inventors: Bradley Richards; Anthony Dyach
Original assignee: BASF Corp
Current assignee: BASF Corp
Priority date: 2002-01-09
Filing date: 2002-12-09
Publication date: 2003-07-24
Anticipated expiration: 2004-07-09
Also published as: MXPA04005198A; AU2002357136A1; CA2466248A1

Abstract

An electroluminescent (EL) coating system is applied to a substrate. The EL coating system includes a color-providing film layer applied to said substrate, a mid-coat film layer applied to the color-providing film layer, and a clearcoat film layer applied to the mid-coat film layer. The color-providing film layer includes an EL phosphor.

Description

ELECTROLUMINESCENT COATING SYSTEM

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention generally relates to an electroluminescent (EL)

coating system, including an EL phosphor, that is applied on a substrate. More

specifically, the subject invention relates to a tri-coat EL coating system applied to an automotive body panel where the EL phosphor is preferably excited by

electrical induction.

2. Description of the Related Art

Use of normal phosphorescent pigments or normal phosphors is known.

Normal phosphors, as opposed to EL phosphors, accumulate energy from an

external light source, such as the sun, and luminesce for a limited period of time as

a result of this accumulated energy, hi United States Patent Nos. 5,472,737 and

5,874,491 normal phosphors are incorporated into phosphorescent paint compositions that are used as highway or roadway paint compositions. Use of

normal phosphors in automotive and other coating systems is also known in the

art. For instance, United States Patent No. 6,242,056 incorporates normal

phosphors, specifically phosphorescent-coated beads, into reflective, heat-cured

paint coating systems to enhance the light emission of the paint coating system.

The conventional use of normal phosphors in conventional coating systems is inadequate for various reasons. For instance, the conventional use of normal

phosphors in conventional coating systems is inadequate because these

conventional coating systems are not tri-coat coating systems. That is, these conventional coating systems do not have a mid-coat film layer applied between a

color-providing film layer, having an EL phosphor, and a clearcoat film layer. As

such, these coatings systems, i.e., coating systems without a mid-coat film layer,

do not provide for the selective masking off of certain portions of the color-

providing film layer to generate unique design effects for a vehicle thereby

enhancing the aesthetics of the vehicle. Such unique design effects can be established by the strategic blocking of certain portions of the EL phosphor in the

color-providing film layer.

The conventional use of phosphorescent pigment in conventional coating

systems is also inadequate because many compositions that are used to form the

coating systems with the phosphorescent pigment are not cross-linkable.

Examples of compositions that are not cross-linkable are disclosed in the '737 and

'491 patents. Due to the lack of cross-linking, these compositions are not suitable

for automotive coating systems where durability and the physical integrity of the

coating system, relative to weathering and exposure, are paramount. Furthermore,

many coating systems, such as the coating system disclosed in United States Patent No. 5,998,525, do not provide for multiple film layers for making-up the

coating system. For example, these coating systems do not include a clearcoat

film layer to achieve excellent gloss and DOI. For these reasons, the prior art

compositions are not suitable for automotive coating systems where multiple film

layers are required that provide acceptable appearance, as measured by gloss and

DOI. hi fact, some DOI measurements for the prior art compositions do not even register on typical DOI meters. EL phosphors exhibit electroluminescence in response to application of an

alternating current voltage to the EL phosphor. EL phosphors may also exhibit

electroluminescence in response to an electrical field generated by the alternative

current voltage. Although EL phosphors are known and used throughout certain

industries, such as the watch and lighting industries, EL phosphors have not been

incorporated into systems that are suitable as automotive coating systems. As

such, an operator of a vehicle cannot selectively activate the coating system on the

vehicle to luminesce whenever the operator desires. Furthermore, because EL

phosphors have not been incorporated into automotive coating systems, there is no

coating system that makes use of the electricity of the vehicle to effectively control

the duration of the luminescence of the coating system. Other coating systems that

merely incorporate a normal phosphor are dependent on the amount of energy

accumulated by the normal phosphor.

The coating systems and compositions of the prior art are characterized by

one or more inadequacy. As a result, it is desirable to implement an EL coating

system that is a tri-coat coating system including a mid-coat film layer that can

selectively mask an EL phosphor to generate unique design effects. It is also

desirable that the EL coating system be cross-linkable and suitable for application to an automotive body panel. It is also desirable for the EL phosphor to be excited

by electrical induction. SUMMARY OF THE INVENTION

An EL coating system is disclosed. The EL coating system includes a

substrate. A color-providing film layer is applied to the substrate. The color-

providing film layer includes an EL phosphor. The color-providing film layer can

be a decal or can be formed from a color-providing composition. An least

partially-transparent mid-coat composition is applied to the color-providing film

layer to form an at least partially-transparent mid-coat film layer. An at least

partially-transparent clearcoat composition is applied to the mid-coat film layer to form an at least partially-transparent clearcoat film layer. The color-providing

film layer, the mid-coat film layer, and the clearcoat film layer establish a tri-coat

coating system. The mid-coat film layer in this tri-coat coating system can be

applied to selectively mask the EL phosphor to generate unique design effects for

the EL coating system. Preferably, at least one of the film layers is formed from a

composition that is cross-linkable such that the EL coating system is optimum for

application to automotive body panels. It is also preferred that the EL phosphor in

the color-providing film layer is excited by electrical induction.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated as the

same becomes better understood by reference to the following detailed description

when considered in connection with the accompanying drawings wherein:

Figure 1A includes a schematic electrical diagram illustrating the use of electrical induction to excite an EL coating system having an EL phosphor; and Figure IB includes a schematic electrical diagram illustrating a primary and

secondary induction coil intertwined with a color-providing film layer, i.e., decal.

DETAILED DESCRIPTION OF THE INVENTION An electroluminescent (EL) coating system according to the subject

invention includes a substrate, a color-providing film layer, an at least partially- transparent mid-coat film layer, and an at least partially-transparent clearcoat film

layer. As such, in the most preferred embodiment, the EL coating system is a tri-

coat coating system, i.e., a coating system having three layers (in addition to the

substrate). The color-providing film layer is applied to the substrate and includes

EL phosphor. The at least partially-transparent mid-coat film layer is formed from

an at least partially-transparent mid-coat composition that is applied to the color-

providing film layer, and the at least partially-transparent clearcoat film layer is

formed from an at least partially-transparent clearcoat composition that is applied

to the mid-coat film layer.

For descriptive purposes of the subject invention, "at least partially- transparent" is intended to describe film layers and compositions that are partially-

transparent as well as fully-transparent. Partially-transparent film layers and

compositions generally transmit at least 10%, preferably at least 30%, of incident

light. The at least partially-transparent mid-coat film layer and the at least

partially-transparent mid-coat composition are hereinafter referred to as the mid-

coat film layer and the mid-coat composition, respectively. Similarly, the at least

partially-transparent clearcoat film layer and the at least partially-transparent

clearcoat composition are hereinafter referred to as the clearcoat film layer and the clearcoat composition, respectively.

The color-providing film layer, i.e., the base or ground coat layer, is

applied to the substrate. The color-providing film layer can be a decal that is

adhered to the substrate. Alternatively, the color-providing fihn layer can be

formed from a color-providing composition that is applied to the substrate. In

either the decal embodiment or the composition embodiment, the color-providing

film layer includes the EL phosphor.

If the color-providing film layer is formed from the color-providing

composition, then the color-providing composition is preferably spray applied to

the substrate. As such, the color-providing composition is preferably a liquid that

is spray applied to the substrate by air- or rotary-atomized application equipment

that is known in the art. However, if the color-providing composition may also be

a powder or powder slurry composition, and may even by applied according to different application methods including, but not limited to, electro-deposition, dip-

applying, roll-applying, and the like.

In the embodiment where the color-providing film layer is formed from a

color-providing composition, the color-providing compositions that are suitable

for use in the subject invention include any of a number of types of color- providing compositions known in the art. For the purposes of the subject

invention, the types of color-providing compositions do not require explanation in

detail as the particular color-providing composition that is utilized does not vary the scope of the subject invention. Generally, the types of color-providing compositions suitable for

application in the subject invention include, but are not limited to, solventborne

and waterborne compositions, refinish and OEM-type compositions, and

thermosetting and thermoplastic compositions. More specifically, polymers

known in the art to be useful in the color-providing compositions include acrylics,

vinyls, polyurethanes, polycarbonates, polyesters, alkyds and polysiloxanes.

Preferred polymers include acrylics, polyurethanes, and polyesters. As indicated above, the polymer in the color-providing composition may be thermoplastic, but

is preferably cross-linkable and therefore includes one or more cross-linkable

functional groups. Suitable cross-linkable functional groups include, but are not

limited to, hydroxy, isocyanate, acid, amine, epoxy, acrylate, vinyl, silane,

anhydride, and acetoacetate cross-linkable functional groups. The cross-linkable

functional groups may be masked or blocked in such a manner that they become

unblocked and therefore available for cross-linking under preferred cure

conditions, such as elevated temperatures. These polymers may be self cross-

linkable, or may require a separate cross-linking agent that is reactive with the

cross-linkable functional groups of the polymer. For example, when the polymer

includes a hydroxy cross-linkable functional group, the cross-linking agent may be

an aminoplast resin, such as melamine, an isocyanate cross-linking agent, a

blocked isocyanate cross-linking agent, an acid, or an anhydride cross-linking

agent.

The color-providing film layer includes the EL phosphor. Although not

preferred, the other film layers, specifically the mid-coat film layer and the clearcoat film layer, may also include EL phosphor. Depending on the color

desired for electroluminescence, the EL phosphor in the color-providing film layer

includes various components. Generally, for green, blue, blue-green, and green-

yellow electroluminescence, the EL phosphor includes copper-doped zinc sulfide.

Alternatively, for these colors of electroluminescence, the EL phosphor may include a zinc-sulfide based phosphor activated with a rare earth element, a

strontium-aluminate based phosphor activated with a rare earth element, or

combinations thereof. Rare earth elements are understood to include the elements

having atomic numbers from 57 to 71 in the Periodic Table of Elements. For red

electroluminescence, the EL phosphor may be described to be of the general

formula SrS:Eu:X, where X is selected from the group consisting of chlorine,

bromine, rare earth elements, and combinations thereof. One suitable EL

phosphor is commercially available as Phosphorescent Pigment 6SSU from

United Mineral & Chemical Corporation, Lyndhurst, New Jersey.

To broaden the range of colors that are available in the color-providing film layer, the color-providing film layer may further include an at least partially-

transparent pigment in combination with the EL phosphor. Generally, any other

pigment, either organic or inorganic is suitable for combination, or co-blending,

with the EL phosphor so long as the pigment is at least partially-transparent such

that the electroluminescence of the EL phosphor can display through the color

effect of the combined pigment. Retroreflective microspheres, as are known in the

art, may also be used in combination with the EL phosphor. Although the EL phosphor may be excited by direct electrical contact, it is

preferably excited by electrical induction. Referring to Figures 1A and IB, a

color-providing film layer forming the letters "B A S F" is applied on a substrate.

In this Figure, the color-providing film layer is a decal adhered on the substrate.

However, it is to be understood that a color-providing composition could also be

applied, e.g. spray applied, to the substrate to form the letters "B A S F" or any

other letters, designs, etc.

In Figures 1A and IB, a power supply, such as a car battery, provides

direct current (DC) to an electrical circuit. This electrical circuit converts the DC

to alternating current (AC), which is required for electrical induction. The AC, at

approximately 800 Hz and 120N, is then supplied to a primary induction coil. The

AC in the primary induction coil generates a magnetic field that induces a current

to flow in a secondary induction coil. The current from the secondary induction

coil excites the EL phosphor in the color-providing film layer to electroluminesce.

The two schematic electrical diagrams included in Figures 1A and IB are examples of the relative positions for the primary and second induction coils.

These diagrams do not necessarily represent the final orientation needed for

optimum excitation of the EL phosphor in the color-providing composition.

Importantly, the use of electrical induction to excite an EL phosphor can be used

in a coating system regardless of whether or not the coating system is a tri-coat

coating system. The EL coating system of the subject invention may also include

normal phosphors such as zinc sulfide, or radioactive substances such as radioisotopes. In the embodiment where the color-providing film layer is formed from the

color-providing composition, the color-providing composition is applied to the

substrate thereby forming an uncured, or wet, film layer of the color-providing

composition. It is to be understood that, for purposes of the subject invention, if

any of the compositions are based on waterborne technology, then the terminology

"uncured" is intended to include the pre-bake or pre-cure conditions (i.e., the low

bakes or warm air drying) that are typically associated with compositions of

waterborne technology. Preferably, the color-providing composition is applied to

a film build that is suitable for completely hiding an underlying color of the

substrate. Of course, this film build is color dependent. Although not required, the

uncured film layer of the color-providing composition is preferably cured to form

the color-providing film layer.

Next, the at least partially-transparent mid-coat composition is applied to

color-providing film layer to form the mid-coat film layer. If the color-providing fihn layer is the decal, then the mid-coat composition is applied over the decal

onto the substrate. The types of compositions suitable for the mid-coat

composition are the same as those described above with respect to the color-

providing composition. The mid-coat composition may include only at least

partially-transparent pigmentation, only opaque pigmentation, or combinations of the two types of pigmentation. Either pigmentation may be organic or inorganic.

Retroreflective microspheres may also be used in the mid-coat composition.

It is preferred that the mid-coat composition include some opaque pigmentation to establish unique design effects between the combination of the color-providing film layer and the mid-coat film layer. The opaque pigmentation

is used to strategically or selectively mask, i.e., block, off certain portions of the

electroluminescence from the EL phosphor. As a non-limiting example, after the

color-providing film layer, with the EL phosphor, is established, certain portions

of the color-providing film layer can be masked off to in the form of a design,

shape, letters, etc., to be visual as a result of the electroluminescence of the EL

phosphor. Of course, if masking of the color-providing film layer is required, then

it is preferred that the color-providing film layer is completely cured so that

masking tape, or some other effective blocking tool, can be conveniently applied

to the layer. After masking, the mid-coat composition, containing some amount of

opaque pigmentation, can be applied to the color-providing film layer (either the

decal or the color-providing composition). The masking can then be removed, and

when the EL phosphor is activated, the design, shape, letters, etc., with

electroluminesce with the mid-coat film layer as a backdrop. The mid-coat

composition can be cured prior to application of the clearcoat composition or the

mid-coat composition can remain wet, in an uncured state, and the clearcoat

composition can be applied wet-on-wet to the uncured mid-coat composition.

Importantly, it is to be understood that there can be more than one mid-

coat film layer depending on the final design that is desired. For example, a first

mid-coat film layer can be established with the primary objective of providing

opaque pigmentation to achieve optimum masking. After masking the

electroluminescence of the EL phosphor where desired, a second mid-coat film

layer can be established on the first mid-coat film layer to add further pigmentation, to improve appearance, to add additional EL or normal phosphor,

and the like. Even if more than one mid-coat film layer is included, the EL

coating system of the subject invention is still effectively a tri-coat coating system

in that there is a color-providing film layer, a mid-coat film layer (formed from

several mid-coat film layers), and a clearcoat film layer. With the tri-coat coating

system, the key is that there is at least one film layer between the color-providing

film layer and the clearcoat film layer to some how modify the

electroluminescence of the color-providing film layer to create designs, shapes,

and the like.

The at least partially-transparent clearcoat composition is applied to the

mid-coat film layer to form the at least partially-transparent clearcoat film layer.

The clearcoat film layer optimizes appearance and durability of the overall EL

coating system. The clearcoat compositions suitable to be utilized in the subject

invention include any of a number of types of clearcoat compositions known in the

art. For the purposes of the subject invention, the types of clearcoat compositions

do not require explanation in detail as the particular clearcoat composition that is

utilized does not vary the scope of the subject invention.

Generally, the types of clearcoat compositions suitable for application in

the subject invention include, but are not limited to, solventborne and waterborne

clearcoat compositions, refinish and OEM-type clearcoat compositions, powder and powder slurry clearcoat compositions, and thermosetting and thermoplastic

clearcoat compositions. More specifically, polymers known in the art to be useful

in the clearcoat compositions include acrylics and polyurethanes cross-linkable with melamine or isocyanate. Polymers for the clearcoat composition preferably

have a cross-linkable functional group including, but not limited to, hydroxy,

phenol, amino, carboxyl, epoxy, or mercaptan functional groups. Other clearcoat

compositions suitable for use in the subject invention are based on carbonate

chemistry, carbamate chemistry, and silane chemistry as known in the art.

Suitable cross-linking agents reactive with the cross-linkable functional group of

the polymer in the clearcoat composition include, but are not limited to, melamine,

blocked and unblocked isocyanate, and combinations thereof. As understood by

those skilled in the art, the clearcoat composition may include additional

components such as ultraviolet light absorbers, hindered amine light stabilizers, surfactants, stabilizers, fillers, wetting agents, rheology control agents, dispersing

agents and adhesion promoters. While use of these additional components in

clearcoat compositions is well known in the art, the amount or amounts used are

varied and controlled to avoid adversely affecting various physical properties of the EL coating system.

Although not required, it is preferred that all of the compositions are cross-

linkable. It is also preferred that all of the uncured film layers are simultaneously

cured to minimize the number of ovens required to establish the EL coating

system of the subject invention. However, as alluded to above, if selective

masking is required, then it may be ideal to include cures between applications of

the various film layers, where necessary. Although various methods may be used

for curing, heat-curing is preferred. Generally, heat curing is conducted by

exposing the coating system on the substrate to elevated temperatures provided primarily by radiating heat sources. As understood by those skilled in the art,

preferred conditions for cure vary depending on the type (i.e., the chemistry and

polymer make-up) of the various compositions. More specifically, curing

temperatures vary depending on the particular blocking groups used in the cross-

linking agents. Generally, however, the curing temperatures range from 250

degree F to 385 degree F. The duration of the cure may also vary depending on

the chemistry and polymer make-up, on the particular cross-linking agents, and on

physical parameters of the coating system such as the film build. Generally, the

duration of the cure ranges from 15 to 60 minutes. Of course, as is known in the

art, if the compositions are refmish-type compositions, which are typically highly

catalyzed compositions, then the curing temperatures range from 120 degree F to

190 degree F.

For purposes of the subject invention, the terminology of color-providing

composition is intended to include any composition that can modify an original

color of an underlying substrate, so long as the color-providing composition

includes the EL phosphor. General examples of such color-providing

compositions include, without limitation, pigmented basecoat compositions

having organic pigments, inorganic pigments, metallic flakes, and/or mica flakes; clear binder compositions including only the EL phosphor, and partially-clear, or

transparent, binder compositions such as tinted clearcoat compositions, so long as

the tinted clearcoat composition also includes the EL phosphor.

As described above, the EL phosphor provides the electroluminescence for

the coating system on the substrate. Although the coating system is preferably provided on a body panel of an automobile, i.e., an automotive body panel, as the

substrate, the coating system may be applied to other suitable substrates such as

concrete, blacktop, highway markers, construction markers, boats, airplanes,

recreational vehicles, appliances, and the like. Furthermore, although the coating

system is preferably applied to an automotive body panel that is metallic, the

coating system may alternatively be applied to other automotive body panels

including, but not limited to, plastic substrates such as a bumper, mirror, or internal dashboard of the automobile, aluminum substrates, and galvanized steel

substrates.

The invention has been described in an illustrative manner, and it is to be

understood that the terminology which has been used is intended to be in the nature

of words of description rather than of limitation. Obviously, many modifications

and variations of the present invention are possible in light of the above teachings,

and the invention may be practiced otherwise than as specifically described.

Claims

CLAIMSWhat is claimed is:

1. An electroluminescent coating system comprising:

a substrate;

a color-providing film layer applied to said substrate, said color-providing

film layer comprising an electroluminescent phosphor; an at least partially-transparent mid-coat film layer formed from an at least

partially-transparent mid-coat composition applied to said color-providing film

layer; and

an at least partially-transparent clearcoat film layer formed from an at least

partially-transparent clearcoat composition applied to said mid-coat film layer.

2. An electroluminescent coating system as set forth in claim 1

wherein said electroluminescent phosphor in said color-providing film layer is

excited by electrical induction.

3. An electroluminescent coating system as set forth in claim 1

wherein said color-providing film layer is further defined as a decal adhered to

said substrate.

4. An electroluminescent coating system as set forth in claim 1

wherein said color-providing film layer is formed from a color-providing

composition applied to said substrate.

5. An electroluminescent coating system as set forth in claim 4

wherein said color-providing composition is spray applied to said substrate.

6. An electroluminescent coating system as set forth in claim 1

wherein said mid-coat composition comprises an opaque pigment for selective

masking of said color-providing film layer.

7. An electroluminescent coating system as set forth in claim 1 wherein said mid-coat composition comprises an at least partially-transparent

pigment.

8. An electroluminescent coating system as set forth in claim 1

wherein said color-providing film layer further comprises an at least partially-

transparent pigment in combination with said electroluminescent phosphor.