WO2003078162A1

WO2003078162A1 - Polycarbonate automotive window panels with coating system blocking uv and ir radiation and providing abrasion resistant surface

Info

Publication number: WO2003078162A1
Application number: PCT/US2002/028355
Authority: WO
Inventors: Steven M. Gasworth; Mark Peters; Ralf Dujardin
Original assignee: Exatec, Llc.
Priority date: 2001-09-06
Filing date: 2002-09-06
Publication date: 2003-09-25
Also published as: KR20040044541A; EP1429921A4; AU2002341608A1; EP1429921B1; CN100430223C; ATE398524T1; JP2005519792A; CN1551830A; EP1429921A1; DE60227182D1

Abstract

An automotive glazing panel is provided by a polycarbonate substrate having a coating system including an inner layer blocking IR and overlying coating material blocking UV radiation and providing a scratch resistant outer coating layer.

Description

POLYCARBONATE AUTOMOTIVE WINDOW PANELS WITH COATING SYSTEM BLOCKING UV AND IR RADIATION AND PROVIDING ABRASION RESISTANT SURFACE

Cross Reference to Related Applications

This application claims the benefit of provisional application 60/317,599 filed

on September 6, 2001.

This application is a continuation-in-part of PCT/EP02/00001 filed on March

16, 2001, designating the United States, published on September 27, 2001 as no. WO

02/053630A.

Incorporation by Reference

The parent application of PCT/EP02/00001 published on September 27, 2001

is here incorporated by reference in its entirety.

Reference is made to U.S. patent nos. 5,298,587; 5,320,875; 5,433,786;

5,494,712; 5,718,967; 5,900,284; 6,376,064; 6,432,494 and 6,397,776 which set forth details

of coating compositions and processes discussed below which patents are hereby each

incorporated by reference in their entirety.

Background of the Invention This invention concerns polymeric glazing panels for use in automotive

windows and more particularly constructs comprised of coating systems in combination with

polycarbonate automotive glazing panels.

The safety, styling and other advantages to be gained by polymeric glazing panels for automotive windows have long been appreciated. Polycarbonate has emerged as a

desirable material for molding these panels due to its superior strength and optical clarity.

Use of polymeric based glazing materials in automotive applications has

raised certain problems. This is due, as least in part, to the unique challenges posed by

automotive service conditions. While not an exhaustive list, these include, but are not limited

to at least one of the following: extremes of temperature and environmental exposure; intense

and prolonged vibrational forces transmitted through the glazing material during normal

operation of the automotive vehicle; occasional instances of intense shock and impact loads

which may be randomly exerted on the glazing material scratching of the surface by

incidental contacts such as in washing of the vehicle or the impacting of dust and other

particles; and routine though prolonged exposure to debilitating environmental factors such

as rain and the ultraviolet and infrared radiation in sunlight.

Another problem encountered in the use of polycarbonate in automotive

glazing applications is the need to reduce the excessive heat load caused by penetration of

solar radiation through the windows into the automobile interior, creating undesirable heat

loads, particularly during summer months. While a similar problem has been encountered

with silica based glass compositions in automotive glazing applications, the heat load

problem can be addressed with the use of inorganic glass coatings or additives which can be

integrated during glass formation or in suitable post formation steps. Heretofore, methods

and strategies for reducing the heat load potential for polycarbonate based glazing

compositions suitable for use in automotive applications has been more problematic.

It has long been recognized that the abrasion resistance of polycarbonate panel exposed surfaces needs to be greatly improved to be adequate for the severe automotive

service requirements in this regard.

Various coatings have been devised to achieve such suitable abrasion

resistance.

The leading candidate for improving abrasion resistance of polycarbonate is

various plasma polymerized organosilicon coatings. Dip coatings are also available to

improve abrasion resistance but generally these have not been found to be as effective for

automotive glazing use.

Another consideration is the need to protect the polycarbonate from UV

exposure to prevent the yellowing of this material which normally results.

It is the object of the present invention to provide a durable coating system on

an automotive glazing panel able to meet all of the above requirements.

Summary of the Invention

The present invention is directed to a polymeric glazing construction suitable

for use in an automotive vehicle. The glazing construction includes a polycarbonate substrate

having an outer surface; a polymeric innermost coating affixed to the exposed outer surfaces

of the polycarbonate substrate, the polymeric coating capable of blocking transmission of at

least a substantial portion of infrared radiation transmitted thereto; an intermediate coating

over the innermost layer capable of blocking at least a substantial portion of UV radiation

transmitted thereto to protect both the first coating and the polycarbonate; and an outer

coating in overlying relationship with the intermediate UV infrared absorbing coating, the outermost coating composed of a material capable of resisting abrasion by exposure external

to the polymeric glazing construction.

The above object as well as other objects which will be understood upon a

reading of the following specification and claims are achieved by a polycarbonate window

panel coated with an innermost layer of BAYTRON P which is a material available from

Bayer A.G. of Leverkusen, Germany, and described in PCT/EP02/00001, which when

applied to the polycarbonate functions as an infrared radiation blocker, a second overlying

coating layer comprised of an UV radiation blocker, and an outermost coating layer providing

an abrasion resistance by being sufficiently hard to be suitable for automotive service.

Suitable primer coatings may also be applied between and/or under these coatings.

Description of the Drawings

Figure 1 is a fragmentary view of an automotive vehicle equipped with coated

polycarbonate glazing panels.

Figure 2 is a diagrammatic depiction of the coating system and automotive

glazing panel substrate according to the invention.

Description of the Preferred Embodiment

In the following detailed description, certain specific terminology will be

employed for the sake of clarity and a particular embodiment described in accordance with

the requirements of 35 USC 112, but it is to be understood that the same is not intended to be

limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims.

The present invention is predicated upon the unexpected discovery that

specific compositions can be successfully imparted in overlying relationship to a

polycarbonate substrate in a manner which provides sufficient durability and utility for

integration of the resulting glazing construct into a various components of an automotive

vehicle.

As used herein, the term "automotive vehicle" is defined as any of a number of

types of vehicles powered by a self contained or remote power plant which can be taken to

include but are not limited to at least one of passenger cars, vans and motorcycles, light

trucks, heavy duty trucks including off road vehicles, recreational vehicles such as mobile

homes and campers, mass transit vehicles such as busses, locomotive vehicles such as trains

and other light rail vehicles such as monorails and the like, as well as marine and air craft.

Referring to the drawings, Figure 1 shows a fragmentary portion of a

passenger car 10 including a body 12 having portions 14, 16 defining a rear quarter window

opening in which a glazing panel 22 is fixed in conventional fashion, such as with an

adhesive bonding. A masking border 18 is typically provided as described in U.S. patent

6,309,755 to conceal the adhesive joint.

A drop glazing panel 20 is also typically included and could also be coated in

the manner of the present invention.

Figure 2 is a diagrammatic representation of a section through the glazing

panel 22, which may be typical of all of the glazing panels incorporated in the vehicle 10.

The glazing panel 22 comprises a polycarbonate substrate 24 having at least one outwardly facing surface having first innermost polymeric layers 26 bonded thereto.

Polycarbonate substrate 24 may have a configuration appropriate for the window opening.

Suitable polycarbonate materials include, but are not limited to materials such

as those well known in the art.

These polycarbonate resins are aromatic carbonate polymers which may be

prepared by reacting one or more dihydric phenols with a carbonate precursor such as

phosgene, a haloformate or a carbonate ester. One example of a polycarbonate which can be

used is polycarbonate LEXAN, manufactured by the General Electric Company.

The first or innermost polymeric layer 26 contains a material which is capable

of blocking the transfer of a substantial portion of transmitted infrared light through the first

or innermost layer and into contact with the polycarbonate substrate while maintaining

characteristic transparency of the polycarbonate substrate. Blocking of IR radiation

transmission prevents at least a substantial portion of transmitted sunlight in the IR spectrum

to penetrate the panel 22. It also includes the deflection of light in the TR spectrum away

from the polycarbonate layer to reduce heat load in the passenger compartment. The degree

of IR light blockage is a function of attributes such as material composition, layer thickness

and the like.

The first or innermost coating layer 26 is of a material such as at least one

from the group which includes substituted polythiophene styrene sulfonate, polypyrrole

styrene sulfonate and substituted polypyrrole styrene sulfonate. Suitable materials also

include 3, 4-dialkoxy substituted polythiophene styrene sulfonates. Suitable materials are

commercially available from Bayer AG under the trade name BAYTRON P. Reference is made to PCT/EP02/00001 incorporated herein by reference

above, for details of the composition of BAYTRON P and the process of forming a coating

on a polycarbonate substrate using BAYTRON P.

BAYTRON P is an aqueous dispersion of polyethylenedioxythiophene

(PEDT) doped with a polymeric acid salt (e.g., polystyrene sulfonate). As commercially

available the material is supplied as a 1.3% solution in water (pH=l-2). It is primarily used

to coat glass and plastic substrates for antistatic finishing but is also used as an electrostatic

coating of non-conductive surfaces. Coatings of BAYTRON P are transparent to light blue in

color. It has been found that they can provide nearly 100% absorption of light in the range of

900 to 2000 nm which includes a large fraction of the infrared range.

The first or innermost polymeric layer 26 may have any suitable thickness

sufficient to provide the IR deflecting/absorbing capacities within the range desired.

Typically, the material is applied to the surface of the polycarbonate substrate by any suitable

application method such as described in PCT/EP02/00001.

The polycarbonate must be shielded from the UN radiation in sunlight. By

applying a second or intermediate coating 28 which blocks transmission of UN radiation over

the innermost BAYTRON P coatings 26, the polycarbonate substrate 24 is shielded as

required. However, in addition, the BAYTRON P is also at the same time shielded from UN

radiation. This is critical since BAYTRON P while having been applied to polycarbonate

substrates, has been found to suffer from poor UN and thermal stability when used alone.

However, when protected by a UN blocking layer 28, BAYTRON P has shown remarkable

stability. U.S. patent 6,376,064 incorporated by reference herein, describes a UN

blocking coating applied over a polycarbonate substrate effective to shield polycarbonate, and

is suitable to be applied over BAYTRON P.

That coating is comprised of a particular diorganodiorgonoxiysilane or a

particular organotriorganoxysilane or both as described in detail therein.

The final or outermost coating 30 overlying the UV blocking coatings 28

comprise an abrasion resistant coating which is sufficiently hard and durable when exposed to

weathering to be acceptable for automotive service.

Such coatings may be of the type comprised of a plasma polymerized and

oxidized organosilicon material. Various forms of such coatings are described in the U.S.

patents incorporated by reference, although the antiabrasion coating and processes described

in U.S. 6,376,064; 6,432,494; and 6,397,776 yield a coating having good weatherability

characteristics and being sufficiently resistant to abrasion, and importantly being adaptable to

the production rates necessary for economic viability for use in the auto industry.

Non plasma generated abrasion resistant coatings have also been developed,

including by Bayer AG such as under Bayer designation number LP065. PCT/EP02/00001

also describes such a scratch resistant coating material which can be applied by conventional

dip or flow technologies.

This three component coating system applied to a polycarbonate substrate

provides ultraviolet (UV) protection for both the polycarbonate and BAYTRON P, provides a

barrier to infrared (IR) radiation and provides adequate scratch resistance for automotive use.

This three component coating system is stable in service for the automotive application. The use of materials such as substituted polythiophene styrene sulfonates

produces a significant reduction in the amount of solar radiation measured as total Solar

Energy Transmission (TSET) that would normally penetrate a polycarbonate window.

Primers may be required for some of these coating layers and UN and

BAYTRON P may in some instances be combined with an interposed primer coating.

HYCAR (GE Trademark) has been found to be compatible with BAYTRON P.

The UN blocking layer could be combined with the outermost abrasion layer

to combine the two outer layers to a single layer of overlying coating material rather than two

layers of overlying coating material. Improved versions of plasma polymerized and oxidized

organosilicon abrasion resistant coatings are typically in development and may be used, and

the same is true for the wet coat abrasion resistant materials.

EXAMPLE I

A BAYTRON P coating was applied to a polycarbonate panel to reduce the

transparency of polycarbonate to the infrared range of solar radiation. This coating was then

coated with a sol-gel coating containing UN absorbers to at least partially block the

ultraviolet range of solar radiation. To reach the required level of abrasion resistance for an

automotive glazing application, this coating system was further improved by deposition of a

plasma enhanced chemically vapor deposited (PECVD) silicon based layer. This coating

system provided ultraviolet (UV) protection, a barrier to infrared (IR) radiation, and also

^• provided superior scratch resistance (delta haze of <2.0% after Taber abrasion using a CS 1 OF

wheel, 500g of load, and 1000 cycles). Dip Coating With CPP 105 (BAYTRON P)

8 OOg of coating material

65% CPP105 = 520g

35% HYCAR = 280g

dip rate: in 50 cm/min. out 50 cm/min.

dwell time: 5 sees.

flash off: 15 mins.

HYCAR Primer was top coated with GE AS4004 (UV blocker) by dip coated with same

parameters listed above and then cured @ 130°C for lh.

% Transmission measured after AS4004 top coat was applied: 76.8%

ΔHaze = 0.76% after TABER

Claims

1. A glazing construction for use in an automotive vehicle comprising:

a polycarbonate substrate having at least one outwardly facing surface, the

polycarbonate substrate having optical transparency;

an inner layer connected thereto including BAYTRON P material capable of

reducing the amount of infrared radiation which penetrates to the polycarbonate substrate

without unduly compromising optical transparency of the polycarbonate substrate; and

coating material overlying said inner polymeric layer blocking transmission of UV radiation

to said inner layer and substrate; and

also imparting scratch resistance to the outwardly facing surface of the

associated glazing construction without unduly compromising optical transparency of the

polycarbonate substrate.

2. The glazing construction of claim 1 wherein the BAYTRON P material

included in the inner layer is at least one of substituted polythiophene styrene sulfonate,

polypyrrole styrene sulfonate and substituted polypyrrole styrene sulfonate.

3. The glazing construction of claim 1 wherein the BAYTRON P material

included in the inner layer is derived from an aqueous dispersion of

polyethylenedioxythiophene (PEDT) doped with a polymeric acid salt.

4. The glazing construction of claim 1 wherein the inner layer can

provide nearly 100% absorption of light in the range of 900 to 2000 nm.

5. The glazing construction of claim 1 wherein said overlying material

includes an outermost layer comprising a plasma polymerized and oxidized organosilicon

material.

6. An automotive window subassembly including a glazing panel, the

glazing panel including:

a polycarbonate substrate having at least one outwardly facing surface, the

polycarbonate substrate having optical transparency;

a first layer connected thereto, the first polymeric layer including BAYTRON

P material capable of reducing the amount of infrared radiation which penetrates to the

polycarbonate substrate with out unduly compromising optical transparency of the

polycarbonate substrate;

an overlaying of coating material above said first layer which blocks

ultraviolet radiation transmission to the first layer and substrate without unduly

compromising optical transparency of the polycarbonate and, which also imparts scratch

resistance to said outer surface of said glazing panel.

7. The automotive window subassembly of claim 6 wherein said first

layer on the polycarbonate substrate comprises at least one of substituted polythiophene styrene sulfonate, polypyrrole styrene sulfonate and substituted polypyrrole styrene sulfonate.

8. The automotive window subassembly of claim 6 wherein the

BAYTRON P material included in said first layer is derived from an aqueous dispersion of

polyethylenedioxythiophene (PEDT) doped with a polymeric acid salt.

9. The automotive window subassembly of claim 6 wherein the first layer

can provide nearly 100% absorption of light in the range of 900 to 2000 nm.

10. The automotive window subassembly of claim 6 wherein said

overlying material includes an outermost layer comprised of a plasma polymerized and

oxidized organosilicon material.

11. An automotive vehicle having at least one window including a glazing

panel which comprises :

a polycarbonate substrate having at least one outwardly facing surface, the

polycarbonate substrate having optical transparency;

a first layer connected thereto, the first polymeric layer including BAYTRON

P capable of reducing the amount of infrared radiation which penetrates to the polycarbonate

substrate without unduly compromising optical transparency of the polycarbonate substrate;

a second layer connected in overlying relationship to the first layer, the second

polymeric layer including a material which blocks transmission of ultraviolet radiation to the substrate and first layer without unduly compromising optical transparency of the

polycarbonate; and

a third outermost layer imparting scratch resistance to said glazing panel.

12. The automotive vehicle of claim 11 wherein said third outermost layer

is composed of a plasma polymerized and oxidized organosilicon material.

13. The automotive vehicle of claim 11 which the window is a fixed panel

and includes at least one structural support associated therewith.

14. The automotive vehicle of claim 11 wherein said third outermost layer

is capable of being applied as a wet coating.