Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
2002-04-08
2004-08-24
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S412000, C428S430000, C428S441000, C359S359000, C359S360000, C359S589000, C264S173110, C264S173120, C264S173160
Reexamination Certificate
active
06780515
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a heat-absorbing layer system and more particularly to a multi-layered system to the use thereof and to products manufactured therefrom.
SUMMARY OF THE INVENTION
A heat-absorbing system comprising at least a first layer (A) containing a ultraviolet absorber, a second layer (B) containing an organic infrared absorber and ultraviolet absorber and a third, interference layer (C) reflecting in the infrared range is disclosed. The system is suitable for shielding plastic glazing elements from heat radiation.
BACKGROUND OF THE INVENTION
In automobile construction, thermoplastic glazing materials instead of glass are desired for safety reasons such as, for example, a high level of safety in the event of traffic accidents, but also for reasons of greater design freedom. A problem of using transparent thermoplastics for glazing elements in automobile construction is the excessive transmission in the near infrared (NIR) which, in summer, may lead to undesirably strong heating of the passenger compartment.
For applications in the automotive glazing sector, transmission in the visible range (LTA value) of at least 70% is specified for most cases. This value is defined in SAE J 1796 (May 1995 edition).
The TDS value (Solar Direct Transmittance) in accordance with SAE J 1796, May 1995 edition, is used for the efficiency of heat absorption. The value describes the percentage of solar energy that penetrates the sample and thus contributes to heating the vehicle interior. The higher the TDS value, the worse the heat-deflecting properties of the system.
Various heat-deflecting systems which have low transmission in the NIR have been described in the literature. On the one hand, surface coatings or lacquer systems are known, on the other hand, there are also infrared-absorbing additives for transparent thermoplastic polymers.
Infrared absorbers which are used as additives to thermoplastics and restrict heating are described, for example, in J. Fabian, H. Nakazumi, H. Matsuoka, Chem. Rev. 92, 1197 (1992), U.S. Pat. No. 5,712,332 and JP 06240146 A). A disadvantage of such additives is the limited heat shielding and/or the low thermal and/or photochemical stability thereof.
Metallized films which are bonded with the transparent thermoplastic material of the glazing element are also known as NIR protection. Such films are available commercially, for example, under the name Scotchtint® from 3M. A disadvantage of such a system, however, is that the transmission in the visible range is too low. An LTA value of more than 70% with simultaneously good heat protection (TDS value <50%) cannot be achieved with this system.
Finally, films which have NIR-reflecting properties due to interference effects are known. Such films and the use thereof as heat-absorbing layer systems for transparent thermoplastic glazing elements are described, for example, in WO 97/01778 and WO 97/01440. Films of this kind are available commercially, for example, under the name “Solar Reflecting Film, N-NPE 1458LP” from 3M. Again, a disadvantage of such systems, however, is that too small a proportion of the solar thermal radiation is screened and the TDS values of the glazing elements provided with such films are too high.
Apart from the required spectral properties, it is also necessary for exterior applications for the heat-absorbing systems to have good long-term weathering resistance, i.e., good long-term light resistance to discoloration and fading.
Thin, film-like, heat-absorbing layer systems which contain (A) a phthalocyanine infrared absorber and (B) an ultraviolet absorber are described in JP 10-077360 A. The weathering resistance of the thermal insulation layer is said to be thereby improved. According to one embodiment, a film-like coating layer with a thickness of 0.13 mm is proposed which contains both phthalocyanine infrared absorber and ultraviolet absorber. A coating layer of this kind exhibits acceptable weathering resistance in 48 hour accelerated weathering tests but a disadvantage is the poor long-term weathering resistance in weathering tests of more than 500 hours. Moreover, the thin, film-like coating layers described in this publication exhibit inadequate optical properties and are therefore unsuitable for use in automotive glazing.
It is also generally known that certain thermoplastics may be protected by the use of UV-absorbing lacquers and/or coextruded layers with a high UV absorber content. It is known, for example, from EP 0 110 221 A, to improve the weathering resistance of polycarbonate plastic panels by coating with a layer containing 3 wt. % to 15 wt. % of a UV absorber. The multi-layer systems described in this document do not contain an infrared absorber.
Finally, EP 0 774 551 A describes heat filters based on inorganic pigments which contain a UV-absorbing protective layer. Inorganic pigments have the disadvantage that they do not dissolve in thermoplastics so that no molded articles which are transparent in the visible range and have little haze are obtained.
The object of the invention is to provide a heat-absorbing layer system which has outstanding long-term weathering resistance and excellent optical properties such as transparency and gloss with the simplest and most economical mode of production possible, and which may be used for thermal insulation of transparent plastics glazing elements. The heat-absorbing coating system has a balanced ratio of LTA and TDS values, determined in accordance with SAE J 1796. More particularly, the heat-absorbing coating systems has a TDS value of less than 50% and LTA value of more than 70%.
The object according to the invention is achieved by a transparent heat-absorbing layer system which contains a first layer (A), a second layer (B) and a third layer (C) and wherein layer (A) contains ultraviolet absorber, layer (B) contains organic infrared absorber and ultraviolet absorber, and layer (C) is an interference layer reflecting in the infrared range.
The heat-absorbing layer system according to the invention is characterized by a three-layer structure in which heat absorption takes place both by means of the interference layer (C) and by means of a layer (B) containing organic infrared absorber and ultraviolet absorber. Moreover, the layer system according to the invention contains a further layer (A) with additional ultraviolet absorber which protects the infrared absorber contained in layer (B) from decomposition due to solar radiation.
Surprisingly, it was found that the layer system according to the invention has excellent weathering resistance in addition to a particularly balanced ratio of LTA and TDS values. The layer systems according to the invention have good transparency with an LTA value of >70% and good heat absorption with TDS values of less than 50%. Moreover, the layer systems according to the invention are characterized by their excellent long-term weathering resistance which makes them particularly suitable for use as glazing elements for exterior applications.
Layer (B) of the layer system according to the invention contains both organic infrared absorber and ultraviolet absorber. Due to the presence of both additives in the same layer, a large proportion of the sensitive organic infrared absorber is protected from UV radiation. In addition, the organic infrared absorber is protected from decomposition by UV radiation by a further layer containing ultraviolet absorber (layer A, “UV layer”). As the UV layer (layer A) is designed, i.a. to protect NIR dye in layer (B) from UV rays, it is advantageous to arrange layer (A) in the direction of the incident light radiation above layer (B).
The interference layer (C) of the layer system according to the invention is an interference layer reflecting in the near infrared range. Interference layers (C) suitable according to the invention include, for example, selectively reflecting alternating layer systems which contain at least two transparent layers (C1) and (C2) with different refractive indices. Suitable alternating layer systems are sys
Bayer Aktiengesellschaft
Blackwell-Rudasill G.
Gil Joseph C.
Jones Deborah
Preis Aron
LandOfFree
Heat-absorbing layer system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Heat-absorbing layer system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heat-absorbing layer system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3335484