Stock material or miscellaneous articles – Composite – Of polycarbonate
Reexamination Certificate
1999-12-09
2001-11-20
Boykin, Terressa M. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polycarbonate
Reexamination Certificate
active
06319613
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a coating solution for forming a film for cutting off solar heat radiation on a sheet of glass or a transparent resin, or other material forming a window of a vehicle, building, office or house, a shopwindow, a lamp, etc., and the film formed therefrom.
2. Description of the Prior Art
It has hitherto been usual to employ an inorganic material or resin reflecting visible light and infrared radiation for forming a film for eliminating or reducing the generating range of solar radiation heat. Typical examples of the inorganic materials which have been employed are a metal oxide, such as FeO
x
, CoO
x
, CrO
x
, or TiO
x
, and a metal having a large quantity of free elections, such as Ag, Au or Al. A typical resin film has been formed from a mixture prepared by adding an organic agent for cutting off near infrared radiation to a resinous binder, and phthalocyanines and metal complexes are known as typical examples of agents for absorbing near infrared radiation.
The known inorganic materials have, however, the property of reflecting or absorbing visible light along with the near infrared radiation which is an important source of solar heat, and are likely to form a surface glittering like a mirror detracting from its appearance, or a surface having an undesirably low transmittance of visible light. When any such inorganic material is used to form a film covering a transparent material on a house, building, or vehicle, it is necessary to ensure that the film be so small in thickness as to be capable of transmitting visible light satisfactorily. It has been necessary to form a film having a very small thickness on the order of 10 nm by using a physical coating method, such as spraying and baking, CVD, sputtering or vacuum vapor deposition. It has been necessary to use a large apparatus, or vacuum equipment resulting in a high film cost which is undesirable from a productivity standpoint, or for the formation of a film covering a large surface. Moreover, the inorganic materials have often tended to make a film of high electrical conductivity which reflects radio waves to be received by e.g. a portable telephone, a television receiver or a car navigation system having an aerial installed within a vehicle, or causes jamming in a neighboring area.
The known organic agents have been fatally low in weatherability because of heavy deterioration by heat or humidity. Moreover, a film having a high transmittance of visible light has little power to cut off heat radiation, while a film having high power to cut off heat radiation has only a low transmittance of visible light.
Antimony-containing tin oxide (hereinafter referred to as ATO) and tin-containing indium oxide (hereinafter referred to as ITO) are known as materials having relatively low absorption or reflection of visible light and high transparency to the human eye, but as they have only low power to cut off solar radiation per unit mass, a film which can cut off heat radiation effectively has had to be prepared from a large amount of material, and has, therefore, been very expensive. Moreover, ATO has been unsatisfactory, as its free electron concentration is too low to enable any satisfactory cutoff of near infrared radiation. A film formed by a physical coating method has been so high in electrical conductivity as to reflect or interfere with radio waves.
SUMMERY OF THE INVENTION
Under these circumstances, it is an object of this invention to provide a coating solution which makes it possible to form an improved film for cutting off heat radiation easily and at a low cost.
It is another object of this invention to provide a film having a high transmittance of visible light, a low reflectivity of radio waves, a low transmittance of near infrared radiation and a high surface resistivity.
We, the inventors of this invention, have found that the use of ultrafine particles of hexaborides having a large quantity of free electrons with ultrafine particles of ATO or ITO makes it possible to form a film having its maximum transmittance of light in the visible range and its minimum transmittance in the near infrared range.
According to a first aspect of this invention, therefore, there is provided a coating solution containing fine particles of at least one kind of hexaboride represented as XB
6
, in which X is Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sr or Ca, and fine particles of ITO or ATO in a weight ratio of from 0.1:99.9 to 90:10.
The solution may further contain fine particles of at least one kind of additional oxide selected from the group consisting of SiO
2
, TiO
2
, ZrO
2
, Al
2
O
3
and MgO.
The solution contains at least one kind of resin selected from the group consisting of ultraviolet-curing, electron beam-curing, cold-curing and thermoplastic resins as a binder.
The fine particles of the hexaboride and ITO or ATO may have a diameter not exceeding 200 nm.
The fine particles of the additional oxide may be in the colloidal state in which they have a diameter not exceeding 200 nm.
According to a second aspect of this invention, there is provided a film formed on at least one side of a base for cutting off heat radiation by applying thereto a coating solution containing fine particles of at least one kind of hexaboride represented as XB
6
, in which X is Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sr or Ca, and fine particles of ITO or ATO in a weight ratio of from 0.1:99.9 to 90:10.
The base may be a film of a polycarbonate resin, a polyacrylate or polymethacrylate resin, a saturated polyester resin or a cyclic olefin resin.
The base may carry an adhesive layer and a release film on one side thereof. The base may also carry a hard coat layer on at least one side thereof as its outermost layer. The hard coat layer may be formed by a solution containing an ultraviolet-curing resin as a binder. The ultraviolet-curing resin may have its principal constituent combined chemically with at least one kind of inorganic substance selected from the group consisting of SiO
2
, TiO
2
, ZrO
2
, Al
2
O
3
and MgO.
The solution applied to the base may further contain fine particles of at least one kind of additional oxide selected from the group consisting of SiO
2
, TiO
2
, ZrO
2
, Al
2
O
3
and MgO.
The film may have a surface resistivity not lower than 10
6
ohms per square.
The film of this invention can cut off solar radiation or its heat energy more effectively than any film formed by using only one of the following: hexaboride, ATO or ITO. The use of the hexaboride makes it possible to reduce the amount of ATO or ITO which is required, and thereby form the film at a lower cost. The film is easy to form, formed simply by coating the base with the solution of this invention without relying upon any physical coating method. The film can be formed on, for example, the windowpanes of a building to reduce the necessity for airconditioning in summer, and is, thus, of great use for energy saving and environmental purposes.
REFERENCES:
patent: 6221945 (2001-04-01), Kuno et al.
Adachi Kenji
Takeda Hiromitsu
Yabuki Kayo
Boykin Terressa M.
Dykema Gossett PLLC
Sumitomo Metal & Mining Co., Ltd.
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