Abstract:
A multilayer structure for shading ultraviolet and infrared light includes two or three layers of Ag; two or three layers of indium tin oxide (ITO); and dielectric oxide layers ranging from two layers to four layers. At least two Ag layers are formed to be in contact with the ITO layers as an upward or downward layer. Each dielectric oxide layer is made of a material which is selected from SiO 2 , TiO 2 , Al 2 O 3 , ZrO 2 , Y 2 O 3  and Ta 2 O 5 . The structure effectively shades ultraviolet and infrared light while transmitting visible light with a transmittance more than 85%.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     (a) Field of the Invention  
         [0002]     The present invention relates to coatings for ultraviolet and infrared reflection, and more particularly to multilayer structures which transmit visible light while effectively shading ultraviolet and infrared light with a plurality of layers having different refractive indices. More particularly, the present invention relates to window constructions on which the multilayer structure is formed.  
         [0003]     (b) Description of the Related Art  
         [0004]     Generally, ultraviolet light of a wavelength ranging between 10-400 nm may cause skin aging, eye fatigue, or cataracts in human bodies, and decolorization in articles, while infrared light of a wavelength ranging over 700 nm may generate heat causing the ambient temperature to rise. Human bodies and indoor articles may be damaged by ultraviolet light, specifically in vehicles or buildings in which windows take up much area. In summer time, the cost for air cooling is increased due to temperature rising because of infrared light.  
         [0005]     In order to shade ultraviolet or infrared light, a color plastic sheet or a metal coating material may be applied to windows. Since the color plastic sheet or metal coating material shades visible light as well as ultraviolet and infrared light, however, it may cause full visibility or forward observation capability to be reduced, especially when driving. It may also cause indoor lighting to be insufficient.  
         [0006]     A multilayer structure for shading infrared light has been developed as disclosed in Korean Patent Publication No. 1988-10930A to shade infrared light from sunlight, but the structure can merely reflect infrared light having a limited wavelength range of 900-1200 nm. The structure can shade neither infrared light having wavelengths over 1200 nm, nor ultraviolet and infrared light simultaneously.  
       SUMMARY OF THE INVENTION  
       [0007]     In view of the prior art described above, it is an object of the present invention to provide a multilayer structure for shading both ultraviolet and infrared light effectively as well as for transmitting visible light, and a window construction in which the structure is formed.  
         [0008]     It is another object of the present invention to provide a multilayer structure with a plurality of materials having different refractive indices and different thicknesses for shading both ultraviolet and infrared light effectively, and a window construction in which the structure is formed.  
         [0009]     It is still another object of the present invention to provide articles including safety glass for vehicles which shade both ultraviolet and infrared light.  
         [0010]     To achieve these and other objects, as embodied and broadly described herein, a multilayer structure for shading ultraviolet and infrared light includes two or three layers of Ag; two or three layers of indium tin oxide (ITO); and dielectric oxide layers ranging from two layers to four layers. At least two Ag layers are formed to be in contact with the ITO layer as an upward or downward layer. Each dielectric oxide layer is made of a material which is selected from SiO 2 , TiO 2 , Al 2 O 3 , ZrO 2 , Y 2 O 3 , and Ta 2 O 5 .  
         [0011]     According to another aspect to the present invention, a window construction for ultraviolet and infrared shading includes a substrate of glass or plastic material;  
         [0012]     two or three layers of Ag; two or three layers of indium tin oxide (ITO); and dielectric oxide layers ranging from two layers to four layers. At least two Ag layers are formed to be in contact with the ITO layer as an upward or downward layer.  
         [0013]     The multilayer structure according to the present invention is formed by stacking a plurality of layers of coating materials having different refractive indices on a substrate of glass or a plastic such as acryl. Each layer of the structure can be deposited by a vapor deposition method such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). The design of the structure employs multiple reflection, which occurs in each thin layer that is made of a coating material different from the others, in order to selectively reflect or transmit light having particular wavelength ranges. Each coating material is selected while taking its refractive index and optical properties into consideration, and the deposition thickness of each layer is determined while considering generation of multiple reflection for the desired wavelength ranges.  
         [0014]     The present invention employs silver (Ag), indium tin oxide (ITO), and dielectric oxides as coating materials.  
         [0015]     Silver (Ag) has good optical transmission properties for visible light and good reflection properties in infrared ranges. The thickness of the Ag layer preferably ranges from 5 nm to 15 nm.  
         [0016]     Indium tin oxide (ITO) is an oxide of indium and tin, in which a ratio of In 2 O 3  to SnO 2  ranges from 85:15 to 95:4. ITO has good optical transmission of more than 80% for visible light, independent of a deposited thickness.  
         [0017]     The dielectric oxide is preferably selected from SiO 2 , TiO 2 , Al 2 O 3 , ZrO 2 , Y 2 O 3 , and Ta 2 O 5 , and its thickness is determined according to each refractive index. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is a graph of wavelength of incident light versus percent transmission of incident light through an optical coating according to a first embodiment of the present invention;  
         [0019]      FIG. 2  is a graph of wavelength of incident light versus percent transmission of incident light through an optical coating according to a second embodiment of the present invention;  
         [0020]      FIG. 3  is a graph of wavelength of incident light versus percent transmission of incident light through an optical coating according to a third embodiment of the present invention;  
         [0021]      FIG. 4  is a graph of wavelength of incident light versus percent transmission of incident light through an optical coating according to a fourth embodiment of the present invention;  
         [0022]      FIG. 5  is a graph of wavelength of incident light versus percent transmission of incident light through an optical coating according to a fifth embodiment of the present invention;  
         [0023]      FIG. 6  is a graph of wavelength of incident light versus percent transmission of incident light through an optical coating according to a sixth embodiment of the present invention; and  
         [0024]      FIG. 7  shows a cross-sectional view of a car window with the multilayer structure of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     Preferred embodiments of the present invention will hereinafter be described in detail with reference to the accompanying drawings.  
       First Embodiment  
       [0026]     A multilayer structure for shading ultraviolet and infrared light according to the first embodiment of the present invention has seven layers, employing four coating materials such as Ag, ITO, SiO 2 , and TiO 2 .  
         [0027]     The arrangement, refractive indices, and thicknesses of coating materials are listed in Table 1 below in order from a substrate.  
                                             TABLE 1                               Refractive Index (reference   Layer       NO.   Material   wavelength 510 nm)   thickness(nm)                                7   TiO 2     2.34867   28.81       6   Ag   0.051   14.38       5   ITO   2.058   84.63       4   Ag   0.051   8.07       3   TiO 2     2.34867   126.06       2   ITO   2.058   38.14       1   SiO 2     1.4618   162.79       Substrate   Glass   1.52077                  
 
         [0028]     As shown in Table 1, the multilayer structure may employ four coating materials to form a seven-layer structure. Specifically, the fifth layer of ITO is embedded between the fourth layer of Ag and the sixth layer of Ag.  
         [0029]     The shading of ultraviolet and infrared light in the multilayer structure is shown in  FIG. 1 , which illustrates a graph of transmission percent of incident light versus the wavelength of the incident light. The multilayer structure transmits about 1.77% of light having a wavelength of 200 nm and about 8% of light having a wavelength of 300 nm, to shade ultraviolet light, while it transmits more than 85% of visible light. Further, the transmittance of the structure is about 31% at a wavelength of 800 nm and is then reduced to less than 8% at a wavelength of 1000 nm, resulting in effective shading of the whole infrared range.  
       Second Embodiment  
       [0030]     A multilayer structure for shading ultraviolet and infrared light according to the. second embodiment of the present invention has seven layers, employing three coating materials such as Ag, ITO, and Y 2 O 3 .  
         [0031]     The arrangement, refractive. indices, and thicknesses of coating materials are listed in Table 2 below in order from a substrate.  
                                             TABLE 2                               Refractive Index (reference   Layer       NO.   Material   wavelength 510 nm)   Thickness(nm)                                7   Y 2 O 3     1.79581   4.08       6   ITO   2.058   36.14       5   Ag   0.051   12.82       4   ITO   2.058   71.91       3   Ag   0.051   9.39       2   Y 2 O 3     1.79581   85.56       1   Ag   0.051   5.79       Substrate   Glass   1.52077                  
 
         [0032]     As shown in Table 2, the multilayer structure may employ three coating materials to form a seven-layer structure. Specifically, the third layer of Ag and fifth layer of Ag are alternatively formed with the fourth layer of ITO and the sixth layer of ITO.  
         [0033]     The shading of ultraviolet and infrared light in the multilayer structure is shown in  FIG. 2 , which illustrates a graph of transmission percent of incident light versus the wavelength of the incident light. The multilayer structure transmits about 3.5% of light having a wavelength of 200 nm and about 9.5% of light having a wavelength of 300 nm, to shade ultraviolet light, while it transmits more than 85% of visible light. Further, the transmittance of the structure is about 32% at a wavelength of 800 nm and then is reduced to less than 4% at a wavelength of 1000 nm, resulting in effective shading of the whole infrared range.  
       Third Embodiment  
       [0034]     A multilayer structure for shading ultraviolet and infrared light according to the third embodiment of the present invention has seven layers, employing three coating materials such as Ag, ITO, and ZrO 2 .  
         [0035]     The arrangement, refractive indices, and thicknesses of coating materials are listed in Table 3 below in order from a substrate.  
                                             TABLE 3                               Refractive Index (reference   Layer       NO.   Material   wavelength 510 nm)   Thickness(nm)                                7   ZrO 2     2.06576   9.58       6   ITO   2.058   29.57       5   Ag   0.051   13.07       4   ITO   2.058   76.34       3   Ag   0.051   10.05       2   ZrO 2     2.06576   63.84       1   Ag   0.051   5.6       Substrate   Glass   1.52077                  
 
         [0036]     As shown in Table 3, the multilayer structure may employ three coating materials to form a seven-layer structure. Specifically, the third layer of Ag and fifth layer of Ag are alternatively formed with the fourth layer of ITO and the sixth layer of ITO.  
         [0037]     The shading of ultraviolet and infrared light in the multilayer structure is shown in  FIG. 3 , which illustrates a graph of transmission percent of the incident light versus the wavelength of the incident light thereof. The multilayer structure transmits about 3.2% of light having a wavelength of 200 nm and about 9.7% of light having a wavelength of 300 nm, to shade ultraviolet light, while it transmits more than 85% of visible light. Further, the transmittance of the structure is about 32.5% at a wavelength of 800 nm, and is then reduced to less than 9% at a wavelength of 1000 nm, resulting in effective shading of the whole infrared range.  
       Fourth Embodiment  
       [0038]     A multilayer structure for shading ultraviolet and infrared light according to the fourth embodiment of the present invention has eight layers, employing four coating materials such as Ag, ITO, SiO 2 , and Ta 2 O 5 .  
         [0039]     The arrangement, refractive indices, and thicknesses of coating materials are listed in Table 4 below in order from a substrate.  
                                             TABLE 4                               Refractive Index (reference   Layer       NO.   Material   wavelength 510 nm)   Thickness(nm)                                8   Ta 2 O 5     2.14455   35       7   Ag   0.051   13.38       6   ITO   2.058   79.89       5   Ag   0.051   11.06       4   Ta 2 O 5     2.14455   72.4       3   Ag   0.051   10.76       2   ITO   2.058   34.18       1   SiO 2     1.4618   103.67       Substrate   Glass   1.52077                  
 
         [0040]     As shown in Table 4, the multilayer structure may employ four coating materials to form an eight-layer structure. Specifically, the third layer of Ag is formed on the second layer of ITO, and the sixth layer of ITO is embedded in the fifth layer of Ag and the seventh layer of Ag.  
         [0041]     The shading of ultraviolet and infrared light in the multilayer structure is shown in  FIG. 4 , which illustrates a graph of transmission percent of the incident light versus the wavelength of the incident light thereof. The multilayer structure transmits about 0.08% of light having a wavelength of 200 nm and about 6.8% of light having a wavelength of 300 nm, to shade ultraviolet light, while it transmits more than 85% of visible light. Further, the transmittance of the structure is about 29% at a wavelength of 800 nm and is then reduced to less than 2% at a wavelength of 1000 nm, resulting in effective shading of the whole infrared range.  
       Fifth Embodiment  
       [0042]     A multilayer structure for shading ultraviolet and infrared light according to the fifth embodiment of the present invention has nine layers, employing four coating materials such as Ag, ITO, SiO 2 , and Al 2 O 3 .  
         [0043]     The arrangement, refractive indices, and thicknesses of coating materials are listed in Table 5 below in order from a substrate.  
                                             TABLE 5                               Refractive Index (reference   Layer       NO.   Material   wavelength 510 nm)   Thickness(nm)                                9   SiO 2     1.4618   3.58       8   ITO   2.058   36.91       7   Al 2 O 3     1.6726   5       6   Ag   0.051   15.28       5   ITO   2.058   78.88       4   Al 2 O 3     1.6726   5       3   Ag   0.051   12.42       2   ITO   2.058   40.64       1   SiO 2     1.4618   78.7       Substrate   Glass   1.52077                  
 
         [0044]     As shown in Table 5, the multilayer structure may employ four coating materials to a form nine-layer structure. Specifically, the third layer of Ag and the sixth layer of Ag are formed on the second layer of ITO and the fifth layer of ITO, respectively.  
         [0045]     The shading of ultraviolet and infrared light in the multilayer structure is shown  FIG. 5 , which illustrates a graph of transmission percent of incident light versus the wavelength of the incident light. The multilayer structure transmits about 5% of light having a wavelength of 300 nm to shade ultraviolet light, while it transmits more than 85% of visible light. Further, the transmittance of the structure is about 24% at a wavelength of 800 nm, and is then reduced to less than 4.2% at a wavelength of 1000 nm, resulting in effective shading of the whole infrared range.  
       Sixth Embodiment  
       [0046]     A multilayer structure for shading ultraviolet and infrared light according to the sixth embodiment of the present invention has ten layers, employing four coating materials such as Ag, ITO, SiO 2 , and Al 2 O 3 .  
         [0047]     The arrangement, refractive indices, and thicknesses of coating materials are listed in Table 6 below in order from a substrate.  
                                             TABLE 6                               Refractive Index (reference   Layer       NO.   Material   wavelength 510 nm)   Thickness(nm)                                10    Al 2 O 3     1.6726   16.21       9   ITO   2.058   12.57       8   Al 2 O 3     1.6726   23.76       7   Ag   0.051   12.29       6   ITO   2.058   74.88       5   Ag   0.051   11.79       4   Al 2 O 3     1.6726   111.82       3   Ag   0.051   10.65       2   ITO   2.058   40.77       1   SiO 2     1.4618   78.9       Substrate   Glass   1.52077                  
 
         [0048]     As shown in Table 6, the multilayer structure may employ four coating materials to form a ten-layer structure. Specifically, the third layer of Ag is formed on the second layer of ITO, and the sixth layer of ITO is embedded in the fifth layer of Ag and the seventh layer of Ag.  
         [0049]     The shading of ultraviolet and infrared light in the multilayer structure is shown in  FIG. 6 , which illustrates a graph of transmission percent of incident light versus the wavelength of the incident light. The multilayer structure transmits about 4.7% of light having a wavelength of 300 nm, to shade ultraviolet light, while it transmits more than 85% of visible light. Further, the transmittance of the structure is about 21% at a wavelength of 800 nm, and is then reduced less than 1.6% at a wavelength of 1000 nm, resulting in effective shading of the whole infrared range.  
         [0050]     The present invention provides the multilayer structure which effectively reflects both infrared and ultraviolet light, while it transmits visible light. The multilayer structure may be employed in various applications such as window glass for vehicles, buildings, or exhibits in museums, in plasma display panels (PDPs), and so forth. The window glass with the multilayer structure may prevent the ambient temperature from rising, and it may protect human skin and avoid decolorization of articles.  
         [0051]     Specifically, the multilayer structure may reduce more than 30% of the inside temperature in a vehicle under sunlight in summer time to save fuel. Further, it may even be applied to a front window of a vehicle on which a color plastic sheet may not legally be attached.  
         [0052]     Referring to  FIG. 7 , a safety glass  100  for vehicles according to the present invention is comprised of two transparent panes  10  of glass or a plastic material, having a plastic film  30  between them. The plastic film  30  is made of plasticized polyvinyl butyral (PVB), and if the glass breaks, the fragments will adhere to the plastic film.  
         [0053]     The multilayer structure  20  according to the present invention is formed between one of the panes  10  and the plastic film  30  to effectively shade ultraviolet light and infrared light incident to the inside of the vehicle. Since the multilayer structure  20  is not exposed to the outside, it may be difficult to damage.  
         [0054]     It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention.