DE3418612A1 - Exothermic transparent body - Google Patents

Abstract

An exothermic transparent body, for example a window pane, a windscreen or the like, contains an electrically conductive transparent film layer which is formed uniformly on at least one surface of a transparent substrate of the body. At least one pair of metal electrodes are located on the electrically conductive film layer, along the two opposite sides of the layer. With their aid, electrical power is supplied into the electrically conductive transparent film layer, so that the surface of the exothermic transparent body is heated. In consequence, it is possible to prevent a reduction in the surface temperature of the body and consequently condensation on the surface of the body. This ensures that the surface of the body is free of streaks and the like. An excellent anti-condensation effect is achieved.

Description

84/8743 ⁴

■ j Description:

The invention relates to an exothermic transparent body in which measures are taken to prevent the accumulation of moisture on the surface of the body impede. Such transparent bodies consist, for example, of transparent glass or transparent Plastic / and by preventing the formation of moisture on the body surface, the transparency of the body -jQ pers received.

From the prior art it is known to use conventional Glass or made of transparent plastic transparent bodies, such as -the window pane be for a building, a shop window, a windshield of a motor vehicle or the like, on the back of the body to provide a reflecting mirror having a transparent body into which by evaporation Silver is introduced. However, this conventional transparent body collects very easily Moisture on the surface when the humidity of the air surrounding the transparent body is relatively high and the surface cools compared to the temperature of the ambient air. For example, one can observe almost every day like the inside of a motor vehicle windshield fogging up when it rains or from the breath of passengers. The side windows of a motor vehicle also fog up often, especially when it rains. In bathrooms, for example, it often happens that mirrors fog up so that the mirror as such cannot be used.

The invention has for its object to provide an exothermic transparent body in which the precipitation of moisture in a desired surface

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area of the body can be reliably avoided. In particular, clouding of the body should be avoided and the transparency of the body can be maintained. In addition, streaks and the like should appear on the body surface be avoided.

The solution to this problem is characterized in the claims.

In the following, exemplary embodiments are based on the Drawing explained in more detail. Show it:

Fig. 1 is a sectional view of an exothermic transparent Body of a first embodiment of the invention,

Fig. 2 is a circuit diagram illustrating the power supply for the first embodiment of the invention;
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3 is a cross-sectional view of a second embodiment of an exothermic transparent according to the invention Body,

Fig. 4 is a graph showing the relationship between film thickness of an electrically conductive transparent film of the body according to embodiment 2 and the sheet resistance of the film illustrates

5 is a graph showing the spectral transmittance characteristic in the second embodiment of the exothermic transparent body; and

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■ j FIG. 6 is a graph showing the increase represents the surface temperature over time for the case that the specific sheet resistance of the exothermic transparent body is changed in various ways.

The present invention provides a transparent body having a transparent one uniformly on its surface and an electrically conductive film layer is formed.

In this transparent and electrically conductive film layer an electric current is fed in through which the surface of the transparent body is heated, whereby a drop in temperature on the surface of the body and consequently the formation of precipitation the surface can be prevented. In a special embodiment of the invention, in which the substrate is a transparent or translucent glass substrate, a known transparent one can be used for the latter Glass, usually a common quartz glass, soda lime glass, borosilicate glass or the like be used. The glass substrate does not necessarily have to be completely transparent, it can be be translucent or be a tinted glass. In this case, however, the glass substrate may be infrared rays, Block ultraviolet rays or the like.

On at least one surface side of this glass substrate is an electrically conductive transparent film formed, which is transparent to rays of visible light and has electrical conductivity. The layer is uniformly thick. The application of the electrically conductive film layer can be done with the help of known film or layer formation processes take place, for example by means of vacuum vapor deposition, Atomization or the like. In such a case it will

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. the film layer consisting of tin dioxide (SnO ₂ ), titanium dioxide (TiO ₂ ), gold (Au), indium oxide (In ₃ O ₃ ) or indium tin oxide (ITO) is formed on the substrate by vacuum evaporation or sputtering. Other methods are possible. Thus one can add a solution of SnCl _2, for example, ethyl alcohol and an acetic acid solution to the mixture the heated to 500 ⁰ C to 600 ⁰ C substrate in the atomized state to spray and thereby to form the film layer. If the film layer is applied by reactive sputtering, tin, for example, is sputtered in an oxygen atmosphere. By controlling the partial pressure of oxygen in the atmosphere, it is possible to control the sheet resistance of the film.

TiO ₂ has an advantage that the film layer can be formed at normal temperature. When TiOj is used, a Ti film is formed by vapor deposition or sputtering, and then this tin film is subjected to an oxygen glow discharge in a weak vacuum to be oxidized. This method has the advantage that the light transmittance (the degree of transmittance of light) and the specific sheet resistance of the film can be controlled practically at will. Such a TiO ₂ film has a slightly higher _{sheet resistivity than a SnO 2} film, but has better properties than the latter in terms of chemical and mechanical resistance or strength. The sheet resistivity (film resistance) can be controlled according to the film thickness, manufacturing conditions and the like.

In order to make the effect achieved by the present invention as great as possible, the sheet resistance is of the film is preferably less than 100 Ohm / O · The diameter

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! Permeability of the film to visible light rays is also as great as possible. Further, if the film thickness is set to a certain value, the electrically conductive transparent film layer can be used as a quarter wave plate. That is, there is a possibility that the film will filter light rays of a predetermined wavelength. In such a case, a protective film is preferably formed on the surface of the electrically conductive transparent film layer. This protective film can be formed by coating the surface of the film layer with a thermosetting urethane paint, an acrylic group paint, an epoxy group paint, or the like.
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The second specific embodiment of the present invention takes the place of what has been explained above Glass substrate a transparent plastic substrate. Farther is a surface hardening film on at least one surface side of the transparent plastic substrate which facilitates the formation of the electrically conductive transparent film layer.

Known plastics are used for the plastic substrate into consideration as long as they are transparent to light. It either a thermosetting plastic or a thermoplastic can be used. Examples of usable Plastics are epoxy resin, acrylic resin, polyester resin, nylon, polystyrene, polycarbonate or the like. The plastic substrate can be translucent or colored.

There are methods for surface hardening of the substrate into consideration, as described below with reference to the examples. For example, the plastic sub-

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strat spray a coating made of polyfunctional acrylate and then spray the substrate treated in this way cure with UV light. It is also possible to paint the substrate using a melamine compound spray on and then heat the substrate to harden. It is also possible to use an organosiloxane group spread spray onto the substrate and then heat the substrate to cure. Farther is used for surface hardening of the plastic substrate a plasma polymerization with a methoxysilane monomer into consideration. Such a surface hardening film enables it is that the electrically conductive transparent film is strongly adhered to the substrate. This was done using tests carried out confirmed.

In one experiment, the electrically conductive transparent film layer was formed directly on the plastic substrate, and the substrate thus formed was examined by an adhesive tape test. This test was the electrically conductive transparent film layer formed directly on the plastic substrate was easily peeled off. On the other hand, however, an electrically conductive transparent film layer formed on the previously one Plastic substrate exposed to surface hardening is formed was not replaced in the test mentioned.

On the surface hardening film, the electrically conductive transparent film layer formed in the manner as

it was explained above.
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On the electrically conductive transparent film layer, at least a pair of metal electrodes are placed along the two opposite sides formed. The metal electrodes can be formed by vapor deposition of aluminum, silicon

be formed over, nickel or the like, or

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by applying an electrically conductive paint to the film layer.

As stated above, the invention provides, on at least one surface of a glass or a plastic substrate, formed of a transparent body, an electrically conductive transparent film layer to form in uniform thickness. The formed film layer has transparency and conductivity. About a Pair of metal electrodes formed on the surface along both opposite sides thereof the film layer is supplied with an electric current, so that the film layer heats up and thereby prevents that the surface temperature of the transparent body • 5 drops. This measure makes it possible to prevent fogging the surface of the transparent body to avoid.

There is also the possibility of ^{providing the} electrically conductive transparent film according to the invention on both sides of the substrate, that is to say on its upper side and on its lower side. In this case, the transparent body can be used as a window glass or the like. On the other hand, if the electrically conductive transparent film is formed on the upper side or on the lower side of the substrate, a reflective layer which reflects visible light can be formed on the respectively remaining side. Such a layer can be formed by vapor deposition of silver, aluminum or the like, so that a mirror surface is obtained. The exothermic transparent body according to the invention therefore has an exothermic and an electrically conductive coating, so that the body can be used, for example, as window glass, as a mirror or the like

can be used.

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* Example 1:

A transparent glass substrate was used as the starting point. Fig. 1 shows the structural design of a exothermic transparent body according to this example .in cross-section. On top of a transparent glass substrate 3 was placed in an oxygen atmosphere With the help of reactive atomization, tin is vapor-deposited to create an electrically conductive

• 0 _{to form the 7} transparent film 2. The film had a thickness of 1500 Å. Then, on top of the electrically conductive transparent film 2, a pair of straight metal electrodes 1a and 1b were applied along the two opposite sides of the film. The metal electrodes were formed on the film 2 by vacuum evaporation of aluminum. Furthermore, a reflective film 4, which reflects visible light rays, was formed on the opposite side, that is to say the underside of the glass substrate 3. This reflective film 4 was formed by vacuum evaporation of aluminum. On the side of the reflective film which is not in contact with the substrate 3, a protective film 5 was also formed by anodically oxidizing aluminum. Such a protective film can also be formed by vapor deposition of MgF in a vacuum.

Fig. 2 is a circuit diagram of an arrangement with the one for heating the exothermic transparent Body this is fed with electric current. This circuit is connected to the metal electrodes 1a, 1b from a DC voltage source 10 an electrical voltage is applied to an electrical current to send through the electrically conductive transparent film 2, the current evenly across the

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entire layer is distributed. As a result of this current flow the surface of the exothermic transparent body heats up evenly.

Example 2:

Fig. 3 shows the structure of a second example of an exothermic transparent body in cross section. This example differs from Example 1 in that a transparent plastic substrate 7 made of acrylic resin is provided as the substrate. An acrylic resin sheet (200 mm x 200 mm x 3 mm) was subjected to ultrasonic cleaning with a neutral detergent / then washed with pure water to clean the surface of the sheet. The surface of the cleaned sheet was then coated with a coating of polyfunctional acrylate and subjected to UV curing to increase the surface hardness. The surface hardening of the plastic substrate 7 was carried out by forming a surface hardening film 6 on the substrate. The thickness of the surface hardening film was 3 μm. Then the sheet treated so far was placed in a vacuum container. Here, the sheet was _{spaced 8 cm from a target composed of In ^ O 3} - SnO ₂ (95: 5 percent by weight). The container was then evacuated to 1 χ 10 Torr. Then, Ar gas was put into the container so that the inside of the container was kept at a negative pressure of 1x10 Torr. Then, the sheet was dusted in the vacuum container for ten minutes at an RF power of 350 W to form an electrically conductive transparent film 2 made of ITO. The film thickness was 1500 Å, the sheet resistance was 30 Ohm / D. The visible light transmittance was 80%. this

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is an excellent transmittance value for film 2. Electrodes 1a and 1b were then attached to the sheet so far processed along two opposite sides with the aid of an electrically conductive paste. A voltage of 12 volts was then applied between the electrodes. After the voltage was applied for 20 minutes, the surface temperature of the sheet increased by about 10 ^° C., and an excellent anti-fogging effect was exhibited; because the surface did not fog up even in extremely high humidity.

Fig. 4 is a graph showing the relationship between the sheet resistance of the exothermic transparent Body according to Example 2 and the film thickness illustrated. It can be seen from Fig. 4 that the sheet resistance increases in inverse proportion to the film thickness.

15 shows the spectral transmittance characteristic of the exothermic transparent body according to Example 2.

In Fig. 5, curve I represents a spectral transmittance curve of the acrylic substrate itself, where a transmittance with respect to visible light of approximately 90% was obtained. Curve II is a spectral transmittance curve of the transparent body that has been subjected to surface hardening so on the acrylic substrate a surface hardening layer was formed. In this case too, the transmittance was about 90% as in the case the curve I. The further curve III is the spectral transmittance curve of the exothermic transparent body according to Example II, on the surface of which an electrically conductive transparent film made of ITO is applied became. Here, the transmittance was slightly lower due to the electrically conductive transparencies that were formed Film layer, however, a transmission

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dance with respect to visible light of 80%. For this

It can be seen that the exothermic transparent body according to Example II has a high degree of efficiency in terms of transmittance.
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Figure 6 is a graph illustrating the increase in surface temperature during the time that a current is injected. The measurement was carried out at a room temperature of 16 ° C. and an applied voltage of 12 volts. Curve I corresponds to an exothermic transparent body with a sheet resistance of 19 Ohm / O and an exothermic power of 84 mW / cm. Curve II corresponds to an exothermic transparent body with a sheet resistance of 24 Ohm / Q and an exothermic power of 67 mW / cm. Curve III represents a comparative body with a sheet resistance of 39 Ohm / Q and an exothermic power of 8.9 mW / cm. As can be seen from FIG. 6, the surface temperatures of the respective exothermic transparent bodies increase to about 50 ^° C. and 30 ^° C. within 10 to 15 minutes after the voltage is applied Body according to curve I by 34 ° C, in the case of curve II by 18 ° C. As a result, no fogging is formed on the exothermic transparent bodies according to the invention.

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Claims (9)

Claims IJ Exothermic transparent body, g e k e η η - e i c h η e t through a transparent or translucent one Glass substrate (3) that allows visible light to pass through, an electrically conductive transparent film (2) that is uniform is formed on at least one side of the glass substrate (3) and transmits visible light, and at least one pair of metal electrodes (1a, 1b) placed on the electrically conductive transparent film along the opposite side thereof Pages are arranged. 2. Body according to claim 1, characterized in that that the electrically conductive transparent film is composed of at least one of the elements selected from the group consists of tin dioxide, titanium dioxide, indium oxide, indium tin oxide (ITO) and gold. 3 »Body according to claim 1 or 2, characterized -, - that the transparent glass substrate with a reflective film that reflects visible light rays, and that the reflective film is on that side is formed which is opposite to the side carrying the electrically conductive transparent film. Radeckestraße 43 8000 Munich 40 Telephone (089) 883603/883604 Telex 5212313 Telegrams Patentconsult • J 4. Body according to one of claims 1 to 3, characterized characterized in that the electrically conductive transparent film is coated with a protective film is. 5. Body according to claim 4, characterized in that the protective film consists of a thermosetting Urethane paint, an acrylic paint and / or an epoxy paint. 6. Exotherini shear transparent body, characterized by a transparent or translucent Plastic substrate (7), the visible light lets through, one on at least one side of the art -j5 fabric substrate uniformly formed surface hardening film, an electrically conductive transparent one uniformly formed on the surface hardening film Film (2) which transmits visible light, and at least one pair of metal electrodes (a, b) which are placed on the electrically conductive transparent film are arranged along the opposite sides thereof. 7. Body according to claim 6, characterized in that the electrically conductive transparent .Film is composed of at least one of the elements selected from the group consisting of tin dioxide, titanium dioxide, indium oxide, Indium tin oxide and gold are selected. 8. Body according to claim 6, characterized in that g e k e η η - indicates that the transparent plastic substrate is provided with a reflective film which Rays of visible light are reflected, and that the reflective film is provided on that side of the substrate which is opposite to the side with the electrically conductive transparent film. 9. Body according to one of claims 6 to 8, characterized in that the electrically conductive transparent film is coated with a protective film. 0O. Body according to claim 9, characterized in that the protective film consists of a thermosetting Urethane paint, an acrylic paint and / or an epoxy paint.