Electrically chargeable substrate

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Reexamination Certificate

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C029S559000, C029S900000, C040S594000, C040S611050, C040S618000, C156S273100, C428S333000, C428S429000, C428S447000, C428S451000

Reexamination Certificate

active

06210793

ABSTRACT:

FIELD OF THE INVENTION
This invention relate to an electrically chargeable material used in an adhesion device, an overhead projector (hereafter referred to as an OHP), a bulletin device, a drafting machine, a plotter device or the like so that a paper, a vinyl sheet or the like adheres in a predetermined position.
BACKGROUND OF THE INVENTION
A material having a volume electric resistivity of 1×10
11
&OHgr;·cm or more can be charged with accumulated charges on the surface by being rubbed with ceramics, glass, resin or the like or by causing a corona discharge or the like. A material capable of accumulating charges on a surface is referred to as an electrically chargeable material and can be applied to various uses. For example, there is an adhesion device that makes a paper, a vinyl sheet or the like adhere utilizing the electrostatic force of a charged material. In the case where a plate for placing a sheet in an OHP is made of glass, the glass and the sheet can be individually charged by rubbing the OHP sheet onto the glass strongly, thus providing an overhead projector in which an OHP sheet does not slip down from the glass surface. Similarly, adhesion of a paper, a vinyl sheet or the like to a dielectric bulletin board, a dielectric drafting board for placing a drawing paper, and a dielectric plate for placing a paper for a plotter device can be realized in the same way, thus creating convenience that, for example, an OHP sheet does not slip down during presentation, or a sheet can be placed on a bulletin board, a drafting board and a plate for placing a paper in a plotter device without using a pressure sensitive adhesive tape or magnets. Theoretically, adhesion of a paper, a vinyl sheet or the like can be realized by charging the surface via rubbing a dielectric material and by utilizing electrostatic forces of the charged material.
However, a charge being accumulated generally escapes from a material easily, since a surface charge of a dielectric material escapes into a substance in contact with the material by means of ions (for example, carbonate ions, sodium ions or chloride ions that originally are present in the air and are dissolved in adsorbed water) in adsorbed water existing on the surface of the dielectric material. This phenomenon is seen especially in the case where humidity of an atmosphere is high and the surface of a dielectric material is hydrophilic. Conventionally, an effective surface treatment in order to prevent this phenomenon for the OHP sheet or the like has not been practiced.
SUMMARY OF THE INVENTION
Objects of the present invention are to solve the conventional problem mentioned above and to provide an electrically chargeable substrate maintaining a charged state for a long time regardless of humidity of an atmosphere.
In order to achieve the objects mentioned above, an electrically chargeable substrate of the present invention is characterized in that a thin film composed of a silane-based compound comprising an alkyl group or a fluoroalkyl group is bonded to the surface of an electrically insulating substrate through a covalent bond.
In the electrically chargeable substrate, it is preferable that the covalent bond is a siloxane bond expressed by Si—O—.
In the electrically chargeable substrate, it also is preferable that the silane-based compound is at least one compound selected from a chlorosilane-based compound, an ethoxysilane-based compound and a methoxysilane-based compound.
Furthermore, in the electrically chargeable substrate, it is preferable that the silane-based compound is a linear compound.
In the electrically chargeable substrate, it is preferable that the silane-based compound comprising an alkyl group is CH
3
(CH
2
)
n
Si(O—)
3
(wherein n is 0~25).
In the electrically chargeable substrate, it also is preferable that the silane-based compound comprising a fluoroalkyl group is CF
3
(CF
2
)
n
(CH
2
)
2
Si(O—)
3
(wherein n is 0~25).
In the electrically chargeable substrate, it is preferable that the electrically insulating substrate is at least one substrate selected from glass, plastic and ceramic.
In the electrically chargeable substrate, it is preferable that the electrically insulating substrate is at least one substrate selected from a plate for placing a sheet in an OHP, a bulletin board of a bulletin device, a drafting board of a drafting machine, and a plate for placing a paper in a plotter device.
In the electrically chargeable substrate, it is preferable that a volume electric resistivity of the electrically insulating substrate on which a thin film has not been formed yet is in the range of 1×10
7
~1×10
19
&OHgr;·cm.
In the electrically chargeable substrate, it is preferable that the thickness of the thin film is in the range of 1~100 nm.
In the electrically chargeable substrate, it is preferable that the thickness of the thin film is in the range of 4~30 nm.
In the electrically chargeable substrate, it is preferable that the contact angle between the thin film and water is in the range of 80~180 degrees.
In the electrically chargeable substrate, it is preferable that a volume electric resistivity of the thin film is in the range of 1×10
11
~1×10
19
&OHgr;·cm. Practically, a volume electric resistivity of the thin film is preferably in the range of 1×10
13
~1×10
18
&OHgr;·cm.
In the electrically chargeable substrate, it further is preferable that the silane-based compound is bonded to the surface of the electrically insulating substrate by at least one reaction selected from a dehydrochlorination reaction and a dealcoholization reaction.
DETAILED DESCRIPTION OF THE INVENTION
According to the electrically chargeable substrate of the present invention, a chemical adsorption film composed of a silane-based compound comprising an alkyl group or a fluoroalkyl group is bonded to the surface of an electrically insulating substrate such as, for example, glass, plastic or ceramic through a covalent bond, for example, a siloxane bond expressed by Si—O— or a bond expressed by Si—N—. Consequently, the thin film does not easily peel off from the substrate, since the thin film is tightly bonded to the electrically insulating substrate, thus obtaining an electrically chargeable substrate maintaining a charged state for a long time regardless of humidity of an atmosphere. That is to say, the thin film restrains the amount of adsorbed water on the substrate, and as a result the escape of the charges accumulated on the surface of the substrate from the surface through the adsorbed water also is restrained, thus maintaining a charged state.
According to a preferable example of the present invention in which the silane-based compound comprises a vinyl group or an acetyl group, after forming a thin film, the strength of the thin film can be improved by crosslinking through electron beam irradiation.
According to a preferable example of the present invention in which the silane-based compound is a chlorosilane-based compound, an ethoxysilane-based compound or a methoxysilane-based compound, a thin film excellent in transparency can be tightly bonded, since a monomolecular film can be easily formed.
According to a preferable example of the present invention in which the silane-based compound is a linear compound, the density of the film can be improved.
According to a preferable example of the present invention in which the electrically insulating substrate is a substrate selected from a plate for placing a sheet in an OHP, a bulletin board of a bulletin device, a drafting board of a drafting machine, and a plate for placing a paper in a plotter device, each device can be provided in which a paper, a vinyl sheet or the like can adhere easily regardless of the humidity of an atmosphere, a charged state can be maintained for a long time, and dirt adhering can be removed easily.
As described above, according to the electrically chargeable substrate of the present invention, a chemical adsorption film composed of a silane-based compound comprising an alkyl group or a fluoroalkyl group is bonded to the

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