JPH06274114A - Method for holding body with electrostatic force - Google Patents

Abstract

PURPOSE:To diversify messages and information transmission means and then improve the quality by providing the new holding method for a body with an electrostatic force. CONSTITUTION:As for the method for fixing and holding the object body on the opposite surface of an electrostatic holding plate, structured by arraying cathode electrodes and anode electrodes alternately in a comb tooth shape in contact with one surface of a plastic plate having the smooth surface and constant electric characteristics, by using the electrostatic holding plate, the hold surface of the object body which can not be held stably since the electrostatic holding force is small is made conductive to increase the electrostatic holding force. Specially, for an object body whose hold surface is not smooth enough, a soft plastic cushion material is interposed between the hold surface of the object body and the conductive surface to give a strong electrostatic holding force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an electrostatic holding device having a function of generating electrostatic force to fix and hold a paper or other held object. Stabilize plastic foam molded products, plywood without smooth surface, various laminated board materials, cardboard or corrugated paper, highly insulating plastic film or sheet or dry paper to the electrostatic holding device. The purpose is to provide a method of fixing and holding.

By implementing the present invention, the electrostatic holding device can be used not only as a paper but also as a bulletin board or a display device for articles that can display a message produced using various materials other than paper. It is possible to provide a new display or display method at the same time.

[0003]

2. Description of the Related Art There have been various kinds of posting methods as means for transmitting messages or information.
Typical examples are handwritten characters or sentences on blackboards and whiteboards, and are often used in public places such as schools and civic halls.Printed materials, etc. can be placed on wooden boards with insect pins or pushpins. Examples thereof include a so-called bulletin board system in which the printed matter is fixed and held, or a printed matter is fixed on a steel plate with a magnet. Also,
In recent years, a display device using an electronic display element such as liquid crystal or electroluminescence has come to be used at a specific place as a means for providing information.

By the way, the bulletins or displays as means for providing information can be roughly classified into transitive ones and semi-permanent ones or permanent ones.

The above-described posting or displaying methods belong to the former, that is, temporary transitive posting or displaying. On the other hand, typical examples of those belonging to the semi-permanent or permanent display are the name of a store and the advertising billboard of a product.

Although there is a clear difference in the method of displaying characters between the two, the basic characteristics required for a bulletin board or display device for transmitting a transitive message to which the present invention belongs are as follows. It is a point. (1) The property of fixing and holding printed matter or paper with a written message for a certain period. (2) A feature that allows printed matter to be easily removed or fixed whenever necessary. And (3) The characteristic that "spots" and "dirt" do not remain after removing printed matter.

In recent years, along with the diversification and flooding of information, there has been a demand for improvement in the quality of information transmission. That is, the conventional medium for transmitting information is mainly paper, as represented by a printed matter, letters written on paper, or a drawing, but recently, a hard plastic foam plate or plywood typified by a polystyrene foam plate. Or, there is a strong demand for more effective information transmission using three-dimensional cut letters made of thick board materials such as corrugated cardboard or three-dimensional objects made of paper or plastic sheets. There is.

However, when it is desired to use the above-mentioned three-dimensional object as a transitive display or a display medium, it is very difficult to use a conventional display method. For example, it is necessary to prepare pushpins with different needle lengths (changing the length of the needle depending on the thickness of the cut letters) to fix the solid cut letters on a wooden board or cork board. It is almost impossible to prepare different pushpins in advance, and even if it is possible, it is not economical.

Further, even if an iron plate is used as a bulletin board or a display device and the above-mentioned three-dimensional object is fixed and held by a magnet, a thick three-dimensional object can be stably used unless at least a very strong magnet is used. It cannot be held fixed. Furthermore, this magnet fixing method is suitable for fixing thin posts such as paper, but it requires a magnet for fixing, and the magnets are exposed to the front of the posts, which can be annoying. is there.

Further, in these posting methods, it is necessary to remove the thumbtack or the magnet one by one in order to remove the printed matter such as the printed matter from the bulletin board or the like.
Various presentation materials (printed materials,
If you want to replace drawings (drawings, graphs, etc.) quickly and frequently according to the progress of the explanation, a bulletin board that requires a material fixing tool such as a thumbtack cannot be used. Furthermore, in such a posting system, as the size of the posting increases,
There is also a problem that a lot of material fixing tools are required, and that fixing work requires a lot of time and labor.

[0011]

A bulletin board made of wood or cork board and an enamel plate are often used as means for displaying various materials such as printed materials and handwritten writings as messages and information transmission media over time. However, these cannot satisfy the above-mentioned demands for various messages or information displays. Therefore, in order to meet such demands, it is necessary to satisfy the above-mentioned three basic characteristics required for a bulletin board for transmitting a transitive message or information transmission, and to secure a fixing tool for a material such as a thumbtack or a magnet. A billing system that is not required is requested.

The inventors of the present invention have noticed that electrostatic force is used as a material fixing method that satisfies such requirements,
We have already conducted research on the application of an electrostatic holding device, which is often used as a holding device for recording sheets or drawings of plotters, digitizers, or XY recorders, to bulletin boards.

The electrostatic holding device mentioned here has the following structure and function. That is, a surface having specific electric characteristics is closely adhered to one surface of a plate-shaped plastic having a smooth surface, and negative electrodes and positive electrodes are alternately paired at a constant interval and arranged in a comb shape. A DC voltage of about 500 to 3000 V is applied to each counter electrode via the negative and positive mother electrodes. When a DC voltage is applied to the counter electrode, induced electric charges are induced on the surface of the plastic plate opposite to the surface on which the electrode is arranged (hereinafter referred to as “adsorption surface”), and an electrostatic field is developed. This makes recording paper,
Most types of paper as well as drawing paper can be adsorbed and fixed on the adsorption surface. The electrostatic field is immediately attenuated and extinguished when the DC voltage to the counter electrode is cut off, so that the object to be held fixed on the adsorption surface can be easily removed. In addition,
The electrode group is covered with a highly insulating plastic plate called a base except for lead electrodes for connecting to a power source because it is dangerous if exposed.

As will be immediately understood from the above description, the electrostatic holding device (here, the device means the entire combination of the electrostatic holding plate and the DC power source. Hereinafter, simply referred to as "electrostatic holding plate". ) Not only has the above-mentioned three basic characteristics of the bulletin board, but since the material is fixed and held by electrostatic force (hereinafter referred to as “electrostatic holding force”), a material fixing tool such as a thumbtack or a magnet is required. Not. Also, the detachment of the paper material that is fixedly held on the electrostatic holding plate can be easily removed by peeling each time without turning off the power (electrostatic holding force is parallel to the suction surface in the same plane). (Shearing force) is extremely high, but peeling to the adsorption surface is smaller than the former). In particular, the electrostatic force is not local and acts on the entire surface of the holding material, so that the holding stability is extremely high.

The characteristics of the electrostatic holding plate as described above are not only effective for fixing materials on large plates, but also suitable for quick and frequent exchange of materials. Therefore, if not only paper materials but also various materials such as expanded polystyrene sheet, plywood or laminated board or cardboard and various plastic sheets or films can be fixedly held, it will meet the demand for various means of message transmission or information provision. In addition to being able to do so, it can bring about an improvement in the quality of communication.

However, although the electrostatic holding plate has an extremely strong electrostatic holding force for thin paper, the electrostatic holding plate as described above, in particular, an electrostatic holding of an object having a non-smooth holding surface is used. The force is smaller than that of thin paper, and it is difficult to stably fix an information transmission medium (for example, cut letters of a rigid polystyrene foam plate) using these materials on the suction surface.

Therefore, the problem to be solved by the present invention is that the electrostatic holding force is small and it is difficult to stably fix and hold the material on the electrostatic holding plate or the object whose surface is not smooth. It is about finding ways to increase power.

[0018]

The electrostatic holding force of the electrostatic holding plate is determined not only by the material of the held body but also by the electric characteristics of the adsorption layer (plastic plate on the surface) (particularly volume resistivity and relative dielectric constant). Rate), its thickness, holding surface area of the object to be held, shadow
It depends on many factors such as the arrangement of the positive electrodes, the relative humidity of the outside air and the operating voltage.

In order to solve the problems of the present invention, first,
Although it is necessary to know the correlation of the above-mentioned factors that control the electrostatic holding force, the present inventors have found that, among these factors that control the electrostatic holding force, the electrical resistance and the operating voltage of the held object are The inventors have found that the holding power is strongly controlled and have reached the present invention. The details will be described below.

As described above, the electrostatic holding plate is in close contact with the opposite surface of the attraction surface (that is, the back surface of the attraction layer) and has a width of 3-10.
Negative electrodes and positive electrodes each having a size of about mm are alternately arranged in pairs at regular intervals and arranged in a comb shape. Now, suppose that the held body is placed in close contact with the suction surface so as to straddle the pair of electrodes. When a DC voltage (operating voltage) V is applied to the pair of electrodes, current flows from the positive electrode to the negative electrode,
This current circuit is composed of the following two circuits: (A) a circuit that passes through the adsorption layer from the positive electrode, flows through the held body, passes through the adsorption layer again to reach the negative electrode, and (B) passes from the positive electrode to the adsorption layer. A circuit is immediately formed which leads to the negative electrode.

A-The current flowing through the circuit is i, the resistance of the circuit from the positive electrode through the adsorption layer to the held body is R _k , the resistance of the held body is R _c, and the resistance from the held body is through the adsorption layer. 'When _k, R _k and R' circuit resistance leading to negative electrode R (corresponding to the thickness of the adsorption layer) circuit length of _k because it may be considered that the same, R _k = R _'k ............... It is (1).

Further, the voltage drops V _k , V _c and V ′ _k due to the respective circuit resistances are V _k = iR _k ………… (2) V _c = iR _c ……………… according to Ohm's law. (3) and V from given by _{'k = iR' k ......... (} 4), the operating voltage V and V _k, V _c and V '
Between the _k, (1) formula to take into account the following _{equation; V = i (R k +} R c + R 'k) = V k + V c + V' k = 2V k + V c ...... (5) is satisfied .

The above-mentioned V _k represents the voltage drop due to the resistance of the adsorption layer, but the adsorption layer (plastic plate) having a constant thickness (d) is sandwiched between the electrode surfaces facing each other in parallel. It may be considered as a voltage (potential difference) applied between the holding surfaces of the body.

On the other hand, according to the teaching of electromagnetics,
The attractive force F acting on the two conductor plates placed in parallel with the distance d in between is V _{d as} the potential difference between the conductor plates and E (= V _d as the potential gradient _).
/ D), the following equation; Indicated by. That is, the attractive force acting on the two parallel plate conductors is proportional to the square of the potential difference V _d between the two.

Also in the electrostatic holding plate, the attractive force acting between the pair of negative and positive electrodes and the held body, that is, the electrostatic holding force F.
_s, when assumed to be proportional to the square of the potential difference V _k between the electrode and the holder, F _s is considering (5) the following equation; Indicated by. Here, V _c is expressed by the equation (3), but when the held body is a metal having a good conductor, R _c may be set to approximately zero, so V _c also becomes approximately zero, and F _s Is the following formula; The electrostatic attractive force F _s given by becomes maximum (however, it depends on the operating voltage V).

Contrary to this case, the resistance R _{c of the} held body increases, and finally the electrostatic holding force F _{s on the} held body having a resistance such that V = V _c becomes zero. That is, it is theoretically predicted that the electrostatic holding force of the held body having a very high resistance becomes extremely small, and stable holding by the electrostatic holding plate becomes difficult. Such theoretical prediction can be verified by experimentally examining the relationship between the held objects having different volume resistivities and the electrostatic holding force under the condition that the operating voltage is constant.

Further, through such research, it has been found that the electrostatic holding force largely depends not only on the electric resistance of the held body but also on the smoothness of the held surface of the held body. That is,
Held object of the same material (that is, having the same electrical resistivity)
However, it was shown that the higher the adhesion (smoothness) of the electrostatic holding plate to the attracting surface, the greater the electrostatic holding force.

This finding also suggests the following. That is, when the surface smoothness of the held body deteriorates, the contact area (effective area on which electrostatic force acts) between the electrostatic holding plate attraction surface and the holding surface of the held body decreases, and The contact resistance between the electrostatic holding plate and the attracting surface increases and V _c
And F _s decreases as a result (see Eq. (7)).

From the analysis of the expression of the electrostatic holding force described above, the following two points were concluded as means for solving the problems of the present invention. (1) For an object to be held, which has a high electric resistance value (volume resistivity) and a small electrostatic holding force, the adsorption force (electrostatic force) can be obtained by imparting conductivity to the entire holding surface or a part of the surface. Holding power) can be increased. And (2) If the holding surface of the object to be held is not smooth, form a conductive coating on one surface of a soft sheet with high cushioning properties such as a soft rubber sheet, and attach the opposite surface of the soft sheet with an adhesive such as an adhesive. Alternatively, by adhering it to the surface of the holding body to be held by some mechanical method such as a thumbtack, the adhesion and the attractive force of the electrostatic holding plate to the attraction surface can be enhanced.

Means for Solving the Problems of the Present Invention
The conductivity imparted to the object to be held mentioned in (1) is performed by metal foil such as aluminum foil, copper foil, iron foil or gold foil, metal vapor-deposited plastic film with metal deposited on the plastic film surface or metal foil and plastic film. Reattach the laminated sheet with and to the surface (holding surface) of the object to be held (holding surface) with a peel-off or permanent type pressure-sensitive adhesive (adhesive), or apply a conductive paint. Executed by

These conductive materials are selected by a voltage drop V _c based on the electric resistance of the conductive material (because conductivity has already been imparted to the held material, as shown in equation (7)). (The voltage drop due to its own resistance may not be considered) The closer the value is to zero, that is, the lower the electric resistance of the conductive material, the greater the electrostatic attraction F _s becomes. Therefore, considering economic efficiency among various conductive materials. However, the one with the lowest volume resistivity should be selected. The metal foil or metal-deposited plastic film described above is suitable for the purpose intended by the present invention. In particular, the latter has rigidity and suppresses the generation of "wrinkles", and is therefore excellent in handling suitability. In addition, as for the method of joining these conductive materials and the object to be held, it is possible to mechanically join them by using a thumbtack or an insect pin without using an adhesive or the like. Bonding with tape or sheet is preferred.

Next, as a soft sheet having a high cushioning property referred to in the above means (2) for solving the problems of the present invention,
Examples thereof include soft plastic or rubber foam sheets such as soft polyurethane foam sheets and low-density polyethylene foam sheets, and elastomer sheets such as soft polyvinyl chloride sheets, ethylene-vinyl acetate copolymer sheets and various rubber sheets. In particular, the elastomeric foamed sheet has a high cushioning property and can enhance the adhesion to the electrostatic holding plate of the held body lacking the smoothness of the surface, so that the effect of the present invention can be sufficiently expressed. Is a preferred sheet material.

The term "conductivity" as used in the present invention means that the volume resistivity of the material is 10 ³ Ω · cm or less in the normal state (20 to 25 ° C.).

[0034]

[Examples and Comparative Examples] The electrostatic holding plates used in the examples and comparative examples had a size of 60 cm in length and 90 cm in width, and the adsorption layer had a thickness of 0.5 mm and a volume resistivity of 1.2 × 10. ¹¹ Ω ・ cm
It is a plastic plate with a smooth surface and a relative permittivity (60Hz) of 8.3. On the back surface of the adsorption layer, negative electrode and positive electrode printed with conductive ink and having a width of 0.5 cm and a length of 55 cm are alternately arranged in a comb shape at intervals of 0.3 cm.

Each of the negative electrode and the positive electrode is connected to a respective mother electrode (corresponding to the root of a comb tooth), and the mother electrode is connected to a DC power source via a lead wire. The electrode is covered with a highly insulating plastic plate (substrate) having a thickness of 1 mm for the purpose of protecting the electrode and preventing electric shock. That is,
The electrostatic holding plate has a three-layer structure of adsorption layer / electrode / substrate, and each layer sheet is heat-fused by a heat press and integrally bonded.

Next, Table 1 shows various specifications such as the types of the objects to be held and the smoothness of the holding surface used in the examples and comparative examples. Here, in the evaluation of smoothness, the surface smoothness of the high-quality copy paper for the electronic copying machine was taken as a standard (good), and any inferior one was judged as poor.

[0037]

[Table 1]

A holding experiment was carried out by using the five kinds of held objects listed in Table 1. The results are shown in Table 2. Here, the treatment of the holding surface of the held body in the comparative example and the example shown in Table 2 is as follows.

Comparative Example: The surface of the object to be held as it is (untreated).

Example 1: Using a double-sided pressure sensitive adhesive tape,
30 μm thick aluminum foil is bonded to the entire holding surface (100%) of the object to be held.

Example 2: Using a double-sided pressure-sensitive adhesive tape,
Aluminum foil with a thickness of 30 μm is bonded to the area of the four corners, which corresponds to about 50% of the entire holding surface of the held object.

Example 3: Using a double-sided pressure-sensitive adhesive tape,
30 μm thick aluminum foil is bonded to the four corners corresponding to about 30% of the entire holding surface of the object to be held.

Example 4 Using a double-sided pressure-sensitive adhesive tape,
30 μm thick aluminum vapor-deposited plastic film is bonded to the area of four corners corresponding to about 50% of the entire holding surface of the object to be held through a soft polyurethane foam sheet having a thickness of about 2 mm (the aluminum vapor-deposited surface is an electrostatic holding plate Join to face the adsorption surface).

The electrostatic holding force of the object to be held in the above Comparative Examples and Examples was evaluated by the following four levels A to D. A: After holding the object to be held on an electrostatic holding plate placed vertically, it remains stable even after 24 hours. B: Dropped from the electrostatic holding plate within 8 to 24 hours in the same experiment as A. C: Dropped from the electrostatic holding plate within 1 to 8 hours in the experiment under the same conditions as A. D: Not held at all in the experiment under the same condition as A, or dropped within 1 hour even if held.

In the comparative example and all the examples, the operating voltage of the electrostatic holding plate was 3000V.

[0046]

[Table 2]

As is clear from the results of the comparative example in Table 2,
If conductivity was not imparted to the holding surface of the held body, the electrostatic holding power of the other four held bodies was extremely weak except for the high-quality paper, and almost none of them could be fixedly held (evaluation D). On the other hand, when the holding surface of the object to be held is made conductive according to the method of the present invention, the holding force is significantly improved. In particular, the effect of the urethane foam cushion material is remarkable with respect to the held objects (identification numbers 2, 3 and 4) having poor surface smoothness (Example 4).

Claims (3)

[Claims] 1. A direct-current voltage is applied to each of a plurality of counter electrodes in which a negative electrode and a positive electrode are alternately arranged in a comb-like shape, in close contact with one surface of a plate-shaped plastic having a smooth surface. , Holding an object to be held in an electrostatic holding plate having a function of generating an electrostatic field on the surface of the plastic plate on which the electrode is placed and fixing and holding various papers and other objects to be held on the plastic plate Conductive coating is formed on the entire surface or part of the surface, or a thin film or sheet made of a conductive material is bonded by a viscous / adhesive agent or a mechanical method to make conductive on the holding surface of the object to be held. Property, thereby enhancing the electrostatic attraction force of the object to be held, and holding the object to be held fixed on the electrostatic holding plate by the electrostatic force. 2. A material to be held is a highly insulating plastic film or sheet which has a weak electrostatic holding force and is difficult to fix on an electrostatic holding plate, or paper or paper board in a dry state, polystyrene foam or The method for holding an object according to claim 1, which is a wooden veneer, plywood, or various laminated wood. 3. A conductive film is formed on one surface of a soft sheet having a cushioning property, and the opposite surface of the soft sheet is covered with a viscous / adhesive agent or by a mechanical method over the entire holding surface of a held body or It is joined to a part of the surface thereof to enhance the adhesion of the held body to the electrostatic holding plate and at the same time enhance the electrostatic holding force to develop a stronger electrostatic holding force. 1. A method for holding an object by electrostatic force according to 1 or 2.