JPH059020B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in electrostatic recording media, and particularly to electrostatic recording media suitable for high-density recording such as 400 dots/inch, electrostatic facsimiles, electrostatic plotters, and the like.

(Prior Art) In recent years, along with advances in communication technology, there has been an increasing technical demand for electrostatic recording as a recording method that simultaneously satisfies high-speed recording and high image quality. In particular, electrostatic printers are preferred for use in optical communications, facsimiles as computer terminal equipment, printers, and CAD, which is a design technology using computers, and for recording and outputting these.

The multi-needle electrode recording method, which is most commonly used in these electrostatic recording methods, includes single-sided control type and double-sided control type. The surfaces of the two must be facing each other. In the conventional recording with a recording density of 200 dots/inch, there was no particular problem in the occurrence of the discharge itself, probably because the area of the recording needle was sufficient.
However, when performing high-density recording such as 400 dots/inch, there are drawbacks such as missing thin lines and abnormal discharge.

The present inventors focused on the relationship between the smoothness of the surface of the dielectric layer and image quality, and in order to accurately keep the distance between the recording needle and the surface of the dielectric layer within an appropriate range, the inventors of the present invention We have tried to improve the surface roughness of the dielectric layer and the number of irregularities while taking into account the conductivity of the support, but when drawing a thin line, normal discharge did not occur.
The current situation is that the problem of so-called abnormal discharges, which can cause thin line omissions or, in some places, discharges that can reach more than 10 times the area of the recording stylus, degrading image quality, remains unsolved. It is.

(Problems to be Solved by the Invention) The present invention is an electrostatic recording medium used in high-density electrostatic recording methods such as 400 dots/inch, and is capable of producing clear images without thin lines or abnormal discharge. The purpose of this invention is to provide a method for manufacturing a body.

(Means for Solving the Problem) The present inventors believe that there is a limit to the degree of improvement in the above-mentioned problem when considering the structure of the recording medium.
Further research was conducted on the discharge and charging conditions on the surface of the dielectric layer. Incidentally, it has conventionally been common general knowledge that the surface of the dielectric layer of an electrostatic recording medium must be free of static charge until an electrostatic charge for a recorded image is applied. Therefore, the conventional thinking has been that if static charges are generated on the surface of the dielectric layer for some reason, it is necessary to remove them. At first glance, the present invention is an idea that goes against such common technical knowledge, but the inventors of the present invention have previously determined that, before applying electrostatic charges for forming a recorded image, they desire electrostatic charges with the opposite polarity to the applied charges. As a result of our research, we have been working on the idea that if the wires are charged to a distribution state of , it might be possible to eliminate thin wire dropouts and abnormal electrical discharges, and it was discovered that a totally unexpected effect could be obtained. . After further investigation, we found that if the static charges that are pre-charged on the surface of the dielectric layer are uniformly or non-uniformly distributed in the form of islands, it is effective if the diameter of each static charge is within the range of 1μ to 300μ. This was confirmed. Incidentally, if the major axis of the electrostatic charge is less than 1μ, the effect is poor, and if it is more than 300μ, abnormal discharge begins to occur, degrading the image quality. Therefore, the inventors of the present invention have conducted studies on a means for controlling the maximum major axis of the electrostatic charges to be formed in the island shape on the surface of the dielectric layer within the above-mentioned appropriate range. As a result, we have arrived at an invention consisting of the following configuration.

That is, the present invention is a method for manufacturing an electrostatic recording medium for an electrostatic recording method, which has a dielectric layer on a conductive support and applies electrostatic charge for forming a recorded image by discharging from a multi-needle electrode. Electrostatic charge is characterized in that an electrostatic charge of the opposite polarity to the charge applied for recording images is previously formed on the surface of the dielectric layer by rubbing the surface of the dielectric layer with an insulating substance and a conductive substance. This is a method for manufacturing a recording medium.

(Function) In the above configuration, the insulating substance used to previously apply an electrostatic charge of opposite polarity to the charge applied for recording images to the surface of the dielectric layer is a polymer compound such as polyethylene, polypropylene, polystyrene,
Thermoplastic resins such as butyral, polyvinyl acetate, polyester, polyvinyl chloride, polyacrylate, polyether, or copolymers thereof, melamine-formalin resin, urea-formalin resin, phenol-formalin resin, epoxy resin, etc. A curable resin or the like can be used, and as the conductive substance, a polymer electrolyte, a surfactant such as anion, nonion, cation or amphoteric ion, metal semiconductor powder, etc. can be used. The material may have both insulating and conductive segments in one molecule, such as a copolymer of styrene and acrylic acid ester quaternary ammonium salt.

Thus, in the structure of the present invention, the insulating substance and the conductive substance may be separate substances, or may be formed into an integrated substance. For example, an insulating substance and a conductive substance individually formed into a rod or a roll, or a conductive substance mixed with an insulating substance and formed into a rod or a roll, and furthermore, It may also be used by coating or impregnating a sheet material and winding it around a rod or roll.

When rubbing the surface of a dielectric layer with an insulating material and a conductive material as described above, if each is configured separately, the order of friction is that the insulating material is rubbed first, then the conductive material is rubbed. It is effective to rub it with If an insulating material and a conductive material are mixed and molded into an integral product, it is sufficient to simply rub the material as it is against the surface of the dielectric layer.

By the way, when the surface of a dielectric layer is rubbed with only an insulating material and static charges are formed, each static charge is generated in a variety of sizes, and there are many with a maximum of over 300μ. Become. Therefore
A huge electrostatic charge of 300μ or more will be adjusted to within the range of 1 to 300μ by friction with a conductive material. Note that this adjustment is
If the conductive material is composed separately from the insulating material, this is done by friction with the conductive material, or if the conductive material and the insulating material are formed into one piece. , or in the case of a substance containing a conductive segment and an insulating segment in one molecule, when it is rubbed with a molded product, an electrostatic charge is generated and the charge is adjusted within the range of 1 to 300μ. . The electrostatic charge is preferably in the range of 1 to 300μ, but in terms of the resolution of the recorded image, it is more desirable to adjust it within a range smaller than the maximum diameter of each pin electrode. .

In order to form an electrostatic charge having the diameter described above on the surface of the dielectric layer, it is possible to apply it by friction using the elasticity applied to the sheet in the final step of the manufacturing process of the electrostatic recording medium, or For example, a method may be adopted in which the recording apparatus has a built-in device for applying the electrostatic charge, separate from the application device for image formation, and applies the electrostatic charge immediately before recording.

The polarity of the electrostatic charge applied in advance to the surface of the dielectric layer can be either positive or negative depending on the recording method, but current electrostatic recording methods have a negative polarity discharge compared to a positive polarity discharge. Negative polarity is often used because of its good discharge efficiency, and therefore it is desirable that the electrostatic charge applied in advance be of positive polarity. A case in which electrostatic charges having a polarity opposite to the charges for a recorded image to be applied are formed will be described below.

If the charge for recording images applied by the electrostatic recording device is of negative polarity, the dielectric layer is first charged to positive polarity and subjected to friction treatment with a substance. According to observation using an electron microscope, the electrostatic charges formed in this process are irregular in size and distributed in islands or in a mesh pattern throughout. If thin lines are recorded with an electrostatic recording device in such a distribution state, thin line omissions will be improved, but abnormal discharge will increase and good recording will not be obtained. However, when subjected to further friction treatment with a conductive material, the spread of each positive polarity charge distributed in an island shape becomes approximately equal to 1 to 300μ, and as a result, not only does it completely eliminate thin lines, especially when recording single dots, but also
The number of abnormal discharges that occur particularly frequently during one-dot recording can be extremely reduced. The improvement effect obtained by the specific friction treatment according to the present invention is treatment 1.
It will be recognized even after 2000 years.

Therefore, it is possible to form an electrostatic charge of the opposite polarity to the charge applied to previously form a recorded image on the surface of the dielectric layer in electrostatic facsimile machines and electrostatic plotters for high-density recording such as 400 dots/inch. The exact reason why a remarkable effect is obtained in preventing thin lines from falling out, especially when drawing thin lines, is not necessarily clear, but the reason why a positive electrostatic charge is formed in advance on the surface of the dielectric layer is , if you want to record,
It is thought that more reliable discharge occurs, probably because the discharge starting voltage is lower than when recording is performed without forming positive electrostatic charges in advance.

Next, as the conductive support for forming the electrostatic recording material, inorganic salts such as sodium chloride, cationic or anionic polymer electrolytes such as polyvinylbenzyltrimethylammonium chloride, surfactants, or zinc oxide, Paper, plastic film, cloth, etc. impregnated or coated with a conductive-treated metal oxide semiconductor such as zinc oxide to have a surface resistance of 10 ⁵ to ^{10 11} Ω are used. As the dielectric layer constituting the electrostatic recording medium, as a resin,
Insulating resins, which are derivatives or copolymers of butyral resin, polyacrylate, polystyrene, polyvinyl acetate, polyester, etc., are used singly or as a mixture, and the spacer pigments to be contained in these resins include calcium carbonate, titanium oxide, and insulating resins. Inorganic pigments such as regular silica and clay, and plastic pigments containing polyethylene, polystyrene, etc., are used. Examples of the present invention will be described below, but it goes without saying that the present invention is not limited to these Examples.

[Preparation of electrostatic recording medium]

1:1 copolymer resin of methyl methacrylate and ethyl acrylate and 1:1 calcium carbonate
An electrostatic recording medium was prepared by coating a coating material for forming a dielectric layer prepared by mixing at a weight ratio of 5 g/m 2 on a conductive support so as to have a dry weight of 5 g/m ² .

Example 1 200 parts by weight of methyl ethyl ketone, polystyrene
A resin liquid prepared by mixing 80 parts by weight of a cationic surfactant (product name: "Cation BB" manufactured by NOF Corporation) with 20 parts by weight was applied to high-quality paper so that the dry weight was 10 g/ ^m2 . After the coating was dried, it was wrapped around a polystyrene rod with a diameter of 150 mm with the coated side facing outward. The surface of the dielectric layer of the electrostatic recording material prepared in advance using such a substance was pressed at room temperature and humidity with a pressure of 260 g/
cm ² at a speed of 10 m/min to obtain an electrostatic recording material according to the present invention.

After the friction, the surface potential of the dielectric layer surface was measured and found to be +2V. The magnitude of this electrostatic charge can be determined by observing a secondary electron image using an electron microscope (JEOL JSM-T-300) at an accelerating voltage of 2 kilovolts (positive electrostatic charges are expressed in black, negative electrostatic charges are (It is expressed as white.) Then, there were almost no objects larger than 300μ. When a single dot is recorded using an electrostatic plotter EP-101 manufactured by Matsushita Densen Co., Ltd., which applies a negative voltage to the needle electrode on the electrostatic recording medium after friction, as shown in Figure 1, thin lines and abnormal discharges occur. It showed good recording aptitude.

Example 2 A resin solution prepared by dissolving 20 parts by weight of polystyrene resin in 200 parts by weight of methyl ethyl ketone and further mixing 10 parts by weight of conductive zinc oxide powder was spread on high-quality paper at a dry weight of 10 g/ ^m2 . After coating and drying, the coated surface was smoothed using a supercalender, and then wrapped around a polystyrene rod with a diameter of 150 mm with the coated surface facing outward. The surface of the dielectric layer of the electrostatic recording material previously prepared using such a substance was pressed at room temperature and humidity with a pressure of 260 g/cm ² and a speed of 10.
The electrostatic recording material according to the present invention was obtained by rubbing at a speed of m/min.

After the friction, the surface potential of the dielectric layer surface was measured and found to be +1.5V. When the electrostatic charge was observed using the same electron microscope as described in Example 1, almost no electrostatic charge larger than 300 μm was observed.
When one-dot recording is performed using an electrostatic plotter EP-101 manufactured by Matsushita Densen Co., Ltd., which applies a negative voltage to the needle electrode on the electrostatic recording medium after friction, there are few thin line omissions and abnormal discharges as shown in Figure 2. , showed good recording aptitude.

Example 3 A polystyrene rod with a diameter of 150 mm was rubbed against the surface of the dielectric layer of the electrostatic recording material prepared in advance at room temperature and humidity at a pressing pressure of 260 g/cm ² and a speed of 10 m/min.
On the surface of this dielectric layer, an amphoteric surfactant (trade name "Anhitor 24B" manufactured by Kao Corporation) is further coated on high-quality paper to a dry weight of 5 g/m ² and dried, with the coated surface facing outward. Using a polystyrene rod with a diameter of 150 mm wrapped ^around the
The electrostatic recording material according to the present invention was obtained by rubbing at a speed of m/min.

After the friction, the surface potential of the dielectric layer surface was measured and found to be +2V. When the electrostatic charge was observed using the same electron microscope as described in Example 1, almost no electrostatic charge larger than 300 μm was observed. After this friction, an electrostatic plotter EP-101 manufactured by Matsushita Densen Co., Ltd. is used to apply a negative voltage to the needle electrode on the electrostatic recording medium.
When dot recording was performed, as shown in FIG. 3, there were few thin line omissions and abnormal discharges, indicating good recording suitability.

Comparative Example 1 One-dot recording was performed on the electrostatic recording medium prepared in advance using an electrostatic plotter EP-101 manufactured by Matsushita Densen Co., Ltd. As a result, as shown in FIG. 4, there were many thin lines missing, and the recording suitability was far inferior to that of the electrostatic recording material according to the present invention.

Comparative Example 2 A polystyrene rod with a diameter of 150 mm was rubbed against the surface of the dielectric layer of the electrostatic recording material previously prepared at room temperature and humidity at a presser pressure of 260 g/cm ² and a speed of 10 m/min.

After the friction, the surface potential of the dielectric layer surface was measured and found to be +2V. When observed with the same electron microscope as described in Example 1, many of the electrostatic charges were larger than 300μ (within a frame of 5cm x 5cm).
200 pieces) were confirmed to exist. When a single dot was recorded on the electrostatic recording medium after friction using an electrostatic plotter EP-101 manufactured by Matsushita Electric Transmission Co., Ltd., which applied a negative voltage to the needle electrode, as shown in Figure 5, there were no thin lines missing in Comparative Example 1.
Although this is a significant improvement compared to the case of
Many abnormal discharges occurred, and the recording suitability was far inferior to that of the electrostatic recording medium according to the present invention.

Comparative Example 3 80 parts by weight of a copolymer consisting of styrene and methyl methacrylate in a ratio of 3:1 and an amphoteric surfactant (trade name "Amhitol 24B" manufactured by Kao Corporation)
Mix at a ratio of 20 parts by weight and dry weight 10 on high-quality paper.
g/m ² and dried, and rubbed with a 150 mm diameter polystyrene rod wound around the coated surface at a presser pressure of 260 g/cm ² and a speed of 10 m/min.

After the friction, the surface potential of the dielectric layer surface was measured and found to be -1V. When the electrostatic charge was observed using the same electron microscope as described in Example 1, almost no electrostatic charge larger than 300 μm was observed. After this friction, an electrostatic plotter EP-101 manufactured by Matsushita Densen Co., Ltd. is used to apply a negative voltage to the needle electrode on the electrostatic recording medium.
When dot recording was performed, there were many thin lines missing as shown in FIG. 6, and the recording suitability was far inferior to that of the electrostatic recording material according to the present invention.

(Effects) Even when the electrostatic recording medium according to the present invention is used in a high-density electrostatic recording system such as 400 dots/inch, it is possible to obtain clear recorded images without thin line omissions or abnormal discharge.

[Brief explanation of drawings]

Figures 1 to 3 show records when one dot recording was performed on the electrostatic recorder according to the present invention described in Examples 1 to 3 using an electrostatic plotter that applied a negative voltage to the needle electrode. It is a sample of aptitude, and the fourth
Figures 6 to 6 are samples showing the recording suitability when one dot recording is performed on the electrostatic recording medium described in Comparative Examples 1 to 3 using an electrostatic plotter that applies a negative voltage to the needle electrode. be.

Claims (1)

[Claims] 1 A method for producing an electrostatic recording medium for an electrostatic recording method, which has a dielectric layer on a conductive support and applies electrostatic charge for forming a recorded image by discharge from a multi-needle electrode, and the dielectric layer A method for producing an electrostatic recording material, characterized in that an electrostatic charge having a polarity opposite to that applied for a recorded image is previously formed on the surface of the dielectric layer by rubbing the surface with an insulating material and a conductive material. .