JPS63143554A - Electrostatic recording body - Google Patents

Abstract

PURPOSE:To remove fine line missing and abnormal discharge of a recording image and to obtain the clear recording image by rubbing on insulating substance and a conductive substance, thereby forming the applied electric charge for the recording image and the electrostatic charge having an opposite porarity on the surface of a dielectrics body layer before applying the electrostatic charge. CONSTITUTION:The each electrostatic charges having 1-300mu diameter are uniformly or unevenly distributed on the surface of the dielectrics body in the form of islands before applying the electrostatic charge for forming the recording image by rubbing the insulating substance of a thermoplastic resin etc., such as polyethylene, polypropylene, polyester, polyvinyl chloride or a copolymer thereof and the conductive substance such as a polyelectrolyte, an anion and a metallic semiconductor powder, etc. whereby the electrostatic charge which has the opposite porality for the applied electric charge for the recording image is previously formed. Thus, even in case of using a high density electrostatic recording system having 400dot/inch, the clear recording image which does not generate the fine line missing and the abnormal discharge is obtd.

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 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 favorably used for optical communication and computer terminal devices such as facsimiles and printers, as well as CAD, which is a design technology using computers, and for recording output of these devices.

The multi-needle electrode recording method that is most commonly used in these electrostatic recording methods includes single-sided control type and double-sided control type.
In either case, the recording needle and the surface of the recording medium must face each other while maintaining a constant gap from the electrostatic recording medium. In the conventional recording with a recording density of 200 dots/inch, there was no particular problem in the generation 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 thin line omissions 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 surface and appropriately control the number of unevenness while taking into account the conductivity of the support, but when drawing a thin line, normal discharge did not occur, and it was difficult to remove the thin line. The current situation is that the problem of so-called abnormal discharge, in which a phenomenon occurs, or conversely, the discharge reaches more than 10 times the area of the recording stylus depending on the location, degrading the image quality, remains unsolved.

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

(Means for Solving the Problem) Since there is a limit to the degree of improvement in the above-mentioned problem when considering the structure of the recording medium, the present inventors further investigated the discharge and charging conditions on the surface of the dielectric layer. conducted research. Incidentally, it has been conventional common knowledge that the surface of the dielectric layer of an electrostatic recording medium must be covered with no electrostatic 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 wire is charged to a distribution state of , it may be possible to eliminate thin wire dropouts and abnormal discharges, and we have discovered that a totally unexpected effect can be obtained. . After further investigation, we found that if the electrostatic charges that are pre-charged on the surface of the dielectric layer are distributed uniformly or unevenly in the form of islands, it is effective if the diameter of each electrostatic charge is within the range of 1μ to 300μ. It was confirmed that there is. Incidentally, if the major axis of the electrostatic charge is 1 μm or less, the effect is poor, and if it is 300 μm or more, abnormal discharge begins to occur, degrading the image quality. Therefore, the inventors of the present invention have been studying methods for controlling the maximum major axis of the electrostatic charges to be formed in the form of islands 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 provides an electrostatic recording medium in which a dielectric layer is formed on a conductive support, in which an insulating substance and a conductive material are applied to the surface of the dielectric layer before applying electrostatic charges for forming a recorded image. It is characterized in that an electrostatic charge having a polarity opposite to the charge applied for recording images is previously formed on the surface of the dielectric layer by friction with a substance.

(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, butyral, polyvinyl acetate, polyester, polyvinyl chloride, polyacrylate,
Thermoplastic resins such as polyether or copolymers thereof, melamine-formalin resins, urea-formalin resins,
Thermosetting resins such as phenol-formalin resin and epoxy resin can be used, and as the conductive substance, polymer electrolytes, surfactants such as anions, nonions, cations, or amphoteric ions, metal semiconductor powders, etc. can be used. It may have both insulating and conductive segments in the molecule, such as a copolymer of styrene and acrylic acid ester quaternary ammonium salt.

Thus, in the structure of the present invention, the insulating material and the conductive material may be different from each other, or may be integrated into one. 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.

Incidentally, when an insulating material alone rubs the surface of a dielectric layer to form static charges, the static charges vary in size, and there are many with a maximum of over 300μ. Become. Therefore, for huge electrostatic charges of 300 μ or more, friction with conductive materials can cause 1 to 300 μ
It will be adjusted so that it is within the range. Note that this adjustment is performed by friction with the conductive material when the conductive material is configured separately from the insulating material, or when the conductive material and the insulating material are integrated into one body. In the case of a molded product or a substance containing a conductive segment and an insulating segment in one molecule, when the molded product is rubbed, an electrostatic charge is generated and the charge is adjusted within the range of 1 to 300μ. That will happen. In addition, the static charge is 1 to 3
Although a range of 00 μm is desirable, from the viewpoint of resolution of a recorded image, it is more desirable to adjust the diameter to 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 good 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.
Further, for example, a method may be adopted in which the recording apparatus has the electrostatic charge applying device built-in separately from the applying device for image formation, and the electrostatic charge is applied 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, although thin line omissions are improved, abnormal discharges increase and good recording cannot be obtained. The spread of each positive polarity charge distributed in an island shape is approximately equal to 1 to 300μ, and as a result, not only does it completely eliminate the omission of fine lines, especially thin lines when recording one dot, but it also eliminates abnormal discharges that occur particularly often when recording one dot. The number can be extremely reduced. The improved effects obtained by the specific friction treatment according to the invention are still visible one year after the treatment.

Therefore, it is possible to form an electrostatic charge having a polarity opposite to that of the charge applied for forming a recorded image in advance on the surface of the dielectric layer.
It is suitable for electrostatic facsimiles and electrostatic blocks for high-density recording such as 0 dots/inch, and is particularly effective in preventing thin lines when drawing thin lines.The exact reason for this is not necessarily clear. However, when recording by forming positive electrostatic charges on the surface of the dielectric layer in advance and applying negative polarity, the discharge is lower than when recording without forming positive electrostatic charges in advance. It is thought that more reliable discharge occurs probably due to a decrease in the starting voltage.

Next, as the conductive support constituting the electrostatic recording material, inorganic salts such as sodium chloride, cationic or anionic polymer electrolytes such as polyvinylbenzyltrimethylammonium chloride, surfactants, or zinc oxide, Impregnated or coated with a metal oxide semiconductor such as zinc oxide that has been treated to make it conductive, with a surface resistance of 105 to 10"Ω.
Paper, plastic film, cloth, etc. are used. The dielectric layer constituting the electrostatic recording medium may be made of insulating resins such as derivatives or copolymers of acrylic acid ester, butyral, polyacrylate, polystyrene, polyvinyl acetate, polyester, etc. alone or as a mixture. As the spacer pigment used and contained therein, inorganic pigments such as calcium carbonate, titanium oxide, amorphous silica, clay, etc., and plastic pigments containing polyethylene, polystyrene, etc., are used. below,
Although examples of the present invention will be described, it goes without saying that the present invention is not limited to these examples.

[Preparation of electrostatic recording medium]

1:1 polymethyl methacrylate and calcium carbonate
An electrostatic recording medium was prepared by coating a dielectric layer-forming coating material prepared by mixing at a weight ratio of 5 g/m' on a conductive support at a dry weight of 5 g/m'.

Example 1 200 parts by weight of methyl ethyl ketone, 80 parts by weight of polystyrene, cationic surfactant (trade name "Cation BBJ")
After applying and drying a resin solution prepared by mixing 20 parts by weight of 20 parts by weight of 20 parts by weight of 10 g/m dry weight on high-quality paper, apply it to a polystyrene rod with a diameter of 150 fins so that the coated side is on the outside. wrapped around. The surface of the dielectric layer of the electrostatic recording material previously prepared using such a material was rubbed at room temperature with a pressure of 260 g/cm'' and at a speed of 10 m/min to obtain an electrostatic recording material according to the present invention.

After friction, the surface potential of the dielectric layer surface is +2■
It was showing. 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 (expressed as white) then 30
Almost no particles with a diameter of 0 μ or more were observed. When a single dot is recorded using an electrostatic block EP-101 manufactured by Matsushita Electric Transmission Co., Ltd., which applies a negative voltage to the needle electrode on the electrostatic recording medium after friction, thin lines and abnormal discharges occur as shown in Figure 1. It showed good recording aptitude.

Example 2 20 parts by weight of polystyrene resin was dissolved in 200 parts by weight of methyl ethyl ketone, and 1 part by weight of conductive zinc oxide powder was added.
A resin liquid prepared by mixing 0 parts by weight was applied to high-quality paper at a dry weight of 10 g/n? After coating and drying, apply a super calender to smooth the coated surface.
It was wrapped around a 0 mm polystyrene rod so that the coated surface was on the outside.

The surface of the dielectric layer of the electrostatic recording material previously prepared using such a material was rubbed at room temperature with a pressure of 260 g/cm2 and a speed of 10 m/min to obtain an electrostatic recording material according to the present invention.

After rubbing, the surface potential of the dielectric layer surface was measured to be +1.
It showed 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 dot recording is performed using an electrostatic plotter EP-101 manufactured by Matsushita Densen Akiku, which applies a negative voltage to the needle electrode on the electrostatic recording medium after friction, there are few thin lines and abnormal discharges as shown in Figure 2. , showed good recording aptitude.

Example 3 The surface of the dielectric layer of the electrostatic recording material prepared in advance with a polystyrene rod with a diameter of 15 ON was pressed at room temperature with a pressure of 260.
Friction was performed at a speed of 10 m/min at a speed of 10 m/min. The surface of this dielectric layer was further coated with an amphoteric surfactant (product name: "Anhitol 24B" manufactured by Kao 01) on high-quality paper at a dry weight of 5 g/n.
? The electrostatic recording medium of the present invention was obtained by applying and drying the coating and rubbing it with a polystyrene rod of 150 nm in diameter wrapped around the coated surface at a pressing pressure of 100 g/cm 2 and a speed of 10 m/min.

After friction, the surface potential of the dielectric layer surface is +2■
It was showing. The magnitude of the electrostatic charge is determined in Example 1.
When observed using the same electron microscope as described in , almost no particles larger than 300 μm were observed.

When one dot recording is performed on the electrostatic recording material after friction using an electrostatic plotter EP-101 manufactured by Matsushita Densen, which applies a negative voltage to the needle electrode, as shown in Fig. 3, there are few thin lines and abnormal discharges. It showed good recording aptitude.

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

After friction, the surface potential of the dielectric layer surface is +2■
It was showing. When the electrostatic charges were observed using the same electron microscope as described in Example 1, it was confirmed that there were many electrostatic charges of 300 μm or more (200 within a frame of 5 cm x 5 cm). Electrostatic plotter EP manufactured by Matsushita Densen, which applies a negative voltage to the needle electrode on the electrostatic recording medium after friction.
When one dot recording is performed at -10i, as shown in Fig. 5, although thin line dropout is significantly improved compared to Comparative Example 1, many abnormal discharges occur, and the electrostatic recording according to the present invention Compared to the body, its aptitude for recording was far inferior.

Comparative Example 3 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 ■) were mixed on high-quality paper in terms of dry weight in Log/m.
It was coated and dried, and rubbed with a polystyrene rod having a diameter of 150 fins wrapped around it so that the coated surface was on the outside at a presser pressure of 260 g/cm'' and a speed of 10 m/min.

After friction, the surface potential of the dielectric layer surface is measured as -IV
It was showing. The magnitude of this static charge is determined by Example 1.
When observed using the same electron microscope as described in , almost no particles larger than 300 μm were observed.

When one-dot recording is performed using an electrostatic plotter EP-101 manufactured by Matsushita Densen 0@, which applies a negative voltage to the needle electrode on the electrostatic recording medium after rubbing, there are many thin line omissions as shown in Fig. 6. Compared to such electrostatic recording media, the recording suitability was far inferior.

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

[Brief explanation of the drawing]

Figures 1 to 3 show the results when one dot recording 11 was performed on the electrostatic recording material according to the present invention described in Examples 1 to 3 using an electrostatic block that applies a negative voltage to the needle electrode. Figures 4 to 6 are samples showing the recording suitability of Comparative Example 1.
This is a sample showing the recording suitability when one dot recording is performed on the electrostatic recording medium described in Sections 3 to 3 using an electrostatic plotter that applies a negative voltage to the needle electrode.

Claims (1)

[Claims] In an electrostatic recording medium formed by forming a dielectric layer on a conductive support, the surface of the dielectric layer is rubbed with an insulating substance and a conductive substance before applying an electrostatic charge for forming a recorded image,
An electrostatic recording material characterized in that an electrostatic charge having a polarity opposite to that of a charge applied for a recorded image is formed in advance on the surface of the dielectric layer.