JPH059021B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in electrostatic recording materials, particularly electrostatic recording materials suitable for electrostatic facsimiles for high-density recording such as 400 dots/inch, electrostatic plotters, etc. It's about the body.

(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 favorably used for optical communication, facsimiles and printers as computer terminal devices, and even as output for CAD, etc., which is a design technology using computers.

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. At the conventional recording density of 200 dots/inch, there was no particular problem in the occurrence of the discharge itself, probably because the area of each recording needle was sufficient. However, using conventional electrostatic recording material, only 400 dots/
When performing high-density recording such as inches, 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 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 material used in a high-density electrostatic recording method such as 400 dots/inch, and is an electrostatic recording material that can obtain 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 charge is generated on the surface of the dielectric layer for some reason, it is necessary to remove it. At first glance, the present invention is an idea that goes against such common technical knowledge, but before applying electrostatic charges for forming a recorded image, electrostatic charges of opposite polarity to the applied charges are brought into a desired distribution state. This was achieved by discovering that charging the battery eliminates thin wire dropout and abnormal discharge.

The present invention is 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 discharging from a multi-needle electrode, By rubbing the surface of the dielectric layer with a substance that can be charged to a positive polarity and a substance that can be charged to a negative polarity through friction treatment, or a mixture of these substances, an application for recording images is applied to the surface of the dielectric layer in advance. This is a method for producing an electrostatic recording material, characterized by forming an electrostatic charge having a polarity opposite to that of the electric charge.

(Function) The friction treatment substance used to form an electrostatic charge of opposite polarity to the charge applied for recording images on the surface of the dielectric layer in advance in the above configuration is selected as appropriate depending on the composition of the dielectric layer, and for example, polymethyl methacrylate. The treatment substance for positively charging the dielectric layer consisting of a (1:1:1) mixture of polybutyl methacrylate and calcium carbonate includes polymethyl methacrylate, polybutyl methacrylate, polystyrene, methyl methacrylate/ethyl acrylate copolymer, There are butyral resins, polyesters, aluminum, ceramics, etc., and the treated substances to be negatively charged include styrene/methyl methacrylate copolymers, styrene/butyl methacrylate copolymers, etc. Processing substances that positively charge a dielectric layer made of a mixture of polymethyl methacrylate and calcium carbonate by friction treatment include butyral resin, styrene-methyl methacrylate copolymer, etc., and processing substances that negatively charge the dielectric layer include polybutyl methacrylate,
There are polyester, polystyrene, etc. Furthermore, treatment substances that positively charge the dielectric layer made of a mixture of polymethyl methacrylate and clay by friction treatment include butyral resin, styrene/methyl methacrylate copolymer, etc., and treatment substances that negatively charge the dielectric layer include polymethyl methacrylate. Examples include butyl methacrylate and polystyrene. By mixing inorganic pigments such as calcium carbonate, clay, silica, plastic pigments, surfactants, etc. with such treatment substances, desired charges can be efficiently obtained.

First, the dielectric layer is subjected to friction treatment at least once with a treatment substance that charges the dielectric layer to a positive polarity and a treatment substance that charges the dielectric layer to a negative polarity, thereby forming a recording image charge applied by an electrostatic recording device. will explain the case where electrostatic charges of opposite polarity are formed.

If the charge for recording images applied by the electrostatic recording device is of negative polarity, the dielectric layer is usually first subjected to friction treatment with a substance that charges it to positive polarity. 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 the dielectric layer is further subjected to friction treatment with a substance that charges the dielectric layer to a negative polarity, the spread of each positive charge distributed in an island shape becomes approximately 1~
300μ, and as a result, it is possible not only to completely eliminate thin lines, especially thin lines missing during one-dot recording, but also to extremely reduce the number of abnormal discharges that occur particularly often during one-dot recording. At this time, if the maximum diameter of each charge is less than 1μ, the effect of preventing thin wires from falling out cannot be obtained.
If the diameter is 300μ or more, abnormal discharge will occur, so it is preferable that the maximum diameter of each charge is in the range of approximately 1 to 300μ, and more preferably adjusted to a range smaller than the diameter of each recording stylus. Good recorded images can be obtained. Incidentally, the improvement effect obtained by the specific friction treatment according to the present invention is observed even one year after the treatment.

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 It is thought that when recording by applying negative polarity, the discharge starting voltage is lower than when recording without forming a positive electrostatic charge in advance, so a more reliable discharge occurs. .

In addition to the method described above, the treatment of the present invention can also be carried out by rubbing the dielectric layer at least once with a mixture of a treatment substance that charges it to an electrostatic charge and a treatment substance that charges it to a negative polarity. . Here, the term "hybrid" refers to a mixture of a treatment substance that charges the dielectric layer to a positive polarity and a treatment substance that charges the dielectric layer to a negative polarity.
Substances having both in one molecule are also included.

The charging state in each friction treatment step can be controlled by adjusting the composition of each treatment substance, the strength of friction pressure, the number of times of treatment, the speed of friction, etc. Such friction treatment is performed by applying the treatment substance to a molded body such as a roll or plate, or applying it to a sheet support and winding it around a roll. Manufacturing process,
It may be carried out in any step of the finishing step or even by a processing device built into the electrostatic recording device. Treatment is usually performed by pressing a treatment substance against the surface of the dielectric layer of a moving electrostatic recording medium. If the treatment substance is in the form of a roll, performing friction treatment while rotating will prevent scratches on the surface of the dielectric layer. It can be prevented. Friction treatment can also be performed without causing scratches by pressing a sheet-like treatment material against a moving electrostatic recording medium while sliding it on a roll-like support.

The above description has mainly focused on the electrostatic recording method in which the applied charges for recorded images are of negative polarity, but of course, even in the electrostatic recording method in which the applied charges for recorded images are of positive polarity, electrostatic charges of the opposite polarity, that is, negative polarity, can be used. A similar effect can be obtained by forming on the surface of the dielectric layer.

The conductive support for forming the electrostatic recording medium may be an inorganic salt such as sodium chloride, a cationic polymer electrolyte such as povinylbenzyltrimethylammonium chloride, an anionic polymer electrolyte, a surfactant, or Impregnate or apply metal oxide semiconductor powder such as zinc oxide or zinc oxide treated to make it conductive, and reduce the surface resistivity to 10 ⁵ to ^{10 11} Ω.
Paper, plastic film, cloth, etc. are used. As the resin for the dielectric layer constituting the electrostatic recording medium, insulating resins such as methacrylic acid derivatives such as methyl methacrylate and butyl methacrylate, various polymers such as acrylic esters, and butyral resins alone or in mixtures are used. Examples of spacer pigments to be mixed with this include calcium carbonate, titanium oxide, amorphous silica, clay, and plastic pigments.

Examples of the present invention will be described below, but it goes without saying that the present invention is not limited to these Examples.

(Example) Preparation of electrostatic recording material Recording material A: Calcium carbonate powder with an average particle size of 5 μm, polymethyl methacrylate resin, and polybutyl methacrylate resin were mixed in a ratio of 2:2:6 on a conductive-treated support. A dielectric layer was formed by applying the paint prepared in the above manner to a dry weight of 5 g/m ² to form an electrostatic recording medium.

Recording medium B: The average particle size is
A paint prepared by mixing 5 μm of calcium carbonate powder and polymethyl methacrylate resin in a 1:1 ratio was applied to give a dry weight of 5 g/m ² to form a dielectric layer, thereby constructing an electrostatic recording medium.

Friction treatment method Place the electrostatic recording material on a glass plate with the dielectric layer facing up, and use the weight of the friction treatment roll (pressure
The electrostatic recording material was rubbed at a speed of 10 m/min (260 g/cm ² , contact width approximately 3 mm).

Observation of electrostatic charge distribution state using an electron microscope A secondary electron image was observed using an electron microscope (JEOL JSM-T-300) at an accelerating voltage of 2 kilovolts.
(Positive electrostatic charges are expressed in black, and negative electrostatic charges are expressed in white.) Recording method Electrostatic plotter EP-101 manufactured by Matsushita Electric Transmission Co., Ltd. (A negative electrostatic charge is applied with a recording needle to form an image)
A thin line of one dot was recorded.

Example 1 A 3:1 copolymer of styrene/methyl methacrylate and a polymethyl methacrylate resin were mixed at a ratio of 3:1 and coated at 10 g/m ² on high-quality paper.
The electrostatic recording material A was subjected to the friction treatment by winding it around a polystyrene roll-shaped body (2 kg) with the coated side facing outward to obtain a roll for friction treatment. Each charge had a positive polarity, and its maximum diameter was in the range of 1 to 300 μm, and there was almost no occurrence of thin line omissions or abnormal discharges, indicating good recording suitability (FIG. 1).

Example 2 Polystyrene resin roll (2Kg) with a diameter of 100mm
The electrostatic recording material A was subjected to a friction treatment.

Furthermore, for this electrostatic recording medium, a 3:1 copolymer of styrene and methyl methacrylate was added to high-quality paper.
The product coated with 10 g/m ² was wound around a polystyrene roll-shaped body having a diameter of 100 mm with the coated side facing outward to form a roll for friction treatment, and friction treatment was performed. Each electrostatic charge had a positive polarity and a maximum diameter in the range of 1 to 300 μm, and there was almost no occurrence of thin line omissions or abnormal discharges, indicating good recording suitability (FIG. 2).

Example 3 A 1:1 mixture of butyral resin and polystyrene resin was coated on high-quality paper at 10 g/m ² and the diameter was 100.
The electrostatic recording material B was subjected to friction treatment by winding it around a polystyrene roll-shaped molded product having a diameter of 1.2 mm, with the coated side facing outward, to use as a roll for friction treatment.

Each electrostatic charge has positive polarity, and its maximum diameter is 1 to
It was in the range of 300μ, and showed good recording suitability with almost no occurrence of thin lines or abnormal discharge (Figure 3).

Comparative Example 1 Electrostatic recording material A and electrostatic recording material B were used without being subjected to friction treatment. No electrostatic charge was observed under an electron microscope. In addition, electrostatic recording material A (Fig. 4) and electrostatic recording material B
(FIG. 5), thin line omissions and abnormal discharge were observed, and the thin line omissions were particularly remarkable, indicating poor recording suitability.

Comparative Example 2 Electrostatic recording material A and electrostatic recording material B were each subjected to friction treatment using a polystyrene roll-shaped molded product (2 kg) having a diameter of 100 mm. The electrostatic recording material A had a positive electrostatic charge, and many had a maximum diameter of 300 μm or more. Although the thin line omission was improved, there were many abnormal discharges and the recording suitability was poor (Fig. 6). The electrostatic recording material B had a negative electrostatic charge, and many had a maximum diameter of 300 μm or more. Since the electrostatic charge had the same polarity as the applied voltage for recording, the recording aptitude was not improved and recording with noticeable thin line omissions was obtained (FIG. 7).

Comparative example 3 Aluminum roll (2Kg) with a diameter of 100mm
Electrostatic recording material A was subjected to friction treatment. The electrostatic charges were of positive polarity, and many had a maximum diameter of 300μ or more. Furthermore, although the problem of thin line omissions was improved, many abnormal discharges occurred and the recording suitability was poor (FIG. 8).

(Effects) The electrostatic recording material according to the present invention has the advantage of being able to obtain clear recorded images without thin line omissions or abnormal discharge even when used in high-density electrostatic recording methods such as 400 dots/inch. It was a record.

[Brief explanation of drawings]

Figures 1 to 3 show records of one-dot recording performed on the electrostatic recorder according to the present invention described in Examples 1 to 3 using an electrostatic plotter that applies a negative voltage to the needle electrode. 4 to 8 are samples showing the recording suitability obtained in the same manner using the electrostatic recording bodies described in Comparative Examples 1 to 3.

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 By rubbing the surface with a substance that is positively charged and a substance that is negatively charged, or a mixture of these substances, the surface of the dielectric layer is preliminarily charged with an electric charge for recording an image. A method for producing an electrostatic recording material, characterized by forming electrostatic charges of opposite polarity.