JPS63243944A - Electrostatic recording body - Google Patents

Abstract

PURPOSE:To prevent the untransfer of thin lines and abnormal electric discharge during high density recording by using resins which are positively and negatively chargeable by triboelectric charge in combination as the insulating resin of a dielectric layer and by previously generating electrostatic charges whose polarity is reverse to the polarity of electrostatic charges impressed for recording on the surface of the dielectric layer by rubbing. CONSTITUTION:When a dielectric layer contg. a pigment and insulating resin is formed to obtain an electrostatic recording body, resins which are positively and negatively charged when rubbed with a rubbing material are used in combination as the insulating resin. Electrostatic charges whose polarity is reverse to the polarity of electrostatic charges impressed for recording are previously generated on the surface of the dielectric layer by rubbing with the rubbing material. The previously generated electrostatic charges are insularly distributed, the size of each of the charges is 1-300mum and the charges are nearly uniform. In case of 1 dot thin line recording with an electrostatic recording device, the recording body forms a clear image without causing the untransfer of thin lines of abnormal electric discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrostatic recording medium suitable for high-density recording electrostatic facsimiles such as 400 dots/inch, electrostatic printers, electrostatic plotters, etc. .

(Prior art) Along with advances in communication technology, electrostatic recording has been widely used as a recording method that simultaneously satisfies high-speed recording and high image quality. Examples include fax machines and printers. Particularly in recent years, electrostatic printers and electrostatic plotters capable of high-density recording have been favorably used for outputting drawings such as CAD systems for designing and drawing using computers.

The multi-needle electrode recording method most commonly used in electrostatic recording methods includes single-sided control type and double-sided control type, but in both cases, recording of about 200 dots/inch is mainly used for recording text. There was no particular problem in the generation of discharge itself, probably because the area of each needle electrode was sufficient in terms of density.

However, when high-density recording of about 400 dots/inch is performed using a conventional electrostatic recording material, mainly for the purpose of recording drawings, when thin lines are drawn, normal discharge does not occur and the recording is not recorded after development. A so-called thin line wave phenomenon occurs where a portion appears, and conversely, depending on the location, the discharge may be as small as 1 part of the area of each needle electrode.
0 times or more, so-called abnormal lightning discharge occurs in which abnormally bulging dots appear in the thin line after development, and good recording cannot be obtained.

(Problems to be Solved by the Invention) An object of the present invention is to provide an electrostatic recording medium that does not cause thin line omission or abnormal discharge in high-density recording such as 400 dots/inch.

(Means for Solving the Problem) The inventors of the present invention believe that there is a limit to the degree of improvement in the above-mentioned problem by considering only the structure of the recording medium. conducted research. Incidentally, it has been conventional common 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. At first glance, the present invention is based on an idea that goes against this common technical knowledge, but the inventors of the present invention have proposed that before applying electrostatic charges for forming a recorded image, they should be charged with an electrostatic charge of the opposite polarity to the applied charges. We have been considering this with the idea that it might be a solution to abnormal electrical discharges. As a result, we have arrived at an invention consisting of the following configuration.

The present invention provides an electrostatic recording material having a dielectric layer containing a pigment and an insulating resin, in which the insulating resin includes a resin that is positively charged when rubbed with a friction treatment material and a resin that is negatively charged when rubbed with a friction treatment material. Electrostatic recording characterized in that at least one of each type is used, and an electrostatic charge having a polarity opposite to that previously applied for recording is formed on the surface of the dielectric layer by friction with a friction treatment material. It is the body.

(Function) In the present invention, the treatment materials for rubbing the surface of the dielectric layer include polyethylene resin, polypropylene resin, polystyrene resin, polyether resin, polyvinyl chloride resin, polymethyl methacrylate resin, melamine resin, urea resin, and phenol resin. There are resins, epoxy resins, amino resins, imide resins, etc., and among these, ease of processing as a processing material, wear resistance, ease of generating static charge when rubbed, and static electricity distributed on the dielectric layer Because of the ease of controlling the charge diameter, thermosetting resins such as polystyrene resin, copolymer resins of styrene-acrylic acid derivatives or styrene-methacrylic acid derivatives, polymethyl methacrylate resin, epoxy resins, melamine resins, and urea-melamine are used. resin,
Thermosetting resins such as benzoguanamine resins are preferably used.

These treatment materials can be used alone or in a mixture.

Next, in the present invention, among the insulating resins constituting the dielectric layer of the electrostatic recording material, the resins that are positively charged when rubbed with the friction treatment material and the resins that are negatively charged are the resins that are negatively charged when rubbed with the friction treatment material. In relation to the pigment used in the dielectric layer, the polarity changes to positive or negative.

However, the charge polarity of the insulating resin does not change depending on the blending ratio of the pigment and the resin.

For example, the friction treatment material is polymethyl methacrylate resin,
When the pigment is calcium carbonate, positively charged insulating resins include methyl methacrylate-ethyl acrylate copolymer, and negatively charged insulating resins include polymethyl methacrylate, polybutyl methacrylate, and styrene.
Examples include methyl methacrylate copolymer, polyester, polystyrene, and polyvinyl butyral.

In addition, when the friction treatment material is polymethyl methacrylate resin and the pigment is fired resin, positively charged insulating resins include polymethyl methacrylate, methyl methacrylate-ethyl acrylate copolymer, polybutyl methacrylate, etc. Examples of the electrically charged insulating resin include styrene-methyl methacrylate copolymer, polyester, polystyrene, and polyvinyl butyral.

Furthermore, the friction treatment material is polymethyl methacrylate resin,
When the pigment is silica, polymethyl methacrylate, methyl methacrylate-ethyl acrylate copolymer, polybutyl methacrylate, styrene-methyl methacrylate copolymer, polyester, polystyrene, polyvinyl butyral, etc. are negatively charged insulating resins.

Next, when the friction treatment material is polystyrene resin and the pigment is calcium carbonate, positively charged insulating resins include methyl methacrylate-ethyl acrylate copolymer, polybutyl methacrylate, styrene-methyl methacrylate copolymer, polyester, and polystyrene. etc., and negatively charged insulating resins include polyvinyl butyral and the like.

In addition, when the friction treatment material is polystyrene resin and the pigment is fired resin, positively charged insulating resins include methyl methacrylate-ethyl acrylate copolymer heavy polybutyl methacrylate, styrene-methyl methacrylate copolymer, polyester, etc. Examples of negatively charged insulating resins include polystyrene and polyvinyl butyral.

Furthermore, when the friction treatment material is polystyrene resin and the pigment is silica, positively charged insulating resins include polymethyl methacrylate, methyl methacrylate-ethyl acrylate copolymer, styrene-methyl methacrylate copolymer, polyester, etc. Examples of negatively charged insulating resins include polybutyl methacrylate, polystyrene, and polyvinyl butyral.

Accordingly, the present invention uses a pigment in the dielectric layer, and at least one type of resin that has a different friction charge polarity when mixed with the pigment, and a charge applied to the surface of the dielectric layer in advance for recording. By forming electrostatic charges of opposite polarity by friction between the friction treatment material and the surface of the dielectric layer, excellent thin line removal and abnormal discharge improvement effects can be obtained. If it is formed on the dielectric layer in advance, when a developer with a polarity opposite to the applied charge for recording is used, a stain called fog will occur on the recorded image regardless of the resin composition of the dielectric layer, and fine line removal will have an improvement effect. I can't get it either. Therefore, in the present invention, it is necessary to adjust the mixing ratio of the resin so that an electrostatic charge having a polarity opposite to that of the applied charge for recording is formed by friction. That is, when the applied charge for recording is of negative polarity, the resin is blended so that positive charges are formed on the dielectric layer in advance by friction.

Among the above resins, for example, when a friction treatment material made of polymethyl methacrylate resin is used, calcium carbonate is used as the pigment contained in the dielectric layer, and methyl methacrylate-ethyl acrylate copolymer is used as the insulating resin. When using a mixture of polybutyl methacrylate or a friction treatment material made of polystyrene resin, a combination such as silica as the pigment contained in the dielectric layer and a mixture of polyester and polyvinyl butyral as the insulating resin is considered. It will be done.

Next, the charging state due to friction can be adjusted by the composition of the treatment material, the strength of the friction pressure, the number of times of treatment, the friction speed, etc. In the friction treatment, the treated material is usually formed into a roll-shaped or plate-shaped body, or is coated on a sheet-like support and wound around a roll, and the treated material is applied to the surface of the dielectric layer of an electrostatic recording medium that normally runs. Processing is carried out by pressing the electrostatic recording material, and the timing depends on the manufacturing process after forming the dielectric layer of the electrostatic recording medium, the finishing process, and also depending on the processing material built into the electrostatic recording device. good. If the treatment material is in the form of a roll, performing the friction treatment while rotating can prevent scratches on the surface of the dielectric layer.

Note that the electrostatic charge formed on the dielectric layer can be observed with an electron microscope. That is, when observing a secondary electron image with an accelerating voltage of about 2 kilovolts, positive electrostatic charges are expressed in black, and negative electrostatic charges are expressed in white. Electrostatic charges of opposite polarity to the electrostatic charges for the recorded image formed in advance according to the present invention are distributed in the form of islands, and the size of each charge is 1
It is approximately uniform within the range of μ to 300 μ. The tapering recording material is a one-dot thin line recorded by an electrostatic recording device.
Clear images without missing fine lines or abnormal discharge can be obtained. In the present invention, the charging state can be adjusted by the friction treatment conditions, but if the diameter of the electrostatic charge is too small, the effect of improving fine wire removal will be insufficient, and if it is too large, abnormal discharge will not be reduced, so each island-like charge It is preferable to adjust the maximum diameter to 1 μ to 300 μ, more preferably slightly smaller than the diameter of each needle electrode of the electrostatic recording device.

On the other hand, in a recording medium made of an insulating resin in which the polarity of charges generated by friction is only one, the electrostatic charges of opposite polarity to the electrostatic charges for the recorded image previously formed on the dielectric layer are formed in the form of a net or island. However, even when distributed like an island, the size of each charge is irregular, and when a thin line of one dot is recorded,
Although fine line omission is improved compared to a recording medium that is not subjected to any friction treatment, abnormal discharges are significantly increased compared to a recording medium that is not subjected to any friction treatment.

Although it is not necessarily clear why the electrostatic recording material of the present invention provides excellent recording without thin line omissions or abnormal discharges, it is clear that when the dielectric layer is rubbed by the friction treatment material, it is possible to obtain good recording. Because it contains a resin that is charged positively and a resin that is negatively charged, the size, strength, and distribution state of the static charge generated by friction can be appropriately adjusted, and as a result, the discharge starts when forming a latent image. It is speculated that a voltage drop will occur and a more reliable discharge will occur.

The conductive support constituting the electrostatic recording medium may be an inorganic salt such as sodium chloride, a cationic polymer electrolyte such as polyvinylbenzyltrimethylammonium chloride, an anionic polymer electrolyte, a surfactant, or an oxidized polymer electrolyte. Impregnated or coated with metal oxide semiconductor powder such as zinc or zinc oxide that has undergone conductive treatment to increase the surface resistance to 105 to 1.
Paper, plastic film, cloth, etc. with a resistance of 0.011Ω are used.

(Examples) Examples of the present invention will be described below, but the present invention is not limited only to these Examples.

Further, unless otherwise specified, parts and % in the examples indicate parts by weight and % by weight, respectively.

Example 1 Preparation of recording medium: A cationic polymer electrolyte (trade name: Chemista Soto 6300
．． (manufactured by Sanyo Chemical Co., Ltd.) with an absolute dry weight of 3 g/m" and 2 g/m" on the back side.
m" to obtain a conductive support. On this conductive support, a dielectric layer paint having the following composition was applied and dried to a dry weight of 5 g/m, and electrostatic recording was performed. I got a body.

Toluene 200 parts Calcium carbonate powder 50 parts Methyl methacrylate-ethyl acrylate copolymer resin (copolymerization ratio 1:1)
25 parts polybutyl methacrylate resin 25
A charging polarity test was conducted on this recording medium, and a recording test was conducted after forming an electrostatic charge on the surface of the dielectric layer by friction.

Datsu 1” company UK polymethyl methacrylate resin roll (friction treatment material)
The surface of the dielectric layer of the electrostatic recording medium was rubbed 20 times, and the polarity of the potential was checked using a surface electrometer.

Shape J of "Snow" Place the electrostatic recording material on a glass plate with the dielectric layer facing up, and use the dead weight (2 kg) of a polymethyl methacrylate resin roll (friction treatment material) with a diameter of 100 mm to cover the surface. (pressure 260g/cm").

Friction treatment was performed at a speed of 10 m/min (contact width 3 mm) to form an electrostatic charge.

Electrostatic block for CAD system manufactured by Matsushita Electric Transmission - EP-1
A fine line of one dot was recorded with 01AI (a latent image is formed by applying a negative electrostatic charge using a needle electrode), and 50
The number of thin wire omissions and abnormal discharges in a cm thin wire was measured.

Comparative Example 1 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 1 except that the composition of the dielectric WJ paint was changed to the following.

Toluene 200 parts Calcium carbonate powder 50 parts Methyl methacrylate-ethyl acrylate copolymer resin (copolymerization ratio 1:1)
50 copies This recording medium was subjected to a charging polarity test in the same manner as in Example 1, and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction.

Comparative Example 2 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 1 except that the composition of the dielectric layer paint was changed to the following.

Toluene 200 parts Calcium carbonate powder 50 parts Polybutyl methacrylate resin 50 parts This recording medium was subjected to a charge polarity test in the same manner as in Example 1, and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction.

Comparative Example 3 A recording test was conducted in the same manner as in Example 1, except that no static charge was formed by friction on the surface of the dielectric layer of the recording medium.

Example 2 Preparation of recording material: 14g of dry dielectric layer paint with the following composition
A recording medium was obtained in the same manner as in Example 1, except that the coating was applied with a coating of 1.2 mm.

Methyl ethyl ketone 200 parts Silica powder 20 parts Polymethyl methacrylate resin 60 parts Polybutyl methacrylate resin
20 copies of this recording material were subjected to a charging polarity test and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction.

The surface of the dielectric layer of the electrostatic recording medium was rubbed 20 times with a polystyrene resin roll (friction treatment material) at 1J1υ, and the polarity of the potential was checked using a surface electrometer.

Transfer of electrostatic charge to the snow collector The electrostatic recorder was placed on a glass plate with the dielectric layer facing up, and the surface was coated using the weight (2 kg) of a polystyrene resin roll (friction treatment material) with a diameter of 100 mm. (pressure 260g/
cm", contact width 3 mm) at a speed of 10 m/min to form an electrostatic charge.

How to present the star court Same as Example 1.

Comparative Example 4 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 2 except that the composition of the dielectric layer paint was changed to the following.

Methyl ethyl ketone 200 parts Silica powder 20 parts Polymethyl methacrylate resin 80 parts This recording medium was subjected to a charging polarity test in the same manner as in Example 2, and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction.

Comparative Example 5 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 2 except that the composition of the dielectric layer paint was changed to the following.

Methyl ethyl ketone 200 parts Silica powder 20 parts Polybutyl methacrylate resin 80 parts This recording medium was subjected to a charging polarity test in the same manner as in Example 2, and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction.

Comparative Example 6 A recording test was conducted in the same manner as in Example 2, except that no static charge was formed on the surface of the dielectric layer of the recording medium due to friction.

Example 3 Preparation of recording medium: A dielectric layer paint having the following composition was subjected to dry fft
A recording medium was obtained in the same manner as in Example 1 except that the coating was applied at 4 g/m''.

Methyl ethyl ketone 200 parts Calcined leh powder 30 parts Polyvinyl butyral resin 40 parts Polyester resin
30 copies of this recording material were subjected to a charging polarity test and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction.

At 1J11, the surface of the dielectric layer of the electrostatic recording medium was rubbed 20 times with a roll made of polystyrene resin (friction treatment material), and the polarity of the potential was checked using a surface electrometer.

Place the electrostatic recording material on a glass plate with the dielectric layer facing up, and cover the surface with a polystyrene resin roll (100 mm in diameter).
Using the own weight (2 kg) of the friction treatment material (pressure 26
0 g/cm2. A charge was formed by friction treatment at a speed of 10 m/min (contact width 3 mm).

Star #Wipe armpit 1 wide Same as Example 1.

Comparative Example 7 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 3 except that the composition of the dielectric layer paint was changed to the following.

Methyl ethyl ketone 200 parts Calcined Ray powder 30 parts Polyester resin
70 copies This recording medium was subjected to a charging polarity test in the same manner as in Example 3, and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction.

Comparative Example 8 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 3 except that the composition of the dielectric layer paint was changed to the following.

Methyl ethyl ketone 200 parts Calcined Ray powder 30 parts Polyvinyl butyral resin 70 parts This recording medium was subjected to a charging polarity test in the same manner as in Example 3, and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction.

Comparative Example 9 A recording test was conducted in the same manner as in Example 3, except that no static charge was formed on the surface of the dielectric layer of the recording medium due to friction.

The above results are shown in Table 1.

Table 1 In Examples 1 to 3 according to the present invention, recordings with almost no thin line omissions or abnormal discharges were obtained.

On the other hand, with the recording material having a dielectric layer consisting only of pigment and positively charged resin (Comparative Examples 1 and 4.7), abnormal discharge was significant even after friction treatment, and Recording body having a dielectric layer (Comparative Example 2.5.8)
), even after abrasion treatment, there were many fine lines missing, fogging, and faintly colored stains on the entire margin area).

Furthermore, even if a positively charged resin and a negatively charged resin are mixed and used, recording materials that do not form static charges due to friction (Comparative Examples 3 and 6.9) have many fine line omissions and abnormal discharges, and both are suitable for recording. It was defective.

(Effects) The electrostatic recording material of the present invention is an excellent electrostatic recording material that can obtain clear recorded images without thin line omissions or abnormal discharge even in the case of high-density electrostatic recording such as 400 dots/inch. It was the body.

Claims (1)

[Claims] In an electrostatic recording material having a dielectric layer containing a pigment and an insulating resin, the insulating resin includes at least one resin that is positively charged when rubbed with a friction treatment material and one resin that is negatively charged when rubbed with a friction treatment material. 1. An electrostatic recording material characterized in that an electrostatic charge is used one by one, and an electrostatic charge having a polarity opposite to that previously applied for recording is formed on the surface of the dielectric layer by friction with a friction treatment material.