JPH03145650A - Electrostatic recording body - Google Patents

Abstract

PURPOSE:To obtain bright recorded images having a high density without generating white voids while the uniformity at the time of all mark recording is maintained by incorporating methyl silicon powder of a specific particle size into a dielectric layer. CONSTITUTION:The dielectric layer essentially consisting of an insulating resin and pigment is formed on a conductive base. The methyl silicon powder having 2 to 15 mum average particle size is incorporated into the dielectric layer. The methyl silicon powder has excellent dispersibility in an org. solvent and does not generate flocs in a solvent and, therefore, has the characteristic that the unequalness and white voids at the time of all mark recording hardly arise even with the powder of the large average grain sizes. A marked effect is obtd. particularly if the powder having such specific particle size is selectively used. The electrostatic recording body which has the high recording density, is free from the white voids and has the low polishing property of multistylus electrodes is obtd. in this way.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an electrostatic recording medium suitable for high-density electrostatic plotters such as 400 dots/inch, electrostatic factor plotters, electrostatic printers, etc. It is.

(Prior technology) Monochrome and color electrostatic recording methods using multi-needle electrodes are
In recent years, it has become popular as a plotting device for computer graphics output and CAD technology. The dielectric layer that makes up the recording medium used in these electrostatic recording methods uses highly insulating and hydrophobic pigments such as calcium carbonate and barium sulfate as spacer pigments, and is good even under high humidity conditions. It is designed to maintain good insulation properties.

However, when ordinary inorganic pigments are used as pigments for these dielectric layers, the resin block surrounding the multi-needle electrodes of the recording device is gradually scraped off during recording, causing scratches on the surface of the needle electrodes and shavings. Defects such as inducing abnormal discharge occur.

Therefore, methods have been proposed to use inorganic pigments such as kaolin and aluminum hydroxide with a Mohs hardness of 3 or less, but it is not possible to completely eliminate the abrasiveness of the pigments, and satisfactory results are not necessarily obtained. Not yet.

A method of using plastic powder with low abrasiveness has been considered, but since plastic powder is usually manufactured by methods such as frozen rice crushing, the particle size distribution is wide and it tends to contain coarse particles. Difficult to adjust as spacer pigment of moderate size. Therefore, electrostatic recording media using this material may lose uniformity when recording all marks, or may lose white spots and
-1 is likely to occur. Dry classification of plastic powder may also be considered, but in general, dry classification is difficult because plastic powder has high insulating properties and tends to generate static electricity.

Furthermore, there is a method in which plastic powder with a primary particle size of 1 μm or less is first agglomerated, then made into a large Fujicock, and then adjusted to an appropriate particle size by wet grinding or classification. Perhaps because the surface area of
When finished on a recording medium, the image density tends to decrease.
As expected, the current situation is that it has not been put into practical use.

(Problems to be Solved by the Invention) The present invention improves the various deficiencies of the prior art as described above, has low abrasiveness of multi-needle electrodes due to spacer pigments, maintains uniformity during all mark recording, and achieves white An object of the present invention is to provide an electrostatic recording material that does not cause omissions and can provide a high-density, clear recording-side image.

(Means for Solving the Problems) The present invention provides an electrostatic recording material in which a dielectric layer mainly composed of an insulating resin and a pigment is formed on a conductive support.
The electrostatic recording material is characterized in that the dielectric layer contains methyl silicon powder having an average particle diameter of 2 to 15 μ+71.

(Function) The present inventors have conducted extensive research on spacer pigments used in electrostatic recording materials, particularly on "Plastic Face 1'". And, nylon powder, acrylic resin powder, epoxy resin powder, polyester resin powder, polyethylene powder, polyacrylic acid powder, polyamide powder, vinyl chloride powder, methacrylic resin powder, methyl methacrylic powder, MBS resin powder, As a result of repeated studies on various plastic pigments such as NBR resin powder and 4-fluoride resin powder, we found that methyl silicon powder has excellent water repellency and hydrophobicity, and is insoluble in organic solvents. 1
Among these, it has been found that this is the most suitable for the initial purpose of the present invention.

In addition, methyl silicon powder has excellent dispersibility in organic solvents and does not form aggregates in organic solvents, so even if the average particle size is large, unevenness and white spots when recording all marks are difficult to occur. have. And especially,
It has become clear that the selective use of powder having a specific particle size can provide a remarkable effect for the purpose of the present invention, and the present invention has been completed.

Accordingly, in the present invention, methyl silicon powder having an average particle diameter of 2 to 15 μm is selectively contained in the dielectric layer. Incidentally, methyl silicon powder with a diameter of less than 2 μm has poor dispersibility and tends to form aggregates.
If it exceeds m, it becomes difficult to maintain an appropriate spacer interval as a spacer pigment for an electrostatic recording medium.

Note that even if the average particle diameter is within the above range, 44μ
It is desirable to avoid the inclusion of giant particles exceeding m, and it is desirable to keep the content below 1%. Also,
The specific surface area of methyl silicon powder is 1 to 30rrT/g
Methyl silicon powder having a specific surface area within this range is particularly preferred because it causes less reduction in image density.

In the present invention, the above-mentioned specific plastic powder is contained in the dielectric layer, but various inorganic pigments may also be used in combination to further satisfy the recording characteristics of the electrostatic recording medium. .

Pigments that can be used in combination include, for example, clay, halisite, hydrated herosite, kaolinite, detsuite, natalite, aluminum hydroxide, calcium carbonate, calcined clay, calcined kaolin, amorphous silica, Al≧su, barium sulfate. , titanium oxide, etc.

By the way, the degree to which the multi-needle electrode surface deteriorates due to polishing is
Since it depends on the material constituting the electrode, for example, in the case of a multi-needle electrode made of a material that is easily polished, it is desirable that the average particle size of the inorganic pigment used in combination be smaller than the average particle size of the methyl silicon powder. Then, the average particle size of the methyl silicon powder is adjusted to 6 to 15 μm, preferably about 8 to 12 μm, and the average particle size of the inorganic pigment used in combination is adjusted to 0.5 μm.
It is desirable to adjust the thickness to about 6 μm.

On the other hand, in the case of a multi-needle electrode with low abrasiveness, an inorganic pigment having an average particle diameter of about 6 to 15 μm can be used in combination.

However, it is preferable to keep the amount used to a minimum.
It is desirable to use a large amount of methyl silicon powder having an average particle size of about 5 μm.

In any case, the blending ratio of the methyl silicon powder and the inorganic pigment is appropriately determined in consideration of the polishability of the electrode.

In the electrostatic recording material of the present invention, the blending ratio of pigments, including methyl silicon powder, in the dielectric layer is in the range of 10 to 60% by weight, more preferably 15 to 5% by weight of the total solid content of the dielectric layer.
It is adjusted to a range of 0% by weight. However, if it is less than 10% by weight, it will be difficult to adjust the smoothness of the resulting recording medium.
On the other hand, if it exceeds 60% by weight, the recording density may decrease or white spots may appear.
There is a possibility that ``no'' will occur more easily.

Examples of the insulating resin forming the dielectric layer include acrylic esters and methacrylic esters such as methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, isobutyl methacrylate, and acrylic acid, methacrylic acid,
Copolymers with small amounts of functional groups such as maleic anhydride, crotonic acid, itaconic acid, acrylonitrile, methacryloni-1-lyl, vinyl acetate, ethylene-vinyl acetate copolymers, butyral resins, polyester resins, nitrocellulose, polystyrene , styrene-acrylic copolymer, styrene-methacrylic acid copolymer, vinylidene fluoride, silicone resin, epoxy resin, styrene/butadiene copolymer, vinyl acetate-methacrylate copolymer, vinyl acetate crotonate ester Examples include copolymers, vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-acrylonitrile copolymers, urethane resins, stearylmethacrylic-chloroprene copolymers, and phenol resins.

The dielectric layer is generally coated with a coating liquid prepared by dissolving and dispersing the dielectric layer resin or pigment in an organic solvent such as toluene, methyl ethyl ketone, xylene, or isopropyl alcohol, using a bar coater, Con I/La coater, gravure coater, curtain coater, or jean coater. Plex coater, roll coater
It is formed by coating on a conductive support using a coating device such as , Play 1 coater or the like.

Examples of the conductive support constituting the electrostatic recording medium include polyvinylhensyltrimethylammonium chlorite,
Cationic polymer electrolytes such as polydimethylallylammonium chloride, styrene acrylate triethylammonium chloride, anionic polymer electrolytes such as polystyrene sulfonate, polyacrylate, polyvinyl phosphate-1, etc., or zinc oxide, tin oxide. Impregnated or coated with a metal semiconductor powder mixed with impurities, etc., along with a binder if necessary, the surface resistance is reduced to 105.
~ Paper with a resistance of about 1011 ohms, plastic twill 1
1. Synthetic paper, Japanese paper, cloth, etc. are used.

(Example) The present invention will be described in more detail with reference to Examples below, but it is of course not limited to these Examples. Further, parts in the examples indicate parts by weight.

Example 1 [Preparation of conductive support] On both sides of a high-quality paper with a basis weight of 60 g, a cationic polymer electrolyte, Kean Stull-7300 (manufactured by Sanyo Chemical Co., Ltd.) was applied in dry weight of 4 g on the front side and on the back side. 2g was applied to the side. after that,
A conductive support having a Bekk smoothness of 700 seconds was obtained by smoothing treatment.

[Adjustment of electrostatic recording medium]

On the surface side of this support, 4 g of a dielectric layer coating liquid having the following composition was applied in dry weight to obtain an electrostatic recording material.

1-L/MEK mixed solvent (1/) 200 parts Methyl silicon powder (average particle size 8 μm) 25 parts Methyl methacrylate 1/resin 45 parts N-Butyl methacrylate 1/resin 30 parts Example Two types of electrostatic recording bodies were obtained in the same manner as in Example 1, except that the average particle diameter of the 2.30 methyl silicon powder was 13 μm (Example 2) and 31 parts m (Example 3).

Example 4 An electrostatic recording material was obtained in the same manner as in Example 1 except that a dielectric layer coating liquid having the following composition was used.

Toluene/MEK mixed solvent (1/1) 200 parts Methyl silicon powder (average particle size 11 μm) 10 parts Calcium carbonate (average particle size 3.5 μm) 30 parts Methyl methacrylate-1 resin 40 parts n-butyl methacrylate resin 20 Example 5 An electrostatic recording material was obtained in the same manner as in Example 1 except that a dielectric layer coating liquid having the following composition was used.

Toluene/MEK mixed solvent (], /1) 200 parts Methyl silicon powder (average particle size 3 μm) 25 parts Aluminum hydroxide (average particle size 37! m) 10 parts Amorphous silica (average particle size 1.5 μm) 5 Part ■ Methyl methacrylate resin 40 parts N-butyl methacrylate resin 20 parts Comparative Example 1.2 Implemented except that the average particle diameter of the methyl silicon powder was 0.8 μm (Comparative Example 1) and 17 μm (Comparative Example 2) Example 1
Two types of electrostatic recording bodies were obtained in the same manner as above.

Comparative Example 3 An electrostatic recording material was obtained in the same manner as in Example 1, except that calcium carbonate (average particle size: 3.5 μm) was used instead of methyl silicon powder.

Comparative Example 4 Aluminum hydroxide (
An electrostatic recording material was obtained in the same manner as in Example 1 except that particles having an average particle diameter of 8 μm were used.

Comparative Example 5 An electrostatic recording material was obtained in the same manner as in Example 1, except that nylon powder (average particle size: 12 μm) was used instead of methyl silicon powder.

Comparative Example 6 Polyacrylonyl l-I instead of methyl silicon powder
An electrostatic recording material was obtained in the same manner as in Example 1, except that Jul powder (average particle size: 3 μm) was used.

The following evaluation tests were conducted on the 11 types of electrostatic recording bodies thus obtained, and the results are listed in the table.

[Evaluation of recording characteristics]

Recording was performed using an electrostatic plotter CV-1424 (manufactured by Parzatic Co., Ltd.), and the recording density and degree of occurrence of white spots were evaluated.

The evaluation criteria for the occurrence of white spots were as follows.

O: Hardly occurred.

×It occurs on the knee surface.

[Evaluation of polishability]

While pressing the electrostatic recording medium at 5 kg/m with a presser roll with a rubber hardness of 60 on a multi-needle electrode manufactured by Matsushita Electric Transmission Co., Ltd.
After recording, the surface of the multi-needle electrode was measured with a stylus-type smoothness meter, and the maximum depth was evaluated.

3 Table (Effects) As is clear from the results in the table, the electrostatic recording materials obtained in each example of the present invention all had high recording density, no white spots in the recorded image, and no polishing of the multi-needle electrode. It was an electrostatic recording material with low performance.

Claims (2)

[Claims] (1) In an electrostatic recording material formed by forming a dielectric layer mainly composed of an insulating resin and a pigment on a conductive support, the dielectric layer contains methyl silicon powder with an average particle size of 2 to 15 μm. An electrostatic recording medium characterized by: (2) The electrostatic recording material according to claim 1, wherein the pigment content in the dielectric layer is 10 to 60% by weight of the total solid content of the dielectric layer including methyl silicon powder.