JP2527218B2 - Electrostatic recording body - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic recording material for high density recording, and more particularly to an electrostatic recording material used in a high density recording color electrostatic plotter.

(Prior Art) In recent years, along with the progress of communication means, there has been an increasing demand for an output method capable of high-density recording, and the electrostatic recording method is superior in image quality and recording speed. It is widely used in various fields such as system output or design design using computer graphics.

Currently, a color electrostatic plotter capable of high-density recording of about 400 dots / inch is commercially available, and the range of use of the color electrostatic plotter capable of obtaining clear color recording on a large screen is expanding. The color electrostatic plotter has four multi-needle electrode heads (cyan, magenta, yellow, and black), each equipped with a developing device, a single-pass system, and one multi-needle electrode and four developments for each color. There is a multi-pass system in which the developing solution is provided for each color or the developing solution is exchanged with only one developing apparatus. The multi-pass system is a multi-needle electrode head, which first forms a latent image of the first color on the electrostatic recording medium and develops it, then temporarily returns the electrostatic recording medium to the original position, and then forms a latent image of the second color and Develop.
This operation is repeated four times to obtain a color image.

In the high-density recording electrostatic plotter, there are problems such as missing dots during fine line recording and abnormal dots in the fine line (there is a point that the dot area reaches ten times or more that of normal discharge).
As a result of earnest studies on the factors that hinder the recording quality, the present inventors have found that the content of quartz is 2 as a pigment in the dielectric layer.
It was concluded that less than or equal to 5% kaolin or aluminum hydroxide should be the main spacer in the dielectric layer.
Such an improvement effect could not be obtained at all by using a pigment such as calcium carbonate, amorphous silica powder, starch, barium sulfate, etc. which have been used conventionally.

However, it has been revealed that problems such as fog stains and fixability of recording remain when the electrostatic recording material is used for a color electrostatic plotter. That is, as in the case of the monochrome plotter, the recording paper is passed only once,
If the development time is also short, it does not pose a problem, but in the case of a color electrostatic plotter, the surface of the recording material passes over the multi-needle electrode head and the developing device many times, and as a result, the surface of the dielectric layer is rubbed. After being developed, fog stains are accumulated after development, and the entire surface stains and streaky stains become noticeable. Further, if the fixability of the first color is insufficient when the recorded images are overlaid, the image of the first color is scraped off when the second color is developed,
There is a problem that baldness occurs.

(Problems to be Solved by the Invention) It is an object of the present invention to provide an electrostatic recording material having a high recording quality used in a color electrostatic plotter, free from fog stains, and having excellent fixability.

(Means for Solving the Problems) The present invention relates to an electrostatic recording body having a dielectric layer formed on a conductive support, the dielectric layer containing at least one of kaolin and aluminum hydroxide, and (A) Styrene, alkylstyrene or methacrylic acid methyl ester, (b) methacrylic acid butyl ester, (c)
(A) a copolymer in which each structural unit of a (meth) acrylic acid ester of an alcohol having 12 or more carbon atoms is essential
It is characterized by containing a mixture of a copolymer of two components of (b) and (c) and a polymer of the remaining one component, or a mixture of each polymer of (a), (b) and (c). It is an electrostatic recording body.

(Function) The average particle size of kaolin or aluminum hydroxide powder contained in the dielectric layer is appropriately 1 to 15 μm, and at least one of these pigments is arranged so as to determine the gap between the powder and the multi-needle electrode. When other pigments are used in combination, the effect of sufficiently suppressing the occurrence of fine line dropouts and abnormal dots is obtained unless the pigments used in combination are smaller than the average particle size of kaolin or aluminum hydroxide. I can't.

The kaolin used herein means a kaolin group mineral such as halloysite, hydrohalloysite, kaylonite, deckite and nacrite, and these may be used alone or in combination. Also, stearic acid, silane coupling agents, organic titanates such as tetraisopropoxy titanium,
It is also possible to use a material whose surface is treated with silicone or the like to facilitate dispersion in an organic solvent. Of these, kaolinite is particularly preferable because it has a particularly excellent effect of improving thin line removal. However, kaolin may contain quartz as an impurity, and if the amount is more than 2% by weight, abnormal dots will occur, so
It is preferably 2% or less.

On the other hand, the aluminum hydroxide is Al ₂ O ₃ · H ₂ O and Al ₂ O ₃ · 3H ₂ O is a crystalline aluminum hydroxide. When these are subjected to the same surface treatment as above, good organic solvent dispersibility and insulating properties can be obtained.

As the pigment, calcium carbonate, calcined clay, alumina, barium sulfate or the like can be used in combination within a range not hindering these properties, but those having a smaller average particle diameter than kaolin or aluminum hydroxide are preferable, and the average particle diameter is If they are equivalent, the amount used should be minimized.

The weight ratio of kaolin or aluminum hydroxide and the insulating resin contained in the dielectric layer is preferably 10:90 to 60:40,
More preferably, it is in the range of 15:85 to 40:60. When the amount of kaolin or aluminum hydroxide is small, it is difficult to maintain the gap between the recording body and the multi-needle electrode at an appropriate distance, and when the amount is too large, good recording density cannot be obtained due to deterioration of insulation.

In the present invention, since (a) styrene, alkyl styrene, or methacrylic acid methyl ester is used as the insulating resin contained in the dielectric layer, a high recording density can be obtained, and (b) methacrylic acid butyl ester can be used. It is possible to reduce recording stains that are particularly likely to occur in a color electrostatic plotter. Further, (c) alcohol (meth) acrylic acid ester having 12 or more carbon atoms is effective for improving toner fixing property and preventing peeling-off of images during color superposition. This is because the component swells in the hydrocarbon solvent used in the liquid developer,
It is presumed that the fixability is improved.

As alkyl styrene, α-methyl styrene, p-
Methyl styrene, m-ethyl styrene, o-butyl styrene, p-octyl styrene and the like are exemplified, and as the methacrylic acid butyl ester, n-butyl ester of methacrylic acid, iso-butyl ester, sec-butyl ester, tert-butyl ester. There are esters, etc. 12 carbon atoms
As the above alcohols, lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol,
Dodecyl alcohol, etc.

Each of the components (a), (b) and (c) does not necessarily have to be a copolymer, and a mixture of polymers of each of these components,
The same effect can be obtained by using a mixture of a two-component copolymer and another polymer.

The proportion of this multi-polymer or mixture can be changed according to the purpose, but usually (a) styrene, alkyl styrene, or (meth) acrylic acid methyl ester and (b) methacrylic acid butyl ester are each a multi-polymer or a The range of 10 to 90% by weight of the mixture is preferable, and the range of (c) (meth) acrylic acid ester of alcohol having 12 or more carbon atoms is preferably 1 to 40% by weight.
(C) If the amount of (meth) acrylic acid ester of alcohol having 12 or more carbon atoms is small, it is difficult to obtain sufficient fixability. If the amount is large, the liquid developer causes swelling of the dielectric layer and the surface of the recording material may be peeled off. .

In the present invention, the three components (a), (b) and (c) are essential, and the components exemplified below can be used in combination within a range that does not impair the effect. That is, acrylic acid esters and methacrylic acid esters such as methyl acrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, decyl acrylate, and acrylic acid. , Methacrylic acid, maleic anhydride, crotonic acid, itaconic acid, acrylonitrile, methacrylonitrile and the like may be copolymerized. Further, a known insulating resin can be mixed within a range that does not impair the effects of the present invention. As such a resin, vinyl acetate, ethylene vinyl acetate copolymer,
Vinyl chloride, vinyl chloride vinyl acetate copolymer, polyacrylic acid ester, polymethacrylic acid ester, butyral resin, polyester resin, nitrocellulose, polystyrene, styrene acrylic acid copolymer, styrene methacrylic acid copolymer, silicone resin , Vinyl acetate methacrylic acid copolymer and the like. These components are (a)
It is desirable that the amount is 1 to 10% by weight based on the three components (b) and (c).

The dielectric layer is usually formed by dissolving and dispersing an insulating resin or pigment in an organic solvent such as toluene or methyl ethyl ketone, and coating and forming it on a conductive support using a coating device such as a bar coater, a contra coater, or a gravure coater.

Incidentally, as the conductive support constituting the electrostatic recording medium, inorganic salts such as sodium chloride and calcium chloride, cations such as polyhinylbenzyltrimethylammonium chloride, polydimethyldiallylammonium chloride and styreneacrylic acid triethylammonium chloride The surface resistance is normally maintained by impregnating or coating a polyelectrolyte, or an anionic polyelectrolyte such as polystyrene sulfonic acid, polyacrylic acid, or polyvinyl phosphate, or metal semiconductor powder containing impurities such as zinc oxide or tin oxide. Paper, plastic film, synthetic paper, Japanese paper, etc., with a humidity of 10 5 to 9 9 Ω are used. The surface Bekk smoothness of the conductive support is preferably 200 seconds or more.

(Examples) Examples of the present invention will be described below, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight", respectively.

Example 1 Preparation of conductive support: Weighed 60 g / m ² of cationic polymer electrolyte (Chemistat 6300, Sanyo Kasei) on the surface of wood free paper 4 g / m ² on the front side and 2 g / m on the back side. ^{It was} coated so as to have a thickness of ^2, and passed through a super calender to give a Beck smoothness of 300 seconds to obtain a conductive support.

4g / m dry weight of the following dielectric layer paint on the conductive support
^The electrostatic recording material was obtained by applying ² to obtain an electrostatic recording material.

Toluene / MEK (50/50) mixed solvent 200 parts Kaolin (average particle size 3.5 μm, quartz content 0.2%) 15 parts Styrene / butyl methacrylate / cetyl methacrylate (25/60/15) copolymer 85 parts Implemented Example 2 An electrostatic recording material was prepared in the same manner as in Example 1 except that the dielectric layer coating composition was as follows.

Toluene / MEK (50/50) mixed solvent 200 parts Kaolin (average particle size 3.5 μm, quartz content 0.2%) 15 parts Styrene / butyl methacrylate / stearyl acrylate / methacrylic acid (35/55/5/5) Combined 85 parts Example 3 An electrostatic recording material was prepared in the same manner as in Example 1 except that the coating composition for the dielectric layer was changed to the following.

Toluene / MEK (2/1) mixed solvent 200 parts Aluminum hydroxide (average particle size 4.5 μm) 25 parts Styrene / butyl methacrylate / lauryl methacrylate / acrylic acid (45/40/10/5) copolymer 75 parts Example 4 An electrostatic recording material was prepared in the same manner as in Example 1 except that the coating composition for the dielectric layer was changed to the following.

Toluene / MEK (50/50) mixed solvent 200 parts Kaolin (average particle size 3.5 μm, quartz content 1.5%) 15 parts Calcium carbonate (average particle size 2.5 μm) 30 parts Methyl methacrylate / stearyl acrylate (85
/ 15) Copolymer 35 parts Polybutyl methacrylate 20 parts Example 5 Electrostatic recording was conducted in the same manner except that kaolin having an average particle diameter of 0.8 μm (quartz content 0.2%) was used instead of kaolin of Example 1. Got the body

Comparative Example 1 An electrostatic recording material was obtained in the same manner as in Example 1 except that amorphous silica (average particle size 2.1 μm) was used instead of kaolin.

Comparative Example 2 An electrostatic recording material was obtained in the same manner as in Example 1 except that 2.5% by weight of quartz was added to the kaolin of Example 1.

Comparative Example 3 An electrostatic recording material was obtained in the same manner except that a cetyl methacrylate / styrene (30/70) copolymer was used instead of the resin of Example 1.

Comparative Example 4 Instead of the resin of Example 3, lauryl methacrylate / butyl methacrylate / methacrylic acid (15/80/5) 7
An electrostatic recording material was obtained in the same manner except that 5 parts were used.

Comparative Example 5 Instead of the resin mixture of Example 4, butyl methacrylate / styrene / methacrylic acid (50/45/5) copolymer 55
An electrostatic recording material was obtained in the same manner except that parts were used.

Color electrostatic plotter (CE-342 for each electrostatic recording medium)
4, manufactured by Versatec).

Recording density: Measured with a Macbeth densitometer (manufactured by Macbeth Co.).

Dot removal evaluation standard (the number of fine lines missing per 1 m of line drawing) ◎ ... 0 ○ ○ 0 to 5 △… 6 to 20 ×… 20 or more Abnormal dot evaluation standard (number per 1 cm of line drawing) ◎… 5 or less ○… 6 to 10 △… 11 to 20 ×… 20 or more Fog stain evaluation criteria (value obtained by subtracting the density before recording from the density of the background after recording) ◎… 0.0 to 0.01 ○… 0.01 to 0.02 Δ: 0.02 to 0.05 ×: 0.05 or more Peeling of image surface (fixability) ◎: No peeling at all ○: Peeling slightly Δ: Peeling like tail ×: Whole surface peeling off (Effect) The electrostatic recording material of the present invention has a high recording quality, is free from missing fine lines, abnormal dots, and fogging, and is an electrostatic recording material having excellent fixability.

Claims (2)

(57) [Claims] 1. An electrostatic recording body having a dielectric layer formed on a conductive support, the dielectric layer containing at least one of kaolin and aluminum hydroxide, and (a) styrene, alkylstyrene or Methacrylic acid methyl ester, (b) Methacrylic acid butyl ester, (c)
(A) a copolymer in which each structural unit of a (meth) acrylic acid ester of an alcohol having 12 or more carbon atoms is essential
It is characterized by containing a mixture of a copolymer of two components of (b) and (c) and a polymer of the remaining one component, or a mixture of each polymer of (a), (b) and (c). Electrostatic recording body. 2. An electrostatic recording material according to claim 1, wherein kaolin has a quartz content of 2% by weight or less, an average particle diameter of 1 to 15 .mu.m, and aluminum hydroxide has an average particle diameter of 1 to 15 .mu.m. .