JPH02244159A - Electrostatic recording body - Google Patents

Abstract

PURPOSE:To obtain a high quality electrostatic recording body well-balanced as a whole by incorporating a specified Al compd. into a dielectric layer forming a recording layer. CONSTITUTION:A dielectric layer based on insulating resin and a pigment is formed on an electrically conductive support and at least one kind of Al compd. such as aluminum isopropylate, mono-sec. butoxy aluminum diisopropylate, aluminum sec. butyrate or aluminum ethylate is incorporated into the dielectric layer. the amt. of the Al compd. incorporated into the dielectric layer is preferably regulated to 0.01-4.0wt.% of the total solid content of the layer. A recording body having well-balanced quality is obtd.

Description

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

"Conventional 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.

In order to increase the recording density of the electrostatic recording material used in these electrostatic plotters, the resin forming the dielectric layer must be a homopolymer such as methyl methacrylate or styrene having a temperature of 40° C. or higher, or a homopolymer such as styrene. A method has been proposed to promote discharge from a multi-needle electrode by using a copolymer containing a large amount or by using a resin copolymerized with a small amount of a polar functional group such as acrylic acid.

Another method is to maintain good insulation even under high humidity by using pigments with high insulating properties and excellent hydrophobicity, such as calcium carbonate and barium sulfate, as spacer pigments contained in the dielectric layer. is proposed.

"Problems to be Solved by the Invention" However, the dielectric layer is required to have not only recording density but also practical properties such as fixing properties, curling, and blocking. - It is necessary to use ethylhexyl methacrylate in combination, which results in a decrease in the insulation properties of the dielectric layer and a decrease in recording density, resulting in lower overall quality characteristics.
However, there is still room for improvement. Furthermore, recording devices such as high-density electrostatic profilers use pigments with low insulating properties, such as kaolin and aluminum hydroxide, to reduce the occurrence of thin lines and abnormal dots, and to prevent friction fog, dye stains, etc. In order to prevent this, it is necessary to consider various recording conditions and developer characteristics, such as the need to use conductive pigments and hydrophilic additives, resulting in an overall well-balanced high quality. A suitable electrostatic recording medium has not yet been obtained.

As a result of intensive research in view of the current situation, the present inventors have found that
It has been discovered that by incorporating a specific aluminum compound into the dielectric layer constituting the recording layer of an electrostatic recording medium, the density of the recorded image can be improved extremely efficiently without deteriorating the practical characteristics or recording characteristics. , we have completed the present invention.

"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 provided on a conductive support. This is an electrostatic recording material characterized by containing at least one of the following.

"Function" In the present invention, the aluminate ester contained in the dielectric layer is a compound represented by the following general formula 2, and is obtained as a grease-like liquid or a solid compound.

CA1 (OR)s )n [wherein, R represents an alkyl group or an aryl group, and n is 3
Indicates an integer between ~5. ] Examples of the aluminum include aluminum isopropylate, mono-secondary-butoxyaluminum diisopropylate, aluminum secondary-butyrate, and aluminum ethylate.

The amount of these aluminate esters added to the dielectric layer is adjusted within the range of 0.01 to 4.0% by weight, preferably 0.1 to 2.0% by weight of the total solids of the dielectric layer. is desirable.

Incidentally, if the amount added is less than 0.01% by weight, the desired effect of improving recording density cannot be obtained, and if it exceeds 4.0% by weight,
Not only does the effect of improving recording density reach a saturation point, but the functional groups contained in the dielectric layer resin and the water in the solvent react with the aluminate ester to form aluminum salt bonds, causing the dielectric layer forming coating solution to deteriorate. There is a risk of causing gelation.

When the gelation phenomenon occurs, the smoothness of the surface of the resulting dielectric layer is impaired and the recording characteristics are deteriorated, and the formation of the dielectric layer itself may become difficult due to the increased viscosity of the coating liquid. Therefore, it is desirable to adjust the amount of aluminate ester added within the above range.

Since aluminate esters have extremely high reactivity, it is necessary to react selectively to the pigment surface. Therefore, it is necessary to add the insulating resin to the pigment dispersion dispersed in the solvent before adding it, or to treat the surface of the pigment with an aluminate ester in advance, and remove the excess unreacted material with an organic solvent such as benzene or xylene. It is desirable to incorporate it into the dielectric layer forming coating solution by a method of removing it.

When an aluminate ester is added by such a method, it reacts with attached water and hydroxyl groups present on the surface of the pigment, and acts preferentially on the surface of the pigment, so that the desired effect of the present invention can be achieved with a relatively small amount of addition. becomes possible.

Examples of pigments constituting the dielectric layer include clay, hallosite, hydrated hallosite, kaolinite, detsuite,
Examples include natalite, aluminum hydroxide, calcium carbonate, calcined clay, amorphous silica, alumina, calcined kaolin, barium sulfate, and titanium oxide.

The weight ratio of the pigment and insulating resin constituting the dielectric layer is 5:95 to 70:30, preferably 10:90.
~50: It is desirable to set the temperature within the range of about 50,
If the blending ratio of the pigment is less than these ratios, the gloss of the surface of the recording medium will increase to such an extent that the natural appearance will be impaired, and if it is too large, the recording density may decrease.

In addition, if the average particle diameter of the pigment is too large, it will be difficult to maintain an appropriate gap between the recording medium surface and the multi-needle electrode, which may cause white spots when recording all marks, and if it is too small, all marks will be recorded. Sometimes sticky spots occur, so
It is desirable to use a pigment having an average particle diameter of about 1 to 15 μm, preferably about 2 to 8 μm.

Examples of the insulating resin include methyl acrylate, methyl methacrylate, ethyl acrylate, isobutyl methacrylate, 2-ethylhexyl acrylate, and dimethacrylate.
- Acrylic esters and methacrylic ester copolymers such as ethylhexyl and decyl acrylate, and small amounts of functional groups such as acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, itaconic acid, acrylonitrile, and methacrylonitrile. Copolymerized copolymer, polyvinyl acetate, ethylene/vinyl acetate copolymer, butyral mJ
]L polyester resin, nitrocellulose resin, polystyrene, styrene/acrylic copolymer, styrene/methacrylic acid copolymer, vinylidene fluoride resin, silicone resin, epoxy resin, urethane resin, phenol resin, etc.

Among these, polyester resins and polymers containing butyl esters of acrylic acid or methacrylic acid are most preferably used because they improve the effect of improving recording density by using the aluminate ester of the present invention.

The dielectric layer is generally prepared using a coating liquid made by dissolving and dispersing an insulating resin or pigment in an organic solvent such as toluene, methyl ethyl ketone, xylene, or isopropyl alcohol using a bar coater, contra coater, gravure coater, curtain coater, champlex coater, roll coater, or the like. It is formed by coating on a conductive support using various coating devices such as a blade coater.

In addition, as the conductive support constituting the electrostatic recording medium, cationic polymer electrolytes such as polyvinylbenzyltrimethylammonium chloride, polydimethylallylammonium chloride, styrene acrylic acid triethylammonium chloride, polystyrene sulfonate, polyacrylic Metal semiconductor powder mixed with impurities such as acid, anionic polymer electrolyte such as polyvinyl phosphate, or zinc oxide or tin oxide is impregnated or coated with a binder, and the surface resistance is adjusted to approximately 10' - 10'' Ω. Paper, plastic film, synthetic paper, Japanese paper, cloth, etc. are used.

"Examples" Examples of the present invention will be described below, but the present invention is not limited to these Examples. Also, parts in examples are parts by weight.

Example 1 [Preparation of conductive support] A cationic polymer electrolyte [styrene acrylate triethylammonium chloride, Chemistat 7300 manufactured by Sanbe Kasei] was applied to the surface of a high-quality paper with a basis weight of 60 g/rrr at a dry weight of 4 g/rr. rd, applied to the back surface at 2 g/d, and smoothed to give a Bekk smoothness of 700 seconds to obtain a conductive support.

[Preparation of electrostatic recording medium]

A dielectric layer coating solution having the following composition was coated on the above support in an amount of 4 glrd (dry weight) to obtain an electrostatic recording material. In addition,
The coating liquid was prepared by dispersing kaolin in a toluene/MEK mixed solvent, adding AIPD, and then adding and mixing the insulating resin.

[Composition of dielectric layer coating liquid]

Toluene/MEK mixed solvent (1/1) 200 parts Kaolin (average particle size 3.5 μm) 15 parts Methyl methacrylate resin 55 parts Normal butyl methacrylate resin 30 parts Aluminum isopropylate (manufactured by Yoken Fine Chemical, AIPD)
0.5 parts Example 2 Aluminum secondary butyrate (manufactured by Yoken Fine Chemicals, ASBD) was used instead of AIPD, and aluminum hydroxide (average particle size 2.5 parts) was used instead of kaolin.
An electrostatic recording material was obtained in the same manner as in Example 1, except that 8 μm) was used.

Example 3 100 parts of kaolin was placed in a mortar, and 50 parts of a 10% xylene solution of aluminum ethoxide (manufactured by Yoken Fine Chemical Co., Ltd., aluminum ethoxide) was added little by little while stirring and mixing to treat the surface of the kaolin. A 1.2% surface-treated kaolin was prepared by washing with xylene, filtering, and drying. An electrostatic recording material was obtained in the same manner as in Example 1 except that this kaolin was used.

Example 4 The following materials were mixed.

Toluene/MEK mixed solvent 200 parts Calcium carbonate (average particle size 3.5 μm) 40 parts Amorphous silica (
Average particle size 1.5 μm) 5 parts styrene/butyl methacrylate/methyl methacrylate copolymer
55 parts Next, 3 parts of AIPD was added and mixed to the obtained mixed solution to prepare a dielectric layer coating solution. This coating liquid was applied onto a conductive support in the same manner as in Example 1 and dried to obtain an electrostatic recording material.

Example 5 An electrostatic recording material was obtained in the same manner as in Example 4, except that a polyester resin (Toyobo type, Vylon 20ss) was used instead of the styrene-acrylic copolymer.

Comparative example 1. 2 AIPD of Example 1 (Comparative Example 1), ASBD of Example 2
Two types of electrostatic recording materials were obtained in the same manner except that (Comparative Example 2) was not added.

Comparative Example 3 An electrostatic recording material was obtained in the same manner as in Example 3, except that during the surface treatment of kaolin, excess aluminum ethoxide was not washed with xylene and was used as it was.

Comparative Examples 4 and 5 The amount of AIPD added in Example 4 was changed to 0.005% (
An electrostatic recording material was obtained in the same manner as in Example 4, except that the content was 5.5% (Comparative Example 4) and 5.5% (Comparative Example 5).

The following quality evaluation tests were conducted on the 10 types of electrostatic recording bodies thus obtained. That is, recording was performed using a practical color electrostatic profiler (manufactured by Xerox Corporation, CE3424), and the recording density of the black pattern portion was measured using a Macbeth densitometer, and the results were as shown in the table below.

(Note) k+1): The coating liquid has extremely thickened* (21:
Although the coating liquid was converted into a pudding, the fixing properties, curling, and blocking suitability of the electrostatic recording materials obtained in each example were the same as those of the electrostatic recording materials that did not contain aluminate ester, indicating that they had good quality. was.

"Effect" As is clear from the above examples, the electrostatic recording medium of the present invention has significantly improved recording density without deteriorating practical characteristics or recording characteristics, and has an extremely well-balanced quality. It was a record.

Claims (1)

[Claims] An electrostatic recording material comprising a dielectric layer containing an insulating resin and a pigment as main components on a conductive support, characterized in that the dielectric layer contains at least one aluminate ester. Electrostatic recorder.