JPH0943865A - Electrostatic recording medium - Google Patents

Abstract

(57) [PROBLEMS] To provide an electrostatic recording medium having a good image uniformity by sequentially providing a conductive layer and a dielectric layer on a sheet-shaped support. SOLUTION: The Oken type smoothness of the surface of the dielectric layer is 10
It has a center line average roughness of 1.2 μm or less based on 0 to 700 seconds and JIS B 0601, and is suitable for recording by an electrostatic transfer system or an ion flow control system for transferring an electrostatic latent image on a photoconductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic recording medium used in an electrostatic recording system in which an electrostatic latent image is formed on the surface of a recording medium and then developed with toner. More specifically, according to the present invention, the electrostatic latent image is directly formed on the surface of the recording medium by the electrostatic transfer system for transferring the electrostatic latent image on the photoconductor or the recording system by the ion flow control system, and then slit development is performed. The present invention relates to an electrostatic recording medium having a good image uniformity in recording by developing with toner by a method such as suction type roll development and reverse roll development.

Further, according to the present invention, an electrostatic latent image is directly formed on the surface of the recording body by a recording system using an electrostatic transfer system for transferring an electrostatic latent image on a photoconductor or an ion flow control system.
The present invention relates to an electrostatic recording material used for a color printer, a color proofer, or the like that forms a high-definition color image by repeating a development process using a toner many times.

[0003]

2. Description of the Related Art In recent years, electrostatic recording materials have been developed to have higher definition of color images such as color printing machines, color printers and color proofers. Instead of the electrostatic recording method that forms an electrostatic latent image, an electrostatic transfer method that transfers an electrostatic latent image on a photoconductor, or an ion that directly forms an electrostatic latent image on the surface of a recording body using an ion stream. Flow control schemes have been developed.

In the conventional electrostatic recording method using electric discharge from electrodes, 400 dots per inch is the limit and only binary recording is possible, so that an image with high resolution cannot be obtained. On the other hand, although the electrostatic transfer method can perform binary recording, a maximum resolution of 1800 dots per inch or more can be realized, and the ion flow control method can change the size of one dot and the charge amount. It became possible to record high-definition images with gradation.

Although the method of forming an electrostatic latent image has changed greatly as described above, as a developing method, a method using toner continues to be used. In order to obtain a particularly high-definition image, it is preferable to use a wet toner having a particle diameter of submicron, rather than using a dry toner having a particle diameter of generally 7 μm or more.

The conventional electrostatic recording medium discharges in the state where the electrodes are in contact with the surface of the recording medium to form an electrostatic latent image. Therefore, it is known that the discharge distance is controlled by the unevenness of the surface of the dielectric layer so that the electrostatic latent image is favorably formed by the discharge from the electrode.

For this reason, Japanese Patent Publication No. 56-33703 and Japanese Patent Publication No. 63-56538 disclose that a specific spacer is added to the dielectric layer to maintain the discharge distance. Also JP-A-60-149047, by containing the following projections 100-300 dielectric layer surface 0.00126Mm ² per equivalent diameter 2 [mu] m, and a protrusion 30 to 100 amino equivalent diameter 3~10μm thin line It discloses that the omission and the generation of huge dots are eliminated. Furthermore, Japanese Unexamined Patent Publication No.
JP-A-3-276053 discloses that in order to stabilize an image, 300 to 1000 protrusions are provided per 1 mm ^{2 of the} dielectric layer surface, and the average height of the protrusions is 6 to 10 μm. .

On the other hand, in the electrostatic transfer method, an appropriate discharge distance is maintained when the photosensitive member on which a latent image is formed and the recording member are contacted and then separated. In the ion flow control method, the latent image head and the recording medium do not come into direct contact with each other. Therefore, in electrostatic recording by the electrostatic transfer method or the ion flow control method, it is not necessary to provide a discharge gap due to the unevenness of the surface of the dielectric layer.

In the electrostatic recording method of developing an electrostatic latent image with toner, the dielectric layer of the electrostatic recording body is formed of the highly insulating resin and the pigment which is the spacer as described above, but the toner is fixed. It is the portion of the highly insulating resin that forms the image, and generally the pigment does not fix the toner. Therefore,
In order to improve the recording density, it is effective to reduce the pigment content. Further, when a large pigment having a particle diameter of more than 10 μm is used, the toner adhesion at a fine level and the flow of the liquid toner in the developing section become non-uniform, so that the image uniformity is deteriorated, which is preferable. Absent. In order to improve the image uniformity, it is preferable to add a small amount of a pigment having a small particle size.

In the conventional electrostatic recording method utilizing the discharge from the electrode, since it is necessary to maintain the discharge distance, the surface of the recording medium is roughened, so that the amount of the pigment compounded and the particle size are reduced. there were. However, in the electrostatic transfer method and the ion flow control method, the compounding amount of the pigment and the particle size can be considerably reduced as compared with the electrostatic recording material of the conventional electrostatic recording method, and the recording density can be improved and the image uniformity can be improved. Can be expected to improve.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrostatic recording medium comprising a sheet-like support, a conductive layer, and a dielectric layer on the conductive layer. An object of the present invention is to provide an electrostatic recording body having a good image uniformity by recording by a control method.

[0012]

The electrostatic recording medium of the present invention comprises:
In an electrostatic recording body comprising a sheet-shaped support and a conductive layer and a dielectric layer provided in this order, the surface of the dielectric layer has an Oken type smoothness of 100 to 700 seconds, and a center line average roughness based on JIS B 0601. Is 1.2 μm or less.

The reason why the image uniformity of the electrostatic recording medium according to the present invention is good is that the electrostatic transfer system and the ion flow control system are different from the electrostatic recording system using the electrode discharge in the conventional method. Since it is not necessary to maintain a discharge distance between the recording medium and the electrophotographic recording medium, the blending amount of the pigment that originally does not adhere to the toner can be reduced, and recording can be performed even when the surface becomes highly smooth. It is considered that the unevenness of the image due to the unevenness of the flow of the liquid toner in the developing section can be reduced.

In order to set the Oken type smoothness of the dielectric layer according to the present invention to 100 to 700 seconds and the center line average roughness according to JIS B 0601 to 1.2 μm or less, a spacer added to the dielectric layer is used. This can be achieved by selecting the particle size and blending amount of the pigment for use, the coating amount of the dielectric layer and the pressure treatment of the calender.

If the Oken type smoothness of the dielectric layer is less than 100 seconds or the center line average roughness based on JIS B 0601 is larger than 1.2 μm, the uniformity of the image becomes poor, which is not preferable.

When the Oken type smoothness of the dielectric layer exceeds 700 seconds, the recording material may stick to the developing device, especially when using a suction type developing device, and paper passing may occur. Even if the paper is printed without problems, the residual developer cannot be removed by suction, and the paper is output in a wet state. Therefore, a large drying capacity is required, which is not preferable.

As described above, the dielectric layer according to the present invention is characterized by containing a spacer pigment and a highly insulating resin as main components.

Examples of spacer pigments to be mixed in the dielectric layer include clay, deckite, nacrite, kaolin, aluminum hydroxide, calcium carbonate,
Calcined clay, amorphous silica, alumina, calcined kaolin,
Barium sulfate, titanium oxide, inorganic pigments whose surface is treated with insulation, or crosslinked polystyrene, polyethylene, polypropylene, crosslinked methacrylic acid ester, benzoguanamine resin, silicone resin, epoxy resin,
Plastic pigments such as melamine resin and phenol resin can be used alone or in combination. Of these, plastic pigments are particularly preferable because they have better charging performance than other pigments and less leakage attenuation of electrostatic charge. The particle size of the pigment used for the dielectric layer is 1 to 10 μm.
m.

Examples of the highly insulating resin forming the dielectric layer include methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, isobutyl methacrylate, and methacrylic acid-2-. Acrylic ester copolymers such as ethylhexyl and methacrylic acid ester copolymers, vinyl acetate resins, ethylene-vinyl acetate copolymers, butyral resins,
Polyester resin, nitrocellulose, cellulose acetate, polystyrene, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, vinylidene chloride resin, vinyl chloride-chloride Vinylidene copolymer,
Phenolic resins and the like can be used alone or as a mixture of two or more kinds.

The Oken type smoothness of the dielectric layer is 100 to 7
In order to set the center line average roughness based on JIS B 0601 to 1.2 μm or less for 00 seconds, the mixing ratio of the spacer pigment and the high insulating resin is 0.5: 9 by weight.
9.5 to 20:80, preferably 2:98 to 15:85
In general, a pigment for spacer and a highly insulating resin are dispersed as a main component in a solvent such as toluene, methyl ethyl ketone, ethyl acetate or xylene to obtain a dielectric layer coating material.

The dielectric layer is formed by a conventional coating method using this dielectric layer coating material such as bar coater, contra coater, gravure coater, curtain coater, champlex coater, roll coater, blade coater and slit die coater. It can be formed by coating on a conductive layer provided on a sheet-like support with a suitable coating device and drying and solidifying with a hot air dryer.

The coating amount of the dielectric layer is 1 to 10 g / m ^2.
(Solid content), preferably in the range of ^{2 to} 6 g / m ² (solid content). Here, if it is less than 1 g / m ² (solid content),
When a coating film defect occurs and exceeds 10 g / m ² (solid content), the recording density decreases, which is not preferable.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The sheet-like support used in the present invention includes various sheet-like materials conventionally used such as paper, woven cloth, non-woven cloth, plastic film, polyester film, polypropylene film, polyethylene film and synthetic paper. Can be used.

The conductive agent used for the conductive layer provided on the sheet-like support is, for example, a quaternary compound such as polyvinylbenzyltrimethylammonium chloride, polydimethyldiallylammonium chloride or styreneacrylic acid trimethylaminoethyl chloride copolymer. Cationic conductive resin such as ammonium salt, polystyrene sulfonate, polyacrylate, anionic conductive resin such as polyvinyl sulfonate, or conductive zinc oxide, conductive stannic oxide, conductive indium oxide, A metal oxide semiconductor such as a conductive alkali metal titanate, carbon black, or an inorganic or organic pigment whose surface is coated with these substances can be used alone or in combination. In particular, the present inventors have found that Japanese Patent Application No. 7-167157
A conductive support having a conductive layer using a needle-shaped conductive titanium oxide powder on a sheet-shaped support as disclosed in No. 1, has a low humidity dependence of the conductive performance and has a high whiteness. Best for recording.

A known binder resin can be used in combination with the conductive agent in the conductive layer of the present invention. As the binder resin, in addition to cation-modified PVA, methylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, PVA, oxidized starch, esterified starch, carboxymethylcellulose, hydroxyethylcellulose, casein, gelatin, soybean protein, polyvinylpyrrolidone, polyacrylamide and polyacrylamide. Water-soluble polymers such as acrylic acid, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer resin, vinylidene chloride resin, vinyl chloride-vinylidene chloride copolymer resin, acrylic ester copolymer resin, methacrylic ester copolymer Polymerized resin,
Butyral resin, silicone resin, polyester resin,
There are water-insoluble polymers such as vinylidene fluoride resin, styrene resin, styrene-acrylic acid ester copolymer resin, and styrene-butadiene copolymer. These resins are used alone or in combination as a solution, emulsion or latex.

Other pigments can be used together with the above components of the conductive layer, for example, inorganic materials such as zinc oxide, titanium oxide, calcium carbonate, amorphous silica, clay, talc, mica, calcined clay, aluminum hydroxide and barium sulfate. Pigment, polystyrene, polyethylene, polypropylene, epoxy resin, melamine resin, phenol resin, styrene-acrylic acid ester copolymer and other organic pigment powder and beads are applied to improve surface strength, wettability, whiteness, etc. May be used for.

As the method for forming the conductive layer on the support, a usual coating method, that is, a Meyer bar method, a gravure roll method, a reverse roll method, a blade method, a slit die method, or the like can be used. The coating amount of the conductive layer thus formed has a surface electric resistance value of 1 × 10 ³ to 1 × 10 ⁷ Ω.
/ □, preferably 1 × 10 ³ to 1 × 10 ⁶ Ω / □. If it is larger than 1 × 10 ⁷ Ω / □, fogging at the tip may occur, which is not preferable. 1 x 10 ³ Ω
Realization of a conductive layer with less than / □ is not realistic from the viewpoint of the conductive performance and cost of the conductive agent.

The surface electric resistance value of the dielectric layer is 1 × 10 ⁹ Ω
/ □ or less, preferably 1 × 10 ⁶ to 1 × 10 ⁸ Ω / □, and as a method for preventing tip fog, the conductive material used for the conductive layer, that is, a cationic polymer electrolyte, an anionic polymer electrolyte , Nonionic polymer electrolyte, metal oxide semiconductor, metal powder, etc. are added in appropriate amounts. Since the effect of lowering the surface electric resistance value of the dielectric layer greatly differs depending on the type of these conductive substances, it is necessary to appropriately adjust the addition amount. In the present invention, the surface electric resistance value of the dielectric layer is 1 × 10 ⁹ Ω / □ or less, preferably 1 × 10 ⁶ to
It may be 1 × 10 ⁸ Ω / □, and the adjustment may be performed by a method other than the above. If the surface electric resistance value of the dielectric layer exceeds 1 × 10 ⁹ Ω / □, tip fogging occurs. If the surface electric resistance value of the dielectric layer is less than 1 × 10 ⁶ Ω / □, the latent image charge leaks and decays sharply, and the recording density decreases, which is not preferable.

The surface electric resistance value of the dielectric layer is 1 × 10.
If it is ⁹ Ω / □ or more, tip fogging occurs, so a conductive band may be provided. The conductive ink used when the conductive band is provided contains a metal powder such as carbon black, nickel or silver as a conductive component, and contains a vinyl chloride-vinyl acetate copolymer or an ethylene-vinyl acetate copolymer. An adhesive is added and dispersed in a solvent.
The solvent used here contains at least one solvent capable of dissolving the highly insulating resin in the dielectric layer, and specifically, carbonyl solvents such as acetone and methyl ethyl ketone, and ethyl acetate. There are various ester solvents, aromatic solvents such as benzene, toluene and xylene.

The conductive strips are formed by using the conductive ink of the present invention at a width of 0.5 to 10 mm, preferably 1 to 5 mm, on both sides of the recording paper in the width direction by a method such as gravure printing.

[0031]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In addition, "part" in each Example and Comparative Example,
"Part by weight (solid content)" is shown.

Example 1 The following composition was put into water and stirred with a Cowles type disperser to obtain a conductive coating material 1 having a solid content concentration of 10%.

Conductive paint 1 Needle-shaped conductive titanium oxide (trademark: FT-3000, manufactured by Ishihara Sangyo Co., Ltd.) 50 parts Quaternary ammonium salt type conductive agent 25 parts (trademark: Gocefimer C-820, manufactured by Nippon Synthetic Chemical Co., Ltd.) ) Cation-modified PVA (trademark: C-118 manufactured by Kuraray Co., Ltd.) 25 parts

After drying the obtained conductive paint 1 having a solid content of 10% on one surface of synthetic paper YUPO FPG-110 (manufactured by Oji Yuka Synthetic Paper Co., Ltd.) containing polypropylene as a main component used as a sheet-like support. Was coated with a bar coater at a coating speed of 40 m / min so that the coating amount was 2.0 g / m ² , dried and solidified to form a conductive layer having a surface electric resistance value of 7 × 10 ⁵ Ω / □. Then, the conductive support 1 was formed.

Dielectric layer paint 1 having a solid content of 20% obtained by stirring on a conductive layer of the conductive support with a Cowles type disperser using a diluent solvent of toluene / ethyl acetate = 1/1.
Was applied at a coating speed of 40 m / min with a bar coater so that the coating amount after drying would be 3.5 g / m ² , and dried and solidified to form a dielectric layer. Obtained.

Dielectric layer coating 1 Crosslinkable polymethylmethacrylate particles 2 parts (trademark: Techpolymer MBX-8 average particle size 8 μm, manufactured by Sekisui Plastics Co., Ltd.) Acrylic resin (trademark: Lunaper 2420, manufactured by Arakawa Chemical Industry Co., Ltd.) 98 copies

Example 2 Dielectric having a solid content of 20% obtained by stirring with a Cowles type disperser using a diluted solvent of toluene / ethyl acetate = 1/1 on the conductive layer of the conductive support of Example 1. The body layer coating material 2 is applied at a coating speed of 40 m / min with a bar coater so that the coating amount after drying is 3.5 g / m ² , and then dried and solidified to form a dielectric layer, An electrographic recording material was obtained.

Dielectric layer paint 2 Crosslinkable polymethylmethacrylate particles 5 parts (trademark: Techpolymer MBX-5 average particle size 5 μm made by Sekisui Plastics Co., Ltd.) Acrylic resin (trademark: Luna Pale 2420 made by Arakawa Chemical Industry Co., Ltd.) 95 copies

Example 3 Dielectric having a solid content of 20% obtained by stirring with a Cowles type disperser using a diluted solvent of toluene / ethyl acetate = 1/1 on the conductive layer of the conductive support of Example 1. The body layer coating material 3 is applied with a bar coater at a coating speed of 40 m / min so that the coating amount after drying is 3.5 g / m ² , dried and solidified to form a dielectric layer, and An electrographic recording material was obtained.

Dielectric Layer Coating 3 Benzoguanamine / Melamine / Formaldehyde Condensed Particles 5 parts (Trademark: Eposter M30 average particle size 3 μm manufactured by Nippon Shokubai Co., Ltd.) Acrylic resin (Trademark: Lunaper 2420 manufactured by Arakawa Chemical Industry Co., Ltd.) 95 parts

Example 4 Dielectric having a solid content of 20% obtained by stirring with a Cowles type disperser using a diluted solvent of toluene / ethyl acetate = 1/1 on the conductive layer of the conductive support of Example 1. The body layer coating material 4 is applied with a bar coater at a coating speed of 40 m / min so that the coating amount after drying is 3.5 g / m ² , and dried and solidified to form a dielectric layer. An electrographic recording material was obtained.

Dielectric Layer Paint 4 Benzoguanamine / Melamine / Formaldehyde Condensed Particles 2 parts (Trademark: Eposter M30 average particle size 3 μm manufactured by Nippon Shokubai Co., Ltd.) Acrylic resin (Trademark: Lunaper 2420 manufactured by Arakawa Chemical Industry Co., Ltd.) 98 parts

Comparative Example 1 The electrostatic recording material of Example 3 was supercalendered to obtain a dielectric layer having an Oken type smoothness of 900 seconds.

Comparative Example 2 Dielectric having a solid content of 20% obtained by stirring with a Cowles type disperser using a diluted solvent of toluene / ethyl acetate = 1/1 on the conductive layer of the conductive support of Example 1. Body layer coating material 5 was applied at a coating speed of 40 m / min with a bar coater so that the coating amount after drying was 3.5 g / m ² , and then dried and solidified to form a dielectric layer, An electrographic recording material was obtained.

Dielectric layer coating 5 Benzoguanamine / formaldehyde condensed particles 5 parts (Trademark: Eposter L15 average particle size 15 μm made by Nippon Shokubai Co., Ltd.) Acrylic resin (Trademark: Lunaper 2420 made by Arakawa Chemical Industry Co., Ltd.) 95 parts

Comparative Example 3 A dielectric layer having a solid content of 20% obtained by dispersing with a sand grinder using a diluted solvent of toluene / ethyl acetate = 1/1 on the conductive layer of the conductive support of Example 1. The coating material 6 is applied with a bar coater at a line speed of 40 m / min so that the coating amount after drying is 3.5 g / m ² , and is dried and solidified to form a dielectric layer. Got

Dielectric layer coating 6 Aluminum hydroxide 15 parts (Trademark: Heidilite H-21 average particle size 25 μm, Showa Denko KK) Acrylic resin (Trademark: Luna Pale 2420, Arakawa Chemical Industry Co., Ltd.) 85 parts

The electrostatic recording bodies of Examples 1 to 4 and Comparative Examples 1 to 3 thus obtained were conditioned for 2 hours in an environment of 20 ° C. and 60% RH, and then a prototype of an electrostatic transfer system was used. , Recorded according to a predetermined image pattern. The recording method is as follows. A predetermined recording latent image is formed on the surface of the photoconductor charged to 600V by a corona charger, an electrostatic recording medium is brought into contact with the surface to form an electrostatic charge image, and then a liquid is drawn by a slit suction type developing device. An image is obtained by wet development using toner. The results are shown in Table 1. The recording density is Macbeth densitometer (trademark: Macbeth RD914 type,
The image uniformity was visually evaluated.

[0049]

[Table 1]

◯: Good image with no white spots or fine density unevenness in the solid area. Δ: Image with no white spots in the solid area and slight fine density unevenness. ×: White spots or fine unevenness in the solid area. Non-uniform image with uneven density

As can be seen from Table 1, the Oken type smoothness of the dielectric layer is 100 to 700 seconds, and JIS B 0601 is used.
The electrostatic recording material having a center line average roughness of 1.2 μm or less based on (3) has good image uniformity, sufficient recording density can be obtained, and is excellent as an electrostatic recording material. (Examples 1 to 4)

On the other hand, when the Oken type smoothness exceeds 700 seconds (Comparative Example 1), the toner developer is not sufficiently sucked and removed by the slit type developing device, resulting in poor drying. In addition, the Oken smoothness is less than 100 seconds (Comparative Example 2),
Alternatively, when the center line average roughness exceeds 1.2 μm (Comparative Example 3), the image uniformity is poor.

[0053]

INDUSTRIAL APPLICABILITY The present invention provides a conductive support on a sheet-like support,
Dielectric layers are sequentially provided, and the Oken type smoothness of the dielectric layers is 1
By setting the average roughness of the center line to be not more than 1.2 μm for 0 to 700 seconds, it is suitable for recording by the electrostatic transfer system or the ion flow control system for transferring the electrostatic latent image on the photoconductor, and a good image is obtained. An effect that uniformity can be obtained is obtained.

Claims (5)

[Claims] 1. An electrostatic recording body comprising a sheet-shaped support and a conductive layer and a dielectric layer sequentially provided on the surface of the dielectric layer, having an Oken type smoothness of 100 to 700 seconds and JIS B 0.
An electrostatic recording material having a center line average roughness based on 601 of 1.2 μm or less. 2. The particle size of the pigment used in the dielectric layer is
The electrostatic recording body according to claim 1, wherein the electrostatic recording body has a thickness of 1 to 10 μm. 3. The blending ratio of the pigment used for the dielectric layer and the highly insulating resin is 0.5: 99.5 to 20: by weight.
The electrostatic recording material according to claim 1 or 2, wherein the electrostatic recording material is 80. 4. The coating amount of the dielectric layer is 1 to 10 g /
The electrostatic recording body according to any one of claims 1 to 3, which is m ² . 5. The electrostatic recording body according to claim 1, wherein the electrostatic recording body is used for recording by an electrostatic transfer system or an ion flow control system.