JPH0854739A - Electrostatic recording body - Google Patents

Abstract

PURPOSE:To prevent tip fogging and the lowering of recording density in recording with ion current control system or electrostatic transfer system by containing a specific acicular conductive titanium oxide having electronic conductivity as a conductive material in a conductive layer. CONSTITUTION:This electrostatic recording body is formed by providing a conductive layer containing the acicular conductive titanium oxide on an insulting supporting body and a dielectric layer on the conductive layer. The acicular conductive titanium oxide is composed of a titanium oxide having acicular shape 2-15mum in major axis and 0.1-0.5mum in minor axis as the base material and a coating film of tin oxide containing antimony as an impurity is formed on the surface. And the dielectric layer has 1X10<6>-1X10<8>OMEGA/square inch of surface electric resistance. It is unsuitable that the surface electric resistance of the dielectric layer exceeds 1X10<9>OMEGA/square inch or the electric resistance between both end parts of the conductive ends is higher than 1X10<8>OMEGA/square inch even in the case of providing an conductive zone since the degradation of the recording quality such as the generation of tip fogging, the lowering of recording density or color mixing due to the increase of residual potential is generated.

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, an electrostatic latent image is directly formed on the surface of a recording medium by an electrostatic recording method such as an ion flow control method or an electrostatic transfer method, and then slit development, suction roll development and reverse roll. In the recording that develops with toner by a method such as development,
The present invention relates to an electrostatic recording body which is free from fog stains (hereinafter, referred to as tip fog) on the surface of the recording body corresponding to the space between the recording head and the developing device, and does not reduce the recording density.

Further, the present invention is a color for forming a high-definition color image by repeating the process of forming an electrostatic latent image directly on the surface of a recording medium by an ion flow control method and then developing it with toner many times. The present invention relates to an electrostatic recording material used for printing machines, color printers, color proofers, and the like.

[0003]

2. Description of the Related Art In recent years, color images such as color printing machines, color printers, color plotters, and color proofers have been improved in definition, and ion flow control methods and electrostatic transfer methods using electrostatic recording methods have been attempted. A scheme has been proposed.

Conventionally, an electrostatic recording material is a conductive material mainly composed of an ion conductive polymer electrolyte (hereinafter referred to as an ion conductive type conductive agent) utilizing ion dissociation on a support such as paper, cloth and film. It is known that the recording layer is formed by sequentially providing a layer and a dielectric layer, and the recording body uses an insulating support made of a plastic film, a thick paper or cloth having a thickness of 100 μm or more. It is also known, but in the recording by the ion flow control method or the electrostatic transfer method, the recording quality such as the occurrence of the tip fog, the extremely low recording density, and the color mixture due to the residual potential deteriorates. There is a problem.

For this reason, Japanese Patent Laid-Open No. 60-43661 discloses a method of grounding from the back surface by using a film which is a support and kneaded with a surfactant or the like to lower the electric resistance value. Has been done. However, this method has a problem that the stiffness of the film is lost, the paper passing property in the recording apparatus is poor, and the cost is increased.

Japanese Unexamined Patent Publication (Kokai) No. 2-59757 discloses a method in which conductive particles are scattered in a dielectric layer to directly ground the surface of a recording medium. This method has a problem that the recording density is lowered due to spontaneous leakage of latent image charges due to excessive addition of conductive particles, and is not suitable for use as it is.

Another method has been considered in which the conductive layer surfaces at both ends of the recording medium are exposed, and the conductive layer surfaces are brought into contact with a metal roll, a charge eliminating brush, or the like to establish grounding at a position immediately before the developing device. For example, Japanese Patent Application Laid-Open No. 60-122943 discloses a method of leaving a part of both ends of a conductive layer uncoated when a dielectric layer is coated. However, this method has a problem that it is very difficult to control the coating width when the dielectric layer is coated. Further, Japanese Patent Application Laid-Open No. 4-168443 discloses a method of applying a conductive coating material to the edge (mirror) portion of a roll or cut sheet for winding recording paper. However, in this method, it is necessary to apply the recording paper after making it into a roll or a cut sheet, and there is a problem that the number of steps is increased and the conductivity is varied.

On the other hand, Japanese Patent Application Laid-Open No. 1-6956 discloses a method of forming a continuous conductive band having an electric resistance value of 1 × 10 ⁵ Ω or less at both ends of the surface of a dielectric layer.
However, even when the conductive band formed by this method is used, in recording by the ion flow control method or electrostatic transfer method, tip fogging, cracking of the conductive layer under low humidity conditions (hereinafter, cracking occurrence) Therefore, it is impossible to completely prevent the deterioration of the recording quality such as the occurrence of stains on the white paper portion and the decrease of the recording density, and it is still impossible to perform high-definition color recording.

The conductive material used for the conductive layer of the electrostatic recording material is an ion conductive type conductive agent which is a polymer compound having a quaternary ammonium ion group or a sulfonic acid group, and conductive tin oxide. It is known to use such a metal oxide semiconductor powder having electronic conductivity. Among them, the conductive layer used for the electrostatic recording body for obtaining a high-definition color image needs to have a small change in conductivity due to environmental humidity. Is suitable. Known as these metal oxide semiconductor powders are conductive zinc oxide containing aluminum as an impurity and conductive tin oxide containing antimony as an impurity.

However, when these conductive metal oxide semiconductor powders are used, in a high-definition color recording material such as a color proof which requires a high whiteness of 80% or more in the white paper portion, the impurities become impurities. Due to this, the white paper portion is strongly colored and is not suitable for color recording. In order to improve this, a needle-like substance, for example, potassium titanate whisker disclosed in JP-A-63-318568, or barium sulfate needle is used as a matrix, and its surface is coated with a conductive substance such as tin oxide. There is a layer of acicular conductive material. But,
When the conductive layer coating material is adjusted by using these needle-shaped conductive powder, the needle-shaped shape is broken by the shearing force such as mechanical agitation. Even if recording is performed by the electrostatic transfer method, the required surface electric resistance value is not obtained, tip fog occurs, and desired recording quality cannot be obtained.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrostatic recording material comprising a conductive layer on an insulative support, and a dielectric layer on the conductive layer in that order. It is an object of the present invention to provide a good electrostatic recording medium that does not cause fog at the tip and does not reduce the recording density when recording by the method.

[0012]

SUMMARY OF THE INVENTION In view of the present situation, the inventors of the present invention have made earnest studies to solve the problems of the prior art, and as a result, as a conductive material of a conductive layer, a specific needle-like material having electronic conductivity is obtained. By including conductive titanium oxide, it was found that there is no deterioration in recording quality such as dirt on the white paper part due to tip fog or cracking and deterioration of recording density when recording by ion flow control method or electrostatic transfer method. The present invention has been reached.

The present invention relates to an electrostatic recording material characterized in that a conductive layer containing acicular conductive titanium oxide is provided on an insulating support, and a dielectric layer is further provided on the conductive layer.

The electrostatic recording material of the present invention is an electrostatic recording material comprising a conductive layer containing acicular conductive titanium oxide on an insulating support, and a dielectric layer on the conductive layer. When the surface electric resistance value of the dielectric layer exceeds 1 × 10 ⁹ Ω / □ and the ground cannot be taken from the surface of the dielectric layer, at least a solvent that dissolves the highly insulating resin used for the dielectric layer is used. A conductive band may be sequentially provided by one or more kinds of conductive ink to ground. The conductive strips provided at both ends on the surface of the dielectric layer have an electrical resistance value of 10 ⁵ Ω or less when the distance between electrodes of the two probe electrodes is 20 Ω or less. The electric resistance between both ends of the is 1 × 10 ⁸ Ω
Or less, preferably 5 × 10 ⁷ Ω or less, more preferably 1
If it is between × 10 ^{4 and} 4 × 10 ⁷ Ω, good recording quality can be stably obtained.

Here, the surface electric resistance value of the dielectric layer is 1 × 1.
Even if the value exceeds 0 ⁹ Ω / □ or if a conductive band is provided, the electric resistance value between both ends of the conductive band is 1 × 10 ⁸ Ω.
Higher values are not suitable because leading to fog generation, lowering of recording density, and lowering of recording quality such as color mixing due to increase of residual potential. The conductive band contains a solvent that dissolves the highly insulating resin in the dielectric layer in the conductive ink, dissolves a part of the highly insulating resin when forming the conductive band, and forms a conductive layer and a conductive band. The conductive layers are directly connected to each other to form an electric circuit between the conductive strips at both ends to impart good conductivity.

Conventionally, a polymer compound having a quaternary ammonium ion group or a sulfonic acid group has been used alone as an ion conductive type conductive agent as a conductive material for a conductive layer of an electrostatic recording medium. However, when the ion conductive type conductive agent is used, cracking of the conductive layer occurs in a low humidity environment such as 40% RH or less, and tip fog occurs when recording is performed. In addition, the temperature and humidity of the atmosphere in which the electrostatic recording medium is used have a great influence, and stable recording quality cannot be obtained.

On the other hand, an electron conductive type conductive agent such as conductive tin oxide or needle-shaped conductive titanium oxide, which is not affected by the temperature and humidity of the atmosphere in which it is used and has no problem as described above, is used. It's coming. However, when the conductive tin oxide was used as a conductive agent, the white paper portion of the electrostatic recording material was colored, which was unsuitable for high-definition color recording.

On the other hand, regarding needle-shaped conductive titanium oxide,
In Japanese Unexamined Patent Publication (Kokai) No. 63-233016, the shape is long axis 1-1.
Disclosed is a powder produced by using a needle-shaped titanium oxide having a diameter ratio of 0 μm and a major axis to a diameter of 3 or more, preferably 10 or more as a base material, and baking a tin oxide film containing antimony as an impurity on the surface thereof. .

The inventors of the present invention have made earnest studies on a good electrostatic recording medium which is free from tip fog and has no decrease in recording density in the recording by the ion flow control system, and as a result, the needle-shaped conductive titanium oxide shape is long. Shaft 2 to 15 μm, Minor axis 0.1 to 0.5 μm
When needle-shaped conductive titanium oxide is used, the probability that the needle-shaped substances will contact each other morphologically increases, and the amount of conductive tin oxide used for surface treatment can be greatly reduced, and the desired whiteness and electrical resistance can be obtained. The inventors have found that it is possible to obtain a value and have reached the present invention.

In the present invention, when the major axis of the acicular conductive titanium oxide is less than 2 μm, the surface treatment amount of the conductive tin oxide on the acicular titanium oxide should be increased in order to obtain the desired conductivity. In addition, the whiteness of the obtained conductive layer is deteriorated, and when the major axis exceeds 15 μm, there is a phenomenon that needle crystals are broken by the shearing force when the conductive titanium oxide powder is dispersed in the paint. As a result of the new surface being exposed, the conductivity is markedly reduced, and the stirring force must be reduced during preparation of the paint, and a process for removing aggregates in the paint is required. Occurs in.

The acicular conductive titanium oxide used in the present invention is
It is necessary to use together with an ion conductive type conductive agent such as a polymer compound having a quaternary ammonium ion group or a sulfonic acid group, and the mixing ratio of the needle-shaped conductive titanium oxide and the ion conductive type conductive agent is 95. : 5 to 20:80 (weight ratio), preferably 80:20 to 30:70 (weight ratio). When the blending weight ratio of the needle-shaped conductive titanium oxide exceeds 95, the dispersibility of the needle-shaped conductive titanium oxide is poor at the time of preparing the conductive coating material. On the other hand, when the blending weight ratio of the needle-shaped conductive titanium oxide is less than 20, the blending ratio of the ion conductive type conductive agent increases,
The humidity dependency of the surface electric resistance value of the conductive layer increases, and tip fogging due to cracking occurs.

The acicular conductive titanium oxide used in the present invention is
It may be dispersed and mixed with a water-soluble resin to form a layer on the surface of the insulating support. As the water-soluble resin used, polyvinyl alcohol, oxidized starch, esterified starch, methoxycellulose, carboxymethylcellulose, hydroxyethylcellulose, casein, gelatin, soybean protein, polyvinylpyrrolidone, water-soluble polymers such as polyacrylamide, polyvinylbenzyl. Cationic polyelectrolytes such as trimethylammonium chloride, polydimethyldiallylammonium chloride, styrene-acrylic acid triethylammonium chloride,
Or polystyrene sulfonate, polyacrylate,
Examples include anionic polyelectrolytes such as polyvinyl phosphate.

Among them, the ionic conductive polymer electrolyte is
The needle-shaped conductive titanium oxide is well dispersed, and has the function of keeping the conductivity of the formed film constant over a wide humidity range.
It is suitable. The polymer electrolyte used here keeps the aqueous coating solution at a low viscosity by keeping the pH of the aqueous coating solution of needle-shaped conductive titanium oxide between 5 and 10, and a good coating surface can be obtained during coating. If the pH is less than 5, the viscosity of the coating composition will increase, causing problems such as aggregation during coating and uneven coating. On the other hand, when the pH is higher than 10, the workability at the time of application is deteriorated due to the odor.

Other pigments may be used together with the above water-soluble resin, for example, inorganic pigments such as zinc oxide, titanium oxide, calcium carbonate, amorphous silica, clay, talc, mica, calcined clay, aluminum hydroxide and barium sulfate. Plastic pigments such as polystyrene, polyethylene, polypropylene, epoxy resins, melamine resins, phenol resins, and styrene-acrylic acid ester copolymers may be used for preventing coloring and improving the surface strength and wettability of the coated surface.

The insulating support used in the present invention is a polymer film such as polyethylene film, polypropylene film, polyester film, synthetic paper, paper having a thickness of 100 μm or more, resin-impregnated paper, polyethylene laminated paper and cloth. Such a substantially insulating support having an electric resistance value in the thickness direction of 10 ⁹ Ω or more is also included. In addition, a back surface layer containing a known resin, pigment, or the like may be provided on the surface opposite to the surface on which the conductive layer is provided, if necessary, in order to improve writing performance and prevent electrification.

In the present invention, the mixing ratio of the water-soluble resin is 90 parts by weight or less, preferably 80 parts by weight or less, based on 100 parts by weight of the total solid content of the acicular conductive titanium oxide and the ion conductive type conductive agent. Create conductive paint, for example, bar coater, contra coater, gravure coater,
It is formed by a method of coating on an insulating support with an appropriate coating device such as a curtain coater, a chanplex coater, a roll coater, a blade coater, and drying with a hot air dryer. The coating amount of the conductive layer is 0.5 to 10 g / m
² (solid content), preferably 1 to 5 g / m ² (solid content). Here, if it is less than 0.5 g / m ² (solid content),
Coating film defects occur, surface electric resistance increases, and tip fog occurs, which is not preferable. If it exceeds 10 g / m ² (solid content), the cost becomes high, which is not preferable.

In the electrostatic recording medium of the present invention, the highly insulating resin forming the dielectric layer is, for example, methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, methyl methacrylate, methacryl. Acrylate ester copolymers such as isobutyl acid and 2-ethylhexyl methacrylate, methacrylate ester copolymers, vinyl acetate polymers, ethylene-vinyl acetate copolymers, butyral resins, polyester resins, nitrocellulose, polystyrene, styrene -Acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, phenol resin and the like.

Examples of pigments to be incorporated in the dielectric layer include clay, deckite, nacrite, kaolin, aluminum hydroxide, calcium carbonate, calcined clay, amorphous silica, alumina, calcined kaolin, barium sulfate and titanium oxide. Inorganic pigments such as, and treated with a hydrophilic group on the surface of the inorganic pigment, insulated pigment, or polystyrene, polyethylene, polypropylene, polymethacrylic acid ester, benzoguanamine resin, silicone resin, epoxy resin, melamine resin, There are plastic pigments such as phenolic resin. Of these, plastic pigments have better chargeability than other pigments,
The leakage attenuation of the latent image charge is small, which is particularly preferable.

When a suction type developing device is used, if the average particle size of the pigment in the dielectric layer is too large, it becomes difficult to maintain the gap between the surface of the recording material and the developing device in an appropriate range. Poor development occurs. On the other hand, if the average particle size is too small, the developing solution cannot be sucked and removed during development, and the solution is output in a wet state. Therefore, the particle size of the pigment used for the dielectric layer is 1
The surface smoothness of the recording material is preferably in the range of 20 seconds to 250 seconds in terms of Beck's smoothness.

The mixing ratio of the highly insulating resin and the pigment in the coating material for the dielectric layer is appropriately adjusted according to the desired characteristics of the recording material and the type of material used, but the weight of the insulating resin and the pigment. The ratio is in the range of 99: 1 to 60:40, preferably 90: 5 to 70:30, and is generally composed of an insulating resin and a pigment as main components in a solvent such as toluene, methyl ethyl ketone, ethyl acetate or xylene. Dissolved as,
Get dispersed. This paint is, for example, bar coater, contra coater, gravure coater, curtain coater,
With a suitable coating device such as a Champlex coater, a roll coater, or a blade coater, it is applied on the surface of the conductive layer formed on the insulating support, using a hot air dryer,
It is formed by a drying method.

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 ^9.
It may be ⁶ to 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 coating amount of the dielectric layer is 1 to 10 g / m ² (solid content), preferably 2 to 6 g / m ² (solid content).
When it is less than 1 g / m ² (solid content), coating film defects occur, and when it exceeds 10 g / m ² (solid content), tip fog occurs, 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 a conductive ink in a width direction of 0.5 to 10 mm, preferably 1 to 5 mm on both ends of the recording paper in the width direction by a method such as gravure printing.

As described above in detail, according to the present invention, in the electrostatic recording body in which the conductive layer is provided on the insulating support and the dielectric layer is further provided thereon, the conductive layer is needle-shaped conductive. When the recording is performed by an ion flow control method or an electrostatic transfer method, good recording quality can be obtained without causing fog at the tip and reduction in recording density.

[0036]

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,
"Parts by weight" is shown.

Example 1 2.5 g / m ² of a conductive layer having the following composition was coated on one surface of synthetic paper YUPO FPG-110 (manufactured by Oji Yuka Synthetic Paper Co., Ltd.) containing polypropylene as an insulating support as a main component. did. As a conductive layer coating material, needle-shaped conductive titanium oxide (trademark; FT-3000, manufactured by Ishihara Sangyo Co., Ltd.) 40 parts Ion conductive type conductive agent 60 parts (quaternary ammonium salt-based trademark; Gocefimer C-820, Nihon Gosei) (Chemical Industry Co., Ltd.) is put into water, and the solid content concentration is 1 by a cowles type disperser.
A coating liquid of 0% was obtained. When the shape of the needle-shaped conductive titanium oxide was observed with an electron microscope, the average long axis was 5.
It was 7 μm and the minor axis was 0.27 μm.

Acrylic ester copolymer 90 parts Crosslinkable polymethylmethacrylate powder 10 parts (Trademark: Techpolymer MBX-8, manufactured by Sekisui Plastics Co., Ltd.) was used as a dielectric layer on the conductive layer in toluene / ethyl acetate. = 1/1 Dispersed in a solvent, adjusted to a solid content concentration of 20%, applied at 3.5 g / m ² (solid content), dried and solidified to prepare an electrostatic recording material.
The surface electric resistance value of the dielectric layer of the recording material thus obtained was adjusted for 2 hours in an environment of 20 ° C. and 80% RH, and then the surface electric resistance meter (trademark: Hiresta resistance meter, Mitsubishi Petrochemical Co., Ltd.) was used. Manufactured) and the value was 1 × 10 ⁷ Ω / □.

Example 2 A synthetic paper YUPO FPG-110 (manufactured by Oji Yuka Synthetic Paper Co., Ltd.) containing polypropylene as an insulating support as a main component was coated with 2.5 g / m ² of a conductive layer having the following composition on one side. did. As a conductive layer coating material, needle-shaped conductive titanium oxide (trademark; FT-3000, manufactured by Ishihara Sangyo Co., Ltd.) 70 parts Ion conductive type conductive agent 30 parts (quaternary ammonium salt-based trademark; Gocefimer C-820, Nihon Gosei) (Manufactured by Kagaku Kogyo Co., Ltd.) was put into water to obtain a conductive paint in the same manner as in Example 1. When the shape of the acicular conductive titanium oxide was observed with an electron microscope, the average major axis was 5.7 μm and the minor axis was 0.27.
μm.

On this conductive layer, the same dielectric layer as in Example 1 was applied at 3.5 g / m ² (solid content), dried and solidified to prepare an electrostatic recording body. The surface electric resistance value of the dielectric layer of this recording medium was measured in the same manner as in Example 1 and was 8 × 10 ⁶ Ω / □.

Example 3 Needle-like conductive titanium oxide (trademark; FT-) used in Example 1
Electrostatic recording material was prepared and evaluated in the same manner as in Example 1 except that needle-shaped conductive titanium oxide (trademark; FT-2000, manufactured by Ishihara Sangyo Co., Ltd.) was used instead of 3000, manufactured by Ishihara Sangyo Co., Ltd. did. The shape of the needle-shaped conductive titanium oxide was observed with an electron microscope, and the average long axis was 2.8 μm and short axis was 0.21 μm.
The surface electric resistance value of the dielectric layer was measured in the same manner as in Example 1 and was 4 × 10 ⁷ Ω / □.

Example 4 Needle-like conductive titanium oxide (trade name; FT-) used in Example 2
Electrostatic recording material was prepared and evaluated in the same manner as in Example 2 except that needle-shaped conductive titanium oxide (trademark; FT-2000, manufactured by Ishihara Sangyo Co., Ltd.) was used instead of 3000, manufactured by Ishihara Sangyo Co., Ltd. did. The shape of the needle-shaped conductive titanium oxide was observed with an electron microscope, and the average long axis was 2.8 μm and short axis was 0.21 μm.
The surface electric resistance value of the dielectric layer was measured in the same manner as in Example 1 and was 1 × 10 ⁷ Ω / □.

Example 5 The same conductive layer as in Example 1 was provided on the insulating support used in Example 1, and a styrene-acrylic acid ester copolymer 90 parts was crosslinked as a dielectric layer on this conductive layer. Polymethylmethacrylate powder (trademark; Techpolymer MBX-8, manufactured by Sekisui Plastics Co., Ltd.) 10 parts were dispersed in a toluene / ethyl acetate = 1/1 solvent and prepared so that the solid content concentration was 20%. , 3.5 g / m ² (solid content) was applied to obtain an electrostatic recording material. The surface electric resistance value of the dielectric layer of this electrostatic recording material was measured in the same manner as in Example 1, and
It was × 10 ¹¹ Ω / □.

The electrostatic recording body has a width of 500 mm and a length of 50.
A conductive ink containing carbon black as a conductive component and toluene as a solvent (trademark; Erdik EC-0528, manufactured by Dainippon Ink and Chemicals, Inc.) was further diluted with ethyl acetate at both ends of the 0 mm dielectric layer surface. The material was applied by a gravure roll coater so as to have a width of 2 mm to form a conductive band and an electrostatic recording body was prepared. The electric resistance value between the conductive bands is 2 in an environment of 20 ° C. and 60% RH.
After time-controlled humidity, it was measured using an ultra-high resistance meter (manufactured by Advantest) and was 2.4 × 10 ⁶ Ω.

Example 6 The same as Example 1 except that needle-shaped conductive titanium oxide (trademark; FT-1000, manufactured by Ishihara Sangyo Co., Ltd.) was used in place of the needle-shaped conductive titanium oxide used in Example 1. Then, an electrostatic recording material was prepared and evaluated. When the shape of the acicular conductive titanium oxide was observed with an electron microscope, the average major axis was 1.7 μm, the minor axis was 0.13 μm, and the surface electric resistance value of the dielectric layer of the obtained electrostatic recording material was 4 μm. It was × 10 ⁸ Ω / □.

Example 7 A conductive band was formed on the dielectric layer of the electrostatic recording body obtained in Example 6 in the same manner as in Example 5. The electric resistance value between the conductive bands was 1 × 10 ⁸ Ω.

Comparative Example 1 Instead of the needle-shaped conductive titanium oxide used in Example 1, conductive potassium titanate whiskers (trademark; DENTOL WK-).
200B, manufactured by Otsuka Chemical Co., Ltd.), and an electrostatic recording material was prepared and evaluated in the same manner as in Example 3. When the shape of the conductive potassium titanate whiskers was observed by an electron microscope, the average major axis was 18 μm and the minor axis was 0.40 μm, and the surface electric resistance value of the dielectric layer of the obtained electrostatic recording body was 1
It was × 10 ¹⁰ Ω / □.

Comparative Example 2 Instead of the acicular conductive titanium oxide used in Example 1, granular conductive titanium oxide (trademark: 600W, manufactured by Ishihara Sangyo Co., Ltd.) having an average particle diameter of the secondary aggregate of 2.5 μm was used. An electrostatic recording material was prepared and evaluated in the same manner as in Example 1 except that it was used. The surface electric resistance value of the dielectric layer of the obtained electrostatic recording material is 5 × 1.
It was 0 ¹⁰ Ω / □.

Comparative Example 3 Only the ion conductive polymer electrolyte (trademark; Gohsefimer C-820, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was used as the conductive layer coating material, and 4.0 g / m ² (solid content) was applied. Is
An electrostatic recording material was prepared and evaluated in the same manner as in Example 1.
The surface electric resistance value of the dielectric layer of the obtained electrostatic recording material is 3 ×.
It was 10 ¹¹ Ω / □.

The electrostatic recording material thus obtained was subjected to wet development using a corona charger to form an electrostatic charge image of 100 V on the surface and then continuously using liquid toner in a slit suction type developing device. The obtained image was evaluated as follows.

To evaluate the fog at the tip, the reflection densities of the non-image part and the white paper part were measured by a reflection densitometer (Macbeth RD-914 was used), and the difference between them was calculated. ) Was calculated. The recording density of the image area was measured with a reflection densitometer. The residual potential is used as a measure of the ease with which tip fog occurs, and the potential of the image area after development is measured using a surface potential meter (344
Was used). The whiteness of the white paper is JIS
It measured based on P8123. Each of the recording bodies obtained in Examples and Comparative Examples was recorded according to a predetermined image pattern by using a recording apparatus of an ion flow control system which is a prototype, and the sharpness of the image was visually evaluated according to the following evaluation criteria. Table 1 shows the results of evaluating the images of the respective recording materials. ○ Clear recorded image without tip fog or decrease in recording density △ Can be used as a recording medium with slight tip fog or decrease in recording density × Blurred recorded image due to tip fog or decrease in recording density

[0052]

[Table 1]

As can be seen from Table 1, an electrostatic recording medium containing needle-shaped conductive titanium oxide having an average major axis of 5.7 μm or 2.8 μm in the conductive layer and satisfying the requirements of the invention has a low fog density. A sufficient recording density is obtained, the whiteness is high, and the recording by the ion flow control method is good. (Example 1
5) Further, although the recording material using the needle-shaped conductive titanium oxide having an average major axis of 1.7 μm (Example 6) causes some fog, recording by the ion flow control method is possible. The recording medium provided with a conductive band (Example 7) has improved fog generation and is sufficiently recordable by the ion flow control method.

On the other hand, in the case of using the conductive potassium titanate whisker (Comparative Example 1), the fog density was high, the whiteness was low, and the tip fog occurred. Further, in the case of using granular conductive titanium oxide (Comparative Example 2), the fog density was high, the whiteness was low, the occurrence of front fog and the recording density were lowered. Further, in the case of using only the ion conductive polymer electrolyte (Comparative Example 3), the fog density was large, and the occurrence of tip fog and the recording density were lowered. All the comparative examples were not suitable for recording by the ion flow control method.

[0055]

INDUSTRIAL APPLICABILITY The present invention provides an electrostatic recording medium in which a conductive layer is provided on an insulating support, and a dielectric layer is further provided thereon.
The conductive layer contains a specific needle-shaped conductive titanium oxide, and when recording by an ion flow control system or an electrostatic transfer system, there is an effect that good recording quality can be obtained without leading edge fogging and reduction in recording density. .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masatoshi Fujino 1-10-6 Shinonome, Koto-ku, Tokyo Shin-Oji Paper Co., Ltd. Tokyo Product Research Institute (72) Satoshi Fukui 1-10 Shinonome, Koto-ku, Tokyo No. 6 Shin Oji Paper Co., Ltd. Tokyo Commodity Research Institute

Claims (7)

[Claims] 1. An electrostatic recording body comprising a conductive layer containing needle-shaped conductive titanium oxide provided on an insulating support, and a dielectric layer provided thereon in sequence. 2. The needle-shaped conductive titanium oxide has a needle-shaped titanium oxide having a major axis of 2 to 15 μm and a minor axis of 0.1 to 0.5 μm as a base material and antimony as an impurity on the surface thereof. The electrostatic recording material according to claim 1, which is needle-shaped conductive titanium oxide formed by firing a tin oxide film. 3. The needle-shaped conductive titanium oxide is used in combination with an ion-conductive type conductive agent, and the mixing ratio of the needle-shaped conductive titanium oxide and the ion-conductive type conductive agent is 95: 5 to 20:80 (weight. The electrostatic recording medium according to claim 1 or 2, wherein 4. The surface electric resistance value of the dielectric layer is 1 × 1.
The electrostatic recording body according to any one of claims 1 to 3, wherein the electrostatic recording body has a resistance of 0 ⁶ to 1 × 10 ⁸ Ω / □. 5. A conductive band formed from a conductive ink containing at least one solvent that dissolves the dielectric layer is provided on both ends of the surface of the dielectric layer. Electrostatic recording body. 6. The electric resistance value between the conductive bands is 5 × 1.
The electrostatic recording body according to claim 4, wherein the electrostatic recording body has a resistance of not more than 0 ⁷ Ω. 7. The electrostatic recording body according to claim 1, wherein the electrostatic recording body is used for recording in an ion flow control system or an electrostatic transfer system.