JPH0352054B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrostatic recording medium, particularly an electrostatic recording medium that can be used multiple times. [Prior Art] Conventionally, electrostatic recording paper in which a conductive layer is provided between the recording layer and the base paper is generally used as a recording medium in an electrostatic recording device, and a needle electrode such as a multi-stylus is attached to the surface of the recording layer. An electrostatic latent image is formed using toner, which is developed and fixed with toner to obtain a recorded image. However, when such electrostatic recording paper is used, it is unavoidable that excess toner adheres to the surface of the recording paper, and it also has disadvantages such as being highly susceptible to the atmosphere (moisture, heat, etc.) during use. Moreover, since electrostatic recording paper itself is special compared to plain paper, it has the disadvantage that running costs are significantly higher when used as a consumable item. To solve these drawbacks, electrostatic recording devices that transfer onto plain paper have been developed (for example, the
Publication No. 34077). According to this method, a recording medium is formed in the form of a belt, in which a dielectric layer having a volume resistivity of 10 ¹² Ω·cm or more is provided on a biaxially stretched polyester base material, and a needle electrode is connected to the recording medium using a multi-stylus. The dielectric surface is charged by applying a high voltage between the surface and the dielectric surface, and the electrostatic latent image formed is then developed with toner to obtain a powder image, which is then printed on plain paper. Images are obtained by electrostatic transfer. However, since this method electrostatically transfers toner images onto plain paper, the transfer efficiency is as low as about 80%, which reduces image density and is disadvantageous in terms of cleaning and scattering of residual toner. Image distortion occurs due to electrical transfer. On the other hand, a dielectric thin layer is provided on the surface of a conductive rigid cylinder, an electrostatic latent image is formed on the surface of this dielectric thin layer, and after this latent image is developed with toner, it is transferred and fixed onto plain paper using pressure. The method is known (for example, JP-A-54-78134, JP-A-55-
134872). In this method, the dielectric thin layer is rubbed by the paper, resulting in its surface being polished. Therefore, in order to increase the hardness of the dielectric layer, inorganic dielectrics such as anodized aluminum, Al ₂ O ₃ formed by thermal spraying, and glass enamel, and organic dielectrics such as polyamide, polyimide, and fluororesin are used. But anodized aluminum, thermal sprayed
Inorganic dielectric layers such as Al ₂ O ₃ and glass enamel suffer from a significant decrease in surface resistance due to adhesion of moisture in the atmosphere, making it impossible to obtain good images. Furthermore, organic dielectric layers such as polyamide and polyimide have insufficient abrasion resistance, resulting in problems such as surface cutting by cleaners and scratches, and sufficient durability cannot be obtained. Particularly when carrying out simultaneous pressure transfer and fixing, friction with the transfer paper is taken into account, making it even more difficult to use an organic recording layer. Furthermore, during long-term use, these organic recording layers are subject to oxidation by ozone under a high electric field, resulting in a decrease in moisture resistance. Polyimide and polyamide resins are weak against impact and are prone to crack-like scratches, causing peeling at these locations.Furthermore, pressure transfer methods have a high surface energy, resulting in a transfer efficiency of 80%.
It tends to be low. Further, although fluororesin has good transfer efficiency, it is soft and easily causes scratches. Further, in the case of the pressure transfer method, the surface of the dielectric layer is brought into contact with the pressure roller under pressure, so that triboelectric charges are induced on the surface of the dielectric layer. The polarity and amount of charge induced at this time vary depending on the material of the pressure contact member, such as the composition of the transfer material and the resin composition of the pressure roller, the surface roughness of the pressure contact member, and the temperature and humidity of the usage environment. The impact is significant. For this reason, if triboelectric charging with a significantly higher potential than the potential of the electrostatic latent image or triboelectrical charging with a polarity opposite to that of the electrostatic latent image occurs, uniform charge removal becomes difficult. In addition, unnecessary tribo-electrification on the dielectric surface promotes the adhesion of discharge products and charged fine particles such as paper dust, and furthermore, as these adhering substances absorb moisture, the surface resistance significantly decreases, resulting in image distortion. have a negative impact on Furthermore, if the distribution of triboelectric charges on the surface of the dielectric layer is non-uniform, ion implantation during formation of an electrostatic latent image may be inhibited, resulting in adverse effects such as image blurring and white spots. In order to eliminate the above-mentioned drawbacks, it is possible to stabilize triboelectric charging by reducing the occurrence of triboelectrification or by increasing the attenuation rate of the triboelectric potential by using a dielectric material with a low insulation resistance value. However, a material with a low resistance value could not be used because the surface resistance of the dielectric material would also decrease, making it impossible to obtain a stable electrostatic latent image and distorting the image. As mentioned above, it is not easily affected by moisture in the air, has good transfer efficiency, and has excellent abrasion resistance, impact resistance,
No material has yet been obtained that simultaneously satisfies all the characteristics of ozone resistance, has no adverse effect on images due to triboelectrification, and is durable for long-term use. [Problems to be Solved by the Invention] The object of the present invention is to provide an electrostatic recording device that can be used in an electrostatic recording device, particularly an electrostatic recording device that uses pressure to transfer a toner image on the surface of an electrostatic layer of a recording medium onto plain paper. It is a recording medium that can be used multiple times, has good toner transfer efficiency, prevents negative effects on images due to frictional charging,
The object of the present invention is to provide a good electrostatic recording medium that can provide high-quality images over a long period of time. That is, the present invention provides an electrostatic recording medium having a dielectric layer and a conductive base material used in a transfer method, in which the dielectric layer has the following components (A) to (C) (A) surface resistance after film formation. Film-forming resin (B) with a static friction coefficient of ^0.4 or less, a lubricant with a static friction coefficient of 0.4 or less, a functional segment that has surface migration properties, and a compatible segment that is compatible with the film-forming resin. , or the fluorine-containing block copolymer (C) contains a mixture containing an inorganic fine powder with a volume resistivity of less than 10 ¹⁰ Ω·cm, and the dielectric layer is applied directly onto the conductive substrate or by other means. This is an electrostatic recording medium characterized in that a film is formed through a dielectric layer. FIG. 1 shows a dielectric drum 1 serving as a recording medium in which a dielectric layer 2 is provided as a recording layer on a conductive base material 3. Here, the shape of the recording body is not limited to the drum shape as shown in FIG. 1, but may be belt-shaped or flat plate-shaped. The conductive base material 3 is selected from aluminum, aluminum alloy, stainless steel, and other metals, and preferably has a thickness that is not deformed by pressure during pressure transfer or pressure transfer and simultaneous fixing. In addition, in order to harden the surface of the conductive substrate or increase the surface area of the conductive substrate to improve the adhesion of the dielectric layer coated, for example, anodizing the aluminum alloy surface or hardening the stainless steel surface. Chrome plating may also be performed. Next, the film-forming resin used as the component (A) constituting the dielectric layer 2 should have a surface resistance of 10 ¹² Ω or more, preferably 10 ¹³ Ω or more after film formation, in order to obtain a stable electrostatic latent image. This is appropriate from the point of view of the situation. Specifically, the film-forming resins used include, for example, polyimide, polyamideimide, polyamide, polyesterimide, polyester, polyvinyl formal, epoxy resin, polyurethane, melamine resin, acrylic resin, polymethylmethacrylate, polyacrylamide, and silicone resin. , silicone polyimide resin, silicone epoxy resin, silicone ester resin, imide epoxy resin, urethane acrylate resin, epoxy acrylate resin, phenolic resin, polyacetal,
Examples include fluororesin. In addition, the static friction coefficient as a component of the dielectric layer is 0.4.
The following lubricants and/or fluorine-containing block copolymers (component B) are used. If the coefficient of static friction exceeds 0.4, sufficient sliding properties and good developer transfer efficiency cannot be obtained. Specific examples of the component (B) lubricant include fluorine-containing compounds such as polytetrafluoroethylene and polycarbon monofluoride, as well as polyethylene and nylon. By using one or more of the above lubricants as component B of the mixture, the releasability, non-adhesiveness, smoothness, and slipperiness of the dielectric layer can be improved, and the transfer efficiency of the developer can be improved. This makes it difficult for organic components in the developer to adhere to the dielectric layer, and improves the abrasion resistance of the dielectric layer. The fluorine-containing block copolymer used in the present invention is
It has a functional segment that has surface migration properties and a compatible segment that is compatible with the above-mentioned film-forming resin. Specifically, it is an A-B type block copolymer obtained by block polymerizing a fluorine-containing monomer component (for example, the fluorine-containing alkyl group described below) that acts as a functional segment on one end of a polymer that acts as a compatible segment. be. The fluorine-containing monomer component that acts as a functional segment is -CH ₂
(CF ₂ ) ₂ H, −CH ₂ (CF ₂ ) ₄ H, −CH ₂ CF ₃ , −CH ₂ CH ₂
Fluoroalkyl groups such as ( _{CF2 ) 7CF3 , -CF3} , _C2F6 are preferred. Further, as the polymer that acts as a compatible segment, one containing a vinyl monomer component is preferable, and specifically, polymethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, etc. are suitable. A-B containing this fluoroalkyl group as one component
The compatible segments of the type fluorine-containing block copolymer are compatible with the film-forming resin, making it possible to improve the adhesion of the coating film to the substrate and the hardness, and also act as functional segments. The fluoroalkyl group migrates to the surface, forming a coating film surface, mold releasability,
Non-adhesiveness and slipperiness can be improved. These points cannot be obtained when random polymers of the same composition are used. These fluorine-containing block copolymers can be synthesized using polymer peroxide as a polymerization initiator [Proceedings of the 33rd Annual Conference of the Society of Polymer Science and Technology, p. 266 (Vol. 33, No. 2, 1984) )]. Furthermore, as the fluorine-containing block copolymer, Moviper F100, F110, F200, and F210 manufactured by NOF Corporation can be used. This fluorine-containing block copolymer is a preferred lubricant not only for improving the transfer efficiency and abrasion resistance as described above, but also for obtaining an electrostatic recording material with always stable electrical properties without being subjected to ozone oxidation. The reason for this has not yet been fully elucidated, but one reason is that fluoroalkyl components are less susceptible to ozone oxidation.
The substrate component obtained by block polymerization is easily compatible with the film-forming resin component C used, and it is presumed that the fluoroalkyl component is regularly distributed on the surface of the recording medium in an extremely microscopic state. The amount of these lubricants added is 0.001 to 300 parts by weight, preferably 0.01 to 100 parts by weight, per 100 parts by weight of the film-forming resin.
If the amount added is less than 0.001 part by weight, the effect of improving mold releasability and slipperiness will not be sufficient;
If it exceeds 300 parts by weight, the impact resistance of the resulting coating film will decrease. Further, the inorganic fine powder used as component C has a volume resistivity of less than 10 ¹⁰ Ω·cm. resistivity is
If it exceeds 10 ¹⁰ Ω・cm, it becomes susceptible to the effects of triboelectric charging. Preferably, the volume resistivity is 10 ⁷ Ω·cm or less. Further, the average particle size of the inorganic fine powder is preferably 10 μm or less, more preferably 5 μm or less.
When the average particle size exceeds 10 μm, the dispersibility of the inorganic fine powder in the coating film tends to decrease. Such inorganic fine powders include, for example, SnO ₂ , SnO ₂ −
Tin oxide-based inorganic oxides such as TiO ₂ , SnO ₂ -BaSO ₄ , iron sesquioxide, triiron tetroxide, nickel sesquioxide, zinc oxide, other metal oxides, or silicon carbide, polycarbon monofluoride, carbon Non-oxidizing inorganic compounds such as black, or copper,
zinc, aluminum, silicon, iron, cobalt,
Fine metal powders such as nickel, manganese, tungsten, tin, and antimony, or fine inorganic powders that have undergone conductive treatment and have a high resistance (volume resistance of 10 ^{to 10} Ωcm or more) such as silicon dioxide, activated clay, acid clay, Gold on kaolin alumina powder, zeolite, etc.
These include electroless plated materials such as silver, copper, and nickel. By using inorganic fine powder with a volume resistivity of less than 10 ¹⁰ Ω・cm as a component for forming the dielectric layer, the surface resistance of the dielectric layer is not significantly reduced.
A dielectric layer is provided that provides a stable electrostatic latent image and at the same time does not cause image disturbance due to frictional charging with plain paper as transfer paper or a pressure roller. The amount added is 0.1 to 100 parts by weight of film-forming resin.
300 parts by weight, preferably in the range of 1 to 100 parts by weight. If the amount added is less than 0.1 part by weight, the effect of suppressing triboelectric charging will not be sufficient, while if it exceeds 300 parts by weight, the adhesion of the coating film to the substrate will decrease. There is a delicate correlation between the mold releasability and smoothness of the dielectric surface, the transfer efficiency ^of the transfer material, and triboelectric charging. Good images can be stably obtained over a long period of time only by using a dielectric layer obtained by adding it to a film-forming resin with a resistance of 10 ¹² Ω·cm or more. Next, preferred embodiments for producing a recording medium will be described. In the case of a drum-shaped recording medium, a cylinder is made of a conductive base material such as aluminum, aluminum alloy, or stainless steel. The wall thickness of the cylinder at this time needs to be thick enough to withstand pressure during pressure transfer or pressure transfer simultaneous fixing. In the case of aluminum and aluminum alloys, it is desirable to have a thickness of 10 mm or more. Next, the film-forming resin used in the present invention, a lubricant, and a volume resistivity of less than 10 ¹⁰ Ω·cm are applied to the cylinder surface directly or through another dielectric layer.
A coating consisting of fine powder with a particle size of 10 μm or less and, if necessary, a solvent, a hardening agent, a dispersion aid, an additive pigment for improving hardness, a dye, etc., is applied and dried to form a film.
The film thickness at this time is preferably at least 3 μm or more, preferably 10 μm or more in order to maintain electrical insulation. Next, the dielectric drum prepared as described above is incorporated into an electrostatic recording apparatus shown in FIG. 2 as a recording medium. The configuration of the electrostatic recording device shown in FIG. 2 will be briefly described as follows.
The electrostatic latent image is formed using the recording head 4,
As a method, the multi-stylus disclosed in Japanese Patent Publication No. 36-4119, or the method disclosed in Japanese Patent Application Publication No. 53-96834,
Any of the ion implantation type disclosed in Japanese Patent Publication No. 54-53537 can be used, and basically any type that can form an electrostatic latent image on the surface of the dielectric 2 in a dot shape may be used. Preferably, a type that does not involve direct discharge between the dielectric 2 and the recording head 4, such as the latter ion implantation type, is used. Next, the electrostatic latent image formed by the above method is visualized in the developing section 5, and then the pressure roller 7
is transferred onto plain paper 9 by pressure. In this case, if a pressure fixable toner is used, the visible image is transferred to the plain paper and fixed at the same time. Next, in accordance with a conventional method, the recording medium after the visible image has been transferred is neutralized by the static eliminator unit 8, and the residual toner remaining after the transfer is removed by the cleaner unit 6. Note that in order to record an electrostatic latent image on the dielectric drum 1 using the electrostatic recording head 4 in accordance with an image signal, Japanese Patent Laid-Open No. 54
The electrostatic recording head (ion generator) disclosed in Japanese Patent No. 78134 can be used. The electrostatic recording head 4 includes a dielectric 3 as shown in FIG.
5, drive electrode 36, control electrode 37,
It consists of a screen electrode 39 with ion emitting apertures 38. An AC voltage is applied between the drive electrode 36 and the control electrode 37 by the power supply 34, and a DC voltage is applied from the power supply 31 between the control electrode 37 and the conductive substrate 3 of the dielectric drum 1 via the switch 33. A voltage is applied, and a DC voltage is applied between the screen electrode 39 and the conductive substrate 3 from the power source 32 . Drive electrode 36
By the alternating current voltage applied between the control electrode 37 and the control electrode 37, positive and negative ions are generated alternately. If the switch 33 is turned on (conducted to the contact Y) by the image signal, the negative ions are accelerated and reach the dielectric layer 2 of the dielectric drum 1, where they are held. At this time, since positive ions are not accelerated, they are discharged between them and the control electrode 37. If there is no image signal and the switch 33 is off (conducting to contact X), both positive and negative ions will not be accelerated and will be discharged between them and the control electrode 37. In this way, an electrostatic latent image can be recorded according to the image signal. An example will be explained. 1 Static friction coefficient is the value when an object (lubricant) is stationary on the same substance, and is actually the value of Toyo Seiki Co., Ltd.
This is a value measured using a TSS type friction coefficient tester. Example 1 After applying cyclized butadiene rubber paint JSR CBR-M (trade name of Japan Synthetic Rubber Co., Ltd., containing 80% by weight of xylene) to the outer peripheral surface of an aluminum alloy cylinder with an inner diameter of 60 mm, an outer diameter of 100 mm, and a length of 230 mm. 180
The cylinder was heated and dried at ℃ for 60 minutes to obtain a cylinder having a coating thickness of 3 μm. In this cylinder, add 100 g of UV-curable epoxy acrylate paint, Unidek V5502 (product of Dainippon Ink and Chemicals Co., Ltd.) (surface resistance after film formation: 8.0 x 10 ¹⁵ Ω), tin oxide powder (average particle size: 0.1 μm, volume resistivity).
1Ω・cm) 10g A-B type block polymer containing a fluoroalkyl group as one component 5g Modiver F200 (product of NOF Corporation) 2-ethylanthraquinone (photoreaction accelerator) 2g methyl ethyl ketone 30g obtained by mixing After drying at 80℃ for 10 minutes, the paint was irradiated with a 4kW concentrating ultraviolet lamp at a distance of 15cm for 1 minute to form a film with a coating thickness of 18μm, which together with the cyclized butadiene rubber layer had a thickness of 21μm. A cylinder having a coating film of . This cylinder was incorporated into the electrostatic recording device shown in FIG. 2, and images were printed using an ion implantation type recording head and a pressure roller whose surface was made of polyacetal. The results are shown in Table 1. Comparative Example 1 A cylinder was prepared and imaged in exactly the same manner as in Example 1, except that Modevar F200 (same as above) used as the paint for coating the cylinder surface in Example 1 was removed. [Coating film thickness 21 μm (including 3 μm lower layer)] The results are shown in Table 1. Comparative Example 2 A cylinder was prepared and printed in exactly the same manner as in Example 1, except that the tin oxide used in the paint for coating the cylinder surface in Example 1 was omitted.
[Coating film thickness 21 μm (including lower layer 3 μm)] The results are shown in Table 1. Example 2 A cylinder provided with the cyclized butadiene rubber layer (3 μm) used in Example 1 was coated with 100 g of UV-curable urethane acrylate paint. (Surface resistance after film formation 5.0×10 ¹⁵ Ω) Polycarbon monofluoride powder (Average particle size
1.0μm, volume resistivity 2.0×10 ³ Ω・cm; static friction coefficient
0.02) 5g A-B type block polymer containing a fluoroalkyl group as one component 1g Modiver F100 (product of NOF Corporation) Alumina powder (for improving hardness, average particle size 1 μm)
5g Polyvinyl butyral (for improving the dispersibility of alumina and polycarbon monofluoride) (Eslec
BMI Sekisui Chemical product) 3g ethyl alcohol 10g and butyl acetate 30g were mixed and the resulting paint was applied, dried at 80℃ for 10 minutes, and then irradiated with a 4kW concentrating ultraviolet lamp at a irradiation distance of 15cm for 1 minute to determine the coating thickness. A cylinder was obtained which had a coating film of 14 μm in thickness including the cyclized butadiene rubber layer formed to a thickness of 11 μm. Using this cylinder, the cylinder was prepared and imaged in exactly the same manner as in Example 1. The results are shown in Table 1.

【table】

〔Effect of the invention〕

As explained above, in a transfer type electrostatic recording device, especially a pressure transfer type electrostatic recording device, a film-forming resin with a surface resistance of 10 ¹² Ω or more has a critical surface tension of 50 dyn/cm or less at 25°C and/or a pressure transfer type electrostatic recording device. Or the coefficient of static friction is
By using a recording medium with a dielectric layer made of a lubricant of 0.4 or less and a fine powder with a volume resistivity of less than 10 ¹⁰ Ω・cm, the slipperiness, mold releasability, and wear resistance of the dielectric surface can be improved. Furthermore, by eliminating the adverse effects of triboelectric charging on images, good images can be stably obtained over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view of a dielectric drum as a recording medium, and FIG. 2 is a schematic diagram of essential parts of an example of an electrostatic recording device incorporating the dielectric drum of FIG. 1.
FIG. 3 shows an electrostatic recording head. 1: dielectric drum, 2: dielectric layer, 3: conductive base material, 4: recording head, 5: developer, 6: cleaner set, 7: pressure roller, 8: static eliminator,
9: Plain paper.

Claims (1)

[Claims] 1. In an electrostatic recording medium having a dielectric layer and a conductive base material used in a transfer method, the dielectric layer contains the following components (A) to (C) (A) after film formation. A film-forming resin (B) with a surface resistance of 10 ¹² Ω or more, a fluorine-containing block containing a lubricant with a static friction coefficient of 0.4 or less, a functional segment with surface migration properties, and a compatible segment that is compatible with the film-forming resin. The polymer or the fluorine-containing block copolymer (C) contains a mixture containing an inorganic fine powder with a volume resistivity of less than 10 ¹⁰ Ωcm, and the dielectric layer is applied directly or directly onto the conductive substrate. An electrostatic recording medium characterized in that a film is formed via another dielectric layer. 2 The mixture contains 100 parts by weight of component (A),
Component (B) 0.001 to 300 parts by weight and component (C) 0.1
3. The electrostatic recording medium according to claim 1, which contains up to 300 parts by weight.