JPH0352052B2 - - 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 method in which a dielectric thin film 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 this latent image is developed with toner and then transferred and fixed onto plain paper using pressure. are 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 emenal, 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. As mentioned above, a dielectric material that is not easily affected by moisture in the air, has good transfer efficiency, and simultaneously satisfies all of the characteristics of wear resistance, impact resistance, and ozone resistance has not been obtained. [Problems to be Solved by the Invention] The purpose of the present invention is to apply it to a pressure transfer type electrostatic recording device, especially a pressure transfer simultaneous fixing type electrostatic recording device, so that it can be used in a high temperature and high humidity environment without being oxidized by ozone or the like. An object of the present invention is to provide an electrostatic recording medium that can record high image quality with high transfer efficiency even after repeated use for a long period of time. [Means for Solving the Problems] That is, the present invention provides an electrostatic recording medium that is used in a transfer method and has a dielectric layer and a conductive base material, in which the dielectric layer contains the following components (A) to (C). ) (A) Inorganic powder with a volume resistivity of ^10-10 Ω・cm or more (B) Film-forming resin with a surface resistance of ^10-12 Ω or more after film formation (C) Lubricant with a static friction coefficient of 0.4 or less and surface migration properties or a mixture containing the fluorine-containing block copolymer, and the dielectric layer contains a fluorine-containing block copolymer having a functional segment having This is an electrostatic recording medium characterized by being formed into a film directly or via another dielectric layer on a conductive base material. 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 medium 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 applied. Next, the dielectric layer 2 is formed by applying a mixture containing (A) component inorganic fine powder, (B) component film-forming resin, and (C) component lubricant onto the conductive substrate directly or through another dielectric layer. It was formed into a film. Here, the surface resistance of component (B) resin for film formation after film formation is
A resistance of 10 ¹² Ω or more, preferably 10 ¹³ Ω or more is suitable from the viewpoint of obtaining a stable electrostatic latent image. 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, component (A) component inorganic fine powder has a volume resistivity of
It is desirable that the resistance is 10 ¹⁰ Ω·cm or more, preferably 10 ¹¹ Ω·cm or more, so that the volume resistivity of the entire dielectric can be increased and a stable electrostatic latent image can be obtained. Furthermore, it is preferable that the average particle size is 10 μm or less, so that the dispersibility of the fine powder in the coating film becomes good and a uniform coating film can be obtained. Specifically, such fine powders include alumina, magnesium oxide, boron nitride,
Asbestos, silica, glass powder, natural mica, synthetic mica, barium titanate, magnesium titanate, zirconium titanate, zircon, beryllia, etc. or mixtures thereof can be used. The particle size distribution of the inorganic fine powder may be uniform, or it may be a combination of particles of different sizes so that the dielectric layer has a structure as dense as possible, and it may also have a scale-like or A fibrous material may also be used. The mixing ratio of component (A) component inorganic fine powder and component (B) component film forming resin is 100 parts by weight of the former and 5 to 300 parts by weight of the latter.
Preferably it is in the range of 20 to 200 parts by weight. If the film-forming resin is less than 5 parts by weight, the impact resistance of the dielectric will decrease and the image will deteriorate in a high humidity environment.
If it exceeds 300 parts by weight, the ozone resistance properties will be reduced and the dielectric surface will be more likely to be cut or scratched by the cleaner, making it impossible to obtain sufficient durability. Next, as component (C) of the above mixture, the coefficient of static friction is
A lubricant of 0.4 or less and a fluorine-containing block copolymer,
Alternatively, a fluorine-containing block copolymer is 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 (C) 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 (C) of the mixture, the releasability, non-adhesiveness, smoothness, and slipperiness of the dielectric layer can be improved, and the transfer of the developer can be improved. Efficiency is increased, organic components in the developer are less likely to adhere to the dielectric layer, and the wear resistance of the dielectric layer is improved. 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 and can improve the water repellency, mold releasability, non-adhesiveness, and slipperiness of the coating surface. 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) )]. Further, 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 is not yet fully understood, but one reason is that fluoroalkyl components are resistant to ozone oxidation.
The substrate component obtained by block polymerization is easily compatible with the film-forming resin (B) component used, and it is inferred that the fluoroalkyl component is regularly distributed on the surface of the recording medium in an extremely microscopic state. be done. The blending amount of these lubricants is 0.001 to 300 parts by weight, preferably 0.01 to 300 parts by weight, per 100 parts by weight of component (A) inorganic powder.
In the range of 100 parts by weight. If the blending amount is less than 0.001 parts by weight, the effect of improving mold releasability and slipperiness will not be sufficient,
On the other hand, if it exceeds 300 parts by weight, the impact resistance of the resulting coating film will decrease. In order to form a dielectric layer as described above on a conductive base material, the mixture is extruded and coated on the conductive base material or on a conductive base material on which another dielectric layer is formed. Alternatively, a diluent may be added to the mixture to make it into a liquid, and this may be used for coating. Next, a preferred mode of creating 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, fine powder, and lubricant used in the present invention are applied directly to the cylinder surface or via another dielectric layer, and if necessary, a solvent,
A film is formed by applying and drying a paint containing a hardening agent, dispersion aid, hardness improving additive, pigment, dye, etc. 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 the contact X), both positive and negative ions will not be accelerated and will be electrically discharged between them and the control electrode 37. In this way, an electrostatic latent image can be recorded according to the image signal. Next, an example will be described. In the examples, the static friction coefficient is the object (lubricant)
This is the value when the friction coefficient is stationary on the same material, and it is actually the value measured by Toyo Seiki's 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, (1) potassium tetrasilicon mica, which is a synthetic mica [KMg _2.5
(Si ₄ O ₁₀ )F ₂ ] powder (volume resistivity 5.0×10 ¹⁴ Ω・
cm, average particle size 2.5μm) 25g (2) Alumina (Al ₂ O ₃ ) powder (volume resistivity 4.0×
10 ¹⁴ Ω・cm, average particle size 1.0μm) 75g (3) A-B type block polymer Modever F200 (product of NOF Corporation) containing a fluoroalkyl group as one component 5g (4) UV-curable epoxy Acrylate paint Unitek V5502 (product of Dainippon Ink and Chemicals Co., Ltd.) (surface resistance after film formation 8.0×10 ¹⁵ Ω) 50g 2-ethylanthraquinone (photoreaction accelerator)
Apply the paint obtained by mixing 1.0g of methyl ethyl ketone and 40g of it, dry it at 80℃ for 10 minutes, and then use a 4kW concentrating ultraviolet lamp at a irradiation distance of 15cm.
The cylinder was irradiated for 30 seconds to obtain a cylinder on which a cyclized butadiene rubber layer was formed with a coating thickness of 18 µm, and a coating film with a thickness of 21 µm was formed. Example 2 In the same cylinder as used in Example 1 (cyclized butadiene rubber layer 3 μm); synthetic mica potassium tetrasilicon mica (KMg _2.5
(Si ₄ O ₁₀ )F ₂ ) powder (volume resistivity 5.0×10 ¹⁴ Ω・cm,
Average particle size: 2.5μm) 5g Alumina (Al ₂ O ₃ ) powder (volume resistivity: 4.0×
10 ¹⁴ Ω・cm, average particle size 1.0μm) 95g polytetrafluoroethylene powder (static friction coefficient
0.06, average particle size 0.3μm) 10g A-B type block polymer Modever F200 (product of NOF Co., Ltd.) containing a fluoroalkyl group as one component 2g UV-curable urethane acrylate paint (resin content
75%) Unidek 17-824 (product of Dainippon Ink & Chemicals Co., Ltd.) (Surface resistance after film formation: 8.2×10 ¹⁵ Ω)
Apply the paint obtained by mixing 60g of butyl acetate and 40g of butyl acetate, dry for 10 minutes at 80℃, and then use a 4kW concentrating ultraviolet lamp at a distance of 15cm.
The cyclized butadiene rubber layer was irradiated for 30 seconds to obtain a cylinder on which a 15 μm thick coating was formed including the cyclized butadiene rubber layer with a coating thickness of 12 μm. Example 3 An electrostatic recording material was prepared in the same manner as in Example 1 except that the potassium tetrasilicon mica used in Example 1 was removed. Final film thickness 19μm (cyclized butadiene rubber layer 3μm
(including) cylinders were obtained. Comparative Example 1 A cylinder with a coating thickness of 19 μm (including a cyclized butadiene rubber layer of 3 μm) was prepared in the same manner as in Example 1, except that the alumina powder and potassium tetrasilicon mica used for surface coating in Example 1 were removed. I got it. Comparative Example 2 The coating film thickness was determined in exactly the same manner as in Example 1, except that the A-B type block polymer (Modevar F200) containing a fluoroalkyl group as one component, which was used for surface coating in Example 1, was removed. A cylinder of 22 μm (including a 3 μm layer of cyclized butadiene rubber) was obtained. The recording cylinders obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were incorporated into the electrostatic recording device described above, and an image forming durability test was carried out.
We also conducted durability tests using corona irradiation. [Test 1] Corona irradiation was performed for Example 1 and Comparative Example 1, and changes in surface conditions were compared. The corona irradiation time was 600 minutes, and the surface resistance of both was measured at room temperature.
Measurements were made under conditions of normal humidity (23°C 60%) and high temperature and high humidity (33°C 90%). The results are shown in Table 1.

[Test 2]

For the above-mentioned Example 2 and Comparative Example 2, durability was conducted by image formation. The durability conditions are such that an electrostatic latent image is formed on the coating film of the recording cylinder using the electrostatic recording device described above, this is developed using dry pressure toner, and this toner image is applied to transfer paper under pressure. Simultaneous transfer and fixing was performed. The durability is 100,000 sheets using A4 paper. The transfer efficiency of both recording cylinders before and after this durability test was compared. The results are shown in Table 2.

〔Effect of the invention〕

As explained above, a recording medium in which a mixture of an inorganic powder, a lubricant, and a film-forming resin is provided on a conductive substrate is used in a transfer type electrostatic recording device, particularly a pressure transfer type electrostatic recording device. As a result, an electrostatic recording material with good corona resistance and high toner transfer efficiency could be obtained.

[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. An electrostatic recording medium having a dielectric layer and a conductive base material used in a transfer method, wherein the dielectric layer has the following components (A) to (C) (A) and has a volume resistivity. Inorganic powder with a resistance of 10 ¹⁰ Ω・cm or more (B) Film-forming resin with a surface resistance of 10 ¹² Ω or more after film formation (C) Film formation with a lubricant with a static friction coefficient of 0.4 or less and a functional segment with surface migration properties containing a fluorine-containing block copolymer having a compatible segment that is compatible with the resin for use, or a mixture containing the fluorine-containing block copolymer, 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 above mixture contains 100 parts by weight of component (A)
The electrostatic recording medium according to claim 1, containing 5 to 300 parts by weight of (B) and 0.001 to 300 parts by weight of component (C).