JPH055347B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to an electrostatic recording medium suitable for high-density recording electrostatic facsimiles such as 400 dots/inch, electrostatic printers, electrostatic plotters, and the like. (Prior art) Along with advances in communication technology, electrostatic recording is widely used as a recording method that simultaneously satisfies high-speed recording and high image quality. Examples of this are optical communications and computer output equipment. Examples include fax machines and printers. Especially in recent years, computers are used for designing and drafting.
Electrostatic printers and electrostatic plotters, which are capable of high-density recording, are preferred for outputting drawings such as CAD systems. The multi-needle electrode recording method that is most commonly used in electrostatic recording methods includes single-sided control type and double-sided control type, but in both cases, recording of about 200 dots/inch is mainly used for recording text. There was no particular problem in the generation of discharge itself, probably because the area of each needle electrode was sufficient in terms of density. However, when high-density recording of around 400 dots/inch is performed using conventional electrostatic recording materials, mainly for the purpose of recording drawings, when thin lines are drawn, normal discharge does not occur and the recording is not recorded after development. The so-called thin line dropout development occurs, in which small areas appear, or conversely, depending on the location, the discharge reaches more than 10 times the area of each needle electrode, and abnormally bulged spots appear in the fine lines after development. Abnormal discharge occurs and good recording cannot be obtained. (Problems to be Solved by the Invention) An object of the present invention is to provide a method for manufacturing an electrostatic recording medium that does not cause thin line dropout or abnormal discharge in high-density recording such as 400 dots/inch. (Means for Solving the Problems) The present inventors believe that there is a limit to the degree of improvement in solving the above problems by considering only the structure of the recording medium.
Further research was conducted on the discharge and charging conditions on the surface of the dielectric layer. Incidentally, it has conventionally been common general knowledge that the surface of the dielectric layer of an electrostatic recording medium must be free of static charge until an electrostatic charge for a recorded image is applied. At first glance, the present invention seems
Although this idea goes against common technical knowledge, the inventors of the present invention have found that, before applying electrostatic charges for forming recorded images, by charging them with electrostatic charges of opposite polarity to the applied charges, abnormal discharge can be resolved. We have been considering this with the idea that it might become a reality. As a result, we have arrived at an invention consisting of the following configuration. The present invention is an electrostatic recording system for electrostatic recording, which has a dielectric layer containing a pigment and an insulating resin on a conductive support, and applies electrostatic charge for forming a recorded image by discharging from a multi-needle electrode. A method for producing a recording medium, in which at least one resin each of a resin that is positively charged when rubbed with a friction treatment material and a resin that is negatively charged when rubbed with a friction treatment material is used as the insulating resin, and the dielectric resin is dielectrically charged with the friction treatment material. This method of manufacturing an electrostatic recording medium is characterized in that an electrostatic charge having a polarity opposite to the charge previously applied for recording is formed on the surface of a dielectric layer by rubbing the body layer. (Function) In the present invention, the treatment materials for rubbing the surface of the dielectric layer include polyethylene resin, polypropylene resin, polystyrene resin, polyether resin, polyvinyl chloride resin, polymethyl methacrylate resin, melamine resin, urea resin, There are phenolic resins, epoxy resins, amino resins, imide resins, etc. Among these, there is ease of processing as a processing material, wear resistance, ease of generating static charge when rubbed, and distribution on the dielectric layer. Due to the ease of controlling the diameter of electrostatic charge, thermoplastic resins such as polystyrene resin, copolymer resins of styrene-acrylic acid derivatives or styrene-methacrylic acid derivatives, polymethyl methacrylate resin, epoxy resins, etc.
Thermosetting resins such as melamine resin, urea melamine resin, and benzoguanamine resin are preferably used. These treatment materials can be used alone or in a mixture. Next, in the present invention, among the insulating resins constituting the dielectric layer of the electrostatic recording material, the resins that are positively charged when rubbed with the friction treatment material and the resins that are negatively charged are the resins that are negatively charged when rubbed with the friction treatment material. In relation to the pigment used in the dielectric layer, the polarity changes from positive to negative. However, the charge polarity of the insulating resin does not change depending on the blending ratio of the pigment and the resin. For example, if the friction treatment material is polymethyl methacrylate resin and the pigment is calcium carbonate, positively charged insulating resins include methyl methacrylate-ethyl acrylate copolymer, and negatively charged insulating resins include polymethyl methacrylate. Examples include methacrylate, polybutyl methacrylate, styrene-methyl methacrylate copolymer, polyester, polystyrene, and polyvinyl butyral. In addition, when the friction treatment material is polymethyl methacrylate resin and the pigment is fired clay, the positively charged insulating resin is polymethyl methacrylate, methyl methacrylate-ethyl acrylate copolymer,
Examples include polybutyl methacrylate, and negatively charged insulating resins include styrene-methyl methacrylate copolymer, polyester, polystyrene, polyvinyl butyral, and the like. Furthermore, if the friction treatment material is polymethyl methacrylate resin and the pigment is silica, polymethyl methacrylate, methyl methacrylate, ethyl methacrylate copolymer, polybutyl methacrylate, styrene-methyl methacrylate copolymer, polyester, polystyrene, polyvinyl butyral, etc. It becomes an insulating resin that is negatively charged. Next, when the friction treatment material is polystyrene resin and the pigment is calcium carbonate, positively charged insulating resins include methyl methacrylate-ethyl acrylate copolymer, polybutyl methacrylate, styrene-methyl methacrylate copolymer, polyester, and polystyrene. There are polyvinyl butyral and the like as negatively charged insulating resins. In addition, when the friction treatment material is polystyrene resin and the pigment is fired clay, positively charged insulating resins include methyl methacrylate-ethyl acrylate copolymer, polybutyl methacrylate, styrene-methyl methacrylate copolymer, polyester, etc. Examples of negatively charged insulating resins include polystyrene and polyvinyl butyral. Furthermore, when the friction treatment material is polystyrene resin and the pigment is silica, polymethyl methacrylate and methyl methacrylate are used as positively charged insulating resins.
Examples include ethyl acrylate copolymer, styrene-methyl methacrylate copolymer, polyester, etc., and negatively charged insulating resins include polybutyl methacrylate, polystyrene, polyvinyl butyral, etc. Accordingly, the present invention uses a pigment in the dielectric layer, and at least one type of resin that has a different friction charge polarity when mixed with the pigment, and a charge applied to the surface of the dielectric layer in advance for recording. By forming electrostatic charges of opposite polarity by friction between the friction treatment material and the surface of the dielectric layer, excellent thin line removal and abnormal electric charge improvement effects can be obtained. If it is formed on the dielectric layer in advance, when a developer with a polarity opposite to the applied charge for recording is used, a stain called fog will occur on the recorded image regardless of the resin composition of the dielectric layer, and it will also have the effect of improving fine line omission. I can't get it. Therefore, in the present invention, it is necessary to adjust the mixing ratio of the resin so that an electrostatic charge having a polarity opposite to that of the applied charge for recording is formed by friction. That is, when the applied charge for recording is of negative polarity, the resin is blended so that positive charges are formed on the dielectric layer in advance by friction. Among the above resins, for example, when a friction treatment material made of polymethyl methacrylate resin is used, calcium carbonate is used as the pigment contained in the dielectric layer, and methyl methacrylate is used as the insulating resin.
A mixture of ethyl acrylate copolymer and polybutyl methacrylate, or when using a friction treatment material made of polystyrene resin, a mixture of silica as the pigment contained in the dielectric layer and polyester and polyvinyl butyral as the insulating resin. The following combinations are possible. Next, the charging state due to friction can be adjusted by the composition of the treatment material, the strength of the friction pressure, the number of times of treatment, the friction speed, etc. In the friction treatment, the treated material is usually formed into a roll-shaped or plate-shaped body, or is coated on a sheet-like support and wound around a roll, and the treated material is applied to the surface of the dielectric layer of an electrostatic recording medium that normally runs. Processing is performed by pressing the electrostatic recording material, and the timing of the processing depends on the manufacturing process after forming the dielectric layer of the electrostatic recording medium, the finishing process, and also depending on the processing material built into the electrostatic recording device. It's good to wear. If the treatment material is in the form of a roll, performing the friction treatment while rotating can prevent scratches on the surface of the dielectric layer. Note that the electrostatic charge formed on the dielectric layer can be observed with an electron microscope. That is, when observing a secondary electron image with an accelerating voltage of about 2 kilovolts, positive electrostatic charges are expressed in black, and negative electrostatic charges are expressed in white. Electrostatic charges of opposite polarity to the electrostatic charges for the recorded image formed in advance according to the present invention are distributed in an island shape, and the size of each charge is 1 μ to 1 μm.
It is almost uniform within the range of 300μ. With such a recording medium, a clear image without missing lines or abnormal discharge can be obtained by recording one dot of a fine line using an electrostatic recording device. In the present invention, the charging state can be adjusted by the friction treatment conditions, but if the diameter of the electrostatic charge is too small, the effect of improving fine line omission will be insufficient, and if it is too large, abnormal discharge will not be reduced, so each island-shaped charge The maximum diameter is preferably adjusted to 1 μ to 300 μ, more preferably slightly smaller than the diameter of each needle electrode of the electrostatic recording device. On the other hand, in a recording medium made of an insulating resin in which the polarity of charges generated by friction is only one, the electrostatic charges of the opposite polarity to the electrostatic charges for the recorded image formed in advance on the dielectric layer are formed in the form of a net or island. However, even when distributed in an island-like manner, the size of each charge is irregular, and when a single dot thin line is recorded, thin line omission is improved compared to a recording medium that does not undergo any friction treatment. However, abnormal discharge increases significantly compared to a recording medium that is not subjected to any friction treatment. Although it is not necessarily clear why the electrostatic recording material of the present invention provides excellent recording without thin line omissions or abnormal discharge, it is clear that when the dielectric layer is rubbed by the friction treatment material, Contains a resin that is positively charged and a resin that is negatively charged, so the size, strength, and distribution of static charges generated by friction can be adjusted appropriately, resulting in the formation of a latent image. It is surmised that this causes a decrease in the discharge starting voltage at the time of discharge, resulting in more reliable discharge. The conductive support constituting the electrostatic recording medium may be an inorganic salt such as sodium chloride, a cationic polymer electrolyte such as polyvinylbenzyltrimethylammonium chloride, an anionic polymer electrolyte, a surfactant, or an oxidized polymer electrolyte. Paper, plastic film, cloth, etc. impregnated with or coated with metal oxide semiconductor powder such as zinc or zinc oxide treated to make it conductive, and having a surface resistance of 10 ⁵ to ^{10 11} Ω, are used. (Examples) Examples of the present invention will be described below, but the present invention is not limited only to these Examples.
Further, unless otherwise specified, parts and % in the examples indicate parts by weight and % by weight, respectively. Example 1 Preparation of recording medium: A cationic polymer electrolyte (trade name: Chemistat 6300, manufactured by Sanyo Chemical Co., Ltd.) was placed on the surface of high-quality paper with a weight of 53 g/m ² at an absolute dry weight of 3
g/m ² , and the back surface was coated at 2 g/m ² to obtain a conductive support. A dielectric layer coating material having the following composition was coated on this conductive support so that the dry weight was 5 g/m ² and dried to obtain an electrostatic recording material. Toluene 200 parts Calcium carbonate 50 parts Methyl methacrylate-ethyl acrylate copolymer resin (copolymerization ratio 1:1) 25 parts Polybutyl methacrylate resin 25 parts This recording material was subjected to a charge polarity test and static charge on the dielectric layer surface due to friction. A recording test was conducted after the formation. Charging polarity test The surface of the dielectric layer of the electrostatic recording medium was rubbed 20 times with a roll made of polymethyl methacrylate resin (friction treatment material), and the polarity of the potential was examined using a surface electrometer. Formation of electrostatic charge on the surface of the dielectric layer The electrostatic recording material was placed on a glass plate with the dielectric layer facing up, and the surface was covered with the weight (2
Kg) (pressure 260g/cm ² , contact width 3mm)
A static charge was created by rubbing at a speed of 10 m/min. Recording test method Electrostatic plotter for CAD system manufactured by Matsushita Electric Transmission Co., Ltd.
A one-dot thin line was recorded using EP-101A1 (which applies a negative electrostatic charge using a needle electrode to form a latent image), and the number of thin line omissions and abnormal discharges in a 50 cm thin line was counted. Comparative Example 1 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 1 except that the composition of the dielectric layer paint was changed to the following. Toluene 200 parts Calcium carbonate powder 50 parts Methyl methacrylate-ethyl acrylate copolymer resin (copolymerization ratio 1:1) 50 parts This recording medium was subjected to a charge polarity test in the same manner as in Example 1, and static electricity was applied to the surface of the dielectric layer by friction. After the charge was formed, a recording test was performed. Comparative Example 2 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 1 except that the composition of the dielectric layer paint was changed to the following. Toluene 200 parts Calcium carbonate powder 50 parts Polybutyl methacrylate resin 50 parts This recording medium was subjected to a charging polarity test in the same manner as in Example 1, and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction. Comparative Example 3 A recording test was conducted in the same manner as in Example 1, except that no electrostatic charge was formed on the surface of the dielectric layer of the recording medium due to friction. Example 2 Preparation of recording material: A recording material was obtained in the same manner as in Example 1, except that a dielectric layer paint having the following composition was applied at a dry weight of 4 g/m ² . Methyl ethyl ketone 200 parts Silica powder 20 parts Polymethyl methacrylate resin 60 parts Polybutyl methacrylate resin 20 parts This recording medium was subjected to a charging polarity test and a recording test after electrostatic charge was formed on the surface of the dielectric layer by friction. Charging polarity test The surface of the dielectric layer of the electrostatic recording medium was rubbed 20 times with a polystyrene resin roll (friction treatment material), and the polarity of the potential was examined using a surface electrometer. Formation of electrostatic charge on the surface of the dielectric layer The electrostatic recording material was placed on a glass plate with the dielectric layer facing up, and the surface was coated using the weight (2 kg) of a polystyrene resin roll (friction treatment material) with a diameter of 100 mm. (pressure 260 g/cm ² , contact width 3 mm) at a speed of 10 m/min to form an electrostatic charge. Recording test method Same as Example 1. Comparative Example 4 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 2 except that the composition of the dielectric layer paint was changed to the following. Methyl ethyl ketone 200 parts Silica powder 20 parts Polymethyl methacrylate resin 80 parts This recording medium was subjected to a charging polarity test in the same manner as in Example 2, and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction. Comparative Example 5 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 2 except that the composition of the dielectric layer paint was changed to the following. Methyl ethyl ketone 200 parts Silica powder 20 parts Polybutyl methacrylate resin 80 parts This recording medium was subjected to a charging polarity test in the same manner as in Example 2, and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction. Comparative Example 6 A recording test was conducted in the same manner as in Example 2, except that no static charge was formed on the surface of the dielectric layer of the recording medium due to friction. Example 3 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 1, except that a dielectric layer paint having the following composition was applied at a dry weight of 4 g/m ² . Methyl ethyl ketone 200 parts Calcined clay powder 30 parts Polyvinyl butyral resin 40 parts Polyester resin 30 parts This recording medium was subjected to a charging polarity test and a recording test after electrostatic charge was formed on the surface of the dielectric layer by friction. Charging polarity test The surface of the dielectric layer of the electrostatic recording medium was rubbed 20 times with a polystyrene resin roll (friction treatment material), and the polarity of the potential was examined using a surface electrometer. Formation of electrostatic charge on the surface of the dielectric layer Place the electrostatic recording material on the glass plate with the dielectric layer facing up, and use the dead weight (2 kg) of a polystyrene resin roll (friction treatment material) with a diameter of 100 mm to cover the surface. A charge was formed by rubbing at a speed of 10 m/min (pressure 260 g/cm ² , contact width 3 mm). Recording test method Same as Example 1. Comparative Example 7 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 3 except that the composition of the dielectric layer paint was changed to the following. Methyl ethyl ketone 200 parts Calcined clay powder 30 parts Polyester resin 70 parts This recording medium was subjected to a charge polarity test in the same manner as in Example 3, and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction. Comparative Example 8 Preparation of Recording Body: A recording body was obtained in the same manner as in Example 3 except that the composition of the dielectric layer paint was changed to the following. Methyl ethyl ketone 200 parts Calcined clay powder 30 parts Polyvinyl butyral resin 70 parts This recording medium was subjected to a charging polarity test in the same manner as in Example 3, and a recording test after forming electrostatic charges on the surface of the dielectric layer by friction. Comparative Example 9 A recording test was conducted in the same manner as in Example 3, except that no electrostatic charge was formed on the surface of the dielectric layer of the recording medium due to friction. The above results are shown in Table 1.

【table】

[Table] In Examples 1 to 3 according to the present invention, recordings with almost no thin line omissions or abnormal discharges were obtained. On the other hand, recording bodies having a dielectric layer consisting only of pigment and positively charged resin (Comparative Examples 1, 4, 7)
In this case, abnormal discharge was significant even after friction treatment, and recording bodies with dielectric layers made only of negatively charged resin (Comparative Examples 2, 5, and 8) had many thin lines missing even after friction treatment. , fog stains (stains in which the margins are thinly colored over the entire surface) occurred. Furthermore, even if a positively charged resin and a negatively charged resin are mixed and used, recording materials that do not form static charges due to friction (Comparative Examples 3, 6, and 9) have many fine line omissions and abnormal discharges.
All had poor recording aptitude. (Effects) The electrostatic recording material of the present invention is an excellent electrostatic recording material that can obtain clear recorded images without thin line omissions or abnormal discharge even in the case of high-density electrostatic recording such as 400 dots/inch. My body was warm.

Claims (1)

[Claims] 1. An electrostatic recording medium for electrostatic recording method, which has a dielectric layer containing a pigment and an insulating resin on a conductive support, and applies electrostatic charge for forming a recorded image by discharging from a multi-needle electrode. The manufacturing method includes at least one resin that is positively charged when rubbed with a friction treatment material and one resin that is negatively charged as the insulating resin.
An electrostatic recording material characterized in that an electrostatic charge having a polarity opposite to the charge previously applied for recording is formed on the surface of the dielectric layer by using seeds one by one and rubbing the dielectric layer with a friction treatment material. manufacturing method.