JPS6338699B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic toner for developing electrostatic latent images used in electrophotography, electrostatic recording, and electrostatic printing. More specifically, it has good fixing properties and offset prevention properties on hot rolls, as well as good thermal stability (storage stability).
The present invention relates to a magnetic toner for developing electrostatic latent images that has excellent fluidity and printing durability (characteristics that do not stain the photoreceptor). In general, there are two types of developers: two-component developers that require a carrier, and one-component developers (magnetic toner) that do not require a carrier.The methods for fixing these developers on a substrate such as paper are , a pressure fixing method in which the material is passed between two or more metal rolls, an oven fixing method in which the material is passed through an atmosphere heated by an electric heater, and a hot roll fixing method in which the material is passed between heated rollers. In the heat roll fixing method, the surface of the heating roller and the surface of the developer on the substrate to be fixed come into pressure contact, so the thermal efficiency when fusing the developer image onto the substrate to be fixed is extremely good, and the fixation is performed quickly. Therefore, it is extremely suitable for electrophotographic copying machines particularly intended for high-speed copying. However, in the hot roll fixing method, since the developer comes into pressure contact with the heated roller surface in a heated molten state, a part of the developer adheres to the roller surface and then adheres to the fixing substrate again, which tends to cause an offset phenomenon that stains the image. There is. Therefore, offset prevention properties are an important and essential requirement for a developer for a hot roll fixing system. Various methods have been proposed to prevent developer offset. For example, a method of using a specific fixing resin for a developer and increasing its molecular weight distribution (Japanese Patent Application Laid-Open No. 134652/1982);
A method of mixing a specific fixing resin with a liquid or solid resin having release properties to prevent the developer from adhering to the hot roll (Japanese Patent Publication No. 53-15655, No. 53-21655)
No. 53-23084, No. 53-25496, No. 53-
25653, 53-25654, 53-25655), etc. These methods were mainly proposed for two-component developers, and for one-component developers, especially magnetic toner, a large amount of magnetic powder (50% of the total toner weight) that does not melt at normal fixing temperatures is used.
(above), there was a difficulty in applying the above-mentioned prior art as is. Therefore, as a method to prevent offset of magnetic toner, the surface of the heating roller is made of a fluorine-based resin or silicone rubber that is heat resistant and has good releasability to the toner, and the surface is further coated with an offset prevention liquid such as silicone oil. A method has been adopted in which the roller surface is coated with a thin film of liquid. In this method, a liquid such as silicone oil is heated and generates an odor, and an extra device for supplying the liquid is required, making the mechanism of the copying device complicated. Also,
In order to prevent offsets with good stability, it is necessary to control the supply of liquid with high precision, which has the drawback of making the copying apparatus expensive. Therefore, there is a long-awaited magnetic toner that does not cause offset and provides a good fixed image even without the supply of an offset prevention liquid such as silicone oil. In view of such circumstances, the present invention can prevent toner offset even when using a heated roller that does not supply offset prevention liquid to its surface.
It is an object of the present invention to provide a magnetic toner that can be efficiently fixed with a good heat roll. Another object of the present invention is to provide a magnetic toner with excellent fixing properties, preservability, fluidity, and printing durability. The present inventors paid attention to the toner fixing resin and found that the present invention can be achieved by controlling its melt properties within an appropriate range. In other words, the secondary transition point of the resin is 60 to 80℃, the weight average molecular weight is 100,000 to 600,000, and the melt viscosity at 150℃ is
5,000 to 30,000P (poise), and the solvent and monomer for resin synthesis contained in the resin are controlled.
They have found that it is essential to achieve the present invention that the content is less than 0.1% by weight. By using such a resin, offset can be prevented without supplying silicone oil to the surface of the heating roller, and a magnetic toner with excellent fixing properties, preservability, fluidity, and printing durability can be obtained. As a result, the mechanism of a copying device using magnetic toner can be simplified, and the accuracy, stability, and reliability of a high-speed copying machine using a hot roll fixing method can be improved. The key point of the present invention is to control the melt properties of the resin, and the values measured by the known methods described below are used for these. In other words, the secondary transition point of the resin is determined by a thermomechanical analyzer, so-called
The weight average molecular weight of the resin is measured using the TMA method, which examines the temperature change in the coefficient of thermal expansion of the resin.
Values measured by gel permeation chromatography using several types of monodisperse polystyrene as standard materials are used. In addition, the melt viscosity of the resin was measured using a Koka type flow tester (manufactured by Shimadzu Corporation), and the content of solvent and monomer in the resin was determined by
Heat at 590°C for 3 seconds and measure the gas components generated using a gas chromatograph. Incidentally, in the present invention, the melt properties of the resin are limited to a certain range, and this is due to the following reasons. That is, it is necessary to set the secondary transition point of the fixing resin from the viewpoint of improving the storage stability of the toner (the property that the toner does not cause a blocking phenomenon during storage or in a developing box) and fixing properties. From the viewpoint of toner storage stability, the secondary transition point of the resin needs to be 60°C or higher, preferably 70°C or higher.
On the other hand, in order to prevent offset, the fixing temperature of the heated roll is set higher than the secondary transition point of the resin and lower than its softening point, and the toner is fixed on the substrate in a semi-molten state by the pressure of the heated roll. . Therefore, from the viewpoint of fixing properties, the lower the secondary transition point of the resin, the better, but on the other hand, the storage stability becomes worse, so taking both into consideration, the secondary transition point of the resin can be set at 60°C or higher and 80°C or lower. . Next, in order to improve the fixing properties and offset prevention properties of the toner, it is necessary to consider the weight average molecular weight and melt viscosity of the resin. Since the melt viscosity of the toner increases with the addition of magnetic powder, it is necessary to lower the melt viscosity of the resin as much as possible in order to improve fixing properties. On the other hand, if the melt viscosity of the resin is lowered, the toner melts too much and adheres to the hot roll, causing offset. Therefore, from the viewpoint of fixing properties and prevention of offset, it is necessary to set the melt viscosity of the resin in an appropriate range. In magnetic toner, the melt viscosity of the resin is 150℃.
5000P (poise) or more and 30000P (poise) or less are required. That is, in terms of weight average molecular weight
100000 or more and 600000 or less. By controlling the melt properties of the resin as described above, a magnetic toner with good storage stability, fixing properties, and offset prevention properties can be obtained. However, if the resin contains a large amount of a solvent for resin synthesis and a monomer component, the toner will generate offset, and its storage stability, flowability, and printing durability will also deteriorate. Therefore, it is necessary to reduce the amount of low molecular weight substances contained in the resin as much as possible, and according to studies by the present inventors, their content should be less than 0.1% by weight. For the reasons mentioned above, the fixing resin of the present invention can be obtained by controlling the melt properties of the resin. However, as the fixing resin of the present invention, vinyl whose melt properties can be easily controlled by controlling the blending of monomers and polymerization conditions is preferred. Polymers are suitable. These polymerization methods include bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization, but suspension polymerization is the most effective in terms of ease of handling of the resulting resin and reduction in manufacturing costs. This is the preferred method. In addition, examples of vinyl polymer monomers include styrenes such as styrene, α-methylstyrene, P-tert-butylstyrene, P-phenylstyrene, and P-chlorostyrene;
Methyl methacrylate, n-butyl methacrylate,
α-methylene aliphatic monocarboxylic acid esters such as isobutyl methacrylate, β-hydroxyethyl methacrylate, glycidyl methacrylate, diethylaminoethyl methacrylate, acrylic acid,
Examples include acrylic acid or methacrylic acid derivatives such as methacrylic acid, acrylonitrile, methacrylonitrile, acrylamide, and various other ethylenically unsaturated monoolefins, vinyl esters, vinyl ethers, vinyl ketones, N
-vinyl compounds, etc. Among these monomers, aromatic vinyl compounds such as styrene and α-methacrylic acid n-butyric acid
Resins containing methylene aliphatic monocarboxylic acid esters as a main component are particularly effective in the present invention. Among α-methylene aliphatic monocarboxylic acid esters, monomers containing polar groups such as hydroxyl groups, glycidyl groups, and amino groups, and acrylic acid and methacrylic acid containing carboxyl groups, etc.
Polymers containing mol% are particularly effective in the present invention because they provide good developability and transferability of the magnetic toner to the photoconductor, and also very good printing durability. The resin of the present invention can be obtained from the above-mentioned various vinyl polymers, but some of the polymers may have melt properties that do not satisfy the values of the present invention. For example, styrene-butadiene-styrene block copolymers and styrene-isoprene-styrene block copolymers have low secondary transition points and may not satisfy the present invention. However, such polymers can be used in combination with other polymers whose melt properties satisfy the requirements of the present invention. In addition, non-vinyl polymers can also be used alone or in a mixed system, but it is necessary that the melt properties of the mixture satisfy the requirements of the present invention. The magnetic toner of the present invention uses the above-mentioned resin and magnetic powder as basic materials, and may also contain a colorant component consisting of a pigment or dye. Furthermore, in order to further suppress the toner offset phenomenon, various compounds having mold releasability can be contained in the toner. Examples of these compounds include fatty acid metal salts, higher fatty acids, natural or synthetic paraffins, fatty acid esters or partially saponified products thereof, and alkylene bis fatty acid amides. It can also be contained in the toner in combination with. The amount of these compounds added to the toner is 5 parts by weight per 100 parts by weight of the resin component of the toner.
It is necessary to keep the content at most parts by weight and not to reduce the melt properties of the resin, especially the melt viscosity. Conductive particles such as carbon black are further added to the magnetic toner, and the electrical properties (electrical conductivity, dielectric constant) of the toner are adjusted by the amount and method of addition. 10 ^-9
・Toner with conductivity and dielectric constant of cm ^-1 (at4000V cm ^-1 ), 4.5 (at100KHz) or more is used for direct recording on zinc oxide photosensitive paper, electrostatic recording paper, etc.
10 ^-9・cm ^-1 (at4000V・cm ^-1 ), 3.5~4.5 (at100K
A toner having an electrical conductivity and a dielectric constant of Hz) is used for indirect recording as a transfer toner from a master photoreceptor using various photoconductors to a transfer sheet. A toner image formed on a fixing sheet using the magnetic toner of the present invention can be fixed without causing offset by a heated roller that does not supply an offset prevention liquid to the surface thereof. As the fixing roller, a releasable plastic roller whose surface is made of heat-resistant Teflon or silicone rubber is used, and in some cases, a roller having a metal surface may be used. Furthermore, since the magnetic toner of the present invention contains magnetic powder, the toner has a ^high melt viscosity and is difficult to fix. Good fixing can be achieved at 190°C with no offset. EXAMPLES The present invention will be explained below with reference to examples, but the present invention is not limited to the illustrated examples in any way. Example 1 Synthesis example of vinyl polymer In a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet, monomers, polymerization initiators, and polymerization initiators were added in the amounts shown in Table 1. Add a chain transfer agent, a dispersant, and ion-exchanged water, replace the air in the flask with nitrogen, raise the temperature while stirring, and bring it to 90℃ for 6 hours.
The polymerization is completed for a certain period of time, and after cooling, the pearl-like polymer is collected by filtration and dried to obtain the vinyl polymer A- Vinyl polymers B-1 to B-4, which are comparative examples of the present invention, were obtained.

【table】

[Table] Example 2 35 parts by weight of A-1 of Example 1 as fixing resin, 60 parts by weight of Magnetite EPT-500 (manufactured by Toda Kogyo) as magnetic powder, Carbon Black #44 (manufactured by Mitsubishi Kasei) as conductive particles. Weigh out 5 parts by weight and dry premix for 5 minutes in a super mixer. next
Co-kneader TR-46 type heated to 190℃ (Switzerland)
After cooling, coarse pulverization and fine pulverization were repeated to obtain a toner having an average particle size of about 3 to 40 μm. Fine silica powder R972 (manufactured by Nippon Aerosil) is added to this finely pulverized powder toner as a fluidity improver.
0.5% by weight was added and thoroughly mixed using a super mixer. Next, apply crushed powder toner containing silica powder.
The toner was dropped into a spheroidizing heat treatment furnace heated to 200 to 300°C to perform a spheroidizing heat treatment on the toner. To the total amount of the obtained spheroidized toner, 0.1% by weight of carbon black was added, and toner particles of less than 5 μm and 20 μm or more were removed using a zigzag classifier (manufactured by Alpine, Germany), and the conductivity was 10 ^-5 cm ^-1. (at 4000 V cm ^-1 ) A magnetic toner for electrostatic transfer with a dielectric constant of 3.65 (at 100 KHz) was obtained. This toner was evaluated using a hot roll fixing type two-component developer copying machine U-BixV (manufactured by Konishiroku Photo Industry Co., Ltd.) which does not use any anti-offset liquid such as silicone oil. That is, copy machine U-BixV
As a result of replacing the developing machine with a developing machine for magnetic toner (manufactured by Hitachi Metals) and evaluating the toner, it was found that good electrostatic transfer images could be obtained. It was also found that the image could be well fixed without offset within the fixing temperature range of 150 DEG C. to 180 DEG C. of the hot roll. This magnetic toner does not aggregate even if left in a constant temperature and humidity chamber at a temperature of 55°C and a humidity of 40% for over 200 hours.
It was also found that the storage stability was good. It was also found that the fluidity was very good and transferred images could be obtained repeatedly. Example 3 A-2, A-3, and A-3 of Example 1 were used as the fixing resin.
A magnetic toner for electrostatic transfer was prepared in the same manner as in Example 2 using A-4. When the toner was evaluated in the same manner as in Example 2, it was found that a good electrostatically transferred image was obtained and that the image could be well fixed without offset at the surface temperature of the hot roll in the range of 160 DEG C. to 190 DEG C. These magnetic toners, like the toner of Example 2, have good storage stability and fluidity. Also,
It was found that printing durability was superior to that of the toner of Example 2. Example 4 A-1, A-2, and A-2 of Example 1 were used as the fixing resin.
A pulverized powder toner containing silica powder was prepared using A-3 and A-4 according to the manufacturing method of Example 2. 2.5% by weight based on the total amount of this crushed powder toner
of carbon black was added thereto, thoroughly mixed in a super mixer, and dropped into a spheroidizing heat treatment furnace heated to 200 to 300°C to fuse and fix the carbon black on the surface of the toner. Toner with zigzag classifier
Excluding toner particles less than 5 μm and 20 μm or more, electrical conductivity 10 ^-4 cm ^-1 (at4000V cm ^-1 ), dielectric constant 5.20
A magnetic toner for direct recording of electrostatic latent images was obtained. The obtained toner has very good storage stability and fluidity. Copy machine PT for direct recording of toner on zinc oxide paper
-510 (manufactured by Ricoh), and image evaluation was performed by removing the pressure fixing roll of the fixing section. As a result, it was found that high quality images with good gradation could be obtained. Next, the image was transferred to the U-BixV of Example 2.
When fusing with a copying machine, the fusing temperature of the heat roll
It was found that there was no offset between 160°C and 190°C, and good fixing was possible. Comparative Example 1 Fixing resin B-1, B-2, B- of Example 1
A magnetic toner for electrostatic transfer and a magnetic toner for direct recording of an electrostatic latent image were prepared in the same manner as in Example 2 and Example 4 using Sample No. 3 and B-4. As a result of evaluating these magnetic toners, regardless of the purpose of the toner, the toner using Resin B-1 causes offset, and the toner using Resin B-2 causes offset and has poor storage stability. I found out something. Further, it was found that the toner using resin B-3 caused offset, and the toner using resin B-4 did not cause offset, but had poor storage stability. It is believed that toners using these resins had poor properties due to inappropriate melting properties of the resins. Example 5 The dispersant and ion-exchanged water in the polymerization reagent of Example 1 were replaced with 60 parts by weight of methyl ethyl ketone to prepare a fixing resin consisting of 50 parts by weight of styrene, 42 parts by weight of n-butyl methacrylate, and 8 parts by weight of acrylic acid. A-
5 was synthesized. Checking the melt properties of A-5, the second-order transition point is 74℃, and the weight average molecular weight is
125000, melt viscosity (at150℃) 9200P (poise),
The content of polymerization reagents in the polymer is 0% by weight of methyl ethyl ketone, styrene and n-methacrylic acid.
Butyl and acrylic acid are 0.42% and 0.05% by weight, respectively.
It was 0.08% by weight. Since Resin A-5 satisfies the present invention, a magnetic toner was prepared using it in the same manner as in Examples 2 and 4, and the toner was evaluated. As a result, it was found that the magnetic toner using Resin A-5 could be well fixed without offset within the fixing temperature range of 160 DEG C. to 180 DEG C. of the hot roll. It was also found that the toner has excellent printing durability and developability, and that high image density can be obtained even when the charging voltage of the photoreceptor is 700V or less. Example 6 In the magnetic toner of Example 5, 10% by weight of thermoplastic styrene-butadiene-styrene block copolymer Cauliflex TR1102 (manufactured by Ciel Chemical Co., Ltd.) was added to resin A-5. Since CALIFLEX TR1102 has a secondary transition point below room temperature (25°C), it is necessary to check the melt properties of the mixed resin. As a result, the secondary transition point of the mixed resin is 71
℃, but other melt properties were found to be almost unchanged. So Califlexus
When a magnetic toner containing TR1102 was prepared and evaluated, it was found that no offset occurred and good fixing could be achieved at a fixing temperature of 150°C to 200°C with a hot roll. The reason why the temperature range in which offset can be prevented was expanded compared to Example 5 is that the calibration
TR1102 is a thermoplastic elastomer and has a large intermolecular cohesive force due to its molecular structure, which is thought to be effective in preventing toner offset.

Claims (1)

[Scope of Claims] 1. In a hot roll fixing magnetic toner for developing electrostatic latent images comprising at least magnetic powder and a fixing resin, the fixing resin contains the solvent or monomer used to obtain the polymer. The main resin component is a vinyl polymer with an amount of less than 0.1% by weight, a secondary rearrangement point of 60~80℃, and a weight average molecular weight of 100,000~
600000, melt viscosity at 150℃ is 5000~30000P
A magnetic toner for developing electrostatic latent images, characterized by using a resin of (Poise). 2. Vinyl copolymerization whose main constituents are aromatic vinyl compounds and α-methylene aliphatic monocarboxylic acid esters containing 5 to 20 mol% of monomers containing hydroxyl, glycidyl, amino, and alkoxyl groups. 2. A magnetic toner for developing electrostatic latent images according to claim 1, characterized in that the main resin component is a magnetic toner.