JPS6325334B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a toner used for developing an electrical latent image or a magnetic latent image in electrophotography or electrostatic printing, and particularly to a toner suitable for pressure fixing. Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
Specification of No. 42-23910 and Special Publication No. 1973
As described in Publication No. 24748, a number of methods are known, but generally a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the A latent image is developed using toner, and after the toner image is transferred to a transfer material such as paper as necessary, it is fixed by heat, pressure, a solvent, steam, etc. to obtain a copy. Various methods are also known for visualizing electrical latent images using toner. For example, the magnetic brush method described in U.S. Pat. No. 2,874,063, the cascade development method described in U.S. Pat. Many developing methods are known, such as the developing method. As toners used in these developing methods, fine powders in which dyes and pigments are dispersed in natural or synthetic resins have conventionally been used. Furthermore, it is also known to use fine developing powder to which a third substance is added for various purposes. The developed toner image is transferred and fixed onto a transfer material such as paper, if necessary. Methods for fixing toner images include a method in which the toner is heated and melted using a heater or a heated roller, and then fused and solidified on the support, a method in which the binder resin of the toner is softened or dissolved with an organic solvent and then fixed on the support, and a method in which the toner is fixed on the support by applying pressure. A method of fixing toner on a support by using a method is known. Toner materials are selected to be suitable for each fixing method, and toners used for a particular fixing method generally cannot be used for other fixing methods. especially,
It is almost impossible to transfer the toner used in the conventionally widely used heat fusion fixing method using a heater to a hot roller fixing method, a solvent fixing method, a pressure fixing method, or the like. Therefore, toners suitable for each fixing method are being researched and developed. The method of fixing toner by applying pressure is based on US Patent No.
It is described in specification No. 3269626, Japanese Patent Publication No. 15876/1976, etc., and is energy saving, non-polluting, allows copying without waiting time when the copying machine is turned on, and there is no risk of burning copies. This method has many advantages, such as high-speed fixing and a simple fixing device. However, there are problems such as toner fixability and offset phenomenon to the pressure roller, and various research and development efforts are being carried out to improve the pressure fixability. For example, Japanese Patent Publication No. 44-9880 describes a pressure fixing toner containing an aliphatic component and a thermoplastic resin.
JP-A-48-75032, JP-A No. 48-78931, JP-A No. 49-
No. 17739 and No. 52-108134, etc., describe a capsule-type pressure fixing toner containing a soft material in the core, and JP-A-48-75033 describes a combination of blocks made of a sticky polymer and a soft polymer. Pressure-fixed toners using polymers have been described. However, it is easy to manufacture, has sufficient pressure fixing performance, does not cause any offset phenomenon to the pressure roller, and has stable development performance and fixing performance even after repeated use. A practical pressure-fixed toner that does not adhere to the surface of a photoreceptor, does not aggregate or form a cake during storage, and has good storage stability has not been obtained. For example, pressure fixing toner made of a soft material has good pressure fixing properties, but it is difficult to finely pulverize it into a toner, tends to cause offset to the pressure roller, and does not transfer to the carrier or photoreceptor surface. There are many problems such as silting and agglomeration and caking during storage. Furthermore, hard resins are easy to form into toners, and toners with excellent chargeability and storage stability can be easily obtained, but their pressure fixability is extremely poor. This is because many hard resins are harder than the cellulose fibers that make up the paper, so when pressure is applied, they are simply crushed inside the paper and do not get entangled with the fibers. Ethylene polymers have excellent pressure fixing properties and have traditionally been added to toners as a component to assist pressure fixing properties. However, in such cases, it is usually difficult to obtain a toner with practically sufficient properties because other properties necessary for the toner cannot be satisfied unless the toner is used together with other components. That is, although ethylene polymers have excellent pressure fixing properties, materials having such properties tend to aggregate. A practical problem is that when the latent image surface of a photoreceptor is repeatedly used for cleaning, agglomeration occurs in the cleaning area and cleaning is not carried out sufficiently, contaminating the latent image forming area and causing adhesion and contamination to the developing area. In addition, the image may be offset by the pressure roller used for fixing, staining the image, or may aggregate and change its characteristics during long-term storage.
In order to improve these drawbacks, ethylene polymers are mixed with other resins, but it has been difficult to find suitable resins. For example, if a cyclized rubber with good compatibility is added to polyethylene in order to improve developability, the pressure fixability will be extremely poor. In addition, in various conventional pressure fixing capsule toners, if a soft material with good pressure fixing properties is used as the core material, the soft material gradually adheres to the pressure roller as pressure fixing is repeated. Eventually, this becomes a cause of offset and wrapping of the transfer paper, which is undesirable, and if such phenomena are avoided, the pressure fixing performance deteriorates. In this way, those with good pressure fixing properties have poor image properties, and those with good image properties have poor fixing properties. Further, in conventional capsule toners, the core material and the outer shell separate due to the slightest impact, resulting in poor image quality and short lifespan. Furthermore, recently, a method has been used in which electrostatic latent images are developed using a one-component developer that contains magnetic fine particles in the toner and does not use carrier particles.
In this case, the toner binder resin is required to have good dispersibility and adhesion with the magnetic fine particles, as well as impact resistance and fluidity of the toner. During development by frictional charging between this one-component developer and the developing sleeve roller, the insulating material separates due to impact or use over time, adheres to the sleeve roller due to triboelectric action, and accumulates, making it extremely durable. A practical one-component developer has not yet been obtained due to its poor properties. An object of the present invention is to provide a pressure fixable toner having good pressure fixability and development durability. Another object of the present invention is to provide a pressure fixable toner that does not cause offset and can provide high quality images with sufficient density and high definition. Another object is to provide a toner that exhibits good fixing properties even at low fixing pressures and has excellent developability and fixing properties in high-speed copying. Another object is to provide a toner that is easy to manufacture, inexpensive, easy to handle, and stable even when stored or left unused for a long period of time. Still another object is to provide a toner that has excellent pressure fixability, development durability, and chargeability even when magnetic powder is contained in the toner. Its characteristics include ethylene polymer A, which has a melt viscosity of less than 1000 CPS at 140°C.
The present invention relates to a pressure fixable toner containing a binder resin containing an ethylene polymer B having a melt viscosity of 1000 CPS or more at 140°C. The melt viscosity is measured by the Bruckfield method. According to the research conducted by the present inventors, the following was found. In other words, if ethylene polymer A, which has a melt viscosity of less than 1000 cps when measured at 140°C, is used as a binder resin for a toner, it will not rub off after fixing with a weak pressure. Although it has excellent pressure fixing properties, such as being difficult to remove, it causes problems in development durability, storage stability, etc. If ethylene polymer B having a melt viscosity at 140° C. is 1000 cps or more is mixed here, development durability etc. can be improved without substantially impairing pressure fixability. The ethylene polymer used in the present invention is polyethylene and copolymers thereof. This ethylene polymer has a density of 0.94 g/cm ³ or more (more preferably
0.96 g/cm ³ or more), the pressure fixing property is better. Furthermore, the ethylene polymers A and B have similar densities (preferably a difference within 0.3 g/cm ³ ).
If their melting points are also similar (preferably a difference within 20°C), their mutual solubility, developability, fixability, etc. will be improved. The mixing ratio of the ethylene polymers A and B is preferably 50:50 to 95:5 by weight. However, when the toner contains 10 to 40% by weight of hydrophobic colloidal silica, even if the mixing ratio of ethylene polymers A and B is in the range of 5:95 to 95:5 by weight, the pressure will not increase. Both fixing properties and development durability are good. The ethylene polymer A has a melt viscosity of 50 to 900 cps at 140°C, and the ethylene polymer B has a melt viscosity of 2000 cps at 140°C.
~20000cps (especially preferably 4000~
When combined with 17000 cps), the pressure fixing properties, development durability, image reproducibility, and storage stability were all good. The binder resin may be composed of only the ethylene polymers A and B, but it may also contain other pressure fixing components in a proportion of 30% by weight or less. This pressure fixing component includes natural wax, synthetic wax,
Higher fatty acids (stearic acid, palmitic acid, lauric acid, etc.), higher fatty acid derivatives, low molecular weight polystyrene, epoxy resins, polyester resins (acid value 10 or less), styrene resins (styrene-butadiene copolymer (monomer ratio 5-30) :95-70), styrene-acrylic copolymer), polyvinylpyrrolidone, polyamide, coumaron-indene resin,
Examples include methyl vinyl ether-maleic anhydride copolymer, maleic acid-modified phenol resin, and phenol-modified terpene resin, and these may be used alone or in combination. The magnetic powder contained in the toner is fine particles of a magnetic or magnetizable material having an average particle size of 0.05 to 5 μm (preferably 0.1 to 1 μm). Examples include metals such as iron, manganese, nickel, cobalt, and chromium, magtite, various ferrites, manganese alloys, and other ferromagnetic alloys. The magnetic powder is contained in an amount of 20 to 70% by weight (more preferably 25 to 45% by weight) based on the weight of the toner. Additives such as polarity control agents, stabilizers, and colorants may be added to the toner as necessary. The image obtained with the toner of the present invention is fixed by passing between a pair of pressure-loaded rollers, but supplementary heating may be applied. Regarding the pressure fixing device, Japanese Patent Publication No. 44-12797,
U.S. Patent No. 3269626, U.S. Patent No. 3612682, U.S. Patent No.
No. 3655282, No. 3731358, etc., and the toner of the present invention can be used. Here, the fixability is evaluated according to the dye fastness test method against friction (JIS-LO849-1971). That is, using a friction tester, the toner fixing surface and a white cotton cloth for friction were rubbed against each other according to a prescribed method (drying test), and the degree of coloring of the white cotton cloth for friction was compared with the gray scale for contamination. This is a grade that indicates the fixability of the product on a scale from grade 1 to grade 10.1,
Practical fixing cannot be obtained with a grade 2, and practical fixing can be obtained with a grade 3 or higher, preferably a grade 4 or higher. Examples are shown below. All parts here are parts by weight. [Example 1] Polyethylene (melt viscosity at 140°C
600CPS, density 0.95, melting point 125℃) 100 parts polyethylene (melt viscosity at 140℃
12500CPS, density 0.95, melting point 128°C) 100 parts Magtite 100 parts The above toner material is kneaded with a heated roller at 140°C, cooled, coarsely ground with a cutter mill, and finely ground with a jet mill to form toner with a particle size of 5 to 35μ. Obtained. A photosensitive plate having a positive electric latent image was developed using this toner, transferred to plain paper, and then fixed using a pressure roller (two upper and lower chrome-plated rigid rollers with a total pressure of 460 kg). Fixability is grade 4-5,
A clear image with no fog was obtained. Further, continuous copying was performed to test the durability of the toner, and even after 20,000 copies were made, images almost the same as the initial images were obtained. During this durability test, the consumed amount of toner was replenished with the same toner as appropriate. Also, store this toner in a container for one month.
A similar test was conducted after storage in an atmosphere at 50°C, but the performance did not change at all. [Comparative Example 1] A similar test was conducted using toners prepared in Example 1 except for high-viscosity polyethylene. Although the fixing performance was sufficient, in a durability test, the image became very faint after approximately 500 sheets, and at the same time, the fluidity of the toner was significantly impaired. [Comparative Example 2] Toners prepared in Example 1 except for low-viscosity polyethylene were prepared and the same tests were conducted. The fixability was only 1st to 2nd grade, which was very poor. [Examples 2 to 7] In Example 1, the composition of the toner material was changed as follows, and the results were good in all cases.

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Claims (1)

[Scope of Claims] 1. The binder resin constituting the toner is an ethylene polymer A having a melt viscosity of 50 to 900 cps at 140°C and a melt viscosity of 2000 to 20,000 cps at 140°C.
, and the difference in density between the ethylene polymer A and the ethylene polymer B is
0.3 g/cm ³ or less, and the difference in melting point between the ethylene polymer A and the ethylene polymer B is 20° C. or less. 2. The toner according to claim 1, wherein the ethylene polymer A and the ethylene polymer B have a density of 0.94 g/cm ³ or more. 3. The toner according to claim 1, wherein the total amount of ethylene polymer A and ethylene polymer B is 70% by weight or more of the binder resin. 4 Hydrophobic colloidal silica to toner
Claim 1 containing in a proportion of ~40% by weight
Toner described in section. 5. The toner according to claim 4, which contains ethylene polymer A and ethylene polymer B in a weight ratio of 5:95 to 95:5. 6. The toner according to claim 1, which contains ethylene polymer A and ethylene polymer B in a weight ratio of 50:50 to 95:5. 7. The toner according to claim 1, which contains magnetic powder in an amount of 20 to 70% by weight based on the weight of the toner.