JP2005352118A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a belt fixing system and capable of forming an image of high image quality excellent also in fixability even on a transfer material having heavy surface irregularity, and to provide an image forming method. <P>SOLUTION: The image forming apparatus has a fixing section in which a plurality of rotary bodies are arranged on the inside of an endless belt having an elastic layer on a surface thereof, at least one of the rotary bodies is a heating roller R3, the endless belt is pinched by a pressure applying rotary body R2 located on the outside of the endless belt and an opposite rotary body R1 disposed opposite to the pressure applying rotary body through the endless belt as another of the plurality of rotary bodies, and a toner image on a transfer material having a smoothness of ≤40 S is heat-fixed by a nip portion formed by the endless belt and the pressure applying rotary body. In the fixing section, a nip time is 35-75 ms, the pressure applying rotary body or the opposite rotary body has an elastic layer whose rubber hardness is 20-40 Hs, and a weight average particle diameter of the toner is 2-5 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a toner fixing system used for a copying machine, a printer, and the like, and for obtaining an image by electrophotography, electrostatic recording, electrostatic printing, or the like.

  As a fixing method for copying machines, printers, etc., there are many examples in which a so-called heat roller fixing method is adopted which has a simple device configuration and is easy to handle. However, in the above-described heat roller fixing that has been frequently used, (1) there is a waiting time for the heat roller to reach a predetermined temperature; (2) the temperature of the heat roller due to the passage of the recording material or other external factors. It is necessary to maintain the heating roller at an optimum temperature in order to prevent fixing failure and offset phenomenon due to fluctuations. For this purpose, the heat capacity of the heating roller or the heating body must be increased. It was.

  Also, in general, full-color toners with low viscosity (3) due to the curvature of the roller, there are also problems of offset and winding around the roller during paper discharge. It was necessary to prepare. To solve these problems, a belt fixing method has been proposed, and a method in which oil is not applied by belt fixing (oilless method) and a method of applying a small amount have been proposed. In recent years, as disclosed in Japanese Patent Laid-Open No. 2-160259 and Japanese Patent Laid-Open No. 2-161462, this method takes into consideration a combination of belt fixing and toner that can be used for belt fixing. And commercialization is progressing.

  Copiers and printers are rapidly expanding from black and white to full color, and the full color market is particularly expanding. Color toners are colored by mixing two or more overlapping toners, but in order to obtain a clear color image with good color reproduction, it is necessary that the toners are sufficiently melted and mixed to produce a glossy color. As a result, a clearer color image is obtained. Gloss is affected by the smoothness of the fixing surface, but pressurization from above the fixing surface is one means for obtaining smoothness. In the roller fixing method, in the case of color toner, a roller made of a thick elastic body is often used, and high pressure is often applied. Compared with that, the pressure in the belt fixing method is small, and the effect of the pressure as a means for obtaining smoothness is small. In order to obtain high gloss in such a situation, it is necessary to use a toner having a lower melt viscosity, which is likely to be offset. Further, the state of the belt surface greatly affects the smoothness of the fixed image.

In view of this, a material in which the volume average particle size and the content of fine powder and coarse powder are defined and the surface of the toner layer is free of irregularities has been proposed [Patent Document 3 (Japanese Patent Laid-Open No. 2-160250)], but a transfer material is proposed. When the surface of the surface is large, it is not always possible to obtain an image having sufficient fixability. Furthermore, there has also been proposed an image that defines the surface roughness of the image on the OHP sheet [Patent Document 4 (Japanese Patent Laid-Open No. 11-125948)], but the surface properties of the OHP sheet and the paper are different. Even if the surface roughness of the image is defined, it cannot be said that the offset property and the glossiness are good depending on the surface property of the paper.
JP-A-2-160259 JP-A-2-161462 JP-A-2-160250 Japanese Patent Laid-Open No. 11-125948

 Accordingly, an object of the present invention is an image forming apparatus equipped with a belt fixing method, which is not only a transfer material excellent in smoothness but also a transfer material having a smoothness of 40 S or less and large surface irregularities, and has high image quality and fixability. It is an object of the present invention to provide an image forming apparatus and an image forming method capable of forming an excellent image.

The present invention
(1) A plurality of rotating bodies are arranged inside an endless belt having an elastic layer on the surface, and at least one of the rotating bodies is a heating roller, and pressure is positioned outside the endless belt. Formed by the endless belt and the pressure rotator by pressing the endless belt between the rotator and an opposing rotator arranged to face the pressure rotator of the plurality of rotators via the endless belt. An image forming apparatus having a fixing portion that heats and fixes a toner image on a transfer material having a smoothness of 40 S or less by a nip portion, and the nip time is 35 to 70 ms, and the pressure rotating body or the counter rotating body is Any one of them has an elastic layer having a rubber hardness of 20 to 40 Hs, and the toner has a weight average particle diameter of 2 to 5 μm,
(2) The image forming apparatus according to (1), wherein the pressure rotating body covers the surface thereof with a fluororesin-based and / or silicone resin-based material,
(3) The image forming apparatus according to (1), wherein the counter rotating body has an elastic layer, and the rubber hardness thereof is smaller than the rubber hardness of the elastic layer of the pressure rotating body.
(4) The image forming apparatus according to (1), wherein the toner has a shape factor SF-1 of 110 to 150.
(5) An image forming apparatus in which the heating roller is made of magnetic metal and is heated by electromagnetic induction from the electromagnetic induction generating unit,
(6) The image forming apparatus according to (5), wherein the electromagnetic induction generating means is provided outside the heating roller via an endless belt, and the opposing rotating body is different from the heating rotating body,
(7) The image forming apparatus according to (1), wherein the pressure rotator has a heating source,
(8) The present invention relates to an image forming method using the image forming apparatus described in (1) to (7).

  With the image forming apparatus and the image forming method of the present invention, it is a matter of course that a transfer material excellent in surface smoothness is used. Even when a transfer material having a smoothness of 40 or less and large unevenness is used, high image quality and sufficient fixing property are obtained. The obtained image can be obtained.

Hereinafter, the present invention will be described in detail.
The present invention can be used for transfer materials with high smoothness without any problems, but particularly in the case of a transfer material having a rough surface with a smoothness of 40 S or less, an image forming apparatus capable of obtaining sufficient fixability, And an image forming method.
The surface property of the transfer material can be expressed by smoothness. The smoothness of the transfer material is usually larger than 40S and up to about 150S in what is called plain paper. However, in this range, sufficient fixing ability can be obtained even with a normal belt fixing device. However, in the case of a transfer material having a rough surface such as a smoothness of 40 S or less, the fixability is insufficient.
Examples of the transfer material having a smoothness of 40S or less include some recycled paper and cotton paper, but are not limited thereto.
In addition, the measuring method of smoothness was performed according to JIS P8119 (Smoothness testing method using paper and paperboard-Beck smoothness tester).
The image forming apparatus of the present invention may include a means for detecting the smoothness of the paper or a means for inputting the smoothness. The fixing conditions may be appropriately changed based on information input from these means. For example, when a transfer material having a lower smoothness is used, the nip time can be made longer.

In general, since the development of the electrostatic latent image is performed by reducing the particle size of the toner, an image with high resolution can be obtained.
It is difficult to apply sufficient energy to a small toner at the time of fixing, and the fixing property tends to be insufficient. In order to solve this, it is necessary to apply a high pressure during fixing. However, applying a high pressure at the time of fixing is not preferable because it shortens the life of the fixing unit. In order to solve this, it is necessary as an appropriate fixing unit condition that the nip time is 35 to 7 ms, and the pressure rotating body (or the counter rotating body) has an elastic layer having a rubber hardness of 20 to 40 Hs. It became clear.

  In order to achieve the object of the present invention, the toner particle diameter is preferably 2 to 5 μm in weight average particle diameter. On the other hand, if it is larger than 5 μm, the dot reproducibility becomes insufficient, the graininess of the halftone part deteriorates, and a high-definition image cannot be obtained, and transfer with large unevenness When the material is used, the fixability may be deteriorated.

In the fixing unit of the present invention, the opposing rotating body and the endless belt are pressed and the nip time, which is the passing time of the nip formed by the endless belt and the pressing rotating body, is 35 to 70 ms. It was revealed that the body or the counter-rotating body has an elastic layer having a rubber hardness of 20 to 40 Hs, so that sufficient fixability can be obtained even when a transfer material with large irregularities is used.
Here, the nip time is a time required for the toner image on the transfer material to pass through the nip portion where the fixing roller and the pressure roller are in contact with each other. The nip time is 35 to 70 ms, and the surface is rough. Even when a toner having a small particle diameter is fixed on a transfer material, sufficient fixing ability and offset resistance can be obtained.
When the nip time is shorter than 35 ms, the fixability may be insufficient, and when it is longer than 70 ms, offset may occur. Further, particularly when the nip time is 40 to 60 ms, further sufficient fixability and offset resistance can be obtained.
The nip time is calculated from the rotational speed of the belt and the nip width. The nip width is preferably 5 to 15 mm in the paper conveyance direction.

Moreover, it is preferable that at least one of the pressure rotator or the counter rotator has an elastic layer with a rubber hardness of 20 to 40 Hs, and when the rubber hardness of the elastic layer of at least one of the rotators is less than 20 Hs, both It is difficult to apply pressure between the rotating bodies, and the toner may not be sufficiently fixed to the transfer material. Also, the elasticity may be low, the mechanical strength may be weakened, and the life of the rotating body itself may be shortened. Conversely, if the rubber hardness of the elastic layer of any of the rotating bodies is greater than 40 Hs, the belt surface may be easily damaged and the life of the belt may be shortened.
The rubber hardness was measured according to JIS K-6253 using a durometer (type A) which is a spring type hardness meter.
In addition, in order to obtain sufficient fixability, the other rotating body needs to maintain a state where an appropriate pressure state is applied to the elastic rotating body, so that the hard type or higher rubber hardness is required. It is preferable to have an elastic body. For example, those having a rubber hardness of 40 Hs or more are preferable, and those having an elastic body of 50 Hs or more are more preferable.

  Furthermore, it is preferable that the surface of the pressure rotator is coated with a fluorine-based or silicon-based material, so that the toner rotates under pressure when an extremely small amount of toner is offset on the belt. There is an effect to prevent adhesion to the body. When the toner adheres to the pressure rotating body, there arises a problem that the back surface of the copy image of the transfer material is stained with the toner.

  In particular, the counter rotator has an elastic layer, and the rubber hardness thereof is preferably smaller than the rubber hardness of the elastic layer of the pressure rotator, which is sufficient even when an uneven transfer material is used. Fixability is obtained, and further, the nip portion is recessed toward the counter rotator, and the nip shape of the fixing tends to face toward the pressure rotator, so the transfer material faces away from the belt and faces the belt. It is possible to prevent the transfer material from being wound.

Further, the toner having a shape factor SF-1 of 110 to 150 and a more nearly spherical shape is excellent in fixability. This is presumably because, in the case of a toner having a nearly spherical shape, heat is uniformly applied to the toner during fixing.
The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (1)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.
Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated.
Further, since the heating roller is made of an image forming apparatus that is made of a magnetic metal and is heated by electromagnetic induction, it is possible to heat the belt at high speed when electromagnetic induction is applied, and there are advantages such as high thermal efficiency.

The electromagnetic induction generating means and the heating roller are provided outside the pressure rotator and the counter rotator via an endless belt, and the heating source is attached to the belt rather than inside the pressure rotator or the counter rotator. Such thermal efficiency is increased, and uniform fixing is possible.
That is, when the heating source is inside the rotating body, it is necessary to pressurize the rotating bodies, so it is necessary to provide a rubber layer or the like having a certain thickness around the heating source. There is a problem that a lot of heat is taken away. On the other hand, the heating roller does not need to have strong pressure resistance like the pressure rotating body and the counter rotating body, and it is not necessary to provide a thick layer for reducing the thermal efficiency around the heating source.

Furthermore, it is preferable to provide the electromagnetic induction generating means outside for the following reasons. That is, when the electromagnetic induction generating means is provided inside the heating roller, it is necessary to extremely increase the diameter of the heating roller, and in accordance with this, it is necessary to improve pressure resistance for internal protection. It is necessary to thicken the layer. This thick layer around the periphery reduces thermal efficiency. In addition, by providing it outside the electromagnetic induction generating means, convenience such as temperature controllability and arrangement applicability is high.
In addition, by having a heating source in the pressure rotating body, it becomes possible to heat a transfer material with large surface irregularities from the back surface of the transfer material, and a sufficient amount of heat can be uniformly applied. It becomes possible to give a good fixing property.

  An example of a fixing device used in the fixing method of the present invention is shown in FIG. Here, R1 is a fixing roller in which a metal (aluminum, iron, etc.) cored bar is coated with an elastic body (silicon rubber, etc.), and R3 is a metallic (pipe made of aluminum, iron, copper, stainless steel, etc.) cored bar. And a heating roller having a heating source H inside. S is a temperature sensor for measuring the surface temperature of the fixing belt B in contact with the heating roller R3. A fixing belt B is stretched between the fixing roller R1 and the heating roller R3. The fixing belt B has a small heat capacity, and on a base (thickness of about 30 to 150 μm such as nickel or polyimide), a release layer (silicon rubber is 50 to 300 μm thick, or fluorine resin is 10 to 50 μm). Etc.). In the case of electromagnetic induction heating, a unit made of magnetic metal is also arranged inside the heating roller, and a layer such as silver foil is provided inside the belt to heat the belt surface.

  R2 is a pressure roller in which a metal core is covered with an elastic body or the like. By pressing the fixing roller R1 from below through the fixing belt B, the fixing roller B is pressed between the fixing belt B and the pressure roller R2. A nip is formed. If necessary, R4 is provided with an oil application roller impregnated with oil for applying oil (silicone oil or the like) to the fixing belt. G is a guide for supporting the print sheet P (paper or the like) carrying the unfixed toner image T. Moreover, the dimension of each member is set by various conditions required. These are only examples, and for example, it is possible to provide a heating source inside the fixing roller R1 or the pressure roller R2. In the present invention, a fixing device using a fixing belt with a configuration other than this example is also applied. Is done.

  In such a fixing device, particularly in an oil-less or small amount application type fixing device, it is preferable to fix a toner containing a release agent and further finely dispersed in the toner. The toner in which the release agent is finely dispersed makes it easy for the release agent to ooze out during fixing, and even if the oil application effect is reduced in an oilless fixing device or a small amount of oil application fixing device, the toner belt To the side can be suppressed. In order for the release agent to be present in a dispersed state in the toner, it is preferable that the release agent and the binder resin are not compatible. Further, in order to finely disperse the release agent in the toner, for example, there is a method using a shearing force of kneading at the time of toner production. The dispersion state of the release agent can be determined by observing a thin film section of the toner with a TEM. The dispersion diameter of the release agent is preferably small, but if it is too small, there may be insufficient bleeding at the time of fixing. Therefore, if the release agent can be confirmed at a magnification of 10,000, it is determined that the release agent exists in a dispersed state. If the size is 10,000 times and the release agent cannot be confirmed, even if finely dispersed, there is a case where the bleeding at the time of fixing is insufficient.

  As the toner used in the present invention, all known materials can be used. As the binder resin, styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene and the like, and polymers of the substitution products thereof; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer Polymer, styrene-vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methacrylic acid Methyl copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer , Styrene-butadiene copolymer, steel -Isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer, and other styrene copolymers; polymethyl methacrylate, polybutyl methacrylate, polychlorinated Examples include vinyl, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, and terpene resin. Can be used.

  As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher, chrome lead , Titanium yellow, Polyazo yellow, Oil yellow, Hansa yellow (GR, A, RN, R), Pigment yellow L, Benzidine yellow (G, GR), Permanent yellow (NCG), Vulcan fast yellow (5G, R), Tartrazine lake, quinoline yellow lake, anthrazan yellow BGL, isoindolinone yellow, bengara, red lead, lead vermilion, cadmium red, cadmium mercurial red, antimon vermilion, permanent red 4R, para red, fise red, parachlor ortho nitro Aniri Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carnmin BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R, Brilliant Carmine 6B, Pogment Scarlet 3B, Bordeaux 5B, Tolujing Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thio Indigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red, Polya Red, Chrome Vermilion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal-free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Phthalocyani Green, anthraquinone green, titanium oxide, zinc white, litbon and mixtures thereof can be used. The amount used is generally 0.1 to 50 parts by weight per 100 parts by weight of the binder resin.

  In the present invention, when the toner contains a release agent, natural wax such as candelilla wax, carnauba wax and rice wax, montan wax, paraffin wax, sazol wax, low molecular weight polyethylene, low molecular weight polypropylene, alkyl phosphorus Acid esters can be used alone or in combination.

  In the present invention, the toner may contain a charge control agent as required. Specific examples of the charge control agent include metal complex salts of monoazo dyes, nitrohumic acid and salts thereof, quaternary ammonium salts, imidazole metal complexes and salts, salicylic acid, naphthoic salts, dicarboxylic acid Co, Cr, Metal complexes such as Fe, Zn, Zr, and Al, metal salts, amino compounds, organic boron salts, calixarene compounds, organic dyes, and the like can be used. Among these, in the case of a color toner, it is preferable to add a transparent to white substance that does not impair the color tone of the toner to stabilize and impart the toner to a negative polarity or a positive polarity.

In the present invention, the amount of charge control agent used is determined by the toner production method including the type of binder resin, the presence or absence of additives used as necessary, and the dispersion method, and is uniquely limited. However, it is preferably used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. The range of 2 to 5 parts by weight is preferable. If it is less than 0.1 part by weight, the toner is insufficiently charged and is not practical. When the amount exceeds 10 parts by weight, the chargeability of the toner is too high, and the electrostatic attraction force with the carrier increases, leading to a decrease in developer fluidity and a decrease in image density.

  In addition, magnetic materials such as ferrite, magnetite and maghemite, iron oxides such as ferrite, magnetite and maghemite, metals such as iron, cobalt and nickel, or alloys of these with other metals can be used alone to introduce the magnetic material into the toner particles. Or it can be mixed and used. Also in this case, in the case of a color toner, it is preferable to select a white substance from a transparent color that does not impair the color tone.

  As additives for improving toner fluidity and environment dependency, generally known additives can be used. For example, zinc oxide, tin oxide, aluminum oxide, titanium oxide, silicon oxide, strontium titanate, barium titanate, calcium titanate, strontium zirconate, calcium zirconate, lanthanum titanate, calcium carbonate, magnesium carbonate, mica, dolomite Inorganic powders such as these and hydrophobized products thereof can be used alone or in combination.

  As other additives, fluororesin fine particles such as polytetrafluoroethylene, tetrafluoroethylene hexafluoropropylene copolymer, and polyvinylidene fluoride may be used as the toner surface modifier. Depending on the type of material to be added, about 0.1 to 10 parts by weight is externally added to 100 parts by weight of the toner base particles, and if necessary, the toner is mixed with an appropriate mixer. It can be adjusted and used so that it adheres to, adheres to the particle surface, or is released in the toner particle gap.

  As a method for producing toner particles, the raw materials as described above are kneaded by a known method such as a two-roll, twin-screw extrusion kneader, or single-screw extrusion kneader, and this is known as a mechanical type or air flow type. The toner base particles can be prepared by pulverization and classification. In addition, toner particles can be prepared by a polymerization method. The granulation method is not limited to these known methods.

Next, a method for measuring the weight average particle diameter of toner particles will be described.
Examples of the measurement device for the particle size distribution of toner particles by the Coulter counter method include Coulter counter TA-II and Coulter Multisizer II (both manufactured by Coulter Electronics Co., Ltd.). The measurement method is described below.
First, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of an aqueous electrolytic solution. Here, the electrolytic solution is a solution prepared by preparing a 1% NaCl aqueous solution using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the measurement device is used to measure the volume and number of toner particles or toner using a 100 μm aperture as an aperture. Volume distribution and number distribution are calculated. From the obtained distribution, the weight average particle diameter (D4) of the toner can be obtained.

  As channels, 2.00 to less than 2.52 μm; 2.52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to less than 6.35 μm; 6 Less than 35 to 8.00 μm; less than 8.00 to less than 10.08 μm; less than 10.08 to less than 12.70 μm; less than 12.70 to less than 16.00 μm; less than 16.00 to less than 20.20 μm; Uses 13 channels of less than 40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm, and targets particles having a particle size of 2.00 μm to less than 40.30 μm.

<SF-1>
Using a FE-SEM (S-800) manufactured by Hitachi, Ltd., 100 toner particle images of 2 μm or more magnified 1000 times were sampled randomly, and the image information is obtained via an interface, for example, an image analysis apparatus (manufactured by Nicole) It was introduced into Luzex III) and analyzed.

  In the present invention, the toner alone may be used as a developer, and development may be performed by a one-component development method, or the toner and carrier may be mixed to form a developer, and development may be performed by a two-component development method. Carriers used in the two-component development method are the same as conventional ones such as iron powder, ferrite, and glass beads. These carriers may be those coated with resin. The resin used in this case is polyfluorinated carbon, polyvinyl chloride, polyvinylidene chloride, phenol resin, polyvinyl acetal, silicone resin or the like. In any case, the mixing ratio of toner and carrier is generally about 0.5 to 6.0 parts by weight of toner with respect to 100 parts by weight of carrier.

Examples Next, the present invention will be described more specifically with reference to examples. In the examples of the present invention, the following fixing device and toner were used.
[Fixing device]
Fixing device A
The fixing device shown in FIG. 1 is set under the following conditions. The standard fixing set temperature of the fixing belt is 130 ° C., but the fixing temperature can be changed.
Belt speed: 222mm / sec
Fixing nip width: 10mm
Fixing nip time: 45 ms
Fixing roller (opposite rotating body) ... Roller outer diameter: Φ40mm
(Inner layer (center): Stainless steel core φ24mm,
Surface layer: Elastic layer of silicone rubber foam 30Hs (spring hardness), thickness 8mm)
Pressure roller: Roller outer diameter: Φ40 mm (inner layer (center part): hollow (cavity diameter φ37 mm), outwardly, 1 mm thick iron core, Si rubber layer: 0.5 mm thick (rubber (Hardness: 75Hs), surface layer is PFA tube layer; thickness 30μm)
Heating roller: Roller outer diameter: Φ30 mm, halogen heater in the center. The outer layer is made of aluminum and has a thickness of 2 mm. Fixing belt ... Belt diameter: Φ60 mm
The following two layers are formed from the inner layer (substrate) toward the surface layer.
・ Substrate: Nickel layer of about 40 μm thickness
Surface layer: Silicon rubber of about 150 μm, surface roughness Rz: 3.3 μm
Belt width: 310mm
Oil application roller: Oil application amount: 2mg / A4 per size

Fixing device B
The following two changes are made from the fixing device A.
(1) Oil application amount: per 0.5 mg / A4 size (2) Change the release layer of the fixing belt to about 50 μm fluororesin and surface roughness 6.0 μm

Fixing device C
FIG. 2 shows an example of a belt induction heating fixing device related to the present invention.
The fixing device shown in FIG. 2 includes a heating roller 1 heated by electromagnetic induction of induction heating means 6, a fixing roller 2 (opposite rotating body) arranged in parallel to the heating roller 1, and the heating roller 1 and the fixing roller 2. And an endless belt-like heat-resistant belt (toner heating medium) 3 that is heated by the heating roller 1 and rotated in the direction of arrow A by the rotation of at least one of these rollers. The pressure roller 4 is a pressure roller 4 (pressure rotator) that is pressed against the fixing roller 2 and rotates in the forward direction with respect to the belt 3.

  The heating roller 1 is made of a hollow cylindrical magnetic metal member such as iron, cobalt, nickel, or an alloy of these metals, and has an outer diameter of 20 to 40 mm and a thickness of 0.3 to 1.0 mm, for example. It has a fast configuration.

  The fixing roller 2 (opposing rotating body) includes a metal core 2a made of, for example, stainless steel, and an elastic member 2b covered with the core 2a in a solid or foamed heat-resistant silicone rubber. In order to form a contact portion having a predetermined width between the pressure roller 4 and the fixing roller 2 by the pressing force from the pressure roller 4, the outer diameter is set to about 20 to 40 mm, which is larger than the heating roller 1. . The elastic member 2b has a thickness of about 4 to 6 mm. With this configuration, the heat capacity of the heating roller 1 is smaller than the heat capacity of the fixing roller 2, so that the heating roller 1 is rapidly heated and the warm-up time is shortened.

The belt 3 stretched between the heating roller 1 and the fixing roller 2 is heated at the contact portion W1 with the heating roller 1 heated by the induction heating means 6. The inner surface of the belt 3 is continuously heated by the rotation of the rollers 1 and 2, and as a result, the entire belt is heated.
The configuration of the belt 3 is as follows.
The following four layers are formed from the inner layer to the surface layer.
・ Substrate (resin layer: polyimide (PI) resin, etc.)
・ Heat generation layer (Ni, Ag, SUS, etc. as conductive material): 3a
・ Intermediate layer (Aiming for uniform fixing with an elastic layer): 3b
・ Surface layer (release layer) (Aimed at release effect and oil-less with fluororesin material): 3c

The thickness of the release layer 3b is preferably about 10 μm to 300 μm, particularly about 200 μm. By doing so, the toner image T formed on the recording material 11 is sufficiently wrapped by the surface layer portion of the belt 3, so that the toner image T can be uniformly heated and melted.
The thickness of the release layer 3b, that is, the surface release layer, is required to be at least 10 μm in order to ensure wear resistance over time.
Further, when the thickness of the release layer 3b is larger than 300 μm, the heat capacity of the belt 3 is increased and the time required for warm-up is increased. In addition, in the toner fixing process, the belt surface temperature is difficult to decrease, the agglomeration effect of the melted toner at the fixing portion outlet cannot be obtained, the belt releasability is reduced, and the toner adheres to the belt. Hot offset occurs.

In addition, as a base material of the belt 3, a heat-resistant resin layer such as a fluorine resin, a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin, a PES resin, or a PPS resin is used instead of the heat generating layer 3a made of the metal. May be used.
The pressure roller 4 includes a cored bar 4a made of a cylindrical member made of a metal having high thermal conductivity such as copper or aluminum, and an elastic member having high heat resistance and toner releasability provided on the surface of the cored bar 4a. 4b. In addition to the above metal, SUS may be used for the core metal 4a.

  The pressure roller 4 presses the fixing roller 2 via the belt 3 to form the fixing nip portion N, but in this embodiment, the pressure roller 4 is harder than the fixing roller 2. As a result, the pressure roller 4 bites into the fixing roller 2 (and the belt 3), and the recording material 11 follows the circumferential shape of the surface of the pressure roller 4 by this biting. Has the effect of facilitating. The outer diameter of the pressure roller 4 is about 20 to 40 mm, which is the same as that of the fixing roller 2, but the wall pressure is about 0.5 to 2.0 mm, which is thinner than the fixing roller 2.

As shown in FIG. 2, the induction heating means 6 that heats the heating roller 1 by electromagnetic induction has an excitation coil 7 that is a magnetic field generation means, and a coil guide plate 8 around which the excitation coil 7 is wound. Yes. The coil guide plate 8 has a semi-cylindrical shape that is disposed close to the outer peripheral surface of the heating roller 1, and the exciting coil 7 is formed by passing a long exciting coil wire along the coil guide plate 8 in the axial direction of the heating roller 1. It is one that is wound around alternately. The exciting coil 7 is connected to a driving power source (not shown) whose oscillation circuit has a variable frequency.
Outside the excitation coil 7, a semi-cylindrical excitation coil core 9 made of a ferromagnetic material such as ferrite is fixed to the excitation coil core support member 10 and is disposed close to the excitation coil 7.

In the above configuration, the following conditions were set as specific examples.
Fixing roller; outer diameter φ38 mm (inner layer (center): stainless steel core metal φ28 mm, outer layer: elastic layer of foam of silicone rubber, layer thickness 5 mm, rubber hardness: 25 Hs))
Pressure roller; outer diameter φ40 mm (inner layer (center): aluminum core metal φ37 mm, iron core bar 1.0 mm thick toward the outside, Si rubber layer: thickness 0.5 mm (rubber hardness: 60 Hs), Furthermore, the surface layer is PFA tube layer; thickness 30μm)
Heating roller; outer diameter φ30mm (inside hollow, surrounding is 0.8mm thick layer of magnetic iron oxide)
Fixing conditions: belt speed: 289 mm / sec, nip width: 13 mm, nip time: 45 ms
Fixing belt: The following four layers from the inner layer to the surface layer (inner layer side) PI (50 μm) + Ni (40 μm) + Si rubber (150 μm) + fluororesin (20 μm) (surface layer side)

〔toner〕
Constituent material for toner a Binder resin: polyol resin (1/2 outflow start temperature 116 ° C.) 100 parts by weight Colorant For yellow toner: benzimidazolone yellow pigment
(C.I. Pigment Yellow 180) 5 parts by weight
For magenta toner: Quinacridone magenta pigment
(C.I. Pigment Red122) 4 parts by weight
For cyan toner: Copper phthalocyanine blue pigment
(C.I. Pigment Blue 15) 2 parts by weight
For black kutner: Carbon black 6 parts by weight Charge control agent: Salicylic acid derivative zinc salt 2 parts by weight

Constituent material of toner b Binder resin ... polyester resin (1/2 outflow start temperature 120 ° C.) 97 parts by weight Release agent ... 3 parts by weight carnauba wax Colorant, charge control agent ... same as toner a

Constituent material of toner c Binder resin: 100 parts by weight of polyester resin (1/2 outflow start temperature 104 ° C.) Colorant, charge control agent: same as toner a

The toner constituent materials a to c were sufficiently mixed with a blender for each color, and then melt-kneaded with a biaxial extruder heated to 100 to 110 ° C. The kneaded product was allowed to cool and then coarsely pulverized by a cutter mill, pulverized by a fine pulverizer using a jet stream, and each color base color particle of each toner was obtained using an air classifier. The weight average particle diameter of the obtained particles is shown in Table 1.

Toner d constituent material Same as toner a. Toner a was obtained by using a surffusion system device (manufactured by Hosokawa Micron Industry Co., Ltd .: air flow set temperature: 270 ° C., feed amount: 1 kg / Hr). The shape factor SF-1 of the matrix coloring particles was 114.
Further, 1.5 parts by weight of hydrophobic silica and 1.0 part by weight of titanium oxide are mixed with 100 parts by weight of the matrix colored particles a to d by a Henschel mixer, and toners of yellow, magenta, cyan, and black colors are mixed. Got.

Preparation of toner e (synthesis of toner binder resin)
724 parts of bisphenol A ethylene oxide 2-mole adduct, 276 parts of isophthalic acid and 2 parts of dibutyltin oxide are placed in a reaction vessel equipped with a cooling pipe, a stirrer and a nitrogen introduction pipe and allowed to react at 230 ° C. for 8 hours at normal pressure. Further, the reaction was carried out at a reduced pressure of 10 to 15 mmHg for 5 hours, and then cooled to 160 ° C., 32 parts of phthalic anhydride was added thereto and reacted for 2 hours. Subsequently, it cooled to 80 degreeC and reacted with 188 parts of isophorone diisocyanate in ethyl acetate for 2 hours, and the isocyanate containing prepolymer (1) was obtained. Next, 267 parts of the prepolymer (1) and 14 parts of isophoronediamine were reacted at 50 ° C. for 2 hours to obtain a urea-modified polyester resin (1) having a weight average molecular weight of 64,000.

In the same manner as above, 724 parts of bisphenol A ethylene oxide 2 mol adduct and 276 parts of terephthalic acid were polycondensed at 230 ° C. for 8 hours under normal pressure, and then reacted at a reduced pressure of 10 to 15 mmHg for 5 hours to modify the peak molecular weight of 5000. An unfinished polyester resin (a) was obtained. 200 parts of urea-modified polyester resin (1) and unmodified polyester resin (a)
800 parts were dissolved and mixed in 2000 parts of an ethyl acetate / MEK (1/1) mixed solvent to obtain an ethyl acetate / MEK solution of the toner binder resin (1). Part of the mixture was dried under reduced pressure to isolate the toner binder resin (1). The Tg was 62 ° C. and the acid value was 10.

(Create toner)
In a beaker, 240 parts of the ethyl acetate / MEK solution of the toner binder resin (1), 20 parts of pentaerythritol tetrabehenate (melting point: 81 ° C., melt viscosity: 25 cps), and 4 parts of copper phthalocyanine blue pigment were placed at 60 ° C. Then, the mixture was stirred at 12000 rpm with a TK homomixer and uniformly dissolved and dispersed. In a beaker, 706 parts of ion-exchanged water, 294 parts of a hydroxyapatite 10% suspension (Superite 10 manufactured by Nippon Chemical Industry Co., Ltd.), sodium dodecylbenzenesulfonate 0. 5 parts were added and dissolved uniformly. Next, the temperature was raised to 60 ° C., and the toner material solution was charged while stirring at 12000 rpm with a TK homomixer and stirred for 10 minutes. The mixture was then transferred to a Kolben equipped with a stir bar and a thermometer, heated to 98 ° C. to partially remove the solvent, returned to room temperature, stirred at 12000 rpm with the same homomixer, and the solvent was completely removed. Removed. Then, after filtering, washing and drying, air classification was performed to obtain base toner particles. The weight average particle size is 3. It was 3 μm.
Further, with respect to 100 parts by weight of the base toner particles, 1.5 parts by weight of hydrophobic silica and 1.0 part by weight of titanium oxide were mixed with a Henschel mixer to obtain toner e.

[Evaluation of fixability]
Two-component development of yellow, magenta, cyan, and black by mixing with a tumbler mixer at a ratio of 5 parts by weight to 100 parts by weight of carrier having silicon particles coated on ferrite particles with an average particle size of 50 μm An agent was used. These developers are loaded into the development section of the Ricoh copier Ipsio 8200, and the transfer material is Gilbert Lancaster bond paper (cotton paper, smoothness 18S) or recycled paper (Ricoh recycled paper, resource type A, smoothness 34S). To obtain a full-color image. The transfer materials used are listed in Table 1.
The obtained images are solid images and halftone images of yellow, magenta, cyan, and black, and solid images of green, blue, and red as intermediate colors. This copier is adjusted so that 1.0 ± 0.1 mg / cm 2 of toner is developed in the solid portion of the single color and 0.4 ± 0.1 mg / cm 2 of toner is developed in the halftone portion of the single color. ing. In addition, the original fixing device is removed and another fixing device can be attached. For the evaluation of the fixability, the minimum fixing temperature is used. This minimum fixing temperature is the fixing minimum temperature at which the residual ratio of the image density after rubbing the obtained fixed image with a pad becomes 70% or more. did.

(Example 1)
The fixing set temperature of the fixing device A was the standard fixing temperature (130 ° C.), and a fixed image of toner a was obtained. The lower limit fixing temperature was 110 ° C., and the fixed image when printing 10,000 sheets at the standard fixing temperature was a clear image with no occurrence of offset. Thereafter, the fixing portion was disassembled and the belt surface and the oil application pad were examined, but no contamination with toner was observed. The evaluation results are shown in Table 1.

(Example 2)
The fixing set temperature of the fixing device B was set to the standard fixing temperature (130 ° C.), and a fixed image of toner b was obtained. The lower limit fixing temperature was 115 ° C., and then the fixing setting temperature was returned to the standard fixing temperature, and 10,000 sheets were printed. Similar to Example 1, an image with no offset was also obtained as a fixed image when printing 10,000 sheets. In addition, the state where the belt surface and the oil application roller were contaminated with toner was not observed. The evaluation results are shown in Table 1.

Example 3
The fixing set temperature of the fixing device C was set to the standard fixing temperature (130 ° C.), and a fixed image of toner b was obtained. The minimum fixing temperature was 110 ° C., and a clear image was obtained. Thereafter, the fixing set temperature was returned to the standard fixing temperature, and 10,000 sheets were printed. Similar to Example 1, an image with no occurrence of offset was obtained as a fixed image when printing 10,000 sheets. In addition, the state where the belt surface and the oil application roller were contaminated with toner was not observed. The evaluation results are shown in Table 1.

(Example 4)
The fixing set temperature of the fixing device C is changed to the standard fixing temperature (130 ° C.), the hardness of the rubber of the elastic layer of the fixing roller is changed from 25 to 35 (Hs), and as a result, the nip time is changed to 36 ms. A fixed image was obtained. The minimum fixing temperature was 105 ° C., and a clear image was obtained. Thereafter, the fixing set temperature was returned to the standard fixing temperature, and 10,000 sheets were printed. Similar to Example 1, an image with no offset was also obtained as a fixed image when printing 10,000 sheets. In addition, the state where the belt surface and the oil application roller were contaminated with toner was not observed. The evaluation results are shown in Table 1.

(Example 5)
The fixing set temperature of the fixing device A was the standard fixing temperature (130 ° C.), and a fixed image of toner d was obtained. The minimum fixing temperature was 105 ° C., and a clear image was obtained. Thereafter, the fixing set temperature was returned to the standard fixing temperature, and 10,000 sheets were printed. Similar to Example 1, an image with no offset was also obtained as a fixed image when printing 10,000 sheets. In addition, the state where the belt surface and the oil application roller were contaminated with toner was not observed. The evaluation results are shown in Table 1.

(Example 6)
The fixing set temperature of the fixing device A was set to the standard fixing temperature (130 ° C.), and a fixed image of toner e was obtained. The minimum fixing temperature was 105 ° C., and a clear image was obtained. Thereafter, the fixing set temperature was returned to the standard fixing temperature, and 10,000 sheets were printed. Similar to Example 1, an image with no offset was also obtained as a fixed image when printing 10,000 sheets. In addition, the state where the belt surface and the oil application roller were contaminated with toner was not observed. The evaluation results are shown in Table 1.

Example 7
The fixing temperature of the fixing device A is set to the standard fixing temperature (130 ° C.), the hardness of the rubber of the elastic layer of the fixing roller is changed from 30 to 25 (Hs), and the rubber hardness of the elastic layer of the pressure roller is 75 to 55. As a result, the nip time was changed from 45 to 36 ms.
Other than that, similarly to Example 1, a fixed image when 10,000 sheets were printed was an image with no occurrence of offset. Further, the state where the belt surface and the oil application roller were contaminated with toner was not observed. The evaluation results are shown in Table 1.

Example 8
The fixing setting temperature of the fixing device C is set to the standard fixing temperature (130 ° C.), the hardness of the elastic layer of the fixing roller is changed from 25 to 60 (Hs), and the rubber hardness of the elastic layer of the pressure roller is changed from 60 to 25. As a result, the nip time was not changed from 45 ms. Similar to Example 3, an image with no offset was also obtained as a fixed image when printing 10,000 sheets. In addition, the state where the belt surface and the oil application roller were contaminated with toner was not observed. The evaluation results are shown in Table 1.

(Comparative Example 1)
The toner a is the same as in Example 1 except that the fixing setting temperature of the fixing device A is set to the standard setting temperature (130 ° C.) and the nip time is changed from 45 ms to 30 ms by changing the pressing conditions of the fixing roller and the pressure roller. A fixed image was obtained. The minimum fixing temperature rose to 160 ° C. The evaluation results are shown in Table 1.

(Comparative Example 2)
Example except that the fixing setting temperature of the fixing device A is the standard fixing temperature (130 ° C.) and the fixing setting temperature is changed from 45 ms to 75 ms by changing the pressing conditions of the fixing roller and the pressing roller. As in Example 1, a fixed image of toner a was obtained. The minimum fixing temperature was 105 ° C. As in Example 1, when a fixed image at the time of printing 10,000 sheets was confirmed, contamination due to an offset corresponding to a solid image occurred on the image surface. The evaluation results are shown in Table 1.

(Comparative Example 3)
Evaluation was performed in the same manner as in Example except that the weight average particle size of toner a used in Example 1 was changed to 6.5 μm. The evaluation results are shown in Table 1.

(Comparative Example 4)
The fixing fixing temperature is standard fixing in the same manner as in Example 1 except that the elastic layer of the fixing roller of the fixing device A is changed to silicon rubber (hardness 50Hs) and the elastic layer of the pressure roller is also changed to silicon rubber (hardness 50Hs). The temperature (130 ° C.) was set, and a fixed image of toner a was obtained. The minimum fixing temperature was 105 ° C. As in Example 1, when a fixed image at the time of printing 10,000 sheets was confirmed, an offset occurred in both the halftone part and the solid part.

1 is a diagram illustrating an example of a fixing device used in a fixing method of the present invention. It is the figure which showed another Example same as the above.

Explanation of symbols

R1: Fixing roller (opposite rotating body)
R2: Pressure roller (Pressure rotating body)
R3: heating roller R4: oil application roller B: fixing belt (endless belt)
T: Unfixed toner image P: Print sheet (transfer material)
S: Temperature sensor G: Guide H: Heat source

Claims (8)

A plurality of rotating bodies are arranged inside an endless belt having an elastic layer on the surface, and at least one of these rotating bodies is a heating roller, and a pressure rotating body positioned outside the endless belt; A nip formed by the endless belt and the pressure rotator by compressing the endless belt with an opposing rotator disposed opposite to the pressure rotator via the endless belt among the plurality of rotators. An image forming apparatus having a fixing unit that heats and fixes a toner image on a transfer material having a smoothness of 40 S or less by a unit,
The nip time is 35 to 75 ms, at least one of the pressure rotator and the counter rotator has an elastic layer with a rubber hardness of 20 to 40 Hs, and the toner has a weight average particle diameter of 2 to 5 μm. An image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the pressure rotating body has a surface coated with a fluororesin-based and / or silicone resin-based material. 2. The image forming apparatus according to claim 1, wherein the counter rotating body has an elastic layer, and the rubber hardness thereof is smaller than the rubber hardness of the elastic layer of the pressure rotating body. 2. The image forming apparatus according to claim 1, wherein the toner has a shape factor SF-1 of 110 to 150. 2. The image forming apparatus according to claim 1, wherein the heating roller is made of a magnetic metal and is heated by electromagnetic induction from electromagnetic induction generating means. 7. The image forming apparatus according to claim 6, wherein the electromagnetic induction generating means is provided outside the heating roller via an endless belt, and the opposing rotating body is different from the heating rotating body. The image forming apparatus according to claim 1, wherein the pressure rotator includes a heating source. An image forming method using the image forming apparatus according to claim 1.

Images