JP5494308B2 - Image forming method - Google Patents

Description

  The present invention relates to an image forming method.

Image formation in an electrophotographic process employed in a copying machine, a printer, or the like is achieved by fixing toner, which is a resin containing a colorant, to paper using a fixing device. As a request for such a fixing process, the toner is firmly fixed on paper to form a high-quality image, and a lot of energy is used in the fixing process during the electrophotographic process. Is desired.
In the fixing process, a nip is formed between a heating roller with a built-in heater and a pressure member provided so as to oppose it, and heat and pressure are applied to the toner on the paper conveyed in the nip. In addition, a roller heat fixing system that is fixed to paper is generally used.
In such a fixing process, when the toner on the conveyed paper enters the fixing nip portion, it is heated and compressed to become more agglomerated. When the toner further proceeds into the fixing nip portion, the toner temperature exceeds the glass transition point (Tg), and toner deformation starts therefrom. As the temperature rises further, melting begins and penetration between the paper fibers occurs. Then, after passing through the fixing nip portion, cooling by heat radiation starts, and the toner is solidified and fixed on the paper.

  In the fixing process, in order to sufficiently supply heat to the toner, it is advantageous to make the nip portion long, and therefore, an elastic layer is widely provided on the surface of the heating roller as a heat source. As a result, the deformation of the fixing roller due to the pressure member is increased, and a nip length for good image formation is secured. In addition, fixing with a hard roller has a problem that characters in a fixed image are crushed and image quality deteriorates. However, in such a process, there is a problem that energy efficiency is deteriorated because heat supplied from a heat source is taken away by the elastic layer. In addition, the elastic layer easily deteriorates due to heat and pressure, and the life of the fixing process is also a problem.

  Therefore, a fixing device using a resistance heating element that supplies heat supplied to the toner to the nip portion from an external heat generating belt instead of from the inside of the fixing roller that forms the nip portion is known (for example, Patent Document 1). In a fixing device using a resistance heating element, an endless heating belt having a resistance heating element layer, an elastic roll arranged inside thereof, an elastic roll that rotates by the elastic roll and passes through the heating belt And a pressure member facing each other, forming a nip portion between the heat generating belt and the pressure member, and passing the sheet (recording medium) through the nip portion to thermally fix the toner on the sheet. ing. In such a fixing device, heat is supplied to the nip portion from an external heat generating belt instead of from the inside of the fixing roller as in the prior art, so the heat supplied to the fixing process is effectively used, and power saving is achieved. Can be achieved. In addition, since the thermal deterioration of the fixing roller is suppressed, the life of the fixing belt is also extended.

JP 2009-258243 A

Even in the fixing device using the above resistance heating element, a sufficient nip length can be ensured between the heat generating belt and the pressure member, so that high-quality image formation is possible.
However, when the heating belt is heated from the end of the heating belt, the temperature variation in the longitudinal direction of the fixing nip increases. In principle, the heat generation amount is constant regardless of the heat generation region even for a small size transfer paper. For this reason, there is a large variation in fixability due to the transfer paper size change. For example, if you change to normal size transfer paper after continuously passing small size transfer paper, the toner melts excessively in the area corresponding to the non-image area of the small size transfer paper, so hot offset that moves the toner to the fixing belt side Or winding around the belt. If the temperature detection unit of the fixing belt corresponds to the non-image portion of the small size transfer paper, there is a problem that cold offset occurs due to insufficient melting of the toner.
The present invention has been made in view of the above circumstances, and an image forming method capable of suppressing hot offset and cold offset, forming a good image, and improving the durability of the fixing device. It is intended to provide.

According to the invention described in claim 1, the heat generating belt having at least a resistance heat generating layer,
An elastic roll disposed inside the heating belt;
A pressure roll having an elastic layer and pressed against the elastic roll from the outside of the heat generating belt via the heat generating belt;
A power supply device for supplying power to the resistance heating element layer,
Forming a nip portion between the heating belt and the pressure roll;
Using a fixing device that passes the recording material through the nip portion and fixes the toner on the recording material,
The toner binder resin has a domain matrix type dispersion structure;
An image forming method is provided in which the domain is a rubber component phase composed of a polymer containing at least a diene unit.

  According to a second aspect of the present invention, there is provided the image forming method according to the first aspect, wherein the glass transition temperature of the rubber component phase in the toner is in the range of -40 ° C to 30 ° C. The

According to the present invention, by forming an image by combining the fixing device and the toner, since the domain portion having a low glass transition temperature exists in the toner, toner deformation easily occurs in the nip portion, As the contact area between the toners increases, heat transfer in the toner is promoted. Therefore, even when the fixing temperature is low and the temperature variation in the longitudinal direction of the nip portion is large, such as immediately after warming up of the fixing device and at the time of restart from the rest, thermal energy is effectively added to the toner, Efficiency of thermal energy can be improved. As a result, a cold offset does not occur and a high-quality fixed image can be obtained. Further, power saving is achieved as a whole fixing process, and it becomes possible to fix the toner to the paper even at a lower temperature, and the crease strength is excellent.
Furthermore, since the rubber component phase in the toner described above is a polymer having a crosslinked structure, it has a characteristic of maintaining elasticity even at a relatively high temperature as compared with a polymer having a linear structure. . For this reason, even if the nip temperature rises under severe conditions such as an increase in the number of continuous paper passes or the use of thick paper, even if temperature variation occurs, an appropriate elastic modulus can be maintained even at high temperatures in the toner. . Since the domain structure that is difficult to melt exists, an excessive decrease in the elastic modulus of the toner is suppressed, and hot offset and winding around the fixing belt are less likely to occur. As a result, the deterioration of the fixing belt is suppressed, and the durability of the fixing device is improved.

It is a figure which shows the internal structure of the digital image forming apparatus used by this invention. 1 is a schematic view of a fixing device. It is arrow sectional drawing at the time of cut | disconnecting by the cutting | disconnection line XX of FIG. FIG. 4 is a cross-sectional view for explaining the configuration of the heat generating belt.

The image forming method according to the present invention will be described below.
[toner]
First, the toner used in the image forming method of the present invention will be described.
The toner contains at least a binder resin, a colorant, and a release agent, the binder resin has a domain / matrix type dispersion structure, and the domain is a rubber component made of a polymer containing at least a diene unit. Consists of phases.

(Rubber component phase consisting of polymers containing diene units)
The rubber component referred to in the present invention refers to a copolymer using a conjugated diene monomer or a homopolymer. Examples thereof include conjugated diene monomer butadiene, isoprene, 2-chloro 1,3-butadiene, 2-methyl-1,3-butadiene and the like. From the viewpoint of securing the fixing strength, butadiene is particularly preferable.
If the copolymer using a conjugated diene monomer is replaced with a common name, styrene butadiene rubber (SBR), nitrile rubber (NR), butadiene rubber (BR), and isoprene rubber (IR) are preferably used. Particularly preferred is styrene butadiene rubber, and the copolymerization ratio of styrene and butadiene is from 30:70 to 50:50.

In the present invention, the glass transition temperature of the rubber component phase in the toner is -85 ° C to 35 ° C. If the temperature is lower than -85 ° C, the heat resistant storage stability of the toner becomes insufficient, and if it is higher than 35 ° C, the expected fixing property cannot be obtained. The glass transition temperature of the rubber component phase is preferably in the range of −40 ° C. or higher and 30 ° C. or lower. This is because the crease fixability is greatly improved within this range.
The glass transition temperature can be confirmed, for example, by nano thermal analysis (Nano-TA). Nano-TA uses a thermal cantilever with a heating function at the tip of the cantilever and performs local thermal analysis, and measures the glass transition point of the domain based on the phenomenon that the cantilever penetrates into the heated sample. can do. When measuring the glass transition point, it is preferable to cool the sample in advance with liquid nitrogen or to install a mechanism for cooling the sample in the apparatus.
The glass transition temperature of the rubber component phase in the toner is measured using a local thermal analysis system using a thermal probe having a heating function at the tip. Specifically, a sample cooled in advance with liquid nitrogen or the like is measured using a local thermal analysis system “Nanothermal Analysis System (Nano-TA)” (manufactured by Nippon Thermal Consulting).
Specifically, when the temperature of the thermal probe is raised by bringing the thermal probe into contact with the measurement surface of the sample surface cut out smoothly, the temperature at which the deflection voltage corresponding to the penetration depth changes from rising to falling is a glass transition. Let it be a point.

(Domain matrix structure)
A domain matrix structure is understood to have the structure of spatially distinct domains in the matrix. In the toner of the present invention, the rubber component is introduced incompatible with a binder resin such as styrene acrylic resin or polyester resin to form a rubber component phase.
This structure can be measured by a conventional method using a transmission electron microscope on a cross section of an osmium-dyed toner. When a slice or slice of toner particles is cut out with an ultramicrotome, the thickness of the slice is set to 100 nm. The particle diameter of the domain part can be shown by the following ferret diameter. In the present invention, the size of the domain phase is specifically determined by preparing a section of the toner particle, photographing a 10,000-fold magnification image of the cross section of the thin piece using a transmission electron microscope, and obtaining 100 domain phases. It is assumed that the horizontal average ferret diameter is measured and the arithmetic average value is calculated.

(Ferre diameter)
The ferret diameter of the domain is calculated from a 10,000-magnification image of the transmission electron microscope.
The ferret diameter simply projects the circumference of the domain onto the X axis of the captured image. When observing and photographing an image, the X axis is synonymous with an arbitrary straight line because the direction is not selected.
When the diameter of the ferret formed by the rubber component phase is 50 to 300 nm, the low-temperature fixability and the crease fixability are improved.
By finely dispersing in the range of 50 to 300 nm, it is presumed that the interface with the matrix resin phase is increased and the effect of modifying the binder resin, that is, the effect of the present invention is exhibited.
By introducing the rubber component into the toner binder resin in a domain form (that is, incompatible), the strength and stress relaxation characteristics of the binder resin are imparted, and fastness can be imparted to the fixed image. A rubber component having a low Tg and a high elastic modulus is particularly effective for developing this performance. Further, by finely dispersing the rubber component phase in the matrix resin, the contact area between the rubber component phase and the matrix resin phase is increased, and the toner modifying effect is great.
The ferret diameter can be made within a corresponding range by creating rubber component particles from a rubber component as a raw material by emulsion polymerization or miniemulsion polymerization and introducing it into toner. At this time, it is preferable to copolymerize 1 to 5% of an acid monomer in addition to the diene monomer as the rubber component because aggregation between the rubber particles can be suppressed. If the rubber component has an acid monomer, it is presumed that the dispersibility in a styrene acrylic resin or polyester resin preferably used as a matrix resin is improved, and the effect of imparting fixing strength is expanded. As the acid monomer, acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid are preferably used. As the method of introducing the acid monomer, (a) it is preferable to copolymerize with a diene monomer, but (b) for example, after copolymerization of an alkyl acrylate such as butyl acrylate with a diene monomer, hydrolysis with a strong acid such as hydrochloric acid is performed. It can also be converted into an acrylic acid copolymer.

(Coloring agent)
As the colorant, a known colorant such as carbon black, a magnetic material, a dye, or a pigment can be arbitrarily used.

  As the black colorant, in addition to carbon black such as furnace black and channel black, magnetic powder such as magnetite and ferrite can be used.

  Examples of colorants include C.I. I. Pigment Red 5, 48: 1, 53: 1, 57: 1, 122, 139, 144, 149, 166, 177, 178, 222, C.I. I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment blue 15; 3, 60, C.I. I. And pigments such as CI Pigment Green 7. In addition, C.I. I. Solvent Red 1, 49, 52, 58, 68, 11, 122, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Examples thereof include dyes such as Solvent Blue 25, 36, 69, 70, 93, and 95. Moreover, you may mix these.

(Release agent)
The release agent is not particularly limited, and a known release agent can be used. Specifically, low molecular weight polyolefins such as polyethylene, polypropylene and polybutene, synthetic waxes such as synthetic ester wax, carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil, montan wax, paraffin wax, micro Examples thereof include minerals such as crystallin wax and Fischer-Tropsch wax, petroleum-based wax, and modified products thereof.

  Among the release agents, a synthetic ester wax having a melting point of 70 ° C. to 95 ° C. is particularly preferably used from the viewpoint of preventing filming. Examples of the synthetic ester wax include behenyl behenate, pentaerythritol tetrabehenate, and tribeenyl citrate. Further, by combining a synthetic ester wax such as behenyl behenate, pentaerythritol tetrabehenate or tribehenyl citrate with a paraffin wax having a melting point of 75 to 100 ° C., the gloss of the toner image is improved and the anti-filling property. It is possible to achieve both improvement in formability.

  Among the paraffin waxes, when a Fischer-Tropsch wax having a melting point of 75 to 100 ° C. is used, the offset property in the high temperature region can be improved at any process speed from the low speed region to the high speed region. In addition, an image forming apparatus using a cleaning blade as a cleaning unit can exhibit good blade cleaning performance.

  The content of the release agent in the toner is preferably 5 to 20% by mass, and more preferably 7 to 13% by mass. If it is less than 5% by mass, offset may occur in the high temperature region, and if it exceeds 20% by mass, the release agent tends to be difficult to be taken into the toner. Since the release agent that floats from the toner particles or is not taken into the toner particles easily adheres to the toner surface, there is a possibility that the filming property may be deteriorated due to the influence of the floating release agent or the attached release agent. is there.

(Other)
The toner in the present invention may use a charge control agent, an external additive, and the like as necessary.
Examples of the charge control agent include nigrosine dyes, naphthenic acid or higher fatty acid metal salts, alkoxylated amines, quaternary ammonium chlorides, azo metal complexes, salicylic acid metal salts or metal complexes thereof. Examples of the metal contained include Al, B, Ti, Fe, Co, and Ni. Particularly preferred as the charge control agent is a metal complex compound of a benzylic acid derivative.

  As the external additive, in addition to the known hydrophobic silica and hydrophobic metal oxide, it is particularly preferable to add cerium oxide particles or higher alcohol particles having 20 to 50 carbon atoms from the viewpoint of filming resistance. In the case of adding cerium oxide particles, those having a number average particle diameter of 150 to 800 nm are preferably used, and more preferably 250 to 700 nm, from the viewpoint of enhancing filming resistance. Further, the addition amount of the cerium oxide particles is preferably 0.5 to 3.5% by mass with respect to the toner, and by setting the amount to 0.5 to 3.5% by mass, good cleaning properties can be obtained. It is maintained and the effect of filming resistance can be stably obtained. In addition, in the case where the addition amount is excessive, the adhesive strength of the toner particles melted during heat fixing is suppressed and the fixing strength is lowered. However, by setting the above range, such a problem of lowering the fixing strength does not occur.

[Toner Production Method]
Next, a method for producing the toner will be described.
As a method for producing the toner of the present invention, a pulverization method in which components such as colorant-carrying resin particles and toner binder resin are heated and melted and kneaded, cooled, pulverized and powdered, and a toner binder resin is obtained. Suspension polymerization method in which a polymerizable monomer, an oil-soluble polymerization initiator, a colorant-carrying resin particle, and the like are emulsified and dispersed in an aqueous medium and then polymerized by heating, and a polymerization property for obtaining a toner binder resin. It consists of an emulsion polymerization method in which monomers and colorant-carrying resin particles are emulsified and dispersed in an aqueous medium, and a water-soluble polymerization initiator is added to this and heated to polymerize, and a toner binder resin produced by an emulsion polymerization method. Examples include an emulsion polymerization aggregation method in which fine particles (hereinafter also referred to as “toner binder resin fine particles”) and colorant-carrying resin particles are dispersed in an aqueous medium, and then added with an aggregating agent and heated to aggregate the fine particles. Can but toner From the viewpoint of uniformly form fine rubber component phase domain, the emulsion polymerization aggregation method is preferable. In this case, the intended toner can be produced by aggregating and fusing the resin fine particles forming the matrix, the rubber component fine particles forming the domains, and the colorant fine particles.

As an example of using the emulsion polymerization aggregation method as a method for producing the toner of the present invention,
(1) A colorant-carrying resin particle forming step for obtaining colorant-carrying resin particles containing a colorant and a coloring medium resin.
(2) A toner binder resin fine particle polymerization step for obtaining resin particles forming a matrix and rubber component fine particles forming a domain.
At this time, resin fine particles containing an anti-offset agent, a charge control agent, and the like can be used as necessary.
(3) A salting out, aggregating, and fusing step in which toner particles are formed by salting out, agglomerating, and fusing the toner binder fine particles, the colorant-carrying particles, and the aqueous medium.
(4) A filtration and washing step of separating the toner particles from the toner particle dispersion system (aqueous medium) and removing the surfactant from the toner particles.
(5) A drying step of drying the washed toner particles.
(6) A step of adding an external additive to the dried toner particles.
Consists of Specific examples of each process are shown below.

(1) Colorant-carrying resin particle forming step for obtaining colorant-carrying resin particles containing a colorant and a coloring medium resin In an aqueous medium typified by an aqueous solution of an ionic surfactant or a nonionic surfactant, A colorant is added and dispersed by a disperser to prepare a colorant dispersion in which the colorant is dispersed in fine particles. The colorant is dispersed in an aqueous medium in which the surfactant concentration is set to a critical micelle concentration (CMC) or higher. The disperser used for the dispersion treatment is not particularly limited, but preferably a pressure disperser such as an ultrasonic disperser, a mechanical homogenizer, a manton gourin, or a pressure homogenizer, or a media disperser such as a sand grinder, a Getzmann mill or a diamond fine mill. Can be mentioned.
It is preferable that the colorant particles in the dispersion have a volume-based median diameter of 40 to 200 nm.

(2-1) Resin Particle Polymerization Step for Forming Matrix Resin particles forming a matrix are prepared by emulsion polymerization. The emulsified resin particles are preferably 30 to 300 nm. For example, a dispersion of resin particles forming a matrix is prepared by emulsifying and dispersing a polymerizable monomer and adding a polymerization initiator to advance the polymerization reaction. Without using the polymerization reaction, the resin particles can be prepared by dissolving or dispersing the resin and, if necessary, the release agent or colorant in the solvent and then dispersing and removing the solvent in the aqueous medium. At this time, if the release agent is dissolved in the polymerizable monomer or resin solution to prepare an emulsified (dispersed) liquid, the release agent particles are detached after the toner particles are completed, thereby contaminating the members of the image forming apparatus. It is preferable because it can be suppressed.

(2-2) Rubber Component Fine Particle Polymerization Step for Forming Domains Rubber component fine particles for forming domains are prepared by, for example, emulsion polymerization.
From the viewpoint of introducing a rubber component as a fine domain in the emulsion polymerization association method, a method of preparing rubber component fine particles in advance and aggregating and fusing the rubber component fine particles and resin fine particles forming the matrix is preferable.
At this time, it is necessary to prepare rubber component fine particles. As this fine particle preparation method, (a) a polymer latex is directly obtained by emulsion polymerization or the like using a polysynthetic monomer that forms a rubber component phase. Method, or (b) an appropriate means (after preparing a (co) polymer comprising a rubber component in advance)
Direct emulsification, dissolution suspension method, miniemulsion polymerization) and emulsification / dispersion can be used.
In the examples described later, rubber component fine particles were directly produced by emulsion polymerization from the viewpoint of ease of fine particle production.

(3) Aggregation / fusion process The dispersion of colorant particles is added to the dispersion of resin fine particles and rubber component fine particles forming the matrix, and the dispersion of release agent particles is added as necessary. . Next, an aggregating agent is added, and when the resin particles, the colorant particles, and the releasing agent are added to the aqueous medium, the added releasing agent particles are aggregated and fused to form toner particles. To do. A series of processes of aggregation and fusion may be referred to as an association process.
As the aggregation / fusion method, a salting-out fusion method is preferable. The salting-out fusion method is a method in which aggregation and fusion are advanced in parallel, and when the aggregated particles have grown to a desired particle size, an aggregation stop agent is added to stop the particle growth. In this method, heating for controlling the particle shape is continued as necessary.

The size of the toner particles is preferably 3 to 10 μm in terms of volume-based median diameter, particularly preferably 3 to 7 nm. The volume-based median diameter of the core particles is a device in which a computer system (Beckman Coulter) equipped with data processing software "Software V3.51" is connected to Coulter Multisizer 3 (Beckman Coulter). Use to measure and calculate.
As a measurement procedure, 0.02 g of a sample is conditioned with 20 ml of a surfactant solution (for example, a surfactant solution in which a neutral detergent containing a surfactant component is diluted 10-fold with pure water for the purpose of dispersing the sample). Then, ultrasonic dispersion is performed for 1 minute to prepare a sample dispersion. The prepared dispersion is pipetted into a beaker containing ISOTON II (manufactured by Beckman Coulter, Inc.) in a sample stand until the display concentration of the measuring instrument becomes 5 to 10%. By setting this concentration range, a reproducible measurement value can be obtained. In the measuring device, the measurement particle count number is 25000, the aperture diameter is 50 μm, and the frequency value is calculated by dividing the measurement range of 1 to 30 μm into 256 parts. The particle diameter of 50% from the larger volume integrated fraction is defined as the volume-based median diameter.

  An aqueous medium means that the main component (50% by mass or more) is made of water. Examples of components other than water include organic solvents that dissolve in water. For example, methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, tetrahydrofuran and the like can be mentioned.

In addition, it is good also as passing through a maturing process after an aggregation / fusion process.
Specifically, the heating temperature is lowered in the agglomeration / fusion process to suppress the progress of fusion between the particles and to make the agglomerated particles uniform. Thereafter, in the ripening step, the surface of the toner particles is controlled to have a uniform shape by lowering the heating temperature and lengthening the time.

(4) Cooling / Washing Step In the cooling / washing step, the obtained dispersion of toner particles is cooled at a cooling rate of, for example, 1 to 20 ° C./min. When cooled to a predetermined temperature, the toner particles are solid-liquid separated from the cooled dispersion of toner particles. Solid-liquid separation may be any method other than centrifugation, such as vacuum filtration using a Nutsche or the like, filtration using a filter press or the like. Next, the toner cake obtained by solid-liquid separation (wet toner particles prepared in a cylindrical shape such as a cake) is washed to remove deposits such as surfactants and salting-out agents.

(5) Drying step In the drying step, the washed toner cake is dried. For the drying treatment, a spray dryer, a vacuum freeze dryer, a vacuum dryer or the like can be used. The water content of the dried toner particles is preferably 5% by mass or less, more preferably 2% by mass or less.

(6) External Addition Processing Step In the external addition processing step, an external additive is mixed with toner particles obtained by drying to obtain an electrostatic charge developing toner.

[Production of developer]
The toner of the present invention may be used, for example, as a one-component magnetic toner containing a magnetic material, used as a two-component developer mixed with a so-called carrier, or a non-magnetic toner alone. Any of these can be suitably used.
In the toner of the present invention, when used as a two-component developer mixed with a carrier, it is possible to suppress the occurrence of toner filming (carrier contamination) on the carrier, and when used as a one-component developer, The occurrence of toner filming on the frictional charging member of the apparatus can be suppressed.

As the carrier constituting the two-component developer, magnetic particles made of conventionally known materials such as metals such as iron, ferrite and magnetite, alloys of those metals with metals such as aluminum and lead can be used, It is particularly preferable to use ferrite particles.
The carrier preferably has a volume average particle diameter of 15 to 100 μm, more preferably 25 to 60 μm. The volume average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  As the carrier, it is preferable to use a carrier coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited, and for example, olefin resin, styrene resin, styrene-acrylic resin, silicone resin, ester resin, or fluorine-containing polymer resin is used. In addition, the resin for constituting the resin-dispersed carrier is not particularly limited, and known resins can be used. For example, styrene-acrylic resin, polyester resin, fluorine resin, phenol resin, etc. are used. can do.

[Image forming method]
Next, the image forming method of the present invention will be described together with the image forming apparatus.
FIG. 1 is a diagram showing an internal configuration of a digital image forming apparatus used in the present invention.
A digital image forming apparatus (hereinafter referred to as a unit “image forming apparatus”) 1 has a plurality of recording material storage portions 20 at the bottom. An image forming unit 40 and an intermediate transfer belt 50 are installed above the recording material storage unit 20, and a document reading unit 30 is installed at the upper part of the apparatus main body.

The recording material storage unit 20 can be pulled out to the front side of the apparatus (the front side in FIG. 1).
The image forming unit 40 includes four sets of image forming units 400Y, 400M, 400C, and 400K for forming toner images for each color of Y, M, C, and K. The image forming units 400Y, 400M, and 400K 400C and 400K are linearly arranged from top to bottom in this order, and each has the same configuration. The configuration of the image forming unit 400Y will be described as an example. The image forming unit 400Y includes a photoreceptor 410 that rotates counterclockwise, a scorotron charging unit 420, an exposure unit 430, and a developing unit 440.
The cleaning unit 450 is disposed to include a region facing the lowermost part of the photoconductor 410.

The intermediate transfer belt 50 located at the center of the apparatus main body is endless and has an appropriate volume resistivity. Further, the intermediate transfer belt 50 is formed on the outside of a semiconductive film substrate in which a conductive material is dispersed in an engineering plastic such as knitted polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, and nylon alloy. It consists of two layers with fluorine coating. Further, there may be a conductive material dispersed in silicon rubber or urethane rubber.
The primary transfer electrode 510 is installed at a position facing the photoconductor 410 with the intermediate transfer belt 50 interposed therebetween.

Next, a process for forming a color image will be described.
The photoconductor 410 is driven by a main motor (not shown), the surface of the photoconductor 410 is supplied with a voltage by a power source (not shown), and is charged positively by the discharge of the scorotron charging means 420 (in this embodiment). + 800V). Next, optical writing according to image information is performed by the exposure unit 430, and an electrostatic latent image is formed on the photoreceptor 410. When the formed electrostatic latent image passes through the developing unit 440, the toner charged positively in the developing unit adheres to the portion of the latent image by application of the positive developing bias, and the toner image is formed on the photoreceptor 410. Is formed. The formed toner image is transferred to the intermediate transfer belt 50 that is pressure-bonded to the photoreceptor 410. The toner on the photoreceptor 410 remaining after the transfer is cleaned by the cleaning means 450. A toner image formed by each of the image forming units 400Y, 400M, 400C, and 400K is transferred to the intermediate transfer belt 50 so that a color image is formed on the intermediate transfer belt 50. The recording material P is discharged one by one by the recording material storage unit 20 and conveyed to the position of the registration roller 60. After the leading edges of the recording material P are aligned by the registration roller 60, the recording material P is fed from the registration roller 60 at a timing when the toner image on the intermediate transfer belt 50 matches the image position. The recording material P fed by the registration roller 60 is guided by a guide plate and fed to a transfer nip portion formed by the intermediate transfer belt 50 and the transfer portion 70. The transfer unit 70 composed of rollers presses the recording material P toward the intermediate transfer belt 50 side. By applying a bias (−500 V) having a polarity opposite to that of the toner to the transfer unit 70, the toner image on the intermediate transfer belt 50 is transferred to the recording material P by the action of electrostatic force. The recording material P is neutralized by a separating means (not shown) composed of a neutralizing needle and separated from the intermediate transfer belt 50, and the fixing device 100 is composed of a pair of an elastic roll 21 and a pressure roll 16 via the heat generating belt 11. Sent to. As a result, the toner image is fixed on the recording material P, and the recording material P on which the image has been formed is discharged out of the apparatus.

FIG. 2 is a schematic view of the fixing device, and FIG. 3 is a cross-sectional view taken along the line XX in FIG.
In the fixing device 100, a recording material P on which an unfixed toner image T is formed is inserted into a nip portion N formed by an elastic roll 21 disposed inside via a pressure roll 16 and a heat generating belt 11. The toner image is fixed.
In FIG. 2, the arrow A indicates the conveyance direction of the recording material P, and the arrow B indicates the rotation direction of the pressure roll 16.

FIG. 4 is a cross-sectional view for explaining the configuration of the heat generating belt.
As shown in FIG. 4, the heat generating belt 11 has a four-layer structure, and includes a reinforcing layer 111, a heat generating layer 112, an elastic layer 113, and a release layer 114 from the side in contact with the elastic roll 21. . The reinforcing layer 111 is necessary for the purpose of controlling and holding the shape of the heat generating layer 2. For example, a polyimide resin is used, and preferably 20 to 80 μm. In the heat generating layer 2, for example, a conductive filler is uniformly dispersed in a polyimide resin. The conductive filler preferably contains a carbon nanomaterial and filamentary metal fine particles. This is because, in order to control the heat generation characteristics of the heat generating belt, for example, to obtain a heat generating belt having low electric resistance, it is necessary to add a large amount of carbon nanomaterial. However, when a large amount of carbon nanomaterial is added, the mechanical strength of the belt is remarkably lowered, so that highly conductive filament-like metal fine particles are required. The elastic layer 113 is formed on the outer side of the heat generating layer 112, and a polyimide resin is mainly used like the reinforcing layer 111. The elastic layer 113 is preferably about 5 to 50 μm in order to increase the heat conduction efficiency from the heat generating layer 112. The release layer 114 is mainly made of fluororesin in order to improve the releasability of the toner from the heat generating belt, and typical examples include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether. A copolymer (PFA) and tetrafluoroethylene-hexafluoropropylene (FEP) are mentioned, and about 5-30 micrometers is preferable.
In addition, the power receiving unit 115 is connected to an electrode or conductor 17 described later.

The elastic layer 12 of the elastic roll 21 inside the heat generating belt 11 is not particularly limited as long as it has heat resistance at 150 ° C. to 250 ° C. necessary for the image fixing temperature as a rubber material. Most preferred in this case is silicon rubber. The elastic roll 21 is manufactured by using a material made of aluminum or iron for the core bar 14 and performing surface treatment such as blasting, and then molding the elastic layer 12 with silicon rubber or the like with a thickness of about 3 to 10 mm. Done with.
The elastic layer 12 needs to adjust thermal conductivity and hardness in addition to heat resistance. In this case, the heat insulating effect can be increased and the heat generating effect of the heat generating belt 11 can be increased by changing the silicon rubber from the solid rubber to the sponge rubber. Further, the hardness depends on the process speed of the image forming apparatus 1, but is 5 degrees or more and less than 60 degrees, more preferably between 30 degrees and less than 50 degrees, between the heat generating belt 11 and the pressure roll 16. Can be designed to have a wide nip area, which is advantageous for image fixability.

  The pressure roll 16 is not particularly limited as long as it has heat resistance at an image fixing temperature of 150 ° C. to 250 ° C. like the elastic roll 21. Similar to the elastic roll 21, silicon rubber is used as the elastic layer, aluminum or iron material is used for the core metal 15, surface treatment such as blasting is performed, and then silicon rubber or the like is used as the elastic layer 3 to 10 mm. It is done using what is molded to the extent.

  In FIG. 2, reference numeral 17 denotes an electrode or a conductor for supplying power to the heat generating layer 112 of the heat generating belt 11, and the electrode or the conductor 17 is provided at both ends (the power receiving unit 115) of the heat generating belt 11. Each of the electrodes or conductors 17 is formed with a roller 13 for feeding. The roller 13 is connected to an AC or DC power source 22. A brush may be used instead of the roller 13.

  An image is formed using the image forming apparatus 1 having the fixing device 100 as described above and the above-described toner.

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.
(1) Colorant-carrying resin particle forming step for obtaining colorant-carrying resin particles containing a colorant and a coloring medium resin 11.5 parts by mass of sodium n-dodecyl sulfate is stirred and dissolved in 160 parts by mass of ion-exchanged water, 25 parts by weight of C.I. I. Pigment Blue 15: 3 was gradually added. This solution was subjected to a dispersion treatment using Clearmix W Motion CLM-0.8 (M-Technique), and the volume-based median diameter of the colorant particles was measured using an electrophoretic light scattering photometer “ELS-800 (Otsuka Electronics Co., Ltd.). ) ", It was 158 nm.

(2-1) Resin Fine Particle Polymerization Step for Forming Matrix “Resin fine particles A” containing a release agent were prepared by the method shown below.
First, 8 parts by mass of sodium dodecyl sulfate and 3000 parts by mass of ion-exchanged water are added to a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device, and the mixture is stirred while stirring at a stirring speed of 230 rpm under a nitrogen stream. The temperature was raised to 80 ° C. After the temperature increase, a polymerization initiator solution prepared by dissolving 10 parts by mass of potassium persulfate in 200 parts by mass of ion-exchanged water was added to adjust the liquid temperature to 80 ° C.
Next, a polymerizable monomer mixture containing the compound shown below was added dropwise to the reaction vessel over 1 hour, followed by polymerization by heating and stirring at 80 ° C. for 2 hours to prepare resin fine particles. . This is referred to as “resin fine particles (1H)”.
Styrene 480 parts by weight n-butyl acrylate 250 parts by weight Methacrylic acid 68 parts by weight n-octyl-3-mercaptopropionate 16 parts by weight

Further, a solution prepared by dissolving 7 parts by mass of polyoxyethylene (2) sodium dodecyl ether sulfate in 800 parts by mass of ion-exchanged water was added to a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device. After the reaction vessel is heated to 98 ° C., 260 parts by mass of the “resin fine particles (1H)” and a polymerizable monomer mixture containing the compound shown below are added as they are, and a machine having a circulation path A dispersion liquid containing emulsified particles (oil droplets) was prepared by mixing and dispersing for 1 hour using a type disperser “CLEAMIX (manufactured by M Technique Co., Ltd.)”.
Styrene 245 parts by mass n-butyl acrylate 120 parts by weight n-octyl-3-mercaptopropionate 1.5 parts by weight polyethylene wax (melting point 81 ° C.) 190 parts by weight

Next, a polymerization initiator solution prepared by dissolving 6 parts by mass of potassium persulfate in 200 parts by mass of ion-exchanged water is added to this dispersion, and polymerization is performed by heating and stirring at 82 ° C. for 1 hour. Fine particles were obtained. This is referred to as “resin fine particles (1HM)”.
Furthermore, a polymerization initiator solution prepared by dissolving 11 parts by mass of potassium persulfate in 400 parts by mass of ion-exchanged water was added, and a polymerizable monomer solution containing the following compounds at a temperature of 82 ° C. It was added dropwise over 1 hour. After completion of the dropping, polymerization was carried out by heating and stirring for 2 hours, and then cooled to 28 ° C. to obtain resin fine particles. This is designated as “resin fine particles A”.
Styrene 435 parts by weight n-butyl acrylate 130 parts by weight Methacrylic acid 33 parts by weight n-octyl-3-mercaptopropionate 8 parts by weight

(2-2) Rubber Component Fine Particle Polymerization Step for Forming Domains “Rubber component fine particle B1” was prepared by the method shown below.
First, 50 parts of butadiene as a polymerizable monomer, 30 parts of styrene, 18 parts of methyl methacrylate, and 2 parts of acrylic acid are charged in a pressure vessel, and further 200 parts of water, 1.0 part of t-dodecyl mercaptan, and dodecylbenzenesulfone. After charging 0.2 parts of sodium acid and 1.0 part of potassium persulfate, polymerization was carried out at 70 ° C. for 2 hours in a nitrogen atmosphere. Then, in order to complete superposition | polymerization, reaction was continued for further 3 hours and superposition | polymerization was complete | finished.
About the obtained copolymer latex, the glass transition point and the latex particle diameter were calculated | required with the following method.
(I) Glass transition point The obtained copolymer latex was vacuum dried at 100 ° C for 20 hours to produce a film. This dry film was measured according to the ASTM method using a differential scanning calorimeter (DSC: manufactured by DuPont).
(II) Latex particle size The average particle size of the obtained copolymer latex was determined by a conventional method using a particle size measuring device manufactured by Otsuka Electronics.
Using similar means, rubber component fine particles B2 to B10 in which only the ratio of the additive component was changed were prepared. The results of additive amount and physical properties are shown in Table 1 below.

(3) Aggregation / fusion process The following substances were added to a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device, and the liquid temperature was adjusted to 30 ° C.
"Resin fine particles A" 300 parts by mass (solid content conversion)
"Rubber component fine particle B1" 15 parts by mass (solid content conversion)
1400 parts by weight of ion-exchanged water 120 parts by weight of “colorant dispersion 1” 123 parts by weight of an aqueous solution obtained by adding 3 parts by weight of polyoxyethylene (2) sodium dodecyl ether sulfate to 120 parts by weight of ion-exchanged water

  Next, a 5 mol / liter aqueous sodium hydroxide solution was added to adjust the pH to 10, and a 30 ° C. aqueous solution in which 35 parts by mass of magnesium chloride was dissolved in 35 parts by mass of ion-exchanged water was stirred. Added to the system over 10 minutes. Then, after 3 minutes had elapsed after the addition, the temperature was started to rise, and the temperature of the reaction system was raised to 90 ° C. over 60 minutes to advance the aggregation. The size of the particles formed by aggregation was observed with “Multisizer 3”. When the median diameter on a volume basis reached 6.5 μm, 750 parts by mass of a 20% aqueous sodium chloride solution was added to stop aggregation.

  After adding the 20% sodium chloride aqueous solution, the liquid temperature was set to 98 ° C., and the stirring was continued. While observing the average circularity of the particles with a flow type particle image analyzer “FPIA-2100”, the aggregated resin fine particles were fused. Proceeded. When the average circularity reached 0.965, the liquid temperature was cooled to 30 ° C., hydrochloric acid was added to adjust the pH to 4.0, and stirring was stopped.

(4) Cooling / washing step, (5) Drying step Particles produced in the aggregation / fusion step are removed from the basket-type centrifuge “MARK III model number 6
Solid-liquid separation was performed with “0 × 40 (manufactured by Matsumoto Machine Co., Ltd.)” to form a wet cake of particles. The wet cake was washed with ion exchange water at 45 ° C. until the electric conductivity of the filtrate reached 5 μS / cm with the basket-type centrifuge, and then transferred to “flash jet dryer (manufactured by Seishin Enterprise Co., Ltd.)”. Particles were produced by drying until the amount was 0.5% by mass.

(6) External addition step 1% by mass of hydrophobic silica (number average primary particle size = 12 nm) and 0.3% of hydrophobic titania (number average primary particle size = 20 nm) are obtained in the particles obtained above. % And mixed with a Henschel mixer to prepare “Toner 1”.
The volume-based median diameter of Toner 1 was 6.5 μm, and the average circularity was 0.965. The median diameter and the average circularity on a volume basis are values obtained by measurement by the above method.

  It was prepared in the same manner as in Toner 1 except that 9 parts of “rubber component fine particle B1” containing a diene unit was changed as shown in Table 2 below. These are designated as toners 2 to 10.

  It was produced in the same manner as in the toner 1 except that the rubber component fine particle B1 was not used and the amount of the resin fine particle A used was 315 parts by mass (in terms of solid content). This is referred to as toner 11.

  Each of the toners 1 to 10 and the comparative toner 11 is mixed with a ferrite carrier having a volume-based median diameter of 60 μm coated with a silicone resin so that the concentration of the developer toner becomes 6% by mass. Agents 1 to 11 were prepared.

なお、表２には各トナー１〜１１におけるトナー粒子中のゴム成分相のフェレ径も示している。

Table 2 also shows the ferret diameter of the rubber component phase in the toner particles of the toners 1 to 11.

The following evaluations were performed using the fixing device and the toners 1 to 11 shown in Table 2.
(1) The fixing device basically has the structure shown in FIGS.
・ Heat belt Reinforcing layer: Polyimide resin, film thickness 70μm
Heat generation layer: Carbon nanofiber and filamentary nickel fine particles added to polyimide resin, film thickness 35μm
Elastic layer: polyimide resin, film thickness 15μm
Release layer: PFA resin, film thickness 15 μm
(2) The system speed (peripheral speeds of the photoconductor 410, the intermediate transfer belt 50, and the heat generating belt 11) was set to 300 [mm / sec].

<Measurement of nip temperature>
The temperature of the heat generating belt is set to 150 ° C. and 180 ° C., the temperature difference between the nip temperature at the initial stage of fixing and the temperature of the heat generating belt, and after passing 100 sheets of plain paper (basis weight 80 g) continuously, the nip temperature is up to how many times. It was confirmed whether it decreased (see Table 3 below).

<Cold offset>
The temperature of the heat generating belt is set to 180 ° C. and 150 ° C., and the toner transferred onto the paper is continuously passed through and fixed by 100 sheets. The presence or absence of the occurrence of cold offset was visually evaluated on the first and 100th fixed images. As the toner, toners 1 to 10 of the present invention and comparative toner 11 were used.

<Hot offset>
The temperature of the heat generating belt is set to 180 ° C., and the toner transferred onto the paper is continuously fed and fixed. The presence or absence of hot offset was visually evaluated on the first and 100th fixed images. As the toner, toners 1 to 10 of the present invention and comparative toner 11 were used.

<Durability test of fixing device>
An image having a pixel rate of 50% was printed using transfer paper having a basis weight of 80 g. Streaky gloss unevenness due to heat generation belt from scratches on the fixed image, or the number of time the image contamination occurs due to toner contamination of the heating belt, replacement time of the heating belt, i.e. it is determined that the service life. Evaluate more than 500,000 copies and pass over 1 million. The evaluation results are shown in Table 4 below. In Table 4, for example, 850K = 850 thousand sheets = 850,000 sheets (passed) is represented.

From Table 3 above, in the fixing device of the present invention, the temperature of the nip portion is lower than the temperature of the heat generating belt in the initial fixing stage. However, after 100 sheets have passed, the nip temperature drops,
Since excessive heat is supplied from the heat source to the nip portion, it can be seen that overheating has occurred. Moreover, it can be confirmed that this tendency becomes remarkable when the set temperature of the heat generating belt is high.

From Table 4 above, in the image forming method combining the fixing device and the toner of the present invention, in the comparative toner 11, a cold offset occurs when the nip temperature is lower than the temperature of the heat generating belt at the initial paper feeding. However, in the toners 1 to 10 of the present invention, the cold offset is suppressed. In the comparative toner 11, hot offset occurs at the time when the temperature of the nip portion becomes high after 100 sheets have passed, but in the toners 1 to 10 of the present invention, hot toner is generated. Offset is suppressed.
Furthermore, in the first to tenth aspects of the present invention, it can be seen that the durability of the fixing device is also improved. This is because the use of the toner component including the rubber component improves the releasability of the heat generating belt and the toner at the time of fixing and suppresses the deterioration of the heat generating belt.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Heat generating belt 12 Elastic layer 13 Roller 15 Core metal 16 Pressure roll 17 Electrode or conductor 20 Recording material storage part 21 Elastic roll 22 Power supply (power supply device)
30 Document reading unit 40 Image forming unit 50 Intermediate transfer belt 60 Registration roller 70 Transfer unit 100 Fixing device 111 Reinforcing layer 112 Heat generation layer (resistance heating element layer)
113 Elastic layer 114 Release layer 115 Power receiving unit 400Y, 400M, 400C, 400K Image forming unit 410 Photoconductor 420 Scorotron charging unit 430 Exposure unit 440 Development unit 450 Cleaning unit P Recording material N Nip

Claims (2)

A heating belt having at least a resistance heating element layer;
An elastic roll disposed inside the heating belt;
A pressure roll having an elastic layer and pressed against the elastic roll from the outside of the heat generating belt via the heat generating belt;
A power supply device for supplying power to the resistance heating element layer,
Forming a nip portion between the heating belt and the pressure roll;
Using a fixing device that passes the recording material through the nip portion and fixes the toner on the recording material,
The toner binder resin has a domain matrix type dispersion structure;
The image forming method, wherein the domain is a rubber component phase made of a polymer containing at least a diene unit.   2. The image forming method according to claim 1, wherein a glass transition temperature of a rubber component phase in the toner is in a range of −40 ° C. to 30 ° C.

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