JP4136668B2 - Image forming toner, toner container, and image forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming toner used in an image forming apparatus using electrophotography.
[0002]
[Prior art]
As a fixing method used in the dry development method, a heating heat roller method is widely used because of its energy efficiency. In recent years, in order to save energy by fixing the toner at a low temperature, the thermal energy given to the toner during fixing tends to be small. The 1999 International Energy Agency (IEA) Demand-Side Management (DSM) program has a technology procurement project for next-generation copiers, and the required specifications are made public. Copiers of 30 cpm or more are on standby. As one of the energy savings in recent years, there is a case where the heat source is turned off when fixing is not performed. In such an apparatus, the heat roller is heated until the desired temperature is reached after the heat source is turned on. Achieving dramatic energy savings compared to conventional copiers is required so that the time is within 10 seconds and the standby power consumption is 10-30 watts or less (differs depending on the copying speed).
[0003]
One method for achieving this requirement is to reduce the heat capacity of a fixing member such as a heated heat roller to improve the temperature responsiveness of the toner, but it is not fully satisfactory.
In order to achieve the above requirement and minimize the waiting time, it is considered to be an essential technical achievement matter to lower the fixing temperature of the toner itself and lower the toner fixing temperature when it can be used.
[0004]
In order to cope with such low-temperature fixing, attempts have been made to use a polyester resin having excellent low-temperature fixing properties and relatively good heat-preserving properties, in place of styrene-acrylic resins that have been frequently used. However, for further low-temperature fixing, it is necessary to control the thermal characteristics of the resin itself. However, if the glass transition temperature (Tg) is lowered too much, the heat-resistant storage stability is deteriorated or the molecular weight is decreased. Softening temperature of resin [T (F_1/2)] Is lowered too much, there are problems such as lowering the hot offset occurrence temperature.
For this reason, even a polyester resin excellent in low-temperature fixability has not yet obtained a toner having excellent low-temperature fixability and high hot offset occurrence temperature by controlling the thermal characteristics of the resin itself.
[0005]
In order to solve this problem, an attempt to add a specific non-olefinic crystalline polymer having a sharp melt property at a glass transition temperature to a binder resin [Japanese Patent Laid-Open No. 62-63940 (Patent Document 1)] There are also attempts to use crystalline polyester [Japanese Patent No. 2931899 (Patent Document 2), Japanese Patent Application Laid-Open No. 2001-222138 (Patent Document 3)]. However, when these materials having sharp melt properties are kneaded, the melt viscosity becomes extremely low, and it is easy to prevent fine dispersion of the colorant and the release agent. When the colorant is not uniformly dispersed, the degree of coloration is lowered, and a high-density image cannot be obtained, or a clear image cannot be obtained with a full-color toner. In addition, when the colorant is a low-resistance material such as carbon, if the dispersion state is poor, the resistance of the toner is lowered, and background stains due to poor developability and uneven density in the solid part due to poor transferability occur. In addition, non-uniform dispersion of the release agent increases the probability of wax existing on the toner surface, and causes a problem due to deterioration of developability as in the case of non-uniform colorant. Further, over time, various problems occur due to fusion of the release agent to the carrier in the case of the two-component developer and the charging roller or blade in the case of the one-component development, and the durability tends to deteriorate.
[0006]
In the state where the particle diameter is reduced as in recent years, the problem due to non-uniform dispersion of the toner constituting material becomes more remarkable.
In order to solve this problem, an attempt is made to agglomerate resin particles having submicron crystallinity together with fine particles of other constituent materials such as an amorphous resin and a release agent to form a toner [JP 2002-108018]. Gazette (patent document 4)]. However, in this method, a resin having crystallinity does not easily exist on the particle surface, and the sharp melt property is not efficiently used for fixing at low temperature.
Therefore, it is necessary to establish a low-temperature fixing technology that is further advanced from the conventional technical field for a further low-temperature fixing toner that satisfies the required specifications of DSM.
[0007]
[Patent Document 1]
JP 62-63940 A
[Patent Document 2]
Japanese Patent No. 2931899
[Patent Document 3]
JP 2001-222138 A
[Patent Document 4]
JP 2002-108018 A
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned background, and can obtain a toner having both low-temperature fixability and offset resistance higher than conventional ones, and further having no problem in heat-resistant storage stability. Further, the resolution is good, and background dirt and density unevenness are obtained. An object is to obtain a high-quality image having no toner, and to obtain a durable toner that does not deteriorate the image quality over time.
[0009]
[Means for Solving the Problems]
  As a result of intensive investigations for effectively expressing the sharp melt property of the resin having crystallinity, the present inventors have found that the above object can be achieved by the following means. That is, according to the present invention,ThirteenIs provided.
[0010]
  First, in claim 1, polyester resin fine particles having crystallinity are present on the surface of base particles containing at least an amorphous binder resin, a colorant, and a release agent.And the amorphous binder resin is mainly a polyester resin.An image forming toner is provided.
[0011]
A second aspect of the present invention is the image forming toner according to the first aspect, wherein the crystalline polyester resin fine particles have a particle diameter of 0.01 to 0.5 μm. Toner is provided.
[0012]
Thirdly, in claim 3, in the toner for image formation according to claim 1 or 2, the content of the fine particles of the polyester resin having crystallinity is 0.5% by weight or more and 20% by weight or less. An image forming toner is provided.
[0015]
  FirstFour, Claims4The above claims 1 to3In the image forming toner according to any one of the above, the crystalline polyester fine particles have a diffraction peak at a position of at least 2θ = 20 to 25 ° in an X-ray diffraction pattern by a powder X-ray diffractometer. An image forming toner characterized by the above.
[0016]
  FirstFiveAnd claims5The above claims 1 to4In the image forming toner according to any one of the above, the maximum endothermic peak temperature of the DSC curve of the polyester resin having crystallinity is 90 to 130 ° C., and the softening temperature [T (F_1/2)] Is 80 to 130 ° C. An image forming toner is provided.
[0018]
  FirstSixAnd claims6The above claims 1 to5In the image forming toner according to any one of the above, the glass transition temperature (Tg) of the amorphous binder resin is 40 to 70 ° C., and the softening temperature [T (F_1/2)] Is 120 to 160 ° C. An image forming toner is provided.
[0019]
  FirstSevenAnd claims7The above claims 1 to6An image forming toner according to any one of the above, wherein the releasing agent has a melting point of 70 to 90 ° C.
[0020]
  FirstEightAnd claims8The above claims 1 to7An image forming toner according to any one of the above, wherein the toner has a volume average particle diameter of 4 to 7 μm.
[0021]
  FirstNineAnd claims9The above claims 1 to8The image forming toner according to any one of the above, wherein the fine particles of the polyester resin having crystallinity are immobilized on the surface of the base particle.
[0022]
  FirstTenAnd claims10The above claims 1 to8The image forming toner according to any one of the above, wherein the fine particles of the polyester resin having crystallinity are mixed and adhered to the surface of the base particle.
[0023]
  FirstelevenAnd claims11The above claim10In the image forming toner described above, there is provided an image forming toner, wherein the fine particle of the crystalline polyester resin has a particle size of 0.01 to 0.1 μm.
[0024]
  FirsttwelveAnd claims12The above claims 1 to11A toner container is provided, which is filled with the image forming toner described in any of the above.
[0025]
  FirstThirteenAnd claims13Then, in the image forming method for forming an image by developing the electrostatic latent image formed on the photoconductive image carrier, the electrostatic latent image developing toner is defined in claims 1 to 3.11An image forming method comprising the image forming toner according to any one of the above.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
The toner of the present invention is one in which polyester resin fine particles having crystallinity are present on the toner surface.
The polyester resin having crystallinity has a melting point, causes a crystal transition at that temperature, and at the same time, the melt viscosity suddenly decreases from the solid state and exhibits a fixing function to a recording medium such as paper.
On the other hand, the amorphous resin gradually decreases in melt viscosity from Tg, and it takes time until the fixing function is exhibited. Therefore, it is necessary to lower the melt viscosity at a low temperature by lowering the Tg or lowering the molecular weight, but the storability and hot offset resistance tend to be insufficient.
However, by including a polyester resin having crystallinity, it is possible to achieve a decrease in melt viscosity without deteriorating storage stability and hot offset resistance, which could not be achieved with an amorphous resin alone.
[0027]
At this time, the more the resin having crystallinity is on the particle surface, the more efficient it is. When the resin is present on the particle surface like the toner of the present invention, it is very efficient. In the method of obtaining particles from the melt-kneading step through the pulverization step, in order to make the resin having crystallinity exist on the particle surface, the content of the resin having crystallinity is increased by increasing the content or by making the dispersion state worse. A method in which the interface is a pulverized interface is conceivable. However, although the method of increasing the content depends on the composition and physical properties of the amorphous resin, the storage stability may deteriorate or the hot offset resistance may be insufficient. Moreover, the method of making a dispersed state worse also makes a dispersed state, such as a coloring agent and a mold release agent, worse. Conversely, in order to improve the dispersion state of the colorant and release agent, when the shearing force during kneading is increased, the resin having crystallinity is compatible with the amorphous resin and the release agent, In some cases, sharp melt properties may not be exhibited. Therefore, it is difficult to make the resin having crystallinity effectively on the particle surface by the method of containing from the time of melt kneading.
[0028]
In the present invention, the polyester resin fine particles having crystallinity are made to exist on the surface of the toner by mixing with the mother particles after preparing the base particles. Since there is no resin having crystallinity at the time of melt kneading, there is no decrease in melt viscosity, and the dispersibility of the colorant and release agent is not hindered. As a result, the polyester resin having crystallinity can exhibit low-temperature fixability in a smaller amount than when it is contained from the time of melt kneading, and obtain a high-quality image without problems in developability and transferability. Can do. In addition, a decrease in chargeability due to fusion of the release agent to the charging member is suppressed, and a toner having excellent durability can be obtained.
[0029]
In addition, the polyester resin having crystallinity is excellent in thermal stability because the melt viscosity is drastically decreased at the melting point, so that it is not necessary to lower the Tg as the amorphous resin. Therefore, the toner of the present invention in which the polyester resin having crystallinity is present on the toner surface is a toner having excellent heat storage stability. Therefore, the Tg of the amorphous resin can be further reduced, and a toner having a lower temperature fixability can be obtained.
[0030]
In order to obtain such a toner configuration, the polyester resin fine particles having crystallinity preferably have a particle size of 0.01 to 0.5 μm. If the particle size of the fine particles is larger than this, it may be difficult to obtain a low-temperature fixable toner that hardly adheres to the base particles. In addition, aggregates of only fine particles may be generated. On the other hand, particles having a particle size smaller than this are difficult to produce and are not realistic.
[0031]
The content of the polyester resin fine particles having crystallinity in the present invention is required to be 0.5% by weight or more based on the toner base material in order to exhibit an effect on low-temperature fixability. If this amount is large, the effect on fixing at low temperature is great, but if it is too large, the surface of the base particles cannot be completely covered, and a resin having crystallinity exists alone. Even if the coating is completed, a colorless resin without a colorant is present in the surface layer thickly, and an image obtained from such particles may not provide a high image density. Therefore, it is preferably at most 20% by weight. More preferably, it is 15 weight% or less.
[0032]
A resin having crystallinity has a melting point, and since the melt viscosity rapidly decreases at the melting point, not only the content but also the melting point and the softening temperature [T (F_1/2)] (Hereinafter “F_1/2The lower limit fixing temperature can also be controlled by the temperature. In the present invention, the minimum fixing temperature is preferably low so long as the heat-resistant storage stability is not deteriorated. The melting point of the polyester resin having crystallinity is in the range of 90 to 130 ° C., F_1/2The temperature is preferably in the range of 80 to 130 ° C. Melting point and F_1/2If the temperature is below the above range, it is difficult to synthesize a crystalline polyester that has sharp melt properties and is likely to exert an effect on low-temperature fixability. Cannot be obtained.
Here, the melting point of the polyester resin having crystallinity refers to the maximum endothermic peak temperature at the second temperature increase in DSC measurement.
[0033]
On the other hand, in order to obtain a toner satisfying the hot offset resistance without hindering the effect of the crystalline resin on the low-temperature fixing, the amorphous resin has a Tg of 40 to 70 ° C., F_1/2It is preferable that temperature is 120-160 degreeC. When Tg is 40 ° C. or lower, the heat-resistant storage stability of the toner is remarkably deteriorated and blocking occurs. On the other hand, when the temperature is 70 ° C. or higher, the low-temperature fixability of the toner deteriorates. F_1/2When the temperature is 120 ° C. or lower, the hot offset property is deteriorated. When the temperature is 160 ° C. or higher, the elasticity tends to be high, the share when the toner constituent material is dispersed becomes high, and there is a problem that it is difficult to disperse. Also, the low-temperature fixability deteriorates.
Here, the Tg of the amorphous resin refers to the glass transition temperature (Tg) obtained by the tangential method at the second temperature increase in DSC measurement.
[0034]
The melting point of the release agent used in the toner of the present invention is preferably 70 to 90 ° C. If it is 70 ° C. or lower, the heat-resistant storage stability of the toner is deteriorated, and if it is 90 ° C. or higher, the releasability at a low temperature is not expressed, cold offset resistance is deteriorated, and paper is wound around the fixing machine.
Here, the melting point of the release agent refers to the endothermic peak temperature at the second temperature increase in DSC measurement.
[0035]
The glass transition temperature (Tg) and the melting point of the present invention are measured using a thermal analyzer DSC-60 manufactured by Shimadzu Corporation at a temperature range of 20 ° C. to 150 ° C. and a heating rate of 10 ° C./min. . When performing the second temperature increase, the temperature was decreased to the measurement start temperature at a temperature decrease rate of 10 ° C./min without a holding time after the first temperature increase.
F of the present invention_1/2The temperature is an elevated flow tester CF-500 manufactured by Shimadzu Corporation, with a die diameter of 1 mm and a pressure of 10 kgf / cm.²1 cm under the condition of a heating rate of 3 ° C./min²This is the temperature at which the stroke when the sample is melted and flowed out becomes half the stroke change amount from the outflow start point to the outflow end point.
[0036]
  crystallineA polyester resin having a diol compound having 2 to 20 carbon atoms, an alcohol component containing these derivatives, a polyvalent carboxylic acid compound such as an aliphatic dicarboxylic acid, an aromatic dicarboxylic acid, and an alicyclic dicarboxylic acid, and these It is an aliphatic polyester synthesized using an acid component containing a derivative of In particular, alcohol components containing linear alkylene glycols having 2 to 6 carbon atoms such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol and derivatives thereof, maleic acid, fumaric acid, succinic acid An aliphatic polyester resin represented by the general formula (1) synthesized using an aliphatic dicarboxylic acid such as the above and an acid component containing these derivatives is preferable.
[0037]
[Chemical 3]
General formula (1) [-O-CO-CR₁= CR₂-CO- (CH₂)_n-]_m
(N and m are the number of repeating units, R₁, R₂Is a hydrocarbon group)
[0038]
From the viewpoint of polyester crystallinity and softening point, in order to synthesize a non-linear polyester resin, a trihydric or higher polyhydric alcohol such as glycerin is added to the alcohol component, or trimellitic anhydride is added to the acid component. The polycondensation may be carried out by adding a trivalent or higher polyvalent carboxylic acid or the like.
[0039]
The fine particles of the polyester resin having crystallinity according to the present invention are not dissolved at room temperature, but after being melted in a solvent that cannot be present in the state of particles by heating, the crystals are rapidly cooled to precipitate crystals. It can obtain as fine particle powder by drying what was further crushed with a sand mill or the like.
[0040]
Whether or not the resin fine particles in the present invention have crystallinity can be confirmed by whether or not a peak exists in the X-ray diffraction pattern by the powder X-ray diffractometer. The polyester resin having crystallinity according to the present invention has a diffraction peak at least at a position of 2θ = 20 to 25 °. The powder X-ray diffraction measurement was performed using a Rigaku Electric RINT1100, using a wide-angle goniometer under the conditions of a tube bulb with Cu and a tube voltage-current of 50 kV-30 mA.
[0041]
The base particles to which the polyester resin fine particles having crystallinity are attached contain at least a binder resin, a colorant, and a release agent. The binder resin here is an amorphous resin, and all conventionally known resins can be used for this. For example, styrene, α-methylstyrene, chlorostyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, Styrene resins such as styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, polyester resin, vinyl chloride resin, rosin modified maleic acid resin, phenol resin, There are epoxy resins, polyethylene resins, polypropylene resins, ionomer resins, polyurethane resins, silicone resins, ketone resins, xylene resins, petroleum resins, hydrogenated petroleum resins, and the like. Of these, styrene resins and polyester resins containing an aromatic compound as a component are preferable. Particularly preferred are polyester resins.
[0042]
The polyester resin is synthesized from a polyhydric alcohol and a polycarboxylic acid. As the polyhydric alcohol and polycarboxylic acid, the components used in the crystalline polyester resin (A) can be used. Besides this, alkylene oxide adducts of bisphenol A, isophthalic acid, terephthalic acid and derivatives thereof are also available. is there. These resins are not limited to single use but can be used in combination of two or more.
[0043]
Waxes as release agents include, for example, low molecular weight polyolefin waxes such as low molecular weight polyethylene and low molecular weight polypropylene, synthetic hydrocarbon waxes such as Fischer-Tropsch wax, beeswax, carnauba wax, candelilla wax, rice wax, and montan. Natural waxes such as wax, petroleum waxes such as paraffin wax and microcrystalline wax, higher fatty acids such as stearic acid, palmitic acid and myristic acid, metal salts of higher fatty acids, higher fatty acid amides, and various modified waxes thereof These can be used alone or in combination of two or more.
The amount of these release agents used is 1 to 20 parts by weight, preferably 3 to 10 parts by weight, based on the toner resin component.
[0044]
Examples of the colorant include carbon black, lamp black, iron black, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa Yellow G, rhodamine 6C lake, calco oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallylmethane. Any conventionally known dyes and pigments such as dyes such as dyes can be used alone or as a mixture, and can be used as a black toner or a full color toner.
The amount of these colorants to be used is usually 1 to 30% by weight, preferably 3 to 20% by weight, based on the toner resin component.
[0045]
The toner of the present invention can be blended with a charge control agent as required.
As the charge control agent, any conventionally known polarity control agent such as a nigrosine dye, a metal complex dye, or a quaternary ammonium salt can be used alone or in combination. The amount of these charge control agents used is 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on the toner resin component.
[0046]
Further, the toner of the present invention can be used as a magnetic toner containing a magnetic material. Examples of magnetic materials contained in the toner include iron oxides such as magnetite, hematite, and ferrite, metals such as iron, cobalt, and nickel, and these. Metal alloys such as aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium, and mixtures thereof. Magnetite is particularly preferable from the viewpoint of magnetic properties.
[0047]
These ferromagnetic materials preferably have an average particle size of about 0.1 to 2 μm. The amount of the ferromagnetic material to be contained in the toner is about 15 to 200 parts by weight, particularly preferably 100 parts by weight of the resin component, with respect to 100 parts by weight of the resin component. 20 to 100 parts by weight per part.
[0048]
In the production of the base particles of the present invention, those obtained by melting and kneading the base particle constituent materials and then pulverizing and classifying are generally used as conventional methods. Is possible.
[0049]
The toner of the present invention preferably has a volume average particle size of 4 to 10 μm in order to obtain a high image quality excellent in fine line reproducibility. When the particle diameter is larger than this range, fine line reproducibility tends to be inferior, and when it is small, poor cleaning tends to occur. Further, since the fixing temperature can be lowered by reducing the particle size, it is more preferably 4 to 7 μm. This is presumably because by reducing the particle size, the number of toners in contact with the fixing member increases, and the thermal response increases.
[0050]
In the toner of the present invention, crystalline polyester resin fine particles are present on the toner surface. This can be easily done by externally adding crystalline polyester resin fine particles. In the external addition, the base particles and the fine particles are mixed and stirred using a mixer to coat the surfaces of the base particles while the fine particles are being crushed. Mixing and stirring are mixers such as Henschel mixer (Mitsui Miike), Super mixer (Kawada Seisakusho), Q mixer (Mitsui Mine), Mechano-fusion system (Hosokawa Micron), Mechano mill (Okada Seiko) To do. At this time, when stirring with strong energy, a toner in a state where the fine particles are immobilized on the base particle surface is obtained, and when stirring with weak energy, a toner with the fine particles attached to the surface of the base particle is obtained. In the latter case, depending on the particle size of the resin fine particles, it can also serve as a fluidity improver. In order to achieve this effect, the volume average particle size is preferably smaller than 0.1 μm.
[0051]
If necessary, a fluidity improver can be added to the toner of the present invention. As the fluidity improver, any conventionally known fluidity improver such as hydrophobic silica, titanium oxide, silicon carbide, aluminum oxide, barium titanate can be used alone or in combination. Titanium is superior in terms of improving fluidity, stabilizing charging, and stabilizing image quality. More preferably, when a combination of hydrophobic silica and titanium oxide is used, a good toner with stable fluidity and chargeability can be obtained. The amount of these fluidity improvers used is 0.1 to 5 parts by weight, preferably 0.5 to 2 parts by weight, based on the toner weight. Addition of the fluidity improver is carried out by stirring and mixing using a mixer, in the same manner as external addition of fine particles having crystallinity. This step may be performed after the external addition of the crystalline polyester resin fine particles, or may be performed simultaneously.
[0052]
The toner of the present invention can be used as a one-component developer or a two-component developer combined with a carrier.
[0053]
As the carrier when the toner of the present invention is used as a two-component developer, all known ones can be used. For example, magnetic powder such as iron powder, ferrite powder, nickel powder, glass beads, and the like, and these The surface of which is treated with a resin or the like.
[0054]
Examples of the resin powder that can be coated on the carrier in the present invention include a styrene-acrylic copolymer, a silicone resin, a maleic acid resin, a fluorine resin, and a polyester resin epoxy resin. In the case of a styrene-acrylic copolymer, those having a styrene content of 30 to 90% by weight are preferred. In this case, when the styrene content is less than 30% by weight, the development characteristics are low, and when it exceeds 90% by weight, the coating film becomes hard and easily peeled, and the life of the carrier is shortened.
Moreover, the resin coating of the carrier in the present invention may contain an adhesion-imparting agent, a curing agent, a lubricant, a conductive material, a charge control agent and the like in addition to the resin.
[0055]
When the toner of the present invention is used as either a one-component developer or a two-component developer, the toner is filled in a container, and the container filled with the toner is distributed separately from the image forming apparatus so that the user can It is common to form an image by mounting on a forming apparatus.
What is used as the container is not limited, and is not limited to the conventional bottle type or cartridge type.
The image forming apparatus is not limited as long as it is an apparatus for forming an image by electrophotography, and includes, for example, a copying machine or a printer.
[0056]
An embodiment of an image forming method and apparatus according to the present invention will be described. Here, FIG. 1 is a schematic configuration diagram showing an example of an image forming method and apparatus according to the present invention.
In FIG. 1, a photoconductor 1 as an image carrier is rotated in the direction of an arrow (counterclockwise) in the figure and is uniformly charged by a charging roller 2. Thereafter, the image is exposed by exposure of an original image from an exposure unit (not shown) or optical writing by a laser beam from an optical writing device (not shown), and an electrostatic latent image is formed on the photoreceptor 1. A developer 4 is contained in the developing device 3. As the developer 4, a two-component developer that is a mixture of a carrier and a toner is used. When the developer 4 is stirred, the toner is charged by frictional charging. A developing sleeve 5 having a plurality of magnets or a magnet roller having a plurality of magnetic poles disposed therein is disposed at a position facing the photoreceptor 1 of the developing device 3, and the developer 4 is developed by a magnetic force. The electrostatic latent image on the photosensitive member 1 is developed with toner.
[0057]
A transfer belt 6 is disposed on the downstream side of the developing device 3 in the rotation direction of the photosensitive member 1, and this transfer belt 6 is stretched around a driving roller and a driven roller and rotated in the direction of the arrow in the figure. . Further, the transfer belt 6 is provided so as to be able to come into contact with and separate from the photosensitive member 1 by a contact / separation mechanism (not shown). Further, a voltage (transfer output) having a polarity opposite to that of the toner is applied to the back side of the transfer belt 6 by a power source (not shown) via a bias roller 6a.
[0058]
The transfer sheet S transported from a sheet feeding unit (not shown) is fed to the nip portion between the photoreceptor 1 and the transfer belt 6 by the registration roller 18 in accordance with the timing of image formation on the photoreceptor 1 and developed on the photoreceptor 1. The toner image thus transferred is transferred onto a transfer sheet S sandwiched between the photoreceptor 1 and the transfer belt 6 by the electric field between the transfer belt 6 and the photoreceptor 1. The transfer sheet S to which the toner image is transferred is then conveyed by the transfer belt 6 and passes through a fixing device (not shown). At this time, the toner image is thermally welded onto the transfer sheet. Then, the fixed transfer sheet S is discharged to a paper discharge section (not shown). On the other hand, the toner remaining on the photosensitive member without being completely transferred is blocked by the cleaning blade 7 and is put on the recovery coil 9 by the recovery spring 8. The recovery coil 9 returns the toner to the developing device 3 as recycled toner. The cleaned photoreceptor 1 is neutralized by a neutralizing lamp 20.
[0059]
【Example】
Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples. In the examples, all parts represent parts by weight.
[0060]
The characteristics of the toner produced in each example of the present invention were evaluated by the following method.
1) Release agent dispersion state in toner
The cross section of the toner was observed with a transmission electron microscope (TEM), and the wax dispersion diameter of the cross section of three fields taken at 10000 times was examined. The cross section of the toner was observed under the condition of an acceleration voltage of 300 kV using a Hitachi transmission electron microscope H-9000, in which the toner particles were ultrathin sliced to about 100 μm and stained with ruthenium tetroxide.
The evaluation criteria of the dispersion diameter are as follows.
5: Dispersion diameter larger than 1.0 μm is not observed
4: Dispersion diameter larger than 1.5 μm is not observed
3: Dispersion diameter larger than 2.0 μm is not observed
2: Dispersion diameter larger than 2.0 μm is observed, but the amount is small
1: Many dispersion diameters larger than 2.0 μm are observed
[0061]
2) Fixability evaluation
Copying machine manufactured by Ricoh Co., Ltd. using a Teflon roller as a fixing roller. Using an apparatus in which the MF2200 fixing unit was modified, type 6200 paper manufactured by Ricoh was set in this, and a copying test was performed. The results at this time are shown in Table 1.
The cold offset temperature (fixing lower limit temperature) and the hot offset temperature (hot offset resistant temperature) were determined by changing the fixing temperature. The minimum fixing temperature of the conventional low-temperature fixing toner is about 140 to 150 ° C. The evaluation conditions for low-temperature fixing are as follows: the linear speed of paper feed is 120 to 150 mm / sec, and the surface pressure is 1.2 kgf / cm.²The evaluation conditions for the nip width of 3 mm and the high temperature offset are as follows: the linear velocity of paper feed is 50 mm / sec, and the surface pressure is 2.0 kgf / cm.²The nip width was set to 4.5 mm.
The criteria for each characteristic evaluation are as follows.
(1) Low-temperature fixability (5-level evaluation)
5: Less than 130 ° C, 4: 130-139 ° C, 3: 140-149 ° C, 2: 150-160 ° C, 1: 160 ° C or more
▲ 2 ▼ Hot offset property (5-level evaluation)
5: 201 ° C or more 4: 200-191 ° C 3: 190-181 ° C 2: 180-171 ° C 1: 170 ° C or less
[0062]
3) Evaluation of heat storage stability
A glass container is filled with toner and left in a constant temperature bath at 55 ° C. for 24 hours. The toner is cooled to 24 ° C., and the penetration is measured by a penetration test (JIS K2235-1991). A toner having a larger value has better storage stability against heat. When this value is 15 mm or less, there is a high possibility of problems in use.
Judgment criteria for thermal storage stability based on the penetration is as follows.
5: penetration, 4:25 mm or more, 3:20 mm to less than 25 mm, 2:15 mm to less than 20 mm, or less than 1:15 mm
[0063]
4) Resolution evaluation
A developer is set in MF-2200 manufactured by Ricoh Co., Ltd., and a 1-dot independent dot image of 600 dots / inch and 150 line / inch is output in the main scanning and sub-scanning directions in an environment of normal temperature / normal humidity. Dropping and image density unevenness were visually evaluated in four stages.
4: Very good, 3: Good, 2: Practical problem level, 1: Practical problem level
[0064]
5) Evaluation of coloring degree
A developer was set in MF-2200 manufactured by Ricoh Co., Ltd., and an image having a solid part was output under a normal temperature / normal humidity environment, and the ID of the solid part was measured with a Macbeth densitometer.
It is very good at 4: 1.4 or more, 3: 1.35-1.39, 2: 1.3-1.34, less than 1: 1.3, and there is a practical problem.
[0065]
6) Durability evaluation
A developer was set on MF-2200 manufactured by Ricoh Co., Ltd., and continuous image output of 1,000,000 sheets was performed in a normal temperature / normal humidity environment, and evaluation was performed in four stages from the charge amount and image quality of the developer thereafter.
4: No significant change in charge amount and image quality compared to the initial stage
3: Although the charge amount is lower than the initial value, there is no significant change in image quality.
2: Level where soiling occurs but there is no practical problem
1: Soil contamination at a level that has a practical problem occurs.
[0066]
Preparation of base particles
The constituent materials of the base particles are sufficiently stirred and mixed in a Henschel mixer, kneaded by a twin screw extruder, cooled, pulverized and classified so that the volume average particle size becomes 9.0 ± 0.5 μm, and the base body A toner was obtained. As the kneading conditions, the temperature of the kneader was set so that the temperature of the kneaded product at the kneader outlet was 130 to 140 ° C. In the pulverization and classification, the volume average particle diameter is 9.0 ± 0.5 μm for the base particles A to C and E, G, and H, and 6.0 ± 0 for the base particles D and F. It adjusted so that it might become 0.5 micrometer.
[0067]
Table 1 shows the types (1 to 6) of resins used as constituent materials of the base particles and their characteristics.
[Table 1]
[0068]
Constituent material of base particle A
Resin 1 (Table 1) 96 parts by weight
Polyethylene wax (melting point 85 ° C) 4 parts by weight
Carbon black (Mitsubishi Chemical # 44) 10 parts by weight
1 part by weight of salicylsan zirconium salt
[0069]
Constituent material of base particle B
Resin 2 (Table 1) 96 parts by weight
Synthetic ester wax (melting point 85 ° C) 4 parts by weight
Carbon black (Mitsubishi Chemical # 44) 10 parts by weight
1 part by weight of salicylsan zirconium salt
[0070]
Constituent material of base particle C and base particle D
Resin 3 (Table 1) 80 parts by weight
Resin 4 (Table 1) 15 parts by weight
Carnauba wax (melting point 83 ° C) 5 parts by weight
Carbon black (Mitsubishi Chemical # 44) 10 parts by weight
1 part by weight of salicylsan zirconium salt
[0071]
Constituent material of base particle E
Resin 5 (Table 1) 95 parts by weight
Carnauba wax (melting point 83 ° C) 5 parts by weight
Carbon black (Mitsubishi Chemical # 44) 10 parts by weight
1 part by weight of salicylsan zirconium salt
[0072]
Constituent material of base particle F
Resin 3 (Table 1) 80 parts by weight
Resin 4 (Table 1) 15 parts by weight
Polyethylene wax (melting point 100 ° C) 5 parts by weight
Carbon black (Mitsubishi Chemical # 44) 10 parts by weight
1 part by weight of salicylsan zirconium salt
[0073]
Constituent material of base particle G
Resin 1 (Table 1) 76.8 parts by weight
Resin 6 (Table 1) 20 parts by weight
Polyethylene wax (melting point 85 ° C) 3.2 parts by weight
Carbon black (Mitsubishi Chemical # 44) 8 parts by weight
0.8 parts by weight of salicylsan zirconium salt
[0074]
Constituent material of base particle H
Resin 1 (Table 1) 40 parts by weight
Resin 6 (Table 1) 56 parts by weight
Polyethylene wax (melting point 85 ° C) 4 parts by weight
Carbon black (Mitsubishi Chemical # 44) 10 parts by weight
1 part by weight of salicylsan zirconium salt
[0075]
Preparation of polyester resin fine particles with crystallinity
20 parts by weight of crystalline polyester resin was added to 100 parts by weight of ethyl acetate and stirred at 75 ° C. for 30 minutes to prepare a transparent molten state. The melt was rapidly cooled to precipitate crystals, which were dispersed with a sand mill to further make fine particles. This dispersion was vacuum dried at 30 ° C. to obtain fine particle powder of each resin.
[0076]
Table 2 shows the types (a to g) and characteristics of the polyester resin fine particles having crystallinity used in the following examples. An example (h) of resin fine particles used for comparison is also shown.
[Table 2]
[0077]
Reference example 1
  80 parts by weight of base particles A, 20 parts by weight of resin fine particles a (Table 2), 0.3 parts by weight of hydrophobic silica, and 0.3 parts by weight of titanium oxide are stirred and mixed with a Henschel mixer (stirring speed: 2000 rpm). The toner was obtained 5 times for 30 seconds). When this toner was observed with an SEM, it was confirmed that a crystalline resin adhered to the particle surface. 2.5 parts by weight of the toner and 97.5 parts by weight of a silicon-coated ferrite carrier (core material particle size: 45 μm) were stirred with a tumbler mixer to obtain a developer.
  Table 3 shows the evaluation results of this toner.
[0078]
Comparative Example 1
  To 100 parts by weight of the base particles G, 0.3 parts by weight of hydrophobic silica and 0.3 parts by weight of titanium oxide were stirred and mixed with a Henschel mixer (5 times for 30 seconds at a stirring speed of 2000 rpm) to obtain a toner. . This tonerReference example1 was used as a developer.
  Table 3 shows the evaluation results of this toner.Reference exampleThe low-temperature fixability as in the toner No. 1 was not obtained. Further, since a resin having crystallinity is contained in the melt-kneading, the dispersion state of the wax is poor, and the image quality and durability are inferior.
[0079]
Example 2
  Using 83 parts by weight of base particles B, 17 parts by weight of resin fine particles a (Table 2), 0.3 parts by weight of hydrophobic silica, and 0.3 parts by weight of titanium oxide,Reference exampleThe same processing as in No. 1 was performed to obtain a toner and a developer. When this toner was observed with an SEM, it was confirmed that a crystalline resin adhered to the particle surface.
  Table 3 shows the evaluation results of this toner. By changing the amorphous resin to polyester resin,Reference exampleThe amount of the polyester resin having crystallinity was smaller than that in the case of 1, but it was fixed at a low temperature.
[0080]
Example 3
  75 parts by weight of the base particles B and 25 parts by weight of the resin fine particles a (Table 2) were stirred and mixed with a Q mixer (6000).rpm for 10 minutes). Thereafter, 0.3 part by weight of hydrophobic silica and 0.3 part by weight of titanium oxide were added, and further stirred and mixed (at 2000 rpm for 2 minutes) to obtain a toner. About this tonerReference exampleThe same processing as in No. 1 was performed to obtain a developer. A part of the toner was sampled before the addition of the fluidity improver and observed with an SEM. As a result, most of the toners had resin fine particles fixed on the surface of the particles. Was confirmed.
  Table 3 shows the evaluation results of this toner. Although the amount of resin having crystallinity was large, the toner was not fixed at a lower temperature than in Example 2. On the contrary, the durability was inferior to that of Example 2 due to the presence of the aggregate of the resin having crystallinity. From this result, it is confirmed that the amount of resin fine particles having crystallinity is preferably not more than 20 parts by weight.
[0081]
Example 4
  90 parts by weight of the base particles C and 10 parts by weight of the resin fine particles b (Table 2) were stirred and mixed under the same conditions as in Example 3 using a Q mixer. Thereafter, a fluidity improver was externally added in the same manner as in Example 3 to obtain a toner. A part of the sample was sampled before external addition of the fluidity improver and observed by SEM. As a result, a toner in which the resin fine particles were fixed on the particle surface was confirmed.
  Table 3 shows the evaluation results of this toner.Reference Example 1, Examples 2-3By using the resin fine particles b having a melting point lower than that of the toner, a toner that can be fixed at a low temperature although being a small amount of use was obtained.
[0082]
Example 5
  95 parts by weight of base particles D, 5 parts by weight of resin fine particles b (Table 2), 0.4 parts by weight of hydrophobic silica, and 0.5 parts by weight of titanium oxide,Reference exampleA toner and a developer were obtained by performing the same treatment as in No. 1. From the observation of the toner, it was confirmed that a crystalline resin was adhered to the particle surface.
  Table 3 shows the evaluation results of this toner. The resolution was improved due to the smaller particle size. Also, the minimum fixing temperature was lowered.
[0083]
Example 6
95 parts by weight of the base particles E and 5 parts by weight of the resin fine particles b (Table 2) were stirred and mixed under the same conditions as in Example 3 using a Q mixer. Thereafter, a fluidity improver was externally added in the same manner as in Example 3 to obtain a toner. A part of the sample was sampled before external addition of the fluidity improver and observed by SEM. As a result, a toner in which the resin fine particles were fixed on the particle surface was confirmed.
Table 3 shows the evaluation results of this toner. Although the preservability is at a level that does not cause a problem in practice, it can be said that the Tg of the amorphous resin is preferably 40 ° C. or higher because there is no room.
[0084]
Example 7
95 parts by weight of the base particles E and 5 parts by weight of the resin fine particles c (Table 2) were stirred and mixed under the same conditions as in Example 3 using a Q mixer. Thereafter, a fluidity improver was externally added in the same manner as in Example 3 to obtain a toner. A part of the sample was sampled before external addition of the fluidity improver and observed by SEM. As a result, a toner in which the resin fine particles were fixed on the particle surface was confirmed.
Table 3 shows the evaluation results of this toner. This is because the storage stability is better than that of the toner of Example 6, but the particle size of the resin having crystallinity which is more stable to heat than the amorphous resin is smaller, and the base particle surface is coated even with a smaller amount. . From this result, it is understood that a toner having excellent storage stability can be obtained when a polyester resin having crystallinity is present on the particle surface.
[0085]
Example 8
  95 parts by weight of base particles D, 5 parts by weight of resin fine particles d (Table 2), 0.4 parts by weight of hydrophobic silica, and 0.5 parts by weight of titanium oxide,Reference exampleA toner and a developer were obtained by performing the same treatment as in No. 1. From the observation of the toner, it was confirmed that the toner having a crystalline resin adhered to the particle surface, but it was confirmed that fine particles not adhering to the base particles were conspicuous.
  Table 3 shows the evaluation results of this toner. Except for the difference in the particle size of the resin fine particles having crystallinity, the same as in the case of Example 5, but the fixing minimum temperature was higher than that of Example 5. Also, the resolution and durability were inferior.
[0086]
Example 9
  97 parts by weight of base particles D and 3 parts by weight of resin fine particles e (Table 2) were stirred and mixed under the same conditions as in Example 3 using a Q mixer. Thereafter, 0.4 part by weight of hydrophobic silica and 0.5 part by weight of titanium oxide were added, and further stirred and mixed (at 2000 rpm for 2 minutes) to obtain a toner. About this tonerReference exampleThe same processing as in No. 1 was performed to obtain a developer. A part of the sample was sampled before external addition of the fluidity improver and observed by SEM. As a result, a toner in which the resin fine particles were fixed on the particle surface was confirmed.
  Table 3 shows the evaluation results of this toner. A toner capable of fixing at a low temperature was obtained although the amount of resin fine particles having crystallinity was small.
[0087]
Example 10
  97 parts by weight of base particles D, 3 parts by weight of resin fine particles f (Table 2), 0.3 parts by weight of hydrophobic silica, and 0.3 parts by weight of titanium oxide,Reference exampleA toner and a developer were obtained by performing the same treatment as in No. 1. From the observation of the toner, it was confirmed that the toner had a crystalline resin adhered to the particle surface.
  Table 3 shows the evaluation results of this toner. There are few fluidity improvers, but the resolution and durability are good because the fine resin particles that have crystallinity also function as fluidity improvers.
[0088]
Example 11
95 parts by weight of base particles C and 5 parts by weight of resin fine particles g (Table 2) were stirred and mixed under the same conditions as in Example 3 using a Q mixer. Thereafter, a fluidity improver was externally added in the same manner as in Example 3 to obtain a toner. A part of the sample was sampled before external addition of the fluidity improver and observed by SEM. As a result, a toner in which the resin fine particles were fixed on the particle surface was confirmed.
Table 3 shows the evaluation results of this toner. It can be said that the Tg of the resin having crystallinity is preferably not lower than 90 ° C. because there is no allowance for storage stability.
[0089]
Example 12
A toner and a developer were obtained in the same manner as in Example 9, except that the base particle C of Example 9 was changed to the base particle F. From the observation of the toner, it was confirmed that the toner had a crystalline resin adhered to the particle surface.
Table 3 shows the evaluation results of this toner. Due to the occurrence of cold offset, the toner was inferior in low-temperature fixability to the toner of Example 9. From this result, it can be said that it is preferable that the melting point of the release agent does not exceed 90 ° C.
[0090]
Comparative Example 2
  For 100 parts by weight of the base particles H, 0.3 parts by weight of hydrophobic silica and 0.3 parts by weight of titanium oxide,Reference exampleThe same processing as in No. 1 was performed to obtain a toner and a developer.
  Table 3 shows the evaluation results of this toner. Since a large amount of resin having crystallinity was contained at the time of kneading, a toner having a low melt viscosity and fixing at a low temperature was obtained, but the dispersion state of the release agent and the colorant was poor and there was a problem in the image quality having a low image density. It became a certain image. Moreover, durability was also inferior.
[0091]
Comparative Example 3
95 parts by weight of base particles C and resin fine particles h (styrene / butyl acrylate copolymer resin, no diffraction peak, Tg 70 ° C., F_1/25 parts by weight of the mixture was stirred and mixed under the same conditions as in Example 3 using a Q mixer. Thereafter, a fluidity improver was externally added in the same manner as in Example 3 to obtain a toner. A part of the sample was sampled before external addition of the fluidity improver and observed by SEM. As a result, a toner in which the resin fine particles were fixed on the particle surface was confirmed.
Table 3 shows the evaluation results of this toner. Since the resin fine particles present on the surface do not have crystallinity, the high Tg hinders fixing and does not become a low-temperature fixing toner. There was also a problem with storage stability.
[0092]
[Table 3]
[0093]
【The invention's effect】
As described above, according to the image forming toner of the present invention, the polyester resin fine particles having crystallinity are present on the surface of the base particles, that is, the fine particles of the polyester resin having crystallinity are prepared after the base particles are prepared. Since it is formed by mixing with particles, it can exhibit low-temperature fixability in a smaller amount than when it is contained from the time of melt kneading, and also has good hot offset resistance, storage stability, and good resolution. In addition, it is possible to obtain a high-quality image without any background contamination or density unevenness. In addition, a decrease in chargeability due to fusion of the release agent to the charging member is suppressed, and a toner having excellent durability can be obtained.
[0094]
According to the image forming toner of claim 2, since the particle size of the crystalline polyester resin fine particles is 0.01 to 0.5 μm, it is easy to adhere to the surface of the base particle, and low temperature fixing can be achieved. It is made like.
[0095]
According to the image forming toner of claim 3, since the content of the fine particles of the polyester resin having crystallinity is 0.5% by weight or more and 20% by weight or less, the surface of the base particle is appropriately coated. , Low-temperature fixing and high image density can be obtained.
[0097]
  Claim4According to the image forming toner, since the fine particles of the polyester resin having crystallinity have a diffraction peak at a position of at least 2θ = 20 to 25 ° in the X-ray diffraction pattern by the powder X-ray diffractometer, Whether or not the resin fine particles in the present invention have crystallinity can be confirmed.
[0098]
  Claim5According to the image forming toner, the maximum endothermic peak temperature of the DSC curve of the polyester resin having crystallinity is 90 to 130 ° C., and F_1/2Since the temperature is 80 to 130 ° C., it is possible to control the minimum fixing temperature within a range that does not deteriorate the heat resistant storage stability.
[0100]
  Claim6According to the image forming toner, the glass transition temperature of the amorphous binder resin is 40 to 70 ° C., and F_1/2Since the temperature is 120 to 160 ° C., a toner satisfying the hot offset resistance can be obtained without hindering the effect of the polyester resin having crystallinity on the low-temperature fixing.
[0101]
  Claim7According to the image forming toner, since the melting point of the release agent is 70 to 90 ° C., neither the heat resistant storage stability nor the cold offset resistance is deteriorated.
[0102]
  Claim8According to the image forming toner, since the volume average particle diameter of the toner is 4 to 7 μm, excellent fine line reproducibility can be obtained and the fixing temperature can be lowered.
[0103]
  Claim9According to the image forming toner, since the fine particles of the polyester resin having crystallinity are immobilized on the surface of the base particle, the above-described effects such as low-temperature fixing can be sufficiently exhibited.
[0104]
  Claim10According to the image forming toner, since the fine particles of the polyester resin having crystallinity are mixed and adhered to the surface of the base particle, it also serves as a fluidity improver as well as the effect of low temperature fixing. Is possible.
[0105]
  Claim11According to the image forming toner, since the particle diameter of the fine particles of the polyester resin having crystallinity is 0.01 to 0.1 μm, it is particularly preferable when it also serves as the fluidity improving material.
[0106]
  Claim12According to the toner container, since the image forming toner described in any one of the above is filled, no aggregation occurs in the container due to the excellent fluidity of the toner.
[0107]
  Claim13According to the image forming method, since the electrostatic latent image is developed with the image forming toner described in any of the above, low-temperature fixing, offset resistance, and high-quality images can be obtained over a long period of time. Can be formed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present invention.
[Explanation of symbols]
1 Photoconductor (image carrier)
2 Charging roller
3 Development device
4 Developer
5 Development sleeve (developer carrier)
6 Transfer belt (transfer means)
6a Bias roller
7 Cleaning blade
8 Collection spring
9 Collection coil
10 Photoreceptor and cleaning unit (PCU)
13 Conveying screw
14 Paddle (stirring mechanism)
16 Reflection density detection sensor (P sensor)
17 Toner density sensor
18 Registration Roller
20 Static elimination lamp
S transfer paper

Claims (13)

Polyester resin fine particles having crystallinity are present on the surface of base particles containing at least an amorphous binder resin, a colorant, and a release agent, and the amorphous binder resin is mainly a polyester resin. toner image forming, characterized in that it.   2. The image forming toner according to claim 1, wherein the crystalline polyester resin fine particles have a particle size of 0.01 to 0.5 [mu] m.   3. The image forming toner according to claim 1, wherein the content of the crystalline polyester resin fine particles is 0.5% by weight or more and 20% by weight or less. The image forming toner according to claim 1, wherein the crystalline polyester resin fine particles are at least at a position of 2θ = 20 to 25 ° in an X-ray diffraction pattern by a powder X-ray diffractometer. An image-forming toner characterized by having a diffraction peak. 5. The image forming toner according to claim 1, wherein a maximum endothermic peak temperature of a DSC curve of the crystalline polyester resin is 90 to 130 ° C., and a softening temperature [T (F _1/2 )] Is 80 to 130 ° C. The image forming toner according to claim 1, wherein the amorphous binder resin has a glass transition temperature (Tg) of 40 to 70 ° C., and a softening temperature [T (F _1/2 )] Is 120 to 160 ° C. 7. The image forming toner according to claim 1, wherein the releasing agent has a melting point of 70 to 90 ° C. 7. The image forming toner according to claim 1, wherein the toner has a volume average particle diameter of 4 to 7 μm. 9. The image forming toner according to claim 1, wherein fine particles of the polyester resin having crystallinity are immobilized on the surface of the base particle. 9. The image forming toner according to claim 1, wherein fine particles of the polyester resin having crystallinity are mixed and adhered to the surface of the base particle. 11. The image forming toner according to claim 10, wherein the crystalline polyester resin fine particles have a particle size of 0.01 to 0.1 [mu] m. A toner container filled with the image forming toner according to claim 1. 12. The image forming method for forming an image by developing an electrostatic latent image formed on a photoconductive image carrier, wherein the toner for developing the electrostatic latent image is any one of claims 1 to 11. An image forming method as described in the above item.