Toner, developer, toner container unit, and image forming apparatus

Abstract

To provide a toner that prevents uneven glossiness of an image and reproduces white or silver glossiness.SOLUTION: A toner according to the present invention is a toner formed into thin pieces and includes a low melting point metal pigment. The low melting point metal pigment is formed into thin pieces. The low melting point metal pigment is an alloy or an intermetallic compound that includes single metal selected from the group consisting of Zn, In, Sn, and Bi or one or more components selected from the group consisting of Zn, In, Ga, Sn, and Bi as main components, and does not include Cu.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a toner, a developer, a toner container unit, and an image forming apparatus.

Background Art

[0002] With the widespread popularity of electrophotographic color image forming apparatuses, their applications have also expanded in various ways. In addition to conventional color images, color images with a luster are required. When forming an image with a luster, a toner that emits a metallic luster color (metallic color) is used.

[0003] As a toner that emits a metallic color, for example, when a metal pigment is included and the metal pigment includes copper and zinc in an alloy form, a toner having a metallic hue is disclosed in which the metal pigment includes an alloy of copper and zinc in a ratio of 90:10 to 70:30 (see, for example, Patent Document 1).

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the toner of Patent Document 1, when copper, which significantly shows a red-orange color in the pigment, is included, the image formed by transferring the toner onto a recording medium shows red-orange or yellow, and there is a problem that it is difficult to reproduce the luster of white and silver in the image.

[0005] One aspect of the present invention aims to provide a toner that suppresses uneven luster of an image and can reproduce the luster of white and silver.

Means for Solving the Problems

[0006] One aspect of the toner according to the present invention is a toner formed in a flake shape, containing a low melting point metal pigment, wherein the low melting point metal pigment is formed in a flake shape, and the low melting point metal pigment is a simple metal selected from the group consisting of Zn, In, Sn, and Bi, or an alloy or intermetallic compound containing one or more components selected from the group consisting of Zn, In, Ga, Sn, and Bi as a main component and not containing Cu.

Advantages of the Invention

[0007] According to the present invention, there is provided a toner capable of suppressing gloss unevenness in an image and reproducing white and silver gloss.

Brief Description of the Drawings

[0008]

Figure 1

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Figure 3

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Figure 9

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail. Note that the embodiments are not limited by the following description and can be appropriately changed without departing from the gist of the present invention. In this specification, the tilde "~" indicating a numerical range means including the numerical values described before and after it as the lower limit value and the upper limit value, unless otherwise specified.

[0010] <Toner> The toner according to one embodiment is a toner (toner particles) formed in a flake shape, contains a low melting point metal pigment, and the low melting point metal pigment is formed in a flake shape and is a simple metal selected from the group consisting of Zn, In, Sn, and Bi, or an alloy or intermetallic compound containing at least one component selected from the group consisting of Zn, In, Ga, Sn, and Bi as a main component and not containing Cu.

[0011] As a result of intensive studies, the present inventors focused on the shape of the toner and the low melting point metal pigment contained therein, and the material of the low melting point metal pigment. Then, the toner and the low melting point metal pigment are formed in a flake shape, and the material of the low melting point metal pigment is a simple metal composed of at least one element among Zn, In, Sn, and Bi, or an alloy or intermetallic compound containing at least one element among Zn, In, Ga, Sn, and Bi as a main component and not containing Cu. Further, since the low melting point metal pigment is in a flake shape with a circular equivalent radius longer than the thickness, the thickness of the toner can be reduced. Therefore, when fixing the toner, heat is easily transferred to the low melting point metal pigment. As a result, the low melting point metal pigment is easily melted on the recording medium, so that the low melting point metal pigment spreads sufficiently wet on the recording medium, suppressing the gloss unevenness of the image (completed image) formed by transferring the toner onto the recording medium, and it has been found that white and silver gloss can be reproduced. Also, it has been found that the generation of dullness derived from oxides in the image can be suppressed over time, and the gloss of the image can be maintained.

[0012] The toner according to one embodiment may have a low melting point metal pigment and an outer shell covering its surface.

[0013] An example of the shape of the toner according to one embodiment is shown in FIGS. 1 and 2. FIG. 1 is a diagram schematically showing the state of the toner according to one embodiment as viewed from its width direction, and FIG. 2 is a diagram schematically showing the state of the toner according to one embodiment as viewed from its thickness direction. As shown in FIGS. 1 and 2, the toner 1 is in the form of a thin sheet and has a low melting point metal pigment 2 and an outer shell 3 that covers its surface.

[0014] The low melting point metal pigment is formed in the form of a thin sheet.

[0015] The low melting point metal pigment is a metal that can be melted by heat. As the low melting point metal, a simple metal composed of Zn, In, Sn, and Bi, or an alloy or intermetallic compound that contains one or more components selected from the group consisting of Zn, In, Ga, Sn, and Bi as a main component and does not contain Cu is used.

[0016] The standard oxidation-reduction potential of the low melting point metal is preferably -0.2 V or more. The standard oxidation-reduction potential of the low melting point metal can be calculated from the atomic weight ratio. If the standard oxidation-reduction potential of the low melting point metal is -0.2 V or more, it becomes difficult for the low melting point metal pigment to be oxidized, and the generation of fog derived from oxides in the image is suppressed.

[0017] Also, the low melting point metal pigment does not contain copper. Copper shows a distinct red-orange color. Since the low melting point metal pigment does not contain copper, the low melting point metal pigment shows white and silver colors, and a more metallic luster can be reproduced.

[0018] Note that the fact that the low melting point metal pigment does not contain copper does not mean excluding those that contain copper as an inevitable impurity. Copper may be contained as an inevitable impurity in the low melting point metal pigment.

[0019] Note that the low melting point metal pigment may be coated with a silica layer or resin as a surface treatment layer.

[0020] The outer shell is formed of a resin component.

[0021] As the resin component, a binder resin used in toner can be used.

[0022] In addition to the resin component, the outer shell may contain an organic low molecular substance in a dispersed state for imparting various functions such as mold release performance and lubrication performance.

[0023] The outer shell may further contain inorganic fine particles or the like as an external additive to impart fluidity, developability, chargeability, etc.

[0024] The melting point of the low melting point metal pigment is preferably 60°C to 200°C, more preferably 90°C to 190°C, and even more preferably 130°C to 185°C. If the melting point of the low melting point metal pigment is within the range of 60°C to 200°C, the low melting point metal can be sufficiently melted and spread on the recording medium during fixing.

[0025] The standard oxidation-reduction potential of the low melting point metal pigment is preferably -0.2 V or more, and more preferably -0.15 V or more. Note that the standard oxidation-reduction potential calculated from the atomic weight ratio may be used. If the standard oxidation-reduction potential of the low melting point metal pigment is -0.2 V or more, the surface of the low melting point metal pigment is difficult to oxidize over time.

[0026] When the standard oxidation-reduction potential is less than -0.2 V, the low melting point metal pigment is likely to be oxidized, and there is a high possibility that an oxide film will be generated on the surface of the low melting point metal pigment. When the oxide film is formed, the melting point of the low melting point metal pigment increases, and when it is spread on the recording medium, it is not sufficiently melted and unevenness occurs. As a result, the glossiness of the image is lost. Furthermore, when an oxide film is formed on the surface of the low melting point metal pigment, the metallic luster of the low melting point metal pigment is lost due to the influence of this oxide film, and the metallic luster is also lost from the image.

[0027] Note that the standard oxidation-reduction potential of the low melting point metal pigment can be obtained from the oxidation-reduction potential of each element constituting the low melting point metal pigment and its mass ratio. Note that known oxidation-reduction potentials of each element can be used, for example, the "standard oxidation-reduction potential" described in the 5th edition of the Electrochemical Handbook (edited by the Electrochemical Society).

[0028] As a method for calculating the specific standard redox potential, the components A (mass %) and B (mass %) contained in the low-melting-point metal pigment are converted into a ratio of atomic weights, and the redox potentials of the respective components A and B contained in the low-melting-point metal pigment are multiplied by the ratio of the atomic weights. Then, the redox potential of the low-melting-point metal pigment is obtained by adding the values obtained by multiplying the redox potential by the atomic weight ratios of the respective components A and B. For example, when the low-melting-point metal pigment contains 70 mass % of component A and 30 mass % of component B, assuming that when components A and B are converted to a ratio of atomic weights, component A is X atm % and component B is Y atm %. When the redox potentials of the respective components A and B are multiplied by this ratio of atomic weights, the part of component A is expressed as X atm % × the redox potential of component A, and the part of component B is expressed as Y atm % × the redox potential of component B. By combining (X atm % × the redox potential of component A) and (Y atm % × the redox potential of component B), the redox potential of the low-melting-point metal pigment is obtained.

[0029] As described above, the low-melting-point metal pigment is formed in a flaky shape, and the average thickness D when viewed from the thickness direction of the low-melting-point metal pigment is preferably 2.0 μm or less. If the average thickness D is 2.0 μm or less, heat is easily transmitted to the low-melting-point metal pigment, and the low-melting-point metal pigment can be smoothly melted and spread on the recording medium, so that sufficient metallic luster can be obtained.

[0030] The average thickness D is the average value when the thicknesses of a plurality of locations of the low-melting-point metal pigment are measured.

[0031] The synthesis method of the low-melting-point metal pigment will be described. The synthesis method of the melting-point metal pigment is not particularly limited as long as it is a low-melting-point metal pigment having the above configuration. As the synthesis method of the low-melting-point metal pigment, a method of simply melting and mixing several kinds of metals, a sintering method of mixing powders of raw materials and heating below the melting point, a membrane emulsification method, an ultrasonic irradiation method, etc. can be used. An example of the synthesis method of the low-melting-point metal pigment is shown below.

[0032] (Membrane Emulsification Method) The method for obtaining low melting point metal pigments using the membrane emulsification method is not particularly limited. For example, a low melting point metal is immersed in a solvent with a protective agent added, and this is passed through an emulsification membrane having pores to obtain a suspension. By purifying the obtained suspension by centrifugation, low melting point metal particles can be obtained.

[0033] (Ultrasonic irradiation method) The method for obtaining low melting point metal particles using the ultrasonic irradiation method is not particularly limited. For example, a melted low melting point metal is immersed in a solvent or the like with a protective agent added and ultrasonic irradiation is performed to obtain a suspension. By purifying the obtained suspension by centrifugation, low melting point metal particles can be obtained.

[0034] The toner according to one embodiment is formed in a flaky shape in which the equivalent circle diameter in the width direction is longer than its thickness.

[0035] The ratio F (= D / R) of the average thickness D of the toner according to one embodiment to the average equivalent circle diameter R is preferably 0.01 to 0.59, more preferably 0.19 to 0.51, and even more preferably 0.20 to 0.48. If the ratio F is 0.59 or less, when transferred onto the recording medium, the width direction of the toner can be oriented in a direction parallel to the surface of the recording medium. As a result, heat can easily be transmitted to the inside, and it can be melted and spread smoothly on the recording medium. If the ratio F is 0.01 or more, the toner can have sufficient strength, the toner does not break in the developing device, and poor transfer of the toner onto the recording medium can be suppressed.

[0036] The average thickness D and the average equivalent circle diameter R are measured by the following method. The toner is placed on a smooth surface, vibrated to disperse it evenly, and for the toner within a predetermined range (for example, a range of 1 mm × 1 mm), it is measured by magnifying 1000 times with a color laser microscope, and the average thickness D of the toner and the equivalent circle diameter R of the surface viewed from above can be measured.

[0037] An example of the configuration of a conventional toner is shown in FIGS. 3 and 4. FIG. 3 is a diagram schematically showing a state of a conventional toner viewed from its width direction, and FIG. 4 is a diagram schematically showing a state of a conventional toner viewed from its thickness direction. As shown in FIGS. 3 and 4, the toner 200A contains flaky luminous pigments 201A, and an outer shell 102 mainly made of resin covers the flaky luminous pigments 201A. Since it is necessary to press the conventional toner during fixing to orient the toner 200A on the recording medium, the flaky luminous pigments 201A contained in the toner 200 are flaky.

[0038] Examples of materials for forming the flaky luminous pigments 201A used in such a conventional toner 200A include metal fine powders such as aluminum, brass, bronze, nickel, stainless steel, and zinc, titanium oxide, yellow iron oxide, coated mica, brass made of copper and zinc, and the like. Since the melting point of any of these materials is high and melting by heat is difficult, unevenness may occur on the paper surface, and there is a high possibility that the metallic luster is suppressed.

[0039] In addition, the flaky luminous pigments 201A may contain materials that significantly show colors such as black, yellow, red, and copper color, such as brass, bronze, yellow iron oxide, coated mica, and brass. In that case, the white and silver lusters characteristic of metal cannot be reproduced in the image.

[0040] An example of another configuration of a conventional toner is shown in FIG. 5. FIG. 5 is a diagram schematically showing a conventional spherical toner. As shown in FIG. 5, the conventional spherical toner 200B contains spherical low-melting-point metal pigments 201B, and an outer shell 202 mainly made of resin covers the low-melting-point metal pigments 201B. Such spherical low-melting-point metal pigments 201B are generally formed to have a large particle size so as not to create gaps during spreading.

[0041] As materials for forming the low melting point metal pigment 201B used in such a conventional toner 200B, examples include one or more metals selected from Ga, Sn, Zn, Al, Bi, Ge, Si, and In, which have a melting point of 50°C to 150°C. Since the low melting point metal pigment 201B has a low melting point, it melts due to heat, spreads on the recording medium, and adheres to the recording medium.

[0042] However, if the toner 200B has a large particle size, heat cannot reach the inside of the low melting point metal pigment 201B, and a portion that cannot be completely melted during fixing occurs. Therefore, the toner 200B cannot spread evenly on the recording medium, and there is a high possibility that gloss unevenness will occur in the image.

[0043] Also, regarding the low melting point metal pigment 201B, when the standard oxidation-reduction potential of the low melting point metal calculated from the atomic weight ratio is less than -0.2V, the low melting point metal pigment 201B is easily oxidized, and the image will have a haze derived from the oxide. In addition, when the low melting point metal pigment 201B is oxidized, its melting point increases, and the metal becomes difficult to melt even when heated, which may cause unevenness and loss of gloss.

[0044] Next, the state where the toner according to one embodiment is fixed on the recording medium will be described. FIG. 6 is an explanatory diagram schematically showing the state where the toner according to one embodiment is fixed on the recording medium. As shown in FIG. 6, when the toner 1 according to one embodiment is fixed on the recording medium 4, since a low melting point metal that can be melted by heat is used as the low melting point metal pigment 2, the low melting point metal is melted by heat during fixing, and a metal film 2A having a uniform flat surface is formed. Also, the outer shell 3 also becomes an outer shell 3A having a uniform flat surface as the low melting point metal pigment 2 melts. Therefore, when the toner according to one embodiment is fixed on the recording medium, the glossiness of the image is sufficiently maintained. Also, the graininess of the image is improved.

[0045] Next, a state where a conventional flat toner as shown in FIGS. 3 and 4 is fixed on a recording medium will be described. FIG. 7 is an explanatory diagram schematically showing a state where a conventional toner is fixed on a recording medium. As shown in FIG. 7, in the conventional toner 200A, due to being pressurized during fixing, the flaky light-emitting pigment 201A is oriented on the recording medium 4. However, because the flaky light-emitting pigments 201A overlap or the pressure is insufficient and they cannot spread out completely, an outer shell 102A with a uniform flat surface is formed. Therefore, the surface of the toner 200A is likely to have irregularities, and due to these irregularities, the glossiness of the image is likely to be lost. Also, a granular feeling is likely to occur in the image.

[0046] When the conventional toner is spherical particles as shown in FIG. 5, a state where the spherical toner is fixed on a recording medium will be described. FIG. 8 is an explanatory diagram schematically showing a state where a conventional spherical toner is fixed on a recording medium. As shown in FIG. 8, if the original particle size of the low-melting-point metal pigment 201B contained in the toner 200B is large, heat is difficult to transfer during heating, so the low-melting-point metal pigment 201B cannot melt completely, and irregularities are likely to be formed on the surface of the outer shell 202B. Due to these irregularities, the glossiness is lost. Also, a granular feeling occurs in the image.

[0047] <Method for manufacturing toner> As a method for manufacturing the toner according to one embodiment, it is not particularly limited as long as the low-melting-point metal pigment can be coated with a binder resin. For example, a seed method, a spray drying method, a dry mixing method, a method using a microchannel, etc. can be mentioned.

[0048] (Seed method) The seed method refers to the process of coating the outside of a low-melting-point metal pigment with a binder resin in latex. Regarding the seed method, specifically, for example, it can be carried out as follows. Prepare a latex by mixing a low-melting-point metal pigment dispersion emulsion, a monomer emulsion as a raw material of the binder resin, a polymerization initiator (for example, potassium persulfate), and ion-exchanged water. By heating and stirring this latex, polymerization of the monomer is carried out to produce toner mother particles containing low-melting-point metal pigments coated with a binder resin. In addition, a release agent such as wax may be dispersed in the latex. In the above example, a monomer emulsion as a raw material of the binder resin was used, but an emulsion, solution or dispersion of the binder resin or a solution or dispersion of the monomer may also be used.

[0049] (Spray drying method) In the spray drying method, it is preferable to include the step of coating the outside of the low-melting-point metal pigment with the binder resin while mixing the low-melting-point metal pigment and the binder resin in the gas phase. Regarding the spray drying method, for example, it can be carried out as follows. Using a fluidized bed coating device, an aqueous solution of resin fine particles containing a pre-polymerized binder resin and a wax such as behenyl behenate is used as a spray liquid for the low-melting-point metal pigment. This can be applied to perform coating.

[0050] (Dry mixing method) Examples of the dry mixing method include the following method. A mixer including a vertical cylindrical treatment tank having stirring blades, low-melting-point metal particles, and resin particles composed of a release agent and a binder resin are charged and mixed. Thereby, a mixture of a release agent, a binder resin, and a low-melting-point metal pigment is obtained. Next, the obtained mixture is charged into a stirring granulation device, and the stirring blades are rotated while flowing oil into the treatment tank. By heating and stirring the treatment tank, toner mother particles coated with a binder resin can be obtained.

[0051] (Method using a microchannel) Examples of synthesis methods using microchannels include the following. The outside of the low melting point metal pigment is coated with a binder resin using a microchannel. Note that the microchannel that can be used in the present embodiment is not particularly limited, and a known one can be used. A solution in which a binder resin and wax are dispersed in water is injected into the outer channel of the microchannel. Next, by injecting the molten low melting point metal into the central channel of the microchannel, droplets with a surface coated with a binder resin and wax are formed, and then dried to obtain toner base particles.

[0052] <Properties> As a property of the toner according to one embodiment, the reflectance is measured.

[0053] [Measurement of Reflectance] By measuring the reflectance of an image created using the toner according to one embodiment, the effect of suppressing gloss unevenness of the toner according to one embodiment can be confirmed. The evaluation of the effect of suppressing gloss unevenness may be performed in two steps. For example, first, in the first step, in order to confirm the effect of suppressing gloss unevenness, the evaluation of reflectance measurement shown below is performed.

[0054] (First Step: Evaluation of Reflectance) The measurement of reflectance is performed by irradiating light onto an image formed using toner according to one embodiment and measuring the light reflected by the image. The reflected light includes specularly reflected light and diffusely reflected light. Specularly reflected light is light that is reflected from a glossy surface like a mirror and is reflected at the same angle as the incident angle. Diffusely reflected light is light that is reflected from a rough surface with irregularities and is diffused in all directions. Also, the combination of specularly reflected light and diffusely reflected light is called total light reflected light. Generally, total light reflection is measured for samples with a rough and glossy surface like plastic or paint. There are relative reflectance measurement and absolute reflectance measurement for measuring reflected light, and the measured value is represented by reflectance. Among them, in relative reflectance measurement, using barium sulfate or a mirror as a reference plate, the reflectance is measured as the ratio of the amount of light reflected by the image to the amount of light reflected by the reference plate. Absolute reflectance measurement is calculated as the ratio of the amount of light reflected by the image to the amount of light directly measured from the light source without using a reference plate such as barium sulfate or a mirror. In the first - stage evaluation of reflectance, specularly reflected light may be measured by absolute reflectance measurement. The incident light may be measured at an incident angle of 60° with sensitivity from low gloss to high gloss.

[0055] (Second stage: Suppression of fogging derived from oxides) In the second stage, the effect of suppressing fogging derived from oxides is confirmed. When confirming the effect of suppressing fogging derived from oxides, an image produced using toner according to one embodiment is left for a long period (e.g., 4 weeks) under conditions such as a temperature of 30°C to 35°C and a humidity of 50% to 60%, and then the specular reflectance is measured again to confirm the effect of suppressing fogging derived from oxides on the surface of the image over time.

[0056] As described above, the toner according to one embodiment is a flake-shaped toner containing a low-melting-point metal pigment. The low-melting-point metal pigment is formed in a flake shape and contains a simple metal selected from the group consisting of Zn, In, Sn, and Bi, or an alloy or intermetallic compound mainly composed of one or more components selected from the group consisting of Zn, In, Ga, Sn, and Bi and not containing Cu. The toner according to one embodiment can reduce the thickness of the toner by making the low-melting-point metal pigment flake-shaped, so that heat is easily transferred to the low-melting-point metal during fixing. In addition, since the low-melting-point metal pigment contains the above simple metal, alloy or intermetallic compound, its melting point is lowered, so it can be easily melted. Therefore, due to the heat during fixing, the low-melting-point metal on the recording medium is likely to melt, and the low-melting-point metal pigment can melt and spread uniformly on the recording medium. Therefore, the toner according to one embodiment can exhibit the effect of suppressing gloss unevenness.

[0057] In addition, since the toner according to one embodiment does not contain a colored metal such as copper, it can maintain the white and silver colors peculiar to metals. Therefore, the toner according to one embodiment contains a low-melting-point metal pigment that can be spread by heating rather than by pressure, so that even if it does not contain copper that can suppress the occurrence of gloss unevenness, the low-melting-point metal pigment can emit white and silver colors and reproduce a more metallic luster.

[0058] Therefore, the toner according to one embodiment can suppress gloss unevenness of the image and reproduce white and silver lusters.

[0059] The melting point of the low-melting-point metal pigment in the toner according to one embodiment can be set to 60°C to 200°C. If the melting point of the low-melting-point metal pigment is 200°C or lower, the low-melting-point metal on the recording medium can be sufficiently melted and spread during fixing, so that the surface of the image can be made smooth. In addition, if the melting point of the low-melting-point metal pigment is 60°C or higher, it can be handled at room temperature. Therefore, the toner according to one embodiment can easily obtain an image with sufficient metallic luster.

[0060] The toner according to one embodiment can have a standard redox potential calculated from the atomic weight ratio of the low melting point metal pigment of -0.2 V or higher. As a result, the surface of the low melting point metal pigment is less likely to be oxidized. Therefore, when the toner according to one embodiment is spread on a recording medium, the toner according to one embodiment is sufficiently melted, so that the occurrence of gloss unevenness in the image formed using the toner according to one embodiment can be more suppressed. In addition, since the oxidation of the surface of the low melting point metal pigment is suppressed, it is possible to make it difficult for the image formed using the toner according to one embodiment to generate fogging derived from oxides. Therefore, the toner according to one embodiment can suppress the reduction of metallic gloss due to oxidation, so that the metallic gloss can be maintained for a longer period of time.

[0061] The toner according to one embodiment can have an average thickness D of the toner of 2 μm or less and a ratio F of the average thickness D of the toner to the equivalent diameter R of the average circle of 0.01 to 0.59. When the average thickness D is 2 μm or less, heat is easily transmitted, and the low melting point metal can be smoothly melted and spread on the recording medium, and metallic gloss can be exhibited. When the ratio F is 0.59 or less, when transferred onto the recording medium, the width direction of the toner can be oriented parallel to the surface of the recording medium, so that heat is easily transmitted to the inside of the toner, and the low melting point metal pigment can be smoothly melted and spread on the recording medium. Therefore, the toner according to one embodiment can exhibit metallic gloss. When the ratio F is 0.01 or more, the strength of the toner can be maintained, so that the toner does not break even in the developing device and can be satisfactorily transferred onto the recording medium. Therefore, the toner according to one embodiment can more reliably form an image on the recording medium, suppress gloss unevenness of the image, and exhibit sufficient metallic gloss.

[0062] The toner according to one embodiment has a core layer and an outer shell that covers at least a part of the core layer, the core layer contains a low-melting-point metal pigment, and the outer shell can contain a resin. As a heating method during toner fixing, there are methods such as an elastic roller, laser, heater, infrared rays, electromagnetic waves, arc discharge, etc. The toner according to one embodiment has the above configuration, so that it can be fixed using an elastic roller during toner formation, and thus can be fixed by heat while applying pressure, and the toner can be sufficiently spread. Therefore, the toner according to one embodiment can more reliably form an image on a recording medium and can emit sufficient metallic luster in the image.

[0063] <Developer> The developer according to one embodiment includes the toner according to one embodiment and can contain other appropriately selected components such as a carrier as necessary. Thereby, the developer according to one embodiment can suppress uneven gloss in the image and form an image that emits white and silver luster.

[0064] The developer may be a one-component developer or a two-component developer. However, when used in high-speed printers and the like that cope with the recent improvement in information processing speed, from the viewpoint of improving the lifespan, it is preferably a two-component developer.

[0065] When the toner according to one embodiment is used in a one-component developer, even if the toner balance is performed, the variation in the toner particle size is small, and there is little toner filming on the developing roller or toner fusion on members such as a blade for thinning the toner. Even in long-term stirring in the developing device, good and stable developability and images can be obtained.

[0066] When the toner according to one embodiment is used in a two-component developer, it can be mixed with a carrier and used as a developer. When the developer is used as a two-component developer, even if the toner balance is performed over a long period, the variation in the toner particle size is small, and good and stable developability and images can be obtained even in long-term stirring in the developing device.

[0067] The content of the carrier in the two-component developer can be appropriately selected according to the purpose. However, with respect to 100 parts by mass of the two-component developer, 90 to 98 parts by mass is preferable, and 93 to 97 parts by mass is more preferable.

[0068] The developer according to one embodiment can be suitably used for image formation by various known electrophotographic methods such as a magnetic one-component development method, a non-magnetic one-component development method, and a two-component development method.

[0069] [Carrier] The carrier is not particularly limited and can be appropriately selected according to the purpose. However, it preferably has a core material and a resin layer (coating layer) that coats the core material.

[0070] (Core material) The material of the core material is not particularly limited and can be appropriately selected according to the purpose. For example, manganese-strontium-based materials of 50 emu / g to 90 emu / g, manganese-magnesium-based materials of 50 emu / g to 90 emu / g, etc. can be mentioned. Also, in order to ensure image density, it is preferable to use high magnetization materials such as iron powder of 100 emu / g or more and magnetite of 75 emu / g to 120 emu / g. In addition, since it can relieve the impact of the developer in a standing state on the photoreceptor and is advantageous for high image quality, it is preferable to use low magnetization materials such as copper-zinc-based materials of 30 emu / g to 80 emu / g. These can be used alone or in combination of two or more.

[0071] The volume average particle diameter of the core material is not particularly limited and can be appropriately selected according to the purpose. However, 10 μm to 150 μm is preferable, and 40 μm to 100 μm is more preferable. If the volume average particle diameter is 10 μm or more, the amount of fine powder in the carrier increases, and the magnetization per particle decreases, which may cause scattering of the carrier. This problem can be effectively prevented. On the other hand, if it is 150 μm or less, the specific surface area decreases, which may cause scattering of the toner, and in full color with many solid parts, the reproduction of the solid parts may particularly deteriorate. This problem can be effectively prevented.

[0072] (Resin layer) The resin layer can contain a resin and other components as necessary. As the resin used for the resin layer, a known material capable of imparting the necessary chargeability can be used. Specifically, it is preferable to use a silicone resin, an acrylic resin, or a combination thereof. Further, the composition for forming the resin layer preferably contains a silane coupling agent.

[0073] The average film thickness of the resin layer is preferably 0.05 μm to 0.50 μm.

[0074] <Toner container unit> The toner container unit according to one embodiment can store the toner according to one embodiment. The toner container unit according to one embodiment refers to a unit having a function of storing toner and containing the stored toner. Here, examples of the form of the toner container unit include a toner container, a developing device, and a process cartridge.

[0075] The toner container refers to a container containing toner.

[0076] The developing device refers to a device having means for storing and developing toner.

[0077] The process cartridge refers to a unit in which at least an electrostatic latent image carrier (also referred to as an image carrier) and developing means are integrated, contains toner, and is detachable from an image forming apparatus. The process cartridge may further include at least one selected from charging means, exposure means, cleaning means, and the like.

[0078] The toner container unit according to one embodiment stores the toner according to one embodiment. By mounting the toner container unit according to one embodiment on an image forming apparatus and forming an image, an image is formed using the toner according to one embodiment. Therefore, the toner container unit according to one embodiment can suppress uneven gloss of the image and form an image that emits white and silver gloss.

[0079] <Image forming apparatus> An image forming apparatus according to an embodiment includes an electrostatic latent image carrier, an electrostatic latent image forming unit that forms an electrostatic latent image on the electrostatic latent image carrier, and a developing unit that develops the electrostatic latent image formed on the electrostatic latent image carrier using toner to form a toner image, and may further have other configurations as necessary.

[0080] An image forming apparatus according to an embodiment preferably further includes a transfer unit that transfers the toner image to a recording medium, and a fixing unit that fixes the transfer image transferred onto the surface of the recording medium, in addition to the above-described electrostatic latent image carrier, electrostatic latent image forming unit, and developing unit.

[0081] In the developing unit, toner according to an embodiment is used. Preferably, a developer containing toner according to an embodiment and further containing other components such as a carrier as necessary may be used to form a toner image.

[0082] (Electrostatic latent image carrier) The material, shape, structure, size, etc. of the electrostatic latent image carrier (which may be referred to as an "electrophotographic photoreceptor" or "photoreceptor") are not particularly limited and can be appropriately selected from known ones. Examples of the material of the electrostatic latent image carrier include inorganic photoreceptors such as amorphous silicon and selenium, and organic photoreceptors (OPCs) such as polysilane and phthalopolymethine. Among these, amorphous silicon is preferable in terms of long life.

[0083] As the amorphous silicon photoreceptor, for example, a photoreceptor having a photoconductive layer made of a-Si can be used by heating a support to 50°C to 400°C and forming the layer on the support by a film-forming method such as vacuum evaporation, sputtering, ion plating, thermal CVD (Chemical Vapor Deposition), photo-CVD, or plasma-CVD. Among these, the plasma-CVD method, that is, a method of decomposing a source gas by DC, high-frequency, or microwave glow discharge to form an a-Si deposition film on a support, is preferable.

[0084] The shape of the electrostatic latent image carrier is not particularly limited and can be appropriately selected according to the purpose, but a cylindrical shape is preferred. The outer diameter of the cylindrical electrostatic latent image carrier is not particularly limited and can be appropriately selected according to the purpose, but is preferably 3 mm to 100 mm, more preferably 5 mm to 50 mm, and particularly preferably 10 mm to 30 mm.

[0085] (Electrostatic latent image forming section) The electrostatic latent image forming section is not particularly limited as long as it is a means for forming an electrostatic latent image on the electrostatic latent image carrier, and can be appropriately selected according to the purpose. The electrostatic latent image forming section includes, for example, a charging member (charger) for uniformly charging the surface of the electrostatic latent image carrier and an exposure member (exposer) for imagewise exposing the surface of the electrostatic latent image carrier.

[0086] The charger is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include a contact charger provided with a conductive or semiconductive roll, brush, film, rubber blade, etc., and a non-contact charger using a corona discharge such as a corotron or scorotron.

[0087] The shape of the charger may take any form such as a magnetic brush or fur brush in addition to a roller, and can be selected according to the specifications and form of the image forming apparatus.

[0088] The charger is preferably arranged in contact with or in a non-contact state with the electrostatic latent image carrier and charges the surface of the electrostatic latent image carrier by superimposing a DC voltage and an AC voltage. Further, it is preferable that the charger is a charging roller arranged in a non-contact proximity to the electrostatic latent image carrier via a gap tape, and charges the surface of the electrostatic latent image carrier by superimposing a DC voltage and an AC voltage on the charging roller.

[0089] The charger is not limited to a contact type charger, but it is preferable to use a contact type charging member in view of obtaining an image forming apparatus with reduced ozone generated from the charger.

[0090] The exposure device is not particularly limited as long as it can expose the surface of the electrostatic latent image carrier charged by the charger in an image pattern to be formed, and can be appropriately selected according to the purpose. For example, various exposure devices such as a copying optical system, a rod lens array system, a laser optical system, a liquid crystal shutter optical system, etc. can be mentioned.

[0091] The light source used for the exposure device is not particularly limited and can be appropriately selected according to the purpose. For example, various light emitters such as fluorescent lamps, tungsten lamps, halogen lamps, mercury lamps, sodium lamps, light-emitting diodes (LEDs), semiconductor lasers (LDs), electroluminescence (EL), etc. can be mentioned.

[0092] In addition, in order to irradiate only light in a desired wavelength range, various filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, a color temperature conversion filter, etc. can also be used.

[0093] Note that a light backside exposure method in which exposure is performed in an image pattern from the backside of the electrostatic latent image carrier may be adopted.

[0094] (Developing unit) The developing unit is not particularly limited as long as it can develop the electrostatic latent image formed on the electrostatic latent image carrier to form a visible image, and can be appropriately selected according to the purpose. For the developing unit, for example, a developing device that accommodates toner and can apply toner to the electrostatic latent image in a contact or non-contact manner can be preferably used, and a developing device provided with a toner-containing container is preferable.

[0095] The developing device may be a single-color developing device or a multi-color developing device. As the developing device, for example, a developing device having a stirrer that stirs and charges toner by friction and a magnetic field generating part fixed inside, and having a developer carrier that carries a developer containing toner on the surface and is rotatable is preferable.

[0096] (Transfer unit) As the transfer unit, an embodiment having a first transfer unit that transfers a visible image onto an intermediate transfer member to form a composite transfer image and a second transfer unit that transfers the composite transfer image onto a recording medium is preferable. Note that the intermediate transfer member is not particularly limited and can be appropriately selected from known transfer members according to the purpose. For example, a transfer belt or the like is preferably used.

[0097] The transfer unit (first transfer means and second transfer unit) preferably has at least a transfer device that peels and charges the visible image formed on the electrostatic latent image carrier (photoconductor) toward the recording medium side. The transfer unit may be one or two or more.

[0098] Examples of the transfer device include a corona transfer device by corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, an adhesive transfer device, and the like.

[0099] Note that the recording medium is typically plain paper, but there is no particular limitation as long as it can transfer the undeveloped image after development, and it can be appropriately selected according to the purpose. A PET base for OHP or the like can also be used.

[0100] (Fixing unit) The fixing unit is not particularly limited and can be appropriately selected according to the purpose, but a known heating and pressing unit is preferable. Examples of the heating and pressing unit include a heated elastic roller, a combination of a heating roller and a pressing roller, and a combination of a heating roller, a pressing roller, and an endless belt. In this embodiment, among these, a heated elastic roller is preferable. The transfer image may be pressed with a heated elastic roller. Thereby, the transfer image can be surely spread on the recording medium.

[0101] The fixing unit preferably has a heating body including a heating element, a film in contact with the heating body, and a pressing member that is in pressure contact with the heating body via the film, and is a heating and pressing unit that can heat and fix by passing a recording medium on which an undeveloped image is formed between the film and the pressing member.

[0102] The heating in the heating and pressing unit is usually preferably 80°C to 200°C.

[0103] The surface pressure in the heating and pressurizing section is not particularly limited and can be appropriately selected according to the purpose, but it is preferably 10 N / cm 2 ~80 N / cm 2 .

[0104] In addition, in this embodiment, depending on the purpose, for example, a known optical fixing device may be used together with or instead of the fixing section.

[0105] (Others) The image forming apparatus according to the primary aspect may further include, for example, a charge removing section, a recycling section, a control section, and the like.

[0106] ((Charge Removing Section)) The charge removing section is not particularly limited as long as it can apply a charge removing bias to the electrostatic latent image carrier, and can be appropriately selected from known charge removing devices. For example, a charge removing lamp is preferably used.

[0107] ((Cleaning Section)) The cleaning section only needs to be able to remove the toner remaining on the electrostatic latent image carrier, and can be appropriately selected from known cleaners. Examples of the cleaning section include a magnetic brush cleaner, an electrostatic brush cleaner, a magnetic roller cleaner, a blade cleaner, a brush cleaner, a web cleaner, and the like.

[0108] By having a cleaning section, the image forming apparatus according to the primary aspect can improve the cleaning performance. That is, by controlling the toner-to-toner adhesion force, the fluidity of the toner can be controlled, and the cleaning performance can be improved. In addition, by controlling the characteristics of the toner after deterioration, excellent cleaning quality can be maintained even under severe conditions such as high life and high temperature and high humidity. Furthermore, since the external additive can be sufficiently released from the toner on the photoreceptor, a high cleaning performance can be achieved by forming a deposition layer (dam layer) of the external additive in the cleaning blade nip section.

[0109] ((Recycling section)) The recycling section is not particularly limited, and examples thereof include known conveying means and the like.

[0110] ((Control section)) The control section can control the movements of the above-described respective sections. The control section is not particularly limited as long as it can control the movements of the above-described respective sections, and can be appropriately selected according to the purpose. Examples thereof include control devices such as sequencers and computers.

[0111] Since the image forming apparatus according to one embodiment can perform image formation using the toner according to one embodiment, it is possible to suppress uneven gloss of the image and provide an image having white and silver gloss.

[0112] ((Image forming method)) The image forming method according to one embodiment includes an electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier, and a developing step of developing the electrostatic latent image using toner to form a toner image, and may further include other steps as necessary. The image forming method can be preferably performed by the image forming apparatus. The electrostatic latent image forming step can be preferably performed by the electrostatic latent image forming section, the developing step can be preferably performed by the developing section, and the other steps can be preferably performed by the other sections.

[0113] Further, the image forming method according to one embodiment more preferably includes, in addition to the above-described electrostatic latent image forming step and developing step, a transfer step of transferring the toner image onto a recording medium, and a fixing step of fixing the transferred image on the surface of the recording medium.

[0114] In the developing step, the toner according to one embodiment is used. Preferably, a developer containing the toner according to one embodiment and further containing other components such as a carrier as necessary may be used to form a toner image.

[0115] The electrostatic latent image forming process is a process of forming an electrostatic latent image on an electrostatic latent image carrier, and includes a charging process of charging the surface of the electrostatic latent image carrier, and an exposure process of exposing the charged surface of the electrostatic latent image carrier to form an electrostatic latent image. Charging can be performed, for example, by applying a voltage to the surface of the electrostatic latent image carrier using a charger. Exposure can be performed, for example, by imagewise exposing the surface of the electrostatic latent image carrier using the exposure device. The formation of the electrostatic latent image can be performed, for example, by uniformly charging the surface of the electrostatic latent image carrier and then imagewise exposing it, and can be performed by an electrostatic latent image forming unit.

[0116] The developing process is a process of sequentially developing the electrostatic latent image with toners of a plurality of colors to form a visible image. The formation of the visible image can be performed, for example, by developing the electrostatic latent image using the toner, and can be performed by a developing device.

[0117] In the developing device, for example, toner and carrier are mixed and agitated, and the toner is charged by the friction during that time, and is held in a standing state on the surface of the rotating magnetic roller, and a magnetic brush is formed. Since the magnetic roller is disposed near the electrostatic latent image carrier (photoconductor), a part of the toner constituting the magnetic brush formed on the surface of the magnetic roller moves to the surface of the electrostatic latent image carrier (photoconductor) by an electric attractive force. As a result, the electrostatic latent image is developed with toner, and a visible image made of toner is formed on the surface of the electrostatic latent image carrier (photoconductor).

[0118] The transfer process is a process of transferring the visible image to a recording medium. The transfer process preferably uses an intermediate transfer body, and transfers the visible image to the intermediate transfer body first, and then secondarily transfers the visible image onto the recording medium. The transfer process more preferably includes a first transfer process of transferring the visible image onto the intermediate transfer body using two or more colors of toner, preferably full-color toner, to form a composite transfer image, and a second transfer process of transferring the composite transfer image onto the recording medium. Transfer can be performed, for example, by charging the electrostatic latent image carrier (photoconductor) using a transfer charger for the visible image, and can be performed by a transfer unit.

[0119] The fixing process is a process of fixing the visible image transferred to the recording medium using a fixing device, and it may be performed each time the recording medium is transferred with respect to the developer of each color, or it may be performed simultaneously at once in a state where these are laminated with respect to the developer of each color.

[0120] In the fixing process, the transferred image may be pressed using a heating and pressing part such as a heated elastic roller and spread on the recording medium.

[0121] The image forming method according to the primary form may further include other processes appropriately selected as needed, for example, a charge elimination process, a cleaning process, a recycling process, and the like.

[0122] The charge elimination process is a process of performing charge elimination by applying a charge elimination bias to the electrostatic latent image carrier, and it can be preferably performed by a charge elimination part.

[0123] The cleaning process is a process of removing the toner remaining on the electrostatic latent image carrier, and it can be preferably performed by a cleaning part.

[0124] The recycling process is a process of recycling the toner removed by the cleaning process to the developing part, and it can be preferably performed by a recycling part.

[0125] Since the image forming method according to one embodiment can perform image formation using the toner according to one embodiment, it is possible to suppress uneven gloss of the image and provide an image that emits white and silver gloss.

[0126] [One aspect of the image forming apparatus] Next, one aspect of an image forming apparatus according to an embodiment will be described with reference to FIG. 9. FIG. 9 is a diagram showing the internal configuration of an image forming apparatus having a lubricant application device. As shown in FIG. 9, an image forming unit 10 is disposed in the approximate center of an image forming apparatus (copying machine) 100, and a paper feed unit 20 is disposed immediately below the image forming unit 10. If necessary, another paper feed unit can be added to the lower portion. In addition, an image reading unit 40 that reads an original is disposed behind the image forming unit 10, across the paper discharge storage unit 30. The recording paper P as a recording material on which an image has been formed is discharged and stored in the paper discharge storage unit 30. In FIG. 13, an arrow A indicates a paper passage path for the recording paper P.

[0127] In the image forming section 10, image forming units 11Y, 11M, 11C, and 11K as a plurality of image creating sections are arranged side by side so as to face the intermediate transfer belt 61. An exposure device 50 as a latent image forming means is installed below the image forming units 11Y, 11M, 11C, and 11K. The suffixes Y, M, C, and K added to the numbers of these image forming units 11 and exposure device 50 correspond to the colors of toner handled by the members etc. indicated by the numbers. Hereinafter, when there is no particular distinction between the colors of toner, the suffixes will simply be omitted.

[0128] The image forming unit 11 is provided with a photoconductor 111 which is a drum-shaped image carrier. Around the photoconductor 111, there are provided a charging device 112 as a charging means for uniformly charging the surface of the photoconductor 111, a photoconductor cleaning device 114 as a cleaning means for removing and collecting transfer residual toner remaining on the photoconductor surface after the toner image formed on the surface of the photoconductor 111 by the exposure device 50 is transferred to the intermediate transfer belt 61, and a lubricant application device 115 for supplying lubricant to the surface of the photoconductor 111. In addition, a primary transfer roller 12 for transferring the toner image formed on the surface of the photoconductor 111 to the intermediate transfer belt 61 is disposed opposite the photoconductor 111 with the intermediate transfer belt 61 interposed therebetween.

[0129] On the right side in the drawing of the intermediate transfer unit 60, there is arranged a secondary transfer device 62 including a secondary transfer roller 621 for secondarily transferring the toner image on the intermediate transfer belt 61, onto which the toner images on a plurality of photoreceptors 111 are superposed and transferred, to the recording paper P. Since toner adhesion to the secondary transfer roller 621 causes backside contamination of the recording paper P, the secondary transfer device 62 is provided with a secondary transfer member cleaning device 622 for removing and recovering the toner adhering to the surface of the secondary transfer roller 621. Further, the secondary transfer device 62 is provided with a secondary transfer member lubricant application device 623 for supplying a lubricant to the secondary transfer roller 621. Also, the intermediate transfer unit 60 is provided with an intermediate transfer body cleaning device 63 for removing and recovering the toner remaining on the surface of the intermediate transfer belt 61 after the second transfer. Also, there is arranged a fixing device 70 as a fixing means for fixing the toner of the recording paper P onto which the toner image has been transferred by the secondary transfer device 62. The recording paper P that has passed through the fixing device 70 is discharged and stored in the paper discharge storage unit 30 via the fixing device 80.

[0130] For easy maintenance, the image forming unit 11 incorporates the photoreceptor 111, charging device 112, developing device 113, photoreceptor cleaning device 114, lubricant application device 115, etc. as a process cartridge into one unit and makes it detachable from the main body of the image forming apparatus 100.

[0131] The paper feed unit 20 stores unused recording paper P. By the rotation of the paper feed roller, the topmost recording paper P is sent out from the paper feed cassette 90 and conveyed to the registration roller 91. The registration roller 91 controls the conveyance and temporary stop of the recording paper P and starts rotating at a timing such that the positional relationship between the toner image on the surface of the intermediate transfer belt 61 and the leading edge of the recording paper P reaches a predetermined position.

[0132] In the image reading unit 40 that reads image information, in order to perform reading and scanning of a document (not shown) placed on the contact glass 41, a reading carriage 42 equipped with a light source for document illumination and a mirror reciprocates along the contact glass 41. The reflected light from the document is received by a CCD 44 installed downstream of the lens 43. The CCD 44 converts the received light into an image signal and outputs this to a control unit (not shown). The control unit performs various image processes on the image information based on the input image signal, and then controls the driving of the light source (such as a laser diode) of the exposure device 50 based on the image information.

[0133] The writing light from the laser diode reaches the surface of the photoreceptor 111 via a known polygon mirror, lens, etc., and thereby an electrostatic latent image corresponding to the image information is formed on the surface of the photoreceptor 111.

Example

[0134] Hereinafter, examples and comparative examples will be shown to more specifically explain the embodiments, but the embodiments are not limited by these examples and comparative examples.

[0135] <Production of Low-Melting-Point Metal Pigments> Elemental metals of Bi, Zn, In, and Sn, or intermetallic compounds composed of two of Bi, Zn, Ga, In, and Sn were prepared as low-melting-point metal pigments A to Z, AA, AB, AC, AD, AE, and AF. The melting points of the respective low-melting-point metal pigments were converted based on the phase diagram. Each low-melting-point metal pigment was determined from the atomic weight ratio and oxidation-reduction potential of each element constituting the respective low-melting-point metal pigment. Details of the calculation method for the standard oxidation-reduction potential of the low-melting-point metal pigment will be described later. Since the elemental metal of Ga has a very low melting point of 30°C and is difficult to handle at room temperature, no evaluation has been performed. The calculation results are shown in Table 1. In Table 1, when the melting point is 400°C or higher, it is indicated as "400°C or higher".

[0136]

Table 1

[0137] The low-melting-point metal pigments using intermetallic compounds containing Bi, Zn, GaIn, or Sn were synthesized by the following synthesis method of low-melting-point metal pigments.

[0138] [Synthesis Method of Low-Melting-Point Metal Pigments] The low-melting-point metal pigments were prepared by the membrane emulsification method or the ultrasonic irradiation method shown below.

[0139] (Membrane Emulsification Method) The low-melting-point metal was immersed in a solvent with a protective agent added, passed through an emulsification membrane having pores, and a suspension was obtained. The obtained suspension was purified by centrifugation to obtain low-melting-point metal particles.

[0140] (Ultrasonic Irradiation Method) First, the molten low-melting-point metal was immersed in a solvent or the like with a protective agent added, ultrasonic irradiation was performed, and a suspension was obtained. The obtained suspension was purified by centrifugation to obtain low-melting-point metal particles.

[0141] <Melting Point> The melting point of the low-melting-point metal pigment was converted based on the phase diagram.

[0142] <Measurement of Standard Redox Potential> The standard redox potential of the low-melting-point metal pigment was determined from the redox potential of each element constituting the low-melting-point metal pigment and its mass ratio. The redox potential of each element used the standard redox potential described in the 5th Edition of the Electrochemical Handbook (edited by the Electrochemical Society).

[0143] The standard redox potential was calculated as follows. The redox potential of each metal was multiplied by the ratio of the atomic weights of each element constituting each low-melting-point metal pigment, and these values were added to calculate the redox potential of the low-melting-point metal pigment. For example, in the case of the low-melting-point metal pigment A, Bi and Zn are contained in an atomic weight ratio of 9:1. Therefore, as shown in the following formulas (1) and (2), the redox potential of Bi was multiplied by the atomic weight ratio of Bi, and the redox potential of Zn was multiplied by the atomic weight ratio of Zn. These calculated values were added to obtain the redox potential of low-melting-point metal A. Bi: 0.9×(0.3172) = 0.28548 ···(1) Zn: 0.1×(-0.7626) = -0.07626 ···(2)

[0144] <Production of Toner> Using low melting point metal pigments A to Z, AA, AB, AC, AD, AE, and AF, toners (toner particles) of Examples 1 to 5 and Comparative Examples 1 to 27 were produced by the seed method as follows. (Seed Method) A latex was prepared by mixing a low melting point metal pigment dispersion emulsion, a monomer emulsion as a raw material of a binder resin, potassium persulfate as a polymerization initiator (potassium persulfate, manufactured by Mitsubishi Gas Chemical Company), and ion-exchanged water. By heating and stirring this latex, polymerization of the monomer was carried out to produce toner mother particles containing low melting point metal pigments covered with a binder resin. The low melting point metal pigment dispersion emulsion and the monomer emulsion were prepared as follows.

[0145] (Production of Low Melting Point Metal Pigment Dispersion Emulsion) For the low melting point metal pigment dispersion emulsion, ion-exchanged water was added to low melting point metal particles so that the solid content concentration became 20% by mass to prepare a low melting point metal particle dispersion liquid. To the low melting point metal particle dispersion liquid, sodium polyoxyethylene-2-dodecyl ether sulfate was added as an emulsifier so that the mass ratio became 200:1, and it was dispersed for 1 hour by a mechanical disperser "CLEARMIX" (manufactured by M Technique Co., Ltd.) having a circulation path to prepare a low melting point metal particle dispersion emulsion.

[0146] (Production of Monomer Emulsion) The monomer emulsion was prepared by first charging a solution of 8 g of sodium dodecyl sulfate as an emulsifier dissolved in 3 L of ion-exchanged water into a 5-L reaction vessel, heating the internal temperature to 80°C while stirring at a stirring speed of 230 rpm under a nitrogen stream, adding a solution of 10 g of potassium persulfate as a polymerization initiator dissolved in 200 g of ion-exchanged water, bringing the solution temperature to 80°C again, and adding a mixture containing 480 g of styrene, 250 g of n-butyl acrylate, 68 g of methacrylic acid, and 16 g of n-octyl-3-mercaptopropionate dropwise over 1 hour, followed by heating and stirring at 80°C for 2 hours to effect polymerization, thereby preparing a resin particle dispersion liquid in which resin particles were dispersed.

[0147] Furthermore, a solution obtained by adding 7 g of polyoxyethylene-2-dodecyl ether sodium sulfate as an emulsifier to 800 mL of ion-exchanged water was charged into a 5-L reaction vessel. After heating to 98°C, 260 g of the resin particle dispersion liquid, a monomer solution obtained by dissolving and mixing 245 g of styrene, 120 g of n-butyl acrylate, 1.5 g of n-octyl-3-mercaptopropionate, 20 g of paraffin wax (melting point 62°C), and 180 g of microcrystalline wax (melting point 82°C) at 90°C were added, and the monomer emulsion was prepared by mixing and dispersing them for 1 hour using a mechanical disperser (“CLEARMIX”, manufactured by M Technique Co., Ltd.).

[0148] [Measurement of Toner Thickness D and Average Circle Equivalent Diameter R] The average thickness D and average circle equivalent diameter R of the toners of each of the prepared examples and comparative examples were measured, and the ratio F (= D / R) of the average thickness D of the toner to the average circle equivalent diameter R was calculated. The average thickness D and average circle equivalent diameter R of the toner, and the ratio F of the average thickness D of the toner to the average circle equivalent diameter R were measured by the following methods. (Measurement Method for Average Thickness D of Toner and Ratio F of Average Thickness D of Toner to Average Circle Equivalent Diameter R) Place the toner on a smooth surface, apply vibration to disperse it evenly without unevenness, and measure the thickness of the toner and the equivalent diameter of the circle of the surface viewed from above for the toner within a range of about 1 mm × 1 mm by magnifying it 1000 times with a color laser microscope. The average thickness of the toner was taken to obtain the average thickness D of the toner. The average of the equivalent diameters of the circles of the toner viewed from above was taken to obtain the average equivalent diameter R. The ratio F of the average thickness D of the toner to the average equivalent diameter R was calculated.

[0149] <Characteristic> As a characteristic of the toner, the reflectance of the created image was measured to confirm the effect of suppressing gloss unevenness of the toner.

[0150] [Evaluation of Reflectance] The reflectance of the image was evaluated in two stages.

[0151] (First stage: Evaluation of the effect of suppressing gloss unevenness) For the output images obtained by outputting solid images at 600 dpi with the toners of Comparative Examples 1 to 27 and Examples 1 to 5 using a printer (MPC307F, manufactured by Ricoh), the specular reflection light reflected at the same angle as the incident angle was measured to measure the reflectance with respect to the output images, and the evaluation was made based on the following evaluation criteria. Note that ◎ and ○ were regarded as passing, and △ and × were regarded as failing. The evaluation results are shown in Table 3. ◎: The reflectance of the specular reflection light is 50% or more ○: The reflectance of the specular reflection light is 40% or more and less than 50% △: The reflectance of the specular reflection light is 30% or more and less than 40% ×: The reflectance of the specular reflection light is less than 30%

[0152] (Second stage: Evaluation of the suppression of fogging) Next, using the toners of Comparative Examples 5, 6, 8, 9, 11 to 14, 17 to 19, and 23 and Examples 1 to 5, in which sufficient reflectance was obtained in the first-stage evaluation and gloss unevenness suppression was recognized, the images produced were left under the conditions of a temperature of 32°C and a humidity of 54% for 4 weeks. Then, the specular reflectance was measured again and evaluated based on the following evaluation criteria. Note that ◎ and ○ were regarded as passing, and △ and × were regarded as failing. The evaluation results are shown in Table 3. As time passes, a haze derived from oxides appears on the surface of the image. Therefore, the suppression effect of the generation of haze derived from oxides on the surface of the image over time under the above conditions was confirmed. ◎: The reflectance of specularly reflected light is 50% or more ○: The reflectance of specularly reflected light is 40% or more and less than 50% △: The reflectance of specularly reflected light is 30% or more and less than 40% ×: The reflectance of specularly reflected light is less than 30%

[0153] Table 2 shows the average thickness D, the average equivalent circle diameter R, and the ratio F (= D / R) of the average thickness D to the average equivalent circle diameter R of the toners of each Example and Comparative Example, as well as the evaluation results of the reflectance in the first and second stages.

[0154]

Table 2

[0155] From Table 2, in the measurement of the reflectance in the first stage, sufficient reflectance was obtained in Examples 1 to 5 and Comparative Examples 5, 6, 8, 9, 11 to 14, 18, 19, 23, and 26 where the melting point of the low-melting-point metal pigment was 209°C or lower. On the other hand, sufficient reflectance was not obtained in Comparative Examples 1 to 4, 7, 10, 15 to 17, 20 to 22, 24, 25, and 27 where the melting point of the low-melting-point metal pigment tail was 217°C or higher.

[0156] The reason why sufficient reflectance was obtained at levels below 209°C is thought to be that if the melting point of the low-melting-point metal pigment is about 200°C or lower, the low-melting-point metal pigment is sufficiently melted and spread on the recording medium during fixing, making the surface of the image smooth. On the other hand, the reason why sufficient reflectance could not be obtained is thought to be that since the melting point is 217°C or higher, the low-melting-point metal pigment did not completely melt on the recording medium, resulting in unevenness on the surface of the image and diffusion of the reflected light. Therefore, it can be said that in order for the image to have sufficient reflectance, the melting point of the low-melting-point metal pigment is preferably 200°C or lower. On the other hand, when the melting point of the low-melting-point metal pigment is less than 60°C, it becomes difficult to handle the toner at room temperature, so the melting point of the low-melting-point metal pigment is preferably 60°C or higher.

[0157] Therefore, it can be said that if the melting point of the low-melting-point metal pigment is between 60°C and 200°C, it is excellent for handling at room temperature, and a toner having an image with sufficient reflectance on the recording medium can be obtained. Therefore, it can be said that using the toner can suppress uneven gloss of the image.

[0158] Also, from Table 2, in the measurement of the reflectance in the second stage, sufficient reflectance could be obtained in Examples 1 to 5, Comparative Examples 6, 8, and 9 where the standard redox potential was -0.207V to 0.181V. This is thought to be because it was difficult to be oxidized due to the high standard redox potential. On the other hand, in Comparative Examples 5, 11 to 14, 18, 19, 23, and 26 where the standard redox potential was -0.218V or lower, dullness occurred and sufficient reflectance could not be obtained. The reason why sufficient reflectance could not be obtained is thought to be that since the standard redox potential was sufficiently lower than -0.218V, it was easily oxidized, and the low-melting-point metal on the recording medium was oxidized during the storage period, and the reflectance was reduced due to the dullness derived from the oxide film.

[0159] Therefore, if the standard redox potential calculated from the atomic weight ratio of the low-melting-point metal pigment is -0.207V to 0.181V, an image having sufficient reflectance over time can be obtained. Since the image has sufficient reflectance over time, it can be said that the occurrence of dullness derived from the oxide film is suppressed.

[0160] Also, it can be said that the problem that the melting point of the toner increases due to oxidation during storage of the unused toner, making it difficult for the low-melting-point metal pigment to melt even when heated, which can cause unevenness and loss of gloss, can be solved.

[0161] <Evaluation of the reflectance of an image when the shape of the toner is changed> The reflectance of an image when the shape of the toner was changed was measured, and the reflectance of the image when the ratio F of the average thickness D of the toner to the equivalent diameter R of the average circle of the average thickness D of the toner was changed was evaluated. [Preparation of toner] In Examples 1 and 3, the toners of Examples 6 to 11 and Comparative Examples 28 to 33 were prepared in the same manner as in Examples 1 and 3, except that the average thickness D and the equivalent diameter R of the average circle of the toner were changed. [Evaluation of reflectance when the shape of the toner is changed] Similar to the measurement of the reflectance in the first stage described above, a solid image was output at 600 dpi using a printer (MPC307F, manufactured by Ricoh), and the reflectance of the output image was measured and evaluated in the same manner as above.

[0162] Table 3 shows the average thickness D, the ratio F (= D / R) of the average thickness D of the toner to the equivalent diameter R of the average circle of the average thickness D, and the evaluation results of the reflectance of the toners of each example and comparative example.

[0163]

Table 3

[0164] From Table 3, in Examples 1, 3, and 6 to 11 where the average thickness D of the toner is 2.1 μm or less and the ratio F of the average thickness D of the toner to the equivalent diameter R of the average circle is 0.59 or less, sufficient reflectance was obtained. This is presumably because when the average thickness D is 2.1 μm or less, heat is easily transferred to the low-melting-point metal pigment during toner fixing, enabling smooth melting and spreading on the recording medium, resulting in a smooth surface of the melted and spread toner on the recording medium. Also, when the ratio F of the average thickness D of the toner to the equivalent diameter R of the average circle is 0.59 or less, when the toner is transferred onto the recording medium, the width direction of the toner is oriented parallel to the surface of the recording medium. Therefore, heat is easily transferred during fixing, enabling smooth melting and spreading on the recording medium, resulting in a smooth surface of the melted and spread toner on the recording medium.

[0165] On the other hand, sufficient reflectance was not obtained for the toners of Comparative Examples 28 to 33.

[0166] Therefore, unlike the toners of Comparative Examples 28 to 33, the toners of Examples 1, 3, and 6 to 11 have an average thickness D of 2 μm or less when viewed from the width direction of the toner, and by setting the ratio F of the average thickness D of the toner to the equivalent diameter R of the average circle to 0.59 or less, uneven gloss of the image can be suppressed, and white and silver gloss can be reproduced. Therefore, it can be said that the toners of Examples 1, 3, and 6 to 11 can be effectively used for forming a color image with a brilliance feeling in an electrophotographic color image forming apparatus.

[0167] On the other hand, when the ratio F of the average thickness D of the toner particles to the equivalent diameter R of the average circle is less than 0.01, the strength of the toner decreases, the toner may break in the developing device, and there is a possibility of poor transfer of the toner onto the recording medium. Therefore, it is preferable that the ratio F of the average thickness D of the toner to the equivalent diameter R of the average circle is 0.01 or more.

[0168] As described above, the embodiments have been explained. However, the above embodiments are presented as examples, and the present invention is not limited by the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, replacements, changes, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

Explanation of Signs

[0169] 100 Image forming apparatus

Prior Art Documents

Patent Documents

[0170]

Patent Document 1

Claims

1. A toner formed in a flake shape, containing a low-melting-point metal pigment, wherein the low-melting-point metal pigment is formed in a flake shape, the low-melting-point metal pigment is an alloy or intermetallic compound that contains one or more components selected from the group consisting of Zn, In, Ga, Sn, and Bi as a main component and does not contain Cu, the melting point of the low-melting-point metal pigment is 60°C to 200°C, the standard oxidation-reduction potential of the low-melting-point metal pigment is -0.198 V or higher, the average thickness of the toner is 2.0 μm or less, a toner in which a ratio F of the average thickness of the toner to the equivalent diameter of an average circle is 0.01 to 0.

59.

2. the toner has a core layer and an outer shell that coats the core layer, the core layer contains the low-melting-point metal pigment, the toner according to claim 1, wherein the outer shell contains a resin.

3. A developer containing the toner according to claim 1 or 2.

4. A toner container unit containing the toner according to claim 1 or 2.

5. An electrostatic latent image carrier, an electrostatic latent image forming unit that forms an electrostatic latent image on the electrostatic latent image carrier, a developing unit that develops the electrostatic latent image using toner to form a visible image, a transfer unit that transfers the visible image to a recording medium, a fixing unit that fixes the transferred image transferred to the recording medium, and is provided with, an image forming apparatus, wherein the toner is the toner according to claim 1 or 2.

6. the fixing unit includes an elastic roller, the image forming apparatus according to claim 5, wherein the transferred image is spread on the recording medium by pressing the transferred image with the heated elastic roller.

Images