JP2011150020A - White toner for developing electrostatic charge image, electrostatic charge image developer, toner cartridge, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide white toner for developing an electrostatic charge image for providing a toner image of high folding strength. <P>SOLUTION: The white toner for developing the electrostatic charge image includes first toner particles containing a white colorant, and second toner particles that contain no colorant or a colorant less than the first toner particles. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a white toner for developing an electrostatic image, an electrostatic image developer, a toner cartridge, a process cartridge, and an image forming apparatus.

For example, Patent Document 1 proposes “a white toner including at least a binder resin and thermosetting resin small particles or resin small particles having a softening point higher than that of the binder resin”.
Patent Document 2 discloses “a toner for forming an electrophotographic image characterized by containing white filler particles”, “a white toner having a specific gravity of 2.5 to 2.7 and a volume average particle diameter of 1 to 100 μm. An electrophotographic image forming toner characterized in that the filler particles are contained in an amount of 0.01 to 0.2% by weight of the total toner has been proposed.
Patent Document 3 states that, in an electrostatic latent image developing toner containing toner particles containing a colorant and a binder resin, the repose angle X (°), volume average particle diameter D50 (μm) of the toner and A "toner characterized by a loose apparent specific gravity AD (g / cc) satisfying a specific condition" has been proposed.
Patent Document 4 states that “a coating formed as an aggregate of crystallized fine particles capable of imparting white color to the surface of the base particle by scattering of light and crystallized fine particles having voids between the crystallized fine particles. A “white color material composition containing a white powder having at least one film” has been proposed.
Patent Document 5 proposes “a white toner having a white portion as a core and a transparent portion on the outside in a white toner fixed on a transfer material”.

Japanese Patent Laid-Open No. 05-107798 Japanese Patent Laid-Open No. 08-339095 JP-A-10-010771 JP 2001-049146 A JP 2002-108021 A

  An object of the present invention is to provide an electrostatic charge capable of obtaining a toner image having a higher bending strength than a case where the amount of the colorant is smaller than that of the first toner particles and the second toner particles containing the colorant or not containing the colorant are not included. It is to provide a white toner for image development.

The above problem is solved by the following means. That is,
The invention according to claim 1
First toner particles comprising a white colorant;
A second toner particle comprising a colorant in a smaller amount of colorant than the first toner particles or no colorant;
A white toner for developing an electrostatic charge image.

The invention according to claim 2
2. The white toner for developing an electrostatic charge image according to claim 1, wherein the content of the second toner particles is 1% by number or more and 30% by number or less with respect to all toner particles.

The invention according to claim 3
The white toner for developing an electrostatic charge image according to claim 1, wherein the first toner particles and the second toner particles contain the same type of binder resin.

The invention according to claim 4
The said 1st toner particle and the said 2nd toner particle contain a release agent, and the release agent amount of the said 2nd toner particle is larger than the release agent amount of the said 1st toner particle. The white toner for developing electrostatic images according to any one of the above items.

The invention according to claim 5
5. The system according to claim 1, wherein the relationship of D50w = D50c ± 0.5 μm is satisfied, where D50w is a volume average particle diameter of the first toner particles and D50c is a volume average particle diameter of the second toner particles. 2. A white toner for developing electrostatic images as described in 1.

The invention according to claim 6
An electrostatic charge image developer comprising at least the white toner for developing an electrostatic charge image according to claim 1.

The invention according to claim 7 provides:
Containing the white toner for developing an electrostatic charge image according to any one of claims 1 to 5;
A toner cartridge to be attached to and detached from the image forming apparatus.

The invention according to claim 8 provides:
A developing means for accommodating the electrostatic charge image developer according to claim 7 and developing a latent image formed on the latent image holding member with the electrostatic charge image developer to form a toner image,
A process cartridge attached to and detached from the image forming apparatus.

The invention according to claim 9 is:
A first image forming unit that forms a white toner image with the white toner for developing an electrostatic charge image according to any one of claims 1 to 5 on a transfer target;
A second image forming means for forming a color image with a color toner for developing an electrostatic image on the transfer member;
An image forming apparatus comprising:

According to the first aspect of the present invention, the white toner image has a higher bending strength than the case where the second toner particles containing the colorant or containing no colorant are contained in a smaller amount of the colorant than the first toner particles. Is obtained.
According to the second aspect of the present invention, a white toner image having a higher whiteness and concealment can be obtained than the content of the second toner particles is out of the above range with respect to all toner particles.
According to the third aspect of the present invention, a white toner image having a higher bending strength can be obtained than when the first toner particles and the second toner particles do not contain the same type of binder resin.

According to the fourth aspect of the present invention, a white toner image having a higher rubbing property can be obtained than when the amount of the release agent of the second toner particles is smaller than the amount of the release agent of the first toner particles.
According to the fifth aspect of the present invention, a white toner image having a high bending strength can be obtained as compared with the case where the relationship between the volume average particle diameters of the first toner particles and the second toner particles does not satisfy the above relationship.
According to the inventions according to claims 6, 7, 8, and 9, for developing an electrostatic charge image that has a colorant amount smaller than that of the first toner particles and does not have the second toner particles that contain the colorant or no colorant. A white toner image having a higher bending strength can be obtained than when white toner is applied.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment.

  Hereinafter, embodiments of the present invention, which are examples of white toner for developing an electrostatic image, an electrostatic image developer, a toner cartridge, a process cartridge, and an image forming apparatus, will be described in detail.

(White toner for developing electrostatic images)
The white toner for developing an electrostatic charge image (hereinafter simply referred to as “white toner”) according to the present embodiment includes a first toner particle containing a white colorant (hereinafter referred to as white toner particle for convenience) and a first toner. And a second toner particle containing a colorant or containing no colorant (hereinafter referred to as transparent toner particles for the sake of convenience) in a smaller amount of colorant than the toner particles.

Here, as a method of using the white toner, for example, a colored transfer object such as colored paper or black paper or a transfer object such as a transparent material is subtracted with a white toner image, that is, the concealing layer is formed with the white toner. There is a method of reducing the influence of the ground color and improving the color developability by forming a color image on it and drawing it. Of course, there is also a method of drawing a white toner image itself on a colored transfer material such as colored paper or black paper or a transfer material such as a transparent material.
The white coloring power and shielding power in this white toner image is based on the principle of scattering light by utilizing the refractive index difference between the white pigment and the binder resin, and essentially blocks light transmission. Therefore, for example, in order to obtain a practically sufficient white coloring power (whiteness) and hiding property, a larger amount of white colorant is added to the binder resin than other color toners. There are many cases.
For this reason, the toner image (fixed image) of this white toner may have a low bending strength.
This is because white toner often adds a larger amount of white colorant to the binder resin than other color toners, so embrittlement of the binder resin by the colorant and high melt viscosity of the toner. This is considered to be because it becomes difficult to melt between the toners (between the toner particles).

Therefore, with the white toner according to the present embodiment, a white toner image having a high bending strength can be obtained with the above-described configuration.
The reason for this is not clear, but is thought to be as follows.
When white toner particles containing a white colorant are used together with transparent toner particles containing a colorant or containing no colorant in a smaller amount of colorant, the transparent toner particles are more colored than the white toner particles. Since the amount is small or does not contain a colorant, it is considered that it is easy to melt and lower the viscosity by heating at the time of fixing. This is thought to be done. As a result, the obtained white toner image is fixed in a state where the white toner particles are bound by the transparent toner particles, so that embrittlement is suppressed as a whole and the image has a high bending strength. Conceivable.

  Further, with the white toner according to the present embodiment, since it is considered that embrittlement is suppressed as a whole of the white toner image, it is considered that a white toner image having high abrasion resistance can be obtained. In addition, since the transparent toner particles have a small amount of colorant or do not contain a colorant, it is difficult to affect the coloring power (whiteness) and concealment of the resulting white toner image, and the coloring power (whiteness) and concealment are difficult. It is considered that a white toner image having

Details of the white toner according to the present embodiment will be described below.
Specifically, the white toner according to this embodiment is, for example, white toner particles (first toner particles), transparent toner particles (second toner particles), and externally added to each toner particle as necessary. And an external additive.

Specifically, the white toner particles include, for example, a binder resin, a white colorant, and, if necessary, a release agent and other additives.
The white toner particles play a role of imparting white color to the obtained white toner image. For example, the content of the white colorant is preferably 3% by mass or more and 70% by mass or less. It is 5 mass% or more and 65 mass% or less, More desirably, it is 10 mass% or more and 65 mass% or less.

On the other hand, the transparent toner particles specifically include, for example, a binder resin, a colorant having a coloring amount smaller than that of the white toner particles, and a release agent and other additives as necessary. Selected from toner particles that do not contain a colorant and contain a binder resin and, if necessary, a release agent and other additives.
The transparent toner particles bind the white toner particles to each other in the obtained white toner image, and also have a role of assisting the coloring power of the white toner image when a colorant is included. When the transparent toner particles contain a colorant, the content of the colorant is, for example, preferably from 0.5% by mass to 30% by mass, and more preferably from 0.5% by mass to 25% by mass. Desirably, it is 0.5 mass% or more and 20 mass% or less.
As the colorant to be included in the transparent toner particles, a white colorant is mainly selected. For example, when a white toner image to be obtained is imparted with a bluish or reddish white color, other colors are used. A colorant may be selected.
The transparent toner particles that do not contain a colorant are light, colorless, or transparent toner particles.

The content of the transparent toner particles is preferably 1% by number to 30% by number, and preferably 1% by number to 10% with respect to the total toner particles (the total number of white toner particles and transparent toner particles). % Or less, more desirably 2% by number or more and 10% by number or less, and further desirably 2% by number or more and 8% by number or less.
When the ratio of the transparent toner particles is in the above range, a white toner image having high whiteness and high concealability can be easily obtained.

Here, the ratio of the transparent toner particles is a value obtained as follows.
The white toner is observed under a microscope, and the number of white toner particles and transparent toner particles is counted, and the number of transparent toner particles present per 1000 total toner particles is calculated. The white toner particles and the transparent toner particles have different colorant contents or the transparent toner particles do not contain a colorant, and therefore, each toner particle is counted separately by microscopic observation.

Further, the white toner particles and the transparent toner particles may contain the same type of binder resin. This makes it easy to obtain a white toner image with high bending strength. This is because at the time of fixing, the affinity between the melted toner particles is improved, and the transparent toner particles are considered to easily bind the white toner particles.
Here, the same type of binder resin means that the constituent units are the same, and those in which the quantity ratios of the constituent units are different or partially substituted are also in the same category.

When the white toner particles and the transparent toner particles contain a release agent, the amount of the release agent of the transparent toner particles is preferably larger than the amount of the release agent of the white toner particles. Specifically, for example, the difference in the amount of the release agent between the white toner particles and the transparent toner particles is preferably 0.2% by mass or more and 5% by mass or less (desirably 0.3% by mass or more and 4% by mass or less). The amount of release agent for white toner particles is 3% or less and 25% by mass or less (desirably 4% or more and 15% by mass or less), and the amount of release agent for transparent toner particles is 3% or less and 30% by mass or less. (Preferably 4.5% or less and 20% by mass or less).
This makes it easy to obtain a white toner image with high abrasion resistance. This is because the amount of the colorant that easily inhibits the release of the release agent during fixing is small, or the transparent toner particles that do not contain the colorant contain more release agent than the white toner particles. This is probably because more release agent sometimes oozes out from the toner particles and easily covers the surface of the white toner image.

Further, when the volume average particle diameter of the white toner particles is D50w and the volume average particle diameter of the transparent toner particles is D50c, the relationship of D50w = D50c ± 0.5 μm should be satisfied, and desirably D50w = D50c ± 0. It is preferable to satisfy the relationship of 4 μm, and more preferably satisfy the relationship of D50w = D50c ± 0.3 μm.
This makes it easy to obtain a white toner image with high abrasion resistance. This is because when the particle size difference between the white toner particles and the transparent toner particles is reduced, the difference in developability and transferability between the toner particles hardly occurs, and the white toner particles and the transparent toner particles are mixed evenly. In this state, a white toner image is easily formed, that is, a white toner image is easily formed in a state where transparent toner particles are interposed between white toner particles, and as a result, the transparent toner particles are easy to bind the white toner particles. This is because it is considered to be.

  The white toner particles and the transparent toner particles should preferably have a specific gravity greater than that of the white toner particles. Specifically, the specific gravity of the white toner particles is, for example, 1.0 or more and 2.2 or less (preferably 1.2 to 1.8), and the specific gravity of the transparent toner particles is, for example, 0.8 to 1.7 (desirably 0.8% to 1.5% by mass). As a result, the transparent toner particles are likely to appear on the surface of the toner image, which is more advantageous in terms of abrasion resistance.

Hereinafter, the components of the white toner particles and the transparent toner particles will be described.
First, the white colorant will be described.
Examples of the white colorant include white pigments and white resin particles in which these are dispersed and contained in a resin.
Specific examples of the white pigment include inorganic pigments (for example, heavy calcium carbonate, light calcium carbonate, titanium dioxide, aluminum hydroxide, titanium white, talc, calcium sulfate, barium sulfate, zinc oxide, magnesium oxide, magnesium carbonate). , Amorphous silica, colloidal silica, white carbon, kaolin, calcined kaolin, delaminated kaolin, aluminosilicate, sericite, bentonite, smectite, etc.), organic pigments (eg polystyrene resin particles, urea polymarin resin particles, etc.) Can be mentioned. Examples of the white pigment include a pigment having a hollow structure (for example, an inorganic pigment such as hollow silica).
Moreover, as resin which comprises white organic particle, the binder resin mentioned later is mentioned, for example.

Next, the binder resin will be described.
Examples of the binder resin include an amorphous resin, and the amorphous resin and the crystalline resin may be used in combination.
The amorphous resin is preferably used in the range of 50% by mass to 90% by mass of the components constituting the toner particles. When the crystalline resin is used in combination, the crystalline resin is a component constituting the toner particles. Among these, it is good to use in the range of 5 mass% or more and 30 mass% or less.

Examples of the amorphous resin include known resin materials, and an amorphous polyester resin is particularly desirable. The amorphous polyester resin is obtained mainly by condensation polymerization of polyvalent carboxylic acids and polyhydric alcohols.
The amorphous polyester resin is preferably produced by subjecting the polyhydric alcohol and polyhydric carboxylic acid to a condensation reaction according to a conventional method. For example, the above polyhydric alcohol and polyvalent carboxylic acid, if necessary, a catalyst, and blended in a reaction vessel equipped with a thermometer, a stirrer, a flow-down condenser, and in the presence of an inert gas (such as nitrogen gas), Heat at 150 ° C. or higher and 250 ° C. or lower to continuously remove low-molecular compounds produced as a by-product from the reaction system, stop the reaction when a specific acid value is reached, cool the target reactant It is good to manufacture by acquiring.

Here, the amorphous resin preferably has a weight average molecular weight (Mw) of 5,000 or more and 1,000,000 or less, as determined by gel permeation chromatography (GPC) method of tetrahydrofuran (THF) soluble matter. Desirably, the molecular weight (Mn) is from 7,000 to 500,000, the molecular weight distribution Mw / Mn is desirably from 1.5 to 100, and more desirably from 2 to 60. It is as follows.
This weight average molecular weight was measured with a THF solvent using a Toso GPC / HLC-8120, a Tosoh column TSKgel SuperHM-M (15 cm), and a molecular weight produced from a monodisperse polystyrene standard sample. The molecular weight was calculated using a calibration curve.

The glass transition temperature of the amorphous resin is desirably 35 ° C. or more and 100 ° C. or less, and more desirably 50 ° C. or more and 80 ° C. or less.
The glass transition temperature of the amorphous resin was determined as the peak temperature of the endothermic peak obtained by differential scanning calorimetry (DSC).

The softening point of the amorphous resin is desirably in the range of 80 ° C. or higher and 130 ° C. or lower. More desirably, it is in the range of 90 ° C. or higher and 120 ° C. or lower.
The softening point of the amorphous resin was measured by a flow tester (manufactured by Shimadzu Corp .: CFT-500C), preheating: 80 ° C./300 sec, plunger pressure: 0.980665 MPa, die size: 1 mmφ × 1 mm, heating rate: The intermediate temperature between the melting start temperature and the melting end temperature under the condition of 0 ° C./min.

Next, the release agent will be described.
The release agent may be used in the range of 1% by mass or more and 10% by mass or less, more preferably in the range of 2% by mass or more and 8% by mass or less, among the components constituting the white toner particles.

As the mold release agent, a substance having a main maximum peak measured according to ASTM D3418-8 in the range of 50 ° C. or higher and 140 ° C. or lower is preferable.
For the measurement of the main maximum peak, for example, DSC-7 manufactured by Perkin Elmer is used. The temperature correction of the detection part of this apparatus uses the melting temperature of indium and zinc, and the correction of heat uses the heat of fusion of indium. As the sample, an aluminum pan is used, an empty pan is set as a control, and the measurement is performed at a heating rate of 10 ° C./min.

  The viscosity η1 at 160 ° C. of the release agent is preferably in the range of 20 cps to 600 cps.

  Specific examples of the release agent include, for example, low molecular weight polyolefins such as polyethylene, polypropylene, and polybutene; silicones having a softening point upon heating; oleic acid amide, erucic acid amide, ricinoleic acid amide, stearic acid amide, and the like Fatty acid amides such as: carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil, etc .; animal waxes such as beeswax; montan wax, ozokerite, ceresin, paraffin wax, microcrystalline Minerals such as wax, Fischer-Tropsch wax and the like; petroleum-based waxes, and modified products thereof.

Next, other additives will be described.
Examples of other additives include various components such as a release agent, an internal additive, a charge control agent, inorganic powder (inorganic particles), and organic particles.
Examples of the internal additive include metals such as ferrite, magnetite, reduced iron, cobalt, nickel and manganese, alloys, and magnetic materials such as compounds containing these metals.
Examples of the inorganic particles include known inorganic particles such as silica particles, titanium oxide particles, alumina particles, cerium oxide particles, or particles obtained by hydrophobizing the surfaces thereof. These inorganic particles may be subjected to various surface treatments, for example, those subjected to surface treatment with a silane coupling agent, a titanium coupling agent, silicone oil or the like.

Next, the external additive will be described.
Examples of the external additive include inorganic particles. Examples of the inorganic particles include SiO ₂ , TiO ₂ , Al ₂ O ₃ , CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , MgO, BaO, and CaO. , K ₂ O, Na ₂ O, ZrO ₂ , CaO.SiO ₂ , K ₂ O. (TiO ₂ ) _n , Al ₂ O ₃ .2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO _{4 and the} like. .

  The surface of the external additive may be hydrophobized in advance. This hydrophobization treatment improves the powder flowability of the white toner particles, and is effective for the environmental dependency of charging and the resistance to carrier contamination. The hydrophobic treatment is performed, for example, by immersing inorganic particles in a hydrophobic treatment agent. The hydrophobizing agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, aluminum coupling agents and the like. These may be used individually by 1 type and may use 2 or more types together.

  The external addition amount of the external additive is preferably 0.5 parts by mass or more and 2.5 parts by mass or less with respect to 100 parts by mass of the white toner particles.

Next, a method for producing white toner according to the present embodiment will be described.
First, each toner particle (white toner particle and transparent toner particle) is prepared by a dry process (for example, a kneading pulverization process), a wet process (for example, an aggregation coalescence method, a suspension polymerization method, a dissolution suspension granulation method, a dissolution method). The suspension may be produced by any of the suspension method, the dissolution emulsion aggregation method, and the like. There is no restriction | limiting in particular in these manufacturing methods, A well-known manufacturing method is employ | adopted.

Then, after the obtained toner particles (white toner particles and transparent toner particles) are mixed, for example, an external additive is added to the mixed toner particles and mixed. Mixing is preferably performed by, for example, a V blender, a Henshur mixer, a ladyge mixer or the like. Further, if necessary, coarse toner particles may be removed using a vibration classifier, a wind classifier, or the like. Here, the volume average particle diameter of the toner particles is preferably in the range of 3 μm to 9 μm.
The external additive may be added before or after mixing the toner particles (white toner particles and transparent toner particles). However, the toner particles are mixed from the viewpoint of mixing the toner particles without variation. After that, it is preferable to add an external additive.

(Electrostatic image developer)
The electrostatic charge image developer according to the exemplary embodiment includes at least the white toner according to the exemplary embodiment.
The electrostatic charge image developer according to this embodiment may be a one-component developer containing only the white toner according to this embodiment, or may be a two-component developer mixed with the white toner and a carrier. .

  There is no restriction | limiting in particular as a carrier, A well-known carrier is mentioned. Examples of the carrier include a resin-coated carrier, a magnetic dispersion carrier, a resin dispersion carrier, and the like.

  The mixing ratio (mass ratio) of the white toner according to the exemplary embodiment and the carrier in the two-component developer is desirably in the range of toner: carrier = 1: 100 to 30: 100, and 3: 100 to 20: A range of about 100 is more desirable.

(Toner cartridge, process cartridge, and image forming apparatus)
The image forming apparatus according to the present exemplary embodiment includes a first image forming unit that forms a white toner image with the white toner according to the present exemplary embodiment on a transfer target, and a color image with a color toner for developing an electrostatic charge image. Second image forming means formed on the body.
In the image forming apparatus according to the present embodiment, as these first and second image forming units, for example, a latent image holding member and an electrostatic latent image formed on the latent image holding member are converted into toner images with toner. Developing means for developing the toner image, transfer means for transferring the toner image formed on the latent image holding member to the transfer target, and cleaning means for cleaning the transfer residual component of the latent image holding member if necessary And fixing means for fixing the toner image (white toner image and color image) transferred to the transfer medium. Of course, the first and second image forming units may have a configuration in which, for example, an image carrier, a transfer unit, and the like are shared.

  The image forming apparatus according to the present embodiment includes, for example, an image forming apparatus that sequentially repeats primary transfer of each toner image held on a latent image holding body to an intermediate transfer body, and a plurality of latent images including developing means for each color. It may be a tandem type image forming apparatus or the like in which the image holding member is arranged in series on the intermediate transfer member.

  In the image forming apparatus according to the present embodiment, for example, a part including a developing unit that stores the electrostatic latent image developer according to the present embodiment has a cartridge structure (process cartridge) that is detachable from the image forming apparatus. In addition, a cartridge structure (toner cartridge) in which the portion for storing the electrostatic latent image developing white toner according to the present embodiment as a replenishing toner to be supplied to the developing means is detachable from the image forming apparatus. May be.

The image forming apparatus according to the present embodiment will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present embodiment. The image forming apparatus according to the present embodiment has a tandem configuration in which a plurality of photosensitive members as latent image holding members, that is, a plurality of image forming units (image forming units) are provided.

As shown in FIG. 1, the image forming apparatus according to the present embodiment includes four image forming units 50Y, 50M, 50C, and 50K that form toner images of yellow, magenta, cyan, and black, respectively, and a white toner image. Are formed in parallel (tandem) at intervals. The image forming units are arranged in the order of the image forming units 50Y, 50M, 50C, 50K, and 50W from the downstream side in the rotation direction of the intermediate transfer belt 33.
Here, each of the image forming units 50Y, 50M, 50C, 50K, and 50W has the same configuration except for the color of the toner in the stored developer, and therefore, here, image formation for forming a yellow image is performed. The unit 50Y will be described as a representative. It should be noted that the same reference numerals with magenta (M), cyan (C), black (K), and white (W) are attached to the same parts as the image forming unit 50Y instead of yellow (Y). Description of the image forming units 50M, 50C, 50K, and 50W is omitted. In the present embodiment, the white toner according to the present embodiment is used as the toner (white toner) in the developer stored in the image forming unit 50W.

  The yellow image forming unit 50Y includes a photoconductor 11Y as a latent image holding member, and this photoconductor 11Y is rotationally driven at a predetermined process speed by a driving unit (not shown) along the direction of an arrow A shown in the drawing. It has come to be. As the photoreceptor 11Y, for example, an organic photoreceptor having sensitivity in the infrared region is used.

  A charging roll (charging means) 18Y is provided above the photoconductor 11Y. A predetermined voltage is applied to the charging roll 18Y by a power source (not shown), and the surface of the photoconductor 11Y is predetermined. Charged to a certain potential.

  Around the photoreceptor 11Y, an exposure device (electrostatic latent image forming unit) 19Y that exposes the surface of the photoreceptor 11Y to form an electrostatic latent image on the downstream side in the rotation direction of the photoreceptor 11Y with respect to the charging roll 18Y. Is arranged. Here, as the exposure device 19Y, an LED array that can be miniaturized is used in terms of space, but the present invention is not limited to this, and an electrostatic latent image forming unit using another laser beam or the like is used. There is no problem even if it is used.

  Further, a developing device (developing unit) 20Y including a developer holding body that holds a yellow developer is disposed around the photoconductor 11Y on the downstream side in the rotation direction of the photoconductor 11Y with respect to the exposure device 19Y. The electrostatic latent image formed on the surface of the photoreceptor 11Y is visualized with yellow toner, and a toner image is formed on the surface of the photoreceptor 11Y.

  Below the photoreceptor 11Y, an intermediate transfer belt (primary transfer means) 33 that primarily transfers a toner image formed on the surface of the photoreceptor 11Y extends below the five photoreceptors 11Y, 11M, 11C, 11K, and 11W. Are arranged as follows. The intermediate transfer belt 33 is pressed against the surface of the photoreceptor 11Y by the primary transfer roll 17Y. Further, the intermediate transfer belt 33 is stretched by three rolls of a drive roll 12, a support roll 13, and a bias roll 14, and is rotated in the direction of arrow B at a moving speed equal to the process speed of the photoconductor 11Y. It has become. A yellow toner image is primarily transferred onto the surface of the intermediate transfer belt 33, and toner images of magenta, cyan, black, and white (white) are sequentially primary transferred and stacked.

  Further, around the photoreceptor 11Y, the toner remaining on the surface of the photoreceptor 11Y and the retransferred toner are cleaned downstream of the primary transfer roll 17Y in the rotation direction (arrow A direction) of the photoreceptor 11Y. A cleaning device 15Y is arranged. The cleaning blade in the cleaning device 15Y is attached so as to be in pressure contact with the surface of the photoreceptor 11Y in the counter direction.

  A secondary transfer roll (secondary transfer unit) 34 is pressed against the bias roll 14 that stretches the intermediate transfer belt 33 via the intermediate transfer belt 33. The toner image that is primarily transferred and laminated on the surface of the intermediate transfer belt 33 is applied to the surface of the recording paper (transfer object) P fed from a paper cassette (not shown) at the pressure contact portion between the bias roll 14 and the secondary transfer roll 34. , Electrostatically transferred. At this time, since the toner image transferred and laminated on the intermediate transfer belt 33 has the white toner image on the top (uppermost layer), the toner image transferred on the surface of the recording paper P has a white toner image. It becomes the lowest (lowermost layer).

  Also, downstream of the secondary transfer roll 34, a fixing device (fixing means) for fixing the toner image transferred on the recording paper P onto the surface of the recording paper P by heat and pressure to form a permanent image. 35 is arranged.

  As the fixing device 35, for example, a low-surface energy material typified by a fluororesin component or a silicone resin is used on the surface, and a fixing belt having a belt shape is represented by a fluororesin component or a silicone resin on the surface. And a cylindrical fixing roll is used.

  In the yellow image forming unit 50Y, the developing device 20Y including a developer holding body for holding the yellow electrostatic latent image developer, the photoconductor 11Y, the charging roll 18Y, and the cleaning device 15Y are integrated into an image. It is configured as a process cartridge that is detachable from the forming apparatus main body. The image forming units 50W, 50K, 50C, and 50M are also configured as process cartridges in the same manner as the image forming unit 50Y.

  The toner cartridges 40Y, 40M, 40C, 40K, and 40W are cartridges that store toner of each color and are attached to and detached from the image forming apparatus, and are connected to a developing device corresponding to each color by a toner supply pipe (not shown). ing. When the toner stored in each toner cartridge becomes low, the toner cartridge is replaced.

  Hereinafter, although an Example and a comparative example are given and this embodiment is described in detail in detail, this embodiment is not limited to these Examples at all. The “part” means “part by mass” unless otherwise specified.

(1) Toner particle size measurement method To measure the toner particle size and particle size distribution, Multisizer 3 type (manufactured by Beckman Coulter) was used as the measuring device, and ISOTON-II (manufactured by Beckman Coulter, Inc.) was used as the electrolyte.
As a measuring method, 0.5 mg to 50 mg of a measurement sample is added to 2 ml of a 5% by weight aqueous solution of a surfactant, preferably sodium alkylbenzenesulfonate, as a dispersant. This was added to the electrolytic solution in a range of 100 ml to 150 ml. The electrolyte solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 minute, and the particle size distribution of particles having a diameter of 2 to 60 μm is measured using the Multisizer 3 type with an aperture diameter of 50 μm. Thus, the volume average particle diameter D50v was determined. The number of particles to be measured was 50,000.

(2) Volume average particle diameter of resin particles, colorant, etc. Measured using a laser diffraction / scattering type particle size distribution analyzer (LS Particle Size Analyzer: LS13 320, manufactured by BECKMAN COULTER). For the particle size range (channel) obtained by dividing the obtained particle size distribution, the volume cumulative distribution is subtracted from the small particle size side, and the particle size at 50% accumulation is defined as the volume average particle size d.

(3) Measurement of molecular weight Molecular weight distribution was performed on condition of the following. Tosoh Corporation HLC-8120GPC, SC-8020 apparatus was used, TSK gei, SuperHM-H (6.0 mm ID × 15 cm × 2) was used as a column, and THF (tetrahydrofuran) was used as an eluent. As experimental conditions, the sample concentration was 0.5%, and the flow rate was 0.6 ml / min. Sample injection volume 10 μl, measurement temperature 40 ° C., calibration curve is A-500, F-1, F-10, F-80, F-380, A-2500, F-4, F-40, F-128, Made from 10 samples of F-700. The data collection interval in sample analysis was 300 ms.

(4) Glass transition temperature The glass transition temperature of the amorphous polyester resin is based on ASTM D3418-8, using a differential scanning calorimeter (manufactured by Shimadzu Corporation: DSC60, with an automatic tangential treatment system), from room temperature to 150 ° C. The temperature at the temperature rising rate of 10 ° C./min was measured, and the temperature at the intersection of the base line and the extension line of the rising line in the endothermic part was defined as the glass transition temperature.

(5) Specific gravity Using a Le Chatelier specific gravity bottle, the specific gravity was measured according to JIS-K-0061 5-2-1 by the following operation.
(1) Put 250 ml of ethyl alcohol into a Le Chatelier specific gravity bottle and adjust so that the meniscus is at the position of the scale.
(2) The specific gravity bottle is immersed in a constant temperature water bath, and when the liquid temperature reaches 20.0 ± 0.2 ° C., the position of the meniscus is accurately read on the scale of the specific gravity bottle (accuracy 0.0025 ml).
(3) Weigh 100 g of sample.
(4) Put the weighed sample in a specific gravity bottle to remove bubbles.
(5) The specific gravity bottle is immersed in a thermostatic bath, and when the liquid temperature reaches 20.0 ± 0.2 ° C., the position of the meniscus is accurately read on the scale of the specific gravity bottle (accuracy 0.0025 ml).
(6) The specific gravity is calculated by the following formula.
Formula: D = W / (L2-L1)
Formula: S = D / 0.9982
In the formula, D is the density of the sample (g / cm ³ , 20 ° C.), S is the specific gravity of the sample (20 ° C.), W is the apparent mass of the sample (g), and L1 is the meniscus before the sample is placed in the specific gravity bottle. Reading (ml, 20 ° C.), L2 is the meniscus reading (ml, 20 ° C.) after placing the sample in a pycnometer, and 0.9982 is the water density (g / cm ³ ) at 20 ° C. .

<Preparation of Amorphous Polyester Resin Dispersion A>
・ Dimethyl terephthalate ・ ・ ・ 116 parts ・ Dimethyl fumarate ・ ・ ・ 22 parts ・ Dodecenyl succinic anhydride ・ ・ ・ 53 parts ・ Trimellitic anhydride ・ ・ ・ 10 parts ・ Bisphenol A ethylene oxide 2 mol adduct ・ ・・ 110 parts ・ Bisphenol A propylene oxide 2-mole adduct ・ ・ ・ 220 parts The above materials are put into a reaction vessel equipped with a stirrer, thermometer, condenser and nitrogen gas introduction tube, and the reaction vessel is replaced with dry nitrogen gas. Then, 2.7 parts of tin dioctanoate was added as a catalyst, and the mixture was stirred for about 6 hours at about 195 ° C. under a nitrogen gas stream. The temperature was further raised to about 240 ° C., and the mixture was stirred for about 6.0 hours. The inside of the reaction vessel was depressurized to 10.0 mmHg, and stirred and reacted for about 0.5 hours under reduced pressure to obtain a yellow transparent amorphous polyester resin A.
Subsequently, the obtained amorphous polyester resin A was dispersed using a disperser in which Cavitron CD1010 (manufactured by Eurotech Co., Ltd.) was modified into a high temperature and high pressure type. The composition ratio is 80% by weight of ion exchange water and the concentration of the polyester resin is 20% by weight. The pH is adjusted to 8.5 with ammonia, the rotational speed of the rotor is 60 Hz, the pressure is 5 kg / cm ² , and the heat exchanger is used. The Cavitron was operated under heating at 140 ° C. to obtain an amorphous polyester resin dispersion A (solid content 20% by weight).
The obtained amorphous polyester resin A has a weight average molecular weight of 105,000, a glass transition temperature of 58.2 ° C., an average particle diameter of the amorphous polyester resin dispersion A of 0.168 μm, and a resin specific gravity of 1.2 g / cm. ³ .

<Preparation of amorphous polyester resin dispersion B>
・ Dimethyl terephthalate ・ ・ ・ 87 parts ・ Dimethyl fumarate ・ ・ ・ 65 parts ・ Dodecenyl succinic anhydride ・ ・ ・ 26 parts ・ Bisphenol A ethylene oxide 2 mol adduct ・ ・ ・ 63 parts ・ Bisphenol A propylene oxide 2 mol addition Material: 275 parts The above material was put into a reaction vessel equipped with a stirrer, thermometer, condenser, nitrogen gas introduction tube, and the reaction vessel was replaced with dry nitrogen gas. The reaction vessel was stirred and reacted at about 195 ° C. for about 5 hours under a nitrogen gas stream. The temperature was further raised to about 240 ° C. and stirred for about 4.0 hours, and then the pressure in the reaction vessel was reduced to 10.0 mmHg, The reaction was stirred for about 0.5 hours under reduced pressure to obtain a single yellow transparent amorphous polyester resin B.
Subsequently, the obtained amorphous polyester resin B was dispersed using a disperser in which Cavitron CD1010 (manufactured by Eurotech Co., Ltd.) was modified to a high temperature and high pressure type. The composition ratio is 80% by weight of ion exchange water and the concentration of the polyester resin is 20% by weight. The pH is adjusted to 8.5 with ammonia, the rotational speed of the rotor is 60 Hz, the pressure is 5 kg / cm ² , and the heat exchanger is used. The Cavitron was operated under heating at 140 ° C. to obtain an amorphous polyester resin dispersion B (solid content 20% by weight).
The obtained amorphous polyester resin B has a weight average molecular weight of 25,000, a glass transition temperature of 63.4 ° C., a resin specific gravity of 1.1 g / cm ^{3 and} an average particle diameter of the amorphous polyester resin dispersion A of 0.142 μm. Met.

<Adjustment of styrene acrylic resin dispersion A>
A mixture of 370 g of styrene, 30 g of n-butyl acrylate, 8 g of acrylic acid, 24 g of dodecanethiol and 4 g of carbon tetrabromide was dissolved in 6 g of a nonionic surfactant (Nonipol 400: manufactured by Sanyo Chemical Co., Ltd.) and anion Ion exchange in which 10 g of a surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is emulsion-polymerized in a flask in which 550 g of ion-exchanged water is dissolved, and 4 g of ammonium persulfate is dissolved in the flask while slowly mixing for 10 minutes. 50 g of water was added. After nitrogen substitution, the contents in the flask were stirred and heated in an oil bath until the content reached 70 ° C., and emulsion polymerization was continued for 5 hours, and styrene having a volume average particle size of 150 nm and a solid content concentration of 35%. An acrylic resin dispersion A was obtained. When the obtained styrene acrylic resin dispersion A was dried, the weight average molecular weight was 11,500, the glass transition temperature was 58 ° C., and the resin specific gravity was 1.0 g / cm ³ .

<Preparation of release agent dispersion A>
Paraffin wax HNP9 (melting point: 74 ° C., manufactured by Nippon Seiwa Co., Ltd., specific gravity: 0.925 g / cm 3): 45 parts Anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., Neogen RK): 5 parts Exchanged water: 200 parts The above materials were heated to 95 ° C. and dispersed using a homogenizer (manufactured by IKA, Ultra Tarrax T50), then dispersed with a pressure discharge type gorin homogenizer (Gorin), and volume averaged. A release agent dispersion (a) having a particle size of 0.21 um (release agent concentration: 20%) was prepared.

<Preparation of white pigment dispersion A>
・ White pigment (titanium oxide, CR-60, manufactured by Ishihara Sangyo Co., Ltd., primary particle size 0.21 μm) ... 100 parts ・ Anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., Neogen R) ... 15 parts -Ion-exchanged water: 400 parts or more are mixed, dissolved, and dispersed for about 1 hour using a high-pressure impact disperser Optimizer (manufactured by Sugino Machine Co., Ltd., HJP30006), resulting in a volume average particle size of 0. A 35 um white pigment dispersion was prepared. The pigment concentration of the dispersion was 23%.

<Preparation of White Toner Particles A to C and Transparent Toner Particles A to C, E, F>
The materials shown in Table 1 were placed in each of the round stainless steel flasks, and were thoroughly mixed and dispersed with a homogenizer (IKA: Ultra Turrax T50). Next, a 1% aqueous solution of aluminum sulfate was added as a flocculant thereto, and the dispersion operation was continued with an ultra turrax.
After installing a stirrer and a mantle heater and appropriately adjusting the rotation speed of the stirrer so that the slurry is sufficiently stirred, the temperature was raised to 40 ° C. at 0.5 ° C./min, and held at 40 ° C. for 15 minutes, The particle size was measured every 10 minutes while raising the temperature at 0.05 ° C./min. When the desired volume average particle size was obtained, the additional amorphous polyester resin dispersion described in Table 2 was added for 3 minutes. Over time. After holding for 30 minutes, the pH was adjusted to 8.0 using a 5% by mass aqueous sodium hydroxide solution. Thereafter, while adjusting the pH to 8.0 every 5 ° C., the temperature was raised to 90 ° C. at a temperature raising rate of 1 ° C./min and held at 90 ° C. The particle shape and surface properties were observed every 30 minutes with an optical microscope and a scanning electron microscope (FE-SEM), and after the aggregated particles were sufficiently fused, the particles were cooled with ice water to immobilize the particles. The product was filtered, washed thoroughly with ion-exchanged water, and then dried using a vacuum dryer to obtain white toner particles A to C and transparent toner particles A to C.
Table 3 shows the volume average particle diameter and specific gravity of the obtained white toner particles A to C and transparent toner particles A to C, E, and F.

<Preparation of white toner particles D>
-Styrene acrylic resin dispersion A ... 94 parts-Release agent dispersion A-35 parts-White pigment dispersion A-174 parts-Ion exchange water-900 parts Put into a stainless steel flask, add 1.8 g of polyaluminum chloride (PAC100W: manufactured by Asada Chemical Co., Ltd.), mix and disperse using Ultra Turrax T50 (manufactured by IKA), and then in an oil bath for heating. While stirring the flask, heat up to 45 ° C at 0.5 ° C / min, hold at 45 ° C for 15 minutes, then measure the particle size every 10 minutes while raising the temperature at 0.05 ° C / min. When the volume average particle diameter reached 4.8 um, 100 parts of additional styrene acrylic resin dispersion A was added over 3 minutes. After maintaining for 30 minutes after addition, 0.1N sodium hydroxide was added to adjust the pH to 7, and then the temperature was raised to 95 ° C. at a rate of temperature increase of 1 ° C./min while continuing stirring. Held in. The particle shape and surface property were observed every 30 minutes with an optical microscope and a scanning electron microscope (FE-SEM). After the aggregated particles were sufficiently fused, the particles were cooled with ice water to fix the particles. Thereafter, the reaction product was filtered, sufficiently washed with ion-exchanged water, and then dried using a vacuum dryer to obtain white toner particles D.
Table 3 shows the volume average particle diameter and specific gravity of the obtained white toner particles D.

<Preparation of transparent toner particles D>
Styrene acrylic resin dispersion A ... 186 partsReleasing agent dispersion A ... 50 partsIon exchange water ... 900 parts The above materials are put into a round stainless steel flask and white toner particles Similarly to D, when the volume average particle diameter reached 4.5 um, 125 parts of additional styrene acrylic resin dispersion A was added over 3 minutes. After maintaining for 30 minutes after addition, 0.1N sodium hydroxide was added to adjust the pH to 7, and then the temperature was raised to 95 ° C. at a rate of temperature increase of 1 ° C./min while continuing stirring. Held in. The particle shape and surface property were observed every 30 minutes with an optical microscope and a scanning electron microscope (FE-SEM). After the aggregated particles were sufficiently fused, the particles were cooled with ice water to fix the particles. Thereafter, the reaction product was filtered, sufficiently washed with ion-exchanged water, and then dried using a vacuum dryer to obtain transparent toner particles D.
Table 3 shows the volume average particle diameter and specific gravity of the obtained transparent toner particles D.

<Examples 1 to 11 and Comparative Example 1>
-Adjustment of white toners A to K-
White toner particles A to D and transparent toner particles A to F are mixed in the ratios shown in Table 4, and hydrophobic silica particles (RY-50, manufactured by Nippon Aerosil Co., Ltd.) 1 are added to 100 parts of the mixed toner particles. The white toners A to K were obtained by adding parts and performing external addition mixing with a Henschel mixer. These were made into Examples 1-11.
Further, 1 part of hydrophobic silica particles (manufactured by Nippon Aerosil Co., Ltd., RY-50) is added to 100 parts of toner particles of the white toner particles A alone, and external addition mixing is performed with a Henschel mixer, whereby white toner WW is obtained. Obtained. This was designated as Comparative Example 1.

<Evaluation>
-Preparation of electrostatic image developer-
A trifunctional isocyanate 80% ethyl acetate solution (into a carbon dispersion obtained by mixing 0.12 part of carbon black (trade name; VXC-72, manufactured by Cabot Corporation) with 1.25 parts of toluene and stirring and dispersing in a sand mill for 20 minutes. Takenate D110N (manufactured by Takeda Pharmaceutical Company Limited)) 1.20 parts of the coating agent resin solution and Mn—Mg—Sr ferrite particles (volume average particle size: 35 μm) mixed and stirred were put into a kneader and mixed and stirred at room temperature for 5 minutes. Then, the temperature was raised to 150 ° C. at normal pressure to distill off the solvent. After further 30 minutes of mixing and stirring, the heater was turned off and the temperature was lowered while stirring to 50 ° C. The obtained coated carrier was sieved with a 75 μm mesh to prepare a carrier. 95 parts of this carrier and 8 parts of each white toner obtained were mixed in a V blender to obtain k electrostatic image developer.

  Each obtained electrostatic charge image developer was evaluated using a 700 Digital Color Press remodeling machine (modified so that the fixing device set temperature and toner development amount can be changed) manufactured by Fuji Xerox Co., Ltd.

Evaluation was carried out from the viewpoints of abrasion resistance, bending, whiteness, and concealment. A patch of 5 cm x 5 cm with a toner amount adjusted to 5.0 g / m ² is prepared on paper (OK top coat 127 gsm; Oji Paper) and fixed under conditions of 180 ° C and a process speed of 300 mm / sec. Went. The results are shown in Table 5.

-Abrasion resistance-
50 fixed images were overlaid, passed through the 700 Digital Color Press document feeder 30 times (50 document feeds counted as one), and the image state before and after passing was visually evaluated. The evaluation criteria are as follows.
◎ ・ ・ ・ No image defect before and after passing, no problem ○ ・ ・ ・ Slight defect is observed in a small part (2 sheets or less out of 50 sheets), but there is no problem in actual use △ ・ ・ ・Minor defects are seen with about 5 sheets, but there is almost no problem in actual use. X ... More than half or severe defects are observed, and there are problems in actual use.

−Bending strength−
The fixed image was folded, and after reciprocating 5 times with a 3 kg weight on the crease, the paper was spread and the image defect at the fold was visually evaluated. The evaluation criteria are as follows.
◎ ・ ・ ・ Folds can be seen or no creases are seen, and the image remains in good condition with no image loss.
○: A crease is seen, and the toner is slightly chipped or broken, but there is no problem in practical use.
Δ: The toner in the crease part is slightly chipped and cracked, and the paper (or the base) is partially visible. There is almost no problem in actual use.
×: The toner in the crease part is chipped and cracked, and the paper and the base are exposed almost throughout. There is a problem in actual use.

-Whiteness-
The whiteness of the fixed image was visually evaluated. The evaluation criteria are as follows.
◎ ... White, white ... Slight, but slightly light △ ... Slight as a single white, but no problem for use as a base x Is problematic

-Concealment-
The hiding property was evaluated according to JISK5101-4. Specifically, by adjusting the commercial hiding test paper toner amount so that 5.0 g / ^{m 2} and 7.0 g / ^{m 2} to (the Japan Paint Inspection Association test article) of 5 cm × 5 cm A patch was prepared and fixed at 180 ° C. and a process speed of 300 mm / sec. When creating the patch, an image was formed so as to straddle the white part and the black part of the cover ratio test paper. Then, the hiding property was evaluated from the transmittance of the fixed image portion. The evaluation criteria are as follows.
◎ ··· 5.0g / ^{m 2} faint background in ○ ··· 5.0g / ^{m 2} of black portion is almost completely hidden it can be seen that a black color but the 7.0 g / ^{m 2} Almost concealed Δ... 7.0 g / m ² , and black is slightly transparent, but there is no problem as a base for other colors.
X: Black can be seen through at 7.0 g / m ² , and there is a problem as a base for other colors.

  From the above results, it can be seen that this example gives better results in terms of abrasion resistance, folding, whiteness, and hiding than the comparative example.

DESCRIPTION OF SYMBOLS 11 Photoconductor 12 Drive roll 13 Support roll 14 Bias roll 15 Cleaning apparatus 16 Belt cleaner 17 Primary transfer roll 18 Charging roll 19 Exposure apparatus 20 Developing apparatus 34 Secondary transfer roll 35 Fixing device 40 Toner cartridge 50 Image forming unit

Claims (9)

First toner particles comprising a white colorant;
A second toner particle comprising a colorant in a smaller amount of colorant than the first toner particles or no colorant;
A white toner for developing an electrostatic charge image.   2. The white toner for developing an electrostatic charge image according to claim 1, wherein the content of the second toner particles is 1% by number or more and 30% by number or less with respect to all toner particles.   The white toner for developing an electrostatic charge image according to claim 1, wherein the first toner particles and the second toner particles contain the same type of binder resin.   The said 1st toner particle and the said 2nd toner particle contain a release agent, and the release agent amount of the said 2nd toner particle is larger than the release agent amount of the said 1st toner particle. The white toner for developing electrostatic images according to any one of the above items.   5. The system according to claim 1, wherein the relationship of D50w = D50c ± 0.5 μm is satisfied, where D50w is a volume average particle diameter of the first toner particles and D50c is a volume average particle diameter of the second toner particles. 2. A white toner for developing electrostatic images as described in 1.   An electrostatic charge image developer comprising at least the white toner for developing an electrostatic charge image according to claim 1. Containing the white toner for developing an electrostatic charge image according to any one of claims 1 to 5;
A toner cartridge to be attached to and detached from the image forming apparatus. A developing means for accommodating the electrostatic charge image developer according to claim 7 and developing a latent image formed on the latent image holding member with the electrostatic charge image developer to form a toner image,
A process cartridge attached to and detached from the image forming apparatus. A first image forming unit that forms a white toner image with the white toner for developing an electrostatic charge image according to any one of claims 1 to 5 on a transfer target;
A second image forming means for forming a color image with a color toner for developing an electrostatic image on the transfer member;
An image forming apparatus comprising:

Images